JP2013033152A - Projecting lens and image display device provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more enhance high resolution, high luminance and a long focal distance of a projecting lens and to allow the projecting lens to be reduced in size.SOLUTION: A projecting lens 28 provided on an optical path for projecting laser light of green, red and blue is constituted of four lenses of first, second, third and fourth lenses L1, L2, L3 and L4 from a projection side. A diaphragm STO is provided between the first and second lenses L1 and L2. The first and fourth lenses L1 and L4 are constituted of plastic lenses, and the second and third lenses L2 and L3 are constituted of glass lenses. By causing lenses disposed at positions where energy density of light emitted from a laser light source device is high to be constituted of the glass lenses, large light resistance, especially light resistance of the blue laser light, can be secured. In addition, by causing outermost lenses to be constituted of the plastic lenses capable of being freely formed in any shape, high resolution, high luminance and a long focal distance can be realized by a compact projecting lens.

Description

  The present invention relates to a projection lens applicable to a small projector and an image display apparatus including the projection lens.

  In recent years, a technique using a semiconductor laser as a light source of an image display device has attracted attention. This semiconductor laser has better color reproducibility, instantaneous lighting, longer life, and higher power consumption compared to mercury lamps that have been widely used in image display devices. It has various advantages, such as being able to be made and being easy to miniaturize.

  The advantage of such an image display device using a semiconductor laser is convenient when it is built in a portable electronic device. For example, a technique for incorporating an image display device using a semiconductor laser into a mobile phone terminal is known. (See Patent Document 1). When the image display device is built in the portable electronic device in this way, the screen can be enlarged and displayed on the screen as needed, so that convenience can be improved. Further, by using the image display device as a small projector built in a portable information processing device (so-called laptop computer), the convenience of the laptop computer can be enhanced.

JP 2007-316393 A JP 2010-91883 A

  In recent years, the above-described small projectors are required to have higher resolution, higher brightness, and longer focal length. Such a requirement can be met by a projection lens capable of reducing the size and size of the optical system. As an example of the projection lens, in order from the projection side, a first lens component having a meniscus negative refractive index and a second lens component having a biconvex positive refractive power, the first lens component and Some lens surfaces of the second lens component are all aspherical surfaces (see Patent Document 2).

  However, when the projection lens is designed using the structure of the above-mentioned Patent Document 2, it can cope only with a low resolution, low luminance, and a short focal length. This is mainly due to the fact that the number of lenses is too small. Increasing the number of lenses can meet the demands for higher resolution, higher brightness, and longer focal length, but the lens length and overall projector thickness can be reduced so that they can be built into portable electronic devices without problems. In order to suppress it, it is necessary to suppress the increase in the number of lenses as much as possible.

  On the other hand, as one using a semiconductor laser as a light source of a small projector, there is one in which red, green, and blue semiconductor lasers are used as disclosed in Patent Document 1. A projection lens used in such a projector needs to be sufficiently resistant to laser light emitted from each semiconductor laser.

  On the other hand, the projection lens disclosed in Patent Document 2 is composed of a plastic lens that is easier to form than a glass lens because of its complicated shape as described above. With regard to a projection lens made of a plastic lens, light resistance must be taken into consideration, and in particular, the damage that a laser beam emitted from a blue semiconductor laser gives to a plastic lens is higher than that of laser beams of other colors. Largely, when the lens deteriorates, the transmittance decreases. Further, in order to cope with the higher brightness, the output of each semiconductor laser is increased, so that there is a problem that the hurdle for clearing the light resistance is further increased.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to increase the resolution and brightness of a projection lens in a small projector using a semiconductor laser as a light source. Another object of the present invention is to provide a projection lens that can further improve the long focal length and can be miniaturized, and an image display apparatus equipped with the projection lens.

  A projection lens of the present invention and an image display device equipped with the projection lens are projection lenses that include at least three lens components and are telecentric on the light modulator side, and both outer sides facing the conjugate point of the projection lens. Each outer lens component disposed in the lens is a plastic lens, the aperture position of the projection lens is between the outer lens components, and the lens components other than the outer lens component of the projection lens are at least closest to the aperture position. It is assumed that the object is a glass lens.

  According to the present invention, a projection lens comprising at least three or more lens components for projecting modulated outgoing light from a light modulator onto a screen, at least the outermost lens component is constituted by a plastic lens, By configuring the lens component closest to the other aperture position with a glass lens, the lens component placed at a position where the energy density of light emitted from the laser light source device is high is made into a glass lens, and has a large light resistance (especially blue). (Light resistance of laser light) can be ensured. Also, at least at the outermost lens component, the energy density of the light emitted from the laser light source device is relatively low, so it can be formed into a complicated shape rather than a glass lens that is difficult to make into a complicated shape. Such a plastic lens can be used as the outermost lens component of the projection lens, so that the resolution and brightness can be increased, and further, the focal length can be increased with a compact projection lens.

The perspective view which shows the example which incorporated the image display apparatus by this invention in the portable information processing apparatus. The schematic block diagram of the optical engine part incorporated in an optical engine unit. The schematic diagram which shows the condition of the laser beam in a green laser light source device. The block diagram of each lens component of a projection lens. The table | surface which shows each item of the lens in FIG. Explanatory drawing which shows image height and object height. The figure which shows spherical aberration. The figure which shows astigmatism. The figure which shows a distortion aberration. The figure which shows chromatic aberration. 4A is a lateral aberration diagram showing coma aberration of P1, FIG. 4B is P2, FIG. 4C is P3 of FIG. 4, and FIG. 4D is P4 of FIG. The block diagram of each lens component of the projection lens 28 of 2nd Embodiment. The table | surface which shows each item of the lens of 2nd Embodiment. The figure which shows the spherical aberration of 2nd Embodiment. The figure which shows the astigmatism of 2nd Embodiment. The figure which shows the distortion aberration of 2nd Embodiment. The figure which shows the chromatic aberration of 2nd Embodiment. FIG. 5A is a lateral aberration diagram showing coma aberration of P1 in FIG. 4, FIG. 4B is P2 in FIG. 4, FIG. 4C is P3 in FIG. 4, and FIG. 4D is P4 in FIG. The block diagram of each lens component of the projection lens 28 of 3rd Embodiment. The table | surface which shows each item of the lens of 3rd Embodiment. The figure which shows the spherical aberration of 3rd Embodiment. The figure which shows the astigmatism of 3rd Embodiment. The figure which shows the distortion aberration of 3rd Embodiment. The figure which shows the chromatic aberration of 3rd Embodiment. FIG. 5A is a lateral aberration diagram showing coma aberration of P1 in FIG. 4, FIG. 4B is P2 in FIG. 4, FIG. 4C is P3 in FIG. 4, and FIG. 4D is P4 in FIG.

  A first invention made to solve the above-mentioned problems is a projection lens having at least three lens components and made telecentric on the light modulator side, both outer sides facing the conjugate point of the projection lens Each outer lens component disposed in the lens is a plastic lens, the aperture position of the projection lens is between the outer lens components, and the lens components other than the outer lens component of the projection lens are at least closest to the aperture position. It is assumed that the object is a glass lens.

  According to this, at least the outermost lens component of the projection lens having at least three or more lens components is configured by a plastic lens, and the lens component closest to the aperture position is configured by a glass lens, thereby providing a laser light source. A lens component arranged at a position where the energy density of light emitted from the apparatus is high can be made into a glass lens, so that high light resistance (particularly, light resistance of blue laser light) can be ensured. Also, at least at the outermost lens component, the energy density of the light emitted from the laser light source device is relatively low, so it can be formed into a complicated shape rather than a glass lens that is difficult to make into a complicated shape. Such a plastic lens can be used as the outermost lens component of the projection lens, so that the resolution and brightness can be increased, and further, the focal length can be increased with a compact projection lens.

  According to a second aspect, in the first aspect, at least one lens surface of the outer lens component is an aspherical surface.

  According to this, since the outer lens component can be a plastic lens and the lens design can be facilitated, the number of lenses can be minimized.

  The third invention is a projection lens comprising a first lens component, a second lens component, a third lens component, and a fourth lens component arranged in order from the projection side, and is made object side telecentric. The first lens component has a stop position between the first lens component and the second lens component, and the first lens component has a pseudo concave meniscus shape and negative refraction in which a central portion of the lens surface protrudes toward the projection side. The fourth lens component is a plastic lens having a pseudo biconvex shape and positive refractive power, and the second lens component and the third lens component are glass lenses. And

  According to this, the lens component close to the stop position where the chief ray that increases the energy density of light is condensed is composed of a glass lens, thereby ensuring high light resistance (particularly light resistance of blue laser light) and comparison. Since the lens component at a position with a small energy density is made of a plastic lens and can easily cope with a complicated shape such as an aspherical surface, a projection lens that enables high resolution, high brightness, and a long focal length is provided. It can be composed of a single lens.

  In a fourth aspect based on the third aspect, the second lens component and the third lens component are composed of compound lenses joined to each other and have a positive refractive power as a whole. .

  According to this, the stop position between the first lens component and the second lens component can be brought close to the second lens component, and since the second lens component and the third lens component are glass lenses, the energy of light. Even if the density increases, the light resistance can be ensured without any problem, and the energy density of the light with respect to the first lens component constituted by the plastic lens can be reduced.

  In a fifth aspect based on the fourth aspect, the second lens component is a biconvex spherical lens or a spherical lens having a concave shape on the first lens component side and a convex shape on the third lens component side. The third lens component is a biconcave shape or a spherical lens having a concave shape on the second lens side and a convex shape on the fourth lens component side.

  According to this, when the second lens component and the third lens component are joined to each other, each is formed by a glass lens, so that the convex surface of the second lens component and the concave surface of the third lens component can be easily made with high accuracy. To form a bonded state.

  According to a sixth aspect, in any one of the third to fifth aspects, the Abbe number of the second lens component is greater than the Abbe number of the third lens component.

  According to this, when the compound lens composed of the second lens component and the third lens component is designed with the same focal length, by relatively increasing the Abbe number of the second lens component, which is a convex lens that tends to cause chromatic aberration, Chromatic aberration can be suppressed.

  According to a seventh invention, in any one of the first to sixth inventions, each laser light source device that emits red, green, and blue laser light, an optical modulator that modulates the laser light, and each of the above An optical system for making each color laser beam emitted from a laser light source device enter the optical modulator along the same optical path, and the projection lens is modulated by the optical modulator and emitted. It is set as the structure arrange | positioned on the optical axis which radiate | emits incident light outside.

  According to this, the lens component arranged at a position where the energy density of the light emitted from the laser light source device is high can be used as the glass lens, and a large light resistance (particularly, the light resistance of blue laser light) can be ensured. Also, at least at the outermost lens component, the energy density of the light emitted from the laser light source device is relatively low, so it can be formed into a complicated shape rather than a glass lens that is difficult to make into a complicated shape. Plastic lens can be used as the outermost lens component of the projection lens, and the projection lens configured for it can be used to achieve high resolution and high brightness, and can be made compact with a longer focal length. An image display device can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing an example in which an image display device 1 according to the present invention is built in a portable information processing device 2. A portable information processing device (for example, a notebook personal computer) 2 has a main body 3 in which a control board (not shown) on which a CPU, a memory, and the like are mounted, and a display unit 4 having a liquid crystal panel. The body part 3 and the display part 4 are connected by a hinge part 5 so that the body part 3 and the display part 4 are overlapped to enhance portability.

  A keyboard 6 and a touch pad 7 are provided on the upper surface 8 a of the housing 8 of the main body 3. In addition, on the back surface side of the keyboard 6 in the housing 8 of the main body 3, an accommodation space in which a peripheral device such as an optical disk device is accommodated in a replaceable manner, a so-called drive bay, is formed. 1 is attached.

  The image display device 1 includes a housing 11 and a movable body 12 provided so as to be able to be taken in and out of the housing 11. The movable body 12 controls an optical engine unit (first unit) 13 in which an optical component for projecting the image Im by the laser light onto the screen S is accommodated, and an optical component in the optical engine unit 13. It is comprised with the control unit (2nd unit) 14 in which the board | substrate etc. were accommodated.

  FIG. 2 is a schematic configuration diagram of the optical engine unit 15 built in the optical engine unit 13. The optical engine unit 15 includes a green laser light source device 22 that outputs green laser light, a red laser light source device 23 that outputs red laser light, a blue laser light source device 24 that outputs blue laser light, and a video signal. The liquid crystal reflection type light modulator 25 that modulates the laser light from each of the laser light source devices 22 to 24, and the laser light from each of the laser light source devices 22 to 24 is reflected and irradiated to the light modulator 25. A polarization beam splitter 26 that transmits the modulated laser light emitted from the modulator 25, a relay optical system 27 that guides the laser light emitted from each of the laser light source devices 22 to 24 to the polarization beam splitter 26, and the polarization beam splitter 26 are provided. A projection lens (projection optical system) 28 for projecting the image Im of the transmitted modulated laser light onto the screen S. Each laser light source device 22-24 may use a semiconductor laser.

  The optical engine unit 15 displays a color image by a so-called field sequential method, and laser beams of each color are sequentially output from the laser light source devices 22 to 24 in a time-sharing manner, and an image by the laser beam of each color is visually displayed. It is recognized as a color image by the afterimage effect.

  The relay optical system 27 includes collimator lenses 31 to 33 that convert the laser beams of the respective colors emitted from the laser light source devices 22 to 24 into parallel beams, and the laser beams of the respective colors that have passed through the collimator lenses 31 to 33 in a predetermined direction. First and second dichroic mirrors 34 and 35 guided to, a diffusion plate 36 for diffusing the laser light guided by the dichroic mirrors 34 and 35, and a field lens for converting the laser light that has passed through the diffusion plate 36 into a convergent laser 37.

  Assuming that the side from which the laser light is emitted from the projection lens 28 toward the screen S is the front side, the blue laser light is emitted backward from the blue laser light source device 24, and a green laser is emitted with respect to the optical axis of the blue laser light. The green laser light and the red laser light are emitted from the green laser light source device 22 and the red laser light source device 23 so that the optical axis of the light and the optical axis of the red laser light are orthogonal to each other. And the green laser light are guided to the same optical path by the two dichroic mirrors 34 and 35. That is, the blue laser light and the green laser light are guided to the same optical path by the first dichroic mirror 34, and the blue laser light, the green laser light, and the red laser light are guided to the same optical path by the second dichroic mirror 35.

  The first and second dichroic mirrors 34 and 35 are formed with films for transmitting and reflecting laser light of a predetermined wavelength on the surface, and the first dichroic mirror 34 transmits blue laser light. And reflects the green laser light. The second dichroic mirror 35 transmits red laser light and reflects blue laser light and green laser light.

  Each of these optical members is supported by the housing 41. The housing 41 functions as a radiator that dissipates heat generated by the laser light source devices 22 to 24, and is formed of a material having high thermal conductivity such as aluminum or copper.

  The green laser light source device 22 is attached to an attachment portion 42 formed on the housing 41 in a state of protruding toward the side. The attachment portion 42 is provided in a state of protruding in a direction perpendicular to the side wall portion 44 from a corner portion where the front wall portion 43 and the side wall portion 44 that are respectively positioned in front and side of the accommodation space of the relay optical system 27 intersect. ing. The red laser light source device 23 is attached to the outer surface side of the side wall 44 while being held by the holder 45. The blue laser light source device 24 is attached to the outer surface side of the front wall portion 43 while being held by the holder 46.

  The red laser light source device 23 and the blue laser light source device 24 are configured by a so-called CAN package, and the optical axis is positioned on the central axis of the can-shaped exterior portion with the laser chip that outputs the laser light supported by the stem. The laser beam is emitted from a glass window provided in the opening of the exterior part. The red laser light source device 23 and the blue laser light source device 24 are fixed to the holders 45 and 46 by, for example, press-fitting into the mounting holes 47 and 48 formed in the holders 45 and 46. The heat generated by the laser chips of the blue laser light source device 24 and the red laser light source device 23 is transmitted to the housing 41 through the holders 45 and 46 to be dissipated, and each of the holders 45 and 46 has a thermal conductivity such as aluminum or copper. It is made of a high material.

  The green laser light source device 22 includes a semiconductor laser 51 that outputs excitation laser light, a FAC (Fast-Axis Collimator) lens 52 that is a condensing lens that condenses the excitation laser light output from the semiconductor laser 51, and a rod. A lens 53, a solid-state laser element 54 that outputs a basic laser beam (infrared laser beam) when excited by an excitation laser beam, and converts a wavelength of the basic laser beam to output a half-wavelength laser beam (green laser beam) A wavelength conversion element 55, a concave mirror 56 that forms a resonator together with the solid-state laser element 54, a glass cover 57 that prevents leakage of excitation laser light and fundamental wavelength laser light, and a base 58 that supports each part, And a cover body 59 that covers each part.

  The green laser light source device 22 is fixed by attaching the base 58 to the mounting portion 42 of the housing 41, and a required width (for example, 0.5 mm) between the green laser light source device 22 and the side wall portion 44 of the housing 41. The following gaps are formed. This makes it difficult for the heat of the green laser light source device 22 to be transmitted to the red laser light source device 23, suppresses the temperature rise of the red laser light source device 23, and allows the red laser light source device 23 with poor temperature characteristics to operate stably. Can do. Further, in order to secure a required optical axis adjustment allowance (for example, about 0.3 mm) of the red laser light source device 23, a required width (for example, 0.3 mm or more) is provided between the green laser light source device 22 and the red laser light source device 23. ) Is provided.

  FIG. 3 is a schematic diagram showing the state of laser light in the green laser light source device 22. The laser chip 61 of the semiconductor laser 51 outputs excitation laser light having a wavelength of 808 nm. The FAC lens 52 reduces the spread of the first axis of the laser beam (the direction perpendicular to the optical axis direction and along the drawing sheet). The rod lens 53 reduces the spread of the slow axis of laser light (in the direction perpendicular to the drawing sheet).

The solid-state laser element 54 is a so-called solid-state laser crystal, and is excited by excitation laser light having a wavelength of 808 nm that has passed through the rod lens 53 to output fundamental wavelength laser light (infrared laser light) having a wavelength of 1064 nm. This solid-state laser element 54 is obtained by doping an inorganic optically active substance (crystal) made of Y (yttrium) VO ₄ (vanadate) with Nd (neodymium), and more specifically, YVO _{4 as} a base material. The Y is doped by substitution with Nd ⁺³ which is an element that emits fluorescence.

  On the side of the solid-state laser element 54 facing the rod lens 53, a film having a function of preventing reflection of excitation laser light having a wavelength of 808 nm and high reflection of fundamental wavelength laser light having a wavelength of 1064 nm and half-wavelength laser light having a wavelength of 532 nm. 62 is formed. On the side of the solid-state laser element 54 facing the wavelength conversion element 55, a film 63 having an antireflection function for a fundamental wavelength laser beam having a wavelength of 1064 nm and a half wavelength laser beam having a wavelength of 532 nm is formed.

  The wavelength conversion element 55 is a so-called SHG (Second Harmonics Generation) element, which converts the wavelength of a fundamental wavelength laser beam (infrared laser beam) having a wavelength of 1064 nm output from the solid-state laser element 54 to a half-wavelength laser having a wavelength of 532 nm. Light (green laser light) is generated.

  On the side of the wavelength conversion element 55 facing the solid-state laser element 54, a film 64 having functions of preventing reflection of the fundamental wavelength laser light having a wavelength of 1064 nm and highly reflecting the half wavelength laser light having a wavelength of 532 nm is formed. On the side of the wavelength conversion element 55 facing the concave mirror 56, a film 65 having an antireflection function for the fundamental wavelength laser beam having a wavelength of 1064 nm and the half wavelength laser beam having a wavelength of 532 nm is formed.

  The concave mirror 56 has a concave surface on the side facing the wavelength conversion element 55, and this concave surface has a function of high reflection with respect to a fundamental wavelength laser beam with a wavelength of 1064 nm and antireflection with respect to a half wavelength laser beam with a wavelength of 532 nm. A film 66 is formed. As a result, the fundamental wavelength laser beam having a wavelength of 1064 nm resonates and is amplified between the film 62 of the solid-state laser element 54 and the film 66 of the concave mirror 56.

  In the wavelength conversion element 55, a part of the fundamental wavelength laser light having a wavelength of 1064 nm incident from the solid-state laser element 54 is converted into a half-wavelength laser light having a wavelength of 532 nm, and the fundamental wavelength of 1064 nm that has passed through the wavelength conversion element 55 without being converted is converted. The wavelength laser beam is reflected by the concave mirror 56 and is incident on the wavelength conversion element 55 again, and is converted into a half-wavelength laser beam having a wavelength of 532 nm. The half-wavelength laser light having a wavelength of 532 nm is reflected by the film 64 of the wavelength conversion element 55 and emitted from the wavelength conversion element 55.

  Here, the laser beam B1 incident on the wavelength conversion element 55 from the solid-state laser element 54, converted in wavelength by the wavelength conversion element 55, and emitted from the wavelength conversion element 55, and once reflected by the concave mirror 56 and converted in wavelength. In the state where the laser beam B2 incident on the element 55, reflected by the film 64 and emitted from the wavelength conversion element 55 overlaps with each other, the half-wavelength laser light having a wavelength of 532 nm and the fundamental wavelength laser light having a wavelength of 1064 nm interfere with each other. Cause output to drop.

  Therefore, here, the wavelength conversion element 55 is inclined with respect to the optical axis direction so that the laser light beams B1 and B2 do not overlap each other by the refraction action on the entrance surface and the exit surface. Interference between the wavelength laser beam and the fundamental wavelength laser beam having a wavelength of 1064 nm is prevented, so that a decrease in output can be avoided.

  The glass cover 57 shown in FIG. 2 is formed with a film that does not transmit these laser beams in order to prevent the excitation laser beam having a wavelength of 808 nm and the fundamental wavelength laser beam having a wavelength of 1064 nm from leaking to the outside. ing.

  Each housing of the optical engine unit 13 and the control unit 14 constituting the movable body 12 has a flat box shape with a short dimension in the height direction. Sliders that slide along guide rails provided in the housing 11 are provided on both side edges of the housings of the optical engine unit 13 and the control unit 14 (not shown). Then, as indicated by an arrow A, the movable body 12 is inserted into and removed from the housing 11. An exit window 74 is provided at the end of the optical engine unit 13 on the side opposite to the hinge 73, and the laser that has passed through the projection lens 28 (see FIG. 2) of the optical engine section 15 from the exit window 74. Light is emitted.

  Next, with reference to FIG. 4, a specific configuration of each lens component showing the first embodiment of the projection lens 28 to which the present invention is applied will be described. In addition, although each lens component is shown with sectional drawing, hatching is abbreviate | omitted from legibility. Further, the modulated outgoing light emitted from the right polarization beam splitter 26 in FIG. 4 is projected toward the screen S disposed on the left side of the drawing via the projection lens 28.

  The projection lens 28 includes a first lens (first lens component) L1, a second lens (second lens component) L2, a third lens (third) in order from the first conjugate point side on the projection side (left side in FIG. 4). A lens component L3 and a fourth lens (fourth lens component) L4 are arranged coaxially. The first and fourth lenses L1 and L4 are plastic lenses formed of a synthetic resin material, and the second and third lenses L2 and L3 are glass lenses formed of a glass material. In the illustrated example, the projection lens 28 is coaxially arranged on the optical axis of the modulated outgoing light from the optical modulator 25. However, a reflecting mirror is arranged on the optical axis of the projection lens 28 and light is emitted laterally. A modulator 25 may be arranged to change the direction of the modulated outgoing light from the optical modulator 25. In that case, the projection lens 28 is coaxially arranged on the optical axis of the modulated outgoing light emitted from the optical modulator 25 and redirected by the reflecting mirror.

  The first lens L1 is formed in a pseudo concave meniscus shape whose central portion protrudes toward the projection side and has negative refractive power. The second lens L2 is a biconvex spherical lens, and the third lens L3 is a biconcave spherical lens. The fourth lens L4 is formed in a pseudo biconvex shape and has a positive refractive power.

  Table 1 shown in FIG. 5 shows the specifications of the lens in FIG. The conditions for setting the lens data in Table 1 are as follows: the F value is 2.8, the focal length is 7.3 mm, the image height of the light modulator 25 is 2.794 mm, and the object height of the projection image Im on the screen S is 385. The distance between the center of the lens surface on the screen S side of the first lens L1 and the screen S is 1000 mm. As shown in FIG. 6, the image height is the height H of the image on the diagonal line from the center Pc of the rectangular irradiation surface of the optical modulator 25 toward the corner portion Pe, and the above numerical value is the maximum value. Similarly, the object height is the height H of the image on the diagonal line from the center Pc of the rectangular projection surface (Im) on the screen S to the corner Pe, and the above numerical value is the maximum value. The weighting of each color laser beam is set to 1 for blue laser beam and red laser beam, and 2 for green laser beam.

  The surface numbers in Table 1 correspond to f2 to f11 shown in FIG. 4, correspond to the order of the lens surfaces from the projection side (f1 corresponds to the screen S, f12 corresponds to the light modulator 25), and STO is Indicates the aperture. The stop STO is provided at a position where the chief ray is condensed. The surface shape indicates whether the lens surface is spherical or aspherical, r is the radius of curvature of each lens surface, and d is from each optical surface f (n) to the next optical surface f (n + 1). (N is 1 to 10), nd is the refractive index with respect to the d-line (wavelength 587.6 nm), νd is the Abbe number with respect to the d-line, D is the aperture diameter, and Co is The conic number of the aspheric lens is shown respectively. The unit of length is “mm” unless otherwise specified.

  Next, aspheric data is described. The fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order coefficients of the aspheric coefficient CEn are represented by CE4, CE6, CE8, CE10, and CE12, respectively.

In face number f2,
CE4 = −0.00019292138
CE6 = 1.7519259e-5
CE8 = −2.6333344e−7
CE10 = −2.897131e−8
CE12 = 1.0282375e-9
It is.

In surface number f3,
CE4 = 0.00048703321
CE6 = −0.00021337964
CE8 = 9.3720993e-6
CE10 = 2.6656592e-6
CE12 = −3.532074e−7
It is.

In surface number f8,
CE4 = −0.00144457748
CE6 = 5.699218e-5
CE8 = -9.94124343e-7
CE10 = -4.38446295e-8
CE12 = 2.2483199e-9
It is.

In face number f9,
CE4 = −6.1165958e−5
CE6 = 7.5395918e-6
CE8 = −6.155347e−8
CE10 = −6.908151e−9
CE12 = 6.04556066e-10
It is.

  In the first embodiment, as shown in FIG. 4, distances R1 to R4 between the principal ray passing through the optical axis C and the points where the principal ray having the highest field angle passes through the lenses L1 to L4 are defined as radii. Assuming that the area of the circle to be irradiated is the irradiation range of each of the lenses L1 to L4, for example, assuming that laser light having a wattage of W1 is irradiated, the energy densities E1 to E4 of the lenses L1 to L4 En = W1 / (π × Rn × Rn).

  Here, as shown in FIG. 4, the sizes of R1 to R4 are R4> R1> R3> R2. Therefore, the energy density of the second lens L2 is the highest. As described above, the second lens L2 is a glass lens, and the second lens L2, which is a lens component arranged at a position where the energy density is high, is a glass lens, thereby ensuring a large light resistance of the second lens L2. Is done.

  In recent projectors, when the amount of light from the light source is increased in response to a request to project a brighter image, the energy density (light power density) increases accordingly, and the light irradiation area is reduced in the vicinity of the stop STO. In addition to an increase in energy density, the stop STO is located at a conjugate position of the light source in the projector optical system, and a portion where the amount of laser light from the laser light source devices 22 to 24 is concentrated appears at the position of the stop STO. .

  In the case of blue laser light, the energy density of the central portion at the stop STO position, that is, the energy density of the principal ray portion at the projection lens 28 increases due to the Gaussian distribution as the far field pattern. In such a case, if a plastic lens is disposed in the vicinity of the stop STO, the energy density at the center of the lens increases, and the photodegradation of the resin of the lens is accelerated. When the transmittance of the resin such as yellowing color is lowered or the resin itself is burnt due to light deterioration, the function as a lens is greatly lowered.

  On the other hand, in the lens at a position far away from the vicinity of the stop STO, the chief ray spreads greatly, so that the light quantity distribution of the laser light is widened, and the light quantity distribution becomes more uniform, and the energy density incident on the lens is reduced. is there. In the present invention, the first and fourth lenses L1 and L4 made of the respective plastic lenses are arranged at such positions, and deterioration of the resin material of the first and fourth lenses L1 and L4 is suppressed. The light source is not limited to the semiconductor laser, and any light source having a function of illuminating the light modulator 25 such as an LED (light emitting diode) OLED (organic EL) may be used.

  In addition, only a limited resin material can be used as a lens material for blue laser light that greatly affects the deterioration of the resin material. However, in a lens processed with the lens material, a combination of the refractive index and the Abbe number (dispersion) is limited, and a lens intended for a so-called achromatic lens for reducing chromatic aberration cannot be obtained. In addition, there may be a demand to increase the light quantity of the light source in the future.

  Therefore, it is effective to configure the achromatic lens with a glass lens. In addition, since the achromatic lens made of glass can be used without worrying about light resistance like a plastic lens, it can be arranged at a position close to the stop STO (high energy density) of the projection lens 28. is there. In the present invention, as described above, the third lens L3 made of a glass lens is disposed at a position close to the stop STO, and an achromatic lens having a two-lens configuration is provided by using the fourth lens L4 made of another glass lens. ing.

  Next, each aberration of the projection lens 28 in the first embodiment will be described.

  First, FIG. 7 shows spherical aberration. In the figure, the vertical axis indicates the position of the image height H, the horizontal axis indicates the magnitude of deviation, the spherical aberration is 0, the solid line is blue laser light, the two-dot chain line is green laser light, and the broken line Is red laser light. The description of these figures is the same for other similar figures, and the description thereof is omitted. The spherical aberration in FIG. 7 is expressed as a function of image height at each wavelength of each color.

  FIG. 8 is a diagram showing field curvature and astigmatism. Each curve on the left side in the figure is sagittal data (Sd in the figure), each curve on the right side is tangential data Td, and ST is astigmatism. In the figure, the distance from the image plane to the paraxial image plane is expressed as a function of field coordinates.

FIG. 9 is a diagram showing distortion aberration. In the figure, the horizontal axis represents the distortion magnitude Dy as a percentage. The distortion magnitude Dy is given by the following equation, where Yc is the actual principal ray height and Yr is the reference ray height.
Dy = 100 × (Yc−Yr) / Yr

  FIG. 10 is a diagram showing lateral chromatic aberration. In the figure, the chromatic aberration of magnification is expressed as a function of the field of view, and the chromatic aberration of magnification of the blue and red laser beams when the green laser beam is used as a reference (the deviation is 0) is shown.

  FIG. 11 is a lateral aberration diagram showing coma aberration. In the figure, the center represents the chief ray, the horizontal axis represents the entrance pupil coordinates (maximum ± 20 μm), and the vertical axis represents the lateral aberration value at each entrance pupil coordinate. Lateral aberration represents the aberration of light as a pupil function. Also, (a), (b), (c), and (d) in FIG. 11 are points P1 (center), P2 (maximum image height position on the vertical axis passing through the center), P3 (center), respectively. , The maximum image height on the horizontal axis passing through), and P4 (corner). Specifically, assuming that P1 is 0 mm, the image heights are P2 = 1.44 mm, P3 = 2.4 mm, and P4 = 2.794 mm.

  According to the projection lens 28 configured in this way, each aberration is small as shown in FIGS. 7 to 11 and can be applied to a small projector without any problem.

  Although the projection lens 28 is made entirely of plastic lenses, the minimum number of lenses can be configured. However, as described above, resin lenses such as plastic lenses have a problem that variations in refractive index and Abbe number are small. . Furthermore, few materials have light resistance to blue laser light, and if used, the cost of the lens increases. Therefore, when a projection lens for a small projector is configured with only a plastic lens, it is difficult to realize high resolution, high brightness, and a long focal length. Further, it is necessary to reduce chromatic aberration in order to reduce the aberration at the point of advantage, and it is difficult to obtain a sufficient chromatic aberration if the number of lenses is too small.

  On the other hand, in the present invention, as described above, the first and fourth lenses L1 and L4 on the outer sides are plastic lenses, and the intermediate second and third lenses L2 and L3 sandwiched between them are glass lenses. The above-mentioned problems were solved, and a configuration with a small number of lenses, ie, four lenses (L1 to L4), which is almost the minimum, was achieved.

  Further, the second and third lenses L2 and L3 made of glass lenses are configured as compound lenses which are joined in close contact with each other with the same curvature of the lens surfaces (f6) adjacent to each other, and are positively refracted as a whole. It is power. Thereby, the position of the stop STO located between the first lens L1 and the second lens L2 can be brought closer to the second lens L2 made of a glass lens, and the energy density with respect to the first lens L1 made of a plastic lens can be further increased. It can be further reduced.

  Further, a resin lens such as a plastic lens has a problem that there are few variations in the refractive index and the Abbe number, but this is also addressed by the second and third lenses L2 and L3 made of glass lenses. Further, the Abbe number of the second lens L2 closer to the stop STO is made larger than the Abbe number of the third lens L3 farther. Accordingly, in addition to the effect of bringing the position of the stop STO closer to the second lens L2 as described above, chromatic aberration can be suitably reduced by combining different Abbe numbers.

  Since the first and fourth lenses L1 and L4 on the outer sides are plastic lenses, the lens shape can be easily changed into a free shape. The first and fourth lenses are designed so that the first lens L1 on the projection side is an aspherical lens to ensure a wide field of view, and the opposite outermost fourth lens L4 is also a spherical lens that is telecentric and ensures a long back focus. L1 and L4 can be easily processed. In this way, as described above, it is possible to configure with a small number of lenses, which is the minimum of four lenses (L1 to L4).

  Further, with the configuration of the projection lens 28 as described above, the thickness of the optical engine unit 13 can be set within 6.9 mm so that the optical engine unit 13 can be accommodated in the casing of the notebook computer 2. The drive bay of the notebook personal computer 2 is generally 9.5 mm in height, and in order to fit in the drive bay with the height of 9.5 mm, the thickness of the optical system should be 6.9 mm or less. Can respond. By using aspherical lenses for the first and fourth lenses L1 and L4 made of plastic lenses as described above, the number of sheets can be reduced and the length in the optical axis direction can be shortened. Even if it is a 22-inch size, it can cope with it. In addition, the total optical length, which is the distance from the first conjugate point side (projection side) surface of the first lens L1 to the light modulator 25, can also be made 40 mm or less, and can be accommodated in the casing of the notebook computer 2. It will not cause any trouble.

  The lens components of the first and fourth lenses L1 and L4 made of a resin material may be made of a cycloolefin polymer or a cycloolefin copolymer. Thereby, the light resistance (especially light resistance of blue laser light) of the lens components of the first and fourth lenses L1 and L4 made of plastic lenses can be further enhanced.

  The lens data of each lens component of the projection lens 28 is not limited to the above embodiment, and a second embodiment as another example will be described below with reference to FIGS. 12 and 13 correspond to FIGS. 4 and 5, respectively, FIGS. 14 to 18 correspond to FIGS. 7 to 11, and parts similar to those in the first embodiment are denoted by the same reference numerals and detailed. Description is omitted.

  In the second embodiment, as shown in FIG. 12, the lens surface f7 on the side (light modulator 25 side) opposite to the projection side of the third lens L3 is formed as a convex spherical lens. The conditions for setting the lens data in Table 2 shown in FIG. 13 are as follows: F value is 2.8, focal length is 9.8 mm, image height of the optical modulator 25 is 3.556 mm, and the projected image on the screen S And the distance between the center of the lens surface on the screen S side of the first lens L1 and the screen S is 1000 mm. The image height and the object height are the same as those described with reference to FIG. 6, and the weighting of each color laser beam is also the same as in the first embodiment.

  Next, aspherical data is described in the same manner as in the first embodiment.

In face number f2,
CE4 = −7.86074481e−5
CE6 = 5.0989131e-6
CE8 = −1.1181951e−8
CE10 = -3.448836e-9
CE12 = 1.88020266e-11
It is.

In surface number f3,
CE4 = −0.000474448961
CE6 = 6.3768493e-5
CE8 = 9.0982912e-9
CE10 = −8.28291e−7
CE12 = 3.804695e-10
It is.

In surface number f8,
CE4 = -0.00062894509
CE6 = 2.6315444e-5
CE8 = -9.0014583e-7
CE10 = 1.51677082e-8
CE12 = -1.1901779e-10
It is.

In face number f9,
CE4 = 0.00019208273
CE6 = −5.8501995e−7
CE8 = 1.2441806e-7
CE10 = −5.088881e−9
CE12 = −1.6966643e−11
It is.

  Also in the second embodiment, as shown in FIGS. 14 to 18, each aberration is within a range where there is no problem. The image height (P1) in FIG. 18A is 0 mm, the image height (P2) in (b) is 1.743 mm, and the image height (P3) in (c) is 3.099 mm. The image height (P4) of (d) is 3.556 mm.

  The third embodiment will be described below with reference to FIGS. 19 and 20 correspond to FIGS. 4 and 5, respectively, FIGS. 21 to 25 correspond to FIGS. 7 to 11, and parts similar to those of the first embodiment are denoted by the same reference numerals and detailed. Description is omitted.

  In the third embodiment, as shown in FIG. 19, the lens surface f5 on the projection side (screen S side) of the second lens L2 is formed as a concave spherical lens as compared with the second embodiment. The conditions for setting the lens data in Table 3 shown in FIG. 20 are as follows: F value is 2.8, focal length is 9.8 mm, image height of the optical modulator 25 is 3.564 mm, and the projected image on the screen S The distance between the center of the lens surface on the screen S side of the first lens L1 and the screen S is 1000 mm. The image height and the object height are the same as those described with reference to FIG. 6, and the weighting of each color laser beam is also the same as in the first embodiment.

  Next, aspherical data is described in the same manner as in the first embodiment.

In face number f2,
CE4 = 6.843509e-5
CE6 = 3.1766495e-6
CE8 = 7.2233378e-8
CE10 = −7.3650241e−9
CE12 = 5.273706e-10
It is.

In surface number f3,
CE4 = 0.00037286867
CE6 = 2.063769e-5
CE8 = −5.374222e−7
CE10 = 1.4666301e-8
CE12 = −7.8445372e−10
It is.

In surface number f8,
CE4 = -1.2843437e-5
CE6 = 1.85851824e-6
CE8 = 6.8899401e-8
CE10 = 3.1354425e-9
CE12 = −1.5794645e−10
It is.

In face number f9,
CE4 = 0.00089271737
CE6 = −8.5790227e−6
CE8 = 2.2007841e-7
CE10 = 1.78773333e-9
CE12 = −2.0959156e−10
It is.

  Also in the third embodiment, as shown in FIGS. 21 to 25, each aberration is within a range where there is no problem. The image height (P1) in FIG. 25 (a) is 0 mm, the image height (P2) in (b) is 1.743 mm, and the image height (P3) in (c) is 3.099 mm. The image height (P4) of (d) is 3.556 mm.

  Furthermore, as a design condition for the first embodiment, the size of the optical modulator 25 is set to 0.22 inch to 0.28 inch, and the glass material of the polarizing beam splitter 26 is BSC7 (Nippon Optical Glass Industry) in the first embodiment. It was SF57HHT (manufactured by SCHOTT) while it was a crown glass designated by the association.

  As a result, the MTF (modulation transfer function) is 100 lp / mm (40% off-axis, 50% on-axis) with respect to 83 lp / mm (40% off-axis, 50% on-axis) of the first embodiment. Improved resolution. In addition, since the thickness of the first lens L1 (thickness on the optical axis) can be reduced from 4.2 mm to 3.1 mm, the cooling time at the time of manufacturing the lens can be shortened, and the manufacturing cost can be reduced. Further, the edge thickness of the fourth lens L4 is changed from 0.5 mm to 1 mm, and the moldability of the plastic lens can be improved. Then, the total optical length of the projection lens 28 is changed from 30 mm to 27 mm, and the miniaturization can be promoted.

  In each of the above embodiments, an example in which four lenses are configured has been described. However, the present invention only needs to have three or more configurations. In the case of using three lenses, the second and third lenses L2 and L3 can be made as a single glass lens, and the resolution and luminance are lower than those in the above embodiments, and the focal length is also shortened. It can be applied when such specifications can be used.

  Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to such embodiments so that those skilled in the art can easily understand, and departs from the spirit of the present invention. It is possible to change appropriately within the range not to be.

  The projection lens according to the present invention and the image display device including the projection lens are useful as a compact projector or the like because they have a compact configuration, can achieve high resolution and high brightness, and can have a long focal length.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 25 Light modulator 22 Green laser light source apparatus 23 Red laser light source apparatus 24 Blue laser light source apparatus 28 Projection lens L1 1st lens (lens component)
L2 Second lens (lens component)
L3 Third lens (lens component)
L3 4th lens (lens component)
STO aperture

Claims (7)

A projection lens comprising at least three or more lens components and telecentric to the light modulator,
Each outer lens component disposed on both outer sides facing the conjugate point of the projection lens is a plastic lens,
The aperture position of the projection lens is between each of the outer lens components;
A projection lens, wherein at least the lens component other than the outer lens component of the projection lens that is closest to the aperture position is a glass lens.   The projection lens according to claim 1, wherein at least one lens surface of the outer lens component is an aspherical surface. A projection lens comprising a first lens component, a second lens component, a third lens component, and a fourth lens component arranged in order from the projection side, and made object side telecentric,
A diaphragm position between the first lens component and the second lens component;
The first lens component is a plastic lens having a pseudo concave meniscus shape and a negative refractive power in which a central portion of the lens surface protrudes toward the projection side,
The fourth lens component is a plastic lens having a pseudo biconvex shape and positive refractive power,
The projection lens, wherein the second lens component and the third lens component are glass lenses.   4. The projection lens according to claim 3, wherein the second lens component and the third lens component are composed of compound lenses bonded to each other and have positive refractive power as a whole. The second lens component is a biconvex shape or a spherical lens having a concave shape on the first lens component side and a convex shape on the third lens component side,
The projection lens according to claim 4, wherein the third lens component is a spherical lens having a biconcave shape or a concave shape on the second lens component side and a convex shape on the fourth lens component side.   6. The projection lens according to claim 3, wherein the Abbe number of the second lens component is larger than the Abbe number of the third lens component. A projection lens according to any one of claims 1 to 6, comprising:
Each laser light source device that emits laser light of each color of red, green, and blue, an optical modulator that modulates laser light, and the optical modulator that uses the laser light of each color emitted from each laser light source device as the same optical path And an optical system for incident on
An image display apparatus comprising a projection lens, wherein the projection lens is disposed on an optical axis that emits modulated outgoing light modulated and emitted by the optical modulator.

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