System for taking displacement measurements having photosensors with imaged pattern arrangement

Abstract

The present invention is generally directed to a system for taking displacement measurements of an object. The invention utilizes the Moiré effect to take precise displacement measurements of an object. In this regard, a visible pattern is disposed on an object, and a plurality of photosensors are uniformly spaced apart from the visible pattern. Importantly, the spacing between the photosensors is slightly different than the spacing between light and dark lines forming a projection or image of the visible pattern. This allows the invention to utilize the Moiré effect to accurately compute precise displacements or movements of the object. In this respect, electrical signal generated by the photosensor array will embody a repeating envelope pattern resulting from the difference in the pitch of the photosensors and the pitch of the projection or image of the visible pattern. This envelope has a spatial frequency that is significantly lower than the fundamental repetition frequency of either the image (or projection) of the visible pattern or the photosensor array, where these frequencies of the image or projection of the visible pattern and the photosensor array are equal to the reciprocal of the distances separating adjacent repetitions of pattern within the image of the visible pattern or the reciprocol of the pitch of adjacent photosensor elements respectively. Thus, small lateral motion of the object bearing the visible pattern, made parallel to the direction of the repetition of the repeating patterns, produces a relatively large shift in the position of the signal envelope which has a lower spatial frequency.

Dependencies are inferred from the claim text.