An AOA lens array is made from an optical epoxy and is supported on a BK7 optical window. The optical epoxy is not as robust as an optical glass, and may be damaged by cleaning techniques typically used on other optical components.

To minimize the risk of damaging your MLM, it should be handled carefully so that no cleaning is necessary. The MLM should be handled by the edges of only. The lens array surface or the glass surface of the MLM should never be touched with anything, especially your fingers. Even with the greatest care, it is reasonable to expect that the MLM may become dirty. If your MLM becomes dirty please follow the steps below.

 

Dust
If dust contaminates either the glass side or the lens array side of the MLM, the dust can generally be removed by blowing the MLM with dry, filtered, compressed air. If the air is not dry and clean, it may spray more contaminates on the MLM making the MLM dirtier instead of cleaner. Blowing off the MLM with clean air is the safest method for cleaning a MLM since it is non-contact and there is a very low risk of damaging the MLM.

It is possible that dust may remain stuck to a surface even under forceful blowing with compressed air. If there are only a few pieces of dust stuck to the MLM, gently brush the MLM surface with a clean, dry cotton swab. It is important to brush very delicately since it is possible to scratch the lens array with the cotton swab. To avoid scratching the MLM with a particle removed on swipe one during swipe two, use a new cotton swab for each swipe across the MLM's surface. If the dust cannot be moved after three or four tries, do not continue. It is probably a different type of contaminant and should be dealt with as such.

Stains, Spots, and Other Particles
It is possible that some other contaminant may be present on the MLM. In this case, isopropyl alcohol may be helpful in cleaning the MLM. However, cleaning with isopropyl alcohol can be difficult, because the evaporating solvent can leave a stain behind, which can be removed with a subsequent wipe, which can leave a new stain behind, etc. Some practice is needed to wipe the surface and leave little or no stain.

Do not soak the MLM in isopropyl or other solvent bath.

Do not use water to clean the MLM.
To clean with isopropyl alcohol, gently and slowly wipe the contaminated surface with a clean wipe that has been slightly dampened with the solvent. Wipes should be disposed of after a single use to avoid damaging the part with a dirty wipe. Many wipes may be needed in order to completely remove the contamination. If after a few wipes the contamination is not being removed at all, do not continue.

Note: Never expose an MLM to methanol! Methanol will remove the epoxy and destroy the MLM.

Please note: cleaning with a solvent can be difficult, because the evaporating solvent can leave a stain behind, which can be removed with a subsequent wipe, which can leave a new stain behind, etc. Some practice is needed to wipe the surface and leave little or no stain.

Materials/Solvents/Wipes
It is very important that all materials used to clean MLMs be clean themselves. Isopropyl alcohol should be as pure as possible, and no other solvents should be attempted since some solvents may damage the epoxy surface. All wipes should be very clean (preferably qualified for clean room use), have low particle generation, be non-abrasive and compatible with isopropyl alcohol. At AOA, we typically use Berkshire Exsorbx 400 Wipers. Also, clean latex (or equivalent) gloves should be worn while cleaning an MLM, and changed often. This will prevent cross-contamination (getting finger oils, etc. onto wipes and putting wipes onto the MLM).

This is very important as finger oils are extremely difficult to remove.