IRWeb INFO

{Image Courtesy Williamson Corporation}
From the Williamson IR website page on Applications of Dual Wavelength infrared thermometers:

“One of the greatest advantages of a dual-wavelength infrared thermometer is that the target can be smaller than the optical resolution of the sensor. This feature is particularly appropriate when viewing past an optical obstruction or when viewing a small or wandering target such as a thin wire…”

“For this application, the dual wavelength sensors are able to provide a relatively large target area of 0.5in diameter while measuring the significantly smaller wire. Using a dual-wavelength sensor it is possible to measure a wire that is less than 0.001in diameter and with a wander from side to side of as much as 0.2in.”

(ED NOTE: This IR thermometer type, dual wavelength or dual waveband wherein the dual signals are ratioed are sensitive to the ratio of the spectral emissivities in the two spectral wavelength bands and are only insensitive to emissivity changes if the emissivity ratio does not change.

In such a situation the object of measurement is called a gray body, and it is relatively rare except for some of the Iron Oxides that are found on Iron & Steel within the wavelength regions used by many commercial relatively “short wavelength”, infrared thermometers, eg: 0.7 to 2.5 micrometers.)

Concord,MA, USA — As seen on the Williamson IR website:

“Single wavelength infrared thermometers filtered in the short wavelength region of 2.0 to 2.5 microns offer good performance when measuring low emissivity materials at low temperatures.”

“The accuracy improvement associated with the shorter wavelength sensor is shown in the figure below. The shorter wavelength sensor shows an improvement in measurement from about 18°F (10°C) to about 5°F (2.8°C) when measuring a 220°F (104°C) target with a 10% variation in emissivity. This alone does not explain the total improvement in accuracy achieved by the component supplier. The short wavelength measurement also benefits from the fact that most metals have a higher emissivity value at the shorter wavelength. Therefore, considering these two benefits the shorter wavelength sensor offers as much as ten times more accurate readings than is a long wavelength sensor.”

{Image: Courtesy Williamson Corporation}

Read the rest of an actual case story at www.williamsonir.com/page.php/id/233

ED NOTE: The terms “Short Wavelength” , “low emissivity” and “low temperature” are relative, of course and here they are used in the context of a measurement in the 150 to 1000°F temperature region of unoxidized metal surfaces.

The web applications at Mikron Infrared encompass both “spot” radiation thermometers and Infrared Imagers. Mikron has been a leader in the field of Industrial Thermal Infrared radiation thermometry for nearly 30 years and has a strong reputation for calibration excellence as well as equipment ruggedness.

There experience is hard-earned and well worth reviewing in our estimation. Below are listed some of their specuialties and links to them.
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This is about an Information Note on the Laytec GmbH website that describes the technology they use in their TT products for semiconductor manufacturing and R&D processes. It is in the form of a PDF document, not easily read online like most web pages. It must be downloaded and then opened, usually in a seperate browser or reader window.

The rationale for using a thermal infrared approach in semiconductor wafer processing is explained at the outset of their note, as follows:

During epitaxial growth the wafer temperature is one of the key parameters. It influences
such elements as growth rate, composition of ternary and quaternary compounds and doping
levels. Wafer temperature also has an important impact on the quality of the grown layer and
its roughness and thereby on the performance of devices based on such epitaxial layers. Thus,careful monitoring and precise control of wafer temperature during the whole growth process are indispensable. Usually the temperature is controlled indirectly, either by thermocouples or by pyrometers.

The article goes on to describe how their pyrometry (radiation thermometry) method obtains the true temperature.
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Double side polished vs. single side polished sapphire substrates
Laytek’s Application note 28 describes the effects of double side polished sapphire wafers versus
single side polished wafers to the true temperature measurement of LayTec’s in situ sensors.

The study was performed on two identical Gallium Nitride (GaN) buffer growth runs monitoring the effect of the Sapphire substrate backside polishing on the true temperature signal using the Laytec IR Pyrometer. The only difference in the growth parameter was the substrate type: wafer #1 was a sapphire 2” wafer with a rough backside, and wafer #2 a double side polished 2”sapphire wafer.

To quote one interesting comment:

“The effect of the double side polished sapphire on the reflectance signal is a certain increase in the average reflectance (the back side reflectance contribution) and a relative shrinking of the Fabry-Perot oscillation amplitude. All these effects could be perfectly modelled by the LayTec’s AnalysR
software”

You can view the complete Applications note, TT measurements: double side polished vs. single side polished sapphire substrates, or download it from the Laytec website by clicking here (PDF - 122 Kb).

pdf - 122 kb

This YouTube video, by FLIR, shows FLIR cameras in the field and why infrared thermal imaging has become a key tool for predictive maintenance programs for utility firms everywhere.

Night vision is greatly improved with infrared thermal imaging cameras, as most people know from scenes in movies, like “Predator”. In real life they are even more compelling.

Here’s a screen grab from a thermal imaging video taken by a private citizen northeast of Douglas, Arizona, Friday evening, November 2, as displayed and described on YouTube.

The video shows four drug “mules” carrying illicit cargo.

Six people were in the group. Four were apprehended by the Border Patrol, after being guided in by the private citizen. 139 pounds of marijuana was confiscated. Two got away.