As professionals, it is incumbent upon us to stay abreast of the latest technological developments in our field. Unlike the human eye, thermal imagers don’t use visible-light to make a picture, they use heat. This gives thermal security cameras distinct advantages over low-light and daylight cameras when lighting is impractical, too expensive or where long-range performance is required.
Why do I care?
The short answer to this question is…range. And, in this business, range equals time: time to react, time to adjust, time to respond. Thermal security cameras detect the minute differences in heat that are all around us, all the time. This heat energy is easier to detect over longer ranges than visible light, giving thermal cameras a distinct advantage.
But that’s not where the thermal advantage ends. Not only can thermal security cameras see from further away, they are not vulnerable to the most common countermeasure open to someone trying to avoid detection with a camera that depends on visible, or reflected, light: camouflage. Why? Simple: you can’t hide your heat.
The thermal security camera picks out the intruder easily. Sure, you might say, but with the infrared illuminated camera you can identify your intruder better than with the thermal camera. True, but face it: if an intruder is so close to your infrared illuminated camera that you can identify him, you’re going to be looking for a new job and he’s probably eating at your snack bar. Use a thermal camera, and identify your intruder when he is in
Thermal security cameras are useful in circumstances that relegate other camera technologies to fighting for second-place. Large facilities commonly have to deal with unfenced and unlit perimeter areas for economic reasons. Thermal cameras can see far enough to make this a non-issue, and they can do it for less money than it would take to install the infrastructure required for lowlight and infrared illuminated cameras.
How does it work?
This may seem unbelievable, but really – this isn’t rocket science; it comes down to some basic physics. We see reflected light. Infrared illuminated cameras, night-vision devices, and the human eye all work on the same basic principle: light energy hits something and bounces off it; a detector then receives it and turns it into an image. The ability a given detector – be it in an eyeball, or a camera – to create that image is directly related to the amount of light available.
At night there isn’t any sunlight to bounce of f any thing, so we’re limited to starlight, moonlight and artificial lights. If there isn’t enough, it’s hard to see. Infrared illuminated cameras compensate for this by transmitting energy that bounces off whatever is in the camera’s view and making a picture out of that.
Thermal cameras have nothing to do with reflected light energy: they see the heat given off by every thing under the sun (literally!). Every thing you see in normal daily life creates heat energy – day and night, in good weather and bad. Just think: as you are sitting there reading this article, you are making a perfect thermal signature all by yourself.
What’s more the signatures of people, cars, buildings and all the other things seen by thermal security cameras generally have better contrast at night than during the day. They work just fine during the day – as long as there is the tiniest bit of temperature contrast between a target and its background, you can see it – but, they work great at night. And nighttime, as we know, is when the we need them most!