JP7312944B2 - Light source device and projection display device - Google Patents

Description

The present disclosure relates to a projection display device that irradiates an image formed on a small light valve with illumination light and projects it in an enlarged manner onto a screen through a projection lens.

A large number of light source devices using long-life solid-state light sources such as semiconductor lasers and light-emitting diodes have been disclosed as light sources for projection display devices that use mirror-deflection type digital micromirror devices (DMDs) and liquid crystal panel light valves. Among them, Patent Literature 1 discloses a compact light source device that efficiently collects light from a solid-state light source by utilizing the polarization characteristics of light emitted from the solid-state light source.
Further, Patent Document 2 discloses a compact and highly efficient light source device using a half-wave plate that converts the polarization direction of light from a fixed light source and controls the P-polarized component and the S-polarized component incident on a dichroic mirror at a constant ratio.

JP 2012-137744 A JP 2014-209184 A

The present disclosure utilizes the polarization characteristics of light emitted from a solid-state light source to provide a light source device using a highly durable and low-cost retardation plate, and a projection display device using the light source device.

A solid light source, a dycloic mirror that separates light from a solid light source, a light gathering element located in a position where one of the biased lights from the dyclock mirror is incident, and the light from the phase difference plate and the phase difference, which is placed in a position where light from the light from the light collector is incident. The reflector is provided, and the phase line is placed in a position where the light integrated light and the radiating light are incident between the collectors and the reflector.

According to the present disclosure, a small and inexpensive light source device can be configured by arranging a retardation plate at a position where light is condensed, so a long-life, bright, and low-cost projection display device can be realized.

Configuration diagram of a light source device according to Embodiment 1 of the present disclosure 4A and 4B are diagrams showing spectral characteristics of the dichroic mirror according to the first embodiment; A diagram showing the angle dependence of the polarization transmittance of a retardation plate. Configuration diagram of a light source device according to Embodiment 2 of the present disclosure FIG. 11 shows spectral characteristics of a dichroic mirror according to Embodiment 2; Configuration diagram of a projection display device according to Embodiment 3 of the present disclosure Configuration diagram of a projection display device according to Embodiment 4 of the present disclosure

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art.
It should be noted that the accompanying drawings and the following description are provided for a thorough understanding of the present disclosure by those skilled in the art and are not intended to limit the claimed subject matter.
(Embodiment 1)
FIG. 1 is a configuration diagram of a light source device according to Embodiment 1 of the present disclosure. The light source device 40 of Embodiment 1 includes a semiconductor laser 21 as a solid-state light source, a heat sink 22, a condenser lens 23, a heat sink 24, a lens 26, a lens 27, a first diffuser plate 28, a dichroic mirror 29, condenser lenses 30 and 31 as first condenser elements, a fluorescent plate 35 composed of an aluminum substrate 33 on which a reflective film and a phosphor layer 32 are formed, and a motor 34, a condenser lens 36 as a second condenser element, a second diffuser plate 37, and a retardation plate. and a reflector 39 . FIG. 1 shows the aspect of each luminous flux 25 emitted from the solid-state light source and the polarization direction of the light incident on and emitted from the dichroic mirror 29 .
Twenty-four (6×4) semiconductor lasers 21 and condensing lenses 23 arranged in a square are two-dimensionally arranged on a radiator plate at regular intervals. A heat sink 24 is for cooling the semiconductor laser 21 . The semiconductor laser 21 emits blue light in a wavelength range of 447 nm to 462 nm and emits linearly polarized light. Each semiconductor laser is arranged so that the polarized light emitted from the semiconductor laser 21 is P-polarized with respect to the incident surface of the dichroic mirror 29 .

Lights emitted from a plurality of semiconductor lasers 21 are condensed by corresponding condensing lenses 23 and converted into parallel light beams 25 . The luminous flux 25 group is further reduced in diameter by the convex lens 26 and the concave lens 27 and enters the first diffusion plate 28 . The first diffusing plate 28 is made of glass and has a fine irregular surface to diffuse light. The diffusion angle, which is the half-value angle width at 50% of the maximum intensity of the diffused light, is as small as about 3 degrees, and the polarization characteristics are maintained. The light emitted from the first diffusion plate 28 enters the dichroic mirror 29 .
FIG. 2 shows the spectral characteristics of the dichroic mirror. Spectral characteristics indicate transmittance with respect to wavelength. The spectral characteristics of the dichroic mirror are such that P-polarized light of semiconductor laser light with a wavelength of 447 to 462 nm is transmitted (18% on average) and reflected (82% on average) at a certain ratio, and S-polarized light is reflected at a high reflectance of 95% or more. Furthermore, P-polarized light and S-polarized light of green and red are transmitted with a high transmittance of 96% or more.

The 82% P-polarized blue light reflected by the dichroic mirror 29 is condensed by the condenser lenses 30 and 31, and if the spot diameter is defined as the diameter at which the light intensity is 13.5% of the peak intensity, the spot diameter is superimposed on the spot light of 1.5 mm to 2.5 mm and enters the fluorescent screen 35. The first diffusion plate 28 diffuses the light so that the diameter of the spot light becomes a desired diameter.

Fluorescent plate 35 is a circular substrate that is rotatably controllable and has aluminum substrate 33 on which reflective film and phosphor layer 32 are formed and motor 34 at the center. The reflective film of the fluorescent screen 35 is a metal film or dielectric film that reflects visible light, and is formed on an aluminum substrate. Furthermore, a phosphor layer 32 is formed on the reflective film. The phosphor layer 32 is formed with a Ce-activated YAG yellow phosphor that is excited by blue light and emits yellow light containing green and red components. A representative chemical structure of the crystal matrix of this phosphor is Y ₃ Al ₅ O ₁₂ . The phosphor layer 32 is formed in an annular shape. The phosphor layer 32 excited by the spot light emits yellow light containing green and red component light. The phosphor plate 35 is an aluminum substrate, and by rotating it, it is possible to suppress the temperature rise of the phosphor layer 32 due to the excitation light and maintain the fluorescence conversion efficiency stably.

The light that has entered the phosphor layer 32 emits green and red color components as fluorescent light, and exits the phosphor plate 35 . Also, the light emitted to the reflecting film side is reflected by the reflecting film and emitted from the fluorescent screen 35 . The green and red colored lights emitted from the fluorescent plate 35 become natural light (non-polarized light), condensed by the condenser lenses 30 and 31 again, converted into substantially parallel light, and then transmitted through the dichroic mirror 29 .

On the other hand, the 18% P-polarized blue light that is transmitted through the dichroic mirror 29 is incident on the condenser lens 36, which is the second light collecting element, and is condensed into condensed light. The focal length of the condenser lens 36 is set so that the condensing angle is 40 degrees or less to form a condensed spot near the reflector 39 . Condensed light condensed by the condenser lens 36 enters the second diffusion plate 37 . The second diffuser plate 37 diffuses the incident light to make the light intensity distribution uniform and to eliminate the speckle of the laser light. The second diffusing plate 37 is formed by forming a diffusing surface with fine irregularities on the surface of a thin glass plate. The second diffuser plate 37 has a diffusion angle of approximately 4 degrees for light transmitted through the diffusion surface once, and maintains the polarization characteristics. The light transmitted through the second diffuser plate 37 enters a quarter-wave plate 38, which is a retardation plate. The 1/4 wavelength plate 38 is a retardation plate that provides a 1/4 wavelength phase difference in the vicinity of the emission center wavelength of the semiconductor laser 21 .

The quarter-wave plate 38 has an optical axis of 45 degrees when the P-polarization direction in FIG. 1 is 0 degrees. The quarter-wave plate 38 is a thin-film retardation plate (see Japanese Unexamined Patent Application Publication No. 2012-242449) that utilizes birefringence due to oblique vapor deposition of a dielectric material. A thin-film retardation plate is made of an inorganic material, and has excellent durability and reliability similar to inorganic optical crystals such as crystal. In addition, since the thin-film wavelength plate is laminated with a film thickness sufficiently thinner than the wavelength of light, the entire oblique deposition layer serves as a retardation plate having one optical axis. Therefore, the change in phase difference with respect to the incident angle is much smaller than that of a retardation plate made of an inorganic optical crystal such as crystal.

FIG. 3 shows an example of the angular dependence of the polarization transmittance of a thin film retardation plate (solid line) and a quartz retardation plate (broken line). Linearly polarized light is incident on the retardation plate, and the transmittance of one of the linearly polarized light components after being converted into circularly polarized light is defined as the polarized transmittance, and the polarized transmittance with respect to the incident angle is shown. The polarization transmittance is normalized as 1.0 when the incident angle is 0 degree. The thin film retardation plate has a 6% decrease in polarized light transmittance at an incident angle of ±30 degrees, while the crystal retardation plate has a 12% decrease in polarized light transmittance at an incident angle of ±5 degrees. Since the thin-film retardation plate is a retardation plate with very small incident angle dependence, it can convert incident linearly polarized light into circularly polarized light with high efficiency even if it is arranged at a position where condensed light or divergent light is incident. In addition, since it is arranged at the position where condensed light or divergent light is incident, the size of the quarter wave plate 38 can be reduced to 1/2 or less compared to the case where it is arranged at the position where conventional parallel light is incident, and the cost of the quarter wave plate can be significantly reduced.

The light transmitted through the quarter-wave plate 38 and converted into circularly polarized light is phase-inverted by the reflector 39 formed with a reflecting film such as aluminum or a dielectric multilayer film, becomes circularly polarized in the opposite direction and diverges, and is transmitted through the quarter-wave plate 38 and converted into S-polarized light. Furthermore, since no member disturbing polarized light is arranged between the quarter-wave plate 38 and the reflector 39, P-polarized light can be converted into S-polarized light with high efficiency.

The S-polarized light converted by the quarter-wave plate 38 is again diffused by the second diffusion plate 37 , converted into parallel light by the condenser lens 36 , and reflected by the dichroic mirror 29 .

In this way, the fluorescent light from the fluorescent plate 35 and the efficiently polarized blue light are synthesized by the dichroic mirror 29 and emitted as white light. The yellow light containing the green and red components of fluorescence emission and the blue light from the semiconductor laser 21 can provide good white balance emission characteristics. With this emission spectrum characteristic, monochromatic light with desired chromaticity coordinates can be obtained even if the light is separated into three primary colors of blue, green and red in the optical system of the projection display device.

Although a thin-film retardation plate is used as the quarter-wave plate in the description, a fine-structured retardation plate using birefringence caused by a fine periodic structure having a wavelength equal to or smaller than the wavelength of light may be used. Since the fine-structure retardation plate has a fine structure equal to or smaller than the wavelength of light, it can be placed at a position where condensed light is incident because the incident angle dependence of the polarization transmittance is small, similar to the thin film retardation plate shown in FIG.

As described above, the light source device of the present disclosure separates light from a plurality of semiconductor lasers by a dichroic mirror, and efficiently collects and synthesizes green and red colored lights excited and emitted by one of the separated lights, and blue light, which is the other light polarized and converted by a small retardation plate placed at the position where the condensed light is incident, to obtain white light. Therefore, a small, highly efficient, and inexpensive light source device can be configured.
(Embodiment 2)
FIG. 4 is a configuration diagram of a light source device according to Embodiment 2 of the present disclosure.

The light source device 72 of Embodiment 2 includes a semiconductor laser 51, a heat sink 52, a condenser lens 53, a heat sink 54, condenser lenses 56 and 59, a mirror 57, a half-wave plate 58 as a first retardation plate, a first diffusion plate 60, a dichroic mirror 61, condenser lenses 62 and 63 as first light collection elements, a fluorescent plate 67, a condenser lens 68 as a second light collection element, a second diffusion plate 69, and a second phase difference plate as a half wave plate. It consists of a four-wave plate 70 and a reflector 71 . The figure shows the aspect of each light beam 55 emitted from the solid-state light source and the polarization direction of the light entering and exiting the dichroic mirror 61 . A fluorescent screen 67 is composed of an aluminum substrate 65 on which a reflective film and a fluorescent layer 64 are formed, and a motor 66 .

The same configuration as the light source device 40 of Embodiment 1 of the present disclosure includes a semiconductor laser 51, a heat sink 52, a condenser lens 53, a heat sink 54, a first diffusion plate 60, condenser lenses 62 and 63, a fluorescent plate 67, a condenser lens 68, a second diffusion plate 69, a quarter-wave plate 70 which is a second retardation plate, and a reflector 71.

24 (6×4) square semiconductor lasers 51 and condensing lenses 53 are two-dimensionally arranged on a radiator plate 52 at regular intervals. A heat sink 54 is for cooling the semiconductor laser 51 . The semiconductor laser 51 emits blue light with a wavelength width of 447 nm to 462 nm and emits linearly polarized light. In FIG. 4, the semiconductor lasers 51 are arranged so that the polarized light emitted from the semiconductor lasers 51 is P-polarized with respect to the incident surface of the dichroic mirror 61 without passing through the retardation plate. Lights emitted from a plurality of semiconductor lasers 51 are respectively condensed by corresponding condensing lenses 53 and converted into parallel light beams 55 . A group of rays 55 is condensed by a convex condenser lens 56 and reflected by a mirror 57 . After the reflected condensed light is condensed, it becomes divergent light and enters the half-wave plate 58, which is the first retardation plate. The incident angle of light to the half-wave plate 58 is 40 degrees or less. A half-wave plate 58 is a retardation plate having a phase difference of 1/2 wavelength in the vicinity of the emission center wavelength of the semiconductor laser 51 . The half-wave plate 58 has an optical axis of 32.5 degrees when the P-polarization direction in FIG. 4 is 0 degrees. The half-wave plate 58 is provided with an adjustment mechanism in the rotational direction so that the arrangement angle of its optical axis can be adjusted.

The P-polarized light from the semiconductor laser 51 is converted to 65 degrees in polarization direction by the half-wave plate 58, and the light intensity of the P-polarized component becomes 18% and the light intensity of the S-polarized component becomes 82%.

The half-wave plate 58 is a thin-film retardation plate that utilizes birefringence due to oblique vapor deposition of a dielectric material. A thin-film retardation plate is made of an inorganic material, and has excellent durability and reliability similar to inorganic optical crystals such as crystal. In addition, since the thin film wave plate is laminated with a film thickness sufficiently thinner than the wavelength of light, the change in phase difference with respect to the incident angle of light is much smaller than that of a phase plate made of an inorganic optical crystal such as crystal. Therefore, even if it is arranged at a position where condensed or divergent light is incident, the direction of P-polarized light from the semiconductor laser 51 can be rotationally converted with high efficiency. In addition, since the half-wave plate 58 is arranged at the position where the condensed light is incident, the size of the half-wave plate 58 can be reduced to 1/2 or less compared to the case where it is arranged at the position where the conventional parallel light is incident, and the cost of the half-wave plate can be significantly reduced.

The light transmitted through the half-wave plate 58 is converted into substantially parallel light by the condenser lens 59 , enters the first diffusion plate 60 , diffuses, and enters the dichroic mirror 61 .

FIG. 5 shows spectral transmittance characteristics of the dichroic mirror 61. As shown in FIG. The dichroic mirror 61 has a characteristic that the wavelength at which the transmittance becomes 50% is 465 nm for S-polarized light and 442 nm for P-polarized light. The S-polarized component of the light incident on the dichroic mirror 61 is reflected, and the P-polarized component is transmitted. Since the optical axis of the half-wave plate 58 is arranged at 32.5 degrees, the polarization direction of the incident light is 65 degrees, and the light intensities of the S-polarized component and the P-polarized component are 82% and 18%, respectively.

The S-polarized light reflected by the dichroic mirror 61 is condensed by condenser lenses 62 and 63 , superimposed on a spot light with a diameter of 1.5 mm to 2.5 mm where the light intensity is 13.5% of the peak intensity, and enters a fluorescent screen 67 . The first diffusion plate 60 diffuses the light so that the diameter of the spot light becomes a desired diameter. Fluorescent plate 67 is a circular substrate that is rotatably controllable and has an aluminum substrate 65 on which a reflective film and a phosphor layer 64 are formed and a motor 66 at the center. The reflective film of the fluorescent screen 67 is a metal film or dielectric film that reflects visible light, and is formed on an aluminum substrate. Furthermore, a phosphor layer 64 is formed on the reflective film. The phosphor layer 64 is formed with a Ce-activated YAG yellow phosphor that is excited by blue light and emits yellow light containing green and red components. A representative chemical structure of the crystal matrix of this phosphor is Y ₃ Al ₅ O ₁₂ . The phosphor layer 64 is formed in an annular shape.

The phosphor layer 64 excited by the spot light emits yellow light containing light of green and red components. The phosphor plate 67 is an aluminum substrate, and by rotating it, it is possible to suppress the temperature rise of the phosphor layer 64 due to the excitation light and maintain the fluorescence conversion efficiency stably. The light that has entered the phosphor layer 64 emits green and red color components as fluorescent light, and exits the phosphor plate 67 . Also, the light emitted to the reflecting film side is reflected by the reflecting film and emitted from the fluorescent screen 67 . The green and red colored lights emitted from the fluorescent plate 67 become natural light, are condensed by the condenser lenses 62 and 63 again, are converted into substantially parallel light, and then pass through the dichroic mirror 61 .

On the other hand, the 18% P-polarized blue light that is transmitted through the dichroic mirror 61 is incident on the condenser lens 68, which is the second light collecting element, and is condensed. The focal length of the condenser lens 68 is set so that the condensing angle is 40 degrees or less to form a condensed spot near the reflector 71 . Condensed light condensed by the condenser lens 68 enters the second diffusion plate 69 . The second diffuser plate 69 diffuses the incident light to make the light intensity distribution uniform and to eliminate the speckle of the laser light. The second diffusing plate 69 is formed by forming a diffusing surface with fine unevenness on the surface of a thin glass plate. The second diffuser plate 69 has a diffusion angle of approximately 4 degrees for light transmitted through the diffusion surface once, and maintains the polarization characteristics.

The light transmitted through the second diffusion plate 69 is incident on the quarter-wave plate 70, which is the second retardation plate. The quarter-wave plate 70 is a retardation plate having a phase difference of 1/4 wavelength in the vicinity of the emission center wavelength of the semiconductor laser 51 . The quarter-wave plate 70 has an optical axis of 45 degrees when the P-polarization direction in FIG. 4 is 0 degrees. The quarter-wave plate 70 is a thin-film retardation plate that utilizes birefringence due to oblique vapor deposition of a dielectric material. A thin-film retardation plate is made of an inorganic material, and has excellent durability and reliability similar to inorganic optical crystals such as crystal.

The light transmitted through the quarter-wave plate 70 and converted into circularly polarized light is phase-inverted by the reflector 71 formed with a reflecting film such as aluminum or a dielectric multilayer film, becomes circularly polarized in the opposite direction and diverges, and is transmitted through the quarter-wave plate 70 and converted into S-polarized light. Furthermore, since no member disturbing polarized light is arranged between the quarter-wave plate 70 and the reflector 71, the P-polarized light can be converted into the S-polarized light with high efficiency.

The S-polarized light converted by the quarter-wave plate 70 is again diffused by the second diffusion plate 69 , converted into parallel light by the condenser lens 68 , and reflected by the dichroic mirror 61 .

In this way, the fluorescent light from the fluorescent plate 67 and the efficiently polarized blue light are synthesized by the dichroic mirror 61 and emitted as white light. The yellow light containing the green and red components of fluorescence emission and the blue light from the semiconductor laser 51 make it possible to obtain emission characteristics with good white balance. With this emission spectrum characteristic, monochromatic light with desired chromaticity coordinates can be obtained even if the light is separated into three primary colors of blue, green and red in the optical system of the projection display device.

In the first embodiment of the present disclosure, the transmittance characteristics of the dichroic mirror 29 in the blue wavelength band determine the blue light separation ratio, and the separation ratio slightly varies. On the other hand, in the second embodiment of the present disclosure, the half-wave plate 58 whose optical axis arrangement angle is adjustable is used to control the separation ratio of the blue light transmitted and reflected by the dichroic mirror 61, so that the separation ratio has very little variation. Therefore, variations in white balance characteristics are extremely reduced.

Although the half-wave plate 58 has been described using a thin-film retardation plate, a fine-structured retardation plate utilizing birefringence caused by a fine periodic structure equal to or smaller than the wavelength of light may be used.

In Embodiment 2, the half-wave plate 58 is used as the first retardation plate, but it may be arranged so that the polarized light emitted from the semiconductor laser 51 is S-polarized light, a quarter-wave plate may be used as the first retardation plate, and the arrangement angle of the optical axis may be adjusted so that the S-polarized component and the P-polarized component of the blue light after transmission have a predetermined ratio.

Further, in the second embodiment, as shown in FIG. 4, the half-wave plate 58 is arranged at the position where the diverging light is incident, but the half-wave plate 58 may be arranged at the position where the condensed light is incident. For example, a half-wave plate 58 may be placed before the condensed light reflected by the mirror 57 is condensed.

As described above, in the light source device of the present disclosure, light from a plurality of semiconductor lasers is polarized and separated at a constant ratio by a small half-wave plate arranged at a position where condensed light or divergent light is incident, and a dichroic mirror, and yellow light including green and red excited and emitted by one of the polarized and separated light and blue light on the other side are efficiently collected and combined to obtain white light.

(Embodiment 3)
FIG. 6 is a diagram showing a configuration of a first projection display device according to Embodiment 3 of the present disclosure. As an image forming element, a TN mode or VA mode active matrix transmissive liquid crystal panel in which thin film transistors are formed in a pixel region is used.

The light source device 40 includes a blue semiconductor laser 21, a radiator plate 22, a condenser lens 23, a heat sink 24, lenses 26 and 27, a first diffuser plate 28, a dichroic mirror 29, condenser lenses 30 and 31, a fluorescent plate 35 composed of an aluminum substrate 33 on which a reflective film and a phosphor layer 32 are formed, and a motor 34, a condenser lens 36, a second diffuser plate 37, a quarter-wave plate 38, and a reflector 39. Since the above is the light source device 40 according to the first embodiment of the present disclosure, redundant description thereof will be omitted.

The projection display device 80 of Embodiment 3 further includes a first lens array plate 200, a second lens array plate 201, a polarization conversion element 202, a superimposing lens 203, a blue reflecting dichroic mirror 204, a green reflecting dichroic mirror 205, reflection mirrors 206, 207, 208, relay lenses 209, 210, field lenses 211, 212, 213, an incident side polarizing plate 214, 215, 216, liquid crystal panels 217, 218, 219, output-side polarizing plates 220, 221, 222, a color synthesizing prism 223 composed of a red-reflecting dichroic mirror and a blue-reflecting dichroic mirror, and a projection lens 224.

White light from the light source device 40 is incident on the first lens array plate 200 composed of a plurality of lens elements. A light beam incident on the first lens array plate 200 is split into a large number of light beams. A large number of split light beams converge on a second lens array plate 201 composed of a plurality of lenses. The lens elements of the first lens array plate 200 have aperture shapes similar to those of the liquid crystal panels 217 , 218 and 219 . The focal lengths of the lens elements of the second lens array plate 201 are determined so that the first lens array plate 200 and the liquid crystal panels 217, 218 and 219 are in a substantially conjugate relationship.

Light emitted from the second lens array plate 201 enters the polarization conversion element 202 . The polarization conversion element 202 is composed of a polarization separation prism and a half-wave plate, and converts natural light from the light source into light of one polarization direction. Since fluorescent light is natural light, it is polarization-converted into one polarization direction, but blue light enters as S-polarized light and exits as S-polarized light without undergoing polarization conversion.

Light from the polarization conversion element 202 enters a superimposing lens 203 . The superimposing lens 203 is a lens for superimposing and illuminating the liquid crystal panels 217 , 218 and 219 with the light emitted from each lens element of the second lens array plate 201 . The first lens array plate 200, the second lens array plate 201, the polarization conversion element 202, and the superimposing lens 203 constitute an illumination optical system.

Light from the superimposing lens 203 is separated into blue, green, and red colored lights by a blue-reflecting dichroic mirror 204 and a green-reflecting dichroic mirror 205, which are color separation elements. The green light passes through the field lens 211 and the incident side polarizing plate 214 and enters the liquid crystal panel 217 . After being reflected by the reflecting mirror 206 , the blue light is transmitted through the field lens 212 and incident side polarizing plate 215 and enters the liquid crystal panel 218 . The red light is transmitted, refracted and reflected by relay lenses 209 and 210 and reflection mirrors 207 and 208 , passes through field lens 213 and incident side polarizing plate 216 , and enters liquid crystal panel 219 .

The three liquid crystal panels 217, 218, and 219 change the polarization state of incident light by controlling the voltage applied to the pixels according to the video signal, and light is modulated by the combination of the incident side polarizing plates 214, 215, and 216 and the output side polarizing plates 220, 221, and 222 arranged on both sides of each of the liquid crystal panels 217, 218, and 219 so that the transmission axes are orthogonal to each other, thereby forming green, blue, and red images. . The colored lights transmitted through the output-side polarizing plates 220, 221, and 222 are reflected by the color synthesizing prism 223, and the red and blue colored lights are reflected by the red-reflecting dichroic mirror and the blue-reflecting dichroic mirror, respectively. The light incident on the projection lens 224 is enlarged and projected onto a screen (not shown).

Since the light source device is composed of a plurality of solid-state light sources in a small size and emits white light with high efficiency and good white balance, it is possible to realize a long-life, high-brightness projection display device. In addition, since the image forming element uses three liquid crystal panels that use polarized light rather than a time-sharing method, it is possible to obtain bright, high-definition projected images with good color reproduction without color breaking. In addition, compared to the case of using three DMD elements, a total reflection prism is not required, and the prism for color synthesis is a small prism with 45-degree incidence.

As described above, the first projection display device of the present disclosure uses a solid-state light source, which is a semiconductor laser, and a light source device capable of obtaining white light by separating P-polarized light from the semiconductor laser light at a constant intensity ratio by a dichroic mirror, and synthesizing yellow light containing green and red components excited and emitted by one of the separated lights and blue light obtained by efficiently polarization-converting the other separated light by a small quarter-wave plate. Therefore, a compact and inexpensive projection display apparatus can be configured. Although the light source device 40 shown in FIG. 1 is used as the light source device, the light source device 72 shown in FIG. 4 may be used. In this case, the light source device has a very small variation in white balance of emitted white light, and an inexpensive light source device and projection display device can be configured.

Although a transmissive liquid crystal panel is used as an image forming element, a reflective liquid crystal panel may be used. By using a reflective liquid crystal panel, a smaller, higher-definition projection display device can be constructed.
(Embodiment 4)
FIG. 7 shows a second projection display device according to a fourth embodiment of the present disclosure. The second projection display device 90 uses three DMDs as image forming elements.

The light source device 40 includes a blue semiconductor laser 21, a radiator plate 22, a condenser lens 23, a heat sink 24, lenses 26 and 27, a first diffuser plate 28, a dichroic mirror 29, condenser lenses 30 and 31, a fluorescent plate 35 composed of an aluminum substrate 33 on which a reflective film and a phosphor layer 32 are formed, and a motor 34, a condenser lens 36, a second diffuser plate 37, a quarter-wave plate 38, and a reflector 39. The above is the light source device 40 according to the first embodiment of the present disclosure.

White light emitted from the light source device 40 is incident on the condenser lens 100 and condensed onto the rod 101 . The light incident on the rod 101 is reflected multiple times inside the rod, so that the light intensity distribution is made uniform and the light is emitted. Light emitted from rod 101 is collected by relay lens 102 , reflected by reflecting mirror 103 , transmitted through field lens 104 , and incident on total reflection prism 105 . Here, the condenser lens 100, rod 101, relay lens 102, reflecting mirror 103, and field lens 104 are an example of an illumination optical system.

The total reflection prism 105 is composed of two prisms, and a thin air layer 106 is formed between adjacent surfaces of the prisms. The air layer 106 totally reflects light incident at an angle equal to or greater than the critical angle. Light from the field lens 104 is reflected by the total reflection surface of the total reflection prism 105 and enters the color prism 107 .

The color prism 107 is composed of three prisms, and a blue-reflecting dichroic mirror 108 and a red-reflecting dichroic mirror 109 are formed on the proximal surface of each prism. The blue, red, and green lights are separated by the blue-reflecting dichroic mirror 108 and the red-reflecting dichroic mirror 109 of the color prism 107, and enter DMDs 110, 111, and 112, respectively. The DMDs 110 , 111 , and 112 deflect the micromirrors according to the video signal and reflect the light incident on the projection lens 113 and the light traveling outside the projection lens 113 . Light reflected by the DMDs 110, 111, and 112 is transmitted through the color prism 107 again. In the process of passing through the color prism 107 , the separated blue, red, and green lights are synthesized and enter the total reflection prism 105 .

The light incident on the total reflection prism 105 is incident on the air layer 106 at a critical angle or less, so that the light is transmitted and is incident on the projection lens 113 . In this manner, image light formed by the DMDs 110, 111 and 112 is enlarged and projected onto a screen (not shown).

Since the light source device is composed of a plurality of solid-state light sources and emits white light with high efficiency and good white balance, it is possible to realize a long-life, high-brightness projection display device. In addition, since a DMD is used as an image forming element, a projection display device having higher light resistance and heat resistance than an image forming element using liquid crystal can be constructed. Furthermore, since three DMDs are used, it is possible to obtain a bright and high-definition projected image with excellent color reproduction.

As described above, the second projection display device of the present disclosure uses a solid-state light source, which is a semiconductor laser, and a light source device capable of obtaining white light by separating P-polarized light from the semiconductor laser light at a constant intensity ratio using a dichroic mirror, and synthesizing yellow light containing green and red components excited and emitted by one of the separated lights and blue light obtained by efficiently polarization-converting the other separated light by a small quarter-wave plate. Therefore, a compact and inexpensive projection display apparatus can be configured. Although the light source device 40 shown in FIG. 1 is used as the light source device, the light source device 72 shown in FIG. 4 may be used. In this case, the light source device has a very small variation in white balance of emitted white light, and an inexpensive light source device and projection display device can be configured.

As described above, Embodiments 1 to 4 have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments with modifications, replacements, additions, omissions, and the like.

INDUSTRIAL APPLICABILITY The present disclosure can be applied to a light source device of a projection display device using an image forming element.

21,51 semiconductor laser 22,52 radiator plate 23,53 condenser lens 24,54 heat sink 25,55 light flux 26,27 lens 28,60 first diffusion plate 29,61 dichroic mirror 30,31,36,56,59,62,63,68 condenser lens 32,64 phosphor layer 33,65 aluminum substrate 3 4, 66 motor 35, 67 fluorescent plate 37, 69 second diffusion plate 38 quarter wave plate 39, 71 reflector 40, 72 light source device 57 mirror 58 half wave plate 70 quarter wave plate 80, 90 projection display device 100 condensing lens 101 rod 102, 209, 210 relay lens 103, 20 6, 207, 208 reflection mirror 104, 211, 212, 213 field lens 105 total reflection prism 106 air layer 107 color prism 108, 204 blue reflection dichroic mirror 109 red reflection dichroic mirror 110, 111, 112 DMD
113, 224 projection lens 200 first lens array plate 201 second lens array plate 202 polarization conversion element 203 superimposing lens 205 green reflecting dichroic mirror 214, 215, 216 incident side polarizing plate 217, 218, 219 liquid crystal panel 220, 221, 222 output side polarizing plate 223 color synthesizing prism

Claims (8)

a solid state light source;
a dichroic mirror for polarization separation of light from the solid-state light source;
a condensing element arranged at a position where one of the lights polarized and separated by the dichroic mirror is incident;
a quarter-wave plate disposed at a position where the light from the light-condensing element is incident, and which converts the direction of polarization of the incident light;
a reflector that reflects light from the quarter-wave plate ;
The light source device, wherein the quarter-wave plate is arranged between the condensing element and the reflecting plate at a position where condensed light and divergent light are incident. 2. The light source device according to claim 1, further comprising a phosphor emitting excitation light at a position on which the other of the lights polarized and separated by said dichroic mirror is incident. 3. The light source device according to claim 2, wherein the light reflected by said reflector and the excitation light emitted by said phosphor are synthesized by said dichroic mirror. 3. The light source device according to claim 1, wherein said solid-state light source is a blue semiconductor laser. 2. The light source device according to claim 1, wherein the light emitted from said solid-state light source is linearly polarized light. comprising a second retardation plate that converts the orientation of polarization of light from the solid-state light source;
6. The light source device according to claim 5, wherein said dichroic mirror polarization-separates the light from said second retardation plate. a light source;
an illumination optical system that condenses the light from the light source and illuminates an area to be illuminated;
an image forming element that forms an image according to a video signal;
a projection lens for enlarging and projecting an image formed by the image forming element,
A projection display device, wherein the light source is the light source device according to claim 1 . 8. The projection display apparatus of claim 7, wherein the imaging element is one of a liquid crystal panel or a mirror-deflected digital micromirror device (DMD).

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