Photoelectric position measuring device

摘要

In a position measuring device, a scale is embodied as a phase grating on which several partial beams impinge and are diffracted and caused to interfere with each other in the scanning unit. The entry angle (alpha) of the partial beams corresponds to the Littrow angle, so that the diffracted partial beams of ±1st diffraction order are diffracted at the same angle beta=alpha. The diffraction efficiency of the scale is particularly great if the flanks of the bars of the scales are at an angle of approximately 70° with respect to the measuring direction, i.e., if the bars and gaps are embodied to be trapezoidal in cross section.