Voltage parabola focussing waveform generating circuit - uses existing CRT sawtooth deflection waveforms as circuit inputs

摘要

The CRT vertical and horizontal scan waveforms are applied to the inputs (10.11) of two similarly constructed circuit paths (8.9). Positive excursions of the sawtooth scan waveforms are directed through a positive detection circuit (12.13) and a function network (16.17), whilst the engative excursions pass through a negative detection circuit (14.15), a function network (18.19) and an inverter (20.21). The four inputs are summed in an adding circuit (22) which feeds the resulting voltage parabola to an output stage (23) for application to a CRT focussing grid or coil assembly. USE/ADVANTAGE - Dynamic focussing of CRT electron beams - suitable for all standards of scanning systems - produces consistant pictrue sharpness as voltage parabola focussing waveform is directly dependent on scanning frequency and amplitude - simple, and inexpensive diode/resistor circuitry.