Thermal

#ThermalThursday

In todays blog we'll take a quick look at one of the Eco-Thermal model cameras from Hikvision.
Recently we have had more and more requests about Thermal cameras and as always we like to know a bit about the products that we sell. For this model demonstration we are using the DS-2TD2617-6/V1 which is a Thermal Bi-spectrum IP Bullet camera which allows for intelligent behaviour analysis. It can be used for perimeter defense as well as fire-prevention purposes.
This camera features an optical image sensor alongside the Thermal Imaging module and as such works well to preview how the thermal image can be used.

The thermal imaging sensor on this camera is only 160x120 resolution, which many people may turn their nose up at with these days of 4K cameras etc, but even at these low resolutions can give excellent results in differentiating between objects of different temperatures between -20°C and +150°C with a temperature accuracy of  ± 8 °C.

Upon first connection to the camera and looking at the Thermal image, I have to say I wasn't impressed. I couldn't make out clearly what objects I was looking at, no definition etc. But, that is not what this kind of camera is for of course. Once somebody walked across in front of the view, my opinion changed, it was now every obvious that the warm body was there, and stood out as a bright white glow in comparison to the rest of the bland grey image. And that is the strength of this camera - ignore colours, ignore shadows and lighting it's all about temperature differences.

Like I say, out of the box the Thermal image may look like it is missing so many details, but this can be tweaked. Temperature settings can be added to allow you to see an approximate dynamic temperature scale (which shows the variance between the highest and lowest temperatures in the scene). Different temperatures can be set to display as different colours, with three main areas of temperature (above a certain temp, between temperatures and below temperatures). This immediately starts to change the look of the camera, and while the detail from a high resolution camera simply isn't there, I was interested in how different objects in a tested scene had the variety of temperatures and how obvious some items became within the scene.

There is also an option to display Picture in Picture, or an overlay. I really like the overlay option, which brought in the definition from the optical lens and overlaid the thermal imagery, for me this made the image I was looking at look more 'intelligent' and what I was looking at appeared more obvious. Rather than varying 'greys' to display the different temperatures, different colour palettes can be used too (Predator-Vision anybody?)

See the below video, which highlights how a thermal camera can be used as security. Admittedly the optical image has been skewed by locking the camera into day mode, but you can still see how obvious a human form appears in the thermal image. Sure, you may not be able to identify who that body is, but sometimes the importance of 'who it is' does not matter, especially in an area where 'nobody' should be. The thermal camera in this case pretty much ignores the surrounding area, and allows the operator to clearly see that there is somebody there. At this point either an alert can be raised, or more traditional CCTV can be used to investigate further.

So, I've mentioned above how I've looked at the thermal camera in the realms of Perimeter defence or security, but there are also other uses for a Thermal Camera.

Thermal camera applications include Industrial uses, for checking long running machinery where heat could cause failure, or fires. They are already being used for mechanical testing to help visualise and detect hotspots so issues can be rectified earlier in testing before failure of components. I'm sure many of you will have seen the Thermal cameras in use on TV from the great height of helicopters, allowing the tracking of people on the run etc. Thermal cameras can even be used by firefighters to give informed decisions an planning related to hotspots of a burning building, or for helping to locate survivors. Of course, some of these applications may not relate to the exact type of camera I have tested here, but hopefully the examples will highlight some of the additional uses that can be had from thermal cameras, and why we should expect to see more development in this area.

The below video, is a very basic example of how this works by setting a couple of temperature thresholds to display as different colours while having the Thermal camera looking over a radiator as it heats up. You can clearly see the heating element at the bottom as it heats up and the heat rises up through the radiator and then starts to heat the air around it. A basic, but obvious demo:

What is the difference between this 'Eco Thermal' camera and one of the more expensive Thermal offerings?

The biggest difference is typically resolution, but also thermal accuracy. The higher the resolution, the better the clarity. This means that you can get more detail from the thermal camera at greater distances too (as you can digitally zoom in before losing image detail - similar to a typical optical camera). Thermal accuracy of this model is stated at +/- 8°C, whereas the more expensive models state +/-2°C,

Thermal Imaging Camera Limitations

The working range of thermal imaging cameras can be affected by rain and dense fog, as the light scatters off the water droplets.

Because thermal energy can be reflected off shiny surfaces, thermal imaging cameras cannot see through glass. Thermal imaging cameras can be used to gather information about the inside of a wall, but they cannot see through walls. See the image below, David is not really wearing sunglasses, yet his ordinary glass lenses cannot see past the glass and hence produces this kind of image - doesn't he look cool!