Laser-marking system

Abstract

An apparatus for laser marking an arcuate surface of an object has a laser source emitting a laser beam and a first reflector assembly for deflecting the beam in a contiguous first field. A second reflector assembly has at least two adjacent second reflectors in the first field for reflecting the beam into at least two separate and not overlapping second fields. Respective third reflectors in the second fields reflect the beam in the respective third fields onto respective adjacent portions of the surface of the object.

Description

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIGS. 1 and 2 show a prior-art system marking a flat and a part-spherical surface of an object;

FIG. 3 shows the system according to the invention for marking a convex portion cylindrical outer surface; and

FIG. 4 shows a system like that of FIG. 3, but marking a cylindrical concave surface of an object.

SPECIFIC DESCRIPTION

As seen in FIG. 1 a known system for laser marking uses a galvanometer scanner. A laser beam 2 generated by a laser emitter 1 is deflected in the x and y directions by means of a freely programmable control system (not illustrated) via deflection mirrors 3b and 4b attached on respective perpendicular axes 3a and 4a of the galvanometer scanners 3 and 4 such that a marking cone 5 is formed that in turn defines a marking field 6.

A focusing lens 7 in the beam path focuses the laser beam 2 at a focal plane 20 on which the laser beam has its focal point and thus its minimum extension in the x and y directions, so that the laser power at the surface is at a maximum. It is necessary for marking that the surface to be marked be placed on this plane, since the most effective marking having the sharpest contour is obtained at this location due to the minimum focal point and the resulting maximum power density.

Displacement of the surface to be marked along the z axis away from the focal plane 20 causes enlargement of the focal point, and thus a quadratic-reduction in the power density, so that satisfactory marking results are obtained only within a focal depth range between upper boundary plane 20a and a lower boundary plane 20b. Outside this region the achievable marking results are unsatisfactory, or marking is not possible at all.

If as shown in FIG. 2 a strongly curved surface 10 is to be inscribed over a large area, it is no longer possible to keep all of the regions of the surface 10 to be inscribed within an allowable region 11, delimited by an upper boundary plane 11a and a lower boundary plane 11b (focal depth region), which is practical for inscription. Instead, at least one region 12 of the surface 10 to be inscribed does not lie in the region 11, so that this region cannot be satisfactorily inscribed or cannot be inscribed at all, or, according to the prior art as previously described, must be inscribed using partial images in one or more further operations.

FIG. 3 shows a first embodiment according to the invention. The laser beam 2 generated by a laser beam source 1 is deflected in the x and y directions by means of a freely programmable controller 30 operating the deflection mirrors 3b and 4b attached on the axes 3a and 4a of the galvanometer scanners 3 and 4, and is focused in a focal plane by means of a subsequent focusing lens 7. On the output side of the lens 7 is a mirror-type optical reflector assembly 31 by means of which the laser beam 2 exiting the lens 7 at different angles, depending on the upstream x and y deflection, is deflected into at least two different second fields 5a and 5b.

When, for example, two deflection mirrors 31a and 31b are used in the mirror system 31 define a given angle, for example 90°, and form a prism-shaped reflector, for example, a laser beam 2 incident on the mirrored surface 31a or 31b is deflected either in direction 32a or 32b, depending on the previous deflection, so that in this example two marking cones 5a and 5b result that form different second fields.

By means of the respective third reflector assembly, composed of deflection mirrors 33a and 33b, provided downstream, these marking cones 5a and 5b are deflected in such a way that the surface of the object 10 to be inscribed, composed of different third fields, is marked in the partial areas 34a and 34b such that the partial areas combine to form a common marking surface 34.

The distance of the respective partial areas 34a and 34b from the focusing lens 7 corresponds to the focal distance of the lens 7 used, so that each partial area 34a and 34b essentially lies in the focal plane. For this purpose, the deflection mirrors 33a and 33b may be displaceably and/or rotatably attached in a mount (not illustrated) in order to conform the respective distances of the partial areas to be inscribed to the marking lens 7.

When objects that essentially are always the same are inscribed, this adjustment is made once. In addition, for a suitable choice of the directions of impingement for the marking cones 5a and 5b on the surface of the object 10 to be marked, the respective partial areas 34a and 34b lie within the allowable focal depth, so that the entire marking in the marking surface 34 as a whole lies within the allowable focal depth, and a high-quality marking is thus possible. Of course, the marking cone may also be split into more than the two partial cones stated as an example, for example into three, four, or more partial cones, in order to inscribe spherical or conical surfaces.

In an alternative embodiment according to the invention, it is also possible to mark elongated concave surfaces as shown in FIG. 4. The configuration is essentially the same as that described in FIG. 3, except for the geometric position of the partial areas 34a and 34b with respect to one another on the surface 10 of the object to be inscribed. In this case, the marking cones (third fields) cross each other so that the partial areas likewise are switched with one another in an intersection region. In order to create a self-contained marking image 34 on the correct side, in this case the respective partial images must be switched in the marking software for the marking unit and also reversed.

It may also be practical to omit a marking lens 7. In this case the deflection mirrors 31a and 31b and/or 33a and 33b are designed as curved mirrors so that the laser beam 2 is similarly focused in a focal plane lying essentially on the surface of the object to be inscribed. The curved mirrors may have spherical, parabolic, hyperbolic, or similar designs, or may also be off-axis mirrors, depending on requirements.

For the inscription, any laser is suitable that has a wavelength, power, and operating system that allows adequate marking in each particular case, for example gas lasers such as CO₂ lasers, argon lasers, metal vapor lasers, ion lasers, excimer lasers, etc., or semiconductor lasers or solid-state lasers such as Nd:solid-state lasers, ruby lasers, alexandrite lasers, sapphire lasers, or also free-electron lasers.

Claims

1. An apparatus for laser marking an arcuate surface of an object, the apparatus comprising: a laser source emitting a laser beam;first reflector means for deflecting the beam in a contiguous first field;second reflector means having at least two adjacent second reflectors in the first field for reflecting the beam into two separate and not overlapping at least second fields; andrespective third reflectors in the second fields for reflecting the beam in the respective third fields onto respective adjacent portions of the surface of the object.

2. The laser-marking apparatus defined in claim 1 wherein there are more than two second reflectors forming more than two second fields and more than two third reflectors reflecting the beams in more than two third fields onto more than two respective adjacent portions of the surface of the object.

3. The laser-marking apparatus defined in claim 1, further comprising at least one focusing optical element preferably a lens or curved mirror in the first field between the first and second reflector means.

4. The laser-marking apparatus defined in claim 1, further comprising: at least one movable or tiltable focusing optical element in the first field between the first and second reflector means.

5. The laser-marking apparatus defined in claim 1 wherein at least one of the reflectors is a focusing reflector.

6. The laser-marking apparatus defined in claim 1 wherein the reflectors are flat and planar.

7. The laser-marking apparatus defined in claim 1 wherein the reflectors are movable or tiltable.

8. The laser-marking apparatus defined in claim 1 wherein the laser beam is focused in each of the third fields onto a corresponding portion of the surface of the object such that the portion of the surface of the object lie within a focal depth.

9. The laser-marking apparatus defined in claim 1 wherein the object surface is concave.

10. The laser-marking apparatus defined in claim 1 wherein the object surface is convex.

11. A method of laser marking an arcuate surface of an object, the method comprising the steps of: emitting a laser beam;deflecting the beam in a contiguous first field;reflecting the beam into at least two separate and not overlapping second fields with at least two adjacent second reflectors in the first field; andreflecting the beam in the respective third fields onto respective adjacent portions of the surface of the object with respective third reflectors in the second fields.

12. The laser-marking method defined in claim 11 wherein information to be marked is split into a number of partial markings, the number being equal to the number of second fields.

13. The laser-marking method defined in claim 12 wherein the partial markings are interchanged or laterally reversed.