JP2002182030A - Polarization conversion element and projector - Google Patents

Abstract

(57) [Problem] To provide a polarization conversion element that can be easily manufactured and reliably reduced in size. SOLUTION: In manufacturing a polarization conversion element 416, a central portion 11 and an outer peripheral portion 13 which are separately provided are combined. For this reason, it is only necessary to fit the central portion 11 into the concave portion provided in the outer peripheral portion 13, and it is possible to eliminate the troublesome positioning work of each other and to facilitate the production. Further, in the polarization conversion element 416, since the outer surface of the reflection film 19 also functions as a conventional light shielding plate due to its structure, it is not necessary to separately provide a conventional light shielding plate, and the polarization conversion element 416 can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization conversion element that separates a light beam emitted from a light source into two types of polarized light, and then converts the light into one type of polarized light having a uniform polarization direction. The present invention relates to a projector including an illumination optical system configured to include:

[0002]

2. Description of the Related Art Conventionally, a light source, an electro-optical device such as a liquid crystal panel for modulating a light beam emitted from the light source according to image information, and a projection optical system for enlarging and projecting the light beam modulated by the electro-optical device. Is used. Such a projector employs an illumination optical system including a light beam splitting optical element and a polarization conversion element on an optical path from the light source to the electro-optical device, thereby using the light from the light source without waste, and improving brightness and color unevenness. The device has been devised so that a projection image without defects can be formed.

[0003] The polarization conversion element used here separates an incident light beam having a random polarization direction into two types of polarized light, and rotates the polarization direction of either one of the polarized light beams, thereby obtaining a light beam having a uniform polarization direction. Is an optical element that emits light.
The specific structure is shown in FIGS.

[0006] In FIG. 6, a polarization conversion element 90 includes a plurality of polarization conversion sections 91 corresponding to a plurality of light source images formed by a lens array (light beam splitting optical element) (not shown) arranged on the light incident side. I have. The polarization converter 91 transmits one (polarized light P in FIG. 6) and the other (polarized light S in FIG. 6) of two types of polarized lights S and P having different polarization directions.
A polarization separating film 92 that reflects the polarized light S, a reflecting film 93 that reflects the other polarized light S, a phase difference plate 94 that rotates the transmitted polarized light P, and the polarized light S to a position corresponding to the reflecting film 93. , P to prevent light from entering.

[0005] By employing such a polarization conversion element 90, the polarized lights S and P of the light beam emitted from the light source can be aligned to only one-way polarized light S. It is possible to reduce the amount of polarized light that is blocked by the disposed polarizing plate, and to improve the utilization efficiency of light from the light source.

[0006]

However, in the polarization conversion element 90, one pair of glass bodies 96 and 97 having a parallelogram or triangular cross section (the hatching in FIG. 6B is omitted) are bonded together. In addition to the structure of the conversion section 91, the polarization conversion section 91 has a structure in which a plurality of layers are stacked, so that it takes time and effort to position the glass bodies 96 and 97 relative to each other. is there. Further, in a structure in which the polarization conversion units 91 are stacked in a plurality of stages, it is necessary to provide a light shielding plate 95 for each polarization conversion unit 91. Therefore, there is a problem that the light shielding plate 95 hinders miniaturization of the polarization conversion element 90. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarization conversion element which can be easily manufactured and reliably miniaturized, and a projector using the polarization conversion element.

[0008]

The polarization conversion element of the present invention is a substantially frustum-shaped element having a substantially conical central portion and an outer peripheral portion provided so as to surround the central conical surface. The element body and the central part have the same spreading direction of the respective conical surfaces, and a polarization separation part is formed at the boundary between the central part and the outer peripheral part. A phase difference portion is formed on the planar portion, and a reflection portion is formed on the conical surface of the element body.

In such a configuration, for example, the central portion and the outer peripheral portion, which are separately provided, are combined in the manufacture thereof, but in this case, it is only necessary to fit the central portion into the concave portion of the outer peripheral portion. Therefore, mutual positioning can be easily performed, and workability is improved. Further, since the polarized light can be made incident on the entire area of the light-incident side planar portion of the element body (outer peripheral portion), the conventional light-shielding plate is not required, and the miniaturization is promoted. As described above, the object of the present invention is achieved.

[0010] In the polarization conversion element of the present invention, a plurality of the element main bodies may be arranged in an in-plane direction. In such a configuration, a light beam emitted from a light source is divided into a plurality of partial light beams by using a light beam splitting optical element such as a lens array, and these partial light beams are made incident on each element body, so that an electro-optical device or the like is obtained. An illumination light beam having a uniform luminance distribution is applied to an illumination area such as an image forming area.

In the polarization conversion device according to the present invention, it is preferable that the apex of the central portion is located at a position shifted from the surface of the planar portion of the device body on the light incident side to the inside on the light emitting side. In such a configuration, since reflection at the planar portion on the incident side of the element body is prevented, the light source light applied to the planar portion enters the element body without leaking, and the utilization efficiency of the light source light is reduced. improves.

[0012] In the polarization conversion element of the present invention, the element body may have a truncated cone shape, and the central portion may have a conical shape. Since the light source light emitted from the light source usually has a circular irradiation shape, if the element main body is made into a truncated cone and the light incident side surface portion is made circular, the light source light is not wasted on this surface portion. In this case, the efficiency of use of light from the light source is improved particularly when one element body constitutes a polarization conversion element.
In addition, when a polarization conversion element is constituted by one element body, a conventional light beam splitting optical element is not required, so that downsizing of the entire illumination optical system including the polarization conversion element is promoted and cost is increased. Be reduced.

On the other hand, in the polarization conversion device of the present invention,
The element body may have a truncated pyramid shape, and the central portion may have a pyramid shape. In such a configuration, since the planar portion on the light emission side of the element main body is a polygonal surface, a plurality of element main bodies are efficiently arranged without gaps by bringing the sides of the planar portion of the element main body close to each other. As a result, the arrangement efficiency in the case where the polarization conversion element is constituted by the plurality of element bodies and the utilization efficiency of the light source light are improved.

On the other hand, a projector according to the present invention includes an illumination optical system including any one of the above-described polarization conversion elements and a light source device disposed on the light incident side of the polarization conversion element. It is characterized by. Even in such a projector, the above-described operation and effect can be similarly obtained by having the polarization conversion element, so that the object of the present invention is achieved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an optical unit 4 used in the front type projector according to the present embodiment.

[1. Overall Description of Optical Unit] The optical unit 4 is a unit that optically processes a light beam emitted from a light source to form an optical image corresponding to image information, and includes an integrator illumination optical system 41 and a color separation optical system 4.
2, a relay optical system 43, an electro-optical device 44, a cross dichroic prism 45, and a projection lens 46.

The integrator illumination optical system 41 supplies an optical beam to an image forming area of three liquid crystal panels 441 (shown as liquid crystal panels 441R, 441G, and 441B for each color light) constituting the electro-optical device 44. And includes a light source device 413, a UV filter 414, a parallelizing lens 415, a polarization conversion element 416, and a convex lens 417.

The light source device 413 has a light source lamp 411 as a radiation light source for emitting a radial light beam, and a reflector 412 for reflecting the radiation light emitted from the light source lamp 411. As the light source lamp 411, a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is often used. Reflector 41
As 2, it is preferable to use an ellipsoidal mirror.

The polarization conversion element 416 includes the UV filter 41
The light from the light source device 413 irradiated through the light source 4 is converted into one type of polarized light, whereby the light use efficiency of the electro-optical device 44 is improved. The polarized light converted into one type by the polarization conversion element 416 is condensed on the condenser lens 418 through the convex lens 417 and the color separation optical system 42, and finally, the liquid crystal panels 441R, 441G, 441B of the electro-optical device 44. It is almost superimposed on the top.

Liquid crystal panel 44 of the type that modulates polarized light
Since only one type of polarized light can be used in the projector 1 (electro-optical device 44) of the present embodiment using No. 1, almost half of the light from the light source lamp 411 that emits another type of random polarized light is not used. Therefore, by using the polarization conversion element 416, all the light emitted from the light source lamp 411 is converted into one kind of polarized light, and the electro-optical device 44 is used.
To increase the efficiency of light use. The polarization conversion element 4
The specific structure of 16 will be described later.

The color separation optical system 42 includes two dichroic mirrors 421 and 422 and a reflection mirror 423. The dichroic mirrors 421 and 422 convert the polarized light emitted from the integrator illumination optical system 41 into red light.
It has a function of separating into three color lights of green and blue.

The relay optical system 43 includes an incident side lens 43.
1, relay lens 433, and reflection mirrors 432, 4
34, and has a function of guiding the color light, for example, blue light, separated by the color separation optical system 42 to the liquid crystal panel 441B.

The electro-optical device 44 includes liquid crystal panels 441R, 441G, and 441B serving as three light modulating devices.
These use, for example, a polysilicon TFT as a switching element, and each color light separated by the color separation optical system 42 is supplied to these three liquid crystal panels 441R and 441R.
The optical image is modulated by 41G and 441B in accordance with the image information.

The cross dichroic prism 45 includes three
A color image is formed by combining images modulated for each color light emitted from the liquid crystal panels 441R, 441G, and 441B. In the prism 45, a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a substantially X shape along the interface between the four right-angle prisms. The three color lights are synthesized by the multilayer film. The color image synthesized by the prism 45 is emitted from the projection lens 46 and is enlarged and projected on a screen.

[2. Description of Polarization Conversion Element] Hereinafter, the most characteristic polarization conversion element 416 in this embodiment will be described in detail with reference to FIGS. The polarization conversion element 416 includes a frusto-conical element main body 10, and the element main body 10 includes a conical central portion 11 and an outer peripheral portion 13 provided so as to surround the conical surface 12 of the central portion 11. Have been. Both the central portion 11 and the outer peripheral portion 13 are made of glass. Conical surface 14 and central portion 1 of element body 10 (outer peripheral portion 13)
The first conical surface 12 is formed so as to expand in the same expanding direction, that is, toward the light emitting side. Note that, in the sectional view of FIG.
The hatching of the glass portion (enriched portion) of the outer peripheral portion 13 is omitted.

Between the conical surface 12 of the central portion 11 and the inner surface 15 of the concave portion provided on the outer peripheral portion 13, the polarized light S of the polarized lights P and S is reflected, and only the polarized light P is transmitted. A polarization splitting film 16 is formed as a polarization splitting section. A central emission surface 17 which is a planar portion on the light emission side of the central portion 11 includes:
(1/1) as a phase difference part for converting the polarized light P into the polarized light S
2λ) A phase difference plate 18 is provided.

On the other hand, a reflection film 19 as a reflection portion is formed on the conical surface 14 of the element body 10. This reflection film 19
Is to further reflect the polarized light S reflected by the polarization splitting film 16 and emit it from the annular outer emission surface 20 of the outer peripheral portion 13. However, on the contrary, it is preferable that the outer surface of the reflection film 19 has a color such as black so as to suppress the reflection of the polarized lights P and S.

The apex portion 21 of the central portion 11 including the polarization splitting film 16 is located on the light emitting side relative to the surface of the incident surface 22 which is a planar portion on the light incident side of the element body 10.
The diameter R1 of the central exit surface 17 of the central portion 11 including the thickness of the polarization separation film 16 is set slightly larger than the diameter R2 of the entrance surface 22 of the element body 10, and the incident polarized light P, S is prevented from being emitted from the outer emission surface 20 as it is, so that the polarized light separating film 16 is reliably irradiated.

In such a configuration, first, the central portion 11 and the outer peripheral portion 13 are separately manufactured in advance, and the conical surface 12 of the central portion 11 or the inner surface 15 of the outer peripheral portion 13 are provided with a polarization separating film 16.
Is formed, and a phase difference plate 18 is provided
And a reflective film 19 is formed on the conical surface 14 of the outer peripheral portion 13 (element body 10).
And the polarization conversion element 416 is completed. Note that the retardation plate 18 and the reflection film 19 may be provided after the central portion 11 and the outer peripheral portion 13 are combined.

[3. Effects of Embodiment] According to the present embodiment, the following effects can be obtained. (1) In manufacturing the polarization conversion element 416, the central portion 11 and the outer peripheral portion 13 which are separately provided are combined. In this case, the central portion 11 is formed in a concave portion provided in the outer peripheral portion 13. It is only necessary to fit them, and it is possible to eliminate the troublesome positioning work of each other, and it is easy to manufacture.

(2) In addition, since the central portion 11 and the outer peripheral portion 13 may be prepared as a pair, it takes only one time to fit each other, and the polarization conversion portion 91 (FIG. 6) is conventionally laminated in a plurality of stages. In comparison, the workability at the time of production can be remarkably improved.

(3) In the polarization conversion element 416, since the outer surface of the reflection film 19 also functions as a conventional light-shielding plate due to its structure, it is not necessary to separately provide the conventional light-shielding plate 95 (FIG. 6). The conversion element 416 can be made compact.

(4) Since the polarization conversion element 416 has one element main body 10 and has only one incident surface 22, a thick and expensive light beam splitting optical element such as a conventional lens array can be used. Instead of providing, it is only necessary to provide a collimating lens 415 for balancing the condensed light source light. Therefore, the size of the entire integrator illumination optical system 41 including the polarization conversion element 416 can be reduced, and the cost can be significantly reduced.

(5) In the polarization conversion element 416, the central portion 11
Is located on the light emission side of the surface of the incident surface 22 so that the incident surface 22 can be completely flattened, and the light source light applied to the incident surface 22 can be internally reflected without being reflected. The light can be incident, and the utilization efficiency of the light from the light source can be improved.

(6) Further, since the entrance surface 22 is also circular due to the frusto-conical element body 10 and the like, the light source light having an originally circular illumination shape can be incident without waste.
From this point as well, the utilization efficiency of the light source light can be improved.

[4. Modification] FIGS. 4 and 5 show a polarization conversion element 516 as a modification of the present invention. Here, the same reference numerals are given to the same functional members as in the above-described embodiment,
Their detailed description is omitted or simplified. The polarization conversion element 516 is configured to include a plurality of element bodies 10 arranged on the same plane.
A hexagonal mounting member 30 as shown by a two-dot chain line therein
Attached to.

The element body 10 has a truncated hexagonal pyramid shape, and the central portion 11 has a hexagonal pyramid shape. One size of the element body 10 is very small as compared to the above embodiment,
The overall size of the polarization conversion element 516 formed by arranging a plurality of element bodies 10 is substantially the same as the polarization conversion element 416 of the above embodiment. In addition, element body 1
The cross-sectional shape of No. 0 and the manufacturing procedure of the element body 10 are the same as those of the above-described embodiment.

Further, in such a polarization conversion element 516, these element bodies 10 are arranged without gaps by making one side of the outer emission surface 20 close to each other. However, on the light incident side, the incident surface 22 of each element body 10
Since the distance is large, a light beam splitting optical element such as a lens array in which each lens shape is hexagonal is used in order to make the light source light incident on the incident surface 22 efficiently.

In such a modification, the effects of the above (1), (3), and (5) can be obtained in the same manner by the same configuration as the above-described embodiment. The following effects are obtained. (7) Since the brightness of the polarized light emitted from each element main body 10 can be made uniform by making the brightness of the split light beam from the light beam splitting optical element equal, the illumination area such as the image forming area of the electro-optical device 44 can be used. On the other hand, an illumination light beam having a uniform luminance distribution can be emitted, and a projection image without unevenness can be realized.

(8) Since the outer emission surface 20 is hexagonal,
By bringing the sides of the outer emission surface 20 close to each other, the respective element bodies 10 can be efficiently arranged without gaps. For example, the element bodies 10 in the mounting member 30 can be more easily arranged than when a frustoconical element body is used. Can be improved, and the utilization efficiency of the light source light can be improved. The element body 1
Since there is no gap between the zeros, there is no need for a shielding member that shields such a gap.

As other modifications, the present invention includes other configurations that can achieve the object of the present invention, and the following embodiments are also included in the present invention. For example, the aforementioned polarization conversion element 41
6 and 516, the central emission surface 17 of the central portion 11 and the outer emission surface 20 of the outer peripheral portion 13 were flush (FIG. 3). You may indent only. In such a case, the concave portion is formed after the center portion 11 and the outer peripheral portion 13 are combined, and the phase difference plate 1 is formed by using the concave portion.
8 can be easily positioned, and the mounting work can be performed quickly.

As in the above embodiment, one element body 1
In the case where the polarization conversion element 416 is constituted by 0, the central emission surface 17 of the central portion 11 and the outer emission surface 20 of the outer peripheral portion 13 are formed.
May not be formed in a flat shape (flat) but may be formed in a continuous spherical shape (convex lens shape). In such a case, the emitted polarized light is condensed, so that the convex lens 417 used in the embodiment can be omitted, and further downsizing and cost reduction can be promoted.

Further, the polarization separation film 16 of the above-described embodiment is used.
The polarized light S is reflected and the polarized light P is transmitted, but a polarized light separating film that reflects the polarized light P and transmits the polarized light S may be used. Instead of the phase difference plate 18, a phase difference plate for rotating the polarized light S into the polarized light P may be used.

The shape of the element body according to the present invention is not limited to a truncated cone or a truncated hexagon, but may be another truncated polygon. Then, the shape of the central portion disposed therein may be appropriately changed according to the shape of the element body. Furthermore, the polarization separation section, the retardation section, and the reflection section according to the present invention may be formed of a film-like or plate-like member, or may be formed of a coated material.

Furthermore, in the above embodiment, only an example of a projector using three light modulation devices has been described, but the present invention uses a projector using only one light modulation device and two projectors using two light modulation devices. The present invention is also applicable to a projector or a projector using four or more light modulation devices.

In the above embodiment, the liquid crystal panel is used as the light modulation device. However, a light modulation device other than liquid crystal, such as a device using a micromirror, may be used.
Further, in the above-described embodiment, the transmission type light modulation device in which the light incident surface and the light emission surface are different is used, but the reflection type light modulation device in which the light incidence surface and the light emission surface are the same is used. Is also good.

Furthermore, in the above-described embodiment, only the example of the front type projector that performs projection from the direction in which the screen is viewed has been described. However, the present invention provides a rear projector that performs projection from the side opposite to the direction in which the screen is viewed. It is also applicable to projectors of the type.

[0048]

As described above, according to the present invention,
There is an effect that the polarization conversion element can be easily manufactured and the size can be reliably reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is an overall perspective view showing the polarization conversion element of the embodiment in an enlarged manner.

FIG. 3 is a sectional view of the polarization conversion element.

FIG. 4 is a view of a polarization conversion element according to a modification of the present invention as viewed from the light emission side.

FIG. 5 is an overall perspective view showing components of the modification in an enlarged manner.

FIG. 6 is a perspective view (A) and a cross-sectional view (B) showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projector 10 Element main body 11 Central part 12,14 Conical surface 13 Outer peripheral part 16 Polarization separation film which is a polarization separation part 17 Central emission surface 18 (1 / 2λ) phase difference plate which is a phase difference part 19 Reflection film which is a reflection part DESCRIPTION OF SYMBOLS 21 Apex part 22 Incident surface 41 Integrator illumination optical system 416,516 Polarization conversion element

Claims (6)

[Claims] 1. A frustum-shaped element body comprising a substantially cone-shaped central portion and an outer peripheral portion provided so as to surround a conical surface of the center portion, wherein the element body and the central portion are respectively provided. The spreading directions of the conical surfaces are the same, a polarization splitting portion is formed at the boundary between the central portion and the outer peripheral portion, and a phase difference portion is formed at the central portion on the light emission side of the light, A polarization conversion element, wherein a reflection part is formed on a conical surface of the element body. 2. The polarization conversion element according to claim 1, wherein a plurality of the element bodies are arranged in an in-plane direction. 3. The polarization conversion element according to claim 1, wherein the apex of the central portion is displaced from the surface of the planar portion on the light incident side of the element body to the inside on the light output side. A polarization conversion element. 4. The polarization conversion device according to claim 1, wherein the device main body has a truncated cone shape, and the central portion has a conical shape. 5. The polarization conversion element according to claim 1, wherein the element body has a truncated pyramid shape, and the central portion has a pyramid shape. 6. An illumination optical system comprising: the polarization conversion element according to claim 1; and a light source device disposed on a light incident side of the polarization conversion element. Projector.