Uploaded May 2021 | Updated September 2026, 1 week ago
The dictionary describes a focal point as that place where parallel rays of light passing through a lens are refracted to converge on a single point. That may apply to visible light for cameras and telescopes where light sources are uniform and lenses are high precision and usually multiples, but in the world of Chinese lasers things are a long way from that dictionary definition. The use of a single lens and then a choice of just two forms, plano convex and meniscus, is the first disadvantage. The simple spherical geometry of these lens forms will never achieve that dictionary perfection. The longer the focal length of the lens, the greater the imperfection. The single feature that ALL lasers beams posses is a non-uniform intensity profile. The perfect laser beam will conform to a Gaussian intensity distribution. ( a bell shape graph) where the central light intensity is many times greater than the outer regions of the beam. Combine the focussing weakness of spherical lens geometry with the non uniform intensity within the laser beam and we no longer have that idealized model of focus that we are all taught.
We set the focal point for a lens to that distance where we create the smallest burn spot or the thinnest drawn line. This is not setting the LIGHT focal point but that point where the the light INTENSITY is sufficient to damage the material we are marking/cutting . I clearly demonstrate that the traditional model of focus is of very limited value in our weird world of lasers.
The dictionary describes a focal point as that place where parallel rays of light passing through a lens are refracted to converge on a single point. That may apply to visible light for cameras and telescopes where light sources are uniform and lenses are high precision and usually multiples, but in the world of Chinese lasers things are a long way from that dictionary definition. The use of a single lens and then a choice of just two forms, plano convex and meniscus, is the first disadvantage. The simple spherical geometry of these lens forms will never achieve that dictionary perfection. The longer the focal length of the lens, the greater the imperfection. The single feature that ALL lasers beams posses is a non-uniform intensity profile. The perfect laser beam will conform to a Gaussian intensity distribution. ( a bell shape graph) where the central light intensity is many times greater than the outer regions of the beam. Combine the focussing weakness of spherical lens geometry with the non uniform intensity within the laser beam and we no longer have that idealized model of focus that we are all taught.
We set the focal point for a lens to that distance where we create the smallest burn spot or the thinnest drawn line. This is not setting the LIGHT focal point but that point where the the light INTENSITY is sufficient to damage the material we are marking/cutting . I clearly demonstrate that the traditional model of focus is of very limited value in our weird world of lasers.
