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    Re: A Ball Bearing in a dish as a reference
    From: Tony Oz
    Date: 2018 Jun 13, 01:59 -0700

    Dear Brad,

    Thank you for the story (of never looking into the laser beam).

    That reminded me my own experience with HeNe laser (sub-milliwatt, I guess). Despite being VERY SERIOUSLY warned I decided that a ~5cm thick pack of coal-black filters (each exceeding a DIN12 welding mask) will save my sight and still let me see the light from the laser.

    It was not so easy to find the beam, when I moved my head around to colineate with the beam - I saw a lot of fancy interference patterns (so many filters in the pack created a lot of internal reflections). Finally I foung the main beam.

    My brain - not even my eye alone! - was filled with the true meaning of Red, the Very Absolute Sense of it.

    Quite satisfied with myself and with the experience thus obtained I moved away from the beam. The eye was still working just fine - to my great satisfaction. But few seconds later there came a feeling as if that eye got professionally hit by a heavy-weight boxer! Now I subscribe to the warning of never ever looking into a laser beam, no matter the power could be!

    Many years passed, my sight is still good - with both eyes.

    Regards,

    Tony

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