Method for using touch signals and a touch unit

• US 20070085553A1
• Filed: 08/29/2006
• Published: 04/19/2007
• Est. Priority Date: 08/29/2005
• Status: Active Grant

• Current Assignee: Frequentis GmbH
• Original Assignee: Frequentis GmbH
• Inventors: Keroe, Nikolaus, Taeubl, Gerhard
• Granted Patent: US 7,633,300 B2
• Time in Patent Office: Days
• US Class Current: 324/713
• 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 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A method for evaluating touch signals on a touch unit which has two resistance foils (1, 2). The current (IX, IY) resulting from applying a given measurement voltage (UX, UY) to at least one of the resistance foils (1, 2) is measured and stored as a desired current value (IXS, IYS). Especially after the presence of at least one touch has been confirmed, the actual current (IX<IY) flowing in the other resistance foil (1, 2) is measured when the test voltage is again applied to at least one of the resistance foils (1, 2), and it is compared with the previously established desired current value (IXS, IYS) for this resistance foil (1, 2). In the event that the actual current (IX, IY) measured in the at least one resistance foil (1, 2) exceeds the desired current value (IXS, IYS), it is judged that a double touch occurred (FIG. 8).

Claims

1. A method for evaluating touch signals applied to an analog resistive touch unit with first and second, spaced-apart resistance foils (1, 2) which have contacts (A, B and B, C, respectively) at their respective opposing end zones arranged in perpendicular directions (X-direction, Y-direction) comprising applying a measurement voltage to at least one of the resistance foils (1, 2) at the end zones (A, B and B, C, respectively), measuring a voltage drop on the other resistance foil in a perpendicular direction thereto, and measuring actual currents (IX, IY) for determining whether a double touch occurred in the resistance foils (1, 2), wherein

(a) a current (IX, IY) is measured which is caused by a given test voltage (UX, UY) being applied to at least one of the resistance foils (1, 2) and is stored as a desired current value (IXS, IYS),

(b) after a determination that at least one touch occurred, the test voltage is applied to at least one of the resistance foils (1, 2), the actual current (IX, IY) in the other resistance foil (1, 2) is measured and compared with the desired current value (IXS, IYS) for this resistance foil (1, 2), and

(c) in the event that the actual current (IX, IY) measured in at least one of the resistance foils (1, 2) is greater than the desired current value (IXS, IYS), especially when it is greater than the given value (LimDT), judging that a double touch occurred.

2. A method according to claim 1 including determining, especially prior to comparing the measured values for the actual current (IX, IY) with the stored desired current value (IXS, IYS), if a touch occurred at all by checking, after applying the measurement voltage (UX, UY) to one of the resistance foils (1, 2), if the current (IX, IY) measured in the other resistance foils (1, 2) is smaller by a given value (LimPress) than the received desired current value (IXS, IYS), and, upon the occurrence thereof, judging that at least one touch occurred.

3. A method according to claim 1 including performing the current measurements and comparisons 100 to 2,000 times, and preferably 200 to 1,000 times per second.

4. A method according to claim 1, including digitizing the measured current values (IX, IY, IXS, IYS) and comparing the digitized current values.

5. A touch unit including a device for determining double touches comprising an analog resistive touch unit with first and second spaced-apart resistance foils (1, 2) which include contacts at respective end zones of the foils that are arranged perpendicular to each other (X-direction, Y-direction), wherein a measurement voltage is applied to the end zones of at least one of the resistance foils for determining the location of the touch and wherein a voltage drop is measured in a perpendicular direction thereto in the other one of the first and second resistance foils,

at least one control and evaluation unit (3) which includes a voltage-current measurement unit (7) for the current flowing in at least one of the resistance foils (1, 2),

the voltage-current measurement unit (7) being adapted to measure the current (IX, IY) caused by applying the given test voltage (UX, UY) in at least one of the resistance foils (1, 2),

a storage device for the received desired current values (IXS, IYS), and

a comparator (5) for comparing, preferably prior to measuring the voltage drop caused in one of the resistance foils (1, 2) by the measurement voltage applied to the other one of the resistance foils (1, 2), the actual current (IX, IY) with the desired current value (IXS, IYS) when the test voltage (UX, UY) is applied to the respective resistance foils (1, 2),

wherein it is judged that a double touch occurred when the resulting actual current (IX, IY) exceeds the desired current value (IXS, IYS) by a given value (LimDT).

6. A touch unit according to claim 5 including a further comparator (6) for determining if at least one of the stored current values (IXS, IYS) exceeds one of the measured current values (IX, IY) by a given value (LimPress) and, if so, judging that a touch occurred.

7. A touch unit according to claim 5 wherein at least one contact point (B, D) of the resistance foils (1, 2) is attached to ground or a zero voltage, if desired via a resistor (RS), and wherein the voltage-current measurement unit (7) is electrically coupled between the contact points (B, D) and the respective resistor (RS).