MULTITOUCH TACTILE DEVICE WITH MULTI FREQUENCY AND BARYCENTRIC CAPACITIVE DETECTION

• US 20140191769A1
• Filed: 12/05/2013
• Published: 07/10/2014
• Est. Priority Date: 12/05/2012
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: CONI, Philippe, ROUZES, Siegfried
• Granted Patent: US 9,453,862 B2
• Time in Patent Office: Days
• US Class Current: 324/679
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• 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 touchpad comprising a plurality of conducting rows and of conducting columns, the said pad being linked to electronic control means. The electronic control means generate two periodic emission voltages emitted at two different frequencies. The analysis of the reception voltages makes it possible to determine the positions of two simultaneous presses on the touchpad, including when the two presses are done on rows or columns that are close. The determination of the presses is performed essentially by calculating the barycentres of the troughs of the reception voltages.

Claims

1. Touchscreen device with projected capacitive detection comprising a matrix touchpad comprising a plurality of conducting rows and of conducting columns, the said pad being linked to electronic control means generating, for each conducting row and for each column, emission voltages and electronic means of reception and analysis of the reception voltages arising from each conducting row and from each column,

the electronic control means generating, for each conducting row arid for each column, a first periodic emission voltage emitted at a first frequency termed the working frequency and a second periodic emission voltage emitted at a second frequency termed the discrimination frequency, different from the first frequency:

in the absence of any press, the value of the working frequency being low enough to cause very low variations of the reception voltages at this working frequency and the value of the discrimination frequency being high enough to cause appreciable variations of the reception voltages dependent on the rows and columns at this discrimination frequency;

the electronic reception and analysis means being arranged so as to determine, for each row and for each column;

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

if, as a function of predetermined values, the values of the two reception voltages are representative of two simultaneous presses on the touchpad and the location of these two presses on the two rows and on the two columns concerned;

wherein, in the case of two simultaneous presses, the first press situated at a first crossover of a first row and of a first column and the second press situated at a second crossover of a second row and of a second column, location of the two presses is performed by means;

of first analysis means making it possible to pinpoint the “

troughs”

of the reception voltages for the first frequency and the “

troughs”

of the reception voltages for the second frequency corresponding to the voltage variations of the two presses;

of second analysis means making it possible to calculate the barycentres of the voltage “

troughs”

;

of third analysis means making it possible to determine, on the basis of the knowledge of the barycentres, the first row and the first column corresponding to the first press and the second row and the second column corresponding to the second press.

2. Touchscreen device according to claim 1, wherein, when the first row is in the neighbourhood of the second row or when the first column is in the neighbourhood of the second column in such a way that the two variations in voltage corresponding to the two close rows or to the two close columns form one single trough, location of the two presses is performed by means:

of the first analysis means making it possible to pinpoint the “

troughs”

of the reception voltages for the first frequency and the “

troughs”

of the reception voltages for the second frequency corresponding to the voltage variations of the two presses on the two neighbour rows or on the two neighbour columns;

of second analysis means making it possible to calculate the barycentres of the two voltage “

troughs”

;

of third analysis means making it possible to determine on the basis of the knowledge of the said two barycentres the first neighbour row and the second neighbour row or the first neighbour column and the second neighbour column corresponding to the first press or to the second press.

3. Touchscreen device according to claim 1, wherein the electronic means of reception and analysis of the reception voltages comprise two synchronous demodulators, the first demodulator working at the working frequency, the second demodulator at the discrimination frequency.

4. Touchscreen device according to claim 1, wherein the electronic reception and analysis means comprise:

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

comparison means establishing, for each row and for each column, the discrepancies between the measured values of the reception voltages and the stored values of the reception voltages so as to determine whether the measured discrepancies are representative of a press on the row or on the column concerned.

5. Touchscreen device according to claim 1, wherein the working frequency lies between 100 kHz and 500 kHz and in that the discrimination frequency lies between 500 kHz and 5 MHz.