Centre for Photonics and Imaging

Project Description: Understanding laser-matter-ambient-interactions is important to realise the potential of high repetition rate, multi-kiloWatt, femtosecond and picosecond laser technologies in scalable production. The fabrication of integrated multifunctional thin film devices by additive (inkjet, spray) and subtractive (laser) manufacturing on Roll to Roll (R2R) production platforms is also suddenly possible and desperately needed to realise new cost effective manufacturing solutions.

Enquiries from potential PhD students are sought to develop new understanding of short pulse laser matter interactions relevant to very thin films and R2R manufacturing platforms. A particular focus will be the development of on-line tools which will create new process monitoring tools for cost effective production based on new nano-inspired materials relevant to flexible large area electronics and medical devices.

Project Description: Moblie phone cameras have developed dramatically in the last few years. Nevertheless, the push towards thinner phones places severe limits on the image quality that can be obtained. A possible solution is to use multiple cameras together with advanced image processing on the phone’s microprocessor. There are many different ways to approach this; for example, different cameras could have different aperture sizes or be sensitive to different wavelengths or even different polarisations. They could be sequenced temporally and have different exposoure times in order to improve the capture of synamic scenes. Applications include 3D/depth information, object recognition through shape, time-signature,wavelength and polarisation, enhancement of resolution, colour fidelity and dynamic range. The project will commence with computer modelling and proceed to developing prototype systems.

Project Description: Imaging and spectroscopy of planetary systems around other stars is one of the most exciting challenges in current astronomy. Dedicated instruments have recently been built for the largest telescopes in the world and are now being commissioned. There is a need for algorithms to extract the information from these instruments in an optimal way, and we have developed a novel approach which we call ‘PEX’ (Plane Extractor). The initial application is to the reconstruction of images of the extrasolar planetary systems. It is also of great interest to apply this approach to extracting spectral information. This has the potential to provide direct spectra of the extrasolar planets, which would allow us to determine physical properties such as atmospheric composition. The holy grail of exoplanet studies is to detect ‘biomarkers’ i.e. the spectral signature of life.

Project Description: Wavefront sensors are used to measure aberrations in optical systems. The measurements can be used to determine the quality of an optical system. Alternatively, the measurements can be used to control wavefront correction in an adaptive optics system. Wavefront sensors usually involve special hardware and a dedicated detector. However, it is also possible to estimate wavefront errors from a pair of images, one of which has a known defocus. This is referred to as ‘phase diversity’ and it is of considerable interest given the simplicity of the hardware involved. The aim of this project is to carry out a direct comparison of wavefront measurements obtained using a ‘standard’ wavefront sensor and phase diversity. The conditions under which phase diversity can compete in performance will be determined experimentally. This project will be of interest for future adaptive optics systems and for systems aiming to correct aberrations in space telescopes.

Project Description: Free-space optical communication uses a laser beam to transmit information through the atmosphere. This can have a very high bandwidth, and has been proposed for communication between points on the ground and between the ground and space satellites. However, when a laser beam propagates through the turbulent atmosphere, the result is variations in the beam amplitude and phase which causes random fluctuations in the intensity. The aim of adaptive optics (AO) is to measure and correct these phase errors in real time. All major astronomical telescopes now employ adaptive optics to provide diffraction- limited imaging, at least in the near infrared. Application to laser beam correction is complicated by the severe turbulence encountered on horizontal paths, while the correction of beams to satellites requires very high speed correction. In this project we will investigate techniques to characterise turbulence over horizontal paths (e.g. across the Corrib river). Based on these measurements, an adaptive optics system will be developed and tested. In particular, a novel wavefront sensors based on ‘point diffraction interferometry’ will be investigated. This sensor is expected to be very efficient, and to be robust to conditions of strong turbulence.

Project Description: The characterization of atmospheric turbulence is vital for imaging and optical communication through the atmosphere. Current techniques to measure the strength of turbulence rely on observing stars or the sun and are therefore restricted in use. Our collaborators in this project, Georgia Tech Research Institute(GTRI), have recently demonstrated a lidar based turbulence profiler which provides the opportunity to measure turbulence at any time and along arbitrary paths. There is now an opportunity to exploit this instrument in order to make detailed studies of atmospheric turbulence at different sites. In this project, new algorithms will be developed to process and analyse data from the lidar profiler. In particular, a robust reconstruction of the turbulence profile in altitude will be demonstrated. A temporal analysis will be developed in order to estimate wind speed profiles. Intensity fluctuations in the data will also be analysed and we will investigate the use of this information in the turbulence profile estimation. This device will potentially be deployed at ground stations for satellite-to-ground laser communication, astronomical observatories and other sites where knowledge of atmospheric turbulence is important, such as airports.

Project Description: Classical ophthalmological instruments have poor resolution and cannot detect the early stages of retinal diseases. The result is that these diseases are not detected until the symptoms become obvious, and then it may be too late for clinical intervention. Adaptive Optics has proven its ability to provide images with resolution at the cellular level, but we lack robust, automatic tools to analyse these images. AO images of the retina may contain a huge amount of information, and it becomes imperative to assist the clinician with automated tools to quantify the information, monitor changes in structures between visits to the clinic and to call attention to signs of disease. This work will build on an international collaboration between ophthalmologists and adaptive optics/image processing specialists in order to develop these tools. They will be tested on images from a large sample of both healthy and diseased eyes. It is expected that the results of this work will have a major impact on the clinical ophthalmology community.

Project Description: The current problems of an earlier onset of myopia (short-sightedness) in young eyes is probably related with excessive use of gadgets for reading, writing and playing, which requires that the eye is kept in the accommodated state (crystalline lens gains more optical power by assuming more convex shape) as a result of this and probably other factors the eye globe undergoes more growth in length than usual. The mismatch of the length of the eye and the optical power of the cornea and the lens leads to myopia, the image formed at the retina is out of focus. One possible explanation for the development of myopia is the signal at the periphery of the visual field (off-axis blur). To study the impact of accommodation on the off-axis blur one needs an accurate model of the crystalline lens, which is in the accommodated state. The optical modelling of the image formation through the accommodated crystalline lens featuring gradient index of refraction and the effect of eye growth on image sharpness is the main topic of this study. The project will commence with computer modelling of the optical system of the eye with an adjustable crystalline lens representing biometrically sound process of accommodation.

Project Description: Every eye a new generation of mobile phone cameras appear on the market, bringing more pixels, sharper images and better low light performance. The missing feature is the optical zoom in the camera lenses, which is obviously not easy to fit into a thin 6-5 mm mobile phone housing. There are possible solutions to locate the zoom lens along the side of the phone gaining sufficient space to perform zoom function, however the solutions are not trivial and require some novel concept to achieve at least 2-3 time zoom, which does not compromise on imaging quality. In addition one would like to attain a wide 60-70 deg field at the short end of the zoom range, this puts extra complexity in the lens design featuring mainly plastic lenses. The initial phase of the project is to show which concept can meet the current requirements in mobile phones. Using optical ray tracing program one could model different scenarios who to design a compact zoom and proceed with the best design to manufacture a prototype system. This project will be in collaboration with the research and development company, FotoNation company, which is based in Galway

Project Description: A typical cataract surgery requires replacement of a partially opaque crystalline lens by a transparent ocular implant. This dramatically reduces internal light scattering and provides unobstructed image formation on the retina. If the optical power of the IOL is chosen correctly, it can compensate for nearor long-sightedness by removing the major refractive error (defocus) of the cornea. IOL power calculations for patients undergoing cataract surgery are usually based on the measurement of the optical power of the cornea and the axial length of the eye. Over the years, dozens of formulae have been proposed for IOL power calculation, in all of them the anterior and posterior corneal surfaces are combined to one surface, and the IOL is approximated by a thin lens. To resolve this problem, one could apply an exact ray-tracing method instead of regression formulae. Individual rays are traced through all refractive surfaces in the eye. The ray-tracing guided prediction of the lens position and IOL customization utilizes a personalized eye model describing all patient-specific parameters, such as corneal topography, the crystalline lens shape, inter-ocular distances and refractive indices. The main advantage of the ray-tracing approach is that one can take into account peculiar features of the patient’s eye including optical irregularities of the cornea. It might be feasible to measure these individual features using current ophthalmic instruments.

Project Description: Modern radiation therapy techniques allow for greater conformity of the radiation dose to the planning target volume (PTV), thus sparing surrounding healthy tissue. Consequently steeper dose gradients have been employed to improve clinical outcome, however to avoid an increased risk to healthy tissue, this has been coupled with a decrease in the PTV margin. This decrease in the PTV margin makes the delivery of radiation therapy more sensitive to geometrical uncertainties, such as patient set-up relative to the coordinate system of the treatment room, and internal organ motion. Image guided radiation therapy (IGRT) is employed to allow precise daily localization of the target, thus minimizing the effect of inter-fraction motion. The goal of this project is to focus on the challenges presented when implementing intramodality 3D ultrasound imaging for IGRT.

Project Description: Pre-clinical imaging technology has developed considerably in recent years. Molecular imaging techniques such as Ultrasound, MRI, SPECT, PET and CT are used routinely in Biomedical research labs around the world. In-vivo imaging can now be considered as an essential component of translational research studies aimed at improving our understanding of the mechanisms of disease and developing therapeutic strategies. Pre-clinical imaging provides the capability to carry out longitudinal studies on same group of animals over time, where previously animal sacrifice and dissection would have been necessary at each time point. This project will focus on the application and optimisation of molecular imaging technology available in state-of-the-art preclinical research facilities.

New carbons, such as graphene, create novel electronics at an ultra-compact scale, replacing metals, silicon and semiconductors, but are disadvantaged by complex and toxic manufacturing methods, requiring process liquids/gases, clean rooms and controlled atmospheres. This project creates flexible polymers, for sensing spatial variations in temperature, moisture and strain for smart polymer skins or smart dressings are required for wound healing, or contaminated or damaged surfaces in structural health monitoring. A single step direct laser writing (DLW) process will structure the solid carbon material in 3D to tune the composite conductivity, functionalization and sensitivity to strain, temperature and moisture.

Prof. Martin Leahy: http://www.nuigalway.ie/science/schoolofphysics/staffprofiles/martinleahy/

Prof. Alan Ryder: https://www.universityofgalway.ie/nanoscale/