Alignment of diffractive optical compensator used for aspheric test

In order to eliminate the influence of the misalignment error of compensator on aspheric test, phase reflective Fresnel zone plate(PRFZP), a kind of diffractive optical regulator, was designed and fabricated surrounding the pattern of compensator. With the help of very large scale integration (VLSI) facilities, compensator and regulator were integrated on the same substrate. Because of the self-alignment function of PRFZP, the wavefront reflected by PRFZP interfered with the reference wavefront and the alignment interference pattern was formed. During the test, the position of compensator could be fine adjusted by adjusting the defocus, bias and tilt misalignments to make the interference pattern in the simplest form. Through fine adjustment, an approximately zero alignment interference pattern was obtained which demonstrated that the misalignment errors of compensator were effectively eliminated.