JPS62237645A - Electron gun - Google Patents

Abstract

PURPOSE:To make it possible to correct the deflecting aberration efficiently without losing the performance, by making furnishing positions and forms of four electrode pieces composing a quadrupole electrode in a position and form almost axis-symmetrical to the elctron beams. CONSTITUTION:A pair of opposing electrode pieces 6a and 6c, and a pair of opposing electrode pieces 6b and 6d compose a horizontal and vertical electric fields respectively. The crossing angle theta of two diagonal planes l and m which combine the middle points in the four gaps 9 formed between the peripheral sides of the four electrode pieces is made within 90 deg.+ or -5 deg., the crossing line p of the two diagonal planes l and m is made almost on the center line of the space surrounded by the four electrode pieces, and the elctron beams 7 are made to pass on the line p. Therefore, the symmetry of the electric field at the center of the space of the quadrupole electrode 6 is maintained, and the section form of the electron beams 7 is converted only from a circular section to a longish oval section including no other excessive deformation. Therefore, the spot image of the electron beams 7 displayed on the fluorescent screen is almost a regular circle, removing only the deflecting aberration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron gun equipped with electrodes forming a quadrupole lens for correcting deflection aberration.

[Conventional technology]

So-called deflection aberration, in which an electron beam is deformed by a deflection magnetic field in a cathode ray tube, is well known.

This is especially noticeable when the deflection magnetic field has a non-uniform distribution, and even if the spot is circular at the center of the phosphor screen, it becomes a horizontally elongated ellipse at the horizontal edge of the central portion, deteriorating the resolution. To solve this problem, there is a method of superimposing a hyperbolic waveform voltage synchronized with the deflection frequency on the focusing voltage applied to the focusing electrode of the electron gun.

However, although this method adjusts the focal length of the focusing lens, it does not eliminate deflection aberrations.

In addition, we will provide an electrode that forms a non-rotationally symmetrical electric field at one 14 extreme end of the electrode pair constituting an electron lens with astigmatism characteristics, and try to electrostatically control the quadruplet lens and astigmatism at the same time. There is a proposal (Japanese Unexamined Patent Publication No. 58-9464). However, in this method, the waveform voltages to satisfy the different purposes of the 7E child lens and astigmatism are mutually exclusive.
Since this interferes with the formation of the electric field, it is necessary to superimpose waveform signals that correct each other in synchronization with the deflection frequency, which makes the operating circuit complicated. Since static convergence is performed electrostatically in the electron lens region, this method has the problem that static convergence is disrupted by changes in the focusing polarization potential.

There is also a proposal to correct deflection aberrations by arranging an electromagnetic coil outside the cathode ray tube and using a magnetic element placed inside the cathode ray tube (Japanese Unexamined Patent Publication No. 57-84688).
. However, this method has problems such as high power consumption of the electromagnet, high cost of electromagnetic coils, etc., and the need to take measures to avoid interference with the deflection magnetic field.

[Problem that the invention seeks to solve]

This invention was made to solve the above-mentioned problems, and it is possible to efficiently correct deflection aberration electrostatically without impairing the performance of acceleration, focusing, and concentration, which are the basic functions of an electron gun. The aim is to obtain an electron gun that can

[Means for solving problems]

The electron gun according to the present invention is composed of four polar pieces that sandwich the electron beam from both sides and from above and below, and
It is equipped with a quadrupole electrode to which a waveform correcting focusing voltage for correcting deflection aberrations synchronized with the deflection magnetic field is applied, and the arrangement position and shape of the four electrode pieces constituting the quadrupole electrode are as follows when viewed from a single beam: It is constructed in a position and shape that are axially symmetrical.

[Effect]

The quadrupole electrode to which a focusing voltage is applied to correct deflection aberration is
Since an electric force is applied to the electron beam passing through the center in the opposite direction to the deflection aberration that the electron beam will later receive, a nearly perfect circular spot shape can be obtained over the entire surface of the phosphor screen.

The electric force applied to this electron beam is constructed so that the electric field formed between the four electrode pieces has good symmetry.
In addition, since the electron beam is configured to pass on the central axes of the four single pole pieces, the roundness of the spot shape on the phosphor screen is less likely to be impaired.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In Figure 1, a cathode (1), a control pole (2), and an accelerating electrode F! are arranged coaxially with each other. 1 (3), the front electrode (4a), the rear electrode (4b), and the anode (5), which constitute the focusing and d poles (4), constitute the basic part of the electron gun αQ. (6) is a four-a N pole, with the front electrode (4a) and the back electrode g
(4b). Control 4 tM (2)
, the accelerating electrode (3), and the front electrode (4a) have an opening (2a)*(8a)*(4C) through which the electron beam (7) passes.
) is provided, and the front electrode (4a) and the rear electrode (4a) are provided. I! It is connected to the pole (4b) by a connecting wire (4d) and held at the same position. Four poles? ! h (6) is the electron beam (7
) on both sides and top and bottom of the pole piece (6a) *
It consists of (6b)-(6c)-(6d), horizontal rβ pole pieces (6a) and (6C), and vertical electrode piece (6b).
and (6d) are paired, and a correction focusing voltage having a waveform necessary to correct the deflection aberration is applied from the correction focusing voltage power source (8), and the electric field in the horizontal and vertical directions is In this example, the electrode piece (6a)
, (6b), (6c), and (6d) are constructed of flat plates, but they may be arcuate and are not limited to flat plates.

The electron gun αQ constructed in this way is yin, IM(1)
The 1(l child flow released from the control 7n := (2)
opening (2a) and opening (8a) of acceleration 1α pole (3)
While passing through the electron beam (7), the flow rate of which is adjusted, is focused through the opening (4C) of the front electrode (4a) of the seven-dimensional image (4).
It enters through the quadrupole electrode (6), the rear electrode (4b),
A spot image is projected on a fluorescent screen (not shown) by a focusing action at the boundary area of the anode (5).

FIG. 2 is a diagram for explaining the action of a single quadrupole (6). For example, the vertical electrodes (6b) and (6d) are given a 1llE position that is more positive than the horizontal electrodes (6a) and (6C). If
While passing through the quadrupole electrode (6), the electron beam (7), which had a circular cross section at the time of incidence, is subjected to a vertical attraction force by the electrostatic field, and is transformed into a new circular surface with a vertical length of t. The deflection aberration that causes the spot shape on the phosphor screen to become a horizontally elongated oval is corrected in advance by the deflection magnetic field before deflection. When projecting a spot image at the center of the screen, use the quadrupole electrode (6) to
Without correcting the cross-sectional shape of the child beam (7), a focusing voltage for correction having a waveform that allows a circular spot shape to be obtained on the phosphor screen is applied in accordance with the amount of deflection of the electron beam (7). The cross-sectional shape of the single beam (7) is successively changed. As shown in FIG. 3, the four electrode pieces constituting the quadrupole electrode (6) are electrode pieces (6a), (6c), and (6b) facing each other.
and (6d) constitute horizontal and vertical electric fields, and two diagonal surfaces l2m connect the midpoints of the four gaps (9) formed between the peripheral edges of these four electrode pieces. The angle θ at which they intersect is within the range of 90'±5°, and the diagonal surface 1
．． A line p where m intersects with the center line of the space surrounded by the four electrode pieces, and the electron beam (7) is configured to pass on this line p. Therefore, since the symmetry of the electric field distribution in the central part of the space of the quadrupole 21E pole (6) is maintained, the cross-sectional shape of the electron beam (7) only changes from a circular cross-section to a vertically oval cross-section. , does not include other unnecessary transformations. Therefore, the spot image of the electron beam (7) projected on the fluorescent screen becomes nearly a perfect circle, and only the deflection aberration can be removed.

In addition, although the example in which the quadrupole electrode is disposed on the axis between the focusing poles (4) divided into front and rear halves, is not limited to this position.

〔Effect of the invention〕

As explained in 1 below, this invention, from the perspective of an electron beam,
A focusing voltage that is approximately axially symmetrical, consists of four electrode pieces arranged at approximately axially symmetrical positions, and has a waveform that corrects deflection aberrations in synchronization with the deflection magnetic field. Because it is an electron gun equipped with a 4 (fi 7?) E pole, the electron gun's essential functions such as focusing or concentration are not disturbed, and even in an in-line type electron gun, static convergence is not broken. There are no drawbacks and deflection aberrations can be corrected.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a partially enlarged perspective view for explaining the operation of the quadrupole electrode, which is the main part of this embodiment, and FIG. 3 is a perspective view of the quadrupole electrode of this embodiment. FIG. 3 is a front view showing the arrangement of electrodes. (4)... Focusing electrode, (6)... Quadrupole electrode, (6a
), (6c)...vertical electrode piece, (6b), (ad
)...Horizontal side, 1 piece, (7)...Electron beam, (9
)...gap, αq...E gun, l9m...diagonal plane, p...line where diagonal planes intersect, 0...crossing angle. Note that in each figure, the same reference numerals indicate the same parts.

Claims (1)

[Claims] (1) In an electron gun that has an electrode that forms and accelerates electrons emitted from a cathode into an electron beam, and an electrode that focuses this electron beam, a pair of electrode pieces that sandwich the electron beam from both sides and above and below. and a quadripolar electrode to which a correction focusing voltage having a waveform for correcting deflection aberration synchronized with the deflection magnetic field is applied to these electrode pieces, and the arrangement position and shape of the four electrode pieces are The intersection angle of the two diagonal planes diagonally connecting the midpoints of the four gaps formed between the peripheral edges of each electrode piece is within the range of 90° ± 5°, and An electron gun characterized in that the electron beam is configured to pass on a line where two diagonal planes intersect.