The Optical Design of Cubic Phase Plate Testing System

Computer-generated holograms (CGH) have been widely used for years in optical testing of aspheric surfaces in combination with Fizeau interferometers. With the development of diffraction optics, computer technology, and micro-processing technology, the accuracy of the CGH testing can achieve a hundredth of a wave, and the cost is reduced greatly. CGH is capable of producing an optical wavefront with any desired shape. So it is fascinating and will have good prospects to test free-form surfaces using CGH. As the CGH can create any wavefront shape, it can also be used in unsymmetrical aspherical surfaces testing. Taking the cubic surface as an example, this paper gives a method to test unsymmetrical surfaces. This paper gives the design to test a cubic surface. And the separation of the diffraction orders and the binary process of the continuous CGH phase function are discussed in detail. The alignment tolerance of the test system and the CGH fabrication tolerance are analyzed. We also present an idea using a CGH and two spherical lenses as null lens to test the cubic surface when the surface deviation is great.