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Laser Flashlight possibility

  1. Aug 18, 2008 #1
    "Laser Flashlight" possibility

    Maybe some of you have seen the video, where they make a match-lighting capable laser pointer out of a DVD burner laser, like the youtube's video CgJ0EpxjZBU.

    Now, it's well known that youtube's bogon emissions are off the charts, nevertheless, having an ample supply of used computer parts, i've tried to make one, putting apart an 8x DVD-R.

    What it ended up is a very bright red flashlight, which is only identifiable as "laser" by the speckles in the light it gives, as the burner does not apparently have anything like a collimator in it. No problems along that line, a lens gets the thing focused in a tight 2-line-like point.

    The diode itself heats up noticeably, yet neither it's light, not the lens-focused point gives any noticeable heat. The diode itself didn't lasted long either without a proper power supply - a couple of days later it suddenly lost all but a tiny speck of it's brightness, becoming less bright than most indicator LED's.

    So, it neither burns, nor it is a laser in a "beam of light" capacity.
    Bogosity proved.

    That experiment left some questions nevertheless.

    First, maybe i did something wrong? After all, the written DVD's are ejected significantly heated, and there are no other power sources in the burner that i know of, so the diode must have some appreciable heat output, no?

    Second, what are the power required for a laser with a beam point the size of a typical laser pointer to light a match or burn thru a piece of paper? That is, what % of wattage inputted in a high-performance diode gets into the light, and what % of the light contributes to actual heating?
  2. jcsd
  3. Aug 18, 2008 #2


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    Re: "Laser Flashlight" possibility

    There is also a bunch of motors and circuit boards - the disc is not significantly heated by the laser.

    Probably more than 200mW.

    Now the fun bit - if you power the device wrongly it could be happily emitting a few hundred mW of invisible IR laser light, which will go straight through most thin black plastic and black insultion tape and straight into your eye.
    Your eye will focus 900-950nm light perfectly well, but you don't see it - so you don't blink, so you don't know anything is happening until you get this little popping sound on your retina.

    Feel free to continue if you either have (a) a lasersafety officer, laser googles and a laser lab, or (b) a supply of spare eyeballs.
  4. Aug 18, 2008 #3


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    Re: "Laser Flashlight" possibility

    Most people don't understand that optical drives do not use focused, collimated lasers to read and write material from the disc. Instead, they use a divergent beam which only reaches focus on the metallic disc surface itself, underneath the transparent plastic exterior. This reduces the effect of dirt, dust, and fingerprints on the plastic, since they are out of the focal plane.

    - Warren
  5. Aug 19, 2008 #4
    Re: "Laser Flashlight" possibility

    I have personally taken out the dvd drive burner laser and used it for a laser. It supplied red light with 3 volts if I'm not mistake and once in its short lifetime was enough to light a match. Soon later I got to exicted and supplied too much voltage causing a very bright red and soon a dim red light like and led...

    The laser should be powerful enough to burn your fnger or at least give you some heat where you feel it. Are you sure that you are using a dvd burner or just a dvd reader?
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