Abstract:
In a sheet-fed scanner capable of scanning multiple scan lines as a calibration standard for an image signal, a scanning module scans a document, which is fed across a scan region by a sheet-feeding mechanism, and a stationary calibration sheet in the scan region. The scanning module includes an image sensor, a lens and at least one reflecting mirror. An actuator actuates the reflecting mirror to enable the image sensor to sense a plurality of scan lines on the calibration sheet through the lens and the reflecting mirror in order to obtain a calibration standard for the image signal of the document. The calibration standard is adopted to calibrate an image signal of the document, and with this invention, it is possible to avert any flaws in image quality caused by the contaminated calibration sheet.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a sheet-fed scanner capable of scanning multiple scan lines for image signal calibration, and more particularly to a sheet-fed scanner capable of scanning multiple scan lines on a calibration sheet for image signal calibration.  
         [0003]     2. Description of the Related Art  
         [0004]     Typically, before scanning a document, a scanner has to scan a calibration sheet with a standard color, such as the standard white, the standard black or the like, to obtain a calibration standard for calibrating an image signal of the document.  
         [0005]     In the conventional sheet-fed scanner, the stationary scanning module scans the document fed by the sheet-feeding mechanism as well as the stationary calibration sheet. Therefore, when the scanning module is scanning the calibration sheet, the data of only one scan line can be obtained as the calibration standard for the subsequent scanning process. If the calibration sheet is contaminated, the data of the single scan line may be flawed, which would greatly influence the subsequent scanning result.  
         [0006]     Thus, providing a sheet-fed scanner capable of scanning multiple scan lines as the calibration standard for the image signal of the document without distorting the calibrated image is an important object to be achieved by the invention.  
       SUMMARY OF THE INVENTION  
       [0007]     It is therefore an object of the invention to provide a sheet-fed scanner capable of scanning multiple scan lines for image signal calibration, wherein at least one reflecting mirror of a scanning module is slightly rotated such that the multiple scan lines on a calibration sheet are scanned as the calibration standard for the image signal of a document.  
         [0008]     To achieve the above-identified object, the invention provides a sheet-fed scanner capable of scanning multiple scan lines for image signal calibration. The scanner includes a housing, a sheet-feeding mechanism, a first scanning module, a first actuator and a first calibration sheet. The sheet-feeding mechanism feeds a document across a scan region. The first scanning module is fixed in the housing and scans a front side of the document. The first scanning module includes a first image sensor, a first lens and at least one first reflecting mirror. The first actuator actuates the at least one first reflecting mirror. The first calibration sheet is fixed in the housing and located in the scan region. The first actuator actuates the at least one first reflecting mirror such that the first image sensor senses a plurality of scan lines of the first calibration sheet through the first lens and the at least one first reflecting mirror, as a calibration standard for a first image signal obtained when the first image sensor senses the front side of the document.  
         [0009]     In the above-mentioned sheet-fed scanner, it is possible to utilize the property of a cam, a piezoelectric material or a bimetal material to rotate the reflecting mirror such that the scanner can scan multiple scan lines of the calibration sheet for obtaining the calibration standard for the image signal of the document. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  shows a sheet-fed scanner according to a first embodiment of the invention.  
         [0011]      FIG. 2  shows a first state of the scanning module of  FIG. 1 .  
         [0012]      FIG. 3  shows a second state of the scanning module of  FIG. 1 .  
         [0013]      FIG. 4  is a side view showing a first state of a first actuating mechanism corresponding to the reflecting mirror of  FIG. 2 .  
         [0014]      FIG. 5  is a side view showing a second state of the first actuating mechanism corresponding to the reflecting mirror of  FIG. 3 .  
         [0015]      FIG. 6  is a top view showing the first actuating mechanism corresponding to the reflecting mirror of  FIG. 4 .  
         [0016]      FIG. 7  shows a second actuating mechanism for the reflecting mirror.  
         [0017]      FIG. 8  shows a third actuating mechanism for the reflecting mirror.  
         [0018]      FIG. 9  shows a sheet-fed scanner according to a second embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The embodiments of the invention will be described with reference to the accompanying drawings.  
         [0020]      FIG. 1  shows a sheet-fed scanner according to a first embodiment of the invention.  FIGS. 2 and 3  respectively show a first state and a second state of the scanning module of  FIG. 1 . As shown in FIGS.  1  to  3 , a sheet-fed scanner  1  of the invention capable of scanning multiple scan lines for image signal calibration is a duplex sheet-fed scanner for scanning a front side and a back side of a document. In fact, the concept of the invention may also be implemented in a simplex sheet-fed scanner.  
         [0021]     The sheet-fed scanner  1  includes a housing  10 , a sheet-feeding mechanism  20 , a first scanning module  40 , a first actuator  50  and a first calibration sheet  60 . The housing  10  has a sheet input tray  12  for supporting a to-be-scanned document P, and a sheet output tray  14  for supporting the document P that is scanned. The sheet-feeding mechanism  20  feeds the document P across a scan region  22 . The first scanning module  40  is fixed in the housing  10  and scans a front side PA of the document P. The first scanning module  40  includes a first image sensor  41 , a first lens  42 , a plurality of first reflecting mirrors  43 A to  43 C, and a first light source  44  for illuminating the front side PA of the document P and the first calibration sheet  60 . The first actuator  50  actuates the first reflecting mirror  43 A. The first calibration sheet  60  is fixed in the housing  10  and positioned in the scan region  22 . A light ray coming from the first calibration sheet  60  is reflected subsequently by the first reflecting mirrors  43 A,  43 B and  43 C to the first lens  42  which focuses the light ray onto the first image sensor  41 . As the first actuator  50  actuates the first reflecting mirror  43 A, the first image sensor  41  senses a plurality of scan lines L 1  and L 2  of the first calibration sheet  60  through the first lens  42  and the first reflecting mirrors  43 A to  43 C, for obtaining a calibration standard for a first image signal acquired when the first image sensor senses the front side PA of the document P. In practice, the number of scan lines may be three or more than three, and the scanning data of all the scan lines may be averaged to generate the calibration standard for the image signal. Alternatively, the scanning data of some scan lines, which is greatly different from the average value, may be omitted in order to get a more accurate calibration standard for the image signal of the document.  
         [0022]     In addition, the duplex sheet-fed scanner  1  further includes a second scanning module  70 , a second actuator  80  and a second calibration sheet  66 , which are constructed similarly to the first scanning module  40 , the first actuator  50  and the first calibration sheet  60 . The second scanning module  70 , which is fixed in the housing  10  and opposite to the first scanning module  40 , scans a back side PB of the document P. Similar to the first scanning module  40 , the second scanning module  70  includes a second image sensor  71 , a second lens  72 , a plurality of second reflecting mirrors  73 A to  73 C, and a second light source  74 . The second actuator  80  actuates the second reflecting mirror  73 A. The second calibration sheet  66  is fixed in the housing  10  and positioned in the scan region  22 . As the second actuator  80  actuates the second reflecting mirror  73 A, the second image sensor  71  senses a plurality of scan lines of the second calibration sheet  66  through the second lens  72  and the second reflecting mirrors  73 A to  73 C in order to obtain a calibration standard for a second image signal acquired when the second image sensor  71  senses the back side PB of the document P. Each of the image sensors  41  and  71  may be a charge coupled device (CCD).  
         [0023]     In the drawings, the illustrated first calibration sheet  60  has a level surface. In other embodiments, however, the first calibration sheet  60  may also have a curved surface, which is capable of reducing the difference between the optical paths corresponding to the scan lines L 1  and L 2  in  FIG. 3  so as to obtain a better calibration effect.  
         [0024]     In the above-mentioned embodiment, the effect of the invention may be achieved as long as at least one of the reflecting mirrors is rotated, and the arrangement and number of the reflecting mirrors are not limited to those as shown in the drawings. Because the rotation of the reflecting mirror is very sensitive to the variation of the optical path, a small angle rotation of the reflecting mirror may achieve the effect of the invention. The rotatable reflecting mirror is preferably close to the calibration sheet such that the allowable rotation angle of the reflecting mirror may be enlarged to facilitate the implementation. The example of the actuator will be described in the following example.  
         [0025]      FIGS. 4 and 5  are side views respectively showing a first state and a second state of a first actuating mechanism corresponding to the reflecting mirror of  FIG. 2 , and  FIG. 6  is a top view showing the first actuating mechanism corresponding to the reflecting mirror of  FIG. 4 . As shown in FIGS.  4  to  6 , the first actuator  50  includes, for example, a motor  51  and a cam  52 , wherein the motor  51  drives the cam  52  to rotate the first reflecting mirror  43 A. The first reflecting mirror  43 A is placed on a base  35 , which may pertain to the housing  10  of the scanner or the housing of the first scanning module  40 . The base  35  has two projections  35 A and  35 B in contact with a lower surface  43 A 1  of the first reflecting mirror  43 A. An elastic member  31  pushes an upper surface  43 A 2  of the first reflecting mirror  43 A toward the base  35 . The elastic member  31  is an elastic arm having one end fixed to the base  35  by a bolt  32 . The elastic arm has a projection  31 A corresponding to a position between the two projections  35 A and  35 B of the base  35  so as to fix the first reflecting mirror  43 A in contact with the projections  35 A and  35 B. To rotate the first reflecting mirror  43 A, the first actuator  50  pushes a side of the first reflecting mirror  43 A upwards such that the first reflecting mirror  43 A parts from the projection  35 B.  
         [0026]     It is to be noted that the first actuator  50  is not in contact with the first reflecting mirror  43 A before the first actuator  50  rotates the first reflecting mirror  43 A, in order to enhance the positioning precision and stability of the first reflecting mirror  43 A when the document is being scanned. Therefore, the reference position of the first reflecting mirror  43 A, when the first scanning module  40  is scanning the document, depends on the positions of the two projections  35 A and  35 B of the base  35  and is free from being influenced by the cam  52 . Hence, the reference position of the first reflecting mirror  43 A may be adjusted to a best position when the scanning module is assembled.  
         [0027]      FIG. 7  shows a second actuating mechanism for the reflecting mirror. As shown in  FIG. 7 , the first actuator  50  is made of a piezoelectric material. When a voltage is applied to the piezoelectric material, the piezoelectric material deforms to rotate the first reflecting mirror  43 A.  
         [0028]      FIG. 8  shows a third actuating mechanism for the reflecting mirror. As shown in  FIG. 8 , the first actuator  50  is made of a bimetal material. When a voltage is applied to the bimetal material, the bimetal material deforms to rotate the first reflecting mirror  43 A.  
         [0029]      FIG. 9  shows a sheet-fed scanner according to a second embodiment of the invention. As shown in  FIG. 9 , a sheet-fed scanner  2  of this embodiment is similar to the sheet-fed scanner  1  of the first embodiment except that the second scanning module  90  of this embodiment is movably mounted in the housing  10  and opposite to the first scanning module  40  so as to provide the functions of flatbed scanning and sheet-fed scanning. Because the second scanning module  90  is movable, multiple scan lines on the second calibration sheet  66  may be scanned without the reflecting mirror corresponding to the second scanning module being rotated. When the sheet-fed scanner is scanning, the second scanning module  90  scans the back side PB of the document P. Similarly, the second scanning module  90  includes a second image sensor  91 , a second lens  92 , a plurality of second reflecting mirrors  93 A to  93 C, and a second light source  94 .  
         [0030]     According to the embodiment of the invention, it is possible to implement the sheet-fed scanner capable of scanning multiple scan lines for obtaining the calibration standard for the image signal. Using the cam, the piezoelectric material, the bimetal material, and the like can achieve the small angle rotation of the reflecting mirror, and can thus effectively increase the number of scan lines when the scanning module is scanning the calibration sheet. Therefore, the distorted calibrated result, due to the contaminated calibration sheet, may be avoided.  
         [0031]     While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.