WO2020079774A1 - Laser light source device - Google Patents

Laser light source device Download PDF

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Publication number
WO2020079774A1
WO2020079774A1 PCT/JP2018/038654 JP2018038654W WO2020079774A1 WO 2020079774 A1 WO2020079774 A1 WO 2020079774A1 JP 2018038654 W JP2018038654 W JP 2018038654W WO 2020079774 A1 WO2020079774 A1 WO 2020079774A1
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WO
WIPO (PCT)
Prior art keywords
polarization
laser
laser light
semiconductor laser
polarization rotation
Prior art date
Application number
PCT/JP2018/038654
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French (fr)
Japanese (ja)
Inventor
博 木田
Original Assignee
三菱電機株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 三菱電機株式会社 filed Critical 三菱電機株式会社
Priority to PCT/JP2018/038654 priority Critical patent/WO2020079774A1/en
Priority to JP2020553114A priority patent/JPWO2020080220A1/en
Priority to PCT/JP2019/039824 priority patent/WO2020080220A1/en
Publication of WO2020079774A1 publication Critical patent/WO2020079774A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings

Definitions

  • the present invention relates to a laser light source device.
  • the semiconductor laser element emits laser light with low power consumption and excellent monochromaticity and high directivity.
  • a semiconductor laser device having such features is expected as a replacement light source for currently popular lamps.
  • a semiconductor laser device has been attracting attention as a light source of a projection type display device such as a projector.
  • the semiconductor laser element When the semiconductor laser element is mounted as a light source in a projection type display device, the semiconductor laser element has a small light emitting area, and therefore, in the optical design thereof, it is possible to miniaturize the optical element necessary for spatial composition of laser beams.
  • miniaturization of optical elements enables miniaturization of display devices such as digital mirror devices (DMD (Digital Mirror Device)) and liquid crystal displays (LCD (Liquid Crystal Display)), resulting in lower system cost. To do.
  • DMD Digital Mirror Device
  • LCD Liquid Crystal Display
  • the light source of the projection display device is composed of a plurality of semiconductor laser elements.
  • the laser light emitted from the semiconductor laser device is composed of waves with the same phase. This feature produces the monochromaticity and high directivity of the semiconductor laser.
  • a striped pattern or speckles are generated due to the coherence of the waves. Speckle is a particle-like pattern due to the coherence of random waves appearing by the laser light irradiated on the screen.
  • Such an interference pattern has been one of the causes of deterioration of image quality when a laser is used as a light source of a projection display device.
  • a means for mixing semiconductor laser light of multiple wavelengths or a means for disturbing the polarization uniformity of the semiconductor laser light is effective.
  • a laser light source device that rotates the polarization of laser light emitted from one or a plurality of light emitting points of a laser light source by 90 ° by a polarization rotation unit arranged on the optical axis thereof.
  • the laser light source device is an array type laser light source in which a plurality of laser beams oscillates from one semiconductor laser chip.
  • Patent Document 1 can reduce interference fringes and speckles, since it is an array type laser light source, the gain is reduced due to the temperature rise due to heat generated from an adjacent laser, and a sufficient output is obtained. Can't get
  • the present invention has been made to solve the above problems, and an object of the present invention is to provide a laser light source device capable of reducing the occurrence of interference fringes and speckles and reducing the temperature rise due to laser oscillation. To do.
  • the laser light source device includes a base, a plurality of semiconductor laser elements each of which is individually held on the upper surface of the base and emits a plurality of laser lights whose polarization directions are aligned in one direction.
  • a polarization conversion unit that rotates the polarization direction of at least a part of the laser light to disturb the polarization directions of the plurality of laser lights so that they are not aligned in one direction.
  • the polarization conversion unit includes a plurality of polarization rotation elements that convert the polarization of the plurality of laser lights into circularly polarized light.
  • the plurality of polarization rotation elements are selectively arranged in correspondence with the semiconductor laser element that emits a part of the laser light among the plurality of semiconductor laser elements, and convert the polarization of a part of the laser light into left-handed circularly polarized light.
  • the first polarization rotation element and the other semiconductor laser element which emits another part of the laser light among the plurality of semiconductor laser elements are selectively arranged to correspond to the polarization of another part of the laser light.
  • a second polarization rotation element that converts the light into right-handed circularly polarized light.
  • the present invention it is possible to provide a laser light source device that reduces the occurrence of interference fringes and speckles, and reduces the temperature rise due to laser oscillation.
  • FIG. 3 is a perspective view showing a configuration of a laser light source device and laser light emitted from the laser light source device according to the embodiment. It is an exploded perspective view showing the composition of the laser light source device in an embodiment. It is a figure which shows the structure of the polarization rotation element in embodiment. It is a figure which shows the structure of the polarization rotation element in embodiment.
  • FIG. 3 is a perspective view showing a detailed configuration of the semiconductor laser device according to the embodiment.
  • FIG. 3 is a perspective view showing configurations of a base and a semiconductor laser device according to the embodiment.
  • FIG. 7 is a cross-sectional view taken along the line A-A ′ shown in FIG. 6. It is a figure explaining operation
  • FIG. 3 is a perspective view showing a configuration of a spacer and a lens in the embodiment.
  • FIG. 13 is a sectional view taken along line B-B ′ shown in FIG. 12.
  • FIG. 8 is a diagram showing a configuration of a spacer and a polarization rotation element of a laser light source device according to Modification 1 of the embodiment.
  • FIG. 9 is a diagram showing a polarization element substrate including a polarization rotation element according to Modification 1 of the embodiment. It is a figure which shows the structure of the spacer and polarization rotation element of the laser light source device in the modification 2 of embodiment. It is a figure which shows the polarization element substrate containing the polarization rotation element in the modification 2 of embodiment.
  • FIG. 1 is a perspective view showing a configuration of a laser light source device 1 according to the embodiment and laser light emitted from the laser light source device 1.
  • FIG. 2 is an exploded perspective view showing the configuration of the laser light source device 1.
  • the laser light source device 1 is composed of a base 30, semiconductor laser elements 101 to 104, lenses 41 to 44, a spacer 20, and polarization rotation elements 51 to 54.
  • the base 30 supports the semiconductor laser elements 101 to 104 on the upper surface 30A.
  • the base 30 has a flat surface on the upper surface 30A, and the semiconductor laser elements 101 to 104 are fixed to the flat surface.
  • the base 30 is, for example, a flat plate.
  • the base 30 is provided with slots 31 to 34.
  • the slots 31 to 34 are here through holes.
  • the long holes 31 to 34 are holes into which the two lead pins 14 of each of the semiconductor laser devices 101 to 104 are inserted.
  • a current is supplied to each semiconductor laser element via the lead pin 14.
  • the x-, y-, and z-axes shown in each figure form a rectangular coordinate system.
  • the x-axis and the y-axis are parallel to the upper surface 30A of the base 30, and the z-axis points above the base 30.
  • Each of the semiconductor laser elements 101 to 104 is an element on which a semiconductor laser chip that oscillates one laser beam is mounted.
  • Each of the semiconductor laser devices 101 to 104 is individually held on the upper surface 30A of the base 30.
  • each semiconductor laser element is fixed to a plane formed on the upper surface 30A of the base 30.
  • Each semiconductor laser element emits laser light upward with respect to the base 30.
  • the semiconductor laser chip may be configured by dividing the oscillator into two or three parts in order to improve efficiency.
  • the semiconductor laser devices 101 to 104 emit laser beams 71 to 74 whose polarization directions are aligned in one direction.
  • the polarization of the laser beams 71 to 74 emitted from the semiconductor laser devices 101 to 104 is parallel to the y-axis direction (not shown).
  • the semiconductor laser elements 101 to 104 emit laser beams 71 to 74 having a cross-sectional shape with a wide width in the x-axis direction in parallel with the z-axis direction.
  • the spacer 20 is provided to cover the semiconductor laser elements 101 to 104 from above.
  • the spacer 20 holds the lenses 41 to 44, which will be described later, and has a function of keeping the distance between each lens and each semiconductor laser element constant.
  • the spacer 20 has spacer windows 21 to 24 on the upper surface.
  • the outer shapes of the spacer windows 21 to 24 have a square shape.
  • the spacer 20 has spacer step portions 25 to 28 provided on the outer peripheries of the spacer window portions 21 to 24, respectively.
  • a polarization rotation element can be installed at each spacer step. Laser beams 71 to 74 emitted from the semiconductor laser devices 101 to 104 respectively pass through the spacer windows 21 to 24. That is, the spacer includes a frame structure including the spacer window portions 21 to 24 and the spacer step portions 25 to 28 at positions where the plurality of laser beams 71 to 74 pass. Each frame structure holds each of the plurality of polarization rotation elements.
  • the spacer 20 may be fastened and fixed to the upper surface 30A of the base 30 with a screw, or may be fixed with an adhesive. Alternatively, the spacer 20 may be fixed by both.
  • the spacer 20 is manufactured by die casting of zinc, aluminum, or the like in consideration of formability. However, since the spacer 20 is not required to have a thermal effect, the spacer 20 may be made of a resin material.
  • the polarization rotation elements 51 to 54 form a polarization conversion unit.
  • the polarization converter rotates the polarization direction of at least a part of the laser lights 71 to 74, and disturbs the polarization directions of the laser lights 71 to 74 so that they are not aligned in one direction.
  • the polarization rotation elements 51 and 53 convert the polarization direction of a part of the laser light 71 to 73 out of the laser light 71 to 74 into left-handed circularly polarized light 91 and 93.
  • the polarization rotation elements 51 and 53 are selectively arranged corresponding to the semiconductor laser elements 101 and 103 that emit a part of the laser beams 71 and 73 among the semiconductor laser elements 101 to 104.
  • the polarization rotation elements 52 and 54 convert the polarization direction of another part of the laser light 72 to 74 out of the laser light 71 to 74 into circularly polarized light 92 and 94 of right rotation.
  • the polarization rotation elements 52 and 54 are selectively arranged corresponding to the other semiconductor laser elements 102 and 104 that emit the other part of the laser beams 72 and 74 of the semiconductor laser elements 101 to 104.
  • FIG. 3 is a diagram showing the configuration of the polarization rotation elements 51 and 53.
  • FIG. 4 is a diagram showing the configuration of the polarization rotation elements 52 and 54.
  • the polarization rotation elements 51 to 54 have a fast axis (F axis) 50A in a direction having a low refractive index and a slow axis (S axis) 50B in a direction having a high refractive index.
  • the polarization rotation elements 51 to 54 are plate-shaped elements having a plane parallel to the FS plane in which the fast axis (F axis) 50A and the slow axis (S axis) 50B are orthogonal to each other.
  • the polarization rotation elements 51 to 54 are quarter-wave plates. The quarter-wave plate delays those components in the slow axis direction by a quarter wavelength with respect to the components of the laser beams 71 to 74 in the fast axis direction.
  • the polarization rotation elements 51 and 53 are arranged such that the fast axis 50A forms an angle of ⁇ 45 ° and the slow axis 50B forms an angle of 45 ° with respect to the polarization directions of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103.
  • the polarization of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103 is linearly polarized light parallel to the y-axis. Therefore, the fast axis 50A forms an angle of ⁇ 45 ° with the y axis, and the slow axis 50B forms an angle of 45 ° with the y axis (see FIGS. 2 and 3).
  • the polarization rotation elements 52 and 54 make an angle of 45 ° with respect to the fast axis 50A and ⁇ 45 ° with respect to the slow axis 50B with respect to the polarization directions of the laser beams 72 and 74 emitted from the semiconductor laser elements 102 and 104.
  • the fast axis 50A forms an angle of 45 ° with the y-axis
  • the slow axis 50B forms an angle of ⁇ 45 ° with respect to the y-axis (see FIGS. 2 and 4).
  • the outer shapes of the polarization rotation elements 51 to 54 have square shapes similar to the outer shapes of the spacer step portions 25 to 28, as shown in FIG.
  • the square consists of sides parallel to the x-axis or the y-axis.
  • the fast axis 50A and the slow axis 50B of the polarization rotation elements 51 to 54 coincide with the diagonal direction of the square.
  • the polarization rotation elements 51 to 54 are held by the spacer step portions 25 to 28, respectively.
  • the polarization rotators 51 and 53 are selectively arranged corresponding to the semiconductor laser devices 101 and 103 by being housed in the spacer step portions 25 and 27.
  • the polarization rotation elements 52 and 54 are selectively arranged corresponding to the other semiconductor laser elements 102 and 104 by being housed in the spacer step portions 26 and 28.
  • the polarization rotation elements 51 to 54 are arranged on the upper surface side of the spacer 20, but the polarization rotation elements 51 to 54 may be arranged on the bottom surface side of the spacer 20. In that case, the polarization rotation element is fixed to, for example, a spacer step portion provided on the back surface of the spacer 20 with an adhesive or a holding member.
  • the shape of the polarization rotation element may be rectangular, circular, elliptical, or the like as long as it covers the laser beams 71 to 74 of the semiconductor laser elements 101 to 104.
  • the lenses 41 to 44 focus the laser beams 71 to 74.
  • the laser beams 71 to 74 transmitted through the lenses 41 to 44 respectively travel in a direction parallel to the z axis.
  • the lenses 41 to 44 are held by the spacer 20.
  • the lenses 41 to 44 are arranged so as to cover the spacer window portions 21 to 24, respectively.
  • FIG. 5 is a perspective view showing a detailed configuration of the semiconductor laser device 101.
  • the semiconductor laser device 101 has a structure in which a semiconductor laser chip is included in a TO-Can type package.
  • the TO-Can type semiconductor laser device 101 mainly includes a cap 11, a glass window 12, a stem 13, a lead pin 14, and a semiconductor laser chip (not shown).
  • the cap 11 is provided above the stem 13.
  • the glass window 12 is provided on the upper surface of the cap 11.
  • the lead pin 14 is provided below the stem 13.
  • the semiconductor laser chip is arranged inside the cap 11.
  • the semiconductor laser chip has a main optical axis in a direction perpendicular to the stem 13. That is, the semiconductor laser chip emits laser light 71 in the z-axis direction. Generally, when moisture or dust in the air adheres to the end surface of the semiconductor laser chip, the semiconductor laser chip is easily destroyed. However, in the TO-Can type package, the semiconductor laser chip is sealed by the cap 11. Therefore, the airtightness inside the cap 11 is maintained, and the conditions required for the driving environment of the semiconductor laser chip are relaxed. Further, the TO-Can type package element is small. Therefore, it is easy to adjust the number of pieces used, that is, to scale the optical output according to the required specifications.
  • a high-power edge-emitting laser chip is used as the light source of the projection display device.
  • the main material of the semiconductor laser chip is a compound semiconductor such as GaAs or GaN.
  • the active layer of the semiconductor laser chip is formed by epitaxial growth.
  • the epitaxial growth direction corresponds to the x-axis direction
  • the horizontal direction of the active layer corresponds to the y-axis direction.
  • the laser light 71 is emitted from the chip end face located in the direction (z-axis direction) orthogonal to the epitaxial growth direction (x-axis direction).
  • the laser light 71 is emitted from an emission bright point of about 1 ⁇ m in the vertical direction (x-axis direction) of the active layer and several tens to several hundreds of ⁇ m in the horizontal direction (y-axis direction) of the active layer on the end face of the chip. Since the emission port in the vertical direction (x-axis direction) of the active layer is very small, the laser light 71 spreads in the x-axis direction due to the diffraction effect. The spread of the laser beam in the x-axis direction is about 60 ° in all angles. The spread of laser light in the vertical direction (x-axis direction) of the active layer is about 10 times larger than the spread of laser light in the horizontal direction (y-axis direction) of the active layer. Therefore, the cross section of the laser light 71, that is, the far-field pattern has an elliptical shape, as shown in FIG.
  • the arrangement direction of the two lead pins 14 is the same as the horizontal direction (y-axis direction) of the active layer of the semiconductor laser chip. Therefore, the laser light 71 has a small spread in the arrangement direction of the lead pins 14 and a large spread in the x-axis direction orthogonal thereto.
  • the polarization of the laser light 71 emitted from the semiconductor laser device 101 having the above configuration is parallel to the direction horizontal to the active layer (y-axis direction). That is, the semiconductor laser device 101 emits linearly polarized light whose electric field oscillates in the horizontal direction (y-axis direction) of the active layer. However, the laser light may be polarized in the vertical direction (x-axis direction) of the active layer depending on the atomic arrangement of the active layer.
  • FIG. 6 is a perspective view showing the configurations of the base 30 and the semiconductor laser devices 101 to 104.
  • FIG. 7 is a cross-sectional view taken along the line A-A ′ shown in FIG.
  • the base 30 is composed of a member having high thermal conductivity.
  • the base 30 includes a metal material such as Cu and Al.
  • the base 30 includes a ceramic having a high thermal conductivity such as SiC or AlN.
  • a fin for improving the heat capacity and the heat radiation area of the stem 13 or a cooling member connected to a heat pipe in which a coolant such as water is sealed may be added to the stem 13.
  • each semiconductor laser element 101 to 104 are fixed in close contact with the flat surface formed on the upper surface 30A of the base 30 via a highly heat-conductive grease or sheet-shaped heat dissipation material.
  • each semiconductor laser element is preferably soldered to the base 30 with a solder material.
  • the solder material contains, for example, SuAgCu, AuSn or the like as a main component.
  • the base 30 is a flat plate, but the base 30 is not limited thereto, and the surface that contacts the stem 13 may be a flat surface.
  • the base 30 may be provided with a spot facing matching the shape of the stem 13.
  • the elongated holes 31 to 34 have a hole shape so that the lead pin 14 and the base 30 do not come into contact with each other, and are arranged so that the lead pin 14 and the base 30 do not come into contact with each other.
  • the base 30 may have a round hole that can avoid contact between the lead pin 14 and the base 30, instead of the elongated holes 31 to 34.
  • the base 30 has, instead of the elongated holes 31 to 34, a groove structure capable of avoiding the contact between the lead pin 14 and the base 30 and ensuring a wiring path for supplying a current to the semiconductor laser elements 101 to 104. May be.
  • the polarization rotation elements 51 to 54 are made of, for example, an inorganic material or a resin material having birefringence.
  • the inorganic material having birefringence is, for example, crystal.
  • the birefringent resin material is, for example, a resin containing polycarbonate as a base material and is stretched in one direction.
  • the polarization rotation elements 51 and 53 are quarter wave plates. As shown in FIG. 8, when the counterclockwise angle is in the positive direction, the fast axis (F axis) forms an angle of 45 ° with the y axis, and the slow axis (S axis) ⁇ with respect to the y axis. Make an angle of 45 °.
  • the propagation of the light beam in the slow axis (S-axis) direction is different from the propagation of the light beam in the fast axis (F-axis) direction. Be late.
  • the propagation delay in the slow axis direction relative to the fast axis direction is designed to be 1/4 wavelength. Only the electric field in the slow axis direction propagates with a delay of 1 ⁇ 4 wavelength, so that the polarization of the laser light transmitted through the polarization rotation elements 51 and 53 changes with the passage of time, as shown in FIG.
  • the polarization directions (electric field vibration directions) at times t0, t1, t2, and t3 are + F, ⁇ S, ⁇ F, and + S directions, respectively.
  • the laser light that has passed through the polarization rotation elements 51 and 53 travels in such a manner that the polarization direction thereof spirals counterclockwise. That is, the polarization rotation elements 51 and 53 convert the polarization direction of the laser light from the linearly polarized light 81 in the y-axis direction to the left-handed circularly polarized light 91 and 93.
  • the polarization rotation elements 52 and 54 are also quarter wave plates. As shown in FIG. 10, the fast axis (F axis) forms an angle of ⁇ 45 ° with the y axis, and the slow axis (S axis) forms an angle of 45 ° with the y axis.
  • F axis fast axis
  • S axis slow axis
  • the polarization directions (vibration directions of the electric field) at times t0, t1, t2, and t3 are + S, ⁇ F, ⁇ S, and + F directions, respectively.
  • the laser light transmitted through the polarization rotation elements 52 and 54 proceeds so that the polarization direction draws a spiral in a clockwise rotation. That is, the polarization rotation elements 52 and 54 convert the polarization direction of the laser light from the linearly polarized light 81 in the y-axis direction into the circularly polarized light 92 and 94 that is rotated clockwise.
  • FIG. 12 is a perspective view showing the configuration of the spacer 20 and the lenses 41 to 44.
  • FIG. 13 is a cross-sectional view taken along line B-B ′ shown in FIG.
  • the laser beams 71 to 74 emitted from the laser light source device 1 are focused on the opening of the optical system of the projection type display device (not shown). Since the distance from the laser light source device 1 to the optical system opening of the projection type display device is not limited, it is preferable that the laser lights 71 to 74 emitted from the laser light source device 1 are parallel lights.
  • each semiconductor laser element emits a spread laser beam.
  • each of the lenses 41 to 44 has a flat surface on the incident surface (a surface in the ⁇ z direction) and an axially symmetric spherical or aspherical convex surface on the output surface (a surface in the + z direction). That is, the lenses 41 to 44 are convex lenses.
  • the incident surfaces of the lenses 41 to 44 do not necessarily have to be flat.
  • Each lens may have a concave surface or a convex surface on the entrance surface or the exit surface as long as it has a function as a convex lens.
  • the surface that may come into contact with the upper surface of the spacer 20 is preferably a flat surface.
  • each lens does not need to be axisymmetric curved surfaces.
  • each lens may be a cylindrical lens having a cylindrical surface on the exit surface or the entrance surface.
  • the cylindrical lens converts the laser light emitted from the semiconductor laser element into parallel light only in the direction having a large divergence angle, that is, in the vertical direction (x-axis direction) with respect to the active layer.
  • the central axes 141 and 144 of the lenses 41 and 44 are arranged so as to coincide with the central axes of the light rays of the semiconductor laser elements 101 and 104, respectively.
  • the lenses 41 and 44 are preferably fixed to the upper surface of the spacer 20 with an adhesive. Note that the lenses 41 and 44 may be fixed to the upper surface of the spacer 20, and the lenses 41 and 44 may be fixed from above by a member that holds each lens down. Although not shown in FIG. 13, the lenses 42 and 43 are also fixed to the upper surface of the spacer 20 like the lenses 41 and 44.
  • the outer shapes of the spacer step portions 25 and 28 are similar to the outer shapes of the polarization rotation elements 51 and 54.
  • the outer shapes of the spacer step portions 25 and 28 are larger than the outer shapes of the polarization rotation elements 51 and 54.
  • the height of the spacer step portions 25 and 28 is larger than the thickness of the polarization rotation elements 51 and 54. Therefore, the polarization rotation elements 51 and 54 are arranged so as to be housed in the space formed by the spacer step portions 25 and 28 and the bottom surfaces of the lenses 41 and 44 without protruding upward from the upper surface of the spacer 20.
  • the outer shapes of the spacer step portions 26 and 27 are similar to the outer shapes of the spacer step portions 25 and 28.
  • the heat generated by driving the semiconductor laser elements 101 to 104 is radiated to the base 30. Since each semiconductor laser element is separated, heat generated in each semiconductor laser element is difficult to be transferred to the semiconductor laser element adjacent thereto. In this way, the laser light source device 1 suppresses the temperature rise of the semiconductor laser element.
  • the polarization directions of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103 are converted into left-handed circularly polarized light 91 and 93 by the polarization rotation elements 51 and 53.
  • the polarization directions of the laser beams 72 and 74 emitted from the semiconductor laser elements 102 and 104 are converted into right-handed circularly polarized light 92 and 94 by the polarization rotation elements 52 and 54.
  • the laser light source device 1 emits left-handed circularly polarized light 91, 93 of laser light 71, 73 and right-handed circularly polarized light of laser light 72, 74.
  • the polarization directions of the laser beams 71 to 74 change temporally.
  • the circularly polarized light 91, 93 has a different rotation direction of polarized light from the circularly polarized light 92, 94.
  • the laser beams 71 to 74 have the same cross-sectional shape (beam profile), but their polarization directions are not aligned in one direction.
  • the laser light source device 1 emits two types of laser light having different polarization directions by rotating the polarization directions of the plurality of laser lights by the polarization rotation elements 51 to 54. Such laser light reduces the generation of interference fringes and speckles.
  • the laser light source device 1 includes a base 30 and a plurality of laser lights each of which is individually held on the upper surface 30A of the base 30 and emits a plurality of laser lights whose polarization directions are aligned in one direction.
  • the polarization conversion unit includes a plurality of polarization rotation elements 51 to 54 that convert the polarization of a plurality of laser lights into circularly polarized light.
  • the plurality of polarization rotation elements 51 to 54 are selectively arranged in correspondence with the semiconductor laser elements 101 and 103 that emit a part of the laser light among the plurality of semiconductor laser elements 101 to 104, respectively, and A first polarization rotator (polarization rotator 51, 54) that converts polarized light into left-handed circularly polarized light, and another one that emits a part of the laser light 72, 74 of the plurality of semiconductor laser elements 101 to 104.
  • a second polarization rotation element (polarization rotation element 52, 54) which is selectively arranged corresponding to the semiconductor laser elements 102, 104 and converts the polarization of another part of the laser light 72, 74 into right-handed circularly polarized light. And, including.
  • the above laser light source device 1 is composed of a plurality of semiconductor laser elements 101 to 104 provided individually on the base 30 having good thermal conductivity. Therefore, the temperature rise due to laser oscillation is reduced, and the gain reduction is suppressed.
  • the laser light source device 1 is unlikely to receive heat generated by the lasers in the central portion from the lasers on both sides, and the gain is unlikely to be greatly reduced. Therefore, a sufficient output can be obtained.
  • the laser light source device 1 also emits two types of circularly polarized laser light whose polarization directions change with time. Since these two types of circularly polarized light are composed of left-handed circularly polarized light 91 and 93 and right-handed circularly polarized light 92 and 94 which proceed while rotating leftward, the two types of polarization directions are continuously matched. There is no such thing.
  • the laser light source device 1 reduces the generation of interference fringes and speckles due to the synthesis of laser light.
  • the projection type display device equipped with the laser light source device 1 does not require a light diffusing element having a high degree of scattering.
  • the laser light source device 1 is mounted on a projection type display device, the generation of interference fringes and speckles is suppressed, so that the image quality is improved and the light output efficiency of the projection type display device itself is also improved.
  • the laser light source device 1 includes a plurality of lenses 41 to 44 provided corresponding to the plurality of semiconductor laser elements 101 to 104, respectively, for converting each of the plurality of laser lights into parallel light. Including further.
  • the spacer 20 is fixed to the base 30 and holds the plurality of lenses 41 to 44.
  • the laser light source device 1 can emit laser beams 71 to 74 with high output and high parallelism.
  • the laser light source device according to the first modification of the embodiment is different from the laser light source device 1 according to the above-described embodiments in the configuration of the spacer and the polarization rotation element.
  • FIG. 14 is a diagram showing a configuration of the spacer 120 and the polarization rotation elements 151 to 154 of the laser light source device according to the first modification of the embodiment.
  • the outer shape of the polarization rotation elements 151 to 154 has a parallelogram shape.
  • the outer shape of the spacer step portions 125 to 128 of the spacer 120 has a parallelogram, which is a similar shape slightly larger than the outer shapes of the polarization rotation elements 151 to 154.
  • the outer shapes of the spacer step portions 126 and 128 have a parallelogram shape in which the outer shapes of the spacer step portions 125 and 127 are rotated by 90 ° in the xy plane.
  • FIG. 15 is a diagram showing a polarization element substrate including polarization rotation elements 151 to 154.
  • the fast axis 50A forms an angle of 45 ° with the y axis
  • the slow axis 50B forms an angle of ⁇ 45 ° with the y axis.
  • the polarization rotation elements 151 to 154 are cut out at a slight angle ⁇ with respect to the x-axis direction.
  • the outer shape of the polarization rotation elements 151 to 154 has a parallelogram shape having one side parallel to the y-axis and the other side having an angle ⁇ with the x-axis. That is, the fast axis 50A of the polarization rotation elements 151 to 154 forms an angle of 45 ° with one side and an angle of 45 ° - ⁇ with respect to the other side intersecting the one side when cut out from the polarization element substrate. .
  • the polarization rotation elements 151 and 153 are arranged on the spacer step portions 125 and 127 while maintaining the directions of the fast axis 50A and the slow axis 50B.
  • the polarization rotation elements 152 and 154 cut out from the polarization element substrate are rotated by 90 ° in the xy plane and arranged on the spacer step portions 126 and 128. Therefore, the fast axis 50A of the polarization rotators 152 and 154 makes an angle of 90 ° with the fast axis 50A of the polarization rotators 151 and 153.
  • the polarization rotation elements 151 and 153 function as left rotation polarization rotation elements
  • the polarization rotation elements 152 and 154 function as right rotation polarization rotation elements.
  • the outer shapes of the spacer step portions 125 to 128 have parallelograms that are similar shapes and are slightly larger than the outer shapes of the polarization rotation elements 151 to 154. Therefore, the polarization rotation elements 151 to 154 are arranged in the spacer step portions 125 to 128 corresponding to the respective shapes, that is, at predetermined positions. The polarization rotation element whose front and back are reversed does not fit into the spacer step portions 125 to 128. Such a spacer 120 limits the arrangement direction of the polarization rotation elements 151 to 154 in the assembly process of the laser light source device and the like.
  • the laser light source device having such a configuration has the same effect as that of the above embodiment. Further, since the shapes of the polarization rotation elements 151 to 154 and the shapes of the spacer step portions 125 to 128 correspond to each other, the arrangement direction of the polarization rotation elements is limited. As a result, in the assembling process of the laser light source device, the assembling direction of the polarization rotation element is designated, and the assembling workability is improved.
  • the laser light source device according to the second modification of the embodiment is different from those of the laser light source device 1 according to the above-described embodiment in the configurations of the spacer and the polarization rotation element.
  • FIG. 16 is a diagram showing a configuration of the spacer 220 and the polarization rotation elements 251 to 254 of the laser light source device according to the second modification of the embodiment.
  • the outer shape of the polarization rotation elements 251 to 254 has a parallelogram shape.
  • the outer shape of the spacer step portions 225 to 228 of the spacer 220 has a parallelogram which is a slightly larger shape than the outer shapes of the polarization rotation elements 251 to 254.
  • the outer shapes of the spacer step portions 226 and 228 have a parallelogram shape in which the outer shapes of the spacer step portions 225 and 227 are inverted with respect to the y axis.
  • FIG. 17 is a diagram showing a polarization element substrate including polarization rotation elements 251 to 254.
  • the fast axis 50A forms an angle of 45 ° with the y axis
  • the slow axis 50B forms an angle of ⁇ 45 ° with the y axis.
  • the polarization rotation elements 251 to 254 are cut out at a slight angle ⁇ with respect to the x-axis direction.
  • the polarization rotating elements 251 to 254 have a parallelogram shape having one side parallel to the y-axis and the other side having an angle ⁇ with the x-axis.
  • the fast axis 50A of the polarization rotation elements 251 to 254 forms an angle of 45 ° with one side and an angle of 45 ° - ⁇ with respect to the other side intersecting the one side when cut out from the polarization element substrate. .
  • the polarization rotation elements 251, 253 are arranged in the spacer step portions 225, 227 while maintaining the directions of the fast axis 50A and the slow axis 50B.
  • the polarization rotation elements 252 and 254 cut out from the polarization element substrate are arranged on the spacer step portions 226 and 228 with their front and back inverted with respect to the x axis or the y axis. Therefore, the fast axes 50A of the polarization rotators 252 and 254 make an angle of 90 ° with the fast axes 50A of the polarization rotators 251 and 253.
  • the polarization rotators 251, 253 function as polarization rotators that convert to left-handed circularly polarized light
  • the polarization rotators 252 and 254 function as right-handed circularly polarized lights.
  • the outer shapes of the spacer step portions 225 to 228 have parallelograms, which are similar shapes and are slightly larger than the outer shapes of the polarization rotation elements 251 to 254. Therefore, the polarization rotation elements 251 to 254 are arranged at the spacer step portions 225 to 228 corresponding to the respective shapes, that is, at predetermined positions.
  • Such a spacer 220 is provided in the assembly process of the laser light source device, etc., where the polarization rotators 251 and 253 for converting it to left-handed circularly polarized light and the polarization rotators 252 and 254 for right-handed circularly polarized light are arranged. Places are limited.
  • the laser light source device having such a configuration has the same effect as that of the above embodiment. Further, since the shapes of the polarization rotation elements 251 to 254 and the shapes of the spacer step portions 225 to 228 correspond to each other, the location where the polarization rotation elements are arranged is limited. As a result, in the assembly process of the laser light source device, the polarization rotation elements 251, 253 for converting the left-handed circularly polarized light and the polarization rotation elements 252, 254 for converting the right-handed circularly polarized light are mistaken at designated positions. It can be installed without the need for assembly workability.
  • the outer shapes of the polarization rotation elements 251 to 254 are determined according to the cross-sectional shapes (beam profiles) of the laser beams 71 to 74.
  • the outer shapes of the polarization rotation elements 251 to 254 have a parallelogram shape that is long in one direction.
  • Each polarization rotation element is arranged so that the length of the parallelogram matches the x-axis direction in which the divergence angle of each laser beam is large. That is, each polarization rotation element is selectively arranged according to the cross-sectional shape of each laser beam.
  • the number of polarization rotation elements that can be cut out from the polarization element substrate increases. As a result, cost reduction of the polarization rotation element and the laser light source device is realized.
  • the laser light source device further includes the spacer 20 provided above the plurality of semiconductor laser elements 101 to 104.
  • the spacer 20 includes a frame structure at a position where each of the plurality of laser beams passes.
  • Each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254) is held in a frame structure.
  • the outer shape of each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254) has a parallelogram shape.
  • the outer shape of the frame structure of the spacer 20 has a similar shape larger than the outer shape of each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254).
  • the polarization rotation elements 151 and 153 (or 251 and 253) that convert to left-handed circularly polarized light and the polarization rotation elements 152 and 154 (or 252 and 254) that convert to right-handed circularly polarized light.
  • the placement direction or location is limited. As a result, the workability of assembling the laser light source device is improved.
  • the first polarization rotating element (polarization rotating elements 251, 253) or the second polarization rotating element (polarization rotating elements 252, 254) is each of a plurality of laser beams. Are selectively arranged according to the cross-sectional shape of.
  • the yield of the polarization rotation element that can be taken from the polarization element substrate is increased, and the cost reduction of the polarization rotation element and the laser light source device can be realized.
  • a laser light source device in which two semiconductor laser elements are arranged in the x-axis direction and two (2 ⁇ 2) semiconductor laser elements in the y-axis direction is shown as an example.
  • the laser light source device may include a plurality of semiconductor laser elements whose mounting numbers are increased in the x-axis direction and the y-axis direction. With such a configuration, a high-power laser light source device can be realized.
  • the array of semiconductor laser elements may be a two-dimensional array such as 2 ⁇ 4 or 4 ⁇ 4 or a one-dimensional array such as 1 ⁇ 4.
  • the laser light source device can further reduce the occurrence of interference and speckle.
  • the semiconductor laser elements 101 and 102 oscillate a red laser with a wavelength of 638 nm
  • the semiconductor laser elements 103 and 104 oscillate a red laser with a wavelength of 642 nm
  • the laser light source device is only required for the above polarization direction. Instead, it is possible to emit four types of laser light having different characteristics with respect to wavelength.
  • the present invention can appropriately modify or omit the embodiments within the scope of the invention.
  • 1 laser light source device 101-104 semiconductor laser device, 20 spacer, 25-28 spacer stepped portion, 30 base, 30A upper surface, 41-44 lens, 50A fast axis, 50B slow axis, 51-54 polarization rotation element, 151- 154 polarization rotator, 251-254 polarization rotator, 71-74 laser light, 81 linear polarization, 91-94 circular polarization.

Abstract

The purpose of the present invention is to provide a laser light source that reduces the occurrence of interference fringes and speckles, and reduces temperature increases due to laser oscillations. The laser light source device comprises: a base; a plurality of semiconductor laser elements that emit a plurality of laser beams having polarization directions that are aligned in one direction, each semiconductor laser element being held by the base; and a polarization converter that provides disturbance so that the polarization directions of the plurality of laser beams are not aligned in one direction. The polarization converter comprises: first polarization rotators that are selectively arranged to correspond to semiconductor laser elements that emit a portion of laser light, and convert the polarized light of the portion of laser light to circularly polarized light having a left rotation; and second polarization rotators that are selectively arranged to correspond to the other semiconductor laser elements that emit another portion of laser light, and convert the other portion of laser light to circularly polarized light having a right rotation.

Description

レーザ光源装置Laser light source device
　本発明は、レーザ光源装置に関する。 The present invention relates to a laser light source device.
　半導体レーザ素子は、消費電力が小さく、また、単色性および高指向性に優れたレーザ光を出射する。このような特長を有する半導体レーザ素子は、現在普及しているランプの置き換え光源として期待されている。例えば、近年、半導体レーザ素子は、プロジェクタ等の投射型表示装置の光源として注目されている。半導体レーザ素子が投射型表示装置に光源として搭載される場合、半導体レーザ素子は発光面積が小さいことから、その光学設計において、レーザ光の空間合成に必要な光学素子の小型化を可能とする。さらに、光学素子の小型化は、デジタルミラーデバイス（ＤＭＤ（Digital Mirror Device））、液晶ディスプレイ（ＬＣＤ（Liquid Crystal Display））などの表示デバイス自体の小型化を可能とし、その結果、システムコストが低下する。 The semiconductor laser element emits laser light with low power consumption and excellent monochromaticity and high directivity. A semiconductor laser device having such features is expected as a replacement light source for currently popular lamps. For example, in recent years, a semiconductor laser device has been attracting attention as a light source of a projection type display device such as a projector. When the semiconductor laser element is mounted as a light source in a projection type display device, the semiconductor laser element has a small light emitting area, and therefore, in the optical design thereof, it is possible to miniaturize the optical element necessary for spatial composition of laser beams. Furthermore, miniaturization of optical elements enables miniaturization of display devices such as digital mirror devices (DMD (Digital Mirror Device)) and liquid crystal displays (LCD (Liquid Crystal Display)), resulting in lower system cost. To do.
　現状の半導体レーザ素子では、１つの素子で投射型表示装置に求められる出力を達成することは困難である。そのため、一般的には、投射型表示装置の光源は、複数の半導体レーザ素子によって構成される。 With the current semiconductor laser device, it is difficult to achieve the output required for a projection display device with a single device. Therefore, in general, the light source of the projection display device is composed of a plurality of semiconductor laser elements.
　半導体レーザ素子から出射されるレーザ光は、位相が揃った波により構成されている。この特徴により、半導体レーザの単色性、高指向性が生み出される。一方で、複数の波が重なり合った場合、互いの波の干渉性により縞模様あるいはスペックルが発生する。スペックルとは、スクリーン上に照射されたレーザ光によって現れるランダムな波の干渉性による粒子状のパターンのことである。このような干渉パターンは、投射型表示装置の光源としてレーザを使用する際に、映像の品位が低下する一因となっていた。 The laser light emitted from the semiconductor laser device is composed of waves with the same phase. This feature produces the monochromaticity and high directivity of the semiconductor laser. On the other hand, when a plurality of waves overlap each other, a striped pattern or speckles are generated due to the coherence of the waves. Speckle is a particle-like pattern due to the coherence of random waves appearing by the laser light irradiated on the screen. Such an interference pattern has been one of the causes of deterioration of image quality when a laser is used as a light source of a projection display device.
　干渉縞やスペックルの軽減手段として、複数の波長の半導体レーザ光を混合する手段、あるいは、半導体レーザ光の偏光の均一性を乱す手段が有効である。 As a means for reducing interference fringes and speckles, a means for mixing semiconductor laser light of multiple wavelengths or a means for disturbing the polarization uniformity of the semiconductor laser light is effective.
　例えば、特許文献１には、レーザ光源が有する１個もしくは複数個の発光点から出射されるレーザ光の偏光を、その光軸上に配置された偏光回転部によって、９０°回転させるレーザ光源装置が提案されている。そのレーザ光源装置は、１つの半導体レーザチップから複数のレーザ光が発振するアレイ型レーザ光源である。 For example, in Patent Document 1, a laser light source device that rotates the polarization of laser light emitted from one or a plurality of light emitting points of a laser light source by 90 ° by a polarization rotation unit arranged on the optical axis thereof. Is proposed. The laser light source device is an array type laser light source in which a plurality of laser beams oscillates from one semiconductor laser chip.
特開２０１１－２４２５７３号公報JP, 2011-242573, A
　上記のように、レーザ光は、その可干渉性による干渉縞やスペックルが発生しやすい。特許文献１のレーザ光源装置は、干渉縞やスペックルを軽減することができるものの、アレイ型レーザ光源であるため、隣接するレーザから発生する熱による温度上昇によって、利得が低減し、十分な出力が得られない。 As mentioned above, laser light is likely to cause interference fringes and speckles due to its coherence. Although the laser light source device of Patent Document 1 can reduce interference fringes and speckles, since it is an array type laser light source, the gain is reduced due to the temperature rise due to heat generated from an adjacent laser, and a sufficient output is obtained. Can't get
　本発明は、上記の課題を解決するためになされたものであり、干渉縞およびスペックルの発生を低減し、かつ、レーザ発振による温度上昇を低減することができるレーザ光源装置の提供を目的とする。 The present invention has been made to solve the above problems, and an object of the present invention is to provide a laser light source device capable of reducing the occurrence of interference fringes and speckles and reducing the temperature rise due to laser oscillation. To do.
　本発明に係るレーザ光源装置は、ベースと、各々が個別にベースの上面に保持され、偏光方向が一方向に揃った複数のレーザ光を出射する複数の半導体レーザ素子と、複数のレーザ光のうち少なくとも一部のレーザ光の偏光方向を回転させることにより、複数のレーザ光の偏光方向が一方向に揃わないように乱す偏光変換部と、を含む。偏光変換部は、複数のレーザ光の偏光を円偏光に変換する複数の偏光回転素子を含む。複数の偏光回転素子は、複数の半導体レーザ素子のうち一部のレーザ光を出射する半導体レーザ素子に対応して選択的に配置され、一部のレーザ光の偏光を左回転の円偏光に変換する第１偏光回転素子と、複数の半導体レーザ素子のうち別の一部のレーザ光を出射する別の半導体レーザ素子に対応して選択的に配置され、別の一部のレーザ光の偏光を右回転の円偏光に変換する第２偏光回転素子と、を含む。 The laser light source device according to the present invention includes a base, a plurality of semiconductor laser elements each of which is individually held on the upper surface of the base and emits a plurality of laser lights whose polarization directions are aligned in one direction. A polarization conversion unit that rotates the polarization direction of at least a part of the laser light to disturb the polarization directions of the plurality of laser lights so that they are not aligned in one direction. The polarization conversion unit includes a plurality of polarization rotation elements that convert the polarization of the plurality of laser lights into circularly polarized light. The plurality of polarization rotation elements are selectively arranged in correspondence with the semiconductor laser element that emits a part of the laser light among the plurality of semiconductor laser elements, and convert the polarization of a part of the laser light into left-handed circularly polarized light. The first polarization rotation element and the other semiconductor laser element which emits another part of the laser light among the plurality of semiconductor laser elements are selectively arranged to correspond to the polarization of another part of the laser light. A second polarization rotation element that converts the light into right-handed circularly polarized light.
　本発明によれば、干渉縞およびスペックルの発生を低減し、かつ、レーザ発振による温度上昇を低減するレーザ光源装置の提供が可能である。 According to the present invention, it is possible to provide a laser light source device that reduces the occurrence of interference fringes and speckles, and reduces the temperature rise due to laser oscillation.
　本発明の目的、特徴、局面、および利点は、以下の詳細な説明と添付図面とによって、より明白になる。 The objects, features, aspects, and advantages of the present invention will become more apparent by the following detailed description and the accompanying drawings.
実施の形態におけるレーザ光源装置の構成およびレーザ光源装置から出射されるレーザ光を示す斜視図である。FIG. 3 is a perspective view showing a configuration of a laser light source device and laser light emitted from the laser light source device according to the embodiment. 実施の形態におけるレーザ光源装置の構成を示す分解斜視図である。It is an exploded perspective view showing the composition of the laser light source device in an embodiment. 実施の形態における偏光回転素子の構成を示す図である。It is a figure which shows the structure of the polarization rotation element in embodiment. 実施の形態における偏光回転素子の構成を示す図である。It is a figure which shows the structure of the polarization rotation element in embodiment. 実施の形態における半導体レーザ素子の詳細な構成を示す斜視図である。FIG. 3 is a perspective view showing a detailed configuration of the semiconductor laser device according to the embodiment. 実施の形態におけるベースおよび半導体レーザ素子の構成を示す斜視図である。FIG. 3 is a perspective view showing configurations of a base and a semiconductor laser device according to the embodiment. 図６に示されたＡ－Ａ’における断面図である。FIG. 7 is a cross-sectional view taken along the line A-A ′ shown in FIG. 6. 実施の形態における偏光回転素子の動作を説明する図である。It is a figure explaining operation | movement of the polarization rotation element in embodiment. 実施の形態における偏光回転素子の動作を説明する図である。It is a figure explaining operation | movement of the polarization rotation element in embodiment. 実施の形態における偏光回転素子の動作を説明する図である。It is a figure explaining operation | movement of the polarization rotation element in embodiment. 実施の形態における偏光回転素子の動作を説明する図である。It is a figure explaining operation | movement of the polarization rotation element in embodiment. 実施の形態におけるスペーサおよびレンズの構成を示す斜視図である。FIG. 3 is a perspective view showing a configuration of a spacer and a lens in the embodiment. 図１２に示されたＢ－Ｂ’における断面図である。FIG. 13 is a sectional view taken along line B-B ′ shown in FIG. 12. 実施の形態の変形例１におけるレーザ光源装置のスペーサおよび偏光回転素子の構成を示す図である。FIG. 8 is a diagram showing a configuration of a spacer and a polarization rotation element of a laser light source device according to Modification 1 of the embodiment. 実施の形態の変形例１における偏光回転素子を含む偏光素子基板を示す図である。FIG. 9 is a diagram showing a polarization element substrate including a polarization rotation element according to Modification 1 of the embodiment. 実施の形態の変形例２におけるレーザ光源装置のスペーサおよび偏光回転素子の構成を示す図である。It is a figure which shows the structure of the spacer and polarization rotation element of the laser light source device in the modification 2 of embodiment. 実施の形態の変形例２における偏光回転素子を含む偏光素子基板を示す図である。It is a figure which shows the polarization element substrate containing the polarization rotation element in the modification 2 of embodiment.
　実施の形態におけるレーザ光源装置を説明する。図１は、実施の形態におけるレーザ光源装置１の構成およびレーザ光源装置１から出射されるレーザ光を示す斜視図である。図２は、レーザ光源装置１の構成を示す分解斜視図である。 A laser light source device according to the embodiment will be described. FIG. 1 is a perspective view showing a configuration of a laser light source device 1 according to the embodiment and laser light emitted from the laser light source device 1. FIG. 2 is an exploded perspective view showing the configuration of the laser light source device 1.
　レーザ光源装置１は、ベース３０、半導体レーザ素子１０１から１０４、レンズ４１から４４、スペーサ２０、偏光回転素子５１から５４により構成されている。 The laser light source device 1 is composed of a base 30, semiconductor laser elements 101 to 104, lenses 41 to 44, a spacer 20, and polarization rotation elements 51 to 54.
　ベース３０は、上面３０Ａにて半導体レーザ素子１０１から１０４を支持する。本実施の形態において、ベース３０は、上面３０Ａに平面を有し、その平面に半導体レーザ素子１０１から１０４が固定されている。ベース３０は、例えば、平板である。 The base 30 supports the semiconductor laser elements 101 to 104 on the upper surface 30A. In the present embodiment, the base 30 has a flat surface on the upper surface 30A, and the semiconductor laser elements 101 to 104 are fixed to the flat surface. The base 30 is, for example, a flat plate.
　ベース３０には、長穴３１から３４が設けられている。長穴３１から３４は、ここでは、貫通穴である。長穴３１から３４は、半導体レーザ素子１０１から１０４の各々が有する２本のリードピン１４が差し込まれる穴である。各半導体レーザ素子には、リードピン１４を介して電流が供給される。なお、各図に記載されたｘ、ｙ、ｚ軸は直交座標系を構成している。ｘ軸とｙ軸とはベース３０の上面３０Ａと平行であり、ｚ軸はベース３０の上方を指している。 The base 30 is provided with slots 31 to 34. The slots 31 to 34 are here through holes. The long holes 31 to 34 are holes into which the two lead pins 14 of each of the semiconductor laser devices 101 to 104 are inserted. A current is supplied to each semiconductor laser element via the lead pin 14. The x-, y-, and z-axes shown in each figure form a rectangular coordinate system. The x-axis and the y-axis are parallel to the upper surface 30A of the base 30, and the z-axis points above the base 30.
　半導体レーザ素子１０１から１０４は、各々が１つのレーザ光を発振する半導体レーザチップが搭載された素子である。半導体レーザ素子１０１から１０４の各々は、個別に、ベース３０の上面３０Ａに保持される。ここでは、各半導体レーザ素子は、ベース３０の上面３０Ａに形成された平面に固定されている。各半導体レーザ素子は、ベース３０に対し、上方にレーザ光を出射する。なお、半導体レーザチップは、効率を改善するため、発振部を２から３分割して構成される場合がある。 Each of the semiconductor laser elements 101 to 104 is an element on which a semiconductor laser chip that oscillates one laser beam is mounted. Each of the semiconductor laser devices 101 to 104 is individually held on the upper surface 30A of the base 30. Here, each semiconductor laser element is fixed to a plane formed on the upper surface 30A of the base 30. Each semiconductor laser element emits laser light upward with respect to the base 30. The semiconductor laser chip may be configured by dividing the oscillator into two or three parts in order to improve efficiency.
　半導体レーザ素子１０１から１０４は、各々の偏光方向が一方向に揃ったレーザ光７１から７４を出射する。本実施の形態において、半導体レーザ素子１０１から１０４から出射されるレーザ光７１から７４の偏光は、ｙ軸方向に平行である（図示せず）。また、半導体レーザ素子１０１から１０４は、ｘ軸方向に幅の広い断面形状を有するレーザ光７１から７４を、ｚ軸方向と平行に出射する。 The semiconductor laser devices 101 to 104 emit laser beams 71 to 74 whose polarization directions are aligned in one direction. In the present embodiment, the polarization of the laser beams 71 to 74 emitted from the semiconductor laser devices 101 to 104 is parallel to the y-axis direction (not shown). Further, the semiconductor laser elements 101 to 104 emit laser beams 71 to 74 having a cross-sectional shape with a wide width in the x-axis direction in parallel with the z-axis direction.
　スペーサ２０は、半導体レーザ素子１０１から１０４の上方を覆って設けられる。スペーサ２０は、後述するレンズ４１から４４を保持し、各レンズと各半導体レーザ素子との間隔を一定に保つ機能を有する。 The spacer 20 is provided to cover the semiconductor laser elements 101 to 104 from above. The spacer 20 holds the lenses 41 to 44, which will be described later, and has a function of keeping the distance between each lens and each semiconductor laser element constant.
　スペーサ２０は、上面に、スペーサ窓部２１から２４を有する。本実施の形態において、スペーサ窓部２１から２４の外形は、正方形を有する。また、スペーサ２０は、スペーサ窓部２１から２４のそれぞれの外周に設けられたスペーサ段差部２５から２８を有する。各スペーサ段差部には、偏光回転素子が設置可能である。半導体レーザ素子１０１から１０４から出射されるレーザ光７１から７４は、それぞれスペーサ窓部２１から２４を通過する。すなわち、スペーサは、複数のレーザ光７１から７４が通過する位置に、スペーサ窓部２１から２４、および、スペーサ段差部２５から２８からなる枠構造を含む。各枠構造は、複数の偏光回転素子の各々を保持する。 The spacer 20 has spacer windows 21 to 24 on the upper surface. In the present embodiment, the outer shapes of the spacer windows 21 to 24 have a square shape. Further, the spacer 20 has spacer step portions 25 to 28 provided on the outer peripheries of the spacer window portions 21 to 24, respectively. A polarization rotation element can be installed at each spacer step. Laser beams 71 to 74 emitted from the semiconductor laser devices 101 to 104 respectively pass through the spacer windows 21 to 24. That is, the spacer includes a frame structure including the spacer window portions 21 to 24 and the spacer step portions 25 to 28 at positions where the plurality of laser beams 71 to 74 pass. Each frame structure holds each of the plurality of polarization rotation elements.
　スペーサ２０は、ベース３０の上面３０Ａに、ねじによって締結固定されてもよいし、接着剤によって固定されてもよい。あるいは、スペーサ２０は、その両方によって固定されていてもよい。スペーサ２０は、例えば、成形性を考慮して亜鉛やアルミ等のダイキャストで製造される。ただし、スペーサ２０に熱的な効果は求められないため、スペーサ２０は、樹脂材料で製造されてもよい。 The spacer 20 may be fastened and fixed to the upper surface 30A of the base 30 with a screw, or may be fixed with an adhesive. Alternatively, the spacer 20 may be fixed by both. The spacer 20 is manufactured by die casting of zinc, aluminum, or the like in consideration of formability. However, since the spacer 20 is not required to have a thermal effect, the spacer 20 may be made of a resin material.
　偏光回転素子５１から５４は、偏光変換部を構成する。偏光変換部は、レーザ光７１から７４のうち少なくとも一部のレーザ光の偏光方向を回転させ、レーザ光７１から７４の偏光方向が一方向に揃わないように乱す。 The polarization rotation elements 51 to 54 form a polarization conversion unit. The polarization converter rotates the polarization direction of at least a part of the laser lights 71 to 74, and disturbs the polarization directions of the laser lights 71 to 74 so that they are not aligned in one direction.
　偏光回転素子５１、５３は、レーザ光７１から７４のうち一部のレーザ光７１、７３の偏光方向を左回転の円偏光９１、９３に変換する。偏光回転素子５１、５３は、半導体レーザ素子１０１から１０４のうち、その一部のレーザ光７１、７３を出射する半導体レーザ素子１０１、１０３に対応して選択的に配置される。 The polarization rotation elements 51 and 53 convert the polarization direction of a part of the laser light 71 to 73 out of the laser light 71 to 74 into left-handed circularly polarized light 91 and 93. The polarization rotation elements 51 and 53 are selectively arranged corresponding to the semiconductor laser elements 101 and 103 that emit a part of the laser beams 71 and 73 among the semiconductor laser elements 101 to 104.
　また、偏光回転素子５２、５４は、レーザ光７１から７４のうち別の一部のレーザ光７２、７４の偏光方向を右回転の円偏光９２、９４に変換する。偏光回転素子５２、５４は、半導体レーザ素子１０１から１０４のうち、その別の一部のレーザ光７２、７４を出射する別の半導体レーザ素子１０２、１０４に対応して選択的に配置される。 Further, the polarization rotation elements 52 and 54 convert the polarization direction of another part of the laser light 72 to 74 out of the laser light 71 to 74 into circularly polarized light 92 and 94 of right rotation. The polarization rotation elements 52 and 54 are selectively arranged corresponding to the other semiconductor laser elements 102 and 104 that emit the other part of the laser beams 72 and 74 of the semiconductor laser elements 101 to 104.
　図３は、偏光回転素子５１、５３の構成を示す図である。図４は、偏光回転素子５２、５４の構成を示す図である。偏光回転素子５１から５４は、屈折率が低い方位に速軸（Ｆ軸）５０Ａを、屈折率が高い方位に遅軸（Ｓ軸）５０Ｂを有する。偏光回転素子５１から５４は、速軸（Ｆ軸）５０Ａと遅軸（Ｓ軸）５０Ｂとが直交したＦＳ面に対し平行な平面を有する板状の素子である。ここでは、偏光回転素子５１から５４は、１／４波長板である。１／４波長板は、速軸方向におけるレーザ光７１から７４の成分に対して、遅軸方向におけるそれらの成分を、１／４波長分遅延させる。 FIG. 3 is a diagram showing the configuration of the polarization rotation elements 51 and 53. FIG. 4 is a diagram showing the configuration of the polarization rotation elements 52 and 54. The polarization rotation elements 51 to 54 have a fast axis (F axis) 50A in a direction having a low refractive index and a slow axis (S axis) 50B in a direction having a high refractive index. The polarization rotation elements 51 to 54 are plate-shaped elements having a plane parallel to the FS plane in which the fast axis (F axis) 50A and the slow axis (S axis) 50B are orthogonal to each other. Here, the polarization rotation elements 51 to 54 are quarter-wave plates. The quarter-wave plate delays those components in the slow axis direction by a quarter wavelength with respect to the components of the laser beams 71 to 74 in the fast axis direction.
　偏光回転素子５１、５３は、半導体レーザ素子１０１、１０３から出射されるレーザ光７１、７３の偏光方向に対し、速軸５０Ａが－４５°、遅軸５０Ｂが４５°の角度をなすように配置される。半導体レーザ素子１０１、１０３から出射されるレーザ光７１、７３の偏光は、ｙ軸に平行な直線偏光である。そのため、速軸５０Ａはｙ軸に対し－４５°の角度をなし、遅軸５０Ｂはｙ軸に対し４５°の角度をなす（図２および図３参照）。 The polarization rotation elements 51 and 53 are arranged such that the fast axis 50A forms an angle of −45 ° and the slow axis 50B forms an angle of 45 ° with respect to the polarization directions of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103. To be done. The polarization of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103 is linearly polarized light parallel to the y-axis. Therefore, the fast axis 50A forms an angle of −45 ° with the y axis, and the slow axis 50B forms an angle of 45 ° with the y axis (see FIGS. 2 and 3).
　一方で、偏光回転素子５２、５４は、半導体レーザ素子１０２、１０４から出射されるレーザ光７２、７４の偏光方向に対し、速軸５０Ａが４５°、遅軸５０Ｂが－４５°の角度をなすように配置される。そのため、速軸５０Ａはｙ軸に対し４５°の角度をなし、遅軸５０Ｂはｙ軸に対し－４５°の角度をなす（図２および図４参照）。 On the other hand, the polarization rotation elements 52 and 54 make an angle of 45 ° with respect to the fast axis 50A and −45 ° with respect to the slow axis 50B with respect to the polarization directions of the laser beams 72 and 74 emitted from the semiconductor laser elements 102 and 104. Is arranged as. Therefore, the fast axis 50A forms an angle of 45 ° with the y-axis, and the slow axis 50B forms an angle of −45 ° with respect to the y-axis (see FIGS. 2 and 4).
　偏光回転素子５１から５４の外形は、図２に示されるように、スペーサ段差部２５から２８の外形と相似関係にある正方形を有する。その正方形は、ｘ軸またはｙ軸に平行な辺からなる。偏光回転素子５１から５４の速軸５０Ａおよび遅軸５０Ｂは、その正方形の対角方向に一致する。偏光回転素子５１から５４は、それぞれスペーサ段差部２５から２８に保持される。偏光回転素子５１、５３は、スペーサ段差部２５、２７に収納されることにより、半導体レーザ素子１０１、１０３に対応して選択的に配置される。また、偏光回転素子５２、５４は、スペーサ段差部２６、２８に収納されることにより、別の半導体レーザ素子１０２、１０４に対応して選択的に配置される。 The outer shapes of the polarization rotation elements 51 to 54 have square shapes similar to the outer shapes of the spacer step portions 25 to 28, as shown in FIG. The square consists of sides parallel to the x-axis or the y-axis. The fast axis 50A and the slow axis 50B of the polarization rotation elements 51 to 54 coincide with the diagonal direction of the square. The polarization rotation elements 51 to 54 are held by the spacer step portions 25 to 28, respectively. The polarization rotators 51 and 53 are selectively arranged corresponding to the semiconductor laser devices 101 and 103 by being housed in the spacer step portions 25 and 27. Further, the polarization rotation elements 52 and 54 are selectively arranged corresponding to the other semiconductor laser elements 102 and 104 by being housed in the spacer step portions 26 and 28.
　なお、本実施の形態において、偏光回転素子５１から５４は、スペーサ２０の上面側に配置されているが、偏光回転素子５１から５４は、スペーサ２０の底面側に配置されてもよい。その場合、偏光回転素子は、例えば、スペーサ２０の裏面に設けられたスペーサ段差部に、接着剤もしくは保持部材によって固定される。 In addition, in the present embodiment, the polarization rotation elements 51 to 54 are arranged on the upper surface side of the spacer 20, but the polarization rotation elements 51 to 54 may be arranged on the bottom surface side of the spacer 20. In that case, the polarization rotation element is fixed to, for example, a spacer step portion provided on the back surface of the spacer 20 with an adhesive or a holding member.
　また、偏光回転素子の形状は、矩形、円形、楕円形などであってもよく、半導体レーザ素子１０１から１０４のレーザ光７１から７４を覆う形状であればよい。 The shape of the polarization rotation element may be rectangular, circular, elliptical, or the like as long as it covers the laser beams 71 to 74 of the semiconductor laser elements 101 to 104.
　レンズ４１から４４は、レーザ光７１から７４を集光する。レンズ４１から４４を透過したレーザ光７１から７４は、それぞれｚ軸に対して平行な方向に進行する。レンズ４１から４４は、スペーサ２０に保持されている。また、レンズ４１から４４は、それぞれスペーサ窓部２１から２４を覆うように配置される。 The lenses 41 to 44 focus the laser beams 71 to 74. The laser beams 71 to 74 transmitted through the lenses 41 to 44 respectively travel in a direction parallel to the z axis. The lenses 41 to 44 are held by the spacer 20. The lenses 41 to 44 are arranged so as to cover the spacer window portions 21 to 24, respectively.
　次に本実施の形態における半導体レーザ素子の詳細な構成について説明する。 Next, a detailed configuration of the semiconductor laser device according to the present embodiment will be described.
　図５は半導体レーザ素子１０１の詳細な構成を示す斜視図である。半導体レーザ素子１０１は、ＴＯ－Ｃａｎタイプのパッケージに半導体レーザチップが内包された構成を有する。ＴＯ－Ｃａｎタイプの半導体レーザ素子１０１は、主にキャップ１１、ガラス窓１２、ステム１３、リードピン１４、および半導体レーザチップ（図示せず）によって構成されている。 FIG. 5 is a perspective view showing a detailed configuration of the semiconductor laser device 101. The semiconductor laser device 101 has a structure in which a semiconductor laser chip is included in a TO-Can type package. The TO-Can type semiconductor laser device 101 mainly includes a cap 11, a glass window 12, a stem 13, a lead pin 14, and a semiconductor laser chip (not shown).
　キャップ１１は、ステム１３の上部に設けられている。ガラス窓１２は、キャップ１１の上面に設けられている。リードピン１４は、ステム１３の下部に設けられている。半導体レーザチップは、キャップ１１の内部に配置されている。 The cap 11 is provided above the stem 13. The glass window 12 is provided on the upper surface of the cap 11. The lead pin 14 is provided below the stem 13. The semiconductor laser chip is arranged inside the cap 11.
　半導体レーザチップは、主光軸をステム１３に対して垂直な方向に有する。すなわち半導体レーザチップは、ｚ軸方向にレーザ光７１を出射する。一般的に、空気中の水分または粉塵が半導体レーザチップの端面に付着した場合、半導体レーザチップは容易に破壊に至る。しかし、ＴＯ－Ｃａｎタイプのパッケージは、キャップ１１によって半導体レーザチップを封止している。そのため、キャップ１１の内部の気密性が保たれ、半導体レーザチップの駆動環境に求められる条件が緩和される。また、ＴＯ－Ｃａｎタイプのパッケージ素子は小型である。そのため、使用個数の調整、すなわち要求仕様に応じた光出力のスケーリングが容易である。 The semiconductor laser chip has a main optical axis in a direction perpendicular to the stem 13. That is, the semiconductor laser chip emits laser light 71 in the z-axis direction. Generally, when moisture or dust in the air adheres to the end surface of the semiconductor laser chip, the semiconductor laser chip is easily destroyed. However, in the TO-Can type package, the semiconductor laser chip is sealed by the cap 11. Therefore, the airtightness inside the cap 11 is maintained, and the conditions required for the driving environment of the semiconductor laser chip are relaxed. Further, the TO-Can type package element is small. Therefore, it is easy to adjust the number of pieces used, that is, to scale the optical output according to the required specifications.
　投射型表示装置の光源には、高出力の端面発光型のレーザチップが使用される。半導体レーザチップの主材料は、ＧａＡｓまたはＧａＮ等の化合物半導体である。半導体レーザチップの活性層は、エピタキシャル成長により形成される。本実施の形態において、エピタキシャル成長の方向はｘ軸方向に、活性層の水平方向はｙ軸方向にそれぞれ対応する。レーザ光７１は、エピタキシャル成長の方向（ｘ軸方向）と直交する方向（ｚ軸方向）に位置するチップ端面から出射する。レーザ光７１は、そのチップ端面において、活性層の鉛直方向（ｘ軸方向）に約１μｍ、活性層の水平方向（ｙ軸方向）に数十から数百μｍの発光輝点から出射される。活性層の鉛直方向（ｘ軸方向）の出射口が非常に小さいため、レーザ光７１は、回折効果によってｘ軸方向に拡がる。そのｘ軸方向のレーザ光の拡がりは、全角で約６０°である。活性層の鉛直方向（ｘ軸方向）のレーザ光の拡がりは、活性層の水平方向（ｙ軸方向）のレーザ光の拡がりに対して約１０倍大きい。したがって、レーザ光７１の断面すなわち遠視野像は、図５に示されるように、楕円形状を有する。 A high-power edge-emitting laser chip is used as the light source of the projection display device. The main material of the semiconductor laser chip is a compound semiconductor such as GaAs or GaN. The active layer of the semiconductor laser chip is formed by epitaxial growth. In the present embodiment, the epitaxial growth direction corresponds to the x-axis direction, and the horizontal direction of the active layer corresponds to the y-axis direction. The laser light 71 is emitted from the chip end face located in the direction (z-axis direction) orthogonal to the epitaxial growth direction (x-axis direction). The laser light 71 is emitted from an emission bright point of about 1 μm in the vertical direction (x-axis direction) of the active layer and several tens to several hundreds of μm in the horizontal direction (y-axis direction) of the active layer on the end face of the chip. Since the emission port in the vertical direction (x-axis direction) of the active layer is very small, the laser light 71 spreads in the x-axis direction due to the diffraction effect. The spread of the laser beam in the x-axis direction is about 60 ° in all angles. The spread of laser light in the vertical direction (x-axis direction) of the active layer is about 10 times larger than the spread of laser light in the horizontal direction (y-axis direction) of the active layer. Therefore, the cross section of the laser light 71, that is, the far-field pattern has an elliptical shape, as shown in FIG.
　また、一般的にＴＯ－Ｃａｎパッケージの半導体レーザ素子において、２本のリードピン１４の配列方向は、半導体レーザチップの活性層の水平方向（ｙ軸方向）と同方向である。そのため、レーザ光７１は、リードピン１４の配列方向に拡がりが小さく、それと直交するｘ軸方向の拡がりが大きい。 Further, generally, in a TO-Can package semiconductor laser element, the arrangement direction of the two lead pins 14 is the same as the horizontal direction (y-axis direction) of the active layer of the semiconductor laser chip. Therefore, the laser light 71 has a small spread in the arrangement direction of the lead pins 14 and a large spread in the x-axis direction orthogonal thereto.
　上記の構成を有する半導体レーザ素子１０１から出射されるレーザ光７１の偏光は、活性層に水平な方向（ｙ軸方向）と平行である。すなわち、半導体レーザ素子１０１は、活性層の水平方向（ｙ軸方向）に電場が振動する直線偏光を出射する。ただし、活性層を構成する原子配列によっては、レーザ光は、活性層の鉛直方向（ｘ軸方向）に偏光する場合もある。 The polarization of the laser light 71 emitted from the semiconductor laser device 101 having the above configuration is parallel to the direction horizontal to the active layer (y-axis direction). That is, the semiconductor laser device 101 emits linearly polarized light whose electric field oscillates in the horizontal direction (y-axis direction) of the active layer. However, the laser light may be polarized in the vertical direction (x-axis direction) of the active layer depending on the atomic arrangement of the active layer.
　図６は、ベース３０および半導体レーザ素子１０１から１０４の構成を示す斜視図である。図７は、図６に示されたＡ－Ａ’における断面図である。 FIG. 6 is a perspective view showing the configurations of the base 30 and the semiconductor laser devices 101 to 104. FIG. 7 is a cross-sectional view taken along the line A-A ′ shown in FIG.
　半導体レーザ素子１０１から１０４の各々は、電流が供給されることによって駆動し、その駆動により熱が発生する。ステム１３の熱容量だけでは、十分な放熱が行われないため、半導体レーザチップが高温となり、急激な光出力低下が起こり得る。また、そのような熱負荷の増大は、半導体レーザチップの短寿命化、もしくは半導体レーザ素子を構成する部品の熱的破壊を引き起こす。そのため、ステム１３からベース３０への放熱が必要である。本実施の形態において、ベース３０は、熱伝導性の高い部材で構成される。ベース３０は、例えば、Ｃｕ、Ａｌなどの金属材料を含む。または、例えば、ベース３０は、ＳｉＣ、ＡｌＮ等の高い熱伝導率を有するセラミックを含む。または、ステム１３における熱容量および放熱面積を向上させるようなフィン、あるいは、水などの冷媒が封入されたヒートパイプに接続された冷却部材がステム１３に付加されてもよい。 Each of the semiconductor laser elements 101 to 104 is driven by being supplied with an electric current, and heat is generated by the driving. Since the heat capacity of the stem 13 alone does not sufficiently radiate heat, the temperature of the semiconductor laser chip becomes high, and a sudden decrease in light output may occur. In addition, such an increase in heat load causes shortening of the life of the semiconductor laser chip, or thermal destruction of parts constituting the semiconductor laser element. Therefore, it is necessary to radiate heat from the stem 13 to the base 30. In the present embodiment, the base 30 is composed of a member having high thermal conductivity. The base 30 includes a metal material such as Cu and Al. Alternatively, for example, the base 30 includes a ceramic having a high thermal conductivity such as SiC or AlN. Alternatively, a fin for improving the heat capacity and the heat radiation area of the stem 13 or a cooling member connected to a heat pipe in which a coolant such as water is sealed may be added to the stem 13.
　半導体レーザ素子１０１から１０４は、熱伝導性の高いグリスもしくはシート状の放熱材を介して、ベース３０の上面３０Ａに形成された平面に密着して固定されている。さらに放熱性を高めるために、各半導体レーザ素子は、はんだ材によって、ベース３０にはんだ接合されることが好ましい。はんだ材は、例えば、ＳｕＡｇＣｕ、ＡｕＳｎ等を主成分に含む。 The semiconductor laser elements 101 to 104 are fixed in close contact with the flat surface formed on the upper surface 30A of the base 30 via a highly heat-conductive grease or sheet-shaped heat dissipation material. In order to further improve heat dissipation, each semiconductor laser element is preferably soldered to the base 30 with a solder material. The solder material contains, for example, SuAgCu, AuSn or the like as a main component.
　次に本実施の形態におけるベース３０の詳細について説明する。 Next, details of the base 30 in the present embodiment will be described.
　上述したように、ベース３０は平板であるが、それに限定されるものではなく、ステム１３と接触する面が平面であればよい。例えば、ベース３０には、ステム１３の形状に合わせたざぐりが設けられていてもよい。 As described above, the base 30 is a flat plate, but the base 30 is not limited thereto, and the surface that contacts the stem 13 may be a flat surface. For example, the base 30 may be provided with a spot facing matching the shape of the stem 13.
　ベース３０が導電性材料である場合、半導体レーザ素子のリードピン１４とベース３０との間で確実な絶縁を確保する必要がある。長穴３１から３４は、リードピン１４とベース３０とが接触しないような穴形状を有し、また、リードピン１４とベース３０とが接触しないように配置されている。ベース３０は、長穴３１から３４に代えて、リードピン１４とベース３０との接触を回避可能な丸穴を有していてもよい。または、ベース３０は、長穴３１から３４に代えて、リードピン１４とベース３０との接触を回避し、かつ、半導体レーザ素子１０１から１０４に電流を供給する配線経路を確保できる溝構造を有していてもよい。 When the base 30 is made of a conductive material, it is necessary to ensure reliable insulation between the lead pin 14 of the semiconductor laser device and the base 30. The elongated holes 31 to 34 have a hole shape so that the lead pin 14 and the base 30 do not come into contact with each other, and are arranged so that the lead pin 14 and the base 30 do not come into contact with each other. The base 30 may have a round hole that can avoid contact between the lead pin 14 and the base 30, instead of the elongated holes 31 to 34. Alternatively, the base 30 has, instead of the elongated holes 31 to 34, a groove structure capable of avoiding the contact between the lead pin 14 and the base 30 and ensuring a wiring path for supplying a current to the semiconductor laser elements 101 to 104. May be.
　次に本実施の形態における偏光回転素子５１から５４の詳細を説明する。 Next, details of the polarization rotation elements 51 to 54 in the present embodiment will be described.
　偏光回転素子５１から５４は、例えば、複屈折性を有する無機材料または樹脂材料によって構成される。複屈折性を有する無機材料とは、例えば、水晶である。また、複屈折性を有する樹脂材料とは、例えば、ポリカーボネートなどを母材として含む樹脂であって、一方向に延伸されたものである。 The polarization rotation elements 51 to 54 are made of, for example, an inorganic material or a resin material having birefringence. The inorganic material having birefringence is, for example, crystal. The birefringent resin material is, for example, a resin containing polycarbonate as a base material and is stretched in one direction.
　図８および図９は、偏光回転素子５１、５３の動作を説明する図である。図１０および図１１は、偏光回転素子５２、５４の動作を説明する図である。空気よりも屈折率が高い媒質中を伝搬する光の速度は、空気中を伝搬する光の速度よりも遅い。すなわち、屈折率の高い媒質ほど、その媒質を伝搬する光の速度は遅い。そのため、偏光回転素子において、遅軸方向に電場が振動する光の伝搬速度は、速軸方向に電場が振動する光の伝搬速度よりも遅い。 8 and 9 are diagrams for explaining the operation of the polarization rotation elements 51 and 53. 10 and 11 are diagrams for explaining the operation of the polarization rotation elements 52 and 54. The velocity of light propagating in a medium having a higher refractive index than that of air is slower than the velocity of light propagating in air. That is, the higher the refractive index of the medium, the slower the speed of light propagating through the medium. Therefore, in the polarization rotator, the propagation speed of light whose electric field oscillates in the slow axis direction is slower than the propagation speed of light whose electric field oscillates in the fast axis direction.
　偏光回転素子５１、５３は、１／４波長板である。図８に示されるように、反時計回りの角度が正方向である場合、速軸（Ｆ軸）はｙ軸に対し４５°の角度をなし、遅軸（Ｓ軸）はｙ軸に対し－４５°の角度をなす。ｙ軸に平行な直線偏光８１のレーザ光が偏光回転素子５１、５３に入射した場合、速軸（Ｆ軸）方向の光線の伝搬に対して、遅軸（Ｓ軸）方向の光線の伝搬が遅れる。１／４波長板においては、速軸方向に対する遅軸方向の伝搬遅延が、１／４波長分に設計されている。遅軸方向の電場のみが１／４波長分遅れて伝搬することにより、偏光回転素子５１、５３を透過したレーザ光の偏光は、図９に示されるように、時間の経過とともに変化する。例えば、時間ｔ０，ｔ１，ｔ２，ｔ３における、偏光方向（電場の振動方向）は、それぞれ、＋Ｆ，－Ｓ，－Ｆ，＋Ｓ方向である。このように、偏光回転素子５１、５３を透過したレーザ光は、その偏光方向が左回転に螺旋を描くように進行する。すなわち、偏光回転素子５１、５３は、レーザ光の偏光方向をｙ軸方向の直線偏光８１から左回転の円偏光９１，９３に変換する。 The polarization rotation elements 51 and 53 are quarter wave plates. As shown in FIG. 8, when the counterclockwise angle is in the positive direction, the fast axis (F axis) forms an angle of 45 ° with the y axis, and the slow axis (S axis) − with respect to the y axis. Make an angle of 45 °. When the laser light of the linearly polarized light 81 parallel to the y-axis is incident on the polarization rotation elements 51 and 53, the propagation of the light beam in the slow axis (S-axis) direction is different from the propagation of the light beam in the fast axis (F-axis) direction. Be late. In the 1/4 wavelength plate, the propagation delay in the slow axis direction relative to the fast axis direction is designed to be 1/4 wavelength. Only the electric field in the slow axis direction propagates with a delay of ¼ wavelength, so that the polarization of the laser light transmitted through the polarization rotation elements 51 and 53 changes with the passage of time, as shown in FIG. For example, the polarization directions (electric field vibration directions) at times t0, t1, t2, and t3 are + F, −S, −F, and + S directions, respectively. In this way, the laser light that has passed through the polarization rotation elements 51 and 53 travels in such a manner that the polarization direction thereof spirals counterclockwise. That is, the polarization rotation elements 51 and 53 convert the polarization direction of the laser light from the linearly polarized light 81 in the y-axis direction to the left-handed circularly polarized light 91 and 93.
　偏光回転素子５２、５４も、１／４波長板である。図１０に示されるように、速軸（Ｆ軸）はｙ軸に対し－４５°の角度をなし、遅軸（Ｓ軸）はｙ軸に対し４５°の角度をなす。ｙ軸に平行な直線偏光８１のレーザ光が偏光回転素子５２、５４に入射した場合、遅軸方向の電場のみが１／４波長分遅れて伝搬する。偏光回転素子５２、５４を透過したレーザ光の偏光は、図１１に示されるように、時間の経過とともに変化する。例えば、時間ｔ０，ｔ１，ｔ２，ｔ３における、偏光方向（電場の振動方向）は、それぞれ、＋Ｓ，－Ｆ，－Ｓ，＋Ｆ方向である。このように、偏光回転素子５２、５４を透過したレーザ光は、その偏光方向が右回転に螺旋を描くように進行する。すなわち、偏光回転素子５２、５４は、レーザ光の偏光方向をｙ軸方向の直線偏光８１から右回転の円偏光９２，９４に変換する。 The polarization rotation elements 52 and 54 are also quarter wave plates. As shown in FIG. 10, the fast axis (F axis) forms an angle of −45 ° with the y axis, and the slow axis (S axis) forms an angle of 45 ° with the y axis. When the laser light of the linearly polarized light 81 parallel to the y axis enters the polarization rotation elements 52 and 54, only the electric field in the slow axis direction propagates with a delay of ¼ wavelength. The polarization of the laser light transmitted through the polarization rotation elements 52 and 54 changes with the passage of time, as shown in FIG. For example, the polarization directions (vibration directions of the electric field) at times t0, t1, t2, and t3 are + S, −F, −S, and + F directions, respectively. In this way, the laser light transmitted through the polarization rotation elements 52 and 54 proceeds so that the polarization direction draws a spiral in a clockwise rotation. That is, the polarization rotation elements 52 and 54 convert the polarization direction of the laser light from the linearly polarized light 81 in the y-axis direction into the circularly polarized light 92 and 94 that is rotated clockwise.
　次に本実施の形態におけるスペーサ２０およびレンズ４１から４４の詳細な構成について説明する。 Next, detailed configurations of the spacer 20 and the lenses 41 to 44 in the present embodiment will be described.
　図１２は、スペーサ２０およびレンズ４１から４４の構成を示す斜視図である。図１３は、図１２に示されたＢ－Ｂ’における断面図である。 FIG. 12 is a perspective view showing the configuration of the spacer 20 and the lenses 41 to 44. FIG. 13 is a cross-sectional view taken along line B-B ′ shown in FIG.
　レーザ光源装置１から出射されたレーザ光７１から７４は、投射型表示装置（図示せず）の光学系の開口に集光される。レーザ光源装置１から投射型表示装置の光学系開口までの間隔は限定されないため、レーザ光源装置１から出射されるレーザ光７１から７４は平行光であることが好ましい。 The laser beams 71 to 74 emitted from the laser light source device 1 are focused on the opening of the optical system of the projection type display device (not shown). Since the distance from the laser light source device 1 to the optical system opening of the projection type display device is not limited, it is preferable that the laser lights 71 to 74 emitted from the laser light source device 1 are parallel lights.
　前述したように各半導体レーザ素子からは、拡がったレーザ光が出射される。それらレーザ光を平行光に変換するためには、凸レンズにより集光する必要がある。図１３に示されるとおり、レンズ４１から４４は、入射面（－ｚ方向の面）に平面を、出射面（＋ｚ方向の面）に軸対称の球面あるいは非球面の凸面を有する。すなわち、レンズ４１から４４は、凸レンズである。半導体レーザ素子１０１から１０４のレーザ発光端面が、レンズ４１から４４の焦点位置近傍に配置されることにより、レンズ４１から４４を透過したレーザ光７１から７４は平行光に変換される。 As described above, each semiconductor laser element emits a spread laser beam. In order to convert the laser light into parallel light, it is necessary to collect the light with a convex lens. As shown in FIG. 13, each of the lenses 41 to 44 has a flat surface on the incident surface (a surface in the −z direction) and an axially symmetric spherical or aspherical convex surface on the output surface (a surface in the + z direction). That is, the lenses 41 to 44 are convex lenses. By arranging the laser emitting end faces of the semiconductor laser elements 101 to 104 near the focal positions of the lenses 41 to 44, the laser beams 71 to 74 transmitted through the lenses 41 to 44 are converted into parallel beams.
　なお、レンズ４１から４４は、必ずしもその入射面が平面である必要はない。各レンズは、凸レンズとしての機能を有する限り、凹面もしくは凸面を入射面または出射面に有していてもよい。ただし、スペーサ２０の上面と接する可能性のある面は、平面であることが好ましい。 The incident surfaces of the lenses 41 to 44 do not necessarily have to be flat. Each lens may have a concave surface or a convex surface on the entrance surface or the exit surface as long as it has a function as a convex lens. However, the surface that may come into contact with the upper surface of the spacer 20 is preferably a flat surface.
　また、各レンズの出射面および入射面は、軸対称の曲面である必要はない。例えば、各レンズは、出射面あるいは入射面に、シリンドリカル面を有するシリンドリカルレンズであってもよい。シリンドリカルレンズは、半導体レーザ素子から出射されるレーザ光を、その拡がり角が大きい方向、つまり活性層に対して鉛直方向（ｘ軸方向）のみ、平行光に変換する。 Moreover, the exit surface and the entrance surface of each lens do not need to be axisymmetric curved surfaces. For example, each lens may be a cylindrical lens having a cylindrical surface on the exit surface or the entrance surface. The cylindrical lens converts the laser light emitted from the semiconductor laser element into parallel light only in the direction having a large divergence angle, that is, in the vertical direction (x-axis direction) with respect to the active layer.
　レンズ４１、４４の中心軸１４１、１４４は、それぞれ半導体レーザ素子１０１、１０４の光線の中心軸と一致するように配置される。レンズ４１、４４は、接着剤によって、スペーサ２０の上面に固定されることが好ましい。なお、レンズ４１、４４がスペーサ２０の上面に固定可能であればよく、レンズ４１、４４は、上部から各レンズを抑える部材によって固定されてもよい。また、図１３には示されていないが、レンズ４２、４３も、レンズ４１、４４と同様に、スペーサ２０上面に固定される。 The central axes 141 and 144 of the lenses 41 and 44 are arranged so as to coincide with the central axes of the light rays of the semiconductor laser elements 101 and 104, respectively. The lenses 41 and 44 are preferably fixed to the upper surface of the spacer 20 with an adhesive. Note that the lenses 41 and 44 may be fixed to the upper surface of the spacer 20, and the lenses 41 and 44 may be fixed from above by a member that holds each lens down. Although not shown in FIG. 13, the lenses 42 and 43 are also fixed to the upper surface of the spacer 20 like the lenses 41 and 44.
　スペーサ段差部２５、２８の外形は、偏光回転素子５１、５４の外形と相似関係にある。スペーサ段差部２５、２８の外形は、偏光回転素子５１、５４の外形より大きい。また、スペーサ段差部２５、２８の高さは、偏光回転素子５１、５４の厚みより大きい。そのため、偏光回転素子５１、５４は、スペーサ２０の上面から上方にはみ出ることなく、スペーサ段差部２５、２８とレンズ４１、４４の底面とによって構成される空間に収納されるように配置される。なお、スペーサ段差部２６、２７の外形形状も、スペーサ段差部２５、２８の外形形状と同様である。 The outer shapes of the spacer step portions 25 and 28 are similar to the outer shapes of the polarization rotation elements 51 and 54. The outer shapes of the spacer step portions 25 and 28 are larger than the outer shapes of the polarization rotation elements 51 and 54. The height of the spacer step portions 25 and 28 is larger than the thickness of the polarization rotation elements 51 and 54. Therefore, the polarization rotation elements 51 and 54 are arranged so as to be housed in the space formed by the spacer step portions 25 and 28 and the bottom surfaces of the lenses 41 and 44 without protruding upward from the upper surface of the spacer 20. The outer shapes of the spacer step portions 26 and 27 are similar to the outer shapes of the spacer step portions 25 and 28.
　次に、レーザ光源装置１の動作を説明する。半導体レーザ素子１０１から１０４の駆動により発生する熱は、ベース３０へ放熱される。各半導体レーザ素子は、分離しているため、各半導体レーザ素子で発生した熱は、その隣の半導体レーザ素子に伝達しにくい。このように、レーザ光源装置１は、半導体レーザ素子の温度上昇を抑える。 Next, the operation of the laser light source device 1 will be described. The heat generated by driving the semiconductor laser elements 101 to 104 is radiated to the base 30. Since each semiconductor laser element is separated, heat generated in each semiconductor laser element is difficult to be transferred to the semiconductor laser element adjacent thereto. In this way, the laser light source device 1 suppresses the temperature rise of the semiconductor laser element.
　また、図１に示されるように、半導体レーザ素子１０１、１０３から出射されたレーザ光７１、７３の偏光方向は、偏光回転素子５１、５３によって、左回転の円偏光９１、９３に変換される。一方で、半導体レーザ素子１０２、１０４から出射されたレーザ光７２、７４の偏光方向は、偏光回転素子５２、５４によって、右回転の円偏光９２、９４に変換される。その結果、レーザ光源装置１からは、左回転の円偏光９１、９３のレーザ光７１、７３と、右回転の円偏光９２、９４のレーザ光７２、７４とが出射される。つまり、レーザ光７１から７４は、時間的に偏光方向が変わる。また、円偏光９１、９３は、円偏光９２、９４に対して偏光の回転方向が異なる。レーザ光７１から７４は、同じ断面形状（ビームプロファイル）を有しながらも、偏光方向が一方向に揃わない。 Further, as shown in FIG. 1, the polarization directions of the laser beams 71 and 73 emitted from the semiconductor laser elements 101 and 103 are converted into left-handed circularly polarized light 91 and 93 by the polarization rotation elements 51 and 53. . On the other hand, the polarization directions of the laser beams 72 and 74 emitted from the semiconductor laser elements 102 and 104 are converted into right-handed circularly polarized light 92 and 94 by the polarization rotation elements 52 and 54. As a result, the laser light source device 1 emits left-handed circularly polarized light 91, 93 of laser light 71, 73 and right-handed circularly polarized light of laser light 72, 74. That is, the polarization directions of the laser beams 71 to 74 change temporally. The circularly polarized light 91, 93 has a different rotation direction of polarized light from the circularly polarized light 92, 94. The laser beams 71 to 74 have the same cross-sectional shape (beam profile), but their polarization directions are not aligned in one direction.
　このように、レーザ光源装置１は、偏光回転素子５１から５４により、複数のレーザ光の偏光方向を回転させることにより、偏光方向が異なる２種類のレーザ光を出射する。このようなレーザ光は、干渉縞やスペックルの発生を低減する。 In this way, the laser light source device 1 emits two types of laser light having different polarization directions by rotating the polarization directions of the plurality of laser lights by the polarization rotation elements 51 to 54. Such laser light reduces the generation of interference fringes and speckles.
　以上をまとめると、本実施の形態におけるレーザ光源装置１は、ベース３０と、各々が個別にベース３０の上面３０Ａに保持され、偏光方向が一方向に揃った複数のレーザ光を出射する複数の半導体レーザ素子１０１から１０４と、複数のレーザ光のうち少なくとも一部のレーザ光の偏光方向を回転させることにより、複数のレーザ光の偏光方向が一方向に揃わないように乱す偏光変換部と、を含む。偏光変換部は、複数のレーザ光の偏光を円偏光に変換する複数の偏光回転素子５１から５４を含む。複数の偏光回転素子５１から５４は、複数の半導体レーザ素子１０１から１０４のうち一部のレーザ光を出射する半導体レーザ素子１０１、１０３に対応して選択的に配置され、一部のレーザ光の偏光を左回転の円偏光に変換する第１偏光回転素子（偏光回転素子５１、５４）と、複数の半導体レーザ素子１０１から１０４のうち別の一部のレーザ光７２、７４を出射する別の半導体レーザ素子１０２、１０４に対応して選択的に配置され、別の一部のレーザ光７２、７４の偏光を右回転の円偏光に変換する第２偏光回転素子（偏光回転素子５２、５４）と、を含む。 To summarize the above, the laser light source device 1 according to the present embodiment includes a base 30 and a plurality of laser lights each of which is individually held on the upper surface 30A of the base 30 and emits a plurality of laser lights whose polarization directions are aligned in one direction. A semiconductor laser device 101 to 104, and a polarization conversion unit that disturbs the polarization directions of the plurality of laser lights by rotating the polarization directions of at least some of the laser lights so that the polarization directions of the plurality of laser lights are not aligned in one direction. including. The polarization conversion unit includes a plurality of polarization rotation elements 51 to 54 that convert the polarization of a plurality of laser lights into circularly polarized light. The plurality of polarization rotation elements 51 to 54 are selectively arranged in correspondence with the semiconductor laser elements 101 and 103 that emit a part of the laser light among the plurality of semiconductor laser elements 101 to 104, respectively, and A first polarization rotator (polarization rotator 51, 54) that converts polarized light into left-handed circularly polarized light, and another one that emits a part of the laser light 72, 74 of the plurality of semiconductor laser elements 101 to 104. A second polarization rotation element (polarization rotation element 52, 54) which is selectively arranged corresponding to the semiconductor laser elements 102, 104 and converts the polarization of another part of the laser light 72, 74 into right-handed circularly polarized light. And, including.
　以上のレーザ光源装置１は、熱伝導性が良好なベース３０に、個別に設けられた複数の半導体レーザ素子１０１から１０４により構成される。そのため、レーザ発振による温度上昇が低減し、利得低下が抑制される。 The above laser light source device 1 is composed of a plurality of semiconductor laser elements 101 to 104 provided individually on the base 30 having good thermal conductivity. Therefore, the temperature rise due to laser oscillation is reduced, and the gain reduction is suppressed.
　また、レーザ光源装置１は、例えば、従来のアレイ型レーザ光源とは異なり、中央部のレーザが両隣のレーザから発生する熱を受けにくく、大きく利得が低減する可能性も少ない。そのため、十分な出力が得られる。 Further, unlike the conventional array type laser light source, for example, the laser light source device 1 is unlikely to receive heat generated by the lasers in the central portion from the lasers on both sides, and the gain is unlikely to be greatly reduced. Therefore, a sufficient output can be obtained.
　また、レーザ光源装置１は、時間的に偏光方向が変わる２種類の円偏光のレーザ光を出射する。それら２種類の円偏光は、左回転しながら進行する左回転の円偏光９１、９３と、右回転の円偏光９２、９４とにより構成されるため、連続的に２種類の偏光方向が一致することはない。レーザ光源装置１は、レーザ光の合成による干渉縞およびスペックルの発生を低減する。 The laser light source device 1 also emits two types of circularly polarized laser light whose polarization directions change with time. Since these two types of circularly polarized light are composed of left-handed circularly polarized light 91 and 93 and right-handed circularly polarized light 92 and 94 which proceed while rotating leftward, the two types of polarization directions are continuously matched. There is no such thing. The laser light source device 1 reduces the generation of interference fringes and speckles due to the synthesis of laser light.
　従来、投射型表示装置にレーザ光源が搭載された場合、レーザ光の干渉縞およびスペックルによる映像品位の低下防止のため、散乱度の強い光拡散素子が必要とされる。しかし、散乱度の強い光拡散素子は、投射型表示装置の光出力の効率を低下させる。一方で、本実施の形態に示されたレーザ光源装置１においては、上述したように、干渉縞およびスペックルが低減する。そのため、レーザ光源装置１を搭載する投射型表示装置には、散乱度の強い光拡散素子が必要ではない。レーザ光源装置１が投射型表示装置に搭載された場合、干渉縞およびスペックルの発生が抑制されることによって映像品位が向上し、かつ、投射型表示装置自体の光出力の効率も向上する。 Previously, when a projection display device was equipped with a laser light source, a light diffusing element with a high degree of scattering was required to prevent image quality deterioration due to laser light interference fringes and speckles. However, the light diffusing element having a high degree of scattering reduces the light output efficiency of the projection display device. On the other hand, in the laser light source device 1 shown in the present embodiment, interference fringes and speckles are reduced as described above. Therefore, the projection type display device equipped with the laser light source device 1 does not require a light diffusing element having a high degree of scattering. When the laser light source device 1 is mounted on a projection type display device, the generation of interference fringes and speckles is suppressed, so that the image quality is improved and the light output efficiency of the projection type display device itself is also improved.
　また、本実施の形態におけるレーザ光源装置１は、複数の半導体レーザ素子１０１から１０４のそれぞれに対応して設けられ、複数のレーザ光のそれぞれを平行光に変換する複数のレンズ４１から４４を、さらに含む。スペーサ２０は、ベース３０に固定され、かつ、複数のレンズ４１から４４を保持する。 Further, the laser light source device 1 according to the present embodiment includes a plurality of lenses 41 to 44 provided corresponding to the plurality of semiconductor laser elements 101 to 104, respectively, for converting each of the plurality of laser lights into parallel light. Including further. The spacer 20 is fixed to the base 30 and holds the plurality of lenses 41 to 44.
　以上の構成により、レーザ光源装置１は、高出力かつ平行度の高いレーザ光７１から７４を出射することを可能にする。 With the above configuration, the laser light source device 1 can emit laser beams 71 to 74 with high output and high parallelism.
　（実施の形態の変形例１）
　実施の形態の変形例１におけるレーザ光源装置は、スペーサおよび偏光回転素子の構成が、上記の実施の形態におけるレーザ光源装置１のそれらとは異なる。 (Modification 1 of Embodiment)
The laser light source device according to the first modification of the embodiment is different from the laser light source device 1 according to the above-described embodiments in the configuration of the spacer and the polarization rotation element.
　図１４は、実施の形態の変形例１におけるレーザ光源装置のスペーサ１２０および偏光回転素子１５１から１５４の構成を示す図である。偏光回転素子１５１から１５４の外形は、平行四辺形を有する。スペーサ１２０のスペーサ段差部１２５から１２８の外形は、偏光回転素子１５１から１５４の外形より少し大きい相似形状である平行四辺形を有する。スペーサ段差部１２６、１２８の外形は、スペーサ段差部１２５、１２７の外形がｘ－ｙ面内で９０°回転した平行四辺形を有する。 FIG. 14 is a diagram showing a configuration of the spacer 120 and the polarization rotation elements 151 to 154 of the laser light source device according to the first modification of the embodiment. The outer shape of the polarization rotation elements 151 to 154 has a parallelogram shape. The outer shape of the spacer step portions 125 to 128 of the spacer 120 has a parallelogram, which is a similar shape slightly larger than the outer shapes of the polarization rotation elements 151 to 154. The outer shapes of the spacer step portions 126 and 128 have a parallelogram shape in which the outer shapes of the spacer step portions 125 and 127 are rotated by 90 ° in the xy plane.
　通常、偏光回転素子は、それよりも大きな板材である偏光素子基板から矩形状に切り出される。その矩形を形成する角度が９０°であるため、偏光素子基板から無駄なく偏光回転素子が切り出される。一方で、本変形例１における偏光回転素子１５１から１５４は、一方向に対し角度をなして切り出される。図１５は、偏光回転素子１５１から１５４を含む偏光素子基板を示す図である。偏光素子基板における速軸５０Ａはｙ軸に対し４５°の角度をなし、遅軸５０Ｂはｙ軸に対し－４５°の角度をなしている。偏光回転素子１５１から１５４は、ｘ軸方向に対し、わずかな角度αをなして切り出される。偏光回転素子１５１から１５４の外形は、ｙ軸に平行な一辺とｘ軸に対し角度αを有する他辺とからなる平行四辺形を有する。つまり、偏光回転素子１５１から１５４の速軸５０Ａは、偏光素子基板から切り出された段階において、一辺に対し４５°の角度をなし、その一辺と交わる他辺に対し４５°－αの角度をなす。 Normally, the polarization rotator is cut out into a rectangular shape from the polarization element substrate, which is a larger plate. Since the angle forming the rectangle is 90 °, the polarization rotation element is cut out from the polarization element substrate without waste. On the other hand, the polarization rotation elements 151 to 154 according to the first modification are cut out at an angle with respect to one direction. FIG. 15 is a diagram showing a polarization element substrate including polarization rotation elements 151 to 154. In the polarizing element substrate, the fast axis 50A forms an angle of 45 ° with the y axis, and the slow axis 50B forms an angle of −45 ° with the y axis. The polarization rotation elements 151 to 154 are cut out at a slight angle α with respect to the x-axis direction. The outer shape of the polarization rotation elements 151 to 154 has a parallelogram shape having one side parallel to the y-axis and the other side having an angle α with the x-axis. That is, the fast axis 50A of the polarization rotation elements 151 to 154 forms an angle of 45 ° with one side and an angle of 45 ° -α with respect to the other side intersecting the one side when cut out from the polarization element substrate. .
　図１４に示されるように、偏光回転素子１５１、１５３は、速軸５０Ａおよび遅軸５０Ｂの方向を維持した状態で、スペーサ段差部１２５、１２７に配置される。一方で、偏光素子基板から切り出された偏光回転素子１５２、１５４は、ｘ－ｙ面内で９０°回転して、スペーサ段差部１２６、１２８に配置される。そのため、偏光回転素子１５２、１５４の速軸５０Ａは、偏光回転素子１５１、１５３の速軸５０Ａに対し、９０°の角度をなす。その結果、偏光回転素子１５１、１５３は、左回転の偏光回転素子として機能し、偏光回転素子１５２、１５４は、右回転の偏光回転素子として機能する。 As shown in FIG. 14, the polarization rotation elements 151 and 153 are arranged on the spacer step portions 125 and 127 while maintaining the directions of the fast axis 50A and the slow axis 50B. On the other hand, the polarization rotation elements 152 and 154 cut out from the polarization element substrate are rotated by 90 ° in the xy plane and arranged on the spacer step portions 126 and 128. Therefore, the fast axis 50A of the polarization rotators 152 and 154 makes an angle of 90 ° with the fast axis 50A of the polarization rotators 151 and 153. As a result, the polarization rotation elements 151 and 153 function as left rotation polarization rotation elements, and the polarization rotation elements 152 and 154 function as right rotation polarization rotation elements.
　上述したとおり、スペーサ段差部１２５から１２８の外形は、偏光回転素子１５１から１５４の外形より少し大きい相似形状である平行四辺形を有する。そのため、偏光回転素子１５１から１５４は、それぞれの形状に対応するスペーサ段差部１２５から１２８に、すなわち予め定められた箇所に配置される。表裏が逆転した偏光回転素子は、スペーサ段差部１２５から１２８に嵌合しない。このようなスペーサ１２０は、レーザ光源装置の組立工程等において、偏光回転素子１５１から１５４の配置方向を限定する。 As described above, the outer shapes of the spacer step portions 125 to 128 have parallelograms that are similar shapes and are slightly larger than the outer shapes of the polarization rotation elements 151 to 154. Therefore, the polarization rotation elements 151 to 154 are arranged in the spacer step portions 125 to 128 corresponding to the respective shapes, that is, at predetermined positions. The polarization rotation element whose front and back are reversed does not fit into the spacer step portions 125 to 128. Such a spacer 120 limits the arrangement direction of the polarization rotation elements 151 to 154 in the assembly process of the laser light source device and the like.
　このような構成を有するレーザ光源装置は、上記の実施の形態と同様の効果を奏する。さらに、偏光回転素子１５１から１５４の形状とスペーサ段差部１２５から１２８の形状とが対応するため、偏光回転素子の配置方向が限定される。その結果、レーザ光源装置の組立工程において、偏光回転素子の組み込み方向が指定され、組立作業性が向上する。 The laser light source device having such a configuration has the same effect as that of the above embodiment. Further, since the shapes of the polarization rotation elements 151 to 154 and the shapes of the spacer step portions 125 to 128 correspond to each other, the arrangement direction of the polarization rotation elements is limited. As a result, in the assembling process of the laser light source device, the assembling direction of the polarization rotation element is designated, and the assembling workability is improved.
　（実施の形態の変形例２）
　実施の形態の変形例２におけるレーザ光源装置は、スペーサおよび偏光回転素子の構成が、上記の実施の形態におけるレーザ光源装置１のそれらとは異なる。 (Modification 2 of Embodiment)
The laser light source device according to the second modification of the embodiment is different from those of the laser light source device 1 according to the above-described embodiment in the configurations of the spacer and the polarization rotation element.
　図１６は、実施の形態の変形例２におけるレーザ光源装置のスペーサ２２０および偏光回転素子２５１から２５４の構成を示す図である。偏光回転素子２５１から２５４の外形は、平行四辺形を有する。スペーサ２２０のスペーサ段差部２２５から２２８の外形は、偏光回転素子２５１から２５４の外形より少し大きい相似形状である平行四辺形を有する。スペーサ段差部２２６、２２８の外形は、スペーサ段差部２２５、２２７の外形がｙ軸に対し反転した平行四辺形を有する。 FIG. 16 is a diagram showing a configuration of the spacer 220 and the polarization rotation elements 251 to 254 of the laser light source device according to the second modification of the embodiment. The outer shape of the polarization rotation elements 251 to 254 has a parallelogram shape. The outer shape of the spacer step portions 225 to 228 of the spacer 220 has a parallelogram which is a slightly larger shape than the outer shapes of the polarization rotation elements 251 to 254. The outer shapes of the spacer step portions 226 and 228 have a parallelogram shape in which the outer shapes of the spacer step portions 225 and 227 are inverted with respect to the y axis.
　図１７は、偏光回転素子２５１から２５４を含む偏光素子基板を示す図である。偏光素子基板における速軸５０Ａはｙ軸に対し４５°の角度をなし、遅軸５０Ｂはｙ軸に対し－４５°の角度をなしている。偏光回転素子２５１から２５４は、ｘ軸方向に対し、わずかな角度αをなして切り出される。偏光回転素子２５１から２５４の外形は、ｙ軸に平行な一辺とｘ軸に対し角度αを有する他辺とからなる平行四辺形を有する。つまり、偏光回転素子２５１から２５４の速軸５０Ａは、偏光素子基板から切り出された段階において、一辺に対し４５°の角度をなし、その一辺と交わる他辺に対し４５°－αの角度をなす。 FIG. 17 is a diagram showing a polarization element substrate including polarization rotation elements 251 to 254. In the polarizing element substrate, the fast axis 50A forms an angle of 45 ° with the y axis, and the slow axis 50B forms an angle of −45 ° with the y axis. The polarization rotation elements 251 to 254 are cut out at a slight angle α with respect to the x-axis direction. The polarization rotating elements 251 to 254 have a parallelogram shape having one side parallel to the y-axis and the other side having an angle α with the x-axis. That is, the fast axis 50A of the polarization rotation elements 251 to 254 forms an angle of 45 ° with one side and an angle of 45 ° -α with respect to the other side intersecting the one side when cut out from the polarization element substrate. .
　図１６に示されるように、偏光回転素子２５１、２５３は、速軸５０Ａおよび遅軸５０Ｂの方向を維持した状態で、スペーサ段差部２２５、２２７に配置される。一方で、偏光素子基板から切り出された偏光回転素子２５２、２５４は、ｘ軸またはｙ軸に対して表裏反転して、スペーサ段差部２２６、２２８に配置される。そのため、偏光回転素子２５２、２５４の速軸５０Ａは、偏光回転素子２５１、２５３の速軸５０Ａに対し、９０°の角度をなす。その結果、偏光回転素子２５１、２５３は、左回転の円偏光に変換する偏光回転素子として機能し、偏光回転素子２５２、２５４は、右回転の円偏光に変換する偏光回転素子として機能する。 As shown in FIG. 16, the polarization rotation elements 251, 253 are arranged in the spacer step portions 225, 227 while maintaining the directions of the fast axis 50A and the slow axis 50B. On the other hand, the polarization rotation elements 252 and 254 cut out from the polarization element substrate are arranged on the spacer step portions 226 and 228 with their front and back inverted with respect to the x axis or the y axis. Therefore, the fast axes 50A of the polarization rotators 252 and 254 make an angle of 90 ° with the fast axes 50A of the polarization rotators 251 and 253. As a result, the polarization rotators 251, 253 function as polarization rotators that convert to left-handed circularly polarized light, and the polarization rotators 252 and 254 function as right-handed circularly polarized lights.
　上述したとおり、スペーサ段差部２２５から２２８の外形は、偏光回転素子２５１から２５４の外形より少し大きい相似形状である平行四辺形を有する。そのため、偏光回転素子２５１から２５４は、それぞれの形状に対応するスペーサ段差部２２５から２２８に、すなわち予め定められた箇所に配置される。このようなスペーサ２２０は、レーザ光源装置の組立工程等において、左回転の円偏光に変換する偏光回転素子２５１、２５３の配置箇所、および、右回転の円偏光に変換する偏光回転素子２５２、２５４の配置箇所を限定する。 As described above, the outer shapes of the spacer step portions 225 to 228 have parallelograms, which are similar shapes and are slightly larger than the outer shapes of the polarization rotation elements 251 to 254. Therefore, the polarization rotation elements 251 to 254 are arranged at the spacer step portions 225 to 228 corresponding to the respective shapes, that is, at predetermined positions. Such a spacer 220 is provided in the assembly process of the laser light source device, etc., where the polarization rotators 251 and 253 for converting it to left-handed circularly polarized light and the polarization rotators 252 and 254 for right-handed circularly polarized light are arranged. Places are limited.
　このような構成を有するレーザ光源装置は、上記の実施の形態と同様の効果を奏する。さらに、偏光回転素子２５１から２５４の形状とスペーサ段差部２２５から２２８の形状とが対応するため、偏光回転素子の配置箇所が限定される。その結果、レーザ光源装置の組立工程において、左回転の円偏光に変換する偏光回転素子２５１、２５３と、右回転の円偏光に変換する偏光回転素子２５２、２５４とを指定された箇所に誤ることなく配置可能となり、組立作業性が向上する。 The laser light source device having such a configuration has the same effect as that of the above embodiment. Further, since the shapes of the polarization rotation elements 251 to 254 and the shapes of the spacer step portions 225 to 228 correspond to each other, the location where the polarization rotation elements are arranged is limited. As a result, in the assembly process of the laser light source device, the polarization rotation elements 251, 253 for converting the left-handed circularly polarized light and the polarization rotation elements 252, 254 for converting the right-handed circularly polarized light are mistaken at designated positions. It can be installed without the need for assembly workability.
　さらに、図１６に示されるように、偏光回転素子２５１から２５４は、レーザ光７１から７４の断面形状（ビームプロファイル）に応じて、その外形が決定される。偏光回転素子２５１から２５４の外形は、一方向に長い平行四辺形を有する。各偏光回転素子は、その平行四辺形の長手が各レーザ光の拡がり角が大きいｘ軸方向と一致するように配置される。すなわち、各偏光回転素子は、各レーザ光の断面形状に応じて選択的に配置される。 Further, as shown in FIG. 16, the outer shapes of the polarization rotation elements 251 to 254 are determined according to the cross-sectional shapes (beam profiles) of the laser beams 71 to 74. The outer shapes of the polarization rotation elements 251 to 254 have a parallelogram shape that is long in one direction. Each polarization rotation element is arranged so that the length of the parallelogram matches the x-axis direction in which the divergence angle of each laser beam is large. That is, each polarization rotation element is selectively arranged according to the cross-sectional shape of each laser beam.
　このように、レーザ光の断面形状に合わせて偏光回転素子を偏光素子基板から切り出すことによって、偏光素子基板から切り出すことができる偏光回転素子の枚数が増加する。その結果、偏光回転素子およびレーザ光源装置の低コスト化が実現する。 By cutting the polarization rotation element from the polarization element substrate in accordance with the cross-sectional shape of the laser light, the number of polarization rotation elements that can be cut out from the polarization element substrate increases. As a result, cost reduction of the polarization rotation element and the laser light source device is realized.
　以上をまとめると、実施の形態の変形例１および２におけるレーザ光源装置は、複数の半導体レーザ素子１０１から１０４の上方を覆って設けられるスペーサ２０を、さらに含む。スペーサ２０は、複数のレーザ光の各々が通過する位置に枠構造を含む。複数の偏光回転素子１５１から１５４（または２５１から２５４）の各々は、枠構造に保持される。複数の偏光回転素子１５１から１５４（または２５１から２５４）の各々の外形は、平行四辺形を有する。スペーサ２０の枠構造の外形は、複数の偏光回転素子１５１から１５４（または２５１から２５４）の各々の外形よりも大きい相似形状を有する。 In summary, the laser light source device according to the modified examples 1 and 2 of the embodiment further includes the spacer 20 provided above the plurality of semiconductor laser elements 101 to 104. The spacer 20 includes a frame structure at a position where each of the plurality of laser beams passes. Each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254) is held in a frame structure. The outer shape of each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254) has a parallelogram shape. The outer shape of the frame structure of the spacer 20 has a similar shape larger than the outer shape of each of the plurality of polarization rotation elements 151 to 154 (or 251 to 254).
　このような構成により、左回転の円偏光に変換する偏光回転素子１５１、１５３（または２５１、２５３）、および、右回転の円偏光に変換する偏光回転素子１５２、１５４（または２５２、２５４）の配置方向または配置箇所が限定される。その結果、レーザ光源装置の組立作業性が向上する。 With such a configuration, the polarization rotation elements 151 and 153 (or 251 and 253) that convert to left-handed circularly polarized light and the polarization rotation elements 152 and 154 (or 252 and 254) that convert to right-handed circularly polarized light. The placement direction or location is limited. As a result, the workability of assembling the laser light source device is improved.
　また、実施の形態の変形例２におけるレーザ光源装置は、第１偏光回転素子（偏光回転素子２５１、２５３）あるいは第２偏光回転素子（偏光回転素子２５２、２５４）は、複数のレーザ光の各々の断面形状に応じて選択的に配置される。 Further, in the laser light source device according to the second modification of the embodiment, the first polarization rotating element (polarization rotating elements 251, 253) or the second polarization rotating element (polarization rotating elements 252, 254) is each of a plurality of laser beams. Are selectively arranged according to the cross-sectional shape of.
　このような構成により、偏光素子基板から取れる偏光回転素子の収量が増加し、偏光回転素子およびレーザ光源装置の低コスト化が実現できる。 With such a configuration, the yield of the polarization rotation element that can be taken from the polarization element substrate is increased, and the cost reduction of the polarization rotation element and the laser light source device can be realized.
　以上の実施の形態および各変形例においては、ｘ軸方向に２個およびｙ軸方向に２個（２×２）の半導体レーザ素子が配列されたレーザ光源装置を一例として示した。しかし、レーザ光源装置が含む半導体レーザ素子の搭載個数は、それに限定されるものではない。レーザ光源装置は、ｘ軸方向およびｙ軸方向に搭載個数を増加させた複数の半導体レーザ素子を含んでもよい。そのような構成により、高出力のレーザ光源装置が実現できる。また、半導体レーザ素子の配列は、２×４、４×４のような２次元アレイであってもよいし、１×４のような１次元アレイであってもよい。 In the above embodiment and each modification, a laser light source device in which two semiconductor laser elements are arranged in the x-axis direction and two (2 × 2) semiconductor laser elements in the y-axis direction is shown as an example. However, the number of semiconductor laser elements included in the laser light source device is not limited to that. The laser light source device may include a plurality of semiconductor laser elements whose mounting numbers are increased in the x-axis direction and the y-axis direction. With such a configuration, a high-power laser light source device can be realized. The array of semiconductor laser elements may be a two-dimensional array such as 2 × 4 or 4 × 4 or a one-dimensional array such as 1 × 4.
　また、隣り合う行もしくは列の半導体レーザ素子の配列ピッチが、互いに半ピッチずれた関係にある場合、最密の配列が可能となる。このような構成は、集光レンズの有効径を縮小化させ、投射型表示装置の小型化、低コスト化に寄与する。 Further, when the arrangement pitches of the semiconductor laser elements in the adjacent rows or columns are shifted from each other by a half pitch, the closest arrangement is possible. Such a configuration reduces the effective diameter of the condenser lens and contributes to downsizing and cost reduction of the projection display device.
　また、半導体レーザ素子の各々が異なる波長のレーザを発振する場合、レーザ光源装置は、さらに干渉およびスペックルの発生を低減することができる。例えば、半導体レーザ素子１０１、１０２が、波長６３８ｎｍの赤色のレーザを発振し、半導体レーザ素子１０３、１０４が波長６４２ｎｍの赤色のレーザを発振する場合、レーザ光源装置は、上記の偏光方向に関してだけでなく、波長に関しても特性が異なる４種類のレーザ光を出射することが可能となる。 Further, when each of the semiconductor laser elements oscillates a laser of a different wavelength, the laser light source device can further reduce the occurrence of interference and speckle. For example, when the semiconductor laser elements 101 and 102 oscillate a red laser with a wavelength of 638 nm and the semiconductor laser elements 103 and 104 oscillate a red laser with a wavelength of 642 nm, the laser light source device is only required for the above polarization direction. Instead, it is possible to emit four types of laser light having different characteristics with respect to wavelength.
　なお、本発明は、その発明の範囲内において、実施の形態を適宜、変形、省略することが可能である。 The present invention can appropriately modify or omit the embodiments within the scope of the invention.
　本発明は詳細に説明されたが、上記した説明は、全ての局面において、例示であって、本発明がそれに限定されるものではない。例示されていない無数の変形例が、この発明の範囲から外れることなく想定され得るものと解される。 Although the present invention has been described in detail, the above description is an example in all aspects, and the present invention is not limited thereto. It is understood that innumerable variants not illustrated can be envisaged without departing from the scope of the invention.
　１　レーザ光源装置、１０１～１０４　半導体レーザ素子、２０　スペーサ、２５～２８　スペーサ段差部、３０　ベース、３０Ａ　上面、４１～４４　レンズ、５０Ａ　速軸、５０Ｂ　遅軸、５１～５４　偏光回転素子、１５１～１５４　偏光回転素子、２５１～２５４　偏光回転素子、７１～７４　レーザ光、８１　直線偏光、９１～９４　円偏光。 1 laser light source device, 101-104 semiconductor laser device, 20 spacer, 25-28 spacer stepped portion, 30 base, 30A upper surface, 41-44 lens, 50A fast axis, 50B slow axis, 51-54 polarization rotation element, 151- 154 polarization rotator, 251-254 polarization rotator, 71-74 laser light, 81 linear polarization, 91-94 circular polarization.

Claims (4)

  1. 　ベースと、
    　各々が個別に前記ベースの上面に保持され、偏光方向が一方向に揃った複数のレーザ光を出射する複数の半導体レーザ素子と、
    　前記複数のレーザ光のうち少なくとも一部のレーザ光の前記偏光方向を回転させることにより、前記複数のレーザ光の前記偏光方向が前記一方向に揃わないように乱す偏光変換部と、を備え、
    　前記偏光変換部は、
    　前記複数のレーザ光の偏光を円偏光に変換する複数の偏光回転素子を含み、
    　前記複数の偏光回転素子は、
    　前記複数の半導体レーザ素子のうち一部のレーザ光を出射する半導体レーザ素子に対応して選択的に配置され、前記一部のレーザ光の偏光を左回転の円偏光に変換する第１偏光回転素子と、
    　前記複数の半導体レーザ素子のうち別の一部のレーザ光を出射する別の半導体レーザ素子に対応して選択的に配置され、前記別の一部のレーザ光の偏光を右回転の円偏光に変換する第２偏光回転素子と、を含む、レーザ光源装置。     Base,
    A plurality of semiconductor laser elements, each of which is individually held on the upper surface of the base, and emits a plurality of laser lights whose polarization directions are aligned in one direction;
    By rotating the polarization direction of at least a part of the laser light of the plurality of laser light, the polarization conversion unit that disturbs the polarization direction of the plurality of laser light so as not to align in the one direction,
    The polarization conversion unit,
    A plurality of polarization rotation elements that convert the polarization of the plurality of laser beams into circularly polarized light;
    The plurality of polarization rotation elements,
    A first polarization rotation device that is selectively arranged corresponding to a semiconductor laser device that emits a part of the laser light of the plurality of semiconductor laser devices and that converts the polarization of the part of the laser light into left-handed circularly polarized light. Element,
    The semiconductor laser device is selectively arranged corresponding to another semiconductor laser device that emits another part of the laser light among the plurality of semiconductor laser devices, and the polarization of the another part of the laser light is a right-handed circularly polarized light. And a second polarization rotation element for converting the laser light source apparatus.
  2. 　前記複数の半導体レーザ素子の上方を覆って設けられるスペーサを、さらに備え、
    　前記スペーサは、前記複数のレーザ光の各々が通過する位置に枠構造を含み、
    　前記複数の偏光回転素子の各々は、前記枠構造に保持され、
    　前記複数の偏光回転素子の各々の外形は、平行四辺形を有し、
    　前記スペーサの前記枠構造の外形は、前記複数の偏光回転素子の各々の前記外形よりも大きい相似形状を有する、請求項１に記載のレーザ光源装置。     Further comprising a spacer provided over the plurality of semiconductor laser devices,
    The spacer includes a frame structure at a position where each of the plurality of laser beams passes,
    Each of the plurality of polarization rotation elements is held in the frame structure,
    The outer shape of each of the plurality of polarization rotation elements has a parallelogram,
    The laser light source device according to claim 1, wherein an outer shape of the frame structure of the spacer has a similar shape to the outer shape of each of the plurality of polarization rotation elements.
  3. 　前記第１偏光回転素子あるいは前記第２偏光回転素子は、前記複数のレーザ光の各々の断面形状に応じて選択的に配置される、請求項２に記載のレーザ光源装置。 The laser light source device according to claim 2, wherein the first polarization rotation element or the second polarization rotation element is selectively arranged according to a cross-sectional shape of each of the plurality of laser beams.
  4. 　前記複数の半導体レーザ素子のそれぞれに対応して設けられ、前記複数のレーザ光のそれぞれを平行光に変換する複数のレンズを、さらに備え、
    　前記スペーサは、前記ベースに固定され、かつ、前記複数のレンズを保持する、請求項２または請求項３に記載のレーザ光源装置。     A plurality of lenses provided corresponding to each of the plurality of semiconductor laser elements, each of which converts each of the plurality of laser light into parallel light,
    The laser light source device according to claim 2 or 3, wherein the spacer is fixed to the base and holds the plurality of lenses.
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