How It Works A laser rangefinder works by emitting laser beams to measure the distance between an object and the receiver. The speed of light is a known number, and the rangefinder uses this along with the time it takes for the laser beam to reach the object and bounce back to calculate the distance. Laser rangefinders use a highly accurate built in clock to measure the time taken from when the laser is emitted to when it returns back to the receiver aperture. The laser beams are also emitted in pulses to prevent the chance of jamming and to help generate more accurate data. Also, with the use of Doppler Effect, technologies can identify if the object is moving away or towards the receiver in the case that the object is not still. "The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842."   https://opticsmag.com/wp-content/uploads/2020/07/How-a-rangefinder-works-1024x685.jpg The precision of a range finder depends on the rise and fall time of the laser pulse. A laser rangefinder that uses very sharp laser pulses and has a very fast detector, usually military grade rangefinders, can be accurate to a few millimeters. Rangefinders emit very narrow beams, however over long distances they eventually begin to spread due to the divergence of laser beams. The quality of the rangefinder is defined on how far the beam can travel before begging to spread. Many factors contribute to the spread of the beam as the distance is increased. One factor is the presence of air bubbles in the air that act as lenses causing the beam to wander. Another factor is leaves and branches that are in the way of the object that is intended for ranging, as the beam becomes more spread out parts of the beam can be reflected off leaves and branches causing and early return and an inaccurate ranging. Below is a figure that shows what happens to the beam over distances:                                                                                                                                                                                                                                                                    http://precisionrifleblog.com/wp-content/uploads/2013/10/rangefinder-beam-divergence-at-1000-yards.jpg?w=640                             http://precisionrifleblog.com/wp-content/uploads/2013/10/rangefinder-beam-divergence-diagram1.jpg

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