Introduction – From Daily Life to Core Technology
Have you ever wondered how your iPhone unlocks with Face ID, or how a robot vacuum knows there’s a wall in front of it?
Behind these everyday smart experiences is a powerful depth-sensing technology called Time-of-Flight (ToF).
What Is a Time-of-Flight (ToF) Sensor?
A Time-of-Flight (ToF) sensor is a distance-mapping technology that measures the time it takes for a light signal (usually infrared) to travel to an object and return to the sensor. Based on the speed of light, it calculates the precise distance and depth, creating a 3D map of the environment.
A typical ToF system includes an emitter (sends light) and a receiver (detects reflected light).
How Does a ToF Sensor Work?
The Basic Principle
Just like bats use echolocation, a ToF sensor sends out light, waits for it to bounce back, and calculates distance from the time delay.
Distance = (Speed of Light × Time) / 2
Types of ToF Sensors: dToF vs iToF
Direct ToF (dToF)
dToF measures the exact time delay of each light pulse. It offers high accuracy and long range, ideal for LiDAR and automotive systems.
Indirect ToF (iToF)
iToF measures the phase shift between emitted and received light waves. It’s compact and perfect for smartphones and indoor robotics.
ToF vs Stereo Vision vs Structured Light
| Feature | ToF | Stereo Vision | Structured Light |
|---|---|---|---|
| Low Light | Excellent | Poor | Good |
| Range | Medium–Long | Short–Medium | Short |
Where Are ToF Sensors Used?
- Smartphones: Face ID, AR, Bokeh
- Robotics & Drones: Obstacle avoidance, SLAM
- Automotive: Driver monitoring, gesture control
Frequently Asked Questions
Does a ToF sensor work in the dark?
Yes. It uses active infrared light.
Is ToF the same as LiDAR?
No. ToF is the principle; LiDAR is a specific implementation.
What is the range of a ToF sensor?
From centimeters to several meters, depending on design.