Design and optimization for microscope autofocus systems based on the analysis of video signals

摘要

An autofocus system applied to microscope has been designed, which is based on the analysis of analog video signals' processing. A multi-feedback band-pass active filter retains high frequency components of analog video signals from CCD, then high frequency components that represent image details information are amplified and performed integral operation, which is defined as focusing measure. After A/D transformation a MCU controls the focusing procedure and drives a stepping motor to find focused-position. The selection of bandwidths of filter, selection of focusing windows, step-size in search and hill climbing algorithms are discussed and optimized to improve focus accuracy and shorten focus time.