JPS607042A - Camera tube - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a false signal by providing an annular flange at the tip edge of a cylindrical section of an acceleration electrode and providing a cylindrical shield electrode enclosing the cylindrical section and facing to a deflectron-type deflection electrode so that its tip edge is covered with the flange. CONSTITUTION:An electron gun sealed in a glass bulb 11 has a cylindrical shield electrode 12 in addition to a cathode 1, a control electrode 2, and an acceleration electrode 3. A film-like deflectron-type deflection electrode 5 is provided on the inner periphery of the bulb 11, and a mesh electrode and a target electrode are arranged in front of the electrode 3. The electrode 12 is insulation-supported with an electrode support mechanism 9 on a flange 12a like the electrode 3. However, the electrode 3 is provided with an annular non-magnetic metal plate 13 at the tip edge of a cylindrical section 3a, thereby the cylindrical section 3a is constituted with a flange at its tip edge. In addition, an electrode 12 coaxially encloses most of the cylindrical section 3a, and it faces to part of an electrode 5 and its tip edge is covered with the metal plate 13. Accordingly, the occurrence of a false signal due to a reflection beam can be prevented and also the beam current can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electromagnetic focusing electrostatic deflection type image pickup tube equipped with a defreftron type deflection electrode.

Conventional configurations and their problems In general, an electrostatic deflection type image pickup tube equipped with a defftron type deflection electrode has an electrode configuration as shown in Fig. 1, and the thermoelectrons emitted from the cathode 1 are The electron beam is drawn out through the fine hole of the control electrode 2 and the electron beam diameter limiting hole 4 of the accelerating electrode 3, and is subjected to a focusing action by a focusing coil (not shown) and a deflecting action by a defreftron type deflection electrode 5, and follows the path shown by the solid line arrow. proceed. And Menoshi, electrode 6
The electron beam passes through the electron beam and scans the photoconductive film 8 of the target electrode 7, but the electron beam that could not enter the target electrode 7 returns to the accelerating electrode 3 side as a so-called return beam.

By the way, unlike the return beam in an electrostatic focusing electrostatic deflection type image pickup tube or an electromagnetic focusing electromagnetic deflection type image pickup tube, the return beam in an electromagnetic focusing electrostatic deflection type image pickup tube has a direction away from the tube axis as shown by the broken line arrow. It is deflected and returns to the accelerating electrode side. When this return beam hits an electron gun electrode such as an accelerating electrode or the surrounding electrode support structure 9, a so-called reflected beam is generated, which takes a path as shown by the dashed line and reaches the target electrode 7■)1. Head over.

Since the reflected beam has low energy and is scattered to some extent, even if it is incident on the scanning area of the photoconductive film 8, it will not adversely affect the key output signal current for which the incident light is not highlighted.

However, when this reflected beam enters the non-scanning area, which is the peripheral area of the photoconductive film 8, a pseudo signal due to this is mixed into the output signal current. The reason for this is that the back surface potential in the central rectangular scanning region of the photoconductive film 8 is lower than the target voltage (usually 20 to 6 oV) applied to the transparent conductive film 10, whereas the back surface potential in the non-scanning region is close to the target voltage, and therefore even a low-energy reflected beam can easily land.

In order to prevent the generation of spurious signals as described above, conventionally, the transparent conductive film 10-1+ or the mesh electrode 6 is trimmed and these electrodes are placed only within the scanning area, so that almost all of the reflected beam is Efforts have been made to reduce the diameter of the electron gun electrode so that it returns to the scanning area. However, trimming requires extremely high precision in the electrode and its assembly, making it unsuitable for mass production. Furthermore, reducing the diameter of the electron gun electrode not only reduces the mechanical strength of the electron gun, but also makes it more likely that the control electrode will become hot during operation and deform due to thermal expansion. As the size of the beam decreases, it becomes difficult to obtain a sufficiently large beam current.

A false signal may also be generated when the accelerating electrode potential is high. This is because the returning beam is attracted toward the accelerating electrode, and the reflected beam toward the target electrode increases from near the side wall of the accelerating electrode. In this case, it would be sufficient to raise the deflection electrode potential or lower the acceleration electrode potential, but the power required for focusing and deflection increases in the foreshore, and the beam current decreases in the latter case.

OBJECTS OF THE INVENTION It is an object of the present invention to prevent the generation of false signals in the reflected beam without reducing the diameter of the electron gun electrode or to perform strict trimming, and to change the acceleration electrode potential to the deflection electrode potential. The purpose of the present invention is to provide an image pickup tube that can be set higher than the standard.

Structure of the Invention In the image pickup tube of the present invention, an annular flange is provided at the tip edge of the cylindrical part of the accelerating electrode, and a deflation valve surrounds the cylindrical part. The cylindrical shield electrode is held at a lower potential than the
The tip edge thereof is provided so as to be covered by the flange, and this will be described in detail below together with the embodiment shown in drawing F.

DESCRIPTION OF EMBODIMENTS In FIG. 2 showing the main parts of an image pickup tube in which the present invention is implemented,
A cathode 1 is connected to an electron gun enclosed in a glass bulb 11.
．． In addition to the electrode structure that extends from the open side electrode 2 and the accelerating electrode 3, a cylindrical shield electrode 12 is provided. A membrane-like defleftron-type deflection electrode 6 is attached to the inner circumferential surface of the glass pulp 11, and in front of the accelerating 'dX pole 3, although not shown, a menue electrode and a target electrode similar to the conventional one are arranged. ing.

The fRj-shaped shield electrode 12 has a non-(I
It is made of HPI stainless steel or a nickel-copper alloy, and is insulated and supported by the electrode support structure 9 at the flange 12&. However, the accelerating electrode 3 is formed by forming a thin annular non-magnetic metal plate 13 on the tip edge of the cylindrical portion 3a, so that the cylindrical portion 3a has a flange on the tip edge. Further, the cylindrical shield electrode 12 coaxially surrounds most of the cylindrical portion 3a of the accelerating electrode 3, faces a part of the deflection electrode 6, and has a tip end formed on the metal plate 1.
3 is covered with said flange.

The terminal of the shield electrode 12 is drawn out of the tube independently of the terminal of the accelerating electrode 3, or is connected to the control electrode 2 or the cathode 1 inside the tube.

In operation of such an image pickup tube, for example, the accelerating electrode 3
A potential of about 200 V is applied to the deflection electrode 5, a potential of about 160 V (average value) is applied to the deflection electrode 5, and a potential of about 10 V is applied to the shield electrode 12, and the acceleration electrode potential is higher than the average potential of the deflection electrode.

In the mutually opposing portion of the shield electrode 12 and the deflection electrode 5, an electric field with a higher potential distribution is generated on the outside than on the inside, so that the return beam 141Li that has entered the mutually opposing portion is bent outward and deflected. , the reflected beam will no longer be directed toward the target electrode. In addition, an annular non-magnetic metal plate 13
Although the reflected beam 15bld from the return beam 14b that has entered toward the target electrode is incident on the scanning area of the photoconductive film, there is almost no problem in practical use. Furthermore, since the return beam 14C that has entered the side circumferential surface of the metal plate 13 narrows toward the back side of the metal plate 13, the reflected beam is directed toward the target electrode.
I don't.

If the metal plate 13 were not present, as shown in FIG. 3, a portion of the return beam 14d that had entered the vicinity of the tip edge of the cylindrical shield electrode 12 would not hit the electrode and instead would flow toward the target electrode. This causes the phenomenon of turning back,
The effect of suppressing the false signal becomes incomplete. Further, in this case, there is a disadvantage that the electric field 16 generated near the tip edge of the accelerating electrode 3 imparts an unwanted lens effect to the electron beam.

The outer diameter of the metal plate 13 must be selected so that the electron beam reflected from the inner part can return to the scanning area of the target electrode. Any material may be used as long as it can provide an annular flange on the edge, and it may be formed as a pair with the accelerating electrode when it is formed.

The shield electrode potential is sufficiently lower than the accelerating electrode potential, and is 0.
The potential can be selected from the range of ~120v, preferably about sov or less, but a negative potential may also be used.

Further, the shield electrode 12 may have a funnel shape, a horn shape, or a cylindrical shape without a flange. Additionally, the mesh electrode may be trimmed, as long as it has a frame-like border that can prevent reflected beams that are largely deflected outward or reflected beams from the electrode support structure from re-entering the target electrode, as described above. In general, it is not necessary to leave a portion of a size that exactly corresponds to the scanning area and to frame and mask the periphery as in the conventional method. Since it is sufficient to leave a part somewhat larger than the area corresponding to the scanning area and mask its surroundings, this requires particularly high precision in the assembly of the shield electrode and electrodes. This is not the case; normal precision is sufficient for practical purposes.

Effects of the Invention Since the image pickup tube of the present invention is constructed as described above, generation of false signals due to reflected beams can be prevented without reducing the diameter of the electron gun electrode. Not only is it possible to pass a sufficiently large beam current by setting the accelerating electrode potential to a relatively high value, but there is also the advantage that an unwanted lens electric field is not generated near the tip edge of the accelerating electrode. Furthermore, there is an advantage that no trimming is required for the mesh electrode, and even when trimming is performed, no particularly high precision is required for the electrode and its assembly.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the relationship between the electrode configuration of a conventional image pickup tube and the electron beam path, FIG. 2 is a sectional view of the main part of an image pickup tube in which the present invention is implemented, and FIG. 3 is an accelerating electrode in the present invention. FIG. 6 is an explanatory diagram of the operation when a flange is not provided on the tip edge of the cylindrical portion.
' 3...Acceleration electrode, 5...Deflection electrode, 11...
...9. Glass bulb, 12... Shield electrode, 1
3...Metal plate. Name of agent: Patent attorney Satoshi Nakao and one other person Figure 1 10 Figure 3 f4d

Claims (1)

[Claims] The accelerating electrode of the electron gun, which is enclosed in a glass bulb with a defreftron type deflection electrode attached to the inner circumference, has an annular flange on the tip edge of the cylindrical part that allows the entire electron beam to pass through the hole for limiting the diameter of the electron beam. A cylindrical shield electrode, which surrounds the cylindrical part and faces the deflection electrode and is held at a potential lower than the potential of the acceleration electrode, is arranged so that the tip ψ11.1 edge of the cylindrical shield electrode is covered by the flange. An imaging tube characterized by being attached to a gun.