Depth from rotating point spread functions

We present a method for passive ranging with incoherent light. The scheme uses a single optical channel and is particularly suitable for locating and ranging particles. Our aim is to create an optical system with increased discrimination among depth planes as compared to classical clear aperture solutions. We thus propose a criterion for evaluating a general point spread function for use in passive ranging. Then, we show that rotating point spread functions are good according to this criterion. An experimental realization of the point spread function by use of a computer-generated hologram is presented as well as a simulation of its depth discrimination.