Use of Computer Generated Holograms for Testing Aspheric Optics

It has been more than 36 years since Lohmann and Paris first described computer generated holograms (CGHs) [1] and CGHs have been used to test aspheric optical elements for more than 35 years [2]. Computer generated holograms are now widely used in the testing of aspheric optical elements and it is expected that their use in aspheric testing will greatly increase the next few years as the superb measurement capability of CGHs are better appreciated by more optical manufacturing personnel. While CGHs are most often used to test rotationally symmetric surfaces, a great advantage of CGHs is that they can be made for testing free form optics almost as simply as for testing rotationally symmetric optics. Crosshairs can be put on the CGH to aid in the alignment of the CGH and additional holograms can be placed on the CGH to aid in the alignment of the optics or to aid in calibration of the CGH. CGH interferometers work well with phase-shifting techniques.