What Measurement Technologies Are Used in Laser Rangefinders?
DISTO distance measurement by Leica is based on the phase measurement principle. The laser diode emits pulsed light with a defined wavelength and pulse repetition frequency. Due to the difference in transit time between the internal reference path and the external measurement path, there is a phase shift between the target reflected pulse light received by the Leica DISTO and the pulse light received via the internal reference path. The phase shift of these two signals is proportional to the distance between the instrument and the target.
Brief Discussion on the Measuring Principles and Methods of Laser Rangefinders
The ranging principle of laser rangefinders can basically be summarized as measuring the round-trip time of light traveling to the target. The distance D is then calculated using the speed of light c=299792458 m/s and the atmospheric refractive index n. Since direct time measurement is difficult, the phase of continuous waves is usually measured; such instruments are known as phase-shift rangefinders. Naturally, there are also pulse rangefinders. It should be noted that phase measurement does not measure the phase of infrared or laser light itself, but the phase of the signal modulated onto the infrared or laser beam. Handheld laser rangefinders used in the construction industry for housing surveys operate on this identical principle.
