Device for inscribing or marking of objects using laser beam

The invention relates to a device for labeling or marking of objects by means of laser beam according to claim. 1

The marking of articles, in particular of packaging materials with laser beams is known for some time. For this scanning systems can be used or working with masks systems. In the former case two rotatable mirrors are arranged perpendicular to each other, so that the deflected laser beam can cover every point of a two-dimensional surface. In the screening method, a laser beam in pulses passed through a mask to produce the writing or marking in one go.

To achieve higher power densities and resultant better qualities label is known to focus the light beam on the workpiece surface. So-called F-theta lenses are used. These have a planar focal surface, so that especially at the edges of the label level, the change in distance is compensated for by the generally spherically symmetric focus surface.

Another possibility to change the focal length in dependence on the solid angle of the deflected laser beam is to mechanically change the focal length of the lens system. For this, the lenses must be moved mechanically, which is connected to a corresponding apparatus complexity.

From US 6,064,032 an apparatus for cutting and perforating of flakes is known, which are respectively wound around a filter plug and the end of a cigarette, to connect them to a filter cigarette. A glued strip is passed through a drum of a cutting and perforating, the cuts, the leaflets and provides with a perforated line. In the cutting and perforating a coherent light beam onto a diffractive focusing lens is focused, which directs the light beam in the form of a plurality of light points on the strip to be perforated. By the strip is conveyed in a direction, and the light is directed only for short time intervals on these, is formed in the conveying direction a perforation strip.

DE 3402871 A1 describes a method for labeling transparent components with a YAG laser. For this purpose, the transparent material is coated with a metal foil, which is bombarded with laser beam. The film material is evaporated by the absorbed energy of the laser beam and causes a local melting of the surface of the component to be labeled. These designated as the local "scarring" surface makes it transparent objects to label legible without disturbing a review.

The invention is based on the object to provide a device for labeling or marking of objects which may have a cylindrical surface.

This object is achieved by a lens system in which the focal plane is a weggekrümmte of the lens system area.

The lens system comprises a first and a second focusing lens defocusing. According to the invention, the defocusing lens to a weak concave / planar lens and the second lens is a plan / convex or slightly concave / convex lens. According to a preferred embodiment of the invention, the second lens is preferably a cylindrical lens. In the labeling of cylindrical surfaces, the distance between the surface and the lens system with the curvature of the cylindrical surface changes. Perpendicular to the cylindrical surface forms each in one direction is a straight line. It is understood that the lens system that addresses this condition.

The invention is explained in detail using a drawing.

The sole figure shows a lens arrangement according to the invention with two laser beams for marking or inscribing a cylindrical surface.

A non-illustrated object such as a bottle, has an area 10 whose curvature lies in the plane. From a laser or a deflecting mirror two outgoing laser beams are shown 12 and 14 respectively. The X-axis may be, for example, in the area of ​​the deflection mirror. The laser beam 12 and 14 has a certain extension in width. It passes through a lens system 16 through which focuses the laser beams 12, 14 on the surface 10, as shown at 18 or twentieth The deflection of the laser beams 12, 14 is, however, not only in the plane of the drawing, but also perpendicular thereto. Such distraction for labeling or marking with the aid of a deflection mirror is however generally known.

The lens system 16 has a first slightly concave / planar lens 22 and behind it a second plan / convex lens 24, which is in the section shown as a cylindrical lens, vertically but molded to a normal convex lens. The refractive index of the lens 22 is smaller than that of the lens 24. The first lens 22 has a defocusing, and the second a focusing effect. In any case, the arrangement of the lenses 22, 24 is such that regardless of the spatial angle of the laser beams 12, 14 they are respectively focused on the surface of the tenth

The principle illustrated in the above description is in principle also applicable to so-called mask systems in which the beam path of the laser, a mirror image punched mask shapes the object to be marked. Finally, it is possible to inscribe on a cylindrical surface moving surfaces. Here, upon writing the speed of the moving tag field is balanced control technology on the scanner.