16.2.2 Autofocus Functions
The autofocus function and its computation are crucial to the accuracy and
efficiency of a microscope autofocusing system. Research on the subject dates
back more than a quarter of a century, and many methods have been developed
[4–17].
A comprehensive comparative study of 11 autofocus functions for bright-
field microscopy established a set of criteria for the design of a microscope
autofocusing system [5], and these have been widely applied [2, 9, 11]. This
study used metaphase chromosome spreads and electron microscopy grids as
the specimens. The conclusions drawn from this study were that autofocus
functions based on intensity gradients or variance yielded the best performance.
Another study tested a number of autofocus