JPS60127643A - Focusing device for camera tube - Google Patents

Abstract

PURPOSE:To excellently focus the electron beam of a camera tube by fitting a magnetic material for magnetic shielding on the circumference of a focusing coil for a camera tube so that the peripheral section of a winding phase shift section is made somewhat thicker than the other peripheral sections. CONSTITUTION:A magnetic shield material 3 made of a high-permeability magnetic material such as permalloy for shielding the effect on the electron beam 7 of a camera tube 4 due to the external magnetic field such as magnetism is fitted to a coil bobbin 8 wound a focusing coil 2 or directly to the focusing coil 2. This magnetic shield material 3 is a cylindrical magnetic material with a thickness of about 0.4-0.7mm., the winding phase rotating angle alpha of the winding phase shift section 1 of the focusing coil 2 is about 60-120 deg.C in width, and the magnetic material is made thicker than the other portions by about 0.2-0.5mm.. That is, the magnetic shield material 3 covering the winding phase shift portion 1 of the focusing coil 2 is made thicker. Accordingly, the focus distortion of the electron beam of the camera tube is made small, thus allowing excellent focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention 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 on 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 into the outer circumference of the focusing coil 2, or It is wrapped around the outer circumference and fixed by soldering, etc. at any desired position. 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 α 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 0 compared to the magnetic flux density on the concentric circle.
．． It decreases by about 5%, and the axial symmetry of the focusing magnetic field is destroyed. 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 will become even greater.
This causes beam distortion in the electron beam 7 that is emitted from the cathode section 5 of the image pickup tube 4 and should be uniformly focused on the target face surface 6, making it difficult to uniformly focus the beam on the target face surface 6. This caused color unevenness, which is an important characteristic of a television camera, and further caused a reduction in uniformity of screen resolution and peripheral resolution, which could not be called a good product.

OBJECTS OF THE INVENTION The present invention reduces these conventional drawbacks and
The purpose of this invention is to form a winding phase shift portion and reduce disturbances in the axial symmetry of a focusing magnetic field of a multilayer wound focusing coil, thereby improving focusing of an image pickup tube electron beam.

Structure of the Invention In order to achieve this object, the present invention involves winding a magnetic material for magnetic shielding 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. It has a mounting configuration.

This configuration prevents the disturbance of the axial symmetry of the focusing magnetic field within the focusing coil, which causes the axial magnetic flux density near the trenched winding phasing section to decrease compared to the magnetic flux density concentrically with that point. By attaching magnetic material for magnetic shielding on the outer periphery of the winding 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 the wire phase shifting section increases, and the axial magnetic flux 1- in the focusing coil and near the winding phasing section generated due to the above reason increases.
This will compensate for the decrease in ＼. 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 addition, in the figure, the same numbers are used for parts that are the same as those shown in the conventional example.

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 attachment may be fixed, or the winding phase shift section 1 may be formed directly on the coil attachment bobbin 8 using heat-sealed copper wire or the like, and aligned winding may be performed in a multilayer solenoid shape to form a focusing coil section. Next, on the outer periphery of the focusing coil 2, a magnetic shielding material 3 made of a magnetic material with high magnetic permeability such as permalloy is placed on the coil bobbin 8 to shield the electron beam 7 of the image pickup tube 4 from the influence of external magnetic fields such as magnetism. Attach directly onto the focusing coil 2.

To explain the shape of this magnetic shielding material 3, the fourth
The thickness is as shown in the figure. , is a cylindrical magnetic material of about 2 to 0.7+ mm, and the winding phase shift rotation angle a of the winding phase shift portion 1 of the focusing coil 2 is about 60° to 120° over the entire axial length. The thickness of the magnetic material is about 0.2 to 0.5 mm thicker than other parts. The direction of increasing the thickness is also in the direction of the outer circumference of the cylindrical shield material as shown in Fig. 4.
Alternatively, it may be thicker in the inner peripheral direction or in the inner and outer image directions.

As another example of the magnetic shielding material 3, as shown in FIG. 6, a plate-shaped magnetic material with a thickness of about 0.1 to 0.6 mm is curled into a cylindrical shape, and the cylindrical magnetic material is focused. It is wound on the coil 2, and the seam (overlapping part) of the magnetic material is the winding phase shift rotation angle α60° of the winding phase shift portion 1 of the focusing coil 2.
Attach so as to cover about 1200 and secure with 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 making the magnetic shielding material 3 thicker than other parts on the outer periphery of the winding phase shift part 1 of the focusing coil 2, the decrease in the focusing magnetic flux due to the winding phase shift part 1 can be prevented. The axial symmetry of the focused magnetic field can be improved from 0.5% (the rate at which the magnetic flux density near the winding phasing section decreases compared to the magnetic flux density on the concentric circle) to about 0.1%.

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 the 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 makes it possible to reduce screen color unevenness, which is an important characteristic for television cameras, and to obtain uniform and good resolution characteristics over 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 the drawing]

Fig. 1 is a sectional view showing a conventional focusing device for an image pickup tube;
Figure 3 is a sectional view showing the winding of a focusing coil; FIG. 4 is a sectional view showing a focusing device for an image pickup tube according to an embodiment of the present invention; FIG. 6 is a sectional view taken along the line AA' in FIG. 4, and FIG. 6 is a sectional view of another embodiment.
FIG. 7 is a sectional view taken along line 8-A' in FIG. 6. 1... Winding phase shift section, 2... Focusing coil, 3...
...Magnetic shielding material, 4...Image tube, 5.
... Cathode, 6... Target face, 7... Electron beam, 8... Coil mounting bobbin. Name of agent: Patent attorney Toshio Nakao and 1 other person @3
Figure 1 - Autopsy Figure 4 Figure 5

Claims (1)

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