JP3893872B2 - Polarization conversion element and projector - Google Patents

Description

[0001]
BACKGROUND 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, and an illumination that includes the polarization conversion element. The present invention relates to a projector provided with an optical system.
[0002]
[Background]
Conventionally, a light source, an electro-optical device such as a liquid crystal panel that modulates a light beam emitted from the light source according to image information, and a projection optical system that enlarges and projects the light beam modulated by the electro-optical device are provided. A projector is being used.
Such a projector employs an illumination optical system including a light beam splitting optical element and a polarization conversion element on the optical path from the light source to the electro-optical device, thereby making it possible to use the light source light without waste and to obtain brightness and color unevenness. Ingenuity is provided so that a projected image can be formed.
[0003]
The polarization conversion element used here separates an incident light beam with a random polarization direction into two types of polarized light, and emits a light beam with a uniform polarization direction by rotating the polarization direction of one of the polarized light. It is an optical element. The specific structure is shown in FIGS. 6 (A) and 6 (B).
[0004]
In FIG. 6, the polarization conversion element 90 includes a plurality of polarization conversion units 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.
The polarization converter 91 transmits one of the two types of polarized light S and P having different polarization directions (polarized light P in FIG. 6) and reflects the other (polarized light S in FIG. 6). 92, the reflecting film 93 that reflects the other separated polarized light S, the retardation plate 94 that rotates the transmitted polarized light P, and the polarized lights S and P are incident on the position corresponding to the reflecting film 93. And a light shielding plate 95 for preventing the above.
[0005]
By adopting such a polarization conversion element 90, it is possible to align the polarized light S and P of the light beam emitted from the light source with only the polarized light S in one direction, so that it is arranged in the optical path to the liquid crystal panel. The polarized light blocked by the polarizing plate can be reduced, and the utilization efficiency of the light source light can be improved.
[0006]
[Problems to be solved by the invention]
However, in the polarization conversion element 90, a pair of parallelogram or triangular glass bodies 96, 97 (hatching in FIG. 6B is omitted) are bonded to form one polarization conversion unit 91. Since the polarization conversion unit 91 has a structure in which a plurality of stages are laminated, there is a problem in that it cannot be easily manufactured because it takes time to position the glass bodies 96 and 97 between each other.
Further, in the structure in which each polarization conversion unit 91 is stacked in a plurality of stages, it is necessary to provide a light shielding plate 95 for each polarization conversion unit 91, so that the light shielding plate 95 hinders the downsizing of the polarization conversion element 90. .
[0007]
An object of the present invention is to provide a polarization conversion element that can be easily manufactured and reliably reduced in size, and a projector using the polarization conversion element.
[0008]
[Means for Solving the Problems]
The polarization conversion element of the present invention includes an element body composed of a substantially pyramid-shaped central portion and an outer shape of a substantially frustum-shaped outer periphery provided so as to surround the conical surface of the central portion. The central part has the same direction of spreading of the respective conical surfaces, and the outer peripheral part is provided on the light incident surface provided on the apex side of the central part and around the central outgoing surface on the light output side of the central part. And an outer emission surface that is provided continuously in an annular shape and faces in the same direction as the central emission surface, and the central portion is fitted into a conical concave portion of the outer peripheral portion, A polarization separation portion is formed at the boundary with the outer peripheral portion, a phase difference portion is formed directly on the central output surface of the central portion over the entire area of the central output surface, and the conical surface of the outer peripheral portion is The reflection portion is formed directly over the entire area.
[0009]
In such a configuration, for example, the center portion and the outer peripheral portion, which are separated from each other, are combined, but in this case, it is only necessary to fit the central portion into the concave portion of the outer peripheral portion. Can be easily positioned and workability is improved.
Further, since it becomes possible to make polarized light incident on the entire area of the light incident side of the element main body (outer peripheral portion), a conventional light-shielding plate becomes unnecessary, and miniaturization is promoted.
Thus, 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 the in-plane direction.
In such a configuration, the light beam emitted from the light source is divided into a plurality of partial light beams using a light beam splitting optical element such as a lens array, and these partial light beams are made incident on each element body, thereby causing an electro-optical device or the like. An illumination light beam having a uniform luminance distribution is irradiated onto an illumination area such as the image forming area.
[0011]
In the polarization conversion element of the present invention, it is preferable that the apex portion of the central portion is located in the light emission side with a shift from the surface of the light incident side of the element main body.
In such a configuration, since the reflection at the planar portion on the incident side of the element body is prevented, the light source light irradiated on the planar portion enters the element body without leakage, and the use efficiency of the light source light is improved. 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 cone shape.
Since the light source light emitted from the light source is usually circular, if the element body is a truncated cone and the surface portion on the light incident side is circular, the light source light is not wasted on the surface portion. In particular, the light source light utilization efficiency is improved in the case where the polarization conversion element is constituted by one element body.
In addition, when a polarization conversion element is configured with a single element body, a conventional beam splitting optical element is not required, so that the entire illumination optical system including the polarization conversion element can be reduced in size and cost can be increased. Reduced.
[0013]
On the other hand, in the polarization conversion element of the present invention, the element body may have a truncated pyramid shape, and the central portion may have a pyramidal shape.
In such a configuration, since the planar portion of the light emitting side of the element body is a polygonal surface, a plurality of element bodies can be efficiently arranged without gaps by bringing the sides of the planar portion of the element 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 is improved.
[0014]
On the other hand, a projector according to the present invention includes an illumination optical system including any one of the polarization conversion elements described above and a light source device disposed on the light incident side of the polarization conversion element. To do.
Even in such a projector, the above-described effects can be obtained in the same manner by having the polarization conversion element, so that the object of the present invention is achieved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing an optical unit 4 used in a front type projector according to the present embodiment.
[0016]
[1. Overall description of the 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, a color separation optical system 42, a relay optical system 43, An electro-optical device 44, a cross dichroic prism 45, and a projection lens 46 are provided.
[0017]
The integrator illumination optical system 41 is an optical system for supplying a light beam to an image forming area of three liquid crystal panels 441 (shown as liquid crystal panels 441R, 441G, 441B for each color light) constituting the electro-optical device 44, A light source device 413, a UV filter 414, a collimating lens 415, a polarization conversion element 416, and a convex lens 417 are provided.
[0018]
Of these, the light source device 413 includes a light source lamp 411 as a radiation light source that emits a radial light beam, and a reflector 412 that reflects 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. As the reflector 412, an ellipsoidal mirror is preferably used.
[0019]
The polarization conversion element 416 converts the light source light of the light source device 413 irradiated through the UV filter 414 into one type of polarized light, and thereby the light use efficiency in the electro-optical device 44 is enhanced. . 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.
[0020]
Since only one type of polarized light can be used in the projector 1 (electro-optical device 44) of this embodiment using the liquid crystal panel 441 of the type that modulates polarized light, the light source lamp 411 that emits other types of randomly polarized light is used. Almost half of the light is not used. Therefore, by using the polarization conversion element 416, all the emitted light from the light source lamp 411 is converted into one kind of polarized light, and the use efficiency of light in the electro-optical device 44 is enhanced.
A specific structure of the polarization conversion element 416 will be described later.
[0021]
The color separation optical system 42 includes two dichroic mirrors 421 and 422, and a reflection mirror 423, and the polarized light emitted from the integrator illumination optical system 41 by the dichroic mirrors 421 and 422 is red, green, and blue. It has a function of separating into colored light.
[0022]
The relay optical system 43 includes an incident side lens 431, a relay lens 433, and reflection mirrors 432 and 434, and has a function of guiding the color light separated by the color separation optical system 42, for example, blue light to the liquid crystal panel 441B. .
[0023]
The electro-optical device 44 includes liquid crystal panels 441R, 441G, and 441B serving as three light modulation devices, which use, for example, polysilicon TFTs as switching elements and are separated by the color separation optical system 42. Each color light is modulated by these three liquid crystal panels 441R, 441G, and 441B in accordance with image information to form an optical image.
[0024]
The cross dichroic prism 45 forms a color image by combining images modulated for each color light emitted from the three 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 interfaces of four right-angle prisms. 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 enlarged and projected on the screen.
[0025]
[2. Explanation of polarization conversion element)
Hereinafter, the most characteristic polarization conversion element 416 in the present embodiment will be described in detail with reference to FIGS.
The polarization conversion element 416 includes a truncated cone-shaped element body 10, and the element 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. Has been. Both the central portion 11 and the outer peripheral portion 13 are made of glass. The conical surface 14 of the element body 10 (outer peripheral portion 13) and the conical surface 12 of the central portion 11 are formed so as to expand toward the same expansion direction, that is, toward the light emitting side.
In the cross-sectional view of FIG. 3, hatching of the glass portions (solid portions) of the central portion 11 and the outer peripheral portion 13 is omitted for easy viewing.
[0026]
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 separation that reflects the polarized light S of the polarized light P, S and transmits only the polarized light P. A polarization separation film 16 as a part is formed. A (1 / 2λ) phase difference plate 18 as a phase difference portion that converts the polarized light P into the polarized light S is provided on the central emission surface 17 that is a planar portion on the light emission side of the central portion 11.
[0027]
On the other hand, a reflective film 19 as a reflective portion is formed on the conical surface 14 of the element body 10. The reflection film 19 further reflects the polarized light S reflected by the polarization separation film 16 so as to be emitted 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 hue such as black so that the reflection of the polarized lights P and S can be suppressed.
[0028]
Further, the apex portion 21 including the polarization separation film 16 in the central portion 11 is located on the light emission side inside 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 incident surface 22 of the element body 10, and the incident polarized light P, The polarization separation film 16 is reliably irradiated by preventing S from being emitted as it is from the outer emission surface 20.
[0029]
In such a configuration, first, the central portion 11 and the outer peripheral portion 13 are manufactured separately in advance, and the polarization separation film 16 is formed on the conical surface 12 of the central portion 11 or the inner surface 15 of the outer peripheral portion 13. A phase difference plate 18 is attached to the central emission surface 17 of the part 11, a reflective film 19 is formed on the conical surface 14 of the outer peripheral part 13 (element body 10), and then the central part 11 is formed into a conical concave part of the outer peripheral part 13. And the polarization conversion element 416 is completed.
The phase difference plate 18 and the reflective film 19 may be provided after combining the central portion 11 and the outer peripheral portion 13.
[0030]
[3. Effects of the embodiment
According to this embodiment, there are the following effects.
(1) In manufacturing the polarization conversion element 416, the central portion 11 and the outer peripheral portion 13 which are separated from each other are combined. In this case, the central portion 11 is attached to the concave portion provided in the outer peripheral portion 13. It only needs to be fitted, so that it is possible to eliminate the time-consuming positioning operation, and the manufacturing can be easily performed.
[0031]
(2) Moreover, since the center part 11 and the outer peripheral part 13 should just prepare one pair, the effort which engages each other is only one time, and compared with the former which laminates | stacks the polarization conversion part 91 (FIG. 6) in multiple steps, Workability at the time of production can be greatly improved.
[0032]
(3) In the polarization conversion element 416, the outer surface of the reflective film 19 also functions as a conventional light shielding plate because of its structure. Therefore, it is not necessary to separately provide the conventional light shielding plate 95 (FIG. 6), and the polarization conversion element 416 Can be made compact.
[0033]
(4) Since the polarization conversion element 416 includes the single element main body 10 and has one incident surface 22, instead of providing a thick and expensive beam splitting optical element such as a conventional lens array. It is only necessary to provide a collimating lens 415 for balancing the condensed light source light. Therefore, the entire integrator illumination optical system 41 including the polarization conversion element 416 can be reduced in size and the cost can be greatly reduced.
[0034]
(5) In the polarization conversion element 416, since the apex portion 21 of the central portion 11 is located inside the light exit side with respect to the surface of the incident surface 22, the incident surface 22 can be completely planarized. Irradiated light source light can be incident inside without being reflected, and the utilization efficiency of the light source light can be improved.
[0035]
(6) Further, since the incident surface 22 is also circular due to the truncated cone-shaped element body 10 or the like, the light source light having an originally irradiated shape can be incident without any waste. Efficiency can be improved.
[0036]
[4. (Modification)
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, and detailed description thereof is omitted or simplified.
The polarization conversion element 516 includes a plurality of element main bodies 10 arranged on the same plane, and these element main bodies 10 are attached to a mounting member 30 having an outer hexagonal shape as indicated by a two-dot chain line in FIG. It is attached.
[0037]
The element body 10 has a hexagonal frustum shape, and the central portion 11 has a hexagonal pyramid shape. One size of the element body 10 is very small as compared with the above embodiment, but the entire size of the polarization conversion element 516 formed by arranging a plurality of element bodies 10 is the polarization conversion element of the embodiment. It is almost the same as 416.
In addition, the cross-sectional shape of the element body 10 and the manufacturing procedure of the element body 10 are the same as those in the above embodiment.
[0038]
Further, in such a polarization conversion element 516, the element main bodies 10 are arranged without gaps by bringing one side of the outer emission surface 20 close to each other. However, since the incident surfaces 22 of the element bodies 10 are separated from each other on the light incident side, in order to make the light source light incident on the incident surfaces 22 efficiently, light beam splitting optics such as a lens array in which each lens shape is a hexagon. An element is used.
[0039]
In such a modified example, the effects (1), (3), and (5) described above can be obtained in the same manner by the same configuration as in the above embodiment, and the following effects can be obtained by the unique configuration. There is.
(7) Since the luminance of the polarized light emitted from each element body 10 can be made uniform by equalizing the luminance of the divided light beams from the light beam dividing optical element, it can be used as an illumination region such as an image forming region of the electro-optical device 44. On the other hand, it is possible to irradiate an illumination light beam having a uniform luminance distribution, and to realize a projection image without unevenness.
[0040]
(8) Since the outer emission surface 20 has a hexagonal shape, by placing the sides of the outer emission surface 20 close to each other, the respective element bodies 10 can be efficiently arranged without gaps. It is possible to improve the arrangement efficiency of the element main body 10 in the mounting member 30 and the utilization efficiency of the light source light, compared with the case where it is used.
Further, since no gap is generated between the element bodies 10, a shielding member that shields such a gap is also unnecessary.
[0041]
Other modifications include other configurations that can achieve the object of the present invention, and the following forms are also included in the present invention.
For example, in the above-described polarization conversion elements 416 and 516, the central emission surface 17 of the central portion 11 and the outer emission surface 20 of the outer peripheral portion 13 are flush with each other (FIG. 3). May be recessed by the thickness of the phase difference plate 18. In such a case, the indented portion is formed after combining the central portion 11 and the outer peripheral portion 13. By using this indented portion, the phase difference plate 18 can be easily positioned, and its mounting operation is performed. Can be done quickly.
[0042]
When the polarization conversion element 416 is configured by one element body 10 as in the above-described embodiment, the central emission surface 17 of the central portion 11 and the outer emission surface 20 of the outer peripheral portion 13 are made flat (flat). Instead of forming, it may be formed in a continuous spherical shape (convex lens shape). In such a case, since the emitted polarized light is condensed, the convex lens 417 used in the embodiment can be made unnecessary, and further miniaturization and cost reduction can be promoted.
[0043]
Further, the polarization separation film 16 of the above embodiment reflects the polarized light S and transmits the polarized light P, but may use a polarization separation film that reflects the polarized light P and transmits the polarized light S. Instead of the phase difference plate 18 that rotates the light P into the polarized light S, a phase difference plate that rotates the polarized light S into the polarized light P may be used.
[0044]
The shape of the element body according to the present invention is not limited to a truncated cone or a hexagonal truncated cone, and may be other polygonal truncated cone shapes. And the shape of the center part arrange | positioned in the inside may be changed suitably according to the shape of an element main body.
Furthermore, the polarization separation part, the phase difference part, and the reflection part according to the present invention may be formed of a film-like or plate-like member, or may be formed of a coated material.
[0045]
Furthermore, in the above-described embodiment, only an example of a projector using three light modulation devices has been described. However, the present invention is a projector using only one light modulation device, a projector using two light modulation devices, or The present invention can also be applied to a projector using four or more light modulation devices.
[0046]
In the embodiment, the liquid crystal panel is used as the light modulation device. However, a light modulation device other than the liquid crystal, such as a device using a micromirror, may be used.
Furthermore, in the above-described embodiment, the transmission type light modulation device having a different light incident surface and light emission surface is used. However, a reflection type light modulation device having the same light incident surface and light emission surface is used. Also good.
[0047]
Furthermore, in the above-described embodiment, only an example of a front type projector that performs projection from the direction of observing the screen has been described. However, the present invention provides a rear type projector that performs projection from the side opposite to the direction of observing the screen. It is also applicable to.
[0048]
【The invention's effect】
As described above, according to the present invention, there is an effect that the polarization conversion element can be easily manufactured and can be reliably reduced in size.
[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 an enlargement of the polarization conversion element of the embodiment.
FIG. 3 is a cross-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 seen from the light exit side.
FIG. 5 is an overall perspective view showing the components of the modified example in an enlarged manner.
FIG. 6 is a perspective view (A) and a cross-sectional view (B) showing the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Projector 10 Element main body 11 Center part 12, 14 Conical surface 13 Outer peripheral part 16 Polarization separation film 17 which is a polarization separation part Central output surface 18 (1/2 (lambda)) phase difference plate 19 which is a phase difference part Reflection film which is a reflection part 21 Vertex 22 Incident surface 41 Integrator illumination optical system 416, 516 Polarization conversion element

Claims (3)

A device body comprising a substantially pyramid-shaped central portion and an outer shape of a substantially frustum-shaped outer periphery provided so as to surround the conical surface of the central portion,
The outer peripheral part and the central part have the same spreading direction of the respective conical surfaces. An outer emission surface provided around the emission surface and continuously provided in an annular shape and facing in the same direction as the central emission surface;
The central part is fitted into a conical concave part provided on the outer peripheral part,
A polarized light separation part is formed at the boundary between the central part and the outer peripheral part,
The phase difference portion is formed directly on the central emission surface of the central portion over the entire area of the central emission surface, and the reflection portion is formed directly on the entire cone surface of the outer peripheral portion. A polarization conversion element.   2. The polarization conversion element according to claim 1, wherein a plurality of the element bodies are arranged in an in-plane direction.   A projector comprising an illumination optical system configured to include the polarization conversion element according to claim 1 or 2 and a light source device disposed on a light incident side of the polarization conversion element.

Images