The Effects Of Geometirc Errors Of Machined Surface On Its Optical Performance

Optical freeform surface is the surface that has no rotational symmetry. It is theadvantage form of non-spherical. Compared with the non-spherical surface, free formoptical components have many advantages, such as improving the quality of theoptical system’s image，reducing the optical system components’ number and size,and increasing the flexibility of optical design. With the increasing demand ofphotonics instruments, Optical system take the direction from spherical and asphericaloptics to freeform optical. However, due to various factors in the process, Opticalprocessing surface of geometry error is inevitable, thereby affecting the opticalcomponents, optical properties of optical system. Therefore, studying the effect of thesurface error and surface roughness on optical properties becomes increasinglyimportant.In this paper, researched the optical components’ surface error and surfaceroughness how to impact on the optical properties. The analysis data is obtained fromthe simulation processing surface of constant radial feed, which using the waveletanalysis method to separate the all date. Assuming the optical components only withsurface error as a model, taking wavefront aberration, modulation transfer functionand point spread function as the evaluation to study surface shape error effecting onthe optical properties. Assuming the optical components only with surface error as amodel, taking wavefront aberration, modulation transfer function and point spreadfunction as the evaluation index to study surface shape error effecting on the opticalproperties.With rough surface as a model, scattering surface transfer function basedon Harvey-Shack scattering theory and point spread function as the evaluation index,study surface roughness and scattering effects on optical properties.In the analysis process of the surface error on the optical properties, Todistinguish between the wavefront aberration,defined the deviate from the actualwavefront and the ideal wavefront in the design of optical components as thewavefront aberration increment. Using ray tracing method for solving the wavefrontaberration and wavefront aberration increment with different surface error. Analysis ofsurface error impacting on the wavefront aberration and wavefront aberrationincrement. Using Zernike polynomial fitting wavefront, and analysis thecorresponding relations of Zernike polynomial fitting coefficients and the Seidelaberrations, then discuss the relations between surface error and Seidel aberration.Researching the surface error effecting on point spread function and modulationtransfer function with twice Fourier transform method. The greater the surface error,wavefront aberration and its incremental is larger. different fitting coefficients of thewavefront aberration, The variation of the corresponding Seidel aberrations change followed. surface error change the surface energy distribution, and reduce imagequality.The surface roughness makes scattering when the light go through the opticalcomponents. In this paper, based on Harvey-Shack scattering theory, the method ofGaussian filter is employed to isolate the surface error and the surface roughness.Rough surface data obtain from the simulation of different feed processing. Calculatethe variance and the correlation length in X/Y axis directions. Describing theroughness of the machined surface with the variance of rough surface heightdistribution and correlation length. Calculate the machined scattering surfaces transferfunction and point spread function with different feed process. Analysis the relationsroughness on the surface of the scattering surface transfer function, point spreadfunction. Analysis shows that the greater the roughness, the surface energy the moredispersed, and the imaging quality of optical parts is the lower.