Cheap technology for making optic lenses that could help 2.5B people and NASA
haaretz.com
haaretz.com
This was developed in India decades ago, but I can't find those kits online. Obsolete?
Helped me figure out what was going on. ( unstable prescription)
Correct me if I've erred in the theory below; eyeglasses can be had online for so little that I'm considering ordering a pair if only to see what how it feels.
Typical glasses/contacts prescriptions aren't enough: To a single eye, a corrective lens is indistinguishable to moving everything in the world closer or farther away, but our binocular vision isn't fooled.[0] Your brain would still think the screen is nearby, only you'd have a hard time focussing on it because of the unexpected power required.[1]
[0] https://en.wikipedia.org/wiki/Vergence
[1] https://en.wikipedia.org/wiki/Accommodation_reflex
But the required trickery is exactly what's prescribed as prism correction[2]--a displacement of the world as seen by each eye by a specified angle. The unit of measure, prism dioptres, is conveniently defined as 100 times the apparent distance that an object at a certain distance is displaced by. In our case, we want to, for each eye, displace the screen (which is a known distance away) by half the distance between the eyes, so that the eye must look straight ahead to see any point on the screen, as it would if the screen were infinitely far away.
i.e., a prism power of:
100 * 0.5 * (pupillary distance) / (distance to screen)
Optical power is approximately additive, so including existing correction:
1 / (distance to screen) + (power of prescription)
[2] https://en.wikipedia.org/wiki/Prism_correction
[3] https://en.wikipedia.org/wiki/Dioptre
[4] http://www.langleyflyingschool.com/Pages/Human%20Factor--Emp...
Edits: clarity; 100x, not 1/100x
Addendum:
The prisms are horizontal and base-in. To actually make something 500 mm from your eyes appear infinitely far away, given a typical pupillary distance of around 30 mm, would require a very high prism power of 6. The typical max seems around 5, though, which isn't too far off.
Illustration: Rays of light (/\) originating from a point (.) pass through the glasses (=<|==|>=), become parallel as if originating from infinity (|| ||), pass through the cornea/lens of each eye (<=> <=>), travel through the eyes (O O), and converge (\/ \/) on the retinas into images (* *).
.
/ \
// \\
// \\
/// \\\
/ / \ \
// / \ \\
/ / \ \
_,,,-^^^| |^^^-,,,_
==<________|=========|________>==
| | | |
|___| |___|
O<_____>O O<_____>O
O \ / O O \ / O
O \ / O O \ / O
O * O O * OYou'd have to be able to touch type though, otherwise every extra inch of distance between keyboard and monitor is somewhat fatiguing when you are constantly glancing up and down.
This is not how it works. You seem to confuse focus and magnification. That said the display in VR goggles is set at a specific focus distance, and there is a fair chance it is set at infinity. When you look in VR goggles you eyes are at rest, focus-wise. Seems to be what you are looking for.
The simple formulae I used only approximate the glasses and eyes as stacked thin lenses, so there'll be a bit of magnification in practice. I think this is the norm in optometry, though--apparently, the brain adapts with no issue to the mismatched peripheral vision when wearing glasses.
Hmm... Actually, I'm not sure whether practical optometry involves any calculation at all: As I understand it, the optometrist has you subjectively compare lenses that are positioned in the phoropter at the same distance to your eyes as those in your spectacles would be. So the required lens power is measured directly, without any maths.
Strangely, info on how a phoropter is used seems to be entirely missing from the web (i.e., search engines). There really isn't any pop-sci interest?
Ultimately one could have a light field display to achieve all this in a flat package. It would be like a display consisting of small directional mini displays. It would have some resolution and brightness issues and would be expensive.
Anyway, the optometrist lenses kits are still there, you can order them from aliexpress.
Basically it is possible to make much more affordable glasses but people like Luxxotica keep it from happening because it cuts into their margins.
That said, making complex lenses this way would make building things like microscope pretty straightforward. There is a lot of optical equipment that needs lenses that this technique could satisfy.
But the real interesting puzzle is why there are so few lens manufacturers.
If you Google the names of these (Zeiss, Leica, Olympus, Corning, etc.), you'll likely quickly figure out that 1. there's about one major optical glass producer per country; and 2. all the ones you'll ever hear about in an Western prescription-glass context are headquartered in countries that are key NATO players; and in fact often in the capitols of those countries.
What's up with that?
"Optical glass", besides being in prescription glasses and smartphone cameras, is the key bottleneck in the resolving power of military imaging satellites.
Each one of these companies is an example of the opposite of "regulatory capture" — these companies exist at the behest of the state, as pseudo-nationalized entities. They're essentially defense contractors that happen to make civilian products on the side.
Competitors to these companies aren't allowed to spring up, because any such a competitor would essentially be a mercenary arms-dealer for IMINT materiel assets.
With exactly one high-quality optical-glass company per country, each under said state's thumb, states can easily track where everything (of sufficient resolving power) that that optical-glass company makes, goes.
It's basically the same reason that there's only a few companies in the world making highly-precise gyroscopes (that could be used for missile guidance); or making industrial-grade cycling centrifuges (that could be used for uranium enrichment.) States will not permit these to be manufactured "out of sight."
There's nothing really stopping anyone from buying from discount eye glass companies online, but you have to guess at which frames you'll like based on pictures and reviews instead of instore.
> These glasses contain lenses which can be self-adjusted by the wearer to their prescription, and were developed as a low-cost and accessible eye care solution for people in developing nations. The lens consists of two membranes, in between which silicon oil can be pumped with the syringes on the side of the frames. As fluid is pumped in or out, the focal length of the lens is changed, meaning the lens can be tuned to the specific requirements of the eye. The syringes can then be removed. The inventor of these glasses was nominated for a 2011 European Invention Award.
Affordable freeform optics is especially exciting:
> These optical components are neither convex nor concave, but instead are shaped as topographic surfaces, with light hitting the surface in different areas to achieve the desired result. Such parts can be found in multi-focal glasses, pilot helmets, advanced projector systems, virtual and augmented reality systems, and elsewhere.
If that could be fast enough, then combined with eye tracking we could have full-field glasses for presbyopia.
As a side note who needs eye tracking when your own retina does that for you. The goal with these IOLs is for their lens power to shift based on contraction of the ciliary muscle (the same way a healthy youthful lens works).
I am certainly curious about the potential impact of this UV curable lens technology on cataract surgery and possibility of new types of IOLs.
Eye tracking and range finding would still be tricky to do in a small space. But something similar-ish was prototyped in 2017 [1]. Not the best source there, but maybe you can find something better with "liquid lens eyeglasses" or use that source to help find the original research.
Also, not sure if liquid lenses will work for astygmatism very well.
[1] https://www.smithsonianmag.com/innovation/these-smart-glasse...
[1]https://www.researchgate.net/publication/354978270_Fabricati...
In this work, we demonstrate curing of PDMS (Sylgard 184, Dow, MI), and UV adhesive (NOA61, NOA63, NOA81, Norland, NJ) lenses. The PDMS lenses are cured by incubating them at 80 C for 1.5 hr, at 60 C for 4 hr, or at room temperature for 24 hr. The UV adhesive is cured by exposure to light at 365 nm (a 36 W consumer grade nail lamp) for 2-5 min, depending on the thickness of the lens and the specific adhesive chosen. Since both PDMS and Norland adhesives are immiscible in water and have densities between ~1.03 (PDMS) g/mL and ~1.12 g/mL (Norland), the water\glycerol-based immersion liquid allowed us to precisely control the density difference. Since preparation of PDMS involves intense mixing of the base resin with a cross-linker, we degassed the PDMS mixture for 20 minutes before injecting it into the bounding surface, in order to eliminate any bubbles trapped in the fluid due to the mixing.
I remember it being described as great for rural areas where it was unlikely / difficult to ensure you would be able to make a return visit or get the people needing glasses to come back when the lenses were eventually ready.
Describes both a dial-based and a less mature fluid-based technology: https://www.youtube.com/watch?v=D9FpEWQkg-w
Dial-based: https://www.designboom.com/technology/eyejusters-self-adjust...
DialVision review: https://www.youtube.com/watch?v=Ge3H0FtGUw8
And yet prescription glasses cost two orders of magnitude more than that.
A good portion of my eyeglasses (custom prescription, with astigmatism correction) have been <$10 drop shipped to the US from Hong Kong, frames and lenses included. The most expensive variations (Transition sunglasses, complicated plastics to be thinner, memory metal frames) were $70, frames and lenses included. Most pairs end up in the $20-$40 range shipped.
All this $150-$600 nonsense in the US just pays for the retail space, the branding, the insurance bureaucracy, and rent-seeking by the Luxxotica cartel.
The downside is that I don't get to try them on beforehand... but nothing so far has been totally unwearable, and buying six pairs for $200, as I did once, addresses that concern pretty well.
Link please!
> The Essilor group has set out to develop this channel with the acquisition of pure-player FramesDirect®, EyeBuyDirect®, Coastal®, Clearly®, VisionDirect, MyOptique, elens, eOtica and Coolwinks.
I've used EyeBuyDirect (US), who recently merged with Coastal (Canada).
Though these are standard material lenses and price really goes up when you want thinner and lighter for higher refraction.
Still, just how cheap something standardised can be even in country with high labor cost is amazing.
The other side is flat.
... after reading the article, spherical lenses are great in many many applications, there is still a place for aspheric optics one of which is large aperture telescopes you can reach without an orchard ladder or drone.
the sibling comment on spinning fluids does lead the question; can the researchers vary the density of their neutral fluid (or polymer) to gradually vary the "local" forces shaping the lens
The original idea (polymer lenses) is definitely a huge potential for amateur astronomes making large refracting telescopes.
At the end of the article they mention being able to make large mirrors with liquid metal using the same technique as for the lenses. I do not quite understand how this is supposed to work.
this is me thinking in terms of "what things about an inflatable structure change how spherical it becomes, when inflated" and adding in "what does it do to optics"
not an optician, a physicist or an inflatable toy clown.
Presumably that's the purpose of the heat-curing process described in their paper, as UV won't be able to penetrate arbitrarily deep into the polymer.
maybe it is possible to create microstructures using a phase array ultrasound emitter?