JP2010217250A - Wavelength conversion device, light source device, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength conversion device capable of efficiently converting wavelengths of a plurality of light beams mutually different by wavelength, a light source device capable of efficiently supplying a plurality of light beams mutually different by wavelength, and a projector capable of displaying a bright and high quality image with reduced speckle noise. <P>SOLUTION: The wavelength conversion device includes: a nonlinear optical element 21 being an optical element with a polarization reversed structure wherein a first polarization layer and a second polarization layer of which the polarization directions are reversed with respect to each other are arranged in parallel in a first direction; a heater 22 being a heat supply part which supplies heat to be conducted to the optical element; and a plurality of thermal conductivity variable elements 24 having variable thermal conductivities which are provided in a route through which the heat supplied from the heat supply part is conducted to the optical element. In the optical element, a plurality of regions arranged in parallel in a second direction approximately perpendicular to the first direction are set, and the thermal conductivity variable elements 24 are provided per region. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wavelength conversion device, a light source device, and a projector, and more particularly to a technology of a wavelength conversion device used for a light source device.

  In recent years, a technique using a laser light source as a light source of a projector has been proposed. Compared with UHP lamps conventionally used as light sources for projectors, laser light sources have advantages such as high color reproducibility, instant lighting, and long life. When the diffusion surface is irradiated with laser light which is coherent light, an interference pattern called a speckle pattern in which bright spots and dark spots are randomly distributed may appear. The speckle pattern is generated when light diffused at each point on the diffusion surface interferes randomly. When a speckle pattern is recognized when an image is displayed, a glimmering flickering feeling is given to the observer, which adversely affects image viewing.

  As a method for reducing the generation of speckle noise, for example, there is a method of widening the spectrum width of laser light. The coherence length and spectral width of laser light are approximately inversely proportional. Shortening the coherence length by broadening the spectrum width of the laser light is effective as a measure for reducing the generation of speckle noise. In order to widen the spectral width, a method of combining laser packages having different wavelengths from each other can easily ensure a wide spectral width, while increasing the size of the light source device. Therefore, conventionally, by using a light emitting device in which a plurality of light emitting portions are arranged in parallel, by changing the resonance wavelength for each light from the light emitting portion, a plurality of laser beams having different wavelengths can be obtained from one package. A method of injecting has been proposed.

  Known laser light sources emit laser light whose wavelength is converted by a wavelength conversion element, in addition to those that emit laser light without converting the wavelength of the fundamental wave light. By using the wavelength conversion element, it is possible to obtain laser light having a desired wavelength and a sufficient amount of light using a general-purpose light-emitting element that can be easily obtained. In order to emit laser beams having different wavelengths by a laser light source using a wavelength conversion element, wavelength conversion of a plurality of lights having different wavelengths is necessary. For example, Patent Document 1 proposes a configuration in which a plurality of temperature control elements are arranged in parallel in a direction along the optical path direction of the nonlinear optical element for the purpose of wavelength conversion of a plurality of lights having different wavelengths. By controlling a plurality of temperature control elements provided in the nonlinear optical element, a temperature gradient is generated in the polarization inversion structure of the nonlinear optical element. In the nonlinear optical element, the phase matching wavelength satisfies the phase matching condition by changing the refractive index distribution due to temperature change.

JP 2005-202334 A

  In order to obtain sufficient wavelength conversion efficiency by the nonlinear optical element, a sufficient interaction length in the polarization inversion structure is required. However, when the temperature gradient is generated in the optical path direction of the nonlinear optical element, there is a problem that the wavelength conversion efficiency is lowered due to the shortened interaction length for each phase matching wavelength. The present invention has been made in view of the above-described problems, and is a wavelength conversion device capable of converting a plurality of lights having different wavelengths with high efficiency, and capable of supplying a plurality of lights having different wavelengths with high efficiency. An object of the present invention is to provide a light source device that can display a high-quality image that is bright and has reduced speckle noise.

  In order to solve the above-described problems and achieve the object, the wavelength conversion device according to the present invention includes a polarization reversal in which a first polarization layer and a second polarization layer whose polarization directions are reversed are parallel to each other in the first direction. An optical element having a structure; a heat supply unit that supplies heat to be conducted to the optical element; and a path that conducts heat supplied by the heat supply unit to the optical element, and the thermal conductivity is variable. A plurality of thermal conductivity variable elements, wherein the optical element has a plurality of regions arranged in parallel in a second direction substantially perpendicular to the first direction, and the thermal conductivity variable elements Is provided for each of the regions.

  The temperature of each region of the optical element is adjusted by heat supplied via the thermal conductivity variable element. By appropriately controlling the thermal conductivity of each thermal conductivity variable element, the wavelength conversion device adjusts the temperature of the optical element for each region and varies the phase matching wavelength for each region. By making it possible to set the phase matching wavelength for each region arranged in parallel in the second direction, a sufficient interaction length can be ensured for any light incident on the optical element. Thereby, the wavelength converter which enables wavelength conversion of the some light from which a wavelength mutually differs with high efficiency can be obtained.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a thermal diffusion unit that diffuses the heat supplied by the heat supply unit and conducts the heat to the plurality of variable thermal conductivity elements. Thereby, heat can be evenly supplied to each thermal conductivity variable element regardless of the position where the heat supply unit is arranged. Moreover, power consumption can be reduced by reducing the number of heat supply units.

  Further, as a preferred aspect of the present invention, it has a heat radiating part for releasing heat from the optical element, the plurality of variable thermal conductivity elements are provided on the first surface of the optical element, It is desirable that the optical element is provided on a second surface opposite to the first surface. By releasing heat from the second surface side of the optical element by the heat radiating portion, heat conduction from the first surface side to the second surface side is promoted, and heat conduction between the regions can be suppressed. Thus, accurate temperature adjustment for each region is possible, and wavelength conversion can be performed with high efficiency in each region.

  Moreover, as a preferable aspect of the present invention, it is desirable that the first polarization layer and the second polarization layer are formed with different periods for each region. The phase matching wavelength of each region is determined by the period and temperature of the domain-inverted structure. Thereby, the structure which enables wavelength conversion about the light of a wide spectral width is easily realizable.

  As a preferred aspect of the present invention, it is desirable that the first polarization layer and the second polarization layer are formed with substantially the same period in each of the plurality of regions. Thereby, the structure which enables wavelength conversion about the light of a mutually different wavelength is realizable using the optical element which can be produced easily.

  Furthermore, the wavelength conversion device according to the present invention includes a plurality of optical elements each having a polarization reversal structure in which a first polarization layer and a second polarization layer whose polarization directions are reversed from each other are arranged in parallel in the first direction, and the optical element A heat supply unit that supplies heat to be conducted to, a heat conductivity variable element that is provided in a path that conducts the heat supplied by the heat supply unit to the plurality of optical elements, and whose thermal conductivity is variable, The plurality of optical elements are provided in parallel in a second direction substantially perpendicular to the first direction via the thermal conductivity variable element.

  The temperature of each optical element is controlled by the heat supplied through the thermal conductivity variable element. By appropriately controlling the thermal conductivity of each thermal conductivity variable element, the wavelength conversion device adjusts the temperature for each optical element and varies the phase matching wavelength for each optical element. By making it possible to set the phase matching wavelength for each optical element arranged in parallel in the second direction, a sufficient interaction length can be secured for any light incident on the optical element. Thereby, the wavelength converter which enables wavelength conversion of the some light from which a wavelength mutually differs with high efficiency can be obtained.

  Moreover, as a preferable aspect of the present invention, the heat supply unit constitutes one end in the second direction in a structure in which a plurality of the optical elements and the thermal conductivity variable element are integrated. It is desirable to be provided in the optical element. Thereby, each optical element arranged in parallel in the second direction can have a temperature gradient.

  Moreover, as a preferable aspect of the present invention, a heat radiating portion that releases heat from the optical element is provided, the heat supply portion is provided in an optical element that constitutes a first end of the structure, and the heat radiating portion is In the structure, it is preferable to be provided in an optical element constituting a second end opposite to the first end. By releasing heat at the second end side by the heat radiating portion, heat conduction from the first end side to the second end side is promoted, and heat conduction in directions other than the second direction can be suppressed. Thereby, the heat supplied by the heat supply unit can be efficiently conducted to each optical element.

  As a preferred aspect of the present invention, it is desirable that the first polarization layer and the second polarization layer are formed with different periods for each of the optical elements. Thereby, the structure which enables wavelength conversion about the light of a wide spectral width is easily realizable.

  As a preferred aspect of the present invention, it is desirable that the first polarization layer and the second polarization layer are formed with substantially the same period in each of the plurality of optical elements. By using an optical element having a domain-inverted structure with substantially the same period, the wavelength converter can be easily manufactured.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a control unit that controls the thermal conductivity of the thermal conductivity variable element. By accurately adjusting the temperature of the optical element by the control unit, it is possible to convert a plurality of lights having different wavelengths with high efficiency.

  Furthermore, the light source device according to the present invention includes a light emitting element including a plurality of light emitting units that emit light, a resonator for resonating light emitted from the plurality of light emitting units, the light emitting element, and the light emitting device. And a wavelength conversion device that is disposed in an optical path between the resonators and converts the wavelength of light emitted from the plurality of light emitting units. The wavelength of light to be resonated using the resonator is set according to the phase matching wavelength of the wavelength converter. Thereby, a light source device capable of supplying a plurality of lights having different wavelengths with high efficiency can be obtained.

  Furthermore, a projector according to the present invention includes the light source device described above, and displays an image using light emitted from the light source device. By using the above light source device, an image is displayed using light with a wide spectral width emitted with high efficiency. As a result, a bright projector capable of displaying a high-quality image with reduced speckle noise can be obtained.

1 is a schematic plan view of a light source device according to Example 1. FIG. It is a side surface schematic diagram of a wavelength converter. It is a perspective schematic diagram of a nonlinear optical element. It is a graph showing the relationship between spectrum width and speckle contrast. It is a perspective schematic diagram of the nonlinear optical element with which the wavelength converter which concerns on a modification is provided. 6 is a schematic plan view of a light source device according to Example 2. FIG. It is a side surface schematic diagram of a wavelength converter. It is a perspective schematic diagram of a structure. It is a side surface schematic diagram in the case of applying a heat sink to a wavelength converter. It is a perspective schematic diagram of the structure with which the wavelength converter which concerns on a modification is provided. FIG. 6 is a schematic configuration diagram of a projector according to a third embodiment.

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

  FIG. 1 is a schematic plan view of a light source device 10 according to Embodiment 1 of the present invention. The light source device 10 is an array laser that emits three laser beams. The light emitting element 11 is a surface light emitting type semiconductor element, and includes three light emitting portions 15 arranged in parallel in a line. The light emitting unit 15 emits fundamental wave light. The fundamental light is, for example, infrared light. The band pass filter 12 and the wavelength conversion device 13 are disposed in the optical path between the light emitting element 11 and the resonance mirror 14.

  The band-pass filter 12 is a narrow-band transmission filter having transmission characteristics with a half-value width of several nm or less. The band pass filter 12 includes a dielectric multilayer film. The wavelength conversion device 13 emits higher harmonic light by converting the wavelength of the fundamental light emitted from the light emitting element 11. The harmonic light is light having a wavelength that is half the wavelength of the fundamental light, and is, for example, visible light. The resonant mirror 14 is a resonator for resonating the light emitted from each light emitting unit 15. The resonant mirror 14 is a broadband reflection mirror that transmits light in a wavelength region including the wavelength of the harmonic light and reflects light in the wavelength region including the wavelength of the fundamental light, and separates the fundamental light and the harmonic light. In the present embodiment, the axis parallel to the principal ray of light emitted from each light emitting portion 15 is defined as the Z axis. Both the X axis and the Y axis are two axes perpendicular to the Z axis and perpendicular to each other. The three light emission parts 15 are arranged in parallel in the X-axis direction.

  The fundamental wave light emitted from each light emitting portion 15 of the light emitting element 11 enters the band pass filter 12. The fundamental light transmitted through the bandpass filter 12 enters the wavelength conversion device 13. The harmonic light generated in the wavelength conversion device 13 passes through the resonance mirror 14 and is emitted to the outside of the light source device 10. The fundamental light transmitted through the wavelength converter 13 from the band pass filter 12 side to the resonant mirror 14 side is reflected by the resonant mirror 14. The fundamental light transmitted from the resonance mirror 14 through the wavelength conversion device 13 and transmitted through the bandpass filter 12 enters the light emitting unit 15. The fundamental wave light incident on the light emitting portion 15 is reflected from a mirror layer (not shown) of the light emitting element 11 and then emitted from the light emitting portion 15. The fundamental wave light reflected by the mirror layer of the light emitting element 11 and the resonance mirror 14 is amplified by resonating with the fundamental wave light newly emitted from the light emitting unit 15.

  FIG. 2 is a schematic side view of the wavelength conversion device 13. The wavelength conversion device 13 includes a nonlinear optical element 21, a heater 22, a heat diffusion plate 23, three thermal conductivity variable elements 24, a heat sink 25, and a control unit 26. In FIG. 1, the wavelength conversion device 13 does not show the configuration other than the nonlinear optical element 21.

FIG. 3 is a schematic perspective view of the nonlinear optical element 21. As the nonlinear optical element 21, for example, a polarization inversion crystal (Periodically Poled Lithium Niobate; PPLN) of lithium niobate (LiNbO ₃ ) is used. The nonlinear optical element 21 includes a first polarization layer 34 and a second polarization layer 35 whose polarization directions are reversed with respect to each other. The first polarization layer 34 and the second polarization layer 35 are alternately arranged in parallel in the Z-axis direction that is the first direction. The first polarization layer 34 and the second polarization layer 35 constitute a polarization inversion structure in which the sign of the nonlinear optical constant is inverted for each coherent length. The first polarization layer 34 is a portion where the spontaneous polarization of the optical crystal is reversed. The second polarization layer 35 is a portion where the spontaneous polarization of the optical crystal is left.

  Three regions 31, 32, and 33 are set in the nonlinear optical element 21. Each area | region 31, 32, 33 is parallel to the X-axis direction which is a 2nd direction. The light from the light emitting part 15 is incident on the respective regions 31, 32, 33 of the nonlinear optical element 21. The polarization inversion structure of the nonlinear optical element 21 is formed such that the pitch at which the first polarization layer 34 and the second polarization layer 35 are arranged in parallel decreases in the order of the region 31, the region 32, and the region 33. The first polarization layer 34 and the second polarization layer 35 are formed with different periods for the regions 31, 32, and 33.

  For the formation of the domain-inverted structure, a method of applying a voltage to a nonlinear optical crystal having spontaneous polarization is often used. The domain-inverted structure can be obtained, for example, by forming a fine pattern of an insulating layer on a lithium niobate substrate (LN substrate) and applying a voltage via a metal film or an electrolytic solution. By patterning the insulating layer with a different period for each of the regions 31, 32, and 33, the first polarization layer 34 and the second polarization layer 35 with a different period for each of the regions 31, 32, and 33 are formed.

  The thermal conductivity variable element 24 is provided on the first surface S <b> 1 of the nonlinear optical element 21 for each of the regions 31, 32, and 33. The thermal conductivity variable element 24 has a property that the thermal conductivity is variable. The thermal conductivity variable elements 24 are arranged at intervals. The heater 22 and the thermal diffusion plate 23 are provided on the first surface S <b> 1 of the nonlinear optical element 21 via the thermal conductivity variable element 24. The heater 22 serving as a heat supply unit supplies heat to be conducted to the nonlinear optical element 21 through the thermal diffusion plate 23 and the thermal conductivity variable element 24. For example, an electric heater is used as the heater 22. By conducting heat from one heater 22 to each of the regions 31, 32, 33 by the heat diffusion plate 23, the configuration can be simplified as compared with the case where the heater 22 is installed for each of the regions 31, 32, 33. Further, since the number of the heaters 22 can be reduced as compared with the case where the heaters 22 are installed in each of the regions 31, 32, and 33, it is possible to reduce power consumption.

  The heat diffusing plate 23 serving as a heat diffusing portion diffuses the heat supplied by the heater 22 and conducts the heat to each thermal conductivity variable element 24. As the heat diffusing plate 23, a highly heat conductive plate member, for example, a copper plate is used. The heater 22 is disposed at the center of the heat diffusion plate 23. The heat diffusing plate 23 is connected to each thermal conductivity variable element 24. The thermal conductivity variable element 24 is provided in a path that conducts the heat supplied by the heater 22 to the nonlinear optical element 21.

  The heat sink 25 that is a heat radiating portion is provided on the second surface S <b> 2 of the nonlinear optical element 21. The heat sink 25 releases heat from the nonlinear optical element 21. The second surface S2 is the surface of the nonlinear optical element 21 opposite to the first surface S1. The control unit 26 is connected to the heater 22 and the thermal conductivity variable element 24 and adjusts the temperature of the nonlinear optical element 21.

  The thermal conductivity variable element 24 is configured using, for example, a magnetic thin film. As the magnetic thin film, a magnetic thin film having a magnetoresistive (MR) effect and made of a material exhibiting an anisotropic MR effect such as NiFe is used. As a specific example of the thermal conductivity variable element 24, a magnetic film formed by alternately laminating a sandwich film (spin valve film) such as Co / Cu / Co with a nonmagnetic layer sandwiched between magnetic layers, a magnetic layer and a nonmagnetic layer. There are artificial lattice films. A magnetic thin film having an MR effect has a property that its thermal conductivity changes when a magnetic field is applied. The principle that the thermal conductivity is changed by applying a magnetic field is the same as the MR effect. That is, the change in thermal conductivity is caused by the change in the mobility of electrons, which is one of the heat flow bearers, with the change in the direction of magnetization caused by the application of a magnetic field. Thermal conductivity changes according to Wiedemann-Franz law due to changes in electron mobility.

  When applying a magnetic field using a magnet, the control unit 26 controls the thermal conductivity of each thermal conductivity variable element 24 by adjusting the distance from the magnet for each thermal conductivity variable element 24. When applying a magnetic field using an electromagnet, the control unit 26 controls the thermal conductivity of each thermal conductivity variable element 24 by adjusting the current value to the electromagnet for each thermal conductivity variable element 24. The control unit 26 adjusts the temperature of the nonlinear optical element 21 for each of the regions 31, 32, and 33 by controlling the amount of heat supplied by the heater 22 and the thermal conductivity of each thermal conductivity variable element 24. The thermal conductivity of the variable thermal conductivity element 24 is set according to the phase matching conditions in the regions 31, 32, and 33 of the nonlinear optical element 21. Note that the control unit 26 performs feedback control of the heater 22 and the thermal conductivity variable element 24 based on the measurement result of the temperature of the nonlinear optical element 21, thereby adjusting each region 31, 32, 33 to the target temperature. Also good.

  The wavelength conversion device 13 can perform wavelength conversion of a plurality of lights having different wavelengths by adjusting the temperature of each of the regions 31, 32, and 33 according to the phase matching condition for each of the regions 31, 32, and 33. By making it possible to set the phase matching wavelength for each of the regions 31, 32 and 33 arranged in parallel in the X-axis direction perpendicular to the light traveling direction, a sufficient interaction length for any light incident on the nonlinear optical element 21 Can be secured. This produces an effect that a plurality of lights having different wavelengths can be wavelength-converted with high efficiency. For each region 31, 32, 33, the period of the domain-inverted structure is appropriately set, and the thermal conductivity of the thermal conductivity variable element 24 is controlled so as to meet the phase matching condition, so that the wavelength of light having a wide spectral width A configuration capable of conversion can be easily realized.

The band pass filter 12 transmits light of different wavelengths for each region where light from the light emitting unit 15 enters. The bandpass filter 12 transmits light having a different wavelength for each region, for example, by a dielectric multilayer film formed by stacking layers having different thicknesses for each region. The light source device 10 is configured such that the phase matching wavelength of the nonlinear optical element 21 matches the wavelength that is selectively transmitted by the bandpass filter 12. The light source device 10 emits three laser beams having different wavelengths λ ₁ , λ ₂ , and λ ₃ by converting the wavelengths of light having different wavelengths. The light source device 10 can supply a plurality of lights having different wavelengths with high efficiency by combining the wavelength conversion device 13 and the band pass filter 12. Even when the wavelength characteristics of the band-pass filter 12 vary, it can be easily adjusted to satisfy the phase matching condition by controlling the thermal conductivity of the thermal conductivity variable element 24.

  The heat supplied by the heater 22 is diffused by the heat diffusing plate 23, and is conducted to each region 31, 32, 33 of the nonlinear optical element 21 through each thermal conductivity variable element 24. The heat conducted to the nonlinear optical element 21 is released from the heat sink 25 to the outside. By releasing heat from the second surface S2 side of the nonlinear optical element 21 by the heat sink 25, heat conduction from the first surface S1 side to the second surface S2 side is promoted, and heat conduction between the regions 31, 32, and 33 is performed. Can be suppressed.

  By making it possible to suppress heat conduction between the regions 31, 32, and 33, even when a temperature difference is created between the regions 31, 32, and 33, accurate temperature adjustment for each of the regions 31, 32, and 33 is possible. It becomes. Thereby, wavelength conversion can be performed with high efficiency in each of the regions 31, 32, and 33. Note that at least one of the heat diffusing plate 23 and the heat sink 25 may be omitted as long as accurate temperature adjustment for each of the regions 31, 32, and 33 is possible.

  FIG. 4 is a graph showing the relationship between the spectral width of laser light and speckle contrast. The speckle contrast is expressed as 100% when the contrast produced by speckle noise is maximum. The graph represents a case where three laser beams having different wavelengths in the spectrum width represented by the horizontal axis are emitted. The speckle contrast is about 60% when the spectral width is 2 nm, and changes at about 60% even if the spectral width is increased. In order to effectively reduce speckle noise, it is desirable to set the wavelengths of the plurality of laser beams so that they are approximately equally spaced.

Therefore, when an image is displayed using the light source device 10 according to the present embodiment, the wavelengths λ ₁ , λ ₂ , and λ ₃ of the laser light emitted from the light source device 10 are different by 1 nm with a spectral width of 2 nm. Thus, speckle noise can be reduced. Since the light source device 10 according to the present embodiment can reduce variations in the intensity of each laser beam having different wavelengths, it can effectively reduce speckle noise.

  The light source device 10 according to the present embodiment is not limited to one that three wavelengths of light are emitted and emitted, and any light source device that emits a plurality of lights after wavelength conversion may be used, and the configuration may be changed as appropriate. The light source device 10 may use a narrow-band reflection mirror, for example, a volume hologram, as a resonator instead of the combination of the resonance mirror 14 that is a broadband reflection mirror and the band-pass filter 12 that is a narrow-band transmission filter. The light source device 10 may be provided with a polarization selection filter or the like as necessary. The light source device 10 may be a semiconductor laser pumped solid state (DPSS) laser.

  FIG. 5 is a schematic perspective view of the nonlinear optical element 36 included in the wavelength conversion device according to the modification. This modification is characterized in that the first polarization layer 34 and the second polarization layer 35 are formed in the same period in each of the regions 31, 32, and 33. Also in this modification, the phase matching wavelength of the nonlinear optical element 36 can be made different for each of the regions 31, 32, 33 by adjusting the temperature of each of the regions 31, 32, 33. The non-linear optical element 36 can be easily manufactured by making the period of the domain-inverted structure the same in any of the regions 31, 32 and 33. Thereby, the structure which enables wavelength conversion of the light from which a wavelength differs mutually is realizable using the nonlinear optical element 36 which can be produced easily.

  FIG. 6 is a schematic plan view of the light source device 40 according to Embodiment 2 of the present invention. The present embodiment is characterized by including a thermal conductivity variable element provided between the nonlinear optical elements. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The wavelength conversion device 41 emits higher harmonic light by converting the wavelength of the fundamental light emitted from the light emitting element 11.

  FIG. 7 is a schematic side view of the wavelength conversion device 41. The wavelength conversion device 41 includes three nonlinear optical elements 42, 43, 44, a heater 22, two thermal conductivity variable elements 45, and a control unit 26. The thermal conductivity variable element 45 is provided between the two nonlinear optical elements 42 and 43 and between the two nonlinear optical elements 43 and 44, respectively. Each nonlinear optical element 42, 43, 44 is provided in parallel in the X-axis direction, which is the second direction, via a thermal conductivity variable element 45. Each nonlinear optical element 42, 43, 44 and the thermal conductivity variable element 45 constitute an integral structure 46 having a rectangular parallelepiped shape. The structure 46 is configured by, for example, bonding each nonlinear optical element 42, 43, 44 and the heat conductivity variable element 45 using a heat conductive adhesive. In FIG. 6, the wavelength conversion device 41 does not show the configuration other than the structure 46.

  FIG. 8 is a schematic perspective view of the structure 46. Each nonlinear optical element 42, 43, 44 has a first polarization layer 34 and a second polarization layer 35. The light from the light emitting part 15 enters each nonlinear optical element 42, 43, 44. The polarization inversion structure of the nonlinear optical elements 42, 43, 44 is such that the pitch at which the first polarization layer 34 and the second polarization layer 35 are arranged in parallel decreases in the order of the nonlinear optical element 42, the nonlinear optical element 43, and the nonlinear optical element 44. Is formed. The first polarization layer 34 and the second polarization layer 35 are formed with different periods for each of the nonlinear optical elements 42, 43, and 44.

  The heater 22 is provided in the nonlinear optical element 42 that constitutes the first end T <b> 1 that is one end of the structure 46 in the X-axis direction. The second end T2 is the end of the structure 46 opposite to the first end T1. The thermal conductivity variable element 45 is provided in a path for conducting the heat supplied by the heater 22 to each nonlinear optical element 42, 43, 44. The control unit 26 is connected to the heater 22 and the thermal conductivity variable element 45 and adjusts the temperature of each nonlinear optical element 42, 43, 44. As in the first embodiment, the thermal conductivity variable element 45 is configured using, for example, a magnetic thin film.

  By providing the heater 22 in the nonlinear optical element 42 that constitutes the first end T1, the structure 46 moves from the nonlinear optical element 42 that constitutes the first end T1 to the nonlinear optical element 44 that constitutes the second end T2. Accordingly, it is possible to provide a temperature gradient that gradually decreases according to the temperature. The control unit 26 adjusts the temperature of each nonlinear optical element 42, 43, 44 by controlling the amount of heat supplied by the heater 22 and the thermal conductivity of each thermal conductivity variable element 45.

  The wavelength converter 41 adjusts the temperature of each nonlinear optical element 42, 43, 44 according to the phase matching condition of each nonlinear optical element 42, 43, 44, thereby performing wavelength conversion of a plurality of lights having different wavelengths. It becomes possible. Also in this embodiment, a sufficient interaction length can be secured for each light, and a plurality of lights having different wavelengths can be wavelength-converted with high efficiency. Further, the wavelength conversion device 41 can suppress the thickness in the Y-axis direction by arranging the nonlinear optical elements 42, 43, 44 and the thermal conductivity variable element 45 in parallel in the X-axis direction. Thereby, the light source device 40 can be reduced in size.

  FIG. 9 is a schematic side view when the heat sink 47 is applied to the wavelength conversion device 41. The heat sink 47 is provided in the nonlinear optical element 44 constituting the second end T2. The heat supplied by the heater 22 is conducted from the nonlinear optical element 42 constituting the first end T1 to the nonlinear optical element 44 constituting the second end T2, and released from the heat sink 47 to the outside. By releasing heat on the second end T2 side by the heat sink 47, heat conduction from the first end T1 side to the second end T2 side is promoted in the structure 46, and heat conduction in a direction other than the X-axis direction is promoted. It can be suppressed.

  Thereby, the heat supplied by the heater 22 can be efficiently conducted to the nonlinear optical elements 42, 43, 44. The positions where the heater 22 and the heat sink 47 are disposed are not limited to those described in the present embodiment, and may be appropriately changed according to the mode of adjusting the temperature of each nonlinear optical element 42, 43, 44. Also in this embodiment, the heat diffusion plate 23 may be applied as appropriate.

  FIG. 10 is a schematic perspective view of the structure 48 included in the wavelength conversion device according to the modification. This modification is characterized in that the first polarization layer 34 and the second polarization layer 35 are formed in the same period in any of the nonlinear optical elements 42, 43, 44. Also in this modification, the phase matching wavelengths of the nonlinear optical elements 42, 43, and 44 can be made different by adjusting the temperatures of the nonlinear optical elements 42, 43, and 44. Any of the nonlinear optical elements 42, 43, and 44 can be manufactured easily by making the period of the domain-inverted structure the same.

  FIG. 11 is a schematic configuration diagram of a projector 50 according to the third embodiment of the invention. The projector 50 is a front projection type projector that projects light on the screen 59 and observes the image by observing the light reflected by the screen 59. The projector 50 includes a red (R) light source device 51R, a green (G) light source device 51G, and a blue (B) light source device 51B. Each color light source device 51R, 51G, 51B has the same configuration as any of the light source devices described in the above embodiments. The projector 50 displays an image using light from each color light source device 51R, 51G, 51B.

  Each color light source device 51R, 51G, 51B emits laser light. The R light source device 51R is a light source device that emits R light. The diffusing element 52 performs shaping and enlargement of the illumination area and uniformizing the light amount distribution in the illumination area. As the diffusing element 52, for example, a computer generated hologram (CGH) which is a diffractive optical element is used. The field lens 53 collimates the light from the R light source device 51R and makes it incident on the R light spatial light modulator 54R. The spatial light modulator 54R for R light is a spatial light modulator that modulates R light in accordance with an image signal, and is a transmissive liquid crystal display device. The R light modulated by the R light spatial light modulator 54R is incident on a cross dichroic prism 55 which is a color synthesis optical system.

  The light source device 51G for G light is a light source device that emits G light. The light that has passed through the diffusing element 52 and the field lens 53 enters the G spatial light modulator 54G. The spatial light modulation device 54G for G light is a spatial light modulation device that modulates G light according to an image signal, and is a transmissive liquid crystal display device. The G light modulated by the spatial light modulator for G light 54G enters the cross dichroic prism 55 from a surface different from the R light.

  The light source device 51B for B light is a light source device that emits B light. The light that has passed through the diffusing element 52 and the field lens 53 enters the spatial light modulator 54B for B light. The B light spatial light modulator 54B is a spatial light modulator that modulates B light in accordance with an image signal, and is a transmissive liquid crystal display device. The B light modulated by the B light spatial light modulator 54B enters the cross dichroic prism 55 from a different surface 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) is used.

  The cross dichroic prism 55 has two dichroic films 56 and 57 arranged substantially orthogonal to each other. The first dichroic film 56 reflects R light and transmits G light and B light. The second dichroic film 57 reflects B light and transmits R light and G light. The cross dichroic prism 55 combines R light, G light, and B light incident from different surfaces and emits the light toward the projection lens 58. The projection lens 58 projects the light combined by the cross dichroic prism 55 toward the screen 59.

  By using each color light source device 51R, 51G, 51B having the same configuration as that of the light source device according to the above embodiment, an image is displayed using light with a wide spectral width emitted with high efficiency. As a result, the projector 50 can display a bright and high-quality image with reduced speckle noise. The projector 50 may be configured so that at least one of the light source devices 51R, 51G, and 51B for each color light has the same configuration as any one of the light source devices according to the above embodiments. For example, the R light source device 51R may emit the light from the light emitting element as it is without converting the wavelength.

  The projector 50 may use a reflective liquid crystal display device (Liquid Crystal On Silicon: LCOS), a DMD (Digital Micromirror Device), a GLV (Grating Light Valve), or the like as a spatial light modulator. The projector 50 may be configured to include a spatial light modulation device that modulates two or three or more color lights in addition to a configuration including a spatial light modulation device for each color light. The projector 50 may be a laser scanning projector that scans the laser light from the light source device by scanning means such as a galvanometer mirror and displays an image on the irradiated surface. The projector 50 may be a slide projector using a slide having image information. The projector 50 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. In addition to being applied to the projector 50, the light source device according to the present invention may be applied to, for example, a light source of a monitor device that monitors a subject.

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

  DESCRIPTION OF SYMBOLS 10 Light source device, 11 Light emitting element, 12 Band pass filter, 13 Wavelength conversion apparatus, 14 Resonant mirror, 15 Light emission part, 21 Nonlinear optical element, 22 Heater, 23 Thermal diffusion plate, 24 Thermal conductivity variable element, 25 Heat sink, 26 control unit, S1 first surface, S2 second surface, 31, 32, 33 region, 34 first polarization layer, 35 second polarization layer, 36 nonlinear optical element, 40 light source device, 41 wavelength conversion device, 42, 43 , 44 Nonlinear optical element, 45 Thermal conductivity variable element, 46 structure, T1 first end, T2 second end, 47 heat sink, 48 structure, 50 projector, 51RR light source device for 51R light, 51G light source device for G light , 51B light source device for B light, 52 diffusing element, 53 field lens, spatial light modulator for 54R R light, spatial light for 54G G light Modulator, 54B spatial light modulator for B light, 55 cross dichroic prism, 56 first dichroic film, 57 second dichroic film, 58 projection lens, 59 screen

Claims (13)

An optical element having a polarization reversal structure in which a first polarization layer and a second polarization layer whose polarization directions are reversed from each other are arranged in parallel in the first direction;
A heat supply unit for supplying heat conducted to the optical element;
A plurality of variable thermal conductivity elements provided in a path for conducting heat supplied by the heat supply unit to the optical element, and having a variable thermal conductivity;
The optical element has a plurality of regions set in parallel in a second direction substantially perpendicular to the first direction,
The wavelength conversion device, wherein the thermal conductivity variable element is provided for each of the regions.   The wavelength conversion device according to claim 1, further comprising a heat diffusion unit that diffuses the heat supplied by the heat supply unit and conducts the heat to the plurality of variable thermal conductivity elements. A heat dissipating part for releasing heat from the optical element;
The plurality of thermal conductivity variable elements are provided on the first surface of the optical element,
3. The wavelength conversion device according to claim 1, wherein the heat radiating unit is provided on a second surface of the optical element opposite to the first surface. 4.   The wavelength conversion device according to any one of claims 1 to 3, wherein the first polarization layer and the second polarization layer are formed with different periods for each of the regions.   4. The wavelength conversion device according to claim 1, wherein the first polarization layer and the second polarization layer are formed with substantially the same period in each of the plurality of regions. A plurality of optical elements comprising a polarization reversal structure in which a first polarization layer and a second polarization layer whose polarization directions are reversed from each other are arranged in parallel in the first direction;
A heat supply unit for supplying heat conducted to the optical element;
A thermal conductivity variable element provided in a path for conducting heat supplied by the heat supply unit to the plurality of optical elements, and having a variable thermal conductivity;
The wavelength conversion device, wherein the plurality of optical elements are provided in parallel in a second direction substantially perpendicular to the first direction via the thermal conductivity variable element.   The heat supply unit is provided in an optical element that constitutes one end in the second direction among a structure in which a plurality of the optical elements and the thermal conductivity variable element are integrated. The wavelength conversion device according to claim 6. A heat dissipating part for releasing heat from the optical element;
The heat supply unit is provided in an optical element constituting the first end of the structure,
The wavelength converter according to claim 7, wherein the heat radiating portion is provided in an optical element constituting a second end of the structure opposite to the first end.   The wavelength conversion device according to any one of claims 6 to 8, wherein the first polarization layer and the second polarization layer are formed with different periods for each of the optical elements.   The wavelength conversion device according to any one of claims 6 to 8, wherein the first polarization layer and the second polarization layer are formed with substantially the same period in each of the plurality of optical elements.   The wavelength conversion device according to claim 1, further comprising a control unit that controls the thermal conductivity of the thermal conductivity variable element. A light emitting device comprising a plurality of light emitting portions for emitting light;
A resonator for resonating light emitted from the plurality of light emitting portions;
The wavelength conversion device according to any one of claims 1 to 11, wherein the wavelength conversion device is disposed in an optical path between the light emitting element and the resonator and wavelength-converts light emitted from the plurality of light emitting units. A light source device comprising:   A projector comprising the light source device according to claim 12, wherein an image is displayed using light emitted from the light source device.

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