JP2015118656A - Touch detection unit, and touch detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable accurate detection of changes in data associated with touch by appropriately reducing superimposed noise and removing an offset from input raw data.SOLUTION: A touch detection unit includes; a first variable recursive filter (10) for generating noise-reduced raw data from input raw data with residual fixed pattern noise; a second variable recursive filter for generating baseline data from the noise-reduced raw data with residual fixed pattern noise; a subtractor (30) for computing difference data from output of these filters; a touch determination section (50) for generating touch determination data based on condition of change in the input raw data relative to the baseline data; and a filter control section (40) for controlling weighted average processing performed by the first recursive filter and second recursive filter in accordance with the touch determination data.

Description

  The present invention relates to a touch detection device and a touch detection method that can detect a change in data associated with a touch more accurately and improve the accuracy of touch coordinates based on low data input from the touch panel side.

  In recent years, a projection capacitive method has been widely used for touch panels in information terminals from the viewpoint of excellent transmissivity and durability in correspondence with multi-touch (for example, see Non-Patent Document 1). ). FIG. 2 is an explanatory diagram of a projection-type capacitance method that is a conventional technique. In this projection type capacitive system, a drive electrode (Tx) and a reception electrode (Rx), which are sensor electrodes, are arranged orthogonally on the upper surface of the display, and a sensor is formed at each intersection (see FIG. 2A). Then, a change in electrostatic capacitance between both electrodes that occurs when the panel surface is touched with a finger or the like is detected from a difference in sensor output signals with and without touch (see FIGS. 2B and 2C).

  FIG. 3 is an overall configuration diagram including a conventional touch detection device, and includes a touch panel 110, a preprocessing unit 120, and a touch detection device 130. An analog signal that is a sensor output signal from the touch panel 110 is taken into the preprocessing unit 120. Then, the preprocessing unit 120 performs necessary analog signal processing and AD conversion to generate raw data (raw data) that is two-dimensional digital data for each scan period.

  Then, the subsequent touch detection device 130 generates difference data in which noise and offset are reduced and removed from the raw data. Then, using the difference data generated in this way, the presence / absence of touch is detected, the coordinates of the touch position are calculated, and the like.

  As the noise filter, there are a recursive filter corresponding to random noise for each two-dimensional element, and an offset removing filter corresponding to random noise for each row (Tx) when a higher effect is expected. Used.

  Here, the difference data is obtained by subtracting baseline data from the low data. In the conventional touch detection device, this baseline data is a signal after noise reduction. Then, the conventional touch detection device sets the initial row data as the initial state and increases or decreases the value of each element of the data for each frame so that the baseline data asymptotically approaches the row data in the state where the value does not change due to the touch. Processing such as updating was performed.

Overview of flat panel display (6) Parts and material technology supporting FPD (1) Touch panel, THE CHEMICAL TIMES 2011, No. 4

However, the prior art has the following problems.
Recently, there has been a strong demand for touch input with a pen as well as a finger. However, in the projection-type capacitance method, when a thin conductive touch instrument such as a pen is used, the change in capacitance in the sensor, that is, the change in sensor output is the case of a finger. For example, it is very weak with about 1/10.

  Therefore, with the noise reduction measures in the conventional touch detection device corresponding to the touch with the finger, in the case of the touch with the pen, the noise becomes relatively large, and the erroneous detection or the deviation of the calculated coordinate is very It becomes easy to happen.

  Further, as an essential problem, there is a kind of noise that is not taken into consideration in the noise reduction measures of the conventional touch detection device. That is, fixed pattern noise (FPN: Fixed-Pattern Noise) superimposed on data in a fixed and steady manner with variations in characteristics for each sensor position and for each Tx circuit or Rx circuit has not been considered. Therefore, the noise component due to the fixed pattern noise remains in the difference data for coordinate calculation and touch determination.

  Further, when it is determined that there is a touch, conventionally, updating of the value of the element in the baseline data is paused during that period. However, in an element that is adjacent to an element that has been determined to be touched and that has a small change in value and that has not been determined to be touched, the value of the baseline data is erroneously updated, and this also causes noise in the difference data. It was left.

  The present invention has been made in order to solve the above-described problems, and it is possible to appropriately reduce and remove superposition noise and offset with respect to the low data input from the touch panel side, thereby changing data accompanying touch. It is an object of the present invention to obtain a touch detection device and a touch detection method that can detect more accurately and improve the calculation accuracy of touch coordinates.

  A touch detection device according to the present invention is a touch detection device that outputs a touched position coordinate on a panel based on input row data that is sensor output data after AD conversion from a touch panel, and each sensor position and sensor In the state where fixed pattern noise that is fixedly and steadily superimposed on sensor output data remains due to variations in the characteristics of each output data generation circuit, random noise is reduced from input raw data to generate noise-reduced low data. The first variable recursive filter and the second variable recursive type that generates baseline data with reduced random noise from the noise reduced raw data generated by the first variable recursive filter in a state where the fixed pattern noise remains. The baseline data generated by the filter and the second variable recursive filter is converted into the first variable recursion. By subtracting from the noise reduction raw data generated by the filter, the subtractor that outputs the difference data, and the touch determination data based on the change state of the input raw data with respect to the baseline data generated by the second variable recursive filter Based on the touch determination unit that outputs, the difference data output from the subtractor, and the touch determination data output from the touch determination unit, the coordinate calculation unit that outputs the touched position coordinates, the difference data includes random noise and A first weighted averaging process for generating noise-reduced low data with a first variable recursive filter based on the touch determination data output from the touch determination unit so that the fixed pattern noise is reduced; And a second weighted averaging process for generating baseline data with a second variable recursive filter In which and a filter control section that controls.

  The touch detection method according to the present invention is applied to a touch detection device that outputs a touched position coordinate on a panel based on input row data that is sensor output data after AD conversion from a touch panel. However, random noise is reduced from input low data with fixed pattern noise remaining superimposed on sensor output data in a fixed and steady state due to variations in the characteristics of each sensor position and sensor output data generation circuit. A first variable recursive filter processing step for generating noise-reduced low data, and a base in which random noise is reduced from the noise-reduced low data generated by the first variable recursive filter with fixed pattern noise remaining A second variable recursive filter processing step for generating line data; and a second variable recursive type A subtraction processing step for outputting difference data by subtracting the baseline data generated in the filter processing step from the noise reduction low data generated in the first variable recursive filter processing step; and a second variable recursive type Touch determination processing step for outputting touch determination data based on the change state of the input raw data with respect to the baseline data generated in the filter processing step, difference data output by the subtraction processing step, and output by the touch determination processing step Based on the touch determination data, the coordinate calculation processing step for outputting the touched position coordinates, and the touch determination data output by the touch determination processing step so that the difference data becomes data with reduced random noise and fixed pattern noise. Based on the first variable Controls a first weighted averaging process for generating noise-reduced low data in a recursive filtering step and a second weighted averaging process for generating baseline data in a second variable recursive filtering step And a filter control step.

  According to the present invention, in the generation of difference data used when performing touch detection, the fixed pattern noise is effectively reduced, and the update accuracy of the baseline data is improved, so that the low data input from the touch panel side. As a result, by appropriately reducing and removing superposition noise and offset, it is possible to obtain a touch detection device and a touch detection method that can detect changes in data associated with touch more accurately and improve touch coordinate calculation accuracy. Can do.

It is a block diagram of the touch detection apparatus in Embodiment 1 of this invention. It is explanatory drawing of the projection-type electrostatic capacitance system which is a prior art. It is a whole block diagram containing the conventional touch detection apparatus.

  Hereinafter, preferred embodiments of a touch detection device and a touch detection method of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a touch detection device according to Embodiment 1 of the present invention. 1 includes a first variable recursive filter 10, a second variable recursive filter 20, a subtractor 30, a variable recursive filter control unit 40, a frame memory 41, The touch determination unit 50 and the coordinate calculation unit 60 are provided.

  The touch detection apparatus according to the first embodiment has such a configuration, and receives the raw data from a preprocessing unit (not shown) as input (hereinafter referred to as input raw data), and the coordinates of the touched position. Data can be calculated with high accuracy. Therefore, each component will be described in detail below.

  The first variable recursive filter 10 is configured to include a frame memory 11 and a variable weighted averaging unit 12, and receives noise-reduced low data with noise reduced as input.

  Specifically, the first variable recursive filter 10 operates as follows. The frame memory 11 sequentially stores noise reduction low data output from the variable weighted averaging unit 12 in the previous frame in accordance with a control signal from the variable recursive filter control unit 40.

  Then, the variable weighted averaging unit 12 controls the variable recursive filter control unit 40 for the elements determined to be non-touched by the continuous frames by the touch determination unit 50 and the elements determined to be touched by the continuous frames. According to the signal, the weighted averaging process is performed with the weight of the average value calculation of the input low data and the noise reduction low data of the previous frame which is the output of the frame memory 11 being set to, for example, 1: 3.

  In addition, the variable weighted averaging unit 12 determines that there is no touch in the previous frame and is determined to be touched in the current frame, or vice versa. In the element which becomes, the weighted averaging process is performed with the weight of the average value calculation described above being set to 1: 1, for example.

  Accordingly, when the no-touch state continues or when the touch-present state continues, the noise can be strongly reduced by increasing the weight on the noise reduction low data side. On the other hand, in the case of transition between with and without touch, the noise reduction effect can be weakened so that the change in value is not hindered. At the time of initialization, the weight of the above average value calculation is set to 1: 0, and the noise reduction low data is the same as the input low data.

  Next, the second variable recursive filter 20 will be described. The second variable recursive filter 20 includes a frame memory 21 and a variable weighted averaging unit 22, and has the same configuration as the first variable recursive filter 10. The second variable recursive filter 20 receives the noise reduction low data corresponding to the output of the first variable recursive filter 10 and outputs baseline data.

  Specifically, the second variable recursive filter 20 operates as follows. The frame memory 21 sequentially stores the baseline data output from the variable weighted averaging unit 22 in the previous frame in accordance with the control signal from the variable recursive filter control unit 40.

  Then, the variable weighted averaging unit 22 outputs noise reduction low data and the output of the frame memory 21 in accordance with the control signal from the variable recursive filter control unit 40 in elements other than the element determined to be touched and the elements adjacent to it. The weighted average processing is performed with the weight of the average value calculation with the baseline data of the previous frame being, for example, 1: 7.

  In addition, the variable weighted averaging unit 22 performs weighted averaging processing with the above-described average value calculation weight set to, for example, 0: 1 for an element determined to be touched and an element adjacent thereto. At this time, the frame memory 21 stops the writing of the baseline data in accordance with the control signal from the variable recursive filter control unit 40, and as a result, the update of the value in the element of the baseline data is stopped. At the time of initialization, the weight of the above average value calculation is set to 1: 0, and the baseline data is the same as the initial noise reduction raw data, that is, the input raw data.

  Here, the variable recursive filter control unit 40 that can read the touch determination result by the touch determination unit 50 for the element adjacent to the element determined to be touched in the frame memory 41 connected to itself, For example, it can be managed as flag data of each element.

  In the noise reduction low data output from the first variable recursive filter 10, the random noise in the input low data is reduced, but the fixed pattern noise remains as it is. On the other hand, the fixed pattern noise remains in the baseline data output from the second variable recursive filter 20 with the noise reduction low data as an input. Therefore, the fixed pattern noise is effectively reduced in the difference data obtained by subtracting the baseline data from the noise reduction low data in the subtractor 30.

  The touch determination unit 50 determines for each element whether or not there is a touch from the difference between the values of each element in the input row data and the baseline data. Since random noise is superimposed on the input raw data, it is possible to prevent the determination from becoming unstable by performing determination with hysteresis using two threshold values.

  As described above, according to the first embodiment, the fixed pattern noise can be effectively reduced in the generation of difference data used when performing touch detection. In addition, it has a configuration that improves the update accuracy of the baseline data in an element close to and adjacent to the touched element. As a result, with respect to the raw data input from the touch panel side, it is possible to more accurately detect changes in the data associated with the touch and improve the calculation accuracy of the touch coordinates by appropriately reducing and removing superposition noise and offset. A touch detection device and a touch detection method can be obtained.

More specifically, the touch detection device according to the first embodiment is technically characterized by having the following configuration.
A variable recursive filter having a variable weighted averaging unit and a frame memory is individually provided for low data and baseline data.
-It has a filter control part for controlling these two variable recursive filters based on the continuous touch determination result.
-It has a touch determination unit with hysteresis characteristics with two thresholds.
A subtractor that generates difference data by subtracting the baseline data from the noise reduction low data using the output of each variable recursive filter is provided.

And by having these structures, the following outstanding effects can be acquired.
・ Random noise can be appropriately reduced in both low data and baseline data.
・ At the time of state transition between touch and non-touch, each level of low data and baseline data can be changed appropriately at high speed to suppress the delay of time change in differential data obtained by subtracting baseline data from low data. Can be reduced and the time waveform can be shaped.
-In the range adjacent to the element determined to be touched, the update of the baseline data is paused, so that the calculation accuracy of touch coordinates performed based on the difference data can be improved.
As a result, the coordinate calculation of the touch position using the difference data can be made more accurate, and in particular, it is effective for improving the position detection accuracy of the pen touch in the projection type capacitive touch panel.

  In addition, the specific example of the weight in Embodiment 1 mentioned above is only an example, and it is possible to apply a suitable ratio suitably. For example, the ratio exemplified as 1: 3 or 1: 7 is exemplified as 1: 1 for the variable weighted averaging unit 12 if the ratio of the former and the latter is 1: n (where 1 <n is a real number). The same effect can be expected if the ratio of the former and the latter is 1: m (where m <n is a real number).

  10 First variable recursive filter, 11 frame memory, 12 variable weighted averaging unit, 20 second variable recursive filter, 21 frame memory, 22 variable weighted averaging unit, 30 subtractor, 40 variable recursive filter control Unit, 41 frame memory, 50 touch determination unit, 60 coordinate calculation unit.

Claims (6)

A touch detection device that outputs a touched position coordinate on a panel based on input low data that is sensor output data after AD conversion from a touch panel,
Random noise is reduced from the input low data in a state where fixed pattern noise that is superimposed on the sensor output data in a fixed and steady manner remains due to variations in characteristics of each sensor position and sensor output data generation circuit. A first variable recursive filter that generates noise reduced low data;
A second variable recursive filter that generates baseline data with reduced random noise from the noise-reduced low data generated by the first variable recursive filter with the fixed pattern noise remaining;
A subtractor that outputs difference data by subtracting the baseline data generated by the second variable recursive filter from the noise reduction low data generated by the first variable recursive filter;
A touch determination unit that outputs touch determination data based on a change state of the input raw data with respect to the baseline data generated by the second variable recursive filter;
A coordinate calculation unit that outputs the touched position coordinates based on the difference data output from the subtracter and the touch determination data output from the touch determination unit;
Based on the touch determination data output from the touch determination unit, the first variable recursive filter performs the noise reduction low data based on the touch determination data so that the difference data becomes data obtained by reducing the random noise and the fixed pattern noise. And a filter control unit for controlling a second weighted averaging process for generating the baseline data by the second variable recursive filter. apparatus. The touch detection device according to claim 1,
The first variable recursive filter has a first frame memory and a first variable weighted averaging unit,
The first frame memory stores the noise reduction low data output from the first variable weighted averaging unit in the previous frame as the latest noise reduction low data in response to the first control command from the filter control unit. And
The first variable weighted averaging unit uses a weight for averaging the input raw data and the latest noise reduction raw data read from the first frame memory as a second control command from the filter control unit. Variable according to the output and output as noise reduction low data,
The second variable recursive filter has a second frame memory and a second variable weighted averaging unit,
The second frame memory stores, as the latest baseline data, the baseline data output from the second variable weighted averaging unit in the previous frame in response to a third control command from the filter control unit. And
The second variable weighted averaging unit averages the noise reduction raw data output from the first variable weighted averaging unit and the latest baseline data read from the second frame memory. The weight to be varied according to the fourth control command from the filter control unit, and output as baseline data,
The filter control unit
The touch detection device that generates the first control command, the second control command, the third control command, and the fourth control command based on the touch determination data output from the touch determination unit. The touch detection device according to claim 2,
When the touch determination data determines that there is a touch, the filter control unit uses the second variable weight when the element determined to be touched and the element adjacent to the element are defined as the first element group. The weight when performing the weighted averaging process on the noise reduction low data and the latest baseline data by the averaging unit,
For the elements other than the first element group, the fourth control command is generated so as to be 1: n (where 1 <n is a real number),
For the elements included in the first element group, the fourth control command is generated so as to be 0: 1, and the update of the latest baseline data in the second frame memory is stopped. 3 Touch detection device that generates control commands. The touch detection device according to claim 2, wherein
The filter control unit is based on the touch determination data.
For the elements for which no touch is determined in the previous frame and the current frame, or for the elements for which no touch is determined in the previous frame and the current frame, the input variable data and the input raw data are The second control command is generated so that a weight when performing the weighted averaging process on the noise reduction low data is 1: n (where n is a real number where 1 <n),
For the element in which the previous frame is a non-touch determination and the current frame is a touch determination, or conversely, the element in which the previous frame is a touch determination and the current frame is a non-touch determination The second control command so that the weight when the weighted averaging process is performed on the input raw data and the noise-reduced low data by the variable weighted averaging unit is 1: m (where m is a real number where m <n). Generate touch detection device. In the touch detection device according to any one of claims 1 to 4,
The filter control unit initializes the noise reduction raw data generated by the first variable recursive filter and the initial value of the baseline data generated by the second variable recursive filter, the same as the input raw data. The touch detection device that controls the first weighted averaging process and the second weighted averaging process. A touch detection method applied to a touch detection device that outputs a touched position coordinate on a panel based on input low data that is sensor output data after AD conversion from a touch panel,
Random noise is reduced from the input low data in a state where fixed pattern noise that is superimposed on the sensor output data in a fixed and steady manner remains due to variations in characteristics of each sensor position and sensor output data generation circuit. A first variable recursive filtering step to generate noise reduced low data;
A second variable recursive filter processing step for generating baseline data in which random noise is reduced from the noise reduction raw data generated by the first variable recursive filter in a state where the fixed pattern noise remains;
Subtraction that outputs difference data by subtracting the baseline data generated in the second variable recursive filter processing step from the noise reduction low data generated in the first variable recursive filter processing step. Processing steps;
A touch determination processing step for outputting touch determination data based on a change state of the input low data with respect to the baseline data generated in the second variable recursive filter processing step;
A coordinate calculation processing step for outputting the touched position coordinates based on the difference data output by the subtraction processing step and the touch determination data output by the touch determination processing step;
Based on the touch determination data output by the touch determination processing step, the first variable recursive filter processing step so that the difference data becomes data obtained by reducing the random noise and the fixed pattern noise. A first weighted averaging process for generating noise-reduced low data, and a filter control step for controlling a second weighted average process for generating the baseline data in the second variable recursive filtering process step A touch detection method comprising:

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