JP2004157252A - Projection type image display device and optical unit used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology in which the contrast of a projection type image display device is increased while the dimension of the display device is suppressed. <P>SOLUTION: A viewing angle compensation phase difference plate which compensates the deviation of phase in polarized light and a 1/4 wavelength phase difference plate which rotates the polarization axis of the polarized light are provided at a position adjacent to an image display element as a liquid crystal panel, and the contrast of an optical image is enhanced by modifying the polarization of R (red), G(green) and B(blue) light which are made incident on or emitted from the image display element. Furthermore, a plurality of phase difference of plates which compensate the phase difference substantially equal to the compensation given by the 1/4 wavelength phase difference plate by rotating the polarization axis of the polarized light of respective colors is provided at a position adjacent to the image display element, thus the contrast of the optical image is enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for improving contrast in a projection-type image display device that irradiates light from a light source side to an image display element such as a liquid crystal panel to form an optical image in accordance with an image signal and to perform enlarged projection.
[0002]
[Prior art]
As a conventional example of a technique for improving contrast in a projection type video display device, for example, Japanese Patent Application Laid-Open No. 2001-209007 (Patent Document 1), Hiroyuki MORI, and others, "Optical Performance of a Novel Compensation Film for Wide-Angling LCD-TN-T-N-LCD"IDW'96 p. 189-192 (Non-Patent Document 1). Japanese Patent Application Laid-Open No. 2001-209007 describes a configuration in which a quarter-wave retardation plate is provided adjacent to a reflective liquid crystal panel. Further, "Optical Performance of a Novel Compensation Film for Wide-Viewing-AngleTN-LCDs" describes a viewing angle compensating phase difference plate.
[0003]
[Patent Document 1]
JP 2001-209007 A (Paragraph Nos. 0041, 0052, 0060, 0069, FIGS. 1, 7, 8, and 9)
[Non-patent document 1]
Hiroyuki MORI et al., "Optical Performance of a Novel Compensation Film for Wide-Viewing-Angle TN-LCDs"IDW'96 p. 189-192
[0004]
[Problems to be solved by the invention]
In the projection type image display device, still higher contrast is desired. For example, in a case where a rubbed liquid crystal panel is used as a video display element, the liquid crystal layer near the light distribution film does not become vertical even when power is applied, thereby deteriorating the contrast.
An object of the present invention is to provide a projection-type image display device capable of increasing contrast while suppressing an increase in device size, in view of the state of the related art.
An object of the present invention is to provide a technique capable of solving such a problem.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention basically provides a projection type image display device, a viewing angle compensation phase difference plate for compensating a phase difference shift of polarized light by a liquid crystal layer or the like, and a polarization axis of polarized light. And a quarter-wave retardation plate for rotating R, R (red), G (green), and B (blue) that enter or exit the image display element such as a liquid crystal panel. The polarization of each color light is corrected to increase the contrast of the optical image. Also, a plurality of phase difference plates are provided adjacent to the image display element to compensate for a phase difference substantially equal to that of a quarter wavelength phase difference plate by rotating the polarization axis of the polarized light of each color light. Is configured to be able to be increased. Specifically, as a projection type image display device, (1) a viewing angle compensation phase difference plate for compensating for a phase difference shift of polarized light of each of R, G, and B color lights entering or exiting the image display element; A quarter-wave retardation plate disposed adjacent to the viewing angle compensating retardation plate for rotating the polarization axis of the polarized light of each color light, and the contrast of an optical image formed by the image display device is provided. Is configured to be able to be increased. (2) Polarization conversion means for aligning the polarization direction of light from the light source side to form P-polarized light or S-polarized light, and separation means for separating the polarized light converted into R, G, and B color lights. An image display element that is irradiated with polarized light of each of the separated color lights and modulates the polarized light based on an image signal; and color light that is disposed adjacent to the image display element and that enters or exits the image display element. A viewing angle compensating phase difference plate for compensating for the phase difference deviation, and rotating the polarization axis of the polarized light of the color light which is arranged adjacent to the viewing angle compensating phase difference plate and which enters or exits the image display element. A 波長 wavelength retardation plate, and color combining means for performing color composition of polarized light of each color light modulated by the video display element and emitted from the viewing angle compensation phase difference plate and the 波長 wavelength phase difference plate, A projection lens unit for enlarging and projecting the optical image of the color-combined polarized light. And a drive circuit for driving the image display element, wherein the compensation of the phase difference with respect to the color light by the viewing angle compensation phase difference plate and the rotation of the polarization axis by the quarter wavelength phase difference plate are performed. The configuration is such that the polarization of the optical image enlarged and projected by the projection lens unit can be increased by performing polarization correction. (3) In the above (1) or (2), the viewing angle compensating phase difference plate is fixed, and the quarter wavelength phase difference plate is rotatable with respect to the optical axis. (4) In the above (1) or (2), the viewing angle compensation phase difference plate and the 波長 wavelength phase difference plate are optically integrated with each other. (5) In any one of the above items (1) to (4), the viewing angle compensating phase difference plate has a configuration having a phase difference in an optical axis direction. (6) The polarization axis of the polarized light of each of the R, G, and B color lights which is disposed adjacent to the image display element and which enters or exits the image display element is rotated by about 1 / m wavelength (m> 0). A first retardation plate, and a second retardation plate disposed adjacent to the first retardation plate for rotating the polarization axis of the polarized light of each color light by approximately 1 / n wavelength (n> 4). A configuration in which the two phase difference plates perform phase difference compensation on the image display element substantially equal to that of a quarter wavelength phase difference plate, thereby increasing the contrast of an optical image formed by the image display element. And (7) Polarization converting means for aligning the polarization directions of light from the light source side to form P-polarized light or S-polarized light, and separating means for separating the polarized light converted into R, G, and B color lights. A video display element that is irradiated with polarized light of each of the separated color lights and modulates the polarized light based on a video signal; and R that is disposed adjacent to the video display element and that enters or exits the video display element. , G, and B, a first retardation plate for rotating the polarization axis of the polarized light of each color light by about 1 / m wavelength (m> 0), and the respective color lights disposed adjacent to the first retardation plate. A second phase difference plate for rotating the polarization axis of the polarized light of about 1 / n wavelength (n> 4), and each color modulated by the image display device and emitted from the first and second phase difference plates A color combining means for combining colors of the polarized light, and a projection lens unit for enlarging and projecting an optical image of the combined polarized light. And a drive circuit for driving the image display element. The two phase difference plates perform the same phase difference compensation on the image display element as that of a quarter-wavelength phase difference plate, and are enlarged by the projection lens unit. The contrast of the projected optical image can be increased. (8) In the above (6) or (7), one of the first and second retardation plates is fixed and the other is rotatable with respect to the optical axis. Further, as an optical unit for a projection type image display device, (9) a polarization conversion unit that aligns the polarization directions of light from the light source side to form P-polarized light or S-polarized light, and converts the polarization-converted polarized light into R light. , G, and B color separation light, a video display element that irradiates polarized light of each of the separated color lights and modulates the polarized light based on a video signal, and is disposed adjacent to the video display element. A viewing angle compensating phase difference plate for compensating a phase difference between color lights incident or emitted to the image display element; and a light incident or emitting to the image display element disposed adjacent to the viewing angle compensation phase difference plate. A quarter-wave retarder for rotating the polarization axis of the polarized light of the color light to be emitted, and each color modulated by the image display device and emitted from the viewing angle compensation retarder and the quarter-wave retarder. Color combining means for combining colors of polarized light, And a projection lens unit for enlarging and projecting the optical image of the polarized light, wherein the compensation of the phase difference with respect to the color light by the viewing angle compensating phase difference plate and the rotation of the polarization axis by the quarter wavelength phase difference plate Thereby, the contrast of the optical image enlarged and projected by the projection lens unit can be increased. (10) As an optical unit, a polarization conversion unit that aligns the polarization directions of light from the light source side to form P-polarized light or S-polarized light, and separates the polarization-converted polarized light into R, G, and B color lights. Separating means, a polarized light of each of the separated color lights is irradiated, and a video display element that modulates the polarized light based on a video signal, and which is disposed adjacent to the video display element and is incident on the video display element or A first retardation plate for rotating the polarization axis of the polarized light of each of the emitted R, G, and B light by approximately 1 / m wavelength (m>0); and a first retardation plate adjacent to the first retardation plate. A second phase difference plate that rotates the polarization axis of the polarized light of each color light by approximately 1 / n wavelength (n>4); and a second phase difference plate modulated by the image display device and provided by the first and second phase difference plates. A color synthesizing means for synthesizing the polarized light of each color light to be emitted, and an enlarged image of the optical image of the color synthesized polarized light; A projection lens unit for performing the same phase difference compensation on the image display element as the 波長 wavelength phase difference plate by the two phase difference plates, and contrast of the optical image enlarged and projected by the projection lens unit. Is configured to be able to be increased.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are explanatory diagrams of a first embodiment of the present invention. FIG. 1 is a diagram showing a configuration example of a projection type video display device, and FIG. 2 is an explanatory diagram of a viewing angle compensation phase difference plate. In the first embodiment, three reflective video display elements corresponding to R, G, and B color lights are used as the video display elements.
In FIG. 1, 1 is a light source unit having a light source, 2 is a reflector that reflects light from the light source, 3 is a polarization conversion element, 6 is a first array lens, 7 is a second array lens, 8 is a collimator lens, 9 is a condenser lens, 17 is a reflection mirror, 18a is a dichroic mirror, 16a is a dichroic filter, 14r and 14gb are incident side polarizing plates, 19r, 19gb and 19w are polarization beam splitters (PBS), and 19wa is polarization of the polarization beam splitter 19w. The surface of the separation film, 23r is a quarter-wave retarder for red light (hereinafter referred to as R light), 23g is a quarter-wave retarder for green light (hereinafter referred to as G light), and 23b is blue light. (Referred to as B light hereinafter) quarter-wave retarder, 25r is a viewing angle compensation retarder for R light, 25g is a viewing angle compensation retarder for G light, and 25b is B light. 13rr is a reflective image display element for R light, 13rg is a reflective image display element for G light, 13rb is a reflective image display element for B light, and 20a and 20b are specific wavelengths. The selection wavelength plate, 5 is a half-wave retardation plate, 12 is a projection lens unit including a projection lens, and 22 is a projection type image display device. As a light source of the light source unit 1, a white lamp such as an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, and a halogen lamp is used. The reflector 2 has an elliptical surface, a parabolic surface, or an aspherical reflecting surface, and collects and reflects light from a light source. Since the temperature of the light source and the reflector 2 becomes high due to the heat generated by the light source, the light source and the reflector 2 are cooled by a cooling fan (not shown). The first array lens 6 is composed of a plurality of condenser lenses provided in a rectangular frame having substantially the same size as the exit aperture of the reflector 2, and forms a plurality of secondary light source images. The second array lens 7 is constituted by a plurality of condenser lenses, and forms an image of each lens of the first array lens 6 on the image display device. The light emitted from the light source unit 1 enters the first array lens 6, where it is condensed to form a plurality of secondary light source images, and further enters the second array lens 7. Light emitted from the second array lens 7 enters the polarization conversion element 3. The polarization conversion element 3 is constituted by a row of rhombic prisms each having a size approximately half the width of each lens and arranged so as to match the horizontal pitch of the lens optical axis of each of the second array lenses 7. Have been. The prism surface is provided with a polarization separation film, and the incident light is separated into P-polarized light and S-polarized light by the polarization separation film. The P-polarized light passes through the polarization separation film and is emitted. On the other hand, the S-polarized light is reflected by the polarized light separating film, reflected again in the original optical axis direction in the adjacent rhombic prism, and then reflected by the half-wave retarder provided on the exit surface of the prism. Then, the polarization direction is rotated by 90 °, converted into P-polarized light, and emitted together with the P-polarized light transmitted through the polarization separation film. In this embodiment, the arrangement of the polarization beam splitter makes the tangent to the surface of the polarization separation film of the polarization conversion element 3 orthogonal to the surface of the polarization separation film of the polarization beam splitters 19r and 19gb used in the color separation / combination system. It is supposed to. This indicates that the light is emitted as P-polarized light when viewed from the film surface of the polarization conversion element 3, but is S-polarized light when viewed from the film surface of the polarization beam splitters 19r and 19gb. Here, in order to make the S-polarized light incident on the color separation / combination system having the prism configuration, the light is emitted here as P-polarized light. The collimator lens 8 has a positive refractive power and collects light. The light (the P-polarized light of white light) that has exited the collimator lens 8 is reflected by the reflection mirror 17, the optical path is bent by approximately 90 degrees, further passes through the condenser lens 9, and is passed through each of the reflective liquid crystal display elements 13rr, 13rg. , 13 rb. Here, the reflection mirror 17 is designed so that the reflectance with P-polarized light becomes good. The reflection mirror 17 is 670 × 10 ^-9 An IR cut mirror that cuts light of m or more may be used. Further, as the reflection mirror 17, an S-polarized light having good reflectance is used, a 波長 wavelength phase difference plate is attached to the transmission optical path side of the polarization conversion element 3, and the S-polarized light is emitted from the polarization conversion element 3. After being reflected by the reflection mirror 17 and bending the optical axis, the light may be converted into P-polarized light by a half-wave retardation plate on the optical path before entering the color separation / combination system. In the above description, the reference of the phase of the polarized light is the polarization splitting film surface of the polarization conversion element 3. In the following description, the reference of the phase of the polarized light is the plane of the polarization separation film of the polarization beam splitter used in the color separation / combination system. The light emitted from the condenser lens 9 is separated into G light + B light and R light by a dichroic mirror 18a (or a color separation prism). That is, the R light is transmitted as it is, the G light and the B light are reflected, the optical path is bent by approximately 90 degrees, and then travels to the polarization beam splitters 19r and 19gb, respectively. Each of the polarizing beam splitters 19r and 19gb is designed so that the contrast is improved exclusively for each wavelength range. The R light transmitted through the dichroic mirror 18a enters the dichroic filter 16a. The dichroic filter 16a transmits the R light, and reflects the G light component and the B light component. The dichroic mirror 18a has a wavelength of 50% transmittance of approximately 575 × 10 ^-9 m, and the dichroic filter 16a sets the wavelength of the transmittance of 50% to approximately 600 × 10 ^-9 m is set. The dichroic filter 16a cuts yellow light to improve the white color balance and the monochromatic color purity of R (red) and G (green). Since the dichroic filter 16a is arranged at an incident angle of 0 degree with respect to the optical axis, the half value shift due to the incident angle is smaller than that of the dichroic mirror 18a inclined at 45 degrees with respect to the optical axis. By arranging the dichroic filter 16a after the dichroic mirror 18a, the leakage of the yellow component can be cut. Therefore, it is possible to improve the white color balance and the color purity of R (red) and G (green) single colors. The R light transmitted through the dichroic mirror 18a then passes through the R-light incident-side polarizing plate 14r for increasing the degree of polarization, and is incident on the polarization beam splitter 19r dedicated to the R light, and is reflected by the polarization separation film surface. The light is reflected and irradiates the red light reflective image display element 13rr. On the other hand, the G light and the B light reflected by the dichroic mirror 18a are incident on the incident side polarizing plate 14gb arranged to increase the degree of polarization. The polarizing plate 14gb cuts a specific polarized light (here, P-polarized light). The light transmitted through the polarizing plate 14gb and having an improved degree of polarization is incident on the specific wavelength selection wavelength plate 20a. The specific wavelength selection wave plate 20a changes the polarization direction only in a specific wavelength range. Here, G light is emitted as S-polarized light, and B light is converted from S-polarized light to P-polarized light and emitted. The B light, which is the P-polarized light, passes through the polarization splitting film surface of the G beam and the B light polarizing beam splitter 19gb, and is emitted to the blue light reflective image display element 13rb. The G light, which is the S-polarized light, is reflected on the polarization splitting film surface of the polarization beam splitter 19gb for the G light and the B light, and then is emitted to the green light reflective image display element 13rg. Each of the irradiated color lights is reflected in each reflection type image display device in a state where the polarization direction is changed based on the video signal, and is again incident on the polarization beam splitters 19r and 9gb for each color light, and the S-polarized light is reflected. , P-polarized light is transmitted. For example, in the case of a liquid crystal panel, each of the reflective video display elements is provided with a liquid crystal display unit (for example, 1365 horizontal pixels, 768 vertical pixels, etc.) corresponding to the pixels to be displayed. Each reflection-type image display element is driven by a drive circuit, and the polarization angle of each pixel changes based on an image signal supplied from the drive circuit, and light having the same polarization direction is converted into G light and B light by a polarization beam splitter 19gb. The R light is detected by the polarization beam splitter 19r. The amount of light having a polarization at an intermediate angle is determined by the polarization beam splitter depending on the degree of polarization of the polarization beam splitters 19gb and 19r. In this way, an image according to the image signal is displayed. The polarization direction when each reflective image display element performs black display is substantially the same as that of the incident light, and the reflected light is returned to the light source along the incident optical path.
[0007]
The reflection type display elements 13rr, 13rg, and 13rb are provided with quarter-wave retarders 23r, 23g, and 23b and viewing angle compensation retarders 25r, 25g, and 25b, respectively, adjacent to each other. Image contrast can be improved. The quarter-wave retarders 23r, 23g, and 23b rotate the polarization axes of the polarized lights of the respective color lights. The viewing angle compensating retarders 25r, 25g, and 25b compensate so that the liquid crystal layer eliminates the phase difference deviation of the polarized light of each color light. The quarter-wave retarders 23r, 23g, and 23b are rotation-adjustable, and the viewing-angle compensating retarders 25r, 25g, and 25b are fixed. Here, the quarter-wave retarders 23r, 23g, and 23b are each composed of a reflective display element 13rr, 13rg, 13rb and a polarizing beam splitter 19gb, 19r, or a reflective display element 13rr, 13rg, 13rb and an incident-side polarizer. The contrast is improved by rotating and adjusting the polarization axes of 14r and 14gb. The viewing angle compensating phase difference plates 25r, 25g, and 25b improve the contrast by compensating for eliminating the phase difference of the polarized light incident on the reflective display elements 13rr, 13rg, and 13rb at an angle. The quarter-wave retarders 23r, 23g, and 23b are incident on the polarizing beam splitters 19gb and 19r at the time of incidence and re-incidence which occur due to the inclination angle of light to the film surface. Compensate for the phase difference at the time and improve the contrast. In the present embodiment, the quarter-wave retarders 23r, 23g, and 23b are in a plane substantially perpendicular to the optical axis incident thereon or in a plane substantially parallel to the reflective surfaces of the reflective display elements 13rr, 13rg, and 13rb. Have a phase difference.
[0008]
FIG. 2 is a diagram for explaining the principle of the viewing angle compensating phase difference plates 25r, 25g, and 25b used in the configuration of FIG. In this description, a case will be described in which the reflective display element 13 is a liquid crystal panel, and the viewing angle compensating phase difference plate 25 also has a liquid crystal layer. In the reflective display element 13 subjected to rubbing, even when power is applied, the liquid crystal layer 13f near the alignment film 13e does not become vertical as shown in FIG. 2 (a). The contrast deteriorates. When the viewing angle compensating phase difference plate 25 is provided adjacent to the reflective display element 13, the viewing angle compensating phase difference plate 25 has its own liquid crystal layer 25f substantially inverted as shown in FIG. 2B. Since the phase difference generated in the reflection type liquid crystal display element 13 can be canceled, the contrast of incident light from an oblique direction can be improved. The same applies to light reflected by the reflective display element 13 and emitted from an oblique direction. As described above, the viewing angle compensating retarder 25 has a different role in improving the contrast from the above-mentioned quarter-wave retarder. In the present embodiment, both are used in combination. In particular, this makes it possible to further improve the contrast of the incident light obliquely. A phase difference plate having a phase difference in the optical axis direction may be used as the viewing angle compensation phase difference plate.
[0009]
Then, either the B light or the G light is converted from the S-polarized light to the P-polarized light by the specific wavelength selection wavelength plate 20b that converts the polarization direction only in the specific wavelength region. In the light incident on the specific wavelength selection wavelength plate 20b, G light is P-polarized light and B light is S-polarized light. Here, only the G light is polarization-converted, and both the G light and the B light are incident on the polarization beam splitter 19w as P-polarized light. The R light transmitted through the polarization beam splitter 19r dedicated to the R light is converted into S-polarized light by the １ ／ wavelength phase difference plate 5, and then enters the polarization beam splitter 19w. In the polarization beam splitter 19w, the R light, the G light, and the B light are color-combined again. The color-combined light passes through the projection lens unit 12, is enlarged and projected, and displays an image on a screen. Power is supplied from a power supply (not shown) to a light source (not shown) and a drive circuit (not shown). The reflective image display elements 13rr, 13rg, 13rb, the incident-side polarizers 14r, 14gb, and the quarter-wave retarders 23r, 23g, 23b may be deteriorated in performance or damaged at high temperatures. There is. For this reason, it is necessary to perform cooling or the like and keep the temperature at, for example, 70 degrees or less.
According to the configuration of the first embodiment, the contrast of the displayed image can be increased without increasing the size of the device.
[0010]
3 and 4 show a second embodiment of the present invention.
The second embodiment is an example in the case of using a 1/4 wavelength phase difference plate and a viewing angle compensation phase difference plate integrated with each other. FIG. 3 is a diagram showing an example of an integrated configuration of a 1/4 wavelength phase difference plate and a viewing angle compensation phase difference plate, and FIG. 4 is a configuration example diagram of a projection type video display device using the same.
In FIG. 3, reference numeral 23 denotes a quarter-wave retarder, 25 denotes a viewing angle compensating retarder, 27 denotes a glass plate, and 24 denotes a quarter-wave retarder 23 and a viewing angle compensating retarder 25 bonded together. This is an integrated structure phase difference plate with an integrated structure. (A) is a structure in which the quarter-wave retardation plate 23 and the viewing angle compensating retardation plate 25 are directly bonded to each other to form an integrated structure. The compensating retardation plate 25 is bonded via a glass plate 27 to form an integrated structure. With these integrated structures, the number of light incident surfaces into the air and the number of light exit surfaces from the air can be reduced. Therefore, the reflection loss that occurs when light passes through these surfaces can be reduced, and the light use efficiency can be increased. Further, it is also possible to suppress the deterioration of the contrast that occurs because the reflected light enters the projection lens unit 12 as stray light.
[0011]
FIG. 4 shows a configuration example of a projection type video display device using the above-mentioned integrated structure phase difference plate. 2 shows a second embodiment of the present invention. In FIG. 4, reference numeral 24r denotes an integrated structure phase plate for R light, 24g denotes an integrated structure phase plate for G light, and 24b denotes an integrated structure phase plate for B light. The integrated structure phase difference plate 24r is obtained by integrating the 1/4 wavelength phase difference plate 23r and the viewing angle compensation phase difference plate 25r in the configuration of FIG. The phase difference plate 23g and the viewing angle compensation phase difference plate 25g are integrated, and the integrated structure phase difference plate 24b is the same as the １ ／ wavelength phase difference plate 23b and the viewing angle compensation phase difference plate 25b integrated. Equivalent to. The configuration of the other parts is the same as in the case of FIG.
Also according to the configuration of the second embodiment, it is possible to increase the contrast of the displayed image without increasing the size of the device. In particular, since the integrated structure phase difference plate is used, the light utilization rate can be improved, and a bright screen can be obtained.
[0012]
FIG. 5 is a diagram showing a third embodiment of the present invention.
The third embodiment is an example in which an optical component having the same function as a quarter-wave retarder is composed of two retarders, thereby increasing the contrast. In FIG. 5, 26r and 26r 'are two retardation plates having the same action as the 1/4 wavelength retardation plate for R light, and 26g and 26g' are the same as 1/4 wavelength retardation plates for G light. The two retardation plates 26b and 26b 'having the function are two retardation plates having the same function as the quarter-wave retardation plate for B light. One of the two is fixed, and the other is rotatable. By making it rotatable, the sensitivity for adjusting contrast can be increased, and adjustment can be easily performed. No viewing angle compensating phase difference plate is used. The configuration of the other parts is the same as in the case of FIGS.
[0013]
When the fixed side is a 1 / m-wavelength phase difference plate (m> 0) and the rotating side is a 1 / n-wavelength phase difference plate (n> 4), the two phase difference plates may satisfy the following.
[0014]
1 / m + 1 / n = 1/4 (Equation 1)
An example of wavelength distribution is shown below. The shorter the wavelength allocated for rotation, the lower the sensitivity of the phase difference plate to rotation.
(1) For rotation: 1/8 wavelength retarder, for fixing: 1/8 wavelength retarder
(2) For rotation: 1/16 wavelength phase difference plate, for fixing: 3/16 wavelength phase difference plate
(3) For rotation: 1/32 wave retarder, for fixing: 7/32 wave retarder
According to the configuration of the third embodiment, it is possible to increase the contrast of the displayed image without increasing the size of the device.
[0015]
FIG. 6 is a diagram showing a fourth embodiment of the present invention.
In the fourth embodiment, in addition to a configuration in which a quarter-wave retardation plate and a viewing angle compensation retardation plate are arranged adjacent to a reflection type display element, a color separation / synthesis is performed by using a rod lens at a subsequent stage of a light source unit. This is an example in which three reflective polarizing plates and one cross dichroic prism are used in the system.
In FIG. 6, 1 is a light source unit, 41 is a rod lens having a polarization conversion function, 43 is an imaging lens group that irradiates an image of the exit of the rod lens 41 onto a reflective liquid crystal panel, and 17a and 17b are reflections. A reflecting dichroic mirror 18b transmits B light, reflects R light and G light, and a reflecting dichroic mirror 18c transmits R light and reflects G light, 14r, 14g, and 14b respectively. , An incident-side polarizing plate for R light, an incident-side polarizing plate for G light, an incident-side polarizing plate for B light, 42r is a reflective polarizing plate for R light, 42g is a reflective polarizing plate for G light, 42b is a reflective polarizing plate for B light, 13r is a reflective video display element for R light, 13g is a reflective video display element for G light, 13b is a reflective video display element for B light, 14r ', 14g 'and 14b' are emission-side polarizations for R light, respectively. , Exit polarizing plate for G light, the second polarizer for B light, 5 '1/2 wave plate for G light, 40 a cross dichroic prism, 12 denotes a projection lens unit. In each of the reflective polarizing plates, the hatched portion in the drawing is on the working surface side. In such a configuration, the light emitted from the light source 1 passes through the rod lens 41, is bent by 90 ° in the reflection mirror 17a, and is further color-separated into R light, G light, and B light by dichroic mirrors 18b and 18c. You. The B light that has passed through the dichroic mirror 18b and has been color-separated has its light ray direction bent by 90 ° by the reflecting mirror 17b, and is incident on the B-light polarizing plate 14b, the B-light reflective polarizing plate 42b, and the B light. Through the 1/4 wavelength phase difference plate 23b for B light and the viewing angle compensation phase difference plate 25b for B light to irradiate the reflection type image display element 13b for B light. The R light that has been reflected by the dichroic mirror 18b and then transmitted through the dichroic mirror 18c and color-separated is R-light incident side polarizer 14r, R-light reflective polarizer 42r, and １ ／ of the R light. The light passes through the wavelength phase difference plate 23r and the viewing angle compensation phase difference plate 25r for R light, and is irradiated on the reflection type image display element 13r for R light. After being reflected by the dichroic mirror 18b, the G light further reflected by the dichroic mirror 18c and color-separated is incident on the G-light polarizing plate 14g, the reflective G-light polarizing plate 42g, and 1 / G of the G light. The light passes through the four-wavelength phase difference plate 23g and the viewing angle compensation phase difference plate 25g for G light, and is irradiated to the reflection type image display element 13g for G light. Each irradiated color light is
Each of the reflective image display elements 13r, 13g, and 13b is reflected in a state where the polarization direction is changed based on the image signal. The R light reflected by the reflection-type image display element 13r again passes through the viewing angle compensation phase difference plate 25r for the R light and the quarter-wave phase difference plate 23r for the R light, and then the reflection type polarization light for the R light. The light enters the plate 42r. The incident R light is reflected by the reflection-type polarizing plate 42r, and enters the cross dichroic prism 40 via the emission-side polarizing plate 14r 'for R light. Similarly, the G light reflected by the reflection-type image display element 13g passes again through the viewing angle compensation phase difference plate 25g for G light and the １ ／ wavelength phase difference plate 23g for G light to pass through the G light. The light enters the reflective polarizing plate 42g. The incident G light is reflected by the reflection-type polarizing plate 42g, and enters the cross dichroic prism 40 via the emission-side polarizing plate 14g 'for G light and a half-wave retardation plate. The B light reflected by the reflection-type image display element 13b also passes through the viewing angle compensation phase difference plate 25b for the B light and the 波長 wavelength phase difference plate 23b for the B light, and then the reflection type polarizing plate for the B light. 42b. The B light is reflected by the reflection-type polarizing plate 42b, and enters the cross dichroic prism 40 via the emission-side polarizing plate 14b 'for B light. In the cross dichroic prism 40, the R light, the G light, and the B light are color-combined into white light, and emitted to the projection lens unit 12 side. From the projection lens unit 12, white image light is enlarged and projected on a screen. Although the rod lens 41 is used as the integrator in the configuration of FIG. 6, the present invention is not limited to this, and a light pipe, a multi-lens, or the like may be used. The operations of the quarter-wave retarders 23r, 23g, 23b and the viewing angle compensating retarders 25r, 25g, 25b are the same as those in the first embodiment.
Also in the configuration of the fourth embodiment, it is possible to increase the contrast of a displayed image without increasing the size of the device.
[0016]
FIG. 7 is a diagram showing a fifth embodiment of the present invention.
The fifth embodiment is an example of a configuration in which each of the color-separated color lights is reflected by a rotating polygonal reflector and irradiated to a reflection-type image display element.
In FIG. 7, reference numerals 8a and 8b denote collimator lenses, and reference numerals 18r, 18g and 18b denote dichroic mirrors each serving as a color separation unit. Among them, 18r denotes a dichroic mirror for reflecting R light and transmitting B light and G light. , 18b are dichroic mirrors for reflecting B light and reflecting G light for reflecting B light, and 18g are dichroic mirrors for reflecting G light which reflect G light. The dichroic mirrors 18r, 18g, and 18b are arranged in a non-parallel state to each other, and the order of arrangement is determined based on the spectral characteristics of the light source and in consideration of the color balance on an image projection surface such as a screen. 8c and 8d are collimator lenses for condensing each color light emitted from the dichroic mirrors 18r, 18g and 18b, 30 is a rotating polygonal reflector, 19 is a polarization beam splitter, and 13 is an image of each irradiated color light. A reflection type image display device such as a reflection type liquid crystal panel which modulates and emits light in accordance with a signal, 14 is an incident side polarizing plate, 14 'is an outgoing side polarizing plate, and 12 is a projection lens unit. The rotating polyhedral reflector 30 has a plurality of reflective surfaces that are annularly continuous on the inner peripheral side (the side facing the central axis) around the central axis. Each of the plurality of reflecting surfaces is arranged axially symmetric with respect to the central axis and inclined with respect to the longitudinal direction of the central axis, and an angle formed by an adjacent reflecting surface or an angle formed by a tangent of the adjacent reflecting surface is formed. The angle is made smaller than 180 ° on the light input / output side. The rotating polygonal reflector 30 is rotated at a predetermined speed around the central axis by a motor, and the plurality of reflecting surfaces on the rotating polygonal reflector 30 are sequentially rotated while rotating about the central axis to form the collimator lens 8c. , 8d is reflected and emitted to the polarization beam splitter 19 side. The direction of the reflected light changes due to the switching of the reflecting surface of the rotating polygonal reflector 30 and the change in the incident point and the incident angle on each reflecting surface, and the direction of the outgoing light toward the polarizing beam splitter 19 is changed. Changes over time. The respective color lights emitted from the polarization beam splitter 19 are applied to the reflection type image display device 13 through the 波長 wavelength phase difference plate 23 and the viewing angle compensation phase difference plate 25. Each color light applied to the reflective image display element 13 is sequentially switched while the incident / reflective point and the incident / reflective angle of the light on the reflective surface are changed based on the rotation of the rotating polygonal reflector 30. , Moves on the image display element 13 in a predetermined direction. Each color light applied to the reflective image display element 13 is
The light is reflected in the reflection type image display element 13 in a state where the polarization direction is changed based on the image signal. Each color light of R light, G light and B light reflected by the reflection type image display element 13 passes through the viewing angle compensating phase difference plate 25 and the quarter wavelength phase difference plate 23 again and is incident on the polarization beam splitter 19. I do. In the polarization beam splitter 19, the R, G, and B light components are color-combined, and emitted as white light to the projection lens unit 12 side. From the projection lens unit 12, white image light is enlarged and projected on a screen. The functions of the viewing angle compensating phase difference plate 25 and the quarter wavelength phase difference plate 23 are the same as those in the first embodiment.
Also in the configuration of the fifth embodiment, the contrast of the displayed image can be increased without increasing the size of the device.
[0017]
Note that the viewing angle compensating phase difference plate in each of the first, second, fourth, and fifth embodiments is not limited to the configuration having a liquid crystal layer, and may have another configuration. In the third embodiment, two retardation plates having substantially the same action as the quarter retardation plate are used for each color light. However, the present invention is not limited to this. Alternatively, a configuration in which three or more sheets are provided for each color light may be used, or a configuration in which two sheets are used for a certain color light and three or more sheets are used for another color light.
[0018]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, in a projection type video display apparatus, the contrast of a display image can be increased.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of the present invention.
FIG. 2 is a diagram illustrating the principle of a viewing angle compensation phase difference plate.
FIG. 3 is a diagram illustrating an example of an integrated configuration of a quarter-wave retardation plate and a viewing angle compensation retardation plate.
FIG. 4 is a diagram showing a second embodiment of the present invention.
FIG. 5 is a diagram showing a third embodiment of the present invention.
FIG. 6 is a diagram showing a fourth embodiment of the present invention.
FIG. 7 is a diagram showing a fifth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source unit, 2 ... Reflector, 3 ... Polarization conversion element, 5, 5 '... 1/2 wavelength phase difference plate, 6 ... 1st array lens, 7 ... 2nd array lens, 8, 8a, 8b, 8c, 8d: collimator lens, 9: condenser lens, 12: projection lens unit, 13, 13r, 13g, 13b, 13rr, 13rg, 13rb: reflective image display element, 13e: alignment film, 13f: liquid crystal layer, 14, 14gb, 14r, 14g, 14b ... incident side polarizing plate, 14 ', 14r', 14g ', 14b' ... exit side polarizing plate, 16a ... dichroic filter, 17, 17a, 17b ... reflection mirror, 18a, 18b, 18c, 18r, 18g, 18b: dichroic mirror, 19, 19gb, 19r: polarizing beam splitter, 20, 20a, 20b: specific wavelength selection wavelength plate, 2 ... Projection type video display device, 23, 23r, 23g, 23b ... 1/4 wavelength phase difference plate, 24 ... Integrated structure phase difference plate, 25, 25r, 25g, 25b ... Viewing angle compensation phase difference plate, 26r, 26g , 26b, 26r ', 26g', 26b ': retardation plate, 27: glass plate, 30: rotating polygonal reflector, 40: cross dichroic prism, 41: rod lens, 42r, 42g, 42b: reflective polarizer, 43 ... imaging lens group.

Claims (10)

In a projection-type image display device that performs polarization conversion of light from the light source side, irradiates the image display element, forms an optical image corresponding to the image signal, and enlarges and projects the image.
A viewing angle compensation phase difference plate for compensating for a phase difference shift of polarized light of each of the R, G, and B color lights that enter or exit from the image display element; and are disposed adjacent to the viewing angle compensation phase difference plate. A quarter-wave retarder for rotating the polarization axis of the polarized light of each color light,
A projection-type image display device characterized by comprising: a configuration capable of increasing the contrast of an optical image formed by the image display element. In a projection-type image display device that irradiates light from a light source side to an image display element to form an optical image according to an image signal and enlarge and project the image,
Polarization conversion means for aligning the polarization direction of light from the light source side to form P-polarized light or S-polarized light,
Separation means for separating polarization-converted polarized light into R, G, and B color lights;
An image display device that irradiates the polarized light of each of the separated color lights and modulates the polarized light based on an image signal;
A viewing angle compensation phase difference plate that is arranged adjacent to the image display element and compensates for a phase difference shift of color light incident or emitted to the image display element;
A quarter-wave retarder disposed adjacent to the viewing angle compensating retarder for rotating the polarization axis of the polarized light of the color light that enters or exits the image display element;
A color synthesizing unit that modulates the color of polarized light of each color light that is modulated by the image display element and emitted from the viewing angle compensation phase difference plate and the quarter wavelength phase difference plate;
A projection lens unit for enlarging and projecting the optical image of the color-combined polarized light,
A drive circuit for driving the video display element,
And the contrast of the optical image enlarged and projected by the projection lens unit by a combination of the phase difference compensation for the color light by the viewing angle compensation phase difference plate and the rotation of the polarization axis by the quarter wavelength phase difference plate. A projection type video display device characterized by a configuration capable of increasing the number of images. 3. The projection type image display device according to claim 1, wherein the viewing angle compensating phase difference plate is fixed, and the quarter wavelength phase difference plate is rotatable with respect to an optical axis. 3. The projection type image display device according to claim 1, wherein the viewing angle compensating phase difference plate and the quarter wavelength phase difference plate are optically integrated with each other. 5. The projection type video display according to claim 1, wherein the viewing angle compensating phase difference plate has a phase difference in an optical axis direction. In a projection-type image display device that performs polarization conversion of light from the light source side, irradiates the image display element, forms an optical image corresponding to the image signal, and enlarges and projects the image.
A second light source which is disposed adjacent to the image display element and rotates the polarization axis of the polarized light of each of the R, G, and B color lights entering or exiting the image display element by approximately 1 / m wavelength (m> 0). 1 retardation plate,
A second retardation plate disposed adjacent to the first retardation plate and rotating the polarization axis of the polarized light of each color light by approximately 1 / n wavelength (n>4);
A configuration in which the two phase difference plates perform phase difference compensation on the image display element substantially equal to that of a quarter wavelength phase difference plate, thereby increasing the contrast of an optical image formed by the image display element. A projection type video display device characterized by the above-mentioned. In a projection-type image display device that irradiates light from a light source side to an image display element to form an optical image according to an image signal and enlarge and project the image,
Polarization conversion means for aligning the polarization direction of light from the light source side to form P-polarized light or S-polarized light,
Separation means for separating polarization-converted polarized light into R, G, and B color lights;
An image display device that irradiates the polarized light of each of the separated color lights and modulates the polarized light based on an image signal;
A second light source which is disposed adjacent to the image display element and rotates the polarization axis of the polarized light of each of the R, G, and B color lights entering or exiting the image display element by approximately 1 / m wavelength (m> 0). 1 retardation plate,
A second retardation plate disposed adjacent to the first retardation plate and rotating the polarization axis of the polarized light of each color light by approximately 1 / n wavelength (n>4);
A color synthesizing unit that performs color synthesis of polarized light of each color light modulated by the video display element and emitted from the first and second retardation plates;
A projection lens unit for enlarging and projecting the optical image of the color-combined polarized light,
A drive circuit for driving the video display element,
And the two phase difference plates perform the same phase difference compensation on the image display element as the １ ／ wavelength phase difference plate, thereby increasing the contrast of the optical image enlarged and projected by the projection lens unit. A projection type video display device having a configuration. 8. The projection display according to claim 6, wherein one of the first and second phase difference plates is fixed and the other is rotatable with respect to an optical axis. In an optical unit for a projection-type image display device that irradiates light from a light source side to an image display element to form an optical image according to an image signal and performs enlarged projection,
Polarization conversion means for aligning the polarization direction of light from the light source side to form P-polarized light or S-polarized light,
Separation means for separating polarization-converted polarized light into R, G, and B color lights;
An image display device that irradiates the polarized light of each of the separated color lights and modulates the polarized light based on an image signal;
A viewing angle compensation phase difference plate that is arranged adjacent to the image display element and compensates for a phase difference shift of color light incident or emitted to the image display element;
A quarter-wave retarder disposed adjacent to the viewing angle compensating retarder for rotating the polarization axis of the polarized light of the color light that enters or exits the image display element;
A color synthesizing unit that modulates the color of polarized light of each color light that is modulated by the image display element and emitted from the viewing angle compensation phase difference plate and the quarter wavelength phase difference plate;
A projection lens unit for enlarging and projecting the optical image of the color-combined polarized light,
And the contrast of the optical image enlarged and projected by the projection lens unit by a combination of the phase difference compensation for the color light by the viewing angle compensation phase difference plate and the rotation of the polarization axis by the quarter wavelength phase difference plate. An optical unit characterized in that it is possible to increase the number. In an optical unit for a projection-type image display device that irradiates light from a light source side to an image display element to form an optical image according to an image signal and performs enlarged projection,
Polarization conversion means for aligning the polarization direction of light from the light source side to form P-polarized light or S-polarized light,
Separation means for separating polarization-converted polarized light into R, G, and B color lights;
An image display device that irradiates the polarized light of each of the separated color lights and modulates the polarized light based on an image signal;
A second light source which is disposed adjacent to the image display element and rotates the polarization axis of the polarized light of each of the R, G, and B color lights entering or exiting the image display element by approximately 1 / m wavelength (m> 0). 1 retardation plate,
A second retardation plate disposed adjacent to the first retardation plate and rotating the polarization axis of the polarized light of each color light by approximately 1 / n wavelength (n>4);
A color synthesizing unit that performs color synthesis of polarized light of each color light modulated by the video display element and emitted from the first and second retardation plates;
A projection lens unit for enlarging and projecting the optical image of the color-combined polarized light,
And the two phase difference plates perform the same phase difference compensation on the image display element as the １ ／ wavelength phase difference plate, thereby increasing the contrast of the optical image enlarged and projected by the projection lens unit. An optical unit having a configuration.

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