Chapter 4. Performing Measurements
Fig. 4-10. Intensity distribution of the detected signal
The dark region in the acquired image corresponds to the light-transmitting region of
the optical tube, that is, light coming to this region will be detected by the PMT
module.
5. To improve positioning of the laser beam, perform scanning over a smaller area.
Repeat the step 4 with value of the
Scan Size parameter being 10 µm. Again,
intensity distribution of the detected signal will be acquired (
Fig. 4-11).
6. Direct the laser beam to the point where the detected signal is maximal. To this
purpose, place the
marker to position where the PMT output is maximal
(Fig. 4-11). Monitor the output level on the oscilloscope.
Fig. 4-11. Arrow indicates the position of the maximum
of the detected signal
7. Mark the centre of the laser spot on the monitor of the optical viewing system using a
mark pen. Position of the new mark will most likely differ from the previous one.
8. Define the PMT control voltage (PMT1 parameter) to be 0 V.
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