JP3914834B2 - Polarization conversion element and liquid crystal projector including the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarization conversion element that separates an incident light beam into two light beams having different polarization components and converts the separated polarization component of one light beam into a polarization component of the other light beam. Furthermore, the present invention relates to a liquid crystal projector using the polarization conversion element.
[0002]
[Prior art]
The polarization conversion element can be used for illumination devices such as a liquid crystal display and a liquid crystal projector because it can align the polarization components and can improve the utilization efficiency of light from the light source.
[0003]
FIG. 9 schematically shows a schematic configuration of a liquid crystal projector including a polarization conversion element. This liquid crystal projector includes a light source lamp 1, and lens arrays 2 a and 2 b, a polarization conversion element 200, a field lens 5, and a mirror 6 are arranged in this order in the traveling direction of a light beam emitted from the light source lamp 1. The polarization conversion element 200 includes a polarization beam splitter (PBS) 3 that separates an incident light beam into two light beams having different polarization components, and a phase difference plate 4 that converts the polarization component of the separated light beam into the other polarization component. Become.
[0004]
A dichroic mirror 7 a that transmits a red (R) color component and reflects a blue (B) component and a green (R) component is disposed in the traveling direction of the light beam reflected by the mirror 6. A mirror 9c is arranged in the traveling direction of the light beam (R) transmitted through the dichroic mirror 7a, and the incident polarizing plate 10R, the liquid crystal panel 11R, and the outgoing polarizing plate 12R are disposed in the traveling direction of the light beam reflected by the mirror 9c. Are arranged in this order. A dichroic mirror 7b that transmits the blue (B) component and reflects the green (R) component is disposed in the traveling direction of the light beam (BR) reflected by the dichroic mirror 7a.
[0005]
An incident polarizer 10G, a liquid crystal panel 11G, and an exit polarizer 12G are arranged in this order in the traveling direction of the light beam (G) reflected by the dichroic mirror 7b. The relay lens 8a and the mirror 9a are arranged in this order in the traveling direction of the light beam (B) transmitted through the dichroic mirror 7b. The relay lens 8b and the mirror 9b are disposed in the traveling direction of the light beam reflected by the mirror 9a. They are arranged in this order. In the traveling direction of the light beam reflected by the mirror 9b, the incident polarizing plate 10B, the liquid crystal panel 11B, and the outgoing polarizing plate 12B are arranged in this order.
[0006]
A cross prism 13 that color-combines these light beams is disposed at a position where the light beams (corresponding to R, G, and B image light) that have passed through the output polarizing plates 12R, 12B, and 12G intersect. A projection lens 14 that projects a light beam (corresponding to color image light) color-combined by the cross prism 13 onto a screen (not shown) is disposed on the exit surface side of the cross prism 13.
[0007]
Next, the operation of the liquid crystal projector will be briefly described. The light beam emitted from the light source lamp 1 enters the polarization conversion element 200 via the lens arrays 2a and 2b, and the polarization components are aligned by the polarization conversion element 200. FIG. 10 schematically shows a state of polarization conversion by the polarization conversion element 200. In FIG. 10, “P” and “S” each represent a polarization component.
[0008]
Referring to FIG. 10, the light beam (P + S) emitted from the light source lamp 1 enters the lens arrays 2a and 2b. The plurality of rectangular lenses 16a constituting the lens array 2a correspond to the plurality of rectangular lenses 16b constituting the lens array 2a, respectively, and a secondary light source image (an arc image of the light source lamp 1) is obtained by each of the corresponding rectangular lenses. ) And project. The luminous flux (P + S) from each rectangular lens 16b is incident on the corresponding divided region of PBS3. In the divided region, two dielectric films 17 configured to transmit the P-polarized component and reflect the S-polarized component are arranged in parallel, and the incident light beam is the first light beam by one dielectric film 17. (P) and the second light beam (S) are separated. Among the separated light beams, the first light beam (P) is emitted as it is, and the second light beam (S) is reflected by the dielectric film 17. Are emitted. A phase difference plate 4 is provided in a portion of each divided region where the second light flux (S) is emitted, and the emitted second light flux (S) passes through the phase difference plate 4. , Converted to a P-polarized component. As a result, all the light beams emitted from the polarization conversion element 200 become P-polarized component light beams.
[0009]
The luminous flux (P-polarized component) having the polarization components aligned as described above is color-separated into three lights of R light, G light, and B light by the dichroic mirrors 7a and 7b. The R light, G light, and B light are modulated by the liquid crystal panels 11R, 11G, and 11B, respectively, to generate R image light, G image light, and B image light. Color image light is generated by color-combining these R image light, G image light, and B image light with a cross prism, and this color image light is projected onto a screen (not shown) by the projection lens 14.
[0010]
In general, a polarization conversion element has a configuration in which a retardation film as a retardation plate is bonded to PBS with an organic adhesive, and is therefore very vulnerable to heat. For example, the characteristics of the retardation film are deteriorated or the film is peeled off by heat. In particular, the liquid crystal projector described above has a configuration in which the secondary light source image (the arc image of the light source lamp 1) generated by each rectangular lens of the lens array 2a is projected by the corresponding rectangular lens of the lens array 2b. In the portion of the polarization conversion element 200 where the light beam (secondary light source light) from each rectangular lens of the lens array 2b passes, the light density increases and the local temperature rises accordingly. The countermeasure against heat for the element 200 is particularly important.
[0011]
Hereinafter, a local temperature rise in the polarization conversion element 200 will be briefly described. FIG. 11 schematically shows a secondary light source image formed by the lens array 2b and a high luminance portion formed on the polarization conversion element 200 by the secondary light source image. In FIG. 11, the hatched portions are the arc image and the high luminance portion, and the light density (transmitted light amount) is higher as the hatched interval is narrower.
[0012]
As shown in FIG. 11, a secondary light source image 20 is formed for each rectangular lens 16b of the lens array 2b, and a high luminance portion 21 corresponding to the secondary light source image 20 is formed on the phase difference plate 4 of the polarization conversion element. Is done. In the secondary light source image 20, the amount of light near the center near the optical axis increases, and therefore the amount of light also increases in the high brightness portion 21 of the phase difference plate 4 near the center. In the phase difference plate 4, a part of the incident light beam is absorbed mainly in the high luminance part 21, and the temperature rises according to the amount of the absorbed light. Since the amount of light in the high brightness portion 21 is higher near the center, the temperature rise due to light absorption in the phase difference plate 4 becomes larger near the center.
[0013]
In general, forced air cooling by a fan is performed as a heat countermeasure for the polarization conversion element. There is also a polarization conversion element to which a countermeasure against heat as described in JP-A-2002-6281 is taken. FIG. 12 shows a schematic configuration of the polarization conversion element. In FIG. 12, the same components as those shown in FIG.
[0014]
Referring to FIG. 12, the polarization conversion element is provided with a heat transfer transparent substrate 201 on the exit surface side of the phase difference plate 4. The heat transfer transparent substrate 201 is made of a material having high thermal conductivity, such as alumina (A ₂ lO _Three Is a transparent substrate made of a crystalline oxide (sapphire). According to this configuration, the heat generated in the phase difference plate 4 moves to the heat transfer transparent substrate 201 and is released from the surface of the heat transfer transparent substrate 201. Thereby, the phase difference plate 4 can be cooled.
[0015]
In addition to the above, there has been proposed one in which the PBS itself to which the phase difference plate is attached is composed of sapphire, and heat generated by the phase difference plate is transferred to the PBS (see JP 2001-318359 A). . Also in this case, it is possible to dissipate heat by dispersing local heat concentration on the retardation plate.
[0016]
[Problems to be solved by the invention]
However, the conventional techniques described above have the following problems.
[0017]
In the case of forced air cooling by a fan, in order to suppress the temperature rise of the polarization conversion element (keep the temperature constant), it is necessary to increase the air volume at a ratio of square to the increase in the heat generation amount. For this reason, it is difficult to suppress the temperature of the polarization conversion element to, for example, 80 to 100 ° C. or less only by forced air cooling with a fan. Further, in order to increase the air volume, the fan itself becomes large, leading to an increase in the size of the apparatus and cost.
[0018]
In the thing of Unexamined-Japanese-Patent No. 2002-6281, since the entrance plane side of a phase difference plate is in contact with PBS, cooling by heat transfer is performed only on the output surface side of a phase difference plate. For this reason, the cooling efficiency is poor.
[0019]
Moreover, although the cooling effect is heightened using sapphire with high heat conductivity for a heat-transfer transparent substrate, in this case, there are the following problems. Since sapphire has high hardness (hardness after diamond) and poor workability, the price increases as the surface polishing area increases, that is, the size increases. As shown in FIG. 12, the size of the heat transfer transparent substrate is equal to or larger than the size of the polarization conversion element, and it is very expensive to configure such a heat transfer transparent substrate with sapphire. It becomes a thing.
[0020]
In the thing of Unexamined-Japanese-Patent No. 2001-318359, while the heat which generate | occur | produced with the phase difference plate is directly radiated | emitted from the surface (output surface) of a phase difference plate, it moves to PBS (sapphire) of the entrance plane side. . Since cooling is performed on both the input and output surfaces in this way, a greater cooling effect than in the above case can be expected. However, since it is very difficult to process sapphire into a complicated shape such as PBS, it has not been put into practical use.
[0021]
An object of the present invention is to solve the above-mentioned problems, and to provide a polarization conversion element with low cost, high cooling efficiency and excellent heat resistance, and a liquid crystal projector using the same.
[0022]
[Means for Solving the Problems]
To achieve the above objective, Main departure The bright polarization conversion element is arranged in a polarization beam splitter in which a polarization separation unit for separating an incident light beam into first and second light beams having different polarization components is arranged in a matrix, and for each column or row of the polarization separation unit A plurality of phase difference plates, and the plurality of phase difference plates And a polarizing beam splitter, for each phase difference plate, a heat transfer transparent substrate for dissipating the heat generated in each phase difference plate is provided. The thermal conductivity of the heat transfer transparent substrate provided for the retardation plate located in the range is higher than the heat conductivity of other heat transfer transparent substrates. It is characterized by that.
[0024]
According to the polarization conversion element of the first and second inventions, the heat generated in the phase difference plate is directly radiated to the space from the surface (emission surface) side of the phase difference plate, and the back surface of the phase difference plate ( Move from the incident surface) side to the heat transfer transparent substrate. As described above, the cooling effect is exerted on both the front surface and the back surface of the phase difference plate, so that the cooling efficiency is exerted only on one surface (outgoing surface) as described in JP-A-2002-6281. It's much better than what you can't. Therefore, it is possible to prevent deterioration of the retardation plate and the adhesive due to heat.
[0025]
Moreover, in the thing of Unexamined-Japanese-Patent No. 2001-318359, since the sapphire was used for PBS of complicated shape, the implementation | achievement was difficult, However, The heat-transfer transparent substrate used for each said invention is a mere plate-shaped. Since it is a thing, it can form with sapphire.
[0026]
In the first and second inventions described above, the heat transfer transparent substrate may be divided into a plurality of parts. According to this configuration, since the size of the heat transfer transparent substrate is reduced, the price when sapphire is used can be further reduced.
[0033]
The liquid crystal projector of the present invention includes any one of the polarization conversion elements described above and a liquid crystal panel that modulates a light beam from the polarization conversion element. Although the deterioration of the retardation plate and the adhesive due to heat affects the image quality (brightness and contrast), according to this configuration, the polarization conversion element suppresses the deterioration of the retardation plate and the adhesive due to the heat due to the above-described action. Therefore, such a deterioration in image quality does not occur.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0035]
FIG. 1 is a cross-sectional view schematically showing a main configuration of a polarization conversion element according to an embodiment of the present invention. In FIG. 1, P and S each represent a polarization component.
[0036]
The main part of the polarization conversion element of this embodiment includes a polarization beam splitter 30 that separates an incident light beam (P + S) into a first light beam (S) and a second light beam (P) having different polarization components, and a first light beam. The phase difference plate 40 that rotates the phase of (S) by approximately 90 degrees and the heat transfer transparent substrate 15 having a predetermined thermal conductivity provided between the polarization beam splitter 30 and the phase difference plate 40 are included. The polarizing beam splitter 30, the heat transfer transparent substrate 15, and the phase difference plate 40 are fixed with an organic adhesive. The polarization beam splitter 30 and the phase difference plate 40 are basically the same as the conventional ones shown in FIGS. 9 to 12, and the same applies to polarization separation and polarization conversion. Only the features of this embodiment will be described.
[0037]
The heat transfer transparent substrate 15 is composed of a glass substrate having a predetermined thermal conductivity. The thickness of the glass substrate is, for example, 0.3 to 1 mm. Here, the predetermined thermal conductivity is a value at which the heat generated in the phase difference plate 4 moves to the heat transfer transparent substrate 15 and the phase difference plate 4 can be sufficiently cooled by this movement. Desirably, the thermal conductivity is 10 W / m · K. By using a material having high thermal conductivity for the heat transfer transparent substrate 15, a high cooling effect can be obtained. An example of a material having a high thermal conductivity is sapphire. However, as described above, sapphire is disadvantageous in terms of cost when the substrate size is increased. Therefore, the heat transfer transparent substrate 15 is divided and used. The divided form will be described in detail in an embodiment described later.
[0038]
According to the configuration shown in FIG. 1, the phase difference plate 40 exhibits a cooling action on both sides thereof. FIG. 2 schematically shows the flow of heat generated in the phase difference plate 40. Referring to FIG. 2, the heat generated in the phase difference plate 40 is directly radiated to the space from the front surface (emission surface) side of the phase difference plate 40, and the heat is transferred from the rear surface (incident surface) side of the phase difference plate 40. Move to the transparent substrate 15. The cooling efficiency in this case is much better than the conventional one shown in FIGS. Further, if another heat transfer transparent substrate 15 is provided on the incident / exit surface side of the phase difference plate 40, the cooling efficiency is further improved.
[0039]
In the polarization conversion element of the present embodiment described above, a high cooling effect can be obtained by using sapphire for the heat transfer transparent substrate. Hereinafter, the example which uses sapphire for a heat-transfer transparent substrate is given.
[0040]
Example 1
3A and 3B are diagrams for explaining the polarization conversion element according to the first embodiment of the present invention. FIG. 3A is a cross-sectional view, and FIG. 3B is a perspective view. In FIG. 3, the lens arrays 2a and 2b, the PBS 3, and the phase difference plate 4 are the same as those shown in FIG.
[0041]
The PBS 3 has a plate-like structure in which the same structure as that of the PBS 30 shown in FIG. Partial light beams from the corresponding rectangular lenses (16a, 16b) of the lens arrays 2a, 2b are incident on the incident surface of the PBS 3, respectively. A heat transfer transparent substrate 151 is provided for each block on the exit surface of the PBS 3.
[0042]
Each of the heat transfer transparent substrates 151 provided in each block is a rectangular glass substrate having the same size, and the size is the exit surface of the block, that is, the separated luminous flux (S, P) is emitted. It is approximately equal to the size of the surface. Therefore, in a state where the heat transfer transparent substrate 151 is attached to the emission surface of each block, the entire emission surface of the PBS 3 is covered with the heat transfer transparent substrate 151, and each heat transfer transparent substrate 151 is separated by the boundary 18 of each block. It is in the state that was.
[0043]
Retardation plates 4 are respectively attached to the emission surfaces of the heat transfer transparent substrate 151 delimited by the boundary 18. The phase difference plate 4 has a rectangular plate shape, and is provided so that one of the end portions on the long side is along the boundary 18 of the block. The size of the phase difference plate 4 is substantially equal to the size of the surface of the light exit surface of the block from which the light flux S out of the separated light fluxes (S, P) is emitted.
[0044]
In the polarization conversion element of this embodiment, the size of the heat transfer transparent substrate 151 disposed between the phase difference plate 4 and the PBS 3 is equal to the size of the exit surface of the block of the PBS 3. According to this configuration, the heat transfer transparent substrate 151 is much smaller than that described in JP-A-2002-6281 described above, and even if sapphire is used as the heat transfer transparent substrate 151, the price can be kept low. it can.
[0045]
The configuration shown in FIG. 3 is an example, and the arrangement of the heat transfer transparent substrate 151 can be changed as appropriate without causing a problem in terms of price when sapphire is used. For example, the heat transfer transparent substrate 151 is divided at each boundary 18, but may be divided every other boundary. In this case, the size of the heat transfer transparent substrate 151 is doubled.
[0046]
Further, the heat transfer transparent substrate 151 may be partitioned in a direction perpendicular to the boundary 18.
[0047]
Further, the heat transfer transparent substrate 151 may be divided into a boundary 18 and a direction perpendicular thereto. Thus, the heat transfer transparent substrate 151 is arranged in a matrix. In this case, the heat conductivity of the heat transfer transparent substrate located in a predetermined range from the center may be higher than the heat conductivity of the heat transfer transparent substrate located around the heat transfer transparent substrate. Furthermore, in this case, it is also possible to configure only the heat transfer transparent substrate located within a predetermined range from the center with sapphire.
[0048]
It is also possible to provide a heat transfer transparent substrate having the same structure as the heat transfer transparent substrate 151 having the above-described structure on the emission surface side of the phase difference plate 4. In this case, a polarization conversion element with better cooling efficiency can be provided.
[0049]
(Example 2)
FIG. 4 is a perspective view of a polarization conversion element according to the second embodiment of the present invention. The polarization conversion element of this embodiment is obtained by dividing the heat transfer transparent substrate 151 of the polarization conversion element shown in FIG. 3 into divided substrates 151 a and 151 b at a boundary 19 perpendicular to the boundary 18. The boundary 19 is disposed in each region (matrix shape) where the partial light beams from the corresponding rectangular lenses (16a, 16b) of the lens array 2a, 2b shown in FIG. In each region, the high brightness portions 21 shown in FIG. 11 are formed.
[0050]
According to the configuration of this example, the substrate size is further reduced by dividing the substrate into the divided substrates 151a and 151b, and the price when sapphire is used can be further reduced.
[0051]
A plurality of boundaries 19 may be provided, in which case the price can be further reduced.
[0052]
It is also possible to provide a heat transfer transparent substrate having the same structure as the heat transfer transparent substrate 151 having the above-described structure on the emission surface side of the phase difference plate 4. In this case, a polarization conversion element with better cooling efficiency can be provided.
[0053]
(Example 3)
FIG. 5 is a perspective view of a polarization conversion element according to a third embodiment of the present invention. In the polarization conversion element of this embodiment, a plurality of phase difference plates 4 are provided at predetermined intervals as shown in FIG. 3, and the phase difference plates 4 are located within a predetermined range from the center. A heat transfer transparent substrate 152 is provided for each of the phase difference plates (here, four phase difference plates located in the center). The size of the heat transfer transparent substrate 152 is equal to the size of the phase difference plate 4.
[0054]
Also in the polarization conversion element of the present embodiment, the size of the heat transfer transparent substrate 152 disposed between the phase difference plate 4 and the PBS 3 is much smaller than that described in JP-A-2002-6281 described above. Thus, the price when sapphire is used as the heat transfer transparent substrate 152 can be kept low.
[0055]
In the configuration shown in FIG. 5, the heat transfer transparent substrate 152 may be provided for all the phase difference plates 4. In this case, the heat conductivity of the heat transfer transparent substrate located in a predetermined range from the center may be higher than the heat conductivity of the heat transfer transparent substrate located around the heat transfer transparent substrate. Furthermore, in this case, it is also possible to configure only the heat transfer transparent substrate located within a predetermined range from the center with sapphire.
[0056]
It is also possible to provide a heat transfer transparent substrate having the same structure as the heat transfer transparent substrate 152 having the above-described structure on the emission surface side of the phase difference plate 4. In this case, a polarization conversion element with better cooling efficiency can be provided.
[0057]
Example 4
FIG. 6 is a perspective view of a polarization conversion element that is a fourth embodiment of the present invention. The polarization conversion element of this embodiment is obtained by dividing the heat transfer transparent substrate 152 of the polarization conversion element shown in FIG. 5 into divided substrates 152 a and 152 b at the boundary 19. The boundary 19 is the same as that shown in FIG.
[0058]
According to the configuration of this example, the substrate size is further reduced by dividing the substrate into the divided substrates 152a and 152b, and the price when using sapphire can be further reduced.
[0059]
A plurality of boundaries 19 may be provided, in which case the price can be further reduced.
[0060]
It is also possible to provide a heat transfer transparent substrate having the same structure as the heat transfer transparent substrate 152 having the above-described structure on the emission surface side of the phase difference plate 4. In this case, a polarization conversion element with better cooling efficiency can be provided.
[0061]
In the polarization conversion element of each of the embodiments described above, a heat conducting member may be provided in connection with the heat transfer transparent substrate in order to further enhance the cooling effect. As an example, FIG. 7 shows an example in which a heat conducting member is provided in the polarization conversion element shown in FIG.
[0062]
In FIG. 7, the heat transfer transparent substrate 151 delimited by the boundary 18 is further divided by the boundary 19 into divided substrates 151 a and 151 b. The end of the divided substrate 151a opposite to the boundary 19 extends longer than the position of the end of the PBS 3 (located on the upper side in FIG. 7) by a predetermined amount. This elongated portion is in contact with the heat conducting member 22a. Similarly, the divided substrate 151b also has an end opposite to the boundary 19 extending by a predetermined amount from the position of the end of the PBS 3 (located on the lower side in FIG. 7). The portion is in contact with the heat conducting member 22b.
[0063]
According to said structure, the heat which moves the inside of the heat-transfer transparent substrate 151 moves to the heat conductive members 22a and 22b, and is thermally radiated there. Therefore, a high cooling effect can be obtained.
[0064]
The heat conducting members 22a and 22b may have any form as long as the cooling effect by the heat radiation can be obtained. For example, in the configuration shown in FIG. 7, the heat conducting member may be provided only on one of the divided substrates 151a and 151b. Moreover, when a heat-transfer transparent substrate is arrange | positioned at the incident / exit surface of a phase difference plate, respectively, you may make it provide a heat conductive member in connection with one or both of these heat-transfer transparent substrates. For example, alumina can be used as the material of the heat conducting member. Moreover, although the shape of a heat conductive member is usually plate shape, in order to perform heat dissipation efficiently, you may provide an uneven | corrugated | grooved part in part.
[0065]
The polarization conversion element of the present invention described above can be applied to existing liquid crystal displays and liquid crystal projectors. As an example, FIG. 8 illustrates an example applied to a liquid crystal projector to which the polarization conversion element of the present invention is applied.
[0066]
The liquid crystal projector shown in FIG. 8 is provided with a polarization conversion element 100 that employs the configuration of the polarization conversion element of the present invention described above, instead of the polarization conversion element 200 of the liquid crystal projector shown in FIG. In FIG. 8, the same parts are denoted by the same reference numerals.
[0067]
Specifically, the polarization conversion element 100 is the polarization conversion element shown in FIG. The lens arrays 2 a and 2 b are configured to project a secondary light source image (an arc image of the light source lamp 1) via the polarization conversion element 100.
[0068]
The light beam (P + S) from the lens arrays 2a and 2b is polarized and separated into a first light beam (P) and a second light beam (S) by the PBS 3, as shown in FIG. The first light beam (P) passes through the heat transfer transparent substrate 15 and is emitted as it is. The second light beam (S) passes through the heat transfer transparent substrate 15 and enters the phase difference plate 4, and is converted into a P-polarized light component by the phase difference plate 4. As a result, all the light beams emitted from the polarization conversion element 100 are P-polarized component light beams.
[0069]
The luminous flux (P-polarized component) having the polarization components aligned as described above is color-separated into three lights of R light, G light, and B light by the dichroic mirrors 7a and 7b. The R light, G light, and B light are modulated by the liquid crystal panels 11R, 11G, and 11B, respectively, to generate R image light, G image light, and B image light. Color image light is generated by color-combining these R image light, G image light, and B image light with a cross prism, and this color image light is projected onto a screen (not shown) by the projection lens 14.
[0070]
Recently, as a liquid crystal projector, a high-brightness projector that can see a projected image on a large screen even in a bright room (for example, a 1.3-inch liquid crystal that can obtain a light output of 3000 ANSI lumens or more), 0.9 type Small and lightweight projectors (equivalent to B5 size) using small liquid crystal panels such as 0.7 and 0.7 type have appeared, and the above-described polarization conversion element of the present invention is particularly suitable for these liquid crystal projectors from the viewpoint of thermal problems. It is valid.
[0071]
【The invention's effect】
As described above, according to the polarization conversion element of the present invention, a cooling effect can be exerted on both the entrance and exit surfaces of the phase difference plate, and therefore, it is possible to provide a polarization conversion element with higher cooling efficiency than the conventional one. Can do.
[0072]
In the present invention, since the size of the electrothermal transparent substrate is smaller than the conventional size, the price when using sapphire with high thermal conductivity can be kept lower. Therefore, it is possible to provide a polarization conversion element that is low in cost and excellent in heat resistance.
[0073]
According to the liquid crystal projector of the present invention, since the above-described polarization conversion element with high cooling efficiency, low cost, and excellent heat resistance is used, it is possible to provide a liquid crystal projector with high image quality and high reliability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a main configuration of a polarization conversion element according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a heat flow generated in the retardation plate shown in FIG. 1;
3A and 3B are diagrams for explaining a polarization conversion element according to a first embodiment of the present invention, in which FIG. 3A is a cross-sectional view, and FIG. 3B is a perspective view.
FIG. 4 is a perspective view of a polarization conversion element according to a second embodiment of the present invention.
FIG. 5 is a perspective view of a polarization conversion element according to a third embodiment of the present invention.
FIG. 6 is a perspective view of a polarization conversion element according to a fourth embodiment of the present invention.
FIG. 7 is a perspective view showing another embodiment of the present invention.
FIG. 8 is a configuration diagram showing an embodiment of a liquid crystal projector to which the polarization conversion element of the present invention is applied.
FIG. 9 is a configuration diagram illustrating an outline of a liquid crystal projector including a conventional polarization conversion element.
10 is a schematic diagram showing a state of polarization conversion by the polarization conversion element shown in FIG. 9. FIG.
11 is a schematic diagram showing a secondary light source image formed by the lens array shown in FIG. 9 and a high-luminance portion formed on the polarization conversion element by the secondary light source image.
FIG. 12 is a cross-sectional view showing a schematic configuration of a polarization conversion element described in JP-A-2002-6281.
[Explanation of symbols]
1 Light source lamp
2a, 2b Lens array
3, 30 Polarizing beam splitter (PBS)
4, 40 phase difference plate
5 Field lens
6, 9a, 9b, 9c Mirror
7a, 7b Dichroic mirror
8a, 8b Relay lens
10B, 10G, 10R Incident polarizing plate
11B, 11G, 11R LCD panel
12B, 12G, 12R Output polarizing plate
13 Cross prism
14 Projection lens
15, 151, 152, 201 Heat transfer transparent substrate
16a, 16b rectangular lens
17 Dielectric film
18, 19 border
20 Secondary light source image
21 High brightness area
22a, 22b Thermal conduction member
151a, 151b, 152a, 152b Divided substrates
100, 200 Polarization conversion element

Claims (2)

A polarization beam splitter in which a polarization separation unit for separating an incident light beam into first and second light beams having different polarization components is arranged in a matrix, and a plurality of retardation plates arranged in each column or row of the polarization separation unit In a polarization conversion element having
Between each of the plurality of phase difference plates and the polarizing beam splitter, a heat transfer transparent substrate for dissipating heat generated in each phase difference plate is provided for each phase difference plate. Among them, the polarization conversion element characterized in that the heat conductivity of a heat transfer transparent substrate provided for a retardation plate located in a predetermined range from the center is higher than the heat conductivity of another heat transfer transparent substrate. The polarization conversion element according to claim 1 ,
A liquid crystal projector comprising: a liquid crystal panel that modulates a light beam from the polarization conversion element.

Images