Pattern comparison by interference fringe scanning

An apparatus for real-time pattern comparison based on the interference method proposed by Weinberger and Almi is described. Particular emphasis is stressed on its use in fingerprint identification. Preliminary experiments confirmed that the apparatus is feasible for the purpose.

Automatic vertometer for spherical ophthalmic lenses

A vertometer for spherical ophthalmic lenses was designed that is automated in focusing a target, in centering a lens being tested, and in marking its center within specified limits of tolerances. Light from the target is introduced into a scanning unit that detects the three-dimensional deviation of its image from a desired position and generates three signals to drive simultaneously the target and the lens so that the image of the target may come to the desired position. This procedure is followed by an automatic measurement of the deviation and marking the center, with an accuracy some five times greater than is attainable by visual examination. The working principle and experimental results are described in detail.

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.