Double-grating diffraction interferometric stylus probing system for surface profiling and roughness measurement

A double-grating diffraction interferometric stylus probing transducer consisting of a cylindrical grating and a planar grating has been presented to transform the surface profile information to electrical signals. The transducer has the merit of compact construction and high resolution. The relationship between the electrical signals and the displacement of the cylindrical grating is briefly reviewed. The existence of the cylindrical grating brings angle and position deviation, and the deviation will affect the interference of the diffracted beams. To ensure the interference of the diffracted beams, the relationships between the angle deviation, the position deviation, and the radius of curvature of the cylindrical grating are analyzed. The analysis shows that the diffracted beams will interfere normally when suitable radius of curvature of the cylindrical grating and suitable distance between the two gratings are adopted, thus the profile information can be obtained.