Prevention of Overexposure by Means of Active Protective Reactions and Magnitude of Temporary Blinding from Visible Laser Radiation

Abstract

It has been shown in a field trial with 205 subjects who got an instruction, that active protective reactions could protect up to 80% of the exposed volunteers against laser radiation during a period of 1.4 seconds. This is a considerable improvement compared with the unreliable blink reflex, which works only in every 5^th case.

Therefore adequate instruction to perform active protective reactions, i. e. moving the head or closing the eyes, might be a valuable contribution to prevent any potentially hazardous laser radiation and increases the safety against laser radiation arising from wrong labeled class 2 laser products and true class 3R lasers emitting in the visible spectrum.

Temporary blinding as the result of a dazzling light in the visual field arising from class-1 and class-2 lasers at wavelength of 632.8 nm and 532 nm has been investigated.

It was found that already at output powers below 30 μW of a He-Ne-laser the subjects reported intense glare effects and felt uncomfortable due to the high brightness. The durations of afterimages took up to 300 s and have been measured as a function of the angle between the line of sight and the laser beam direction for exposure durations up to 10 s. A dose relationship has been found which determines the afterimage duration. The inability to read due to the disturbance produced by afterimages lasts for about 20 s even if the exposure is not more than 0.25 s from a laser with about 0.8 mW.