Page 2 of 13 FirstFirst 12345612 ... LastLast
Results 11 to 20 of 128

Thread: NUBM44 blue- New Video

  1. #11
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    To try to address the power discrepancy I will retest the collimated diode without any additional optics and in order to evaluate the meter, also test a couple of DPSS lasers as well as one of the previous blue diodes.

    Meanwhile, if you look at the far field pattern, you will see what appears to be a double stripe. The main stripe is clearly that, the main stripe, but there is a significant stripe lying below it that cannot be focused into it. Typically, when a blue diode is brought to a far field focus the single main stripe is obvious and there are several symmetrical and much fainter stripes that are parallel to the main stripe, lying on each side of it. Have there been any divergence measurements of the near field and the far field dimensions?

  2. #12
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    OK, I've done some additional testing and I am narrowing down the sources of the discrepancy, but it still remains. I went back to DTR's site and copied down the relative output in watts vs input current for two diodes I have used many times in the past; the P73 and the earlier generation, 9mm, 445nm diodes. The P73 is using Dave's 2mm aspheric lens and the 9mm is using the G-9 collimator. A table of the results would be burdensome to generate, but to summarize, my Ophir meter is 10% conservative relative to DTR's for the P73 at all posted current settings and 5% conservative for the 9mm tested all the way to 2.6A. I am not claiming my meter is more accurate ( or conceding that it is less so), but assuming the meters haven't changed then the NUBM44 diode I have is not performing as well as it should.

    I then tested the NUBM44 with only the G-9 collimator and the maximum output is 5.6W at4.4A. Increasing the current further causes the power to decrease. I also measured the beam dimensions of the two blue diodes and this is eye opening. At 50cm from the front of the collimator lens, the "3W", 9mm beam is 3mm high and 2mm wide. The beam from the NUBM44 at the same distance from its collimator is 3mm high and 7mm wide. In the far field and at the same 14M distance the 3W is 9mm high and 58mm wide while the NUBM44 is 12 mm high and 180mm wide!

    These beam dimensions suggest that much more aggressive beam expansion will be necessary for the NUBM44 to produce a similar far field spot size, but the near field beam is already fatter and so this will constrain the potential expansion more for the diode that needs it more. This is not good.

    I'm looking forward to some posts that analyze the beam quality of this diode rather than focusing only on the RAW output. Hopefully, there will be some better methods to limit divergence than I have tried.

  3. #13
    Join Date
    May 2007
    Location
    1 hr from everything in SoCal
    Posts
    2,753

    Default

    Is it possible that your diode may be defective? I am curious to see others' far field spots in comparison to yours to see if maybe the emitter on yours has a defect.
    If you're the smartest person in the room, then you're in the wrong room.

  4. #14
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    921

    Default

    Looks like the emitter is about 3X the width of the NDB7875 and 2X the NDB7A75. Or, about the same as the p73. I would imagine it should do 7-9 watts. I read, some time ago, the facet of the first generation 445's could handle 8W optical power.

    It sounds like the diode under test is not transferring heat to the mount. This could be tested by driving it with a 25% duty cycle square wave to see if the power output is 1/4 what it is at CW drive. If it is far from 1/4 the CW measurement it could be concluded the diode is getting too hot.

    Is is possible to test a diode in its original mount?

    Also, it would be nice to know what current it gets in the projector it came from.

  5. #15
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Is it possible that your diode may be defective?
    At this point, I am assuming it is.

    I am curious to see others' far field spots in comparison to yours to see if maybe the emitter on yours has a defect.
    Ya, where is everyone?

    I read, some time ago, the facet of the first generation 445's could handle 8W optical power.
    I don't know. When I super-cooled one of these diodes in LN2 it went LED with a crappy emission pattern at somewhere around 150% of the RT maximum output.

    It sounds like the diode under test is not transferring heat to the mount.
    Why do you say this? The copper mount is a pretty good starting point and nowhere during the current ramp up do I show a hump where a thermal constraint is becoming a problem. The 1A/1W ratio holds until the max is reached and the power begins to reduce with increasing current.. I do suspect that the beam may be so bad that the beam does not all fit on my meter's input aperture. This is probably not very significant however, as it all appears to do so.

  6. #16
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    921

    Default

    I read, some time ago, the facet of the first generation 445's could handle 8W optical power.
    This was from an engineering doc from the manufacturer. There was no duty cycle data with that statement. I meant it to mean pulsed.

    Why do you say this? The copper mount is a pretty good starting point and nowhere during the current ramp up do I show a hump where a thermal constraint is becoming a problem. The 1A/1W ratio holds until the max is reached and the power begins to reduce with increasing current.. I do suspect that the beam may be so bad that the beam does not all fit on my meter's input aperture. This is probably not very significant however, as it all appears to do so.
    Its hard to say without a PI graph. I noticed the same phenomena (much lower I and P) with the first gen 445's when mounted in a o-like mount. The foldback happened at some "knee" that was much lower than when the diode was better heatsinked.

  7. #17
    Join Date
    Jun 2007
    Location
    Monroe, Mi USA
    Posts
    818

    Default

    Well...I will run some optic tests as soon as I receive my diode !!!.. My "tests" will pale in comparison to Eric's.....but the greater the sample population, the more likely we will have some true handle on this diode's nature.

    Perhaps the aspect ratio on this is even worse than the P73/HL63193....Dunno....wouldn't that be a PITA !!! We have some options for optical correction/adaptation... Fun times again !!! Let's hammer this beam into sweet submission !!!!
    Beam Axiom #1 ~The Quantum well is DEEP ! Photons for ALL !!
    .
    Beam Axiom #2 ~Yes...As a matter of fact...I DO wear tinfoil on my head !!
    .
    Beam Axiom #3 ~Whe'n dout...Po ah Donk awn et !!
    .
    Beam Axiom #4 ~A Chicken in every Pot, and a Laser Lumia in every Livingroom !!
    .
    Beam Axiom #5 ~"Abstract Photonic Expressionism"....is "Abstractonimical" !!
    .
    Beam Axiom #6 ~ "A Posse ad Essea" ~ From being possible to being actual ...is the beam target !

  8. #18
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Based on what my set up looks like and my experience with diode cooling, does it seem likely that I am the only one with poor heat sinking? This is not meant to put anyone down, just a straight question. It's possible that the residual solder on just this diode is elevating it away from the copper mount. Look at the Apollo in my video. This temperature is measured approximately 2mm from the diode flange. The only place that the temperature could have a large unmeasured gradient is at the flange and it would have to have a really large gradient.

    I think it's more likely this diode is defective. But, stepping back, 5.6W vs 7.0W is not huge. What is huge is the divergence. 25% more power would be nice, but what are you going to do with it? If the divergence numbers I found hold when other, maybe better diodes are evaluated how will you combine this with lasers that have substantially lower divergence? For the laser pointer crowd this will matter less and as a matter of fact, provide an increased level of safety, kinda like wearing a helmet on a 200MPH motorcycle

  9. #19
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    We have some options for optical correction/adaptation... Fun times again !!!
    Comparing the measured near and far field dimensions in the video vs the uncorrected beam in post#12 above you'll see that when expanded, the near field is actually smaller at a similar distance from the diode when the far field is 10X smaller. Placing the cylindrical beam expansion even closer to the diode may improve things even more. I say this because if you imagine placing the expansion at 50cm. then no expansion at all would be possible.

  10. #20
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    921

    Default

    It's possible that the residual solder on just this diode is elevating it away from the copper mount.
    That's what I was thinking. Or a small burr or something. The copper mount with tec should be more than adequate.

    Its probably more likely the diode is defective.

    If the diodes are good for 6-7w stable and the emitter is 3X the 2-2.5 watt diodes I would say its a win. Power density is about the same but complexity is greatly reduced. Plus the difficulties in correcting knife edged beams would be gone.

Posting Permissions

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