US2152487A - Cathode ray oscillograph - Google Patents

Description

March 28 1939. M. KNOLL 2,152,487

CATHODE RAY OSCILLOGRAPH Original Filed Nov. 18, 1929 3 Sheets-Sheet 1 Fig.1 1 Fi .3

lnvento h' flax Knoll March 28, 1939. M.KNOLL CATHODE RAY OSCILLOGRAPH Original Filed Nov. 18, 1929 3 Sheets-Sheet 2 u o o o no a o o o o 0 on unnonouun /nvenz"on: flax Knoll d1 28,1939- M. KNOLL 2,152 487 CATHODE RAY OSC ILLOGRAPH Original Filed Nov. 18, 1929 5 Sheets-Sheet 3 /n ven tor: flax 770i? Patented Mar. 28, 1939 CATHODE RAY OSCILLOGRAPH Max Knoll, Berlin-Charlottenburg, Germany Original application November 18, 1929, Serial No. 408,006. Divided and this application February 5, 1935, Serial No. 5,136. In Germany December 12, 1928 6 Claims.

This invention has for its object improvements in cathode-ray cscillographs, and is a division of patent application, Serial No. 408,006, filed November 18, 1929, Paint No. 2,036,532, dated April 7, 1936 to Knoll et al.

According to the invention special means are provided in order to keep the focusso long as it is not moving at its great recording or scanning speeddiverted from the window or other electron beam receiving member. This may be efiected in a manner known per se, by diverting the electronic rays sideways by means of a constant magnetic or purely electrical field or a combination of both. Preferably a plate of beryllium or other substance of low atomic weight may be arranged, against which the raysstrike during their diversion, in order to prevent as much as possible the generation of X-rays. For the further protection of the observer and of the photographic layer against X-rays this plate is in turn covered with an envelope of material of high atomic weight, e. g. lead.

According to the invention the protection of the window may be efiected by intercepting the electron rays instead of diverting them, i. e. by arranging in the path of the electronic rays a beam intercepting means in the form of a boredthrough negatively charged stopping-electrode, the negative charge of which is led off at the beginning of the recording operation. As the cathode-ray oscillograph which isthe subject of the invention is intended to be used for rendering visible or recording extraordinarily rapidly occuring phenomena, or for television purposes, the switching on or off of the diverting or stopping device has to be eflected in an extraordinarily short space of time, e. g. in 10- sec. This problem may be solved by a purely electrical switching device with two stable positions of equilibrium, e. g. by the employment of electron tubes, glow-lamps or spark gaps. purpose a specially simple and rapidly reacting electron-tube device, which is actuated simultaneously with the start of the voltage to be recorded by the oscillograph. In this way the voltage of the grid-potential of another valve (the so-called deflector tube) can at the same time be maintained at the same value, and its saturation current made to iiow through a condenser connected in parallel with the controls, the voltage of which is thus varied proportionally withthe time.

With apparatus for picture-te'legraphy or television in which the whole area of the picture both in transmitter and receiver is scanned by the The invention provides for this focal spot in a zig-zag path consisting of upward and downward straight-line branches, one set of branches, say the upward, can be described at a constant relatively slow velocity, and theother set, the downward, at a constant relatively high velocity by suitably varying the control voltage, as by charging or discharging inserted condensers by means of a constant current, e. g. the saturation current of electron tubes. This must be effected by employing two difierent constant intensities of current. Thus only the one set of parallel branches is valid for the chemical and physical effects, in contrast to the hithertoused sinusoidal records, in which, on each of both branches, the recording velocity and the distance from the neighboring branch are continually changing.

The cathode-ray oscillograph forming the subject of this invention can be used in picture-telegraphy and television also in the transmitting station for scanning the picture to be transmitted, and further for frequency-multiplication for secret telegraphy and the like by scanning separated electrodes arranged chess-boardvwise behind the window and easily exchangeable.

Since neither for transmission nor reception need any mechanical parts he moved, the new cathode-ray oscillograph, especially for picturetelegraphy and television offers a number of such important advantages as to enable both these operations to be carried out with hitherto unattainable perfection.

The synchronization which must be maintained between transmitting and receiving apparatus,

is obtained with the utmost ease and with absolute exactitude by simultaneously affecting the corresponding controls of the transmitter and the receiver by the voltage either directly by wire, or indirectly by wireless waves.

The recording velocity obtainable is so great that e. g. a picture of 6 x 6 cm. may easily be scanned in 5 sec., or even in w sec., and reproduced with suificient intensity.

If a picture-frequency of not more than 16 pictures per second (which is adequate for the human eye) is required, pictures of such intensity may be obtained, that they may be projected on, a much enlarged scale on to a screen and made visible to a large company of spectators.

Picture-telegraphy can be extraordinarily cheapened and its field of application extended beyond all anticipation.

For instance, the transmitting of a picture, which hitherto required about ten minutes, can

be reduced to ,3 of a second. An entire newssheet, for instance, can be swiftly transmitted by picture-telegraphy, provided only the sheets to be transmitted and the receiving film are moved with sufiicient velocity.

cinematographic films can be copied by wireless transmission at any distance.

The speed with which the pictures can be scanned in the transmitter and receiver makes it possible to scan, transmit, and reproduce in one continuous line pairs of stereoscopic pictures, so that either static or in process of production plastic picture-telegraphy and plastic television are made possible in the simplest manner by one and the same apparatus.

The extraordinary speed with which a picture can be scanned at the transmitting station and recorded at the reception station, and the possibility of extremely rapid withdrawal of the focus after the picture has been completely scanned, enable also the transmitting and reception devices to be used for super-speed recording of slow motion pictures, in which case a much greater number of pictures per second can easily be recorded, than has been possible with "slow motion" apparatus hitherto used.

If a very high number of pictures per second is to be obtained, it is, for instance, only necessary, firstly, in the receiving apparatus, to double the, length of the picture, that is to say the sum of the intervals between all the branches of the zig-zag path, so that with a stationary photographic plate one would obtain a distorted picture double the width; and secondly, to run the receiving film constantly at half speed. This gives the slow motion" pictures, the optical compensation otherwise required being here replaced by the swift withdrawal of the focus.

The invention is exemplified in the drawings.

Fig. 1 shows schematically a cathode-ray oscillograph, such as can be employed for the various above mentioned purposes.

Fig. 2 shows on a larger scale-schematically drawn-an example of the window of a cathoderay oscillograph used for the transmission of pictures or for television.

Fig. 3 shows a window of the same sort in the receiving apparatus, for the photographic record of the wir'elessly transmitted picture.

Fig. l shows schematically, how the cathoderay tube of the transmitter and the cathode-ray tube of the receiver work together in picture telegraphy or television.

Fig. 5 shows on a larger scale a vacuum-proof pliable device for shifting movable parts, such as, e. g., a deflector plate.

Fig. 6 is the schematic representation of a tube for auto-electronic discharge with a cold cathode and supplied with electrostatic concentrating device.

Fig. 7 represents a thermionic cathode-ray tube with an intercepting electrode, the latter actuated by a tip-action electron-tube device.

Fig. 8 shows, a connection-scheme for the production of oscillations with linear variations of voltage, as used especially for televisional or picture telegraphic apparatus.

Fig. 9 shows the wave-shape of the linear oscillations produced by means of such a connection.

In thecathode-ray oscillograph represented in Fig. 1 the cathode-raybeam is produced in the metallic discharge-tube I, which serves at the same time as an anode, and into which the cathode 2 is introduced by means of the bushing 3. 'Thecathode 21s connected with the feedchamber 1 and difierent parts of the picture.

voltage by means of the rod 3 lodged in the bushing 3. The coil 4 serves to concentrate the ray beambefore it passes through the narrow aperture of the diaphragm 5 into the actual diversiononto the electro-permeab window 6.

8, 8' are the deflector plates, which can be adjusted under a high vacuum with the help of elastic bodies 9 or membranes ill by means of screws II, which are lodged in supporting tubes I2. 15 is a spy-hole, through which the oscillogram to be recorded can be observed also while the photographic record is being taken, provided that the inner side of the electron-permeable layer 6 or parts of the grid IQ-are overlaid with a phosphorescent substance. The photographic layer (plate or mm H) is situated during the taking of the record in the shutter i3.

Fig. 2 shows on an enlarged scale in section an example of a photoelectric-cell arrangement for taking pictures. Close behind the electron-permeable window 6, which is also held by the grid 19, is situated the photoelectric mosaic plate 8| of a type generally understood in the art and similar to that shown in the patent'to Zworykin No. 1,691,324 granted November 13, 1928. This is subdivided by means of insulation-layers indicated in Fig. 2 by the short vertical lines, into as many small fields or photoelectric cathodes as picture stippiing points are desired. These small photo-electric cathodes forming the plate iii are then supplied successively with negative voltage by the electronic beam passing rapidly across amplifier I06 (Fig. 4) to provide an amplified modulating current, modulated according to the resistance effective at any given moment dependent on the exposure of the cell in question.

Instead of a photo-electric cell an exchangeable electrode arrangement of any desired formation can also be fixed on the recording apparatus behind the electron-permeable window, enabling a definite succession of current impulses to be sent out for which the receiving apparatus must be arranged accordingly.

A simple method of transmitting pictures also consists in first copying the picture according to a certain process onto a metal plate in such a manner that definite conductivity-values at dlfierent points of the surface of the metal plate correspond to the varying intensities of light on For example, the picture on the metal plate may be a photographic reproduction in carbon or other resistance substance, or a print made with resistance substance. Some forms of printing ink may have suficient electrical resistance for the purpose. The electronic beam passing through the electron-permeable window and the resistance image to the plate can excite directly fluctuations of current in the amplifier Hi6 (Fig. 4) which will serve to vary the intensity of the cathode-ray in the receiver.

A further possible method of application of the invention to picture-telegraphy consits e. g. in utilizing the travelling point of light produced outside the transmitter-tube on the fluorescent screen over a system of lenses for scanning the,

example of the construction of an electron-permeable layer 6 for cathode-ray oscillographs with a supporting grid I9 of metal strips placed edgewise. The electronic beam when not in use falls behind one of the aluminium blades 99; the

x-rays then generated are .screened oil? by a lead 8 mantle 99. The oscillogram or picture appears on a fluorescent layer fixed onto the exterior side of the electron-permeable foil 9. If photographic records have to be made, the light sensitive film or plate It is pressed closely onto the electronpermeable window 9 by means of the light-proof shutter I3.

Fig. 4 shows an example of an arrangement for a cathode-ray osclllograph in accordance with the invention, applicable for picture telegraphy and television, a denoting the receiver arrangement, b the transmitter arrangement; both are, wireless transmission being pre-supposed, connected with each other by way of antennae 9| and 9|. For sending and receiving there serve respectively the cathode-ray oscillographs 92' and 92 with hotcathode discharge devices 99 and 93 respectively, pairs of deflector plates 99', 95' and 99, 95 for producing a scanning movement of the cathoderay beamsoi' the respective osclllographs and 25 electron- permeable windows 9 and 9. The pairs of deflector plates 99, 95, and 99, 95 respectively shown in the diagram for the sake of clearness as parallel lie in the actual apparatus in each tube in planes at right angles to each other. The feed voltage for the discharge tubes lies at points 91, 99', and 91, 99 respectively.

By means of intercepting-electrodes 99' and 99 respectively, arranged between the hot-cathodes in the tubes 99' and 99 respectively, and the corresponding anode 91 and 91, the generation of electronic-rays during the pauses in the scanning movement as controlled by plates 99', and thereby the fusing of the window, is prevented in a manner to be hereinafter described. The electrons passing through the electron permeable layer 6' of the transmitter tube 92' fall upon a photoelectric mosaic of known construction I99, the photo-electrically active layer SI of which is divided in a manner known per se (for example, as disclosed in Patent No. 1,691,329 to Zworykin dated November 13, 1928, and Patent No. 1,780,- 364 to Reynolds dated November 4, 1939), into a large number of small separate areas shown enlarged in Fig. 2. n the photo-electric layer there is formed by means of lenses I9I according to the known laws of optics, a picture of the object I92 to be reproduced, so that there falls upon each of the areas a definite, in general varying intensity of light. The illumination of each area 55 takes place through the wide-meshed grid 92,

which serves as common anode for all the small photo-electric cells. The actual transmission is eflected by means of the high-frequency transmitter I93, of any known or suitable form for 30 multiple signal transmission, as for example that described in the Zworykin patent above referred to, and provided with a common transmitting antenna 9| and modulated in known manner by the oscillators I96 and I95 as well as by the g fluctuations of the photo-electric cells 9| conducted by way of amplifier I96. Both oscillators I99 and I95 produce, by means of a device known per se, and represented diagrammatically in Fig. 8, oscillations with a time-proportional 7o voltage-variation of the wave-shape sketched in Fig. 9. In this manner there is insured, in contrast to what happens in the case of the sinusoidal oscillations frequently used for such purposes, a precisely time-proportional scanning of 75 the picture to be transmitted.

The transmission of a picture from the transmitter to the receiver takes place in the followingmanner:

The deflecting or sweep circuit oscillator I99 produces continuously oscillations of a definite frequency, about 10 per sec., which aflect the pair of deflector plates 95 of the transmitter tube 92', and are transmitted by way of the highfrequency transmitter I99, the transmitting antenna 9 I the receiving antenna 9i, and the selective amplifier I99 operating in known manner as for example the selective amplifier 91-" of the Zworykin patent above referred to, to the pair of plates 99 of the receiver tube 92. when oscillator I99 is alone working, the scanning sweep or oscillations of the electronic beam describe a stationary line equal to the height of the picture to be transmitted, both in the transmitter tube and receiver tube.

If now the deflecting or sweep circuit oscillator I94 is also switched on (frequency about 10 per sec.), which afiects the second pair of deflector plates 94 standing at right angles to 99 of the transmitter tube, these oscillations are transmitted by way of the same path as those from oscillator I95, through a selective amplifier I99, tothe pair of deflector plates 94 ot the receiver tube 92 and the original line is once again transformed into a progressive zig-zag record. If the frequency of the oscillator I99 is properly adjusted, the record produced has the width of the picture transmitted. If in addition the width of the oscillator I99 is not greater than about the width of the line described by the focus spot, each point of the picture being transmitted, both in the transmitter tube and in the receiver tube, is scanned simultaneously and for an equal period by the cathode-ray beam.

The interception of the electronic beam when not being used is here eifected by means of the intercepting electrodes 99 and 99' respectively by way of a-not here shown--tip-action electrontube device similar to that represented in Fig. 7, which is controlled by means of the oscillator I94 and the amplifier I99 which latter two elements produce the scanning movement of the beams. As the cathode-ray beam on its way through the transmitter tube 92' meets'with varying degrees of resistance according to the conductivity of the photo-electric cell with which it happens to be in contact, fluctuations of current take place -corresponding to the occuring differences of intensity. 'These fluctuations are transmitted by way of the amplifier I99, the high frequency transmitter I93, the transmitting antenna 9|, the receiving antenna 9|, and a selecting amplifier I99, onto the control grid ll of the receiver tube 92, there giving rise to corresponding fluctuations of the beam-intensity, which in turn cause the requisite fluctuations in intensity of the picture reproduced on the fluorescent screen 9.

The arrangement schematically represented in Fig. 4both the transmitting and the reception apparatusallows also in the simplest manner possible of transmitting stereoscopic pictures to any distance and likewise of stereoscopic television. A stereoscopic picture, as is well known, consists of a pair of pictures side by side, representing respectively the right and left eye views of a scene or object. Ii the window 6' and Ii are made so long in one direction, e. g., in a direction perpendicular to the plane of the drawings, that apair of stereoscopic pictures can be scanned adiacently and adjacently reproduced in the receiver, then both pictures may be scanned by the focal spot in one continuous line in each of both apparatus. The stereoscopic transmission of pictures and stereoscopic television may be thus realised by simply transmitting as a single picture, a pair of stereoscopic pictures side by side. The pair of stereoscopic pictures thus received side by side at the receiving station may be synthesized in known manner.

In Fig. 5 is exemplified on a larger scale the pliable device shown in Fig. 1 employed for shifting movable parts under a high vacuum. The device here serves for the adjustment of the electrostatic deflector-plate 8, by means of the pliable metal body 9 actuated by nut I01, pressing upon the carrier-bush 24. This is Joined by means of three screws 25, sliding in slots of the jacket 28, with the guide-ring 21, into which, by means of an insulating washer 29, e. g. of Bakelite, is fixed the supporting rod 28 of the deflector plate 8. The pliable body 9 is Joined in a vacuum-tight manner at both ends with its guide-rings, and likewise the insulating washer 29 with guide-ring 21; furthermore the supporting rod 28 is guided by another perforated insulating washer 30. The ring 3| carrying washer 30 is fixed directly into the jacket 1 of the cathode-ray tube.

The tube 32 for auto-electronic discharge shown in Fig. 6 contains an anode 33 and an intercepting electrode (auxiliary anode) 34 which during the release of the beam functions as an anode. The release is effected by two spark gaps or glow- lamps 35 and 38 connected by way of windings 31, 38 with the perforated intercepting electrode 34 and by way of a high resistance element 89 with the cold cathode 4B. The hightension continuous current required for feeding the tube is generated in the known manner by means of transformer 4i, valve 42, and condenser 43, the valve 42 acting in known manner as a rectifier permitting current to pass only down wardly therethrough, thus maintaining the condenser 43 charged with the lower plate positive and the upper plate negative. If the gaps 35 and 36 are properly adjusted, any sudden surge of voltage arising from the transmission line or antenna 44 and inducted from the winding 45 according to the polarity of the surge, either onto the winding 31 or 38, causes a sparking o! the gap 35 or 36, the duration of which depends upon the value of the capacity 46 and the resistance t7. By this the electrode 34, which has hitherto intercepted the beam, becomes an anode, and the extremely sharp point of the cathode 4t elects an electronic beam through the perforations in the electrodes 3% and t3, the intensity of the beam can further be varied by means of the controlling electrode 33 by varying the angle of the coneshaped electronic beam.

In the lower part of Fig. 6 is-shown schematb cally an electrostatic device for concentrating the electronic beam. It consists of cylindrical metal tubes as, sustained by supports '39 in such a posi tion as to allow of the electronic beam passing freely through it, and of the metal ring washers be between the tubes 68. If the washers 6d are charged negatively to the tubes 48, divergent electric fields are formed, which exercise a force concentrating radially the beam. Thus an exceptionally minute focal spot is obtained. Adjustment of the voltage applied to the tube and washer elements at the polarity indicated in the diagram, and according to the spacing of the electron-permeable window will bring the rays to a focus at the window, as will be understood by those skilled in the art.

The thermionic cathode-ray tube ll shown in Fig. 7, is provided with the hot cathode I2, anode I3, and control-grid l4 controlling the intensity of the electrons in the beam while the latter is working. In order to prevent the fusing of the window during periods when the focal spot is at rest, an intercepting electrode is provided, actuated by a tip-action electron-tube device. This device consists of the electron- tubes 56, 51, and It, the anodes of which are connected on theone hand by way of resistances I9 and ill with the positive pole of a storage battery, and on the other hand crosswise by way of condensers SI, 62 with the grids of the tubes 56 and I1. Thus far the circuit arrangement is quite similar to the well known multivibrator circuit. However, in the present system the circuit is intended to function not as a multivibrator, but as a trigger or tipacting device for releasing the blocking charge on the intercepting electrode 55. This change in the function is accomplished by substituting for the usual grid leak between grid and cathode, a battery 63 to the potential of the battery 63 and which by way of the high resistances 64, 65 keeps the condenser 6i charged, the grid potential of the tube 56 at a lower level than the anode potential of tube 51, the amount of the diminution being about the same as the anode potential itself so as to bring the said grid potential to zero or negative. The potential between the grid and filament of tube 58 will be the algebraic sum of the potential of the anode of tube 51 and the battery 63. If the grid of the tube 51, which tube is fully emitting during the interception of the cathode-ray beam, is afl'ected by a surge of negative voltage issuing from the antenna or transmission line 66 by way of the resistances 61 or 68, and by way of the condenser 69, the arrangement tips over into its other position of stable equilibrium. In that case tube 51 is blocked. The grid potential of tube 56 and therewith that of the intercepting electrode, hitherto negative, now receive the same potential as hot cathode 52, or a potential positive to it due to the rise in potential across the terminals of tube 51, and the cathode-ray beam is released. If the surges issuing from the antenna or line 86 are positive, the tube it acts in the same manner. By means of resistance ID, the time of the tipping-over of the device back into the position of equilibrium corresponding to the period of interception of the cathode ray beam may be adjusted at will, thus enabling the release to be maintained for any length of time desired. I

Fig. 8 refers to a device suitable for the production of oscillations with linear variation of voltage, such as is provided for the oscillators tilt and m5 in Fig. 4. In Fig. 8, ii and H are triode-valves, fed by the batteries 12 and 72'. By the saturation-current of these valves, the condenser 13 is alternately charged and discharged by way of the resistances l4 and 14. The charging and discharging is automatically controlled by the grids I6 or it, the potential of which is maintained at a suitable level by means of batteries 15 and i5. By varying the capacity of the condenser 13. the required frequency may easily and swiftly be obtained when working.

If the saturation-currents of the valves ii and H are selected at various values, or the resistances M and I4 are given different resistlvities, the upward branches '51 of the oscillations taking place proportionally with the time (see Fig. 9) become less steep than the downward branches I8.

whereby both in the transmitter and in the receiver the effect of the downward branches is diminished in comparison with that of the upward branches.

If the batteries 15 and I shown in the connection-scheme Fig. 8 and their connections are omitted, the grid I6 joined with the hot cathode of its tube, and the grid I6 affected by the voltage of a control of the cathode-ray oscillograph,-

predetermined continuous-wave electrical variations for energizing the same, another deflecting means to deflect the said beam transversely to the said direction with a source of predetermined continuous-wave electrical variations for energizing the same, a receiving member lying in the path of the beam, and means to automatically prevent the rays from striking the said receiving member while one of said beam deflecting means is ineffective to maintain motion of the beam over the receiving member, the automatic means comprising a charged intercepting electrode arranged to be discharged by an electron tip-acting device controlled by the continuous-wave electrical variations of said one deflecting means to repeatedly release and intercept the beam.

2. A cathode-ray oscillograph comprising means for generating a beam of electrons, a receiving member in the path of said beam, a scanning control oscillator for producing predetermined timed electrical variations, deflecting means for moving said beam over said receiving member uninterruptedly from side to side with substantially constant amplitude in response to said electrical variations, means for normally preventing the generation of said beam, and means controlled by said scanning control oscillator for rendering said last named means ineffective.

3. In a cathode-ray oscillograph, means for producing a beam of electron-rays, a device for intercepting the rays, a scanning control device for the beam, means for applying electrical en ergy to said scanning device, a device tip -acting between two positions of stable equilibrium controlling said intercepting device, said tip-acting device being connected for control by the electrical energy supply means for the scanning device whereby the tipping over from'one position of equilibrium to the other position is effected by the start of the electrical energy applied to the scanning device, and means for returning the tip-acting device to the previous position of equilibrium after a predetermined interval of time adjustable at will.

4. A cathode-ray oscillograph comprising means for generating a beam of electrons, a receiving member in the path of said beam, means for intercepting the beam, beam deflecting means, a signal circuit, a deflecting control circuit separate from said signal circuit, said intercepting means being operatively connected with said deflecting control circuit for control thereby independently of said signal-circuit.

5. A cathode-ray oscillograph comprising means for generating, a beam of electrons, a receiving member in the path of said beam, means for intercepting the beam, beam deflecting means, a signal circuit, a deflecting control circuit separate from said signal circuit and including means for producing electrical variations for efiecting a predetermined time-proportional scanning movement of the beam independently of the electrical condition of the signal circuit, said intercepting means being operatively connected with said deflecting control circuit for control thereby independently of said signal circuit.

6. A cathode-ray oscillograph comprising means for generating a beam of electrons, a receiving member in the path of said beam, means for intercepting the beam, beam deflecting means, a signal circuit, a deflecting control circuit operatively separate from said signal circuit, and common control means for controlling said intercepting means and said beam deflecting means.

MAX KNOLL. 5o

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