Planar Light-sheet Microscopy with Curved Airy Beams

The Airy beam extends the imaging volume of a light-sheet microscope ten-fold. However, its unusual curved structure hampers its use with two-photon excitation. We demonstrate a planar Airy light-sheet for two-photon excitation that does not rely on deconvolution

Extended field-of-view light-sheet microscopy

Light-sheet fluorescence microscopy enables rapid 3D imaging of biological samples. Unlike confocal and two-photon microscopes, a light-sheet microscope illuminates the focal planewith an objective orthogonal to the detection axis and images it in a single snapshot. Its combination of high contrast and minimal sample exposure make it ideal to image thick samples with sub-cellular resolution. To uniformly illuminate a wide field-of-view without compromising axial resolution, propagation-invariant light-fields such as Bessel and Airy beams have been put forward. These beams do however irradiate the sample with a relatively broad transversal structure. The fluorescence excited by the side lobes of Bessel beams can be blocked physically during recording; though at the cost of increased sample exposure. In contrast, the Airy beam has a fine transversal structure that is both curved and asymmetric. Its fine structure captures all the high-frequency components that enable high axial resolution without the need to discard useful fluorescence. This advantage does not carry over naturally to two-photon excitation where the fine transversal structure is suppressed. We demonstrate a symmetric and planar Airy light-sheet that can be used with two-photon excitation and that does not rely on deconvolution

Planar Light-sheet Microscopy with Curved Airy Beams

The Airy beam extends the imaging volume of a light-sheet microscope ten-fold. However, its unusual curved structure hampers its use with two-photon excitation. We demonstrate a planar Airy light-sheet for two-photon excitation that does not rely on deconvolution

Optimal design of hybrid optical digital imaging systems

Several types of pupil modulation have been reported to decrease the aberration variance of the modulation-transfer-function (MTF) in aberration-tolerant hybrid optical-digital imaging systems. It is common to enforce restorability constraints on the MTF, requiring trade of aberration-tolerance and noise-gain. In this thesis, instead of optimising specific MTF characteristics, the expected imaging-error of the joint design is minimised directly. This method is used to compare commonly used phase-modulation functions. The analysis shows how optimal imaging performance is obtained using moderate phasemodulation, and more importantly, it shows the relative merits of different functions. It is shown that the technique is readily integrable with off-the-shelf optical design software, which is demonstrated with the optimisation of a wide-angle reflective system with significant off-axis aberrations. The imaging error can also be minimised for amplitudeonly masks. It is shown that phase aberrations in an imaging system can be mitigated using binary amplitude masks. This offers a low-cost, transmission-mode alternative to phase correction as used in active and adaptive optics. More efficient masks can be obtained by the optimisation of the imaging fidelity

Extended field-of-view light-sheet microscopy

Light-sheet fluorescence microscopy enables rapid 3D imaging of biological samples. Unlike confocal and two-photon microscopes, a light-sheet microscope illuminates the focal planewith an objective orthogonal to the detection axis and images it in a single snapshot. Its combination of high contrast and minimal sample exposure make it ideal to image thick samples with sub-cellular resolution. To uniformly illuminate a wide field-of-view without compromising axial resolution, propagation-invariant light-fields such as Bessel and Airy beams have been put forward. These beams do however irradiate the sample with a relatively broad transversal structure. The fluorescence excited by the side lobes of Bessel beams can be blocked physically during recording; though at the cost of increased sample exposure. In contrast, the Airy beam has a fine transversal structure that is both curved and asymmetric. Its fine structure captures all the high-frequency components that enable high axial resolution without the need to discard useful fluorescence. This advantage does not carry over naturally to two-photon excitation where the fine transversal structure is suppressed. We demonstrate a symmetric and planar Airy light-sheet that can be used with two-photon excitation and that does not rely on deconvolution

Planar light-sheet microscopy with curved Airy beams

Light-sheet microscopy enables rapid 3D imaging of biological samples. Its field-of-view can be extended ten-fold by relying on propagation-invariant Airy beams. However, such beams propagate on a parabolic trajectory. By consequence, a light-sheet formed by Airy beams is not planar, thus warping the images. Here, we demonstrate a planar Airy light-sheet that does not rely on digital image restoration techniques for two-photon microscopy

Computing coherent light scattering on the millimetre scale using a recurrent neural network without training

Heterogeneous materials such as biological tissue scatter light in random, yet deterministic, ways. Wavefront shaping can reverse the effects of scattering to enable deep-tissue microscopy. Such methods require either invasive access to the internal field or the computational solving of an inverse problem. However, calculating the coherent field on a scale relevant to microscopy remains excessively demanding for consumer hardware. Here we show how a recurrent neural network can mirror Maxwell's equations without training. By harnessing public machine learning infrastructure, the light-field throughout a $6 \, \textrm{mm}^2$ area or $110^3 \, \mu\textrm{m}^3$ volume can be calculated in 16 minutes. The elimination of the training phase cuts the calculation time and, importantly, it ensures a fully deterministic solution, free of training bias. We integrated our method with an open-source electromagnetic solver. This enables any researcher with an internet connection to calculate complex light-scattering in volumes that are larger by two orders of magnitude.Comment: 7 pages, 3 figure

A universal matrix-free split preconditioner for the fixed-point iterative solution of non-symmetric linear systems

We present an efficient preconditioner for linear problems $A x=y$. It guarantees monotonic convergence of the memory-efficient fixed-point iteration for all accretive systems of the form $A = L + V$, where $L$ is an approximation of $A$, and the system is scaled so that the discrepancy is bounded with $\lVert V \rVert<1$. In contrast to common splitting preconditioners, our approach is not restricted to any particular splitting. Therefore, the approximate problem can be chosen so that an analytic solution is available to efficiently evaluate the preconditioner. We prove that the only preconditioner with this property has the form $(L+I)(I - V)^{-1}$. This unique form moreover permits the elimination of the forward problem from the preconditioned system, often halving the time required per iteration. We demonstrate and evaluate our approach for wave problems, diffusion problems, and pantograph delay differential equations. With the latter we show how the method extends to general, not necessarily accretive, linear systems.Comment: Rewritten version, includes efficiency comparison with shift preconditioner by Bai et al, which is shown to be a special cas