Browse Prior Art Database

Grey Scale Tracking in Color VDUs

IP.com Disclosure Number: IPCOM000109565D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 112K

Publishing Venue

IBM

Related People

Grant, DA: AUTHOR [+2]

Abstract

Disclosed is a circuit to improve the set up of a color point in a VDU by collapsing the frame to provide a more intensely illuminated screen area. Benefits arising are utilized by manufacturing line test departments.

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This is the abbreviated version, containing approximately 52% of the total text.

Grey Scale Tracking in Color VDUs

       Disclosed is a circuit to improve the set up of a color
point in a VDU by collapsing the frame to provide a more intensely
illuminated screen area.  Benefits arising are utilized by
manufacturing line test departments.

      The CRT-based display has three electron guns.  Each
contributes to the overall luminance of the displayed picture.  The
ratios of the individual drives determine the color of the display.
The human eye is sensitive to coloration.  Some areas of a display
may only contain shades of grey which must be faithfully reproduced.
Adjustment of the picture contrast or drive level is as important a
part of displays as is the volume control on an audio product.  As
the drive levels are adjusted, a change in the hue of the display can
be detected.

      The display industry has adopted a color standard, based on the
illuminant D65 standard used by the TV studios for monitors, since
this point gave the most faithful reproduction.  The standard is
checked by all in assessment of product quality.  Many circuits exist
to attempt to control the tracking of the three CRT guns to meet this
standard over the full range of the controls.  The problem is that
the eye is most likely to detect chroma non-linearity in the lower
luminance levels which contain insufficient brightness for the
measurement equipment to operate.  If the tracking controls of any
given circuit could be set at low levels, 1 candela per meter squared
is ideal, then better performance is gained from any given circuit.

      The solution is a piece of circuitry which allows the picture
on a monitor to be collapsed to allow accurate set up of color-point
at low light levels.  It has the following features; requires minimal
additional components within the monitor; has a simple connection to
an external voltage source...