This invention provides two methods for improving performance of an energy-discrimination detection device with an energy filter of reflective type for a charged particle beam. The first method employs a beam-adjusting means to improve the energy-discrimination power, and the second method uses an electron-multiplication means to enhance the image signal without noise raise. A LVSEM with such an improved energy-discrimination detection device can provide variant high-contrast images of interested features on a specimen surface for multiple application purposes.