The roots of image analysis
The invention of the first microscopes inevitably led to the question of the size of the objects viewed through the eyepiece and their relationship to each other. Another equally important question was how to deduce the volumes of the objects from a 2D section. These quantitative microscopy questions were addressed initially by stereology, which in turn contributed to the principles on which image analysis is based.
The first experiments and results are attributed to Achille Delesse, who demonstrated that the area fraction is proportional to the volume fraction. In 1930, Thompson and Glagolev established the pioneering formula PP (point count) = LL (linear fraction) = AA (area fraction) = VV (volume fraction).
The first TV-based image analyser
Image analysis as we know it today was only made possible by the development of television technology: 50 years ago, in 1962, the first television-based image analyzer of microscopic images was developed by Metals Research – a Cambridge-based company that became part of the Leica Group. Using a television camera as input device, the so called QTM A (Quantitative Television Microscope) was totally analogue in operation. A threshold was applied to the video signal, shown as a binary image on a second TV screen and the area measurement read from a meter. Nevertheless it marked the beginning of automation in image analysis – and with 20 msec per image it was quite fast, even compared with today's instruments.
The initial acceptance of the concept spurred the development of the QTM B in 1963 which proved to be the first commercially successful automated instrument in this field. These early image analysis systems were mainly used for scientific purposes. The users came from the steel industry or from metallurgic and mineralogical research institutes, but the potential in life sciences was rapidly recognized.