Abstract:
A dual direction driving apparatus and method for driving an optical scanning module of an image scanning device are provided. The driving apparatus includes a first driving mechanism installed in the scanner and a second driving mechanism installed in the optical scanning module. The first driving mechanism and the second driving mechanism are simultaneously driven in order to drive the optical scanning module to move along a driving direction for performing image scanning on a document to be scanned. The second driving mechanism drives the optical scanning module to move in either the same or opposite direction with respect to the driving direction of the first driving mechanism for responding to different scanning resolution requirements of scanning operations.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a driving technique of an image scanning device, and more especially to a dual direction driving apparatus and method for driving an optical scanning module of the image scanning device.  
           [0003]    2. Description of the Prior Art  
           [0004]    Conventional flat-bed image scanning devices have been widely used to scan/read image of documents, configured as shown in FIGS. 1 and 2. The conventional scanner comprises a scanner frame  11 , a light transmittable document positioning plate  12  for positioning the document to be scanned, an optical scanning module  13 , and a pair of guiding rails  14   a,    14   b.  Also referring to FIG. 3, the optical scanning module  13  comprises an image sensing element  14  such as a charge coupling device (CCD) or a contact image scanning (CIS), a focus lens  15 , a light source  16 , and a plurality of light reflection mirrors  171 ,  172 ,  173 , and  174 .  
           [0005]    The optical scanning module  13  is driven by a conventional driving mechanism comprising such as a motor  18  and a transmission rope  19 , and moved along the guiding rails  14   a,    14   b  for scanning the original document  2  positioned on the document positioning plate  12 . In the conventional mechanism designing, the optical scanning module  13  is driven by a single driving module for movement. For example, one end of the optical scanning module  13  is fixed on the transmission rope  19  by a fixing component  131 . Therefore, the optical scanning module  13  may be moved along the guiding rails  14   a,    14   b  when the transmission rope  19  is driven by the motor  18 .  
           [0006]    It is known that the scanning resolution of the scanner is determined by the moved distance per unit time of the optical scanning module. When a high scanning resolution is required, the optical scanning module has to be moved for a relatively short distance per unit time, i.e., the moving speed is relatively low. On the contrary, when a low scanning resolution is required, the optical scanning module has to be moved for a relatively long distance per unit time, i.e., the moving speed is relatively high. In the conventional technique, the scanner can not provide both high and low resolution scanning functions because it utilizes a single driving mechanism for moving the optical scanning module.  
           [0007]    For example, if a same driving mechanism is used for resulted in two scanning resolutions 50 dpi and 2400 dpi, the ratio between the corresponding moving speeds of the optical scanning module for the two resolutions is 48. It will be very difficult if a single driving mechanism is used for achieving the two different scanning resolutions with such a wide range. In case that a single driving mechanism for the optical scanning module is desired to meet the requirements of both high and low scanning resolutions, the component cost of the driving motor will be increased, the torque of the motor will be decreased, and the designing difficulty will be increased.  
           [0008]    Thus, it is desirable to provide a new driving mechanism for the optical scanning module of the image scanning device to overcome the problems described above and facilitate scanning operation.  
         SUMMARY OF THE INVENTION  
         [0009]    Consequently, a primary purpose of the present invention is to provide a driving apparatus for an optical scanning module of a scanner. The driving apparatus comprises a first driving mechanism installed in the scanner, a second driving mechanism installed in the optical scanning module and engaged with the first driving mechanism. The optical scanning module may move on the first driving mechanism when driven by the second driving mechanism for scanning an original document positioned in the scanner.  
           [0010]    Another purpose of the present invention is to provide a dual direction driving apparatus for an optical scanning module of a scanner. The optical scanning module may be moved by cooperation of a first driving mechanism and a second driving mechanism of the driving apparatus. The first driving mechanism and the second driving mechanism may provide the same or the opposite driving directions so that the optical scanning module can scan a document to be scanned with different speeds for meeting the different resolution requirements.  
           [0011]    Further another purpose of the present invention is to provide a dual direction driving method for an optical scanning module of a scanner. A first driving mechanism is firstly driven to move in a first transmission direction. Simultaneously, a second driving mechanism is driven to move in a second transmission direction. The optical scanning module is driven by cooperation of the first driving mechanism and the second driving mechanism and moved along the first transmission direction for scanning a document positioned in the scanner.  
           [0012]    Accordingly, one aspect of the present invention is to provide a dual direction driving apparatus for driving an optical scanning module of a scanner to move with respect to an original document to be scanned. The driving apparatus comprises a first driving mechanism installed in the scanner, and a second driving mechanism installed in the optical scanning module and movably engaging with the first driving mechanism. The optical scanning module is driven by the second driving mechanism to engageably move with respect to the first driving mechanism for scanning the original document to be scanned.  
           [0013]    Another aspect of the present invention is to provide a dual direction driving method for driving an optical scanning module of a scanner. The method comprises steps of providing a first driving mechanism installed in the scanner and driving the optical scanning module in a first direction, providing a second driving mechanism which is installed in the optical scanning module and driving the optical scanning module to move in a second direction parallel to the first direction, and scanning an original document to be scanned by movement of the optical scanning module.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a perspective view of a conventional flat-bed image scanning device;  
         [0015]    [0015]FIG. 2 is a partially exploded perspective view illustrating a driving mechanism is arranged in the conventional image scanning device of FIG. 1;  
         [0016]    [0016]FIG. 3 is a schematic view showing an optical path of the conventional scanner of FIG. 1;  
         [0017]    [0017]FIG. 4 is a perspective view of a first embodiment of the present invention;  
         [0018]    [0018]FIG. 5 is a partially exploded perspective view showing a driving mechanism of the present invention is arranged in the image scanning device of FIG. 4;  
         [0019]    [0019]FIG. 6 is a schematic view showing an optical path of the scanner of FIG. 5;  
         [0020]    [0020]FIG. 7 is a perspective view of a second embodiment of the present invention; and  
         [0021]    [0021]FIG. 8 is a perspective view of a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring to FIGS. 4 and 5, a first embodiment of a dual direction driving apparatus for an optical scanning module of a scanner is shown. The driving apparatus comprises a scanner frame  31 , a document positioning plate  32  for position of a document to be scanned, an optical scanning module  33 , and a guiding rail  34 .  
         [0023]    A transmission belt  4  is arranged in the scanner frame  31 . The transmission belt  4  extends along the moving direction of the optical scanning module  33  and it is fixed at one end thereof by a fixing component  41  while driven by a driving motor  42  at the other end. The transmission belt  4  and the driving motor  42  together constitute a first driving mechanism for moving the optical scanning module  33  with respect to the document positioning plate  32  mounted on the scanner frame  31 , where an original document to be scanned is located.  
         [0024]    Also referring to FIG. 6, a gear  5  extends from one end of the optical scanning module  33  and it can be driven by a driving motor  51  arranged in the optical scanning module  33 . The gear  5  together with the driving motor  51  constitute a second driving mechanism of the present invention for moving the optical scanning module  33  with respect to the transmission belt  4 .  
         [0025]    When the gear  5  and the driving motor  51  operate, the optical scanning module  33  may be driven to move along the guiding rail  34  and the transmission belt  4  because the gear  5  engages with an inner tooth portion  40  formed in an inner periphery of the transmission belt  4 . Therefore, the moving speed of the optical scanning module  33  with respective to the document to be scanned may be calculated from two components, one driven by the first driving mechanism and the other driven by the second driving mechanism.  
         [0026]    Suppose the moving speed of the optical scanning module  33  due to the gear  5  and the driving motor  51  is V 1  and suppose the moving speed of the optical scanning module  33  due to the transmission belt  4  and the driving motor  42  is V 2 . If V 1  and V 2  are in the same direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  plus V 2  (i.e., V=V 1 +V 2 ). This speed is relatively high suitable for low resolution scanning.  
         [0027]    If V 1  and V 2  are in the opposite direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  minus V 2  (i.e., V=V 1 −V 2 ). This speed is relatively low suitable for high resolution scanning.  
         [0028]    The driving motors  42 ,  51  may be well known stepping motors or DC motors. If the driving motors  42 ,  51  are stepping motors, the stepping modes thereof may be full step, half step, quarter step, or one eighth step. Therefore, the speed modes of the optical scanning module  33  may be varied according to the different rotation directions and stepping modes of the stepping motors  42 ,  51 .  
         [0029]    Referring to FIG. 7, a second embodiment of the driving apparatus is shown. The second embodiment is similar to the first embodiment except that the transmission belt  4  of the first driving mechanism has an outer tooth portion  43  formed on the outer periphery thereof and capable of engaging with the gear  5  of the second driving mechanism of the scanner.  
         [0030]    The transmission theory of the second embodiment is similar to that of the first embodiment. Suppose the moving speed of the optical scanning module  33  due to the gear  5  and the driving motor  51  is V 1  and suppose the moving speed of the optical scanning module  33  due to the transmission belt  4  and the driving motor  42  is V 2 . If V 1  and V 2  are in the same direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  plus V 2  (i.e., V=V 1 +V 2 ). If V 1  and V 2  are in the opposite direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  minus V 2  (i.e., V=V 1 −V 2 ).  
         [0031]    Referring to FIG. 8, a third embodiment of the driving apparatus is shown. Similar to the previous two embodiments described above, the third embodiment comprises a first driving mechanism for carrying the optical scanning module  33  to move with respect to the document to be scanned and a second driving mechanism installed associated with the optical scanning module  33  for directly driving the optical scanning module  33  to move with respect to the first driving mechanism.  
         [0032]    In the third embodiment, the first driving mechanism comprises a threaded guiding rod  6 , a driving motor  61 , and a slant gear assembly  62  driven by the driving motor  61  and engaged with the threaded guiding rod  6 . The second driving mechanism is similar to that of the first embodiment except that the gear  5  of FIG. 6 is replaced by a slant gear  5   a.  The slant gear  5   a  is used to engage with the threaded guiding rod  6 . The threaded guiding rod  6  is driven to rotate by the driving motor  61  and the slant gear assembly  62 . The optical scanning module  33  will be moved along the guiding rail  34  and the threaded guiding rod  6  when the threaded guiding rod  6  is driven to rotate. The optical scanning module  33  may also move with respect to the document to be scanned when it is driven by the second driving mechanism which comprises the slant gear  5   a  and the driving motor  51  (see FIG. 6).  
         [0033]    Similar to the previous two embodiments, there are two moving speeds for the optical scanning module  33 , one from the first driving mechanism and the other from the second driving mechanism. Suppose the moving speed of the optical scanning module  33  due to the slant gear  5   a  and the driving motor  51  is V 1  and suppose the moving speed of the optical scanning module  33  due to the threaded guiding rod  6 , the driving motor  61 , and the slant gear assembly  62  is V 2 . If V 1  and V 2  are in the same direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  plus V 2  (V=V 1 +V 2 ). If V 1  and V 2  are in the opposite direction, the finalized moving speed V of the optical scanning module  33  with respect to the document to be scanned will be V 1  minus V 2  (V=V 1 −V 2 ).  
         [0034]    From the above embodiments, it can be appreciated that the scanning speed may be increased or decreased via cooperation of the first driving mechanism and the second driving mechanism for meeting different resolution requirements of the scanner. The moving speed of the optical scanning module may be determined by the relative movement between the first driving mechanism and the second driving mechanism, which in turn determines the scanning resolution of the scanner. If the moving speeds caused by the two driving mechanism are in the same direction, the finalized moving speed will be a plus result of both speed components, otherwise the finalized moving speed will be a minus result of the two speed components. Accordingly, the scanning speed and the scanning resolution can be well controlled by the cooperation of the two driving mechanisms.  
         [0035]    While the present invention has been described with reference to the specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications to the present invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.