Illustrated in Figure 1 is a cut-away diagram of a Yokogawa Electric Corporation CSU-X1 spinning disk confocal scanning unit equipped with filter wheels and two camera ports for dual-color fluorescence imaging. This laser-based instrument represents the state-of-the-art in high speed spinning disk microscopy. The collimated excitation light produced by a diode or gas laser is optically folded and passed through a series of microlenses on the surface of the first disk before traversing the 50-micrometer pinholes in the second (Nipkow) disk and entering the microscope optical camera port. Emission light from the specimen passes back through confocal pinholes in the Nipkow disk closer to the microscope port and is directed via a dichromatic beamsplitter to a mirror in the lower part of the unit housing. A second dichromatic beamsplitter sends the shorter emission wavelengths (green) through a filter wheel to the first camera port, while the longer wavelengths (red) proceed through a second filter wheel to the second camera port. Depending upon the configuration, the CSU-X1 scanning unit is capable of reaching spinning speeds of 5,000 or 10,000 rpm, corresponding to an image capture rate of 1,000 or 2,000 frames per second, respectively.
