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Thread: LOW LTM (Light Transmission)

  1. #1
    OptiBoard Novice
    Join Date
    Oct 2009
    Lens Manufacturer

    LOW LTM (Light Transmission)

    I have problem after AR coated (Vacuum coat). Normally LTM should get around 97%.
    but this month sometimes I get only 95%. I had checked all process parameter and coating materials.
    We didn't change any things. Do someone know what should be cause of this low LTM?

  2. #2
    OptiBoard Novice
    Join Date
    May 2008
    Other Eyecare-Related Field
    Did you check the LT before the AR? Are you at the same level as you were before you started seeing the issues?
    this could be to prior steps....

    Another point: is the degasing /dryingworking well and long enought?
    Good luck!

    Question on my end nd maybe you can help me with this: what percentage of ophthalmic lab lens production are polarized?
    thank you

  3. #3
    OptiBoard Novice seree1997's Avatar
    Join Date
    Mar 2016
    Lens Manufacturer
    Yes, we had checked the LT before. Normally by our AR process we always get more than 97% LTM. and always the result like this. But now just only some batch which we get lower than normal. I had checked my process parameter and all handlings, but I could not find any changed or abnormal. First, I guess some coating materials are changed (quality) but all are the same quality. Vacuum inside chamber while AR process run is as process. By the way, this problem is happening only some production batch. it is not permanent.
    About the degassing or drying. we checked all ovens, all are OK (Temperature profile as standard).

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