In spectral imaging and linear unmixing, one of the most efficient mechanisms to gather spectral information involves coupling a diffraction grating with an adjustable slit system that can be mechanically translated across the input window of the photomultiplier detector. Fluorescence emission passing through the pinhole is reflected onto the diffraction grating surface, and the spectrally separated light is then projected through the slit and into the photomultiplier. The spectral bandwidth can be modulated by increasing or decreasing the slit size and the wavelength region presented to the photomultiplier is determined by the position of the slit in relation to the dispersed light from the grating. The ZEISS QUASAR detection technology goes a step further by incorporating individually-adjustable twin beam stops (that act as a slit) and a pair of prism wedges that direct selected wavelengths to auxiliary photomultipliers
The tutorial initializes with emission light (entering the window from the right) being diffracted at the surface of a grating and subsequently entering a lens that directs all spectral components to a central photomultiplier in the ZEISS QUASAR detector. In order to operate the tutorial, use the Left Slider and Right Slider controls to translate the sliding light stops back and forth in the light path to narrow the number of wavelengths reaching the photomultiplier. The Left Prism and Right Prism sliders can be used to directed a selected band of wavelengths to the auxiliary photomultipliers on the left and right hand side of the central photomultiplier.
The ZEISS QUASAR photomultiplier detection technology is based on a filter-free system that guides the desired wavelength range to the target detector using adjustable optical wedges and slider light stops. In detail, the detector operates such that the tips of the wedges serve as one detection border while the light stop sliders act as the other. By configuring these elements to create custom spectra, any longpass, bandpass, or shortpass filter strategy can be achieved without the need for traditional dichromatic mirrors or emission filters.
Tadja Dragoo and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.