Scale for an absolute position detection type photoelectric encoder with three or more two-bit combination patterns are used to represent a two-level code pattern

Abstract

There is provided an absolute position detection type photoelectric encoder which improves robustness to dirt while maintaining high resolution. A two-level code pattern according to a pseudo random code sequence is provided on a scale along a length measurement direction. Each code of the two-level code pattern indicates a code “1” or a code “0”, and includes two bits. Each of the two bits is L or H. The code “1” is represented by an A pattern which is a combination of L and H, and the code “0” is represented by a B pattern which is a combination of L and L or a C pattern which is a combination of H and H. When the codes “0” are continued, the B pattern and the C pattern are alternately used.

Dependencies are inferred from the claim text.