Multitouch touch-sensitive device with multifrequency capacitive detection

• US 9,092,100 B2
• Filed: 06/15/2012
• Issued: 07/28/2015
• Est. Priority Date: 06/17/2011
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Sontag, Yves, Coni, Philippe
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): Patel, Sanjiv D
• Application Number:
  US13/525,235
• Publication Number:
  US 20120319993A1
• Time in Patent Office: 1,138 Days
• Field of Search: 345173-174, 178/18.06
• US Class Current: 1/1
• 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 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

The general field of the invention is that of touchscreen devices with projected capacitive detection comprising a matrix-form touch pad comprising conductive rows and columns, said pad being linked to control means and electronic reception and analysis means. The control means generate, for each conductive row and column, a first periodic emission voltage emitted at a first working frequency and a second periodic emission voltage emitted at a second discrimination frequency, different from the first frequency. The electronic reception and analysis means are arranged so as to determine, for each row and for each column, the impedance of a first reception voltage at the working frequency and the impedance of a second reception voltage at the discrimination frequency. According to predetermined values, the values of the two impedances are representative of a touch on the touch pad and its location on the row or on the column concerned.

Claims

1. A dual touchscreen device with projected capacitive detection comprising a matrix-form touch pad comprising a plurality of conductive rows and conductive columns, the pad being linked to:

electronic control means generating, for each conductive row and column, emission voltages and;

electronic reception and analysis means for receiving and electronically analyzing reception voltages from each conductive row and column, wherein;

the electronic control means generate, for each conductive row and column, a first periodic emission voltage emitted at a first frequency denoted working frequency and a second periodic emission voltage emitted at a second frequency denoted discrimination frequency that is different from the first frequency;

the electronic reception and analysis means are arranged to determine, for each row and for each column;

a first reception voltage at the working frequency and a second reception voltage at the discrimination frequency;

when, according to predetermined values, the first and second reception voltages are representative of at least a touch on the touch pad and a location of the touch on the row and/or on the column concerned,

the working frequency being sufficiently low to provoke very small variations of the reception voltages at the working frequency due to changes in a resistive portion of an impedance of the reception voltages and the discrimination frequency being sufficiently high to provoke significant variations of the reception voltages at the discrimination frequency due to changes in the resistive portion of the impedance, the variations of the resistive portion being representative of the location of at least the touch,

when the touch includes a simple touch, a position of the touched row and/or column is computed by the electronic reception and analysis means based on a weighted barycentre around the row signal and the column signal of maximum deviation, a doublet of points giving a coordinate of the touch;

when the touch includes at least two aligned touches, a position of the touched row and/or that is common to the two aligned touches is computed by the electronic reception and analysis means, a triplet of points giving coordinates of the two aligned touches; and

when the touch includes at least two non-aligned touches, a quadruplet of points is measured at the working frequency and at the discrimination frequency, a variation of a signal following a variation of the working frequency and/or the discrimination frequency is used by the electronic reception and analysis means to determine a rejection of a ghost and the quadruplet of points giving coordinates of the at least two non-aligned touches.

2. The dual touchscreen device as claimed in claim 1, wherein the electronic reception and analysis means comprise two synchronous demodulators, the first demodulator working at the working frequency, the second demodulator at the discrimination frequency.

3. The dual touchscreen device as claimed in claim 1, wherein the electronic reception and analysis means comprise:

a table of stored values of the reception voltages at the working frequency of each row and of each column in the absence of any touch;

electronic comparison means establishing, for each row and for each column, deviations between measured values of the reception voltages and the stored values of the reception voltages to determine whether the deviations are representative of a touch on the row and/or on the column concerned.

4. The dual touchscreen device as claimed in claim 1, wherein the working frequency is between 100 kHz and 500 kHz and the discrimination frequency is between 500 kHz and 5 MHz.

5. The dual touchscreen device as claimed in claim 2, wherein the electronic reception and analysis means comprise:

a table of stored values of the reception voltages at the working frequency of each row and of each column in the absence of any touch;

electronic comparison means establishing, for each row and for each column, deviations between measured values of the reception voltages and the stored values of the reception voltages to determine whether the deviations are representative of a touch on the row and/or on the column concerned.