Lens/zone plate combination for chromatic dispersion correction

摘要

Chromatic dispersion between first and second wavelengths of light is corrected by a lens/zone plate combination. The zone plate is adapted both to send most of the first wavelength light into its zeroth order and to send most of the second wavelength light into its first order and to change the focal length of the second wavelength light to coincide with the focal length of the first wavelength light. A preferred embodiment includes a zinc/selinide sulfide lens having a zone plate etched onto one of its surfaces. The zone plate has a multi-step phase profile including four phase levels. The lens/zone plate combination is particularly adapted for use with CO2 and HeNe lasers to bring their focal lengths into coincidence.