SURVEILLANCE SYSTEM

• US 3,740,466 A
• Filed: 12/14/1970
• Issued: 06/19/1973
• Est. Priority Date: 12/14/1970
• Status: Expired due to Term

• Current Assignee: James M. Marshall, James W. Biglow
• Original Assignee: James M. Marshall, James W. Biglow
• Inventors: Marshall, James M., Biglow, James W.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/098,002
• Time in Patent Office: 918 Days
• Field of Search: 178/DIG.33,DIG.3,6.8
• US Class Current: 348/154
• 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 13/19641 Multiple cameras having overlapping views on a single scene
• CPC Class Codes: G08B 13/19669 Event triggers storage or change of storage policy
• CPC Class Codes: G08B 13/19693 using multiple video sources viewed on a single or compound screen
• CPC Class Codes: G08B 26/00 Alarm systems in which substations are interrogated in succession by a central station

Abstract

A method and apparatus by which surveillance can be maintained over a domain for detecting changes of interest in the domain and ignoring other changes. A parameter of the domain under surveillance is scanned resulting in an electrical signal which is sampled. The resulting sample signals each correspond to an individual sample point or line segment in the domain under surveillance and are digitized. Digitized samples are stored in a memory unit. An arithmetic unit based on a Karnaugh mapping technique compares to current sample with a prior sample from the memory unit for the same sample point or segment in the domain and provides an alert signal when these differ by more than a predetermined amount. A plurality of scanning devices may be provided to a monitor. If an alert occurs, an intrusion logic unit determines if an alert signal previously occurred during a prior scanning period for the same scanning device and if so an alarm is actuated and the monitor is switched to display the signal from that scanning device.

Claims

1. In a system for maintaining surveillance over a scene, capable of sensing changes in a parameter of the scene and of discriminating between changes of interest and changes not of interest in the scene, the combination comprising:

scanning means for scanning the scene and producing a scan signal which varies with changes in a sensed parameter of the scene;

sampling means for taking samples from said scan signal, said samples corresponding to spaced, discrete locations in said scene;

digitizing means for digitizing said samples and having K output lines so as to produce for each sample a digitized sample in parallel form;

memory means for storing each said digitized sample and capable of retrieving a stored digitized sample for a particular discrete location in the scene when said location is again scanned by said scanning means, said memory means having K output lines for providing a stored sample in parallel form;

arithmetic means having 2K inputs receiving in parallel the multibit outputs of said digitizing means and memory means and responsive to a difference of preselected magnitude between a digitized sample and a stored sample for the same location in the scene obtained in a prior scan, for producing an alert signal;

output means responsive to a preselected number of alert signals from different scans of said scene for providing an output indicating that a change of interest has taken place in the scene.

2. The system defined in claim 1, in which said digitizing means includes means for generating a time duration proportional to the value of each said sample and means responsive to said time duration for generating a parallel, multi-bit digital value proportional to said time duration and comprising said digitized sample.

3. The system defined in claim 1, in which said memory means includes first shift register means for receiving a newly digitized sample in parallel form and second shift register means for receiving said newly digitized sample in serial form from said first shift register means and for returning same in serial form to said first shift register means after a preselected time delay synchronized with a full cycle of scanning by said scanning means, said first shift register means having outputs for producing said stored sample in parallel form.

4. The system defined in claim 1, in which said arithmetic means comprises at least one digital multiplexer having an output terminal, 2n input terminals and n address terminals wherein signals applied to the address terminals uniquely determine which of said input terminals is connected to said output terminal;

and including means applying to said address terminals signals which include at least a part of one of the digitized sample and stored sample and means for providing to said input terminals functions of at least one variable representing a further portion of the other of said digitized sample and stored sample, wherein said functions are determined in accordance with the relationship of the values of the digitized sample and stored sample required to produce an alert signal.

5. The system defined in claim 1, including means responsive to an alert signal for preventing storage in said memory means of the digitized sample causing such alert signal, means for storing an alert signal while the scanning means responsible for such alert signal completes at least a single scan of the scene and for reading out said stored alert signal during another scan of the scene by said scanning means, and means responsive to the occurrence of an alert signal and a stored alert signal for producing said output.

6. The system defined in claim 1, in which said digitized sample and said stored sample each comprise a multi-bit number, in which the condition for an alert signal comprises a minimum numerical value for the difference of the digitized sample number and the stored sample number;

and wherein said arithmetic means comprises at least one digital multiplexer device having an output terminal, a plurality of address input terminals and a plurality of data input terminals, means for generating functions of at least one of said least significant bits of one of said digitized sample nUmber and said stored sample number and for applying said functions to preselected ones of said data input terminals, and means for applying in parallel to the address inputs of said digital multiplexer remaining ones of said bits of said digitized sample number and said stored sample number.

7. The system defined in claim 1, in which said arithmetic means comprises an array of digital multiplexer devices comprising at least one first digital multiplexer device having data inputs connected to the outputs of a plurality of further digital multiplexer devices, means providing functions of at least one portion of the digital representation for one of said stored sample and said digitized sample to the data inputs of said further digital multiplexer devices and means for providing remaining portions of said stored sample and digitized sample to address inputs of all of said digital multiplexer devices, said functions being selected to provide an output from said first digital multiplexer device which changes when the difference between said digitized sample and stored sample exceeds a preselected difference, said changed output constituting said alert signal.

8. The system defined in claim 1 in which said arithmetic means includes an output and means including a plurality of paralleled data flow paths coupling said parallel inputs of said arithmatic means to said output thereof for producing an alert signal pulse without conversion of said samples to serial digital form.

9. The system defined in claim 1, in which said arithmetic means comprises a first circuit including a digital multiplexer having an output terminal, 2n input terminals and n address terminals wherein signals applied to the address terminals uniquely determine which of said input terminals is connected to said output terminal;

means applying to said address terminals signal which include at least a part of one of the digitized sample and stored sample;

a second circuit having 2n further output terminals connected to said input terminals on a one to one basis and a plurality of further input terminals, means applying to said other input terminals the remaining part of said digitized sample and stored sample and means in said second circuit interconnecting said further input terminals with said further output terminals in accordance with the relationship of the values of the digitized sample and stored sample required to produce an alert signal.

10. The system defined in claim 1 in which said digitized sample and said stored sample each comprise first and second multi-bit numbers, said arithmetic means being arranged for comparing such first and second multi-bit numbers and comprising:

a digital multiplexer having an output terminal, N address terminals and 2N input terminals;

means applying to said address terminals bits of at least one of said first and second multi-bit numbers;

a cooperating circuit having 2N outputs each connected to a corresponding input of said multiplexer;

means applying to corresponding inputs of said cooperating circuit the remaining ones of said bits of said multi-bit numbers, said cooperating circuit including means interconnecting said inputs and outputs thereof in accordance with a Karnaugh map arranged to indicate the desired signals to appear on said output terminal for all values of said first and second numbers, whereby for any values of said first and second numbers a signal will appear on said output terminal of said multiplexer indicating whether the difference between such first and second numbers falls within a preselected limit.

11. The system defined in claim 1, in which a plurality of scanning devices are provided, each capable of scanning a separate scene;

and including monitor means for displaying signals from said scanning devices; and

wherein said output means includes means storing an alert signal from one scanning device discreetly from alert signals from other scannIng devices for producing an output only in response to said number of alert signals generated by processing samples from the same scanning device.

12. The system defined in claim 11, in which said output means includes means providing an intrusion signal in response to said number of alert signals from a given scanning device, intrusion storage means for each scanning device actuable by a corresponding intrusion signal and means responsive to such intrusion storage for switching the scan signal of the one of the scanning devices responsible for said intrusion signal to said monitor means.

13. The system defined in claim 11, including sequencing means cooperable with said sampling means for sampling the scan signals of the several scanning devices in a predetermined sequence, said sequencing means including means coordinated with the scanning rate of said scanning devices for providing coded digital signals and gate means responsive to said coded signals for determining said sampling sequence.

14. The system defined in claim 1 in which said scanning means scans a series of paths across the scene, the length of a given scan path being at least a multiple of the length of a sample to enable detection of changes along the path with substantial definition, the length of a sample substantially exceeding the length of typical random noise spikes for averaging out the contribution of such spikes.

15. The system defined in claim 14 in which the sample length is about 4 microseconds.

16. The system defined in claim 14 in which said digitizing means includes first capacitive storage means for receiving and holding said sample in analog form until said digitizing means is ready to digitize said sample, said digitizing means further including a further capacitive storage means, a current source for charging same, and means establishing a pulse count at a constant rate during charging of said further capacitive storage means to the level of said first capacitive storage means for providing thereafter said digitized sample as an output thereof.

17. In a surveillance system, the combination comprising:

a plurality of scanning devices;

timing means for controlling the scanning of said scanning devices;

sample generator means for generating a sample pattern;

sampling means for applying the sample pattern to the outputs of said scanning devices to provide a series of output samples for a given scanning device;

means responsive to said timing means for providing a sequentially occurring plurality of code signals each assigned to a corresponding scanning device and occurring when the corresponding scanning device is being sampled, each code signal lasting at least one scanning field;

gating means assigned to each scanning device and responsive to said code signals for gating said sample pattern therethrough in said sequence to the sampling means for the corresponding scanning device;

processor means for processing said output samples in digital form and providing an alarm upon occurrence of change of interest in the domain monitored by any scanning device.

18. The system defined in claim 17 in which said processor means includes means responsive to such change of interest for providing an intrusion signal, a plurality of intrusion storage devices assigned to corresponding ones of said scanning devices and each responsive to a corresponding one of said code signals for achieving a storage condition upon occurrence of an intrusion signal from the corresponding scanning device, indicator means responsive to each storage device for indicating which scanning device is responsible for an intrusion signal;

a monitor for displaying the output of a selected scanning device; and

monitor control means responsive to said storage means for switching to said monitor the output said responsible scanning device.

19. The system defined in claim 18 including means responsive to the output of said monitor control means for preventing diSplay on said monitor of more than one scanning device output at a time.

20. The system defined in claim 18 including further indicator means responsive to said monitor control means for indicating which of said scanning devices is responsible for the display on said monitor.

21. In a surveillance system for maintaining surveillance over a domain, capable of discriminating between changes of interest and changes not of interest in the domain, and usable with at least one sensor capable of providing an electrical output signal comprising first and second sets of samples, the samples of said first set being spaced in and representative of the condition of corresponding portions of said domain during a first time period, the samples of said second set being spaced in time in the same manner as the samples of the first set and representative of the condition of the same corresponding portions of said domain during a second time period, corresponding samples of said first and second set differing in accordance with a change in the condition of the corresponding portion of the domain from said first to said second time periods, the combination comprising:

digitizing means for digitizing a sample of said first set and a sample of said second set;

memory means for storing said digitized sample of said first set;

arithmetic means responsive to a difference of preselected magnitude between said stored sample and said corresponding sample of said second set for generating an alert signal, said alert signal indicating a moderate probability that the change in this scene is a change of interest;

logic means responsive to a preselected number of alert signals for providing an output, said output indicating a high probability that a change of interest has occurred in the domain; and

output means responsive to said output of said logic means for indicating an alarm condition in said domain.

22. The system defined in claim 21 in which said sample of said first set and said corresponding sample of said second set each comprise a multi-bit number, said digitizing means having a plurality N of sample output lines for providing the several bits of said digitized sample of said second set in parallel, said memory means having a plurality N of sample output lines for providing the several bits of said stored sample in parallel and said arithmetic means having 2N input lines for receiving the bits of said digitized samples of said second set and said stored sample in parallel.

23. In a surveillance system capable of providing multi-bit numbers representative of a parameter of a domain being monitored and more particularly capable of providing two multi-bit numbers for the same portion of the domain taken at two successive times, apparatus for comparing such first and second multibit numbers, comprising:

at least one digital multiplexer having an output terminal, N address terminals and 2N input terminals;

means applying to said address terminals bits of at least one of said first and second multi-bit numbers and means for generating and applying to the input terminals of said digital multiplexer functions of said remaining ones of said bits of said first and second multi-bit numbers, said functions being selected to provide at said output an indication of whether the difference between said first and second numbers is less than a preselected reference value.

24. The system defined in claim 23, including one first level digital multiplexer and eight second level digital multiplexers, the outputs of each second level multiplexer being connected to a corresponding input of said first level multiplexer, said means for establishing functions comprising NAND and inverter gating circuitry having the least significant bits of one of said first and second numbers applied thereto, said gating circuitry providing Boolean algebra functions of said least significant bits;

means for applying said functions to the input of saiD second level multiplexers in accordance with a Karnaugh map arranged to indicate desired outputs for all values of said first and second numbers;

means connecting first and second portions of the remaining ones of said bits of said first and second numbers to the address inputs of said first and second level multiplexers, respectively, whereby for any values of said first and second numbers an output will appear on said first level multiplexer indicating whether the difference between such first and second numbers falls within a preselected limit.

25. In a surveillance system capable of discriminating between changes of interest and other changes not of interest, both types of changes being sensed by the system, the combination comprising:

a set of N television cameras and a television monitor capable of displaying the output of said cameras;

a timing counter providing a plurality of timing signals of different periods;

sync logic means responsive to said timing signals for generating horizontal and vertical sync signals for said cameras, a sync signal for said monitor having superimposed horizontal and vertical sync components, an end of field signal occurring at the end of each field of scan of each camera and a field signal which cycles once for each two fields of scan;

video amplifier means for each camera for providing video output signals having the same dark level voltage and maximum voltage for each camera;

sample generator means responsive to said timing signals for generating a basic sample pattern and vertical and horizontal masking signals and including means for combining said basic sample signal with said vertical and horizontal masking signals and with a further one of said timing signals for providing a series of sampling signals of length determined by said further timing signal and defining a final sampling pattern of M sample segments per field;

a set of N sample and hold circuits responsive to said video amplifier means for providing samples;

means responsive to said field signal for providing a frame signal which cycles once in every four fields;

decoding means responsive to said field signal and said frame signal and comprising N decoding gates actuable in a predetermined sequence and further gates responsive to the output of said decoding gates for applying said sampling signals to said N sample and hold circuits in said predetermined sequence for sampling the output of said N cameras in sequence for at least one field at a time;

matched first and second electronic switches controlled by sample storage means and ramp storage means, respectively, said sample storage means receiving samples from said sample and hold circuits;

a constant current source for charging said ramp storage means and discharge means for preventing charging of said ramp storage means;

a bistable device responsive to initiation of sampling signals by said sample generator means for achieving an actuated state and A/D counter means responsive to occurrence of said actuated state and to timing signals from said main timing counter unit for producing a parallel digital output;

means responsive to occurrence of said actuated state for disabling said discharge means and enabling said constant current source for charging said ramp storage means;

comparator means responsive to achievement of a preselected relationship between the storage levels in said sample storage means and said ramp storage means for producing an end of conversion signal and for returning said bistable device to a deactuated state, said A/D counter means responding to occurrence of said deactuated state by cessation of counting, the output of said A/D counter comprising a digitized sample;

means responsive to said end of conversion signal and one of said timing signals and including a further counter and further decoding means responsive thereto for providing a series of control pulses including an alert clock pulse, the last of said control pulses resetting said A/D counter means;

memory means for storing digitized samples and including a shiftable data storage device having a capacity of at least N times M bits and an input-output shift register having a serial output and a serial input in circuit with said shiftable memory means, said input-output shift register having parallel inputs connected to the parallel outputs of said A/D counter means and having parallel outputs for providing in parallel bits of a previously stored digitized sample at the time of the parallel input thereto of a new sample for the same location in the field of the same camera;

frame counting means for counting a quantity T of scanning frames of said cameras and at least indirectly responsive to said field signal;

means responsive to the output of said frame counting means for allowing updating of said memory means once every T frames;

combinational logic means responsive to signals corresponding to the least significant digits of said newly digitized one of said digitized samples for producing Boolean functions of variables representing said least significant digits;

an array of digital multiplexers having a plurality of inputs connected to the output of said combinational logic means, address inputs supplied with the remaining ones of said digits of said newly digitized sample and corresponding stored sample from said A/D counter means and memory means, respectively, said inputs of said array being crosswired in a manner to provide an output when the value of the newly digitized sample and stored sample differs by at least a preselected reference number R;

means responsive to said alert clock signal and to said output of said array for providing an alert signal;

first alert signal storage means for storing said alert signal for the remainder of a field and resettable by said end of field signal and second alert signal storage means for receiving an alert signal from said first alert signal storage means upon occurrence of said end of field signal and for storing said alert signal at least until the end of the next field for the camera having produced said alert signal;

means responsive to a further alert signal from a given camera while said first mentioned alert signal for the same camera remains in said second alert signal storage means for producing an intrusion signal;

a set of N intrusion storage devices, each responsive to said intrusion signal and connected to corresponding outputs of said further decoding means for assuming an actuated condition upon occurrence of an intrusion signal resulting from scanning by the corresponding one of said cameras;

a set of N intrusion indicator devices connected to corresponding ones of said intrusion storage devices and responsive to actuation thereof for indicating the one of said cameras responsible for said intrusion signal;

means responsive to actuation of any one of said intrusion storage devices for allowing updating of aid memory means;

a set of N monitor control switches actuable in response to the occurrence of an end of field signal and actuation of a corresponding one of said intrusion storage devices and a set of N video monitor switches each responsive to actuation of a corresponding monitor control switch for coupling the video output of a corresponding one of said cameras to said monitor;

means responsive to an actuated condition of one of said monitor control devices for preventing actuation of others of said monitor control devices for preventing the appearance of double images on said monitor;

alarm and monitor indication means responsive to actuation of one of said monitor control devices for indicating which of said cameras is connected to said monitor and the occurrence of said intrusion signal;

amplifier means interposed between said video monitor switching means and said monitor and actuable for superimposing upon the image carried by said monitor, a representation of said final sampling pattern. 26. In a method for maintaining surveillance over a domain, for discriminating between changes of interest and changes not of interest in the domain, and usable with at least one sensor capable of providing an electrical output signal comprising first and second sets of samples, the samples of said first set being spaced in and representative of the condition of corresponding portions of said domain during a first time period, the samples of said second set being spaced in turn in the same manner as the samples of the first set and

27. In a surveillance system, the combination comprising:

a plurality of scanning devices;

timing means for controlling the scanning of said scanning devices;

sample generator means for generating a sample pattern;

means for applying the sample pattern to the outputs of said scanning devices in a predetermined sequence for producing samples; and

sequencing means for processing the output samples for each said scanning device in sequence and providing an alarm upon occurrence of change of interest in the domain monitored by any scanning device and including means responsive to a change of interest in the scene scanned by one of said scanning devices for providing an intrusion signal, a plurality of intrusion storage devices, each assigned to a corresponding one of said scanning devices and each responsive to a code signal indicating sampling of the output of such corresponding scanning device for achieving a storage condition upon occurrence of an intrusion signal, whereby achievement of a storage condition by one of said storage devices indicates the particular one of said scanning devices responsible for said intrusion signal, memory means for storing said samples, means for controlling updating of said memory means and normally preventing storage in said memory means of new samples from said scanning devices except on preselected periodic occasions, and means responsive to achievement of a storage condition by one of said intrusion storage devices for causing updating of said memory means with fresh samples at times other than on said periodic occasions.