A method of relaying the transverse profile of a laser beam and its application to holography

The holography of engineering plant where only restricted access is available requires a method of piping the pulsed laser beam to a compact, remote head. Because amplifier distortions which occur in pulsed lasers result in far field beam break-up, it is not possible to simply collimate the beam as normally possible with a continuous wave laser. A possible way to transmit the pulsed laser beam is by an optical relay which repeatedly images the output until the launching point is reached.

The use of a relay system to transmit the pulsed laser output 20 m has been demonstrated in the laboratory. Holograms taken at the output of the relay showed a resolution of 18l.p. mm^-1, the same as that achieved when a hologram was taken by expanding the beam immediately at the laser output.