Research on field calibration of optical-mechanical axis parallelism for electro-optical sighting devices

Purpose Modern electro-optical sighting devices integrate multiple sensors, including visible light, infrared and laser rangefinders, which enable functions such as imaging, targeting and optical signal transmission. However, external factors such as temperature fluctuations and mechanical vibrations can cause parallelism deviations between the optical axes and the reference axis, thereby reducing target sighting accuracy, rangefinding precision and guidance reliability. Design/methodology/approach To address the on-site measurement requirements for the parallelism between the optical axes of various electro-optical sensors and the vehicle’s aiming reference axis, this paper proposes a comprehensive optical–mechanical axis parallelism measurement method integrating inertial measurement, target simulation and autocollimation measurement. The objective is to achieve online calibration of the parallelism between the complex multi-aperture, multi-spectral optical axes and the reference axis. First, based on the off-axis two-mirror coaxial optical principle, combined with target detection and recognition algorithms and high-precision inertial measurement technology, an accurate optical–mechanical axis measurement model is constructed, and the influence mechanisms of various factors on parallelism are systematically analyzed. Second, a set of optical–mechanical axis calibration devices is developed, followed by systematic functional testing, performance evaluation and measurement uncertainty analysis. Findings Experimental results show that the measurement uncertainty of this method is better than 10″ (k = 2), verifying its high-precision characteristics. Finally, this paper objectively discusses the limitations of this technology in static base applications and provides an outlook on research related to dynamic base technologies. Originality/value This paper proposes an innovative aspheric reflective coaxial optical system integrated with an off-axis two-mirror configuration, infrared/visible-laser beam splitting and an anastigmatic cylindrical lens, realizing the collaborative optimization of short focal length, coaxial alignment, high-definition imaging and lightweight design. A multi-source optical–inertial axis calibration and synchronous data-link mechanism is further established to achieve spatiotemporal synchronous acquisition of images and deviation angles, ensuring reference consistency and supporting accurate on-site calibration.