What Is a ToF Sensor?
A ToF sensor is a sensor that measures distance based on the time it takes for a pulse of light to be reflected back from the surface of an object.
ToF sensors measure time and convert it into distance, so that the detection accuracy can be maintained at a constant level regardless of the distance.
ToF sensors are used to measure the distance to an object, as a level sensor, to locate and position objects, and to check the number of people in a space.
Uses of ToF Sensors
1. Recognition for VR and AR
ToF sensors are used for VR (Virtual Reality) and AR (Augmented Reality) recognition, which have become popular in recent years, because of their accurate measurement of distance from the object, enabling images to be displayed with a more three-dimensional effect.
2. Monitoring
ToF sensors can be used as level sensors to monitor machine lifts, monitor the amount of material remaining in tanks, check warehouse inventory, check the amount of material remaining in rolls, and check the availability of materials in automated warehouses.
3. Confirmation of Workpiece Seating
ToF sensor is used to confirm that a workpiece is seated on a jig in a production line.
4. Confirmation of the Number of Persons in a Space
The number of people in a specific space can be counted by the 3D ToF sensor. The distance to an object is converted into data, and AI is used to determine the number of people by identifying them.
5. Measurement of Object Dimensions and Volume
3D ToF sensor can be used to measure the dimensions of each part of an object and measure its volume.
6. Smartphone Face Recognition Function
Since ToF sensors can capture the image of an object in three dimensions even in dark areas and enhance the autofocus function, their application to face recognition functions in smartphones is expected to increase in the future.
Principle of ToF Sensors
The principle of the ToF sensor is relatively simple. First, a laser diode inside the sensor projects modulated near-infrared light. The near-infrared rays that hit the object and are reflected return to the light-receiving element in the sensor. The phase difference between the emitted and reflected near-infrared rays is converted into a time difference, and multiplied by the speed of the emitted light to determine the distance.
In addition to measuring the phase difference, there is also a method of directly measuring the time difference, which is superior to other sensors in that the ToF sensor can maintain constant detection accuracy regardless of distance and can operate with good depth accuracy even in dark environments.
Infrared or near-infrared light is often used for lasers, but it depends on the sensor, and some wavelengths are harmful to the human eye, so care must be taken depending on the application.
In the case of infrared or near-infrared lasers, the measurement point cannot be visually confirmed. A separate scope, guide laser, or other device is required to check whether the laser is irradiating the object.
Types of ToF Sensors
There are two types of ToF sensors: 1DToF and 3DToF.
1. 1DToF Sensor
1DToF sensors measure the distance from a sensor to a specific point. They are used in motion sensors and level sensors that measure the amount of liquid or powder.
2. 3DToF Sensor
3DToF sensors can acquire distance information with an image, just like a camera. It measures the distance to an object in the entire space.
Other Information About ToF Sensors
Advantages of ToF Sensors
1. Long-Distance Installation Is Possible
ToF sensors can be installed at a distance from an object because they can detect with high accuracy even at a long distance. They can be installed in locations that avoid the lines of movement of people and robots. For large objects such as automobiles, multiple ToF sensors can be installed for positioning from multiple directions.
2. High Degree of Freedom of Installation
The sensor itself is compact and can be installed in a small space. The irradiation direction can also be freely selected, such as up and down, horizontal, or diagonal.
3. Independent of the Surface Condition of the Object
The ToF sensor performs high-speed sampling and averaging processing, allowing stable detection regardless of the object’s color, material, etc., even if the amount of light received is insufficient.