US2289500A - Electron image dissecting arrangement - Google Patents

Description

Patented July 14, 1942 ELECTRON WAGE DISSECTING ARRANGEMENT Ivanhoe John Penfound James, London, England,

assignor to Electric & Musical Industries Limited, Hayes, Middlesex, England, a company of Great Britain Application November 22, 1940, Serial No. 366,639 In Great Britain November 13,1939

14 Claims.

The present invention relates to improvements in television or like signal transmitters in which signals are derived by scanning an electron or electric charge image. The invention is applicable to electron image dissecting tubes and to the use of such tubes for the purpose of television transmission.

It has been proposed to use in a television system an image dissecting tube in which an image of the object to be transmitted is projected on a photo-electric surface which serves to produce an electron image of the object. The electron image is scanned by suitable magnetic or electrostatic fields over a small aperture behind which is a collecting electrode which produces electric signals corresponding to the elemental areas of the scanned object as defined by said aperture.

The number of electrons collected by the electrode from each elemental area is extremely small and thus the signals derived from such a tube have a very poor signal-to-noise ratio.

The object of the present invention is to provide methods and arrangements for transmitting television or like signals which will enable an improved signal to noise ratio to be obtained.

According to the present invention, a method of deriving from an image of an object a train of electric signals corresponding to elemental areas of said image is provided, said method comprising producing an electron or charge image corresponding to said image, scanning said electron or charge image to derive simultaneously but in difierent phase a plurality of discrete signal trains of the desired form, and adding said signal trains delayed individually in such manner as to produce an augmented signal train of the same form.

In the application of the invention in connection with electron image dissecting tubes three separate methods may be adopted.

Thus in one aspect, the invention provides a method of deriving from an image of an object a train of electrical signals corresponding to elemental areas of said image, said method comprising projecting said image on an electron emitting surface to provide a composite beam of electrons in which the electron distribution is determined by said image, focusing said composite beam to form an electron image, receiving said electron image on a plurality of collecting electrodes arranged within said tube in a predetermined order and each receiving an elemental area of said electron image at any instant of time and each being connected in a separate signal circuit, scanning said composite beam across said collecting electrodes in such manner that each elemental area of said electron image focusing said composite beam to form an elec-.

tron image, receiving said electron image on a plurality of collecting electrodes arranged within said tube in staggered relation and each receiving an elemental area of said electron image and being connected in a common signal circuit, and scanning said composite beam across said collecting electrodes in such manner that each elemental area of said electron image is scanned across said collecting electrode in turn and the desired train of signals is produced in said common signal circuit.

In accordance with still another aspect, the invention provides a method of deriving from an image of an object a train of electrical signals corresponding to elemental areas of said image, said method comprising projecting an image of the object on an electron emitting surface to provide a composite beam of electrons in which the electron distribution is determined by said image, focusing said composite beam to form an electron image, receiving said electron image on an apertured electrode or screen having apertures therein arranged in predetermined order, each aperture being adapted to pass a fasciculated beam of electrons corresponding to an elemental area of electron image, and applying said fasciculated beams through a. selectively operating delay means to an output electrode connected in a signal circuit wherein the desired train of signals is produced.

In accordance with the first-mentioned aspect of the invention, an embodiment is provided in the form of an electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam in which the electron distribution is determined by an optical image which it is desired to transmit, means for focusing said electron beam to form an electron image, a pluvrality of collecting electrodesarranged in predetermined order and each arranged to receive an elemental area of said electron image, means for scanning said electron image across said collecting electrodes in such manner that each elemental area of said electron image falls on each of said collecting electrodes in turn, signal circuits connected one to each of said collecting electrodes, delay means associated with said signal circuits, and an output combining circuit connected with said delay means, the arrangement being such that in operation similar signal currents of differing phase are produced in said signal circuits and are eflectively delayed individually by the operation of said delay means and combined in said output combining circuit to produce a further augmented signal current similar in form to the currents in said signal circuits. In this case, each of said circuits preferably comprises an electron discharge valve of which the control grid is connected to the appropriate collecting electrode, said valve being arranged to operate as a cathode follower valve and being so arranged that its cathode impedance provides a matching termination for effectively connecting said collecting electrode to said delay means.

In accordance with the second-mentioned aspact of the invention an embodiment is provided in the form of an electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam of electrons in which the electron distribution is determined by an image which it is desired to transmit, means for focusing said electron beam to form an electron image, a plurality of collecting electrodes arranged within said tube in staggered relation, each collecting electrode being arranged to receive electrons from an elemental area of said electron image, means for scanning said electron image across said collecting electrodes in such manner that each elemental area of said image falls on each of said collecting electrodes in turn, and a common signal circuit connected with said collecting electrodes, the arrangement being such that in operation similar signal currents in substantially identical phase are derived through said collecting electrodes and combine in said signal circuit to produce a further augmented signal current similar in form to the current derived through each collecting electrode.

In accordance with the third-mentioned aspect of the invention an embodiment is provided in the form of an electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam of electrons in which the electron distribution is determined by an image which it is desired to transmit, means for focusing said electron beam to form an electron image, an apertured electrode or screen having apertures therein arranged in predetermined order and each adapted to pass a fasciculated beam of electrons corresponding to an elemental area of said electron image, means for scanning said electron image across said apertures in such manner that each elemental area of the image passes across said apertures in turn. means for delaying individually the fasciculated beams so obtained, an output electrode for receiving all said fasciculated beams, and a signal circuit connected to said output electrode,--the arrangement being such that said fasciculated beams are received by said output electrode in substantially identical phase and are additive in efiect thereby producing an augmented signal .current similar in form to the current in each of said fasciculated beams in said signal circuit.

A feature of the invention is the provision of novel electron discharge devices. Thus the invention provides an electron discharge device comprising an envelope or tube comprising a source of electrons adapted to be excited to .produce a composite electron beam corresponding to an optical image to be transmitted and a plurality of collecting electrodes arranged in predetermined order, adapted to have said composite beam of electrons focused on them in such manner that each electrode receives an elementary area of the electron image so formed and so arranged that said electron image can be scanned across said electrodes in such manner that each elementary area of said electron image falls on each of said collecting electrodes" in turn. In such a device the collecting electrodes may be disposed in staggered relation in such manner that the paths of electrons from said source to said electrodes vary in a predetermined manner in accordance with the order of electrodes so that in operation similar signal currents can be derived from said collecting electrons in substantially identical phase. The invention further provides an electron discharge device comprising an envelope or tube comprising a source of electrons adapted to be excited to produce a composite electron beam corresponding to an optical image to be transmitted, an apertured electrode or screen and a single collecting electrode, said apertured electrode .being adapted to have said beam focused to form an electron image thereon and having a plurality of apertures arranged in predetermined order therein, each aperture permitting the passage of a fasciculated beam from an elementary area of the electron image, and said apertures being so arranged that in operation said electron image can be scanned across the apertured electrode in such manner that each elemental area of said electron image falls on each of said apertures in turn, and said collecting electrode being so disposed with regard to said apertures and to the operation of delay means which may be arranged to act on said fasciculated beams individually in such manner that when said composite beam is so scanned, the currents in the fasciculated beams will be received in the collecting electrode in substantially the same phase.

For the purpose of describing the nature of the invention and the method of carrying the invention into effect, reference will now be made to the accompanying drawing in which:

Figure 1 diagrammatically represents a dissector tube according to the invention,

Figure 2 is a circuit arrangement for-use with the invention, and

Figure 3 represents an arrangement of electrodes for avoiding the use of the delay network of the wave filter type shown in the above-mentioned Figure 2 while Fig. 4 shows a modification of the electrode arrangement shown in Fig. 1.

Referring to Figure l of the drawing, the arrow represents an object which it is-desired to scan so as to produce an electrical signal for the purpose of transmitting areproduction'of the object by means of wires or byxradio to a suitable receiver, as, for example,' a tel'evisionor facsimile receiver. -An optical image of the object is produced, as for example, by the lens III, on the electron emitting cathode i2, which is located on the inside surface of an evacuated glass cylinder I I. The surface l2 may comprise a thin layer of silver having a silver oxide surface on which is deposited a layer of caesium: The surface may not be on the glass wall itself, but it may be mounted on a mica or glass plate with a preferably non-microphonic suspension. For television purposes the surface is photo-electrically active in the visible light spectrum, but for other uses the surface may be sensitive to radiation of a different wavelength from that of light, e. g., the surface may be thermo-electrically active. The optical image on the photo-cathode l2 causes the latter to emit electrons from elemental areas to an extent proportional to the light falling on each point. Further along the glass cylinder is arranged an electrode [3 in the form of a preferably metal cylinder .co-axial with the glass cylinder, thepurpose of the electrode beingto accelerate the electrons emitted from the photo-cathode l2 towards the other end of the cylinder. For this reason the potential of the electrode I3 is made positive with respect to the cathode l2. The electron image emanating from the cathode i2 is maintained in focus by a coil IS in known manner.

At the end of the tube remote from the oathode I2 are arranged a plurality of collecting electrodes M. These are preferably screened from each other by the screening electrodes I5. In a practical example, there may be ten such collecting electrodes arranged in line and close together. 7

Suitable means, not shown, are provided for scanning the electron image emitted by the cathode i2 over the collecting electrodes I l. The scanning preferably is carried in a line-by-line manner and may be interlaced.

In operation, the electron image is so deflected that elemental areas of the image are scanned over each collecting electrode in succession. Thus, assuming that the scanning is of the lineby-line system, then the electrodes are arranged in such a relationship with the deflecting fields that each line of the image passes across the series of collecting electrodes which are arranged in the same plane as the line scan. Thus each collecting electrode receives a signal corresponding to each elemental area of the scanned object, but each signal is displaced in time depending on the spacing of the electrodes and the scanning velocity at the electrodes. In order that the signals thus obtained may be usefully employed, it is necessary to delay the individual signals in the correct order and by the right amount of time so that they add together to form one single electrical signal corresponding to each elemental area of the scanned object. By this means the signal potentials obtained are much greater than those obtained by an electron image dissector using only a single collecting electrode. In addition, the ratio of signal to noise is improved, since the signal potentials are mixed additively whereas the potentials due to the noise currents being of a random nature are mixed according to the root mean square value.

Each of the collecting electrodes is connected by means of a suitable circuit to time delay devices, as for example, to tappings on a time delal network. In a preferred arrangement each electrode is connected to the control grid of a cathode follower valve, and the output circuit of each valve supplies the signals to a tapping on the delay network.

Figure 2 of the drawing illustrates a suitable circuit for utilising the signals from three collecting electrodes. Each of the valves 20, 2| and 22 acts as a cathode follower, the cathode output impedances being resistances 23, 24 and 25. Each of the collecting electrodes is connected to the grid of one of the valves 20, 2| or 22, the grids of which are provided with suitable loading impedances shown as resistances 26, 21 and 28. Each of the valves 20, 2| and 22 is connected by suitable matching resistances 29, 30 and 3| to tappings 32, 33 and 34 on the time delay network 35 comprising series inductances 36 and shunt capacitances 31 and terminating resistances 38 and 39. The delay network is so designed by suitably choosing the values of inductance and capacitance that the cut-ofi frequency of the circuit is well above the highest signal frequency in order that the time delays will be independent of the signal frequencies. In this connection it is preferred to arrange for the series inductances to be mutually coupled so as to improve the efiiciency of the network. The termination impedances 38 and 39 in conjunction with resistances 29, 30 and 3| are chosen with reference to the characteristic impedance of network 35 so that no harmful reflections are obtained. In this connection it may be necessary to provide suitable matching pads between the various sections of the network which are tapped. The cathode follower valves are used to-connect the collecting electrodes to the delay network because the impedance of each collecting electrode is very high and it would be almost impossible to match this impedance into any known delay network by a direct connection. In addition, the use of a cathode follower coupling valve reduces the effective capacity on each electrode and thus a higher value of collecting electrode load impedance can be employed with a resultant increase in sensitivity; there is also the linearising of the valve characteristic by the negative feedback and the low output impedance makes it a comparatively simple matter to match the valve to the delay network. The output of the network 35 is taken from resistor 30 via grid condenser 43 and grid leak 44 to the grid of an amplifier valve 40 which is provided with a bias resistance 4| and output load 42.

In designing a tube according to the invention it is necessary that the total length of the number of electrodes along a scanning line be small compared with the length of a line since portions of the picture are lost at the ends of each line. In the normal television transmission systems employed nowadays about 10 per cent of the line scanning period is occupied by a synchronising pulse. In carrying out the present invention it can be arranged that the lost portion of the signal occurs during the synchronising pulse period so that no disadvantage is entailed. The length of electrodes should therefore not exceed about 5 per cent of the line length.

' In practice about 10 electrodes could be fairly easily arranged in such a space.

Various methods of construction of the electrodes are possible. For example, each electrode may comprise a thin film of metal arranged between two insulating plates, say of mica, which may be coated on the outside with a film of conductive materials for screening purposes. Each electrode is arranged side by side and so positioned in respect to the moving electron image that the latter traverse each electrode in turn. A metal plate with a narrow transverse slit may be arranged in front of the electrodes so that only one line width of electrons is permitted to reach the electrodes during one line scan. It will be seen that the structure is equivalent to a number of separately screened apertured electrodes. To increase the sensitivity these electrodes may be coated with or constructed of a secondary electron emissive substance, further electrodes being provided for collecting the multiplied electrons.

In order that the design of the electrodes may be rendered easier-it will be appreciated that in a tube of the type already described the dimensions of the electrodes are extremely small-it is possible to employ means for magnifying the size of the electron image before it reaches the collecting electrodes.- One way of achieving this is to reduce the length of the focusing coil l6. Thus, instead of producing a substantially parallel beam of electrons along the tube, the beam is caused to diverge and it therefore produces a larger effective scanning length at the collecting electrodes and makes their construction more practicable. It will be found that magnetic magnification of this type will be limited in extent by the amount of spiral distortion caused by the rotation of the electrons at the ends of the scanning lines. In addition, it is necessary to ar range the collecting electrodes at an angle with the optical image on the photo-cathode in order to correct for the rotation of the electron image due to the magnetic field.

An alternative method of magnifying the electron image is by the use of electrostatic fields. Thus, the electrodes in Figure 1 may be replaced by selecting means comprising a metal plate having a slit and the electrons entering the slit are acted upon by suitable accelerating electrical fields to produce an enlarged electron image of the slit, the electron image being collected by suitable collecting electrodes. A combination of magnetic and electrostatic methods may be employed for image magnification purposes.

Whilst a time delay network comprising condensers and inductances has been described it will be apparent that other types of time delay devices capable of dealing satisfactorily with the side band of frequencies involved may be utilised. For example, a quartz crystal may be placed in a liquid cell provided with electrodes so that the signal are applied to the quartz crystal and after passage through the liquid the signals are detected; the time delay being due to the time taken for the passage of the signals through the liquid. Each collecting electrode may serve to excite different quartz crystals arranged at different distances from the receiving electrode.

Alternatively time delay devices of the type described in British patent specification No. 471,913 may be employed.

In order to reduce the number of sections of delay network for a given time delay it is also possible to utilise reflected signals. It is known that if a time delay network is mismatched at one end then the signal arriving at that end is reflected back to the other end. If use is made of the reflected signal then a longer time delay can be obtained. As an example, a delay network may be correctly terminated at the input end and be mismatched, say, openor shortcircuited at the other end. If a signal A1 is applied to the input of the delay network a reflected signal A2 is obtained at the input with a delay equal to twice that between the input and output ends of the network. By using a suitable circuit it is possible to cancel the signal A1,

leaving only the signal A2. Thus, a delay network may be fed by means of a cathode follower valve and the input end may be correctly terminated, whilst the other end is mismatched. A load resistance may be arranged in the anode circuit of the valve and a potentiometer (with suitable blocking condenser in series) connected between the anode and cathode of the valve. The output is taken from the tapping on the potentiometer and the earth line. In one position of the tapping the input signal A1 is balanced out whereas the reflected signal A2 is transmitted. Alternatively, a two valve mixing arrangement may be used for cancelling out the unwanted signal.

In a television system operating at 400 lines and 25 pictures per second, the time taken to scan one picture element is approximately a quarter microsecond. Thus, ten collecting electrodes each receiving a picture point and separated one from another by an amount corresponding to the width of one picture point would require a total time delay of the order of five microseconds.

In an alternative type of tube construction the collecting electrodes instead of being arranged equi-distant from the photo-cathode, might be placed in staggered relationship, the transverse separation of the electrodes being such that the time taken for the scanning image to traverse the distance is equal to the difference in the time taken for the electron image to strike one electrode and then the next. Thus, if a particular picture point on the electron image strikes one electrode at a certain time an interval of time elapses before it strikes the next electrode. The direction of stagger and direction of scanning could be so arranged that the signals for one particular point of the image from the separate electrodes occur at the same instant in the output circuit. However, this arrangement has the disadvantage that an excessive length of tube would be required to accommodate the collecting electrodes, and to overcome this difllculty the collecting electrodes of Figure 1 may be replaced by an arrangement similar to that represented in Figure 3.

The electrode system shown in Figure 3 comprises an apertured electrode or shield 50 provided with a plurality of apertures 5|a to 5le disposed in line. The electrode 50 has a composite beam of electrons such as that from cathode I! of Figure 1 focused on it and the apertures 5| are positioned to correspond with the collecting electrodes l4 of Figure 1. Although only five apertures 5| are shown, any convenient number of apertures, for example, ten, may be provided. Behind the electrode 50 is a further electrode 52 similar to the electrode 50 and having apertures 53a. to 53c aligned with the correspondingly referenced apertures 5| in electrode 50. Between electrode 52 and another plate electrode 54 are arranged two deflecting electrodes 55 and 56 termed lifting plates between which, in operation, a magnetic field is maintained in the direction indicated by the arrow H. Between the lifting plates 55 and 56 and the electrode 54 are provided further deflecting plate pairs 51a to 51 disposed perpendicularly with respect to electrodes 54, 55, 56 and each pair being located between the parallel' lines through the centres of the registering apertures 5| and 53 in electrodes 50 and 52.

In the lower part of electrode 54 is an aperture 58, behind which is an output electrode 59 connected to an amplifier 60.

In operation, the electrode 50 serves as an anode and is maintained at a positive potential with respect to the cathode from which the electrons focused on electrode 50 are emitted, electrode 52 is maintained at approximately cathode potential; electrode 54 is preferably maintained slightly below cathode potential; suitable potential differences are established between the lifting plates 55 and .56 and between the plates of deflecting plate pairs 51; and output electrode 59 is preferably maintained at a positive potential. The electron image formed on the apertured electrode 50 is scanned, preferably line-byline, across the apertures Electrons passing through the apertures 5| also pass through the registering apertures 53 in electrode 52 in the deflecting fields between the deflecting plates 55 and 56. These fields co-operate to produce a deflection of the electrons parallel to the lifting plates in the manner represented by the zig-zag lines in the drawing. On emergence from between the lifting plates 55 and 56 the electrons move either between one of the deflecting plate pairs 5! towards the plate electrode 55 or towards the aperture 58 in electrode 54 and through that aperture into the output electrode 59, which is preferably in the form of a Faraday cylinder to collect electrons effectively without appreciable losses due to secondary emission. Thus electrons passing through the aperture 5|a in electrode 50 pass through the registering, aperture 53a in electrode 52 and thence into the space between plates 55 and 56 where the electrons become deflected in a direction parallel to the plates 55, 58 as shown in the drawing. After emerging from between the plates 55, 56 the electrons pass between the plates 57a towards the negatively charged electrodes 58, the retarding field of which cause the electrons to be reflected back into the space between the plates 55, 56 where the electrons are deflected in the same direction as before together will only be equal to half the length and so that they move towards the aperture 535 as represented in the drawing. The deflection produced between plate pairs 51 is intended to ensure that the reflected and deflected electrons from one aperture '53 such as, for example, 53a, do not pass out through the next aperture such as 53b, but are deflected slightly in a plane perpendicular to the plane of the paper so that they miss aperture 53b and are reflected again into the space between the deflecting plates 55, 55. The electron stream is, after further reflection at electrode 53, augmented by the electron stream coming through the apertures 5|b and 5%.. Thus, if it is arranged that the electrons passing through the aperture 5|a are subsequently reflected once at electrode 54 are mixed with the electrons passing through aperture 5|b and corresponding to the same elemental area of the electron image, the effect of the two electron streams will be to produce a signal current in which signal amplitudes are doubled or very nearly so. Likewise, in the stream coming from apertures 5| 0 and 530 the signal amplitudes will be trebled, and so on. Thus, if there are n apertures 5| or 53,'theoretically, an amplification of n times can be obtained in the streamof electrons passing from the last aperture through the space between the plates 55, 56. This amplified or augmented stream is collected in the output electrode 59. Moreover, the length of tube required to produce the delays in the respective electron streams before they are added in a stream of electrons coming from one aperture before the stream is mixed with electrons from the next aperture and will be independent of the multiplication efiected. Moreover the time delay can be adjusted by adjusting the velocity of the beams of electrons between electrodes 52 and 54 or by increasing the number of reflections which take place between them so that the beam coming from one aperture 5| is reflected more than once before it is combined with the beam coming from the next succeeding aperture.

Electromagnetic or electrostatic electron image magnifying arrangements such as are described above with reference to Figure 1 can be used with the arrangement of Figure 3 to produce the image which is scanned across the apertured electrode 5B.

The invention may also be applied to the transmission by television of'films. Either the whole of a film frame may be focused on to the photocathode of the tube, or only a single line transverse to the direction of motion of the film. In the former case a continuous film projector, say

of the Mechau type, may be employed, whilst,

in the second case the film may be passed continuously through a projector in such a way as to produce the frame scanning by the movement of the film, the line scanning being performed by the electric or magnetic field of the tube.

I claim: a

1. A method of deriving from an image of an object a train of electrical signals corresponding to elemental areas of said image, said method comprising the steps of producing an electron image corresponding to said image, scanning successively said electron image a plurality of times, the time interval between successive scannings being less than the time required to scan the entire said electron image to derive in different time phase a plurality of discrete signal trains, each of said signal trains being substantially the same, delaying each of said trains in accordance with its time phase for a time interval less than the time required to scan the entire said electron image and adding said delayed signal trains delayed to produce an augmented signal train of the same form of each of said signal trains prior to transmission.

2. In an image transmitting system wherein is provided an electron discharge device having an electron emitting surface and a plurality of collecting electrodes arranged in a predetermined order, each of said collecting electrodes being connected to a separate signal circuit, the meth- 0d of deriving from an image of an object a train of. electrical signals corresponding to elemental areas of an image comprising the steps of projecting said image on an electron emitting surface to provide a composite beam of electrons in which the electron distribution is determined by said image, focusing said composite beam to form an electron image, receiving said electron image on said plurality of collecting electrodes, each of said plurality of collecting electrodes receiving an elemental area of said electron image at any instant of time, scanning said composite beam acrosssaid 'collecting'electrodes so that each elementalarea of said electron image is scanned across each of said collecting electrodes in turn to produce outputs from said signal circuits, delaying said outputs in accordance with the order of their production and combining the 3. In an image transmitting system wherein is provided an electron discharge device having an electron emitting surface and a plurality of collecting electrodes positioned at successively increasing distances from said surface, the method of deriving from an image of an object a train of electrical signals corresponding to elemental areas of said image comprising the steps of projecting said image on said electron emitting surface to provide a composite beam of electrons in which the electron distribution is determined by said image, focusing said composite beam to form an electron image, receiving said electron image on said plurality of collecting electrodes, each receiving an elemental area of said electron image, scanning said composite beam across said collecting electrodes so that each elemental area of said electron image is scanned across each of said collecting electrodes in turn, deriving electrical signals representative of said elemental area from each of the collecting electrodes and combining the derived signals to form a composite signal having substantially the same wave form of each of the derived signals.

4. In an image transmitting system wherein is provided an electron discharge device having an electron emitting surface and an accelerating electrode perforated according to a predetermined design, the method of deriving from an image of an object a train of electrical signals corresponding to elemental areas of said image comprising the steps of projecting said image on an electron emitting surface to provide a composite beam of electrons in which the electron distribution is determined by said image, focusing said composite beam to form an electron image, receiving said electron image at the perforated electrode, passing through the perforations a fasciculated beam of electrons corresponding to an elemental area of said electron image, delaying the passed fasciculated beam having successively increasing time and finally collecting all of said beams at a common point.

5. An electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam of electrons in which the electron distribution is determined by an image which it is desired to transmit, means for focusing said electron beam to form an electron image, a plurality of collecting electrodes arranged in predetermined order and each arranged to receive an elemental area of said electron image, means for scanning said electron image across said collecting electrodes in such manner that each elemental area of said electron image falls on each of said collecting electrodes in turn, signal circuits connected one to each of said collecting electrodes, delay means associated with said signal circuits, and an output combining circuit connected with said delay means.

6. An electric circuit arrangement according to claim 5, wherein said signal circuits each comprise an electron discharge valve having a control grid connected its associated collecting electrode, said valve being arranged to operate as a cathode follower valve and being so arranged that its cathode impedance provides a matching termination for effectively connecting said collecting electrode to said delay means.

7. An electric circuit arrangement according to claim 5, wherein said delay means comprises a single network having tappings to which the outputs to be combined are applied.

8. An electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam of electrons in which the electron distribution is determined by an image which it is desired to transmit, means for focusing said electron beam to form an electron image, a plura ty of collecting electrodes arranged within said tube in staggered relation positioned at progressively increasing distances from said beam producing means, each collecting electrode being arranged to receive electrons from an elemental area of said electron image, means for scanning said electron image across said collecting electrodes so that each elemental area of said image falls on each of said collecting electrodes in turn, and a common signal circuit connected with said collecting electrodes, whereby similar signal currents in substantially identical phase are derived through said collecting electrodes and combine in said signal circuit to produce a further augmented signal current similar in form to the current derived through each collecting electrode.

9. An electric circuit arrangement comprising in combination an electron discharge tube, means for producing within said tube a composite beam of electrons in which the electron distribution is determined by an image which it is desired to transmit, means for focusing said electron beam to form an electron image, an apertured electrode having apertures therein arranged in predetermined order and each adapted to pass a fasciculated beam of electrons corresponding to an elemental area of said electron image, means for scanning said electron image across said apertures so that each elemental area of the image passes across said apertures in turn, means for delaying individually the fasciculated beams, and means including an output electrode for receiving said fasciculated beams substantially simultaneously by said output electrode in substantially identical phase, thereby producing an augmented signal input corresponding in form to the current in each of said fasciculated beams in said signal circuit.

10. An electric circuit arrangement according to claim 5, wherein the means for focusing said electron beam produces a magnified electron miage.

11. The circuit claimed in claim 9, wherein selecting means are provided for receiving said focused composite beam, said selecting means affording passage for electrons from a portion only of the area of said electron image, electrostatic means for accelerating said electrons passing said selecting means and focusing said electrons to form a magnified image of said portion of said area on said collecting electrodes, said scanning means being arranged to scan said composite beams across said selecting means to vary the portion of said electron image to which passage is afforded.

12. An electron discharge device comprising an envelope comprising a source of electrons adapted to-be excited by radiant energy to produce a composite electron beam in which the electron distribution is determined by an optical image to be transmitted, a plurality of collecting electrodes arranged in predetermined order, said collecting electrodes being adapted to have said composite beam of electrons focused on them so that each electrode receives simultaneously an elementary area of the electron image so formed, and scanning means to scan said electron image across said collecting electrodes whereby each elementary area of said electron image falls on each of said collecting electrodes in turn, each of said plurality of collecting electrodes contributing to a single final train of signal impulses representive of the optical image to be transmitted.

13. An electron discharge device according to claim 12, wherein said collecting electrodes are disposed in staggered relation of successively increasing distances from said source so that the paths of electrons from said source to said electrodes vary in a predetermined manner in acenvelope'comprising a source of electrons adapted to be excited by radiant energy to produce a composite electron beam in which the electron distribution is determined by an image to be transmitted, an apertured electrode, an output electrode, said apertured electrode being adapted to have said beam focused to form an electron image thereon and having a plurality of apertures arranged in predetermined order therein, each aperture permitting the passage of a fasciculated beam from an elementary area of the electron means to have each elemental area of said electron imagefall on each of said apertures in turn, and path delay means acting on said cordance with the order of electrodes to obtain 15 'fasciculated beams individually to insure subsimilar signal currents from said collecting electrodes in substantially identical phase.

14. An electron discharge device comprising an stantially identical phase of arrival of said fasciculated beam at said output electrode.

IVANHOE JOHN PENFOUND JAMES.

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