JPH0117809Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Technical field of invention] This invention relates to improvement of an image pickup tube.

[Technical background of the invention and its problems]

Conventionally, an image pickup tube is configured as shown in FIG.
At the open end of the bottomed simple glass vacuum envelope 5,
The face plate structure 4 is hermetically sealed via an indium metal layer 13, and a metal ring 14 made of a non-magnetic material is pressed into contact with the outer periphery of the indium metal layer 13 to form a signal electrode 15. The above face plate structure 4
In this method, a transparent conductive film 2 such as SnO ₂ or In ₂ O ₃ is deposited on the inner surface of a transparent plate 1 made of a transparent material such as transparent glass, and further on this transparent conductive film 2.
A photoconductive film 3 mainly composed of Sb ₂ S ₃ , CdSe, etc. is deposited thereon. And this photoconductive film 3
The indium metal layer 13 is electrically connected to the indium metal layer 13, and the image signal projected on the transparent conductive film 2 is taken out to the outside via the signal electrode 15. Further, inside the vacuum envelope 5, from the photoconductive film 3 side, there are a mesh electrode 6, a cylindrical electrode 7 serving as an acceleration and focusing electrode, a second grid electrode 8, a first grid electrode 9, a cathode 10, and a heater 11. An electron gun assembly 12 is housed in which the electron gun structures 12 are arranged on the same axis at predetermined intervals. Furthermore, a plurality of electrode terminals 16 are implanted through the stem portion of the vacuum envelope 5 to supply signals and power to the internal electrode groups, respectively ^. An exhaust section 17 is provided to evacuate to a high degree of vacuum of ⁶ to 10 ^-7 Torr. Further, a focusing/deflection coil 19 for focusing and deflecting the electron beam 18 emitted from the cathode 10 is disposed on the outer peripheral surface side of the vacuum envelope 5 .

In the image pickup tube configured as described above, the electron beam 18 generated from the cathode 10 heated by the heater 11 has its beam amount controlled by the first grid electrode 9, and the beam shape is shaped by the second grid electrode 8. The light is further accelerated and focused by the cylindrical electrode 7, and is focused and scanned on the photoconductive film 3 by the action of the focusing/deflection coil 19.

However, in the above-mentioned image pickup tube, the return beam 20 is focused on the second grid electrode 8, and is further reflected to produce a so-called spurious signal that re-enters the photoconductive film 3. Therefore, conventionally, the second grid electrode 8
The surface of the cylindrical electrode 7 can be roughened to diffusely reflect the return beam 20, or a disk-shaped electrode anti-reflection plate 21 can be attached in the middle of the cylindrical electrode 7 to separate the focal point and reflection point of the return beam 20. By methods such as shifting the
This prevents false signals from occurring on the face plate structure 4.

By the way, when we carefully examine the pseudo signals, we find that, for example, as shown in FIG. It has been found that the manner in which pseudo signals are generated differs between an image pickup tube that scans an electron beam and an image pickup tube that uses an electromagnetic deflection, electromagnetic focusing method, and an electromagnetic deflection or electrostatic focusing method shown in FIG. That is, in the case of a pseudo signal from an image pickup tube using electrostatic deflection or electromagnetic focusing, a no-pseudo signal region 25 always exists near the center of a pseudo signal image 24, as shown in FIG. What can be said from this development is that reflection of electrons, secondary electron emission, etc. due to the return beam colliding with electrodes or other materials can cause false signals; Even if there are discontinuities or changes in shape of other substances, they will not appear in the image as false signals. Empirically, the area of no pseudo signals is approximately rectangular, approximately 1/2 or less of the horizontal scanning distance of the electron beam scanning the photoconductive film of the image pickup tube, and approximately 1/2 or less of the vertical scanning distance.

In addition, in an image pickup tube using electrostatic deflection or electromagnetic focusing, in order to prevent spurious signals caused by return beams from the photoconductive film, any uniform electrodes should not be provided in areas other than those corresponding to the non-pseudo signal area. However, as long as there is reflection of the return beam or secondary electron emission, due to the contrast difference on the image with the non-pseudo signal area,
In fact, as shown in FIG. 5, the entire image is disturbed. Therefore, the method shown in FIG. 2 for preventing false signals is considered to be insufficiently effective in electrostatic deflection and electromagnetic focusing type image pickup tubes.

[Purpose of invention]

The purpose of this invention is to provide an image pickup tube that prevents the generation of false signals due to return beams.

[Summary of the idea]

This device provides a non-pseudo signal on the exit side of the second grid electrode with an internal space cross-sectional area of approximately 1/2 or less of the horizontal scanning distance of the electron beam on the photoconductive film and approximately 1/2 or less of the vertical scanning distance. This image pickup tube is equipped with a cylindrical electrode that is set to be smaller than the area and whose length is set to be 1/2 or more of the maximum diameter of the second grid electrode.

[Example of idea]

The main parts of the electrostatic deflection and electromagnetic focusing image pickup tube according to this invention are constructed as shown in FIG. 6, and the same parts as in the conventional example (FIG. 1) are given the same reference numerals. That is, in this invention, a cylindrical electrode 23 is attached to the exit side (reticular electrode side) of the second grid electrode (limiting aperture electrode) 8.
In this case, the second grid electrode 8 has an inlet side portion 8a.
and an outlet side portion 8b, the cylindrical electrode 23 is attached to the outlet side portion 8b and electrically integrated therewith. Further, the cylindrical electrode 23 has an internal space cross-sectional area that is less than about 1/2 of the horizontal scanning distance of the electron beam 18 on the photoconductive film 3 and less than about 1/2 of the vertical scanning distance from a non-pseudo signal region. The diameter of the second grid electrode 8 is also set to be small, and its length is set to be at least 1/2 of the maximum diameter of the second grid electrode 8. Furthermore, since the image pickup tube of this invention is of an electrostatic deflection type, the cylindrical electrode 7 as shown in FIG. Two pairs of electrostatic deflection electrodes 22 made of conductive layers are formed. Although not shown, a focusing coil is disposed around the outer periphery of the vacuum envelope 5.
Incidentally, since the structure around the face plate structure is the same as that in FIG. 1, illustration and explanation are omitted.

Now, during operation, the cylindrical electrode 23 is attached to the second grid electrode 8, and its internal space cross-sectional area is set smaller than the non-pseudo signal area.
Return beam 26 and return beam 27 as shown
No spurious signals are generated under the influence of . Furthermore, the length of the cylindrical electrode 23 is 1/2 of the maximum diameter of the second grid electrode 8.
Since the setting is above, the second grid electrode 8
When the voltage Ec ₂ is lower than the voltage Edef of the electrostatic deflection electrode 22, the return beam 20 is bent toward the vacuum envelope 5 as shown in FIG. does not generate spurious signals. On the other hand, when Ec ₂ is higher than Edef, as shown in FIG. 9, the beam is bent in the direction of the cylindrical electrode 23, so that the focal point is shifted and no pseudo signal is generated on the photoconductive film 3.

Note that the cathode 10 and heater 11 are omitted in FIGS. 8 and 9.

[Effect of idea]

According to this invention, generation of false signals due to return beams can be prevented, and an imaging tube with good image quality can be obtained.

Incidentally, FIG. 10 shows a modification of this invention, in which the cylindrical electrode 24 is formed completely integrally with the second grid electrode 8. That is, in the above embodiment, the second grid electrode 8 consists of an inlet side part 8a and an outlet side part 8b, and the cylindrical electrode 23 is attached to this outlet side part 8b, but in this modification, the cylindrical electrode One end of 24 becomes a flange-shaped portion 24a, and this flange-shaped portion 24a also serves as the exit side portion of the second grid electrode 8. For convenience, the first grid 9, cathode 10, and heater 11 are omitted in FIG.

Further, as long as the cylindrical electrodes 23 and 24 have an internal space cross-sectional area smaller than the non-pseudo signal area on the photoconductive film 3, the cross-sectional shape is not limited to a circle, but may be triangular or rectangular.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional image pickup tube, FIG. 2 is a sectional view showing another image pickup tube, FIG. 3 is a perspective view showing an example of an electrostatic deflection electrode, and FIG. 4 is a sectional view showing an electrostatic deflection electrode.
A plan view showing a pseudo signal in an image pickup tube using an electromagnetic focusing method. FIG. , FIG. 6 is a sectional view showing an image pickup tube according to an embodiment of this invention, FIG. 7 is a sectional view showing the return beam trajectory near the cylindrical electrode used in this invention, and FIG _. 8 is a sectional view showing the return beam trajectory near the cylindrical electrode used in this invention. A cross-sectional view showing the return beam trajectory when Ec ₂ >
A sectional view showing the return beam trajectory in the case of Edef, and FIG. 10 is a sectional view showing a modification of this invention. DESCRIPTION OF SYMBOLS 1... Face plate, 2... Transparent conductive film, 3... Photoconductive film, 4... Face plate structure, 5... Vacuum envelope, 6...
mesh electrode, 8... second grid electrode, 9... first
Grid electrode, 10... cathode, 11... heater, 18... electron beam, 20... return beam, 22... electrostatic deflection electrode, 23... cylindrical electrode.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A face plate structure in which a transparent conductive film and a photoconductive film are sequentially formed on the inner surface of the face plate is hermetically sealed to the open end of a bottomed cylindrical vacuum envelope, and Inside the vacuum envelope, from the photoconductive film side, a mesh electrode, a second grid electrode,
A first grid electrode, a cathode, and a heater are disposed coaxially at predetermined intervals, and electrostatic deflection electrodes are arranged on the inner surface of the side wall of the vacuum envelope from the mesh electrode to the second grid electrode.
In the image pickup tube formed across the grid electrode, on the exit side of the second grid electrode, the internal space cross-sectional area is about 1/2 or less of the horizontal scanning distance of the electron beam on the photoconductive film and about the vertical scanning distance. An image pickup tube characterized in that a cylindrical electrode is attached which is set to be smaller than a non-pseudo signal area of 1/2 or less and whose length is set to be 1/2 or more of the maximum diameter of the second grid electrode. (2) The imaging tube according to claim 1, wherein the cylindrical electrode is integrated with the second grid electrode.