JPH0580779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cathode ray tube that can be applied to an image pickup tube to obtain ultra-high resolution characteristics.

[Background of the invention]

Conventionally, electromagnetic focusing/electrostatic deflection type image pickup tubes are known. In principle, this electron optical system has small deflection aberration and excellent uniformity of resolution. (For example, see Japanese Patent Application Laid-open No. 100343/1983.) However, in this electron optical system, the principle imaging magnification is 1.
Therefore, it is difficult to reduce the imaging magnification for the purpose of ultra-high resolution.

On the other hand, an example of achieving high resolution by reducing the imaging magnification by imaging an electron beam twice is published in the Journal of the Television Society, Vol. 37, No. 9 (1983). However, since this conventional technique is based on an electromagnetic focusing/electromagnetic deflection type electron optical system, the imaging magnification remains at about 0.4, and there are also problems in that an increase in deflection aberration cannot be suppressed.

[Purpose of the invention]

An object of the present invention is to provide a cathode ray tube that has extremely reduced imaging magnification, has ultra-high resolution, and has extremely small deflection aberrations.

[Summary of the invention]

In order to achieve the above object, the present invention adds an electrostatic focusing section to the electromagnetic focusing/electrostatic deflection method, and realizes an electron optical system that uses a two-loop electron beam to reduce the imaging magnification and at the same time minimizes deflection aberration. This is what I did.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. This embodiment is an example in which the present invention is applied to a high-resolution image pickup tube.

In FIG. 1, 1 is a vacuum outer tube, 2 and 3 are cathodes and accelerating electrodes constituting an electron beam generating section, 4 is a photoconductive film target, 5 is an electrostatic deflection electrode formed on the inner wall surface of the outer tube, 6 is a mesh electrode that forms a collimation lens that allows the deflected electron beam 10 to be incident almost perpendicularly onto the photoconductive film target 4; 7 is a solenoid coil that forms an electromagnetic focusing lens; 8, 81, and 82 are power saving devices. A cylindrical electrode group forming a focusing lens, 9 a face plate, and 10 an electron beam. 31 is a beam limiting aperture provided in the accelerating electrode 3. 11 is the electron beam 10
The first image point is shown. In this embodiment, a bipolar electron gun is used in the electron beam generating section, and a positive voltage of 10 to several tens of volts is applied to the accelerating electrode. Deflection electrode 5
is 4 to generate horizontal and vertical deflection electric fields.
The deflection voltage is superimposed on a DC voltage of several hundred volts. mesh electrode 6
A high voltage of about 300 to 1000V is applied to the The beam 10 emitted from the beam limiting aperture 31 is once imaged near the exit of the electrostatic focusing lens section 8 to form a first imaged point 11 . This imaging point is focused on the target 4 by an electromagnetic focusing lens formed by the solenoid coil 7.
re-imaged on top.

FIG. 2 shows this embodiment in detail. Electrostatic focusing section 8
is composed of two cylindrical electrodes 81, 82, the inner diameter of the cylindrical electrodes 81, 82 is 7.2 mm, and the length of each electrode is 81.
The length of the first cylindrical electrode 81 is set to be about twice the inner diameter, and the length of the second cylindrical electrode 82 is set to about one time the inner diameter. In addition, a high voltage of 100 to 2000V is applied to the electrode 81, and a voltage of several tens to 2000V is applied to the electrode 82.
A low voltage of 0V is applied.

Further, the deflection electrode 5 has a diameter of 16 mm and a curved arrow pattern of 16 pitches with a pitch of 4.5 mm, and a 90° twist is added to the pattern electrode. From the beam limiting aperture 31 to the mesh electrode 6
The length is 76mm, and the length of soenoid coil 7 is 57mm.
mm and the center is placed 45mm from the beam limiting aperture.

FIG. 2 shows the distribution of magnetic field strength B and potential V on the axis. Accelerating electrode 3 is 20V, cylindrical electrode 81,
82 are respectively 500V and 0V, and the DC voltage of the deflection electrode 5 is
The voltage is 550V, and the mesh electrode 6 is 1000V.
11 indicates the first imaging point of the electron beam in this case, and it can be seen that the first imaging point exists at a position where the potential V increases.

3 and 4 show beam characteristics when the voltage V ₈₁ of the first cylindrical electrode 81 of the electrostatic focusing section is changed. The second cylindrical electrode 82 is fixed at 0V. In FIG. 3, the imaging magnification M is reduced in proportion to V ₈₁ and is approximately 0.2 when V ₈₁ is 200V. The imaging magnification in a conventional single-loop system without an electrostatic focusing section is 0.445, and in this embodiment, a reduction magnification of about 1/2 of that of the conventional example is obtained, and an extremely narrow beam spot is obtained.

In conventional electron optical systems (beam focusing/deflection systems), the reduction in imaging magnification and the deflection characteristics (spot diameter and shape distortion during deflection) are in a contradictory relationship. In this case, the deflection characteristics deteriorate to impractical values. On the other hand, the deflection characteristics of this example are good, and _the deflection beam spot diameter _r shown in FIG. It has become an extremely small value. Furthermore, as shown in Fig. 4, the figure distortion characteristic y is 0.8% in the conventional example, whereas in this example it is approximately 0.1% regardless of _V81 .
It shows good characteristics with almost no distortion.

FIG. 4 shows the position x of the first imaging point of the electron beam. This is the position of point 11 in Fig. 2 measured from the exit side tip of the cylindrical electrode 82, and the first imaging point is at a position of 1.5 mm to 3.5 mm, and the axial potential increases ( Accelerating electric field)
It can be seen that an imaged point is formed.

FIG. 5 shows another embodiment of the invention. In other embodiments, the structure of the electrostatic focusing section 8 is different,
The other parts are the same as the embodiment shown in FIG. 1, and therefore will be omitted. In FIG. 5A, the diameter of the second cylindrical electrode on the exit side is reduced, for example, the inner diameter is set to 3 mm. The voltage _V81 of the first cylindrical electrode 81 is 300 to 1000V,
When the second cylindrical electrode 83 is set to 0V, the imaging magnification M is
0.16~0.21, deflection beam spot diameter r is 15~12μ
Good characteristics are obtained with m and figure distortion y of 0.13 to 0.11%.

In FIG. 5B, the diameter of the second cylindrical electrode on the inlet side is reduced, for example, the inner diameter is set to 3 mm. 1st
When the voltage V ₈₁ of the cylindrical electrode 81 is 300 to 1000 V and the second cylindrical electrode 84 is 0 V, the imaging magnification M is 0.22 to 1000 V.
0.25, the deflection beam spot diameter r is 14 to 8 μm, and the figure distortion y is 0.12 to 0.10%, so good characteristics can be obtained.

FIG. 5C shows an electrostatic focusing section 8 on the inner wall surface of the vacuum outer tube 1.
This is an example of forming a . 85 is the first cylindrical electrode, 86
is the second cylindrical electrode.

FIG. 5D shows an example in which a second cylindrical electrode 87 is formed on the inner wall surface of the vacuum outer tube 1.

In the embodiment of the present invention, a bipolar electron gun consisting of a cathode 2 and an accelerating electrode 3 was used as the electron beam generating section, but a triode electron gun consisting of a cathode, a control electrode and an accelerating electrode was used. You may also use Furthermore, although the above embodiment is an example in which the present invention is applied to an image pickup tube, the present invention is not limited thereto, and can be similarly applied to cathode ray tubes such as storage tubes and scan converters.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize an ultra-high resolution cathode ray tube that can reduce the imaging magnification to an extremely small value while maintaining good deflection beam characteristics.

[Brief explanation of the drawing]

Fig. 1 is a sectional view for explaining an embodiment of the present invention, Figs. 2 to 4 are diagrams showing characteristics of the embodiment of Fig. 1, and Fig. 5 shows another embodiment of the invention. It is a diagram. Explanation of symbols, 1... Vacuum outer tube, 2... Cathode, 3
... Accelerating electrode, 4... Photoconductive film target, 5...
... Deflection electrode, 6 ... Mesh electrode, 7 ... Solenoid coil, 8 ... Electrostatic focusing section, 9 ... Face plate, 10 ... Electron beam, 11 ... First imaging point of electron beam.

Claims (1)

[Scope of Claims] 1. A cathode ray tube for obtaining high resolution characteristics by imaging an electron beam twice, the vacuum tube having at one end an electron beam generating means for generating the electron beam. and a target provided at the other end of the vacuum tube and scanned by the electron beam, and an object point provided in a region on the target side of the electron beam generating means and formed by the electron beam generating means. an electrostatic focusing means for imaging and creating a first focusing point; an electromagnetic focusing means provided surrounding the vacuum tube and generating a magnetic field for focusing the electron beam diverged from the first focusing point;
An electric field is generated by a predetermined applied DC voltage provided on the inner surface of the vacuum tube to deflect the electron beam diverged from the first imaging point, and together with the electromagnetic focusing means, the electron beam is redirected onto the target. an electrostatic deflection means for forming an image, and the electrostatic focusing means is provided on the side of the electron beam generating means and a first electrode to which a predetermined first applied voltage is applied, and the electrostatic focusing means is provided on the side of the target. and a second electrode to which a second applied voltage lower than the applied DC voltage is applied, so that the first imaging point of the electrostatic focusing means is A cathode ray tube characterized in that an image is formed at a position of an accelerating electric field region where a potential on the axis of the tube increases in the vicinity of an exit. 2. Claims characterized in that the electromagnetic focusing means is an electromagnetic coil provided outside the vacuum tube, and the electrostatic deflection means is comprised of a zigzag pattern electrode group formed on the inner wall surface of the vacuum tube. The cathode ray tube according to item 1.