How Do Laser Range Finders Work?

by Les Moore

Laser rangefinders are used for finding distances between two points. The accuracy and distance parameters vary depending on the product and price. Laser rangefinders are not as precise as more complicated methods of measurement, but they are useful in situations where a small amount of error is acceptable.


Light travels at a constant speed, which makes it useful as a method of measurement. Lasers generate a powerful, highly coherent beam of light. Laser rangefinders take advantage of the physical properties of this light in order to generate their measurements. Laser rangefinder manufacturers make their tools to various degrees of accuracy for different purposes.


This method of laser measurement uses the light beam's time-of-flight to calculate the distance. A laser sends out a light pulse and measures the amount of time it takes for the pulse to bounce back. The time-of-flight method is best used for large distances and has an accuracy of a few centimeters.

Phase Shift

The phase shift laser is good for longer distances, but not as accurate. It uses an intensity-modulated beam to determine distance. When the beam returns from the target, a comparison between the modulations of the sent light and the reflected light is used to determine the distance. It is sometimes mistaken for the time-of-flight method because the phase shift is mathematically related to the time of flight and the light beam's frequency.

About the Author

Now living in Arizona, Les Moore has written reports of motorcycle races for "Cycle News" and "Midwest Motorcycling" since 1969. He has provided technical and procedural data for the Intra and Internet. Moore received a Certificate of Drafting from San Jose Community College in 1982.

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  • photo_camera Laser Entfernungsmesser image by Otmar Smit from