The lenses use to concentrate the laser beam in CO2 laser machines. There are many lens options and these depend on the laser wavelength, power, focal length, etc … . That is why there is so much variety of optical elements. We will find several types of lenses that can use: concave convex, flat-convex . Normally in our machines, we use the flat-convex.

What is the focal length?

Focal length is one of the parameters that define the lens. When the laser beam concentrate, an inverted double cone effect occurs, where the center point between the 2 cones (junction point) becomes the focal point or spot. The size of the focal point is directly proportional to the focal length of the lens. And inversely proportional to the diameter of the beam at the lens inlet.

The distance between the underside of the lens and the focal point is called the focal length and is measured in inches. The greater the focal length, the greater the depth of field. In this way, a short focal lens is ideal for cutting fine materials or making engraving. Since the point is smaller, there is more energy concentration. And we can achieve a greater definition of marking / engraving.

On the other hand, a lens with a greater focal length (from 2.5 ″) will be perfect for cutting thick materials. The cut will be straight due to a smaller divergence of the laser beam. If we try to cut fine materials, we will find that it has a lower concentration of energy and low resolution in the marking, so it will not be adequate.

For the wavy material, on the other hand, a long focal lens will go very well because, having greater depth of field, in the highest and lowest areas you can cut evenly, however with a short focal lens, the cut will not be uniform.