Abstract

A laser beam impinging at grazing incidence on a 3-D surface produces a diffraction edge wave whose obliquity factor contains, among other things, the information concerning the local radius of curvature of the surface in the plane of incidence. In this paper we show how to retrieve this curvature radius information from light irradiance measurements of the edge wave and from exact electromagnetic diffraction calculations. This new method of optical metrology gives the curvature radius of a surface in the incident plane and at a given point by a single measurement at that point, while other techniques depend on a scanning or a mapping in the vicinity of the point of interest. Moreover, a measuring system using this diffractional method is very easily implemented and can yield a precision in the 5–10-μm range. Experimental results are presented for six metallic circular cylinders and two metallic spheres.

© 1985 Optical Society of America

Electromagnetic diffraction of a three-dimensional Gaussian laser beam at grazing incidence upon a large absorbing circular cylinder

P. Langlois, A. Boivin, and R. A. Lessard
J. Opt. Soc. Am. A 2(6) 858-862 (1985)

Field spread of a diffracted Gaussian beam through a circular aperture

Kazumasa Tanaka, Nobuhiro Saga, and Hiromu Mizokami
Appl. Opt. 24(8) 1102-1106 (1985)

Edge Diffraction of a Convergent Wave

Alexander C. Livanos and Nicholas George
Appl. Opt. 14(3) 608-613 (1975)

Edge-On Diffraction of a Gaussian Laser Beam by a Semi-Infinite Plane

G. Otis and J. W. Y. Lit
Appl. Opt. 14(5) 1156-1160 (1975)

Real-time measurement of large liquid surface deformation using a holographic shearing interferometer

K. Matsuda, S. Watanabe, and T. Eiju
Appl. Opt. 24(24) 4443-4447 (1985)