Page 1 of 9 12345 ... LastLast
Results 1 to 10 of 89

Thread: Improving Red (Maybe ALL) Beams

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

    Default Improving Red (Maybe ALL) Beams

    In the Oclaro diode thread I posted about my experience with beam manipulation with the P73 diodes. It got me to thinking about low order aberrations ie the ones we can afford to do something about. I isolated a single P73 diode ran it at 500 mA and measured the near field dimensions at 6mm x 3.2mm and @ 16.0 M the spot measured 14mm x 4mm. You can calculate the divergence if you want. I also noticed that no mater how carefully I adjusted the cylinder pair and the two 75mm PCX lenses there was always a significant amount of "junk" around the far field spot. This is why I like spatial filtering so much. But, I digress. I then started reversing the orientation of the lenses ie which face was closest to the diode and...


    EUREKA!


    All this should have changed is the spherical aberration that the lenses add, but because there is a cylinder pair and a radially symmetric pair then you can add or subtract negative or positive spherical aberration in any rotational orientation you require. In my case, I even changed the cylinder pair FL's. I didn't change the magnification, but both lenses were increased in power allowing a stronger spherical aberration compensation. The source of the spherical aberration is unclear, but likely due to the complex nature of the diode emission, the housing windows (in my case) and the thick glass cube when a PBS is used in the uni-axially expanding beams. In any case, I suppose you want the numbers? The near field remained at 6mm x 3.2mm and the baseline as well @ 16.0M, but the far field decreased to 10mm x 4 mm and was much crisper with significantly less "junk". It looked a lot better! I have ordered some more lenses including meniscus and bi-convex lenses to see if I can carry this any further.

    The lenses I am using are the 4mm Optima aspherical collimators, a 10mm PBS cube, a -25mm cylinder @ 6mm from the cube face (curve away from the diodes), a 100mm positive cylinder (curve toward the diodes) @ 50mm from the negative cylinder. The first 75mm PCX is located 50mm later and both 75mm PCX lenses have their flat surfaces closest to the mid point focus. The cylinder lens pair orientation goes against convention, but the spherical aberration introduced seems to counteract what is introduced earlier.

    Calculations of divergence can be misleading because as the beam is expanded in the near field, the far field shrinks and the differential rapidly disappears, but these results are pretty impressive. 1/4 mRad by zero as is and 0.43mRad by zero if the beam was shrunk to fit a 5mm width.

  2. #2
    Bradfo69's Avatar
    Bradfo69 is online now Pending BST Forum Purchases: $47,127,283.53
    Join Date
    Jul 2010
    Location
    Wilmington, DE
    Posts
    5,902

    Default

    Not being well versed in the optics and the technical end of what you are talking about, I don't know if this will be of any revelation but, could you (in your spare time, haha) see what the testing does for 650nm?

    I still have often wondered with ALL of the experimentation people have done, if there still isn't some sort of correction with optics - even in an unconventional way - to discover improvement with 650. (Simply because it is so inexpensive.)

    Maybe not, but I keep thinking "someday" somebody will stumble upon an as yet undiscovered answer.

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

    Default

    What diode are you thinking about?

  4. #4
    Bradfo69's Avatar
    Bradfo69 is online now Pending BST Forum Purchases: $47,127,283.53
    Join Date
    Jul 2010
    Location
    Wilmington, DE
    Posts
    5,902

    Default

    Not a specific diode per se as I don't know all the available ones. I was thinking about how a "module" could be improved initially but, I know there are various powers of diodes as well - i,e 200mW, etc.

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

    Default

    I probably wouldn't go that way because the cost of a module is not dominated by the diode. You can get a $30 G71 and a dual with nearly 2W of output for $60, but irrespective of the diode, the driver, prisms, cube, mounts, folding mirrors and dichroics will cost a couple of hundred at least and the visibility at 638nm will be several times that of 650nm per watt.

    I am excited because the red has been the low pow "fat" beam for years and OPSL and fiber are so expensive that you could build several good projectors for the cost of a single "advanced" red source.

  6. #6
    Bradfo69's Avatar
    Bradfo69 is online now Pending BST Forum Purchases: $47,127,283.53
    Join Date
    Jul 2010
    Location
    Wilmington, DE
    Posts
    5,902

    Default

    Actually, now that I think about it a little more, I recall that being the case when I've wondered and asked in the past. 2 watts of home built 638 for a couple hundred buck does make more sense that a couple PBS'd one or even two watt 650's even though they too are only a couple hundred bucks as well.

    I'll shut up now and await your results.

  7. #7
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Just finished swapping, in and out, bi-convex and meniscus lenses for the one power telescope optics and there is basically no improvement available. I could make things a little worse with the PCX lenses flipped 180 degrees (front to back), but I already knew that. So, this might be it until the Oclaro diodes arrive and we see what a reduction in emitter size does with optimized optics.

  8. #8
    Join Date
    Dec 2012
    Location
    Norway, Stavanger
    Posts
    69

    Default

    Hey Planters, are you going to make a video of this? (Love your videos) Can't wait to hear what you have to say about the Oclaro diodes! But im guessing that you would still need to spatial filter the beam to get a very usable output of this? Or does this method reduce wings and scatter anything more then the usual setup?

    -Hybrid
    1x - 2W RGB DT40Pro (Currently building)
    1x - 1W RGB PT25K
    ------------------------------------
    EtherDream, LaserShowExpress, Ipad (TouchOSC)
    -Hybridz0rz

  9. #9
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,594

    Default

    not totally on topic but relevent.

    with regards to your filtering thing to clean a beams up. simon aka pitbull did a quad 500mw red build for mark, there is no filtering of the beam, just diode lens and clyindrical lens. the final beam is perfect and i mean perfect no mess or junk around it.

    the reason for this is his attention to detail and getting the diode perfectly centered in the lens and again perfectly centered in the clyindrical lens.

    the final far feidl beam of simons quad red is perfectly matched to the green and blue and with no crap around it. you could easily mistake it for a single mode build
    Eat Sleep Lase Repeat


    Aluminium Optic Mounts

    http://www.laser-man.co.uk/opticmounts/

  10. #10
    Join Date
    Jan 2013
    Location
    Detroit, USA
    Posts
    558

    Default

    Quote Originally Posted by andy_con View Post
    not totally on topic but relevent.

    with regards to your filtering thing to clean a beams up. simon aka pitbull did a quad 500mw red build for mark, there is no filtering of the beam, just diode lens and clyindrical lens. the final beam is perfect and i mean perfect no mess or junk around it.

    the reason for this is his attention to detail and getting the diode perfectly centered in the lens and again perfectly centered in the clyindrical lens.

    the final far feidl beam of simons quad red is perfectly matched to the green and blue and with no crap around it. you could easily mistake it for a single mode build
    Do you have pictures?

Posting Permissions

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