Browse Prior Art Database

Programmable Very Low Frequency Magnetic Compensation for Displays

IP.com Disclosure Number: IPCOM000035672D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Anstrup, F: AUTHOR [+4]

Abstract

There is a growing concern that very low frequency (VLF) magnetic fields may have ill effects on human beings. A major source of the low frequency magnetic fields in display monitors comes from the high voltage deflection system. Generally, maximum intensity of this field exists on the side or in the rear of the monitor in close proximity to the physical location of the flyback transformer. In some cases, the deflection yoke is the largest contributor. Thus, front-of-screen radiation will be of greater concern.

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Programmable Very Low Frequency Magnetic Compensation for Displays

There is a growing concern that very low frequency (VLF) magnetic fields may have ill effects on human beings. A major source of the low frequency magnetic fields in display monitors comes from the high voltage deflection system. Generally, maximum intensity of this field exists on the side or in the rear of the monitor in close proximity to the physical location of the flyback transformer. In some cases, the deflection yoke is the largest contributor. Thus, front-of-screen radiation will be of greater concern.

During production of monitors/displays, the magnetic "signature" could be obtained with equipment shown in Fig. 1. Stored signatures

(Image Omitted)

and correction waveform data from previous monitors would be used as a starting reference for generating a correction waveform for the monitor under test.

Active coils placed on the deflection yoke, CRT, and interior of the monitor are driven by a waveform generator, (see Fig. 2). Under program control, the PC would vary each correction parameter of the waveform while monitoring signals fed back from the equipment shown in Fig. 1. A final correction waveform would then be loaded into a PROM or fed across the I2C bus to the waveform generator.

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