JP2009259854A - Solid-state laser device, and image display using the same - Google Patents

Abstract

An object of the present invention is to realize a multi-beam in a transverse mode by tilting a reflecting mirror by a set angle and to expand a transmission region of a laser beam in a solid laser crystal or a wavelength conversion element to suppress heat generation and to be stable. And an image display apparatus using the same.
A semiconductor laser light source that emits a pump laser beam, a solid-state laser crystal that is excited by the incidence of the laser beam and oscillates a fundamental laser beam, and a position between which the solid-state laser crystal is sandwiched. An optical resonator 14 including mirrors 16 and 17 disposed, and an SHG element 18 that is disposed inside the optical resonator 14 and converts the wavelength of the fundamental laser beam 20. One of 17 has a configuration in which an inclination angle set with respect to the optical axis of the laser beam 19 is provided.
[Selection] Figure 1

Description

  The present invention relates to a solid-state laser device using a solid-state laser crystal and a wavelength conversion element, and more particularly to a solid-state laser device that is excellent in thermal stability and can stably obtain a high output and an image display device using the solid-state laser device.

  The semiconductor laser excitation solid-state laser device excites a solid-state laser crystal by laser light from a semiconductor laser light source to cause laser oscillation, and is compact and lightweight, long life, high electro-optical conversion efficiency, stable operation, etc. It has characteristics and is used in various industrial fields. In such a solid-state laser device, laser light from a semiconductor laser light source is incident on a solid-state laser crystal by a coupling lens system, and the fundamental laser light is oscillated by exciting the solid-state laser crystal sandwiched between mirrors. In general, the laser light is incident on the wavelength conversion element of the nonlinear optical medium, thereby generating the second harmonic component of the incident light and emitting it to the outside through the output side mirror.

If such a solid-state laser device is used, high output green light (G light) can be obtained. As a specific configuration example, for example, a semiconductor laser light source is used to excite a solid laser crystal made of Nd: YVO ₄ or the like, thereby causing laser oscillation of the solid laser crystal between the reflection mirror and the output mirror. By this laser oscillation, a fundamental wave laser beam having a wavelength of 1064 nm is obtained. By making the fundamental laser beam incident on the wavelength conversion element, a second harmonic having a wavelength of 532 nm is obtained. With such a configuration, high output G light can be obtained, so that it can be applied to a laser display, a projection type liquid crystal display, and the like, and thus development is being actively carried out.

  For example, a solid-state laser device that has high output and high efficiency and enables speckle noise reduction and an image display device using the solid-state laser device are disclosed (for example, see Patent Document 1). This solid-state laser device uses a one-dimensional transverse multimode laser as a laser light source, includes a pumping light source, a solid-state laser crystal in an optical resonator, and a wavelength conversion element, and has a solid-state laser crystal in an elliptical transverse mode pattern. Is excited to obtain a linear beam, and this linear beam is incident on a wavelength conversion element to output linear light. Thereby, a high-power and high-efficiency solid-state laser device can be realized using an elliptical transverse mode pattern. Moreover, speckle noise can be reduced by reducing the coherence due to the excitation in the transverse multimode. Further, it is shown that since the wavelength conversion element is disposed in the optical resonator, the power density of the oscillation light confined inside the optical resonator can be increased, and wavelength conversion can be performed with high efficiency.

  However, solid laser crystals and wavelength conversion elements are damaged when irradiated with high-density laser light, and have a problem that it is difficult to oscillate harmonic laser light stably for a long time.

  On the other hand, a configuration is shown in which a transmission plate for shifting the optical path of laser light is arranged on the laser beam incident side of the wavelength conversion element in the optical resonator, and this transmission plate is vibrated (for example, patents). Reference 2). When wavelength conversion is performed by transmitting laser light to the wavelength conversion element in the optical resonator to generate harmonics, the optical path of the laser light is shifted by oscillating the transmission plate described above. As a result of the enlargement of the laser beam passage region, the temperature rise can be mitigated.

  Furthermore, a solid laser crystal and a wavelength conversion element are arranged in an optical resonator composed of a reflection mirror and an output mirror, and a moving mechanism for moving the position of the wavelength conversion element in a direction perpendicular to the optical axis of the laser beam is provided. In this configuration, there is also shown a solid-state laser device configured to move the moving mechanism in conjunction with laser light irradiation (see, for example, Patent Document 3). With such a configuration, the entire surface of the wavelength conversion element can be used effectively, the life of the wavelength conversion element can be extended, and as a result, the life of the solid-state laser device can be extended.

Combining a solid-state laser device capable of outputting such high-output G light and a semiconductor laser device, and irradiating laser light from the back surface of the liquid crystal panel, it can be used for a liquid crystal display device such as a projection-type liquid crystal display device or a thin television Has also been considered. However, in order to use a laser light source for a backlight unit such as a thin television, a configuration having a uniform luminance distribution over a relatively large area must be realized. It is also important to suppress speckle noise.
JP 2006-100772 A JP-A-7-22686 JP 2004-22946 A

  In the first example, the solid-state laser device outputs a linear laser beam using a one-dimensional transverse multimode laser and is used in a projection type liquid crystal display device. However, in this example, no countermeasure is disclosed or suggested for damage caused by overheating of the solid laser crystal or the wavelength conversion element of the solid laser device.

  Further, in the second example, the transmission region of the laser beam is expanded by vibrating the transmission plate while maintaining the laser beam deflection direction and the crystal orientation necessary for phase matching to prevent overheating. However, according to this method, it is necessary to constantly vibrate the transmission plate while operating the solid-state laser device, and the device configuration becomes complicated and it is difficult to reduce the cost.

  In the third example, the wavelength conversion element is electrically moved to prevent damage to the wavelength conversion element and the entire surface can be used effectively. It is difficult to reduce the cost because the mechanical structure becomes complicated because the mechanical movement mechanism must be provided.

  Furthermore, when used as a light source of a backlight unit of a liquid crystal display device, it is required to realize an illumination light source that is thin and has a uniform luminance over a large area at a low cost. In order to use a solid-state laser device for such a backlight unit, it is preferable to set the laser beam output from the solid-state laser device to a multimode. However, in particular, in a laser light source (G light source) that emits G light, a multi-mode configuration has not yet been realized.

  The present invention solves the above-described conventional problems, and realizes a multi-beam in a transverse mode by tilting the reflecting mirror by a set angle without having a moving mechanism or a vibrating mechanism, and in a solid-state laser crystal or a wavelength conversion element. An object of the present invention is to provide a stable solid-state laser device that expands the laser light transmission region and suppresses overheating. It is another object of the present invention to provide an image display device that can increase the screen size with high brightness by using a multi-beam solid-state laser device.

  In order to achieve the above object, the planar illumination device of the present invention includes a semiconductor laser light source that emits laser light for a pump, a solid-state laser crystal that is excited by the incidence of the laser light and oscillates fundamental laser light, and the solid-state laser. An optical resonator including mirrors disposed at positions sandwiching the crystal, and a quasi phase matching wavelength conversion element (hereinafter, SHG element) disposed inside the optical resonator and converting the wavelength of the fundamental laser beam And one of the mirrors is arranged with an inclination angle set with respect to the optical axis of the laser beam.

  By adopting such a configuration, the transverse mode of the G light becomes a multi-mode, the laser light passing region in the solid laser crystal or the wavelength conversion element is expanded, and the heat generating region is expanded accordingly. Can be prevented, and the harmonic laser beam can be stably emitted with high output.

  In the above configuration, the mirror provided on the side from which the harmonic laser light converted by the SHG element is emitted is a concave mirror, and the concave mirror may be set at an inclination angle set with respect to the optical axis of the laser light. Good. In this case, the radius of curvature of the concave mirror may be 50 mm or less. Furthermore, the inclination angle of the concave mirror may be set in a range of 0.1 ° to 0.5 °. By adopting such a configuration, the transverse mode can be changed to a multimode by tilting only the concave mirror without changing the configuration of the semiconductor laser light source, the solid laser crystal, the SHG element, and the like.

  In the above configuration, the semiconductor laser light source may have means for fixing the oscillation wavelength of the laser light. By adopting such a configuration, the oscillation wavelength of the semiconductor laser light source is kept substantially constant even when a temperature change occurs, so that it is not necessary to perform highly accurate temperature control on the semiconductor laser light source. As a means for fixing the oscillation wavelength, for example, there is VBG (Volume Bragg Grating) which is a transmission type diffraction grating. The laser beam emitted from the semiconductor laser light source is incident on this VBG, but a part of it is reflected and fed back to the semiconductor laser light source, and the oscillation wavelength of the semiconductor laser light source is fixed to the wavelength selected by the VBG. is there. Further, as a structure having wavelength selectivity in the semiconductor laser light source, there are a DFB laser and a DBR laser as described later, and such a laser light source may be used.

  Furthermore, the image display apparatus of the present invention is an apparatus including an image conversion device and an illumination light source for irradiating the image conversion device, and the illumination light source is at least red light (R light) and green light (G light). ) And blue light (B light), and at least one of these laser light sources has the above-described solid-state laser device. In this case, the solid-state laser device may be used as a laser light source that emits G light, and a semiconductor laser light source may be used as a laser light source that emits R light and B light. Furthermore, the semiconductor laser light source that emits the R light and the B light may be configured to have a plurality of active layers and emit a plurality of beams.

  With such a configuration, it is possible to use a high-power laser light source for both R light, G light, and B light, and to realize a bright image display device with a wide color reproduction range, good image quality, and high brightness. it can. As the image display device, a two-dimensional spatial modulation element as an image conversion device, for example, a projection type image display device using a configuration in which a large number of micromirrors formed by MEMS technology are arranged, and a liquid crystal display panel are two-dimensional. There is an image display device having a projection type configuration used as a spatial modulation element, or an image display device having a thin television configuration using a backlight unit and a liquid crystal display panel.

  In particular, for an image display device such as a thin television, the image conversion device is a liquid crystal display panel, and the illumination light source is a back light that irradiates the entire surface of the liquid crystal display panel with laser light emitted from an R light source, a G light source, and a B light source. It is good also as a structure which consists of a light unit. With such a configuration, the color reproduction range of an image display apparatus using a liquid crystal display panel can be expanded, and the image quality can be greatly improved. In addition, low power consumption can be realized as a whole.

  The backlight unit includes a first light guide plate in which at least one corner of the four corners is processed into a curved shape, and a second light guide plate disposed in close contact with the first light guide plate. A corner end face incident type light guide plate, an optical path conversion unit disposed along a curved surface shape formed at the corner of the first light guide plate, a red light source, a green light source, and a laser beam incident on the optical path conversion unit; The configuration may include a blue light source.

  With such a configuration, the red light source, the green light source, and the blue light source can be disposed on the surface of the first light guide plate, so that the overall shape of the image display device can be reduced.

  The backlight unit includes a first light guide plate having a curved surface portion in which at least one corner of the four corners has a concave shape, and a second light guide plate disposed in close contact with the first light guide plate. A red light source that emits laser light to the first light guide plate through the curved surface portion, and a green light source, which is disposed at a position facing the curved surface portion of the first light guide plate. You may consist of a structure provided with the light source and the blue light source.

  By adopting such a configuration, the laser light can be directly incident on the first light guide plate from the curved surface portion of the first light guide plate without providing an optical path conversion unit, so that the configuration of the illumination light source is simplified. It is possible to cope with an increase in screen size.

  ADVANTAGE OF THE INVENTION According to this invention, there exists a big effect that a solid laser crystal and a wavelength conversion element can be prevented from being damaged, and a long-life and high-power solid-state laser device can be realized. In addition, since this solid-state laser device has a multi-mode transverse mode, when it is used as a light source of a backlight unit of a liquid crystal display device, an image display device that has a simple structure and can be manufactured at low cost can be realized. It has a great effect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element and description may be abbreviate | omitted.

  FIG. 1 is a configuration diagram of a solid-state laser device 1 according to an embodiment of the present invention. The solid-state laser device 1 of the present embodiment includes a semiconductor laser light source 10 that emits a pumping laser beam 19, a solid-state laser crystal 15 that is excited by the incidence of the laser beam 19 and oscillates a fundamental laser beam 20, and a solid-state laser crystal. 15 includes an optical resonator 14 including mirrors 16 and 17 disposed at positions sandwiching 15, and an SHG element 18 that is disposed inside the optical resonator 14 and converts the wavelength of the fundamental laser beam 20. ing. One of the mirrors 16 and 17 is arranged with an inclination angle θ set with respect to the optical axis 22 of the laser light 19. In the present embodiment, the mirror 17 provided on the side from which the harmonic laser light 21 converted by the SHG element 18 is emitted is a concave mirror, and this concave mirror is set with respect to the optical axis 22 of the laser light 19. The inclined angle θ. Hereinafter, the mirror 17 is referred to as a concave mirror 17. Further, the semiconductor laser light source 10 has means for fixing the oscillation wavelength of the laser light 19.

  In the present embodiment, pump light having a transmission wavelength of 808 nm is incident as the laser light 19, the basic light of 1064 nm is generated as laser light 20, and this is emitted as a 532 nm harmonic laser light 21 by the SHG element 18. The configuration of the laser device 1 will be described as an example. Therefore, the harmonic laser beam 21 is G light.

  In the solid-state laser device 1 of the present embodiment, the laser light 19 is emitted from the semiconductor laser light source 10 and enters the optical resonator 14 through the rod lens 11, VBG 12, and ball lens 13. The laser light 19 having a wavelength of about 808 nm emitted from the semiconductor laser light source 10 is incident on the VBG 12 after the vertical component is collimated by the rod lens 11. A part of the laser light 19 incident on the VBG 12 is reflected and fed back to the semiconductor laser light source 10. Thereby, the oscillation wavelength of the semiconductor laser light source 10 is locked to the wavelength (808 nm) selected by the VBG 12. As described above, by using the VBG 12, the oscillation wavelength of the semiconductor laser light source 10 can be kept substantially constant even when the temperature changes, and the highly accurate temperature control of the semiconductor laser light source 10 can be made unnecessary.

  In the present embodiment, the case where the VBG 12 is used to lock the oscillation wavelength of the semiconductor laser light source 10 has been described. However, a band-pass filter composed of a dielectric multilayer film may be used. Alternatively, the semiconductor laser light source 10 itself may be a DFB (Distributed FeedBack) laser or a DBR (Distributed Bragg Reflector) laser having a wavelength lock function.

  The laser beam 19 whose wavelength is locked by the VBG 12 is focused on the solid laser crystal 15 by the ball lens 13. The laser light 19 becomes pump light, the solid laser crystal 15 is excited, and a fundamental laser light 20 having a wavelength of 1064 nm is generated. The fundamental laser beam 20 resonates in an optical resonator 14 formed by a mirror 16 and a concave mirror 17 provided so as to sandwich the solid-state laser crystal 15. Then, a part of the fundamental laser beam 20 is wavelength-converted by the SHG element 18 disposed in the optical resonator 14, and G light having a wavelength of 532 nm, which is the harmonic laser beam 21, is output to the outside.

In the present embodiment, a YVO ₄ crystal doped with 3% Nd is used as the solid-state laser crystal 15. As the SHG element 18, a quasi-phase matching type element in which a domain-inverted region is periodically formed on a Mg-doped LiNbO ₃ substrate was used. The LiNbO ₃ substrate doped with Mg has a large nonlinear constant, and the thickness of the SHG element can be reduced. Further, as described above, the laser light 19 that is pump light is incident on the optical resonator 14, the generated fundamental wave laser light 20 is confined in the optical resonator 14, and the harmonic laser light is emitted from the concave mirror 17. A dielectric multilayer film is formed on each end face of the mirror 16, the SHG element 18 and the concave mirror 17 formed on the surface of the solid laser crystal 15 so that 21 is emitted.

  In the solid-state laser device 1 of the present embodiment, the concave mirror 17 is arranged with an inclination angle θ set with respect to the optical axis 22 of the laser light 19. That is, as shown in FIG. 1, the angle formed between the perpendicular 23 perpendicular to the bottom of the concave surface of the concave mirror 17 and the optical axis 22 of the laser light 19 is θ, and this inclination angle θ is set in advance. By providing the tilt angle set in this way, the width of the passing region is widened when the fundamental laser beam 20 or the like is transmitted through the solid laser crystal 15 and the SHG element 18. As a result, there is no locally overheated region, the steepness of the heat distribution is improved, and a relatively gentle heat distribution can be obtained. Therefore, the occurrence of damage to the solid laser crystal 15 and the SHG element 18 can be suppressed, and high output can be stably maintained over a long period of time. In addition, since the harmonic laser beam 21 becomes a multimode in the transverse mode, it is thin and can easily realize a large area when used as a light source of a backlight unit of a liquid crystal display device.

  2 to 4 are diagrams showing comparison data of G light output between the solid-state laser device 1 of the present embodiment and the solid-state laser device of the conventional configuration. 2A is a diagram showing the beam shape of the G light output of the solid state laser device of the conventional configuration, that is, the tilt angle θ = 0 °, and FIG. 2B is a laser beam that is pump light (in the following, It is a figure which shows the relationship between the light quantity of 19 (it may be called pump light) and G light output. FIG. 3A is a diagram showing a beam shape when the tilt angle θ is 0.2 ° in the solid-state laser device 1 of the present embodiment, and FIG. It is a figure which shows the relationship with G light output. 4A is a diagram showing a beam shape when the tilt angle θ is 0.3 ° in the solid-state laser device 1 of the present embodiment, and FIG. It is a figure which shows the relationship with G light output. In the measurement in FIGS. 2 to 4, the case where the resonator length L of the optical resonator 14 is 10 mm and the radius of curvature R of the concave mirror 17 is 20 mm will be described.

  As shown in FIG. 2, in the case of the tilt angle θ = 0 ° (conventional solid-state laser device), the beam shape is circular and single mode. Further, the G light output was saturated when the light amount of the pump light 19 was around 2.5 W, and the maximum value became 0.65 W. Furthermore, in the light amount range until the light amount of the pump light 19 is saturated, a phenomenon that a point P where the G light output decreases despite the increase in the light amount of the pump light 19 occurs. As for the saturation of the G light output, when the light amount of the pump light 19 is about 2.5 W, the solid laser crystal 15 generates a large amount of heat, and thermal saturation occurs. This is because the amount of light is saturated. Further, the decrease in the output at the point P occurs because the G light that is the harmonic laser beam 21 interferes inside the optical resonator 14.

  In contrast, the solid-state laser device 1 of the present embodiment has the inclination angle θ, so that the above phenomenon can be suppressed.

  For example, when the inclination angle θ of the concave mirror 17 is 0.1 °, the electric field distribution in the optical resonator 14 is changed, and the transverse mode is multiplexed.

  Further, when the inclination angle θ of the concave mirror 17 is 0.2 °, a transverse mode having three beams is obtained as shown in FIG. At this time, the light amount of the pump light 19 at which output saturation of the G light output occurs was 2.8 W, and the maximum value of the G light output was 0.7 W. Furthermore, the output fluctuation due to the interference of the G light which is the harmonic laser light 21 inside the optical resonator 14 can also be suppressed. This is because the transverse mode becomes multi-dimensional, so that the heat distribution inside the solid-state laser crystal 15 is broader than that in the single mode shown in FIG. 2, and the region where local overheating occurs can be eliminated. As a result, a gentle heat distribution is obtained as a whole. When the transverse mode is multi- pleted, it becomes difficult for G light interference to occur inside the optical resonator 14, so that the G light output fluctuation as shown at point P in FIG. 2 can hardly occur. Even when θ = 0.2 °, the generation efficiency (slope efficiency) of the G light output with respect to the light amount of the pump light 19 was almost the same as that in the single mode as shown in FIG.

  Further, when the tilt angle θ = 0.5 °, a transverse mode having five beams was obtained as shown in FIG. In this case, the light amount of the pump light 19 in which the output saturation of the G light output occurs can be increased to 3 W, but the maximum value of the G light output is 0.7 W, which is the same as when θ = 0.2 °. . In addition, the slope efficiency was slightly reduced compared to the case of θ = 0.2 °. This is because the conversion efficiency of the SHG element 18 is slightly reduced because the cross-sectional area of the fundamental wave laser beam 18 when passing through the SHG element 18 is enlarged. In addition, even in the case of this inclination angle, the fluctuation of the G light output was not observed.

  As can be seen from the above results, the maximum value of the G light output is as large as 0.7 W in the solid-state laser device 1 of the present embodiment, compared to 0.65 W in the conventional solid-state laser device that outputs a single mode. We were able to. As a result of measuring the beam shape and the G light output with various tilt angles, the oscillation state is maintained even if the tilt angle θ is larger than 0.5 °, but the oscillation efficiency is reduced. As a result, the G light output was found to decrease. Therefore, it was found that θ = 0.1 ° to 0.5 ° is desirable as the optimum range of the inclination angle θ. Further, it is more preferable that the range of θ = 0.2 ° to 0.4 ° is obtained because the respective beam shapes of the multi-beams are relatively uniform and the maximum value of the G light output can be stably obtained. It turned out to be a range.

  Further, as a result of examining various shapes of the radius of curvature R of the concave mirror 17, it has been found that if it is larger than 50 mm, it becomes difficult to make a multimode. Therefore, it is desirable that the radius of curvature R be 50 mm or less. The lower limit value of the radius of curvature R may be set to an optimum value depending on the configuration of the optical resonator 14, that is, the design of the resonator length L and the like.

  5A and 5B are diagrams showing a first example of the image display device 30 using the solid-state laser device 1 according to the present embodiment. FIG. 5A is a perspective view showing an outline of the configuration, and FIG. 5B is an image conversion device. The top view seen from 31 side, (c) is the schematic of the cross section cut | disconnected along the 5A-5A line. In FIG. 5, the respective configurations are arranged separately for easy understanding, but in an actual configuration, they are installed on a base plate (not shown) and fixed as a whole.

  As shown in FIG. 5, the image display device 30 of the first example includes an image conversion device 31 and an illumination light source 40 for irradiating the image conversion device 31 as a basic configuration. The image conversion device 31 includes a liquid crystal display panel, and the illumination light source 40 includes a backlight unit that irradiates the entire surface of the liquid crystal display panel with illumination laser beams 44 and 45 emitted from the R light source, the G light source, and the B light source. Hereinafter, the illumination light source 40 will be described as the backlight unit 40, and the image conversion device 31 will be described as the liquid crystal display panel 31. In the image display device 30 of the first example shown in FIG. 5, the solid-state laser device 1 of the present embodiment is used as the G light source, and the semiconductor laser light source 41 is used as the R light source and the B light source.

  First, the configuration of the backlight unit 40 that is an illumination light source will be described. The backlight unit 40 includes a semiconductor laser light source 41 formed by integrating an R light source and a B light source, and an illumination laser light 44 in which the R light and the B light emitted from the semiconductor laser light source 41 are combined. Is provided with a light guide plate 43 that emits light from one main surface portion 43a. The R light and the B light are expanded to approximately the same size as the end face portion of the end face light guide plate 42 using a beam expander (not shown) provided in the semiconductor laser light source 41, and then the end face light guide plate. The illumination laser beam 44 enters the end surface light guide plate 42 from the end surface portion 42. The semiconductor laser light source 41 of the present embodiment integrates the semiconductor laser light sources that respectively emit R light and B light, and the R light and B light are combined and emitted as illumination laser light 44. It is configured.

  The end face light guide plate 42 is provided with a semi-transmission mirror 42a at a constant pitch, and a part of the illumination laser beam 44 incident with a constant spread is reflected by the semi-transmission mirror 42a. Is incident on the end surface portion 43c of the first mirror, and the rest is incident on the next semi-transmissive mirror 42a. The semi-transmissive mirror 42 a is also partially reflected and incident on the end surface portion 43 c of the light guide plate 43. Hereinafter, by repeating this sequentially, the illumination laser beam 44 can be incident on the entire surface of the end surface portion 43 c of the light guide plate 43 from the end surface light guide plate 42. The illumination laser light 44 incident on the light guide plate 43 is reflected and scattered by the side surface portion and the other main surface portion 43b of the light guide plate 43, and the illumination laser light 44 directed toward one main surface portion 43a is finally one main surface portion 43a. The light exits from the surface portion 43a.

  On the other hand, the solid-state laser device 1 which is a G light source is disposed on the other end surface portion 43 d facing the end surface portion 43 c of the light guide plate 43. In the present embodiment, three solid-state laser devices 1 are arranged on the other end surface portion 43d side, and G light, that is, illumination light is applied to the entire surface of the other end surface portion 43d of the light guide plate 43 by these solid-state laser devices 1. Laser light 45 can be incident. The illumination laser beam 45 incident on the light guide plate 43 is reflected and scattered by the side surface portion of the light guide plate 43 and the other main surface portion 43b in the same manner as the illumination laser beam 44 obtained by combining the R light and the B light. And the laser beam 45 for illumination which goes to one main surface part 43a finally radiate | emits from one main surface part 43a. Thereby, illumination laser beams 44 and 45 composed of R light, B light, and G light are emitted from the entire surface of one main surface portion 43a of the light guide plate 43 with uniform brightness.

  Next, the configuration of the liquid crystal display panel 31 will be described. The liquid crystal display panel 31 has a transmissive or transflective configuration, for example, a TFT active matrix configuration, and has a red pixel portion (R subpixel) R and a green pixel portion (G sub) in the display area as shown in FIG. A large number of pixels having a pixel) G and a blue pixel portion (B sub-pixel) B as one pixel 35 are provided and driven by TFTs. A liquid crystal 33 is provided between the two glass substrates 32 and 34, and a TFT for driving the liquid crystal 33 is formed on one of the glass substrates 32 and 34. Absent. Further, polarizing plates 36 and 37 are provided on the respective surfaces of the glass substrates 32 and 34. As described above, the liquid crystal display panel 31 of the present embodiment has the same configuration as that conventionally used, and thus further description thereof is omitted.

  The image display device 30 having the above configuration can be easily expanded in the length direction of the other end surface portion 43d of the light guide plate 43 because the solid-state laser device 1 as the G light source is in the transverse mode and the multimode. Can do. As a result, the configuration of the image display device 30, particularly the configuration of the backlight unit 40, can be simplified.

  6A and 6B are diagrams showing an image display device 50 of a second example using the solid-state laser device 1 according to the present embodiment, where FIG. 6A is a plan view seen from the illumination light source 51 side, and FIG. 6B is 6A. It is the schematic of the cross section cut | disconnected along the -6A line. The image display device 50 of the second example also includes an image conversion device 31 and an illumination light source 51 for irradiating the image conversion device 31 as a basic configuration. The image conversion device 31 includes a liquid crystal display panel, and the illumination light source 51 includes a backlight unit that irradiates the entire surface of the liquid crystal display panel with illumination laser light 62 emitted from the R light source, the G light source, and the B light source. Hereinafter, the illumination light source 51 will be described as the backlight unit 51 and the image conversion device 31 will be described as the liquid crystal display panel 31. However, the liquid crystal display panel 31 is the same as the image display device 30 of the first example, and the description thereof will be omitted. . Note that the second image display device 50 shown in FIG. 6 uses the solid-state laser device 1 of the present embodiment as the G light source, and emits transverse mode laser light having three beams as shown in FIG. Use what you want. The R light source and the B light source use semiconductor laser light sources 52 and 53. The R light source and the semiconductor laser light sources 52 and 53, which are B light sources, are provided with a plurality of active layers, and are solid lasers of the G light source. Similar to the apparatus 1, three beams are emitted.

  A configuration of the backlight unit 51 used in the image display device 50 of the second example will be described. The backlight unit 51 is disposed on the back side of the liquid crystal display panel 31, and the shape thereof is substantially the same as the shape of the liquid crystal display panel 31. The R light, B light, and G light emitted from the semiconductor laser light sources 52 and 53 and the solid-state laser device 1 are combined by the dichroic mirror 54 to become illumination laser light 62 and enter the reflection mirror 55. The illumination laser light 62 reflected by the reflection mirror 55 is spread by the microlens array 56 and enters the light guide plate 61 for the conversion unit. The illumination laser light 62 incident on the conversion unit light guide plate 61 is reflected and diffused on the outer peripheral surface, enters the optical path conversion unit 60, the direction is changed, and the first light guide plate 58 of the end surface incident type light guide plate 57. Is incident on. The illumination laser light 62 is reflected and diffused in the first light guide plate 58 and is incident on the second light guide plate 59. The illumination laser light 62 is further diffused by the second light guide plate 59 to have a uniform luminance distribution over the entire surface, and then emitted from the second light guide plate 59 to illuminate the liquid crystal display panel 31. Thereby, the liquid crystal display panel 31 is illuminated and an image is displayed.

  In this case, the R light, the B light, and the G light emitted from the semiconductor laser light sources 52 and 53 and the solid-state laser device 1 each have three beams in a direction parallel to the surface of the light guide plate 61 for the conversion unit. . Therefore, the illumination laser beam 62 can be expanded by an optical system simpler than before and can be incident on the entire surface of the light guide plate 61 for the conversion unit, and a large-screen image display device can be easily realized. Furthermore, speckle noise can be effectively reduced.

  7A and 7B are diagrams showing an image display device 70 of a third example using the solid-state laser device 1 according to the present embodiment, in which FIG. 7A is a plan view seen from the illumination light source 71 side, and FIG. 7B is 7A. It is the schematic of the cross section cut | disconnected along the -7A line. The image display device 70 of the third example also includes an image conversion device 31 and an illumination light source 71 for irradiating the image conversion device 31 as a basic configuration. The image conversion device 31 is also composed of a liquid crystal display panel in the third example, and the illumination light source 71 irradiates the entire surface of the liquid crystal display panel with illumination laser light 77 emitted from the R light source, G light source, and B light source. It consists of a light unit. Hereinafter, the illumination light source 71 is described as the backlight unit 71, and the image conversion device 31 is described as the liquid crystal display panel 31, but the liquid crystal display panel 31 is the same as that described in the image display device 30 of the first example. Description is omitted.

  In the third image display device 70 shown in FIG. 7, the solid-state laser device 1 according to the present embodiment is used as a G light source, and a transverse mode laser beam having three beams as shown in FIG. 3 is emitted. Is used. The R light source and the B light source use a semiconductor laser light source. The semiconductor laser light source, which is the R light source and the B light source, is provided with a plurality of active layers. One beam is emitted. In the third image display device 70, the R light source, the semiconductor laser light source as the B light source, and the solid-state laser device 1 as the G light source are in close contact with each other on a single mounting board (not shown). It is mounted so that R light, G light, and B light are emitted from a relatively small area. Hereinafter, this is referred to as an integrated light source 72.

  After the R light, G light, and B light emitted from the integrated light source 72 are guided to the optical path conversion units 73 respectively disposed at the four corners of the corner end face incident type light guide plate 74, the optical paths are converted. The incident light is incident on the first light guide plate 75 of the corner end face incident type light guide plate 74. Note that the first light guide plate 75 of the corner end face incidence type light guide plate 74 has four corners processed into a curved surface shape as shown in FIG. 7, and the optical path conversion unit 73 is set to a shape along this curved surface shape. ing. In this way, the laser light can be diffused over the entire corner end face incident type light guide plate 74, and the illumination light 77 having uniform brightness can be emitted from the second light guide plate 76.

  Hereinafter, the configuration of the backlight unit 71 used in the image display device 70 of the third example will be described. In the image display device 70, the backlight unit 71 includes a first light guide plate 75 in which all corners of the four corners are processed into a curved surface shape, and a second light guide plate 75 disposed in close contact with the first light guide plate 75. A corner end face incident type light guide plate 74 made of a light guide plate 76, an optical path conversion unit 73 arranged along a curved surface formed at the corner of the first light guide plate 75, and a laser beam on the optical path conversion unit 73 And an integrated light source 72 for making the light incident. The backlight unit 71 is disposed on the back side of the liquid crystal display panel 31.

  The R light, B light, and G light emitted from the integrated light source 72 are incident on the optical path conversion unit 73, converted in direction, and incident on the first light guide plate 75 of the corner end surface incident type light guide plate 74. The R light, the B light, and the G light are reflected and diffused in the first light guide plate 75, enter the second light guide plate 76, and further diffused by the second light guide plate 76 to be uniform as a whole surface. After the luminance distribution is obtained, it is emitted as illumination laser light 77 to illuminate the liquid crystal display panel 31. Thereby, the liquid crystal display panel 31 is illuminated and an image is displayed.

  In this case, since the R light, B light, and G light emitted from the integrated light source 72 are spread and incident in the length direction of the curved surface of the optical path conversion unit 73, the light is guided over a wide area of the first light guide plate 75. Can be made. In addition, since the integrated light source 72 and the optical path conversion unit 73 are provided at the four corners of the first light guide plate 75, a uniform luminance distribution can be realized by mixing the laser beams from these. As a result, since the liquid crystal display panel 31 can be illuminated by the illumination laser beam 77 having a uniform luminance distribution, the image display device 70 that is bright and excellent in color reproducibility can be realized. Furthermore, speckle noise can be effectively reduced.

  In the case of the third image display device 70, the optical path conversion unit 73 and the integrated light source 72 are arranged at the respective corners of the four corners of the first light guide plate 75. However, the present invention is not limited thereto. It is not limited. A configuration in which the optical path conversion unit 73 and the integrated light source 72 are disposed in only one corner of the first light guide plate 75, a configuration in which the light path conversion unit 73 and the integrated light source 72 are disposed, or a configuration in which the light guide plate 75 is disposed at three corners. It may be. Furthermore, instead of the integrated light source 72, the semiconductor laser light source that emits R light, B light, and G light may be separated from the solid-state laser device. In this case, the optical path changing unit 73 is disposed at at least three corners, and the respective semiconductor laser light sources that emit R light and B light and solid laser devices that emit G light are disposed at the respective positions. do it.

  FIG. 8 is a view showing a fourth example of the image display device 80 using the solid-state laser device 1 according to the present embodiment. FIG. 8A is a plan view seen from the illumination light source 81 side, and FIG. It is the schematic of the cross section cut along the -8A line. The image display device 80 of the fourth example also includes an image conversion device 31 and an illumination light source 81 for irradiating the image conversion device 31 as a basic configuration. The image conversion device 31 also includes a liquid crystal display panel in the fourth example, and the illumination light source 81 irradiates the entire surface of the liquid crystal display panel with illumination laser light 85 emitted from the R light source, the G light source, and the B light source. It consists of a light unit. Hereinafter, the illumination light source 81 is described as the backlight unit 81 and the image conversion device 31 is described as the liquid crystal display panel 31. The liquid crystal display panel 31 is the same as that described in the image display device 30 of the first example. Description is omitted.

  The fourth image display device 80 shown in FIG. 8 uses the solid-state laser device 1 of the present embodiment as a G light source, and emits a transverse mode laser beam having three beams as shown in FIG. Is used. The R light source and the B light source use a semiconductor laser light source. The semiconductor laser light source, which is the R light source and the B light source, is provided with a plurality of active layers. One beam is emitted. In the fourth image display device 80, as in the case of the third image display device 70, the R light source, the semiconductor laser light source that is the B light source, and the solid-state laser device 1 that is the G light source are one sheet. The integrated light source 72 is used which is closely mounted on a mounting substrate (not shown) and arranged so that R light, G light and B light are emitted from a relatively small area. The integrated light source 72 is disposed at a position facing the curved surface portions 83 a formed at the four corners of the first light guide plate 83 that constitutes the corner end face incidence type light guide plate 82. The R light, G light, and B light emitted from the integrated light source 72 are incident on the first light guide plate 83 from the curved surface portion 83a. The R light, G light, and B light incident on the first light guide plate 83 are further diffused by the second light guide plate 84 and emitted as illumination laser light 85 to illuminate the liquid crystal display panel 31.

  Hereinafter, the configuration of the backlight unit 81 used in the image display device 80 of the fourth example will be described. In the image display device 80 of the fourth example, the backlight unit 81 includes a first light guide plate 83 having a curved surface portion 83a in which all corners of the four corners are concave shapes, and the first light guide plate 83. The corner end face incidence type light guide plate 82 including the second light guide plate 84 disposed in close contact with the curved surface portion 83a of the first light guide plate 83, and the curved surface portion 83a through the curved surface portion 83a. And an integrated light source 72 for allowing laser light to enter the first light guide plate 83. The backlight unit 81 is disposed on the back side of the liquid crystal display panel 31.

  The R light, B light, and G light emitted from the integrated light source 72 enter the first light guide plate 83 from the curved surface portion 83 a of the first light guide plate 83. In this case, the R light source and the B light source use a semiconductor laser light source that emits three beams by providing a plurality of active layers, and the solid-state laser device 1 of the G light source similarly emits three beams. Therefore, when these laser beams are incident from the curved surface portion 83a, they are spread over the entire surface of the first light guide plate 83, and are reflected and diffused. Further, these laser beams are incident on the second light guide plate 84 and further diffused by the second light guide plate 84 to obtain a uniform luminance distribution over the entire surface, and then emitted as illumination laser light 85, The liquid crystal display panel 31 is illuminated. Thereby, the liquid crystal display panel 31 is illuminated and an image is displayed.

  In this case, since the R light, B light, and G light emitted from the integrated light source 72 are incident from the curved surface portion 83a of the first light guide plate 83, the optical path changes due to refraction by the curved surface portion 83a. The light can be guided over a wide area of one light guide plate 83. In addition, since the integrated light source 72 is provided at the four corners of the first light guide plate 83, the laser light 85 with a more uniform luminance distribution can be emitted by mixing the laser light from these. As a result, since the liquid crystal display panel 31 can be illuminated with the illumination laser beam 77 having a uniform luminance distribution, the image display device 80 that is bright and excellent in color reproducibility can be realized. Furthermore, speckle noise can be effectively reduced.

  In the case of the fourth image display device 80, curved surface portions 83a are provided at the respective corners of the four corners of the first light guide plate 83, and the integrated light sources 72 are disposed at positions facing the corner portions 83a. However, the present invention is not limited to this. The curved surface 83a may be provided only at one corner of the first light guide plate 83, and the integrated light source 72 may be disposed opposite to the curved surface 83a. Or it is good also as a structure which provides the curved surface part 83a in two corner | angular parts, and each arrange | positions the integrated light source 72 in the position facing these. Or it is good also as a structure which provides the curved surface part 83a in three corner | angular parts, and arrange | positions the integrated light source 72 in the position facing these. Furthermore, instead of the integrated light source 72, the semiconductor laser light source that emits R light, B light, and G light may be separated from the solid-state laser device. In this case, a curved surface portion 83a is provided at at least three corners, and a semiconductor laser light source that emits R light and B light and a solid-state laser device that emits G light are respectively arranged at positions facing these. That's fine.

  FIG. 9 is a schematic diagram illustrating a configuration of an image display device 90 of a fifth example using the solid-state laser device 1 of the present embodiment. Since the image display device 90 of the fifth example has a configuration of a projection-type image display device, it will be described as the projection-type display device 90 in the following description. The projection display device 90 includes image conversion devices 102, 103, and 104 and illumination light sources for irradiating the image conversion devices 102, 103, and 104. The illumination light sources are an R light source 91, a G light source 92, and a B light source. The G light source 92 of the R light source 91, the G light source 92, and the B light source 93 is formed of the solid-state laser device 1 of the present embodiment. The R light source 91 and the B light source 92 are semiconductor laser light sources, and have a configuration in which a plurality of active layers are provided so as to emit a plurality of beams in the same manner as the solid-state laser device 1 of the G light source 92. Further, in the case of the projection display device 90, the image conversion devices 102, 103, and 104 are formed of a transmissive liquid crystal display panel that is a kind of two-dimensional spatial modulation device, and R light sources 91 and G that constitute an illumination light source. The light sources 92 and the B light sources 93 are respectively arranged corresponding to the laser beams, and the image light transmitted through the transmissive liquid crystal display panel is combined by the combining prism 105 and then projected. Yes. Hereinafter, the image conversion devices 102, 103, and 104 will be described as transmissive liquid crystal display panels 102, 103, and 104.

  A more specific configuration will be described in detail with reference to FIG. The laser light output from the R light source 91, the G light source 92, and the B light source 93 is made uniform in light amount distribution using rod integrators 94, 95, and 96, respectively. The laser light emitted from the R light source 91 and the laser light emitted from the B light source 93 are guided to the reflection mirrors 100 and 101 through the lenses 97 and 99, and the optical paths are converted by the reflection mirrors 100 and 101, so that a transmissive liquid crystal display is obtained. They are led to panels 102 and 104, respectively. On the other hand, the laser light emitted from the G light source 92 is directly guided to the transmissive liquid crystal display panel 103 through the lens 98. The respective laser beams that have passed through the transmissive liquid crystal display panels 102, 103, and 104 are combined by the combining prism 105, transmitted through the exit lens 106, and output as image light.

  The light source control circuit 107 controls the light output of the R light source 91, the G light source 92, and the B light source 93. Then, the display device control circuit 108 drives the three transmissive liquid crystal display panels 102, 103, and 104 based on the video display signal. That is, based on the video display signal, the transmissive liquid crystal display panel 102 that receives the laser light from the R light source 91 is driven corresponding to the red video signal, and the transmissive liquid crystal display panel 103 that receives the laser light from the G light source 92. The display device control circuit 108 performs driving corresponding to the green video signal, and driving the liquid crystal display panel 104 that receives the laser light from the B light source 93 corresponding to the blue video signal.

  Note that the display device control circuit 108 may also control the light source control circuit 107 as necessary. For example, control such as stopping the oscillation of the laser beams of the R light source 91, the G light source 92, and the B light source 93 may be performed corresponding to black display. Alternatively, the output of the laser light from the R light source 91, the G light source 92, or the B light source 93 may be varied as necessary. By performing such control, display image quality can be improved and power consumption can be reduced. The transmissive liquid crystal display panels 102, 103, and 104 can be configured in a conventional transmissive liquid crystal display device, for example, a panel configuration provided with a polysilicon TFT driving circuit, and the description thereof is omitted. .

  This projection type display device 90 uses a laser light source that has monochromatic light and good color purity for each of the RGB light sources, so that the displayable color range is widened, color purity is high, and vivid images can be displayed. It can be. In addition, power consumption can be reduced as compared with the case where a lamp is used as the light source. Furthermore, since the multi-beam solid-state laser device 1 and the semiconductor laser light source are used, the optical system can be simplified and a low-cost image display device can be realized.

  In the image display device of the present embodiment, a laser light source that emits R light, G light, and B light is used. However, a laser light source that emits another color may be added. Further, the solid-state laser device of the present invention is not limited to the configuration of the image display device of the present embodiment, and can be applied without particular limitation as long as it is used for illumination of the display device.

  According to the solid-state laser device of the present invention, damage to the solid-state laser crystal and the wavelength conversion element can be prevented with a simple configuration, a long life and high output can be achieved, and a large-screen thin display device and a projection display This is useful in the field of image display devices such as devices.

1 is a configuration diagram of a solid-state laser device according to an embodiment of the present invention. (A) Inclination angle θ = 0 °, that is, a diagram showing a beam shape of a G light output of a solid-state laser device having a conventional configuration. (B) A diagram showing a relationship between the amount of laser light that is pump light and the G light output. In the solid-state laser device of the present embodiment, (a) a diagram showing a beam shape when the tilt angle θ is 0.2 °, and (b) a diagram showing a relationship between the light amount of pump light and the G light output. In the solid-state laser device of the present embodiment, (a) a diagram showing a beam shape when the tilt angle θ is 0.3 °, (b) is a diagram showing a relationship between the amount of pump light and the G light output. (A) The perspective view which shows the outline | summary of a structure of the 1st image display apparatus using the solid-state laser apparatus concerning this Embodiment (b) The top view seen from the one main surface part side of the light-guide plate (c) 5A- Schematic of the cross section cut along line 5A (A) Plan view as viewed from the light guide plate side of the second image display device using the solid-state laser device according to the present embodiment. (B) Schematic of a cross section cut along line 6A-6A. (A) Plan view of the third example image display device using the solid-state laser device according to the present embodiment as viewed from the illumination light source side (b) Schematic of a cross section cut along line 7A-7A 4A is a plan view of an image display device of a fourth example using the solid-state laser device according to the present embodiment as viewed from the illumination light source side. FIG. 8B is a schematic view of a cross section cut along the line 8A-8A. Schematic which shows the structure of the 5th image display apparatus using the solid-state laser apparatus of this Embodiment.

Explanation of symbols

1 Solid-state laser device 10, 41, 52, 53 Semiconductor laser light source 11 Rod lens 12 VBG
13 Ball lens 14 Optical resonator 15 Solid-state laser crystal 16 Mirror 17 Mirror (concave mirror)
18 Pseudo phase conversion type wavelength conversion element (SHG element)
19 Laser light (pump light)
20 Fundamental laser light 21 Harmonic laser light (G light)
22 Optical axis 23 Perpendicular 30, 50, 70, 80 Image display device 31 Image conversion device (liquid crystal display panel)
32, 34 Glass substrate 33 Liquid crystal layer 35 Pixel 36, 37 Polarizing plate 40, 51, 71, 81 Illumination light source (backlight unit)
42 end face light guide plate 42a transflective mirror 43, 51 light guide plate 43a one main surface portion 43b other main surface portion 43c end surface portion 43d other end surface portion 44, 45, 62, 77, 85 illumination laser light 54 dichroic mirror 55 reflection mirror 56 Microlens array 57 End-incident light guide plate 58, 75, 83 First light guide plate 59, 76, 84 Second light guide plate 60, 73 Optical path conversion unit 61 Light guide plate for conversion unit 72 Integrated light source 74, 82 Angle Part end face incidence type light guide plate 83a Curved surface part 90 Image display device (projection type display device)
91 R light source 92 G light source 93 B light source 94, 95, 96 Rod integrator 97, 98, 99 Lens 100, 101 Reflection mirror 102, 103, 104 Image conversion device (transmission type liquid crystal display panel)
105 multiplex prism 106 exit lens 107 light source control circuit 108 display device control circuit

Claims (11)

A semiconductor laser light source that emits laser light for a pump;
An optical resonator configured to include a solid-state laser crystal that is excited by incidence of the laser light and oscillates a fundamental laser light, and a mirror that is disposed at a position sandwiching the solid-state laser crystal;
A quasi-phase-matching wavelength conversion element that is disposed inside the optical resonator and converts the wavelength of the fundamental laser beam;
One of the mirrors is disposed with an inclination angle set with respect to the optical axis of the laser beam. The mirror provided on the side from which the harmonic laser beam converted by the quasi phase matching type wavelength conversion element is emitted is a concave mirror, and the concave mirror is set with respect to the optical axis of the laser beam. The solid-state laser device according to claim 1, wherein the solid-state laser device is an angle. The solid-state laser device according to claim 2, wherein a radius of curvature of the concave mirror is 50 mm or less. 4. The solid-state laser device according to claim 2, wherein the inclination angle of the concave mirror is in a range of 0.1 ° to 0.5 °. 5. 5. The solid-state laser device according to claim 1, wherein the semiconductor laser light source has means for fixing an oscillation wavelength of the laser light. 6. An image display device comprising an image conversion device and an illumination light source for illuminating the image conversion device,
The illumination light source includes a laser light source that emits at least red light, green light, and blue light, and at least one of the laser light sources includes the solid-state laser device according to any one of claims 1 to 5. An image display device characterized by that. 7. The image display device according to claim 6, wherein the solid-state laser device is used as a laser light source that emits green light, and a semiconductor laser light source is used as a laser light source that emits the red light and the blue light. . The image display apparatus according to claim 7, wherein the semiconductor laser light source that emits the red light and the blue light has a configuration that includes a plurality of active layers and emits a plurality of beams. The image conversion device includes a liquid crystal display panel, and the illumination light source includes a backlight unit that irradiates laser light emitted from the red light source, the green light source, and the blue light source over the entire surface of the liquid crystal display panel. The image display device according to any one of claims 6 to 8. The backlight unit is
A corner end face incident type light guide plate comprising a first light guide plate in which at least one corner portion of the four corners is processed into a curved shape and a second light guide plate disposed in close contact with the first light guide plate; ,
An optical path conversion unit disposed along a curved surface formed at the corner of the first light guide plate;
The image display device according to claim 9, comprising the red light source, the green light source, and the blue light source that cause the laser light to enter the optical path conversion unit. The backlight unit is
A corner end face incident type comprising a first light guide plate having a curved surface portion in which at least one of the four corners has a concave shape and a second light guide plate disposed in close contact with the first light guide plate. A light guide plate;
The red light source, the green light source, and the blue light source, which are disposed at positions facing the curved surface portion of the first light guide plate, and make the laser light incident on the first light guide plate through the curved surface portion. The image display device according to claim 9, comprising the configuration provided.

Images