Expert Control in Cutting and Welding Applications Using High-Speed Deformable Mirror

Advances in speed and quality throughout laser machining applications enhanced by Piezo-driven laser focus shifter module.

Piezo ceramic actuators bring together higher resolutions with high-speed response and high-force generation, the properties that are perfect to drive highly dynamic deformable mirrors. These concepts have been in use throughout adaptive optics for applications such as astronomy, surveillance, microscopy, and defense. Imaging applications such as these tend to involve a multitude of actuators per mirror to ameliorate wave-front aberrations.

Advantages of Active and Adaptive Optics

Furthermore, applications beyond imaging such as machining can also gain advantage from active and adaptive optics. Lasers made the leap from the lab to the manufacturing floor long ago - utilized in a wide range of production processes and offer assurances regarding greatly repeatable workpiece quality. Improvements can be made by controlling and geometrically influencing the laser beam. High-frequency beam oscillation in the XY plane using scanning mirrors has already been completed with considerable success.

Piezo-Driven Deformable Mirror

Capable of operating with modulation frequencies up to 2 kHz, the piezo-driven deformable mirror equipped with an internal active piezo element can offer a motion range of 28 μm: comparable to a focal place shift to 15 mm (with appropriate optical setup).

Principle operation of the adaptive mirror

Piezo-driven deformable mirror installed in module for laser focus shifting with high-dynamics laser cutting with 3 kW laser power

The video shows the laser beam focus control module in a laser cutting application

Another process that increases the usable feed rate during laser beam cutting of thick sheet metal requires actively shifting the beam focus on the workpiece. In the case of laser beam welding, it can also allow for improved weld seam quality and process stability.

Piezo-Based, High-Dynamics Z-Axis Focus Shifter Module

PI engineered a piezo-based, high-dynamics Z-axis focus shifter module in collaboration with the Fraunhofer IWS, Fraunhofer IOF, and the industrial partners Heliatek, Kjellberg Finsterwalde, and Optics Balzers. The module can be used in conjunction with traditional methods and also 2-D beam manipulation in the XY machining plane, adding highly dynamic Z-axis focus manipulation capabilities in the direction of the beam axis, increasing the speed of machining while overall quality also showed improvement.

Featuring an elliptical aspheric mirror membrane to circumvent imaging errors the design intends to maximize the aperture of the beam. High reflectivity is provided by the dielectric coating.

PICA-Thru piezo actuator family

E-482 high-power piezo driver with energy  recovery technology

PICA-Thru Piezo Actuator Element

Manufactured at PI’s piezo ceramics division, the PICA-Thru piezo actuator elementproduces the required force to deform the mirror. This type of actuator is dependable to the extreme and enables fully optimized cooling for applications that necessitate an aperture for optical or mechanical purposes. The actuator is driven by a superior performance piezo amplifier of the E-481/E-482 series. These amplifiers notably utilize a patented energy recovery circuit, improving the efficiency in comparison with conventional piezo amplifiers.

Animation: Operating principle of the deformable piezo mirror

This information has been sourced, reviewed and adapted from materials provided by PI (Physik Instrumente) LP.

For more information on this source, please visit PI (Physik Instrumente) LP.