US2015133A - Photo-electric tube - Google Patents

Description

Sept 24, 11935,. w. BARSTIES PHOTO ELECTRIC TUBE Filed Ndv. 5, 1931 lnvenm r wwm W wwww Patented Sept. 24, 1935 PATENT OFFIE PHOTO-ELECTRIC TUBE Wilhelm Barsties, Berlin, Germany, assignor to Albert Patin, Berlin-Wilmersdorf, Germany Application November 5,1931, Serial No. 573,281 In Belgium December 9, 1930 4 Claims.

5 ing drawing of illustrative embodiments of said invention, the true scope of the invention being more particularly pointed out in the appended claims.

Figs. 1 to 4 show different illustrative forms of tubes embodying features of the invention.

In the controlling of electrical working circuits as heretofore effected, the controlling capacity of the tube depends upon the output or magnitude of the ion alternating current or the electron alternating current. By increasing the polarizing potential, greater controlling capacity or power for the tube may be secured.

The possibility of securing an increase in the alternating current output or power and therefore in the control capacity of the tube is further limited by the fact that when greater polarizing potentials are used, there is created, in utilizing the methods heretofore known, a strong dependency upon the frequency which increases with.

every increase in the polarizing potential. S ocalled layers are formed at the junction of cathode and gas space, which layers'increase the work necessary for the release and passage of the electrons. As a result the release and passage of the electrons is no longer effected in synchronism with the variations in the intensity of the light beam falling upon the tube. The situation is made more difficult owing to the fact that this impeding action of the layers referred to varies with the height of the polarizing potential and the frequency of the light intensity. With a tube thus dependent upon frequency a loud speaker in reproducing a sound fihn would emit defective, distorted sounds. V

The disturbing action of this occurrence is particularly noticeable when the photo cathode used is composed of materials which are sensitive to the long wave portion of the spectrum of approximately 500 [LIL and upwards. In order to decrease the dependency on frequency to a sufferable degree in practice, it therefore became necessary to make the pho-toelectrodes of materials the spectral sensitivity of which was below 500 ,lL/L and to operate with polarizing potentials that were even lower than was necessitated by the danger of premature discharge and ignition'or sparking.

I have found further that'ionization at the anode can be varied by varying the intensity of the illumination of the photo electrode, and that :In certain cases it may be advantageous to add to the gas content of the tube the vapors of variations in the resistance also occur in the tube as a whole under such conditions. Such variations in the ionization may be efiected for example by varying the area or width of the light beam falling upon the photo-electrode and thus 5 enlarging or contracting the luminous spot upon the photo electrode whereupon said unstable ionization will respond with exactly corresponding increases and decreases.

Another possible way of creating resistance va- 1O riations in the tube as a whole by the use of said newly discovered phenomenon, results from the fact that if a limited luminous spot be projected upon the photo-electrode the unstable ionization occurs upon the anode in the form of a limited spot which, on movement or displacement of the luminous spot upon the photo-electrode will undergo an exactly corresponding movement or displacement upon the anode. The strength of the unstable ionization will also vary responsive to variations in the intensity of the light beam falling upon the photo-electrode. This furnishes a further possibility for controlling the resistance of the tube as a whole. Other possibilities result from the combination of two or of all three of the referred to methods. Still other possibilities growing out of my invention will readily suggest themselves to those skilled in the art. All these and other variations of the unstable ionization follow the changes in illumination practically without inertia.

As with my novel tube the ion current remains always controllable it is possible to work with much higher polarizing potential than has heretofore been possible. One advantage among others hereby gained is that as distinguished from tubes heretofore used one can approach-the very limit of incandescent or sparking potential without sacrificing one iota of the tubes capacity'of control. While in the tubes heretofore used it 40 has been necessary, by the use of anode surfaces of as large an area as possible to try and obtain as homogeneous a field as possible, it will be noted that in tubes embodying my invention it is adr visable to keep the anode surface small, by constructing the anodes in the form of thin drawn wires or bands or ribbons, so as to obtain as nonhomogeneous a field, of great density, as possible.

metals or of alkalies or the vapors ofhalogens and of their metallic compounds, or the vapors ,of other suitable metal salts and their complex compounds, as thereby, among other things, the

work required for producing the excitation within the gas chamber is lessened.

Another advantage of my invention resides in the fact that the non-homogeneous field makes for a substantial reduction in the work necessary for the release of the electrons from the cathode, because the previously mentioned layers formed in tubes heretofore'used at the junction of gas and cathode surface, are completely eliminated. The lessening of the work necessary to release the electrons from the cathode is so considerable that photo-electrically sensitive materials can be utilized which are suited to light of any wave length until far into the infra-red portion of the spectrum. Thus, for cathodes, photo-electrically sensitive materials can be used which are sensitive to red light of a wave length of 6,000 This has the further advantage that my invention enables the full extent of the spectrum of the artificial light generally used for the excitation of photo-electric tubes to be utilized to control the tube, while in methods heretofore used only the short wave length light, which constitutes but a small part of the light from artificial sources, iseffective. The most favorable output is derived from electrodes composed of materials which are sensitive to the complete extent of the spectrum of the source of light employed, for example cesium, cesium alloys, tellurium, selenium compounds, tellurium-seleniurn compounds, thallium compounds, metallic sulphides and similar substances, all of which can be used in accordance with my invention, but which could be used only to a limited degree in methods heretofore used, because when utilized in said known methods the work necessary to release the electrons is so great, owing to the formation of the interfering layers already referred to, that an interfering periodicity dependance becomes noticeable.

lubes in accordance with my invention utilizing the unstable ionization or preliminary glow discharge at the anode can be developed along different lines in order to increase the control efficiency or power; for example by using electrodes that are not parallel (Fig. 1) or by so constructing or forming at least one of the electrodes that its natural resistance shall be of the same magnitude order as that of the resistance of the discharge path (Fig. 2) or by combining both of these features. All of these types of tubes are suited to carrying out my novel process.

As the path of discharge forms a sort of contact bridge between the electrodes it will be apparent that if the electrodes be not parallel, i. e. divergent, movement or change of position of the unstable ionization caused by movement or change of position of the light spot upon the photo-electrode, will effect a lengthening or shortening as the case may be of the path of discharge acting as a contact bridge and thereby a variation in the resistance of the tube in rhythm or synchronism with the movement or travel of the light spot upon the photo-electrode. If one of the electrodes possesses a resistance itself, it will readily be seen that a change in the resistance of the tube in rhythm or synchronism .with the movement of the spot of light upon the' photo-electrode can also be produced by movement or displacement of the unstable ionization and of the path of discharge, dependent upon the movement or displacement of the spot of light upon the photo-electrode.

In Fig. 3,.the anode of the tube is conveniently divided into two anode bands or ribbons l5, l1

cathode.

positioned symmetrically relatively to the cathode l9 so that the part thereof to be illuminated shall receive the full illumination without any shading. The anode bands or ribbons l5, I! have their narrow edges directed toward the cathode, thus producing a field of great density 4! 5| as diagrammatically illustrated in said Fig. 3. Fig. 1 shows another view of the tube bringing out the fact that in that embodiment of the tube the electrodes are divergent relative to each other. That is to say the two anode bands may be divergent relative to the cathode while parallel to each other or divergent relative to each other.

This arrangement is preferable in the reproduction of sound records or films of the socalled indented or notched types or of the type in which the sound fluctuations are recorded in the form of a sinuous line. With the latter type of film, diaphragm means is used whereby only the limited portion of the light band or ribbon that falls upon'the film is caused to fall, in the form of a limited spot of light, upon the oathode l 9. This spot of light travels, in correspondence with the amplitude of the curves, from the point D to the point 1 (Figs. 1 and 2) and with it the path of discharge and the released unstable ionization travel correspondingly from the point a. to the point e. The divergency of the anodes and the cathode relative to each other produces a variation in the length of the path of discharge and therefore also a variation in the strength of the resistance of the tube.

This variation therefore corresponds to the amplitude of the curve of the sound record, and if the electrode be straight it will be proportional to said amplitude. When the light spot falls upon the cathode at the point d or for example, the discharge path will extend through the path cd in the former case, and through the path e' f in the latter case. As in this way, discharge paths of different lengths are placed in circuit, the tube resistance that is operative in the circuit will be varied, and this continuously, since the spot of light travels continuously over the The variations in the resistance work out correspondingly in the working circuit, the greatest amplitude of the sinuous photogram on the film or record producing the greatest potenftial fluctuation in the coupling resistance. Similar conditions obtain when an indented type or notched type of record is used. The width of the band of light limited by the diaphragm means varies in correspondence with the depth of the indentation. For example, the band or ribbon of light can reach to the point f or to the point (1 or to the point D. The path of discharge will correspondlnglyextend through the distance ef, cd, or ab. In this case therefore the amount of light falling upon the cathode varies and With it varies the extent or magnitude of the discharge. In this case also, the resistance of the path of discharge itself changes, said resistance diminishing with an increase in width.

'of the same magnitude as that of the resistance possessed by the path of discharge. In both methods described, the strength of the anode resistance varies with variations in the length of the section of the anode included in the circuit,

said anode resistance being added 'to the resistance of the discharge path and thereby increasing the control capacity of the tube.

If electrodes be used which possess a resistance itself substantially equal to that of the discharge path, the divergency of the electrodes can be dispensed with and the electrodes disposed parallel to each other. Both types of tubes are suited to the reproduction of a record of the variable density type. Here the illuminated surf-ace of the cathode remains constant, only the intensity of the incident light being varied. This, however, also results in a variation in the electrons released and consequently in the ion current released by the unstable ionization which is in itself amply sufiicient to furnish the required high control capacity of the tube. In this case the anode may be as usual: it need not possess a high resistance of its own.

In Fig. 3, reference numerals 4s and 5! indicate the dense, non-homogeneous fields engendered at the anodes i5 and I! and which result in the unstable ionization, providing the voltage or potential of battery 2i remains below the sparking voltage and the light falls upon the cathode.

In Fig. 4, another suitable illustrative type of tube in accordance with the invention is shown, said tube comprising two auxiliary electrodes 53 and 55 in addition to cathode it and anodes i5 and H. In this form'of tube there is complete separation of working circuit and control circuit. A polarizing battery 2| is in circuit with a cathode 19 and the band or ribbon-shaped anodes I5 and H, the voltage or potential of said battery being kept below the sparking voltage. Upon illumination of the cathode ii) a current of electrons will be released, which in turn produces the unstable ionization at the anodes l5 and H. The resulting path of discharge touches in its passage the auxiliary electrodes 53 and 55 and thus forms an inertialess contact bridge between said auxiliary electrodes 53 and 55 which closes the working current circuit 51. Control of the working current circuit 51 may be effected either by variation of the density of the discharge, a denser discharge forming a contact bridge of less resistance, or by shifting of the discharge, for

example, in correspondence to a sound record of the indented or notched types or of the type in which the sound fluctuations are recorded in the form of a sinuous line. If the latter type be used the auxiliary electrode must possess a resistance itself of substantially the strength of the partial length of the path of discharge involved. As in this instance the auxiliary electrodes can be placed in relatively close proximity to each other, the resistance of said auxiliary electrodes can be kept within much closer bounds than is necessary with the type of tube shown in Figs. 1 or 2, in which the working'current flows from one main electrode directly to the other. The potential difference across the ends of the loading resistance 59 may be conducted directly to the point of consumption, or first to an output reinforcing tube. As the tube resistance is relatively weak in the working circuit it is possible to include the primary coil of a transformer in the working circuit instead of a coupling resistance.

I am aware that my present invention may 'be carried out and embodied in other specific forms from those herein described without departing from the spirit or essential attributes thereof, and I therefore desire the herein described embodiments of said invention to be considered in. all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

I claim:

1. A gas filled photo-electric tube comprising a light sensitive cathode of extended superficial area and an anode consisting of a very thin band positioned opposite said cathode and having its thin edge turned toward said cathode.

2. A gas filled photo-electric tube comprising a light sensitive cathode and an anode positioned in non-parallel relation relative to said cathode and consisting of a very thin band having its edge turned toward said cathode.

3. A gas-filled photo-electric tube comprising a cathode and an anode disposed in non-parallel relation relative to each other, said anode presenting two relatively thin bands between which a ray of light is to. be directed upon the cathode.

4. A gas filled photo-electric tube comprising a light sensitive cathode of extended superficial area and an anode consisting of a relatively thin band positioned opposite said cathode and having its' edge turned toward said cathode; and a plurality of control electrodes.

WILI-IELM BARSTIES.

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