Measuring distance by angular domain filtering

In this paper a paraxial imaging system with incoherent illumination is interpreted as a signal processing system in which a thin lens performs a forward angular transform on light rays traveling through it. Inverse angular transform exists and could be performed by another thin lens which coincides its focus plane with the first. The common focus plane acts as an angular domain, on which filtering is possible by placing aperture stops. A symmetrically angular filtering results in a direct correspondence between a recorded signal and its object distance. Such a “transform-filtering-inverse transform” system could be understood as a modified tele-centric system, with which a novel concept for measuring a distance without focusing on the target is suggested.