STMicroelectronics VB56G4A global-shutter image sensor

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STMicroelectronics is enhancing vehicle safety with its latest global-shutter image sensors for driver monitoring systems (DMSs). DMSs continually watch the driver’s head movements to recognise signs of drowsiness and distraction, enabling systems in the vehicle to generate warnings that can preserve the safety of occupants.

The VB56G4A global-shutter sensor leverages ST’s in-house investment in manufacturing advanced 3D-stacked back-side illuminated (BSI-3D) image sensors, which are claimed to be smaller and more sensitive than conventional front-side illuminated (FSI) sensors typically used in first-generation DMSs. Global-shutter sensors offer advantages over rolling-shutter imagers, the company says.

By simultaneously exposing all pixels to the image, a global-shutter sensor allows simple synchronisation with NIR illumination, improving the illumination-subsystem power budget. Moreover, the sensor achieves high quantum efficiency (QE), reaching 24% at 940 nm near-infrared wavelength, with linear dynamic range up to 60 dB. This enables a simple, low-power, non-visible LED emitter to provide adequate illumination for the sensor. Operating outside the visible spectrum also ensures consistent response in day or night driving and in bright or overcast conditions.

The sensor’s high QE, combined with a pixel size of just 2.6 µm, helps optimise total power consumption and camera size. In addition, integrated automatic exposure control eases use and simplifies the application-software design by minimising system interaction with the sensor.

The sensor also provides flexible operating modes that help optimise system features and performance. These include programmable sequences of 4-frame contexts, illumination control outputs synchronised with sensor integration periods, an input for an external frame-start signal, automatic dark calibration, dynamic defective-pixel correction, image cropping and a mirror/flip-image readout.

External connections include eight programmable general-purpose I/O (GPIO) pins and a dual-lane MIPI CSI-2 transmitter interface operating up to 1.5 Gbps/lane. The sensor can operate at up to 88 fps at full resolution and typical power consumption is 145 mW at 60 fps.

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