AUTOMATIC TARGET RECOGNITION SYSTEM

• US 3,779,492 A
• Filed: 10/18/1971
• Issued: 12/18/1973
• Est. Priority Date: 10/18/1971
• Status: Expired due to Term

• Current Assignee: Alex Grumet
• Original Assignee: Alex Grumet
• Inventors: Grumet, Alex
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Webb, Thomas H.
• Application Number:
  US05/189,875
• Time in Patent Office: 792 Days
• Field of Search: 244/3.17,17 350/3.5,162SF
• US Class Current: 244/3.17
• CPC Class Codes: F41G 7/2226 comparing the observed data with stored target data, e.g. target configuration data
• CPC Class Codes: F41G 7/2246 Active homing systems, i.e. comprising both a transmitter and a receiver
• 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: F41G 7/343 comparing observed and stored data of target position or of distinctive marks along the path towards the target
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters

Abstract

A coherent, optical signal processor for recognition of specific known targets at extremely high speeds, applying matched-filter techniques. A modified matched filter includes a pair of matched filters that will separately process the high and low spatial frequencies. By properly combining the outputs in a logical AND operation, the target may be interrogated for fine features as well as for correct size and shape. The optical memory bank of matched-filter pairs comprises known diffraction patterns of all resolvable views, in both azimuth and elevation, of the target, thus forming a target recognition comb-filter bank. All views of the recognition bank are simultaneously interrogated optically according to the diffraction pattern of the detected object to determine whether the detected object is the desired target as stored in any of the views in the memory bank.

Claims

1. In a device of the character described for automatically recognizing the presence of a given object in a region under observation, means for storing light variations in said observed region, a source of coherent, collimated light energy, means for modulating said light energy amplitude according to said stored light variations, optical means for transforming said amplitude modulated light energy into an unidentified diffraction pattern generated by said modulated light energy, memory means including a plurality of different matched filter means containing a known diffraction pattern produced by said given object under known conditions, each of said matched filter means comprising at least two matched filters, severally matched to a preselectEd band of the spatial frequencies comprising said known diffractional pattern, optical means for interrogating said memory means with the unidentified diffraction patterns of said modulated light energy, and detecting means for producing an output signal whenever correlation of said unidentified diffraction pattern with all of said matched filters in any one of said matched filter means exists.

2. The device as described in claim 1, wherein the means for storing said light variations includes a photographic transparency of the given region, and the optical means for generating the diffraction pattern includes a lens system, said transparency being situated at the front focal plane of said lens system and said memory means being located at the back focal plane of said lens system.

3. The device as described in claim 2, wherein said lens system includes means for generating a multiplicity of identical outputs at said memory means for simultaneously interrogating all of said matched filter means.

4. The device of claim 3, wherein said lens means comprises a hologram.

5. The device of claim 1, in which each of said matched filter means includes a pair of matched filters, one being a high frequency pass filter and the other being a low frequency pass filter.

6. The device as described in claim 5, in which said plurality of matched filters is arranged in a regular geometric array, the low pass filter of every filter pair occupying the same relative position with respect to the corresponding high pass filter.

7. The device as described in claim 5, wherein one low pass filter is common to a plurality of high pass filters.

8. The device as described in claim 7, wherein said plurality of high pass filters are superimposed on one another.

9. The device as described in claim 1, wherein the optical means for interrogating said memory means includes means for generating multiple identical diffraction patterns from a single light modulated input for simultaneously interrogating all of said matched filter means in said memory means.

10. The device as described in claim 9, wherein said multiple diffraction pattern generating means is a hologram.

11. The device as described in claim 1, wherein said means for storing light variations includes a transducer for real time observation of said region.

12. The device in claim 1 wherein said given object may be any one of a plurality of preselected objects and said memory means includes a plurality of matched filter means containing diffraction patterns produced by each of said plurality of preselected objects, whereby said given object also can be identified as one of said preselected objects.

13. In an automatic navigation system for guiding a vehicle over known territory along a predetermined course, observing means on said vehicle for viewing that portion of said territory which is located at a known direction in relation to said vehicle, storing means for storing light variations reaching said observing means as said vehicle proceeds over said territory, memory means including a plurality of matched filter means, each filter means containing the diffraction pattern produced by the observed view when said vehicle is at a predetermined position, and altitude, a source of coherent, collimated light energy, modulating means for modulating said light energy amplitude according to said stored light variations, optical means for transforming said amplitude modulated light energy into a diffraction pattern, optical means for interrogating said memory means with the diffraction pattern generated by said modulated light energy, detecting means for producing a signal whenever correlation exists between said generated diffraction pattern and one of said matched filter means, means responsive to said signal for producing an error signal indicative of the difference between the actual course of said vehicle and the predetermined course, and means On said vehicle to change the course of said vehicle to reduce said error signal to zero.

14. The device in claim 13, in which each of said matched filter means comprises at least two matched filters, severally matched to a preselected band of spatial frequencies comprising the diffraction pattern.

15. The device in claim 13, in which the matched filters of said memory device are arranged in sequential order representing views as observed along the predetermined course.

16. The device as described in claim 13, in which said error signal-producing means produces a second error signal indicative of the difference between the actual altitude of said vehicle and the predetermined altitude, and including means on said vehicle to change the altitude of said vehicle to reduce said second error signal to zero.

17. In a method for recognizing a given object, the steps of obtaining the diffraction pattern representative of a predetermined view of a known object, memorizing said diffraction pattern in a pair of high pass and low pass optical matched filters, repeating said steps until a plurality of diffraction patterns representing a plurality of views of at least one known object are memorized in a plurality of matched filter pairs, obtaining the diffraction pattern of said given object to be recognized, comparing the diffraction pattern of said given object with each of the diffraction patterns memorized in said high and low pass matched filter pairs, and recognizing said given object when correlation exists between the diffraction pattern of said given object and one of said matched filter pairs as being similar to the known object from which said one matched filter pair was made.

18. The method described in claim 17, in which the step of obtaining the diffraction pattern of said object to be recognized includes the steps of photographing said object and preparing a transparency of the photographed image, placing said transparency at the front focal plane of a lens, transmitting laser light through the transparency, placing said matched filter pairs at the back focal plane of said lens, whereby the diffraction pattern of said object is obtained at the matched filters.

19. The method described in claim 17, in which the step of recognizing is accomplished automatically by placing said matched filter pair at the front focal plane of a lens system, and placing an optoelectrical pickoff device at the back focal plane of said lens system, and connecting an electrical system to said optoelectrical pickoff.

20. The method described in claim 17, in which the step of obtaining the diffraction pattern of said object to be recognized includes the steps of storing an image of said object in a real time transducer, amplitude modulating a laser beam according to the image stored in said transducer, and obtaining the diffraction pattern of said amplitude modulated laser beam.