Aberration Free Refocusing for High Numerical Aperture Systems

Department of Engineering Science, University of Oxford, UK

3:30 pm Friday, 30 May 2008, EN101 (Ground Floor, EN Building), Hawthorn.

A common requirement in many kinds of optical imaging applications is to refocus the optical system to interrogate different axial regions of the sample. For example, in high resolution microscopy it is often necessary to obtain a series of high- resolution, through-focus images. Although it is often desired to hold the sample still and refocus the system by an optical means, this can be problematic because operation is often degraded by the introduction of aberrations. For this reason, commercial systems generally shift the sample instead to access different planes, a technique that can be both slow and invasive.

In this seminar a new method of optical refocusing will be presented that does not suffer from aberrations and therefore enables diffraction limited performance over a large range of sample depths. This method is therefore truly non-invasive and could be especially useful for non-linear microscopy. Furthermore, an improvement in axial scan rates has also been achieved which could allow for real-time in-vivo imaging. It is also expected that this technique will find application in fields of nanofabrication, for example in the manufacturing of optical lattices, cell surgery and three dimensional optical trapping.

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