  On the basis of the data given in the works of different authors a criterion
of phase-photometric method of measurement of energy angle of divergence has
been formulated. Validity of application of the obtained relations for a ray
beam with an arbitrary diameter and an arbitrary shape of the wave front has
been proved. Advantages of the proposed phase-photometric method in comparison
with the focal-spot method have been confirmed. Necessity and possibility of
building a standard solid angle has been proved.
