Theory Of Operation - Symbol LS 1220 Product Reference Manual

Introduction
Figure 1-1. LS 1220

Theory of Operation

A laser diode produces a single beam of coherent light which is deflected off of an
oscillating mirror to create the laser scan beam.
When the laser light strikes a bar code, the dark bars absorb the laser light and the light
spaces reflects it. A photo diode senses the reflected light and generates a proportional
current. That current is amplified and filtered to produce an analog voltage which is sent to
a digitizer. The digitizer transforms the signal into a digital representation of the bar code
called the Digitized Bar Pattern (DBP) and the DBP data is sent to the host or decode board
for processing.
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