A lateral pn-junction detector (l-pn detector) for low energy backscattered electrons has been designed, fabricated, and characterized. General design rules for l-pn detectors have been established. The detector assembly consists of a n-type finger structure diffused in p-type silicon. It was fabricated using standard clean room technologies and tested in a conventional scanning electron microscope under conditions similar to those in electron beam microcolumns. With this setup, images of Au/Si alignment marks were obtained with primary beam currents around 1 nA at 1 keV electron energy. The gain was measured for 1 and 2 keV primary beam energy. Signal to noise ratio and bandwidth were determined from image data. It is demonstrated that l-pn detectors are well suited for imaging in microcolumns.