Photoelectric sensor in bar code scanning pen

When the scanning pen head moves on the bar code, if it encounters a black line, the light of the light-emitting diode will be absorbed by the black line, and the phototransistor will not receive the reflected light, presenting a high impedance and being in a cut-off state. When encountering a white interval, the light emitted by the light emitting diode is reflected to the base of the photosensitive transistor, and the photosensitive transistor generates a photocurrent to conduct. After the entire bar code is scanned, the phototransistor deforms the bar code into individual electrical pulse signals. The signal is amplified and reshaped to form a pulse train, and then processed by the computer to complete the identification of the bar code information.