Abstract:
A calibrating apparatus for scanner in searching for reference of absolute or relativistic position is disclosed. The calibrating apparatus includes a cross-sectional area that generates a drop in elevation and creates a border between dark area and light are in photograph. The cross-sectional area can be formed by using the rib in housing formation or creation of trench. Furthermore, a white calibration target is included.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a calibrating apparatus and method, and more particularly to a calibration target in a scanner. 
     2. Description of the Prior Art 
     FIG. 1 shows the external features of a scanner wherein machine base  30  includes main component parts such as, light source, sensors, analog-to-digital converter, amplifier and I/O interface. The material of transparent glass  40  on housing  20  can be replaced by other transparent materials, such as acrylic resin. Picture for scanning is downward on transparent glass  40 , and lid  10  covers picture to scan where scanning direction is from A to A′. 
     FIG. 2 shows the inside structure of housing  20  in FIG.  1 . Picture for scanning is upward under transparent glass  40 . Because a dark-white calibration is necessary before scanning, a calibration target  60  is in the housing  20  of a scanner where the calibration target  60  in the front of transparent glass  40  is perpendicular to scanning direction. 
     The scanning direction is from A to A′, and scanning order is calibration target to picture in sequence. 
     The structure of calibration target is a white calibrating area and a dark calibrating area, as shown in FIG.  3 . The white calibrating area gives sensors white calibration and steady output, and also defines the brightness of photography. The border between white calibrating area and dark calibrating area is set up the reference of scanning origin, because distance between the border and scanning document can be determined. The dark calibrating area does not provide dark calibration. The scanning direction in calibration target is from white calibrating area  62  to dark calibrating area  64 . 
     The fabrication of calibration target is that prints a long black bar in white board and paste on the transparent glass after appropriately cutting. However, system will have higher tolerance after cutting and sticking. Moreover, the cutting process will make more scrap materials higher cost in materials. 
     SUMMARY OF THE INVENTION 
     The present invention provides a cross-sectional area for calibration target to substitute dark calibrating area. Because cross-sectional area is formed with housing, the white board dose not need to print black bar and cost is down. Moreover, steps of process and assembler tolerance are reduced. 
     In one embodiment, the cross-sectional area for calibration target is formed by using housing formation in which cross-sectional area can be one of the rib on housing or trench in design. The dark calibrating area is substituted by a cross-sectional area that generates a drop in elevation and creates a border between dark area and light. The actual output by this invention is equivalent to prior art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 shows the external features of a scanner. 
     FIG. 2 shows the inside structure of housing. 
     FIG. 3 is a schematic diagram of a calibration target. 
     FIG. 4 a  shows a preferred embodiment of this invention. 
     FIG. 4 b  shows a cross-section diagram of the preferred embodiment of this invention. 
     FIG. 5 a  is a schematic diagram illustrating a scanner in practicing the present invention of a preferred embodiment. 
     FIG. 5 b  is a schematic diagram illustrating the shadow region produced by light sensors passing through rib. 
     FIG. 5 c  is a cross section diagram illustrating the shadow region produced by light sensors passing through rib. 
     FIG. 5 d  shows the result of sensors scanning through rib. 
     FIG. 6 a  shows another preferred embodiment of this invention. 
     FIG. 6 b  shows a cross-section diagram of another preferred embodiment of this invention. 
     FIG. 7 a  is a schematic diagram illustrating a scanner in practicing the present invention of another preferred embodiment. 
     FIG. 7 b  is a schematic diagram illustrating the shadow region produced by light sensors passing through trench. 
     FIG. 7 c  is a cross section diagram illustrating the shadow region produced by light sensors passing through trench. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following is the preferred embodiment of this invention. The cross-sectional area of this invention has two types. One is protuberant rib and the other is indented trench. FIG. 4 a  shows the interior structure of housing  120  in which transparent glass  140  is in center, picture for scanning is upward under transparent glass  140 , a white calibration area  160  is placed beside transparent glass  140  near B, and a rib  180  is distanced to white calibration area  160 . 
     Referring to FIG. 4 b,  a rib  180  that is formed with housing  120  formation is perpendicular to the scanning direction. Transparent glass  140  is placed in the center of housing  120  and a white calibration area is attached below transparent glass  140  near B. Calibrating target is rib  180  plus white calibration area  160  in this embodiment. 
     When a scanner starting to scan, light source  210  moves from B to B′ and photosensor  220  receives signal in-situ, as shown in FIG. 5 a.  Because rib  180  will generate a drop in elevation, photosensor  220  can not receive any signal from light source  210  from X to Y, as shown in FIG. 5 b.  FIG. 5 c  is a cross section diagram illustrating the shadow region produced by photosensor  220  passing through rib  180 . When light source  210  from X to Y, rib  180  stops reflected light such that photosensor  220  receives no signal from Z to W. FIG. 5 d  shows the result of photosensor  220  scanning through the rib  180  and a shadow region scanned from Z to W is the same with prior art. In this embodiment, the border between white and dark can be treated as starting point for scanning. 
     The following is another embodiment. FIG. 6 a  shows another interior structure in housing  120  in which transparent glass  140  is in center, picture for scanning is upward under transparent glass  140 , a white calibration area  160  is placed beside transparent glass  140  near B, and a trench  182  is distanced to white calibration area  160 . 
     Referring to FIG. 6 b,  a trench  182  that is formed with housing  120  formation is perpendicular to the scanning direction. Transparent glass  140  is placed in the center of housing  120  and a white calibration area is attached below transparent glass  140  near B. Calibrating target is trench  182  plus white calibration area  160  in this embodiment. 
     When a scanner starting to scan, light source  210  moves from B to B′ and photosensor  220  receives signal in-situ, as shown in FIG. 7 a.  Because trench  182  will generate a drop in elevation, photosensor  220  can not receive any signal from light source  210  from X to Y, as shown in FIG. 7 b.  FIG. 7 c  is a cross section diagram illustrating the shadow region produced by photosensor  220  passing through trench  182 . When light source  210  from X to Y, trench  182  stops reflected light such that photosensor  220  receives no signal from Z to W. The result of photosensor  220  scanning through the trench  182  is the same with in FIG. 5 d  and a shadow region scanned from Z to W is the same with prior art. Equivalently, the border between white and dark can be treated as starting point for scanning. 
     The length, width and height of the rib  180  in first embodiment are not important as long as the drop in elevation generated by rib  180  can create shadow region for photosensor  220 , similarly for trench  182  in the second embodiment. In this invention, the rib and trench are formed with housing and can get accurate position with prior art. Moreover, white calibrating area is for white calibration so the position of white calibrating area is not important, i.e. it is not important that the white calibrating area lays aslant and rib or trench is located at the front or back of the white calibrating area. In our invention, black bar does not need to be printed on white calibrating area, and can reduce costs. 
     In the preceding description of invention, any apparatus comprising a cross-sectional area that generates a drop in elevation and creates a border between dark area and light is available. The size of cross-sectional area only affects offset. 
     Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.