JPS58169759A - Electron gun for pickup tube - Google Patents

Abstract

PURPOSE:To reduce the unevenness of characteristics following the deformation of a focussing electrode by thickening a tip tubular area with a specific length range on the edge of the mesh electrode side of the focusing electrode as compared with the remaining tubular area. CONSTITUTION:A focusing electrode 8 arranged coaxially between a G2 electrode 3 acting as an accelerating electrode and a mesh electrode has a tip tubular area 8b of approximately 2 to 15mm. in length on the end edge of the mesh electrode 5 side of tubular section 8a with a large diameter and the thickness t1 is larger than that t2 of the remaining tubular area 8c with a larger diameter. Besides, an annular insulator piece 6 is made of ceramic and two metal rings 9 and 10 are spot-welded in the tip tubular area 8b so as to prevent the shift of the insulator. Further, a metal cylinder 5a that fixes the mesh electrode 5 is caulked on the external surface of the annular insulator piece 6. As a result, the degree of roundness of the G3 electrode can be kept without deteriorating the deflection sensitivity and generating any eddy current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun for an image pickup tube, in which a focusing electrode coaxially arranged between an accelerating electrode and a mesh electrode has a length of about 2 m to 16 m at an edge on the mesh electrode side. By making the tip tubular region thicker than the remaining tubular region, variations in characteristics due to deformation of the focusing electrode are reduced.

Generally, an electron gun applied to an electromagnetic focusing type image pickup tube has a first
As shown in the figure, cathode 1. 01 electrode as control electrode2.
02 electrode as an accelerating electrode3. A 03 electrode 4 and a mesh electrode 5 are provided as focusing electrodes. The cathode 1 is insulated and supported within the G1 electrode 2 by an insulator (not shown).1. The mesh electrode 5 is insulated and supported by the G3 electrode 4 by an insulator 6. Further, the G3 electrode 4 has a small diameter tubular portion 4a and a large diameter tubular portion 4.
b, and is insulated and supported on a glass insulating support 7 together with the G2 electrode 3 and the G1 electrode 2.

The 05 electrode 4 is usually made of nonmagnetic stainless steel, nickel-copper alloy (50% Ni, 50% Cu), or nickel-chromium alloy (8Q%Niy 20% Cr), but the tubular part 4b of the 03 electrode 4 is 1. Positioned within the deflection magnetic field. Decrease in deflection sensitivity and generation of eddy currents should be avoided (a relatively small wall thickness of o-1am-o-2m*).In this case, a relatively small deflection power is sufficient. If the thickness is selected to be too thick, the roundness of the Crs electrode 4, especially at the edge on the menosh electrode side, will decrease during electrode assembly and heat treatment, resulting in unwanted distortion of the electric field between it and the menosh electrode 6. If the above-mentioned distortion occurs in the image pickup tube used in a three-image pickup tube type color television camera, misregistration will result in clumping that will cause color shift in the reproduced image.

The present invention has been made with the above-mentioned points in mind,
Next, an electron gun for an image pickup tube according to the present invention will be explained together with embodiments shown in the drawings.

In FIG. 2, the focusing electrode 8, which is coaxially arranged between the 02 electrode 3 as an accelerating electrode and the mesh electrode 6, is made of non-magnetic stainless steel, nickel-copper alloy, nickel-chromium alloy, etc. At the tip of the tubular portion 8a, that is, at the edge on the mesh electrode 6 side, a length of approximately 21111 to 15 m is provided.
a distal tubular region 8, preferably about 6 mm in length;
It has b. Then, the wall thickness t1 of the tip tubular region bl a' b is the remaining (f thickness 1 of the large tubular region 8 C!;
When the wall thickness t2 is larger than t2 and the wall thickness t2 is Q-15m'llr, it is selected from the range of about 026 to 06, which is about 1.6 to 3.3 times that.

The ring body forming the tip tubular region 8b is formed separately from the tubular body forming the remaining tubular region, and then the two are welded together by spot welding, and the joint between the two is shown in Fig. 3. The fitting structure is as shown.

The annular insulator 6 surrounding the tip tubular region 8b is made of ceramic, and two metal rings 9 and 1o to prevent its displacement are spot welded to the tip tubular region 8b. Furthermore, a metal cylinder 6a for fixing the mesh electrode 5 is crimped to the outer peripheral surface of the annular insulator 6.

In the electron gun for an image pickup tube according to the present invention configured as described above, a tip tubular region having a length of about 2 mm and 15 mm is provided on the edge of the mesh electrode side of the G5 electrode, which is a focusing electrode, and this tip tubular region is used as the remaining tip tubular region. Larger wall thickness compared to the tubular region (
(at least 1.6 times), it is possible to maintain good roundness of the 03 electrode without reducing the deflection sensitivity or generating eddy currents. Still, by insulatingly supporting the mesh electrode in the tip tubular region, the support strength of the mesh electrode is increased, and unwanted distortion of the electric field generated between the G3 electrode and the mesh electrode is reduced.

Although the embodiments in which the present invention is applied to an electron gun of an electromagnetic focusing type image pickup tube have been described above, it goes without saying that the present invention can be similarly applied to an electron gun of an electrostatic focusing type image pickup tube. . Also,
It is also possible to form the focusing electrode from a single metal tube.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional image pickup tube electron gun, FIG. 2 is a side sectional view of an image pickup tube electron gun embodying the present invention, and FIG. 3 is a perspective view of the mounting part of the electron gun. , 3...G2 electrode, 6...Mesh electrode, 8...G5
Electron 14.8b...Tip tubular region of G3 electrode, 6
・・・・・・Annular insulator. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure, Figure 2, Figure 3

Claims (2)

[Claims] (1) A tip tubular region having a length of about 2 mm to 15 mm is provided at the edge of the mesh electrode of the focusing electrode coaxially arranged between the accelerating electrode and the mesh electrode, and the tip tubular region is left behind. An electron gun for an image pickup tube, characterized by having a wall thickness larger than that of a tubular region. (2) The electron gun for an image pickup tube according to claim 1, wherein the mesh electrode is insulated and supported in the tip tubular region.