BUCHI NIRMaste Pro IP65 User Manual
Page 16
4 Description of function
16
NIRMaster Operation Manual, Version B
Reference laser control
The laser deliveres a constant, wavelength-stable beam of 633 nm. The laser beam a is coupled into
the NIR beam b to pass the interferometer before being decoupled d and analysed by the “Laser
feedback sensor” e. A fraction of the beam is splitted at the polarizer b and picked up by an inten-
sity sensor c to monitor the laser beam quality. The position and movement-frequency of the wedge
by the linear drive f causes an alternating relative phase shift of the laser light. Being reflected by the
second polarizer d, the phase shift generates an alternating amplitude. This alternating amplitude is
detected via the the “Laser sensor” e, giving precise information about velocity and (relative) position
of the wedge. The feedback signal is used to control the velocity of the linear drive f as well as to set
the sampling-points of the NIR interferogram.
A
B
+
d
C
D
E
H
G
e
a
f
LASER – 633 nm
F
+
b
c
Spare lamp
Effective NIR light path
A
NIR light source assembly with spare lamp and motorized parabolic reflector
B
First polarizer
C
Comparator (double refracting block)
D
Stationary double refracting wedge
E
Moving double refracting wedge
F
Second polarizer
G
Sample
H
Interferogram detector
Reference laser signal path
a
Laser output window
b
Second polarizator (works as a beam splitter for the laser)
c
Laser output-power sensor
d
First polarizer
e
Laser feedback detector
f
Linear motor for wedge movement