Abstract:
A multi-wavelength light emitting device includes the following three sections; a light source section having multiple luminous points that emit multiple light beams, a condenser lens section that concentrates the light beams emitted from the luminous points, and a light guide section that propagates superposedly and mixedly the light beams concentrated by the condenser lens section after emission thereof from the luminous points.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application JP 2009-212648 filed on Sep. 15, 2009, the content of which is hereby incorporated by reference into this application. 
     FIELD OF THE INVENTION 
     The present invention relates to a multi-wavelength light emitting device and more particularly to a multi-wavelength light emitting device applicable to an image projector. 
     BACKGROUND OF THE INVENTION 
     A projection-type image display apparatus (projector) for displaying images on a large screen is used highly frequently at presentations in such places as conference halls and assembly rooms. In a conventional projector, a large-sized light source typified by a halogen lamp or a metal halide lamp is adopted for the purpose of use at presentations to a relatively large audience. 
     In recent years, however, there has been an increasing demand for a type of projector that is connected to or incorporated in a mobile phone terminal or a notebook PC for the purpose of use at presentations to a few or several viewers. In this trend, particular attention is being given to a projector equipped with light emitting elements (light emitting diodes (LED) or semiconductor lasers) as light sources to display an image by raster-scanning light beams from the light emitting elements. Such a projector is called a “micro-projector” because of the size thereof. In operation of the micro-projector, light beams having wavelengths that approximately correspond to three RGB primary colors (red, blue, green) from light emitting elements are raster-scanned across a screen or applied thereon to provide still image projection. 
     A projector of a common type is designed to operate in a fashion that light beams emitted from RGB light sources are scanned by using an optical part such as an MEMS (micro electro mechanical systems) mirror for direct projection onto a screen. In the case of a projector using laser light beams, since each of RGB light sources can be controlled independently, there is no need to use RGB subpixels for forming each pixel as required in a flat display panel such as is represented by a liquid crystal display panel. In optical axial alignment of the projector using laser light beams, RGB beam positions are superposed on a screen so as to form a white beam spot thereon. 
     Japanese patent document JP-A-2008-309935 discloses a technique for optical axial alignment by using two dichroic mirrors in projection of spatially propagating light beams from R, G, and B light sources. 
     SUMMARY OF THE INVENTION 
     With the technique for optical axial alignment by using two dichroic mirrors disclosed in the JP-A-2008-309935, however, an effective beam diameter is extremely small since a spectrum of light intensity with respect to a beam diameter is centerwardly overconcentrated ( FIG. 2A  shows a spectrum of light intensity with respect to a beam diameter in projection of spatially propagating light from a conventional multi-wavelength light emitting, device disclosed in the JP-A-2008-309935, and  FIG. 2B  shows on-screen beam positioning in projection of three RGB light source beams propagating spatially from the conventional multi-wavelength light emitting device disclosed therein). Hence, in the conventional multi-wavelength light emitting device, it is rather difficult to properly accomplish optical axis alignment, giving rise to a problematic tendency to positional deviation of three RGB light source beams on a screen. In the use of a light emitting element or a semiconductor laser in particular, since a beam diameter and a beam axial position vary with time due to an increase in local temperature or other variations in operating environmental conditions, three RGB light source beams are liable to deviate on a screen. Therefore, with the technique disclosed in the JP-A-2008-309935, the degree of relative deviation with respect to a beam spot diameter is likely to increase to cause misreproduction of colors and attenuation of light intensity. That is, an optimal module structure as a projector light source is not attainable through use of the technique disclosed in the JP-A-2008-309935. Further, this technique requires an increase in component part count due to the provision of such parts as dichroic mirrors, thus disadvantageously causing higher levels of total part cost and assembly cost. 
     It is therefore an object of the present invention to provide a multi-wavelength light emitting device wherein misreproduction of colors and attenuation of light intensity due to axial misalignment can be reduced in projection of light beams having different wavelengths that are superposed at a target position on a screen. 
     The multi-wavelength light emitting device of the present invention includes multiple sections for solving the above-mentioned problem with the conventional technique. The representative features of these sections disclosed by the present invention are briefed below: 
     In carrying out the present invention and according to a specific aspect thereof, there is provided a multi-wavelength light emitting device for addressing the above-mentioned problem, the multi-wavelength light emitting device comprising: a light source section; a condenser lens section; and a light guide section; wherein the light source section is arranged to include multiple luminous points that emit multiple light beams, the condenser lens section is arranged to concentrate the light beams emitted from the luminous points, and the light guide section is arranged to propagate superposedly and mixedly the light beams concentrated by the condenser lens section after emission thereof from the luminous points. The provision of the light guide section thus arranged facilitates optical axial alignment of the light beams, making it possible to reduce misreproduction of colors and attenuation of light intensity due to axial misalignment. 
     Further, according to a preferable aspect of the present invention, at least either one of input and output end faces of the light guide section of the multi-wavelength light emitting device is provided with an optical element. In an arrangement wherein a refracting optical element is disposed at the input end face (light source side) of the light guide section, multiple reflections of the light beams can be repeated efficiently during propagation thereof through a light guiding medium in the light guide section so as to adequately mix the light beams. Contrastingly, in an arrangement wherein a refracting optical element is disposed at the output end face (outlet side) of the light guide section, the light beams issued from the light guide section can be collimated so as to display high-definition color images on a screen located at a distance of approximately one meter in the case of RGB light source, for example. The term “optical element” as used herein indicates a component element that exerts any optical effect (e.g., reflection, transmission, refraction, or diffraction) on a light beam applied thereto; more specifically, an optical element is a lens or a diffraction grating, for example. 
     Still further, according to another preferable aspect of the present invention, the light source section, the condenser lens section, and the light guide section of the multi-wavelength light emitting device are contained in one modular package, which is mounted on a can-stem. This arrangement makes it possible to form a small type of multi-wavelength light emitting device featuring general versatility. 
     Furthermore, according to another preferable aspect of the present invention, the light guide section of the multi-wavelength light emitting device has an internal structural component that is selected from an optical fiber cable, a bundle optical fiber cable, liquid crystalline fiber cable, a light guide plate, a light tunnel, and a light pipe. 
     Moreover, according to another preferable aspect of the present invention, the light source section of the multi-wavelength light emitting device includes multiple light source components each of which is selected from a semiconductor laser and a semiconductor light emitting element. This arrangement makes it possible to implement small-sized optics capable of displaying color images on a screen in the case of RGB light source, for example. 
     Still further, according to another preferable aspect of the present invention, the light source section of the multi-wavelength light emitting device includes multiple light source components each of which is selected from a wavelength conversion laser (second-harmonic-generation (SHG) laser) formed with a fundamental-wave semiconductor laser and a nonlinear crystal part serving as a wavelength conversion element, a semiconductor laser, and a semiconductor light emitting element (light emitting diode (LED)). This arrangement is advantageous in that each color light source having a single wavelength provides a high level of color purity and a high degree of coherence to allow easy beam shaping (convergence), thus making it possible to display high-definition color images on a screen. 
     Still further, according to another preferable aspect of the present invention, each of the light source components is mounted by using a multilayer laminate substrate. More specifically, it is preferable to provide a recess in a top layer of the multilayer laminate substrate and to mount optical elements such as light emitting elements and mirror elements by using an inner wiring layer. Since signal wiring connections to the light source components are simplified, it is possible to reduce the size of each light source unit including lenses and other optical parts. 
     Still further, according to another preferable aspect of the present invention, the nonlinear crystal part included in the wavelength conversion laser is mounted by using a multilayer laminate substrate. This arrangement allows connections between wiring lines of the multilayer laminate substrate and temperature control terminals of the nonlinear crystal part, contributing to facilitation in assembly process. 
     In addition, according to another preferable aspect of the present invention, the multi-wavelength light emitting device is arranged in combination with MEMS mirror optical components to configure an image projector. The image projector thus configured is applicable as an optical engine for a raster-scan display device. 
     As set forth hereinabove and according to the present invention, in the multi-wavelength light emitting device that superposes light beams having different wavelengths at a target position on a screen, it is possible to reduce misreproduction of colors and attenuation of light intensity due to axial misalignment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram of a multi-wavelength light emitting device according to a first preferred embodiment of the present invention; 
         FIGS. 2A to 2D  are diagrams for explaining the principle of how to suppress optical axial misalignment by using multiwavelength light sources in the present invention, in which  FIG. 2A  shows a spectrum of light intensity with respect to a beam diameter in projection of spatially propagating light from a conventional multi-wavelength light emitting device,  FIG. 2B  shows on-screen beam positioning in projection of three RGB light source beams propagating spatially from the conventional multi-wavelength light emitting device,  FIG. 2C  shows a spectrum of light intensity with respect to a beam diameter in projection of light propagating through a light guide section of the present invention, and  FIG. 2D  shows on-screen beam positioning in projection of three RGB light source beams propagating through the light guide section of the present invention; 
         FIG. 3  is a diagram for explaining the outline of the multi-wavelength light emitting device according to a second preferred embodiment of the present invention; 
         FIG. 4  is a diagram for explaining the outline of an image projector using the multi-wavelength light emitting device according to a third preferred embodiment of the present invention; 
         FIG. 5  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a fourth preferred embodiment of the present invention; 
         FIG. 6  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a fifth preferred embodiment of the present invention; 
         FIG. 7  is a diagram for explaining the outlines of a nonlinear crystal part and a holding part therefor of a wavelength conversion laser in the multi-wavelength light emitting device according to the fifth preferred embodiment of the present invention; 
         FIG. 8  is a diagrammatic perspective view of the light source section in the multi-wavelength light emitting device according to the fifth preferred embodiment of the present invention; 
         FIG. 9  is an exploded perspective view of a multilayer laminate substrate according to the fifth preferred embodiment of the present invention; 
         FIG. 10  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a sixth preferred embodiment of the present invention; 
         FIG. 11  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a seventh preferred embodiment of the present invention; 
         FIG. 12  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to an eighth preferred embodiment of the present invention; and 
         FIG. 13  is a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a ninth preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in detail by way of example with reference to the accompanying drawings as related to structural and functional features of a variety of preferred embodiments thereof. Throughout the accompanying drawings, like reference characters designate like or corresponding parts to avoid repetitive description thereof. It is to be understood that parts described hereinbelow are not necessarily depicted in accurate dimensional ratios in the accompanying drawings. 
     First Preferred Embodiment 
     Referring to  FIG. 1 , the structure of a multi-wavelength light emitting device according to a first preferred embodiment of the present invention is described below. With reference to  FIGS. 2C and 2D , there is also described below an arrangement for light beam propagation through a light guide section after emission from a multiwavelength light source. 
       FIG. 1  shows the structural arrangement of the multi-wavelength light emitting device according to the first preferred embodiment. In  FIG. 2C , there is shown a spectrum of light intensity with respect to a beam diameter in projection of light propagating through the light guide section of the present invention, and in  FIG. 2D , there is shown on-screen beam positioning in projection of three RGB light source beams propagating through the light guide section of the present invention. 
     In the first preferred embodiment, a multi-wavelength light emitting device  800  includes a light source section  100 , a condenser lens section  10 , and a light guide section  1 . 
     The light source section  100  includes multiple luminous points, i.e., a red light source unit (lens  101 R, light emitting element  102 R, submount  103 R), a blue light source unit (lens  101 B, light emitting element  102 B, submount  103 B), and a green light source unit (lens  101 G, light emitting element  102 G, submount  103 G). Each of these three light source units is mounted on one of three side faces of a square-pole-like protrusion stage  9  that is disposed to protrude perpendicularly from a stem retained by a stem holder  8 . In the red light source unit, taken as a representative example of the three light source units, the submount  103 R having the light emitting element  102 R mounted thereon is secured to one side face of the protrusion stage  9  on the stem so that the light emitting element  102 R emits light in the protruding direction of the protrusion stage  9  on the stem, i.e., in the upward direction in  FIG. 1 . At an upper position with respect to the submount  103 R, the lens  101 R is secured on an optical axis in an emitting direction of the light emitting element  102 R. Thus, the light source section  100  is disposed in a space of a cylindrical cover holder  7  secured to the stem. 
     The condenser lens section  10  includes a condenser lens  11 , and a lens holder  12 ; and the condenser lens section  10  is supported by the cover holder  7 . 
     The light guide section  1  includes a collimating optical element (collimating lens)  2  serving for collimation at light emission, a light guiding medium  3 , and a sleeve  4 ; and the light guide section  1  is supported by a cover holder  5 . 
     As indicated by the arrowed lines in  FIG. 1 , the condenser lens  11  concentrates multiple light beams emitted from the multiple luminous points which forms the light source section  100  to introduce thereof into the light guide section  1 . 
     Through the light guiding medium  3  included in the light guide section  1 , each of the multiple light beams thus introduced thereinto propagates while repeating multiple reflections. 
     At output from the light guide section  1 , a single light beam is formed as a result of mixing the multiple light beams through the light guiding medium  3  (refer to  FIGS. 2C and 2D ). Thus, the emission light beam from the light guiding medium  3  is collimated through the collimating lens  2  for light emission. 
     In the multi-wavelength light emitting device shown in  FIG. 1 , the multiple light beams emitted from the three RGB light sources are concentratedly introduced into the light guide section so as to align the axes of the light beams. As compared with the technique for axial adjustment by using two dichroic mirrors disclosed in the patent document JP-A-2008-309935, a relatively low degree of accuracy is therefore required for axial adjustment in the multi-wavelength light emitting device according to the first preferred embodiment. Thus, in the use of the multi-wavelength light emitting device that superposes light beams having different wavelengths at a target position of projection, it is possible to reduce misreproduction of colors and attenuation of light intensity attributable to axial misalignment. Further, substantial reductions in component part count and assembly cost can be achieved advantageously according to the first preferred embodiment. 
     Second Preferred Embodiment 
     Referring to  FIG. 3 , there is shown a diagram for explaining the outline of the multi-wavelength light emitting device according to a second preferred embodiment of the present invention. 
     In the second preferred embodiment, a multi-wavelength light emitting device  800   a  includes a light source section  100 , a condenser lens section  10 , and a light guide section  1 . The light source section  100  and the condenser lens section  10  are arranged similarly to those of the first preferred embodiment. 
     Differently from the case of the first preferred embodiment wherein the light guiding medium  3  is formed in a short cylindrical shape, an optical fiber cable is used as a light guiding medium  3   a  in the second preferred embodiment as shown in  FIG. 3 . Since the optical fiber cable used as the light guiding medium  3   a  has a small diameter, there is disposed a sleeve  4   a  having a relatively large thickness in the radial direction thereof. 
     Regarding the light guiding medium  3   a , the length of propagation can be increased by using an optical fiber cable having a longer length so that the multiple light beams are mixed adequately through the optical fiber cable. Thus, a single light beam having a uniform intensity distribution is emitted from the light guiding medium  3   a . It is to be noted that, even in the use of an optical fiber cable having a considerable length, the optical fiber cable can be contained in a limited space by neatly arranging the optical fiber cable in a coiled form as shown in  FIG. 3 . 
     In the second preferred embodiment, a collimating lens  2   a  is disposed at the output end face of the light guiding medium  3   a  similarly to the case of the first preferred embodiment. Thus, a collimated light beam is issued from the light guide section  1 . In addition to the advantageous effects of the first preferred embodiment, a uniform level of light intensity distribution is provided in the second preferred embodiment. Hence, according to the second preferred embodiment, it is possible to suppress color variations and luminance variations in a beam spot. 
     Third Preferred Embodiment 
     Referring to  FIG. 4 , there is shown a diagram for explaining the outline of an image projector using the multi-wavelength light emitting device according to a third preferred embodiment of the present invention. 
     In the third preferred embodiment, an image projector cabinet  901  contains the multi-wavelength light emitting device  800 , a beam scanning section  903  having MEMS mirror optics, and a beam outlet  902 . 
     The multi-wavelength light emitting device  800  is the same as that used in the first or second preferred embodiment. More specifically, the stem holder  8  of the multi-wavelength light emitting device  800  is secured to the image projector cabinet  901  in a fashion that lead pins are arranged to protrude from the stem. The beam scanning section  903  includes MEMS mirror optical components. 
     A light beam issued from the multi-wavelength light emitting device  800  is raster-scanned by the beam scanning section  903  for RGB image formation. Thus, through the beam outlet  902 , RGB light is projected onto a screen  904  to provide color imaging thereon. 
     Since the multi-wavelength light emitting device  800  described in the first or second preferred embodiment is employed in the image projector according to the third preferred embodiment, it is possible to reduce misreproduction of colors and attenuation of light intensity attributable to axial misalignment in image projection where light beams having different wavelengths are superposed at a target position on the screen  904 . Further, substantial reductions in component part count and assembly cost can be achieved advantageously according to the third preferred embodiment. 
     Fourth Preferred Embodiment 
     Referring to  FIG. 5 , there is shown a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a fourth preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the fourth preferred embodiment, there is provided a light source section  200  comprising a red light source unit (lens  201 R, semiconductor laser diode  202 R, submount  203 R), a blue light source unit (lens  201 B, semiconductor laser diode  202 B, submount  203 B), and a green light source unit (light emitting diode (LED) array  204 G). 
     A condenser lens section  10   a , comprising a condenser lens  11   a  and a lens holder  12   a , is supported by a cover holder  7 . The light guide section  1  is arranged similarly to that of the first preferred embodiment. 
     In the green light source unit  204 G according to the fourth preferred embodiment, multiple green light emitting semiconductor elements are integrated in the form of an LED array to produce a high-power level of green light. Further, differently from the case of the first preferred embodiment wherein the three light source units are mounted on the three side faces of the protrusion stage  9  disposed on the stem, the green light source unit  204 G is disposed on the top face of the protrusion stage  9  on the stem while the red and blue light source units are disposed on the side faces thereof in the fourth preferred embodiment. Thus, a larger mounting area is provided for the LED array of the green light source unit  204 G. The configuration mentioned above enables emission of a high-power level of green light. 
     As illustrated in  FIG. 5 , the condenser lens  11   a  concentrates multiple light beams emitted from multiple luminous points included in the light source section  200  for introduction thereof into the light guide section  1 . The other arrangements are similar to those of the first preferred embodiment. 
     Where the multi-wavelength light emitting device according to the fourth preferred embodiment is employed in the image projector according to the third preferred embodiment, it is possible to suppress misreproduction of colors and attenuation of light intensity in on-screen image projection. 
     Fifth Preferred Embodiment 
     Referring to  FIG. 6 , there is shown a diagram for explaining a light source section in the multi-wavelength light emitting device according to a fifth preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the fifth preferred embodiment, a light source section  300  includes a red-light edge-emitting semiconductor laser  306 R, a blue-light edge-emitting semiconductor laser  306 B, and a green-light-emission wavelength conversion laser. The green-light-emission wavelength conversion laser includes a wavelength conversion element (nonlinear crystal part  304 , holding part  303 ), a fundamental-wave infrared edge-emitting semiconductor laser  306 G (wavelength λ=1060 nm), and a right-angle (90° angle) mirror  309  for upward bending of light beams emitted from the edge-emitting semiconductor lasers. For infrared light emitted from the fundamental-wave infrared edge-emitting semiconductor laser  306 G, it is required to perform wavelength control in phase matching with the nonlinear crystal part  304 . For this purpose, a temperature control mechanism is provided additionally. In the above-mentioned wavelength conversion laser where a laser beam having a wavelength of 1060 nm is used as a fundamental wave, a green light beam having a wavelength of 530 nm can be obtained by virtue of the nonlinear effect of second-harmonic generation (SHG). 
     The red-light edge-emitting semiconductor laser  306 R, the blue-light edge-emitting semiconductor laser  306 B, and the fundamental-wave infrared edge-emitting semiconductor laser  306 G included in the green-light-emission wavelength conversion laser are mounted on a multilayer laminate substrate  305  (to be described in detail later). 
     Lenses  307  are provided to serve as collimating lenses for collimation of light beams emitted from the red-light edge-emitting semiconductor laser  306 R and the blue-light edge-emitting semiconductor laser  306 B. In addition, a lens  308  is provided to serve as a condenser lens for introducing a light beam from the infrared edge-emitting semiconductor laser  306 G into the nonlinear crystal part  304 . These lenses  307  and  308  are mounted on the multilayer laminate substrate  305 . 
     The periphery of the holding part  303  is secured to a cover holder  7 , and the holder part  303  is formed in a cylindrical configuration having an arc-segment rectangular-parallelepiped recess with rectangular side faces. The nonlinear crystal part  304  included in the wavelength conversion laser is secured to the rectangular side faces of the holding part  303 . 
     A condenser lens section  10   a , includes a condenser lens  11   a  and a lens holder  12   a , is supported by the holding part  303 . 
     As shown in  FIG. 6 , the condenser lens  11   a  concentrates multiple light beams emitted from multiple luminous points included in the light source section  300  for introduction thereof into the light guide section  1 . 
     The light guide section  1  is arranged similarly to that of the first preferred embodiment. 
     Referring to  FIG. 7 , there is shown a diagram for explaining the outlines of the nonlinear crystal part  304  and the holding part  303  of the wavelength conversion laser in the multi-wavelength light emitting device according to the fifth preferred embodiment. 
     For wavelength conversion through use of the nonlinear crystal part  304 , it is required to provide phase matching between the nonlinear crystal part  304  and fundamental-wave infrared light. In common practice, tuning for phase matching adjustment in a nonlinear crystal part is performed by temperature control. In the fifth preferred embodiment, two temperature control terminals and two temperature monitor terminals, i.e., a total of four terminals, are provided for temperature control of the nonlinear crystal part  304 . Since the multilayer laminate substrate  305  is used as a submount in the fifth preferred embodiment, temperature control wiring lines can be laid in a high-density low-noise arrangement without the need for intricate wiring line routing. 
     The holding part  303  having the nonlinear crystal part  304  mounted thereon is secured to the cover holder  7  as shown in  FIG. 6 . 
     Referring to  FIGS. 8 and 9 , there are shown explanatory diagrams regarding a mounting arrangement of multiple light sources in the multi-wavelength light emitting device according to the fifth preferred embodiment.  FIG. 8  shows a diagrammatic perspective view of the light source section in the multi-wavelength light emitting device, and  FIG. 9  shows an exploded perspective view of the multilayer laminate substrate  305 . 
     The multilayer laminate substrate  305  shown in  FIG. 8  is a low-temperature co-fired ceramics (LTCC) substrate. The red-light edge-emitting semiconductor laser  306 R, blue-light edge-emitting semiconductor laser  306 B, infrared edge-emitting semiconductor laser  305 G, and right-angle mirror  305   f  are mounted on a first layer  305   c  of the multilayer laminate substrate  305 . A second layer  305   b  serving as a spacer is disposed over the first layer  305   c , and further a third layer  305   a  is disposed thereover. 
     As shown in  FIG. 9 , using a stepped recess formed on the third layer  305   a , a plate lid having the collimating and condenser lenses is secured to the third layer  305   a . More specifically, the plate lid is sealingly secured to the upper-stage recess of the third layer  305   a . Instead of using the stepped recess formed on the third layer  305   a , there may also be provided a modified arrangement wherein the third layer  305   a  is configured to have a recess larger than a recess of the second layer  305   b  so that an inner peripheral edge of the recess of the second layer  305   b  is exposed through the recess of the third layer  305   a , and wherein the plate lid is secured to the inner peripheral edge of the recess of the second layer  305   b . In this modified arrangement, the second layer  305   b  should be arranged to provide adequate sealing space for serving as a spacer capable of protecting the semiconductor lasers, i.e., the second layer  305   b  should have a larger thickness, and the recess thereof should have a depth larger than the heights of optical components such as the semiconductor lasers and the right-angle mirror  305   f  to be disposed inside the recess. 
     As shown in  FIG. 8 , on the multilayer laminate substrate  305 , optical devices and components may be mounted after the first layer  305   c , second layer  305   b , and third layer  305   c  are assembled. 
     Sixth Preferred Embodiment 
     Referring to  FIG. 10 , there is shown a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a sixth preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the sixth preferred embodiment, a light source section  400  includes a blue-light edge-emitting semiconductor laser ( 403 B), a green-light-emission wavelength conversion laser (fundamental-wave infrared edge-emitting semiconductor laser  403 G, nonlinear crystal part  401 ), and a red-light-emission wavelength conversion laser (fundamental-wave infrared edge-emitting semiconductor laser  403 R, nonlinear crystal part  401 ). Light beams emitted from the semiconductor lasers are reflected by a right-angle (90° angle) mirror  405  disposed in a multilayer laminate substrate  402  and then output through lenses  404  disposed thereon. 
     In display applications, it is generally regarded as preferable that a red light source should have a wavelength of 620 nm from a viewpoint of color visibility. However, at present, a red light source having a wavelength shorter than 638 nm is not obtainable by using a semiconductor laser. Hence, to provide a red light source having a wavelength of 620 nm in the sixth preferred embodiment, the red-light-emission wavelength conversion laser is employed. Where a fundamental-wave infrared semiconductor laser having a wavelength of 1240 nm is used in wavelength conversion for red light emission, red light having a wavelength of 620 nm can be provided. 
     In the field of wavelength conversion laser technology, significant advances have recently been made to improve the quality of nonlinear crystal material, resulting in the efficiency of conversion exceeding 20%. This level of conversion efficiency of wavelength conversion lasers can be rated as being comparable to that of semiconductor lasers. On account of the characteristics of wavelength conversion lasers, the level of power consumption thereof in a high power output region is commonly recognized to be almost equivalent to that of semiconductor lasers. Hence, there is a growing interest in using wavelength conversion lasers wherein any wavelength is selectable as a light source wavelength as well as a green light source wavelength. 
     In the arrangement shown in  FIG. 10 , only one nonlinear crystal part is used to form two wavelength conversion lasers, i.e., a green-light-emission wavelength conversion laser and a red-light-wavelength conversion laser. Thus, a substantial increase in component part count is not incurred in cases where the arrangement including two wavelength conversion lasers and one semiconductor laser is adopted to provide an RGB light source instead of the foregoing arrangement including one wavelength conversion laser and two semiconductor lasers. 
     In the use of one nonlinear crystal part, temperature control can be carried out collectively. This contributes to a decrease in the number of wiring terminals as compared with the case where multiple nonlinear crystal parts are subjected to temperature control. 
     As can be seen from  FIG. 10 , it is allowed to arrange multiple wavelength conversion lasers in an array form to meet the purpose of application, e.g., the sixth preferred embodiment is applicable to a requirement level of high power output exceeding the order of 10 W. 
     The other arrangements are similar to those of the fifth preferred embodiment. 
     Seventh Preferred Embodiment 
     Referring to  FIG. 11 , there is shown a diagram for explaining the outline of a light source section in the multi-wavelength light emitting device according to a seventh preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the seventh preferred embodiment, a light source section  500  includes a blue-light surface-emitting semiconductor laser ( 503 B), a green-light-emission wavelength conversion laser (fundamental-wave infrared surface-emitting semiconductor laser  503 G, nonlinear crystal part  501 ), and a red-light-emission wavelength conversion laser (fundamental-wave infrared surface-emitting semiconductor laser  503 R, nonlinear crystal part  501 ). Light beams emitted from the semiconductor lasers are output through lenses  504  and  508  disposed on a multilayer laminate substrate  502 . 
     The term “surface-emitting semiconductor laser” as used herein indicates VCSEL (Vertical-Cavity Surface-Emitting Laser), HCSEL (Horizontal-Cavity Surface-Emitting Laser), or LISEL (Lens Integrated Surface-Emitting Laser). 
     As shown in  FIG. 11 , no right-angle mirror is required in the light source arrangement of the multi-wavelength light emitting device according to the seventh preferred embodiment, thereby leading to a decrease in component part count. 
     The other arrangements are similar to those of the fifth preferred embodiment. 
     Eighth Preferred Embodiment 
     Referring to  FIG. 12 , there is shown a diagram for explaining the outline of a light source section in the multiwavelength apparatus according to an eighth preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the eighth preferred embodiment, a light source section  600  includes a red-light edge-emitting semiconductor laser  603 R, a blue-light edge-emitting semiconductor laser  603 B, and a green-light surface-emitting element  603 G. In a multilayer laminate substrate  602 , there are provided a right-angle (90° angle) mirror  602  and lenses  604  through which light beams are output. 
     Since the red-light and blue-light edge-emitting semiconductor lasers  603 R and  603 B are provided as shown in  FIG. 12 , the right-angle mirror  605  is used for upward bending of light beams emitted from these edge-emitting semiconductor lasers. Contrastingly, for the green-light surface-emitting element  603 G, it is not required to use a right-angle mirror. As the green light source in the eighth preferred embodiment, there may also be provided such a modified arrangement that green light emitting elements are formed in an array to meet particular application specifications. 
     The other arrangements are similar to those of the fifth preferred embodiment. 
     Ninth Preferred Embodiment 
     Referring to  FIG. 13 , there is shown a diagram for explaining a light source section in the multi-wavelength light emitting device according to a ninth preferred embodiment of the present invention. 
     In the multi-wavelength light emitting device according to the ninth preferred embodiment, a light source section  700  includes a red light source  703 R, a blue light source  703 B, and a green light source  703 G, all of which are of a surface-emitting element type. Light beams emitted from these light sources are output through lenses  704  disposed on a multilayer laminate substrate  702 . 
     In the ninth preferred embodiment wherein all the light sources are of a surface-emitting element type, there is no need to provide a right-angle mirror that is required for upward bending of light beams in the case where edge-emitting semiconductor lasers are used. 
     The other arrangements are similar to those of the fifth preferred embodiment. 
     While the present invention has been described as related to the preferred embodiments wherein the multiwavelength light source is configured as an RGB light source module, it is to be understood that the present invention is not limited thereto. For example, there may also be provided a modified form wherein the multi-wavelength light emitting device includes an arrayed identical-wavelength light source, an arrayed identical-color light source, or a combination thereof.