Related: https://en.wikipedia.org/wiki/Linear_encoder https://en.wikipedia.org/wiki/Linear_encoder >"A linear encoder is a sensor, transducer or readhead pair

Related: https://en.wikipedia.org/wiki/Linear_encoder https://en.wikipedia.org/wiki/Linear_encoder >"A linear encoder is a sensor, transducer or readhead paired with a scale [measuring device] that encodes [retrieves, gets, fetches] position [from a physical system]." (Patent (now expired) is one method of making an Optical Linear Encoder based on Holographic principles... a Holographic Optical Linear Encoder -- or perhaps just Holographic Linear Encoder -- for short...)