Imaging Strategies in Scanning Optical Microscopy.
Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the brightfield, fluorescence and direct-view imaging modes of scanning optical microscopy. A number of application-specific imaging strategies are discussed and, where appropriate, experimental results are presented. We compare the image formation properties of brightfield and fluorescence scanning microscopes employing point and slit detectors. Particular attention is given to the three -dimensional aspects of the imaging and we show, inter alia, that acceptable, albeit asymmetrical, images result from a slit-detector system at low levels of defocus. A large-area coherent-detector scanning microscope is shown to have identical image formation properties to a confocal scanning microscope employing a suitable apodising filter. We then specialise to the imaging of line structures and suggest a simple filter function which gives enhanced imaging. We consider the value of the intensity image at the geometrical position of a generalised straight-edge object and obtain, rigorously, analytic expressions for the cases of coherent, incoherent and full-illumination partially coherent imaging. Expressions are also derived for the intensity gradient at the edge. The use of pupil-plane filters to tune the imaging properties in confocal scanning microscopy is discussed. We specialise to the annular filter and show, inter alia, that it may be used to significantly reduce the effects of spherical aberration. The problem of where best to place the apodising filters in a reflection system is investigated. We described three pupil-plane filter combinations which, when used in conjunction with a confocal optical system, achieve super-resolution. This, in turn, results in edge gradients up to 2.36 times those of the circular -lens confocal instrument. Various methods of changing both the lateral and the axial definition of the scanning microscope are discussed. Techniques based on using different wavelengths, different sized detectors and laterally displaced detectors are considered. We discuss how the optical sectioning strength of the direct-view microscope varies with the size and distribution of the pinholes in the source and detector arrays. Finite-sized circular pinholes are considered and the results are compared with those of the scanning optical microscope.
- Pub Date:
- Physics: Optics; Engineering: Electronics and Electrical