JP2008122767A - Projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type display device that has a wide dynamic range by allowing an increase and decrease in only a quantity of light without increasing or decreasing the number of fly eye cells or peripheral luminous fluxes. <P>SOLUTION: In the projection type display device, light from a light source 10 is divided into luminous fluxes by a fly eye integrator including first and second fly eye lenses 13 and 14. Each of the luminous fluxes converges and enters a polarization conversion element 15. Light emitted after its polarizing direction is aligned is modulated by liquid crystal display elements OR, 20G and 20B so as to correspond to image signals, and the image light thus produced is enlarged and projected by a projection lens 30. A variable diaphragm mechanism 40 for varying a luminous flux width is disposed between the emission face of the second fly eye lens 14 and the polarization conversion element 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projection display device.

  There is known a projection display apparatus that receives illumination light output from an illumination optical system and modulates the illumination light to generate image light and project the generated image light on a screen.

  In this projection display device, a typical configuration of a projection display device capable of color display is known that uses three primary colors of red (R), green (G), and blue (B). . FIG. 8 is a schematic diagram showing a dichroic prism type three-plate liquid crystal panel (3LCD) projection display device as a conventional projection display device.

  A dichroic prism type 3LCD projection display device will be described with reference to FIG. The light source 101 of the 3LCD projection display device 100 includes a high-pressure mercury lamp 101a and a parabolic reflector 101b that converts the white light emitted from the lamp 101a into a substantially parallel light flux. The light emitted from the light source 100 is removed by a UVIR filter (not shown) to reduce the thermal load on the subsequent optical member.

  The light emitted as parallel light by the parabolic reflector 100b is split into light beams by a so-called fly eye integrator including first and second fly eye lenses 103 and 104 formed of a convex lens group. The respective light beams converge and enter the polarization conversion element 105, and are emitted with the polarization directions aligned.

  Then, the light whose polarization directions are aligned passes through the condenser lens 106 and the like, and then the red to green band light is transmitted by the dichroic mirror 107 and the blue band light is reflected.

  The blue band light reflected by the dichroic mirror 107 and whose optical path is changed by 90 degrees is changed by the total reflection mirror 108 and the optical path is changed by 90 degrees and is incident on the blue liquid crystal display element 120B for displaying the blue band light component image via the field lens 109B. Here, the light is modulated according to the input signal.

  The light modulated light enters the dichroic prism 121, enters the projection lens 130 with the optical path changed by 90 degrees in the dichroic prism 121, is enlarged and projected, and is imaged on a screen (not shown).

  On the other hand, the red to green band light transmitted through the dichroic mirror 107 enters the dichroic mirror 112. Since the dichroic mirror 112 has a characteristic of reflecting the green band light, the green band light is reflected here, the optical path is changed by 90 degrees, and the green band light component image is displayed via the field lens 119G. The light enters the liquid crystal display element 120G and is optically modulated according to the input signal. The light-modulated green band light enters the dichroic prism 121 and the projection lens 130 in this order, and is enlarged and projected to form an image on the screen.

  The red band light transmitted through the dichroic mirror 112 is incident on the red liquid crystal display element 120R for displaying the red band light component image from the field lens 129R via the lenses 123 to 124 and the total reflection mirrors 126 and 127, where the input signal The light is modulated in response to. The light-modulated red band light is incident on the dichroic prism 121, is incident on the projection lens 130 with the optical path changed by 90 degrees by the dichroic prism 121, is enlarged and projected, and is imaged on the screen.

  Each of the liquid crystal display elements 120B, 120G, and 120R includes an incident side polarizing plate PI, a liquid crystal LC, and an output side polarizing plate PO. The liquid crystal display element is provided with an incident side polarizing plate PI and an output side polarizing plate PO.

  In the above-described projection display device, the brightness of the projected image is increased in order to obtain a more easily viewable screen.

  A method of adjusting luminance and contrast by changing the brightness of illumination light according to the surrounding environment is used. As a method of changing the brightness of the illumination light, there is a method of limiting the luminous flux with a variable stop. As shown in FIG. 8, the variable stop 140 b is provided in the illumination optical system, or the variable stop 140 is provided in the projection lens 30. In addition, a projection display device has been proposed in which a variable stop is provided in both the illumination optical system and the projection lens. Patent Document 1 discloses an example in which a variable stop is provided between the illumination optical system and the projection lens.

As described above, in the projection display device, a light beam split by a so-called fly eye integrator is used. Patent Document 2 discloses a variable aperture provided between the fly-eye integrator and the polarization conversion element group, and a variable aperture provided between the fly-eye integrators.
Japanese Patent Laid-Open No. 2005-3744 JP 2002-72361 A (FIGS. 1 and 5)

  The configuration disclosed in Patent Document 2 uses a fly eye integrator that divides illumination light into a plurality of light beams and then superimposes the divided light beams for illumination. Then, the divided light flux is shielded from the peripheral portion by a variable diaphragm. In this case, a light beam that is shielded from light and a light beam that is not shielded are superimposed on the surface to be irradiated. Thereby, the phenomenon of non-uniform illuminance distribution on the irradiated surface can be alleviated to some extent. However, fly eye integrators are optically designed on the assumption that a uniform illuminance distribution is obtained by superimposing a plurality of light beams that are generally not shielded at all. For this reason, in a general integrator, if a part of the divided light flux is shielded, the balance of the illuminance distribution is lost and uniform illuminance cannot be obtained. In particular, the illuminance distribution collapses significantly when the light shielding area becomes large with respect to the divided light flux.

  Further, in the configuration shown in FIG. 5 among the configurations disclosed in Patent Document 2, a plurality of circular apertures are provided at the fly-eye lens arrangement pitch in the direction in which the fly-eye lenses are arranged, and the wings that shield the apertures are provided. A diaphragm unit provided with is arranged between the fly eye integrators. However, in such a configuration, when there is a change in the number of fly-eye lens cells, there is a problem that it is necessary to prepare a shielding plate having an opening corresponding to each change.

  The present invention has been made in view of the above-described conventional problems, and provides a projection display device having a wide dynamic range that can increase or decrease only the amount of light without increasing or decreasing the number of fly-eye cells and the peripheral luminous flux. This is the issue.

  In the present invention, light from a light source is split by a fly-eye integrator, and each light beam converges and enters a polarization conversion element. A projection-type display device that modulates and modulates generated image light with a projecting means, and has a variable aperture mechanism for changing a light beam width in the vicinity of the polarization conversion element. .

  The variable aperture mechanism may have a slit-like opening corresponding to the pitch of the polarization conversion element, and the opening width may be variable.

  The variable aperture mechanism may be disposed between the exit surface of the fly eye integrator and the polarization conversion element or on the exit surface side of the polarization conversion element.

  The variable aperture mechanism may be configured such that the movable slit plate is slidable relative to the fixed slit plate, and the light beam aperture width changes corresponding to the video signal.

  In the present invention, by providing a variable aperture mechanism that can change the aperture width in the vicinity of the polarization conversion element, it is possible to increase or decrease only the amount of light without increasing or decreasing the number of fly-eye cells and peripheral light flux, and a wide dynamic range. A projection display device can be provided.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a projection display device according to the first embodiment of the present invention, and FIGS. 2 and 3 are main parts of the projection display device according to the first embodiment of the present invention. FIG. 4 is a schematic view showing a diaphragm mechanism used in the projection display device according to the first embodiment of the present invention, and FIG. 5 is a projection display according to the first embodiment of the present invention. FIG. 6 is a block diagram showing a control circuit for the diaphragm mechanism used in the projection display apparatus according to the first embodiment of the present invention. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated in order to avoid duplication of description.

  In the present invention, as shown in FIG. 1, the light of the light source 10 is separated into three colors of red (R), green (G), and blue-blue by a color separation optical system, and each light is given to a light modulation element. After modulating with the color signal of each color, it is given to the color synthesis means. The light combining means combines the three colors of video light and projects the light from the projection lens 30 onto the screen.

  In this embodiment, the light emitted as parallel light by the parabolic reflector 2 is split by a so-called fly eye integrator composed of first and second fly eye lenses 13 and 14 formed of convex lens groups. Is done. Each light beam converges and enters the polarization conversion element 15, and is emitted with the polarization directions aligned.

  In the present invention, a slit corresponding to the pitch of the polarization conversion element 15 in the vicinity of the polarization conversion element 15, that is, in the first embodiment, between the second fly-eye lens 14 and the polarization conversion element 15. A variable aperture mechanism 40 is provided which has a shaped opening and is configured so that the opening width can be varied. As will be described later, the variable aperture mechanism 40 is configured such that the movable slit plate can be slid relative to the fixed slit plate, and the light beam aperture width is changed in accordance with the video signal or the like. . By providing the variable aperture mechanism 40 configured so that the aperture width can be varied in the vicinity of the polarization conversion element 15, it is possible to increase / decrease only the light amount without increasing / decreasing the number of fly-eye cells and the peripheral luminous flux.

  As described above, the polarization conversion element 15 is disposed between the variable aperture mechanism 40 and the condenser lens 16, and the condenser lens 16 is disposed between the polarization conversion element 15 and the dichroic mirror 17.

  The dichroic mirror 17 is disposed between the total reflection mirror 18 and the dichroic mirror 22 and the condenser lens 16. The total reflection mirror 18 is disposed between the dichroic mirror 17 and the condenser lens 19B.

  The condenser lens 19B is disposed between the total reflection mirror 18 and the liquid crystal display element 20B. The condenser lens 19G is disposed between the liquid crystal display element 20G and the dichroic mirror 22. The condenser lens 19R is disposed between the liquid crystal display element 20R and the total reflection mirror 27.

  The liquid crystal display element 20B is disposed between the condenser lens 19B and the dichroic prism 21. The liquid crystal display element 20G is disposed between the condenser lens 19G and the dichroic prism 21. The liquid crystal display element 20R is disposed between the condenser lens 19R and the dichroic prism 21. Each of the liquid crystal display elements 20B, 20G, and 20R includes an incident side polarizing plate PI, a liquid crystal LC, and an output side polarizing plate PO.

  The dichroic prism 21 is disposed between the liquid crystal display elements 20B, 20G, and 20R and the projection lens 30. The dichroic mirror 22 is disposed between the condenser lens 19G and the lens 23 and the dichroic mirror 17. The lens 23 is disposed between the dichroic mirror 22 and the total reflection mirror 26. The total reflection mirror 26 is disposed between the lenses 23 and 24. The lens 24 is disposed between the total reflection mirrors 26 and 27. The total reflection mirror 27 is disposed between the condenser lens 19R and the lens 24. The projection lens 30 is disposed to face the emission surface 21A of the dichroic prism 21.

  The light source 10 converts white light emitted from the lamp 1 into white light composed of parallel light and emits the white light from the front glass 3 to the fly-eye lens 13.

  The fly eye integrator composed of the fly eye lenses 13 and 14 splits the white light emitted from the light source 10, converges the split white light and adjusts the amount of light with the variable aperture mechanism 40, and the polarization conversion element 15. To enter. The polarization conversion element 15 aligns the polarization direction of each of the white light beams divided from the light beam received from the variable aperture mechanism 40 and outputs the white light to the condenser lens 16. The condenser lens 16 guides white light from the polarization conversion element 15 to the dichroic mirror 17.

  Of the white light from the condenser lens 16, the dichroic mirror 17 reflects blue band light in the direction of the total reflection mirror 18 and transmits red band light to green band light to the dichroic mirror 22.

  Total reflection mirror 18 changes the optical path of the blue band light received from dichroic mirror 17 by 90 degrees and guides it to condenser lens 19B. The condenser lens 19B guides the blue band light from the total reflection mirror 18 to the liquid crystal display element 20B. The liquid crystal display element 20B optically modulates the blue band light received from the condenser lens 19B in accordance with the input signal and enters the dichroic prism 21.

  The dichroic mirror 22 reflects the green band light of the red band light to green band light received from the dichroic mirror 17 to the condenser lens 19 </ b> G and transmits the red band light to the lens 23.

  The condenser lens 19G guides the green band light received from the dichroic mirror 22 to the liquid crystal display element 20G, and the liquid crystal display element 20G optically modulates the green band light received from the condenser lens 19G in accordance with the input signal, and thereby the dichroic prism 21. To enter.

  The lens 23 guides the red band light from the dichroic mirror 22 to the total reflection mirror 26, and the total reflection mirror 26 changes the optical path of the red band light by 90 degrees to guide the red band light to the lens 24. The lens 24 guides the red band light from the total reflection mirror 26 to the total reflection mirror 27, and the total reflection mirror 27 guides the red band light to the condenser lens 19R.

  The condenser lens 19R guides the red band light from the total reflection mirror 27 to the liquid crystal display element 20R, and the liquid crystal display element 20R optically modulates the red band light from the condenser lens 19R with an input signal and enters the dichroic prism 21. .

  The dichroic prism 21 changes the optical paths of the blue band light and the red band light received from the liquid crystal display elements 20B and 20R by 90 degrees, and transmits the green band light received from the liquid crystal display element 20G as it is. The band light and the red band light are incident on the projection lens 30. The projection lens 30 enlarges and projects the blue band light, the green band light, and the red band light received from the dichroic prism 21 and forms an image on a screen (not shown).

  Hereinafter, specific embodiments of the present invention will be further described with reference to FIGS.

  The light source 10 includes a lamp 1 composed of a high-pressure mercury lamp or a xenon lamp, a parabolic metal reflector 2 that converts the white light emitted from the lamp 1 into a substantially parallel light flux, and a front explosion-proof glass 3. The Since the metal reflector 2 is used as the reflector, breakage is prevented, the cooling characteristics of the reflector 2 are improved, and the time during which the lamp 1 can be relighted can be shortened. The metal reflector 2 reflects all UVIR components other than visible light forward. For this reason, although not shown in the figure, a filter, a cold mirror, and the like for removing the UVIR component are provided to emit the UVIR component to the outside of the optical path and reduce the thermal load on the subsequent optical member.

  The light emitted as parallel light by the parabolic reflector 2 is split into light beams by a so-called fly eye integrator including first and second fly eye lenses 13 and 14 formed of a convex lens group.

  The first fly-eye lens 13 is a lens in which minute lenslets 13a having a rectangular outline are arranged in a matrix of M rows in the vertical direction and N columns in the horizontal direction. The shape is set so as to be almost similar to the shape of the transmissive liquid crystal panels 20R, 20G, and 20B.

  The partial light beams divided by the first fly-eye lens 13 are converged by the plurality of lenses 14a of the second fly-eye lens 14 and incident on the polarization conversion element 15, and the polarization directions are aligned. Emitted.

  The polarization conversion element 15 includes a polarization beam splitter array and a λ / 2 phase difference plate that is selectively disposed on a part of the light exit surface of the polarization beam splitter array. As shown in FIGS. 2 and 3, a polarizing film 151... That forms an angle of 45 degrees with respect to the optical axis of the optical system, a reflective film 152, and a transparent member 150 that sandwiches the polarizing film and the reflective film, respectively. Is provided.

  As the transparent member 150, for example, glass is used. Then, a transparent member such as a glass plate having a polarizing film on the front surface and a reflecting film on the back surface is sequentially closely arranged at an angle of 45 degrees, and a predetermined emission surface and incident surface are 45 degrees with respect to the polarizing film and the reflection film. The polarization conversion element 15 as shown in FIG. 2 and FIG. The λ / 2 phase difference plate 153 is attached to the emission side surface of the transparent member 150 on the polarizing film 151.

  In this embodiment, a λ / 2 phase difference plate 153 is affixed, and a polarization changing portion 160 is configured by a transparent member portion sandwiching the polarizing film 151 and a transparent member portion sandwiching the adjacent reflective film. Yes. The pitch (X) between the polarizing films 151 and the reflective films 152 provided alternately is formed to be larger than approximately ½ of the width (W) of the lens cell 14 a of the second fly-eye lens 14. The incident light is separated into S-polarized light and P-polarized light by the polarization separation film 151. The S-polarized light is reflected substantially perpendicularly by the polarizing film 151 and further reflected by the reflecting film 152 and emitted. On the other hand, the P-polarized light is transmitted through the polarizing film 151 as it is. A λ / 2 phase difference plate 153 is disposed on the exit surface from which the P-polarized light transmitted through the polarizing film 151 is emitted. The P-polarized light transmitted through the polarizing film 151 is s-polarized by the λ / 2 phase difference plate 153. It is converted into and emitted. Therefore, most of the light that has passed through the polarization conversion element 15 is emitted as S-polarized light. In addition, when the light emitted from the polarization conversion element 13 is desired to be P-polarized light, a λ / 2 phase difference plate may be disposed on the emission surface from which S-polarized light reflected by the reflective film is emitted.

  In the present invention, as shown in FIGS. 2 and 3, a slit-shaped opening 41 a corresponding to the pitch (X) of the polarization conversion element 15 is provided between the second fly-eye lens 14 and the polarization conversion element 15. , 42a, and an aperture mechanism 40 configured to be variable in opening width. The variable aperture mechanism 40 is configured such that the movable slit plate 41 is slidable relative to the fixed slit plate 42, and is configured such that the light beam aperture width changes corresponding to a video signal or the like.

  As shown in FIGS. 2 to 5, the variable aperture mechanism 40 has a movable slit plate 42 having an opening 42 a and a light shielding portion 42 b with respect to the fixed slit plate 41 having an opening 41 a and a light shielding portion 41 b. Is slidably mounted.

  As shown in FIG. 2 and FIG. 4A, if the relative position of both is controlled so that the opening 41a of the movable slit plate 41 and the opening 42a of the fixed slit plate 42 coincide, the maximum amount of light can be obtained. This is given to the polarization conversion element 15. Moreover, if the relative position of both is controlled so that the opening part 41a of the movable slit plate 41 and the light shielding part 42b of the fixed slit plate 42 coincide, the light from the light source 10 is not given to the polarization conversion element 15, It becomes a black state. In this way, by sliding the movable slit plate 41, the amount of light transmitted from the variable aperture mechanism 40 can be continuously changed from the fully open state to the fully closed state. The sliding amount of the movable slit plate 41 is controlled by the drive unit 45.

  As shown in FIG. 5, in the drive unit 45, a rack gear 42 d provided on the movable slit plate 41 and a pinion gear 452 mesh with each other. The pinion gear 452 meshes with a gear 451 attached to the motor 450, and the movable slit plate 41 slides when the motor 450 is driven. The driving of the motor 450 is controlled by the location where the video signal and the projection display device are installed, and the amount of light transmitted from the variable aperture mechanism 40 is controlled. In order to widen the dynamic range of the projected image, the amount of transmitted light may be controlled by the brightness of the projected image signal input to the projection display device.

  FIG. 6 shows an example of the control circuit of this projection apparatus. As shown in the figure, an input signal is supplied to the video circuit 501 from a video input unit 500 from a tuner circuit or a video input terminal. The video circuit 501 converts the input signal into a signal to be given to the liquid crystal display units 20R, 20G, and 20B, and the video signal is given to each of the liquid crystal display units 20R, 20G, and 20B and optically modulated.

  From the video circuit 501, the luminance of the video signal is given to the luminance level detection circuit 502. With this brightness level detection circuit 502, the diaphragm mechanism control circuit 503 controls the slide amount of the variable slit plate 41 of the variable diaphragm mechanism 40. The variable slide plate 41 is driven by a motor 450. The amount of displacement of the variable slide plate 41 changes continuously according to the amount of rotation of the motor 450.

  As the motor 450, for example, a pulse motor whose rotation amount and rotation direction are determined according to a given drive pulse is used.

  The aperture control circuit 503 determines the rotation direction and the rotation amount of the motor 450 based on the luminance level given from the luminance level detection circuit 502. Thereby, the effective light beam diameter is continuously adjusted. The luminance level detection circuit 502 calculates the luminance level of each frame based on the received video signal. The luminance level is calculated, for example, by obtaining the average luminance of each pixel constituting the frame. That is, a frame with many white parts has a high luminance level, and a frame with many black parts has a low luminance level.

  The aperture control circuit 503 includes a look-up table that stores a correspondence relationship between a luminance level and an effective light beam width corresponding to the luminance level. The effective luminous flux width is adjusted to be large when the luminance level is high and to be small when the luminance level is low. In an image with a high luminance level, a brighter portion such as a white portion is more shining when the brightness is emphasized, so the effective light beam width is increased to increase the amount of light. On the other hand, in a video with a low luminance level, the black portion is more vividly displayed when the brightness is lowered, so the effective light beam width is reduced to reduce the amount of light. In addition, if the effective light flux width is reduced, the peripheral edge of the effective light flux is blocked, so that light scattering in the optical path caused by the light at the peripheral edge is reduced, harmful light is reduced, and the screen contrast is increased. it can. Such adjustment of the effective light beam width is performed for each frame, for example.

  The aperture mechanism control circuit 503 reads the effective light beam width corresponding to the brightness level calculated by the brightness level detection circuit 502 from the lookup table, and based on the read effective light beam width and the current position of the movable slit plate 41, Determine the rotation method and rotation amount of the motor. Then, a drive pulse corresponding to the determined rotation amount and rotation direction is given to the motor 450.

  As shown in FIG. 6, when a video signal is input, the luminance level detection circuit 502 calculates a luminance level, and the diaphragm mechanism control circuit 503 determines an optimum effective light beam width based on the calculated luminance level. Then, the movable slit plate 41 is moved so that the determined effective light flux width is obtained. Thus, when the video brightness level is high, a brighter screen is displayed on the screen, and when the video brightness level is low, a high contrast screen is displayed. Moreover, since the effective light flux width is continuously adjusted according to the luminance level, an optimal screen suitable for viewing can be displayed.

  As shown in FIGS. 2 and 3, the light shielding part 42 b of the fixed slit plate 42 of this embodiment matches the pitch of the reflecting part of the polarization conversion element 15, so that the light entering the polarization conversion element 15 Can also prevent leakage light and the like.

  FIG. 7 is a schematic diagram showing a configuration of a projection display apparatus according to the second embodiment of the present invention. In the first embodiment, the variable aperture mechanism 40 is disposed between the second fly's eye lens 14 and the polarization conversion element 15. On the other hand, in the second embodiment, the variable aperture mechanism 40 is disposed on the exit surface side of the polarization conversion element 15. That is, the variable aperture mechanism 40 in the second embodiment is disposed between the polarization conversion element 15 and the condenser lens 16. The variable diaphragm mechanism 40 also has a slit-shaped opening 40 having a slit-like opening corresponding to the pitch of the polarization conversion element 15 and having a variable opening width. By providing the aperture mechanism 40 configured to allow the aperture width to be variable in the vicinity of the polarization conversion element 15, it is possible to increase or decrease only the amount of light without increasing or decreasing the number of fly-eye cells or peripheral light fluxes.

  The configuration itself of the variable aperture mechanism 40 in the second embodiment is the same as that of the first embodiment, and the other configurations are also the same as those of the first embodiment. In order to avoid duplication of explanation, explanation here is omitted.

  In the above embodiment, the example in which the effective light beam width is adjusted according to the luminance level has been described. However, in addition to this, the effective light beam width may be determined in consideration of the brightness and darkness of the surrounding environment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention can be used for projection display devices such as projectors and rear projectors.

It is a schematic diagram which shows the structure of the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the principal part structure of the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the principal part structure of the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the aperture mechanism used for the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the drive mechanism of the aperture mechanism used for the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the control circuit of the aperture mechanism used for the projection type display apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the projection type display apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the 3LCD projection type display apparatus of the conventional dichroic prism system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Light source, 13, 14 Fly eye lens, 15 Deflection conversion element, 16 Condenser lens, 17 Dichroic mirror, 18, 26, 27 Total reflection mirror, 22 Dichroic mirror, 19R, 19G, 19B Condenser lens, 20R, 20G, 20B Liquid crystal Display element, 21 dichroic prism, 30 projection lens, 40 aperture mechanism, 41 movable slit plate, 42 fixed slit plate.

Claims (3)

The light from the light source is split by the fly-eye integrator, and each light beam converges and enters the polarization conversion element. The emitted light with the polarization direction aligned is modulated by the light modulation element according to the video signal. A projection display device that enlarges and projects the generated image light by a projection means, wherein a variable aperture mechanism that changes a light beam width is provided in the vicinity of the polarization conversion element. . 2. The projection display device according to claim 1, wherein the variable aperture mechanism has a slit-like opening corresponding to the pitch of the polarization conversion element, and the opening width thereof is variable. . The variable aperture mechanism is configured such that the movable slit plate is slidable relative to the fixed slit plate, and the beam aperture width is configured to change in accordance with the video signal. 3. The projection display device according to 2.

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