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Thread: Omnichrome 643

  1. #1
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    Default Omnichrome 643

    I managed to pickup an Omnichrome 643 at an excellent deal on eBay. Shipping was expensive from Quebec to California, but it arrived in great shape. I had to wire up a cable from my clothes dryer plug so I could power it, and a cable to power the fan box, but it was really complete—even included the original user manual.

    I posted a bunch of details about it and photos on my blog here: https://www.joeyhagedorn.com/2017/02...hrome-643.html

    So far I've been really happy with it, though I'm kind of hoping I can find an RGB OC optic instead of the stock RYB so it'll be more appropriate for graphics, though I realize it is risky to take apart a perfectly good ion laser…

    I think more immediately I'm going to focus on building a really nice digitally controlled remote for it. I've got a small OLED display that will be perfect to display output power and current at the same time. Wondering what features I should build into it beyond the basics—maybe memory for different power settings? Perhaps a web API so I could control power output from my phone or computer? Anyway, it's been a blast so far; so happy to finally have all the beautiful colors of an an Ar-Kr.

    Click image for larger version. 

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  2. #2
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    Default

    I've not seen RGB optics for these, MG didn't list them, but many of the 643s were used by OEMs and it's pretty much impossible to identify what optics they used, so they may exist.

  3. #3
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    Default

    I have a set that a forum member installed on mine. So they do exist. Where or how he got them, I dont know.
    Will there be three phase!!!!

  4. #4
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    If you add in the green line overall power can take a dive by design in order to prevent power shifts between lines. A Krypton head can oscillate between the 568 and 530 nm lines, as they share the same upper state. Yes, they do exist, the optic part number is a internal MG item, there are however head part numbers for RGB NO Yellow in the manual... In a Krypton, 647 Red and Yellow can oscillate back and forth with changes in alignment, pressure, and magnetic field. In a short tube 568 nm Yellow and 530 Green can also oscillate back and forth in power under certain circumstances...
    ~
    In a large frame this can be of little consequence, in a short, very hot, air cooled resonator that is always slightly changing in length, it can get quite noticeable, unless you adjust the fill pressure to favor one side of the gain curves.
    ~
    Hence RGBY would be a special order, likely designed with reduced power (Change in OC transmission vs wavelength, or change in fill pressure or gas ratio) in order to have stability.. From a system designer's point of view, killing either green or yellow by adjusting the OC transmittance curve made sense. You usually will find that MG broad spectrum products ship with a 400-700 nm HR, so you need a new OC. However they are scarce. I have used them.
    ~
    As most biology applications do not need the green, RYB became a standard item, and is a reasonably stable combination in a short tube.
    ~
    Sam Goldwasser may have a few of the RGB or RYGB optics, however without a spectrophotometer, he may have a hard time recognizing what is what. Mine (RYGB) is not for sale at this time.
    ~
    If you look at the IVP-RYB table on page 12 of this patent, you can understand that getting a balanced output from a small tube is difficult. Having helped a friend repump a few 543s to make 643s with a whitelight mix, I can tell you that getting a stable 643 with good color balance is exceptionally tricky. In fact I'd wager that there are internal gas flow design differences between a 543 and a 643 series tube, although externally they can look identical.
    ~
    Good color balance in a mid frame tube is say 15% argon, Good color balance in a very short tube may approach 30-40% Argon.
    ~ See US PAT 214658 By Ostler. Incidentally, the two tables presented are for two different tube lengths. When they wrote that patent they were not interesting in "Giving away the farm" with all the details.


    ~

    Steve
    Last edited by mixedgas; 02-14-2017 at 06:49.
    Qui habet Christos, habet Vitam!
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    When I still could have...

  5. #5
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    Wow, thanks Steve for all the info here—I'll keep my eyes open, but it sounds like it might be another 10-year kinda project looking for one of those RGB(no Y) OCs from MG. Never know when you'll encounter a shipping disaster. Happy to know the part exists, even if rare and not sold individually. The prevalence of RYB makes a lot of sense.

    I had also idly wondered if an optic from a similarly sized unit, like a LaserPhysics Reliant, might be possible to mount with a custom machined holder, but it sounds like there isn't much margin when working down at this small scale to mess with something like that, nor a dearth of those available.

    Patents are a really interesting source of information here I hadn't considered to learn about this stuff, so I'll be sure to spend some time reading up. My background is computer software where I've found patents tend to be less… informative. You sure that's the right patent number you pasted?

  6. #6
    mixedgas's Avatar
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    Melles just downsized their gas laser production line. Sam got many of the optics, both HENE and ION.

    ~
    In fact, I'm pretty sure the last Melles Ions have been made. They are still making HENEs. Sam will rapidly sell all those mirrors, so you might want to start now, rather then wait.
    ~
    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  7. #7
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Try US 5214658
    ~
    World Patent WO 1992002977
    ~

    Sorry about the clipping of the "5"
    `

    Kevin D. Ostler is the engineer...
    ~
    Assignee is "Ion Laser Technology"
    ~
    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

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