An all-silica three-element wide-field corrector for GMT

TL;DR

This paper introduces a simplified all-silica wide-field corrector for GMT, achieving high image quality with minimal lenses and innovative tilt/translation ADC mechanisms, enhancing performance and transmission.

Contribution

It presents a novel three-element silica corrector with integrated ADC using tilt and translation, reducing complexity and improving image quality for GMT.

Findings

Achieves d80<0.043" polychromatic image quality at zenith

Uses only three silica lenses with a single low-precision asphere

Provides superb transmission across 360nm-1300nm

Abstract

We present an alternative Corrector-ADC design for GMT. The design consists of just 3 silica lenses, of maximum size 1.51m, and includes only a single low-precision asphere for 20' field-of-view, and none for 10'. The polychromatic (360nm-1300nm) image quality is d80<0.043" at zenith and d80<0.20" for ZD<60 degrees. The monochromatic image quality is d80<0.1" everywhere, and typically ~0.05". The ADC action is achieved by tilt and translation of all three lenses; L1 and L2 via simple slide mechanisms each using a single encoded actuator, and L3 via a novel 'tracker-ball' support and three actuators. There is also a small motion of M2 via the hexapod, automatically generated by the AGWS system. The ADC action causes a small non-telecentricity, but this is much less than the unavoidable chromatic effects shared with the baseline design. The ADC action also changes the distortion pattern of the telescope, but this can be used positively, to reduce the maximum image motion due to differential refraction by a factor of three. The transmission is superb at all wavelengths, because of the reduced number of air/glass surfaces, and the use only of fused silica.