Generic Misalignment Aberration Patterns and the Subspace of Benign Misalignment

TL;DR

This paper uses aberration theory to analyze misalignment patterns in three mirror anastigmats, explaining why specific sensor placements and control degrees are sufficient for effective optical alignment.

Contribution

It introduces a theoretical framework for understanding misalignment aberration patterns and the subspace of benign misalignments in complex optical systems.

Findings

Aberration theory explains sensor placement choices.

Misalignment patterns form a subspace of benign configurations.

Theoretical insights guide optimal control of mirror degrees of freedom.

Abstract

Q1: Why deploy N wavefront sensors on a three mirror anastigmat (TMA) and not N + 1? Q2: Why measure M Zernike coefficients and not M + 1? Q3: Why control L rigid body degrees of freedom (total) on the secondary and tertiary and not L + 1? The usual answer: "We did a lot of ray tracing and N,M, and L seemed OK." We show how straightforward results from aberration theory may be used to address these questions. We consider, in particular, the case of a three mirror anastigmat.