We mathematically analyze the phase-only hologram constructed by takin
g the phase corresponding to the linear combination of two weighted ph
ase functions. We show that this phase-only hologram may be written as
a new linear combination for the original phase functions with new we
ights. Expressions for the new weights are developed to control the pe
rformance of the hologram. Also, some nondesired new terms appear and
are written in terms of the original. phase functions. The particular
case of a bifocal lens is analyzed. (C) 1995 Optical Society of Americ
a