Guy Macon on cleaning optics


Hmm...points of agreement, points of disagreement. The first point of

Guy Macon on cleaning optics

Hmm...points of agreement, points of disagreement. The first point of
disagreement is style. 'Guy Macon on X' isn't necessarily the most
confidence-inspiring title in the world. (This is not a personal
remark--it would be equally applicable to me or anyone else. A post
from Person Y entitled 'Person Y on Thing X' sort of suggests that
Person Y has ego issues, which reduces his credibility very
substantially, regardless of whether or not he's right about Thing X.)

Opticlean polymer is poly(vinyl alcohol) in a variety of solvents. The
old stuff (circa 1990) was in stabilized tetrahydrofuran, and was great.
Slightly newer stuff (circa 1997) used some sort of alcohol solvent,
and was much less good because it exhibited an unstable fluid
surface--thin spots spontaneously thinned further, and those places
won't peel properly. I bought a quart of the THF stuff and haven't run
out yet.

Old fashioned washing with detergent, followed by a few deionized water
rinses, is better than most methods unless the glass or coatings are
especially prone to weathering. Mag fluoride coatings are fine in
water, but cryolite (soft AR coatings) aren't. If you're
ultrasonicating, be careful to mount the optics by the ground
edges--sitting a lens on its side in an ultrasonic bath is an expensive
mistake.

Brushing dusty lenses is a disaster--almost as big a disaster as using
lens paper dry. Scratches and particles tend to scatter proportionally
to their perimeter rather than their area. Trading a boulder for a
furrow is a really bad deal in general. Even alpha-particle brushes are
a last resort for built-up assemblies such as camera lenses, which you
can't just run through the dishwasher.

Cleaning really sensitive things, e.g. laser tube Brewster windows,
usually involves electronic-grade solvent and the best lens paper. You
put a drop of solvent on the window, drape the lens paper over it so
that it absorbs the drop, and then slowly drag it across the window with
a haemostat or some stout tweezers (suitably degreased). Then you
blow off any remaining liquid drops with dry nitrogen.

Using cheesecloth to remove polymer lens cleaner is an interesting idea,
but it would probably suck up a lot of material and take a long time to
dry, would it not? Collodion might be cheap enough for this to be okay,

but with Opticlean I usually use ordinary 3M white PVC tape, which isn't
quite sticky enough but works well and is very clean itself.

Guy Macon wrote:

Guy Macon on cleaning optics

My most frequent method of cleaning optics is to use the little bucket
and squeegee at the gas station. Wet the window down, scrape at the
bugs till most of the goo is gone, rinse the window again then wipe it.

Maybe it would help to mention what kind of optics are to be cleaned
and what is contaminating them before leaping into a dissertation on the
cleaning method.

Does anybody have a technique to spin clean items, like they do wafers in
semiconductor processing?

Does anybody have a technique to spin clean items, like they do wafers in
semiconductor processing?

na..but you could try spinning 'em like a pizza cook.

Guy Macon on cleaning optics

I have worked with optics and lasers off and on for many years, and
am also an amateur astronomer. The question of cleaning high-quality
optics comes up every so often on these forums, so I am weighing in
with some techniques that I have had good results with.

STEP ONE: BLOW OFF THE DUST:

Get a large rubber bulb ear cleaner at your local drug store (look in
the baby section). It will look like a one-piece soft plastic bulb
with a tapered snout. Make sure you get a ear aspirator (narrow
snout) and not a nasal aspirator (wide snout). These work better than
the smaller and more expensive models available at camera stores. Do
a web search for "Goodhealth Faultless Ear Syringe" for one example.
Don't use your breath; it isn't clean enough. Avoid compressed or
canned gasses, they come out cold and the thermal shock isn't good
for your optics.

STEP TWO: BRUSH OFF WHAT YOU CAN'T BLOW OFF:

There are a lot of lens cleaning brushes, but in my opinion the best
are the Staticmaster Alpha Ionizing Brushes made by Company 7
(www.company7.com). Make sure you use the ionizing feature as
directed, and use the lightest possible touch. If you can, skip this
step altogether; any time you touch the surface you are taking a big
chance that you might damage it.

STEP THREE: VAPOR PHASE CLEANING:

I have always used commercial systems to do this, but it looks like a
reasonable home project (it's up to you to not start a fire, though!)
In vapor phase cleaning, the optics (either at ambient temperature or
after being kept in cold storage) are lowered into the vapor over
some gently boiling solvent. The vapor condenses on the part runs
off, dissolving and flushing away contamination. The optics are then
lifted out and the solvent is allowed to evaporate from the optics.

Choice of solvents: In the "Good Old Days" we used solvents such as
trichloroethylene, 1,1,1-trichloroethane and CFC-113, but these are
no longer used because of environmental concerns. Nowadays I usually
set up two vapor phase cleaners, one using pure distilled water, and
the other using 95% pure (*not* denatured) ethanol mixed with 5% pure
water, AKA 190 proof. Because this is the azeotropic mix for ethanol
and water it is the highest concentration that can be obtained by
distillation. Because further concentration of ethanol is often
obtained with various additives, I advise against using 100% pure
ethanol. You also need to know whether the temperature of the solvent
vapor (100 degrees C for water, 78.4 degrees C for ethanol) is too
high for your optics, and whether the solvent will dissolve any
plastics or adhesives that are exposed to it.

STEP FOUR: PEEL-OFF FILM CLEANING:

This technique consists of painting or spraying a special material on
the optical surface, letting it cure, and then peeling it off, taking
any contamination with it. For years we in the industry have used
pure U.S.P. Collodion (cellulose nitrate in an ether-methanol
solution) for doing this. Note: "Flexible Collodion" contains added
oils, and is not suitable for this application.

Please note that this is a mainstream technique, not some weird new
idea. It has been used to clean the 23-inch Alvan Clark objective
lens at the Charles E. Daniel Observatory and the 30-inch mirror at
the University of Washington Observatory, for example.

At least two manufacturers are selling what may be the same or almost
the same solution. Caliope (www.caliope.co.uk) sells Opticlean (for a
review of it being used to clean a 24-inch mirror see
[ lists.tako.de/Olympus-OM/1999-07/msg01559.html ], and Photonic
Cleaning Technologies (www.photoniccleaning.com) sells "First
Contact", which has been used to clean the Keck hexagonal segmented
primary mirror.

I have not tried Opticlean or First Contact, because they are very
expensive and U.S.P. Collodion works great for me. A couple of tips
that I don't see on the Opticlean or First Contact websites are:

[1] Works great on dust and dirt. Not so great on grease. Imagine
picking up dust with some scotch tape. Now imagine trying to pick up
an oil droplet with scotch tape. I suspect that you are just removing
the top layer of that fingerprint on your mirror.

[2] The longer you wait the easier the film is to peel off.

[3] Two or three thin coats peel off better than one thick one.

[4] If you lay a large cheesecloth on a coat while it is still a
bit sticky and then later cover it with another coat, it eliminates
all tearing problems when you peel off the layer.

[3] Try it on a small spot on the edge before trying it on the entire
lens/mirror.

--
Guy Macon <http://www.GuyMacon.com/> Guy Macon <http://www.GuyMacon.com/
Guy Macon <http://www.GuyMacon.com/> Guy Macon <http://www.GuyMacon.com/
Guy Macon <http://www.GuyMacon.com/> Guy Macon <http://www.GuyMacon.com/
Guy Macon <http://www.GuyMacon.com/> Guy Macon <http://www.GuyMacon.com/

Alas, even if there are
hundreds of high-quality posts actually written by Guy Macon, all
someone has to do is to write "Guy Macon is a [deleted]" in the
subject line and it pops right up at the top of the search results.
Well, it did, until I started putting up my own posts with my name
in the subject line. Many employers search on a person's name
before hiring them. I don't like the impression the name in the
title gives either, but I like having a bogus post accusing me
of arson showing up at the top of a Google search a lot less.

Cleaning optics...

Want to add a remark:
Forget everything you ever heard about LENS TISSUE !

Use cleanroom wipes
http://itwtexwipe.com/pdf/msds_tds/aaa/TX8670TDS_en.pdf

They are made of soft fibers, absolutely lint free,
but cannot be used with certain solvents, be careful.
Acetone and Isopropanol are fine.

I used to wash the optics with normal household dishwashing detergent,
rinse with deionized water, and blow off (not wipe) the droplets with
clean room grade nitrogen.

Frequently we cleaned optic parts in a standard kitchen
dishwashing machine.....try your wine and beer glasses at home,
what's good for them is also good for a lens.

Some coatings would not like that procedure, though.

If lens "tissue" has to be used instead I recommend old cotton underwear,
which having been washed many times before (one would hope so) the fabric
thereof is now completely lint free.

Gaaah! Nooooooooo!

Guy Macon <http://www.guymacon.com/> writes:

Alas, even if there are
hundreds of high-quality posts actually written by Guy Macon, all
someone has to do is to write "Guy Macon is a [deleted]" in the
subject line and it pops right up at the top of the search results.
Well, it did, until I started putting up my own posts with my name
in the subject line. Many employers search on a person's name
before hiring them. I don't like the impression the name in the
title gives either, but I like having a bogus post accusing me
of arson showing up at the top of a Google search a lot less.

You are saying, any of us can be anonymously libeled to any degree of harm,
in a permanent, worldwide, searchable, first-resort archive, without any
chance of consequence to the libeler or effective defense from the libeled.
Employers or other persons of weight will give credence to this libel.

Your proper response: Abandon all hope.

Or maybe it's nothing of substance but a lot of arbitrary, microscopic
patterns of magnetism on tiny spinning disks.

Your proper response: Never mind.

Richard J Kinch wrote:

Guy Macon <http://www.guymacon.com/> writes:

Alas, even if there are
hundreds of high-quality posts actually written by Guy Macon, all
someone has to do is to write "Guy Macon is a [deleted]" in the
subject line and it pops right up at the top of the search results.
Well, it did, until I started putting up my own posts with my name
in the subject line. Many employers search on a person's name
before hiring them. I don't like the impression the name in the
title gives either, but I like having a bogus post accusing me
of arson showing up at the top of a Google search a lot less.

You are saying, any of us can be anonymously libeled to any degree of harm,
in a permanent, worldwide, searchable, first-resort archive, without any
chance of consequence to the libeler or effective defense from the libeled.
Employers or other persons of weight will give credence to this libel.

Your proper response: Abandon all hope.

Or maybe it's nothing of substance but a lot of arbitrary, microscopic
patterns of magnetism on tiny spinning disks.

Your proper response: Never mind.

Or maybe there does exist an effective defense. In fact, I
know that there does. Reputation Defender will do it for a
nominal charge, or you can do it yourself, as I have done.

If someone were to put up a web page that libels you (perhaps
in revenge for a certain Brief of Amici Curiae where you express
a somewhat controversial opinion) and did it so that it shows
up in a google search for "Richard J Kinch", where it shows
up in the search results is important.

Studies have shown that 67 percent of those who do a Google
search look past the first page (the first 10 results), 23
percent look past the second page, 10.3 percent look past
the third page, 2.7 percent look past the fifth page, and
it keeps dropping from there. So if you can fill up enough
of the results with favorable material so that the undesirable
result is on the 11th page, it might as well not be there at
all as far as you being harmed by people seeing it goes.

Worst case is having a unique text string as a user name
("Richard J Kinch" finds mostly posts about you, "Guy Macon"
finds posts about Larry the Cable Guy appearing in Macon,
Georgia) and few results (not like your case, with a
boatload of web pages with your name and TrueTeX on them).