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Hydration/dehydration of sodium chloride salt crystals (1986)

Color images composed by directly superimposing successive combinations of the output signal from two symmetrical backscattered electron detectors . No computer image averaging was used, only raw BSE signals. The contrast corresponds to atomic number and topography variation. The sequence shows wetting and drying of salt crystals resting on Teflon surface without any charging problems. The electron beam used was at 10 keV, 50 pA, 200 m m field width, at the pressures given with each image (2021).  It should be pointed out that artificial color imaging has been used in many instances with electron microscopes, but the mode of color composition herewith is unique with a "natural" meaning:  Two colors are provided for topography (corresponding to two illumination directions) and a third for atomic number contrast (see details in the original papers 2021.  Another color can be added for the secondary electron image obtained with the gaseous detector (showing additional material contrast) as can be seen in the color image elsewhere.  Color does not create only "beautiful pictures", as it can primarily be used to encode a large amount of information on a single image (which is impossible with monochrome images). For example, compare the color page 14 from paper (20) with a grayscale conversion of the same page, in which much topographical and other information is lost or difficult to interpret.  The superimposition of color was obtained with mechanical means, namely, by successive exposure of the same negative frame after changing the color filter with each signal combination.  The same principle of color composition and detectors can be used with superior ease after the advent of modern computers aiding the microscopes of today.  It is surprising that no manufacturer has undertaken this important task to increase the power not only of the ESEM but of other microscopes as well. 

6.7 mbar (dry)

17 mbar

16.9 mbar

16.6 mbar

6 mbar (dry)


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