PerkinElmer Spotlight 400 Series, User Manual

Page: 35 / 120

Overview of the Spotlight Imaging System . 35
Collecting an Image
The upper cassegrain is used for both visible light and infrared radiation. For this reason,
when you adjust the sample position so that the visible image of the sample is in focus, the
sample is also correctly positioned for collecting the infrared image. Similarly, when you
adjust the aperture in Point mode so that the required area of the sample is isolated visually,
you have also isolated the area of the sample from which the image is to be collected. In
Image mode the apertures are not used to isolate the sampling area, and the visible image is
used to determine the dimensions of the IR image.
Collecting an Image in Transmittance
Collecting an image in transmittance differs from viewing in transmittance as follows
(Figure 12):
•
Instead of receiving light from the illuminator, light from the spectrometer is reflected
off the toroid onto the lower dichroic mirror which sends it through the lower
cassegrain.
• The upper dichroic mirror reflects the beam onto the detector cassegrain.
• The detector cassegrain focuses the beam on to the detector.
Figure 12 Path of the infrared beam for collecting an image in transmittance
Dichroic mirror
Variable
aperture
Upper
cassegrain
Sample position
Lower
cassegrain
Lower dichroic
mirror
Detector cassegrain
Detector
Source toroid