Infrared Cameras Take Off in New Directions

Anne L. Fischer

The principles behind infrared technology have not changed much since they were developed in the 1800s, yet advances in sensors, electronics and optics give rise to new applications for IR cameras every day. Higher speed, greater field of view, smaller sizes and ease of use are the key changes that are pushing IR cameras into places they have never been before.

Smaller array platforms are enabling manufacturers to produce handheld cameras, and because the optics are more affordable, those cameras are used in applications where cost was previously a deterrent. Tom Scanlon of Flir Systems Infrared indicated that, while small, these new sensors can still do the job. “With some of these advancements, these more affordable sensors are delivering fantastic sensitivity.”

In this collection of articles, industry leaders offer insight into new twists on familiar technology and take a look at some specific applications. But before we delve into what the experts have to say, let’s define just what we mean by “infrared.”

In the past, we’ve used the terms “near-, mid-, and thermal or far-infrared.” As reader Fred Schaff pointed out in a letter to the editor printed in our January issue, there is a difference of opinion over how the IR spectrum should be subdivided. In talking to the industry experts who contributed to this feature, it’s clear that the issue is still not resolved. For example, Raytheon Infrared defines near-IR as 780 nm to 2 μm, mid as 3 to 5 μm, and thermal and far as 8 to 12 μm, while in Mikron Infrared Inc.’s view, near is 650 nm to 1.8 μm, mid is 1.8 to about 5.8 μm and far is 5.8 to 20 μm.

To help the photonics industry communicate, we have defined the ranges in our Photonics Dictionary and on our Photonic Spectrum Reference Wall Chart. We realize, however, that the ranges are not always straightforward. Mikron’s William Fullam believes that there are two standard definitions of near-infrared — one from astronomy and the other from spectroscopy — which vary based on detector characteristics. He says that the designations are often based on the available technology, citing as an example near-infrared, which, “to one of our design engineers, is 650 nm to 1.8 μm because InGa detectors end there.” However, he suggests that “as detectors and circuits get better, the sharp demarcation tends to blur. That is why the question is so difficult to resolve.”

So although we acknowledge variation by application, we define the ranges in an attempt to set a standard for the photonics community as a whole. Because we use the terms “near,” “mid” and “far,” we need to be clear about just what they mean to us. And in response to Schaff, we will use these distinctions within infrared more often.

The ranges as defined by the Photonics Dictionary:

Near-infrared:   0.75 to 3 μm

Mid-infrared:   3 to 30 μm

Far-infrared:    30 to 1000 μm, or 1 mm

It may not be possible to adopt a standard for the entire industry, but we believe it’s important that the terms we use are defined. We welcome further input from readers and encourage dialogue about variations in definition by application.