Abstract

A recently developed technique for continuous-phase determination of interferograms with a digital phase-locked loop (PLL) is applied to the null testing of aspheres. Although this PLL demodulating scheme is also a synchronous or direct interferometric technique, the separate unwrapping process is not explicitly required. The unwrapping and the phase-detection processes are achieved simultaneously within the PLL. The proposed method uses a computer-generated holographic compensator. The holographic compensator does not need to be printed out by any means; it is calculated and used from the computer. This computer-stored compensator is used as the reference signal to phase demodulate a sample interferogram obtained from the asphere being tested. Consequently the demodulated phase contains information about the wave-front departures from the ideal computer-stored aspheric interferogram. Wave-front differences of ∼1 λ are handled easily by the proposed PLL scheme. The maximum recorded frequency in the template's interferogram as well as in the sampled interferogram are assumed to be below the Nyquist frequency.

© 1994 Optical Society of America

Sub-Nyquist null aspheric testing using a computer-stored compensator

M. Servin, Daniel Malacara, Z. Malacara, and Valentine I. Vlad
Appl. Opt. 33(19) 4103-4108 (1994)

Testing aspheric surfaces with computer-generated holograms: analysis of adjustment and shape errors

Bernd Dörband and Hans J. Tiziani
Appl. Opt. 24(16) 2604-2611 (1985)

Dual-wave-front computer-generated holograms for quasi-absolute testing of aspherics

Mathias Beyerlein, Norbert Lindlein, and Johannes Schwider
Appl. Opt. 41(13) 2440-2447 (2002)

Analysis of the disturbing diffraction orders of computer-generated holograms used for testing optical aspherics

Norbert Lindlein
Appl. Opt. 40(16) 2698-2708 (2001)

Using Computer Generated Holograms to Test Aspheric Wavefronts

J. C. Wyant and V. P. Bennett
Appl. Opt. 11(12) 2833-2839 (1972)