JPS604543B2 - Focusing device for electron tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam concentration technique in an electron tube.

It is well known that an electron tube is provided with a device that prevents the divergence of the electron beam, and this device is known as a Shuto device.

In some applications, for example electron tubes used in cameras in television equipment, a particularly tight focusing of the beam on the target is required. In practice, in electron tubes of this type, the target consists of a photosensitive surface on which the image to be transmitted is projected, the electron tube has a device for generating an electron beam and a device for generating a deflecting electric or magnetic field; An electron beam is scanned over the photosensitive surface, thereby forming a video signal. In order to improve the transmission of the image and also the efficiency of pupillage, it is necessary to concentrate the beam as much as possible when impinging on the photosensitive target. Known Shuto devices generally use a directional magnetic field generated by a magnetic coil placed around the electron tube, a solution that has the drawbacks of being power consuming, bulky and heavy, and in some cases This limits the quality of the transmitted image and is caused by heating of the coil and target.

Furthermore, a Shuto device constructed using a permanent magnet that can avoid the above-mentioned limitations is also known.

They consist, for example, of a generally cylindrical and radially magnetized magnet placed around an electron tube.
The field lines of the magnetic field are oriented along the axis of the electron tube over a portion of the length of the magnets. However, in devices of this type, only half of their total length is generally
Because of the shape of the magnetic field in these devices, it can only be effectively used to create a focusing field, resulting in these devices being highly biased. According to this invention, the coaxial stack of rings has a permanent magnet that surrounds an electron tube through which an electron beam propagates in an annular manner in the propagation direction of the electron beam when in use, and the permanent magnet is magnetized in a direction substantially perpendicular to the plane. There is provided a concentration device for an electron tube characterized by comprising:

The invention will be better understood from the following description taken in conjunction with the accompanying drawings.

FIG. 1 shows a basic annular magnet 1 according to the present invention.
It is shown in a cross-sectional view together with magnetic lines of force 11 and 21 generated by.

According to this embodiment, the magnet 1 is composed of a flat circular ring with a rectangular cross section and an outer diameter De and an inner diameter Di, and the rotation axis X'X is approximately the propagation axis of the electron beam passing through the electron tube. Match.

The magnet 1 consists of a magnetic material magnetized along an axis X'X perpendicular to the plane, ie perpendicular to the plane of the ring, said plane being represented in the drawing by the axis Y'Y. In a preferred embodiment, the magnetic body is comprised of a plastic material mixed with ferrite powder. Elastic bodies may equally be used.
As is known to those skilled in the art, magnets of the type denoted by 1 are made from a solid disk of diameter De uniformly magnetized over its entire surface on the one hand, and from said disk also over its entire surface on the other hand. The diameter Di uniformly magnetized in opposite directions
generates a magnetic field of a shape commensurate with that obtained from a solid disk.

The drawing shows half of the magnetic field lines corresponding to this type of configuration,
The other half of the magnetic field lines are induced simply symmetrically with respect to the above-mentioned half of the magnetic field lines and the Fuji line X'X. Two coarses (1!, 21, respectively) of magnetic field lines are thus obtained, which lead to a change in the direction of the magnetic field along the wisteria line X'X,
Points A and B are called singular points. The position of these singular points symmetrical about the axis Y'Y is a function of the ratio of diameter to diameter. In other words, the larger the inner flea Di becomes, the more these singular points move away from each other. Figure 2 shows the mari line X'X.
Graph 20 shows the variation of the magnetic field strength along .

Graph 20' shows that the axial component Hx of the magnetic field is symmetrical about the axis YY, is maximum at the center of magnet 1 on line YY, zero at singular points A and 8, and its sign is different from these singularities. It shows that there is a change after the point. The strength of the magnetic field at the center of the magnet is naturally related to the diameter Di, ie the smaller the diameter Di, the stronger the magnetic field. To manufacture the Shuto device according to the invention, preferably a stack of elementary annular magnets with the same axis X'X is used, the magnets are of the same dimensions and all have the same magnetization level, and the electron tube is It is arranged on the axis inside the stack.

Contact is made between opposite magnetic surfaces. A graph showing the variation of the axial component Hx of the magnetic field generated by this type of stack structure is obtained from a graph corresponding to each magnet, the general shape of which is not shown in the figure, but is shown in Figure 2. is the same as , and has two singularities. In this type of stack, the singularities of each magnet must be far enough apart from each other for the component Hx of the magnetic field generated by one elementary magnet to be subtracted from the component generated by the next elementary magnet. 2, and this leads to the selection of a large diameter Di, which further increases the level of the ordinate position of the points located below the abscissa axis in FIG. Furthermore, the diameter Di should not be too large in order for the component Hx to be large enough in accordance with what has been said above. At least o. 6' Seeing that this request would be fulfilled by the Lord and the Lord, it was sent to him. FIG. 3 shows another embodiment of the basic magnet according to the invention.

This basic magnet is constituted by a ring 30 with a chamfered traverse and a rotation axis X'X, its cross section is rectangular, and the surfaces 32 and 33 are not flat surfaces, but the axis X'X
It is a truncated conical surface. This magnet can be made of the same magnetic material as magnet 1. FIG. 4 is a cross-sectional view of magnet 30 showing the magnetic field lines generated by this type of magnet when magnetized in a direction perpendicular to surfaces 32, 33. The form of the magnetic field is as shown in Figure 1.
, but is no longer symmetrical with respect to the plane passing through the center of the cross section of the ring, and the lines of magnetic field are the axis Y'Y in the plane of the drawing, and the cross section 31 is no longer symmetrical with respect to said plane.

In this way, two sets of magnetic lines of force 41 and 51 are obtained, and the two singular points C and D are not symmetrical with respect to the wisteria line Y'Y, and the singular point C is the farthest from the axis Y'Y. Fifth
The figure shows the variation of the magnetic field component Hk along the axis X'X.

This component is maximum on axis YY as before, zero at the singularities C, D, and after these singularities it has an opposite sign and is no longer symmetrical about axis YY.

FIG. 6 shows a preferred embodiment of the focusing device according to the invention, consisting of two half-stacks of basic magnets as described in FIG. It is the same as the thing.

Each half-stack is arranged on one and the same axis X' They are coaxially disposed face-to-face and in contact with each other via the base. The two end magnets of each half-stack are shown in the drawing, ie magnets 61, 62 for the half-stack with apex on the left side of the drawing and magnets 71, 72 for the other half-stack.

FIG. 7 shows a graph of the variation of the component Hx along the axis X'X of the magnetic field generated by the device shown in FIG.

This graph is a composite graph of the graphs corresponding to each magnet, i.e. it is the plane (
It is symmetrical with respect to the plane of symmetry of the device) and has two singular points E and F.

This graph is the same as the graph corresponding to a stack of magnets as shown in Figure 1, but for each magnet the singularities E are further apart due to the asymmetrical use shown in Figures 4 and 5.
. It is arranged like this. The Yakuto device according to this invention is
Heating and power consumption can be avoided compared to devices using magnetic coils, and thus limits can be placed on the operating voltage of the electron tube.

The device according to the invention has the advantage of being able to be further reduced in size, the overall length of the device being practically related to the shape of the focused magnetic field. Moreover, the materials used, which are electrical insulators with a certain degree of elasticity, can on the one hand avoid attenuation and interference of the signal by Foucault currents, and on the other hand provide the electron tube around which the magnet is arranged with a certain degree of resistance to mechanical shock. can provide protection.

Finally, the device has a very simple construction, which allows the manufacturing costs to be substantially reduced. This focusing device, applied to an electron tube for a television camera, can transmit an image consisting of 900 points through 12.6 willow lines. As mentioned above, due to the classification of the device according to the invention into basic ring magnets, other than the embodiments described above, in which rings of different dimensions and different magnetization levels are used,
Variant embodiments can be created for special applications.

All these variations are within the scope of this invention.
This invention can be implemented as follows. '11 The inner diameter of each ring is equal to at least 6/10 of the outer diameter of each ring. '21 Each ring is a thin, flat, rectangular cross-section ring.

[31 Each ring is a thin, frustoconical ring with a rectangular cross section.

■ All rings are identical and have the same magnetic level.

{5) A magnet is constituted by two coaxial half-stacks, each of the various stacks consisting of a number of rings assembled together and in contact with each other through faces of opposite magnetic type, the two half-stack being The large bases are arranged opposite each other, and their mutually opposite surfaces have opposite magnetic types.

The kicking consists of a plastic material filled with ferrite powder. '7) The ring is made of an elastic body containing ferrite powder filler.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of one embodiment of the basic annular magnet according to the present invention, Fig. 2 is a graph showing changes in the magnetic field generated by the magnet shown in Fig. 1, and Fig. 3 is another example of the basic annular magnet according to the invention. Figures 4 and 5 are similar to Figures 1 and 2 regarding the embodiment shown in Figure 3; Figure 6 is a diagram showing a preferred embodiment of the Shuto device according to the present invention; FIG. 7 is a graph showing the variation of the magnetic field generated by the apparatus shown in FIG. In the drawing, 1, 30, 61, 62, 71, and 72 are permanent magnets. FIG-I FIG. 2 FIG. 3 FIG. 4 FIG. S FIG. 6 FIG. centre

Claims (1)

[Scope of Claims] 1. A coaxial stack of rings having a permanent magnet that surrounds an electron tube through which an electron beam propagates in an annular manner in the propagation direction of the electron beam during use, and the permanent magnet is magnetized in a direction substantially perpendicular to the plane. each ring is a thin trapezoidal ring with a rectangular cross section, the contact of each ring is between opposite magnetic surfaces, and the inner diameter of each ring is at least as large as the outer diameter of each ring. A focusing device for an electron tube, characterized in that the focusing device is equal to 0.6 times. 2. The focusing device for an electron tube according to claim 1, wherein all the rings have the same shape and size and have the same magnetization level. 3. The permanent magnet is constituted by two coaxial half-stack, each coaxial half-stack consisting of a certain number of said rings, said two coaxial half-stack being in contact with each other via faces of opposite magnetic type. Claim 1, characterized in that the two coaxial half-stacks are arranged with their large bases facing each other, their mutually facing surfaces having opposite magnetic types. A focusing device for an electron tube described in . 4. A focusing device for an electron tube according to claim 1, wherein each ring is made of a plastic material filled with ferrite powder. 5. The focusing device for an electron tube according to claim 1, wherein each of the rings is made of an elastic body containing a ferrite powder filler.