Linearity correction apparatus
AssigneeInternational Business Machines Corporation
InventorsTerence K. Gibbs, Graham Luck
Life of this patent
Estimating the term…
Abstract
Linearity correction apparatus for a raster scanned cathode ray tube display device is presented. The apparatus comprises first means (16) for generating a correction signal to correct an asymmetric non linearity in a sawtooth electron beam line deflection current. The line deflection current is generated by a line timebase circuit for energising electromagnetic electron beam deflection coils of the cathode ray tube. The apparatus further comprises second means (70,90,91) cooperative with the first means (16) and responsive to a change in line timebase frequency for compensating a variation in the correction signal generated by the first means (16) in response to said change in line timebase frequency.
Claims25
Linearity correction apparatus comprising first means for generating a correction signal to correct an asymmetric non linearity in a sawtooth electron beam deflection current generated by a line timebase circuit for energizing an electromagnetic deflection coil within a cathode ray tube display device, including:
- second means cooperative with the first means and responsive to a change in line timebase frequency for compensating a variation in the correction signal generated by the first means in response to said change in line timebase frequency;
- wherein the improvement comprises:
- the first means including a non-linear inductor comprising a core of a magnetically permeable material, a permanent magnet fastened to the core, a first coil wound onto the core, and wherein the second means comprises a second coil wound onto the core and insulated from the first coil, and
- regulating means for regulating current in the second coil induced by changes in current in the first coil.
A deflection circuit for energizing an electromagnetic deflection coil of a cathode ray tube display device comprising:
- sawtooth wave generating means for supplying a sawtooth current to said electromagnetic deflection coil;
- linearity correction means for generating a correction signal to correct an asymmetric non-linearity in said sawtooth current, said linearity correction means including:
- a non-linear inductor having a first coil in series with said deflection coil, and a second coil electromagnetically coupled to said first coil,
- regulating means connected across said second coil for regulating the amount of current flowing in said second coil as a result of voltage induced in said second coil by changes in current in said first coil, and
- control means for controlling said regulating means in response to a supply voltage supplied to energize said sawtooth wave generating means.
Dependencies are inferred from the claim text.