Abstract:
A scanner includes a light source, a reflect piece, a lens, and a sensor. The light source generates light. The reflective piece includes one protrusion for reflecting the light from the light source. The lens transmits the light from the light source and the reflect piece. The sensor detects the light from the lens.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a scanner, and more particularly, to a scanner that can generate uniform light.  
           [0003]    2. Description of the Prior Art  
           [0004]    The typical method for capturing an image with a scanner requires using a light source to illuminate a document, the light reflecting from the document being transmitting to a sensor through a lens. Because the document has dark sections reflecting less light and light sections reflecting more light, the sensor senses different intensities of light from different sections and transforms the reflective light into digital data represented by binary values 0 and 1. Finally, software of the scanner saves the digital data as an image file. Most scanners use a charge coupled device (CCD) as the sensor and a florescent tube as the light source. An ideal light source must have uniform light distribution. However, because properties of the tube and the lens, such as the length from the two ends of the tube to the two ends of the CCD being longer than the length from the center of the tube to the center of the CCD, the center of the CCD senses brighter light. For this reason, a reflective piece having a dark section according to the light distribution of the tube is installed at the back of the tube so that the CCD can receive uniform light.  
           [0005]    Please refer to FIG. 1. FIG. 1 is a perspective view of the reflective piece  10  according to the prior art. The color and material of the reflective piece  10  are designed according to the light distribution of the tube. The reflective piece  10  comprises a dark section  14  and a light section  16 . The dark section  14  absorbs more light than the light section  16 , and the light section  16  reflects more light than the dark section  14 . The center of the tube is brighter than the two ends of the tube, so the light section  16  of reflective piece  10  is decreasingly distributed from the two ends of the reflective piece  10  to the center of the reflective piece  10 . That is to say, the reflective piece  10  has more of dark section  14  located at the center and more light section  16  located at the two ends. In this way, the dark section  14  absorbs more light from the center of the tube, and the light section  16  reflects more light from the two ends of the tube, so that the CCD receives as uniform as possible light intensity through the lens from the center and the two ends of the tube.  
           [0006]    Please refer to FIG. 2. FIG. 2 shows graphs of light intensity curves of light received by the CCD. Curve CCD 1  is an ideal light intensity curve, curve CCD 2  is an actual light intensity curve of the tube, while CCD 3  is a light intensity curve using the reflective piece  10 . The ideal light intensity curve is between an upper limit L+ and a lower limit L−. The curve being above the upper limit L+indicates the light is too bright, and the curve being under the lower limit L−indicates the light is too dark. Before using the reflective piece  10 , light, as the curve CCD 2  shows, is seriously reduced at the two ends of the tube. After using the reflective piece  10 , as the curve CCD 3  shows, the light from the center of the tube is decreased but above the lower limit L−, and the two ends of the curve are more or less evenly bright. The reflective piece  10  improves the problem of insufficient light at the two ends of the tube. However, according to this method, the CCD cannot receive light of adequate uniform light intensity.  
           [0007]    From the above description, the scanner uses the tube as the light source, but the tube has the problem of the center being brighter than the two ends. The reflective piece  10  is installed at the back of the tube to reduce this problem. After using the reflective piece  10 , the CCD receives reduced light from the center of the tube and more light from the two ends of the tube. The reflective piece  10  partially solves the problem of the tube, however, the light distribution of the tube is not uniform, and such variance in light intensity decreases the quality of the scanner.  
         SUMMARY OF INVENTION  
         [0008]    It is therefore a primary objective of the claimed invention to provide a scanner that can generate uniform light to solve the above-mentioned problem.  
           [0009]    According to the claimed invention, a scanner comprises a light source for generating light; a reflective piece having one protrusion for reflecting the light from the light source; a lens for transmitting the light from the light source and the reflective piece; and a sensor for detecting the light from the lens.  
           [0010]    According to another claimed invention, a scanner comprises a light source for generating light; a reflective piece for reflecting the light from the light source, the reflective piece having a dark section decreasingly distributed from the center to the two sides of the reflective piece for absorbing part of the light from the light source, and two protrusions located at the two sides of the dark section for reflecting part of the light from the light source to the two sides of the light source; a lens for transmitting the light from the light source and the reflective piece; and a sensor for detecting the light from the lens.  
           [0011]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    [0012]FIG. 1 is a perspective view of a reflective piece according to prior art.  
         [0013]    [0013]FIG. 2 shows graphs of light intensity curves received by the CCD.  
         [0014]    [0014]FIG. 3 is a schematic view of a scanner according to the present invention.  
         [0015]    [0015]FIG. 4 is a perspective view of a first reflective piece according to the present invention.  
         [0016]    [0016]FIG. 5 shows graphs of light intensity curves received by the CCD according to the present invention.  
         [0017]    [0017]FIG. 6 is a perspective view of a second reflective piece according to the present invention.  
         [0018]    [0018]FIG. 7 shows light intensity curves received by the CCD according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]    Please refer to FIG. 3 to FIG. 5. FIG. 3 is a schematic diagram of a scanner  20  according to the present invention. FIG. 4 is a perspective view of a first reflective piece  24  according to the present invention. FIG. 5 illustrates light intensity curves according to the present invention. The scanner  20  comprises a tube  22 , the reflective piece  24 , a lens  26 , and a CCD  28 . The scanner  20  uses the tube  22  to illuminate a document  18 , and the CCD  28  receives the light through the lens  26  reflected from the document  18 . The CCD  28  senses the different light intensities reflected from the different sections of the document  18 . Because the tube  22  is brighter at the center and darker at the two ends, the reflective piece  24  is used to improve the light distribution. As shown in FIG. 4, the reflective piece  24  has a protrusion  30  located corresponding to the center of the tube  22 . The peak of the protrusion  30  is located corresponding to the center of the tube  22 , and the right and left slopes are extended corresponding to the two ends of the tube  22 . The two slopes reflect part of the light from the center of the tube  22  to the two sides of the tube  22  so that the CCD  28  can receive uniform light. As shown in FIG. 5, a curve CCD 1  is an ideal light intensity curve, a curve CCD 2  is a light intensity curve of the tube  22 , and a CCD 4  is a light intensity curve using the reflective piece  24 . After applying the reflective piece  24 , the uneven light distribution, particularly at the two ends of the tube  22 , is improved.  
         [0020]    Please refer to FIG. 6. FIG. 6 is a perspective view of a second reflective piece  32  according to the present invention. After applying the reflective piece  24 , the uneven light distribution, particularly at the two ends of the tube  22 , is improved. As shown in FIG. 6, in a preferred embodiment according to the present invention, the reflective piece  32  has a dark section  34  and a light section  36 . The reflective piece  32  further has two protrusions located at the two ends of the reflective piece  32  respectively. The dark section  34  absorbs more light than the light section  36 , and the light section  36  reflects more light than the dark section  34 . The light section  36  is decreasingly distributed from the two ends to the center of the reflective piece  32  according to the light distribution of the tube  22 . Because of the dark section  34  and the light section  36  of the reflective piece  32 , the CCD  28  receives the most light at the two ends of the tube  22 . Two protrusions  38  are located corresponding to the two brightest sections for reflecting part of the light to the two sides of the two brightest sections. In this way, the CCD  28  can receive uniform light intensity from the length of the tube  22 .  
         [0021]    Each protrusion  38  reflects light to the two sides of the located section. The protrusion  38  of the reflective piece  32  is triangular or arc-shaped. For example, consider the platform of the scanner  20  being about A4 (210 mm*297 mm) in size, the length of the tube being 238 mm, and the scanning section being 216 mm. Because of the dark section  34  and light section  36 , the CCD  28  receives the highest light intensity at an inner 20 mm from the two ends of the tube  22 . Thus, the two triangular protrusions  38  is 2 mm high at the inner 20 mm from the two sides of the reflective piece  32 . The protrusion  38  has a right and a left slope. The horizontal length of the slope is 15 mm. The surface of the slope is light section  36 . With the protrusion  38 , the reflective piece  32  can reflect part of the light to the two sides of the brightest section so that the CCD  28  can receive uniform light intensity from the tube  22 .  
         [0022]    Please refer to FIG. 7. FIG. 7 illustrates light intensity curves received by the CCD  28 . The curve CCD 1  is the ideal light intensity curve, the curve CCD 2  is a light intensity curve of the tube  22 , and a curve CCD 5  is a light intensity curve using the reflective piece  32 . The ideal light intensity curve is between an upper limit L+ and a lower limit L−. Because the tube  22  is brighter at the center and darker at the two ends, the light, as curve CCD 2  shows, is seriously reduced at the two ends of the tube. After the reflective piece  32  is installed at the back of the tube  22 , the CCD  28  receives a light distribution tending to the ideal, as curve CCD 5  shows. The curve CCD 5  decreases gently at two ends of the tube  22  but everywhere is between the upper limit L+ and the lower limit L−.  
         [0023]    From the above description, the protrusion  30  of the reflective piece  24  is located according to the light distribution of the tube  22  to reflect part of the light from the brighter section to the darker section of the tube to reduce the problem of uneven light distribution. For the CCD  28  to receive uniform light, in the preferred embodiment according to the present invention, the protrusions  38  of the reflective piece  32  are located at the brightest sections resulting from the dark section  34  and the light section  36 , that is, the location corresponding to the two ends of the tube  22 . The protrusions  38  can be adjusted to suit the light profile provided by the dark section  34  and the light section  36  to reflect part of the light of the brighter section to the darker section of the tube  22 . After the reflective piece  32  is installed, the CCD  28  receives a light profile tending to the ideal curve.  
         [0024]    In contrast to the prior art, the reflective piece according to the present invention allows the tube to generate uniform light thereby solving the problem of low light intensity at the two ends of the tube. The reflective piece according to the prior art only improves the problem of the darker two ends of the tube, and results in the brightest sections being at the two ends of the tube decreasing the quality of the scanner. The reflective piece according the present invention has two protrusions installed at the two ends of the reflective piece respectively to reflect part of the light to the two sides of the brightest section so that the CCD receives a nearly ideal light profile, enhancing the quality of the scanner.  
         [0025]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.