IISW Summary from TechInsights

The International Image Sensor Workshop 2023 offered an excellent overview of sensors past, present and future

John-Scott Thomas PhD, TechInsights (Image Sensor Subject Matter Expert)

After a long hiatus courtesy of COVID, the International Image Sensor Workshop (IISW) 2023 was held in-person at the charming Crieff Hydro Hotel in the highlands of Scotland from May 21-25. With over two hundred attendees by my count, the workshop presented a lively and informative forum for image sensor devices past, present and future. TechInsights was honored to open the meeting with a presentation on the state-of-the-art in small pixel (mobile) devices. With fifteen minutes available only the briefest overview was possible, and we focused on the technologies that enable the transition to the 0.56 micron pixel pitch (Samsung and OmniVision) and 0.70 micron (Sony) pixel pitch. You can read the TechInsights paper here.

Sony (presented by Masatak Sugimoto) then described the structure of a two-layer image sensor where the photodiode and transfer gate of the pixel is placed on one semiconductor layer and the reset, source-follower, and select transistors are placed on a lower layer. This structure allows optimization of the two layers with different processes for each and pushes the current limits of hybrid bonding. This was all the more interesting as TechInsights located a Sony sensor using 2-layer transistor pixels (in the Xperia 1V smartphone) as the workshop began. We’ll have plenty more analysis in our channels for this world-first device. Samsung (Sungsoo Choi) and OmniVision (Chung Yung Ai) then presented further technical details of the 0.56 micron pixels the two companies are producing. The first session was rounded out with another Samsung (Minho Kwon) presentation on a switchable resolution sensor and an onsemi (Vladi Korobov) surveillance sensor optimized for low light and Near Infra-red (NIR).
Following sessions discussed noise and pixel design. The Automotive session focused on High Dynamic Range, and a presentation by Manual Innocent (onsemi) shared an impressive video clip showing an automotive camera emerging from a dark tunnel to bright sunlight with excellent image quality using  a 150 dB sensor. Automotive cameras will be a high growth segment and are particularly suited to sensing outside the visible spectrum. More exotic applications included X-ray sensors, Ultraviolet and Short Wavelength Infrared sensors, discussed later in the conference. The final two sessions covered Time of Flight and SPAD sensors; already used in mobile applications, these are promising technologies in surveillance and automotive devices.

Of particular note were the discussions about digital image processing, artificial intelligence, and cybersecurity. There was general agreement that future devices will have much more digital processing included in the stacked Image Signal Processor, although many attendees felt most of the image processing should be performed on the applications processor when possible since this device uses a more advanced process node. The younger attendees showed a significant interest in digital image processing through their presentations, posters, and questions; a sign of things to come no doubt. This was highlighted by the two invited speakers. Charles Bouman (Purdue University) provided an overview of the abilities of computational imaging and emphasized the need for more dialogue between the image sensing community and the digital processing community. Jerome Chossat (STMicroelectronics) presented trends analysis clearly showing there will be plenty of computational power available in future stacked image sensors.

A banquet concluded the workshop – complete with a starlit (electric, of course) hall, bagpipes and kilts. Neil Dutton (STMicroelectronics) opened the evening and in general provided excellent management of the sessions. Boyd Fowler (OmniVision) presented awards to the best papers and posters, and finally three awards to seasoned veterans of the image sensor world. John Tower was recognized for his contributions to Image Sensor publications, Takeharu Goji Etoh for his sustained contributions to High Speed Cameras and Edoardo Charbon for imaging using SPAD arrays. Edoardo showcased an amazing video clip of a light pulse travelling through air and bouncing from mirrors. If you haven’t seen this before, you really should check it out.

Much of the value at a workshop happens with the conversations that take place out of session and at the many social events happening beyond formalities. This event reminded me of the importance of in-person meetings. TechInsights will continue to participate and watch this exciting field for further innovation. The International Image Sensor Society intends to provide all of the workshop papers on their website in the next few weeks.

You can also read the TechInsights paper here.