US2156932A - Signaling system - Google Patents

Description

'May 2, 1939- R. URTEL SIGNALING SYSTEM Filed May 20, 1936 Adi-143K v14 .4 SA

M M n m Fur/g0 V/ N w L u R Y B Patented May 2, 1939 UNITED STATES PATENT OFFICE SIGNALING SYSTEM Germany Application May 20,

1936, Serial No. 80,691

In Germany April 1, 1935 9 Claims.

The invention is concerned with a picture scanner, more particularly a scanner adapted to television Work, in which capacities are charged up in accordance with the brightness of the constit- 5 uent or elementary picture points or units, during a length of time which is greater than the time being available for the utilization of the charges, and in which utilization is insured by the carrying off of the stored-up charges. Ac-

l cording to the present invention, the initial or original state of charge of the capacities, in other words, the state of charge which is established or restored after the carrying away of the accumulated charges is to be determined by means in 1.1 parallel relation to the capacities which becomes conductive or transmissive for current upon the potential across the capacities having reached a pre-arranged value.

A number of practical embodiments of the invention shall be explained in what follows by reference to the attached drawing; in which Fig. 1 shows diagrammatically one embodiment of my invention; 7

Fig. 2 shows schematically a simplified portion of Fig. 1 for explaining the operation of my invention;

Figs. 3, 4 and 8 are certain curves for aiding in the explanation of my invention;

Fig. 5 shows another embodiment of my invention, diagrammatically, and

Figs. 6 and '7 are simplified portions of the embodiments shown in Fig. 5, for aiding in explaining the invention.

Referring to-Fig. 1, Ill-l3 denote the photoelectric cells co-ordinated to the constituent picture elements contained in a line of the picture to be televised and upon which in sequence all lines of the picture are projected, say, by the aid of a suitable mirror arrangement. M to II designate a number of condensers, and in each of these the right-hand plate is united with cathode K of one of the photo-cells Ill-I3. In parallel relation to the condensers M-I'l, respectively, are the rectifiers l82l. In all of these rectifiers, the anode has been denoted by A and the cathode by K. All of the rectifiers are connected in series with a joint source of D. C. voltage 22 and also in series with a resistance 23. The auxiliary voltage which is commonly supplied for all of the photo-electric cells is designated by 24.

Fig. 1 shows in addition a cathode-ray switch which comprises a cathode K and a plurality of anodes A10, A11 etc. These anodes are united by way of wires 26-29 with the right-hand plates of condensers I4-I'l. The source of anode potential for the cathode-ray switch 25 is designated by 30. The circuit arrangement for the other photocells, condensers, etc., which are co-ordinated to the other picture units contained in the line, should be imaged to be represented in the same manner as for the photo-cells Iii-I3, condensers i441, etc., being indicated in Fig. 1 merely by the beginnings of leads 3l-38.

To explain more clearly the operation of the arrangement shown in Fig. 1, an elementary circuit scheme shall be examined, that is to say, a scheme showing the course of the current for charge-up in accordance with the brightness or the shading value of an elementary picture point, and the same scheme for the utilization of this charge. Such an elementary circuit scheme is illustrated in Fig. 2' for photocell l0, Fig. 1.

Referring to Fig. 2, l0 denotes the photocell with cathode K and 25a designates a cathoderay tube comprising cathode K and anode A10. A condenser is designated by I4. In parallel relation thereto is a rectifier H8 in series with a source of biasing voltage 22 and a resistance 23. The plate potential for the photocell Ill and the cathode-ray tube 250. is designated by 24 and 39, respectively. First the assumption shall be made that the photocell I0 is not subjected to luminous action so that the photocell will not cause any charge at the condenser I4. Hence, the condenser I4 is only charged by the electron current in tube 25a 'in such a way that its lower plate assumes a positive potential in reference to its other plate.

However, this potential can be built up to such a value as Will correspond to the current-voltage characteristic of the rectifier l8 together with its biasing voltage source 22 which is illustrated in Fig. 3, in other words, only to a value U0. Any charge flowing to the condenser 14 over and above that value will be drained (allowed-to leak away) through the rectifier l8.- Below value U0, however, no drain of charge occurs any more inasmuch as the branch parallel to the condenser will not transmit current for potentials at condenser |4 less than U0. In other words, as long as the photocell is not illuminated, the charge across the condenser l4 shows time constancy in spite of the fact that the cathode-ray pencil in tube 25a strikes the anode A10 merely intermittently. The steady voltage trend at condenser I4 is shown in Fig. 4 for the time interval between t1 and 152. When the photocell I0 is illuminated there will flow in the circuit comprising cathode K, anode of photocell, source of potential 24 and condenser M an electronic current whose intensity is a function of the illumination acting upon the photocell. This electron current causes the bottom plate of condenser I4 to be charged up to a potential being negative in reference. to that of its upper plate. This charge occasioned by the photo-electric cell rises with the time and thus diminishes the voltage U0 across the condenser l4. The decline of potential at the condenser is also shown in Fig. 4 during the time interval t2t3. Voltage U0 shall be assumed to be low in comparison to voltage 24 so that there must be a linear rise between t2 and is. At the instant in the cathode ray beam in tube 25a will again impinge upon the anode A10 and restore the charge of the condenser to the value U0 inside a very brief time, that is to say, during the time elapsing at t4.

The shape of the potential curve between 3 and i4 is again rectilinear since also voltage 30 is high compared to voltage U0. At the instant t4 the rectifier l8 becomes again conductive for current so that during the balance of the time for which the cathode-ray pencil strikes anode A10 in tube 25a a steady and constant current will flow through the rectifier 18, the source of voltage 22 and the resistance 23. Suppose that at instant i the cathode ray pencil again leaves the anode A10 so that a new condition of charge of the condenser I4 may occur in accordance with a possibly altered value of brightness or shading of the picture element to which photocell i0 is coordinated. Assuming that this shading value differs from that prevailing at $2, s, then, at instant 6 there prevails across the condenser 14 another voltage than at instant is so that voltage Uo at this condenser will be attained again inside a shorter or a longer period of time during the interval 3 i4 so that also the duration for which the electronic current of tube 25a, is conducted through the resistance 23 will be different.

Fig. 4 thus shows that the current flowing through the resistance 23 is a'function of'the intensity of the illumination acting upon the photoelectric cell Ill. The process such as before described happens in reference to the other photo-cells of each line in the same manner, only in the presence of a different phase shift. In other words, each one of the condensers l4, [5, etc., Fig. 1 is charged in accordance with the brightness of each picture unit, and this during a time which is greater than the time available for the utilization of the charge. The utilization moreover resides in, or is predicated upon, the carrying off of the accumulated charge, in this manner that the circuits connected in parallel to the capacities with the rectifiers [8, I9, etc. becomes transmissive or conductive for currents in the presence of a definite voltage, that is to say, the voltage U0, with the consequence that the duration of the current impulses which flow through the resistance 23 is altered with the brightness or shading value of a given picture element. In other words, the voltage drop across the resistance 23 may be used for the modulation of a transmitter apparatus by Ways and means known in the art.

Another practical embodiment of the invention is illustrated in Fig. 5. This scheme differs from the one shown in Fig. 1 by that in parallel relation to the condensers, grid tubes 3942 operating with a negatively biased grid are provided. Tubes of this kind also have a current-voltage characteristic of the kind shown in Fig. 3.

The embodiment Fig. 5 comprises secondary emission photo-electric cells 4346 with cathode K, anode A and secondary anode SA, rather than the photo-cells I0I3 shown in Fig. 1; and these cells operating with secondary electron emission by way of a joint source of voltage 41 are connected with the connecting wire of the left-hand condenser plates. An elementary circuit corresponding to the one shown in Fig. 2 is indicated in Fig. 6. The same shows that the charge at the condenser I4 set up by the secondary electrons of the photo-cell 43 so far as sign is concerned corresponds to the condenser charge in Fig. 2. In other words, the explanation regarding the shape of the current given by reference to V Fig. 4 holds good also for Fig. 6.

What is to be noted also is that the biasing voltage for the rectifiers [8 Fig. 1 could be also chosen as indicated in Fig. '7 for the elementary circuit which corresponds to Fig. 1. The corresponding current-voltage characteristic of the rectifiers is shown in Fig. 8. The charge of the condenser l4 for which the rectifiers will conduct current, corresponds to the point P of the negative abscissa axis, while the voltage of the biasing voltage source 22' corresponds to the distance of this point from the zero or origin of the coordinates.

What may also be noted is that the production of the potential U0 in Fig. 4 at the condensers may not only be effected directly by means of a cathode-ray switch, but also, for instance, in this manner that a cathode-ray switch controls amplifier tubes which raise the voltage of the condensers to a point where the parallel branch becomes conductive for current. The charging of the condensers to value U0, finally, could be accomplished also by the aid of some suitable switch mechanism, for example, by the agency of a mechanical switch.

Having described my invention, what I claim 1. The method of signaling, which comprises cyclically storing energy from a source of potential, limiting the value of the stored energy to a predetermined value of potential, maintaining the value of stored energy constant for a time period, said time period being an inverse function of the amount of energy stored, and discharging the stored energy at a rate determined by the intensity of light energy.

2. The method of signaling which'comprises cyclically storing energy electrostatically from a source of potential, limiting the value of the stored energy to a predetermined value of potential, maintaining the value of stored energy constant for a time period, said time period being an inverse function of the amount of energy stored, and discharging the stored energy in accordance with the intensity of light energy.

3. The method of signaling which comprises developing a plurality of electrostatic charges, limiting the charges to a fixed common value, maintaining the value of the individual charges constant for a time period, said time period being an inverse function of the value of the individually developed charge, sequentially discharging the individual charges, controlling the discharge in accordance with the intensity of different light energy, and subsequentlyrestoring the charges totheir original value.

4. The method of signaling which comprises developing a plurality of electrostatic charges, limiting the charges to a fixed common value, maintaining the value of the individual charges constant for a time period, said time period being an inverse function of the value of the individually developed charge, sequentially discharging the individual charges at rates varied in accordance with the intensity of different co-related light intensities, subsequently restoring the charges to their original value, and deriving a useful output from the charging current.

5. In combination means for cyclically storing energy from a source of potential, means for limiting the value of the stored energy to a predetermined value of potential, maintaining the value of the stored energy constant for a time period, said time period being an inverse function of the quantity of energy stored, and means for sequentially discharging the stored energy at a rate determined by the intensity of light energy.

6. In combination, means for cyclically storing energy electrostatically from a source of potential, rectifier means for limiting the value of the stored energy to a predetermined value of potential, maintaining the value of the stored energy constant for a time period, said time period being an inverse function of the quantity of energy stored, and photoelectric means for sequentially discharging the stored energy in accordance with the intensity of light energy.

7. In combination means for developing a plurality of electrostatic charges, means for limiting the charges to a fixed common value, maintaining the value of the individual charges constant for a time period, said time period being an inverse function of the value of the individually developed charge, secondary emission means for sequentially discharging the individual charges in accordance with the intensity of different corelated light energies, and means for subsequently restoring the charges to their original value.

8. In combination, means for developing a plurality of electrostatic charges, rectifier means for limiting the charges to a fixed common value, maintaining the value of the individual charges constant for a time period, said time period being an inverse function of the value of the individually developed charge, electronic means for sequentially discharging the individual charges in accordance with the intensity of different 00- related light energies, means for subsequently restoring the charges to their original value, and means for deriving a useful output from the charging current.

9. In combination, means for developing a plurality of electrostatic charges, thermionic means for limiting the charges to a fixed common value, electronic means for sequentially discharging the individual charges in accordance with the intensity of difierent correlated light energies, means for subsequently restoring the charges to their original value, and means for deriving output energy from the charging current.

RUDOLF URTEL.

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