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Proceedings Paper

Eye safety analysis for non-uniform retinal scanning laser trajectories
Author(s): Uwe Schelinski; Hans-Georg Dallmann; Heinrich Grüger; Jens Knobbe; Tino Pügner; Peter Reinig; Franziska Woittennek
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Paper Abstract

Scanning the retinae of the human eyes with a laser beam is an approved diagnosis method in ophthalmology; moreover the retinal blood vessels form a biometric modality for identifying persons. Medical applied Scanning Laser Ophthalmoscopes (SLOs) usually contain galvanometric mirror systems to move the laser spot with a defined speed across the retina. Hence, the load of laser radiation is uniformly distributed and eye safety requirements can be easily complied. Micro machined mirrors also known as Micro Electro Mechanical Systems (MEMS) are interesting alternatives for designing retina scanning systems. In particular double-resonant MEMS are well suited for mass fabrication at low cost. However, their Lissajous-shaped scanning figure requires a particular analysis and specific measures to meet the requirements for a Class 1 laser device, i.e. eye-safe operation. The scanning laser spot causes a non-uniform pulsing radiation load hitting the retinal elements within the field of view (FoV). The relevant laser safety standards define a smallest considerable element for eye-related impacts to be a point source that is visible with an angle of maximum 1.5 mrad. For non-uniform pulsing expositions onto retinal elements the standard requires to consider all particular impacts, i.e. single pulses, pulse sequences in certain time intervals and cumulated laser radiation loads. As it may be expected, a Lissajous scanning figure causes the most critical radiation loads at its edges and borders. Depending on the applied power the laser has to be switched off here to avoid any retinal injury.

Paper Details

Date Published: 18 March 2016
PDF: 12 pages
Proc. SPIE 9700, Design and Quality for Biomedical Technologies IX, 97000B (18 March 2016); doi: 10.1117/12.2209296
Show Author Affiliations
Uwe Schelinski, Fraunhofer Institute for Photonics Microsystems (Germany)
Hans-Georg Dallmann, Fraunhofer Institute for Photonics Microsystems (Germany)
Heinrich Grüger, Fraunhofer Institute for Photonics Microsystems (Germany)
Jens Knobbe, Fraunhofer Institute for Photonics Microsystems (Germany)
Tino Pügner, Fraunhofer Institute for Photonics Microsystems (Germany)
Peter Reinig, Fraunhofer Institute for Photonics Microsystems (Germany)
Franziska Woittennek, Fraunhofer Institute for Photonics Microsystems (Germany)


Published in SPIE Proceedings Vol. 9700:
Design and Quality for Biomedical Technologies IX
Ramesh Raghavachari; Rongguang Liang, Editor(s)

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