Abstract:
The light emitted from a bank of light emitting diodes is converted through a set of lenses into parallel light beams, which, in turn, is focused or diversified as projection light source. Such a light source can replace traditional incandescent bulb. Reflection mirrors can be used to deflect or reflect the light beams. Phosphorescent material can be added in the transmission path to convert blue or ultraviolet short wave light into white light.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to light emitting diodes (LED), in particular to LED for projection light source. 
     (2) Brief Description of Related Art 
     FIG. 1 shows a prior art light bulb. The light bulb has a shell  10  and a filament  12 . When an electric current flows through the filament  12 , the filament  12  is heated up and emits light. This kind of light bulb is inefficient and generates a great deal of heat. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide an efficient light source. Another object of this invention is to generate less heat from the light source. 
     These objects are achieved by using a number of LEDs as a light source. The light emitted from the LEDs is converted through lenses to produce parallel light beams. The parallel light beams are focused or diversified as projection light source. The light source can replace traditional incandescent light bulb. Reflection mirrors can be used to deflect or reflect the light beams. Phosphorescent material can be added in the transmitting media or coated on the light transmitting surface to convert blue or ultraviolet short wavelength light into white light. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a traditional prior art light bulb 
     FIG. 2 shows the first embodiment of the present invention with multiple LEDs to first generate parallel light beams through a first set of lenses and then focused light source through a Fresnel lens. 
     FIG. 3 shows a second embodiment of the invention where a LED light source is enclosed in a bulb. 
     FIG. 4 shows a third embodiment of the invention to generate a focused light through a convex lens from parallel light beams converted from the LEDs. 
     FIG. 5 shows a fourth embodiment of the invention, where a focused light is transmitted through a pinhole. 
     FIG. 6 shows a fifth embodiment of the invention where a focused light emitted from short wavelength LEDs through a pinhole is projected on a screen coated with phosphorescent material to produce white light. 
     FIG. 7 shows a sixth embodiment of the invention where a focused light is reflected from a Fresnel lens with parallel light beam converted from the LEDs. 
     FIG. 8 shows a seventh embodiment of the invention where a focused light is reflected from a concave focusing lens. 
     FIG. 9 shows an eighth embodiment of the invention where a focused beam reflected from a Fresnel lens is transmitted through a pinhole. 
     FIG. 10 shows a ninth embodiment of the invention where a focused beam is deflected by a mirror. 
     FIG. 11 shows a tenth embodiment of the invention where the parallel beam from the LEDs are reflected from reflecting cups underneath. 
     FIG. 12 shows an eleventh embodiment of the invention where the parallel light beam from the LEDs diverges with a concave lens. 
     FIG. 13 shows a twelfth embodiment of the invention where the parallel beams from the LEDs are generated from a matrix of LEDs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2 shows the basic projection light source system of the present invention. Multiple light emitting diodes (LED)  201 ,  202 ,  203  are mounted on a substrate  21 . Each of these LEDs is placed at the respective focal points of a set of lenses  22 , so that the light beams emitted from the LED become parallel. The first set of lenses  22  can be a single lens or multiple lenses. The parallel light beams are then focused through a second set of lens  23  at a focal point  24 . The second set of lens shown here is a Fresnel lens. 
     FIG. 3 shows a second embodiment of the present invention. The light source system  200  shown in FIG. 2 is mounted inside a conventional light bulb  10 . The second set of lens shown is a Fresnel lens. The light bulb  10  then can be used as a conventional light bulb. 
     FIG. 4 shows a third embodiment of the present invention. The light source system is similar to that in FIG. 2 with LEDs  201 ,  202 ,  203  mounted on substrate  21 . The difference is that the second set of focal lens is a conventional convex lens  231  to focus the parallel light beams at a focal point  24 . 
     FIG. 5 shows a fourth embodiment of the present invention. The light system is similar to FIG. 2 except that the parallel light beams, which are emitted from the LEDs  201 ,  202 ,  203  mounted on substrate  21  through first set of lenses  22  and focused by the second set of lens  23 , transmit through a pinhole  26  of a plate  25  placed at the focal point of the focused light beams. The purpose of the of the pinhole  26  is to correct the departure of the focused light as a point source due to aberrations in the first set of lens  22  and the second set of lens  23 , thus sharpening the light beam. With the light beaming through the pinhole  26 , the light source approaches that of a point source. 
     FIG. 6 shows a fifth embodiment of the present invention. The light source system is similar to that shown in FIG.  5 . In addition, a transparent plate  28  coated with phosphorescent material is placed in the path of the light beam radiated from the pin hole  26  in plate  25 . The LEDs  201 ,  202 ,  203  mounted on the substrate  21  emit short wavelength light such as blue light, blue-purple light, purple light, ultra-violet light, etc. When such short wavelength light beams impinges on the transparent phosphorescent plate  28 , the transmitted light becomes a white light. 
     FIG. 7 shows a sixth embodiment of the present invention. The light source is based on reflected light. The lights emitted from the multiple LEDs  201  and  202 , which are mounted on respective substrates  211  and  212 , are converted into parallel light beams through first set of lenses  233  and projected on a second set of Fresnel lens  27 , which reflects the parallel light beams. The reflected light beams is then focused at a point  24 . 
     FIG. 8 shows a seventh embodiment of the present invention The light source system is similar to that in FIG. 7, except that the second set of reflecting Fresnel lens  27  is replaced by a conventional concave lens  271 . Other parts with same reference numerals corresponds to the same parts in FIG. 7 
     FIG. 9 shows an eighth embodiment of the present invention The light source system is similar to that in FIG. 7, except that the that the focused light transmit through a pinhole  26  of a plate  25  place at the focal point of the reflected light from the optical element  27 . The pinhole sharpens the focused reflected light transmitted through the pinhole  26 . 
     FIG. 10 shows a ninth embodiment of the present invention. The light source system is similar to that in FIG. 9 up to the pinhole  26 . The light transmitted through the pinhole  26  is transmitted further through a magnifying lens  43  and deflected by a mirror  37 . Thus, the direction of the light bean is deflected. 
     FIG. 11 shows a tenth embodiment of the present invention The LEDs  201 ,  202 ,  203  are mounted underneath the substrate  21 . The LEDs are covered with a reflecting hemispheric cups  32  to reflect the light emitted from the LEDs into parallel light beams. The parallel light beams are then focused by a Fresnel lens  23  with focal point  24 . 
     FIG. 12 shows an eleventh embodiment of the present invention. The light source system is similar to that in FIG. 4, except that the second set of lens is a concave lens  232 . The lights emitted from the LEDs  20  mounted on a substrate  21  are converted into parallel through a first set of lens  233 . The parallel light beams are then transmitted through the concave lens  232  to become divergent. The divergent light has a virtual focal point F. 
     FIG. 13 shows a twelfth embodiment of the present invention. More than one substrate  21 , each mounted with LEDs  201 ,  202 ,  203  similar to that shown in FIG. 1, are arranged as a matrix. Then, the light from the matrix projects as a wide angle light source. 
     While the preferred embodiments have been described, it will be apparent to those skilled in the art that various modifications may be made in the embodiment without departing from the spirit of the present invention. Such modifications are all within the scope of this invention.