JP2019045530A - projector - Google Patents

Abstract

To provide a projector in which a contrast ratio can be improved.SOLUTION: The projector includes: an illumination device; a uniform illumination optical system; a liquid crystal optical modulation device that is disposed on an optical path of illumination light transmitted through the uniform illumination optical system, has a diffracting function and modulates the illumination light in accordance with image information to generate image light comprising a plurality of diffracted light beams; a retardation plate that receives the image light; a polarizing plate that receives the image light transmitted through the retardation plate; and a projection optical system that is disposed on an optical path of the image light transmitted through the polarizing plate. The projection optical system has a plurality of lenses and a light-shielding element receiving the image light. The light-shielding element has at least one light-shielding part and a plurality of light-transmitting parts. One light-transmitting part of the plurality of light-transmitting parts is disposed in a region where at least one 0-order diffracted light beam of the image light passes. The at least one light-shielding part is disposed on an optical path of a first-order or higher order diffracted light beam corresponding to the at least one 0-order diffracted light passing through the light-transmitting part.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a projector.

  As means for enhancing the contrast ratio of the projector, Patent Document 1 below discloses that a retardation plate is provided between the liquid crystal panel and the exit-side polarizing plate. Since the liquid crystal panel functions as a diffraction grating, light transmitted through the liquid crystal panel includes zero-order diffracted light and diffracted light of first or higher order.

Patent No. 4744606

  By the way, the incident angle of the diffracted light of first order or higher to the retardation plate is different from the incident angle of the diffracted light of zero order to the retardation plate. In general, a retardation plate is designed to give a predetermined phase difference to zero-order diffracted light, so it can not give a predetermined phase difference to first-order or higher-order diffracted light. Therefore, when transmitted through the retardation plate, the polarization state of the first or higher order diffracted light is not optimized, and becomes different from the polarization state of the zeroth order diffracted light. Therefore, for example, when performing black display, the zeroth-order diffracted light is cut by the exit side polarizing plate, but a part of the first or higher order diffracted light is transmitted through the exit side polarizing plate, thereby reducing the contrast ratio of the displayed image I will do it.

  One aspect of the present invention is provided to solve the above-described problem, and provides a projector capable of improving the contrast ratio.

  According to the first aspect of the present invention, an illumination device for emitting illumination light, a uniform illumination optical system provided on the optical path of the illumination light, and an optical path of the illumination light transmitted through the uniform illumination optical system A liquid crystal light modulation device provided with a diffraction function and modulating the illumination light according to image information to generate image light composed of a plurality of diffracted lights; and the image light emitted from the liquid crystal light modulation device A retardation plate on which light is incident, a polarization plate on which the image light transmitted through the retardation plate is incident, and a projection optical system provided on an optical path of the image light transmitted through the polarization plate, The projection optical system includes a plurality of lenses and a light blocking element on which the image light is incident, and the light blocking element includes at least one light blocking portion and a plurality of light transmitting portions, and the plurality of light blocking elements One of the light transmitting portions is at least one of the image light. The at least one light shielding portion is provided in a region through which the zeroth order diffracted light passes, and the at least one light shielding portion is provided on the optical path of first or higher order diffracted light corresponding to the at least one zeroth order diffracted light passing through the light transmitting portion. Projectors are provided.

The zeroth-order diffracted light included in the image light emitted from the liquid crystal light modulation device is in a predetermined polarization state by transmitting through the retardation plate. On the other hand, the 1st or higher order diffracted light corresponding to the 0th order diffracted light passes through the retardation plate to be in a polarization state different from that of the 0th order diffracted light.
In the projector according to the present embodiment, the light shielding element can block the first or higher order diffracted light. As a result, it is possible to reduce the light leakage due to the first or higher order diffracted light in the case of black display, and as a result, it is possible to reduce the decrease in the contrast ratio.

  In the first aspect, it is preferable that the at least one light shielding portion be formed of a lattice-shaped light shielding member.

  According to this configuration, it is possible to effectively block the first or higher order diffracted light by the grid-like light shielding member. This can further reduce the decrease in the contrast ratio of the image.

  In the first aspect, the uniform illumination optical system includes: a first lens array that divides the illumination light into a plurality of partial light beams; and a second lens array provided downstream of the first lens array And a condenser lens provided downstream of the second lens array, wherein the light blocking element is provided in the vicinity of a position optically conjugate with the second lens array in the projection optical system. Is preferred.

  According to this configuration, since the light shielding element is disposed at a position where the zeroth order diffracted light and the first or higher order diffracted light are separated from each other, the zeroth order diffracted light is incident on the light transmitting portion with high efficiency, and the first order or more The diffracted light of the light enters the light shielding portion with high efficiency. Thus, the reduction in contrast ratio of the image can be further reduced.

FIG. 1 is a view showing a schematic configuration of a projector 1 according to a first embodiment. The figure which looked at the light-incident surface of the 1st lens array in the direction parallel to an optical axis. The figure which shows the secondary light source image formed in the 2nd small lens of a 2nd lens array. The elements on larger scale of a liquid crystal light modulation device. The figure for demonstrating typically the diffraction by a liquid-crystal light modulation apparatus. FIG. 7 schematically shows a part of a plurality of light source images formed at the stop position of the projection optical system. It is a figure showing composition of a projection optical system. FIG. 2 is a plan view showing the configuration of a light shielding element. FIG. 5 is an enlarged view showing a peripheral configuration of one light transmitting portion of the light shielding element. The figure for demonstrating the effect | action of a projector. FIG. 7 is a view showing a schematic configuration of a projector according to a second embodiment. The figure which shows the optical path of the light which injected into the rod. FIG. 6 schematically shows a light source image formed at the stop position of the projection optical system. The figure which shows the structure of the light shielding element which concerns on a modification. The figure which shows the structure of the light shielding element which concerns on a modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the drawings used in the following description, in order to make the features easy to understand, the features that are the features may be enlarged for the sake of convenience, and the dimensional ratio of each component may be limited to the same as the actual Absent.

First Embodiment
First, an example of a projector according to the present embodiment will be described.
FIG. 1 is a view showing a schematic configuration of a projector 1 according to the present embodiment.
As shown in FIG. 1, the projector 1 of the present embodiment is a projection type image display device that displays a color image on a screen SCR. The projector 1 includes an illumination device 2, a uniform illumination optical system 23, a color separation optical system 3, a liquid crystal light modulation device 4R, a liquid crystal light modulation device 4G, a liquid crystal light modulation device 4B, a combining optical system 5, and a projection optical system. The system 6 is provided.

  In the present embodiment, the lighting device 2 emits white light WL including blue light LB, green light LG, and red light LR. The white light WL corresponds to "illumination light" in the claims.

  The illumination device 2 of the present embodiment includes a light source lamp 21 that emits white light, and a reflector 22 having a paraboloidal reflection surface. The white light WL emitted from the light source lamp 21 is reflected by the reflector 22 in one direction to form a substantially parallel light flux.

  The light source lamp 21 is constituted of, for example, a metal halide lamp, a xenon lamp, an extra-high pressure mercury lamp, a halogen lamp or the like. The reflecting surface of the reflector 22 may be a spheroidal surface, and in this case, a collimating lens for collimating the white light WL emitted from the reflector 22 is separately combined and used.

  The uniform illumination optical system 23 is provided on the optical path of the white light WL emitted from the illumination device 2 and makes the illuminance of the white light WL in the illuminated area uniform. The uniform illumination optical system 23 includes a first lens array 24, a second lens array 25, a polarization conversion element 26, and a superimposing lens 27.

FIG. 2 is a view of the light incident surface of the first lens array 24 viewed in the direction parallel to the optical axis ax.
As shown in FIG. 2, the first lens array 24 has a plurality of first small lenses 24 a for dividing the white light WL into a plurality of partial light beams. The plurality of first small lenses 24 a are arranged in a matrix of M in length and N in number in a plane orthogonal to the optical axis ax of the light source lamp 21. For example, M = 7 and N = 6.
The outer shape of each first small lens 24a is substantially rectangular, which is substantially similar to the shape of the image forming area of liquid crystal light modulation devices 4R, 4G, 4B described later.

  The second lens array 25 includes a plurality of second small lenses 25 a corresponding to the plurality of first small lenses 24 a. That is, like the first lens array 24, the second lens array 25 has a configuration in which the second small lenses 25a are arranged in a matrix of M in length and N in number in a plane orthogonal to the optical axis ax. Have (see Figure 3).

  The second lens array 25 forms an image of each first small lens 24 a of the first lens array 24 in the vicinity of the image forming area of the liquid crystal light modulation devices 4 R, 4 G, 4 B together with the superimposing lens 27.

  The outer shape of the second small lens 25a may not necessarily be substantially similar to the shape of the image forming area of the liquid crystal light modulation devices 4R, 4G, 4B, but is substantially similar in the present embodiment.

  The partial light beams emitted from the respective first small lenses 24 a of the first lens array 24 form an image on the second small lenses 25 a corresponding to the first small lenses 24 a.

  FIG. 3 is a view showing a secondary light source image formed on the second small lens 25 a of the second lens array 25. As shown in FIG. 3, the secondary light source image 30 of the light source 20 is formed on each of the second small lenses 25a.

  The polarization conversion element 26 has a plurality of cells one-dimensionally arranged in a plane orthogonal to the optical axis ax of the light source 20. Each cell has a polarization separation film, a half wave plate, and a reflection mirror. The partial luminous flux emitted from the second small lens 25 a enters one of the cells of the polarization conversion element 26.

  The partial luminous flux incident on the cell of the polarization conversion element 26 is split into P-polarization and S-polarization with respect to the polarization separation film. The separated S-polarized light passes through the half-wave plate after being reflected by the reflection mirror and is converted into P-polarized light.

  The plurality of partial light beams emitted from the polarization conversion element 26 are superimposed by the superimposing lens 27 on the image forming areas of the liquid crystal light modulators 4R, 4G, 4B. The superposing lens 27 corresponds to the "condensing lens" described in the claims.

  The color separation optical system 3 separates white light WL composed of a plurality of partial light beams into red light LR, green light LG, and blue light LB. The color separation optical system 3 includes a first dichroic mirror 7a and a second dichroic mirror 7b, a first total reflection mirror 8a, a second total reflection mirror 8b and a third total reflection mirror 8c, and a first color reflection optical system. A relay lens 9a and a second relay lens 9b are provided.

  The first dichroic mirror 7a separates the white light WL from the illumination device 2 into red light LR and the other light (green light LG and blue light LB). The first dichroic mirror 7a transmits the red light LR and reflects the other light. The second dichroic mirror 7b reflects the green light LG and transmits the blue light LB.

  The first total reflection mirror 8a reflects the red light LR toward the liquid crystal light modulation device 4R. The second total reflection mirror 8b and the third total reflection mirror 8c guide the blue light LB to the liquid crystal light modulation device 4B. The green light LG is reflected from the second dichroic mirror 7b toward the liquid crystal light modulator 4G.

  The first relay lens 9a and the second relay lens 9b are disposed downstream of the second dichroic mirror 7b in the optical path of the blue light LB.

  The liquid crystal light modulation device 4R modulates the red light LR according to the image information to form red image light IR. The liquid crystal light modulation device 4G modulates the green light LG in accordance with the image information to form green image light IG. The liquid crystal light modulation device 4B modulates the blue light LB in accordance with the image information to form blue image light IB.

  For example, a transmissive liquid crystal panel is used for the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G, and the liquid crystal light modulation device 4B. The liquid crystal panel includes, for example, a liquid crystal layer provided between a TFT substrate and a counter substrate facing the TFT substrate. The liquid crystal panel has a function as a diffraction grating due to its structure.

  A field lens 10R, a field lens 10G, and a field lens 10B are disposed on the light incident side of the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G, and the liquid crystal light modulation device 4B, respectively. The principal rays of the partial light fluxes are substantially vertically incident on the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G, and the liquid crystal light modulation device 4B in a substantially parallel state.

  In the present embodiment, a light incident side polarization plate 60R, a light incident side is provided between the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G and the liquid crystal light modulation device 4B and the field lens 10R, the field lens 10G and the field lens 10B. The polarizing plate 60G and the light incident side polarizing plate 60B are respectively disposed.

  The light incident side polarizing plate 60R, the light incident side polarizing plate 60G, and the light incident side polarizing plate 60B are disposed corresponding to the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G, and the liquid crystal light modulation device 4B, respectively. Each of the light incident side polarizing plate 60R, the light incident side polarizing plate 60G and the light incident side polarizing plate 60B transmits light of a predetermined polarization state.

  In the present embodiment, a light emitting side polarizing plate 61R is disposed between the liquid crystal light modulation device 4R and the combining optical system 5. A light emitting side polarizing plate 61 G is disposed between the liquid crystal light modulator 4 G and the combining optical system 5. A light emitting side polarizing plate 61 B is disposed between the liquid crystal light modulation device 4 B and the combining optical system 5. Each of the light emitting side polarizing plate 61R, the light emitting side polarizing plate 61G and the light emitting side polarizing plate 61B transmits light of a predetermined polarization state.

  By the way, for example, the partial light beam incident on the liquid crystal light modulation device 4R includes a nonparallel component nonparallel to the chief ray of the partial light beam and a parallel component parallel to the chief light beam. Since the incident angle of the parallel component to the liquid crystal layer of the liquid crystal light modulation device 4R is different from the incident angle of the non-parallel component to the liquid crystal layer, after transmitting through the liquid crystal layer, the polarization state of the nonparallel component is the polarization state of the parallel component It is different from

  Therefore, the polarization state of the non-parallel component and the polarization state of the parallel component, that is, the polarization state of the image light IR are determined by the retardation compensation plate 55R disposed between the liquid crystal light modulation device 4R and the light emission side polarization plate 61R. adjust. The retardation compensation plate 55R can give a predetermined phase difference to light of a predetermined incident angle, but gives a predetermined phase difference to light of an incident angle that is not a predetermined incident angle. Can not do it. In the present embodiment, the retardation compensation plate 55R imparts a predetermined phase difference to light traveling along the same direction as the zeroth-order diffracted light. In other words, the retardation compensation plate 55R can not adjust the polarization state of the first or higher order diffracted light to a desired polarization state. That is, the polarization state can not be adjusted to a desired state for both zero-order light and first-order or higher-order diffracted light emitted from the liquid crystal light modulation device 4R at different angles.

  A retardation compensation plate 55G is disposed between the liquid crystal light modulation device 4G and the light emission side polarization plate 61G. A retardation compensation plate 55B is disposed between the liquid crystal light modulation device 4B and the light emission side polarization plate 61B. Similar to the retardation compensation plate 55R, the retardation compensation plate 55G and the retardation compensation plate 55B respectively adjust the polarization states of the image light IG and the image light IB. In the present embodiment, the retardation compensation plate 55R, the retardation compensation plate 55G, and the retardation compensation plate 55B correspond to the “retardation plate” described in the claims.

  The image light IR whose polarization state is adjusted by the retardation compensation plate 55R is transmitted through the light emission side polarization plate 61R, and the image light IG transmitted through the emission side polarization plate 61G and the image light IB transmitted through the emission side polarization plate 61B. And the light is incident on the synthetic optical system 5. For example, a cross dichroic prism is used for the combining optical system 5. For example, a cross dichroic prism is used for the combining optical system 5.

  The combining optical system 5 combines the respective image lights, and emits the combined image light toward the projection optical system 6. The projection optical system 6 includes a projection lens group, and enlarges and projects the image light combined by the combining optical system 5 toward the screen SCR. Thereby, the enlarged color image is displayed on the screen SCR.

  Hereinafter, the liquid crystal light modulation device 4R, the liquid crystal light modulation device 4G, and the liquid crystal light modulation device 4B are simply referred to as the liquid crystal light modulation device 4 when not particularly distinguished. Further, when the image lights IR, IG, and IB are not particularly distinguished, they are simply referred to as image light IL. Further, the retardation compensation plate 55R, the retardation compensation plate 55G and the retardation compensation plate 55B are simply referred to as a retardation compensation plate 55 when not particularly distinguished. In addition, the light emitting side polarizing plate 61R, the light emitting side polarizing plate 61G, and the light emitting side polarizing plate 61B are simply referred to as a light emitting side polarizing plate 61 when not particularly distinguished.

  FIG. 4 is a partially enlarged view of the liquid crystal light modulation device 4. FIG. 5 is a view for schematically explaining the diffraction by the liquid crystal light modulation device 4.

  As shown in FIG. 4, the liquid crystal light modulation device 4 includes a plurality of pixels 51 forming an image, and a black matrix 52 formed between the pixels 51 and having a light shielding property.

  Since the plurality of partial light beams enter the liquid crystal light modulator 4 from different directions, the liquid crystal light modulator 4 emits a plurality of zero-order diffracted lights in different directions. However, FIG. 5 illustrates the diffraction phenomenon of the partial light beam vertically incident on the liquid crystal light modulation device 4.

As shown in FIG. 5, the light emitted from the liquid crystal light modulation device 4 is composed of zeroth-order diffracted light and first- or higher-order diffracted light (eg, ± 1st-order diffracted light). That is, the liquid crystal light modulation device 4 generates image light IL composed of a plurality of diffracted lights.
Although the image light IL (one diffracted light) shown in FIG. 5 is composed of a light beam bundle including the number of light rays in proportion to the number of the pixels 51 of the liquid crystal light modulation device 4, in the present specification I will call it ".

  As the first or higher order diffracted light, there are also second order diffracted light and third or higher order diffracted light, but generally, the intensity of the second order diffracted light or the third order or higher diffracted light is greater than the intensity of the first order diffracted light Too weak. Therefore, in the present embodiment, attention is focused on first order diffracted light. The influence of second or higher order diffracted light can be ignored. However, when there is diffracted light whose intensity is higher than that of the first-order diffracted light in the second- or higher-order diffracted light, attention should be paid to the diffracted light.

  In the present embodiment, as described above, the retardation compensation plate 55 is designed to give a predetermined phase difference to light emitted from the liquid crystal light modulation device 4 along the same direction as the zeroth-order diffracted light. There is. That is, although the retardation compensation plate 55 adjusts the polarization state of the zeroth-order diffracted light included in the image light IL to a desired polarization state, it can not adjust the polarization state of the first-order diffracted light to a desired polarization state. Therefore, at the rear stage of the retardation compensation plate 55, the polarization state of the first-order diffracted light is different from the polarization state of the zero-order diffracted light.

Here, a case where black display is performed in the projector 1 will be considered.
When performing black display, the liquid crystal light modulation device 4 adjusts the polarization state of the zeroth-order diffracted light so that the zeroth-order diffracted light passes through the retardation compensation plate 55 and is blocked by the light emitting side polarizing plate 61.

  However, the polarization state of the first-order diffracted light is not adjusted by the retardation compensation plate 55 to a desired polarization state. Therefore, as described above, the polarization state of the first-order diffracted light is different from the polarization state of the zero-order diffracted light in the rear stage of the retardation compensation plate 55. Therefore, at least a part of the zero-order diffracted light passes through the light emitting side polarizing plate 61, and the contrast ratio of the image displayed on the screen SCR is lowered.

In the present embodiment, the stop position of the projection optical system 6 is optically conjugate with the light exit surface (the second small lens 25 a) of the second lens array 25.
Therefore, the partial luminous fluxes that have passed through the respective second small lenses 25 a form an image at the diaphragm position 6 a (see FIG. 1) of the projection optical system 6 through the liquid crystal light modulation device 4. Therefore, in the same way as the plurality of secondary light source images 30 are formed on the second lens array 25, a plurality of light source images are formed at the diaphragm position 6 a of the projection optical system 6.

  FIG. 6 is a view schematically showing a part of a plurality of light source images formed at the stop position 6 a of the projection optical system 6. The light source image 31 shown in FIG. 6 is a light source image of a partial light beam transmitted through the second small lens 25a1 located at the uppermost side and the rightmost side of the second lens array 25 shown in FIG.

As shown in FIG. 6, the partial light beam is diffracted by the liquid crystal light modulator 4 to form a light source image 31 of zeroth-order diffracted light, and a plurality of light source images 32 of first-order diffracted light (for example, , Light source images 32a, 32b, 32c, 32d).
Note that FIG. 6 illustrates a part of the light source image 32 of the first order diffracted light formed around the light source image 31 of the zero order diffracted light, and the number of light source images 32 is not limited to four.

  The plurality of first-order diffracted lights forming the light source images 32 a to 32 d reduce the contrast ratio of the image as described above. As shown in FIG. 3, there are M × N second small lenses 25 a of the second lens array 25. Therefore, although illustration is omitted here, a plurality of light source images by the first-order diffracted light around the zeroth-order diffracted light are also diffracted by the liquid crystal panel 50 that the respective partial light fluxes passing through the other second small lenses 25a are also diffracted. Form. That is, M × N light source images are formed by 0th order diffracted light, and a plurality of light source images by ± 1st order diffracted lights are formed around each of the light source images by each 0th order diffracted light.

  On the other hand, in the projector 1 of the present embodiment, a light shielding element described later is disposed in the vicinity of the diaphragm position 6a of the projection optical system 6 which is a position optically conjugate with the second lens array 25, The ratio is improved.

FIG. 7 is a view showing the configuration of the projection optical system 6 of the present embodiment.
As shown in FIG. 7, the projection optical system 6 of the present embodiment has a plurality of lenses 40 and 41, a light shielding element 45, and a main body 49 that holds the lenses 40 and 41 and the light shielding element 45. .

  The light blocking element 45 is disposed in the vicinity of the diaphragm position 6 a which is an optically conjugate position with the second lens array 25 in the projection optical system 6 (inside of the main body 49). In the projection optical system 6, the number of the plurality of lenses 40 and 41 constituting the projection lens is not limited to two.

  FIG. 8A is a plan view showing the configuration of the light shielding element 45. FIG. FIG. 8A is a plan view of the light shielding element 45 as viewed from the incident side of the image light IL along the surface normal direction of the light incident surface of the light shielding element 45. FIG.

  As shown in FIG. 8A, the light blocking element 45 has a light blocking portion 46 and a plurality of light transmitting portions 47. The constituent material of the light shielding portion 46 is not particularly limited as long as it exhibits a light shielding property to incident light. The constituent material of the light transmitting portion 47 is not particularly limited as long as it does not exhibit birefringence with respect to incident light. For example, a transparent substrate or an air layer can be used.

  In the present embodiment, the plurality of light transmitting portions 47 are provided at positions where the plurality of zero-order diffracted lights pass, specifically, at positions where the plurality of light source images 31 are formed. The light transmitting portion 47 has, for example, a rectangular shape.

  The number of light source images 31 is the same as the number of second small lenses 25a. Therefore, in the present embodiment, the number of light transmission parts 47 is the same as the number of second small lenses 25a.

  In the present embodiment, as described above, the light blocking element 45 is disposed in the vicinity of a position optically conjugate with the second lens array 25 in the projection optical system 6, that is, in the vicinity of the position where the light source images 31, 32 are formed. It is arranged. That is, the light shielding element 45 is disposed at a position where the zeroth order diffracted light and the first order diffracted light are separated from each other. Therefore, the zero-order diffracted light is incident on the light transmitting portion 47 with high efficiency and transmitted through the light transmitting portion 47, and the first-order diffracted light is incident on the light shielding portion 46 with high efficiency and blocked by the light shielding portion 46. Therefore, the reduction in contrast ratio of the image due to the diffraction effect of the liquid crystal light modulation device 4 can be reduced.

  As shown in FIG. 8A, the light shielding portion 46 is formed of a lattice-shaped light shielding member. The light shielding portion 46 surrounds the periphery of each light transmitting portion 47. The plurality of light transmission parts 47 are provided in the area divided by the grid-like light shielding part 46.

  FIG. 8B is an enlarged view showing one light transmitting portion 47 and the structure around it. The light transmitting portion 47 shown in FIG. 8B corresponds to the light source image shown in FIG.

  As shown in FIG. 8B, a light source image 31 of zeroth-order diffracted light is formed in the light transmitting portion 47. The light transmitting portion 47 transmits the zero-order diffracted light without changing the polarization state.

  The light shielding portion 46 is provided on the optical path of the first order diffracted light corresponding to the zeroth order diffracted light entering the light transmitting portion 47. That is, the light source images 32a, 32b, 32c, and 32d of the four first-order diffracted lights corresponding to the zero-order diffracted lights are provided. Thus, each first-order diffracted light is blocked by the light blocking portion 46.

  The first-order diffracted light is formed obliquely in addition to the top, bottom, left, and right with respect to the zero-order diffracted light. Therefore, in a diagonally outer area (hereinafter referred to as a diagonal area) at the corner of the light transmitting portion 47, the first or higher order first corresponding to the first zero-order diffracted light of the plurality of zero-order diffracted lights In some cases, a light source image of the diffracted light and a light source image of the first or more second diffracted light corresponding to the second 0 th diffracted light among the plurality of 0 th diffracted lights may be formed.

  In the light shielding element 45 of the present embodiment, the light shielding portion 46 surrounding the periphery of the light transmitting portion 47 is provided, so that the first or higher order diffracted light entering the diagonal area is reliably shielded by the light shielding portion 46. Therefore, the contrast ratio of the image can be further improved.

  FIG. 9 is a schematic view for explaining the operation of the projector 1. Although the light shielding element 45 actually includes a plurality of light transmitting parts 47, one zeroth-order diffracted light IL0 included in the image light IL and the zeroth-order diffracted light IL0 are incident to avoid complexity of the drawing. Only the light transmitting portion 47 is illustrated.

  When black display is performed in the projector 1 of the present embodiment, as shown in FIG. 9, the zeroth-order diffracted light IL0 passes through the retardation compensation plate 55 to become zero-order diffracted light IL0p in a predetermined polarization state.

  The zero-order diffracted light IL 0 p is incident on the light emitting side polarizing plate 61. Since the polarization state of the zeroth-order diffracted light IL0p is properly adjusted, the zeroth-order diffracted light IL0p is blocked by the light emission side polarizing plate 61.

  On the other hand, the polarization state of the first-order diffracted light IL1, which is -1st-order diffracted light corresponding to the 0th-order diffracted light IL0, is not properly adjusted by the retardation compensation plate 55, and thus the polarization state is the polarization state of the 0th-order diffracted light IL0p. It is different. Therefore, at least a part of the component of the first-order diffracted light IL1 passes through the light emitting side polarizing plate 61. However, the component transmitted through the light emitting side polarizing plate 61 is shielded by the light shielding portion 46.

  This makes it possible to prevent the first-order diffracted light IL1 from being projected onto the screen SCR when performing black display. The above effects can also be obtained for the other zeroth-order diffracted light IL0 included in the image light IL and the first-order diffracted light IL1 incidental thereto. Therefore, the reduction in contrast ratio due to the diffraction effect of the liquid crystal light modulation device 4 can be reduced.

Second Embodiment
Subsequently, a projector according to a second embodiment will be described. The same reference numerals as in the above embodiment denote the same parts as in the above embodiment, and a detailed description will be omitted.

  FIG. 10 is a view showing a schematic configuration of the projector 101 of the present embodiment. As shown in FIG. 10, the projector 101 of this embodiment includes the illumination device 2, uniform illumination optical system 123, color separation optical system 3, liquid crystal light modulation device 4R, liquid crystal light modulation device 4G, liquid crystal light modulation device 4 B, a combining optical system 5, and a projection optical system 6.

  In the present embodiment, the uniform illumination optical system 123 includes a condensing lens 70, a rod 71 provided downstream of the condensing lens 70, and a pickup optical system 72 provided downstream of the rod 71. .

  FIG. 11 is a view showing an optical path of light incident on the rod 71. As shown in FIG. The rod 71 is a quadrangular prism-shaped optical member having a longitudinal direction in a direction parallel to the optical axis ax of the illumination device 2. The rod 71 has an incident end surface 71a, an inner surface 71b and an exit end surface 71c. The incidence end surface 71a and the emission end surface 71c are substantially parallel to each other, and substantially orthogonal to the optical axis ax. The inner surface 71 b is an inner surface of a side surface connecting the incident end surface 71 a and the emission end surface 71 c, and is substantially parallel to the optical axis ax of the lighting device 2.

  The incident end face 71 a is disposed, for example, at or near a position where a light source image is formed by the condensing lens 70. The white light WL emitted from the illumination device 2 is incident on the incident end face 71 a via the condenser lens 70.

  The light incident on the incident end surface 71 a of the rod 71 is guided to the emission end surface 71 c by multiple reflection on the inner surface 71 b. The number of reflections of light on the inner surface 71b differs for each angle component, and the number of reflections of the wide-angle component is greater than the number of reflections of the telephoto component.

  On the exit end face 71c of the rod 71, the light flux with the number of reflections on the inner surface 71b is zero (i.e., the light flux that travels straight through the rod 71), the light flux Lb with one reflection frequency as shown in FIG. A plurality of light beams having different numbers of reflections, such as two light beams Lc, are superimposed, whereby the illuminance distribution at the emission end surface 71c is made uniform.

  In the present embodiment, the image forming area of the liquid crystal light modulation device 4 is set to be optically conjugate with the emission end face 71 c of the rod 71. Therefore, the illuminance distribution is uniformed also in the image forming area of the liquid crystal light modulation device 4.

  As shown in FIG. 11, a plurality of light beams having different numbers of reflections on the inner surface 71 b enter each point of the emission end surface 71 c of the rod 71. Therefore, when observed from the side of the emission end surface 71c of the rod 71, it appears that the real image Im1 of the light source image and the plurality of virtual images Im2 are arranged on the surface including the incident end surface 71a.

  In the present embodiment, the stop position 6 a of the projection optical system 6 is set to be optically conjugate with the incident end face 71 a of the rod 71. Therefore, the light from the incident end face 71a of the rod 71 forms a light source image at the stop position 6a.

  If the liquid crystal light modulation device 4 does not have a diffractive function, a secondary light source image consisting of one real image Im1 and a plurality of virtual images Im2 arranged around the real image Im1 is formed at the diaphragm position 6a.

FIG. 12 is a view schematically showing a light source image formed at the diaphragm position 6a when the liquid crystal light modulation device 4 has a diffractive function.
As shown in FIG. 12, the real image Im1 forms a light source image 131 by zero-order diffracted light. In addition, each virtual image Im2 forms a light source image 231 by 0th order diffracted light.
Although FIG. 12 exemplifies the case where 24 virtual images Im2 are formed around the real image Im1, the number of virtual images Im2 is not limited to this.

  A plurality of light source images 132 (for example, light source images 132a, 132b, 132c, 132d) by first-order diffracted light accompanying the real image Im1 are formed around the light source image 131 by the zero-order diffracted light. A plurality of light source images 232 (for example, light source images 232a, 232b, 232c, and 232d) of first-order diffracted light accompanying the virtual image Im2 are formed around the light source image 231 of the zeroth-order diffracted light. In FIG. 12, a part of a light source image by a plurality of first-order diffracted lights is illustrated. The number of each of the light source images 132 and 232 is not limited to four.

  The plurality of first-order diffracted lights forming the light source images 132a to 132d and the light source images 232a to 232d reduce the contrast ratio of the image.

  On the other hand, in the projector 101 according to the present embodiment, the light blocking element 45 is disposed in the vicinity of the stop position 6a optically conjugate with the incident end face 71a of the rod 71 to improve the contrast ratio of the image. The configuration of the light shielding element 45 is the same as that shown in FIG. 8A, and the detailed description will be omitted.

  In the present embodiment, the plurality of light transmitting portions 47 are positions where the 0th order diffracted light corresponding to the real image Im1 passes (positions of the light source image 131) and positions where the 0th order diffracted light corresponding to the virtual image Im2 passes (light source image And the formation position 231).

  The light shielding portion 46 is provided in a region through which first order diffracted light corresponding to zeroth order diffracted light incident on the light transmitting portion 47 passes. That is, the light source image 132 or the light source image 232 is provided at the formation position of the four first-order diffracted lights corresponding to the zero-order diffracted light.

  Also in the present embodiment, the first-order diffracted light that forms the light source image 132 or the light source image 232 can be blocked by the light blocking unit 46.

  According to the projector 101 of the present embodiment, even in the structure using the uniform illumination optical system 123 having the rod 71, by providing the light shielding element 45 at a position optically conjugate with the incident end face 71a of the rod 71, the first As in the embodiment, an image with a high contrast ratio can be displayed.

  The present invention is not limited to the contents of the above-described embodiment, and can be appropriately modified without departing from the scope of the invention.

  For example, in the first embodiment, the case where one light source image of zeroth-order diffracted light is formed for one light transmitting portion 47 is described as an example. However, for example, when the pixel pitch of the liquid crystal light modulator 4 in one direction is small, there may be a case where the zeroth order diffracted light and the first order diffracted light corresponding to the zeroth order diffracted light next to the zero order diffracted light overlap each other in one direction. is there. In this case, it is difficult to arrange the light shielding portion 46 at the position of the light source image by the first order diffracted light.

  In this case, for example, as shown in FIG. 13, it is preferable to adopt a light shielding element 145 having a plurality of light transmitting portions 147 having a longitudinal direction in the one direction. The light shielding portion 46 of the light shielding element 145 does not have a useless area that does not contribute to the light shielding of the first-order diffracted light, and therefore the cost is lower than that of the light shielding element 45 described above. Further, as shown in FIG. 14, a plurality of light shielding portions 246 may be disposed, and a region between two adjacent light shielding portions 246 may be used as the light transmitting portion 47. In this case, the light blocking element 245 has a structure including a plurality of light blocking portions 246 and a plurality of light transmitting portions 247.

  Moreover, in the said embodiment, although the structure which several 1st order diffracted light injects into the one light-shielding part 46 was mentioned as the example, this invention is not limited to this. For example, a plurality of light shields may be provided corresponding to each first-order diffracted light. That is, the shape and the number of at least one light shielding portion are not limited.

  Further, in the above-described embodiment, although the case where the light shielding portion 46 shields only the first order diffracted light has been described, for example, second order or higher order diffracted light may also be shielded. The contrast ratio can be further improved by blocking second- or higher-order diffracted light.

  Moreover, in the said embodiment, although the example which used the light source lamp 21 as the illuminating device 2 was mentioned, this invention is not limited to this. For example, a solid light source may be used as the lighting device. When a semiconductor laser is used as a light source, linearly polarized light is emitted from the illumination device, so the light incident side polarizing plate 60R, the light incident side polarizing plate 60G, and the light incident side polarizing plate 60B may be omitted.

  Further, in the above embodiment, the projector 1 including the three liquid crystal light modulation devices 4R, 4G, and 4B is illustrated, but the present invention can be applied to a projector that displays a color image with one light modulation device. .

  DESCRIPTION OF SYMBOLS 1, 101 ... Projector, 2 ... Illuminator, 4, 4B, 4G, 4R ... Liquid crystal light modulator, 6 ... Projection optical system, 23, 123 ... Uniform illumination optical system, 24 ... 1st lens array, 25 ... The 1st 2 lens array 40, lens 45, 145, 245 light shielding element 46, 146, 246 light shielding portion 47, 147 light transmitting portion 55, 55B, 55G, 55R phase difference compensator (phase difference Plates, 70: Condenser, IB, IG, IL, IR: Image light, IL0, IL0p: 0th order diffracted light, IL1, IL1p: 1st order diffracted light, WL: White light (illumination light).

Claims (3)

An illumination device for emitting illumination light;
Uniform illumination optical system provided on a light path of the illumination light;
Liquid crystal light modulation provided on the optical path of the illumination light transmitted through the uniform illumination optical system, having a diffractive function, and modulating the illumination light according to image information to generate image light composed of a plurality of diffracted lights A device,
A retardation plate on which the image light emitted from the liquid crystal light modulation device is incident;
A polarizing plate on which the image light transmitted through the retardation plate is incident;
And a projection optical system provided on the light path of the image light transmitted through the polarizing plate,
The projection optical system includes a plurality of lenses and a light blocking element on which the image light is incident,
The light blocking element includes at least one light blocking portion and a plurality of light transmitting portions.
One of the plurality of light transmitting portions is provided in a region through which at least one zero-order diffracted light of the image light passes.
The at least one light shielding portion is provided on an optical path of primary or higher order diffracted light corresponding to the at least one zero-order diffracted light passing through the light transmitting portion. Projector. The projector according to claim 1, wherein the at least one light blocking portion is formed of a grid-like light blocking member. The uniform illumination optical system comprises: a first lens array for dividing the illumination light into a plurality of partial light beams; a second lens array provided at a later stage of the first lens array; and the second lens And a condenser lens provided downstream of the array;
The projector according to claim 1, wherein the light blocking element is provided in the vicinity of a position optically conjugate with the second lens array in the projection optical system.

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