Angular position indicator using Moire fringes - has rotatable part pivoted on straight-edged stationary part for use like bubble level

摘要

An instrument for the indication or checking of the angular position of an object, comprises a stationary part and a movable part, the movable part being pivoted to the stationary part, and rotatable about an axis which is not coincident with the mass centre of the movable part, and the stationary part having at least one straight edge that can be placed against a surface of the object. Each part has a pattern of equally wide, parallel lines separated by interspaces of the same width as the lines, the interspaces being transparent on at least of the parts, and the two line patters together forming a Moire pattern.