Electromagnetic sensing touch screen

摘要

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.

主权项

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.