Chapter 17Microscope Objectives
17.1 General Considerations
An ordinary microscope objective has an image field with a diameter of about 20 mm; the image distance is about 160 mm. The total field of view is thus about 7° or less. The exit pupil diameter is typically about 8 mm; with the 160-mm image distance, the numerical aperture (NA) of the image cone is about 0.025. Therefore, the object-side NAis about 0.025M, where M is the magnification of the objective.
A microscope objective may be designed to be used with or without a cover plate (or cover slip) over the object. The cover glass is nominally 0.18 mm (0.16 to 0.19 mm) thick with an index of 1.523 ± 0.005 and a V-value of 56 ± 2 (close to Schott K4 or K5 glass). This thickness of glass ...