The Research Of Aspherical Testing Base On Digital Moiré Patterns

Optical system application aspherical can correct differ, improve image quality,improve optical performance, reduce the dimensions and weight, so in recent yearsoptical instrument design and manufacturing, and established various aspheric opticsfabrication with its superior optical properties are increasingly applied in precisionoptical instruments, however aspheric mirrors variety, size and accuracy requirementis different, its testing methods than spherical complex and difficult, especially largeprecisionasphericsurfaceopticalelement,faceshapemeasuringmoredifficult.This paper aim at aspherical testing problem, puts forward a new method ofaspherical testing base on sub_region splicing digital moirépatterns, this methodcontains digital grating technology, digital phase shifting technique ,moire technique,image processing technology, unwrapping and stitching technique .this paper hascarriedondetailedandthethoroughanalysistothiskindoftesting.1.phasemeasurementprincipleofsub_regionphaseshiftingdigitalmoirépatternsIntroduced phase measurement principle of sub_region phase shifting digitalmoirépatterns,including sub_region digital moirépatterns acquisition and themathematical model, the phase_shifting,sub_region division goal,the key question ofthistesting.2.DigitalmoirépatternsfilterprocessingThis paper conducted the research from the space domain filter method and thefrequency domain filter method to the digital moirépatterns,through massive simulationcarrierfrequencyinterferenceprocessing,has obtainedjudgmentmethodofthe space domain and the frequency range cut-off frequency of filter,has analyzed thedifferent filter method characteristic and performance,has obtained the quite suitablethisarticlefilterparameter.3.unwrappingIntroduced several common unwrapping technology,through digital moirépatterns filtering processing,on the basis of the phase launched by partition methodandresidualpointcentrifugedtheoryrealizeunwrappingprocessing.4.phasesplicingandpolynomialfittingReference subaperture phase stitching method, using the error homogenizationtechnology,we unifysub_region phase into the same reference datum byleast-squaresfitting method.finally base on the Gram_schmidt algorithm and utilizes zernikepolynomial fitting the same under reference of discrete points, can get asphericalphasedistribution.5.TestingexamplesThe asphere whose diameter is 130mm has carried on the actual examination, thefaceshapeprecisionachieved rms ? 0.0321?intheeffectiveaperture.Practice proves sub-region splicing digital moirépatterns technology does notneed compensator can realize aspherical testing, to avoid the compensatorintroduction of error and the difficulty of assembly and adjustment, Through thepartition acquisition interference patterns, solve the CCD camera cut-off frequencylimit,Usingdigitalphaseshiftingtechnology,avoidpiezoelectricceramicmovephasenonlinearerrorofmeasurementinfluence.