JPH0793108B2 - Cathode ray tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an observation CRT (cathode ray tube) used in an oscilloscope or the like.

[0002]

PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION Cathode,
A control electrode, an acceleration electrode, a unipotential type first and second quadrupole lens, a vertical deflection system, a unipotential type third quadrupole lens, a horizontal deflection system, a scanning magnifying lens, and a screen on the axis of the exhaust pipe body. The arrangement of the CRT of the oscilloscope by arranging them in parallel is disclosed in, for example, JP-A-63-23733 and JP-A-63-237335.
JP-A-64-6348.

The principle of imaging in these CRTs can be shown in FIG. In FIG. 1, the first, second and third quadrupole lenses Q1, Q2 and Q3 are arranged on the tube axis 1. In FIG. 1, a vertical lens action (focusing state) is displayed in the upper region 2 of the tube axis 1 facing the image 5 on the image plane 4 from the object point 12 (crossover), and the horizontal lens action is displayed in the lower region 3. (Focus state) is displayed. Q
The first and third quadrupole lenses 6 and 8 indicated by 1 and Q3 act as concave lenses in the vertical direction and convex lenses in the horizontal direction, respectively.
The second quadrupole lens 7 shown by 2 acts as a convex lens in the vertical direction and as a concave lens in the horizontal direction. By providing the three quadrupole lenses Q1, Q2 and Q3 in this way, the image 5 can be brought close to a perfect circle.

At the object point 12 in FIG. 1, the electrons emitted from the cathode 9 shown in FIG. 2 are the cathode 9, the control electrode 10 and the acceleration electrode 11.
It is a point (crossover) which is converged to approximately one point by the lens constituted by and.

The distance from the object point 12 (crossover) to the first quadrupole lens Q1 is v, the distance from the first quadrupole lens Q1 to the second quadrupole lens Q2 is d, and the distance from the second quadrupole lens Q2 to It is assumed that the distance from the third quadrupole lens Q3 is q, the distance from the third quadrupole lens Q3 to the image plane 4 is z, and the quadrupole lenses Q1, Q2, and Q3 have the same focal length, and the reciprocal thereof is S1. , S2, S3, S1, S2
, S3 can be expressed by the following equations (1), (2) and (3).

[0006]

[Equation 1]

In FIG. 2, when the voltage of the control electrode 10 is changed and the amount of the electron beam is controlled, the position of the object point 12 changes. That is, the distance v from the object point 12 to the first quadrupole lens Q1 changes. This means that if the lens constant of each quadrupole lens is changed according to the change of v, the image
Means that you will not be able to. One of the weak points of the electron gun using the quadrupole lens is that when the electron beam amount is changed,
There is the complexity of adjusting the voltage on each quadrupole lens. A measure for eliminating this complexity is disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-237334.

However, in these CRTs, at least two variable resistors must be adjusted according to the change in the electron beam amount.

Japanese Unexamined Patent Publication No. 63-237334 discloses that
As shown in principle in FIG. 3, an axisymmetric lens 13 is arranged between the object point 12 and the first quadrupole lens Q1, and the position of the object point 12 is made substantially constant by the action of the lens. Is disclosed. In FIG. 3, the axisymmetric lens 13 and the first
It is assumed that the distance from the quadrupole lens 13 is set to e, and the position of the object point is changed from v to v ′ by adjusting the control electrode 10. When this is actuated by the axially symmetric lens 13 and returned to v, the size of the object point becomes (v−e) / (v′−) due to the action of this lens.
e). When increasing the electron beam amount, the relationship of v> v 'is satisfied. Therefore, when the beam amount is increased, the object point 12 is enlarged by the action of the axisymmetric lens 13. In this example, the axially symmetric lens 1 corresponds to the change of the control electrode 10.
If only the voltage of 3 is adjusted, the image formation 5 can be obtained without changing the others. However, when the beam amount is increased, the object point 12 becomes large, the image formation 5 becomes large, and the quality deteriorates.

Therefore, an object of the present invention is to provide a CRT capable of adjusting the change in the focus state due to the change in the electron beam amount with a single variable voltage source.

[0011]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a control electrode for controlling the amount of electron beam.
And a cathode ray tube further comprising at least first, second and third quadrupole lenses, wherein at least the first and second quadrupole lenses are arranged at right angles to the tube axis. Each of the plurality of plate-shaped electrodes comprises a combination of a plurality of first polarity electrodes for applying a voltage of a first polarity and a plurality of second polarity electrodes for applying a voltage of a second polarity, The first polar electrode of the quadrupole lens and the first polar electrode of the second quadrupole lens are connected to the same constant voltage source, and the second polar electrode of the first quadrupole lens is connected. a portion of the second polarity electrode of all and the second quadrupole lens is connected to the same variable voltage source, constant voltage source remainder of another of said second polarity electrode of the second quadrupole lens And the third quadrupole lens is connected to a constant voltage source.
When the electron beam amount is changed by the control electrode
Focus adjustment of only one variable voltage source
The present invention relates to a cathode ray tube characterized by being configured .

[0012]

[Function] First part of the second polar electrode of the second quadrupole lens
By applying the same voltage as the quadrupole lens of
An effect equivalent to changing the lens length of the quadrupole lens occurs. The contribution of the change in the lens length of the lens of the second quadrupole lens to the lens constant is used to correct the change in the focus state due to the change in the electron beam amount. As a result, focus adjustment up to low brightness can be performed with one variable voltage source.

[0013]

Next, a CRT of an oscilloscope according to an embodiment of the present invention will be described. In FIG. 4, a cathode 9 arranged along the tube axis 1, a control electrode 10, an accelerating electrode 11, and unipotential type first and second quadrupole lenses Q1, Q2.
2, a vertical deflection system 40 including a pair of deflection plates, a unipotential type third quadrupole lens Q3, a horizontal deflection system 41 including a pair of deflection plates, a dome mesh 42, an image plane, that is, a screen 4. A CRT consisting of
The exhaust pipe of the CRT is omitted. Since the basic structure and operation of each part are substantially the same as those disclosed in Japanese Patent Laid-Open No. 63-237334, detailed description thereof will be omitted.

The dome mesh 42 is formed so as to have axial symmetry, has a function of forming an image point of an image formed on the image plane 4 on the screen surface, and is further deflected by the deflection systems 40 and 41. It has a function of expanding the beam (scanning expansion function).

First, second and third quadrupole lenses Q1, Q
2 and Q3 are the first electrodes 2 shown by hatching for convenience of explanation
0 and the second electrode 21 shown without hatching. In this embodiment, the first and second quadrupole lenses Q1 and Q2 are respectively configured by alternately arranging three first electrodes 20 and three second electrodes 21.
The third quadrupole lens Q3 is constructed by alternately arranging two first electrodes 20 and two second electrodes 21. . In order to obtain the lens action shown in FIG. 1 by each quadrupole lens Q1, Q2, Q3, the first and second
The arrangement order of the electrodes 20 and 21 of the first and third quadrupole lenses Q1 and Q3 is different from that of the second quadrupole lens Q2. That is, in the first and third quadrupole lenses Q1 and Q3, the first electrode 20 serves as a positive polarity (first polarity) electrode, the second electrode 21 serves as a negative polarity (second polarity) electrode, and the second quadrupole lens In the lens Q2, the second electrode 21 serves as a positive electrode and the first electrode 20 serves as a negative electrode.

FIG. 5 shows the electrode 20 of the first quadrupole lens Q1,
21 shows the arrangement of 21 and the centers of the electrodes 20 and 21 coincide with the tube axis 1. The electrodes 20, 21 are arranged in parallel with each other with a space 1 and at right angles to the tube axis 1. The total length of this lens is L.

FIG. 6 is a perspective view showing the first and second electrodes 20 and 21 in detail. The first and second electrodes 20 and 21 made of a metal plate have holes 20a and 21a, respectively. Hole 2
0a and 21a are a pair of peripheral edges 2 projecting toward the shaft 1.
2 and a pair of peripheral edges 23 recessed away from the shaft 1
And have respectively. The pair of peripheral edges 22 symmetrically arranged about the tube axis 1 have a curvature that substantially satisfies the equation x ² −y ² = ± a ² indicating a right-angled hyperbola. Similarly, a pair of peripheral edges 23 symmetrically arranged around the tube axis 1 are circular expressions x ² + y ² =
It has a curvature that substantially satisfies b ² . The distance a from the center of the xy coordinates, ie, the tube axis 1 to the apex of the peripheral edge 22 of the first pair, and the distance b from the center to the apex of the peripheral edge 23 of the second pair.
The relationship with is b> a. The hole 21a of the second electrode 21 is different from the hole 20a of the first electrode 20 rotated by 90 degrees.

In this embodiment, the first and second electrodes 2
The thicknesses of 0 and 21 are 0.5 mm, the hyperbolic constant a is 5, and the electrode interval l is 1 mm.

In FIG. 4, the three first electrodes 20 of the first quadrupole lens Q1 and the three second electrodes 21 of the second quadrupole lens Q2 are connected to the power supply terminal 43 of + 300V, The three second electrodes 21 of the first quadrupole lens Q1 and the first electrode 20 of the second quadrupole lens Q2 are connected to the variable resistor 44. The variable resistor 44 is connected to the negative power supply terminal 45 and applies a negative voltage of, for example, about −300 V to the line 44a. Second of the second quadrupole lens Q2
The th first electrode 20 is connected to the negative power supply terminal 46 of -40V. The two first electrodes 20 of the third quadrupole lens Q3 are connected to the + 250V positive power supply terminal 47,
The two second electrodes 21 are connected to the ground. A positive / negative symmetrical voltage is not applied to the third quadrupole lens Q3 for the purpose of reducing the number of power sources, but (250 + 0) / 2 =
The same effect can be obtained by applying a positive voltage of + 125V and a negative voltage of -125V from 125.

In FIG. 4, the axial lengths L1, L2, L3 of the first, second and third quadrupole lenses Q1, Q2, Q3 are shown.
Is 10 mm, 7.5 mm, and 6 mm, and the distance v from the crossover (object point) to the center of the first quadrupole lens Q1
Is 30 mm, the distance d from the center of the first quadrupole lens Q1 to the center of the second quadrupole lens Q2 is 30 mm, and the distance q from the center of the second quadrupole lens Q2 to the center of the third quadrupole lens Q3 is 60 mm. , The distance z from the center of the third quadrupole lens Q3 to the image plane 4 is 120 mm.

Next, the focus shift due to the movement of the crossover caused by changing the voltage of the control electrode 10 to change the amount of electron beam is changed by a single variable resistor 44.
Explain that can be adjusted with.

The lens constant S1 of each quadrupole lens Q1, Q2, Q3 given by the above equations (1), (2) and (3),
The following expressions (4) and (5) are obtained based on S2 and S3.

[0023]

[Equation 2]

If the distance from the crossover to the center of the first quadrupole lens Q1 is changed from v to v-Δv by adjusting the voltage of the control electrode 10, it corresponds to the equations (4) and (5). Differential coefficient S1 '(v), S of S1, S2, S3
Equations (6) and (7) indicating 2 ′ (v) and S3 ′ (v) are obtained.

[0024]

[Equation 3]

In equations (6) and (7), with v constant, Q1,
Even if the ratio of the lens constants of Q2 and Q3 is determined by the equations (4) and (5), it means that no image is formed at the image point if there is a change in v. That is, according to the equations (6) and (7), the equation (4) and (5) deviate from the equations (4) and (5) depending on the change of -Δv,
The image forming condition is no longer satisfied. JP-A-63-23 mentioned above
In the method disclosed in Japanese Patent No. 7334, there is no problem when v does not change much, but when v changes greatly, that is, when the beam current is increased, the image is not formed.

The reciprocal S of the focal length of the quadrupole lens as shown in FIGS. 5 and 6 is given by the following equation (8). Note that V in the following equation is a positive and negative voltage applied to the electrodes 20 and 21,
L is the lens length.

[0027]

[Equation 4]

In the equation (8), S1, S2, and S2 which satisfy the equations (4) and (5) are obtained by appropriately selecting the lens length L.
It is shown that S3 can be obtained. That is, the lens length L1 of the first quadrupole lens Q1 and the lens lengths L2 and L3 of the second and third quadrupole lenses Q2 and Q3 are (4),
It may be determined based on the expressions (5) and (8) so as to comply with the following expressions (9) and (10).

[0029]

[Equation 5]

When the lens lengths L1, L2 and L3 of the quadrupole lenses Q1, Q2 and Q3 are set so as to satisfy the expressions (9) and (10) and the crossover is constant, that is, v is constant, each quadrupole An image can be formed by applying a voltage of ± V to the lenses Q1, Q2 and Q3. But,
When the crossover point, that is, v changes (6),
As shown in the equation (7), an additional factor is added and the image is not formed on the image plane. That is, when the lens length is determined by the equations (9) and (10), the image is not formed on the image plane, the quality of the image point is deteriorated, and the focus is deviated.

The present invention provides a method capable of adjusting the defocus as described above with a single power source. The principle of the present invention basically considers the additional factors of the expressions (6) and (7). FIG. 7 illustrates the principle. The quadrupole lenses Q1, Q2, and Q3 each have a lens length of L1.
, L2, L3. Each of the quadrupole lenses is composed of an electrode having a hyperbolic electron passage hole shown in FIG. . That is, the quadrupole lenses Q1, Q2 and Q3 in FIG. 7 are shown in the same manner as the quadrupole lenses Q1, Q2 and Q3 in FIG. However, the number of electrodes 20 and 21 is appropriately increased or decreased. The three quadrupole lenses Q1, Q2, Q3 are connected to a common positive power supply terminal 30, but not all are commonly connected to a negative power supply. Part of the second and third quadrupole lenses Q2 and Q3 is connected to the negative power supply terminal 31,
The rest is connected to the variable resistor 34 together with the first quadrupole lens Q1. The variable resistor 34 is connected to the negative power supply terminal 33 and folds to apply a negative potential to the output line 34a. The lens lengths .DELTA.L2 and .DELTA.L3 based on the electrodes connected to the variable resistor 34 of the second and third quadrupole lenses Q2 and Q3 are set so as to satisfy the following equations (11) and (12).

[0032]

[Equation 6]

Positive and negative voltages are alternately applied to the respective electrodes constituting the quadrupole lens, and the positive electrode is supplied with + by the power source 30.
V is applied. When the crossover point, that is, v is constant, -V is applied to the divided voltage output line 34a of the variable resistor 34, and -V is also applied to the power supply terminal 31. Object 12 to 1st
+ Is on the positive side when the distance to the quadrupole lens Q16 is v
If V is applied to the negative side and -V is applied to the negative side, it is clear from the above description that an image can be formed on the image plane 4.

Next, when v changes to v-Δv, Δv
Is smaller than the geometrical quantities v, d, q, and z, but the variation S1 ′ (v) of the lens constant S1 is S1 (v−Δv) = S
1 (v) −S1 ′ (v) Δv. Therefore, S
Assuming that the voltage changes by ΔV corresponding to the change amount of 1 ′ (v) Δv, the voltage applied to the first quadrupole lens is ± V
To ± V (V + ΔV). When + V is kept constant, the negative voltage is -V (1-2ΔV). However, ΔV is the adjustment voltage of the first quadrupole lens corresponding to the change of −Δv. That is, the above is S1 (v-Δv)
Means that L 1 (V + ΔV) / a ² substantially matches. Since this voltage is applied to the portion corresponding to the lens length ΔL2 of the second quadrupole lens Q2, the lens length ΔL2
The contribution S'of 2 to the lens constant can be expressed by the following equation (13).

[0035]

[Equation 7]

The contribution S ″ of the second quadrupole lens Q2 before v is changed is expressed by the following equation (14).
The sum S2 of "'and S2" is expressed by equation (15).

[0037]

[Equation 8]

The expression (15) includes the expression (6). That is,
This means that the focus condition can be satisfied even if the distance v changes due to the change of the object point 12. The third quadrupole lens Q3 has the same effect as the second quadrupole lens Q2. Therefore, it becomes possible to perform focus adjustment with one variable resistor 34.
In the above description, the effect of the end portion of the quadrupole lens is not considered for the sake of clarity. Actually, the lens length is obtained experimentally or by numerical calculation, but the basic idea is not different.

Although FIG. 4 showing the embodiment of the present invention is not the same as FIG. 7 showing the principle, the principle of focus adjustment is exactly the same, and the structure of FIG. 4 enables focus adjustment. In FIG. 4, the negative potential of the output line 44a of the variable resistor 44 is -300 V when the luminance is low, that is, when the beam current is small. At this time, the lens length .DELTA.L2 based on the electrode connected to the line 44a among the electrodes of the second quadrupole lens Q2 is about. It is 1.9 mm. Since L2 is set to 7.5 mm, the ratio ΔL2 / L2 to this L2
Is 0.25. On the other hand, the additional factor v (q +
z) / {2d (v + q + z + d) + v (q + z)} is 0.273. In the case of this example, although slightly deviated from the expression (6), the focus can be adjusted up to 20 μA in screen current (corresponding to 1 mA when converted into beam current). Estimating from equation (1), the change in v at this time is about 8 mm.

[0038]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) The negative potentials of the first and second quadrupole lenses Q1 and Q2 are set to be the same or fixed, and one selected from the electrodes to be given a positive potential of the second quadrupole lens Q2 is the first quadrupole lens Q1. It may be connected to a positive variable voltage source together with the electrode for applying the positive potential of. (2) Instead of the dome mesh 42 which is an axially symmetric post-acceleration system, Japanese Patent Laid-Open No. 63-2373.
CRT using a post-acceleration method using a meshless lens such as a box-type scanning magnifying lens known in Japanese Patent No. 34
The present invention can also be applied to. When using a meshless lens, the distance to the image plane differs in the horizontal and vertical directions. Therefore, (1), (2), (3)
The equation is modified, but a similar relation is obtained. That is, the additional factor is calculated in the same manner as the method described in the embodiment, and one or both of the second quadrupole lens Q2 and the third quadrupole lens Q3 is divided to correspond to this additional factor, Is connected to the first quadrupole lens Q1, the same result can be obtained.

[0039]

As described above, focus adjustment from low brightness to high brightness can be performed with one variable voltage source.

[Brief description of drawings]

FIG. 1 is a diagram showing the image formation principle by three quadrupole lenses by optical analogy.

FIG. 2 is a diagram showing generation of an object point by a lens system including a cathode of a CRT, a control electrode, and an acceleration electrode.

FIG. 3 is a diagram showing a lens system having an axially symmetric lens.

FIG. 4 is a diagram showing in principle a part of a CRT according to an embodiment of the present invention.

5 is a diagram showing the first quadrupole lens of FIG. 4. FIG.

FIG. 6 is a perspective view showing first and second electrodes of FIG.

FIG. 7 is a diagram showing three quadrupole lenses for explaining the principle of the present invention.

[Explanation of symbols]

 1 Tube Axis 4 Image Surface 9 Cathode 10 Control Electrode 11 Accelerating Electrode 44 Variable Resistors Q1, Q2 Q3 Quadrupole Lens

Claims (1)

[Claims] 1. A control battery for controlling the amount of an electron beam.
In a cathode ray tube having a pole and further having at least first, second and third quadrupole lenses, a plurality of plate electrodes in which at least the first and second quadrupole lenses are arranged at right angles to the tube axis. Wherein each of the plurality of plate-shaped electrodes comprises a combination of a plurality of first polarity electrodes for applying a voltage of a first polarity and a plurality of second polarity electrodes for applying a voltage of a second polarity, The first polarity electrode of the first quadrupole lens and the first polarity electrode of the second quadrupole lens are connected to the same constant voltage source, and all of the second polarity electrodes of the first quadrupole lens and the A part of the second polarity electrode of the second quadrupole lens is connected to the same variable voltage source, and the rest of the second polarity electrode of the second quadrupole lens is different.
Is connected to a constant voltage source, the third quadrupole lens is connected to a constant voltage source, off when changing the electron beam amount by said control electrode
Configured to adjust the focus with only the variable voltage source
Cathode ray tube, characterized in that it is.