Research of precision interference locating method for a partial null compensator at aspheric testing

Based on the difference between theoretical with real interferogram images the figure of original aspheric surface can be obtained using an algorithm of Reverse iterate Optimization Reconstruction (ROR) calculating technique. Because the procedure of ray tracing path needed an accurate geometry of optical structure size so the aspheric and compensator LC must be located in the optical path. To avoid the compensator LC resulted in bigger spherical aberration a smart located method is proposed in this paper. Before measurement an aplanatic lens consists of compensator LC and another removable lens LM that the last surface is a standard one. So Fiezau interference is formed by the standard one with reflected ray from the vertex of aspheric that the aspheric surface detected can be accurately located. At testing the lenses LM will be removed and the aspheric is moved to an adapted position. The experiments show the displacement locating accuracy is an amount of micron. The RMS for aspheric testing of ROR calculating technique is better than 1/200 wavelength.