JP2008216852A - Video display device and head-mounted display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display device and a head-mounted display which allows an observer to observe bright and high-quality video, even in a configuration that uses a means of diffusing incident light in one direction. <P>SOLUTION: In a configuration of diffusing light from a light source 2 with a diffusing means 3 for guiding the light to a display element 4 and guide video light from the display device 4 to an optical pupil E via a lens 5, the diffusing means 3 has a second diffusing means 3b, other than a first diffusing means 3a. The first diffusing means 3a constituted of unidirectional diffusion plate and a second diffusion means 3b is constituted of unidirectional diffusion plate or a normal diffusion plate. The light from the light source 2 is diffused by a second diffusing means 3b, thereby since the light which is not emitted from the first diffusing means 3a is complimented in the incident light from a prescribed direction, the occurrence of shadowing due to the first diffusing means 3a is suppressed and uneveness in an observed video is reduced. Furthermore, the first diffusing means 3a can be arranged so as to be placed close to the display device 4, and as the result, the efficiency of using light is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device that provides an observer with an image displayed on a display element as a virtual image, and a head mounted display (hereinafter also referred to as an HMD) including the image display device.

  2. Description of the Related Art Conventionally, for example, Patent Documents 1 and 2 disclose image display devices that allow an observer to observe an image displayed on a display element such as an LCD as a virtual image. In each of the video display devices of Patent Documents 1 and 2, light emitted from the LED is diffused by a diffusion plate and incident on the LCD, and the video light from the LCD is optically pupild through optical elements such as a prism and a lens. It is the composition which leads to. When the observer's pupil is aligned with the position of the optical pupil, the observer can observe the virtual image of the image displayed on the LCD.

  By the way, in order to make it easy for an observer to observe an image (virtual image), it is necessary to brighten the image while widening the optical pupil. At this time, if incident light is diffused in all directions by the diffusion plate, the image becomes dark even though the optical pupil can be expanded in all directions. Therefore, it is very effective to use a diffuser plate that diffuses incident light in one direction (one-way diffuser plate) rather than diffuses incident light in all directions. In other words, by using a unidirectional diffuser plate, incident light can be diffused in one direction to make the optical pupil larger in one direction, making it easier for the observer to observe the image, and perpendicular to the diffusion direction. The light from the light source can be condensed in the direction to allow the observer to observe a bright image. Further, it is known that the diffusion due to the unevenness of the transparent material can be controlled to an appropriate diffusivity and light absorption is low, so that the light use efficiency can be increased.

Japanese Patent Laid-Open No. 11-326821 JP 2000-249976 A

  Incidentally, FIG. 16A is a cross-sectional view showing a configuration example of the unidirectional diffusion plate 101. The light exit surface 101a of the unidirectional diffuser plate 101 has a concavo-convex shape. In such a configuration, when light is incident on the unidirectional diffuser plate 101 from the light incident surface 101b, there is a portion where light is not emitted by total reflection on the light emitting surface 101a. For this reason, a shadow P corresponding to a portion where the light is not emitted appears in the light emitted from the unidirectional diffusion plate 101.

  Therefore, when the unidirectional diffuser plate 101 is applied to the above-described conventional image display device, as shown in FIG. 16B, the shadow P of the unidirectional diffuser plate 101 is superimposed on the observed image (virtual image) Q, resulting in uneven luminance. As a result, the quality of the observation image Q decreases. In order to avoid this problem, for example, if the unidirectional diffuser plate 101 is simply disposed at a position far from the display element, the light use efficiency is lowered and the observation image Q becomes dark.

  The present invention has been made to solve the above-described problems, and its purpose is to produce a bright and high-quality image even in a configuration using means for diffusing incident light in one direction. An object of the present invention is to provide an image display device that can be observed by an observer, and a head-mounted display using the image display device.

  An image display apparatus according to the present invention includes a light source that emits light, a diffusion unit that diffuses light emitted from the light source, a display element that modulates the light diffused by the diffusion unit and displays an image, and a display element The image display apparatus includes an observation optical system that allows the observer to observe a virtual image of the display image by guiding the image light from the optical pupil to the optical pupil, and the diffusion means transmits the incident light in one direction due to surface irregularities. A first diffusing means for diffusing light and a second diffusing means for diffusing incident light, and the optical pupil is perpendicular to the diffusing direction with respect to the diffusing direction of the incident light in the first diffusing means. It is characterized by being small in the direction.

  According to the above configuration, the light emitted from the light source is diffused by the diffusing means, then modulated by the display element, and emitted from there as video light. This image light is guided to the optical pupil via the observation optical system. Thereby, the observer can observe the virtual image of the image displayed on the display element at the position of the optical pupil.

  Here, the diffusion means has a first diffusion means and a second diffusion means. The first diffusion means diffuses incident light in one direction, but the second diffusion means may diffuse incident light in one direction or diffuse in all directions. There may be. As the incident light is diffused in one direction by the first diffusion means, the optical pupil is formed relatively large in one direction, that is, the diffusion direction in the first diffusion means, while the other direction, That is, the diffusion direction is relatively small in the vertical direction.

  By thus forming the optical pupil large in one direction, the observer can easily observe the image at the position of the optical pupil. On the other hand, by making the optical pupil small in the other direction, the utilization efficiency of light emitted from the light source can be increased, and the observer can observe a bright image (virtual image) even with a small and light device. Can do.

  Further, the light incident on the diffusing means is diffused not only by the first diffusing means but also by the second diffusing means, so that incident light from a predetermined direction is emitted from the first diffusing means. The light that is not complemented by the second diffusing means. Thereby, the occurrence of shadows due to the first diffusing means is suppressed, and the occurrence of unevenness (brightness unevenness, color unevenness) in the observed image is reduced. The closer the first diffusing unit is to the display element, the more easily the unevenness in the observed image is generated. Further, the smaller the diffusivity of the first diffusing unit is, the larger the pitch of the surface irregularities becomes. The shadow caused by the diffusing means increases, and the observed image tends to be uneven. However, according to the above configuration, since the unevenness of the observation image is reduced by the second diffusing unit, the first diffusing unit is arranged close to the display element, or the diffusivity of the first diffusing unit is reduced. It becomes possible. Thereby, the utilization efficiency of the light from the light source can be further increased to allow the observer to observe a bright and high-quality image.

  In the video display device of the present invention, the second diffusing unit diffuses incident light in one direction due to surface irregularities, and the diffusing direction of the incident light in the second diffusing unit is the first diffusing direction. May substantially coincide with the diffusion direction of incident light in the diffusing means.

  By diffusing incident light in approximately the same direction with the two diffusing means of the first and second diffusing means, the optical pupil can be compared with the case where the diffusing direction is omnidirectional, for example. It can be surely made small in the other direction, and the light use efficiency can be made higher to allow the observer to observe a bright image.

  In the video display apparatus of the present invention, the second diffusing unit is disposed in an optical path between the light source and the first diffusing unit, and the second diffusing unit is arranged in the diffusing direction of the first diffusing unit. The diffusion degree of the diffusion means may be smaller than the diffusion degree of the first diffusion means.

  In the case of this configuration, of the first and second diffusing means, the diffusing means (first diffusing means) having a higher diffusivity in the diffusing direction of the first diffusing means is connected to the other diffusing means (second diffusing means). Since the position is relatively closer to the display element than the means), it is possible to increase the light utilization efficiency and allow the observer to observe a bright image.

  In the video display device of the present invention, the light source includes a light emitting diode (hereinafter also referred to as an LED) that emits light of three colors of red, green, and blue, and each light emitting diode has a first diffusion. You may arrange | position along with the spreading | diffusion direction of a means.

  By arranging the light emitting diodes of the respective colors side by side in the diffusion direction of the first diffusion means, the respective colors are mixed in the diffusion direction, so that a color image with little color unevenness can be observed by the observer.

  In the image display device of the present invention, the light source has two sets of light emitting diodes that emit light of three colors of red, green, and blue, respectively, and the center of the display area of the display element and the center of the optical pupil are When the optically connecting axis is an optical axis, each set of light emitting diodes may be arranged symmetrically with respect to the optical axis of the observation optical system for each color.

  In this way, the centroids of the light intensity of each color of the emitted light from each LED (added between each set) coincide (for example, located on the optical axis). As a result, an image having no color unevenness at or near the center of the optical pupil can be observed by the observer as a high-quality image with little aberration.

  In the video display device of the present invention, it is desirable that the diopter difference between the virtual image by the observation optical system of the first diffusing means and the virtual image of the display image of the display element is 10 diopters or less. 10 diopter indicates the maximum adjustment range of the focus of the human eye. When the diopter difference between the virtual image by the observation optical system of the first diffusing unit and the virtual image of the display image of the display element is 10 diopter or less, The first diffusing unit is arranged at a position close to the display element, and not only a virtual image of the display image but also a virtual image (including a shadow) by the observation optical system of the first diffusing unit is located in a range that can be observed by human eyes. It will be.

  However, according to the present invention, the occurrence of shadows due to the first diffusing means can be reduced by the second diffusing means, so that the first diopter difference between the two virtual images is 10 diopters or less. Even if the diffusing means is arranged (at a position close to the display element), it is possible to suppress the occurrence of unevenness in the virtual image of the display image, and the configuration of the present invention in which the second diffusing means is provided is very effective. .

  The video display apparatus according to the present invention further includes a condensing unit that condenses light from the light source in a direction perpendicular to the diffusion direction of the first diffusing unit and guides the light to the display element. The structure arrange | positioned in the position which becomes conjugate about the direction perpendicular | vertical to the diffusion direction of the said spreading | diffusion means may be sufficient.

  In this configuration, the light from the light source is collected in the direction perpendicular to the diffusion direction of the first diffusion means by the light collecting means and guided to the display element. At this time, since the light source and the optical pupil are arranged at conjugate positions in the direction perpendicular to the diffusion direction of the first diffusion means, the optical pupil can be made smaller in the direction perpendicular to the diffusion direction. It is possible to increase the efficiency of light utilization from the light source in the above direction and allow the observer to observe a bright image.

  In the video display device of the present invention, it is desirable that the light converging means has no optical power or is negative in a direction parallel to the diffusion direction of the first diffusion means. Since the light from the light source is not collected in the direction parallel to the diffusion direction of the first diffusing means by the condensing means, luminance unevenness (intensity unevenness) of the light source is not amplified in the above direction, It is possible to make an observer observe an image of image quality.

  In the video display device of the present invention, the display element may be a reflective liquid crystal display element (hereinafter also referred to as LCD). The reflective LCD has a high aperture ratio and a small diffusion at the edge of each pixel. Therefore, by using a reflective LCD as a display element, it is possible to make an observer observe a brighter and higher-quality image as compared with, for example, a transmissive LCD.

  In the video display device of the present invention, the light condensing means is composed of a mirror having a positive optical power in a direction perpendicular to the diffusion direction of the first diffusing means, and is observed from the reflective liquid crystal display element. A light path directed to the optical system is disposed on the opposite side of the light source, reflects light from the light source and guides it to a reflective liquid crystal display element, and the first and second diffusing means include the reflective type The liquid crystal display element may be arranged between the light path from the liquid crystal display element toward the observation optical system and the light collecting means.

  In this configuration, the light from the light source is reflected by the light collecting means (mirror) and collected, and enters the reflective LCD. The light incident on the reflective LCD is modulated there and enters the observation optical system as image light. At this time, the light condensing means is disposed on the opposite side of the light source from the light path from the reflective LCD toward the observation optical system, and the first and second diffusing means include the light path and the light converging means. The light emitted from the light source and reflected by the light collecting means is diffused in a predetermined direction by the first and second diffusing means, and then is reflected on the reflective LCD. It will be incident.

  In this way, in the configuration in which the light path from the light source toward the reflective LCD is bent by the light collecting means, the first and second light paths are arranged between the light path from the reflective LCD to the observation optical system and the light collecting means. When the first and second diffusing means are arranged, the first and second diffusing means are inclined with respect to the reflective LCD, and one end thereof is very close to the reflective LCD. The closer the first diffusing unit is to the display element, the more easily the unevenness in the observation image occurs. However, according to the present invention in which the second diffusing unit is provided, the unevenness of the observation image can be reduced. The invention is very effective even in a compact configuration in which the light path from the light source toward the reflective LCD is bent by the light collecting means.

  In the image display device of the present invention, the observation optical system includes a volume phase type reflection hologram optical element, and the hologram optical element is configured to diffract and reflect image light from the display element and guide it to the optical pupil. May be.

  Volume phase type and reflection type hologram optical elements have high diffraction efficiency and a narrow half-value wavelength width of the diffraction efficiency peak. Therefore, by using such a hologram optical element and adopting a configuration in which image light from the display element is diffracted and reflected by the hologram optical element and guided to the optical pupil, a bright image with high color purity is provided to the observer. be able to. In addition, since the transmittance of external light is increased, a bright external image can be provided to the observer. That is, it is possible to provide a viewer with a bright and highly visible video superimposed on a bright external image.

  In the video display device of the present invention, the hologram optical element may have an axially asymmetric positive optical power. By providing the hologram optical element with axially asymmetric and positive optical power, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily downsized.

  In the video display device of the present invention, if the optical axis is an axis that optically connects the center of the display area of the display element and the center of the optical pupil, the diffusion direction of the first diffusion means is the light of the hologram optical element. It may be substantially parallel to the direction perpendicular to the axis incidence surface. The optical axis incident surface of the hologram optical element refers to a plane including the optical axis of incident light and the optical axis of reflected light in the hologram optical element.

  When the hologram optical element is axially asymmetric, the wavelength characteristic (wavelength selectivity) of the hologram optical element is large in the direction parallel to the optical axis incident surface of the hologram optical element, and the diffraction wavelength shifts when the incident angle of incident light shifts. Cheap. Therefore, the diffusion direction of the first diffusing means is set to a direction substantially parallel to the direction perpendicular to the optical axis incident surface, and light is diffused in a direction in which the wavelength selectivity of the hologram optical element is small, thereby suppressing occurrence of color unevenness. An image that is easy to observe by enlarging the optical pupil in the above direction can be provided to the observer. In addition, the optical pupil is relatively smaller in the direction parallel to the optical axis incident surface than in the direction perpendicular to the optical axis incident surface, so that the light from the light source can be collected without waste in the parallel direction. A bright image can be provided to the observer.

  In the video display device of the present invention, the light source is formed of a light emitting diode, and a wavelength at which the diffraction efficiency of the hologram optical element reaches a peak and a wavelength at which the intensity of light emitted from the light source peaks. The configuration may be approximately equal. In this case, light near the wavelength at which the light intensity reaches a peak among the light emitted from the light source (LED) is efficiently diffracted by the hologram optical element. Can be provided to the observer.

  In the video display device of the present invention, the observation optical system first reflects the video light from the display element to the observer's pupil while transmitting the external light to the observer's pupil. You may have a transparent substrate. Since the first transparent substrate advances the image light from the display element by total reflection inside thereof, the transmittance of external light is increased. Therefore, a bright external image can be observed by the observer while allowing the observer to observe the image on the display element.

  In the video display device of the present invention, the observation optical system may include a second transparent substrate for canceling refraction of external light on the first transparent substrate. In this case, distortion can be prevented from occurring in the external image observed by the observer through the observation optical system.

  The head-mounted display of the present invention includes the above-described video display device of the present invention and support means for supporting the video display device in front of an observer's eyes. In this configuration, since the video display device is supported by the support means, the observer can observe the video provided from the video display device in a hands-free manner.

  According to the present invention, since the optical pupil is formed relatively large in one direction by the first diffusion means, the observer can easily observe the image at the position of the optical pupil, and in the other direction. Since the optical pupil is formed to be relatively small, the utilization efficiency of light emitted from the light source can be increased, and a bright image (virtual image) can be observed by a viewer even with a small and lightweight device. Further, image unevenness caused by the first diffusing means is reduced by the second diffusing means, so that the first diffusing means is arranged close to the display element, or the diffusion of the first diffusing means is performed. The degree of use can be reduced, and the use efficiency of light from the light source can be further increased to allow the observer to observe a bright and high-quality image.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

  1 (a) and 1 (b) are explanatory views schematically showing a conceptual configuration of the image display device 1 of the present invention by developing an optical path, and FIG. 1 (a) shows an optical path in a horizontal direction. FIG. 1B shows a developed optical path in the vertical direction. The video display device 1 includes a light source 2, a diffusing unit 3, a display element 4, and a lens 5.

  The light source 2 is composed of, for example, a three-color integrated LED that emits red (R), green (G), and blue (B) light. The RGB LEDs are arranged in the horizontal direction when viewed from the observer's eyes.

  The diffusing means 3 diffuses the light emitted from the light source 2, and is composed of a plurality of diffusing means, that is, a first diffusing means 3a and a second diffusing means 3b. The first diffusing unit 3a and the second diffusing unit 3b are respectively configured by unidirectional diffusing plates having different diffusivities depending on directions. More specifically, the first diffusing unit 3a and the second diffusing unit 3b diffuse incident light by 40 degrees in the horizontal direction and 0.5 degrees in the vertical direction as viewed from the observer's eyes. To do. The surfaces on the light exit side of the first diffusing unit 3a and the second diffusing unit 3b are concavo-convex surfaces with less light absorption formed with concavo-convex so as to realize such diffusion. That is, the first diffusing unit 3a and the second diffusing unit 3b hardly diffuse the incident light in the vertical direction, so there is no undulation in the vertical direction (see FIG. 1B), and the horizontal direction (one direction) B) Concavities and convexities with randomly formed undulations.

  The first diffusing unit 3a is arranged in the vicinity of the display element 4 so that the diopter difference between the virtual image by the lens 5 of the first diffusing unit 3a and the virtual image of the display image on the display element 4 is 3 diopters. Is arranged. Further, the second diffusing unit 3b is arranged so that the diopter difference between the virtual image by the lens 5 of the second diffusing unit 3b and the virtual image of the display image of the display element 4 is 5 diopters. It arrange | positions in the optical path between these diffusing means 3a.

  Here, the above diopter will be briefly described. The diopter is represented by the reciprocal (1 / m) of the value of the focal length of the lens in meters, and is generally used as a unit indicating diopter, that is, the power (refractive power) of the lens. . Therefore, in this embodiment, if the virtual image of the display image of the display element 4 is located, for example, 1 m ahead from the observer's eye (if the virtual image of the image is at the position of −1d (diopter)), the first The position of the virtual image by the lens 5 of the diffusing means 3a is + 4d (a position 25 cm ahead of the eye) to + 2d (a position where the distance from the eye is infinite (0d and the distance from the eye to the infinite distance) ))).

  The display element 4 is a light modulation element that modulates the light diffused by the diffusing means 3 and displays an image. In the present embodiment, the display element 4 is configured by a transmissive color LCD having RGB color filters. .

  The lens 5 has, for example, positive optical power, and constitutes an observation optical system that allows the observer to observe a virtual image of the display image by guiding the image light from the display element 4 to the optical pupil E. . That is, the lens 5 forms the optical pupil E so that the observer can observe the display image of the display element 4 as a virtual image.

  In the above configuration, the light emitted from the light source 2 close to the point light source is diffused by the diffusing means 3, then modulated by the display element 4, and emitted therefrom as video light. This image light is guided to the optical pupil E through the lens 5. Thereby, the observer can observe the virtual image of the video displayed on the display element 4 at the position of the optical pupil E.

  At this time, the light emitted from the light source 2 is diffused in the horizontal direction by the second diffusing unit 3b of the diffusing unit 3, and then enters the first diffusing unit 3a. By such diffusion in the second diffusing unit 3b, incident light from a predetermined direction can be supplemented with light that is not emitted from the first diffusing unit 3a, and such light is used as the first diffusing unit 3a. Can be injected from. Therefore, since homogeneous light is emitted from the first diffusing unit 3a and is incident on the display element 4, the shadow of the first diffusing unit 3a is not observed on the observed image (virtual image). That is, the observer can observe a high-quality image free from luminance unevenness and color unevenness as a virtual image.

  In addition, since the light exit surface of the first diffusing unit 3a is an uneven surface, the closer the first diffusing unit 3a is to the display element 4, the more easily the observation image becomes uneven. As described above, since the unevenness of the observation image can be reduced by the second diffusing unit 3b, the first diffusing unit 3a can be arranged close to the display element 4. Thereby, the utilization efficiency of the light from the light source 2 can be further increased, and the observer can observe a bright and high-quality image.

  Further, the incident light is diffused in one direction by the first diffusing means 3a, so that the optical pupil E is formed relatively large in one direction (the horizontal direction which is the diffusion direction), while the other direction ( It is formed relatively small in the direction perpendicular to the diffusion direction. Thus, the optical pupil E is formed large in one direction, so that the observer can easily observe the image at the position of the optical pupil E. On the other hand, since the optical pupil E is formed small in the other direction, the utilization efficiency of the light emitted from the light source 2 can be increased, and a bright image can be observed by an observer even with a small and light device. it can.

  In the present embodiment, both the first diffusing unit 3a and the second diffusing unit 3b are configured by a unidirectional diffusing plate that diffuses incident light in one direction, and the diffusing directions thereof are aligned. That is, the diffusion direction of the incident light in the second diffusing unit 3b coincides with the diffusion direction of the incident light in the first diffusing unit 3a. Note that the diffusion direction of the both may be slightly deviated from the horizontal direction. In this case, for example, the optical pupil E can be reliably formed smaller in the other direction (vertical direction) as compared with the case where the diffusing direction of incident light is omnidirectional as the second diffusing unit 3b. It is possible to make the observer observe bright images with higher light utilization efficiency.

  Further, in this embodiment, the diopter difference between the virtual image by the lens 5 of the first diffusing unit 3a and the virtual image of the display image of the display element 4 is 3 diopters, which is the maximum focus adjustment range of the human eye. It is less than 10 diopters. As described above, when the diopter difference between the two virtual images is 10 diopters or less, the first diffusing unit 3a is disposed at a position close to the display element 4, and the lens of the first diffusing unit 3a as well as the virtual image of the display image. The virtual image by 5 is located in the range which can be observed with human eyes. However, in the present embodiment, since the occurrence of shadow caused by the first diffusing unit 3a can be reduced by the second diffusing unit 3b, the diopter difference between both virtual images is 10 diopters or less as described above. Even if the first diffusing unit 3a is arranged at a position close to the display element 4, it is possible to suppress the occurrence of unevenness in the virtual image of the display image, and the configuration of the present invention in which the second diffusing unit 3b is provided. Is very effective.

  In the present embodiment, the surface of the second diffusing unit 3b is also an uneven surface, and the virtual image by the lens 5 of the second diffusing unit 3b and the virtual image of the display image of the display element 4 are used. And the diopter difference is 5 diopters and 10 diopters or less, it is considered that the shadow caused by the second diffusing means 3b is superimposed on the virtual image of the display image. However, in the present embodiment, by the diffusion of the incident light in the first diffusing unit 3a, the light in the direction not emitted from the second diffusing unit 3b is complemented by the first diffusing unit 3a and is incident on the display element 4. be able to. Therefore, the occurrence of shadows caused by the second diffusing unit 3b is reduced by the first diffusing unit 3a. Therefore, the image quality of the virtual image of the display image does not deteriorate due to the provision of the second diffusing means 3b made of a unidirectional diffusing plate.

  By the way, in this embodiment, the horizontal diffusivities of the first diffusing unit 3a and the second diffusing unit 3b are both set to 40 degrees, but both of these diffusivities are set to be less than 40 degrees. For example, they may be aligned at 30 degrees. Further, the diffusivities in the horizontal direction of the first diffusing unit 3a and the second diffusing unit 3b may be different from each other. For example, the horizontal diffusion degree of the first diffusion means 3a may be 40 degrees, and the horizontal diffusion degree of the second diffusion means 3b may be 30 degrees. Thus, in the diffusion direction (horizontal direction) of the first diffusion means 3a, the diffusion degree of the second diffusion means 3b is set to be smaller than the diffusion degree of the first diffusion means 3a, and the diffusion having a larger diffusion degree. By arranging the means (first diffusing means 3a) close to the display element 4, it is possible to increase the light use efficiency and allow the observer to observe a bright image.

  In the present embodiment, as the first diffusing unit 3a and the second diffusing unit 3b, a diffusion plate that diffuses incident light by 0.5 degrees in the other direction (vertical direction) Although a unidirectional diffusion plate that is not diffused is used, for example, even if a diffusion plate that diffuses about 3 degrees in the vertical direction is used, a bright and high-quality image can be observed by an observer.

  In the present embodiment, the example in which the diffusing unit 3 is configured by two diffusing units, the first diffusing unit 3a and the second diffusing unit 3b has been described. However, the diffusing unit 3 may be configured by three or more diffusing units. . Further, the diffusing direction of the second diffusing means 3b may be omnidirectional. That is, as the second diffusing unit 3b, instead of the unidirectional diffusing plate described above, a normal diffusing plate that diffuses incident light in all directions is used, and the first diffusing unit 3a is brought close to the display element 4. It is possible to arrange it so that an observer can observe a bright and high-quality image.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

  2A and 2B are explanatory views schematically showing the configuration of the video display device 1 of the present embodiment by developing the optical path, and FIG. 2A shows the optical path in the horizontal direction. FIG. 2B shows a developed optical path in the vertical direction. The video display device 1 of the present embodiment has the same configuration as that of the first embodiment except that the diffusivity and the arrangement position of the diffusing unit 3 are slightly changed and the condenser lens 6 is added.

  Also in this embodiment, the diffusing means 3 is composed of a first diffusing means 3a and a second diffusing means 3b, both of which are composed of unidirectional diffusing plates having different diffusivities depending on directions. Yes. However, in the present embodiment, the first diffusing unit 3a and the second diffusing unit 3b diffuse incident light by 20 degrees in the horizontal direction when viewed from the observer's eyes and 0.5 degrees in the vertical direction. Spread. The surfaces on the light exit side of the first diffusing unit 3a and the second diffusing unit 3b are concavo-convex surfaces with less light absorption formed with concavo-convex so as to realize such diffusion. That is, the first diffusing unit 3a and the second diffusing unit 3b hardly diffuse the incident light in the vertical direction, so there is no undulation in the vertical direction (see FIG. 2B), and the horizontal direction (one direction) B) Concavities and convexities with randomly formed undulations.

  The first diffusing unit 3a is arranged at a position where the diopter difference between the virtual image by the lens 5 of the first diffusing unit 3a and the virtual image of the display image of the display element 4 is 20 diopters. The second diffusing unit 3b is disposed in the optical path between the light source 2 and the first diffusing unit 3a.

  The condensing lens 6 is an illumination lens that condenses light from the light source 2 incident via the diffusing unit 3 and illuminates the display element 4, and an optical path between the first diffusing unit 3 a and the display element 4. Is placed inside.

  In the above configuration, the light emitted from the light source 2 is diffused by the diffusing unit 3, condensed by the condenser lens 6, then modulated by the display element 4, and emitted therefrom as video light. . This image light is guided to the optical pupil E through the lens 5. Thereby, the observer can observe the virtual image of the video displayed on the display element 4 at the position of the optical pupil E.

  Further, by providing the condenser lens 6, the diffusivity of the diffusing unit 3 is reduced, and the diopter difference between the virtual image by the lens 5 of the first diffusing unit 3a and the virtual image of the display image of the display element 4 is reduced. Even if it is wider than 20 diopters and the 3 diopters of the first embodiment as described above, it is possible to efficiently illuminate the display element 4 by the condensing lens 6 and allow a viewer to observe a bright image.

  In this way, by widening the diopter difference between the two virtual images, the shadow caused by the first diffusing unit 3a becomes difficult to be recognized by the observer. However, in the present embodiment, since the horizontal diffusion degree of the first diffusion means 3a is as small as 20 degrees and the pitch of the unevenness is large, the shadow generated due to the first diffusion means 3a becomes large. This is a factor that degrades the image quality of the displayed video.

  However, in this embodiment as well, as in the first embodiment, the light from the light source 2 is diffused in the horizontal direction by the second diffusing unit 3b and enters the first diffusing unit 3a. Complementary light that is not emitted by the incident light from can be complemented and uniform light can be emitted from the first diffusion means 3a toward the display element 4. Therefore, the shadow of the first diffusing unit 3a is not observed on the observed image (virtual image), and the observer can observe a high-quality image without luminance unevenness and color unevenness as a virtual image. In other words, the configuration in which the second diffusing unit 3b is provided can reduce the diffusivity of the first diffusing unit 3a so that the shadow caused by the first diffusing unit 3a is likely to appear as in the present embodiment. It becomes effective.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings.

(1. Configuration of HMD)
3A is a plan view showing a schematic configuration of the HMD according to the present embodiment, FIG. 3B is a side view of the HMD, and FIG. 3C is a front view of the HMD. is there. The HMD has an image display device 11 and support means 12 that supports the image display device 11, and as a whole, has an appearance in which one lens (for example, for the left eye) is removed from general glasses.

  The video display device 11 allows an observer to observe an external image in a see-through manner, displays an image, and provides it to the observer as a virtual image, and corresponds to the video display device 1 of the first or second embodiment. Is. In the video display device 11 shown in FIG. 3C, a portion corresponding to the right eye lens of the spectacles is configured by bonding an eyepiece prism 32 and a deflection prism 33 described later. The detailed configuration of the video display device 11 will be described later.

  The support unit 12 supports the video display device 11 in front of the observer's eyes (for example, in front of the right eye), and includes a bridge 13, a frame 14, a temple 15, a nose pad 16, a cable 17, and external light. And a transmittance control means 18. The frame 14, the temple 15 and the nose pad 16 are provided as a pair on the left and right sides. However, when these are distinguished from each other, the right frame 14R, the left frame 14L, the right temple 15R, the left temple 15L and the right nose pad 16R. The left nose pad 16L is expressed.

  One end of the video display device 11 is supported by the bridge 13. In addition to the image display device 11, the bridge 13 supports the left frame 14 </ b> L, the nose pad 16, and the external light transmittance control means 18. The left frame 14L supports the left temple 15L so as to be rotatable. On the other hand, the other end of the video display device 11 is supported by the right frame 14R. An end of the right frame 14R opposite to the support side of the video display device 11 supports the right temple 15R so as to be rotatable. The cable 17 is a wiring for supplying an external signal (for example, a video signal, a control signal) and power to the video display device 11, and is provided along the right frame 14R and the right temple 15R. The external light transmittance control means 18 is provided in the bridge 13 in order to control the transmittance of external light (light of the external image), and is positioned in front of the video display device 11 (on the side opposite to the observer). is doing.

  When the observer uses the HMD, the right temple 15R and the left temple 15L are brought into contact with the right and left heads of the observer, and the nose pad 16 is placed on the nose of the observer so as to wear general glasses. The HMD is attached to the observer's head. When an image is displayed on the image display device 11 in this state, the observer can observe the image on the image display device 11 as a virtual image and observe the outside image through the image display device 11 in a see-through manner. Can do.

  At this time, if the external light transmittance control unit 18 sets the external light transmittance to be low, for example, 50% or less, the observer can easily observe the image on the video display device 11, and conversely, the external light transmission. If the rate is set as high as, for example, 50% or more, the observer can easily observe the external image. Therefore, the external light transmittance in the external light transmittance control means 18 may be set as appropriate in consideration of ease of observation of the video and the external image on the video display device 11.

  Note that the HMD is not limited to one having only one video display device 11. For example, FIG. 4A is a plan view showing another configuration of the HMD, FIG. 4B is a side view of the HMD, and FIG. 4C is a front view of the HMD. . Thus, HMD may be the structure provided with the two video display apparatuses 11 * 11 arrange | positioned in front of an observer's both eyes. In this case, the video display device 11 arranged in front of the left eye is supported between the bridge 13 and the left frame 14L. Further, both the video display apparatuses 11 and 11 are also connected by the cable 17, and an external signal or the like is supplied to both the video display apparatuses 11 and 11 through the cable 17.

(2. Details of video display device)
Next, a detailed configuration of the video display device 11 will be described.
FIG. 5 is a cross-sectional view illustrating a schematic configuration of the video display device 11, and FIG. 6 is an explanatory diagram illustrating the optical path in the video display device 11 optically developed in one direction. The video display device 11 includes a light source 21, a condenser lens 22, a diffusing unit 23, a display element 24, and an eyepiece optical system 31. As shown in FIG. 5, the light source 21, the condenser lens 22, the diffusing unit 23, and the display element 24 are accommodated in the housing 20, and are part of the eyepiece optical system 31 (part of the eyepiece prism 32 described later). ) Is located in the housing 20.

  Here, for convenience of explanation below, directions are defined as follows. First, an axis that optically connects the center of the display area of the display element 24 and the center of the optical pupil E formed by the eyepiece optical system 31 is defined as an optical axis. The optical axis direction when the optical path from the light source 21 to the optical pupil E is developed is taken as the Z direction. In addition, a direction perpendicular to an incident surface of an optical axis to a hologram optical element 34 to be described later of the eyepiece optical system 31 is an X direction, and a direction perpendicular to the ZX plane is a Y direction. The plane of incidence of the optical axis on the hologram optical element 34 refers to a plane including the optical axis of incident light and the optical axis of reflected light in the hologram optical element 34, that is, the YZ plane. Hereinafter, the incident surface is simply referred to as an incident surface or an optical axis incident surface.

  The light source 21 is configured by an RGB integrated LED (for example, manufactured by Nichia Corporation) having three light emitting chips that emit light having wavelengths corresponding to the three primary colors of RGB as light emitting units 21R, 21G, and 21B (see FIG. 6). Has been. The LED is inexpensive and small in size, and has a high color purity because the emission wavelength width is narrow as will be described later. Therefore, by configuring the light source 21 with RGB LEDs, an inexpensive and small image display device 11 can be realized, and the color purity of the image provided to the observer can be increased.

  Further, the light emitting portions 21R, 21G, and 21B have a size of about 0.3 mm square, and are arranged in the X direction at a pitch of 0.5 mm. As described above, the light emitting units 21R, 21G, and 21B are arranged side by side in the X direction that is the diffusion direction of the first diffusion unit 23a described later of the diffusion unit 23, so that each color of RGB is the first diffusion. Since the means 23 mixes in the diffusion direction, the intensity unevenness of each color on the optical pupil E is reduced, and the color unevenness can be reduced.

  Note that the light emitting units 21R, 21G, and 21B may not be completely aligned in the X direction. For example, part of the light emitting units 21R, 21G, and 21B may be shifted in the Y direction by 0.5 mm. At this time, the light source 21 may be arranged so that the direction in which more light emitting units are linearly arranged is the X direction.

  The condensing lens 22 is a condensing unit that condenses the light from the light source 21 in a direction (Y direction) perpendicular to the diffusing direction of the first diffusing unit 23 a described later of the diffusing unit 23 and guides it to the display element 24. For example, it is composed of a cylinder lens. The optical power of the condenser lens 22 in the direction parallel to the diffusion direction of the first diffusion means 23a (X direction) is zero or negative. Thereby, since the light from the light source 21 is not condensed in the X direction, luminance unevenness (intensity unevenness) of the light source 21 is not amplified in the X direction, and the observer can observe a high-quality image. it can.

  The condensing lens 22 is arranged so that the light diffused by the diffusing means 23 after the light from the light source 21 is condensed efficiently forms the optical pupil E. Further, the condenser lens 22 and the hologram optical element 34 to be described later are arranged so that the light source 21 and the optical pupil E are conjugate with respect to a direction (Y direction) perpendicular to the diffusion direction of the first diffusion means 23a. . In this embodiment, the optical pupil E has a size in the X direction of 6 mm and a size in the Y direction of 2 mm. Note that, in the Y direction of the optical pupil E, the light emission area (for example, 0.3 mm square) of the light source 21 is diffused by 0.5 degrees in the diffusing unit 23 and diffused by about 2 degrees in the display element 24. It is formed slightly larger than the pupil formed at the conjugate image magnification.

  Thus, the optical pupil E has a size of 6 mm, which is larger than the human pupil (about 3 mm) in one direction (X direction), so that the observer can easily observe the image. On the other hand, since the optical pupil E has a size of 2 mm which is smaller than the human pupil in the other direction (Y direction), the light from the light source 21 is condensed on the optical pupil E in the above direction without waste. Thereby, the observer can observe a bright image. In this embodiment, a brighter image is provided by making the optical pupil smaller than the human pupil. However, if the optical pupil is small in one direction, a bright image is provided even if it is larger than the human pupil. be able to.

  Further, since the light source 21 and the optical pupil E are arranged in a conjugate position in the Y direction perpendicular to the diffusion direction of the first diffusion means 23a, the optical pupil E can be further reduced in the Y direction. In the Y direction, the light use efficiency from the light source 21 can be further increased to allow the observer to observe a bright image. In the X direction, since the incident light is greatly diffused by the first diffusing unit 23a, the conjugate relationship between the light source 21 and the optical pupil E is not established, but the light from the light source 21 is highly efficiently obtained by the conjugate arrangement. It can be used and a bright video display is possible.

  The diffusing means 23 diffuses the light emitted from the light source 21, and is composed of a plurality of diffusing means, that is, a first diffusing means 23a and a second diffusing means 23b. The first diffusing unit 23a is arranged in the vicinity of the display element 24 so that the diopter difference between the virtual image by the eyepiece optical system 31 of the first diffusing unit 23a and the virtual image of the display image of the display element 24 is 5 diopters. Is arranged. The second diffusing unit 23b also has a light source 21 so that the diopter difference between the virtual image by the eyepiece optical system 31 of the second diffusing unit 23b and the virtual image of the display image of the display element 24 is 5 diopters. And in the optical path between the first diffusion means 23a. That is, the first diffusing unit 23a and the second diffusing unit 23b are arranged at almost the same position.

  The first diffusing unit 23a and the second diffusing unit 23b are respectively constituted by unidirectional diffusing plates having different diffusivities depending on directions. More specifically, the first diffusion unit 23a and the second diffusion unit 23b diffuse incident light by 40 degrees in the X direction and 0.5 degrees in the Y direction. Since the diffusing unit 23 includes a plurality of diffusing plates, the diffusivity in the X direction may be 40 degrees or less per one diffusing plate. The surfaces on the light emission side of the first diffusing unit 23a and the second diffusing unit 23b are concavo-convex surfaces formed with concavo-convex so as to realize such diffusion.

  The display element 24 modulates the light emitted from the light source 21 in accordance with image data and displays an image. The display element 24 includes an RGB color filter, and has a pixel-shaped transmission pixel having light transmission regions. Type LCD. The display element 24 is arranged so that the long side direction of the rectangular display region is the X direction and the short side direction is the Y direction.

  The eyepiece optical system 31 is an observation optical system that guides the image light from the display element 24, that is, the light corresponding to the image displayed on the display element 24, to the observer's pupil, and the eyepiece prism 32 (first transparent prism). Substrate), a deflection prism 33 (second transparent substrate), and a hologram optical element 34.

  The eyepiece prism 32 totally reflects the image light from the display element 24 and guides it to the observer's pupil through the hologram optical element 34, while transmitting external light to the observer's pupil. Along with the deflection prism 33, it is made of, for example, an acrylic resin. The eyepiece prism 32 is formed in a shape in which the lower end portion of the parallel flat plate is thinned toward the lower end to be wedge-shaped, and the upper end portion is thickened toward the upper end. Further, the eyepiece prism 32 is joined to the deflection prism 33 with an adhesive so as to sandwich the hologram optical element 34 disposed at the lower end thereof.

  The deflection prism 33 is configured by a substantially U-shaped parallel plate in plan view (see FIG. 3C), and is attached to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 32. The eyepiece prism 32 is integrated into a substantially parallel flat plate. By joining the deflection prism 33 to the eyepiece prism 32, it is possible to prevent distortion in the external image observed by the observer through the eyepiece optical system 31.

  That is, for example, when the deflection prism 33 is not joined to the eyepiece prism 32, the external light is refracted when passing through the wedge-shaped lower end portion of the eyepiece prism 32, so that the external field image observed through the eyepiece prism 32 is distorted. Arise. However, the deflection prism 33 is joined to the eyepiece prism 32 to form an integral substantially parallel plate, whereby the deflection prism 33 cancels refraction when external light is transmitted through the wedge-shaped lower end of the eyepiece prism 32. Can do. As a result, it is possible to prevent distortion in the external image observed through the see-through.

  Each surface (light incident surface, light exit surface) of the eyepiece prism 32 and the deflection prism 33 may be a flat surface or a curved surface. If each surface of the eyepiece prism 32 and the deflection prism 33 is a curved surface, the eyepiece optical system 31 can have a function as a correction spectacle lens.

  The hologram optical element 34 magnifies the image displayed on the display element 24 by diffracting and reflecting image light (light having a wavelength corresponding to the three primary colors) emitted from the display element 24 and guiding it to the optical pupil. It is a volume phase reflection hologram guided as a virtual image to the observer's pupil and has positive optical power that is axially asymmetric. That is, the hologram optical element 34 has the same function as an aspherical concave mirror having positive power. Thereby, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily reduced in size, and an image with good aberration correction can be provided to the observer.

(3. Operation of video display device)
Next, the operation of the video display device 11 having the above configuration will be described. The light emitted from the light source 21 is condensed by the condenser lens 22, and then sequentially diffused by the second diffusing unit 23b and the first diffusing unit 23a of the diffusing unit 23, so that RGB color mixing is sufficiently performed. The uniform illumination light made is incident on the display element 24. The light incident on the display element 24 is modulated for each pixel based on the image data and is emitted as video light. That is, a color image is displayed on the display element 24.

  The image light from the display element 24 enters the inside of the eyepiece prism 32 of the eyepiece optical system 31 from its upper end surface (surface 32a), and is totally reflected a plurality of times by the two opposing surfaces 32b and 32c, thereby being a hologram optical element. 34 is incident. The light incident on the hologram optical element 34 is reflected there and reaches the optical pupil E. At the position of the optical pupil E, the observer can observe an enlarged virtual image of the video displayed on the display element 24.

  On the other hand, the eyepiece prism 32 and the deflecting prism 33 transmit almost all the external light, so that the observer can observe the external image. Therefore, the virtual image of the image displayed on the display element 24 is observed while overlapping a part of the external image.

  As described above, in the video display device 11, since the video light emitted from the display element 24 is guided to the hologram optical element 34 by total reflection in the eyepiece prism 32, similarly to a normal eyeglass lens, The thickness of the eyepiece prism 32 and the deflection prism 33 can be about 3 mm, and the video display device 11 can be reduced in size and weight. Further, by using the eyepiece prism 32 that totally reflects the image light from the display element 24, a high external light transmittance can be secured and a bright external image can be provided to the observer.

  The hologram optical element 34 functions as a combiner that simultaneously guides the image light and the external light from the display element 24 to the observer's pupil, and the observer can connect the display element 24 via the hologram optical element 34. The provided image and the external image can be observed simultaneously.

  Further, in this embodiment, the diopter difference between the virtual image by the eyepiece optical system 31 of the first diffusing unit 23a of the diffusing unit 23 and the virtual image of the display image of the display element 24 is 5 diopters, and the virtual image of the display image In addition, the virtual image by the eyepiece optical system 31 of the first diffusing unit 23a is located in a range (10 diopters or less) that can be observed by human eyes. However, as in the first or second embodiment, the second diffusing unit 23b can reduce the occurrence of shadows caused by the first diffusing unit 23a, so that the first diffusing unit 23a is added to the display element 24. Even if they are arranged close to each other, it is possible to suppress the occurrence of unevenness in the virtual image of the display image. As a result, a bright and high-quality image (virtual image) can be observed by the observer.

  In particular, in the video display device 11 capable of observing an external image in a see-through manner as in the present embodiment, it is necessary to brighten the display video (virtual image) superimposed on such an external image so that the observer can easily observe it. Therefore, the configuration in which the second diffusing unit 23b is provided is very effective particularly for the see-through video display device 11 and the HMD.

(4. Characteristics of light source and hologram optical element)
Next, characteristics of the light source 21 and the hologram optical element 34 will be described.
FIG. 7 is an explanatory diagram showing the spectral intensity characteristics of the light source 21, that is, the relationship between the wavelength of the emitted light and the light intensity. The light source 21 emits light in three wavelength bands, for example, 462 ± 12 nm, 525 ± 17 nm, and 635 ± 11 nm in terms of the peak wavelength of light intensity and the wavelength width of the light intensity half value. The light intensity on the vertical axis in FIG. 7 is shown as a relative value when the maximum light intensity of B light is 100.

  The peak wavelength of light intensity is the wavelength at which the light intensity reaches a peak, and the wavelength width at half value of the light intensity is the wavelength width at which the light intensity is at half value of the light intensity peak. is there. The RGB light intensity of the light source 21 is adjusted in consideration of the diffraction efficiency of the hologram optical element 34 and the light transmittance of the display element 24, thereby enabling white display.

  On the other hand, FIG. 8 is an explanatory diagram showing the wavelength dependence of the diffraction efficiency in the hologram optical element 34. As shown in the figure, the hologram optical element 34 is, for example, 465 ± 5 nm (B light), 521 ± 5 nm (G light), 634 ± 5 nm (R light) at the peak wavelength of diffraction efficiency and the half width of the diffraction efficiency. ) Is diffracted (reflected) in the three wavelength regions. Here, the peak wavelength of diffraction efficiency is the wavelength at which the diffraction efficiency reaches a peak, and the wavelength width at half maximum of the diffraction efficiency is the wavelength width at which the diffraction efficiency is at half the peak of the diffraction efficiency. It is. The diffraction efficiency in FIG. 8 is shown as a relative value when the maximum diffraction efficiency of B light is 100.

  As described above, the hologram optical element 34 is fabricated so as to diffract only light having a specific wavelength at a specific incident angle, and therefore hardly affects the transmission of external light. Therefore, the observer can see the external image as usual through the eyepiece prism 32, the hologram optical element 34, and the deflection prism 33.

  Further, the volume phase type reflection type hologram optical element 34 has a high diffraction efficiency as shown in FIG. 8, and the half-value wavelength width of the diffraction efficiency peak is narrow. Therefore, by using such a hologram optical element 34 and diffracting and reflecting the image light from the display element 24 by the hologram optical element 34 and guiding it to the optical pupil E, a bright image with high color purity is observed. Can be provided.

  Furthermore, from the above numerical values, it can be said that the peak wavelength of the diffraction efficiency of the hologram optical element 34 and the peak wavelength of the light intensity emitted from the light source 21 are substantially equal. In such a setting, light in the vicinity of the wavelength at which the light intensity reaches a peak among the light emitted from the light source 21 is efficiently diffracted by the hologram optical element 34, so that it is bright even when superimposed on the external image, An easy-to-view video can be provided to the observer.

(5. Effect of reducing color unevenness)
By the way, in this embodiment, as described above, the optical pupil E is set to have a half intensity value of 6 mm in the X direction and 2 mm in the Y direction. That is, the optical pupil E is larger in the X direction, that is, the direction perpendicular to the incident surface than in the Y direction, that is, the direction parallel to the incident surface (YZ plane) of the optical axis to the hologram optical element 34. By setting the size of the optical pupil E in this way, the observer can observe a high-quality image with little color unevenness without being greatly affected by the wavelength characteristics (wavelength selectivity) of the hologram optical element 34. Can do. The reason is as follows.

  First, the relationship between the incident angle and the wavelength selectivity in the hologram optical element 34 will be described. In the hologram optical element 34 having an interference fringe that diffracts light having an incident angle greater than 0 degrees, the wavelength selectivity is smaller in the direction perpendicular to the incident surface than in the direction parallel to the incident surface (diffraction due to deviation of the incident angle). The wavelength shift is small. In other words, the angle selectivity with respect to the shift of the incident angle to the interference fringes is lower in the direction perpendicular to the incident surface than in the direction parallel to the incident surface. This is because when the light is incident on the interference fringes of the hologram optical element 34 with an incident angle, the angle shift of the incident angle in the incident plane (YZ plane) becomes the angle shift of the incident angle as it is. Although the influence on the wavelength is large, the angle shift in the direction perpendicular to the incident surface is small as the shift of the incident angle, and the influence on the diffraction wavelength is small.

  Accordingly, when light having an angle deviated from a predetermined incident angle is incident on the interference fringes of the hologram optical element 34, the angle deviation in the direction parallel to the incident surface is the angle in the direction perpendicular to the incident surface even with the same angle deviation. The diffraction wavelength is greatly shifted from the shift (that is, the direction parallel to the incident surface has a high wavelength selectivity).

  Here, FIG. 9 is an explanatory diagram showing the relationship between the pupil position in the optical pupil E and the main diffraction wavelength (for example, R light) in the present embodiment. In the figure, a broken line A1 indicates a change in the diffraction wavelength of the optical pupil E in the X direction, and a solid line A2 indicates a change in the diffraction wavelength of the optical pupil E in the Y direction pupil. As described above, the change in the diffraction wavelength is larger in the Y direction parallel to the incident surface than in the X direction perpendicular to the incident surface.

  Therefore, by forming the optical pupil E small in the Y direction where the change in the diffraction wavelength is large, the range of change in the diffraction wavelength is narrowed, so that color unevenness on the optical pupil E can be reduced. Moreover, even if the optical pupil E is formed large in the direction perpendicular to the incident surface, an image with high color purity can be provided to the observer. In addition, although the incident surface of the light outside the optical axis incident surface is not slightly parallel to the optical axis incident surface, as described above, since the angle shift in the direction perpendicular to the incident surface has little influence on the diffraction wavelength, the optical axis incident surface The color unevenness does not increase even if the standard is used.

  In the present embodiment, the diffusion direction of the first diffusion means 23 a is the X direction perpendicular to the optical axis incident surface of the hologram optical element 34. In this way, by diffusing the light in the direction in which the wavelength selectivity of the hologram optical element 34 is small, the diffusion direction of the first diffusion means 23a is the X direction perpendicular to the optical axis incident surface or a direction substantially parallel thereto. It is possible to provide an observer with an easy-to-observe image by enlarging the optical pupil E in the above direction while suppressing occurrence of color unevenness. Further, since the optical pupil E is relatively smaller in the Y direction parallel to the optical axis incident surface than in the X direction perpendicular to the optical axis incident surface, the light from the light source 21 is collected without waste in the Y direction. And bright images can be provided to the viewer.

  In addition, as described above, the three light emitting units 21R, 21G, and 21B of the light source 21 are arranged in the X direction, which is the direction in which the first diffusion unit 23a has a large diffusion. It means that the three light emitting portions 21R, 21G, and 21B are arranged in a direction perpendicular to the incident surface of the optical axis. The direction perpendicular to the incident surface is a direction in which the wavelength selectivity in the hologram optical element 34 is small, so that the optical pupil E can be enlarged by arranging the three light emitting units 21R, 21G, and 21B in the X direction. Even when the light source 21 that emits three colors of RGB is used, a high-quality image with little color unevenness can be provided to the observer.

[Embodiment 4]
The following will describe still another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the third embodiment are denoted by the same member numbers, and description thereof is omitted.

  FIG. 10 is an explanatory view showing the optical path in the image display device 11 of the present embodiment, which is optically developed in one direction. In the present embodiment, the configuration is the same as that of the third embodiment except that the light source 21 includes two light source groups 21P and 21Q.

Here, FIG. 11 shows a plan view when the light source 21 in the present embodiment is viewed from the display element 24 side. The light source group 21P of the light source 21 includes RGB integrated LEDs having three light emitting portions 21R ₁ , 21G _1, and 21B ₁ that emit light of RGB colors. Similarly, the light source group 21Q is composed of RGB integrated LEDs having three light emitting portions 21R ₂ , 21G _2, and 21B ₂ that emit light of RGB colors. That is, the light source 21 has two sets of three light emitting units (LEDs) that emit RGB light.

The light emitting units of the light source groups 21P and 21Q are arranged side by side in a direction perpendicular to the incident surface (YZ plane) of the optical axis with respect to the hologram optical element 34. Each color is arranged so as to be plane symmetric. More specifically, the light emitting portions 21R ₁ and 21R ₂ are arranged so as to be plane symmetric at positions close to the incident surface, and the light emitting portions 21G ₁ and 21G ₂ are plane symmetric with respect to the incident surface outside the X direction. Further, the light emitting portions 21B ₁ and 21B ₂ are arranged on the outer side in the X direction so as to be plane-symmetric with respect to the incident surface. That is, in each light source group 21P * 21Q, each light emission part is arrange | positioned in the order that the wavelength of an emitted light becomes short as it goes to the X direction outer side from the said incident surface side.

In this way, by arranging each light emitting unit symmetrically with respect to the incident surface for each color (symmetric with respect to the optical axis of the eyepiece optical system 31), two light emitting units (for example, 21R ₁ ) for the same color are arranged. And 21R ₂ ), the centroid of the total light intensity obtained by adding the light intensities of the light emitted from the 21R ₂ ) can be positioned in the symmetry plane (in the incident plane, on the optical axis) for each of the RGB colors. That is, the intensity distribution of each color of RGB can be symmetric in the X direction with the symmetry plane as the center. Accordingly, an image with little color unevenness at the center of the optical pupil E can be provided to the observer.

  Note that the plane that is the center of plane symmetry of each light emitting unit may be a plane parallel to the incident plane. In other words, the surface that is the center of symmetry of each light emitting unit may be a surface that is slightly deviated in the X direction from the incident surface. In this case, an image with little color unevenness near the center of the optical pupil E can be provided to the observer.

  By the way, when the light source 21 is composed of two light source groups and the light emitting units are arranged in plane symmetry for each color, the arrangement order of the light emitting units in the direction perpendicular to the incident surface is set to each adjacent group. Vice versa. On the other hand, even if the number of light source groups constituting the light source 21 is an even number of 4 or more, that is, even when the light source 21 is configured by providing an even number of 4 or more RGB light emitting units, If the arrangement order of the light emitting units in the direction perpendicular to the surface is reversed between adjacent pairs, the total light intensity centroid of the light intensity of the emitted light from each light emitting unit is added to the RGB Each color can be positioned in the same plane (including the incident plane) parallel to the incident plane, and an image with little color unevenness at the center of the optical pupil E or in the vicinity thereof can be provided to the observer.

  Therefore, in summary, the light source 21 eventually has two or more even three sets of RGB light-emitting portions, and the arrangement order of the light-emitting portions in the direction perpendicular to the incident surface is as follows. It can be said that an image with little color unevenness can be provided to the observer at the center of the optical pupil E or in the vicinity thereof if the pair is adjacent to each other.

  Further, even if the number of light source groups constituting the light source 21 is an even number of 4 or more, the light emitting units are arranged in plane symmetry with respect to the incident surface and are perpendicular to the incident surface. If the light emitting units located at the same distance from the incident surface on both sides are arranged to emit light of the same color, the center of gravity of the light intensity for each color of the emitted light from each light emitting unit is on the incident surface. Match. Therefore, if the number of light source groups constituting the light source 21 is an even number, by arranging the light emitting units as described above, an image with little color unevenness at the center of the optical pupil can be provided to the observer. It can be said.

  Further, as described above, the hologram optical element 34 is fabricated so as to diffract the image light of each wavelength of 465 ± 5 nm, 521 ± 5 nm, and 634 ± 5 nm at the diffraction efficiency peak and its half-value wavelength width. Thus, since the half-value wavelength width of the diffraction efficiency is the same for each color, the longer the wavelength, the greater the angle selectivity (the smaller the incident angle shift with respect to the wavelength change). Therefore, in each of the light source groups 21P and 21Q, the light emitting units are arranged in such an order that the wavelength of the emitted light becomes shorter from the optical axis incident surface side toward the outer side in the X direction. The intensity difference between the colors can be reduced, and an image with little color unevenness in the optical pupil E can be provided to the observer. Hereinafter, this point will be described in detail.

Assuming that the wavelength of the diffraction efficiency peak is λ, the refractive index of the medium (interference fringe) of the hologram optical element 34 is n, the thickness of the medium is h, and the incident angle is θ,
λ = 2nhcosθ
The relationship holds. Here, in the B light having a short wavelength and the R light having a long wavelength, when the respective wavelengths are shifted by, for example, the same 5 nm, the rate of change in wavelength is 465/470 for the B light and 634 for the R light. / 639. That is, the rate of change in wavelength is smaller for R light having a longer wavelength than for B light having a shorter wavelength. Therefore, the R light having a longer wavelength is smaller in the incident angle θ with respect to the change in wavelength (the angle selectivity is greater) than the B light having a shorter wavelength. Therefore, when the RGB wavelength width of the light emitted from the light source 21 is the same, the size of the optical pupil diffracted by the hologram optical element 34 is smaller as the wavelength is longer. The optical pupil E includes the entire optical pupil range of each color.

  On the other hand, the intensity of light emitted from the LED (each light emitting unit) of the light source 21 is generally stronger near the center and weaker toward the periphery. Each light emitting unit is arranged so as to be substantially conjugate with the optical pupil in the Y direction, but is diffused by the diffusing unit 23 in the X direction and is not conjugate with the optical pupil. However, the position with the strongest intensity in the optical pupil is substantially the same as the conjugate position with each light emitting unit when the diffusing means 23 is not provided.

  Therefore, the pupil center of the long wavelength (R light) with the small optical pupil is positioned on the center side of the optical pupil E, and the pupil center of the short wavelength (B light) with the large optical pupil is positioned outside the center of the optical pupil E. By doing so, the intensity difference depending on the pupil position in the optical pupil E can be reduced for each color. This point will be described in a little more detail.

FIG. 12 is an explanatory diagram showing the relationship between the pupil position in the X direction and the light intensity in the optical pupil E. The light intensity is shown as a relative value for the same color. The curve indicated by _{21R 1 · 21R 2 · 21G 1} · 21G 2 · 21B 1 · 21B 2 in the figure, from the respective light emitting unit _{21R 1 · 21R 2 · 21G 1} · 21G 2 · 21B 1 · 21B 2 It corresponds to the emitted light.

  As described above, due to the angle selectivity of the hologram optical element 34, the longer the wavelength, the smaller the optical pupil. Therefore, the longer the wavelength, the greater the intensity difference depending on the pupil position (optical). The intensity difference between the center and the end of the pupil E is large). On the contrary, since the optical pupil E is larger as the wavelength is shorter, the intensity difference depending on the pupil position is smaller as the wavelength is shorter.

  In addition, since the light emitting portion that emits light having a longer wavelength is disposed on the optical axis incident surface side, the position with higher light intensity is closer to the center of the optical pupil E as the light has a longer wavelength. On the contrary, since the light emitting part that emits light having a short wavelength is arranged at a position farther from the optical axis incident surface, the position where the light intensity is high is around the optical pupil E.

  In other words, the longer the wavelength, the greater the difference in intensity depending on the pupil position, but the light emitting units are arranged in such an order that the wavelength of the emitted light becomes shorter from the optical axis incident surface side toward the outside in the X direction. By bringing the position with a high light intensity closer to the center of the optical pupil E, the intensity difference depending on the pupil position, that is, the intensity difference between the center and the end of the optical pupil E can be reduced for light having a long wavelength. As a result, an image with little color unevenness can be provided to the observer over the entire optical pupil E (the pupil center and the periphery of the pupil).

  In addition, since the light emitting units of the light source groups 21P and 21Q are arranged in the X direction in the order of wavelengths in which the diffusion by the diffusing means 23 is large (diffuses as the wavelength is shorter), the intensity of each color on the optical pupil E The difference is further reduced, and color unevenness can be further reduced. That is, an image with high color purity can be provided to the observer.

  By the way, in the above description, an example in which the light source 21 is configured by the light source groups 21P and 21Q in which two sets of RGB light emitting units are provided and each set is an individual package has been described. However, each set has one package. Also good. FIG. 13 shows another configuration example of the light source 21 and shows a plan view when the light source 21 is viewed from the display element 24 side.

As described above, the light source 21 may be configured by a single package of the light emitting units 21R ₁ , 21R ₂ , 21G ₁ , 21G ₂ , 21B _1, and 21B ₂ that emits RGB light. Also in this configuration, by applying the above-described arrangement method of the light emitting units, the intensity difference of each color on the optical pupil E can be reduced and color unevenness can be reduced. Also, as the distance between the light emitting points is shorter, RGB colors are more likely to be mixed and a brighter image can be provided. Therefore, in this respect, the configuration of FIG. 13 that can easily reduce the distance between the light emitting units is desirable.

[Embodiment 5]
The following will describe still another embodiment of the present invention with reference to the drawings. In addition, the same member number is attached to the same structure as Embodiment 3 or 4, and the description is abbreviate | omitted.

  FIG. 14 is a cross-sectional view showing a schematic configuration of the video display device 11 of the present embodiment. FIGS. 15A and 15B are explanatory views schematically showing the configuration of the video display device 11 of the present embodiment by developing the optical path, and FIG. 15A shows the horizontal optical path. FIG. 15B shows the optical path in the vertical direction. The video display device 11 of the present embodiment includes a light source 21, a diffusing unit 23, a display element 24 ', a concave mirror 25, a first polarizing plate 26, a second polarizing plate 27, and a third polarization. A plate 28 and an eyepiece optical system 31 are provided. Hereinafter, differences from the third or fourth embodiment will be described.

  The light source 21 is the same as in the third or fourth embodiment in that the RGB light is emitted toward the display element 24 ′. However, in this embodiment, the display element 24 ′ is driven in a time division manner as described later. Therefore, the light source 21 sequentially emits RGB light in a time division manner.

  The display element 24 ′ is a light modulation element that displays an image by modulating light emitted from the light source 21 for each pixel according to image data. In the present embodiment, the display element 24 ′ is a reflective ferroelectric liquid crystal display element. It is configured. This reflection type ferroelectric liquid crystal display element has a ferroelectric liquid crystal sandwiched between two substrates, and a reflection film (reflection electrode, pixel electrode) is formed on one substrate side. The display element 24 ′ does not have a color filter, and each pixel of the display element 24 ′ is ON / OFF in time division corresponding to each of the three primary color lights sequentially supplied from the light source 21 in time division. Driven. Thereby, a color image can be provided to the observer.

  In the reflective display element 24 ′, a semiconductor such as silicon can be used as a substrate, so that a small and highly integrated display element can be manufactured. In addition, since a peripheral circuit including a switching element (for example, TFT) and wiring for turning on / off each pixel can be disposed on the substrate on the side opposite to the display side, the aperture ratio can be easily improved. In addition, the diffusion at the edge of each pixel can be kept small. Therefore, by configuring the display element 24 ′ with a reflective LCD, a bright and high-quality image can be displayed and observed by an observer.

  In addition, since the ferroelectric liquid crystal display element has an advantage in that the driving speed is high, it is possible to adopt the above time-division driving method by configuring the display element 24 ′ with a ferroelectric liquid crystal display element. it can. In the time-division driving method, the light emitting units 21R, 21G, and 21B are sequentially turned on by the light source 21, so that, for example, when displaying a single color, the remaining two light emitting units are turned off. Thereby, an image with high color purity and high contrast can be displayed.

  Further, the reflective ferroelectric liquid crystal display element is superior in that it has a wider viewing angle characteristic than a TN (Twisted Nematic) liquid crystal display element, and light incident from the concave mirror 25 to the display element 24 'is incident. Even when the corner is large, an image with high contrast, high color reproducibility (wide color reproduction region), and high display quality can be provided. Further, the degree of freedom of arrangement of each optical element constituting the illumination optical system is increased, and a compact and high-performance illumination optical system can be constructed.

  The display element 24 ′ may be configured by improving the viewing angle characteristics by combining a phase compensation plate and a TN liquid crystal display element. The display element 24 ′ may be a reflective display element that can be time-division driven, and may be constituted by, for example, DMD (Digital Micromirror Device; manufactured by Texas Instruments, USA).

  The concave mirror 25 is a condensing unit that condenses the light from the light source 21 in the Y direction perpendicular to the diffusing direction of the first diffusing unit 23a and guides it to the display element 24 ′, and has positive optical power in the Y direction. It consists of a cylindrical mirror with The concave mirror 25 is disposed on the side opposite to the light source 21 with respect to the optical path of light from the display element 24 ′ toward the eyepiece optical system 31, reflects the light from the light source 21 and guides it to the display element 24 ′. Therefore, the concave mirror 25 functions as an optical path bending member that bends the optical path from the light source 21 to the display element 24 ′. The concave mirror 25 may be constituted by a spherical mirror, an aspherical mirror, or an axially asymmetric concave mirror.

  In the present embodiment, the light source 21 and the optical pupil E have a conjugate positional relationship in the Y direction. However, as described above, the display element 24 ′ has a high aperture ratio and a small diffusion. 21 and the optical pupil E are almost conjugate. However, since there is no optical power of the concave mirror 25 in the X direction, it is not conjugate.

  The first polarizing plate 26 transmits light in a predetermined polarization direction (for example, P-polarized light) out of the light emitted from the light source 21 and guides it to the concave mirror 25, and the optical path is bent by the concave mirror 25. It is a polarizer that transmits light that has the same polarization direction as the predetermined polarization direction (for example, P-polarized light) and guides it to the display element 24 ′. The first polarizing plate 26 is disposed on the concave mirror 25 side with respect to the optical path of light traveling from the display element 24 ′ to the eyepiece optical system 31.

  The second polarizing plate 27 is an analyzer that transmits light (for example, S-polarized light) whose polarization direction is orthogonal to light transmitted through the first polarizing plate 26 out of incident light and guides it to the eyepiece prism 32. The eyepiece prism 32 and the gap are provided. The second polarizing plate 27 may be attached to the light incident surface (surface 32a) of the eyepiece prism 32.

  The third polarizing plate 28 transmits light having the same polarization direction as the light transmitted through the first polarizing plate 26 (for example, P-polarized light) out of the light emitted from the light source 21 and guides it to the concave mirror 25. It is. The third polarizing plate 28 is disposed on the light source 21 side with respect to the optical path of light from the display element 24 ′ toward the eyepiece optical system 31.

  The first diffusing unit 23a and the second diffusing unit 23b constituting the diffusing unit 23 are configured to diffuse incident light by 40 degrees in the X direction and 0.5 degrees in the Y direction, as in the third or fourth embodiment. Each of them is composed of a directional diffuser, and is arranged so that the first diffusing means 23a is on the display element 24 ′ side between the optical path of light from the display element 24 ′ toward the eyepiece optical system 31 and the concave mirror 25. Has been. That is, the first diffusing unit 23a and the second diffusing unit 23b are disposed between the concave mirror 25 and the display element 24 ′ so that the RGB light from the light source 21 has uniform luminance in the X direction. And inclined with respect to the display element 24 '.

  When the first diffusing unit 23a is thus inclined with respect to the display element 24 ', the first diffusing unit 23a is very close to the display element 24' at one end and the display element at the other end. It will move away from 24 '. Therefore, the diopter difference between the virtual image of the display image on the display element 24 ′ and the virtual image by the eyepiece optical system 31 of the first diffusing means 23a has a certain range, and in the present embodiment, a range of 5 to 15 diopters. It has become. That is, the virtual images (including shadows) by the eyepiece optical system 31 of the first diffusing unit 23a include those belonging to a range that can be observed by human eyes (10 diopters or less).

  In the present embodiment, the first diffusing unit 23a and the second diffusing unit 23b are arranged so that the respective diffusing surfaces face the opposite side without facing each other, as shown in FIG. Yes. That is, the diffusion surface of the first diffusion means 23a is located on the light source 21 side (display element 24 'side), and the diffusion surface of the second diffusion means 23b is located on the concave mirror 25 side. Each of the first diffusing unit 23a and the second diffusing unit 23b diffuses light, for example, by an uneven surface provided with an uneven surface on one surface of a thin film having a thickness of 0.1 mm.

  In the video display device 11 having the above-described configuration, the light (P-polarized light) transmitted through the third polarizing plate 28 out of the light from the light source 21 is transmitted through the first polarizing plate 26, and the first diffusion means 23a. Then, after passing through the second diffusing means 23b in this order, it is reflected by the concave mirror 25. The light reflected by the concave mirror 25 is sequentially diffused by the second diffusing unit 23b and the first diffusing unit 23a, and then enters the display element 24 '. The light incident on the display element 24 ′ is modulated there to become image light (S-polarized light), passes through the second polarizing plate 27, and enters the surface 32a of the eyepiece prism 32a (a convex curved surface in this embodiment). After being totally reflected by the surfaces 32 b and 32 c a plurality of times, the light is guided to the optical pupil E through the hologram optical element 34.

  At this time, the first diffusing unit 23a and the second diffusing unit 23b complement each other with the light that is not emitted by the incident light from the predetermined direction by the diffusion of the incident light in each case. Homogeneous light is emitted from the diffusing means 23a toward the display element 24 '. That is, at least the generation of shadows caused by the first diffusion means 23a is reduced by the second diffusion means 23b.

  In the configuration in which the first diffusing unit 23a is inclined with respect to the display element 24 ′ as in the present embodiment, one end of the first diffusing unit 23a is very close to the display element 24 ′. The shadow caused by the first diffusing unit 23a is easily superimposed on the virtual image of the display image. However, by providing the second diffusing unit 23b, the shadow of the first diffusing unit 23a is not superimposed on the virtual image of the display image, and the observer observes a high-quality image having no luminance unevenness or color unevenness as a virtual image. It becomes possible to do. That is, the configuration in which the second diffusing unit 23b is provided is very effective even in a compact configuration in which the optical path of light from the light source 21 toward the display element 24 ′ is bent by the concave mirror 25 as in the present embodiment. Become.

  Further, in the diffusing unit 23, the light diffused by the second diffusing unit 23b has a certain amount of light flux by disposing the diffusing surfaces of the first diffusing unit 23a and the second diffusing unit 23b away from each other. Since the light is incident on the first diffusion means 23a, the display element 24 'can be illuminated more uniformly.

  Note that the non-diffusing surfaces (surfaces facing each other in the first diffusing unit 23a and the second diffusing unit 23b) of the first diffusing unit 23a and the second diffusing unit 23b may be bonded to each other. In this case, unnecessary reflection at the interface can be reduced, so that the display element 24 ′ can be illuminated with more uniform bright light.

  Note that the diffusing means 23 may not be constituted by two diffusing plates, but may be constituted by one diffusing plate in which unevenness is provided on both surfaces of one film. In this case, one uneven surface (diffusion surface) constitutes the first diffusion means, and the other uneven surface (diffusion surface) constitutes the second diffusion means. If the diffusing unit 23 is constituted by one diffusing plate in this way, it is possible to control both the image quality and the brightness by controlling the thickness of the diffusing plate (film).

  In the present embodiment, the third polarizing plate 28 is disposed in the vicinity of the light source 21. By disposing the third polarizing plate 28 in this way, the light in the polarization direction (S-polarized light) that can pass through the second polarizing plate 27 out of the light emitted from the light source 21 is converted to the third polarizing plate 28. Can be cut in advance. That is, by arranging the third polarizing plate 28, the S-polarized light reaches the eyepiece optical system 31 directly from the light source 21, or is reflected by the surface of the first polarizing plate 26 and reaches the eyepiece optical system 31. There is nothing. Thereby, it is possible to prevent the occurrence of ghost (flare) due to such light, and it is possible to reliably avoid the deterioration of the image quality.

  In particular, as in the present embodiment, the third polarizing plate 28 is disposed in the vicinity of the light source 21, that is, the third polarizing plate 28 is directed to the optical path of light traveling from the display element 24 ′ to the eyepiece optical system 31. By disposing on the light source 21 side, the S-polarized light emitted from the light source 21 can be efficiently cut, and the deterioration of the image quality due to the ghost light can be surely avoided.

  In each of the above embodiments, various video display devices suitable for the HMD have been described. However, the video display device of each embodiment can be applied to other devices such as a head-up display.

  Of course, it is possible to realize the video display apparatus and the HMD by appropriately combining the configurations of the respective embodiments described above.

  The video display device of the present invention can be used for a head-up display or a head-mounted display, for example.

(A) is explanatory drawing which shows the conceptual structure of the video display apparatus based on one Embodiment of this invention which expand | deployed the optical path of a horizontal direction, (b) is a structure of the said video display apparatus. It is explanatory drawing which expand | deploys and shows the optical path of a perpendicular direction. (A) is explanatory drawing which expands the optical path of a horizontal direction, and shows the structure of the video display apparatus based on other embodiment of this invention, (b) is the structure of the said video display apparatus perpendicular | vertical. It is explanatory drawing which expand | deploys and shows the optical path of a direction. (A) is a top view which shows schematic structure of HMD which concerns on further another embodiment of this invention, (b) is a side view of said HMD, (c) is the front of said HMD FIG. (A) is a top view which shows the schematic structure of another HMD, (b) is a side view of the said HMD, (c) is a front view of the said HMD. It is sectional drawing which shows the structure of the outline of the video display apparatus applied to HMD. It is explanatory drawing which optically expands and shows the optical path in the said video display apparatus in one direction. It is explanatory drawing which shows the spectral intensity characteristic of the light source of the said video display apparatus. It is explanatory drawing which shows the wavelength dependence of the diffraction efficiency in the hologram optical element of the said video display apparatus. It is explanatory drawing which shows the relationship between the pupil position in an optical pupil, and the main diffraction wavelength. It is explanatory drawing which optically expands and shows the optical path in the video display apparatus based on further another embodiment of this invention in one direction. It is a top view when the light source of the said video display apparatus is seen from the display element side. It is explanatory drawing which shows the relationship between the pupil position of the X direction in an optical pupil, and light intensity. The other example of a structure of the said light source is shown, Comprising: It is a top view when the said light source is seen from the display element side. It is sectional drawing which shows the structure of the outline of the said video display apparatus which concerns on further another embodiment of this invention. (A) is explanatory drawing which shows the structure of the said video display apparatus expand | deployed the optical path of a horizontal direction, (b) is the description which expands | deploys the optical path of a vertical direction, and shows the structure of the said video display apparatus. FIG. (A) is sectional drawing which shows the example of 1 structure of the unidirectional diffuser plate applicable to the conventional video display apparatus, (b) is the shadow of the unidirectional diffuser superimposed on the observation image (virtual image) It is explanatory drawing which shows a state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Light source 3 Diffusion means 3a 1st diffusion means 3b 2nd diffusion means 4 Display element 5 Lens (observation optical system)
11 image display unit 12 the supporting means 21 the light source 21R, 21R _1, 21R ₂ emitting portion (LED)
21G, 21G ₁ , 21G ₂ light emitting part (LED)
21B, 21B ₁ , 21B ₂ light emitting part (LED)
22 Condensing lens (condensing means)
23 diffusing means 23a first diffusing means 23b second diffusing means 24 display element 24 'display element 25 concave mirror (condensing means)
31 Eyepiece optical system (observation optical system)
32 Eyepiece prism (first transparent substrate)
33 Deflection prism (second transparent substrate)
34 Hologram optical element E Optical pupil

Claims (17)

A light source that emits light;
Diffusing means for diffusing the light emitted from the light source;
A display element for displaying an image by modulating the light diffused by the diffusion means;
An image display device including an observation optical system that allows an observer to observe a virtual image of a display image by guiding image light from a display element to an optical pupil,
The diffusing means has a first diffusing means for diffusing incident light in one direction by unevenness on the surface, and a second diffusing means for diffusing incident light,
An image display device, wherein an optical pupil is smaller in a direction perpendicular to the diffusion direction than a diffusion direction of incident light in the first diffusion means. The second diffusing means diffuses incident light in one direction by surface irregularities,
The video display device according to claim 1, wherein a diffusion direction of incident light in the second diffusion unit substantially coincides with a diffusion direction of incident light in the first diffusion unit. The second diffusing means is disposed in an optical path between the light source and the first diffusing means,
3. The video display device according to claim 1, wherein a diffusion degree of the second diffusion means is smaller than a diffusion degree of the first diffusion means in a diffusion direction of the first diffusion means. The light source includes a light emitting diode that emits light of three colors of red, green, and blue,
4. The video display device according to claim 1, wherein the light emitting diodes are arranged side by side in a diffusion direction of the first diffusion means. 5. The light source has two sets of light emitting diodes that emit red, green, and blue light, respectively.
When the axis that optically connects the center of the display area of the display element and the center of the optical pupil is the optical axis,
5. The video display device according to claim 4, wherein the light emitting diodes of each set are arranged symmetrically with respect to the optical axis of the observation optical system for each color.   6. The image according to claim 1, wherein a diopter difference between a virtual image obtained by the observation optical system of the first diffusion means and a virtual image of a display image on the display element is 10 diopters or less. Display device. A light collecting unit that collects light from the light source in a direction perpendicular to the diffusion direction of the first diffusion unit and guides the light to the display element;
The video display device according to claim 1, wherein the light source and the optical pupil are arranged at a conjugate position in a direction perpendicular to the diffusion direction of the first diffusion means.   8. The video display device according to claim 7, wherein the light collecting means has no optical power or is negative in a direction parallel to a diffusion direction of the first diffusion means.   9. The video display device according to claim 7, wherein the display element is a reflective liquid crystal display element. The condensing means is composed of a mirror having a positive optical power in a direction perpendicular to the diffusing direction of the first diffusing means, and in the optical path of the light from the reflective liquid crystal display element to the observation optical system. On the other hand, it is arranged on the opposite side of the light source and reflects the light from the light source to the reflective liquid crystal display element,
10. The first and second diffusing means are arranged between an optical path of light from the reflective liquid crystal display element toward an observation optical system and the light collecting means. Video display device. The observation optical system includes a volume phase reflection hologram optical element,
11. The image display apparatus according to claim 1, wherein the hologram optical element guides the image light from the display element to the optical pupil by diffracting and reflecting the image light.   12. The image display device according to claim 11, wherein the hologram optical element has an axially asymmetric positive optical power. When the axis that optically connects the center of the display area of the display element and the center of the optical pupil is the optical axis,
13. The video display device according to claim 12, wherein a diffusion direction of the first diffusion means is substantially parallel to a direction perpendicular to the optical axis incident surface of the hologram optical element. The light source is composed of a light emitting diode,
14. The image display according to claim 11, wherein a wavelength at which the diffraction efficiency of the hologram optical element reaches a peak is substantially equal to a wavelength at which the intensity of light emitted from the light source reaches a peak. apparatus.   The observation optical system includes a first transparent substrate that totally reflects the image light from the display element and guides the light to the observer's pupil while transmitting the external light to the observer's pupil. The video display device according to claim 1, wherein:   The video display apparatus according to claim 15, wherein the observation optical system includes a second transparent substrate for canceling refraction of external light on the first transparent substrate. A video display device according to any one of claims 1 to 16,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.