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I am pretty sure, diamonds would make awful eyeglasses. While their index of refraction is high, which makes glasses thin, their chromatic dispersion is high. T

by _ph_ 2y ago

I am pretty sure, diamonds would make awful eyeglasses. While their index of refraction is high, which makes glasses thin, their chromatic dispersion is high. That is the very thing which makes their glitter so colorful. For good optical systems you want to try to reduce the dispersion, to 0, if possible. Another story is the scratch-resistance. For that it would be sufficient to coat the surface of the lens with a thin layer of diamond. Which is done in several applications.

amelius 2y ago
Maybe we can have diamond-based scratch protection on smartphones?
- callalex 2y ago
  I wonder if the process would be cheaper than the current high end (smart)watch and lens practice of sapphire coating?
  - namibj 2y ago
    No, it's substantially more expensive. At least for anything too large to just cut out of HPHT chunks, just due to CVD at optical grade being pretty slow.
    - Animats 2y ago
      Diamond coated glass is available and is sometimes used for checkout lane scanners.[1] It's not common. [1] https://www.diamonex.com/wear-resistant-glass/ https://www.diamonex.com/wear-resistant-glass/
- opan 2y ago
  Don't we already have good scratch protection? Cracks from drops seem like the main issue.
  - perth 2y ago
    So scratching definitely still happens, both on sapphire camera lenses and new scratch-resistant screen technology. I’ve mainly had it happen with concrete. I think concrete sometimes just has some rocks in it that have a very high hardness because I’ve gotten pretty thick scratches in new iPhones when they’ve taken a slide over a rough concrete sidewalk due to a drop while walking.
    - HWR_14 2y ago
      Aren't both the lens and the screen are resilient to steel/metal scratches? I'm not willing to run keys or a knife over a phone on purpose.
    - kuschku 2y ago
      I've similarly experienced bad scratches whenever my phone and my keys come into contact, hardened steel may still be able to cause scratches?
      - IgorPartola 2y ago
        Your keys are by no means hardened steel. If they are steel at all (most are brass or silver/zinc), they would be mild steel. If they were hardened they would be really difficult to cut. The harder you make a steel the more brittle it gets. Think about what happens when you slam a file with a hammer vs a large nail.
        kuschku 2y ago
        Considering how easy it is to break keys in the lock, I'd say they're definitely more brittle than malleable?
        serf 2y ago
        I think that's mostly from mild work-hardening, I haven't experienced that with a brand new key.
- nytesky 2y ago
  I’m surprised no one has mentioned the ending of 2061 https://en.wikipedia.org/wiki/2061:_Odyssey_Three?wprov=sfti1 https://en.wikipedia.org/wiki/2061:_Odyssey_Three?wprov=sfti...
- chasil 2y ago
  Gorilla glass is already some percentage of "Prince Rupert's Drop" in strength. This is not sufficient? https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_drop https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_drop
  - Stedag 2y ago
    It’s definitely price performant at 6.5 on the mohs scale, sapphire panels are 2-4x more expensive to produce but 9 on the mohs scales so they’re typically only found in watches I bet. At a 10 on the mohs scale diamond is still best for hardness. Maybe the same effect of the prince Rupert’s drop could be induced on a round diamond with an alpha particle beam treatment where you add these ions primarily on the surface of the stone.
    - vladvasiliu 2y ago
      I'm not exactly a watch nerd, so don't know how true this is, but I hear that sapphire shatters on impact. Or maybe that's just an excuse for people peddling "alternative" materials for their watches? But if it is true, then I'd say that sapphire is a poor choice for mobile phones. IME I'm far more likely to drop the phone, preferably on some form of hard surface, that to scratch it. Phones are nowadays so ridiculously big, that there's zero chance I'll have anything else in my pocket.
      - saagarjha 2y ago
        I believe Apple tried to get sapphire for phones screens at some point, but their supplier folded.
        dijit 2y ago
        They did however manage to get Sapphire on the watch display (at least on the stainless steel LTE edition of the apple watch series 4 and 8, which I'm aware of). The difference between my watch (which was 4 years old at the time) and a colleagues almost brand new apple watch (without the sapphire) was really telling, is his was lightly scratched on the edges despite him being quite careful, and I was exceedingly reckless with mine as I considered it old- yet there was not a single defect. That was a major reason for me to upgrade to the LTE of the next version of apple watch that I bought.
- pie_flavor 2y ago
  It's possible, and I remember seeing a very expensive prototype for it, but sapphire is already Good Enough for almost any cause of scratching you're likely to find.
- david38 2y ago
  We already have sapphire
shiroiushi 2y ago
Before I got to the end of your comment, I was just about to ask if it's possible to make a diamond coating. The scratch resistance would be very valuable, and I'm guessing if it's very thin, the chromatic dispersion wouldn't be an issue. This would probably be valuable for other applications too. However, I don't see how this would work on today's predominantly plastic (polycarbonate) eyeglass lenses, and switching back to glass lenses would make eyeglasses much heavier. It'd be great for smartphone screens though.
- brohee 2y ago
  Diamond coating is a thing for IR optics: https://sinoptix.eu/2023/10/27/what-is-dlc-coating-in-optics/ https://sinoptix.eu/2023/10/27/what-is-dlc-coating-in-optics...
rlpb 2y ago
> While their index of refraction is high, which makes glasses thin, their chromatic dispersion is high Isn’t the layer caused by the former? For a given required refraction, isn’t the chromatic dispersion the same? In complex lenses corrections can be made, but for a simple single eyeglass lens, how is chromatic dispersion affected by anything apart from simple refraction?
- namibj 2y ago
  No, chromatic dispersion is due to wavelength/chroma dependant refraction. This is a separate thing from the overall/average index of refraction.
basementcat 2y ago
So… great for certain colorblind individuals? Edit: Achromotopsia https://en.m.wikipedia.org/wiki/Achromatopsia https://en.m.wikipedia.org/wiki/Achromatopsia
- almostnormal 2y ago
  Unlikely. Same as under low-light conditions where everything is grayscale. The light is still colored and just not perceived in color, so it should be blurred grayscale.

by _ph_ 2y ago

amelius 2y ago

Maybe we can have diamond-based scratch protection on smartphones?

callalex 2y ago
I wonder if the process would be cheaper than the current high end (smart)watch and lens practice of sapphire coating?
- namibj 2y ago
  No, it's substantially more expensive. At least for anything too large to just cut out of HPHT chunks, just due to CVD at optical grade being pretty slow.
  - Animats 2y ago
    Diamond coated glass is available and is sometimes used for checkout lane scanners.[1] It's not common. [1] https://www.diamonex.com/wear-resistant-glass/ https://www.diamonex.com/wear-resistant-glass/
opan 2y ago
Don't we already have good scratch protection? Cracks from drops seem like the main issue.
- perth 2y ago
  So scratching definitely still happens, both on sapphire camera lenses and new scratch-resistant screen technology. I’ve mainly had it happen with concrete. I think concrete sometimes just has some rocks in it that have a very high hardness because I’ve gotten pretty thick scratches in new iPhones when they’ve taken a slide over a rough concrete sidewalk due to a drop while walking.
  - HWR_14 2y ago
    Aren't both the lens and the screen are resilient to steel/metal scratches? I'm not willing to run keys or a knife over a phone on purpose.
  - kuschku 2y ago
    I've similarly experienced bad scratches whenever my phone and my keys come into contact, hardened steel may still be able to cause scratches?
    - IgorPartola 2y ago
      Your keys are by no means hardened steel. If they are steel at all (most are brass or silver/zinc), they would be mild steel. If they were hardened they would be really difficult to cut. The harder you make a steel the more brittle it gets. Think about what happens when you slam a file with a hammer vs a large nail.
      - kuschku 2y ago
        Considering how easy it is to break keys in the lock, I'd say they're definitely more brittle than malleable?
        serf 2y ago
        I think that's mostly from mild work-hardening, I haven't experienced that with a brand new key.
nytesky 2y ago
I’m surprised no one has mentioned the ending of 2061 https://en.wikipedia.org/wiki/2061:_Odyssey_Three?wprov=sfti1 https://en.wikipedia.org/wiki/2061:_Odyssey_Three?wprov=sfti...
chasil 2y ago
Gorilla glass is already some percentage of "Prince Rupert's Drop" in strength. This is not sufficient? https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_drop https://en.m.wikipedia.org/wiki/Prince_Rupert%27s_drop
- Stedag 2y ago
  It’s definitely price performant at 6.5 on the mohs scale, sapphire panels are 2-4x more expensive to produce but 9 on the mohs scales so they’re typically only found in watches I bet. At a 10 on the mohs scale diamond is still best for hardness. Maybe the same effect of the prince Rupert’s drop could be induced on a round diamond with an alpha particle beam treatment where you add these ions primarily on the surface of the stone.
  - vladvasiliu 2y ago
    I'm not exactly a watch nerd, so don't know how true this is, but I hear that sapphire shatters on impact. Or maybe that's just an excuse for people peddling "alternative" materials for their watches? But if it is true, then I'd say that sapphire is a poor choice for mobile phones. IME I'm far more likely to drop the phone, preferably on some form of hard surface, that to scratch it. Phones are nowadays so ridiculously big, that there's zero chance I'll have anything else in my pocket.
    - saagarjha 2y ago
      I believe Apple tried to get sapphire for phones screens at some point, but their supplier folded.
      - dijit 2y ago
        They did however manage to get Sapphire on the watch display (at least on the stainless steel LTE edition of the apple watch series 4 and 8, which I'm aware of). The difference between my watch (which was 4 years old at the time) and a colleagues almost brand new apple watch (without the sapphire) was really telling, is his was lightly scratched on the edges despite him being quite careful, and I was exceedingly reckless with mine as I considered it old- yet there was not a single defect. That was a major reason for me to upgrade to the LTE of the next version of apple watch that I bought.
pie_flavor 2y ago
It's possible, and I remember seeing a very expensive prototype for it, but sapphire is already Good Enough for almost any cause of scratching you're likely to find.
david38 2y ago
We already have sapphire

shiroiushi 2y ago

Before I got to the end of your comment, I was just about to ask if it's possible to make a diamond coating. The scratch resistance would be very valuable, and I'm guessing if it's very thin, the chromatic dispersion wouldn't be an issue. This would probably be valuable for other applications too. However, I don't see how this would work on today's predominantly plastic (polycarbonate) eyeglass lenses, and switching back to glass lenses would make eyeglasses much heavier. It'd be great for smartphone screens though.

brohee 2y ago
Diamond coating is a thing for IR optics: https://sinoptix.eu/2023/10/27/what-is-dlc-coating-in-optics/ https://sinoptix.eu/2023/10/27/what-is-dlc-coating-in-optics...

rlpb 2y ago

> While their index of refraction is high, which makes glasses thin, their chromatic dispersion is high Isn’t the layer caused by the former? For a given required refraction, isn’t the chromatic dispersion the same? In complex lenses corrections can be made, but for a simple single eyeglass lens, how is chromatic dispersion affected by anything apart from simple refraction?

namibj 2y ago
No, chromatic dispersion is due to wavelength/chroma dependant refraction. This is a separate thing from the overall/average index of refraction.

basementcat 2y ago

So… great for certain colorblind individuals? Edit: Achromotopsia https://en.m.wikipedia.org/wiki/Achromatopsia https://en.m.wikipedia.org/wiki/Achromatopsia

almostnormal 2y ago
Unlikely. Same as under low-light conditions where everything is grayscale. The light is still colored and just not perceived in color, so it should be blurred grayscale.