Sensing apparatus and method, and program therefor

• US 8,106,893 B2
• Filed: 09/08/2008
• Issued: 01/31/2012
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Kinoshita, Masahiro, Fujita, Hiroyuki, Horiuchi, Takeshi, Sumino, Teppei, Kurosawa, Seiichi
• Primary Examiner(s): Beck, Alexander S
• Assistant Examiner(s): RAYAN, MIHIR K
• Application Number:
  US12/206,409
• Publication Number:
  US 20090073140A1
• Time in Patent Office: 1,240 Days
• Field of Search: 324/658, 324/669, 345/173
• US Class Current: 345/178
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/94026 Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

Human contact/non-contact is detected speedily and accurately. A measurement section measures capacitance of each of sites to which a plurality of electrodes are connected where a human body touches, a comparison section compares the capacitance with a threshold value for each contacting electrode, and a control section determines whether a human body has come in contact based on the comparison result. A reference value calculation section calculates a reference value serving as electrode-specific reference capacitance based on the measurement results corresponding to the plurality of electrodes cumulatively stored in a storage section, a difference calculation section calculates an absolute difference value between the electrode-specific reference capacitance and a plurality of measurement results, and a threshold value adjustment section adjusts the threshold value by subtracting from the electrode-specific threshold value a value of the sum of the calculated absolute difference value for each of the electrodes other than the absolute difference value of each of the electrodes. The present invention can be applied to a touch sensor.

Claims

1. A sensing apparatus comprising:

a measurement section that measures capacitance of each of a plurality of first electric capacitors having unknown capacitance;

a plurality of contact sections that are electrically connected to the plurality of first electric capacitors and that a human body disposed proximally contacts directly or indirectly through an insulator;

a determination section that determines whether the human body has contacted the contact section either directly or indirectly based on a result of comparison between the capacitance of the plurality of first electric capacitors measured by the measurement section and a threshold value for each of the plurality of first electric capacitors;

a storage section that cumulatively stores a result of measurement for each of the plurality of first electric capacitors, the result of measurement being the result of measurement by the measurement section;

a reference capacitance calculation section that calculates reference capacitance for each of the plurality of first electric capacitors based on the result of measurement stored in the storage section;

a difference calculation section that calculates an absolute difference value between the reference capacitance for each of the plurality of first electric capacitors and the result of measurement measured by the measurement section for each of the plurality of first electric capacitors; and

an adjustment section that adjusts the threshold value for each of the plurality of first electric capacitors based on a sum of the absolute difference value of the other first electric capacitors in the plurality of first electric capacitors calculated by the difference calculation section.

2. The sensing apparatus according to claim 1, further comprising:

a third electric capacitor whose first end is connected to a second end of a circuit whose first end is grounded and which connects in series a second electric capacitor having known capacitance with the first electric capacitors and whose second end is grounded, to apply a charging voltage of the third electric capacitor itself to the second end of the circuit, so as to charge the first electric capacitors and a plurality of second electric capacitors identical to the second electric capacitor having the known capacitance and respectively corresponding to the first electric capacitors;

a first discharge section that discharges the third electric capacitor partly and the second electric capacitor totally;

a second discharge section that discharges the first electric capacitors totally at substantially the same timing as the first discharge section;

a counter section that measures the number of times of discharging by the first discharge section and the second discharge section; and

a comparison section that compares a charging voltage for the first electric capacitors and a reference voltage,

wherein in a case where discharging is repeated by the first and second discharge sections and when a result of comparison by the comparison section indicates that the charging voltage for the first electric capacitors agrees with the reference voltage or smaller than the reference voltage, the measurement section calculates the capacitance of the first electric capacitors based on the current number of times of discharging measured by the counter section, thereby measuring the capacitance of the first electric capacitors.

3. The sensing apparatus according to claim 2, wherein the first discharge section discharges the third electric capacitor which has been charged for a predetermined time through a resistor connected in series with the third electric capacitor, to discharge the third electric capacitor partly.

4. The sensing apparatus according to claim 3, further comprising a charge section that charges the third electric capacitor at a predetermined charging voltage, wherein the charge section charges the third electric capacitor directly.

5. The sensing apparatus according to claim 3, further comprising a charge section that charges the third electric capacitor at a predetermined charging voltage,

wherein the first discharge section has a first end thereof grounded and a second end thereof connected between the circuit and the resistor, and

the charge section charges the third electric capacitor from the same position as the second end of the first discharge section.

6. The sensing apparatus according to claim 5, further comprising a diode in parallel with the resistor and in a forward direction toward the third electric capacitor.

7. The sensing apparatus according to claim 2, further comprising a switch section that switches one of the second electric capacitors having the known capacitance and the plurality of first electric capacitors to connect them in series.

8. The sensing apparatus according to claim 2,

wherein the second electric capacitor further includes an electrode, and

the electrode is contacted by a human body directly or indirectly through an insulator.

9. The sensing apparatus according to claim 1, wherein the adjustment section adjusts the threshold value by subtracting from the threshold value for each of the first electric capacitors a value of the sum of the absolute difference value calculated by the difference calculation section for each of the plurality of first electric capacitors other than the absolute difference value of each of the first electric capacitors.

10. A sensing method comprising:

a measurement step of measuring capacitance of each of a plurality of first electric capacitors having unknown capacitance;

a determination step of determining whether a human body has contacted a contact section either directly or indirectly based on a result of comparison between the capacitance of the plurality of first electric capacitors measured by a measurement section and a threshold value for each of the plurality of first electric capacitors;

a storage step of cumulatively storing a result of measurement for each of the plurality of first electric capacitors, the result of measurement being the result of measurement through processing of the measurement step;

a reference capacitance calculation step of calculating reference capacitance for each of the plurality of first electric capacitors based on the result of measurement stored through processing of the storage step;

a difference calculation step of calculating an absolute difference value between the reference capacitance for each of the plurality of first electric capacitors and the result of measurement measured through processing of the measurement step for each of the plurality of first electric capacitors; and

an adjustment step of adjusting the threshold value for each of the plurality of first electric capacitors based on a sum of the absolute difference value of the other first electric capacitors in the plurality of first electric capacitors calculated through processing of the difference calculation step.

11. A non-transitory computer readable medium that causes a computer to perform a method, comprising:

a measurement step of measuring capacitance of each of a plurality of first electric capacitors having unknown capacitance;

a determination step of determining whether a human body has contacted a contact section either directly or indirectly based on a result of comparison between the capacitance of the plurality of first electric capacitors measured by a measurement section and a threshold value for each of the plurality of first electric capacitors;

a storage step of cumulatively storing a result of measurement for each of the plurality of first electric capacitors, the result of measurement being the result of measurement through processing of the measurement step;

a reference capacitance calculation step of calculating reference capacitance for each of the plurality of first electric capacitors based on the result of measurement stored through processing of the storage step;

a difference calculation step of calculating an absolute difference value between the reference capacitance for each of the plurality of first electric capacitors and the result of measurement measured through processing of the measurement step for each of the plurality of first electric capacitors; and

an adjustment step of adjusting the threshold value for each of the plurality of first electric capacitors based on a sum of the absolute difference value of the other first electric capacitors in the plurality of first electric capacitors calculated through processing of the difference calculation step.