Phase Difference Microscopy

Abstract

I HAVE read with much interest the description by Mr. O. W. Richards of his own and his colleagues' recent work on Zernike's phase contrast method. Everyone who is interested in the microscopical observation of living cells should be grateful to him for having once again directed attention to its value as applied to microscopy. It possesses the advantage over ordinary trans-illumination that fine unstained structural detail is seen in greatest contrast by focusing exactly on the specimen, so that we may expect a closer geometrical correspondence between the appearance seen and what is 'really there'.