C. D. Saunter

Modal liquid crystal wavefront corrector.

Results are presented of the properties of a liquid crystal wavefront corrector for adaptive optics. The device is controlled using modal addressing in which case the device behaves more like a continuous facesheet deformable mirror than a segmented one. Furthermore, the width and shape of the influence functions are electrically controllable. We describe the construction of the device, the optical properties, and we show experimental results of low order aberration generation.

Multipoint viscosity measurements in microfluidic channels using optical tweezers

We demonstrate the technique of multipoint viscosity measurements incorporating the accurate calibration of micron sized particles. We describe the use of a high-speed camera to measure the residual motion of particles trapped in holographic optical tweezers, enabling us to calculate the fluid viscosity at multiple points across the field-of-view of the microscope within a microfluidic system.

SPARTA: the ESO standard platform for adaptive optics real time applications

ESO is starting a number of new projects collectively called Second Generation VLT instrumentation. Several of them will use Adaptive Optics (AO). In comparison with todays ESO AO systems, the 2nd Generation VLT AO systems will be much bigger (in terms of degrees of freedom) and faster (in terms of loop frequency). Consequently the Real-Time Computer controlling these AO systems will be significantly bigger and more challenging to build compared with todays AO systems in operation. To support the new requirements ESO started the development of a common flexible platform called SPARTA for Standard Platform for Adaptive optics Real Time Applications. The guidelines along which SPARTA is developed recognize the importance of industry standards over custom development to lower the development costs, ease the maintenance and make the system upgradeable thus delivering the performance required. SPARTA is based on a hybrid architecture that comprises all the major computing architectures available today: the high computational throughput is achieved through the combination of FPGA and DSP usage, where DSP are used as fast coprocessors and FPGA are used as front and as communication infrastructure, thus guaranteeing also the low latency. The flexibility is spread between the usage of both high-end CPUs and again the DSPs. All three technologies are organized in a parallel system interconnected by fast serial fabrics based on standard protocols. External input / output interfaces are also based on industry standard protocols, thus enabling the usage of commercially available tools for development and testing.

Multiconjugate adaptive optics: laboratory experience

We present the results from a laboratory multiconjugate adaptive optics experiment. The experiment is differentiated from other published work in that it has a programmable deterministic turbulence generator and an output science camera. The turbulence was generated using a dual layer turbulence emulator, and then corrected using an AO system with 2 wavefront correctors and a Shack-Hartman wavefront sensor, which processed information from five artificial guide stars. We report our results and also describe some of the problems.

Technology and electro-optical properties of modal liquid crystal wavefront correctors

A multi-channel liquid crystal modal wavefront corrector is presented and the manufacturing procedure, which was developed especially for this type of corrector, is described in detail. An experimental analysis of the static and dynamic properties of the corrector and the results of close-loop wavefront correction are also presented.

Low-cost high-speed control for adaptive optics

The outcomes of research at the Durham University Centre for Advanced Instrumentation into the use of low cost devices in the construction and operation of adaptive optics systems is presented. An embedded low cost sensing and control system for high speed AO is presented where the components for sensing and control cost under us

Horizontal turbulence measurements using SLODAR

400 and we demonstrate the possibility to build and operate an AO system where the sensor and controller have a combined cost of under us

Shack-Hartmann sensor improvement using optical binning

150. An alternative application of the work as a data processing smart camera is presented.

Light sheet adaptive optics microscope for 3D live imaging

SLODAR (slope detection and ranging) is a technique we have developed to monitor the vertical profile of atmospheric phase distortions, for application to astronomical adaptive optics systems. The technique uses the correlation between slope measurements made using a Shack-Hartmann wavefront sensor observing a binary star. In this paper we describe the principle of SLODAR and then describe our work on using a system for the measurement of horizontal turbulence profiles for application to free space optical communications.

Prospective gating for 3D imaging of the beating zebrafish heart in embryonic development studies

We present a design improvement for a recently proposed type of Shack-Hartmann wavefront sensor that uses a cylindrical (lenticular) lenslet array. The improved sensor design uses optical binning and requires significantly fewer detector pixels than the corresponding conventional or cylindrical Shack-Hartmann sensor, and so detector readout noise causes less signal degradation. Additionally, detector readout time is significantly reduced, which reduces the latency for closed loop systems and data processing requirements. We provide simple analytical noise considerations and Monte Carlo simulations, we show that the optically binned Shack-Hartmann sensor can offer better performance than the conventional counterpart in most practical situations, and our design is particularly suited for use with astronomical adaptive optics systems.