Creating Camera Lenses with Stereolithography

http://amosdudley.com/weblog/SLO-Camera

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.

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.

PS: The page so heavily depends on JS that it literally gives me a blank page unless I disable JS in browser :D :(

They really changed the game with their SLS. We bought it last year and it performs much better then an EOS device that was 5x more expensive…

Hoping to see similar effects with this line…

> The lens was clear as a magnifying glass, but as a focusing lens it wasn’t accurate enough.

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'.) :(

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