JPS6117333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun, particularly an electron gun having a lens function used in a cathode ray tube.

Conventionally, there are two types of electron guns with a lens function used in cathode ray tubes: unipotential type and bipotential type. First, in the case of a unipotential electron gun, three focusing electrodes arranged on one axis are used to form the main lens, and two of these electrodes on both sides are connected to a high voltage of about 25 kV, for example. is applied, and a voltage close to ground potential is applied to the remaining electrodes.

On the other hand, in the case of a bipotential electron gun, two focusing electrodes arranged on one axis are used to form the main lens;
A high voltage of about 25 kV is applied, and a medium voltage of 3 to 6 kV is applied to the remaining electrodes.

In these types of electron guns, electrodes are arranged to constitute one main lens, and the main lens 1
This means that a cathode image is formed on the image-receiving surface. However, in a cathode ray tube, the aperture of the electron gun is limited by the inner diameter of the neck that houses it, so there is also a limit to the aperture of the main lens formed, and there is a limit to the improvement of aberrations. This is especially true for the three electron guns housed in the network section.
This is an important problem in electron gun type cathode ray tubes.

The present invention aims to solve such problems and will be described in detail below.

FIG. 1 shows the basic structure of the main lens used in the electron gun according to the present invention.
Lm is composed of two electronic lens systems L ₁ and L ₂ , and these electron lens systems L ₁ and L ₂ are composed of either a unipotential lens Lu or a bipotential lens Lb. .
These electron lens systems L ₁ and L ₂ apparently form one large-diameter main lens Lm'. Note that l ₁ to l ₈ are the trajectories of the electron beam.

In this way, the main lens Lm is divided into two electronic lens systems.
When L ₁ and L ₂ are used, the aperture of the main lens can be made larger in appearance, and aberrations can therefore be easily reduced. In this case, the two electronic lens systems L ₁ and L ₂ are unipotential lenses.
Since Lu and bipotential lens Lb are combined, the unipotential lens Lu can reduce the focal fluctuation in response to voltage fluctuations, and the unipotential lens Lu can reduce the focus fluctuation in response to blooming. It can also be reduced when the current increases. Furthermore, since the bipotential lens Lb is used, a narrow beam can be easily obtained.

2 and 3 show an example of an electron gun separately proposed by the present inventors, in particular, the main lens Lm
Only the electrodes forming the are shown. In the figure _, the main lens Lm is composed of four first to fourth electrodes P 1 to P ₄ arranged on one axis, and the first electrode P ₁ is arranged on the stem side of the cathode ray tube. , the fourth electrode _P4 is arranged on the face side of the cathode ray tube. The first electrode P ₁ and the third electrode P ₃ are connected in common to the high voltage source Ea,
The second electrode P ₂ and the fourth electrode P ₄ are connected in common to the medium voltage source Eb. In this way, the first to third electrodes P 1 to P ₃ form a unipotential lens Lu, and _the third electrodes P ₃ and P ₄ form a bipotential lens Lb. As explained in FIG. 1, these lenses Lu and Lb apparently form one large-diameter main lens Lm. In this example, the length of the electrode _P2 (the length in the direction parallel to the tube axis) is different from that of the electrode _P4 to which the same voltage Eb is applied.

In addition, Figure 3 shows four first
Of the to fourth electrodes P ₁ to P ₄ , the first and third electrodes P ₁ and P ₃ are commonly connected to the high voltage source Ea, and the second and fourth electrodes P ₂ and P ₄ are connected to different medium voltage sources Eb ₁ and Eb ₂ , respectively. In this way, as in the case of FIG. 2 described above, the first to third electrodes P 1 to P ₃ form a unipotential lens Lu, and the third and fourth electrodes _{P 3 and} P ₄ form a bipotential lens Lu. A shaped lens Lb is formed. In this example, the electrode length of _{the electrode P 3 disposed} adjacent to the electrode P 2 is different from that of the electrode P ₂ . FIGS. 4 and 5 show an embodiment of the electron gun according to the present invention, and like FIGS. 2 and 3, particularly only the electrodes forming the main lens Lm are shown.

First, Figure 4 shows the four first
Of the to fourth electrodes P ₁ to P ₄ , the first and third electrodes P ₁ and P ₃ are commonly connected to the medium voltage source Eb, and the second and fourth electrodes P ₂ and P ₄ are connected in common to the high voltage source Ea. In this way, contrary to the case described above, the first and second electrodes P1 and _P2 form a bipotential lens Lb, and the second to fourth electrodes P1 _{and P2} form a bipotential lens Lb.
Electrodes P ₂ to P ₄ are unipotential lenses Lu
form. Note that in this example, the electrode lengths of the electrode P ₁ and the electrode P ₂ are different.

Furthermore, in FIG. 5, 4
Of the first to fourth electrodes _P1 to _P4 , the second
and the fourth electrodes P ₂ and P ₄ are connected in common to a high voltage source Ea, and the first and third electrodes P ₁ and P ₃ are respectively connected to different medium voltage sources Eb ₁ ,
Connected to Eb ₂ . In this way, as in FIG. 4, the first and second electrodes P 1 and P ₂ form a bipotential lens Lb, and _the second to fourth electrodes P ₂ to P ₄ form a unipotential lens.
Form Lu. Note that in this example, electrode P ₃ is the electrode
P ₂ and P ₄ have different electrode lengths.

As described above, by using the electron gun according to the present invention, a narrow beam electron gun can be obtained with small aberrations, and an electron gun with extremely high resolution can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the basic configuration of the main lens used in the electron gun according to the present invention, and FIGS. 2 and 3 are simplified electrode arrangement diagrams of an electron gun separately proposed by the present inventors. , 4 and 5 are simplified electrode arrangement diagrams showing an embodiment of an electron gun according to the present invention. Lm...main lens, Lu...unipotential lens, Lb...bipotential lens.

Claims (1)

[Claims] 1. In an electron gun in which a main lens is formed from a combination of a plurality of electrodes, the main lens is formed by a combination of electron lens systems forming a bipotential lens and a unipotential lens, and the bipotential The shaped lens is placed before the unipotential lens, and the potential of the rearmost electrode of the electrodes forming the bipotential lens and the potential of the rearmost electrode of the electrodes forming the unipotential lens are set. An electron gun characterized by having the same potential.