Reflectance Intensity Assisted Automatic and Accurate Extrinsic Calibration of 3D LiDAR and Panoramic Camera Using a Printed Chessboard

This paper presents a novel method for fully automatic and convenient extrinsic calibration of a 3D LiDAR and a panoramic camera with a normally printed chessboard. The proposed method is based on the 3D corner estimation of the chessboard from the sparse point cloud generated by one frame scan of the LiDAR. To estimate the corners, we formulate a full-scale model of the chessboard and fit it to the segmented 3D points of the chessboard. The model is fitted by optimizing the cost function under constraints of correlation between the reflectance intensity of laser and the color of the chessboard's patterns. Powell's method is introduced for resolving the discontinuity problem in optimization. The corners of the fitted model are considered as the 3D corners of the chessboard. Once the corners of the chessboard in the 3D point cloud are estimated, the extrinsic calibration of the two sensors is converted to a 3D-2D matching problem. The corresponding 3D-2D points are used to calculate the absolute pose of the two sensors with Unified Perspective-n-Point (UPnP). Further, the calculated parameters are regarded as initial values and are refined using the Levenberg-Marquardt method. The performance of the proposed corner detection method from the 3D point cloud is evaluated using simulations. The results of experiments, conducted on a Velodyne HDL-32e LiDAR and a Ladybug3 camera under the proposed re-projection error metric, qualitatively and quantitatively demonstrate the accuracy and stability of the final extrinsic calibration parameters.Comment: 20 pages, submitted to the journal of Remote Sensin

Symmetry breaking and mechanical filter make a pseudo-gimbal-less two-dimensional MEMS scanning mirror with multiple scanning modes

Miniaturized two-dimensional scanning mirror based on microelectromechanical systems (MEMS) technology has great potential in automotive industry, consumer electronics, and biomedicine, etc. Due to its high frequency and large angle, resonant scanning is the mainstream in all MEMS actuation mechanisms, such as harmonic resonant electromagnetic scanner and parametric resonant electrostatic scanner. Although electrostatic scanner has the advantages of low power consumption and IC process compatibility, some shortcomings of parametric resonance, including double frequency of driver electronics and additional feedback control or frequency stabilization system, limit its further application. The symmetry of coplanar electrostatic comb actuator is broken in this paper, and harmonic resonant electrostatic scanner with excellent performance is realized. Further, through adopting mechanical filter, two-dimensional scanning can be achieved through one set of actuators, which avoids the problem that two sets (each for one dimension) of electrostatic actuators must be insulated each other through complicated and expensive processes. A two-dimensional MEMS scanner based on symmetry breaking and mechanical filter was proposed and demonstrated. Multiple scanning modes can be achieved through selective control of a set of four identical actuators.Comment: 20 pages, 8 figure