Optical positioning theory, if the distance can be measured, then the location can be determined. Visible light, infrared light, laser, and other light sources that can measure the distance between the light source and the receivers, can also be used for positioning purposes. They have a variety of applications in practical scenarios.
Visible Light Positioning Technology
Visible light communication technology (VLC) can realize Internet information transmission. Generally speaking, the Light Fidelity technology is taking all kinds of the visible light as the signal source. The controller turns the light on and off, to control the communication between the light source and the terminal receiver. Among them, visible light positioning technology based on LEDs is widely used:
- LED-ID positioning method
- TOF (Time of Flight) positioning method
- RSSI (Received Signal Strength Indication) positioning method
The LED-ID positioning method assigns a fixed ID to each LED. Then the receiver determines its position by obtaining the ID information in the signal. The accuracy of this positioning method mainly depends on the layout of the LEDs. Increasing the number of LEDs can effectively increase the accuracy, but the complexity of the corresponding algorithm will also increase. It can be used for presence location, like checking whether a receiver is in a room.
TOF location method uses LED time information sent to a receiver, and the information time difference allows the measurement the distance, which then uses triangulation and other methods for positioning. The main difficulty of this method is that the chronometers of the transmitter and receiver must strictly align. The accuracy can be within a centimeter.
The RSSI positioning method measures the distance between the detection point and LED by receiving the received signal strength. It can achieve a more accurate positioning effect without any requirements of sender and receiver chronometers. It has a simple structure and is easy to realize. It is a widely used indoor visible light positioning method.
The main problem with visible light positioning is that the light can easily be blocked, and there are many limitations in practical use.

Infrared Positioning Technology
There are two kinds of infrared positioning technology:
The first is that the target to be located uses an IR Locator, which emits a modulated infrared ray. The infrared ray is received by a positioning sensor installed in the room.
The second is to cover the space to be measured by several pairs of transmitters and receivers. The transmitters and receivers weave an infrared net to locate a moving target.
At present, it is only suitable for the accurate positioning and recording of the trajectory of simple objects in the laboratory and the tracking of indoor self-propelled robots.
Computer Visual Positioning
The visual positioning system is divided into two categories. One is to determine the position of the sensor by collecting images of moving sensors. Based on the selection of different reference points, it can be divided into referencing a 3D building model, image, predeployed target, target projection, referencing other sensors, and no reference, which is called SLAM (Simultaneous Localization and Mapping). It can also be used to determine the position of a target in an image with a fixed position sensor.
Referencing 3D building models and images means comparing them with the existing building structure database and pre-calibrated images. To improve the robustness, referencing the pre-deployed target uses a specific image sign (such as a QR code) arranged as a reference point. Referencing the projection target is to project the reference point in the indoor environment based on the reference to the predeployment target. Referencing other sensors allows for the combination of other sensor data to improve accuracy, coverage, or robustness.
The other catagory is to use image recognition to compare the real-time image information with the database and then perform positioning. The disadvantage is that image processing is timeconsuming and has poor real-time performance.
SLAM technology is widely used in autonomous driving and robot control.
Infrared Positioning Advantages
- Relatively high accuracy
- Locate moving target
Infrared Positioning Disadvantages
- Short transmission distance
- Poor penetration ability
- Complex layout
- High cost
Explore the Whitepaper: Introduction to the Basic Principles of Positioning Technology