Line scan area signature detection system

• US 3,974,328 A
• Filed: 01/28/1974
• Issued: 08/10/1976
• Est. Priority Date: 07/23/1971
• Status: Expired due to Term

• Current Assignee: Martin Marietta Corporation
• Original Assignee: Martin Marietta Corporation
• Inventors: Thomas, Frank J., Farrow, Max W.
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): Masinick, Michael A.
• Application Number:
  US05/437,406
• Time in Patent Office: 925 Days
• Field of Search: 178/6.8, 178/DIG. 1, 178/DIG. 33, 178/DIG. 20, 178/DIG. 21, 178/DIG. 36, 250/203 CT, 343/5 MM, 244/3.17
• US Class Current: 348/169
• CPC Class Codes: F41G 7/20 based on continuous observation of target position
• CPC Class Codes: F41G 7/2226 comparing the observed data with stored target data, e.g. target configuration data
• CPC Class Codes: F41G 7/2253 Passive homing systems, i.e. comprising a receiver and do not requiring an active illumination of the target
• CPC Class Codes: F41G 7/2293 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 13/72 for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar
• CPC Class Codes: G01S 3/7865 using correlation of the live video image with a stored image

Abstract

An area signature detection system arranged to receive an output from a sensor operative in the electromagnetic spectrum, where the output from the sensor is an amplitude varying electrical signal representing the field-of-view beheld by the sensor, and to utilize this high frequency information in such a manner that low frequency scene content, necessary for area correlation processing, can be extracted and effectively utilized. Our invention involves certain highly advantageous techniques for generating area signatures from line scan sensors, and may be applied to cartesian, circular or polar scan formats. In one particular embodiment of our invention, we describe how orthogonally disposed area signatures can be used to generate area correlation tracking signals that can be used in the derivation of appropriate missile guidance commands. Our teachings are also useful in providing line-of-sight stabilization for fire control systems, alignment and position errors for landing and hovering control systems, as well as intrusion detection systems. In the case of a system using a television camera as the sensor, this invention provides a way of obtaining an operator display and system control signals despite the fact that only a single such sensor is used.

Claims

1. An area signature detection system arranged to receive the output of a sensor operative in the electromagnetic spectrum, comprising at least one area signature detector, said area signature detector connected to receive as an input, an output signal from the sensor involving an amplitude varying electrical signal representing the field of view beheld by the sensor, said area signature detector having gating means for selecting portions of such signal from the sensor representing related portions of the field of view, area signature synthesizer means receiving the output from said gating means and serving to provide a unique real time representation of each related portion of the sensor field of view selected by said gating means, said representation being in the form of an area signature, memory means for storing such signature, means for comparing such stored signature with a new signature obtained by further operation of said area signature detector, and means for generating an error signal proportional to the degree of similarity between such new signature and the stored signature.

2. The area signature detection system as defined in claim 1 wherein a time base generator is utilized in conjunction with said area signature detector in order to synchronize the time base of the sensor as well as to synchronize certain sequential operations of said gating, area signature synthesizer, and memory means.

3. The area signature detection system as defined in claim 1 in which processing means in the form of a time edge coincidence correlator are utilized.

4. The area signature detection system as defined in claim 1 in which processing means in the form of an exclusive OR function are utilized.

5. The area signature detection system as defined in claim 1 in which said memory means involves a plurality of memories to enable different areas to be monitored.

6. The area signature detection system as defined in claim 1 in which a pair of area signature detectors is utilized, and the sensor employs a scan format involving rectilinear scan.

7. The area signature detection system as defined in claim 6 in which each of said area signature detectors is operable to create an analog signature characterizing area variations within the sensor field of view, as selected by said gating means, the analog signature from one of said detectors being orthogonal to the signature from the other of said detectors, said error signal generating means generating line of sight error information in response to said signature.

8. The area signature detection system as defined in claim 1 in which the sensor utilizes a scan format involving radial scan.

9. The area signature detection system as defined in claim 8 in which the area signature detector includes means for creating an analog signature characterizing area variations within the sensor field of view, as selected by said gating means, said error signal generating means generating line of sight error information in response to said signature.

10. The area signature detection system as defined in claim 1 in which the sensor utilizes a scan format involving circular scan.

11. The area signature detection system as defined in claim 10 in which the area signature detector includes means for creating an analog signature characterizing area variations within the sensor field of view, as selected by said gating means, said error signal generating means generating line of sight error information in response to said signature.

12. The area signature detection system as defined in claim 1 in which said area signature detector encompasses the use of a horizontal signature detector and a vertical signature detector, said detectors being usable either individually or together.

13. The area signature detection system as defined in claim 12 in which said detectors have analog signature outputs, with the signature from one detector being orthogonal to the signature from the other detector.

14. The area signature detection system as defined in claim 1 in which said area signature detector includes means for integrating the gated output signal, and performing a sample and hold upon the results of such integration in order to form a low frequency content area signature.

15. The area signature detection system as defined in claim 14 in which multiple lines of such output signal are sampled and held in order to form a low frequency content area signature.

16. The area signature detection system as defined in claim 15 in which such multiple lines originate from a polar scanned system.

17. The area signature detection system as defined in claim 15 in which such multiple lines originate from a cartesian coordinate scanning system.

18. The area signature detection system as defined in claim 15 in which such multiple lines originate from a circularly scanned system.

19. The area signature detection system as defined in claim 1 in which said area signature detector includes means for gating portions of the input signal, and for summing such gated input signal to form a composite high frequency content area signature.

20. The area signature detection system as defined in claim 19 in which means are provided for summing multiple lines of such input signal in order to form a high frequency content area signature.

21. The area signature detection system as defined in claim 20 in which such multiple lines originate from a polar scanning system.

22. The area signature detection system as defined in claim 20 in which such multiple lines originate from a cartesian coordinate scanning system.

23. Apparatus comprising:

means for generating a current electronic signature of selected related portions of a field of view;

display means electrically connected to said current electronic signature generating means for displaying the field of view including the selected portions represented by said electronic signature;

means for storing a reference electronic signature; and

,

means for correlating said current electronic signature with said stored reference electronic signature and for generating tracking signals responsively to the correlation whereby said electronic signature may be utilized both for tracking and display.

24. The apparatus of claim 23 wherein said correlation means includes:

means for delaying said current electronic signature and said stored reference electronic signature;

means for comparing said current electronic signature with said delayed stored electronic signature to produce a first error signal;

means for comparing said stored reference electronic signature with said delayed current electronic signature to produce a second error signal;

means for subtracting one of said first and second error signals from the other of said first and second error signals to provide a difference error signal; and

,

means for integrating said difference error signal to generate one of said tracking signals.

25. An area signature detection system arranged to receive an output from a sensor operative in the electromagnetic spectrum, the sensor being a synchronizable scanning sensor having a line divisible time base, where the output from the sensor is an amplitude varying electrical signal representing the field of view beheld by the sensor, said area signature detection system comprising an area signature detector, and memory means used therewith, said area signature detector including input means, gating means, area signature synthesizer means, signature processor means, and output means, said input means being used to receive the output from the sensor, said gating means receiving the output from said input means and serving to provide related selected segmental portions of the sensor field of view to said area signature synthesizer means, said area signature synthesizer serving to provide a unique real time representation of the selected related portions of the field of view selected by said gating means and being the real time area signature in the form of an amplitude varying electrical signal, said signature processor means receiving the output from said area signature synthesizer and serving to process and condition the real time area signature into a form which may be stored in said memory means and utilized as the real time output of said area signature detector, said real time area signature being one output of said area signature detector, another output of said area signature detector being a stored signature from said memory means, with these two outputs thereafter being provided to an error processor for the generation of error signals proportional to the degree of similarity between said real time area signature and said stored area signature.

26. An area signature detection system as defined in claim 25 in which said gating means and said time base generator means operate in synchronism with the scan format of the sensor so as to electronically select the portions of the sensor field of view which are desired for processing into an area signature by said area signature processor.

27. The area signature detection system as defined in claim 25 in which said area signature processors are used simultaneously for obtaining orthogonal area signatures.

28. The area signature detection system as defined in claim 25 in which said memory means is capable of storing the zero crossings of the said reference area signature in the form of a fixed amplitude, width varying digital waveform.

29. An area signature detection system as defined in claim 25 in which at least one area signature processor means generates an area signature in the form of an amplitude varying electrical waveform by integrating the gated portion of the sensor field of view and sample and holding the result of said integration on a scan line basis so as to form an amplitude varying waveform describing the area variation within the gated portion of the sensor field of view.

30. The area signature detection system as defined in claim 29 in which said gated portions originate from a polar coordinate scanning sensor.

31. The area signature detection system as defined in claim 29 in which said gated portions originate from a cartesian coordinate scanning sensor.

32. An area signature detection system as defined in claim 25 in which at least one area signature processor means generates an area signature in the form of an amplitude varying electrical waveform by a repetitive summing process wherein the first scan line of the gated portion is added to the next scan line and this result added to the next scan line, and this procedure continued through scan line N, until the arithmetic sum of scan lines 1 through N contained within the gated portion is available and forms the amplitude varying waveform describing the area within the gated portion of the sensor field of view, thus forming the area signature.

33. The area signature detection system as defined in claim 32 in which said gated portions originate from a polar coordinate scanning sensor.

34. The area signature detection system as defined in claim 32 in which said gated portions originate from a cartesian coordinate scanning sensor.

35. The area signature detection as defined in claim 25 in which said memory means is capable of storing the amplitude variations of said reference area signature in the form of digital coded words.

36. The area signature detection system as defined in claim 35 in which the said memory means can include capability for storing more than one said reference area signature in order to provide a prestored operational capability.

37. An area signature detection system as defined in claim 25 in which said area signature detector means generates an area signature in the form of an amplitude varying electrical waveform by integrating on a scan line basis, said gated portion of the sensor field-of-view and sampling the result of said integration, the output of said area signature detector when considered over a number of scan lines of the sensor field-of-view being the real time area signature of an area having dimensions which are proportional to the gated segment width and the number of scan lines processed.

38. The area signature detection system as defined in claim 37 in which said gated portions originate from a cartesian coordinate scanning sensor.

39. The area signature detection system as defined in claim 37 in which said gated portions originate from a polar coordinate scanning sensor.

40. An area signature detection system as defined in claim 25 in which said area signature detector means includes means for generating an area signature in the form of an amplitude varying electrical waveform by a repetitive summing process, wherein the first scan line of said gated portion is added to the next scan line and this result added to the next scan line, and this procedure continued through scan line N, thus generating the arithmetic sum of scan lines 1 through N, contained within the gated segment, the output of said area signature detector, when considered as the arithmetic sum of the gated portion of the sensor field-of-view, being the real time area signature of an area having dimensions which are proportional to the gated segment width and the sum of lines 1 through N.

41. The area signature detection system as defined in claim 40 in which said gated portions originate from a cartesian coordinate scanning sensor.

42. The area signature detection system as defined in claim 40 in which said gated portions originate from a polar coordinate scanning sensor.