Stray Light Testing Technology Research Of Long Focal Length And Large Aperture Optical System

Veiling glare index is the effective indicator to evaluate the optical system stray light suppression capability,space optics systems,especially the large aperture optical systems,their veiling glare index testing is difficult,mainly due to keep the black-spot to sub-imaging on the optical system image plane,When large-diameter integrating sphere can't be made,the collimating lens must be added.However aperture of long focal length optical systems are generally very large,collimating lens of large aperture can not be processed.In addition,once the size of the lens increase,its surface flaws and internal bubbles will be difficult to avoid,so the test error of collimating lens will be very large,aiming at the long focal length and large aperture optical system,it must find new and improved method to solve the problem of stray light testing.The paper based on solving the stray light testing method of long focal length and large aperture system,on the basis of saving extended source size,we propose an off-axis reflective structures,which are still using the collimating lens to reduce device size,by replacing transmissive collimating lens to an off-axis parabolic mirrors to solve the large-diameter collimating lens design and processing problems.Under the optical design premise of the off-axis parabolic mirror,the device's target simulator and detector are designed,in which the target simulator is integrating sphere form,black-spot through latch plate to replace,the design achieves a superior contrast in 1: 1000,providing cover for high precision testing of stray light;based on estimates of the integrating sphere energy,photomultiplier tube is selected as a detector,then the detector was calibrated and corrected in low responsibility area,and ultimately the linearity is better than 2.1%,and the dynamic range is better than 3000 times;we have also designed the comparison lens,and designed the baffle of comparison lens.In the system modeling process,bidirectional reflectance distribution function of the painted surface is measured,and substituted into the Table model,the analysis of the less affected lens surface is using the Harvey-Shack model,through the power spectral density of the materials to derive ABg model parameters.After modeling analysis,simulation,error of reflective system and transmissive system is less than 0.09%,it has proved the feasibility of the reflective system for stray light testing.Finally,the comparison lens and reflective system are manufactured,and veiling glare index of comparison lens was measured by transmissive system and reflective system,results show that,compared to the transmissive systems,test error of reflective system is less than 0.15%,less than the error capacity of 1%,it has proved the correctness of the reflective system for testing,data also shows that the error of these two systems were 0.26% and 0.3%,taking into account the manufacturing factors,it has proved the modeling and simulation are correct.Finally,experimental data of some long focal length collimators shows that precision of reflective system meets the test requirements of long focal length optical system.Comprehensive analysis of the measured data and modeling,the successful design of the reflective system will solve veiling glare index test problems of long focal length and large aperture optical system,it provides security for a veiling glare index test of this kind of optical system.