ToF sensor for multi-object, -array scanning in mobiles

February 21, 2017 // By Graham Prophet
STMicroelectronics has released its third-generation laser-ranging sensor based on its FlightSense technology. The VL53L1 sensor uses new silicon- and module-level architectures, adding optical lenses to the module. These sensors are used in autofocus, presence-detection, and power-saving functions. ST says its VL53L1 offers “best-ever” Time-of-Flight sensor performance. Features include multi-target detection, cover-glass crosstalk immunity at long distance, and programmable multi-zone scanning. These advances deliver new levels of sensor performance to robotics, user detection, drones, IoT, and wearable applications. With a form factor of 4.9 x 2.5 x 1.56 mm, the sensor module integrates a new lens system, a 940 nm VCSEL (vertical cavity surface-emitting laser) invisible-light source, a processing core, and a SPAD (single-photon avalanche diode) photon detector. The addition of the optical lens system increases the photon detection rate to boost the module’s ranging performance. The embedded microcontroller manages the complete ranging function and runs digital algorithms to minimize host-processing overhead and system power consumption, maximizing battery life for mobile applications. “ST has already shipped hundreds of millions of Time-of-Flight sensors, which have been designed by OEMs into over 70 smartphone models as well as many other consumer devices,” said Eric Aussedat, General Manager of ST’s Imaging Division. “The third-generation FlightSense product uses its improved performance to support new applications, including human-presence detection, while continuing to improve sensor performance for existing use cases.” The VL53L1 performs a full measurement operation in as little as 5 msec for high speed applications. For autofocus applications in smartphones, the sensor detects objects twice as fast as earlier-generation devices. It has doubled the maximum ranging distance of sensors to beyond 4.5 metres, ensuring it is well matched to the hyper-focal distance of widely used 21-megapixel camera optics. The design architecture can detect multiple targets within the scene and also allows manufacturers to sub-divide the SPAD sensing matrix into custom-defined zones. These small zones can then provide spatial ranging information that the customer application can use for dual-camera computation in stereoscopy as well as simple depth-map use cases. In contrast to technology used by other ranging sensors, ST’s algorithms and direct Time-of-Flight architecture are immune to crosstalk at longer distances making the VL53L1 fully compatible with a larger selection of cover-glass materials and design artwork than before. The I²C-based VL53L1 module comes with a full package of software drivers and documentation for quick and simple integration. “ST has already shipped hundreds of millions of Time-of-Flight sensors, which have been designed by OEMs into over 70 smartphone models as well as many other consumer devices,” said Eric Aussedat, General Manager of ST’s Imaging Division. “The third-generation FlightSense product uses its improved performance to support new applications, including human-presence detection, while continuing to improve sensor performance for existing use cases.” STMicroelectronics; www.st.com