By Adam Reimel

Introduction Pit Configuration CD media DVD media Blu-Ray Disc Ongoing Developments BD-ROM Media Holographic Versatile Disc Technology Further Development

Optical media stores information using nanotechnology. Data is read and written by using Laser light in the order of Nano meters. The Laser light shines on the surface of the media and when it hits a pit of bump, the light gets reflected back to the light sensing diode which detects light and converts them into electrical energy. Thus 1s and 0s are formed. CD-ROM drive uses Laser beams of the order 780nm and CD-ROM media with pit configuration 800nm x 600nm can store up to 700MB of data.

1 0

As the technology grew DVD format came up. DVD’s use a lesser wavelength laser (650nm). As the laser light is of lesser wave length, it could be focused to smaller pit configuration and hence for the same media it could accommodate 4.3 GB of data. This is made possible by reducing the dimensions of the pit and as well as the distance between them. Double sided DVDs are also available, which can store up to 8.6 GB of data. Multi layered DVDs also came up, which can store up to 15 GBs of data.

Stores 25GB in single layer disc Stores 50GB in dual layer disc Uses Blue-Violet laser to read Wavelength is 405nm Stores six times data than a DVD

Hitachi developed a disc to store seven hours of 32Mbit/s video (HDTV) or 3.5 hours of 64 Mbit/s video (Cinema 4K). TDK have created a Disc capable of 200GB of data on a single side, using six 33GB data layers. Ongoing development is under way to create a 1TB Blu-ray disc as soon as 2013

The laser used in the BD-ROM drives are 405nm As the read/write head has to be very close to the media it could scratch the BD-ROM medium. So, TDK developed a scratch-proof translucent material.

Ultra high density optical disc Developed by HSD Forum Currently in generation 1 stage (300GB) Eventually will store 1 to 6 TB

Use Collinear Holography Green Laser reads data Red Laser used as reference beam to read A Dichroic layer allows red light to pass through Holographic Versatile Disc structure 1. Green writing/reading laser (532 nm) 2. Red positioning/addressing laser (650 nm) 3. Hologram (data)(shown here as brown) 4. Polycarbonate layer 5. Photopolymeric layer (data-containing layer) 6. Distance layers 7. Dichroic layer (reflecting green light) 8. Aluminum reflective layer (reflecting red light) 9. Transparent base P. Pit pattern (Illustration is not to scale.)

Forward Versatile Disc Same as DVD but shorten length to have up to 5.4 GB of storage per layer. 135 minutes of 720p video on a dual layer disc. 135 minutes of 1080i video on a 3-layer disc. Digital Multilayer Disc 3D optical data storage Store between 22 and 32 GB Protein Coated Disc Coating a DVD with a special light-sensitive protein made from a genetically altered microbe Allows storage up to 50 TB