Radar VS Lidar 1

• Radar 

- A sensor technology that detects and tracks objects using electromagnetic waves that have longer wavelengths than infrared rays.
- It uses reverberation, that is, when it shoots radio waves, it hits and reflects the surrounding object, which gives information such as the direction in which the object is located, the distance to the object, the size of the object, etc
- Also used to measure the direction and speed of moving objects by sending multiple waves.

 

Echo radar	- It operates in the manner described above. - Data collected from two or more mounted echo gauges can be used to obtain additional information (e.g., angles) related to the location of the object.
Doppler radar	- Enhances the function of the echo radar by analyzing the phase of the wave. - Processed by tracking a particular wave and detecting differences in the position, shape, or shape of the reflected wave.

 

• Merits and Demerits of Radar 

- It detects long-range (250 m) objects and can measure the location and speed of the detected objects using the Doppler.
- More and less poor performance for non-metallic objects and narrow opening angles.
- When a car is driving at a high speed, the opening angle is reduced to maximize the distance from objects.

- When driving at a low speed, such as when driving in the city, by reducing the distance and maximizing the opening angle, it is possible to detect objects that are around, including pedestrians and bicycles.

 

• Lidar

- Unlike radars that use radio waves, Lidars use pulsed laser light sources.
- High resolution and capable of detecting non-metallic objects.
- When the transmitted laser pulse hits the object, it is reflected back to the sensor.
- At this time, it calculates the distance to the object by measuring the travel time of the pulse.
- It can shoot laser light sources at speeds of hundreds of thousands of pulses per second.
- Multiple vertical pulses (channels) are sent in a single scan, and the height of the object can be measured.
- It is used in cognitive algorithms such as noise filtering and object recognition.

 

• Components of Lidar

Laser diode	Create laser beam
Photodiod	Receive reflected signals
Servo-mounted mirror	Adjust the laser beam vertically and horizontally
The reflected signal is collected by the Photodiode and processed by the signal processing unit of the sensor. The sensor outputs the detected object in the form of a series of point clouds. For each pixel, the measured distance and location are expressed in 3d coordinates of the sensor reference.

 

• operating principles of the Lidar

1. The generated laser pulse passes through a tilting mirror that rotates with a servo motor.
2. This mirror may be inclined to transmit pulses at various vertical angles.
3. Optical rotary encoders provide feedback to servo motors to accurately control the mirror.
4. The reflected signal is collected by the description-detector in front of the photodiode and processed by the signal processing unit of the sensor.

 

• Merits and Demerits of Lidar

- Beamwave is narrow and reaches long distances, appropriate for high resolution 3d mapping.
- Stable day and night detection by measuring the intensity of received infrared light.
- Laser beams are highly sensitive to the environment because they reflect even small particles such as fog and dust, and produce more noise than Radar on bad weather days.