Model establishment and error correction of FMCW lidar

The geometry of frequency-modulated continuous-wave lidar deviates from that of the design model owing to the mechanical machining and assembly of the lidar. In this study，the effect of the sub-coordinate system offset and roll on the coordinate measurement accuracy of the instrument is investigated，and a correction model is developed for the geometric error of the lidar. This model can increase the measurement accuracy of the measurement system without changing the hardware structure of the system. First，a set of lidar coordinate systems is established，and the sources of spatial coordinate measurement errors are analyzed. The geometric error transfer of the measurement coordinates is achieved by applying the transformation matrix between the coordinate systems. Then，the geometric errors of the different coordinate systems are combined，and an explicit expression for the geometric spatial coordinate error of the lidar is established. Based on this，a least-squares optimization objective is established for obtaining the error factors and the corrected coordinates. The obtained error factors can be used as corrections for subsequent coordinate measurements. Finally，this method is used to design a calibration field with a laser tracker as the high-precision measurement instrument and the spherical center of the target sphere as the standard point. A system error correction experiment is performed by employing the laser tracker and lidar to evaluate the target sphere at the same position. The experimental results indicate that the average error of the lidar spatial distance measurement is reduced from 0. 044 8% to 0. 003 8% and the maximum error value is reduced from 4. 17 to 0. 30 mm after the correction，thereby confirming the effectiveness of the lidar geometric error calibration and error correction method. © 2023 Chinese Academy of Sciences. All rights reserved.