Patent Publication Number: US-2011061721-A1

Title: Lens with increasing pitches

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to patent application Ser. No. ______, entitled “LENS WITH A DETERMINED PITCH” and filed on ______, 2010 (Attorney Docket No. US26737) and patent application Ser. No. ______, entitled “LENS WITH MULTIPLE PROTRUSIONS” and field on ______, 2010 (Attorney Docket No. US26739). Such applications have the same inventors and assignee as the present application. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure relates generally to lenses, and more particularly to a lens for condensing the solar light. 
     2. Description of the Related Art 
     Generally, solar light is considered to be aligned. A standard Fresnel lens is configured for concentrating solar light for a solar cell. However, the intensity of light through the Fresnel lens is not uniform. When the solar light passes through the Fresnel lens, the intensity of the center is normally higher than that of periphery. Thus, what is called for is a lens that can overcome the limitations described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a non-imaging lens in accordance with a first embodiment of the disclosure. 
         FIG. 2  is a cross-section along line II-II of the non-imaging lens in  FIG. 1 . 
         FIG. 3  is a cross-section of the non-imaging lens in  FIG. 1 . 
         FIG. 4  is a cross-section of the non-imaging lens in  FIG. 1  in a vertical orientation, showing an optical path of the non-imaging lens in  FIG. 1 . 
         FIG. 5  is a cross-section of a non-imaging lens in accordance with a second embodiment of the disclosure. 
         FIG. 6  is a cross-section of a non-imaging lens in accordance with a third embodiment of the disclosure. 
         FIG. 7  is a view similar to  FIG. 4 , showing a solar cell module utilizing the non-imaging lens in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1  and  FIG. 2 , a non-imaging lens  10  in accordance with a first embodiment of the disclosure includes a transparent member  11 , a conical protrusion  12  and a plurality of annular protrusions  13 . 
     The transparent member  11  is circular. The transparent member  11  includes a first surface  110  and a second surface  112 . The second surface  112  is configured for receiving the solar light. The first surface  110  and the second surface  112  are planar. The transparent member  11  is made of resin or glass. 
     The conical protrusion  12  is defined at a center  114  of the first surface  110 . The annular protrusions  13  are concentrically defined on the first surface  110  and configured around the conical protrusion  12 . Each of cross-sections along the line II-II of the protrusions  13  approximately forms a right-angled triangle at a side of the center  114  of the first surface  110  of the transparent member  11 . Each of the triangles includes a bottom surface  130 , a first surface  132  which is perpendicular to the bottom surface  130 , a second surface  134  which is slantwise to the bottom surface  130 , a first angle θ and a second angle α and a third angle γ. The bottom surfaces  130  of the triangles are on the first surface  110 . The second surfaces  132  are located toward the conical protrusion  12 . The radius of the conical protrusion  12  and the widths of the bottom surfaces  130  increase in turn outwards from the center  114 . The second angles α increase in turn outwards from the conical protrusion  12 . In the first embodiment, a relation among the radius of the conical protrusion  12  and the widths of the bottom surfaces  130  outwards from the center  114  of the transparent member  11  provide an increasing arithmetical progression. 
     A cross section of the conical protrusion  12  could be considered as consisting of two right-angled triangles beside the center  114 . A width of a bottom surface of each of the triangles defined by the conical protrusion  12  equals to the radius of the conical protrusion  12 . The radius of the conical protrusion  12  is less than any of the widths of the bottom surfaces  130 . 
     The transparent member  11  can be triangular or elliptical, there being no limitation to the shape as disclosed. 
     Referring to  FIG. 3  and  FIG. 4 , the second surface  134  is configured for refracting the solar light. The widths of light spots corresponding to the annular protrusions  13  are in an increasing arithmetical progression along a radially outward direction. The intensities of the light spots are uniform. 
     Referring to  FIG. 5 , a non-imaging lens  40  in accordance with a second embodiment of the disclosure is similar to the first embodiment, differing only in that the first angle θ is between 45° and 90° and the first angle θ exceeds the second angle α. For example, the first angle θ can be between 87° and 90° 
     Referring to  FIG. 6 , a non-imaging lens  50  in accordance with a third embodiment of the disclosure is similar to the non-imaging lens  40  of the second embodiment, differing only in that a corner  536  of each of the triangles formed by the annular protrusions  13  in cross section corresponding to the third angle γ is a smooth corner. 
     Referring to  FIG. 7 , a solar cell module  20  includes a solar cell plate  21  and a non-imaging lens  10  as shown in  FIG. 1 . The solar cell plate  21  is defined on L plane as shown in  FIG. 4  towards the annular protrusions  13  of the lens  10  for efficiently receiving the solar light. The number of the annular protrusions  13 , a radius of the transparent member  11  and a radius of the solar cell plate  21  can be determined according to specific requests. When the parameters of the solar device  20  satisfy formula (1) and formula (2), the uniform solar light is received by the solar cell plate  21 . 
     
       
         
           
             
               
                 
                   
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     R 1  is the radius of the transparent member  11 . R 2  is the radius of the solar cell plate  21 . D is a distance between the solar cell plate  21  and the first surface  110  of the transparent member  11 . m max  is total number of the triangles at a side of the transparent member  11  relative to the center  114 , which in the embodiment of  FIG. 7  is seven (7). The conical protrusion  12  forms two triangles besides the center  114 . Either of the triangles defined by the conical protrusion  12  is considered as the first triangle. Either of the triangles defined by the outermost annular protrusion  13  is considered as the last triangle. α m  is the second angle of the m th  triangle. β m  is an incident angle relative to the solar light plate  21  of the light through the m th  triangle. n is a refractive coefficient of the non-imaging lens  10 . 
     Uniform intensity can be easily obtained utilizing the non-imaging lens  10  satisfying the formulae (1) and (2). 
     While the disclosure has been described by way of example and in terms of exemplary embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.