Aligning The Light Lever Force Sensor - AFM Workshop TT-AFM User Manual

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4.4. Aligning the Light Lever Force Sensor
Aligning the light lever force sensor is greatly facilitated by understanding the optical path of the light in the
sensor. The following figure shows the light path and the effect of turning the adjustment knobs on the light lever.
Gain Switch
Laser
Left to Right
Up Down
Detector
Left to Right
Up Down
Red Dot in Pre-Scan
Video Microscope View
•
Motion of the laser spot vvhen the
Motion of the red dot in the "Pre-Scan"
window vvhen the detector adjust knobs are
laser adjust knobs are turned
clockwise.
tumed clockwise.
Tips for aligning the laser in the light lever force sensor:
a) After replacing a cantilever, the laser and photodetector adjustments are usually less than a single turn.
b) It is often difficult to see the laser spot on the cantilever because the cantilever reflects the light.
c) Bringing the cantilever within a mm of the sample's surface can help because you can see the laser on the
sample's surface.
d) If the cantilever does not alight within a few minutes, try another cantilever.
e) The adjustment screws have backlash, so sometimes the motion is not perfectly linear.
f) When in "Vibrating" mode, if the resonance peak appears inverted at the top, move the detector gain from
"High" to "Low."