“What’s in a name? That which we call a rose, By any other name would smell as sweet;”
In other words, what we call something does not change its characteristics and function. There seems to be no end to the alternative names for thermal reflecting film. It has been called:
Low Emissivity Film
Thermal Film
Passive Film
No Power Film
Reverse Polarity Film
What’s in a name? In this case we are talking about the same Thermal Film.
This film is very poor at giving off thermal infrared energy while being very good at reflecting thermal infrared energy.
Low Emissivity Film
Specifically, we can look at the measured reflectance of one film from 2 micron to 12 micron wavelength. Here we see the reflectance (R) is roughly .9 or 90% for that spectrum.
Furthermore, emissivity (e) is related to reflectivity by the following equation:
e = 1 – R
Therefore, the emissivity is roughly .1 or 10% for the above spectrum. The lower the emissivity, the easier it is for thermal imaging cameras to detect.
Most materials in the world have a high emissivity and low reflectivity, the exact opposite of no power film. Because of the disparity, this film can be detected by a thermal imaging camera, which detects thermal energy in the environment and creates a picture of the scene much like our eye does with visible light.
Passive Film
The name passive film reflects the film’s difference from active thermal panels. Active thermal panels (think heating pad on your sore back) give off their own thermal energy. The energy is produced most often using electricity, but chemical heaters are also used. Passive film reflects infrared energy in the environment without actively producing thermal energy.
No Power Film
The name No Power Film reflects how the film appears on the screen of a thermal infrared camera. The film generally appears black and cold. It looks like there is No Power coming from the surface. Conversely, a warm object in the scene is white and has a lot of power coming from it. When this film was first invented for use as targets, No Power Film was the name given.
Reverse Polarity Film
It seems like we saved the hardest for last. Most thermal imagers have two modes of operation. One is white hot (and black cold) and the other is black hot (and white cold). When a user switches from white hot to black hot, everything white on the screen becomes black, and everything black becomes white. This operation is called reversing the polarity on the imager.
A human being generally appears to be white and hot when viewed through a thermal imager. However, a human target made with this film will appear to be black and cold. It is as if the person’s “polarity” was switched. So this name reflects the similarity of the films operation to changing modes on the thermal imager.
Conclusion
Romeo and Juliet would have been confused by all the names. But you don’t have to be. Don’t let the terms Passive, No Power, Low Emissivity and Reverse Polarity cause confusion. Be able to recognize all the names, and just realize they are all the same product. If you have questions, connect with us and we would be happy to help.
Thermal imaging is finding more and more applications, and anywhere thermal imaging technology is used, there is the potential need for no power film as well. For example:
