JPS6334581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image pickup tube that does not require alignment correction work.

It is extremely desirable, based on common sense, that the central axes of the electrodes constituting the image pickup tube all lie on a straight line. If the central axes of adjacent electrodes are not at the same position at the boundary between the two electrodes and have different directions,
It is easy to imagine that these electrodes will not be able to perform their intended function completely, resulting in a decrease in performance, such as resolution. Therefore, in the past, efforts have been made to align the central axes of the electrodes of the image pickup tube in a straight line, that is, to achieve good alignment, but since it is difficult to achieve perfect alignment, the imaging So-called alignment correction has been performed by energizing a so-called alignment coil provided outside the tube and appropriately adjusting the direction of the electron beam inside the imaging tube using its magnetic field. It has been determined that the smaller the magnetic field that requires alignment correction, and therefore the smaller the alignment coil current, the more accurately the center axes of each electrode are aligned.

Alignment correction work must be performed separately for each tube even when using tubes of the same type, so it must be performed each time the image pickup tube is replaced, as well as when it is newly installed in a television camera. Alignment correction work is unnecessary (alignment-free) because it is necessary and troublesome.
There has been a demand for the development of an image pickup tube that is alignment-free.

An object of the present invention is to provide an image pickup tube that does not require alignment correction work.

In order to achieve the above object, the present inventors first attempted to improve the precision of assembling each electrode and their combinations, and endeavored to improve the precision of alignment. As a result of investigating the characteristics of a considerable number of image pickup tubes obtained in this way, which have been confirmed to have achieved extremely good mechanical alignment accuracy, we found that:
It has been found that these image pickup tubes also require substantially constant alignment correction using the alignment coil.

As an example, we investigated the results of a study on a sample group using an electrostatic focusing and electromagnetic deflection type 1-inch diameter vidicon for which alignment accuracy was confirmed, with the electrode center axis position deviation within 3 μm and the center axis tilt angle within 3 minutes.
Shown in Figure 1.

FIG. 1 shows the alignment correction amount for making the scanning electron beam perpendicular to the target surface when the target surface is viewed from the cathode side. The arrow direction in the figure indicates the electron beam scanning direction, which is indicated as a horizontal direction H and a vertical direction V. The amount of alignment correction changes depending on the level of the target voltage, the amount of light incident on the target, and the deflection direction of the electron beam. It is thought that this is influenced by the potential distribution on the surface on the cathode side. In other words, as shown in Figure 2, the potential distribution on the cathode side surface of the target changes from the positive potential transparent electrode on the light incident side of the target to the conductivity of the photoconductive film depending on the amount of incident light on each part. Therefore, the positive charge conductively accumulated on the cathode side surface of the target is
In part A, which has been scanned by the electron beam, it is neutralized by the electrons of the beam, and the potential of part A is almost zero.On the other hand, in part B, which will be scanned by the electron beam, the positive charge is present. , at a positive potential of 2 to 4 V, although it varies depending on the amount of incident light, etc. When the electrons of the electron beam enter the target surface, they are influenced by the potential on the cathode side of the target, and as shown in Figs. In the case of Figure 2, it seems to be drawn horizontally to the right by 1, vertically downward by 2, and enters the target surface while taking a trajectory slightly inclined to the vertical line of the target surface. . In contrast, alignment correction is performed so that the electron beam takes an electron trajectory that is incident on the target surface at right angles to the center of the imaging screen, resulting in good results in terms of resolution and distortion. It has gained.

If the electron beam of an image pickup tube whose central axes of each electrode are well aligned and mechanically aligned with high precision is not corrected by an alignment coil, the angle at which it is inclined with respect to the perpendicular to the target surface is As mentioned above, it is affected by the target voltage, incident light amount, electrode dimensions, etc., but for a particular product (electrode dimensions, etc.), almost constant usage conditions (voltage, light amount, etc.) are assumed. is,
Therefore, the angle of inclination can also be assumed.

In order to achieve the purpose of providing an alignment-free image pickup tube, the present invention assembles mechanically precisely manufactured electrodes with high mechanical precision to mainly direct the direction of the electron beam emitted from the cathode. Approximately in the horizontal direction of the imaging screen with respect to the central axis of the lens electrode system.
10 minutes in the vertical direction, approximately 20 minutes in the vertical direction, that is, the electron beam is tilted by an angle that cancels the assumed angle of incidence when the electron beam without alignment compensation is incident on the target surface, and the electron beam is incident at right angles to the center of the imaging screen on the target surface. I did it like that.

FIG. 3 is a sectional view of an electrode of an image pickup tube according to an embodiment of the present invention. In the figure, 1 is a cathode, 2 is a first grid, 3 is a second grid, 4 is an electron beam restriction hole, 5 is a lower third grid, 6 is a third grid cylinder, 7 is a fourth grid cylinder, 8 is the fifth grid cylinder, 9 is the sixth grid mesh, and 10 is the target. θ is the inclination angle between the electron beam emitted from the cathode and the central axis of the main lens electrode system (consisting of the third to fifth grids), that is, the direction perpendicular to the target plane. This figure shows the inclination angle θ greatly exaggerated, but in reality it is a very small angle that is difficult to illustrate.
A slope is provided at the connection between the grid cylinder 6 and the lower third grid. Incidentally, the electron beam limiting hole 4 of the second grid may be tilted at the position of the hole.

In the case of the 1-inch diameter vidicon shown in FIG. 1, the tilt angle θ in FIG.
It took 15 minutes in the vertical plane. Although this angle is small, it is a value that can be reliably set using a precision jig. Figure 4 shows the measurement results for the 1-inch vidicon sample group according to the present invention using electrodes assembled with the same accuracy as in Figure 1 and with the above-mentioned tilt angle, using the same scale. .
Even without correction using an alignment coil,
It can be seen that the electron beam is incident on the target surface almost at right angles.

Furthermore, when the above-mentioned inclination angle θ for alignment free is determined for the currently most common 2/3-inch vidicon, it is approximately 10 minutes in the horizontal direction and approximately 20 minutes in the vertical direction.

Note that in order to deflect the electron beam of the image pickup tube, a deflection coil is required, and it cannot be expected that all deflection coils are manufactured uniformly and perfectly, so for broadcasting where images of extremely good quality are required. In the case of commercial use, it may be difficult to completely eliminate alignment coils at once because the present invention relies on improving the accuracy of only the electrodes of the image pickup tube, but the amount of correction by alignment coils is extremely large. It is certain that there will be fewer
For general uses other than broadcasting, the image pickup tube of the present invention can be put to practical use without correction using an alignment coil.

As described above, according to the present invention, there is an effect that an image pickup tube that does not require alignment correction and is sufficiently practical for general use can be obtained.

[Brief explanation of the drawing]

Figure 1 is an alignment correction amount distribution diagram for a sample group in which the center axis of each electrode was aligned with high precision.
Fig. 2 is a potential distribution diagram near the electron beam incident position on the surface of the cathode side of the target, Fig. 3 is a cross-sectional view of the electrode of the image pickup tube according to an embodiment of the present invention, and Fig. 4 is an alignment correction for a sample group according to the embodiment of the present invention. Amount distribution map. 1... cathode, 2... first grid, 3... second
Grid, 4... Beam disk, 5... Lower third grid, 6... Third grid cylinder, 7...
...4th grid cylinder, 8...5th grid cylinder, 9...6th grid mesh, 10...
Target.

Claims (1)

[Claims] 1 The electron beam emitted from the cathode is tilted approximately 10 minutes in the horizontal direction and approximately 20 minutes in the vertical direction of the imaging screen with respect to the central axis of the main lens electrode system.
An image pickup tube, characterized in that the scanning electron beam is inserted into the main lens electrode system so that the scanning electron beam is incident at right angles to the target surface at the center of the scanning surface during operation of the image pickup tube.