What is Lidar? How does Lidar work in self driving cars?

Self Driving Car Using Lidar
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      According to Merriam-Webster dictionary," A device that is similar in operation to radar but emits pulsed laser light instead of microwaves"

     In simple words, LIDAR - Light Detection and Ranging is a technology which uses laser light beams to know the distance of the of the objects surrounding it instead of microwaves used in Radar.

     Lidar uses a sensor which shoots eye safe laser beams at very high speed -150,000 beams per second through a camera which collide with the surrounding objects and reflect back to a sensor. The sensor measures the time required for the laser beams to reflect back to it. It also uses the speed of light to calculate the distance.The result is a 3-dimensional map of the surrounding or the target object and the characteristics of its surface.

Lidar System Working
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     Lidar  systems are very beneficial to self driving cars.The self driving cars have a sensor on their roof, which spins and shoots infrared laser beams which are not visible to human eyes in 360 degrees and calculates the time required for the beams to reflect back.Thus it is able to measure the distance between itself and the objects around it, which object or person is near and which objects are at a distance.The lidar than creates a 3-dimensional map of the surrounding which is sent to the car's computer who makes prediction of the moving objects and  directs how or in which direction the car should move.

      The Lidar technology has been helping us since years before it was used in self driving cars. Lidar has many other applications other than self driving cars. Lidar technology can be used for mapping the density of a dense forest, knowing the height of the trees. It is also beneficial for mapping the topography of a river bed, a farm or a city. Here the scanning is done by flying a plane with Lidar technology over a specific area through which a 

3-dimensional map of that area is created which is further used to study that area in factors such as distance between the plane and the building, sea level etc.

3-Dimensional Map Of a City
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Solid State Lidar Systems
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      There are many such applications of lidar systems. As it shoots infrared laser beams, its wavelength is shorter. This helps to image the matter which is of the same or larger wavelengths. Thus, it can detect pollutants such as sulphur dioxide, carbon dioxide and methane.This study helps the researcher to create a pollution density map of a area. These were some of the many applications of the lidar technology.

      Now coming back to self driving car, you might have seen there is a sensor or bulky 'thing' on the roof of the car which spins fast and scans the area surrounding it by shooting laser beams which are reflecting back, which helps in calculating the distance of the close objects. But would you like a bulky thing on the roof of your car. So, thus came Solid State Lidar Systems. In these systems, the whole sensor need not to spin, shoot laser beams and receive, rather just a small mirror inside the system which spins and does the same job, making the whole system more compact.

      Lidar is a very complex technology which has many applications. It has been for use since years and also is beneficial for the self driving cars thus bringing our dream of self driving into reality.