JPH069132B2 - Electrostatic deflection type image pickup tube - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic deflection type image pickup tube having a deflectron type deflection electrode.

Conventional technology Generally, an electromagnetic focusing / deflectron type deflection electrode equipped
The electrostatic deflection type image pickup tube is constructed as shown in FIG. 3, and the deflector type horizontal / vertical deflection electrode 4 is attached to the inner peripheral surface of the glass bulb 3 accommodating the electron gun 1 and the mesh electrode 2. . Then, a target electrode 6 made of a transparent conductive film and a photoconductive film is provided on the inner surface of the transparent face plate 5 hermetically sealed to the glass bulb 3.
The electron beam 7 emitted from the electron gun 1 is focused by a focusing coil 8
After being subjected to the focusing action by the focusing magnetic field by and the deflection action by the deflection electric field by the horizontal / vertical deflection electrodes 4,
The rectangular effective scanning area of the target electrode 6 is scanned by passing through the mesh electrode 2, and the image signal corresponding to the optical image provided on the target electrode 6 through the optical lens (not shown) causes the transparent face plate 5 to pass through. It is taken out from the signal output terminal 9 which is hermetically penetrated and connected to the transparent conductive film.

By the way, in the thus-configured image pickup tube, surplus electrons generated by the electron beam 7 scanning the target electrode 6 become the return beam 10 and are again subjected to the focusing / deflecting action. Then, of the low-energy reflected beams generated by the return beam 10 striking the electron gun 1,
The reflected beam 11 directed to the target electrode 6 is also subjected to the focusing / deflecting action, and when the reflected beam 11 flows into the target electrode 6, a signal due to the reflected beam 11 is added to the output signal of the original electron beam 7 as a pseudo signal and is incident. It becomes difficult to obtain an image signal that faithfully corresponds to the optical image. The reflectance of the return beam on the surface of the electron gun is only several tenths, but the amount of the return beam generated in the dark part of the optical image on the target electrode surface is several tens of times that of the return beam generated in other parts. Therefore, the generation of the pseudo signal due to the reflected beam cannot be ignored. Further, such development is not limited to the electromagnetic focusing type image pickup type, but similarly occurs in the electrostatic focusing / electrostatic deflection type image pickup tube.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Therefore, an object of the present invention is to provide an image pickup tube capable of suppressing the generation of the pseudo signal as described above.

According to the present invention, the electron beam path from the electron gun to the effective scanning area of the target electrode through the deflection electric field generated by the deflectron-type deflection electrode is surrounded, and from the electron gun electrode to the target electrode. A conductive cylindrical body that obstructs the path of the reflected beam that extends outside the effective scanning area is provided at the tip of the electron gun.

Operation With this structure, most of the reflected beam from the tip of the electron gun toward the target electrode goes into the effective scanning area. On the other hand, the potential in the effective scanning area of the target electrode is kept relatively low by the electron beam scanning, and most of the reflected beam that goes into the effective scanning area is inclined with respect to the target electrode surface, so that it is low. The noise generated when the reflected beam of energy lands here is negligible in practice.

EXAMPLE The difference between the image pickup tube of the present invention shown in FIG. 1 and the conventional image pickup tube shown in FIG. 3 is that a cylindrical conductive tube 12 is coaxially provided at the tip of the electron gun 1. That is the point.
This tubular body 12 is a horizontal deflector type electron from the electron gun 1.
The target electrode 6 passes through the deflection electric field by the vertical deflection electrode 4.
Has a diameter and length sufficient to surround the electron beam path reaching the effective scanning area A of the target electrode 6 without encroaching on the path and to prevent the reflected beam path extending from the electron gun electrode to the outside of the effective scanning area of the target electrode 6. ing. The reflected beam passage 11 ′ shown by the broken line in the figure originally extends outside the scanning region in contact with the outermost periphery of the effective scanning region A of the target electrode 6, and this reflected beam passage 11 ′ is defined by the cylindrical body 12. Blocked by the tip. Therefore, the reflected beam 11 generated by the return beam 10 impinging on the tip of the electron gun 1 impinges on the inner peripheral surface of the cylindrical body 12, and here the secondary reflected beams 11a and 11b. Is newly generated. The secondary reflected beam is much smaller than the primary reflected beam 11 and has low energy. Therefore, even if a part of the secondary reflected beam 11 lands on the target electrode surface outside the effective scanning area A, the noise level becomes a support. Does not reach. Also, the effective scanning area A
The secondary reflected beam 11a which goes inward is not supported as described above.

Even when the electron beam 7 is deflected more than the state shown in the figure, the same action as described above works, and the reflected beam 11 when the amount of deflection of the electron beam 7 is small does not enter the inner peripheral surface of the cylindrical body 12 and is effective. Since it goes into the scanning area A, there is no problem.

Another embodiment of the present invention is shown in FIG. In this case, a large-diameter cylindrical conductive tubular body 13 and a small-diameter cylindrical conductive tubular body 14 are provided in a protruding manner at the tip of the electron gun 1 in a double arrangement. This may be a multiple array of double or more, but in any case, the generation of the pseudo signal can be more completely suppressed.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to sufficiently suppress the generation of a pseudo signal based on the reflected beam generated by the return beam, and to obtain a high S / S ratio that faithfully corresponds to the incident optical image.
N image signals can be taken out.

[Brief description of drawings]

FIG. 1 and FIG. 2 are side sectional views of an essential part of an image pickup tube embodying the present invention, and FIG. 3 is a side sectional view of a conventional image pickup tube. 1 ... Electron gun, 4 ... Deflectron type deflection electrode, 6 ...
Target electrode, 12, 13, 14 Conductive tubular body.

Claims (1)

[Claims] 1. Reflection extending from an electron gun through an electric field deflected by a deflectron-type deflection electrode to surround an electron beam path reaching an effective scanning area of a target electrode and from the electron gun electrode outside an effective scanning area of the target electrode. An electrostatic deflection type image pickup tube, characterized in that a conductive cylindrical body that obstructs a beam path is provided so as to project from a tip portion of the electron gun.