Optical tracking system utilizing spaced-apart detector elements

• US 4,227,077 A
• Filed: 02/26/1973
• Issued: 10/07/1980
• Est. Priority Date: 02/26/1973
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Slater, Arthur B., Hopson, James E.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US05/337,049
• Time in Patent Office: 2,780 Days
• Field of Search: 250/203 R, 250/338, 250/342, 250/578, 250/209, 244/3.16
• US Class Current: 250/203.1
• CPC Class Codes: F41G 7/2213 maintaining the axis of an orientable seeking head pointed at the target, e.g. target seeking gyro
• 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 3/786 the desired condition being maintained automatically

Abstract

An optical tracking system in which an image of an object to be tracked is nutated about the image plane. Individual detector elements are arranged in a hexagonal array within the image plane such that each of the individual detector elements are located at respectively the centers of contiguous hexagonal cells. The nutation is provided, in one embodiment, by means of a tiltable mirror which rotates about an axis through the center of the mirror. The angle of tilt is variable so that the nutation can be varied to provide circular motion of an image point in circles concentric with a hexagonal cell and of varying diameter and, in particular, the image point can thereby be made to spiral inwardly toward the center of a hexagonal cell. The nutation of image points relative to the positions of the detector elements permit the various portions of an image to be scanned by individual detector elements. The inward spiraling of image points is utilized to provide for acquisition of the image points, and the position of an image point relative to a detector element at a given instant of time is utilized to provide elevation and azimuthal tracking data for tracking a desired object.

Claims

1. In combination:

a plurality of elements spaced apart in a first dimension and in a second dimension, said elements being responsive to radiant energy for providing a signal when illuminated by such energy;

means for directing rays of radiant energy towards said elements such that successive ones of said rays impinge sequentially in a first dimension and in a second dimension upon selected ones of said elements; and

means coupled to said directing means for selecting a number of said elements upon which said rays are to impinge, said directing means scanning said rays along arcuate paths, said directing means including means for varying the radii of said arcuate paths, said selecting means comprising;

first means responsive to said signals of said elements for signaling the position of one of said elements relative to one of said arcuate paths;

second means responsive to said signals of said elements for signaling the position of a second one of said elements relative to one of said arcuate paths; and

third means responsive to said first and to said second signaling means for selecting an arcuate path providing for said impinging of said rays of radiant energy upon a said number of said elements.

2. A scanning system comprising:

means for providing an image of an object to be scanned, said image being located upon an image plane;

a plurality of elements responsive to radiant energy of said image for providing signals indicating the presence of such radiant energy, each of said elements being positioned along a first dimension and along a second dimension within respective contiguous portions of said image plane for scanning respective portions of said image;

means for inducing a relative motion of each of said elements in a first dimension and in a second dimension relative to said respective portions of said image for scanning the areas of said portions, said motion means including means for scanning said areas at a uniform rate and means for varying said rate during a scanning of said portions; and

means responsive to said signals of said elements for shifting a portion of an image scanned by one of said elements in one of said elements in one of said contiguous portions of the image plane to another of said contiguous portions scanned by a second of said elements.

3. The system of claim 2 including means responsive to data obtained simultaneously from said scannings of the areas of said portions of said image plane for designating the area to be scanned by one of said elements.

4. A system for locating an image within an image plane, said system comprising:

a plurality of elements responsive to radiant energy of said image for providing signals when illuminated by such energy;

means for generating a relative motion between said image and said elements such that each of said elements moves within said image plane in arcuate paths relative to said image;

means for selecting a signal of at least one of said elements, said selecting means being responsive to the signals received from a plurality of said elements;

means responsive to said selected signal for accumulating occurrences of said selected signal when the element providing said selected signal lies exteriorly to an arcuate path containing a point of said image, said accumulating means also accumulating occurrences of said selected signal when the element providing said selected signal lies interiorly of the arcuate path containing said point of said image; and

wherein

said motion generating means includes means responsive to the difference between said exterior accumulation and said interior accumulation for varying said arcuate path to provide an equality between said exterior accumulation and said interior accumulation.

5. The system of claim 4 further comprising means for repositioning said image plane such that at least one point of said image coincides with at least one point of the arcuate path traced by a preselected one of said elements.

6. The system of claim 5 wherein said arcuate paths varying means comprises means for varying the radii of curvature of said arcuate paths.

7. The system of claim 6 further comprising means responsive to said signals for signaling an intersection of said image with at least one of said arcuate paths.

8. The system of claim 6 wherein said image plane repositioning means includes means for combining data obtained from a plurality of said elements to effect a tracking of said image.

9. A radiation tracker system for tracking an incident beam of radiation comprising:

a hexagonal detector array, each detector of said array being positioned at the vertex of a hexagon, each of said detectors being spaced apart with a spacing between neighboring detectors which is larger than the sizes of said neighboring detectors;

focusing means positioned relative to said hexagonal detector array to direct rays of radiation towards the hexagonal detector array; and

means for driving said focusing means to scan said rays of radiation in a spiral scan, said driving means comprising;

means for providing a predetermined value of radius of said spiral scan;

means responsive to signals received by detectors of said detector array for varying said predetermined value of radius; and

means for generating a modulating signal, said modulating signal being combined with said predetermined value of radius to provide said spiral scan.

10. A radiation tracker system for tracking an incident beam of radiation comprising:

a hexagonal detector array, each detector of said array being positioned at the vertex of a hexagon, each of said detectors being spaced apart with a spacing between neighboring detectors which is larger than the sizes of said neighboring detectors;

focusing means positioned relative to said hexagonal detector array to direct rays of radiation towards the hexagonal detector array;

means for driving said focusing means to scan said rays of radiation in a spiral scan; and

wherein

the center of said spiral scan is substantially coincident with the center of said hexagonal detector array, and the maximum radius of the spiral scan is substantially equal to the distance between the center and vertex of the hexagonal detector array.

11. The system of claim 10 including a central detector located at the center of said hexagonal detector array.

12. The system of claim 11 wherein said focusing means comprises an optical reflector adapted to be positioned by said driving means to direct the rays of radiation towards said central detector in the manner of a circular scan.

13. The system of claim 12 including receiving means synchronized with said optical reflector and connecting with said central detector for correlating radiation received by the central detector with the position of the optical reflector.

14. The system of claim 13 including positioning means responsive to said receiving means for orienting said focusing means relative to said incident beam of radiation to center said circular scan on the periphery of said central detector.

15. A radiation tracker system comprising:

a gyroscopically stabilized platform;

means for deflecting radiation;

a hexagonal detector array supported by said platform and positioned relative to said deflecting means to intercept rays of radiation deflected by said deflecting means; and

a spiral scanner supported by said platform, the spiral scanner positioning and driving said deflecting means to scan said radiation towards said hexagonal detector array in a spiral scan.

16. The system of claim 15 including receiving means synchronized to said spiral scanner and connecting with detectors in said hexagonal detector array for correlating radiation received by the detectors with the position of said deflecting means.

17. In combination:

a plurality of detectors positioned for receiving radiation, said detectors being positioned on the vertices of at least one triangle within the plane of an image provided by radiation;

means for scanning incident radiation about said plurality of detectors;

means coupled to individual ones of said detectors and synchronized with said scanning means for signaling the presence of the path of a point of said image when said point is scanned past said plurality of detectors;

said scanning means including means coupled to said signaling means for varying a path of said scanning; and

means coupled to said signaling means and to said path varying means for controlling said path varying means to provide a repetitive scan pattern when said point of said image passes within a predetermined distance of one of said detectors.

18. In combination:

a plurality of detector elements arranged on an image plane and being spaced apart by distances greater than a diagonal of one of said detector elements;

means for scanning radiation from a distant object past said plurality of detector elements, points of said object imaging on said image plane;

means coupled to said detector elements for directing said scanning means to provide a plurality of paths along which a point of said object is scanned on said image plane, one of said paths intercepting a detector element, and another of said paths passing between neighboring ones of said detector elements; and

said directing means including means for signaling the position of one of said paths relative to at least one of said detector elements, and means responsive to signals of said signaling means for redirecting said scanning means to scan said point of said object sequentially on different ones of said scanning paths to bring the image point from a path between neighboring ones of said detector elements to a path contiguous to at least one of said detector elements.