US3659140A

US3659140A - Image pickup tube device utilizing a magnetic field generator to reverse the leakage field

Info

Publication number: US3659140A
Application number: US833645A
Authority: US
Inventors: Shoichi Miyashiro; Shunzi Shirouzu; Mineo Iwasawa
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1968-06-20
Filing date: 1969-06-16
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25
Also published as: GB1275303A

Abstract

An image pickup tube device has an evacuated container including a scanning section and an image section. In the sections are respectively mounted first and second magnetic means; the former generating a magnetic field in the image section and producing a leakage of magnetic field in the other section, the latter producing a magnetic field to reverse the polarity of the leakage field.

Description

United 1; States Patent Miyashiro et al.

[ 51 Apr. 25, 1972 IMAGE PICKUP TUBE DEVICE UTILIZING A MAGNETIC FIELD GENERATOR TO REVERSE THE LEAKAGE FIELD Inventors: Shoichi Miyashiro, Yokohama-shi; Shunzi Shirouzu, Kawasaki-shi; Mineo lwasawa, Kanagawa-ken, all of Japan Assign cc: Tokyo Shibauru Electric C0,, Ltd.,

Knwumrkiuhi, .Iupmt Filed: June [6, 1969 Appl. No.: 833,645

Foreign Application Priority Data June 20, 1968 Japan ..43/42225 u.s. Cl .315/10, 315/31 Int: Cl. ..H01J 31/26 FieldoiSearch ..3i5/l0,11, l2,3l;313/65;

250/213 R, 213 VT SOURCE OF SUPPLY SOURCE OF SUPPLY [56] References Cited UNITED STATES PATENTS 3,437,867 4/1969 Miyashiro et al. ..3 1 3/79 X 3,462,601 8/1969 Sternglass ...250/2l3 VT X 3,478,213 12/1969 Simon et al ..250/2 13 VT X FOREIGN PATENTS OR APPLICATIONS 664,8l3 1/1952 Great Britain .315/10 Primary lzlt'arniner-Carl D. Quarforth Assistant Examiner-J. M. Potenza Attorney-Flynn & Frishauf [57] ABSTRACT An image pickup tube device has an evacuated container including a scanning section and an image section. ln the sections are respectively mounted first and second magnetic means; the former generating a magnetic field in the image section and producing a leakage of magnetic field in the other section, the latter producing a magnetic field to reverse the polarity of the leakage field.

6 Claims, 7 Drawing Figures DEFLECTING SOURCE 24 GENERATlNG DEVICE FIG.3

D I STANCE Patented April 25, 1972 4 Sheets-Sheet 3 FIG.4

D I STANCE Patented April 25, 1972 4 Sheets-Sheet 4 IMAGEPICKUP TUBE DEVICE UTILIZING A MAGNETIC FIELD GENERATOR TO REVERSE THE LEAKAGE FIELD BACKGROUND OF THE INVENTION Thisinvention is. concerned with an image pickup tube device. The invention is an improvement or modification of that disclosed in our U.S. Pat. No. 3,437,867.

In said earlier application, there is described and claimed an image. pickup tube device comprising an electron scanning section including a vacuum container defining a longitudinal axis an electron gun mounted for emitting an electron beam along said axis, focussing means for focussing the electron beam from said electron gun, electrostatic means for electrostatically deflecting the focussed electron beam, cylindrical electrode mounted coaxially with said electron. gun, a field mesh electrodefor supplying the highest electrical potential to saidelectron beam for making said electron beam parallel to said axis, a collimation lens mounted coaxially with said electrodes andformed bythe electrostatic field of said field mesh electrode, and a target mounted in close parallel to said field mesh electrode and scanned at a low speed by said electron .beam, an image section including a photoelectron cathode imounted at the otherend of said vacuum container, and a magnetictfield generator provided outside the container on said imagesection said for focussing the image electrons from said cathode on said target, which produces a leakage of a maximum of 25 gauss of magnetic field on the axis of the containeron said target.

In the above described device, it is difficult to control a leakageof magnetic field in the image section and cause electron beams from the electron gun to enter the target exactly at rightangles,

SUMMARY OF THE INVENTION An image, pickup tube device comprising an image section and a scanning section, the former having a first magnetic generating means to generate a magnetic field in said section and produces a leakage of magnetic field in the scanning section, the latter including a second magnetic generating means which provides a magnetic field in said section to reverse the polarity of the leakage field (reversion of the leakage field), thereby allowing the intensity of said leakage field to be controlled to a desired value.

, BRIEF EXPLANATION OF THE DRAWINGS FIG. 1 is a diagram illustrating an image pickup tube device according to an embodiment of this invention applied to an imageprthicon type pickup tube;

F [6.2 is a schematic diagram of the part near the target used in thepickup tube shown in FIG. 1;

FIG. 3 is a diagram showing the distribution of a magnetic field along the axis generated by the electromagnet at the part shown in FIG. 2;

FIG. 4 is a schematic diagram showing the part of a pickup tube according to another embodiment of the invention, whose magnetic generating means is a permanent magnet;

FIG. is a diagram showing the distribution of a magnetic field alongithe axis formed by the permanent magnet shown in FIG; 4;

FIG. 16 is a diagrammatic sectional view of an intensifier vidicon in which the fundamental idea of the invention is applied; and FIG; 7 is a diagram showing the intensity of a magnetic field along the axis of the device of FIG. 6.

DESGRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the terms listed hereinafter are construed as follows. A magnetic field along the axis means a magnetic field along the longitudinal axis of the image new that the intensity of the resultant field becomes zero in terms of vector values in axial direction.

Now an image pickup tube device according to this invention as it is applied to an image orthicon tube will be described with reference to FIG. 1.

On the internal surface of the face plate on one edge of an evacuated container 1 is provided a photoelectric cathode 2, with which coaxially provided are a first cylindrical electrode 3 and a target electrode 4. At the end of the electrode 4 is mounted a disc-shaped target mesh electrode 5 in parallel to said photoelectric cathode 2, and a disc target 6 is provided closely in parallel to said mesh electrode 5 to form an image section 7. Coaxially with the said target 6 are provided a second cylindrical electrode 8 and a third cylindrical electrode 9. At the end of said second electrode 8 is mounted a field mesh electrode 10. Said mesh, second and

third electrodes

8, 9 and 10 form a collimation lens 11, when the voltage is applied to these three electrodes respectively.

On the other end of said evacuated container 1 is provided an electron gun 12, with which are coaxially mounted a fourth cylindrical electrode 13, a focussing electrode 14 and a fifth electrode 15. Between said electrode 15 and said third electrode 9, a deflecting assembly 16 is provided for deflecting the electron beam vertically and horizontally, in such a way that the center of deflection of said assembly 16 agrees with the focal point of said collimation lens 11. A secondary electron multiplier section 27 is provided around said electron gun 12 to form a scanning section 17. Said scanning section 17 and the image section 7 make up an image orthicon 18. The air surrounding said orthicon 18 is covered with an enclosure 19, whose scanning section 17 is made of a magnetic shield case 20. In the neighborhood of said photoelectric cathode 2 of the said enclosure 19 is positioned magnetic field generating device such as a solenoid coil 21 and a magnet 34, for which coil 21 is provided a power source 22. Further a solenoid coil 32 connected to a power source 33 is accommodated in the enclosure 19 of the scanning section near the second electrode 8. In front of the incident light side of said photoelectron cathode 2 is provided an optical lens 28. Around the tube 1 in the neighborhood of said electron gun 12 is disposed an alignment coil 23, which is provided with a power source 24. Furthermore, an electric power source 25 is provided for supplying an operation voltage for each electrode of said image orthicon 18 to form an image pickup tube device 26.

Now, the operating principle of this device is explained with reference to FIG. 1.

The various parts of an image pickup device are supplied with operating voltage at the following levels: 500V for the photoelectron cathode 2 of the image orthicon I8, -400V for the first electrode 3, 2V for the target electrode 4, CV for the cathode of the electron gun l2, 250V for the fourth electrode 13, about V for the focussing electrode 14, 900V for the field mesh electrode 10, and 1,250V for the anode of the secondary electron multiplier section 27. After said voltage supply, an optical image is formed at the photoelectron cathode 2 by means of the optical lens 28, which in turn generates image electron beams from said cathode 2. The electron beam is electromagnetieally focussed by the axially symmetrical magnetic field generated by the solenoid coil 21 and the magnet 34 and by the electrical field formed by the first electrode 3 and target electrode 4, and is accelerated and projected as an image on the surface of the target 6. In this manner, the positive charge image is stored in said target 6.

0n the other hand, the primary electron beam 30 projected from the electron gun 12 is focussed by the focussing electrode l4, and then is deflected vertically and horizontally by the deflecting means 16. Then the primary electron beam 30 is allowed vertically to incide into the target 6 by the collimation lens 11 formed of the third electrode 9, second electrode 8 and field mesh electrode 10 and the axially symmetrical magnetic field formed by the said

solenoid coils

21 and 32. At this time, the field mesh 10 of the collimation lens llflis impressed with the highest of those voltages required in focussing the primary electron beam 30, and the target is supplied with a voltage of 2V. Accordingly, from the field mesh electrode to the target 6 is formed a sharply decelerated electrical field, so that the primary electron beam 30 impinges at a low speed on the surface of the target 6. At this time, the positive charge image stored in the target is scanned and discharged efficiently by said primary electron beam to generate a return beam corresponding to the positive charge image. The return electron beam 31 passes through the deflecting assembly 16 and the focussing electrode 14 and is led to the secondary electron multiplier section 27 where it is multiplied to the desired value and is taken out as an output signal.

The image pickup tube described above is substantially the same type as that disclosed in U. S. Pat. No. 3,437,865 except that there are provided a solenoid coil 32 and power source 33 associated therewith. Accordingly, there occurs a bad effect such as a corner shading, if the intensity of a leakage magnetic field at the image section is met controlled to 25 gauss at maximum. The leakage field generated by the magnet 21 is distributed in one direction. Consequently, the beam emitted from the electron gun is deflected toward said direction, thereby preventing incidence to the target from being carried out at right angles. In the invention, there is provided the magnetic generating means 32 for the scanning section to cause the leakage magnetic field to be reversed in the scanning section near the target, i.e., the reversion of the magnetic field in the scanning section. The beam emitted from the electron gun is apparently prevented from being deflected because the magnetic lines of force of the two magnetic fields are offset by each other, so that the resultant beam vertically impinges on the target. There will now be detailed the aforementioned characteristics of the invention referring to FIGS. 2 and 3. The same parts of FIGS. 2 and 3 as those of FIG. 1 are denoted by the same numerals and description thereof is omitted. The magnetic lines of force of a magnetic field formed by the coil 21 extend outwardly from the longitudinal axis of the pickup tube. The intensity of this magnetic field along the axis is shown by a dotted curve b in FIG. 3. On the other hand, the magnetic lines of force of a magnetic field generated by the solenoid coil 32 extend inwardly and the intensity of the magnetic field is indicated by a dotted curve c. A solid curve a represents the true intensity of the magnetic field along the axis, which is a sum of said two magnetic fields. That is, the curve a is a sum of the curves c and b. The reversing point is shown by a mark p which is movable along the axis according to variations in the intensity or distribution of the field generated by the coil 32. Accordingly, the leakage magnetic field in the scanning section near the target may be controlled to obtain a desired value of less than 25 gauss by adjusting the current passing through the solenoid coil and/or the locating thereof.

As shown in FIGS. 4 and 5, permanent magnets 40 and 41 may be used instead of the solenoid coils 21 and 32 of said device. Both magnets are prepared in the annular form, one magnet 40 being provided with the north pole at the inner side and the south pole at the outer side thereof while the other magnet 41 the south and north poles at the inner and outer sides respectively. The magnetic lines of force are consequently distributed as shown by the dotted lines of FIG. 4. The intensities of the magnetic fields along the axis are respectively indicated by the dotted curves b, c and solid curve a in FIG. 5, which respectively correspond to the three curves in FIG. 3.

The image pickup device using a permanent magnet displays an excellent edge effect by means of controlling the intensity of black border effect for a reproduced image picture because it elevates the intensity of a magnetic field in the image section near the target so as to shorten the scanning distance of the secondary electrons from the target.

As mentioned above, the present invention enables the intensity of a leakage magnetic field in the scanning section to be controlled to a desired value by suitably changing the position of the reversing point through adjustment of an additional coil. Further the invention not only prevents the occurrence of image shading, for example, parabolic shading caused by the axial distortion of an image pickup tube or the deflection of a magnetic field, but also eliminates irregularities in output signals which appear crosswise and lengthwise of a reproduced image.

There will now be described by reference to FIGS. 6 and 7 an intensifier vidicon assembled from a multi-stage type image tube and vidicon, to which the idea of the present invention is applied.

A multi-stage type image tube 50 and vidicon 51 are connected, as illustrated, by a large number of juxtaposed optical fibers 52 to form an intensifier vidicon. Like those in common use, this tube 50 has a photoelectric plane 54 mounted on one end of an evacuated container 53 and a fluorescent layer or plane 55 provided in the container to face to said plane 54. Between these two

layers

54 and 55 are juxtaposed dynodes 56 at a prescribed space using the known method. Around the tube 50 is disposed a convergence magnetic coil 57. On the other hand the vidicon 51 is provided at one end with a photoelectric layer 58, which is optically connected to the fluorescent plane 55 by the optical fibers and at the other end with an electron gun assembly 59 for scanning said photoelectric layer 58. Further, around the vidicon section of the container is formed a separate magnetic coil 60 from the aforementioned magnetic coil 57 to converge and deflect electron beams from the assembled electron guns 59.

With a device according to this embodiment having the aforesaid arrangement, the magnetic coil 57 of the multi-stage image tube 50 is so designed that a magnetic field along the axis of the tube has a value of 250 to 200 gauss units as indicated by the dotted curve d of FIG. 7. On the other hand the magnetic coil 60 of the vidicon 51 is so designed that a magnetic field (denoted by the dotted curve 2 of FIG. 7) along the axis of the tube is oriented in the opposite direction to the first mentioned magnetic field and displays a value of 200 gauss units. Accordingly, the resultant magnetic field (indicated by the solid curve f of FIG. 7) has an intensity of 250 to 300 gauss units in the image tube section 50 of the container 53 and an intensity of 50 gauss units in the vidicon section 51, thus enabling both sections to perform a prescribed operation. In the device described above, a single image-converting plane or target may be used instead of assembling the fluorescent layer 55, photoelectric layer 58 and optical fibers 52 provided therebetween.

It is generally required for an intensifier vidicon that the magnetic field along the axis displays an intensity of 250 to 300 gauss units in the section of a multi-stage type image tube and a fairly low intensity of about 50 gauss units in the vidicon section. However, a mere combination of both sections, as is usually the case with the prior art device, causes the elevated magnetic field of the image tube section to leak toward the vidicon section, with the result that the magnetic field along the axis of the vidicon section rises beyond gauss units to prevent said vidicon section from carrying out a prescribed operation. If, however, there is applied the fundamental idea embodying the present invention of impressing one magnetic field with another reverse field, then it will be possible unfailingly to control the intensity of a magnetic field along the axis of the vidicon section to about 50 gauss units.

What we claim is:

1. An image pickup tube device comprising an evacuated container defining a longitudinal axis, which is divided into a scanning section and image section, said scanning section including an electron gun mounted for emitting and electron beam along said axis, focussing means for focussing the electron beam from said electron gun, electrostatic means for electrostatically deflecting the focussed electron beam, a cylindrical electrode mounted coaxially with said electron gun, a field mesh electrode for supplying the highest electrical potential to said electron beam for making said electron beam parallel to said axis, a collimation lens mounted coaxially with said electrodes and formed by the electrostatic field of said field mesh electrode, and a target mounted in close parallel relationship to said field mesh electrode and scanned at a low speed by said electron beam, an image section including a photoelectron cathode mounted at the other end of said vacuum container and a first magnetic field generator provided outside the container on said image section side for focussingflthe image electrons from said cathode on said target, which produces a leakage magnetic field on the axis of the containenon said target, characterized in that said scanning section further includes a second magnetic field generator to generate a magnetic field which reverses the polarity of the leakage field produced by said first generator near said target.

2. An image pickup tube according to claim 1 wherein said both magnetic field generators are annular electromagnets.

3. An image pickup tube according to claim 1 wherein said both magnetic field generators are annular permanent magnets.

4. An intensifier vidicon comprising a multi-stage type imagesection and a vidicon section which are provided in a common evacuated container, said image section including a photoelectric layer mounted on one end of said container, a fluorescent layer provided in said container said photoelectric layer, a plurality of dynodes disposed between said both layers, and a first magnetic field generator for focussing the electron beams from said photoelectric layer, which produce a leakage magnetic field in the vidicon section; and said vidicon section including an image converting means, an electron gun assembly emitting electron beams to scan the fluorescent layer of this section and a second magnetic field generator to focus said electron beam, which generates a magnetic field to reverse the polarity of said leakage field.

5. An intensifier vidicon according to claim 4 wherein said image converting means comprises of a fluorescent layer, a photoelectric layer and light conductive means provided therebetween.

6. An intensifier vidicon according to claim 5 wherein said light conductive means comprises of a plurality of optical fibers.

t i i i t

Claims

1. An image pickup tube device comprising an evacuated container defining a longitudinal axis, which is divided into a scanning section and image section, said scanning section including an electron gun mounted for emitting and electron beam along said axis, focussing means for focussing the electron beam from said electron gun, electrostatic means for electrostatically deflecting the focussed electron beam, a cylindrical electrode mounted coaxially with said electron gun, a field mesh electrode for supplying the highest electrical potential to said electron beam for making said electron beam parallel to said axis, a collimation lens mounted coaxially with said electrodes and formed by the electrostatic field of said field mesh electrode, and a target mounted in close parallel relationship to said field mesh electrode and scanned at a low speed by said electron beam, an image section including a photoelectron cathode mounted at the other end of said vacuum container and a first magnetic field generator provided outside the container on said image section side for focussing the image electrons from said cathode on said target, which produces a leakage magnetic field on the axis of the container on said target, characterized in that said scanning section further includes a second magnetic field generator to generate a magnetic field which reverses the polarity of the leakage field produced by said first generator near said target.

4. An intensifier vidicon comprising a multi-stage type image section and a vidicon section which are provided in a common evacuated container, said image section including a photoelectric layer mounted on one end of said container, a fluorescent layer provided in said container said photoelectric layer, a plurality of dynodes disposed between said both layers, and a first magnetic field generator for focussing the electron beams from said photoelectric layer, which produce a leakage magnetic field in the vidicon section; and said vidicon section including an image converting means, an electron gun assembly emitting electron beams to scan the fluorescent layer of this section and a second magnetic field generator to focus said electron beam, which generates a magnetic field to reverse the polarity of said leakage field.