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Thread: Blu Ray Really Safe?

  1. #1
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    Default Blu Ray Really Safe?

    Is anyone else worried about Blu Ray as a laser source.

    Several ebay sellers are already selling Blu Ray projectors which look great, a really unique colour: http://uk.youtube.com/watch?v=_DgjhVvJLXk

    However, I have to wonder if irradiating customers with high levels of UV light can really be eye / skin safe. I know UV canons are common in clubs, but even though their tubes are measured in watts, the actual levels of UV delivered are far less than from a laser, you can see that simply from the light which is diffuse from a canon but intense from a laser.

    Anyone else have safety concerns?

    I'm kind of thinking that maybe these lasers need high attenuation UV filters to take out the uv element to be safe.

  2. #2
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    http://www.rp-photonics.com/eye_safe_lasers.html
    © Dr. Rüdiger Paschotta
    Last update: 2008-05-21
    Eye-safe Lasers previous | next | feedback
    Ask RP Photonics for advice concerning which types of eye-safe lasers could be suitable for your application. Definition: lasers emitting in a wavelength region with relatively low hazards for the human eye

    Lasers with emission wavelengths longer than ∼ 1.4 μm are often called “eye-safe”, because light in that wavelength range is strongly absorbed in the eye's cornea and lens and therefore cannot reach the significantly more sensitive retina. This makes e.g. erbium lasers and erbium-doped fiber amplifiers used in 1.5-μm telecom systems or 2-μm thulium lasers far less dangerous than e.g. 1-μm lasers with similar output powers.

    On the other hand, the absorption length of the cornea reaches very small values (well below 0.1 mm) at longer wavelengths, particularly around 3 μm and around 10 μm (near the wavelength of CO2 lasers). This means that optical pulses at such wavelengths are absorbed in a very thin layer, so that the damage threshold of the cornea is relatively low. Therefore, lasers emitting around 3 μm or 10 μm are less eye-safe than e.g. lasers emitting around 1.5 μm, even though they are “retina-safe”. While the outer surface of the cornea (the epithelium) can at least heal after damage, this is not the case for the inner part (the endothelium). Also, corneal injuries can be very painful.

    Obviously, the quality “eye-safe” depends not only on the emission wavelength, but also on the power level and the optical intensity which can reach the eye. With sufficient power, such as is reached with a fiber amplifier or with a Q-switched laser, the eye can still be damaged. However, it can already be very helpful if at least weak parasitic reflections of some main beam are not dangerous for the eyes.
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  3. #3
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    Sorry Bridge, you're way more advanced than me here. Whilst I understand the gist of what you're saying, I can't relate the wavelengths you've posted to the 405nm of the Blu Ray.

    Also, I understand UV attacks the lens of the eye and not the retina - I understand UV is responsible for cataracts, hence the reason for my original question.

  4. #4
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    UV is generally considered dangerous at wavelengths higher than 400nm. If you buy sunglasses you may have noticed a label on them stating that they are 'UV blocking lenses' and therefore 'eye' Safe, they usually block all UV light to 400nm. It is generally accepted that 400nm is the start point (or end point ) at which light becomes visible to the human eye. In our Lab we have to test ALL lenses that are to be used for sunglasses to ensure that they block ALL UV wavelengths to 400nm.

    UVC (& above) is the very worst light for crystalline lens damage in the eye and as you rightly state can be a factor in the cause of cataracts, but thankfully most of this light is filtered out / scattered by the atmosphere.

    Next comes UVB, this is where you really should be wearing your sunglasses! See the chart below for a description of the different wavelengths of UV light.

    Ultraviolet A or long wave UVA 400 nm – 315 nm

    Ultraviolet B or medium wave UVB 315 nm – 280 nm

    Ultraviolet C or short wave UVC 280 nm – 100 nm

    Plus the 'other' UV wavelengths... Far UV 200 nm – 122 nm, Vacuum UV 200 nm – 10 nm and finally Extreme UV 121 nm – 10 nm

    So, in conclusion. the visible spectrum is ~400 to 700nm with the peak of sensitivity at around 515nm. When you're using 405nm as a lightsource it is on the fringes of true UV light and therefore not as dangerous.

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

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    that makes sense of why its so easy to adjust the focus to a fine point when im wearing sunglasses!
    -Josh

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    Thanks Jem that clears my understanding a lot.

    So basically so long as the diode is accurately centered around 405nm and not pumping out large amounts of non visible light as well, it should be eye safe.

  7. #7
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    The power of blu ray diodes is underestimated. I think it's absolutely irresponsible to tell it is "safe".
    The beam does'nt look very bright to the human eye but has a lot of energy.
    The first accident is just a matter of time. Be very careful, don't do beamshows with 405nm.
    It's only good for projection on flourescent screen, there you will get a nice blue.

  8. #8
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    Quote Originally Posted by decix View Post
    The power of blu ray diodes is underestimated. I think it's absolutely irresponsible to tell it is "safe".
    The beam does'nt look very bright to the human eye but has a lot of energy.
    The first accident is just a matter of time. Be very careful, don't do beamshows with 405nm.
    It's only good for projection on flourescent screen, there you will get a nice blue.
    Yes, quite correct. A blu ray laser should be treated with the same respect as any other laser, just because it's less visible doesn't mean it's less dangerous.

    Now i've re-read my post I should make it clear that I was talking specifically regarding the UV content when I said "less dangerous".

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

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