Abstract:
A color printer with a single photo sensor for detecting the position of the ink ribbon. A single photo sensor is place so that it can detect transparent and opaque sections of the ink ribbon. The ribbon winds at a constant speed, so the pattern of transparent and opaque sections periodically repeats. The controller can use the periodicity of the transparent and opaque sections to calculate which dye frame the print head is positioned over. Using this information, the printer can advance the ink ribbon to the desired dye frame for printing onto the photo paper.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a color printer and more particularly, to a color printer with a single photo sensor for detecting the position of an ink ribbon.  
           [0003]    2. Description of the Prior Art  
           [0004]    Please refer to FIG. 1, FIG. 1 is a perspective view of a ribbon apparatus  10  of a prior art color printer. As shown in FIG. 1, the ribbon apparatus  10  of the color printer comprises an ink ribbon  12 , two light sources  32 ,  52 , and two sensors  36 ,  56 . The ink ribbon  12  comprises a plurality of sequentially arranged dye regions  14 . Each dye region  14  comprises four dye frames  16 ,  18 ,  20 ,  22  for placing yellow dye, magenta dye, cyan dye, and over coating dye. An opaque dividing section  24  is located between an over coating dye frame  22  and a yellow dye frame  16 . An opaque dividing section  27  and a transparent dividing section  26  are installed between the yellow dye frame  16  and a magenta dye frame  18 . An opaque dividing section  27  and a transparent dividing section  26  are installed between the magenta dye frame  18  and a cyan dye frame  20 . An opaque dividing section  27  and a transparent dividing section  26  are installed between the cyan dye frame  20  and the over coating dye frame  22 .  
           [0005]    The light sources  32 ,  52  are located on one side of the ink ribbon  12  for producing light beams  34 ,  54  with two predetermined colors. The sensors  36 ,  56 , corresponding to the light sources  32 ,  52 , are located on the opposite side of the ink ribbon  12 . The sensors  36 ,  56  are used to detect light beams  34 ,  54  penetrating through the ink ribbon  12  and produce corresponding signals to determine the position of the ink ribbon. The detection of an opaque dividing section  24  signals the beginning position of a new dye region  14  of the ink ribbon  12 , and also corresponds to the beginning position of a yellow dye frame  16 . The detection of an opaque dividing section  27  and a transparent dividing section  26  by the sensors  36 ,  56  corresponds to the beginning position of the magenta dye frame  18 , cyan dye frame  20 , or over coating dye frame  22 . The use of two sets of light sources  26 ,  28  and sensors  30 ,  32  for detection of the position of the ink ribbon  12  is a disadvantage of the prior art color printer because it increases the amount of parts used, resulting in higher production costs.  
         SUMMARY OF INVENTION  
         [0006]    It is therefore a primary objective of the claimed invention to provide a color printer with a single sensor for detecting the position of the ink ribbon for solving the above-mentioned problem.  
           [0007]    According to the claimed invention, a color printer with a photo sensor for detecting the position of the ink ribbon is provided. The color printer includes an ink ribbon, a print head, a ribbon-driving device, a controller, and a photo sensor. The ink ribbon includes a plurality of sequentially arranged dye regions. Each dye region includes a plurality of dye frames of different colors. The print head is used to thermally transfer the dye on the ink ribbon onto photo paper. The ribbon-driving device is used to move the ink ribbon in a predetermined direction at a predetermined speed. The print head transfers the dye on each of the dye frames of one dye region onto the photo paper one by one in order to form a color picture. The controller is used to control the operations of the color printer. The photo sensor is used to illuminate the ink ribbon and produce corresponding output signals. The photo sensor outputs a signal of either a first status or a second status. When the controller utilizes the ribbon-driving device to move the ink ribbon in the predetermined direction, a period of time that has passed since the last change in status generated by the photo sensor is used to identify the position of the ink ribbon.  
           [0008]    It is an advantage compared to the prior art that the color printer of the claimed invention only needs a single optical sensing system to detect the position of the ink ribbon. The beginning position of each dye frame in the ink ribbon is determined by a digital method, fewer parts are used, and production costs are lowered.  
           [0009]    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, which is illustrated in the multiple figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of a ribbon apparatus  10  of a prior art color printer.  
         [0011]    [0011]FIG. 2 is a functional block diagram of a color printer  60  according to the present invention.  
         [0012]    [0012]FIG. 3 is a perspective view of a ribbon apparatus  60  of a color printer according to the present invention.  
         [0013]    [0013]FIG. 4 is a table contrasting output signals with each corresponding dye frame and dividing section.  
         [0014]    [0014]FIG. 5 is a time sequence diagram of the output signals generated by the optical sensing system shown in FIG. 3.  
         [0015]    [0015]FIG. 6 is a schematic diagram of a ribbon apparatus  100  of a color printer according to the second embodiment of the present invention.  
         [0016]    [0016]FIG. 7 is a time sequence diagram of the output signals generated by the optical sensing system shown in FIG. 6. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Please refer to FIG. 2 and FIG. 3. FIG. 2 is a functional block diagram of a ribbon apparatus  60  of a color printer according to the present invention. FIG. 3 is a perspective view of a ribbon apparatus  60  of a color printer according to the present invention. The ribbon apparatus  60  is a part of a photo printer for printing on photo paper. The ribbon apparatus  60  comprises an ink ribbon  70 , an optical sensing system, a controller  90 , a print head  92 , and a ribbon driving device  94 . The optical sensing system further comprises a green light source  72  and a photo sensor  74 . The ink ribbon  70  is installed inside a ribbon cartridge in a windable manner. The ribbon driving device  94  is used for winding the ink ribbon  70  inside the ribbon cartridge so that the ink ribbon  70  is rolled in a predetermined direction. The ink ribbon  70  comprises a plurality of sequentially arranged dye regions  80 . Each of the dye regions  80  comprises four dye frames  62 ,  64 ,  66 ,  68  for carrying dye of different colors, and each of the dye frames  62 ,  64 ,  66 ,  68  has a substantially equal first length  86 . The dye frames  62 ,  64 ,  66 ,  68  are used for separately placing yellow dye, magenta dye, cyan dye, and over coating dye. Dividing sections  82 ,  84   a ,  84   b ,  84   c  are positioned at the front end of each of the dye frames  62 ,  64 ,  66 ,  68  respectively. Each of the dividing sections  82 ,  84   a ,  84   b ,  84   c  has a substantially equal second length  88 , which is shorter than the first length  86 . The dividing sections  82 ,  84   a ,  84   b ,  84   c  are opaque, transparent, transparent, and transparent, respectively, and are used to signal to the controller  90  a beginning position of each of the dye frames  62 ,  64 ,  66 ,  68 . The controller  90  is utilized to control the color printer  60 . The controller  90  comprises a timer  96 , which is used to record a time required for the ribbon driving device  94  to move the ink ribbon  70  to different dye regions  80 . The details of the operating mechanism are described in FIG. 5 and FIG. 7. The print head  92  is used to print the dye on the ink ribbon  70  onto the photo paper. The ribbon driving device  94  winds the ink ribbon  70  inside the ribbon cartridge at a constant linear speed or at a constant angular speed, and the print head  92  prints the dye on the dye frames  62 ,  64 ,  66 ,  68  in the dye region  80  onto photo paper sequentially so as to form a pattern of colors.  
         [0018]    As shown in FIG. 2 and FIG. 3, the optical sensing system of the color printer  60  is located on both sides of the ink ribbon  70 . The optical sensing system comprises a green light emitting diode (i.e. green light source  72 ) positioned on one side of the ink ribbon  70  for emitting a green light beam  76  toward the ink ribbon  70 , and a photo sensor  74  positioned on the other side of the ink ribbon  70  for detecting the green light beam  76  penetrating the ink ribbon  70  and generating corresponding output signals  78 . The output signals  78  comprise either a first status or a second status. In the present embodiment, the output signals  78  are voltage signals where the first status is high voltage status and the second status is low voltage status. When the controller  90  utilizes the ribbon driving device  94  to wind the ink ribbon  70 , the photo sensor  74  detects the green light beam  76  penetrating the dye region  80  and generates output signals  78 . The controller  90  will then determine the position of the ink ribbon  70  according to a duration of time that has passed since the output signals  78  last shifted from one status to another status. This duration is referred to as the status-to-status duration. Once the position of the ink ribbon  70  is known, the controller  90  will control the ribbon driving device  94  and the print head  92  to move the ink ribbon  70  to the proper location and complete the printing process.  
         [0019]    Please refer to FIG. 4 and FIG. 5. FIG. 4 is a table contrasting output signals with each corresponding dye frame and dividing section. FIG. 5 is a time sequence diagram of the output signals generated by the optical sensing system shown in FIG. 3. As shown in FIG. 4, the green light source  72  has higher penetration rates for the yellow dye frame  62 , the over coating dye frame  68 , and the transparent dividing sections  84   a ,  84   b ,  84   c . As a result, when the green light beam  76  passes through the yellow dye frame  62 , the over coating dye frame  68 , and the transparent dividing sections  84   a ,  84   b ,  84   c , the output signal  78  is of the first status (i.e. high voltage status), and its digital signal is represented by “1”. The green light source  72  has lower penetration rates for the magenta dye frame  64 , the cyan dye frame  66 , and the opaque dividing section  82 . Therefore, when the green light beam  76  passes through the magenta dye frame  64 , the cyan dye frame  66 , and the opaque dividing section  82 , the sensing signal  78  is of the second status (i.e. low voltage status), and its digital signal is represented by “0”.  
         [0020]    As shown in FIG. 5, when two adjacent sections of an ink ribbon  70  having different penetration rates pass by the photo sensor  74  sequentially, the photo sensor  74  will detect a status variation. For example, the output signal  78  of the photo sensor  74  could go from high voltage status to low voltage status, or from low voltage status to high voltage status. In the present embodiment, when the controller  90  receives the output signal  78  generated by the photo sensor  74 , the timer  96  records the status-to-status duration of the output signal  78  and compares the status-to-status duration with a threshold time T th  to determine the position of the ink ribbon  70 . After the controller  90  determines the position of the predetermined dye frame, the controller  90  discerns the position of the other dye frames, and the print head  92  prints the dye on other dye frames onto the photo paper sequentially.  
         [0021]    When printing the dye on the dye frame  62 ,  64 ,  66 ,  68  in a dye region  80  of the ink ribbon  70  onto the photo paper, the ribbon driving device  94  winds the ink ribbon  70  inside the ribbon cartridge at the constant linear speed. Therefore, each of the dye frames  62 ,  64 ,  66 ,  68  has a sensing time equal to that of any other dye frame, referred to as first time T p , generated by the timer  96  inside the controller  90 . Similarly, each of the dividing sections  82 ,  84 ,  84 ,  84  has another sensing time equal to that of any other dividing section, referred to as second time T b . The first time T p  is longer than the threshold time T th , which is longer than the second time T b . In general, the printing order of the ink ribbon  70  is the yellow dye frame  62 , the magenta dye frame  64 , the cyan dye frame  66 , and the over coating dye frame  68 . As a result, when determining the beginning position of the ink ribbon  70 , the color printer has to search for the yellow dye frame  62 , the magenta dye frame  64 , the cyan dye frame  66 , and the over coating dye frame  68 , in that order. The details is described as follows (please refer to FIG. 3, FIG. 4 and FIG. 5): Step  160 : Search for the yellow dye frame  62 . Turn on the green light source  72  and the photo sensor  74 , and wind the ink ribbon  70  at the constant linear speed or at the constant angular speed.  
         [0022]    Step  162 : When the digital signal of the output signal goes from “1” to “0”, the timer  96  starts to count time, and the ink ribbon  70  is continuously wound at the constant linear speed.  
         [0023]    Step  164 : When the digital signal of the output signal goes from “0” to “1”, and the time recorded by the timer  96  is shorter than the threshold time T th , the beginning position of the yellow dye frame  62  is detected, and the color printer  60  can start to print the dye on the yellow dye frame  62  onto the photo paper. When the time recorded by the timer  96  is longer than the threshold time T th  and the digital signal of the output signal doesn&#39;t go from “0” to “1” yet, the photo sensor  74  is still positioned within the magenta dye frame  64  or the cyan dye frame  66 , and the search process goes back to step  162  to keep searching for the yellow dye frame  62 .  
         [0024]    Step  166 : Search for the magenta dye frame  64 . Because printing of the dye on yellow dye frame  62  onto the photo paper has just finished, the photo sensor  74  must still be within the yellow dye frame  62 . Continuously wind the ink ribbon  70 . When the digital signal of the output signal generated by the photo sensor  74  goes from “1” to “0”, the beginning position of the magenta dye frame  64  is detected. Then, start to print the dye on the magenta dye frame  64  onto the photo paper. Thereafter perform step  168  to search for the cyan dye frame  66 .  
         [0025]    Step  168 : Search for the cyan dye frame  66 . Because printing of the dye on the magenta dye frame  64  onto the photo paper has just finished, the photo sensor  74  must still be within the magenta dye frame  64 . Continuously wind the ink ribbon  70 . When the digital signal of the output signal generated by the photo sensor  74  goes from “0” to “1”, the beginning position of the transparent dividing section  84  is detected. When the digital signal of the output signal generated by the photo sensor  74  goes from “1” to “0” again, the beginning position of the cyan dye frame  66  is detected. Then, start to print the dye on the cyan dye frame  66  onto the photo paper. Thereafter perform step  170  to search for the over coating dye frame  68 .  
         [0026]    Step  170 : Search for the over coating dye frame  68 . Because printing of the dye on the cyan dye frame  66  onto the photo paper has just finished, the photo sensor  74  must still be within the cyan dye frame  66 . Continuously wind the ink ribbon  70 . When the digital signal of the output signal generated by the photo sensor  74  goes from “0” to “1”, the beginning position of the over coating dye frame  68  is detected. Then, start to print the dye on the over coating dye frame  68  onto the photo paper.  
         [0027]    According to the above-mentioned steps, the color printer  60  in the present invention utilizes the timer  96  to record the status-to-status duration, and the status-to-status duration is compared with a threshold time T th . As mentioned above, when the output signal goes from “1” to “0”, the timer  96  starts to record the duration of “0”, and the controller  90  compares the duration with the threshold time T th , thereby determining the beginning position of the yellow dye frame  62 . The yellow dye frame  62  serves as the beginning position of the ink ribbon  70  for printing the dye onto the photo paper. Thereafter, utilizing the variation in the output signals, the beginning position of the magenta dye frame  64 , the cyan dye frame  66 , and the over coating dye frame  68  can be determined. In this manner, the color printer according to the present invention can detect the position of the ink ribbon  70 .  
         [0028]    Please refer to FIG. 6 and FIG. 7. FIG. 6 is a schematic diagram of a color printer  100  according to the second embodiment of the present invention. FIG. 7 is a time sequence diagram of the output signals generated by the optical sensing system shown in FIG. 6. As shown in FIG. 6 and FIG. 7, the optical sensing system of the color printer  100  comprises a green light emitting diode as a green light source  92 . The ink ribbon  110  comprises a plurality of sequentially arranged dye regions  120 . Each of the dye regions  120  consists of three dye frames  102 ,  104 ,  106  for carrying dye of different colors and each of the dye frames  102 ,  104 ,  106  has a substantially equal first length  126 . The dye frame  102 ,  104 ,  106  are used for separately placing yellow dye, magenta dye, and cyan dye. A dividing section  122  is positioned at the front end of each of the dye frames  102 ,  104 ,  106 , and each dividing section  122  has a substantially equal second length  128 . The dividing section  122  is transparent so that the controller  90  can discern a beginning position of each of the dye frame  102 ,  104 ,  106 . Wherein the first length  126  is greater than the second length  128 . In addition, the green light beam  76  emitted by the green light source  72  has higher penetration rates for the yellow dye frame  102  and the transparent dividing section  122 . As a result, when the green light beam  76  passes through the yellow dye frame  102  and the transparent dividing sections  122 , the output signal  78  is of the first status (i.e. high voltage status), and its digital signal is represented by “1”. The green light beam  76  emitted by the green light source  72  has lower penetration rates for the magenta dye frame  104  and the cyan dye frame  106 . Therefore, when the green light beam  76  passes through the magenta dye frame  104  and the cyan dye frame  106 , the output signal  78  is the of second status (i.e. low voltage status), and its digital signal is represented by “0”. When the controller  90  receives the output signal  78  generated by the photo sensor  74 , the timer  96  records the status-to-status duration (such as the a low voltage status shifting from the high voltage status) of the output signal  78 , and the controller  90  compares the status-to-status duration to a threshold time T th  thereby determining the beginning position of the ink ribbon  110  (that is, the beginning position of the yellow dye frame  102 ) for printing the photo paper.  
         [0029]    When the controller  90  utilizes the ribbon driving device  94  to wind the ink ribbon  110  inside the ribbon cartridge to make each of the dye frames  102 ,  104 ,  106  in the dye region  120  pass by the print head  92  sequentially, the photo sensor  74  detects the dye region  120  of the ink ribbon  110  to generate an output signal  78 . When printing the dye on the dye frame  102 ,  104 ,  106  in a dye region  120  of the ink ribbon  110  onto the photo paper, the ribbon driving device  94  winds the ink ribbon  110  inside the ribbon cartridge at the constant linear speed. Each of the dye frames  102 ,  104 ,  106  has an equal sensing time generated by the timer  96  inside the controller  90 . The sensing time of the yellow dye frame  102  and the two dividing sections  122   a ,  122   b  adjacent to the yellow dye frame  102  is referred to as a first time T p . Similarly, the dividing section  122   a ,  122   b ,  122   c  has another sensing time, referred to as a second time T b . The first time T p  is longer than the threshold time T th , which is longer than the second time T b . In general, the printing order of the ink ribbon  110  is the yellow dye frame  102 , the magenta dye frame  104 , and the cyan dye frame  106 . As a result, when determining the beginning position of the ink ribbon  110 , the color printer has to search for the yellow dye frame  102 , the magenta dye frame  104 , and the cyan dye frame  106  in that order. The details are described as follows (please to FIG. 4, FIG. 6 and FIG. 7):Step  180 : Search for the yellow dye frame  102 . Turn on the green light source  72  and the photo sensor  74 , and wind the ink ribbon  110  at the constant linear speed or at the constant angular speed.  
         [0030]    Step  182 : When the digital signal of the output signal goes from “0” to “1”, the timer  96  starts to count time, and the ink ribbon  110  is continuously wound at the constant linear speed.  
         [0031]    Step  184 : When the digital signal of the output signal goes from “1” to “0” and the time recorded by the timer  96  is shorter than the threshold time T th , the photo sensor  74  is still positioned within the cyan dye frame  106 , and the search process goes back to step  182 . When the time recorded by the timer  96  is longer than the threshold time T th  and the digital signal of the output signal hasn&#39;t gone from “1” to “0” yet, the beginning position of the yellow dye frame  102  is detected and the color printer can start to print the dye on the yellow dye frame  62  onto the photo paper. Thereafter perform step  186  to search for the magenta dye frame  104 .  
         [0032]    Step  186 : Search for the magenta dye frame  104 . Because printing the dye on the yellow dye frame  102  onto the photo paper has just finished, the photo sensor  74  must be within the yellow dye frame  102 . Continuously wind the ink ribbon  110 . When the digital signal of the output signal generated by the photo sensor  74  goes from “1” to “0”, the beginning position of the magenta dye frame  104  is detected. Then, start to print the dye on the magenta dye frame  104  onto the photo paper. Thereafter perform step  188  to search for the cyan dye frame  106 .  
         [0033]    Step  188 : Search for the cyan dye frame  106 . Because printing the dye on the magenta dye frame  104  onto the photo paper has just finished, the photo sensor  74  must still be within the magenta dye frame  104 . Continuously wind the ink ribbon  110 . When the digital signal of the output signal generated by the photo sensor  74  goes from “0” to “1”, the beginning position of the transparent dividing section  122  is detected. When the digital signal of the output signal generated by the photo sensor  74  goes from “1” to “0” again, the beginning position of the cyan dye frame  106  is detected. Then, start to print the dye on the cyan dye frame  106  onto the photo paper.  
         [0034]    According to the above-mentioned steps, the color printer  100  according to the second embodiment of the present invention utilizes the timer  96  to record the status-to-status duration, and the status-to-status duration is compared with a threshold time T th . As mentioned above, when the digital signal of the output signal goes from “0” to “1”, the timer  96  starts to record the duration of “1” and the controller  90  compares the duration with the threshold time T th , thereby determining the beginning position of the yellow dye frame  102 . The yellow dye frame  102  serves as the beginning position of the ink ribbon  110  for printing the dye onto the photo paper. By utilizing the variation of the output signals, the beginning position of the magenta dye frame  104  and the cyan dye frame  106  can be determined. In this manner, the color printer according to the present invention can detect the position of the ink ribbon  110 .  
         [0035]    A green light source  72  is used as an example in the above-mentioned embodiments of the present invention. However, the present invention is not limited to a green light source  72 . Light source emitting light beams of other colors can be utilized to detect the position of the ink ribbon  70 ,  110 . Only a slight modification in signaling orders is required to achieve the same purpose as the present invention. The embodiments mentioned in this specification only describe cases where the light source and the optical sensor are installed on opposite sides of the ribbon. However, the light source and the optical sensor may be installed on the same side if a reflector is installed on the opposite side of the ink ribbon for reflecting the light beam emitted from the light source back to the optical sensor for generating output signals. In addition, the above-mentioned timer can be replaced with a pedometer. When a step motor winds an ink ribbon, a pedometer counts steps of the step motor when winding the ink ribbon, thereby determining the position of the ink ribbon.  
         [0036]    Compared to the prior color printer, the color printer of the present invention needs only a single optical sensing system to detect the position of the ink ribbon. The beginning position of each dye frame in the ink ribbon is determined by a digital method, and therefore, production costs are lowered.  
         [0037]    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 bound of the appended claims.