When do aspherically ground lenses date from?

[pgk]

I am aware that such lenses were made (for telescope-photographic use using steam powered grinding machines) in late Victorian times, but does anyone know who first came up with the idea and first put it into practice it?

[xkaes]

I think Canon used it in a very fast normal focal length lens in the 1960's.

[Dan Fromm]

The first series production lens with an aspherical element that I'm aware of is the Elgeet 12/1.2 Cine Navitar. In C-mount, for 16 mm cine.

[Bernice Loui]

If Wiki can be believed:
"Early attempts at making aspheric lenses to correct spherical aberration were made by René Descartes in the 1620s, and by Christiaan Huygens in the 1670s; the cross-section of the shape devised by Descartes for this purpose is known as a Cartesian oval. The Visby lenses found in Viking treasures on the island of Gotland dating from the 10th or 11th century are also aspheric, but exhibit a wide variety of image qualities, ranging from similar to modern aspherics in one case to worse than spheric lenses in others."

https://en.wikipedia.org/wiki/Aspheric_lens#:~:text=The%20origin%20of%20the%20lenses,February%2027%2C%201667%2F8.


Dan's assertion, "Elgeet for use in the Golden Navitar 12 mm f/1.2 normal lens for use on 16 mm movie cameras in 1956." appears correct. Long before Canon or Leica produced aspheric Foto lenses.


Bernice

[pgk]

Thanks. I never thought to check on wiki. Next time.

[Drew Wiley]

I'm getting glad my security filter doesn't even allow me to pull up Wicki anymore. Take it with a grain of salt. A Cartgesian oval involves a ground flat spot, and is a far cry from the current meaning of an aspheric element, which involves something of an S-curve. The real deal had to evolve parallel to serious improvements in glass itself anyway. But it's probable that, just like in many alleged new things film and optical, secret surveillance applications preceded commercial ones. I'm unaware of any actual old astronomical telescope use of it; but the person who would really know, I haven't spoken to in person for awhile because he's still under immune system pandemic isolation due to cancer treatment. Maybe it will come to mind next time I see him again. It's an interesting question, regardless. But I was distinctly under the impression that LARGE aspherics, needed for actual astro observatory scopes, were simply not realistic to precisely make or mount until the latter half of the 20th C. That is based on conversations with the person who owned the company actually specializing in that application, who is now deceased, though the corporation itself is certainly still alive and well. Maybe if I have time later in the day, I might remember to look them up an see whether or not their website still has a historical background section to it. Until then, take my own words with a grain of salt.

[Michael R]

I imagine the first lenses ever ground were at least slightly aspheric.



Thanks you've been a great crowd!

[Nodda Duma]

Foucault devised a tester to allow deterministic fabrication of aspheric surface for telescope mirrors in 1858. Before the Foucault tester was invented, aspherics were made but couldn’t be measured to a high level of accuracy (not that it stopped them from being made).

Eyeglasses have often historically had aspheric surfaces.

Being able to generate optics with surfaces which deviate from spherical is nothing new. Spherical optics got popular when mass production became popular and people decided they wanted to make bunches all at once.

[Drew Wiley]

Thanks, Jason. It's always welcome when you chime in on such subjects.

[pgk]

Foucault devised a tester to allow deterministic fabrication of aspheric surface for telescope mirrors in 1858. Before the Foucault tester was invented, aspherics were made but couldn’t be measured to a high level of accuracy (not that it stopped them from being made).

Being able to generate optics with surfaces which deviate from spherical is nothing new.

Thanks. My readng suggests that Thomas Grubb was probably aware of Foucault's test when he built the Great Melbourne Telescope in 1866, but it was his son Howard who used 'a small amount of non-spherical figuring on one of the surfaces' when building Astrographic Telescope lenses in the 1880s working on the Carte du ciele' project apparently. I assume that this was a deliberate use of an aspheric surface. I am not sure of the accuracy to which his lenses were ground but from what information is available it appears that he was 'fastidious' to saythe least. Howard went on to make some photographic lenses but not many. It may turn out that he produced photographic lenses almost on a bespoke basis and there are a few anomalous ones amongst those known which are not in the lists of available lenses from his resellers. I'm just wondering whether he applied similar ideas to any of these? Both the Grubbs seem to have been optical experimenters and innovators.

[Eric Woodbury]

The Schmidt corrector plate is an aspheric surface with a 'wave shape' cross-section. Originally used in some telescopes, it is now used for other applications. About 100 years old.

[Drew Wiley]

Well, I found at least one page of history intact at Tinsley's website. Tinsley Lab began as a local telescope manufacturer nearly a hundred years ago (1926); but due to their govt connection making artillery scopes during WWII, starting getting major space application contracts in the 60's, and have since merged into Coherent laser imaging (also local), and have also acquired Quantum coatings, overall now becoming the most significant space optics and major ground telescope supplier in the world as far as specialized elements are concerned, especially aspherics. I don't know if the virtual tour of that facility is still buried somewhere in the current site; but at least a few pictures are still there. It's just two Freeway exits from my house. Be fun to see in person; but all the real deal work is clean suit stuff, just like satellite making, so not open to public tours. But just perusing a site like that gives one an idea of the scale of what is necessary to a modern astro operation. And nowadays, things like aspheric mirrors have be made in precisely matching high multiples. Just spitting on the end of a Millers beer bottle and grinding away with it with some beach sand doesn't do it anymore.

The Schmidt telescope design dates from the 1930's. The 41 inch mirror for the well-known Kitt Peak Schmidt scope was made by Tinsley in 1960. But there are all kind of historic links showing just how darn big the mirrors many amateurs ordered from them were over years, plus a few of the huge teaching telescopes in this area.

[pgk]

That's the problem. I got interested in the Grubb's and their photographic lenses but it so easy to get sidetracked and I've ended up with many more related questions than I started with. And two Grubb telescopes too! One is an astronomic 3" but the other is a miltary scope and was never taken into miltary use. It took a lot of figuring out but seems to be a varaible power artillery spotting scope with a horizontal reticle with angular offsets for flash spotting. At 103 years old it is still very usable. The astronomic 'scope is earlier but has had a Barlow eyepiec by Dolland fitted not long after it was made - another photographic lens maker and for me a connection because when I was a student I worked for camera dealer R G Lewis in High Holborn, London which was then owned by Dollands. And yes, still looking into the Grubb photographic lenses which has revealed an interesting world of Victorian science and engineering. Makers like the Grubbs were extraordinarily competent. Howard not only built world class telescopes and numerous other scientific instruments but went on to create the basis of what is now referred to as the Red Dot Sight and built Periscopes for most British submarines used in WW1. And he made a fe photographic lenses as a bit of an aside too. Too easy to get diverted.

[Nodda Duma]

Polishing optical surfaces is as much craft / art as it is science and method. Before telescope making moved into proper shops, final polishing often took place at night under the stars, with the optician closely examining a star image and polishing away aberrations with their thumb. Alvan Clark finished off the world’s largest refractor (the 40” at Yerkes Observatory) that way.

I’ve tried this before, and it is doable but easy to overdo it and get poor surface irregularity as well as blowing through your intended goal and leaving a “hole” in your otherwise perfect surface.