Computational localization microscopy with extended axial range

A new single-aperture 3D particle-localization and tracking technique is presented that demonstrates an increase in depth range by more than an order of magnitude without compromising optical resolution and throughput. We exploit the extended depth range and depth-dependent translation of an Airy-beam PSF for 3D localization over an extended volume in a single snapshot. The technique is applicable to all bright-field and fluorescence modalities for particle localization and tracking, ranging from super-resolution microscopy through to the tracking of fluorescent beads and endogenous particles within cells. We demonstrate and validate its application to real-time 3D velocity imaging of fluid flow in capillaries using fluorescent tracer beads. An axial localization precision of 50 nm was obtained over a depth range of 120μm using a 0.4NA, 20× microscope objective. We believe this to be the highest ratio of axial range-to-precision reported to date

3D extended-range particle-localization microscopy using Airy-beam-based point-spread functions

The precise localization of point emitters in optical microscopy has revolutionized our ability to super resolve subcellular structures beyond the diffraction limit and to study fundamental biological dynamics through single-molecule tracking. It also found its applications on a larger scale in blood-flow characterization, traction-force microscopy and microfluidic research including lab-on-chip experiments. However, traditional optical microscopy is typified by a restrictively small depth of field, i.e. the operable range in the axial direction is severely limited by diffraction to a thin layer in contrast to the relatively large field of view in the xy directions. This precludes the probing of three-dimensional (3D) behaviors of the sample. A number of techniques have emerged recently for 3D point localization, typically exploiting characteristic axial variations in the optical point-spread function (PSF) to deduce the axial coordinate of the emitter. However, existing approaches suffer from limitations such as small depth ranges, low optical throughput, complicated implementations or degraded performance in presence of overlapping PSFs. In this work, the lateral translation of the Airy beam is exploited to encode the emitters' axial coordinates and two novel approaches, namely the Airy-CKM (i.e. complementary kernel matching) and the twin-Airy techniques, are reported for 3D point-localization microscopy. The following advantages are clearly demonstrated: (1) The Airy-beam-based PSFs yield diffraction-free propagation, i.e. little diffractive spreading, which provides a greater axial range than existing techniques and makes them suitable for imaging thick samples. (2) Deconvolution-based localization algorithms are utilized, allowing for imaging of high emitter densities with overlapping PSFs. (3) The continuous phase profiles used to generate the Airy-beam-based PSFs can be implemented with refractive phase masks, which yield nearly 100% broadband optical throughput avoiding the photon inefficiency of spatial light modulators. (4) The simplicity in implementations (especially the twin-Airy technique) makes them applicable to most fluorescence microscopes. A statistical comparison to existing methods is performed by calculating their Cramer-Rao lower bounds, where the proposed approaches compare favorably to the state-of-the-art. The reported techniques are demonstrated to in vivo measurement of blood-flow dynamics in zebrafish embryos, which, to the best of the author's knowledge, is the first the application of pupil-engineered PSFs to hemodynamic measurements. In addition, time-resolved traction-force microscopy will be discussed briefly as an ongoing work

Video-rate 3D Particle Tracking with Extended Depth-of-field in Thick Biological Samples

We present a single-aperture 3D particle localisation and tracking technique with a vastly increased depth-of-field without compromising optical resolution and throughput. Flow measurements in a FEP capillary and a zebrafish blood vessel are demonstrated experimentally

Advances in 3D single particle localization microscopy

The spatial resolution of conventional optical microscopy is limited by diffraction to transverse and axial resolutions of about 250 nm, but localization of point sources, such as single molecules or fluorescent beads, can be achieved with a precision of 10 nm or better in each direction. Traditional approaches to localization microscopy in two dimensions enable high precision only for a thin in-focus layer that is typically much less than the depth of a cell. This precludes, for example, super-resolution microscopy of extended three-dimensional biological structures or mapping of blood velocity throughout a useful depth of vasculature. Several techniques have been reported recently for localization microscopy in three dimensions over an extended depth range. We describe the principles of operation and typical applications of the most promising 3D localization microscopy techniques and provide a comparison of the attainable precision for each technique in terms of the Cramér-Rao lower bound for high-resolution imaging

High-speed extended-volume blood flow measurement using engineered point-spread function

Experimental characterization of blood flow in living organisms is crucial for understanding the development and function of cardiovascular systems, but there has been no technique reported for snapshot imaging of thick samples in large volumes with high precision. We have combined computational microscopy and the diffraction-free, self-bending property of Airy-beams to track fluorescent beads with sub-micron precision through an extended axial range (up to 600 \textmu m) within the flowing blood of 3 days post-fertilization (dpf) zebrafish embryos. The spatial trajectories of the tracer beads within flowing blood were recorded during transit through both cardinal and intersegmental vessels, and the trajectories were found to be consistent with the segmentation of the vasculature recorded using selective-plane illumination microscopy (SPIM). This method provides sufficiently precise spatial and temporal measurement of 3D blood flow that has the potential for directly probing key biomechanical quantities such as wall shear stress, as well as exploring the fluidic repercussions of cardiovascular diseases. Although we demonstrate the technique for blood flow, the ten-fold better enhancement in the depth range offers improvements in a wide range of applications of high-speed precision measurement of fluid flow, from microfluidics through measurement of cell dynamics to macroscopic aerosol characterizations

Twin-Airy point-spread function for extended-volume particle localization

The localization of point sources in optical microscopy enables nm-precision imaging of single-molecules and biological dynamics. We report a new method of localization microscopy using twin Airy beams that yields precise 3D localization with the key advantages of extended depth range, higher optical throughput, and potential for imaging higher emitter densities than are possible using other techniques. A precision of better than 30 nm was achieved over a depth range in excess of 7μm using a 60×, 1.4 NA objective. An illustrative application to extended-depth-range blood-flow imaging in a live zebrafish is also demonstrated

Optimizing AES Threshold Implementation under the Glitch-Extended Probing Model

Threshold Implementation (TI) is a well-known Boolean masking technique that provides provable security against side-channel attacks. In the presence of glitches, the probing model was replaced by the so-called glitch-extended probing model which specifies a broader security framework. In CHES 2021, Shahmirzadi et al. introduced a general search method for finding first-order 2-share TI schemes without fresh randomness (under the presence of glitches) for a given encryption algorithm. Although it handles well single-output Boolean functions, this method has to store output shares in registers when extended to vector Boolean functions, which results in more chip area and increased latency. Therefore, the design of TI schemes that have low implementation cost under the glitch-extended probing model appears to be an important research challenge. In this paper, we propose an approach to design the first-order glitch-extended probing secure TI schemes when quadratic functions are employed in the substitution layer. This method only requires a small amount of fresh random bits and a single clock cycle for its implementation. In particular, the random bits in our approach are reusable and compatible with the changing of the guards technique. Our dedicated TI scheme for the AES cipher gives 20.23% smaller implementation area and 4.2% faster encryption compared to the TI scheme of AES (without using fresh randomness) proposed in CHES 2021. Additionally, we propose a parallel implementation of two S-boxes that further reduces latency (about 39.83%) at the expense of increasing the chip area by 9%. We have positively confirmed the security of AES under the glitch-extended probing model using the verification tool - SILVER and the side-channel leakage assessment method - TVLA

Precise 3D particle localization over large axial ranges using secondary astigmatism

No abstract available

Measuring the Sum-of-Squares Indicator of Boolean Functions in Encryption Algorithm for Internet of Things

Encryption algorithm has an important application in ensuring the security of the Internet of Things. Boolean function is the basic component of symmetric encryption algorithm, and its many cryptographic properties are important indicators to measure the security of cryptographic algorithm. This paper focuses on the sum-of-squares indicator of Boolean function; an upper bound and a lower bound of the sum-of-squares on Boolean functions are obtained by the decomposition Boolean functions; some properties and a search algorithm of Boolean functions with the same autocorrelation (or cross-correlation) distribution are given. Finally, a construction method to obtain a balanced Boolean function with small sum-of-squares indicator is derived by decomposition Boolean functions. Compared with the known balanced Boolean functions, the constructed functions have the higher nonlinearity and the better global avalanche characteristics property

3D microfluidic particle image velocimetry with extended depth-of-field and a single camera

We describe a novel 3D particle image velocimetry (PIV) technique in microscopy using the wave-front coding method. Unlike conventional stereoscopic PIV, this technique has an extended depth-of-field (DOF) and requires only a single lens and detector