 This helps in system alignment and enables collection LEEM, PEEM and ARPES data of a single sample in a single instrument.In mirror electron microscopy, electrons are slowed in the retarding field of the condenser lens to the limit of the instrument and thus, only allowed to interact with the “near-surface” region of the sample.It is very complicated to understand the exact contrast variations come from, but the important things to point out here are that height variations at the surface of the region change the properties of the retarding field, therefore influencing the reflected (specular) beam.