grinding my own lens ? grinding my own lens !

Discussion in 'Camera Building, Repairs & Modification' started by Rock Poper, Jun 10, 2005.

  1. Rock Poper

    Rock Poper Member

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    might seem a bit far fetched but I've only been at this site a little while and have learned so much, no question unanswered yet - so I'll have a go with this:

    Any advice/tips/starting points on how to go about grinding and polishing my own lens ?

    ... like I guess the old astronomers would have had to ...

    some sort of lathe ? and then months of polishing ?

    probably a maths degree ?

    I dont want to make a super correct lens, and dont expect to be able to understand centuries of design in one go, but it would be nice to attempt to make one using the original old old (old) method/s

    cheers!
    nick
     
  2. medform-norm

    medform-norm Member

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    I know an educational institution in Leiden, Netherlands, where they have a deparment for people like you. It's called fine optics - and you only get admitted after severe selection, as we were told by the head of this department...go give it a try. Maybe you can get funding as a kind of 'back to school project'.

    Regards, Norm
     
  3. Terence

    Terence Member

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    The astronomy guys do it all the time. Do a google search for it. However, the quality they need for viewing is pretty far below what most of us would consider acceptable for film. Most of us. I looked into it and wisely got over the urge. The astro folks say they can do it over the course of a few weekends. Longer lens typically have a shallower curvature, so that makes sense. Trying to makea wide angle would probably take a LOT longer, and be less forgiving. I keep thinking someone should be able to make a hypergon-clone at a reasonable cost. It's only two elements. Surely there's a suitable optical plastic that could be easily molded.
     
  4. medform-norm

    medform-norm Member

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    ~certainly if you'd outsource it to a Chinese partner. The Chinese just love copying things. Question is: where to find a reliable Chinese partner. You could set up a program for copies of all desired lenses, and start out with a top ten of the most wanted...

    Oh boy, my entrepeneurial genes are certainly in full flight today.
     
  5. Ole

    Ole Moderator Staff Member Moderator

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    Didn't Wisner try this - and give up?
    The inside curvature is too deep for automatic grinding, I think. So maybe the Chinese could do it by hand :smile:

    I just got hold of Rudolf Kingslake's "A History of the Photographic Lens", an interesting read for anyone into this sort of stuff. If you want to avoid cementing lenses (or antireflex-coating them), the Steinheil Periskop and Zentmayer hemisymmetrical would be the easiest to get anywhere near decent results from. After those a Cooke Triplet, perhaps?
     
  6. janvanhove

    janvanhove Member

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    Aren't most aspherical elements in modern lenses simply molded anyway? Shouldn't be too hard to mold those hypergon elements... the fact that they are symmetrical makes it even simpler !

    People could then buy all the hypergons they dream about and realize how much the wide-angle lens design process has improved over the last 150 years ! :tongue:

    But then again, there are no modern lenses that go that wide...

    Cheers,

    PJ
     
  7. Donald Qualls

    Donald Qualls Member

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    As one who has made a telescope, including grinding, polishing and figuring the parabolic primary mirror (starting from a cast Pyrex blank), I've got a little idea what goes on. Yes, making lenses is well within reach of amateurs. No, you don't want to start with lenses -- optical glass is expensive. Start with mirrors -- the techniques are the same, and you can work with plain soda-lime float glass (i.e. window glass) in thicker sizes, which will save you a lot of money. What makes lenses trickier than mirrors are that they have to be made from a particular glass (to have the correct index and dispersion), with pretty exact control of surface curvature, centering, wedge, and thickness, usually with final figuring based on optical testing because it's impossible to measure the surface accurately enough by any other means. Often it's necessary to make a number of other optics (which can often be reflective, and so require only a single perfect surface without constraints on those other qualities, and can be from nearly any material) just to test the one you're working on.

    Even very experienced amateur opticians blanch at the thought of making cemented surfaces, but some of them have done it; there's nothing that would prevent a dedicated amateur from making a copy of a Tessar, Doppel-Anastigmat, or Rapid Rectilinear if so inclined.

    Machines are often used, but they bear more resemblance to a potter's wheel than to a lathe in most cases, at least for astonomical optics (though very small lenses have been ground on machines with horizontal spindles).

    The time factor is tricky -- you might well spend only 10-20 hours actually grinding and polishing each surface of a lens, but intersperse that with two or three times as much time making test equipment and testing in order to bring the lens to the correct final prescription. Add to that the cost of suitable pieces of certain exotic glasses needed for achromatizing and aberration correction, and things quickly get ugly, even if you can find the necessary information to duplicate the prescription for a particular lens.

    If you want to design your own, then you add the complications of obtaining and using suitable software that can correctly deal with multiple elements and glass types; OSLO is the only package I'm aware of, and the full version is comparably priced to an industrial CAD/CAM package. There's a trial version, but it may be too limited to deal with deep curves or more than two or three elements.

    Coating a lens isn't out of the question -- I read somewhere (can't remember now if it was on APUG or the Camera-Fix list) that there is a Ukrainian service that will multi-coat loose glass for quite reasonable prices, including strips and recoats of existing lenses (the tricky part being you have to remove them from any cells before shipping); there's speculation they're piggybacking on the coating equipment at the Arsenal optical factory. This would be a perfect way to get a one-off handmade lens coated. Cement first, please...
     
  8. Ian Grant

    Ian Grant Subscriber

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    While not home polishing I did find this company when doing a search to see if the UK based Ross Company was still trading.

    http://www.rossoptical.com/

    Wonder if they are any use to any of us ?

    Ian
     
  9. Dan Fromm

    Dan Fromm Member

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    As much use to those of you in the UK as Edmund Industrial Optics, formerly Edmund Scientific, is to us in the US. I live a couple of miles from Edmund, get the catalog, visit the suplus shop from time to time. So far all I've found that's obviously useful for any of my photographic gear projects is adhesive-backed flocking paper.
     
  10. Ole

    Ole Moderator Staff Member Moderator

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    That Ross site looks interesting... Make your own petzval portrait lens?

    I have OSLO Edu - the trial version. The limitation is six surfaces, so you can calculate a triplet or half a Dagor (up to 5 cemented elements), but not a Tessar or a dialyte :sad:
     
  11. Ian Grant

    Ian Grant Subscriber

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    Dan's mention of Edmund Industries is also interesting, they have a UK facility just across the North Sea from you Ole in the old Viking capital York :smile:

    http://www.edmundoptics.com
     
  12. wfwhitaker

    wfwhitaker Member

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    You would no doubt find the three-volume series Amateur Telescope Making very interesting. Originally published by Scientific American quite some time ago, it's probably out of print, but perhaps has been reprinted or can be found in a good library. While most of it pertains to mirrors and other trappings of amateur astronomy, there are some chapters dealing with lenses. My books are packed away right now, so I can't give you a specific reference, but I believe volume 3 has a chapter on making a triplet of the Cooke type.

    It's one thing to make a single surface as in a telescope mirror. A simple lens is a bit more work since the two surfaces must share the same optical axis. A multiple element lens is something else altogether. Did you plan on leaving any time for photography?
     
  13. Rock Poper

    Rock Poper Member

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    thats exactly what I was thinking! (re. the hypergon) -
    this lens particularly excited me as it had an almost similar system i was thinking of for a centre ND filter - I was thinking a rotating disk with slots in it - rotating around an axis in the centre of the lens for centre ND falloff correction or off axis for general ND - if you made a big one and placed it near the focal plane - the slots would be big enough to make adjustable -

    Of course tho like all good and bad ideas its prob been done 80 years ago or something -

    Anyways, I want to make a 8x10 - the lens, shutter and holder systems were the ones I thought I would have trouble with, but upon purchasing a holder and looking a few systems, this is easy to make -

    shutters not sure yet, need to pull a few apart and get my head around them (lens cap, long expsosure in the meantime) -

    but wouldn't be great to have made a full 8x10 from scratch - including the lens (grin)

    Once exams are over here (I'm an architecture drop out now engineering student soon to be a arch student (again) engineering drop out) I'm going to put my nose to the grindstone and do it! (the extra hard way)

    cheers,
    rock


    (prob have some more questions once I get going - thanks for the replies!)
     
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  15. Rock Poper

    Rock Poper Member

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    I guess I am a gear head yes - I do take photos occasionally - as i cant access the gallery yet - I'm going to go and try uploading here :wink:

    excuse the bad scans ...
     

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  16. Murray@uptowngallery

    Murray@uptowngallery Member

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    Go to google, click on groups, search or otherwise
    http://groups-beta.google.com/group...q=metrogon+help&rnum=1&hl=en#4803ef321eaee53c

    If that link is garbage (doesn't look too alive when pasted), go to
    http://groups-beta.google.com/group/rec.photo.equipment.large-format?hl=en
    And search for
    Metrogon cell spacing revisited HELP

    Brian Caldwell responded. He wrote one of the major optics design programs AND made his own 11x14 Topogon (predecessor of the Metrogon, but follower of Hypergon). He explains why it can be done with relatively cheap variety of optical blanks, discusses some problems he had, but he's no amateur...he does seem to think it was not a big deal. He didn't say how long it took, or what his perspective for inexpensive means (compared to paying someone to do it?)

    I think the achromatizing on that design (oops, I'm diverging to Metrogon again) was accomplished thru the degree of symmetry), and other aberrations corrected thru symmetry and aperture reduction (you don't see smaller f/# than 6.3 to my knowledge on Metrogons. I don't know about Topo- or Hyper- types)

    I can link you to the patents on Metrogon Topogon and an English variant that might not have been commercially popularized.

    Murray
    Murray
     
  17. Murray@uptowngallery

    Murray@uptowngallery Member

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    Well, the first link I gave looks truncated, but it works.

    M
     
  18. Rock Poper

    Rock Poper Member

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    great - thanks for that Murray - I'm playing with other recent finds (bolex cine camera) but still have a mind to grind sooner rather than later ...

    it is tho a bit of a long-term project ...
     
  19. Neanderman

    Neanderman Member

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    Get the latest version of Oslo -- it now allows up to 10 surfaces. I've been inputing data for some of the classic lenses (triplet, Tessar, Dagor, etc) from their patent descriptions. It is a great way to learn something about optics.
     
  20. phfitz

    phfitz Member

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    Neanderman:

    "Get the latest version of Oslo "

    Where??

    Thanks.
     
  21. Lee L

    Lee L Member

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    http://www.sinopt.com/

    Lee
     
  22. Mongo

    Mongo Member

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    The book "Primitive Photography" has a section on some of the classic lens designs. The assumption in the book is that you'll buy the individual elements already made (not at all far-fetched...SurplusShed sells lots of individual lens elements in many sizes and focal lengths) and build the lens from those. No Hyper- or Metro-gons, but a few classic designs that should give you a good foundation to work from. The books well worth it as the ultimate "build everything yourself from scratch" resource...it even gives detailed instructions on making your own paper negatives.

    Using the book, your time, and very little money, you could be making prints using negatives you coated, shot in a camera you built with a lens that you built and a negative holder that you built. Pretty fun stuff to read even if you never intend to do any of it. And it's the ultimate antidote to digital angst...even if every supplier in the world gets out of the analog photography business, you'll be able to make pictures using the instructions in the book.

    Be well.
    Dave
     
  23. Rock Poper

    Rock Poper Member

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    thats the idea! - neg's I coated ? thats one I hadnt thought about yet -
     
  24. phfitz

    phfitz Member

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    Lee L:

    thanks for the link, the program looks interesting. 10 surfaces would cover Heliar, maybe I can find the reason for the magic;-))

    Now to find what to polish a lens with and where to get it. Any ideas people?

    Thanks.
     
  25. Lee L

    Lee L Member

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    Willman-Bell has stuff for making astronomical optics, especially mirrors, that might be applicable to refractive lenses as well. However, I don't know where to find that part of their catalog online. Find them online and ask for a copy of their catalog, which lists those supplies.

    I'm sure there are other suppliers, but I don't know them off the top of my head.

    Lee
     
  26. Donald Qualls

    Donald Qualls Member

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    Yep, look up astronomical suppliers. There used to be a place called "got-grit.com" (give or take a hyphen) that would sell all the grits you could want from 60 carborundum down to rouge. For grinding a lens, you're going to want 60 to 90 for roughing, then 120, 220, 320, 600 (silicon carbide to this point), 15 micron, 10 micron, and 5 micron (aluminum oxide for the fine stuff). Some folks use 3 micron alox as well.

    Once you're done removing glass, you'll need to polish; that calls for optical pitch (though I've heard of one fellow successfully using road tar and another tempering roofing tar to get usable pitch) and some kind of rouge. The most common now is cerium oxide, but some folks use tin oxide and a few prefer to finish with genuine rouge, an iron oxide compound (but watch out for lumps in the red rouge, they'll scratch your glass).

    I'd also very strongly recommend working with a local telescope making group to gain the hands-on experience you'll need to make a lens. A simple lens (one element, plano-convex, like the objectives Galileo used 400 years ago) isn't difficult to make, but if you want to make an achromat or more complicate lens you'll be looking at developing some considerable skill before you get one that's usable.