Predictive wavefront sensorless adaptive optics for time-varying aberrations

A new wavefront sensorless adaptive optics method is presented that can accurately correct for time-varying aberrations using a single focal plane image at each sample instance. The linear relation between the mean square of the aberration gradient and the change in second moment of the image forms the basis of the presented method. The new...

Sequential convex relaxation for robust static output feedback structured control

We analyse the very general class of uncertain systems that have Linear Fractional Representations (LFRs), and uncertainty blocks in a convex set with a finite number of vertices. For these systems we design static output feedback controllers. In the general case, computing a robust static output feedback controller with optimal performance...

Modal-based phase retrieval using Gaussian radial basis functions

In this paper, we propose the use of Gaussian radial basis functions (GRBFs) to model the generalized pupil function for phase retrieval. The selection of the GRBF hyper-parameters is analyzed to achieve an increased accuracy of approximation. The performance of the GRBF-based method is compared in a simulation study with another modal-based...

Fast Calculation of Computer Generated Holograms for 3D Photostimulation through Compressive-Sensing Gerchberg–Saxton Algorithm

The use of spatial light modulators to project computer generated holograms is a common strategy for optogenetic stimulation of multiple structures of interest within a three-dimensional volume. A common requirement when addressing multiple targets sparsely distributed in three dimensions is the generation of a points cloud, focusing excitation...

Phase retrieval based on the vectorial model of point spread function

We present an efficient phase retrieval approach for imaging systems with high numerical aperture based on the vectorial model of the point spread function. The algorithm is in the class of alternating minimization methods and can be adjusted for applications with either known or unknown amplitude of the field in the pupil. The algorithm...

Identification of affinely parameterized state–space models with unknown inputs

The identification of affinely parameterized state–space system models is quite popular to model practical physical systems or networked systems, and the traditional identification methods require the measurements of both the input and output data. However, in the presence of partial unknown input, the corresponding system identification...

Extended-image-based correction of aberrations using a deformable mirror with hysteresis

With a view to the next generation of large space telescopes, we investigate guide-starfree, image-based aberration correction using a unimorph deformable mirror in a plane conjugate to the primary mirror.We designed and built a high-resolution imaging testbed to evaluate control algorithms. In this paper we use an algorithm based on the...

Imaging & identification of malaria parasites using cellphone microscope with a ball lens

We have optimized the design and imaging procedures, to clearly resolve the malaria parasite in Giemsa-stained thin blood smears, using simple low-cost cellphone-based microscopy with oil immersion. The microscope uses a glass ball as the objective and the phone camera as the tube lens. Our optimization includes the optimal choice of the ball...

Convex optimization-based blind deconvolution for images taken with coherent illumination

A rank-constrained reformulation of the blind deconvolution problem on images taken with coherent illumination is proposed. Since in the reformulation the rank constraint is imposed on a matrix that is affine in the decision variables, we propose a novel convex heuristic for the blind deconvolution problem. The proposed heuristic allows for...

Shack-Hartmann reflective micro profilometer

We present a quantitative phase imaging microscope based on a Shack-Hartmann sensor, that directly reconstructs the optical path difference (OPD) in reflective mode. Comparing with the holographic or interferometric methods, the SH technique needs no reference beam in the setup, which simplifies the system. With a preregistered reference, the...

Identification of the dynamics of time-varying phase aberrations from time histories of the point-spread function

To optimally compensate for time-varying phase aberrations with adaptive optics, a model of the dynamics of the aberrations is required to predict the phase aberration at the next time step. We model the time-varying behavior of a phase aberration, expressed in Zernike modes, by assuming that the temporal dynamics of the Zernike coefficients...

Optical path difference microscopy with a Shack-Hartmann wavefront sensor

In this Letter, we show that a Shack-Hartmann wavefront sensor can be used for the quantitative measurement of the specimen optical path difference (OPD) in an ordinary incoherent optical microscope, if the spatial coherence of the illumination light in the plane of the specimen is larger than the microscope resolution. To satisfy this...

Affinely parametrized state-space models: Ways to maximize the Likelihood Function

Using Maximum Likelihood (or Prediction Error) methods to identify linear state space model is a prime technique. The likelihood function is a nonconvex function and care must be exercised in the numerical maximization. Here the focus will be on affine parameterizations which allow some special techniques and algorithms. Three approaches to...

Optimal model-based sensorless adaptive optics for epifluorescence microscopy

We report on a universal sample-independent sensorless adaptive optics method, based on modal optimization of the second moment of the fluorescence emission from a point-like excitation. Our method employs a sample-independent precalibration, performed only once for the particular system, to establish the direct relation between the image...

Proximal-based recursive implementation for model-free data-driven fault diagnosis

We present a novel problem formulation for model-free data-driven fault diagnosis, in which possible faults are diagnosed simultaneously to identifying the linear time-invariant system. This problem is practically relevant for systems whose model cannot be identified reliably prior to diagnosing possible faults, for instance when operating...

Temperature-immune readout of an integrated optical wavelength meter based on microring resonators

Wavelength meters are central for many applications such as in telecommunication systems or laser monitoring. The primary function of a wavelength meter is to provide an output signal that changes sensitively with the wavelength of the input light. Of central importance is the reproducibility of the output signal even in the presence of external...

Preconditioning optimal in-domain control of navier-stokes equation using multilevel sequentially semiseparable matrix computations

In this manuscript, we study preconditioning techniques for optimal in-domain control of the Navier-Stokes equation, where the control only acts on a few parts of the domain. Optimization and linearization of the optimal in-domain control problem results in a generalized linear saddle-point system. The Schur complement for the generalized saddle...