Abstract:
Scanners are provided. A scanner includes a housing, a scanning module, and a light source. The housing comprises a transparent plate bearing a target. The scanning module is movably disposed in the housing and scans the target through the transparent plate. The light source is disposed outside the scanning module and generates a light beam detectable by the scanning module.

Description:
BACKGROUND  
       [0001]     The invention relates to scanners.  
         [0002]     Scanners are commonly used to scan documents or images, such that users can process the electronic documents or images on computers conveniently.  
         [0003]     Generally, a scanner comprises a housing and a scanning module. The scanning module is disposed in the housing. The housing comprises a transparent plate bearing a document. The scanning module moves forward and backward to scan the document through the transparent plate. Typically, before a scan, the scanning module returns to an initial location to fully scan the document. The initial location is the location where the scanning module is located when the scanner is turned on.  
         [0004]     In a conventional scanner, the housing has a specific pattern thereon, such as a bar code, disposed in a location corresponding to the initial location of the scanning module. Thus, the scanning module can determine whether it is in the initial location according to a captured image. If the captured image matches the specific pattern, it is determined that the scanning module is in the initial location. The document or dust on the transparent plate can, however, interfere with the specific pattern since the specific pattern is located in a scan area of the scanning module, such that the scanning module may mistakenly scan the document.  
       SUMMARY  
       [0005]     Scanners are provided. An exemplary embodiment of a scanner comprises a housing, a scanning module, and a light source. The housing comprises a transparent plate bearing a target. The scanning module is movably disposed in the housing and scans the target through the transparent plate. The light source is disposed outside the scanning module and generates a light beam detectable by the scanning module.  
       DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0007]      FIG. 1  is a diagram of an embodiment of a scanner, wherein a scanning module is in an initial location.  
         [0008]      FIG. 2  is a schematic diagram of a charge coupled device (CCD) of a scanning module below a light exit area of a light guiding plate when the scanning module is in an initial location.  
         [0009]      FIG. 3  is a diagram showing the back of a light guiding plate.  
         [0010]      FIG. 4  is a diagram of an embodiment of a scanner, wherein a scanning module is not in an initial location. 
     
    
     DETAILED DESCRIPTION  
       [0011]     The invention is described in greater detail in the following.  
         [0012]     A principle aim of the invention is to add a new light source to a scanner. The new light source is disposed outside a scanning module and a transparent plate generating a light beam detectable by the scanning module. The scanning module then determines whether it is substantially in an initial location according to strength of the detected light beam.  
         [0013]      FIG. 1  is a diagram of an embodiment of a scanner  10 , wherein a scanning module  12  is in an initial location.  FIG. 2  is a schematic diagram of a charge coupled device (CCD)  19  of the scanning module  12  below a light exit area  17  of a light guiding plate  14  when the scanning module  12  is in the initial location.  FIG. 3  is a diagram showing the back of the light guiding plate  14 .  
         [0014]     As shown in the drawings, the scanner  10  comprises a housing  11 , a scanning module  12 , a light source  13 , and a light guiding plate  14 .  
         [0015]     The housing  11  comprises a transparent plate  15  bearing a document.  
         [0016]     The scanning module  12  is disposed in the housing  11 . The scanning module  12  can move forward and backward to scan the document through the transparent plate  15 . Before a scan, the scanning module  12  returns to an initial location to fully scan the document. The initial location, as shown in  FIG. 1 , is the location where the scanning module  12  is located when the scanner  10  is turned on.  
         [0017]     The light source  13  is fixed in the housing  11 . The light source  13  is a light-emitting diode (LED) outside the scanning module  12  and the transparent plate  15 . The light source  13  generates a light beam  18  detectable by the scanning module  12 . The light beam  18  is monochromatic, such as green light. Frequency f of the light beam  18  is adjustable.  
         [0018]     The light guiding plate  14  is fixed in the housing  11 . The light guiding plate  14  comprises a light entrance area  16  and a light exit area  17 . The light entrance area  16  is adjacent to the light source  13  to receive the light beam  18  generated by the light source  13 . The light exit area  17  is outside the transparent plate  15 . The light guiding plate  14  guides the light beam  18  to the light exit area  17 . It is noted that the outer surface of the light guiding plate  14  is covered with light reflecting material except for the light entrance area  16  and the light exit area  17 , forcing the light beam  18  to enter or exit the light guiding plate  14  only via the light entrance area  16  and the light exit area  17 .  
         [0019]     The scanning module  12  comprises a charge coupled device (CCD)  19 . The CCD  19  can detect the light beam  19  generated by the light source  13  periodically according to the frequency f of the light beam  18  when necessary. The scanning module  12  thus determines whether it is substantially in the initial location according to strength of the detected light beam  18 . If the strength exceeds a reference value, the scanning module  12  is substantially in the initial location, and vice versa.  
         [0020]     When the scanning module  12  is in the initial location, as shown in  FIG. 1 , the CCD  19  is below the light exit area  17 . The strength of the light beam  18  emitted from the light exit area  17  detected by the CCD  19  exceeds the reference value, so it is determined that the scanning module  12  is in the initial location exactly.  
         [0021]      FIG. 4  is a diagram of an embodiment of the scanner  10 , wherein the scanning module  12  is not in the initial location. As shown in  FIG. 4 , when the scanning module  12  is not in the initial location, the CCD  19  is not below the light exit area  17 . The strength of the light beam  18  emitted from the light exit area  17  detected by the CCD  19  does not exceed the reference value, so it is determined that the scanning module  12  is not in the initial location.  
         [0022]     In some embodiments, a new light source is added. The new light source is disposed outside a scanning module and a transparent plate generating a light beam detectable by the scanning module. The scanning module then determines whether it is substantially in an initial location according to strength of the detected light beam.  
         [0023]     It is advantageous that a document or dust on the transparent plate can not interfere with the new light source because the new light source is disposed outside the transparent plate, thus preventing the scanning module from mistakenly scanning the document.  
         [0024]     Moreover, because the light beam generated by the light source is monochromatic, a charge coupled device (CCD) of the scanning module needs only one channel to detect the light beam. The CCD can easily distinguish the light beam from normal images or documents, thus accelerating the process to determine whether the scanning module is in the initial location.  
         [0025]     While the invention has been described in terms of preferred embodiment, it is to be understood that the invention 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.