JEOL JSPM-5200 Instructions Manual page 34

3 CONFIGURAT ON AND DESCRIPTIONS OF COMPONENTS I
② Indicator selection knob
Used to select the photodiode output (SUM, AFM, FFM), the values (RMS, FMD)
corresponding to the vibration amplitude and the frequency of the cantilever during
AFM observation in the AC mode, and the phase output value (PHASE).
The positional relationship between the photodiode, mirror and cantilever is shown
below.
• SUM
A+B output
The summation of the output from all four detector elements is shown on the
indicator when the knob is in this position.
• AFM
(A-B)/(A+B) output
The relative difference between the total laser beam intensity of the two upper
detector elements and that of the two lower detector elements is indicated. If the
laser beam irradiates the center of the detector, the indication is zero. If the beam
irradiation point shifts upward, the indication becomes negative, and if it shifts
downward, the indication becomes positive.
• FFM
(C-D)/(C+D) output
The relative difference between the total beam intensity of the two right detector
elements and that of the two left detector elements is indicated. If the laser beam
irradiates the center of the detector, the indication is zero. If the beam irradiation
point shifts to the right, the indication becomes negative, and if it shifts to the left,
the indication becomes positive.
• RMS
This value is the RMS (root mean square) of (A-B)/(A+B) and corresponds to the
vibration amplitude at or near the characteristic frequency of the cantilever during
the AC mode AFM operation with the Slope-detection method. This value can be
changed by setting gain (1 × , 5 × , 10 × , 50 × ) using the software.
3-10
Mirror
a a
１
２
ｂ
ｂ
2
１
4-segment PD
+ =
⎛
a a A
⎜ ⎜
1 2
+ =
⎝
a b C
1 1
Laser beam
Cantilever
+ =
⎞
b b B
⎟ ⎟
1 2
+ =
⎠
a b D
2 2
TMPM5200-2