Need Optical Quality Plastics 1

[LWB3]

I am looking for optical quality plastics. I need a suitable material to build a 21" dia and 0.5" thick window that will provide good photographic images without much distortion. Any suggestions or recommendations???

Thanks,

Leonard.

 

[nbucska]

Specify the window (pressure etc. ) and define "GOOD".
Try PMMA.

<nbucska@pcperipherals.com>

 

[IRstuff]

Perhaps you should consult with some molded optics manufacturers:

http://www.prisma-optics.com/

http://www.fosta-tek.com/

http://www.motionnet.com/cgi-bin/search.exe?a=cat&no=4169

TTFN

 

[LWB3]

The pressure delta is from 1 Atm to vac. By Good, I mean the best possible (flatest curve) transmittance in the visible range.

The motionnet links were pretty useful, but for some reason the Wavelenght Optics link isn't the safest thing to link to at work.

 

[Timelord]

Leonard,

Common acrylic is one of the clearest plastics available (in the optical wavelengths). A bonus is you can get it in all kinds of thicknesses and it machines like a dream. I suspect that 1/2&quot; is way to thin for a 21&quot; window if you want it to stand up to vacuum. A quick calc in my head says 2-1/2 tons of force on the window.

Timelord

 

[LWB3]

Agreed. The window will have a stack of 3 or 4 panes with a gradient pressure between each pane. Only the outer and inner pane will be plastic, the other two will be quartz or something similar. I'm not so much worried about the load that the plastic will take, just that it is durable, scratch resistant, and has good optical qualities in the visible range.

 

[Timelord]

Acrylic is not very scratch resistant. Another candidate which is more scratch resistant is polycarbonate but it has some filter characteristics, a very slight blue tint as I recall. There are some acrylics that have scratch resistant coatings (used in aircraft windows i.e.), but I don't know off hand where to get them. Are you going to attempt radiometry or just take photographs thru the window? Polycarbonate would be good enough for photos.

Timelord

 

[IRstuff]

I think that depends on the type of polycarbonate, as that is also what's used in children's eye-glasses, and I haven't seen any hint of blueness.

TTFN