Computer Generated Holograms for Optical Testing

Computerized interferometric surface measurements [invited]

The addition of electronics, computers, and software to interferometry has enabled enormous improvements in optical metrology. This paper discusses four areas in which computerized interferometric measurement improvements have been made in the measurement of surface shape and surface roughness: (a) The use of computer-generated holograms for the testing of aspheric optics, (b) phase-shifting interferometry for getting interferometric data into a computer so the data can be analyzed, (c) computerized interference microscopes, including multiple-wavelength and coherence scanning, for the precision measurement of surface microstructure, and (d) vibration-insensitive dynamic interferometers for enabling precise measurements in noncontrolled environments.

Aspherical Mirror Testing using a CGH with Small Errors

A method for reducing errors in aspherical mirror testing using a computer-generated hologram (CGH) is described. By using a modified filtering method the carrier frequency in the CGH can be reduced by two-thirds, and the resulting error due to distortion is only one-half of that of a conventional CGH. By adopting a Fizeau-type optical setup, only the surface quality of the reference affects the measured results.

Plotting Errors Measurement of CGH using an Improved Interferometric Method

An improved interferometric method is described for measuring plotting errors of desk-top computer plotters used to make computer-generated holograms. The plotting errors are measured using moiré fringes formed using Young’s fringes and straight lines drawn by the plotters. The Young’s fringes are produced by laser beams originating from two single-mode fibers. Using this method, plotting errors of Hewlett-Packard 7225A and 7470A plotters are measured.

Computer Generated Hologram; Null Lens Test of Aspheric Wavefronts

  • J. C. Wyant and P. K. O’Neill
  • APPLIED OPTICS, Vol. 13, page 2762, December 1974
  • Download PDF

Interferometric Method of Measuring Plotter Distortion

  • J. C. Wyant, P. K. O’ Neill, and A. J. MacGovern
  • APPLIED OPTICS, Vol. 13, page 1549, July 1974
  • Download PDF

Using Computer Generated Hologram to Test Aspheric Wavefronts

The use of computer generated holograms for the testing of aspheric wavefronts is described. An analysis of the errors produced by emulsion movement, incorrect hologram size and position, and distortion in hologram plotter and photoreduction lens is given, and it is shown that all the errors are proportional to the slope of the aspheric wavefront. Experimental results verifying the error analysis are shown for testing rotationally nonsymmetric wavefronts having slopes as large as 125 waves per radius and departures as large as sixty-five waves.

Computer Generated Holograms for Testing Optical Elements

The application of computer generated holograms to the interferometric testing of aspheric optical elements has been investigated, and it has been shown that they provide a convenient and practical method of producing an aspheric reference wavefront.

Computer Generated Holograms for Testing Aspheric Optical Elements

  • J. C. Wyant and A. J. MacGovern
  • Applications de L’Holographie, Laboratoire de Physique Generale et Optique, Universite de Besancon, Besancon, France, 13-8, July, 1970.
  • Download PDF

<< Back to Published Papers