Sensitivity of Remote Focusing Microscopes to Magnification Mismatch

TL;DR

This paper investigates how small deviations in magnification affect the performance of remote focusing microscopes, quantifying residual aberrations and their impact on imaging depth range through simulations and experiments.

Contribution

It provides a detailed analysis of the tolerance to magnification mismatch in RF systems and offers an empirical method to assess phase matching based on spherical aberration signs.

Findings

50% reduction in dynamic range with 1% magnification mismatch for high NA objectives

Simulation predictions are validated by experimental measurements

Residual spherical aberration increases with magnification deviation

Abstract

Remote focusing (RF) is a technique that greatly extends the aberration-free axial scan range of an optical microscope. To maximise the diffraction limited depth range in an RF system, the magnification of the relay lenses should be such that the pupil planes of the objectives are accurately mapped on to each other. In this paper we study the tolerance of the RF system to magnification mismatch and quantify the amount of residual spherical aberration present at different focusing depths. We observe that small deviations from ideal magnification results in increased amounts of residual spherical aberration terms leading to a reduction in the dynamic range. For high numerical aperture objectives, the simulation predicts a 50% decrease in the dynamic range for 1% magnification mismatch. The simulation has been verified against an experimental RF system with ideal and non-ideal magnifications. Experimentally confirmed predictions also provide a valuable empirical method of determining when a system is close to the ideal phase matching condition, based on the sign of the spherical aberration on either side of focus.