Modeling the Effect of Wave-front Aberrations in Fiber-based Scanning Optical Microscopy

In scanning microscopy and optical coherence tomography, aberrations of the wave-front cause a loss in intensity and resolution. Intensity and resolution are quantified using Fresnel propagation, Fraunhofer diffraction, and the calculation of overlap integrals.

Real-time wavefront reconstruction from intensity measurements

We propose an efficient approximation to the nonlinear phase diversity method for wavefront reconstruction from intensity measurements. The new method, iterative linear phase diversity (ILPD), assumes that the residual phase aberration is small and makes use of a first order Taylor expansion of the point spread function (PSF) performed for an...

Fault tolerant wind turbine production operation and shutdown (Sustainable Control)

Extreme environmental conditions as well as system failure are real-life phenomena. Especially offshore, extreme environmental conditions and system faults are to be dealt with in an effective way. The project Sustainable Control, a new approach to operate wind turbines (Agentschap NL, grant EOSLT02013) pro- vides the concepts for an integrated...

Sparse prediction of turbulence in time and space

Using a matching pursuit (MP) approach to solve least squares problems with a sparsity constraint sparse controllers are computed to compensate for atmospheric turbulence. The method has been validated by simulation of von K´arm´an turbulence with frozen flow for the case of prediction, reconstruction and control.

Validation of a new adaptive deformable mirror concept

A new prototype adaptive deformable mirror for future AO-systems is presented that consists of a thin continuous membrane on which push-pull actuators impose out-of-plane displacements. Each actuator has ±10?m stroke, nanometer resolution and only mW’s heat dissipation. The mirror’s modular design makes the mechanics, electronics and control...

Distributed control in adaptive optics: Deformable mirror and turbulence modeling

Future large optical telescopes require adaptive optics (AO) systems whose deformable mirrors (DM) have ever more degrees of freedom. This paper describes advances that are made in a project aimed to design a new AO system that is extendible to meet tomorrow’s specifications. Advances on the mechanical design are reported in a companion paper ...

Adaptive optics H2-optimal control design applied on an experimental setup

Most adaptive optics systems (AO) are based on a simple control law that is unable to account for the temporal evolution of the wavefront. In this paper, a recently proposed data-driven H2-optimal control approach is demonstrated on an AO laboratory setup. The proposed control approach does not assume any form of decoupling and can therefore...

H2-optimal control of an adaptive optics system: Part II, closed-loop controller design

The problem of finding the closed-loop optimal controller is formulated in an H2-optimal control framework. This provides a natural way to account for the fact that in many AO systems the wavefront phase cannot be measured directly. Given a multi-variable disturbance model of both wavefront slopes and wavefront phases,3 this provides a general...

H2-optimal control of an adaptive optics system: Part I, data-driven modeling of the wavefront disturbance

Even though the wavefront distortion introduced by atmospheric turbulence is a dynamic process, its temporal evolution is usually neglected in the adaptive optics (AO) control design. Most AO control systems consider only the spatial correlation in a separate wavefront reconstruction step. By accounting for the temporal evolution of the...

Optimal control strategy to reduce the temporal wavefront error in AO systems

An Adaptive Optics (AO) system for astronomy is analysed from a control point of view. The focus is put on the temporal error. The AO controller is identified as a feedback regulator system, operating in closed-loop with the aim of rejecting wavefront disturbances. Limitations on the performance of feedback regulator systems are discussed. The...

The Bounded Real Lemma for Discrete Time-Varying Systems with Application to Robust Output Feedback