All-optical microscope autofocus based on an electrically tunable lens and a totally internally reflected IR laser

M. Bathe-Peters, P. Annibale*, M. J. Lohse

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)
2 Downloads (Pure)

Abstract

Microscopic imaging at high spatial-temporal resolution over long time scales (minutes to hours) requires rapid and precise stabilization of the microscope focus. Conventional and commercial autofocus systems are largely based on piezoelectric stages or mechanical objective actuators. Objective to sample distance is either measured by image analysis approaches or by hardware modules measuring the intensity of reflected infrared light. We propose here a truly all-optical microscope autofocus taking advantage of an electrically tunable lens and a totally internally reflected infrared probe beam. We implement a feedback-loop based on the lateral position of a totally internally reflected infrared laser on a quadrant photodetector, as an indicator of the relative defocus. We show here how to treat the combined contributions due to mechanical defocus and deformation of the tunable lens. As a result, the sample can be kept in focus without any mechanical movement, at rates up to hundreds of Hertz. The device requires only reflective optics and can be implemented at a fraction of the cost required for a comparable piezo-based actuator.

Original languageEnglish
Pages (from-to)2359-2368
Number of pages10
JournalOptics Express
Volume26
Issue number3
Early online date23 Jan 2018
DOIs
Publication statusPublished - 5 Feb 2018

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