PRODUCTION OF DISTORTION-FREE COMPUTER GENERATED HOLOGRAMS.

Computer Generated Holograms (CGH) are useful for testing optical elements. The distortions of a plotter and a photographic lens are main difficulties for generating distortion-free CGHs. These two distortions were estimated using an interferometry of higher order conjugate diffraction waves caused by the nonlinear transmittance of CGHs. It turned out that primary distortion is significant as the lens aberrations. The lens distortion was separated from the plotter distortion by varying the magnification of CGHs. A CGH grating with a distortion less than lambda /40 was obtained after correcting distortions by a computer programming.