Passive range finder based on moiré images of Ronchi-like gratings with bilateral asymmetry.
A passive range-finding technique utilizing moiré images of Ronchi-like gratings with bilateral asymmetry, specifically fork gratings, is explored. Fork gratings are used as opposed to Ronchi gratings due to their asymmetry in the spatial and frequency domains, which enable the resolution of certain ambiguities in analysis that would otherwise be present. The two patterns which are convolved to produce the moiré image are the fork grating and the nailbed pattern of the pixelated detector. A fork grating of known size and spatial frequency is imaged with a detector of a fixed pixel pitch. Multiple analysis techniques are applied in frequency space, which lead to both relative and absolute measures of distance.