Everything You Need To Know About – Optical Disc Reader & Writer

From time immemorial we have been using various kinds of data storage devices like gramophones, audio cassettes, floppy, and now compact discs like DVDs, Blu-Ray Discs, etc. Have you ever wondered how these devices work?




We are sure, at some point, you must have been amazed by these technologies. Here we are is going to reveal all the secrets and science behind one of the modern devices i.e. the Optical Discs and we will answer you how an Optical Disc Writer actually works.

#Construction Of An Optical Disc

There is no rocket science behind the construction of a disc; it contains only a few logical coding in the form of numbers wiz 0 and 1.

A picture may have a code something like 110001110100011110 and so do a video clip. The task here is how to plant these coding on a fine surface of a disc.

For this, you need to understand the step by step of manufacturing of a disc:

  • First of all, there is a plastic surface on the base which is cut out for this purpose. This is also the reason why these discs are so cheap. You are paying for nothing more than a piece of plastic. It is also a part of the disc on which you can paste any label of your company.
  • On the other end of the plastic, an aluminum film is fixed. This is the core of this device. Owing to the malleability of the metal coating, we can instill so many coding.
  • Finally, there is a thin plastic covering which protects the film from any damage.




#Working Of A Disc

As we said above it is a technology based on optical media, which means all the work is done with the help of light rays.

A laser beam burns the surface of aluminum in a particular pattern which ultimately etches a coding called bumps and pits.

Usually, the coding 0 is termed for a pits/groove and the 1 is labeled to a bump. These bumps and pits are drawn throughout the disc in a spiral shape starting from the center.

These two patterns are too small to be seen by your naked eyes, one bump might be merely 150-200 nanometer small.

What’s The Difference Between CD/DVD/Blu-Ray? Fundamentally, the basic difference we all know is in their memory. A CD can accommodate around 600-700 MB whereas a DVD has a room for more than four times of it i.e. around 4.7 GB and coming to the Blu-Ray disc; these are the most advanced plates that have ever been invented. It has a tremendous storage of 50 GB!

The reason why similar size plates have different memory is the engineering done on their structure. The bumps and pits in a DVD are relatively smaller and finer as compare to a CD. The Blu-Ray discs too have the similar story but with more polish. With smaller room (Bump and Pit) we can accommodate more coding within the same plate.

For smaller pits and holes, the light also needs to be of smaller wavelength. Therefore, we have replaced the infrared rays (in CDs) by red light in DVDs.

Lastly, we have another type of finest disc system called Blu-Ray that uses the blue colored light of shortest wavelength. The name that fits the job!

Now, What About Rewritable Discs? The problem here is how we can make the structures of pits and bumps dynamic so that it can change its shape according to the different data we write on it.

In another word, we wish it should be amorphous. Again, technology wins the game. We have a special kind of alloy which can not only change its shape but also remain rigid until we command it to be flexible next time.

The structure of these advanced discs is pretty similar to that of the normal ones. You can replicate as many data as you want.

#So, Now Let’s Look Over To The Working Of Writing Process;

All the videos/audio we enjoy is basically in the form of analog which has to be converted into digital format at around 44 KHz so that it can be embedded on the disc easily.

Our disc driver which can even burn a new blank disc looks very small and simple, though it consists of various incredible instruments.

Your Disc drive basically has two devices, first is the laser diode and the second one is the lens. A laser diode can move from the center of a disc to its outer circumference according to the need. The job of the laser diode is to direct the laser beam onto the surface of a disc and reflect it on a photocell.

As the laser bounces off the surface of a disc, if it hits a bump it will be reaching its destination in the different interval of time and with a different intensity as compared to the case of light hitting a pit.

All these differences, helps the photocell determine which code it is. And finally, a coding is generated.

Another important factor needs to be considered is that the speed at which the disc rotates. Usually, we need a higher speed when the laser is at the center of the disc and if the laser is reading it around the outer edges, the disc will rotate slower.

That means your driver must have a very precise customization of the speed in RPM during different time rather than just rolling at any speed like Ferris wheels.

How Do We Burning A Compact Disc?

You may find this question quite ridiculous. As it is not possible for every one of us to install the big laser machine to engrave the data at home, therefore, a newer methodology was adopted.

In this technique, the blank CDs come with not only the raw aluminum but also a type of transparent dye which becomes opaque when heated.

When the high power laser of our PC strikes the disc, some part of the dye burns and forms a pattern of bump and pits. The opaque part acts as if it were a bump and so do the transparent part as a pit.

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“And that’s all for now, thanks for sticking with the article, and you know it will always good to let me know about the article, in the comments down below.” 🙂


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