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Selected PhD projects

Efficient LED light multiplexing for innovative operative tissue discrimination

Chris Price, WORIC, PhD student

Mr. Chris Price

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The minimal invasive surgical procedure of endoscopy is becoming increasingly utilised, particularly for the identification of cancer in the human body. Until recently the technology has been dominated by halogen and xenon light based systems due to the available optical power and colour temperature produced. Lately LED replacement systems are becoming more prominent, partly due to the increased meantime to failure. This means less service intervals are required to change the lamp, not only therefore saving on the high cost of the replacement lamps but also the even higher cost of the apparatus not being available for surgery or even stopping the procedure mid operation. 

Commonly available UV/Blue pumped phosphor LEDs provide white light as an alternative to halogen and xenon lamp sources though to date have not been powerful enough to provide the luminous output to match that of the predecessors. This has been overcome for the illumination market by creating chip on board (COB) large area LED arrays that combine many LEDs to increase the optical power and luminous output. Unfortunately, it is currently not possible to adopt the same principle for endoscopy systems due to etendue of the system being restricted by the requirement to carry the light through an optical fibre or liquid light guide. Furthermore, as the concept relies on phosphor being pumped by light in the UV/blue wavelength spectrum range, increasing the power of pump wavelength is likely to increase the emittance of the phosphor, though the saturation point and stability of the agents used to bind the phosphor material are unknown. It is a technical challenge therefore to increase the emitted optical output power possible from a phosphor material at the desired wavelength, under stable conditions, whilst also keeping the etendue of the optical system low enough to couple into an optical fibre or liquid light guide. 

The aim of the now 2-year industrial PhD programme is to design and implement such an optical system by exploring an advanced concept proposed under Cymtec’s patent PCT/GB2012/051910, of pumping a phosphor material from both sides to increase efficiency per unit area of phosphor material. 

The new concept is to pump the phosphor from two or more sides, whilst encapsulating the phosphor material in an optically transparent material to direct the light along a guided path. The advantages are two-fold in firstly providing a mass to protect the phosphor from intense power and to maintain the etendue of light in the system. 

The target outcome of the project is to produce a prototype optical system that will provide a greater optical power white light phosphor LED based system than is currently on the market, by utilising the concepts stated.

This project aims to design and investigate endoscopic light sources to assist in the detection and removal of cancerous tissue in the breast. There are currently no endoscopy products utilising LASER as the excitation source for imaging available on the market however, there are many commercially available medical devices comprising LASER source of varying wavelengths and power.

General background research into available LASER devices has shown that there are plenty of clinically approved products however, there is a lack of diversity amongst applications. Many devices using the traditional bulb technology have, or are beginning to migrate over to LED technology. LED’s are cheaper and better suited to medical applications where energy is required locally over a large area, LASERs provide a monochromatic, coherent and collimated beam with much faster on/off switching. Depending on the pulse frequency required for the pump, LASERs are much easier to pulse and this is why I suggest that fluorescence endoscopy is an ideal application for LASER technology. 

From experience, there are other parameters to consider which will contribute to the success of a medical device including but not limited to; eye safety, ease of use and public perception. The proposed experiments will excite the fluorescent marker using either an NIR LED and NIR LASER as well as imaging the field of view (FOV) so that a comparative analysis can be carried out. Due to closure of the company partner, the focus of the research needed to change in order to complete the work in a timely manner. Specifically, with support withdrawn, it was not feasible to move forward with the original design and research plan as the expertise required to design and build was no longer available.

Experiments will be setup under lab conditions, for simplicity smaller experiments have been designed so that time in the lab is used efficiently. Setting up and designing experiments following collapse of the company partner has been challenging without their support, separating the project into smaller experiments should help in keeping project context and the characteristics of the original scope.

The aim remains to design and test a system which would allow a surgeon to visualise the fluorescent signal and the bright field signal in real-time using off the shelf components without the use of filters.

Fluorescence and white light signal will be captured and processed to assess image quality. Following procurement, prototyping and testing, a final design will be presented for the future work component of the PhD without a commercialisation plan as the company partner is no longer trading and no longer supporting the project. 

Novel NIR Endoscopic Techniques for Medical Imaging - An Investigation Considering both LED and LASER Excitation Sources

                                                                  WORIC-Angharad PhD student

Miss. Angharad Curtis

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Study of an external-cavity-based low speckle laser diode module

Chris Evered, WORIC

Mr. Chris Evered

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Chris is developing a commercial external-cavity-based low speckle laser diode module. He will study new methods of laser beam shaping which could lead to entirely new approaches in enhancing low power laser illumination for applications such as machine vision, metrology, and imaging.

Dun designs an  active/passive nanophotonic devices through numerical simulation and improving their performance via optimization and corresponding experiment. The OLED and QLED devices are my current interest. We dedicated to improving their external quantum efficiency via optical manipulating based on nanostructure design. At current stage, I am focusing on the numerical simulation, the methods I adopt including FDTD and FEM achieved by commercial software (Lumerical, Comsol) and customized code. The corresponding experiment and test are preparing with our partner. Besides, I also designed the nano-waveguide and optical coupler for next-gen interferometric metrology system, which is part of the project in partnership with NPL.

An investigation of optical properties in passive and active nanophotonic structures and devices.                                                                         

Dun Qiao, PhD student, WORIC

Mr. Dun Qiao

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Developing a low cost, high resolution, handheld 3D thermal imaging device

Mahmod Sahal, WORIC PhD student

Mr. Mahmod Sahal

The project addresses challenges of high cost, large Scanning volume and low resolution of 3D thermal imaging systems which are inhibit the applications of the 3D thermal imaging technology in many sectors.

The proposed imagery system is based on 3D stitching/reconstruction technology. It does not need scanning part and can obtain a 3D image based on stereovision technique and fusion of visible and thermal data that provided by visible and thermal cameras. in addition the project is addressed low resolution issue in the thermal cameras by developing a super-resolution logarithm to meet the needs of applications that require a greater resolution such as inspection of electronics industry where the needs of difficult materials and small components to be inspected. So that, The project is about developing a higher resolution, handhold and low cost 3D thermal imaging system to meet the needs of complex thermal imaging applications.