Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

Figure A-11 shows transmission curves for various samples of glass and
quartz. Upon seeing these, our first impression is that glass is opaque at 10
µm where ambient (30°C) surfaces radiate their peak energy (?). This
impression is correct and, although in theory, infrared measurements can be
made of 30°C targets through glass, it is hardly practical. The first approach
to the problem is to attempt to eliminate the glass, or at least a portion of it,
through which the instrument can be aimed at the target. If, for reasons of
hazard, vacuum, or product safety, a window must be present; a material that
transmits in the longer wavelengths might be substituted.
Charlie Chong/ Fion Zhang