SYSTEM AND METHOD FOR FIELD CALIBRATING VIDEO AND LIDAR SUBSYSTEMS USING FACIAL FEATURES
A system uses range and Doppler velocity measurements from a lidar subsystem and images from a video subsystem to estimate a six degree-of-freedom trajectory of a target. The video subsystem and the lidar subsystem may be aligned with one another by mapping the measurements of various facial features obtained by each of the subsystems to one another.
1 . A system for calibrating a lidar subsystem, the system comprising:
a lidar subsystem configured to:
direct at least two beams toward a target, wherein the at least two beams comprises a first beam directed toward the target via a first scanning mirror and a second beam directed toward the target via a second scanning mirror,
generate a first set of three-dimensional measurements for a plurality of points on the target for the first beam, and
generate a second set of three-dimensional measurements for a plurality of points on the target for the second beam; and
a processor configured to:
receive, from the lidar subsystem, the first set of three-dimensional measurements and the second set of three-dimensional measurements,
compare the first set of three-dimensional measurements with the second set of three-dimensional measurements;
determine one or more offsets in locations of a plurality of facial features between the first set of three-dimensional measurements and the second set of three-dimensional measurements based on the comparison; and
determine one or more calibration adjustments to be made between the first scanning mirror and the second scanning mirror based on the one or more offsets.
2 . The system of claim 1 , wherein the one or more offsets are determined at a plurality of scanning positions.
3 . The system of claim 1 , wherein the processor is further configured to:
adjust one or more transformation parameters that transform a coordinate system of the first set of three-dimensional measurements to a coordinate system of the second set of three-dimensional measurements based on the one or more calibration adjustments.
4 . A system for calibrating a lidar subsystem and a video subsystem, the system comprising:
a lidar subsystem configured to direct at least two beams toward a target and that generates a set of three-dimensional measurements for a plurality of points on the target for each of the at least two beams;
a video subsystem configured to provide at least one image of the target; and
a processor configured to:
receive, from the lidar subsystem, the set of three-dimensional measurements,
receive, from the video subsystem, the at least one image of the target,
determine locations of a plurality of symmetrical facial features based on the at least one image of the target and a 3D symmetry place, wherein the 3D symmetry plane is determined based on the set of three-dimensional measurements,
determine a noseridge relative to the 3D symmetry plane,
determine a horizontal offset between the locations of the plurality of symmetrical facial features and the 3D symmetry plane,
correct the horizontal offset by a shift between the 3D horizontal offset and the noseridge,
determine a first location of lip line based on the at least one image of the target;
determine a second location of the lip line based on the set of three-dimensional measurements,
determine a vertical offset based on the first location and the second location, and
determine one or more calibration adjustments based on the corrected horizontal offset and the vertical offset.
5 . The system of claim 4 , wherein the plurality of symmetrical facial features comprises eyes and nostrils.