They’re called digital holographic microscopes. Until now however, they haven’t been able to make images of high enough quality to use to diagnose diseases.
The holographic microscope works by beaming partially coherent light down through the sample the pathologist wants to examine. The light projects a holographic image of the sample onto an image-sensing chip, which is positioned below the sample. The chip collects data about the light and sends the data to a computer, where specially developed algorithms reconstruct a high-resolution image of the sample.
Researchers are especially interested in digital holographic microscopes because their parts can be fairly cheap.