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Vision on tracks

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How would you sneak up on a tank? With armoured vehicles now frequently equipped with low light and thermal cameras, covering all angles of approach, it would not be easy. Stephen Mounsey looks at vision systems for armoured vehicles

Although it’s difficult to say exactly when it happened, modern warfare has changed substantially in recent times. Improvised explosive devices, or IEDs, represent one of the most significant threats faced by soldiers in the modern theatres of war, i.e. Afghanistan and Iraq. As part of the process of minimising such risks, imaging technology is increasingly becoming a central feature of modern fighting vehicles.

David Strong is vice president of marketing for the Government Systems Division at Flir Systems – the US-based developer of night vision and thermal imaging. According to Strong, there are three ways in which imaging technology has found its way into applications in fighting vehicles: ‘The first area is driver’s vision,’ he says, referring either to ways of allowing the vehicle to be driven with limited or no conventional visibility, or ways of augmenting the driver’s vision with additional information – such as thermal video images. ‘Low cost is a deciding factor here,’ he adds; ‘people don’t want to spend vast sums of money putting vision systems on armoured vehicles, and certainly not more than the vehicle is worth.’ Additionally, he says, the field of view and where the sensors are positioned are very important to the human factor of how the vehicle is driven using only the sensor.

According to Strong, the second area of application is within more general situational awareness, in which vision systems are used to give the passengers an understanding of what’s going on outside of the vehicle. ‘This is particularly important in modern mine-protected vehicles, which don’t have a lot of visibility out of them. If you’re inside the vehicle, you want to be able to be sure of your surroundings before you open the door and get out,’ he explains.

The third area highlighted by Strong is given the acronym ‘RESTA’ by the US military, which stands for reconnaissance, surveillance, and target acquisition. ‘That’s an application in which we would use a fairly long-range, multi-sensor camera; not only infrared night vision, but also daylight TV and maybe a laser range finder. This could be placed on a mast raised above the vehicle, so as to look over a hill at what’s going on in a valley, for example,’ says Strong. ‘In all cases we need to work closely with the vehicle manufacturer for the integration aspect of it. We don’t go bolting these cameras on willy-nilly; they have to be integrated carefully.’

Driving changes

Looking more closely at the first two categories Strong listed, i.e. enhancing driver’s vision and using vision systems for situational awareness, military manufacturers and contractors in recent years have used more and more cameras as they work to counter the IED threat. George Chamberlain, president of Pleora Technologies, explains how vision systems in these applications meet the demands of the modern military: ‘In tank and troop-carrier applications, the military is trying to remove as many windows as possible from the vehicles, as these are weak points in the armour. Obviously that raises the question of how you are going to drive the vehicle, and how you are going to achieve local situational awareness for the troops inside. The answer for them is to increase the video system capabilities on the exterior of that vehicle dramatically.’

Pleora specialises in providing both the cameras and networking equipment for these cameras, although the devices are usually customised by a third-party military contractor prior to installation. Cameras are networked by Gigabit Ethernet, and the networking introduces some special considerations when it comes to meeting the requirements of driving applications: ‘If you can imagine the difference between just driving with your eyes looking through a glass window, versus driving by looking at a screen and watching the video on it, you can imagine that latency and jitter are going to be incredibly important in these applications,’ says Chamberlain. ‘Our military contractors are telling us that they can live with latencies in the 50 to 60ms range, and this is something we can achieve using Gigabit Ethernet and GigE Vision today.’ Fifty to 60ms, he says, is around the optimum latency, as it leads to an unobtrusive disparity between somebody’s action – i.e. turning the steering wheel – and an observable reaction – i.e. the vehicle’s viewpoint turns. ‘If there’s too much disconnection between turning the wheel and the visual representation, then the human brain has a hard time coping, and the vehicle becomes very difficult to drive. Even driving in our daily lives it would be very difficult to cope with, but when translated into the deserts of Iraq or Afghanistan, where people’s lives are on the line, it becomes something else entirely,’ he says.

In order to ensure that the cameras and the networks by which they’re connected perform to the required specifications, Pleora’s development kit contains drivers that optimise the Gigabit Ethernet cards so as to minimise both the latency and the jitter of the video. Rigorous testing is also important: ‘Our military contractors will do what they call photon-to-photon testing, taking a measurement of when the photon of light goes into the camera, passes through the system, and comes out at the monitor… and if that is within an acceptable range, then they certify the product,’ says Chamberlain.

Working with military customers

The military can be a difficult market to navigate, with various tiers of bureaucracy between the high-level body commissioning a new tank, aircraft, or capital ship and the various developers of the imaging equipment, which finally makes its way into the final piece of material. For the UK’s MoD, for example, defence procurement is largely handled by the Defence Equipment and Support organisation based at Abbey Wood, near Bristol. Ian Palmer, a project manager at UK-based night vision specialist e2v, has worked with the specification writers based at Abbey Wood, and he has found that the first step is ensuring that the customer has a sufficient understanding of the capabilities of cutting-edge technology. ‘When it came to some of our customers’ low light requirements, we had to do some significant work with members of the contracting project teams in order to make sure they had an understanding of reality – that their specifications were realistic,’ he recounts.

Palmer gives the example of a specification for imaging equipment for a certain military vehicle, which was initially supposed to be able to allow the users to see a person in a ‘threatening posture’ at 600m in low light conditions. In this case, Palmer says, convincing the customer of the impracticality of their expectations was made easy by the use of e2v’s dark tunnel facility. ‘We brought the project team down to our facility, and made targets that corresponded to what the cameras can see at 600m, and then we ask if they can see it… and of course they can’t. It’s a bit of a challenge to bring them back to the reality of what is practically possible. We still fit into the category of having the most sensitive cameras in the world, and so we can say “that’s as good as you’re going to get.” Everybody’s always pushing the boundaries,’ says Palmer, ‘but there are fundamental limits of noise and frame rate that come together to say “if you want to run at this speed, under these lighting conditions, with the inherent noise of the system, then that’s the contrast and target recognition that you’ll be able to achieve.”’ In other low-light applications, he adds, a slowed frame rate could be used to integrate-up image data so as to achieve better contrast, but driving or spotting a moving target requires a certain frame rate.

Is mil-spec really so special?

Imaging performance aside, military applications have traditionally meant harsh working conditions, and so the systems will often be specified with highly specialised mechanical or environmental tolerances, including temperature, shock and vibration, and electromagnetic interference. According to Chamberlain, Pleora meets these requirements through thoughtful design, rather than through use of certified military specification (mil-spec) components. ‘The way our military contractors will typically engage with us is to use our off-the-shelf products for initial tests, prototyping, and proof of concept, and then they will use our hardware as a reference in order to ruggedize that design. ‘They will take our proven hardware design, lay it out in the form factor they want, and then they’ll change-out certain components for mil-spec components,’ he says. The company ensures throughout the design process that it uses components that have a mil-spec equivalent. ‘It costs some effort on our part, and it doesn’t come easily, but it’s worth it in the end. Our military contractors can just do a simple one-to-one replacement, and they can go back to the component manufacturers and say “give me the footprint-compatible mil-spec component for that device,” and they will supply one.’ This swapping-out approach keeps the costs of the devices down, and most military contractors wish to re-arrange the devices anyway, he says, laying out the components in their own way. ‘They all have the capability of doing this; it’s not magic to them. They understand what we’re providing and what they need to do with it, but this approach is a far lower risk to them than if they were going to design the devices themselves,’ says Chamberlain.

A low light camera from e2v technologies of the type often integrated into armoured vehicles. Such devices are allowing military contractors to build vehicles with enhanced situational awareness and fewer windows

Strong, from Flir, does not believe that mil-spec components are as important as they once were, although he is quick to point out that operating environment requirements have not gotten any less stringent. ‘Ten or 20 years ago there were a lot of mil-spec components produced specifically for military applications, but the reality today is that, for the most part, industrial grade components meet or exceed military requirements. Basically we use whatever components are appropriate in order for the final product to be qualified to military standards,’ he says. One reason for the declining importance of mil-spec components, he adds, is that many modern imaging systems make use of FPGA processors: ‘What used to go on an entire circuit board now goes on a single FPGA, and there really aren’t any mil-spec FPGAs to speak of. The latest and greatest stuff is coming out in industrial temperature ranges, and it works just as well in a military environment. Instead, the key is to design [the device’s] thermal management so that the end product can be qualified to the relevant standard.’

While industrial electronic components are often sufficiently durable for military applications, some commercially available sensors are also capable of sufficient performance to replace their specially developed military counterparts – particularly where low cost is paramount. Palmer describes a trade-off in terms of the capability of the cameras selected by military contractors: ‘The standard Sony sensors are getting progressively more capable with low light imaging, and are also relatively small. The overall size of the camera system, therefore, gets smaller through using these sensors – which, for an armoured vehicle, is good; having breaks in the hull, or anything bolted to the outside is not popular. One of the downsides of meeting the customer’s specifications at low light levels is that the lens sensor required to undertake that level of light gathering is often larger than the customer would like,’ he says, adding that customers may choose to settle for compromised low-light performance in exchange for inexpensive wide-angle sensors with a very small footprint. For good low light performance, however, the sensor must be large in order to gather sufficient photons. ‘What we’ve found is that, because of cost cutting and changes to [the nature of] perceived threats, there’s a gradual move to accepting lower capability solutions,’ says Palmer, adding that the hot, dry climates of current warzones mean that thermal imaging is more effective than it would be in a damp European forest, and military customers choose the mix of cameras they install accordingly.

Military imaging is here to stay, but its cost and complexity mean that it may be some time before all armoured vehicles come with 360° multispectral imaging as standard. In the meantime, many existing vehicles are in need of upgrades. ‘Military vehicles and troop carriers out in the field today are, by and large, outfitted with analogue cameras. Various military organisations want to modernise their fleets of vehicles,’ says Pleora’s Chamberlain, adding that the company’s IP Engine products can be used to convert the analogue output and put it onto a GigE Vision network for distribution throughout the vehicle. ‘The cameras themselves are incredibly expensive, and Gigabit Ethernet provides an incredibly inexpensive way of modernising the vehicle.’ Ultimately, we can expect many more cameras to be integrated into new vehicles, covering all angles at several wavelengths, as designers look to further minimise the threats to soldiers on the modern battlefield.

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