The future of CCD image sensors: the end of an era?

Question: CCD sensors have been the key enabler of the imaging and machine vision market, with Sony being the largest vendor of CCDs to this market. What has driven this decision?

Williamson: Before the CCD arrived video cameras were based on tube technology which were free running only and came from the broadcast industry. When CCD technology launched it became possible to add specialist features in cameras to enable triggering and hence the ability to synchronise to the production line. This enabled the explosive growth of industrial vision which developed into the industry we know today. However, while Sony CCDs have the largest market share in industrial imaging, the biggest market for image sensors has been larger markets such as consumer cameras, mobile phones, CCTV and broadcast. The importance of the CCD to mankind was recognised by a Nobel prize in Physics in 2009. In the last few years there has been a big shift from CCD to CMOS in these high-volume markets which has left the CCD wafer line very underutilised even with the high number of machine vision sensors sold. This makes the factory no longer financially viable.

Question: Historically CCD sensors have outperformed CMOS sensors in terms of image quality. Will Sony's decision reduce the availability of high image quality sensors?

Williamson: Absolutely not, CMOS has traditionally had a reputation for lower image quality; however, recent sensors have surpassed the image quality of Sony CCDs in terms of noise and dynamic range. This, coupled with the numerous advantages of CMOS sensors such as speed, lower power consumption, less support electronics and the elimination of tap balancing is the natural evolution of technology. The higher end CCDs from ON Semiconductor (formerly Truesense and Kodak) and the full frame CCDs used in professional photography from Teledyne DALSA are still available for high-end applications although over time CMOS will affect this market segment also.

Question: Are there other advantages of CMOS over CCD technology?

Williamson: From a manufacturing point of view CMOS sensors can be built on standard wafer lines which utilise mainstream manufacturing capacity and competition. From a technical point of view the ability to mix sensor and support circuits on to one device simplifies camera design and allow additional features to be integrated. Multiple regions of interest, and linear scaling of frame rate versus readout region provide application flexibility and high dynamic range modes, additionally the reduction in oversaturated image bleed makes the cameras more tolerant of changing illumination.

Question: What is the share of CCD cameras compared with CMOS cameras Stemmer Imaging is selling today?

Williamson: In 2010, 22 per cent of cameras we sold were based on CMOS sensors. This has risen to 58 per cent in 2014 with 32 per cent of cameras using Sony CCDs and the remainder other high-end CCDs. With nearly all new camera designs using CMOS the prediction is that in a further 4 years the natural shift would make the CMOS market share approximately 80 per cent.

Question: What is your expectation of how Sony's decision will change that ratio in the future?

Williamson: Although Sony has announced the closure, production will not cease until 2017 with the last deliveries in 2020 or even later, depending on the sensor model. This time scale is designed to follow the natural declining trend which is expected to continue and maybe slightly accelerate. With the attractive price to performance ratio of new CMOS cameras new designs are expected to use CMOS anyway.

Question: What are Stemmer Imaging's plans with regards to the announcement?

Williamson: While Sony CCD availability will continue until at least 2020 the camera manufacturers will need to commit to quantities much earlier. Each camera manufacturer may choose to take a different approach, to commit to stock sensors or asking customers to make future commitments. Stemmer Imaging are liaising with all our camera manufacturers to agree their policy and we will communicate this policy if it has any effect on availability to customers. Some models will be available even after 2020.

Question: What is your advice for imaging and machine vision integrators and users that have used CCD cameras in the past?

Williamson: If you build an OEM product that utilises a CCD camera we believe there is no immediate need to change the camera. If there is any risk of your particular camera being made obsolete we will inform you normally with 6 months notice under our End of Life programme. However, when selecting a product for a new application we would recommend selecting CMOS sensor-based cameras as availability will be longer and also the price to performance ratio will be better. If CCD capability is important remember CCD sensors are available from other companies.

Question: Are Sony leaving the machine vision sensor market by discontinuing its CCD sensors?

Williamson: Sony have been innovating with CMOS sensors for some time and are investing significantly in expanding their CMOS wafer production capability. They have announced their first CMOS global shutter sensor family under the Pregius name aimed directly at the imaging and machine vision market. The first model named IMX174 is already shipping in a number of our cameras and outperforms the Sony CCD equivalent. With a clear roadmap of further models we will still see Sony sensors in the machine vision market.

Question: Which other players are in the imaging and machine vision sensor market?

Williamson: Over the last 10 years we have seen many small companies launch CMOS image sensors addressing the low-cost or high-speed market where CCDs could not compete. In recent years a number of these have become significant providers through a combination of innovation and acquisition. While Sony has been the dominant supplier of CCDs to the imaging and machine markets, this dominance is not evident with CMOS giving more market choice. Key players besides Sony are ON Semiconductor, CMOSIS, e2v and Teledyne DALSA. Our direct relationship with Teledyne DALSA allows us influence over their sensor strategy so customer needs are valuable input.

Question: With so many manufacturers and sensors how do I choose what's right for my application?

Williamson: Like any product each manufacturer's design has advantages and disadvantages. Stemmer Imaging has an in-house EMVA 1288 camera testing facility which is used to characterise cameras and hence the sensors beyond the spec sheet. With this capability, our immense knowledge of sensor and camera technologies and access to the largest number of camera manufacturers and possibly all sensors relevant to our market we are well placed to advise customers as to the sensors and cameras that are best suited to their application. When you are ready to migrate to the new generation of CMOS sensors we are here ready to assist.

For further information about machine vision system products from Stemmer, please visit www.stemmer-imaging.co.uk.