Patent Publication Number: US-2015062092-A1

Title: Baseline calibration method and system thereof for touch panel

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a baseline calibration method; in particular, to a baseline calibration method and a system thereof for touch panel. 
     2. Description of Related Art 
     Recently, great improvements have been made to the touch sensing technology, which greatly increases its convenience of use. Because touch panels have advantages such as small volume, low cost, low power consumption and long life time. Therefore, the technology for the touch sensing has been widely used in various types of electrical devices. 
     Some of the manufacturers integrate pressure sensors in the touch panel during the manufacturing process of the touch panel to reduce the manufacturing cost of touch panel while meet the current design trend of light, thin, and compact. However, the pressure sensor may sense the pressing point when the user does nothing because of the components of the factors which aren&#39;t predicated drift in the process, that is the “Initial Touch Point”, and so as to affect the accuracy when operating the touch panel. Furthermore, the above issue may get worse with the area of the touch panel increasing suddenly. In the other hand, there usually exists mismatch between the each sensing channel on the touch panel. When the users do nothing, every sensing channel receives the value of the initial touch points may be different, causing to decrease the preciseness and inducing inconvenient to the users. 
     Thus, calibrating the initial touch point is one of the important factors to operate correctly and detect the user action in accuracy for touch panel. 
     SUMMARY 
     An exemplary embodiment of the present disclosure provides a baseline calibration method for a touch panel. The baseline calibration method comprises calculating each first differential value associated with each respective transmission electrode through a first-axis calculation procedure, calculating each second differential value associated with each respective sensing electrode through a second-axis calculation procedure and calculating a baseline calibration value based on each of the first differential values and each of the respective second differential values calculated. 
     An exemplary embodiment of the present disclosure provides baseline calibration system. The baseline calibration system comprises a touch panel and a baseline calibration unit. The baseline calibration unit is coupled to the touch panel. The touch panel having a plurality of transmission electrodes and sensing electrodes disposed thereon, the transmission electrodes being arranged on the touch panel along a first axis and the sensing electrodes being arranged along a second axis, wherein each of the transmission electrodes and each of the respective sensing electrode form a crossover point. The baseline calibration unit calculates each first differential value associated with each transmission electrode through a first-axis calculation procedure and calculates each second differential value associated with each sensing electrode through a second-axis calculation procedure; the baseline calibration unit calculates a baseline calibration value based on each of the first differential value and each of the respective second differential value. 
     To summary up, the manufacturing company of the touch panel can improve the judgment accuracy decreased when users employ the touch panel. The improvement exploits the baseline calibration unit to resolve the mismatch between each sensing channel or the manufacturing for touch panel originally, and the mismatch may further affect the judgment accuracy. Firstly the baseline calibration unit calibrates the crossover points arranged with first-axis, secondly the baseline calibration unit bases on the result of calibrating the crossover points arranged with first-axis to calibrate the crossover points arranged with second-axis again, so as to cancel the part of the un-flatness for each axis. Therefore, the baseline calibration unit achieves the gradient approximating agreed for whole touch panel, so as to increase the judgment accuracy. It&#39;s worth noting, wherein using the method arranged with first-axis and second-axis to calibrate the crossover points may reduce the circuit cost by N 2 −2N. 
     In order to further the understanding regarding the present disclosure, the following embodiments are provided along with illustrations to facilitate the disclosure of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagram of a baseline calibration system according to an embodiment of the present disclosure; 
         FIG. 2  shows a diagram of a touch panel according to an embodiment of the present disclosure; 
         FIG. 3  shows a flow diagram of a baseline calibration method according to an embodiment of the present disclosure; 
         FIG. 4  shows a flow diagram of a baseline calibration method according to other embodiment of the present disclosure; 
         FIG. 5  shows a flow diagram of a baseline calibration method according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the present disclosure. Other objectives and advantages related to the present disclosure will be illustrated in the subsequent descriptions and appended drawings. 
     Please refer to  FIG. 1 ,  FIG. 1  shows a diagram of a baseline calibration system according to an embodiment of the present disclosure. The baseline calibration  1  system includes a touch panel  11 , an operating unit  14 , a detection front end  12  and a baseline calibration unit  13 . The detection front end  12  is coupled to the touch panel  11 , the baseline calibration unit  13  is coupled to the detection front end  12  and the operating unit  14  is coupled between the touch panel  11  and the detection front end  12 . In addition, the output of the baseline calibration unit  13  is coupled to the operating unit  14 . 
     Please refer to  FIG. 2 ,  FIG. 2  shows a diagram of a touch panel according to an embodiment of the present disclosure. The touch panel  11  includes a plurality of transmission electrodes TX i  on first-axis and a plurality of sensing electrodes RX j  on second-axis, each transmission electrodes TX i  and each sensing electrodes RX j  form each crossover point wherein the i, j≧1 and the i, j are integers. For instance, shown as  FIG. 2 , the touch panel  11  has the transmission electrodes TX 1 ˜TX 7  on first-axis and the sensing electrodes RX 1 RX 13  on second-axis. Each transmission electrodes TX i  and each sensing electrodes RX j  form each crossover point P i,j , such as the crossover point P 1,1  formed by the transmission electrodes TX 1  and the sensing electrodes RX 1 , or the crossover point P 1,2  formed by the transmission electrodes TX 1  and the sensing electrodes RX 2 . 
     The baseline calibration system  1  further includes an analogy-to-digital converter (not illustrated), the analogy-to-digital converter is the circuit for transforming the received continues analogy signal to discrete digital signal and then measuring the discrete digital signal, wherein the expression is the digital signal in fixed ratio voltage usually. The digital signal may be outputted by different coding type. The analogy-to-digital converter provides the digital signal to the detection front end  12 . In more specifically, when the scanning signals scan the transmission electrodes TX i  on the touch panel, sensing the sensing values of the crossover points P i,j  on the sensing electrodes RX j  corresponded to the transmission electrodes TX i , and then the sensing values are transformed from the analogy signal into the digital signal. After that, the values of digital signals are provided to the baseline calibration unit  13 . 
     The operating unit  14  includes a first input terminal, a second input terminal and an output terminal. The first input terminal is coupled to the touch panel  11 , the second input terminal is coupled to the baseline calibration unit  13 , and the output terminal is coupled to the detection front end  12 . The operating unit  14  is used for operating the baseline calibration value CRT(P i,j ) of the baseline calibration unit  13  received from the second input terminal and each crossover point P i,j  outputted by the touch panel  11 , and then outputs the sensing value to calibrate each crossover point at the output terminal. 
     The detection front end  12  is coupled to the touch panel  11 , which is being the multi-channels circuit of the signal transmission. The signal transmission channel of the detection front end  12  is used for receiving the sensing value of the crossover point P i,j  of the sensing electrode on the touch panel  11 . In other words, the each channel of detection front end  12  is coupled to at least one of the sensing electrodes RX j  on the touch panel  11 . 
     An end of the baseline calibration unit  13  is coupled to the detection front end  12 , and another of the baseline calibration unit  13  is coupled to the operating unit  14 . The baseline calibration unit  13  is the operating circuit or other calculating circuit having the same function. The baseline calibration unit  13  receives the transformed scanning signal by the detection front end  12 . When the scanning signals scan the transmission electrodes TX j  sequentially, sensing the sensing value of the crossover point P i,j  on the transmission electrodes TX j  by the sensing electrodes RX j  corresponding to the transmission electrodes TX j . 
     The baseline calibration unit  13  is used for executing the calculation procedures. Firstly, the baseline calibration unit  13  presets the predetermined reference value BKTH, which is the calibrating target for the user. Then, the baseline calibration unit  13  scans the transmission electrode TX i  on first-axis by at least one of the scanning signal SCAN a (TX i ), and each transmission electrode TX i  has the “a” number of the scanning signal SCAN a (TX i ), the “a”≧1 and the “a” is the integer. The each scanning signal SCAN a (TX i ) of the scanning transmission electrode TX i  will calculate average AVG a  (TX i ) associated with each scanning signal SCAN a (TX i ). The average AVG a  (TX i ) calculates the all crossover point P i,j  associated with the transmission electrode TX i  by averaging, when each scanning signal SCAN a (TX i ) scans the transmission electrode TX i . Following, the baseline calibration unit  13  further bases on the predetermined reference value BKTH in the search process to calculate the first differential value DIF(TX i ) associated with the transmission electrode TX i  from the averages AVG a  (TX i ) of the scanning signals SCAN a (TX i ). On the other hand, when in the calculation process, the first differential value DIF(TX i ) of each transmission electrode TX i  stores a respective set of least significant bits (LSB) TX i     —   LSB(RX j ) to the value of the sensing electrode RX j  calculating. 
     Hereafter, the baseline calibration unit  13  obtains the each average value AVG (RX j ) of the sensing electrode RX j  by averaging the sensing value of the all crossover point P i,j  associated with the sensing electrode RX j , and obtaining the baseline calibration value CRT(P i,j ) by calculating the average value AVG (RX j ) with the set of least significant bits (LSB) TX i     —   LSB(RX j ). Finally, posting back the each calculating baseline calibration value CRT(P i,j ) to the operating unit  14 , so as to calibrate each crossover point P i,j  calculated by the baseline calibration value CRT(P i,j ). 
     For instance, please refer to the  FIGS. 1 and 2 , when the scanning signal scans the sensing electrode TX 1 , the analogy-to-digital converter transforms the analogy type to the digital signal type for the scanning signal corresponding with the sensing value of the crossover point P 1,1 , P 1,2  . . . , P 1,13  associated with the sensing electrode RX 1 , RX 2 , . . . , RX 13 . Then the detection front end  12  outputs the sensing value transformed as the digital signal type to the baseline calibration unit  13 . 
     When scans the transmission electrode TX 1  arranged along first-axis, providing the binary type scanning signal 1000, 0100, 0110 and 0101 to scan the transmission electrode TX 1  (i.e. the each bit set shows as the scanning signal SCAN 1 (TX 1 )˜SCAN 4 (TX 1 )). The sensing electrodes RX 1 ˜RX 13  obtain the sensing values of every crossover points P 1,1 , P 1,2  . . . , P 1,13  associated with the transmission electrode TX 1  when the scanning signal 1000 is signaled onto the transmission electrode TX 1 . At the same time, the baseline calibration unit  13  averages the sensing values of the all crossover points P 1,1 , P 1,2  . . . , P 1,13  to obtain the average AVG 1 (TX 1 ) belonging to the scanning signal 1000. Following, calculating the scanning signals 0100, 0110 and 0101 sequentially and obtaining the every averages AVG 2 (TX 1 )˜AVG 4 (TX 1 ) belonging to the scanning signals 0100, 0110 and 0101, the calculating is same as scanning signal 1000, so it doesn&#39;t repeat here. It&#39;s worth noting, when processing the each scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ), the baseline calibration unit  13  further bases on the predetermined reference value BKTH to calculate the first differential value DIF(TX 1 ) for the transmission electrode TX 1  from the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ). However, the scanning signals SCAN 2 (TX)˜SCAN 4 (TX 1 ) said is determined by the previous scanning signal. Such as the instance abovementioned, the 0100 of the scanning signal SCAN 2 (TX 1 ) is determined according to the 1000 of the scanning signal SCAN 1 (TX 1 ) and the predetermined reference value BKTH in the binary search algorithm. 
     Be more carefully, the 1000 of the scanning signal SCAN 1 (TX 1 ) is signaled onto the transmission electrode TX 1  when processing the binary search. When the average AVG 1 (TX 1 ) calculated is greater than the predetermined reference value BKTH, doesn&#39;t save. In other words, the bit of “1” for 1000 isn&#39;t saved, and then continuously signaling the 0100 of the scanning signal SCAN 2 (TX 1 ). 
     Nevertheless, when the average AVG 2 (TX 1 ) calculated for the 0100 of the scanning signal SCAN 2 (TX 1 ) is less than the predetermined reference value BKTH, the bit of “1” for 0100 is saved in the binary search, and then continuously signaling the 0110 of the scanning signal SCAN 3 (TX 1 ). 
     When the average AVG 3 (TX 1 ) calculated for the 0110 of the scanning signal SCAN 3 (TX 1 ) is greater than the predetermined reference value BKTH, the bit of 01“1”0 isn&#39;t saved in the binary search algorithm. 
     Finally, the 0101 of the scanning signal SCAN 4 (TX 1 ) is signaled, when the average AVG 4 (TX 1 ) calculated for the scanning signal SCAN 4 (TX 1 ) is less than the predetermined reference value BKTH, the bit of 010“1” is saved in the binary search algorithm. 
     Therefore, calculating four scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) with the predetermined reference value BKTH to find the first differential value DIF(TX 1 ) (that is, the 0101 of the scanning signal SCAN 4 (TX 1 ) in the example). 
     After calculated the first differential value DIF(TX 1 ) for the transmission electrode TX 1 , calculating two sensing values for the 0101 of the first differential value DIF(TX 1 ) and the 0110 of the scanning signal SCAN 3 (TX 1 ) respectively with the first differential value DIF(TX 1 ) in the process for the scanning electrode TX 1 . The baseline calibration unit  13  will obtain and store each least significant bit TX 1     —   LSB(RX 1 )˜TX 1     —   LSB(RX 13 ) on each sensing electrode RX 1 RX 13  on the transmission electrode TX 1 . Each least significant bit TX 1     —   LSB(RX 1 )˜TX 1     —   LSB(RX 13 ) above may be expressed as follows: 
         TX   1     —     LSB ( RX   j )=[SCAN 3 ( TX   1 )_( RX   j )−SCAN 4 ( TX   1 )_( RX   j )]/[SCAN 3 ( TX   1 )−SCAN 4 ( TX   i )]  (1)
 
     Each least significant bit TX 1     —   LSB(RX 1 )˜TX 1     —   LSB(RX 13 ) associated with each sensing electrode RX 1 ˜RX 13  belong to the temporary set of the first differential value DIF(TX 1 ) in the binary search algorithm. In the embodiment of present disclosure, while achieving by the binary search algorithm, but the person skill in the art should understand that can be implemented by replacing with other algorithm. The present disclosure is not limited thereto. 
     Sequentially executing the first differential value DIF(TX 2 )˜DIF(TX 7 ) for the other transmission electrodes TX 2 ˜TX 7  after finishing the calculating of the first differential value DIF(TX 1 ) for the transmission electrode TX 1 , and then completing the calculation procedure on first-axis. The calculation procedure is same as the transmission electrode TX 1 , so it doesn&#39;t repeat here. It&#39;s worth noting, the sensing electrodes RX j  corresponding to every transmission electrodes TX i  are similar. In the other word, all sensing electrodes RX j  are coupled to the channels of the detection front end  12 . Thus, after finishing the calculating of the first differential value DIF(TX 1 ) for the transmission electrode TX 1 , obtaining the effect of each sensing electrodes RX j  to the transmission electrodes TX i  on the touch panel  11 , also wouldn&#39;t calculate the first differential value DIF(TX 2 )˜DIF(TX 7 ). Therefore, it could only use the first differential value DIF(TX 1 ) of the transmission electrode TX 1  being as other first differential values DIF(TX 2 )˜DIF(TX 7 ) of the transmission electrodes TX 2 ˜TX 7 , the present disclosure is not limited thereto. 
     Hereafter, the baseline calibration unit  13  finishes the calculation procedure for the transmission electrodes TX 1 ˜TX 7  arranged along first-axis, then calculating the sensing values of the sensing electrode RX 1  arranged along second-axis, that is the average AVG(RX 1 ) calculated by the sensing values associated with the each crossover point P 1,1 , P 2,1  . . . P 7,1 . After calculating the average AVG(RX 1 ) for the sensing electrode RX 1 , the baseline calibration unit  13  further calculates the average AVG(RX 1 ) with the least significant bits TX 1     —   LSB(RX 1 )˜TX 7     —   LSB(RX 1 ) stored in the process of the first differential values DIF(TX 1 )˜DIF(TX 7 ) for the transmission electrodes TX 2 ˜TX 7 , and obtaining the second differential values DIF 1 (RX 1 )˜DIF 7 (RX 1 ) for the sensing electrode RX 1 . The second differential values DIF 1 (RX 1 )˜DIF 7 (RX 1 ) for the sensing electrode RX 1  can be calculated by the equation (2) as following: 
         DIF   i ( RX   j )=[AVG( RX   j )− BKTH]TX   i     —     LSB ( RX   j )  (2)
 
     The baseline calibration unit  13  calculates the sensing value on the sensing electrode RX 2  sequentially to obtain the average AVG(RX 2 ) for the sensing electrode RX 2  by the values of the crossover points P 1,2 , P 2,2  . . . , P 7,2 . Identically, the baseline calibration unit  13  calculates the average AVG(RX 2 ) with the least significant bits TX 1     —   LSB(RX 2 )˜TX 7     —   LSB(RX 2 ) stored in the process of the first differential values DIF(TX 1 )˜DIF(TX 7 ) for the transmission electrodes TX 1 ˜TX 7  after calculating the average AVG(RX 2 ) for the sensing electrode RX 2  by the equation (2), and obtaining the second differential values DIF 1 (RX 2 )˜DIF 7 (RX 2 ) for the sensing electrode RX 1 . Repeatedly, the baseline calibration unit  13  sequentially calculates the sensing electrodes RX 1 ˜RX 13  to obtain all the second differential values [DIF 1 (RX 1 )˜DIF 7 (RX 1 )], [DIF 1 (RX 2 )˜DIF 7 (RX 2 )] . . . , [DIF 1 (RX 13 )˜DIF 7 (RX 13 )] until completing the calculation procedure on second-axis. 
     Similarly, the method only calculates the transmission electrode TX 1  while doesn&#39;t calculate the transmission electrodes TX 2 ˜TX 7 , thence the sensing electrode RX 1  also only bases on the transmission electrode TX 1  to calculate the second differential value DIF 1 (RX 1 ) being as other second differential values DIF 2 (RX 1 )˜DIF 7 (RX 1 ). In other words, the sensing values of the crossover points on the sensing electrodes RX j  are calibrated by the calculating result of the transmission electrode TX 1 , the present disclosure isn&#39;t limited thereto. 
     Then, the baseline calibration unit  13  further calculates the calculating result for arranged along second-axis associated with the calculating result arranged along first-axis by the equation (3) as following: 
         CRT ( P   i,j )= DIF ( TX   i )+ DIF   i ( RX   j )  (3)
 
     The baseline calibration unit  13  sequentially calculates all the baseline calibration values [CRT(P 1,1 ), CRT(P 1,2 ) . . . , CRT(P 1,7 )], [CRT(P 2,1 ), CRT(P 2,2 ) . . . , CRT(P 2,7 )]. . . , [CRT(P 13,1 ), CRT(P 13,2 ) . . . , CRT(P 13,7 )]. Finally, the baseline calibration unit  13  sends all the baseline calibration values [CRT(P 1,1 ), CRT(P 1,2 ) . . . , CRT(P 1,7 )], [CRT(P 2,1 ), CRT(P 2,2 ) . . . , CRT(P 2,7 )] . . . , [CRT(P 13,1 ), CRT(P 13,2 ) . . . , CRT(P 13,7 )] returned to the operating unit  14  for calibrating the each crossover point on the touch panel  11 . 
     It&#39;s worth noting, the channels of the detection front end  12  which are coupled to the touch panel  11  are less than the sensing electrodes RX j  of the touch panel  11 . Therefore, in the scanning process, classifying the sensing electrodes RX j  into a plurality of scanning groups G k  (k≧1 and k is an integer), such as the group G 1  and G 2  in  FIG. 2 . For instance, the baseline calibration unit  13  scans the transmission electrode TX 1  of group G 1  on first-axis by the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) sequentially for several times. Calculating each scanning signal SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) scans the transmission electrode TX 1  of group G 1  to obtain the average AVG 1 (TX 1 )˜AVG 4 (TX 1 ) for each scanning signal SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) which are belonged to the group G 1 . 
     The baseline calibration unit  13  further bases on the predetermined reference value BKTH, calculating the first group differential value DIF 1 (TX 1 ) belonged the transmission electrode TX 1  of group G 1  from the averages AVG 1 (TX 1 )˜AVG 4 (TX 1 ) of the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) associated the transmission electrode TX 1  of group G 1 . 
     Finally, repeating the step abovementioned to calculating the first group differential values DIF 1 (TX 2 )˜DIF 1 (TX 7 ) for transmission electrodes TX 2 ˜TX 7 . After completing the group G 1 , sequentially scanning and calculating to obtain the second group differential values DIF 2 (TX 2 )˜DIF 2 (TX 7 ), and then finishing the calculation procedure for transmission electrodes TX 1 ˜TX 7  arranged along first-axis. 
     Hereafter, the baseline calibration unit  13  calculates the sensing values of the sensing electrode RX 1  on second-axis, that is the average AVG(RX 1 ) calculated by the sensing values on the each crossover point P 1,1 , P 2,1 , . . . , P 7,1 . Then, the baseline calibration unit  13  calculates the average AVG(RX 1 ) with the first group differential value DIF 1 (TX 1 ), DIF 1 (TX 2 ) . . . , DIF 1 (TX 7 ) of the transmission electrodes TX 1 ˜TX 7  by the equation (2) to obtain the second differential values DIF 1 (RX 1 ), DIF 2 (RX 1 ) . . . , DIF 7 (RX 1 ) for sensing electrode RX 1  and the second differential values DIF 1 (RX 11 ), DIF 2 (RX 11 ) . . . , DIF 7 (RX 11 ) for sensing electrode RX 11  at same time. The baseline calibration unit  13  sequentially calculates the sensing electrodes RX 1 ˜RX 13  arranged along second-axis for touch panel  11  to obtain all the second differential values [DIF 1 (RX 1 )˜DIF 7 (RX 1 )], [DIF 1 (RX 2 )˜DIF 7 (RX 2 )] . . . , [DIF 1 (RX 13 )˜DIF 7 (RX 13 )] for all the crossover points P i,j  of the sensing electrodes RX 1 ˜RX 13  on touch panel  11  until completing the calculation procedure on second-axis. 
     Then, the baseline calibration unit  13  further calculates the calculating result arranged along second-axis with the calculating result arranged along first-axis (such as the equation (3) above). For calculating all the baseline calibration values CRT(P i,j ) of the crossover points P i,j  disposed on the touch panel  11 . 
     On another hand, by the classifying groups method for the transmission electrodes TX 1 ˜TX 7  disposed on the touch panel  11 , Thus, in the embodiment of the present disclosure, further using the first group differential values DIF 1 (TX 1 ), DIF 1 (TX 2 ) . . . , DIF 1 (TX 7 ) as the second group differential values DIF 2 (TX 1 ), DIF 2 (TX 2 ) . . . , DIF 2 (TX 7 ) after calculating the first group differential value DIF 1 (TX 1 ), DIF 1 (TX 2 ) . . . , DIF 1 (TX 7 ). In other words, the crossover points P 1,1 , P 1,2 , . . . P 1,10  associated with the transmission electrodes TX 1  decide all the first group differential values DIF(TX 1 ), DIF(TX 2 ) . . . , DIF(TX 7 ) associated with the transmission electrodes TX 1 . 
     Please synchronously refer  FIG. 2  and  FIG. 3 .  FIG. 3  shows a flow diagram of a baseline calibration method according to an embodiment of the present disclosure. The touch panel  11  includes a plurality of transmission electrodes TX i  arranged along first-axis and a plurality of sensing electrodes RX j  arranged along second-axis, each transmission electrodes TX i  and each sensing electrodes RX j  form each crossover point wherein the i, j≧1 and the i, j are integers. Firstly, In the step S 101 , calculate each first differential value DIF(TX i ) for each transmission electrode TX i  arranged along first-axis. In the step S 102 , calculate each average AVG(RX j ) for each sensing electrode RX j  arranged along second-axis. In the step S 103 , calculate each second differential value DIF i (RX j ) associated with each sensing electrode RX j  by the least significant bit temporarily stored in the calculation procedure and the each average AVG(RX j ) associated with each sensing electrode RX j . In the step S 104 , adds each first differential value DIF(TX i ) arranged along first-axis and each second differential value DIF i (RX j ) arranged along second-axis to calculate all baseline calibration values CRT(P i,j ), and calibrate all crossover points P i,j  through the baseline calibration values CRT(P i,j ). 
     Please synchronously refer  FIG. 2  and  FIG. 4 ,  FIG. 4  shows a flow diagram of a baseline calibration method according to other embodiment of the present disclosure. The baseline calibration method of the embodiment of the present disclosure comprises a first-axis calculation procedure and a second-axis calculation procedure. The first-axis calculation procedure comprises the step S 201 , the step S 202 , the step S 203 , the step S 204  and the step S 205 . The second-axis calculation procedure comprises the step S 206 , the step S 207 , the step S 208  and the step S 209 . 
     Firstly, in the step S 201 , the baseline calibration unit  13  will set the initialization. When the user processes the baseline calibrating process, setting the predetermined reference value BKTH, transmission electrodes TX i  number and the sensing electrodes RX j  number (such as the TX 1 ˜TX 7  and the RX 1 ˜RX 13  in  FIG. 2 ). The predetermined reference value BKTH is the target that the user wanted for all the crossover points P i,j  disposed on the touch panel  11 . 
     In the step S 202 , scan each transmission electrode TX i  sequentially. In carefully, the baseline calibration unit  13  receives a plurality of the scanning signals for scanning the transmission electrode TX 1  sequentially. After finish scanning the transmission electrode TX 1 , receive a plurality of the scanning signals for scanning the transmission electrode TX 2  continuously, until complete all the transmission electrodes TX i  arranged along first-axis. 
     In the step S 203 , calculate each average AVG a (TX i ) associated with each scanning signal SCAN a (TX i ) according to at least one of the scanning signals SCAN a (TX i ) when scan each transmission electrode TX i . The baseline calibration unit  13  calculates the averages AVG a  (TX i ) belonged to each scanning signal SCAN a (TX i ) associated with each scanning signal SCAN a (TX i ) of the scanning transmission electrodes TX i . When baseline calibration unit  13  receives the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) which are scanned the transmission electrodes TX 1 , obtain the average AVG 1 (TX 1 ) of the scanning signal SCAN 1 (TX 1 ) by averaging the sensing values of each crossover points P 1,1 , P 1,2 , . . . , P 1,13  which are obtained when scanning signal SCAN 1 (TX 1 ) scans the transmission electrode TX 1 . Following, sequentially calculate the scanning signals SCAN 2 (TX 1 )˜SCAN 4 (TX 1 ) and then obtain the average AVG 2 (TX 1 )˜AVG 4 (TX 1 ) for each scanning signals SCAN 2 (TX 1 )˜SCAN 4 (TX 1 ), the calculating is same as the scanning signal SCAN 1 (TX 1 ), it doesn&#39;t repeat here. 
     In the step S 204 , calculate first differential value DIF(TX i ) for transmission electrode TX i  by the averages AVG a (TX i ) obtained when the scanning signals SCAN a (TX i ) scan the transmission electrode TX i  through a search process. It&#39;s worth noting, in the process for calculating each first differential value DIF(TX i ) of each transmission electrode TX store a set of the least significant bits TX 1     —   LSB(RX j ) corresponding to the sensing electrodes RX j . Wherein the calibration bits BKunit is obtained when baseline calibration unit  13  scans the transmission electrode TX i  by the scanning signals SCAN a (TX i ), that is the first differential value DIF(TX i ). For instance, the baseline calibration unit  13  further bases on the predetermined reference value BKTH in the search process, calculate and obtain the first differential value DIF(TX 1 ) of the transmission electrode TX 1  from the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ). The first differential value DIF(TX 1 ) is the calibration bits BKunit calculated by the transmission electrode TX 1  (such as the scanning signal 0101). 
     In the step S 205 , detect whether the count of transmission electrodes TX i  less than the total number of the transmission electrodes TX i . In other words, determine whether finish all the transmission electrodes TX i  arranged with first-axis calculation procedure. In detail, after the baseline calibration unit  13  finishes the step S 202 ˜S 204 , detect whether the count of the transmission electrodes TX i  are calculated to find all the first differential value DIF(TX i ). If not, repeat the step S 202 ˜S 204  until find all the first differential value DIF(TX i ) for the count of the transmission electrodes TX i  which is set in the step S 201 . The embodiment of the present disclosure further may use the first differential value DIF(TX 1 ) of the transmission electrode TX i  being as other first differential value DIF(TX 2 ) DIF(TX i ). In other words, leapfrog the step S 202  and S 205  detecting the first differential values DIF(TX 1 )˜DIF(TX i ) according to the count of other transmission electrodes TX 2 ˜TX i , just only achieve by the first differential value DIF(TX 1 ) of the transmission electrode TX 1 , the present disclosure is not limited thereto. 
     Finish the first-axis calculation procedure, in the step S 206 , the baseline calibration unit  13  will process the second-axis calculation procedure, calculate and obtain each average AVG(RX j ) by the sensing values of the crossover points P i,j  for each sensing electrode RX j  arranged along second-axis. 
     In the step S 207 , calculate each average AVG(TX j ) and the temporarily stored least significant bit TX i     —   LSB(RX j ) to obtain each second differential value DIF i (RX j ). For example, the least significant bit TX i     —   LSB(RX 1 ) stores by calculating the first differential value DIF(TX 1 ) of the transmission electrodes TX 1  in the process with the average AVG(RX 1 ) of the sensing electrode RX 1  according to the equation (2), and obtains the second differential values DIF i (RX j ) of crossover points on the sensing electrode RX 1 . 
     In the step S 208 , add each first differential value DIF(TX i ) on first-axis and each second differential value DIF i (RX j ) arranged with second-axis to calculate all baseline calibration values CRT(P i,j ). 
     Finally, in the step S 209 , calibrate all crossover points P i,j  by the baseline calibration values CRT(P i,j ) calculated by each transmission electrode TX j  and each sensing electrode RX j . 
     Please refer  FIG. 5 ,  FIG. 5  shows a flow diagram of a baseline calibration method according to another embodiment of the present disclosure. The baseline calibration method of the embodiment of the present disclosure comprises a first-axis calculation procedure and a second-axis calculation procedure. The first-axis calculation procedure comprises the step S 301 , the step S 302 , the step S 303 , the step S 304 , the step S 305 , the step S 306  and the step S 307 . The first-axis calculation procedure comprises the step S 308 , the step S 309 , the step S 310  and the step S 311 . 
     Firstly, in the step S 301 , the baseline calibration unit  13  will set the initialization. When the user processes the baseline calibrating process, setting the predetermined reference value BKTH, transmission electrodes TX i  number, the sensing electrodes RX j  number (such as the TX 1 ˜TX 7  and the RX 1 ˜RX 13  in  FIG. 2 ) and the groups G k  number (such as the group G 1  and the group G 2 ). The predetermined reference value BKTH is the target that the user wanted for all the crossover points P i,j  disposed on the touch panel  11 . 
     In the step S 302 , scan each group G k  sequentially. In carefully, the channels of the detection front end  12  which are coupled to the touch panel  11  are usually less than the sensing electrodes RX j  of the touch panel  11 . Thus, the scanning process divides the sensing electrodes RX j  into several groups G k  (k≧1 and k is the integer), such as the group G 1  and G 2  in  FIG. 2 . 
     In the step S 303 , scan each transmission electrode TX i  sequentially. In carefully, the baseline calibration unit  13  provides a plurality of the scanning signals SCAN a (TX 1 ) for scanning the transmission electrode TX 1  in the group G k  sequentially. After finish scanning the transmission electrode TX 1 , provide a plurality of the scanning signals SCAN a (TX 1 ) for scanning the transmission electrode TX 2  in the group G k  continuously, until complete all the transmission electrodes TX i  associated with first-axis. 
     In the step S 304 , calculate each average AVG a (TX i ) associated with each scanning signal SCAN a (TX i ) according to the scanning signals SCAN a (TX i ) when scan each transmission electrode TX i  in each group G k . For instance, the baseline calibration unit  13  calculates the averages AVG a  (TX i ) belonged to each scanning signal SCAN a (TX i ) for each scanning signal SCAN a (TX i ) of the scanning transmission electrodes TX i  in the group G 1 . When baseline calibration unit  13  receives the scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) which are scanned the transmission electrodes TX 1 , obtain the average AVG 1 (TX 1 ) of the scanning signal SCAN 1 (TX 1 ) by averaging the sensing values of each crossover points P 1,1 , P 1,2 , . . . , P 1,13  which are obtained when scanning signal SCAN 1 (TX 1 ) scans the transmission electrode TX 1  in the group G 1 . Following, sequentially calculate the scanning signals SCAN 2 (TX 1 )˜SCAN 4 (TX 1 ) and then obtain the average AVG 2 (TX 1 )˜AVG 4 (TX 1 ) for each scanning signals SCAN 2 (TX 1 )˜SCAN 4 (TX 1 ), the calculating is same as the scanning signal SCAN 1 (TX 1 ), it doesn&#39;t repeat here. 
     In the step S 305 , calculate each group differential value DIF k (TX i ) for transmission electrode TX i  by the averages AVG a (TX i ) obtained when the scanning signals SCAN a (TX i ) scan the transmission electrode TX i  through a search process. For example, when calculate each scanning signals SCAN 1 (TX 1 )˜SCAN 4 (TX 1 ) in the group G 1 , the baseline calibration unit  13  further bases on the predetermined reference value BKTH in the search process, calculate the first group differential value DIF 1 (TX 1 ) for the transmission electrode TX 1  in the group G 1 . It&#39;s worth noting, in the process of calculating the first differential value DIF(TX i ) of each transmission electrode TX 1 , store a set of least significant bits TX 1     —   LSB(RX 1 )˜TX 1     —   LSB(RX 10 ) corresponding to the value of the sensing electrode RX 1 ˜RX 10  calculating. In the embodiment of present disclosure, while achieving by the binary search algorithm, but the person skill in the art should understand that can be implemented replacing by the linear search algorithm or other algorithms. The present disclosure is not limited thereto. 
     In the step S 306 , detect whether the count of transmission electrodes TX i  less than the total number of the transmission electrodes TX i  in the group G k  arranged with first-axis. If not, return to the step S 303  for executing the calculation procedure in the group G k  associated with first-axis. If yes, enter the step S 307 . 
     After finish the group G k  on first-axis calculation procedure, in the step S 307 , further detect whether completing the group G k  in the first-axis calculation procedure, that is detecting whether the count of the group G k  less than the total number of the group G k . If not, repeat the step S 302 ˜S 307 , calculate the other group G k  in the first-axis calculation procedure again. If yes, it expresses finishing the first-axis calculation procedure for the touch panel  11 , and executing the second-axis calculation procedure. 
     Then, in the step S 308 , the baseline calibration unit  13  calculates each sensing value of each crossover point P i,j  for each sensing electrode RX j  arranged with second-axis to obtain each average AVG(TX j ) for each sensing electrode RX j . 
     In the step S 309 , calculate each average AVG(TX j ) and the temporary stored least significant bit TX i     —   LSB(RX j ) when calculate the group differential value DIF k (TX i ) to obtain each second differential value DIF i (RX j ). In the step S 310 , add each group differential value DIF k (TX i ) arranged with first-axis and each second differential value DIF i (RX j ) arranged with second-axis to calculate all baseline calibration values CRT(P i,j ). 
     Finally, calibrate all crossover points P i,j  by the baseline calibration values CRT(P i,j ) calculated by each transmission electrode TX j  and each sensing electrode RX j . 
     It&#39;s worth noting, the embodiment of the present disclosure further may use the first group differential value DIF 1 (TX 1 ) of the transmission electrode TX i  being as other first group differential values for the sensing values of the crossover points P i,j  in other groups G k . In other words, by first time scanning group G 1 , the least significant bit TX 1     —   LSB(RX i ) stored in the process of the first group differential value DIF 1 (TX i ) for the transmission electrodes TX i  in the group G 1  decides the whole first differential value DIF(TX i ) and after the least significant bit needed by calculating each sensing electrodes RX j  on second-axis. For instance, in the transmission electrode TX 1 , the least significant bit TX 1     —   LSB(RX 1 ) stored in the process of the first group differential value DIF 1 (TX 1 ) for the transmission electrodes TX 1  in the group G 1  is used as the least significant bit TX 1     —   LSB(RX 11 ) stored originally in the process of the second group differential value DIF 2 (TX 1 ) for the transmission electrodes TX 11 . The reason is that the divergence between each of the groups G k  isn&#39;t obvious for the average by calculating from the crossover points P i,j , thence the average calculated by the differential value with the predetermined reference value BKTH also doesn&#39;t differ too much similarly. Thus, the embodiment of the present disclosure further reduces the calculation procedure of other groups (such as the step S 302  and S 307 ) to upgrade the speed of the calculating by only calculating the group G 1 . 
     In summary, the manufacturing company of the touch panel can improve the judgment accuracy decreased when users employ the touch panel. The improvement is exploiting the baseline calibration unit to resolve the mismatch between each sensing channel or the manufacturing for touch panel originally, and the mismatch may further affect the judgment accuracy. Firstly the baseline calibration unit calibrates the crossover points arranged with first-axis, secondly the baseline calibration unit bases on the result of calibrating the crossover points arranged with first-axis to calibrate the crossover points arranged with second-axis again, so as to cancel the part of the un-flatness for each axis. Therefore, the baseline calibration unit achieves the gradient approximating agreed for whole touch panel, so as to increase the judgment accuracy. It&#39;s worth noting, wherein using the method arranged with first-axis and second-axis to calibrate the crossover points may reduce the circuit cost for N 2 −2N. 
     The descriptions illustrated supra set forth simply the preferred embodiments of the present disclosure; however, the characteristics of the present disclosure are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present disclosure delineated by the following claims.