Technology insights

Time-of-Flight principle

For range-finding and distance sensing, Time-of-Flight (ToF) is very powerful when emitting light rather than sound. Compared to ultrasound, it provides far greater range, faster readings, and greater accuracy whilst still maintaining small size, low weight and low power consumption characteristics.
structured light sensor camera Time-of-Flight principle

Time-of-Flight (ToF) sensors are used for a range of applications, including robot navigation, vehicle monitoring, people counting, and object detection. ToF distance sensors use the time that it takes for photons to travel between two points to calculate the distance between the points.


The Time-of-Flight principle (ToF) is a method for measuring the distance between a sensor and an object, based on the time difference between the emission of a signal and its return to the sensor, after being reflected by an object. Various types of signals (also called carriers) can be used with the Time-of-Flight principle, the most common being sound and light.

TeraRanger sensors use light as their carrier because it is uniquely able to combine higher speed, longer range, lower weight, and eye-safety. By using infrared light we can ensure less signal disturbance and easier distinction from natural ambient light, resulting in the highest performing distance sensors for their given size and weight.


All Time-of-Flight (ToF) sensors measure distances using the time that it takes for photons to travel between two points, from the sensor’s emitter to a target and then back to the sensor’s receiver.

Indirect and direct ToF both offer specific advantages in specific contexts. Both can simultaneously measure intensity and distance for each pixel in a scene.

Direct ToF sensors send out short pulses of light that last just a few nanoseconds and then measure the time it takes for some of the emitted light to come back. Indirect ToF sensors send out continuous, modulated light and measure the phase of the reflected light to calculate the distance to an object.

Direct And Indirect Time-of-Flight principle


Time-of-Flight principle Technology distance sensor


Time-of-Flight (ToF) sensors are used for a range of applications, including robot navigation, vehicle monitoring, people counting, and object detection.

ToF sensors in people counting

Conventional imaging systems are great for capturing basic information about an object or a scene but fail to give an accurate impression of distance. Human perception is such that we can often intuit the depth of field in a photograph and understand – albeit vaguely – how far away the sensor is positioned from the subject. Autonomous systems like people counters and motion detectors have no such luxury. They rely on the Time-of-Flight principle to calculate the distance between a sensing element and the subject/s of interest.

Time-of-Flight (ToF) sensors have proven a revolutionary concept in people counting applications worldwide. With the utmost precision guaranteed and unique considerations in place regarding personal privacy and data protection, ToF sensors enable people counting applications which offer superb insights into a variety of key business metrics, from periodic occupancy counting to space optimization.

Time-of-Flight principle For People Counting


Time-of-Flight (ToF) is a powerful technology for accurate, affordable distance and depth-sensing technology.

Small and lightweight

ToF sensors are the small size and light weight while ensuring high performance level (a TeraRanger Evo weighs just 9g!). This means that sensors can be placed in locations not previously possible when using larger, heavier sensors. For smart buildings and level monitoring, this is a real advantage!

Long range

Despite their small size and light weight, tof distance sensors pack a powerful performance punch! TeraRanger Evo can measure distances at up to 60m range. And this is done with LED technology, not a laser! (See section on LED illumination.)

Fast refresh rates

ToF sensors are optimized for high-speed readings. In addition to being small and lightweight, high data refresh rates are central to our design ethos, making the sensors ideal for fast-moving applications, from counting people to industrial automation.

Led illumination

Instead of using laser emitters we use Infrared LED technology. This brings a number of important benefits.

  • Eye-safety: TeraRanger sensors remain eye-safe in all conditions, with no need for Laser Class 1 safety precautions!
  • Field-of-View: Rather than measuring a very small point, we can allow the emitted light to spread and form a Field-of-View. In many applications, this can be a distinct advantage. Imagine a sensor trying to detect a tree. With a laser, you might detect the leaves, or pass through the gaps and detect something much further away. In a robotics safety or anti-collision situation, this could spell disaster. With TeraRanger technology you are far more likely to detect the hazard you want to avoid. Generally, at 1m to the target, a TeraRanger One sensor is measuring an area approximately 4cm by 4cm.
  • Power consumption: Compared to some laser devices, LED’s consume far less power; something all users relying on battery-power will enjoy.

Related products

Terabee People Flow Counting L-XL

GDPR compliant people counting device. Optimize value and reduce costs from your retail operation, smart building or office space
Using advanced Time-of-Flight technology, Terabee People Flow Counting L-XL is GDPR compliant and provides accurate people counting data (98% accuracy or more) by monitoring the number of people entering and exiting doorways or corridors.

Easy to configure and install on high ceilings, the Terabee People Flow Counting L-XL fits any kind of wide indoor entrance, up to 15 meters in a multi-device setup. Our people counting algorithm is capable of filtering out static objects and counting multiple people passing in both directions below the device as they enter or leave a space.

The solution consists of an IoT people counting device and an optional IoT platform. Two product variations allow transmission of the data via Power over Ethernet or LoRaWAN. Interested? Contact us.

Terabee People Flow Counting M 2.0

Get real-time people counting data for single doorways and narrow corridors
Real-time data is the backbone of our modern, fast-paced world especially when it comes to monitoring space usage, occupancy, energy efficiency, security, building performance or tailored services. The Terabee People Flow Counting M 2.0 device is GDPR compliant by design, with a real-time data capability, providing seamless, accurate, and highly effective footfall measurement, at a competitive price.

Using Time-of-Flight technology, the People Flow Counting M 2.0 solution guarantees anonymity in its operations, prioritizing data privacy protection while offering robust, reliable occupancy monitoring.

People Flow Counting M 2.0 is the perfect addition to your Building Management System. The “smaller sibling” of People Flow Counting L-XL, People Flow Counting M 2.0 is designed for smaller doorways and narrow corridors. It comes in both Power over Ethernet (PoE) and LoRa models to best suit your needs.

Terabee 3Dcam 80×60

3D Time-of-Flight depth camera
Purchase from Reseller
Enable the third dimension with an 80 × 60 pixel resolution and 74° × 57° Field-of-View. The 3D Time-of-Flight camera benefits from a robust aluminum casing while still offering a compact (83 grams) and discrete design. It is easy to set up and to stream depth data via the USB interface on Windows or Linux OS. Terabee 3Dcam 80×60 comes with an OpenNI-based SDK, C/C++ samples, Python samples, and ROS package.

The Terabee 3Dcam 80×60 is no longer available. You can purchase available stock from our Reseller partners using the link below.

Terabee 3Dcam VGA

Versatile, lightest, smallest and most affordable industrial-grade ToF depth camera in its class
Purchase from Reseller
The latest addition to Terabee’s Industry 4.0 offering, 3Dcam VGA combines price, performance and versatility to come out a winner. Robust, IP65- and IP67-rated, this device is the smallest, lightest and most affordable industrial-grade Time-of-Flight 3D camera in its class.

With the widest Field-of-View (90° × 67.5°), VGA resolution (640 × 480 pixels) and as a Class 1 laser product, Terabee 3Dcam VGA is a key component in industrial automation and industry 4.0 solutions. It is suitable for applications such as logistics, mobile robotics, human-machine interaction, level monitoring, smart agriculture and people and movement detection.

Its onboard computing and open software platform mean you are free to use existing code libraries and to run applications on the edge for even greater process efficiency.

The Terabee 3Dcam VGA is no longer available. You can purchase available stock from our Reseller partners using the link below.

TeraRanger Evo 60m

Extra long-range ToF distance sensor (60 m)
Purchase from Reseller
TeraRanger Evo 60m is our longest range Time-of-Flight sensor. Thanks to its 60 meter detection range within indoor environments, it is often used as a range finder, navigation and collision-avoidance tool for robotics and for materials stock level sensing.

The TeraRanger Evo 60m is no longer available. You can purchase available stock from our Reseller partners using the link below.

TeraRanger Evo 3m

Close-range ToF distance sensor
Purchase from Reseller
With its 10 cm to 3 m range, fixed 100 Hz update rate and greater accuracy, TeraRanger Evo 3m is perfectly suited to close-range distance sensing applications at higher speed. Applications include, presence and proximity detection, object detection/counting and robot navigation. All in a small and lightweight form-factor.

The TeraRanger Evo 3m is no longer available. You can purchase available stock from our Reseller partners using the link below.

TeraRanger Neo ES

TeraRanger Neo ES - Extra compact, low-power ToF distance sensor
Purchase from Reseller
The TeraRanger Neo ES provides the best combination of small size, low power consumption and distance ranging on the market. Weighing only 6 g and consuming just 50 mA, it can measure distances up to 30 m. Its flat front panel and rectangular shape greatly simplify mechanical integration. The sensor is ideally suited for applications where space and power need to be conserved, such as drone navigation and collision avoidance, and other battery-powered range finding solutions. It also delivers high performance outdoors in bright sunlight.

The TeraRanger Neo ES is no longer available. You can purchase available stock from our Reseller partners using the link below.
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