JPH0145937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a focusing device for an image pickup tube used in a television camera.

Structure of a conventional example and its problems A conventional focusing device for an image pickup tube is shown in FIGS. 1 and 2. A cylindrical magnetic shielding material 3 of equal thickness is inserted and fixed to the outer periphery of a focusing coil 2 consisting of a multi-layer aligned solenoid coil having a winding phase shift part 1, or a plate-shaped magnetic shielding material 3 is inserted and fixed to the outer periphery of a focusing coil 2 consisting of a multi-layer aligned solenoid coil having a winding phase shift part 1. It is wrapped around the outer periphery and fixed at any position with soldering, etc. Note that an imaging tube 4 is inserted into the focusing coil 2.

Since the above-mentioned focusing coil 2 forms a winding phase shift part 1, a winding phase shift angle a occurs as shown in FIGS. In section 1, the copper wires do not enter between the wires of the layer one step below, but cross over, and the outer diameter of the winding phase shift section 1 becomes larger than the other outer diameters. As a result, the focused magnetic flux density by the focusing coil 2 is locally disturbed, and the axial magnetic flux density near the winding phase shift section 1 inside the focusing coil 2 is about 0.5% compared to the magnetic flux density on the concentric circle. The axial symmetry of the focused magnetic field is lost. Furthermore, if the magnetic shielding material 3 is attached to the outer periphery of the focusing coil 2 in this state, the collapse of the axial symmetry becomes even greater, and the cathode portion 5 of the image pickup tube 4
This causes beam distortion in the electron beam 7, which should be emitted from the target surface and uniformly focused onto the target surface 6, making it difficult to uniformly focus the beam onto the target surface 6. This caused color unevenness, which is an important characteristic of a television camera, and further caused a decrease in uniformity of screen resolution and peripheral resolution, which could not be called good.

Purpose of the Invention The present invention is intended to reduce such conventional drawbacks, and to form a winding phase shift portion and reduce disturbances in the axial symmetry of the focusing magnetic field of a multilayer-wound focusing coil, thereby improving the image pickup tube electron beam. The purpose is to achieve good focusing.

Structure of the Invention In order to achieve this object, the present invention provides a structure in which a magnetic material for magnetic shielding is wound on the outer periphery of a focusing coil for an image pickup tube so that the outer periphery of the phase shift part is slightly thicker than the other outer periphery. The configuration is as follows:

With this configuration, the axial symmetry of the focusing magnetic field in the focusing coil is disturbed, that is, the axial magnetic flux density near the winding phase shift part is reduced compared to the magnetic flux density on a concentric circle with that point. By attaching the magnetic material for magnetic shielding on the outer periphery of the wire phase shift part so that it is thicker than the other outer periphery, the magnetic resistance of the winding phase shift part is reduced compared to other winding parts. The axial magnetic flux created by this increases, and compensates for the decrease in the axial magnetic flux within the focusing coil and near the phase shift portion of the winding, which occurs due to the above-mentioned reasons. This makes it possible to reduce disturbances in the axial symmetry of the focused magnetic flux within the focusing coil (reduction in the winding phase shift portion).

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS. 4 to 7. In the figure, the same parts as those shown in the conventional example are given the same numbers.

In FIGS. 4 to 7, a focusing coil 2 formed with a winding phase shift part 1 and wound in a solenoid-like manner in multiple layers with heat-sealed copper wire or the like is mounted on a coil mounting bobbin 8 made of a resin molded body or the like. The winding phase shifting section 1 is either fixedly attached or directly formed on the coil mounting bobbin 8 using a heat-sealed copper wire or the like, and is wound in alignment in a multilayer solenoid shape to form a focusing coil section. Next, on the outer periphery of the focusing coil 2, a magnetic shield material 3 made of a magnetic material with high magnetic permeability such as permalloy is placed on the coil bobbin 8 in order to shield the electron beam 7 of the image pickup tube 4 from being affected by an external magnetic field such as earth's magnetism. or directly on the focusing coil 2.

To explain the shape of this magnetic shielding material 3, as shown in FIG. 4, it is a cylindrical magnetic material with a thickness of about 0.2 to 0.7 mm. The thickness of the magnetic material is about 0.2 to 0.5 mm thicker than other parts over the entire axial length with a linear phase shift rotation angle a of about 60° to 120°.
The thickness may be increased either in the outer peripheral direction of the cylindrical shield material or in the inner peripheral direction, as shown in FIG. 4, or in both the inner and outer directions.

As another example of the magnetic shielding material 3, as shown in FIG. Attach it so that the seam (overlapping part) of the magnetic material covers the winding phase shift rotation angle α60° to 120° of the winding phase shift portion 1 of the focusing coil 2, and fix it by soldering etc. . There is no particular direction in which the magnetic materials are stacked. In this way, the point is to make the magnetic shielding material 3 thicker in the portion that covers the winding layer transition portion 1 of the focusing coil 2.

In this way, by attaching the magnetic shielding material 3 to the outer periphery of the winding phase shifting section 1 of the focusing coil 2 so as to be thicker than other parts, the reduction in the focusing magnetic flux due to the winding phase shifting section 1 can be compensated for. The axial symmetry of the focused magnetic field can be changed from 0.5% (the rate at which the magnetic flux density near the winding phase shift part decreases compared to the magnetic flux density on the concentric circle) to 0.1
It can be improved to about %.

Effects of the Invention According to the focusing device for an image pickup tube of the present invention as described above, the focusing distortion of the image pickup tube electron beam, which occurs due to non-uniformity of the axial symmetry of the focusing coil magnetic field as in the conventional case, is reduced, and the beam is uniform and stable. electron beam focusing becomes possible. This is an important characteristic for television cameras. Screen color unevenness can be reduced, and uniform and good resolution characteristics can be obtained across the entire screen. Furthermore, the color unevenness correction circuit of the television camera can be omitted, resulting in cost reduction, which is of great industrial value.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional focusing device for an image pickup tube, FIG. 2 is a sectional view taken along line A-A', and FIGS. FIG. 4 is a cross-sectional view showing a focusing device for an image pickup tube according to an embodiment of the present invention, FIG. 5 is a cross-sectional view taken along line A-A' in FIG. 4, FIG. 6 is a cross-sectional view of another embodiment, and FIG. is the 6th
It is a sectional view taken along the line AA' in the figure. 1... Winding phase shifter, 2... Focusing coil, 3...
Magnetic shielding material, 4... Image pickup tube, 5... Cathode, 6... Target face surface, 7... Electron beam, 8... Coil mounting bobbin.

Claims (1)

[Claims] 1. A magnetic material for magnetic shielding is applied to the outer periphery of a focusing coil which is formed by forming a winding phase shifter and heat-sealed copper wire etc. is wound in a solenoid-like multi-layer alignment. A focusing device for an image pickup tube installed with a thick wall.