Position encryption of extended surfaces for subpixel localization of small-sized fields of observation

A vision system is used for measuring in-plane target position, displacement and orientation. An encrypted pseudo-periodic pattern fixed on the target forms a phase reference. Absolute position is determined with subpixel accuracy by phase computations from any local view of a small zone of the pattern. Method principle is presented and performances are characterized. The capability to resolve position on depth ranges larger than the lens depth of focus is demonstrated. The method is applied to position referencing of live cell culture boxes and could be used as visual control sensor in other applications.