JPS59201345A - Camera tube - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a false signal due to a reflected beam without requiring to decrease the diameter of an electron gun electrode or the strict trimming by adding to an electron gun a cylindrical shield electrode held at a lower potential than that of an acceleration electrode, encircling the cylindrical portion of the acceleration electrode, and facing part of a deflection electrode. CONSTITUTION:An electron gun enclosed in a glass bulb 11 has a cylindrical shield electrode 12 in addition to a conventional electrode configuration consisting of a cathode 1, a control electrode 2, and an acceleration electrode 3. A film-like deflectron-type deflection electrode 5 is arranged on the inner periphery of the glass bubl 11. The cylindrical shield electrode 12 is made of non-magnetic stainless steel or an alloy of nickel and copper, etc. like the acceleration electrode 3, it has a flange portion 12a, it is insulated and supported by an electrode supporting body structure 9, it coaxially encircles most of the cylindrical portion 3a of the acceleration electrode and it faces part of the deflection electrode 5. During the operation, a potential of about 200V is applied to the acceleration electrode 3, about 150V (average value) to the deflection electrode, and about 10V to the shield electrode 12, for instance.

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 defleftron type deflection electrode.

Conventional configurations and their problems In general, an electromagnetic focusing electrostatic deflection type image pickup tube equipped with a defleftron type deflection electrode has an electrode configuration as shown in Fig. 1.
Thermionic electrons emitted from the cathode 1 are extracted through the pores of the control electrode 2 and the electron beam diameter limiting holes 4 of the accelerating electrode 3, and are subjected to a focusing action by a focusing coil (not shown) and a deflection action by a deflectron-type deflection electrode 6. Then proceed along the route shown by the solid arrow. Then, the electron beam passes through the mesh electrode 6 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, the return beam in such an electromagnetic focusing electrostatic deflection type image pickup tube differs from the return beam in an electrostatic focusing electromagnetic deflection type image pickup tube or an electromagnetic focusing electromagnetic deflection type image pickup tube, in that the return beam is directed away from the tube axis as shown by the dashed 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 electrode support groove 9 surrounding it, a so-called reflected beam is generated, and this beam takes a path as shown by the dashed line and travels to the target electrode 7 side. Head over.

Since the reflected beam has low energy and is scattered by 3 degrees to some extent, even if it is incident on the scanning area of the photoconductive film 8, the output signal will not be generated unless the incident light is Highlight 1-. It has no negative effect on current.

However, when the reflected beam enters the non-scanning area that is the peripheral area of the photoconductive film 8, a false signal due to this is mixed into the output signal current. The reason for this is that the back surface potential in the medium rectangular scanning region of the photoconductive film 8 is lower than the target voltage (usually 20 to 50 V) applied to the transparent conductive film 10, whereas in the non-scanning region This is because the back surface potential is close to the target voltage, so even a low-energy reflected beam will easily land.

In order to prevent the generation of the above-mentioned spurious signals, the diameter of the electron gun electrode is conventionally reduced so that almost all of the reflected beam returns within the scanning area, or the transparent conductive film 10'! ! , a method has been adopted in which the bamboo mesh electrodes 6 are trimmed and these electrodes are provided only within the scanning area. However, trimming requires extremely high precision in electrodes and their assembly, making them unsuitable for mass production. Also,
Reducing the diameter of the electron gun electrode not only reduces the mechanical strength of the electron gun, but also causes the control electrode in particular to become hot and easily deform due to thermal expansion. 1 da yin (if you miniaturize solstice,
It becomes impossible to obtain a beam current of sufficient magnitude.

A false signal may also be generated when the accelerating electrode potential is high. This is because the return beam is attracted toward the accelerating electrode, and a counter beam is generated that heads toward the target electrode from near the side wall of the accelerating electrode. In this case, the deflection electrode potential is ]−
It would be better to reduce the accelerating electrode potential, but in the former case the power required for focusing and deflection increases, and in the latter case the beam current becomes smaller.

Purpose of the Invention The purpose of the present invention is to prevent the generation of false signals due to a foul beam without reducing the diameter of the electron gun electrode or to perform strict trimming, and to make the acceleration electrode potential higher than the deflection electrode potential. Our goal is to provide an image pickup tube that can be set up.

Structure 5 of the Invention In the image pickup tube of the present invention, a cylindrical shield electrode laminated gun is held at a potential lower than the accelerating electrode potential, surrounds the cylindrical part of the accelerating electrode, and faces a part of the deflection electrode. This will be explained in detail below together with the embodiments shown in the drawings.

DESCRIPTION OF EMBODIMENTS In FIG. 2 showing the main parts of an image pickup tube in which the present invention is implemented,
The electron gun enclosed in the glass pulp 11 has a cathode 1,
In addition to the conventional electrode configuration consisting of a control electrode 2 and an acceleration electrode 3, a cylindrical shield electrode 12 is included. A film-like defleftron type deflection electrode 5 is provided on the inner peripheral surface of the glass pulp 11.
In front of the accelerating electrode 3, although not shown, a mesh electrode and a target electrode similar to conventional ones are arranged.

Like the accelerating electrode 3, the cylindrical shield electrode 12 is made of non-magnetic stainless steel or a nickel-copper alloy, and has a flange portion 12ai as shown in FIG. The flange portion 122L is insulated and supported by the electrode support structure 9, and coaxially surrounds most of the cylindrical portion 3a of the accelerating electrode 3. Either the terminal of the electrode 12 is drawn out of the tube regardless of the terminal of the accelerating electrode 3, or
is connected within the pipe.

In operation of such an image pickup tube, for example, the accelerating electrode 3
There is a potential of about 200V on the deflection electrode 5, about 150V (average value) on the deflection electrode 5, and about 10V on the shield electrode 12! j- is obtained, and the acceleration electrode potential is higher than the average potential of the deflection electrode.

On the other hand, in the mutually opposing portion of the shield electrode 12 and the deflection electrode 6, an electric field with a higher potential distribution is generated on the outside than on the inside, so that the return beam 132L that has progressed toward the vicinity of the peripheral edge of the accelerating electrode 3 is It is deflected outward and the offending beam is no longer directed towards the googet electrode [11+].

In addition, the return beam 1 designed in the cylindrical part 3a of the accelerating electrode 3 is
Although the reflected beam 14b by 3b is directed toward the target electrode, it is incident on the central rectangular scanning area of the photoconductive film, so there is almost no problem in practical use.

7.' Therefore, the outer diameter of the cylindrical part of the cylindrical shield electrode 12 is such that the electron beam reflected from the inner part of the outer diameter of the cylindrical shield electrode 12 is
It must be sized so that it falls within the scanning area of the electrode. The shield electrode potential is lower than the accelerating electrode potential,
It can be selected from a range of ○ to about 120 V, preferably about 30 V or less, but a negative potential may also be used. The shield electrode 12 has a funnel shape as shown in FIG. Alternatively, it may have a horn shape as shown in FIG. 5, or it may have a cylindrical shape without a flange.

Additionally, the mesh electrode may be trimmed.

However, as mentioned above, it is sufficient to have a frame-shaped border that can prevent the reflected beam from the electrode supporting groove and the repulsed beam that is largely deflected outward from re-entering the target electrode 1. There is no need to leave a part of a size that exactly corresponds to the area and frame the area around it to mask it. In other words, all you have to do is leave a part slightly larger than the area corresponding to the scanning area and mask the surrounding area, which means that a particularly high precision is required in the mesh electrode and electrode assembly. For practical purposes, ordinary precision is sufficient.

Effects of the Invention As mentioned above, since the image pickup tube of the present invention is yellowed, it is possible to prevent the generation of spurious signals due to a foul beam without reducing the diameter of the electron gun electrode. A sufficiently large beam current can be passed by setting the electrode potential to a relatively high value.Furthermore, there is no need to trim the mesh electrode, and even when performing 1-rimming, a particularly high precision is required for the electrode and its assembly. It has the advantage of being easy to implement.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the relationship between the electrodes (refining and electron beam path) of a conventional image pickup tube, Figure 2 is a sectional view of the main parts of an image pickup tube in which the present invention is implemented, and Figure 3 is a sectional view of the same image pickup tube. FIG. 4 and FIG. 6 are partially cutaway perspective views of the cylindrical shield electrode of other embodiments of the present invention, respectively. 3... Acceleration 'Electrode, 5... Deflection electrode, 1
1...Glass pulp, 12...Name of shield electrode representative Patent attorney Toshio Nakao et al.'
1 person Figure 1 Figure 0 Figure 4 Figure 5

Claims (1)

[Claims] The accelerating electrode of the electron gun, which is enclosed in a galanu bulb with a defreftron-type deflection electrode attached to the inner circumferential surface, is an electromagnetic focusing station having a cylindrical part through which the electron beam passes through a hole for limiting the diameter of the electron beam. In the electric deflection type image pickup tube, a cylindrical shield electric field FM that is held at a potential lower than that of the accelerating electrode, surrounds the cylindrical part, and faces a part of the deflection electrode is added to the electron gun. An imaging tube featuring: