| Although the reflective optical system is relatively simple in configuration with a small number of optical elements,the aberration increases exponentially with the increase of focal length and aperture.It turns out that a small error perturbation can cause significant degradation of image quality.Systematic and strict control of the processing and assembly accuracy of optical elements,the use of high-quality and stable optical and mechanical structures,and the use of precision thermal control are the conventional methods to ensure the high performance imaging of large-aperture reflective optical systems in the past.However,the implementation of this strategy also brings high economic and resource costs to the realization of optical systems.While ensuring the imaging performance,reducing the error sensitivity of the optical system is a subject to be solved.Therefore,it is of great theoretical significance and application value to investigate the mechanism of error sensitivity of reflective optical systems and to realize the design of reflective optical systems with reduced sensitivity.To deal with this problem,this paper starts with the theoretical research of reflective optical error sensitivity,deeply explores the key factors affecting the error sensitivity of optical system,establishes the optimization method of optical system error sensitivity,and provides theoretical support for improving the ability of optical system to resist error interference.The specific research contents are as follows:Based on the theory of geometric optics,the mathematical expressions of the optical path difference variation caused by the tilt of the single-mirror optical system and the two-mirror optical system are derived,and the mathematical expressions of the three-mirror optical system and the multi-mirror optical system are analyzed.From the angle of optical path difference variation,the factors affecting the tilt error sensitivity are analyzed,and the influence of the tangent slope of optical element at the intersection of incident ray and optical element on the error sensitivity of optical element is revealed.The corresponding evaluation function of the tilt error sensitivity of the optical system is proposed,and a design method for reducing the sensitivity of the reflective optical system is established.The error sensitivity analysis of the initial structure of the off-axis three-mirror reflective optical system is conducted based on the error sensitivity evaluation function of the reflective optical system.It is found that the error sensitivity of the optical system is closely related to the selection of the initial structure,and a desensitized design method of the freeform off-axis three-mirror reflective optical system based on the initial structure screening is proposed.A non-dominated genetic algorithm(NSGA-II)is used to screen the initial structure of the conic off-axis three-mirror reflective optical system with good imaging quality and low error sensitivity,and then the freeform surface is introduced into the off-axis three-mirror reflective optical system to further improve the system performance.The combination of multiple types of freeform surfaces in the mirror surface pattern is screened and optimized to obtain the best combination of surface pattern in terms of the imaging quality and error sensitivity of the optical system.The theoretical research on the error sensitivity of the freeform optical system is carried out,and the mathematical relationship between the error sensitivity of freeform surface optical elements and the local curvature of optical elements is obtained by means of ray tracing.Based on the idea of micro-element,an evaluation method of error sensitivity of the freeform reflective optical system is proposed,and a desensitization design method of the freeform optical system is established.This method is applied to desensitization design of an off-axis three-mirror optical system with a large field of view,and compared with the desensitization design method built in the optical design software.The results show that the method proposed in this paper demonstrates better desensitization effect and higher efficiency.After further analysis and research,the error sensitivity evaluation function and the desensitization design method are extended from reflective optical systems to transmissive optical systems.After simple adjustments,the error sensitivity evaluation function for refractive optical systems is proposed and the desensitization design method for refractive optical systems is established.The method is applied to a refractive optical system high-resolution imaging camera.After the desensitization optimization,the design results show low error sensitivity while ensuring the imaging quality. |
