22 – LSM 880 Training Guide
Understanding Image Quality
Detector Sensitivity
The sensitivity of the PMT is a function of the high voltage gain applied
to it. The gain setting (as discussed elsewhere in this manual) controls
the sensitivity of the detector to photons of light emitted from the
sample fluorescence.
Increasing gain provides the most flexible and impactful way of
improving image quality, but it has some drawbacks. The most obvious
is when you increase the gain you also increase the noise in the
resulting image. There are various forms of noise that we won’t discuss
here, but they are readily apparent when using a gain value > 500V.
Below 500V it is very difficult to detect much noise at faster scan speeds,
however when using the detector above this value you will find that you
will need to make some adjustments to reduce this.
If laser power is high and the confocal aperture cannot be
compromised there are a few methods to dealing with noisy signal due
to high detector gain.
There are 2 main methods for dealing with high image noise. The first is reducing the scan speed to a slower rate. This will
increase the pixel dwell time which will improve the signal-to-noise ratio. The second is signal averaging which will scan the same
image multiple times and average the result to produce an image that has an improved signal-to-noise ratio.
