Directed registration of three-dimensional scan measurements using a sensor unit

• US 9,134,339 B2
• Filed: 09/24/2014
• Issued: 09/15/2015
• Est. Priority Date: 09/24/2013
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Becker, Reinhard, Ossig, Martin, Becker, Bernd-Dietmar
• Primary Examiner(s): Toatley, Gregory J
• Assistant Examiner(s): ALLI, IYABO
• Application Number:
  US14/494,887
• Publication Number:
  US 20150085301A1
• Time in Patent Office: 356 Days
• Field of Search: 382100-156, 356/489, 356/502, 356/5.01, 356/475, 356/445, 356/608
• US Class Current: 1/1
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01C 3/06 Use of electric means to obtain final indication
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• 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 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A laser scanner measures 3D coordinates from a first position and a second position and uses a sensor unit that includes at least an accelerometer and gyroscope to register the 3D coordinates, the registration based at least in part on comparison to a measured sensor displacement to a preferred displacement value.

Claims

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

providing the laser scanner having integral components that include a light emitter, a light receiver, a first angle measuring device, a second angle measuring device, a control and evaluation unit, and a sensor unit, the sensor unit including at least an accelerometer and a gyroscope;

moving the laser scanner to a first position and a first orientation in the environment;

for each of a plurality of first object points;

measuring a first angle with the first angle measuring device;

measuring a second angle with the second angle measuring device;

emitting with the light emitter an emission light beam;

reflecting the emission light beam from the object to produce a reception light beam;

receiving with the light receiver the reception light beam and obtaining a first electrical signal in response;

determining with the control and evaluation unit a distance based at least in part on the first electrical signal and on a speed of light in air;

determining with the control and evaluation unit first three-dimensional (3D) coordinates of the first object points in a first instrument frame of reference, the 3D coordinates based at least in part on the first angles, the second angles, and the distances to the plurality of object points on the object;

determining a preferred displacement value and a displacement tolerance;

taking initial readings from the sensor unit;

moving the laser scanner from the first position to a second position by incremental steps, at each incremental step;

taking current readings of the sensor unit;

calculating a measured sensor displacement based at least in part on the current readings of the sensor unit and the initial readings of the sensor unit;

stopping movement of the laser scanner at the second position when the measured sensor displacement is within the displacement tolerance of the preferred displacement value;

for each of a plurality of second object points;

measuring the first angle with the first angle measuring device;

measuring the second angle with the second angle measuring device;

emitting with the light emitter the emission light beam;

reflecting the emission light beam from the object to produce the reception light beam;

receiving with the light receiver the reception light beam and obtaining the first electrical signal in response;

determining with the control and evaluation unit the distance based at least in part on the first electrical signal and on a speed of light in air;

determining with the control and evaluation unit second 3D coordinates of the object in a second instrument frame of reference, the 3D coordinates based at least in part on the first angles, the second angles, and the distances to the plurality of object points on the object;

registering the first 3D coordinates and the second 3D coordinates into a common set of 3D coordinates in a common frame of reference based at least in part on the first 3D coordinates, the second 3D coordinates, and the measured sensor displacement; and

storing the common set of 3D coordinates.

2. The method of claim 1, wherein in the step of providing the laser scanner, the sensor unit further includes a magnetometer.

3. The method of claim 1, wherein in the step of providing the laser scanner, the sensor unit further includes a pressure sensor.

4. The method of claim 1, wherein in the step of providing the laser scanner, the sensor unit further includes a GPS unit.

5. The method of claim 1, wherein in the step of providing the laser scanner, the accelerometer is a three-axis accelerometer.

6. The method of claim 1, wherein in the step of providing the laser scanner, the gyroscope is a three-axis gyroscope.

7. The method of claim 1, wherein in the step of providing the laser scanner, the accelerometer is a microelectromechanical system (MEMS) device and the gyroscope is a MEMS device.

8. The method of claim 1, wherein the object includes a plurality of targets.

9. The method of claim 8, wherein the targets are selected from the group consisting of spheres and checkerboards.

10. The method of claim 8, wherein the targets are natural features.

11. The method of claim 10, wherein the natural features are selected from the group consisting of edges, planes, and corners.

12. The method of claim 1, wherein, in the step of determining a preferred displacement value, the preferred displacement value is based at least in part on an expected overlap of regions scanned by the laser scanner from the first position and the second position.