Abstract: A digital optical micrometer for mounting on an optical instrument and having an optical flat plano-parallel window which is connected to a micrometer drum. The drum can pivot or incline the optical plano-parallel window to cause displacement of a line of sight. The digital optical micrometer further has an LCD read-out that indicates the amount of displacement of the line of sight, a circuit that is connected to the optical plano-parallel window and provides an electrical signal having a signal property which varies in proportion to the inclination of the line of sight, and an analog-to-digital converter that is connected to the circuit and converts the electrical signal to a digital word having a binary value representative of the inclination of the line of sight. The optical micrometer further has a computer which has a clock input that provides for an automatic power down of the micrometer.