Page 3 of 140 FirstFirst 123456713 ... LastLast
Results 21 to 30 of 1395

Thread: Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

  1. #21
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    I think that is where possibly some are saying that these are not usable. I am just after 500mW, corrected to fit on some 3mm mirrors. I don't care if I lose 75% in all the optics (collimaters, prisms, wave plates, PBS and pinhole). If I need 2W to manipulate it down to a usable beam and get 500mW, I would be fine with this. The price of these will still be cheaper. These have also been overdriven by a lot and hold up well. Of course, overdriving them will shorten the lifespan, but if you only get 2500 hours out of them that is still a lot of time (unless you do gigs every night). I use my projector in the garage so, not a lot of use. I just want something to go with my 300mW green and my corrected 445, which after optics, is about 600mW. My LW 640nm is not able to keep up without attenuating the blue a little and the green a lot. 500mW of 635 would look mighty sweet.

    I do see, however, Steve's point here. When you start stacking beams and try to get multi-watts out of them, you are going to get a shit beam. Stacking too many diodes is pointless if you are going to pinhole. It may be possible to run a quad, knife edge the pairs tightly and combine them in the same orientation via wave plate and PBS, correct them via prism and then pinhole with a slightly larger diameter aperature (say 4mm), this is what I have in mind for my setup. Beyond that, kinfe edging a quad, or knife edging two groups of 3 or more and PBSing them... now the pinhole idea will start cutting off the additional beams and would be the same effect of trying to make a sailboat move by aiming a large fan at the sail from inside the boat. So yes, I can see where Steve is coming from. 2W of graphics capable red... I think we would seriously need Indiana Jones and his dad to help us find that grail.
    If you're the smartest person in the room, then you're in the wrong room.

  2. #22
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,590

    Default

    Quote Originally Posted by absolom7691 View Post
    When you start stacking beams and try to get multi-watts out of them, you are going to get a shit beam.
    thing is even if you stack a bunch of the opnext diodes you still get a shit beam... or you have high power 650 red diodes, shit beam...

    if you want a lot of red for cheap you need to come to terms with giant beams... get bigger scanner mirrors or go home

    anyway I would not want a 1W red with a LOC type beam, think of the power density! would be pretty dangerous

  3. #23
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    I hear ya. I am itching for my weekend to start so I can play with the ones I just got. Honestly, as has been said before, it seems like the public doesn't care if beams are too big. So, there you have it.

    Can you guys stop being so selfish. One of you needs to stop what you are doing, go to school and get a phD in optical and chemical engineering. Then, you can find us better lasing mediums!
    If you're the smartest person in the room, then you're in the wrong room.

  4. #24
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,590

    Default

    Quote Originally Posted by absolom7691 View Post
    I hear ya. I am itching for my weekend to start so I can play with the ones I just got. Honestly, as has been said before, it seems like the public doesn't care if beams are too big. So, there you have it.
    I find it amusing that on one end we have the people with the endless quest for tiny HeNe like beams, then on the other end we have people developing lenses to diverge your output for safety... umm... so if we are going to diverge it who cares if the beam is big to begin with?

    we can just get bigger scanner mirrors and diverge the other colors to match

  5. #25
    Join Date
    Feb 2010
    Location
    Melbourne, Australia
    Posts
    1,106

    Default

    I love the enthusiasm in this thread, it's infectious and I hope you guys come up with something workable.

    Quote Originally Posted by CDBEAM View Post
    But Absol's point is that the Opnext 637 cost about $ 0.87/mW....and the ML520G71 cost about $ 0.14/mW....( assuming driving the Opnext to 200mW @ $ 175.00 @ and driving the ML520G71 to 500mW @ $ 70.00 @)
    I'm not sure I agree with your maths.

    mW/$ comparisons should be calculated post optics losses and should factor in power density and divergence. I would be interested to see if there's an equation demonstrating same or better (preferably) power density and divergence from these Mitsubishi diodes compared to their OpNext cousins.

    I suspect the cost of the holy grail of optics to produce an ideal beam from the Mitsubishi diodes would be more than the cost of getting an equivalent beam using the OpNexts.

  6. #26
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,590

    Default

    ya but when you inevitably kill them the opnexts are more expensive to replace

  7. #27
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    Not to mention that people have run these things way beyond spec. Again, how long will they run like that?? Still a mystery, but these things are though as nails. Some have run these things up to 800mW at some length. Still, for satellites of something like that, even a PBS dually at this power for this price, nothing comes close. Like I said before, these are cheap enough to experiment with... That's all.
    If you're the smartest person in the room, then you're in the wrong room.

  8. #28
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    Quote Originally Posted by taggalucci View Post
    I love the enthusiasm in this thread, it's infectious and I hope you guys come up with something workable.



    I'm not sure I agree with your maths.

    mW/$ comparisons should be calculated post optics losses and should factor in power density and divergence. I would be interested to see if there's an equation demonstrating same or better (preferably) power density and divergence from these Mitsubishi diodes compared to their OpNext cousins.

    I suspect the cost of the holy grail of optics to produce an ideal beam from the Mitsubishi diodes would be more than the cost of getting an equivalent beam using the OpNexts.
    I agree with most of this. After we play around with these and get the verdict in, then we will know. Like said, the good thing is, these are cheap enough to play around with. For me, I have a few things these can go in if they are worthless for graphics. So it won't be any loss. The lumia that they would be going needed big reds anyway so, cheap red... Perfect. ...and I get to experiment with them too!
    If you're the smartest person in the room, then you're in the wrong room.

  9. #29
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    There is characteristic feature in the part that allows it to be driven hard under certain conditions, but not as much as you describe. I cannot disclose how it works, nor do I have all the conditions under which to use it. But it is deceptive. You may go a bit over the data sheet. But that feature will not protect you from long term gross overdrive. You cannot morally go out and do a professional show with over driven diodes.

    At 800 mW, bah, your taking advantage of the feature, and not using the way it was designed, the MTBF would be very short, on the order of hours. A few selected devices would make it that high. Of course, the only way you can select them is to burn them out.

    I've also had it in front of corrective optics a year ago. Losses approached 50% for a good beam symmetry, after some of the best optics on the market. Not the cheap ones. Color "Donuts" in your beams are un-acceptable.

    You need to design for 8500 hours of life if your a hobbyist, I'm not going to get into the math of that.


    A certain other forum is all about reckless overdrive. It gets me angry often, because they never study enough devices to get a good MTBF. The problem is too many people get burned when they follow the "Imax" folklore. Failure of a laser when doing a show is unacceptable. There is a time when you get too cheap, and it backfires on the business. The factory de-rates devices for a reason.

    Dr. Arrhenius would perhaps be amused.

    Yes, I'm conservative, but I have been at this a long time.

    Steve
    Last edited by mixedgas; 09-29-2011 at 01:14.

  10. #30
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    I have read, yes, they do overdrive quite a bit. I guess in a pointer, that is on for no longer than a minute at a time would work for overdriving. Well, I have 2 to play with that will most likely go in a lumia. Thanks for setting this straight as I have wondered about the lifespan for these, being driven that hard. I was thinking no more than 50% over spec for mine. That other forum is going 100%~200% over. That has got to be bad.
    Last edited by absolom7691; 09-29-2011 at 01:26.
    If you're the smartest person in the room, then you're in the wrong room.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •