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Is it possible for a hobbyist to create/mold/grind/polish a lens element?

There seems to be lots of astronomy hobbyists polishing mirrors and occasionally a large lens element. Is there an equivalent hobby of creating (very rudimentary-quality) element or objective lenses for photography? I couldn't Google up any good info on this.

The Kodak Brownie was single-element and manufactured quite cheaply. What would it take to make something like that? What would be the simplest and/or cheapest way?

(Yes, I do know this is not practical. Yes, I could just strip old objective lenses. And yes, I do know the quality would be quite low.)

  • While you're talking about creating the elements themselves, so this isn't an answer, I found this blog post on building lenses with cheap or scavenged elements to be very interesting. – mattdm May 28 '12 at 0:04
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    Can you link to astro folks making lenses? I know lots about mirrors there, but they're very different beasts. – rfusca May 28 '12 at 2:30
  • The manufacture of a lens element that is pure enough to be used for photography is pretty complex. You need materials with adequate purity, light transmission, and hardness, not to mention a fair bit of precision in your grinding mechanism to ensure you refract light enough to focus it where you want it focused, and do so evenly across the surface of the lens. Even on an amateur level, it would be pretty expensive to do. This video might be insightful regarding lens manufacture: youtube.com/watch?v=OkWsk9rXpcU – jrista May 28 '12 at 2:49
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There are separate issues.

  1. "Create" a lens - let's interpret that to be a design act - designing the curve according to focal length, required dispersion, etc. Yes, that's doable. There's lens design software around that will take a set of optimization criteria and some constraints and spit out a set of curves and glass types. Rustle up specific software recommendations on the amateur telescope making lists, I know I've seen them there.
  2. Mold a lens - not without herculean effort. The homogeneity required of optical glass is, according to every thread on the topic I've been able to find, pretty much out of reach for garage tinkerer types. This isn't to permanently dissuade you from trying - I'd love few things more than to see another "you can't do this at home" techno-cultural touchstone falling. But you'll have to get (and maintain!) sufficiently transmissive glass, of sufficiently controlled optical parameters (index of refraction, dispersion), completely free of bubbles, and completely homogeneous. These are partially conflicting requirements, as it's difficult to, for example, have a thoroughly homogeneous melt without stirring, which can easily introduce bubbles.
  3. Grind a lens - Definitely. I can't find the link now, but I saw an argument once that grinding (and, by extension, polishing) a good lens is easier than grinding a mirror, since the curves for a given f ratio are steeper with a lens, so errors show up more prominently during testing.
  4. Polishing a lens - Yes again, as at this point it's the same as polishing a mirror surface, except perhaps for the steeper curve. Figuring an aspherical lens surface might be harder than figuring an aspherical mirror surface, for the same reason testing a lens is easier: the curves are steeper on a lens, so the lap has to flow a lot more as it mates to the lens in various positions.

Disclaimer: This is mostly book-knowledge, not so much hands-on knowledge. While I've ground and just started polishing a small mirror, I've never tried making a lens.

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I can't address your question with personal experience, but the astronomy hobbyists get very good results. They not only polish their lenses, but they make them from a flat piece of glass.

Its hard to see why you would not be able to do it. it may take a lot of time, and as you suggest, its not economical, but this is a hobby. I say go for it if you have the interest.

I suggest you read Roger's Cicala blog, he has written a lot on the history of various lens designs. http://www.lensrentals.com/blog

As far as I can tell, a lens is a lens and doesn't know if you are pointing it at a star or a pretty face.

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    Note that amateur astronomers routinely grind their own mirrors, not lenses. With a mirror, the interior condition of the glass doesn't matter--it's just a mechanical substrate to hold the aluminum. – coneslayer May 27 '12 at 20:38
  • they could make lenses just as easily as mirrors, given the availability of the raw materials. I have made optical lenses for scientific instruments by modifying lenses for eyeglasses for example. While that project didn't require the quality glass needed for a $1000+ Nikkor, just windowpane wouldn't do either. – jwenting Nov 7 '12 at 11:55
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How about this? Since acrylic is easily mouldable, make a thin shell for the lens, prism, or whatever you wish to make. Then, fill it with glycerine, which has a refractive index almost similar to glass. However, due to double refraction by acrylic and glass, the focal length may slightly vary — so necessary adjustments are required. Please try this method and revert to to me if it works! By the way, the refractive index of acrylic is almost similar to water.

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Yes, you certainly could make a lens element. Amateur telescope makers grind their mirrors from glass blanks, so there's no reason why you couldn't make a lens that way.

However, it's a time consuming process, and the reason why most amateur telescope makers make mirror rather than lenses is that with a reflector scope, you only need to shape ONE surface of the main mirror (you also need a smaller flat secondary mirror, but those are fairly readily available commercially - not sure whether ATMs tend to make their own or buy them in).

With a lens, on the other hand, you have to shape BOTH surfaces, and to avoid chromatic aberration, you need to make at least two elements (from different glass types , so you're looking at four surfaces, not one - and the blanks need to be clear glass (with a mirror, you just need to avoid cavities at the surface). (And big lens quality blanks are probably more expensive than equivalent mirror ones).

On the plus side, you can get away with a bit less accuracy for the lens surfaces (better than half a wavelenth rather than the better than a quarter wavelength for mirrors), but most ATMS go for the simpler mirror.

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The first lens was made by an amateur. Why not you?

Start with a drop of water. This Scientific American article about using a drop of water as a lens will get you started.

You can use this lens for making portrait photographs for making close-up macro photographs and as an iPhone auxiliary lens.

The next step would be using plastic such as epoxy. The experiments in epoxy show more promise as you hove some time to work with it before it hardens. The surface tension is much less but the result is more durable. Bubbles in the mix have less effect than surface distortions. There have been bubbles in lens glass - their effect is to add flare rather than compromise the sharpness.

Have fun. Good luck.

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It is possible to grind and polish a lens at home as the present writer did back in 1971.

The aim was to build a homemade hand-cranked cine-camera. Being unable to find a 1" focal length lens at reasonable cost, I embarked on producing one at home. In essence, I used the concave bottom of an aerosol can, grinding the blank, a piece of window glass about 1/2" in diameter using progressively finer carborundum powder and water. Finally, all that was cleaned off, the aerosol can bottom coated with a thin layer of molten pitch (roofing) material. Once the pitch was set, some squares were scratched into the surface and wet jeweller's rouge or cerium oxide applied until the frosted surface became once more transparent. Camera worked and still exists though I had to wait until 2007 to get the 16mm negative transferred to DVD! All this was quite labour intensive and I think a Plano-convex lens sufficed. The quality was not exactly "Carl Zeiss" but good enough to produce recognisable pictures.

Best regards!

Jozef

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