Research on the influences of carrier deviation on digital moire interferometric technique

Existing aspheric testing methods are sensitive to environmental effects. The digital moire interferometric technique (DMIT) demodulates surface errors from a single interferogram by building a virtual interferometer to avoid environmental effects. This method requires the actual carrier and the virtual carrier to be the same. In this paper, the effect of carrier deviation on DMIT is investigated. It was found that the carrier deviation would extend the spectrum of low-frequency information. Spectrum expansion can deteriorate the noise immunity of DMIT. Spectrum expansion may also lead to spectrum overlap. Method for determining the actual carrier from frequency domain is analyzed. A carrier alignment algorithm is proposed, and the simulation results deviate from the true value by only 6%.