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Blu-ray

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By way of background, know that this feuding between Sony and Toshiba is as time worn as the Hatfield’s and the McCoy’s.  Way back when, when standard DVD’s were being born, it was again Sony vs. Toshiba.  On one side was Warner/Toshiba with their SD (SuperDisc) format; and on the other were Philips/Sony and their MMCD (MultiMedia CD).

The two feuding formats were both offering DVD storage of approximately 4 to 5 gigabytes per side. Both camps also proposed a dual layer technology that effectively doubled single side capacity. The two opposing factions finally joined forces to come up with a single format, which today we know as DVD. This not so loving marriage probably would never have come about were it not for the intervention of a powerful behind the scenes matchmaker, IBM.

IBM got the warring DVD parties to adopt Toshiba’s SD architecture, which consisted of two 0.6-millimeter discs bonded together, while the losing Sony/Philips MMCD design used a single 1.2-millimeter thick platter, just like a CD. Both DVD proposals used relatively long, 630 nm red wavelength lasers, but which today can go as high as 750 nm in some applications.

IBM preferred a 0.6 mm disc, because it believed the thinner SD platter would make it easier to adopt blue lasers when they finally became available at consumer electronics prices. It was believed that using thinner platters would result in less light scattering (signal attenuation) off the disc at the shorter blue wavelength.

IBM knew, as did others in the industry, that blue lasers would one day bring tremendous increases in DVD storage capacity. So this is why today’s DVD’s are two thin disks glued together, and it’s also why Toshiba believed it held the winning manufacturing hand with its bonded HD DVD proposal.

 

IBM thought it had all the high-def laser moves figured out. Guess what?

But the future is never what you expect.  As it turned out, both HD DVD and Blu-ray were to use not a blue laser, which is typically 473 nm in wavelength, but a much shorter 405 nm blue-violet laser. 

Sony also persisted with its single thick platter notion. It’s engineers were finally able to solve the light scattering problems that can cause signal attenuation and its resulting errors. A Blu-ray disc consists of a 0.1 mm optical transmittance protection layer sitting on top of a 1.1 mm substrate.

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