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Browse Prior Art Database

Raster Tilt Control for CRT Displays

IP.com Disclosure Number: IPCOM000117273D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Hillan, JM: AUTHOR [+2]

Abstract

Displayed images on monochrome monitors, as received and upon rotation in situ can appear tilted to the operator. This effect is caused by monochrome displays response to the earths magnetic fields relating to set field at manufacture.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Raster Tilt Control for CRT Displays

      Displayed images on monochrome monitors, as received and upon
rotation in situ can appear tilted to the operator.  This effect is
caused by monochrome displays response to the earths magnetic fields
relating to set field at manufacture.

      Disclosed is a technique to provide user control (digital) to
counteract earths field and to provide square image whatever
orientation of the display.  According to the technique, current is
driven into a coil fitted around the CRT (neck or bell) dependent on
design.  Adjustment of the tilted image is allowed, together with
storage of set values for subsequent power off/on cycle.  The
technique does not require a microprocessor to operate, just a simple
logic circuit of up/down counter / DAC and Sram with Op-amp final
drive to coil (Fig. 1).

Fig. 2 shows an example implementation.

      This solution is advantageous in that it can be retrofitted to
existing designs, or incorporated into new designs, easily.  It also
has memory function, without a need for a microprocessor.