Scanning focus-sensing method for measuring the surface shape of a fish scale

Abstract

A scanning focus-sensing (SFS) method has been developed for measuring the surface shape of a fish scale. This method uses an acousto-optic deflector as a diffractive scanner to allow the laser beam to scan an objective lens, and then uses the resulting focused spot to scan the sample surface. The focus information contained in the laser beam scattered from the sample surface is then transformed into the movement of the spot on a position sensor for detection. The measurement error caused by variations in the shape or intensity of the spot can therefore be reduced. We successfully applied the method to measure the surface shape of a fish scale.