TRUE COLOR X-RAY VISION FOR ELECTRON-MICROSCOPY AND MICROANALYSIS

Secondary and backscattered electron signals in the SEM provide high r esolution images and features of interest are selected for subsequent microanalysis based on recognisable topography and morphology. However the images are intrinsically monochrome so contrast is the only diffe rentiator. Colour aids recognition of familiar objects and can provide warning of unusual situations so a true colour image would provide ma ny more cues to guide the observer. The X-ray spectrum detected by EDX can be used to construct a true colour response that would be obtaine d if we offset the human visual sensitivity to the electromagnetic spe ctrum into the X-ray wavelength region (<5 nm). This colour input can then be used to augment a conventional electron image just like the ch rominance signal is used to augment the luminance to give colour telev ision.While this coloured image still retains the detail of the origin al electron signal image, it also portrays the underlying elemental co mposition because the spectrum from each compound gives it a character istic colour. Furthermore, the colour does not change with beam curren t and is not subjective as it would be with pseudo-coloured BSED image s or combinations of X-ray maps from user-defined energy windows. Chan ges in topography and shadowing affect the colour in the same way as v isible objects so the effect is still intuitive. Thus, topographic and compositional information from all elements is compressed into a sing le view. This true colour ''television'' image gives the analyst a use ful first look to guide further microanalysis.