Sony Corp. and Prophesee S.A. have jointly developed a stacked event-based vision sensor with the industry's smallest 4.86μm pixel size and the industry's highest 124dB (or more) HDR performance.

The new sensor and its performance results were announced at the International Solid-State Circuits Conference (ISSCC) held in San Francisco in the United States.

The new stacked event-based vision sensor detects changes in the luminance of each pixel asynchronously and outputs data including coordinates and time only for the pixels where a change is detected, thereby enabling high efficiency, high speed, low latency data output. This vision sensor achieves high resolution, high speed, and high time resolution despite its small size and low power consumption. This accomplishment was made possible by combining technical features of Sony's stacked CMOS image sensor, resulting in small pixel size and excellent low light performance that are achieved by the use of Cu-Cu connection, with Prophesee's Metavision event-based vision sensing technologies leading to fast pixel response, high temporal resolution and high throughput data readout.

In addition to the 4.86μm pixel size, the sensor also delivers 1/2 type, 1280x720 HD resolution by achieving high density integration with a fine 40nm logic process.

The 124dB (or more) HDR performance is made possible by placing only back-illuminated pixels and a part of N-type MOS transistor on the pixel chip (top), thereby allowing the aperture ratio to be enhanced by up to 77%. High sensitivity/low noise technologies Sony has developed over many years of CMOS image sensor development enable event detection in low-light conditions (40mlx).

The newly developed sensor is suitable for various machine vision applications, such as detecting fast moving objects in a wide range of environments and conditions.

The Cu-Cu connection technology that provides electrical continuity via connected Cu (copper) pads when stacking the back-illuminated CMOS image sensor section (top chip) and logic circuits (bottom chip). Compared with through-silicon via (TSV) wiring, where the connection is achieved by penetrating electrodes around the circumference of the pixel area, this method gives more freedom in design, improves productivity, allows for a more compact size, and increases performance.

While a frame-based sensor outputs entire images at fixed intervals according to the frame rate, an event-based sensor selects pixel data asynchronously using a row selection arbiter circuit. By adding time information at 1μs precision to the pixel address where a change in luminance has occurred, event data readout with high time resolution is ensured. Furthermore, a high output event rate of 1.066Geps has been achieved by efficiently compressing the event data, i.e. luminance change polarity, time, and x/y coordinate information for each event.