Browse Prior Art Database

Permanent CRT Image Centering

IP.com Disclosure Number: IPCOM000100909D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 77K

Publishing Venue

IBM

Related People

Dickerson, JA: AUTHOR [+4]

Abstract

Correction for beam landing errors is required for all CRT/ITC (Cathode Ray Tube/Integrated Tube & Component) assemblies to compensate for the effects of external magnetic field and CRT manufacturing variations. Compensation has traditionally been accomplished with the use of discrete centering rings. A pair of adjustable ring magnets (assembled into one unit) is placed on the neck of the CRT near the focus electrode. This magnet-pair has two poles. The ring assembly is physically rotated until the image is centered on the face of the CRT (Fig. 1).

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Permanent CRT Image Centering

       Correction for beam landing errors is required for all
CRT/ITC (Cathode Ray Tube/Integrated Tube & Component) assemblies to
compensate for the effects of external magnetic field and CRT
manufacturing variations. Compensation has traditionally been
accomplished with the use of discrete centering rings.  A pair of
adjustable ring magnets (assembled into one unit) is placed on the
neck of the CRT near the focus electrode.  This magnet-pair has two
poles.  The ring assembly is physically rotated until the image is
centered on the face of the CRT (Fig. 1).

      Heat-shrinkable tubing has already been used to provide
non-slip attachment between a CRT and deflection yoke.  A dual-wall
shrink tube is now modified to include a thin sleeve of barium
ferrite-loaded polypropylene (Fig. 2). This material (considered to
be a soft magnetic compound due to mechanical flexibility) will be
magnetized with a pole-pattern and strength unique to this CRT
assembly.

      A TV/camera/monitor system is used for yoke alignment and
centering.  Vertical, horizontal and centering patterns are
externally generated for both the alignment monitor and CRT assembly
to be aligned.  When yoke alignment is completed, a hot air gun is
used to shrink the tubing for firm attachment between the CRT and
yoke.

      Centering is accomplished with an electromagnet assembly which
is placed temporarily around the barium ferrite sleeve.  Six
electromagnet...