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Thread: How to create super bright laser beams

  1. #161
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    Quote Originally Posted by planters View Post
    Do you mean you are not sure if you could use say a typical 10k thermistor input?
    I would use 10k thermistors for sensors. Not sure how I would enter set-point data..... Data wheel, keypad, POT, pushbutton, etc. I admit I am a little out of date on all the new microcontroller stuff that is available. The h bridge chips i planned on using are 5amp continuous, 6amp peak. If it needs more amps I think I would go with Kecked's idea of a realy to set heat/ cool and a discrete fet as the PWM switch. I'm still on the lookout for a higher powered h bridge IC just because of the simplicity. Most the h bridge IC's have built in diodes, short circuit protection, and are easy to drive.

  2. #162
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    I think you could get away with a series of pots with the display divided into two haves. One side is the set temperature the other side is the measured temperature. You could probably get away with 6A if you can accommodate up to 24V. A multistage cooler can be assembled to run in series and take advantage of the additional V headroom.

    When the time comes, I think a rebuild of my set up with 4 TEC cooled diodes would be best with the Mitsu G71 diodes. I would also move to the 4mm aspheric Optima lenses. These changes would make the beam expansion within the projector much more manageable. These diodes are less powerful than the P73's, but they have proportionally better beams and so are just as bright. The first prism holder could be designed to be more compact because its precision is low (it only narrows the package). The second prism/rotation stage is the only precise movement required.

    I'll try to do the video tonight, but I will wait to modify the set up until a good driver option is available.

  3. #163
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    The video is up and available.
    https://www.youtube.com/watch?v=UE-73EWUapw

    I make a few small mistakes that I noticed while watching. The three lasers have a wavelength centered around 636nm, not 536nm. I also do not demonstrate the fact that the multiplexed beam does not move at all when modulating the drive current. It does not.

    Let me know what you think.

  4. #164
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    nice! I wonder if you can find binned diodes so you don't need to do any temp control. That assumes....they change wavelength the same between them as the room changes. I think if you can get diodes already spread a sufficient thermal mass IE chunk of metal should hold them near in temp to each other or at least you'd only need to temp control the block as a whole.

    What is the pointing stability of the beam? IE does it move much in space? RBG next!

  5. #165
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    I checked 5 diodes and only one had a manufactured difference in wavelength and that was 0.25nm. I feel the temperature method is the way to go. The beam does not move at all with modulation. It should be proportional to a fraction of the spacing of the stripes just before the second prism. At the far field this will be around100 urad or less. We NEED a multichannel TEC controller. I plan to mount the diodes in pairs on each TEC stack, one for each polarization. I'll PBS them then multiplex them and then expand,shape and spatial filter, 8x G71 diodes.
    You could also use this method to combine 520 and 532nm beams as well as 445 and 462nm beams. Here, the manufactured wavelengths would not require temperature tuning.

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