Real time three dimensional sensing system

• US 5,589,942 A
• Filed: 04/05/1990
• Issued: 12/31/1996
• Est. Priority Date: 04/05/1990
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: Intelligent Automation Systems, Inc. (Azenta, Inc.)
• Inventors: Gordon, Steven J.
• Primary Examiner(s): HANTIS, KAREN
• Application Number:
  US07/505,722
• Time in Patent Office: 2,462 Days
• Field of Search: 356/376, 250/558, 382/1, 382/151, 364/516
• US Class Current: 356/611
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

The invention is a three dimensional sensing system which utilizes two flexibly located cameras for receiving and recording visual information with respect to a sensed object illuminated by a series of light planes. Each pixel of each image is converted to a digital word and the words are grouped into stripes, each stripe comprising contiguous pixels. One pixel of each stripe in one image is selected and an epi-polar line of that point is drawn in the other image. The three dimensional coordinate of each selected point is determined by determining the point on said epi-polar line which also lies on a stripe in the second image and which is closest to a known light plane.

Claims

1. A three dimensional object sensing apparatus comprising:

an electromagnetic radiation source for illuminating an object to be sensed with a plurality of electromagnetic radiation patterns,

first and second electromagnetic recording means for recording first and second images, respectively, of the reflection of said patterns off of said object as it is illuminated by said electromagnetic radiation source, wherein said first and second electromagnetic recording means are positioned in any manner relative to each other such that said first electromagnetic recording means records an image containing at least some of the reflected patterns which said second electromagnetic recording means records, and

data processing means for correlating the reflections of each of said patterns as recorded by said first recording means with the reflection of each of said patterns as recorded by said second recording means and determining the shape or position of said object therefrom,

wherein said data processing means comprises;

means for converting each of said images into a series of digital pixel words,

means for grouping said digital pixel words of each image into stripes, each stripe comprising the digital pixel words corresponding to points illuminated by a single one of said patterns,

means for selecting a single digital pixel word from each stripe from said first image, each of said selected digital pixel words representing a selected point on said object which is illuminated by the associated pattern,

means for determining an epipolar line in said second image associated with each of said selected digital pixel words,

means for determining each digital pixel word representing a point in said second image which is both part of a stripe in said second image and part of an epipolar line, said points termed intersection points,

means for determining the three dimensional coordinate of each of said intersection points,

means for selecting the single intersection point on each of said epipolar lines which lies closest to one of said patterns as the selected point from said first image associated with each of said epipolar lines, and

means for determining the shape or position of said object based on the known position of said selected points.

2. An apparatus as set forth in claim 1 wherein said electromagnetic radiation source comprises a light source and said patterns comprise a plurality of light planes.

3. An apparatus as set forth in claim 1 wherein said first and second images are captured simultaneously.

4. An apparatus as set forth in claim 1 further comprising;

means for separating said images into sections, said sections in said first and second images comprising corresponding pixels of said images, and

wherein said data processing means comprises a plurality of data processing means, each of said data processing means operating simultaneously on one of said sections of said first and second video images.

5. An apparatus as set forth in claim 4 wherein said sections each comprise a stripe of the associated image.

6. An apparatus as set forth in claim 1 wherein said grouping means comprises;

means for separating said pixels into first and second groups, said first group comprising pixels illuminated at a level above a specified threshold illumination level and said second group comprising pixels illuminated at a level below said threshold level, and

means for further separating said pixels from said first group into said stripes.

7. An apparatus as set forth in claim 1 wherein said electromagnetic recording means comprise video cameras.

8. An apparatus as set forth in claim 2 wherein said light source comprises a laser light source.

9. An apparatus as set forth in claim 1 wherein said data processing means comprises a plurality of pipelined data processing means, each of said data processing means performing a sequential portion of said data processing.

10. An apparatus as set forth in claim 1 further comprising means for rejecting a selected digital pixel word if none of the intersection points lie within a specified distance of any of said patterns.

11. A method for sensing an object in three dimensional space, said method comprising the steps of:

illuminating said object with a pattern of electromagnetic radiation,

obtaining first and second images of the reflection of said light pattern off of said object, said images comprising pixels,

correlating the reflection of said light pattern as recorded by said first camera with the reflection of said light pattern as recorded by said second camera by first determining the position of an epi-polar line in said second image of at least one selected pixel from said first image, then determining the position in space of the point corresponding to each of said pixels in said second image which lies on said epi-polar line, and thereafter determining which of said points lies closest to said light pattern.

12. A method for sensing an object in three dimensional space, said method comprising the steps of:

illuminating said object with a plurality of patterns of electromagnetic radiation,

obtaining first and second images of said object,

converting each image into a series of pixel words, each pixel word representing the intensity level of a point on said video image,

collecting said pixel words of each image into stripes, each stripe comprising contiguous pixels illuminated above a specified threshold intensity,

selecting a single pixel word from each stripe from said first image,

for each selected pixel word, determining the position of an epi-polar line in said second image of said selected pixel word,

for each epi-polar line, determining each pixel word from said second image which is both part of a stripe and part of said epi-polar line in said second image, these pixel words termed intersection words,

for each epi-polar line, determining the three dimensional coordinates of the point corresponding to each intersection word,

for each epi-polar line, selecting the single intersection word whose corresponding point lies closest to one of said patterns, and

determining the shape or position of said object based on the known positions of said points corresponding to said selected pixel words.

13. A method as set forth in claim 12 wherein said first and second images are captured simultaneously.

14. A method as set forth in claim 12 wherein said grouping step comprises the substeps of;

separating said pixel words into first and second groups, said first group comprising pixel words having a value above a specified threshold value and said second group comprising pixel words having a value below said specified threshold value, and

separating said pixels in said first group into said stripes.

15. A method as set forth in claim 12 further comprising the step of rejecting a selected pixel word if none of the points corresponding to the intersection words lies within a specified distance of any of said patterns.