JPH04340918A - Polarized light illumination element and projection type display device with the same - Google Patents

Abstract

PURPOSE:To improve the picture quality of an image and to relax design conditions of a projection lens as to the polarized light illumination element and projection type display device with the element. CONSTITUTION:The polarization light illumination element 20 consists of a polarization beam splitter 21 which has an operation surface 21a for splitting parallel white light LS+LP emitted by a light source part 10 into 1st P-polarized light LP and 1st S-polarized light Ls, a total reflecting prism 22 which projects the 1st P-polarized light LP, a lambda/4 optical phase plate 23 and a reflecting plate 24 which rotate the plane of polarization of the S-polarized light LS by 90 deg. to convert the light into 2nd P-polarized light LP* and then projects the 2nd P-polarized light LP* from the projection surface of the polarization beam splitter 21 in the same direction with the 1st P-polarized light LP, and a piano- convex lens 25 which is provided having its plane side in contact with the projection surface of the polarization beam splitter 21 and the projection surface of the total reflecting prism 22.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized illumination element and a projection type display device having the element.

0002

[Prior Art] Conventionally, in order to increase the brightness of an image projected on a screen, undefined polarized light emitted from a light source is
separating into two linearly polarized lights having planes of polarization perpendicular to each other, and making the planes of polarization of the two separated linearly polarized lights equal;
A projection type display device has been proposed in which a liquid crystal light valve is illuminated by a polarized illumination element that separately emits two linearly polarized lights having the same polarization plane.

FIG. 5 is a schematic diagram showing the construction of a projection type display device described in Japanese Patent Laid-Open No. 61-90584, which is one of the conventional examples of this type of projection type display device.

[0004] This projection display device includes a light source section consisting of a light source 301, a reflecting mirror 302, an infrared cut filter 303, and a condenser lens 304, a polarizing beam splitter 305, a total reflection prism 321, and a λ
It consists of a polarized illumination element consisting of a /2 optical phase plate 322 and first and second wedge-shaped lenses 323 , 324 , a liquid crystal light valve 310 , a polarizing plate 325 , and a projection lens 326 .

[0005] White light, which is undefined polarized light, emitted from the light source 301 is converted into parallel white light LS+LP by a condenser lens 304 after light such as infrared light other than visible light is absorbed by an infrared cut filter 303 . The parallel white light LS+LP enters the polarizing beam splitter 305, and the working surface of the polarizing beam splitter 305 (a vapor deposited film formed on the slope where two right angle prisms are bonded to each other)
311a transmits the P-polarized light and reflects the S-polarized light upward at a right angle, thereby separating the first P-polarized light LP and the first S-polarized light LS. Here, S-polarized light refers to linearly polarized light with a plane of polarization parallel to the working surface 311a of the polarizing beam splitter 305, and P-polarized light refers to linearly polarized light with a plane of polarization perpendicular to the S-polarized light. That's true. The first P-polarized light LP is transmitted by the polarizing beam splitter 30
The light is emitted from the exit surface of 5. In addition, the first S-polarized light LS
is incident on the total reflection prism 321, and the total reflection prism 3
After being reflected at right angles to the right on the slope of 21, the first P
The light is emitted from the exit surface of the total reflection prism 321 in parallel to the polarized light component LP. At this time, the first S-polarized light LS is
By passing through the λ/2 optical phase plate 322 provided opposite to the output surface of the total reflection prism 321, the plane of polarization is rotated by 90 degrees, and the second P-polarized light LP*
is converted to Polarizing beam splitter 305 and λ
First and second wedge-shaped lenses 323 and 324 for changing the optical path are respectively disposed on each output surface side of the /2 optical phase plate 322 , and the polarizing beam splitter 305
The first P-polarized light LP emitted from the λ/2 optical phase plate 322 and the second P-polarized light LP* emitted from the λ/2 optical phase plate 322 are
The first and second wedge-shaped lenses 323, 3 intersect at a point P0 on the incident surface of the liquid crystal light valve 310.
At step 24, the optical paths are changed and combined at point P0. The first and second P-polarized lights LP, LP* are modulated by the liquid crystal light valve 310 according to an image signal, and converted into image light including P-polarized light and S-polarized light. After the P-polarized light of the image light passes through the polarizing plate 325, it is projected onto a screen (not shown) by a projection lens 326, thereby enlarging and projecting the image onto the screen.

Therefore, in this projection display device, the parallel white light LS+LP (undefined polarized light) emitted from the light source is split into the first P-polarized light LP and the first S-polarized light LS (orthogonal to each other) by the polarization beam splitter 305. 2 with a plane of polarization that
The first S-polarized light LS is separated into λ
The liquid crystal light valve 3 uses the first P-polarized light LP and the second P-polarized light LP*, which have the same plane of polarization, by converting the second P-polarized light LP* into the second P-polarized light LP* with the /2 optical phase plate 322.
10, the first S-polarized light L
The brightness of the image enlarged and projected onto the screen is higher than that of a projection display device in which the polarizing plate disposed in front of the liquid crystal light valve 310 absorbs the light S and illuminates the liquid crystal light valve 310 with only the first P-polarized light LP. can be improved.

[0007]

However, the above-described projection type display device has the following three drawbacks.

(1) If the positional relationship between the wedge-shaped lenses 323 and 324 and the liquid crystal light valve 310 is not precisely set, there is a drawback that a difference in brightness will occur in the image projected on the screen. That is, each wedge-shaped lens 32
When the distance from 3,324 to the liquid crystal light valve 310 is shortened, as shown in FIG. Since the second P-polarized light LP* emitted from the liquid crystal light valve 310 only partially overlaps with the second P-polarized light LP* on the incident surface of the liquid crystal light valve 310, a difference in brightness occurs between the central part and the peripheral part of the image projected on the screen. Therefore, each wedge-shaped lens 323, 324 and the liquid crystal light valve 310
The distance between the first P-polarized light LP emitted from the first wedge-shaped lens 323 and the second wedge-shaped lens 32 is
The second P-polarized light LP* emitted from the liquid crystal light valve 310 must be adjusted so that they all overlap on the incident surface of the liquid crystal light valve 310.

(2) There is a drawback that the quality of the image projected onto the screen deteriorates. That is, since the liquid crystal light valve 310 generally has a property that the modulation characteristics and transmission characteristics deteriorate as the incident angle of the incident light increases, the first and second P-polarized lights LP, LP* of the liquid crystal light valve 310 Incident angle θ1 for all incidence planes
In the above-mentioned projection display device in which light is incident at

(3) Projection lens 326 with a large effective diameter
is necessary, so when considering aberration correction, the projection lens 326
As design conditions become stricter, the lens focal length (
In other words, there is a drawback that the projection distance of the projection display device becomes long. That is, as shown in FIG. 7, since the image light emitted from an arbitrary point on the liquid crystal light valve 310 is emitted with a spread angle of 2θ1 relative to the incident angle θ1, the image light emitted from the periphery of the liquid crystal light valve 310 is In order to capture all the image light including the light, it is necessary to make the effective diameter of the projection lens 326 considerably large.

On the other hand, in order to eliminate the drawbacks (1) to (3) above, in order to reduce the angular spread of the image light, instead of each wedge-shaped lens 323, 324, an incident angle θ1 is used.
Even if each wedge-shaped lens is used to reduce the
In order for P* and P* to all overlap at the incident surface of the liquid crystal light valve 310, it is necessary to make the distance between each wedge-shaped lens and the liquid crystal light valve 310 longer than the distance shown in FIG. This makes it impossible to make the display device more compact.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarized illumination element that can improve image quality and ease design conditions for a projection lens, and a projection type display device having the element.

[0013]

[Means for Solving the Problems] In the polarized illumination element of the present invention, an optical element having positive power is provided on the output surface side.

The projection display device of the present invention includes the polarized illumination element of the present invention.

[0015]

[Operation] The polarized illumination element of the present invention emits two linearly polarized lights with equal polarization planes separately through an optical element with positive power, thereby preventing the linearly polarized lights from overlapping each other. In addition, since the light can be emitted so as to be condensed to one point, the emission angle of each linearly polarized light emitted from the center of the emission surface is made smaller than the emission angle of each linearly polarized light emitted from the periphery of the emission surface. be able to.

Furthermore, the projection type display device of the present invention illuminates the liquid crystal light valve with the polarized illumination element of the present invention, so that each linearly polarized light beam separately emitted from the polarized illumination element is illuminated with the liquid crystal light without overlapping each other. It can be injected into the valve. In addition, by focusing each linearly polarized light beam using an optical element with positive power, the entrance pupil of the projection lens can be made smaller than the major axis of the liquid crystal light valve, so the effective diameter of the projection lens can be made smaller. Can be done.

[0017]

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

FIG. 1 is a schematic diagram showing a first embodiment of the polarized illumination element of the present invention.

The polarized illumination element 20 of this embodiment has a light source section 1
Parallel white light LS+LP (undefined polarized light) emitted from By rotating the polarization plane of the first S-polarized light LS by 90 degrees and converting it into the second P-polarized light LP*, the polarization planes of the first P-polarized light LP and the first S-polarized light LS are made equal. , the first and second P-polarized lights LP, LP* (two linearly polarized lights with equal polarization planes) are separately emitted. Here, the light source section 10 includes a light source 11 that emits white light, which is made of a halogen lamp, a metal halide lamp, etc., a reflecting mirror 12 that reflects a part of the white light emitted from the light source 11, and a light source 11 that is directly or reflected from the light source 11. A heat ray cut filter 13 that absorbs or reflects the heat rays of the white light incident through the mirror 12, and a condenser lens 1 that converts the white light from which the heat rays have been removed into parallel white light LS+LP.
It consists of 4. In addition, the polarized illumination element 20 has a working surface 21a (a vapor deposited film formed on a slope where two right-angle prisms are bonded to each other) whose one end is in contact with one end of the incident surface at an angle of 45 degrees, and a working surface 21a that is 90 degrees with one end of the incident surface. a polarizing beam splitter 21 having an exit surface whose one end touches at an angle of
and a total reflection surface 22a whose one end is in contact with the other end of the working surface 21a of the polarizing beam splitter 21 at an angle of 90°, and reflects the first P-polarized light LP at right angles to the right and outputs it from the output surface. The total reflection prism 22 is in contact with the other end of the working surface 21a of the polarizing beam splitter 21 at an angle of 45 degrees, and the polarizing beam splitter 21
The other end is in contact with the other end of the incident surface at an angle of 90°, and the first S-polarized light LS is perpendicularly incident on the λ/4 optical phase plate 23. A reflective surface is bonded to the surface of the λ/4 optical phase plate 23 opposite to the polarizing beam splitter 21, and the first S-polarized light LS transmitted through the λ/4 optical phase plate 23 is converted into a λ/4 optical phase plate 23. A reflector 24 that reflects the light in the direction of the phase plate 23, and a plano-convex lens 25, which is an optical element with positive power and whose flat side is in close contact with the exit surface of the polarizing beam splitter 21 and the exit surface of the total reflection prism 22. It consists of.

The parallel white light LS+LP emitted from the condenser lens 14 is converted into a first P polarized light by transmitting the P polarized light at the working surface 21a of the polarizing beam splitter 21 and reflecting the S polarized light at right angles to the left. The light is separated into polarized light LP and first S-polarized light LS. First S-polarized light LS
is perpendicularly incident on the λ/4 optical phase plate 23, and then λ/4
By passing through the optical phase plate 23, being reflected by the reflective surface of the reflection plate 24, and passing through the λ/4 optical phase plate 23 again,
The plane of polarization is rotated by 90° and converted into second P-polarized light LP*. The second P-polarized light LP* passes through the working surface 21a of the polarizing beam splitter 21 as it is and exits from the exit surface of the polarizing beam splitter 21. At this time, the second P-polarized light LP* emitted from the upper end of the output surface of the polarizing beam splitter 21 is emitted from the plano-convex lens 25 substantially parallel to the optical axis indicated by the dashed line, and is emitted from the plano-convex lens 25.
The second P-polarized light LP* emitted from the lower end of the output surface of lens 1 is condensed by an angle θ as shown by the broken line, and then passes through plano-convex lens 2.
It emits from 5. On the other hand, the first P-polarized light LP is reflected at right angles to the right by the total reflection surface 22a of the total reflection prism 22, and then exits from the output surface of the total reflection prism 22. At this time, the first P-polarized light LP that is emitted from the lower end of the total reflection prism 22 is emitted from the plano-convex lens 25 almost parallel to the optical axis indicated by the dashed line, and is emitted from the upper end of the exit surface of the total reflection prism 22. The first P-polarized light LP is focused by an angle θ and exits from the plano-convex lens 25, as shown by the broken line.

Therefore, the polarized illumination element 20 of this embodiment
is such that the first P-polarized light LP and the second P-polarized light LP* are condensed to one point without overlapping each other. can be emitted. In addition, as shown in FIG.
Since the polarized light LP and the second P-polarized light LP* can be emitted with the same optical path length, it is possible to prevent illuminance imbalance when using the light source 11 that emits non-collimated light. .

FIG. 2 is a schematic diagram showing a second embodiment of the polarized illumination element of the present invention.

The polarized illumination element 40 of this embodiment differs from the polarized illumination element 20 shown in FIG.
is emitted as it is from the exit surface of the polarizing beam splitter 41, and the active surface 41a of the polarizing beam splitter 41
The first S-polarized light LS separated at The light is reflected to the right at a right angle and exits from the exit surface of the total reflection prism 22. Therefore, in the polarized illumination element 20 shown in FIG.
In this case, the traveling directions of the incident light and the outgoing light can be matched without adding any other optical components.

FIG. 3 is a schematic diagram showing a third embodiment of the polarized illumination element of the present invention.

The polarized illumination element 60 of this embodiment differs from the polarized illumination elements 20 and 40 shown in FIGS. 1 and 2 in that it emits the first S-polarized light LS and the second S-polarized light LS*. It is to be. That is, the polarized illumination element 60 of this embodiment
is P of parallel white light LS+LP emitted from the light source section 50
A first working surface (deposited film formed on one of the two slopes to which three right-angle prisms are bonded) 61a that transmits polarized light and reflects S-polarized light upward at right angles; A similar second surface that is in contact with the working surface 61a at right angles
action surface (deposited film formed on the other one of the two slopes)
a polarizing beam splitter 61 having a polarizing beam splitter 61b, one end of which has a second
A λ/
4 optical phase plate 63, a reflection plate 64 having a reflective surface bonded to the opposite side of the polarization beam splitter 61 of the λ/4 optical phase plate 63, and a flat surface provided in close contact with the output surface of the polarization beam splitter 61. It consists of a convex lens 65.

The parallel white light LS+LP emitted from the condenser lens 54 has P-polarized light that is transmitted to the polarizing beam splitter 6.
The S-polarized light is transmitted through the first working surface 61a of the first working surface 61a and is reflected upward at right angles on the first working surface 61a.
The first P-polarized light LP and the first S-polarized light LS are separated. The first P-polarized light LP is transmitted by the polarizing beam splitter 61
It passes through the second working surface 61b of the λ/4 optical phase plate 63.
After being incident perpendicularly to , the light passes through the λ/4 optical phase plate 63, is reflected by the reflective surface of the reflection plate 64, and passes through the λ/4 optical phase plate 63 again, thereby rotating the plane of polarization by 90°. and is converted into second S-polarized light LS*. The second S-polarized light LS* is reflected upward at a right angle from the second working surface 61b of the polarizing beam splitter 61 and exits from the exit surface of the polarizing beam splitter 61. At this time, the second S-polarized light LS* that is emitted from the center of the exit surface of the polarizing beam splitter 61 is emitted from the plano-convex lens 65 substantially parallel to the optical axis indicated by the dashed line, and is emitted from the exit surface of the polarizing beam splitter 61. The second S-polarized light LS* emitted from the left end is focused by an angle θ and emitted from the plano-convex lens 65, as shown by the broken line. On the other hand, the first S-polarized light LS is emitted from the exit surface of the polarization beam splitter 61, and the first S-polarized light LS is emitted from the center of the exit surface of the polarization beam splitter 61 along the optical axis indicated by the dashed line. The first S-polarized light LS is emitted from the plano-convex lens 65 substantially parallel to the angle θ and emitted from the right end of the polarizing beam splitter 61. The first S-polarized light LS is focused by an angle θ and exits from the plano-convex lens 65, as shown by the broken line. Therefore, the polarized illumination element 60 of this embodiment is configured so that the first S-polarized light LS* and the second S-polarized light LS* are condensed to one point without overlapping each other.
and second S-polarized light LS* can be emitted.

In the above explanation, the plano-convex lens 25 shown in FIG. or may be provided separately from the polarizing beam splitter 21 and the total reflection prism 22. Note that when integrated with the polarizing beam splitter 21 and the total reflection prism 22, the effect of reducing surface reflection loss between optical components (between the polarization beam splitter 21 and total reflection prism 22 and the plano-convex lens 25) is obtained. arise. Furthermore, if the polarizing beam splitter 21 and the total reflection prism 22 are provided apart from each other, surface reflection loss occurs between the optical components.
By applying an antireflection coating to the exit surface of 2 or the entrance surface of the plano-convex lens 25, surface reflection loss between optical components can be prevented. Plano-convex lens 4 shown in Figure 2
5 and the plano-convex lens 65 shown in FIG. Further, the structure of the polarized illumination element includes λ/4 optical phase plates 23, 43, 63 and reflection plates 24, 44, 64, like the polarized illumination elements 20, 40, 60 shown in FIGS. 1 to 3. using the first S-polarized light LS or the first P-polarized light LP
For example, plano-convex lenses may be used in place of the first and second wedge-shaped lenses 323 and 324 of the polarized illumination element shown in FIG. 5. . Furthermore, instead of the plano-convex lenses 25, 45, and 65 shown in FIGS. 1 to 3, a lens group having a positive power as a whole or a mirror having a positive power may be used.

Next, an embodiment of a projection type display device constructed by combining the polarized illumination element according to the present invention with other optical components will be described.

FIG. 4 is a diagram showing a main part of an embodiment of a projection type display device having the polarized illumination element 20 shown in FIG.

The projection type display device of this embodiment includes the light source section 10 shown in FIG.
P is a first P-polarized light LP having planes of polarization perpendicular to each other.
and the first S-polarized light LS (two linearly polarized lights), and the polarization plane of the first S-polarized light LS is rotated by 90 degrees to convert it into the second P-polarized light LP*. 1 P
The planes of polarization of the polarized light LP and the first S-polarized light LS are made equal, and the first and second P-polarized lights LP and LP* (two linearly polarized lights whose planes of polarization are made equal) are separately emitted. The polarized illumination element 20 shown in FIG. 1 and the first and second P-polarized lights LP and LP separately emitted from the polarized illumination element 20.
* A liquid crystal light valve 71 into which the light enters, a polarizing plate 72 provided facing the output surface of the liquid crystal light valve 71, and a projection lens 73 provided on the opposite side of the polarizing plate 72 from the liquid crystal light valve 71. Consisting of Here, the focal position of the plano-convex lens 25 (see FIG. 1) of the polarized illumination element 20 and the pupil of the projection lens 73 almost match.

The projection type display device of this embodiment has the following advantages by illuminating the liquid crystal light valve 71 with the polarized illumination element 20 shown in FIG.

(1) Polarized illumination element 20 and projection lens 73
The first and second P-polarized lights LP, LP* separately emitted from the polarized illumination element 20 are condensed by the plano-convex lens 25 (see FIG. 1), and the projection lens 7
By setting the image of the light source 11 (see FIG. 1) to be created on the pupil plane of the projection lens 73, the entrance pupil of the projection lens 73 can always be made smaller than the major axis of the liquid crystal light valve 71. The effective diameter can be made very small, and a bright image with little aberration can be formed on the screen.

(2) Since the first and second P-polarized lights LP and LP* separately emitted from the polarized illumination element 20 enter the liquid crystal light valve 71 without overlapping each other, the image projected on the screen is This prevents brightness differences from occurring.

(3) When the distance between the polarized illumination element 20 and the liquid crystal light valve 71 is the same, the first light emitted from the upper and lower ends of the polarized illumination element 20 as shown by broken lines in FIG.
The incident angle θ1 of the second P-polarized light LP, LP* into the liquid crystal light valve 71 is the same as that of the conventional projection display device shown in FIG. Since the angle of incidence of the first and second P-polarized lights LP, LP* on the liquid crystal light valve 71 is always smaller than the incident angle θ1, it is possible to improve the modulation characteristics and transmission characteristics in the central part of the liquid crystal light valve 71. Therefore, the quality of the image projected on the screen can be improved. In other words, when projecting an image on the screen that has the same image quality as the conventional projection display device shown in FIG. 5, the distance between the polarized illumination element 20 and the liquid crystal light valve 71 can be shortened. Therefore, the entire projection display device can be made more compact. Further, by further increasing the power of the plano-convex lens 25 (see FIG. 1) of the polarized illumination element 20, the entire projection display device can be made more compact.

Note that instead of the polarized illumination element 20,
Similar effects can be obtained by using the polarized illumination element 40 shown in FIG. 3 or the polarized illumination element 60 shown in FIG.

The present invention is also applicable to the polarized illumination element shown in FIG.

[0037]

[Effects of the Invention] As explained above, the present invention has the following effects. The invention of claim 1 focuses the linearly polarized lights onto one point without overlapping each other by separately emitting two linearly polarized lights with equal polarization planes through an optical element having positive power. can be done. Further, the invention of claim 2 is such that by illuminating the liquid crystal light valve with the polarized illumination element of the present invention, each linearly polarized light emitted from the polarized illumination element can be made to enter the liquid crystal light valve without overlapping each other. Therefore, it is possible to prevent differences in brightness from occurring in the image projected onto the screen, and the effective diameter of the projection lens can be made smaller by focusing each linearly polarized light beam using an optical element with positive power. , the entire device can be made more compact, and the design conditions for the projection lens can be relaxed.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a polarized illumination element of the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the polarized illumination element of the present invention.

FIG. 3 is a schematic configuration diagram showing a third embodiment of the polarized illumination element of the present invention.

4 is a diagram showing a main part of an embodiment of a projection display device having the polarized illumination element 20 shown in FIG. 1. FIG.

FIG. 5 is a configuration diagram of main parts of a projection display device described in Japanese Patent Application Laid-Open No. 61-90584.

6 is a diagram showing a drawback when the distance between the first and second wedge-shaped lenses 323, 324 and the liquid crystal light valve 310 is shortened in the projection display device shown in FIG. 5. FIG.

7 is a diagram showing the angular spread of image light emitted from the liquid crystal light valve 310 of the projection display device shown in FIG. 5. FIG.

[Explanation of symbols]

10, 30, 50 Light source section 11, 21, 31 Light source 12, 22, 32 Reflection mirror 13, 23,
33 Heat ray cut filter 14, 24, 34
Condenser lens 20, 40, 60
Polarized lighting elements 21, 41, 61 Polarized beam splitters 21a, 41a, 61a, 61b
Working surfaces 22, 42 Total reflection prisms 22a, 42a Total reflection surfaces 23, 43, 63 λ/4 optical phase plate 24,
44, 64 Reflector 25, 45, 65 Plano-convex lens 71
Liquid crystal light valve 72 Polarizing plate 73 Projection lens LP First P-polarized light LS
First S-polarized light LP* Second P-polarized light LS* Second S-polarized light LS+
LP parallel white light θ, θ1 angle

Claims (2)

[Claims] Claim 1: Separating undefined polarized light emitted from a light source into two linearly polarized lights having mutually orthogonal polarization planes,
In a polarization lighting element that equalizes the planes of polarization of the two separated linearly polarized lights and separately emits the two linearly polarized lights with the planes of polarization made equal, an optical element with positive power is placed on the exit surface side. A polarized illumination element comprising: 2. A light source unit that emits undefined polarized light; and a light source unit that separates the undefined polarized light output from the light source unit into two linearly polarized lights having planes of polarization perpendicular to each other;
A polarized lighting element that makes the polarization planes of two linearly polarized lights equal and separately emits the two linearly polarized lights that have the same polarization planes; 2. A projection type display device comprising a liquid crystal light valve into which two linearly polarized lights are incident, wherein said polarized illumination element is the polarized illumination element according to claim 1.