Upright

• The base of an upright compound light microscope contains a light source that illuminates a specimen sitting above on a flat stage. A condenser underneath the stage focuses the light, and passes it through the specimen into an objective lens above. An objective lens first magnifies the image of the specimen, then an ocular lens located in the eyepiece magnifies it. The user views the image by looking through the eyepiece at the top of the microscope.
  
  

Inverted

• As the name implies, the light source in an inverted compound light microscope is located above the specimen, which again rests on a flat stage. The light passes downward through the specimen. An objective lens positioned directly underneath the stage first magnifies the image, then an ocular lens located in the eyepiece magnifies it. Because the objectives are located beneath the stage, users can manipulate the specimens while viewing them with the microscope.
  
  

Phase Contrast

• Phase contrast microscopes are basically compound light microscopes equipped to enhance contrast without using stains or fixatives that would kill a live specimen. This type of microscope has two extra components. The first is a phase plate located in the objective and the second is an annulus -- or phase -- ring found in the condenser. The condenser has several settings designed to work in conjunction with specific objectives to provide contrast between the specimen and the background.
  
  

Forensic Comparison

• The forensic comparison microscope allows a user to view two separate samples through the same pair of eyepieces. This type of microscope consists of two upright compound light microscopes connected by a bar to a single set of eyepieces and ocular lenses. Light is directed from the base of each microscope through the samples and objectives, and into the pair of eyepieces at the top. The microscope has controls that allow the user to see either sample alone, or both samples side by side or overlapping.