SCANNING FOCUS-SENSING METHOD FOR MEASURING THE SURFACE SHAPE OF A FISH SCALE

A scanning locus-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 s ample surface. The focus information contained in the laser beam scatt ered from the sample surface is then transformed into the movement of the spot on a position sensor:or detection. The measurement error caus ed by variations in the shape or intensity of the spot can therefore b e reduced. We successfully applied the method io measure the surface s hape of a fish scale.