Optical imaging of the surface profiles of biological cells and tissues with nanometer resolution

摘要

We proposed and developed an optical system for imaging of the surface profiles of biological cells and tissues with nanometer resolution. The system is a low-cost system which can perform the imaging of the surface morphology in a large area and large depth range without any special preparation of the sample. The system consists of two interferometers in which one is in the configuration of a Michelson interferometer and the other is in the configuration of a Mach-Zehnder interferometer. The former is used for scanning of the surface profile of the sample, and the latter is used to compensate the phase shift due to the different traveling ranges of the reference mirror in successive scannings. The phase difference between the interferograms detected in both interferometers is proportional to the surface height of the sample at that point. The system was demonstrated to possess the axial resolution within ±5 nm and its lateral resolution is at the diffraction limit. We used the system for the imaging of various samples including biological cells and tissues. The system was also used for dynamic imaging to observe the morphological change of the surface of biological cells.