Abstract: A timing and mirror position detector for use in a bar code scanner having a rotating optical assembly. The optical assembly is rotated by a motor which produces a fixed number of pulses per rotation, at least one of the pulses occurring each time the motor passes through a reference position as it rotates. The pulses are continuously monitored and counted. Elapsed time from the time a reference pulse occurs is accurately measured and correlated by a processor with events of interest. When an event of interest, such as a bar code scan, occurs, the timing and pulse count are evaluated and processed to determine the angle of rotation of the motor at the time the scan occurred.

Abstract: A system for digital barcode processing. A light reflected from a barcode is captured by a photodetector to produce a photocurrent. The photocurrent is converted to a voltage, amplified and filtered to produce a photovoltage. The photovoltage is differentiated to form a first derivative signal and the first derivative signal is converted to a digital first derivative signal and processed to identify logic transitions represented by the barcode. The processing system subjects the photosignal to Gaussian filtering and differentiates the digital first derivative signal to form a second derivative signal. The digital first derivative signal is compared against a positive and a negative threshold and the second derivative signal is examined to detect zero crossings.