Abstract:
Disclosed are a light source system and a laser light source ( 300 ). The laser light source includes two groups of laser groups ( 20   a,    20   b ), wherein at least one group of laser groups includes at least two lasers ( 21   a,    21   b,    21   c,    21   d ), and the light beams (L 1 ) generated by the two groups of laser groups are in the same direction and parallel to each other. The first projections of the two groups of laser groups on the cross section of the light beams formed by the respective emergent light rays thereof are partially overlapped with the second projections in a first direction, which first direction is the connection direction of at least two laser centres of a group of laser groups. The laser light source has the effects of being able to effectively increase the light power density and at the same time reduce the volume of the light source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to optical technologies, and in particular, it relates to light source systems and laser light sources. 
         [0003]    2. Description of the Related Art 
         [0004]    In conventional technologies, the light power of a typical single semiconductor laser device is about a few hundred mW, or up to 1-2 W for higher powered ones. It is currently difficult to achieve output power of a few watts or over 10 W for single semiconductor laser devices. 
         [0005]    In some applications that require high power semiconductor lasers, such as projector, stage lighting system, etc., where the required light output is a few tens of watts, arrays of semiconductor lasers may be employed. Conventional semiconductor laser arrays simply arrange semiconductor lasers such as laser diodes in two-dimensional arrays, and use collimating lenses to collimate the light from the laser diodes. 
         [0006]      FIG. 1   a  shows a 4×4 laser diode array. Typical light distribution of a laser diode  11  is an elliptical Gaussian distribution, with a relatively large divergence angle. The collimating lens (not shown) is typically a lens with rotational symmetry, which can collimate the light from the laser diode  11 . 
         [0007]    Also as shown in  FIG. 1   a , conventional laser diode arrangements are typically a planar arrangement with output light in the normal direction, where each laser diode  11  is mounted on a base  12 . The projected area of the base  12  is larger than the area of the corresponding laser diode  11 . The inventors of the present invention discovered through research that such a normal planar arrangement has certain disadvantages as follows: 
         [0008]    Referring to  FIG. 1   b , because the output light distribution of the laser diode  11  is an elliptical Gaussian distribution, an elliptical light spot  13  is formed by the collimating lens (not shown in the drawing), and the area of the elliptical light spot  13  is much smaller than the corresponding projected area  14  of the base  12 . Because the projected area  14  of the base  12  is larger than the corresponding projected area of the laser diode  11 , the density of arrangement of the laser diode  11  cannot be too small; moreover, because the area of the elliptical light spot  13  is much smaller than the corresponding projected area  14  of the base  12 , large gaps are formed between the light spots  13  in the array, so that the light spots  13  cannot be densely packed. Therefore, the light power density is impacted by the size of the base  12  and cannot be further increased. As a result, the advantages of high power density of laser cannot be fully realized. Although the light beams can be focused by focusing lenses into one light spot, the focused light beams are no longer parallel but have relatively large divergent angles, which is disadvantageous to the design of downstream optical systems. 
         [0009]    To increase light power density, Chinese patent CN101937163 provides a light source unit that can achieve a tight packing of laser light spots. As shown in  FIG. 2 , the light source unit  200  includes a light source group  210  and a reflector group  220 . The light source group  210  includes 6 light sources  201 , and each light source  201  is formed by a light emitting device  205  and a collimating lens  207 . The reflector group  220  includes 6 parallel reflectors  225  corresponding to the light sources  201 , to reflect the light beams from the light sources  201  into light beams having smaller spacing between each other. As shown in  FIG. 2 , if the diameter of the collimating lens  207  of the light source  201  is a, and the row space between two light sources is b, then the total column length of the light source group  210  with 6 light sources is 6a+5b. Because the light beams from the collimating lenses  207  of the light sources  201  are parallel lights, the light beam from the light source group  210  has a cross-sectional size of 6a+5b in the column direction of the array. If one reflector  220   e  is used to directly reflect the light beams from the light source group  210  relative to the column direction, the reflected light beam from the reflector  220   e  will have a cross-sectional size of 6a+5b in its column direction. But, if a rectangular reflector  225  is provided for each row of light sources, and the reflectors are arranged in a way that the spacing between adjacent rectangular reflectors  225  is reduced in the direction of the optical axis of the light source group  210 , then the reflected beam from the rectangular reflectors  225  will eliminate the spacing b between the light sources  201  in the light source group  210 . Thus, the length of the reflected beam in its column direction becomes 6a, resulting in more tightly packed laser light spots. 
         [0010]    By studying the conventional technology, the inventors of this invention discovered that, each group of parallel reflectors can only compress light spot spacing in one direction, and the light spot spacing in the other, perpendicular direction is still large. To obtain a light spot array with compressed spacing in both directions, two groups of reflectors are required, increasing the volume of the light source unit and making it inconvenient in actual products. 
       SUMMARY OF THE INVENTION 
       [0011]    Embodiments of the present invention provide a light source system and laser light source which can realize tight packing of the laser light spots, effectively increasing light power density and reducing product size. 
         [0012]    Embodiments of the present invention provide a light source system, including at least one group of light sources, the one group of light sources including: 
         [0013]    two laser groups, at least one laser group including at least two lasers, wherein the light beams generated by each laser group are in the same direction and parallel to each other; 
         [0014]    two reflector groups corresponding to the two laser groups, at least one reflector group including at least two reflectors, each reflector being disposed on the optical axis of a corresponding laser, each reflector group reflecting the light beams generated by the corresponding laser group, wherein the spacing between light beams output from the reflector group is smaller than the spacing between light beams inputted to the reflector group; 
         [0015]    wherein the light beams from the two laser groups are parallel to each other, and the light beams from the two reflector groups are in the same direction and parallel to each other; 
         [0016]    wherein the first projections of the light beams of the two laser groups on their respective cross-sections partially overlap with each other when they are projected in a first direction as second projections, the first direction being along a line connecting the centers of the at least two lasers in one of the laser groups. 
         [0017]    Embodiments of the present invention further provides a laser light source, including two laser groups, at least one laser group including at least two lasers, wherein the light beams from the two laser groups are in the same direction and parallel to each other; wherein the first projections of the light beams of the two laser groups on their respective cross-sections partially overlap with each other when they are projected in a first direction as second projections, the first direction being along a line connecting the centers of the at least two laser in one of the laser groups. 
         [0018]    Embodiments of the present invention further provides a laser light source, including two laser groups, at least one laser group including at least two lasers, wherein the light beams from each of the two laser groups are in the same direction and parallel to each other, and the light beams from the two laser groups are in opposite directions and parallel to each other; two reflector groups for respectively reflecting the light beams generated by the two laser groups, wherein the reflected light of the two laser groups after being reflected by the reflectors are in the same direction and parallel to each other; wherein the first projections of the light beams of the two laser groups on their respective cross-sections partially overlap with each other when they are projected in a first direction as second projections, the first direction being along a line connecting the centers of the at least two laser in one of the laser groups. 
         [0019]    Compared to the conventional technologies, embodiments of the present invention have the following advantages: 
         [0020]    For convenience of description, the partial overlap of the first projections of the two laser groups when they are projected in a first direction as second projections is referred to as the offset arrangement of the laser groups. Using the offset arrangement of the laser diode groups, the spacing of light beams between groups of laser diodes can be compressed. Compared to conventional technologies, it significantly reduces the volume of the optical system and increases the light power density of the light source system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1   a  is a diagram illustrating an arrangement of semiconductor lasers in a conventional semiconductor laser array; 
           [0022]      FIG. 1   b  is a diagram illustrating the light spot arrangement generated by the laser array of  FIG. 1 ; 
           [0023]      FIG. 2  is a diagram illustrating the structure of the light source unit in Chinese patent CN 101937163; 
           [0024]      FIG. 3  is a diagram illustrating the structure of a light source system according to an embodiment of the present invention; 
           [0025]      FIG. 4  is a top view of one laser group and one reflector group in the light source system of  FIG. 3 ; 
           [0026]      FIG. 5  is a diagram illustrating adjacent light spots on the screen of  FIG. 3  viewed in an incident direction toward the screen; 
           [0027]      FIG. 6  is a diagram illustrating the first projections and second projections of the laser groups in  FIG. 3 ; 
           [0028]      FIGS. 7   a  and  7   b  are diagrams illustrating the projections of two laser groups in their respective light output directions in two light source systems according to two other embodiments of the present invention; 
           [0029]      FIGS. 8   a ,  8   b  and  8   c  are light spot patterns on a screen viewed in the incident direction toward the screen for the embodiment of  FIG. 3 , the conventional technology, and Chinese patent CN 101937163, respectively; 
           [0030]      FIG. 9  is a diagram illustrating the structure of a light source system according to another embodiment of the present invention; 
           [0031]      FIG. 10  is a diagram illustrating the first projections of the laser diode groups on the respective cross-sections of their output light beam in the embodiment of  FIG. 9 ; 
           [0032]      FIG. 11  shows a light spot pattern on the screen of  FIG. 9   viewed  in the incident direction toward the screen; 
           [0033]      FIG. 12  is a diagram illustrating the first projections and second projections of the laser groups of the embodiment in  FIG. 9 ; 
           [0034]      FIG. 13  is a diagram illustrating the first projections of laser groups in a light source system according to another embodiment of the present invention; 
           [0035]      FIG. 14  is a diagram illustrating the first projections of laser groups in a light source system according to another embodiment of the present invention; 
           [0036]      FIG. 15  is a diagram illustrating the structure of a light source system according to an embodiment of the present invention; 
           [0037]      FIG. 16  is a diagram illustrating the first projections and second projections of the laser groups of the embodiment in  FIG. 15 ; 
           [0038]      FIG. 17  is a diagram illustrating the structure of a light source system according to another embodiment of the present invention; 
           [0039]      FIG. 18  is a diagram illustrating the first projections and second projections of the laser groups of the embodiment in  FIG. 17 ; 
           [0040]      FIG. 19  is a diagram illustrating the structure of a light source system according to another embodiment of the present invention; and 
           [0041]      FIG. 20  is a light spot pattern on the screen of  FIG. 19  viewed in the incident direction toward the screen. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    Referring to  FIG. 3 , which illustrates the structure of a light source system according to an embodiment of the present invention, the light source system includes a set of laser source  300 , where each laser source  300  includes: 
         [0043]    two laser groups  20   a  and  20   b , where the laser group  20   a  includes two lasers  21   a  and  21   b , and the laser group  20   b  includes two lasers  21   c  and  21   d . The two laser groups are arranged in parallel, and the two light beams from the two lasers of the same laser group are in the same direction and parallel to each other; 
         [0044]    two reflector groups  30   a  and  30   b  respectively corresponding to the two laser groups  20   a  and  20   b , where the reflector group  30   a  includes two reflectors  31   a  and  31   b  respectively corresponding to the two lasers  21   a  and  21   b , and the reflector group  30   b  includes two reflectors  31   c  and  31   d  respectively corresponding to the two lasers  21   c  and  21   d ; each reflector is disposed on the optical axis of its corresponding laser; 
         [0045]    each reflector group reflects the light beams generated by the corresponding laser group; specifically, the reflector group  30   a  reflects the two light beams L 1  generated by the laser group  20   a , and the reflector group  30   b  reflects the two light beams L 2  generated by the laser group  20   b , such that the spacing between output beams from the reflector group is smaller than the spacing between input beams to the reflector group. 
         [0046]    Refer to  FIG. 4 , which is a top view of one laser group and one reflector group in the light source system of  FIG. 3 . As shown in  FIG. 4 , the reflector group  30   a  includes a body  32  and two reflectors  31   a  and  31   b  disposed on the same side of the body  32 . Of course, the number of reflectors provided on the same side of the body  32  may be other numbers, and it is not limited in this invention. The adjacent reflectors  31   a  and  31   b  form a step arrangement, i.e., the adjacent reflectors are disposed on different planes and are offset from each other. The distance between adjacent steps of the step arrangement, i.e. the height difference between the bottom of reflector  31   a  and the top of reflector  31   b  is smaller than the spacing between the light spots of the two light beams L 1  that are incident on the adjacent reflectors  31   a  and  31   b , so that the spacing between the light spots is reduced from the spacing between the light spots of the two light beams L 1  incident on the reflector group  30  to the spacing between the light spots of the two light beams L 1  output from the reflector group. The principle of spacing reduction is similar to that explained in CN101937163 and will not be described in detail here. 
         [0047]    Preferably, the projections of the two reflectors  31   a  and  31   b  in the direction of their respective output light are in contact with each other, i.e., the line connecting the bottom of the reflector  31   a  and the top of the reflector  31   b  is parallel to the output light direction of the reflectors, so as to reduce the size of the reflector group  30   a.    
         [0048]    Further, the reflector group reduces the spacing between the light spots, so that adjacent light beams from the same laser group, such as the adjacent light beam from the lasers  21   a  and  21   b , are reflected into adjacent light spots that contact each other. When the projections of the two reflectors  31   a  and  31   b  in the direction of their respective output light are in contact with each other, as long as the width of the cross-sectional light spot of the lasers&#39; output beams is equal to the projected size of the reflectors in their incident direction,—here, the width is the width of the cross-sectional light spot when projected in the second direction, the second direction being parallel to both the cross-section of the incident light of the reflector and the cross-section of the output light of the reflector,—the adjacent light spots formed by the adjacent light beams after reflection can be in contact each other in the width direction. The cross-sectional light spot of the lasers&#39; output light can also be elliptical, rectangular, regular hexagon, circle, or other shapes. The incident angle of the light incident onto the reflector can be any angle. 
         [0049]    For ease of understanding, take as example where the incident angle of the light onto the reflector is 45 degrees and the cross-section of the output beam of the laser is elliptical. When the direction of major axis of the cross-sectional light spot of the laser output beam is parallel to the output direction of that light beam after reflection by the reflector, i.e., the major axis is the width of the cross-sectional light spot when projected in the second direction, and when the major axis of the cross-sectional light spot is equal to the length of a side of the reflector that reflect that light beam (i.e. the projection of the reflector in the direction of its incident light), shown in  FIG. 5  which illustrates adjacent light spots on the screen of  FIG. 3  viewed in the incident direction toward the screen, and also with reference to  FIG. 4 , the light spots  51   a ,  51   b  are respectively the light spots of the light beams L 1  from the lasers  21   a  and  21   b  after being reflected toward the screen  40 . The adjacent light spots formed by adjacent light beams L 1  after reflection by the reflector are in contact with each other in the direction of the major axis of the light spots (i.e. the above-referenced width direction), so that the spacing between the adjacent light sports in the direction of the major axis is zero. Similarly, the direction of the minor axis of the cross-sectional light spot of the laser output beam can be made to be parallel to the direction of the output light of the reflectors, and the minor axis can be made equal to the length of the side of the reflector that reflect the light beam; hence, the adjacent light spots formed by adjacent light beams L 1  after reflection by the reflector are in contact with each other in the direction of the minor axis of the light spots (i.e. the minor axis is in the above-referenced width direction), so that the spacing between the adjacent light sports in the direction of the minor axis is zero. 
         [0050]    The above descriptions describe the reduction of light spot spacing of lasers in the same laser group. The reduction of light spot spacing of lasers between different laser groups is described below. 
         [0051]    As shown in  FIG. 3 , the output lights L 1  and L 2  from the two respective laser groups are parallel to each other, and the reflected light L 1  and L 2  from the two reflector groups are in the same direction and are parallel to each other. Refer further to  FIG. 6 , which illustrates the first projections and second projections of the laser groups of  FIG. 3 . Referring to  FIG. 3  and  FIG. 6  together, the first projections of laser group  20   a  (lasers  21   a  and  21   b ) on the cross-section of their output light beam are respectively  61  and  62 , and the first projections of laser group  20   b  (lasers  21   c  and  21   d ) on the cross-section of their output light beam are respectively  63  and  64 . The second projections of the two sets of projections  61 ,  62  and  63 ,  64  in the first direction are line segments P and N, respectively, where the first direction is the direction of a line connecting the centers of the lasers of either the first or the second laser group. The overlapping portion of the second projection line segments P and Q is the portion M shown in the figure. Due to the overlapping in portion M, the spacing between light beams from lasers of different laser groups is smaller than that of the conventional technology; therefore the light power density is increased. In such a situation, the factor that limits the spacing between light spots is no longer the sizes of the lasers, but the sizes of the reflectors. Compared to lasers, the reflectors have an advantage that they can be cut into sizes equal to the sizes of the light spot. As long as the height of the reflectors (i.e. the distance from the bottom to the top of the reflector) is equal to the height of the light stop (i.e. the distance from the bottom to the top of the light spot), and as long as the projections of the two reflector groups in the incident direction of the reflectors are in contact with each other, it is possible to make the light beams from one laser group and the light beams from the other laser group, after reflection by the reflectors, come in contact with each other in the second direction, where the second direction is parallel to both the cross-section of the incident light of the reflector and the cross-section of the output light of the reflector. This achieves the result that the light spots of the two laser groups are in contact with each other. In this invention, the top to bottom direction mentioned above is the up-down direction in the drawing. 
         [0052]    In this embodiment, because the incident angle of the incident light onto the reflectors is 45 degrees, the output light direction of the reflectors is parallel to the direction of the line connecting the centers of the lasers in the same laser group. In other words, the second projections of the first projections in the direction of the reflectors output partially overlap. Specifically, in this embodiment, each laser group is arranged linearly, and the two laser groups face against each other (i.e. with one to one correspondence); the two groups of first projections of the two opposing laser groups in their respective output direction partially overlap with each other, so that the projections of the first projections in the first direction partially overlap. Specifically, as shown in  FIG. 6 , the projections of the bottom of one laser group (lasers  21   c  and  21   d ) and of the top of the other laser group (lasers  21   a  and  21   b ) in their respective light output directions overlap each other. 
         [0053]    In the embodiment of  FIG. 3 , the first projections of the two laser groups in their respective output light directions can also be separate from each other, rather than corresponds to each other. Refer to  FIG. 7   a  and  FIG. 7   b , which illustrate the projections of two laser groups in their respective light output directions in two light source systems according to two other embodiments of the present invention. As shown in  FIG. 7   a , the first projections  71  and  72  of the two laser groups in their respective light output directions overlap each other when they are projected in the first direction as second projections, but the first projections  71  and  72  are separated from each other. As shown in  FIG. 7   b , the first projections  73  and  74  of the two laser groups in their respective light output directions overlap each other when they are projected in first direction as second projections, but the first projections  73  and  74  are interleaved. 
         [0054]    Refer to  FIG. 8   a , which shows the light spot patterns on the screen  40  of the embodiment of  FIG. 3  viewed in the incident direction toward the screen. As shown in  FIG. 3  and  FIG. 8   a , if the major axis of the elliptical light spot of the laser output light is parallel to the light output direction of the reflector, then the reflectors  31   a  and  31   b  respectively reflect light from the laser  21   a  and  21   b  to form light spots  51   a  and  51   b , and the reflectors  31   c  and  31   d  respectively reflect light from the laser  21   c  and  21   d  to form light spots  51   c  and  51   d . Because the height of the reflectors is equal to the height of the elliptical light spot (i.e. its minor axis), and because the projections of the two reflector groups in their incident light direction are in contact with each other, light spots  51   a ,  51   b  are in contact with light spots  51   c ,  51   d  in the second direction, where the second direction is parallel to both the cross-section of the incident light of the reflector and the cross-section of the output light of the reflector, i.e. the up-down direction in the drawing. Thus, densely packed light spots as shown in  FIG. 8   a  are achieved. In comparison, refer to  FIGS. 8   b  and  8   c , which are corresponding light spot patterns achieved by the conventional technology and Chinese patent CN 101937163, respectively. The light spot pattern achieved by the conventional technology is shown as  51   a - 51   d  in  FIG. 8   b , and that of CN 101937163 is shown as  51   a - 51   d  in  FIG. 8   c.    
         [0055]    For convenience of description, the partial overlap of the first projections of the two laser group, when projected in a first direction as second projections, is referred to as the offset arrangement of the different laser groups. As described above, by using the reflectors, the spacing between light beams from lasers within the same group can be reduced; and by using the offset arrangement of the different laser groups, the spacing between light beams from lasers in different groups can be reduced. Therefore, the spacing between the laser diodes are reduced in two dimensions. Compared to conventional technologies, it significantly reduces the volume of the optical system and increases the light power density of the light source system. 
         [0056]    Refer to  FIG. 9 , which illustrates the structure of a light source system according to another embodiment of the present invention. The light source system includes a set of laser sources  900 . The laser source  900  includes two laser groups  20   a  and  20   b , which are laser diode groups. The laser diode group  20   a  includes laser diodes  21   a  and  21   b , and the laser diode group  20   b  includes laser diodes  21   c  and  21   d . Each laser diode group is arranged in a linear manner, and the two laser diode groups are disposed in the same plane. The light beams from the same laser group are in the same direction and parallel to each other, and the light beams are perpendicular to the plane of the laser diodes. 
         [0057]    The two laser diode groups are disposed in the same direction but in an offset manner. The same direction here means that the light beams from the two laser diode groups are in the same direction. The offset manner here means that the first projections of the two laser diode groups in their respective light output directions, when projected in a first direction as second projections, partially overlap each other. The first direction is the direction of a line connecting the centers of at least two lasers of a laser group. As shown in  FIG. 9 , in this embodiment, the same direction but offset arrangement is as follows: the two lines that the two laser groups are located respectively on are in the same plane perpendicular to the output light direction of the lasers; in the laser diode group  20   a , the adjacent laser diodes  21   a  and  21   b  are spaced from each other, in the laser diode group  20   b , the adjacent laser diodes  21   c  and  21   d  are also spaced from each other, and the laser diode groups are disposed on their respective lines in an offset and interleaved manner. 
         [0058]    The laser source  900  further includes two reflector groups corresponding to the laser groups; the reflector group  30   a  includes two reflectors  31   a  and  31   b  respectively corresponding to the two laser diodes  21   a  and  21   b , and the reflector group  30   b  includes two reflectors  31   c  and  31   d  respectively corresponding to the two laser diodes  21   c  and  21   d . Each reflector is disposed on the optical axis of its corresponding laser for reflecting the light beams generated by the corresponding lasers. The reflected light beams remain parallel to each other, and the spacing between the reflected light beams is smaller than the spacing between the light beams incident on the reflector groups. 
         [0059]    Refer to  FIG. 10 , which illustrates the first projections of the laser diode groups on the respective cross-sections of their output light beams in the embodiment of  FIG. 9 . As shown in  FIG. 10 , the output light from the laser diode groups form a light beam, and a cross-section of the light beam is in a plane A. The cross-section of the light beam is shown in  FIG. 10 , where light spots  51   a - 51   d  respectively correspond to the light beam emitted by laser diodes  21   a - 21   d , while the circles  101 - 104  respectively correspond to projections of the outline of the laser diodes  21   a - 21   d  in the plane A. Each light spot is an elliptical shape. The minor axis of the output light of the lasers is parallel to the output light direction of the reflectors. 
         [0060]    Refer to  FIG. 11 , which shows a light spot pattern on the screen in  FIG. 9  viewed in the incident direction toward the screen. Similar to the working principle of the embodiment shown in  FIG. 3 , as shown in  FIG. 11 , in this embodiment, the reflectors  31   a  and  31   b  respectively reflect light from the lasers  21   a  and  21   b  to obtain light spots  51   a  and  51   b  which are in contact with each other in the direction of the minor axis; the reflectors  31   c  and  31   d  respectively reflect light from the lasers  21   c  and  21   d  to obtain light spots  51   c  and  51   d  which are in contact with each other in the direction of the minor axis. In practice, to lessen the difficulty in assembling, the projections of the reflectors in their incident light direction are often made slightly larger than the width of the light beams, and the projections of the adjacent reflectors in the output light direction also have certain spacing between them. In such situations, the light spots  51   a  and  51   b , and  51   c  and  51   d  are no longer in contact but have a slight space in between; nevertheless, the spacing is still smaller than that between the light beam directly from the laser diodes  92  and  94 . 
         [0061]    The reduction of the spacing between light beams of different laser groups is explained below. Refer to  FIG. 12 , which illustrates the first projections and second projections of the laser groups of the embodiment in  FIG. 9 . As shown in  FIG. 12 , in this embodiment, the first projections of the laser diode group  20   a  in the plane A are  101  and  102 , and the second projections of the first projections  101  and  102  in the first direction is  109 , where the first direction is along the line connecting the centers of two lasers of any of the laser groups; the first projections of the laser diode group  20   a  in the plane A are  103  and  104 , and the second projection of the first projections  103  and  104  in the first direction is  1010 . The second projection  109  and the second projection  1010  overlap in the region M. 
         [0062]    The reflectors do not change the relative positions of the laser diodes  20   a  and  20   b  in the vertical direction, the vertical direction being the direction perpendicular to the plane formed by the incident and output lights of the reflector, therefore, the relative positions of the projection of the two laser diode groups in the plane A, after they are further projected in the output light direction of the reflectors, determines the relative position of the laser diodes  20   a  and  20   b  in the vertical direction. Therefore, the fact that projections  109  and  1010  overlap with each other means that the vertical spacing between the light spots of these two laser diode groups are smaller than that spacing if the laser diodes  20   a  and  20   b  were arranged in orthogonal columns and rows. 
         [0063]    The most preferred arrangement of laser diodes in this embodiment is shown in  FIG. 13 , which illustrates the first projections of two laser groups in a light source system according to another embodiment of the present invention. The output light spots of a laser diode group are  51   a ,  51   b  and their second projection in the first direction is  1301 ; the output light spots of another laser diode group are  51   c ,  51   d  and their second projection in the first direction is  1302 . The second projections  1301  and  1302  are in contact with each other. In this situation, to completely reflect the light reflected by the laser diodes, the two reflector groups must be in contact with each other, and the reflected light spots of the two laser diode groups on the screen are also in contact with each other in the vertical direction. As shown in  FIG. 11 , light spots  51   a ,  51   b  are respectively in contact with light spots  51   c ,  51   d  in the direction of their major axes. 
         [0064]    The arrangement where the two laser diode groups are disposed in the same direction but in an offset manner can also be achieved by placing the two lines of the two laser diode groups in different sectional planes in the output light direction of the lasers. The adjacent lasers in one laser group are spaced apart, the adjacent lasers in the other laser group are also spaced apart, and the projections of the two laser groups in their respective output light directions are offset in the direction of the two lines and are interleaved. It should be noted that, being “interleaved” does not require the projections of the adjacent lasers in their respective output light direction to be tangential and in contact with each other; the projections can be separated from each other (such as that shown in  FIG. 14 ). In short, the arrangement where the two laser diode groups are disposed in the same direction but in an offset manner can reduce the spacing between the light beams in different laser diode groups. By adjusting the offset, it is possible to make the light beams from one laser group and the light beams from the other laser group, after reflection by the reflectors, in contact with each other in the second direction, where the second direction is parallel to both the cross-section of the incident light of the reflector and the cross-section of the output light of the reflector. 
         [0065]    As described above, by using the reflectors, the spacing between light beams from laser diodes in the same group can be reduced; and by using the offset arrangement of the laser diode groups, the spacing between light beams from laser diodes in different groups can be reduced. Therefore, the spacing between the laser diodes is reduced in two dimensions. Compared to conventional technologies, it significantly reduces the volume of the optical system and increases the light power density of the light source system. 
         [0066]    In the above embodiments, laser groups of 1×2 arrays are used as examples. In other embodiments, the lasers in the laser groups can have other numbers and arrangements, and the lasers do not have to be arranged in a regular array of columns and rows. The invention is not limited to the specific arrangements. It should be pointed out that, as long as the number of lasers in at least one laser group is two or more, the spacing of light beams between different laser groups can be reduced in the manners described above. 
         [0067]    Refer to  FIGS. 15 and 16 , where  FIG. 15  illustrates the structure of a light source system according to an embodiment of the present invention, and  FIG. 16  illustrates the first projections and second projections of the laser groups of the embodiment in  FIG. 15 . As shown in  FIG. 15 , the laser source  1500  includes two laser groups  20   a  and  20   b . The laser group  20   a  includes two lasers  21   a  and  21   b , and the laser group  20   b  includes one laser  21   c . The light beams from the two laser groups are in the same direction and parallel to each other. As shown in  FIGS. 15 and 16 , the first projections of the laser groups  20   a  and  20   b  in the cross-sections of their respective output light beams are  1501  and  1502 , and the second projections of the first projections  1501 ,  1502  in the first direction are  1503  and  1504 . The second projections  1503  and  1504  partially overlap with each other. The first direction is the direction along the line connecting the centers of the two lasers in the laser group  20   a . Because the second projections  1503  and  1504  partially overlap with each other, the spacing between light spots of light beams in different laser groups is reduced as compared to the conventional technology. This increases the light power density of the laser light source and reduces its volume. 
         [0068]    As in the embodiment of  FIG. 9 , in this embodiment, preferably, each laser group has a linear arrangement, and the two lines of the two laser groups are located in the same sectional plane in the output light direction of the lasers, to make it easy to install a heat dissipating device for the lasers. Also, the adjacent lasers in the same laser group can be spaced apart, and the two laser groups are offset in the direction of their respective lines and are interleaved. It should be understood that other technical features of the embodiment of  FIG. 9  can also be applied to this embodiment. 
         [0069]    Refer to  FIGS. 17 and 18 , where  FIG. 17  illustrates the structure of a light source system according to another embodiment of the present invention, and  FIG. 18  illustrates the first projections and second projections of the laser groups of the embodiment in  FIG. 17 . As shown in  FIG. 17 , the laser source  1700  includes two laser groups  20   a  and  20   b . The laser group  20   a  includes two lasers  21   a  and  21   b , and the laser group  20   b  includes one laser  21   c . The light beams from the same laser group are in the same direction and parallel to each other. The light beams from the two laser groups are in the opposite direction and parallel to each other. 
         [0070]    The laser source  1700  further includes two reflector groups  30   a  and  30   b  for respectively reflecting the light beams from the two laser groups  20   a  and  20   b . After reflection, the light beams from the two laser groups are in the same direction and parallel to each other. 
         [0071]    As shown in  FIGS. 17 and 18 , the first projection of the laser groups  20   a  and  20   b  in the cross-sections of their respective output light beams are  1701  and  1702 , and the second projections of the first projections  1701  and  1702  in the first direction are  1703  and  1704 . The second projections  1703  and  1704  partially overlap with each other. The first direction is the direction along the line connecting the centers of the two lasers in the laser group  20   a . Because the second projections  1703  and  17504  partially overlap with each other, the spacing between light spots of light beams in different laser groups is reduced compared to the conventional technology. This increases the light power density of the laser light source and reduces its volume. 
         [0072]    Similar to the embodiment of  FIG. 3 , in this embodiment, preferably, each laser group has a linear arrangement, and the two laser groups face against each other (i.e. with one to one correspondence); the two first projections of the two opposing laser groups in their respective output direction partially overlap with each other. This reduces the volume of the light source and increases light power density. In addition, the adjacent lasers in the same laser group can contact each other, further reducing volume and increasing light power density. It should be understood that other technical features of the embodiment of  FIG. 3  can be applied to this embodiment as well. 
         [0073]    This embodiment uses a simple example of 3 lasers to illustrate the invention. It should be understood that as long as one laser group has at least two lasers, the spacing of light beams between different laser groups can be reduced in the above manners, so the number of lasers in the other laser group is not limited. 
         [0074]    Refer to  FIGS. 19 and 20 , where  FIG. 19  illustrates the structure of a light source system according to another embodiment of the present invention, and  FIG. 20  is a light spot pattern on the screen of  FIG. 19  viewed in the incident direction toward the screen. In this embodiment, the light source system  1900  includes two of the above-described laser sources  1901  and  1902 , and further includes a light combining device  60  and a reflector  70 . The light beam L 1  from the laser source  1901  is incident on the first side of the light combining device  60 , and the light beam L 2  from the laser source  1902  is reflected by the reflector  70  and then incident on the second side of the light combining device  60 . The light combining device respectively transmits and reflects the light beams L 1  and L 2  that are incident on its two sides, so that the light spots of the light beams, after the transmission and reflection, at least partially overlap with each other. 
         [0075]    Specifically, in this embodiment, the light combining device  60  reflects the light that is reflected onto its surface by the reflector  70 , and transmits the other light. It should be understood that the light combining device is not limited by which light it transmits and which light it reflects. Further, preferably, the position of the reflector is adjustable, so that the incident angle of the light onto the reflector is adjustable. This makes it easy to exchange laser sources. The reflector  70  can significantly reduce the size of the laser source, so that the two laser groups can be arranged in parallel, rather than perpendicularly. This type of design which uses reflectors to reduce light source sizes is advantageous when many semiconductor lasers are employed; in particular, when heat dissipating devices are arranged in parallel, it is easier to design the cooling air path than when the heat dissipating devices are arranged perpendicularly. In fact, the light beam L 2  from the laser source  1902  can be directly incident on the second side of the light combining device  60 ; thus, the reflector  70  may be omitted. 
         [0076]    The polarization directions of the two laser sources may be perpendicular to each other. In such a situation, the light combining device may be a polarization-based light combining device, which respectively transmits and reflects light beams from the two laser sources. For example, the laser source  1902  may be turned 90 degrees with respect to the laser source  1901 , so that its light is now reflected by the polarization-based light combining device, rather than transmitting through the device. This causes the light spots of the two laser beams to overlap with each other, so that light having different positions and directions can be combined into the same direction. Of course, when the light combining device is a polarization-based light combining device, the polarization directions of the light beams from the two laser sources can be identical, and a ½ wave plate can be used to change the polarization direction of one of the light beams so that it is now perpendicular to the polarization of the other beam, before it is incident on the polarization-based light combining device. 
         [0077]    The wavelengths of the two laser sources may be different from each other. In such a situation, the light combining device may be a wavelength selection device, which transmits the light form one laser source and reflects the light from the other laser source. 
         [0078]    Preferably, the light spots of the transmitted and reflected light beams overlap in their center regions, so as to increase the overlapping portions of the light spots and increase the light power density. For example, when the polarization direction of the two light beams from the two laser sources are perpendicular to each other, as shown in  FIG. 20 , the light spot of one laser source is  2001  and the light spot of another laser source is  2002 , which overlap with each other in the center region. 
         [0079]    Compared to conventional technologies, by using the polarization-based light combining device to combine the light beams from the laser sources, the light power density is 9 times that achieved by conventional technologies. 
         [0080]    It should be noted that the various embodiments of the present invention, or their technical features, can be combined in any suitable manner to achieve other embodiments with new technical effects. 
         [0081]    While embodiments of the present invention are described above, the invention is not limited to the embodiments. Any equivalent structures or equivalent methods based on this disclosure and drawings, or any direct or indirect applications in other relevant technical fields, are within the protection scope of this patent.