Estimation of the size parameters of fine rectangular grooves based on Fraunhofer diffraction

A non-contact measuring method based on Fraunhofer diffraction which can estimate quantitatively the size parameters of fine rectangular grooves with periodic square-wave in cross section is described. The relation between a model of rectangular grooves and diffraction intensity pattern is analyzed theoretically. Equations which can estimate the size parameters of rectangular grooves such as pitch, width, and depth from the diffraction intensity pattern are derived. The numerical analysis of the equations and the computer simulations are performed. In order to verify the validity of the proposed method, the measurement of the size parameters of the rectangular grooves of a high precision grating plate is carried out.