Color-coded optical profilometry with >10/sup 6/ optically resolved depth steps

Abstract

Summary form only. Light stripe triangulation configuration based on a color-coded arrangement allows parallel, fast, real-time 3-D surface profilometry with an extended depth-measuring range and high axial and lateral resolution. The method exploits polychromatic illumination and a cylindrical element that disperses the incident light along the axis, leading to an increased depth-measuring range without any decrease in the axial or the lateral resolution. In our recent experiments the cylindrical element was a combined diffractive-refractive optical element in which many light stripes, each of a different wavelength, are simultaneously focused at different focal lengths, forming a rainbow light sheet. The discrimination of each color stripe was further improved by a color decoding technique, in which a spectral filter simultaneously matched the entire wavelength distribution of the light sheet during detection. A 20-fold increase in the depth of focus was experimentally obtained, while diffraction-limited light stripes with extremely small sidelobes were completely maintained.