LASER RADAR PROJECTION WITH OBJECT FEATURE DETECTION AND RANGING

• US 20120154784A1
• Filed: 12/23/2011
• Published: 06/21/2012
• Est. Priority Date: 02/01/2005
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Laser Projection Technologies, Inc. (Faro Technologies Incorporated)
• Inventors: Kaufman, Steven P., Savikovsky, Arkady, Chagaris, Christopher C., Stave, Joel
• Granted Patent: US 8,582,087 B2
• Time in Patent Office: Days
• US Class Current: 356/4.01
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G01N 2021/8411 Application to online plant, process monitoring
• CPC Class Codes: G01N 2021/8472 Investigation of composite materials
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24
• CPC Class Codes: G01N 21/95623 using a spatial filtering method per se G02B
• CPC Class Codes: G01N 2201/0642 Light traps; baffles
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 30/56 by projecting aerial or floating images
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: G03B 35/18 by simultaneous viewing
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A laser projection system is disclosed. The system includes a laser projector that projects a light beam to the surface of an object and scans that projected light beam over at least a portion of the surface, wherein a portion of the projected beam is diffusely reflected from the surface back to the system. The system further includes an optical signal detector that receives the feedback light beam and converts it to an image signal, a light suppression means for suppressing unwanted light from entering the optical signal detector, and a computer for producing a measurement of the distance from the projector to the object surface, and controlling the system to buck the laser projector into a coordinate system of the object using three or more features on the object, wherein at least one of the three or more features serves as a targetless fiducial point.

Claims

1. A laser projection system, comprising:

a laser projector that projects a light beam to the surface of an object and scans that projected light beam over at least a portion of the surface, wherein a portion of the projected light beam is diffusely reflected from the surface back to the system as a feedback light beam;

a first optical signal detector that receives the feedback light beam and converts it to an image signal, wherein the projected light beam and the feedback light beam are associated with a given point on the surface and propagate in opposite directions along a common propagation path;

a light suppression system for suppressing unwanted light from entering the first optical signal detector; and

a computer for comparing the image signal with a corresponding reference signal to produce a measurement of the distance from the laser projector to the object surface, and controlling the system to buck the laser projector into a coordinate system of the object using three or more features on the object, wherein at least one of the three or more features serves as a targetless fiducial point.

2. The system of claim 1 wherein the computer is further configured for calculating the elapsed time-of-flight and distance traveled of light beams from the laser projector, to multiple points on the object surface, and back, and generating a three-dimensional point cloud of the object.

3. The system of claim 1 wherein the system further comprises:

a beam splitter located in the propagation path that divides the projected light beam into a reference beam portion and a signal beam portion; and

a second optical signal detector that converts the reference beam portion into a corresponding electrical reference signal.

4. The system of claim 3 wherein the system further includes a lens that focuses the reference beam portion onto the second optical signal detector.

5. The system of claim 3 wherein the system further comprises an electronic circuit that samples the reference beam and the image signal at a rate sufficient to provide accurate values for elapsed time-of-flight and intensity of the feedback light beam.

6. The system of claim 5 wherein the laser projector is a pulsed laser and the projected light beam is pulsed at 50 kHz or faster, and sampling by the electronic circuit occurs at 5 gigasamples per second or faster.

7. The system of claim 5 further comprising a clock that synchronizes operation of the laser projector, electronic circuit, and computer.

8. The system of claim 3 wherein the first optical signal detector and the second optical signal detector are coupled to the system by optical fibers.

9. The system of claim 1 wherein the laser projector is a pulsed laser.

10. The system of claim 1 further comprising a dynamic range modulator that adjusts operation of the system in response to light reflective characteristics of the object, wherein the dynamic range variation is on the order of at least 100,000.

11. The system of claim 10 wherein the dynamic range modulator includes an acousto-optical modulator located in the propagation path and operable to vary the intensity of the projected light beam.

12. The system of claim 11 wherein the acousto-optical modulator splits the projected beam into a first order beam and a zero order beam, where the first order beam is scanned on the object and the zero order beam is suppressed.

13. The system of claim 10 wherein the dynamic range modulator further comprises at least one of:

a variable gain amplifier for receiving the digital image signal output by the first optical signal detector; and

a variable power supply for the first optical signal detector that varies its dynamic response to the received feedback light beam.

14. The system of claim 1 wherein the light suppression system comprises a spatial light filter that admits the feedback light beam to the first optical signal detector while substantially blocking stray light.

15. The system of claim 16 wherein the spatial filter comprises an optical fiber with a central light-conducting core aligned with the first optical signal detector and a converging lens that brings the feedback light beam to a focus at one end of the central light receiving core.

16. The system of claim 1 wherein the light suppression system comprises:

a beam splitter located in the propagation path that decouples the projected light beam from the feedback light beam; and

a light dump that eliminates a split portion of the projected light beam that is not projected to the object.

17. The system of claim 1 wherein the computer controls scanning of the laser projector to produce a scan box glowing template, and processes the digital image signal.

18. The system of claim 1 wherein the computer controls scanning of the laser projector as an iterated raster scanning over all or a selected portion of the object to obtain valid three-dimensional and related light information for substantially all scan pixels.

19. A laser projection system, comprising:

a laser projector that projects a light beam to the surface of an object and scans that projected light beam over at least a portion of the surface, wherein a portion of the projected light beam is diffusely reflected from the surface back to the system as a feedback light beam;

a first optical signal detector that receives the feedback light beam and converts it to an image signal, wherein the projected light beam and the feedback light beam are associated with a given point on the surface and propagate in opposite directions along a common propagation path;

a light suppression system for suppressing unwanted light from entering the first optical signal detector, and comprising a spatial light filter that admits the feedback light beam to the first optical signal detector while substantially blocking stray light;

a computer for comparing the image signal with a corresponding reference signal to produce a measurement of the distance from the laser projector to the object surface, and controlling the system to buck the laser projector into a coordinate system of the object using three or more features on the object, wherein at least one of the three or more features serves as a targetless fiducial point, and wherein the computer further controls scanning of the laser projector as an iterated raster scanning over all or a selected portion of the object to obtain valid three-dimensional and related light information for substantially all scan pixels;

a beam splitter located in the propagation path that divides the projected light beam into a reference beam portion and a signal beam portion;

a second optical signal detector that converts the reference beam portion into a corresponding electrical reference signal;

an electronic circuit that samples the reference beam and the image signal at a rate sufficient to provide accurate values for elapsed time-of-flight and intensity of the feedback light beam;

a clock that synchronizes operation of the laser projector, electronic circuit, and computer; and

a dynamic range modulator that adjusts operation of the system, including varying the intensity of the projected beam, in response to light reflective characteristics of the object, wherein the dynamic range variation is on the order of at least 100,000.

20. A method for making a laser projection system, the method comprising:

providing a laser projector configured for projecting a light beam to the surface of an object and scanning that projected light beam over at least a portion of the surface;

providing a first optical signal detector configured for receiving a feedback light beam, the feedback light beam being a portion of the projected light beam that is diffusely reflected from the surface back to the laser projector, and for converting that feedback light beam to an image signal, wherein the projected light beam and the feedback light beam are associated with a given point on the surface and propagate in opposite directions along a common propagation path;

providing a light suppression system configured for suppressing unwanted light from entering the first optical signal detector; and

providing a computer configured for comparing the image signal with a corresponding reference signal to produce a measurement of the distance from the laser projector to the object surface, and for controlling the laser projection to buck the laser projector into a coordinate system of the object using three or more features on the object, wherein at least one of the three or more features serves as a targetless fiducial point.