ToF ranging sensor detects PC user presence

By Majeed Ahmad, contributing writer

The FlightSense time-of-flight (ToF) ranging sensor from STMicroelectronics will be incorporated into the Intel Context Sensing technology that aims to facilitate PC data security as well as reduce power consumption and improve user experience.

STMicro’s ToF FlightSense technology employs miniature and low-cost sensors to provide ranging and proximity sensing for highly accurate distance measurements. Unlike traditional infrared (IR) ranging sensors, which rely on the reflected signal strength and cannot directly measure distance, the ToF sensor works by measuring the time taken by a photon to travel from the sensor, reflect from a target, and be received again by the sensor.

The ToF sensor is hidden behind a cover glass in the bezel of a laptop while it monitors the user’s presence in front of the PC. When a user leaves the PC, the ToF sensor detects the absence, immediately locks the system, and directs it into the Windows Modern Standby low-power state. The ToF sensor itself also enters into a low-power autonomous mode, scanning the scene for the user to return while keeping the PC asleep to save power.

When the user returns, the ToF sensor wakes the laptop and automatically enables facial recognition to log in without waiting for a key press or mouse movement. Here, ST’s patented algorithm can distinguish an immobile person sitting in front of a PC from an inanimate object like a chair. That circumvents the reliance on video analytics from the power-hungry and potentially intrusive webcam.