INTERFEROMETRIC APPARATUS WITH COMPUTER-GENERATED HOLOGRAM FOR MEASURING NON-SPHERICAL SURFACES

摘要

Method and system of interferometrically measuring, in reflection, a non-spherical surface with two diffracted beams (of different diffraction orders) formed by a diffractive element positioned transversely to the axis of a common-path interferometer. The first diffracted beam substantially maintains the wavefront of a beam incident onto the diffractive element, while the second diffracted beam has a wavefront profile corresponding to the profile of the measured surface. The first diffracted beam may be reflected by the surface in a cat's eye configuration, while the second diffracted beam is reflected by the surface in a confocal configuration. The surface being measured can be modified to substantially balance radiant powers of the first and second diffracted beams upon reflection off the surface.

主权项

1. A method for interferometric testing with a common-path interferometer system, the method comprising:
reflecting first and second beams of light, formed by a diffractive element from an input beam of light having an input beam wavefront and incident onto the diffractive element along an optical axis, from a non-spherical surface (SUT) to form first and second reflected beams such that
characteristics of a first wavefront corresponding to said first reflected beam are the same as characteristics of the input beam wavefront, andcharacteristics of a second wavefront corresponding to said second reflected beam include characteristics of the input beam wavefront that have been modified by interaction of said input beam with the SUT; and determining, with the use of a control unit that includes data-processing circuitry, a non-spherical profile of the SUT based on optical data, said optical data derived from a distribution of irradiance that is interferometrically formed by said first and second reflected beams upon co-axial propagation thereof.