PerkinElmer EnVision, Instrument Manual

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Functional description
22
The polarized emission light passes through the excitation beamsplitter in
the optical module. If the instrument has two detectors enabling dual
emission measurements, the mirror module has a second emission
beamsplitter which directs a portion of the emission light to the second
detector. This second beamsplitter separates light according to its plane of
polarization.
The emission light then passes through the emission filters in the emission
filter slide. These filters are equipped with polarization filters to ensure that
the right plane of polarization is being measured. Hence there are separate
filters for S and P polarized emission light. If the system does not support
dual emission measurements the two planes will be measured sequentially
by changing the emission filter.
The final result is calculated by combining these measurements using the
formula
Polarization (mP) = 1000 * (S – G*P)/(S + G*P)
where S and P are the measured results with the S and P emission filters
respectively. G is a factor to correct for the effect of emission filter
transmission variations, differences in the emission light paths and sample
viscosity. In instruments with two detectors the G factor can be set to 1 and
the polarization value can be adjusted by changing the separate gain of the
detectors.
In EnVision, a background correction can be done before calculating the
final results. It is done by subtracting measured S and P results obtained
from a buffer sample from the actual measured S and P results respectively.
Figure 25. Excitation from above/Reading from above (two readings
necessary, one with the S polarizor and one with the P polarizor)