New ultrahigh-sensitivity absolute, linear, and rotary encoders

Abstract

Several new types of absolute optical encoders of both rotary and linear function are discussed. The means for encoding are complete departures from conventional optical encoders and offer advantages of reliability, compact form, immunity to damage-induced dropouts of position information, and about an order of magnitude higher sensitivity over what is commercially available. Rotary versions have sensitivity from 0.02 arcseconds down to 0.003 arcsecond while linear models have demonstrated sensitivity of 10 nm (0.01 micrometers ) with higher sensitivities possible.