DIFFRACTION GRATINGS AND THE MANUFACTURE THEREOF

摘要

A diffraction grating 1 includes a surface 12 having grooves 14 therein, each groove 14 providing a diffracting surface for light incident upon the diffracting surface. The grooves 14 are separated from each other by lands 20 upon the surface 12. The lands 20 are of predetermined varying width, whereby the diffractive efficiency of the grating 1 varies across the extent of the grating 1.