1. A slide rack auto-loader for use in a digital microscope slide scanning system comprising: a first user removable rack comprising multiple slide holders; a first laser that directs a first amount of light toward the first user removable rack; and a first detector that detects a second amount of light after the light from the first laser has been directed toward the first user removable rack, and wherein a determination is made that at least one slide is present in the slide holder or that no slide is present in the slide holder, based on the second amount of light sensed by the detector.