DYNAMIC-RANGE OF RONCHI TEST WITH A PHASE-SHIFTED SINUSOIDAL GRATING

The dynamic range of a Ronchi test with a phase-shifted sinusoidal gra ting was investigated theoretically and experimentally. As the number of fringes in a Ronchi interferogram increases, Be fringe visibility d ecreases, which results in a decrease of phase-measurement resolution. It is shown that in order to optimize the dynamic range the effective wavelength of the interferogram should be tuned to the characteristic wavelength of Be object wave front. The maximum dynamic range achieva ble is estimated to be 16 times larger than that of a Fizeau interfero meter. Suppressing higher-order diffraction components has achieved sh eared interferograms with a signal-to-noise ratio in excess of 60:1. T he effects of nonsinusoidal transmittance of the grating and the phase -shift errors were minimized by a seven-sample phase-shifting algorith m, and a phase measurement uncertainty of less than 1/700 has been ach ieved. (C) 1991 Optical Society of America.