beam is reflected. These requirements are impractical for many biological
applications, since specimens typically exhibit variable depth and multiple
reflective surfaces [2].
The second type is known as passive focusing because it is based only on the
analysis of the content of captured images. The in-focus position is determined by
searching for the maximum of an autofocus function using measurements from
a series of images captured at different focal planes. The passive autofocus
methods, albeit slower due to the acquisition time required for capturing multiple
images, are not affected by the reflective surfaces of a specimen and therefore are
often more suitable for biomedical microscopy applications. In this chapter, we
limit our discussion to pass ...