Micropower capacitance-based proximity sensor

• US 6,307,384 B2
• Filed: 01/07/1999
• Issued: 10/23/2001
• Est. Priority Date: 01/07/1999
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Lewis, Steven A., Havey, Gary D.
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): KERVEROS, DEMETRIOS C
• Application Number:
  US09/227,140
• Publication Number:
  US 20010011894A1
• Time in Patent Office: 1,020 Days
• Field of Search: 324/662, 324/671, 324/452, 348/341, 348/333, 396/114
• 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 power control device for detecting the presence of a users body in a predetermined position proximate one of a plurality of capacitors and thus causing power to be supplied, the power control device comprising:

an electronic device requiring power for operation;

a power supply for selectively supplying power to the electronic device;

a first capacitor within the electronic device proximate the predetermined position;

a second capacitor coupled and positioned adjacent to the first capacitor such that the presence of the user'"'"'s body in the predetermined position will effect the capacitance of the first capacitor or the second capacitor, but not both; and

a circuit, coupled to the first and second capacitor to detect a capacitance mismatch between the first and second capacitors, the circuit providing a first output when the capacitance mismatch does not exist, and a second output when the capacitance mismatch does exist, 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.

2. The power control device of claim 1, further comprising:

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

3. The power control device of claim 2, further comprising:

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

the first capacitor and the second capacitor are proximate the outer wall.

4. The power control device of claim 3, further comprising:

an eyepiece, the eyepiece coupled to the outer wall and the electronic device, the eyepiece positioned adjacent both the first capacitor and the second capacitor such that the first capacitor and the second capacitor are on opposite sides of the eyepiece 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 thus causing the capacitance mismatch.

5. The power control device of claim 4, wherein the electronic device is a digital camera.

6. The power control device of claim 4, wherein the electronic device is a video camera.

7. The power control device of claim 4, wherein the electronic device is a monocular scope.

8. The power control device of claim 7, wherein the monocular scope is a night vision device.

9. The power control device of claim 4, wherein the electronic device is a binocular device.

10. The power control device of claim 4, wherein the electronic device is a portable computer display.

11. The power control device of claim 2, wherein the power supply is a battery.

12. The power control device of claim 11, wherein the battery is rechargeable.

13. A proximity detector for detecting the presence of a user in a predetermined location adjacent to 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 comprised of the first electrode and the second electrode;

a second capacitor comprised of the second electrode and the third electrode, the first electrode, second electrode and third electrode positioned within the housing such that the presence of the user at the predetermined location will effect either the first capacitor or the second capacitor, but not both;

a proximity detection circuit coupled to the electronic device, the first capacitor, the second capacitor, 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.

19. A proximity based power system for use in automatically activating an electronic device in response to the presence of a user at a predetermined location relative to the electronic device, the power system comprising:

a first electrode mounted within a housing;

a second electrode mounted with the housing on a first side of the first electrode;

a third electrode mounted within the housing on a second side of the first electrode, the second side being opposite the first side;

a capacitance mismatch detection circuit for monitoring a first capacitance level between the first electrode and the second electrode, and for monitoring a second capacitance between the first electrode and the third electrode, the capacitance mismatch detection circuit for producing a first output signal when the first capacitance and the second capacitance are substantially equal, and producing a second output signal when the first capacitance and the second capacitance are mismatched due to the presence of the user at the predetermined location;

a power supply; and

a power controller coupled to the output of the power supply and the mismatch detection circuit, wherein the power controller will allow power to be applied to the electronic device when the second output signal is present.

20. The proximity detector of claim 19, wherein the electronic device is a digital camera and the predetermined location at an eyepiece of the digital camera.

21. The proximity detector of claim 19, wherein the electronic device is a video camera and the predetermined location at an eyepiece of the video camera.

22. The proximity detector of claim 19, wherein the electronic device is a monocular scope and the predetermined location at an eyepiece of the monocular scope.

23. The proximity detector of claim 22, wherein the monocular scope is a night vision device.

24. The proximity detector of claim 19, wherein the electronic device is a binocular device and the predetermined location at an eyepiece of the binocular device.

25. The proximity detector of claim 19, wherein the electronic device is a portable computer display and the predetermined location at an eyepiece of the portable computer display.

26. The proximity detector of claim 19, wherein the power supply is a battery.

27. The proximity detector of claim 26, wherein the battery is rechargeable.

28. A power up system for activating an electronic device when the user is detected to be using an eyepiece of the electronic device and deactivating the electronic device when the user is no longer using the eyepiece, the power up system comprising:

a clocking circuit for providing an driving signal;

a first capacitor positioned adjacent the eyepiece and attached to the clocking circuit so as to receive the driving signal;

a second capacitor positioned adjacent the eyepiece and opposite the first capacitor, the second capacitor is attached to the clocking circuit so as to receive the driving signal, the first capacitor and the second capacitor having substantially equal capacitance values when a user is not using the eye piece, but having different capacitance values when the user is using the eyepiece;

a first amplifier coupled to the first capacitor to receive a first capacitor signal from the first capacitor and produce a first amplifier output signal proportional to the first capacitor signal;

a second amplifier coupled to the first capacitor to receive a second capacitor signal from the second capacitor and produce a second amplifier output signal proportional to the second capacitor signal;

an inverter coupled to the second amplifier to receive the second amplifier output signal and produce an inverted signal; and

a summing circuit for receiving the first amplifier output and the inverted signal and producing a summing output equal to the sum of the first amplifier output and the inverted signal, wherein the summing output is substantially zero when the first capacitance and second capacitance are substantially equal, and wherein the summing output is a non-zero value when either the first capacitor or the second capacitor are occluded by the user, the non-zero value being output to the electronic device causing the electronic device to be activated.