Frequently Asked Questions
Image provided by Phoenix Aerial Systems
How does Velodyne's LiDAR work?
Velodyne’s 3D, real-time LiDAR sensors measure distances by measuring the Time of Flight (TOF) that it takes a short laser pulse to travel from the sensor to an object and back, calculating the distance from the known speed of light. Combining multiple laser/detector pairs (up to 64) into one sensor and pulsing each at 20kHz allows for measurements of up to 1.3million data points per second.
Vertical fields of view of 30° to 40° (depending on model) are covered with full 360° horizontal field of view by rotating the laser/detector pairs up to 20 times per second.
In addition to each distance measurement, Velodyne’s LiDAR sensors also measure calibrated reflectivities that allow for easy detection of retro-reflectors like street-signs, license-plates and lane-markings.
What is the difference between a camera sensor and a LiDAR sensor?
Cameras measure light reflected from an object into the camera. Images are typically in color and display a visual image of the surrounding similar to what the human eye experiences. Unlike LiDAR, Camera images do not measure distance in three dimensions. Cameras work in a number of controlled scenarios, but are ultimately unreliable as single data source. Camera data is typically directional, meaning it’s only into one direction compared with Velodyne's LiDAR sensors, which have full 360° coverage. Cameras are easily blinded by oncoming light or don’t see anything in twilight or shadows. Cameras cannot distinguish important items at a distance, such as traffic signals. Velodyne's LiDAR sensor are independent from such environmental factors as the LiDAR sensor itself illuminates the objects while avoiding any environmental influences by means of spectral and temporal filtering.
What are the different kinds of LiDAR available on the market today?
There are high-functionality and low-functionality LiDAR sensors. Velodyne's high-functionality sensors are unique as they use multiple laser beams (patented technology) to measure its environment in 3D very fast and accurate, ideal for quick detection, mapping and localization. Since each laser beam is matched to the numerical aperture of the detector, minimum power consumption is needed, which is especially useful in power conscientious mobile applications like backpack systems and for the use on Unmanned Aerial Vehicles (UAV/Drone). Also, since the lower power lasers allows for precise reflectivity measurement to quickly locate lanes, street signs, etc... This technology is very mature and thousands of Velodyne's proven concept, real-time 3D LiDAR sensors are deployed world-wide measuring distances and calibrated reflectivities in mission critical applications.
Flash LiDAR is a lower functionality alternative technology that illuminates a narrow field of view with one big flash while measuring the time it takes for the reflected light to return to a sensor array and calculate the individual distances. Flash LiDAR requires a much larger and more costly light source to illuminate the whole scene while only a fraction of the light that is reflected into the direction of the sensor is detected by the individual pixels, hence a lot of the illuminating light is wasted which makes Flash LiDAR not only a bulky but also an energy in-efficient technology. Flash LiDAR requires 6 or more sensors to achieve a full 360° view. Also, the bright flash that is needed to illuminate objects in the far distance blinds objects that are much closer thereby eliminating the possibility to measure reflectivities meaningfully.
Solid State approaches are experimental , and in the early stages of research. Especially for distance measurements above 20 meters with meaningful field of views, no proven concept has been offered as a commercial solution, and it is doubtful any will emerge in the near future due to challenges based on the fundamental laws of physics. Future sensors would be only directional and therefore multiple sensors would be needed for a full surround view if this technology ever matures to a commercially useful level.
How important is abundant data and good resolution for object detection?
Different applications require different demands on the data quality, however it is universally accepted that an abundance of data is absolutely necessary for the most reliable object detection. While LiDAR sensors with only one or a few laser channels can give a general indication that an object is in front of the sensor, Velodyne's data rich point clouds allow for the highest level of object recognition in real-time. The real-time aspect is of uttermost importance here as sensors with only one or few laser channels might be able to accumulate data over time, however that is not sufficient in real-world applications for localization and safety-related data for critical real-time safety decisions. Only Velodyne's LiDAR 3D data is abundant enough to make those life saving determinations within the short amount of time available.
Velodyne's wide field of view (up to 360°) allows not only to make object recognition decisions for objects directly in front, but also towards objects on the side and rear. LiDAR data can discern a person from streetlight standing on the curb, as well as identify a fast-closing object from the sides or rear. The surround view capability is a major advantage of Velodyne's sensor in terms of object recognition and safety when compared with mostly directional, limited field of view, limited laser count sensors.
How well does Velodyne LiDAR work in snow?
Velodyne's LiDAR sensors work well in snow, sleet, and rain. The multiple beam approach of Velodyne's LiDAR sensors with laser beams with millions of laser beams at different angles enables to find "holes" in-between the snowflakes to "see" the environment. An inferior LiDAR with only one or a few laser beams would not work as well as one with 16, 32 or 64 laser beams.