Abstract:
An opening method for a double-sided scanner is provided. A light source of one particular color inside a first group of light sources and a light source of a different color (or the same color) inside a second group of light source are lit to scan the front and back surface of a scan document. Optical signals from the front and back surface of the scan document are received and converted into analogue electrical signals. Thereafter, the analogue electrical signals are converted into digital electrical signal. Finally, the digital electrical signals are output to a host computer. This invention utilizes two groups of light sources (for example, light-emitting diodes) to serve as light sources for the double-sided scanner. Because light-emitting diodes require no warm-up period and is quick to switch, double-sided scanning is simplified.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 10/248,866, filed on Feb. 26, 2003, now U.S. Pat. No. 7,388,691 which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a method of operating a scanner. More particularly, the present invention relates to a method of operating a double-sided scanner. 
     2. Description of Related Art 
     A scanner is a machine that can be regarded as an intermediate between a photocopier and a camera. In the past, a scanner is an expensive piece of equipment that is deployed by a special user such as an artist. With the progress in computer technologies, there is tremendous drop in the price of the scanner so that a scanner has become an essential peripheral device in most personal computers. 
     According to the price or function, a scanner may be categorized into several types. In general, scanners can be divided into palm top scanners, paper feed scanners, card scanners, negative film scanners and flatbed scanners. A flatbed scanner has a glass platform for holding a document or a pattern thereon. Data is read into the scanner through the movement of a sensor over the document. Since most flatbed scanner is structurally simple, easy to handle and functionally highly expendable, this is the type of scanner that computer users are equipped. 
     Most scanners use a fluorescence lamp to serve as a light source because fluorescence lamps require little warm-up time. However, the lamp has an unstable period after the scanner is activated. If the lamp is used for scanning during the unstable period, a flickering of the image may occur. One method of removing such flickering is to use a cold cathode ray tube. However, one major disadvantage of using a cold cathode ray tube is that a longer warm-up period is required. Furthermore, for a double-side scanning operation, two sets of cold cathode ray tubes must be employed. Aside from the long warming period, scanning of both sides of a document of an image simultaneously is not recommended because the light from the two sets of cold cathode ray tubes might interfere with each other. Typically, the scanning of the front and back of a document needs to be carried out with a slight shift in position. Thus, if cold cathode ray tubes are used as the light source of a double-side scanner, complicated control circuits are demanded. 
     SUMMARY OF INVENTION 
     Accordingly, one object of the present invention is to provide a method of operating a double-sided scanner. This invention uses two groups of light sources (for example, light-emitting diodes) to serve as the light source for the double-sided scanner. Because the light-emitting diodes need no warm-up period and can be switched on or off quickly, the scanner is able to scan two sides at the same time. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of operating a double-sided scanning device. First, the illuminating range of a first group of light sources is controlled such that there is no overlapping with a second group of sensors. At the same time, the illuminating range of a second group of light sources is controlled such that there is no overlapping with a first group of sensors. Thereafter, light sources within the first group of light sources and the second group of light sources having the same color are triggered to illuminate the front and back of a scan document. After receiving the optical signals from the front and back surface of the scan document, the optical signals are converted into analogue electrical signals. The analogue electrical signal is next converted into digital electrical signals. Finally, the digital electronic signals are output to an external device. 
     In one embodiment of this invention, the first group of light sources includes a red, a green and a blue light source. The second group of light sources also includes a red, a green and a blue light source. 
     In one embodiment of this invention, the first group of light sources is a first group of light-emitting diodes and the second group of light sources is a second group of light-emitting diodes. 
     This invention also provides an alternative method of operating a double-sided scanner. First, the light sources within a first group of light sources and a second group of light sources having a different color are triggered to illuminate the front and back surface of a scan document. After receiving the optical signals from the front back surface of the scan document, the optical signals are converted into analogue electrical signals. The analogue electrical signals are next converted into digital electrical signals. Finally, the digital electrical signals are output to an external device. 
     In one embodiment of this invention, the first group of light sources and the second group of light sources are located at the same location. 
     In one embodiment of this invention, the illuminating range of the first group of light sources overlaps with the scanning range of the second group of sensors. 
     In one embodiment of this invention, the illuminating range of the second group of light sources overlaps with the scanning range of the first group of sensors. 
     In one embodiment of this invention, the illuminating range of the first group of light sources overlaps with the scanning range of the second group of sensors and the illuminating range of the second group of light sources overlaps with the scanning range of the first group of sensor. 
     In one embodiment of this invention, the first group of light sources and the second group of light sources are in different locations. 
     In one embodiment of this invention, the illuminating range of the first group of light sources does not overlap with the scanning range of the second group of sensors. 
     In one embodiment of this invention, the illuminating range of the second group of light sources does not overlap with the scanning range of the first group of sensors. 
     In one embodiment of this invention, the illuminating range of the first group of light sources does not overlap with the scanning range of the second group of sensors and the illuminating range of the second group of light sources does not overlap with the scanning range of the first group of sensors. 
     In brief, this invention utilizes two groups of light sources (for example, light-emitting diodes) to serve as the light source for a double-sided scanning device. Since light-emitting diodes need no warm-up period and can be switched on or off quickly, scanning both sides of a document concurrently is relatively simple. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
         FIG. 1  is a schematic structural layout of a double-sided scanner according to a first preferred embodiment of this invention; 
         FIG. 2  is a schematic diagram showing a first group of light-emitting diodes and a second group of light-emitting diodes at different locations in the process of a document; 
         FIG. 3  is a diagram showing a group of timing control signals produced by a light-emitting module control circuit to the light-emitting module for triggering light emission; 
         FIG. 4  is a diagram showing an alternative group of timing control signals produced by a light-emitting module control circuit to the light-emitting module for triggering light emission; 
         FIG. 5  is a schematic diagram showing a first group of light-emitting diodes and a second group of light-emitting diodes at the same location in the process of scanning a document; and 
         FIG. 6  is a diagram showing a third group of timing control signals produced by a light-emitting module control circuit to the light-emitting module for triggering light emission. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 1  is a schematic structural layout of a double-sided scanner according to a first preferred embodiment of this invention. As shown in  FIG. 1 , the double-sided scanner  10  is used for scanning a document  102 . The double-sided scanner  10  includes a light-emitting module  104 , a light-emitting module control circuit  106 , a first group of sensors  108  and a second group of sensors  110 , an image processor  112  and an interface circuit  114 . The light-emitting module  104  further includes a first group of light sources and a second group of light sources. In the following embodiment of this invention, the first group of light sources is a first group of light-emitting diodes  116  and the second group of light sources is a second group of light-emitting diodes  118 . However, anyone familiar with the technology may notice that light-emitting diodes are not the only light sources available. Other types of light sources can be used. 
     In the following, a description of various sections of the double-sided scanner  10  is presented. The first group of light-emitting diodes  116  serves as a group of light sources for scanning the front surface of the scan document  102 . The second group of light-emitting diodes serves as a group of light sources for scanning the back surface of the scan document  102 . The first group of light-emitting diodes  116  at least includes diodes for producing red, green and blue light. Similarly, the second group of light-emitting diodes  118  at least includes diodes for producing red, green and blue light. The light-emitting module control circuit  106  is coupled to the light-emitting module  104  for triggering the light-emitting module  104  on to produce light. The first group of sensors  108  receives optical signals reflected from the positive surface of the scan document  102  and converts the optical signals to analogue electrical signals. In this embodiment, the first group of sensors  108  and the second group of sensor  110  can be, for example, charge-coupled devices (CCD) or complementary metal-oxide-semiconductor (CMOS) sensing devices. The image processor  112  receives the analogue electrical signals and converts the signals to digital electrical signals. The interface circuit  114  is coupled to the image processor  112  for outputting the digital electrical signals to a host computer  120 . 
     To simplify the description, the first group of light-emitting diodes  116  includes a first red light-emitting diode, a first green light-emitting diode and a first blue light-emitting diode only. Similarly, the second group of light-emitting diodes  118  includes a second red light-emitting diode, a second green light-emitting diode and a second blue light-emitting diode only. However, anyone familiar with the technology may notice that the first and the second group of light-emitting diodes can include diodes for producing some other colors. 
     The following is a description of how, with the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  on different locations on the scan document  102 , the light-emitting module control circuit  106  is able to control the timing of light emission in the light-emitting module  104  and hence achieve double-sided scanning.  FIG. 2  is a schematic diagram showing the first group of light-emitting diodes  114  and the second group of light-emitting diodes  116  at different locations in the process of scanning a document. As shown in  FIG. 2 , the irradiating light-emitting diodes within the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  can be the same color or of different colors. That is, the light-emitting module control circuit  106  may trigger all the diodes within the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  with the same color to emit light. Alternatively, light-emitting diodes of different colors within the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  emit light. In the following, two embodiments are used to illustrate the aforementioned conditions in more concrete detail. 
       FIG. 3  is a diagram showing a group of timing control signals produced by the light-emitting module control circuit  106  to the light-emitting module  104  for triggering light emission. Typically, if a light-emitting diode is maintained at a low potential, this indicates the diode emits light. On the other hand, if the light-emitting diode is maintained at a high potential, this indicates the diode is off. In  FIG. 3 , the double-sided scanner  10  also controls the first group of light-emitting diodes  116  such that its range of illumination does not overlap with the scanning range of the second group of sensors  110 . Similarly, the double-sided scanner  10  also controls the second group of light-emitting diodes  118  such that its range of illumination does not overlap with the scanning range of the first group of sensors  108 . The light-emitting module control circuit  106  also controls the triggering sequence of the light-emitting module  104  in such a way that the first red light-emitting diode, the second red light-emitting diode, the first green light-emitting diode, the second green light-emitting diode, the first blue light-emitting diode and the second blue light-emitting diodes are lighted up in that order. 
       FIG. 4  is a diagram showing an alternative group of timing control signals produced by the light-emitting module control circuit  106  to the light-emitting module  104  for triggering light emission. In this embodiment, the light-emitting module control circuit  106  triggers the light-emitting diodes within the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  to emit different colors. Typically, if a light-emitting diode is maintained at a low potential, this indicates the diode emit light. On the other hand, if the light-emitting diode is maintained at a high potential, this indicates the diode is off. In  FIG. 4 , the double-sided scanner  10  positions the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  at different locations. In addition, the double-sided scanner  10  controls the first group of light-emitting diodes  116  such that its range of illumination does not overlap with the scanning range of the second group of sensors  110  or controls the second group of light-emitting diodes  118  such that its range of illumination does not overlap with the scanning range of the first group of sensors  108 . Alternatively, the double-sided scanner  10  controls the first group of light-emitting diodes  116  such that its range of illumination does not overlap with the scanning range of the second group of sensors  110  and controls the second group of light-emitting diodes  118  such that its range of illumination does not overlap with the scanning range of the first group of sensors  108 . The light-emitting module control circuit  106  also controls the triggering sequence of the light-emitting module  104  in such a way that the first red light-emitting diode, the first green light-emitting diode, the first blue light-emitting diode, the second red light-emitting diode, the second green light-emitting diode and the second blue light-emitting diodes are lighted up in that order. 
     The following is a description of how, with the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  at the same location on the scan document  102 , the light-emitting module control circuit  106  is able to control the timing of light emission in the light-emitting module  104  and hence achieve double-sided scanning.  FIG. 5  is a schematic diagram showing the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  at the same location in the process of scanning a document. In  FIG. 5 , color of the light-emitting diodes within the first group of light-emitting diodes  116  lit up is different from color of the light-emitting diodes within the second group of light-emitting diodes  118 . In other words, the light-emitting module control circuit  106  triggers one particular color of the light-emitting diodes within the first group of light-emitting diodes  116  but triggers another color of the light-emitting diodes within the second group of light-emitting diodes  118  simultaneously. 
       FIG. 6  is a diagram showing a third group of timing control signals produced by the light-emitting module control circuit  106  to the light-emitting module  104  for triggering light emission. In this embodiment, the light-emitting module control circuit  106  triggers the light-emitting diode of one color in the first group of light-emitting diodes  116  and the light-emitting diode of a different color in the second group of light-emitting diodes  118  simultaneously. Typically, if a light-emitting diode is maintained at a low potential, this indicates the diode emit light. On the other hand, if the light-emitting diode is maintained at a high potential, this indicates the diode is off. In  FIG. 6 , the double-sided scanner  10  positions the first group of light-emitting diodes  116  and the second group of light-emitting diodes  118  at the same locations. In addition, the double-sided scanner  10  controls the first group of light-emitting diodes  116  such that its range of illumination overlaps with the scanning range of the second group of sensors  110  or controls the second group of light-emitting diodes  118  such that its range of illumination overlaps with the scanning range of the first group of sensors  108 . Alternatively, the double-sided scanner  10  controls the first group of light-emitting diodes  116  such that its range of illumination overlaps with the scanning range of the second group of sensors  110  and controls the second group of light-emitting diodes  118  such that its range of illumination overlaps with the scanning range of the first group of sensors  108 . The light-emitting module control circuit  106  also controls the triggering sequence of the light-emitting module  104  in such a way that the first red light-emitting diode and the second green light-emitting diode are lit simultaneously, then the first green light-emitting diode and the second blue light-emitting diode are lit simultaneously, and finally, the first blue light-emitting diode and the second red light-emitting diode are lit simultaneously. 
     In summary, this invention utilizes two groups of light-emitting diodes to serve as the light source for a double-sided scanning device. Since light-emitting diodes need no warm-up period and can be switched on or off quickly, scanning both sides of a document concurrently is simplified. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.