JP3713969B2 - Projection display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display apparatus that modulates light emitted from a light source in accordance with image information by a light modulation element and enlarges and projects the modulated light onto a projection surface via a projection unit.
[0002]
[Prior art]
The projection display device basically includes a light source unit, an optical unit that optically processes the luminous flux emitted from the light source unit so as to synthesize a color image corresponding to the image information, and the synthesized luminous flux. It consists of a projection lens that magnifies and projects on the screen.
[0003]
FIG. 9A is a schematic configuration diagram of an optical unit and a projection lens among the above-described components. As shown in this figure, the optical system of the optical unit 3 includes a light source 20 included in the light source unit and a light flux W emitted from the light source 20 of red (R), green (G), and blue (B). A color separation optical system 40 that separates primary color lights R, G, and B; three liquid crystal panels (light modulation elements) 5R, 5G, and 5B that modulate the separated color lights according to image information; A dichroic prism 60 that synthesizes the modulated color lights is provided. A light beam W emitted from the light source 20 is separated into color lights R, G, and B by a color separation optical system 40 having various dichroic mirrors. Among the color lights, red light R and green light G are color separation optics. The light is emitted from the respective light emitting portions provided in the system 40 toward the corresponding liquid crystal panels 5R and 5G. The blue light B is guided to the corresponding liquid crystal panel 5B through the light guide optical system 50.
[0004]
As shown in enlarged views in FIGS. 9B and 9C, in the optical unit 3, polarizing plates 100R, 100G, and 100B are arranged on the light incident surface sides of the liquid crystal panels 5R, 5G, and 5B. . These polarizing plates 100R, 100G, and 100B are for aligning the polarization planes of the respective color lights incident on the liquid crystal panels 5R, 5G, and 5B. In addition, polarizing plates 110R, 110G, and 110B are also disposed on the light emission surface side of the liquid crystal panels 5R, 5G, and 5B. These polarizing plates 110R, 110G, and 110B are for aligning the polarization planes of the respective color lights modulated by the respective liquid crystal panels 5R, 5G, and 5B. In the projection display device, a projected image with excellent contrast is projected on the surface of the screen 120 by the polarization separation action of each polarizing plate arranged on the light incident surface side and the light emitting surface side of each liquid crystal panel 5R, 5G, 5B. It can be done.
[0005]
A general polarizing plate has a structure in which a protective layer is laminated on a polarizer made of a dichroic material such as iodine or organic dye. In addition, as the liquid crystal panel, an active matrix type liquid crystal device that controls pixels arranged in a matrix by switching elements is generally used.
[0006]
[Problems to be solved by the invention]
Here, in order to improve the contrast of the image that is enlarged and projected on the screen 120, it is only necessary to make the liquid crystal panels 5R, 5G, and 5B enter highly accurate polarized light that is less mixed with other polarized light. In order to do this, a polarizing plate having a good selection characteristic of polarized light (high degree of polarization) may be disposed on the light incident surface side of each of the liquid crystal panels 5R, 5G, and 5B.
[0007]
However, since the polarizing plate having excellent selection characteristics absorbs much light, the amount of heat generated increases. When the amount of heat generated by the polarizing plate is large, the amount of heat transferred to the liquid crystal panel also increases and the temperature of the liquid crystal panel rises. As the temperature rises, the optical characteristics of the liquid crystal panel deteriorate, and the contrast of the projected image deteriorates.
[0008]
In a projection display device, a cooling device is usually incorporated inside the device, and the cooling device forms an air flow as indicated by arrows in FIG. 9C to cool the polarizing plate. Yes. However, in order to sufficiently cool the polarizing plate having a large calorific value, it is necessary to increase the cooling efficiency by the air flow using a large cooling device. When such a large cooling device is incorporated in a projection display device, the size of the device becomes large, and noise of the cooling device also becomes a problem.
[0009]
In view of the above points, an object of the present invention is to provide a projection that can improve the cooling efficiency of the polarizing plate without using a large cooling device and prevent the optical characteristics of the light modulation element from deteriorating due to the heat generation of the polarizing plate. To provide a mold display device.
[0010]
[Means for Solving the Problems]
  In order to solve the above problems, in the projection display device of the present invention,A polarization conversion element array that converts light emitted from a light source into one type of linearly polarized light and emits the light, and one type of linearly polarized light converted by the polarization conversion element array is converted into red light, green light, and blue light. A color separation optical system that separates light, the light modulation elements for red light, green light, and blue light that respectively modulate the three colors of light separated by the color separation optical system; and the red light, green A projection display apparatus comprising: a color synthesis optical system that synthesizes light modulated by light and blue light modulation elements; and a projection unit that enlarges and projects the light synthesized by the color synthesis optical system onto a projection surface And, only between the color separation optical system and the blue light modulation element, a plurality of polarizing plates for aligning the polarization plane of the blue light incident on the light modulation element is arranged, The color separation optical system and the red color And each polarizing plate between the optical modulation element for green light 1 Placed one by oneIt is characterized by that.
[0011]
  In the projection display device of the present invention,To align the polarization plane of the blue light incident on the light modulator only between the color separation optical system and the light modulator for blue lightA plurality of polarizing plates are arranged, and these polarizing platesFor blue lightThe plane of polarization of light incident on the light modulation element is aligned. That is, in the projection display device of the present invention, the light emitted from the light sourceFor blue lightPolarized light that is not desired to be guided to the light modulation element is not absorbed by a single polarizing plate, but is absorbed by a plurality of polarizing plates. For this reason, the heat generation of the polarizing plate in the conventional projection display device is dispersed among the plurality of polarizing plates, and the heat generation of each polarizing plate is less than the heat generation of the polarizing plate in the conventional projection display device. Therefore, since heat radiation of each polarizing plate is facilitated, each polarizing plate can be efficiently cooled without using a large cooling device, and the thermal load applied to the light modulation element can be reduced. Therefore, the temperature rise of the light modulation element due to the heat generation of the polarizing plate can be suppressed, and deterioration of the optical characteristics of the light modulation element can be prevented in advance. Further, since it is not necessary to use a large cooling device, the projection display device does not increase in size and the noise of the cooling device does not increase.
[0013]
  AlsoIn a general polarizing plate, since the spectral characteristics when transmitting through the polarizing plate are lower on the short wavelength side (transmittance on the blue side is lower), the temperature of the polarizing plate that absorbs blue light becomes higher. That is, in a projection display device that separates light of three colors of red, green, and blue, the amount of heat generated when aligning the polarization plane of blue light is the amount of heat generated when aligning the polarization planes of other color lights. More than that. Therefore,Only between the color separation optical system and the light modulator for blue light,For aligning the polarization plane of blue lightMultiple sheetsDispersing the amount of heat generated when arranging the polarizing plate and aligning the polarization plane of blue light to multiple polarizing platesdoing.
[0014]
The number of polarizing plates arranged on the light incident surface side of the light modulation element should be determined in consideration of the space for installing the polarizing plates and the amount of heat generated per polarizing plate. For example, when priority is given to compacting the optical system, two polarizing plates may be disposed on the light incident surface side of the light modulation element. In this case, it is desirable to use one polarizing plate having higher transmittance (lower polarization degree) than the other polarizing plate. In this way, light loss can be suppressed compared to the case where two polarization degrees with low transmittance (high degree of polarization) are provided.
[0015]
When two such polarizing plates are arranged, the light source side polarizing plate (one polarizing plate) has a high transmittance (low polarization degree), and the light modulating element side polarizing plate (the other polarizing plate) When the polarizing plate has a low transmittance (a high degree of polarization), heat absorption per polarizing plate can be reduced. Thereby, deterioration of a polarizing plate can be prevented and the cooling efficiency of a polarizing plate can be improved. Further, since heat absorption per polarizing plate is reduced, the amount of heat generated by the polarizing plate can be reduced, and the other polarizing plate can be attached to the light incident surface of the light modulation element. In other words, even if this polarizing plate is attached to the light modulation element, the amount of heat generated by the polarizing plate is small, so that the temperature increase of the light modulation element can be suppressed and the contrast of the projected image can be prevented from being lowered.
[0016]
When two polarizing plates are arranged, among these polarizing plates, the polarizing plate on the light source side is a reflective polarizing plate, that is, one of two types of linearly polarized light whose polarization planes are orthogonal to each other is transmitted. If the polarizing plate reflects the other, light absorption in the polarizing plate with the largest amount of light can be reduced. Therefore, heat generation in the polarizing plate can be suppressed.
[0017]
Further, when three or more polarizing plates are disposed, when at least one polarizing plate is reflective, it is desirable that the polarizing plate disposed at a position farthest from the light modulation element is of a reflective type. If the polarizing plate arranged at such a position is a reflection type, the absorption of light in the polarizing plate with the largest amount of light can be reduced as in the case of using two polarizing plates.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description, unless otherwise specified, the light traveling direction is the Z direction, and when viewed from the Z direction, the 12 o'clock direction is the Y direction, and the 3 o'clock direction is the X direction.
[0019]
FIG. 1 is a schematic plan view showing the configuration of the projection display apparatus of the present invention. The projection display device 1 includes a light source unit 2, an optical unit 3, and a projection lens 4.
[0020]
The optical unit 3 includes an integrator optical system 30 having a first optical element 31, a second optical element 32, and a superimposing lens 33. A color separation optical system 40 including dichroic mirrors 41 and 42 and a reflection mirror 43 is also provided. Furthermore, a light guide optical system 50 including an incident side lens 51, a relay lens 52, and reflection mirrors 53 and 54 is provided. In addition, three field lenses 61, 62, and 63, three liquid crystal panels 5R, 5G, and 5B, and a cross dichroic prism 60 are provided.
[0021]
The light source unit 2 is disposed on the incident surface side of the first optical element 31 of the optical unit 3. The projection lens 4 is disposed on the exit surface side of the cross dichroic prism 60 of the optical unit 3.
[0022]
FIG. 2 is an explanatory diagram showing an integrator illumination optical system that illuminates three liquid crystal panels that are illumination areas of the projection display device shown in FIG. This integrator illumination optical system includes a light source 20 provided in the light source unit 2 and an integrator optical system 30 provided in the optical unit 3. The integrator optical system 30 includes a first optical element 31, a second optical element 32, and a superimposing lens 33. The second optical element 32 includes a condenser lens 34, a light shielding plate 35, and a polarization conversion element array 36. FIG. 2 shows only main components for explaining the function of the integrator illumination optical system for ease of explanation.
[0023]
The light source 20 includes a light source lamp 21 and a concave mirror 22. Radial rays (radiated light) emitted from the light source lamp 21 are reflected by the concave mirror 22 and emitted in the direction of the first optical element 31 as a substantially parallel light bundle. As the light source lamp 21, a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is often used. As the concave mirror 22, a parabolic mirror is preferably used.
[0024]
FIG. 3 is a front view and a side view showing an appearance of the first optical element 31. The first optical element 31 is a lens array in which minute lenslets 311 having a rectangular outline are arranged in a matrix of M rows in the vertical direction and 2N columns in the horizontal direction. From the center in the lateral direction of the lens, there are N columns in the left direction and N columns in the right direction. In this example, M = 10 and N = 4. The outer shape of each small lens 311 viewed from the Z direction is set to be substantially similar to the shape of the liquid crystal panel 5. For example, if the aspect ratio (the ratio between the vertical and horizontal dimensions) of the image forming area of the liquid crystal panel is 4: 3, the aspect ratio of each small lens 311 is also set to 4: 3.
[0025]
The condenser lens 34 of the second optical element 32 is a lens array having the same configuration as that of the first optical element 31. Note that the orientation of the first optical element 31 and the condenser lens 34 may be in either the + Z direction or the −Z direction. Moreover, as shown in FIG. 2, you may face the mutually different direction.
[0026]
As shown in FIG. 2, in the polarization conversion element array 36, two polarization conversion element arrays 361 and 362 are arranged in a symmetrical direction with the optical axis in between. FIG. 4 shows a polarization conversion element 361.arrayIt is a perspective view which shows the external appearance. This polarization conversion elementarray361 includes a polarizing beam splitter array 363 and a polarizing beam splitter array.RayAnd a λ / 2 phase difference plate 364 (shown by hatching in the drawing) which is selectively disposed on a part of the light emission surface 363. The polarization beam splitter array 363 has a shape in which a plurality of columnar translucent members 365 each having a parallelogram cross section are sequentially bonded. Polarization separation films 366 and reflection films 367 are alternately formed on the interface of the translucent member 365. The λ / 2 phase difference plate 364 is selectively attached to the X-direction mapping portion of the light exit surface of the polarization separation film 366 or the reflection film 367. In this example, a λ / 2 phase difference plate 364 is attached to a mapping portion in the X direction on the light exit surface of the polarization separation film 366.
[0027]
The polarization conversion element array 361 has a function of converting an incident light beam into one type of linearly polarized light (for example, S-polarized light or P-polarized light) and emitting it. FIG. 5 is an explanatory diagram showing the function of the polarization conversion element array 361. Polarization conversion elementArray 361Non-polarized light (incident light having a random polarization direction) including an S-polarized component and a P-polarized component is incident on the incident surface. The incident light is first separated into S-polarized light and P-polarized light by the polarization separation film 366. The S-polarized light is reflected substantially perpendicularly by the polarization separation film 366, is further reflected by the reflection film 367, and then emitted. On the other hand, the P-polarized light passes through the polarization separation film 366 as it is. A λ / 2 phase difference plate 364 is disposed on the exit surface of the P-polarized light transmitted through the polarization separation film 366, and this P-polarized light is converted into S-polarized light and emitted. Therefore, the polarization conversion elementArray 361Most of the light that has passed through is emitted as S-polarized light. Also, the polarization conversion elementArray 361When it is desired that the light emitted from the P-polarized light is P-polarized light, the λ / 2 phase difference plate 364 may be disposed on the exit surface from which the S-polarized light reflected by the reflective film 367 is emitted.
[0028]
Note that a block including one polarization separation film 366 and one reflection film 367 adjacent to each other and further including one λ / 2 phase difference plate 364 can be regarded as one polarization conversion element 368. The polarization conversion element array 361 includes a plurality of such polarization conversion elements 368 arranged in the X direction. In this embodiment, it is composed of four rows of polarization conversion elements 368.
[0029]
Since the polarization conversion element array 362 is exactly the same as the polarization conversion element array 361, the description thereof is omitted.
[0030]
  FIG. 6 is a plan view of the light shielding plate 35. The light shielding plate 35 has two polarization conversion elements.arrayOf the light incident surfaces 361 and 362, an opening 351 is provided in a substantially rectangular plate-shaped body so that light is incident only on the light incident surface corresponding to the polarization separation film 366. Yes.
[0031]
Non-polarized light emitted from the light source 20 shown in FIG. 2 is emitted from the plurality of small lenses 311 of the first optical element 31 and the condenser lens 34 included in the second optical element 32 constituting the integrator optical system 30. The light beams are divided into a plurality of partial light beams 202 by a plurality of small lenses 341 and condensed in the vicinity of the polarization separation films 366 of the two polarization conversion element arrays 361 and 362. In particular, the condensing lens 34 has a function of guiding the plurality of partial light beams 202 emitted from the first optical element 31 so as to be condensed on the polarization separation films 366 of the two polarization conversion element arrays 361 and 362. are doing. As described above, the plurality of partial light beams 202 incident on the two polarization conversion element arrays 361 and 362 are converted into one type of linearly polarized light and emitted. A plurality of partial light beams emitted from the two polarization conversion element arrays 361 and 362 are superimposed on the liquid crystal panel 5 (5R, 5G, and 5B) described later by the superimposing lens 33. Thereby, this integrator optical system 30 can illuminate the liquid crystal panel 5 uniformly.
[0032]
In the projection display device 1 shown in FIG. 1, the reflection mirror 56 is provided to guide the light beam emitted from the superimposing lens 33 in the direction of the color separation optical system 40. This is not always necessary depending on the configuration of the illumination optical system.
[0033]
The color separation optical system 40 includes two dichroic mirrors 41 and 42, and has a function of separating light emitted from the superimposing lens 33 into three color lights of red, green, and blue. The first dichroic mirror 41 transmits the red light component and reflects the blue light component and the green light component in the light emitted from the superimposing lens 33. The red light R that has passed through the first dichroic mirror 41 is reflected by the reflection mirror 43, passes through the field lens 61, and reaches the red liquid crystal panel 5R. The field lens 61 converts each partial light beam emitted from the superimposing lens 33 into a light beam parallel to the central axis (principal light beam). The same applies to the field lenses 62 and 63 provided in front of the other liquid crystal panels 5G and 5B.
[0034]
  Of the blue light B and green light G reflected by the first dichroic mirror 41, the green light G is reflected by the second dichroic mirror 42 and passes through the field lens 62 to reach the green liquid crystal panel 5G. On the other hand, the blue light B passes through the second dichroic mirror 42, passes through the light guide optical system 50, that is, the incident side lens 51, the reflection mirror 53, the relay lens 52, and the reflection mirror 54, and further passes through the field lens 63. It reaches the liquid crystal panel 5B for blue light. The light guide optical system 50 is used for the blue light B because the optical path length of the blue light B is longer than the optical path lengths of the other color lights. This is to prevent the decrease. That is, the field lens remains as the partial light beam incident on the incident side lens 51.63It is for telling.
[0035]
The three liquid crystal panels 5R, 5G, and 5B have a function as light modulation means that modulates incident light according to given image information. Thereby, each color light incident on the three liquid crystal panels 5R, 5G, and 5B is modulated in accordance with given image information to form an image of each color light.
[0036]
The three colors of modulated light emitted from the three liquid crystal panels 5R, 5G, and 5B are incident on the cross dichroic prism 60. The cross dichroic prism 60 has a function as a color synthesizing optical system for synthesizing three colors of modulated light to form a color image. In the cross dichroic prism 60, a dielectric multilayer film that reflects red light R and a dielectric multilayer film that reflects blue light B are formed in an approximately X shape at the interface of four right-angle prisms. These dielectric multilayer films combine three colors of modulated light to form combined light for projecting a color image. The combined light generated by the cross dichroic prism 60 is emitted in the direction of the projection lens 4. The projection lens 4 has a function of projecting the combined light on the projection screen, and displays a color image on the projection screen.
[0037]
7A and 7B are enlarged views of the liquid crystal panels 5R, 5G, and 5B and their peripheral portions. As shown in these drawings, each of the liquid crystal panels 5R, 5G, and 5B is disposed at a predetermined interval from the remaining side surfaces (three light incident surfaces) excluding the exit surface of the cross dichroic prism 60. The liquid crystal panels 5R, 5G, and 5B are arranged in a state that is substantially orthogonal to the optical paths of the color lights R, G, and B. Polarizing plates 8R, 8G, and 8B are attached to the three light incident surfaces of the cross dichroic prism 60, respectively. When each color light R, G, B modulated by the liquid crystal panels 5R, 5G, 5B passes through the corresponding polarizing plates 8R, 8G, 8B, one polarized light component (for example, S-polarized light) is absorbed, Only the other polarized light component (for example, P-polarized light) is transmitted and enters the cross dichroic prism 60.
[0038]
One polarizing plate 6R, 6G is arranged on the light incident surface side of the liquid crystal panels 5R, 5G for red light and green light, respectively. Here, in the projection display apparatus 1, the light emitted from the light source 20 using the integrator illumination optical system 30 is aligned with S-polarized light, and this S-polarized light is used as light for image formation. However, since it is impossible to completely convert the light into S-polarized light by the integrator illumination optical system 30, P-polarized light is mixed in each color light R, G, B directed to the liquid crystal panels 5R, 5G, 5B. Yes. Each of the polarizing plates 6R and 6G absorbs the P-polarized light mixed in the red light R and the green light G, and makes the light beams R and G containing little P-polarized light enter the liquid crystal panels 5R and 5G. This is an optical element. When the red light R and the green light G pass through the polarizing plates 6R and 6B, almost all of the P-polarized light contained in each color light is removed and becomes light with substantially the same plane of polarization (S-polarized light).
[0039]
A polarizing plate 6B is attached to the light incident surface of the blue light liquid crystal panel 5B. Further, another polarizing plate 7B is arranged on the incident side of the polarizing plate 6B. That is, two polarizing plates 6B and 7B are disposed on the light incident surface side of the liquid crystal panel 5B. These polarizing plates 6B and 7B are also optical elements for absorbing the P-polarized light contained in the blue light B, like the polarizing plates 6R and 6G. When the blue light B passes through these polarizing plates 6B and 7B, almost all of the P-polarized light contained in the blue light B is absorbed and becomes light having substantially the same plane of polarization (S-polarized light).
[0040]
Further, in the projection display device 1 of the present example, a polarizing plate 7B is used which has inferior polarized light selection characteristics as compared to the polarizing plate 6B, that is, has a low degree of polarization. Since the transmittance of the polarized light of the polarizing plate 7B having a low degree of polarization is higher than the transmittance of the polarized light of the polarizing plate 6B, most of the P-polarized light contained in the blue light B from the field lens 63 is polarized. The light is absorbed by 7B, and the remaining P-polarized light is absorbed by the polarizing plate 6B. Therefore, in the projection display device 1 of this example, the heat absorption amount per polarizing plate can be reduced.
[0041]
That is, when the polarization plane of the blue light B is aligned using one polarizing plate, the amount of heat generated in the process of aligning the polarization plane is concentrated on one polarizing plate. In the type display device 1, the amount of heat is distributed to the two polarizing plates 6B and 7B. For this reason, the calorific value of each polarizing plate 6B, 7B is smaller than the calorific value of the polarizing plate when the polarizing plane is aligned with one polarizing plate. Therefore, it is possible to prevent deterioration of the polarizing plate due to heat.
[0042]
Furthermore, by using the two polarizing plates 6B and 7B, heat radiation of the individual polarizing plates 6B and 7B is facilitated, so that each polarizing plate 6B and 7B can be efficiently cooled without using a large cooling device. it can. Therefore, the temperature rise of the liquid crystal panels 5R, 5G, and 5B due to the heat generation of the polarizing plate can be suppressed, and the deterioration of the optical characteristics of those liquid crystal panels can be prevented. Further, since a large cooling device is unnecessary, it is possible to prevent the projection display device from becoming large, and it is possible to reduce the noise of the cooling device.
[0043]
Here, if both of the polarizing plates 6B and 7B are polarizing plates having a high degree of polarization, there is a possibility that the amount of light transmitted through the respective polarizing plates 6B and 7B is reduced and the loss of light is increased. On the other hand, in the projection display apparatus 1, the polarization degree of the polarizing plate 7B is reduced (high transmittance), and the polarization degree of the polarizing plate 6B is increased. For this reason, the loss of light generated by using two polarizing plates having a high degree of polarization can be prevented.
[0044]
The polarizing plate 6B has a higher degree of polarization than the polarizing plate 7B, but most of the polarized light is absorbed by the polarizing plate 7B before entering the polarizing plate 6B. Compared to the amount of heat generated when used in For this reason, even if the polarizing plate 6B is affixed to the liquid crystal panel 5B, the amount of heat transferred to the liquid crystal panel 5B is small, so that an increase in the temperature of the liquid crystal panel 5B can be suppressed.
[0045]
Further, in the projection display device 1 of the present example, the two polarizing plates 6B and 7B are disposed only for the blue light B. This is because the transmittance on the short wavelength side is low in a general polarizing plate, and the amount of heat generated when aligning the polarization plane by absorbing the P-polarized light contained in the blue light B is the polarization of the other color lights R and G. This is because the amount of heat generated when aligning the surfaces increases.
[0046]
Of course, the polarizing plate 6B may be arranged away from the liquid crystal panel 5B. Further, the position where the polarizing plate 7B is disposed is the polarizing plate 6B and the field lens.63It is not limited to the optical path between, and may be in the optical path of the light guide optical system 50. In particular, if the arrangement position of the polarizing plate 7B is set to a position where the air flow formed in the projection display device circulates efficiently, the cooling efficiency of the polarizing plate 7B increases.
[0047]
The projection display device 1 incorporates an integrator optical system 30 having a function of converting randomly polarized light emitted from the light source 20 into almost one type of polarized light (S-polarized light). For this reason, each color light R, G, B of the polarized light with little mixing of other polarized light is guided to the polarizing plate arranged on the light incident surface side of the liquid crystal panels 5R, 5G, 5B. Thus, since the polarization planes of the respective color lights R, G, and B guided to the respective polarizing plates are prepared in advance, the amount of heat generated by each polarizing plate can be suppressed also from this point.
[0050]
[Other embodiments]
  Between the light separation optical system and the liquid crystal panel for blue lightThe number of polarizing plates to be arranged is not limited to two and may be three or more. The number of polarizing plates may be determined in accordance with the size of the optical system and the degree of dispersion of the amount of heat generated in the process of aligning the polarization plane. For example, when priority is given to compacting the size of the optical system, the number of polarizing plates may be two.
[0051]
【The invention's effect】
  As described above, in the projection display device of the present invention,Only between the light separation optical system and the light modulation element for blue light,A plurality of polarizing plates are arranged, and these polarizing platesFor blue lightThe planes of polarization of light incident on the light modulation elements are made uniform. ThisBlueThe amount of heat generated in the process of aligning the polarization plane of light is dispersed in a plurality of polarizing plates. For this reason, the calorific value of each polarizing plate is smaller than the calorific value of the polarizing plate when the polarizing plane of light is aligned using one polarizing plate. Therefore, heat radiation of each polarizing plate is facilitated, and each polarizing plate can be efficiently cooled without using a large cooling device. As a result, the thermal load applied to the light modulation element can be alleviated, so that the temperature rise of the light modulation element due to the heat generation of the polarizing plate can be suppressed, and deterioration of the optical characteristics of the light modulation element can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a configuration of a projection display apparatus to which the present invention is applied.
2 is an explanatory diagram showing an integrator illumination optical system that illuminates three liquid crystal panels that are illumination regions of the projection display device shown in FIG. 1; FIG.
FIGS. 3A and 3B are a front view and a side view showing an appearance of a first optical element. FIGS.
FIG. 4 is a perspective view showing an appearance of a polarization conversion element array.
FIG. 5 is an explanatory diagram showing functions of a polarization conversion element array;
FIG. 6 is a plan view of a light shielding plate.
FIG. 7 is a plan view showing a liquid crystal panel and its peripheral portion in an extracted manner.
8 is a plan view showing an example different from FIG. 7. FIG.
FIG. 9 is a schematic configuration diagram showing an optical system incorporated in an optical unit of a conventional projection display device.
[Explanation of symbols]
1 Projection display
2 Light source unit
3 Optical unit
4 Projection lens
5R, 5G, 5B LCD panel
6R, 6G, 6B Polarizing plate
7R, 7G, 7B Polarizing plate
8R, 8G, 8B Polarizing plate
20 Light source
30 Integrator optical system
40 color separation optical system
50 Light guide optical system
60 Cross Dichroic Prism

Claims (6)

A polarization conversion element array that converts the light emitted from the light source into one type of linearly polarized light and emits the light;
A color separation optical system that separates one type of linearly polarized light converted by the polarization conversion element array into red light, green light, and blue light;
The light modulation elements for red light, green light, and blue light that respectively modulate the light of the three colors separated by the color separation optical system;
A color synthesizing optical system for synthesizing the light modulated by the red, green and blue light modulators, and
A projection display apparatus having a projection means for enlarging and projecting the light synthesized by the color synthesizing optical system onto a projection surface,
A plurality of polarizing plates for aligning the polarization plane of the blue light incident on the light modulation element is disposed only between the color separation optical system and the light modulation element for blue light, and the color separation optical system and projection display device, wherein a polarizing plates are arranged one by one between the optical modulation element for the red light and green light. The projection display device according to claim 1 , wherein one of the plurality of polarizing plates has a higher transmittance than the other polarizing plate. 3. The projection display device according to claim 2 , wherein the other polarizing plate is attached to a light incident surface of the light modulation element. According to claim 2 or 3, wherein one polarizing plate is characterized in that polarization planes of the two types of linearly polarized light that are orthogonal to each other, a polarizing plate of a reflection type for reflecting the other passes through one Projection display device. 2. The reflective polarizing plate according to claim 1 , wherein at least one of the plurality of polarizing plates transmits one of two types of linearly polarized light whose polarization planes are orthogonal to each other and reflects the other. A projection display device characterized by the above. 6. The projection display device according to claim 5 , wherein the reflective polarizing plate is disposed at a position farthest from the light modulation element among the plurality of polarizing plates.

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