Abstract:
A light source control method and apparatus of an image scanner is disclosed. The invention utilizes a determination means and an illumination control device to perform partial or full illumination and adjust brightness so that the light source can be operated more efficiently and more economically.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light source control method and apparatus of an image scanner, and more particularly to a light source control method and apparatus of an image scanner which can automatically perform partial or full illumination and adjust brightness according to the scan area and the scan mode. 
     2. Description of the Related Art 
     Optical scanners are used to capture and digitize images. For example, an optical scanner can be used to capture the image of printed matter on a sheet of paper. The digitized image can then be electronically stored and/or processed with character recognition software to produce ASCII text. The typical optical scanner includes a light source, a linear array of photoelectric sensing elements (generally a CCD sensor or a CMOS sensor, or a CIS sensor), an analog amplifier, an analog to digital converter (ADC), a controller and a random access memory (RAM). 
     The CCD sensor includes a large number (e.g., 2000) of photoelectric sensing elements arranged in a linear array. Each photoelectric sensing element will capture light representing a single pixel of the image. The array will capture a line of pixels. By moving the CCD sensor across a document, the entire document can be scanned one line at a time. 
     The conversion into digital signals of light reflected from or transmitted through the document takes place in essentially three steps. First, each photoelectric sensing element will convert the light which it receives into an electric charge. The magnitude of the charge will depend on the intensity of the light and the exposure time. Second, the charges from each of the photoelectric sensing elements are converted into analog voltages via the analog amplifier. Finally, the analog voltages are digitized by the analog to digital converter for digital image processing and storage in the RAM. 
     In conventional image scanner, the light source always maintains constant illumination during scanning. However, constant illumination of the light source wastes power and is lack of efficiency when only part of scan area is needed to be scanned. Furthermore, constant illumination of the light source for multiple scan modes (Color, Gray and Line art) of an image scanner is not economical either. Hence it is desirable to provide a light source control method of an image scanner which can automatically perform partial or full illumination and adjust brightness according to the scan area and the scan mode so as to utilize the light source more efficiently and economically. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a light source control method and apparatus of an image scanner which can automatically perform partial or full illumination and adjust brightness. 
     It is another object of this invention to provide a light source control method and apparatus of an image scanner that can utilize the light source more efficiently and economically. 
     To achieve these objects, and in accordance with the purpose of the invention, the invention provide a light source control method of an image scanner. The method comprises the following steps. First of all, a light source having a plurality of sections is provided, wherein power supplies of said sections are controlled separately. Then a scan boundary of a document is determined. Finally, a portion of said sections which cover said scan boundary are provided with electric powers. 
     In another embodiment, the method comprises the following steps. A light source having at least two sections is provided, wherein power supplies of said sections are controlled separately. Then a first section of said sections is provided with electric powers. Next said light source is moved to scan a document along a first direction. Then a second section of said sections is provided with electric powers. Finally, said light source is moved to scan said document along a second direction. 
     In another embodiment, the method comprises the following steps. First of all, a light source having a plurality of sections is provided, wherein power supplies of said sections are controlled separately. Then a document is preview scanned to generate a preview image of said document. Next a scan boundary of said document is determined by said preview image and a portion of said sections which cover said scan boundary is provided with electric powers. 
     In another embodiment, the method comprises the following steps. First of all, a light source having at least two sections and image sensors are provided, wherein power supplies of said sections are controlled separately. Then said light source and said image sensors are moved to a scan line. Next a first section of said light source is provided with electric power to scan a first portion image of said scan line. Then a second section of said light source is provided with electric power to scan a second portion image of said scan line. Finally, said first portion and said second portion images of said scan line are processed to generate an image of said scan line. 
     In another embodiment, the method comprises the following steps. First of all, a light source having at least two sections and image sensors are provided, wherein power supplies of said sections are controlled separately. Then a first section of said light source is provided with electric power to scan a document. Next said light source and said image sensors are moved from a start position to scan a first portion of said document. Then said light source and said image sensors are moved back to said start position after scanning said document. Next a second section of said light source is provided with electric power to scan said document. Then said light source and said image sensors are moved from said start position to scan a second portion of said document. Finally, images of said first portion and said second portion of said document are processed to generate an image of said document. 
     In another embodiment, the method comprises the following steps. First of all, a light source having a controllable power supply is provided. Then a default scan mode of the image scanner is accessed and said light source is provided with electric powers according to said scan mode to generate a bright level of said light source of said scan mode. 
     In another embodiment, a light source control apparatus of an image scanner is provided. The light source control apparatus comprises a light source having a plurality of light-emitting devices divided into a plurality of sections, a scan boundary determining portion for determining a scan boundary and a power supply control means for providing and controlling said sections of said light source with electric power, wherein power supplies of said sections can be controlled respectively. 
     In another embodiment, a light source control apparatus of an image scanner is provided. The light source control apparatus comprises a light source having a plurality of light-emitting devices divided into at least two sections, and a power supply control means for providing and controlling said sections of said light source with electric power, said power supply control means provides a first section of said light source with electric power when said light source moves alone a first direction to scan a document, and provides a second section of said light source with electric power when said light source moves alone a second direction to scan said document, wherein power supplies of said sections can be controlled respectively. 
     In another embodiment, the method comprises the following steps. First of all, a light source having a plurality of light-emitting devices divided into at least two sections is provided, wherein power supplies of said sections can be controlled respectively. Then a scan boundary is determined. Next a default scan mode of the image scanner is accessed. Then a portion of said sections which cover said scan boundary is provided with electric power. Finally, said light source is provided with electric powers according to said scan mode to generate a bright level of said light source of said scan mode. 
     In another embodiment, the method comprises the following steps. First of all, a light source having a plurality of light-emitting devices divided into at least two sections is provided, wherein power supplies of said sections can be controlled respectively. Then a default scan mode of the image scanner is accessed. Next a first section of said light source is provided with electric power according to said scan mode to generate a bright level of said light source of said scan mode to scan a document. Then said light source and said image sensors are moved alone a first direction to scan said document. Next a second section of said light source is provided with electric power according to said scan mode to generate said bright level. Finally, said light source and said image sensors are moved alone a second direction to scan said document. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       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 a light source control apparatus according to one embodiment of this invention; 
         FIG. 2  shows a light source divided into three sections and a document placed on a scan area of an image scanner; 
         FIG. 3  shows one embodiment of the power supply control means; 
         FIG. 4  shows one embodiment of this invention; 
         FIG. 5  shows one embodiment of this invention; 
         FIG. 6  shows one embodiment of this invention; 
         FIG. 7  shows a flow chart of one embodiment of this invention; 
         FIGS. 8A and 8B  show a first surface and a second surface of a holder; 
         FIG. 9A  shows a housing  900  of a scanner; and 
         FIG. 9B to 9D  show three holders having three different scan areas respectively. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     It is to be understood and appreciated that the method and the apparatus described below do not cover a complete system and method. The present invention can be practiced in conjunction with various software and hardware that are used in the art, and only so much of the commonly practiced components and steps are included herein as are necessary to provide an understanding of the present invention. 
     The present invention will be described with six embodiments in detail with reference to the accompanying drawings. It should be noted that the drawings are in greatly simplified form. 
     In one embodiment of this invention, the invention provides a light source control method and apparatus of an image scanner.  FIG. 1  shows a light source control apparatus having a light source  106 , a scan boundary determining portion  102  and a power supply control means  104 . The light source  106  includes a plurality of linearly arranged light-emitting devices. The light source  106  is divided into a plurality of sections and the light-emitting devices of each section are separately controlled by the power supply control means  104 . The light-emitting device of the light source  106  comprises a light-emitting diode (LED). Moreover, each light-emitting device can also be set as one section of the light source  106 .  FIG. 3  shows one embodiment of the power supply control means  104 . The power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the transistor  304  is used as a switch. The turn-on/turn-off of the transistor  304  is controlled by digital signals ( 1  or  0 ) from a shift register  302 . For example, if a signal is applied to the transistor  304  and turns on the gate of the transistor  304  thereby conducts an electric current through the light-emitting diode  306  and renders the light-emitting diode  306  illuminating. By using software or firmware, all light-emitting diodes  306  can be divided into a plurality of sections or each light-emitting diode  306  can be set as a section since each light-emitting diode  306  corresponds to a transistor  304  and each transistor  304  is controlled by the shift register  302 . As shown in  FIG. 2 , a light source  206  is divided into three sections, and a document  204  is placed on a scan area  202  of an image scanner. The light source control method of this invention divides the light source  206  into a plurality of sections, wherein the power supply of each section is separately controlled. Then a preview image of the document  204  is generated by a preview scan. The scan boundary determining portion  102  comprises a user interface and one user can utilize the user interface to select the scan area or the scan boundary of the document  204  according to the preview image of the document  204 . The scan area or the scan boundary can also be determined by other methods. The method and apparatus for determining scan boundary of this invention are example only. The power supply control means  104  provides the sections of the light source  206  covering the width of the scan boundary of the document  204  with electric power. For example, if the width of the scan boundary of the document  204  is 216 millimeters and the light source  206  has  50  light-emitting devices, then the location of the first light-emitting device is at 216/50 and the locations of other light-emitting devices can also be determined. Since only those light-emitting devices within the sections covering the width of the scan boundary of the document  204  are needed to be illuminated, less electric power is needed. Furthermore, because only the scan area or the scan boundary of the document  204  generate images, the image processing of the area outside the scan boundary of the document  204  is omitted. Moreover, due to the selective and sectional illumination of the light source, limited electric power can be utilized more efficiently and applied to the section covering the width of the scan boundary of the document only, and the scanning speed can be upgraded. 
     In a second embodiment of this invention, the invention provides a second light source control method of an image scanner. As the light source control apparatus shown in  FIG. 1 , in this embodiment, the light source  106  is divided into two sections, wherein the power supply of each section is separately controlled by the power supply control means  104 . While the light source moves to scan a document along the scanning direction, the power supply control means  104  controls and provides one section with electric power only to illuminate a first half of the document. When the light source moves back to the start position, the power supply control means  104  controls and provides the other section with electric power only to illuminate the other half of the document. As shown in  FIG. 3 , the power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the turn-on/turn-off of the transistor  304  is controlled by digital signals ( 1  or  0 ) from a shift register  302 . By using software or firmware, all light-emitting diodes  306  can be divided into two sections since each light-emitting diode  306  corresponds to a transistor  304  and each transistor  304  is controlled by the shift register  302 . As shown in  FIG. 4 , a light source  404  is divided into two sections  406  and  408  to illuminate a scan area  402 . When proceeding scan, the light source  404  moves along the scanning direction and only section  406  is provided with electric power or illuminated to scan one half of a document, and the light source  404  moves back to the start and only section  408  is provided with electric power or illuminated to scan the other half of a document. Due to the selective and sectional illumination of the light source, limited electric power can be utilized more efficiently and the scanning speed can be upgraded. 
     In a third embodiment of this invention, the invention provides a third light source control method of an image scanner. As shown in  FIG. 2 , a light source  206  is divided into three sections, and a document  204  is placed on a scan area  202  of an image scanner. The light source control method of this invention divides the light source  206  into a plurality of sections, wherein the power supply of each section is separately controlled. The dividing and control embodiment of the light source is shown in  FIG. 3 . The power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the transistor  304  is controlled by the shift register  302 . By using software or firmware, all light-emitting diodes  306  can be divided into a plurality of sections or each light-emitting diode  306  can be set as a section since each light-emitting diode  306  corresponds to a transistor  304  and each transistor  304  is controlled by the shift register  302 . Then a preview image of the document  204  is generated by a preview scan and is transmitted to image sensors of an image scanner. The optical signals received by the image sensors are then converted to analog signals, and the analog signals are finally converted to digital signals. The digital signals comprise the digital signals of the document  204  as well as the digital signals of the area which is not occupied by the document  204 . By using the digital signals of the document  204  and the digital signals of the area which is not occupied by the document  204 , the scan boundary of the document  204  can be determined. For example, the variation of bright levels of pixels across the scan boundary can be used to recognize the scan boundary. The power supply control means  104  then provides the sections of the light source  206  covering the width of the scan boundary of the document  204  with electric power to illuminate the document  204 . Moreover, due to the selective and sectional illumination of the light source, limited electric power can be utilized more efficiently and applied to the section covering the width of the scan boundary of the document only, and the scanning speed can be upgraded. 
     In a fourth embodiment of this invention, the invention provides a fourth light source control method of an image scanner. A light source of an image scanner is divided into at least two sections. The dividing and control embodiment of the light source is shown in  FIG. 3 . The power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the transistor  304  is controlled by the shift register  302 . By using software or firmware, a light source can be divided into two sections  502  and  504  as shown in  FIG. 5 . When proceeding scan, the light source and image sensors move to a scan line  506  and the sections  502  and  504  are separately and sequentially provided with electric power to illuminate the scan line  506 . While the light source and image sensors move to a scan line  508  and the sections  502  and  504  are separately and sequentially provided with electric power to illuminate the scan line  508 , the image signals of the scan line  506  are processed. Then the light source and image sensors move to the next scan line and repeat the processes set forth until all scan lines are scanned. 
     In a fifth embodiment of this invention, the invention provides a fifth light source control method of an image scanner. A light source of an image scanner is divided into at least two sections. The dividing and control embodiment of the light source is shown in  FIG. 3 . The power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the transistor  304  is controlled by the shift register  302 . By using software or firmware, a light source  604  can be divided into two sections  606  and  608  to illuminate a scan area  602  as shown in  FIG. 6 . When proceeding scan, the light source  604  and image sensors move along the scanning direction and only section  606  is provided with electric power or illuminated to scan one half of a document, and the light source  604  and the image sensors move back to the position of start. Then the light source  604  and the image sensors move along the scanning direction again and only section  608  is provided with electric power or illuminated to scan the other half of a document. Due to the selective and sectional illumination of the light source, limited electric power can be utilized more efficiently and the scanning speed can be upgraded. 
     In a sixth embodiment of this invention, the invention provides a sixth light source control method of an image scanner. The control embodiment of the light source is shown in  FIG. 3 . The power supply of a light-emitting diode  306  is controlled by a transistor  304 , and the transistor  304  is controlled by the shift register  302 . By using software or firmware, the power supply of a light source can be control according to scan modes of an image scanner. Scan modes of an image scanner comprise color scan mode, gray scale scan mode and line art scan mode.  FIG. 7  shows a flow chart of this embodiment. In step  702 , default scan mode of an image scanner is accessed. Then in step  704 , according to the default scan mode, the power supply of a light source is provided, wherein color scan mode uses the brightest illumination of the light source and thereby utilizes most power, and the line art scan mode uses the dimmest illumination of the light source and thereby utilizes less power. Next in steps  706 ,  708  and  710 , the brightness of the light source is adjusted by controlling the power supply of the light source according to the default scan mode. Then in steps  712 ,  714  and  716 , color mode scan, gray scale mode scan and line art mode scan are performed in accordance with the default scan mode. 
     In a seventh embodiment of this invention, the invention provides a holder to select scan areas.  FIG. 8A and 8B  show a first surface  804  and a second surface  806  of a holder  800 . The holder  800  is placed on a scan window of an image scanner during scanning. The holder  800  pre-selects and determines a maximum scan area  802 . The first surface  804  contacts with the document to be scanned while the second surface  806  contacts with the scan window of the image scanner during scanning. The second surface  806  includes a pattern  808  corresponding to the scan area  802 . Each pattern represents a corresponding maximum scan area. The pattern  808  is scanned by a scan head of the image scanner to determine the scan area during scanning. The holder  800  can also be utilized in the embodiments of the invention mentioned above to determine scan areas or scan boundaries. The pattern  800  can be scanned during the original calibration of an image scanner. That is, the pattern  800  is scanned to determine scan areas or scan boundaries after scanning a calibration target during the calibration of an image scanner. 
     In an eighth embodiment of this invention, the invention provides a holder and a housing of a scanner with sensors to select scan areas.  FIG. 9A  shows a housing  900  of a scanner. The housing  900  has a scan window  902  and a sensor area  904  having sensors.  FIG. 9B to 9D  show holders  906 ,  912  and  918  having scan areas  910 ,  914  and  920  respectively. The holders  906 ,  912  and  918  also comprise bulge portions  908 ,  916  and  922  respectively. The bulge portions  908 ,  916  and  922  correspond to the sensor area  904  and each bulge portion is used to cover a corresponding sensor of the sensor area  904 . The sensors of the sensor area  904  correspond to the scan areas  910 ,  914  and  920  of the holders  906 ,  912  and  918  respectively. During scanning, one of the holders  906 ,  912  and  918  is placed on the housing  900  to cover the sensor corresponding to one of the bulge portions  908 ,  916  and  922 , and determine the scan area by the scan areas  910 ,  914  and  920 . This embodiment can also be applied in the embodiments of the invention mentioned above to determine scan areas or scan boundaries. 
     Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.