JP4007682B2 - Illumination optics - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illumination optical apparatus that uniformly irradiates a rectangular illumination area by aligning the polarization axes of randomly polarized light emitted from a light source using an integrator and a polarization conversion optical system.
[0002]
[Prior art]
FIG. 5 is a diagram showing an illumination optical apparatus composed of a conventional polarization conversion optical system and an integrator illumination system. FIG. 6 is a perspective view showing a polarization conversion element constituting a conventional polarization conversion optical system, and FIG. 7 is a principle diagram for explaining the operation of the polarization conversion optical system.
[0003]
The illumination optical device shown in FIG. 5 includes light composed of a reflector 6 and a light source 7, first and second integrators 8 and 9, a polarization separation element 95, and a polarization conversion element 10 composed of a phase difference plate 11. The field lens 12 is used to uniformly illuminate an illumination area such as the liquid crystal panel 13.
[0004]
The light emitted from the light source 7 is randomly polarized light including polarization axes in random directions. The randomly polarized light is reflected by the reflector 6 and then irradiates the first integrator 8 disposed in front. The light incident on the first integrator 8 is divided into a plurality of spot lights, and a light source image is formed in the vicinity of the second integrator 9. Each of the divided spot lights is superimposed on the illumination area of the liquid crystal panel 13 by the second integrator 9 via the field lens 12. The polarization conversion element 10 composed of the polarization separation element 95 and the phase difference plate 11 is inserted immediately after the second integrator 9, and the random polarized light incident on the polarization separation element 95 is a straight line having a polarization axis in a certain direction. Convert to polarized light.
[0005]
As shown in FIG. 6, the conventional polarization beam splitting element 95 is configured by joining and arranging a plurality of parallelogram prisms having the same shape. A polarizing separation film 1 and a reflection film 2 are interposed every other joint surface of each prism, and a strip-shaped opening is formed by a phase difference plate 11 that rotates the polarization separation film 1 and the polarization axis. Randomly polarized light incident from the surface is separated into light having a uniform polarization direction and emitted.
[0006]
As shown in FIG. 7, for example, when the polarization separation film 1 is configured as a selection surface for P-polarization transmission and S-polarization reflection, polarization separation is performed on the randomly polarized light 16 incident on the polarization separation film 1 from the effective aperture 17. The film 1 transmits only the P-polarized light 14 and reflects the S-polarized light 19. The reflected S-polarized light 19 is further reflected by the adjacent reflection film 2 and emitted from the polarization conversion element 10 as S-polarized light 20. On the other hand, the P-polarized light 14 transmitted through the polarization separation film 1 is emitted as S-polarized light 18 with the polarization axis rotated by the phase difference plate 11 attached to the exit surface of the polarization conversion element 10.
[0007]
As a result, all the light emitted from the polarization conversion element 10 is converted into S-polarized light. Here, the incident surface of the polarization conversion element 10 forms every other opening that faces the polarization separation film 1. Only the strip portion of the prism is an effective aperture 17 for the randomly polarized light 16. Therefore, it can be used as an illumination optical apparatus such as a projector that projects an image of a liquid crystal panel on a screen using only light having a polarization axis in one direction. And even if it is the polarization conversion element 10 which has such a limited effective aperture surface, a bright screen can be enjoyed by improving the utilization efficiency of the light of an illumination optical apparatus.
[0008]
[Problems to be solved by the invention]
In the conventional illumination optical device described above, since the light source 7 is a light source having a finite size, each spot condensed on the incident surface of the polarization conversion element 10 is also divided into a plurality of finite sizes. It is formed as a spot. FIG. 8 shows a spot shape formed on the incident surface of the polarization conversion element 10 when the integrators 8 and 9 having 8 × 8 lens elements are used, for example.
[0009]
However, in an illumination optical apparatus configured with a conventional polarization conversion optical system and an integrator illumination system, an elliptical spot 24 whose major axis faces the radiation direction is projected onto the polarization conversion element 10 as shown in FIG. In addition, the light out of the effective aperture 17 in the spot 24 is not accurately polarized and cannot be used for illumination of the liquid crystal panel 13.
[0010]
Further, since the spot shape differs between the spot corresponding to the central axis of the integrator illumination system and the spot in the peripheral portion, the width of the effective aperture 17 of the randomly polarized light is optimally determined, and the amount of light incident on the polarization conversion element 10 is determined. It was difficult to take out efficiently. In particular, when a rectangular polarization conversion optical system is used, both ends of the spot at the peripheral portion thereof deviate from the effective aperture 22, so that there is a problem that the loss of incident light amount is large.
[0011]
The present invention has been made to solve the above-mentioned problems, and can efficiently convert a spot-shaped randomly polarized light having a finite area into a polarized light and has a compact polarization conversion optical system. An object is to provide an optical device.
[0012]
[Means for Solving the Problems]
The illumination optical device according to the present invention includes a light source that emits light including a polarization axis in a random direction, a first integrator that forms an image of the light source as a plurality of divided spots, and each spot by the first integrator. A second integrator that forms an image by superimposing them on a predetermined illumination area, and is disposed in the vicinity of the second integrator, and has a plurality of strip-shaped effective aperture surfaces and is incident on the effective aperture surfaces. In an illumination optical device having a plurality of prism blocks that convert the light to be polarized light having the same polarization direction, the longitudinal direction of each effective aperture surface approximates the longitudinal direction of each spot within the incident surface of the prism block prism blocks are arranged as a prism block, the first longitudinal direction of the effective opening surface are orthogonal to each other, those which are arranged in a second direction
[0014]
The illumination optical device according to the present invention includes a light source that emits light including a polarization axis in a random direction, a first integrator that forms an image of the light source as a plurality of divided spots, and each of the first integrators. A second integrator that forms an image by superimposing a spot on a predetermined illumination area, and a plurality of strip-shaped effective aperture surfaces that are arranged in the vicinity of the second integrator, and have an effective aperture surface In an illumination optical device having a plurality of prism blocks that convert light incident on the prism into light having a uniform polarization direction, the longitudinal direction of each effective aperture surface is the longitudinal direction of each spot within the incident surface of the prism block is arranged a prism block to approximate, prism block, distribution in first and second directions, and oblique directions in the longitudinal direction of the effective opening surface are orthogonal to each other Those which are.
[0015]
In the prism block of the illumination optical device according to the present invention, the effective aperture surfaces and the ineffective aperture surfaces are alternately arranged in a strip shape, and the pitch of the effective apertures is different for each prism block.
[0016]
Furthermore, the prism block of the illumination optical device according to the present invention has a function of rotating the polarization axis of the polarized light that is disposed at an inclination of 45 degrees with respect to the incident surface and the polarized light that is transmitted through the polarized light separation film to the output surface. And a phase difference plate having.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0018]
Embodiment 1 FIG.
FIG. 1 and FIG. 2 are a perspective view showing a polarization conversion element used in the illumination optical apparatus of Embodiment 1, and a plan view of an incident surface. This polarization conversion element is used in the same manner as the conventional illumination optical apparatus shown in FIG.
[0019]
In FIG. 1, for example, when an integrator having an 8 × 8 lens element is used, an incident light spot shape 5 formed on the incident surface of the polarization conversion element 10 is indicated by a broken line. The polarization conversion element 10 includes three prism blocks 10a, 10b, and 10c. The prism block 10a is disposed at the center, and the prism blocks 10b and 10c are disposed on the left and right of the prism block 10a.
[0020]
As shown in FIG. 2, the prism block 10a has strip-shaped effective aperture surfaces 251 and non-effective aperture surfaces 252 formed alternately in the vertical direction (in the example of FIG. 2, there are four effective aperture surfaces 251). In the left and right prism blocks 10b and 10c, strip-shaped effective aperture surfaces 261 and ineffective aperture surfaces 262 are alternately formed in the lateral direction (effective aperture surfaces in the figure). 8 is 261, and 9 are non-effective opening surfaces 262). Each of the prism blocks 10a, 10b, and 10c is arranged such that the polarization separation films 1 and the reflection films 2 are alternately interposed between a plurality of prisms. The plate 11 is attached, and for example, the randomly polarized light 3 incident on the effective aperture surface 251 of the prism block 10a is converted into S-polarized light 4 having a uniform polarization direction and emitted. The effective apertures of the prism blocks 10a, 10b, and 10c are all configured at the same pitch.
[0021]
FIG. 3 is a partial perspective view showing the principle of polarization conversion by the polarization conversion element 10. In order to carry out the basic polarization conversion method, the same polarized light selection and conversion structure as in the prior art is provided here.
[0022]
FIG. 3 shows only the upper left part of the polarization conversion element 10 shown in FIGS. Randomly polarized light 27 incident on the prism block 10a having an effective aperture 251 that is long in the vertical direction on the paper surface is separated into P-polarized light and S-polarized light in the lateral direction, and S-polarized light is reflected by the reflective film 2 and emitted. The P-polarized light that has passed through the polarization separation film 1 is also converted by the phase difference plate 11 on the exit surface, and all the polarization axes are aligned with the S-polarized light 34 and emitted. In the prism block 10b having an effective aperture 261 that is long in the horizontal direction on the paper surface, the P-polarized light and the S-polarized light are separated in the vertical direction, and the P-polarized light is converted into S-polarized light by the phase difference plate 11 on the exit surface. All the polarization axes are aligned with the S-polarized light 29 and emitted.
[0023]
In the polarization conversion element 10 of the first embodiment configured as described above, an elliptical spot light is formed on the incident surface of the polarization conversion element 10 as shown in FIG. It is a direction. That is, the spots incident on the vertical position of the prism block 10a are formed long in the vertical direction, and the spots incident on the middle four of the eight effective openings 261 of the prism blocks 10b and 10c are obviously long in the horizontal direction. Is formed. Here, although the shape of the light spot is schematically shown as an elliptical shape, the eight effective apertures of the prism blocks 10b and 10c are compared with the effective apertures in the conventional polarization conversion element shown in FIG. It can be understood that the incident spots are efficiently used by the four effective apertures 261 in the middle of the H.261.
[0024]
Therefore, the use efficiency of light in the illumination optical device can be improved by using the polarization conversion element composed of the prism blocks 10a, 10b, and 10c arranged as in the first embodiment, and the same light source As a result, the amount of light reaching the illumination area such as the liquid crystal panel 13 shown in FIG.
[0025]
As described above, according to the first embodiment of the present invention, focusing on the fact that the spot shape becomes an ellipse having a large ellipticity (eccentricity) as it goes to the peripheral portion of the polarization conversion element 10, a plurality of prism blocks are used. In the first and second directions in which the longitudinal directions of the effective aperture surfaces are orthogonal to each other, that is, on the left and right sides, the strip-shaped effective apertures are arranged horizontally, so that the entire spot can enter the effective aperture region. . Therefore, when a rectangular polarization conversion optical system is used, the loss of the incident light amount of the spot in the peripheral portion can be reduced, and the projector that projects the image of the liquid crystal panel using only light having a unidirectional polarization axis When used as a light source, etc., a bright screen can be enjoyed.
[0026]
Embodiment 2. FIG.
FIG. 4 is a plan view showing an incident surface of a polarization conversion element used in the illumination optical apparatus according to the second embodiment. The optical system other than the polarization conversion optical system is the same as that of the first embodiment.
[0027]
The polarization conversion element 20 is composed of five prism blocks 20a to 20e, and a rectangular prism block 20a in which strip-shaped effective aperture surfaces and non-effective aperture surfaces are alternately arranged in the vertical direction in the central portion. The prism blocks 20b to 20b are arranged (four effective aperture surfaces and five non-effective aperture surfaces in the figure), and in the vicinity thereof strip-shaped effective aperture surfaces and ineffective aperture surfaces are alternately arranged in the oblique direction. 20e is arranged (in the figure, there are 9 effective aperture surfaces and 8 ineffective aperture surfaces).
[0028]
That is, in the second embodiment, the peripheral effective openings 34 are arranged radially from the central prism block 20a so as to approximate the longitudinal direction of the elliptical spot shape 5 incident from the rectangular polarization conversion optical system. It is configured by combining five prism blocks. Further, in the peripheral prism blocks 20b to 20e having radial effective openings, the strip-shaped opening pitch 37 is configured to be narrower than the opening pitch 36 of the central prism block 20a. Therefore, it can be understood that the light is incident from the effective aperture 34 more efficiently as compared with the first embodiment shown in FIG.
[0029]
In any of the first and second embodiments, the illumination area is provided with a display element such as a transmissive liquid crystal panel, and the illumination optical apparatus has been described as used in a projector or the like that enlarges and projects the image with a projection lens or the like. Therefore, it can be widely used as an illumination optical device having a polarization axis in a single direction by aligning the polarization axes of randomly polarized light emitted from a light source using an integrator and a polarization conversion optical system.
[0030]
【The invention's effect】
Since the present invention is configured as described above, there are the following effects.
[0031]
According to the first aspect of the present invention, by arranging the plurality of prism blocks so that the longitudinal direction of the effective aperture surface approximates the longitudinal direction of each spot, more light can be taken into the prism block and polarized light can be obtained. Provided is an illumination optical apparatus that can improve the polarization conversion efficiency in the conversion optical system and has a polarization conversion optical system with a compact configuration. Further, by disposing the prism block in the first and second directions in which the longitudinal directions of the effective aperture surfaces are orthogonal to each other, it is possible to reduce the loss of the incident light amount of the spot in the peripheral portion.
[0033]
In the illumination optical device according to claim 2 , the prism block is arranged in the first and second directions and the oblique directions orthogonal to each other in the longitudinal direction of the effective aperture surface, so that the incident of the spot at the peripheral portion is performed. Loss of light quantity can be further reduced.
[0034]
In the illumination optical device according to the third aspect, the effective aperture surfaces and the ineffective aperture surfaces are alternately arranged in a strip shape, and the pitch of the effective apertures is different for each prism block. A prism block with good polarization conversion efficiency can be arranged corresponding to the spot shape.
[0035]
The illumination optical device according to claim 4, wherein the phase separation has a function of rotating the polarization axis of the polarized light transmitted through the polarization separation film on the exit surface and the polarization separation film disposed at an inclination of 45 degrees with respect to the entrance surface. Since the plate is provided, the polarization axes can be reliably aligned.
[Brief description of the drawings]
FIG. 1 is a diagram showing a polarization conversion optical system according to a first embodiment of the present invention.
FIG. 2 is a conceptual diagram of a polarization conversion optical system according to Embodiment 1 of the present invention and a spot shape of light incident thereon.
FIG. 3 is a principle diagram showing a polarization conversion operation according to the first embodiment of the present invention.
FIG. 4 is a conceptual diagram of a polarization conversion optical system according to Embodiment 2 of the present invention and the spot shape of light incident thereon.
FIG. 5 is a diagram illustrating an example of an illumination optical apparatus using a polarization conversion optical system.
FIG. 6 is a diagram illustrating an example of a conventional polarization conversion optical system.
FIG. 7 is a diagram illustrating the principle of conversion operation of a polarization conversion optical system.
FIG. 8 is a conceptual diagram showing a conventional polarization conversion optical system and a spot shape of light incident thereon.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polarization separation film, 2 Reflection film, 3 Random polarized light, 4 S polarized light, 5 Incident light spot shape, 6 Reflector, 7 Valve, 8 1st integrator, 9 2nd integrator, 10, 20 Polarization conversion element, 10a, 10b, 10c prism block, 11 phase difference plate, 12 field lens, 13 liquid crystal panel, 14 Ρ polarized light, 16 random polarized light, 17 effective aperture, 18-20 S polarized light, 22 effective aperture, 24 incident light spot, 251 261 effective aperture surface, 252, 262 non-effective aperture surface, 27 random polarized light, 29 S-polarized light, 34 radial effective aperture, 36 center aperture pitch, 37 peripheral aperture pitch.

Claims (4)

A light source that emits light including a polarization axis in a random direction;
A first integrator for forming an image of the light source as a plurality of divided spots;
Each of the spots by the first integrator is incident, and a second integrator that forms an image by superimposing the spots on a predetermined illumination area;
A plurality of prism blocks disposed in the vicinity of the second integrator, having a plurality of strip-shaped effective aperture surfaces, and converting light incident on the effective aperture surfaces into light having a uniform polarization direction;
In an illumination optical device having
The prism block is arranged so that the longitudinal direction of each effective aperture surface approximates the longitudinal direction of each spot within the incident surface of the prism block,
The prism block, the valid first longitudinal opening surfaces are perpendicular to each other, the illumination optical apparatus characterized in that it is arranged in the second direction. A light source that emits light including a polarization axis in a random direction;
A first integrator for forming an image of the light source as a plurality of divided spots;
Each of the spots by the first integrator is incident, and a second integrator that forms an image by superimposing the spots on a predetermined illumination area;
A plurality of prism blocks disposed in the vicinity of the second integrator, having a plurality of strip-shaped effective aperture surfaces, and converting light incident on the effective aperture surfaces into light having a uniform polarization direction;
In an illumination optical device having
The prism block is arranged so that the longitudinal direction of each effective aperture surface approximates the longitudinal direction of each spot within the incident surface of the prism block,
The prism block, the valid first longitudinal opening surfaces are perpendicular to each other, the second direction, and the illumination optical system you characterized in that oblique arranged in a direction. 3. The illumination according to claim 1, wherein the prism block has a strip shape in which effective aperture surfaces and non-effective aperture surfaces are alternately arranged, and the pitch of the effective apertures is different for each prism block. 4. Optical device. The prism block includes a polarization separation film disposed at an inclination of 45 degrees with respect to an incident surface, and a retardation plate having a function of rotating a polarization axis of polarized light transmitted through the polarization separation film on an output surface. The illumination optical apparatus according to claim 1, further comprising: an illumination optical apparatus according to claim 1 .

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