Driving imaging innovation
Jessica Rowbury reports from an automotive session at the Image Sensors conference in London, which included speakers from Valeo Systems, BMW, Melexis and Jaguar Land Rover
It is not just safety but position sensing, speed and temperature monitoring, among other applications, that has driven the requirement for cameras and image sensors in the automotive sector, according to speakers at the Image Sensors 2014 conference in London on 20 March.
‘The number of applications for cameras in cars is quickly increasing,’ said Cliff de Locht, image sensors marketing manager for Melexis in Belgium. And, cars will be equipped with more and more of them in the near future, according to Dr Thomas Niemczyk, system architect for BMW in Germany: ‘The amount of cameras and image sensors in the car will increase tremendously in the next few years.’
But, experts also stated that as sensors are set to increase, there needs to be increased communication between OEMs, Tier 1 supplies, and image sensor vendors to meet all the specifications required in an automotive camera system. Professor Patrick Denny, senior research engineer for Valeo Systems in Ireland, commented: ‘There is a clear lack of understanding among these three parties [OEMs, Tier 1 suppliers and sensor integrators] in an industry that has started to have the largest growth in image sensors of an application. It is being used in life and death situations in vehicle, and people really need to talk to each other and we need to bridge this gap.’
According to Denny, the specification guidelines from OEMs to sensor manufacturers are not clear enough, which is part of the reason why the technology is not matching stringent requirements from OEMs. ‘It is very difficult for OEMs close to vehicular end customers to articulate their needs,’ he said. ‘One of our OEMs comes to us and tries to describe an application, but it is very hard to express it in a language where he leads us into the application and gives us boundaries. It is very difficult for sensor vendors to understand what is required, and it is very difficult for us [Tier1] to mediate.’
This is similarly the case where sensor vendors often design a chip without understanding the specific application or requirements. ‘On the other end you have the sensor suppliers who, in the past, would come and say “we have a security camera chip − can you do something with it?” And it doesn’t really work well.’
By 2015, all cars sold in the USA will be required by law to have a rear-view camera. This has been sparked by statistics that more than two children every week in the USA are fatally injured on the road. The cause of this in part has been due to the design of many modern vehicles that give very low rear-view visibility to the driver (see figure 1). ‘With some of the SUV vehicle you can put many children behind the car without seeing them,’ said Denny in his presentation.
Figure 1: Comparision of rear-view visibility between old and new car designs. Credit: Prof Patrick Kenny, Valeo Systems/ Image Sensors 2014
Currently, the newer premium cars, such as those from Land Rover and BMW, typically have forward looking cameras located at the front of the car, surround cameras at the side of the car, and rear-view cameras at the back of the car. The integration of cameras, without compromising the aesthetics of the car, is important, according to Niemczyk: ‘Cameras are becoming a design issue. The design of every car is different, and there are very special needs for every OEM.’
For BMW, the integration of cameras into the side mirrors of a car is a challenge due to limited room, as shown in figure 2. ‘What can be inside such a mirror and the available space for the camera is very small. We are constantly asked to make the camera smaller,’ explained Niemczyk. ‘There are quality issues; how it has to be resistant to water and dust for example. This will be a big challenge in the near future.’
Figure 2: The side mirrors have limited space to integrate camera systems. Credit: BMW/Image Sensors 2014
Martin Edney, lead system engineer for Jaguar Land Rover in the UK agreed that, as the number of cameras in cars increase in the near future, their integration will become more difficult. ‘Adding more sensors to the vehicles is a major challenge,’ he said at the conference. ‘Particularly with a design driven company that like to put sensors behind bodywork.’
This requirement from OEMs has led to a decrease in the size of packaging, which has led to problems caused by excess heat. ‘As we are always moving smaller and smaller to hide these cameras from the customer, this is then increasing the heat inside the camera,’ said Edney.
The issue of heat is a major challenge for Tier 1 suppliers and image sensor vendors, emphasised Valeo Systems’ Denny: ‘Denser packages with enhanced image signalling processing were squeezed into smaller housings with other electronics and power supplies. This resulted in greater heat experienced at the imager,’ he outlined. And, environmental temperatures that the camera has to withstand also add to this problem. ‘The typical automotive temperature range is -40°F to +85°F,’ Denny added. ‘So, if you add another 15 degrees for the actual electronics, you’re up to above 100°F. When you add certain applications, you have to add an extra 20°F. So you’re into very difficult territory.’
The perspective of the OEMs was that they wanted image sensor manufacturers to come up with a solution that would not affect the size. ‘We don’t want to have to add extra components to keep them cool,’ stated Jaguar Land Rover’s Edney during his presentation. ‘We want clever techniques to be able to manage our own thermal heat.’
Another major requirement that OEMs were demanding at the conference was high dynamic range (HDR), the ability of a camera system to image both bright lights and dark shadows in the same scene. ‘We will never again touch an image sensor with no HDR,’ declared BMW’s Niemczyk. Edney of Jaguar Land Rover also agreed that this was a vital feature for its customers: ‘We need to be able to see complex scenes going through tunnels, humans in the entrance to car parks.’
However, Denny of Valeo Systems was concerned that the necessity for HDR by image sensor vendors was being underestimated, and gave an example: ‘A CTO of a large sensor company asked me if HDR was important in the automotive sector. I was shocked by this.’ The importance of having HDR was demonstrated by a photograph comparing the visual effects with and without HDR (see figure 3). ‘If you’re in a garage and you’re looking out − if there is no HDR you’re blind.’
Figure 3: Comparision of a garage scene with (right) and without (left) HDR enabled. Credit: Patrick Kenny, Valeo Systems/ Images Sensors 2014
The ranges of brightness in a single scene that camera systems have to deal with are shown in figure 4, which highlights the factors that the image sensor vendor has to overcome. At the conference, it was mentioned by Land Rover Jaguar that OEMs would still like to see this capability improved. ‘We still see issues here with the [HDR] technology today,’ Edney said.
Figure 4: Graph demonstrating possible brightness variations in the same scene. Credit: Patrick Kenny, Valeo Systems/ Images Sensors 2014
According to a report from Smithers Apex, the market for Advanced Driver Assistance Systems (ADAS) is predicted to grow by 50 per cent CAGR until 2018, rising to $165 billion in the next five years. This suggests there will be a huge market for image sensor technology in the automotive sector in the coming years.