最近有許多種類的平板電腦陸續上市。
平板電腦的主要使用者介面為電容式觸控螢幕。無可置疑地，電容式觸控螢幕提供了流暢且直覺式的手勢多點觸控功能。 
也因如此，電容式觸控介面藉由導電性物體的接觸，可以感測到非常微小電荷的變化。
但另一方面，良好的靈敏度卻可能造成其他不便。當使用者用手指或其他導電物體在觸控螢幕上寫字或繪圖時，很可能因為拿平板電腦的單手或雙手，發生了錯誤的不良接觸。
本次研究的重點，就是從如何抑制意外觸控的影像處理角度來切入探討。

Many kinds of tablet computers (tablets for short) have been recently released onto the market. There is no doubt that the primary interface of the tablet is a capacitive touchscreen that can provide users with a fluid and intuitive multi touch function. It is attributable to the fact that the capacitive touchscreen can measure a minute change of a capacitance.
On the other hand, the high sensitivity of the touchscreen can cause an undesirable effect when users write or draw. Base on user feedbacks, this has been causing some inconvenience.
This study is focusing on how to discriminate non-fingertip contact such as a grip, palm and fist, and to suppress them from image processing point of view.

CONTENTS
Chapter 1. Introduction	1
Chapter 2. Principle of Capacitive Touch	3
             2.1 Capacitive Touchscreens	3
             2.2 Projected capacitive touchscreens	3
             2.3 Touch algorithms	8
             2.4 Undesirable touch	9
Chapter 3. Related Works	11
             3.1 Special Gloves	11
             3.2 The application Programs built in a palm rejection function	11
             3.3 Palm and grip suppression using image processing	13
             3.4 The proposed method in this research	14
Chapter 4. Implementation and Algorithms	15
             4.1 Hardware specifications	15
             4.2 Measuring capacitance and display with the touchscreen	16
             4.3 The Algorithm to discriminate palm and grip contacts	19
             4.3.1 TAS (Temporal Analysis of frame Sequence)	19
             4.3.2 SAA ( Spatial Analyis of a contacted Area)	22
Chapter 5. Experimental results	31
             5.1 Experiment process	31
             5.2 Analyze the results	34
Chapter 6. Conclusions	40
Reference	43
Appendix	45

LIST OF FIGURES
Figure 2.1 Self-capacitance and Mutual-capacitance	 6
Figure 2.2 Touch controller: a) + b) + c) + d)	7
Figure 2.3 A conventional procedure of touch algorithms	9
Figure 3.1 Special gloves for palm rejection	11
Figure 3.2 An application program with protection window	12
Figure 4.1 The touchscreen and control board used in this research	15
Figure 4.2 Matlab source code for image acquisition and display	17
Figure 4.3 2D and 3D view of captured capacitance	18
Figure 4.4 TAS Algorithm to suppress the palm contact	20
Figure 4.5 TAS Algorithm to suppress the grip contact	21
Figure 4.6 The extrema of two different regions	24
Figure 4.7 The Adjacent IDs and Extrema with Euclidian distance	24
Figure 4.8 The sparse matrix of figure 4.7	25
Figure 4.9 The procedure of finding SCC	26
Figure 4.10 The biograph from Matlab function ‘graphconncomp’	27
Figure 4.11 SAA Algorithm to suppress the palm contact	28
Figure 4.12 SAA Algorithm to suppress the grip contact	29
Figure 4.13 More complicated scenario: both palms contact	30
Figure 5.1 User scenarios that can cause an undesirable touch	 33
Figure 5.2 Experiment process	34
Figure 5.3 The result of scenario 1	35
Figure 5.4 The result of scenario 2	35
Figure 5.5 The result of scenario 3	36
Figure 5.6 The result of scenario 4	37
Figure 5.7 The result of scenario 5	37
Figure 5.8 The result of scenario 6	38
Figure 5.9 The result of scenario 7	38
Figure 5.10 The result of scenario 8	39

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