Understanding the limits of remote focusing

TL;DR

This paper investigates the residual spherical aberration in remote focusing microscopes, demonstrating how a correction collar can compensate for it, and analyzes the limits imposed by inherent aberrations on system performance.

Contribution

It provides an experimental validation of aberration compensation using a correction collar and analyzes the fundamental limits of remote focusing due to inherent aberrations.

Findings

Correction collar effectively compensates residual spherical aberration.

Residual aberrations are consistent with optical model predictions.

Inherent aberrations limit the diffraction-limited range of remote focusing systems.

Abstract

It has previously been demonstrated in both simulation and experiment that well aligned remote focusing microscopes exhibit residual spherical aberration outside the focal plane. In this work, compensation of the residual spherical aberration is provided by the correction collar on the primary objective, controlled by a high precision stepper motor. A Shack-Hartmann wave front sensor is used to demonstrate the magnitude of the spherical aberration generated by the correction collar matches that predicted by an optical model of the objective lens. The limited impact of spherical aberration compensation on the diffraction limited range of the remote focusing system is described through a consideration of both on-axis and off-axis comatic and astigmatic aberrations, which are an inherent feature of remote focusing microscopes.