Holographic two-beam interferometry using multiple-reflected light beams.

A holographic real-time Fizeau interferometer was devised and applied to an accurate measurement of silvered flat surfaces. It consists of recording and reconstructing light waves reflected from an air wedge between the flats, isolating a wave of the nth reflection and making it interfere with the mth beam directly reflected from the wedge. The sensitivity was enhanced by m - n, compared with the conventional interferometer. Experiment using m - n = 16 was carried out and fringes of high contrast were obtained whose interval indicates a height difference of lambda/32.