Apparatus for deflecting electron beams and color cathode ray tube apparatus incorporating this deflecting apparatus

A deflecting apparatus includes a saturable reactor, and this saturable reactor is constituted by a first saturation control coil and a second saturation control coil for generating a magnetic field having an opposite polarity to that of the first saturation control coil. The first saturation control coil is connected to a resistor to form a first deflection current system, and the second saturation control coil is connected in series with a pair of diodes that are connected to have opposite polarities, thereby forming a second deflection current system connected in parallel with the first deflection current system. The first and second saturation control coils are magnetically coupled to first and second impedance control coils respectively connected to horizontal deflection coils. Thus, a horizontal deflection current is controlled by the first and second impedance control coils in accordance with the vertical deflection current flowing through the first and second saturation control coils, thereby adjusting the horizontal deflection magnetic field in accordance with vertical deflection of the electron beams. As a result, a cross convergence error between the pair of side beams can be corrected simultaneously. This correction can be performed even when the deviation amounts of the cross convergence error differ among the intermediate and upper and lower end portions of the screen.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a deflecting apparatus for a color cathode 
ray tube and a color cathode ray tube apparatus, and more particularly, to 
a deflecting apparatus for a color cathode ray tube which has a saturable 
reactor for changing a horizontal deflection current flowing through a 
horizontal deflection coil that generates a magnetic field deflected in a 
direction parallel to a direction along which electron beams are aligned, 
in synchronism with a vertical deflection current flowing through a 
vertical deflection coil that generates a magnetic field deflected in a 
direction perpendicular to the electron beam aligning direction, and a 
color cathode ray tube apparatus. 
2. Description of the Related Art 
Generally, a color cathode ray tube apparatus shown in FIG. 1 has an 
envelope having a panel 1 and a funnel 2 that are integrally bonded to 
each other. A shadow mask 3 having a large number of apertures formed 
therein to pass electron beams therethrough is mounted on the inner side 
of the panel 1, and a phosphor screen 4 having a three color phosphor 
layers that emit blue light, green light, and red light is formed on the 
inner surface of the panel 1 to oppose the shadow mask 3. In this color 
cathode ray tube apparatus, three electron beams BR, BG, and BB emitted 
from an electron gun assembly 6 disposed in a neck 5 of the funnel 2 are 
deflected in the horizontal and vertical directions by a magnetic field 
generated by a deflection yoke 7 mounted on the outer side of the funnel 2 
to scan the phosphor screen 4. As the result of this electron beam 
defection scanning, a color image is displayed on the phosphor screen 4. 
The deflection yoke 7 for deflecting the electron beams BR, BG, and BB is 
usually constituted by a pair of saddle type horizontal deflection coils 8 
through which a horizontal deflection current flows to scan the electron 
beams in the horizontal direction, a pair of vertical deflection coils 9 
through which a vertical deflection current flows to scan the electron 
beams in the vertical direction, and separators 10 between the horizontal 
and vertical deflection coils 8 and 9, as shown in FIG. 2. I the 
deflecting apparatus shown in FIG. 2, the vertical deflection coils 9 
comprise a pair of upper and lower toroidal deflection coils. The vertical 
deflection coils 9 may comprise a pair of right and left saddle type 
deflection coils, as is known well. 
In color cathode ray tube apparatuses of this type, an in-line type color 
cathode ray tube apparatus is widely used. In an in-line type color 
cathode ray tube apparatus, an in-line type electron gun assembly is 
incorporated, in which three electron guns are horizontally aligned in 
line to emit three electron beams consisting of a center beam and a pair 
of side beams. The in-line type color cathode ray tube apparatus employs a 
self convergence system to form an non-uniform magnetic field, in which 
horizontal and vertical deflection magnetic fields generated by the 
deflection yoke have a pin cushion shape and a barrel shape, respectively. 
The three electron beams are self-focused on the phosphor screen by this 
non-uniform magnetic field. 
In this self convergence and in-line type color cathode ray tube apparatus, 
however, various types of screen distortions occur due to the 
characteristics of the tube and the tube assembly error. One of such 
screen distortions is a cross convergence error, in which deflection of 
the electron beams in the horizontal direction and a convergence error 
occur simultaneously. Due to the convergence error, cross convergence 
error patterns as shown in FIGS. 3A to 3D are displayed on the screen. 
Regarding correction of such a cross convergence error pattern, 
conventionally, Published Unexamined Japanese Patent Application Nos. 
57-206184, 2-194791, and the like disclose a color cathode ray tube 
apparatus comprising a saturable reactor for differentially changing the 
current flowing through a pair of horizontal deflection coils in 
synchronism with a vertical deflection current to change the shape of the 
horizontal deflection magnetic field on a time-base manner, thereby 
correcting the convergence error. 
Usually, the saturable reactor consists of a first impedance control coil 
connected to an upper one of a pair of upper and lower horizontal 
deflection coils and wound on a saturable core, a second impedance control 
coil connected to the lower horizontal deflection coil and wound on 
another saturable core, and saturation control coils connected to the 
vertical deflection coils. 
The direction of a magnetic field generated by the saturation control coil 
similarly wound on the saturable core on which one impedance control coil 
is wound is opposite to that of the magnetic field generated by one 
impedance control coil, and static magnetic fields are applied to these 
impedance control coils in advance. 
The function of the saturable reactor will be described with reference to 
FIGS. 4A and 4C. Referring to FIG. 4A, an axis of abscissa H represents 
the strength of the magnetic field generated outside the saturable core, 
and an axis of ordinate L represents the inductance of the impedance 
control coils. Referring to FIG. 4A, solid and broken lines 12 and 13 
represent the L-H characteristics of the two impedance control coils. 
Reference symbol H.sub.mag indicates a static magnetic field applied from 
the outside of the saturable cores; and H.sub.vm, a magnetic field 
generated by the saturation control coils. A curve 12 indicated by the 
solid line and a curve 13 indicated by the broken line are symmetric with 
each other about the static magnetic field H.sub.mag, because the magnetic 
fields generated by the saturation control coils and applied to the two 
impedance control coils are directed in opposite directions. When a 
vertical deflection current flows in the saturation control coils, the 
magnetic field H.sub.vm is generated, and the static magnetic field 
H.sub.mag and the magnetic field H.sub.vm are added so that inductances 
L.sub.u and L.sub.d of the impedance control coils are changed in 
synchronism with vertical deflection. FIG. 4B shows changes in inductances 
L.sub.u and L.sub.d. Referring to FIG. 4B, the axis of ordinate represents 
the inductance, and the axis of abscissa represents a vertical deflection 
current. The correction amount for a cross convergence error by such a 
saturable reactor is almost proportional to the difference between the 
inductances L.sub.u and L.sub.d of the two impedance control coils. Thus, 
the correction amount plots the correction pattern indicated by a curve 16 
shown in FIG. 4C. 
Conventionally, a cross convergence error pattern of a color cathode ray 
tube apparatus has patterns represented in FIGS. 3E and 3F. In the recent 
years, however, as the panel of a color cathode ray tube is flatly formed, 
and complicated convergence and distortion correction mechanisms are 
added, a pattern in which the cross convergence error amount at each of 
the upper and lower end portions of the screen is smaller than that at 
each of the upper and lower intermediate portions of the screen, as shown 
in FIG. 3G, and a pattern in which the polarity of the cross convergence 
error at each of the upper and lower end portions of the screen is 
opposite to that at each of the upper and lower intermediate portions of 
the screen, as shown in FIG. 3H, are often formed. 
In the conventional saturable reactor, since the correction amount is 
monotonously increased with respect to the vertical deflection current, 
although correction of the cross convergence error patterns as shown in 
FIGS. 3E and 3F is possible, it is difficult to correct the cross 
convergence error patterns as shown in FIGS. 3G and 3H. Hence, in the 
color cathode ray tube apparatus incorporating a conventional saturable 
reactor, a sufficient improvement in the image quality cannot be obtained. 
Another screen distortion is a coma error which is generated since the 
deflection sensitivity for the center beam becomes relatively higher than 
that for a pair of side beams. More specifically, in the self convergence 
system in-line type color cathode ray tube apparatus, rasters 11B and 11R 
of the pair of side beams BB and BR can be set to coincide with each other 
throughout the entire area of the screen, as shown in FIG. 5, without 
requiring a correcting circuit means. However, due to the difference in 
deflection sensitivity between the center beam BG and the pair of side 
beams BB and BR, it is difficult to set a raster 11G of the center beam BG 
and the rasters 11B and 11R of the pair of side beams BB and RB to 
coincide with each other, and a coma error, i.e., horizontal and vertical 
direction coma errors HCR and VCR occur on each end of the horizontal axis 
(X axis) and each end of the vertical axis (Y axis), respectively, of the 
screen. 
In the ordinary in-line type color cathode ray tube apparatus, this coma 
error can be corrected by disposing, to the electrode of the beam-emitting 
end portion of the electron gun assembly, a magnetic element called a 
field controller which has a function of relatively decreasing the 
deflection sensitivity for the pair of side beams to be lower than that 
for the center beam. When, however, a horizontal deflection frequency is 
changed to a high frequency, a convergence deviation is caused by the AC 
loss of the magnetic element. Therefore, many in-line type color cathode 
ray tube apparatuses correct the coma by the magnetic field of the 
deflection yoke itself without using a magnetic element. In this case, the 
coma error HCR can be corrected by the horizontal deflection coil itself 
as the deviation amount is small. However, it is difficult to correct the 
coma error VCR by the vertical deflection coil, as it has a large 
correction amount, and the coma error VCR remains uncorrected. Therefore, 
the coma error VCR is corrected by the following deflecting system. That 
is, auxiliary cores, obtained by winding coils respectively on a pair of 
U-shaped cores and connecting these coils to vertical deflection coils in 
series, are disposed at a side end portion (rear end portion) of the 
electron gun assembly of the deflection yoke to be vertically symmetric 
about the horizontal axis, and a pin cushion shape magnetic field is 
generated to correspond to the barrel vertical deflection magnetic field 
for vertical deflection. A means for controlling the operation of the 
auxiliary coils by diodes in order to efficiently correct the coma VCR 
throughout the entire area of the screen is shown in, e.g., Published 
Unexamined Japanese Patent Application No. 63-225462 (U.S. Pat. No. 
4,818,919). 
When the screen distortion is increased from the central portion of the 
screen toward the upper and lower end portions of the screen, as described 
above, it can be corrected to a certain degree. However, when the screen 
distortion at each of the upper and lower intermediate portions of the 
screen is larger than the screen distortion at each of the upper and lower 
end portions of the screen, sufficient correction cannot be performed. 
Published Unexamined Japanese Patent Application Nos. 63-195935, 1-175150, 
and 1-183042 describe a means for forming a saturation control coil with 
two coils and controlling one coil by a diode. With this means, although 
cross convergence errors having patterns as shown in FIGS. 3E and 3F can 
be corrected, cross convergence errors having patterns as shown in FIGS. 
3G and 3H cannot be corrected. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a deflecting apparatus 
for a color cathode ray tube, which can effectively correct screen 
distortions at upper and lower intermediate portions and upper and lower 
end portions of a screen and which has a high degree of design flexibility 
for a correction amount, and a color cathode ray tube apparatus. 
According to the present invention, there is provided an apparatus for 
deflecting electron beams in accordance with first and second deflection 
currents comprising: 
a pair of first deflection coils, energized by the first deflection 
currents, for generating a first magnetic field to deflect the electron 
beams in a first direction; 
at least one second deflection coil, energized by the second deflection 
current, for generating a second magnetic field to deflect the electron 
beams in a second direction; 
first and second impedance control coils connected to first deflection 
coils and having first and second impedances, respectively; 
a saturable core on which the impedance control coils are wound; 
a first saturation control coil, supplied with the second deflection 
current and magnetically coupled with the first and second impedance 
control coils, for generating a first control magnetic field having a 
polarity and changing the first and second impedance of the first and 
second impedance control coils to restrict the level of the first 
deflection current flowing through the first deflection coils; 
a second saturation control coil, connected in parallel with said first 
saturation control coil and magnetically coupled with the first and second 
impedance control coils, for generating a second control magnetic field 
having an opposite polarity to that of the first control magnetic field 
and changing the first and second impedance of the first and second 
impedance control coils to restrict the level of the first deflection 
current flowing through the first deflection coils; and 
a parallel diode circuit connected in series with the second saturation 
control coil and including a pair of parallel-connected diodes having 
opposite directions. 
According to the present invention, there is also provided a deflecting 
apparatus for a color cathode ray tube, wherein at least a resistor is 
connected in series with the first saturation control coil to constitute a 
first deflection current system, and a second deflection current system 
constituted by the second saturation control coil and a pair of diodes 
having opposite polarities is connected in parallel with the first 
deflection current system, so that the deflection current flowing through 
the second deflection coils can be shunted into the first and second 
deflection current systems, and that generation of magnetic fields having 
opposite polarities can be controlled by the diodes. 
According to the present invention, there is also provided a deflecting 
apparatus for a color cathode ray tube, comprising, in addition to the 
arrangement described above, two pairs of sub coils for generating 
auxiliary magnetic fields in synchronism with the current flowing through 
the second deflection coils, wherein one of the two pairs of sub coils are 
connected to the second deflection current system. 
According to the present invention, there is also provided a color cathode 
ray tube apparatus comprising: 
first signal generating means for generating a first deflection signal; 
second signal generating means for generating a second deflection signal; 
an in-line type electron gun assembly for generating a center beam and a 
pair of side beams that are aligned in line in a first direction; 
a pair of first deflection coils, energized by the first deflection 
currents, for generating a first magnetic field to deflect the electron 
beams in a first direction; 
at least one second deflection coil, energized by the second deflection 
current, for generating a second magnetic field to deflect the electron 
beams in a second direction; 
first and second impedance control coils connected to first deflection 
coils and having first and second impedances, respectively; 
a saturable core on which the impedance control coils are wound; 
a first saturation control coil, supplied with the second deflection 
current and magnetically coupled with the first and second impedance 
control coils, for generating a first control magnetic field having a 
polarity and changing the first and second impedance of the first and 
second impedance control coils to restrict the level of the first 
deflection current flowing through the first deflection coils; 
a second saturation control coil, connected in parallel with said first 
saturation control coil and magnetically coupled with the first and second 
impedance control coils, for generating a second control magnetic field 
having an opposite polarity to that of the first control magnetic field 
and changing the first and second impedance of the first and second 
impedance control coils to restrict the level of the first deflection 
current flowing through the first deflection coils; and 
a parallel diode circuit connected in series with the second saturation 
control coil and including a pair of parallel-connected diodes having 
opposite directions. 
According to the present invention, there is also provided a color cathode 
ray tube apparatus, wherein at least a resistor is connected in series 
with the first saturation control coil to constitute a first deflection 
current system, and a second deflection current system constituted by the 
second saturation control coil and a pair of diodes having opposite 
polarities is connected in parallel with the first deflection current 
system, so that the deflection current flowing through the second 
deflection coils can be shunted into the first and second deflection 
current systems, and that generation of magnetic fields having opposite 
polarities can be controlled by the diodes. 
According to the present invention, there is also provided a color cathode 
ray tube apparatus, comprising, in addition to the arrangement described 
above, two pairs of sub coils for generating auxiliary magnetic fields in 
synchronism with the current flowing through the second deflection coils, 
wherein one of the two pairs of sub coils are connected to the second 
deflection current system. 
The deflecting apparatus according to the present invention basically 
corrects, of the screen distortions, the cross convergence errors of a 
pair of side beams. The inductances of the impedance control coils 
connected to a pair of first deflection coils that deflect the electron 
beams in a direction along which they are aligned are changed by the 
magnetic field generated by the saturation control coils, through which 
the deflection current flowing through the second deflection coils flows, 
in synchronism with the deflection in the second direction, so as to 
generate a differential current between the pair of first deflection 
coils, thereby correcting the cross convergence error. 
At this time, the saturation control coils are constituted by the first and 
second saturation control coils. At least a resistor is connected in 
series with the fist saturation control coil to constitute the first 
deflection current system. The second deflection current system 
constituted by the second saturation control coil and a pair of diodes 
having opposite polarities is connected in parallel with the first 
deflection current system, thereby forming a shunt path of the deflection 
currents. Therefore, before the diodes are turned on, the deflection 
current flows through the first deflection current system, and no current 
flows through the second deflection current system. When the diodes are 
turned on, the deflection current is shunted to the second deflection 
current system. At this time, since the first and second deflection 
current systems are connected in parallel with each other, when the diodes 
are turned on, the deflection current is shunted to the second deflection 
current, and the current that has been flowing through the first 
deflection current system no longer increases. Since the second saturation 
control coil generates a magnetic field having a polarity opposite to that 
of the magnetic field generated by the first saturation control coil, a 
magnetic field opposite to the magnetic field generated by the first 
saturation control coil is also applied to the saturable core on which the 
impedance control coils of the saturable reactor are wound. That is, up to 
the upper and lower intermediate portions of the screen, the saturable 
reactor is operated by the first saturation control coil. When the diodes 
are turned on, the amount of the entire magnetic field as the whole 
saturation control coils is adjusted by the shunt ratio of the first to 
second deflection current systems and the magnetic field generated by the 
second saturation control coil itself. 
As a result, the correction pattern of a required cross convergence error 
can be obtained by appropriately setting the amount of magnetic field 
which is generated by the saturation control coils in synchronism with the 
deflection current. 
Furthermore, according to the present invention, a coma error VCR caused 
between the center beam and the side beams in the upper and lower sides of 
the screen can also be corrected simultaneously based on the following 
principle. 
More specifically, correction of the coma error VCR is performed by two 
pairs of sub coils for generating auxiliary magnetic fields in synchronism 
with the current flowing through the second deflection coil, which is 
generates a deflection magnetic field that deflects the electron beams in 
the second direction perpendicular to the first direction. Correction of 
the cross convergence error caused by the pair of side beams is performed 
by changing the inductances of the impedance control coils connected to 
the pair of first deflection coils, which deflect the electron beams in 
the direction along which they are aligned, by the magnetic field 
generated by the saturation control coils through which the deflection 
current flowing through the second deflection coil flows in synchronism 
with deflection in the second direction, so that a differential current is 
generated between the pair of first deflection coils. 
At this time, according to the present invention, the saturation control 
coils are constituted by the first and second saturation control coils. 
One of the two pairs of sub coils constitute the second deflection current 
system together with the diodes connected to the second saturation control 
coil to have opposite polarities. The first deflection current system 
constituted by the first saturation control coil and the resistor is 
connected in parallel with the second deflection current system. Hence, 
substantially no current flows to the second deflection current system 
until the diodes are turned on. Thus, the correction amount of the coma 
error VCR can be freely set by controlling one of the two pairs of sub 
coils by the diodes in synchronism with deflection in a direction 
perpendicular to the direction along which the electron beams are aligned. 
Since the first and second deflection current systems are connected in 
parallel with each other, when the diodes are turned on, the deflection 
current is shunted to the second deflection current system, and the 
current flowing through the first deflection current system no longer 
increases. Since the second saturation control coil is so wound as to 
generate a magnetic field having an opposite direction to that of the 
magnetic field generated by the first saturation control coil, when the 
diodes are turned on, the impedance control coils generate a magnetic 
field having an opposite polarity to that of the magnetic field generated 
by the first saturation control coil. Accordingly, the entire magnetic 
field generated by the saturation control coils as a whole of the 
saturable reactor is controlled by the turn-on operation of the diodes, so 
that the correction amount of the cross convergence error is also changed 
as the magnetic field is changed. 
In this manner, both the coma error VCR and the cross convergence error are 
corrected simultaneously in synchronism with deflection, thereby obtaining 
a desired correction pattern. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will be described with 
reference to the accompanying drawings. 
Embodiment 1 
FIG. 6 shows a saturable reactor circuit incorporated in a color cathode 
ray tube apparatus according to an embodiment of the present invention. As 
shown in FIG. 6, a horizontal deflection signal generating circuit 20 is 
connected to one end of each of a pair of upper and lower horizontal 
deflection coils 21 and 22, and impedance control coils 24a and 24b wound 
on a saturable core 23 are connected in series between the other end of 
the horizontal deflection coil 21 disposed in the upper side of the tube 
and the horizontal deflection signal generating circuit 20. Similarly, the 
horizontal deflection signal generating circuit 20 is connected to one end 
of the horizontal deflection coil 22 disposed in the lower side of the 
tube, and impedance control coils 26a and 26b wound on a saturable core 25 
are connected in series between the horizontal deflection signal 
generating circuit 20 and the other end of the horizontal deflection coil 
22 disposed in the lower side of the tube. Vertical deflection coils 31 
and 32 are connected in series with a vertical deflection signal 
generating circuit 30, and both of two saturation control coils 35a and 
35b are connected in series with the series circuit of the vertical 
deflection coils 31 and 32. The saturation control coils 35a and 35b are 
magneticaly coupled to the impedance control coils 24a, 24b, 26a and 26b. 
Accordingly, the impedance control coils 24a, 24b, 26a, and 26b, together 
with the saturation control coils 35a and 35b, constitute a saturable 
reactor for differentially changing the current flowing through the pair 
of horizontal deflection coils 21 and 22 in synchronism with the vertical 
deflection current. 
The saturable reactor differentially changes the horizontal deflection 
current having a high frequency in synchronism with the vertical 
deflection current having a relatively low frequency, as described above. 
Static magnetic fields are applied from magnets (not shown) to the 
impedance control coils 24a, 24b, 26a, and 26b. Furthermore, the two 
saturation control coils 35a and 35b have opposite polarities, that is, 
the magnetic field generated by the first saturation control coil 35a has 
an opposite polarity to that of the magnetic field generated by the second 
saturation control coil 35b. To obtain magnetic fields having opposite 
polarities, for example, the second saturation control coil 35b may be 
wound coaxially with and in the opposite direction to the first saturation 
control coil 35a. 
The total magnetic field from the saturation coils 35a and 35b has a same 
polarity to that of the static magnetic field of the one of the magnets 
and an opposite polarity to that of the static magnetic field of the other 
of the magnets. 
A resistor 40 and a choke coil 41 are connected to the first saturation 
control coil 35a to form a first deflection current system, and a pair of 
parallel-connected diodes 42 and 43 having opposite polarities are 
connected to the second saturation control coil 35b to form a second 
deflection current system. The first and second deflection current systems 
are connected in parallel with each other to constitute a circuit for 
shunting the vertical deflection current. 
The operation and function of the saturable reactor of this embodiment will 
be described. 
FIG. 7 shows the configuration of the series circuit connected to the 
vertical deflection signal generating circuit 30 of FIG. 6. In the 
deflecting apparatus having a saturable reactor according to this 
embodiment, a vertical deflection current I.sub.v flowing through the 
vertical deflection coils 31 and 32 is shunted into a current I.sub.1 
flowing through the first deflection current system and a current I.sub.2 
flowing through the second deflection current system, and the current 
I.sub.2 flowing through the second deflection current system is controlled 
by the pair of diodes 42 and 43. 
The relationship between the vertical deflection current I.sub.v and the 
correction amount will be described with reference to FIGS. 8A and 8B. 
FIG. 8A shows the relationship between the vertical deflection current 
I.sub.v and the currents I.sub.1 and I.sub.2 flowing through the first and 
second deflection current systems. The current I.sub.2 does not flow until 
either the diode 42 or 43 is turned on, and the current I.sub.2 is rapidly 
increased after the pair of diodes 42 and 43 are turned on. At this time, 
since the first and second deflection current systems are connected in 
parallel with each other, when the current I.sub.2 is shunted to the 
second deflection system, as the vertical deflection current I.sub.v is 
increased, the current I.sub.1 flowing through the first deflection 
current system is not linearly increased, as indicated by a broken line, 
but is gradually decreased as indicated by a solid line. The second 
saturation control coil 35b in the second deflection current system 
generates a magnetic field having an opposite polarity to that of the 
magnetic field generated by the first saturation control coil 35a. 
Accordingly, after either the diode 42 or 43 is turned on, a magnetic 
field H.sub.2 generated by the second saturation control coil 35b is 
rapidly increased, as shown in FIG. 8B. At this time, since the current 
I.sub.1 flowing through the first deflection current system is decreased, 
as the vertical deflection current I.sub.v is increased, the magnetic 
field H.sub.1 generated by the first saturation control coil 35a is not 
increased linearly, as indicated by the broken line, but an increase in a 
magnetic field H.sub.1 is declined. As a result, the magnetic field as the 
saturation control coil as a whole is decreased compared to that obtained 
by only the first saturation control coil 35a before the diode 42 or 43 is 
turned on, and the external magnetic field applied to the impedance 
control coils 24a, 24b, 26a and 26b is decreased. That is, the magnetic 
field obtained by the saturation control coils 35a and 35b becomes maximum 
at the intermediate portion of the screen where the diode 42 or 43 is 
turned on. The saturable reactor controls the horizontal deflection 
current by changing the inductances of the impedance control coils 24a, 
24b, 26a and 26b by the magnetic fields generated by the saturation 
control coils 35a and 35b, as described above. Thus, the correction amount 
of the cross convergence error can be changed between the central portion 
and the upper and lower end portions of the screen by controlling the 
magnetic fields generated by the saturation control coils 35a and 35b. 
Various types of correction patterns can be formed by adjusting the 
magnetic fields generated b the first and second saturation control coils 
35a and 35b and the turn-on points of the diodes 42 and 43, and any cross 
convergence error can be accurately corrected by appropriately selecting a 
correction pattern. More specifically, when the curve of the correction 
amount has a gradient as shown in FIG. 3C, the gradient of curve of 
correction amount can be adjusted by the amplitude of the magnetic field 
generated by the first saturation control coil 35a, the position on the 
screen where the maximum correction amount is obtained can be adjusted by 
the current level that turns on the diode 42 or 43, in other words, the 
maximum correction amount can be adjusted by the position on the screen to 
which the beam is directed by vertical deflection, and the gradient of the 
curve of the correction amount after the diode 42 or 43 is turned on can 
be adjusted by a shunt ratio I.sub.1 /I.sub.2 of the first and second 
deflection current systems or the strength of the magnetic field generated 
by the second saturation control coil 35b. The magnetic field can be 
adjusted by changing the shunt ratio of the first and second deflection 
current systems and the number of turns of each saturation control coil. 
In the circuit shown in FIG. 7, the choke coil 41 is arranged in the 
circuit. The choke coil 41 adjusts the induced electromotive force 
generated in a closed circuit constituted by the first and second 
deflection current systems. That is, the sum of the induced electromotive 
forces generated by coils in other closed circuits is adjusted by the 
induced electromotive force generated by the choke coil 41, thereby 
relaxing the transitional induced electromotive force at start of 
scanning. 
In this embodiment, the configuration of the saturable reactor, especially 
the configuration of the the impedance coils connected to horizontal 
deflection signal generating circuit 20, is not described in detail. 
However, any type of conventional saturation reactor can be utilized as 
far as its saturation control coils connected to the vertical deflection 
coils have arrangements as shown in this embodiment. 
In FIGS. 6 and 7, the saturation control coils 35a and 35b are connected to 
the vertical deflection coils 31 and 32. However, the saturation control 
coils may not be connected to the vertical deflection coils to directly 
flow the vertical deflection current. 
As described above, according to this embodiment, the various types of 
deviation patterns of the cross convergence errors can be corrected by 
dividing the saturation control coils of the saturable reactor into a coil 
of the forward direction and a coil of the reverse direction, connecting 
these saturation control coils in parallel with each other, and 
controlling the saturation control coils by diodes. Circuit design for 
this purpose can be easily performed. 
Embodiment 2 
The deflecting apparatus for a color cathode ray tube described in 
Embodiment 1 is incorporated in a color cathode ray tube apparatus as 
follows. 
The color cathode ray tube apparatus has a general structure as shown in 
FIG. 1 and has an envelope consisting of a panel 1 and a funnel 2 that are 
integrally bonded. A shadow mask 3 having a large number of electron beam 
holes formed therein is mounted on the inner side of the panel 1. A 
phosphor screen 4 having three color phosphor layers that emit blue light, 
green light, and red light upon landing of the electron beams is formed on 
the inner surface of the panel 1 to oppose the shadow mask 3. An electron 
gun assembly 6 is disposed in a neck 5 of the funnel 2. Three electron 
beams BR, BG, and BB emitted by the electron gun assembly 6 are deflected 
by the magnetic field generated by a deflection yoke 7 mounted on the 
outer side of the funnel 2. The phosphor screen 4 is scanned in the 
horizontal and vertical directions by the three deflected electron beams 
BR, BG, and BB, to display a color image on the phosphor screen 4. 
As described above, the deflection yoke 7 for deflecting the electron beams 
BR, BG, and BB is constituted by a pair of saddle type horizontal 
deflection coils 8 through which a horizontal deflection current flows to 
scan the electron beams in the horizontal direction, a pair of vertical 
deflection coils 9 through which a vertical deflection current flows to 
scan the electron beams in the vertical direction, and separators 10 
between the horizontal and vertical deflection coils 8 and 9, as shown in 
FIG. 2. In FIG. 2, the vertical deflection coils 9 comprise a pair of 
upper and lower toroidal type deflection coils. However, the vertical 
deflection coils 9 may comprise a pair of right and left saddle type 
deflection coils. Generally, the electron guns are horizontally aligned in 
line to form in-line type electron guns for emitting three electron beams 
consisting of a center beam and a pair of side beams. Horizontal and 
vertical deflection magnetic fields generated by the deflection yoke have 
a pin cushion shape and a barrel shape, respectively, to constitute an 
non-uniform magnetic field. The three electron beams are self-converged on 
the phosphor screen by this non-uniform magnetic field. Namely, the 
in-line type color cathode ray tube apparatus employs the self convergence 
system. 
The deflecting apparatus of this embodiment has a circuit as shown in FIG. 
6. In the embodiment shown in FIG. 6, the second deflection current system 
constituted by a second saturation control coil 35b and a pair of diodes 
42 and 43 is connected in parallel with the first deflection current 
system including a first saturation control coil 35a. This aims at 
shunting the current flowing through the first saturation control coil 35a 
to the diodes 42 and 43 to decline its increase, and to generate in the 
second saturation control coil 35b a magnetic field of the opposite 
direction to that generated by the first saturation control coil 35a, 
thereby effectively performing magnetic field inversion. 
Embodiment 3 
In some color cathode ray tube apparatus, in addition to a cross 
convergence error, a coma error VCR appears simultaneously. An embodiment 
for solving this problem will be described. 
FIG. 9 is a perspective view showing a deflecting apparatus for a color 
cathode ray tube according to still another embodiment of the present 
invention. A deflecting apparatus 50 is mainly constituted by first 
deflection coils (not shown in FIG. 9) for deflecting the electron beams 
aligned in line in their aligning direction, second deflection coils 51 
for deflecting the electron beams in a direction perpendicular to the 
aligning direction of the beams, separators 52 located between these 
deflection coils, and two pairs of sub coils 54a and 54b, and 55a and 55b 
disposed at an electron gun-side rear end portion 53 of the separators 52. 
The sub coils 54a and 54b are respectively wound on a pair of U-shaped 
cores 56a and 56b disposed to be substantially symmetric about the 
aligning axis (X-axis) of the electron beams, and the sub coils 55a and 
55b are respectively wound on a pair of rod-like cores 57a and 57b 
disposed on the aligning axis (X-axis) of the electron beams. Although not 
shown in FIG. 9, the first and second deflection coils are connected to a 
saturable reactor that differentially changes the output current in 
synchronism with the input current by utilizing a change in inductance 
caused by the magnetic field. Usually, the electron beams are horizontally 
aligned in line, the first deflection coils correspond to the horizontal 
deflection coils 8 shown in FIG. 2, and the second deflection coils 
correspond to the vertical deflection coils 9 shown in FIG. 2. 
The circuit configuration of the deflecting apparatus shown in FIG. 9 will 
be described with reference to FIG. 10. As shown in FIG. 10, a horizontal 
deflection signal generating circuit 60 is connected to one end of each of 
a pair of upper and lower horizontal deflection coils 61 and 62, and 
impedance control coils 64a and 64b wound on a saturable core 63 are 
connected in series between the other end of the upper horizontal 
deflection coil 61 and the horizontal deflection signal generating circuit 
60. Impedance control coils 66a and 66b wound on a saturable core 65 are 
connected in series between the other end of the lower horizontal 
deflection coil 62 and the horizontal deflection signal generating circuit 
60. Furthermore, a vertical defection signal generating circuit 70 is 
connected in series with vertical deflection coils 71 and 72, the series 
circuit of the vertical deflection coils 71 and 72 is connected in series 
with first sub coils 73a and 73b, the series circuit of the first sub 
coils 73a and 73b is connected in series with second sub coils 74 a and 
74b. Saturation control coil 75a is connected in series with the series 
circuit of the first sub coils 73a and 73b and saturation control coil 75b 
is connected in series with the series circuit of the second sub coils 74a 
and 74b and saturation control coils 75a and 75b is in a parallel 
relation. The impedance control coils 64a and 64b are wound on the 
saturable core 63, and the impedance control coils 66a and 66b are wound 
on the saturable core 65. The saturation control coils 75a and 75b are 
magnetically coupled to the impedance control coil 64a, 64b, 66a, and 66b. 
Accordingly, the impedance control coils 64a, 64b, 66a, and 66b, together 
with the saturation control coils 75a and 75b, constitute a saturable 
reactor for differentially changing the current flowing through the pair 
of horizontal deflection coils 61 and 62 in synchronism with the vertical 
deflection current. 
The saturable reactor differentially changes the horizontal deflection 
current in synchronism with the vertical deflection current, as described 
above. The total magnetic field from the saturation coil 75a and 75b has 
the same polarity as the static magnetic field of one of the magnets and 
an opposite polarity to the static magnetic field of the other of the 
magnets. Static magnetic fields are applied by magnets (not shown) in 
advance to the saturable cores 63 and 65 on which the impedance control 
coils 64a and 64b, and 66a and 66b are wound. Furthermore, the two 
saturation control coils 75a and 75b have opposite polarities, that is, 
the magnetic field generated by the first saturation control coil 75a has 
an opposite polarity to that of the magnetic field generated by the second 
saturation control coil 75b. To obtain magnetic fields having opposite 
polarities, for example, the second saturation control coil 75b may be 
wound coaxially with and in the opposite direction to the first saturation 
control coil 75a. 
A resistor 80 and a choke coil 81 are connected in series with the first 
saturation control coil 75a to form a first deflection current system DC1, 
and a pair of parallel-connected diodes 91 and 9 having opposite 
polarities are connected in series with the series circuit of the second 
sub coils 74a and 74b and the second saturation control coil 75b to form a 
second deflection current system DC2. The second deflection current system 
is connected in parallel with the first deflection current system. 
The operation and function of the circuit shown in FIG. 10 will be 
described. 
FIG. 11 shows the configuration of the series circuit connected to the 
vertical defection signal generating circuit 70 of FIG. 10. In the 
circuits shown in FIGS. 10 and 11, the deflecting apparatus mainly has a 
saturable reactor and sub coils. A vertical deflection current I.sub.v 
flowing through the vertical deflection coils 71 and 72 and a pair of sub 
coils 73a and 73b, of the two pairs of sub coils, is shunted into a 
current I.sub.10 flowing through the first deflection current system DC1 
constituted by the series circuit of the first saturation control coil 75a 
and the resistor 80, and a current I.sub.20 flowing through the second 
deflection current system DC2 constituted by the other pair of sub coils 
74a and 74b, of the two pairs of sub coils, the second saturation control 
coil 75b, and the pair of diodes 91 and 92 having opposite polarities. The 
current flowing through the second deflection current system DC2 is 
controlled by the diodes 91 and 92. 
The relationship between the vertical deflection current and the correction 
amount will be described with reference to FIGS. 12A, 12B, and 12C. FIG. 
12A shows the relationship between the vertical deflection current I.sub.v 
and the currents I.sub.10 and I.sub.20 flowing through the first and 
second deflection current systems DC1 and DC2. The current I.sub.20 does 
not flow until either the diode 91 or 92 is turned on, and the current 
I.sub.20 is rapidly increased after the pair of diodes 91 and 92 are 
turned on. Of the two pairs of sub coils, one pair of sub coils 74a and 
74b are connected to the second deflection current system DC2. 
Accordingly, when the diodes 91 and 92 are turned on, a correction B 
obtained by the sub coils 74a and 74b is added to the correction amount A 
obtained by the sub coil 73a and 73b, as shown in FIG. 12B. As a result, a 
coma error VCR in which the deviation amount is increased toward the upper 
end of the screen can be corrected. That is, the vertical deflection 
current I.sub.v is flowed to the first deflection current system DC1 up to 
the turn-on point of the diode, e.g., up to the intermediate portion of 
the screen. Accordingly, only a VCR correction A is applied to the 
electron beams by the pin-cushion magnetic fields generated by the sub 
coils 73a and 73b wound on a pair of U-shaped cores. The VCR correcting 
function by means of the pin-cushion magnetic fields is based on the same 
principle as that of the conventional correction. In the intermediate 
portion toward the upper and lower end portions of the screen, when the 
diodes are turned on and the deflection current is shunted also to the 
second deflection current system DC2, the correction B obtained by the 
barrel magnetic fields generated by the second sub coils 74a and 74b wound 
on the pair of rod-like cores is also applied to the electron beams. The 
VCR correction by means of the barrel magnetic fields is based on the same 
principle as that of the conventional correction. 
Since the first and second deflection current systems DC1 and DC2 are 
connected in parallel with each other, as the current is shunted to the 
second deflection current system DC2 because the diodes are turned on, an 
increase in current I.sub.10 of the first deflection current system DC1 is 
declined or the current I.sub.10 is decreased. The second saturation 
control coil 75b generates a magnetic field having a polarity opposite to 
that of the magnetic field generated by the first saturation control coil 
75a. Thus, after the diodes are turned on, a magnetic field H.sub.v2 
generated by the second saturation control coil 75b is rapidly increased, 
as shown in FIG. 12C. Therefore, when the diodes are turned on, the 
deflection current is shunted to the second deflection current system DC2, 
and the second saturation control coil 75b starts to generate a magnetic 
field having an opposite polarity. Also, since the current flowing through 
the first deflection current system DC1 is decreased, an increase in 
magnetic field generated by saturation control coil 75a is declined. As a 
result, the magnetic field generated by the saturation control coil as a 
whole is decreased when compared to the magnetic field obtained by only 
the first saturation control coil 75a before the diodes are turned on, and 
the external magnetic field applied to the impedance control coils is 
decreased. Therefore, the correction amount of the cross convergence error 
can be changed between the intermediate portion and the upper and lower 
end portions of the screen. 
The correction pattern of the cross convergence error can be changed by 
adjusting the magnetic fields generated by the first and second saturation 
control coils 75a and 75b and the scanning points of the electron beams 
when the diodes 91 and 92 are turned on, thereby forming an appropriate 
correction pattern. More specifically, when the curve of the correction 
amount has a gradient as shown in FIG. 3C, the gradient can be adjusted by 
the amplitude of the magnetic field generated by the first saturation 
control coil 75a, the position on the screen where the maximum correction 
amount is obtained can be adjusted by the turn-on positions of the diodes, 
and the gradient of the curve of the correction amount after the diode 91 
or 92 is turned on can be adjusted by a shunt ratio of the first and 
second deflection current systems or the strength of the magnetic field 
generated by the second saturation control coil 75b. The magnetic field 
can be adjusted by changing the shunt ratio of the first and second 
deflection current systems and the number of turns of each saturation 
control coil. 
In this embodiment, the choke coil 81 is arranged in the circuit. The choke 
coil 81 adjusts the induced electromotive force generated in a closed 
circuit constituted by the first and second deflection current systems. 
That is, the sum of the induced electromotive forces generated by coils in 
other closed circuits is adjusted by the induced electromotive force 
generated by the choke coil 81, thereby relaxing the transitional induced 
current at start of scanning. 
In this embodiment, the configuration of the saturable reactor, especially 
the configuration of the horizontal deflection signal generating circuit 
60, is not described in detail. However, any type of conventional 
saturation reactor can be utilized as far as its saturation control coils 
connected to the vertical deflection coils have arrangements as shown in 
this embodiment. 
In this embodiment, concerning correction of the coma VCR, positive 
correction is performed in the intermediate portion of the screen by one 
of two pairs of sub coils, and is performed in the intermediate portion 
toward the upper and lower end portions of the screen by the other pair of 
sub coils. The magnetic fields generated by the two pairs of sub coils can 
be set in accordance with the pattern of the coma error VCR, and this 
embodiment can also be applied to decreasing the correction amount of the 
coma VCR in the intermediate portion toward the upper and lower end 
portions of the screen by performing negative correction. 
In FIGS. 10 and 11, the saturation control coils and the sub coils are 
connected to the vertical deflection coils. However, the saturation 
control coils may not be connected to the vertical deflection coils to 
directly flow the vertical deflection current. 
As described above, according to this embodiment, the various types of 
deviation patterns of the cross convergence errors can be corrected by 
constituting the sub coils for performing VCR correction with two pairs of 
sub coils, providing two saturation control coils as the saturation 
control coil of the saturable reactor, and controlling one pair of sub 
coils and one of two pairs of saturation control coils by diodes. Circuit 
design for this purpose can be easily performed. 
Embodiment 4 
Still another embodiment of the present invention will be described. 
Embodiment 3 described above shows an arrangement in which the sub coils 
of each of two pairs are wound on different cores. However, one sub coil 
of one of the two pairs can be wound on the same core as that on which the 
other sub coil of the other of the two pairs is wound. FIG. 13 shows a 
circuit configuration in which one sub coil of one of the two pairs is 
wound on the same core as that on which the other sub coil of the other of 
the two pairs is wound. Note that in FIG. 13 the same reference numerals 
indicate the same parts as in FIG. 10. In this embodiment, two pairs of 
sub coils are wound on one pair of U-shaped cores. Before the diodes are 
turned on, VCR correction is performed by the pin-cushion magnetic fields 
formed by one pair of sub coils, and after the diodes are turned on, 
pin-cushion magnetic fields formed by the other pair of sub coils are 
applied. Connection among the sub coils to be connected to the vertical 
deflection signal generating circuit, the saturation control coils, the 
diodes, the resistor, and the like is the same as that shown in FIG. 11, 
and the operational principle of this embodiment is the same as that 
described in above Embodiment 3. 
Embodiment 5 
Both Embodiments 3 and 4 described above are related to a deflecting 
apparatus for a color cathode ray tube. A color cathode ray tube apparatus 
according to an embodiment of the present invention will be described. 
The overall configuration of the color cathode ray tube apparatus is the 
same as that shown in FIG. 1, and its deflecting apparatus for deflecting 
the electron beams is the same as that shown in FIG. 2. 
The deflecting apparatus of this embodiment has a circuit configuration as 
that shown in FIG. 10 or 13. Accordingly, its detailed arrangement and 
function are the same as those of Embodiments 3 and 4. The coma VCR and 
the cross convergence error can be corrected simultaneously, and the 
correction pattern at this time can be adjusted by a shunt ratio of the 
first to second deflection current systems, the number of turns of the 
first and second saturation control coils, and the like. 
The screen distortion cannot sometimes be sufficiently corrected even if 
optimum design is performed by using the circuits indicated in some of the 
embodiments described above. That is, an imbalance to the polarity of the 
deflection current sometimes occurs due to the influences of the 
difference between the turn-on/turn-off characteristics of the diodes, the 
difference between the upper and lower blank portions of vertical 
deflection of the color cathode ray tube, and the like. An imbalance can 
be caused by asymmetry in design of a deflection yoke and a color cathode 
ray tube. In addition, an imbalance can be caused by a manufacturing 
variation in the deflection yoke or the color cathode ray tube. These 
imbalances cause correction imbalance between the upper and lower sides of 
the screen, thus degrading the convergence characteristics of the color 
cathode ray tube. 
These imbalances can be decreased by using a pair of diodes having 
different operating voltages or by adhering a magnetic or magnet piece to 
the deflection yoke portion. When, however, a pair of diodes having 
different operating voltages are used, problems such as an increase in 
types of diode pairs to be used, an increase in selection range of the 
operating voltage, and the like are posed. Also, when the imbalances are 
to be corrected by adhering a magnetic or magnet piece to the deflection 
yoke portion, only an imbalance in the peripheral portion of the screen 
can be mainly corrected, and an imbalance in the central portion of the 
screen cannot be easily corrected. 
In this case, an impedance element is connected in series with at least one 
of parallel-connected diodes having opposite polarities, thereby adjusting 
the impedance. 
More specifically, when a resistor 93 is connected in series as an 
impedance element with one of parallel-connected diodes having opposite 
polarities, as shown in FIG. 14, the diode resistance obtained when the 
diode to which the impedance element is connected is operative is 
increased. Also, when a resistor 94 is connected as shown in FIG. 15, the 
resistance of the diode pair can be controlled. Then, the shunt ratio of 
the current I.sub.10 to the current I.sub.20 can be adjusted between the 
upper and lower sides of the screen. More specifically, when an imbalance 
occurs in shunt ratio between the upper and lower sides of the screen, 
modulation characteristics well-balanced between the upper and lower sides 
of the screen can be obtained by connecting an appropriate impedance 
element in series with one diode. Hence, in a color cathode ray tube 
having an intentionally designed imbalance, the resistance is adjusted in 
accordance with the imbalance of a necessary correction amount to adjust 
the correction pattern within the regions indicated by hatched lines in 
FIGS. 16A and 16B, thereby improving the image characteristics. 
Also, a variable resistor or a variable inductance element may be connected 
in parallel with a pair of diodes having opposite polarities in a 
deflection signal generating circuit, as shown in FIG. 17, thereby 
controlling the modulation characteristics of the deflection current 
obtained by the diode pair. 
In FIG. 17, a bypass circuit is connected in parallel with the pair of 
diodes. Therefore, even when the diodes are insulated, the current I.sub.v 
is shunted into the first and second defecting systems in accordance with 
the impedance of the bypass circuit, and the current I.sub.2 in FIG. 18 
has a certain current value within the zero region. Similarly, the current 
I.sub.1 is decreased by I.sub.v -I.sub.2, and the operating point of the 
diodes is shifted toward the end of the vertical axis. 
FIG. 18A shows changes in currents I.sub.1 and I.sub.2 caused by the 
presence/absence of the bypass circuit, and FIGS. 18B and 18C show changes 
in correction patterns of the coma error VCR and the cross convergence 
error, respectively. The resistance of the bypass circuit is adjusted in 
accordance with the imbalance of a necessary correction amount to adjust 
the correction pattern with in the regions indicated by hatched lines in 
FIGS. 18B and 18C. 
In this manner, the correction pattern of mainly the diode non-operative 
region can be changed by the bypass circuit. Since this bypass circuit 
does not generate an induced electromotive force or hardly changes the 
resistance in the closed circuit portion, it does not cause an adverse 
influence by the induced current of the closed circuit portion when 
scanning is started. Namely, since re-adjustment of the choke coil is not 
needed, the impedance of the bypass circuit can be independently adjusted, 
so that the bypass circuit can easily serve as the means for absorbing the 
variation in the color cathode ray tube. 
In FIGS. 14, 15, and 17, sub coils for correcting the coma VCR are also 
connected. However, these sub coils need not be connected so that only the 
cross convergence error can be corrected. 
As has been described above, according to the present invention, a 
saturation control coil assembly constituting a saturable reactor is 
constituted by two parallel-connected coils having opposite directions, 
and the reverse-direction saturation control coil is controlled by diodes, 
so that screen distortion correction can be performed even when screen 
distortions at upper and lower intermediate portions of the screen are 
larger than those at upper and lower end portions of the screen. 
Furthermore, a desired correction pattern can be obtained by controlling 
the turn-on timings of the diodes and the shunt ratio of the deflection 
currents. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept a defined by the 
appended claims and their equivalents.