Television – Video display – Cathode-ray tube
Reexamination Certificate
1999-10-27
2003-05-13
Miller, John (Department: 2614)
Television
Video display
Cathode-ray tube
C348S805000, C348S806000, C348S380000, C315S370000, C315S401000
Reexamination Certificate
active
06563552
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image correcting method and device for correcting an image displayed on a cathode ray tube (CRT), for example, and a cathode ray tube display unit to which they are applied.
2. Description of the Background Art
FIG. 24
is a block diagram showing an image correcting device according to the prior art. The image correcting device shown in
FIG. 24
comprises a CR timer
1
, a microcomputer
2
a
, drivers
3
to
7
, first to fourth coils
8
to
11
for correcting landing (which will be hereinafter referred to as landing correcting coils), and a coil
12
for correcting convergence (which will be hereinafter referred to as a convergence correcting coil). The first to fourth landing correcting coils
8
to
11
and the convergence correcting coil
12
are fixed to a cathode ray tube (not shown).
When the cathode ray tube is turned on (the time that the cathode ray tube is turned on will be hereinafter referred to as “power ON”), a deterioration in the landing and convergence of the cathode ray tube starts to be caused. When the cathode ray tube is turned off (the time that the cathode ray tube is turned off will be hereinafter referred to as “power OFF”), the deterioration starts to be recovered. The CR timer
1
always operates also when the cathode ray tube is turned on and off. The CR timer
1
outputs a deterioration detecting signal TS according to the degree of the deterioration in the landing and the convergence.
The microcomputer
2
a
calculates an optimum correction current value from the deterioration detecting signal TS when a time passes after the power ON. The drivers
3
to
7
cause a correction current having the value calculated by the microcomputer
2
a
to flow to the first to fourth landing correcting coils
8
to
11
and the convergence correcting coil
12
. The first to fourth landing correcting coils
8
to
11
and the convergence correcting coil
12
properly regulate the landing and the convergence according to the correction current.
As described above, the image correcting device automatically corrects the landing and convergence of an image displayed on the cathode ray tube by supplying the correction current to the cathode ray tube.
FIGS. 25 and 26
show a state obtained immediately after the power ON and conventional changes in the landing and the convergence to a state obtained after the time fully passes (for example, three hours) since the state obtained immediately after the power ON. As shown in
FIGS. 25 and 26
, the landing and the convergence are not deteriorated immediately after the power ON. Therefore, an image is displayed in a desired position (that is, a displacement from the desired position of the image is a minimum (zero)). Thus, a state in which the image is displayed in the desired position will be referred to as a “just state”. The states of the landing and the convergence which are obtained at that time will be referred to as “just landing” and “just convergence”, respectively.
As the time passes after the power ON, the landing and the convergence are deteriorated and the image is shifted from the desired position and is displayed. When the time fully passes (for example, three hours) after the power ON, the deteriorations in the landing and the convergence are brought into a saturation state and the displacement from the desired position of the image becomes a maximum.
As shown in
FIG. 25
, for example, as the time passes after the power ON, an upper left portion of the image is shifted from the left to the right (in a direction F) from the desired position. In this case, if a proper correction current is caused to flow to the landing correcting coil provided for correction on the upper left portion of the image to move the upper left portion of the image in a direction reverse to the direction F, the just state can be obtained, that is, the image can be displayed in the desired position.
FIG. 27
shows a conventional relationship between a time (an elapsed time) which has passed after the power ON and a correction current and a displacement from a desired position of an image. As shown in
FIG. 27
, conventionally, the correction current has been increased with the passage of the time in order to keep the just state all the time.
However, after the time fully passes after the power ON, the correction current always flows at a maximum value. Accordingly, there has been a problem in that power is largely consumed when the cathode ray tube is to be used for a long time.
In order to solve the above-mentioned problem, it is an object of the present invention to provide an image correcting method and device capable of reducing power consumption required for correcting an image for a long-time use, and a cathode ray tube display unit.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to a method for automatically correcting an image displayed on a cathode ray tube by supplying a correction current to the cathode ray tube, comprising the step of monotonously decreasing the correction current more as a time passes after the cathode ray tube is turned on.
A second aspect of the present invention is directed to the image correcting method, further comprising the step of reducing a rate of the decrease in the correction current more as a time passes after the cathode ray tube is turned on.
A third aspect of the present invention is directed to the image correcting method, further comprising the step of causing the correction current to approximate to zero after the cathode ray tube is turned on.
A fourth aspect of the present invention is directed to the image correcting method, wherein an object for automatically correcting the image includes at least one of landing, convergence and a horizontal image position.
A fifth aspect of the present invention is directed to an image correcting device for automatically correcting an image displayed on a cathode ray tube by supplying a correction current to the cathode ray tube, comprising a calculating circuit for calculating a value of the correction current in such a manner that the correction current is more decreased monotonously as a time passes after the cathode ray tube is turned on, a driver for generating and outputting the correction current in accordance with a result of the calculation obtained by the calculating circuit, and a correcting device provided in the cathode ray tube for correcting the image displayed on the cathode ray tube on receipt of the correction current from the driver.
A sixth aspect of the present invention is directed to the image correcting device, wherein the calculating circuit calculates the value of the correction current in such a manner that a rate of the decrease in the correction current is more reduced as a time passes after the cathode ray tube is turned on.
A seventh aspect of the present invention is directed to the image correcting device, wherein the calculating circuit calculates the value of the correction current in such a manner that the correction current is caused to approximate to zero after the cathode ray tube is turned on.
An eighth aspect of the present invention is directed to the image correcting device, wherein the correcting device includes at least one of a coil for correcting landing, a coil for correcting convergence and a yoke for correcting a horizontal image position.
A ninth aspect of the present invention is directed to the image correcting device, further comprising an external terminal for giving data necessary for the calculating circuit to calculate the value of the correction current from an outside.
A tenth aspect of the present invention is directed to a cathode ray tube display unit comprising the image correcting device according to any of the fifth to ninth aspects of the present invention, and the cathode ray tube.
According to the first aspect of the present invention, the correction current is more decreased as the time passes. Consequently, the power consumption necessary for correcting the ima
Birch & Stewart Kolasch & Birch, LLP
Miller John
Natnael Paulos
NEC-Mitsubishi Electric Visual Systems Corporation
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