JP2883382B2 - Color cathode ray tube - Google Patents

Description

Description of the Invention [Object of the Invention] (Industrial application field) The present invention relates to a color cathode ray tube, and particularly when the convergence of electron beams fluctuates, the concentration of three electron beams is excessive or insufficient. The present invention relates to a color cathode ray tube provided with an in-run type electron gun having means for compensating for the color cathode ray tube.

(Prior Art) As shown in FIG. 9, a conventional color cathode ray tube has an in-line type electron gun structure including a cathode (2) containing a heater (1), a first grid (3) integrally formed,
The main electron lens (L ₁₀₀ ) includes a second grid (4), a third grid (5), and a fourth grid (6). Jujiku (Z _G), the gun axis of each side electron gun _{(Z B), (Z R} )穿殺are openings around the _{(5 G), (5 B} ), a third with a (5 _R)
A grid (5), an opening (6 _G ) drilled about the gun axis (Z _G ) of the central electron gun at the bottom of a bottomed cylindrical body also formed mechanically integrally, and a gun for both electron guns axis _{(Z B), (Z R} )
穿殺been opening off-center with respect to (6 _B), is formed between the (6 _R). In this case, as shown in JP-B-52-32714, in central electronic gun opening and (5 _G) and (6 _G) are drilled around the Jujiku (Z _G) Therefore, the central electron beam (9 _G ) goes straight toward the phosphor screen (not shown) as it is. However, in the case of a double-sided electron gun, the electric field is asymmetrical so that the two-sided electron beams (9 _B ), (9 _R ) allowed bending the central electron beam (9 _G) direction, these three electron beams _{(9 B), (9 G} ),
( _9R ) is designed to be concentrated on the phosphor screen.
As a means for making the electric field asymmetric, Japanese Patent Publication No. 53-3807
As disclosed in Japanese Patent Application Publication No. 6-206, there is a device using an inclined opening electrode.

The above-mentioned electron gun assembly is preferable in terms of cost and accuracy because the configuration of each electrode is mechanically simple and the relative positions of the electron lenses of the three electron guns are determined accurately. There is something to be done. That is, eccentric or inclined openings are used to concentrate the three electron beams at predetermined positions. The tendency of the electron beam by the asymmetric electron lens formed by the eccentric or inclined opening is approximately proportional to the amount of eccentricity or inclination and the potential difference between the electrodes forming the electron lens. That is, the tendency angle (amount) due to the asymmetric electron lens is approximately given by the following equation.

θ = k · p · q (1) Here, θ is a tendency angle, k is a constant, p is the amount of eccentricity that normalizes the electron lens diameter, and q is the voltage ratio of the electron lens.

Therefore, if the voltage applied between the electrodes forming the electron lens is inaccurate, the tendency angle θ changes, and as a result, there arises a problem that the static concentration of the color picture tube when the tendency magnetic field is not applied is shifted.

For example, a bipotential electron lens (Bi Potenti
al Focus: hereafter abbreviated as BPF).
A high voltage of 25 to 32 kV is applied to the grid as an accelerating voltage, and a medium voltage designed to be 25 to 35% of the focusing voltage is applied to the third grid. ± 1% of the applied voltage
A degree of error occurs. This is a size that cannot be ignored with respect to the concentration of the electron beam.

In particular, a recent color cathode ray tube is finally adjusted as a cathode ray tube before being attached to a receiver, for example, Japanese Patent Publication No. 51-45936.
As shown in the publication, the adjustment of the magnetic field strength of the multi-pole magnetized permanent magnet mounted on the outer wall of the neck of the vacuum envelope of the cathode ray tube results in three axes: a tube axis, an electron gun axis, and a tilt device axis. In the case of the preset type, in which the axes are aligned and no adjustment is made after it is mounted on the receiver, the potential difference between the electrodes forming the electron lens, especially when the potential difference between the electrodes forming the electron lens needs to be accurate, such as the electron gun structure with the structure described above If the operating conditions of the electron gun during adjustment of the picture tube, especially the voltage applied to the third grid (5) are incorrect, then it is necessary to perform readjustment after mounting on the picture receiver, which leads to an increase in working efficiency. It will cause deterioration.

Several proposals have been made for the problem caused by such a change in the focusing electric field. For example, as shown in FIG. 10, in Japanese Patent Publication No. 1-42109, a first electron lens (L ₁₁₀ ) is placed between a third grid (5), a fourth grid (6), and a fifth grid (7). 5 grid (7) and 6 grid (8)
A second electronic lens (L ₁₂₀ ) is formed between the first electronic lens (L ₁₁₀ ) and the second electronic lens (L ₁₂₀ ).
There is shown an example in which two asymmetric electron lenses having eccentric apertures opposing each other are made to tend electron beams on both sides and concentrate them at a predetermined position. However, exclusively in such a structure, the electron beam directed by the first electron lens (L ₁₁₀ ) passes through the tube axis side of the second electron lens (L ₁₁₀ ), and the electron beam is directed by the second electron lens (L ₁₂₀ ). It will be subject to aberration. As a result, there is a problem that the electron beam on both sides produces a halo in the lateral direction.

In Japanese Patent Application Laid-Open No. 55-37798, in an electron gun composed of a first asymmetric electron lens and a second asymmetric electron lens, both-sided electron beams tended by the first electron lens (L ₁₁₀ ) is incident is inclined approximately at the center portion of the second electron lens (L _120), a second electron lens (L ₁₂₀₎
Are also eccentric. This complicates the electrode structure and increases the types of electrodes. Therefore, it is extremely difficult to assemble each electrode of the electron gun with high precision, and the resolution may be degraded.

Further, in JP-A-1-42109 and JP-A-55-37798, a first electron lens (L ₁₁₀₎ and a second electron lens (L ₁₂₀₎ only together tend both sides electron beam in the inline direction And has the effect of focusing in the in-line direction and in the direction perpendicular to the in-line direction. FIG. 11 schematically shows the positional relationship between the electron lens system and the object point. If the first electron lens (L ₁₁₀ ) for concentration correction is ignored, for focusing, the electron beam emitted from the virtual object point VP on the axis is given by the second electron lens (L ₁₂₀ ). A system that forms an image at a position has been established. However, in practice, the first electron lens ( _L110 ) also has a converging action, so that there is a drawback that the virtual object point VP moves forward and backward. In particular, since the first electron lens ( _L110 ) is an asymmetric electron lens, the electron beam incident on the second electron lens ( _L120 ) is distorted.
Therefore, since the object point viewed from the second electron lens (L ₁₂₀ ) is deteriorated, there is a disadvantage that the spot diameter on the phosphor screen is increased and the resolution is reduced.

(Problems to be Solved by the Invention) The present invention suppresses a substantial change in the degree of concentration of a plurality of electron beams due to a change in the degree of electron beam convergence of an in-line type electron gun in a color cathode ray tube as described above, and It is an object of the present invention to provide a color cathode ray tube having a high-resolution electron gun without deterioration of a spot diameter at a predetermined position on a phosphor screen.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, an electron beam forming unit including a cathode for generating, accelerating, and controlling a plurality of electron beams in an in-line direction, and the electron beam An in-line type electron gun composed of a main electron lens unit that focuses and concentrates
In a color cathode ray tube having at least a phosphor screen facing the electron gun, a first part having an opening for passing a plurality of electron beams in the inline direction through a main electron lens of the inline electron gun. And the second electrode opposed to the first electrode and having a common opening, and the opening of the first electrode and the opening of the second electrode are overlapped in the tube axis direction. A first electron lens portion having a substantially rectangular shape of an electron lens having an overlapping common opening shape, which is a portion where the opening regions of the two opening portions are common, and a phosphor screen side with respect to the first electron lens portion. And a second electron lens portion including a plurality of electrodes for focusing and concentrating the plurality of electron beams at a predetermined position, and the opening of the first electrode is positioned in the inline direction from the overlapping common opening. Partial at right angles Alternatively, the first electron lens portion is enlarged by making the shape of the first electron lens portion into a shape having an overhang portion of the opening portion as a whole, and making the overhang portion in the in-line direction shorter than the in-line opening length of the second electrode. It is characterized by having an asymmetrical lens.

In the above color cathode ray tube, a fixed high voltage is applied as an accelerating voltage to the phosphor screen side electrode of the second electron lens portion of the in-line type electron gun, and the cathode side electrode of the second electron lens portion is connected to the second electrode portion. A variable intermediate voltage is applied to the second electrode of the first electronic lens unit as a focusing voltage, and a fixed intermediate voltage having substantially the same potential as the intermediate voltage is applied to the first electrode of the first electronic lens unit. Thus, the first electronic lens unit compensates for the excess or deficiency of the degree of concentration of the electron beam of the second electronic lens unit.

(Operation) As described above, in the present invention, the main electron lens portion of the in-line type electron gun in the color cathode ray tube is divided into a first electron lens portion and a second electron lens portion,
The first electronic lens has a function of compensating the degree of concentration of the second electronic lens. That is, by making the first electronic lens an asymmetric lens that acts only when a potential difference occurs between the electrodes forming the electronic lens,
The electron beams on both sides of the plurality of electron beams are deflected in the in-line direction to compensate for the excessive or insufficient degree of concentration of the electron beams of the second electron lens. In addition, by making the asymmetric lens large in diameter, each electron beam has a small function of focusing and diverging, and has a sufficient function to deflect both side electron beams in the in-line direction. The compensation operation will be described as follows. When the strength of the second electron lens matches the design value, there is no potential difference between the opposing electrodes forming the first electron lens, so that the first electron lens does not act and only the second electron lens operates. The plurality of electron beams are appropriately focused and focused on the phosphor screen. However, when the electron beam is properly focused on a predetermined position in a state where the strength of the second electron lens is higher than the design value, the second electron lens alone causes an over-concentration state. In this case, the first electron lens acts to deflect the electron beams on both sides in a direction away from the central electron beam, so that the plurality of electron beams are appropriately concentrated on the phosphor screen. On the other hand, when the electron beam is properly focused at a predetermined position in a state where the strength of the second electron lens is weaker than the design value, the plurality of electron beams are under-concentrated. At this time, the first electron lens deflects the electron beams on both sides in a direction approaching the central electron beam, so that the electron beams are appropriately concentrated on the phosphor screen.

(Embodiment) An embodiment in which the present invention is applied to a color cathode ray tube that emits three electron beams in an inline direction will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing an in-line surface of an electron gun applied to a color cathode ray tube according to an embodiment of the present invention. A first grid (3), a second grid (4), a third grid (5), a fourth grid (6), and a fifth grid (7) each integrally formed with a cathode (2) containing a heater (1). The first electron lens is formed between the third grid (5) and the fourth grid (6). The opening shape of the electrode forming the first electron lens as viewed from the tube axis direction is the second shape.
This is shown in FIGS. FIG. 2 (a) shows a substantially rectangular opening (10) in the bottom of the third grid (5) as a first electrode on the phosphor screen side, and FIG. 2 (b) shows a fourth grid (2) as a second electrode. 6) shows a substantially rectangular opening (11) at the bottom of the cathode side. As shown in FIG. 2 (a), when the in-line direction is the horizontal direction and the in-line direction is the vertical direction, three electron beams (9 _B ) are provided at the bottom of the third grid (5) on the phosphor screen side. , (9 _G ), (9 _R ), a substantially rectangular opening (10) having a height h ₅ and a width w _{5, and} a bottom portion on the cathode side of the fourth grid (6) are shown in FIG. 2 (b). Like three electron beams (9 _B ),
(9 _G), common longitudinally (9 _R) h _6, a substantially rectangular opening in the lateral w ₆ and a (11), between each of the opening length h ₆ <h _5, w ₆ >
w has a relationship of ₅ . FIG. 2 (c) is a schematic plan view when the two openings (10) and (11) are overlapped in the tube axis direction. In FIG. 2 (c), the solid line is a substantially rectangular opening (10) at the bottom of the third grid (5) on the phosphor screen side, and the broken line is a substantially rectangular opening (1) at the cathode side of the fourth grid (6).
1), hatched portions indicate overlapping common openings. Since superimposed common aperture is common to have portions of among opening regions of the two apertures in the tube axis direction, the opening length of the overlapping common aperture in the present embodiment vertically h _6, the horizontal w ₅ . As shown in FIG. 2 (c), a substantially rectangular opening (10) at the bottom of the phosphor screen side of the third grid (5), which is the first electrode, has an opening in a direction perpendicular to the overlapping common opening and in-line. overhang of but with (10a), a substantially rectangular opening in the cathode side bottom of the fourth grid line direction of the opening length w ₅ of the projecting portion (10a) which is the second electrode (6) (11) opening length of the in-line direction w ₅
If it is in a smaller range, the overhang (10a) may partially overhang the overlapping common opening or may entirely overhang as in this embodiment. A second electron lens (L ₁₂₀ ), which is a focusing lens, has a gun shaft (Z _G ) of a central electron gun at the bottom of a mechanically integrally formed bottomed cylinder,
Sides electron gun gun axis (Z _B), and (Z _R) drilled openings around the _{(6 G), (6 B} ), a fourth grid having (6 _R) (6), also mechanical An opening (7 _G ) drilled around the gun axis (Z _G ) of the central electron gun and gun axes (Z _B ), (Z openings drilled off-center with respect to _R) (7 _B), it is formed between the (7 _R).

At this time, a high voltage ( _Eb ) is applied to the fifth grid (7) as an anode acceleration voltage, and a medium voltage as a focusing voltage designed to be about 25 to 35% of the anode acceleration voltage is applied to the fourth grid (6). Apply voltage (Vf). In this case, in the central electron gun, the openings (6 _G ) and (7 _G ) are drilled about the gun axis (Z _G ), so that the central electron beam (9 _G ) is not directly shown on the fluorescent screen (not shown). However, the electron beams (9 _B ) and (9 _R ) passing through the electric field are bent in the direction of the central electron beam (9 _G ). Book electron beam ( _9B ), ( _9G ),
( _9R ) is designed to concentrate on the phosphor screen. Here, when a voltage having substantially the same potential as that of the fourth grid (6) is supplied to the third grid (5) from a power source different from that of the fourth grid (6), the fourth grid (6) and the third grid (6) are connected to the third grid (5). Since there is no potential difference between the grids (5), no electron lens is formed. However, as described above, when the medium voltage (Vf ') fluctuating from the value designed as the focusing voltage is applied to the fourth grid (6) and the three beams are concentrated on the screen, the third grid (5 ) And the fourth grid (6). The potential difference and the opening shape shown in FIG. 2C form an asymmetric lens as the first electronic lens (L ₁₁₀ ) having a concentration correcting action.

The asymmetric lens in this embodiment is a quadrupole lens, and the operation of the quadrupole lens is shown in FIGS. 3 (a) and (b) on the potential distribution diagram, and FIGS. 4 (a) and (b) on the XY plane. FIG. 5 shows the lens action on the XZ plane and the trajectory of the electron beam. In the figure, the X axis indicates the inline direction, the Y axis indicates the direction perpendicular to the inline direction, and the Z direction indicates the axis of the central electron beam. As shown in FIGS. 3A and 3B, an axially asymmetric lens is formed between the third grid (5) and the fourth grid (6).

As shown in FIG. 3 (a), in the Y-axis direction, the electron beam trajectory is substantially located near the center of the lens, so that the effect of the lens on the electron beam in the Y-axis direction is small. Further, as shown in FIG. 3 (b), in the X-axis direction, a weak lens typified by equipotential lines is formed, and the electron beams on both sides are subjected to an appropriate deflection action. In FIG. 5, the trajectory is the case where the voltage of the fourth grid (6) is the same as the medium voltage (Vf) designed as the focusing voltage and there is no potential difference between the third grid (5). Therefore, the first electron lens is not shown and is not shown.
In this case each side electron beam _{(9 B), (9 R} ) is focused simultaneously is focused on the phosphor screen by the focusing lens is a second electron lens (L _120). Next, when the focusing voltage of the fourth grid (6) is a medium voltage (Vf1 ') higher than the design voltage (Vf), the voltage of the third grid (5) is fixed at the designed medium voltage (Vf). Therefore, the quadrupole lens (L ₁₁₀ ) as the first electron lens acts as an electron lens (L ₁₁₁ ) having convergence in the in-line direction (X-axis direction) as shown in FIG. Both sides electron beam ( _9B ), ( _9R )
Is deflected toward the central electron beam (9 _G ). At the same time, the electron lens (L ₁₁₁ ) acts as a divergent lens in the direction perpendicular to the in-line direction, but does not participate in the deflection of the three electron beams. At this time, since the degree of concentration of the focusing lens (L ₁₂₀ ), which is the second electronic lens, is lower than the design value, the degree of concentration is substantially the same as the design value as a whole. The trajectory in FIG. 5 corresponds to the state at this time. on the other hand,
When the focusing voltage of the fourth grid (6) is a medium voltage (Vf2 ') lower than the design voltage (Vf), the first grid is contrary to the previous example.
Quadrupole lens (L ₁₁₀₎ is an electron lens showing the divergence inline direction (X axis direction) of the electron lens (L ₁₁₂₎
And the two-sided electron beams (9 _B ) and (9 _R ) are deflected away from the central electron beam (9 _G ). At the same time, the electron lens (L ₁₁₂ ) acts as a focusing lens in the direction perpendicular to the in-line direction, but does not participate in the deflection of the three electron beams. At this time, the concentration of the focusing lens (L ₁₂₀ ) increases contrary to the previous example, so that the concentration becomes substantially the same as the design value as a whole. The trajectory in FIG. 5 shows the state at this time.

FIG. 6 shows the deviation (ΔV) of the focusing voltage from the designed value.
The relationship between f) and the amount of deviation of the concentration level is shown. FIG. 6 shows the relationship in the embodiment of the present invention, and FIG. 6 shows the relationship in the conventional in-line type electron gun. FIG. 6 shows that in the above embodiment, even if the focusing voltage of the second electron lens, that is, the main electron lens in the in-line type electron gun of the conventional color cathode ray tube, was changed, the degree of concentration of the three electron beams was substantially almost zero. It turns out that it does not change. Further, in the present invention, since the first electron lens having the convergence correction function is constituted by a quadrupole lens, as described above, a convergence or divergence electron lens is also formed in the heavy direction, but three electron Since it is a large lens that passes the beams in common, it has been confirmed that the vertical lens effect acting on each of the three electron beams is extremely small, and the distortion of the electron beams is negligibly small.

Embodiment 2 FIGS. 7 (a) to 7 (c) show another embodiment of the first electron lens of the in-line type electron gun applied to the color cathode ray tube of the present invention. FIG. 7A shows a third electrode as the first electrode.
A substantially rectangular opening (10) at the bottom of the grid (5) on the phosphor screen side,
FIG. 7 (b) shows a substantially rectangular opening (11) at the cathode-side bottom of the fourth grid (6) as a second electrode. FIG. 7 (a)
As shown in (5), the length of the opening of the third grid (5) in the in-line direction may be longer than the length in the vicinity of the region substantially passing the three electron beams. FIG. 7 (c) shows a schematic plan view when the two openings (10) and (11) are overlapped. In FIG. 7 (c), the solid line is a substantially rectangular opening (10) at the bottom of the third grid (5) on the phosphor screen side, and the broken line is a substantially rectangular opening (1) at the cathode side of the fourth grid (6).
1), hatched portions indicate overlapping common openings. As can be seen from FIG. 7 (c), the first electrode partially has an overhang (10a) in a direction perpendicular to the in-line direction from the overlapping common opening, and the first electrode has an overhang in the in-line direction of the overhang (10a). aperture length w ₅ is is smaller than the aperture length w ₆ in-line direction of the first electrode, forming a quadrupole lens.

FIGS. 8A and 8B show the potential distribution of the first electron lens portion of the electrode structure shown in FIG. By adopting the opening shape as described above, the opening length in the in-line direction of the overlapping common opening can be increased as compared with the first embodiment, and as shown in FIG. The equipotential lines become gentler, and the beam spot distortion due to the deflection of the electron beam on both sides can be reduced.

In the above two embodiments, the first electron lens portion is described as a quadrupole lens. However, the present invention is not limited to this. The first electron lens is in the inline direction, and the potential of the first electrode is the second electrode. When it is higher than the potential of the electrode, it has a divergent effect,
When the potential of the first electrode is lower than the potential of the second electrode, it suffices that the first electrode has at least a focusing action. Further, the positional relationship between the first electrode and the second electrode of the first electron lens portion is opposite to that in the above-described embodiment, that is, the first electrode is opposed to the fluorescent screen side of the second electrode, A variable middle voltage may be applied to the electrode, and a fixed middle voltage may be applied to the first electrode. Further, the electrode of the first electron lens portion may be a combination of the electrode shown in FIG. 2 and the electrode shown in FIG.

In both embodiments, the overlapping common opening shape is elongated in the in-line direction, but may be elongated in the direction perpendicular to the in-line direction. Ideally, an aperture that is elongated in the direction perpendicular to the in-line direction is preferable from the viewpoint of the lens action acting in the direction perpendicular to the in-line direction and from the viewpoint of distortion of the beam spot. However, a neck for sealing the electron gun inside is preferable. Due to the limitation of the diameter of the portion, the opening is elongated in the in-line direction in the embodiment.

Furthermore, in the above two embodiments, the BPF type electron lens is used as the focusing lens system of the main electron lens,
Unipotential Focu
Also applicable to s: UPF) electron guns or other compound electron guns. Further, although the electrode structure of the second electron lens of the main electron lens has been described only for an electrode structure decentered with respect to both-side electron beams, the structure of the second electron lens is not limited to this.

Further, a voltage fixed to one of the focusing voltages constituting the first electron lens having the focusing correction function may be supplied by incorporating a resistor in the tube and dividing the anode voltage at a predetermined ratio.

[Effects of the Invention] As described above, according to the present invention, even if the focusing voltage deviates from the design value, the concentration of the three electron beams at a predetermined position on the phosphor screen is kept constant. It is possible to obtain an extremely practical high-resolution electron gun without deterioration of the beam spot due to the action of correcting the degree of concentration.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an in-line surface showing an embodiment of the in-line type electron gun of the present invention, and FIGS. 2 (a) to 2 (c) are schematic plan views showing an opening shape of a first electron lens portion. FIGS. 3 (a) and 3 (b) are potential distribution diagrams of the first electron lens portion, and FIG. 4 is a schematic plan view for explaining the operation of the convergence correction lens on the XY plane in the present invention. Figure, fifth
FIG. 6 is a schematic plan view for explaining the operation of the convergence correction lens on the XZ plane in the present invention. FIG. 6 is a characteristic diagram showing the relationship between the convergence voltage of the electron gun and the deviation of the degree of concentration in the embodiment of the present invention. FIGS. 7 (a) to 7 (c) are plan views showing another embodiment of the first electron lens of the present invention, and FIGS. 8 (a) and 8 (b) are shown in FIG. FIG. 9 is a sectional view showing an in-line surface of a conventional in-line type electron gun, and FIG. 10 is a sectional view showing an in-line surface of a conventional concentration correcting in-line type electron gun. ,
FIG. 11 is a schematic plan view for explaining the relationship between the electron lens system and the object point position in FIG. (1)… heater (2)… cathode (3)… first grid (4)… second grid (5)… third grid (6)… fourth grid (7)… 5 grids (8) Electron beam (10) Opening (11) Opening area ( _L110 ) First electron lens ( _L120 ) Second electron lens

Claims (2)

(57) [Claims] 1. An in-line type electron gun comprising an electron beam forming section including a cathode for generating, accelerating and controlling a plurality of electron beams in an in-line direction, and a main electron lens section for focusing and concentrating said electron beams. A color cathode-ray tube having at least a phosphor screen facing the electron gun, wherein the main electron lens portion of the in-line type electron gun has an opening for passing a plurality of electron beams in the in-line direction in common. A superimposed common opening shape, comprising a first electrode and a second electrode facing the first electrode and having a common opening, wherein the opening of the first electrode and the opening of the second electrode overlap. A first electron lens part whose electron lens is substantially rectangular, and a plurality of electrodes which are closer to the phosphor screen than the first electron lens part and focus and concentrate the plurality of electron beams at predetermined positions. A second electron lens portion, wherein the opening portion of the first electrode has an overhang portion of an opening portion in a direction perpendicular to the in-line direction from the overlapping common opening portion, and has an in-line opening length of the overhang portion. Is a color cathode ray tube having a length smaller than an opening length of the second electrode in an in-line direction. 2. A color cathode ray tube according to claim 1, wherein
A fixed high voltage is applied as an accelerating voltage to the phosphor screen side electrode of the second electron lens unit of the in-line type electron gun, and the cathode side electrode of the second electron lens unit and the first electrode of the first electron lens unit. By applying a variable medium voltage as a focusing voltage to the second electrode and applying a fixed medium voltage having substantially the same potential as the medium voltage to the first electrode of the first electron lens portion, A color cathode ray tube, wherein the electron lens unit compensates for an excess or deficiency of the degree of concentration of the electron beam of the second electron lens unit.