Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2001-10-17
2003-02-18
Nguyen, Hoang (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S370000
Reexamination Certificate
active
06522091
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a raster display system and, more particularly, to a circuit and method that allows the amplitudes of vertical correction signal components to be adjusted independently.
2. Related Art
Raster display system are used in a variety of application such as televisions and computer displays.
FIG. 1A
shows a cross-sectional side view of a conventional raster display system
100
. Raster display system
100
includes an electron gun
110
, a deflection system
120
, and a screen
130
. Electron gun
110
generates and accelerates an electron beam
115
toward deflection system
120
. Deflection system
120
deflects electron beam
115
horizontally and/or vertically at screen
130
. Screen
130
includes a phosphor-coated faceplate that glows or phosphoresces when struck by electron beam
115
.
Deflection system
120
includes a horizontal deflection generator
122
, a horizontal deflection coil
124
, a vertical deflection generator
126
, and a vertical deflection coil
128
. Horizontal deflection coil
124
and vertical deflection coil
128
are collectively referred to as the yoke. Although not shown, horizontal deflection coil
124
and vertical deflection coil
128
are wound a ninety-degree angle relative to one another. Horizontal deflection generator
122
generates a horizontal deflection current signal I
H
. When horizontal deflection current signal I
H
passes through horizontal deflection coil
124
, a magnetic field is created that deflects electron beam
115
horizontally. The horizontal angle of deflection (not shown) is proportional to the direction and the magnitude of horizontal deflection current signal I
H
. Similarly, vertical deflection generator
126
generates a vertical deflection current signal I
V
. When vertical deflection current signal I
V
passes through vertical deflection coil
128
, a magnetic field is created that deflects electron beam
115
vertically. The vertical angle of deflection &thgr; is proportional to the direction and the magnitude of vertical deflection current signal I
V
.
FIG. 1B
is a front view of raster display system
100
. Deflection system
120
deflects electron beam
115
from a first side of screen
130
to a second side of screen
130
to draw a first line L
1
. Electron beam
115
is then briefly turned off, moved downward, and brought back to the first side of screen
130
by deflection system
120
. Electron beam
115
is then turned on and deflection system
120
deflects electron beam
115
from the first side of screen
120
to the second side of screen
130
to draw a second line L
2
. This process continues very rapidly so that lines L
3
through L
N
(where N=1, 2, 3, . . . , N) are drawn thereby creating a raster on screen
130
.
To produce an accurate image, the distance d
N
(where n=1, 2, 3, . . . , N) between each horizontal line L
N
drawn on screen
130
must be equal as shown in FIG.
1
B. The distance between each horizontal line d
N
is a function of two factors: the vertical angle of deflection &thgr; and the shape of screen
130
. If the shape of the screen is spherical, a vertical deflection current signal I
V
having a sawtooth shaped waveform can be used. A sawtooth shaped waveform can be used since the distance from the point of deflection
129
to the upper, center, and lower portions of the curved screen is constant. If the shape of the screen is non-spherical (e.g., a flat screen), a vertical deflection current signal I
V
having a more complex S-shaped waveform must be used. An S-shaped waveform must be used since the distance from the point of deflection
129
to the upper and lower portions of a non-spherical screen is greater than the distance from the point of deflection
129
to the center portions of a non-spherical screen. Note that if the shape of the screen is non-spherical and a vertical deflection current signal I
V
having a sawtooth shaped waveform is used, the distance d
N
between horizontal lines L
N
drawn on screen
130
will not be an equal from one another as shown in FIG.
1
C. This degrades the quality of the image drawn on screen
130
and thus is commercially undesirable.
As is well-known in the art, an S-shaped waveform can be produced by combining a sawtooth waveform with higher-order odd multiples of the sawtooth waveform. In particular, S-shaped waveforms be produced by combining the following components: a first-order signal component (i.e., a sawtooth signal), a third-order signal component, and a fifth-order signal component. Other higher-order odd signal components can also be combined with the sawtooth waveform to produce a more complex S-shaped waveform.
FIG. 2
shows waveforms for a first-order signal component
210
, a third-order signal component
220
, and a fifth-order signal component
230
, respectively.
FIG. 3
shows a conventional horizontal deflection generator circuit
300
that can be used to generate a vertical deflection current signal I
V
having an S-shaped waveform. Horizontal deflection generator circuit
300
includes a first-order signal generator
302
, a first-order amplitude signal generator
304
, a multiplier
306
, a third-order signal generator
308
, a third-order amplitude signal generator
310
, a multiplier
312
, a fifth-order signal generator
314
, a fifth-order amplitude signal generator
316
, a multiplier
318
, and a signal combiner
320
.
In operation, first-order signal generator
302
generates a first-order signal S
1
and first-order amplitude signal generator
304
generates a first-order amplitude signal A
1
. Multiplier
306
multiplies first-order signal S
1
with first-order amplitude signal A
1
to generate a first-order vertical correction signal component A
1
S
1
. Third-order signal generator
308
generates a third-order signal S
3
and third-order amplitude signal generator
310
generates a third-order amplitude signal A
3
. Multiplier
312
multiplies third-order signal S
3
with third-order amplitude signal A
3
to generate a third-order vertical correction signal component A
3
S
3
. Fifth-order signal generator
314
generates a fifth-order signal S
5
and fifth-order amplitude signal generator
316
generates a fifth-order amplitude signal A
5
. Multiplier
318
multiplies fifth-order signal S
5
with fifth-order amplitude signal A
5
to generate a fifth-order vertical correction signal component A
5
S
5
.
Signal combiner
320
combines the vertical correction signal components A
1
S
1
, A
3
S
3
, and A
5
S
5
to produce vertical correction signal A
V
S
V
. Vertical correction signal A
V
S
V
can be equivalent to vertical deflection current signal I
V
, or vertical correction signal A
V
S
V
can be further processed (e.g., amplified) prior to becoming vertical deflection current signal I
V
.
During the manufacturing process of a raster display system, a user must adjust amplitude signals A
1
, A
3
, and A
5
so that lines L
1
through line L
N
(where N=1, 2, 3, . . . , N) are properly drawn on screen
130
. First, the user adjusts amplitude signal A
1
so that line L
1
is drawn at the proper position at the top of screen
130
. This is referred to as setting the vertical size (i.e., the maximum angle of vertical deflection &thgr;
MAX
). Next, the user adjusts amplitude signals A
3
and A
5
so that the distances d
N
between each horizontal line L
N
drawn on screen
130
are equal as shown in FIG.
1
B. Unfortunately, when the user adjusts amplitude signals A
3
and A
5
, the vertical size changes. As a result, the user must readjust amplitude signal A
1
to reposition line L
1
at the proper position at the top of screen
130
. However, the readjustment of amplitude signal A
1
causes the distances d
N
between each horizontal line L
N
drawn on screen
130
to become unequal again. Consequently, the user must readjust amplitude signals A
3
and A
5
so that the distances d
N
between each horizontal line L
N
drawn on screen
130
are equal. Unfortunately, the adjustment of amplitude signal
Nguyen Hoang
Skjerven Morrill LLP
ZiLOG, Inc.
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