ELECTROMAGNETIC SENSING TOUCH SCREEN

• US 20150277632A1
• Filed: 03/25/2014
• Published: 10/01/2015
• Est. Priority Date: 03/25/2014
• Status: Active Grant

• Current Assignee: Netio Technologies Co., Ltd.
• Original Assignee: Netio Technologies Co., Ltd.
• Inventors: Wang, Chun Hsiao
• Granted Patent: US 9,158,427 B1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

The present invention discloses an electromagnetic sensing touch screen, which includes a display panel, a sensing capacitor matrix, select units, voltage controlled oscillators (VCOs), digital potentiometers, EM (electromagnetic) wave receive/detection units, a standard EM wave transmit unit and a control unit. A single detection unit consists of a corresponding select unit, VCO, digital potentiometer and EM wave receive/detection unit. The control unit drives the standard EM wave transmit unit to transmit standard EM wave, and further controls the EM wave receive/detection units to receive sensed capacitance values from the sensing capacitor matrix in a scanning manner. As a result, each EM wave receive/detection unit generates a respective detection signal for determining the location of the finger(s) and checking how the finger(s) approaches to or actually touches the sensing capacitor matrix, thereby generating finger location information and implementing the multipoint touch and display function.

Claims

1. An electromagnetic sensing touch screen for detecting a location of at least one finger by use of frequency drift for electromagnetic (EM) wave to implement a multi-touch display function, comprising a display panel, a sensing capacitor matrix, select units, voltage controlled oscillators (VCOs), digital potentiometers, EM (electromagnetic) wave receive/detection units, a standard EM wave transmit unit and a control unit,

wherein the corresponding select unit, VCO, digital potentiometer and EM wave receive/detection unit constitutes a single detection unit;

wherein the display panel is connected to an external image input device to receive image information and display an image;

wherein the sensing capacitor matrix possesses full or part transparency, and is provided close to the display panel, the sensing capacitor matrix comprising a plurality of sensing capacitor units, each corresponding to one specific region of the image displayed by the display panel, the sensing capacitor unit used to generate a sensed capacitance value by changing an equivalent capacitance value according to how the finger approaches;

wherein the select unit is connected to a corresponding one of the sensing capacitor units of the sensing capacitor matrix, and comprises a plurality of multiplexers hierarchically arranged for selecting one of the sensed capacitance values from the sensing capacitor matrix as a final sensed capacitance value and a resonant capacitance for the VCO based on a scan select signal generated by the control unit, and transferring the sensed capacitance value selected;

wherein the VCO receives the final sensed capacitance value and a voltage control signal generated by the digital potentiometer for controlling a varactor diode so as to generate a local oscillation signal with a local oscillation frequency;

wherein the EM wave receive/detection unit uses the local oscillation signal of the VCO to receive a standard EM wave from the standard EM wave transmit unit, a detection signal is generated through a detection operation, and the standard EM wave contains a standard signal;

wherein the control unit is connected to the select units, the digital potentiometers and the EM wave receive/detection units to perform a finger detection operation for generating the scan select signal used to control each select unit to select the final sensed capacitance value, and the control unit simultaneously receives the detection signal and performs frequency modulation to generate the frequency control signal;

wherein the digital potentiometer receives the frequency control signal to perform potential adjustment so as to generate the voltage control signal such that the VCO adjusts the local oscillation frequency of the local oscillation signal according to the voltage control signal; and

wherein the standard EM wave transmit unit is driven by the control unit to generate and transmit the standard EM wave to the EM wave receive/detection units.

2. The electromagnetic sensing touch screen as claimed in claim 1, wherein the sensing capacitor units are arranged in a matrix having X columns and Y rows.

3. The electromagnetic sensing touch screen as claimed in claim 1, wherein the EM wave receive/detection unit comprises an antenna and a signal detector, the antenna receives the standard EM wave, and the signal detector detects the detect signal indicating the intensity of the standard EM wave received.

4. The electromagnetic sensing touch screen as claimed in claim 1, wherein the control unit is implemented by a MCU (microcontroller).

5. The electromagnetic sensing touch screen as claimed in claim 1, wherein the digital potentiometer comprises an electrically erasable potentiometer (EEPOT).

6. The electromagnetic sensing touch screen as claimed in claim 1, wherein the finger detection operation of the control unit comprises an initialization operation and a detection operation, the initialization operation corrects the touch operation by compensating the drift caused by the respective units or environment, and the detection operation detects the location of the finger to generate finger location information, and transfers the finger location information to an external processing unit or device, comprising a USB (Universal Serial Bus) device or computer.

7. The electromagnetic sensing touch screen as claimed in claim 6, wherein the initialization operation comprises steps of:

checking whether it is needed to correct after power on, if not, the sensing capacitor units are corrected, and if yes, performing subsequent steps;

driving the standard EM wave transmit unit to transmit the standard EM wave when the finger is away from the sensing capacitor matrix;

the control unit transferring the scan select signal to each of the select units such that the select unit sequentially receives the sensed capacitance values generated by the sensing capacitor units, and generates the final sensed capacitance value for scanning all effective regions of the display panel;

the VCO generating the local oscillation signal based on the final sensed capacitance value; and

the control unit at the same time receiving the local oscillation signals of all the VCOs and generating the frequency control signal for compensation, the digital potentiometer generating the voltage control signal, and the VCO receiving the voltage control signal to adjust the local oscillation frequency of the local oscillation signal until the control unit correctly determines the finger does not approach to or touch the sensing capacitor unit, and the control unit storing the frequency control signal as voltage control information such that the sensing capacitor units are corrected.

8. The electromagnetic sensing touch screen as claimed in claim 6, wherein the detection operation comprises steps of:

sequentially scanning all the sensing capacitor units to determine whether a touch action occurs;

the control unit directly employing the voltage control information previously stored to transfer the frequency control signal to the digital potentiometer for generating the voltage control signal when the finger approaches to or touches any one of the sensing capacitor units;

the digital potentiometer receiving the voltage control signal and adjusting the local oscillation frequency of the local oscillation signal according to the final sensed capacitance value of the select unit, and the final sensed capacitance value changes if the finger approaches to or touches the sensing capacitor unit such that the local oscillation frequency changes and a frequency drift with respect to the standard EM wave occurs;

the EM wave receive/detection unit employing the local oscillation signal to detect the standard EM wave, and generating the detection signal representing how close the finger approaches to the sensing capacitor units or the finger touches the sensing capacitor units; and

the control unit determining whether the frequency drift occurs or the degree of the frequency drift according to the detection signal such that the location of the corresponding sensing capacitor unit is taken as the location of the finger if the intensity of the detection signal is lower than a preset threshold, the finger location information further transferred, the finger location information is generated and transferred, returning to the step of sequentially scanning all the sensing capacitor units to determine whether the touch action occurs, and repeating the subsequent steps.

9. The electromagnetic sensing touch screen as claimed in claim 1, wherein the sensing capacitor unit are substantially sensing capacitor nodes formed by a plurality of horizontal driving lines and a plurality of vertical sensing lines, which are interlaced to each other, and the driving line and the sensing lines interlaced are not physically in contact, but separated by a distance or by a high impedance film.