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In later years, the compact disc was adapted for non-audio computer data storage purposes as CD-ROM and its derivatives. First released in Japan in October 1982, the CD was the second optical disc technology to be invented, after the much larger LaserDisc (LD). By 2007, 200 billion CDs (including audio CDs, CD-ROMs and CD-Rs) had been sold ...
CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can only be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the introduction of CD-R, unlike CD-RW discs.
Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standard format for audio compact discs. The standard is defined in the Red Book technical specifications , which is why the format is also dubbed "Redbook audio" in some contexts. [ 1 ]
High Definition Compatible Digital (HDCD) is a proprietary audio encode-decode process that claims to provide increased dynamic range over that of standard Compact Disc Digital Audio, while retaining backward compatibility with existing compact disc players. Originally developed by Pacific Microsonics, the first HDCD-enabled CD was released in ...
A keratoscope, sometimes known as Placido's disk, is an ophthalmic instrument used to assess the shape of the anterior surface of the cornea.A series of concentric rings is projected onto the cornea and their reflection viewed by the examiner through a small hole in the centre of the disk.
Different kinds of Secchi disks. A marine style on the left and the freshwater version on the right. The Secchi depth is reached when the reflectance equals the intensity of light backscattered from the water. 1.7 divided into this depth in metres yields an attenuation coefficient (also called an extinction coefficient), for the available light averaged over the Secchi disk depth.
The DualDisc is a type of double-sided optical disc product developed by a group of record companies including MJJ Productions Inc., EMI Music, Universal Music Group, Sony BMG Music Entertainment, Warner Music Group, and 5.1 Entertainment Group [1] and later under the aegis of the Recording Industry Association of America ().
Double-sided discs have two grooved, recordable disc sides, and require the user to flip the disc to access the other side. Compared to a CD's 1.2 mm thickness, a DVD's laser beam only has to penetrate 0.6 mm of plastic in order to reach the dye recording layer, which allows the lens to focus the beam to a smaller spot size to write smaller pits.