  Proposed, justified and tested measuring of beam spatial coherence, based on
the detection of an interference visibility of the equal to intensity of beam
replicas emerging under reflection from the rotated plane-parallel plate. The
method consists in measuring the interference contrast at the simultaneous
change of the longitudinal path difference and transverse shift of named
replicas. Accurate measurement of the angle of rotated plate and the amplitude
distribution of interferential minimaxes allows to determine the width of the
beam spatial coherence. Spatial coherence of some types of multimode lasers has
been measured by the method. Keywords: coherence measurements, interference in
2 move apart beam, rotable interferometer
