[Diffraction halo]

Diffraction halo
produced by a coarse speckle
pattern transparency placed in the
focal plane of a helium-neon
laser, photographed by I M
Andrews and M H Dossett of
IBM United Kingdom Laboratories,
Hursly Park. This photograph
was taken during the setting
up of equipment for analysing
speckle pattern photographs,
during measurements of the inplane
strain of a component. This
successful technique can measure
displacements down to a fraction
of 0'001 in, without any contact
being made with the object.