Snapshot coherence-gated direct wavefront sensing for multi-photon microscopy

Abstract

Abstract:Deep imaging in turbid media such as biological tissue is challenging due to scattering and optical aberrations. Adaptive optics has the potential to compensate the tissue aberrations. We present a wavefront sensing scheme for multi-photon scanning microscopes using the pulsed, near-infrared light reflected back from the sample utilising coherence gating and a confocal pinhole to isolate the light from a layer of interest. By interfering the back-reflected light with a tilted reference beam, we create a fringe pattern with a known spatial carrier frequency in an image of the back-aperture plane of the microscope objective. The wavefront aberrations distort this fringe pattern and thereby imprint themselves at the carrier frequency, which allows us to separate the aberrations in the Fourier domain from low spatial frequency noise. A Fourier analysis of the modulated fringes combined with a virtual Shack-Hartmann sensor for smoothing yields a modal representation of the wavefront suitable for correction. We show results with this method correcting both DM-induced and sample-induced aberrations in rat tail collagen fibres as well as a Hoechst-stained MCF-7 spheroid of cancer cells.

Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging

“…The combination of coherence-gated wavefront sensing with two-photon microscopy was reported using a virtual Shack-Hartmann sensor35. Alternative approaches to coherence-gated wavefront sensing using a virtual Shack-Hartmann sensor have also been reported3637. The combination of coherence-gated detection with a lenslet-based Shack-Hartmann wavefront sensor was reported as well3839.…”

Multi-scale sensorless adaptive optics: application to stimulated emission depletion microscopy

“…4, which was enabled by inserting BS1. After tilting flat mirror M in the reference arm, one could extract the wrapped phase from a single interferogram using Fourier-based fringe analysis [31,32], and subsequently apply a phase unwrapping algorithm [33]. We obtained the influence matrix H of the DM as outlined in [34].…”

Optimization-based wavefront sensorless adaptive optics for multiphoton microscopy

“…For this calibration we use the alignment laser, which is a continuous wave. We used the method described in [6] to decode the wavefront from the fringe patterns.…”

“…A reference arm is created using beam splitter BS1, flat mirrors M3, M4, M5, and beam splitter BS2. A coherence-gated fringe analysis method described elsewhere [6] is applied to the fringe pattern generated onto the CCD. 0.79 rms rad at 900 nm, mostly astigmatism).…”

“…One solution involves measuring the aberrations of the excitation light that is back-scattered from the specimen [5][6][7][8][9][10]. In this case, the difficulty arises in excluding the light that is reflected from the out-of-focus layers of the specimen [5,6].…”