JP4258293B2 - 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 transmissive liquid crystal panel or a reflective image display device, for example, a liquid crystal projector device, a reflective image display projector device, a projection type The present invention relates to a projection type video display device such as a display device.
[0002]
[Prior art]
As a configuration of a conventional projection type image display device, a projection type image display device using a combination of a polarization conversion element and a light pipe is disclosed in Japanese Patent Application Laid-Open Publication No. 2003-259542, which uses a chromatic dispersion performance of a diffractive optical element. The configuration of a projection-type image display device using a color filter is disclosed in Patent Document 2 below, and the configuration of a projection-type image display device using the polarization separation characteristic of a diffractive optical element as a polarization conversion element is disclosed in Patent Document 3 below.
[0003]
[Patent Document 1]
JP 2000-131647 A
[Patent Document 2]
JP-A-8-240717
[Patent Document 3]
JP 2000-292745 A
[0004]
[Problems to be solved by the invention]
In a projection display apparatus, high brightness and downsizing are important issues. In general, the larger the reflector and the larger the panel, the brighter the projector, but the larger the set size. That is, conventionally, there has been a problem of achieving both high brightness and downsizing.
[0005]
An object of the present invention is to provide a projection type video display device that solves the above-described problems and realizes high luminance and miniaturization.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a light source unit that emits light, an illumination optical system that irradiates a video display element with light from the light source unit, and a light valve unit that forms an optical image according to a video signal. A projection-type image display device comprising: an image display element, and projection means for projecting light emitted from the image display element, wherein the illumination optical system converts substantially elliptically polarized light into substantially linearly polarized light. The polarization conversion element has two optical paths, one of the optical paths is reflected by the polarization separation element and emitted toward the image display element, and the other optical path is transmitted through the polarization separation element. Then, the light is transmitted through the substantially half-wave retardation plate, reflected by the reflecting element, and then emitted toward the image display element.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0008]
FIG. 1 is a configuration diagram of an embodiment of the present invention, and shows a projection type video display device 22 using one reflection type video display element 13 as a light valve.
[0009]
The projection display device 22 includes a light source unit 1 having a light source 1a. The light source 1a is a white lamp such as an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, or a halogen lamp. Due to the heat generated from the light source 1a, the light source 1a and the reflector 2 are heated to high temperatures, so that they are cooled by a cooling fan (not shown) arranged at the rear. The light emitted from the light bulb of the light source 1a is collected and reflected by the ellipsoidal, parabolic or aspherical reflector 2. In this embodiment, the light is collected by an elliptical reflector and enters the concave lens 7. Since the condensed light is incident on the concave lens 7, the incident angle is reduced by the concave lens and is emitted to the incident side light pipe. Thereby, the angle distribution of the incident angle to the reflection type image display element 13 and the polarization separation element as the analyzer can be narrowed, so that the contrast can be improved.
[0010]
The incident side light pipe 6 has the polarization conversion element 3 at its rear end. The light that has passed through the incident-side light pipe enters the polarization conversion element 3. As the polarization conversion element 3, a combination of the polarization separation element 3a, the half-wave retardation plate 3b, and the reflection mirror 3c is used. As the polarization separation element 3a, a reflective polarizing plate that transmits P-polarized light and reflects S-polarized light by a diffraction effect is used. Here, the S-polarized light is reflected by the reflective polarizing plate 3a and enters the light pipe 5i. The P-polarized light passes through the reflective polarizing plate 3a, passes through the half-wave retardation plate 3b, is converted to S-polarized light, is reflected by the reflecting mirror 3c, and enters the light pipe 5h. With this configuration, the set size can be reduced because the polarization conversion element has a function of bending the optical path by 90 degrees. The incident side light pipe 6 is constituted by a mirror pipe formed by joining four reflecting mirrors.
[0011]
Since the incident side light pipe is also configured by a reflecting mirror in the vicinity of the wall surface that holds the polarization conversion element 3, it has a function of holding the polarization conversion element and a function of making the illuminance uniform. Thereby, since the length of the part which has the effect of making illumination intensity uniform becomes long, illumination intensity can be made more uniform. Alternatively, the length can be shortened and the apparatus can be further downsized as compared with a light pipe that obtains the same level of illuminance uniformity. In addition, since the polarization conversion element 3 is located behind the light pipe, incident light can be averaged, and damage caused by light on a polarization separation surface formed of a film or a diffraction surface can be reduced.
[0012]
The polarization separation element and the reflection mirror are inclined with an incident angle larger than 45 degrees with respect to the optical axis from the lamp. Here, the incident angle is 55 degrees, and the reflection angle to the light pipe is also 55 degrees. The angle formed by the light source unit 1 and the reflective image display element 13 is 110 degrees. Considering the light of the optical axis, the light enters the light pipes 5h, 5i from the polarization conversion element at an incident angle of 0 degree. By tilting in this way, the apertures of the polarization separating element and the reflecting surface can be effectively increased, so that the efficiency can be improved.
[0013]
Thereafter, the light enters the two-stage light pipes 5h and 5i, and enters the light pipe 5j having an incident opening area approximately equal to or larger than the areas of the two exit openings. With this configuration, since the number of reflections on the wall surface increases, the illuminance can be averaged over a shorter distance, and thus the apparatus can be miniaturized. The light pipes 5h, 5i, and 5j are rod lens type light pipes made of a glass cuboid. The light pipes 5h and 5i are attached to the light pipe 5j. The light pipes 5h, 5i, and 5j may be made from the same member.
[0014]
The light pipe 5j has an exit opening that is substantially the same as or slightly larger than the reflective image display element 13. The image emitted from the light pipe 5j is projected as it is. This eliminates the need for a relay lens for projecting the output image of the light pipe 5j onto the reflective image display element 13, thereby reducing the cost.
[0015]
The irradiation area of the illumination light on the display element 13 is larger than the display element 13 because the area is enlarged with respect to the exit opening of the light pipe 5j. This irradiation area is shifted vertically or horizontally with respect to the display area of the display element 13 or becomes smaller during mass production due to variations in the size and position of the light pipe and the like. Therefore, it is necessary to make this irradiation region larger than the display element 13 as a mass production margin, and this configuration can satisfy this, so that the yield during mass production is improved and the cost can be reduced.
[0016]
Thereafter, a microlens 35 composed of a plurality of microlenses is provided, and an image of the exit opening of the light pipe is formed on the reflective image display element 13. Thereby, diffusion of light is prevented, and deterioration of ambient illuminance and brightness are prevented. When the microlens cannot form an image up to the display element 13 due to its performance, the microlens forms an image between the exit aperture and the reflection type image display element to prevent light diffusion even a little.
[0017]
An incident polarizing plate 14 is arranged on the exit side to improve the degree of polarization, and then enters the electronic color separation means 11.
[0018]
The electronic color separation means 11 has an R-polarization rotation control element, a G-polarization rotation control element, and a B-polarization rotation control element for each color, and the polarization rotation control element has a specific wavelength range unless a voltage is applied thereto. The polarization axis of the light is converted, and when a voltage is applied, the polarization axis of the light is emitted as it is without being converted. Thereby, the electronic color separation means 11 sequentially converts the polarized light of each color as R, G, B. Here, since it is incident on the electronic color separation means 11 as S-polarized light, G and B are converted into B-polarized light at the next timing, and R and G are converted into P-polarized light at the next timing and emitted. With this configuration, the P-polarized light is transmitted and the S-polarized light is reflected to the reflective image display element side by the polarization beam splitter 19 disposed on the output side, so that R, G, and B are reflected to the reflective image display element side. Are emitted in this order. The image for each color is displayed on the reflective image display element 13 in accordance with the timing of the color light irradiation. Since the switching timing of each color light is as fast as 180 Hz or more, an image projected on a screen (not shown) is displayed to the human eye as a combination of three color images.
[0019]
The reflective liquid crystal display element 13 is arranged in a direction in which incident light is transmitted by the polarization separation element. Since the display element 13 is arranged so that the display region is vertically long, the size of the polarization separation element 19 (hereinafter abbreviated as PBS) can be reduced. Thereby, since the distance from the light pipe 5 to the display element 13 can be shortened, the expansion of the irradiation area on the display element 13 can be reduced and the brightness can be further increased.
[0020]
The display element 13 is provided with a number of liquid crystal display portions corresponding to the pixels to be displayed (for example, 1365 pixels in the horizontal direction and 768 pixels in the vertical direction). Then, according to a signal driven from the outside, the polarization angle of each pixel of the display element 13 changes, and the light having the same polarization direction is analyzed by the PBS 19. The amount of light having polarized light at this midway angle is determined by the PBS 19 in relation to the degree of polarization of the PBS 19. In this way, an image according to a signal input from the outside is displayed. At this time, when the display element 13 performs black display, the polarization direction is substantially the same as the incident light, and the light is returned to the light source side along the incident optical path. On the display element 13, images corresponding to the irradiated color light are sequentially displayed. That is, R video information is displayed for R light, B video information is displayed for B light, and G video information is displayed for G light.
[0021]
In order to improve the contrast immediately before the display element 13, a quarter-wave retardation plate 23 is arranged in a state in which the rotation can be adjusted.
[0022]
The light transmitted through the PBS 19 passes through the projection lens 12 such as a zoom lens and reaches the screen. An image formed on the reflective video display element 13 by the projection lens 12 is enlarged and projected on a screen to function as a display device.
[0023]
The position of the wall surface 19c facing the projection lens of the PBS 19 and the position of the outer wall surface 5jc of the light pipe are made substantially the same, whereby the PBS wall surface 19c can also have a function of making the illuminance uniform, As much as possible, light diffusion is prevented and brightness is improved. On the wall surface 19c, the effective light that becomes the image light in the reflected light from the display element 13 is reflected by the film surface 19a before reaching the wall surface. On the other hand, the ineffective light passes through the PBS 19 and does not enter the projection lens side even if the light is reflected by this wall surface. On the other wall surfaces, the size is made larger than the exit opening of the light pipe 5 to prevent the reflected light from the display element 13 from reaching the wall surface before being reflected by the film surface. As a result, the light reflected by the reflective image display element 13 is reflected by the wall surface of the PBS 19 and then reflected by the film surface to prevent leakage into the projection lens 12 and ghosting.
[0024]
FIG. 2 is a block diagram of an embodiment of the present invention.
[0025]
The incident-side light pipe 6 disposed on the emission side of the light source unit 1 increases the amount of light taken into the polarization conversion element 3 to improve the brightness. Comparing the optical path reflected by the polarization separation element 3a and the optical path transmitted therethrough, the latter optical path passes through the half-wave retardation plate 3b and the reflecting mirror 3c. There is little light quantity. In order to obtain a uniform illuminance distribution on the reflective image display element, it is desirable that the light incident on both sides is uniform. The focal point of the elliptical reflector is arranged so that the amount of light that is reflected and incident is substantially equal to the amount of light that is transmitted and incident. Alternatively, the center position of the polarization conversion element is shifted to the rear end side, and the exit opening of the first optical path is made larger than the exit opening of the second optical path, so that the illuminance is made uniform. As a result, even with a short light pipe, a projection-type image display device having a uniform illuminance distribution can be obtained, and the device can be miniaturized.
[0026]
A reflective polarizing plate 42 is disposed at an inclination of 45 degrees on the light exit side of the light pipe 5. The mirror pipe type light pipe 5 is composed of four reflecting mirrors, and creates a cylinder having a rectangular opening with the reflecting surface facing inward. The exit surface of the light pipe has a shape substantially parallel to the reflective polarizing plate 42, and only the reflective video display element 13 exists on the outgoing side of the reflective polarizing plate 42. As a result, the light pipe exit surface can be brought close to the reflective image display element 13 to prevent light diffusion and brightness deterioration. In addition, since the light pipe 5 does not exist on the display element 13 side of the reflective polarizing plate 42, it is possible to prevent the occurrence of ghost.
[0027]
FIG. 3 is a block diagram of an embodiment of the present invention.
[0028]
An end face on the light emission side of the light pipe 5 has an angle of 45 degrees, and a polarization separation film surface is formed there. Here, the S-polarized light is reflected by the polarization separation element, and the P-polarized light is transmitted through the polarization separation element, is transmitted through the substantially half-wave retardation plate, is reflected by the reflection element, and then is incident on the incident polarizing plate 14. Incident. The outer surface of the polarization conversion element is polished so that when the internal light satisfies the total reflection condition and enters the wall surface, it is substantially totally reflected, and has a function of making the illuminance uniform. With this configuration, even the polarization conversion element can perform the function of making the illuminance uniform, so that the length of the light pipe 5 can be shortened and the apparatus can be downsized. Further, since the polarization conversion element has a function of bending the optical path by 90 degrees, the apparatus can be miniaturized.
[0029]
The light pipe 5 and the polarization conversion element 3 are optically integrated. Thereby, the loss at the interface with air can be reduced, the transmittance can be improved, and it can be brightened.
[0030]
FIG. 4 is a configuration diagram of an embodiment of the present invention.
[0031]
The light source unit 1, the light pipe 5, the transmissive image display element 13t, and the projection lens 12 are arranged in a straight line. A double-sided polarization conversion element is disposed after the incident-side light pipe 6. Thereafter, the light pipe 5 is disposed, and is further arranged in a straight line with the incident side polarizing plate 14, the display element 13 t, the output side polarizing plate 14 ′, and the projection lens 12. With this configuration, it is possible to obtain an elongated cylindrical outer shape in which the cylindrical width and thickness are suppressed as compared with a configuration in which the optical path is bent. The display element 13t has a three-color pixel configuration having RGB color filters therein.
[0032]
Further, the cylindrical case 52 containing the optical system is configured to be rotatable in the arrow direction with respect to the outer frame case 51 having legs. The cylindrical case claw 52 is fitted to the outer case claw 51a to ensure positional accuracy. Accordingly, since the tilt of the irradiation position can be adjusted while the projection display apparatus is fixed, it is easy for the user to use. In order to improve the imaging performance, two rows of micro lenses may be arranged in the optical axis direction.
[0033]
Here, the color band is scrolled up and down by the electronic color separation means 11. The image of the color band of the electronic color separation means is formed on the transmission type image display element 13t by the microlens 35. A micro lens is an image of a small area formed by one or more micro lens systems, and a large surface is imaged by arranging a large number of micro lens systems on a surface substantially perpendicular to the optical axis. Can do. In order to improve the aberration, two rows are arranged in the optical axis direction here.
[0034]
The distance can be shortened and the apparatus can be downsized as compared with the conventional imaging using an imaging lens group using a plurality of single lenses. The display element 13t is driven by a method of displaying a video signal line by line from the upper part to the lower part, and the video signal corresponding to the color is synchronized with the scroll of the color band of the electronic color separation means 11. Is displayed. As a result, the loss due to the display time can be minimized and the apparatus can be made brighter than the method of irradiating colored light after the display of one surface.
[0035]
FIG. 5 is a block diagram of an embodiment of the present invention.
[0036]
The rear end of the light pipe 5 is inclined at an angle of 45 degrees, and a polarization separation film is deposited thereon and used as an analyzer. Thereby, the loss at the interface with air can be reduced, the transmittance can be improved, and it can be brightened. The reflective image display element 13 has a three-color pixel configuration having RGB color filters therein.
[0037]
FIG. 6 is a block diagram of an embodiment of the present invention.
[0038]
The projection display apparatus includes a light source unit 1 having a light source 1a, and the light source 1a is a white lamp such as an ultrahigh pressure mercury lamp. The light emitted from the light bulb of the light source 1a is condensed and reflected by the reflector 2 having a parabolic surface. A UV filter (not shown) for cutting the UV light is disposed after the reflector.
[0039]
Thereafter, a diffractive optical element 44 composed of a hologram or the like is disposed. The element 44 emits light in a smaller area than the incident area. Since the element 44 has an angular dispersion in principle, in order to reduce the emission area by the element 44, the reflector shape is preferably a surface having a narrow angle of emitted light.
[0040]
Under the condition that the same reflection type image display element 13 is irradiated with the same optical path length, the incidence angle is increased when the area of the incident region is wide according to Etendue's law. The greater the incident angle, the lower the contrast. Therefore, the narrower the exit area using this embodiment, the narrower the angle of incidence on the reflective image display element 13 and the higher the contrast.
[0041]
Further, in this configuration, both the direction in which the area of light is reduced by the element 44 and the direction in which the area is expanded by the polarization conversion element 3 are both in the lateral direction of the reflective liquid crystal display element 13. The area of the light emitted from the conversion element 3 can be made closer to a square, and the length of the illumination lens system constituted by the subsequent collimator lens and condenser lens can be shortened, so that the set size can be reduced.
[0042]
This light enters the polarization conversion element 3. The prism surface is provided with a polarization separation film 3a, and incident light is separated into P-polarized light and S-polarized light by the polarization separation film 3a. The P-polarized light passes through the polarization splitting film 3a as it is, and the polarization direction is rotated by 90 ° by the λ / 2 phase difference plate 3b provided on the exit surface of the prism, is reflected by the reflection surface, and then exits. Is done. On the other hand, the S-polarized light is reflected and emitted by the polarization separation film 3a. That is, S-polarized light is emitted from the polarization conversion element 3.
[0043]
With this configuration, the set size can be reduced because the polarization conversion element has a function of bending the optical path by 90 degrees.
[0044]
Consists of a plurality of condenser lenses, condenses the light emitted from the lamp unit, enters the first array lens 32 for forming a plurality of secondary light source images, and further comprises a plurality of condenser lenses Then, it passes through the second array lens 33 that is arranged in the vicinity of the above-described plurality of secondary light source images and that forms the individual lens images of the first array lens 32 on the liquid crystal display element 13.
[0045]
The collimator lens 34 has a positive refractive power and has a function of condensing light, passes through the condenser lens 9 and irradiates the reflective liquid crystal display element 13.
[0046]
FIG. 7 is a block diagram of an embodiment of the present invention.
[0047]
The projection display apparatus has a light source 1a. The light emitted from the light bulb of the light source 1a is collected and reflected by the ellipsoidal reflector 2. A UV filter (not shown) for cutting the UV light is disposed after the reflector. Thereafter, a dichroic prism 36 for separating the three primary colors of RGB is disposed. The G light passes through the dichroic prism, is emitted with the illuminance being substantially uniform by the light pipe 5g, and is incident on the G transmissive liquid crystal display element 13tg. The R light is reflected by the R reflecting surface 36r of the dichroic prism, emitted from the light pipe 5r with substantially uniform illuminance, and enters the R transmissive liquid crystal display element 13tr. The B light is reflected by the B reflecting surface 36b of the dichroic prism, emitted from the light pipe 5b with substantially uniform illuminance, and enters the B transmissive liquid crystal display element 13tb. The light transmitted through the three color liquid crystal display elements is color-combined by the dichroic prism 36 ′, and then enlarged and projected onto the screen by the projection lens 12. Since an array lens and an illumination system lens can be eliminated, the cost can be reduced. Further, since no collimator lens or the like is used, the size can be reduced accordingly.
[0048]
Here, the exit opening of the light pipe is substantially the same as the display area of the transmissive image display element, or is slightly larger in consideration of the dimensional variation of parts during mass production.
FIG. 8 shows another embodiment of the polarization conversion element 3 and the light pipe 5 that can be used in the projection type image display apparatus shown in FIGS. 1 to 5 and 7. Here, up to the light pipe 5 is described. The subsequent configuration is the same in each figure and is omitted. In this configuration, the axis of the polarization conversion element and the axis of the light pipe are shifted. Thereby, since the diagonal direction of the light pipe 5 is the longest, the size of the polarization separation element and the incident side light pipe can be increased by bringing the polarization separation direction of the polarization conversion element 3 in the diagonal direction. Thus, the vignetting from the light source unit 1 when entering the light source unit 1 can be reduced, so that the efficiency can be increased and the brightness can be increased. For example, when the aspect ratio of the video display element 13 is 4: 3, the diagonal length is 5 in ratio. Therefore, the width of the polarization separating element and the incident side light pipe 6 can be increased by 1.25 times compared to the case where the width is adjusted to the horizontal width, thereby improving the brightness. Here, since the polarization separation element is arranged almost in a diagonal manner, the polarization separation element 3 is inclined about 37 degrees with respect to the light pipe 5. Since the polarized light emitted from the polarization separation element is also tilted by about 37 degrees, the half-wave plate is shifted to the slow axis of 18.5 degrees and attached to the light pipe 5 incident side.
Here, P-polarized light and S-polarized light coming out of the polarization conversion element are incident as 45-degree and -45-degree linearly polarized light. Therefore, the 1/2 wavelength phase difference plate is set to the slow axis of 22.5 degrees and -22.5 degrees on the emission side, respectively, and is rotated to the same linearly polarized light as viewed from the light pipe. Let
[0049]
Other embodiments of the light pipe 5 that can be used in the projection type image display apparatus shown in FIGS. 1 to 5 and 7 are shown in FIGS. 9, 10, and 11. FIG. Here, up to the light pipe 5 is described. The subsequent configuration is the same in each figure and is omitted.
[0050]
The light pipe 5 shown in FIG. 9A includes a trapezoidal rod lens 5b and a triangular prism 5a having different refractive indexes. The refractive index of the trapezoidal rod lens 5b is larger than that of the triangular prism 5a. The trapezoidal rod lens has a divergent configuration toward the exit side. On the contrary, the triangular prism is configured to narrow toward the emission side. The triangular prism 5a is joined with an adhesive so as to sandwich the upper and lower sides of the trapezoidal rod lens 5b. A reflective film is coated on the interface with other air except for the incident surface 5aa on the lamp side of the triangular prism 5a. A light beam that satisfies the total reflection condition repeats internal reflection in the glass material 5b, so that the angle component can be reduced as compared with the case where 5a and 5b are made of the same glass material. On the other hand, since the light incident from 5aa can be finally taken into the trapezoidal rod lens 5b, the efficiency can be improved.
[0051]
The light pipe 5 shown in FIG. 9B includes a trapezoidal rod lens 5b and a mirror pipe 5c surrounding it. As a result, the light beam satisfying the total reflection condition repeats internal reflection in the trapezoidal rod lens 5b, so that the angle component can be made smaller than when the trapezoidal rod lens 5b and the mirror pipe 5c are made of a single glass material. On the other hand, since the light incident on the opening between the trapezoidal rod lens 5b and the mirror pipe 5c can be finally taken into the trapezoidal rod lens 5b, the efficiency can be improved.
[0052]
In FIG. 10A, the shape of the trapezoidal rod lens 5b is substantially parallel, the opening on the incident side of the triangular prism 5a is wide and gradually narrows. The refractive index of the trapezoidal rod lens 5b is larger than that of the triangular prism 5a. A reflective film is coated on the interface with other air except for the incident surface 5aa on the lamp side of the triangular prism 5a. The effect is the same as in FIG.
[0053]
In FIG. 10B, the shape of the trapezoidal rod lens 5b is a substantially parallel glass material, and the opening on the incident side surrounded by the mirror pipe 5c and the trapezoidal rod lens 5b is wide and gradually narrows. The effect is the same as in FIG.
[0054]
In FIG. 11A, the four surfaces of the trapezoidal rod lens 5b are surrounded by a mirror pipe 5c. FIG. 11B shows a trapezoidal rod lens 5b used for this. Up to the middle, the side faces expand in a divergent shape in both the vertical and horizontal directions, and from the middle become substantially parallel to the optical axis. The mirror pipe 5c is joined to the substantially parallel portion 5ba to facilitate the creation. In this configuration, the effect described in FIG. 10 can be obtained in both the vertical direction and the horizontal direction, and thus a greater effect can be obtained.
[0055]
FIGS. 12A and 12B show the movement of the light beam 30 in the light pipe shown in FIG. 9B as viewed from the side. As shown in FIG. 12A, the light beam 30 incident from the opening between the trapezoidal rod lens 5b and the mirror pipe 5c is incident from the side surface of the trapezoidal rod lens 5b and is reflected from the mirror pipe when exiting from the side surface. The light is reflected by the surface and reenters the trapezoidal rod lens 5b. Since the trapezoidal rod lens 5b has a divergent shape while the above process is repeated, the incident angle of light rays on the wall surface of the trapezoidal rod lens 5b gradually increases, eventually reaching the total reflection condition, and within the trapezoidal rod lens 5b. Finally, the light is totally reflected and finally exits from the exit surface of the trapezoidal rod lens 5b. As a result, only the trapezoidal rod lens 5b can increase the amount of light to be captured and brighten it as compared with the case where the light pipe is formed. In addition, since the trapezoidal rod lens has a divergent configuration, the angle component based on the optical axis can be gradually reduced. As shown in FIG. 12B, the light beam 30 incident from the front surface of the rod lens 5b is substantially totally reflected from the side surface in the rod lens 5b, and the angle component based on the optical axis is gradually reduced. The light exits from the exit surface. Since the display element 13 can increase the contrast as the angle component is smaller, the contrast of the device can be increased.
[0056]
FIG. 11 shows another embodiment of the light pipe 5 that can be used in the projection type image display apparatus shown in FIGS. 1 to 5 and 7. Here, only the light pipe 5 is shown. Other configurations are the same in each figure and are omitted.
[0057]
In addition, since the light emitted from the light pipe tends to have an approximately elliptical illuminance distribution, the central portion of the illuminance distribution on the reflective video display device swells. Therefore, by using the light pipe 5 having the exit opening 5z having a recessed center as shown in FIGS. 13A and 13B in advance, light loss due to expansion of the illuminance distribution can be suppressed. Can be improved.
[0058]
Red, orange, green, cyan, blue, and other LEDs may be used as the light source units in all the above embodiments. Thereby, the purity and size reduction of a single color can be achieved.
[0059]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a projection-type image display device that achieves both miniaturization and high brightness.
[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.
FIG. 6 is a configuration diagram of a projection type liquid crystal display device showing a sixth embodiment of the present invention.
FIG. 7 is a configuration diagram of a projection type liquid crystal display device showing a sixth embodiment of the present invention.
FIG. 8 is a configuration diagram of an embodiment of a polarization conversion element and a light pipe used in the present invention.
FIG. 9 is a configuration diagram of an embodiment of a light pipe used in the present invention and a trapezoidal rod lens used therefor.
FIG. 10 is a configuration diagram of another embodiment of a light pipe used in the present invention and a trapezoidal rod lens used therefor.
FIG. 11 is a configuration diagram of another embodiment of a light pipe used in the present invention and a trapezoidal rod lens used therefor.
FIG. 12 is a diagram showing the movement of light rays in the light pipe used in the present invention.
FIG. 13 is a configuration diagram of an embodiment of a light pipe used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source unit, 1a ... Light source, 2 ... Reflector, 3 ... Polarization conversion element, 3a ... Polarization separation element, 3b ... 1/2 wavelength phase difference plate, 3c ... Reflection mirror 5, 5h, 5i, 5j ... Light pipe 5jc ... side surface, 5a ... triangular prism, 5aa ... incident surface, 5b ... trapezoidal rod lens, 5ba ... substantially parallel portion, 5c ... mirror pipe, 5z ... output aperture, 6 ... incident side light pipe, 7 ... concave lens, 9 ... Condenser lens, 10 ... Color wheel, 11 ... Electronic color separation means, 12 ... Projection lens, 12 '... Removable mechanism, 13 ... Reflective display device, 14 ... Incident polarizing plate, 14' ... Outgoing polarizing plate, 15 ... Incident side light pipe, 19... Polarization separation element, 19 a... Polarization separation film, 21... Power source, 22... Projection type image display device, 23. Retardation plate DESCRIPTION OF SYMBOLS 30 ... Light ray, 32 ... 1st array lens, 33 ... 2nd array lens, 34 ... Collimator lens, 35 ... Micro lens, 36 ... Dichroic prism, 37 ... Chassis, 42 ... Reflective type polarizing plate, 43 ... Imaging Lens group, 44: diffractive optical element.

Claims (3)

A light source unit that emits light;
An illumination optical system for irradiating the image display element with light from the light source unit;
An image display element for forming an optical image corresponding to the image signal;
Projecting means for projecting light emitted from the image display element;
A projection-type image display device having a polarization conversion element that converts substantially elliptically polarized light emitted by an illumination optical system into substantially linearly polarized light,
The polarization conversion element is integrated with a light pipe that makes the light emitted from the light source unit incident and uniforms the illuminance of the light,
The polarization conversion element is composed of a polarization separation element, a half- wave retardation plate and a reflection element,
S- polarized light of light emitted from the light source unit and guided from the end face of the light pipe is reflected by the polarization separation element, the optical path is bent 90 degrees, and is emitted from the wall surface of the light pipe.
The P- polarized light emitted from the light source unit and guided from the end face of the light pipe is transmitted by the polarization separation element, converted to S- polarization by the half- wave retardation plate, and reflected by the reflection element. Then, the optical path is bent 90 degrees and emitted from the wall surface of the light pipe . In the projection type video display device according to claim 1,
The polarization separation element is formed as a polarization separation film on an end face of the light pipe having an angle of 45 degrees,
  The light pipe and the polarization conversion element are optically formed integrally. In the projection type video display device according to claim 1,
  A projection-type image display apparatus, wherein the position of the illumination optical system is changed so that an emitted light amount of light reflected by the polarization separating element and an emitted light amount of light reflected by the reflecting element are substantially equal.

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