One embodiment disclosed relates to an apparatus for detecting defects in substrates. An irradiation source is configured to generate an incident beam, and a lens system configured to focus the incident beam onto a target substrate so as to cause emission of electrons. A multiple-bin detector is configured to detect the emitted electrons, and each bin of the detector detects the emitted electrons within a range of energies. A processing system configured to process signals from the multiple-bin detector. Other embodiments are also disclosed.