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ISE 2011 showcases diverse image sensing technology

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'The European image sensor market is vibrant and diverse, with strengths in R&D and novel applications.' These were the closing remarks made by Lindsay Grant, Imaging Division process manager at St Microelectronics, at Image Sensors Europe 2011. Grant was a co-chair at the image sensors conference, which took place from 22-24 March in London, UK and covered market analysis, novel sensor applications, system architecture, and developments in large-area sensors.

Two presentations focused on sensor technology developed for positron emission tomography (PET), a nuclear medicine imaging technique, which can be used to locate tumours inside the body, for instance. Dr Edoardo Charbon, professor of microelectronics at Delft University, The Netherlands, spoke about the SPADnet project, a Seventh Framework programme that aims to develop large-area image sensors and build ring-assembly modules for PET imaging. The sensor technology builds on that developed in the earlier Megaframe project, which was a single photon avalanche diode (SPAD) array integrated into a CMOS platform.

Current PET devices typically use analogue photomultipliers that are large, high voltage detectors compared to their digital counterparts. The digital silicon photomultiplier (SiPM) developed in SPADnet has a high optical timing resolution, able to detect photons in 50ps bursts. Charbon commented that he hopes the detector will eventually have a clinical use and that the developments in SiPM technology will contribute to the adoption of radio-guided surgery. However, the fill factor of the sensor is around 15 per cent, which, according to Charbon, is not high enough for PET and is an area of ongoing research in the SPADnet project.

Dr York Hämisch, senior director at Philips Research Laboratories, presented on a sensor developed at the laboratories suitable for PET scanners. This project is on the brink of application. The sensor has a fill factor of 50 per cent and Dr Hämisch explained that one of the big advantages with digital SiPM technology is its much lower power consumption compared to analogue photomultipliers. However, he commented that the cost of the digital machines would have to equal that of the analogue technology for its uptake in industry.

Elsewhere during the conference, Dr Yang Ni, CTO at New Imaging Technologies (NIT), spoke about NIT's logarithmic image sensor using a photodiode, called Magic. The logarithmic design means it has a particularly wide native dynamic range (120dB), which is especially useful for daytime imaging, where the sensor could be required to image in bright sunlight and deep shadows. Dr Ni admitted that very low light imaging at night would be more of a problem as the sensor operates with a similar performance to a linear sensor under these conditions. He said that imaging in traffic and transport or video surveillance are applications where the sensor would be particularly suited – the frame rate could be slowed to operate at night, but the image wouldn't be lost in the beam of a car's headlights, for instance.

Dr Sami Khawam, CTO of RICAtek in the UK, presented on a smart Image Signal Processor (ISP), which has additional image processing capabilities compared to standard ISPs. The product is easier to program than FPGAs and GPUs and can be used to run face recognition algorithms, for instance. Dr Sandro Tedde, research scientist at Siemens in Germany, discussed organic photodiodes (OPDs) and their potential use in X-ray radiography, while Dr Renato Turchetta, CMOS sensor design group leader at Rutherford Appleton Laboratory in the UK, and Jan Bosiers, R&D director at Teledyne Dalsa, both gave presentations on large-area sensor technology.

The next ISE will be held in London on 20-22 March 2012.