Сalibration technique for a binocular vision system with variofocal lenses

The relevance of calibration of the binocular machine vision system is due to the need to use it as a high-precision meter of navigation parameters. Known approaches to calibration of the binocular machine vision system either do not provide the necessary level of compensation for errors caused by the relative position of the cameras, or are very labor-intensive. In addition, the desire to ensure high-precision navigation of unmanned aerial vehicles in variable flight conditions necessitates the use of varifocal motorized lenses, while the calibration of such systems by classical methods becomes even more labor-intensive. The aim of article is to development of a calibration technique for a binocular technical vision system with varifocal lenses for the purpose of algorithmic compensation over the entire range of focal length changes for errors caused by the relative position of cameras. The conducted research resulted in the development of a mathematical model, in which calibration parameters are introduced, the calculation and consideration of which ensures a significant increase in the accuracy of measurements, provided that preliminary mechanical adjustment is performed. The adjustment is based on photo exposure by means of cameras of the binocular technical vision system of a special calibration target in the form of a constellation (triple) of beacons and combination by means of adjustment elements of beacon images with software-generated marks. The calibration technique is based on the calculation of calibration parameters of the relative position of the cameras, remaining after the adjustment is performed. It was found that when using varifocal lenses, the calibration parameters can be represented as functions of the focal length parameter in the form of power series polynomials. The obtained results of the study of the accuracy characteristics of binocular technical vision systems confirmed the possibility of algorithmic compensation for errors caused by the relative position of cameras for the selected configuration with varifocal lenses in the entire range of change in focal length in a navigation task requiring precision measurements.