Patent Publication Number: US-2023134966-A1

Title: Optical module positioning method

Description:
FIELD OF THE INVENTION 
     The present invention relates to an optical module positioning method, and more particularly to an optical module positioning method for realizing the stayed region of an optical module on a scanning platform according to color recognition when an image processing device is turned on and further moving the optical module back to a scan initial position. 
     BACKGROUND OF THE INVENTION 
     With the increasing development of image processing technologies, the applications of the image processing technologies are very popular to modern people. As is well known, image scanners are important peripheral devices of the computer system. The image scanners can be used for scanning documents. The images of the scanned documents can be converted into digital files. The digital files can be subjected to various image processing operations and applications. In other words, the image scanners are indispensable devices for the modern people to process images. 
     As known, a multifunction peripheral is a multifunctional image processing device. In addition to the general scanning function, the multifunction peripheral also has the printing, storing and transmitting functions. The multifunction peripheral is usually equipped with an automatic document feeder (ADF). The automatic document feeder is located over a placement platform. A single paper or sheet-like document can be placed on the placement platform in order to be scanned. After a stack of papers or sheet-like documents are placed on the automatic document feeder, the papers or sheet-like documents can be successively fed into the multifunction peripheral in order to be scanned. Consequently, the efficiency of the scanning task is enhanced. 
     The scanning mechanism of the placement platform and the scanning mechanism of the automatic document feeder are integrated into an optical module. During the scanning operation, the optical module projects a light beam to the document to be scanned. After the reflected light beam from the document is received, the scanned image of the document is acquired by the optical module. In case that the optical module or the document is not moved, the optical module is only able to scan a portion of the document. According to the structural design, the optical module is driven to be moved within the multifunction peripheral by a motor, or the document is fed by the automatic document feeder and simultaneously sensed by the optical module. Consequently, the complete image of the whole document can be acquired. 
     In order to accurately scan the image of the whole document, the optical module has to be stayed in the accurate position before the scanning operation is started. However, in some situations (e.g., the occurrence of a power failure event or an accidental shutdown event in the previous scanning operation), the scanning procedure is not normally completed. Since the optical module is not returned to the default initial position, the next scanning operation cannot be normally implemented. 
     For solving this problem, the image processing device is additionally equipped with a sensing element. When the image processing device is restarted or the power is restored, the optical module is returned back to the initial position regardless of the previous position. Moreover, the sensing element is used to detect whether the optical module is returned back to the accurate position. Generally, according to the structural design, the initial position is located near the automatic document feeder, and the sensing element is correspondingly located beside the initial position. After the image processing device is turned on and the scanning operation is completed, the optical module is moved toward the initial position. Until the sensing element detects the optical module, the motor is stopped. Consequently, the optical module is stayed in the initial position. 
     In other words, if the image processing device is not equipped with the sensing element, the image processing device is unable to realize whether the optical module is accurately returned to the initial position. Moreover, if the sensing element is not used, the optical module may be excessively moved to collide with the casing. Consequently, the optical module is possibly damaged. However, except for the function of detecting whether the optical module is accurately stayed in the initial position before the scanning operation, the sensing element has no other functions. When compared with the scanning mechanism, the printing mechanism or other components of the image processing device, the applicability of the sensing element is not high enough. In addition, the sensing element is not cost-effective. If the sensing element is damaged and needs to be replaced with a new one, the material cost is increased and the process of assembling the sensing element is labor-intensive and time-consuming. 
     Therefore, there is a need of providing an optical module positioning method for accurately confirming the position of the optical module and successfully completing the scanning operation without the need of installing the sensing element. 
     SUMMARY OF THE INVENTION 
     The present invention provides an optical module positioning method. When the optical module positioning method is applied to an image processing device such as a multifunction peripheral, the image processing device can realize the stayed region of the optical module on the scanning platform according to color recognition when the image processing device is turned on. Moreover, the optical module can be returned to the initial position before the scanning operation is started. Especially, the image processing device is not equipped with the sensing element. The use of the optical module positioning method can effectively avoid the collision between the optical module and the casing. 
     In accordance with an aspect of the present invention, an optical module positioning method for an image processing device is provided. The image processing device includes a scanning platform and an optical module. The scanning platform includes a first region, a second region, a third region and a fourth region. The fourth region is arranged between the first region and the second region. The first region is arranged between the third region and the fourth region. An initial position is included in the third region. A length of the fourth region is larger than a length of the third region. The optical module positioning method includes the following steps. Firstly, the optical module is driven to perform a scanning operation to acquire a scanned image while the optical module is not moved. If a color value of a first end of the scanned image and a color value of a second end of the scanned image are in a first color range or a second color range, it is determined that the optical module is stayed in the third region. If the color value of the first end of the scanned image is in a third color range and the color value of the second end of the scanned image is in the second color range, it is determined that the optical module is stayed in the first region. If the color value of the first end of the scanned image is in the second color range and the color value of the second end of the scanned image is in a fourth color range, it is determined that the optical module is stayed in the second region. If the color value of the first end of the scanned image and the color value of the second end of the scanned image are in the fourth color range, it is determined that the optical module is stayed in the fourth region. 
     The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically illustrates an image processing device using an optical module positioning method of the present invention; 
         FIG.  2    is a flowchart illustrating a region judgment process of the optical module positioning method according to the embodiment of the present invention; 
         FIG.  3    schematically illustrates the detailed arrangement of the first region of the scanning platform according to an embodiment of the present invention; 
         FIG.  4    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the first region; 
         FIG.  5    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the second region; 
         FIG.  6    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the third region; and 
         FIG.  7    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the fourth region. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
     The present invention provides an optical module positioning method. An example of the optical module positioning method will be described as follows.  FIG.  1    schematically illustrates an image processing device using an optical module positioning method of the present invention. In this embodiment, the image processing device  1  is an image scanner. More especially, the image processing device  1  is a multifunctional peripheral with a scanning function and an automatic document feeding function. As shown in  FIG.  1   , the image processing device  1  comprises a scanning platform  100  and an optical module  10 . The optical module  10  is located under the scanning platform  100  for performing the image scanning operation. For clearly describing the concepts of the present invention, only the internal structure of the image processing device  1  and the scanning platform  100  are shown in  FIG.  1   . In addition, only the portion of a scanning head of the optical module  10  for scanning the document is shown in  FIG.  1    and indicated as dashed lines. 
     In accordance with a feature of the present invention, a middle area of the scanning platform  100  is divided into four regions. That is, the scanning platform  100  comprises a first region  21 , a second region  22 , a third region  23  and a fourth region  24 . An initial position A 1  corresponding to the starting position of the scanning operation (i.e., the position of the optical module  10  as shown in  FIG.  1   ) is included in the third region  23 . The fourth region  24  is arranged between the first region  21  and the second region  22 . The first region  21  is arranged between the third region  23  and the fourth region  24 . In other words, the third region  23  is the closest to the initial position A 1 . The second region  22  is the farthest from the initial position A 1 . 
     In an embodiment, the scanning platform  100  further comprises a casing  20 , a separation part  34 , a first scanning glass plate  11  and a second scanning glass plate  12 . The first scanning glass plate  11  and the second scanning glass plate  12  are enclosed by the casing  20 . The separation part  34  is arranged between the first scanning glass plate  11  and the first region  21 . The first scanning glass plate  11  is aligned with the third region  23  and an automatic document feeder (ADF) of the image processing device  1 . For succinctness, the automatic document feeder is not shown. That is, the first scanning glass plate  11  is related to the scanning application in the automatic document feeding mode. In addition, the first scanning glass plate  11  is aligned with a document press chart (not shown) of the image processing device  1 . The document press chart is installed on a top cover (not shown) of the image processing device  1 . The top cover can be selectively uplifted from the scanning platform  100  or moved downwardly to cover the scanning platform  100 . When the scanning platform  100  is covered by the top cover, the ambient light can be sheltered. In other words, the document press chart is located over the first scanning glass plate  11 , and the size of the document press chart matches the size of the first scanning glass plate  11 . When the document press chart is moved downwardly to cover the scanning platform  100 , the document press chart is completely aligned with the first scanning glass plate  11 . The second scanning glass plate  12  is aligned with the fourth region  24  and the second region  22 . That is, a single paper or sheet-like document can be placed on the second scanning glass plate  12  so as to be scanned. 
     Particularly, the second region  22 , the third region  23  and the fourth region  24  are virtual regions, but the first region  21  is a physical region defined by an object. In addition, the first region  21  is installed on the casing  20  and located beside the second scanning glass plate  12 . The first scanning glass plate  11  and the separation part  34  are included in the third region  23 . Moreover, the fourth region  24  contains a portion of the second scanning glass plate  12  and portions of the casing  20  corresponding to two ends of the second scanning glass plate  12 . 
     Please refer to  FIG.  1    again. The initial position A 1  is located at a first side of the third region  23 . The separation part  34  is located at a second side of the third region  23 . That is, the initial position A 1  and the separation part  34  are located at two opposite sides of the third region  23 , respectively. The distance between the initial position A 1  and the first region  21  can be previously set as a known distance. Depending on the actual fabricating method, the initial position A 1  is completely attached on the first side of the third region  23 , or there is a small distance between the initial position A 1  and the first side of the third region  23 . 
     In an embodiment, the length of the fourth region  24  is larger than the length of the third region  23 , and the length of the fourth region  24  is also larger than the length of the second region  22 . In addition, the length of the second region  22  is larger than the length of the third region  23 . The overall profile of the third region  23 , the first region  21 , the fourth region  24  and the second region  22  has a rectangular shape. In other words, the widths of the third region  23 , the first region  21 , the fourth region  24  and the second region  22  are equal. Accordingly, the area of the fourth region  24  is the largest, the area of the second region  22  is the second largest, the area of the third region  23  is the third largest, and the area of the first region  21  is the smallest. In this context, the lengths are related to the distances along the Y direction as shown in  FIG.  1   , and the widths are related to the distances along the X direction as shown in  FIG.  1   . 
     For implementing the optical module positioning method of the present invention, the scanning width of the optical module  10  is equal to the width of each of the first region  21 , the second region  22 , the third region  23  and the fourth region  24 . Moreover, as shown in  FIG.  1   , the position of the optical module  10  is substantially center-aligned with all of the four regions  21 ,  22 ,  23  and  24 . In other words, while the optical module  10  is moved relative to the scanning platform  100  to perform the scanning operation, the two ends of the optical module  10  are respectively aligned with the two ends of each of the four regions  21 ,  22 ,  23  and  24 . Consequently, the two ends of each of the four regions  21 ,  22 ,  23  and  24  can be scanned by the optical module  10 . In an embodiment, the scanning width of the optical module  10  is equal to the width of the first scanning glass plate  11 . That is, the scanning width of the optical module  10  is also equal to the width of the separation part  34 . Moreover, the scanning width of the optical module  10  is larger than the width of the second scanning glass plate  12 . In other words, the width of the second scanning glass plate  12  is smaller than the width of the first scanning glass plate  11 . 
     In accordance with another feature of the present invention, the scanning platform  100  comprises plural characteristic charts. For example, the scanning platform  100  comprises a first characteristic chart  31 , a second characteristic chart  32  and a third characteristic chart  33 . These characteristic charts are formed on the casing  20 . In the embodiment of  FIG.  1   , the first characteristic chart  31  and the second characteristic chart  32  are respectively formed located at two ends of the first region  21 , and the third characteristic chart  33  is located at an end of the second region  22 . For example, as shown in  FIG.  1   , the first characteristic chart  31  is located at the left end of the first region  21 , the second characteristic chart  32  is located at the right end of the first region  21 , and the third characteristic chart  33  is located at the left end of the second region  22 . Moreover, the second region  22  contains the third characteristic chart  33 , a portion of the second scanning glass plate  12  and a portion of the casing  20  corresponding to the right end of the second scanning glass plate  12 . 
     In an embodiment, these characteristic charts  31 ,  32  and  33  have specified colors. Preferably, these characteristic charts are monochromatic charts, and the contrast between these monochromatic charts is high. Due to this design, the scan recognition efficacy is enhanced. For example, the first characteristic chart  31  is a black chart, and the second characteristic chart  32  and the third characteristic chart  33  are white charts. That is, the colors of the characteristic charts  31  and  32  at the two ends of the first region  21  are different. A 1 though the second characteristic chart  32  and the third characteristic chart  33  are white, the second characteristic chart  32  and the third characteristic chart  33  are diagonally arranged at two opposite sides. Moreover, the casing  20  and the separation part  34  are monochromatic. Especially, the colors of the casing  20  and the separation part  34  are different from the colors of theses characteristic charts  31 ,  32  and  33 . For example, the casing  20  has a light gray color, and the separation part  34  has a dark gray color. Moreover, the document press chart is also monochromatic. In order to avoid the influence of the document press chart on the scanned result, the document press chart has a white color. 
     Please refer to  FIG.  1    again. In this embodiment, the widths of the characteristic charts  31 ,  32  and  33  are equal. During the scanning operation, the widths of the characteristic charts  31 ,  32  and  33  are aligned with the two ends of the optical module  10 . Moreover, the total width of the first characteristic chart  31 , the second scanning glass plate  12  and the second characteristic chart  32  is equal to the scanning width of the optical module  10 . In an embodiment, each of the two ends of the optical module  10  is designed to scan a specified number of pixels. The specified number of pixels is equal to or slightly smaller than the width of each of the characteristic charts  31 ,  32  and  33 . Especially, the widths of the characteristic charts  31 ,  32  and  33  are designed to fill in or trim the width gap between the first scanning glass plate  11  and the second scanning glass plate  12 . 
     Due to the above design, the following functions can be achieved. Even if the image processing device is not equipped with the sensing element, the position of the optical module  10  can be realized. For example, when the optical module  10  is in a ready-to-scan status, in an incomplete scanning status, in a restart status after power failure or in any other possible status, the position of the optical module  10  in one of the four regions  21 ,  22 ,  23  and  24  can be realized. Consequently, a preliminary classification about the position of the optical module  10  can be made. 
       FIG.  2    is a flowchart illustrating a region judgment process of the optical module positioning method according to the embodiment of the present invention. Firstly, a scanning operation is performed to acquire a scanned image while the optical module  10  is not moved (Step S 11 ). Then, a step S 12  is performed to judge whether the color values of a first end and a second end of the scanned image are in a first color range or a second color range. If the judging condition of the step S 12  is satisfied, it is determined that the optical module  10  is stayed in the third region  23  (Step S 13 ). Whereas, if the judging condition of the step S 12  is not satisfied, a step S 14  is performed to judge whether the color value of the first end of the scanned image is in a third color range and the color value of the second end of the scanned image is in the second color range. If the judging condition of the step S 14  is satisfied, it is determined that the optical module  10  is stayed in the first region  21  (Step S 15 ). Whereas, if the judging condition of the step S 14  is not satisfied, a step S 16  is performed to judge whether the color value of the first end of the scanned image is in the second color range and the color value of the second end of the scanned image is in a fourth color range. If the judging condition of the step S 16  is satisfied, it is determined that the optical module  10  is stayed in the second region  22  (Step S 17 ). Whereas, if the judging condition of the step S 16  is not satisfied, a step S 18  is performed to judge whether the color values of the first end and the second end of the scanned image are in the fourth color range. If the judging condition of the step S 18  is satisfied, it is determined that the optical module  10  is stayed in the fourth region  24  (Step S 19 ). 
     In the step S 11 , regardless of the position of the optical module  10  in the ready-to-scan status, in the incomplete scanning status or in the restart status after power failure, the optical module  10  performs the scanning operation once in situ in the beginning. That is, the optical module  10  performs the scanning operation while the optical module  10  is not moved. The purpose of this design can avoid the damage of the optical module  10 . For example, the optical module  10  is possibly located at any position after the previous operation is stopped. If the optical module  10  is moved forth or back after being enabled, the possibility of causing the optical module  10  to collide with the internal side of the casing  20  increases. The in-situ scanning operation of the optical module  10  can avoid the above problem. 
     In accordance with a feature of the present invention, the color-related region where the optical module  10  is stayed can be determined according to the scanned result of judging and recognizing the two ends of the scanned image (i.e., the color values). According to the characteristic charts  31 ,  32  and  33 , the separation part  34  and the distribution of the regions  21 ,  22 ,  23  and  24 , it is found that the colors of the two ends of the fourth region  24  are identical and the colors of the two ends of each of the first region  21  and the second region  22  are different. The different colors indicate that there is an obvious contrast between two colors. In case that the optical module  10  is stayed in the fourth region  24 , the color values of the two ends of the scanned image are equal because the two ends of the fourth region  24  have the light gray color corresponding to the casing  20 . Since the document press chart has the white color, the result of scanning the document press chart through the first scanning glass plate  11  by the optical module  10  is also white. In case that the optical module  10  is stayed in the third region  23 , both of the two ends of the scanned image have the same white color corresponding to the document press chart or the same dark gray color corresponding to the separation part  34 . 
     However, the scanned result of the optical module  10  on the image usually has an error. That is, there is possibly a slight color level difference. For example, after a pure white or pure black chart is scanned, the scanned result is possibly not pure white or pure black. In the above embodiment, the associated color range represents the judgement allowance. In addition, each color range may be a color level setting of the related color within a specific value range. Particularly, if the color value of the scanned image is in the corresponding color range, it means that the corresponding color chart is scanned by the optical module  10 . 
     As mentioned above, if the judging result indicates that the colors of the two ends of the scanned image are identical, it means that the optical module  10  is possibly stayed in the third region  23  or the fourth region  24 . Whereas, if the judging result indicates that that colors of the two ends of the scanned image are different, it means that the optical module  10  is possibly stayed in the second region  22  or the first region  21 . Consequently, the scanned result can be further judged according to the associated color range. 
     In the steps S 12  and S 13 , the first color range is related to the color value of the dark gray color, and the second color range is related to the color value of the white color. In other words, the first color range is an allowable range of successfully recognizing the scanned result of the dark gray image. The scanned result with the color slightly darker than or lighter than the dark gray color may be considered as the dark gray color that complies with the first color range. In addition, the second color range is an allowable range of successfully recognizing the scanned result of the white image. The scanned result with the color slightly darker than the pure white color may be considered as the white color that complies with the second color range. 
     Consequently, if the judging result indicates that the two ends of the scanned image have the dark gray color, it means that the separation part  34  with the dark gray color is scanned by the optical module  10 . Moreover, if the judging result indicates that the two ends of the scanned image have the white color, it means that the document press chart with the white color is scanned by the optical module  10 . In these two situations, it is determined that the optical module  10  is stayed in the third region  23 . If the judging condition of the step S 12  is not satisfied, i.e., the color values of the first end and the second end of the scanned image are not in the first color range or the second color range, the scanned result is further judged according to other conditions. 
     In the steps S 14  and S 15 , the third color range is related to the color value of the black color, and the second color range is related to the color value of the white color. In other words, the third color range is an allowable range of successfully recognizing the scanned result of the black image. The scanned result with the color slightly lighter than the pure black color may be considered as the black color that complies with the third color range. In addition, the second color range is an allowable range of successfully recognizing the scanned result of the white image. The scanned result with the color slightly darker than the pure white color may be considered as the white color that complies with the second color range. In the example of  FIG.  1   , the first end of the scanned image is the left end of the scanned image corresponding to the first characteristic chart  31 , and the second end of the scanned image is the right end of the scanned image corresponding to the second characteristic chart  32 . 
     Consequently, if the judging result indicates that the color value of the first end (i.e., the left end) of the scanned image represents the black color and the color value of the second end (i.e., the right end) of the scanned image represents the white color, it means that the first characteristic chart  31  with the black color is scanned by the left end of the optical module  10  and the second characteristic chart  32  with the white color is scanned by the right end of the optical module  10 . Under this circumstance, it is determined that the optical module  10  is stayed in the first region  21 . If the judging condition of the step S 14  is not satisfied, i.e., the color value of the left end of the scanned image is not in the third color range or the color value of the right end of the scanned image is not in the second color range, the scanned result is further judged according to other conditions. 
     In the steps S 16  and S 17 , the second color range is related to the color value of the white color, and the fourth color range is related to the color value of the light gray color. In other words, the second color range is an allowable range of successfully recognizing the scanned result of the white image. The scanned result with the color slightly darker than the pure white color may be considered as the white color that complies with the second color range. In addition, the fourth color range is an allowable range of successfully recognizing the scanned result of the light gray image. The scanned result with the color slightly darker than or slightly lighter than the light gray color may be considered as the light gray color that complies with the fourth color range. In the example of  FIG.  1   , the first end of the scanned image is the left end of the scanned image corresponding to the third characteristic chart  33 , and the second end of the scanned image is the right end of the scanned image corresponding to the casing  20 . 
     Consequently, if the judging result indicates that the color value of the first end (i.e., the left end) of the scanned image represents the white color and the color value of the second end (i.e., the right end) of the scanned image represents the light gray color, it means that the third characteristic chart  33  with the white color is scanned by the left end of the optical module  10  and the casing  20  with the light gray color is scanned by the right end of the optical module  10 . Under this circumstance, it is determined that the optical module  10  is stayed in the second region  22 . If the judging condition of the step S 16  is not satisfied, i.e., the color value of the left end of the scanned image is not in the second color range or the color value of the right end of the scanned image is not in the fourth color range, the scanned result is further judged according to other conditions. 
     In the steps S 18  and S 19 , the fourth color range is related to the color value of the light gray color. In other words, the fourth color range is an allowable range of successfully recognizing the scanned result of the light gray image. The scanned result with the color slightly darker than or slightly lighter than the light gray color may be considered as the light gray color that complies with the fourth color range. 
     Consequently, if the judging result indicates that the color values of the left end and the right end of the scanned image represent the light gray color, it means that the casing  20  with the light gray color are scanned by the left end and the right end of the optical module  10 . Under this circumstance, it is determined that the optical module  10  is stayed in the fourth region  24 . If the judging condition of the step S 18  is not satisfied, i.e., the color values of the two ends of the scanned image are not in the fourth color range, the step S 12  is performed again to repeat the judging procedure. 
     As mentioned above, the optical module  10  in the initial status is possibly stayed in any region. Consequently, the sequence of the judging steps S 12 , S 14 , S 16  and S 18  may be adjusted in other embodiments. That is, the sequence of these judging conditions is not restricted. In most situations, the position where the optical module  10  can be recognized by referring to the colors of the characteristic charts  31 ,  32 ,  33 , the separation part  34 , the document press chart and the casing  20  after the judging steps S 12 , S 14 , S 16  and S 18  are completed. 
     As mentioned above, the optical module  10  in the initial status is possibly stayed in any region. Moreover, in some situations, the optical module  10  is possibly spanned across two regions. Under this circumstance, the above judging conditions need to be modified. For example, in some embodiments, the judging conditions of the steps S 12 , S 14 , S 16  and S 18  are related to the judgment and identification about the color values of the two ends of the first scan line of the scanned image. That is, the region where the optical module  10  is stayed is only determined according to the region of the first scan line of the scanned image. 
     From the above descriptions, even if the image processing device is not equipped with the sensing element, the optical module positioning method of the present invention can realize the region where the optical module  10  is stayed. In accordance with another feature of the present invention, even if the image processing device is not equipped with the sensing element, the optical module  10  can be accurately moved back to the initial position A 1  after the stayed region of the optical module  10  is realized. In other words, after the judging result of the step S 13 , S 15 , S 17  or S 19  recognizes the stayed region of the optical module  10 , the optical module  10  is moved back to the initial position A 1  according to the designated flowchart. The method of moving the optical module  10  from the stayed region to the initial position A 1  will be described as follows. 
       FIG.  3    schematically illustrates the detailed arrangement of the first region of the scanning platform according to an embodiment of the present invention. The first region  21  contains a main characteristic chart  211  and plural minor characteristic charts  212 . In this embodiment, the area of the main characteristic chart  211  is larger than the area of each of the plural minor characteristic charts  212 . The areas of the plural minor characteristic charts  212  are different. The main characteristic chart  211  is substantially located at a middle position of the first region  21 . Moreover, the main characteristic chart  211  and the plural minor characteristic charts  212  are located at the side of the first region  21  adjacent to the fourth region  24 . That is, the main characteristic chart  211  and the plural minor characteristic charts  212  are located at the bottom side of the first region  21  and close to the fourth region  24 . 
     The main characteristic chart  211  has a main characteristic width. Each of the minor characteristic charts  212  has a minor characteristic width. The thicknesses of the main characteristic chart  211  and the plural minor characteristic charts  212  are identical. Since the main characteristic chart  211  is larger, the main characteristic width is larger than each minor characteristic width. In addition, the distance between each of the main characteristic chart  211  and the plural minor characteristic charts  212  and the initial position A 1  is known. In this embodiment, the main characteristic chart  211  and plural minor characteristic charts  212  have the same color (e.g., a black color). Except for the first characteristic chart  31 , the main characteristic chart  211  and the plural minor characteristic charts  212 , the rest of the first region  21  has the white color. 
       FIG.  4    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the first region  21 . Firstly, plural scan lines are successively searched from the scanned image (Step S 21 ). Then, a step S 22  is performed to judge whether the color value of first-portion pixels in a specified scan line of the plural scan lines is in the third color range and the color value of second-portion pixels on two sides of the first-portion pixels is in the second color range. If the judging condition of the step S 22  is satisfied, a block width corresponding to the first-portion pixels is generated (Step S 23 ). Then, a step S 24  is performed to judge whether the block width matches the main characteristic width or one of the plural minor characteristic widths. If the judging condition of the step S 24  is satisfied, the position of the main characteristic chart  211  or the corresponding minor characteristic chart  212  in the scanned image is determined (Step S 25 ). That is, if the block width matches the main characteristic width, the position of the main characteristic chart  211  in the scanned image is determined. Moreover, if the block width matches one of the plural minor characteristic widths, the position of the corresponding minor characteristic chart  212  in the scanned image is determined. Then, a moving information is obtained according to the position of the main characteristic chart  211  or the corresponding minor characteristic chart  212  in the scanned image (Step S 26 ). Then, the optical module  10  is moved toward the initial position A 1  according to the moving information and stayed in the initial position A 1  (Step S 27 ). 
     In the step S 21 , the acquired scanned image (not shown) is an image composed of plural horizontal scan lines. In this stage, the plural scan lines are successively recognized. Consequently, the pixel arrangement to form the scanned image can be realized. In this embodiment, the plural scan lines are successively recognized and searched from top to bottom. That is, the scan line closest to the initial position A 1  is recognized and searched at first, and then the other scan lines are successively recognized and searched from top to bottom (i.e., along the Y direction as shown in  FIG.  1   ). Among the four regions, the first region  21  is the shortest. In addition, the width of the first region  21  is equal to the scanning width of the optical module  10 . Consequently, if the optical module  10  is stayed in the first region  21  in the beginning, the scanned image acquired by the optical module  10  through the in-situ scanning operation may contain the entire image of the first region  21 , or the scanned image may at least contain the images of the main characteristic chart  211  and the minor characteristic charts  212 . 
     In the step S 22 , the plural scan lines are searched successively. Consequently, the portion of the first region  21  with the white color is first searched. At this moment, the first end (i.e., the left end) of the scanned image is aligned with the first characteristic chart  31 . However, only the right side of the first characteristic chart  31  has the white color. In other words, the first characteristic chart  31  does not match the feature of the main characteristic chart  211  or the minor characteristic charts  212 . Consequently, the first characteristic chart  31  is not recognized as the main characteristic chart  211  or one of the minor characteristic charts  212 . 
     During the searching process, if the first-portion pixels (especially the middle portion of the scanned image) in the specified scan line have the black color and the second-portion pixels on two sides of the first-portion pixels (i.e., the blank portions B 1  and B 2  beside the main characteristic chart  211  or the minor characteristic charts  212 ) have the white color, the white-black-white arrangement is recognized. Under this circumstance, the main characteristic chart  211  or the minor characteristic charts  212  have been searched. The first scan line with the white-black-white arrangement is equivalent to the topmost edge of the main characteristic chart  211  or the minor characteristic charts  212 . The ways of judging whether the associated color values are in the third color range and the second color range are similar to those of the flowchart as described in  FIG.  2   , and not redundantly described herein. If the judging condition of the step S 22  is not satisfied, the step S 21  is performed again. 
     For further confirming whether the searched object is the main characteristic chart  211  or the minor characteristic chart  212  in the step S 23 , the pixels complying with the judging condition of the step S 22  are processed. That is, the range of the black first-portion pixels is calculated, and thus the block width is obtained. Particularly, after the positions of the two sides of the first-portion pixels (i.e., the black block) are confirmed, the distance between the two sides of the first-portion pixels can be determined as the block width. 
     In the step S 24 , the main characteristic width of the main characteristic chart  211  is known, and the minor characteristic width of each minor characteristic chart  212  is known. By comparing the block width of the first-portion pixels (i.e., the black block) with the main characteristic width and each minor characteristic width, the first-portion pixels (i.e., the black block) can be recognized. In case that the block width matches the main characteristic width, the first-portion pixels (i.e., the black block) represent the main characteristic chart  211 . In case that the block width matches one of the plural minor characteristic widths, the first-portion pixels (i.e., the black block) represent the corresponding minor characteristic chart  212 . Moreover, when the two widths are equal to each other or the two widths with a small width difference due to the scanning error, it is determined that the two widths match each other. 
     In the step S 25 , the pixels complying with the judging condition of the step S 24  are processed. That is, the position of the main characteristic chart  211  or the corresponding minor characteristic chart  212  represented by the first-portion pixels (i.e., the black block) in the scanned image is recognized. Particularly, after the main characteristic chart  211  or the corresponding minor characteristic chart  212  related to a specified horizontal scan line of the scanned image is recognized, the position of the main characteristic chart  211  or the corresponding minor characteristic chart  212  in the scanned image is determined. After calculation, the actual position of the optical module  10  in the scanning platform  100  can be realized. 
     In the above embodiment, the plural scan lines are successively searched from top to bottom. It is noted that numerous modifications and alterations may be made while retaining the teachings of the invention. For example, in another embodiment, the plural scan lines are successively searched from bottom to top. That is, the plural scan lines of the scanned image are successively and upwardly searched from the bottommost scan line. As mentioned above, the thicknesses of the main characteristic chart  211  and the plural minor characteristic charts  212  are known. That is, the number of scan lines corresponding to the thickness is known. Consequently, the accurate position can be realized through calculation. 
     After the position of the main characteristic chart  211  or the corresponding minor characteristic chart  212  is determined, the step S 26  and S 27  are performed. Meanwhile, the linear distance between the optical module  10  and the main characteristic chart  211  or the corresponding minor characteristic chart  212  can be realized. Since the distance between the main characteristic chart  211  and the initial position A 1  and the distance between the corresponding minor characteristic chart  212  and the initial position A 1  are known fixed values, the distance between the current position of the optical module  10  and the initial position A 1  is also known. Consequently, the moving information is related to the distance between the current position of the optical module  10  and the initial position A 1 . According to the moving information, the optical module  10  is driven to be accurately moved back to the initial position A 1 . 
       FIG.  5    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the second region. Firstly, the optical module  10  is moved toward the initial position A 1  for a specified backward length, and the optical module  10  is moved for a predetermined scan length while performing an additional scanning operation to acquire an additional scanned image (Step S 31 ). Then, plural scan lines are successively searched from the additional scanned image (Step S 32 ). Then, a step S 33  is performed to judge whether the color value of a first end of a specified scan line is in the second color range and the color value of a first end of a previous scan line of the specified scan line is in the fourth color range. If the judging condition of the step S 33  is satisfied, it is determined that the specified scan line is located at a boundary of the second region  22  adjacent to the fourth region  24  (Step S 34 ). Then, a moving information is obtained according to the position of the specified scan line at the boundary of the second region  22  adjacent to the fourth region  24  (Step S 35 ). Then, the optical module  10  is moved toward the initial position A 1  according to the moving information and stayed in the initial position A 1  (Step S 36 ). 
     The flowchart of  FIG.  5    is designed to search the junction between the second region  22  and the fourth region  24 . Particularly, the line passing through the topmost edge of the third characteristic chart  33  represents the junction between the second region  22  and the fourth region  24 . As mentioned above, the third characteristic chart  33  has a white color. The color of the third characteristic chart  33  is different from the light gray color of the casing  20  on the upper side of the third characteristic chart  33  (i.e., the left end of the fourth region  24 ). In other words, the junction can be recognized according to the color difference. After the junction between the second region  22  and the fourth region  24  is searched, the junction between the third characteristic chart  33  and the casing  20  on the upper side can be searched. 
     In the step S 31 , the optical module  10  is moved backwardly toward the initial position A 1 . Particularly, the optical module  10  has to be moved back to the fourth region  24 . In such way, the junction between the second region  22  and the fourth region  24  can be searched successfully. As mentioned above, the fourth region  24  is the longest among the four regions. Consequently, the maximum of the backward length is set as the length of the second region  22 . Even if the optical module  10  is located at the bottommost side of the second region  22  in the beginning, the optical module  10  can be moved back for the length equal to the second region  22  (i.e., the maximum of the backward length) because the optical module  10  has the inherent thickness. In this way, the optical module  10  is certainly moved to the fourth region  24 . 
     Then, the optical module  10  is driven to be moved for the predetermined scan length along the Y direction as shown in  FIG.  1   . That is, the moving action and the scanning operation of the optical module  10  are simultaneously performed. According to the settings of this embodiment, the maximum of the predetermined scan length is equal to a total length of the third region  23  and the first region  21 , and the total length of the third region  23  and the first region  21  is smaller than the length of the second region  22 . The optical module  10  is moved backwardly to the fourth region  24 . Ideally, the optical module  10  is moved backwardly to the position near the bottommost side of the fourth region  24 . In case that the predetermined scan length is equal to a total length of the third region  23  and the first region  21 , and the optical module  10  is moved for the predetermined scan length to perform the additional scanning operation. Meanwhile, the junction between the third characteristic chart  33  and the casing  20  on the upper side of the third characteristic chart  33  is still contained in the additional scanned image, and the portion of the casing  20  on the lower side of the third characteristic chart  33  is not collided by the optical module  10 . 
     In an embodiment, a pixel averaging method is used to process the additional scanned image. While the optical module  10  is moved, several scan lines of the additional scanned image are combined as a scan line unit, and the mean pixel value of the scan line unit is calculated. That is, the number of scan lines to be recognized is reduced. Consequently, the image processing time and the calculation time are reduced. For example, in case that the additional scanned image has  200  scan lines, every  10  scan lines are combined as a scan line unit, and the mean pixel value of the  10  scan lines of the scan line unit is calculated. In other words, only  20  scan line units need to be recognized. Consequently, the image processing time and the calculation time are reduced. 
     Similarly, in the step S 32 , the additional scanned image (not shown) is an image composed of plural scan lines. In this stage, the plural scan lines are successively recognized. Consequently, the pixel arrangement to form the additional scanned image can be realized. In this embodiment, the plural scan lines are successively recognized and searched from top to bottom. 
     Similarly, in the step S 33 , the first end of the corresponding scan line is aligned with the left end of the third characteristic chart  33  along the direction of  FIG.  1   . The second color range is an allowable range of successfully recognizing the scanned result of the white image while the optical module  10  performs the additional scanning operation. The fourth color range is an allowable range of successfully recognizing the scanned result of the light gray image while the optical module  10  performs the additional scanning operation. 
     If the color value of the first end (i.e., the left end) of a specified scan line (e.g., the n-th scan line) represents the white color and the color value of the first end (i.e., the left end) of the previous scan line (e.g., the (n−1)-th scan line) of the specified scan line represents the light gray color, the specified scan line is located at the boundary of the second region  22  adjacent to the fourth region  24  (Step S 34 ). In other words, the specified scan line is the first scan line from the second region  22 . Whereas, if the judging condition of the step S 33  is not satisfied, the step S 32  is performed again to repeat the searching procedure. 
     It is noted that the specified backward length and the predetermined scan length may be varied according to the practical requirements. That is, the specified backward length and the predetermined scan length are not restricted to their maximum values. It is noted that numerous modifications and alterations may be made while retaining the teachings of the invention. For example, if the judging condition of the step S 33  is not satisfied, the step S 31  is performed again. However, the procedure of moving the optical module  10  backwardly is omitted, but the optical module  10  performs the additional scanning operation with the predetermined scan length for one time. 
     After the specified scan line is located at the boundary of the second region  22  adjacent to the fourth region  24 , the step S 35  and S 36  are performed. Similarly, after the boundary of the second region  22  adjacent to the fourth region  24  related to a specified horizontal scan line of the additional scanned image is recognized, the position of the boundary in the additional scanned image is determined. After calculation, the actual position of the optical module  10  in the scanning platform  100  can be realized. Meanwhile, the linear distance between the optical module  10  and the boundary can be realized. Since the distance between the boundary and the initial position A 1  is a known fixed value, the distance between the current position of the optical module  10  and the initial position A 1  is also known. Consequently, the moving information is related to the distance between the current position of the optical module  10  and the initial position A 1 . According to the moving information, the optical module  10  is driven to be accurately moved back to the initial position A 1 . 
     As mentioned above, the initial position A 1  is located at a side of the third region  23  that is the closest to the casing  20 , and the second region  22  is farther from the initial position A 1 . The optical module  10  may collide with the casing  20  under the long-distance accelerated movement. For solving the above drawbacks, the step S 36  can be further modified. 
     For example, in another embodiment, the optical module  10  is moved to the first region  21  and stayed in the first region  21 . Under this circumstance, the moving information is related to the distance of moving the optical module  10  to the first region  21 . Then, the flowchart of  FIG.  2    and the flowchart of  FIG.  4    are performed again, and thus the optical module  10  is moved back to the initial position A 1 . Due to the stepwise movement, the collision between the optical module  10  and the casing  20  is avoided. 
       FIG.  6    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the third region. Firstly, the optical module  10  is moved for a predetermined scan length while performing an additional scanning operation to acquire an additional scanned image (Step S 41 ). Then, plural scan lines are successively searched from the additional scanned image (Step S 42 ). Then, a step S 43  is performed to judge whether the color value of a first end of a specified scan line is in the third color range, the color value of a second end of the specified scan line is in the second color range and the color values of a first end and a second end of a previous scan line of the specified scan line are in the first color range. If the judging condition of the step S 43  is satisfied, it is determined that the specified scan line is located at a boundary of the first region  21  adjacent to the third region  23  (Step S 44 ). Then, a moving information is obtained according to the position of the specified scan line at the boundary of the first region  21  adjacent to the third region  23  (Step S 45 ). Then, the optical module  10  is moved toward the initial position A 1  according to the moving information and stayed in the initial position A 1  (Step S 46 ). 
     The flowchart of  FIG.  6    is designed to search the junction between the first region  21  and the third region  23 , especially the junction between the first region  21  and the separation part  34 . After the first region  21  is searched, the optical module  10  can be moved to the initial position A 1  according to the main characteristic chart  211  or the plural minor characteristic charts  212 . Particularly, the line passing through the topmost edges of the first characteristic chart  31  and the second characteristic chart  32  represents the junction between the first region  21  and the separation part  34 . As mentioned above, the first characteristic chart  31  has a black color, the second characteristic chart  32  has the white color, and the separation part  34  on the upper side of the first region  21  has the dark gray color. In other words, the junction can be recognized according to the color difference. After the junction between the first region  21  and the third region  23  is searched, the junction between the first characteristic chart  31  and the separation part  34  on the upper side can be searched. 
     In the step S 41 , the optical module  10  is driven to be moved for the predetermined scan length along the Y direction as shown in  FIG.  1   . That is, the moving action and the scanning operation of the optical module  10  are simultaneously performed. According to the settings of this embodiment, the maximum of the predetermined scan length is equal to a total length of the third region  23  and the first region  21 . For example, the predetermined scan length is equal to a total length of the third region  23  and the first region  21 , and the optical module  10  is moved for the predetermined scan length to perform the additional scanning operation. Even if the optical module  10  is located at the topmost initial position A 1  in the beginning, the junction between the first characteristic chart  31  and the separation part  34  on the upper side of the first characteristic chart  31  is still contained in the additional scanned image. In other words, the junction between the first region  21 , the second characteristic chart  32  and the separation part  34  on the upper side of the second characteristic chart  32  is still contained in the additional scanned image. In addition, the pixel averaging method can be used to process the additional scanned image. 
     The steps S 42 —S 46  are similar to the steps S 32 —S 36  in the flowchart of  FIG.  5   . In contrast, the flowchart of  FIG.  6    performs the associated judgment according to the first color range, the second color range and the third color range. If the judging result indicates that the color value of the first end (i.e., the left end) of the specified scan line represents the black color, the color value of the second end (i.e., the right end) of the specified scan line represents the white color and the color values of the first end (i.e., the left end) and the second end (i.e., the right end) of the previous scan line of the specified scan line represents the dark gray color, the specified scan line is located at the boundary of the first region  21  adjacent to the third region  23 . Similarly, after the position of the boundary in the additional scanned image is determined, the linear distance between the optical module  10  and the boundary can be realized. Moreover, since the distance between the boundary and the initial position A 1  is a known fixed value, the moving information related to the distance between the current position of the optical module  10  and the initial position A 1  can be calculated. According to the moving information, the optical module  10  is driven to be accurately moved back to the initial position A 1 . 
     This embodiment can be further modified. For example, in another embodiment, the optical module  10  is moved to the first region  21  and stayed in the first region  21 . Then, the flowchart of  FIG.  2    and the flowchart of  FIG.  4    are performed again, and thus the optical module  10  is moved back to the initial position A 1 . 
       FIG.  7    is a flowchart illustrating the optical module positioning method of the present invention after the optical module is determined to be stayed in the fourth region. Firstly, the optical module  10  is moved for a predetermined scan length while performing an additional scanning operation to acquire an additional scanned image (Step S 51 ). Then, plural scan lines are successively searched from the additional scanned image (Step S 52 ). Then, a step S 53  is performed to judge whether the color value of a first end of a specified scan line is in the second color range and the color value of a first end of a previous scan line of the specified scan line is in the fourth color range. If the judging condition of the step S 53  is satisfied, it is determined that the specified scan line is located at a boundary of the second region  22  adjacent to the fourth region  24  (Step S 54 ). Then, a moving information is obtained according to the position of the specified scan line at the boundary of the second region  22  adjacent to the fourth region  24  (Step S 55 ). Then, the optical module  10  is moved toward the initial position A 1  according to the moving information and stayed in the initial position A 1  (Step S 56 ). 
     The flowchart of  FIG.  7    is designed to search the junction between the second region  22  and the fourth region  24 . Like the example of  FIG.  5   , the junction between the second region  22  and the fourth region  24  is searched by recognizing the color different in the junction. As mentioned above, the third characteristic chart  33  has a white color, and the casing  20  corresponding to the left end of the fourth region  24  has the light gray color. After the junction between the third characteristic chart  33  and the casing  20  on the upper side of the third characteristic chart  33  is recognized, the junction between the second region  22  and the fourth region  24  is searched. 
     When compared with the flowchart of  FIG.  5   , the flowchart of  FIG.  7    only has the following difference. In the beginning of the flowchart of  FIG.  7   , the optical module  10  is stayed in the fourth region  24 . In the step S 51 , the optical module  10  is directly driven to be moved for the predetermined scan length along the Y direction as shown in  FIG.  1    without the need of moving backwardly. According to the settings of this embodiment, the maximum of the predetermined scan length is equal to a total length of the third region  23  and the first region  21 . As shown in  FIG.  1   , the fourth region  24  is the longest among the four regions. In an embodiment, the total length of the third region  23  and the first region  21  is appropriately one third of the length of the fourth region  24 . If the optical module  10  is located at the topmost side of the fourth region  24  (i.e., the position adjacent to the first region  21 ), the junction between the third characteristic chart  33  and the casing  20  on the upper side of the third characteristic chart  33  is not contained in the additional scanned image that is acquired through a single moving and scanning operation of the optical module  10 . 
     If the judging condition of the step S 53  is not satisfied, the step S 51  is performed again. That is, the optical module  10  performs an additional scanning operation with the predetermined scan length to acquire a new additional scanned image, and the new additional scanned image is subjected to the searching and judging procedures again. In case that the predetermined scan length is equal to a total length of the third region  23  and the first region  21 , and the optical module  10  is moved for the predetermined scan length to perform the additional scanning operation, the third characteristic chart  33  can be scanned by the optical module  10  after the optical module  10  is moved in the fourth region  24  for at most three times. That is, the optical module  10  can be moved to the junction between the second region  22  and the fourth region  24 . 
     The subsequent steps are similar to the corresponding steps of the flowchart of  FIG.  5   . For example, the moving information is obtained according to the position of the specified scan line at the boundary, and the optical module  10  is moved to the initial position A 1  or sequentially moved to the first region  21  and the initial position A 1 . However, in case that the boundary is located at an edge of the additional scanned image, the boundary cannot be clearly recognized. For solving this drawback, the optical module positioning method can be further modified. For example, after the optical module  10  is moved from the fourth region  24  to the second region  22 , the steps of the flowchart as shown in  FIG.  5    are performed. That is, after the optical module  10  is moved backwardly to the fourth region  24 , the optical module  10  is moved forwardly to perform an additional scanning operation. Due to this design, the optical module  10  stayed in the fourth region  24  in the beginning can be moved back to the initial position A 1  after the optical module  10  is moved for at most six times. 
     From the above descriptions, the present invention provides an optical module positioning method. When the optical module positioning method is applied to an image processing device such as a multifunction peripheral, the image processing device can realize the stayed region of the optical module on the scanning platform according to color recognition without the need of moving the optical module. Since the image processing device is not equipped with the sensing element, the fabricating cost is effectively reduced. Moreover, the distance of moving the optical module back to the initial position can be accurately calculated according to the position of the boundary of associated characteristic chart in the scanned image. Not only the image processing device is not equipped with the sensing element, the collision between the optical module and the casing is avoided. Consequently, the possibility of resulting in damage of the optical module is effectively reduced. 
     Consequently, the optical module positioning method of the present invention is capable of effectively overcoming the drawbacks of the conventional technologies and achieving the purposes of the present invention. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all modifications and similar structures.