Abstract:
A method and an apparatus for obtaining a magnification error in a first direction for an image scanning apparatus is disclosed. The method includes steps of (a) providing a marking pattern having a particular length in the first direction, (b) scanning the marking pattern to obtain a scanning length in the first direction, and (c) calculating the magnification error in the first direction from scanning length and the particular length.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and an apparatus for obtaining a magnification error in a first direction, and particularly to a method and an apparatus for obtaining a magnification error in the longitudinal direction for an image scanning apparatus. 
     BACKGROUND OF THE INVENTION 
     In recent years, an image scanner has become an indispensable peripheral equipment of personal computers. Many manufacturers are trying their best to improve the scanning quality. 
     In a scanner, the driving device for driving the image-picking device has a mechanical error in the moving direction of the image-picking device (or the longitudinal direction). For a scanner with a resolution of 600 dots per inch (DPI), the image-picking device driven by the driving device will move 6000 steps for scanning a document with a length of 10 inches to obtain an image having 6000 dots in length. However, due to above-described error, the image-picking device must move 6060 steps to finish the scanning process so that the actual length of the scanned image is up to 6060 dots, resulting in that the length of the scanned image changes from 10 inches to 10.1 inches. 
     Therefore, it is desirable to provide a method and an apparatus for obtaining a magnification error in the longitudinal directions to improve the scanning quality. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method for obtaining a magnification error in a first direction for an image scanning apparatus. The method includes steps of (a) providing a marking pattern having a particular length in the first direction, (b) scanning the marking pattern to obtain a scanning length in the first direction, and (c) calculating the magnification error in the first direction from the scanning length and the particular length. 
     According to the present invention, the marking pattern is mounted on one side of an object to be scanned and the marking pattern further includes a rectangular pattern with a first color and a background with a second color. Preferably, the first color and the second color are black and white respectively. The marking pattern further includes a plurality of spaced rectangular patterns and a background. Besides, the step (b) is executed by an image-picking device. The marking pattern intersects with a moving path of the image-picking device. In addition, the first direction is a moving direction of the image-picking device driven by a driving device, that is, a longitudinal direction. The driving device is connected with the image-picking device for driving the image-picking device to scan in the first direction. 
     Another object of the present invention is to provide an image scanning apparatus obtaining a magnification error in a first direction. The image scanning apparatus includes an image-picking device for picking digital data representative of an image, a driving device connected to the image-picking device for driving the image-picking device to scan in the first direction, a scanning platform for placing thereon an object to be scanned, and a marking pattern having a particular length in the first direction on the scanning platform. 
     In accordance with the present invention, the image scanning apparatus is one selected from a group consisting of an image scanner, a photocopier, and a fax machine. The image-picking device is preferably a charge coupled device (CCD). In addition, the first direction is a moving direction or a longitudinal direction of the image-picking device driven by the driving device. 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically shows a preferred embodiment of an scanning apparatus according to the present invention; 
     FIG. 2 is a flowchart of the method according to the present invention; and 
     FIGS.  3 ( a ) and ( b ) are another preferred embodiments of marking patterns according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to FIG. 1 showing a preferred embodiment of an image scanning apparatus. The image-picking device  11  is used for picking digital data representative of an image and the driving device  12  is connected to the image-picking device  11  for driving the image-picking device  11  to scan in a first direction. The scanning platform  13  is for placing thereon an object  15  to be scanned and the marking pattern  14  has a particular length in the first direction. The marking pattern is usually mounted on the side of the object  15  to be scanned and has a color for being easily distinguished from the background. 
     While the driving device  12  drives the image-picking device  11  to scan the object  15 , the marking pattern  14  is also scanned. Take the rectangular marking pattern, as shown in FIG. 1, for example, the rectangular marking pattern has a particular length in the longitudinal direction. When the driving device  12  drives the image-picking device  11  to scan from the top of the marking pattern (line  141 ) to the bottom of the marking pattern (line  142 ) in the longitudinal direction, the scanning length is obtained. Therefore, the magnification error can be calculated from the scanning length and the particular length. 
     For a scanner with a resolution of 600 dots per inch (DPI), if the particular distance between the line  141  and the line  142  in the longitudinal direction is 2 inches, the driving device should move the image-picking device along the longitudinal direction 1200 steps representative of 1200 dots. However, in fact, the driving device moves the image-picking device 1212 steps so that the magnification error in the longitudinal direction is 1%. The magnification error can be corrected by inserting points or erasing points which are well known for those skilled in the art. The flowchart of the method according to the present invention is shown in FIG.  2 . 
     Preferably, the image-picking device is a charge couple device (CCD). This method can be applied to other devices, such as photocopier and fax machine. The longer the particular length is, the more precise the magnification error is obtained. Therefore, the particular length had better be the same as the length of the object to be scanned. 
     Please refer to FIG.  3 ( a ) showing another preferred embodiment of the marking pattern. The marking pattern is consisting of two rectangular patterns  31  and  32 , and the color of the patterns can be easily distinguished from that of the background, such as black and white. There is a particular distance between the line  311  and  312  in the longitudinal direction. When the driving device  12  drives the image-picking device  11  to scan the object  15 , the two black rectangular patterns is also scanned. The magnification error can also be calculated from the scanning length and the particular length. 
     Besides, if the length of the object is know before the scanning process starts, the time for obtaining the magnification error in the longitudinal direction can be saved. For example, if the length of the object to be scanned is 3 inches and has been input by the user, the driving device can drive the image-picking device only 3 inches in the longitudinal direction to finish a scanning process. Certainly, the marking pattern can be designed as shown in FIG.  3 ( b ) to adjust different scanning length. The marking pattern in FIG.  3 ( b ) is consisting of a plurality of rectangular marking patterns  41 ,  42 , . . . and  4   n . The spaces between each rectangular pattern is the same. The scanner can get the particular length easily according to the length input by the user. Then, the magnification error can also be calculated from the scanning length and the particular length. 
     The method for obtaining the magnification error is executed before executing the scanning process and can be applied to an image scanner, a photocopier, or a fax machine. The pattern and the background have different colors which are easily distinguished by the image-picking device. With these methods and apparatus, the magnification errors can be easily rectified to the best state even after being used for a period of time or under the careless operation. 
     While the invention has been described in terms of what are 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 embodiment. 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 such modifications and similar structures.