LiDAR vs. Time of Flight (ToF) Sensors: Key Differences

lidar
time of flight
tof sensor
sensing technology
distance measurement

This article compares LiDAR and Time of Flight (ToF) technologies, outlining the key differences between LiDAR and ToF sensors.

Introduction

Various depth-sensing technologies exist, including Radar, Ultrasound, LiDAR, 2D cameras with NIR illumination, Stereo vision, Structured Light, and 3D Time of Flight (ToF). These technologies are used in diverse applications, with choices dictated by performance, accuracy, cost, response time, power consumption, and range.

Typical applications include:

  • Games
  • 3D movies
  • 3D scanning
  • User interface control
  • Augmented reality
  • Autonomous driving
  • Robotics
  • Gesturing
  • 3D printing
  • Enemy target detection
  • Premises security (monitoring surroundings)

What is LiDAR?

LiDAR, short for Light Detection and Ranging (also known as LADAR), uses a laser diode or LED to emit infrared light. The receiver employs a photo-receptor to detect reflected light rays. The time interval and phase of these reflections are used to calculate the distance to an object.

LiDAR systems use pulsed lasers to build a “point cloud” of the surface being measured. This point cloud is then used to create 3D images or maps.

LIDAR or LADAR Block Diagram

LiDAR is an optical sensing technique used to estimate the range and other parameters of a target. Different laser wavelengths are used depending on the target material. It commonly uses Near Infrared (NIR) and Visible Light (VL) frequencies to image objects.

What is a Time of Flight (ToF) Sensor?

A ToF sensor illuminates a scene with modulated light and captures the reflected light. It determines distance by measuring the phase shift between the emitted light and the received reflection.

ToF applications construct depth maps using an RGB camera, based on the reflected light detected from the target object or plane. It uses a solid-state laser or LED in the near-infrared range (around 850nm). An imaging sensor receives the reflected light spectrum and converts the photonic energy into electric current.

Time of Flight (ToF) measurement

The depth (d) can be calculated using the following formula:

d = c * ΔT / 2

Where:

  • c = Speed of light (3 x 10^8 m/s)
  • ΔT = Time interval between light emission and light received by the camera sensor

There are several methods to measure ΔT. The most common are the Continuous Wave (CW) method and the pulse-based method.

  • CW Method: Uses a periodic modulated signal source, typically a sinusoid or square waveform, for active illumination. CW ToF sensors measure the distance at each pixel by sampling the correlation function of the received and demodulated signals.
  • Pulse-based Method: The illuminating source emits a series of short light pulses. Reflected light pulses are captured in a series of short temporal windows using a sensor equipped with an electronic shutter.

LiDAR vs. Time of Flight (ToF) Sensor: Key Differences

The following table highlights the key differences between LiDAR and Time of Flight (ToF) sensor technologies:

Comparison ParametersLiDAR3D ToF Sensor
Operating PrincipleEmits laser signals and measures the reflection from an obstacle to calculate the time and distance.Illuminates a scene using a modulated light source and observes reflected light. Uses a solid-state laser or LED for illumination and an imaging sensor for reflected light detection. The photonic energy is converted into electrical current at the receiver.
RangeHigherMedium
Field of View (FoV)MediumHigh
ResolutionLow/MediumHigh
Accuracy of Distance MeasurementMediumHigh
Performance of Object ClassificationLowerHigher
Processing CostLowerMedium
Ultrasonic Sensor Calculator: Distance and Time

Ultrasonic Sensor Calculator: Distance and Time

Calculate distance and time using ultrasonic sensors. Understand the formulas for distance calculation based on round trip time and speed of sound.

ultrasonic sensor
distance measurement
time calculation
RF Capture Technology Basics: How It Works

RF Capture Technology Basics: How It Works

Learn the fundamentals of RF capture technology, including its features, working principles, and capabilities, for applications like detecting people behind walls.

rf capture
signal processing
sensing technology
LiDAR: Advantages and Disadvantages

LiDAR: Advantages and Disadvantages

Explore the advantages and disadvantages of LiDAR technology, including its applications in various fields like transportation, geology, and robotics.

lidar
3d mapping
remote sensing