Abstract: A bar code reader and the mirror oscillating system thereof are disclosed herein. The bar code reader is of the type which produces a scanning light beam by oscillating at least one mirror with a electromagnetic oscillator. The electromagnetic oscillator includes a winding which is energized with an alternating current signal produced based upon a position signal generated by a magnetic pickup. The position signal is representative of the location of the mirror. The position signal is amplified, phase-shifted, and assigned a duration based upon the difference between the desired angle of mirror oscillation and the actual angle of oscillation to produce the alternating current signal which is applied to the winding. When applied to the winding, the alternating current produces an alternating magnetic field which interacts with a permanent magnet fixed relative to the mirror to oscillate the mirror.

Abstract: A bar code reader for reading two-dimensional bar codes is disclosed herein. The reader includes first and second oscillating mirrors which oscillate to scan the light beam of the reader over the code. The first mirror is oscillated about a horizontal axis at a first velocity during the first half of its oscillating cycle, and at a second velocity during the second half of the oscillating cycle. The second mirror is oscillated about a vertical axis at a generally constant frequency. The reader varies the first and second velocities based upon the error rate monitored during decoding. By varying the first and second velocities, the slope of the scanning lines can be varied to enable reading two-dimensional bar codes which are oriented at slopes which differ from bar code to bar code.

Abstract: A system for filtering electrical signals and cancelling large amplitude disturbance events contaminating such signals which might otherwise interfere with these signals being further processed. The system includes a disturbance filter which is operative for identifying disturbance events and passing an inverted signal corresponding solely to these events to a summing junction for use in cancelling these events as they occur. In the preferred embodiment this system is adapted for use in a bar code reader.