JP2000131648A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a cost of a polarization separation element and to obtain a compact projector by making a polarization separation element to a curved polarization separation sheet. SOLUTION: Light emitted from a illumination optical system 7 is made incident on a polarization separation sheet 9 through a cylinder lens 8, only a S polarization component is reflected, and given to a reflection type liquid crystal display element 10. The polarization separation sheet 9 is curved so that the sheet operates as a recess faced mirror having curvature in only a direction parallel to a paper surface for reflected illumination light. Therefore, as the device can be constituted so that a luminous flux (inverse luminous flux) projected toward the illumination optical system 7 from the polarization separation sheet 9 is converged, the cylinder lens 8 and an illumination optical system 7 can be constituted compactly. Further, the polarization separation sheet 9 has sufficient magnitude for receiving illumination light, but as it is curved, influence given to lens-back of projection optical system 11 by magnitude of the polarization separation sheet 9 is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector having a configuration in which a projection element is formed by illuminating a display element with an illumination optical system and the projection image is projected by the projection optical system. The present invention relates to a projector having a polarization splitting element that reflects light to provide it to a reflective liquid crystal and transmits light from the reflective liquid crystal to give it to a projection optical system.

[0002]

2. Description of the Related Art As a display element in a projector, there is, for example, a reflection type liquid crystal display element. This has advantages such as a larger aperture ratio than a transmissive liquid crystal display element. In particular, a reflection type liquid crystal made of a cholesteric liquid crystal has a high reflectivity, and a driver IC on a silicon substrate
There are many advantages such as being able to be configured integrally with the, and it has attracted attention in recent years.

In order to illuminate the reflection type liquid crystal display element most efficiently, it is desirable to illuminate the display element from directly in front. However, when the illumination device is arranged in such a manner, the illumination device blocks reflected light from the display element, and observation is not possible. In order to prevent this, a conventional projector uses, for example, a polarization splitting prism.

FIG. 6 shows an example of a conventional projector using a polarization splitting prism. FIG. 6 is a horizontal sectional view showing a schematic configuration of the projector. The projector 100 includes an illumination optical system 107 including a light source 101, a reflector 102, and a parallel conversion lens 103, a polarization separation prism 104, a reflective liquid crystal display device 105, and a telecentric projection optical system 106 including a plurality of lenses. Have been.

The white light emitted from the light source 101 is reflected by a reflector 102, converted into parallel light by a parallel conversion lens 103, and incident on a polarization splitting prism 104. The polarization splitting prism 104 has a polarization splitting surface 104a that reflects the S-polarized light component and transmits the P-polarized light component. The S-polarized light component reflected by the polarization splitting surface 104a illuminates the reflective liquid crystal display element 105, where an optical image is formed. Light that forms an optical image is polarized into a P-polarized component by reflection at the reflective liquid crystal display element 105.

[0006] The P-polarized light component forming an optical image emitted from the reflection type liquid crystal display element 105 passes through the polarization splitting surface 104a and is projected on a screen (not shown) by the projection optical system 106. In the projector 100, illumination from the front of the reflective liquid crystal display element 105 is achieved without blocking image light. The illumination light for illuminating the reflective liquid crystal display element 105 must be polarized. This is also achieved by the polarization splitting prism 104. The polarization splitting prism 104 not only achieves illumination from the front, but also plays a role of extracting only a specific polarization component from random polarized light emitted from the white light source 101 to produce illumination light.

[0007]

However, in the above-mentioned conventional projector, a large prism is required as a polarization splitting prism, so that the cost is increased.
In order to solve this problem, a configuration in which a recently developed less expensive polarization separation sheet is replaced with a polarization separation prism may be considered. The polarized light separating sheet is publicly known and will not be described in detail.

[0008] However, when the polarization separation sheet is provided, the glass block portion of the polarization separation prism becomes air, so that the optical path length becomes long. Therefore, the lens back of the projection optical system becomes longer, and the projection optical system becomes larger.

In a projection optical system having a long lens back,
In order to reduce the size of each projection lens, the projection optical system may be a non-telecentric optical system (a non-telecentric optical system in which a principal ray is reduced in a direction from the reflective liquid crystal display element to the projection optical system). In this case, a problem arises. Hereinafter, this problem will be described with reference to FIG.

FIG. 7 is a horizontal sectional view showing an example of a schematic configuration of a projector having a polarization separation sheet and a non-telecentric projection optical system. The projector 108
The projector 100 shown in FIG. 10 includes an illumination lens group 109 in place of the parallel conversion lens 103, a polarization separation sheet 110 in place of the polarization separation prism 104, and a non-telecentric projection optical system 111 in place of the telecentric projection optical system 106. Is different only in the configuration. Since other configurations, operations, and the like are the same, duplicate description will be omitted.

In the projector 108, each projection lens can be miniaturized as the degree of non-telecentricity of the projection optical system 111 is increased.
The illuminating light required is a luminous flux that diverges from the reflective liquid crystal display element 105 in the reverse direction, and a large polarization separation sheet 110 that receives the luminous flux is required. When the large polarization separation sheet 110 is provided, the lens back of the projection optical system 111 is lengthened by the amount of disposition. Further, the illumination lens group 109 also becomes large.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a small-sized projector with a reduced cost for a polarization splitting element.

[0013]

According to one aspect of the present invention, there is provided a reflective liquid crystal display device which forms an optical image for projection by spatially modulating illumination light based on a video signal. An illumination optical system that generates the illumination light, a projection optical system that projects the optical image on a projection screen, and a first polarization component of the illumination light that is reflected and provided to the reflective liquid crystal display element. A polarization separating element that transmits light forming the optical image, which is reflected by the reflection type liquid crystal display element and is polarized from a first polarization component to a second polarization component, and transmits the light to the projection optical system. In the above structure, the polarization separation element is a curved polarization separation sheet.

[0014] The invention described in claim 2 is the first invention.
, The polarized light separating sheet is curved so as to act as a concave mirror having a curvature in only one direction with respect to the reflected illumination light.

Further, according to a third aspect of the present invention, in the projector according to the first or second aspect, the projection optical system is a non-telecentric optical system.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> FIG.
FIG. 1 is a horizontal cross-sectional view illustrating a schematic configuration of a projector according to an embodiment. The projector 1 includes an illumination optical system 7 including a light source 2, a reflector 3, a parallel conversion lens 4, a first lens array 5, and a second lens array 6, a cylinder lens 8,
The configuration includes a polarization separation sheet 9 that reflects an S-polarized component and transmits a P-polarized component, a reflective liquid crystal display element 10, and a non-telecentric projection optical system 11 including a plurality of projection lenses.

The white light emitted from the light source 2 is directly or reflected by the reflector 3 and enters the parallel conversion lens 4, is converted into parallel light, is emitted, and enters the first lens array 5. Then, after being separated into a plurality of light beams by the first lens array 5, the light beams are incident on the second lens array 6, and a plurality of light source images are formed. The first lens array 5 has a conjugate relationship with the reflection type liquid crystal display element 10. The second lens array 6 has a conjugate relationship with the light source 2 and each lens is a secondary light source. The illumination optical system 7 achieves uniform illumination of the reflective liquid crystal display element 10.

The light emitted from the illumination optical system 7 is incident on the polarized light separating sheet 9 via the cylinder lens 8, and only the S-polarized light component is reflected and provided to the reflection type liquid crystal display device 10. In the reflective liquid crystal display element 10, an optical image is formed. Light forming an optical image is reflected by the reflective liquid crystal display element 10 and is polarized from an S-polarized component to a P-polarized component. This light passes through the polarization separation sheet 9 and is projected on a screen (not shown) by the projection optical system 11.

The projection optical system 11 of the projector 1 according to the present embodiment is a non-telecentric optical system in a direction in which a principal ray is reduced from the reflection type liquid crystal display device 10 to the projection optical system 11. With such a configuration,
Each projection lens of the projection optical system 11 can be downsized.

The polarized light separating sheet 9 is curved so as to act as a concave mirror having a curvature only in a direction parallel to the plane of FIG. (Hereinafter referred to as concave cylinder surface shape). Therefore, since the light beam (reverse light beam) traveling from the polarization separation sheet 9 toward the illumination optical system 7 can be converged, the cylinder lens 8 and the illumination optical system 7 can be made small. Further, the polarization separation sheet 9 has a size sufficient to receive the illumination light, but has a small influence on the lens back of the projection optical system 11 because the polarization separation sheet 9 is curved.

In the polarization separating sheet 9, at both ends in a direction having a curvature (parallel to the paper surface), the other end (indicated by B in FIG. 1) on the side of the reflection type liquid crystal display element 10 (A in FIG. 1). (Indicated by). Although the incident angle of the reverse light beam at each position of the polarized light separating sheet 9 is different, the reverse light beam converges favorably by changing the degree of curvature in this way.

The cylinder lens 8 has a convex lens shape having a curvature only in a direction perpendicular to the plane of FIG. FIG. 2 shows a cylinder lens 8, a polarization separation sheet 9,
1 shows a top perspective view of a portion including a reflective liquid crystal display element 10. In FIG. 2, the direction perpendicular to the paper surface of FIG. 1 is indicated by an arrow C of the double head.

As can be seen from FIG. 2, the cylinder lens 8 has a curvature only in the direction of arrow C. Since the polarized light separating sheet 9 has a concave cylinder surface shape, there is a cross section having power and a cross section having no power. If there is no other optical element having different power depending on the cross section, astigmatism will occur in illumination light. The cylinder lens 8 is an optical element that prevents this astigmatic difference from occurring. As described above, the cylinder lens 8 has a shape in which the polarized light separating sheet 9 has power in a cross section having no power. The polarization separating sheet 9 may have a curvature also in the direction of the arrow C. However, a polarizing separation sheet having power in only one direction can be easily manufactured, and thus the above-described configuration is adopted.

Although the first lens array 5 has a conjugate relationship with the reflection type liquid crystal display element 10, the two optical elements have powers in different directions between the two elements (see the paper of FIG. 1). For the parallel direction, polarized light separating sheet 9
Have a power, and the cylinder lens 8 has a power in the direction perpendicular to the plane of the paper).

<Second Embodiment> FIG. 3 is a horizontal sectional view showing a schematic configuration of a projector according to a second embodiment.
The projector 12 can project a color image. The projector 12 includes an illumination optical system 7 having the same configuration as the projector 1 of the first embodiment, a cross dichroic mirror 13 for separating the illumination light by color, and a dichroic mirror 1.
5, reflection mirrors 14a and 14b, and three polarization separation sheets 16R that reflect the S-polarized component and transmit the P-polarized component,
16G and 16B, and reflective liquid crystal display elements 17R and 17R corresponding to red (R), green (G), and blue (B), respectively.
7G and 17B, a cross dichroic prism 18 for synthesizing optical images of three colors, and a non-telecentric projection optical system 19 including a plurality of projection lenses.

The illumination light emitted from the illumination optical system 7 enters the cross dichroic mirror 13. Dichroic mirror 13a of cross dichroic mirror 13
Reflects only light in the B wavelength range. The dichroic mirror 13b reflects light in the R and G wavelength ranges.

The light in the B wavelength range reflected by the dichroic mirror 13a is reflected by the reflection mirror 14a, and only the S-polarized light component is reflected by the polarization separation sheet 16B to illuminate the reflection type liquid crystal display element 17B. In the reflection type liquid crystal display element 17B, an optical image of B is formed. The light forming the optical image B is reflected by the reflective liquid crystal display element 17B,
The light is polarized into the P-polarized light component, passes through the polarization separation sheet 16 </ b> B, and enters the cross dichroic prism 18.

The light in the R and G wavelength ranges reflected by the dichroic mirror 13b is reflected by the reflection mirror 14b and enters the dichroic mirror 15. The dichroic mirror 15 reflects only light in the G wavelength band. With respect to the light in the G wavelength range reflected by the dichroic mirror 15, only the S-polarized light component is reflected by the polarization separation sheet 16G, and illuminates the reflection type liquid crystal display element 17G. A G optical image is formed on the reflective liquid crystal display element 17G. The light forming the G optical image is reflected by the reflective liquid crystal display element 17B, is polarized into a P-polarized component, and is polarized.
And enters the cross dichroic prism 18.

R transmitted through the dichroic mirror 15
In the light of the wavelength range described above, only the S-polarized light component is reflected by the polarization separation sheet 16R, and illuminates the reflective liquid crystal display element 17R. An R optical image is formed on the reflective liquid crystal display element 17R. The light forming the R optical image is reflected by the reflective liquid crystal display element 17R, is polarized into a P-polarized component, passes through the polarization separation sheet 16R, and enters the cross dichroic prism 18.

Surface 1 of cross dichroic prism 18
8a is provided with a dichroic coat that reflects only light in the B wavelength range. The surface 18b is provided with a dichroic coat that reflects only light in the R wavelength range. In the dichroic prism 18, among the incident light forming the optical image of each color, light in the B wavelength range is reflected by the surface 18a, light in the R wavelength range is reflected by the surface 18b, and light in the G wavelength range is Optical images of three colors are synthesized by transmitting without being reflected on any of the surfaces. The synthesized optical image is projected on a screen (not shown) by the projection optical system 19.

The projection optical system 19 of the projector 12 according to the present embodiment includes reflection type liquid crystal panels 17R, 17G, 17B.
The optical system is a non-telecentric optical system in the direction in which the principal ray is reduced from the optical system to the projection optical system 19. With such a configuration, each projection lens of the projection optical system 19 can be downsized.

The polarized light separating sheets 16R, 16G, 1
6B is curved so as to act as a concave mirror having a curvature in two directions with respect to the reflected illumination light (hereinafter, referred to as a concave shape). Therefore, each polarization separation sheet 16R, 1R
Since the reverse light beam from the 6G and 16B to the illumination optical system 7 can be configured to converge, the dichroic mirror 1
3, 15, and the illumination optical system 7 can be downsized.

<Third Embodiment> FIG. 4 is a horizontal sectional view showing a schematic configuration of a projector according to a third embodiment.
The projector 20 can project a color image. The projector 20 is a projector 12 according to the second embodiment.
This means that condenser lenses 21R, 21G, and 21B are provided on the front surface of each of the reflective liquid crystal display elements 17R, 17G, and 17B;
Polarization separation sheet 2 having different shape instead of 6G and 16B
It differs only in having 2R, 22G, and 22B. Therefore,
Description overlapping with the second embodiment will be avoided.

Condenser lenses 21R, 21G, 21B
Is a light beam in the direction of the projection optical system 19 or the illumination optical system 7.
Converge the reverse light beam in the direction. Therefore, the reverse luminous flux from each of the reflection type liquid crystal display elements 17R, 17G, 17B to the corresponding polarization separation sheet 22R, 22G, 22B is also converged,
Since the width of the light beam incident on the polarization separation sheets 22R, 22G, and 22B is reduced, the polarization separation sheets 22R, 22
G and 22B can be made small. Therefore, the projection optical system 1
9 can be made shorter.

However, if the degree of convergence of the reverse light beam is too large, a sufficient space for disposing elements such as the dichroic mirror 13 between the polarization separation sheets 22R, 22G and 22B and the illumination optical system 7 cannot be secured. Can occur. In order to secure a sufficient space, the polarization separation sheets 22R, 22G,
22B is curved so as to act as a convex mirror having a curvature in two directions with respect to the reflected illumination light (hereinafter, referred to as a convex mirror).
Convex shape). The operation of the convex polarization separating sheets 22R, 22G, and 22B will be described with reference to FIG.

FIG. 5 shows a polarized light separating sheet 22 having a convex shape.
The difference in the degree of convergence of the reverse luminous flux between the R, 22G, and 22B and the plane-shaped polarization separating sheet 22 ′ having no curvature is shown. The reverse light flux when the polarization separation sheets 22R, 22G, and 22B are provided is indicated by a dotted line 23, and the planar polarization separation sheet 2
The reverse light flux in the case where 2 ′ is provided is shown by a solid line 24.

As can be seen from FIG. 5, the degree of convergence of the reverse light beam can be reduced by the polarized light separating sheets 22R, 22G, and 22B having a convex shape. Therefore, the configuration can be such that a sufficient space for disposing the dichroic mirror 13 and the like can be secured. The polarization separation sheets 22R, 22G, 22
The curvature of B is set to a size that can secure a space of an optimum size.

[0038]

According to the projector of the first aspect, the cost can be reduced by using the polarization splitting sheet as the polarization splitting element. In addition, by using a curved polarized light separating sheet, the illumination optical system and the projection optical system can be configured to be small, and it is possible to achieve downsizing of the entire apparatus.

According to the projector of the third aspect,
Since the constituent lenses of the projection optical system can be reduced in size, the entire apparatus can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view showing a schematic configuration of a projector according to a first embodiment.

FIG. 2 is a top perspective view of a part of the projector according to the first embodiment.

FIG. 3 is a horizontal sectional view showing a schematic configuration of a projector according to a second embodiment.

FIG. 4 is a horizontal sectional view showing a schematic configuration of a projector according to a third embodiment.

FIG. 5 is a diagram showing reverse light beams in two types of polarized light separating sheets having different shapes.

FIG. 6 is a diagram showing a configuration example of a conventional projector using a polarization splitting prism.

FIG. 7 is a diagram showing a configuration example of a projector using a planar polarization separation sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 12, 20 Projector 2 Light source 3 Reflector 7 Illumination optical system 8 Cylinder lens 9 Polarization separation sheet of concave cylinder surface 10 Reflection type liquid crystal display element 11, 19 Projection optical system 13 Cross dichroic mirror 15 Dichroic mirror 16R, 16G, 16B Concave polarized light separating sheet 17R, 17G, 16B Reflective liquid crystal display element 18 Cross dichroic prism 21R, 21G, 21B Condenser lens 22R, 22G, 22B Convex polarized light separating sheet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 33/12 G03B 33/12 F term (Reference) 2H088 EA14 EA15 EA16 EA18 HA13 HA18 HA21 HA24 HA25 HA28 MA16 2H091 FA05X FA08X FA08Z FA14Z FA26Z FA29Z FA41Z LA11 MA07 2H099 AA12 BA09 CA11

Claims (3)

[Claims] 1. A reflection type liquid crystal display element for spatially modulating illumination light based on a video signal to form an optical image for projection, an illumination optical system for generating the illumination light, and displaying the optical image on a projection screen. A projection optical system for projecting, and reflecting the first polarization component of the illumination light to the reflection-type liquid crystal display element, and reflecting the reflection-type liquid crystal display element from the first polarization component to the second polarization component. A polarization splitting element for transmitting the light forming the optical image polarized to the projection optical system and transmitting the light to the projection optical system, wherein the polarization splitting element is a curved polarization splitting sheet. . 2. The polarization separation sheet according to claim 1, wherein the polarization separation sheet is curved so as to act as a concave mirror having a curvature in only one direction with respect to the reflected illumination light.
The projector according to 1. 3. The projector according to claim 1, wherein the projection optical system is a non-telecentric optical system.