DEFERANCE BETWEEN ORIGINAL CD & CD-R

Other topics related to computer science
Post Reply
User avatar
Face
Major
Major
Posts: 727
Joined: Thu Feb 18, 2010 5:06 pm
Location: SRI LANKA.KANDY.

DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Face » Mon Apr 05, 2010 7:49 am

Generally we use CD-R in Sri lanka.Because it is cheep.normal price RS.20.But original CD s are very expensive & data safe.
one of my friend told that it has 2 different technologies to make them.

what are those technologies.???
User avatar
Neo
Site Admin
Site Admin
Posts: 2642
Joined: Wed Jul 15, 2009 2:07 am
Location: Colombo

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Neo » Mon Apr 05, 2010 6:59 pm

Just a bit of a confusion I think. In all the optical disk media like CD, DVD, etc... it is the same technology to read and write. I'm not going to go in to fundamentals of Optical Disk since you can read it on the internet. But I thought it would be better if I clarify the writing techniques a bit.

First see What are the recording methods of CD/DVD/Blu-Ray.

Once you understand the differences between each method, we can now analyse the optical media in terms of quality and durability.

Basically for the first two methods, a laser light is involved to make holes on the optical layer. When the laser beam is pointed at a particular location, that point is getting melted and a hole is made. The readability may depend on the depth of the whole (which is a standard), power of the laser light (red laser is used for CD/DVDs and blue-violet laser is used for Blue-ray disks) and chemical used for the optical layer (I have seen blue, green, orange and red coloured optical layers in different brands). CD-R, DVD-R and BD-R are disks that can be written only ones. The chemical composition of optical layer on those disk are made specifically for melt and make holes whereas for CD-RW, DVD-RW and BD-RE, the holes can be remelted to make peaks back (The process is called Erase). If the laser beam is not powerful as required (lasers are getting degraded over time), the quality of the writing may vary.

When we refer CD-ROM, those are made from prepressing (Method 3) (that involves no laser beam). Just imagine the way the statues are created by a moulding. That's what they do in this method 3. This method can't be used by us as it is a very expensive approach to prepare the moulding, etc... But it is cheap to do mass recording. These CDs are long lasting that the CDs we write as the materials used here don't need to be melted with a laser beam.

I'm sure you are now clear on the differences between writeable and prepressed types.
User avatar
Face
Major
Major
Posts: 727
Joined: Thu Feb 18, 2010 5:06 pm
Location: SRI LANKA.KANDY.

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Face » Mon Apr 05, 2010 8:25 pm

yep friend.I read your article.But it don't contain what I need to know.!
May be the problem is mine.because I don't have much knowledge in English.That's why you get wrong idea.Sorry about that. :(

I mean that in Srilanka we have original CDs in shops.They are very expensive.

But in Sri lanka many People use CD-R technology to copy CDs.

I want to know that is there any deferant those 2.?(Because they have deferant qualities CD-R & those Original comapany made CDs.)
Do they use deferant recording methords when "original CD making" in company & burning "CD-R" in our computer?

That's what I ask...

(sorry BRO i waste your time...because of my lack knowladge! :| )
User avatar
Neo
Site Admin
Site Admin
Posts: 2642
Joined: Wed Jul 15, 2009 2:07 am
Location: Colombo

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Neo » Mon Apr 05, 2010 8:57 pm

No..no worries.

However I'm a bit confused.
I mean that in Srilanka we have original CDs in shops.They are very expensive.
Are you referring branded (Sony, Imation) and unbranded CDs that usually called blank CDs ?
If that is the problem, yes, branded CDs are better than unbranded. However it is difficult to find true branded once as there are lots of duplicates that looks similar.

CD-R standard for Compact Disk Recordable. It is a type of CD. You can buy branded or unbranded CDs with type CD-R.
Another type is CD-RW. With this type, you'll be able to erase and reuse the same disk.
Again CD-RW is available both branded and unbranded.
Do they use deferant recording methords when "original CD making" in company & burning "CD-R" in our computer?
Are you referring original CDs to the ones that contain movies, audio CDs, etc... ? For example, original Avatar DVD.
Those are created by a method called pre-pressing that involves using a mould. Though the initial investment is high to create the mould, it is very cheap to produce CDs in mass scale after that.

So you need to clarify what is your definition of "Original CD", is it the branded CD-R disks or the disks that contains software/movies/audio CDs ?
User avatar
Face
Major
Major
Posts: 727
Joined: Thu Feb 18, 2010 5:06 pm
Location: SRI LANKA.KANDY.

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Face » Mon Apr 05, 2010 9:11 pm

BR
Are you referring original CDs to the ones that contain movies, audio CDs, etc... ? For example, original Avatar DVD.
Those are created by a method called pre-pressing that involves using a mould. Though the initial investment is high to create the mould, it is very cheap to produce CDs in mass scale after that.
this is the thing i ask..!! :D

deference between the method pre-pressing & normal "cd writer" writing technology we use???
User avatar
Neo
Site Admin
Site Admin
Posts: 2642
Joined: Wed Jul 15, 2009 2:07 am
Location: Colombo

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Neo » Tue Apr 06, 2010 2:42 am

Okay. So clearly you need to read What are the recording methods of CD/DVD/Blu-Ray. I have updated some more information to 3rd method so read it back.

Basically the first two method are about writing using a laser beam (The 1st one is about using a writer connected to a computer). 3rd one is about the pre-pressing method.
Moulding.jpg
Moulding.jpg (21.02 KiB) Viewed 9997 times
CD moulding machines have an average through-put of 550-900 discs per hour, per moulding line. See-through polycarbonate pellets are initially dried at approximately 130 degrees Celsius for three hours. These are then fed by vacuum transfer into the one end of the injection moulder's drum and are moved to the injection compartment by way of a huge coil inside this drum. The drum is wrapped with heater bands, which melt the polycarbonate. As soon as the mould is closed, the screw moves forward to insert molten plastic into the mould hollow. Cold water runs through the mould halves outside the hollow, which cools the plastic so it becomes somewhat solid. The entire process takes 3 to 5 seconds.

Obviously the 3rd is the most cost effective and durable method for large productions. The reason is the chemical composition of the reflecting layer (which doesn't required to carry melting features over a laser beam as in a CD-R) is having the perfect reflecting properties.
When manufacturing CR-R, it is very important to consider the melting features of the reflecting layer for recording from a laser beam.

Is it clear now?
User avatar
Face
Major
Major
Posts: 727
Joined: Thu Feb 18, 2010 5:06 pm
Location: SRI LANKA.KANDY.

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Face » Tue Apr 06, 2010 4:30 pm

yep BRO clear..
I got some word from your post to search more details.
For an example I used "pre-molding"
Before read this post i even don't know the name.great help from you brother.
Specially i should soy SORRY what happen in this question.because I don't even basics to ask that question..
Now I got a clear picture....

THANK YOU!
User avatar
Neo
Site Admin
Site Admin
Posts: 2642
Joined: Wed Jul 15, 2009 2:07 am
Location: Colombo

Re: DEFERANCE BETWEEN ORIGINAL CD & CD-R

Post by Neo » Tue Apr 06, 2010 6:18 pm

You are welcome!
Post Reply

Return to “Other”