Multispectral imaging microscope with millisecond time resolution.
A new multispectral imaging microscope with micrometer spatial resolution and millisecond temporal resolution has been developed. The imaging microscope is based on the use of an acousto-optic tunable filter (AOTF) for spectral tuning and a progressive scan camera capable of snapshot operation for recording. It can operate in two modes: images are recorded as a function of time or wavelength. When operated as a function of time, the microscope is configured so that as many images as possible are recorded, grabbed, and stored per one wavelength. Upon completion, the AOTF is scanned to a new wavelength, and a new set of images are recorded. Up to 33 images/ second (i.e., 30 ms/image) can be recorded in this mode. In the other configuration, the recording wavelength is rapidly scanned (by means of the AOTF) and only one image is rapidly recorded, grabbed, and stored for each wavelength. Because additional time is needed to scan the AOTF, the maximum number of images can be grabbed in this case is 16 frames/s. Preliminary applications of the imaging microscope include measurements of photoinduced changes of a single unit cell in temperature-sensitive cholesteric liquid crystals as a function of time and wavelength. The changes were found to be varied with time and wavelength. Interestingly, the photoinduced changes of unit cells in the liquid crystal are not the same but different from cell to cell. This imaging microscope is particularly useful for measurements of small-size samples that undergo rapid chemical or biochemical reactions, e.g., activities of a single biological cell.