An Improved, Manufacturable Position Sensor for Cryogenic Cooler's Moving Parts

"An optically encoded position sensor simplifies manufacturing and reduces cost relative to LVDT technology. Encoders use several readily available COTS or easily manufactured components, are easy to install and align in a cryocooler, and are compact,lightweight, and highly reliable. These elements lend themselves to low cost production. Furthermore, a single encoder design can be readily adapted to work in different cooler designs by simply changing one component - an easily manufacturedlight-modulating grid. This passive element modulates light intensity seen at a detector such that motion steps can be accurately counted. The remaining elements of the sensor, including light source, detectors, and electronics, are unaffected by changesin piston motion over the range of Stirling-class cooler designs planned for development over the next five to ten years.Optical encoders benefit cryocooler manufacturing and producibility in several ways:1. Procurement and stocking of these sensors in production programs is simplified by their increased use of COTS parts compared to existing LVDT technology.2. The high degree of parts commonality in encoders designed for different piston stroke ranges reduces design cycle cost for new coolers and cooler variants.3. The simplicity of installing encoders reduces assembly labor cost. 1. The absolute-incremental encoder is a novel approach that allows, in certain applications, absolute position detec