Pincushion correction in a dual deflection CRT system
AssigneeMotorola, Inc.
InventorFreeman E. Smith
Life of this patent
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Abstract
Correction of pincushion distortion in a dual deflection CRT display system is achieved by applying identical correction functions to a major deflection signal and a combined deflection signal and by substracting the corrected major deflection signal from the corrected combined deflection signal. A particular circuit performs this correction method through the novel interconnection of two standard pincushion correction modules. This circuit is essentially transparent to the remainder of a display system and is adaptable to any CRT display within the operating range of the correction modules. Furthermore, the disclosed circuit is simple in design and construction, thus entailing the addition of little hardware to an existing system.
Claims6
A CRT display system having first and second major deflection signals and first and second minor deflection signals wherein the improvement comprises:
- first means for combining the first major deflection signal and the first minor deflection signal to produce a first combined signal;
- second means for combining the second major deflection signal and the second minor deflection signal to produce a second combined signal;
- first correction means responsive to said first and second combined signals for producing first and second corrected combined signals;
- second correction means responsive to the first and second major deflection signals for producing first and second corrected major deflection signals;
- third means for combining said first corrected combined signals and said first corrected major deflection signal to produce a first corrected minor deflection signal;
- and
- fourth means for combining said second corrected combined signal and said second corrected major deflection signal to produce a second corrected minor deflection signal.
A method of correcting pincushion distortion in a dual deflection CRT display system comprising the steps of:
- summing a first major deflection signal and a first minor deflection signal to produce a first summed signal;
- summing a second major deflection signal and a second minor deflection signal to produce a second summed signal;
- correcting said first and second summed signals according to a predetermined correction function;
- correcting said first and second major deflection signals according to a correction function substantially identical to said predetermined correction function;
- subtracting said first corrected major deflection signal from said first corrected summed signal;
- and
- subtracting said second corrected major deflection signal from said second corrected summed signal.
A pincushion correction circuit for a dual deflection CRT display system, comprising:
- a first summing circuit having inputs being a first major deflection signal and a first minor deflection signal and an output being a first summed signal;
- a second summing circuit having inputs being a second major deflection signal and a second minor deflection signal and an output being a second summed signal;
- a first pincushion correction module having inputs being said first and second summed signals and outputs being first and second corrected summed signals;
- a second pincushion correction module substantially identical to said first module, said second module having inputs being said first and second major deflection signals and outputs being first and second corrected major deflection signals;
- a first inverter means for inverting said first corrected major deflection signal;
- a second inverter means for inverting said second corrected major deflection signal;
- a third summing circuit having inputs being said first inverted corrected major deflection signal and said first corrected summed signal and an output being a first corrected minor deflection signal;
- and
- a fourth summing circuit having inputs being said second inverted corrected major deflection signal and said second corrected summed signal and an output being a second corrected minor deflection signal.
Dependencies are inferred from the claim text.