Abstract:
An electromagnetic manuscript input apparatus and a method thereof are provided for providing a manuscript input function. The electromagnetic manuscript input apparatus includes an electromagnetic pen and a digitizer. The electromagnetic pen includes a winding, a capacitor, and a circuit board. The electromagnetic pen is a pen shaped input apparatus capable of emitting electromagnetic waves, which can be either an active type having a power supply or a passive type having no power supply. The digitizer includes a plurality of antennas and windings orthogonally distributed for inducing the electromagnetic waves of the electromagnetic pen. According to the electromagnetic manuscript input method, a controller of the digitizer is used to perform a whole region scanning process to find out a position of a winding having a maximum induction potential, and further find out positions of two immediately adjacent windings.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to an electromagnetic manuscript input apparatus and a method thereof, and more particularly, to an electromagnetic manuscript input apparatus and a method thereof adapted for precision positioning. 
         [0003]    2. The Prior Arts 
         [0004]    Computers, terminals, and other similar electronic devices should be provided with suitable input apparatuses for allowing users to input instructions, data, or select menus displayed on displays. In such a way, the computer, the terminals and the electronic devices can be controlled to work. Input apparatuses are normally categorized into contact type input apparatuses and noncontact type input apparatuses. The contact type input apparatuses include keyboard, mouse, joystick, touch panel, lightpen, remote control, digitizer, while the noncontact type input apparatuses include voice input device. 
         [0005]    A digitizer or an electromagnetic white board should be facilitated by an electromagnetic pen for operation. In operation, the electromagnetic pen approaches or touches the digitizer, in accordance with a cursor or an image displayed on the display apparatus, to select a function menu, handwrite characters or draw a diagram. The electromagnetic pen is a very convenient input apparatus. Currently, the electromagnetic pen, and particularly the handwriting and drawing function thereof, has become widely employed in a variety of electronic products, such as computers, terminals, mobile phones, handheld digital secretaries, and touch panels. 
         [0006]    An electromagnetic pen is a pen shaped input apparatus, including a winding, a capacitor, and a circuit board. The electromagnetic pen is capable of emitting electromagnetic waves. An electromagnetic pen may be either an active type, or a passive type. An active type electromagnetic pen includes a power supply, and a passive type electromagnetic pen does not include a power supply. The power supply of the active type electromagnetic pen is usually a battery. The passive type electromagnetic pen usually obtains power from the electromagnetic waves emitted by the digitizer, in which the electromagnetic pen has to obtain power by inducing the electromagnetic waves emitted from the digitizer. 
         [0007]    Referring to  FIG. 1 , there is shown a functional block diagram illustrating a conventional electromagnetic manuscript input apparatus. The conventional electromagnetic manuscript input apparatus includes an electromagnetic pen  10  and a digitizer  20 . The electromagnetic pen  10  includes a winding, a capacitor, and a circuit board (not shown in the drawing), and is capable of emitting electromagnetic waves. The digitizer  20  includes a plurality of X windings, a plurality of Y windings, an X scanning circuit  22 , a Y scanning circuit  23 , a signal detection circuit  24 , a scan driver  26 , an analog to digital converter (ADC)  28 , and a coordinate controller  29 , for generating a coordinate output signal  32  and transmitting the same to a posterior stage processing device, e.g., a computer, or a transmission interface such as a universal serial bus (USB) interface. 
         [0008]    Reference numerals X 1 , X 2 , X 3  . . . , represent the X windings. For example, Xn represents the n th  X winding. Reference numerals Y 1 , Y 2 , Y 3  . . . , represent the Y windings. For example, Ym represents the m th  Y winding. The X windings and the Y windings are adapted for inducing the electromagnetic waves emitted from the electromagnetic pen  10 , and generating an induction potential. 
         [0009]    The coordinate controller  29  controls all operations of the electromagnetic manuscript input apparatus. The scan driver  26  receives a control driving signal from the coordinate controller  29 , and transmits a scan driving signal  25  to the X scanning circuit  22  and the Y scanning circuit  23 . The X scanning circuit  22  and the Y scanning circuit  23  drive a plurality of X windings and a plurality of Y windings, respectively. When an X winding or a Y winding is driven, an induction potential of the X winding or the Y winding is detected by the signal detection circuit  24 . Correspondingly, the posterior stage ADC  28  generates a digital signal, and transmits the digital signal to the coordinate controller  29 . The coordinate controller  29  receives and processes the digital signal (e.g., compare the digital signal with a noise threshold, or compare values of adjacent windings) so as to determine a maximum value and obtain a correct induction potential value. Then, the coordinate controller  29  repeats the foregoing steps, so as to obtain induction potential values of all of the X windings and the Y windings. One of the X windings having the maximum induction potential value represents an X coordinate to which the electromagnetic pen most approaches. Similarly, one of the Y windings having the maximum induction potential value represents a Y coordinate to which the electromagnetic pen most approaches. Precision coordinate values are usually obtained by calculations according to different algorithms. Generally, interpolation algorithms, such as first order approximation or a second order parabolic approximation, are often employed in conventional calculation methods. 
         [0010]    Referring to  FIG. 2 , it is a schematic diagram illustrating an electromagnetic field of the electromagnetic pen  10 . When the electromagnetic pen  10  defines a tilt angle with the digitizer  20 , the tilt angle between the electromagnetic pen  10  and the digitizer  20  may apply an affection to the induction potential which should be further considered. As shown in  FIG. 2 , a larger tilt angle (θ) indicates that the winding immediately adjacent to the tilt angle (θ) generates a larger induction potential. As such, the affection caused by the tilt angle (θ) should be compensated or regulated. 
         [0011]    Referring to  FIG. 3 , it illustrates an induction potential distribution of the electromagnetic pen relative to the digitizer. As shown in  FIG. 3 , the curves are not bilateral symmetrical. This indicates that the electromagnetic pen  10  is tilt. An X winding XP 0  most adjacent to the electromagnetic pen  10  has an induction potential having a maximum peak value VP 0 , and a limit value (VPR, VPL) at a right side XPR and a left side XPL respectively. Further, two immediately adjacent windings (XP+, XP−) of the XP 0  winding have corresponding induction potentials (VP+, VP−), respectively. Referring to  FIG. 4 , it illustrates an induction potential distribution of an antenna winding of the digitizer, in which the slashed filled columns represent induction potentials of the X windings, while the blank columns represent that there is no X winding. Comparing with  FIG. 3 ,  FIG. 4  is simplified for more clearly depicting the coordinate positioning method of the conventional technologies, in which same numerals represent similar matters. 
         [0012]    According to the first order approximation of the conventional technology, the coordinates of the electromagnetic pen  10  can be obtained by an interpolation algorithm. For example, the X coordinate of the electromagnetic pen  10  can be obtained from positions the windings XP 0 , XPR, XPL, XP+, XP−, and their corresponding induction potentials VP 0 , VPR, VPL, VP+, VP−, facilitated by a memory (e.g., a ROM) recording regulation values. Similarly, the Y coordinate of the electromagnetic pen  10  can also be obtained. A correct X coordinate can be obtained according to equation (1) as below: 
         [0000]        D=Sx*T+Q/G+H ( f )   (1), 
         [0000]    in which D represents the correct X coordinate, Sx represents a serial number of the wiring having the maximum induction potential, T represents a coordinate value represented by a space between wirings (for the purpose of simplification, the wirings are uniformly-spaced hereby), G represents a constant, Q represents parameters related to the induction potentials VP 0 , VPR, VPL, f represents parameters related to the induction potentials VPR, VPL, and H(f) represents regulation values related to f. Further, 
         [0000]        Q =( VP 0− VP +)/( VP 0− VP −),  VP+≧VP −; or 
         [0000]        Q =( VP 0− VP −)/( VP 0− VP +),  VP+&lt;VP−,    
         [0000]    while the regulation values of H(f) are recorded in the memory. 
         [0013]    According to the second order parabolic approximation of the conventional technology, the coordinates of the electromagnetic pen  10  are obtained by a second order approximation interpolation algorithm. For example, the wiring positions XP 0 , XPR, XPL and their corresponding induction potentials VP 0 , VPR, and VPL are accorded for calculating the X coordinate of the electromagnetic pen  10  by an equation (2) as: 
         [0000]        VPL=a *( XPL−D ) 2   +b    
         [0000]        VP 0= a *( XP 0− D ) 2   +b    
         [0000]        VPR=a *( XPR−D ) 2   +b    (2). 
         [0000]    Solving the equation (2), it can be obtained as: 
         [0000]        D=XPL+T/ 2*{(3* VPL− 4* VP 0+ VPR )/( VPL− 2* VP 0+ VPR )} 
         [0014]    The conventional first order approximation interpolation has some disadvantages. For example, the induction potentials of the first order approximation interpolation are similar to a Gauss distribution, thus having a large error, and requiring a memory recording regulation values to provide compensation thereto. However, a system having more windings requires a larger memory, and therefore the hardware cost and complexity are increased correspondingly. This may even impair the reliability of the product. Further, mutual inductions between adjacent windings may also lower the precision of the method. 
         [0015]    The conventional second order approximation interpolation also has disadvantages. For example, the induction potentials of the second order approximation interpolation are similar to a Gauss distribution, thus also having a large error. Therefore, the layout of the adjacent windings is restricted. For example, the space between the adjacent windings should be lowered, and the electromagnetic pen is restricted from being too close to the windings, for compensating the large error. 
         [0016]    As such, it is very much desired to provide an apparatus and a method for accurately positioning the coordinate positions of the electromagnetic pen, for satisfying the higher system requirement for accuracy, and decreasing the complexity of the hardware design, and further improving the reliability of the product. 
       SUMMARY OF THE INVENTION 
       [0017]    A primary objective of the present invention is to provide an electromagnetic manuscript input method. The electromagnetic manuscript input method employs a log coordinate positioning equation deducted from a Gauss distribution function to conduct log, multiply, and add operations to obtain precision coordinates of an electromagnetic pen. 
         [0018]    Another objective of the present invention is to provide an electromagnetic manuscript input apparatus. The electromagnetic manuscript input apparatus is adapted to realize a log coordinate positioning equation capable of conducting log, multiply, and add operations, by utilizing a log circuit and an operation circuit. In such a way, precision coordinates of the electromagnetic can be obtained by the real Gauss distribution function can be approximated to. 
         [0019]    A further objective of the present invention is to provide an electromagnetic manuscript input apparatus. The electromagnetic manuscript input apparatus utilizes a processor in a coordinate controller to conduct a log coordinate positioning equation capable of conducting log, multiply, and add operations, so as to obtain precision coordinates of the electromagnetic and approximate to the real Gauss distribution function. 
         [0020]    A still another objective of the present invention is to provide an electromagnetic manuscript input method. According to the electromagnetic manuscript input method, a winding position having a maximum value of induction potential and positions of two immediately adjacent windings are detected by a whole region scanning process, and then induction potentials corresponding to the foregoing three windings are detected, for precisionally calculate the coordinates. 
         [0021]    As such, the foregoing method and apparatus are provided for eliminating the disadvantages of the conventional technology, so as to obtain precision coordinates of the electromagnetic pen, thus lowering the complexity of hardware, and improving the reliability of the product. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
           [0023]      FIG. 1  is a functional block diagram illustrating a conventional electromagnetic manuscript input apparatus; 
           [0024]      FIG. 2  is a schematic diagram illustrating an electromagnetic field of the electromagnetic pen; 
           [0025]      FIG. 3  illustrates an induction potential distribution of the electromagnetic pen relative to the digitizer; 
           [0026]      FIG. 4  illustrates an induction potential distribution of an antenna winding of the digitizer; 
           [0027]      FIG. 5  is a functional block diagram of a first embodiment of the present invention; 
           [0028]      FIG. 6  is a functional block diagram of an operational circuit of the present invention; 
           [0029]      FIG. 7  is a functional block diagram of a second embodiment of the present invention; and 
           [0030]      FIG. 8  is a functional block diagram of a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    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. 
         [0032]      FIG. 3  illustrates an induction potential Gauss distribution of the electromagnetic pen relative to the digitizer. The present invention provides an operation equation directly deducted from the Gauss distribution, as to be exemplified below. The Gauss distribution function is as equation (3) 
         [0000]        V ( Xi )= A 0/(σ*(2*π) 1/2 )*exp(−( Xi−D )/(2*σ 2 ))   (3), 
         [0000]    in which σ is a standard deviation. 
         [0033]    The wiring positions XP 0 , XPR, XPL and their corresponding induction potentials VP 0 , VPR, and VPL are calculated according to the equation (3), an X coordinate D of the electromagnetic pen can be obtained as of equation (4) as: 
         [0000]        D=XP 0+ T/ 2*ln( VPR/VPL )/ln( VP 0 2   /VPR/VPL )   (4), 
         [0000]    in which XP 0 , XPR, XPL, VP 0 , VPR, VPL, and T are as above defined, and are not to be iterated hereby. 
         [0034]    Further, the equation (4) can be simplified by a of equation (5): 
         [0000]      α=ln( VPR/VPL )/ln( VP 0 2   /VPR/VPL )   (5). 
         [0035]    Equation (6) can be obtained from the equation (4): 
         [0000]        D=XP 0+ T/ 2*α  (6). 
         [0036]    Similarly, the Y coordinate of the electromagnetic pen can be obtained. 
         [0037]    In the foregoing discussion, the Gauss distribution unction is used for representing the induction potentials, and deducting the coordinate equation of the electromagnetic pen, i.e., equation (4). In such a way, when the position of the winding having the maximum induction potential and the positions of two immediately adjacent winding, and the induction potentials thereof are known, the X coordinate and the Y coordinate of the electromagnetic pen can be obtained. In other words, positions of the three windings and three induction potentials thereof are required. 
         [0038]    As such, the method of the present invention further includes a process of finding out the required positions of the three windings and the three induction potentials. The process includes: (1) conducting a whole region scanning process to find out the positions of the three required windings; (2) inputting the positions of the three windings to obtain the three induction potentials of the three windings; and (3) calculating with the positions of the three windings and the three induction potentials to obtain the coordinates of the electromagnetic pen. The process can be achieved by a hardware circuit, or a software program. Details are going to be discussed below. 
         [0039]    First, a first embodiment of the present invention is to comply with the foregoing process by a hardware circuit. 
         [0040]    Referring to  FIG. 5 , it is a functional block diagram of a first embodiment of the present invention illustrating an electromagnetic manuscript input apparatus. The electromagnetic manuscript input apparatus includes an electromagnetic pen  10 , and a digitizer  40 . The digitizer  40  includes a plurality of X windings (not shown), a plurality of Y winding (not shown), an X-axis scanning circuit (not shown), a Y-axis scanning circuit (not shown), a scan driver (not shown), an ADC  28 , a multiplexer  52 , an amplifier  53 , a bandpass filter  54 , a sample-and-hold circuit  55 , a frequency counter  56 , a log circuit  62 , an operational circuit, and a coordinate controller  29 . It should be noted that in the current embodiment those similar to the conventional technology can be learnt by referring to the discussion above and are not to be iterated, and for purpose of simplification and clarity of illustration, only one X winding, one Y winding, one X-axis scanning circuit, one Y-axis scanning circuit, and one scan driver are shown in the drawing without defining the amounts of the elements in the first embodiment. Further, the multiplexer  52 , the amplifier  53 , the bandpass filter  54 , and the sample-and-hold circuit  55  have the similar function of the signal detection circuit  24  of the above discussed conventional technology. All of the multiplexer  52 , the amplifier  53 , the bandpass filter  54 , and the sample-and-hold circuit  55  should have been well known to those skilled in the art, thus are not to be iterated hereby. 
         [0041]    The coordinate controller  29  further includes a processor (not shown) of executing a software program. The software program can be recorded in an external memory (ROM or Flash), or recorded in an internal memory built in the coordinate controller  29 . Further, the coordinate controller  29  may further include a RAM, for accelerating the processing speed. 
         [0042]    First, the coordinate controller  29  executes a whole domain scanning process to all of the windings. Similar to conventional technologies, in the whole domain scanning process, the coordinate controller  29  emits a driving control signal to drive each of the X windings and Y windings, and detects induction potentials corresponding to the windings. However, differing from the conventional technologies, the present invention sequentially compares the values of all of the induction potentials of the windings to find out the position of the winding having the maximum induction potential, and then finds out the positions of two windings immediately adjacent thereto. Therefore, the present invention needs to find out three windings positions. On the contrary, in addition to the positions of the three windings, the conventional technologies must record induction potentials of the three windings, as well as positions of two lateral windings having relative limit peak values and the induction potentials thereof. Therefore, the conventional technologies have to find out positions of five windings and five induction potentials. 
         [0043]    In the current embodiment, the frequency counter  56  of  FIG. 5  counts the amount of inputted signals, which is equivalent to the scanning times executed to the windings. When all windings are scanned, a Pass signal is then outputted to notify the coordinate controller  29 . In such a way, the coordinate controller  29  can reconfirm for avoiding misoperation caused by other interferences. 
         [0044]    After finding out positions of the three windings, the coordinate controller  29  emits driving signals with respect to these three windings to obtain corresponding induction potential values. Then, precision coordinates of the electromagnetic pen are obtained by calculating the equation (4) with the log circuit  62  and the operation circuit  64 , as shown in  FIG. 5 . The log circuit  62  is controlled by an enabling signal. When the enabling signal is at a high level, the log circuit  62  works, and when the enabling signal is at a low level, the log circuit  62  does not work. As such, when executing the whole region scanning process, the coordinate controller  29  emits low level enabling signals, and when conducting position calculation of the electromagnetic pen, the coordinate controller  29  emits high level enabling signals. 
         [0045]    When the coordinate controller  29  emits a high level enabling signal to initiate the log circuit  62 , the log circuit  62  converts six digital signals inputted by the ADC  28  into log values, and transmits the log values to the operational circuit  64 . The six digital signals are induction potentials of the three X windings and the three Y windings, respectively, which constitute three pairs of coordinates numbered as the first, the second, and the third coordinates. Referring to  FIG. 6 , it is a functional block diagram of an operational circuit of the present invention. The operational circuit  64  includes two ×2 multipliers  71 ,  73 , a ×4 multiplier  72 , two subtractors (SUB 1  and SUB 2 )  74 ,  75 , and a divider (DIV)  76 , for processing the first, the second and the third coordinates, as shown in  FIG. 6 . The operational circuit  64  is responsible for executing the calculation of the equation (5) to obtain the a value, and transmits the a value to the coordinate controller  29 . The processor (not shown) of the coordinate controller  29  then calculates the equation (6) to obtain the coordinates of the electromagnetic pen. 
         [0046]      FIG. 7  is a functional block diagram of a second embodiment of the present invention. Referring to  FIG. 7 , the input signal of the log circuit  62  is provided by the coordinate controller  29 . As such, in the second embodiment, the digital signal of the ADC  28  is indirectly provided to the log circuit  62  via the coordinate controller  29 , and the other configuration is similar to the first embodiment. 
         [0047]      FIG. 8  is a functional block diagram of a third embodiment of the present invention. Referring to  FIG. 8 , the third embodiment of the present invention does not include the log circuit  62  and the operational circuit  64 . Instead, the coordinate controller  29  executes the log conversion and calculation of the log circuit  62  and the operation circuit  64 . In other words, the third embodiment of the present invention realizes the equation (3) with a software program to obtain the electromagnetic pen. 
         [0048]    As such, the method and apparatus of the present invention are adapted for fast obtaining precision coordinates of the electromagnetic pen, thus lowering the complexity of hardware, and improving the reliability of the product. 
         [0049]    Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.