OFF-AXIS FOCAL SHIFT FOR ROTATIONALLY NONSYMMETRIC SCREENS

We report on an analytical formulation for evaluating the amplitude di stribution along any line directed toward the geometrical focus of a s pherical wave front that passes through a rotationally nonsymmetric di ffracting screen. our formula consists of two factors. The first facto r involves the one-dimensional Fourier transform of the projection of the screen function onto the off-axis line. The second factor depends on the inverse distance to the screen and permits us to recognize the existence of focal shift along off-axis lines.