Abstract: When a laser beam is focussed onto a substrate for the purpose of substrate processing, the optical units such as beam expander, deflecting unit, and optical imaging device prescribe the range of depth of focus in which it is possible to work with a minimum spot size. The difficulty of boring thin holes, especially in thick substrates, is overcome with a second laser beam that is widened via a second beam expander and likewise focused onto the substrate via the deflecting unit and the optical imaging device. The position and the length of the second range of depth of focus can be varied by selecting the magnification of the second beam expander or by maladjustment. Thin holes can also be bored into thick substrates by using the two laser beams one after another.

Abstract: When a laser beam is focussed onto a substrate for the purpose of substrate processing, the optical units such as beam expander, deflecting unit, and optical imaging device prescribe the range of depth of focus in which it is possible to work with a minimum spot size. The difficulty of boring thin holes, especially in thick substrates, is overcome with a second laser beam that is widened via a second beam expander and likewise focused onto the substrate via the deflecting unit and the optical imaging device. The position and the length of the second range of depth of focus can be varied by selecting the magnification of the second beam expander or by maladjustment. Thin holes can also be bored into thick substrates by using the two laser beams one after another.