MICROPOWER CAP ACITANCE-BASED PROXIMITY SENSOR

• US 20010011894A1
• Filed: 01/07/1999
• Published: 08/09/2001
• Est. Priority Date: 01/07/1999
• Status: Active Grant

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: LEWIS, STEVEN A., HAVEY, GARY D.
• Granted Patent: US 6,307,384 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence

Abstract

The present invention is a proximity detector for an electronic device. The proximity detector utilizes two capacitors which share a common electrode. The two capacitors are located on the housing of the electronic device. The capacitors are arranged so that when the electronic device is used in its normal orientation, a portion of the operator'"'"'s body will occlude one of the capacitors, but not the other. The close proximity of the operator'"'"'s body will change the electric field surrounding the capacitor. Thus, the capacitance of the occluded capacitor will be different than the unencumbered capacitor. A detection circuit is coupled to the capacitors and to the power supply of the device. The circuit uses very little power, and maintains the electronic device in a standby or powered down mode. Only when the circuit detects a difference in the capacitance generated by the two capacitors, will it allow full power to be delivered to the electronic device.

Claims

1. A capacitance based proximity detector for detecting the presence of an object proximate one of a plurality of capacitors, comprising:

a first capacitor;

a second capacitor coupled to the first capacitor; and

a circuit, coupled to the first and second capacitor to detect a capacitance of the first and second capacitors, the circuit providing a first output when the capacitance of the first capacitor is equal to the capacitance of the second capacitor, and a second output when the capacitance of the first capacitor is not equal to the capacitance of the second capacitor.

2. The proximity detector of

claim 1

, further comprising:

an electronic device;

a power supply;

a housing, the housing containing the electronic device, the first capacitor, the second capacitor, the circuit, and the power supply;

wherein the circuit is coupled between the power supply and the electronic device so that power is supplied to the electronic device only when the circuit provides the second output.

3. The proximity detector of

claim 2

, further comprising:

an outer wall, the outer wall providing one surface of the housing; and

the first capacitor is mounted proximate the second capacitor in the outer wall.

4. The proximity detector of

claim 3

, further comprising:

an eyepiece, the eyepiece is coupled to the outer wall and the electronic device;

wherein the first capacitor and the second capacitor are mounted within the outer wall so that when an operator views through the eyepiece, either the first capacitor or the second capacitor, but not both, is occluded by a portion of the operator'"'"'s face, causing an electric field surrounding the first capacitor to be different than an electric field surrounding the second capacitor.

5. The proximity detector of

claim 4

, wherein the electronic device is a digital camera.

6. The proximity detector of

claim 4

, wherein the electronic device is a video camera.

7. The proximity detector of

claim 4

, wherein the electronic device is a monocular scope.

8. The proximity detector of

claim 7

, wherein the monocular scope is a night vision device.

9. The proximity detector of

claim 4

, wherein the electronic device is a binocular device.

10. The proximity detector of

claim 4

, wherein the electronic device is a portable computer display.

11. The proximity detector of

claim 2

, wherein the power supply is a battery.

12. The proximity detector of

claim 11

, wherein the battery is rechargeable.

13. A proximity detector for an electronic device, comprising:

a housing, the housing containing the electronic device;

a power supply, the power supply providing power to the electronic device, and mounted within the housing;

a first electrode, a second electrode and a third electrode mounted in an outer wall of the housing;

a first capacitor, the first capacitor including the first electrode and the second electrode;

a second capacitor, the second capacitor including the second electrode and the third electrode;

a proximity detection circuit coupled to the electronic device and to the power supply, the proximity detection circuit including;

a logic gate driven by a clock, the logic gate coupled to the first capacitor and the second capacitor, and receiving power from the power supply, the logic gate and clock providing an input signal into the first capacitor and the second capacitor;

a first amplifier and filter coupled to the first capacitor for receiving a first signal from the first capacitor, and providing a first output;

a second amplifier and filter coupled to the second capacitor for receiving a second signal from the second capacitor, and providing a second output;

an inverter coupled to the second amplifier and filter, for inverting the second output; and

a summing circuit, the summing circuit coupled to the inverter and the first amplifier and filter, wherein the summing circuit produces a first control signal when the first output is equal to the second output, and produces a second control signal when the first output is not equal to the second output;

wherein, the electronic device only receives full power from the power supply when the summing circuit generates the second output.

14. The proximity detector of

claim 13

, further comprising an eyepiece, the eyepiece coupled to the housing, wherein the first, second, and third electrodes are mounted in the housing in a configuration relative to the eyepiece, so that when an operator views through the eyepiece, two, but only two, of the electrodes are occluded by a portion of the operator'"'"'s face.

15. The proximity detector of

claim 13

, wherein the electronic device is changed from a no-power status to a full power status by the summing circuit.

16. The proximity detector of

claim 13

, wherein the electronic device is changed from a low power status to a full power status by the summing circuit.

17. The proximity detector of

claim 13

, wherein the power supply includes a battery.

18. The proximity detector of

claim 17

, wherein the battery is rechargeable.