Principle of operation of LIDAR technology

Triangulation LIDAR

YDLIDAR

When the laser beam irradiates an object that is at the minimum measurable distance, the receiver‘s optics focuses the reflected radiation on pixel N. The reflected radiation from an object at the maximum measurable distance is focused on pixel 1. The distances and angles between the laser, the sensor‘s optics and the sensor itself are precisely defined, allowing the use of goniometric equations to calculate the distance between the object and the LIDAR. LIDAR uses an infrared laser with a wavelength of 793 nm.

The principle of operation shows that most of the sensor's pixels are used to measure smaller distances, so the LIDAR measures smaller distances more accurately. For example, for the image above with a sensor with 2048 pixels, approximately 1200 pixels (1pixel = 1.67mm) are used for a range up to 2m, and 848 pixels (1pixel = 9.43mm) are available for a range of 2 to 10m.

In a real LIDAR, the distances and angles are chosen to allow the distance measurement in the required range, for example, for Ydlidar G4 it is 0.28 to 16m with an accuracy of ±20mm for distances <1m and ±2% for a range of 1...8m.

A sensitive sensor can be "blinded" more easily, therefore this type of LIDAR is more suitable for indoor use with an illumination intensity of up to 550 Lux, above 2,000 Lux there is already a risk of damage to the sensor. The exception is the Ydlidar X4 Pro, which also works at 2,000 Lux lighting and its maximum is 40,000 Lux.

Time of Flight LIDAR (ToF LIDAR)

YDLIDAR

The laser periodically emits short light pulses in the infrared region. The light reflected from the object is detected by a photodetector. LIDAR measures the time between the emitted pulse and the time when the reflection was detected. LIDAR uses an infrared laser with a wavelength of 905 nm.

YDLIDAR

Max. measurable distance is defined by the period T, Dmax. = 0.5cT and the signal/noise ratio. The minimum measurable distance is limited by the accuracy of the time measurement.

If we compare, for example, the accuracy of the LIDAR TG30 and G4, we find out that the G4 is more accurate up to a distance of 3m and TG30 is more accurate for longer distances.

The photodetector has a significantly higher resistance to "blinding" than the sensor used in triangulation LIDARs. It typically works up to 70,000 Lux, and can withstand a maximum of 100,000 Lux. It is therefore more suitable for working in an outdoor environment.

2D LIDARs in SOS electronic’s offer

We have included 2D lidars from Ydlidar in our offer. Available models can be found on our website.

Meaning of important parameters

The upper part of the LIDAR (in which the laser, photodetector and optics are located) rotates, so the field of view (Horizontal FoV) is 360˚. The rotation speed is typically 5...12 revolutions/s (Motor Frequency) and is adjustable using PWM or a command via the UART interface. The measuring frequency (Ranging Frequency) is in the range of 3,000 to 20,000 Hz depending on the type and is not adjustable. At a frequency of 3,000Hz and 6 revolutions/s, the lidar makes 500 measurements per revolution (360˚). This results in another parameter, angle resolution. For this case, the angular resolution is 360/500=0.72˚. The meaning of the other parameters is obvious.

How to start with LIDAR

Each lidar development kit contains the LIDAR itself, a converter from the LIDAR interface (UART, PWM) to USB and a USB cable. For the Windows operating system, you will need to install the VCP drivers for the CP2102 and download the LidarViewer (TOOL) from the Ydlidar website.

For Linux testing, you will need to install ROS (Robot Operating System) for your Linux distribution, download SDK and driver source codes for a specific LIDAR from the Ydlidar site, compile and install them. See the user manual for details.

We have extended our product offer by the YDlidar range of sensors measuring the distance that have the greatest potential to be successful in many current and future applications. Choose from the range of products available directly from our warehouse. We will be happy to provide you with other LIDARs upon order in a short time and under favourable conditions. You can find more technical information about the individual sensors directly on our website.

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