Characterization of deformable mirrors for spherical aberration correction in optical sectioning microscopy

Shaw, Michael J.; Hall, Simon R. G.; Knox, Steven; Stevens, R. F.; Paterson, Carl

doi:10.1364/oe.18.006900

Cited by 23 publications

(11 citation statements)

References 24 publications

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“…This provides the information required to drive the DM with chosen aberration modes, rather than directly with individual actuator signals. A range of such methods have been developed specifically for use in microscopes, using interferometry, 23 image based measurements 24,25 and phase diversity. 26,27 Spatial light modulators have been used less frequently in microscopes for aberration correction, due to their polarisation dependent operation and sensitivity to wavelength when used in the common modulo 2p mode.…”

Section: Adaptive Correction Elementsmentioning

confidence: 99%

Adaptive optical microscopy: the ongoing quest for a perfect image

2014

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Adaptive optics is becoming a valuable tool for high resolution microscopy, providing correction for aberrations introduced by the refractive index structure of specimens. This is proving particularly promising for applications that require images from deep within biological tissue specimens. We review recent developments in adaptive microscopy, including methods and applications. A range of advances in different microscope modalities is covered and prospects for the future are discussed. INTRODUCTIONOptical microscopes have for a long time played a vital role in biomedical research. Their ability to provide multidimensional structural and functional information about a specimen in a non-invasive manner has permitted numerous scientific advances. These microscopes rely upon high-quality optical systems to operate at the optimum resolution, which is determined by the diffraction limit of light for conventional microscopes. However, even with perfect optical components, the performance of the microscope is affected by the optical properties of the specimen. Spatial variations in refractive index introduce aberrations as the light passes through the specimen-a problem that is exacerbated when imaging deeps into tissue. These aberrations detrimentally affect the resolution and contrast of microscope images, ultimately limiting the depth at which imaging is practical. Adaptive optics (AO) was introduced into microscopy in order to overcome this limitation. Dynamic correction elements, such as deformable mirrors (DMs) or spatial light modulators (SLMs) have been employed to compensate specimen-induced aberrations (Figure 1). New wavefront sensing and control schemes have been developed to adapt the correction elements.The first demonstrations of adaptive optical microscopy took place in the early 2000s. In the few years that followed, there were several innovative advances that set the scene for further research. The research in this period is well covered by two review articles 1,2 and a recent compiled volume, 3 so this will not be reproduced here. This present article provides a review of advances in aberration correction in adaptive microscopy that have taken place in the last half-decade. During this period, a wide range of AO techniques have emerged, which have considerably enhanced the available toolkit. Furthermore, the benefit of correction of specimen-induced aberrations has been shown in different areas, particularly (although not exclusively) in biomedical applications. We outline these technological

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Section: Adaptive Correction Elementsmentioning

confidence: 99%

Adaptive optical microscopy: the ongoing quest for a perfect image

2014

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“…This matrix describes the relation between measured responses of actuator and coefficient associated with the basis employed for least square, to replicate ideal DM shape. 14,15 The column vectors of the transfer matrix, which represent the slope of the phase generated by the DM, form the natural (zonal) bases for DM beam shaping by iterative algorithms. However, due to the linear dependence between the columns of the matrix due to the cross-coupling effect, it is suboptimal choice for expressing the measured wavefronts.…”

Section: Openloop Characterisationmentioning

confidence: 99%

Characterization of double-deformable-mirror adaptive optics for IR beam shaping in hyperspectral imaging

Kalkhoran

Fitzpatrick

Winter

et al. 2020

Unconventional Optical Imaging II

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Vibrational microspectroscopy via Fourier transform infrared (FTIR) faces an experimental trade-off among the signal to noise ratio (SNR), acquisition time, spatial resolution, and sample coverage. This is mainly associated with broadband source type: e.g. low brightness thermal sources with high flux for large field of view imaging at low resolution, or lowétendue of synchrotron radiation infrared (SRIR) for diffraction-limited scanning microanalysis at high magnification. 1 Adaptive optics (AO), in this case deformable mirror (DM), is a potent tool in tackling the problem by modulating the intensity of high brightness structured SRIR beam toward a homogeneous field illumination for IR imaging at high magnification. The latter is required for an efficient coupling of SRIR source to a multi-pixel detector such as focal plane array (FPA). 2 Additionally, DM enables to achieve different shapes, optimized for different Cassegrain IR objective. Regardless, the quality of the generated beam relies upon the performance of the adaptive elements, i.e. actuators and their linear and reproducible response to the applied voltage. Moreover, the beam shaping capability of a single DM in controlling light beam position and angle is limited by its actuators influence function. In this work, we implemented two DMs for intensity shaping for the complex SRIR beam. A variation of multi-conjugate AO is implemented to characterize the performance of DMs and their actuators transfer function at multiple locations. An IR sensitive microbolometer array has been optically conjugated to the focal plane of individual actuators and the far-field of DM, in order to probe the corresponding actuating response. By analysing each actuator's response individually, a measure of linear independence, uniformity in response, and cross-coupling can be obtained in a spectral range, from visible to near and mid IR. Additionally, by assembling the vectorized version of each actuator response, the transfer matrix can be formed. This matrix describes the relationship between the actuation effect on the beam and the response of the IR microbolometer, at the given conjugate planes. Based on such discussion, we assess the stability of the deformable mirror for open-loop (i.e. without feedback) operation.

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“…Different models are used amongst the literature. [22][23][24] Taking the median of the normalized radial profiles within the linear region (-40 to +40 V), we fit the DM influence function with a 2D Gaussian model (see Fig. 5, bottom right) possessing the following parameters: amplitude = 0.97 and standard deviation = 0.494.…”

Section: Modeling Of the Influence Functionmentioning

confidence: 99%

Development of an ELT XAO testbed using a Mach-Zehnder wavefront sensor: calibration of the deformable mirror

Delacroix¹,

Langlois²,

Loupias³

et al. 2015

Unconventional Imaging and Wavefront Sensing 2015

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Extreme adaptive optics (XAO) encounters severe difficulties to cope with the high speed (>1kHz), high accuracy and high order requirements for future extremely large telescopes. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor (MZWFS) allows counteracting these limitations. This sensor estimates very accurately the wavefront phase at small spatial scale by measuring intensity differences between two outputs, with a λ/4 path length difference between its two legs, but is limited in dynamic range due to phase ambiguity. During the past few years, such an XAO system has been studied by our team in the framework of 8-meter class telescopes. In this work, we report on our latest results with the XAO testbed recently installed in our lab, and dedicated to high contrast imaging with 30m-class telescopes (such as the E-ELT or the TMT). After reminding the principle of a MZWFS and describing the optical layout of our experiment, we will show the results of the assessment of the woofer-tweeter phase correctors, i.e., a Boston Micromachine continuous membrane deformable mirror (DM) and a Boulder Nonlinear Systems liquid crystal spatial light modulator (SLM). In particular, we will detail the calibration of the DM using Zygo interferometer metrology. Our method consists in the precise measurement of the membrane deformation while applying a constant deformation to 9 out of 140 actuators at the same time. By varying the poke voltage across the DM operating range, we propose a simple but efficient way of modeling the DM influence function using a Gaussian model. Finally, we show the DM flattening on the MZWFS allowing to compensate for low order aberrations. This work is carried out in synergy with the validation of fast iterative wavefront reconstruction algorithms, and the optimal treatment of phase ambiguities in order to mitigate the dynamical range limitation of such an MZWFS.

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Characterization of deformable mirrors for spherical aberration correction in optical sectioning microscopy

Cited by 23 publications

References 24 publications

Adaptive optical microscopy: the ongoing quest for a perfect image

Adaptive optical microscopy: the ongoing quest for a perfect image

Characterization of double-deformable-mirror adaptive optics for IR beam shaping in hyperspectral imaging

Development of an ELT XAO testbed using a Mach-Zehnder wavefront sensor: calibration of the deformable mirror

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