JPS61211940A - Permanent magnet for electron lens - Google Patents

Abstract

PURPOSE:To acquire an electron lens with little aberration and no halation, by furnishing at least two permanent magnets combined in the direction of the same magnetic pole. CONSTITUTION:Permanent magnets 1 and 2 for an electron lens are arranged in front of an anode 7, and the magnetic pole plates 3 installed at the both magnets act as a spacer, at the same time, to adjust accurately. Instead of the pole plates, accurate adjusting coils can be used. It is effective practically to adjust the magnets so that the half width of the magnetic flux density distri bution on the Z axis is equal to the value of 80-200% of the inside diameter of the permanent magnets 1 and 2, for an electron lens.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to improvements in electronic lenses using permanent magnets.

B. Preparation of at least two separately magnetized ring-shaped permanent magnets (16) located on the Z-axis and connected in the direction of the magnetic poles,
By making the half-width of the magnetic flux density distribution equal to or more than w% of the inner diameter of the water-filled stone, an electron lens with less spherical aberration can be obtained without taking up the lens diameter.

C. Prior Art Conventional electronic lenses using ring-shaped permanent magnets have used either one magnet or a combination of 21 magnets with opposite magnetic pole directions, as shown in FIG.

D Problems that the invention attempts to solve However, when such conventional electron lenses are used as converging lenses for cathode ray tubes, for example, even if you try to focus the electron beam spot beyond a certain level, there is a large amount of spherical aberration that causes halation. There were drawbacks such as dust.

An object of the present invention is to provide a water-immersed magnet for an electronic lens that has small spherical aberration and does not cause halation.

E Means to solve the problem 2! ! In order to achieve this, the water-immersed magnet for an electronic lens according to the present invention is composed of a small number (or two) of ring-shaped permanent magnets that are separately magnetized and connected in the same magnetic pole direction. In an advantageous embodiment of the invention, the half width of the magnetic flux density distribution on 2@ is equal to 8 of the inner diameter of the permanent magnet.
It has a value of 0% to 200%.

F Function: First, the principle of the basic operation of the permanent projection for electronic lenses of the present invention will be explained.

The spherical aberration of a lens system is related to the lens diameter and focal length, but the lens diameter is often subject to the physical control #':l (.

Therefore, only the lens strength (focal length) will be discussed here, but since it can be qualitatively understood by comparing it with an optical lens, the case of an optical lens will be explained first.

In the case of an optical lens, the spherical aberration coefficient (C8) is proportional to the reciprocal of 3 Ei of the focal length (f) as shown in the following equation.

C3” 1/f3 Therefore, N1- weak lens (focal length @Nf) 4
When combined, the spherical aberration of the composite lens becomes 1
It becomes 7N. Cameras, fireworks, etc. are used.

The gist of the present invention is to realize this principle with a water-immersed magnet for an electronic lens. The magnetic flux density distribution of permanent spiders has an anti-bee component, so it becomes as shown in Figure 2, and its focal length is
Show.

The problem is the region of action B (z) (m undivided), but since the main region of action can be determined correctly, the half width of the positive distribution is taken as the parameter of B (z). In order to increase the half width (Bw), the lens diameter (L) and the magnetic ring (M) can be considered as shown in FIG.

FIG. 4 shows the relationship between the width of the cow m1 (B) and the lens diameter (&innerity of the stone = L) in an arbitrary section 1-, which was determined by experiment.

B=0.5SL Reducing the lens properties has a considerable effect on increasing the half-width, but there are many restrictions and it cannot be changed.
Add this to the parameters as well. In other words, H=half value@/lens property is a parameter of B(z).

The straight line a in Fig. 5 is H'4 thick (@s'4! with the magnet width, which is another parameter to can get.

H=0.004M+0.49 As is clear from this equation, the effect of Ka stone is small.

Therefore, as shown in FIG. 6, for example, two separately magnetized weak permanent magnets 1 and 2 are connected in the same magnetic pole direction via a magnetic pole plate 3, and the relationship with H is changed comically. The result is the curve line in Figure 5, from which the equation below can be approximately extended.

1-1= 0.01 M+ 0.53 As can be seen from the above equation, the capstone configuration in Fig. 6 and the deviation are H? regardless of the lens diameter. : It becomes possible to increase it significantly.

G. Example 1 The first figure is a sectional view of the vicinity of the cage of a cathode ray tube housing an electron lens according to the present invention, where 4 is a cathode, 5 is a first grid, 6 is a second grid, and 7 is an anode. Anode 7
Water-immersed magnets 1 and 2 for electronic lenses as shown in Fig. M6 are arranged in front of the magnet, and the m-pole plate 3 provided on each magnet also serves as a spacer for the s-key a. Alternatively, a fine adjustment coil may be provided. Figure 7 shows the magnetic flux density distribution on z@B by the electron lens shown in Figure WJ1 using an actual machine. ◎Due to the relative softness, the magnetic flux density distribution in the case of a single water-immersed magnet is highlighted with a broken line.

Figure 8 shows h and clean surface aberration coefficient ratio (C, R) shown in Figure 5 MC.
This relationship was determined through experiments.

It was found that CsR decreased as H increased and was saturated at 0.8 or higher.

When H=0.5 and H=1.0 are softened, the spherical aberration coefficient is improved by 70%. From this, for the electron lens of the present invention, it is effective to make the practical trap such that the half value of the aX density distribution on the z-axis has a value of % to 200% of the inner diameter of the permanent magnets 1 and 2. One thing is clear.

In FIG. 9, the beam convergence characteristic of the electron lens according to Akira Ishikawa is shown by a solid line, and the beam convergence characteristic by monoaite is shown by am due to the relative softness.

As explained in detail about the H invention, according to Mototaka and Tsuyoshi, an electronic lens with small aberrations and no helation can be obtained by connecting and using at least two permanent magnets in four directions. It doesn't matter.

[Brief explanation of the drawing]

wi, Figure 1 is a cross-sectional view of a cathode ray tube including an electron lens according to the present invention, the second factor is a magnetic flux superimposition distribution diagram of a single permanent magnet, and the third factor is a magnetic flux division of a ring-shaped permanent magnet. figure,
Figure 4 is a graph showing the relationship between the half width (BW) and the magnet inner diameter (L), Figure 5 is a graph showing the relationship between the output width (Mu) and the parameter (H) representing the half width, and Figure 6 is FIG. 7 is a side view of the electron lens according to the present invention, and FIG. 7 is a diagram showing the magnetic Jf [degree distribution diagram] in the electron lens according to the present invention. The graph shown in Figure 9 shows the beam convergence characteristics of a permanent magnet!
-This is the graph below. 1.2... Permanent magnet, 3... i-pole plate, 4...-cathode, 5... first grid, 6... second grid,
7...Anode.

Claims (2)

[Claims] (1) A permanent magnet for an electronic lens, comprising at least two ring-shaped permanent magnets that are separately magnetized and connected in the same magnetic pole direction. (2) Claim 1, wherein the permanent magnet is characterized in that the half width of the magnetic flux density distribution on the Z-axis is 80% to 200% of the inner diameter of the permanent magnet. Permanent magnet for electronic lenses described.