As I understand it, one of the major reasons why a Blu-Ray can store so much more data than a CD or DVD of the same size is that the player uses a laser with a shorter wavelength, allowing it to read smaller regions of the disc. I’m not sure I would’ve come up with that, but in retrospect it seems somewhat obvious. Why didn’t CD and DVD players use shorter wavelength lasers?
20-25 years ago, solid-state blue lasers or LEDs suitable for use in home electronics were some combination of non-existent or wildly expensive.
Yes, the shorter blue-range wavelengths allow you to carve (and read) smaller pits, thus leading to greater data density.
A very interesting story about the struggle to develop a diode-based blue laser:
http://archive.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm
They were made of unobtainium, which has become more available in recent years.
I should’ve figured something like that. As time goes by and laser technology improves, should we expect to see even shorter wavelengths being used?
[QUOTE=ultrafilter]
As I understand it, one of the major reasons why a Blu-Ray can store so much more data than a CD or DVD of the same size is that the player uses a laser with a shorter wavelength, allowing it to read smaller regions of the disc. I’m not sure I would’ve come up with that, but in retrospect it seems somewhat obvious. Why didn’t CD and DVD players use shorter wavelength lasers?
[/QUOTE]
Remember, they started inventing CDs in the late 1970s. The first mass-market CDs were released in 1982. At the time, the only solid-state lasers that could be made cheaply were infra-red, so that was the limiting factor.
Later, they invented cheap solid-state red lasers (Cool, let’s put movies on them!) Then even later they invented cheap solid-state blue lasers (Cool, let’s put HD movies on them, but have a stupid format war first because we’re idiots!)
[QUOTE=ultrafilter]
I should’ve figured something like that. As time goes by and laser technology improves, should we expect to see even shorter wavelengths being used?
[/QUOTE]
Why yes you should – the logical next step has been taken:
Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone.
[QUOTE=Q.E.D.]
Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone.
[/QUOTE]
Only for killer movies where the hero also dies.
[QUOTE=Duckster]
Only for killer movies where the hero also dies.
[/QUOTE]
Yeah, the gamma ray and x-ray laser apps. I’ve seen discussed are generally so energetic that they are being discussed for weapons. Energy increases linearly with frequency.
Like some sort of 1920’s-style Death Ray?
[QUOTE=ultrafilter]
As time goes by and laser technology improves, should we expect to see even shorter wavelengths being used?
[/QUOTE]
Probably, but at some point it becomes impractical. Even if we knew how to make an x-ray or gamma ray laser, using them in consumer electronics would be problematic. Obviously, there’s a much bigger containment issue since x-rays and gamma rays are much worse for you than visible or UV light.
Secondly, as the frequency of light increases, the amount of energy in a single quantum increases. As a consequence, the photoelectric effect comes into play. Basically, if you slam an x-ray or gamma ray at a chunk of metal, it emits an electron. CDs and DVDs contain a metallic reflective layer, which is not going to react well to being struck with high energy photons. Have you ever seen a CD in a microwave? It would be kind of like that everywhere that the laser hit it.
[QUOTE=Q.E.D.]
Eventually, they’ll use gamma rays. We’ll only need one disk–for everyone.
[/QUOTE]
And you thought a scratch messed up a movie now…
Time again to post one of my favorite projects.
A real attention getter at the corporate meetings when you need to make a point.
[QUOTE=Huerta88]
Yes, the shorter blue-range wavelengths allow you to carve (and read) smaller pits, thus leading to greater data density.
A very interesting story about the struggle to develop a diode-based blue laser:
http://archive.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm
[/QUOTE]
Just wanted to say thanks for that link. Fascinating stuff. I’d heard of Shuji Nakamura before while reading about blue LEDs, but I didn’t know his story.
[QUOTE=Projammer]
Time again to post one of my favorite projects.
A real attention getter at the corporate meetings when you need to make a point.
[/QUOTE]
Awesome , now thats the killer app.
Declan
[QUOTE=Projammer]
Time again to post one of my favorite projects.
A real attention getter at the corporate meetings when you need to make a point.
[/QUOTE]
What’s that saying about not looking into the laser with your remaining eye?
That thing is scary, and isn’t a toy.
[QUOTE=Projammer]
Time again to post one of my favorite projects.
A real attention getter at the corporate meetings when you need to make a point.
[/QUOTE]
I note to my dismay that Metacafe has started superimposing ads across the bottom of their videos while they are playing. Ick.