Image Contrast in Phase-Contrast Microscopy

The development of applications of the Zernike, or phase-contrast, principle in microscopy offers not only an image of the object more precisely resembling it than any other heretofore obtainable, but even a new method of perception, by means of which certain characteristics of objects heretofore invisible may be determined by immediate inspection. The application of the fullest capability of this method waits the development of procedures for more exactly determining the optical characteristics of objects, particularly the effect on the light of refraction and absorption characteristics combined at single points. The studies and conclusions reported in this paper represent an effort to simplify the evaluation procedure, and present a first approximation of the influence of the factors involved in phase-contrast image formation. They are no more than logical consequences of the Zernike principle.