# US 10,120,068 B1 · Calibration of laser sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,120,068 B1 - Document ID: US10120068B1 - Status: Granted - Kind: B1 - Application number: 15/730,572 - Filed: 2017-10-11 - Published: 2018-11-01 - Granted: 2018-11-06 - Earliest claimed: 2017-04-28 - Assignees: Sz Dji Technology Co., Ltd. - Applicants: Sz Dji Technology Co., Ltd. - Inventors: Kanzhi Wu; Lu Ma - Web page: https://patentgrep.com/patent/US10120068B1 ## CPC - G01S 7/4972: {Alignment of sensor} - G01B 11/24: for measuring contours or curvatures - G01B 11/26: for measuring angles or tapers; for testing the alignment of axes - G01B 21/042: {Calibration or calibration artifacts (G01B3/30, G01B9/02072 take precedence)} - G01S 7/4808: {Evaluating distance, position or velocity data} - G01S 13/867: {Combination of radar systems with cameras} - G01S 13/931: of land vehicles - G01S 17/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) - G01S 17/89: for mapping or imaging - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS ## Abstract Automatic calibration of laser sensors carried by a mobile platform, and associated systems and methods are disclosed herein. A representative method includes determining an overlapping region of point cloud data generated by laser sensors, comparing surface features of the point clouds within the overlapping region, and generating calibration rules based thereon. ## Claims ### Claim 1 A computer-implemented method for calibrating a first laser unit and a second laser unit both affixed to a common autonomous car, comprising: transforming point cloud information obtained from the first laser unit into a first point cloud in a coordinate system associated with the autonomous car based at least in part on a first transformation matrix, the first transformation matrix defined at least in part by a position and orientation of the first laser unit relative to the autonomous car; transforming point cloud information obtained from the second laser unit into a second point cloud in the coordinate system associated with the autonomous car based at least in part on a second transformation matrix, the second transformation matrix defined at least in part by a position and orientation of the second laser unit relative to the autonomous car; determining an overlapping region between the first and second point clouds based at least in part on paired points between the first and second point clouds, wherein the paired points include at least a nearest neighbor in the second point cloud for at least one point in the first point cloud; deriving a plurality of first features that at least partially characterize a surface of the first point cloud in the overlapping region; deriving a plurality of second features that at least partially characterize a surface of the second point cloud in the overlapping region; generating at least one calibration rule for calibration between the first and second laser units based at least in part on evaluating a function that includes at least the first and second features, wherein the at least one calibration rule includes at least one of a translational transformation or a rotational transformation; and causing calibration between the first and second laser units based on the at least one calibration rule. ### Claim 2 A computer-implemented method for calibrating at least a first emitter/detector unit and a second emitter/detector unit both carried by a common mobile platform, comprising: transforming point cloud information obtained from the first emitter/detector unit into a first point cloud in a reference system associated with the mobile platform; transforming point cloud information obtained from the second emitter/detector unit into a second point cloud in the reference system associated with the mobile platform; determining an overlapping region between the first and second point clouds based at least in part on identifying at least a nearest neighbor in the second point cloud for at least one point in the first point cloud; comparing surface attributes of the first and second point clouds in the overlapping region; and generating at least one calibration rule for calibration between the first and second emitter/detector units based at least in part on comparing the surface attributes, wherein the at least one calibration rule includes at least one of a translational transformation or a rotational transformation. ### Claim 3 (depends on 2) The method of claim 2, wherein transforming point cloud information obtained from the first emitter/detector unit is based at least in part on a first set of transformation rules. ### Claim 4 (depends on 3) The method of claim 3, wherein the first set of transformation rules is at least partially defined in accordance with a position and orientation of the first emitter/detector unit relative to the mobile platform. ### Claim 5 (depends on 3) The method of claim 3, wherein transforming point cloud information obtained from the second emitter/detector unit is based at least in part on a second set of transformation rules and wherein the second set of transformation rules differs from the first set of transformation rules. ### Claim 6 (depends on 3) The method of claim 3, wherein the reference system associated with the mobile platform comprises a coordinate system. ### Claim 7 (depends on 3) The method of claim 3, wherein the first set of transformation rules comprises a transform matrix. ### Claim 8 (depends on 2) The method of claim 2, wherein determining an overlapping region comprises creating a tree-structured data structure for at least one of the first or second point clouds. ### Claim 9 (depends on 8) The method of claim 8, wherein the tree-structured data structure comprises a K-Dimensional (KD) tree data structure. ### Claim 10 (depends on 2) The method of claim 2, further comprising causing calibration of the first and second emitter/detector units in accordance with the at least one calibration rule. ### Claim 11 A non-transitory computer-readable medium storing computer-executable instructions that, when executed, cause one or more processors associated with a mobile platform to perform actions comprising: transforming point cloud information obtained from a first emitter/detector unit into a first point cloud in a reference system associated with the mobile platform; transforming point cloud information obtained from a second emitter/detector unit into a second point cloud in the reference system associated with the mobile platform; determining an overlapping region between the first and second point clouds based at least in part on identifying at least a nearest neighbor in the second point cloud for at least one point in the first point cloud; comparing surface attributes of the first and second point clouds in the overlapping region; and generating at least one calibration rule for calibration between the first and second emitter/detector units based at least in part on comparing the surface attributes, wherein the at least one calibration rule includes at least one of translational transformation or a rotational transformation. ### Claim 12 (depends on 11) The computer-readable medium of claim 11, wherein the first emitter/detector unit includes at least one laser sensor. ### Claim 13 (depends on 12) The computer-readable medium of claim 12, wherein the at least one laser sensor has a field of view (FOV) that is smaller than at least one of 360 degrees, 180 degrees, 90 degrees, or 60 degrees. ### Claim 14 (depends on 12) The computer-readable medium of claim 12, wherein the first emitter/detector unit includes a plurality of laser sensors rigidly fixed relative to each other. ### Claim 15 (depends on 11) The computer-readable medium of claim 11, wherein comparing surface attributes comprises matching a surface associated with the first point cloud with a surface associated with the second point. ### Claim 16 (depends on 15) The computer-readable medium of claim 15, wherein matching a surface associated with the first point cloud with a surface associated with the second point comprises determining normal vector information with respect to at least a portion of the first point cloud. ### Claim 17 (depends on 11) The computer-readable medium of claim 11, wherein comparing surface attributes further comprises evaluating a target function defined at least in part by a plurality of points of the first and second point clouds that are within the overlapping region. ### Claim 18 (depends on 17) The computer-readable medium of claim 17, wherein the target function comprises a rotational component and a translational component. ### Claim 19 (depends on 18) The computer-readable medium of claim 18, wherein comparing surface attributes further comprises keeping the translational component fixed. ### Claim 20 (depends on 17) The computer-readable medium of claim 17, wherein generating at least one calibration rule comprises optimizing the target function. ### Claim 21 (depends on 20) The computer-readable medium of claim 20, wherein optimizing the target function is based at least in part on a least squares method. ### Claim 22 A vehicle including a programmed controller that at least partially controls one or more motions of the vehicle, wherein the programmed controller includes one or more processors configured to: transform point cloud information obtained from a first emitter/detector unit into a first point cloud in a reference system associated with the vehicle; transform point cloud information obtained from a second emitter/detector unit into a second point cloud in the reference system associated with the vehicle; determine an overlapping region between the first and second point clouds based at least in part on identifying at least a nearest neighbor in the second point cloud for at least one point in the first point cloud; compare surface attributes of the first and second point clouds in the overlapping region; and generate at least one calibration rule for calibration between the first and second emitter/detector units based at least in part on the comparison of surface attributes, wherein the at least one calibration rule includes at least one of a translational transformation or a rotational transformation. ### Claim 23 (depends on 22) The vehicle of claim 22, wherein determining an overlapping region comprises creating a tree-structured data structure for at least one of the first or second point clouds. ### Claim 24 (depends on 22) The vehicle of claim 22, wherein comparing surface attributes comprises matching a surface associated with the first point cloud with a surface associated with the second point. ### Claim 25 (depends on 22) The vehicle of claim 22, wherein comparing surface attributes further comprises evaluating a target function defined at least in part by a plurality of points of the first and second point clouds that are within the overlapping region. ### Claim 26 (depends on 22) The vehicle of claim 22, wherein the at least one calibration rule comprises a rule for transformation between coordinate systems of the first emitter/detector unit and the second emitter/detector unit. ### Claim 27 (depends on 22) The vehicle of claim 22, wherein the one or more processors are further configured to detect a difference between the generated at least one calibration rule against one or more previously generated calibration rules. ### Claim 28 (depends on 22) The vehicle of claim 22, wherein the vehicle includes at least one of an unmanned aerial vehicle (UAV), a manned aircraft, an autonomous car, a self-balancing vehicle, or a robot.