JP2004272057A - Single plate type liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single plate type liquid crystal projector which has an inexpensive and simple structure and which is made small and thin. <P>SOLUTION: The single plate liquid crystal projector is equipped with: a light source which emits a white luminous flux in a first linearly polarized state; a reflective liquid crystal element which modifies the incident luminous flux in accordance with specified information and converts the first linearly polarized state into a second linearly polarized state by 90° rotation; a projecting lens group which projects the luminous flux modified by the reflective liquid crystal element onto a screen, and a rotary color separating plate. The rotary color separating plate is disposed between the light source and the reflective liquid crystal element, and between the reflective liquid crystal element and the projection lens group, as freely rotatable around the axis. The color separating plate subsequently separates the incident luminous flux into three color components corresponding to the primary colors of light while keeping the polarized state by at least three color separation regions almost equally dividing the plate, deflects the separated color components in the direction to the reflective liquid crystal element, and transmits and guides the color components reflected on the reflective liquid crystal element in the direction to direction of the projection lens group. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a single-panel type color liquid crystal projector using a reflection type liquid crystal element.
[0002]
[Prior art]
Conventionally, color liquid crystal projectors are classified into two types, a transmission type and a reflection type, according to the type of liquid crystal element used as a light modulation unit. The latter has advantages over the former in that the liquid crystal is made thinner, the ON-OFF speed is faster, the life cycle is longer, and the light use efficiency is higher. Therefore, reflective color liquid crystal projectors are becoming mainstream in recent years.
[0003]
The color liquid crystal projector can be further divided into two types, a single-panel type and a three-panel type. Specifically, the former is characterized by using one common reflective liquid crystal element for each of the R, G, and B color components as the light modulating means. The latter is characterized by using three reflective liquid crystal elements corresponding to R (red), G (green), and B (blue) components. The former can reduce the number of parts and reduce the size of the entire apparatus as compared with the latter. A single-panel color projector is disclosed, for example, in Patent Document 1 below.
[0004]
[Patent Document 1]
JP-A-10-133197 (FIG. 1)
[0005]
Generally, in order to obtain a high-quality and clear image using a reflection type liquid crystal element, it is necessary to make a light beam incident on the liquid crystal surface (incident end face) of the liquid crystal element at a substantially right angle. Therefore, as exemplified in FIG. 1 of Patent Document 1, a conventional single-panel color projector uses a cube-shaped deflection beam between an optical path, a light source and a reflective liquid crystal element, and a reflective liquid crystal element and a projection lens. By providing a configuration in which a splitter is provided, an optical path is provided such that a light beam enters the liquid crystal element at right angles.
[0006]
With the above configuration, the distance between the projection lens and the liquid crystal element is designed to be long. That is, the dimension of the projector in the depth direction increases. Further, if the distance between the projection lens and the liquid crystal element is increased, a projection lens having a long back focus must be used. However, such projection lenses are expensive because they require very high precision. As a result, the conventional single-panel liquid crystal projector cannot be avoided from increasing in size and cost.
[0007]
[Problems to be solved by the invention]
In view of the above circumstances, an object of the present invention is to provide a single-panel type liquid crystal projector that is inexpensive and has a simple configuration, but is small and thin.
[0008]
[Means for Solving the Problems]
In order to solve the above problem, a single-panel liquid crystal projector according to claim 1 irradiates a light source unit that emits a white light beam in a first linear polarization state, and modulates an incident light beam according to predetermined information. A reflective liquid crystal element for rotating the first linear polarization state by 90 ° to a second linear polarization state, a projection lens group for projecting a light beam modulated by the reflective liquid crystal element onto a screen, and a light source unit. The light flux is disposed rotatably about the center between the reflection type liquid crystal element and between the reflection type liquid crystal element and the projection lens group, and the incident light beam is polarized by at least three color separation regions substantially equally divided. While maintaining the state, the light is sequentially decomposed into three color components corresponding to the three primary colors of light, and the decomposed color components are deflected toward the reflective liquid crystal element, and the color components reflected by the reflective liquid crystal element are transmitted and the projection lens is transmitted. It characterized by having a a rotating color separation plate for guiding the direction.
[0009]
According to the single-panel type liquid crystal projector of the first aspect, a rotating color separation plate as a color separation means is used as a member for splitting a light beam, instead of a polarization beam splitter prism. By thus using the rotating color separation plate not only as the color separation means but also as the light beam branching means, it is possible to contribute to the miniaturization and thinning of the whole liquid crystal projector. Further, since the distance between each liquid crystal element and the projection lens can be set short, it is easy to shorten the focal length of the projection lens group, and the projector can be configured at low cost.
[0010]
Furthermore, the conventional single-panel type liquid crystal projector requires an extremely high-precision assembly process such as alignment of the optical axis of each polarizing beam splitter and the synthesizing prism. , The relative positioning of each optical member becomes easy.
[0011]
2. The rotating color separation plate according to claim 1, wherein the white light flux incident on the first end face is emitted from a second end face different from the first end face so as to be incident on the reflective liquid crystal element at substantially right angles, and the reflective liquid crystal is provided. A second linearly polarized light beam reflected on the element and incident on the second end face is converted into a third end face substantially parallel to and opposite to the second end face at the same exit angle as the incident angle on the second end face. It is desirable to adopt a configuration in which the light is ejected from the surface (claim 2).
[0012]
Here, the first end surface and the third end surface can be the same surface. In other words, the end face on which the light beam from the light source unit is incident and the end face on which the light beam is deflected and emitted from the rotary color separation plate may be substantially parallel. In this case, a color separation function is provided by disposing an optical member having a reflection characteristic for separating a color component corresponding to each color separation region on the first end surface of each color separation region. As the optical member, a dichroic mirror is exemplified.
[0013]
When configured as described above, the positional relationship between the light source unit and the rotating color separation plate is such that the white luminous flux has a predetermined incident angle θ with respect to the first end surface. ₃ (However, 0 ° <θ ₃ It is desirable to make the light obliquely incident at <90 °). By defining the incident angle in this manner, it is possible to design the diameter of the white light beam to be small.
[0014]
The rotating color separation plate has a plurality of transparent substrates each having a reflection surface coated with an optical film having predetermined characteristics, and is disposed between both end surfaces in a state of being inclined by a first inclination angle with respect to a normal line of each end surface. It is preferable to have a multilayer structure that is periodically laminated at a predetermined pitch. The predetermined characteristic is a characteristic in which the first linearly polarized light is substantially totally reflected and the second linearly polarized light is substantially completely transmitted (Claim 5). With this configuration, the rotating color separation plate can have a function as a light beam branching unit.
[0015]
According to the invention described in claim 6, in the light beam branching member, each of the end faces and the liquid crystal surface of the reflection type liquid crystal element have the second inclination angle θ. ₂ And the second inclination angle θ ₂ Is 0 ° ≦ θ ₂ It is desirable to be within the range of <90 °. And the second inclination angle θ ₂ Is 0 ° <θ ₂ <90 °, relative positional relationship between the light source unit and the rotating color separation plate such that each color component in the first linear polarization state enters the light beam splitting member from a direction parallel to the liquid crystal surface. Is preferably determined (claim 7).
[0016]
In particular, the second inclination angle θ ₂ Is set to 0 °, relative positioning between the reflective liquid crystal element and the light beam branching member becomes extremely easy. However, in this case, the relative positional relationship between the light source unit and the rotating color separation plate may be determined so that each color component in the first linear polarization state enters the light beam splitting member from a direction non-parallel to the liquid crystal surface. Desirable (claim 8).
[0017]
According to the ninth aspect, the first end face may be substantially orthogonal to the second end face and the third end face. In this case, it is preferable that the light source unit and the rotating color separation plate have a relative positional relationship such that a white light beam is incident on the first end surface substantially at a right angle.
[0018]
The rotating color separation plates configured as in claims 9 and 10 are arranged substantially parallel to each other and at a predetermined angle with respect to the first to third end faces. It has a plurality of optical films having predetermined characteristics. The predetermined characteristic of each optical film is that, for the first linearly polarized light of the specific color component corresponding to the color separation area, the total light amount of the light beams reflected by all the optical films is the total light amount of the incident light beam. The light is reflected at different reflectivities so as to be substantially equal, and almost completely transmits the second linearly polarized light of the specific color component.
[0019]
Specifically, the characteristic of each optical film is such that the predetermined reflectance of the k-th optical film counted from the predetermined optical film provided farthest from the first end face is set to (100 / k)%. It is desirable to be performed (claim 12). This makes it possible to make each light beam reflected by each optical film an even light amount.
[0020]
Further, it is preferable that the optical films are disposed so as to partially overlap each other when viewed from the second end face side (claim 13). Thereby, it becomes possible to make the light flux enter into almost the entire liquid crystal surface of the reflection type liquid crystal element, and an image having no bright and dark areas can be displayed on the screen. However, with the configuration as in claim 14, the light quantity of the light beam incident on the liquid crystal surface corresponding to the region where the optical films overlap is larger than in other regions. Such unevenness or variation in light amount can be eliminated by performing correction processing on data for generating a predetermined modulation signal (claim 14).
[0021]
The non-uniformity of the light quantity of the incident light beam caused on the reflective liquid crystal element due to the partial overlap of the optical films can be solved by using the light beam width adjusting means provided in the light source section. ). That is, the light beam width adjusting means adjusts the light beam width of the white light beam so that the light beam enters only one of the optical films in a region where the optical films adjacent to each other partially overlap. An example of the light beam width adjusting means is a light tunnel used to make the light beam intensity uniform. The light tunnel has cavities mirror-finished on all sides through which light beams pass. The light beam width can be adjusted by sliding one mirror surface forming the cavity in a direction perpendicular to the mirror surface.
[0022]
According to the sixteenth aspect, it is preferable that the first linearly polarized light is designed as the S-polarized light.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram illustrating a schematic configuration of a single-panel liquid crystal projector 100 according to the first embodiment. The single-panel type liquid crystal projector 100 includes a light tunnel 2, an illumination system lens group 3, a single polarizer 4, a rotating color separation plate 10, a reflective liquid crystal element 5, and a projection lens in the order in which the white luminous flux emitted from the light source 1 is incident. Group 6 is provided. FIG. 2 is a schematic view of the rotating color separation plate 10 as viewed from the first end face 11 side. As shown in FIG. 2, the rotating color separation plate 10 has a substantially perfect circular shape, and is rotated at a predetermined speed about a center O by a motor M.
[0024]
The light source 1 has a high-pressure mercury lamp 1a and an elliptical reflector 1b. White light emitted from the high-pressure mercury lamp 1a is reflected by the elliptical reflector 1b and guided to the light tunnel 2. The light tunnel 2 guides the incident white light to the illumination system lens group 3 at the subsequent stage while making the intensity distribution uniform. The illumination lens group 3 guides the white light incident through the light tunnel 2 to the single polarizing plate 4 while converging the white light in a predetermined direction. Specifically, the cross-sectional shape of the white light transmitted through the illumination system lens group 3 on the surface including the first end surface 11 is converged toward the central axis O, and the white light on the surface orthogonal to the first end surface 11 is The cross-sectional shape is a parallel light beam. As a result, the light rays included in the white light beam enter at any position on the first end surface 11 at substantially the same incident angle. The single polarizing plate 4 aligns the polarization state of the incident white light so as to be S-polarized with respect to the rotating color separation plate 10 at the subsequent stage.
[0025]
The white light flux converted to the S-polarized state by the single polarizing plate 4 enters the first end face 11 of the rotating color separation plate 10. The rotating color separation plate 10 has three color separation regions 10R, 10G, and 10B corresponding to the three primary colors of light substantially equally divided by the plurality of boundary surfaces B. Therefore, the white luminous flux sequentially enters the first end faces 11 of the color separation regions 10R, 10G, and 10B.
[0026]
FIG. 3 is a diagram showing a cross section of the rotating color separation plate 10 and an arrangement relationship between the rotating color separation plate 10 and the reflective liquid crystal element 5. Note that the cross section of the rotating color separation plate 10 shown in FIG. 3 is a cross section in the color separation region 10R. The cross-sectional shapes of the other color separation regions are substantially the same as those shown in FIG. Therefore, the following mainly describes the color separation region 10R and the light beam incident on the region 10R.
[0027]
As shown in FIG. 3, the rotating color separation plate 10 has a transparent substrate 13 and a multilayer structure 14. In the multilayer structure 14, a plurality of transparent substrates 15 each having a reflection surface 16 having predetermined characteristics according to the polarization state are laminated with the reflection surface 16 as a bonding surface. Specifically, the multilayer structure 14 has a reflection surface 16 having a first inclination angle θ with respect to a normal N of the transparent substrate 13. ₁ It is fixed in a state of being inclined so as to form. That is, the reflecting surface 16 is in a state of being disposed substantially concentrically with respect to the center O. The multilayer structure 14 is fixed to the surface of the transparent substrate 13 opposite to the first end surface 11 in order to increase the bonding strength. The color separation region 10 </ b> R is configured such that the first end surface 11 of the transparent substrate 13 and the end surface (second end surface) 12 of the multilayer structure 14 opposite to the fixing surface with the mirror 13 are substantially parallel to each other. . The transparent substrate 15 constituting the multilayer structure 14 may be made of glass or plastic. In this embodiment, a glass substrate that is less affected by environmental changes is used.
[0028]
As shown in FIG. 4, the reflecting surface 16 transmits approximately 100% of S-polarized light of a specific color component (here, an R component) corresponding to each color separation region, and transmits P-polarized light of the specific color component. In other words, it has a characteristic of reflecting approximately 100%. FIG. 5 shows a graph relating to the reflection characteristics of the reflection surface 16 provided in the color separation region 10G, and FIG. 6 shows a graph relating to the reflection characteristics of the reflection surface 16 provided in the color separation region 10B. As shown in FIGS. 4 to 6, the S-polarized white luminous flux incident on each reflection surface 16 in each of the color separation regions 10 </ b> R to 10 </ b> B reflects only the color components corresponding to each of the regions 10 </ b> R to 10 </ b> B on the reflection surface 16. As a result, the light is deflected toward the reflective liquid crystal element 5.
[0029]
In the present embodiment, as shown in FIG. 3, the optical path of the white light flux is substantially parallel to the liquid crystal surface 5a of the reflective liquid crystal element 5. Therefore, the rotation color separation disk 10 is provided with the second inclination angle θ with respect to the liquid crystal surface 5a so as to capture the entire diameter of the white luminous flux that travels straight along the optical path substantially parallel to the liquid crystal surface 5a of the reflective liquid crystal element 5. ₂ (However, 0 ° <θ ₂ <90 °). Note that since the projector 100 itself becomes large, θ ₂ Does not assume 90 °.
[0030]
Therefore, the white luminous flux is shifted from 90 ° to the second inclination angle θ. ₂ Angle of incidence θ minus ₃ Obliquely enters the first end surface 11. That is, in the present embodiment, the incident angle θ ₃ Also 0 ° <θ ₃ <90 °. Where incident angle θ ₃ Is too large, the amount of light reflected on the first end face 11 may increase. Therefore, an antireflection film for a color component corresponding to each region is provided on the first end surface 11 of each of the regions 10R to 10B.
[0031]
Here, the first inclination angle θ ₁ And the second inclination angle θ ₂ And the incident angle θ ₃ Is appropriately set so that each color component in the S-polarized state emitted from each of the color separation regions 10R to 10B is incident on the liquid crystal surface 5a substantially at right angles (incident at an incident angle of 0 °). With this setting, the white luminous flux obliquely incident on the first end face 11 of the rotating color separation plate 10 is sequentially color-separated and emitted from the second end face 12 so as to be incident on the liquid crystal surface 5a at right angles. In addition, the optical path of the R component indicated by the arrow line in FIG. 2 is in a state where the refraction phenomenon at the time of incidence / emission at the end faces 11 and 12 is omitted for convenience.
[0032]
The reflection type liquid crystal element 5 modulates each color component according to a modulation signal generated based on video information of a color corresponding to a color component sequentially incident by a control unit (not shown). At the time of modulation, the polarization state of the reflected light beam is a P-polarized state in which the polarization state of the incident light beam is rotated by 90 ° due to the properties of the liquid crystal. The color component in the P-polarized state is reflected by the liquid crystal element 5 and again enters the rotating color separation plate 10 via the second end face 12. In FIG. 3, for convenience, the incident light beam and the reflected light beam (emitted light beam) in the reflection type liquid crystal element 5 are shown by different optical paths, but actually, the reflected light beam returns substantially the same optical path as the incident light beam. That is, the color component in the P-polarized state is emitted from the reflective liquid crystal element 5 at a substantially right angle (emitted at an emission angle of 0 °).
[0033]
As described above, each reflecting surface 16 has a property of transmitting substantially all the P-polarized light. Therefore, each color component in the P-polarized state sequentially incident on the second end face 12 of the rotating color separation plate 10 is emitted from the first end face 11 with little loss of light quantity.
[0034]
Each color component of the P-polarized light emitted from the first end face 11 is sequentially enlarged and projected on a screen (not shown) by the projection lens group 11. As a result, a bright full-color image of a large screen is displayed on the screen.
[0035]
The above is the first embodiment of the present invention. Note that the single-panel liquid crystal projector 100 of the first embodiment is not limited to the above configuration. For example, in the above embodiment, the optical path of the white light beam emitted from the light source 1 and the liquid crystal surface 5a of the reflective liquid crystal element 5 are configured to be parallel. In this regard, the single-panel type liquid crystal projector 100 of the first embodiment is not limited to the configuration as long as the rotating color separation plate 10 can capture the entire diameter of the white light beam by the first end surface 11. For example, if the light source 1 and the reflective liquid crystal element 5 are arranged so that the optical path of the white light beam and the liquid crystal surface 5a are non-parallel, the second tilt angle θ ₂ Can be set to 0 °.
Second tilt angle θ ₂ Is set to 0 °, the first end face 11 or the second end face 12 is substantially parallel to the liquid crystal surface 5a. Thereby, there is an advantage that the relative positioning between the rotary color separation plate 10 and the reflection type liquid crystal element 5 becomes easier than the configuration shown in FIG.
[0036]
Further, the rotating color separation plate 10 of the first embodiment can be used even if it has a configuration other than the above. For example, as an alternative to the above-described multilayer structure 14, a rotating color separation plate having a liquid crystal film disclosed in Japanese Patent Application No. 2003-23413 filed by the present applicant can be used. However, in this case, instead of the transparent substrate 13, a dichroic mirror having a characteristic of transmitting only color components corresponding to the regions 10R, 10G, and 10B is provided. This provides a rotating color separation plate capable of performing color separation while utilizing the disclosure content of the above application.
[0037]
FIG. 7 is a diagram illustrating a schematic configuration of a single-panel liquid crystal projector 200 according to the second embodiment of the present invention. In the single-panel type liquid crystal projector 200 shown in FIG. 7, the same components as those of the projector 100 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The rotating color separation plate 20 used in the projector 200 of the second embodiment has an external shape as shown in FIG. That is, the rotating color separation plate 20 has a substantially circular shape like the rotating color separation plate 10 shown in FIG. 2, and includes three color separation regions 20R, 20G, and 20B corresponding to the R, G, and B color components. Have. Each color separation area is substantially equally divided. As shown in FIG. 7, the rotating color separation plate 20 is disposed such that a surface (second end surface) 22 facing the reflective liquid crystal element 5 and the liquid crystal surface 5a of the element 5 are substantially parallel. . In addition, since the reflection type liquid crystal element 5 and the rotating color separation plate 20 are disposed substantially in parallel, the single-panel type liquid crystal projector 200 of the second embodiment is very easy to relatively position each optical member. There are advantages.
[0038]
FIG. 9 is a diagram showing a cross section of the rotating color separation plate 20 and an arrangement relationship between the rotating color separation plate 20 and the reflective liquid crystal element 5. Note that the cross section of the rotating color separation plate 20 shown in FIG. 9 is a cross section in the color separation region 10R. Since the cross-sectional shapes of the other color separation regions 20G and 20B are substantially the same as those shown in FIG. 9, the following mainly describes the color separation region 20R and the light beam incident on the region 20R. The rotating color separation plate 20 includes a first end face 21 on which a principal ray of a white light beam incident through the single polarizing plate 4 is incident at a substantially right angle, a second end face 22 orthogonal to the first end face 21 and parallel to each other. It has three end faces 23.
[0039]
As described above, the rotating color separation plate 20 and the reflective liquid crystal element 5 are arranged in parallel with each other. Therefore, the optical path of the white light flux that is incident on the first end face 21 at a right angle is substantially parallel to the second end face 22, the third end face 23, and the liquid crystal surface 5a. In the single-panel liquid crystal projector 200 according to the second embodiment, the first end face 21 on which the white light beam is incident is an arc shape because the first end face 21 is the outer peripheral face of the rotary color separation plate 20. Therefore, when a parallel light beam is made incident on the first end surface 21, the incident angle varies depending on the incident position, and the amount of light incident on the reflective liquid crystal element 5 at the subsequent stage may be reduced. Therefore, the illumination system lens group 3 ′ of the second embodiment always causes the white light flux emitted from the light source 1 and incident via the light guide 2 to enter each of the optical films C1, C2, and C3 at a constant incident angle. Has an action.
[0040]
As shown in FIG. 9, three optical films C <b> 1 to C <b> 3 are arranged inside the color separation region 20 </ b> R in order from the first end face 21 side. Each of the optical films C1 to C3 is disposed so as to form an angle of 45 ° with each of the first to third end surfaces 81 to 83. Further, in order to allow the light flux to enter almost all over the liquid crystal surface 5a of the reflective liquid crystal element 5, adjacent optical films (for example, C1 and C2) are viewed from the second end face 82 or the third end face 83. Are arranged so as to partially overlap each other.
[0041]
FIG. 10 is a graph showing the reflection characteristics of the optical film C1. FIG. 11 is a graph showing the reflection characteristics of the optical film C2. Since the reflection characteristics of the optical film C3 have substantially the same characteristics as the reflection characteristics of the dichroic mirror 13 of the first embodiment, reference is made to FIG. As shown in FIGS. 3 to 5, each of the optical films C1 to C3 has different reflection characteristics with respect to the R component light (about 600 nm or more) in the S-polarized state. Further, the reflection characteristics are set so as to reflect approximately 100% of the incident light beam by using all the optical films C1 to C3. Specifically, the k-th optical film counted from the optical film C3 farthest from the first end face 81 has a reflection characteristic of about (100 / k)% with respect to the R component light in the S-polarized state. That is, in the present embodiment, as shown in each drawing, the optical film C1 has a reflection characteristic of about 33%, the optical film C2 has a reflection characteristic of about 50%, and the optical film C3 has a reflection characteristic of about 100%. As a result, the amount of light reflected by any of the optical films becomes substantially equal. In addition, as shown in each drawing, each optical film transmits substantially the entirety of the P-polarized light of the corresponding color component (here, the R component) and the other color components.
[0042]
Therefore, the R component of the S-polarized light beam that has entered the first end face 21 in the color separation region 20R is gradually reflected at substantially right angles by the optical films C1 to C3. The R component in the S-deflected state reflected by each of the optical films C1 to C3 is emitted from the second end face 82 and is incident on the liquid crystal surface 5a of the reflective liquid crystal element 5 at a substantially right angle. Here, by setting the reflectance of each optical film as described above, except for the region where the light flux from the part where the optical films shown by the hatched areas in FIG. 9 partially overlap is incident on the liquid crystal surface 5a. A substantially uniform amount of light enters each point. In the present embodiment, light of approximately 33% of the light amount of the light beam incident on the first end surface 21 is incident on any point on the liquid crystal surface 5a.
[0043]
FIG. 12 shows the reflection characteristics of the optical film C1 in the color separation region 20G for color separation of the G component, and FIG. 13 shows the reflection characteristics of the optical film C2. Since the reflection characteristics of the optical film C3 in the color separation region 20G have substantially the same characteristics as the reflection characteristics of the dichroic mirror 13 provided in the color separation region 10G of the first embodiment, FIG.
[0044]
Similarly, FIG. 14 shows the reflection characteristics of the optical film C1 and FIG. 15 shows the reflection characteristics of the optical film C2 in the color separation region 20B for color-separating the B component. Since the reflection characteristics of the optical film C3 in the color separation region 20B have substantially the same characteristics as the reflection characteristics of the dichroic mirror 13 provided in the color separation region 10B of the first embodiment, reference is made to FIG.
[0045]
As in the first embodiment, the reflection type liquid crystal element 5 modulates the R component incident upon the ON bit in accordance with a modulation signal transmitted from a control unit (not shown). Here, in FIG. 9, light from a part where the optical films indicated by hatched areas partially overlap is reflected by the two optical films twice, so that the R component is reflected twice by the liquid crystal surface 5a as compared with the other areas. The amount of light incident on the light source increases. For example, the light beam incident through the overlapping area of the optical film C1 and the optical film C2 has about 22% more light than the other areas. If the amount of light incident on the liquid crystal surface 5a is uneven, the quality of the generated image is degraded. For this reason, in the present embodiment, a modulation signal generated based on video information that has been previously darkened and corrected is given to a pixel on which a light beam with a large amount of light is incident. By performing the modulation process based on such a modulation signal, even if the light flux incident on the reflective liquid crystal element 5 has a non-uniform light amount depending on the pixel, the light flux (ON light) emitted from the element 5 The light quantity of the pixel is also substantially uniform.
[0046]
As described above, the reflected light beam (ON light) from the reflective liquid crystal element 5 is in the P-polarized state. The ON light of the R component is incident on the second end face 22 of the rotating color separation plate 20 at a substantially right angle (incident at an incident angle of 0 °).
[0047]
As shown in FIG. 4 to FIG. 6 and FIG. 10 to FIG. 15, the optical films C1 to C3 of the respective color separation regions have a characteristic that the reflectance for P-polarized light is almost 0 regardless of the color component. Therefore, substantially the entire amount of the ON light of the R component incident on the second end face 22 passes through each of the optical films C1 to C3. Then, the ON light is emitted from the third end face 23 at a substantially right angle, and travels to the projection lens group 6.
[0048]
Note that the light beam (OFF light) incident at the time of the OFF bit in the modulation signal is not modulated and reenters the rotating color separation plate 20 in the S-polarized state. At this time, the light beam incident on the optical films C1 to C3 as OFF light remains in the S-polarized state. Therefore, when the OFF light is incident on a color separation area different from the color separation area at the time of color separation, the OFF light is transmitted to the projection lens group 6 together with the ON light according to the reflection characteristics of the optical films C1 to C3 in the different color separation areas. The light enters at almost right angles. For example, assume that OFF light of the R component separated by the color separation region 20R is incident on the color separation region 20G. In this case, as shown in FIGS. 12, 13, and 5, each of the optical films C1 to C3 in the color separation region 20G transmits substantially the entire R component regardless of the polarization state. Therefore, the OFF light of the R component incident on the color separation region 20G is guided to the projection lens group 6 together with the ON light.
[0049]
If the OFF light is projected on the screen via the projection lens group 6, the quality of the image displayed on the screen S is degraded. Therefore, in the single-panel liquid crystal projector 200 of the second embodiment, the absorbing polarizer 7 is provided between the rotating color separation plate 20 and the projection lens group 6. The absorbing polarizer 12 cuts off almost all of the color components that have passed through the rotary color separation plate 20 despite being OFF light, and avoids entering the projection lens group 11.
[0050]
In this way, only the ON light components of the respective colors of R, G, and B sequentially enter the projection lens group 11. A large full screen bright full-color image is displayed on the screen S by the R, G, and B images sequentially enlarged and projected from the projection lens group 11.
[0051]
The above is the second embodiment of the present invention. The single-panel type liquid crystal projector 200 of the second embodiment is not limited to the above embodiment.
[0052]
For example, it has been described that each of the optical films C1 to C3 is partially overlapped so that the light flux is completely incident on the entire liquid crystal surface. However, in the design stage, there is no need to overlap the optical films C1 to C3 as long as they can be disposed seamlessly when viewed from the second end face 22 side. In this case, since the luminous flux incident on the liquid crystal surface has almost the same light amount, there is no need to perform the correction processing for matching the light amounts.
[0053]
In addition, it has been described that the non-uniformity of the incident light amount on the liquid crystal surface 5a, which is caused by partially overlapping the optical films C1 to C3, is eliminated by performing a correction process on the video information for generating the modulation signal. It is also possible to make the light amount uniform by another method. For example, a mirror surface forming the light guide 2 is slid in a direction perpendicular to the mirror surface while referring to an image actually displayed on a monitor (not shown). Thereby, the width of the light beam incident on the rotary color separation plate 20 changes as shown by the outline arrow line in FIG. It is also possible to fix the mirror surface at the position where the quality of the image is the best, that is, at the time when the light beam width (broken line in FIG. 2) where the light amount difference on the liquid crystal surface disappears.
[0054]
Further, it has been described that the rotating color separation plate 20 includes three optical films C1 to C3 having different reflection characteristics in all the color separation regions 20R to 20B. However, the number of optical films is an example, and the same effect as in the second embodiment can be obtained if at least two optical films are used. Further, even if the amount of light flux incident on the reflection type liquid crystal element 5 is uneven, if the modulation signal for controlling the liquid crystal element can be dealt with more flexibly, the number of the optical films is one. good.
[0055]
Further, the absorbing polarizer 7 can be integrally formed with the rotating color separation plate 20 by joining to the third end face 23.
[0056]
As described above, two preferred embodiments of the single-panel liquid crystal projector according to the present invention have been described. In each embodiment, the light beam from the light source 1 is described as S-polarized light, but may be P-polarized light. Further, in each of the above-described embodiments, a circular rotating color separating plate is assumed, but a rotating color separating plate other than a circular shape may be used. Further, in each of the above embodiments, each of the rotating color separation plates includes one color separation region corresponding to each of R, G, and B. However, the number of each color separation region corresponding to each color is equal to the number of the same number. You may have.
[0057]
【The invention's effect】
As described above, the single-panel type liquid crystal projector according to the present invention has a reflection type liquid crystal device in which a rotating color separation plate having both a color separation function and a light beam branching function is disposed in a preferable positional relationship with respect to a reflection type liquid crystal element. The distance between the liquid crystal element and the projection lens group can be reduced. This makes it possible to reduce the size of the configuration in the vicinity of the projection lens group, and to further reduce the length of the projector in the depth direction. That is, a single-panel type liquid crystal projector having a simpler configuration, smaller size, and thinner than a conventional projector is provided.
[0058]
The single-panel liquid crystal projector according to the present invention can reduce the diameter of the light beam incident on the rotating color separation plate. Thus, unlike the conventional configuration using the polarizing beam splitter cube, the space to be secured as an optical path can be reduced. From this point, further miniaturization of the entire projector is realized.
[0059]
Further, for example, as in the second embodiment, the single-panel liquid crystal projector according to the invention is configured such that each optical member is bent at an integral multiple of substantially 90 °. Thereby, each optical member can be arranged at a position with high accuracy in a simple assembly process.
[0060]
In addition, since the distance between each liquid crystal element and the projection lens can be shortened, even a projector that projects an image on a screen from a short distance, such as a rear projector, has a high performance projection lens. It is possible to project a clear image with a sufficiently wide angle without using the image. Therefore, the cost of the projector itself can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a single-panel liquid crystal projector according to a first embodiment of the invention.
FIG. 2 is a diagram illustrating a rotating color separation plate of the single-panel liquid crystal projector according to the first embodiment.
FIG. 3 is a diagram illustrating a cross-section of a rotating color separation plate according to the first embodiment and an arrangement relationship between the rotation color separation plate and a reflective liquid crystal element.
FIG. 4 is a graph showing reflection characteristics of a dichroic mirror provided in the rotating color separation plate of the first embodiment.
FIG. 5 is a graph showing reflection characteristics of a dichroic mirror provided in the rotating color separation plate of the first embodiment.
FIG. 6 is a graph showing reflection characteristics of a dichroic mirror provided on the rotating color separation plate of the first embodiment.
FIG. 7 is a diagram illustrating a schematic configuration of a single-panel liquid crystal projector according to a second embodiment of the present invention.
FIG. 8 is a diagram illustrating a rotating color separation plate of a single-panel liquid crystal projector according to a second embodiment.
FIG. 9 is a diagram illustrating a cross section of a rotating color separation plate according to a second embodiment, and an arrangement relationship between the rotation color separation plate and a reflective liquid crystal element.
FIG. 10 is a graph showing reflection characteristics of an optical film provided on a rotating color separation plate according to a second embodiment.
FIG. 11 is a graph showing reflection characteristics of an optical film provided on a rotating color separation plate according to the second embodiment.
FIG. 12 is a graph showing reflection characteristics of an optical film provided on a rotating color separation plate according to the second embodiment.
FIG. 13 is a graph showing reflection characteristics of an optical film provided on a rotating color separation plate according to the second embodiment.
FIG. 14 is a graph showing reflection characteristics of an optical film provided on a rotating color separation plate according to the second embodiment.
FIG. 15 is a graph illustrating reflection characteristics of an optical film provided on a rotating color separation plate according to the second embodiment.
[Explanation of symbols]
1 light source
5 Reflective liquid crystal device
6. Projection lens group
10,20 rotating color separation plate
11, 21 First end face
12, 22 Second end face
23 Third end face
100, 200 Single-panel LCD projector

Claims (16)

A light source unit that emits a white light beam in a first linear polarization state,
A reflective liquid crystal element that modulates the incident light beam in accordance with predetermined information and changes the first linear polarization state to a second linear polarization state rotated by 90 °;
A projection lens group that projects a light beam modulated by the reflective liquid crystal element on a screen,
The light source unit and the reflection type liquid crystal element, and the reflection type liquid crystal element and the projection lens group are rotatably disposed around a center, and divide the incident light beam into at least three light beams. The three color separation regions sequentially separate the light into three color components corresponding to the three primary colors of light while maintaining the polarization state, deflect the separated color components toward the reflective liquid crystal element, and reflect the deflected color components toward the reflective liquid crystal element. A rotating color separation plate that transmits the selected color component and guides the color component toward the projection lens group. The single-panel liquid crystal projector according to claim 1,
The rotating color separation plate emits the white light flux incident on the first end face from a second end face different from the first end face so as to be incident on the reflective liquid crystal element at a substantially right angle, and the reflective liquid crystal element The light beam in the second linearly polarized state that has been reflected and incident on the second end face, from the third end face that is substantially parallel to and opposite to the second end face at the same exit angle as the incident angle on the second end face. A single-panel liquid crystal projector characterized by emitting light. The single-panel liquid crystal projector according to claim 2,
The first end surface and the third end surface are the same surface, and an optical member having a reflection characteristic for separating a color component corresponding to each color separation region is provided on the first end surface in each color separation region. Single-panel LCD projector. The single-panel liquid crystal projector according to claim 3,
The light source unit and the rotating color separation plate are in a positional relationship such that the white light beam is obliquely incident on the first end face at a predetermined incident angle θ ₃ (where 0 ° <θ ₃ <90 °). , A single-panel liquid crystal projector. The single-panel liquid crystal projector according to claim 3 or 4,
The rotating color separation plate has a plurality of transparent substrates having a reflective surface coated with an optical film having predetermined characteristics, and is disposed between both end surfaces in a state of being inclined by a first inclination angle with respect to a normal line of each end surface. It is periodically laminated at a predetermined pitch,
The single-panel type liquid crystal projector, wherein the predetermined characteristic is a characteristic that the first linearly polarized light is substantially totally reflected and the second linearly polarized light is substantially totally transmitted. The single-panel liquid crystal projector according to any one of claims 3 to 5,
It said beam dividing element includes a liquid crystal surface of the reflective type liquid crystal element and each said end face being disposed to form a second inclination angle theta _2, the inclination angle theta ₂ of the second is 0 ° ≦ θ ₂ <90 °, a single-panel liquid crystal projector. The single-panel liquid crystal projector according to claim 6,
When the second inclination angle theta ₂ is at the 0 ° _{<θ 2} <range of 90 °, the rotary color separation plate and the light source unit, each color component of the first linear polarization state, to the liquid crystal surface A single-panel type liquid crystal projector characterized in that it has a relative positional relationship such that light enters the light beam splitting member from a direction substantially parallel to the light beam splitting member. The single-panel liquid crystal projector according to claim 6,
The second inclination angle theta ₂ is 0 °, the rotational color separation plate and the light source unit, each color component of the first linear polarization state, the light beam branched from the non-parallel direction with respect to the liquid crystal surface A single-panel liquid crystal projector characterized by having a relative positional relationship such that light enters a member. The single-panel liquid crystal projector according to claim 2,
A single-panel liquid crystal projector, wherein the first end face, the second end face, and the third end face are substantially orthogonal to each other. The single-panel liquid crystal projector according to claim 9,
The single-panel type liquid crystal projector, wherein the light source unit and the rotating color separation plate are in a relative positional relationship such that the white light beam is incident on the first end surface at a substantially right angle. The single-panel liquid crystal projector according to claim 9 or 10,
The rotating color separation plate has a plurality of optical films that are substantially parallel to each other and form a predetermined angle with respect to each of the first to third end faces,
Each optical film is such that, for the first linearly polarized light of the specific color component corresponding to the color separation region, the sum of the light amounts of the light beams reflected by all the optical films is substantially equal to the total light amount of the incident light beam. A single-panel type liquid crystal projector characterized in that the single-panel type liquid crystal projector has characteristics of reflecting at different reflectances and transmitting substantially all of the second linear polarized light of the specific color component. The single-panel liquid crystal projector according to claim 11,
A single-panel type liquid crystal projector, wherein the reflectance of a k-th optical film counted from a predetermined optical film provided farthest from the first end surface is set to (100 / k)%. The single-panel liquid crystal projector according to claim 11 or 12,
The single-panel liquid crystal projector, wherein the optical films adjacent to each other are disposed so as to partially overlap as viewed from the second end surface side. The single-panel liquid crystal projector according to claim 13,
The single-panel type liquid crystal projector according to claim 1, wherein the variation in the amount of light on the liquid crystal surface of the reflection type liquid crystal element caused by the partial overlap is eliminated by performing a correction process on data for generating the predetermined modulation signal. The single-panel liquid crystal projector according to claim 13,
The light source unit has a light source that emits a white light beam, and a light beam width adjusting unit that adjusts the light beam width of the white light beam,
The light beam width adjusting means adjusts the light beam width of the white light beam so that the light beam enters only one of the optical films in the partially overlapping region of the optical films adjacent to each other. Single-panel LCD projector. The single-panel liquid crystal projector according to any one of claims 1 to 15,
The first linearly polarized light is S-polarized light;
2. The single-panel liquid crystal projector according to claim 1, wherein the second linearly polarized light is P-polarized light.

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