Method for determining absolute position of measuring head of portal machine in e.g. automated production plant, involves determining absolute position of object based on coarse-information and phase shift

摘要

The method involves detecting intensity of a measuring signal after traversing a measuring path (8) as a function of time so as to determine coarse-information for length of the measuring path. Phase shift between an interferometer-object beam and an interferometer-reference beam based on intensity of an interference signal, which is produced by superimposition of the interferometer-object beam and the interferometer-reference beam, where the phase shift is associated with the measuring path. An absolute position of an object (15) is determined based on the information and the phase shift. An independent claim is also included for a device for determining an absolute position of an object.