Electric lamp and discharge devices: systems – Cathode ray tube circuits – Compensating for stray deflecting fields
Reexamination Certificate
1999-10-26
2002-12-31
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Compensating for stray deflecting fields
C315S370000
Reexamination Certificate
active
06501222
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a correction of earth magnetic field for a monitor of a computer, and more particularly, to an apparatus for automatically correcting an earth magnetic field for a monitor by which a correction of an earth magnetic field is automatically performed to thereby obtain a highly improved picture quality with distinct colors and an improved screen centering.
2. Description of the Background Art
In general, a magnetic field in a space is represented by a three dimensional vector, which affects a deflection of a monitor of a computer.
Accordingly, if a direction of the monitor is changed or the monitor is moved to other area, a peripheral magnetic field is changed, causing a damage to the picture quality of the monitor.
In order to resolve such a problem, some techniques for correcting an earth magnetic field has been proposed, which guarantees a distinct picture quality of the monitor
Of those are a Korean patent publication No. 96-16849 and a Korean Laid Open No. 95-24598.
First, one of conventional arts, the patent publication No. 96-16849 discloses an apparatus for correcting an earth magnetic field including: a standby power supply unit
11
for outputting a constant voltage Vcc as power is supplied; a remote controller
20
for setting an operation state of a TV system and selecting an earth magnetic field correction mode; a remote-controller receiving unit
19
for receiving a transmission signal of the remote-controller
20
; a pre-amplifier
18
for amplifying the output signal from the remote-controller receiving unit
19
to a predetermined level; a microprocessor
15
for decoding the output signal from the pre-amplifier
18
and outputting an on-screen display indicating a compass direction of a corresponding mode for setting a correction mode and a signal for controlling the corresponding mode when the earth magnetic field correction function is selected, upon receipt of the output Vcc from the standby power supply unit
1
; a chroma unit
16
for indicating the compass direction according to the setting of the correction mode of the CPT (color picture tube) upon receipt of the output signal from the microprocessor
15
; a current switching unit
14
for switching on and switching off a current flow of a device coil
12
according to a relay drive signal S
1
of the microprocessor
15
; and an earth magnetic field correction unit
17
for controlling the direction and the strength of the current according to mode signals S
3
-S
5
of the microprocessor
15
to minimize influence of the earth magnetic field.
The current switching unit
14
includes a transistor Q
1
and a relay RY
1
.
The earth magnetic field correction unit
17
includes transistors Q
7
and Q
8
of which an emitter is grounded through resistances R
10
and R
13
and a base is connected to output terminals S
3
and S
5
of the microprocessor
15
through resistances R
11
and R
14
, a transistor Q
2
of which an emitter is grounded and a base is connected to an output terminal S
4
of the microprocessor
15
through a resistance R
2
, transistors Q
3
, Q
4
, Q
5
and Q
6
of which each base is commonly connected to a terminal at one end of each resistance R
3
and R
4
and each emitter is commonly connected and an earth magnetic field correction coil L
2
and a condensor Cl are respectively connected between the contact points, transistors Q
3
and Q
5
of which collectors are commonly connected and its contact point is connected to a voltage B+through a resistance R
7
and the collector of the transistor Q
7
and a terminal at other end of the resistance R
3
are commonly connected through the resistance R
9
, and a collector of the transistor Q
8
is connected to a terminal at the other end of the resistance R
4
and its contact point is connected to the voltage B+through the resistance R
12
, and transistors Q
4
and Q
6
of which collectors are commonly connected and its contact point is grounded through a resistance R
5
, a resistance R
6
is connected to the collector of the transistor Q
2
through a resistance R
6
.
The remote-controller
20
includes a compass to identify a direction of the TV position, for the purpose of correcting the earth magnetic field.
The operational process of the apparatus for correcting an earth magnetic field in accordance with the conventional art will now be described with reference to
FIGS. 2 through 4
.
First, when the power is ON, the standby power supply unit
11
outputs the constant voltage Vcc to the input terminal S
2
of the microprocessor
15
, and accordingly, the microprocessor
15
in a standby state checks the output signal of the pre-amplifier
18
.
At this time, when the power key is in an OFF-state, the microprocessor
15
outputs the relay drive signal S
1
to the current switching unit
14
to turn off the transistor Q
1
to thereby turn off the relay RY
1
, and also outputs the earth magnetic field correction signals S
3
-S
5
of low voltage to maintain OFF-state of the system.
And, when a power key is inputted from the remote-controller by the user, the transmission signal of the remote-controller
20
is received by the remote-controller receiving unit
19
, and the received signal is amplified by the preamplifier
18
to a predetermined level and then outputted to the microprocessor
15
.
Upon receipt of the output signal from the pre-amplifier
18
, when the microprocessor
15
discriminates the input of the power supply key by decoding and outputs the relay drive signal S
1
to the current switching unit
14
, the transistor Q
1
is turned on to drive the relay RY
1
, according to which the contact points ‘a’ and ‘b’ are connected and power is supplied to the power supply unit
13
, so that the device coil
12
controls the current flow.
In other words, when the power is ON, a current flows through a thermister TH and the coil L
1
of the device coil
12
, and as time goes by, since a resistance value is increased according to temperature characteristics of the thermister TH, and thus, few current flows through the coil L
1
, the magnetic field of the monitor is degaussed.
Meanwhile, when the power is ON, the microprocessor
15
discriminates whether or not the earth magnetic field correction key was selected. In this respect, if there is no key selection, it returns to the initial step of the operation, while if the earth magnetic field correction key is selected by the remote-controller
20
by the user, the microprocessor
15
senses the key input through the remote-control receiving unit
19
and the pre-amplifier
18
and performs decoding. The microprocessor discriminates the selection of the earth magnetic field correction function by this decoding.
As the microprocessor
15
discriminates the selection of the earth magnetic field correction function by decoding the output signal from the preamplifier
18
, it outputs a compass direction indication signal OSD to the chroma unit
16
. Then, an on-screen display is displayed on a CPT (color picture tube) screen, and the user selects a corresponding key of the remote-controller
20
after ascertaining a direction of the TV position by using the compass attached on the remote-controller
20
, so that a mode corresponding to the direction of the TV set position can be set by shifting the earth magnetic field correction mode one step by one step.
That is, as the user presses down the earth magnetic field correction mode setting key of the remote-controller
20
after ascertaining the direction of the TV position, the microprocessor
15
outputs the on-screen display signal OSD of the corresponding mode to the chroma unit
16
, so that the on-screen display according to each mode is sequentially displayed on the screen of the CPT In this respect, at the time when the on-screen display identical to the direction of the TV position as identified by the compass attached on the remote-controller
20
is displayed, the user selects a set key to set a corresponding mode.
For example, if the TV set is
Kim Jin Sik
Kim Kyung Sic
LG Electronics
Ostrolenk Faber Gerb & Soffen, LLP
Vu David
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