An Interferometer Microscope for the Accurate Measurement of Optical Thickness

THE methods developed by Barer1 and Davies and Wilkins2 for the measurement of the dry weights of cells involve the accurate measurement of the optical thickness of the cell at a number of points on its surface. In many cases, the optical thickness is quite a small fraction of a wave-length, so the measurement must be made with considerable accuracy; furthermore, in the case of a living cell, speed of measurement is essential.