Development and Prospect of Stray Light Suppression and Evaluation Technology (Invited)

With the rapid development of space optical technology and the continuous improvement of the performance of photoelectric detection devices, remote sensing systems with high resolution, multispectral, and low detection threshold are more and more widely used in aviation, aerospace and other fields. And the capabilities and evaluation indicators for the stray light suppression of electric-optic load are gradually becoming stricter. The stray light suppression technology and simulation analysis has become one of the indispensable links. Although the domestic stray light suppression and evaluation technology have developed earlier, a systematic method is still needed to lead the development of this technology to change the current research status of decentralization and fragmentation. Therefore, it is necessary to establish an integrated stray light suppression and evaluation method system, and conduct in-depth research in four key technical modules, including the formulation of stray light suppression scheme, suppression model surface characteristic measurement and modeling, stray light suppression effect simulation, and stray light test and evaluation and so on. Based on the theory of stray light radiation transfer, we give the corresponding suppression methods according to the stray light inside and outside the field of view, and the internal thermal radiation stray light. But the actual stray light sources are complex and in various forms, often requiring various suppression methods together, such as selecting the configuration of the optical system, setting the baffle and vanes, adding the stops, coating the optical surface, and blackening the surface of the structural parts. In addition, in some specific cases, filtering method, adjacent frame subtraction method, polarization method , numerical aperture method , and image correction method can also be used to suppress stray light. Opto-mechanical systems are generally composed of various surfaces with different materials and properties and they have different characteristics such as reflection, scattering, and absorption. Therefore, studying the surface characteristics of the system is the basis for stray light analysis. The measurement of surface properties can be used as a preliminary method to obtain the surface information of the material. On this basis, modeling calculations can be performed to make up for the deficiency that the experimental measurement cannot obtain any direction of incidence and observation. It can be widely promoted and applied in engineering. Computer simulation is an important means of stray light analysis, which can solve the problems of too cumbersome and high testing costs for stray light experiments in optical systems with high suppression ratios, and improve the efficiency of stray light analysis. The Monte Carlo method has been widely used in a variety of commercial software due to its high accuracy and computational simplicity. With the rapid development of computer technology and the emergence of new algorithms, the number, speed, and accuracy of ray tracing will be improved. It can more accurately simulate the influence of stray light on the whole system. Stray light measurement is the key to the final determination and verification of the system' s true stray light suppression capability. The measurement methods of stray light have formed two evaluation methods. The veiling glare index is suitable for general optical systems with low precision and small aperture, and the point source transmittance method is suitable for optical systems with large aperture and high stray light suppression ratio requirements. Xi' an Institute of Optics and Precision Mechanism of the Chinese Academy of Sciences has developed the first domestic point source transmittance stray light test device with the strongest capability of testing. It has been successfully applied to the stray light measurement of space equipped with high accuracy and served many scientific institutes and universities. This paper gives a set of the overall technical route and provides the idea for better promoting the development and application of stray light suppression and evaluation technology.