Third case

This is an example of a very unlucky person. During some experiments involving a femtosecond pulsed laser, the researcher was measuring the beam width using a camera specially designed for this kind of measurements. The detection head was placed on a stand in order to be at the center of the beam, but was badly fixed. He acquired his measurements, and then wanted to copy the results on his lab book, placed on a desk next to the experiment. A computer was situated on this desk. The experimentalist sat down on a chair, turning his back to the experiment, aware that the beam was behind him. While he was writing on the book, the detection head ripped and the beam was now aimed at the computer. The beam then got reflected on the computer screen situated at the same height. The experimentalist then straightened up and his eye got briefly exposed to the reflected beam. He was instantly bedazzled. Hopefully, due to the blink reflex of his eye, he didn't experience permanent lesions. He only experienced headache during a few days related to the bedazzlement.

This accident, which finally ends pretty well, could have been easily avoided simply by correctly fixing the detection head. Then, the the beam would have been stopped all along the data acquisition and copying. But this protection was still not sufficient. The laser should have been isolated from the desk by an opaque partition – at least opaque to the laser wavelength. Such a partition permits to isolate the experiment part of the room from the “paper work” part. Nonetheless, if the screen had been placed at higher than the beam, the reflection would never have occurred.