In the area of long-range measurement, the significance of minimizing beam divergence cannot be overstated. Every laser beam exhibits a specific degree of divergence, causing the beam diameter to expand as it travels over a distance. In an ideal measurement scenario, the laser beam’s size matches or is smaller than the target, creating a “beam-filling target.”
In this scenario, the entire beam energy from the LRF is reflected from the target, facilitating distance determination. Conversely, when the beam size is bigger than the target, a portion of the beam’s energy is lost beyond the target, which results in weaker reflections and performance decrease. Hence, in the context of long-range measurement, our primary goal is to maintain minimal beam divergence to maximize the number of reflections received from the target.
To illustrate the impact of divergence on beam diameter, let’s consider the following examples:
LRF with a divergence of 0.5 milliradians
Beam diameter @1 km: 0.5 meters
Beam diameter @10 km: 5 meters
Beam diameter @30 km: 15 meters
LRF with a divergence of 2 milliradians
Beam diameter @1 km: 2 meters
Beam diameter @10 km: 20 meters
Beam diameter @30 km: 60 meters
These figures show that the difference in beam size increases significantly as the distance to the target grows. It becomes clear that beam divergence has an important influence on the range and the ability to measure a target. This is precisely why, for long-range measurement applications, we use fiber lasers with a remarkably small divergence of 0.5 mrad. In our opinion, divergence is a key feature that strongly affects the performance of long-range measurements in real situations out in the field.
Insights: Beam divergence and beam size
Beam divergence is a specification that describes how the diameter of a laser beam increases as it travels away from the optical transmitter (Tx) of the laser module. We typically express beam divergence in milliradians (mrad). For example, if a LRF has a beam divergence of 0.5 mrad, this means that at a distance of 1 km, the beam diameter will be 0.5 meters. At a distance of 2 km, the beam diameter doubles to 1 meter. Conversely, if the beam divergence of a LRF is 2 mrad, the beam diameter will be 2 meters at 1 km and 4 meters at 2 km, and so forth.