Integrated system for quickly and accurately imaging and modeling three-dimensional objects

• US 6,246,468 B1
• Filed: 10/23/1998
• Issued: 06/12/2001
• Est. Priority Date: 04/24/1996
• Status: Expired due to Term

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Cyra Technologies, Inc. (Hexagon AB)
• Inventors: Dimsdale, Jerry
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/177,913
• Time in Patent Office: 963 Days
• Field of Search: 356/4.02, 356/5.01, 356/4.09, 702/159, 702/167
• US Class Current: 356/4.02
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4818 using optical fibres

Abstract

An integrated system generates a model of a three-dimensional object. A scanning laser device scans the three-dimensional object and generates a point cloud. The points of the point cloud each indicate a location of a corresponding point on a surface of the object. A first model is generated, responsive to the point cloud, that generates a first model representing constituent geometric shapes of the object. A data file is generated, responsive to the first model, that can be inputted to a computer-aided design system.

Claims

1. A system for calibrating the timing electronics in a device which requires monitoring the time of flight of the output pulses transmitted from a laser to a remote target and back to a detector, the output of which is supplied to the timing electronics comprising:

a single mode optical fiber with one end of the fiber positioned to periodically receive the output pulses of the laser, said single mode optical fiber having a known length and wherein partial reflectors are located at each end of the optical fiber such that for each laser pulse entering the fiber a train of pulses will exit the fiber, said pulses being directed to the detector, said detector generating output signals in response thereto, said signals being passed through the timing electronics; and

a processor for calculating a theoretical length of the fiber based on the detection of the train of pulses exiting the fiber and comparing that calculated length with the known length of the fiber to calibrate the timing electronics to improve the accuracy of the time of flight measurements of the laser pulses sent to and returning from the remote target.

2. A system as recited in claim 1 further including delay measurement electronics and wherein the train of pulses have a fixed delay therebetween whereby the monitoring of the train of pulses can be used to further calibrate the timing electronics.

3. A system as recited in claim 2 further including a means for varying the power of the pulses monitored by the detector and wherein said detector functions to generate a signal when the power of the detected light exceeds a predetermined threshold and wherein said processor functions to track the variation in the delay of the generation of the output signal by the detector as a function of the power of the output pulses, said processor further functioning to calibrate the measurement of the delay based on the measured power of successive pulses used for monitoring the time of flight.

4. A system for calibrating the measuring electronics in a device which requires monitoring frequency changes in a light beam generated by a laser used to measure distance to an object, wherein said beam has frequency chirp imposed thereon comprising:

a single mode optical fiber with one end thereof positioned to receive light from the laser;

a detector positioned to receive light which has travelled through and exited the fiber in combination with light from the laser which has not traveled through the fiber, said detector for monitoring the changes in the frequency of the combined beam; and

processor for determining the linearity of the chirp on the beam based on uniformity of the frequency changes measured by the detector and using the result to calibrate the measuring electronics.

5. A system as recited in claim 4 wherein the fiber has known length and includes a partial reflector on said one end and at least a partial reflector on the other end, and wherein light reflected from said one end of the fiber which has not traveled in the fiber is measured by the detector and wherein the processor further functions to calculate a theoretical length of the fiber based on the frequency changes measured by the detector and compares that calculated length with the known length of the fiber to calibrate the measuring electronics.

6. A method for calibrating the timing electronics in a device which requires monitoring the time of flight of the output pulses transmitted from a laser to a remote target and back to a detector, the output of which is supplied to the timing electronics comprising the steps of:

providing a single mode optical fiber of a known length and having partial reflectors located at each end thereof,

periodically injecting selected ones of the output pulses from the laser in one end of the fiber such that a train a pulses will exit the other end of the fiber;

monitoring the pulses exiting the fiber with the detector and generating a signal in response thereto;

passing the signal through the timing electronics to be calibrated; and

calculating a theoretical length of the fiber based on the signal passed through the timing electronics and comparing that calculated length with the known length of the fiber to calibrate the timing electronics to improve the accuracy of the time of flight measurements of the laser pulses sent to and returning from the remote target.

7. A method as recited in claim 6 further including the step of monitoring the delay between pulses to further calibrate the timing electronics.

8. A method as recited in claim 7 further including the steps of varying the power of the laser pulses and generating a signal when the monitored laser pulses exceeds a predetermined threshold and tracking the variation in the delay of the generation of the output signal as a function of the power of the output pulses and calibrating the measurement of the delay based on the measured power of successive pulses used for monitoring the time of flight.

9. A system for calibrating the timing electronics in a device which requires monitoring the time of flight of the output pulses transmitted from a laser to a remote target and back to a detector, the output of which is supplied to the timing electronics comprising:

an optical fiber with one end of the fiber positioned to periodically receive the output pulses of the laser, said optical fiber having a length whose variation with temperature can be accurately characterized, and wherein partial reflectors are located at each end of the optical fiber such that for each laser pulse entering the fiber a train of pulses will exit the fiber, said pulses being directed to the detector, said detector generating output signals in response thereto, said signals being passed through the timing electronics; and

a processor for monitoring variations in the delay between successive pulses in the train exiting the fiber, said variations induced by time and/or temperature changes, said processor further functioning to calibrate the timing electronics based on these monitored variations to improve the accuracy of the time of flight measurements of the laser pulses sent to and returning from the remote target.

10. A system as recited in claim 9 wherein said optical fiber is a single mode optical fiber.

11. A system as recited in claim 10 wherein the length of the fiber does not vary with temperature.

12. A system as recited in claim 9 further including delay measurement electronics and wherein the train of pulses have a fixed delay therebetween whereby the monitoring of the train of pulses can be used to further calibrate the timing electronics.

13. A system as recited in claim 12 further including a means for varying the power of the pulses monitored by the detector and wherein said detector functions to generate a signal when the power of the detected light exceeds a predetermined threshold and wherein said processor functions to track the variation in the delay of the generation of the output signal by the detector as a function of the power of the output pulses, said processor further functioning to calibrate the measurement of the delay based on the measured power of successive pulses used for monitoring the time of flight.

14. A method for calibrating the timing electronics in a device which requires monitoring the time of flight of the output pulses transmitted from a laser to a remote target and back to a detector, the output of which is supplied to the timing electronics comprising the steps of:

providing an optical fiber having a length whose variation with temperature can be accurately characterized and having partial reflectors located at each end thereof,

periodically injecting selected ones of the output pulses from the laser in one end of the fiber such that a train a pulses will exit the other end of the fiber;

monitoring the pulses exiting the fiber with the detector and generating a signal in response thereto;

passing the signal through the timing electronics to be calibrated; and

monitoring variations in the delay between successive pulses in the train exiting the fiber, said variations induced by time and/or temperature changes and calibrating the timing electronics based on these monitored variations to improve the accuracy of the time of flight measurements of the laser pulses sent to and returning from the remote target.

15. A method as recited in claim 14 wherein said optical fiber is a single mode optical fiber.

16. A method as recited in claim 15 wherein the length of the fiber does not vary with temperature.

17. A method as recited in claim 14 further including the step of monitoring the delay between pulses to further calibrate the timing electronics.

18. A method as recited in claim 17 further including the steps of varying the power of the laser pulses and generating a signal when the monitored laser pulses exceeds a predetermined threshold and tracking the variation in the delay of the generation of the output signal as a function of the power of the output pulses and calibrating the measurement of the delay based on the measured power of successive pulses used for monitoring the time of flight.