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Thread: IR Filter cleaning

  1. #1
    Join Date
    Dec 2006
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    Pflugerville, TX, USA
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    Default IR Filter cleaning

    I disected an old Quickcam VC and removed what I think is an IR filter. It is a blueish looking filter in front of the CCD. When I put it in the path of my laser I get some speckle and it looks pretty dirty. I have no idea how it got dirty...

    Anyway, how can I clean it? I tried a little water and a Q-tip and made it a lot better but I might as well try to get it as clean as I can.

    Also, how can I confirm that it really is an IR filter?

  2. #2

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    Safest way to be really thorough, on the assumption that sensitive plastic might be used is:

    Mix a little pure white spirit with distilled water, in a small jar, one part water to two parts spirit, and add three drops of concentrated washing up liquid as an emulsifier. Shake the stuff to mix it. Dip the cotton bud in it to dampen it, don't make it soaked. Use as expected, clean area to contact the filter with each pass, to prevent scratching with any dust picked up on the earlier passes.

    Finish up with a second cotton bud dipped in isopropanol (IPA, isopropyl alcohol).

    If the filter is glass and can stand more aggressive solvents, try methanol, or even acetone, but take care with acetone, if plastics or glues are likely to get any on them.


    To confirm its usefulness, see if it lets most of your visible laser light through. If it does, then find an IR remote control, hold it in front of the IR LED output, take that right up to the sensor for the gadget it's meant to control, and see if the filter stops the remote working as it should, even at point blank range.
    Last edited by The_Doctor; 03-04-2007 at 10:10.

  3. #3
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    Default

    1) What do you mean by spirits? We don't have any ghosts in my house. Do you mean mineral spirits? That would seem harsh.

    2) Excellent idea about using a TV remote to test! I wouldn't have thought of that but it is so obvious.

  4. #4
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    Default

    Just tested the filter on an IR remote. It stops the remote from working unless I am at least 4ft or closer to the TV. So is the filter any good for a laser (30mw green DPSS)?

  5. #5

    Default

    Sounds like it isn't very strong. Probably not strong enough.

    Spirit = white spirit in this case. If you're in the UK, you can get it from a hardware shop. It's usually fine enough to be free of contaminants, just don't get turpentine, that's a lower grade, very impure and greasy. White spirit isn't harsh, just don't leave it soaking on anything for long. Long exposure will affect come plastics, but a quick wipe won't harm them, even the really sensitive polarizer layers on LCD's can stand a quick wipe with it. The followup isopropanol wipe is even more gentle, and will take care of whatever impurites might have been in the white spirit.

  6. #6
    Join Date
    Mar 2007
    Location
    North Iowa
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    Doc --

    Now I'm curious. What is White Spirits ? Is this basic mineral spirits known as paint thinner ?? I don't think it will mix with water unless there's a sufficient amount of soap. I'd prefer basic IPA as a quick wash.

    Mike

  7. #7

    Default

    It is. This is why I suggest the few drops of washing up liquid. That allows an emulsion (formed by vigorous shaking) to be stable for up to an hour, after which the paint thinner separates and sits on top. The long molecules in the washing up liquid also help with the cleaning.

    IPA (isopropanol) is good, but best for finishing. It won't remove sticky deposits that need water as solvent. IPA won't remove all grimes either, many have compounds in that white spirit will remove, but IPA won't touch them any more effectively than water does. The mixed solvent emulsion is the best first base, and I choose white spirit because it's cheap, clean (unlike turpentine), doesn't attack things except some plastics, and only then if it is allowed to remain on them for a long time. The stuff evaporates anyway. If it is absorbed and allowed to release slowly into a confined space it can do harm, but a wipe on a surface won't let it do that. Take care with natural rubbers though, they can absorb it given long enough chance, AND be deformed by it, though they can recover if held in shape under gentle pressure for a long time.

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