A Projection Microphotometer for Quantitative Microscopy

Quantitative measurement of the characteristics of microscopic objects has become an increasingly important technique particularly in the field of biology. This paper describes an instrument used for obtaining the size and optical density of objects on the specimen slide. Although methods for making these measurements have long been available, they are usually tedious and time-consuming, and little attention has been paid to the adaptation of the system to human requirements for comfort and ease. This is particularly true for cytological measurements where variations in individual cells are such that large numbers of cells must be selected before, the results are statistically significant. A projection system overcomes many of the disadvantages of the other methods by not constraining the eyepoint to a fixed position, permitting direct measurement of size or area with a scale or planimeter, and allowing the photometer field to stop to be always under direct visualization. The design, and performance of a projection microphotometer and its application to several biological measurement problems is thoroughly discussed.