Multitouch tactile device with multi frequency and barycentric capacitive detection

• US 9,453,862 B2
• Filed: 12/05/2013
• Issued: 09/27/2016
• Est. Priority Date: 12/05/2012
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Coni, Philippe, Rouzes, Siegfried
• Primary Examiner(s): Baldridge, Benjamin M
• Application Number:
  US14/098,407
• Publication Number:
  US 20140191769A1
• Time in Patent Office: 1,027 Days
• Field of Search: 324/679
• US Class Current: 1/1
• 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 matrix touchpad linked to an emission voltages electronic control system and a reception voltages electronic system. The emission voltages electronic control system generates two periodic emission voltages emitted at two different frequencies. The analysis of the reception voltages, by the reception voltages electronic system, 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 barycenters of the troughs of the reception voltages.

Claims

1. A touchscreen device with projected capacitive detection comprising:

a matrix touchpad comprising a plurality of conducting rows and of conducting columns, the matrix touchpad linked to an emission voltages electronic control system that generates, for each conducting row and for each column, emission voltages, and a reception voltages electronic system that receives and analyzes reception voltages arising from each conducting row and from each column,

wherein the emission voltages electronic control system is configured to generate, for each conducting row and for each conducting column, a first periodic emission voltage at a first frequency and a second periodic emission voltage at a second frequency different from the first frequency;

wherein, in the absence of a press on the touchscreen, the first periodic emission voltage at the first frequency causes the reception voltages to have minimal variations; and

wherein the second emission voltage at the second frequency causes the reception voltages to have distinguishable variations dependent on the rows and columns;

wherein the reception voltages electronic system determines, for each row and for each column, the value of a first reception voltage at the first frequency and the value of a second reception voltage at the second frequency; and

if the values of the two reception voltages are determined by the reception voltages electronic system to be representative of two simultaneous presses on the touchpad, location of the two presses is performed,

wherein a first analysis determines the minima of the reception voltages for the first frequency and the minima of the reception voltages for the second frequency corresponding to the voltage variations caused by the two presses on the touchscreen; and

a second analysis calculates positions of barycentres of the voltage minima; and

a third analysis determines, based on the positions 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. The touchscreen device according to claim 1, wherein, when the first row is adjacent to the second row or when the first column is adjacent to the second column in such a way that the two variations in voltage corresponding to the two adjacent rows or to the two adjacent columns form one single minimum, location of the two presses is performed, wherein

the first analysis determines the minima of the reception voltages for the first frequency and the minima of the reception voltages for the second frequency corresponding to the voltage variations of the two presses on the two adjacent rows or on the two adjacent columns;

the second analysis calculates the positions of the barycentres of the two voltage minima;

the third analysis determines, based on the said positions of the two barycentres, the first adjacent row and the second adjacent row or the first adjacent column and the second adjacent column corresponding to the first press or to the second press.

3. The touchscreen device according to claim 1, wherein the reception voltages electronic system comprises two synchronous demodulators, wherein the first demodulator operates at the first frequency, and the second demodulator operates at the second frequency.

4. The touchscreen device according to claim 1, wherein the reception voltages electronic system comprises:

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

wherein the reception voltages electronic system performs a comparison analysis establishing, for each row and for each column, the differences between the measured values of the reception voltages and the stored values of the reception voltages so as to determine whether the differences represent a press on the row or on the column.

5. The touchscreen device according to claim 1, wherein the first frequency is between 100 kHz and 500 kHz and the second frequency is between 500 kHz and 5 MHz.