US2181720A - Television receiver - Google Patents

Description

NOV. 28, 1939. `l1. BARTHELEMY 2,181,720

TELEVISION RECEIVER Filed March 19, 1937 Patented Nov. 28, 1939 UNITE TELEVISION RECEIVER France Application March 19, 1937, Serial No. 131,836 In France March 21, 1936 2 Claims.

The present invention relates to television receivers and has for its object improvements whereby these receivers are rendered both simpler and more eicient.

According to these improvements, in the said television receivers use is made of the amplifiers known as electron multipliers, in which a primary electronic emission of thermionic or photosensitive origin is amplied owing to the production of secondary electrons by successive impacts on the auxiliary electrodes of great secondary emissivity. Such tubes may in certain cases advantageously replace the ampliers comprising thermionic tubes in cascade.

In this application of such an electron multiplier to television receivers, the invention provides for the use of a common high tension source of electricity, serving wholly or in part to feed the electron multiplier and to feed the image-reproducing cathode tube, and, in a general manner, to feed the various elements of the receiver.

The invention also provides an improved television receiver in which the electron multiplier and the image-receiving cathode tube are connected in a common vessel, the various electrodes of which are fed by a common source of electricity.

The invention also covers, in television receivers with electron multiplier, certain other improvements which will appear from the following description and from the accompanying drawings.

In these drawings,

Figure 1 shows diagrammatically a television receiver in which an electron multiplier and a cathode tube associated therewith are fed by a common source of electricity.

Figure 2 illustrates diagrammatically a television receiver comprising the connection of the electron multiplier and the cathode tube in a common vessel.

The radioelectric receiver I, which may be extremely simple and comprise a single tuning circuit 2, is connected to an aerial 3. It may be connected by a change-over switch 4 placed in the position 4a with a detector stage 5, the circuit of which may be closed by a switch 6 on a resistance 1, which serves as a coupling element between the detector stage 5 and an electron multiplier 8, of which Figure 1 diagrammatically shows a form.

This multiplier acts as an aperiodical amplifier. A voltage divider 9 permits of feeding the different electrodes Il) of this tube by means of the feeding source II of the cathode tube I2 for the reception of images. 'Ihis constitutes one of the principal advantages of the invention, because the production of a separate high-tension'source for the electron multiplier would entail expense which would be prohibitive for a receiver.

A modulating electrode I3 is provided in the tube 8 to be influenced by the detector stage 5. The cathode I4 may be heated as is assumed in Figure l, or photo-sensitive-ancl subjected to the action of a source of light as in Figure 2. The invention also covers the following functional modifications given by way of example: If the wave on which the transmissions to be received take place is not too short, the high-frequency current received in the receiver I may be amplified directly by the tube 8 by placing the change-over switch 4 in the position 4b and opening the switch 6. In this case, the detection only takes place at the exit from the tube 8 by a detector I5, or use may be made for the detection of the Wehnelt cylinder (modulating electrode) of the cathode 20 tube I2, in which case, the detector I5 being dispensed with, the two connections 4I5a are connected respectively to the cathode and to the Wehnelt cylinder of the tube I2.

I f, on the other hand, it is a question of very short waves, the known frequency-changing method may be applied before the application of the oscillations received at the amplier 8. In this case, the change-over switch 4 being still in the position 4b and the switch 6 open, the frequency changing may be effected, for example, with the aid of a local auxiliary oscillator I6 acting on the rst accelerating electrode Il of the tube 8. It is also possible, should the cathode I4 be photosensitive, to modulate `by the auxiliary oscillator the source of light I8 (Figure 2) acting on the cathode I4.

The invention also covers the use of the nonlinear characteristics of the electrodes emitting secondary electrodes (acting as negative resistances) for producing automatically self sustained oscillations in the circuit of the tube 8 by inserting a suitable oscillatory circuit therein.

It may be observed that the high-frequency amplification with or without frequency chang- Ling is of interest in that it permits of transmitting without diiculty the continuous component, the importance of which to the quality of the images is known. It is sucient to establish the connection with the nal detector by magnetic or electric coupling.

Another improvement according to the present invention is characterised by the assembly of the electron multiplier 8a and of the cathode tube |28* in a. common vessel I9 (Figure 2), the final col- 55 lecting anode 20 of the multiplier being made to emit secondary electrons and serving as a cathode for the Braun tube |22.

The collecting anode 2l! of the multiplier has, for example, the form of a sphere, but any other form may be selected without departing from the spirit of the invention. Under the influence of the ux of electrons coming from the multiplier formed by the series of electrodes l0 of high secondary emissivity, this anode 20 emits secondary electrons. These secondary electrons, accelerated by the known syst/em of electrodes of the tube I2a, form the cathode beam, the impact of which on the fluorescent screen 2l constitutes the luminous image point.

The modulation of the intensity of this beam takes place, according to the invention, directly by variation of the flux of electrons, through the tube 8a in accordance with the potential of the modulating electrode i3, which is controlled by the intensity of the radio-electric signals received. The synchronisation of the sweeping of the image point may be carried out, also according to the invention, by doubling the last electrode but one of the tube 8a so as to form a condenser lla, Mib, through which the synchronising signals act on the sweeping circuit 22 according to a known process. A suitable impedance 23 is then inserted in the feed circuit of the electrode lila.

The same method (use of an electron multiplier fed by the general high-tension source) may be used, according to the invention, for the radiophonic receiver combined with the television receiver. The necessary selectivity may then be obtained by the loose coupling of supplementary oscillatory circuits disposed before or after the multiplier, or inserted in the anode circuits thereof with or without retroactice coupling.

What I claim is:

l, In a television receiver comprising an electron multiplier and a cathode ray oscillcgraph the combination with a single source of electricity of a potentiometer in shunt with said source, a plurality of taps on said potentiometer for feeding the diierent multiplier and oscillograph electrodes, an auxiliary electrode arranged within said multiplier and forming a condenser with the last but one electrode of said multiplier for tapping the synchronization signals in the electron flux traversing said multiplier, and means controlled by the circuit of said auxiliary electrode for synchronizing the sweeping of the image point in said oscillograph.

2. In a television receiver comprising an electron multiplier and a cathode ray oscillograph enclosed in a common vessel the combination with a single source of electricity of a potentiometer in shunt with said source, a plurality of taps on said potentiometer for feeding the diierent multiplier and oscillograph electrodes, an auxiliary electrode arranged within said multiplier and forming a condenser with the last but one electrode of said multiplier for tapping the synchronization signals in the electron flux travers- 5 ing said multiplier, and means controlled by the circuit of said auxiliary electrode for synchronizing the sweeping of the image point in said oscillograph.

RENE' BARTHELEMY.

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