AUTOMATIC PERSONNEL INTRUSION ALARM

• US 3,766,539 A
• Filed: 05/01/1972
• Issued: 10/16/1973
• Est. Priority Date: 05/01/1972
• Status: Expired due to Term

• Current Assignee: Bobbie G. Bradshaw, Howard T. Graves
• Original Assignee: Bobbie G. Bradshaw, Howard T. Graves
• Inventors: Graves, Howard T., Bradshaw, Bobbie G.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/249,256
• Time in Patent Office: 533 Days
• Field of Search: 340/258D,228R,228S 250/83.3H 178/DIG.33,DIG.38
• US Class Current: 340/567
• CPC Class Codes: G08B 13/19 using infrared-radiation detection systems G08B13/194 takes precedence
• CPC Class Codes: Y10S 250/01 Passive intrusion detectors

Abstract

The invention is concerned with infrared viewing systems, particularly those operating in the spectral wavelength regions between 3 to 5 and 8 to 14 microns. An alarm is provided for these systems to draw particular attention to subtle or drastic changes in the scene being viewed, thereby reducing operator fatigue or relieving the operator to perform other tasks simultaneously.

Claims

1. In combination with a far infrared viewer wherein an infrared image is scanned by a detector diode to produce a video output signal:

a bandpass AGC amplifier having its input coupled to said viewer to monitor sAid video signal;

a highpass amplifier with a low frequency cutoff at approximately two kilocycles serially coupled to said bandpass amplifier;

a signal detector with a time constant less than three seconds serially coupled to said highpass amplifier; and

an alarm means coupled to said detector to emit an alarm signal when significant changes occur in the video signal amplitude.

2. The combination according to claim 1 wherein said AGC amplifier includes a feedback circuit for automatic gain control with a 3 second time constant.

3. The combination according to claim 1 wherein said signal detector has a time constant of 0.15 second.

4. The combination according to claim 1 wherein said AGC and high-pass amplifiers have a band pass of approximately 40 kilohertz.

5. The combination according to claim 1 wherein said alarm means emits an audible alarm signal.

6. The combination according to claim 1 wherein said alarm means emits a visible signal.