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argh1984
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Join Date: May 2008
Location: The only place where hell can really freeze over.....Michigan
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Optical Coating

02/19/2010 7:37 AM

I have a project that i am working on that uses a flat acrylic lens tipped on approximately 10°. When looking thru this lense there is a glare (or reflection depending on who you talk to) that is interfering with the view. I have found several coatings that are "baked" onto glass lenses, but has a concern that the acrylic lense would deform when "baked".

My question is 2 part. First am i mis-understanding the coating process for lenses? And second, is there a thin film that could be applied to these lenses that is "peel and stick" that does not effect the clarity of the lense it is applied to?
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johnfotl
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Join Date: Oct 2007
Posts: 734
Good Answers: 70
#1

Re: Coating for Optics

02/19/2010 11:46 AM

Have you done a ray trace on your design?

When you say a 'flat' lens, do you mean plano convex, or is this a fresnel lens (a fresnel lens can have a lot of glare off-axis)?

I have done some work with PMMA and other plastic lenses, and internal reflections can be a real problem. I'm not sure that an anti reflection coating will help much with this.

Are you certain that the glare comes from the lens and not from the lens mount or inside surface of the lens tube?
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argh1984
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Join Date: May 2008
Location: The only place where hell can really freeze over.....Michigan
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#2
In reply to #1

Re: Coating for Optics

02/19/2010 11:56 AM

hmmm.....all great questions.....unfortunately i am relying on feedback from the sales guy (you know where that gets us )....maybe i need to take a road trip and see this in use and talk to the end user and try and figure out the problems that way.

Flat lens....really just a window no curvature to the lens at all..... .09" thick all the way across it and 3.5" diameter
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RHABE
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Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
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#3

Re: Optical Coating

02/20/2010 2:53 AM

Hi,

have a look to the catalogue of Edmund-scientific (or any other seller of optical elements), there is a lot about optical thin film coatings.

Nearly all these coatings are vacuum deposited as deposition from the wet is more complicated and suited only for large batches.

If you want anti-reflection then the coating has to have a quarter wavelength (optical) thickness. Optical thickness is mechanical thickness divided by refractive index.

Additionally the deposited material has to have a refractive index that is the square root of the acrylic lens and the adjacent air? or whatever fluid adjacent to the lens.

Unfortunately this low refractive index material does not exist so a stack of coatings is often used to compensate for.

This is also necessary if you want to eliminate reflection at more than one wavelength.

Achromatic: two wavelength , apochromatic: three wavelength reflection eliminated and very low in-between.

Acrylic will deform, you are right. COC is much better but sensitive to more cleaning fluids.

None of these optical films affect the clarity, look at optical lenses - all are multiple anti-reflection coated. Cleanliness is mandatory else you will spoil the effect.

Anti-reflection coating is the same as impedance-matching, this needs a transformer, the quarter-wavelength layer.

RHABE
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argh1984
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Join Date: May 2008
Location: The only place where hell can really freeze over.....Michigan
Posts: 63
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#4
In reply to #3

Re: Optical Coating

02/20/2010 8:12 AM

good information......thanks.....i will check out the Edmund optics catalog i have and see what i can find
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ddphillips
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Hobbies - DIY Welding - New Member

Join Date: Oct 2007
Location: Cincinnati Ohio USA
Posts: 46
#5

Re: Optical Coating

02/22/2010 8:02 AM

Acrylic lenses can be coated with a multi-layer, broadband anti-reflection coating that will cover the visible spectrum. The coating is typically done by vacuum deposition. Edmunds generally deals in finished components. Some of the optical coating houses would be a better source for coating customer supplied substrates.
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argh1984
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Location: The only place where hell can really freeze over.....Michigan
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#6
In reply to #5

Re: Optical Coating

02/22/2010 8:48 AM

Do you have any suggestions as to good optical coating houses? I am sure i can google some, but it is always better to use one that someone else has had good success with.
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ddphillips
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Hobbies - DIY Welding - New Member

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Location: Cincinnati Ohio USA
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#7

Re: Optical Coating

02/22/2010 8:56 AM

ZC&R and Cascade come to mind. It's been a while since I worked in the field and a lot of my memory has gone away. (At least that's what my wife tells me) A Google search will list numerous others.

Regards,
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Anonymous Poster
#8

Re: Optical Coating

02/23/2010 11:45 AM

3M has a line of films that you can laminate to LCD displays to reduce glare. This may work for you. Google 3M anti glare and see what they have.
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Anonymous Poster (1); argh1984 (3); ddphillips (2); johnfotl (1); RHABE (1)

Previous in Forum: Welded Samples   Next in Forum: SS904L and SS316L comparison? and can we use ss904L with Formic Acid and H2SO4

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