JP2008153332A - Light source apparatus and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source apparatus, along with a projector that uses it, capable of uniformizing the temperature of the entire wavelength conversion element, for supplying laser beam of stable quantity of light at high efficiency. <P>SOLUTION: The light source apparatus includes a light source part for supplying laser beam, an SHG element 14 which is a wavelength conversion element equipped with a first surface S1 and a second surface S2 provided to the side opposite to the first surface S1, for converting wavelength of laser beam from the light source part, a heater 19 which is provided on the side of first surface S1 of the wavelength conversion element and is a heat supplying part for supplying heat, a heat diffusing plate 18 which is a heat diffusing part that is provided between the first surface S1 and the heat supplying part for diffusing heat from the heat supplying part, and a support part 17 for supporting the wavelength conversion element on the second surface S2 side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source device and a projector, and more particularly to a technology of a light source device that supplies laser light.

  Conventionally, in a light source device that supplies laser light, a wavelength conversion element, for example, a second-harmonic generation (SHG) element is used. By using the SHG element, for example, it is possible to supply laser light having a desired wavelength using a general-purpose laser that can be easily obtained. In the SHG element, it is known that when the refractive index distribution changes due to a temperature change, the phase matching condition is broken and the wavelength conversion efficiency is lowered. In order to supply a highly efficient and stable laser beam, it is desired to reduce the temperature change of the wavelength conversion element. For example, in the technique proposed in Patent Document 1, the temperature is controlled using a thin film heater formed in the waveguide of the wavelength conversion element.

Japanese Patent Laid-Open No. 5-53163

  In addition to a configuration having a waveguide, the wavelength conversion device includes a so-called bulk type configuration that does not have a waveguide and enables wavelength conversion of light in the entire device. When the thin film heater is applied to the bulk type wavelength conversion element, it is necessary to provide the thin film heater in a very wide range. Thin film heaters are more likely to have uneven heat generation because it is more difficult to have a uniform resistance as the area becomes wider. Furthermore, if an electrode for driving the thin film heater is provided in a part of the wavelength conversion element, it is difficult to uniformly supply heat to the entire wavelength conversion element when the electrode itself does not generate heat. Thus, according to the conventional technique, there arises a problem that it is difficult to make the temperature of the entire wavelength conversion element uniform. The present invention has been made in view of the above-described problems, and a light source device capable of uniformizing the temperature of the entire wavelength conversion element and supplying high-efficiency and stable amount of laser light, and a projector using the light source device The purpose is to provide.

  In order to solve the above-described problems and achieve the object, according to the present invention, a light source unit for supplying laser light, a first surface, and a second surface provided on the side opposite to the first surface are provided. A wavelength conversion element that converts the wavelength of the laser light from the light source unit, a heat supply unit that is provided on the first surface side with respect to the wavelength conversion element, and that supplies heat, and between the first surface and the heat supply unit It is possible to provide a light source device including a heat diffusion unit that is provided and diffuses heat from the heat supply unit, and a support unit that supports the wavelength conversion element on the second surface side.

  The heat supplied from the heat supply unit is made uniform on the first surface of the wavelength conversion element through diffusion in the heat diffusion unit. The heat supplied to the wavelength conversion element propagates from the second surface side to the support portion. In this way, the uniform heat can be supplied to the wavelength conversion element, whereby the temperature of the entire wavelength conversion element can be made uniform. By making the temperature uniform, the wavelength conversion efficiency in the wavelength conversion element can be made uniform. Thereby, it is possible to obtain a light source device capable of uniformizing the temperature of the entire wavelength conversion element and supplying laser light with high efficiency and stable light quantity.

  Moreover, as a preferable aspect of the present invention, it is desirable that the thermal diffusion portion covers the entire first surface. By setting it as the structure which covers the whole 1st surface with a thermal-diffusion part, the uniform heat | fever can be supplied to the whole 1st surface of a wavelength conversion element. Thereby, the temperature of the wavelength conversion element can be made more uniform.

  Moreover, as a preferable aspect of the present invention, a temperature measurement unit that is provided on the second surface and measures the temperature of the wavelength conversion element, and a control unit that controls the heat supply unit based on a measurement result by the temperature measurement unit, It is desirable to have. By providing the temperature measurement unit on the second surface, the temperature of the wavelength conversion element can be accurately measured. The temperature change of the wavelength conversion element can be reduced by controlling the heat supply unit based on the measurement result by the temperature measurement unit. As a result, it is possible to supply a laser beam having a stable light quantity with higher efficiency.

  Moreover, as a preferable aspect of the present invention, it is desirable that the temperature measurement unit is disposed with a space between the support unit and the temperature measurement unit. By providing a space between the temperature measurement unit and the support unit, it is possible to prevent heat from being transmitted from the temperature measurement unit to the support unit. By preventing the propagation of heat from the temperature measurement unit to the support unit, the temperature measurement unit can be kept at the same temperature as the wavelength conversion element. As a result, the temperature of the wavelength conversion element can be accurately measured, and the temperature change of the wavelength conversion element can be further reduced.

  Moreover, as a preferable aspect of the present invention, it is desirable that the support portion has a shape in which the width is gradually reduced as the distance from the second surface increases. By using the support portion having such a shape, heat can be actively radiated in the central portion where heat is likely to concentrate, and the peripheral portion can be made difficult to radiate heat. Thereby, the temperature difference of the center part of a wavelength conversion element and a peripheral part can be decreased, and the temperature of a wavelength conversion element can be made further uniform.

  Moreover, as a preferable aspect of the present invention, it is desirable that the support portion has a trapezoidal shape. Thereby, it can be set as the shape which made the width | variety gradually small as it left | separated from the 2nd surface side, and a wavelength conversion element can be supported stably.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a heat insulating part provided in at least one of the heat supply part and the heat diffusion part. Direct heat dissipation from the heat supply unit and the heat diffusion unit to the outside may be a factor that hinders the uniformity of the heat supplied to the first surface. By preventing direct heat radiation from at least one of the heat supply unit and the heat diffusion unit to the outside by the heat insulating unit, it is possible to further uniformize the heat supplied to the first surface. Thereby, the temperature of the wavelength conversion element can be further uniformized.

  Furthermore, according to the present invention, it is possible to provide a projector including the light source device described above and a spatial light modulation device that modulates light from the light source device in accordance with an image signal. By using the light source device described above, the temperature of the wavelength conversion element can be made uniform, and a laser beam having a stable light quantity can be supplied with high efficiency. Thereby, a projector capable of stably displaying a bright image with high efficiency can be obtained.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a light source device 10 according to Embodiment 1 of the present invention. The light source device 10 is a semiconductor laser pumped solid state (DPSS) laser oscillator. The light source device 10 has a resonator structure using the resonant mirrors 12 and 15. The excitation laser 11 is a semiconductor laser that supplies laser light having a wavelength of 808 nm, for example. The laser light from the excitation laser 11 passes through the resonance mirror 12 and then enters the laser crystal 13. As the laser crystal 13, for example, an Nd: YVO ₄ crystal or an Nd: YAG (Y ₃ Al ₅ O ₁₂ ) crystal can be used. The laser crystal 13 oscillates when excited, and supplies laser light having a wavelength of about 1060 nm, for example. The excitation laser 11 and the laser crystal 13 are light source units that supply laser light.

  The SHG element 14 is a wavelength conversion element that converts the wavelength of laser light from the laser crystal 13. The SHG element 14 converts the laser beam from the laser crystal 13 into a laser beam having a half wavelength and emits it. As the SHG element 14, for example, a nonlinear optical crystal can be used. For example, the SHG element 14 converts a 1064 nm laser beam into a 532 nm laser beam. The laser light converted into a desired wavelength passes through the resonance mirror 15 and is emitted from the light source device 10. Laser light having a wavelength other than the desired wavelength is reflected by the resonance mirror 15. The laser light converted to a desired wavelength between the two resonance mirrors 12 and 15 passes through the resonance mirror 15 and is emitted from the light source device 10. In this way, laser light with a desired wavelength can be emitted efficiently.

  FIG. 2-1 shows the SHG element 14 and each part around it. The SHG element 14 includes a first surface S1 and a second surface S2 provided on the side opposite to the first surface S1. Both the first surface S1 and the second surface S2 have a substantially rectangular shape. The heater 19 is provided on the heat diffusion plate 18 on the first surface S1 side with respect to the SHG element 14. The heater 19 is a heat supply unit that supplies heat. The heat diffusing plate 18 is provided between the first surface S <b> 1 and the heater 19. The thermal diffusion plate 18 is a thermal diffusion unit that diffuses the heat from the heater 19. The thermal diffusion plate 18 can be formed using a member having high thermal conductivity, for example, copper.

  FIG. 2B is a top view of the configuration shown in FIG. The heat diffusion plate 18 is provided so as to cover the entire first surface S1. The heater 19 is provided substantially at the center of the heat diffusion plate 18. The heat diffusion plate 18 diffuses heat mainly in the horizontal direction, which is a direction parallel to the paper surface of FIG. Returning to FIG. 2A, the thermistor 16 is provided at the center of the second surface S <b> 2 of the SHG element 14. The thermistor 16 is a temperature measurement unit that measures the temperature of the SHG element 14. The thermistor 16 is bonded to the second surface S2 using, for example, a heat conductive adhesive. The support part 17 supports the SHG element 14 on the second surface S2 side. The support portion 17 is a structure having a rectangular parallelepiped shape. A concave portion 31 for inserting the thermistor 16 is provided in a portion corresponding to the central portion of the SHG element 14 in the support portion 17.

  The heat supplied by the heater 19 diffuses in the horizontal direction in the heat diffusing plate 18 as shown by the broken line arrows. The center part in which the heater 19 is provided among the heat diffusing plates 18 will show a high temperature with respect to the peripheral part. The temperature difference between the central portion and the peripheral portion of the heat diffusion plate 18 is determined by the thermal resistance and the amount of heat. By configuring the heat diffusion plate 18 with a member having high thermal conductivity and having a sufficient thickness, the temperature difference in the heat diffusion plate 18 can be reduced as much as possible.

  The heat from the heater 19 is made uniform on the first surface S <b> 1 by being diffused in the thermal diffusion plate 18. By adopting a configuration in which the entire first surface S1 is covered with the heat diffusing plate 18, heat can be uniformly supplied to the entire first surface S1. The heat supplied to the first surface S1 propagates from the second surface S2 side of the SHG element 14 to the support portion 17. In this way, uniform heat can be supplied to the SHG element 14. By making the heat uniform on the first surface S1 side, heat can be propagated in the direction across the SHG element 14 as indicated by the broken line arrows in the thermal diffusion plate 18, the SHG element 14 and the support portion 17. By making the distance for conducting heat in the SHG element 14 as short as possible, the temperature difference between the first surface S1 side and the second surface S2 side of the SHG element 14 can be reduced. In this way, the temperature of the entire SHG element 14 can be made uniform.

  In addition, by configuring the support portion 17 with a member having low thermal conductivity, the SHG element 14 can be maintained at a high temperature with a small amount of heat. From the viewpoint of low power consumption configuration, it is desirable that the temperature of the SHG element 14 can be adjusted with as little heat as possible. By appropriately selecting the members constituting the support portion 17, it is possible to efficiently adjust the temperature of the SHG element 14 and to achieve a configuration with low power consumption.

  By providing the concave portion 31 in the support portion 17, the thermistor 16 is arranged at a distance from the support portion 17 in the space surrounded by the second surface S <b> 2 and the support portion 17. By providing a space between the thermistor 16 and the support portion 17, it is possible to prevent heat from being transmitted from the thermistor 16 to the support portion 17. By preventing the propagation of heat from the thermistor 16 to the support portion 17, the thermistor 16 can be kept at the same temperature as the SHG element 14. Thereby, the thermistor 16 can accurately measure the temperature of the SHG element 14.

  FIG. 3 shows a block configuration for adjusting the temperature of the SHG element 14 based on the measurement result by the thermistor 16. The control unit 43 controls the heater driving unit 44 according to the output of the thermistor 16. The heater drive unit 44 drives the heater 19 according to control by the control unit 43. Thus, the control unit 43 performs feedback control of the heater 19 based on the measurement result by the thermistor 16. With this configuration, the temperature change of the SHG element 14 can be reduced.

  As described above, it is possible to make the wavelength conversion efficiency in the SHG element 14 uniform by making the temperature of the entire SHG element 14 uniform and reducing the temperature change. Thereby, the temperature of the whole wavelength conversion element is made uniform, and there is an effect that it is possible to supply a laser beam with a high efficiency and a stable light amount. The light source device of the present invention is not limited to a DPSS laser oscillator. A light source device that makes laser light from a semiconductor laser, which is a light source unit, incident on a wavelength conversion element may be used. In this case, a semiconductor laser may be used as the light source unit, and a solid laser, liquid laser, gas laser, or the like may be used.

  FIG. 4 is for explaining a first modification of the present embodiment, and shows the SHG element 14 and its surrounding parts. The support portion 21 of the present modification has a trapezoidal shape in which the width is gradually reduced as the distance from the second surface S2 increases. By using the support portion 21 having such a shape, heat can be actively radiated in the central portion where heat is likely to concentrate, and the peripheral portion can be made difficult to radiate heat. Thereby, the temperature difference between the central portion and the peripheral portion of the SHG element 14 can be reduced, and the temperature of the SHG element 14 can be made more uniform. Further, the SHG element 14 can be stably supported. In addition to using the trapezoidal support portion 21, another polygonal support portion having a gradually reduced width as the distance from the second surface S2 may be used.

  FIG. 5 is for explaining a second modification of the present embodiment, and shows the SHG element 14 and its surrounding parts. In this modification, a heat insulating layer 23 is added. The heat insulating layer 23 is a heat insulating portion provided on the heater 19 and the heat diffusion plate 18. The heat insulation layer 23 is provided so as to cover a surface of the heater 19 and the heat diffusion plate 18 other than the surface in contact with the first surface S1. The heat insulating layer 23 is made of a heat insulating material such as a resin member.

  Direct heat dissipation from the heater 19 and the heat diffusing plate 18 to the outside can be a factor that hinders the uniformity of the heat supplied to the first surface S1. By preventing direct heat radiation from the heater 19 and the heat diffusion plate 18 to the outside by the heat insulating layer 23, it is possible to further uniformize the heat supplied to the first surface S1. Thereby, the temperature of the SHG element 14 can be made more uniform. The heat insulating layer 23 is not limited to being provided on both the heater 19 and the heat diffusion plate 18, and may be provided on at least one of the heater 19 and the heat diffusion plate 18.

  FIG. 6 shows a schematic configuration of a projector 70 according to Embodiment 2 of the present invention. The projector 70 is a front projection type projector that views light by supplying light to the screen 88 and observing light reflected by the screen 88. A duplicate description with the first embodiment is omitted. The projector 70 includes a red (R) light source device 80R, a green (G) light source device 80G, and a blue (B) light source device 80B. Each of the color light source devices 80R, 80G, and 80B has the same configuration as the light source device 10 (see FIG. 1) of the first embodiment. The projector 70 displays an image using light from each color light source device 80R, 80G, 80B.

  The R light source device 80R is a light source device that supplies R light. The diffractive optical element 81 shapes and enlarges the illumination area by diffracting the laser light. The diffractive optical element 81 also makes the light amount distribution of the laser light uniform. As the diffractive optical element 81, for example, a computer generated hologram (CGH) can be used. The field lens 82 collimates the laser light from the diffractive optical element 81 and enters the R light spatial light modulator 83R. The spatial light modulator 83R for R light is a spatial light modulator that modulates R light according to an image signal, and is a transmissive liquid crystal display device. The R light modulated by the R light spatial light modulator 83R is incident on a cross dichroic prism 84 which is a color synthesis optical system.

  The G light source device 80G is a light source device that supplies G light. The laser light that has passed through the diffractive optical element 81 and the field lens 82 enters the G light spatial light modulator 83G. The G light spatial light modulator 83G is a spatial light modulator that modulates G light according to an image signal, and is a transmissive liquid crystal display device. The G light modulated by the G light spatial light modulator 83G enters the cross dichroic prism 84 from a side different from the R light.

  The light source device for B light 80B is a light source device that supplies B light. The laser light that has passed through the diffractive optical element 81 and the field lens 82 enters the spatial light modulator 83B for B light. The spatial light modulator for B light 83B is a spatial light modulator that modulates B light according to an image signal, and is a transmissive liquid crystal display device. The B light modulated by the B light spatial light modulator 83B enters the cross dichroic prism 84 from a side different from the R light and the G light. As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used.

  The cross dichroic prism 84 has two dichroic films 85 and 86 disposed substantially orthogonal to each other. The first dichroic film 85 reflects R light and transmits G light and B light. The second dichroic film 86 reflects B light and transmits R light and G light. The cross dichroic prism 84 combines the R light, the G light, and the B light incident from different directions and emits them in the direction of the projection lens 87. The projection lens 87 projects the light combined by the cross dichroic prism 84 in the direction of the screen 88.

  By using each color light source device 80R, 80G, 80B having the same configuration as that of the light source device 10 described above, the temperature of the wavelength conversion element can be made uniform, and a laser beam having a high efficiency and a stable light amount can be supplied. Thereby, there is an effect that a bright image can be stably displayed with high efficiency. The projector 70 is not limited to the case where a transmissive liquid crystal display device is used as the spatial light modulation device. As the spatial light modulator, a reflective liquid crystal display (Liquid Crystal On Silicon; LCOS), DMD (Digital Micromirror Device), GLV (Grating Light Valve), or the like may be used.

  The projector 70 is not limited to a configuration including a spatial light modulator for each color light. The projector 70 may be configured to modulate two or three or more color lights with one spatial light modulator. The projector may be a so-called rear projector that supplies light to one surface of the screen and observes an image by observing light emitted from the other surface of the screen. Furthermore, the light source device of the present invention is not limited to being applied to a projector. For example, the present invention may be applied to an exposure apparatus that performs exposure using laser light, a monitor apparatus that monitors an image illuminated by laser light, and the like.

  As described above, the light source device according to the present invention is suitable for use in a projector.

The figure which shows schematic structure of the light source device which concerns on Example 1 of this invention. The figure which shows each part of a SHG element and its periphery. FIG. 2 is a top view of the configuration shown in FIG. The figure which shows the block structure for adjusting the temperature of a SHG element. FIG. 6 is a diagram for explaining a first modification of the first embodiment. FIG. 6 is a diagram illustrating a second modification of the first embodiment. FIG. 5 is a diagram illustrating a schematic configuration of a projector according to a second embodiment of the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Light source device, 11 Excitation laser, 12 Resonance mirror, 13 Laser crystal, 14 SHG element, 15 Resonance mirror, 16 Thermistor, 17 Support part, 18 Thermal diffusion plate, 19 Heater, S1 1st surface, S2 2nd surface, DESCRIPTION OF SYMBOLS 21 Support part, 23 Thermal insulation layer, 31 Recessed part, 43 Control part, 44 Heater drive part, 70 Projector, 80R R light source device, 80G G light source device, 80B B light source device, 81 Diffractive optical element, 82 Field lens, spatial light modulator for 83R R light, spatial light modulator for 83G G light, spatial light modulator for 83B B light, 84 cross dichroic prism, 85 first dichroic film, 86 second dichroic film, 87 projection lens 88 screens

Claims (8)

A light source unit for supplying laser light;
A wavelength conversion element that includes a first surface and a second surface provided on the opposite side of the first surface, and converts a wavelength of the laser light from the light source unit;
A heat supply unit that is provided on the first surface side with respect to the wavelength conversion element and supplies heat;
A thermal diffusion unit that is provided between the first surface and the heat supply unit and diffuses heat from the heat supply unit;
A light source device comprising: a support portion that supports the wavelength conversion element on the second surface side.   The light source device according to claim 1, wherein the thermal diffusion unit covers the entire first surface. A temperature measurement unit that is provided on the second surface and measures the temperature of the wavelength conversion element;
The light source device according to claim 1, further comprising: a control unit that controls the heat supply unit based on a measurement result by the temperature measurement unit.   The light source device according to claim 3, wherein the temperature measurement unit is disposed with a space between the support unit and the temperature measurement unit.   5. The light source device according to claim 1, wherein the support portion has a shape in which a width is gradually reduced as the distance from the second surface is increased.   The light source device according to claim 5, wherein the support portion has a trapezoidal shape.   It has a heat insulation part provided in at least one of the said heat supply part and the said thermal diffusion part, The light source device as described in any one of Claims 1-6 characterized by the above-mentioned. The light source device according to any one of claims 1 to 7,
And a spatial light modulator that modulates light from the light source device in accordance with an image signal.

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