[HN Gopher] Creating Camera Lenses with Stereolithography
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Creating Camera Lenses with Stereolithography
Author : _Microft
Score : 71 points
Date : 2022-02-03 12:26 UTC (2 days ago)
(HTM) web link (formlabs.com)
(TXT) w3m dump (formlabs.com)
| progre wrote:
| Example photos with these lenses here:
| https://formlabs.com/blog/photos-from-a-3d-printed-camera/
| can16358p wrote:
| I think it's a nice start. As materials and tech get more
| precise, I see a good future of people making their own lenses,
| at least for general hobby purposes.
| gswdh wrote:
| dekhn wrote:
| People (hobbyist astronomers) make their own lenses (well,
| mirrors) starting from glass blanks and tediously grinding
| and polishing them to precise shapes. However, it's quite
| challenging and time consuming and you'd only do it if you
| absolutely needed a mirror of a specific geometry. And it's
| quite hard to reach the levels of accuracy that a routine
| mirror or lens making operation can.
| Wistar wrote:
| When I was a young kid, my father ground a 6in mirror with
| a 48in focal length. I remember him walking around a table
| at night for weeks. The first mirror didn't work out so he
| had to grind a second.
|
| The resulting telescope was, and still is, a remarkable
| device, although we had to have the mirror re-silvered a
| few years ago.
|
| The first time I saw Saturn in all its glory was through
| that telescope, looking the size of a softball, and I
| remember thinking, Wow, it really exists!
| dekhn wrote:
| Sure, but these days you can buy most any lens or mirror
| you need rather than grinding it yourself, and then spend
| more time viewing stars and planets and less time
| breathing glass particulates.
|
| I think in most cases making your own lenses is just a
| labor of love, not a way to save money or achieve better
| results. This is merely because lens and mirror making
| was industrialized and has impressive economies of scale.
| Wistar wrote:
| This was back in the early 60s and although he could
| probably have purchased a ground mirror, I think getting
| one with a 48in focal length may have been beyond his
| budget.
| frxx wrote:
| Thank you.
| carapace wrote:
| > the first fully 3D printed, interchangeable lens camera
|
| Wow!
|
| I bet you could print those mustache-shaped cross-section lens
| that correct chromatic aberration? (I can't find the paper at the
| mo'.) :(
| _Microft wrote:
| Like this?
|
| https://www.researchgate.net/figure/Spherical-aberration-cor...
| carapace wrote:
| Ah, _spherical_ aberration! Not chromatic aberration, d 'oh!
| Thank you!
|
| Found it: "General formula for bi-aspheric singlet lens
| design free of spherical aberration"
| https://opg.optica.org/ao/abstract.cfm?uri=ao-57-31-9341
|
| https://petapixel.com/2019/07/05/goodbye-aberration-
| physicis...
|
| https://phys.org/news/2019-08-physicists-year-old-optical-
| pr...
|
| https://news.ycombinator.com/item?id=20369960 and
| https://news.ycombinator.com/item?id=20703140
| camtarn wrote:
| The blog about the camera is fascinating too, especially the
| shutter mechanism:
|
| http://amosdudley.com/weblog/SLO-Camera
| [deleted]
| billfruit wrote:
| Not related to article, but can anyone comment how development of
| liquid lenses are coming along for photography applications.
| 4gotunameagain wrote:
| They seem to be a bit confused with optics. What they minimise by
| reducing the aperture size is the _spherical aberration_ , if
| they used a spherical lens as pictured.
|
| Coma is present on parabolic mirrors, which do not exhibit
| spherical aberration or any shape related aberration when the
| rays are parallel to the boresight of the camera, but only when
| at an angle.
| PragmaticPulp wrote:
| Cool article. It's too bad they didn't include more photos of the
| earlier steps. They mention them in text, but they'd be far more
| interesting to see:
|
| > The lens was clear as a magnifying glass, but as a focusing
| lens it wasn't accurate enough.
| quells wrote:
| I think this article was mostly a summary of the engineer's
| personal blog post: http://amosdudley.com/weblog/SLO-Camera -
| linked from the post with example photos in another comment.
| sydthrowaway wrote:
| Can we do this on an ender3
| [deleted]
| samwillis wrote:
| This is super interesting, I wander if 3d printing lenses could
| be a good way to explore light field photography and projection?
|
| You could potentially design and print some quite complicated
| lenses. I suppose the one difficulty would be the epoxy pooling
| in small crevices when dipping. But then if you take that into
| account in the design it could be compensated for. You would need
| to find a way to predict the flow of the epoxy over the printed
| substrate.
| daniel_reetz wrote:
| Have a look at luxecxel. They manufactory lens arrays using a
| proprietary printing process.
| abdullahkhalids wrote:
| The problem is that if concave parts are dipped, the epoxy
| would pool and form a small flat surface at the bottom. You
| can't out-design that.
|
| But perhaps, there is a way of holding the concave part upside
| down and spraying epoxy on it that might work. No idea.
| samwillis wrote:
| Quite true, alternatively you could hold the part inside a
| rotating drum, a bit like rotational moulding. But then it
| will be harder to predict the thickness.
|
| I suspect you are right about spraying, much more likely to
| get a uniform thickness. Maybe a combination of the two spray
| a constantly rotating (in 2 axis) part.
| numpad0 wrote:
| One problem that remains for home 3D printed lenses is chromatic
| aberration.
|
| Refractive index(angular multiplier for lights entering at
| angles) is wavelength and material dependent, which means
| magnifications/focal distances vary for each colors, causing
| rainbow-blurred images at image planes. btw this is obviously how
| prisms work.
|
| The variance is largely monotonic and the effect is well studied;
| the coefficient of this aberration is called Abbe number or Vd,
| defined as Vd = (nD-1)/(nF-nC) where nD, nF, nC is indices at
| 656.3, 589.3, 486.1nm respectively. Materials that shows Vd > 50
| is called "crown" glasses and materials with Vd < 50 is called
| "flint" glasses. There are lens materials with Vd of exactly 50,
| such as Fluorite(CaF2) crystals as well as other engineered
| materials such as borosillicate "Extra-low Dispersion(ED)"
| glasses. These lenses show abnormally low aberrations, at cost.
|
| Wikipedia[3] explains the legendary Carl-Zeiss Tessar design by
| Paul Rudolph as follows:
|
| > A Tessar comprises four elements in three groups, one positive
| crown glass element at the front, one negative flint glass
| element at the center and a negative plano-concave flint glass
| element cemented with a positive convex crown glass element at
| the rear.
|
| Without relying purely on such exotic materials, lenses are
| designed with pair and triple elements(doublets and triplets) to
| counter aberration. A convex crown glass may be used to focus
| light, then convex flint glass lens are added so as to cause
| focal point for both red and blue lights to coincide(achromat, or
| _non-chromatic_ , doublet). Or an another convex lens can be
| added to force RGB lights to converge at a same point(apochromat
| triplet, APO). Focus errors dependent on wavelengths follow an
| exponential curve to the power of lens count. An achromatic
| doublet consists of Schott BK7 and Schott F2 is often used in
| textbook exercise questions.
|
| There are other types of aberration such as "the five Seidel
| aberrations", and some might be able to be solved by clever use
| of same materials, but as far as I understand, chromatic
| aberration cannot be solved by computational force alone. Maybe
| it's something dumb and obvious to materials scientists as adding
| certain baby powder with specific composition into the resin,
| like how obvious a UART console pads are to PCB designers, but
| for now this rules out high quality lens manufacturing by direct
| stereolithography, as there is no hobbyist known way of
| controlling and modifying Abbe number for UV resin materials,
| save for using metamaterial surfaces. If someone could dump that
| here it'll probably be a decade worth of progress, for both
| hobbyist photography lens creation AND likely for entire optics
| industries as well!
|
| 1: https://en.wikipedia.org/wiki/Abbe_number 2:
| https://en.wikipedia.org/wiki/File:Comparison_chromatic_focu...
| 3: https://en.wikipedia.org/wiki/Tessar
| dekhn wrote:
| You can buy a wide range of UV resin materials (with a range of
| refractive index) as a hobbyist.
|
| I can think of any number of alternative ways to deal with
| this, for example you can project a series of colored images
| and measure the response, then use that to back-correct images.
| We're in an era of fast computers and powerful software, which
| can correct for things that are normally corrected by expensive
| techniques.
| numpad0 wrote:
| Refractive index isn't a problem, but the problem is the
| index gradient over wavelengths(Abbe number). VR goggles and
| some digital cameras does software correction but that is
| unheard of, in, e.g. film photography.
| dekhn wrote:
| So it's impossible to take a matched pair of UV resins and
| make a pair of lenses to construct an apochromat, which you
| can do with glass?
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