Ranging apparatus and method implementing stereo vision system

• US 5,684,531 A
• Filed: 04/10/1995
• Issued: 11/04/1997
• Est. Priority Date: 04/10/1995
• Status: Expired due to Fees

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Cox, Brian J., Li, Larry C.
• Primary Examiner(s): Faile, Andrew
• Assistant Examiner(s): Boccio, Vincent F.
• Application Number:
  US08/425,002
• Time in Patent Office: 939 Days
• Field of Search: 348/139, 348/113, 348/114, 348/115, 348/116, 348/118, 348/119, 348/140, 348/142, 901/47, 369/106, 369/121, 356/3.14, 356/3.15, 356/3.08, 382/106, 382/153, 382/154
• US Class Current: 348/139
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 3/085 with electronic parallax measurement
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G06T 2207/10021 Stereoscopic video; Stereoscopic image sequence
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• 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
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 13/296 Synchronisation thereof; Control thereof
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

A laser-directed ranging system for use in telerobotics applications and other applications involving physically handicapped individuals. The ranging system includes a left and right video camera mounted on a camera platform, and a remotely positioned operator. The position of the camera platform is controlled by three servo motors to orient the roll axis, pitch axis and yaw axis of the video cameras, based upon an operator input such as head motion. A laser is provided between the left and right video camera and is directed by the user to point to a target device. The images produced by the left and right video cameras are processed to eliminate all background images except for the spot created by the laser. This processing is performed by creating a digital image of the target prior to illumination by the laser, and then eliminating common pixels from the subsequent digital image which includes the laser spot. The horizontal disparity between the two processed images is calculated for use in a stereometric ranging analysis from which range is determined.

Claims

1. A ranging system for telerobotics applications, comprising:

a first video camera;

a second video camera spaced from said first video camera, said first and said second video cameras being located in a common plane;

a directional light source positioned relative to said first and said second video cameras for illuminating a portion of a selected target during selected periods;

capture means, associated with said video cameras, for capturing a first set of stereoscopic images of the target while said directional light source is illuminating a portion of the target, and for capturing a second set of stereoscopic images of the target while said directional light source is not illuminating a portion of the target, and means for generating a third set of stereoscopic images of the target eliminating common elements of the first and second set of images;

a robotic device; and

a processor electrically associated with said capture means and said robotics device, said processor including a ranging algorithm for determining the range to said target based upon remaining elements in the third set of stereoscopic images.

2. A system as in claim 1, wherein said video cameras are mounted on a camera platform.

3. A system as in claim 2, wherein said camera platform is electrically coupled to said processor, further comprising a position and orientation sensor coupled to said processor, and wherein said processor positions said camera platform based upon electrical signals generated by said position and orientation sensor.

4. A system as in claim 3, wherein said position and orientation sensor comprises means for generating signals indicative of the movement of an operator'"'"'s head.

5. A system as in claim 4, wherein the operator is positioned remotely from said video cameras.

6. A system as in claim 1, wherein said directional light source is activated by an operator remote from said light source.

7. A system as in claim 1, wherein said light source is activated by a physically handicapped person.

8. A system as in claim 1, wherein said directional light source illuminates a spot on said target.

9. A system as in claim 8, wherein said means for capturing a first set of stereoscopic images of the target while said directional light source is illuminating a portion of a selected target, and for capturing a second set of stereoscopic images of the target while said directional light source is not illuminating a portion of the selected target include first and second frame grabbers associated with said first and second video cameras, respectively, and wherein said first frame grabber generates a first image of said target with said spot, and said second frame grabber generates a second image of said target with said spot, and said processor determines the disparity in said plane between the position of the spot in said first image and the position of the spot in said second image.

10. A system as in claim 1, wherein said first frame grabber is electrically coupled to said first video camera, and said second frame grabber is electrically coupled to said second video camera, and wherein the output signals from said first and said second frame grabbers are provided as input signals to said processor.

11. A system as in claim 5, further comprising a remote display for said operator, said display receiving images from said video cameras through said processor.

12. A system as in claim 1, wherein said directional light source is positioned in the same plane as said video cameras.

13. A system as in claim 1, wherein said processor determines the disparity in said plane between the illuminated image of said first camera and the illuminated image of said second camera.

14. A system as in claim 1, wherein said video cameras lie in a horizontal plane with respect to each other, for determining horizontal disparity.

15. A system as in claim 1, wherein said light source comprises a laser.

16. An apparatus for determining range to a target, comprising:

a directional light source operable to selectively illuminate a portion of a target to selectively create an illuminated spot on said target;

a first video camera for capturing a first digital image of said spot;

a second video camera for capturing a second digital image of said spot; and

a computer operably associated with said first video camera and said second video camera for determining the range to said target by comparing said first and said digital images to determine disparity, wherein the range is determined from a look-up table for the determined disparity value.

17. An apparatus as in claim 16, wherein said computer obtains the stereoscopic digital images of said spot by eliminating common pixels between an image of said target without said spot and an image of said target with said spot.

18. An apparatus as in claim 17, wherein said directional light source is a laser and wherein said computer turns off and on said laser.

19. An apparatus as in claim 18, further comprising a means for directing the directional light source on said target.

20. An apparatus as in claim 19, wherein said video cameras are mounted on a platform, and said platform is positioned by an operator to obtain said images.

21. An apparatus as in claim 20, comprising means for positioning the platform in response to head movement of the operator.

22. An apparatus as in claim 21, further including an operator display receiving images from said video cameras.

23. An apparatus as in claim 22, including a head mounted unit, and wherein said operator display is provided in said head-mounted unit.

24. An apparatus as in claim 23, further comprising a robotics device connected to said computer, wherein said operator activates said robotics device and said computer provides an electrical signal indicative of target location to said robotics device.

25. An apparatus as in claim 24, wherein said robotics device is activated by a voice command from the operator.

26. An apparatus as in claim 25, further comprising a voice recognition system connected to said computer, said voice recognition system comprising means for converting said voice command to an electrical output signal.

27. A method for determining range to a target, comprising the steps of:

(a) capturing a first set of stereoscopic images of a target;

(b) activating a directional light source for illuminating a portion of said target;

(c) capturing a second set of stereoscopic images of the target while the light source is directed onto the portion of said target;

(d) generating a third set of stereoscopic images of the target by eliminating common elements of the first and second set of images; and

(e) determining range to the target based upon remaining elements in the third set of stereoscopic images.

28. A method as in claim 27, wherein the range to the target is determined by calculating the disparity between the remaining elements of the third set of stereoscopic images.

29. A method as in claim 27, wherein said stereoscopic images includes a left video image and a right video image.

30. A method as in claim 29, wherein said video images are digitized.

31. A method for remotely controlling a robotics device to manipulate a target device, comprising the steps of:

(a) remotely viewing the target device;

(b) capturing a left and a right video image of said target device;

(c) activating a light source to generate a spot on said target device;

(d) capturing a left and a right video image of said target device with said spot thereon;

(e) eliminating common pixels between said video images captured in step (b) and said video images captured in step (d) to obtain a left and right image of said spot;

(f) determining disparity between said left and right image obtained in step (e);

(g) calculating range to said target device based upon said disparity determination;

(h) positioning said robotics device to contact said target device based upon said range calculation.

32. A method as in claim 31, wherein the step of remotely viewing the target device includes positioning a left and right video camera to view the target device.

33. A method as in claim 32, wherein the positioning of said left and right cameras is performed by moving the head of an operator.

34. A method as in claim 31, wherein the video images are captured by a left and right frame grabber circuit.

35. A method as in claim 31, wherein said laser is positioned by an operator and activated by said operator.

36. A method as in claim 31, wherein said laser is activated by a computer after said target device is selected by an operator.

37. An apparatus for determining range to a target, comprising:

a directional light source for illuminating a portion of a selected target during selected periods;

means including first and second video cameras for capturing a first set of stereoscopic images of the target while said directional light source is illuminating a portion of a selected target, and for capturing a second set of stereoscopic images of the target while said directional light source is not illuminating a portion of the selected target, and for generating a third set of stereoscopic images, of the illuminated portion of the target, by eliminating common elements of the first and second set of images;

a computer operably associated with said first and second video cameras and said robotics device for determining the range to said target by comparing the positions of the illuminated portion of the target within said third set of images, based upon elements remaining in the third set of stereoscopic images and with common elements in said first and second sets of stereoscopic images eliminated, to determine disparity.