Light display panel control

Details Light display panel control Light display panel control

2002-02-15

2004-06-29

Wu, Xiao (Department: 2674)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

Reexamination Certificate

active

06756952

ABSTRACT:

FIELD OF THE DISCLOSURE
The present invention relates to illuminated display panels.
BACKGROUND OF THE DISCLOSURE
More specifically, the invention relates to an illuminated display panel having at least one matrix of light pixels, each pixel comprising at least three monochrome electric light elements emitting light respectively in at least three complementary colors, operation of the light elements being controlled by an electronic control system which determines an electrical power P applied to each light element, this electrical power being expressed in the form of P=k.Pr, where:
Pr is a reference electrical power specific to the light elements of each color
and k is a real number at least equal to 0, selected as a function of the display to be presented on the panel.
Known display panels of this type enable illuminated displays to be presented in color.
However, the light elements are generally provided in the form of electroluminescent diodes of differing technologies depending on the colors, which means that aging in these diodes differs from one color to another. This results in a drift in the colors of the illuminated panel over a period of time.
The particular objective of this invention is to overcome this disadvantage.
SUMMARY OF THE DISCLOSURE
To this end, the invention proposes an illuminated display panel of the type in question essentially characterized in that the electronic control system is set up to vary the reference electrical power Pr specific to the light elements of each color over time, in accordance with a different predetermined variation depending on the colors, in order to compensate, at least partially, for the effects of aging of the light elements.
As a result of these features, any drift in the colors of the illuminated panel over time is prevented or at least reduced.
In preferred embodiments of the invention, one and/or the other of the following features may be incorporated:
the electronic control system is set up so as to measure and store an operating time of the light elements, this electronic control system also having numerical values in memory enabling a theoretical reference electrical power Pt to be determined depending on the operating time of said light elements, this theoretical reference electrical power differing depending on the colors, and said electronic control system being set up to determine the reference electrical power Pr corresponding to each color by means of the formula: Pr=a.Pt+b, where a is a positive constant that is not zero and b is a constant at least equal to 0, a and b being specific to each color;
a=1; b=0;
a=1 and b is a value determined on the basis of experimental light intensity measurements conducted on the panel;
b=0 and a is a value determined on the basis of experimental light intensity measurements conducted on the panel;
the operating time of the light elements is measured per group of light elements and the theoretical reference electrical power Pt is also determined for the same groups of light elements;
the values a and b are common to all the light elements of a same color belonging to the panel;


REFERENCES:
patent: 5493183 (1996-02-01), Kimball
patent: 5812105 (1998-09-01), Van de Ven
patent: 5936599 (1999-08-01), Reymond
patent: 6618031 (2003-09-01), Bohn et al.
patent: 0 702 347 (1996-03-01), None
patent: 2 106 299 (1983-04-01), None
French Preliminary Search Report dated May 25, 1999, French Application FR 9900475.

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