JP2007279763A - Projection type video display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type video display apparatus which is compact, lightweight and bright and uses a reflection type video display element free from contrast reduction due to light leakage in black display. <P>SOLUTION: Reflection type polarizing plates having a grating action in the same specific direction as a polarizer and an analyzer for the reflection type video display element and functioning as polarizing plates are used and disposed on an optical path and just before and just after the reflection type video display element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projection device that projects an image on a screen using a reflective liquid crystal panel, for example, a projection video display device such as a reflective liquid crystal projector or a reflective liquid crystal rear projector, and a projection video display device. This relates to the optical unit.

  2. Description of the Related Art Conventionally, there is known a projector that projects light on a screen or the like by controlling light from a light source by changing light and shade for each pixel with a light valve element. Light valve elements include transmissive liquid crystal panels, reflective liquid crystal panels, and micromirror panels. Reflective liquid crystal panels have a high aperture ratio, so that both high brightness and high resolution can be achieved. Because it does not depend on mechanical operation, it has a long life.

  The optical unit of the reflective liquid crystal projector using the reflective liquid crystal panel will be described below. The non-polarized light emitted from the light source is converted into linearly polarized light by the polarization conversion element and enters the polarizer. Since the polarizer can transmit only the polarization component in a specific direction and absorb (or reflect) the component orthogonal to it, the incident light to the polarizer is reflected after the unnecessary polarization component is removed by the polarizer. Incident on the liquid crystal panel. The light incident on the reflective liquid crystal panel is modulated in polarization state for each pixel in accordance with the video signal by the reflective liquid crystal panel. The light reflected by the reflective liquid crystal panel enters the analyzer. The analyzer can also transmit only the polarized component in a specific direction and absorb (or reflect) the component orthogonal thereto, so that the amount of light transmitted or reflected by the analyzer is determined by the polarization state of the outgoing light from each pixel. The video thus obtained is enlarged and projected by the projection lens.

  In general, a polarizing beam splitter prism (hereinafter referred to as a PBS prism) is used for the polarizer and the analyzer. The PBS prism has a dielectric multilayer film surface, and transmits P-polarized light and reflects S-polarized light by the film surface (hereinafter referred to as PBS film). Therefore, if the PBS prism is arranged so that the PBS film is 45 ° with respect to the reflective liquid crystal panel, the optical axis of the incident light to the reflective liquid crystal panel and the optical axis of the reflected light from the reflective liquid crystal panel should be matched. This is advantageous in realizing a small reflective liquid crystal projector.

  A reflection type liquid crystal projector using a PBS prism as an analyzer is introduced in, for example, Japanese Patent Application Laid-Open No. 2001-142028. In the configuration of this publication, leakage light from the PBS prism during black image display is generated according to the following principle. Since the S-polarized light and the P-polarized light with respect to the PBS film are determined according to the angle of the incident light beam, the S-polarized direction when the light beam parallel to the main incident surface including the optical axis and the normal line of the PBS film is transmitted or reflected by the PBS prism. The S-polarization direction coincides with the P-polarization direction when the light beam is reflected by the reflective liquid crystal panel (not polarized during black display) and re-enters the PBS prism. On the other hand, the S-polarization direction and the P-polarization direction when a light beam not parallel to the main incident surface is transmitted or reflected by the PBS prism, and the S-polarization light when the light beam is reflected by the reflective liquid crystal panel and reenters the PBS prism. The direction and the P polarization direction are different. However, since the polarization direction of the light beam that has been transmitted or reflected through the PBS prism is maintained even when re-incident, light rays that are parallel to the main incident surface are completely transmitted or reflected when re-incident, but are not parallel to the main incident surface. The light beam reflects the S-polarized component of the polarized light and transmits the P-polarized component. For this reason, light rays that are not parallel to the main incident surface cause leakage light, which causes light leakage during black images, that is, a factor in reducing contrast. In order to prevent this reduction in contrast, a quarter-wave plate is disposed between the PBS prism and the reflective liquid crystal panel so that the slow axis or the fast axis is parallel to the main incident surface. The light beam transmitted or reflected through the PBS prism is reflected by the reflective liquid crystal panel and is transmitted through the quarter wavelength plate twice while re-entering the PBS prism, which is equivalent to transmitting through the half wavelength plate. Therefore, the P-polarized light or the reflected S-polarized light transmitted after being incident on the PBS prism after being incident on the main incident surface is rotated by the quarter-wave plate, and becomes P-polarized light or S-polarized light when the PBS prism is re-entered. Therefore, no leakage light is generated, and a decrease in contrast can be prevented.

  A method of improving the contrast by inserting a λ / 4 plate between the projection lens and the cross dichroic prism has also been proposed (see, for example, Patent Document 1).

JP 9-251150 A

  However, in a configuration using a PBS prism as a polarizer and an analyzer for a reflective liquid crystal panel as in the above-mentioned document, even when a quarter-wave plate is used to prevent contrast reduction, the effect is not perfect. The wave plate is made of a transparent material having birefringence that the refractive index varies depending on the polarization direction of the transmitted light, the slow axis direction is the direction with the highest refractive index, and the fast axis direction is the most refractive index. Is in the lower direction. The quarter wave plate is the product of the difference in refractive index between the slow axis and the fast axis when a light ray perpendicular to the wave plate is incident and the distance (¼ wave plate thickness) through which the light ray passes through the wave plate ( The phase difference is designed to be 1/4 of the design center wavelength. For this reason, the wave plate has a wavelength characteristic and an angle characteristic, and the function decreases as the incident light beam moves away from the design center wavelength and as the incident angle increases. For this reason, even if a quarter wavelength plate is used to prevent light leakage of oblique incident light when a PBS prism is used as a polarizer and analyzer of a reflective liquid crystal panel, light leakage of oblique incident light is completely prevented. The contrast cannot be achieved. Even if a polarizing plate is placed between the PBS prism and the projection lens in an attempt to prevent projection of this leakage light onto the screen, this leakage light is mostly prevented because it is the same polarization component as the transmission axis direction of the polarizing plate. I can't.

  Use of a PBS prism is disadvantageous in terms of weight. Furthermore, it is necessary to use a glass material having a low photoelastic coefficient for the PBS prism so that the contrast does not decrease due to leakage light caused by polarization disturbance when light passes through the glass material. Such a glass material is particularly heavy because of its large specific gravity, and is expensive because of its small circulation. When a PBS film is formed on a transparent parallel plate for weight reduction, it is generally difficult to design a PBS film and it is difficult to realize a high-performance PBS film, so it is difficult to realize high brightness and high contrast. In order to avoid this, when it is formed between two transparent parallel plates, astigmatism occurs and the resolution is lowered. Therefore, a correction part is required to prevent the resolution from being lowered.

  An object of the present invention is to solve the above-mentioned problems and to provide a projection-type image display apparatus using a reflection-type image display element that is small and light and has good image quality performance such as brightness, contrast, and resolution.

  In order to solve the above problems, the present application relates to a light source unit that emits light, three reflective video display elements that are light valve means for forming an optical image corresponding to a video signal, and light from the light source unit. A color separation system that color-separates into three color lights and enters the reflective image display element corresponding to each color light, a color composition system that synthesizes the three color lights from the reflective image display element, and a color-combined optical image. A projection-type image display device comprising projection means for projecting, wherein a first polarized light having a predetermined polarization direction is reflected by a diffraction action as a polarizer and an analyzer for the reflection-type image display element, and the predetermined direction A flat plate-type reflective polarizing plate that transmits the second polarized light having a polarization direction substantially perpendicular to the first polarizing light beam, and one of the first polarized light and the first polarized light on the output side of the reflective polarizing plate. And an auxiliary analyzer that passes through the color The composition system is configured by a color synthesis prism, and each color light separated by the color separation system is incident on the reflection type image display element via the reflection type polarizing plate, and is formed by the reflection type image display element. The optical image of the reflected light is arranged so as to be incident on the color composition system via the reflective image display element.

  As described above, the reflection type liquid crystal projector optical unit and the reflection type liquid crystal projector according to the present invention are configured as described above using the reflection type polarizing plate that acts as a polarizing plate by having a lattice action only in a specific direction. This eliminates the need for a PBS prism and a quarter-wave plate for PBS prism correction, and prevents the projection lens and the structural parts holding the reflective liquid crystal panel from interfering with each other. Improvement, reduction in the number of parts (improvement of brightness), and reduction in size and weight can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of an optical unit for a reflective liquid crystal projector according to the present invention.

  The projection display device 22 includes a light source unit 1 having a light source 1a. The light source 1a is a white lamp such as an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, or a halogen lamp. The light emitted from the light bulb 1a of the light source 1 is collected and reflected by the ellipsoidal, parabolic or aspherical reflector 1b. Since the light source 1 becomes high temperature due to the heat generated from the light bulb 1a, the light source 1 is cooled by the cooling fan 40 disposed at the rear.

  This is composed of a plurality of condensing lenses provided in a rectangular frame of substantially the same size as the exit aperture of the reflector 1b, and condenses light emitted from the lamp unit to form a plurality of secondary light source images. The first array lens 32 is incident on one array lens 32, further includes a plurality of condensing lenses, is disposed in the vicinity of the plurality of secondary light source images, and is formed on the reflective liquid crystal panel 10. The light passes through the second array lens 33 that forms individual lens images.

  The first array lens 32 and the second array lens 33 have vertically long cells in order to bend the optical path in the vertical direction in order to irradiate the reflection type image display element at the subsequent stage. This outgoing light is polarized light conversion constituted by a row of rhombus prisms of approximately ½ size of each lens width arranged so as to match the longitudinal pitch of each lens optical axis of the second array lens 33. Incident on the element 31.

  A polarization separation film is provided on the prism surface, and 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 as it is. On the other hand, the S-polarized light is reflected by the polarization separation film, reflected once again in the original optical axis direction in the adjacent rhomboid prism, and then polarized by the λ / 2 phase difference plate provided on the exit surface of this prism. The direction is rotated by 90 °, converted into P-polarized light, and emitted. That is, P-polarized light is emitted from the polarization conversion element 31. The collimator lens 34 has a positive refractive power and has a function of condensing light. The light irradiates the reflective liquid crystal panel 11 of three colors RGB.

  This configuration is a two-stage configuration, and after color separation by the RB transmission G reflection dichroic mirror 36, the G light is reflected upward by the white reflection mirror 5. The R transmission B reflection dichroic mirror 37 transmits the B light, reflects the R light upward, and separates the RB light in color. The B light is also reflected upward by the reflecting mirror 5 via the imaging lens group 4.

  In this way, the light separated into the optical paths of the three colors is respectively an R auxiliary polarizer (not shown), a G auxiliary polarizer 92, and a B auxiliary polarizer arranged to improve the contrast. 93, and passes through a reflective polarizing plate for R (polarization separation element) 101, a reflective polarizing plate for G (polarization separation element) 102, and a reflective polarizing plate for B (polarization separation element) 103, for R use. The light enters the reflective liquid crystal panel 111, the G reflective liquid crystal panel 112, and the B reflective liquid crystal panel 113.

  The reflective polarizing plate 10 has a substantially rectangular shape, and the short side is inclined by approximately 45 degrees with respect to the optical axis. By doing so, the distance from the reflective liquid crystal panel 10 to the reflective polarizing plate 11 can be shortened, and the back focus of the projection lens can be shortened. Thereby, the aberration of a projection lens can be improved.

  The reflective liquid crystal panel 11 is provided with a number of liquid crystal display units having an aspect ratio of 16: 9 corresponding to the pixels to be displayed (for example, 3900 horizontal pixels by 1080 vertical pixels). The phase angle of the polarization of each pixel of the panel 11 changes according to a signal driven from the outside, and the light having the same polarization direction is analyzed by the reflective polarizing plate and the auxiliary analyzer. The amount of light having polarized light at an intermediate angle is determined by the relationship between the polarization degree of the reflective polarizing plate and the auxiliary analyzer. In this way, an image according to a signal input from the outside is displayed. At this time, when the reflective liquid crystal panel 11 performs black display, the polarization direction is substantially the same as the incident light, and the light is returned to the light source side along the incident optical path.

  In each optical path, the optical axis of the reflective surface of the reflective liquid crystal panel 11 is orthogonal to the optical axis of the incident surface of each color light of the cross dichroic prism 14, and each light is positioned in the vicinity of the position where the optical axes of both are substantially orthogonal. The reflective polarizing plate 10 is disposed so as to be inclined at about 45 degrees with respect to the axis. With this configuration, the components arranged in the optical path of each color light of the cross dichroic prism 14 are arranged from the reflective polarizing plate to the auxiliary analyzer as viewed from the incident surface of the cross dichroic prism 14. Are symmetric in each optical path and are substantially equivalent. From the viewpoint of image formation, the optical path length from each panel 11 to the projection lens 15 needs to be substantially equal in each optical path. Therefore, by arranging them symmetrically as described above, interference between components and optical path interference occurs. Can be minimized and the design is easy. Further, by arranging them symmetrically in this way, the space can be used more efficiently and the size can be reduced.

  The light reflected by the R, G, and B reflective liquid crystal panels is reflected by the R reflective polarizing plate 101, the G reflective polarizing plate 102, and the B reflective polarizing plate 103, respectively, so that the direction of the light beam is substantially reduced. It is bent by 90 °, passes through the auxiliary analyzer 121 for R, the auxiliary analyzer 122 for G, and the auxiliary analyzer 123 for B, and G passes through the G half-wave plate 13 and is converted to P-polarized light. , R, G, and B are incident on the cross dichroic prism 14.

  In this embodiment, the optical axes of the reflective surfaces of the three reflective liquid crystal panels 11 face the same direction, and the three reflective surfaces are arranged at substantially the same height with respect to a certain one. is there. By adopting this configuration, the adjustment work of the pixel alignment of the three panels 11 and the work of fixing the panel 11 to the holding parts after the adjustment can be performed by jigs from the same direction. As a result, the working time can be shortened and the cost can be reduced. Moreover, if a rotation mechanism is attached to a jig, all the panels 11 can be adjusted using the same jig, and a jig design and production cost can be reduced.

  Further, since the reflective liquid crystal panel has no optical path on the back side, it can be cooled by attaching a heat sink to the back side. With this configuration, it is possible to cool the three reflective liquid crystal panels more efficiently than the upper surface side by arranging only one cooling fan (not shown) on the upper surface side.

  In this embodiment, the three reflective liquid crystal panels 11 are arranged on the upper surface side that is not used in the optical path of the cross dichroic prism 14, and the height of the reflective liquid crystal panel 11 is higher than the upper surface of the cross dichroic prism 14. It is arranged in. Alternatively, as another embodiment, three reflective liquid crystal panels 11 are arranged on the lower surface side not used in the optical path of the cross dichroic prism 14, and the reflective liquid crystal panel 11 is below the lower surface of the cross dichroic prism 14. It may be arranged on the side. With such a configuration, interference between the panel 11 or the panel holding member and the cross dichroic prism 14 can be prevented, so that the size of the optical engine can be reduced.

  In this embodiment, the reflective polarizing plate 10 is fixedly held by providing a three-point projecting portion on the structural chassis, pressing the reflective surface side against it, and applying a force with a leaf spring or the like from the opposite direction. . The inclination of the reflective surface of the reflective polarizing plate 10 that reflects after being emitted from the panel affects the position on the screen and must be strictly managed. Since the structural chassis is made of a mold, it is easy to accurately manage the position and shape of the three-point protrusion in a mass-produced product. By directly pressing and holding the reflecting surface side against the three-point protrusions, the inclination of the reflecting surface in mass-produced products can be managed with high accuracy.

  In the present embodiment, the surface shapes of the reflective polarizing plates 101, 102, and 103 for R, G, and B are set within ± 3 (λ / inch) on the basis of a certain sheet. This is because the light is emitted from the reflective liquid crystal panel 11 and then reflected from the reflective polarizing plate 10. Therefore, when the reflective polarizing plate has a concave or convex shape, the reflective polarizing plate has a lens effect. And affects the imaging performance on the screen. Therefore, it is necessary to manage the surface shape of the reflective polarizing plate 10. In particular, in this method using three panels, it is important to secure the imaging performance to suppress the deviation of the mutual surface shape on the basis of a certain one sheet. FIG. 2 shows a result obtained by calculating the surface shape of the reflective polarizing plate and the converter shift relationship of each pixel by a ray tracing simulation. From this, it can be seen that in order to suppress the deviation of the conversion of each pixel within 0.3 pixel, it should be suppressed within ± 4 (λ / inch). The amount of deviation is preferably within ± 3 (λ / inch), and within ± 4 (λ / inch), which is a range that does not affect image quality deterioration. The deviation of the surface shape from the plane can be corrected to some extent by the focus adjustment function of the projection lens. For example, as another embodiment, as a method for easily managing and selecting parts, all of the three reflective polarizing plates are convex on the reflective surface side. Alternatively, all three reflection surfaces are effective as a concave shape.

  In general, the chromatic magnification aberration of the imaging performance depends on the wavelength, and therefore, either the order of R, G, and B becomes better or worse. That is, G takes the center value. Therefore, it is effective to adopt the G-use as a reference and suppress the deviation between them within Newton ± 3λ.

  The contrast and transmittance of the auxiliary polarizer 9, the reflective polarizing plate 10, and the auxiliary analyzer 12 used in this embodiment are in a trade-off relationship. That is, when the contrast is improved, the transmittance is deteriorated, and when the transmittance is improved, the contrast is deteriorated. Therefore, when this is seen as the performance of the projection display apparatus, it means that the contrast and the brightness are in a trade-off relationship.

  In this embodiment, a single component is not used to ensure contrast, but an auxiliary polarizer 9, a reflective polarizing plate 10, an auxiliary analyzer 12 and a plurality of components are used. It is effective to combine the performance of the optical components in accordance with the following rules in order to ensure high efficiency and high contrast of the projection display apparatus.

  The contrast of the optical system is obtained as follows.

1 / (Contrast of optical system = 1 / (Optical system contrast on the panel entrance side) + 1 / (Optical system contrast on the panel exit side)
It is understood from this that even if only the optical system contrast on the panel entrance side is improved or only the exit side is improved, it is not efficient. Balancing the contrast between the entrance side and the exit side is a method that optimally brings both brightness and contrast.

  The optical system contrast is obtained by the product of each component. That is, if the contrast of the auxiliary polarizer is A, the contrast of the auxiliary analyzer is D, the transmission contrast of the reflective polarizer is B, and the reflection contrast of the reflective polarizer is C, the incident side optical system contrast is A. * B, the optical system contrast on the exit side is obtained by C * D. Therefore, in order to balance both, an auxiliary polarizer, an auxiliary analyzer, and a reflective polarizing plate that satisfy the formula A * B = (0.1 to 10) * C * D may be used. When the auxiliary polarizer or the auxiliary analyzer is not used, 1 is substituted as the contrast and the above equation is satisfied.

  FIG. 3A shows a method for measuring the contrast of the absorption polarizing plate used for the auxiliary polarizer and the auxiliary analyzer. Light is emitted from the measurement light source 50. The spread of light incident on the measurement object by providing an opening after the light source 50 is approximately F20. Thereafter, the measurement polarizing plate 51 is arranged with its transmission axis aligned so that the P-polarized light is transmitted. Thereafter, the measurement object is placed and measured. The light passes through the object to be measured and enters the measurement light receiver 52, whereby the brightness of the transmitted light can be measured. The transmission axis of the absorptive polarizing plate is measured in two modes of S-polarized light transmission and P-polarized light transmission, and the contrast is obtained by taking the ratio of the measured values at each rotation angle. Brightness can be obtained by multiplying the spectral distribution of the measured transmittance by the visibility. That is, assuming that the transmittance T (λ) and the visibility A (λ), the brightness is theoretically the wavelength integral ∫T (λ) * of T (λ) * A (λ) in the used wavelength range. It is obtained by A (λ) dλ. In the actual measurement value, the transmittance T (λ) takes an intermittent value, so that the brightness is obtained by the sum of T (λ) * A (λ) in the used wavelength range. In the case of reflection, the reflectance R (λ) may be used instead of the transmittance T (λ).

  When the absorptive polarizing plate is arranged with P-polarized light transmission, the contrast is (P-polarized light brightness) / (S-polarized light brightness), and when it is arranged with S-polarized light transmission, the contrast is (S-polarized light brightness) / It is obtained by (brightness of P-polarized light).

  FIG. 3B shows a contrast measurement method for the reflective polarizing plate. The reflective polarizing plate is arranged with the transmission axis aligned with the P-polarized light and inclined by 45 degrees with respect to the optical axis. Brightness is measured by transmission and reflection when S-polarized light and P-polarized light are incident. Since the transmission axis is aligned with the P-polarized light, the contrast is (P-polarized light) / (S-polarized light) for transmission, and (S-polarized reflectance) / (P-polarized light reflection) for reflection. Rate).

  Here, in general, the contrast of the reflective polarizing plate is better when the P-polarized light is transmitted than when the S-polarized light is reflected. Therefore, from the above relationship, when the contrast of the auxiliary analyzer is higher than the contrast of the auxiliary polarizer, high efficiency and high contrast are possible. In other words, the above relationship can achieve high efficiency and high contrast when the transmission of the auxiliary analyzer is lower than that of the auxiliary polarizer.

  As shown in FIG. 4A, the display unit of the reflective liquid crystal panel 11 is held by a non-target structure 11b when viewed from the center a of the display unit. FIG. 4B shows a top view of the vicinity of the reflective liquid crystal panel and the cross dichroic prism 14. The reflective liquid crystal panel 11 is arranged on the side close to the cross dichroic prism 14 so that the shorter one of the structures 11b is seen from the display portion center 11a. That is, W1> W2 with respect to the center reference, and W2 is arranged on the cross dichroic prism side. With this configuration, since the reflective liquid crystal panel 11 can be disposed closer to the cross dichroic prism 14, the size of the apparatus can be reduced, and the distance from the reflective liquid crystal panel 11 to the cross dichroic prism 14 can be shortened. Therefore, the back focus of the projection lens 15 can be shortened, and aberrations can be improved.

  A second embodiment will be described with reference to FIG. Except for the following, the embodiment is the same as the embodiment of FIG. A polarization separation prism 38 that reflects S-polarized light that is substantially linearly polarized light and transmits P-polarized light that is substantially linearly polarized light substantially orthogonal thereto is disposed on the incident side of the reflective polarizing plate. When the polarization separation prism 38 is used, unlike the auxiliary polarizer 9 made of film, the heat resistance is increased, and cooling with a cooling fan is unnecessary, so that noise can be further reduced.

  A third embodiment will be described with reference to FIG.

  The first array lens and the second array lens have horizontally long cells, the polarization conversion elements 31 are arranged so as to conform to the vertical pitch, and the optical path is bent by about 90 degrees by the reflection mirror 5. Except for this, the configuration from the light source 1 to the collimator lens 34 is the same as the embodiment of FIG.

After color separation into R (red), G (green), and B (blue) by the dichroic mirrors 6 and 7, the direction of the light beam of B is bent by 90 ° by the B reflection mirror 17. , G auxiliary polarizer 92, B auxiliary polarizer 93, R reflective polarizer 101, G reflective polarizer 102, B reflective polarizer 103, and R corresponding to R, G, and B The light enters the reflective liquid crystal panel 111, the reflective liquid crystal panel 112 for G, and the reflective liquid crystal panel 113 for B. The light reflected by the R, G, and B reflective liquid crystal panels is reflected by the R reflective polarizer 101, the G reflective polarizer 102, and the B reflective polarizer 103, respectively, to change the direction of the light beam by 90. Are bent and respectively transmitted through the auxiliary analyzer 121 for R, the auxiliary analyzer 122 for G, and the auxiliary analyzer 123 for B, and G is transmitted through the G half-wave plate 13 and converted into P-polarized light, R, G, and B are incident on the cross dichroic prism 14. R, G, and B are combined into white by the cross dichroic prism 14 and enlarged and projected onto the screen by the projection lens 15.

  A viewing angle compensation phase difference plate 41 is disposed immediately in front of the reflective liquid crystal panel to improve the contrast of oblique light. In the reflective liquid crystal panel 41 subjected to rubbing, the liquid crystal layer in the vicinity of the alignment film does not become vertical even when power is applied, and there is a problem that the contrast deteriorates due to incident light from an oblique direction. On the other hand, since the viewing angle compensation phase difference plate 41 has a configuration in which the liquid crystal layer included in the viewing angle compensation phase difference plate 41 is substantially inverted, the phase difference generated in the reflective liquid crystal panel can be canceled. Thereby, the contrast of oblique light can be improved and the contrast can be improved.

  Next, the reflective polarizing plate will be described. A normal polarizing plate (polarizing film) performs its function with aligned dichroic molecules, transmits polarized light orthogonal to the molecular arrangement direction, and absorbs polarized light parallel to the molecular arrangement direction. A reflective polarizing plate that acts as a polarizing plate by having a lattice action only in a specific direction reflects polarized light parallel to the lattice direction and transmits polarized light orthogonal to the lattice direction. Therefore, there is no difference in basic polarization characteristics between the two polarizing plates. For example, the contrast is almost the same for all rays in the plane including the transmission axis of the polarizing plate and the normal line of the polarizing plate and in the plane including the absorption axis or reflection axis of the polarizing plate and the normal line of the polarizing plate. The characteristics are common to both polarizing plates.

  Therefore, in this configuration, no oblique light leakage occurs in the configuration using the PBS prism immediately before and after the panel, so that high contrast is possible without adding components such as a quarter-wave plate. Since most of the leakage light from the PBS prism is the same polarization component as the transmission axis direction of the polarizing plate, leakage light can be prevented even if a polarizing film (analyzer) is placed between the projection lens and the reflective liquid crystal panel. On the other hand, leakage light when using a reflective polarizing plate is often due to insufficient contrast of the reflective polarizing plate. In such a case, leakage is caused by using an auxiliary polarizer and an auxiliary analyzer. Since most of the light can be prevented, high contrast can be achieved.

  For example, the contrast (measured by replacing the reflective liquid crystal panel with a mirror) of the optical unit when the luminous flux incident on the reflective liquid crystal panel is F2.5 is 500 to 1000 when the PBS prism is used. In the case of using a reflective polarizing plate, it is 5000 to 10,000. In this configuration, the reflective surface of the reflective polarizing plate is on the reflective liquid crystal panel side, and the light reflected from the reflective liquid crystal panel does not pass through the transparent parallel plate that is the substrate of the reflective polarizing plate. Therefore, no astigmatism is generated, so that the resolution is not lowered. Further, in this configuration, since the prism uses only a cross dichroic prism, the weight equivalent to that of the optical unit for the transmissive projector can be realized.

  The auxiliary polarizer 9, the reflective polarizing plate 10, the reflective liquid crystal panel 11, and the auxiliary analyzer 12 are cooled by the cooling fan 40. Since both the auxiliary polarizer 9 and the auxiliary analyzer 12 are made of absorption film materials, it is necessary to cool them to about 70 degrees or less. The unnecessary light incident on the auxiliary analyzer 12 at the time of black display is light that has been cut once by the reflective polarizing plate 10 located on the incident side, so that the unnecessary light absorbed by this is small. On the other hand, the auxiliary polarizer 9 has a large amount of unnecessary light that is absorbed because light including unnecessary light is directly incident thereon, and thus generates a large amount of heat. Therefore, the auxiliary polarizer 9 needs to be cooled more strongly than the auxiliary analyzer 12, and the wind sent by the cooling fan is stronger for the auxiliary analyzer 12 than for the auxiliary polarizer 9.

  An exit-side quarter-wave plate 35 is bonded to the exit surface of the cross dichroic prism 14. Since the emission side quarter-wave plate 35 is disposed in the combined optical path, a broadband one may be used. The slow axis 35a of the output-side quarter-wave plate 35 is used with the angle θ of the auxiliary analyzer 12 with respect to the absorption axis 12a being set in a range of approximately 40 to 50 degrees, or approximately −40 to −50 degrees. . In this embodiment, it is set to approximately 45 degrees. When the contrast of the auxiliary polarizer 9 and the reflective polarizing plate 10 is insufficient and the contrast incident on the reflective liquid crystal panel 11 is low, or when the phase difference is not completely applied to the reflective liquid crystal panel 11 during black display The outgoing light from the reflective liquid crystal panel 11 during black display includes S-polarized light that cannot be cut by the reflective polarizer 10 and the auxiliary analyzer 12. S-polarized light passes through the reflective polarizing plate 10 and the auxiliary analyzer 12 and enters the projection lens 15. Since the projection lens 15 has a large number of lenses, the total transmittance is about 85%, and 15% is reflected. This reflected light is substantially S-polarized light that is approximately 90 degrees different from the substantially P-polarized light that is the original light entering the reflective liquid crystal panel 11 when the output-side quarter-wave plate 35 is not provided. At this time, it is emitted as substantially S-polarized light, which cannot be cut by the reflective polarizing plate 10 and the auxiliary analyzer 12, so that it reaches the screen via the projection lens 15 and degrades the contrast. As in the present embodiment, when the emission-side quarter-wave plate 35 is provided, the leaked substantially S-polarized light passes through the emission-side quarter-wave plate 35 with the slow axis set to about 45 degrees, When reflected by the projection lens 15 and transmitted through the output-side quarter-wave plate 35 again, the light is converted into substantially P-polarized light. Therefore, since it is absorbed by the auxiliary analyzer 12, the contrast can be improved.

  The exit side quarter-wave plate 35 is formed on the exit surface of the combined light of the cross dichroic prism 14, the auxiliary analyzer 121 for R is incident on the incident surface of the R optical path, the auxiliary analyzer 121 for B is incident on the incident surface of the B optical path, and the incident light of the G optical path The G half-wave plate 13 is attached to the surface, and a wave plate or a polarizing plate is attached to all four surfaces of the optical path. By the way, the cross dichroic prism 14 needs to be formed with high accuracy in order to reduce the shift of the position of each color pixel on the screen. The cross dichroic prism 14 is formed by bonding four triangular prisms, but each vertex is easy to break and difficult to handle. As described above, by bonding to all four surfaces, the AR process of the prism 14 which is difficult to handle can be omitted, and the cost can be reduced. Further, when AR is applied, residual stress is generated in the prism 14 because it is heated during the process. As described above, in this configuration, the reflected light from the projection lens is rotated by the output-side quarter-wave plate 35 and absorbed by the auxiliary analyzer 12 to improve the contrast, but remains in the prism 14. When there is stress, birefringence occurs and black unevenness occurs. Therefore, by attaching wave plates or polarizing plates to all four surfaces as in the present invention, all four AR processes can be omitted, the residual stress in the prism 14 is reduced, and black unevenness is reduced. Is possible. Further, since the four residual stresses are the same, when light is projected, the four residual stresses expand substantially uniformly, so that there is little angular deviation from the initial positions of the blue reflecting surface and the red reflecting surface of the cross dichroic prism 14. Therefore, the amount by which the pixel position of each panel gradually shifts during use is small. In addition, since the interface with air is reduced by bonding, deterioration of contrast due to reflection at the interface can be prevented. Further, quartz is used as the material of the emission side quarter-wave plate 35. Thereby, since the in-plane change of the birefringence which generate | occur | produces with heat is few compared with a film, a black nonuniformity can be reduced.

  The reflective polarizing plate 10 applies a diffraction effect with a shorter pitch than the wavelength of light to separate light into P-polarized light and S-polarized light, but has a relatively short B optical path and a contrast compared to the R and G optical paths. Becomes worse. Therefore, here, the auxiliary polarizer 93 and the auxiliary analyzer 123 in the B optical path have higher contrast than the auxiliary polarizers 91 and 92 and the auxiliary analyzers 121 and 122 in the R and G optical paths, and three colors are used. The balance of contrast is balanced and the color when black is displayed is improved.

  As another example, when the G contrast of the reflective liquid crystal panel 10 is poor, the auxiliary polarizer 93 and the auxiliary analyzer 123 in the G optical path are higher in contrast of other colors. When the R (or B) contrast of the reflective liquid crystal panel 10 is poor, the auxiliary polarizer and auxiliary analyzer for the R (or B) optical path are higher than the contrast of other colors.

  FIG. 7 shows a fourth embodiment. Except for the following, the embodiment is the same as the embodiment of FIG. Here, two auxiliary analyzers 12 are configured to increase the heat resistance of the auxiliary analyzer 12. Therefore, the cooling air may be weak and the number of rotations of the cooling fan can be reduced, so that the noise of the cooling fan can be reduced.

  FIG. 8 shows a fifth embodiment. Except for the following, the embodiment is the same as the embodiment of FIG. The reflective polarizing plate 10, the reflective liquid crystal panel, and the auxiliary analyzer 9 are provided on the boundary surface with the outside of the sealed structure chassis 42. The sealed chassis 42 has a sealed dust-proof structure, prevents dust from adhering to the reflective polarizing plate 10 and the reflective liquid crystal panel 11 and prevents image loss and image quality deterioration on the screen. It is out. By using optical components such as the reflective polarizing plate 10 and the auxiliary analyzer 9 as boundaries, the sealing performance is secured without obstructing the optical path. A hermetic seal is applied to the gap between the optical component and the structural chassis 42 to ensure hermeticity. The auxiliary analyzer is cooled by a cooling fan. Only the back surface side of the reflective liquid crystal panel 11 can be cooled to the outside.

  FIG. 9 shows a sixth embodiment. Except for the following, the embodiment is the same as the embodiment of FIG. The R, G, and B lights separated by the color separation system pass through the auxiliary analyzers 91, 92, and 93 and the reflective polarizing plate 10 and enter the reflective liquid crystal panel 11. The image light modulated and reflected by the reflective liquid crystal panel 11 is reflected by the reflective polarizing plate 10 and enters the color combining prism. The reflective polarizing plate 10, the reflective liquid crystal panel, the cross dichroic prism 14, and the auxiliary analyzer 9 are provided inside the sealed chassis 42, and the auxiliary polarizer 9 is provided at the boundary. The auxiliary analyzer 9 is cooled by a cooling fan.

  Further, the reflective polarizing plate 10, the reflective liquid crystal panel, the cross dichroic prism 14, and the λ / 4 wavelength plate may be provided at the boundary of the sealed structure chassis 42.

  In addition, the reflective polarizing plate has a configuration in which the long side is not fixed and the long side can be thermally expanded. With this configuration, deformation at the time of thermal expansion can be reduced, and pixel shift on the screen can be reduced.

  In the above embodiment, the case where three reflective liquid crystal panels are used has been described. However, the present invention is not limited to this, and even when one or two reflective liquid crystal panels are used. The same effect can be obtained.

1 is a configuration diagram of a projection type liquid crystal display device showing a first embodiment of the present invention. FIG. It is a figure which shows the simulation result of the surface shape of a reflection type polarizing plate, and the converter shift | offset | difference of each pixel. It is a figure which shows the measuring method of the contrast of an absorption type polarizing plate and a reflection type polarizing plate. Diagram of the reflective liquid crystal panel used in the present invention and the vicinity of the reflective liquid crystal panel and the cross dichroic prism It is a block diagram of the projection-type liquid crystal display device which shows 2nd one Embodiment of this invention. It is a block diagram of the projection-type liquid crystal display device which shows 3rd one Embodiment of this invention. It is a block diagram of the projection-type liquid crystal display device which shows 4th one Embodiment of this invention. It is a block diagram of the projection-type liquid crystal display device which shows 5th one Embodiment of this invention. It is a block diagram of the projection-type liquid crystal display device which shows 6th one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 1a ... Light bulb, 1b ... Reflector, 2 ... Optical axis, 4 ... Imaging lens group, 5 ... White reflection mirror, 6 ... B transmission RG reflection dichroic mirror, 7 ... R transmission G reflection dichroic mirror, 8 ... B reflection mirror, 91 ... R auxiliary polarizer, 92 ... G auxiliary polarizer, 93 ... B auxiliary polarizer, 10 ... reflection polarizing plate, 101 ... R reflection polarizing plate, 102 ... G Reflective polarizing plate for 103, reflective polarizing plate for B, 11 ... reflective liquid crystal panel, 11a ... center of display portion of reflective liquid crystal panel, 11b ... structure of reflective liquid crystal panel, 111 ... reflective type for R Liquid crystal panel, 112 ... Reflective liquid crystal panel for G, 113 ... Reflective liquid crystal panel for B, 12 ... Auxiliary analyzer, 12a ... Transmission axis of auxiliary analyzer, 121 ... Auxiliary analyzer for R, 122 ... Auxiliary analyzer for G Photon, 123 ... B auxiliary analyzer, 13 ... G 1 2 wavelength plate, 14 ... cross dichroic prism, 15 ... projection lens, 31 ... polarization conversion element, 32 ... first array lens, 33 ... second array lens, 34 ... collimator lens, 35 ... emission side 1/4 wavelength Plate, 35a: slow axis of the output side quarter-wave plate, 36: RB transmission G reflection dichroic mirror, 37: R transmission B reflection dichroic mirror, 381 ... polarization separation prism, 381 ... R polarization separation prism, 382... G polarization separation prism, 383... B polarization separation prism, 40... Cooling fan, 41. Viewing angle compensation phase difference plate, 42... Sealed structure chassis, 50. ... Measurement receiver.

Claims (19)

A light source unit that emits light, three reflective image display elements that are light valve means for forming an optical image corresponding to a video signal, and light from the light source unit are color-separated into three-color lights to obtain respective color lights. Projection type comprising a color separation system incident on the corresponding reflective video display element, a color synthesis system for synthesizing the three color lights from the reflective video display element, and a projection means for projecting the color synthesized optical image A video display device,
A flat plate type that reflects the first polarized light of a predetermined polarization direction as a polarizer and an analyzer for the reflective image display element by a diffraction action and transmits the second polarized light of a polarization direction substantially orthogonal to the predetermined direction. Reflection type polarizing plate,
An auxiliary analyzer that transmits one of the first polarized light and the second polarized light on the exit side of the reflective polarizing plate;
The color composition system includes a color composition prism,
Each color light separated by the color separation system enters the reflective video display element via the reflective polarizing plate, and an optical image of the reflected light formed by the reflective video display element is the reflective type. A projection-type image display device, wherein the projection-type image display device is arranged so as to be incident on the color composition system via an image display element. A light source unit that emits light, three reflective image display elements that are light valve means for forming an optical image corresponding to a video signal, and light from the light source unit are color-separated into three-color lights to obtain respective color lights. Projection type comprising a color separation system incident on the corresponding reflective video display element, a color synthesis system for synthesizing the three color lights from the reflective video display element, and a projection means for projecting the color synthesized optical image A video display device,
A flat plate type that reflects the first polarized light of a predetermined polarization direction as a polarizer and an analyzer for the reflective image display element by a diffraction action and transmits the second polarized light of a polarization direction substantially orthogonal to the predetermined direction. Reflection type polarizing plate,
An auxiliary polarizer that transmits polarized light of either the predetermined polarization direction or a polarization direction substantially orthogonal to the predetermined direction on the exit side of the reflective polarizing plate;
On the exit side of the reflective polarizing plate, an auxiliary analyzer that transmits polarized light in the other polarization direction different from the polarization direction transmitted by the auxiliary polarizer,
The color composition system includes a color composition prism,
Each color light separated by the color separation system enters the reflective video display element via the reflective polarizing plate, and an optical image of the reflected light formed by the reflective video display element is the reflective type. A projection-type image display device, wherein the projection-type image display device is arranged so as to be incident on the color composition system via an image display element.   On the incident side of the reflective polarizing plate, a polarization separation prism that reflects either one of the predetermined polarization direction or the polarization direction substantially orthogonal to the predetermined direction and transmits the other polarization light. The projection type image display device according to claim 1, wherein the projection type image display device is arranged.   The projection type image display device according to claim 2, wherein the contrast of the auxiliary analyzer is higher than the contrast of the auxiliary polarizer.   5. The projection display apparatus according to claim 1, wherein the reflective polarizing plate is held with respect to a reflective surface side. 6.   The projection according to any one of claims 1 to 5, wherein the reflective polarizing plate has a substantially rectangular shape, and a short side is inclined by approximately 45 degrees with respect to the optical axis. Type image display device.   The surface shape of the reflection surface of the three reflection-type polarizing plates is within ± 3 (λ / inch) on the basis of a predetermined sheet, 7. The projection-type image display device according to item.   The projection according to any one of claims 1 to 7, wherein the reflective polarizing plate, the reflective image display element, and the auxiliary analyzer are in a sealed structure or at a boundary thereof. Type image display device.   The projection-type image display according to claim 2, further comprising a cooling fan, wherein an amount of cooling air from the cooling fan to the auxiliary polarizer is larger than an amount of air to the auxiliary analyzer. apparatus.   The reflection type liquid crystal display element is arranged on an unintended composition as viewed from the pixel center, and arranged so that the shorter the length of the structure is from the pixel center, closer to the cross dichroic prism. The projection-type image display device according to claim 1, wherein the projection-type image display device is provided.   11. The projection display apparatus according to claim 1, wherein optical axes of reflection surfaces of the three reflection image display elements are directed in substantially the same direction.   The projection according to any one of claims 1 to 11, wherein the reflection surfaces of the three reflective image display elements have substantially the same height with reference to a predetermined one. Type image display device. The optical axes of the reflecting surfaces of the three reflection type image display elements are orthogonal to the optical axes of the incident surfaces of the respective color lights of the color synthesis prism;
13. The reflective polarizing plate according to claim 1, wherein the reflective polarizing plate is disposed in the vicinity of a position substantially perpendicular to both optical axes so as to be inclined by approximately 45 degrees with respect to each optical axis. The projection-type image display device according to item.   The three color lights are R, G, and B color lights, and the contrast of the reflection type polarizing plate arranged in the B optical path is larger than that of the reflection type polarizing plate arranged in the optical path of the other color light. The projection type image display device according to claim 1, wherein the projection type image display device is provided.   The projection type image display device according to any one of claims 1 to 14, wherein the auxiliary analyzer is constituted by two auxiliary analyzers arranged apart from each other.   The three color lights are R, G, and B color lights, and the reflective polarizing plate disposed in the B optical path has a shorter diffraction pitch than the reflective polarizing plate disposed in the R optical path. The projection type image display apparatus according to any one of claims 1 to 15. A light source unit that emits light, three reflective image display elements that are light valve means for forming an optical image corresponding to a video signal, and light from the light source unit are color-separated into three-color lights to obtain respective color lights. Projection type comprising a color separation system incident on the corresponding reflective video display element, a color synthesis system for synthesizing the three color lights from the reflective video display element, and a projection means for projecting the color synthesized optical image A video display device,
A flat plate type that reflects the first polarized light of a predetermined polarization direction as a polarizer and an analyzer for the reflective image display element by a diffraction action and transmits the second polarized light of a polarization direction substantially orthogonal to the predetermined direction. Reflection type polarizing plate,
An auxiliary analyzer that transmits one of the first polarized light and the second polarized light on the output side of the reflective polarizing plate;
A quarter-wave plate disposed between the color synthesis system and the projection means;
A half-wave plate disposed between the color synthesis system and the reflective image display element and rotating the phase of substantially linearly polarized light by approximately 90 degrees;
The color composition system includes a color composition prism,
Each color light separated by the color separation system enters the reflective video display element via the reflective polarizing plate, and an optical image of the reflected light formed by the reflective video display element is the reflective type. Arranged so as to be incident on the color composition system via an image display element,
A projection-type image display device, wherein the auxiliary analyzer is attached to three incident surfaces of the color combining prism serving as an optical path, and a quarter-wave plate is attached to one outgoing surface. . The auxiliary analyzer has an action of absorbing a component in the polarization direction other than the polarized light in the polarization direction to be transmitted,
The quarter wavelength plate is disposed between the prism and the projection means, and the slow axis of the quarter wavelength plate is approximately 40 to 50 degrees with respect to the absorption axis of the auxiliary analyzer, or approximately The projection type image display apparatus according to claim 17, wherein the projection type image display apparatus is inclined at -40 to -50 degrees. When the contrast of the auxiliary polarizer is A, the contrast of the auxiliary analyzer is D, the transmission contrast of the reflective polarizer is B, and the reflection contrast of the reflective polarizer is C,
The projection type image display device according to claim 2, wherein A * B = (0.1-10) * C * D is satisfied.

Images