JP4283569B2 - Single-panel LCD projector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single-plate color liquid crystal projector using a reflective liquid crystal element.
[0002]
[Prior art]
Conventional color liquid crystal projectors are classified into two types, a transmission type and a reflection type, depending on the type of liquid crystal element used as the light modulation means. Compared to the former, the latter has advantages such as a thin liquid crystal and a fast ON-OFF speed, a long life cycle, and high light utilization efficiency. 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 of single plate type and three plate type. Specifically, the former is characterized in that a single reflective liquid crystal element is used 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 the respective components of R (red), G (green), and B (blue). Compared to the latter, the former can reduce the number of parts and reduce the size of the entire apparatus. As a single-plate type color projector, for example, it is disclosed in the following Patent Document 1.
[0004]
[Patent Document 1]
JP-A-10-133197 (FIG. 1)
[0005]
In general, in order to obtain a clear image with high image quality using a reflective liquid crystal element, it is necessary to make a light beam incident at a substantially right angle with respect to the liquid crystal surface (incident end face) of the liquid crystal element. Therefore, as illustrated in FIG. 1 of Patent Document 1, a conventional single-plate color projector has a cube-shaped deflection beam between a light source and a reflective liquid crystal element and between the reflective liquid crystal element and a projection lens on an optical path. By adopting a configuration in which a splitter is provided, an optical path is ensured so that a light beam enters the liquid crystal element at a right angle.
[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 is increased. 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 a projection lens is expensive because it requires very high accuracy. As a result, the conventional single-plate type liquid crystal projector cannot avoid the increase 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-plate liquid crystal projector that is small and thin with an inexpensive and simple configuration.
[0008]
[Means for Solving the Problems]
Accordingly, in order to solve the above problem, a single-plate liquid crystal projector according to claim 1 modulates a light source unit that emits a white light beam in a first linear polarization state and an incident light beam in accordance with predetermined information. And a reflection type liquid crystal element that 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 reflection type liquid crystal element on the screen, and a light source unit. Between the reflection type liquid crystal elements and between the reflection type liquid crystal elements and the projection lens group, it is rotatably arranged with the center as an axis, and the incident light beam is polarized by at least three color separation regions divided substantially equally. The lens is sequentially decomposed into three color components corresponding to the three primary colors of light while maintaining the state, and the separated color components are deflected toward the reflective liquid crystal element, and the color components reflected by the reflective liquid crystal element are transmitted to the projection lens. It characterized by having a a rotating color separation plate for guiding the direction.
[0009]
According to the single plate type liquid crystal projector of the first aspect, the rotating color separation plate as the color separation means is used as the member for branching the light beam instead of the polarization beam splitter prism. Thus, by 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 reduction in size and thickness of the entire liquid crystal projector. Furthermore, since the distance between each liquid crystal element and the projection lens can be set short, the projection lens group can be made short-focused easily, and the projector can be configured at low cost.
[0010]
Further, the conventional single-plate type liquid crystal projector requires an assembly process with very high accuracy such as optical axis alignment of each polarization beam splitter and the combining prism. According to the invention described in claim 1, the number of constituent members Therefore, relative positioning of each optical member becomes easy.
[0011]
The rotating color separation plate according to claim 1, wherein the white light beam incident on the first end face is emitted from a second end face different from the first end face so as to enter the reflective liquid crystal element at a substantially right angle, and the reflective liquid crystal A third end face that is reflected by the element and incident on the second end face is a second end face that is substantially parallel to and opposite to the second end face at the same exit angle as the incident angle at the second end face. It is desirable to make it inject | emitted from (Claim 2).
[0012]
Here, the first end surface and the third end surface can be the same surface. That is, the end face on which the light beam from the light source unit enters and the end face on which the light beam is deflected and emitted from the rotating color separation plate may be configured to be substantially parallel. In this case, the first in each color separation region two A color separation function is provided by disposing an optical member having a reflection characteristic for separating color components corresponding to each color separation region on the end face. An example of the optical member is a dichroic mirror.
[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 light beam has a predetermined incident angle θ with respect to the first end surface. ₃ (However, 0 ° <θ ₃ It is desirable that the light is incident obliquely at <90 °. By defining the incident angle in this way, the diameter of the white light beam can be designed to be small.
[0014]
The rotating color separation plate includes a plurality of transparent substrates having reflective surfaces coated with an optical film having predetermined characteristics, which are disposed between both end surfaces in a state where the first inclined angle is inclined with respect to the normal line of each end surface. It is preferable to provide a multilayer structure 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 totally transmitted. With this configuration, the rotating color separation plate can have a function as a light beam branching unit.
[0015]
According to the invention of claim 6, Rotating color separator Each of the end surfaces and the liquid crystal surface of the reflective liquid crystal element has a second tilt angle θ. ₂ 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 When it is within the range of <90 °, each color component in the first linear polarization state is from a direction parallel to the liquid crystal surface. Rotating color separator It is desirable to determine the relative positional relationship between the light source unit and the rotating color separation plate so as to be incident on the light source.
[0016]
In particular, the second inclination angle θ ₂ If the angle is set to 0 °, the reflective liquid crystal element and Rotating color separator Relative positioning becomes extremely easy. However, in this case, each color component in the first linear polarization state is not in a direction parallel to the liquid crystal surface. Rotating color separator It is desirable to determine the relative positional relationship between the light source unit and the rotating color separation plate so as to be incident on the light source.
[0017]
According to the ninth aspect of the present invention, the first end face, the second end face, and the third end face can be substantially orthogonal to each other. In this case, it is preferable that the light source unit and the rotating color separation plate have a relative positional relationship such that the white light beam is incident at a substantially right angle with respect to the first end surface.
[0018]
The rotary color separation plates configured as described in claim 9 and claim 10 are arranged substantially parallel to each other and at a predetermined angle with respect to the first to third end faces. A plurality of optical films having predetermined characteristics are provided. The predetermined characteristic of each optical film is that for the first linearly polarized light of a specific color component corresponding to the color separation region, the total amount of light beams reflected by all the optical films is the total amount of incident light beams. The characteristic is that the light is reflected at different reflectances so as to be substantially equal, and the second linearly polarized light of the specific color component is transmitted almost entirely.
[0019]
Specifically, the characteristic of each optical film is such that the predetermined reflectance of the kth optical film is set to (100 / k)%, counting from the predetermined optical film provided farthest from the first end surface. (Claim 12). Thereby, each light beam reflected by each optical film can be made into an equal amount of light.
[0020]
Moreover, it is preferable that each optical film is disposed so as to partially overlap when viewed from the second end face side. As a result, it is possible to allow the light flux to be incident on almost the entire liquid crystal surface of the reflective liquid crystal element, and to display an image without a bright and dark area on the screen. However, when configured as in the fourteenth aspect, the light amount of the light beam incident on the liquid crystal surface corresponding to the region where the optical films overlap is larger than that in the other regions. Such unevenness and variation in the amount of light can be eliminated by correcting the data for generating a predetermined modulation signal.
[0021]
The non-uniformity in the amount of incident light beam that occurs on the reflective liquid crystal element due to the overlapping of the optical films is also eliminated by using the light beam width adjusting means provided in the light source section. ). In other words, the light beam width adjusting means adjusts the light beam width of the white light beam so that the light beam is incident only on one of the optical films in a region where the adjacent optical films partially overlap. The light beam width adjusting means is exemplified by a light tunnel used to make the intensity of the light beam uniform. The light tunnel has a cavity portion that is mirror-finished in all directions through which the light beam passes. The light flux width can be adjusted by sliding one mirror surface forming the hollow portion in a direction perpendicular to the mirror surface.
[0022]
According to the invention as set forth in claim 16, it is preferable to design the first linearly polarized light as S-polarized light.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram illustrating a schematic configuration of a single-plate liquid crystal projector 100 according to the first embodiment. The single-plate liquid crystal projector 100 includes a light tunnel 2, an illumination system lens group 3, a single polarizing plate 4, a rotating color separation plate 10, a reflective liquid crystal element 5, and a projection lens in the order in which the white light beam emitted from the light source 1 enters. Group 6 is included. 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 circle shape, and is rotated at a predetermined speed about the center O by the motor M.
[0024]
The light source 1 includes a high-pressure mercury lamp 1a and an elliptic 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 in the subsequent stage while making the intensity distribution uniform. The illumination system lens group 3 guides the white light incident through the light tunnel 2 to the single polarizing plate 4 while converging it in a predetermined direction. Specifically, the white light transmitted through the illumination system lens group 3 has a cross-sectional shape converged toward the central axis O on the surface including the first end surface 11, and is a surface orthogonal to the first end surface 11. The cross-sectional shape is a parallel light beam. Thereby, the light beam included in the white light beam is incident at substantially the same incident angle at any position on the first end surface 11. The single polarizing plate 4 aligns the polarization state so that the incident white light becomes S-polarized light with respect to the subsequent rotating color separation plate 10.
[0025]
The white light beam converted into the S-polarized state by the single polarizing plate 4 enters the first end surface 11 of the rotating color separation plate 10. The rotating color separation plate 10 includes three color separation regions 10R, 10G, and 10B corresponding to the three primary colors of light that are substantially evenly divided by the plurality of boundary surfaces B. Accordingly, the white light beam sequentially enters the first end surfaces 11 of the color separation regions 10R, 10G, and 10B.
[0026]
FIG. 3 is a diagram illustrating a cross section of the rotating color separating plate 10 and an arrangement relationship between the rotating color separating plate 10 and the reflective liquid crystal element 5. 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 in the other color separation regions are substantially the same as those shown in FIG. Therefore, in the following, description will be made mainly on 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 reflective surface 16 having a predetermined characteristic corresponding to a polarization state are laminated with the reflective surface 16 as a bonding surface. Specifically, in the multilayer structure 14, the reflective surface 16 has a first inclination angle θ with respect to the normal N of the transparent substrate 13. ₁ It is fixed in a tilted state to form That is, the reflecting surface 16 is in a state of being arranged substantially concentrically with respect to the center O. The multilayer structure 14 is fixed to the surface opposite to the first end surface 11 of the transparent substrate 13 in order to increase the bonding strength. The color separation region 10R is configured such that the first end surface 11 of the transparent substrate 13 and the end surface (second end surface) 12 on the opposite side of the fixing surface of the multilayer structure 14 to the mirror 13 are substantially parallel. . 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 is approximately 100% for S-polarized light of a specific color component (here, R component) corresponding to each color separation region. Reflection About 100% for the P-polarized light of the specific color component Transparent It has the characteristic to do. FIG. 5 shows a graph regarding the reflection characteristics of the reflection surface 16 provided in the color separation region 10G, and FIG. 6 shows a graph regarding the reflection characteristics of the reflection surface 16 provided in the color separation region 10B. As shown in FIGS. 4 to 6, only the color component corresponding to each of the regions 10R to 10B is reflected by the reflecting surface 16 of the S-polarized white light beam incident on each of the reflecting surfaces 16 in the color separation regions 10R to 10B. Thus, the light is deflected in the direction of the reflective liquid crystal element 5.
[0029]
In the present embodiment, as shown in FIG. 3, the optical path of the white light beam is substantially parallel to the liquid crystal surface 5 a of the reflective liquid crystal element 5. Therefore, the rotating color separation disk 10 has a second inclination angle θ with respect to the liquid crystal surface 5a so that the entire diameter of the white light beam traveling straight in the optical path substantially parallel to the liquid crystal surface 5a of the reflective liquid crystal element 5 can be captured. ₂ (However, 0 ° <θ ₂ <90 [deg.] Is disposed to be inclined. Since the projector 100 itself becomes large, θ ₂ Is not assumed to take 90 °.
[0030]
Therefore, the white luminous flux is from 90 ° to the second inclination angle θ. ₂ Angle of incidence θ minus ₃ Is obliquely incident on the first end surface 11. That is, in this embodiment, the incident angle θ ₃ Is also 0 ° <θ ₃ <90 °. However, incident angle θ ₃ If it becomes too large, the amount of light reflected by the first end surface 11 may increase. Therefore, an antireflection film for color components corresponding to each region is provided on the first end surface 11 of each region 10R to 10B.
[0031]
Where the first tilt angle θ ₁ And the second tilt 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 enters the liquid crystal surface 5a substantially perpendicularly (incident at an incident angle of 0 °). With this setting, the white light beam obliquely incident on the first end surface 11 of the rotating color separation plate 10 is sequentially color-separated and emitted from the second end surface 12 so as to enter at right angles to the liquid crystal surface 5a. Note that the optical path of the R component indicated by the arrow line in FIG. 2 is in a state in which the refraction phenomenon at the time of incidence / exit on the end faces 11 and 12 is omitted for convenience.
[0032]
The reflective 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 becomes a P polarization state obtained by rotating the polarization state of the incident light beam 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 enters the rotating color separation plate 10 again through the second end face 12. In FIG. 3, for the sake of convenience, incident light and reflected light (emitted light) in the reflective liquid crystal element 5 are shown as different optical paths, but actually the reflected light returns in substantially the same optical path as the incident light. 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 characteristic of substantially completely transmitting the P-polarized light. Therefore, each color component in the P-polarized state that sequentially enters the second end surface 12 of the rotating color separation plate 10 is emitted from the first end surface 11 with almost no loss of light quantity.
[0034]
Each color component of P-polarized light emitted from the first end surface 11 is a projection lens group. 6 Are sequentially enlarged and projected onto a screen (not shown). 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. The single-plate 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 5 a of the reflective liquid crystal element 5 are configured to be parallel. In this regard, the single-plate liquid crystal projector 100 according to the first embodiment is not limited to this 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 surface 11 and the second end surface 12 and the liquid crystal surface 5a are substantially parallel to each other. Thereby, there is an advantage that the relative positioning of the rotating color separation plate 10 and the reflective 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 that described above. For example, as an alternative to the multilayer structure 14 described above, a rotating color separation plate having a liquid crystal film disclosed in Japanese Patent Application No. 2003-23413, which is an application of the present applicant, can also be used. However, in this case, a dichroic mirror having a characteristic of transmitting only the color components corresponding to the regions 10R, 10G, and 10B is provided instead of the transparent substrate 13. This provides a rotating color separation plate capable of color separation while utilizing the disclosure of the above application.
[0037]
FIG. 7 is a diagram showing a schematic configuration of a single-plate liquid crystal projector 200 according to the second embodiment of the present invention. In the single-plate liquid crystal projector 200 shown in FIG. 7, the same components as those in the projector 100 shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted here. 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 separating plate 20 is substantially circular like the rotating color separating plate 10 shown in FIG. 2, and includes three color separating regions 20R, 20G, and 20B corresponding to the R, G, and B color components. Have. Each color separation area is divided substantially equally. As shown in FIG. 7, the rotating color separation plate 20 is disposed so that the 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 reflective liquid crystal element 5 and the rotating color separation plate 20 are disposed substantially in parallel, the single-plate liquid crystal projector 200 according to the second embodiment makes it very easy to relatively position each optical member. There are advantages.
[0038]
FIG. 9 is a diagram illustrating a cross-section of the rotating color separating plate 20 and an arrangement relationship between the rotating color separating plate 20 and the reflective liquid crystal element 5. 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 description will be made mainly on the color separation region 20R and the light beam incident on the region 20R. The rotating color separation plate 20 includes a first end surface 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 surface 22 orthogonal to the first end surface 21 and parallel to each other, A three end face 23 is provided.
[0039]
As described above, the rotating color separation plate 20 and the reflective liquid crystal element 5 are arranged in parallel to each other. Accordingly, the optical path of the white light beam incident at a substantially right angle with respect to the first end surface 21 is in a substantially parallel relationship with the second end surface 22, the third end surface 23, and the liquid crystal surface 5a. In the single-plate liquid crystal projector 200 of the second embodiment, the first end surface 21 on which the white light beam is incident is an arc shape because it is the outer peripheral surface of the rotating color separation plate 20. Accordingly, when a parallel light beam is incident on the first end surface 21, the incident angle varies depending on the incident position, and the amount of light incident on the subsequent reflective liquid crystal element 5 may be reduced. Therefore, the illumination system lens group 3 ′ of the second embodiment always causes the white light beam irradiated from the light source 1 and incident through the light guide 2 to be incident on each of the optical films C1, C2, and C3 at a constant incident angle. Has an effect.
[0040]
As shown in FIG. 9, in the color separation region 20R, three optical films C1 to C3 are disposed in order from the first end face 21 side. Each of the optical films C1 to C3 has first to third end faces. 21 ~ 23 It is arrange | positioned so that 45 degrees may be made with respect to each of these. In addition, the adjacent optical films (for example, C1 and C2) are provided on the second end face so that the light beam is incident on substantially the entire area of the liquid crystal surface 5a of the reflective liquid crystal element 5. 22 Or third end face 23 When viewed from above, they are arranged so as to partially overlap.
[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. The reflection characteristic of the optical film C3 has substantially the same characteristic as the reflection characteristic of the dichroic mirror 13 of the first embodiment, so refer to FIG. As shown in FIGS. 3 to 5, each of the optical films C <b> 1 to C <b> 3 has different reflection characteristics with respect to R component light in an S polarization state (about 600 nm or more). The reflection characteristics are set so as to reflect almost 100% of the incident light beam by using all the optical films C1 to C3. Specifically, the first end surface 21 The kth optical film counted from the optical film C3 farthest from the optical film 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 optical film becomes substantially equal. As shown in each drawing, each optical film transmits substantially the entire amount of the P-polarized light of the corresponding color component (here, R component) and other color components.
[0042]
Accordingly, the R component of the S-polarized light beam incident on 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 deflection state reflected by each of the optical films C1 to C3 is the second end face. 22 And enters the liquid crystal surface 5a of the reflective liquid crystal element 5 at a substantially right angle. Here, by setting the reflectivity of each optical film as described above, the liquid crystal surface 5a except for the region where the light beam from the part where the optical films shown by hatching in FIG. 9 partially overlap is incident. A substantially uniform amount of light is incident on any point. In the present embodiment, about 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]
Note that the reflection characteristic of the optical film C1 in the color separation region 20G for color-separating the G component is shown in FIG. 12, and the reflection characteristic of the optical film C2 is shown in FIG. Since the reflection characteristic of the optical film C3 in the color separation region 20G has substantially the same characteristic as that of the dichroic mirror 13 provided in the color separation region 10G of the first embodiment, reference is made to FIG.
[0044]
Similarly, FIG. 14 shows the reflection characteristics of the optical film C1 in the color separation region 20B for color separation of the B component, and FIG. 15 shows the reflection characteristics of the optical film C2. Since the reflection characteristic of the optical film C3 in the color separation region 20B has substantially the same characteristic as that of the dichroic mirror 13 provided in the color separation region 10B of the first embodiment, refer to FIG.
[0045]
Similar to the first embodiment, the reflective liquid crystal element 5 modulates the R component incident upon the ON bit according to a modulation signal transmitted from a control unit (not shown). Here, in FIG. 9, the light from the portion where the optical films indicated by the hatched areas partially overlap is reflected twice by the two optical films, so that the liquid crystal surface 5a is compared with the other areas. The amount of light incident on is increased. For example, the light beam incident through the overlapping region of the optical film C1 and the optical film C2 has a light amount of about 22% compared to other regions. As described above, if the amount of light incident on the liquid crystal surface 5a is uneven, the quality of the generated image is deteriorated. For this reason, in the present embodiment, a modulation signal generated based on video information that has been darkly corrected in advance is given to a pixel on which a light beam with a large amount of light is incident. By performing a modulation process based on such a modulation signal, the luminous flux (ON light) emitted from the element 5 is incident on the reflective liquid crystal element 5 even if the quantity of light is nonuniform by the pixels. The light quantity of the pixel is also a substantially uniform light beam.
[0046]
As described above, the reflected light beam (ON light) from the reflective liquid crystal element 5 is in the P-polarized state. The R component ON light 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 FIGS. 4 to 6 and FIGS. 10 to 15, the optical films C <b> 1 to C <b> 3 in each color separation region have a characteristic that the reflectance with respect to the P-polarized light is almost zero regardless of the color component. For this reason, the R component ON light incident on the second end face 22 passes through each of the optical films C1 to C3 with substantially the entire light amount. The ON light is emitted from the third end face 23 at a substantially right angle and travels toward the projection lens group 6.
[0048]
The light beam (OFF light) incident at the OFF bit in the modulation signal is incident on the rotating color separation plate 20 again without being modulated and 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 OFF light is incident on a color separation area different from the color separation area at the time of color separation, the OFF light enters 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. Incidently at a right angle. For example, it is assumed that R component OFF light 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, the optical films C1 to C3 in the color separation region 20G almost completely transmit the R component regardless of the polarization state. Accordingly, the R component OFF light 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 onto the screen via the projection lens group 6, the quality of the image displayed on the screen S is degraded. Therefore, in the single-plate liquid crystal projector 200 of the second embodiment, the absorption polarizing plate 7 is provided between the rotating color separation plate 20 and the projection lens group 6. Absorbing polarizing plate 7 In this case, almost all the color components that have been transmitted through the rotating color separation plate 20 despite being OFF light are cut off and are prevented from entering the projection lens group 11.
[0050]
In this way, only the ON light components of R, G, and B colors are sequentially incident on the projection lens group 11. A bright full-color image on a large screen is displayed on the screen S by 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-plate liquid crystal projector 200 of the second embodiment is not limited to the above embodiment.
[0052]
For example, each of the optical films C1 to C3 has been described as being partially overlapped so that the light beam is incident on the entire liquid crystal surface. However, in the design stage, if the optical films C1 to C3 can be arranged seamlessly when viewed from the second end face 22 side, there is no need to overlap them. In this case, since the light beams incident on the liquid crystal surface have almost the same light amount, correction processing for matching the light amounts does not have to be performed.
[0053]
In addition, it has been described that the non-uniformity in the amount of incident light on the liquid crystal surface 5a caused by partially overlapping each of the optical films C1 to C3 is eliminated by correcting the video information for generating the modulation signal. It is also possible to make the light quantity uniform by another method. For example, the mirror surface forming the light guide 2 is slid in a direction orthogonal to the mirror surface while referring to an image actually projected on a monitor (not shown). As a result, the width of the light beam incident on the rotating color separation plate 20 changes as indicated by the white arrow line in FIG. It is also possible to fix the mirror surface when a position where the image quality is the best, that is, when a light beam width (dashed line in FIG. 2) that eliminates the light amount difference on the liquid crystal surface is obtained.
[0054]
Further, it has been described that the rotating color separation plate 20 includes three optical films C1 to C3 each having different reflection characteristics in any color separation region 20R to 20B. However, the number of optical films is only an example, and if there are at least two optical films, the same effect as in the second embodiment can be obtained. Further, even if there is unevenness in the light amount of the light beam incident on the reflective liquid crystal element 5, even if one optical film can be used as long as the modulation signal for controlling the liquid crystal element can be changed more flexibly. good.
[0055]
Further, the absorbing polarizing plate 7 can be integrally formed with the rotating color separation plate 20 by being bonded to the third end face 23.
[0056]
In the above, two preferred embodiments of the single-plate liquid crystal projector according to the present invention have been described. In each embodiment, the light beam from the light source 1 has been described as being S-polarized light, but may be P-polarized light. In each of the above embodiments, a circular rotating color separation plate is assumed, but a rotating color separation plate other than a circular shape may be used. In each of the above embodiments, each rotating color separation plate includes one color separation region corresponding to each of R, G, and B. However, any number of color separation regions corresponding to each color may be used. You may have.
[0057]
【The invention's effect】
As described above, the single-plate type liquid crystal projector according to the present invention has a reflection-type liquid crystal projector by arranging a rotating color separation plate having both a color separation function and a light beam branching function with a suitable positional relationship with respect to the reflection type liquid crystal element. The distance between the liquid crystal element and the projection lens group can be shortened. As a result, the configuration in the vicinity of the projection lens group can be reduced in size, and the length of the projector in the depth direction can be shortened. That is, a single-plate liquid crystal projector that has a simpler configuration than that of a conventional projector and is reduced in size and thickness is provided.
[0058]
The single-plate liquid crystal projector according to the present invention can reduce the diameter of the light beam incident on the rotating color separation plate. Thereby, unlike the conventional configuration using the polarization beam splitter cube, a space to be secured as an optical path can be reduced. From this point, further downsizing of the entire projector is realized.
[0059]
Further, for example, as in the second embodiment, the single-plate liquid crystal projector according to the present invention is configured such that each optical member is bent at an integral multiple of approximately 90 ° in each optical path. Thereby, each optical member can be arrange | positioned in the position with a high precision by the 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. A clear image can be projected at a sufficiently wide angle without using the. 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-plate 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-plate liquid crystal projector according to the first embodiment.
FIG. 3 is a diagram illustrating a cross-section of a rotating color separation plate of the first embodiment, and an arrangement relationship between the rotating color separation plate and a reflective liquid crystal element.
FIG. 4 is a graph showing reflection characteristics of a dichroic mirror provided on the rotating color separation plate of the first embodiment.
FIG. 5 is a graph showing reflection characteristics of a dichroic mirror provided on 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-plate liquid crystal projector according to a second embodiment of the invention.
FIG. 8 is a diagram illustrating a rotating color separation plate of a single-plate liquid crystal projector according to a second embodiment.
FIG. 9 is a diagram showing a cross section of a rotating color separating plate according to a second embodiment, and an arrangement relationship between the rotating color separating plate and a reflective liquid crystal element.
FIG. 10 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
FIG. 11 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
FIG. 12 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
FIG. 13 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
FIG. 14 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
FIG. 15 is a graph showing reflection characteristics of an optical film provided on the rotating color separation plate of the second embodiment.
[Explanation of symbols]
1 Light source
5 reflective liquid crystal elements
6 Projection lens group
10, 20 Rotating color separator
11, 21 First end surface
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 an 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 onto a screen;
At least 3 divided between the light source unit and the reflective liquid crystal element and between the reflective liquid crystal element and the projection lens group so as to be rotatable about the center and split the incident light beam substantially evenly. The three color separation regions are sequentially decomposed into three color components corresponding to the three primary colors of light while maintaining the polarization state, and the separated color components are deflected toward the reflective liquid crystal element and reflected by the reflective liquid crystal element. A single color liquid crystal projector, comprising: a rotating color separation plate that transmits the color component transmitted and guides the color component in the direction of the projection lens group. The single-plate liquid crystal projector according to claim 1,
The rotating color separation plate allows the white light beam incident on the first end surface to be emitted from a second end surface different from the first end surface so as to be incident on the reflective liquid crystal device at a substantially right angle, and in the reflective liquid crystal device. The second linearly polarized light beam reflected and incident on the second end face is reflected from the third end face that is substantially parallel to the second end face at the same exit angle as the incident angle at the second end face. A single-plate liquid crystal projector characterized by being ejected. The single-plate liquid crystal projector according to claim 2,
The first end surface and the third end surface are the same surface, and the rotating color separation plate includes an optical member having a reflection characteristic for separating color components corresponding to each of the color separation regions, and the optical member is provided for each color. A single-plate liquid crystal projector, which is disposed on the second end face in the separation region. In the single-plate liquid crystal projector according to claim 3,
The light source unit and the rotating color separation plate have a positional relationship such that the white light beam is obliquely incident on the first end surface at a predetermined incident angle θ ₃ (where 0 ° <θ ₃ <90 °). , A single-plate liquid crystal projector. In the single-plate liquid crystal projector according to claim 3 or 4,
The rotating color separation plate includes a plurality of transparent substrates having reflection surfaces coated with an optical film having predetermined characteristics, and are inclined between the both end surfaces in a state where the first inclined angle is inclined with respect to the normal of each end surface. It is laminated periodically at a predetermined pitch,
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. In the single plate type liquid crystal projector according to any one of claims 3 to 5,
The rotating color separation plate is disposed such that each end face and the liquid crystal surface of the reflective liquid crystal element form a _second inclination angle θ ₂ , and the second inclination angle θ ₂ is 0. A single-plate type liquid crystal projector characterized by being in a range of ° ≦ θ ₂ <90 °. In the single-plate liquid crystal projector according to claim 6,
When the second tilt angle θ ₂ is in the range of 0 ° <θ ₂ <90 °, the light source unit and the rotating color separation plate have each color component in the first linear polarization state on the liquid crystal surface. A single plate type liquid crystal projector having a relative positional relationship such that the light enters the rotating color separation plate from a substantially parallel direction. In the single-plate liquid crystal projector according to claim 6,
The second inclination angle θ ₂ is 0 °, and the light source unit and the rotating color separation plate are configured so that each color component in the first linear polarization state is rotated in a direction that is not parallel to the liquid crystal surface. A single plate type liquid crystal projector characterized by being in a relative positional relationship so as to be incident on a separation plate . The single-plate liquid crystal projector according to claim 2,
The single-plate type liquid crystal projector, wherein the first end surface, the second end surface, and the third end surface are in a substantially orthogonal relationship. The single-plate liquid crystal projector according to claim 9,
The single plate 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 at a substantially right angle with respect to the first end surface. The single-plate 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 the first to third end faces,
For each optical film, the total amount of light beams reflected by all the optical films is substantially equal to the total amount of incident light beams for the first linearly polarized light of a specific color component corresponding to the color separation region. A single-plate type liquid crystal projector characterized by reflecting at different reflectances and having substantially the entire transmission of the second linearly polarized light of the specific color component. The single-plate liquid crystal projector according to claim 11,
A single-plate liquid crystal projector, wherein the reflectance of a kth optical film counted from a predetermined optical film provided at a position furthest from the first end surface is set to (100 / k)%. The single-plate liquid crystal projector according to claim 11 or 12,
A single-plate liquid crystal projector, wherein the optical films adjacent to each other are disposed so as to partially overlap each other when viewed from the second end face side. The single-plate liquid crystal projector according to claim 13,
The single-plate type liquid crystal projector, wherein the variation in the amount of light on the liquid crystal surface of the reflective liquid crystal element caused by the partial overlap is eliminated by correcting the data for generating the predetermined modulation signal. The single-plate liquid crystal projector according to claim 13,
The light source unit includes a light source that emits a white light beam, and a light beam width adjusting unit that adjusts a light beam width of the white light beam,
The luminous flux width adjusting means adjusts the luminous flux width of the white luminous flux so that the luminous flux is incident on 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-plate liquid crystal projector according to any one of claims 1 to 15,
The first linearly polarized light is S-polarized light;
The single plate type liquid crystal projector, wherein the second linearly polarized light is P polarized light.

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