Proximity detector and proximity detecting method

• US 20080265914A1
• Filed: 04/24/2008
• Published: 10/30/2008
• Est. Priority Date: 04/24/2007
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Matsushima, Kenichi
• Granted Patent: US 8,106,668 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2017/9613 using two electrodes per touch switch
• 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
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches

Abstract

A differential electrode is charged and discharged in the opposite phases. By obtaining the sum of stray capacitances of the differential electrode from charge/discharge characteristics, the approach or the position of an object is detected based on the stray capacitances from which noise is cancelled.

Claims

1. A proximity detector for detecting approach of an object based on a stray capacitance, comprising:

a differential electrode changing an apparent stray capacitance by the approach of the object;

a stray capacitance detector for repeatedly charging and discharging the differential electrode in opposite phases to obtain an apparent composite stray capacitance of the differential electrode; and

a proximity calculator for detecting the approach of the object based on the apparent composite stray capacitance.

2. A proximity detector for detecting approach of an object based on a stray capacitance, comprising:

a differential electrode changing an apparent stray capacitance by the approach of the object;

an individual capacitance detector for detecting an individual stray capacitance of the differential electrode based on a stray capacitance of the differential electrode, obtained by repeatedly charging and discharging the differential electrode in opposite phases, and a stray capacitance of the differential electrode, obtained by repeatedly charging and discharging the differential electrode in the same phase; and

a proximity calculator for detecting the approach of the object based on the individual stray capacitance.

3. A proximity detector for detecting at least one of approach and position of an object based on a stray capacitance, comprising:

a plurality of differential electrodes arranged on a support;

a stray capacitance detector for repeatedly charging and discharging each of the plurality of differential electrodes in opposite phases to obtain a composite stray capacitance of each of the plurality of differential electrodes; and

a proximity calculator for computing at least one of the approach and the position of the object based on the composite stray capacitance of each of the plurality of differential electrodes.

5. A proximity detector according to claim 3, wherein the plurality of differential electrodes is arranged in one of a uniaxial positional detection direction and multiple axial positional detection directions.

6. A proximity detector according to claims 3, wherein the differential electrode comprises at least two multiple element electrodes, each of the multiple electrodes has one of a positive attribute and a negative attribute, and the element electrode having the same attribute included in the differential electrode is electrically connected to one corresponding terminal.

7. A proximity detector according to claim 3, wherein the plurality of differential electrodes are systematically grouped, each of the plurality of differential electrodes comprises at least two multiple element electrodes, each of the multiple electrodes has one of a positive attribute and a negative attribute, and element electrodes having the same attribute in the same group are electrically connected to the same corresponding terminal.

8. A proximity detector according to claim 6, wherein the multiple element electrodes constituting the differential electrode are arranged in one of substantially parallel to each other and a twisted wire pattern.

9. A proximity detector according to claim 6, wherein the multiple element electrodes constituting the differential electrode are arranged to alternate the positive attribute and the negative attribute.

10. A proximity detector according to claim 6, wherein the multiple element electrodes constituting the differential electrode are arranged in a zigzag pattern.

11. A proximity detector according to claim 3, wherein each of the plurality of differential electrodes is present on the support to correspond to a coordinate value on two axes, and a differential electrode corresponding to the coordinate value on a first coordinate axis and a differential electrode corresponding to the coordinate value on a second coordinate axis are connected to exterior of the support without crossing each other.

12. A proximity detector according to claim 3, wherein each of the plurality of differential electrodes comprises multiple element electrodes, and a distance between element electrodes simultaneously charged and discharged in the same phase is smaller than a distance between element electrodes which are not simultaneously charged and discharged in the same phase.

13. A proximity detector according to claim 3, wherein the stray capacitance detector comprises:

a differential charger/discharger for repeatedly charging and discharging the differential electrode in opposite phases; and

a capacitance accumulation/composition unit for obtaining a composite stray capacitance of the differential electrode from a characteristic of one of the repeated charge, the repeated discharge, and the repeated charge/discharge for the differential electrode.

14. A proximity detector according to claim 13, wherein the differential charger/discharger comprises calculator for charging and discharging a capacitor corresponding to the stray capacitance when no object is approaching the differential electrode and subtracting the charge/discharge characteristic for the capacitor from the charge/discharge characteristic for the differential electrode.

15. A proximity detector according to claim 13, wherein the differential charger/discharger comprises:

a first charger/discharger; and

a second charger/discharger, and

wherein a phase of charge/discharge by the first charger/discharger is opposite to a phase of charge/discharge by the second charger/discharger.

16. A proximity detector according to claim 15, wherein each of the first charger/discharger and the second charger/discharger comprises:

a DC power supply for supplying an electric charge;

a selector switch to be connected during the charge; and

a selector switch to be connected during the discharge.

17. A proximity detector according to claim 15, wherein each of the first charger/discharger and the second charger/discharger comprises:

AC power supply for supplying an electric charge; and

an electric resistor for increasing an impedance of the AC power supply, and

wherein a phase of the AC power supply of the first charger/discharger is opposite to a phase of the AC power supply of the second charger/discharger.

18. A proximity detector according to claim 13, wherein the capacitance accumulation/composition unit comprises:

a first accumulation unit for accumulating a characteristic of one of the charge, the discharge, and the charge/discharge by the first charger/discharger;

a second accumulation unit for accumulating a characteristic of one of the charge, the discharge, and the charge/discharge by the second charger/discharger; and

a capacitance calculator for obtaining a composite stray capacitance of the differential electrode from the characteristics accumulated in the first accumulation unit and the second accumulation unit.

19. A proximity detector according to claim 18, wherein each of the first accumulation unit and the second accumulation unit comprises:

a capacitor for accumulating an electric charge from one of the differential charger/discharger and the differential electrode; and

a switch for connecting the capacitor to an initial voltage to initialize the capacitor.

20. A proximity capacitor according to claim 18, wherein each of the first accumulation unit and the second accumulation unit comprises

a detector for detecting a waveform of the charge/discharge repeated by the differential charger/discharger for the differential electrode;

and

a filter for filtering an output from the detector.

4. A proximity detector for detecting at least one of approach and position of an object based on a stray capacitance, comprising:

a plurality of differential electrodes arranged on a support;

an individual capacitance detector for detecting an individual stray capacitance of each of electrodes constituting each of the plurality of differential electrodes from a stray capacitance of each of the plurality of differential electrodes, obtained by repeatedly charging and discharging each of the plurality of differential electrodes in opposite phases, and a stray capacitance of each of the plurality of differential electrodes, obtained by repeatedly charging and discharging each of the plurality of differential electrodes in the same phase; and

a proximity calculator for computing at least one of the approach and the position of the object based on the individual stray capacitances of the electrodes of the plurality of differential electrodes.

21. A proximity detecting method of detecting approach of an object based on a stray capacitance, comprising:

a stray capacitance detection step of repeatedly charging and discharging a differential electrode for changing an apparent stray capacitance by the approach of the object in opposite phases to obtain an apparent composite stray capacitance of the differential electrode; and

a proximity computation step of detecting the approach of the object based on the apparent composite stray capacitance.

22. A proximity detecting method of detecting approach of an object based on a stray capacitance, comprising:

an individual capacitance detection step of detecting an individual stray capacitance of a differential electrode for changing an apparent stray capacitance by the approach of the object based on a stray capacitance of the differential electrode, obtained by repeatedly charging and discharging the differential electrode in opposite phases, and a stray capacitance of the differential electrode, obtained by repeatedly charging and discharging the differential electrode in the same phase; and

a proximity computation step of detecting the approach of the object based on the individual stray capacitance.

23. A proximity detecting method of detecting at least one of approach and position of an object based on a stray capacitance, comprising:

a stray capacitance detection step of repeatedly charging and discharging each of a plurality of differential electrodes arranged on support in opposite phases to obtain a composite stray capacitance of each of the plurality of differential electrodes; and

a proximity computation step of computing at least one of the approach and the position of the object based on the composite stray capacitance of each of the plurality of differential electrodes.

25. A proximity detecting method according to claim 23, wherein the stray capacitance detection step comprises:

a differential charge/discharge step of repeatedly charging and discharging the differential electrode in opposite phases; and

a capacitance accumulating/combining step of obtaining a composite stray capacitance of the differential electrode from a characteristic of one of the repeated charge, the repeated discharge, and the repeated charge/discharge for the differential electrode.

26. A proximity detecting method according to claim 25, wherein the differential charge/discharge step comprises a computation step of subtracting the charge/discharge characteristic for a capacitor corresponding to the stray capacitance when no object is approaching the differential electrode, from the charge/discharge characteristic for the differential electrode.

27. A proximity detecting method according to claim 25, wherein the differential charge/discharge step comprises:

a first charge/discharge step; and

a second charge/discharge step, and

wherein a phase of charge/discharge in the first charge/discharge step is opposite to a phase of charge/discharge in the second charge/discharge step.

28. A proximity detecting method according to claim 27, wherein the capacitance accumulating/combining step comprises:

a first accumulation step of accumulating a characteristic of one of the charge, the discharge, and the charge/discharge in the first charge/discharge step;

a second accumulation step of accumulating a characteristic of one of the charge, the discharge, and the charge/discharge in the second charge/discharge step; and

a capacitance computation step of obtaining a composite stray capacitance of the differential electrode from the characteristics accumulated in the first accumulation step and the second accumulation step.

24. A proximity detecting method of detecting at least one of approach and position of an object based on a stray capacitance, comprising:

an individual capacitance detection step of detecting an individual stray capacitance of each of electrodes constituting each of a plurality of differential electrodes arranged on support from a stray capacitance of each of the plurality of differential electrodes, obtained by repeatedly charging and discharging each of the plurality of differential electrodes in opposite phases, and a stray capacitance of each of the plurality of differential electrodes, obtained by repeatedly charging and discharging each of the plurality of differential electrodes in the same phase; and

a proximity computation step of computing at least one of the approach and the position of the object based on the individual stray capacitances of the electrodes of the plurality of differential electrodes.