From filters to features:Scale-space analysis of edge and blur coding in human vision

To make vision possible, the visual nervous system must represent the most informative features in the light pattern captured by the eye. Here we use Gaussian scale-space theory to derive a multiscale model for edge analysis and we test it in perceptual experiments. At all scales there are two stages of spatial filtering. An odd-symmetric, Gaussian first derivative filter provides the input to a Gaussian second derivative filter. Crucially, the output at each stage is half-wave rectified before feeding forward to the next. This creates nonlinear channels selectively responsive to one edge polarity while suppressing spurious or "phantom" edges. The two stages have properties analogous to simple and complex cells in the visual cortex. Edges are found as peaks in a scale-space response map that is the output of the second stage. The position and scale of the peak response identify the location and blur of the edge. The model predicts remarkably accurately our results on human perception of edge location and blur for a wide range of luminance profiles, including the surprising finding that blurred edges look sharper when their length is made shorter. The model enhances our understanding of early vision by integrating computational, physiological, and psychophysical approaches. © ARVO.

Advances in femtosecond micromachining and inscription of micro and nano photonic devices

This thesis has focused on three key areas of interest for femtosecond micromachining and inscription. The first area is micromachining where the work has focused on the ability to process highly repeatable, high precision machining with often extremely complex geometrical structures with little or no damage. High aspect ratio features have been demonstrated in transparent materials, metals and ceramics. Etch depth control was demonstrated especially in the work on phase mask fabrication. Practical chemical sensing and microfluidic devices were also fabricated to demonstrate the capability of the techniques developed during this work. The second area is femtosecond inscription. Here, the work has utilised the non-linear absorption mechanisms associated with femtosecond pulse-material interactions to create highly localised refractive index changes in transparent materials to create complex 3D structures. The techniques employed were then utilised in the fabrication of Phase masks and Optical Coherence Tomography (OCT) phantom calibration artefacts both of which show the potential to fill voids in the development of the fields. This especially the case for the OCT phantoms where there exists no previous artefacts of known shape, allowing for the initial specification of parameters associated with the quality of OCT machines that are being taken up across the world in industry and research. Finally the third area of focus was the combination of all of the techniques developed through work in planar samples to create a range of artefacts in optical fibres. The development of techniques and methods for compensating for the geometrical complexities associated with working with the cylindrical samples with varying refractive indices allowed for fundamental inscription parameters to be examined, structures for use as power monitors and polarisers with the optical fibres and finally the combination of femtosecond inscription and ablation techniques to create a magnetic field sensor with an optical fibre coated in Terfenol-D with directional capability. Through the development of understanding, practical techniques and equipment the work presented here demonstrates several novel pieces of research in the field of femtosecond micromachining and inscription that has provided a broad range of related fields with practical devices that were previously unavailable or that would take great cost and time to facilitate.

Deep brain stimulation for chronic pain investigated with magnetoencephalography

Deep brain stimulation has shown remarkable potential in alleviating otherwise treatment-resistant chronic pain, but little is currently known about the underlying neural mechanisms. Here for the first time, we used noninvasive neuroimaging by magnetoencephalography to map changes in neural activity induced by deep brain stimulation in a patient with severe phantom limb pain. When the stimulator was turned off, the patient reported significant increases in subjective pain. Corresponding significant changes in neural activity were found in a network including the mid-anterior orbitofrontal and subgenual cingulate cortices; these areas are known to be involved in pain relief. Hence, they could potentially serve as future surgical targets to relieve chronic pain. © 2007 Lippincott Williams & Wilkins, Inc.

A novel actuated digit with tactile feedback for clinical applications

This thesis describes the work carried out on the development of a novel digit actuator system with tactile perception feedback to a user and demonstrated as a master-slave system. For the tactile surface of the digit, contrasting sensor elements of resistive strain gauges and optical fibre Bragg grating sensors were evaluated. A distributive tactile sensing system consisting of optimised neural networking schemes was developed, resulting in taxonomy of artificial touch. The device is suitable for use in minimal invasive surgical (MIS) procedures as a steerable tip and a digit constructed wholly from polymers makes it suitable for use in Magnetic Resonance Imaging (MRI) environments enabling active monitoring of the patient during a procedure. To provide a realistic template of the work the research responded to the needs of two contrasting procedures: palpation of the prostate and endotracheal intubation in anaesthesia where the application of touch sense can significantly assist navigation. The performance of the approach was demonstrated with an experimental digit constructed for use in the laboratory in phantom trials. The phantom unit was developed to resemble facets of the clinical applications and digit system is able to evaluate reactive force distributions acting over the surface of the digit as well as different descriptions of contact and motion relative to the surface of the lumen. Completing control of the digit is via an instrumented glove, such that the digit actuates in sympathy with finger gesture and tactile information feedback is achieved by a combination of the tactile and visual means.

May the contact lens force be with you

FULL TEXT: Like many people one of my favourite pastimes over the holiday season is to watch the great movies that are offered on the television channels and new releases in the movie theatres or catching up on those DVDs that you have been wanting to watch all year. Recently we had the new ‘Star Wars’ movie, ‘The Force Awakens’, which is reckoned to become the highest grossing movie of all time, and the latest offering from James Bond, ‘Spectre’ (which included, for the car aficionados amongst you, the gorgeous new Aston Martin DB10). It is always amusing to see how vision correction or eye injury is dealt with by movie makers. Spy movies and science fiction movies have a freehand to design aliens with multiples eyes on stalks or retina scanning door locks or goggles that can see through walls. Eye surgery is usually shown in some kind of day case simplified laser treatment that gives instant results, apart from the great scene in the original ‘Terminator’ movie where Arnold Schwarzenegger's android character encounters an injury to one eye and then proceeds to remove the humanoid covering to this mechanical eye over a bathroom sink. I suppose it is much more difficult to try and include contact lenses in such movies. Although you may recall the film ‘Charlie's Angels’, which did have a scene where one of the Angels wore a contact lens that had a retinal image imprinted on it so she could by-pass a retinal scan door lock and an Eddy Murphy spy movie ‘I-Spy’, where he wore contact lenses that had electronic gadgetry that allowed whatever he was looking at to be beamed back to someone else, a kind of remote video camera device. Maybe we aren’t quite there in terms of devices available but these things are probably not the behest of science fiction anymore as the technology does exist to put these things together. The technology to incorporate electronics into contact lenses is being developed and I am sure we will be reporting on it in the near future. In the meantime we can continue to enjoy the unrealistic scenes of eye swapping as in the film ‘Minority Report’ (with Tom Cruise). Much more closely to home, than in a galaxy far far away, in this issue you can find articles on topics much nearer to the closer future. More and more optometrists in the UK are becoming registered for therapeutic work as independent prescribers and the number is likely to rise in the near future. These practitioners will be interested in the review paper by Michael Doughty, who is a member of the CLAE editorial panel (soon to be renamed the Jedi Council!), on prescribing drugs as part of the management of chronic meibomian gland dysfunction. Contact lenses play an active role in myopia control and orthokeratology has been used not only to help provide refractive correction but also in the retardation of myopia. In this issue there are three articles related to this topic. Firstly, an excellent paper looking at the link between higher spherical equivalent refractive errors and the association with slower axial elongation. Secondly, a paper that discusses the effectiveness and safety of overnight orthokeratology with high-permeability lens material. Finally, a paper that looks at the stabilisation of early adult-onset myopia. Whilst we are always eager for new and exciting developments in contact lenses and related instrumentation in this issue of CLAE there is a demonstration of a novel and practical use of a smartphone to assisted anterior segment imaging and suggestions of this may be used in telemedicine. It is not hard to imagine someone taking an image remotely and transmitting that back to a central diagnostic centre with the relevant expertise housed in one place where the information can be interpreted and instruction given back to the remote site. Back to ‘Star Wars’ and you will recall in the film ‘The Phantom Menace’ when Qui-Gon Jinn first meets Anakin Skywalker on Tatooine he takes a sample of his blood and sends a scan of it back to Obi-Wan Kenobi to send for analysis and they find that the boy has the highest midichlorian count ever seen. On behalf of the CLAE Editorial board (or Jedi Council) and the BCLA Council (the Senate of the Republic) we wish for you a great 2016 and ‘may the contact lens force be with you’. Or let me put that another way ‘the CLAE Editorial Board and BCLA Council, on behalf of, a great 2016, we wish for you!’

State-of-the-art in integrated vehicle health management

Cranfield University in collaboration with The Boeing Company have set up a Centre of Excellence in IVHM on the University?s technology park. Sponsored by the East of England Development Agency (EEDA), the Centre carries out pre-competitive research and development of IVHM technologies for the benefit of industrial partners. In addition, the dedicated facilities and university staff provide an unparalleled educational environment for learning and applying IVHM technologies. Boeing is actively involved in the creation and work of the Centre through its enterprise-wide Phantom Works technology organization. This paper will describe the organisation and operation of the Centre and will illustrate its activities by describing a research project being carried out in the Centre. This project is a demonstration of an end to end IVHM system beginning with cost/benefit analysis and extending to maintenance, logistics and operations decision support.

Flexible tactile digital feedback for clinical applications

Trauma and damage to the delicate structures of the inner ear frequently occurs during insertion of electrode array into the cochlea. This is strongly related to the excessive manual insertion force of the surgeon without any tool/tissue interaction feedback. The research is examined tool-tissue interaction of large prototype scale (12.5:1) digit embedded with distributive tactile sensor based upon cochlear electrode and large prototype scale (4.5:1) cochlea phantom for simulating the human cochlear which could lead to small scale digit requirements. This flexible digit classified the tactile information from the digit-phantom interaction such as contact status, tip penetration, obstacles, relative shape and location, contact orientation and multiple contacts. The digit, distributive tactile sensors embedded with silicon-substrate is inserted into the cochlea phantom to measure any digit/phantom interaction and position of the digit in order to minimize tissue and trauma damage during the electrode cochlear insertion. The digit is pre-curved in cochlea shape so that the digit better conforms to the shape of the scala tympani to lightly hug the modiolar wall of a scala. The digit have provided information on the characteristics of touch, digit-phantom interaction during the digit insertion. The tests demonstrated that even devices of such a relative simple design with low cost have potential to improve cochlear implants surgery and other lumen mapping applications by providing tactile feedback information by controlling the insertion through sensing and control of the tip of the implant during the insertion. In that approach, the surgeon could minimize the tissue damage and potential damage to the delicate structures within the cochlear caused by current manual electrode insertion of the cochlear implantation. This approach also can be applied diagnosis and path navigation procedures. The digit is a large scale stage and could be miniaturized in future to include more realistic surgical procedures.

Using an Infra-red sensor to measure the dynamic behaviour of N2O gas escaping through different sized holes

An anastomosis is a surgical procedure that consists of the connection of two parts of an organ and is commonly required in cases of colorectal cancer. About 80% of the patients diagnosed with this problem require surgery. The malignant tissue located on the gastrointestinal track must be resected and the most common procedure adopted is the anastomosis. Therefore, an anastomotic leak represents a significant problem and increases the duration of hospital stay, which is associated with remedial treatment and recovery, causing, as a result, a negative financial impact. A number of techniques to treat, prevent and even detect an anastomotic leakage are under investigation. However, studies show that these techniques are not always able to prevent an anastomotic leak from occurring. This paper discusses the monitoring of leakage through differently sized and differently positioned leak holes in phantom colons, using physical experiments and a Computational Fluid Dynamics package called FloWorks. © 2011 Taylor & Francis Group.