Lasers use a beam of light to engrave or etch information directly on the surface of a variety of materials.
When the beam exits the laser system it passes through an f-theta lens which focuses the light to a small point suitable for marking. This point where the beam is focused perfectly is called the focal point.
The distance from the lens to the focal point is called the focal distance or working distance.
There is a small amount of distance above and below the exact focal point where the beam is still focused enough to make a good looking mark. This is called the focal range. This varies from laser to laser.
Each f-theta focusing lens has its own unique focal length, which determines:
1. The focal distance. This is how far away the lens must be from the material being marked.
2. The marking window. This is the amount of surface area on the material that the laser can mark.