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HankScorpio-vs-World t1_j31bb27 wrote

I think the track density is actually more limited by the reading method than the stamping method.

The laser focus is the limiting factor, had to move from a low frequency red laser for a normal CD, to a high frequency blue laser (it’s actually violet) to get the data capacity higher for blue Ray. I believe “multi layer reading” is already being exploited for 4K use on a 5” disc which takes advantage of even finer stamping methods.

I think 25gb is the standard single layer capacity and the current disks in use are dual layer at 50gb… this is expected to rise with XL disk players/writers where the capacity is stretched to 128GB using 4 layers on a single disc using even finer laser targeting/focussing methods.

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HankScorpio-vs-World t1_j31cwia wrote

Link to Wikipedia picture of the dot spacings on blue Ray discs https://en.wikipedia.org/wiki/Blu-ray#/media/File:Comparison_CD_DVD_HDDVD_BD.svg

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ChronoX5 OP t1_j32ea85 wrote

That's a helpful picture. Thank you! It blows my mind that they can manufacture physical bumps smaller than the wavelength of light.

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rudy21SIDER t1_j34ap9g wrote

Light wavelength can be as big as the empire state ( radio) or as small as a Planck 's length (lethal radiation) so there is a big "not impressive" margin.

Still very impressive precision in nanometers but we gave way smaller things (chip manufacturering).

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Insertsociallife t1_j35wv04 wrote

Couldn't the wavelength of light considered to have a limit at infinity? If frequency has a limit at 0, it could still multiply to c, right?

Edit - should clarify, calc definition of limit, infinitely close to but is never the value it's limited by

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katt2002 t1_j32p5le wrote

Is that limited to visible light only? How about wavelength shorter than ultraviolet? X-ray, gamma? They are also electromagnetic wave, right? Same question for tools used to manufacture CPU chips.

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HankScorpio-vs-World t1_j32sz9q wrote

It’s about safety and cost when it comes to data storage… yes shorter wavelength emission/reading systems are possible but are they necessary. At the moment we are yet to have a video encoding system that needs a disc bigger than 128GB for a movie. Chances are by the time we do it will be streamed via the internet and a physical disc will be redundant.

But who knows what future tv formats will need for storage, when I was a kid a 240line VHS tape was astounding now 1080 lines is considered old technology.

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Prestigious_Carpet29 t1_j36fn03 wrote

I have a broad knowledge of physics and engineering, but pressing/stamping is not my particular area of expertise.

The Wikipedia image linked by HankScorpi-vs-the-World indicates feature sizes almost as small as 100nm for Blu-ray (that's maybe a factor of 2- or 3 smaller than I was expecting, but may well be correct).

I suspect the problem of how small features can be pressed comes down to economics: I expect the metal stamping tool will wear with use, so that as the feature sizes get smaller probably you get get fewer good-quality stampings out of it before you need a new tool.

Although progress is being made in making LEDs deeper into the ultraviolet, given that once you get into the UVB range the light is strongly absorbed by plastic lenses and discs, I can't imagine this technology has a whole lot further to run anyway.

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