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Laser beams emitted from the laser
diode hit the polygon mirror and scan a bar code.
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The light-receiving element (photodiode)
receives the light of diffuse reflection from
the bar code.
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The diffuse reflection looks like
an analog waveform as illustrated.
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The bar code reader converts the
waveform from analog to digital (A/D conversion).
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The bar code reader identifies
the narrow/wide bars and narrow/wide spaces using
digital signals.
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The bar code reader converts the
signal combination of the bars and spaces into
data according to the bar code rules (decoding).
It outputs the decoded data to the external unit
through RS-232C or an equivalent interface.
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