Optical axis parallelism calibration in three-channel filter-based non-imaging passive ranging system based on oxygen absorption

摘要

In order to solve the problem of the poor real-time measurements caused by using hyperspectral imaging spectrometers in previous work and simplify the system structure, a three-channel filter-based non-imaging passive ranging system based on oxygen absorption is designed. In this system, there are three independent spectral measurement channels, which are corresponded to the oxygen A absorption band and its left and right non-absorption band shoulders respectively, and there is a sighting telescope for aiming at the target. Optical axis parallelism calibration between each spectral measurement channel and the aiming optical path is critical to ranging accuracy of this passive ranging system. A digital self-collimation optical axis parallelism calibration method is proposed. In this method, optical axis of the spectral measurement channel is drew out by a rhombic prism in parallel, and then reversed by a cube-corner prism into the aiming telescope. Both the focal plane of the spectral measurement channel and the cross reticle of the aiming telescope are imaged in the same CCD camera, the optical axis non-parallel error is measured by comparing the position of image center of the focal plane of the spectral measuring channel and the cross reticle of the aiming telescope. Then by adjusting the attitude of the spectral measurement channel until the center of the two images coincide, the optical axis parallelism can be calibrated. Potential errors of this calibration method are analyzed, and it is concluded that the precision is less than 2", and the feasibility and accuracy of this method are verified by experiments.