JPH11326833A - Liquid crystal projector device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use light of two kinds of polarizing directions. SOLUTION: At a predetermined position between multi-lens arrays 3, 6, a polarized light separating block 4, which can separate polarized light made incident by double refraction and also make it each polarized light exit in the predetermined direction, is arranged, and further, in a pre-stage or post-stage of the multi-lens array 6, a half-wave length plate 5 is arranged at a position corresponding to one of the light paths of the polarized light separated by the polarized light separating block 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector for forming an image by effectively utilizing light having two orthogonal polarization directions.

[0002]

2. Description of the Related Art There is known a liquid crystal projector which modulates light output from a light source by, for example, a liquid crystal panel to form image light and projects the image light on a screen or the like.

[0003]

By the way, the light emitted from the light source is unpolarized light. However, the liquid crystal panel uses only one of two orthogonal polarization directions due to the nature of the liquid crystal. Has been. That is, a polarizing plate is provided on the light incident side of the liquid crystal panel so that light in one polarization direction is transmitted and light in the other polarization direction is blocked by the polarizing plate. Therefore, in actuality, only about half of the total luminous flux from the light source can be used for image formation by the liquid crystal panel. As a result, the light from the light source cannot be used effectively, and it is also difficult to project an image with an effective luminance.

Therefore, a polarization conversion block for aligning the polarization direction using a polarization beam splitter or the like is known. FIG. 8 shows a configuration example of the polarization conversion block. In addition,
In this drawing, for the sake of convenience, description will be made on the assumption that light in one of the polarization directions is a P-polarized wave and light in the other polarization direction is an S-polarized wave. In the polarization conversion block 40, non-polarized light from a not-shown lamp or the like enters a prism element 41 forming an incident portion. The light that has entered the prism element 41 reaches a polarization splitting film (polarization beam splitter) 42 where, for example, a P-polarized wave is transmitted and an S-polarized wave is reflected, thereby separating the light into two orthogonal polarized waves. Is done.

[0005] The P-polarized wave transmitted through the polarization separation film 42 is emitted from the prism element 43 by proceeding as it is. Also,
The S-polarized wave reflected by the polarization separation film 42 is reflected by a mirror 44 and further rotated by a half-wave plate 45 disposed on the exit side of the prism element 41 into a P-polarized wave. Is converted. That is, non-polarized light is converted into light in one polarization direction (for example, a P-polarized wave) by passing through the polarization conversion block 40.

By using such a polarization conversion block 40, it is possible to effectively use light. However, it is the prism element 41 that can actually enter the light on the incident surface of the polarization conversion block 40,
The prism element 43 is configured, for example, for polarization conversion. In other words, there is a limit on the incident portion of the polarization conversion block 40. For example, when light is condensed using a multi-lens array, it is necessary to precisely match the position of the lens cell and the position of the prism element 41 in the multi-lens array. . Therefore, there is a problem that the production efficiency is not good in order to perform accurate positioning.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a light source and a pair of first and second multi-lenses arranged as light condensing means for the light output from the light source. In a liquid crystal projector device including an array and a light modulation element that performs light modulation by receiving light condensed by the second multi-lens array, a predetermined distance between the first and second multi-lens arrays In the position, while performing polarization separation of the incident light, a polarization separation block that can emit each polarized light beam in a predetermined direction is arranged, and further, at a stage before or after the second multi-lens array, A half-wave plate is arranged at a position corresponding to the optical path of one of the polarized light beams separated by the polarization separation block.

According to the present invention, by constructing the polarization separation block with a prism element having birefringence, non-polarized light can be incident on all the surfaces on the incident side, and optical elements such as lamps and multi-lens arrays can be used. High positional accuracy is not required in the direction perpendicular to the optical axis of the component. Thereby, the assembly of the optical system can be facilitated, and the productivity can be improved. In addition, since light of two polarization directions can be used efficiently, an illumination optical system having substantially high luminance can be configured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid crystal projector according to the present invention will be described below. FIG. 1 is a diagram illustrating a configuration example of a main part according to the present invention as a part of the liquid crystal projector device of the present embodiment. The lamp 1 is configured as a light source of the liquid crystal projector device shown in this figure, and can emit unpolarized light. The lamp 1 includes, for example, a parabolic reflector 1a, and can emit light whose principal ray is parallel. The light emitted from the lamp 1 enters the first multi-lens array 3 via the UV-IR cut filter 2. This multi-lens array 3
Is incident on the polarization separation block 4.

As will be described in detail later, the polarization separating block 4 is configured as a generally known Wollaston prism having birefringence. That is, the polarization separation block 4 separates the light from the lamp 1 into two types of polarized light rays, which are an ordinary ray (ordinary ray) and an extraordinary ray whose polarization directions are orthogonal to each other due to birefringence, and respectively. Can be emitted in a predetermined direction.

The half-wave plates 5, 5, 5 are arranged at positions corresponding to either the ordinary light path or the extraordinary light path, and rotate the polarization direction of the incident light. Therefore,
The second multi-lens array 6 receives light whose polarization direction as an ordinary ray or an extraordinary ray is aligned in a predetermined direction. The half-wave plate 5 is a multi-lens array 6
Are formed so as to be half of the division pitch at which each lens cell is formed. Therefore, the angles given to the ordinary ray and the extraordinary ray in the polarization separation block 4 are also set so as to correspond to the pitch of the half-wave plate 5. The multi-lens array 6 is a multi-lens array 3
The light focused in the step is focused. Further, in this example, the light is arranged so that the light incident by the polarization separation block 4 can be deflected so that the principal ray becomes parallel light.

The first condenser lens 7 condenses the light incident from each lens cell of the multi-lens array 6 on the second condenser lens 8, and the light passing through this condenser lens 8 is For example, they are synthesized in the irradiation area of the transmission type liquid crystal panel 9. The light from the condenser lens 8 is selectively modulated based on a required driving signal supplied from a path (not shown) to the liquid crystal panel 9. The light transmitted by this light modulation is enlarged and projected by the projection lens 10.

Next, the principle of polarization separation by the polarization separation block 4 will be described. FIG. 2 is a schematic diagram for explaining the principle of polarization separation, and shows a half of the polarization separation block 4 shown in FIG. That is, the one corresponding to one Wollaston prism is shown. Here, an example in which the relationship of no> ne holds between the refractive index no of the ordinary ray and the refractive index ne of the extraordinary ray will be described as an example.

The polarization separation block 4 (Wollaston prism) is configured by combining two uniaxial crystals. The optical axis of the crystal 4a on the incident side is in the direction of the arrow on the paper, and the crystal on the output side is The optical axis of 4b is a direction (+ mark) perpendicular to the paper surface. That is, they are joined so that the optical axes are orthogonal to each other and each optical axis is orthogonal to the incident light beam.

The light (unpolarized light) incident on the crystal 4a is first separated into an ordinary ray and an extraordinary ray here. Further, the ordinary ray and the extraordinary ray enter the crystal 4b via the refraction surface (the junction surface between the crystal 4a and the crystal 4b). At this time, since the optical axes of the crystals are orthogonal to each other, by passing through the refraction surface, the ordinary ray in the crystal 4a becomes an extraordinary ray in the crystal 4b, and the extraordinary ray in the crystal 4a becomes the extraordinary ray in the crystal 4b. Will behave as an ordinary ray. That is, the ordinary ray (black circle) and the extraordinary ray (double ray) are refracted in different directions on the refraction surface, and the same angle αw with respect to the incident light from the crystal 4b.
Are emitted.

Assuming that the angle at which the crystals 4a and 4b are formed is θ, as generally known, if the angle θ is not so large, the following equation (1) holds.

(Equation 1)

Next, an optical path when a Wollaston prism is used as the polarization separation block 4 will be described. FIG. 3 is an enlarged view of the multi-lens array 3, the polarization separation block 4, the half-wave plate 5, and the multi-lens array 6 shown in FIG. The example shown in FIG.
Is assumed to correspond to, for example, the polarization direction of ordinary light. Light emitted from a lamp 1 (not shown) and passing through a lens cell 3a of a multi-lens array 3 is
Due to the birefringence at a and 4b, it is separated into an ordinary ray (black circle) and an extraordinary ray (double ray). Then, for example, the ordinary ray directly enters the lens cell 6a of the multi-lens array 6, and the extraordinary ray is rotated as a normal ray by rotating the polarization direction by the half-wave plate 5.
Incident on. This is the same for all the lens cells in each of the multi-lens arrays 3 and 6. As described above, after the light from the lamp 1 is separated into an ordinary ray and an extraordinary ray, for example, by rotating the polarization direction of the extraordinary ray, the polarization direction can be made uniform according to the polarizing plate of the liquid crystal panel 9. become.

The ordinary ray from the polarization separation block 4 and the ordinary ray converted by the half-wave plate 5 enter the multi-lens array 6 at a predetermined angle. Therefore, by arranging the multi-lens array 6 so that each light beam can be incident on a position shifted from the center of the lens cell, the incident light beam is incident on the multi-lens array 3 by the refractive power of the lens cell. Similar chief rays are deflected to be parallel light. Then, the light enters a condenser lens 7 (not shown).

The polarization separation block 4 is arranged between the multi-lens arrays 3 and 6 at a position where ordinary rays and extraordinary rays can enter the lens cell or the half-wave plate 5, respectively. Therefore, for example, the arrangement position is set corresponding to the emission angle αw of the polarization separation block 4, or the emission angle αw corresponding to the pitch of the lens cells is set in a state where the arrangement position is set in advance.

If, for example, the polarizing plate corresponds to the polarization direction of the extraordinary ray, the half-wave plate 5 is placed at a position corresponding to the optical path of the ordinary ray from the polarization separation block 4.
May be arranged so as to be incident on the multi-lens array 6 in a state where ordinary rays are converted into extraordinary rays.

In the examples shown in FIGS. 1 and 3, two Wollaston prisms are arranged so as to be symmetrical around the optical axis of the lamp 1, for example. It is only necessary to dispose a crystal corresponding to the crystal 4a on the incident side and the crystal 4b on the output side, so that one Wollaston prism shown in FIG. Furthermore, for example, when a plurality of small Wollaston prisms corresponding to each lens cell of the multi-lens arrays 3 and 6 are arranged, and the angle of the refraction surface (joining surface) is the same, the polarization separation block 4 can be made thinner. Can be formed.

In FIG. 3, a configuration has been described in which the multi-lens array 6 is used as deflecting means to return incident light to parallel light. However, as shown in FIGS. 4 and 5, separate deflecting means are used. It is also possible to provide. In the example shown in FIG. 4, for example, a wedge-shaped prism 15 having a convex incident side is disposed immediately before the polarizing plate 5. Thereby, the ordinary ray and the extraordinary ray separated by the polarization separation block 4 are respectively refracted by being incident on the inclined surface of the prism 15, and the principal ray is emitted from the exit surface as parallel light. Then, for example, each of the extraordinary rays
Is incident on the multi-lens array 16 as an ordinary ray. The multi-lens array 16 is divided so as to correspond to the optical path of the light beam separated by the polarization separation block 4, so that the main light beam can enter the central portion of each lens cell. Therefore, the multi-lens array 16 emits light beams whose polarization directions are uniform and whose main light beams are parallel.

Further, as shown in FIG. 5, for example, a deflection block 17 composed of a Wollaston prism is disposed immediately before the polarizing plate 5. The configuration of the deflection block 17 is such that the crystal 17a on the incident side has the same optical axis as the crystal 4b on the output side of the polarization separation block 4, and the crystal 1a on the output side
7b has the same optical axis as the crystal 4a on the incident side of the polarization separation block 4. That is, the light beam incident on the deflecting block 17 is refracted in the opposite direction to the polarization separating block 4, so that the ordinary light beam and the extraordinary light beam are deflected to light beams whose main light beams are parallel to each other. Then, for example, the extraordinary rays are respectively incident on the half-wavelength plate 5, whereby the polarization direction is rotated, and are incident on the multi-lens array 16 configured as in FIG. 4 as ordinary rays.

In the examples shown in FIG. 4 and FIG.
Although the example in which the wave plate 5 is disposed immediately before the multi-lens array 16 has been described, the same polarization rotation can be performed even when the half-wave plate 5 is disposed immediately after the multi-lens array 16. If the polarizing plate of the liquid crystal panel 9 (not shown) is adapted to handle an extraordinary ray, the half-wave plate 5 may be arranged at a position corresponding to the optical path of the ordinary ray.

As described above, by forming the polarization separation block 4 with, for example, a Wollaston prism, non-polarized light can be incident on all surfaces on the incident side. As a result, high positional accuracy is not required in the direction perpendicular to the optical axis of the optical components such as the lamp 1 and the multi-lens array 3, and the assembly of the optical system is facilitated to improve the productivity. Can be.

In FIGS. 1 to 5, the lamp 1 is described as having a parabolic reflector 1a.
The present invention can also be applied to a liquid crystal projector using a lamp having an elliptical reflector.

FIG. 6 is a diagram for explaining a configuration of a main part of a liquid crystal projector according to another embodiment. The lamp 20 is provided with an elliptical reflector 20a, and can emit non-polarized light so as to converge in a predetermined direction. The light emitted from the lamp 20 is U
The light enters a first multi-lens array 22 via a V-IR cut filter 21. This multi-lens array 2
The lamp image formed in 2 is incident on a polarization separation block 23 configured by combining a Wollaston prism, for example, like the polarization separation block 4.

In the example shown in FIG.
Are converged, the half-wave plates 24, 24, 24 are arranged at positions corresponding to the optical paths. Further, the second multi-lens array 25 is also configured to be smaller than the multi-lens array 22 corresponding to the convergence direction of the light beam.

The light that has passed through the multi-lens array 25 is configured to be condensed on a condenser lens 26, and is combined in an irradiated area of a liquid crystal panel 27 through the condenser lens 26. Then, the light transmitted by the required light modulation is enlarged and projected by the projection lens 28.

In the example shown in FIG. 6, an elliptical reflector 2
Due to Oa, the light beam incident on the polarization separation block 23 has a required incident angle. Therefore, when compared with the polarization separation block 4 shown in FIG. 1, it is necessary to adjust the arrangement position and the emission angle αw. Therefore, the output angles αw (corresponding to the angles θ and αw shown in FIG. 2) of the ordinary ray and the extraordinary ray are adjusted by, for example, the angle θ of the crystals 23a and 24a with the arrangement position of the polarization separation block 23 fixed. Or multi-lens array 2
By moving the position of the polarization separation block 23 between 2 and 25 along the traveling direction of the light, the interval between the light beams is set, and the separated light beams can be used effectively.

Although the liquid crystal projector shown in FIGS. 1 and 6 is exemplified by using, for example, transmissive liquid crystal panels 9 and 27, the present invention uses a reflective liquid crystal panel. The present invention can also be applied to a liquid crystal projector configured as described above.

In the above, FIGS. 1 to 6 show an example in which the polarization separation block 4 and the polarization separation block 23 are constituted by Wollaston prisms. However, the polarization separation blocks 4 and 23 may be constituted by other optical elements. Is possible. FIGS. 7 (a), 7 (b), 7 (c), 7 (d) to 10 show an example of an optical element that can be configured as the polarization separation blocks 4 and 23, and explain the configuration example and the optical path of the separated light beam. FIG. In this case, also, as an example, between the refractive index no of the ordinary ray and the refractive index ne of the extraordinary ray,
A case where the relationship of no> ne holds will be described as an example.

The Lochon prism 30 shown in FIG. 7A has a configuration in which two uniaxial crystals are combined. The optical axis of the incident side crystal 30a is in the direction of the arrow (left and right) on the paper. The optical axis of the crystal 30b on the emission side is set to a direction (+ sign) perpendicular to the paper surface. That is,
The optical axes are orthogonal to each other, and the crystal 30a is joined so that the optical axis is orthogonal to the incident light beam. The ordinary ray (black circle) in the Rochon prism 30 goes straight as it is, and the extraordinary ray (double line) is emitted as a ray having an angle αr with respect to the ordinary ray.

Assuming that the angle at which the crystals 30a and 30b are formed is θ, as generally known, if the angle θ is not so large, the following equation (2) is established.

(Equation 2)

In the Senarmont prism 31 shown in FIG. 7B, the optical axis of the crystal 31a on the incident side is set to the direction of the arrow (left and right) on the paper surface, and the crystal 31a on the output side is changed.
The optical axis b is in the direction of the arrow (up and down) on the paper. The ordinary ray (black circle) in the Senarmont prism 31 goes straight as it is, and the extraordinary ray (double line) is emitted as a ray having an angle αs with respect to the ordinary ray.

When the angle at which the crystals 30a and 30b are formed is θ, the following equation (3) is established as in the case described above.

(Equation 3)

Furthermore, as shown in FIG. 7C, one wedge-shaped crystal 3 is used without combining two crystals.
The same effect can be obtained with the use of 2. In this case, the optical axis of the crystal 32 is in the direction of the arrow (up and down) on the paper. In the crystal 32, the ordinary ray (black circle) is a ray having an angle αo with respect to the incident light, and an extraordinary ray (double ray).
Are emitted as light rays having an angle αe with respect to the incident light.

When the angle at which the crystal 32 is formed is θ, the following equations (4) and (5) hold as in the case described above.

(Equation 4)

(Equation 5)

Further, the optical element 33 having a function as a Savart plate shown in FIG.
For example, it is a single plate, and its optical axis is in the direction of the arrow (oblique) on the paper. And this optical element 33
When an unpolarized light beam enters the device, the ordinary light beam is emitted so as to go straight, and the extraordinary light beam is emitted as a light beam parallel to the ordinary light beam at a predetermined interval. Here, assuming that the angle of the optical axis with respect to the incident light is θ, the plate thickness is d, and the interval between the ordinary ray and the extraordinary ray is h, the following equation (6) is used, as in the above case.
Holds.

(Equation 6)

When the optical element 33 is applied to, for example, the liquid crystal projector shown in FIG. 1, it is possible to obtain an ordinary ray and an extraordinary ray as parallel rays. In other words, the arrangement relationship between the optical element 33 and the multi-lens array 6 may be such that the ordinary ray and the extraordinary ray enter the lens cell or the half-wave plate 5, respectively. Furthermore, the arrangement in this state is not limited to, for example, the vicinity of the multi-lens array 3.

As described above, according to the present invention, by using the optical element shown in FIG. 2 or FIG. 7 to FIG. 10 as a polarizing element, non-polarized light can be incident on the entire surface on the incident side.

[0042]

As described above, according to the present invention, the polarization separation block is constituted by a prism element such as a Wollaston prism, a Rochon prism, a Senarmont prism, etc., so that all surfaces on the incident side are non-polarized. Can be incident. This eliminates the need for high positional accuracy in the direction perpendicular to the optical axis of optical components such as lamps and multi-lens arrays, making it easier to assemble the optical system and improving productivity. it can. Further, since light of two polarization directions can be used efficiently, there is an advantage that an illumination optical system having substantially high luminance can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main part of a liquid crystal projector device according to an embodiment of the present invention.

FIG. 2 is a view for explaining a Wollaston prism constituting the polarization separation block shown in FIG. 1;

FIG. 3 is a diagram illustrating optical paths of an ordinary ray and an extraordinary ray when the polarization separation block shown in FIG. 1 is used.

FIG. 4 is a diagram illustrating a configuration example of a deflection block that returns separated ordinary and extraordinary rays to parallel rays.

FIG. 5 is a diagram illustrating a configuration example of a deflection block that returns separated ordinary and extraordinary rays to parallel rays.

FIG. 6 is a diagram illustrating an example in which the present invention is applied to a liquid crystal projector using a lamp having an elliptical reflector.

FIG. 7 is a diagram illustrating a modification of the polarization separation block.

FIG. 8 is a diagram illustrating a configuration example of a polarization conversion block as a conventional example.

[Explanation of symbols]

1,20 lamp, 1a, 20a reflector, 3,
6, 16, 22, 25 multi-lens array, 4 polarization separation block, 4a, 4b, 17a, 17b, 32 crystal, 5 1/2 wavelength plate, 15 wedge prism, 17 deflection block, 17a, 17b crystal, 30b Prism, 31 Senarmont prism, 33 optical elements

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03B 33/12 G03B 33/12 G09F 9/00 337 G09F 9/00 337E H04N 5/74 H04N 5/74 A

Claims (4)

[Claims] 1. A light source, first and second multi-lens arrays arranged as a pair of light condensing means for light output from the light source, and light condensed by the second multi-lens array is incident thereon. A light modulation element for performing light modulation; and a liquid crystal projector device comprising: a first and second multi-lens array; A polarized light separating block capable of emitting each polarized light beam in a predetermined direction, and further, at a stage before or after the second multi-lens array, one of the polarized lights separated by the polarized light separating block. A liquid crystal projector device comprising a half-wave plate disposed at a position corresponding to an optical path of a light beam. 2. The liquid crystal projector according to claim 1, wherein said polarization separation block is constituted by a prism element having birefringence. 3. The liquid crystal according to claim 1, wherein the second multi-lens array is arranged so that light emitted from the polarization separation block can be deflected in a predetermined direction. Projector device. 4. The liquid crystal projector device according to claim 1, further comprising a deflecting unit capable of deflecting a polarized light beam emitted from the polarized light separating block in a predetermined direction.