Spatial coherence of a ruby laser beam by interferometry

The importance of spatial coherence of a pulsed ruby laser beam is pointed out. The spatial and temporal coherences of light are defined. Spatial coherence of the beams from a ruby laser, operating in either the Q-switched or normal lasing modes, is deduced from the degree of visibility of fringes formed by a Michelson interferometer in which the laser beam interferes with itself after being rotated 180 degrees . The results are physically and analytically interpreted.