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Browse Prior Art Database

Video Signal Regulation using Luminance Measurement

IP.com Disclosure Number: IPCOM000109004D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 102K

Publishing Venue

IBM

Related People

Harley, M: AUTHOR

Abstract

Disclosed is a method for regulating the levels of input to VDUs driven by widely toleranced video signals derived from external adapters. Regulation of such signals at the input to displays is required for consistent set-up and inspection to ensure greater adherence to product front-of-screen specifications. The measurement principle used is to relate observed screen luminance to controlled video signal variations while holding all other conditions constant. No extra equipment other than that already in use for production is needed.

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Video Signal Regulation using Luminance Measurement

       Disclosed is a method for regulating the levels of input
to VDUs driven by widely toleranced video signals derived from
external adapters.  Regulation of such signals at the input to
displays is required for consistent set-up and inspection to ensure
greater adherence to product front-of-screen specifications.  The
measurement principle used is to relate observed screen luminance to
controlled video signal variations while holding all other conditions
constant.  No extra equipment other than that already in use for
production is needed.

      Over the period of the regulation process, there will be no
variation of any image characteristic (if conditions such as stable
magnetic field, power supply and ambient lighting are ensured) other
than those caused by variation in the input video signals.  If the
level of video signals only is changed with the same pattern
displayed, then luminance measured at the screen center will vary in
accordance.  If these signal levels are not so low as to fail to turn
on the screen phosphor, or so high as to cause saturation effects,
then any input level will have a uniquely associated luminance.
Thus, two input levels must be equal if the luminance levels they
produce in the same display, under the same conditions, are equal.

      To regulate a set-up or inspection system configuration, a
display is placed on the relevant set-up/inspection fixture and
driven by known reference video signals from a calibrated pattern
generator or a preselected "standard" display adapter.  The luminance
of the display is measured at the screen center and recorded as in
Fig. 1: an input signal of say 0.7 volt will give a luminance
response of Y Cd/m2 .

      The system to be regulated is connected to the display using
the hardware configuration that is used in the conventional
set-up/inspection process; i.e., any video extension cables, buffers,
etc.  This system is then used to display the same pattern as before.
Changes in the luminance of the image will be in accordance with
difference between the system's video signal levels and those of the
reference.  Fig. 2 shows the effect of the difference in video signal...