Whatever happened to green pens?

[Anonymous]

Mr Modesty:I didn't think anyone believed in the silly green pen idea.

I tried it, as I did the frozen CD trick. Can't say it made a difference, but the theory was interesting.ÿ

 

[chebby]

And how does using green pen at the perimeter of the disc help improve replay once the laser is reading the rest of the surface not coated in green?

The bit you are colouring green contains the TOC (table of contents), with all the track details, so is unlikely to have much music on it anyway.

 

[Anonymous]

chebby:
And how does using green pen at the perimeter of the disc help improve replay once the laser is reading the rest of the surface not coated in green?

The bit you are colouring green contains the TOC (table of contents), with all the track details, so is unlikely to have much music on it anyway.

None of the playing surface is coated, only the edges of the disc.
It's all about refraction. Shine a light into any transparent object and you will see that the light is scattered. The most obvious case is to shine white light into a prism, the white light will be broken up into its seven separate wavelengths.

The same with CD, when the laser light "enters" the disc (don't forget that the data layer is on the top of the disc and the laser has to travel through the clear part of the disc to reach it) the light can be scattered and bounce around inside the disc. The green on the edges helps to prevent this bouncing around and so improve accuracy of reading the data on the disc.

 

[Anonymous]

Quenzer:The green on the edges helps to prevent this bouncing around and so improve accuracy of reading the data on the disc.

How exactly does it do that then? My understanding of optics is clearly incomplete, not to mention my understanding of how CDs are read...

 

[Anonymous]

A green surface is theoretically the best colour to absorb red light, so I'd image when the red light from the laser beam is scattered, it will hit the green surface and it will not be scattered any further by reflection off the edges.

 

[idc]

Quenzer: The same with CD, when the laser light "enters" the disc (don't forget that the data layer is on the top of the disc and the laser has to travel through the clear part of the disc to reach it) the light can be scattered and bounce around inside the disc. The green on the edges helps to prevent this bouncing around and so improve accuracy of reading the data on the disc.

I don't follow that bit. I thought the laser was a tiny pin point of light that reflects back, not something that scatters all over the place. If this was such an issue surely CDs would be manufactured with green rims.

 

[Anonymous]

idc:
Quenzer: The same with CD, when the laser light "enters" the disc (don't forget that the data layer is on the top of the disc and the laser has to travel through the clear part of the disc to reach it) the light can be scattered and bounce around inside the disc. The green on the edges helps to prevent this bouncing around and so improve accuracy of reading the data on the disc.

I don't follow that bit. I thought the laser was a tiny pin point of light that reflects back, not something that scatters all over the place. If this was such an issue surely CDs would be manufactured with greenÿrims.

CDs rely on a reflective coating. Therefore, if any light is scattered during the reading process, it can bounce back and cause less than perfect reading and sound reproduction. Green prevents this.

But you have hit one of the problems with the theory, and why felt pens have more or less ceased to exist. There isn't much scatter anyway, and no proof that the minimal amount there is has any impact on the sound. CDs are a digital medium, after all.ÿ