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DVD burner optics ...

Things

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Well I recently ripped apart a DVD burner, and found a few neat little optics, but I wanna know what they are for. I think there may be a beam combining cube? If so, it would save me blowing $55 on a PBS cube. Any ideas ?
 





Krutz

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yes, there are nice things in dvd-drives!
there are other threads which discuss optics found in a particular sled. you will recognize all parts you see in yours, since all parts are very different from each other, and every sled has the same stuff. though you will miss a few things found in 3-laser-things like bluray and hd-dvd.

look for those threads, i will make a short list of what i remember and tried:

laserdiode: sure, thats what you were after, not? forget the IR one, its useless in almost every possible application one could think of. and so dangerous that its simply worthless altogether.

"cube": there are cubic glass thingies in there. come in 3mm and 5mm, and have a diagonal glue-line visible on the top-side. they are either dichroic, or polarising, or both.
dichroic: shine a red through it and a IR in 90° to the red, both beams will be coming out of the same side (one will be reflected at the inner glue-line, the other not). doesnt matter how you rotate the pointers. those have little use.
polarising: you can combine any laser-color, and even two lasers of the same color. you arrange them the same way as above. you have to rotate the lasers to the right polarising, you can only combine two lasers this way, the doubled output-beam cant be combined any further.
both: in that case, the polarising cube is like the regular polarising one, but works only for limited colors. means, it wouldnt do anything useful with green lasers, for example.
how to check: use any laserdiode-pointer, shine it through the cube. watch where the laser goes to (straight or right-angle reflection). rotate the laser, watch if the output changes. ideally, you can "dial" the point to go through 100% to right-angle 100%, and any value in between.
i consider a 5mm polarising cube (as found in kes-300a ps3 sleds) the most valuable part, after the diode itself.

pickup-diode:
the one directly under the cd/dvd. they are really cool, in fact! very low focus-distance, so you have to bring them very close to the laserdiode, 1 to 2 mm, to work. but then they will collect all light from the laserdiode, no light wasted outside the lens-diameter. then they are AR-coated, antireflective-coated. adds anothe 8% to the output. and finally, because of the short disctance, the beam will be around 1 to 2 mm thin only! unfortunately this means the beam will spread out more with distance (its always one of these two, you cant have a thin and well collimated/parallel beam at the same time). i wrote about using that lens as collimater. besides that, no use. you cant use it well to play with an already collimated laserbeam, like for burning or something.
note: only take lenses from a blu-ray pickup to collimate your bluray-diode. taking a dvd-pickup-lens, you could lose as much as 50% of the laserpower, because of the wrong (=bluray-blocking) antireflex-coating!

thats the parts i actually use. other interesting stuff:

"waveplate": a thin piece of glass, with no wires attached. you can perhaps use it like a polarising cube, i didnt experiment with that yet.

gratings: apparently clear, or smeared small pieces of flat plastic, sometimes with integrated lens as well. shine a laser through, and you get a line of several dots out of it.

circuit: you can get tiny switches, potentiometers and leds out of it. the motors are only useful when they have 2 wires, else they need a complex (step-motor-) driver.

turning-mirror: the thing that reflects the beam through the final lens. it is relatively large, glass, often weird triangle-shaped. this is about the best mirror you will get for low money. its not with reflecting silver or aluminium, but with dichroic coatings. you will have your beam reflected from it (be sure to have the mirror 45° from the beam, like it was in the drive!) perfectly. no loss, no distortion, no ghost-image. well, the ones from cd drives work for IR only, the dvd-ones for IR and red, the blu-ray ones for blu-ray, red and IR. obvious, not?

the metal-sled itself: someone posted a vid where he ignited the metal with a torch. its aluminium-magnesium-alloy, once it burns, it burns blindingly bright. well, its magnesium, duh!


okay, this got longer than i planned.. i bet you knew some of it already, dont worry, its intended for all the people reading here as well ;-)

so, conclusion: take the shiny stuff out of your diode-donor drive, hold it into laserbeams, play around and see funny things! :)
theres nothing with so many cool parts inside as a dvd-drive! well, next would be a laserprinter, with liquid-sky-generating rotating mirror, some funny lenses, some fibers..

manuel
 

daguin

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Krutz said:
so, conclusion: take the shiny stuff out of your diode-donor drive, hold it into laserbeams, play around and see funny things! :)
theres nothing with so many cool parts inside as a dvd-drive! well, next would be a laserprinter, with liquid-sky-generating rotating mirror, some funny lenses, some fibers.

Try salvaging out an electron microscope or a DNA sequencer ;)

Peace,
dave
 

Things

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Thanks for the post! I am trying to combine 2 open can reds, so hopefully that will work. Dave, send me a DN sequencer and I will happily play around with it :p
 




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