Sensor/regulation element assembly for regulating the beam of high-power lasers

for adjusting the beam of high power lasers.

A sensor assembly-actuator element, for adjusting the beam of high power lasers for machining materials, which it is placed, which assembly is provided with a mirror plate provided with cooling ducts optical and having a reflective surface.

In the different device models beam adjusting lasers mentioned forming part of the prior art, several sensor assemblies-correction element separated were still required so far, as disclosed in the documents DE-OS 31,34 555 Al, DE-OS 38,00 427 Al or DE-PS 32,02 432 C2 belonging to the precipitating. In addition to the space required, the work required only for the adjustment and securing of the various elements or module is considerable.

The aim of the invention is to provide a sensor assembly-device for adjusting the type indicated above, that enables simultaneous, as single member, detect and correct angular errors and for focusing errors of laser beams of high power.

The problem is solved according to the invention by the fact that a four-quadrant detector coupled in series with a DC light, and two or more adjustment elements of the mirror plate to correct the focussing are mounted on the base plate and for securing a body housing dimensionally stable, pressure-resistant, on the upper edge of which is attached an annular elastic member for supporting the mirror plate, , whose rear face supports a holographic optical pattern, which performs the focus of the laser beam by fraction of the detached portions of astigmatism for a determined curvature of the mirror.

According to one embodiment of the invention, the mirror plate consists of a disc transparent silicon to the surface of which is applied a dielectric coating, and over the rear face of which are milled cooling channels.

According to a preferred embodiment of the invention, the dielectric coating of the mirror plate to 99% reflects the laser radiation wavelength 10.6 [...].

According to one embodiment of the invention, the holographic element is a transparent sheet having a hologram pattern etched, which covers the cooling channels.

The invention is described in detail in the following using an exemplary embodiment represented schematically, in cross-section, on the sole figure of the drawing.

The sensor assembly-adjusting element described below is placed as a complete unit to the beam path systems to high-power laser, used to machine materials, to detect and correct angular errors and for focusing errors the machining beam. The assembly simultaneously fulfils the function of detection and correction. The surface of the workpiece struck by the laser beams is cooled by a liquid in a manner known per se.

The sensor assembly-adjustment means comprises a body 10 housing dimensionally stable, pressure-resistant, preferably cylindrical and a base plate and fixing 11 dimensionally stable closing the body 10 at its lower end. The plate is used for fixing the assembly in a predetermined position within the transport line of the beam from laser machining apparatus, and integrating element for a set of components, as described below.

A the upper end of the body 10 is attached an elastic member annular 12, in the form of a bellows, which supports a thin mirror plate 13 internally provided with cooling channels, which is made of silicon. A mirror plate of that type has been disclosed by the precipitating in the document DE-PS 34,08 263 Cl. The surface of the mirror plate 13 herein is coated a dielectric layer, which reflects a high percentage-typically 99% -of the laser radiation wavelength 10.6 [...]. The remaining fraction of 1% is detached from the beam by a process that is similar to that described in the document DE-PS 31,33 823 Cl belonging to the precipitating. On the rear side of the mirror plate 13 is applied, by an etching technique by etching, a holographic optical element 13a, determined which provides for focusing light on a four-quadrant detector 14 disposed on the base plate 11. The holographic focusing element 13a is configured such that the focusing is obtained by portions of astigmatism.

Is determined using an electronic 14a, as described for example in German Patent P 40,12 927,6-33 deposited the 24.04.1990, the angular deviation and the focus error of the laser beam 20,21 from the signals of the four-quadrant detector 14, and is derived in an electronic 14a known per se the corresponding values are transmitted as control signals to the adjusting elements 16,12 etc... described below, to correct the angular deviation and the focus error. The correction of the angular distance is carried out by means of two or more adjustment members 16, which are arranged on the base plate and fixing and 11 act via elastic elements 12 on the mirror plate 13 to obtain, at a particular angular position. Alternatively, the adjusting elements 16 may be in the form of piezoelectric actuators or magnetostrictive.

The correction of the focussing is effected by a defined modification of the curvature of the mirror plate 13, by corresponding increase or decrease of the pressure of a gas into the interior of the body 10 from the gas inlet 18. Adjusting the pressure respective theoretical takes place through the differential pressure sensor 17 and a control valve (not shown) integrated in the base plate 11 and fixing.

The four-quadrant detector 14 is preferably in the form of a pyro-electric sensor, in front of which is placed a light chopper of mechanical 15 to allow operating in ac. The described correction of the angular error and the focus error is performed by a regulating circuit or a control circuit open. Alternatively, the assembly can also be used in a closed control loop, wherein the correction is performed by correction elements separated, placed in the path of the beam.