JP3658404B2 - Projection device - Google Patents

Description

  The present invention relates to a projection apparatus, and is particularly suitable for a liquid crystal projector that enlarges and projects an image of a liquid crystal display element (liquid crystal panel) onto a screen or a wall with a projection lens.

  Conventionally, various liquid crystal projectors have been proposed in which a liquid crystal panel is illuminated with 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 onto a screen or a wall by a projection lens.

  A TN type liquid crystal panel that can obtain a high-contrast image relatively easily utilizes the polarization characteristics of the liquid crystal. For this purpose, a polarizer and an analyzer are usually provided before and after the liquid crystal panel. Such polarizing filters have a characteristic of transmitting polarized light having a specific polarization direction of incident light and blocking polarized light having a polarization direction orthogonal to the polarization direction. For this reason, at least half of the light from the light source of the liquid crystal projector is blocked by the polarizer, and the brightness of the projected image is not sufficient.

  FIG. 23 is a schematic diagram of a main part of a projector proposed in Patent Document 1 that solves this brightness problem.

  The liquid crystal projector shown in FIG. 1 enters a light beam from a light source 201 into a polarization separation element 202 that separates randomly polarized light into two orthogonal polarization components (P-polarized light and S-polarized light) via an infrared cut filter 208 and a lens 207. I am letting. A half-wave plate 203 is provided in the optical path of S-polarized light that is reflected light out of the light beam that has passed through the polarization separation element 202. The polarization direction of the polarized light transmitted through the half-wave plate is rotated by 90 ° and emitted in the same manner as the P-polarized light that is transmitted light. Then, the optical paths of the two polarized lights from the polarization separation element 202 are overlapped on the liquid crystal panel 205 using the bending mirror 209 and the prism 204 so that all the light from the light source 201 can be used.

In the liquid crystal projector shown in the figure, the polarization separation element 202 needs to be approximately the same size as the lens 207 and the reflector 206, and is disadvantageous in that it becomes large and expensive, and further separates the light beam into two. Therefore, in order to make the illumination light beam approximately twice as large as the conventional light beam and to transmit all of the illumination light beam through the projection lens, the aperture diameter (F _NO ) of the projection lens is required to be twice or more that of the conventional design. There were also disadvantageous problems.

On the other hand, the illumination device for a liquid crystal projector of Patent Document 2 achieves a thinner polarization conversion unit by arraying a polarization separation element, a bending mirror, and a half-wave plate, respectively, and also increases the size of the illumination light beam. This is maintained at the same level as before, so that a conventional projection lens can be used.
JP-A 61-90584 JP-A-8-304739

  However, at present, there is a demand for an illuminating device or a projection device having a polarization conversion unit smaller than that of JP-A-8-304739.

  It is an object of the present invention to provide a projection apparatus such as a liquid crystal projector that can make the polarization conversion unit smaller than the conventional one, and can make the polarization conversion unit smaller than the conventional one.

An imaging apparatus according to a first aspect of the present invention is a projection apparatus including a plurality of image display elements and an illumination optical system that illuminates the plurality of image display elements with light from a light source.
The illumination optical system reflects the light from the light source and converts it into parallel light, a parabolic mirror that converts the parallel light from the parabolic mirror into convergent light, and the converged light in parallel. A first lens array that includes a concave lens that converts the light into a certain state and a plurality of first lenses having a positive refractive power, and that divides the light from the light source into a plurality of light fluxes, and a vicinity of the condensing position of the first lens array In addition, a second lens array having a plurality of second lenses having a positive refractive power and arranged corresponding to the plurality of first lenses, and a plurality of light beams respectively receiving the plurality of light beams from the second lens array. And a polarization conversion element array for converting each of the plurality of light beams into linearly polarized light polarized in a specific direction.

  Invention of Claim 2 is arrange | positioned between the color separation optical system which color-separates the light from the said polarization conversion element array in the invention of Claim 1, and the said polarization conversion element array, and the said color separation optical system, And a condenser lens having a positive refractive power, and a plurality of condenser lenses disposed on an optical path between the color separation optical system and each of the plurality of image display elements.

  According to a third aspect of the present invention, in the second aspect of the present invention, the surfaces of the plurality of condenser lenses on the side of the plurality of image display elements are flat.

  The invention of claim 4 is the invention of any one of claims 1 to 3, wherein the convex lens is a plano-convex lens, and a plane of the plano-convex lens faces the light source side.

The invention of claim 5 is the invention according to any one of claims 1 to 4, wherein the concave lens is a plano-concave lens, and the concave surface of the plano-concave lens faces the light source side.
According to a sixth aspect of the present invention, there is provided the color separation optical system according to any one of the first to fifth aspects, wherein the light emitted from the polarization conversion element array is color-separated, and the plurality of color separation optical systems. A plurality of condenser lenses disposed on an optical path between the plurality of image display elements; a condenser lens disposed between the polarization conversion element and the color separation optical system; and And a projection optical system for projecting light.

  According to the present invention, as described above, by setting each element, it is possible to achieve a projection apparatus such as a liquid crystal projector that can make the polarization conversion unit smaller than the conventional one and can make the polarization conversion unit smaller than the conventional one. .

  FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention. In the figure, reference numeral 230 denotes a part or all of the lighting device, and reference numeral 1 denotes a radiation light source such as a metal halide lamp. A parabolic mirror 2 is a reflector whose reflecting surface is a parabolic surface, and reflects the light beam from the light source 1 to convert it into parallel light, which is incident on the lens 3. The lens 3 has a positive refractive power.

  Reference numeral 4 denotes a first convex lens array, which is composed of a plate having a plurality of lenses 4a having a positive refractive power. A concave lens 5 has a negative refractive power. Reference numeral 6 denotes a second convex lens array, which is composed of a plate having lenses 6 a having positive refractive power corresponding to the individual lenses 4 a of the first convex lens array 4. Reference numeral 7 denotes a polarization conversion element array, which has the configuration shown in FIG. 2, and emits unpolarized (randomly polarized) light incident on each polarization conversion element as linearly polarized light polarized in a specific direction. As shown in FIG. 2, the polarization directions of the polarized light emitted from the respective polarization conversion elements coincide with each other.

  A condensing lens 8 has a positive refractive power. A condenser lens 9 condenses the illumination light on the entrance pupil (aperture stop) of the projection lens 11 via the panel 10. Reference numeral 10 denotes an image display element composed of a liquid crystal panel. The projection lens 11 has a positive refractive power, and magnifies and projects an image formed by the image display element 10 on a screen or a wall.

  The concave lens 5 makes a plurality of non-parallel light beams from the first convex lens array 4 parallel to each other and parallel to the optical axis so that the corresponding light beams in each polarization conversion element 7 are incident only on the light receiving portion 7i of the element 7. To make sure

  In the present embodiment, the light source 1 is preferably a point light source, but the light source 1 may have a spread. When the light source 1 has a spread, the light flux from the first convex lens array 4 also spreads, so that each lens of the first convex lens array 4 is located near the condensing position of each light flux by the first convex lens array 4. Is provided with a second convex lens array 6 in which convex lenses (field lenses) corresponding to the above are arranged.

  In the present embodiment, by providing the first convex lens array 4 in the optical path of the convergent light, the size of the secondary light source generated thereby is reduced, so that the size of the polarization conversion element array 7 is also the secondary light source. The outer diameter of each of the concave lens 5, the second convex lens array 6, and the polarization conversion element array 7 is made smaller than the outer diameter of the condensing mirror, thereby reducing the overall size of the apparatus. We are trying to make it.

  Here, what is described as a convex lens refers to a lens having positive refractive power. Therefore, in the present invention, a Fresnel lens having a positive refractive power and a refractive index distribution type lens having a positive refractive power which does not have a so-called convex surface can be used. What is described as a concave lens refers to a lens having negative refractive power. Therefore, in the present invention, a Fresnel lens having a negative refractive power and a gradient index lens having a negative refractive power which do not have a so-called concave surface can be used.

  Next, the configuration of the polarization conversion element array 7 will be described with reference to FIG. The polarization conversion element array 7 is an array of polarization conversion elements corresponding to the individual lenses 6a of the second convex lens array 6, and each element has a polarization separation surface 7a and S-polarized light reflected by the polarization separation surface 7a. And a half-wave plate (λ / 2 plate) 7c provided on the optical path of the P-polarized light transmitted through the polarization separation surface 7a or the optical path of the reflected S-polarized light. doing. In FIG. 2, a λ / 2 plate 7c is provided in the optical path of S-polarized light reflected by the polarization separation surface 7a.

  Next, the optical path from the light source 1 of this embodiment is demonstrated using FIG. 3 and FIG. In FIGS. 2 and 3, the light emitted from the light source 1 is reflected by the parabolic mirror 2 in a certain direction, becomes parallel light, enters the first lens array 4 via the convex lens 3, and is reflected in plural. The plurality of light beams form a plurality of condensing points in a range smaller than the outer diameter of the parabolic mirror 2 in the vicinity of the second convex lens array 6. The concave lens 5 guides the plurality of light beams from the first convex lens array 4 to the second convex lens array 6 after aligning the directions of the respective light beams incident on the polarization conversion element array 7 in parallel with each other. Each light beam transmitted through the second convex lens array 6 is incident on a corresponding polarization conversion element of the polarization conversion element array 7.

  The light beam incident on each polarization conversion element is separated into S-polarized light and P-polarized light whose polarization directions are orthogonal to each other by the polarization separation surface 7a (← →,...), Of which S reflected by the polarization separation surface 7a The polarized light (← →) is reflected by the reflecting surface 7b, transmitted through the half-wave plate 7c, and transmitted in the same polarization direction as the P-polarized light (· ). Accordingly, a plurality of light beams having the same polarization direction are emitted from the polarization conversion element array 7. A plurality of light beams from the polarization conversion element array 7 are combined on the image display element 10 by the condenser lens 8 and the condenser lens 9.

  The light beam transmitted through the image display element 10 is guided to the projection lens 11, and an image formed by the image display element 10 by the lens 11 is formed on a screen or a wall.

  4 and 5 are enlarged explanatory views of a part of FIG. 4 and 5 show optical paths in a normal case where the light flux from the light source 1 is spread. If the light flux from the light source 1 is spread, the angle of the light emitted from the parabolic mirror 2 is not uniform, the light flux collected by the first convex lens array 4 is also spread, and the imaging point is also widened.

  Therefore, in the present embodiment, the light beams from the respective lenses of the first convex lens array 4 are included by the action of the respective lenses 601 of the second convex lens array 6 provided in the vicinity of the condensing point of the plurality of light beams from the first convex lens array 4. The direction of a plurality of light beams whose traveling directions are different from each other is aligned to suppress the spread of the light flux.

  In the present embodiment, the convex lens 3 and the first convex lens array 4 may be an integrated lens La1 as shown in FIG. 6, or each lens of the first convex lens array 4 is decentered in the center direction as shown in FIG. Only the lens La2 having the above-described configuration may be used.

  Further, the concave lens 5 and the second convex lens array 6 may be only the lens La3 having a configuration in which each lens of the second lens array 6 is decentered in the peripheral direction as shown in FIG. Further, the second convex lens array 6 may be provided between the polarization conversion element array 7 and the condenser lens 8 as shown in FIG. 9, and further, each lens of the second convex lens array 6 is arranged in the center direction as shown in FIG. Only the lens La4 having a configuration decentered to the center may be used.

  In this embodiment, as shown in FIG. 22, a color separation system 101 including a plurality of dichroic mirrors or the like is provided between the condenser lens 8 and the image display element 10, and the image display element 10 and the projection lens 11 are provided. By providing the color composition system 109 including a dichroic prism or the like, the image display element 10 can be used as it is for a three-plate liquid crystal projector using three RGB display elements.

  FIG. 11 is a schematic view of the essential portions of Embodiment 2 of the present invention. In the figure, reference numeral 230 denotes a part or all of the lighting device, and the same elements as those shown in FIG. This embodiment omits the lens 3 as compared with the first embodiment of FIG. 1, and instead of the parabolic mirror 2, the light source 1 placed at the focal position by an elliptical mirror, which is a reflector 2 whose reflecting surface is an elliptical surface. The light beam is converted into a convergent light beam, and the converged light beam is incident on the first convex lens array 4, and the other configurations are the same.

  FIG. 12 is a schematic view of the essential portions of Embodiment 3 of the present invention. In the figure, reference numeral 1 denotes a radiation light source such as a metal halide lamp. Reference numeral 2 denotes an elliptical mirror which is a reflector whose reflecting surface is an elliptical surface. The mirror 2 reflects and condenses the light beam from the light source 1 placed at the focal position to convert it into a convergent light beam, which is incident on the concave lens 5. Yes. The concave lens 5 has a negative refractive power.

  Reference numeral 4 denotes a first convex lens array, which is composed of a plate in which a plurality of convex lenses 4a having positive refractive power are arranged. Reference numeral 6 denotes a second convex lens array, which is composed of a plate in which a plurality of convex lenses 6 a having positive refractive power corresponding to the individual lenses 4 a of the first lens array 4 are arranged. Reference numeral 71 denotes a polarization conversion element array having the configuration shown in FIG. 14, which converts incident non-polarized light (random polarized light) into linearly polarized light polarized in a specific direction and emits it. A condensing lens 8 has a positive refractive power. A condenser lens 9 condenses the illumination light on the entrance pupil (aperture stop) of the projection lens 11 via the liquid crystal panel 10. Reference numeral 10 denotes an image display element composed of a liquid crystal panel. The projection lens 11 has a positive refractive power, and magnifies and projects the projection image formed by the image display element 10 on a screen or a wall.

  Next, the configuration of the polarization conversion element array 71 will be described with reference to FIG. Each polarization conversion element of the polarization conversion element array 71 is provided corresponding to each lens 6a of the second convex lens array 6, and this element includes a polarization separation surface 71a and S-polarized light reflected by the polarization separation surface 71a. A reflection surface 71b that bends the optical path, a first half-wave plate 71c that is provided in the optical path of P-polarized light that has passed through the polarization separation surface 71a, and a second half that is provided in the optical path of S-polarized light. A single wavelength plate (λ / 2 plate) 71d is provided. As a result, the emitted light beams are emitted in the same polarization state.

  Next, the optical path of this embodiment will be described with reference to FIGS. 13 and 14, the light emitted from the light source 1 is reflected by the elliptical mirror 2 in a specific direction (the direction in which the image display element 10 is present), converted into convergent light, and enters the concave lens 5. The concave lens 5 converts convergent light into parallel light. The parallel light from the concave lens 5 enters the first convex lens array 4 and is divided into a plurality of light beams by the array 4, and the plurality of light beams are larger than the outer diameter of the elliptical mirror 2 that is close to the second convex lens array 6. The light is incident on the second convex lens array 6 while forming a plurality of condensing points in a small range. A plurality of light beams that have passed through the second convex lens array 6 are incident on the polarization conversion element array 71. The light beam incident on each polarization conversion element of the polarization conversion element array 71 is separated into S-polarized light and P-polarized light whose polarization directions are orthogonal to each other by the polarization separation surface 71a (← →,...), Of which the polarization separation surface 71a The reflected S-polarized light (← →) is reflected by the reflecting surface 71b and transmitted through the second half-phase plate 71d to be converted into linearly polarized light (/) polarized in an oblique direction and emitted. . The P-polarized light (·) transmitted through the polarization splitting surface 71a is transmitted through the first half-wave plate 71c, thereby being deflected in an oblique direction (the same direction as the S-polarized light) (/). It becomes and it injects.

  As a result, a plurality of light beams having the same polarization direction are emitted from the polarization conversion element array 71. A plurality of light beams from the polarization conversion element array 71 are combined on the image display element 10 by the condenser lens 8 and the condenser lens 9.

  The light beam transmitted through the image display element 10 forms an image formed by the image display element 10 guided to the projection lens 11 on the screen or wall by the projection lens 11.

  In this embodiment, the concave lens 5 and the first convex lens array 4 may be constituted by a lens La5 integrated as shown in FIG. Further, as shown in FIG. 16, each lens of the first lens array may be constituted by a lens La6 decentered in the central direction.

  FIG. 17 is a schematic view of the essential portions of Embodiment 4 of the present invention. In the figure, reference numeral 230 denotes a part or all of the lighting device, and reference numeral 1 denotes a radiation light source such as a metal halide lamp. A parabolic mirror 2 is a reflector whose reflecting surface is a parabolic surface. The light beam from the light source 1 at the focal position is reflected and converted into parallel light, and is incident on the first convex lens array 81. The first convex lens array 81 is composed of a plate in which a plurality of lenses 81a having positive refractive power are arranged.

  A concave lens 5 has a negative refractive power. Reference numeral 6 denotes a second convex lens array. A polarization conversion element array 82 has the configuration shown in FIG. 18 and converts incident non-polarized light (random polarized light) into linearly polarized light polarized in a specific direction and emits it. Reference numeral 8 denotes a condenser lens. A condenser lens 9 condenses the illumination light on the entrance pupil (aperture stop) of the projection lens 11.

  Reference numeral 10 denotes an image display element composed of a liquid crystal panel. The projection lens 11 has a positive refractive power, and magnifies and projects the projection image formed by the image display element 101 on the screen surface.

  Next, the configuration of the polarization conversion element array 82 will be described with reference to FIG. As shown in FIG. 18, the polarization conversion element array 82 includes one plate-like member 82d having a chevron-shaped surface and a plane, four rod-like prisms 82b, and two half-phase plates 82c. Each member is joined by providing a polarization separation surface 82a on one surface of each rod prism 82b and providing a half-wave plate 82c in the optical path of S-polarized light or P-polarized light separated by the polarization separation surface 82a. And make up.

  In FIG. 18, a half-wave plate 82c is sandwiched between a rod-shaped prism and a mountain-shaped plate member so that the half-wave plate 82c receives S-polarized light. With such a configuration, the polarization separation surfaces 82a are not formed at equal intervals. However, as shown in FIG. 19, the optical axis O of the lens 81a is set to the center of each lens 81a. By decentering the configuration, the condensing point by each lens 81a of the first convex lens array 81 can correspond to the corresponding polarization separation surface 82a as shown in FIG.

  In FIG. 20, the light emitted from the light source 1 is reflected by the parabolic mirror 2 in a certain direction to be converted into parallel light, enters the first convex lens array 81, and is converted into a plurality of light beams by the array 81. The plurality of light fluxes are divided to form a plurality of condensing points in a range smaller than the outer diameter of the reflector 2 near the second convex lens array 6. The concave lens 5 converts a plurality of light beams from the first convex lens array 5 into parallel light beams and guides them to the second convex lens array 6. The light beam transmitted through the second convex lens array 6 is incident on the polarization conversion element array 82.

  The light beam incident on each polarization conversion element of the polarization conversion element array 82 is separated into S-polarized light and P-polarized light whose polarization directions are orthogonal to each other by the polarization separation surface 82a (← →,...). The reflected S-polarized light (← →) is reflected by the reflecting surface 82e and transmitted through the half phase plate 82c, so that the linearly polarized light is polarized in the same direction as the P-polarized light transmitted through the polarization separating surface 82a. The light is converted into light (·) and emitted from the polarization conversion element 82 as a plurality of linearly polarized light having the same polarization direction. A plurality of light beams from the polarization conversion element 82 are combined on the image display element 10 by the condenser lens 8 and the condenser lens 9.

  The light beam transmitted through the image display element 10 is guided to the projection lens 11. An image formed on the image display element 10 is formed on a screen or a wall by a projection lens 11.

  FIG. 21 is a schematic view of the essential portions of Embodiment 5 of the present invention. In the present embodiment, the second concave lens array 91 and the polarization conversion element array 92 are different in shape from the fourth embodiment of FIG. 17, and a polarizing plate 93 is disposed between the condenser lens 9 and the image display element 10. The only difference is that the rest of the configuration is the same. Here, the polarization conversion element array 92 is obtained by halving the array 82 of the fourth embodiment in the array direction.

  The polarization conversion element array 92 in this embodiment does not correspond to all the individual lenses constituting the second convex lens array 91, but performs polarization conversion only on a light beam that passes through the central lens array of the second lens array 91. Yes. This is because the intensity of the parallel light beam from the parabolic mirror 2 is concentrated in the central portion, so that polarization conversion is performed so that only the central portion of the parallel light beam is a predetermined linearly polarized light. The portion is converted into linearly polarized light.

  At this time, in the second convex lens array 91, the central lens size a21 for receiving the central light for polarization conversion is set to be larger than the peripheral lens size a22 for more efficient polarization conversion. To be able to.

  Further, in such a configuration, a light beam that is not subjected to polarization conversion illuminates the liquid crystal panel 10 in a non-polarized state as it is, so a polarizing plate 93 is provided in the vicinity of the panel. With such a configuration, the number of parts used for the polarization conversion element 92 can be reduced to, for example, half, which facilitates downsizing.

  The illumination devices of Embodiments 2 to 4 described above can also be applied to the liquid crystal projector of FIG.

Schematic diagram of main parts of Embodiment 1 of the present invention 1 is an explanatory diagram of a part of FIG. Optical path explanatory drawing of Embodiment 1 of this invention 3 is an enlarged explanatory view of a part of FIG. 4 is an enlarged explanatory view of a part of FIG. Explanatory drawing of other embodiment of the one part of FIG. Explanatory drawing of other embodiment of the one part of FIG. Explanatory drawing of other embodiment of the one part of FIG. Explanatory drawing of other embodiment of the part of FIG. Explanatory drawing of other embodiment of the one part of FIG. Main part schematic of Embodiment 2 of this invention Main part schematic of Embodiment 3 of this invention Optical path explanatory drawing of Embodiment 3 of this invention 13 is an explanatory diagram of a part of FIG. Explanatory drawing of other embodiment of the part of FIG. Explanatory drawing of other embodiment of the part of FIG. Main part schematic of Embodiment 4 of this invention 17 is an explanatory diagram of a part of FIG. 17 is an explanatory diagram of a part of FIG. Optical path explanatory drawing of Embodiment 4 of this invention Main part schematic of Embodiment 5 of this invention Schematic of a three-plate color liquid crystal projector to which the illumination device 230 of the present invention is applied Schematic diagram of the main parts of a conventional lighting device

Explanation of symbols

1 Light source lamp 2 Reflector (reflection mirror)
3 Lens 4, 21, 81 First convex lens array 5 Concave lens 6 Second convex lens array 7, 22, 31, 41, 71, 82 Polarization conversion element 8 Condensing lens 9 Condenser lens 10 Image display element 11 Projection lens 11a Entrance pupil 7a Polarization separating surface 7b Reflecting mirror 7c λ / 2 plate

Claims (6)

A projection device having a plurality of image display elements and an illumination optical system that illuminates the plurality of image display elements with light from a light source,
Parallel the illumination optical system, a parabolic mirror that converts to a parallel light reflecting light from the light source, and a convex lens that converts the collimated light from the parabolic surface mirror convergent light, the convergent light A first lens array that includes a concave lens that converts the light into a certain state and a plurality of first lenses having a positive refractive power, and that divides the light from the light source into a plurality of light fluxes, and a vicinity of the condensing position of the first lens array In addition, a second lens array having a plurality of second lenses having a positive refractive power and arranged corresponding to the plurality of first lenses, and a plurality of light beams respectively receiving the plurality of light beams from the second lens array. And a polarization conversion element array that converts each of the plurality of light beams into linearly polarized light polarized in a specific direction.   A color separation optical system that separates light from the polarization conversion element array; a condenser lens that is disposed between the polarization conversion element array and the color separation optical system and has a positive refractive power; and the color separation. The projection apparatus according to claim 1, further comprising: a plurality of condenser lenses disposed on an optical path between an optical system and each of the plurality of image display elements. The projection apparatus according to claim 2 , wherein surfaces of the plurality of condenser lenses on the side of the plurality of image display elements are flat surfaces.   The projection apparatus according to claim 1, wherein the convex lens is a plano-convex lens, and a plane of the plano-convex lens faces the light source side. 5. The projection apparatus according to claim 1, wherein the concave lens is a plano-concave lens, and a concave surface of the plano-concave lens faces the light source. A color separation optical system that separates light emitted from the polarization conversion element array, a plurality of condenser lenses disposed on an optical path between the color separation optical system and each of the plurality of image display elements, and 6. A condenser lens disposed between a polarization conversion element and the color separation optical system, and a projection optical system that projects light from the plurality of image display elements . The projection device according to any one of the above.