JPH10319349A - Polarized light converting element and projecting device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To emit luminous flux after arranging a polarization direction while contriving the effective utilization of incident luminous flux by arraying plural optical units on a transparent base plate at appropriate pitch and specifying the shape of each optical unit. SOLUTION: The luminous flux from an ellipsoidal mirror 3 is made incident to be converged at a 2nd focus. A main light beam emitted from a 2nd lens array 5 is made incident in parallel with a polarized light converting element 9 by a concave lens 8 for making the main light beam of the luminous flux from a 1st lens array 4 parallel. The elements 9 where a polarizing beam splitter part 11 and a reflection part 12 are set as a unit member (optical unit) are plurally arranged. The luminous flux made incident on the element 9 is separated to the different light by a polarized light separating plane 11, reflected by a reflection surface 12 and transmitted through a λ/2 plate 13. All the luminous flux emitted from the element 9 is in a polarized state and illuminates a picture display element 6 at the focus position of a condensing lens 10. Then, picture information formed on the element 6 is projected on a screen surface by a projection lens 15.

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 and a projection apparatus using the same, and more particularly, to a liquid crystal display element (liquid crystal panel) as an image display element and illuminating an image to be displayed on the image while effectively utilizing a light beam. Thus, the present invention is suitable for a liquid crystal projector that projects the image on a screen with a projection lens.

[0002]

2. Description of the Related Art Conventionally, an image is displayed using a liquid crystal panel, the liquid crystal panel is illuminated by a light beam from a light source, and an image based on transmitted light or reflected light from the liquid crystal panel is enlarged and projected on a screen by a projection lens. Various liquid crystal projectors have been proposed.

A TN type liquid crystal panel from which a high-contrast image can be obtained relatively easily utilizes the polarization characteristics of liquid crystal. For this purpose, a polarizing filter such as a polarizer or an analyzer is usually provided before and after the liquid crystal panel. The polarizing filter has a characteristic of transmitting a specific polarization direction of incident light and blocking a polarization direction orthogonal thereto. Therefore, at least half of the light used in the liquid crystal projector is blocked by the polarizing filter, and the brightness of the projected image tends to decrease.

As a lighting device for a liquid crystal projector,
Efficient use of luminous flux from the light source using a polarization conversion element that converts incident light into a luminous flux having a polarization plane in a specific direction and emits it, and a uniform illuminating means (optical integrator) for uniformly illuminating the illuminated slope For example, Japanese Patent Laid-Open Publication No. Hei 8-
No. 304739 proposes. FIG. 6 is a schematic view of a main part of a polarized light illuminating device proposed in the publication.

In the polarized light illuminating device shown in FIG. 6, reference numeral 310 denotes a polarization conversion element, which is arranged near the condenser lens array 304. The polarization separation prism array (polarization conversion element) 310 is formed of a plate-like element in which a plurality of polarization beam splitters 305 and a total reflection prism unit 306 are arranged as one unit (optical unit). Reference numeral 303 denotes a first lens plate, of which one array lens 3
Reference numeral 07 condenses the image of the light source 301 on the corresponding array lens 308 of the condensing lens array 304, and thereafter, makes it incident on the optical unit of the polarizing beam splitter 305. The polarization beam splitter 305 splits the incident light into two linearly polarized lights (P-polarized light and S-polarized light) whose polarization planes are orthogonal to each other.
Among them, the linearly polarized light (for example, P-polarized light) transmitted through the polarization beam splitter 305 is converted into the plate-shaped polarization conversion element 31.
The phase is 9 with the half-wave plate 309 arranged on the exit surface
The light is inverted by 0 degrees and becomes linearly polarized light (S-polarized light) having a different polarization plane from the transmitted light. On the other hand, the linearly polarized light (S-polarized light) reflected by the polarization beam splitter 305 is further reflected by the total reflection unit 306 and emitted in the same direction as the transmitted light. However, a half-wave plate 309 is provided at the exit of the reflected light.
Is not applied, the transmitted light (P-polarized light) has the same polarization plane as the phase-converted light (S-polarized light).
The array lenses 307 and the like of the first lens plate 303 are eccentric and have a positive refractive power as a whole. Thus, the light beam from the first lens plate 303 is emitted in parallel and guided to the polarization conversion element 310. Here, the reason why the light is guided to the polarization conversion element 310 with substantially parallel light is to reduce the angle dependence of the polarization beam splitter 305 as much as possible. The linearly polarized light having the same polarization plane is configured to illuminate the liquid crystal panel surface 312 in a rectangular shape by the condenser lens 311 on the emission side.

[0006]

In the polarized light illuminating device shown in FIG. 6, a light beam emitted from a light source 301 passes through a first lens plate 303 in which a plurality of rectangular lenses are arranged in a matrix, and then a condensing lens is formed. The polarization state is made uniform by the polarization splitting prism array 310 and the λ / 2 plate 309 via the array 304 to make oblique light, and then the light is condensed by the emission side lens 311 to illuminate the illumination area 312.

At this time, the size of the light source image of the light source 1 formed near the condenser lens array 304 is smaller at the peripheral portion than at the central portion (near the optical axis). At this time, if the condenser lens arrays 304 are all configured to have the same size and the arrangement pitches of the optical units of the change conversion element 310 are all the same, the size of the light source image protrudes from one lens array near the optical axis. However, since the protruding light flux is not effectively guided to the panel surface, it becomes completely lost light. In the conventional example shown in FIG. 6, the polarization conversion element 310 is used for this improvement.
The arrangement pitch of the optical units is different between the central part and the peripheral part.

Since the polarization conversion element 310 is configured by arranging the polarization beam splitter section 305 and the total reflection prism section 306 at approximately 45 degrees, the polarization conversion element 310 has to be stepped in the thickness direction (optical axis direction). There is a problem that manufacturing is extremely difficult.

According to the present invention, a plurality of optical units each composed of a polarization splitting surface and a reflecting surface are arranged at an appropriate pitch in a transparent substrate, and the light is incident by appropriately setting the shape of each optical unit. An object of the present invention is to provide a polarization conversion element suitable for a lighting device for a liquid crystal display device and a liquid crystal projector, and a projection device using the same, for example, which can make the polarization direction uniform while emitting light beams while effectively utilizing the incoming light beam.

[0010]

According to the present invention, there is provided a polarization conversion element comprising: (1-1) a polarization separation surface for separating incident light into reflected light and transmitted light whose polarization planes are orthogonal to each other; An optical unit having a reflecting surface for reflecting one light and aligning the other light in the same direction is arranged at a predetermined pitch in a transparent substrate, and a λ is provided in one of the optical paths of the reflected light and the transmitted light. The arrangement pitch of the optical units in the polarization conversion element in which the / 2 plate is arranged is different between the central portion and the peripheral portion of the substrate, and the substrate has a thickness in the light input / output direction of the central portion and the peripheral portion. It is characterized by being equal.

In particular, (1-1-1) the arrangement pitch of the optical units is smaller in a peripheral portion than in a central portion of the substrate.

(1-1-2) In the optical unit at the periphery of the substrate, the length of the polarization separation surface and the reflection surface projected in the light traveling direction is shorter than the thickness of the substrate. And so on.

[0013] The illumination device of the present invention comprises: (2-1) receiving a light beam from a light source using a polarization conversion element and a lens array in which a plurality of lenses are arranged corresponding to the arrangement pitch of the optical units of the polarization conversion element. Light is guided to the illumination area.

The projection apparatus according to the present invention is characterized in that (3-1) an image to be projected provided in an illuminated area in the illumination apparatus having the configuration (2-1) is projected onto a predetermined surface by a projection optical system. I have.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment when an illumination device having a polarization conversion element according to the present invention is used as a part of a projection device. FIG. 2 is an enlarged explanatory view of the polarization conversion element of FIG. In the figure, reference numeral 1 denotes a light source lamp (light source) such as a metal halide lamp. Reference numeral 2 denotes a light emitter of the light source 1, which has a shape close to a cylindrical shape. Reference numeral 3 denotes a reflector (condensing mirror) composed of a paraboloid or an ellipsoid, and a light source 1
The light flux from the luminous body 2 is reflected and condensed, and is incident on the first lens array (first lens array plate) 4. In this embodiment, an elliptical mirror is used as the reflector 3. The first lens array 4 has a plurality of lenses 4b each having a rectangular outer shape and a positive refractive power and arranged in a lattice pattern. 4a is the center of the effective area of the first lens array 4.

Reference numeral 8 denotes a concave lens (negative lens), which emits the principal ray of the light beam from the first lens array 4 in a substantially parallel manner.

A second lens array (second lens array plate) 5 has a plurality of lenses 5b having a positive refractive power corresponding to the individual lenses 4b of the first lens array 4.

5a is the center of the effective area of the second lens array. An image of the luminous body 2 is formed on each lens 4b surface of the second lens array 5 by the first lens array 4 and the concave lens 8.

Thus, a plurality of secondary light source images are formed.

At this time, in order to effectively form the image of the luminous body 2 on the second lens array plate 5, the plurality of lenses arranged in the second lens array 5 are such that the center lens is larger than the peripheral lens. It has an area.

Reference numeral 9 denotes a polarization conversion element which has a plate-like configuration shown in FIG.
An optical unit composed of two λ / 2 plates 13 is arranged at a predetermined pitch, and the plane of polarization of incident unpolarized light is aligned in a specific direction and emitted as a linearly polarized light beam.
The λ / 2 plate 13 is provided on the exit surface of the light reflected by the polarization beam splitter 11.

Reference numeral 10 denotes a condensing lens (optical member) having a positive refracting power, on the surface of the image display element 6 provided with diffused light from each optical unit of the polarization conversion element 9 in the illuminated area. It is focused so that it is superimposed on.

The image display element 6 comprises a light valve such as a liquid crystal panel. 6a is an image display element 6
Is the center of Reference numeral 7 denotes a main optical axis (center axis) of the illumination system.

Reference numeral 14 denotes a condenser lens, which efficiently condenses the illumination light on the projection lens 15.

The projection lens (projection optical system) 15 projects the projection image displayed on the image display element 6 onto a screen surface (not shown).

The secondary light source image formed by the first lens array 4 and the concave lens 8 and the entrance pupil 15a of the projection lens 15 have an optically conjugate positional relationship via the condenser lens 10 and the condenser lens 14. ing.

In the present embodiment, the center 6a of the illuminated area from the light emitter 2 passes through the center 4a of the effective area of the first lens array 4 and the center 5a of the effective area of the second lens array 5.
Leads to. However, the main optical axis 7 and the rotationally symmetric axis of the ellipsoidal mirror 3 coincide. The luminous body 2 has its major axis direction aligned with the direction of the main optical axis 7 so that its center of gravity is located at or near the focal point of the elliptical mirror 3. The light beam from the light emitter 2 is incident on the first lens array 4 in a state where the light beam is slightly converged rather than parallel to the main optical axis 7. Strictly, the light beam emitted from the focal point of the ellipsoidal mirror 3 enters the second focal point (not shown) of the elliptical mirror 3 so as to converge. The concave lens 8 for collimating the principal ray of the light beam from the first lens array 4 converts the principal ray emitted from the second lens array 5 into a plate-shaped polarization conversion element 9.
Are incident substantially in parallel.

In the present embodiment, the light beam incident on the first lens array 4 does not necessarily need to be convergent light, and a parabolic mirror is used instead of the elliptical mirror 3 and the concave lens 8 is omitted. Is also good. In the case of elliptical light collection, the first lens array 4 may have the function of the concave lens 8 in combination.

Next, the configuration of the polarization conversion element 9 of this embodiment will be described.

A plurality of polarization conversion elements 9 are arranged with the polarization beam splitter section 11 and the reflection section 12 as one unit member (optical unit). The polarization conversion element 9 includes a plurality of polarization separation surfaces (polarization beam splitters) 11 corresponding to the individual lenses 5 b of the second lens array 5, a reflection surface 12 that bends an optical path separated by the polarization separation surface 11, and a polarization separation surface 11. P-polarized light or S-polarized light whose incident light is polarized in a specific direction using a half-wave plate (λ / 2 plate) 13 provided in a transmission optical path or a reflection optical path of the optical path separated by
The light is emitted as linearly polarized light.

The arrangement pitch of the optical units of the polarization conversion element 9 is smaller at the peripheral portion than at the central portion in accordance with the size of each lens 5b of the second lens array 5.

It should be noted that the image of the luminous body 2 is
When it is formed larger in the peripheral part than in the central part, each lens of the second lens array plate 5 is made to have a larger area in the peripheral part than in the central part. The arrangement pitch of the optical units is larger in the peripheral part than in the central part.

Specifically, the light beam incident on the polarization conversion element 9 has different polarization states (S component and P
The light separated by the polarization separating surface 11 is reflected by the reflecting surface 12 and passes through the half-wave plate 13.

Then, the light is converted into the same polarization state as the light transmitted through the polarization separation surface 11, and the polarization conversion element 9 is emitted in the same polarization state.

The light beams emitted from the polarization conversion element 9 are all in the same polarization state, and this light beam is used for image display provided near the focal point (surface to be irradiated) of the condenser lens 10 via the condenser lens 10 and the condenser lens 14. Element 6 is illuminated.

At this time, the opening of each lens 4b of the first lens array 4 is rectangular, and the area to be illuminated by the image display element 6 is rectangular.

The image information formed on the image display element 6 is projected on the screen surface by the projection lens 15.

Incidentally, the polarization state may be arbitrarily determined without combining the P-polarized light and the S-polarized light in a plane direction orthogonal to the paper surface of FIG.

Since one unit of the polarization conversion element 9 corresponds to one array lens 5b of the second lens array 5, the pitch of the unit constituting the polarization conversion element 9 is also wide at the center and at the periphery. It is getting smaller.

At this time, as shown in FIGS. 1 and 2, the peripheral polarizing beam splitter 11a and the reflecting surface 12a
Only approximately the same pitch length is provided in the plate thickness direction (optical axis direction). This is a case where the inclination of the inclined portion (polarizing beam splitter, reflection surface) is set to approximately 45 degrees, but is not limited to this. Actually, in order to partially arrange the polarization reflection portion or the total reflection portion in the plate thickness direction, a masking process is performed on a glass plate serving as a substrate with a dielectric multilayer film or the like to form the above function. I have.

Next, a method for manufacturing the polarization conversion element 9 according to this embodiment will be described with reference to FIG. In FIG. 3, for convenience, a description will be given by stacking glass substrates at 45 degrees in a manufacturing stage and cutting the glass substrates vertically. For the unit 21 having a large pitch width (length 22a), that is, the unit thickness of the glass substrate is large, the polarizing film (polarizing beam splitter) or the reflecting film is deposited on substantially the entire slope. Incidentally, the reflective film may have the same film configuration as the polarizing film. On the other hand, with respect to the unit 23 having a small pitch width (length 24a), that is, the thin plate thickness of the glass substrate, the polarizing film or the reflective film is formed at the light incident side end as a length in the plate thickness direction. It has a length 24b substantially equal to the pitch 24a. The polarizing film of the unit having a narrow peripheral pitch is laminated so that the incident side ends of the reflective film are aligned, and the inclined portion is cut so as to be approximately 45 degrees with respect to the incident surface, thereby using a simple method. A polarization conversion element having a different unit pitch is produced. The half-wave plate 13 is disposed on the exit surface of the polarization conversion element thus created. The pitch of the half wavelength at this time is also wider at the center than at the periphery according to the unit pitch. In this embodiment, FIG. 4 is a schematic view showing a main part of a part of a second embodiment of a projection apparatus using the polarization conversion element of the present invention.

This embodiment is different from the first embodiment in FIG. 1 in that the polarization conversion element 9 is provided between the first lens array 4 and the second lens array 5, and the concave lens 8 is omitted. Only the difference is that the other basic configuration is exactly the same. The optical function is the same as that of the first embodiment.

FIG. 5 is a schematic diagram when the illumination device having the polarization conversion element of the present invention is applied to a three-plate type color liquid crystal projector. In the figure, each element 1, 2, 3,
4, 5, 8, 9, 10, and 13 are the same as those in FIG. 10
Reference numeral 1 denotes a color separation system that separates incident light into three color lights. The light beam from the condenser lens 10 is a dichroic mirror 102
Green light (G light) is transmitted, and blue light (B light) and red light (R
Light) is reflected.

Of the B light and the R light from the dichroic mirror 102, the R light is reflected by the dichroic mirror 103, and the B light is transmitted. The G light transmitted through the dichroic mirror 102 is the mirror 1
The liquid crystal panel 6G for G light is illuminated via the liquid crystal panel 04G and the condenser lens 14G. Dichroic mirror 102, 1
The R light reflected at 03 illuminates the R light liquid crystal panel 6R via the condenser lens 14R.

The B light reflected by the dichroic mirror 102 and transmitted through the dichroic mirror 103 illuminates the B light liquid crystal panel 6B via a lens 105, a mirror 106, a lens 107, a mirror 108, and a condenser lens 14B in order. I have.

Images based on the liquid crystal panels 6B, 6G, 6R are synthesized by a color synthesizing system 109 composed of dichroic prisms, and the synthesized images are projected on a screen (not shown) by a projection lens 15.

[0047]

According to the present invention, as described above, a plurality of optical units each including a polarization splitting surface and a reflecting surface are arranged at an appropriate pitch in a transparent substrate, and the shape of each optical unit is changed. By appropriately setting, it is possible to make the polarization direction uniform and to emit the light beam while effectively utilizing the incident light beam. For example, a polarization conversion element suitable as a lighting device and a liquid crystal projector for a liquid crystal display element and a polarization conversion element are used. A projection device can be achieved.

In addition, according to the polarization conversion element of the present invention,
Even if the central part and the peripheral part have different unit pitches, the thickness in the optical axis direction is not stepwise as in the conventional case, a glass plate serving as a material substrate is laminated, and only the parts necessary in advance, By forming the polarization splitting part and the reflecting part in advance, it is possible to easily manufacture.

In addition, since the polarization conversion element is for synthesizing P and S polarized lights by dividing a minute secondary light source image into units, the deviation between the polarization splitting surface and the reflecting surface is severe. It will be. On the other hand, according to the present invention, since there is no joining after cutting, it is possible to easily manufacture a polarization conversion element having high accuracy in terms of accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a projection apparatus having a polarization conversion element according to a first embodiment of the invention.

FIG. 2 is an enlarged explanatory view of the polarization conversion element in FIG.

FIG. 3 is an explanatory diagram of a method for manufacturing the polarization conversion element in FIG.

FIG. 4 is a schematic diagram of a main part of a second embodiment of the projection apparatus having the polarization conversion element of the present invention.

FIG. 5 is a schematic view of a main part of a third embodiment of the projection apparatus having the polarization conversion element of the present invention.

FIG. 6 is a schematic view of a main part of a conventional polarized lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal halide lamp 2 Light-emitting body 3 Ellipsoidal mirror (reflector) 4 1st lens array 5 2nd lens array 6 Light valve (liquid crystal display element) 8 Concave lens 9 Polarization conversion element 10 Convex lens 13 λ / 2 plate

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G02F 1/1335 530 G02F 1/1335 530 H04N 5/74 H04N 5/74 A

Claims (5)

[Claims] 1. A polarized light separating surface for separating incident light into reflected light and transmitted light whose polarizing planes are orthogonal to each other, and one of the lights separated by the polarized light separating surface is reflected and aligned in the same direction as the other light. The arrangement pitch of the optical units in a polarization conversion element in which an optical unit having a reflective surface is arranged at a predetermined pitch in a transparent substrate and a λ / 2 plate is arranged in one of the optical paths of the reflected light and the transmitted light Wherein the thickness of the substrate is different between the central portion and the peripheral portion of the substrate, and the thicknesses of the central portion and the peripheral portion in the light input / output direction are equal. 2. The polarization conversion element according to claim 1, wherein an arrangement pitch of the optical units is smaller in a peripheral portion than in a central portion of the substrate. 3. The polarized light according to claim 2, wherein the length of the optical unit at the peripheral portion of the substrate, which is obtained by projecting the polarization splitting surface and the reflection surface in the light traveling direction, is shorter than the thickness of the substrate. Conversion element. 4. A light source from a light source using the polarization conversion element according to claim 1 and a lens array in which a plurality of lenses are arranged corresponding to an arrangement pitch of an optical unit of the polarization conversion element. A lighting device, wherein a light beam is guided to a region to be illuminated. 5. A projection apparatus according to claim 4, wherein an image to be projected provided in an illuminated area is projected onto a predetermined surface by a projection optical system.