4 Description of function
19
NIRFlex N-500
Operation Manual, Version G
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
