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    Re: A Ball Bearing in a dish as a reference
    From: Brad Morris
    Date: 2018 Jun 13, 16:03 -0400
    Hi Tony

    The reason it hurt so much is that your filters merely attenuated the power of the coherent light but did nothing to change the coherence.  It was still coherent light 

    The attenuated coherent light that struck your retina essentially overloaded the receptor cells (rods and cones).  That overload can cause severe alteration in the receptor function.  If indeed you experienced no vision loss, you are a very, very lucky man.   

    Please don't ever repeat that experiment!! 

    Brad





    On Wed, Jun 13, 2018, 7:17 AM Tony Oz <NoReply_TonyOz@fer3.com> wrote:

    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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