Modelling of Standard Solid Angle
  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. 
Rahul Malik