STMicroelectronics launches global-shutter image sensors to improve DMS performance

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Semiconductor developer STMicroelectronics has released details of its latest global-shutter image sensors for driver monitoring systems (DMSs).

DMSs continually watch a driver’s head movements to recognize signs of drowsiness and distraction, enabling systems in the vehicle to generate warnings that can preserve the safety of occupants. Traffic agencies estimate that about 95% of road-traffic accidents result from human error, many of which could be avoided using systems such as DMSs.

“Drivers may not realize that they are unsafe to drive due to tiredness or distraction. DMS removes uncertainty by detecting the problem automatically, which protects all occupants as well as others traveling on the road,” said Eric Aussedat, EVP and Imaging Sub-Group GM at STMicroelectronics. “Our latest global-shutter sensors deliver sensitivity and compactness, simplifying DMS hardware and reducing the overall system cost. This enables our customers and partners to deliver high-performing and reliable DMS systems reaching the legislation expectations.”

The company’s VB56G4A global-shutter sensor has leveraged in-house investment in manufacturing of advanced 3D-stacked back-side illuminated (BSI-3D) image sensors. These are more sensitive, smaller and more reliable than conventional front-side illuminated (FSI) sensors typically used in first-generation DMSs.

Global-shutter sensors offer notable advantages over rolling-shutter imagers. By simultaneously exposing all pixels to the image, a global-shutter sensor allows simple synchronization with NIR illumination, improving the illumination-subsystem power budget. Moreover, the sensor achieves high Quantum Efficiency (QE), reaching 24% at 940nm near-infrared wavelength, with linear dynamic range up to 60dB. 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 2.6µm, helps optimize total power consumption and camera size. In addition, integrated automatic exposure control eases use and simplifies the application-software design by minimizing system interaction with the sensor.

The sensor also provides flexible operating modes that help optimize system features and performance. These include programmable sequences of four-frame contexts, illumination control outputs synchronized 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 1.5Gbps per lane. The sensor can operate at up to 88 frames per second (fps) at full resolution and typical power consumption is 145mW at 60fps.

ST is supplying samples of its new sensor to lead customers now and mass production is scheduled for the beginning of 2023 for adoption in model year 2024 vehicles.

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Lawrence has been covering engineering subjects – with a focus on motorsport technology – since 2007 and has edited and contributed to a variety of international titles. Currently, he oversees Automotive Powertrain Technology and Professional Motorsport World magazines as editor.

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