by October 11, 2003 0 comments



First we had floppies. Then there was a huge leap forward in the form of CDs. The CD could hold up to 485 times the data a floppy could store. At this point, the focus shifted from magnetic portable storage media to optical media. This was also the time when technology in digital audio and video advanced rapidly, highlighting the need for high speed, high capacity media, leading to the proliferation of CDs and subsequently DVDs. Today DVDs are easily available with 4.7 GB capacity, and one might think that this is more than enough. 

Actually, further developments in digital Audio/video technology need yet higher capacities and throughputs. One such development is the HDTV (High-Definition Television), which needs data transfer rates of 2.4 MBps, and its video data which requires around 145 MB per minute or 8.5 GB per hour of storage capacity. 

Different wavelengths of CD, DVD, BD result in different recording patterns on media. 

The current DVD technology can’t handle this. Therefore, there are lots of developments in this area. Some exciting ones include Blu-ray, Fluorescent Multilayer Disc, and holographic discs.

Blu-ray Disk or BD 
BD is a joint effort by nine consumer electronics companies, namely Hitachi, LG, Matsushita (Panasonic), Pioneer, Philips, Samsung, Sharp, Sony, and Thomson. This technology will make recording possible of up to 2-3 hours of HDTV on a 27 GB disk.

The 30 mm BD being developed by Philips

Such high capacities have been made possible by using a blue laser (that’s why the name Blu-ray) instead of the regular red laser used in CD/DVD. The blue laser has a shorter wavelength of 405 nanometers as compared to 650 nanometers of the red laser. This makes it easier to focus the laser beam with more precision, thus making it possible to hold more data on the disk.

The disk features a data transfer rate of 36 MBps and will be compatible with the prevailing optical disk technologies. So a BD drive will be able to playback CDs and DVDs. An interesting feature of this technology is that it can simultaneously record from TV and play pre-recorded video from the same disk.

Another exciting form of Blu-ray disks is being developed along the lines of the Sony Minidisk, which is fairly popular today.

A transparent Fluorescent Multi-layer Disk

Philips has already showcased a 30mm re-writable disk, code named SFFO (Small Form Factor Optical Storage) based on the Blu-ray technology that can hold upto one GB of data. The company plans to use these disks in mobile phones and PDAs instead of existing memory cards. The showcased drive measures just 5.6 x 3.4 x 0.75cm in size. 

Talking of miniature storage, Iomega has also announced a 1.5 GB capacity magnetic digital capture technology (DCT) disk. It is a small form factor disk that weighs just 9 grams and is the size of a small coin. It comes in its own stainless steel casing to protect the data from being damaged.

Fluorescent Multi-layer Disc
A DVD can record data on a maximum of two layers since an increase in the number of layers in the disk increases the interference and the data cannot be read properly. A company called Constellation 3D had developed a technology by which data could be recorded on up to 20 layers in a disk. Instead of using a reflective surface, the FMD technology used a disk that can appear transparent to the human eye. It used layers of fluorescent dyes. This technology was also red-laser based and thus compatible with the legacy CD/DVD media. 

With the use of this technology, the company promised approx 100 GB of data on each disk. Quite impressive technology!
If you are surprised at the sudden use of past tense about the fluorescent multi-layer disc in the previous paragraph, it is because the company now ceases to exist. It filed for bankruptcy in December last year. Thus, the future of this remarkable technology is uncertain, if not dead.

Holographic storage
Holographic Storage is another technology that has been promising to solve the ever-increasing demands of the video industry. It promises to store 2 GB data on a postage stamp-sized medium, or for that matter around 200 GB on a regular optical media disk.

How is this achieved? The light from a single laser is split into two beams, the reference beam and the data carrying or the signal beam. The signal beam is then passed through the Spatial Light Modulator (SLM) that translates the binary data into a pattern of dark and light pixels. Depending upon the pixel count of the SLM, the data is arranged in an array or a page of around a million bits. At the point of intersection of the two beams, the data is recorded on a light sensitive medium through a chemical reaction. For reading the data, the reference beam is deflected from the hologram to a detector array that reads the data in parallel. 

Reading and writing through Holographic Storage

By now, you must be beginning to feel, that having heard about this for a really long time, why are the products not there? The biggest reason as in the case of most hi-tech technologies is cost. In this case, the manufacturing process compounds the cost. It is very difficult to manufacture and store the media needed to record the process. Plus, there is no procedure yet as to how to commercially replicate this media.

Though it sounds simple in theory, it is very difficult to make a device of this kind for the masses, because of the complex manufacturing process. Another hindrance that this technology faces is that it is not backward compatible, i.e. it won’t be able to use the current CD/DVDs. InPhase technologies, a Bell Labs spin-off, is however developing this technology and plans to take it to the market in 2004.

But which technology will actually reach your living room or PC depends largely on its commercial viability.

Geetaj Channana

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