Laser device for tempering metal-containing or metal-oxide-containing coatings on large-area glass substrates having at least: a) at least one laser source, b) at least two bridges spanning a conveyor belt with the glass substrate, wherein each bridge contains a plurality of optical arrangements, which are alternatingly arranged on the bridges, each optical arrangement generates a laser line, and the laser lines of all optical arrangements together cover the entire width of the glass substrate.