JP3633471B2 - Projection-type image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection device for projecting an image on a screen using a light valve element such as a liquid crystal panel or a reflective video display device, for example, a liquid crystal projector device, a reflective video display projector device, a projection type rear projection. The present invention relates to a projection display apparatus such as a television.
[0002]
[Prior art]
Paper Gary D. Sharp et al. In “Throughput Color Switch for Sequential Color Projection” SID 2000 DIGEST, a polarization rotation control element capable of polarizing the optical axis in a specific wavelength band, for example, rotating the polarization axis of R (red) light that is P-polarized light. R-polarization rotation control element for converting to S-polarized light, G-polarization rotation control element for rotating the polarization axis of G (green) light that is P-polarized light and converting it to S-polarized light, B (blue) for P-polarized light ) Electronic time-division optical characteristic switching element (hereinafter referred to as optical) that can periodically switch the color incident on the liquid crystal panel using the B polarization rotation control element that rotates the polarization axis of the light and converts it into S-polarized light. It is referred to as a characteristic switching element).
[0003]
In the above paper, the light from the light source is reflected by the reflector, passed through the first lens array and the second lens array, converted into P-polarized light by the polarizing beam splitter, and then passed through the condenser lens. , R light, B light and G light are sequentially output after entering the optical characteristic switching element, transmitted through a polarization beam splitter (hereinafter referred to as PBS), and incident on a reflective liquid crystal panel. It is shown that when the video signal is white display, the P-polarized light is converted to S-polarized light by the liquid crystal panel and reflected by PBS, and the reflected light is obtained through the projection lens. Yes.
[0004]
[Problems to be solved by the invention]
As shown in the prior art, when the time division optical characteristic switching element is placed in the vicinity of the panel after exiting the condenser lens, in-plane non-uniformity such as the thickness, material component, stress, etc. Therefore, when there is in-plane non-uniformity in optical performance, illuminance unevenness and color unevenness due to the in-plane non-uniformity are easily mapped onto the panel. For this reason, the in-plane non-uniformity of the time-division optical characteristic switching element directly causes illuminance unevenness and color unevenness on the screen.
[0005]
[Means for Solving the Problems]
By placing the electronic time-division optical property switching element closer to the lamp than the condensing lens that collects light on the panel, projection with less illuminance unevenness and color unevenness without changing the arrangement of the lens, etc. A type display device can be provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0007]
FIG. 1 is an optical configuration diagram of an embodiment of a projection-type image display device according to the present invention, and shows a single-plate projection-type display device using one reflective liquid crystal panel 12 as a light valve. In the above apparatus, the color is displayed by periodically changing the color incident on the liquid crystal panel.
[0008]
The light emitted from the light source 7 is collected by an ellipsoidal, parabolic or aspherical reflector 1, and a plurality of light collections provided in a rectangular frame having substantially the same size as the exit aperture of the reflecting mirror reflector 1. Consists of a lens cell, condenses the light emitted from the reflector 1, enters the first array lens 2 for forming a plurality of secondary light source images, and further comprises a plurality of condensing lens cells, It passes through the second array lens 3 that is arranged in the vicinity where the plurality of secondary light source images are formed and that forms the individual lens images of the first array lens 2 on the liquid crystal panel 12.
[0009]
The outgoing light is a polarization beam splitter constituted by a row of rhombus prisms of approximately ½ size of each lens width arranged so as to match the lateral pitch of each lens optical axis of the second array lens 3. 4 is incident. The prism surface is provided with a polarizing beam splitter film 4a, and incident light is separated into P-polarized light and S-polarized light by the polarizing beam splitter film 4a. The P-polarized light passes through the polarizing beam splitter film as it is, and the polarization direction is rotated by 90 ° by the λ / 2 phase difference plate 4a provided on the exit surface of the prism, and is converted into S-polarized light and emitted. On the other hand, the S-polarized light is reflected by the polarization beam splitter film, reflected once again in the original optical axis direction in the adjacent rhomboid prism, and then emitted as S-polarized light.
[0010]
The purity of the degree of polarization is increased by the specific polarization by the polarizing plate 8a, and enters the electronic time-division optical characteristic switching element 9. Thereafter, the light enters the condenser lens 5. The condenser lens 5 includes a collimator lens 5a that condenses light on the panel and a condenser lens 5b that converts light incident on the panel into a telecentric state. In order to make the optical engine compact, the optical path is bent by the reflection mirror 14.
[0011]
The time division optical characteristic switching element 9 converts the output light having different polarization axes into a specific wavelength band and a different wavelength band, and periodically switches the wavelength band. For example, the light emitted from the time-division optical characteristic switching element 9 includes red light for S polarization, blue light and green light for P polarization, blue light for S polarization at the next time point, red light and green light for P polarization, and the next At that time, green becomes S-polarized light, blue and red become P-polarized light, and the above three states are periodically switched.
[0012]
In the subsequent optical path, only a specific polarization axis, here, S-polarized light is reflected, and P-polarized light is incident on a rectangular parallelepiped polarizing beam splitter 10 formed with a polarizing beam splitter film 10a, so that only red is reflected at a certain time. Then, only blue and then green will be reflected. Since the unnecessary color is P-polarized light, it passes through the polarizing beam splitter film 10 a and does not enter the liquid crystal panel 12. As described above, after time-division color separation is performed, the light irradiates the reflective liquid crystal panel 12 which is a modulation element. Here, a λ / 4 phase difference plate 11 that can improve contrast by phase compensation is disposed in front of the liquid crystal panel 12.
[0013]
The reflective liquid crystal panel 12 is provided with a number of liquid crystal display units corresponding to the pixels to be displayed (for example, horizontal 1024 pixels and vertical 768 pixels). Then, the polarization angle of each pixel of the liquid crystal panel 12 changes in accordance with a signal input from the outside, and finally light that is orthogonal to the incident polarization direction is emitted. Light is detected by the film 10a. The amount of light passing through the polarizing beam splitter film 10a and the amount of light detected by the light having polarized light at an intermediate angle are determined by the degree of polarization of the polarizing beam splitter film 10a. In this way, an image according to the external signal is projected. At this time, when the reflective liquid crystal panel 12 performs black display, the rectangular parallelepiped polarization beam splitter 10 has the polarization direction equivalent to that of the incident light and is returned to the light source side as it is along the incident light path.
[0014]
Thereafter, the light that is the image passes through the projection lens 13 that is a zoom lens, for example, and reaches the screen. An image formed on the reflective liquid crystal panel 12 by the projection lens 13 is enlarged and projected on a screen to function as a display device. In this video liquid crystal display device, the light source 7 and the liquid crystal panel 12 are driven by a power source.
[0015]
As described above, the electronic time-division optical characteristic switching element 9 is placed closer to the lamp 1 than the condensing lens that condenses the light on the liquid crystal panel 12 by the array lenses 2 and 3. Even if there is in-plane non-uniformity in optical performance due to in-plane non-uniformity such as thickness, material composition, stress, etc. of the characteristic switching element 9, illuminance unevenness and color non-uniformity due to the in-plane non-uniformity described above. There is no mapping on the panel. Therefore, the in-plane non-uniformity of the time division optical characteristic switching element 9 can reduce the influence on the illuminance unevenness and color unevenness on the screen.
[0016]
The action of reducing unevenness in illuminance and color unevenness on the screen due to in-plane non-uniformity of the time-division optical characteristic switching element by the array lenses 2 and 3 and the condenser lens 5 will be described. The array lenses 2 and 3 finely divide the distribution of light having uneven illuminance and uneven color caused by the in-plane non-uniformity of the time-division optical characteristic switching element into the number of cells of the array lens. Thereafter, the light is condensed on the panel surface by a condensing lens, thereby acting to obtain a uniform illuminance and color distribution on the liquid crystal panel 12.
[0017]
Depending on the angle, the electronic time-division optical characteristic switching element 9 changes the purity of the color of the emitted light, mixes other color components to generate color mixing, or the half-value wavelength during color separation. There may be a problem that the purity of the color on the screen is deteriorated due to the occurrence of the shift. Therefore, reducing the angle component of the light incident on the time division optical characteristic switching element 9 as much as possible is a method for obtaining better color performance on the screen. The angle component of incident light is smaller at the position in front of the condenser lens 5 than at the position after the condenser lens 5. By arranging the time-division optical characteristic switching element 9 at this position, the color purity can be improved. Can be better.
[0018]
Further, as shown in the figure, the polarizing plate 8a and the time-division optical characteristic switching element 9 are arranged close to each other in order to be cooled by one air cooling fan 6. However, since the polarizing plate 8a dissipates heat by absorbing heat, the polarizing plate 8a and the time-division optical characteristic switching element 9 need to be separated by 3 mm or more so that a sufficient flow path by an air cooling fan can be secured between them.
[0019]
By the way, from the viewpoint of energy saving and noise reduction, the number of rotations of the cooling fan is desired to be as low as possible. However, since the cooling effect is reduced when the rotational speed is lowered, more efficient cooling is necessary for sufficient cooling. For this purpose, it is preferable that wind strikes as large a surface area as possible of the polarizing plate 8a and the time-division optical characteristic switching element 9. Therefore, the cooling fan 6 needs to be arranged at a position where air can be sent between the polarizing plate a and the time-division optical characteristic switching element 9. For example, as shown in the figure, the cooling fan 6 is disposed at a position where air is blown from the side of the polarizing plate 8a and the time division optical characteristic switching element 9.
[0020]
In order to suppress the temperature rise of the time-division optical characteristic switching element 9 due to radiant heat accompanying heat absorption by the polarizing plate 8a, the surface of the polarizing plate 8a on which the film is pasted is disposed toward the light source side.
[0021]
Alternatively, as a heat countermeasure for the polarizing plate 8a itself, the surface on which the polarizing film is attached may be directed toward the liquid crystal panel 12, the back surface thereof may be directed toward the light source side, and UV and IR cuts may be provided on the back surface. If necessary, a dichroic cut for cutting unnecessary color light for obtaining better color purity on the screen is provided on the back surface. By providing the dichroic cut on the optical component at a position away from the liquid crystal panel as in this configuration, the cut light does not enter the projection lens and the contrast is not deteriorated.
[0022]
FIG. 2 is a diagram showing a second embodiment according to the present invention. A polarizing beam splitter 4 is disposed after the reflector 1, and a time-division optical characteristic switching element 9 is disposed thereafter. In the polarizing beam splitter 4 of FIG. 1, every other effective incident aperture is present, so that the light flux entering the intervening line is not effectively utilized. In the present embodiment, the effective incident aperture of the polarizing beam splitter 4 has an incident aperture substantially equivalent to that of the reflector 1, and therefore, all the incident light from the reflector 1 can be utilized, so that it is brighter on the screen. Illuminance can be obtained. Further, by improving the film characteristics of the polarizing beam splitter 4, the polarizing plate 8a in front of the time division optical characteristic switching element 9 can be eliminated. In such a case, since there is no absorption loss due to the polarizing plate 8a, a brighter illuminance can be obtained on the screen. In addition, heat is not generated by the polarizing plate 8a, and it is not necessary to install a cooling fan, which makes it possible to save energy and reduce noise. The first array lens 2 and the second array lens 3 are disposed after the time-division optical characteristic switching element 9, and then a condenser lens is disposed. The structure and operation of the other parts are the same as in FIG.
[0023]
FIG. 3 is a diagram showing a third embodiment according to the present invention. This uses a time-division optical characteristic switching element 9 using a diffraction phenomenon as another method for color separation. The ON light 6a shown by the solid line in FIG. 3 is reflected by the time division optical characteristic switching element 9 and is emitted toward the optical path reaching the liquid crystal panel 12, while the OFF light 6b shown by the broken line is time division. The light passes through the optical characteristic switching element and is emitted to the black light-shielding plate 15 in order to prevent a decrease in contrast. At some point, the ON light 6a is blue, and the OFF light is green and red. At the next point, the ON light 6a is red, and the OFF light is green and blue. At the next point, the ON light 6a is green and the OFF light is red. Color separation is performed by switching the above three states as blue and blue. The structure and operation of the other parts are the same as in FIG.
[0024]
FIG. 4 is a diagram showing a fourth embodiment according to the present invention. This is a two-plate projection type image display apparatus using two reflective liquid crystal panels 12a and 12b.
[0025]
One color is displayed on one panel 12a, and two colors are alternately displayed on the other panel 12b. For example, blue is assigned to one panel 12a, and red and green are assigned to the other panel 12b. Of course, one panel 12a may be red, the other panel 12b may be green and blue, one panel 12a may be green, and the other panel 12b may be red and blue.
[0026]
Hereinafter, a description will be given by using a combination of green on one panel 12a and red and blue on the other panel 12b. The light source 7, the reflector 1, the first array lens 2, the second array lens 3, and the polarization beam splitter 4 have the same functions as in the embodiment of FIG.
[0027]
Here, the electronic time division optical characteristic switching element 9 converts the output light having different polarization axes into a specific wavelength band and a wavelength band different from the specific wavelength band, and periodically switches the wavelength band. Specifically, the wavelength band is divided and switched periodically. For example, the light emitted from the element 9 is always emitted with P-polarized light for green, red for P-polarized light, blue for S-polarized light at one point, blue for P-polarized light, and red for S-polarized light at the next time point. Switch states periodically.
[0028]
Thereafter, the light passes through a specific polarization axis, here, a color separation polarizing beam splitter that transmits only P-polarized light or the color separation polarizing plate 8b, so that only green and blue are transmitted at a certain point, and then only green and red are transmitted. As a result, time-division color separation is performed.
[0029]
Next, the specific wavelength selection wave plate 16a converts the polarization direction of light in a predetermined wavelength band. In this case, the specific wavelength selection wave plate 16a converts green from P-polarized light to S-polarized light, and green is emitted as P-polarized light, and red and blue are emitted as S-polarized light. Thereafter, green that is S-polarized light is reflected by the polarization beam splitter film 10a and emitted to the liquid crystal panel 12b, and red and blue that are P-polarized light are transmitted and alternately emitted to the liquid crystal panel 12a. The time-separated color-separated light enters the reflective liquid crystal panel as readout light, and is modulated, reflected, and emitted by the liquid crystal panel. Thereafter, the light as an image is synthesized again by the polarization beam splitter film 10a. The light passes through the projection means 13, which is a zoom lens, and reaches the screen. The image formed on the reflective liquid crystal panels 12a and 12b by the projection means 13 is enlarged and projected on a screen to function as a display device.
[0030]
A specific wavelength selection wavelength plate 16b that converts the polarization direction of a specific wavelength band is inserted on the output side of the rectangular parallelepiped polarization beam splitter 10 to align the polarization directions of all red, green, and blue light. Thereby, use of the output polarizing plate 8c and the polarizing screen becomes possible. Moreover, since the output polarizing plate 8c is provided, the purity of the polarization degree can be improved and the contrast can be improved. Compared with the other embodiments, this configuration can obtain a brighter illuminance on the screen as much as one liquid crystal panel is used.
[0031]
FIG. 5 is a diagram showing a fifth embodiment according to the present invention. A polarizing plate 8a is disposed after the reflector 1, and a time-division optical characteristic switching element 9 is disposed thereafter. Thereafter, the first array lens 2 and the second array lens 3 are arranged. Depending on the angle, the electronic time-division optical characteristic switching element 9 changes the purity of the color of the emitted light, mixes other color components to generate color mixing, or the half-value wavelength during color separation. There may be a problem that the purity of the color on the screen is deteriorated due to the occurrence of the shift. Therefore, reducing the angle component of the light incident on the time division optical characteristic switching element 9 as much as possible is a method for obtaining better color performance on the screen. In this configuration, since it is immediately after the reflector 1, the angle component of the incident light is the smallest in the optical path after the reflector 1, and the time-division optical characteristic switching element 9 is arranged at this position, so that it can be compared with the other embodiments. The purity of the color can be improved. The structure and operation of the other parts are the same as in FIG.
[0032]
【The invention's effect】
By placing the electronic time-division optical characteristic switching element on the lamp side with respect to the condensing lens that functions to condense on the panel, it is possible to improve illuminance unevenness and color unevenness without changing the arrangement of the lens and the like.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a projection type liquid crystal display device showing a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a projection type liquid crystal display device showing a second embodiment of the present invention.
FIG. 3 is a configuration diagram of a projection type liquid crystal display device showing a third embodiment of the present invention.
FIG. 4 is a configuration diagram of a projection type liquid crystal display device showing a fourth embodiment of the present invention.
FIG. 5 is a configuration diagram of a projection type liquid crystal display device showing a fifth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reflector 2 ... 1st array lens 3 ... 2nd array lens 4 ... Polarizing beam splitter 4a ... (lambda) / 2 phase difference plate 5 ... Condensing lens 5a ... Collimator lens 5b ... Condenser lens,
6a ... ON light 6b ... OFF light 7 ... Light source 8a ... Incident side polarizing plate 8b ... Color separation polarizing plate 8c ... Outgoing side polarizing plate 9 ... Electronic time-division optical characteristic switching element 10 ... Cuboid polarization beam splitter 10a ... Polarization beam splitter film 11 .lamda. / 4 phase difference plates 12, 12a, 12b ... reflection type liquid crystal panel 13 ... projection lens 14 ... reflection mirror 15 ... light shielding plate 16a ... incident side specific wavelength selection polarization conversion element 16b ... output side specific wavelength Selective polarization conversion element

Claims (4)

A light source unit that emits light, a video display element that is a light valve means for forming an optical image corresponding to a video signal from light emitted from the light source unit, and light emitted from the light source unit on the video display element Projection-type video comprising: an illumination optical system to be projected; projection means for projecting light emitted from the video display element; and a time-division switching system capable of periodically switching the wavelength band of light incident on the video display element A display device,
The illumination optical system includes:
A first array lens comprising a plurality of condensing lens cells, condensing light from the light source unit to form a plurality of secondary light source images;
A second array lens composed of a plurality of condensing lens cells, disposed in the vicinity of the plurality of secondary light source images formed, and forms an individual lens image of the first array lens;
In the vicinity of the second array lens, a polarization beam splitter that separates light into P-polarized light and S-polarized light, and a polarization direction of either P-polarized light or S-polarized light that is output from the polarization beam splitter. A polarization conversion element comprising a λ / 2 phase difference plate for rotation, and a reflection part for reflecting any one of the P-polarized light and the S-polarized light;
A condensing lens for condensing light on the image display element;
The wavelength band time-division switching system includes a polarizing plate and an electronic time-division optical property switching element into which light having a higher degree of polarization is incident by the polarizing plate,
The electronic time-division optical characteristic switching element is disposed closer to the light source unit than the condenser lens and closer to the video display element than the second array lens and the polarization conversion element. Projection-type image display device. A light source unit that emits light, a video display element that is a light valve means for forming an optical image corresponding to a video signal from light emitted from the light source unit, and light emitted from the light source unit on the video display element Projection-type video comprising: an illumination optical system to be projected; projection means for projecting light emitted from the video display element; and a time-division switching system capable of periodically switching the wavelength band of light incident on the video display element A display device,
The illumination optical system includes:
A first array lens comprising a plurality of condensing lens cells, condensing light from the light source unit to form a plurality of secondary light source images;
A second array lens composed of a plurality of condensing lens cells, disposed in the vicinity of the plurality of secondary light source images formed, and forms an individual lens image of the first array lens;
In the vicinity of the second array lens, a polarization beam splitter that separates light into P-polarized light and S-polarized light, and a polarization direction of either P-polarized light or S-polarized light that is output from the polarization beam splitter. A polarization conversion element comprising a λ / 2 phase difference plate for rotation, and a reflection part for reflecting any one of the P-polarized light and the S-polarized light;
A condensing lens for condensing light on the image display element;
The wavelength band time division switching system is:
A polarizing plate;
Light from the polarizing plate is incident, and the light of a specific wavelength band and the light of a different wavelength band are converted into outgoing light having different polarization directions and the specific wavelength band is periodically switched. A time-division optical property switching element,
The electronic time-division optical characteristic switching element is disposed closer to the light source unit than the condenser lens and closer to the video display element than the second array lens and the polarization conversion element. Projection-type image display device. 3. The projection type image display according to claim 1, wherein the wavelength band time division switching system further includes a polarizing element that transmits or reflects only substantially linearly polarized light of a specific wavelength band. apparatus. 6. The projection type image display device according to claim 5, wherein the electronic time-division optical characteristic switching element and at least one polarizing element can be cooled by a single air-cooling fan.

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