JPS6256625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a yoke assembly for an image pickup tube that is capable of correcting slight distortions in the electron beam scanning area of the photoconductive film surface of the image pickup tube.

The optical image formed on the photoconductive film in the image pickup tube corresponds to the brightness of each pixel, and the charge corresponding to each pixel accumulated on the cathode side surface of the photoconductive film within one scanning period is released from the cathode. The emitted electron beam causes sequential scanning discharge, which is extracted as a video signal current.

Usually, the scanning area on the photoconductive film surface by the electron beam is a rectangle with a ratio of 4 to 3 long sides to short sides. However, in reality, the deflection magnetic field generated by a pair of deflection coils built into the yoke assembly is caused by disturbances in the linearity of the sawtooth wave current flowing through the deflection coils.
Due to the asymmetry or non-linearity of the magnetic field caused by irregularities in the shape of the deflection coil or asymmetry in the arrangement of the deflection coil, the electron beam scanning area cannot be correctly set to the desired rectangular shape. Distortions such as pinking, barreling, and bending are likely to occur in the scan area. In a multi-tube color television camera that uses a combination of multiple image pickup tubes and yoke assemblies, such distortion causes different image distortions on the screen imaged by each image pickup tube, resulting in color shift phenomena or resolution deterioration. It causes. Furthermore, in a single-tube color television camera that uses a single-tube color image pickup tube that has a striped color reflection filter that reflects a specific color light, and that reproduces color information using a modulated wave generated by the striped filter. In this case, color uniformity is impaired due to the distortion. Distortion in the electron beam scanning area that causes these problems can be countered by improving the manufacturing precision or assembly precision of the coil of the yoke assembly.Furthermore, correcting the linearity of the current flowing through the coil in a circuit is another way to counter distortion. It is valid. However, even if the above-mentioned various measures are taken, it often happens that slight disturbances in the magnetic field remain uncorrected.

An object of the present invention is to provide a yoke assembly for an image pickup tube that can correct even minute disturbances in the magnetic field that remain after the various measures described above.

In order to achieve the above object, in the present invention,
A minute permanent magnet is disposed at an arbitrary position on the circumference surrounding the image pickup tube in substantially the same plane as the photoconductive film surface of the image pickup tube attached to a predetermined position of the yoke assembly.

FIG. 1 shows a yoke assembly 1 implementing the present invention.
3 is a diagram showing a state in which the image pickup tube 2 is combined, 3 is a glass face plate of the image pickup tube with a transparent electrode and a photoconductive film provided on the inner surface, 4 is an electron beam scanning area, and 5 is a front holding plate of the yoke assembly 1. (A plate that determines the image pickup tube holding position attached to the yoke assembly so that the axis of the yoke assembly and the axis of the image pickup tube are correctly aligned)
This is a narrow circumferential groove located concentrically with the image pickup tube.
FIG. 2 is an enlarged view of the vicinity of the face plate of the image pickup tube 2. A plurality of minute permanent magnets 6 are fitted into the groove 5, and the groove 5
It is designed so that it can be moved along the By appropriately moving the position of the magnet 6, and using the weak correction magnetic field 7 generated by the magnet 6, distortion of the electron beam scanning trajectory due to minute magnetic field distortion slightly remaining around the electron beam scanning area is removed. can be corrected and removed. In this way, it is no longer necessary to require excessively high precision in the manufacturing process of the yoke assembly.
It is easier to manufacture the yoke assembly, there is no need to add a complicated correction circuit to the circuit for passing the deflection current through the coil, and it is easier to correctly superimpose images from multiple image pickup tubes (accurate registration). Obtainable.

As explained above, according to the present invention, accurate registration can be easily obtained, and furthermore, the manufacturing of the yoke assembly is facilitated, the deflection coil current circuit is simplified, and camera adjustment is generally facilitated. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a combination of the yoke assembly of the present invention and an image pickup tube, and FIG. 2 is an enlarged view of the vicinity of the image pickup tube face plate according to an embodiment of the present invention. 1... Yoke assembly, 2... Image pickup tube, 3...
...Face plate of image pickup tube, 4...Electron beam scanning area, 5...
...Circumferential groove, 6...Minute magnet, 7...Weak correction magnetic field.

Claims (1)

[Claims] 1. A plurality of pieces fitted into a circumferential groove provided in a position surrounding the image pickup tube in substantially the same plane as the photoconductive film surface of the image pickup tube attached to a predetermined position so as to be movable in the groove. What is claimed is: 1. A yoke assembly for an image pickup tube, characterized in that the yoke assembly is equipped with a minute magnet, and is capable of correcting scanning distortion of an electron beam by moving and adjusting the position of the minute magnet along the groove.