Question

What is optical memory? explain all kinds of optical memory?

Answer 1

Optical memory is the storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light, usually a beam of laser light precisely focused on a spinning optical disc.

compact disc The average CD allows for up to 700 MB of data storage. Digital bits are stored as pits on the reflective material in the disc. A red wavelength laser detects these pits and converts them to a digital signal.

Digital Versatile/Video Disc
DVD was an excellent choice for personal backups of data on a DVD-R or movie media. DVD is not only used for data and video. DVD-Audio discs are uncompressed studio master recordings that offer much higher bit-rate than a standard CD. DVDs used a red wavelength laser, much like CDs.

High Definition DVD
HD-DVD was released by Toshiba as a competing format to Sony's Blu-ray disc. HD-DVD offered enough storage space for full-length, high-definition movies on a single disc. HD-DVD discs were capable of holding 15 GB per layer with a maximum of two layers. Toshiba had planned on eventually releasing three-layer discs; however, with shifts of movie production studios, support for HD-DVD dwindled until Toshiba announced it would no longer continue the format. HD-DVD drives use a blue wavelength laser that is able to read smaller pits on the optical media.

Blu-ray
Blu-ray is the newest high-definition optical format. Developed by Sony, Blu-ray discs offer 25 GB per layer with up to two layers per disc. Blu-ray discs have a protective coating that reduces the number of scratches and makes the disc durable. Like HD-DVD, Blu-ray offers a full-length, high-definition movie on one disc. Blu-ray recordable, or BD-R, drives are becoming more common in home computers. The BD-R drives allow for up to 50 GB of storage on one disc. Blu-ray drives use the same type of laser as HD-DVD drives to allow for greater storage on the optical disc.

Legacy Optical Devices
There have been a number of optical media that are no longer in production. Laser discs were one of the first optical media. A laser disc was a 12-inch disc that held a digital copy of a movie. Laser discs were not efficient at storage; it often took multiple discs for a full-length movie. Other proprietary, short-lived formats included the GD-Rom from Sega's DreamCast gaming system, Sony's MiniDisc and SuperAudio-CD.