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Details of Grant 

EPSRC Reference: EP/C534689/1
Title: Parrallel Near-Field Optical Microscopy
Principal Investigator: Barnes, Professor WL
Other Investigators:
Winlove, Professor CP Petrov, Dr PG Sambles, Professor Sir JR
Researcher Co-Investigators:
Project Partners:
Department: Physics
Organisation: University of Exeter
Scheme: Standard Research (Pre-FEC)
Starts: 01 December 2005 Ends: 31 March 2010 Value (£): 467,468
EPSRC Research Topic Classifications:
Instrumentation Eng. & Dev. Lasers & Optics
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:  
Summary on Grant Application Form
The wavelength of visible light varies from around 700nm (deep red) to just less than 400nm (violet). The manner in which microscopes form their images was investigated over a hundred years ago and this understanding led to improvements in the design of microscopes. However, such understanding meant that limitations in their ultimate performance was also recognised - resolution was limited to be close to the wavelength of the light used.The real challenge in microscopy lies in improving this resolution, thereby allowing two objects separated by a distance much less than the optical wavelengh to be distinguished. Diffraction typically limits resolution to about half the wavelength of the probe radiation. The obvious way to improve the lateral resolution is to reduce the wavelength into the ultraviolet or X-ray region. Although this is sometimes appropriate it is not always practical, especially in biology where the samples are often damaged or even destroyed by such short wavelengths.Recent research has developed ways of overcoming the diffraction limit by using either non-linear (4pi confocal microscopy) or near-field effects. The latter is the focus of this proposal. When light is passed through a hole in an otherwise opaque screen, the hole being much smaller than the wavelength of the light, some light still gets through. Although this transmitted light quickly spreads out, in the close vicinity of the hole it is localised on a length scale comparable with the hole. The trick is to scan the small aperture or tip very close to the sample so that only objects within this range will contribute to the collected signal. Near field microscopy as it is called has been used with great success, and in fact one can use sharp tips as well as holes. However there are two obvious drawbacks to scanning near-field microscopy. The first is the need to keep the tip close to the sample, this is inherent to all near-field microscopies. The second is that the image is acquired one point at a time, so that the tip needs to be moved mechanically over the sample, and the image is recovered in a computer. By contrast the great advantage of conventional microscopy is that the image is seen immediately.This research programme goes some of the way to making near-field microscopy more like conventional microscopy. Instead of using a single tip we will use an array of tips (64 by 64) to obtain 4096 image points simultaneously; this will then be combined with new detector arrays to acquire the optical signal. We still need to scan to some degree in order to fill the gaps (spaced about 1 micron) between the tips because conventional optics is still used to record the light scattered from the tips. Even though our system scans the sample, the amount of scanning is very small since we only need to scan over a tiny fraction of the image. The system has the obvious advantage that it allows one to cover a large area far more quickly (3 orders of magnitude quicker) than would be possible otherwise.In addition to building the new 'parallel near field' microscope we will use it to study samples where the resolution of conventional optical microscopes is insufficient. One area we intend to examine is cell membrane structures since many of the key functions of living cells are controlled by the properties of the cellular membranes. It is now realised that membranes have a highly complex local structure, which is responsible for their behaviour and ultimately the way that whole organisms respond to disease. A great deal of interest at present is centred on the ability of these membranes to form 'rafts' which are local regions with a different structure, it is clear they are key to much that goes on in the cell, but how? Imaging techniques with very fine lateral resolution like the one being developed here will help to tell us this.
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Organisation Website: http://www.ex.ac.uk