Process and apparatus for determining surface information using a projected structure with a periodically changing brightness curve

• Main Author: SCHOEPPE GUENTER
• Format: Patent
• Language: English
• Published: 15.05.2003
• Edition: 7
• Subjects: MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; PHYSICS; TESTING

A process is disclosed for determining surface information by a projected structure with periodically changing brightness curve which is shifted by 1/n, n=whole number greater than two, of the grating constant, and the projection image is acquired of a CCD camera, and information is determined for every image point, which information represents the brightfield intensity multiplied by the respective grating phase, the sine components and cosine components are extracted from these images and gives: I. Ixy=Iobxy*m*sin x II. Ixy=Iobxy*m*cos x, where <math-cwu id="MATH-US-00001"> 1 m = I obxy * sin 2 it x + cos 2 it x I obxy <mathematica-file id="MATHEMATICA-00001" file="US20030090680A1-20030515-M00001.NB"/> </math-cwu> and the modulation factor m is calculated from I. and II. and is used for representation, An arrangement is also disclosed for changing the projection direction of a grating which is projected on a surface via at least one wedge-shaped prism body which is rotatable about the optical axis and a parallel plate which is tiltable relative to the optical axis, wherein the control of the tilting movement of the parallel plate is coupled with the rotational movement of the prism body in such a way that a change in the orientation of the prism body is carried out after at least three tilting steps.