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RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

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Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

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    1. Rich Felker‏ @RichFelker 7 Apr 2017

      Why can't we get synthetic sapphire eyeglasses? Abbe number 72.2 (!!!!) and high index of refraction.

      2 replies 1 retweet 4 likes
    2. whitequark‏ @whitequark 7 Apr 2017
      Replying to @RichFelker @bofh453

      1) fragile? 2) I bet milling it to size is going to be a real pain at an ophtalmologist's shop

      1 reply 0 retweets 1 like
    3. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
      Replying to @whitequark @RichFelker

      1) Um. You've worked with synthetic sapphire before, right? http://www.mt-berlin.com/frames_cryst/descriptions/sapphire.htm … vs http://www.mt-berlin.com/frames_cryst/descriptions/quartz%20.htm …

      1 reply 0 retweets 0 likes
    4. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
      Replying to @bofh453 @whitequark @RichFelker

      You're looking at Mohs hardness 9.0, Young's/Bulk/Shear moduli 345/240/145 (all GPa), 400MPa tensile strength. No glass is that strong.

      1 reply 0 retweets 1 like
    5. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
      Replying to @bofh453 @whitequark @RichFelker

      Ironically this makes your 2nd point much stronger, since I imagine actually milling/cutting/making adjustments to Sapphire is much harder.

      1 reply 0 retweets 0 likes
    6. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
      Replying to @bofh453 @whitequark @RichFelker

      But honestly I think the main reason is even simpler: cost. Glass is cheap as hell.

      2 replies 0 retweets 0 likes
    7. Rich Felker‏ @RichFelker 7 Apr 2017
      Replying to @bofh453 @whitequark

      Glass lenses are actually rather expensive compared to CR39 which is almost as good (within 1.0 Abbe value diff) & better at blocking UV.

      2 replies 0 retweets 0 likes
    8. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
      Replying to @RichFelker @whitequark

      Oh that's another issue with sapphire: uncoated, it passes down to 195nm (UVC) with almost zero attenuation.

      1 reply 0 retweets 2 likes
    9. whitequark‏ @whitequark 7 Apr 2017
      Replying to @bofh453 @RichFelker

      so you'd need to wear glasses under your glasses. I fail to see the problem with this. Imagine the memes

      1 reply 0 retweets 2 likes
      Rich Felker‏ @RichFelker 7 Apr 2017
      Replying to @whitequark @bofh453

      The way I look at that, wrt UV, my eyes are still no worse off than people who don't need glasses.

      3:09 PM - 7 Apr 2017
      2 replies 0 retweets 0 likes
        1. New conversation
        2. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @RichFelker @whitequark @bofh453

          You could do a coating though if it doesn't affect the optical properties badly.

          1 reply 0 retweets 0 likes
        3. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
          Replying to @RichFelker @whitequark

          So the TiO2 thin film coating I put on my glasses b/c it annoys me when they fog up apparently blocks everything below UVA.

          2 replies 0 retweets 3 likes
        4. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @bofh453 @whitequark

          A film that blocks everything below ~480nm would probably actually help a lot with chromatic aberration.

          1 reply 0 retweets 1 like
        5. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
          Replying to @RichFelker @whitequark

          Don't you mean ~415nm? 445nm for instance is what InGaN blue LEDs emit...

          2 replies 0 retweets 0 likes
        6. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @bofh453 @whitequark

          No, I specifically mean getting rid of the awful blue-led light that spatially diverges so much from everything else. :-)

          1 reply 0 retweets 0 likes
        7. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @RichFelker @bofh453 @whitequark

          The worst is in headlights. Every car with those f*%&ing things looks like a cop in rear-view.

          1 reply 0 retweets 3 likes
        8. Peter Barfuss 𒀱‏ @bofh453 7 Apr 2017
          Replying to @RichFelker @whitequark

          Oh, so notching that out is *desired*? Heh. (Also those aren't blue LEDs, but HID Xenon bulbs... the peak is around 475nm or so).

          1 reply 0 retweets 0 likes
        9. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @bofh453 @whitequark

          I think I've seen LEDs too now, but yeah, the xenon ones definitely do it too.

          0 replies 0 retweets 0 likes
        10. End of conversation
        1. New conversation
        2. whitequark‏ @whitequark 7 Apr 2017
          Replying to @RichFelker @bofh453

          they wear sunglasses sometimes though and you'll need two glasses in that case, I mean

          2 replies 0 retweets 0 likes
        3. Rich Felker‏ @RichFelker 7 Apr 2017
          Replying to @whitequark @bofh453

          BTW, know anyone who does milling/polishing of these types of materials who might could give me a quote on making such lenses?

          2 replies 0 retweets 0 likes
        4. David Crawshaw‏ @davidcrawshaw 7 Apr 2017
          Replying to @RichFelker @whitequark @bofh453

          A web search brings up some names, but when the ad copy mentions ITAR certs, I'm guessing not cheap:http://www.guildoptics.com 

          0 replies 0 retweets 2 likes
        5. End of conversation

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