IRIDESCENT UNEVENNESS OF PRECISELY TURNED SURFACE.

Abstract

The iridescent unevenness of a precisely turned surface is investigated by a ray-tracing procedure with reference to the pitch unevenness of turned grooves. The surface is illuminated at an oblique angle with a linear light source which is crossed at a right angle to the cylindrical axis of the surface, and the image of the light source focused by the surface is observed in the direction of diffraction. The image is smoothly parabolic when no pitch unevenness is present on the surface. In the image calculated on the assumption of sinusoidal pitch unevenness, a disturbance is involved corresponding to the change of pitch. When the surface is illuminated with a white light source, this disturbance turns out as iridescent unevenness.