Abstract: An interferometrically readable optical encoder for sensing linear position includes an optical medium movable in a linear direction and having a data storage layer, a plurality of uniformly sized sectors being defined in the layer. A linear absolute track is defined in the layer parallel to the linear direction and a plurality of absolute marks is formed in the layer in sequence along the absolute track within each sector, each such absolute mark being detectable by interferometric reflection of coherent light as representative of a binary 1 or a binary 0 and each such plurality of absolute marks defining a binary word. A linear incremental track is defined in the layer parallel to the linear direction with a series of incremental marks formed in the layer and evenly spaced along the first incremental track, each such incremental mark being detectable by interferometric reflection of coherent light.

Abstract: An optical encoder for sensing angular position includes a rotatable optical medium having a major surface and an axis of rotation perpendicular to the surface, with a plurality of uniformly sized angular sectors defined on the surface. An annular absolute track is defined on the surface concentric with the axis, a plurality of digital bits being formed on the surface in sequence along the absolute track within each sector. Each such bit is optically readable as a binary 1 or a binary 0, with each plurality of bits defining a binary word. A first series of optically detectable incremental marks are evenly spaced around a first incremental track on the surface. The binary word in a sector is optically read to identify the angular position of that sector and indicate the approximate angular position of the medium, while the first series of incremental marks can be optically detected to refine the approximate angular position indication.