Chapter 3. Preparing for Operation
Fig. 3-26. Spot of the detection system laser on the cantilever
9. For fine aiming the laser beam at the end of the cantilever, use adjusting the total
signal of the photodiode. With laser positioning screws 1 and 2, move the beam a
little against the cantilever and find the position at which the total signal (
Laser) is at
its maximum. Expected level of the
Laser signal is in the range 15÷45 nA.
10. Adjust the laser spot at the center of the photodiode (see Fig. 3-27) by moving the
photodiode with the screws 4 and 5. For higher precision, find a position where the
signals
DFL and LF are close to zero, with the total signal Laser being sufficiently
high. Recommended level of the signal
Laser ≥15 nA (it depends on reflectivity of the
cantilever and on factory adjustments of the measuring head).
Fig. 3-27. Laser spot adjusted at the center of the photodiode
This completes adjusting the optical cantilever deflection detection system.
The PNL is now prepared for measurements with the aperture probe.
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