Abstract:
A thin image reading device includes a housing, a lens installed inside the housing for focusing light, a photosensor installed on a first side of the lens for converting light outputted from the lens into digital signals, and a plurality of reflectors installed on a second side of the lens for reflecting light inputted into the image reading device to form a linear optical path in order to guide the light to the photosensor via the lens. In addition, no reflector is installed on the first side of the lens.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to an image reading device, and more specifically, to a thin image reading device. 
   2. Description of the Prior Art 
   In the modern age, it is important to make electronic products more compact in size. For a scanner, which scans documents and pictures, the major obstacle to compactness is the size of the scanning module. The design of the scanning module is greatly influenced by the optical path and corresponding reflector installation of the scanning module. In particular, the thickness of the scanning module is closely related to the thickness of the reflectors and their subsequent position and installation. One option to reduce the size of the scanning module is to reduce the thickness of the reflectors. However, if the reflectors are not thick enough, they may be too fragile for use, meaning that they could be broken due to collision, and thus worsening the quality of scanning. Therefore, changing the position and the installation of the reflectors is a preferable manner. 
   Please refer to  FIG. 1  showing the optical path of a conventional scanning module  10  using four reflectors. The scanning module  10  includes a housing  12 , a lens  14  for focusing light, a photosensor  16  for converting light from the lens  14  into digital signals, and four reflectors a first reflector  18 , a second reflector  20 , a third reflector  22  and a fourth reflector  24 . The first reflector  18 , the second reflector  20 , and the fourth reflector  24  are installed on a first side of the lens  14 , and the third reflector  22  is installed above the lens  14  on a second side. 
   When scanning a document, the light is reflected by the document through a slit  26  off the first reflector  18 , then the second reflector  20 , then the third reflector  22 , then the fourth reflector  24 , and finally through the lens  14  where it is focused on the photosensor  16 , which converts the light into digital signals. As shown in  FIG. 1 , the first reflector  18 , the second reflector  20 , and the fourth reflector  24  are installed on the first side of the lens  14 , and the third reflector  22  is installed on the second side of the lens  14 . Since the third reflector  22  is installed on the opposite side of the first reflector  18 , the second reflector  20 , and the fourth reflector  24 ; it needs to be installed above the lens  14  to prevent the lens  14  from interfering with the light reflected from the second reflector  20  to the third reflector  22  and the light reflected from the third reflector  22  to the fourth reflector  24 . Because the third reflector  22  is installed above the lens  14 , the housing  12  of the scanning module  10  has a height at least equal to the height of the third reflector  22  plus the height of the lens  14 . 
   Therefore, the height of the scanning module  10  can be only reduced in a limited fashion according to the prior art meaning that the thickness of the scanning module can hardly be reduced if the using the conventional installation of reflectors. 
   SUMMARY OF INVENTION 
   It is therefore a primary objective of the present invention to provide a thin image reading device in order to minimize size of an electronic product using the image reading device. 
   Briefly summarized, the claimed invention provides an image reading device including a housing, a lens installed inside the housing for focusing light, a photosensor installed on a first side of the lens for converting light outputted from the lens into digital signals, and a plurality of reflectors installed on a second side of the lens for reflecting light inputted into the image reading device to form a linear optical path in order to guide the light to the photosensor via the lens. In addition, no reflector is installed on the first side of the lens. 
   The claimed invention also provides a scanning module of a scanner including a housing, a lens installed inside the housing for focusing light, a photosensor installed on a first side of the lens for converting light outputted from the lens into digital signals, and a plurality of reflectors installed on a second side of the lens for reflecting light inputted into the scanning module to form a linear optical path in order to guide the light to the photosensor via the lens. In addition, no reflector is installed on the first side of the lens. 
   These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments that are illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  illustrates the optical path of a conventional scanning module using four reflectors. 
       FIG. 2  illustrates a scanning module using four reflectors according to the first embodiment of the present invention. 
       FIG. 3  illustrates a scanning module using three reflectors according to the second embodiment of the present invention. 
       FIG. 4  illustrates a scanning module using five reflectors according to the third embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   The present invention provides several embodiments, wherein the reflector installation of a scanning module is changed as follows, in order to reduce the thickness of the scanning module. 
   Please refer to  FIG. 2  showing a scanning module using four reflectors according to the first embodiment of the present invention. The scanning module  30  includes a housing  32 , a lens  34  for focusing light, a photosensor  36  installed on a first side of the lens  34  for converting light outputted from the lens  34  into digital signals, and four reflectors a first reflector  38 , a second reflector  40 , a third reflector  42  and a fourth reflector  44  installed on a second side of the lens  34  for reflecting light coming from a scanned document to the lens  34 . As shown in  FIG. 2 , when scanning a document, the light is reflected by the document through a slit  46  off the first reflector  38 , then the second reflector  40 , then the third reflector  42 , then the fourth reflector  44 , and through a space between the first reflector  38  and the second reflector  40  to the lens  34 . The lens  34  then focuses the light on the photosensor  36 , where it is converted into digital signals. The photosensor  36  can be a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). 
   As shown in  FIG. 2 , the reflectors  38 ,  40 ,  42 ,  44  are all installed on the second side of the lens  34  for reflecting light coming from the scanned document. The first reflector  38  and the third reflector  42  partially cover the edge ring of the lens  34  but not the main part of the lens  34  so that the light can be still focused on the photosensor  34  by the lens  34 . Moreover, the four reflectors in the present embodiment are all located on the second side of the lens  34  so that the optical path does not need to pass over or below the lens  34 , and no reflector is required to be installed above or below the lens  34 . Thus the thickness of the scanning module  30  can be reduced. 
   Please refer to  FIG. 3  showing a scanning module using three reflectors according to the second embodiment of the present invention. The scanning module  50  includes a housing  52 , a lens  54  installed inside the housing  52  for focusing light, a photosensor  56  installed on a first side of the lens  54  for converting light outputted from the lens  34  into digital signals, and three reflectors a first reflector  58 , a second reflector  60  and a third reflector  62  installed on a second side of the lens  54  for reflecting light coming from a scanned document to the lens  54 . As shown in  FIG. 3 , when scanning a document, the light is first reflected by the document through a slit  64  off the first reflector  58 , then the second reflector  60 , then the third reflector  62 , and then off to the second reflector  60  again before finally passing through a space between the first reflector  58  and the third reflector  62  to the lens  54 . The lens  54  focuses the light on the photosensor  56  where it is converted into digital signals. As shown in  FIG. 3 , the reflectors  58 ,  60 ,  62  are all installed on the second side of the lens  54  for reflecting light from the document. The first reflector  58  and the third reflector  62  partially cover the edge ring of the lens  54  but not the main part of the lens  54  so that the light can be still reflected from the second reflector  60  to the lens  54 . Moreover, the three reflectors are all located on the second side of the lens  54  so that the optical path does not need to pass over or below the lens  54 , and no reflector is required to be installed above of below the lens  54 . Thus the thickness of the scanning module  50  can be reduced. 
   Please refer to  FIG. 4  showing a scanning module using five reflectors according to the third embodiment of the present invention. The scanning module  70  includes a housing  72 , a lens  74  installed inside the housing  72  for focusing light, a photosensor  76  installed on a first side of the lens  74  for converting light from the lens  74  into digital signals, and five reflectors a first reflector  78 , a second reflector  80 , a third reflector  82 , a fourth reflector  84  and a fifth reflector  86  installed on a second side of the lens  74  for reflecting light from a document to be scanned to the lens  74 . As shown in  FIG. 4 , when scanning a document, the light is first reflected by the document through a slit  88  off the first reflector  78 , then the second reflector  80 , then the third reflector  82 , then the fourth reflector  84 , then off the second reflector  80  again, and then off the fifth reflector  86  before finally passing through a space between the second reflector  80  and the third reflector  82  to the lens  74 . The lens  74  focuses the light on the photosensor  76  where it is converted into digital signals. 
   As shown in  FIG. 4 , the reflectors  78 ,  80 ,  82 ,  84 ,  86  are all installed on the second side of the lens  74  for reflecting light coming from the scanned document. The second reflector  80  and the third reflector  82  partially cover the edge ring of the lens  74  but not the main part of the lens  74  so that the light can be still focused on the photosensor  76  by the lens  74 . Moreover, the five reflectors are all located on the second side of the lens  74  so that the optical path does not need to pass over or below the lens  74 , and no reflector is required to be installed above of below the lens  74 . Thus the thickness of the scanning module  70  can be reduced. 
   In contrast to the prior art, the reflectors of the scanning modules  30 ,  50 ,  70  according to the present invention are all installed on the second side of the lens  34 ,  54 ,  74  so that the optical path does not need to pass over or below the lens  34 ,  54 ,  74 , and no reflector is required to be installed above or below the lens  34 ,  54 ,  74 . Thus, the thickness of the scanning modules can be greatly reduced. 
   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.