TWI463358B - Ghost cancellation method for multi-touch sensitive device - Google Patents

Description

Ghost point removal method for multi-touch sensing device

The present invention relates to multi-touch technology, and more particularly to ghost point removal methods for multi-touch sensing devices.

In a multi-touch sensing device, such as a touch panel, there are generally two types of sensing methods for sensing one or more touches. One method is called a projection sensing method, and the other is a matrix sensing method. In the projected sensing method, the device senses an entire line of the sensing array each time.

In a matrix sensing method, the device senses one node of the touch sensing array each time (ie, the intersection of one row and one column). As can be seen, the implementation of the matrix sensing method takes significantly more time than the projection sensing method. In the case of a 20×30 sensing array (that is, a sensing array with 20 columns and 30 rows), there are 20+30=50 lines in total, so when using the projection sensing method, only 50 detections are required. . In contrast, there are 20 × 30 = 600 nodes, so when using the matrix sensing method, 600 tests are required.

Today's speed and cost considerations, projection sensing methods are widely used in a variety of touch devices. However, the disadvantage of the projection sensing method is the so-called "ghost point problem", which will be described below.

Fig. 1 schematically shows a general multi-touch sensing device 1. The multi-touch sensing device 1 has a sensing array 10. The sensing array 10 includes a plurality of longitudinal transmissive rails (i.e., lines a to f) and a plurality of lateral transmissive rails (i.e., lines 1 through 7) arranged in rows and columns of X-Y coordinate systems. Alternatively, the transfer guides may be arranged in a polar coordinate system. Sensing elements (not shown) are provided at respective intersections of the transfer guides. For example, the sensing element is typically implemented as a resistor or capacitor. The touch sensor circuits 22, 24 apply drive signals to the tracks to sense if there is a touch. Each of the touch sensor circuits 22, 24 includes a plurality of touch sensors (not shown). Each touch sensor is responsible for driving and sensing one or more tracks. Touch sensor circuits 22 and 24 are controlled by controller 30.

In this example, assume that two touches occur simultaneously at points B and C, with coordinates (e, 2), (c, 6), respectively. Use a projected sensing method. In the X-axis direction, it is found that there are two peaks at the line c and the line e. In the Y-axis direction, it is found that there are two peaks at line 2 and line 6. According to the principle of permutation and combination, the four peaks can form four sets of coordinates: (c, 2), (c, 6), (e, 2), and (e, 6). In other words, in addition to the actual touch points B and C, the device 1 misjudges that a touch occurs also at point A (c, 2) and point D (e, 6). Points A and D that have not been touched but are misjudged and touched are called "ghost points".

If the matrix sensing method is used to detect each node of the sensing array 10, the actual touch points B and C can be determined, and the ghost point problem can be eliminated. However, as described above, it takes so much time.

It is an object of the present invention to provide a ghost point removal method for a multi-touch sensing device that can effectively and efficiently eliminate ghost points when multiple touches occur in the device.

According to the present invention, the multi-touch sensing device includes a sensing array, the sensing array having a plurality of lines of the first axis and a plurality of lines of the second axis intersecting each other, and the ghost point removing method includes applying the first driving signal to Each line of the first axis; detecting each line driven by the first axis to determine whether the line is touched; applying a second driving signal to each line of the second axis; detecting each of the second axis being driven a line to determine whether the line is touched; determining a candidate touch point according to a line touched by the first axis and a line touched by the second axis; applying a third driving signal to the first of each candidate touch point a line of the axis; and a line detecting the second axis of each candidate touch point to determine whether the candidate touch point is touched.

As described, for the multi-touch device 1, the projection sensing method can quickly complete the detection to determine the touch point. However, the touch points determined may include ghost points. It takes too much time to detect all nodes using the matrix sensing method to find the actual touch point. The present invention provides a ghost point removal method that can solve the above problems.

In the ghost point removing method of the present invention, candidate touch points are first determined by using a projection sensing method, and then the candidate touch points are tested by using a matrix sensing method to verify the actual touch points and exclude ghost points.

FIG. 2 is a diagram schematically showing an example of a touch sensing method performed by the touch sensor 220. As shown, touch sensor circuits 22 and 24 each include a plurality of touch sensors to drive and sense the lines of sense array 10 of FIG. The touch sensor 220 has a waveform generator 221 that generates a square wave (or sine wave) having a frequency f1. The square wave system is applied to a voltage driver 223 to drive an alternating current (AC) voltage source 224. The AC voltage source 224 generates a drive signal Vd based on the square wave. The drive signal Vd has an amplitude V1. The voltage source 224 is coupled to a line 13 (e.g., one track of the sensing array 10 of FIG. 1) via a resistor divider Rz. One end of the resistor divider Rz is connected to the voltage source 224, and the other end is connected to the line 13 and one end (ie, the input end) of a buffer 226. The sense signal Vs is detected at the other end (ie, the output) of the buffer 226. The sensing signal Vs is transmitted to a sensing circuit (not shown) of the touch sensor 220. The buffer 226 is used to isolate the impedance at both ends so that the sensing circuit is not affected by external impedance. The buffer 226 has a characteristic that the input impedance is high and the output impedance is low, so that the sensing circuit (not shown) of the touch sensor 220 passes the buffer 226 to measure the voltage dividing value of the line 13, because The input impedance of the buffer 226 is high enough not to affect the voltage division of the sensing lines of the previous stage, and because the output impedance is low enough to act as a voltage source to drive the sensing of the touch sensor 220. Circuit. The buffer 226 can be implemented using an operational amplifier (Operational Amplifier).

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When the line 13 is not touched, the line 13 is floating, so ideally the sense signal Vs should be substantially the same as the voltage value V1 of the drive signal Vd. When the line 13 is touched by a human finger, the line 13 is grounded via the human body, causing a voltage drop such that the sensing signal Vs is equal to the divided voltage Vp, and the divided voltage Vp can be calculated by the following formula:

Where Cf is the coupling capacitance between the human finger and the line 13, Cb represents the equivalent capacitance of the human body, Rb represents the equivalent resistance of the human body, and ω = 2πf1. When the line 13 is touched, the amplitude of the sensing signal Vs drops due to the voltage drop. That is, the amplitude of the sensing signal Vs is smaller than the amplitude (Vp < V1) when it is touched when it is touched. Therefore, it is possible to determine whether or not the line 13 is touched by checking the amplitude of the sensing signal Vs. All rows and columns of the sensing array 10 (Fig. 1) are detected in this manner, so that which rows and which columns are touched are known. It should be noted that more than one line can be driven simultaneously by utilizing different drive signals, such as drive signals having different frequencies. In addition, more than one line can be detected simultaneously. The candidate touch points can be determined by the touched rows and columns. It should be noted that these candidate touch points include the actual touch points and ghost points as described above. For a two-dimensional sensing array, the number of rows touched should be the same as the number of columns touched. The candidate touch point is the intersection of the touched line and the touched column. The number of candidate touch points is the product of the number of touched lines and the number of columns touched. For example, if there are two columns and two rows being touched, there are four candidate touch points.

FIG. 3 is a schematic diagram showing another form of touch sensor 240 that implements a projection sensing method. The touch sensor 240 has a waveform generator 241 that generates a square wave (or sine wave) having a frequency f1. The square wave system is applied to a current driver 243 to drive an alternating current (AC) current source 244. The AC current source 244 generates a drive signal Id according to the square wave. The drive signal Id is used to drive a line 12. In the figure, capacitor Cs represents the capacitance observed from line 12. When line 12 is touched, the capacitance of Cs changes. Therefore, it can be determined whether the line 12 is touched by observing the capacitance of Cs. It should be noted that other suitable types of touch sensors can also be used to detect all lines of the sensing array (ie, all rows and columns) to determine candidate touch points, and the buffer 246 is used to isolate the impedance at both ends. The sensing circuit (not shown) of touch sensor 240 is not affected by external impedance. The purpose of the buffer 246 is the same as that of the buffer 226 described above, and details are not described herein again. .

If two fingers touch the multi-touch sensing device 1 at the same time, there will be at most four candidate touch points. In the method of the present invention, the candidate touch points are examined using a matrix sensing method. It will be detailed below.

Figure 4 is a schematic diagram showing the testing of one of the touch sensing array nodes using a matrix sensing method in accordance with the present invention. As shown, in the present embodiment, each line of the sensing array is connected to the touch sensor 220 of FIG. 2 (or the touch sensor 240 of FIG. 3). A number of lines can also share one touch sensor in a multiplex manner. For simplicity and clarity, only two columns (line 1 and line 2) and two rows (line a and line b) are shown in this figure. In the example shown in Fig. 4, it is assumed that both the E point and the F point are known as candidate touch points (in this example, point E is the actual touch point and point F represents a ghost point). Point E is the intersection of line a and line 2, so its coordinates are (a, 2). Point F is the intersection of line b and line 2, so its coordinate is (b, 2). To test a node (the intersection of a particular column and a particular row), a drive signal (eg, Vd) is applied to the line of the first axis (eg, the X axis), ie, the column associated with the node, and the second axis ( A line such as the Y-axis is detected, that is, a line associated with the node is detected to obtain a sensing signal (e.g., Vs). Alternatively, the drive signal is transmitted to the row associated with the node and the column associated with the node is detected.

To check if the E point is touched, the drive signal Vd is applied to the line 2, and the line a is detected. Since the point E is actually touched by the finger, a conductive loop is formed between the line 2 and the line a via the human body, so that the sensing signal Vs can be measured from the line a. Ideally, the sense signal Vs is substantially the same as the drive signal Vd.

To check if the F point is touched, the drive signal Vd is applied to the line 2, and the line b is detected. Since point F is not touched, no conductive loop is formed between line 2 and line b. Therefore, when the line b is detected, the sensing signal is not measured. According to this, it can be determined that point F is a ghost point.

Figures 5A through 5D illustrate testing candidate touch points by a method in accordance with an embodiment of the present invention. The multi-touch sensing device shown in the drawing is the same as that in FIG. 1, and the same component symbols denote the same components, and the related description is omitted here to avoid redundancy. As shown, each of the touch sensor circuits 22 and 24 includes a plurality of touch sensors (for example, the touch sensor 220 shown in FIG. 2 or the touch sensor 240 shown in FIG. 3; ).

All rows and columns of sense array 10, i.e., lines 1-7 and lines a-f, are scanned using projection sensing methods to determine which one is touched. By doing so, several candidate touch points can be determined. As described above, when point B and point C are touched at the same time, in addition to point B and point C, by using the projection sensing method, the device 1 may mistakenly point that point A and point D are touch points. In other words, there are four candidate touch points A, B, C, D. In this embodiment, the candidate touch points are checked one by one.

As shown in Figure 5A, check point A. The drive signal is applied to line 2 and line c is detected. Since point A is not touched, the sensing signal is not detected from line c. As shown in Fig. 5B, check point B. The drive signal is applied to line 2 and line e is detected. Since the point B is touched, the sensing signal is detected from the line e. As shown in Figure C, check point C. The drive signal is applied to line 6 and line c is detected. Since the point C is touched, the sensing signal is detected from the line c. As shown in Fig. 5D, the point D is checked. The drive signal is applied to line 6 and line e is detected. Since point D is not touched, the sensing signal is not detected from line e.

FIGS. 6A and 6B illustrate testing candidate touch points by a method in accordance with another embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the candidate touch points of the same column are simultaneously checked. As shown in Fig. 6A, the candidate touch points A and B are simultaneously checked. The drive signal is applied to line 2 and simultaneously detects line c and line e. Since point A is not touched and point B is touched, the sensing signal is not detected from line c, but a sensing signal is detected from line e.

Similarly, as shown in FIG. 6B, the candidate touch points C and D are simultaneously checked. The drive signal is applied to line 6 and simultaneously detects line c and line e. Since the point C is touched and the point D is not touched, the sensing signal is detected from the line c, but the sensing signal is not detected from the line e.

The ghost point removing method for the multi-touch sensing device of the present invention can be summarized into the flowchart shown in FIG. The multi-touch sensing device 1 has a sensing array 10. The sensing array 10 has a plurality of lines of a first axis (such as an X axis) and a plurality of lines of a second axis (such as a Y axis). The line of the first axis intersects the line of the second axis to form, for example, an orthogonal coordinate system or a polar coordinate system. The program begins in step S710. At step S720, the first drive signal is applied to each of the first axes (e.g., the X-axis), and the same line is detected. As described above, if a particular line is not touched, the sensed signal detected from this line is substantially the same as the drive signal. If a particular line is touched, the amplitude of the sensed signal detected from this line decreases. In this step, the line touched by the first axis is found. In step S730, a second driving signal is applied to each of the second axes (such as the Y-axis), and the same line is detected. In this step, the line where the second axis is touched is found. At step S740, the touch point is determined by analyzing the sensing signal. In other words, the touch point is initially determined based on the line touched by the first axis and the line touched by the second axis. At step S750, it is judged whether or not the determined touch point is ambiguous. Various rules can be utilized in this step. The judgment technique is not the subject of the present invention. If the initially determined touch point is not ambiguous, the process returns to step S710 to perform the next round of sensing touch. If the initially determined touch point is not clear, meaning that the determined touch points include ghost points, the program proceeds to S760 to exclude ghost points.

Now, unclear touch points are candidate touch points. At step S760, the candidate touch points are checked. A third drive signal is applied to a line of a first axis of a candidate touch point and a line of the second axis of the candidate touch point is detected. In this step, it is determined that the candidate touch point to be inspected is an actual touch point or a ghost point, and the third driving signal and the first driving signal and the second driving signal are both generated by the touch sensor 220. The difference is that the purpose of the third driving signal is to detect ghost points. At step S770, ghost points are removed according to the result of step S760. At step S780, it is decided whether or not the test for the next candidate touch point is to be performed. If so, the program returns to step S760.

It is feasible to simultaneously drive a plurality of lines of the first plurality of axes of the plurality of candidate touch points by using different driving signals, that is, applying third driving signals of different frequencies to the two or more first axes, so that each of the first axes Corresponding to the third drive signal of different frequencies. In addition, as described in the figures of FIGS. 6A and 6B, for example, two or more second axes corresponding to the candidate touch points can be simultaneously detected by different touch sensors, so that they are on the same first axis. Multiple candidate touch points can be tested simultaneously.

While the preferred embodiment of the invention has been shown and described in detail Therefore, the description of the embodiments of the invention is merely illustrative and not limiting. The invention is not limited to the specific forms of the invention, and all modifications and substitutions of the spirit and scope of the invention are defined in the scope of the appended claims.

1. . . Multi-touch sensing device

10. . . Sensing array

12‧‧‧ line

13‧‧‧ line

22‧‧‧Touch sensor circuit

24‧‧‧Touch sensor circuit

220‧‧‧ touch sensor

221‧‧‧ Waveform Generator

223‧‧‧Voltage Driver

224‧‧‧AC voltage source

226‧‧‧buffer

240‧‧‧Touch sensor

241‧‧‧ Waveform Generator

243‧‧‧current drive

244‧‧‧AC current source

Figure 1 is a schematic view showing a general multi-touch sensing device;

FIG. 2 is a schematic diagram showing a touch sensor performing a projection sensing method;

Figure 3 is a schematic diagram showing another touch sensor performing a projection sensing method;

4 is a schematic diagram showing testing a node of a touch sensing array using a matrix sensing method according to the present invention;

5A-5D illustrate the testing of candidate touch points by a method in accordance with an embodiment of the present invention;

6A and 6B illustrate the testing of candidate touch points by a method in accordance with another embodiment of the present invention;

Fig. 7 is a flow chart showing the method of removing ghost points of the present invention.

220. . . Touch sensor

Claims (9)

A ghost point removing method for a multi-touch sensing device, the multi-touch sensing device comprising a sensing array having a plurality of lines of a first axis and a plurality of lines of a second axis Crossing each other, the method comprising: applying a first driving signal to each of the first axes; detecting a driven line of the first axis to determine whether the line is touched; applying a second driving signal to the second axis Each line; detecting a driven line of the second axis to determine whether the line is touched; determining a candidate touch point according to the touched line of the first axis and the touched line of the second axis; a line of the third driving signal to the first axis of each candidate touch point; and detecting a line of the second axis of the candidate touch point to determine whether the candidate touch point is touched. The method of claim 1, wherein the candidate touch points are the intersection of the touched line of the first axis and the touched line of the second axis. The method of claim 1, wherein the first axis and the second axis are arranged in an orthogonal coordinate system. The method of claim 1, wherein the first axis and the second axis are configured as a polar coordinate system. The method of claim 1, wherein the third driving signal of different frequencies is simultaneously applied to the lines of the two or more first axes, so that the line of each of the first axes corresponds to the third driving of different frequencies. signal. The method of claim 1, wherein the lines of the two or more second axes corresponding to the candidate touch points are simultaneously detected. The method of claim 1, wherein after the first driving signal is applied to the line of the first axis, if the line is touched, The sensed signal detected by the line has a smaller amplitude than the first drive signal. The method of claim 1, wherein after the second driving signal is applied to the line of the second axis, if the line is touched, the sensing signal detected from the line has a ratio The second drive signal has a small amplitude. The method of claim 1, wherein after the third driving signal is applied to the line of the first axis of the candidate touch point, if the candidate touch point is actually touched, the candidate is available The line of the second axis of the touch point detects the sensing signal, however, after applying the third driving signal to the line of the first axis of the candidate touch point, if the candidate touch point is not touched, then no A sense signal is detected from a line of the second axis of the candidate touch point.