SURVEILLANCE SYSTEM

• US 3,825,676 A
• Filed: 07/07/1972
• Issued: 07/23/1974
• Est. Priority Date: 07/07/1972
• Status: Expired due to Term

• Current Assignee: Paul S. Ramsden Jr
• Original Assignee: Paul S. Ramsden Jr
• Inventors: Ramsden, Paul S. Jr.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/269,663
• Time in Patent Office: 746 Days
• Field of Search: 178/DIG.1,DIG.33,DIG.36,DIG.37,DIG.38,DIG.21 340/258D
• US Class Current: 348/155
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19634 Electrical details of the system, e.g. component blocks for carrying out specific functions
• CPC Class Codes: G08B 13/19676 Temporary storage, e.g. cyclic memory, buffer storage on pre-alarm

Abstract

A surveillance system using a closed circuit television installation is described in which a single integrating circuit is used to obtain two distinct measurements of the average value of the video signal pertaining to a preselected portion of the scene being viewed. The first measurement is made during one or more successive fields and this measurement is stored. The integrating circuit is then reset to zero and a second measurement made during a like number of subsequent fields. The measurement just made is then compared with the stored measurement. Any difference in excess of a predetermined threshold is indicative of the motion of an object within the preselected portion of the scene. Continuous operation can be obtained by resetting the storage device, storing the most recent measurement, resetting the integrating circuit, making another measurement, comparing, etc.

Claims

1. A surveillance system including a closed circuit television arrangement having a camera viewing a scene which includes the area to be protected and having a monitor for displaying an image of the scene viewed by said camera, said system including means for separating the horizontal and vertical synchronizing signals from the video signals generated by said camera, first means responsive to said synchronizing signals for generating a window signal indicative of that portion of the time during each field that a preselected rectangular fraction thereof is being scanned, and second means responsive to said synchronizing signals and said window signal for generating a plurality of sequentially and repetitively occurring timing gates, characterized in that said system includes an integrator, an amplifier connected to the output of said integrator, as storage capacitor, and a comparator having an output and first and second inputs connected to the output of said amplifier and to said storage capacitor respectively, said comparator being for generating a signal at its output when said inputs differ by more than a preselected amount, and means controlled by said timing gates for sequentially resetting said integrator, applying the window portion of said video signal to said integrator, enabling said comparator, removing the charge from said capacitor and connecting the output of said amplifier to said storage capacitor.

2. A surveillance system in accordance with claim 1 further including an alarm circuit connected to the output of said comparator.

3. A surveillance system in accordance with claim 1 in which said gates generated by said second means responsive to said synchronizing signals comprise first, second, third, fourth and fifth successively occurring gates spaced apart by time intervals approximately equal to an integral multiple of the duration of one television field.

4. A surveillance system in accordance with claim 3 in which said means controlled by said gates includes means controlled by said first gate for resetting said integrator, means controlled by said second gate for applying said video signal to said integrator, means controlled by said third gate for enabling said comparator, means controlled by said fourth gate for removing the charge from said capacitor and means controlled by said fifth gate for connecting the outPut of said amplifier to said storage capacitor.

5. A surveillance system in accordance with claim 4 in which each of said first, third, fourth and fifth gates has a duration approximately equal to an integral multiple of the duration of one television field and in which said second gate represents said window signal occurring during an integral multiple of television fields.