Integrated optical design for highly dynamic laser beam shaping with membrane deformable mirrors

The utilization of membrane deformable mirrors has raised its importance in laser materials processing since they enable the generation of highly spatial and temporal dynamic intensity distributions for a wide field of applications. To take full advantage of these devices for beam shaping, the huge amount of degrees of freedom has to be considered and optimized already within the early stage of the optical design. Since the functionality of commercial available ray-tracing software has been mainly specialized on geometric dependencies and their optimization within constraints, the complex system characteristics of deformable mirrors cannot be sufficiently taken into account yet. The main reasons are the electromechanical interdependencies of electrostatic membrane deformable mirrors, namely saturation and mechanical clamping, that result in non-linear deformation. This motivates the development of an integrative design methodology. The functionality of the ray-tracing program ZEMAX is extended with a model of an electrostatic membrane mirror. This model is based on experimentally determined influence functions. Furthermore, software routines are derived and integrated that allow for the compilation of optimization criteria for the most relevant analytically describable beam shaping problems. In this way, internal optimization routines can be applied for computing the appropriate membrane deflection of the deformable mirror as well as for the parametrization of static optical components. The experimental verification of simulated intensity distributions demonstrates that the beam shaping properties can be predicted with a high degree of reliability and precision

К вопросу о расчете подпорных стенок

Laser processing applications such as heat treatment require the transformation of the raw intensity distribution into a beam profile of homogeneous intensity. Further the adaption of this profile to altering working geometries results in improved energy coupling and in more efficient material processing. For the utilization of CO2-laser radiation an optical system is developed that both transforms the raw intensity distribution into a homogeneous beam profile and contains the ability to continuously change the spot size independently into two directions

Model-based analysis of highly dynamic laser beam shaping using deformable mirrors

Deformable mirrors show large potential for the dynamic beam shaping in high power laser applications. A model which is based on influence functions is used to systematically investigate the beam shaping capabilities of several deformable mirrors based on the underlying technology and the number of actuators

Thermo-Optical (TOP) analysis of transmissive elements for laser systems

Increasing laser beam qualities make thermal lensing again a hot topic and demand for a thermo-optical simulation for improving classical ray tracing and enabling optimization possibilities for thermally aberrated optical systems. This paper summarizes the approach for coupling FEM and ray tracing using a weighted least squares approximation algorithm and demonstrates the abilities of the coupled simulation in the case of a CO2 laser system for polishing of glass and plastics. It can be demonstrated that the algorithm can be used for the analysis of higher order aberrations, since the application contains a Gaussian to top-hat conversion lens group which suffers from thermal gradients. Finally, the benefits and further developments of analyzing thermal gradients in optical simulation are being discussed

Koaxiale Laserstrahlformung für die Lasermaterial-Bearbeitung mit Zusatzwerkstoff

Die koaxiale Zuführung von Zusatzwerkstoffen innerhalb eines geschlossenen Ringstrahlprofils führt zu signifikanten prozessspezifischen und maschinentechnologischen Vorteilen

Active optical system for advanced 3D surface structuring by laser remelting

Structuring by laser remelting enables completely new possibilities for designing surfaces since material is redistributed but not wasted. In addition to technological advantages, cost and time benefits yield from shortened process times, the avoidance of harmful chemicals and the elimination of subsequent finishing steps such as cleaning and polishing. The functional principle requires a completely new optical machine technology that maintains the spatial and temporal superposition and manipulation of three different laser beams emitted from two laser sources of different wavelength. The optical system has already been developed and demonstrated for the processing of flat samples of hot and cold working steel. However, since particularly the structuring of 3D-injection molds represents an application example of high innovation potential, the optical system has to take into account the elliptical beam geometry that occurs when the laser beams irradiate a curved surface. To take full advantage of structuring by remelting for the processing of 3D surfaces, additional optical functionality, called EPS (elliptical pre-shaping) has to be integrated into the existing set-up. The development of the beam shaping devices not only requires the analysis of the mechanisms of the beam projection but also a suitable optical design. Both aspects are discussed in this paper

Schwer betroffene Patienten mit Kraniektomie nach Hirninfarkt profitieren von einer Frührehabilitation

Structuring by remelting is an innovative approach for structuring metallic surfaces with laser radiation, where no material is removed but reallocated while molten. Based on this remelting principle an innovative structuring technique is investigated, where laser beams are superposed. A melt pool is generated by a cw laser beam with constant feed rate. A pulsed laser is superposed onto the cw laser and evaporates a small amount of molten material and, therefore, generates vapour pressure, which shapes the melt pool surface. The solidification follows this newly shaped surface. For this process a new optical system was designed and built up, which allows the combination of cw and pulsed laser beams

Development of an adaptive laser beam shaper

The intensity distribution of a laser beam has a high impact on laser processing applications. In many applications, the emitted light of a laser beam source is transformed from a Gaussian intensity distribution into other intensity distributions with the intent to improve the process quality. Numerous approaches have been pursued for this purpose in the past. The vast majority of these optical systems is static. As a result the laser material processing process is limited to a specific intensity distribution. Different systems like membrane deformable mirrors can be used for shaping multiple intensity distributions. However, the control of such systems is complex and requires a deep understanding of the underlying operating principle of the specific mirror system. In this paper a new approach for active beam shapers made of catalog components, like spherical and cylindrical lenses, is introduced. Two optical systems for active beam shaping are designed which can change between two different intensity distributions by moving an individual spherical/ cylindrical lens along the beam path. One system forms a laser spot with Gaussian like intensity distribution and a TopHat shaped intensity distribution respectively. The second optical system is capable of forming a laser spot with Gaussian intensity distribution and a homogenous line shaped intensity distribution respectively. Also the mechanical housing for these optical systems is presented

Coaxial beam shaping for laser materials processing

The coaxial feeding of additional material within a closed annularly shaped intensity profile leads to significant process-specific and machine-technological advantages