Automatic TV ranging system

• US 4,601,053 A
• Filed: 11/21/1983
• Issued: 07/15/1986
• Est. Priority Date: 11/21/1983
• Status: Expired due to Term

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Grumet, Alex
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Couso, Jose L.
• Application Number:
  US06/553,623
• Time in Patent Office: 967 Days
• Field of Search: 356/3, 356/12, 250/558, 382/1, 358/88, 358/107, 358/10, 358/139, 377/17, 364/561
• US Class Current: 382/106
• CPC Class Codes: G01C 3/085 with electronic parallax measurement
• CPC Class Codes: G06T 2207/10012 Stereo images
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence

Abstract

A range-finding system comprising the hardwired video processing of two side-by-side TV stereo images of a scene to provide automatic, rapid, quantitative ranging to noncooperative objects. A single TV camera with appropriate optics to provide stereo inputs or, in a preferred embodiment, two TV cameras, provide the stereo images. Range is determined for any change of contrast in the common TV stereo scene to obtain the parallax displacement of corresponding object features with a three scan line delay of less than 200 microseconds. The video of the synchronized line scan of both cameras is stored as they are scanned, thus range can be determined with relative motion between the stereo camera and objects in the scene. Range is stored in on-board RAM'"'"'s for each pixel of the TV scene and is available after three TV lines of delay. Range up-dating is continuous as the TV raster is scanned, or the range of a particular TV frame may be frozen for detailed study. Any part of the electromagnetic spectrum that can provide TV imagery can be used in the ranging system.

Claims

1. A TV system for the automatic quantitative ranging on at least a single remote, non-cooperating, passive object comprising:

means for presenting a scene containing said object on a light-sensitive mosaic of a line-scannable image sensing means in the form of a pair of side-by-side split-screen stereo images of said scene;

means for scanning said mosaic in a horizontal sequence of scanning lines for successively analyzing the image energy along said scanning lines and deriving output signals proportional to the light energy of features of said stereo object images, each of said scanning lines having a predetermined number of scan points;

means for counting the scan points in each image of the stereo image pair in each scanning line to said features of said object in each scene from the left side of each image pair such that the parallax displacement Δ

of corresponding object features in the two stereo images can be determined; and

means for processing said parallax displacements and producing an output indication of the range characterized by said parallax displacements.

2. The TV ranging system recited in claim 1 wherein the scan points in each image of the stereo image pair are counted from the right side of each image pair.

3. The TV ranging system recited in claim 1 wherein the scan points in each image of the stereo image pair are counted sequentially from the left and then from the right side of each image pair.

4. The TV ranging system recited in claim 1 wherein the means for counting the scan points are forward and backward processors and wherein the processing scan of said forward processor is from the left to the right side of each image pair alternating with a processing scan from right to left by said backward processor.

5. The TV ranging system recited in claim 1 wherein the means for presenting a scene is a single TV camera having input optics forming a stereo pair of images of the scene containing the object being ranged on the light-sensitive mosaic of said camera.

6. The TV ranging system recited in claim 1 wherein the means for presenting a scene are two side-by-side TV cameras such that the two light-sensitive mosaics of said cameras form a stereo pair of images of the scene containing the object being ranged.

7. The TV ranging system recited in claim 6 wherein the means for presenting a scene are two side-by-side solid state imaging Charge Coupled Devices (CCD'"'"'s).

8. The TV ranging system recited in claim 1 wherein the spatial parallax displacement Δ

is determined in terms of time delays.

9. The TV ranging system recited in claim 1 wherein each scanning line in each stereo image has at least about 500 scan points.

10. The TV ranging system recited in claim 1 wherein hard-wired logic is used for processing the parallax displacement.

11. The TV ranging system recited in claim 1 wherein a microprocessor is used to output the range data generated.

12. A TV system for the automatic quantitative ranging on at least a single remote, non-cooperating, passive object comprising:

a pair of side-by-side TV cameras spaced a distance d apart, said pair consisting of a left camera and a right camera generating a split-screen stereo image of a scene containing at least said object;

scanning means associated with each camera for simultaneously scanning both camera stereo-images from left to right in a horizontal sequence of scanning lines and generating left and right camera video output signals proportional to the light energy of the scanning points, each camera scanning line having predetermined number of scan points;

means for converting the analog video output of said cameras to a digitized form;

switching means for switching said digitized signals representing the stereo images of said left and right cameras for the simultaneous storing of said signals into left and right respectively random access memory means;

forward and backward scanning processors in a time-sharing arrangement with counting means for addressing said memory means, said processors having means for comparing signals from said left memory means with signals from said right memory means to determine time differences Δ

for corresponding changes of contrast indicated by said video output signals and characterizing the spatial parallax displacements of corresponding objects in said stereo images, said time differences Δ

being stored in a Δ

memory means;

accessing means for the address scanning of said Δ

memory means and for providing an output to a reciprocal read-only memory means, said reciprocal memory means having look-up means for converting Δ

to range and outputting said range to range storage and utilizing means.

13. The TV ranging system recited in claim 12 wherein said TV cameras are solid state imaging Charge Coupled Devices (CCD'"'"'s).

14. The TV ranging system recited in claim 12 wherein the spatial parallax displacement Δ

is determined in terms of time delays.

15. The TV ranging system recited in claim 12 wherein the video signals are stored in the random access memory means at one clock rate and addressed and read out by the processors at another clock rate.

16. The TV ranging system recited in claim 15 wherein the video signals are addressed and read out at double the storage rate.

17. The TV ranging system recited in claim 15 wherein the video signals are stored in the random access memory means at a 10 Mhz clockrate and addressed and read out by the processors at a 20 Mhz clock rate.

18. The TV ranging system recited in claim 12 wherein the processors read out the scanning line corresponding to the left stereo-image scanline at the time the right stereo-image is scanned such that decisions of spatial parallax displacement characterizing range are made during the time the right stereo-image is scanned.

19. The TV ranging system recited in claim 12 wherein the processors have comparison means for comparing the video outputs of the left and right line scans for matching corresponding changes of contrast indicative of a specific target in the scene.

20. The TV ranging system recited in claim 19 wherein the changes in contrast indicate amplitude and slope of the video output signals.

21. The TV ranging system recited in claim 19 wherein the counting means in the processors are provided with latches that are used as temporary memories such that said processors return to an earlier state of conditions if an unacceptable match is encountered whereby counting can proceed from an intermediate point rather than being required to return to the original starting point of counting such that an excessive loss of counting time is avoided.

22. The TV ranging system recited in claim 12 wherein the video stereo-image output signals are stored in pairs of left and right random access memories and wherein the memory pairs in the store mode are addressed in sequence with address zero corresponding to the left side of each image pair and with address n corresponding to the right side of each image pair whereby the random access memories can be accessed in any order by correct addressing.

23. The TV ranging system recited in claim 22 wherein address n is typically 499.

24. The TV ranging system recited in claim 12 wherein the random access memory means comprises a number of random access memory pairs and wherein the video output signals representing a stereo-image scanning line are stored in a random access memory pair at the same time two previously stored scanned lines pairs from two other of said memory pairs are being processed by the processors.

25. The TV ranging system recited in claim 12 wherein the counting means in the processors for addressing the random access memory means containing the stereo-image video output signals comprise a left counter and a right counter and the time differences Δ

are determined by a Δ

counter.

26. The TV ranging system recited in claim 25 wherein the initiation of Δ

measurements will be triggered by the right video output signals for the forward scanning processor and by the left video output signals for the backward scanning processor.

27. The TV ranging system recited in claim 26 wherein slope and amplitude comparison means provided in the forward scanning processor detect a signal slope and amplitude in the right video output voltage indicating a target is sensed to thereby reset the left counter to the count of the right counter and to set the Δ

counter to zero, and whereby said right counter is stopped and said left and Δ

counters continue counting until said slope and amplitude comparison means indicate a match between the right and left signal slope and amplitude such that a Δ

count used for the determination of range is generated.

28. The TV ranging system recited in claim 26 wherein slope and amplitude comparison means provided in the backward scanning processor detect a signal slope and amplitude in the left video output voltage indicating a target is sensed to thereby reset the right counter to the count of the left counter and to set the Δ

counter to zero, and whereby said left counter is stopped and said right and Δ

counters continue counting until said slope and amplitude comparison means indicate a match between the right and left signal slope and amplitude such that a Δ

count used for the determination of range is generated.

29. The TV ranging system recited in claims 27 or 28 wherein the forward and backward scanning processors each have a left and a right counter and wherein said counters in said forward scanning processor are initially set at zero and said counters in said backward scanning processor are initially set at 499 at the beginning of a processor interval, said counters in said forward scanning processor being incremented during processing and said counters in said backward scanning processor being decremented during processing.

30. The TV ranging system recited in claim 29 wherein the right counter in the forward scanning processor and the left counter in the backward scanning processor are stopped when a target is sensed and the Δ

counters in both processors are set to zero and wherein the left counter in said forward scanning processor is incremented and the right counter in said backward scanning processor is decremented and said Δ

counters are incremented until the slope and amplitude comparison means indicate a match between the right and left signal slope and amplitude such that a Δ

count used for the determination of range is generated.

31. The TV ranging system recited in claim 29 wherein a 499 count in the left and right counters in the forward scanning processor and a zero count in the left and right counters in the backward scanning processor determine the end of processing of a scan line.

32. A method for the automatic quantitative ranging on at least a single remote, non-cooperating, passive object P comprising the steps of:

spacing a pair of TV cameras a distance d apart, said pair consisting of a left camera and a right camera, said cameras providing a line-scannable light-sensitive image mosaic in the form of a pair of side-by-side split-screen stereo images of a scene containing at least said object P, said cameras each having a FOV subtending an angle α

, the width W of said FOV'"'"'s at different ranges from said cameras varying with the range R, there being a specific width for a specific range ##EQU10## scanning said stereo image pair mosaic in a horizontal sequence of scanning lines having a predetermined number C of scan points in each scan line in each image of said stereo pair;

analyzing the image energy along said scanning lines to derive output signals proportional to the light energy of features such as object P such that a count l of scanning points from the left side to object P in said left FOV and a count r from the left side to object P in said right FOV can be derived;

subtracting count r from count l to obtain the difference Δ

which is the equivalent of distance such that ##EQU11## whereby the range to object P in the combined FOV'"'"'s is ##EQU12## where K is a design parameter ##EQU13##

34. The method recited in claims 32 or 33 wherein the angle α

is the view angle of the stereo camera lenses and wherein the range ratio ##EQU18## is changed by changing the lenses to change angle α

.

33. A method for the automatic quantitative ranging on at least a single remote, non-cooperating, passive object P comprising the steps of:

spacing a pair of TV cameras a distance d apart, said pair consisting of a left camera and a right camera, said cameras providing a line-scannable light-sensitive image mosaic in the form of a pair of side-by-side split-screen stereo images of a scene containing at least said object P, said cameras each having a FOV subtending an angle α

, the width W of said FOV'"'"'s at different ranges from said cameras varying with the range R, there being a specific width for a specific range ##EQU14## scanning said stereo image pair mosaic in a horizontal sequence of scanning lines having a predetermined number C of scan points in each scan line in each image of said stereo pair;

analyzing the image energy along said scanning lines to derive output signals proportional to the light energy of features such as said object P such that a count 1 of scanning points from the right side to object P in said left FOV and a count r from the right side to object P in said right FOV can be derived;

subtracting count l from count r to obtain the difference Δ

which is the equivalent of distance such that ##EQU15## whereby the range to object P in the combined FOV'"'"'s is ##EQU16## where K is a design parameter ##EQU17##

35. A method for the automatic quantitative ranging on at least a single remote, non-cooperating, passive object comprising the steps of:

presenting a scene containing said object on a light-sensitive mosaic of a line-scannable image sensing means in the form of a pair of side-by-side split-screen stereo images of said scene;

scanning said mosaic in a horizontal sequence of scanning lines for successively analyzing the image energy along said scanning lines and deriving output signals proportional to the light energy of features of said stereo object images, each of said scanning lines having a predetermined number of scan points;

counting the scan points in each image of the stereo image pair in each scanning line to said features of said object in each scene from the left side of each image pair such that the parallax displacement Δ

of corresponding object features in the two stereo images can be determined; and

processing said parallax displacements and producing an output indicative of the range characterized by said parallax displacements.

36. The method recited in claim 35 wherein the scan points in each image of the stereo image pair are counted from the right side of each image pair.

37. The method recited in claim 35 wherein the scan points in each image of the stereo image pair are counted sequentially from the left and then from the right side of each image pair.