An optical drive uses a laser to read or write information to a disc, and can be found in devices like DVD and Blu-ray players. The drive consists of a laser, lens, and photodiode, and uses different wavelengths for different types of media. It can read-only or record media on specific discs, and rewritable media allows for repeated writing on special discs.
An optical drive is a piece of equipment that uses a laser to read or write information to a disc. While this type of equipment is often associated with computers, it can be considered an appliance on its own. For example, a Digital Versatile Disc (DVD) player, Blu-ray disc (BD) player, and Compact Disc (CD) player are considered optical drives even though they may not be in a computer system. Many video games also use this type of device to read the game disc. Regardless of the type of disc they read or write to, all of these applications have the same basic operation.
The optical path drives an optical drive. The optical path consists of three components: a laser, a lens, and a photodiode. The laser writes and reads data. The lens guides the laser onto the disc surface. Finally, the photodiode detects the light reflected from the disc surface. The drive also uses two servos, or servos: one to maintain the correct distance between the puck and the laser, and the other to make sure the laser moves in a continuous spiral path.
Lasers of different wavelengths are used to read different types of media. A CD player uses a laser with a wavelength of 780 nm. This is in the infrared light range. DVD players use wavelengths in the 650 nm range. This is why you will see a red light when the player is running. Blu-Ray® players use a much shorter wavelength: 450nm. This puts it in the violet range and explains the bluish light.
Discs read and written by an optical drive vary. Read-only media (ROM), such as CD-ROM or DVD-ROM, do not write to media, only read to it. These are the types of disks that the software is written on. The manufacturer will create the disc by embedding dimples, called grooves, into the flat surface of the disc. Then, when a user inserts the disc into an optical drive, a reading laser lights up the disc. The light is reflected and sensed by the photodiode which then translates the data into a form that the computer or reader can understand and display.
An optical drive can also record media. This type of recording must be done on specific recordable (R) discs such as CD-R, DVD-R and BD-R. When writing, the recording laser fuses organic dyes to the surface of the disc and embeds grooves in the surface. As with ROMs, the read laser, which is at a much shorter wavelength than the write laser, shines on the disc and reflects the light. The reflection is then detected by the photodiode and information is displayed.
Rewritable media is capable of writing media to rewritable discs (RW or RE, in the case of Blu-Ray®), such as CD-RW, DVD-RW and BD-RE, over and over again. The surface of these discs is made of a special crystalline alloy that allows data to be repeatedly written on its surface. The individual data is embedded in the disc on grooves which reflect the laser differently. The photodiode is then able to distinguish between the different reflections and display the correct information.
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