Although the more common SEM images are formed with emitted secondary electrons, electrons that are backscattered (from the nucleus of an atom) can also contain quite valuable information about a sample's topography and composition. The larger the nucleus, the more the electrons that are backscattered. Often times, one need not resort to the use of EDS (energy dispersive spectroscopy) for elemental information, yet the use of a good, reliable backscattered electron (BSE) detector can give similar information far faster and for lower cost.
Earlier SEMs typically came from the manufacturer without any BSE detector and if the user needed to obtain this type of information, a separate detector had to be purchased. At some point, some of the manufacturers started incorporating BSE detectors into their new instruments, and the detector used the most frequently was of course the original Robinson BSE detector. We want to stress ""original"" because over the years, there have been some who have tried to copy the design of the original BSE detector design but they have never been able to duplicate its performance.
Today, there are essentially two different approaches to BSE detectors, the first being the Robinson design, which is based on the use of scintillator technology, and the other based on a solid state detector which utilizes silicon diodes. Dr. Robinson has spent nearly his entire professional life time looking at how to improve an already outstanding product even better. However, every time he has compared what one could get using a solid state detector vs. one based on scintillator detection, he has concluded, as have also most of the major column instrument manufacturers, that scintillator technology is clearly superior for most users.