Flir ThermovisionPathFindIR LE User Manual

334-0001-00-10-LE, rev. 100 May ’0825
8
8 – Infrared Technology8 – Infrared Technology
true only until 1830, when the Italian investigator, Melloni, made his great 
discovery that naturally occurring rock salt (NaCl)—which was available in 
large enough natural crystals to be made into lenses and prisms—is 
remarkably transparent to the infrared. The result was that rock salt 
became the principal infrared optical material, and remained so for the 
next hundred years, until the art of synthetic crystal...

8 – Infrared Technology
26May ’08 334-0001-00-10-LE, rev. 1008 – Infrared Technology
Figure 8-4: Samuel P. Langley (1834–1906)
The improvement of infrared-detector sensitivity progressed slowly. 
Another major breakthrough, made by Langley in 1880, was the invention 
of the bolometer. This consisted of a thin blackened strip of platinum 
connected in one arm of a Wheatstone bridge circuit upon which the 
infrared radiation was focused and to which a sensitive galvanometer 
responded. This instrument is...

334-0001-00-10-LE, rev. 100 May ’0827
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8 – Infrared Technology8 – Infrared Technology
converter and the photon detector. At first, the image converter received 
the greatest attention by the military, because it enabled an observer for 
the first time in history to literally ‘see in the dark’. However, the 
sensitivity of the image converter was limited to the near infrared 
wavelengths, and the most interesting military targets (i.e. enemy soldiers) 
had to be illuminated by infrared search beams....

8 – Infrared Technology
28May ’08 334-0001-00-10-LE, rev. 1008 – Infrared Technology
The primary source of infrared radiation is heat or thermal radiation. Any 
object which has a temperature radiates in the infrared portion of the 
electromagnetic spectrum. Even objects that are very cold, such as an ice 
cube, emit infrared. When an object is not quite hot enough to radiate 
visible light, it will emit most of its energy in the infrared. For example, hot 
charcoal may not give off light, but it does...

334-0001-00-10-LE, rev. 100 May ’08i
 –  – 
Document History
Table -1: Revision History
Revision Date Comment
100 May 15, 2008 Initial release 

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