Passive range finding apparatus utilizing television sensors

• US 4,969,735 A
• Filed: 03/07/1989
• Issued: 11/13/1990
• Est. Priority Date: 03/07/1989
• Status: Expired due to Term

• Current Assignee: Sperry Marine, Inc. (Northrop Grumman Corporation)
• Original Assignee: Sperry Marine, Inc. (Northrop Grumman Corporation)
• Inventors: Gilligan, Lawrence H.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/320,010
• Time in Patent Office: 616 Days
• Field of Search: 356/1,4, 356/9, 356/12, 250/558, 358/88, 358/107, 382/1
• US Class Current: 356/3.14
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves

Abstract

The range to an object is obtained by conveying light rays from the object through an afocal telescope to spatially displaced objective lenses that view the scene from two displaced points of view. The scene images from the objective lenses are focussed on two television sensors, respectively. The video frame from the TV sensors are digitized and stored in respective frame grabbers. A timing and logic circuit controls the television sensors and frame grabbers to alternately provide frames from the two television sensors to a monitor. The timing and logic circuit time shifts the output of one of the frame grabbers with respect to the output of the other frame grabber. A correlator responsive to the frame grabber outputs provides the correlation therebetween. The time shift required to bring the video images of the object into coincidence, at the correlation peak, provides a measure of the range to the object.

Claims

1. Range finding apparatus for passively finding the range to an object, comprising:

afocal lens means for conveying light rays from said object,

first and second spatially displaced television sensor channels positioned to receive light rays conveyed by said afocal lens means for providing first and second video signals representative of spatially displaced images of said object, respectively,

shifting means for time shifting said second video signal with respect to said first video signal, and

means coupled to said shifting means and to said first and second television sensor channels for determining a time shift at which said spatially displaced images of said object are in coincidence,

said time shift providing a measure of said range to said object.

2. The apparatus of claim 1 wherein each of said first and second television sensor channels comprises:

a television sensor,

object lens means positioned to receive light conveyed by said afocal lens means for focussing an image thereof on said television sensor, and

frame grabber means for storing a television frame from said television sensor in digital format and providing an output signal in accordance therewith, and wherein

said output signal from said frame grabber means of said first television sensor channel provides said first video signal and said output signal from said frame grabber means of said second television sensor channel provides said second video signal, and

said objective lens means of said first and second television sensor channels have said spatial displacement therebetween.

3. The apparatus of claim 2 wherein said shifting means for controlling said frame grabber means comprises,

timing and logic circuit means for controlling said frame grabber means in order to effect said time shift between said first and second video signal, and

correlator means responsive to said timing and logic circuit means and to said first and second video signals as shifted by said timing and logic circuit means for providing a correlation signal in accordance with said time shift in order to provide said measure of said range to said object.

4. The apparatus of claim 1 further including monitor means responsive to said first and second video signals for displaying said images of said object.

5. The apparatus of claim 3 further including monitor means responsive to said output signals of said first and second frame grabber means for displaying said images of said object.

6. The apparatus of claim 5 wherein said monitor means comprises means responsive to said timing and logic circuit means for alternately displaying stored television frames from said frame grabber means of said first and second television sensor channels.

7. The apparatus of claim 1 wherein said afocal lens means comprises an afocal telescope.

8. The apparatus of claim 1 wherein said afocal lens means comprises a zoom lens.