US2170251A - Television tube - Google Patents

Description

A. 22, 1939. K. SCHLESINGER TELEVISION TUBE Filed NOV. 2, 1934 1 gr n n a 8 F}; i :l J ilL Ufiueniac:

Patented Aug. 22, 1939 PATENT OFFEQE TELEVISION TUBE Kurt Schlesinger, Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe, Berlin- Steglitz, Germany Application November 2, 1934, Serial No. 751,190 In Germany November 8, 1933 17 Claims.

The subject matter of the invention is a television tube with high vacuum, which may be operated with magnetic deflection, and also with a special electrostatic deflection according to the invention.

The drawing shows a possible form of embodiment of the invention, which is described more particularly in the following. The stated values and dimensions refer only to the form of embodiment of the invention quoted by way of example, and are not to be looked at as a limitation.

A hot cathode consisting of an incandescent head portion l and a sufliciently large spot of oxide 2 of approximately 1 mm. diameter applied to the centre thereof is heated in the manner known per se by means of an internally arranged simple or bifilar filament 3.

An electrode 4 mounted in front of the same and comprising a perforated disc having an aperture amounting for example to approximately 1 -2 mm. acts as control grid, whilst a perforated plate 5 having a fairly large aperture (2 mm.) and raised to a positive potential of approximately 500 volts extracts from the cathode an emission of several milliamperes with grid bias Behind the suctional anode there is situated in the first place a cylinder 6, and behind the latter an additional diaphragm I. If, for example, 1 is raised to the same potential as 5, a part of the rays pass through the aperture of l, which is very small. Other rays, however, are intercepted by the diaphragm l. The aperture of l, the object which is optically reproduced, is furnished with the form of the desired image point, and with the dimensions of the tube quoted afterwards is of the order of 1 mm. By a negative bias applied to the intermediate cylinder 6 it may be accomplished that in the position light the entire emission passes through I unweakened. The geometrical dimensions of 6 may be easily so selected that it is possible to connect 6 with the cathode in direct fashion as shown in the drawing. In other cases a suitable bias source may be provided.

The optical reproduction is performed by generating an electrically refractive plane 8, which in accordance with the invention is obtained by the fact that the bulb is provided at its inside with a metallic coating and that this coating is interrupted at a point 8, and the thus resulting metallic coatings of the neck and the bulb-abutting portion 9 and the body of the bulb H] on the screen side are linked up with difierent potentials. The more the line of intersection 8 is approached towards the screen, the smaller will be the image point on the screen. The potential at 9 amounts to approximately 500 volts assuming the potential of the bulb coating l0 amounts to approximately 2000 volts. The more the line of intersection 8 is approached towards the screen, the greater fi requires to be the difference in potential between 9 and 10, as it is all the greater that the refractive power of this electrostatic lens requires to be.

The applicant has found that it is possible to- 0 perform the deflection of the bundle of cathode rays in the space between the cathode and the electron optical lens, provided that 1. The cross-sectional area marked by the oscillating cone of rays in the plane of the lens 8 is small in comparison to the total cross-section of the lens (in the model made approximately mm. movement of ray within 80 mm. lens diameter);

2. The fields necessary for deflection in no way 0 affect the electrostatic field of the lens. This condition is readily fulfilled if the deflection takes place by magnetic fields, which are superposed to the electric fields in undisturbed fashion in the interior of the bulb. The same is not readily fulfilled if in the case of condenser deflection two unprotected plates II and [2 are employed. According to the invention there is placed about the plate l2 a guard plate l3, which is connected with the coating 9 and also with the plate 1 I I. In the case of counter-cadence operation the plate II should also be surrounded by a corresponding, earthed plate, which screens off the same completely against the outside. A screening of the lateral plate edges may also be performed, but in numerous cases is not necessary. The term counter-cadence-operation means that one deflecting plate is supplied with a deflecting voltage and the other deflecting plate is supplied with a voltage of the same amplitude as said deflecting voltage but reverse phase. Deflecting voltages of this kind may be produced for example with the use of counter-cadence amplifiers arranged in the output circuit of a thyratron valve and the use of such arrangements forms also a part of the present invention.

For the purpose of the second deflection in a direction vertical to the plane of the paper there may be employed a corresponding condenser system, which is screened off in similar fashion. A trapezoidal error does also not occur in the case of these systems even if the systems are fitted in close proximity to each other, assuming that the length of the reversed edges of i3 amounts to approximately 5 mm. and more.

of intersection, i. e. 'two lenses. 'the second line of intersection [.9 in Fig. 1 is pro- The supply of potential to the plates may take place directly through the bulb or by leads con.- ducted in screened insulating tubes I4, preferably in small silvered glass tubes 2|, the metallic coating of which is connected with the neighbouring'wall coatings of the tube, respectively 20.

The tube surrounding the deflecting plates, in the same manner as the dynamically earthed condenser plate, is preferably connected with earth in direct fashion. There are then conveniently employed in place of one mains-connected condenser two such condensers I5- and 16, there being obtained on the one hand a dynamic earthing of the cathode and on'the other hand a dynamic earthing of the high-potential coating [0, and the load on the condensers l5 and I6 is decreased (of the order of .5 mi.) A potential distributor H permits of veryexact adjustment of the maximum sharpness of image.

Since in the method according to the'invention the deflection takes place in a low-potential space the same is comparatively sensitive. In this manner there may be avoided the considerable disadvantage existing in the caseof the known highvacuum tubes consisting in the fact that each known tube possesses an excessive overall length. Namely, it is possible, despite the very small free length of ray in the case of this tube (approximately 200 mm. from the line of intersection 8 up to the'screen) to perform-sensitive deflection with relatively small potentials, there being obtained nevertheless with a length of tube amounting to approximately'BOO mm. a very favourable scale of reproduction as regards the reproduction of the opening of the diaphragm I, viz., 2:3, and accordingly'an image :point of approximately .5 mm. diameter may be produced, which with complete extent of movement amounting to 100 mm. permits of 200 lines. The total length of the tube is then not more than approximately 550 mm. The same advantage as regards the deflection may also be obtained with a tube having two lines If, for example,

vided behind and the line of intersection'B in front of the deflecting system, the middle annular coating 20 formed over the deflecting system may be connected with a lower potential than the front and rear coatings 9' and I0. Two-electrostatic lenses are then connected in'series, and there is then obtained 'a certainly somewhat poorer scale of reproduction, i. e., a somewhat larger image point than in 'the case of the previous tube with one line of intersection. An advantage of this connection, however, consists in the fact that the electrons possess'high-speeds in the relatively long tube between the diaphragm 1 and the line of intersection l9 and, therefore, are not so readily deflected byundesired external fields, and inner charges within'the tube are less easily deflected at any free insulating surfaces. The use of means I3 (eliminating marginal fields is very important also in this arrangement, so that the rear condenser field of H and 12 will not react on the focal distance of the lens 9/19/20.

In the drawing there is shown an external metallic coating l8, which is passed to earth. Thish-as the object of avoiding electrophorus effects when placing the hand on the body of the tube.

' Separate means may be provided (for example potentiometers) for being able to adjust the potential of each'o'fthe electrode coatings independently of one another.

I claim:

1. A cathode ray tube comprising an evacuated envelope enclosing a cathode and an anode mounted in operative relationship thereto for producing a. cathode ray, a control electrode mounted in the vicinity of said cathode for controlling the intensity of said cathode ray, a picture receiving screen, an electrostatical electron-optical system for focussing the cathode ray onto said screen, two deflecting systems mounted between said anode and said screen for deflecting the cathode ray in two directions perpendicular to one another for the purpose of scanning said e'creen, 'each of said deflecting systems comprising two deflecting, plates, and connecting leads for said deflecting plates, said leads extending in the direction of the tube axis and being provided with a cover-of insulating material,

2. A cathode ray tube comprising an evacuated envelope enclosing a cathode for producing a cathode ray, an anode mounted in operative relationship to said cathode, a picture receiving screen, an electron-optical system mounted between said anode and said screen for focussing the cathode ray onto said screen, said electronoptical system comprising a plurality of metallic Wall coatings mounted along the axis of said envelope on. the wall of said envelope and being insulated from one another by the wall of said envelope and by the vacuum, each of said metallic wall coatings having a circular crosssection, said wall coatings being adapted to have 'diiferent voltages impressed thereon, two pairs of deflecting plates mounted between said anode and said screen for deflecting the cathode ray in two directions perpendicular to one another for the purpose of scanning said screen, connecting leads for said deflecting plates, said connecting leads extending in the direction of the axis of said envelope, tubes of insulating material surrounding said connecting leads, a plurality of metallic coatings surrounding each of said tubes, the number and length of said coatings corresponding to the number and length 'of-said wall coatings forming said electron-optical system, and means forconnecting each of said coating with the corresponding wall coating of the electron-optical system.

3. In and for a cathode ray tube a deflecting condenser for deflecting the cathode ray comto those edges of the adjacent condenser plate which are to be dispensed transversely to the cathode 'ray direction turned over edges which embrace the adjacentcondenser plate edges.

5. For a cathode ray tube comprising means. to produce a cathode ray the combination comprising at least one deflecting condenser mounted in said tube and comprising two deflecting plates, means/to supply at least one of said deflecting plates with alternating deflecting potentials, at least one'auxiliary plate mounted adjacent and substantially parallel to any such of said deflecting plates as has alternating deflectingpotentials applied thereto, said auxiliary plate having, at its side situated adjacent to those edges of the adjacent condenser plate which are disposed transversely to the cathode ray direction turned over edges which embrace the adjacent condenser plate edges, and means for earthing said auxiliary plate dynamically.

6. For a cathode ray tube comprising means to produce a cathode ray the combination comprising at least one deflecting condenser comprising two deflecting plates, means for supplying one of said deflecting plates with alternating deflecting potentials, means for earthing the other one of said deflecting plates dynamically, an auxiliary plate mounted adjacent and substantially parallel to the first said deflecting plate, said auxiliary plate having at its sides situated adjacent to those edges of the adjacent condenser plate which are disposed transversely to the cathode ray direction, turned over edges which embrace the adjacent condenser plate edges, and means for earthing said auxiliary plate dynamically.

7. For a cathode ray tube comprising means to produce a cathode ray, the combination comprising at least one deflecting condenser comprising two deflecting plates, means for supplying one of said deflecting plates with alternating deflecting potentials, means for supplying the other one of said deflecting plates with alternating deflecting potentials having at each moment the same amplitude as the first mentioned deflecting potentials but opposite sign, and two auxiliary electrodes each mounted adjacent and substantially parallel to one of said deflecting plates, said auxiliary electrodes having, at their sides situated adjacent to those edges of the adjacent condenser plates which are disposed transversely to the cathode ray direction, turned over edges which embrace the adjacent condenser plates edges, and means for earthing said auxiliary electrodes dynamically.

8. In a cathode ray tube comprising means including a cathode for producing a cathode ray, a picture receiving screen and an electron-optical lens system for focussing said cathode beam onto said picture receiving screen: an electronoptical pre-concentrator mounted between said cathode and said lens system and comprising two apertured plate electrodes mounted transverse to the axis of the cathode ray tube and having their apertures axially aligned with said cathode, and a cylindrical electrode mounted between said two plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being adapted to be maintained negative relatively to said plate electrodes.

9. In a cathode ray tube comprising means including a cathode for producing a cathode beam, a picture receiving screen and an electron-optical lens system for focussing said cathode beam onto said picture receiving screen: an electronoptical pre-concentrator mounted between said cathode and said lens system and comprising two apertured plate electrodes mounted transverse to the axis of the cathode ray tube and having their apertures axially aligned with said cathode, and a cylindrical electrode mounted between said two plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being directly connected with said cathode.

10. In a cathode ray tube comprising means including a cathode for producing a cathode beam, a picture receiving screen, a main anode for accelerating said cathode beam onto said picture receiving screen, and an electron-optical lens system for focussing said cathode beam onto said picture receiving screen: an electron-optical pre-concentrator mounted between said cathode and said lens system and comprising two apertured plate electrodes mounted transverse to the axis of the cathode ray tube and having their apertures axially aligned with said cathode, at least one of said plate electrodes being directly connected with said main anode, and a cylindrical electrode mounted between said two plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being adapted to be maintained negative relatively to said plate electrodes.

11. In a cathode ray tube comprising means including a cathode for producing a cathode beam, a picture receiving screen and an electronoptical lens system for focussing said cathode beam onto said picture receiving screen: an electron-optical ore-concentrator mounted between said cathode and said lens system and comprising three apertured plate electrodes mounted transverse to the axis of the cathode ray tube and having their apertures axially aligned with said cathode, that one of said plate electrodes disposed nearest said cathode having a short cylindrical abutment projecting in the direction away from said cathode, and a cylindrical electrode mounted between the two ones more remote from said cathode of said plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being adapted to be maintained negative relatively to those two of said plate electrodes between which it is mounted.

12. For a cathode ray tube having 'a wall of insulating material and comprising means for producing a cathode beam and a picture receiving screen, the combination comprising an electron lens system comprising two metal coatings on the inside of the wall of said tube, said twowall coatings being separated by a ring-shaped non-conductive zone of the wall of the tube the axis of which ring-shaped zone coincides with the axis of said tube, and means for applying to said two coatings a potential difference of at least several hundreds of volts so that an image producing lens field is formed between said two coatings.

13. For a cathode ray tube having a wall of insulating material and comprising means for producing a cathode beam and a picture receiving screen, the combination comprising an electron lens system comprising three metal coatings on the inside of the wall of said tube, every two adjacent ones of said wall coatings being separated by a ring-shaped non-conductive zone of the wall of the tube the axis of which ringshaped zone coincides with the axis of said tube, and means for applying to every two adjacent ones of said coatings a potential difference of at least several hundreds of volts so that an image producing lens field is formed between every two adjacent ones of said coatings.

14. The combination defined in claim 12 plus cathode ray deflecting means disposed in the area of the lower-potentialled one of said Wall coatings.

15. The combination defined in claim 13 plus cathode ray deflecting means disposed in the area of the lowest-potentialled one of said wall coatings.

16. A cathode ray tube comprising an evacuated envelope of insulating material enclosing a cathode and an anode mounted in operative relationship thereto for producing a cathode beam, a picture receiving screen, an electron lens system for focussing said cathode beam onto said picture receiving screen, said lens system comprising metal coatings on the inside of the wall of said tube, every two adjacent ones of said metal coatings being separated by a ring-shaped zone of the wall of the tube the axis of which ring-shaped zone coincides with the axis of said tube, every two adjacent ones of said coatings being adapted to have different potentials im pressed thereon, an electron-optical preconcentrator mounted between said cathode and said lens system and comprising three apertured plate electrodes mounted transverse to the axis of said cathode ray tube and having their apertures axially aligned with said cathode, that one of said plate electrodes disposed nearest said cathode having a short cylindrical abutment projecting in the direction away from said cathode, and a cylindrical electrode mounted between the two ones more remote from said cathode of said plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being adapted to be maintained negative relatively to those two of said plate electrodes between which it is mounted, at least one deflecting condenser mounted between said anode and said screen for applying scanning deflections to the cathode beam and comprising two deflecting plates and at least one auxiliary plate mounted adjacent and substantially parallel to one of said deflecting plates, said auxiliary plate having turned-over edges which embrace the adjacent condenser plate edges, connecting leads for said deflecting plates, said connecting leads extending in the direction of the axis of said envelope, tubes of insulating material surrounding said connecting leads, said insulating tubes being provided with metallic coatings equal in extension with and connected to the above said inside metal coatings of the wall of said tube, and a ferro-magnetic, non-magnetized, coherent metal coating adapted to be earthed, on the outside of the wall of said tube.

17. A cathode ray tube comprising an evacuated envelope of insulating material enclosing a cathode and an anode mounted in operative relationship thereto for producing a cathode beam, a picture receiving screen, an electron lens system for focussing said cathode beam onto said picture receiving screen, said lens system comprising metal coating on the inside of the wall of said tube, every two adjacent ones of said metal coatings being separated by a ringshaped zone of the wall of the tube the axis of which ring-shaped zone coincides with the axis of said tube, every two adjacent ones of said coatings being adapted to have different potentials impressed thereon, an electron-optical preconcentrator mounted between said cathode and said lens system and comprising three apertured plate electrodes mounted transverse to the axis of said cathode ray tube and having their apertures axially aligned with said cathode, that one of said plate electrodes disposed nearest said cathode having a short cylindrical abutment projecting in the direction away from said cathode, and a cylindrical electrode mounted between the two ones more remote from said cathode of said plate electrodes and having its axis aligned with the apertures in said plate electrodes, said cylindrical electrode being adapted to be maintained negative relatively to those two of said plate electrodes between which it is mounted, at least one deflecting condenser mounted between said anode and said screen for applying scanning deflections to the cathode beam'and comprising two deflecting plates and at least one auxiliary plate mounted adjacent and substantially parallel to one of said deflecting plates, said auxiliary plate having turned-over edges which embrace the adjacent condenser plate edges.

KUR-T SCI-ILESINGER.

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