D. Lebrun et al., ENHANCEMENT OF WIRE DIAMETER MEASUREMENTS - COMPARISON BETWEEN FRAUNHOFER-DIFFRACTION AND LORENZ-MIE THEORY, Optical engineering, 35(4), 1996, pp. 946-950
The Fraunhofer diffraction is compared with a numerical simulation bas
ed on the Lorenz-Mie theory to improve the performance of a laser diff
raction instrument. This instrument, based on the analysis of diffract
ion fringes at the focal plane of a lens, is especially suitable for i
ndividual wire diameter measurements. We show that the error due to Fr
aunhofer approximation increases with an increase of the reflectivity
and a decrease of the object diameter. Comparison with Lorenz-Mie theo
ry enables us to correct these errors. For a given object, the laser d
iffraction instrument reproduces diameter measurements with a very sma
ll dispersion. (C) 1996 Society of Photo-Optical instrumentation Engin
eers.