PerkinElmer Spotlight 400 Series, User Manual

Page: 36 / 120

36 . Spotlight 400 Series User’s Guide
Collecting an Image in Reflectance/Diffuse
Reflectance
Collecting an image in reflectance or diffuse reflectance differs from viewing as follows
(Figure 13):
• The toroid moves to send the beam to the Reflectance illuminator assembly dichroic
mirror, which sends it through the upper cassegrain.
• The beam is reflected off the sample and back through the other side of the cassegrain,
toward the remote aperture.
•
The detector cassegrain focuses the beam on to the detector.
Figure 13 Path of the infrared beam for collecting an image in reflectance/diffuse
reflectance
Changing the IR Magnification
Between the upper cassegrain and the variable aperture there is a mechanism for changing
the IR magnification. This is not shown in Figure 10 to Figure 13 for simplicity, as for visible
viewing and for low IR magnification, it is not used. When changing from low IR
magnification, which gives a pixel size of 25 µm, to high IR magnification, which gives a pixel
size of 6.25 µm, the mechanism rotates to place a series of magnifying mirrors in the IR
beam.
Dichroic mirror
Variable aperture
Reflectance
illuminator
assembly
Upper
cassegrain
Sample position
Lower cassegrain
Detector cassegrain
Detector
Source toroid