As the technologies are advancing, the future is swiftly moving towards the commercialization of self-driving cars. Light detection and ranging (LIDAR) – sometimes called as time of flight (ToF), or LADAR (Laser Detection and Ranging), laser radar or laser sensor – is a sensing method, which detects and senses objects and maps their distances.
The automotive LiDAR sensor technology with an optical pulse, illuminates a target and measures the characteristics of the mirrored return signal. In the optical-pulse, the width-range can vary from a few nanoseconds to quite a few microseconds.
Detection and Imaging of LiDAR in Autonomous Cars
As per an analyst review, the manufacturers are now supplying a wide range of modern cars with advanced sensing and control functions. Avoidance systems and collision warning, lane-keeping assistance, blind-spot monitors, adaptive cruise control, and lane departure warning are examples of established features automated certain driving tasks by assisting drivers in order to make driving an easier and safer experience.
Automotive LiDAR sensor, ultrasonic sensor, cameras, and radar have their own niche set of benefits and disadvantages. Typically, a highly or fully autonomous vehicle makes use of multiple sensor technologies to generate an accurate short and long-range map of the environment around a vehicle. This range-map is created under a range of lighting and weather conditions. Although the technologies are complementing each other, having a sufficient overlap to improve safety and increase redundancy is also important. The concept of using multiple sensory technologies is sensor fusion, which creates a reliable and accurate map of the vehicle’s surroundings.
Primarily, ultrasonic sensors are used for short-range object sensing. This is because the ultrasonic waves suffer from solid attenuation in air beyond a few meters.
Cameras are easily available and cost-efficient sensors. However, as they depend strongly on the ambient light conditions, they require significant processing to extract useful information. Cameras are one of the most unique technology sensors with its best-of-a-kind feature to “see color.”
The Comparison of Radar and Automotive LiDAR Sensor
Radar and automotive LiDAR sensors share a broad array of complementary and common features that can map-range surroundings and measure object velocity. The comparison of these two technology sensors in several categories is as follows:
Radar and automotive LiDAR sensors’ distance ranges to detect objects varies from a few meters to more than 200 meters. For automotive LiDAR sensor, detecting objects at close distance is difficult. Whereas, radar can sense objects from less than a meter to more than 200m. However, this range totally depends on the system type,
- Short range radar
- Medium range radar
- Long range radar
This is where automotive LiDAR truly shines owing to its short 905m to 1,550m wavelength, ability to collimate laser light. The spatial resolution of infrared (IR) light on the order of 0.1° is possible with automotive LiDAR sensor. Thus, without any significant backend processing, this spatial resolution allows for extreme high-resolution 3D classification of objects in a scene. Besides, the wavelength (4mm for 77GHz) of radar struggles to resolve small features, specifically as distances increase.
Field of View (FOV)
Radar and solid-state type of automotive LiDAR sensor have excellent horizontal FOV (azimuth). Also, the mechanical automotive LiDAR systems type have a 360o rotation, which possess the widest FOV of all the technologies of Advanced Driver Assistance Systems (ADAS). Automotive LiDAR sensor has better vertical FOV (elevation) than radar.
Radar systems’ one of the biggest benefits is their robustness in snow, fog, and rain, fog. On the other hand, the performance of automotive LiDAR sensor generally degrades under such weather conditions. However, using the IR wavelengths of 1,550nm helps automotive LiDAR sensor to achieve better performance under adverse weather conditions.
In modern-day cars, the mainstream use of radar is made possible by increased integration, which reduces the cost as well as system size. Over a few years ago, the mechanical scanning of automotive LiDAR sensor is found to be bulky. Although, advances in technology have shrunk automotive LiDAR sensor over the years. Hence, the industry shift to solid-state automotive LiDAR sensor will further shrink system size.