JPS6322608Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electromagnetic focusing type image pickup tube device, and its purpose is to improve the characteristics of the image pickup tube by correcting the focusing magnetic field distribution by improving the focusing coil. It is.

As an example of an image pickup tube device used in a television camera, FIG. 1 shows the state in which an electromagnetic focusing/electrostatic deflection type image pickup tube and its coil components are installed. The configuration of an electromagnetic focusing/electrostatic deflection type image pickup tube (commonly known as an M-S type image pickup tube) includes a triode electron gun section 1 which serves as an electron beam generation source, a deflection electrode 2 formed of a vapor-deposited electrode with a cosine distribution, and a parallel There are a mesh electrode 3 that forms an electric field and a collimation lens, a photoconductive film that converts optical information into an electrical signal on the inner surface of the face plate 4, and a signal electrode 5 that extracts a signal from the photoconductive film to the outside. It is held by a glass bulb 6 in the envelope. On the other hand, the coil component has a structure in which a focusing coil 9 is wound around a bobbin 8 and the outer periphery is covered with a magnetic shielding material 10, and an electric signal is extracted from the tip of the bobbin by bringing the tongue piece 7 into contact with the signal electrode 5.

Incidentally, the magnetic field distribution of the focusing coil greatly affects various performances such as resolution, shading, and screen distortion of the image pickup tube, and the distribution near the mesh electrode is particularly important. Figures 2 and 3 show the state of the electromagnetic field near the mesh electrode. The electron beam, which is focused by the constant current drive of the focusing coil 9, is deflected by the deflection electrode 2, but due to the collimation electric field formed by the potential difference between the mesh electrode 3 and the deflection electrode 2, the deflected beam becomes light. It is corrected to be perpendicular to the conductive film 11, and further lands while decelerating in a parallel electric field generated between the mesh electrode 3 and the photoconductive film 11. The coil end of the focusing coil 9 is located near the mesh electrode. Now, the focused magnetic field distribution on the A-A' plane is the tube axis O as shown in Figure 3a.
A so-called barrel magnetic field is formed in which the magnetic field strength decreases as the distance increases in the radial direction, and this is because the focusing coil 9 has a finite length and is particularly noticeable near the ends of the coil. 3A shows the focused magnetic field distribution (uniform magnetic field) in the tube diameter direction after correction.

Similarly, as shown in FIG. 3b, the focusing magnetic field from the vicinity of the electron gun to the vicinity of the mesh electrode becomes closer to the end of the focusing coil, the difference between the focusing magnetic field on the tube axis and the focusing magnetic field in the tube radial direction increases. The difference between the focusing magnetic field on the tube axis (a in Figure 3b) and the focusing magnetic field in the tube radial direction (b in Figure 3b) affects the focusing of the electron beam more on the deflection side than on the electron gun side. Needless to say, it will become larger. In other words, the non-uniformity of the focused magnetic field distribution in the tube diameter direction near the mesh electrode disturbs the vertical landing state of the electron beam on the photoconductive film 11 during deflection, further impeding shading and uniformity of resolution, and causing spiral distortion. This was the cause of the increase.

The present invention aims to improve the characteristics of the image pickup tube by correcting the uniformity of the focusing magnetic field in the tube radial direction by improving the configuration of the focusing coil. explain.

As a means of achieving a uniform magnetic field distribution in the radial direction of the focusing coil as shown in Fig. 2A and A', first, as shown in Fig. 4a, the current of the focusing coil itself is changed. Means for modulating in accordance with the amount of deflection, secondly a correction focusing coil 13
There are means for generating a correction focusing magnetic field by overlapping the main focusing coil 14, and thirdly, means for arranging a correction focusing coil 16 at the end of the focusing coil 15 to generate a correction focusing magnetic field. However, the frequency of the correction focusing magnetic field must be at least equal to or higher than the horizontal scanning frequency. In the first case, generally the focusing coil 12
Since the inductance is large, even if a control current for the correction magnetic field is directly passed through it, the frequency response is poor and correction is difficult. In the second case, since the correction focusing coil 13 is independent, the number of turns can be reduced and the inductance can be sufficiently small.
Therefore, there is no problem with the frequency response, and it is possible to achieve uniformity of the focused magnetic field distribution in the tube radial direction in the correction coil power source. However, since the correction focusing coil faces the main focusing coil in the direction of the tube axis, the degree of coupling between the two is high, resulting in deterioration of the frequency response due to mutual inductance and an increase in the power of the correction focusing coil. Since the magnetic field is corrected, the scanning screen width and scanning screen rotation angle change. On the other hand, in the third case, the correction focusing coil 16
is placed at the coil end of the main focusing coil 15, the degree of coupling between the two is low, the frequency response is good, and it can be driven with a small corrected focusing power. Furthermore, by positioning the correction focusing coil close to the mesh electrode from the face plate, superimposition with the correction focusing magnetic field can be avoided, so that the scanning screen width and scanning screen rotation angle can be changed by the correction focusing magnetic field as in the second case. There are no problems associated with change.

From the above, the best way to correct the non-uniformity of the focusing magnetic field distribution in the tube radial direction by improving the configuration of the focusing coil is to install a correction focusing coil near the mesh electrode, facing the coil end of the main focusing coil. It can be said to be a means of attachment.

FIG. 5 shows a focusing coil component in an embodiment of the present invention. In FIG. 5, the same parts as in FIG. 1 are given the same numbers. The focusing coil part is bobbin 8
A focusing coil consisting of a main focusing coil 11a and a correction focusing coil 11b is wound around the magnetic shielding material 10.
It has a structure that covers the surrounding area. As described above, the correction focusing coil 11b is set near the face plate 4 and closer to the face plate than the focusing coil 11a. The focused magnetic field distribution according to the present invention is shown in FIG.

First, a constant DC current is passed through the main focusing coil 11a to focus the electron beam. At this time, the focused magnetic field distribution on the tube axis becomes B _ZO . However, the focused magnetic field distribution in the tube radial direction becomes B _ZD , and near the coil opening,
This results in a magnetic field that is attenuated compared to B _ZO , resulting in a so-called barrel magnetic field in the radial direction. If a constant DC current similar to that of the main focusing coil 11a is simply passed through the correction focusing coil 11b, a fixed correction focusing magnetic field distribution B _ZC is simply superimposed, and the tendency of the barrel magnetic field in the tube radial direction does not change at all. In this state, as the electron beam is deflected toward the periphery, the intensity of the focusing magnetic field that the electron beam receives becomes weaker, and the landing angle of the electron beam with respect to the photoconductive film 11 becomes larger. As a result, the characteristics of the image pickup tube at the periphery of the scanning screen deteriorate. To solve this problem, the intensity of the focusing magnetic field at each deflection position is approximately equal to the focusing magnetic field distribution on the tube axis B _ZO (the intensity of the focusing magnetic field that the electron beam receives when it is not deflected). Correct the focused magnetic field distribution B _ZC so that it has the same value.
A control current synchronized with the deflection of the electron beam is passed through the correction focusing coil _11b so that the more the electron beam is deflected to the periphery _, the stronger the correction focusing magnetic field becomes. The focusing magnetic field in the tube radial direction is substantially uniform at all deflection positions.

Therefore, the landing of the electron beam on the photoconductive film 11 can be carried out vertically on all scanning planes, and the uniformity of the shedding and resolution characteristics can be dramatically improved, as well as the non-uniformity of the focused magnetic field distribution in the tube radial direction. This also eliminates so-called spiral distortion in which the scanning screen is distorted into an S-shape due to the difference in rotation angle of the electron beam.

Furthermore, since the correction focusing magnetic field area is separate and independent from the deflection electric field area of the image pickup tube, there is no mutual interference, and there are no problems such as variations in the scanning screen width or rotation of the scanning screen due to the correction focusing magnetic field.

Although the present invention has been described using an electromagnetic focusing/electrostatic deflection type image pickup tube as an example, it is also effective for improving the focusing magnetic field distribution of the focusing coil in the case of an electromagnetic focusing/electromagnetic deflection type image pickup tube. Needless to say.

As described above, according to the present invention, in the focusing coil of an electromagnetic focusing type image pickup tube, a correction focusing coil is wound around the face plate of the image pickup tube, and a control current synchronized with the electron beam deflection is passed through this coil. The focusing magnetic field distribution in the tube diameter direction near the coil end of the focusing coil is modulated, and as a result, the vertical landing of the electron beam on the photoconductive film and the constant focusing angle improve the resolution of the image pickup tube, the uniformity of the shedding characteristics, and the spiral distortion. It is possible to provide a screen without

[Brief explanation of the drawing]

Figure 1 is a sectional front view of a conventional image pickup tube device, Figure 2 is a diagram showing the electric field distribution of the same device, Figures 3a and b are diagrams showing the magnetic field distribution for explaining the same device, and Figure 4 a, b, and c are diagrams of a focusing coil and a circuit for explaining the image pickup tube device of the present invention, FIG. 5 is a sectional front view of the image pickup tube device in an embodiment of the present invention, and FIG. 6 is an explanation of the device FIG. 8... Bobbin, 11a... Main focusing coil, 11
b...Correction focusing coil, 3...Mesh electrode, 6
...Glass bulb.

Claims (1)

[Scope of utility model registration request] A focusing coil attached to an electromagnetic focusing type image pickup tube is divided in the tube axis direction of the image pickup tube into a main focusing coil and a correction focusing coil, and the correction focusing coil is arranged near the mesh electrode of the image pickup tube, The main focusing coil is arranged behind the correction focusing coil, the main focusing coil is driven by a constant current, and the correction coil is superimposed with a constant current and a control current synchronized with the deflection of the electron beam of the image pickup tube. An image pickup tube device designed to flow.