Diffraction-limited constant-resolution zoom lens across multi-wavelengths for the Advanced Technology Solar Telescope

摘要

Zoom lenses are usually designed for a specified waveband and change magnification, and thus resolution, for different object sizes or different object distances. However, the Advanced Technology Solar Telescope (ATST)/ Visible Light Broadband Imager (VLBI), under development by the National Solar Observatory, require constant resolution for different wavelengths over a wide spectral range (388.3 nm 3o 854.2 nm). An eight-element zoom lens meeting this requirement is presented, and yields diffraction-limited performance over the field of view at nine specific wavelength/zoom positions. Each zoom position, corresponding to a specific wavelength, has a focal length and fumber for achieving constant CCD sampling. The Strehl ratio of the telescope is greater than 90% over all zoom positions.