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.
Four different methods for the fast robustness estimation of lens systems are presented and their values for two test cases with simple lens systems are calculated. These methods are evaluated in terms of computation time and their estimations are compared to the results of a Monte-Carlo analysis.
Process monitoring is used in many different laser material processes due to the demand for reliable and stable processes. Among different methods, on-axis process monitoring offers multiple advantages.
To observe a laser material process it is unavoidable to choose a wavelength for observation that is different to the one used for material processing, otherwise the light of the processing laser would outshine the picture of the process. By choosing a different wavelength, lateral chromatic aberration occurs in not chromatically corrected optical systems with optical scanning units and f-Theta lenses. These aberrations lead to a truncated image of the process on the camera or the pyrometer, respectively. This is the reason for adulterated measurements and non-satisfying images of the process.
A new approach for solving the problem of field dependent lateral chromatic aberration in process monitoring is presented. Therefore, the scanner-based optical system is reproduced in a simulation environment, to predict the occurring lateral chromatic aberrations. In addition, a second deflecting system is integrated into the system. By using simulation, a predictive control is designed that uses the additional deflecting system to introduce reverse lateral deviations in order to compensate the lateral effect of chromatic aberration.
This paper illustrates the concept and the implementation of the predictive control, which is used to eliminate lateral chromatic aberrations in process monitoring, the simulation on which the system is based the optical system as well as the control concept.