Optics Cleaning in a nutshell

Discussion in 'Displays' started by Robert P. Jones, Sep 11, 2003.

  1. Robert P. Jones

    Robert P. Jones Second Unit

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    This is a reprint from an answer to a question in another forum about a certain type of optics cleaner - one of the dry type, I believe - and whether it should be used on RPTVs:



    My optics cleaning technique is to suspend ALL the gritty particulates that have built up over the years in liquid before attempting to do ANYTHING with them.

    Lenses are usually made of plastic, and are extremely susceptible to being scratched. Even glass lenses can be scratched.

    High voltage attracts the smallest of particulates to your optics, including smoke, and it is VERY IMPORTANT not to scratch your optics.

    It is also important not to allow any of the liquid to go down into the space between the edge of the lens and the lens barrel. If it does, it will cause the inner lenses to fog up. There are usually 4 lenses in a stack, in each lens pack. 3 guesses as to why I know that...

    So when you send your spray to the optics, you DIVE, DIVE, DIVE with your aborbent material to the lowest part of the lens surface, to make sure that doesn't happen - that the liquid doesn't penetrate to the lower levels of the stack, to the inner lenses.

    The best stuff I've found for wetting the surface is an aerosol, because it foams up and doesn't run. Don't know what the name of it is, I've only used it a couple of times, when the customer already had it lying around. I usually use non-ammoniated Windex, or Glass Plus, and very very carefully. Non-ammoniated because of the first surface mirrors used in HDreadys. Don't want to be mixing aluminum with ammonia.

    Once the mist has penetrated the contaminants and lifted the grit off the surface, a careful swipe in one direction only will get the critical mass of grit off the surface, to one side of the lens. A rolling motion as you do so, like a streetsweeper, is best and will very cleanly remove the bad stuff.

    Usually takes several very careful swipes, all in the same direction, to gather and remove all the particulates - and you're done. Then one more very light cleaning swipe -

    It is better to leave trace streaks than to rub till the surface is clean. Rubbing is VERBOTEN! Doing so will "scuff" the plastic with thousands of permanent streaks, which you will then rub harder and harder only to find out they don't come out, and you've just exacerbated the situation gravely. 3 guesses as to how I found out about THAT one...


    As such, no I don't think these things are the thing to use, unless and until the surface is 99% clean already. I use pure wood fiber paper towels - not shop towels, which contain lanolin and will NEVER get your mirror clean - and the wetting materials mentioned above. On the outer lenses, the mirror, and the inner CRT coolant covers, where you remove the lenses to get to them.

    This method has been doing it for me - and very pristinely - for years and years and years.

    It's all in the wrist.


    Mr Bob





    Later:


    Some further notes -


    When you check ANY of the optics for contaminants, shoot your flashlight at the lens surface FROM THE SIDE. It never looks that bad when you hit it head-on - but Lordy, when you shoot it from the side, MAN, that's dirty...

    I usually do just a quick bump from the back of one of my fingers - no more than 3/8" long - to the surface, just to see if that bump turns clear black, in the middle of the gray dust. If it is dirty, it does. If not - if that surface was black and remains black after bumping it with the back of my finger - I may just leave that surface alone.

    On the lenses facing up, often to make my point in front of the client, I wet one finger - don't want to DRYRUB any gritty particulates - and draw a happy face in the middle. Viewed from the front at an oblique angle, with the flashlight hitting it from the side, that usually does the trick, when that happy face jumps off the surface at you, revealing how clear your optics are SUPPOSED to be...


    If you are removing and going under the lenses, be sure and check the rear surface of the lens pack - the one the becomes exposed when you remove the lenspack, whose surface faces the CRT. It is usually full of smoke, and responds the same way to the "touch" test mentioned above.

    When you shoot the Windex in there, be sure and clean the outer surfaces of overspray, before cleaning the lens itself. If you don't - if you just leave it - its moisture is trapped and will eventually fog everything up in there, after you have put things back together.

    3 guesses as to how I found out about THAT one...

    If you do it after cleaning the surfaces in question, more lint - and other new contaminants - fall onto the surface you just cleaned, than if it is the other way around.


    I have found that the actual coolant covers themselves are usually plastic, tho I have seen glass ones - very expensive to do it that way - on Runcos and Pioneer Elites. You can tell by looking at the edge. If it is plastic, you won't really see that edge, it will be inside where the coolant is and not available to your view.

    If it is glass, you will see the curvature end, and straight flat glass will go to the edge of the circular chamber, usually just over 1/4" in all directions.


    I just completed this protocol on a 6 year old Runco 770 at Harbin Hot Springs last week, and a 9 year old Pioneer PRO-119 last night in Redwood City. The Runco had VERY thick dust on the entire lower half of its glass coolant cover, and its keeper couldn't get over how distinct and impressive the colors had become, later.

    The response from the Elite owners was that they had NEVER seen it look that good, even when new. At 9 years old...


    Naturally, the rest of my calibration protocol was also applied in each case, after hours of fine precision work.

    But the importance of the light path remaining clear as glass in a projection system cannot be stated strongly enough. There are MANY surfaces to deal with in a projection environment, NONE of which exist in a directview environment.

    EACH of those surfaces needs its own individual attention.

    Especially in the face of the high voltage of the CRTs, which always wants to cause floating airborne contaminants to cling to nearby surfaces over time, hour after hour - multiplied by hundreds of hours of use over time - PER YEAR!

    This is definitely an op that cannot be left to chance.


    Mr Bob





    Later again:


    I just learned the name of the foam, which I think has been the same in all cases, just from the look of it.

    It is SprayWay Glass Cleaner. Locally, it is available at Restoration Hardware, somewhere here on the Peninsula in the Bay Area.

    Elsewhere, I do not know where to get it.



    Mr Bob
     
  2. Kimi-R

    Kimi-R Agent

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    Wouldn't it be smart to lay a piece of 1/8 glass over each lens? I'm sure you could affix it to the lens barrel somehow if the len's aren't nearly level. That way the lens should stay mostly dust free and the glass can be cleaned without you having to be delicate.
     
  3. Robert P. Jones

    Robert P. Jones Second Unit

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    Great suggestion, but I think the losses would not be worth the gains.

    Interior reflections are quite bothersome in rear projection systems - esp. since none of the internal lenses in the lens pack are coated. It just wouldn't be cost effective, and I have never yet seen an RPTV with internally coated lenses, tho the outermost lenses are coated on some brands - the ones that face the mirror.

    To see evidence of this, just look at how popular the duvetyne op is.

    You would be adding 2 more uncoated reflective surfaces to the array, times 3. I don't think that would be wise - it would compromise your black detail the same way dirty optics do.

    I have heard that using an ionizer nearby, outside your optical cavity, would help, tho. It makes the outside of the unit attract the dust and won't allow the dust floating in the air to penetrate the cracks and get into the optical cavity. The particulates are sucked to the edges rather than floating in.


    Mr Bob
     

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