Welch Allyn SCANTEAM 3000PDF, Techical Manual

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2–4
Operational Description
3. A portion of the scattered light re-enters the scanner's
optical system and is detected by the CCD (Charged
Coupled Device) sensor.
4. The CCD converts the analog light signal into a sequence of
electrical pulses with amplitude proportional to the energy
level of the scattered light.
5. The digitizer converts the analog light signal to a bit serial
representation of the bar code symbol. The width of the
binary signal pulse is proportional to the width of the bars
and spaces of the bar code symbol.
6. The Decoding Circuitry decodes the digitized pulses into
characters of data representative of the bar code symbol.
7. After the scanning cycle is complete, a Good Read" LED on
top of the scanner turns ON, and a beeper is sounded if the
Beep On Good Read option is enabled. The decoded
information is prepared for transmission to the host.
8. Depending upon the trigger mode chosen, the scanner
either initiates another scan cycle or returns to the wait or
standby" state.
2.2.1 LED Bar
The bar code symbol is illuminated with a bank of 12 LEDs and
a reflector assembly. The LEDs are pulsed resulting in
stroboscopic illumination to stop the relative motion.
2.2.2 CCD Sensor
The optical energy scattered from the bar code symbol is focused
with a custom lens onto the CCD sensor array. The CCD sensor
array is a linear array with 2048 pixels. The nominal signal
amplitude from the CCD is approximately 200 mV p-p. The
output is black high with an offset level of 5 to 9V. The analog
portion of the CCD requires a power supply of +12V and all of
the drive logic is at 5V levels. The output level is shifted to the
signal processing level with a Black Level Clamping circuit.