We have greatly developed from measuring temperature with a simple thermometer today. There are a lot of new and further developed technologies that are present to the world, promising much more effective results and outcomes than the traditional methods. Infrared and thermal imaging are game changing technologies that are growing in popularity rapidly. In fact, these two technologies share one common characteristic – the ability to represent the value for the temperature of a specific object in a form of a visual information.
To cover the concept and the difference of both devices, first let’s talk about the specific technology each of those devices use to fully understand how they operate and what is the implemented technology behind them.
Let’s start with a little bit of a background first, shall we?
Basically, our eyes are capable of seeing reflected light. Daylight camera devices, night vision devices and even the naked human eye all work based on the same principle: a visible light energy reaches something and literally ‘’bounces’’ off it and then further a detector receives it and turns that light that bounced off into an image. At first it may sound strange, but as you think about it, it would definitely make sense.
Whether it would be a human eye or in a camera, it is crucial that the mentioned detectors receive enough light to operate or otherwise they would not be capable of delivering an image at all. Obviously there isn’t any sunlight that could possibly ‘’bounce’’ off at night, so this limits the light sources to starlight or moonlight as well as artificial lights like street lamp posts etc. If there is not enough of those ambient lights, they won’t really be of that much of help.
Thermal Imaging Cameras
Thermal images are basically different altogether. If we want to be as precise as possible, they are not really ‘’cameras’’ but more of like sensors. To understand their concept, the first thing to consider is to literally forget everything you think you know about how regular cameras take pictures. Thermal imaging cameras take pictures based on heat, not visible light and details. Heat and light are both of the biggest and most crucial elements of the electromagnetic spectrum, but a camera that can detect visible light won’t have the ability to see thermal energy and the other way around.
Thermal cameras don’t only detect heat though: they actually detect heat differences very sensitive as well – as small of a change as 0.01 degree can be picked up by the thermal camera.
Everything we encounter in our daily lives gives off some kind of a thermal energy, even ice. The hotter a specific object is; the more thermal energy it emits – logical. This emitted thermal energy is called an object’s heat signature. When two close-of-a-kind objects next to one another have even the slightest different heat signatures, they appear on the thermal image camera clearly, regardless of other factors, weather and lighting conditions.
Thermal energy comes from a specific combination of sources, depending on what the user is viewing at the current time. Some things, even warm-blooded animals (in that category fall humans too), engines and specific machinery create a heat of their own, naturally or mechanically. Other things like land, rocks and even plants and vegetation in general are on the other spectrum – they absorb heat from the sun during the day and actually radiate the heat that was absorbed through the day during the night.
Because different materials absorb/radiate different thermal energies at extremely different rates, an area that we consider has one temperature is actually in reality possessing a very different temperature than what we first thought of. This is why a log that has been in the water for a few days will appear to be a much different temperature than the water itself, and will therefore be caught on the Thermal Image camera. All of this information may seem quite complex at first but the reality is that current-technology thermal image cameras are extremely easy to use. Their received image is very clear and easy to perceive and understand and requires close to no training or further interpretation – even when watching TV you can use a Thermal Imaging camera and there will most likely be no difficulties.
On the other part of the spectrum, there are the Infrared Cameras, literally!
The Infrared cameras have the power of generations their own reflected light that is invisible to the human eye by projecting a beam of nearly-infrared energy that the imager that is built into the camera can see when the projected light bounces off an object. This, to some extent, could come in handy but Infrared Cameras still rely on a reflected light source to be present for them to have an image, so they will pretty much have the same limitations as any other night vision camera that depends on light energy that is reflected – the main disadvantages of the Infrared Camera won’t take long to be noticed if used by a more experienced user – poor contrast and shorter range.
All of the visible light gear work by simply detecting reflected energy light. But the amount of that mentioned reflected light that they receive is not the only factor that will determine whether or not the user will have the ability to see with those devices – this is where we mention image contrast and its importance.
If you are simply looking at something with a lot more saturated contrast, compared to its surroundings, you will have a much better chance in detecting it with a visible light device too – a daylight camera for an instance. If it doesn’t have a good contrast though, it comes to mind that you won’t be able to see it well, no matter how bright the sun is shining. A whiter object seen on top of a dark background has lots of contrast. On the other hand, a dark object however, will be much harder for those mentioned daylight devices to detect it against a dark background. This phenomenon is called ‘’ poor contrast’’.
At night, when the missing visible light naturally decreases image contrasts, visible light cameras get affected by this even more. Thermal images don’t have any of those disadvantages whatsoever. First they have nothing in common and nothing to do with reflected light energy: they literally just see and detect emitted heat. Everything you see in normal daily life has a specific heat signature, as we mentioned. This is why there is a much MUCH better chance of detecting something at night with a thermal imager than you will be able to with an infrared camera or a night vision camera.
In fact, many of the looked-for objects like people for instance, which comes first in mind, generate their own contract as well as their own heat. Thermal imagers can detect them very well because they don’t just simply make pictures from heat, they deliver the user a picture from the minute difference in heat between close-to-one-another objects.
The Main Differences Between Thermal and Infrared Cameras.
1. Contrast and light spectrum region difference.
On the side of the Thermal cameras, the light they use to create and process a picture is in the much further region of the light spectrum, while on the other hand the Infrared Cameras use light from a much higher frequency, compared to that of the Thermal camera.
At first sight, both of those points may seem like a not-so-major difference, but when we talk about the light spectrum, even the slightest of frequency change will greatly affect the picture that is received by the user.
This point can be proven by comparing both a picture taken from a Thermal Camera as well as a picture taken from an Infrared Camera – this way when looking at both pictures, the difference you are going to see will be quite significant, wouldn’t it? If we want to get a bit geeky and talk scientific, the wavelengths of the Infrared Camera ranges from 0.75 to 1.4 micrometers, while the Thermal Camera ranges from 8-15 micrometers – so even if you have no clue at what those micrometers are, you can’t not notice that there is definitely a HUGE difference between both wavelengths. On the side of contrast, the Infrared Camera has a much more common and visible light than the Thermal camera – but this makes sense as Infrared Cameras rely on an ambient light source while the Thermal Camera relies purely on emitted heat, which actually points us to the other significant difference!
2. Technology that both cameras rely on.
Even though they have a few similarities, the technology that is used in both of the devices is totally different. The Infrared Camera works more like an image intensification device that makes pictures from the same visible light our naked eye can see. The Infrared Cameras although can also use an invisible to the naked human eye light source – a self-projected infrared flashlight that comes in handy when in a pitch black environment.
The ‘’infrared flashlight’’ illuminate’s areas that the Infrared Camera detects and this way creates its own light source, creating a picture. Unlike the Thermal Camera, the Infrared Camera projects low-contrast images and for that case, people can easily hide in shadows or just use a simple camouflage to conceal themselves because the infrared illuminator is not very powerful and is quite narrow and cannot aid in seeing at greater distances – no more than 30 meters. The Thermal Camera on the other hand is quite the nighttime object hunter.
It can detect any object/person/animal that emits heat – hiding from a Thermal camera using a camouflage or trying to hide in shadows will definitely not work this time. Shortly – the activity of a Thermal Camera is passive, as they do not project any possible light while on the other hand, the Infrared night vision camera is considered an active device as it has the ability to detect ambient present light as well as project infrared beams, if the ambient light is not currently present.
3. Performance under different conditions.
Durability – one of the most crucial elements in a night vision device. Although both devices are quite complex, the Thermal night vision camera would definitely be the more sensitive one. Thermal night vision cameras rely on heat to create a picture, as we already stated. So it could come in mind that if exposed to very bright daylight, the heat received can become a bit too much for a lower generation Thermal camera to handle and that could permanently damage the system, making heat readings very inaccurate.
On the side of the Infrared Camera, exposing it to daylight won’t really damage the device itself, as it only relies on ambient night lights and self-projected infrared lights, but it wouldn’t be very handy to use during the daytime.
The other thing that both devices differ from one another is their ability to perform under certain weather changes and drastic conditions. The Thermal Camera is the big bully here. It can perform under any extreme condition if set up properly – pouring rain, thick mists, seeing through shadows and certain camouflages are never a problem for the Thermal Camera.The Infrared camera on the other hand is a bit more sensitive to those factors. Most of the time for the best performance of the Infrared Camera the night must be clear and there shouldn’t be pouring rain or other extreme weather conditions as they greatly hinder the picture quality received.
As we discussed what technologies both the Thermal and Infrared cameras use, we can’t help but notice that there are definitely quite the differences between the two. Nevertheless, both of the devices are very complex and powerful, and both can be the perfect fit – you just have to decide the activity that you are going to use it for and the weather conditions that the specific night vision gear will be used at.