Light source device, lighting device, monitor device, and projector

A light source device includes a light source section for supplying a laser beam, a wavelength conversion element for converting a wavelength of the laser beam from the light source section, a temperature measuring section for measuring temperature, a temperature adjusting section for adjusting the temperature of the wavelength conversion element in accordance with a result of the measurement by the temperature measuring section, and a thermal diffusion section for diffusing heat to be conducted to the wavelength conversion element, wherein the thermal diffusion section is provided with a first surface disposed on a side of the wavelength conversion element and a second surface disposed on an opposite side to the first surface, and the temperature measuring section is provided to a part of the thermal diffusion section, which is located on a side of the second surface and has higher thermal conductivity of the thermal diffusion section between the side of the first surface and the side of the second surface than the other part of the thermal diffusion section.

This application claims priority from Japanese Patent Application No. 2007-026455 filed in the Japanese Patent Office on Feb. 6, 2007, the entire disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a light source device, a lighting device, a monitor device, and a projector, and in particular to a technology of a light source device for supplying a laser beam.

2. Related Art

In recent years, as a light source device for a monitor device or a projector, a technology for using a laser source for supplying a laser beam has been proposed. In comparison with a UHP lamp, which has been used as a light source of a monitor or a projector in the past, the laser source device using a laser source has advantages such as high color reproducibility, instant-lighting capability, and long life. As the light source device using the laser source, besides the device for directly supplying the fundamental laser beam from the laser source, a device for converting the wavelength of the fundamental laser beam and then supplying the laser beam with the converted wavelength is known. As a wavelength conversion element for converting the wavelength of the fundamental laser beam, for example, a second harmonic generation/generating (SHG) element has been used. By using the wavelength conversion element, it becomes possible to supply a laser beam with a desired wavelength using an easily available multipurpose laser source. Further, a configuration capable of supplying a laser beam with sufficient intensity can also be provided. Regarding the SHG element, it is known that in the case in which the refractive index distribution is varied by the temperature variation, the phase matching condition is broken, and the efficiency of converting the wavelength is deteriorated. In order for supplying a laser beam with stable intensity with high efficiency, it is desirable to reduce the temperature variation of the wavelength conversion element. For example, in the technology proposed in JP-A-5-198870 (hereinafter referred to as a Document 1), the wavelength conversion element is attached to a substrate having thermal conductivity, and temperature control of the substrate is performed based on the temperature measured by a thermistor disposed in the substrate.

As a factor for varying the temperature of the wavelength conversion element, there can be cited a variation in the amount of absorption of the laser beam to the wavelength conversion element caused by a variation in the laser output, a variation in the ambient temperature of the light source device, and so on. In order for controlling the temperature of the wavelength conversion element with good accuracy even in the condition with such factors, it is desirable to detect the temperature close to the temperature of the wavelength conversion element itself. In this respect, in the configuration proposed in the Document 1 described above, the substrate with a volume several times as large as the wavelength conversion element is shown. Since such a big substrate has a large heat capacity, when a factor for causing the temperature of the wavelength conversion element to vary occurs, a large temperature difference should be caused between the wavelength conversion element and the substrate. Therefore, even if the thermistor disposed in such a substrate is used, there arises a problem that it is sometimes difficult to control the temperature of the wavelength conversion element with good accuracy.

SUMMARY

An advantage of some aspects of the invention is to provide a light source device capable of reducing the temperature variation of the wavelength conversion element by accurate temperature control, and thereby supplying a laser beam with stable intensity with high efficiency, a lighting device, a monitor device, and a projector each using the light source device.

According to an aspect of the invention, it is possible to provide a light source device including a light source section for supplying a laser beam, a wavelength conversion element for converting a wavelength of the laser beam from the light source section, a temperature measuring section for measuring temperature, a temperature adjusting section for adjusting the temperature of the wavelength conversion element in accordance with a result of the measurement by the temperature measuring section, and a thermal diffusion section for diffusing heat to be conducted to the wavelength conversion element, wherein the thermal diffusion section is provided with a first surface disposed on a side of the wavelength conversion element and a second surface disposed on an opposite side to the first surface, and the temperature measuring section is provided to a part of the thermal diffusion section, which is located on a side of the second surface and has higher thermal conductivity of the thermal diffusion section between the side of the first surface and the side of the second surface than the other part of the thermal diffusion section.

By disposing the temperature measuring section on the part of the second surface side of the thermal diffusion section, having high thermal conductivity, the temperature close to the temperature of the wavelength conversion element itself can be detected. It becomes possible to control the temperature of the wavelength conversion element with good accuracy even if a cause of varying the temperature of the wavelength conversion element occurs. Thus, the light source device capable of reducing the temperature variation of the wavelength conversion element by the accurate temperature control, thereby supplying the laser beam with stable intensity with high efficiency can be obtained.

Further, in another preferable aspect of the invention, it is desirable that the thermal diffusion section includes a connection section connected to the temperature measuring section. By connecting the temperature measuring section and the thermal diffusion section to each other using the connection section, the thermal conduction through the connection section becomes possible. By the thermal conduction using the connection section, accurate temperature control of the wavelength conversion element can be performed.

Further, in another preferable aspect of the invention, it is desirable that there is further provided an insulating layer disposed on a part of the second surface of the thermal diffusion section other than a part of the second surface, on which the connection section is disposed. Thus, unnecessary conduction between the wiring patterns respectively connected to the temperature measuring section and the temperature adjusting section can be blocked.

Further, in another preferable aspect of the invention, it is desirable that the thermal diffusion section is composed using a metallic material. Thus, the heat to be conducted to the wavelength conversion element can effectively be diffused.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section and the insulating layer, and for supporting the wavelength conversion element, and a substrate on which the support section is disposed, the supporting section being disposed on the substrate using the part thereof to which the insulating layer is provided. By disposing the part of the support section, to which the insulating layer is provided, on the substrate, it becomes possible to reduce the heat conduction from the support section to the substrate. Thus, the temperature close to the temperature of the wavelength conversion element itself can be detected by the temperature measuring section. Further, by reducing the heat conduction from the support section to the substrate, the temperature control of the wavelength conversion element can efficiently be executed with a little amount of heat.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section, and for supporting the wavelength conversion element, and a substrate on which the support section is disposed, the supporting section being disposed on the substrate using the part thereof other than the part to which the wavelength conversion element is provided. According to such a configuration, it becomes possible to make the temperature of the part of the support section, to which the wavelength conversion element is provided closer to the temperature of the wavelength conversion element. Thus, the temperature close to the temperature of the wavelength conversion element itself can be detected by the temperature measuring section. Further, the temperature of the wavelength conversion element can be equalized.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section, and for supporting the wavelength conversion element, the connection section being disposed on the centerline passing through a substantial center location of the support section. By disposing the connection section on the centerline, it becomes possible to measure the temperature of the wavelength conversion element at a position the most distant from the abutting section of the support section with the substrate. Thus, the temperature of the wavelength conversion element can accurately be measured.

Further, in another preferable aspect of the invention, it is desirable that the thermal diffusion section includes a heat insulating section for reducing heat conduction between the connection section and a part of the thermal diffusion section surrounding the connection section. By providing the heat insulating section, the heat capacity of an area from the wavelength conversion element to the temperature measuring section can be reduced, thus the temperature difference between the wavelength conversion element and the temperature measuring section can also be reduced. Thus, the temperature of the wavelength conversion element can accurately be measured.

Further, in another preferable aspect of the invention, it is desirable that the thermal diffusion section includes a thinner section having a smaller distance between the first surface and the second surface, and the temperature measuring section is provided to the thinner section. By providing the temperature measuring section to the thinner section, the temperature close to the temperature of the wavelength conversion element itself can be detected. Thus, the accurate temperature control of the wavelength conversion element can be performed. Further, the strength necessary for supporting the wavelength conversion element can be ensured by a part of the thermal diffusion section other than the thinner section thereof.

Further, in another preferable aspect of the invention, it is desirable that the thermal diffusion section is composed of an insulating material. Thus, unnecessary conduction between the wiring patterns respectively connected to the temperature measuring section and the temperature adjusting section can be blocked.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section, and for supporting the wavelength conversion element, a substrate on which the support section is disposed, and a heat insulating section for reducing heat conduction between the support section and the substrate. By reducing the heat conduction from the support section to the substrate, the temperature close to the temperature of the wavelength conversion element itself can be detected by the temperature measuring section. Further, by reducing the heat conduction from the support section to the substrate, the temperature control of the wavelength conversion element can efficiently be executed with a little amount of heat.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section, and for supporting the wavelength conversion element, and a substrate on which the support section is disposed, the supporting section being disposed on the substrate using the part thereof other than the part to which the wavelength conversion element is provided. According to such a configuration, it becomes possible to make the temperature of the part of the support section, to which the wavelength conversion element is provided closer to the temperature of the wavelength conversion element. Thus, the temperature close to the temperature of the wavelength conversion element itself can be detected by the temperature measuring section. Further, the temperature of the wavelength conversion element can be equalized.

Further, in another preferable aspect of the invention, it is desirable that the light source device further includes a support section provided with the thermal diffusion section, and for supporting the wavelength conversion element, the thinner section being disposed on the centerline passing through a substantial center location of the support section. By disposing the thinner section on the centerline, it becomes possible to measure the temperature of the wavelength conversion element at a position distant from the abutting section of the support section with the substrate. Thus, the temperature of the wavelength conversion element can accurately be measured.

Further, according to another aspect of the invention, there is provided a lighting device including the light source device described above, wherein the lighting device lights an object using a light beam from the source device. By using the light source device described above, a laser beam with stable intensity can be supplied with high efficiency. Thus, the lighting device capable of supplying a laser beam with stable intensity with high efficiency.

Further, according to another aspect of the invention, there is provided a monitor device including the lighting device described above, and an imaging section for imaging a subject lighted by the lighting device. By using the lighting device described above, a laser beam with stable intensity can be supplied with high efficiency. Thus, the monitor device capable of monitoring a bright image can be obtained.

Further, according to another aspect of the invention, there is provided a projector including the lighting device described above, and a spatial light modulation device for modulating a light beam from the lighting device in accordance with an image signal. By using the lighting device described above, a laser beam with stable intensity can be supplied with high efficiency. Thus, the projector capable of stably displaying a bright image with high efficiency can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

FIG. 1is a diagram for schematically representing a rough configuration of a light source device10according to a first embodiment of the invention. The light source device10is a diode-pumped solid-state (DPSS) laser oscillator. The light source device10has a resonator structure using a first resonator mirror12and a second resonator mirror16. A pump laser11is a semiconductor laser for supplying a laser beam with a wavelength of, for example, 808 nm, and an edge-emitting laser. The laser beam from the pump laser11enters a laser crystal13after passing through the first resonance mirror12. As the laser crystal13, a Nd:YVO4crystal or a Nd:YAG (Y3Al5O12) crystal, for example, can be used. The laser crystal13performs laser oscillation when pumped, and supplies a laser beam with a wavelength of, for example, 1064 nm. The pump laser11and the laser crystal13form a light source section for supplying a laser beam.

The SHG element14is a wavelength conversion element for converting the wavelength of the laser beam from the laser crystal13. The SHG element14converts the laser beam from the laser crystal13into a laser beam with a half wavelength thereof, and emits the converted laser beam. As the SHG element14, nonlinear optical crystal can be used, for example. As the nonlinear optical crystal, for example, periodically poled lithium niobate (PPLN), which is a periodically poled crystal of lithium niobate (LiNbO3), can be used. A support section15supports the SHG element14. The second resonator mirror16is disposed on an opposite side to the laser crystal13with respect to the SHG element14.

The SHG element14converts a laser beam of, for example, 1064 nm into a laser beam of 532 nm. The second resonator mirror16has a function of selectively reflecting a laser beam with a predetermined wavelength, for example, 1064 nm and transmitting laser beams with other wavelengths. The laser beam converted by the SHG element to have a wavelength of, for example, 532 nm passes through the second resonator mirror16and is emitted from the light source device10. The laser beam with a wavelength other than the desired wavelength is reflected by the second resonator mirror16. Similarly to the second resonator mirror16, the first resonator mirror12selectively reflects the laser beam with a predetermined wavelength, for example, 1064 nm, and transmits light beams with other wavelengths. According to the resonator structure, the laser beam with a desired wavelength can efficiently be emitted. The pump laser11, the first resonator mirror12, the laser crystal13, the support section15, and the second resonator mirror16are disposed on a substrate17.

The pump laser11is not limited to the edge-emitting laser, but can be a surface emitting laser. The light source device10is not limited to the DPSS laser oscillator. It can be a light source device in which a laser beam from a semiconductor laser as a light source section is input to the wavelength conversion element. In this case, as the light source section, besides the semiconductor laser, a solid-state laser, a liquid laser, a gas laser, and so on can also be used.

FIG. 2shows a perspective configuration of the SHG element14and the support section15. The support section15has a thermal diffusion section20and an insulating layer21. The thermal diffusion section20diffuses heat to be conducted to the SHG element14. The thermal diffusion section20is composed using a material with high thermal conductivity such as copper as a metallic material. The thermal diffusion section20has a rectangular planar shape. The thermal diffusion section20is formed to have a thickness in a range of about 40 μm through 1 mm, for example. The SHG element14is disposed on a first surface22of the thermal diffusion section20. The SHG element14is disposed so that the center location of the SHG element14and the center location of the thermal diffusion section20are conformed to each other.

The SHG element14has an oblong planar shape, which is shorter than the thermal diffusion section20in the longitudinal direction of the thermal diffusion section20. The first surface22of the thermal diffusion section20and the SHG element14are bonded with each other using, for example, a thermally conductive adhesive. The insulating layer21is disposed on a second surface23of the thermal diffusion section20. The second surface23is one of the surfaces of the thermal diffusion section20, and disposed on the side opposite to the side of the first surface22. The insulating layer21is composed using a material with an insulating property such as epoxy resin. The insulating layer21is formed to have a thickness in a range of about 10 through 200 μm, for example.

FIG. 3shows a perspective configuration, namely the configuration shown inFIG. 2viewed from a side of an insulating layer21. On the insulating layer21, there is formed a wiring pattern25. The wiring pattern25is composed using an electrically conductive material such as a copper foil as a metallic material. The wiring pattern25includes a first thermistor land26and a second thermistor land27to which a thermistor described later is connected. The wiring pattern25includes a first heater land29and a second heater land30to which a heater described later is connected. Conductive wire sections28each supply the thermistor or the heater with an electrical current. The centerline C of the support section15is a line passing through the center location of the support section15and dividing the support section15into two equal parts with respect to the longitudinal direction of the support section15. The first thermistor land26is disposed on the centerline C.

FIG. 4shows a cross-sectional configuration of the SHG element14, the support section15, and the wiring pattern25along the centerline C shown inFIG. 3. The thermal diffusion section20has a connection section31formed on the side of the second surface23. The connection section31is formed at a position corresponding to the first thermistor land26, namely on the centerline C. The connection section31is connected to the thermistor described later via the first thermistor land26. The connection section31is composed using a material with high thermal conductivity such as copper as a metallic material.

The insulating layer21is provided to a part of the second surface23of the thermal diffusion section20other than a part thereof provided with the connection section31. The connection section31is formed using copper with high thermal conductivity compared to a resin material forming the insulating layer21. Therefore, the connection section31out of the thermal diffusion section20is a section having high thermal conductivity between the side of the first surface22and the side of the second surface23compared to the part provided with the insulating layer21, which is the other part of the thermal diffusion section20.

The connection section31abuts only on the first thermistor land26out of the wiring pattern25. The second thermistor land27, the first heater land29, the second heater land30(seeFIG. 3), and the conductive wire sections28out of the wiring pattern25are all disposed on the thermal diffusion section20via the insulating layer21intervening therebetween. By providing the insulating layer21, unnecessary connection among the lands26,27,29, and30or between the conductive wire sections28via the thermal diffusion section20can be blocked.

The connection section31can be formed by, for example, etching the other part of a plate like copper member than the connection section31. The insulating layer21can be formed by applying an insulating material on the part of the second surface23of the thermal diffusion section20other than the connection section31. The wiring pattern25can be formed by executing plating on the insulating layer21and the connection section31to form a copper foil, and then executing patterning and etching on the copper foil.

FIG. 5is a diagram for explaining an arrangement of the thermistor33and the heater34. The thermistor33is fixed to the first and second thermistor lands26,27by, for example, soldering. The thermistor33is a temperature measuring section for measuring the temperature. The heater34is fixed to the first and second heater lands29,30by, for example, soldering. The heater34is a temperature adjusting section for adjusting the temperature of the SHG element14by supplying heat based on the result of the measurement by the thermistor33. InFIG. 5, the thermistor33is disposed on the near side of the heater34in the sheet of the drawing. The first and second thermistor lands26,27are disposed on the near side of the first and second heater lands29,30in the sheet of the drawing.

FIG. 6shows a block configuration for controlling the temperature of the SHG element14based on the result of the measurement by the thermistor33. The thermistor33outputs a variation in the temperature to the temperature control section35in the form of a variation in resistance. The temperature control section35calculates an amount of electric power to be supplied to the heater34based on a temperature difference between the temperature measured by the thermistor33and the set temperature of the SHG element14, and supplies the heater34with the electric power corresponding to the calculated amount of electric power. The temperature control section35performs feedback control of the heater34based on the result of the measurement by the thermistor33. The heater34adjusts the temperature of the SHG element14based on the result of the measurement by the thermistor33.

By connecting the thermistor33and the thermal diffusion section20to each other using the connection section31(seeFIG. 4), the thermal conduction through the connection section31becomes possible. By the thermal conduction using the connection section31which is a part of the thermal diffusion section20having higher thermal conductivity compared to the other part of the thermal diffusion section20, the temperature closer to the temperature of the SHG element14itself can be detected. Further, by using the thermal diffusion section20with a small volume, the heat capacity of the thermal diffusion section20can be reduced.

FIG. 7is a diagram for explaining a condition in which the configuration shown inFIG. 5and the substrate17are combined. The thermistor33and the heater34are disposed inside a recess section36of the substrate17. The support section15is disposed on the substrate17so that abutting areas38of the insulating layer21abut on the substrate17. The abutting areas38are areas corresponding to the four corners of the insulating layer21having a rectangular shape. The support section15is disposed on the substrate17using a part provided with the insulating layer21. The recess section36is provided to an area corresponding to the support section15and other than the parts to abut on the abutting areas38.

By disposing the abutting areas38provided to the part of the support section15provided with the insulating layer21on the substrate17, it becomes possible to reduce the heat conduction from the support section15to the substrate17. By reducing the heat conduction from the support section15to the substrate17, the temperature control of the SHG element14can efficiently be executed with a little amount of heat. Further, by disposing the support section15with the abutting areas38each having a small area, the heat conduction from the support section15to the substrate17can be reduced. By using the four corners of the insulating layer21as the abutting areas38, the heat conduction from the support section15to the substrate17can be reduced while fixing the support section15on the substrate17. Further, the temperature of the SHG element14can be equalized.

The abutting areas38are each a part of the insulating layer21, having contact with a part of the thermal diffusion section20, on which the SHG element14is not mounted. The support section15is disposed on the substrate17using the abutting areas38. Further, as described above, by adopting the configuration of connecting the thermistor33to the connection section31(seeFIG. 4) on the centerline C (seeFIG. 3), it becomes possible to measure the temperature of the SHG element14at a position in the support section15, the most distant from the abutting areas38.

According to the configuration described hereinabove, it becomes possible to approximate the temperature of the part of the support section15, provided with the SHG element14to the temperature of the SHG element14. Thus, the temperature close to the temperature of the SHG element14itself can be detected by the thermistor33. Further, the temperature of the SHG element14can be equalized.

Regarding the SHG element14, it is known that in the case in which the refractive index distribution is varied by the temperature variation, the phase matching condition is broken, and the efficiency of converting the wavelength is deteriorated. For example, in order for maintaining high wavelength conversion efficiency in PPLN, it is desirable that the range of the temperature variation is controlled within about one degree. Further, it has been confirmed that the laser beam from the pump laser11is an infrared beam, and that about 10−2through 10−4of the energy of the laser beam input to the SHG element14is absorbed by the SHG element14. Such absorption of the energy can be a principal factor for varying the temperature of the SHG element14. When the output of the laser beam from the pump laser11(seeFIG. 1) is varied, the temperature of the SHG element14should easily be varied. Further, in accordance with the environment in which the light source device10is disposed, the temperature of the SHG element14should also be varied easily.

As described above, the light source device10according to the embodiment of the invention can detect the temperature close to the temperature of the SHG element14itself by the thermistor33. It becomes possible to control the temperature of the SHG element14with good accuracy even if a cause of varying the temperature of the SHG element14occurs. Thus, the advantage that the temperature variation of the wavelength conversion element is reduced by the accurate temperature control, thereby supplying the laser beam with stable intensity with high efficiency can be obtained.

FIG. 8is a diagram for explaining a modified example 1 of the present embodiment, and shows a cross-sectional configuration of the SHG element14, the support section15, and the wiring pattern25, and a cross-sectional view of a thermal diffusion section40along the A-A line in the configuration. The present modified example is characterized in providing a heat insulating section42to the thermal diffusion section40. The thermal diffusion section40has a connection section41penetrating from the side of the first surface22to the side of the second surface23. The connection section41has, for example, a cylindrical shape. The heat insulating section42is formed in the thermal diffusion section40on the periphery of the connection section41. Similarly to the connection section41, the heat insulating section42is provided so as to penetrate from the side of the first surface22to the side of the second surface23.

The heat insulating section42reduces the heat conduction between the connection section41and a part of the thermal diffusion section40surrounding the connection section41. The heat insulating section42is composed using a heat insulating material such as epoxy resin. By providing the heat insulating section42, the heat capacity from the SHG element14to the thermistor not shown can be reduced, thus the temperature difference between the SHG element14and the thermistor can also be reduced. Thus, the temperature of the SHG element14can accurately be measured. The heat insulating section42can be composed using other resin than the epoxy resin. Further, it is possible to use a layer of air formed by providing a gap around the periphery of the connection section41as the heat insulating section42.

FIG. 9is a diagram for explaining a modified example 2 of the present embodiment. The present modified example is characterized in including a thermal diffusion section45having a thinner section46. The thermal diffusion section45is a support section for supporting the SHG element14. The thermal diffusion section45is composed using a material having an insulating property in addition to high thermal conductivity such as aluminum nitride as a ceramic material. By composing the thermal diffusion section45using the insulating material, unnecessary conduction between the lands or the conductive wire sections can be blocked.

The thinner section46is a part of the thermal diffusion section45provided with a smaller distance between the first surface22and the second surface23. The thinner section46is formed by providing the thermal diffusion section45with a recess on the side of the second surface23. The thinner section46is formed at substantially the central portion of the second surface23. The thinner section46is a part of the thermal diffusion section45, having higher thermal conductivity between the side of the first surface22and the side of the second surface23compared to the other part thereof.

The wiring pattern25(seeFIG. 3) is formed on the second surface23of the thermal diffusion section45. The first and second thermistor lands26,27are provided to the thinner section46in the second surface23of the thermal diffusion section45. The thermistor33is also provided to the thinner section46. InFIG. 9, the thermistor33is disposed on the near side of the first and second heater lands29,30in the sheet of the drawing. By providing the thermistor33to the thinner section46, the temperature close to the temperature of the SHG element14itself can be detected. Further, the strength necessary for supporting the SHG element14can be assured by the other part of the thermal diffusion section45than the thinner section46. Further, by using the thermal diffusion section45with a small volume, the heat capacity of the thermal diffusion section45can be reduced.

A heat insulating section47is disposed between the thermal diffusion section45and the substrate17. The heat insulating section47reduces the heat conduction between the thermal diffusion section45and the substrate17. The heat insulating section47can be disposed at the same areas as the abutting areas38(seeFIG. 7) described above. By providing the heat insulating section47, the heat conduction from the thermal diffusion section45to the substrate17can be reduced. By reducing the heat conduction from the thermal diffusion section45to the substrate17, the temperature control of the SHG element14can efficiently be executed with a little amount of heat.

The heat insulating section47is provided to a part of the second surface23of the thermal diffusion section45other than a part thereof corresponding to the SHG element14. The thermal diffusion section45is disposed on the substrate17using the other part than the part provided with the SHG element14. Further, it becomes possible for the thermistor33provided to substantially the central section of the thermal diffusion section45to measure the temperature of the SHG element14at a position the most distant from the part of the thermal diffusion section45, abutting on the substrate17via the heat insulating section47.

According to the configuration described above, it becomes possible to make the temperature of the thinner section46of the thermal diffusion section45to be closer to the temperature of the SHG element14. Therefore, the temperature of the SHG element14can be control with good accuracy, thus the accurate temperature control of the SHG element14can be performed. A material for composing the thermal diffusion section45is only required to have high thermal conductivity and an insulating property, and other ceramic materials than the aluminum nitride, such as alumina can also be used.

The light source device10is not limited to have the configuration of using the heater34as the temperature adjusting section. As the temperature adjusting section, for example, a peltiert element can also be used. In the case of using the peltiert element, the temperature of the SHG element14can be adjusted not only by supplying heat but also by absorbing heat. The light source device10is not limited to the DPSS laser oscillator. It can be a light source device in which a laser beam from a semiconductor laser as a light source section is input to the wavelength conversion element. In this case, the light source device10can adopt an external resonator structure using the mirror provided to the semiconductor laser as the first resonator mirror. Further, as the light source section, besides the semiconductor laser, a solid-state laser, a liquid laser, a gas laser, and so on can also be used.

Second Embodiment

FIG. 10shows a schematic configuration of a monitor device50according to a second embodiment of the invention. The monitor device50has a device main body51and an optical transmission section52. The device main body51is provided with the light source device10according to the first embodiment described above. The same parts as in the first embodiment are denoted with the same reference numerals, and the duplicated explanations will be omitted.

The optical transmission section52has two light guides54,55. A diffusing plate56and an imaging lens57are disposed at an end of the optical transmission section52on the side of the subject (not shown). A first light guide54transmits a light beam from the light source device10to the subject. The diffusing plate56is provided on an emission side of the first light guide54. The light beam propagated inside the first light guide54passes through the diffusing plate56to be diffused on the side of the subject. The sections in the light path from the light source device10to the diffusing plate56form a lighting device for lighting the subject.

The second light guide55transmits the light beam from the subject to a camera53. The imaging lens57is disposed on an entrance side of the second light guide55. The imaging lens57focuses the light beam from the subject on an entrance surface of the second light guide55. The light beam from the subject is input to the second light guide55by the imaging lens57, and then propagated inside the second light guide55to enter the camera53.

As each of the first and second light guides54,55, a bundle of a number of optical fibers can be used. By using the optical fibers, the laser beam can be transmitted to a distance. The camera53is provided inside the device main body51. The camera53is an imaging section for imaging the subject lighted by the sections in the light path from the light source device10to the diffusing plate56. By inputting the light beam input from the second light guide55to the camera53, imaging of the subject can be executed by the camera53. By adopting the lighting device equipped with the light source device10according to the first embodiment described above, the laser beam with stable intensity can be supplied with high efficiency. Thus, the advantage that a bright image can be monitored is obtained.

Third Embodiment

FIG. 11shows a schematic configuration of a projector70according to a third embodiment of the invention. The projector70is a front projection projector, which supplies the screen88with light for allowing the viewer to appreciate an image by viewing the light reflected on the screen88. The projector70has a red (R) light source device80R, a green (G) light source device80G, and a blue (B) light source device80B. The light source devices80R,80G, and80B for respective colored light beams are each provided with the same configuration as the light source device10(seeFIG. 1) of the first embodiment described above. Duplicate explanations of the first embodiment will be omitted. The projector70displays an image using light beams from the respective colored light sources80R,80G, and80B.

The R-light source device80R is a light source device for supplying the R-light beam. A diffusing element81performs fairing and enlarging the irradiated area, and equalizing the intensity distribution of the laser beam in the irradiated area. As the diffusing element81, for example, a computer generated hologram (CGH), which is a diffractive optical element, can be used. The field lens82parallelizes the laser beam from the diffusing element81, and make the laser beam enter the R-light spatial light modulation device83R. The R-light source device80R, the diffusing element81, and a field lens82form a lighting device for lighting the R-light spatial light modulation device83R. The R-light spatial light modulation device83R is a spatial light modulation device for modulating the R-light beam from the lighting device in accordance with an image signal, and is a transmissive liquid crystal display device. The R-light beam modulated by the R-light spatial light modulation device83R enters a cross dichroic prism84as a color composition optical system.

The G-light source device80G is a light source device for supplying the G-light beam. The laser beam passing through the diffusing element81and the field lens82enters a G-light spatial light modulation device83G. The G-light source device80G, the diffusing element81, and the field lens82form a lighting device for lighting the G-light spatial light modulation device83G. The G-light spatial light modulation device83G is a spatial light modulation device for modulating the G-light beam from the lighting device in accordance with the image signal, and is a transmissive liquid crystal display device. The G-light beam modulated by the G-light spatial light modulation device83G enters the cross dichroic prism84from a different side from the R-light beam.

The B-light source device80B is a light source device for supplying the B-light beam. The laser beam passing through the diffusing element81and the field lens82enters a B-light spatial light modulation device83B. The B-light source device80B, the diffusing element81, and a field lens82form a lighting device for lighting the B-light spatial light modulation device83B. The B-light spatial light modulation device83B is a spatial light modulation device for modulating the B-light beam from the lighting device in accordance with the image signal, and is a transmissive liquid crystal display device. The B-light beam modulated by the B-light spatial light modulation device83B enters the cross dichroic prism84from a different side from the R-light beam and the G-light beam. As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used.

The cross dichroic prism84is provided with two dichroic films85,86disposed so as to be substantially perpendicular to each other. The first dichroic film85reflects the R-light beam and transmits the G-light beam and the B-light beam. The second dichroic film86reflects the B-light beam and transmits the R-light beam and the G-light beam. The cross dichroic prism84combines the R, G, and B-light beams entering in directions different from each other to emit the combined light in the direction towards the projection lens87. The projection lens87projects the light combined by the cross dichroic prism84towards the screen88.

By using the light source devices80R,80G, and80B for respective colored light beams each having a similar configuration to the light source device10described above, laser beams with stable intensity can be supplied with high efficiency. Thus, an advantage that a bright image can stably be displayed with high efficiency is obtained. The projector70is not limited to the case of using the transmissive liquid crystal display devices as the spatial light modulation devices. As the spatial light modulation device, a reflective liquid crystal display device (liquid crystal on silicon; LCOS), a digital micromirror device (DMD), a grating light valve (GLV), and so on can also be used.

The projector70is not limited to having a configuration provided with the spatial light modulation device for every colored light beam. The projector70can be arranged to have a configuration of modulating two or more colored light beams by a single spatial light modulation device. The projector can be a so-called rear projector, which supplies one of the surfaces of the screen with light and allows the viewer to appreciate an image by viewing the light emitted from the other surface of the screen. Further, the application of the light source device according to the embodiment of the invention is not limited to the projector or the monitor device. For example, it can also be applied, for example, to a lithography for performing exposure using a laser beam.

As described above, the light source device according to the embodiment of the invention is suitable for applying to monitor devices or projectors.