Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: My scanner is finally back on track!

  1. #1
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default My scanner is finally back on track!

    ok got my 400mw 532nm from lasever today once warm its kicking out 530mw which is good.

    so ive got -
    500mw of 532nm
    600mw 650nm
    100mw 473nm


    also spoke to bill today about my dt40's, this is his reponse -

    We have an intern at Pangolin for the next six months. Actually, before even coming to Pangolin, he posted on PL. His name is Uncle Worm or something like that. Since one of the things he is studying is servos, I wanted to wait for our joint availability, and show him what we do on a DSA, etc.

    So that happened yesterday. Your system had multiple problems. You did have it tuned -- probably the way Jian would have done it. Unfortunately, this is with way too much high frequency damping, and way too much servo gain. But at least it did something, and in fact Worm thought it didn't look too bad. But what I saw was that it looked worst and worst over time. Upon close examination, I found the Y mirror wasn't even bonded properly. Someone used super glue to attach it, but it had come loose. Also, once I attached it correctly, and then moved it under a microscope, I can see the whole shaft moving. This is caused by a combination of cheep bearings, and what's known as an improper pre-loading technique. Nevertheless, I was able to do one of my old tricks -- put epoxy on the back side of the mirror. This artificially makes the mirror thicker, and also kills resonances. And lastly, I threw away the connection style you had up until now (single ended, with a pot) and made a DB25 connector and fashioned true differential connection into the amp. This really does a lot for quality. When you receive the system, you will need to hook the only "free" wire (DB25 pin 25) to the ground of the power supply, or the images will wobble all over the place. This ground connection can be made with an additional wire inside your projector, that's why I didn't do it myself (I used a clip-lead for testing).

    So, to get this looking good, it actually illustrated a lot of things I have been talking about all along. One thing it illustrated is -- you must use differential input TO THE AMPS (remember, differential has nothing to do with the transmitter, and everything to do with the receiver). The mirrors must be thick, or can be artificially thickened with epoxy or even silicone. Mechanical problems will definitely manifest themselves in the images (I took pictures of all of this, and will post them too), etc. Basically, it was good for Worm, since he saw all of the things I have been talking about in action.

    In the end, the system looks OK. Not perfect, but OK...


    in my next e-mail i asked what not perfect means?

    what he was getting at is, they are running great just not up to his standards, which im guessing are pretty dam high.

    hes gona post some pics at some point.
    Eat Sleep Lase Repeat

  2. #2
    Join Date
    May 2007
    Location
    Milwaukee WI
    Posts
    1,355

    Default

    --- waiting patiently ---

    Very interesting - I have to get my DT40s out to Bill at some point... Maybe I will just keep using them until I see him in person at a LEM.

  3. #3
    Join Date
    Jan 2007
    Location
    Yorkshire, UK
    Posts
    4,585

    Default

    Hi Andy

    What make is your 650nm 600mW red?

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.... Douglas Adams 1952 - 2001

  4. #4
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default

    its home made 2x 300mw open can diodes
    Eat Sleep Lase Repeat

  5. #5
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,762

    Default

    Hi Andy,

    WOW, I was going to post a description of what I did and such, but I see that you have already done my work by simply posting my email to you. Good thing there wasn't anything controversial in my email .

    Anyway, I decided to post a few pictures here to the forum, just to show the results. Andy, please save me some time and reply to this post with a link to your original post, which had the pictures. I didn't take any "before" pictures because... well... most of the time I just never take them.

    Click image for larger version. 

Name:	Andy1.jpg 
Views:	143 
Size:	109.0 KB 
ID:	2176

    The first picture (above) shows something we have been discussing recently. For absolute best quality scanning, you need to go INTO the scanner amp as a differential signal. For a complete discussion about why differential INPUT is important, see another post of mine.

    Note that differential OUTPUT gives essentially no benefit, but differential INPUT is very important. Moreover, you don't want to connect ANYTHING to the ground connection of the scanner amps themselves. You connect the ground connection of the ILDA DB25 to the ground pin of the power supply itself, thus giving you a single-point grounding scheme. Without this, the images will tend to look a bit bent-up, because without this, some of the X scanning signal will enter the Y input, and some of the Y scanning signal will enter the X axis, through the common ground connection. With only a single ground, and all differential inputs, we eliminate the possibility of this happening. So that was one problem .

    Note that, actually, the older DT-40 didn't even have a differential input, so there is no way for a typical user to do this. Of course, I am not a typical user so I made my own damn differential input.



    Click image for larger version. 

Name:	Andy2.jpg 
Views:	134 
Size:	97.9 KB 
ID:	2177

    The second picture (above) shows a frequency sweep of this scanner. Actually, both scanners. The bright green trace is one of them, and dim green trace is the other. I forget which is the X and which is the Y, but neither of them are perfect... The dim green trace is a bit worst than the other. You see some bumps at around 4kHz, 7.5kHz and 11kHz (the 11kHz is only one one axis). This is definitely poor mirror mounting, and also too thin of mirrors. The 11kHz is probably the way Jian fitted the output shaft onto the magnet.

    In fact, this was Andy's biggest problem. Yes, the tuning was off, but the mirrors were so damn thin that they resonate. So to solve this problem, I put a strip of epoxy on the back of the mirror, to artificially thicken it, and also to add damping.



    Click image for larger version. 

Name:	Andy3.jpg 
Views:	131 
Size:	58.6 KB 
ID:	2178

    The third picture (above) is what the scanning system looks like now. As I said, Andy will have to put a post to show the before pictures. These pictures are still not perfect, but they are as good as this scanning system is going to get. The only way to make these pictures better woudl be to replace the bearings, and also change the preload system.

    These pictures show one more thing -- actually, everything. This is what the ILDA test pattern looks like without blanking. Our intern found it confusing, and asked why I do it that way. Well, looking at it this way is kinda like an X-ray machine. A doctor can press on your body and listen to your heart, but he learns a lot more by looking at an X-ray. By looking at the ILDA test pattern with no blanking, I see an X-ray image of what is going on. And if "no blanking" is like an X-ray, then my DSA picture (above) is like 3D coronary angiography.

    Also, it is a good example of everything I have been talking about -- thicker mirrors, artificially creating thicker mirrors if you don't have them already, differential INPUT, proper mechanical construction of the scanner, viewing the ILDA test pattern with no blanking, single point grounding, etc. If we had to pick just one scanning system to show our new intern what you should do, and why, it seems like this was the one.

    Best regards,

    William Benner

  6. #6
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default

    i wouldnt have posted your e-mail were there something dodgy in there bill.

    here my original problem -
    http://www.photonlexicon.com/forums/...highlight=dt40

    just so im clear, all i need to do it connect any ground to the db25 that you have highlighted below. so i could use the ground from the dt40 psu???



    what twat super glued the mirrors on!? ops that may have been me!

    wont be doing that again.

    bill what an awesome service you have provided, im very very greatful.

    many thanks
    Andy
    Eat Sleep Lase Repeat

  7. #7
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default

    just need my scanners now and a new diode for my red which should be here tomorrow



    Eat Sleep Lase Repeat

  8. #8
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default

    guys could i just confirm, i dont need the cable with the big pot on it anymore??

    i use the new 25pin plug for x and y?? tthere used to be a cable that connected to the red arrows?

    Eat Sleep Lase Repeat

  9. #9
    Join Date
    May 2007
    Location
    Milwaukee WI
    Posts
    1,355

    Default

    Yep Andy you are correct. One of the things Bill did in his fix is jump two pins in the POTs input connector to bypass it.

  10. #10
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,647

    Default

    yeah so now its
    pin 1 to X+
    pin 14 to X-
    pin 2 to Y+
    pin 15 to Y-
    Eat Sleep Lase Repeat

Posting Permissions

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