An automatic zoom lens system for laser cutting with no need of optical axis readjustment has been developed to overcome drawbacks of conventional single-lens (fixed-focal-length lens) laser machine, which requires lenses with different focal lengths for different thickness of materials. Different focal lengths are realized by a combination of basically the three lenses of an enlargement optical lens and condenser optical lenses. It is a conbination of practical lenses, which can be mostly ready-made lenses, and no special lenses like aspherical lenses are used. The different of focal length is determined by the positional relationships of the lenses. We designed a test machine based on the theory of this lens combination and made a CNC-driven zoom lens processing optical system.
To verify the effect, we compared the cutting of this system with the conventional single-lens (fixed-focal-length) laser cutting. As a result, we have found the quality of the cutting of this system is much the same as that of a single-lens laser cutting from the viewpoint of optical performance, cutting properties on kerf of width, surface roughness, etc.