The Light Of An Off-axis Three-mirror System Integration Analysis

Opto-mechanical systems design is confronted with record-breaking challengebecause of the complication and diversification of optical systems. For precise opticalapparatus and kinds of space optical apparatus, the designed mechanical structures mustmeet optical conditions. It must provide enough mechanical strength and be as light aspossible at the same time. What the designers concern is whether the designed resultsare up to the mustard. Thereout, integrated opto-mechanical analysis emerged as timesrequire. It’s such a method that the whole system which includes designs of differentsubjects is analyzed through the support and assistant of some software. According tothe analysis results, original design is checked up and modified. The updating speed ofsoftware and hardware of computer is so fast that integrated analysis is a necessarytache of development of complicated system.This paper introduced the study background of integrated opto-mechanicalanalysis in the beginning, then made an analysis according to an off-axis three-mirroroptical system. The opto-mechanical structures was designed based on the off-axisthree-mirror optical system. Because the primary mirror and tertiary mirror in thissystem are unrotational-symmetric conic surface, their mounting is different to sphericalmirror. The mechanical structure must assure the mirrors can be adjusted in six degreesof freedom. Structure design and mounting method are discussed particularly in thispaper.The CAD model of this opto-mechanical system was built through Solidworks.After the primary mirror and tertiary mirror were mounted in their mechanical structuresrespectively, gravity will bring surface distortion to them. The statics analysis of thiscondition was done by ANSYS. So the displacement and von misses were got.The transform method of opto-mechanical data was founded. The anamorphicsurfaces of primary mirror and tertiary mirror were fitted by Zernike polynomials. The PV value and RMS value of these anamorphic surfaces can be calculated through thecoefficients of Zernike polynomials, which can be used for evaluating weather theprimary mirror and tertiary mirror were eligible and the mounting structures were inreason. Primary aberration caused by distortion can be decomposed through dealingwith the coefficients of Zernike polynomials. Improving measures of aberrations wereput forward also.The primary mirror and tertiary mirror were tested through experiment. Theinterference stripes of these two mirrors were tested by interferometer Zygo before theywere mounted and after they were mounted. The collected results were analyzed andcompared. Meanwhile, the correctness of theoretical analysis in this paper was validatedthrough the testing results.