Electron gun with a dynamic driving quadrupole lens for a color cathode ray tube

An electron gun having an improved circuitry for driving the electron gun, which includes a cathode ray tube accommodating at least a cathode, a control electrode, a first acceleration electrode, a convergence electrode comprising first and second grids sandwiching at least a quadrupole lens and a second acceleration electrode. The circuitry is provided with a voltage divider having first and second ends which are electrically connected between the control electrode and the first grid respectively. The voltage divider being electrically connected to at least a dc power supply to apply a bias between the first and second ends of the voltage divider so that the first and second ends of the voltage divider have first and second voltage levels which are different by the bias from each other. The voltage divider has a voltage dividing point between the first and second ends. The voltage dividing point further has a third voltage level which is leveled between the first and second voltage levels which are applied to the control electrode and the first grid respectively. The voltage dividing point is electrically connected to the first the acceleration electrode so that the first acceleration electrode has the third voltage level.

BACKGROUND OF THE INVENTION 
The present invention relates to an electron gun, and more particularly to 
an electron gun with a dynamic driving quadrupole lens for a color cathode 
ray tube. 
A color cathode ray robe having an in-line electron gun has been known in 
the art, to which the invention pertains. The color cathode ray tube 
utilizes a self-convergence system, wherein a deflection yoke is used to 
generate non-uniformly deflected magnetic fields which comprise a 
horizontal deflection magnetic field whose magnetic field distribution has 
a pincushion shape and a vertical deflection magnetic field whose magnetic 
field distribution has a barrel shape. The non-uniformly deflected 
magnetic fields may act as a magnetic lens having an astigmatism, which 
provides electron beams with both a divergence in a horizontal direction 
and a convergence in a venial direction. For this reason, electron beams 
shows a long-side way strain. The divergence force in the vertical 
direction and the convergence force in the horizontal direction are 
dynamically changed depending upon a deflection position of beam spot on a 
screen. 
In order to settle the above problem, it was proposed to use an electron 
gun having a dynamic driving quadrupole lens. This is disclosed in the 
Japanese laid-open patent application No. 2-183946. As illustrated in FIG. 
1, the electron gun having the dynamic driving quadrupole lens comprises a 
cathode 1, a control electrode 20 a first acceleration electrode 3, a 
first grid 4, a second grid 5 and a second acceleration electrode 6. The 
first and second grids 4 and 5 form a convergence electrode. Namely, the 
first grid 4 has three pairs of circular arc burrings 4a which face to 
each other in a horizontal direction. The second grid 5 has three pairs of 
circular arc burrings 5a, both of which face to each other in a vertical 
direction. The first and second grids 4 and 5 are combined with each other 
so that the circular arc burrings 4a and the circular arc burrings 5a are 
engaged with each other whereby the circular arc burrings 4a and the 
circular arc burrings 5a form a quadrupole lens 7 as illustrated in FIG. 
2. 
The above conventional electron gun is driven as follows. The control 
electrode 2 is applied with a control voltage Ec1. The first acceleration 
electrode 3 is applied with a first acceleration voltage Ec2. The first 
grid 4 of the convergence electrode is applied with a constant focus 
voltage Ec3. The second grid 5 of the convergence electrode is applied 
with a dynamic voltage Ec3d which dynamically varies, as illustrated in 
FIG. 3, depending upon positions on a screen receiving irradiation of 
electron beam. As a result, the quadrupole lens 7 provides the electron 
beam with the divergence force in the vertical direction and the 
convergence force in the horizontal direction as illustrated in FIG. 4. 
Those vertical divergence and horizontal convergence forces do compensate 
the long side way strain of the electron beam, wherein the long side way 
strain is due to the deflected magnetic field caused by the deflection 
yoke. Namely, the long side way strain of the electron beam, which is 
caused by the deflected magnetic field generated by the deflection yoke, 
is canceled by the vertical divergence and horizontal convergence forces 
provided by the quadrupole lens 7, whereby beam spot free of strain can be 
obtained. 
The above electron gun with the quadrupole lens 7 is, however, engaged with 
the following disadvantages. As illustrated in FIG. 5, the cathode 1, the 
control electrode 2, the first acceleration electrode 3, the first grid 4, 
the second grid 5 and the second acceleration electrode 6 are arranged in 
turn. In addition, the second acceleration electrode 6 is connected via a 
resistor 9 to the ground and connected to a dc power supply so that the 
second acceleration electrode 6 is applied with a high voltage, for 
example, about 25 kV. The convergence electrode 8 is connected to a 
desired intermediate point of the resistor to achieve a resistive division 
of the resistor 9 so that the convergence electrode 8 is applied with a 
desired voltage generated by the voltage division due to the resistive 
division. Since, however, the high voltage, for example, about 25 kV is 
divided by the resistive division, there exists problems in withstand 
voltage and in reliability of the electron gun device. In order to prevent 
the problems, an extremely careful operation is required to manufacture 
the electron gun. Those matters are disclosed in the Japanese laid-open 
patent application No. 3-67442. Further, in order to drive the dynamic 
quadrupole lens 7, it is required to apply not only the constant focus 
electrode Ec3 but also the dynamic voltage Ec3d. This means that it is 
required to provide not only a power supply for supplying the constant 
focus electrode Ec3 but also another power supply for supplying the 
dynamic voltage Ec3d. This further means that it is required to provide an 
additional voltage supply pin for the additional power supply for driving 
the dynamic quadrupole lens 7. Namely, the number of the voltage supply 
pins provided in the conventional electron gun with the dynamic quadrupole 
lens 7 has to be larger by at least one than the number of the voltage 
supply pins provided in the standard electron gun free of any dynamic 
quadrupole lens. The conventional and standard voltage supply pin 
connection configuration is inapplicable to the conventional dynamic 
quadrupole lens electron gun. In the above circumstances, it had been 
required to develop a novel dynamic driving quadrupole lens electron gun 
having the same number of voltage supply pins as the normal electron gun 
free of dynamic quadrupole lens. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
electron gun with dynamic driving quadrupole lens, which is free from the 
above disadvantages and problems. 
It is a further object of the present invention to provide an electron gun 
with dynamic driving quadrupole lens, which is provided with an improved 
and simple driving circuit configuration making the electron gun free from 
the above disadvantages and problems. 
It is a furthermore object of the present invention to provide an electron 
gun with dynamic driving quadrupole lens, which is provided with an 
improved and simple driving circuit configuration having the same 
connection configuration for voltage supply pin, as an electron gun free 
of dynamic driving quadrupole lens. 
It is moreover an object of the present invention to provide an electron 
gun with dynamic driving quadrupole lens, which is provided with an 
improved and simple driving circuit configuration having the same number 
of voltage supply pins as an electron gun free of dynamic driving 
quadrupole lens. 
It is still more object of the present invention to provide an electron gun 
with dynamic driving quadrupole lens, which is provided with an improved 
and simple driving circuit configuration requiring no extra power supply 
for driving the dynamic driving quadrupole lens. 
It is still a further object of the present invention to provide an 
electron gun with dynamic driving quadrupole lens, which is provided with 
an improved and simple driving circuit configuration being compatible to 
standard interfaces. 
The above and other objects, features and advantages of the present 
invention will be apparent from the following descriptions. 
The present invention also provides an electron gun having an improved 
circuitry for driving the electron gun. The electron gun includes a 
cathode ray tube which accommodates at least a cathode, a control 
electrode, a first acceleration electrode, a convergence electrode 
comprising first and second grids sandwiching at least a quadrupole lens 
and a second acceleration electrode. The circuitry is provided with a 
voltage divider having first and second ends which are electrically 
connected between the control electrode and the first grid respectively. 
The voltage divider being electrically connected to at least a dc power 
Supply to apply a bias between the first and second ends of the voltage 
divider so that the first and second ends of the voltage divider have 
first and second voltage levels which are different by the bias from each 
other. The voltage divider has a voltage dividing point between the first 
and second ends. The voltage dividing point further has a third voltage 
level which is leveled between the first and second voltage levels which 
are applied to the control electrode and the first grid respectively. The 
voltage dividing point is electrically connected to the first the 
acceleration electrode so that the first acceleration electrode has the 
third voltage level. 
In the above case, it is not necessary to provide any further power supply 
for exclusively supplying the third voltage level to the first 
acceleration electrode. This results in a reduction of the manufacturing 
cost. It is also required to carry out an adjustment process for the 
reduced number of the power supplies. The voltage divider divides the high 
voltage into the low level first, second and third voltages in the range 
of about 6 kV to about 0 kV to be applied to the control electrode, the 
first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun. 
The present invention also provides an electron gun for a color cathode ray 
tube with dynamic driving quadrupole lens. The electron gun includes a 
cathode ray tube having a cathode side and a screen side. The cathode ray 
tube accommodates a cathode in the cathode side. The cathode ray tube also 
accommodates a control electrode adjacent to the cathode. The cathode ray 
tube also accommodates a first acceleration electrode adjacent to the 
control electrode so that the first acceleration electrode and the cathode 
sandwich the control electrode. The cathode ray tube also accommodates a 
convergence electrode adjacent to the first acceleration electrode so that 
the convergence electrode and the control electrode sandwich the first 
acceleration electrode. The cathode ray tube also accommodates a second 
acceleration electrode in the screen side and adjacent to the convergence 
electrode so that the second acceleration electrode and the first 
acceleration electrode sandwich the convergence electrode. The convergence 
electrode comprises a first grid adjacent to the first acceleration 
electrode and a second grid adjacent to the second acceleration electrode. 
The first grid of the convergence electrode may have a plurality of pairs 
of circular arc burrings which face to each other in a horizontal 
direction. The second grid of the convergence electrode may have a 
plurality of pairs of circular arc burrings which face to each other in a 
vertical direction. The first and second grids are combined with each 
other so that the circular arc burrings of the first and second grids are 
engaged with each other whereby the circular arc burrings form a 
quadrupole lens. 
The control electrode, the first acceleration electrode and the first grid 
of the convergence electrode are applied with first, second and third 
constant voltages different from each other. The second grid of the 
convergence electrode is applied with a dynamic voltage. 
It is important for the present invention to use a power supply and a 
voltage divider having first and second ends which are electrically 
connected between the control electrode and the first grid of the 
convergence electrode respectively. The power supply is electrically 
connected to the voltage divider so as to apply a bias between the first 
and second ends of the voltage divider. As a result, the first and second 
ends of the voltage divider have first and second voltage levels which are 
different by the bias from each other. The voltage divider also has a 
voltage dividing point between the first and second ends. The voltage 
dividing point has a third voltage level which is leveled between the 
first and second voltage levels which are applied to the control electrode 
and the first grid of the convergence electrode. The first acceleration 
electrode is electrically connected to the voltage dividing point of the 
voltage divider so that the first acceleration electrode has the third 
voltage level. 
In the above case, it is not necessary to provide any further power supply 
for exclusively supplying the third voltage level to the first 
acceleration electrode. This results in a reduction of the manufacturing 
cost. It is also required to carry out an adjustment process for the 
reduced number of the power supplies. The voltage divider divides the high 
voltage into the low level first, second and third voltages in the range 
of about 6 kV to about 0 kV to be applied to the control electrode, the 
first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun.

DISCLOSURE OF THE INVENTION 
An electron gun for a color cathode my tube with dynamic driving quadrupole 
lens is provided. The electron gun includes a cathode ray tube having a 
cathode side and a screen side. The cathode ray tube accommodates a 
cathode in the cathode side. The cathode ray tube also accommodates a 
control electrode adjacent to the cathode. The cathode ray tube also 
accommodates a first acceleration electrode adjacent to the control 
electrode so that the first acceleration electrode and the cathode 
sandwich the control electrode. The cathode ray tube also accommodates a 
convergence electrode adjacent to the first acceleration electrode so that 
the convergence electrode and the control electrode sandwich the first 
acceleration electrode. The cathode ray tube also accommodates a second 
acceleration electrode in the screen side and adjacent to the convergence 
electrode so that the second acceleration electrode and the first 
acceleration electrode sandwich the convergence electrode. The convergence 
electrode comprises a first grid adjacent to the first acceleration 
electrode and a second grid adjacent to the second acceleration electrode. 
The first grid of the convergence electrode may have a plurality of pairs 
of circular arc burrings which face to each other in a horizontal 
direction. The second grid of the convergence electrode may have a 
plurality of pairs of circular arc burrings which face to each other in a 
vertical direction. The first and second grids are combined with each 
other so that the circular arc burrings of the first and second grids are 
engaged with each other whereby the circular arc burrings form a 
quadrupole lens. 
The control electrode, the first acceleration electrode and the first grid 
of the convergence electrode are applied with first, second and third 
constant voltages different from each other. The second grid of the 
convergence electrode is applied with a dynamic voltage. 
It is important for the present invention to use a power supply and a 
voltage divider having first and second ends which are electrically 
connected between the control electrode and the first grid of the 
convergence electrode respectively. The power supply is electrically 
connected to the voltage divider so as to apply a bias between the first 
and second ends of the divider. As a result, the first and second ends of 
the voltage divider have first and second voltage levels which are 
different by the bias from each other. The voltage divider also has a 
voltage dividing point between the first and second ends. The voltage 
dividing point has a third voltage level which is leveled between the 
first and second voltage levels which are applied to the control electrode 
and the first grid of the convergence electrode. The first acceleration 
electrode is electrically connected to the voltage dividing point of the 
voltage divider so that the first acceleration electrode has the third 
voltage level. 
In the above case, it is not necessary to provide any further power supply 
for exclusively supplying the third voltage level to the first 
acceleration electrode. This results in a reduction of the manufacturing 
cost. It is also required to carry out an adjustment process for the 
reduced number of the power supplies. The voltage divider divides the high 
voltage into the low level first, second and third voltages in the range 
of about 6 kV to about 0 kV to be applied to the control electrode, the 
first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun. 
It may be available that the voltage divider comprises a voltage dividing 
resistor which is accommodated in the cathode ray tube to improve a 
withstand voltage and a reliability. This accommodation structure makes it 
necessary to provide any further pin of stem and makes the cathode ray 
tube compatible to the standard interface, for example, socket and base 
pins. The voltage dividing resistor may comprise two resistors in series. 
The first acceleration electrode is connected to an intermediate between 
the two resistors. 
It may also be available that the first and second ends of the voltage 
divider are electrically connected to first and second dc power supplies 
which supply the first and second voltage levels respectively. 
It may also be available that the first end of the voltage divider is 
electrically connected to a first dc power supply which supplies the first 
voltage level and that the second end of the voltage divider is 
electrically connected to a ground via a floating capacitor. In this case, 
no further power supply is required, which supply the second voltage level 
to the first grid of the convergence electrode. This results in a 
reduction of the manufacturing cost. It is also required to carry out an 
adjustment process for the reduced number of the power supplies. Further, 
the floating capacitor is provided in order to provide a floating 
capacitance to the first grid of the convergence electrode. The floating 
capacitance provides a flat and smooth ac-voltage component applied to the 
second acceleration electrode. This flat and smooth ac-voltage component 
has a similar voltage waveform to that of dc voltage. The first grid of 
the convergence electrode is thus applied with the flat and smooth 
ac-voltage having a similar voltage waveform to that of dc voltage. 
It may also be available that the first end of the voltage divider is 
electrically connected to a first dc power supply which supplies the first 
voltage level and that a capacitor is electrically connected between the 
first and second ends of the voltage divider. This results in a reduction 
of the manufacturing cost. It is also required to carry out an adjustment 
process for the reduced number of the power supplies. Further, the 
capacitor is provided in order to provide a floating capacitance between 
the first grid of the convergence electrode and the other electrode, for 
example, the control electrode. The floating capacitance provides a flat 
and smooth ac-voltage component applied to the second acceleration 
electrode. This flat and smooth ac-voltage component has a similar voltage 
waveform to that of dc voltage. The first grid of the convergence 
electrode is thus applied with the flat and smooth ac-voltage having a 
similar voltage waveform to that of dc voltage. 
It may also be available that the first and second grids of the convergence 
electrode are electrically connected to each other via a resistor so that 
the first grid of the convergence electrode, the first acceleration 
electrode and the control electrode are applied with voltages which are 
different from each other and which are divided and reduced, by the 
resistor and the voltage divider, from the dynamic driving voltage applied 
to the second grid of the convergence electrode. The existence of the 
voltage divider and the resistor makes it necessary to provide only a 
single power supply for supplying the first, second and third voltage 
levels different from each other to the control electrode, the first 
acceleration electrode and the first grid of the convergence electrode. 
This makes it unnecessary to provide any further pin of stem and makes the 
cathode ray tube compatible to the standard interface, for example, socket 
and base pins. Providing the single dc power supply also results in a 
reduction of the manufacturing cost. It is also required to carry out an 
adjustment process for the reduced number of the power supplies. 
It may also be available that the first grid has a plurality of pairs of 
first circular arc burrings which face to each other in a horizontal 
direction, and that the second grid has a plurality of pairs of second 
circular arc burrings which face to each other in a vertical direction, as 
well as that the first and second grids are combined with each other so 
that the first and second circular arc burrings are engaged with each 
other to form a plurality of quadrupole lenses. 
It may also be available that the first grid has a plurality of first 
openings having a vertical length and a horizontal length which is larger 
than the vertical length, and that the second grid has a plurality of 
second openings having a vertical length and a horizontal length which is 
smaller than the vertical length, as well as that the first and second 
grids are combined with each other so that the first and second openings 
face to each other to form a plurality of quadrupole lenses. 
It may also be available that the first grid has a plurality of first 
openings having a vertical length and a horizontal length which is smaller 
than the vertical length, and that the second grid has a plurality of 
second openings having a vertical length and a horizontal length which is 
larger than the vertical length, as well as that the first and second are 
combined with each other so that the first and second openings face to 
each other to form a plurality of quadrupole lenses. 
The present invention also provides a circuitry being electrically 
connected to an electron gun for driving the electron gun. The electron 
gun includes a cathode ray tube which accommodates at least a cathode, a 
control electrode, a first acceleration electrode, a convergence electrode 
comprising first and second grids sandwiching at least a quadrupole lens 
and a second acceleration electrode. The circuitry is provided with a 
voltage divider having first and second ends which are electrically 
connected between the control electrode and the first grid respectively. 
The voltage divider being electrically connected to at least a dc power 
supply to apply a bias between the first and second ends of the voltage 
divider so that the first and second ends of the voltage divider have 
first and second voltage levels which are different by the bias from each 
other. The voltage divider has a voltage dividing point between the first 
and second ends. The voltage dividing point further has a third voltage 
level which is leveled between the first and second voltage levels which 
are applied to the control electrode and the first grid respectively. The 
voltage dividing point is electrically connected to the first the 
acceleration electrode so that the first acceleration electrode has the 
third voltage level. 
In the above case, it is not necessary to provide any further power supply 
for exclusively supplying the third voltage level to the first 
acceleration electrode. This results in a reduction of the manufacturing 
cost. It is also required to carry out an adjustment process for the 
reduced number of the power supplies. The voltage divider divides the high 
voltage into the low level first, second and third voltages in the range 
of about 6 kV to about 0 kV to be applied to the control electrode, the 
first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun. 
It may be available that the voltage divider comprises a voltage dividing 
resistor which is accommodated in the cathode ray tube to improve a 
withstand voltage and a reliability. This accommodation structure makes: 
unnecessary to provide any further pin of stem and makes the cathode ray 
tube compatible to the standard interface, for example, socket and base 
pin. The voltage dividing resistor may comprise two series resisters. The 
first acceleration electrode is connected to an intermediate between the 
two resistors. 
It may also be available that the first and second ends of the voltage 
divider are electrically connected to first and second dc power supplies 
which supply the first and second voltage levels respectively. 
It may also be available that the first end of the voltage divider is 
electrically connected to a first dc power supply which supplies the first 
voltage level and that the second end of the voltage divider is 
electrically connected to a ground via a floating capacitor. In this case, 
no further power supply is required, which supply the second voltage level 
to the first grid of the convergence electrode. This results in a 
reduction of the manufacturing cost. It is also required to carry out an 
adjustment process for the reduced number of the power supplies. Further, 
the floating capacitor is provided in order to provide a floating 
capacitance to the first grid of the convergence electrode. The floating 
capacitance provides a flat and smooth ac-voltage component applied to the 
second acceleration electrode. This flat and smooth ac-voltage component 
has a similar voltage waveform to that of dc voltage. The first grid of 
the convergence electrode is thus applied with the flat and smooth 
ac-voltage having a similar voltage waveform to that of dc voltage. 
It may also be available that the first end of the voltage divider is 
electrically connected to a first dc power supply which supplies the first 
voltage level and that a capacitor is electrically connected between the 
first and second ends of the voltage divider. This results in a reduction 
of the manufacturing cost. It is also required m carry out an adjustment 
process for the reduced number of the power supplies. Further, the 
capacitor is provided in order to provide a floating capacitance between 
the first grid of the convergence electrode and the other electrode, for 
example, the control electrode. The floating capacitance provides a flat 
and smooth ac-voltage component applied to the second acceleration 
electrode. This flat and smooth ac-voltage component has a similar voltage 
waveform to that of dc voltage. The first grid of the convergence 
electrode is thus applied with the flat and smooth ac-voltage having a 
similar voltage waveform to that of dc voltage. 
It may also be available that the first and second grids of the convergence 
electrode are electrically connected to each other via a resistor so that 
the first grid of the convergence electrode, the first acceleration 
electrode and the control electrode are applied with voltages which are 
different from each other and which are divided and reduced, by the 
resistor and the voltage divider, from the dynamic driving voltage applied 
to the second grid of the convergence electrode. The existence of the 
voltage divider and the resistor makes it necessary to provide only a 
single power supply for supplying the first, second and third voltage 
levels different from each other to the control electrode, the first 
acceleration electrode and the first grid of the convergence electrode. 
This makes it unnecessary to provide any further pin of stem and makes the 
cathode ray tube compatible to the standard interface, for example, socket 
and base pins. 
It may also be available that the first grid has a plurality of pairs of 
first circular arc burrings which face to each other in a horizontal 
direction, and that the second grid has a plurality of pairs of second 
circular arc burrings which face to each other m a vertical direction, as 
well as that the first and second grids are combined with each other so 
that the first and second circular arc burrings are engaged with each 
other to form a plurality of quadrupole lenses. 
It may also be available that the first grid has a plurality of first 
openings having a vertical length and a horizontal length which is larger 
than the vertical length, and that the second grid has a plurality of 
second openings having a vertical length and a horizontal length which is 
smaller than the vertical length, as well as that the first and second 
grids are combined with each other so that the first and second openings 
face to each other to form a plurality of quadrupole lenses. 
It may also be available that the first grid has a plurality of first 
openings having a vertical length and a horizontal length which is smaller 
than the vertical length, and that the second grid has a plurality of 
second openings having a vertical length and a horizontal length which is 
larger than the vertical length, as well as that the first and second 
grids are combined with each other so that the first and second openings 
face to each other to form a plurality of quadrupole lenses. 
The above described present inventions may be applicable to any electron 
guns having quadrupole lens. 
Whereas modifications of the present invention will be apparent to a person 
having ordinary skill in the art, to which the invention pertains, it is 
to be understood that embodiments to be hereinafter shown and described by 
way of illustrations are by no means intended to be considered in a 
limiting sense. Accordingly, it is to be intended to cover by claims all 
modifications which fall within the spirit and scope of the present 
invention. 
EMBODIMENTS 
A first embodiment according to the present invention will be described in 
detail with reference to FIG, 6. An electron gun for a color cathode ray 
tube with dynamic driving quadrupole lens is provided. The electron gun 
includes a cathode ray tube having a cathode side and a screen side. The 
cathode ray tube accommodates a cathode 11 in the cathode side. The 
cathode ray robe also accommodates a control electrode 12 which is 
provided adjacent to the cathode 11. The cathode ray tube also 
accommodates a first acceleration electrode 13 which is provided adjacent 
to the control electrode 12 so that the first acceleration electrode 13 
and the cathode 11 sandwich the control electrode 12. The cathode ray tube 
also accommodates a convergence electrode which is provided adjacent to 
the first acceleration electrode 13 so that the convergence electrode and 
the control electrode 12 sandwich the first acceleration electrode 13. The 
cathode ray robe also accommodates a second acceleration electrode 16 in 
the screen side and adjacent to the convergence electrode so that the 
second acceleration electrode 16 and the first acceleration electrode 13 
sandwich the convergence electrode. The convergence electrode comprises a 
first grid 14 which is provided adjacent to the first acceleration 
electrode 13 and a second grid 15 which is provided adjacent to the second 
acceleration electrode 16. The first grid 14 of the convergence electrode 
has a plurality of pairs of circular arc burrings which face to each other 
in a horizontal direction. The second grid of the convergence electrode 
may have a plurality of pairs of circular arc burrings which face to each 
other in a vertical direction. The first and second grids 14 and 15 are 
combined with each other so that the circular arc burrings of the first 
and second grids are also engaged with each other whereby the circular arc 
burrings form a plurality of quadrupole lenses 17. The control electrode 
12, and the first acceleration electrode 13 the first grid 14 of the 
convergence electrode are applied with first, second and third constant 
voltages Ec1, Ec2 and Ec3 respectively. The first, second and third 
constant voltages Ec1, Ec2 and Ec3 are different from each other. The 
second grid of the convergence electrode is applied with a dynamic voltage 
Ec3d=Ec3+Ed. 
It is important for the present invention to use power supplies and a 
voltage divider comprising first and second resisters 18 and 19 in first 
and second ends respectively. The first and second ends of the voltage 
divider are connected to the control electrode 12 and the first grid 14 of 
the convergence electrode respectively. The first and second resistors 18 
and 19 are connected in series between the control electrode 12 and the 
first grid 14 of the convergence electrode. The power supplies are 
electrically connected to the first and second ends respectively of the 
voltage divider so as to apply a bias over the voltage divider. As a 
result, the first and second ends of the voltage divider have first and 
third voltage levels Ec1 and Ec3 which are different by the bias from each 
other. The voltage divider also has a voltage dividing point having a 
voltage level of Ec2. The voltage dividing point of the voltage divider is 
positioned between the first and second resisters 18 and 19. The voltage 
dividing point has the second voltage level Ec2 which is leveled between 
the first and third voltage levels Ec1 and Ec3 which are applied to the 
control electrode 12 and the first grid 14 of the convergence electrode. 
The first acceleration electrode 13 is electrically connected to the 
voltage dividing point of the voltage divider, namely connected to between 
the first and second resisters 18 and 19 so that the first acceleration 
electrode 13 has the second voltage level. 
The above novel electron gun is driven as follows. The control electrode 12 
is applied with the control voltage Ec1. The first acceleration electrode 
13 is applied with the acceleration voltage Ec2. The first grid 4 of the 
convergence voltage is applied with the constant focus electrode Ec3. The 
second grid 5 of the convergence electrode is applied with the dynamic 
voltage Ec3d which dynamically varies, as illustrated in FIG. 3, depending 
upon positions on a screen receiving irradiation of electron beam. As a 
result, the quadrupole lens 17 provides the electron beam with the 
divergence force in the vertical direction and the convergence force in 
the horizontal direction as illustrated in FIG. 4. Those vertical 
divergence and horizontal convergence forces do compensate the long side 
way strain of the electron beam, wherein the long side way strain is due 
to the deflected magnetic field caused by the deflection yoke. Namely, the 
long side way strain of the electron beam, which is caused by the 
deflected magnetic field generated by the deflection yoke, is canceled by 
the vertical divergence and horizontal convergence forces provided by the 
quadrupole lens 17, whereby a beam spot free of strain can be obtained. 
In the above case, it is not necessary to provide any further power supply 
for exclusively supplying the second voltage level to the first 
acceleration electrode 13. This results in a reduction of the 
manufacturing cost. It is also required to carry out an adjustment process 
for the reduced number of the power supplies. The voltage divider 
comprising the series resistors 18 and 19 divides the high voltage into 
the low level first, second and third voltages in the range of about 6 kV 
to about 0 kV to be applied to the control electrode, the first 
acceleration electrode and the first grid of the convergence electrode. 
This settles the problems in withstand voltage and a low reliability with 
the conventional electron gun. 
The voltage divider comprising the series resistors 18 and 19 is 
accommodated in the cathode ray tube to improve a withstand voltage and a 
reliability. This accommodation structure makes it unnecessary to provide 
any further pin of stem and makes the cathode ray tube compatible to the 
standard interface, for example, socket and base pins. The voltage 
dividing resistor may comprise two series resistors. The first 
acceleration electrode is connected to an intermediate between the two 
resistors. 
As a modification, in place of the above quadrupole lens structure, it is 
available that as illustrated in FIG. 9 a first grid 34 has a plurality of 
first openings 32 having a vertical length and a horizontal length which 
is smaller than the vertical length, and a second grid 35 has a plurality 
of second openings 33 having a vertical length and a horizontal length 
which is larger than the vertical length. The first and second grids 34 
and 35 are combined with each other so that the first and second openings 
32 and 33 face each other to form a plurality of quadrupole lenses. 
A second embodiment according to the present invention will be described in 
detail with reference to FIG. 7. An electron gun for a color cathode ray 
tube with dynamic driving quadrupole lens is provided. The electron gun 
includes a cathode my robe having a cathode side and a screen side. The 
cathode ray tube accommodates a cathode 11 in the cathode side The cathode 
ray tube also accommodates a control electrode 12 which is provided 
adjacent to the cathode 11. The cathode ray tube also accommodates a first 
acceleration electrode 13 which is provided adjacent to the control 
electrode 12 so that the first acceleration electrode 13 cathode 11 
sandwich the control electrode 12. The cathode ray tube also accommodates 
a convergence electrode which is provided adjacent to the first 
acceleration electrode 13 so that the convergence electrode and the 
control electrode 12 sandwich the first acceleration electrode 13. The 
cathode ray tube also accommodates a second acceleration electrode 16 in 
the screen side and adjacent to the convergence electrode so that the 
second acceleration electrode 16 and the first acceleration electrode 13 
sandwich the convergence electrode. The convergence electrode comprises a 
first grid 14 which is provided adjacent to the first acceleration 
electrode 13 and a second grid 15 which is provided adjacent to the second 
acceleration electrode 16. The first grid 14 of the convergence electrode 
has a plurality of pairs of circular arc burrings which face to each other 
in a horizontal direction. The second grid of the convergence electrode 
may have a plurality of pairs of circular arc burrings which face to each 
other in a vertical direction. The first and second grids 14 and 15 are 
combined with each other so that the circular arc burrings of the first 
and second grids are also engaged with each other whereby the circular arc 
burrings form a plurality of quadrupole lenses 17. 
The control electrode 12, and the first acceleration electrode 13 the first 
grid 14 of the convergence electrode are applied with first, second and 
third constant voltages respectively. The first, second and third constant 
voltages are different from each other. The second grid of the convergence 
electrode is applied with a dynamic voltage Ec3d=Ec3+Ed. 
It is important for the present invention to use a single dc power supply 
and a voltage divider comprising first and second resistors 18 and 19 in 
first and second ends respectively. The first and second ends of the 
voltage divider are connected to the control electrode 12 and the first 
grid 14 of the convergence electrode respectively. The first and second 
resistors 18 and 19 are connected in series between the control electrode 
12 and the first grid 14 of the convergence electrode. The first end of 
the voltage divide is electrically connected to a single dc power supply 
which supplies the first voltage level. The second end of the voltage 
divider is electrically connected to a ground via a floating capacitor 10. 
A bias is applied over the voltage divider. As a result, the first and 
second ends of the voltage divider have first and third voltage levels 
which are different by the bias from each other. The voltage divider also 
has a voltage dividing point having a voltage level of Ec2. The voltage 
dividing point of the voltage divider is positioned between the first and 
second resistors 18 and 19. The voltage dividing point has the second 
voltage level Ec2 which is leveled between the first and third voltage 
levels Ec1 and Ec3 which are applied to the control electrode 12 and the 
first grid 14 of the convergence electrode. The first acceleration 
electrode 13 is electrically connected to the voltage dividing point of 
the voltage divider, namely connected to between the first and second 
resistors 18 and 19 so that the first acceleration electrode 13 has the 
second voltage level. 
In this embodiment, no further power supply is required, which supply the 
third or second voltage level to the first grid of the convergence 
electrode or to the first acceleration electrode 13. This results in a 
reduction of the manufacturing cost. It is also required to carry out an 
adjustment process for the reduced number of the power supplies. Further, 
the floating capacitor 10 is provided in order to provide a floating 
capacitance to the first grid of the convergence electrode. The floating 
capacitance 10 provides a flat and smooth ac-voltage component applied to 
the second acceleration electrode 13. This flat and smooth ac-voltage 
component has a similar voltage waveform to that of dc voltage. The first 
grid 14 of the convergence electrode is thus applied with the flat and 
smooth ac-voltage having a similar voltage waveform to that of dc voltage. 
The voltage divider comprising the series resistors 18 and 19 divides the 
high voltage into the low level first, second and third voltages in the 
range of about 6 kV to about 0 kV to be applied to the control electrode, 
the first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun. 
The voltage divider comprising the series resistors 18 and 19 is 
accommodated in the cathode my tube to improve a withstand voltage and a 
reliability. This accommodation structure makes it unnecessary to provide 
any further pin of stem and makes the cathode ray tube compatible to the 
standard interface, for example, socket and base pins. The voltage 
dividing resistor may comprise two series resistors 18 and 19. The first 
acceleration electrode 13 is connected to an intermediate between the two 
resistors 18 and 19. 
The first and second grids 14 and 15 of the convergence electrode are 
electrically connected to each other via a resistor 21 so that the first 
grid 14 of the convergence electrode, the first acceleration electrode 13 
and the control electrode 12 are applied with voltages which are different 
from each other and which are divided and reduced, by the resistor 21 and 
the voltage divider, from the dynamic driving voltage applied to the 
second grid 15 of the convergence electrode. The existence of the voltage 
divider and the resistor 21 makes it necessary to provide only a single 
power supply for supplying the first, second and third voltage levels 
different from each other to the control electrode 12, the first 
acceleration electrode 13 and the first grid 14 of the convergence 
electrode. This makes it unnecessary to provide any further pin of stem 
and makes the cathode ray tube compatible to the standard interface, for 
example, socket and base pins. Providing the single dc power supply also 
results in a reduction of the manufacturing cost. It is also required to 
carry out an adjustment process for the reduced number of the power 
supplies. 
The above novel electron gun is driven as follows. The control electrode 12 
is applied with the control voltage Ec1. The first acceleration electrode 
13 is applied with the acceleration voltage Ec2. The first grid 4 of the 
convergence electrode is applied with the constant focus voltage Ec3. The 
second grid 5 of the convergence electrode is applied with the dynamic 
voltage Ec3d which dynamically varies, as illustrated in FIG. 3, depending 
upon positions on a screen receiving irradiation of electron beam. As a 
result, the quadrupole lens 17 provides the electron beam with the 
divergence force in the vertical direction and the convergence force in 
the horizontal direction as illustrated in FIG. 4. Those vertical 
divergence and horizontal convergence forces do compensate the long side 
way strain of the electron beam, wherein the long side way strain is due 
to the deflected magnetic field caused by the deflection yoke. Namely, the 
long side way strain of the electron beam, which is caused by the 
deflected magnetic field generated by the deflection yoke, is canceled by 
the vertical divergence and horizontal convergence forces provided by the 
quadrupole lens 17, whereby a beam spot free of strain can be obtained. 
As a modification, in place of the above quadrupole lens structure, it is 
available that as illustrated in FIG. 9 a first grid 34 has a plurality of 
first openings 32 having a vertical length and a horizontal length which 
is smaller than the vertical length, and a second grid 35 has a plurality 
of second openings 33 having a vertical length and a horizontal length 
which is larger than the vertical length. The first and second grids 34 
and 35 are combined with each other so that the first and second openings 
32 and 33 face each other to form a plurality of quadrupole lenses. 
A third embodiment according to the present invention will be described in 
detail with reference to FIG. 8. An electron gun for a color cathode ray 
tube with dynamic driving quadrupole lens is provided. The electron gun 
includes a cathode ray tube having a cathode side and a screen side. The 
cathode ray tube accommodates a cathode 11 in the cathode side. The 
cathode ray tube also accommodates a control electrode 12 which is 
provided adjacent to the cathode 11. The cathode my tube also accommodates 
a first acceleration electrode 13 which is provided adjacent to the 
control electrode 12 so that the first acceleration electrode 13 and the 
cathode 11 sandwich the control electrode 12. The cathode ray tube also 
accommodates a convergence electrode which is provided adjacent to the 
first acceleration electrode 13 so that the convergence electrode and the 
control electrode 12 sandwich the first acceleration electrode 13. The 
cathode ray tube also accommodates a second acceleration electrode 16 in 
the screen side and adjacent to the convergence electrode so that the 
second acceleration electrode 16 and the first acceleration electrode 13 
sandwich the convergence electrode. The convergence electrode comprises a 
first grid 14 which is provided adjacent to the lust acceleration 
electrode 13 and a second grid 15 which is provided adjacent to the second 
acceleration electrode 16. The first grid 14 of the convergence electrode 
has a plurality of pairs of circular arc burrings which face to each other 
in a horizontal direction. The second grid of the convergence electrode 
may have a plurality of pairs of circular arc burrings which face to each 
other in a vertical direction. The first and second grids 14 and 15 are 
combined with each other so that the circular arc burrings of the first 
and second grids are also engaged with each other whereby the circular arc 
burrings form a plurality of quadrupole lenses 17. 
The control electrode 12, and the first acceleration electrode 13 the first 
grid 14 of the convergence electrode are applied with first, second and 
third constant voltages respectively. The first, second and third constant 
voltages are different from each other. The second grid of the convergence 
electrode is applied with a dynamic voltage Ec3d=Ec3+Ed. 
It is important for the present invention to use a single dc power supply 
and a voltage divider comprising first and second resistors 18 and 19 in 
first and second ends respectively. The first and second ends of the 
voltage divider are connected to the control electrode 12 and the first 
grid 14 of the convergence electrode respectively. The first and second 
resistors 18 and 19 are connected in series between the control electrode 
12 and the first grid 14 of the convergence electrode. The first end of 
the voltage divider is electrically connected to a single dc power supply 
which supplies the first voltage level. A capacitor 20 is electrically 
connected to between the first and second ends of the voltage divider. A 
bias is applied over the voltage divider. As a result, the first and 
second ends of the voltage divider have first and third voltage levels 
which are different by the bias from each other. The voltage divider also 
has a voltage dividing point having a voltage level of Ec2. The voltage 
dividing point of the voltage divider is positioned between the first and 
second resistors 18 and 19. The voltage dividing point has the second 
voltage level Ec2 which is leveled between the first and third voltage 
levels Ec1 and Ec3 which are applied to the control electrode 12 and the 
first grid 14 of the convergence electrode. The first acceleration 
electrode 13 is electrically connected to the voltage dividing point of 
the voltage divider, namely connected to between the first and second 
resistors 18 and 19 so that the first acceleration electrode 13 has the 
second voltage level. 
In this embodiment, no further power supply is required, which supply the 
third or second voltage level to the first grid of the convergence 
electrode or to the first acceleration electrode 13. This results in a 
reduction of the manufacturing cost. It is also required to carry out an 
adjustment process for the reduced number of the power supplies. 
Further, the capacitor 20 is provided in order to provide a floating 
capacitance to the first grid of the convergence electrode. This results 
in a reduction of the manufacturing cost. It is also required to carry out 
an adjustment process for the reduced number of the power supplies. 
Further, the capacitor is provided in order to provide a floating 
capacitance between the first grid of the convergence electrode and the 
other electrode, for example, the control electrode. The floating 
capacitance provides a flat and smooth ac-voltage component applied to the 
second acceleration electrode. This flat and smooth ac-voltage component 
has a similar voltage waveform to that of dc voltage. The first grid of 
the convergence electrode is thus applied with the flat and smooth 
ac-voltage having a similar voltage waveform to that of dc voltage. 
The voltage divider comprising the series resistors 18 and 19 divides the 
high voltage into the low level first, second and third voltages in the 
range of about 6 kV to about 0 kV to be applied to the control electrode, 
the first acceleration electrode and the first grid of the convergence 
electrode. This settles the problems in withstand voltage and a low 
reliability with the conventional electron gun. 
The voltage divider comprising the series resisters 18 and 19 is 
accommodated in the cathode ray tube to improve a withstand voltage and a 
reliability. This accommodation structure makes it unnecessary to provide 
any further pin of stem and makes the cathode ray tube compatible to the 
standard interface, for example, socket and base pins. The voltage 
dividing resistor may comprise two series resisters 18 and 19. The first 
acceleration electrode 13 is connected to an intermediate between the two 
resisters 18 and 19. 
The first and second grids 14 and 15 of the convergence electrode are 
electrically connected to each other via a resistor 21 so that the first 
grid 14 of the convergence electrode, the first acceleration electrode 13 
and the control electrode 12 arc applied with voltages which are different 
from each other and which are divided and reduced, by the resistor 21 
divider, and the voltage divider, from the dynamic driving voltage applied 
to the second grid 15 of the convergence electrode. The existence of the 
voltage divider and the resistor 21 makes it necessary to provide only a 
single power supply for supplying the first, second and third voltage 
levels different from each other to the control electrode 12, the first 
acceleration electrode 13 and the first grid 14 of the convergence 
electrode. This makes it unnecessary to provide any further pin of stem 
and makes the cathode ray tube compatible to the standard interface, for 
example, socket and base pins. Providing the single dc power supply also 
results m a reduction of the manufacturing cost. It is also required to 
carry out an adjustment process for the reduced number of the power 
supplies. 
The above novel electron gun is driven as follows. The control electrode 12 
is applied with the control voltage Ec1. The first acceleration electrode 
13 is applied with the acceleration voltage Ec2. The first grid 4 of the 
convergence voltage is applied with the constant focus electrode Ec3. The 
second grid 5 of the convergence electrode is applied with the dynamic 
voltage Ec3d which dynamically varies, as illustrated in FIG. 3, depending 
upon positions on a screen receiving irradiation of electron beam. As a 
result, the quadrupole lens 17 provides the electron beam with the 
divergence force in the vertical direction and the convergence force in 
the horizontal direction as illustrated in FIG. 4. Those vertical 
divergence and horizontal convergence forces do compensate the long side 
way strain of the electron beam, wherein the long side way strain is due 
to the deflected magnetic field caused by the deflection yoke. Namely, the 
long side way strain of the electron beam, which is caused by the 
deflected magnetic field generated by the deflection yoke, is canceled by 
the vertical divergence and horizontal convergence forces provided by the 
quadrupole lens 17, whereby a beam spot free of strain can be obtained. 
As a modification, in place of the above quadrupole lens structure, it is 
available that as illustrated in FIG. 9 a first grid 34 has a plurality of 
first openings 32 having a vertical length and a horizontal length which 
is smaller than the vertical length, and a second grid 35 has a plurality 
of second openings 33 having a vertical length and a horizontal length 
which is larger than the vertical length. The first and second grids 34 
and 35 are combined with each other so that the first and second openings 
32 and 33 face each other to form a plurality of quadrupole lenses.