Abstract

Theory and experiments on the use of an incoherent double-grating interferometer for optical testing is described. In our theory, the cross-spectral-density function and Fresnel diffraction are used to either explain or derive the intensity distribution of the interferogram for a lens under test. When only zeroth- and first-order diffracted beams are taken into account, the intensity distribution can be reduced to a simple form that is similar to the intensity distributions obtained by either a Ronchi sine-grating interferometer or a coherent double-grating interferometer. In our experiments we focus the laser beam from a 5 mW He:Ne laser on a rotating ground glass to generate spatially incoherent light that is then focused on the first Ronchi ruling. The light also propagates through the lens under test, the second Ronchi ruling, and the imaging lens. At the conjugate plane of the lens under test, all the diffracted beams interfere and are recorded. The pattern of the recorded interferogram agrees with our theoretical predictions.

© 1990 Optical Society of America