How original cd's are made?

FriBogdan

Hm...I'm just wondering this because some cd players don't read home made audio cd's (with the pc) or some don't read cd'rw Cd's. Why is this happening?

What is the difference between a original cd and a home made cd? What is the difference between a normal one write cd and a cd-rw ?

4ndY

The difference is that original CD/DVDs have real holes on its surface, when "home made"/burned have only darken part of surface where is going bit 1.
When laser beam cross over CD, on 1 bit it doesnt reflect back, on 0 bit it does. So try too figure why original CD/DVD is more reliable then burned one in home's R\RW recorders... Smile

FriBogdan

Ok....but how is a original cd made? The "home made" are burned with a laser...the original...?

4ndY

Well, that process isnt so simple like "home" one.
On wikipedia i found nice text about it:

Mastering Process: First, in a clean room, a glass master is prepared by coating a perfectly flat piece of half inch thick circular glass with a layer of nickel. The nickel is transfered by exciting the nickel to a plasma state whereupon a thin layer of nickel will adhere to the glass. The glass is coated with an emulsion. Source material is encoded into the appropriate format whereupon a computer controlled machine "burns" the pits into the emulsion layer of the glass master. The glass master produced is quality checked before it moves to the next stage.

Stamper Process: Next the glass master is used to create nickel stampers using an electroplating technique. Multiple stampers can be made from one glass master. Each stamper is quality checked. This process is also done in a clean room environment.

Pressing: Each stamper is mounted in an injection moulding machine. Melted polycarbonate resin is injected into the chamber and the CD is pressed using up to 40 tons of pressure. The chamber opens and a robotic arm grabs the disc and transfers it to the next stage. At this point the disc is clear, so a coating of aluminum is applied to the disc for reflectivity. A laquer is spin coated onto the disc and the disc is tranfered to a spindle. The discs are sampled by QC to ensure quality product.
<source>

FriBogdan

Interesting...this is how mass production of cd's is made?...because it looks so complicated...and expensive...and time consuming.

4ndY

atomictoyz

bluefossil

I'm not sure if it applies to CD; but on DVDs, there is a field called "book type" in the first 4 bits of the DVD that determine what type the DVD is. i.e. Manufactured DVD, DVD-R, DVD+R, etc.
Some DVDs does not work on certain DVD players because the DVD players were manufactured before that particular Book Type was been defined.

These are the possible values of the Book Type Field:
0000 DVD-ROM1
0001 DVD-RAM
0010 DVD-R, DVD-R DL2
0011 DVD-RW
1001 DVD+RW
1010 DVD+R
1101 DVD+RW DL
1110 DVD+R DL

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