We calculate the beaming of coherent emission by means of geometrical
optics. When spherical elementary waves are phase-coupled in that way
that constructive interference occurs along one axis, the intensity is
lower for off-axis viewing angles. The spatial angle of constructive
interference shrinks to a fraction of 4 pi when the length scale of th
e emission region is larger than the wavelength of the radiation. This
leads to an amplification of the received radiation in addition to th
e relativistic beaming caused by the relativistic radial outflow which
is thought to be important for the radio emission of pulsars. The eff
ect will be calculated by numerical methods and can be approximated by
a simple analytic expression.