Time of Flight Sensors

Introduction

A time of flight sensor measures range from the time a pulse takes to go to an object and come back. It is one of the two principles of Range Sensing.

How it works

The sensor sends a pulse and measures the time until the echo returns. The distance and the direction of the beam together give a part of a 3D spherical shell. The object is somewhere on that shell.

Key equations

The pulse travels to the object and back, so divide by 2:

$$\boxed{\text{Distance}=\frac{\text{Time of flight}\times \text{Speed in medium}}{2}}$$

The beam gets wider with distance:

$$\text{Beam diameter}=2\times \text{Distance}\times \tan (\text{beam angle})$$