KR20210099727A - Stylus pen and control method thereof - Google Patents

Abstract

Disclosed are a stylus pen and a control method thereof wherein the position, pressure, etc. of the pen can be detected only using the drive frequency of the pen without a separate RF device. The stylus pen adopted for a touch sensing system, which determines a touch position and detects pen pressure by multi-frequency drive, multi-frequency reception and FFT, comprises: a conductive tip capable of touching a touch panel; a pen pressure sensor for measuring the pressure of the conductive tip applied to the touch panel and outputting a pen pressure signal; a frequency signal generator for generating a set position transmission frequency to detect the position of the stylus pen and generating a pressure transmission frequency based on the pen pressure signal; and a mixer for mixing the position transmission frequency and the pressure transmission frequency and transmitting a mixing signal via the conductive tip to the surface of the touch panel. The frequency signal generator (I) defines a gap between a first pressure reference frequency and a second pressure reference frequency as delta, (ii) divides pressure to be detected by pressure resolution and subdivide the pressure into step units, (iii) sets a pressure step frequency by mapping detected pressure to the subdivided pressure steps as the pressure is detected, and (iv) sets a pressure transmission frequency by multiplying the pressure step frequency by delta and adding the result to the first pressure reference frequency.

Description

STYLUS PEN AND CONTROL METHOD THEREOF

The present invention relates to a stylus pen and a control method thereof, and more particularly, to a stylus pen implemented to sense a position, pressure, etc. of a pen only with a driving frequency of the pen without a separate RF element and a control method thereof.

The use of touch screen interfaces and styluses is well established. Touch screen designs incorporate a number of different technologies including resistive, capacitive, inductive, and radio frequency sensing arrays. For example, resistive touch screens are passive devices well suited for use with a passive stylus.

Although resistive touch screens can sense pressure from any nearby object, multi-touch is generally not supported. An example of a multi-touch application may be applying two or more fingers to a touch screen. Another example may be inputting a signature including simultaneous palm and stylus input signals. Because of these and many other shortcomings, capacitive touch screens are increasingly replacing resistive touch screens in the customer market.

In the conventional frequency transmission method, point information is frequency f0, tilt information is frequency f1, pen pressure information is frequency f2~f10 (a method that transmits 9 frequencies as if 8-bit data was transmitted), button information ( If 3 buttons are implemented, 3 frequencies) are assigned as frequencies f11~f13, and other function information is assigned as frequencies f14~.

That is, the active stylus pen function was implemented by allocating 15 or more frequencies per stylus pen. At this time, in the case of two or four stylus pens, there was a problem of having to drive a frequency 2 to 4 times the frequency of each frequency set and wasting the frequency, and PAPR (Peak) due to the increase in the number of pen frequencies. -to-Average Power Ratio), it was difficult to achieve commercial feasibility.

Meanwhile, conventionally, pressure information of the stylus pen is transmitted to a host system (eg, a touch panel or a readout circuit disposed on the touch panel, etc.) through an RF device such as ZigBee or Bluetooth. However, when the RF device is used, the cost increases, there is a limitation in using several stylus pens, and there are problems in that power consumption increases. In addition, in order to globally sell stylus pens employing RF devices, there was a hassle to obtain electromagnetic wave certification for each country.

Korean Patent Application Laid-Open No. 2012-0095376 (Title: Multi-touch touch device having multiple driving frequencies and maximum likelihood estimation) (published on August 28, 2012) Korean Patent Application Laid-Open No. 2011-0134886 (Name: Multi-Function Capacitance Sensing Circuit with Current Conveyor) (published on December 15, 2011)

Accordingly, the technical task of the present invention is based on this point, and an object of the present invention is to transmit a position transmission frequency and a pressure transmission frequency using a multi-frequency transmission/reception technique, which is a capacitive touch technology, to drive a pen without a separate RF device. An object of the present invention is to provide a stylus pen embodied to detect the position, pressure, etc. of the pen only by frequency.

Another object of the present invention is to provide a method for controlling the above-described stylus pen.

Another object of the present invention is to provide a touch sensing system including the above-described stylus pen.

Another object of the present invention is to provide a touch sensing method using the above-described touch sensing system.

According to one embodiment in order to realize the object of the present invention, a stylus pen employed in a touch sensing system for determining a touch position and sensing pen pressure through multi-frequency driving, multi-frequency reception, and FFT is in contact with the touch panel. possible conductive tips; a pen pressure sensor measuring the pressure of the conductive tip applied to the touch panel and outputting a pen pressure signal; a frequency signal generator for generating a position transmission frequency set to detect the position of the stylus pen, and generating a pressure transmission frequency based on the pen pressure signal; and a mixer for mixing the position transmission frequency and the pressure transmission frequency to transmit a mixing signal to the surface of the touch panel via the conductive tip, wherein the frequency signal generator comprises: (i) a first pressure reference frequency and a second pressure reference frequency; 2 Define the interval of the pressure reference frequency as delta, (ii) divide the pressure to be sensed by the pressure resolution and subdivide it into step units, (iii) map the pressure sensed as pressure is sensed to the subdivided pressure step to set the pressure step frequency, and (iv) multiply the pressure step frequency and the delta, and then add to the first pressure reference frequency to set the pressure transmission frequency.

에 의해 산출될 수 있다. In one embodiment, the delta that is the basis of the pressure resolution is,

can be calculated by

In one embodiment, the first pressure reference frequency and the second pressure reference frequency are allocated for pen pressure sensing, and the separation of pressure is divided into a plurality of intervals between the first pressure reference frequency and the second pressure reference frequency. is set, and each pressure step may be determined by multiplying the first pressure reference frequency by the division of the pressure.

According to an embodiment, in order to realize another object of the present invention, a control method of a stylus pen employed in a touch sensing system for determining touch coordinates through multi-frequency driving, multi-frequency reception, and FFT is defined as delta. dividing the interval between the first pressure reference frequency and the second pressure reference frequency by the pressure resolution; subdividing the pressure to be sensed in steps; setting a pressure step frequency by mapping the sensed pressure to the subdivided pressure step as the pressure is sensed; setting a pressure transmission frequency by multiplying the pressure step frequency by the delta and adding the multiplication to the first pressure reference frequency; and transmitting the pressure transmission frequency to the surface of the touch panel.

According to one embodiment, in order to realize another object of the present invention, a touch sensing system for determining a touch position and sensing a pen pressure through multi-frequency driving, multi-frequency reception, and FFT is a driving electrode that transmits a pen driving signal. and a touch panel including a sensing electrode transmitting a sensing signal induced by the driving electrode; (i) The interval between the first pressure reference frequency and the second pressure reference frequency is defined as delta, (ii) the pressure to be sensed is divided by the pressure resolution and subdivided into step units, (iii) detected as pressure is sensed Setting the pressure step frequency by mapping the applied pressure to the subdivided pressure step, (iv) multiplying the pressure step frequency and the delta, and adding the first pressure reference frequency to the first pressure reference frequency to set the pressure transmission frequency, (v) ) a stylus pen for transmitting the pressure transmission frequency to the surface of the touch panel; and a readout circuit configured to detect the position information of the stylus pen and the pressure information of the stylus pen through calculation of a weight position for each position of the driving electrodes and the sensing electrodes and a relation between display resolutions.

(Psum(x)는 X축 가중치 합이고,

는 센싱전극들의 터치 변화값의 합)에 서로 인접하는 센싱전극의 분해능을 승산하여 산출되고, Y축 상의 터치 위치는,

(Psum(y)는 Y축 가중치 합이고,

는 구동전극들의 터치 변화값의 합)에 서로 인접하는 구동전극의 분해능을 승산하여 산출될 수 있다. In one embodiment, the readout circuit calculates virtual touch coordinates, the touch position on the X-axis,

(Psum(x) is the X-axis weighted sum,

is calculated by multiplying the sum of the touch change values of the sensing electrodes by the resolution of the sensing electrodes adjacent to each other, and the touch position on the Y-axis is,

(Psum(y) is the Y-axis weighted sum,

may be calculated by multiplying the sum of touch change values of the driving electrodes) by the resolution of the driving electrodes adjacent to each other.

In an embodiment, the readout circuit may subtract offset values set as weights from the virtual touch coordinates.

(여기서, f20mag는 제1 압력기준주파수(f20)의 크기이고, f21mag는 제2 압력기준주파수(f21)의 크기이고, offset1은 f20의 가중치이고, offset2는 f21의 가중치인 것)에 의해 복원될 수 있다. In one embodiment, the received pressure value is

(here, f20mag is the size of the first pressure reference frequency f20, f21mag is the size of the second pressure reference frequency f21, offset1 is the weight of f20, and offset2 is the weight of f21) can

According to one embodiment, in order to realize another object of the present invention, a touch sensing method using a touch sensing system for determining a touch position through multi-frequency driving, multi-frequency reception, and FFT is a pressure for transmitting a pen pressure signal. determining a transmission frequency; transmitting the determined pressure transmission frequency to the surface of the touch panel; receiving a sensing frequency through a surface of the touch panel; calculating a touch position of the pen based on the sensing frequency; and calculating the pen pressure of the pen based on the sensing frequency.

In one embodiment, the step of determining the pressure transmission frequency, dividing the interval between the first pressure reference frequency and the second pressure reference frequency defined as delta by the pressure resolution; subdividing the pressure to be sensed in steps; setting a pressure step frequency by mapping the sensed pressure to the subdivided pressure step as the pressure is sensed; and setting the pressure transmission frequency by multiplying the pressure step frequency by the delta and then summing it to the first pressure reference frequency.

(여기서, f20mag는 제1 압력기준주파수(f20)의 크기이고, f21mag는 제2 압력기준주파수(f21)의 크기이고, offset1은 f20의 가중치이고, offset2는 f21의 가중치인 것)에 의해 복원될 수 있다. In one embodiment, the received pressure value is

(here, f20mag is the size of the first pressure reference frequency f20, f21mag is the size of the second pressure reference frequency f21, offset1 is the weight of f20, and offset2 is the weight of f21) can

According to this stylus pen and its control method, the position and pressure transmission frequency are transmitted using the multi-frequency transmission/reception technique, which is a capacitive touch technology, so that the position, pressure, etc. of the pen can be controlled only with the driving frequency of the pen without a separate RF element. can detect In addition, even if a significantly smaller number of touch sensors than the resolution of the actual display panel are used, not only the precise position information of the stylus pen but also the pressure information of the stylus pen through the calculation of the weight position for each position of the touch sensors and the calculation of the relationship between the display resolution can be detected.

1 is a schematic diagram illustrating a touch sensing system employing a stylus pen according to an embodiment of the present invention.
FIG. 2 is a configuration diagram for explaining touch coordinate determination by the touch sensing device shown in FIG. 1 .
FIG. 3A is a schematic diagram for explaining the appearance of the stylus pen illustrated in FIG. 1 , and FIG. 3B is a configuration diagram schematically illustrating the stylus pen illustrated in FIG. 4 .
FIG. 4 is a block diagram illustrating the stylus pen shown in FIG. 1 .
5 is a plan view for explaining position detection and coordinate calculation of a touch screen.
6 is a plan view for explaining a coordinate system of a region for simply calculating a touch position.
7 is a plan view illustrating final touch coordinates calculated by acquiring touch sensitivity and calculating touch coordinates.
8 is a plan view for explaining a pen pressure sensing method according to an embodiment of the present invention.
9 is a graph for explaining the resolution determination slope with respect to the pressure value and the pressure transmission frequency.
Figure 10a is a diagram for explaining the pressure transmission frequency when the pressure is 0.25, Figure 10b is a diagram for explaining the pressure transmission frequency when the pressure is 0.5, Figure 10c is a diagram for explaining the pressure transmission frequency when the pressure is 0.75 is a drawing for
11 is a graph for explaining an FFT value (magnitude) of a pen reception frequency according to a transmission pressure value.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail. Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

The present invention relates to a new frequency operation used by a stylus pen (especially an active stylus pen) to transmit point information, tilt information, pen pressure information, button information, etc., which are information to be transmitted to a touch screen surface. Here, the button information includes a click, such as a mouse button, forward, backward, and special functions (eg, eraser, other user-defined commands).

1 is a schematic diagram illustrating a touch sensing system employing a stylus pen according to an embodiment of the present invention.

Referring to FIG. 1 , the touch sensing system includes a touch sensing device 100 and a stylus pen 200 , and recognizes a touch operation (position information of the pen and pressure information of the pen) of the stylus pen 200 . The touch sensing apparatus 100 detects the position of the stylus pen 200 to determine the touch coordinates of the stylus pen 200 . Also, the touch sensing device 100 detects the pressure of the stylus pen 200 .

In the present embodiment, even when using a significantly smaller number of touch sensors (eg, 4×4) than the resolution (eg, 400×400) of the actual display panel, the weight for each position of the touch sensors A touch sensing system capable of detecting not only precise position information of the stylus pen but also pressure information of the stylus pen is provided by calculating the relationship between the position calculation and the display resolution.

FIG. 2 is a configuration diagram for explaining touch coordinate determination by the touch sensing device 100 shown in FIG. 1 .

1 and 2 , a plurality of driving signals are applied to different driving electrodes provided in the touch panel. Each of the driving signals has different frequency components. Hereinafter, for convenience of description, an example in which the first driving signal TX0, the second driving signal TX1, the third driving signal TX2, and the fourth driving signal TX3 are applied to the touch panel will be described as an example. Here, the first driving signal TX0 has a first frequency component f0, the second driving signal TX1 has a second frequency component f1, and the third driving signal TX2 has a third frequency component. (f2), and the fourth driving signal TX3 has a fourth frequency component f3. Each of the first to fourth frequency components f0, f1, f2, and f3 is different from each other.

The sensing electrode RX of the touch panel receives the sensing signal SRX sensed in response to the first to fourth driving signals TX0, TX1, TX2, and TX3. Although the sensing signal is mixed by the touch panel, the amplitude is attenuated compared to the first to fourth driving signals TX0, TX1, TX2, and TX3.

The sensing signal SRX is amplified by an amplifier and then provided to the FFT processing block. The FFT-processed sensing signals are decomposed and analyzed to derive the coordinates of where the touch occurred. The amplifier or the FFT processing block may be provided in a touch sensing controller provided in the touch sensing apparatus 100 .

FIG. 3A is a schematic diagram for explaining the appearance of the stylus pen 200 illustrated in FIG. 1 , and FIG. 3B is a configuration diagram for schematically explaining the stylus pen 200 illustrated in FIG. 1 .

Referring to FIGS. 3A and 3B , the stylus pen 200 includes a pencil-shaped conductive case 202 , a conductive tip 204 connected to one side of the conductive case 202 , a conductive case 202 and a conductive tip 204 . It includes a pen pressure sensor 206 , a frequency signal generator 208 and a mixer 210 disposed therebetween.

The conductive tip 204 has a shape capable of contacting the touch panel.

The pen pressure sensor 206 outputs a pen pressure signal by measuring the pressure of the conductive tip 204 applied to the touch panel. That is, the pen pressure sensor 206 generates an electric signal according to the pressure applied to the conductive tip 204 protruding from the end of the stylus pen body. For example, the pen pressure sensor 206 generates an electrical signal according to the pressure applied to the conductive tip 204 by the user's writing operation. To this end, the conductive tip 204 may be connected to the pen pressure sensor 206 to transmit the pressure generated in the conductive tip 204 to the pen pressure sensor 206 .

The frequency signal generator 208 generates a frequency signal (hereinafter, referred to as a position transmission frequency) (SPO) for measuring the pen position set to detect the position of the stylus pen 200, and determines the pen pressure of the stylus pen based on the pen pressure signal. A frequency signal for measuring pen pressure (hereinafter referred to as pressure transmission frequency) (SPR) set for measurement is generated. Hereinafter, for convenience of description in the present specification, an example in which four driving electrodes and four sensing electrodes are disposed on the touch panel will be described. At this time, a first driving signal TX0, a second driving signal TX1, a third driving signal TX2, and a fourth driving signal TX3 are applied to each of the driving electrodes. Accordingly, the first driving signal TX0 has a first frequency component f0, the second driving signal TX1 has a second frequency component f1, and the third driving signal TX2 has a third frequency component f2, and the fourth driving signal TX3 has a fourth frequency component f3. Each of the first to fourth frequency components f0, f1, f2, and f3 is different from each other. In addition, the fifth frequency component (f4) of the position transfer frequency (SPO) and the sixth frequency component (f5) of the pressure transfer frequency (SPR) are first to fourth frequency components (f0, f1, f2, f3), respectively different from

In this embodiment, the frequency signal generator 208 defines the interval between the first pressure reference frequency and the second pressure reference frequency as delta, divides the pressure to be sensed by the pressure resolution, and subdivides it into step units, and the pen pressure sensor ( 206) sets the pressure step frequency by mapping the sensed pressure to the subdivided pressure step, multiplies the pressure step frequency by the delta, and adds the pressure to the first pressure reference frequency to transmit the pressure Set the frequency.

The mixer 210 mixes the position transfer frequency (SPO) and the pressure transfer frequency (SPR) and outputs a mixing signal to the conductive tip 204 . The mixing signal output to the conductive tip 204 is sensed in a capacitive manner by a touch sensor provided in the touch panel.

As described above, different from the frequency of the driving signal applied to the touch panel, by designing the stylus pen to set the frequency of the pen frequency signal to detect the position of the stylus pen and the stylus pen pressure and apply it to the touch panel. , a plurality of stylus pens can be used on one touch panel.

FIG. 4 is a block diagram illustrating the stylus pen 200 shown in FIG. 1 .

Referring to FIG. 4 , the stylus pen 200 includes buttons 250 , a button processing unit 252 , a pen control unit 260 , a pen pressure sensor 206 , a pen pressure processing unit 207 , a pen control unit 260 , and a power management unit. 270 , a battery 272 , a waveform generator 280 , and a waveform driver 290 .

The buttons 250 are varied according to a user's manipulation and provide a button signal to the button processing unit 252 . The buttons 250 may be mechanical buttons or capacitive buttons. Buttons 250 may provide additional functionality, including but not limited to "left click" and "right click" functions, similar to that of a computer mouse. The buttons 250 of the stylus pen 200 may be coupled to a pen control unit (CPU) 260 . Buttons 250 may be mechanical, electrical, capacitive, or other types known to those skilled in the art.

The button processing unit 252 digitally converts the button signal provided from the buttons 250 and provides it to the pen control unit 260 .

The pen pressure sensor 206 senses the pressure applied by the stylus pen 200 to the touch panel and provides the sensed pressure signal to the pen pressure processing unit 207 .

The pen pressure processing unit 207 provides the pressure signal provided from the pen pressure sensor 206 to the waveform generating unit 280 .

The pen controller 260 may control operations of components included in the stylus pen 200 . For example, the pen control unit 260 determines the pen pressure frequency to be transmitted in response to the pressure value sensed by the pen pressure sensor 206 and processed by the pen pressure processing unit 207 , and the frequency shown in the waveform generating unit 280 (or 3b). A signal generator 208 provides a frequency control signal.

The power management unit 270 supplies power from the battery 272 to each component. The power is boosted as necessary, and the boosted power is supplied to each component. In general, a stylus pen may be classified into an active type or a passive type stylus pen depending on the presence or absence of a battery. According to the present invention, since the battery 272 is provided in the stylus pen 200, the stylus pen according to the present invention is an active stylus pen.

The waveform generating unit 280 generates a first waveform for generating a position transmission frequency (SPO) or a second waveform for generating a pressure transmission frequency (SPR) in response to the control of the pen control unit 260, the waveform driving unit 290 provided to The first waveform or the second waveform may be a sine wave.

The waveform driver 290 amplifies the first waveform or the second waveform generated by the waveform generator 280, respectively, and mixes the amplified waveforms to output a mixing signal. In this embodiment, the pen pressure processing unit 207 , the waveform generating unit 280 , and the waveform driving unit 290 may define the frequency signal generator 208 shown in FIG. 3 .

5 is a plan view for explaining position detection and coordinate calculation of a touch screen.

Referring to FIG. 5 , the touch panel includes a plurality of Tx sensors (Tx0, Tx1, Tx2, Tx3) extending in the X-axis direction and disposed along the Y-axis, and a plurality of Rx extending in the Y-axis direction and disposed along the X-axis. It includes sensors Rx0, Rx1, Rx2, Rx3. In this embodiment, Tx sensors Tx0, Tx1, Tx2, Tx3 and Rx sensors Rx0, Rx1, Rx2, Rx3 define touch sensors. That is, the Tx sensors Tx0, Tx1, Tx2, and Tx3 are driving electrodes that transmit a pen driving signal, and the Rx sensors Rx0, Rx1, Rx2, and Rx3 are sensing units that transmit a sensing signal induced by the driving electrode. electrode. In the description with reference to FIG. 5, an example of detecting finger coordinates is described.

Position detection and coordinate calculation will be described on the assumption that one point is touched through a finger on the touch panel slightly below the center of Tx1 and in the middle area between Rx0 and Rx1.

It is assumed that frequencies f1, f2, f3, and f3 are allocated to each of the Tx0 sensor, the Tx1 sensor, the Tx2 sensor, and the Tx3 sensor to apply the driving signal. In this case, the sensing signal sensed through each Rx sensor is subjected to FFT processing. When the frequency change of the FFT-processed sensing signal is calculated and the result is expressed, the amount of change in the touch value caused by the touch is converted into a two-dimensional table, and the touch sensitivity table is expressed as follows.

[Table 1]

In the multi-frequency driving scheme, f0 is assigned to Tx0, f1 is assigned to Tx1, f2 is assigned to Tx2, and f3 is assigned to Tx3. In this case, the coordinates of the vertical axis of the touch point are determined by using the sum of the vertical axes where the touch occurs.

To simplify the calculation, the coordinate system of the inner region is as follows.

That is, the coordinate system of the vertical axis is defined with Tx0 as virtual reference coordinate 1, Tx1 as virtual reference coordinate 2, Tx2 as virtual reference coordinate 3, and Tx3 as virtual reference coordinate 4, Rx0 is virtual reference coordinate 1, If the horizontal axis coordinate system is defined with Rx1 as virtual reference coordinate 2, Rx2 as virtual reference coordinate 3 and Rx3 as virtual reference coordinate 4, the two-dimensional coordinate system in which the actual touch is reported is expressed as follows.

6 is a plan view for explaining a coordinate system of a region for simply calculating a touch position.

As shown in FIG. 6 , both the horizontal axis and the vertical axis of the outer area are extended by 0.5 each outside the inner area.

The coordinates of the outer area are usually calculated in a separate way, and the coordinate system of the inner area is calculated using the normal weighted average value.

If the coordinates of the inner region are expressed as four vertices in the form of (horizontal, vertical), it is formed as (1,1)-(1,4)-(4,1)-(4,4).

In the touch sensitivity table of Table 1, the sum of the vertical and horizontal axes of each area in which the touch value is changed is calculated as shown in Table 2 below.

[Table 2]

With reference to Table 2, the position of the horizontal axis (X axis) is calculated as follows.

Originally, only the part with the change of value in Table 2 should be involved in the calculation, but in this embodiment, even if the part with the remaining value <0> is included, there is no significant difference in the result, so all values are included in the calculation for convenience of explanation explain it by Below, Psum(x) is the X-axis weighted sum, and Psum(y) is the Y-axis weighted sum.

수식(1)

Formula (1)

수식(2)

Formula (2)

수식(3)

Formula (3)

수식(4)

Formula (4)

When the actual values of Table 2 are reflected in Equation (1), it is as follows.

수식(5)

Formula (5)

When the actual values of Table 2 are reflected in Equation (2), it is as follows.

수식(6)

Formula (6)

When the actual values of Table 2 are reflected in Equation (3), it is as follows.

수식(7)

Formula (7)

When the actual values of Table 2 are reflected in Equation (4), it is as follows.

수식(8)

Formula (8)

The calculation of the actual touch position of the touch point is as follows.

The calculation of the touch position on the X-axis is as follows.

수식(9)

Formula (9)

수식(10)

Formula (10)

수식(11)

Formula (11)

The calculation of the touch position on the Y-axis is as follows.

수식(12)

Formula (12)

수식(13)

Formula (13)

수식(14)

Formula (14)

In the end, the virtual touch coordinates calculated from the touch sensitivity acquisition and touch coordinate calculation are as follows.

수식(15)

Formula (15)

As shown in Equation 15, it is preferable to subtract offset values from the virtual touch coordinates.

A schematic diagram of the virtual touch coordinates obtained by the above operation is shown in FIG. 7 .

7 is a plan view illustrating final touch coordinates calculated by acquiring touch sensitivity and calculating touch coordinates.

X-axis virtual coordinates 0.5 to 4.5 and Y axis virtual coordinates 0.5 to 4.5 are converted to correspond to a real display panel having 400×400 pixels, and a two-dimensional structure composed of 4 Tx sensors and 4 Rx sensors on the actual display panel. A touch sensing system is implemented by arranging a touch panel.

Here, the resolution between each sensor channel is in charge of 100 pixels between Tx-Tx and 100 pixels between Rx-Rx. When expressed by multiplying the virtual touch coordinates obtained in the above-mentioned equations by 100, the position expression according to each display resolution of X and Y exactly matches. That is, the X-coordinate value is 1.593×100=159.3, and the Y-coordinate value has touch coordinates of 2.186×100=218.6.

Through the above calculation, even with a significantly smaller number of touch sensors (eg, 4 × 4) than the resolution (eg, 400 × 400) of the actual display panel, the Tx sensor and the Rx sensor for each position Precise position can be found using weight position calculation and relationship calculation of display resolution.

The present invention proposes a method of transmitting position information and pressure information (ie, pen pressure information) of a stylus pen in consideration of this point.

8 is a plan view for explaining a pen pressure sensing method according to an embodiment of the present invention.

Referring to FIG. 8 , in the stylus pen, it is assumed that f10 is used as a position frequency allocated for sensing touch coordinates, and f20 and f21 are used as first and second pressure frequencies allocated for sensing pen pressure. In this embodiment, the pressure transmission frequency is used by subdividing the frequency between f20 and f21. In the following description, an example of allocating f20 and f21 as the first and second pressure frequencies to one stylus pen and subdividing between them and utilizing them as the pressure transmission frequency will be described. However, it is also possible to extend to a plurality of stylus pens by allocating f20 and f21 to the first stylus pen, allocating f31 and f32 to the second stylus pen, and allocating f41 and f42 to the third stylus pen.

In the case of FFT processing, when the sampling frequency of the analog-to-digital converter (ADC) is defined as 3.072 MHz and the number of FFT points is 1,024, the frequency resolution of the FFT obtained as a result of the FFT is 3 kHz intervals according to the following equation.

수식(16)

Formula (16)

In this case, the FFT window function used when performing the FFT is usually a function such as a Rectangular Window, Hanning (Hann) Window, Hamming Window, Blackman Window, Gaussian Window, Kaiser-Bessel Window, depending on the purpose of frequency decomposition. can be used In this embodiment, a rectangular function is used as the FFT window function. In general, similar results can be obtained by using other window functions. However, a rectangular window is suitable for calculations based on the definition of the window function (Equation) and experimental results.

To process the signals within the frequency resolution range (3 kHz to 1536 kHz) among the received signals, using a rectangular window, the resolution frequency of the FFT (steps of 3 kHz between 3 kHz to 1536 kHz) The frequency of the input signal that matches one of the 512 frequencies with

When a frequency other than the decomposition frequency of the FFT is received, the lower decomposition frequency and the upper decomposition frequency closest to the received frequency include a frequency component inversely proportional to the deviation from the received frequency and are measured. This is characteristic of rectangular windows.

For example, when an adjacent FFT frequency f20 is assigned to 300 kHz (100th FFT frequency) and f21 is assigned to 303 kHz (101st FFT frequency), the interval between FFT frequencies (that is, the decomposition frequency) is 3 kHz. The above 3 kHz is defined as an FFT frequency interval (or delta) and will be described below.

The resolution of the FFT is determined by the sampling frequency and the number of FFT points, as shown in Equation (16).

When the sampling frequency and the number of FFT points are set to 3.072 MHz and 1,024, respectively, the FFT frequency interval (or decomposition frequency, delta) becomes 3 kHz, a range that is 1/2 of the sampling frequency, and 3 Hz where the lower frequency is a half period It is possible to detect 512 characteristics of each frequency in the frequency band of ~1536 kHz.

At this time, f20 is assigned as 300 kHz (100th FFT frequency), f21 is assigned as 303 kHz (101st frequency), and the information of pressure is transferred from the pen to the frequency of 300 kHz to 303 kHz (100th FFT frequency and 101st FFT). frequency between frequencies), and if the division of pressure is set to 100 steps, each pressure step is determined by multiplying the basic frequency f20 by a value of 30 Hz, respectively.

For example, the pressure stage 1 may be represented by 30Hz×1, the pressure step 2 as 30Hz×2, the pressure step 3 as 30Hz×3, ..., the pressure step 100 may be represented by 30Hz×100.

수식(17)

Formula (17)

수식(18)

Formula (18)

As described above, a pressure transmission frequency expressing pressure is generated by the stylus pen and transmitted to the surface of the touch panel.

After all, the pressure stage 1, which is the point at which the pen pressure first appears, is calculated as f20+f (pressure stage 1)=f20+30Hz=300.03kHz, and the pressure stage 2 is f20+f(pressure stage 2)=300kHz+60 Hz = 300.06 kHz, and the pressure stage 3 is calculated as f20 + f (pressure stage 3) = 300 kHz + 90 Hz = 300.09 kHz. In this way, the pressure stage 100 is f20 + f (pressure stage 100) =300 kHz + 3 kHz = 303 kHz. Here, the pressure step 100 corresponds to f21.

In this way, the relationship between the pen pressure value and the pressure transmission frequency of the stylus pen is the same as the graph shown in FIG. 9 .

9 is a graph for explaining the resolution determination slope with respect to the pressure value and the pressure transmission frequency.

Referring to FIG. 9 , a range detectable by the pressure sensor of the stylus pen is defined as 0 to 1 and is illustrated. In fact, for 8-bit resolution, the detectable range is 0 to 255, for 10-bit resolution, the detectable range is 0 to 1023, and for 12-bit resolution, the detectable range is 0 to 4095. to express

F20 corresponds to the first pen pressure <0>, and f21 is defined as a pressure transmission frequency of the stylus pen corresponding to the second pen pressure <1>.

In this embodiment, the case where f20 is 300 kHz, f21 is 303 kHz, and delta is 3 kHz is described. In addition, the sampling frequency for the FFT is 3.072 MHz, and the number of FFT points is described based on 1,024.

If the pressure resolution is set to 10, f20~f21 can be divided into 10 steps, and the sensed pressure (ie, pen pressure) is measured in units of 0.1 step and calculated as the pressure transmission frequency. If the pressure resolution is set to 50, f20~f21 can be divided into 50 steps, and the sensed pressure is measured in 0.02 steps and calculated as the pressure transmission frequency. If the pressure resolution is set to 100, f20~f21 can be divided into 100 steps, and the sensed pressure is measured in 0.01 step units and calculated as the pressure transmission frequency.

When the pressure detected by the pressure sensor is 0.25, the stylus pen transmits a pressure transmission frequency (f (pen pressure)) defined as f20+(0.25×delta).

When the pressure detected by the pressure sensor is 0.5, the stylus pen transmits a pressure transmission frequency (f (pen pressure)) defined as f20+(0.5×delta).

When the pressure sensed by the pressure sensor is 0.75, the stylus pen transmits a pressure transmission frequency (f (pen pressure)) defined as f20+(0.75×delta).

After all, the pressure transmission frequency f (pen pressure) is defined as follows.

수식(19)

Formula (19)

This is schematically shown in FIGS. 10A, 10B and 10C.

Figure 10a is a diagram for explaining the pressure transmission frequency when the pressure is 0.25, Figure 10b is a diagram for explaining the pressure transmission frequency when the pressure is 0.5, Figure 10c is a diagram for explaining the pressure transmission frequency when the pressure is 0.75 is a drawing for

As shown in FIG. 10A, when the pressure transmission frequency (f (pen pressure)) defined as f20+(0.25×delta) is FFT-processed using a square window function, a side lobe having a size of 75% at f20 ), and a side lobe with a size of 25% appears at f21. Here, if the pressure resolution is 10, the pressure value is equal to ((0.75×1+0.25×2)/(0.75+0.25))×10-10=2.5. If the pressure resolution is 50, the pressure value is equal to ((0.75×1+0.25×2)/(0.75+0.25))×50-50=12.5. If the pressure resolution is 100, the pressure value is equal to ((0.75×1+0.25×2)/(0.75+0.25))×100-100=25.

As shown in FIG. 10B, when the pressure transfer frequency (f (pen pressure)) defined as f20+(0.5×delta) is FFT-processed using a square window function, a side lobe having a size of 50% at f20 ), and a side lobe with a size of 50% appears at f21. Here, if the pressure resolution is 10, the pressure value is equal to ((0.5×1+0.5×2)/(0.5+0.5))×10-10=2.5. If the pressure resolution is 50, the pressure value is equal to ((0.5×1+0.5×2)/(0.5+0.5))×50-50=25. If the pressure resolution is 100, the pressure value is equal to ((0.5×1+0.5×2)/(0.5+0.5))×100-100=50.

As shown in Fig. 10c, when the pressure transfer frequency (f (pen pressure)) defined as f20 + (0.75 × delta) is FFT-processed using a rectangular window function, a side lobe having a size of 25% at f20 ), and a side lobe with a size of 75% appears at f21. Here, if the pressure resolution is 10, the pressure value is equal to ((0.25×1+0.75×2)/(0.25+0.75))×10-10=7.5. If the pressure resolution is 50, the pressure value is equal to ((0.25×1+0.75×2)/(0.25+0.75))×50-50=37.5. If the pressure resolution is 100, the pressure value is equal to ((0.25×1+0.75×2)/(0.25+0.75))×100-100=75.

In the above, it has been described that the stylus pen senses the pressure and transmits the pressure transmission frequency f (pen pressure) corresponding to the sensed pressure.

Then, a series of processes for obtaining the pressure on the touch screen receiving side will be described below.

Similar to the process of obtaining the above-mentioned coordinates, the touch screen receiving side calculates the weight through the weight of the process of finding the pressure according to the pressure resolution of the pen.

According to the pressure transmission frequency, the size of f20 and the size of f21 are represented by the following relational expressions. That is, according to the FFT theory and the definition of a rectangular window function, a received frequency is divided into an adjacent frequency by the same ratio to form a magnitude.

For example, if the pressure transmission frequency is f20+ (0.25×delta), a side lobe having a size of 75% appears at f20, and a side lobe having a size of 25% appears at f21.

This means that the pressure transmission frequency (f20+(0.25×delta)) is received as it is, and the FFT proceeds as a square window function, and for the frequency deviation (1.0 delta) of f20 and f21, the position on the frequency of f20 to f21 has a ratio of 1:3. , and looking at the resolution of 10, in f20, 75% of the received energy appears as a magnitude, and in f21, 25% of the component appears as a magnitude. 11 is a graph showing this.

11 is a graph for explaining an FFT value (magnitude) of a pen reception frequency according to a transmission pressure value.

The magnitudes of the frequencies f20 and f21 shown in FIG. 11 are expressed as a normalized equation as follows.

수식(20)

Formula (20)

수식(21)

Formula (21)

Here, f20mag is the magnitude of the frequency f20, and f21mag is the magnitude of the frequency f21.

In order to calculate the pressure information through the distribution of the reception frequency, f20 assigns an offset1 as a weight, and f21 assigns an offset2 as a weight to perform an operation. For example, in 0.25×delta transmission, the magnitude of the received f20 is 0.75, and the magnitude of the received f21 is 0.25.

When transmitted with a pressure resolution of 10, the received pressure value is restored through the following operation.

[Relational Expression 1]

That is, it is calculated that a pressure of 2.5 out of 10 levels is sensed, and 25% of the total expressible pressure is sensed.

When transmitted with a pressure resolution of 50, the received pressure value is restored through the following operation.

[Relational Expression 2]

That is, it is calculated that pressure of 12.5 out of 50 levels is sensed, and 25% of the total expressible pressure is sensed.

When transmitted with a pressure resolution of 100, the received pressure value is restored through the following operation.

[Relational Expression 3]

That is, it is calculated that pressure of 25 out of 100 levels is sensed, and 25% of the total expressible pressure is sensed.

As in Relations 1, 2, and 3 above, if the pressure resolution (eg, 10, 50, 100) is defined, the pressure value is sensed as it is at the receiving end at the same ratio (25% in all). Therefore, the above Relations 1, 2, and 3 can be applied to various pressure resolutions in the same way as long as variables for pressure resolution are defined.

Meanwhile, in 0.5×delta transmission, the size of the received f20 is 0.5, and the size of the received f21 is 0.5.

When transmitted with a pressure resolution of 10, the received pressure value is restored through the following operation.

[Relational Expression 4]

In the case of transmission with a pressure resolution of 50, the restored pressure value through a similar calculation is 25. In the case of transmission with a pressure resolution of 100, the restored pressure value through a similar calculation is 50.

In both of these 0.5×delta transmissions, the ratio of the pressure resolution of the received energy is the same as 50%.

Meanwhile, in 0.75×delta transmission, the size of the received f20 is 0.25, and the size of the received f21 is 0.75.

The reception pressure value of the pressure resolution 10 is 7.5, the reception pressure value of the pressure resolution 50 is 37.5, and the reception pressure value of the pressure resolution 100 is 75.

In both of these 0.75×delta transmissions, the ratio of the pressure resolution of the received energy is the same as 75%.

If three pressure transmission frequency bands, ie, f20, f21, and f22, are used in a method similar to the above-mentioned method, when the delta resolution is 10, it can have a total pressure resolution of 20, and when the delta resolution is 50, the entire It may have a pressure resolution of 100, and when the delta resolution is 100, it may have a total pressure resolution of 200.

Therefore, if the range of the pressure transmission frequency is extended, a higher pressure resolution can be obtained than at the same delta resolution.

In the (1-delta) structure using f20 and f21 in the same way, if the resolution is expanded to 1,000, the pressure resolution is also expanded to 1,000. Accordingly, a method for transmitting and receiving sophisticated pen pressure from the pen with high pressure resolution can be applied in various ways.

As described above, according to the present invention, the position and pressure of the pen are transmitted using the multi-frequency transmission/reception technique, which is a capacitive touch technology, to transmit the position transmission frequency and the pressure transmission frequency, so that only the driving frequency of the pen without a separate RF element is required. back can be detected. In addition, even if a significantly smaller number of touch sensors than the resolution of the actual display panel are used, not only the position information of the stylus pen but also the pressure information of the stylus pen is obtained through the calculation of the weight position for each position of the touch sensors and the calculation of the relationship between the display resolution. can be detected.

Although the above has been described with reference to the embodiments, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below You will understand.

100: touch sensing device 200: stylus pen
202: conductive case 204: conductive tip
206: pen pressure sensor 207: pen pressure processing unit
208: frequency signal generator 210: mixer
250: buttons 252: button processing unit
260: pen control unit 270: power management unit
272: battery 280: waveform generator
290: waveform driver

Claims (15)

In the stylus pen employed in the touch sensing system that determines the touch position and detects the pen pressure through multi-frequency driving, multi-frequency reception and FFT,
a conductive tip capable of contacting the touch panel;
a pen pressure sensor measuring the pressure of the conductive tip applied to the touch panel and outputting a pen pressure signal;
a frequency signal generator for generating a position transmission frequency set to detect the position of the stylus pen, and generating a pressure transmission frequency based on the pen pressure signal; and
A mixer for mixing the position transmission frequency and the pressure transmission frequency to transmit a mixing signal to the surface of the touch panel via the conductive tip,
The frequency signal generator (i) defines the interval between the first pressure reference frequency and the second pressure reference frequency as delta, (ii) divides the pressure to be sensed by the pressure resolution and subdivides it into steps, (iii) When the pressure is sensed, the pressure sensed is mapped to the subdivided pressure step to set the pressure step frequency, (iv) multiplied by the pressure step frequency and the delta, and then summed to the first pressure reference frequency to the pressure transmission frequency Stylus pen, characterized in that set. The method of claim 1, wherein the delta, which is a criterion for the pressure resolution,

Stylus pen, characterized in that calculated by. The method of claim 1, wherein the first pressure reference frequency and the second pressure reference frequency are allocated for pen pressure sensing, and the separation of the pressure is divided into a plurality of intervals between the first pressure reference frequency and the second pressure reference frequency. is set,
Each pressure step is a stylus pen, characterized in that determined by multiplying the division of the pressure by the first pressure reference frequency. In a control method of a stylus pen employed in a touch sensing system that determines a touch position and detects pen pressure through multi-frequency driving, multi-frequency reception, and FFT,
dividing an interval between the first pressure reference frequency and the second pressure reference frequency defined by delta by the pressure resolution;
subdividing the pressure to be sensed in steps;
setting a pressure step frequency by mapping the sensed pressure to the subdivided pressure step as the pressure is sensed;
setting a pressure transmission frequency by multiplying the pressure step frequency by the delta and adding the multiplication to the first pressure reference frequency; and
and transmitting the pressure transmission frequency to the surface of the touch panel. 5. The method of claim 4,
The touch position on the X-axis is,

(Psum(x) is the X-axis weighted sum,

is calculated by multiplying the sum of touch change values of the sensing electrodes) by the resolution of the sensing electrodes adjacent to each other,
The touch position on the Y-axis is

(Psum(y) is the Y-axis weighted sum,

is calculated by multiplying the sum of touch change values of the driving electrodes) by the resolution of the driving electrodes adjacent to each other. 5. The method of claim 4, wherein the received pressure value is

(here, f20mag is the size of the first pressure reference frequency (f20), f21mag is the size of the second pressure reference frequency (f21), offset1 is the weight of f20, and offset2 is the weight of f21) Control method of the stylus pen, characterized in that. 5. The method of claim 4,
For pen pressure sensing, the first pressure reference frequency and the second pressure reference frequency are allocated, and the division of pressure is set by dividing the interval between the first pressure reference frequency and the second pressure reference frequency into a plurality,
The control method of the stylus pen that each pressure step is determined by multiplying the first pressure reference frequency by the division of the pressure. In a touch sensing system that determines the touch position and detects pen pressure through multi-frequency driving, multi-frequency reception and FFT,
a touch panel including a driving electrode transmitting a pen driving signal and a sensing electrode transmitting a sensing signal induced from the driving electrode;
(i) The interval between the first pressure reference frequency and the second pressure reference frequency is defined as delta, (ii) the pressure to be sensed is divided by the pressure resolution and subdivided into step units, (iii) detected as pressure is sensed Setting the pressure step frequency by mapping the applied pressure to the subdivided pressure step, (iv) multiplying the pressure step frequency and the delta, and adding the first pressure reference frequency to the first pressure reference frequency to set the pressure transmission frequency, (v) ) a stylus pen for transmitting the pressure transmission frequency to the surface of the touch panel; and
and a read-out circuit for detecting the position information of the stylus pen and the pressure information of the stylus pen through calculation of a weight position for each position of the driving electrodes and the sensing electrodes and a relation between display resolution touch sensing system. The touch sensing system of claim 8 , wherein a resolution of the touch panel is lower than a resolution of the display panel. The method of claim 8, wherein the readout circuit calculates virtual touch coordinates,
The touch position on the X-axis is,

(Psum(x) is the X-axis weighted sum,

is calculated by multiplying the sum of touch change values of the sensing electrodes) by the resolution of the sensing electrodes adjacent to each other,
The touch position on the Y-axis is

(Psum(y) is the Y-axis weighted sum,

is calculated by multiplying the sum of touch change values of the driving electrodes) by the resolution of the driving electrodes adjacent to each other. The touch sensing system of claim 10 , wherein the readout circuit subtracts offset values set as weights from the virtual touch coordinates. 9. The method of claim 8, wherein the received pressure value is

(here, f20mag is the size of the first pressure reference frequency (f20), f21mag is the size of the second pressure reference frequency (f21), offset1 is the weight of f20, and offset2 is the weight of f21) A touch sensing system, characterized in that. In a touch sensing method using a touch sensing system that determines a touch position through multi-frequency driving, multi-frequency reception, and FFT,
determining a pressure transmission frequency for transmitting the pen pressure signal;
transmitting the determined pressure transmission frequency to the surface of the touch panel;
receiving a sensing frequency through a surface of the touch panel;
calculating a touch position of the pen based on the sensing frequency; and
and calculating the pen pressure of the pen based on the sensing frequency. The method of claim 13, wherein the determining of the pressure transmission frequency comprises:
dividing an interval between the first pressure reference frequency and the second pressure reference frequency defined by delta by the pressure resolution;
subdividing the pressure to be sensed in steps;
setting a pressure step frequency by mapping the sensed pressure to the subdivided pressure step as the pressure is sensed; and
and setting the pressure transmission frequency by multiplying the pressure step frequency by the delta and adding the multiplication to the first pressure reference frequency. 14. The method of claim 13, wherein the received pressure value is:

(here, f20mag is the size of the first pressure reference frequency (f20), f21mag is the size of the second pressure reference frequency (f21), offset1 is the weight of f20, and offset2 is the weight of f21) A touch sensing method, characterized in that.

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