Optofluidic adaptive optics
TL;DR: A transmissive refractive adaptive optics system featuring a deformable transparent optofluidic wavefront modulator and a sensorless wavefront error estimation algorithm is introduced and high-fidelity recreation of Zernike modes up to the fourth order is experimentally demonstrated.
Abstract: We introduce a transmissive refractive adaptive optics system featuring a deformable transparent optofluidic wavefront modulator and a sensorless wavefront error estimation algorithm. The wavefront modulator consists of a cavity filled with an optical liquid which is sealed by a deformable elastic polymer membrane. Deformation of the membrane is achieved through electrostatic actuation using 25 transparent indium tin oxide electrodes buried in the cavity. Modulation of the two-dimensional phase distribution generated by the system is performed using open loop control both with and without active wavefront sensing. For the latter, a progressive modal decomposition algorithm is used to estimate and correct distortion in the point-spread function (PSF) of the wavefront arising due to the optical system and other sources of wavefront distortion. Using this control method, we experimentally demonstrate high-fidelity recreation of Zernike modes up to the fourth order, and blind (sensorless) PSF correction in a wide-field microscope.
Citations
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Journal Article•
TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
3,742 citations
14 Oct 2021
TL;DR: This Primer provides an overview of the general principles of adaptive optics and explores the different ways in which adaptive optics can correct optical aberrations for high-resolution imaging in the fields of astronomy, vision science and microscopy.
Abstract: Adaptive optics (AO) is a technique that corrects for optical aberrations. It was originally proposed to correct for the blurring effect of atmospheric turbulence on images in ground-based telescopes and was instrumental in the work that resulted in the Nobel prize-winning discovery of a supermassive compact object at the centre of our galaxy. When AO is used to correct for the eye’s imperfect optics, retinal changes at the cellular level can be detected, allowing us to study the operation of the visual system and to assess ocular health in the microscopic domain. By correcting for sample-induced blur in microscopy, AO has pushed the boundaries of imaging in thick tissue specimens, such as when observing neuronal processes in the brain. In this primer, we focus on the application of AO for high-resolution imaging in astronomy, vision science and microscopy. We begin with an overview of the general principles of AO and its main components, which include methods to measure the aberrations, devices for aberration correction, and how these components are linked in operation. We present results and applications from each field along with reproducibility considerations and limitations. Finally, we discuss future directions. This Primer provides an overview of the general principles of adaptive optics and explores the different ways in which adaptive optics can correct optical aberrations for high-resolution imaging in the fields of astronomy, vision science and microscopy.
63 citations
TL;DR: A novel optofluidic device with potential applications in imaging, adaptive optics, optical detection and so on is reported, which can be obtained by applying a voltage.
Abstract: The optofluidic devices including optofluidic lens, optical switch and liquid prism have found widespread applications in imaging, optical communication and lighting. Here, we report a novel optofluidic device called optofluidic variable optical path modulator. Our proposed modulator consists of two main chambers. The two chambers are connected by two tubes to form a closed-loop fluidic system. Two immiscible liquids are filled into the two chambers and form two L-L interfaces. A transparent sheet is placed between one L-L interface to get flat interface. When a voltage is applied on the device, the flat interface can move up and down. Thus, variable optical path can be obtained by applying a voltage. To prove the concept, we fabricate an optofluidic device whose largest movable distance of L-L interface is ~7.5 mm and the optical path length change is ~1.15 mm. The proposed optofluidic device has potential applications in imaging, adaptive optics, optical detection and so on.
11 citations
19 Nov 2020
TL;DR: In this article, the authors discuss the implementation and performance of an adaptive optics (AO) system that uses two cascaded deformable phase plates (DPPs), which are transparent optofluidic phase modulators, mimicking the common woofer/tweeter-type astronomical AO systems.
Abstract: We discuss the implementation and performance of an adaptive optics (AO) system that uses two cascaded deformable phase plates (DPPs), which are transparent optofluidic phase modulators, mimicking the common woofer/tweeter-type astronomical AO systems. One of the DPPs has 25 electrodes forming a keystone pattern best suited for the correction of low-order and radially symmetric modes; the second device has 37 hexagonally packed electrodes better suited for high-order correction. We also present simulation results and experimental validation for a new open-loop control strategy enabling simultaneous control of both DPPs, which ensures optimum correction for both large-amplitude low-order, and complex combinations of low- and high-order aberrations. The resulting system can reproduce Zernike modes up to the sixth radial order with stroke and fidelity up to twice better than what is attainable with either of the DPPs individually. The performance of the new AO configuration is also verified in a custom-developed fluorescence microscope with sensorless aberration correction.
11 citations
Cites background or methods from "Optofluidic adaptive optics"
...More details on the structure, operation principle, and experimental performance of the DPP can be found elsewhere.(14,21) In this work, we used two variants of the DPP, one with 25 keystone-patterned electrodes (DPP1) and a second one with 37 hexagonally-patterned electrodes (DPP2)....
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...The DPP is an optofluidic transmissive spatial phase modulator with a 2D array of electrostatic actuators.(14) Compared to other transmissive phase modulators such as LC-SLMs,(15) the DPP is higher in transmission efficiency, free from diffraction effects, and polarization independent....
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TL;DR: A novel open-loop control method for an electrostatically actuated optofluidic refractive phase modulator is presented, and its performance for high-order aberration correction is demonstrated.
Abstract: We present a novel open-loop control method for an electrostatically actuated optofluidic refractive phase modulator, and demonstrate its performance for high-order aberration correction. Contrary to conventional electrostatic deformable mirrors, an optofluidic modulator is capable of bidirectional (push-pull) actuation through hydro-mechanical coupling. Control methods based on matrix pseudo-inversion, the common approach used for deformable mirrors, thus perform sub-optimally for such a device. Instead, we formulate the task of finding driving voltages for a given desired wavefront shape as an optimization problem with inequality constraints that can be solved using an interior-point method in real time. We show that this optimization problem is a convex one and that its solution represents a global minimum in residual wavefront error. We use the new method to control both the refractive phase modulator and a conventional electrostatic deformable mirror, and experimentally demonstrate improved correction fidelity for both.
11 citations
References
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Journal Article•
TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
3,742 citations
Book•
01 Jan 1998
TL;DR: In this paper, the authors present a comparison of the main two-wave interferometric systems and their configurations used in optical testing and digital image processing, as well as some useful Spatial Filters.
Abstract: (condensed). Review and Comparison of the Main Interferometric Systems: Two-Wave Interferometers and Configurations Used in Optical Testing. Twyman-Green Interferometer. Fizeau Interferometers. Typical Interferograms in Twyman-Green and Fizeau Interferometers. Lateral Shear Interferometers. Ronchi Test. Hartmann Test. Fringe Projection. Talbot Interferometry and Moire Deflectometry. Common Light Sources Used in Interferometry. Aspherical Compensators and Aspheric Wavefronts. Imaging of the Pupil on the Observation Plane. Multiple-Wavelength Interferometry. Fourier Theory Review: Introduction. Fourier Series. Fourier Transforms. The Convolution of Two Functions. The Cross-Correlation of Two Functions. Sampling Theorem. Sampling of a Periodical Function. Sampling of a Periodical Function with Interval Averaging. Fast Fourier Transform. Digital Image Processing: Introduction. Histogram and Gray-Scale Transformations. Space and Frequency Domain of Interferograms. Digital Processing of Images. Some Useful Spatial Filters. Square Window Filter. Hamming and Hanning Window Filters. Cosinusoidal and Sinusoidal Window Filters. Extrapolation of Fringes Outside of the Pupil. Light Detectors Used To Digitize Images. Fringe Contouring and Polynomial Fitting: Fringe Detection Using Manual Digitizers. Fringe Tracking and Fringe Skeletonizing. Global Polynomial Interpolation. Local Interpolation by Segments. Wavefront Representation by an Array of Gaussians.References. Periodic Signal Phase Detection and Algorithms Analysis: Least Squares Phase Detection of a Sinusoidal Signal. Quadrature Phase Detection of a Sinusoidal Signal. Discrete Low-Pass Filtering Functions. Fourier Description of Synchronous Phase Detection. Synchronous Detection Using a Few Sampling Points. Signal Amplitude Measurement. Characteristic Polynomial of a Sampling Algorithm. General Error Analysis of Synchronous Phase-Detection Algorithms. Some Sources of Phase Error. Shifting Algorithms with Respect to the Phase Origin. Optimization of Phase-Detection Algorithms. Influence of Window Function of Sampling Algorithms. Conclusions. Appendix: Derivative of the Amplitude of the Fourier Transform of the Reference Sampling Functions. References. Phase-Detection Algorithms: General Properties of Synchronous Phase-Detection Algorithms. Three-Step Algorithms To Measure the Phase. Four-Step Algorithms To Measure the Phase. Five-Step Algorithm. Algorithms with Symmetrical N +1 Phase Steps. Combined Algorithms in Quadrature. Detuning-Insensitive Algorithms for Distorted Signals. Algorithms Corrected for Nonlinear Phase-Shifting Error. Continuous Sampling in a Finite Interval. Asynchronous Phase-Detection Algorithms. Algorithm Summary. References. Phase-Shifting Interferometry: Phase-Shifting Basic Principles. An Introduction to Phase Shifting. Phase-Shifting Schemes and Phase Measurement. Heterodyne Interferometry. Phase-lock Detection. Sinusoidal Phase Oscillation Detection. Practical Sources of Phase Error. Selection of the Reference Sphere in Phase-Shifting Interferometry. Paraxial Focus. Best Focus. Marginal Focus. Optimum Tilt and Defocusing in Phase-Shifting Interferometry. References. Spatial Linear and Circular Carrier Analysis: Spatial Linear Carrier Analysis. Space-Domain Phase Demodulation with a Linear Carrier. Basic Space-Domain Phase Demodulation Theory. Circular Spatial Carrier Analysis. Phase Demodulation with a Circular Carrier. Fourier Transform Phase Demodulation with a Linear Carrier. Fourier Transform Phase Demodulation with a Circular Carrier. References. Interferogram Analysis with Moire Methods: Moire Techniques. Moire Formed by Two Interferograms with a Linear Carrier. Moire Formed by Two Interferograms with a Circular Carrier. Summary of Moire Effects. Holographic Interpretation of Moire Patterns. Conclusion. References. Interferogram Analysis without a Carrier: Introduction. Mathematical Model of the Fringes. The Phase Tracker. The N-Dimensional Quadrature Transform. Conclusion. References. Phase Unwrapping: The Phase Unwrapping Problem. Unwrapping Consistent Phase Maps Unwrapping Noisy Phase Maps. Unwrapping Subsampled Phase Maps. Conclusions. References. Wavefront Curvature Sensing: Wavefront Determination by Slope Sensing. Wavefront Curvature Sensing. Wavefront Determination with Defocused Images. Conclusions. References. Index. Short TOC
597 citations
TL;DR: How technologies such as deformable mirrors and spatial light modulators, which compensate for aberrations by locally controlling the wavefront of a light wave, are now improving the performance of multiphoton, confocal, widefield and super-resolution microscopes are reviewed.
Abstract: 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. Adaptive optics is used to improve image quality across a wide range of microscopy techniques. Martin Booth from the University of Oxford in the UK reviews how technologies such as deformable mirrors and spatial light modulators, which compensate for aberrations by locally controlling the wavefront of a light wave, are now improving the performance of multiphoton, confocal, widefield and super-resolution microscopes. The benefits of such improvements are especially appealing for images captured from within biological tissue (focal distances of tens to hundreds of micrometres), where low-order aberrations associated with smooth phase variations occur. One future challenge is the development of efficient measurement and correction schemes for higher-order phase variations.
522 citations
TL;DR: An adaptive confocal fluorescence microscope incorporating this modal sensor together with a deformable membrane mirror for aberration correction is demonstrated, which shows considerable improvement in contrast and apparent restoration of axial resolution.
Abstract: The main advantage of confocal microscopes over their conventional counterparts is their ability to optically “section” thick specimens; the thin image slices thus obtained can be used to reconstruct three-dimensional images, a capability which is particularly useful in biological applications. However, it is well known that the resolution and optical sectioning ability can be severely degraded by system or specimen-induced aberrations. The use of high aperture lenses further exacerbates the problem. Moreover, aberrations can considerably reduce the number of photons that reach the detector, leading to lower contrast. It is rather unfortunate, therefore, that in practical microscopy, aberration-free confocal imaging is rarely achieved. Adaptive optics systems, which have been used widely to correct aberrations in astronomy, offer a solution here but also present new challenges. The optical system and the source of aberrations in a confocal microscope are considerably different and require a novel approach to wavefront sensing. This method, based upon direct measurement of Zernike aberration modes, also exhibits an axial selectivity similar to that of a confocal microscope. We demonstrate an adaptive confocal fluorescence microscope incorporating this modal sensor together with a deformable membrane mirror for aberration correction. Aberration corrected images of biological specimens show considerable improvement in contrast and apparent restoration of axial resolution.
472 citations
"Optofluidic adaptive optics" refers methods in this paper
...The technique is now being adapted for different life-science microscopy methods [5–9], such as laser scanning confocal microscopy [10,11], multi-photon microscopy [12–14], and optical coherence tomography [15,16], particularly for deep-tissue imaging....
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TL;DR: Recent work on incorporating adaptive optics, a technology originally applied in astronomical telescopes to combat atmospheric aberrations, to improve image quality of fluorescence microscopy for biological imaging is reviewed.
Abstract: This Perspective introduces the development and use of adaptive optics in correcting aberrations in deep optical imaging applications.
396 citations