Michael Henrichsen’s research while affiliated with Fraunhofer Institute of Optronics, System Technologies and Image Exploitation and other places

The application of a high energy laser beam in a maritime scenario necessitates a laser safety concept to prevent injury to personnel or uninvolved third parties from uncontrolled reflections of laser light from the sea surface. Therefore, it is crucial to have knowledge of the amount and direction of reflected laser energy, which varies statistically and depends largely on the dynamics of the wavy sea surface. These dynamics are primarily influenced by wind speed, wind direction, and fetch. An analytical model is presented for calculating the time-averaged spatial intensity distribution of the laser beam reflected at the dynamic sea surface. The model also identifies the hazard areas inside which laser intensities exceed a fixed exposure limit. Furthermore, as far as we know, our model is unique in its ability to calculate the probabilities of potentially eye-damaging glints for arbitrary observer positions, taking into account the slope statistics of gravity waves. This is a critical first step toward an extensive risk analysis. The simulation results are presented on a hemisphere of observer positions with fixed radii from the laser spot center. The advantage of the analytical model over our numeric (dynamic) model is its fast computation time. A comparison of the results of our new analytical model with those of the previous numerical model is presented.

Our study examines how laser dazzling affects human performance, specifically accuracy and reaction times, using a laser dazzling shooting simulator at the Royal Military Academy, Belgium. The research assesses the performance degradation under laser dazzling in a simple, baseline scene, including different target contrasts and the use of laser eye protection. Utilizing a 532 nm green laser for a safe yet effective dazzle, trained shooters’ performances were measured and analyzed. The results align strongly with a live shooting trial and correlate with Adrian/CIE visibility levels. Additionally, electrical brain activity data, acquired via electro-encephalography (EEG), provided insights into the shooters’ mental states. EEG-derived metrics, particularly frontal alpha asymmetry and frontal alpha power, revealed that participants experienced heightened negative and avoidance emotions, coupled with increased cognitive load prior to shooting. These responses returned to baseline levels postshooting. Moreover, distinct cognitive and emotional states were observed in relation to different types of laser eye protection goggles, potentially correlating with variations in shooting performance. These findings pave the way for future research with more advanced simulation scenes and deepen understanding of the effects of laser dazzle.

This study investigated the perforation time of polyamide 6.6 using fiber lasers at two different wavelengths: 1070 and 1943 nm. The novelty of this research lies in the comparison of perforation times at equivalent laser irradiances on the polymer sample with two different colors of polyamide 6.6: natural and black. The results revealed that, at comparable irradiance levels and beam diameters, the 1943 nm laser source perforated the polyamide 6.6 sample faster than the 1070 nm laser source. The difference in perforation time was found to be significantly higher for natural-colored polyamide 6.6 compared to black-colored polyamide 6.6. These findings suggest that, for material processing of polyamide 6.6, especially in terms of perforation, the use of 2 μm laser sources should be privileged over 1 μm laser sources.