Laser scanner having a multi-color light source and real-time color receiver

• US 9,551,575 B2
• Filed: 10/28/2014
• Issued: 01/24/2017
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E., Becker, Reinhard
• Primary Examiner(s): RATCLIFFE, LUKE D
• Application Number:
  US14/525,316
• Publication Number:
  US 20150043009A1
• Time in Patent Office: 819 Days
• Field of Search: 356/4.01
• US Class Current: 1/1
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A laser scanner includes a light emitter that generates a modulated light beam for measuring distance and red, blue, and green lights for capturing colors. The beam is collimated and directed to an object point with a steering mirror. Reflected light from the object point is directed by the steering mirror onto scanner optics. The reflected light is directed to an optical receiver that sends the first light in a first path and the second, third and fourth lights in a second path to a color receiver. The first light is demodulated to determine distance to the target. The second, third, and fourth lights are separated and measured to determine three color values. The color values are combined with the measured distance value to determine a color 3D coordinate for the object point.

Claims

1. A laser scanner for optically scanning and measuring an environment, comprising:

a light emitter configured to emit an emission light beam, the emission light beam being a superposition of a first light, a second light, a third light, and a fourth light, the first light being modulated, the second, third, and fourth lights each having a different wavelength in the visible spectrum;

a collimator configured to collimate the emission light beam;

a steering mirror having a reflective surface and configured to rotate about a first axis, the steering mirror further configured to deflect the emission light beam onto an object point in the environment and to receive a reception light beam reflected from the object point;

scanner optics configured to receive the reception light beam from the steering mirror;

an optical receiver configured to receive the reception light beam from the steering mirror, the optical receiver further configured to send the first light in a first path and to send the second, third, and fourth lights in a second path;

a control and evaluation unit configured to receive the first light in the first path, to convert the first light into a first electrical signal, and to determine a distance to the object based at least in part on the first electrical signal;

a color receiver configured to receive the second, third, and fourth lights on the second path, to convert the second, third, and fourth lights into second, third, and fourth electrical signals, and to determine a first color value, a second color value, and a third color value based at least in part on the second, third, and fourth electrical signals;

a measuring head configured to rotate around a second axis perpendicular to the first axis, the first axis and the second axis intersecting in a gimbal point, the gimbal point being located on the steering mirror; and

a processor configured to determine a three-dimensional color representation of the object point, the three-dimensional color representation based at least in part on the distance to the object, the first color value, the second color value, and the third color value.

2. The laser scanner of claim 1 further comprising:

a first angular encoder configured to measure a first angle of rotation about the first axis; and

a second angular encoder configured to measure a second angle of rotation about the second axis.

3. The laser scanner of claim 2 wherein the processor is further configured to determine a three-dimensional color representation of the object point based on the first angle of rotation and the second angle of rotation.

4. The laser scanner of claim 1 wherein the color receiver further includes a first optical element configured to separate the second, third, and fourth lights.

5. The laser scanner of claim 4 wherein the first optical element is configured to direct the second light, third light, and fourth light to a second optical detector, a third optical detector, and a fourth optical detector, respectively, to obtain the second electrical signal, the third electrical signal, and the fourth electrical signal, respectively.

6. The laser scanner of claim 5 wherein the color receiver further includes an analog-to-digital converter configured to receive the second electrical signal, the third electrical signal, and the fourth electrical signal, and to determine in response the first color value, the second color value, and the third color value, respectively.

7. The laser scanner of claim 5 wherein the color receiver further comprises an optical bandpass filter optically disposed in front of each one of the second, third, and fourth optical detectors, respectively.

8. The laser scanner of claim 5 wherein the light emitter includes a second optical element configured to combine the first, second, third, and fourth lights, the second optical element including a plurality of dichroic beam splitters.

9. The laser scanner of claim 5 wherein the second, third, and fourth lights are modulated at a second, third, and fourth frequency respectively, the second, third, and fourth frequencies each being a different frequency.

10. The laser scanner of claim 9 wherein the second electrical signal, the third electrical signal, and the fourth electrical signal are sent through a first bandpass filter, a second bandpass filter, and a third bandpass filter, respectively, each of the first bandpass filter, the second bandpass filter, and the third bandpass filter having a different center frequency.

11. The laser scanner of claim 1 wherein the processor is further configured to determine a three-dimensional color representation of a plurality of object points, the three-dimensional color representation based at least in part on the distance to the object, the first color value, the second color value, and the third color value measured for each of a plurality of object points.

12. A method for optically scanning and measuring an environment with a laser scanner, the method comprising:

providing a light emitter, a collimator, a steering mirror rotatable about a first axis, scanner optics, an optical receiver, a control and evaluation unit, a color receiver, a measuring head rotatable about a second axis, and a processor;

modulating a first light;

combining the first light with a second light, a third light, and a fourth light to obtain an emission light beam, the second, third, and fourth lights each having a different wavelength in the visible spectrum;

collimating the emission light beam with the collimator;

deflecting the emission light beam onto an object point in the environment with the steering mirror and in response receiving a reception light beam reflected from the object point;

receiving with the optical receiver the reception light beam from the steering mirror;

sending with the optical receiver the first light in the reception beam in a first path and the second, third, and fourth light in the reception beam in a second path;

receiving with the control and evaluation unit the first light in the first path, converting the first light into a first electrical signal, and determining a distance to the object based at least in part on the first electrical signal;

receiving with the color receiver the second, third, and fourth lights on the second path, converting the second, third, and fourth lights into second, third, and fourth electrical signals, and determining a first color value, a second color value, and a third color value based at least in part on the second, third, and fourth electrical signals;

rotating the measuring head around the second axis perpendicular to the first axis, the first axis and the second axis intersecting in a gimbal point, the gimbal point being located on the steering mirror; and

determining with the processor a three-dimensional color representation of the object point, the three-dimensional color representation based at least in part on the distance to the object, the first color value, the second color value, and the third color value; and

storing the three-dimensional color representation of the object point.