Diffraction-limited Endoscope System
J. Brian Caldwell
Acommon approach in designing an objective-relay system is to design the objective and relay subsystems separately and then simply put them together without further optimization. Although this approach is straightforward, it requires that each subsystem be well corrected, particularly for field curvature and astigmatism. In the case of an endoscope system, which consists of an objective and several sets of relay lenses, it is particularly
important that the individual relay sub-units have a very flat anastigmatic field. This is because the field curvature of the complete relay system is equal to that of a single sub-unit multiplied by the number of units, typically four or five.
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