JP2012118452A - Polarization-converting light source device and projection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization-converting light source device reduced in size while maintaining high use efficiency of light.SOLUTION: The light source device includes a non-polarizing cross dichroic prism 13 having two reflection faces 13r, 13b substantially orthogonal to each other and reflecting light at predetermined wavelengths, three light sources 11r, 11g, 11b emitting light at wavelengths different from one another, three reflectors 12r, 12g, 12b corresponding to the respective light sources, and a reflective polarization separator 14. The reflectors 12r, 12g, 12b are arranged in such a manner that the light of the respective colors reflected by the polarization separator 14 is reflected by the respective reflectors to be incident to the non-polarizing cross dichroic prism 13.

Description

  The present invention relates to a polarization conversion light source device that converts a light beam emitted from a light source into polarized light having a uniform polarization direction, and a projection-type liquid crystal display device using the same.

  2. Description of the Related Art Conventionally, as a liquid crystal display device such as a liquid crystal display, a device that forms a projection image via a projection optical system after modulating light emitted from a light source corresponding to a display image is known. The liquid crystal light valve used in this liquid crystal display device uses only one polarization component of light from the light source, and usually does not use the other polarization component of light from the light source.

  In recent years, in order to improve the utilization efficiency of light from a light source, a configuration has been proposed in which the above-described polarized light that is not used is converted into polarized light that can be used using a polarization conversion device. For example, Patent Document 1 discloses a projector that uses a large number of polarizing plates, cross dichroic prisms, and the like as a polarization conversion device.

  In the polarization conversion light source device described in Patent Document 1, one polarization component of the incident light to the polarization conversion device is transmitted through the polarization separation surface, is transmitted through the half-wave retardation film and is orthogonally polarized light. Converted. On the other hand, another polarized component of incident light is reflected by the polarization separation surface, then reflected by the reflecting mirror, and emitted in substantially the same direction as the converted polarized light. That is, the polarized light reflected by the polarization separation surface and the polarized light that has been transmitted through the polarization separation surface and subjected to polarization conversion are emitted in substantially the same direction as light having substantially the same phase. As described above, in the polarization conversion light source device described in Patent Document 1, the use efficiency of light incident on the liquid crystal light valve is improved by converting one polarization component of incident light into another polarization component. Is done.

JP 2009-258744 A

  However, the polarization conversion light source device described in Patent Document 1 separates white light from a white light source into red, green, and blue color lights with a dichroic mirror, and further, red, green, and blue color lights with cross dichroic. Since an optical image is formed by combining, there is a problem that the apparatus becomes large. FIG. 4 is a schematic diagram showing a configuration example of a liquid crystal projector using a conventional polarization conversion light source device 41. In the polarization conversion light source device 41 shown in FIG. 4, the light emitted from the white light source 42 is color-separated by the dichroic prism 43 having polarization, and then transmitted and reflected by the polarization separators 44r, 44g, and 44b. Separated into light. The transmitted light of each color is transmitted through the transmissive liquid crystal valves 45r, 45g, and 45b, and is again synthesized by the dichroic prism 46 having polarization, and an image is projected through the projection lens 47. In the polarization conversion light source device 41 having such a configuration, a complicated lens design and a long optical path are required to efficiently collect and transmit light from the light source to the polarization separation surface of each color. For this reason, it is difficult to reduce the size of the apparatus.

  SUMMARY An advantage of some aspects of the invention is that it provides a polarization conversion light source device that is miniaturized while maintaining high light use efficiency and a projection type liquid crystal display device using the polarization conversion light source device.

  The polarization conversion light source device of the present invention includes a non-polarization cross dichroic prism having two reflecting surfaces that are substantially orthogonal to each other and reflect light of a predetermined wavelength, three light sources that respectively emit light of different wavelengths, and each light source The first light source is arranged so that the light from the light source enters the first surface of the non-polarized cross dichroic prism. Arranged on the first surface side, the second light source is disposed on the second surface side so that light from the light source enters the second surface facing the first surface of the non-polarized cross dichroic prism The third light source is disposed on the third surface side so that light from the light source enters the third surface adjacent to the first surface and the second surface of the non-polarized cross dichroic prism. The polarized light separator is The non-polarized cross dichroic prism is arranged on the fourth surface side so that light emitted from the fourth surface facing the third surface is incident, and the first reflector is reflected by the polarization separator. The second reflector is reflected by the polarization separator so that the light emitted from the first surface is incident, and the light emitted from the second surface is incident. Arranged on the second surface side, and the third reflector is arranged on the third surface side so that light reflected from the polarization separator and light emitted from the third surface enters. It is characterized by that.

  According to the said structure, while using three light sources and providing the reflecting plate corresponding to each light source, the reflected light from a polarized light separator can be utilized effectively. For this reason, the intensity | strength of the output light from a polarization conversion light source device can fully be ensured. In addition, since a plurality of light sources that emit light of different wavelengths are used without using a white light source, the optical system can be easily designed, and the polarization conversion light source device can be miniaturized.

  In the polarization conversion light source device of the present invention, the light from the first light source that has entered the first surface is reflected by the first reflection surface of the non-polarization cross dichroic prism and transmits the second reflection surface. The light is emitted from the fourth surface, a part of the light is reflected by the polarization separator, and the reflected light enters the fourth surface, is reflected by the first reflective surface, and is reflected by the second reflective surface. The light from the second light source that is transmitted through the surface and exits the first surface, is reflected by the first reflector, enters the first surface again, and enters the second surface. , And transmitted through the first reflecting surface and reflected by the second reflecting surface to emit light from the fourth surface, a part of which is reflected by the polarization separator, and the reflected light is reflected on the fourth surface. Incident light, transmitted through the first reflecting surface, and the second Light from the third light source that is reflected by the incident surface and emitted from the second surface, reflected by the second reflector, incident again on the second surface, and incident on the third surface Is transmitted through the first reflecting surface and transmitted through the second reflecting surface and exits from the fourth surface, a part of which is reflected by the polarization separator, and the reflected light is reflected by the fourth surface. Is incident on the first reflecting surface, passes through the second reflecting surface, exits from the third surface, is reflected by the third reflector, and enters the third surface again. May be.

  In the polarization conversion light source device of the present invention, a polarization rotator may be provided between the optical paths of the reflector and the polarization separator. Further, in the polarization conversion light source device of the present invention, the polarization rotator may be a broadband ¼ wavelength phase difference film. In the polarization conversion light source device of the present invention, the polarization rotator may be a laminate of at least one quarter-wave retardation film and at least one half retardation film.

  According to the above configuration, since the polarization direction of the reflected light from the polarization separator can be appropriately converted, the reflected light from the polarization separator can be used more effectively.

  In the polarization conversion light source device of the present invention, the polarization separator may be a wire grid polarizer. In the polarization conversion light source device of the present invention, the polarization separator may be a multilayer film having a birefringent material.

  In the polarization conversion light source device of the present invention, a lens may be provided between the light source and the non-polarization dichroic prism.

  The projection type liquid crystal display device of the present invention comprises the polarization conversion light source device, a transmission type liquid crystal element, and a projection lens, and the transmission type liquid crystal element transmits the light emitted from the polarization conversion light source device. The projection lens is disposed so as to enter the liquid crystal element, and the projection lens is disposed so that light emitted from the transmissive liquid crystal element enters the projection lens.

  In the projection type liquid crystal display device of the present invention, an absorption polarizing plate may be provided on the light output side of the polarization conversion light source device.

  The projection type liquid crystal display device of the present invention comprises the polarization conversion light source device, a reflection type liquid crystal element, a polarizing beam splitter, and a projection lens, and the reflection type liquid crystal element and the polarizing beam splitter are: The light emitted from the polarization conversion light source device is disposed so as to enter the reflective liquid crystal element through the polarizing beam splitter, and the projection lens has the light emitted from the reflective liquid crystal element as the polarizing beam splitter. The projection lens is arranged so as to be incident on the projection lens.

  According to the present invention, by using three light sources and providing a reflecting plate corresponding to each light source, the reflected light from the polarization separator can be used effectively. For this reason, the intensity | strength of the output light from a polarization conversion light source device can fully be ensured. In addition, since a plurality of light sources that emit light of different wavelengths are used without using a white light source, the optical system can be easily designed, and the polarization conversion light source device can be miniaturized. For this reason, the polarization conversion light source device reduced in size while keeping the light use efficiency high is provided.

It is a schematic diagram which shows the structure of the polarization conversion light source device which concerns on embodiment, and the optical path of red light. It is a schematic diagram which shows the structure of the polarization conversion light source device which concerns on embodiment, and the optical path of blue light. It is a schematic diagram which shows the structure of the polarization conversion light source device which concerns on embodiment, and the optical path of green light. It is a schematic diagram which shows the structure of the transmissive liquid crystal projector using the polarization conversion light source device which concerns on embodiment. It is a schematic diagram which shows the structure of the reflection-type liquid crystal projector using the polarization conversion light source device which concerns on embodiment. It is a schematic diagram which shows the structural example of the liquid crystal projector using the conventional polarized light conversion light source device.

  The present inventors have found that by using three light sources and providing a reflecting plate corresponding to each light source, the reflected light from the polarization separator can be used effectively while downsizing the apparatus. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1A, FIG. 1B, and FIG. 1C are schematic diagrams showing the configuration of the polarization conversion light source device 1 according to the present embodiment. The polarization conversion light source device 1 shown in FIGS. 1A, 1B, and 1C includes three light sources 11r, 11g, and 11b, and three reflectors 12r, 12g, and 12b arranged corresponding to the light sources 11r, 11g, and 11b. And a non-polarization cross dichroic prism 13 that reflects or transmits incident light, and a reflective polarization separator 14.

  The light source 11r is configured to emit red light. Similarly, the light source 11g is configured to emit green light, and the light source 11b is configured to emit blue light. The light source 11r is arranged on the one surface side so that light from the light source 11r is incident on the one surface (first surface) on the left side of the non-polarization cross dichroic prism 13 substantially perpendicularly. Similarly, the light source 11g is arranged on the one surface side so that light from the light source 11g is incident on the one surface (third surface) on the lower side of the non-polarization cross dichroic prism 13 substantially perpendicularly. . The light source 11b is disposed on the one surface side so that light from the light source 11b is incident on the one surface (second surface) on the right side of the non-polarizing cross dichroic prism 13 substantially perpendicularly.

  The reflectors 12r, 12g, and 12b are disposed on the first surface side, the third surface side, and the second surface side, respectively, corresponding to the light sources 11r, 11g, and 11b. The reflectors 12r, 12g, and 12b have a function of condensing and reflecting the light reflected by the reflective polarization separator 14 and causing the light to enter the non-polarization cross dichroic prism 13. Moreover, the reflectors 12r, 12g, and 12b may have a function of condensing light from the light sources 11r, 11g, and 11b.

  The non-polarization cross dichroic prism 13 has two reflecting surfaces 13r and 13b that reflect light of a predetermined wavelength and transmit light of other wavelengths. The reflection surfaces 13r and 13b are substantially orthogonal to each other. Specifically, the reflection surface 13r of the non-polarization cross dichroic prism 13 reflects red light and transmits light of other colors. The reflective surface 13b reflects blue light and transmits light of other colors. For this reason, the red light from the light source 11r enters the non-polarization cross dichroic prism 13 from the first surface, passes through the reflection surface 13b and is reflected by the reflection surface 13r, and is a surface on the upper side of the drawing which is a light exit surface ( Light is emitted from the fourth side. Similarly, blue light from the light source 11b enters the non-polarization cross dichroic prism 13 from the second surface, passes through the reflecting surface 13r, is reflected by the reflecting surface 13b, and exits from the light emitting surface (fourth surface). . Further, the green light from the light source 11g is collected by the reflector 12g, enters the non-polarization cross dichroic prism 13, passes through the reflection surfaces 13r and 13b without being reflected, and exits (fourth surface). I come out of light. Thereby, the red light, the blue light, and the green light emitted from the light exit surface of the non-polarization cross dichroic prism 13 are combined to obtain a non-polarized combined light (white light).

  Here, the reflection surfaces 13r and 13b are configured to reflect red light or blue light, but the present invention is not limited to this. For example, a reflective surface that reflects green light may be used. In this case, it is necessary to arrange the light source 11g and the reflector 12g so that the green light is reflected on the reflection surface and is emitted from one surface above the non-polarization cross dichroic prism 13. Further, the arrangement of the light sources 11r, 11g, and 11b can be appropriately changed according to the configuration of the reflection surface of the non-polarization cross dichroic prism 13.

  The polarization separator 14 is disposed on the light exit surface (fourth surface) side of the non-polarization cross dichroic prism 13 so that the combined light emitted from the non-polarization cross dichroic prism 13 enters. The polarization separator 14 transmits one polarization component (hereinafter referred to as first polarization) of the combined light incident on the polarization separator 14 and reflects the other polarization component (hereinafter referred to as second polarization). Is configured to do. For this reason, the first polarized light of the combined light is transmitted through the polarization separator 14 to be emitted, and the second polarized light is reflected by the polarization separator 14. Note that the polarization separator 14 may have a planar shape or a curved surface shape. By using a curved shape, the function of a lens can be added to the polarization separator 14.

  In the polarization conversion light source device 1 configured as described above, light from the light sources 11r, 11g, and 11b enters the non-polarization cross dichroic prism 13 and is extracted as combined light from the light exit surface of the non-polarization cross dichroic prism 13. It is. The combined light enters the polarization separator 14, and the first polarized light is emitted from the polarization separator 14. The second polarized light reflected by the polarization separator 14 enters the non-polarized cross dichroic prism 13 from the upper surface, which is the light exit surface of the non-polarized cross dichroic prism 13, and the two reflective surfaces 13r, 13b. Is again separated into light of each color. That is, the red light component of the reflected composite light enters the light exit surface (fourth surface), is reflected by the reflective surface 13r, passes through the reflective surface 13b, and exits from the first surface. Further, the blue light component enters the light exit surface (fourth surface), passes through the reflective surface 13r, is reflected by the reflective surface 13b, and exits from the second surface. The green light component enters the light exit surface (fourth surface), passes through the reflective surface 13r and the reflective surface 13b, and exits from the third surface. The color lights thus separated are collected by the reflectors 12r, 12g, and 12b, and enter the non-polarization cross dichroic prism 13 again.

  Here, for example, a polarization rotator 15 such as a random polarization element for randomizing the polarization direction or a phase difference plate for changing the phase by a predetermined amount is used as the light source 11r, 11g, 11b (or the reflector 12r, 12g, 12b). ) To the polarization separator 14, the polarization state of the second polarized light reflected by the polarization separator 14 can be changed. Therefore, one polarization component of the light reflected by the polarization separator 14 and again incident on the non-polarization cross dichroic prism 13 can be transmitted through the polarization separator 14, and the polarization conversion light source device 1 can be used as the output light from 1. In addition, when using a phase difference plate, compared with the case where a random polarizing element is used, it is possible to align the polarization of the reflected light from the polarization separator 14 and extract it as output light with a smaller number of reflections. That is, in the case of using the phase difference plate, the dissipation of light due to reflection can be suppressed and the loss can be reduced as compared with the case of using a random polarizing element.

  More specifically, for example, red light from the light source 11r is extracted as output light as shown in FIG. 1A. First, red light emitted from the light source 11r enters the non-polarization cross dichroic prism 13, passes through the reflection surface 13r, and is extracted from the light exit surface as red light R1. The extracted red light R1 enters the polarization separator 14, and the red light R2 polarized in the first direction is emitted from the polarization separator 14. The red light polarized in the second direction reflected by the polarization separator 14 passes through the polarization rotator 15 and becomes red light R3 including polarized light in a direction different from the second direction. The red light R3 enters the non-polarization cross dichroic prism 13 and is reflected again by the reflecting surface 13r. The light reflected by the reflecting surface 13r is collected by the reflector 12r and enters the non-polarized cross dichroic prism 13 again. The light incident on the non-polarization cross dichroic prism 13 is reflected by the reflecting surface 13r and extracted as red light R4. The red light R4 enters the polarization separator 14 via the polarization rotator 15. . From the polarization separator 14, red light R5 polarized in the first direction is emitted.

  Further, the blue light from the light source 11b is extracted as output light as shown in FIG. 1B. First, the blue light emitted from the light source 11b enters the non-polarized cross dichroic prism 13, passes through the reflection surface 13b, and is extracted from the light exit surface as blue light B1. The extracted blue light B1 enters the polarization separator 14, and the blue light B2 polarized in the first direction is emitted from the polarization separator 14. Further, the blue light polarized in the second direction reflected by the polarization separator 14 passes through the polarization rotator 15 and becomes blue light B3 including polarized light in a direction different from the second direction. The blue light B3 enters the non-polarization cross dichroic prism 13 and is reflected again by the reflecting surface 13b. The light reflected by the reflecting surface 13b is collected by the reflector 12b and enters the non-polarization cross dichroic prism 13 again. The light incident on the non-polarization cross dichroic prism 13 is reflected by the reflecting surface 13b and extracted as blue light B4. The blue light B4 enters the polarization separator 14 via the polarization rotator 15. . From the polarization separator 14, the blue light B5 polarized in the first direction is emitted.

  Further, the green light from the light source 11g is extracted as output light as shown in FIG. 1C. First, green light emitted from the light source 11g enters the non-polarization cross dichroic prism 13, passes through the reflection surface 13r and the reflection surface 13b, and is extracted from the light emission surface as green light G1. The extracted green light G <b> 1 enters the polarization separator 14, and the green light G <b> 2 polarized in the first direction is emitted from the polarization separator 14. The green light polarized in the second direction reflected by the polarization separator 14 passes through the polarization rotator 15 and becomes green light G3 including polarized light in a direction different from the second direction. The green light G3 enters the non-polarization cross dichroic prism 13 and passes through the reflection surface 13r and the reflection surface 13b. The light transmitted through the reflecting surface 13r and the reflecting surface 13b is collected by the reflector 12g and enters the non-polarization cross dichroic prism 13 again. The light that has entered the non-polarization cross dichroic prism 13 passes through the reflection surface 13r and the reflection surface 13b and is extracted as green light G4. The green light G4 passes through the polarization rotator 15 and then passes through the polarization separator 14. Incident light. From the polarized light separator 14, green light G5 polarized in the first direction is emitted.

  As the above-described light sources 11r, 11g, and 11b, for example, LEDs can be used. In addition, you may attach a lens to the front-end | tip of light source 11r, 11g, and 11b, and may control a light emission angle.

For example, a concave mirror can be used as the reflectors 12r, 12g, and 12b arranged around the light sources 11r, 11g, and 11b. The reflective layers of the reflectors 12r, 12g, and 12b can be formed, for example, by laminating a metal such as aluminum on the main surface of the reflector using a method such as vacuum deposition or sputtering. Note that the material used for the reflective layer is not particularly limited as long as it reflects light, and various materials such as various metal materials such as aluminum and silver can be used. From the viewpoint of suppressing the light reflectivity and the decrease in the amount of light due to light absorption, it is preferable to use a multilayer film of dielectric material such as aluminum, SiO ₂ , or TiO ₂ . From the viewpoint of productivity, it is preferable to use aluminum. A layer structure such as aluminum and SiO ₂ or TiO ₂ may be used.

  The thickness of the reflective layer is preferably 5 nm to 300 nm, and more preferably 10 nm to 200 nm. If it is 5 nm or more, the reflection efficiency does not decrease, and if it is 300 nm or less, the productivity is excellent.

  The reflectors 12r, 12g, 12b and the reflective layer are not limited as long as they have a function of reflecting at least the light reflected from the polarization separator 14 again. It is more preferable to design using simulation or the like so that the light reflected again becomes parallel light.

  The non-polarization cross dichroic prism 13 is not particularly limited as long as red light, blue light, and green light can be decomposed and synthesized. For example, a non-polarization cross dichroic prism disclosed in International Publication No. 2009/041038 pamphlet can be used.

  The polarization separator 14 is not particularly limited as long as it is a reflective member capable of polarization separation, and for example, a wire grid polarizing plate, a multilayer film using a birefringent material, or the like can be used. In particular, a wire grid polarizing plate is preferable because good reflection characteristics and transmission characteristics in visible light can be obtained. Examples of the wire grid polarizing plate include WGF (manufactured by Asahi Kasei Corporation). Examples of the multilayer film using a birefringent material include D-BEF (manufactured by 3M).

  Examples of the random polarizing element used as the polarization rotator 15 include a diffusion film and a lens film. By using such a random polarization element, the polarization separator 14 can be transmitted, and the light utilization efficiency can be improved.

  Examples of the retardation plate used as the polarization rotator 15 include a retardation film such as a quarter-wave retardation film. As the retardation film, a stretched product of COP or TAC substrate can be used. Moreover, it is preferable to use the retardation film corresponding to the wavelength of each color. A plurality of retardation films can be used in combination. In addition, when using it combining a lens film and a diffusion film with a wavelength phase difference film, it is preferable that a lens film and a diffusion film do not have a phase difference rotation function or birefringence.

  In addition, the retardation film should just convert 2nd polarization | polarized-light into 1st polarization | polarized-light, and the number of retardation films and the phase rotation angle of retardation film are not limited. For example, when one quarter retardation film is used, one quarter retardation film and one half retardation film are combined to adjust the wavelength at which the conversion efficiency reaches a peak. It is good also as a structure used. In this case, two retardation films may be laminated, and an intermediate layer may be interposed between the two retardation films. Also, two 1/8 retardation films may be used.

  Further, as the retardation plate, a broadband wavelength plate in which a plurality of birefringent crystals are combined to suppress the wavelength dependence of the retardation can be used. When a broadband wavelength plate is used, the phase conversion of each color can be performed only by arranging one sheet between the light exit surface of the non-polarization cross dichroic prism 13 and the polarization separator 14. Of these broadband wave plates, it is more preferable to use a broadband quarter wave plate.

  The polarization rotator 15 arranged in the optical path between the light sources 11r, 11g, 11b (or the reflectors 12r, 12g, 12b) and the polarization separator 14 is particularly limited as long as the polarization direction can be rotated. Alternatively, various polarization rotation elements other than a random polarization element and a phase difference plate can be used.

  The above-described polarization conversion light source device 1 according to the present embodiment can be used as a light source device such as a projection display device, a direct-view display, a liquid crystal display device, and a liquid crystal projector.

  FIG. 2 is a schematic diagram showing a configuration of a liquid crystal projector 2 using the polarization conversion light source device 1 and the transmissive liquid crystal bulb (LCD) 21 according to the present embodiment.

  As shown in FIG. 2, the transmissive liquid crystal projector 2 according to the present embodiment uses the polarization conversion light source device 1. The transmissive liquid crystal projector 2 includes a transmissive liquid crystal bulb 21, a polarizing plate 22, and a projection lens 23 in addition to the polarization conversion light source device 1. The details of the optical path and the like in the polarization conversion light source device 1 are as described above. The transmissive liquid crystal bulb 21 is arranged so that light emitted from the polarization separator 14 of the polarization conversion light source device 1 enters. The polarizing plate 22 is disposed so that light transmitted through the transmissive liquid crystal bulb 21 is incident thereon. The projection lens 23 is arranged so that light transmitted through the polarizing plate 22 enters. The polarized light having a high light intensity from the polarization conversion light source device 1 and having the same polarization is projected via the transmissive liquid crystal bulb 21, the polarizing plate 22, and the projection lens 23. A polarizing plate may be provided on the transmission liquid crystal bulb 21 side of the polarization separator 14.

  FIG. 3 is a conceptual diagram of a liquid crystal projector 3 using the polarization conversion light source device 1 and the reflective liquid crystal bulb (Lcos) 31 according to the present embodiment.

  As shown in FIG. 3, the reflective liquid crystal projector 3 according to the present embodiment uses the polarization conversion light source device 1. The reflective liquid crystal projector 3 includes a reflective liquid crystal bulb 31, a PBS or reflective polarizing plate 32, and a projection lens 33 in addition to the polarization conversion light source device 1. The details of the optical path and the like in the polarization conversion light source device 1 are as described above. The reflection type liquid crystal bulb 31 is arranged so that light emitted from the polarization separator 14 of the polarization conversion light source device 1 is reflected by the PBS or the reflection type polarizing plate 32 and enters. In addition, the projection lens 33 is arranged so that the light modulated and reflected by the reflective liquid crystal bulb 31 enters. Polarized light having a high light intensity from the polarization conversion light source device 1 and having the same polarization is reflected by the PBS or the reflective polarizing plate 32, projected onto the reflective liquid crystal bulb 31, and modulated and reflected. Then, the light passes through the PBS or the reflective polarizing plate 32 and is projected via the projection lens 33. A polarizing plate may be provided on the side of the polarizing separator 14 on the PBS or the reflective polarizing plate 32 side.

  As described above, in the polarization conversion light source device 1 according to the present invention, it is possible to effectively use the reflected light from the polarization separator by using three light sources and providing a reflecting plate corresponding to each light source. it can. For this reason, the intensity | strength of the output light from a polarization conversion light source device can fully be ensured. In addition, since a plurality of light sources that emit light of different wavelengths are used without using a white light source, the optical system can be easily designed, and the polarization conversion light source device can be miniaturized.

  In addition, in the polarization conversion light source device 1 according to the present invention, by using a non-polarization dichroic prism, light emitted from the non-polarization dichroic prism becomes non-polarization, so that the light is separated and polarized by a separate polarization rotator. There is no need to align the direction. That is, since it is not necessary to separate the emitted light, the light utilization efficiency can be increased. In addition, since it is not necessary to separate the emitted light, the polarization conversion light source device can be reduced in size. In addition, the light source, the reflector, the non-polarizing dichroic prism, and the reflective polarization separator are arranged on the same axis for light of each wavelength, so that polarization conversion is performed on the same axis. Realized. That is, since it is not necessary to separate the light and perform polarization conversion, the polarization conversion light source device can be downsized.

  Thus, according to the present invention, there is provided a polarization conversion light source device that is miniaturized while keeping the light use efficiency high.

  The polarization conversion light source device of the present invention can be suitably used for various optical devices such as a liquid crystal display and a liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 Polarization conversion light source device 2 Transmission type liquid crystal projector 3 Reflection type liquid crystal projector 11r, 11g, 11b Light source 12r, 12g, 12b Reflector 13 Non-polarization cross dichroic prism 13r, 13b Reflecting surface 14 Polarization separation body 15 Polarization rotating body 21 Transmission type Liquid crystal bulb 22 Polarizing plate 23 Projection lens 31 Reflective liquid crystal bulb 32 PBS or reflective polarizing plate 33 Projection lens

Claims (11)

A non-polarization cross dichroic prism having two reflecting surfaces that are substantially orthogonal to each other and reflect light of a predetermined wavelength, three light sources that respectively emit light of different wavelengths, and three reflectors corresponding to each light source, A reflective polarization separator,
The first light source is disposed on the first surface side so that light from the light source enters the first surface of the non-polarized cross dichroic prism,
The second light source is disposed on the second surface side so that light from the light source enters the second surface facing the first surface of the non-polarized cross dichroic prism,
The third light source is disposed on the third surface side so that light from the light source enters the third surface adjacent to the first surface and the second surface of the non-polarized cross dichroic prism,
The polarization separator is disposed on the fourth surface side so that light emitted from a fourth surface facing the third surface of the non-polarization cross dichroic prism enters,
The first reflector is arranged on the first surface side so that light reflected from the polarization separator and emitted from the first surface enters the first reflector,
The second reflector is disposed on the second surface side so that light reflected from the polarization separator and emitted from the second surface enters the second reflector;
The polarization conversion light source device, wherein the third reflector is arranged on the third surface side so that light reflected from the polarization separator and emitted from the third surface enters. The light from the first light source that has entered the first surface is reflected by the first reflecting surface of the non-polarized cross dichroic prism and passes through the second reflecting surface to be emitted from the fourth surface. Part of the light is reflected by the polarization separator, and the reflected light enters the fourth surface, is reflected by the first reflective surface, and passes through the second reflective surface to transmit the first surface. From the first reflector and reflected again on the first surface,
The light from the second light source that has entered the second surface passes through the first reflecting surface and is reflected by the second reflecting surface to be emitted from the fourth surface, and part of the light is polarized. Reflected by the separator, the reflected light enters the fourth surface, passes through the first reflecting surface, is reflected by the second reflecting surface, and exits from the second surface, and the second surface. The light is reflected by the reflector and enters the second surface again,
The light from the third light source that has entered the third surface passes through the first reflecting surface, passes through the second reflecting surface, and exits from the fourth surface, part of which is the polarized light. Reflected by the separator, the reflected light enters the fourth surface, passes through the first reflecting surface, passes through the second reflecting surface, and exits from the third surface, and the third surface. 2. The polarization conversion light source device according to claim 1, wherein the light is reflected by the reflector and enters the third surface again. 3.   The polarization conversion light source device according to claim 1, wherein a polarization rotator is provided between the optical paths of the reflector and the polarization separator.   The polarization conversion light source device according to claim 3, wherein the polarization rotator is a broadband ¼ wavelength phase difference film.   The polarization conversion light source device according to claim 3, wherein the polarization rotator is a laminate of at least one quarter-wave retardation film and at least one half retardation film.   The polarization conversion light source device according to claim 1, wherein the polarization separator is a wire grid polarizing plate.   The polarization conversion light source device according to claim 1, wherein the polarization separator is a multilayer film having a birefringent material.   The polarization conversion light source device according to any one of claims 1 to 7, further comprising a lens between the light source and the non-polarization dichroic prism. A polarization conversion light source device according to any one of claims 1 to 8, a transmissive liquid crystal element, and a projection lens,
The transmissive liquid crystal element is arranged so that light emitted from the polarization conversion light source device enters the transmissive liquid crystal element,
The projection type liquid crystal display device, wherein the projection lens is arranged so that light emitted from the transmission type liquid crystal element enters the projection lens.   The projection type liquid crystal display device according to claim 9, further comprising an absorptive polarizing plate on a light output side of the polarization conversion light source device. The polarization conversion light source device according to any one of claims 1 to 8, a reflective liquid crystal element, a polarizing beam splitter, and a projection lens,
The reflective liquid crystal element and the polarizing beam splitter are arranged so that light emitted from the polarization conversion light source device enters the reflective liquid crystal element through the polarizing beam splitter,
The projection type liquid crystal display device, wherein the projection lens is arranged so that light emitted from the reflective liquid crystal element enters the projection lens through the polarizing beam splitter.

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