Abstract:
An exemplary liquid crystal display ( 200 ) includes at least two light guide plates ( 211, 212 ) laminated to each other. Each light guide plate includes a light emitting surface and a bottom surface opposite to the light emitting surface, each light guide plate is divided into at least three parts, one light guide plate includes micro-structures on the light emitting surface and the bottom surface in any part, and the parts with the micro-structures of the same light guide plate are separated from each other. A related method for driving the liquid crystal display is also provided.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to liquid crystal displays and driving methods thereof, and particularly to a liquid crystal display with micro-structures and a driving method for the same. 
       GENERAL BACKGROUND 
       [0002]    Because liquid crystal displays have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants, video cameras, and the like. Furthermore, liquid crystal displays are considered by many to have the potential to completely replace cathode ray tube monitors and televisions. 
         [0003]      FIG. 9  is a schematic, pre-assembled view of a conventional liquid crystal display. The liquid crystal display  1  includes a liquid crystal panel  10  and a backlight module  12 . 
         [0004]      FIG. 10  is a block diagram illustrating circuitry of the liquid crystal display  1 . The liquid crystal panel  10  includes a gate driving circuit  14 , a data driving circuit  16 , a timing controller  18 , a plurality of parallel scan lines  101 , a plurality of parallel data lines  103 , a plurality of pixel electrodes  105 , a plurality of thin film transistors  107 , and a plurality of common electrodes  109 . 
         [0005]    The timing controller  18  is electrically coupled to the gate driving circuit  14  and the data driving circuit  16 , respectively. The gate driving circuit  14  drives the scan lines  101 , and the data driving circuit  16  drives the data lines  103 . The scan lines  101  are orthogonal to and isolated from the data lines  103 . The scan lines  101  and data lines  103  thereby cooperatively define a plurality of pixel regions  108  arranged in a regular array. In each pixel region  108 , a pixel electrode  105  and a corresponding common electrode  109  are disposed generally opposite to each other. Each thin film transistor  107  is positioned near a crossing of a corresponding scan line  101  and a corresponding data line  103 . A gate electrode of the thin film transistor  107  is electrically coupled to the scan line  101 , and a source electrode of the thin film transistor  107  is electrically coupled to the data line  103 . Further, a drain electrode of the thin film transistor  107  is electrically coupled to the corresponding pixel electrode  105 . 
         [0006]    The backlight module  12  comprises an inverter  15  and a plurality of lamps  13 . In operation, the inverter  15  provides voltage signals to drive the lamps  13  to emit light beams, thereby illuminating the liquid crystal panel  10 . 
         [0007]      FIG. 11  shows waveform diagrams of scanning signals transmitted in the liquid crystal panel  10 . Under control of the timing controller  18 , the gate driving circuit  14  respectively provides a plurality of scanning signals X 1 ˜Xn to the plurality of scan lines G 1 ˜Gn during a frame time period T. Taking a scan line G 2  as an example, when the scanning signal X 2  is transmitted to the scan line G 2 , the thin film transistors  107  electrically coupled to the scan line G 2  are turned on. 
         [0008]    Simultaneously, under the control of the timing controller  18 , the data driving circuit  16  provides a plurality of data signals to the plurality of data lines  103  respectively, wherein the data signals are high-voltage signals. During the time the scanning signals X 2  are transmitted to the scan line G 2 , the data signals are transmitted to the pixel electrodes  105  via the source electrode and the drain electrode of each of the thin film transistors  107  electrically coupled to the scan line G 2 . Pixel regions  108  coupled to the scan line G 2  display an image accordingly, and maintain the data signals for a total period of time equal to one frame time period T. That is, before subsequent scanning signals are provided to the scan line G 2 , the pixel regions  108  coupled to the scan line G 2  maintain the data signals. 
         [0009]    In the next frame time period (not labeled), the scanning signal X 2  is provided to the scan line G 2  to turn on the thin film transistors  107  electrically coupled to the scan line G 2 , and simultaneously subsequent data signals are provided to the pixel electrodes  105  via the source electrode and the drain electrode of each of the thin film transistors  107  electrically coupled to the scan line G 2 . Thereby, the pixel regions  108  coupled to the scan line G 2  display a subsequent image, and maintain subsequent data signals for a total period of time equal to one frame time period T. 
         [0010]    However, when the pixel regions  108  of the liquid crystal panel  10  display the same image for a sustained period, image-sticking may be generated on the liquid crystal panel  10 . When the liquid crystal panel  10  switches to display a subsequent image, the data signals maintained in the pixel regions  108  cannot be rapidly released, and offset voltages are liable to be generated between the pixel electrodes  105  and the common electrodes  109  of the pixel regions  108 . The offset voltages may affect the display quality of the liquid crystal panel  10  during the subsequent time period, such that the liquid crystal panel  10  experiences image-sticking. 
         [0011]    What is needed, therefore, is a liquid crystal display and a driving method for the same that can overcome the limitations described. 
       SUMMARY 
       [0012]    A liquid crystal display comprises at least three light sources and at least two light guide plates laminated to each other. Each light guide plate includes a top light emitting surface and a bottom surface, and is divided into at least three parts. Only one light guide plate comprises micro-structures on the light emitting surface and the bottom surface in any part, and the parts with micro-structures of the same light guide plate are separated from each other. Each light source is disposed adjacent to one of the light incident surfaces of the at least two light guide plates. 
         [0013]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view of a liquid crystal display according to a first embodiment of the present invention, the liquid crystal display including a backlight module. 
           [0015]      FIG. 2  is an exploded, isometric view of the backlight module of  FIG. 1 , comprising two light guide plates with V-cut groove structures, and first, second, third, and fourth light sources. 
           [0016]      FIG. 3  is a coordinate diagram of pitch between V-cut groove structures and the total number of the V-cut groove structures, in respect of the light guide plates of the liquid crystal display of  FIG. 1 . 
           [0017]      FIG. 4  is an optical path diagram of the backlight module of  FIG. 1  when the second light source is turned on. 
           [0018]      FIG. 5  is an optical path diagram of the backlight module of  FIG. 1  when the fourth light source is turned on. 
           [0019]      FIG. 6  is a block diagram illustrating abbreviated circuitry of the liquid crystal display of  FIG. 1 . 
           [0020]      FIG. 7  is a waveform diagram showing driving signals generated by the liquid crystal display of  FIG. 1 . 
           [0021]      FIG. 8  is a side view of a liquid crystal display according to a second embodiment of the present invention. 
           [0022]      FIG. 9  is a schematic, pre-assembled view of a conventional liquid crystal display. 
           [0023]      FIG. 10  is a block diagram illustrating abbreviated circuitry of the liquid crystal display of  FIG. 9 . 
           [0024]      FIG. 11  is a waveform diagram showing scanning signals transmitted in the liquid crystal display of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]    Reference will now be made to the drawings to describe preferred and exemplary embodiments in detail. 
         [0026]      FIG. 1  is a side view of a liquid crystal display according to a first embodiment of the present invention. The liquid crystal display  200  includes a backlight module  21  and a liquid crystal panel  20  disposed thereon. The backlight module  21  comprises a first light guide plate  211 , a second light guide plate  212 , a reflector  213 , a first light source L 1 , a second light source L 2 , a third light source L 3 , and a fourth light source L 4 . The first light guide plate  211  is disposed between the liquid crystal panel  20  and the reflector  213 , and the second light guide plate  212  is disposed between the liquid crystal panel  20  and the first light guide plate  211 . The first and second light guide plates  211 ,  212  are rectangular. The first and second light guide plates  211 ,  212  are made of polymethyl methacrylate. Refractive indices of the first and second light guide plates  211 ,  212  are both 1.49. Each of light guide plate  211 ,  212  includes a first light incident surface (not labeled), a second light incident surface (not labeled), a top light emitting surface (not labeled), and a bottom surface (not labeled). The first and second light incident surfaces are at opposite sides of the light plate  211 ,  212 . The first light incident surface is perpendicularly connected with both the light emitting surface and the bottom surface. Each of the light guide plates  211 ,  212  is divided into a first part A 1 , a second part A 2 , a third part A 3 , and a fourth part A 4 , all having the same area. A display area of the liquid crystal panel  20  is divided into a first part B 1  corresponding to the first part A 1 , a second part B 2  corresponding to the second part A 2 , a third part B 3  corresponding to the third part A 3 , and a fourth part B 4  corresponding to the fourth part A 4 . 
         [0027]    The first light source L 1 , the second light source L 2 , the third light source L 3 , and the fourth light source L 4  may be cold cathode fluorescent lamps. The first light source L 1  is disposed adjacent to the first light incident surface of the first light guide plate  211 . The second light source L 2  is disposed adjacent to the first light incident surface of the second light guide plate  212 . The third light source L 3  is disposed adjacent to the second light incident surface of the first light guide plate  211 . The fourth light source L 4  is disposed adjacent to the second light incident surface of the second light guide plate  212 . 
         [0028]      FIG. 2  is an exploded, isometric view of the backlight module  21 . The light emitting surface of the first part A 1  of the first light guide plate  211 , the light emitting surface of the third part A 3  of the first light guide plate  211 , the light emitting surface of the second part A 2  of the second light guide plate  212 , and the light emitting surface of the fourth part A 4  of the second light guide plate  212  all comprise micro-structures, such as V-cut groove structures. In the illustrated embodiment, pitches of the V-cut groove structures are constant, and extension axes of the V-cut groove structures are all perpendicular to the four light sources L 1 , L 2 , L 3 , L 4 . 
         [0029]    The bottom surface of the first part A 1  of the first light guide plate  211 , the bottom surface of the third part A 3  of the first light guide plate  211 , the bottom surface of the second part A 2  of the second light guide plate  212 , and the bottom surface of the fourth part A 4  of the second light guide plate  212  all comprise micro-structures, such as V-cut groove structures. Pitches of the V-cut groove structures are variable, as shown in  FIG. 3 . Extension axes of the V-cut groove structures are all parallel to the four light sources L 1 , L 2 , L 3 , L 4 . 
         [0030]      FIG. 4  is an optical path diagram of the backlight module when the second light source L 2  is turned on, and  FIG. 5  is an optical path diagram of the backlight module when the fourth light source L 4  is turned on. When the second light source L 2  is turned on, light beams emitted from the second light source L 2  enter the second light guide plate  212 , with most being totally reflected by the light emitting surface and the bottom surface of the first part A 1  of the second light guide plate  212  and then entering the second part A 2  of the second light guide plate  212 . A few of the light beams exit from the light emitting surface of the first part A 1  of the second light guide plate  212 . 
         [0031]    A first portion of the light beams entering into the second part A 2  of the second light guide plate  212  is directly emitted from the light emitting surface of the second light guide plate  212  and enters the liquid crystal panel  20 . A second portion of the light beams entering the second part A 2  of the second light guide plate  212  is refracted by the V-cut groove structures of the bottom surface of the second part A 2  of the second light guide plate  212 , then passes through the first light guide plate  211  and is reflected by the reflector  213 , finally passing through the first light guide plate  211 , the second light guide plate  212  and entering the liquid crystal panel  20 . A third portion of the light beams entering the second part A 2  of the second light guide plate  212  enters the third part A 3  and the fourth part A 4  of the second light guide plate  212 . The third portion of the light beams entering the second part A 2  of the second light guide plate  212  is much less than the first portion of the light beams entering the second part A 2  of the second light guide plate  212  or the second portion of the light beams entering the second part A 2  of the second light guide plate  212 . 
         [0032]    Thus, when the second light source L 2  is turned on, most of the light beams emitted from the second light source L 2  exit from the light emitting surface of the second part A 2  of the second light guide plate  212 , and a minimum of the light beams emitted from the second light source L 2  exit from the light emitting surface of the first part A 1  of the second light guide plate  212 , the light emitting surface of the third part A 3  of the second light guide plate  212 , and the light emitting surface of the fourth part A 4  of the second light guide plate  212 . Accordingly, the second parts A 2  of the first light guide plate  211  and the second light guide plate  212  are defined as strong light parts, and the first parts A 1  of the first light guide plate  211  and the second light guide plate  212 , the third parts A 3  of the first light guide plate  211  and the second light guide plate  212 , and the fourth parts A 4  of the first light guide plate  211  and the second light guide plate  212  are defined as weak light parts. The second part B 2  of the liquid crystal panel  20  is correspondingly defined as a strong light part, and the first part B 1  of the liquid crystal panel  20 , the third part B 3  of the liquid crystal panel  20 , and the fourth part B 4  of the liquid crystal panel  20  are correspondingly defined as weak light parts. 
         [0033]    When the fourth light source L 4  is turned on, light beams emitted from the fourth light source L 4  enter the second light guide plate  212 . A first portion of the light beams directly exit from the light emitting surface of the fourth part A 4  of the second light guide plate  212  and enter the liquid crystal panel  20 . A second portion of the light beams is refracted by the V-cut groove structures of the bottom surface of the fourth part A 4  of the second light guide plate  212 , then passes through the first light guide plate  211  and is reflected by the reflector  213 , finally passing through the first light guide plate  211 , the second light guide plate  212  and entering the liquid crystal panel  20 . A third portion of the light beams enters the third part A 3 , the second part A 2 , and the first part A 1  of the second light guide plate  212 . The third portion of the light beams is much less than the first portion of the light beams or the second portion of the light beams. 
         [0034]    Further, when the fourth light source L 4  is turned on, most of the light beams emitted from the fourth light source L 4  exit from the light emitting surface of the fourth part A 4  of the second light guide plate  212 , and a minimum of the light beams emitted from the fourth light source L 4  exit from the light emitting surface of the first part A 1  of the second light guide plate  212 , the light emitting surface of the second part A 2  of the second light guide plate  212 , and the light emitting surface of the third part A 3  of the second light guide plate  212 . Accordingly, the fourth parts A 4  of the first light guide plate  211  and the second light guide plate  212  are defined as strong light parts, and the first parts A 1  of the first light guide plate  211  and the second light guide plate  212 , the second parts A 2  of the first light guide plate  211  and the second light guide plate  212 , and the third parts A 3  of the first light guide plate  211  and the second light guide plate  212  are defined as weak light parts. The fourth part B 4  of the liquid crystal panel  20  is correspondingly defined as a strong light part, and the first part B 1  of the liquid crystal panel  20 , the second part B 2  of the liquid crystal panel  20 , and the third part B 3  of the liquid crystal panel  20  are correspondingly defined as weak light parts. 
         [0035]    As a result, when the first light source L 1  is turned on, most of the light beams emitted from the first light source L 1  exit from the light emitting surface of the first part A 1  of the first light guide plate  211 , and a minimum of the light beams emitted from the first light source L 1  exit from the light emitting surface of the second part of the first light guide plate  211 , the light emitting surface of the third part of the first light guide plate  211 , and the light emitting surface of the fourth part of the first light guide plate  211 . Thus, the first parts A 1  of the first light guide plate  211  and the second light guide plate  212  are defined as strong light parts, and the second parts of the first light guide plate  211  and the second light guide plate  212 , the third parts of the first light guide plate  211  and the second light guide plate  212 , and the fourth parts of the first light guide plate  211  and the second light guide plate  212  are defined as weak light parts. The first part B 1  of the liquid crystal panel  20  is correspondingly defined as a strong light part, and the second part B 2  of the liquid crystal panel  20 , the third part B 3  of the liquid crystal panel  20 , and the fourth part B 4  of the liquid crystal panel  20  are correspondingly defined as weak light parts. 
         [0036]    When the third light source L 3  is turned on, most of the light beams emitted from the third light source L 3  exit from the light emitting surface of the third part A 3  of the first light guide plate  211 , and a few of the light beams emitted from the third light source L 3  exit from the light emitting surface of the first part of the first light guide plate  211 , the light emitting surface of the second part of the first light guide plate  211 , and the light emitting surface of the fourth part of the first light guide plate  211 . Accordingly, the third parts of the first light guide plate  211  and the second light guide plate  212  are defined as strong light parts, and the first parts of the first light guide plate  211  and the second light guide plate  212 , the second parts of the first light guide plate  211  and the second light guide plate  212 , and the fourth parts of the first light guide plate  211  and the second light guide plate  212  are defined as weak light parts. The third part B 3  of the liquid crystal panel  20  is correspondingly defined as a strong light part, and the first part B 1  of the liquid crystal panel  20 , the second part B 2  of the liquid crystal panel  20 , and the fourth part B 4  of the liquid crystal panel  20  are correspondingly defined as weak light parts. 
         [0037]      FIG. 6  is a block diagram illustrating abbreviated circuitry of the liquid crystal display  200 . The liquid crystal panel  20  includes a scanning circuit  24 , a data circuit  26 , a timing controller  28 , a plurality of scanning lines G 1 ˜Gn, a plurality of data lines C 1 ˜Cm, and a plurality of pixels  208  cooperatively defined by the crossing scanning lines G 1 ˜Gn and data lines C 1 ˜Cm. The plurality of scanning lines G 1 ˜Gn are distributed across different parts of the liquid crystal panel  20 . For example, when n is equal to  1024 , the scanning lines G 1 ˜G 256  belong to the first part B 1  of the liquid crystal panel  20 , the scanning lines G 257 ˜G 512  belong to the second part B 2  of the liquid crystal panel  20 , the scanning lines G 513 ˜G 768  belong to the third part B 3  of the liquid crystal panel  20 , and the scanning lines G 769 ˜G 1024  belong to the fourth part B 4  of the liquid crystal panel  20 . 
         [0038]    Each of the pixels  208  comprises a pixel electrode  205 , a thin film transistor  207 , and a common electrode  209  generally opposite the pixel electrode  205 . The thin film transistor  207  is disposed near an intersection of a corresponding one of the scanning lines G 1 ˜Gn and a corresponding one of the data lines C 1 ˜Cm. A gate electrode of the thin film transistor  207  is electrically coupled to the corresponding one of the scanning lines G 1 ˜Gn, and a source electrode of the thin film transistor  207  is electrically coupled to the corresponding one of the data lines C 1 ˜Cm. Further, a drain electrode of the thin film transistor  207  is electrically coupled to the pixel electrode  205 . 
         [0039]    The backlight module  21  includes an inverter  25  and a light source module  23 . The light source module  23  includes the first light source L 1 , the second light source L 2 , the third light source L 3 , and the fourth light source L 4 . 
         [0040]    The timing controller  28  generates first control signals, second control signals, and third control signals. The scanning circuit  24  receives the first control signals and generates scanning signals to scan the plurality of scanning lines G 1 ˜Gn. The data circuit  26  receives the second control signals and generates data signals to drive the plurality of data lines C 1 ˜Cm. The inverter  25  receives the third control signals and generates backlight control signals to drive the light sources L 1 ˜L 4 . 
         [0041]    When the liquid crystal display  200  operates normally, the first to fourth light sources L 1 ˜L 4  are sequentially turned on or turned off. Only one of the light sources L 1 ˜L 4  is turned on at any one time, and others are turned off at such time. 
         [0042]      FIG. 7  is a waveform diagram showing driving signals generating by the driving circuit. In  FIG. 7 , X 1 ˜X 1024  represent the scanning signals of the scanning lines G 1 ˜G 1024  (n=1024) respectively, and Y 1 ˜Y 4  represent the backlight control signals of the light sources L 1 ˜L 4  respectively. 
         [0043]    The timing controller  28  generates the first control signals, the second control signals, and the third control signals. The scanning circuit  24  receives the first control signals and generates the scanning signals X 1 ˜X 1024  to scan the plurality of scanning lines G 1 ˜G 1024 . A time period in which the scanning line G 1  is firstly scanned and secondly scanned is defined as a frame time period T. The data circuit  26  receives the second control signals and generates a plurality of data signals. The data signals are transmitted to the data lines C 1 ˜Cm. The inverter  25  receives the third control signals and generates backlight control signals to turn on or turn off the light sources L 1 ˜L 4 . 
         [0044]    During a first time period T/4, the scanning lines G 1 ˜G 256  are scanned and the first light source L 1  is turned on. Accordingly, the first parts A 1  of the first light guide plate  211  and the second light guide plate  212  are strong light parts, and other parts A 2 , A 3 , A 4  of the first light guide plate  211  and the second light guide plate  212  are weak light parts. The first part B 1  of the liquid crystal panel  20  is a strong light part, and other parts B 2 , B 3 , B 4  of the liquid crystal panel  20  are weak light parts correspondingly. 
         [0045]    During a second time period T/4 (not labeled), the scanning lines G 257 ˜G 512  are scanned and the second light source L 2  is turned on. Accordingly, the second parts A 2  of the first light guide plate  211  and the second light guide plate  212  are strong light parts, and other parts A 1 , A 3 , A 4  of the first light guide plate  211  and the second light guide plate  212  are weak light parts. The second part B 2  of the liquid crystal panel  20  is a strong light part, and other parts B 1 , B 3 , B 4  of the liquid crystal panel  20  are weak light parts correspondingly. 
         [0046]    During a third time period T/4 (not labeled), the scanning lines G 513 ˜G 768  are scanned and the third light source L 3  is turned on. Accordingly, the third parts A 3  of the first light guide plate  211  and the second light guide plate  212  are strong light parts, and other parts A 1 , A 2 , A 4  of the first light guide plate  211  and the second light guide plate  212  are weak light parts. The third part B 3  of the liquid crystal panel  20  is a strong light part, and other parts B 1 , B 2 , B 4  of the liquid crystal panel  20  are weak light parts correspondingly. 
         [0047]    During a fourth time period T/4 (not labeled), the scanning lines G 769 ˜G 1024  are scanned and the fourth light source L 4  is turned on. Accordingly, the fourth parts A 4  of the first light guide plate  211  and the second light guide plate  212  are strong light parts, and other parts A 1 , A 2 , A 3  of the first light guide plate  211  and the second light guide plate  212  are weak light parts. The fourth part B 4  of the liquid crystal panel  20  is a strong light part, and other parts B 1 , B 2 , B 3  of the liquid crystal panel  20  are weak light parts correspondingly. 
         [0048]    After the 1024 th  scanning line G 1024  is scanned, a frame picture is formed on the liquid crystal panel  20 . By repeating the process, continuous images can be viewed. 
         [0049]    Because the strong light parts of the liquid crystal panel  20  change during the frame time period T, image-sticking can be minimized, with display quality of the liquid crystal panel  20  enhanced correspondingly. 
         [0050]      FIG. 8  is a side view of a liquid crystal display according to a second embodiment of the present invention. Characteristics of the liquid crystal display  300  differing from the liquid crystal display  200  are as follows: 
         [0051]    The backlight module  31  includes a first light source L 5 , a second light source L 6 , and a third light source L 7 . The first light source L 5  is disposed adjacent to the first light incident surface of the first light guide plate  311 . The second light source L 6  is disposed adjacent to one of the light incident surfaces of the second light guide plate  312 . The third light source L 7  is disposed adjacent to the second light incident surface of the first light guide plate  311 . Each of the light guide plates  311 ,  312  is divided into a first part A 5 , a second part A 6 , and a third part A 7 . A display area of the liquid crystal panel  30  is divided into a first part B 5  corresponding to the first part A 5 , a second part B 6  corresponding to the second part A 6 , and a third part B 7  corresponding to the third part A 7 . 
         [0052]    The bottom surface of the first part A 5  of the first light guide plate  311 , the bottom surface of the third part A 7  of the first light guide plate  311 , and the bottom surface of the second part A 6  of the second light guide plate  312  all comprise micro-structures, such as V-cut groove structures. Pitches of the V-cut groove structures are variable. Extension axes of the V-cut groove structures are all parallel to the three light sources L 5 , L 6 , L 7 . 
         [0053]    The light emitting surface of the first part A 5  of the first light guide plate  311 , the light emitting surface of the third part A 7  of the first light guide plate  311 , and the light emitting surface of the second part A 6  of the second light guide plate  312  all have micro-structures, such as V-cut groove structures. Pitches of the V-cut groove structures are constant, and extension directions of the V-cut groove structures are all perpendicular to the three light sources L 5 , L 6 , L 7 . 
         [0054]    It can thus be concluded that when a number K (K is an integer, and ≧2) of the light sources is even, a number of light guide plates is K/2, the light guide plates and the liquid crystal panel are divided into K parts respectively, and a time period during which each light source is turned on is T/K. When K is an odd number, the number of light guide plates is (K+1)/2, the light guide plates and the liquid crystal panel are divided into K parts respectively, and the time during which each light source is turned on is T/K. 
         [0055]    In alternative embodiments, the light sources can be linear-type light sources, such as a plurality of light emitting diodes connected in series. 
         [0056]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.