Abstract: A tomogram taken on an imaging path of a tomograph is corrected by using sets of tomogram correction data for neighbouring positions on that path, in an interpolative process. An error map of a tomograph is built up by comparing tomograms of a phantom with the expected appearance of the phantom at the tomogram positions. Also provided is a phantom having a body with one or more imaging fluid receptacles formed therein.

Abstract: The invention relates to a device and method for analysis of a tool (50) e.g. used on a machine tool. A tool detector (5) includes a light emitter (12) and a light receiver (34). Tool (50) when progressed into a beam (20) of light emitted from the emitter (12) will cause a signal from the receiver to change. Circuitry (32) includes a digital signal processor which processes the signal from the receiver and produces an output only if the signal conforms to a predetermined condition. Preferably this predetermined condition could be e.g. a characteristic shape of the signal from the receiver, a change in a value derived from a succession of such signals or a change in the minimum or maximum values of a succession of signals from the receiver.