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Using optics inside a dvd rw drive laser sled

thebouljello

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I have decided that I will be using dvd rw drives to build my laser engraver in order to save space and reduce overall cost. Rather than extracting the red diode and putting it into an aixiz module, would it be possible to keep the diode inside the sled and use the preexisting optics? Although the lens on the sled is not adjustable, I could just attach the sled to aluminum extrusion with sliding nuts to adjust the beam. Thanks for any replies.
 



hakzaw1

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... interesting approach... are you using a different diode?? ... or the one in the sled already..I think that would work best with a 12X or16 X 405nm Blu-ray sled. not a red.
history:
sleds have been used to build white lasers--like the early 'white fusion'.. there is threads on this ..also the various optics inside have been removed and used again and a former member (UK) sells an assortment lot of sled optics on geekbay- and there is NO 'item' in hs pics that clearly shows the buyers the size of these.. I Ebaymailed him asking why no reference to size and why the high cost for basically free optics??.. I touched a nerve-- he was indignant and bragged about how happy all his buyers were.=-- and here ==all this time we throw most of that away.. IIRC tho.. Pyro still wants the sleds for his fireworks.
 

thebouljello

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If this is possible, I would use the preexisting red diode to make use of it already being there. What would make blu ray lasers work better than the red diodes for doing it this way? Also, I looked up the white fusion lasers and they reminded me of when I prototyped an rg yellow laser with a dichro and two cheap ebay lasers. It could have been better with higher quality lasers though.
 

paul1598419

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Those lenses in DVD R/W devices are adjustable, but because the focal length to the DVD is so short, they are unusable for this purpose. They have to focus down to ~1000nm to read or write to the DVD, IIRC. The polymer used for the DVD has it's own refraction index too, so the overall distance is very small.
 
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thebouljello

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@paul, with that being said, I take it that a blu ray sled would not work either because the focal length is too short. For my application, an aixiz module with a glass lens would probably be the best configuration. I may just buy a bdr209 and extract the red laser from the sled but keep it for a future project.
 

paul1598419

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@paul, with that being said, I take it that a blu ray sled would not work either because the focal length is too short. For my application, an aixiz module with a glass lens would probably be the best configuration. I may just buy a bdr209 and extract the red laser from the sled but keep it for a future project.
That is what I would do. You can get 850 mW safely out of the BDR-209 with a single element aspherical lens. You have the choice of either modulating the etching beam with PWM or TTL which will only give you the capability of turning the diode on and off. PWM is more involved, but you have the ability to vary the power on the fly.
 

thebouljello

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Bionic Badger made a post a while ago featuring a simple and efficient laser driver that supports PWM. Most G code streamers allow the user to modulate the power of the spindle (in this case the laser) if the driver supports PWM. I will probably use a bdr209 with the driver mentioned in order to vary the laser power.
 

paul1598419

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It's not really all that complicated. There are several ways I can think of to get variable power as long as the peak power is set. Then you vary the power down from there.
 
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hakzaw1

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I just removed a red diode from a sled LCC and looked at what is left.. for engraving --don't you need to cool the diode? That may not be easy aside from a fan or two.... these sleds do not have much in the way of heat sinking.
they must underdrive them or is it pulsed? f

or ~$16 usd you can buy a lab laser kit w/ big (1X1X2) heat sink, diode holder, fan and lens for your choice of wavelengths. all the hardware.. just add 405 diode and driver..
good luck---len
 

Cyparagon

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Yeah, unless you've already got the burner, it's cheaper to buy a module. You CAN re-configure the optics in the sled to collimate the beam, but it is a lot more trouble than it's worth. You'd be spending a lot of time to save $3 or whatever on a proper housing and lens.

They have to focus down to ~100nm to read or write to the DVD, IIRC.
Diffraction limitation says even with perfect/ideal optics, a 650nm beam cannot be focused to a spot any smaller than 650nm. Given the wave/particle duality, it's obvious why.
 

diachi

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Diffraction limitation says even with perfect/ideal optics, a 650nm beam cannot be focused to a spot any smaller than 650nm. Given the wave/particle duality, it's obvious why.

Think Paul maybe missed a 0...? Spot diameter for a DVD is about 1µm (1.1µm to be more precise) or 1000nm if you're not being all that accurate...
 

paul1598419

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I'm glad you noticed that. It was a typo. Sorry. And I was talking specifically about the 405nm diodes. But, yeah, optics won't allow one to focus a spot lower than the WL of the laser. And that is in a perfect world. My point was that the optics used for focusing the beam onto a DVD is not capable of being used for etching purposes.
 

aaronnoraa

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You can use the sled and get a standard, collimated output from it with the included optics after a small modification but this will not work for engraving without adding another lens to bring the collimated output to a focal point for engraving (and as others have said, the sled before modifying will be focused to an unusably short distance). The sled will provide poor heat dissipation abilities and likely will limit the output of the diode from what it may be able to achieve in a proper heatsink. The way to get a normal, collimated beam out of a sled is to remove the final lens assembly (the 'floating' lens on the top of the sled) and remove the diffraction grating (which if left in place will cause multiple beams) which is usually located directly in front of the diode's output. You will need to run your own regulated power to the diode in the sled.
 
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