System and method for refining coordinate-based three-dimensional images obtained from a three-dimensional measurement system
A system uses range and Doppler velocity measurements from a lidar system and images from a video system to estimate a six degree-of-freedom trajectory of a target and generate a three-dimensional image of the target. The system may refine the three-dimensional image by reducing the stochastic components in the transformation parameters between video frame times.
1. A system for refining 3D images, the system comprising:
a lidar subsystem configured to direct at least two beams toward a target, generate a first set of line scan 3D measurements for a plurality of points on the target for a first beam of the at least two beams, and generate a second set of overscan 3D measurements for the plurality of points on the target for a second beam of the at least two beams;
a video subsystem configured to provide a set of video frames of the target; and
a processor configured to:
receive, from the lidar subsystem, the first set of line scan 3D measurements and the second set of overscan 3D measurements,
receive, from the video subsystem, the set of video frames of the target,
determine, at each frame time, a plurality of Δz offsets between pre-overscan measurements and the line scan 3D measurements and between post-overscan measurements and the line scan 3D measurements, and
adjust a plurality of transformation parameters based on a least square optimization and the plurality of Δz offsets.
2. The system of claim 1 , wherein the pre-overscan measurements correspond to those measurements from the second set of overscan measurements taken during the inter-frame time interval immediately before said each frame time and wherein the post-overscan measurements correspond to those measurements from the second set of overscan measurements taken during the inter-frame time interval immediately after said each frame time.
3. A method for refining 3D images, the method comprising:
receiving, from a lidar subsystem configured to direct at least three beams toward a target, a set of line scan 3D measurements for a plurality of points on the target from two beams of the at least three beams, and a set of overscan measurements for a plurality of points on the target from an overscan beam of the at least three beams;
receiving, from a video subsystem, a set of video frames of the target;
determining, at each frame time, a first plurality of Δz offsets between pre-overscan measurements and the line scan 3D measurements and a second plurality of Δz offsets between post-overscan measurements and the line scan 3D measurements; and
adjusting a plurality of transformation parameters to minimize a difference between the first plurality of Δz offsets and the second plurality of Δz offsets.
4. The method of claim 3 , wherein the pre-overscan measurements correspond to those measurements from the set of overscan measurements taken during the inter-frame time interval immediately before said each frame time and wherein the post-overscan measurements correspond to those measurements from the set of overscan measurements taken during the inter-frame time interval immediately after said each frame time.