613728.fig.001a
(a)
613728.fig.001b
(b)
Figure 1: (a) The geometry of the Fresnel diffraction of light from a 1D phase step. By displacing point on the step, the point on the screen is shifted to satisfy equation . Therefore, the complex amplitude varies as a function of . (b) A phase step in transmission is formed at the edges of a transparent plate of refractive index that is immersed in a transparent gas or liquid of refractive index .