How does time of flight sensing measure distance?

At Sensor Expo 2017, John from ST Microelectronics explains the FlightSense principle for his company’s time of flight (ToF) sensor to show how it can be used to measure distance from an object. The ToF chips emits a tiny beam of laser light from its emitter (a Vertical Cavity Surface-Emitting Laser (VCSEL) that hits a target and the light bounces back that a single photon avalanche diode (SPAD) sensor integrated in the chip detects when the photons arrive. The travel time divided by 2 (sent and received time) and multiplied by the speed of light provides the distance from the source to the target. Distances from several centimeters up to 2 meters can be measured. The relatively low power device consumes from approximately 60 to 600 microamps and provides accurate distance measurements with even very low target reflectance.

Housed in a 4.4 x 2.4 x 1.0-mm package with an embedded microcontroller, the VL53L0X is one of the smallest if not the smallest laser-ranging package on the market today. The device operates in high infrared ambient light levels and includes advanced embedded optical cross-talk compensation to simplify cover glass selection. It is ST’s second generation FlightSense patented technology.

Using a single power supply and no additional optics, the ToF sensor has an I2C interface for device control and data transfer with a programmable I2C address. It is a Class 1 laser device that is compliant with the latest standard: IEC 60825-1:2014 – 3rd edition.

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