Electro-optic displacement device

Claim 1

In an electro-optic displacement measuring device comprising means for deriving a pattern of regularly varying light intensities from a scale element having a regular array of optically discernible indicia, said pattern being positionally displaced with displacement of said scale element; means for distributing said light pattern among a plurality of photocells variously positioned with respect to said light pattern so as to generate a plurality of electrical signals varying in predetermined phase relationship with said pattern displacement; and electronic counter means utilizing said plurality of signals to indicate the extent of said scale displacement; the improvement in said pattern-deriving and light-distributing means which comprises: a. means for imaging a substantial number of indicia in said scale array at an image plane; and b. image-dividing and light-directing means comprising a multiplicity of contiguous reflective elements situated substantially at said image plane and arranged seriatim in the direction of periodicity of said scale image, said multiplicity of elements being further arranged in a sequence of groups wherein each group comprises a regular plurality of said elements and is of a dimension substantially equal to a period of said scale image, and respective elements in each group being arranged to direct incident light comprising said scale image to different respective ones of said plurality of photocells.