How it works
3D laser scanners work by emitting light and detecting the reflection of the light in order to accurately determine the distance to the reflected object. Rather than making a single point measurement as the traditional instruments (i.e. total stations), 3D laser scanners have rotating mirrors (or the entire unit rotates) that allow millions of measurements to be made over a scene in just a few minutes. There are two primary types of laser scanners: time-of-flight scanners and phase-shift scanners. The time of flight scanners are capable of surveying at longer ranges (up to 150m) where the latter can reach distances of up to 45m although being capable of surveying much quicker (each set up takes a few minutes).
Immediately after one pulse is received and measured, the scanner transmits another optical pulse slightly horizontal (or vertical - depending on the scanner) to the previous pulse using a rotating mirror. This process is repeated thousands of times per second, thus generating distance values for millions of points on a reflected surface. From the distance and the orientation of the laser pulse, the xyz co-ordinates associated with each reflected pulse can be determined. In addition, the intensity of the returned pulse is determined. In general, light coloured objects and closer objects give a higher reflection compared with darker objects and objects further away thus giving a photographic quality because of the intensity values.
Together, the xyz co-ordinates and associated intensity values for millions of data points output by the laser make up the point cloud which is then processed to produce drawings or 3D models or directly put into software packages like Inventor, PDMS that accept such a file format.