A computerised microscope focusing technique

An automatic focusing technique for a computer-controlled optical microscope is described, which is based on an algorithm originally proposed by Mendelsohn and Mayall. The procedure is capable of attaining a focusing accuracy of less than 1/20 micron in the slide-objective distance. The dependence of focusing accuracy and time to focus on the scanner signal-to-noise ratio, and the change in the focus position with time, are discussed.