A flexible, computer-controlled video microscope capable of quantitative spatial, temporal, and spectral measurements.

A video microscope system has been constructed and tested that incorporates computer-controlled video cameras for high-resolution and low-light microscopy. The low-light camera system involves a dual microchannel plate-image intensifier capable of photon gain as high as 500 000 and a gated silicone-intensified target vidicon to achieve usable photon sensitivity with a noise equivalent signal of only 2 photons (500 nm) per pixel per second. We have compared the limitations and capabilities of this camera system with those of a high-resolution video camera and conventional photomicroscopy. Uses of the low-light camera coupled to a computer system include image acquisition of weak-light images from self-luminous specimens, fluorescence microscopy with weak exciting light, kinetic resolution of calcium-mediated events as monitored by the calcium-sensitive bioluminescence of aequorin, and spatially resolved spectroscopic measurements. Flexible use of this system in these various applications is possible because it allows operation with illumination intensities over a dynamic range of 100 000:1.