38 BD FACSAria User’s Guide
Collection Optics
From the cuvette flow cell, laser light is collected by a fluorescent objective lens
that is gel-coupled to the cuvette to transmit the maximum amount of light. The
lens collects and focuses fluorescent light emitted at each of the laser focal points
onto individual collection fibers. These fibers transfer the emitted light to the
collection optics, as shown in the following figure.
The collection optics are set up in octagon- and trigon-shaped arrays that are
engineered to maximize signal detection from each laser. This is accomplished by
transmitting the highest wavelengths to the first photomultiplier tube (PMT), and
reflecting lower wavelengths to the next PMT through a series of longpass
dichroic mirrors. Bandpass filters in front of each PMT allow fine-tuning of the
spectral wavelengths that need to be collected. Since reflection is more efficient
than transmittance, this design greatly increases the multicolor detection
capabilities of the cytometer.
cuvette
stream
fluorescent objective lens
individual
collection
fibers
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