Abstract:

An edge location algorithm based on optical mechanism was proposed. By the combination of fresnel diffraction theory and transmission attenuation law, the edge of the projection image was precisely located. First, the monochromatic light diffraction model and its limitations in transmission environment were presented. After analyzing the attenuation characteristic of the transmitted light, an intensity distributing optical model dually affected by transmission and diffraction was proposed. Finally, the edge location algorithm was derived. The optical model extended the fresnel diffraction theory to the transmission condition. The edge location was an important one of its applications. For engineering application, the calculation of the attenuation coefficients was given. Therefore, the algorithm was independent on the material of the exposure object. The experimental results proved that the accuracy and the efficiency were superior to operator method.

Key words:  edge location, diffraction, transmission attenuation, intensity distributing, optical model