Valolevyjä

Valolevyjä, often translated as optical discs, are a data storage medium that uses a laser to read and write data. The most common types of valolevyjä are CDs, DVDs, and Blu-ray discs. These discs are made of a polycarbonate plastic and have a reflective layer, typically aluminum, that stores the data. Data is encoded as microscopic pits and lands on the disc's surface. When a laser beam strikes the disc, it reflects differently off the pits and lands, and this difference is interpreted as binary data.

CDs (Compact Discs) were the first widely adopted optical disc format, initially used for audio but later adapted for data storage. DVDs (Digital Versatile Discs) offer significantly higher storage capacity than CDs, allowing for the storage of full-length movies and larger software applications. Blu-ray discs represent the latest generation, boasting even greater storage capacity and enabling the playback of high-definition video content.

The manufacturing process for valolevyjä involves pressing a master disc, which is then used to create copies through electroplating or injection molding. The data layer is then applied, followed by a protective lacquer coating. While once ubiquitous, the popularity of valolevyjä has waned with the rise of flash memory, cloud storage, and streaming services. However, they remain relevant for archival purposes, in regions with limited internet access, and for specific applications requiring physical media.