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Re: Laser Diodes from Laser Printers?

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  • tfrohaly
    ... include the ... if any ... using them ... Yeah, I ve got a recommendation. Have you seen those labels inside the printers, the ones that say something to
    Message 1 of 14 , Aug 1, 2003
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      --- In SeattleRobotics@yahoogroups.com, Tom Capon <robot@d...> wrote:
      > Hey,
      > I've taken apart a couple of laser printers in the past few months, and
      > i've managed to salvage a great deal of parts from them. These
      include the
      > laser mechanisms used for writing to the paper. I'm just wondering
      if any
      > of you guys have any ideas / recommendations / warnings about
      using them
      > for anything? I think I've got two of them around here
      > somewhere. Thanks. --Robot256

      Yeah, I've got a recommendation. Have you seen
      those labels inside the printers, the ones
      that say something to the effect of "Warning:
      invisible laser radiation, avoid exposure to beam" ?
      Nothing personal, but only an idiot would
      consider using those laser diodes in a way
      where other people could unknowingly get their
      retinas fused. Most, if not all, robotics
      applications fall into that category.

      Besides the fact that it's dumb, using the
      lasers in this manner can be illegal (especially
      if you also drive excess current through them to
      increase the power).

      Tim.
    • David VanHorn
      ... Flame Off Johnny! If you look, he asked for ideas AND WARNINGS. Would you make the statement that only an idiot would use gears, because someone might
      Message 2 of 14 , Aug 1, 2003
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        At 03:52 PM 8/1/2003 +0000, tfrohaly wrote:

        >--- In SeattleRobotics@yahoogroups.com, Tom Capon <robot@d...> wrote:
        >> I'm just wondering if any of you guys have any ideas / recommendations /
        >>warnings about using them for anything?


        >Nothing personal, but only an idiot would
        >consider using those laser diodes in a way
        >where other people could unknowingly get their
        >retinas fused.

        Flame Off Johnny!

        If you look, he asked for ideas AND WARNINGS.

        Would you make the statement that only an "idiot" would use gears, because someone might stick their fingers in them? Of course not. But you might recommend a guard to avoid the problem. We use lots of things that you can hurt yourself with. Any decent sized battery pack has a risk of fire and burns associated with it, if you don't take proper precautions.

        These lasers are perfectly safe, when used with proper precautions.

        I don't have any real ideas on where you'd use one in a robotics application, but as long as you take measures to keep the collimated beam from getting into open space, and an interlock to prevent accidental exposure, I don't see a problem.

        Warning labels can be applied to the housing, just like the big guys do it.

        That said, a visible beam is much safer, since you can see that it's on.
      • tfrohaly
        ... recommendations / ... Yup, I saw that, that s why I volunteered a warning . This issue has come up several times in the past few months, but I haven t
        Message 3 of 14 , Aug 1, 2003
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          --- In SeattleRobotics@yahoogroups.com, David VanHorn <dvanhorn@c...>
          wrote:
          > At 03:52 PM 8/1/2003 +0000, tfrohaly wrote:
          >
          > >--- In SeattleRobotics@yahoogroups.com, Tom Capon <robot@d...> wrote:
          > >> I'm just wondering if any of you guys have any ideas /
          recommendations /
          > >>warnings about using them for anything?
          >
          >
          > >Nothing personal, but only an idiot would
          > >consider using those laser diodes in a way
          > >where other people could unknowingly get their
          > >retinas fused.
          >
          > Flame Off Johnny!
          >
          > If you look, he asked for ideas AND WARNINGS.

          Yup, I saw that, that's why I volunteered a "warning".

          This issue has come up several times in the past few
          months, but I haven't seen any posts that recommend
          caution. That's why I wanted to make my point in no
          uncertain terms. Specifically, I wasn't flaming the
          poster - I intended that to be clear by saying
          "nothing personal".

          > Would you make the statement that only an "idiot" would use gears,
          because someone might stick their fingers in them? Of course not. But
          you might recommend a guard to avoid the problem. We use lots of
          things that you can hurt yourself with. Any decent sized battery pack
          has a risk of fire and burns associated with it, if you don't take
          proper precautions.

          Your statements are irrelevant. The issue is not whether
          you are free to mangle your own fingers or burn your own
          retinas (go ahead, I don't care) but whether you should feel
          free to expose innocent bystanders to the risk of these lasers,
          without their knowing or consent. Isn't that what I said?

          "...only an idiot would consider using those laser
          diodes in a way where other people could unknowingly
          get their retinas fused."

          Note that my whole point is danger to OTHERS brought
          on by the irresponsibility of a hobbyist who doesn't
          know better.

          Part of what makes infrared lasers dangerous is that they
          are *invisible*. Kids examining your robot closely at Robothon,
          or simply observing a competition, could receive eye damage
          without the slightest idea that they've been exposed. And,
          since the beam is highly collimated, injury can occur a long
          distance away - the injured party may not even be aware they
          are anywhere near a laser.

          Lasers light is also outside normal experience and the caution
          learned from that experience. It won't hurt to look into the
          laser (heck, you won't even *see* it if it's infrared) so your
          blink reflexes won't help to keep you safe.

          And, as I implied, there are laws and regulations governing
          the proper use of lasers. Attempting to incorporate these
          devices into your own design without full knowledge of what
          you're doing is, I will repeat, idiotic. That goes double
          for pumping up the current to increase the range (therefore
          power) of the laser, as previous posts have suggested.

          Tim.
        • Alan King
          ... Agreed, tool just like any other tool. Amazing though how many even adults think lasers are toys though, I ve wanted to knock some people upside the head
          Message 4 of 14 , Aug 1, 2003
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            David VanHorn wrote:

            > These lasers are perfectly safe, when used with proper precautions.

            Agreed, tool just like any other tool. Amazing though how many even
            adults think lasers are toys though, I've wanted to knock some people
            upside the head on more than a few occasions after seeing them stick a
            laser pointer right in their friend's eye playing around. There are
            some people who really are just too dumb to be allowed anything,
            hopefully not too many in this group though..


            >
            > I don't have any real ideas on where you'd use one in a robotics application, but as long as you take measures to keep the collimated beam from getting into open space, and an interlock to prevent accidental exposure, I don't see a problem.
            >
            > Warning labels can be applied to the housing, just like the big guys do it.
            >
            > That said, a visible beam is much safer, since you can see that it's on.
            >

            The one thing I have thought about them for is a long range IR link,
            spread the beam just a bit and it's much less likely to cause any type
            of eye damage yet should still get much longer range than just an IR
            LED, and could easily be set up over normal head height etc. Really for
            longer distance telemetry more than robotics, since it'd be hard to keep
            it on target beyond a certain point. Requires modulation but that's
            already in the board for a laser printer, but info can be very difficult
            to find so you just about have to get a working printer to see how to
            run the board. A printer junked because of a bad fuser would be fine
            though, everything else should be working.

            The most interesting thing to do with most laser printers is take the
            5, 6, or sometimes 8 sided mirror and get it spinning and point a
            visible laser diode at it. Then you get to see how the mirrors are
            precisely ground and slightly offset to produce multiple lines from the
            single laser. Not very useful except to see how it works.

            While it's fun to junk stuff, it will usually limit what can be done
            and take more time than it's worth. Motors are the main things useable,
            and it's many times better to just spend $50 and get 10 steppers off
            Ebay, and $10 or $20 more and get transistors etc to make your own
            drivers. Engineer once, and use over and over, just buy more motors etc
            when needed. While it's not "free" it's cheap, and you have to have a
            whole lot of the same junk to make up the difference in time and work.
            It's not the cost but the time spent pulling the parts, and having to
            slightly reengineer the solutions when you run out of a few parts that
            make it not worthwhile unless the motors are especially large. Only if
            you have 10 or 20 of the exact same printer etc does it become useful
            for general components.

            That said the rails from old dot matrix printers are the one thing
            that doesn't generally apply to. Rails from even 2 or 3 printers can be
            quite useful, and with their relatively high cost to purchase and having
            to engineer most solutions seperately anyway they often move back into
            the worth pulling category.
          • David VanHorn
            ... That s true of batteries, gears, sharp edges, and lasers, and probably other bits I didn t think of. An improperly charged Li-Ion cell is every bit as
            Message 5 of 14 , Aug 1, 2003
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              >
              >
              >Note that my whole point is danger to OTHERS brought
              >on by the irresponsibility of a hobbyist who doesn't
              >know better.

              That's true of batteries, gears, sharp edges, and lasers, and probably other bits I didn't think of.
              An improperly charged Li-Ion cell is every bit as dangerous as an IR laser, even more so since it will splatter highly reactive chemicals over a broad area, where you have to intercept the very small beam of the laser with your very small pupil to cause eye damage. We aren't even considering power here, but just assuming that it is above the optical damage threshold, and that the beam is collimated such that it is a danger at any reasonable distance.

              >Part of what makes infrared lasers dangerous is that they
              >are *invisible*. Kids examining your robot closely at Robothon,
              >or simply observing a competition, could receive eye damage
              >without the slightest idea that they've been exposed. And,
              >since the beam is highly collimated, injury can occur a long
              >distance away - the injured party may not even be aware they
              >are anywhere near a laser.

              Which is why guards and interlocks are used.
              We hand CD players containing these lasers to millions of children.
              The guards and interlocks are quite simple.

              >Lasers light is also outside normal experience and the caution
              >learned from that experience.

              In general I agree, but you are making it out to be some deep dark secret, when really it's rather simple. If there is no way for the collimated beam to escape the enclosure, and no way for the beam to be on if the enclosure is intact, then you're done. A diffuse (paper) reflection isn't going to cause any problem, only a specular (mirror) reflection will.

              >It won't hurt to look into the
              >laser (heck, you won't even *see* it if it's infrared) so your
              >blink reflexes won't help to keep you safe.
              >
              >And, as I implied, there are laws and regulations governing
              >the proper use of lasers.

              Certainly.

              > Attempting to incorporate these
              >devices into your own design without full knowledge of what
              >you're doing is, I will repeat, idiotic.

              You're pushing it.
              A laser in a complete metal enclosure presents no hazard at all.
              You need an interlock to prevent exposure when the enclosure is open.
              As long as there's no specular or direct path out of the enclosure, you're fine.
              I do agree that Ir presents additional hazards since it's not visible, and you stated those nicely.

              Every CD player you've ever seen incorporates those features.

              >That goes double
              >for pumping up the current to increase the range (therefore
              >power) of the laser, as previous posts have suggested.

              That's quickly self limiting, as they are normally run very close to their damage thresholds, and any significant increase in power will give you a brief pulse in the 10 micron band, as it converts to a dark emitting diode.
            • Bob Dyer
              It s pretty hard for IR light to make it through the water filling the eyeball to reach the retina. Laser damage to the retina is more likely to be caused by
              Message 6 of 14 , Aug 1, 2003
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                It's pretty hard for IR light to make it through the water filling the eyeball
                to reach the retina. Laser damage to the retina is more likely to be caused by
                visible lasers, especially when the eye is focused to infinity. That's when the
                collimated laser light is brought to the smallest point on the retina. The main
                danger from IR light is to the cornea and that's minimal at these levels.

                These warnings are for lawyers. This doesn't mean you should be staring into
                laser diodes intentionally, but the "danger" is much overstated in our litigious
                society.

                Bob

                -----Original Message-----
                From: tfrohaly

                Yeah, I've got a recommendation. Have you seen
                those labels inside the printers, the ones
                that say something to the effect of "Warning:
                invisible laser radiation, avoid exposure to beam" ?
                Nothing personal, but only an idiot would
                consider using those laser diodes in a way
                where other people could unknowingly get their
                retinas fused. Most, if not all, robotics
                applications fall into that category.

                Besides the fact that it's dumb, using the
                lasers in this manner can be illegal (especially
                if you also drive excess current through them to
                increase the power).
              • David VanHorn
                ... True, but I didn t want to complicate the discussion any further. :) ... I was at a gas station a couple days ago, fueling, sitting next to a liquid oxygen
                Message 7 of 14 , Aug 1, 2003
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                  At 11:39 AM 8/1/2003 -0700, Bob Dyer wrote:

                  >It's pretty hard for IR light to make it through the water filling the eyeball
                  >to reach the retina. Laser damage to the retina is more likely to be caused by
                  >visible lasers, especially when the eye is focused to infinity. That's when the
                  >collimated laser light is brought to the smallest point on the retina. The main
                  >danger from IR light is to the cornea and that's minimal at these levels.

                  True, but I didn't want to complicate the discussion any further. :)

                  >These warnings are for lawyers. This doesn't mean you should be staring into
                  >laser diodes intentionally, but the "danger" is much overstated in our litigious
                  >society.

                  I was at a gas station a couple days ago, fueling, sitting next to a liquid oxygen truck, with a cryogenic liquid (lox?) leaking out of the back, dribbling down a very frosty stairstep, and spattering on the concrete next to the gas pump.

                  As I put the grounded nozzle into my ungrounded truck, which had some unknown static charge built up on it from driving, I briefly thought that I might pull out my cell phone... Funny how you can't SMOKE within 25' of the lox truck (a placard on the truck just above the leak said so), and you apparently DARE NOT use your cell phone at a gas station, but apparently it's ok for a LOX truck to sit there leaking cryojuice (presumably LOX) at a GAS STATION, next to a GAS PUMP with heavier than air GAS VAPOURS, while I spark the grounded GAS nozzle into my ungrounded and charged GAS TANK inlet full of GAS VAPOURS.

                  But since I wasn't using my cell phone, I was perfectly safe, and of course able to concentrate on their commercials over the speakers at the pump...

                  What the hell. :)
                • tfrohaly
                  ... the eyeball ... caused by ... That s when the ... retina. The main ... levels. Actually, no - that isn t true. Just the opposite in fact. Laser light in
                  Message 8 of 14 , Aug 1, 2003
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                    --- In SeattleRobotics@yahoogroups.com, "Bob Dyer" <bd@t...> wrote:
                    > It's pretty hard for IR light to make it through the water filling
                    the eyeball
                    > to reach the retina. Laser damage to the retina is more likely to be
                    caused by
                    > visible lasers, especially when the eye is focused to infinity.
                    That's when the
                    > collimated laser light is brought to the smallest point on the
                    retina. The main
                    > danger from IR light is to the cornea and that's minimal at these
                    levels.

                    Actually, no - that isn't true. Just the opposite in fact.

                    Laser light in the visible to near infrared spectrum
                    (400 - 1400 nm) is *focused* by the eye onto the retina.
                    These wavelengths are known, in laser eye safety literature,
                    as the "retinal hazard region".

                    The near infrared band (~780 - 1400nm) is the *most* dangerous
                    part of this region, since invisible infrared doesn't trigger
                    the blink reflex that protects eye in the visible region.

                    Laser light in the ultraviolet (290 - 400 nm) or far infrared
                    (1400 - 10,600 nm) spectrum is *absorbed* before it reaches
                    the retina, so causes damage to the cornea and/or the lens.

                    Google "laser eye safety" for more information.
                    Much of it is derived from the OSHA regulations
                    based on ANSI standards, backed of course by
                    decades of clinical research.

                    Tim.
                  • tfrohaly
                    My last words on this topic... I urge anyone contemplating using a laser in a robotics project to first learn about laser eye safety. A good starting point is
                    Message 9 of 14 , Aug 1, 2003
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                      My last words on this topic...

                      I urge anyone contemplating using a laser
                      in a robotics project to first learn about
                      laser eye safety. A good starting point is
                      the widely referenced website at:

                      http://www.repairfaq.org/sam/lasersaf.htm#saftoc

                      One of the interesting calculations you will find
                      there is a comparison of the intensity of light
                      falling on the retina from staring directly at the
                      Sun vs. staring directly into a 1mW laser (most
                      laser pointers are more like 5mW...). Turns out
                      that the laser can have an intensity on the retina
                      150 times MORE than the Sun. So if you believe
                      that staring into the Sun can cause eye damage,
                      you should have no problem believing that a low power
                      laser can also damage the eye. And infrared lasers
                      are worse, because they don't cause you to blink so you
                      tend to get longer exposures than with visible light.
                      (Power density is not the only factor determining
                      when damage occurs, but is is a significant factor).

                      There is a lot of great information on the web,
                      including more formal documentation like:

                      http://www.osha.gov/SLTC/laserhazards/index.html
                      or
                      http://www.princeton.edu/~ehs/laserguide/laserguideTOC.htm

                      Tim.
                    • Bob Dyer
                      Well, I stand corrected - if these are near-IR lasers. Of course all this begs the question of beam shape. A 1mW, collimated beam pointed directly into the eye
                      Message 10 of 14 , Aug 2, 2003
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                        Well, I stand corrected - if these are near-IR lasers.

                        Of course all this begs the question of beam shape. A 1mW, collimated beam
                        pointed directly into the eye is a lot different than the amount of energy that
                        enters the pupil from a widely divergent source way past the focal point of the
                        lens. Aren't these printers focusing the beam to a very small point at very
                        close distances? That beam pattern has to be highly non-collimated and fairly
                        large at any significant distance from the laser.

                        We used to get annual "LASER-eye exams" until they discovered that flashing a
                        retina through a dilated pupil with enough light to take a photograph was much
                        worse for the eye compared to the chance of injury from any of our equipment. I
                        still think the danger is over-blown for legal reasons (OSHA regs included), but
                        better safe than sorry - play with at your own risk.

                        Anyway, I prefer LEDs and visible ones at that, primarily because you can "see"
                        where the light is impinging.

                        Bob

                        -----Original Message-----
                        From: tfrohaly

                        Laser light in the visible to near infrared spectrum
                        (400 - 1400 nm) is *focused* by the eye onto the retina.
                        These wavelengths are known, in laser eye safety literature,
                        as the "retinal hazard region".
                      • Tom Capon
                        Thanks for all your replies! Now I know that I should wait until I have a really good reason before trying to do anything with them, and where to go for
                        Message 11 of 14 , Aug 3, 2003
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                          Thanks for all your replies! Now I know that I should wait until I have a
                          really good reason before trying to do anything with them, and where to go
                          for safety considerations. --Tom


                          At 10:01 PM 8/2/2003 -0700, Bob Dyer wrote:
                          >Well, I stand corrected - if these are near-IR lasers.
                          >
                          >Of course all this begs the question of beam shape. A 1mW, collimated beam
                          >pointed directly into the eye is a lot different than the amount of energy
                          >that
                          >enters the pupil from a widely divergent source way past the focal point
                          >of the
                          >lens. Aren't these printers focusing the beam to a very small point at very
                          >close distances? That beam pattern has to be highly non-collimated and fairly
                          >large at any significant distance from the laser.
                          >
                          >We used to get annual "LASER-eye exams" until they discovered that flashing a
                          >retina through a dilated pupil with enough light to take a photograph was much
                          >worse for the eye compared to the chance of injury from any of our
                          >equipment. I
                          >still think the danger is over-blown for legal reasons (OSHA regs
                          >included), but
                          >better safe than sorry - play with at your own risk.
                          >
                          >Anyway, I prefer LEDs and visible ones at that, primarily because you can
                          >"see"
                          >where the light is impinging.
                          >
                          >Bob
                          >
                          >-----Original Message-----
                          >From: tfrohaly
                          >
                          >Laser light in the visible to near infrared spectrum
                          >(400 - 1400 nm) is *focused* by the eye onto the retina.
                          >These wavelengths are known, in laser eye safety literature,
                          >as the "retinal hazard region".
                          >
                          >
                          >Visit the SRS Website at http://www.seattlerobotics.org
                          >
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