Automatic focusing of optical microscope using off-the-shelf hardware components and in house software

Abstract

Optical microscope is one of the most important instruments in medical diagnostic. It is also one which requires high mental concentration and eye strain for extended periods of time. To make a microscope into real high throughput instrument, as much as possible routine work has to be shifted to the computer. Some commercial systems exists, but for a premium price. The system developed here is proof of concept that the required performance can be achieved with the reduction in cost for two orders of magnitude. Two computer systems were used: Desktop PC for data collection and analysis and indirect hardware control through the communications with a Raspberry Pi computer which controlled the step motors. Our first effort was directed toward focusing of the microscope (Z-axis control). In plane control (X & Y-axis) is conceptually much simpler. The focal point was found using Haar transform with inter and intra application of the least squares. The real life examples were taken from medical imaging of stained human cells as they are used in medical pathology.