Abstract
An objective has been designed which is particularly suitable for the study of tissue sections. It consists of a large opening polepiece system operated at a focal length of 12 mm. It includes a diaphragm which can be centered (not during operation) and translated on the axis. Angular apertures of as low as 2×10−3 radian with large areas of bright field can be achieved. A simple method of aligning the aperture is described.