Laser beam steerer-expander.
A two-mirror laser beam expander can be used to provide small amounts of beam steering by moving one mirror. Such a motion would generally introduce aberrations into the output wavefront that would restrict the amount of diffraction-limited beam steering achievable to very small amounts. This paper describes how some or all of the third-order aberrations introduced by moving one mirror can be eliminated. By proper design, substantial amounts of diffraction-limited beam steering can be achieved.
Shafer
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