Patent Publication Number: US-8995481-B2

Title: Light generating system and method

Description:
This is a divisional application of U.S. application Ser. No. 13/272,277, entitled “Light Generating System and Method,” filed on Oct. 13, 2011 which is a continuation of International Application No. PCT/US2010/030912, filed Apr. 13, 2010, which designated the United States and which claims the benefit of U.S. Provisional Application No. 61/168,853, entitled “Light Generating System and Method,” filed on Apr. 13, 2009, all of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a laser system and, in particular embodiments, to a multicolor wavelength light system, e.g., where light of one wavelength can be used to generate light of another wavelength. 
     BACKGROUND 
     A laser is an optical source that emits photons in a coherent beam. Laser light is typically a single wavelength or color, and emitted in a narrow beam. Many materials have been found to have required characteristics to form the laser gain medium needed to power a laser, and these have led to innovations of many types of lasers with different characteristics suitable for different applications. 
     A semiconductor laser is a laser in which the active medium is a semiconductor. A common type of semiconductor laser is formed from a p-n junction, a region where p-type and n-type semiconductors meet. The semiconductor laser is powered by injecting electrical current into the gain region. 
     The gain region is surrounded by an optical cavity. An optical cavity is an arrangement of minors, or reflectors that form a standing wave cavity resonator for light waves. Optical cavities surround the gain region and provide feedback of the laser light. 
     SUMMARY OF THE INVENTION 
     The illustrated embodiments provide an apparatus, a system, and a method to generate red green blue (RGB) or any white laser light. The present invention may also relate to light sources and generated light providing wavelengths from far infrared (IR) to ultra violet (UV). 
     Aspects of the invention provide an efficient method for producing laser light at single or multiple simultaneous wavelengths, which might serve in applications including the compact light engine of a red-green-blue (RGB) module to be incorporated into an image projector. 
     In accordance a preferred embodiment, a method for generating laser light of sequentially differing wavelengths is disclosed. Laser light of a first wavelength is generated from an electrically pumped source. At a first time, the laser light is directed in a first direction, and, at a second time, the laser light is directed in a second direction toward an optically pumped laser source. The laser light directed in the second direction is used to generate laser light with a second wavelength at the optically pumped laser source. 
     In accordance with another preferred embodiment of the present invention, an optical system includes an electrically pumped laser light source and an optically pumped laser light source. The optical system further includes a micro-electro-mechanical system (MEMS) switch located in a light path of the electrically pumped laser light source such that when the optical switch is in a first position, light from the electrically pumped laser light source is directed toward the optically pumped laser light source, and when the optical switch is in a second position, light from the electrically pumped laser light source is directed away from the optically pumped laser light source. 
     In accordance with another preferred embodiment of the present invention, a light engine includes a blue laser source, a green laser source comprising an optically pumped solid state laser and a red laser source. The engine further includes an optical switch in an optical path between the blue laser source and the green laser source, wherein, when the optical switch is in a first position, light from the blue laser source is directed toward the optically pumped solid state laser and, when the optical switch is in a second position, light from the blue laser source is directed toward an optical output. Furthermore, the light engine includes an optical device in an optical path of the red laser source, the optical device directing light from the red laser source toward the optical output. 
     In accordance with yet another preferred embodiment of the present invention, an optical system includes a first infrared laser light source and a second infrared laser light source. A first optical component generates visible light of a first color from light from the first and second infrared laser light sources, a second optical component generates visible light of a second color from light from the first and second infrared laser light sources, and a third optical component generates visible light of a third color from light from the first and second infrared laser light sources. An optical switch is coupled between the first and second infrared laser light sources and the first, second and third optical components to sequentially direct light from the first and second infrared laser light sources toward the first, second and third optical components. 
     Other embodiments and refinements of the above-discussed embodiments are also disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is an architecture of an optical system comprising three semiconductor lasers; 
         FIG. 2   a  describes how light from two infrared laser sources can be combined to do two-photon up-conversion; 
         FIG. 2   b  is an energy level diagram showing how two infrared photons can be used to pump an excited state, when can then emit green laser light; 
         FIG. 3  is an architecture of an optical system comprising two semiconductor lasers; 
         FIG. 4  is an architecture of an optical system comprising one semiconductor laser; 
         FIG. 5  is another embodiment architecture of an optical system comprising two semiconductor lasers; 
         FIG. 6  is another embodiment architecture of an optical system comprising one semiconductor laser; 
         FIG. 7 , which includes  FIGS. 7   a  and  7   b , is an architecture showing pumping optical materials with two infrared lasers; 
         FIG. 8  is another embodiment architecture showing pumping optical materials with two infrared lasers; and 
         FIG. 9  is an optical diagram of a projector application. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention. 
     The present invention will be described with respect to preferred embodiments in a specific context, namely an optical system with novel architectures of semiconductor lasers to efficiently generate multi-colored light, e.g., red green blue (RGB) or white light. The invention may also be applied, however, to other optical systems with lasers and light sources other than semiconductor lasers. Further, the invention still may also be applied to light sources providing wavelength from far infrared (IR) to ultra violet (UV). 
     As will be discussed in more detail below, the present invention discloses a number of novel architectures to generate efficient RGB light in a module. For example, a first architecture uses two semiconductor lasers emitting in the red and blue. The green light is generated by optically pumping a solid state laser. The solid state laser may be, but is not limited to, a Praseodymium ion-doped host material, which may be YLF, glass, crystal, polymer, ceramic, or other adequate host material. The solid state laser is directly pumped by a semiconductor pump source. 
     A second architecture uses two semiconductor lasers emitting in the red and blue. The green light is generated by optically pumping a solid state laser. The solid state laser may comprise, but not limited to, a Pr doped crystal/material, which may be YLF or glass or other adequate host materials. The solid state laser is directly pumped by the blue light source, whereas the beam can be re-directed via a mirror, e.g., a MEMS minor, that is transparent to green and reflects blue. By this the blue light source is used either as a pump source to generate green or directed to the output of the module. 
     A third architecture uses only one semiconductor laser, e.g., blue and the beam can be re-directed either in the direction to serve as a pump for the green DPSS or red DPSS or directly to the output of the module. Again, the visible DPSS maybe constructed in a similar way as in the first and second architectures. An additional minor, one that is transparent to red and reflects blue and green, is used. Each of these embodiments will be discussed in more detail below. 
     The optical system may be arranged in a stand alone system or module. In fact, the optical system may be arranged in any desired way. 
     In one embodiment, semiconductor lasers may serve as pump sources to excite dopant ion species in a host material to an elevated energy level and thus allowing spontaneous or stimulated photo emission at one or more wavelengths. These wavelengths correspond to transitions from the elevated energy level to one of the discrete lower energy levels characteristic to the specific dopant ion species. 
     The semiconductor pump source may employ a shorter wavelength (higher photon energy) than the wavelength emitted from the solid state laser to directly elevate the dopant ion to the desired high energy state with a single photon. This results in a single photon down-conversion between the pump and the emitted laser wavelength. 
     Alternatively, the semiconductor pump source may employ two or more longer wavelengths each with lower photon energy than the desired wavelength emitted from the solid state laser, thus indirectly elevating the dopant ion in multiple intermediate steps to the desired high energy state through multiple photon absorption. This results in a multi-photon up-conversion between the pump and the emitted laser wavelength. 
     For either method of optical pumping, the net result is that an ion is elevated to a specific higher energy level that corresponds to the desired laser output wavelength when the ion transitions to a lower energy level either through spontaneous or through stimulated emission. 
     The embodiment has the advantage that the ion transition from the higher to lower energy level may produce the final output wavelength needed for the application. The stimulated emission has further the advantage to eliminate the need for additional wavelength conversion, for instance, by second harmonic generation to obtain the needed final wavelength. 
     With reference now to  FIG. 1 , a first architecture of an optical system  100  to generate an efficient RGB light is shown. The optical system  100  includes a first semiconductor laser  101 , a second semiconductor laser  102 , and a laser  103 . The first semiconductor laser  101  may typically be a conventional diode laser but any other semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) or vertical-external cavity surface emitting laser (VECSEL) may be suitable. The first semiconductor laser  101  may comprise GaAs, AlGa x Ga (1-x )As or any other suitable material. The first semiconductor laser  101  may comprise a distributed Bragg reflector (DBR) laser, distributed feedback (DFB) lasers, Fabry Perot lasers, fiber Bragg grating lasers, or volume Bragg lasers. The first semiconductor laser  101  may emit red light or blue light. Alternatively, laser  101  may emit light of any other color including UV and far IR. 
     The second semiconductor laser  102  may typically be a conventional diode laser but any other semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) or vertical-external cavity surface emitting laser (VECSEL) may be suitable. The second semiconductor laser  102  may comprise GaAs, Al x Ga (1-x) As or any other suitable material. The second semiconductor laser  102  may comprise a distributed Bragg reflector (DBR) laser, distributed feedback (DFB) lasers, Fabry Perot lasers, fiber Bragg grating lasers, or volume Bragg lasers. The second semiconductor laser  102  may emit red light or blue light. Alternatively, semiconductor laser  102  may emit light of any other color including UV and far IR. Semiconductor laser  102  is configured to emit a different light than semiconductor laser  101 . For example, if semiconductor laser  102  emits blue light semiconductor laser  101  emits red light. 
     Laser  103  may be an optically pumped solid state laser or an infrared laser. However, any other laser may be suitable. Laser  103  may emit green light. Alternatively, laser  103  may emit light of any other color. Laser  103  is configured to emit a different light than semiconductor laser  101  and/or semiconductor laser  102 . For example, if laser  103  emits green light semiconductor laser  101  emits red light and semiconductor laser  102  emits blue light. 
     The laser  103  may be an optically pumped solid state laser, e.g. a crystal laser. The gain medium of the solid state laser may comprise, but is not limited to, a praseodymium ion-doped host material, which may be yttrium lithium fluoride (YLF), glass, crystal, polymer, ceramic or other adequate host materials. 
     In one embodiment, the solid state laser  103  may be pumped by a semiconductor laser  120 . The semiconductor laser  120  may be directly attached to the solid state laser  103 . The semiconductor laser  120  may comprise the same types and materials as the semiconductor lasers  102  and  103  and may emit preferably blue light. 
     In another embodiment, the laser  120  may be an infrared laser.  FIG. 2   a  shows an arrangement that includes a first infrared laser  222  and a second infrared laser  224 . Light from each of these lasers is combined in optical component  226 , which transmits light from laser  222  and reflects light from laser  224  toward lens  228 .  FIG. 2   b  shows an energy level diagram showing how two infrared photons can be used to pump an excited state, when can then emit green laser light. As will be discussed below, other colors could be generated from the lasers. 
     Returning to  FIG. 1 , the optical system  100  further comprises focusing lenses  104 ,  105  which focus the emitted light beams. An output coupler  106  may be placed in the output light beam of the solid state laser  103 . The output coupler  106  may reflect the light or energy that is not absorbed by the solid state laser  103  in order to increase optical efficiency. 
     The optical system  100  also includes minors  108  and  110 . For example, the minor  108  may reflect the focused red light of laser  101  towards the output  112  and, similarly, the minor  110  may reflect the focused blue light of laser  102  towards the output  112 . Minor  108  is transparent for the green light emitted by laser  103  and the blue light emitted by laser  102  so that the green and blue light can propagate towards output  112 . Similarly, mirror  110  is transparent for the green light emitted by laser  103 . 
       FIG. 3  shows an embodiment of an optical system  300 . In this embodiment similar numerals will be used for similar elements of previous embodiments. The optical system  300  comprises a first semiconductor laser  301 , a second semiconductor laser  302  and a solid state laser  303 . The first laser  301 , the second laser  302  and the solid state laser  303  may comprise similar types of and similar materials as disclosed with respect to the arrangement disclosed in  FIG. 1 . In this figure, along with later figures, the lasers are labeled with R, G and B only to simplify the understanding of operation. It must be understood that the lasers can be interchanged and other, more or fewer colors can be used. 
     The optical system  300  further comprises focusing lenses  304 ,  305  which focus the emitted light beams. An output coupler  306  may be placed in the output light beam of the solid state laser  303 . The output coupler  306  may reflect the light or energy that is not absorbed by the solid state laser  303  in order to increase optical efficiency. 
     Optical switch element  330  may be a movable wavelength selective element or optical mirrors. As one example, the optical switch element  330  can be a MEMS minor. The optical switch element  330  may direct the focused beam of semiconductor laser  302  towards the solid state laser  303  or towards an output  312 . In other words, the position of a minor of a optical switch element  330  can be switched. The optical switch element  330  may be controlled by a controller (not shown; see, e.g.,  FIG. 9 ). 
     If the optical switch element  330  directs the focused beam of semiconductor laser  302  towards the solid state laser  303  and the solid state laser  303  may produce green light. Accordingly, the optical switch element  330  and the mirror  308  are transparent for green light so that the green light, when emitted, can propagate towards the output  312 . 
     The green light is generated by optically pumping the solid state laser  303 . The solid state laser  303  is directly pumped by the second semiconductor laser or the blue light source  302 , where the beam can be redirected via the optical switch element  330  that is transparent to green light and reflective to blue and possibly red light. With such an arrangement the second semiconductor laser  302  is used either as a pump source to generate green light with solid state laser  303  or as a blue light source directed to the output  312  of the optical system  300 . 
       FIG. 4  shows another embodiment of an optical system  400 . Once again, similar numerals will be used for similar elements of previous embodiments. The optical system  400  comprises a semiconductor laser  402 , a first solid state laser  450  and a second solid state laser  403 . The semiconductor laser  402 , the first solid state laser  450  and the second solid state laser  403  may comprise similar types of and materials as disclosed with respect to the arrangement disclosed in  FIG. 1 . However, solid state laser  450  may comprise a different material than solid state laser  403 .  FIG. 4  shows only one semiconductor laser  402 , which may emit a blue laser light. The beam of semiconductor laser  402  can be redirected either in the direction to serve as pump for the green solid state laser  403  or the red solid state laser  450 . The beam can also be directed directly to the output  412 . 
     The optical system  400  further comprises a focusing lens  405  which focuses the emitted light beams. Output couplers  406 ,  407  may be placed in the output light beam of the solid state lasers  403 ,  450 . The output couplers  406 ,  407  may reflect the light or energy that is not absorbed by the solid state lasers  403 ,  450  in order to increase optical efficiency. 
     Optical switch elements  430 ,  440  may be MEMS mirrors or other types of micro-electronic actuators. The optical switch element  430  may direct the focused beam of semiconductor laser  402  towards the second solid state laser  403 . The optical switch element  430  may be transparent for the focused green light of solid second state laser  403  and reflective for the focused blue light of the semiconductor laser  402 . 
     The optical switch elements  430 ,  440  may direct the focused beam of semiconductor laser  402  towards the first solid state laser  450 . The optical switch element  440  may be reflective for the focused blue light of the semiconductor laser  402 . The optical switch element  440  may also be reflective for the focused green light of the second solid state laser  403  and transparent for the focused red light of the first solid state laser  450 . The optical switch element  430  may be different from the optical switch element  440 . In other words, the positions of the minor of the optical switch elements  430 ,  440  may be switched. The optical switch elements  430 ,  440  may be controlled by a controller (not shown). 
     Red light is generated by optically pumping the first solid state laser  450 . Green light is generated by optically pumping the second solid state laser  403 . The solid state lasers  403 ,  450  may be directly pumped by the semiconductor laser or the blue light source  402 . The beam of the semiconductor laser can be redirected via optical switch elements  430 ,  440  either to the first solid state laser  450  or the second solid state laser  403 . With such an arrangement the semiconductor laser  402  can be used either as a pump source to generate green and red light with solid state lasers  403 ,  450  or as a blue light source directed to the output  412  of the optical system  400 . 
       FIGS. 5 and 6 , which resemble  FIG. 3  and  FIG. 4 , respectively, show that blue source can optically generated. In these embodiments similar numerals are used for similar elements of previous embodiments. However,  FIGS. 5 ,  6  show optical systems using high power semiconductor lasers, e.g. lasers with an output of more than 7 Watts. 
       FIG. 5  shows an optical system  500  comprising two high power semiconductor lasers, i.e., a first semiconductor laser  301  and a second semiconductor laser  560 ,  570 . The first semiconductor laser  301  may provide a red high power laser beam and the second semiconductor laser  560 ,  570  may provide a blue high power laser beam. The second semiconductor laser  560 ,  570  may comprise a semiconductor laser  570  emitting light within the infra red spectrum or, in a particular example, within the spectrum of 9xx nm. The emitted light of the semiconductor laser  570  is converted by the optical converter  560  using second harmonic generation (SHG) or frequency doubling. The optical converter  560  may convert the incoming beam by a non-linear optical process, in which photons interacting with a nonlinear material are effectively “combined” to form new photons with twice the energy, i.e. twice the frequency but half the wavelength of the initial photons. The red laser beam can be either produced directly from a semiconductor, or it can be produced from an infrared laser and converted to red through second harmonic generation using a non-linear optical crystal, such as periodically poled lithium niobate (PPLN). 
       FIG. 6  shows an optical system  600  wherein the high power semiconductor laser  660 ,  670  resembles the features of high power semiconductor laser  560 ,  570 . However,  FIG. 6  shows an optical system  600  wherein only one high power semiconductor light source  660 ,  670  is used in order to provide RGB or white light. RGB or white light is provided by “redirecting beams” of the high power semiconductor light source  660 ,  670  using solid state lasers  403 ,  450 . 
       FIG. 7   a  shows an optical system  700  where each of the visible light producing lasers  703 ,  750  and  751  are optically pumped lasers that are excited by infrared lasers  720  and  722 . For example, IR1 and IR2 together can be considered a “blue equivalent” in that the sum of the reciprocals of their photon energies is equal to the reciprocal of the photon energy of the blue photon. 
     In one example, the optical component  750  generates light of a first color, e.g., red, from light from the infrared laser light sources  720  and  722 , the optical component  703  generates light of a second color, e.g., green, from light from the infrared laser light sources  720  and  722 , and the optical component  751  generates light of a third color, e.g., blue, from light from the infrared laser light sources  720  and  722 . While RGB components are discussed, it is understood that other colors and a different number of colors could alternatively be produced. (This same caveat applies to all of the embodiments described herein.) 
     An optical switch  780  is coupled between the first and second infrared laser light sources  720  and  722  and the first, second and third optical components  703 ,  750  and  751  to sequentially direct light from the infrared laser light sources toward the optical components. For example, the configuration of  FIG. 2   a  could be used to generate a light source with multiple wavelengths that could be directed to one or more of the other optical components. For example, the architecture of  FIG. 6  could be used where the infrared light generates one of the visible wavelengths, which is in turn used to generate the other wavelengths. 
       FIG. 7   b  shows one particular embodiment of the architecture of  FIG. 7   a . In this example, the optical switch  780  includes a beam combiner  740  and three optical elements  730 ,  732  and  734 . During operation, the light from the IR laser light sources  720  and  722  are directed toward the beam combiner  740 , from which they are combined and directed toward optical element  730 . The optical element  730  will be configured to either transmit the combined light wave toward the blue laser  751  or reflect the combined light toward optical switch element  732 . For example, the optical element  730  can be an optical switch, e.g., a MEMS device, that is reflective when impinged upon at one surface and transmissive when impinged upon a second surface. 
     The light that is directed down the laser light source  751  will be used to optically pump the source  751  to generate light that can be output to minor  712 . The light reflected toward optical element  732  will be either redirected to laser light source  703  or transmitted to optical element  734 . The configuration of the optical element  734  can be identical (in function and/or form) to that of optical element  730 . The optical element  734  can be a mirror (since in the three color system there is no additional laser light source). 
     An advantage of the architecture of  FIG. 7  is that relatively inexpensive semiconductor lasers can be used for the infrared sources  720  and  722 . These relatively inexpensive light sources could then be used to generate light at a desired wavelengths without need for more expensive lasers. 
       FIG. 8  shows a further embodiment that similar to that of  FIG. 7 . In this example, two IR lasers  720  and  722  of different wavelengths alternately pump a green optically pumped laser  751  and a blue optically pumped laser  703 . A red laser light source  755  is also included. Red lasers are sufficiently well developed so that this embodiment is a cost-effective alternative. 
     In the embodiments of  FIGS. 7 and 8 , there are a number of possibilities on how to implement the infrared lasers  720  and  722 . In a first example, one laser is wavelength stabilized (which could be either distributed Bragg reflector, distributed feed back, fiber Bragg laser or volume Bragg grating, as examples) and the other is a free running (e.g., Fabry Perot) laser. In a second example, both lasers are wavelength stabilized. In a third example; both lasers are free running, but at least one of them should to be temperature stabilized to keep the wavelength from drifting. 
     In each of the previous architectures, the semiconductor pump source serves to excite the dopant ion species in the host material to an elevated energy level thus allowing spontaneous or stimulated photon emission at one or more wavelengths. These wavelengths correspond to transitions from the elevated energy level to one of the discrete lower energy levels characteristic to the specific dopant ion species. 
     The semiconductor pump source may employ a shorter wavelength (higher photon energy) than the wavelength emitted from the solid state laser to directly elevate the dopant ion to the desired high energy state with a single photon. This results in single photon down-conversion between the pump and emitted laser wavelength. 
     Alternately, the semiconductor pump source may employ two or more longer wavelengths each with lower photon energy than the desired wavelength emitted from the solid state laser, thus indirectly elevating the dopant ion in multiple intermediate steps to the desired high energy state through multiple photon absorption. This results in multi-photon up-conversion between the pump and emitted laser wavelength. 
     For either method of optical pumping, the net result is that an ion is elevated to a specific high energy level that corresponds to the desired laser output wavelength when the ion transitions to a lower energy level either through spontaneous or stimulated emission. 
     One advantage to either pumping method is that the ion transition from the higher to lower energy level produces the final output wavelength needed for the application directly from the solid-state laser, thus eliminating the need for additional wavelength conversion (for instance by second harmonic generation) to obtain the needed final output wavelength. 
     As one example, these architectures will enable compact and efficient RGB sources for handheld display units using direct laser output wavelengths thus bridging the “green gap” that describes the current lack of green semiconductor laser sources for display applications. These architectures also enable RGB laser output that could form white light from a common laser material. 
     The light engines described above can be used in a number of systems. One example will be described with respect to  FIG. 9 , which shows a simplified block diagram of a display system. For example, the system of  FIG. 9  could be used for a pico projector since the light engine  800  can have a very small form factor. 
     The light engine  800  can be implemented with any of the embodiments described above. For example, the light engine can generate red, blue or green laser light sequentially or at the same time. Light generated by the light engine  800  is directed toward a spatial light modulator  804 , where it is modulated and redirected toward display  808 . For the sake of simplicity, optics such as mirrors and lenses are not included in the drawing. 
     Spatial light modulator can be either reflective (as shown) or transmissive (in which case the light  806  would be shown as be emitted from an opposite surface of the modulator). In one embodiment, the spatial light modulator is a digital minor device (DMD). In another embodiment, the spatial light modulator is a liquid crystal on silicon (LCOS) device. In a third embodiment, it is a holographic optical element (HOE). 
     A controller  810  is coupled to control both the light engine  800  and the spatial light modulator  804 . The controller  810 , which may include a digital signal processor for example, receives a video signal from a video source (not shown). The controller causes the light engine  800  to sequentially emit red, green and blue light while at the same time causing the spatial light modulator to reflect the desired pattern of the light toward the display  808 . The frequency of the display of the colors is high enough so that the viewer integrates colors to see the desired picture. 
     The display  808  can be either transmissive (e.g., rear projection) or reflective (e.g., front projection). In one example, as noted above, the display  808  can be the display of a pico projector (pocket projector or hand-held projector). In other embodiments, the display can be a television or a projector. 
     A further application of the embodiments of the inventive optical system may be for a laser television. This embodiment can use a light engine as shown in  FIGS. 5 and 6 , for example, to generate the high power required for laser television. Any display configuration, e.g., as shown in  FIG. 8 , could be used with the light engine. 
     While the present invention has been described primarily with respect to the primary colors, it is understood that complementary colors could also be used. The actual colors will be application dependent and may include any color of light, including both visible and invisible light. For example, the invention could produce a hyperspectral source, for example, wherein the laser wavelengths (“colors”) range from UV to far infrared. There could also be more than three colors (or only two colors). For example, a hyperspectral imaging system may require light from the UV to the mid or far IR to provide the discrimination required for certain applications. Such a system may use one UV laser, a red, a green, a blue, plus one in the near IR around 1000 microns, one at 3000 microns, and one at 7000 microns. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.