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Making light work in microscopy

Professor Tony Wilson

Department of Engineering Science, University of Oxford.

Monday, 19th February 2007, 3.30PM, Lecture Theatre EN101 - Ground Floor of EN (Engineering) Building, Hawthorn.

The confocal microscope is now an instrument in widespread use in laboratories around the world. It is probably fair to say that its popularity and importance is due to its unique optical sectioning or depth discrimination property, which gives rise to the instrumentís unique volume imaging capability. The key elements of a traditional confocal microscope system are a laser light source (required since standard microscope illuminators are insufficiently bright), a pinhole point detector together with an appropriate scanning mechanism. It could be argued, in some cases, that the traditional approach has some drawbacks, for example, the use of laser illumination may be thought to be undesirable (limited wavelengths, expense etc.) as may the lack of real-time image acquisition. In order to overcome these limitations and produce light-efficient real-time confocal instruments we have developed two distinct new approaches. In the first we retain the confocal principle of using pinholes to prevent out-of-focus light from contributing to the image and use aperture correlation techniques to eliminate cross-talk between closely packed parallel confocal systems. The second approach discards the traditional confocal principle and uses a fringe projection technique based on spatial heterodyning to obtain optically sectioned images from a conventional widefield microscope. This use of structured illumination allows us to obtain both optically sectioned and conventional images from a standard conventional microscope with a minimal modification to its illumination system.

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