Optical alignment method for transmitter-receiver terminals based on camera focusing and transmitter defocus...

Laser optoelectronic transceiver systems are widely used in space, aviation, and ground platforms. Accurate control of focal positions in the terminal optical path is critical for energy concentration and imaging quality. Conventional laboratory focusing methods use large-aperture, long-focal-length collimators or star-point targets. These systems are bulky and difficult to deploy with the terminal. After environmental tests, they hardly support refocusing calibration or quantitative evaluation of transmitter defocus and divergence. To address these issues, a Gaussian-beam-based alignment and calibration method is proposed. The method enables camera focusing and the measurement of the object-side defocus and beam divergence angle of the transmitting fiber collimator, while a corresponding theoretical model is established. It employs a fiber collimator with fixed divergence. Gaussian spot profiles are fitted within a limited space, which allows high-accuracy quantification of focal length and object-side defocus. Simulation and experimental results consistently confirm the effectiveness of the proposed approach. Compared with the collimator-based focusing method, the mean focal length is closer to the nominal value. The maximum relative error of the focal length is reduced by about 81.3%, and the root-mean-square deviation is reduced by about 80.7%. The deviations of object-side defocus and divergence from theory are within 2%. The method has a compact structure and modest calibration requirements. It is suitable for terminal alignment, recalibration, and focus inspection under static or quasi-static conditions, and provides an effective technical approach for high-precision, miniaturized, and scalable engineering implementation of focusing.