Laser Applications | Britannica

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Optical discs

What happens inside a CD player?1 of 2
What happens inside a CD player?An infrared laser is focused onto the metallic reflective layer of the disc, where a spiral track of “pits” and “lands” represents the zeros and ones of digital signals. The return signal is converted by a photodiode sensor into a digital electric signal, which is converted to analog form for reproduction of the original recorded sound. Optical recording, introduced by the Sony Corporation and Philips Electronics NV in 1982, allows accurate reproduction of sound over virtually the entire range of human hearing.(more)See all videos for this article
the laser scanning method employed in compact disc players2 of 2
the laser scanning method employed in compact disc playersAn infrared laser is focused onto the metallic reflective layer of the disc, where a spiral track of “pits” and “lands” represents the zeros and ones of digital signals. The return signal is converted by a photodiode sensor into a digital electric signal, which is converted to analog form for reproduction of the original recorded sound. Optical recording, introduced by Sony Corporation and Philips Electronics NV in 1982, allows accurate reproduction of sound over virtually the entire range of human hearing.(more)

Tiny, inexpensive semiconductor lasers read data from a growing variety of optical compact disc formats to play music, display video recordings, and read computer software. Audio compact discs, using infrared lasers, were introduced around 1980; CD-ROMs (compact disc read-only memory) for computer data soon followed. Newer optical drives use more powerful lasers to record data on light-sensitive discs called CD-R (recordable) or CD-RW (read/write), which can be played in ordinary CD-ROM drives. DVDs (digital video, or versatile, discs) work similarly, but they use a shorter-wavelength red laser to read smaller spots, so the discs can hold enough information to play a digitized motion picture. A new generation of discs called Blu-ray uses blue-light lasers to read and store data at an even higher density.

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