Consideration of wave optical phenomena for retinal images in laser safety evaluations

Abstract

Laser systems emitting in the visible and near infrared wavelength range between 400 nm and 1400 nm represent a potential hazard for the retina. The accessible emission limits depend on the angular subtense of the apparent source which is determined by the size of the retinal image. Usually, the retinal image is calculated using geometric optical propagation methods, e.g. ray tracing techniques. In case of coherent laser radiation this might be insufficient since wave optical phenomena can influence the retinal image. Especially by the presence of apertures, diffraction needs to be taken into account. In this paper we analyse the impact of wave optics for laser safety evaluations and show the difference to geometric optical calculations. Both propagation methods are compared for relevant examples.Laser systems emitting in the visible and near infrared wavelength range between 400 nm and 1400 nm represent a potential hazard for the retina. The accessible emission limits depend on the angular subtense of the apparent source which is determined by the size of the retinal image. Usually, the retinal image is calculated using geometric optical propagation methods, e.g. ray tracing techniques. In case of coherent laser radiation this might be insufficient since wave optical phenomena can influence the retinal image. Especially by the presence of apertures, diffraction needs to be taken into account. In this paper we analyse the impact of wave optics for laser safety evaluations and show the difference to geometric optical calculations. Both propagation methods are compared for relevant examples.