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because it affects only a small portion of each
circular data track, which can be fully compensated
by the player's error-correction circuits. But a
circular scratch that follows a data track may
damage such a long continuous segment of data
that it cannot be corrected.
ABOUT THE LASER
The Compact Disc player uses a solid-state
semiconductor diode laser, mounted on a tracking
servo mechanism, to play the disc. The laser
illuminates
the
track
of
microscopic
pits
representing the digital data bits, while photo-
diodes detect the reflected illumination from the
disc and convert it into an electronic signal which is
then decoded to recover the musical waveform in
each stereo channel.
You cannot see the laser operating, because it
operates at wavelength of 7800 Angstroms, which
is in the infrared and thus invisible to the human
eye.
The Compact Disc player is completely safe for
children to use. The laser operates at very low
power and is concealed within the player
mechanism. Even when the player is disassembled,
the laser remains sealed within an optical system
that causes its light to focus only 1 millimeter from
the lens and then diverge rapidly, reducing its
intensity to negligible levels.
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