Aside from a gas bubble, no. The problem with gas bubbles is that as the external pressure increases, the structure creating the bubble compresses, changing the focal length (and probably the aberrations). I suppose one could design a structure that would compress without too much optical change (a parallel to isothermal design), but it's likely to be a complicated thing.
Joe Gwinn
Like about 2 Atm pO2. Oh, that's got to be a good story. Can you suggest any URLs or reports?
I wonder is silicon oil would work. In any event, it's a closed container, so the oxygen can be purged from the oil. I think helium is used for such things.
Thanks,
Joe Gwinn
AFAIK the lowest index material that is both hard and water-insoluble is MgF2 at n=1.38, still higher than water.
Cryolite, which comes in at n=1.35, is both soft and water-soluble.
Cheers
Phil Hobbs
Unfortunately sapphire is pretty birefringent--n_o-n_e ~0.008 iirc. That makes for some gnarly looking images unless the aperture is small and the sapphire is C-axis oriented.
You can get polydimethylsiloxane (dimethicone) for pretty cheap from a variety of places, e.g. Clearco. Nice and nontoxic, as well as essentially completely inert.
Ouch. Shades of Apollo 1. :(
Cheers
Phil Hobbs
Granted, the focus will not be absolutely perfect, bit if you've ever looke d at an aquarium, I doubt you would notice much distortion due to the bound aries between water, glass and air...
Yet another thing I hadn't considered...but as I don't expect to have any o ther oxidizers in the system (certainly worth some thought), once the oxyge n in those bubbles is consumed, the combustion should stop. Burning a few m illigrams out of a few kilos of oil, surrounded by cold water, in a flexibl e container should not even be noticeable. (The plastic bag idea someone me ntioned is not that far off, I actually considered that to show off the con cept, but it sounded a bit fragile).
And - I think a two-part 'optically clear' silicone will come in
You do, actually. The image is reasonable-looking despite the gross geometrical distortion at large angles, but that's because the aperture of your eye is so small, but that's far from true if you use something like an f/1.4 lens at any close distance.
Cheers
Phil Hobbs
Again, I guess I was being unclear/incomplete. For now at least, I'd be usi ng a TINY camera. I don't heave detailed specs on it, but I'd take a wild g uess that it's equivalent of f/16 or smaller with a lens a couple of MILlIM ETERS across. Without knowing the sensitivity of the CCD, which I don't, it 's hard to take a decent guess, but if I have to set it back an inch and th e image still looks like you're looking through a spherical fish bowl, and unfocused off center, I'm still good to go.
To help with some of the confusion, while I'm by no means rich, much of my cheaping-out is really part of the proof-of-concept notion. While I'd love to make some money off this, if JQP can look at it and say "I could do tha t with $100 and an afternoon", so much the better...
I think Joe meant to use silicon OIL instead of the mineral oil, to overcome the "spontaneous combustion" issue but I'm not too concerned about that one.
erything has a bulk modulus. I'm sure you can look it up for plastic.
I may have been arguing with a straw-man I imagined, based on various artic les/pages I've come across while looking for anyone who has done something similar. I keep running across comments (not directly related) like "water is incompressable, so you don't have to worry about that", where steel will compress measurably at the pressures I'm eventually shooting for. That sub tlety might seem obvious in this crowd...
One problem is that the plastics involved are unknown and might well be sec ret, so finding an accurate bulk modulus might be impossible. With real mon ey, I could get everything fabbed with chips mounted on ceramic, without an y plastic or air-apaces (speed is hardly an issue)... I haven't quite worke d up the ambition to sacrifice a processor to see if the plastic on the chi ps will melt,especially without damaging the electrical components (or if t hey will support themselves without the plastic. I do have a stash of old, obsolete ICs that I could do some gorilla experiments on... Of course, some of the chips on my computer are surface mounted, so melting those without damaging the circuit board could be problematic.
After educating myself a bit about the concept of bulk modulus (thanks, tha t was the term I needed), struggling a bit with things being published in d ifferent units, and assuming I didn't mix up any kilo's, mega's and giga's, if looks like while silicon and a random plastic have significantly differ ent\ bulk moduli, they are both far less compressible than I had assumed (l ike I said, I'm a programmer, not a chemist (in Scotty's voice)), so this m ight well not be an issue...
On Fri, 9 May 2014 11:31:00 -0700 (PDT), snipped-for-privacy@yahoo.com Gave us:
Use
I suspect you included the wrong link... But I could be missing something.
I wonder if you can get cheap zirconia optical components?
+1
I don't think anyone was killed in the German incident although it is so long ago that it was almost apocryphal when I was a physics student.
The pO2 > 1atm problem and accelerated fire is a recurring theme.
"DuPont(tm) Teflon(R) AF 1601S and 2400S Amorphous Fluoroplastic solutions"
It's Teflon dissolved in Fluorinert, a Teflon "paint"/casting resin.
"Teflon(R)AF can be used as a low-refractive-index coating or covering for optical devices, including those that must operate over a wide temperature range and in chemically aggressive environments. Teflon(R)AF offers a high level of transmission throughout the optical spectrum from infrared through ultraviolet.
"In electronics, Teflon(R)AF may be used in optoelectronic devices where its optical clarity, temperature resistance, and dielectric properties are beneficial."
The PDF lists dielectric constant and dissipation factor in the range from 1 MHz to 13.6 GHz but its not clear if that's for the solution or the "dried" Teflon coating/casting. I suspect it's for the latter.
The visible-range properties mentioned seem a little vague to me though.
Mark L. Fergerson
I looked into that back in the day, like about 1990. Interestingly, pure zirconia has a tetragonal structure and is horribly birefringent. To get the cubic structure, they mix in a bit of yttria, which cubic zirconia is also called "yttrium-stabilized zirconia". It turns out that as the crystal grows, it makes layers of different yttrium concentrations, which make the refractive index fairly seriously nonuniform. It was bad enough to screw up my laser-based application at the time, but I don't know how bad it would be for a webcam.
Cheers
Phil Hobbs
the "spontaneous combustion" issue but I'm not too concerned about that one.
Yep - I was just commenting on lens materials. The Silicone oil was widely used in diffusion pumps. Those pumps get brought up to atmos. Pressure by accident sometimes, say by a gate valve not getting pressure, and vacuum system operators like to avoid an explosion. Plays havoc with switch contacts, I've heard.
DuPont Kynar is another fluorocarbon dissolved coating material - Poly vinylidene fluoride I think. I think it dissolves in acetone. DuPont made a paint from it for $400 a gallon. This is cost-effective for places like the tops of radio towers, since the paint lasts for decades.
On Mon, 12 May 2014 20:33:54 -0700 (PDT), snipped-for-privacy@yahoo.com Gave us:
Oops
How about Fluorinert FC-72 (n=1.25) with LASFN-35 (n=2.02) lenses ? I might be visiting a few lens suppliers next week at Optatec exhibition. If I do that, I can ask if someone has LASFN35 lenses in their standard offering.
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