JP2009168882A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector, reducing deterioration of contrast of an image in the projector configured to use diffraction light emitted from a diffraction optical element. <P>SOLUTION: This projector includes: light source devices 12G, 12R, 12B emitting one or more coherent light beams; a diffraction optical element 14 for diffracting the coherent light beams emitted from the light source devices 12G, 12R, 12B to emit diffraction light; a parallel lens 15 for paralleling the light beams of diffraction light emitted from the diffraction optical element 14; and space light modulators 16R, 16G, 16B for modulating the light emitted from the parallel lens 15 according to an image signal, wherein the optical distance between the diffraction optical element 14 and the parallel lens 15 is eight times as large as the maximum value of a length between the position where the optical axis of the parallel lens 15 intersects in an incident plane or an extended plane of extending the incident plane of the diffraction optical element 14 where the coherent light beams from the light source devices 12G, 12R, 12B enter and the incident position of the coherent light beams in the incident plane. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projector, and more particularly to a technology of a projector that displays an image using laser light.

  In recent years, a technique using a laser light source as a light source of a projector has been proposed. For example, a diffractive optical element can be used as superimposing means for superimposing laser light in the spatial light modulation device of the projector. The diffractive optical element diffracts the laser beam, which is coherent light, to shape and enlarge the irradiation region and to uniformize the light amount distribution in the irradiation region. By performing a plurality of functions with the diffractive optical element, the projector can have a small number of parts, and can be easily reduced in size and space. Conventionally, a technique using a diffractive optical element as superimposing means has been proposed in Patent Document 1, for example.

JP 2007-33576 A

  As the spatial light modulation device, for example, a transmissive liquid crystal display device can be used. In the transmissive liquid crystal display device, linearly polarized light having a predetermined polarization plane is incident on the liquid crystal layer using a polarizer provided on the incident side of the liquid crystal layer. The liquid crystal layer appropriately changes the polarization direction of linearly polarized light. An analyzer provided on the exit side of the liquid crystal layer transmits only a specific linearly polarized light, thereby converting a change in the polarization direction in the liquid crystal layer into a change in light intensity. If only linearly polarized light whose polarization direction can be controlled by the liquid crystal layer can be incident on the liquid crystal layer from the polarizer, an image with high contrast can be obtained. In order to allow only linearly polarized light having a predetermined polarization plane to be emitted from the polarizer, it is desirable to supply light having a light beam angle as small as possible between the optical axis and the light beam to the polarizer. Thus, the projector can obtain a high-contrast image by efficiently supplying light having a light beam angle that can be effectively modulated by the spatial light modulator to the spatial light modulator. On the other hand, when the diffracted light emitted from the diffractive optical element is used for illumination of the spatial light modulator, the light whose beam angle is widened by the expansion of the diffractive optical element enters the spatial light modulator. According to the prior art, when a diffractive optical element is used, there is a problem that the contrast of an image may be lowered due to light having a large light beam angle entering the spatial light modulator. SUMMARY An advantage of some aspects of the invention is that it provides a projector that can reduce a decrease in contrast of an image in a configuration using diffracted light emitted from a diffractive optical element.

  In order to solve the above-described problems and achieve the object, a projector according to the present invention emits diffracted light by diffracting one or more light sources that emit coherent light, and coherent light emitted from the light source device. A diffractive optical element; a collimating lens that collimates a light beam of diffracted light emitted from the diffractive optical element; and a spatial light modulator that modulates light emitted from the collimated lens according to an image signal. The optical distance between the optical element and the collimating lens is such that the optical axis of the collimating lens intersects the incident surface of the diffractive optical element on which coherent light from the light source device is incident or the extended surface obtained by extending the incident surface; It is more than 8 times the maximum value of the length between the incident surface and the position where the coherent light is incident.

  By making the optical distance between the diffractive optical element and the collimating lens at least eight times the maximum length between the optical axis and the position where the coherent light is incident, the light incident on the spatial light modulator is reduced. Suppresses the spread of the ray angle. By making light of a light beam angle that can be effectively modulated by the spatial light modulation device efficiently incident on the spatial light modulation device, it is possible to reduce a decrease in contrast of the image. As a result, a projector capable of reducing a decrease in image contrast in a configuration using diffracted light emitted from the diffractive optical element can be obtained.

  Furthermore, a projector according to the present invention includes a light source device that emits one or more coherent lights, a diffractive optical element that diffracts the coherent light emitted from the light source apparatus, and emits diffracted light, and a diffraction that is emitted from the diffractive optical element. A collimating lens that collimates the light beam of light; and a spatial light modulator that modulates the light emitted from the collimating lens in accordance with an image signal, and reflects and collimates the diffracted light emitted from the diffractive optical element. It has the reflection part which injects into an optical lens, It is characterized by the above-mentioned.

  By providing the reflecting portion in the optical path between the diffractive optical element and the collimating lens, it is possible to ensure a long optical distance between the diffractive optical element and the collimating lens in a certain space. By appropriately securing the optical distance between the diffractive optical element and the collimating lens, the spread of the light beam angle of the light incident on the spatial light modulator is suppressed. As a result, a projector capable of reducing a decrease in image contrast in a configuration using diffracted light emitted from the diffractive optical element can be obtained. Moreover, the projector can be made compact by making it possible to install the diffractive optical element and the collimating lens in a fixed space.

  In a preferred embodiment of the present invention, the optical distance between the diffractive optical element and the collimating lens is an incident surface of the diffractive optical element on which coherent light from the light source device is incident or an extended surface obtained by extending the incident surface. It is desirable that it is 8 times or more the maximum value of the length between the position where the optical axes of the collimating lenses intersect and the position where the coherent light is incident on the incident surface. Thereby, light having a light beam angle that can be effectively modulated by the spatial light modulator can be efficiently incident on the spatial light modulator.

  Furthermore, a projector according to the present invention includes a first illumination device that supplies first color light, a second illumination device that supplies second color light, a third illumination device that supplies third color light, and a first illumination device. A first spatial light modulator that modulates the supplied first color light according to the image signal; a second spatial light modulator that modulates the second color light supplied by the second illumination device according to the image signal; A third spatial light modulation device that modulates the third color light supplied by the three illumination devices in accordance with an image signal, and the first illumination device, the second illumination device, and the third illumination device include at least one A light source device that emits coherent light, a diffractive optical element that diffracts coherent light emitted from the light source device, and emits diffracted light; and a parallelizing lens that collimates a light beam of diffracted light emitted from the diffractive optical element. And diffraction in the first lighting device The optical distance between the optical element and the collimating lens is the optical distance between the diffractive optical element and the collimating lens in the second illumination device, and the optical distance between the diffractive optical element and the collimating lens in the third illumination device. It is characterized by being longer than any of the above.

  It is assumed that the first color light is light that the human eye feels stronger than the second color light and the third color light, in other words, light with high visibility. With respect to the first illumination device, it is possible to reduce the decrease in contrast of the first color light by appropriately securing the optical distance between the diffractive optical element and the collimating lens. A high contrast color image can be obtained by reducing the decrease in contrast of the first color light having high visibility with respect to the second color light and the third color light. As a result, a projector capable of reducing a decrease in image contrast in a configuration using diffracted light emitted from the diffractive optical element can be obtained. Further, the projector can be made compact as compared with the case where the optical distance between the diffractive optical element and the collimating lens is increased for all color lights.

  In a preferred embodiment of the present invention, the first color light is desirably green light. A high contrast color image can be obtained by reducing the decrease in contrast of green light having the highest visibility among red light, green light, and blue light.

  As a preferred aspect of the present invention, in the first illumination device, the optical distance between the diffractive optical element and the collimating lens extends the incident surface or the incident surface of the diffractive optical element on which coherent light from the light source device is incident. It is desirable that it is 8 times or more of the maximum value of the length between the position where the optical axes of the collimating lenses intersect and the position where the coherent light is incident on the incident surface. As a result, light having a light beam angle that can be effectively modulated by the first spatial light modulator can be efficiently incident on the first spatial light modulator.

  Moreover, as a preferable aspect of the present invention, it is desirable that the first illumination device has a reflection portion that reflects the diffracted light emitted from the diffractive optical element and enters the collimating lens. Thereby, a long optical distance can be ensured between the diffractive optical element and the collimating lens in a certain space for the first illumination device.

  As a preferred aspect of the present invention, the optical distance between the diffractive optical element and the collimating lens in the second illumination device is longer than the optical distance between the diffractive optical element and the collimating lens in the third illumination device. desirable. It is assumed that the second color light has low visibility compared to the first color light and high visibility compared to the third color light. As a result, a reduction in contrast of the image can be further reduced.

  As a preferred embodiment of the present invention, the second color light is desirably red light. It is possible to obtain a color image with a higher contrast by reducing the decrease in contrast of red light having the highest visibility after green light among red light, green light, and blue light.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic top configuration of a projector 10 according to a first embodiment of the invention. The projector 10 is a front projection type projector that appreciates an image by projecting light onto a screen (not shown) and observing the light reflected by the screen. The projector 10 includes a first lighting device 11G, a second lighting device 11R, and a third lighting device 11B. The first lighting device 11G supplies green (G) light that is first color light. The second illumination device 11R supplies red (R) light that is second color light. The third lighting device 11B supplies blue (B) light that is third color light.

  The first illumination device 11G includes a light source device 12G that emits G light, a diffractive optical element 14, and a collimating lens 15. The light source device 12G emits twelve laser beams that are coherent light. The light source device 12G has twelve laser light sources 13 that emit laser light. The twelve laser light sources 13 are arranged in an array of four in a direction parallel to the paper surface and three in a direction perpendicular to the paper surface. In FIG. 1, only four laser light sources 13 arranged in a line on the front side of the paper are shown among the twelve laser light sources 13 of the light source device 12G. The laser light source 13 includes, for example, an edge-emitting semiconductor laser.

  The diffractive optical element 14 diffracts G light from the light source device 12G and emits diffracted light. The diffractive optical element 14 forms an irradiation region of a rectangular shape and a uniform light amount distribution on the irradiated surface of the first spatial light modulator 16G. The diffractive optical element 14 shapes and enlarges the irradiation area and makes the light amount distribution uniform in the irradiation area. The collimating lens 15 collimates the diffracted light beam emitted from the diffractive optical element 14. The first spatial light modulation device 16G is a spatial light modulation device that modulates the G light emitted from the collimating lens 15 of the first illumination device 11G according to an image signal, and is a transmissive liquid crystal display device. The G light emitted from the first spatial light modulator 16G enters the cross dichroic prism 17.

  The second illumination device 11R includes a light source device 12R that emits R light. The second lighting device 11R has the same configuration as the first lighting device 11G except that the colored light to be supplied and the direction in which the second lighting device 11R is arranged are different. The second spatial light modulation device 16R is a spatial light modulation device that modulates the R light emitted from the collimating lens 15 of the second illumination device 11R according to an image signal, and is a transmissive liquid crystal display device. The R light emitted from the second spatial light modulator 16R is incident on a surface of the cross dichroic prism 17 different from the surface on which the G light is incident.

  The 3rd illuminating device 11B has the light source device 12B which inject | emits B light. The third lighting device 11B has the same configuration as the first lighting device 11G, except that the colored light to be supplied and the direction in which it is arranged are different. The third spatial light modulation device 16B is a spatial light modulation device that modulates the B light emitted from the collimating lens 15 of the third illumination device 11B according to an image signal, and is a transmissive liquid crystal display device. The B light emitted from the third spatial light modulator 16B is incident on a surface of the cross dichroic prism 17 that is different from the surface on which the G light is incident and the surface on which the R light is incident.

  Each illumination device 11G, 11R, and 11B can use, for example, a computer generated hologram (CGH) as the diffractive optical element 14. As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used.

  The cross dichroic prism 17 has two dichroic films 18 and 19 arranged substantially orthogonal to each other. The first dichroic film 18 reflects R light and transmits G light and B light. The second dichroic film 19 reflects B light and transmits R light and G light. The cross dichroic prism 17 combines the R light, G light, and B light incident from different directions and emits the light toward the projection lens 20. The projection lens 20 projects the light emitted from the cross dichroic prism 17.

  FIG. 2 schematically shows the diffraction grating 22 formed in the diffractive optical element 14. FIG. 3 shows an AA cross-sectional configuration of FIG. The diffraction grating 22 is formed at each position of the diffractive optical element 14 where the laser beam is incident. The diffraction grating 22 is formed on the surface of the diffractive optical element 14, for example, an exit surface that emits light. The diffraction grating 22 includes a plurality of irregularities formed with the rectangular region 21 as a unit. Such irregularities are rectangular in the cross section shown in FIG. In FIG. 2, each rectangular area 21 is filled or hatched to indicate that a height difference in a direction perpendicular to the paper surface is provided.

  The diffraction grating 22 changes the phase of the laser beam for each rectangular region 21. The diffractive optical element 14 generates diffracted light by spatially changing the phase of the laser light in the diffraction grating 22. By optimizing the surface conditions including the pitch of the rectangular region 21 and the height of the unevenness, the diffractive optical element 14 can have a predetermined function. As a design method for optimizing the surface condition of the diffraction grating 22, a predetermined calculation method (simulation method) such as an iterative Fourier transform can be used. The diffractive optical element 14 may be provided with a diffraction grating 22 having irregularities having a rectangular shape in cross section, or a diffraction grating having irregularities having a triangular shape in cross section.

  For example, the diffractive optical element 14 can be manufactured using a so-called nanoimprint technique in which a mold having a desired shape is formed and then the shape of the mold is thermally transferred to the substrate. In addition, the diffractive optical element 14 may be manufactured by other conventionally used methods as long as a desired shape can be formed.

  FIG. 4 shows a schematic side configuration of the first illumination device 11G and the first spatial light modulation device 16G in the projector 10. Hereinafter, the first illumination device 11G and the first spatial light modulation device 16G provided for the G light among the configurations provided for the respective color lights will be described as representative examples. FIG. 4 shows only three laser light sources 13 arranged in a line on the front side of the paper among the twelve laser light sources 13 of the light source device 12G. Both the diffractive optical element 14 and the first spatial light modulator 16G are provided on the optical axis AX of the collimating lens 15. The diffractive optical element 14 is disposed such that the optical axis AX passes through the center position of the incident surface S1 on which the laser light from the light source device 12G is incident. The first spatial light modulation device 16G is arranged so that the optical axis AX penetrates the center position of the irradiation region of the irradiated surface S3 on which the G light supplied by the first illumination device 11G is incident. The front focal point of the collimating lens 15 substantially coincides with the exit surface S2 on which the diffraction grating 22 (see FIG. 2) of the diffractive optical element 14 is formed. Thereby, the light beam diffused from the diffractive optical element 14 can be collimated by the collimating lens 15.

  FIG. 5 illustrates the light beam angle of light incident from the diffractive optical element 14 to the first spatial light modulator 16G. FIG. 6 shows the incident surface S1 of the diffractive optical element 14. The light ray angle is an angle formed by the optical axis AX and the light ray. The incident surface S1 of the diffractive optical element 14 has a rectangular shape having a height h, a width w, and a diagonal length D. For example, it is assumed that light incident on a position P that is one end of a diagonal line on the incident surface S1 is diffused from the exit surface S2 of the diffractive optical element 14 as shown in FIG. The ray angle θ of the light that has passed through the position P and exited from the exit surface S2 can be obtained by the following equation (1).

The position P is a position farthest on the incident surface S1 from the central position O where the optical axes AX intersect on the incident surface S1. The light ray angle θ of the light passing through the position P and exiting from the exit surface S2 can be regarded as the maximum light ray angle of the light incident on the first spatial light modulator 16G from the diffractive optical element 14. In the above equation (1), D / 2 represents the maximum value of the length between the center position O of the incident surface S1 where the optical axis AX intersects and the position of the incident surface S1 where the laser beam is incident. . The optical distance f between the diffractive optical element 14 and the collimating lens 15 satisfies the following condition.
f ≧ 4 × D (= 8 × D / 2) (2)

For example, it is assumed that the height h of the diffractive optical element 14 is 3 mm, the width w is 4 mm, and the optical distance f between the diffractive optical element 14 and the collimating lens 15 is 20 mm. The length D of the diagonal line is 5 mm {= (3 ² +4 ² ) ^1/2 }. At this time, since the relationship of f = 4 × D (= 20 mm) is established, the above formula (2) is satisfied. If each numerical value is substituted into the above equation (1), the maximum light ray angle θ is approximately 7.1 degrees. Therefore, by securing an optical distance f corresponding to eight times D / 2, the light beam angle of light incident on the first spatial light modulator 16G can be reduced to approximately 7.1 degrees or less.

  Next, it is assumed that the height h of the diffractive optical element 14 is 3 mm, the width w is 4 mm, and the optical distance f between the diffractive optical element 14 and the collimating lens 15 is 100 mm. The optical distance f corresponds to 20 times D (40 times D / 2). Since the relationship of f> 4 × D (= 20 mm) is established, the above formula (2) is satisfied. If each numerical value is substituted into the above equation (1), the maximum light ray angle θ is about 1.4 degrees. Therefore, by ensuring an optical distance f that is greater than 8 times D / 2, it is possible to further suppress the spread of the ray angle of the light incident on the first spatial light modulator 16G.

  By supplying light having the smallest possible beam angle to the first spatial light modulator 16G, the first spatial light modulator 16G can effectively modulate the light. In order to obtain a high-contrast image using a transmissive liquid crystal display device, it is desirable that the light ray angle of light incident on the transmissive liquid crystal display device is, for example, 6 degrees or less. As described above, by securing an optical distance f corresponding to 8 times D / 2, the maximum value of the light ray angle of light incident on the first spatial light modulator 16G is approximately 7.1 degrees, which is close to 6 degrees. Can be. By securing an optical distance f greater than 8 times D / 2, the maximum value of the light beam angle can be further reduced.

  Thus, by securing an optical distance f that is at least eight times the maximum value of the length between the position where the optical axis AX intersects on the incident surface S1 and the position where the laser light is incident on the incident surface S1. The spread of the light beam angle of the light incident on each of the spatial light modulators 16G, 16R, and 16B is suppressed. It is possible to reduce a decrease in contrast of an image by efficiently causing light having a light beam angle that can be effectively modulated by each of the spatial light modulators 16G, 16R, and 16B to enter each of the spatial light modulators 16G, 16R, and 16B. Become. Thereby, in the configuration using the diffracted light emitted from the diffractive optical element 14, an effect of reducing the contrast of the image can be achieved.

  Here, the maximum value of the optical distance f between the diffractive optical element 14 and the first spatial light modulator 16G will be described. As the optical distance f increases, the projector 10 becomes larger. For example, the optical distance f can be set to 50 times or less of D (100 times or less of D / 2). Similarly to the above, when the length D of the diagonal line is 5 mm, it is assumed that the optical distance f is 250 mm (= D × 50 = D / 2 × 100). If each numerical value is substituted into the above equation (1), the maximum light ray angle θ is approximately 0.57 degrees.

  FIG. 7 explains one of the reasons why the optical distance f is desirably 50 times or less of D. As shown in FIG. 7, for example, the projector 10 may arrange the first spatial light modulation device 16G at a position away from the optical axis AX. The diffracted light emitted from the diffractive optical element 14 travels obliquely with respect to the optical axis AX, and enters the first spatial light modulator 16G via the collimating lens 15. Zero-order light emitted from the diffractive optical element 14 is incident on a light absorbing unit 24 provided on the optical axis AX. There is an advantage that the light quantity distribution in the irradiated region can be easily uniformed by causing the zero-order light to travel to a position other than the irradiated surface S3. Moreover, the generation of stray light can be reduced by absorbing the zero-order light by the light absorption unit 24.

  It is assumed that the full width at half maximum (FWHM) of laser light emitted from the light source device 12G is, for example, 10 to 20 mrad. In this case, the light beam angle (α / 2) of the zero-order light emitted from the diffractive optical element 14 is, for example, 0.6 degrees to 1.2 degrees. Since the zero-order light diffuses as the optical distance f becomes longer, the light absorbing portion 24 becomes larger. The larger the light absorbing portion 24, the more the diffracted light emitted from the diffractive optical element 14 needs to travel farther from the optical axis AX. As the diffracted light travels farther from the optical axis AX, the first spatial light modulator 16G is arranged at a position farther from the optical axis AX. It is difficult to make the width L of the space where the diffractive optical element 14 and the first spatial light modulation device 16G are arranged larger than about 30 mm, for example. Considering these, it is desirable that the optical distance f is about 50 times the maximum of the diagonal length D of the diffractive optical element 14.

  FIG. 8 shows the relationship between f / D and the maximum ray angle θ. From the relationship shown in FIG. 8, it can be seen that even when f / D is set to 50 or more, the maximum ray angle θ hardly changes. From the description using FIG. 7 and FIG. 8, it can be said that the optical distance f is desirably 50 times or less of D (100 times or less of D / 2). As described above, the optical distance f between the diffractive optical element 14 and the collimating lens 15 is the length between the position where the optical axis AX intersects in the incident surface S1 and the position where the laser beam enters in the incident surface S1. It can be set to 8 times or more and 100 times or less of the maximum value.

  The light source devices 12G, 12R, and 12B provided in each of the lighting devices 11G, 11R, and 11B are not limited to the configuration described in the present embodiment. The light source devices 12G, 12R, and 12B only need to have one or more laser light sources 13. The light source devices 12G, 12R, and 12B are not limited to those having the laser light source 13 that includes the edge emitting semiconductor laser, and may include a surface emitting semiconductor laser. The light source devices 12G, 12R, and 12B may emit a plurality of laser beams using a semiconductor laser having a plurality of light emitting units.

  In the present embodiment, the range of the optical distance f is set by using the rectangular diagonal length D of the diffractive optical element 14, but the present invention is not limited to this. Regardless of the shape of the diffractive optical element 14, the length between the position where the laser beam is incident on the incident surface S1 and the position farthest from the optical axis AX and the position where the optical surface AX intersects the incident surface S1. Using this, the range of the optical distance f can be set.

  The diffractive optical element 14 is not limited to the case where the optical axis AX passes through the center position O of the incident surface S1. The diffractive optical element 14 may be arranged so that the optical axis AX penetrates a position other than the center position O of the incident surface S1. Furthermore, the diffractive optical element 14 may be disposed at a position away from the optical axis AX. In this case, the optical distance f is a length between the position where the optical axis AX intersects the extended surface obtained by extending the incident surface S1 of the diffractive optical element 14 and the position where the laser light is incident on the incident surface S1. It can be 8 times or more of the maximum value.

  FIG. 9 is a diagram for explaining a characteristic part of the projector according to the second embodiment of the invention. The projector of the present embodiment can apply the lighting device 30 described below for each color light. The same parts as those in the above embodiment are denoted by the same reference numerals, and redundant description is omitted. The illumination device 30 includes a light source device 31, a diffractive optical element 32, a first mirror 33, a second mirror 34, and the collimating lens 15. The light source device 31 includes a plurality of laser light sources 13 that emit laser light that is coherent light. FIG. 9 shows only two laser light sources 13 arranged in a row on the front side of the drawing among the plurality of laser light sources 13 arranged in an array.

  The diffractive optical element 32 diffracts the laser light from the light source device 31 and emits diffracted light. The first mirror 33 reflects the diffracted light emitted from the diffractive optical element 32 toward the second mirror 34. The second mirror 34 reflects the diffracted light reflected by the first mirror 33 toward the collimating lens 15. The first mirror 33 and the second mirror 34 function as a reflection unit that reflects the diffracted light emitted from the diffractive optical element 32 and enters the collimating lens 15. The first mirror 33 and the second mirror 34 are configured using a highly reflective member such as a metal member or a dielectric multilayer film. The collimating lens 15 collimates the light beam of the diffracted light from the second mirror 34. The spatial light modulator 16 is a transmissive liquid crystal display device that modulates light emitted from the collimating lens 15 of the illumination device 30 in accordance with an image signal.

  The first mirror 33 and the second mirror 34 are disposed at an angle of approximately 45 degrees with respect to the optical axis AX. The light that has entered the first mirror 33 from the diffractive optical element 32 has its optical path bent by approximately 90 degrees due to reflection by the first mirror 33. The light that has entered the second mirror 34 from the first mirror 33 has its optical path bent by approximately 90 degrees due to reflection by the second mirror 34. Due to the reflection at the first mirror 33 and the second mirror 34, the optical path is bent approximately 180 degrees. As described above, the light emitted from the diffractive optical element 32 is folded by the first mirror 33 and the second mirror 34 so that the traveling direction is reversed, and then enters the parallelizing lens 15.

  As in the first embodiment, the optical distance f between the diffractive optical element 32 and the collimating lens 15 intersects the optical axis AX of the incident surface S1 of the diffractive optical element 32 or the extended surface obtained by extending the incident surface S1. It is 8 times or more of the maximum value of the length between the position and the position where the laser beam is incident on the incident surface S1. Furthermore, the optical distance f is the maximum value of the length between the position where the optical axis AX intersects the incident surface S1 or the extended surface obtained by extending the incident surface S1 and the position where the laser beam is incident on the incident surface S1. 8 times or more and 100 times or less.

  The light is turned back by the first mirror 33 and the second mirror 34 to cause the light to travel straight from the diffractive optical element 32 to the collimating lens 15, but in a limited space inside the projector, the diffractive optical element 32 and parallel It is possible to ensure a long optical distance between the conversion lenses 15. By appropriately securing an optical distance between the diffractive optical element 32 and the collimating lens 15, the spread of the light beam angle of light incident on the spatial light modulator 16 is suppressed. Thereby, in the configuration using the diffracted light emitted from the diffractive optical element 32, it is possible to reduce a decrease in contrast of the image. In addition, since the diffractive optical element 32 and the collimating lens 15 can be installed in a certain space, the projector can be made compact.

  FIG. 10 illustrates a characteristic part of a projector according to a modification of the present embodiment. The projector of this modification can apply the illumination device 35 described below for each color light. The illumination device 35 includes a light source device 31, a diffractive optical element 36, a mirror 37, and the collimating lens 15. The diffractive optical element 36 diffracts the laser light from the light source device 31 and emits diffracted light.

  The mirror 37 reflects the diffracted light emitted from the diffractive optical element 36 toward the parallelizing lens 15. The mirror 37 functions as a reflecting unit that reflects the diffracted light emitted from the diffractive optical element 36 and enters the collimating lens 15. The mirror 37 is configured using a highly reflective member such as a metal member or a dielectric multilayer film. The collimating lens 15 collimates the diffracted light beam from the mirror 37.

  The light emitted from the diffractive optical element 36 is reflected by the mirror 37 so that the traveling direction is close to the opposite direction, and then enters the parallelizing lens 15. In this modification, the illumination device 35 uses a single mirror 37 as a reflecting portion. Therefore, compared to the case where two mirrors 33 and 34 (see FIG. 9) are used, the number of parts of the projector is reduced and the projector is simplified. Can be configured. In the case of this modification, the diffractive optical element 36 is arranged at a position away from the optical axis AX. Compared with the case of FIG. 9 in which the diffractive optical element 32 is arranged on the optical axis AX, the light ray angle of the light incident on the collimating lens 15 becomes larger. Accordingly, when the diffractive optical element 32 is arranged on the optical axis AX by using the two mirrors 33 and 34, the diffractive optical element 36 is arranged at a position away from the optical axis AX by using one mirror 37. In contrast to this, there is an advantage that the spread of the ray angle can be suppressed. In addition, the reflection part is not limited to one that folds the diffracted light from the diffractive optical elements 32 and 36 so that the traveling direction is reverse or close to the reverse direction. The reflection part should just be what can change the advancing direction of diffracted light by reflection. The number of mirrors (reflection optical elements) is not limited to one or two, and may be three or more (that is, at least one mirror may be provided).

  FIG. 11 shows a schematic top configuration of the projector 40 according to the third embodiment of the invention. The projector 40 of the present embodiment is characterized in that the optical distance between the diffractive optical element 43 and the collimating lens 15 is varied for each color light. The same parts as those in the above embodiment are denoted by the same reference numerals, and redundant description is omitted. The projector 40 includes a first lighting device 41G, a second lighting device 41R, and a third lighting device 41B. The first lighting device 41G supplies G light that is first color light. The second lighting device 41R supplies R light that is second color light. The third lighting device 41B supplies B light that is third color light.

  The first illumination device 41G includes a light source device 42G that emits G light, a diffractive optical element 43, a first mirror 44, a second mirror 45, and a collimating lens 15. The light source device 42G emits a plurality of laser beams that are coherent light. The light source device 42G includes a surface emitting semiconductor laser including a plurality of light emitting units. The diffractive optical element 43 diffracts the G light from the light source device 42G and emits diffracted light. The first mirror 44 reflects the diffracted light emitted from the diffractive optical element 43 toward the second mirror 45. The second mirror 45 reflects the diffracted light reflected by the first mirror 44 toward the collimating lens 15. The first mirror 44 and the second mirror 45 function as a reflection unit that reflects the diffracted light emitted from the diffractive optical element 43 and enters the collimating lens 15. The collimating lens 15 collimates the diffracted light beam from the second mirror 45.

  The second illumination device 41R includes a light source device 42R that emits R light, a diffractive optical element 43, a third mirror 46, and the collimating lens 15. The light source device 42R emits a plurality of laser beams that are coherent light. The light source device 42R includes a surface emitting semiconductor laser including a plurality of light emitting units. The diffractive optical element 43 diffracts the R light from the light source device 42R and emits diffracted light. The third mirror 46 reflects the diffracted light emitted from the diffractive optical element 43 toward the collimating lens 15. The third mirror 46 functions as a reflection unit that reflects the diffracted light emitted from the diffractive optical element 43 and enters the collimating lens 15. The collimating lens 15 collimates the diffracted light beam from the third mirror 46. The first mirror 44, the second mirror 45, and the third mirror 46 are all configured using a highly reflective member, for example, a metal member or a dielectric multilayer film.

  The third illumination device 41B includes a light source device 42B that emits B light, a diffractive optical element 43, and a collimating lens 15. The light source device 42B includes a surface emitting semiconductor laser including a plurality of light emitting units. The diffractive optical element 43 diffracts the B light from the light source device 42B and emits diffracted light. The collimating lens 15 collimates the diffracted light beam from the diffractive optical element 43. The cross dichroic prism 47 has two dichroic films 48 and 49 arranged substantially orthogonal to each other. The first dichroic film 48 reflects G light and transmits B light and R light. The second dichroic film 49 reflects R light and transmits B light and G light. The cross dichroic prism 47 combines R light, G light, and B light incident from different directions and emits the light toward the projection lens 20.

  The housing 50 houses each component for forming an image according to the image signal. The housing 50 has a substantially rectangular shape. The light source device 42G, the first mirror 44, and the second mirror 45 that constitute the first illumination device 41G occupy three locations among the four corners of the rectangular shape of the housing 50. A third mirror 46 constituting the second illumination device 41R is provided at the remaining one of the four corners. The light source device 42R constituting the second lighting device 41R is provided in the vicinity of the light source device 42G of the first lighting device 41G. The third illumination device 41B is provided between the optical path between the diffractive optical element 43 and the first mirror 44 constituting the first illumination device 41G, and the cross dichroic prism 47. The projector 40 is configured such that the optical distance between the diffractive optical element 43 and the collimating lens 15 becomes longer in the order of the third illumination device 41B, the second illumination device 41R, and the first illumination device 41G. In the first illumination device 41G, the optical distance between the diffractive optical element 43 and the collimating lens 15 is such that the optical axis of the incident surface of the diffractive optical element 43 or the extended surface of the incident surface intersects with the laser of the incident surface. It is 8 times or more of the maximum value between the positions where light is incident.

  With respect to the first illumination device 41G, by appropriately securing the optical distance between the diffractive optical element 43 and the collimating lens 15, it is possible to reduce the contrast reduction for the G light. The visibility of each color light increases in the order of B light, R light, and G light. By ensuring a long optical distance between the diffractive optical element 43 and the collimating lens 15 in the order of B light, R light, and G light, a high-contrast color image can be obtained. Further, the projector 40 can be made compact as compared with the case where the optical distance between the diffractive optical element 43 and the collimating lens 15 is increased for all color lights.

  In the projector 40, the optical distance between the diffractive optical element 43 and the collimating lens 15 only needs to be longer in the order of B light, R light, and G light, and is not limited to the configuration described in this embodiment. Further, the projector 40 only needs to have a longer optical distance between the diffractive optical element 43 and the collimating lens 15 than the R light and B light for at least G light among R light, G light, and B light. For example, for R light and G light, the length of the optical distance between the diffractive optical element 43 and the collimating lens 15 may be substantially the same.

  The projectors of the above embodiments are not limited to the case where a laser light source including a semiconductor laser is used, and a laser light source including a solid laser, a liquid laser, a gas laser, or the like may be used. The light source device is not limited to one having a laser light source. The light source device may have a solid light source such as a light emitting diode (LED) or a super luminescence diode (SLD). The projector is not limited to the case where a transmissive liquid crystal display device is used as the spatial light modulation device. As the spatial light modulator, a reflective liquid crystal display (Liquid Crystal On Silicon; LCOS), DMD (Digital Micromirror Device), GLV (Grating Light Valve), or the like may be used. The projector is not limited to a configuration including a spatial light modulator for each color light. The projector may be configured to modulate two or three or more color lights with one spatial light modulator. The projector is not limited to using a spatial light modulator. The projector may be a slide projector that uses a slide having image information. The projector may be a so-called rear projector that supplies light to one surface of the screen and observes an image by observing light emitted from the other surface of the screen.

1 is a diagram illustrating a schematic top configuration of a projector according to a first embodiment of the invention. The figure which represented the diffraction grating typically. The figure which shows the AA cross-section structure of FIG. The figure which shows the side surface schematic structure of a 1st illumination device and a 1st spatial light modulation apparatus. The figure explaining the light ray angle of the light which injects into a 1st spatial light modulation apparatus. The figure which shows the entrance plane of a diffractive optical element. The figure explaining the range of the optical distance between a diffractive optical element and a parallelizing lens. The figure which shows the relationship between f / D and the maximum ray angle. FIG. 6 is a diagram illustrating a characteristic part of a projector according to a second embodiment of the invention. FIG. 10 is a diagram illustrating a characteristic part of a projector according to a modification example of the second embodiment. FIG. 10 is a diagram illustrating a schematic top configuration of a projector according to a third embodiment of the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Projector, 11G 1st illumination device, 11R 2nd illumination device, 11B 3rd illumination device, 12G, 12R, 12B Light source device, 13 Laser light source, 14 Diffractive optical element, 15 Parallelizing lens, 16G 1st spatial light modulation device , 16R second spatial light modulator, 16B third spatial light modulator, 16 spatial light modulator, 17 cross dichroic prism, 18 first dichroic film, 19 second dichroic film, 20 projection lens, 21 rectangular area, 22 diffraction Lattice, AX optical axis, S1 incident surface, S2 exit surface, S3 irradiated surface, 24 light absorbing unit, 30 illumination device, 31 light source device, 32 diffractive optical element, 33 first mirror, 34 second mirror, 35 illumination device , 36 Diffractive optical element, 37 Mirror, 40 Projector, 41G First illumination device, 41R First Illumination device, 41B third illumination device, 42G, 42R, 42B light source device, 43 diffractive optical element, 44 first mirror, 45 second mirror, 46 third mirror, 47 cross dichroic prism, 48 first dichroic film, 49th 2 dichroic membrane, 50 cases

Claims (9)

A light source device that emits one or more coherent lights;
A diffractive optical element that diffracts the coherent light emitted from the light source device and emits diffracted light;
A collimating lens that collimates the light beam of the diffracted light emitted from the diffractive optical element;
A spatial light modulator that modulates light emitted from the collimating lens according to an image signal,
An optical distance between the diffractive optical element and the collimating lens is such that the collimating lens is an incident surface of the diffractive optical element on which the coherent light from the light source device is incident or an extended surface obtained by extending the incident surface. The projector is characterized in that it is at least eight times the maximum value of the length between the position where the optical axes intersect and the position where the coherent light is incident on the incident surface. A light source device that emits one or more coherent lights;
A diffractive optical element that diffracts the coherent light emitted from the light source device and emits diffracted light;
A collimating lens that collimates the light beam of the diffracted light emitted from the diffractive optical element;
A spatial light modulator that modulates light emitted from the collimating lens according to an image signal,
A projector, comprising: a reflection unit configured to reflect the diffracted light emitted from the diffractive optical element and to enter the collimating lens.   The collimating lens has an optical distance between the diffractive optical element and the collimating lens that is an incident surface of the diffractive optical element on which the coherent light from the light source device is incident or an extended surface obtained by extending the incident surface. 3. The projector according to claim 2, wherein the projector is at least eight times as long as a maximum value between a position where the optical axes intersect and a position where the coherent light is incident on the incident surface. A first lighting device for supplying a first color light;
A second lighting device for supplying second color light;
A third lighting device for supplying third color light;
A first spatial light modulator that modulates the first color light supplied by the first illumination device according to an image signal;
A second spatial light modulator that modulates the second color light supplied by the second illumination device according to an image signal;
A third spatial light modulator that modulates the third color light supplied by the third illumination device according to an image signal;
The first lighting device, the second lighting device, and the third lighting device are:
A light source device that emits one or more coherent lights;
A diffractive optical element that diffracts the coherent light emitted from the light source device and emits diffracted light;
A collimating lens that collimates the light beam of the diffracted light emitted from the diffractive optical element,
The optical distance between the diffractive optical element and the collimating lens in the first illumination device is equal to the optical distance between the diffractive optical element and the collimating lens in the second illumination device, and in the third illumination device. A projector having a longer optical distance between the diffractive optical element and the collimating lens.   The projector according to claim 4, wherein the first color light is green light.   In the first illumination device, the optical distance between the diffractive optical element and the collimating lens is an extension of the incident surface of the diffractive optical element on which the coherent light from the light source device is incident or an extension of the incident surface. 5. The surface is at least eight times the maximum value of the length between the position where the optical axes of the collimating lenses intersect and the position where the coherent light is incident on the incident surface. Or 5. The projector according to 5.   The said 1st illuminating device has a reflection part which reflects the said diffracted light inject | emitted from the said diffractive optical element, and injects into the said parallelizing lens, It is any one of Claims 4-6 characterized by the above-mentioned. projector.   The optical distance between the diffractive optical element and the collimating lens in the second illumination device is longer than the optical distance between the diffractive optical element and the collimating lens in the third illumination device. Item 8. The projector according to any one of Items 4 to 7.   The projector according to claim 8, wherein the second color light is red light.

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