Browse Prior Art Database

Generation of User Perceived Linear Gray Scaling

IP.com Disclosure Number: IPCOM000103727D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Stein, F: AUTHOR

Abstract

Gray scales in LCD computer displays are typically generated by turning each individual pixel on for some frames and off for others, and allowing the LCD to average the value. Thus, a 50 percent gray is produced by turning a pixel on every other frame.

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This is the abbreviated version, containing approximately 51% of the total text.

Generation of User Perceived Linear Gray Scaling

       Gray scales in LCD computer displays are typically
generated by turning each individual pixel on for some frames and off
for others, and allowing the LCD to average the value.  Thus, a 50
percent gray is produced by turning a pixel on every other frame.

      Existing technology typically generates gray scales for LCD
displays in linear amplitude steps, which the eye perceives as
non-linear (non-equal) steps.  As a result, some gray scales are
harder to distinguish than others.

      This invention generates a non-linear series of gray scales to
compensate for the eye's perception of brightness.

      A linear gray scale is depicted in the table below.
           Color          Linear         Duty
                          Value          Ratio
           0              0              0
           1              .0625          1/10
           2              .125           2/16
           3              .1875          3/16
           4              .250           4/16
           5              .3125          5/16
           6              .375           6/16
           7              .4375          7/16
           8              .50            8/16
           9              .5625          9/16
           10             .625          10/16
           11             .6875         11/16
           12             .75           12/16
           13             .8125         13/16
           14             .875          14/16
           15             .9375         15/16
           16            1              16/16

      In the table above, 16 shades are generated.  These shades of
gray are relatively linear in intensity, but are not perceived as
having linear brightness by the users.  To design a series of easily
distinguished gray scales for the LCD, it was necessary to produce a
series of gray scales which, when measured by a photometer, are
spaced non-linearly.  The human eye perceives these gray shades as
being evenly spaced.

      One o...