JP2005292358A - Projection-type image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the light utilization efficiency of a projection-type image display device which uses illumination light of randomly polarized light and color filters. <P>SOLUTION: A reflector 7 is arranged between a light source part 5 and a rod integrator 8. Illumination light, radiating from the light source part 5, is made incident on the rod integrator 8 through an aperture 7a of the reflector 7. The illumination light of random polarized light which is totally reflected in the rod integrator 8 is separated into R, G and B light beams by R, G and B color filters of a color wheel 9. Although R light, e.g. in the illumination light, is transmitted through the R filter, G light and B light are reflected to the side of the light source part 5 by the R filter. Since the reflected G light and B light are reflected by the reflecting surface 7c of the reflector 7 and are made incident on the rod integrator 8 again, efficiency of light utilization can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a projection type image display apparatus, and more particularly to improvement of light utilization efficiency of a projection type image display apparatus using randomly polarized illumination light or a color filter.

  The energy distribution of the illumination light emitted from the light source is made uniform by a light guide means such as a rod integrator, and the image light generation unit that receives this uniformed illumination light modulates the light to generate and generate image light. A projection-type image display device that projects image light onto a screen is known. As this projection type image display device, there are a transmission type image display device and a reflection type image display device according to the difference in the light modulation method. In the transmissive image display device, a transmissive liquid crystal panel is used as an image light generation unit, and light is modulated by driving each liquid crystal cell of the liquid crystal element according to a video signal.

  In the reflection type image display device, a reflection type display panel is used as the image light generation unit. The reflective display panel includes a digital micromirror device (DMD), a liquid crystal on silicon (LCOS) element, and the like. The DMD has a matrix of light reflection angle variable mirror elements that are variable between an on position where reflected illumination light is reflected toward the projection optical system and an off position where the illumination light is reflected in a direction away from the projection optical system. Many are arranged. When the pixel is displayed brightly, the mirror element is moved to the on position, and when the pixel is darkly displayed, the mirror element is moved to the off position. By controlling the reflection direction of the illumination light in this way, light modulation according to the video signal is performed.

  The LCOS element is a reflection type liquid crystal panel formed on a silicon substrate. The LCOS element has high drive capability for driving the liquid crystal with a transistor provided on the silicon substrate, and has the features of high aperture ratio, small size and high resolution. ing.

  For example, in a conventional projection-type image display device, the polarization direction of illumination light emitted from a light source is converted by a quarter wavelength plate, the intensity distribution of illumination light is made uniform by a rod integrator, and a specific light is separated by a polarization separation element. Only illumination light in the polarization direction is transmitted and used for projecting the image, and illumination light in other polarization directions is reflected toward the light source side.

  In order to effectively use the illumination light reflected by the polarization separation element, the projection-type image display devices described in Patent Documents 1 and 2 have a reflecting plate disposed between the light source and the quarter-wave plate. In this reflection plate, a light transmission part that transmits light emitted from the light source toward the quarter-wave plate is formed at the center, and illumination light reflected from the polarization separation element is provided around the light transmission part. Is provided for reflecting the light toward the quarter-wave plate. Illumination light reflected by the reflecting surface and incident again on the quarter-wave plate is converted in polarization direction again, so that it is transmitted through the polarization separation element and used effectively.

  The reflecting plate is made of a transparent glass plate, and an anti-reflection film (AR film) is formed on a surface that is a light source and a translucent portion of the surface that is the image light generating unit, and the surface of the surface that is facing the image light generating unit. A reflection film is formed of aluminum, silver, or the like around the light transmitting portion.

JP 2003-202523 A JP 2003-233032 A

  Unlike the above-described Patent Documents 1 and 2, a projection-type image display device that projects an image with non-polarized (randomly polarized) illumination light without using a quarter-wave plate or a polarization separation element has also been known. It has been. Even in the projection type image display apparatus using the randomly polarized illumination light, the illumination light is reflected by the rod integrator, the relay lens, the prism or the like, and may be wasted without being used for projection.

  In addition, in a reflective image display device using a DMD, illumination light emitted from a light source is separated into colors by, for example, RGB color filters and incident on the DMD. The DMD emits light based on an input video signal. The image light is generated by reflection. However, since RGB color filters reflect light other than the corresponding color, there is still illumination light that is not used for projection and is wasted. The above-mentioned Patent Documents 1 and 2 do not describe effective use of randomly polarized illumination light or illumination light that is wasted by reflection of a color filter.

  Further, since the reflection plate is formed by separately forming the AR film and the reflection film on the surface with respect to the image light generation unit, 1. 1. A resist mask is formed at a site where the light transmitting part is to be formed. 2. A reflective film is formed around the part where the light transmitting part is formed. 3. Remove the resist mask at the site where the light transmitting part is formed by etching; 4. A resist mask is formed on the reflective film. 5. An AR film is formed at the site where the light transmitting part is formed; 6. Form an AR film on the light source side surface; The work of removing the resist mask on the reflective film by etching has been performed. However, since the formation and etching of the resist mask is very costly, the conventional reflector is expensive. Further, since the DMD and LCOS elements are expensive in the reflection type image display device, it is desired to reduce the cost of the reflection plate which is a peripheral component.

  In order to solve the above-described problems, the present invention makes it possible to effectively use illumination light even in randomly polarized illumination light or a projection-type image display device using a color filter, and to provide a reflector at a low cost. For the purpose.

  In order to solve the above problems, the projection type image display apparatus of the present invention allows illumination light emitted from a light source to pass through the optical path between the light source and the image light generation unit toward the image light generation unit. A reflector having an aperture and a reflecting surface that reflects the randomly polarized illumination light reflected by the image light generator toward the image light generator is disposed. Further, when a color filter and a display panel are used as the image light generation unit, the randomly polarized illumination light reflected by the color filter by the reflector is reflected and incident on the display panel. Further, the reflecting surface is inclined so that the reflected illumination light is condensed on the image light generation unit.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a projection type image display apparatus which uses the illumination light of a random polarization, the illumination light reflected in the optical path can be reflected by a reflecting plate, and can be utilized effectively. Further, even in a projection type image display device using a color filter, illumination light reflected by the color filter can be used effectively. In particular, a projection-type image display device that uses randomly polarized illumination light does not use a quarter-wave plate, a polarization separation element, or the like, and thus effectively uses all the light reflected by the optical elements after the light source. be able to. Furthermore, since the reflecting surface is inclined so that the illumination light is collected, the light utilization efficiency can be further improved. Further, since it is not necessary to separately coat the reflection film and the AR film on the reflection plate, it is not necessary to form a resist mask or perform an etching operation, and the reflection plate can be manufactured at low cost.

  FIG. 1 is a schematic diagram showing the configuration of a reflective image display apparatus embodying the present invention. The reflective image display device 2 includes a control unit 3 and an optical system 4. The optical system 4 includes a light source unit 5, a condenser lens 6, a reflecting plate 7, a rod integrator 8, a color wheel 9, a relay lens 10, a total reflection prism 11, a DMD 12, and a projection lens 13. The reflection type image display device 2 is a single plate type that generates image light of three colors by one DMD 12.

  The control unit 3 includes a microcomputer 17 that comprehensively controls each unit of the reflective image display device 2 based on a video signal input to the video signal receiving unit 16. A video signal such as a composite signal or a component signal is input to the video signal receiving unit 16 from a tuner or a video player connected to an external input terminal or the like.

  The light source unit 5 includes a light source 5 a and a reflector 5 b that reflects the illumination light emitted from the light source 5 a toward the condenser lens 6. As the light source 5a, for example, a white light source such as a xenon tube or a mercury lamp is used.

  The rod integrator 8 has a kaleidoscope formed inside, for example, a square glass rod, and superimposes the luminous flux by totally reflecting the illumination light incident on the incident end face 8a from the light source unit 5 inside. The energy distribution of the illumination light emitted from the emission end face 8b is made uniform. Thereby, the intensity distribution of the illumination light incident on the light receiving surface of the DMD 12 becomes uniform.

  As shown in FIG. 2, the color wheel 9 has an R-shaped filter 9b that transmits only R light and reflects other light on a substantially disk-shaped substrate 9a, and transmits only G light and reflects other light. The three filters of the G filter 9c and the B filter 9d that transmits and transmits only the B light and reflects the other light are arranged at substantially the same distance from the rotation center of the substrate 9a. The color wheel 9 is driven by the color wheel driving unit 20, and the timing and rotation speed of the rotation start are controlled by the microcomputer 17. By rotating the color wheel 9, the filters 9b to 9d of each color selectively face the emission end face 8b of the rod integrator 8, and the illumination light is color-separated into three colors B, G, and R in a time-sharing manner. .

  The total reflection prism 11 is for separating incident light incident on the DMD 12 from the relay lens 10 and reflected light reflected by the DMD 12. The total reflection prism 11 is composed of, for example, two triangular prisms having different refractive indexes, and a reflection surface 11a is formed at the boundary between the two triangular prisms. Since the incident light has an incident angle larger than the critical angle, the incident light is totally reflected by the reflecting surface 11 a and enters the DMD 12. On the other hand, the reflected light reflected by the DMD 12 passes through the reflecting surface 11a because the incident angle is smaller than the critical angle.

  The DMD 12 is driven by the DMD driving unit 23 connected to the microcomputer 17 based on the video signal input to the video signal receiving unit 16. In the DMD 12, a large number of mirror elements corresponding to pixels are arranged in a matrix on the light receiving surface. Each mirror element changes the reflection direction of the received illumination light by changing the angle based on the video signal. When displaying a pixel, the mirror element is displaced to the ON position, and the received light is reflected toward the projection lens 13 as ON light. On the other hand, when the pixel is not displayed, the mirror element is displaced to the off position, and the received light is reflected as off light in a direction away from the projection lens 13. The image light is constituted by a set of on-lights directed toward the projection lens 13.

  The projection lens 13 is shown in a simplified manner in the drawing, but actually includes a plurality of lens groups arranged on the optical axis and a lens moving mechanism for zooming and focus adjustment. The image light generated by the DMD 12 is imaged on the screen 26 by the projection lens 13. Note that the reflection type image display device 2 of the present invention does not use a quarter-wave plate or a polarization separation element that converts the polarization direction of illumination light. Therefore, the illumination light incident on the DMD 12 is non-polarized light (random polarized light).

  The reflection plate 7 disposed between the light source unit 5 and the rod integrator 8 is generally called an input aperture or a recycling plate, and is used for improving the utilization efficiency of illumination light in the optical system 4. As shown in FIGS. 3 and 4, the reflecting plate 7 is formed in a plate shape from, for example, white plate glass or heat-resistant glass such as Tempax (registered trademark), and a circular opening 7 a is formed at the center thereof. A reflection surface 7c made of a reflection layer 7b coated with aluminum, silver or the like by vacuum deposition or the like is formed on the surface of the rod integrator 8 around the opening 7a. As shown in FIG. 5, the illumination light emitted from the light source unit 5 passes through the opening 7 a of the reflection plate 7 and enters the rod integrator 8.

  As shown in FIG. 6, illumination light reflected by the filters 9b to 9d of the color wheel 9, for example, G light and B light reflected by the R filter 9b, and as shown in FIG. The illumination light reflected by the incident end face 8 a of the relay lens 10 and the rod integrator 8 is incident on the light source unit 5. In conventional projection type image display devices that use randomly polarized illumination light and projection type image display devices that use color filters, these reflected lights are wasted.

  However, in the projection type image display apparatus 2 of the present embodiment, since the reflecting plate 7 is provided in the optical path between the light source unit 5 and the rod integrator 8, the illumination light reflected by the optical elements after the light source unit 5 is used. Since the light is reflected by the reflecting surface 7c on the surface of the reflecting plate 7 and enters the rod integrator 8 again, the utilization efficiency of the illumination light can be improved.

  In the conventional reflector, a transparent portion coated with an AR film is formed at the center of one surface of a transparent glass plate, and a reflective surface coated with a reflective film is formed around it. An AR film was also formed over the entire area. Therefore, in order to separately coat the AR film and the reflective film, it is necessary to form a resist mask many times and remove the mask by etching, which is expensive. On the other hand, the reflecting plate 7 of the present invention has the light-transmitting region formed by the opening 7a, so that it is not necessary to separately coat a plurality of types of films, and can be manufactured at low cost. The surface on the light source unit 5 side of the reflecting plate 7 may be AR coated on the front surface or may be uncoated.

  Next, the effect | action by the said structure is demonstrated. When the reflective image display device 2 is turned on, the light source 5a of the power supply unit 5 is turned on. The DMD driving unit 23 drives the DMD 12 based on the video signal input to the video signal receiving unit 16, and the color wheel driving unit 20 rotates the color wheel 9 in accordance with the driving timing of the DMD 12.

  The illumination light emitted from the light source 5a is reflected by the reflector 5b and collected by the condenser lens 6 in front. The illumination light emitted from the condenser lens 6 passes through the opening 7a of the reflecting plate 7 and enters the rod integrator 8. The rod integrator 8 totally reflects the illumination light internally to make the energy distribution uniform, and emits it from the emission end face 8b. The illumination light emitted from the rod integrator 8 is separated into three colors of RGB by the color wheel 9 and is incident on the total reflection prism 11 by the relay lens 10.

  The randomly polarized illumination light incident on the total reflection prism 11 is reflected by the reflection surface 11 a and is incident on the light receiving surface of the DMD 12. On the light receiving surface of the DMD 12, a large number of mirror elements are moved between the ON position and the OFF position by the DMD driving unit 23, and the mirror elements in the ON position reflect illumination light toward the projection lens 13 as ON light. The mirror element at the off position reflects the illumination light as off light at a position off the projection lens 13. On-light, that is, image light is projected onto the screen 26 by the projection lens 13.

  During the reflection projection operation described above, the illumination light is reflected toward the light source unit 5 by the incident end face 8a of the rod integrator 8, the filters 9b to 9d of the color filter 9, the relay lens 10, the total reflection prism 11, and the like. . However, most of the illumination light reflected toward the light source unit 5 is reflected by the reflecting surface 7 c of the reflecting plate 7 and enters the rod integrator 8 again. Thereby, since the utilization efficiency of illumination light improves, it is possible to obtain a bright projected image without using a light source with a large amount of light.

  In the above embodiment, a glass plate is used as the material of the reflecting plate 7, but a metal plate such as aluminum may be used. In this case, one surface of the metal plate may be mirror-finished or the like to form a reflecting surface. According to this, since it is not necessary to form a reflecting surface by vacuum deposition or the like, the cost of the reflecting plate 7 can be further reduced.

  Further, although the flat reflection plate 7 is used, a reflection plate 30 in which the reflection surface 30b around the opening 30a is inclined toward the center of the rod integrator 8 as shown in FIG. According to the reflecting plate 30, the illumination light reflected by the reflecting surface 30b is collected toward the rod integrator 8, so that the utilization efficiency of the illumination light can be further increased. In addition, when forming the reflecting plate 30 having the inclined reflecting surface 30b, a glass plate or a metal plate formed in this shape may be used, and the reflecting surface 30b may be formed thereon. Moreover, when using a metal plate, you may make it bend after formation of the reflective surface 30b.

  In the above embodiment, the reflective image display device using DMD has been described as an example. However, the reflective image display device using LCOS, and the transmissive image display device using random polarized illumination light and color filters. It can also be applied to. Furthermore, although the rod integrator has been described as an example of the light guiding means, the reflector of the present invention can be used in combination with a glass rod, a light tunnel, or a polarizing rod.

It is the schematic which shows the structure of a reflection type image display apparatus. It is a front view of a color hole. It is an external appearance perspective view which shows the structure of a reflecting plate. It is principal part sectional drawing of a reflecting plate. It is explanatory drawing which shows the reflection state of the illumination light by a reflecting plate. It is explanatory drawing which shows the reflection state of the illumination light by a color hole. It is explanatory drawing which shows the reflection state of the illumination light by the reflecting plate using another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Reflection type image display apparatus 3 Control part 4 Optical system 5 Light source part 7 Reflector 7a Aperture 7b Reflective layer 7c Reflective surface 8 Rod integrator 9 Color wheel 11 Total reflection prism 12 DMD
13 Projection lens 26 Screen

Claims (3)

A light source that emits illumination light, an image light generator that generates light by modulating the received randomly polarized illumination light according to an input video signal, and projection that projects the generated image light on a screen In a projection-type image display device comprising an optical system,
In the optical path between the light source and the image light generation unit, an opening through which illumination light emitted from the light source passes toward the image light generation unit, and randomly polarized illumination light reflected by the image light generation unit A projection-type image display device comprising a reflector having a reflecting surface that reflects toward an image light generator.   The image light generation unit transmits only light of a specific color from randomly polarized illumination light irradiated from a light source and reflects other light to the light source side, and transmits through these color filters. A display panel that receives imaged light and generates image light, wherein the reflector reflects the randomly polarized illumination light reflected by the color filter by a reflecting surface and enters the display panel. The projection type image display apparatus according to claim 1.   3. The projection type image display apparatus according to claim 1, wherein the reflecting surface of the reflecting plate is inclined so that the reflected illumination light is condensed on the image light generation unit.

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