Infrared Training Center

Monday, January 30, 2012

Measuring Thin Film Plastics

A common application that is well suited to IR filters is that of measuring thin film plastics. Since the process of making thin plastic film itself is highly temperature critical, it is imperative to evaluate both the temperature and the uniformity of the plastic as it exits the extruder or web process. The product is typically moving at high speeds which precludes the use of contact temperature methods.

Most plastic films have spectral characteristics similar to polyethylene (depicted in the figure below) which is transmissive in both the short wave and long wave IR regions. Measuring thin film plastics can be challenging since without using a filter, you see “through” the plastic and measure the objects behind the plastic, rather than the plastic itself.

Transmission plastics and filter

Spectral transmission of Polyethylene film with spectral response of plastics filter

Thursday, January 19, 2012

Monday, January 16, 2012

Infrared Wildlife and Black Ice Detector - Looking for Feedback

by Rosaele Tremblay

Hello, I am a high school student writing a paper for my science project and I would like any feedback from the InfraMation readers (scientists or thermographers to see if I am on track with this idea or if anyone has suggestions as to how we can make this work. Thank you for any input.

You can provide comments and suggestions for Rosaele by leaving a comment on this post - Editor

Introduction
The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, and radio waves and each of them has a different wavelength and frequency. Infrared radiation is between visible light and the microwave portions of the electromagnetic spectrum and it is not visible to the human eye. Some animals do exist which see in infrared such as a few different snakes. Three categories exist in infrared: near, mid and far-infrared. Near-infrared is the closest to visible light and far-infrared is closer to the microwave portions. Infrared radiations are all around us every day coming from sunlight, a fire, radiator, a warm sidewalk and the TV remote. Everything on earth gives off heat when molecules begin to move and the higher the temperature of an object, the more the atoms and molecules will be moving which will produce a greater amount of infrared radiation. Objects with a temperature above absolute 0 radiate in infrared including the objects we perceive to be cold or freezing such as ice cubes or objects which are hot but do not visibly appear to be hot emit heat.

These shots of a coffee mug are in three different palettes to show that we assign the colors to gray steps. Human eyes see ten gray steps so to see the colors in definition we can assign 10 colors to them like in these shots. In these, white is hot and black is cool, but we can also invert these so that white is cool and black is hot, this is up to the thermographer.

image image

Wednesday, January 4, 2012

Analyzing Building Images Acquired at Different Times

A camera user writes:

"I find that images taken of the same structure, not much separated in time, sometimes look very different.  This poses a problem for me as I’m trying to compare the heat images of different houses (to detect homes that need weatherization).  Presently I’m not confident that images of two homes reflect actual differences in the structures, or are caused by minor environmental changes or even by artifacts in the photography.  Here is an example.

Attached are two nighttime images of the front of my house, which faces east.  IR0310 was taken at 10:40 PM, IR0408 at 11:11 PM. (The clock on the camera is two hours fast.)  It was a cold night with little temperature change over the half hour between pictures.  The house thermostat was constant. 

I've set the palette and temperature range to give me good differentiation of houses along the street.  I took the first image of my house as I began imaging houses on my street, and I took the second image when I finished the street scan. 

I am surprised, first, that my house looks so different in the two images. And second, that the outside looks warmer in the later image.  If anything, I'd have expected the outside to have cooled.

Glad for any interpretation of this.  Needless to say, with this kind of variation on a single house, it is hard to get good images for comparing houses. "