Abstract:
A power-saving method with integrated photodiode light source. This device has a circuit board with a plurality of red, green and blue photodiodes as the device&#39;s light source. Additionally, a light control circuit is used to control light beam from the light source illuminating a reflector and then reflecting to a reflective display panel in order to reflect the light beam and generate an image. Thus, a projection module can project the image on a viewing plate. As cited, the inventive device includes: a light control circuit, a light source module, a polarizing beam splitter (PBS), a reflective display panel and a projection module.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This continuation-in-part application is related to and claims the benefit of filing date of a Taiwan patent application which is entitled “Image Projection Device” and which was filed Dec. 21, 2001 as Application Ser. No. 90131751.  
         BACKGROUND  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to an image projection device and more particularly, to an image projection device with integrated photodiode light source.  
           [0004]    2. Description of the Related Art  
           [0005]    [0005]FIG. 1 is a schematic diagram of a typical image projector. As shown in FIG. 1, the typical projector includes a light source module  1 , an image module  2  and a projection module  3 , wherein module  1  further includes a plural-metal halogen lamp  1   a , a lens array  1   b  an a PS (p-s polarized) converter  1   c.    
           [0006]    As shown in FIG. 1, in the typical projector, module  1  can effectively convert an unpolarized light beam illuminated by the lamp  1   a  into a polarized light beam. However, the lamp&#39;s F/# limits the size of the light source module so that the entire size of the projector cannot be reduced. Additionally, the lamp in the typical projector consumes major power and generates heat that is a problem in development.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, an object of the invention is to provide an image projection device with an integrated-photodiode light source that uses an integrated photodiode light source (having back-to-back symmetric configuration of photodiodes) as the device&#39;s light source. Additionally, a light control circuit is used to control light beam from the light source illuminating a reflector and then reflecting to a reflective display panel in order to reflect the light beam and generate an image. Thus, a projection module can project the image on a viewing plate. The display panel is preferably a liquid-crystal-on-silicon (LCOS) display.  
           [0008]    The invention provides an image projection device with an integrated-photodiode light source, and includes a light source module, a polarizing beam splitter, a reflective display panel and a projection module, wherein the light source module uses a plurality of photodiodes as light sources and the display panel is preferably an LCOS display.  
           [0009]    A characteristic of the invention is that the light source module includes at least one illuminating unit with a light source of random RGB photodiode arrangement on a circuit board.  
           [0010]    Another characteristic of the invention is that the light source module includes a plurality of illuminating units, a polarizing beam splitter, a reflector and a wave-retardation (half-wave) plate.  
           [0011]    Another characteristic of the invention is that the light source module includes a plurality of illuminating units, at least one prism and a polarizer, wherein each illuminating unit illuminates an unpolarized light beam and all unpolarized light beams are combined by the prism into a single unpolarized light beam.  
           [0012]    Another characteristic of the invention is that the light source module includes a plurality of illuminating units and a photoguider, wherein the photoguider is formed of four reflection mirrors.  
           [0013]    A further characteristic of the invention is that a light control circuit is used to control the light source module for the photodiode&#39;s illumination, thereby controlling projection quality.  
           [0014]    A still further characteristic of the invention is that the photodiodes are symmetrically implemented on both sides of the circuit board 22 mm long, 8.5 mm wide and 0.8 mm thick. Additionally, the light source array is 11.461 mm long, 8.5 mm wide and 1.2 mm thick. In current technologies, each side of the polarizing beam splitters can be less than 13 mm, the LCOS display panel can be 12.5 mm, and the projection module can have a width of 15 mm and a length of 25 mm. As such, the invention can achieve the space requirements for the projection device.  
           [0015]    An advantage of the invention is reduced volume and weight of the projection device.  
           [0016]    Another advantage of the invention is reduced power consumption and heat generation for the projection device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic diagram of a typical image projector;  
         [0018]    [0018]FIG. 2 is a schematic diagram of a first embodiment of an image projection device according to the invention;  
         [0019]    [0019]FIG. 3 is a schematic diagram of a second embodiment of the image projection device according to the invention;  
         [0020]    [0020]FIG. 4 is a schematic diagram of a third embodiment of the image projection device according to the invention;  
         [0021]    [0021]FIG. 5 is a schematic diagram of another form of the third embodiment of the image projection device according to the invention;  
         [0022]    [0022]FIG. 6 is a schematic diagram of a fourth embodiment of the image projection device according to the invention;  
         [0023]    [0023]FIG. 7 is a schematic diagram of a fifth embodiment of the image projection device according to the invention;  
         [0024]    [0024]FIG. 8 is a schematic diagram of a sixth embodiment of the image projection device according to the invention;  
         [0025]    [0025]FIG. 9 is a schematic diagram of a seventh embodiment of the image projection device according to the invention;  
         [0026]    [0026]FIG. 10 is a schematic diagram of another form of the seventh embodiment of the image projection device according to the invention;  
         [0027]    [0027]FIG. 11 is a schematic diagram of an eighth embodiment of the image projection device according to the invention;  
         [0028]    [0028]FIG. 12 is a schematic diagram of an illuminating unit according to the invention;  
         [0029]    [0029]FIG. 13 is a partially detailed diagram of an embodiment of FIG. 12 according to the invention;  
         [0030]    [0030]FIG. 14 is a partially detailed diagram of another form of the embodiment of FIG. 12 according to the invention;  
         [0031]    [0031]FIG. 15A is a schematic diagram of an embodiment of a light control circuit in conjunction with FIG. 14 according to the invention;  
         [0032]    [0032]FIG. 15B is a schematic diagram of another form of the embodiment of the light control circuit in conjunction with FIG. 14 according to the invention; and  
         [0033]    [0033]FIG. 16 is a timing diagram of FIG. 15B according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    Similar elements denote the same numbers throughout the description and drawings.  
         [0035]    [First Embodiment] 
         [0036]    [0036]FIG. 2 is a schematic diagram of a first embodiment of an image projection device according to the invention. As shown in FIG. 2, the device includes: a light source module  10 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses a semiconductor LED array  11  as a light source.  
         [0037]    As shown in FIG. 2, module  10  further includes a second polarizing beam splitter  12 , a reflector  13  and a wave-retardation (half-wave) plate  14 . The array  11  generates a generally straight light beam a which is unpolarized. The beam a incident on the splitter  12  is split by an interface  12   a  of the splitter  12  into a p-polarized light beam b and an s-polarized light beam c, wherein the beam b is directly propagated through the interface  12   a  and the beam c is reflected by the interface  12   a . The beam a is further propagated through the plate  14  and converted as an s-polarized light beam d while the beam c is reflected by the reflector  13 . The reflector  13  can be, for example, a prism or a reflective mirror.  
         [0038]    As shown in FIG. 2, the beams c, d are propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be an LCOS display. Next, the beams c, d are reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0039]    [Second Embodiment] 
         [0040]    [0040]FIG. 3 is a schematic diagram of a second embodiment of the image projection device according to the invention. As shown in FIG. 3, the device includes: a light source module  10 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses two semiconductor LED arrays  11 ,  15  as the light source. As shown in FIG. 3, module  10  further includes a second polarizing beam splitter  12  and a reflector  13 . The arrays  11 ,  15  generate generally straight light beams a 1 , a 2  which are unpolarized. The beam a 1  incident on the splitter  12  is split by an interface  12   a  of the splitter  12  into a p-polarized light beam b 1  and an s-polarized light beam c 1 . The beam b 1  is directly propagated through the interface  12   a  and the splitter  20 . The beam c 1  is reflected by the interface  12   a  and the reflector  13 . The reflector  13  can be, for example, a prism or a reflective mirror. Also, the beam a 2  incident on the splitter  12  is split by the interface  12   a  of the splitter  12  into a p-polarized light beam b 2  and an s-polarized light beam c 2 . The beam b 2  is directly propagated through the interface  12   a  and reflected by the reflector  13  so as to pass through the splitter  20 . The beam c 2  is reflected by the interface  12   a.    
         [0041]    As shown in FIG. 3, the beams c 1 , c 2  are propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be an LCOS display. Next, the beams c 1 , c 2  are reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane. [Third Embodiment] 
         [0042]    [0042]FIG. 4 is a schematic diagram of a third embodiment of the image projection device according to the invention. As shown in FIG. 4, the device includes: a light source module  10 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses two semiconductor LED arrays  11 ,  15  as the light source.  
         [0043]    As shown in FIG. 4, module  10  further includes a prism  16  and a polarizer  17 . The arrays  11 ,  15  generate generally straight light beams a 1 , a 2  which are unpolarized. Additionally, the arrays  11 ,  15  are respectively displaced on two sides of the prism  16 . The beam a 1  incident on the prism  16  generates full reflection and the beam a 2  incident on the prism  16  at a specific angle generates a propagation direction the same as that of the beam a 1 . Next, the beams a 1 , a 2  are polarized by the polarizer  17  as an s-polarized light beam c. As shown in FIG. 4, the beam c is propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be an LCOS display. Next, the beam c is reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0044]    [0044]FIG. 5 is a schematic diagram of another form of the third embodiment of the image projection device according to the invention. This example is identical to FIG. 4 except that two light source modules are used to increase the projection luminance.  
         [0045]    [Fourth Embodiment] 
         [0046]    [0046]FIG. 6 is a schematic diagram of a fourth embodiment of the image projection device according to the invention. As shown in FIG. 6, the device includes: a light source module  10 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses a semiconductor LED array  11  as a light source.  
         [0047]    As shown in FIG. 6, module  10  further includes a photoguider  18 . The photoguider  18  can be a hollow mirror cuboid consisting of four reflective mirrors or a solid glass cube. The array  11  generates an unpolarized light beam a. The beam a incident on the photoguider  18  forms a uniformly unpolarized light beam a.  
         [0048]    As shown in FIG. 6, the beam a′ is propagated into the splitter  20  and generates a p-polarized light beam b and an s-polarized light beam c. The beam b is propagated directly through an interface of the splitter  20  and the beam c is reflected by the interface. Next, the beam c is reflected by the splitter  20  to the panel  30 . The panel  30  can be an LCOS display. Next, the beam c is reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0049]    In the first to third embodiments of the invention, the first polarizing beam splitter  20  is used to separate the sand p-polarized beams. Further, the splitter  20  guides the s-polarized beam to illuminate on the panel  30 .  
         [0050]    In all cited embodiments, the arrays are controlled by a light control circuit to emit R, G, B in turn under a stable frequency.  
         [0051]    Additional Embodiments:  
         [0052]    [Fifth Embodiment] 
         [0053]    [0053]FIG. 7 is a schematic diagram of a fifth embodiment of the image projection device according to the invention. As shown in FIG. 7, the device includes: a light source module  10 , a light control circuit  19 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses an illuminating unit  11 ′ as the light source. The unit  11 ′ has plural photodiodes  101  (described in FIGS.  12  to  14  later) as the required light source, and a shade  102  to collect the intensity of light from the photodiodes  101 . The photodiodes can be LEDs. The light source is controlled by the circuit  19  (described in FIGS. 15A to  16 ).  
         [0054]    As shown in FIG. 7, module  10  further includes a second polarizing beam splitter  12 , a reflector  13  and a wave-retardation (half-wave) plate  14 . The plural photodiodes  101  generate a generally straight unpolarized light beam a through the shade  102 . The beam a incident on the splitter  12  is split by an interface  12   a  of the splitter  12  into a p-polarized light beam b and an s-polarized light beam c, wherein the beam b is directly propagated through the interface  12   a  and the beam c is reflected by the interface  12   a . The beam a is further propagated through the plate  14  and converted as an s-polarized light beam d while the beam c is reflected by the reflector  13 . The reflector  13  can be, for example, a photoguider (described in FIG. 11), a prism (described in FIG. 9) or a reflective mirror. As shown in FIG. 7, the beams c, d are propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be a TFT-LCD, an LCOS display or an MEM display, wherein the LCOS display is preferred in view of current technique and cost. Next, the beams c, d are reflected and converted by the panel  30  in to a p-polarized image light beame. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0055]    [Sixth Embodiment] 
         [0056]    [0056]FIG. 8 is a schematic diagram of a sixth embodiment of the image projection device according to the invention. As shown in FIG. 8, the device includes: a light source module  10 , a light control circuit  19 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses two illuminating units  11 ′,  15 ′ in a right-angled configuration as the light source. Each unit  11 ′ or  15 ′ includes plural photodiodes  101  (described in FIGS.  12 - 14 ) as the required light source, and a shade  102  to collect the intensity of light from the photodiodes  101 . The photodiodes can be LEDs. The light source is controlled by the circuit  19  (described in FIGS. 15A to  16 ).  
         [0057]    As shown in FIG. 8, module  10  further includes a second polarizing beam splitter l 2  and a reflector  13 . The photodiodes  101  generate generally straight unpolarized light beams a 1 , a 2  through the shade  102 . The beam a 1  incident on the splitter  12  is split by an interface  12   a  of the splitter  12  into a p-polarized light beam b 1  and an s-polarized light beam c 1 . The beam b 1  is directly propagated through the interface  12   a  and the splitter  20 . The beam c 1  is reflected by the interface  12   a  and the reflector  13 . The reflector  13  can be, for example, a photoguider (described in FIG. 11), a prism (described in FIG. 9) or a reflective mirror. Also, the beam a 2  incident on the splitter  12  is split by the interface  12   a  of the splitter  12  into a p-polarized light beam b 2  and an s-polarized light beam c 2 . The beam b 2  is directly propagated through the interface  12   a  and reflected by the reflector  13  so as to pass through the splitter  20 . The beam c 2  is reflected by the interface  12   a.    
         [0058]    As shown in FIG. 8, the beams c 1 , c 2  are propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be a TFT-LCD, an LCOS display or an MEM display, wherein the LCOS display is preferred in view of current technique and cost. Next, the beams c 1 , c 2  are reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0059]    [Seventh Embodiment] 
         [0060]    [0060]FIG. 9 is a schematic diagram of a third embodiment of the image projection device according to the invention. As shown in FIG. 9, the device includes: a light source module  10 , a light control circuit  19 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses two illuminating units  11 ′,  15 ′ in an acute angle configuration as the light source. Each unit  11 ′ or  15 ′ includes plural photodiodes  101  (described in FIGS.  12 - 14 ) as the required light source, and a shade  102  to collect the intensity of light from the photodiodes  101 . The photodiodes can be LEDs. The light source is controlled by the circuit  19  (described in FIGS. 15A to  16 ).  
         [0061]    As shown in FIG. 9, module  10  further includes a prism  16  as a reflective and refractive device, and a polarizer  17  with the use of the prism  16 . The photodiodes  101  generate generally straight unpolarized light beams a 1 , a 2  through the shade  102 . Additionally, the units  11 ′,  15 ′ are respectively displaced on two sides of the prism  16 . The beam a 1  incident on the prism  16  generates full reflection and the beam a 2  incident on the prism  16  in a specific angle generates a propagation direction the same as that of the beam a 1 . Next, the beams a 1 , a 2  are polarized by the polarizer  17  as an s-polarized light beam c.  
         [0062]    As shown in FIG. 9, the beam c is propagated into and further reflected by the splitter  20  to the panel  30 . The panel  30  can be a TFT-LCD, an LCOS display or an MEM display, wherein the LCOS display is preferred in view of current technique and cost. Next, the beam c is reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0063]    [0063]FIG. 10 is a schematic diagram of another form of the seventh embodiment of the image projection device according to the invention. This example is identical to FIG. 9 except that two light source modules are used to increase the projection luminance. The two light source modules represent four illuminating units as configured in FIG. 10.  
         [0064]    [Eighth Embodiment] 
         [0065]    [0065]FIG. 11 is a schematic diagram of an eighth embodiment of the image projection device according to the invention. As shown in FIG. 11, the device includes: a light source module  10 , a light control circuit  19 , a first polarizing beam splitter  20 , a reflective display panel  30  and a projection module  40 , wherein module  10  uses an illuminating unit  11 ′ as the light source. The unit  11 ′ has plural photodiodes  101  (described in FIGS.  12  to  14  later) as the required light source, and a shade  102  to collect the intensity of light from the photodiodes  101 . The photodiodes can be LEDs. The light source is controlled by the circuit  19  (described in FIGS. 15A to  16 ).  
         [0066]    As shown in FIG. 11, module  10  further includes a photoguider  18  as the reflector. The photoguider  18  can be a hollow mirror cuboid consisting of four reflective mirrors, or a solid glass cube. The photodiodes  101  generate an unpolarized light beam a through the shade  102 . The beam a incident on the photoguider  18  forms a uniformly unpolarized light beam a′.  
         [0067]    As shown in FIG. 11, the beam a′ is propagated into the splitter  20  and generates a p-polarized light beam b and an s-polarized light beam c. The beam b is propagated directly through an interface of the splitter  20  and the beam c is reflected by the interface. Next, the beam c is reflected by the splitter  20  to the panel  30 . The panel  30  can be a TFT-LCD, an LCOS display or an MEM display, wherein the LCOS display is preferred in view of current technique and cost. Next, the beam c is reflected and converted by the panel  30  into a p-polarized image light beam e. Finally, the beam e is propagated through the splitter  20  and projected by the module  40  on a viewing plane.  
         [0068]    In the fifth to seventh embodiments of the invention, the first polarizing beam splitter  20  is used to separate the sand p-polarized beams. Further, the splitter  20  guides the s-polarized beam to illuminate on the panel  30 .  
         [0069]    [Light Source] 
         [0070]    [0070]FIG. 12 is a schematic diagram of an illuminating unit according to the invention. For the illuminating units  11 ′ or  15 ′ used to the embodiments, the photodiodes are implemented on one or two sides of a circuit board  103 . As shown in FIG. 12, for example, the circuit board  103  has two photodiode groups  112 L,  112 R and four metallization pads R, G, B, GND coupled between the groups  112 L,  112 R and the light control circuit  19  (FIGS.  15 A- 16 ). The group  112 L is implemented on one side of the circuit board  103  and the group  112 R is implemented on the other side opposite to the group  112 L. Additionally, the pad R is for the photodiodes with red light, the pad G is for the photodiodes with green light, the pad B is for the photodiodes with blue light and the pad GND is commonly for the ground.  
         [0071]    An example of the group  112 L is described in detail for simplicity in view of symmetric configuration of the illuminating units.  
         [0072]    [0072]FIGS. 13 and 14 are two embodiments of the group  112 L in FIG. 12 according to the invention. In practice, red-light, blue-light and green-light dies  101  are implemented on the board  103  in any arrangement that can illuminate uniformly integrated red, blue and green light, as shown in FIGS. 13 and 14.  
         [0073]    As shown in FIGS. 13 and 14, the group  112 L was symmetrically arranged in the board  103  with a length of 22 mm, a width of 8.5 mm and a thickness of 0.8 mm. Occupied area of the group  112 L can be varied as desired and with physical room, for example, the occupied area is different in FIGS. 13 and 14. Additionally, for current fabricating technique, the side of the splitter  20  can obtain a lateral length of about 13 mm, the size of the panel  30  is up to 12.5 mm and the module  40  can obtain a length of about 25 mm and a width of about 15 mm. As cited, the inventive device can achieve space requirements.  
         [0074]    As shown in FIG. 13, in this embodiment, when two 2×7 photodiode arrays are in the top and the bottom and one 2×10 photodiode array is in the middle, a like-lateral T profile is formed. As shown in FIG. 14, in this embodiment, when two 2×6 photodiode arrays are in the top and the bottom and one 2×9 photodiode array is in the middle, a like-lateral T profile is also formed. The red, green and blue photodiodes respectively adopted DL-AV0001 LEDs, DL-AV0002 and DL-AV0003 Zener diodes sold by Delta Electronics Inc., based on cost and photo-utility.  
         [0075]    As shown in FIG. 13, in this embodiment, the same color light photodiodes are electrically connected in series as a group by a wire to the respective pad (described in FIGS. 15A and 15B). For example, the connected red photodiodes are connected to the pad R, the connected green photodiodes are connected to the pad G, and the connected blue photodiodes are connected to the pad B. Additionally, all photodiodes are connected in series to the pad GND to avoid circuit errors. All pads are connected to the circuit  19  for light control, which is described in detail in FIGS.  7 - 11 .  
         [0076]    [Light Control Circuit] 
         [0077]    [0077]FIG. 15A is a schematic diagram of an embodiment of the light control circuit  19  in conjunction with FIG. 14 according to the invention. As shown in FIG. 15A, the circuit  19  essentially includes: three discontinuous pulse generators ( 80 ,  82 ,  84 ) and three driving circuits ( 800 ,  820 ,  840 ). The light control circuit  19  drives and control RGB photodiode groups (red photodiode group  801 , green photodiode group  821 , blue photodiode group  841 ) for illumination. The discontinuous pulse generators ( 80 ,  82 ,  84 ) generate pulses in turn. The outputs of the generators ( 80 ,  82 ,  84 ) are electrically connected to the driving circuits ( 800 ,  820 ,  840 ), respectively. The outputs of the driving circuits ( 800 ,  820 ,  840 ) are electrically connected to the RGB groups ( 801 ,  821 ,  841 ) in order to sequentially illumination of red, green, blue photodiodes as an image. The image is projected on a viewing plane to form a color image due to persistence of vision when viewed.  
         [0078]    [0078]FIG. 15B is a schematic diagram of another form of the embodiment of the light control circuit in conjunction with FIG. 14 according to the invention. As shown in FIG. 15B, the light control circuit essentially includes: three DC-DC voltage converter  71 - 73 , an RGB field-sequential color microdisplay  75  (this can be CMD8X6DDI Field Sequential Control ASIC produced by Three Five System, Inc.) and three MOSFET switches Q 1 -Q 3 . The circuit  19  can further include an illumination controller  74  in front of the microdisplay  75  to control the luminance of the photodiodes  101 .  
         [0079]    [0079]FIG. 16 is a timing diagram of FIG. 15B according to the invention. As shown in FIG. 16 with reference to FIG. 15B, the microdisplay  75  outputs Red, Green, Blue pulses. The pulses are electrically connected to gates of the switches Q 1 -Q 3  one to one. Sources of the switches Q 1 -Q 3  are grounded. Drains of the switches Q 1 -Q 3  are respectively connected to one side of at least one resistor R 1 . The other side of the resistor R 1  is connected to the reverse side of a relative cascade photodiode group. For example, the switch Q 1  is connected to the reverse side of the red photodiode group  801  through the relative resistor R 1 ; the switch Q 2  is connected to the reverse side of the green photodiode group  821  through the relative resistor R 1 ; and the switch Q 3  is connected to the reverse side of the blue photodiode group  841  through the relative resistor R 1 . Every group is connected to a specific DC-DC voltage converter. In this embodiment, the group  801  is connected to the converter  71 , the group  821  is connected to the converter  72 , and the group  841  is connected to the converter  73 . The converters  71 - 73  consistent with the relative RGB pulses drive the corresponding photodiode groups  801 ,  821 ,  841  to sequentially illuminate. A DC voltage Vin is supplied to the converters  71 - 73  and the controller  74 . The output of the controller  74  (adopted CMD3XLB Illumination Controller produced by Three Five System, Inc.) is electrically connected to the input of the microdisplay  75 .  
         [0080]    As shown in FIG. 15B, an explanation is given with reference to FIG. 14. Each of the groups  801 ,  821  and  841  has a separate operating voltage provided by the connected converters  71 - 73 , as cited above.  
         [0081]    Additionally, the controller  74  connected to the microdisplay  75  sequentially controls the luminance of the RGB photodiodes  101  using the prior pulse width modulation (PWM) technique and the resulting pulses are output to the microdisplay  75 . The microdisplay  75  changes the output frequency CLK according to the received pulses with different pulse widths to adjust a rate of data bus DATA to the switches Q 1 -Q 3 . Therefore, the photodiode groups  801 ,  821 ,  841  continuously and sequentially illuminate lights Red, Green, Blue as desired. The switches can be MOSFETs.  
         [0082]    The cited photodiodes  101  are wired with same color photodiodes (i.e., LEDs) as a group with plural cascade rows even though the same color photodiodes are not arranged adjacent to each other in the light source modules or illuminating units. For example, the first row in FIG. 14 includes the group  801  of red LEDs D 11 , D 13 , D 15 , . . . , the group  821  of blue LEDs D 12 , . . . , and the group  841  of green LEDs D 11 , . . . D 1n ; the second row includes the group  801  of red LEDs D 22 , . . . , the group  821  of blue LEDs D 24 , . . . , D 22 , and the group  841  of green LEDs D 21 , D 23  D 25 , . . . ; and so on. All photodiodes are connected commonly to the pad GND for the ground. All the same color rows are connected in parallel as a color group. Therefore, the RGB groups are formed as shown in the circuits  801 ,  821 ,  841  of FIG. 15B.  
         [0083]    As shown in FIG. 15B, the DC-DC voltage converters  71 - 73  provide the operating voltage by converting a cell voltage of 5V into the desired voltage of 12V. Instead of the converters  71 - 73 , AC-DC converters (not shown) can be used to provide the groups  801 ,  821 ,  841  with the operating voltage as required.  
         [0084]    These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiment disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.