Virtual multiple aperture 3-D range sensor

• US 6,271,918 B2
• Filed: 02/04/1999
• Issued: 08/07/2001
• Est. Priority Date: 02/04/1999
• Status: Expired due to Fees

• Current Assignee: National Research Council Canada
• Original Assignee: National Research Council Canada
• Inventors: Blais, François
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US09/244,207
• Publication Number:
  US 20010001578A1
• Time in Patent Office: 915 Days
• Field of Search: 356/376, 306/3.13, 306/3.14, 306/3.15, 306/9, 306/12
• US Class Current: 356/625
• CPC Class Codes: G01C 3/14 with binocular observation at a single point, e.g. stereoscopic type G01C3/20 takes precedence

Abstract

A 3-D range sensor for measuring range from the sensor to a target surface by imaging a plurality of points projected onto the target surface is disclosed. The range sensor comprises an optical system for imaging a first image and a second other image of each of the plurality of points on the target surface, whereby the second other image is obtained from a different predetermined location than the first image. The optical system comprises an optical medium for combining the first image and the second other image, at least a reflective means for imaging at least one of the first and the second other image and for reflecting it to the optical medium such that the first image and the second other image are combined and a converging lens system for focussing the first image and the second other image. A position sensitive light detector detects the focussed first image and the focussed second other image. Using a processor, a distance between the detected first image and the detected second other image is determined and based on the determined distance and a known spatial relation between the first and the second other image the range is then calculated.

Claims

1. A range sensor for measuring a range from the range sensor to a target point on a surface comprising:

a light source for projecting a target at the target point on the surface;

a detector for capturing an image;

a first optical path having a first optical axis for providing a first image of the target point to the detector the first image provided from a first viewing angle;

a second optical path having a second different optical axis for providing a second other image of the same target point to the detector from a different viewing angle such that the two different viewing angles enclose a sufficient angle to provide a large base for triangulation between two different range measurements;

a combining optical element for combining the first optical path and the second optical path into an approximately third optical path to redirect light travelling along the first optical path and light travelling along the second optical path along approximately a same optical path, the third optical path being incident upon the detector;

a processor for determining a distance measurement in dependence upon the two captured images, the distance measurement determined using at least two imaged target points, imaged target point positions used to determine a range measurement, the processor for validating the determined range measurement.

2. A range sensor as defined in claim 1 wherein the range sensor comprises at least a lens for focussing the first image and the second other image onto the detector.

3. A range sensor as defined in claim 2 wherein at least one of the at least a lens comprise a pinhole lens.

4. A range sensor as defined in claim 1 wherein the processor comprises means for executing suitably programmed instructions for performing the steps of:

selecting a first detected target point position;

determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

determining a presence or absence of a target point at the corresponding position; and

, when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement.

5. A range sensor as defined in claim 1 wherein the processor comprises means for executing suitably programmed instructions for performing the steps of:

a) selecting a first detected target point position;

b) determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

c) determining a presence or absence of a target point at the corresponding position;

d) when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement; and

, when no target point is detected at the corresponding position, selecting a new first target point position and repeating steps (b), (c) and (d).

6. A range sensor for measuring a range from the range sensor to a target point on a surface comprising:

a light source for projecting a target at the target point on the surface;

a detector for capturing an image;

a first optical path having a first optical axis for providing a first image of the target point to the detector the first image provided from a first viewing angle;

a second optical path having a second different optical axis for providing a second image of the same target point to the detector from a different viewing angle such that the two different viewing angles enclose a sufficient angle to provide a large base for triangulation between two different range measurements;

a combining optical element for combining the first optical path and the second optical path into an approximately third optical path to redirect light travelling along the first optical path and light travelling along the second optical path along approximately a same optical path, the third optical path being incident upon the detector;

a lens for focussing the first image and the second image onto the detector;

a processor for determining a distance measurement in dependence upon a captured image, the distance measurement determined using at least two detected target points.

7. A range sensor as defined in claim 6 wherein a distance traveled by light within the first and the second optical path is approximately a same.

8. A range sensor as defined in claim 6 wherein the processor comprises means for validating the determined range.

9. A range sensor as defined in claim 6 wherein the processor comprises means for executing suitably programmed instructions for performing the steps of:

selecting a first detected target point having a position;

determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

determining a presence or absence of a target point at the corresponding position; and

,

when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement.

10. A range sensor as defined in claim 6 wherein the processor comprises means for executing suitably programmed instructions for performing the steps of:

a) selecting a first detected target point having a position;

b) determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

c) determining a presence or absence of a target point at the corresponding position;

d) when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement; and

, when no target point is detected at the corresponding position, selecting a new first target point position and repeating steps (b), (c) and (d).

11. A range sensor as defined in claim 6 wherein the target consists of a single point of light.

12. A range sensor as defined in claim 6 wherein the target comprises a pattern of points of light.

13. A range sensor as defined in claim 12 wherein the pattern consists of one or more straight lines of light.

14. A method of determining a distance between a detector and a surface comprising the steps of:

projecting a target from a source onto the surface;

using a detector, imaging the target through two different optical paths, each optical path having a different optical axis, and wherein the two different optical paths are combined into an approximately third optical path to redirect light travelling along the two different optical paths along approximately a same optical path, the third optical path being incident upon the detector; and

determining the distance to the surface based on the location of the source, the location of the detector, and the images of the target, the distance determined using triangulation.

15. A method as defined in claim 14 comprising the steps of

detecting target point positions within an image captured with the detector;

selecting a first detected target point position;

determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

determining a presence or absence of a target point at the corresponding position; and

,

when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement.

16. A method as defined in claim 15 wherein corresponding peak positions are disposed on different scan lines of the imaged image.

17. A method as defined in claim 15 wherein corresponding peak positions are determined accounting for scaling resulting from differences in optical path lengths between the first optical path and the second optical path.

18. A method as defined in claim 15 wherein for a first target point position, a single unique position exists for another corresponding target point for validating a range determined from the first target point position, the target point position assumed detected along a first optical path.

19. A method as defined in claim 14 comprising the steps of

a) detecting target point positions within an image captured with the detector;

b) selecting a first detected target point position;

c) determining from the first detected target point position a corresponding position of another detected target point, the corresponding position of a target point imaged along a different optical path and relating to an approximately same determined range measurement;

d) determining a presence or absence of a target point at the corresponding position;

e) when a target point is detected at the corresponding position, determining a range measurement from the two corresponding target point positions and validating the determined range measurement; and

, when no target point is detected at the corresponding position, selecting a new first target point position and repeating steps (c), (d) and (e).

20. A method as defined in claim 19 wherein a new first target point position is selected in dependence upon a known target geometry and previously validated first target point positions.

21. A method as defined in claim 20 comprising the step of validating determined corresponding peak positions in dependence upon other corresponding peak positions and the known target geometry.

22. A method as defined in claim 19 wherein a range measurement is determined based on the two corresponding peak positions and the distance therebetween.