Mr. Sebastian Kotzur Profile

Sebastian Kotzur

at Robert Bosch GmbH

Publications (6)

Proceedings Article | 18 June 2024 Presentation + Paper

Simulated thermal retinal damage thresholds for coherent optical sources forming asymmetrical retinal images in the eye

Marc Herbst, Sebastian Kotzur, Annette Frederiksen, Wilhelm Stork

Proceedings Volume 13010, 130100B (2024) https://doi.org/10.1117/12.3017019

KEYWORDS: Laser induced damage, Laser tissue interaction, 3D modeling, Eye models, Laser safety, Thermal modeling, Laser damage threshold, Eye, Tissues, Simulations, Standards development

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Laser safety calculations for optical systems are often based on the assumption of ideal symmetrical retinal images or exposure scenarios. The laser safety standard IEC 60825-1:2014 uses exposure limits from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines, which refer to symmetrical spots. Further, the standard is premised on retinal damage thresholds of symmetrical exposure scenarios, which are empirically determined in laser damage experiments or simulations. In reality, retinal images of laser systems feature aberration-afflicted, asymmetrical retinal geometries, for example resulting from optical aberrations such as coma and astigmatism. Especially for these asymmetrical retinal exposure scenarios, the laser safety standard ensures that the optical systems are eye-safe by specifying a symmetrization of the retinal image, emission limits and safety factors. In terms of safety and performance of the laser systems, it is particularly important to directly consider asymmetrical retinal images and therefore be able to assess the size of the safety factors. For this consideration, a computer model is recommended, which is an eye and thermal simulation model, handles asymmetrical retinal images and calculates damage thresholds of these exposure scenarios.

A computer model for symmetrical retinal geometries exists, which is validated on experimental data of nonhuman primates (NHP) and uses a finite element method (FEM) simulation to solve the heat transfer equation. Further, it is also used to calculate retinal damage thresholds by inserting the temperature behavior into the Arrhenius equation. The focus of the work presented here is the extension and further development of the computer model and elaborates the difficulties to simulate retinal damage thresholds of asymmetrical exposure scenarios. In particular, the extension of this computer model to asymmetrical retinal images while maintaining validation is addressed. An exemplary case of an asymmetrical retinal image is calculated with the model and the results are presented.

SPIE Journal Paper | 2 December 2023 Open Access

Nanosecond multipulse retinal damage thresholds of elongated irradiance profiles in explant measurements and simulations

Marc Herbst, Sebastian Kotzur, Annette Frederiksen, Wilhelm Stork

JBO, Vol. 28, Issue 12, 125001, (December 2023) https://doi.org/10.1117/12.10.1117/1.JBO.28.12.125001

KEYWORDS: Laser damage threshold, Biological samples, Tissues, Simulations, Laser safety, Explants, Laser irradiation, Standards development, Eye, LIDAR

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SPIE Journal Paper | 25 January 2023

Image analysis of retinal images in eye safety evaluations for optical systems

Sebastian Kotzur, Siegfried Wahl, Annette Frederiksen

OE, Vol. 62, Issue 01, 016102, (January 2023) https://doi.org/10.1117/12.10.1117/1.OE.62.1.016102

KEYWORDS: Image analysis, Safety, Standards development, Eye, Retina, Laser safety, Lamps, Optical engineering, Laser radiation, Eye models

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SPIE Journal Paper | 25 June 2021

Simulation of laser-induced retinal thermal injuries for non-uniform irradiance profiles and the applicability of the laser safety standard

Sebastian Kotzur, Siegfried Wahl, Annette Frederiksen

OE, Vol. 60, Issue 06, 066115, (June 2021) https://doi.org/10.1117/12.10.1117/1.OE.60.6.066115

KEYWORDS: Laser safety, Injuries, Standards development, Retina, Computer simulations, Optical simulations, Transmittance, Rutherfordium, Eye, Optical engineering

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Significance: A validated biophysical computer model simulating retinal thermal damage thresholds is used to investigate elongated retinal images. The International Commission on Non-Ionizing Radiation Protection Guideline and the laser safety standard IEC 60825-1:2014 include a method for averaging non-uniform extended sources, however, there are no studies that have examined the applicability in detail. Our study represents a method that can also support future research in the field of eye safety. Aim: As there is currently no experimental data available for non-uniform irradiance profiles, the calculation procedure given in the laser safety standard is derived from symmetric retinal images. We aim to verify this calculation procedure for such profiles on the retina in the thermal hazard regime. Approach: A three-dimensional computer model, which solves the heat transfer equation and the Arrhenius equation describing the denaturation of the proteins in the retina, is used to simulate the threshold values for the retinal thermal injury. Three different non-uniform irradiance profiles, elliptical Gaussian, elliptical top-hat, and rectangular top-hat distributions, are investigated for a wavelength of 530 nm. The profiles are varied in their sizes and simulated for different single-pulse durations. By applying the laser safety standard, the maximum allowed energies are calculated and divided by the corresponding threshold values to obtain the reduction factor (RF) which is a crucial parameter. Results: Due to the thermal behavior in the retinal tissues, the Gaussian irradiance profiles yield larger threshold values than both top-hat profiles. Furthermore, the ratio between the threshold values and the maximum allowed energies are found to be the lowest for the Gaussian profiles. Conclusion: The simulated retinal thermal injury thresholds for the three investigated non-uniform irradiance profiles show larger RFs than the minimum RF found for symmetric profiles. This supports the applicability of the evaluation scheme of the laser safety standard for non-uniform retinal images.