US-12625270-B2 - Alignment and registration system and method for coordinate scanners

Abstract

An example method includes moving a base unit through an environment, the base unit comprising the first scanner and the second scanner. The method further includes capturing, by the first scanner, a first scan of the environment, the first scan comprising at least one first scanline. The method further includes capturing, by the second scanner, a second scan of the environment, the second scan comprising at least one second scanline, wherein the second scanner scans about a first axis at a first speed and scans about a second axis at a second speed. The method further includes determining, by a processing system, an intersection at an object surface between one of the at least one first scanline and one of the at least one second scanline. The method further includes aligning, by the processing system, the first scan and the second scan based at least in part on the intersection.

Inventors

• Johannes Buback
• Martin Ossig
• Igor Sapina

Assignees

• FARO TECHNOLOGIES, INC.

Dates

Publication Date

20260512

Application Date

20210513

Claims (20)

1. 1 . A method for aligning scans from a first scanner and a second scanner, the method comprising: moving a base unit through an environment, the base unit comprising the first scanner and the second scanner; capturing, by the first scanner, a first scan of the environment, the first scan comprising at least one first scanline; capturing, by the second scanner, a second scan of the environment, the second scan comprising at least one second scanline, wherein the second scanner scans about a first axis at a first speed and scans about a second axis at a second speed; determining, by a processing system, an intersection at an object surface between one of the at least one first scanline and one of the at least one second scanline; aligning, by the processing system, the first scan and the second scan based at least in part on the intersection; determining at least one of a relative position and orientation of the first scanner and at least one of a relative position and orientation of the second scanner, based on the aligning of the first scan captured by the first scanner and the second scan captured by the second scanner; and optimizing the aligning by: identifying a natural target based at least in part on a minimum fit line length of the at least one first scanline and the at least one second scanline; wherein the minimum fit line length comprises a length of the at least one first scanline without a discontinuity and a length of the at least one second scanline without a discontinuity; and iteratively including other natural targets having a reduced fit line length; wherein the reduced fit line length comprises a length of a line without a discontinuity, and the reduced fit line length is less than the minimum fit line length.
2. 2 . The method of claim 1 , wherein the one of the at least one first scanline and the one of the at least one second scanline are captured respectively by the first scanner and the second scanner within a predetermined time interval.
3. 3 . The method of claim 1 , wherein the at least one first scanline is approximately horizontal, and wherein the at least one second scanline is approximately vertical.
4. 4 . The method of claim 1 , wherein the at least one first scanline is orthogonal to the at least one second scanline.
5. 5 . The method of claim 1 , wherein the at least one first scanline is not parallel to the at least one second scanline.
6. 6 . The method of claim 1 , wherein the determining the intersection comprises generating a plurality of conditions used to perform an optimization, the method further comprising: performing the optimization by varying one or more parameters to determine a relative position or a relative orientation between the first scanner and the second scanner.
7. 7 . The method of claim 6 , wherein the optimization is performed iteratively by varying one of the one or more parameters during each iteration.
8. 8 . The method of claim 7 , wherein the one of the one or more parameters comprises an orientation angle about a z-axis between the first scanner and the second scanner.
9. 9 . The method of claim 6 , wherein the optimization is performed iteratively by varying more than one of the one or more parameters during each iteration.
10. 10 . The method of claim 1 , further comprising: prior to capturing the first scan or capturing the second scan, providing a predetermined initial position and orientation of the base unit.
11. 11 . The method of claim 1 , further comprising optimizing the aligning based at least in part on stationary data and moving data.
12. 12 . The method of claim 1 , wherein the determining and the aligning are performed while capturing the first scan and capturing the second scan.
13. 13 . The method of claim 1 , wherein the determining and the aligning are performed subsequent to capturing the first scan and capturing the second scan.
14. 14 . The method of claim 1 , wherein the first scanner is a 2D scanner, the first scan is a 2D scan, the second scanner is a 3D scanner, and the second scan is a 3D scan.
15. 15 . The method of claim 1 , wherein the first scanner is a first 3D scanner, the first scan is a first 3D scan, the second scanner is a second 3D scanner, and the second scan is a second 3D scan.
16. 16 . The method of claim 1 , further comprising: calculating, by the processing system, an initial 3D trajectory of the base unit; calculating, by the processing system, an initial 3D point cloud based at least in part on the first scan and the second scan; and improving, by the processing system, the initial 3D trajectory of the base unit to generate an improved 3D trajectory of the base unit based at least in part on the intersection at the object surface between the one of the at least one first scanline captured by the first scanner and the one of the at least one second scanline captured by the second scanner.
17. 17 . The method of claim 1 , wherein the first scanline is a virtual scanline.
18. 18 . A method comprising: moving a base unit through an environment, the base unit comprising a first scanner and a second scanner; capturing, by the first scanner, a first scan of the environment, the first scan comprising at least one first scanline; capturing, by the second scanner, a second scan of the environment, the second scan comprising at least one second scanline; aligning, by a processing system, the first scan and the second scan based at least in part on an intersection at an object surface between one of the at least one first scanline and one of the at least one second scanline; calculating, by the processing system, an initial 3D trajectory of the base unit; calculating, by the processing system, an initial 3D point cloud based at least in part on the first scan and the second scan; improving, by the processing system, the initial 3D trajectory of the base unit to generate an improved 3D trajectory of the base unit based at least in part on the intersection at the object surface between the one of the at least one first scanline captured by the first scanner and the one of the at least one second scanline captured by the second scanner; and optimizing the aligning by: identifying a natural target based at least in part on a minimum fit line length of the at least one first scanline and the at least one second scanline; wherein the minimum fit line length comprises a length of the at least one first scanline without a discontinuity and a length of the at least one second scanline without a discontinuity; and iteratively including other natural targets having a reduced fit line length; wherein the reduced fit line length comprises a length of a line without a discontinuity, and the reduced fit line length is less than the minimum fit line length.
19. 19 . The method of claim 18 , wherein the improving, by the processing system, the initial 3D trajectory further comprises: minimizing a cost function by adjusting the initial 3D trajectory based at least in part on one or more of the at least one first scanline and one or more of the at least one second scanline.
20. 20 . The method of claim 19 , wherein minimizing the cost function comprises at least one of applying a gradient descent technique or applying a least squares regression technique.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application Ser. No. 63/031,825, filed May 29, 2020, the entire disclosure of which is incorporated herein by reference. BACKGROUND The present application is directed to a system that optically scans an environment, such as a building, and in particular to a mobile scanning system that generates three-dimensional scans of the environment. The automated three-dimensional (3D) scanning of an environment is desirable as a number of scans may be performed in order to obtain a complete scan of the area. 3D coordinate scanners include time-of-flight (TOF) coordinate measurement devices. A TOF laser scanner is a scanner in which the distance to a target point is determined based on the speed of light in air between the scanner and a target point. A laser scanner optically scans and measures objects in a volume around the scanner through the acquisition of data points representing object surfaces within the volume. Such data points are obtained by transmitting a beam of light onto the objects and collecting the reflected or scattered light to determine the distance, two-angles (i.e., an azimuth and a zenith angle), and optionally a gray-scale value. This raw scan data is collected, stored and sent to a processor or processors to generate a 3D image representing the scanned area or object. It should be appreciated that where an object (e.g. a wall, a column, or a desk) blocks the beam of light, that object will be measured but any objects or surfaces on the opposite side will not be scanned since they are in the shadow of the object relative to the scanner. Therefore, to obtain a more complete scan of the environment, the TOF scanner is moved to different locations and separate scans are performed. Subsequent to the performing of the scans, the 3D coordinate data (i.e. the point cloud) from each of the individual scans are registered to each other and combined to form a 3D image or model of the environment. Some existing measurement systems have been mounted to a movable structure, such as a cart, and moved on a continuous basis through the building to generate a digital representation of the building. However, these provide generally lower data quality than stationary scans. These systems tend to be more complex and require specialized personnel to perform the scan. Further, the scanning equipment including the movable structure may be bulky, which could further delay the scanning process in time sensitive situations, such as a crime or accident scene investigation. Further, even though the measurement system is mounted to a movable cart, the cart is stopped at scan locations so that the measurements can be performed. This further increases the time to scan an environment. Accordingly, while existing scanners are suitable for their intended purposes, what is needed is a system for having certain features of embodiments of the present invention. BRIEF DESCRIPTION According to one aspect of the invention, a method is provided for aligning scans from a first scanner and a second scanner. The method includes moving a base unit through an environment, the base unit including the first scanner and the second scanner. The method further includes capturing, by the first scanner, a first scan of the environment, the first scan including at least one first scanline. The method further includes capturing, by the second scanner, a second scan of the environment, the second scan including at least one second scanline, wherein the second scanner scans about a first axis at a first speed and scans about a second axis at a second speed. The method further includes determining, by a processing system, an intersection at an object surface between one of the at least one first scanline and one of the at least one second scanline. The method further includes aligning, by the processing system, the first scan and the second scan based at least in part on the intersection. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include that the one of the at least one first scanline and the one of the at least one second scanline are captured within a predetermined time interval. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include that the aligning determines at least one of a relative position and orientation of the first scanner and the second scanner. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include that the at least one first scanline is approximately horizontal, and wherein the at least one second scanline is approximately vertical. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include that the at least one first scanline is orthogonal to the at