1. FIELD OF THE INVENTION 
       [0001]    The present invention relates to an input apparatus and a scanning method for locating the coordinates of a touch point, and more particularly to an infrared type input apparatus and a scanning method for locating the coordinates of a touch point with low cost. 
       2. DESCRIPTION OF THE PRIOR ART 
       [0002]    Apparatuses that use touch technologies for inputting instruction or information such as touch-panel monitor can accurately locate the coordinates of touch points within effective sensing range. Among various techniques of touch panel, one technique is to place both light emitting modules and light sensor modules at corners of the screen of the display. When a pointer such as user&#39;s finger, a pen or other object contacts or approaches the screen of the display, light emitted from the light emitting modules will be reflected back to a portion of sensors of the light sensor modules. The relative angles between the location of the touch point and the positions of the sensors receiving the reflected light can be used to determine the coordinate of the touch point of the pointer through the principles of geometry and trigonometry. The advantages of this technique of detecting the coordinates of touch point include obtaining enough resolution or accuracy with few devices, etc. however, this technique of detecting the coordinates of touch point also has disadvantages including dragged responding rate. Since the detection of the touch point is performed via scanning all sensors to detect the variation of light sensing signals and the touch point usually moves continuously without rapid jump between largely spaced positions, the responding speed will be dragged if all sensors are continuously and repeatedly scanned to detect the trace of the touch point. 
         [0003]    Another technique of detecting the coordinate of a touch point is to locate the light emitting module and the light sensor module on opposing sides of a display respectively. The position of the touch point is detected by the position of the sensor of the light sensor module which does not receive light emitted from the corresponding the light emitter of the light emitting module. That is, the location of the touch point is determined by the blocking of light by the pointer such as a user&#39;s finger or a pen. Such technique of detecting the coordinate of a touch point is widely applied upon apparatuses with a large sensing area, and the resolution depends on the number or density of the light emitters and the sensors of the light emitting module and the light sensor module respectively. Conventional input apparatuses and techniques using infrared light emitting diodes (LED) are disclosed in U.S. Pat. No. 3,764,813, U.S. Pat. No. 4,928,094, U.S. Pat. No. 5,162,783 and U.S. Pat. No. 6,677,934. These prior arts disclose light emitters and sensors on opposing sides of a display respectively. The location of the touch point is determined by the blocking of the straight light by the pointer such as an user&#39; finger or a pen. Since the resolution of this touch technique depends on the number or density of the light emitters and the sensors as mentioned above, the light emitters and the sensors must be arranged on the sides of the sensing area with a large number and a high density in order to cover the sensing area and to have a sufficient resolution. However, such design not only increases the production cost, but also raises the difficulties of assembling. Moreover, the signal processing would be more complicated due to more signal need to be processed and more components need to be controlled. 
         [0004]    In order to solve the above-mentioned drawbacks of the conventional input apparatus and a scanning method for locating a coordinate of a touch point, a new infrared type input apparatus and a scanning method for locating a coordinate of a touch point are thus provided. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the present invention is to provide an input apparatus and a scanning method for locating a coordinate of a touch point which arrange the light emitters and the light sensors at one side of the sensing area so as to reduce the number of devices and the cost. 
         [0006]    According to the object of the present invention, an input apparatus is provided. The input apparatus comprises a plurality of light emitters and light sensors arranged at same one side of a sensing area of the input apparatus, a control device and a signal processing device. The control device controls the light emitters to emit light beams and the light sensors to receive the light beams reflected from a pointer in the sensing area. The signal processing device processing light sensing signals generated by the light sensors and output the processed light sensing signals to the control device. 
         [0007]    According to the object of the present invention, a scanning method for locating a coordinate of a pointer of an input apparatus is provided. The input apparatus comprises a plurality of light emitters and light sensors arranged at same one side of a sensing area of the input apparatus and a control device, the control device controls the light emitters to emit light beams and the light sensors to receive the light beams reflected from a pointer in the sensing area. The scanning method comprises the following steps. Firstly, the control device controls one of the light emitters to emit light beams into the sensing area. Secondly, one by one the light sensors are enabled by the control device to receive the light beams reflected from the pointer. Next the steps set forth are repeated until all the light emitters had emitted light beams. Then the values of light sensing signals generated by all the light sensors are compared to determine a rough position of the pointer along a Y axis. Then the control device enables one light emitter within the region in which the light sensor has highest signal amplitude to emit light beams. Next the control device controls the light sensors one by one to receive the light beams reflected from the pointer. Then the amplitude values of light sensing signals generated by the light sensors can be used to determine precise Y coordinate of the pointer. Finally, precise X coordinate of the pointer is calculated by using the Y coordinate of the pointer and the distances between the pointer and two light sensors closest to the pointer respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention. 
           [0009]      FIG. 1  shows a schematic illustration of an input apparatus of one embodiment of the present invention. 
           [0010]      FIG. 2  shows a schematic illustration of signal emitting and receiving of an input apparatus of one embodiment of the present invention. 
           [0011]      FIG. 3  shows the geometry used to calculate the X coordinate of the pointer in the sensing area. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]    The detailed description of the present invention will be discussed in the following embodiments, which are not intended to limit the scope of the present invention, but can be adapted for other applications. While drawings are illustrated in details, it is appreciated that the scale of each component may not be expressly exactly. 
         [0013]      FIG. 1  shows a schematic illustration of an input apparatus of one embodiment of the present invention. The location of a pointer or indicator in a sensing area  101  such as a user&#39;s finger or a stylus is determined through the sensing signals received by light sensors  112 . The sensing signals are generated from the light reflected from the pointer, wherein the maximum value of the sensing signal is generated at the light sensor  112  which is closest to the pointer. When light emitters  110  emit light in to the sensing area  101 , the light sensors  112  which are located close to the pointer and with specific angles relative to the pointer will generate higher amplitude value of sensing signals resulting from the reflection of light from the pointer, while other light sensors  112  which are located more far away from the pointer will receive less strength of light and generate weaker sensing signals. Most light beams emitted from the light emitters  110  are not blocked and reflected from the pointer and will only generate much weaker sensing signals on the light sensors  112 . All sensing signals generated on the light sensors  112  are then processed by a signal processing device  104  to form a curve of signal strength distribution. The coordinate of the pointer can be calculated by the signal strength distribution and suitable algorithms. That is, the coordinate of the pointer can be calculated by the strength variation of the sensing signals and suitable algorithms. The light emitters  110  and the light sensors  112  are preferably arranged in an interlaced configuration, but not limited to an interlaced configuration. The light emitters  110  are linearly arranged and each light emitter  110  is controlled by a control device  102  through a switch of a multiplexer  106 . The light sensors  112  are also linearly arranged and each light sensor  112  is controlled by the control device  102  through a switch of a multiplexer  108 . The control device  102  comprises a micro-controller unit (MCU), but not limited to a micro-controller unit. The light emitter  110  comprises an infrared light emitting diode (LED), but not limited to an infrared light emitting diode. The light sensor  112  comprises a charged-couple device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor or other photoelectric effect sensor, but not limited to a charged-couple device sensor or a complementary metal oxide semiconductor sensor. If the infrared light emitting diode is used as the light emitter  110 , an infrared sensor can be used as the light sensor  112 . Each light emitter  110  corresponds to a switch of the multiplexer  106  which is controlled by the control device  102 . According to firmware program, the control device  102  controls the on/off and scanning modes of the light emitters  110 . The light sensors  112  are turned on according the control signals from the control device  102  through the switches of the multiplexer  108  to receive light beams reflected from a pointer such as a user&#39; finger. Light sensing signals are then generated in the light sensors  112  and are transmitted to the signal processing device  104 . The light sensing signals are then processed by the signal processing device  104  and the processed light sensing signals are then transmitted to the control device  102  to calculate the coordinate of the pointer in the sensing area. It is noted that the input apparatus shown in  FIG. 1  only shows a schematic configuration which only discloses main features of the invention. Other well known minor features are omitted and can be made or used according to related prior art by one with ordinary skill in the art to carry out the invention. The input apparatus of the invention can be integrated into a whiteboard or integrated with a display apparatus such as a liquid crystal display, a plasma display and a projection display, or a cathode ray tube display etc, but not limited to an electronic white board, a liquid crystal display, a plasma display a projection display or a cathode ray tube display. Various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims. The input apparatus may integrate with a flat display including a liquid crystal display, a plasma display and a projection display, etc, but cathode ray tube displays are not excluded. The elements and devices of the above mentioned embodiments are only example, instead of limitations. It will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims. 
         [0014]      FIG. 2  shows a schematic illustration of signal emitting and receiving of an input apparatus of one embodiment of the present invention. In  FIG. 2 , a light emitter  110  emits light beams into the light sensing area  101 , wherein a portion of the light beams are blocked and reflected from the pointer or the user&#39;s finger. The reflected light beams are received by all light sensors  112  to generate light sensing signals thereon. The strength of the light sensing signal decreases when the distance between the light sensor  112  and the pointer or the user&#39;s finger increases. The strength of the light sensing signal increases when the distance between the light sensor  112  and the pointer or the user&#39;s finger decreases. Thus a distribution of light sensing signals can be obtained. Since the light emitters  110  and the light sensors  112  are arranged along Y axis, the light sensing signals are distributed along Y axis and the Y coordinate of the pointer or user&#39;s finger can be obtained. In  FIG. 2 , the light sensor  112  closest to the pointer or user&#39;s finger generates the light sensing signal with a highest strength, and the signal strengths of the distribution of the light sensing signals gradually decrease from the center or peak toward two sides. The distribution of the strengths of the light sensing signals shown in  FIG. 2  is generated by all light sensors  112  receiving the light beams emitted from the light emitter  110  closest to the pointer or user&#39;s finger. The distribution of the strengths of the light sensing signals generated by all light sensors  112  receiving the light beams emitted from other light emitter  110  will be different, but the light sensor  112  closest to the pointer or user&#39;s finger will generate the light sensing signal with a highest strength. 
         [0015]    As shown in  FIG. 1 , in order to detect whether a pointer is in the sensing area of the input apparatus, the control device  102  controls the light emitter  110  to emits light beams and the light sensors  112  to receive the light beams reflected from the pointer or user&#39;s finger so as to calculate the coordinate of the pointer in the sensing area. The control device  102  sends control signals to the multiplexer  106  to sequentially turn on the switches so that the corresponding light emitters  110  sequentially emit light beams. The control device  102  sends control signals to the multiplexer  108  to turn on the switches and the corresponding light sensors  112  to receive the light beams. In one embodiment, a full scan on a sensing area is performed by the following steps. First of all, the control device  102  controls the multiplexer  106  to turn on a light emitter  110  to emit light beams, and the control device  102  controls the multiplexer  108  to sequentially turn on all light sensors  112  to receive the reflected light beams emitted from the first light emitter  110 . Then the control device  102  controls the multiplexer  106  to turn on a second light emitter  110  to emit light beams, and the control device  102  controls the multiplexer  108  to turn on all light sensors  112  to receive the reflected light beams emitted from the second light emitter  110 . The control device  102  then controls the multiplexer  106  to turn on the light emitter  110  and controls the multiplexer  108  to turn on all light sensors  112  to receive the reflected light beams until all remain light emitters  110  are sequentially turned on. If a pointer appears in the sensing area of the input apparatus, the light sensors  112  receive the light beams reflected from the pointer sequentially emitted from all light emitters  100 . Since the distances between each light emitter  110 /light sensor  112  and the pointer are different, the distribution of the strengths of the light sensing signals along Y axis is thus formed. The rough position/coordinate along Y axis of the pointer in the sensing area  101  can be estimated by comparing the strengths of the light sensing signals. 
         [0016]    A partial scan on the sensing area is then performed after the rough position/coordinate along Y axis of the pointer in the sensing area  101  is determined. The control device  102  sends control signals to the multiplexer  106  to turn on the light emitters  110  closest to the rough position/coordinate along Y axis of the pointer to emit light beams. The control device  102  sends control signals to the multiplexer  108  to turn on all light sensors  112  to receive the reflected light beams emitted by this light emitter  110 . The values of the signal strengths of the light sensing signals are compared according to the distribution of the signal strengths of the light sensing signals to obtain, for example, but limited to, 3 highest values of the signal strengths of the light sensing signals. The accurate Y coordinate of the pointer in the sensing area  101  can be calculated through algorithms, the distances between the light sensors  112 , and the 3 highest values of the signal strengths of the light sensing signals. That is to say, the Y coordinate of the pointer in the sensing area  101  can be calculated by the following equation: 
         [0000]        Y   R ={( Y   1st   −Y   2nd )/[( Y   1st   −Y   2nd )+( Y   1st   −Y   3rd )]}×( L×K   R )
 
         [0000]        Y= ( n− 1)×( L×K   R )+ Y   R  
 
         [0000]    wherein L (inch) is the distance between two adjacent light sensors  112 , and K R  is the resolution per inch. Y 1st  is the highest light sensing signal value generated by the light sensor  112 , Y 2nd  and Y 3rd  are the second and the third highest light sensing signal values generated by the corresponding light sensors  112 . Y R  is the relative Y coordinate of the pointer relative to the light sensor  112 , Y is the Y coordinate of the pointer. 
         [0017]    In order to calculate the X coordinate of the pointer in the sensing area  101 , the geometry shown in  FIG. 3  is utilized. The light sensor N is the light sensor generating the highest value of the light sensing signal, the light sensor N+ 1  is the light sensor generating the second highest value of the light sensing signal. Since the y coordinates of the light sensors N and N+ 1  are known, Y 1  and Y 2  which are the distances between the Y coordinate of the pointer and the light sensors N and N+ 1  respectively can be calculated, wherein Y 1  plus Y 2  equals L. L 1  and L 2  which are the distances between the pointer and the light sensors N and N+ 1  respectively can be obtained through the values of the light sensing signals generated by the light sensors N and N+ 1  since the distance between the pointer and the light sensor  112  is inversely proportional to the strength of the light sensing signal generated by the light sensor  112 . X 1  and X 2  can be calculated through known Y 1  and L 1 , Y 2  and L 2  respectively, wherein the distance between two adjacent light sensors  112  is L. the X coordinate of the pointer in the sensing area  101  can be calculated by the following equations: 
         [0000]    
       
      
       X 
       1 
       2 
       =L 
       1 
       2 
       −Y 
       1 
       2  
      
     
         [0000]    
       
      
       X 
       2 
       2 
       =L 
       2 
       2 
       −Y 
       2 
       2  
      
     
         [0000]        X= ( X   1   +X   2 )/2 
         [0018]    The light emitters and the light sensors of the input apparatus of the invention are arranged at same one side of the sensing area. In one embodiment, the light emitters and the light sensors are arranged in an interlaced configuration so as to reduce the cost. The scanning method for locating a coordinate of a touch point includes performing full scans and partial scans on the sensing area through the corresponding firmware of the control device. The method of the invention scans all light sensors to detect the light sensor generating the light sensing signal with a highest value. Then partial scans are then performed instead of full scans. Only light emitters within a certain range adjacent the light sensor generating the light sensing signal with a highest value are scanned, such as three light emitters on each side of the light sensor generating the light sensing signal with a highest value. When the pointer moves, the partial scans are performed to detect the movement of the light sensing signal with a highest value relative to the pointer. Thus only the light sensors within a certain range adjacent the light sensors to be scanned are needed to be refreshed so that the speed of scan and tracking the pointer can be upgraded. 
         [0019]    Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
An infrared type handwriting input apparatus and scanning method are disclosed. The input apparatus comprises a plurality of light emitters and a plurality of light receivers aligned along one side of a sensing area of the input apparatus, a control device and a signal processing device. The control device controls the light emitters to emit light and to control the light receivers to receive the light reflected from a pointer in the sensing area. The signal processing device processes the signals generated from the light receivers and transmits the processed signals to the control device.