Reference signal generating configuration for an interferometric miniature grating encoder readhead using fiber optic receiver channels

摘要

A fiber optic readhead and scale arrangement for measuring displacement provides a reference position indication. The scale includes a scale track comprising a first type of track portion providing first level of zero order reflectance, such as a grating, and a reference mark providing a second level of zero order reflectance, such as a mirror. The reference mark is configured with certain length or boundary spacing dimensions determined based on certain fiber optic receiver channel aperture dimensions in the readhead. In some configurations a fiber optic readhead and track that provides the reference position indication is separate from a fiber optic readhead and track that provides periodic incremental measurement signals. In some configurations an integrated fiber optic readhead and an integrated track structure provide both the reference position indication and the periodic incremental measurement signals.