2.The black bars on the symbol absorb the LED light, while the white spaces scatter the LED light.
3.A portion of the scattered light
4.The CCD converts the returned light 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 being 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 a successful decode is complete, a beeper is sounded (if enabled to indicate a Good Read). The decoded information is transmitted to the host.
8.Depending upon the trigger chosen, the scanner either continuously initiates another scan cycle or waits for the next trigger to scan.
LED Reflector
The bar code symbol is illuminated with a bank of LEDs with a proprietary reflector. The LEDs are pulsed, strobing illumination, to stop relative motion of the scanner and the label.
CCD Sensor
The optical energy scattered from the bar code symbol is focused with a custom lens onto the pixel array of the CCD sensor.
The switching transients from the CCD are removed with analog filters. This filtered signal is then an analog representation of scattered light incident on the CCD.
Peak Detectors and Comparator
The positive and negative peak detectors retain the signal level associated with the minimum black and maximum white reflectances respectively. The comparator threshold is then set at a point between the black and white peak reflectance levels. The threshold level and the analog representation of the scattered light are then compared with a comparator, generating the bit serial digital representation of the bar code symbol.
CCD Operation and Bar Code Scanning |
