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This work presents an objective performance analysis of statistical tests for edge detection which are suitable for textured or cluttered images. The tests are subdivided into two-sample parametric and non-parametric tests and are applied using a dual-region based edge detector which analyses local image texture difference. Through a series of experimental tests objective results are presented across a comprehensive dataset of images using a Pixel Correspondence Metric (PCM). The results show that statistical tests can in many cases, outperform the Canny edge detection method giving robust edge detection, accurate edge localisation and improved edge connectivity throughout. A visual comparison of the tests is also presented using representative images taken from typical textured histological data sets. The results conclude that the non-parametric Chi Square and Kolmogorov Smirnov statistical tests are the most robust edge detection tests where image statistical properties cannot be assumed a priori or where intensity changes in the image are nonuniform and that the parametric Difference of Boxes test and the Student’s t-test are the most suitable for intensity based edges. Conclusions and recommendations are finally presented contrasting the tests and giving guidelines for their practical use while finally confirming which situations improved edge detection can be expected.

The Boundary Element Method for solving the Laplace and Poisson equations for electrostatic systems will be outlined, with the emphasis on 3D systems and the commercial CPO programs. Some applications to charged particle optics will be described. Since the BEM is a charge-based method it is ideally suited for systems that include space-charge and/or cathodes. It is also exceptionally accurate and can deal easily with electrodes of very different sizes. Several ‘benchmark tests will be presented, in which systems with known analytic solutions are used to illustrate the accuracy and versatility of the programs.

A technique is described of simulating thermionic cathodes in the Boundary Element Method by replacing the space charges in the cathode region by a set of thin sheets of charge. These sheets are subdivided into segments in the same way that the cathode itself is subdivided. This technique has been applied to cathodes that have zero and non-zero temperature T. It is shown that for T>0 the potential and position of the virtual cathode is well reproduced. Planar and non-planar cathodes are considered as well as unsaturated cathodes.

The effects of electron–electron coulomb interactions have been simulated by a general computational technique that can be applied to almost any system, independently of the shape of the beam or the regimes that might be present, provided that the ‘closest-encounter’ approximation is valid for the system. The technique has been applied to the ‘benchmark test’ of the energy spreading in a converging round beam. The results are compared with previous analytical results.

We have constructed a simple and inexpensive diode laser spectrometer in which the source is locked to and tracked by a scanning Fabry–Perot interferometer and in which absolute frequency measurements are made by markers generated by a further Fabry–Perot interferometer, itself locked either to a selected spectral line of the sample or to the saturated absorption of a D2 line in atomic Rb at 780 nm. With this technique we have been able to obtain near-continuous spectra stretching over the range from 12 640 to 12 780 cm-1 at Doppler-limited resolution. In this paper we describe the principles of the spectrometer along with absolute frequency measurements of a number of overtone rovibrational transitions in two isotopomers of acetylene. The combination relations formed by these transitions demonstrate the accuracy of our measurements to be typically ±0.0002 cm-1.

Angle and spin–orbit resolved photoelectron spectra of O 2 are presented in the photon energy range 13.06–13.15 eV where strong autoionization processes dominate the spectra. The angular measurements have been obtained using a newly constructed photoelectron spectrometer featuring a magnetic angle-changing device. β -Parameters and intensity ratios have been obtained for the two spin–orbit components of the O 2 + X 2 Π g ground ionic state.

When a conducting partially-transparent mesh is used to separate two regions of different electrostatic field strength there are short-range changes to the field and potential distributions in the vicinity of the mesh and also long-range changes far from the mesh. The forms and magnitudes of these changes are investigated computationally for meshes that consist of parallel or crossed round wires or crossed flat strips.

The properties have been studied of an electrostatic three-cylinder lens-deflector in which the middle cylinder is split longitudinally into four parts, allowing the system to be used to simultaneously focus and deflect a beam of charged particles. The aberrations are found to be of first order in the deflection.

A novel technique using a two-pulse sequence and four-level double resonance has extended the use of Fourier transform techniques to collisionally transferred signals. Results for the microwave spectrum of formaldehyde have shown a useful bandwidth of at least 100 MHz.