Patent Publication Number: US-2005128107-A1

Title: Photoconductive encoder wheel

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a photoconductive encoder structure, and especially to a photoconductive encoder with more cogs surrounded a grating cogwheel and a better focusing effect of a light source. Furthermore, the production process of the grating cogwheel is more convenient.  
      2. Description of Related Art  
      A prior art mouse comprises an X-axis encoder and a Y-axis encoder with output logic sequence signals such as, for example,  11 ,  10 ,  00 ,  01 . The mouse is placed on a top or other surface of a desk and is moved in designated directions to move a cursor on a monitor to corresponding positions. The movement of the cursor on the monitor made by the mouse adopts a principle that the X-axis and the Y-axis encoders together produce control signals to move the cursor.  
      Reference is made to  FIG. 1 ; an encoder mainly comprises a light source  60 , an encoder wheel  65 , and a sensor (using two juxtaposed sensing chips S 1  and S 2  to produce phase signals)  70 . When the encoder is in operation, light emitted by the luminescence element  60  and received by the sensor  70  is sheltered or not sheltered by the encoder wheel  65 . The sensor  70  generates sequence signals including OFF ( 0 ) and ON ( 1 ). For example, when the grating cogwheel  65  rotates clockwise, the sensor  70  generates repeated and continuous sequence signals  111000011  . . . ; and when the grating cogwheel  65  rotates counterclockwise, the sensor  70  generates repeated and continuous sequence signals  01001011010001  . . . for circuit encoding.  
      Reference is made to  FIG. 2A  and  FIG. 2B , in which the grating cogwheel  65  comprises a housing  67  having square cogs  66 . A cylinder  68  with a cylindrical space defined therein protrudes from the center of the housing  67 . A plurality of bumps  69  are set on the corresponding square teeth  66  along the circumference of an incident surface on the housing  67 . Therefore, the light emitted by the luminescence element  60  is projected on the incident surface of the grating cogwheel  65  and then focused. The focused light is refracted by a triangle-shaped section  671  to the top of the square cogs  66  and then projected to the sensor  70 . Because of the rotation of the grating cogwheel  65 , the sensitization chips S 1  and S 2  produce OFF ( 0 ) and ON ( 1 ) sequence signals for circuit encoding.  
      The depth and the width of the two adjacent square cogs  66 , and the numbers of the granules  69  in the structure of the grating cogwheel  65 , are also important factors in the production process. Therefore, the numbers of the square cogs  66  and the granules  69  on the grating cogwheel  65  are limited to a fixed value.  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to provide a photoconductive encoder structure with a greater number of teeth without affection the manufacturing process of the photoconductive encoder wheel.  
      Another object of the present invention is to provide a photoconductive encoder structure, which can focus light of a light source, refract the light, and finally refocus the light onto a sensor.  
      To achieve the object of the present invention, an incident surface of a grating cogwheel is surrounded by a protruding surface. Divided protruding wheel parts in equal arc-shapes surround the grating cogwheel. Light from a light source is first focused by the protruding surface of the grating cogwheel and then refracted to the corresponding protruding wheel parts for focusing. Finally, the light is transmitted to the sensor to produce different phase sequence signals.  
      Furthermore, the above-mentioned grating cogwheel includes a disk-shaped housing, and a cylinder with a columnar space in it protrudes from the center of the housing.  
      The above-mentioned housing of the grating cogwheel includes a refracting space to conduct the light focused by the protruding surface to the protruding wheel parts.  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: 
    
    
     BRIEF DESCRIPTION OF DRAWING  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:  
       FIG. 1  shows a perspective view of a prior art photoconductive encoder;  
       FIG. 2A  shows a front view of a prior art grating cogwheel;  
       FIG. 2B  shows an exploded view of the prior art grating cogwheel;  
       FIG. 3  shows a perspective view of the present invention;  
       FIG. 4A  shows a front view of a grating cogwheel of the present invention;  
       FIG. 4B  shows an exploded view of the grating cogwheel of the present invention; and  
       FIG. 5  shows front views of four signals ( 0 , 0 ), ( 1 , 1 ), ( 1 , 1 ), ( 1 , 0 ) on the oscilloscope when the grating cogwheel of the present invention rotates continuously. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Reference is made to  FIG. 3 ; the present invention is a photoconductive encoder wheel comprising a grating cogwheel  1  made of light-transparent materials such as, for example, acrylic, polycarbonate, or glass, two light sources  2  and a sensor  3  having two rows of sensing chips S 1 , S 2 . Light emitted by the luminescence elements  2  is first focused by the grating cogwheel  1  and then refracted; finally, the light is refocused onto the sensing chips S 1 , S 2  of the sensor  3 .  
      Reference is made to  FIG. 4A  and  FIG. 4B . The grating cogwheel  1  includes a disk-shaped housing  11  with a protruding surface  12 , and the light emitted by the luminescence elements  2  will first be focused by the protruding surface  12  when the light is projected on it. A cylinder  13  with a space in it protrudes from the center of the housing  11 . A plurality of oblique-conic spaces  14  is set concavely in the housing  11 , equidistant from each other and surrounding the circumference of the cylinder  13 . There is an inclined plane  141  between the oblique-cone spaces  14  and the housing  11 . Separate protruding wheel parts  15  in equal arc-shapes surround the grating cogwheel  1 . The light first focused by the protruding surface  12  is refracted to the corresponding protruding wheel parts  15  for focusing again, and then the light is conducted to the sensing chips S 1  and S 2  of the sensor  3  to produce different phase sequence signals.  
      The light emitted by the luminescence element  2  is focused by the protruding surface  12  of the grating cogwheel  1  at first, and the inclined plane  141  refracts the light and conducts it to the protruding wheel parts  15  for focusing again. Finally, the light is conducted to the sensing chips S 1  and S 2  of the sensor  3  to generate different phase sequence signals. When light is detected by the sensitization chips S 1  and S 2 , ON signals are produced; and OFF signals are produced when the sensitization chips S 1  and S 2  do not detect the light. As  FIG. 5  shows, when the grating cogwheel  1  rotates continuously, the oscilloscope displays four signals ( 0 , 0 ), ( 0 , 1 ), ( 1 , 1 ), ( 1 , 0 ).  
      The improved structure of the present invention as mentioned above has the following features: 
          1. The grating cogwheel can focus the light once and refract the light for focusing again.     2. Due to the protruding wheel parts being in equal arc-shapes, the number of the cogs on the grating cogwheel is increased, and the structure of the present invention does not affect the production process.     3. The structure of the present invention uses a circular protruding surface as the incident surface on the grating cogwheel for focusing, and the number of the granules on the grating cogwheel will not be limited.        

      Although the present invention has been described with reference to the preferred embodiment therefore, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.