ORTHOGONAL FREQUENCY SCAN SCHEME IN TOUCH SYSTEM

• US 20170205947A1
• Filed: 03/31/2017
• Published: 07/20/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Tactual Labs Co.
• Original Assignee: Tactual Labs Co.
• Inventors: Wigdor, Daniel, Leigh, Darren
• Granted Patent: US 9,830,015 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 2203/0382 Plural input, i.e. interface arrangements in which a plurality of input device of the same type are in communication with a PC
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• CPC Class Codes: G06F 3/03542 Light pens for emitting or receiving light
• CPC Class Codes: G06F 3/03545 Pens or stylus
• 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 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

System and processes for transmitting orthogonal frequencies on a touch sensor are provided. In one example process, the rows of the sensor panel can have signals transmitted thereon having orthogonal frequencies. The orthogonal frequencies can be separated by a frequency spacing (Δf) that is at least the reciprocal of a measurement period τ (e.g., an integration time) of the touch sensor. Touch events cause and correspond to signals on the columns, which can be received by a receive system including appropriate amplifiers. The orthogonal frequencies can be detected by the receiver with a Fourier Transform or filter bank. Separate digitization and signal processing can be implemented for every column. The receiver can measure the quantity of each of the orthogonal transmitted signals present on each column, identifying the rows in touch with each column and may also provide additional (e.g., qualitative) information concerning the touch.

Claims

1. A system comprising:

signal generator operable to generate a plurality of signals having a plurality of orthogonal frequencies, each orthogonal frequency of the plurality of orthogonal frequencies being a different frequency, the plurality of signals for simultaneously driving a plurality of rows of a touch sensor, wherein frequencies of the plurality of orthogonal frequencies are spaced by a frequency that is at least the reciprocal of a measurement period of the touch sensor.

2. The system of claim 1, wherein the system further comprises:

the touch sensor, the touch sensor comprising;

the plurality of rows, wherein each of the plurality of rows is coupled to receive a different signal of the plurality of stimulation signals from the signal generator; and

a plurality of columns capacitively coupled to the plurality of rows; and

receiver coupled to receive a plurality of signals from the plurality of columns and operable to detect a touch event associated with the touch sensor based on the received plurality of signals.

3. The system of claim 2, wherein the receiver comprises, for each of the plurality of columns:

an amplifier coupled to receive a signal of the plurality of touch signals from a column;

a digitizer coupled to receive an output of the amplifier;

a signal processor adapted to perform a Fourier transform on an output of the digitizer, the Fourier transform comprising;

a plurality of demodulation mixers, wherein the plurality of demodulation mixers are operable to demodulate the output of the digitizer by multiplying the output of the digitizer by a plurality of signals having frequencies corresponding to the plurality of orthogonal frequencies; and

a plurality of integrators, each integrator coupled to receive a demodulated signal output by one of the plurality of demodulation mixers and operable to integrate the received demodulated signal over the measurement period of the touch sensor.

4. The system of claim 2, wherein the signal processor for each of the plurality of columns are the same signal processor.

5. The system of claim 1, wherein the signal generator comprises, for each of the plurality of signals:

a digital generator;

a digital to analog converter coupled to receive an output of the digital generator; and

a transmitter coupled to receive an output of the digital to analog converter and coupled to output a signal of the plurality of signals to a row of the plurality of rows.

6. A system comprising:

a touch sensor comprising;

a first row; and

a second row; and

signal generator coupled to the first and second rows and operable to;

generate on the first row a first signal having a first frequency; and

generate on the second row a second signal having a second frequency, the second frequency different from the first frequency, wherein;

a difference between the first frequency and the second frequency is at least the reciprocal of a measurement period of the touch sensor, and

the signal generator simultaneously generating signals on the first row with the first signal and the second row with the second signal.

7. The system of claim 6, wherein the touch sensor further comprises a plurality of columns capacitively coupled to the first and second rows, and wherein the system further comprises receiver coupled to receive a plurality of signals from the plurality of columns and operable to detect a touch event associated with the touch sensor based on the received plurality of signals.

8. The system of claim 7, wherein the receiver is operable to detect the touch event associated with the touch sensor by:

amplifying the plurality of signals;

converting the amplified plurality of signals into a plurality of digital signals;

performing a Fourier transform on the digital signals, the Fourier transform comprising;

demodulating the plurality of digital signals using a signal having the first frequency and a signal having the second frequency; and

integrating the demodulated plurality of digital signals over the measurement period of the touch sensor.

9. The system of claim 6, wherein the system is included within a computer display, flat panel display, LCD display, plasma display or OLED display.

10. A system comprising:

a touch sensor comprising;

a plurality of rows; and

a column capacitively coupled to the plurality of rows; and

signal generator coupled to the plurality of rows and operable to simultaneously generate on the plurality of rows a plurality of row signals, each row signal of the plurality of row signals having a different frequency, wherein;

the plurality of row signals are spaced by a frequency that is at least the reciprocal of a measurement period of the touch sensor,

the column is operable to generate a column signal in response to the plurality of rows being driven by the row signals, and

the column signal comprises an interference component having a frequency corresponding to a difference in frequency between the frequencies of the row signals.

11. The system of claim 10, wherein the system further comprises receiver coupled to receive the column signal from the column and operable to detect a touch event associated with the touch sensor based on the received column signal.

12. The system of claim 10, wherein the receiver is operable to detect the touch event associated with the touch sensor by:

amplifying the column signal;

converting the amplified column signal into a digital column signal;

performing a Fourier transform on the digital column signal, the Fourier transform comprising;

demodulating the digital column signal using each of the frequencies of the row signals; and

integrating the demodulated digital column signals over the measurement period of the touch sensor.

13. The system of claim 12, wherein after integrating the demodulated digital column signals over the measurement period of the touch sensor, the interference component is substantially zero.

14. The system of claim 10, wherein the frequencies of the row signals are orthogonal.

15. A method for stimulating a touch sensor, the method comprising:

simultaneously transmitting on a plurality of sets of rows a plurality of row signals having orthogonal frequencies, the plurality of row signals comprising a first signal having a first frequency and a second signal having a second frequency different from the first frequency;

receiving a plurality of column signals generated in response to the plurality of row signals;

performing a Fourier transform on the digital column signal, the Fourier transform comprising;

demodulating the plurality of column signals using the orthogonal frequencies of the plurality of row signals; and

integrating the demodulated plurality of column signals over a measurement period of the touch sensor, the measurement period being at least the reciprocal of a difference between the first frequency and the second frequency.

16. The method of claim 15, wherein each of the plurality of sets of rows consists of one row.