A plea to users of coated optics (G1 and G2) lenses

Seoul_lasers · May 1, 2012

I just had an opportunity to inspect and benchmark/measure a laser that was purchased by a local Korean member. I met the member in central Seoul on Saturday. The member was kind enough to allow me to "borrow" it overnight. The build in question is an all copper laser, copper heatsink, and diode "host". The optics is a 405-G2 lens.
The owner of the laser had made mention that the optics seemed to be dirty and that he had tried to carefully clean it.

I decided to have a round on the G2 lens, and use and ultrasonic cleaner with 20% Ethanol sol. This usually gets any crap off the lens that would otherwise not be able to come off.
It was no use.

I noticed a very very slight improvement in the splash pattern after allow the lens to dry on an optical cloth.

I sent the picture of the splash pattern to Nikon optics division.
Their response was quite a surprise. MgF2 coated optics are apparently susceptible to Aspergillis mould. If the lenses are stored improperly, they can be a host for spores. When the mould starts to grow it will strip the coating off the lens creating dark oval circular patterns. since we are dealing with coherent light, these marks tend to show up much better.
The pattern to the Nikon representative looked exactly like a case of mould contamination.

So, for those people who live in humid climates take note. keep your lasers in a sealed box with desiccant. Aspergillis fungus is a coated lens worst enemy.

note the last picture is an old MgF2 coated vivatar lens. You can see the coating is gone on the sides of the lens.
Magnified you would be able to see the pattern match our G2 lens splash in pic2/3.

DTR · May 1, 2012

If you use your laser every once in a while I would think it would sterilize the lens if you did have fungi on it.:thinking:

JLSE · May 1, 2012

DTR said:
If you use your laser every once in a while I would think it would sterilize the lens if you did have fungi on it.:thinking:

That may be true, but if you store a laser improperly for a long time, those
little guys will get baked on.. Along with any other debris which may have accumulated..

For every day use, I doubt it would be an issue.

@OP, still interesting that this can happen. One that blew me away was bacteria
that live on reactor core rods

Seoul_lasers · May 1, 2012

The problem here is that the damage has occurred long before the lens was added to the build. So I suspect that the lenses became contaminated sometime between manufacturing and shipping out to the original vendor.
If a Nikon optics representative was pretty certain about what we are seeing as a mould issue then... I duuno.. I am shocked about the prognosis too.

I guess we need more lens experts to weight in.

A quote taken from photo.net

Tommy Lee , Jan 23, 2010; 01:42 p.m.
UV from the sun light can kill the fungus and prevent it from growing and making the lens worst in time. It won't clean up the remaining dead fungus bodies and improve the lens optics. For that you need to take apart the lens or lens cell to clean off the remain using a right solution for the job. Assuming you can put the lens and alight the lens properly afterward, you still won't be able to repair the eaten part of the lens surface (by the fungus). If there was a small infestation, chances are you won't see the damage after the cleaning.

Again another quote from Photography on the net forums

1. Glass

The glass of a lens can have numerous problems. Most easily detected are scratches on the exposed glass elements. Sometimes, lighter scratches caused by poor cleaning technique can be present and are more difficult to detect, especially in listing photos. Bright reflected light is usually sufficient to see "cleaning marks": once you receive your ebay win, examine the lens with the light reflecting off surfaces at several angles and you should be able to tell if any light scratches are present.

Blemishes:

Lens elements are generally "multicoated" with layers of nonreflective optical material. This minimizes light reflection and the resulting lens flare and ghosting associated with the multiple reflective surfaces of these complex optical devices. "Blemishes", areas in the multicoating where material has been smeared or removed by a bump to the glass, manufacture defect or a solvent splash are less critical flaws provided they are very small (< 1mm diameter) and few in number. A small blemish shouldn't affect image reproduction. For the sake of listing accuracy, they should be noted in the description if present.

Fungus:

A lens that has been stored in a dark and moist (and/or humid environment) or stored after getting wet can have a fungus bloom inside the lens. Fuzzy spots and mycelial filaments are both bad news. The fungus can secrete an acid that etches the multicoating of the lens elements, so even if you can disassemble and clean the lens, the damage is likely permanent and will to some degree, affect the sharpness of the lens' image reproduction. Examine the lens by peering through it from the lens mount side and look at a bright surface such as an opaque light shade (not the Sun!). Open the aperture to ensure you get a good look. (Read on for information on how to do this in the "The Aperture" section). If there is anything visible inside the lens, this is not good news. The light path inside the lens should be completely clear of any opacities. You can try the same technique looking from the front element into the barrel as I have in the next set of photos. Note the fungus deep inside this Beercan. What a shame!

Tech_Junkie · May 1, 2012

So are you trying to say all our G1 and G2 lenses are all contaminated because of the poor dot quality? Or just the one you are looking at?

Seoul_lasers · May 1, 2012

I am just talking about this particular lens at the moment. This is by far the worst lens I have EVER seen
I had one other lens that was an Aixiz, about a year ago have the exact same patterning on it, nowhere near as bad.

I think this problem could be widespread. Some people in this forum are most diefinately in possession of contaminated optics.
Also, we need to be storing our optics in a dry case and with some sort of humidity control.

Tech_Junkie · May 1, 2012

You have to remember we get our lenses without a barrel. The members selling the lenses all make their own barrels. I doubt a bare lens could support mold. Or at least not as easily as ones in an enclosed barrel.

Dogs Best Friend · May 1, 2012

Certainly, not all G-1/2 lenses are affected by this, but the point is that improper storage of a coated lens can cause fungal growth which can destroy the sensitive coating.

This is true of optical (camera) lenses as well, but coherent laser light is a totally different animal. I have been a photographer for many years, and I have seen many cases of fungal damage to lenses. In cameras, it's not a serious issue until very advanced cases because camera lenses are not focusing coherent light. Since laser light is coherent, it shows very minor imperfections that would normally be well within the tolerances of optical lenses.

I don't know how much this affects the dot when it is focused into a tight beam, but bad cases would definitely scatter the light to some extent affecting power and causing splash.

This is definitely something to be aware of when storing lenses which are not being used daily. Humidity is BAD for lenses. Aspergillis is very xerophylic, and although it can grow and reproduce more easily in high humidity (such as inside of a lens barrel trapping humididty), a dry lens can be infected for a long time before the fungus begins to grow. Storing lenses in a dry environment is important, and since we have no control over what happens to our lenses before we get them, it is a good idea to check new lenses for damage as well.

Seoul_lasers · May 1, 2012

Another question might be, where (in what country)
are g2 and g1 lenses manufactured?
My guess is China. Juhai ?

I agree with Dogsbestfriend, I am not saying all lenses are like this, just that I was a bit shocked about NIKONs prognosis.
Also I have never seen a lens with this terrible a splash.

It doesn't matter that the they were sold without a barrel, the act of allowing humid air to be around the lens allows fungal spores to grow on the coating's surface.
Doesn't matter if it is the front or back side. Once the bacterium is deposited on the coating surface, they produce an acid that etches holes in the coating causing the patterns.
The lens is basically throw away after this occurs.

Varsis · May 1, 2012

Thanks for the heads up. i hope the semi weekly use is enough to keep them good to go, hawaii is humid as hell sometimes.

Tech_Junkie · May 1, 2012

Seoul_lasers said:
the act of allowing humid air to be around the lens allows fungal spores to grow on the surface of the lens.
Doesn't matter if it is the front or back side. Once the bacterium is deposited on the coating surface, they produce an acid that etches holes in the coating causing the patterns.

Your flare for redundancy is a flame we all circle with fated anticipation. :beer:

Seoul_lasers · May 1, 2012

Tech_Junkie said:
Your flare for redundancy is a flame we all circle with fated anticipation. :beer:

Thanks for the constructive comment. I am being redundant aren't I. I'm tired...

Dogs Best Friend · May 1, 2012

Seoul_lasers said:
Once the bacterium is deposited on the coating surface, they produce an acid that etches holes in the coating causing the patterns.

Not that it matters, but Aspergillus is a fungus, not a bacterium. :na:
I'm a biologist... I had to say something, haha.

Seoul_lasers · May 1, 2012

Dogs Best Friend said:
Not that it matters, but Aspergillus is a fungus, not a bacterium. :na:
I'm a biologist... I had to say something, haha.

Thanks.

Putting this to bed now. Fungus Fungus .... not bacterium

ryansoh3 · May 1, 2012

Great informative post SL!

I'm glad that my bad lens condition was used for a good cause. :beer:

TomD · May 1, 2012

Thanks for the heads up. I also live with a tropical climate, currently looking for a nice Pelican case to stuff with dessicant for mine that has a G1.

Just barely attached, the G1 shows a lot of spots and streaks, just like what S_L posted. Screwing in about halfway, the stuff's less noticeable.

I'd like to ask something though. For all intents and purposes, will this kind of issue affect beam focusing and, ultimately, burning capabilities? If it will, just how bad should it be? Is the level we're at (Ryansoh3 and mine) already severe?

p.s. don't mind the really tiny pixelations--those were due to the resizing program I used.

A plea to users of coated optics (G1 and G2) lenses

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