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Feb. 22, 1938. A. KAROLUS 2,109,198 TELEVISION APPARATUS Filed March 23, 1935 AUGUST KAROLUS BY 7%. gm» ATTORNEY Patented Feb. 22, 1938 2,16%,198 UNlTED STATES FATEN'E‘ GFFIQE 2,109,198 TELEVISION APPARATUS August Karolus, Leipzig, Germany, assignor to Radio Corporation of America, a corporation of Delaware Application March 23, 1935, Serial No. 12,536 In Germany March 26, 1934 5 Claims. This invention relates to television apparatus and to the method of transmission and recep tion of television signaling impulses. The trans mission apparatus herein disclosed is of a type 5 which is particularly adapted for use in conjunc tion with the receiving apparatus shown and de scribed in my copending application Serial No. 15,156, ?led April 8, 1935 (?led in Germany as Serial No. K.l33,879 on April 19, 1934) although 10 it is to be understood that the disclosure is in no way limited as to the particular form of the cooperating receiver device. The invention is predicated upon the suppo sition and fact that for satisfactory television work, the ?neness of scanning or resolution of the picture must correspond to a ruled plate or screen of 100 picture lines or better. In addi tion to developments in this direction designed so as to ful?ll these requirements so far as the 20 equipment and the transmission methods are concerned, i. e., of adapting ever increasing line numbers, a, marked expansion in the transmission range of electric telegraph channels has of late become noticeable. It is a fact that both on ultra 25 short waves as well as on special cable lines fre quency bands of 106 cycles may be transmitted over satisfactory ranges of distance without the requirements respecting the provision of ampli (Cl. 178-71) This invention is based upon the last mentioned fact, and it is concerned with a television system in which, in accordance with what precedes, the picture modulation is conveyed from the sending to the receiving apparatus over a single modu 5 lated carrier wave or over a single conductor, Whereas at the sending or at the receiving points, or at both places, if necessary, simultaneous scanning and re-creation, as the case may be, of a multiplicity or plurality of picture elements takes place. What is thus secured, on the one hand, is such a great Working safety and re liability in transmission that it would be inob tainable in paralleling several telegraphic chan nels because of the dif?culties associated with 15 the balancing of the same. On the other hand, because of the multiple scanning, it will be possible to transmit scenes and pictures of lower luminosity or with a greater line division than has heretofore been the case, while so far as reception is concerned, there are available the advantages residing in greater lu minosity of the televised picture and in ?ner screening of the same. In fact, it is only in this manner that in the scanning, for instance, of 25 living or moving persons the ?neness of scan ning which is nowadays demanded becomes feas ible at all. It is, fundamentally speaking, known in the art of television to subdivide the entire picture 30 ?er means being unduly severe. This fact places 30 a different aspect upon the future and devel opment of the television problem. In the past, limitations were ‘imposed upon every television development by the restricted frequency transmission range of telegraphic 35 channels, and the ?neness of scanning, or in other words, the number of picture lines, had to be adapted to these resistance conditions. Hence, it was not usually feasible to go beyond com voltages generated in them is accomplished in time sequence. However, in the arrangements previously suggested for this purpose serious dif ?culties arise inasmuch as, without exception, paratively coarse screens. With these coarse 40 screens it was not any too difficult to transmit into an uninterrupted series or sequence of cur- 40 area or a single picture line so that each area is associated with a separate photocell and then to illuminate these cells simultaneously, while the evaluation of the photoelectric currents or they cause the conversion of luminous values objects of moderate luminosity and to insure ad rent impulses directly from the photo-elements. equately bright received television Inasmuch as the voltages thus becoming active and operative, especially where the luminosity or brightness of the picture is poor, turn out to be extremely low, it follows that the stray or in- 45 terference level is comparatively high. On the other hand, in case of a so-called picture mosaic, the high frequency of line change-over presup pictures. When the demand for substantially ?ner screens became acute and inescapeable, it proved nec essary in view of the unaltered or unimproved transmission ranges of telegraphic channels to connect a plurality of these in parallel so that a portion or component of the picture could be transmitted over each of these separate ~chan~ 50 nels. Today, however, there are means and ways known in the art making it possible to transmit on a single modulated carrier wave or poses a low coupling resistance in the input of the modulation ampli?er and thus, so far as the 50 transmission process is concerned, an unfavorable relationship between the useful or working am over a single cable conductor the frequency band of a picture divided almost into any desired ?neq 55 ness or any desired high number of lines, plitude and the stray or interference level, not to mention this circumstance that for arrange ments of this sort it is, for the time being, still 55 2 2,109,198 impossible to insure adequate uniformity of pho toelectric responsiveness throughout the whole line sequence by simple ways and means. The present invention has therefore as one of its primary objects that of obviating these di?i culties and defects by reason of the fact that the scanning of luminous values occurring in time sequence along a picture line composed of indi vidual photocells is not brought about with the may by means of subsequent ampli?cation be raised to such amplitudes that, even in the pres ence of lower brightness of the original picture and or" marked irregularity of sensitiveness in the p many scanning or pick-up photocells, very powerful and balanced picture impulses lying away above the stray level are obtained. Because of the time-paralleled operation of the 29 many photelectric cells the maximum frequency vanishingly low individual potentials of these cells of brightness change amounts then to only 1/t, 10 themselves as is usually the custom, but rather are brought about by an ampli?er associated with each separate photocell so as to secure sufficient whereas in the mode of scanning heretofore cus tomary in the art it was p/t. As a result, it is feasible to raise the grid resistances on which preliminary or input ampli?cation of the signal amplitude. In this connection, far more favor able conditions respecting the stray or interfer the various cells operate, seeing that because of the reduced frequency of the photoelectric cur rent harmful circuit capacitances no longer play ence level as well as utilization of light are ob the same harmful part as shunt resistances. tainable, not to speak of the chance of equalizing Hence, the control voltage of the photocells is already multiplied at the input grid of the 10 many ampli?ers, though it will be raised to useful values faithfully reproducing the brightness val sensitivity disparities of the photoelectric cells 20 simply by adjusting the sensitiveness or response of the various ampli?ers. The invention has been illustrated according to two preferred forms thereof by the accompanying drawing wherein Fig. 1 shows one suitable ar rangement for accomplishing the aims and ob jects above set forth, and Fig. 2 shows a modi?ed arrangement. According to the invention, the optical trans mitter causes the picture to be moved line by line over a linear row of photoelectric cells extending in the direction of the lines scanned and com prising a plurality of constituent photocells, the number of the latter being equal to the number of picture elements or elementary areas contained 35 in a full line. For the purpose of considering the method of television in this case the number of separate points to be scanned may be denoted by the letter in. In order that the original picture may be scanned or resolved in the said manner, there is used, for instance, a projection device in conjunction with a mirror wheel which directs the light from each elemental strip of the sub ject to be scanned so that all of the p many points or “picture points” of a line are simultaneously scanned photoelectrically with the result that 29 many current and voltage values are produced. These current and voltage values must be evaluated and utilized for the control of the trans mitter during the length of time t available for scanning each picture line. For this purpose, a high speed inertialess switch means, Within time interval t, picks up p many different voltages (in su?iciently ampli?ed form) and thus converts the transmission values available in time sequence into a series of corresponding telegraphic im pulses. Between each photoelectric cell and the corre sponding scanning device which may be a switch photocell or contact of a cathode ray change-over 60 switch means or distributor, to be discussed later, there is interposed a single-stage or multi-stage variable tube type ampli?er having such a high grid resistance that the time constant of the input circuit is of the same order of magnitude as the line duration 15. By suitable adjustment of the gain of each ampli?er a compensation of the sensitiveness disparities of each or" the p many photoelectric cells is insured. This arrangement makes it feasible to cause the photoelectric e?ect produced from the picture point brightness, that is the luminosity of each elementary area of the subject, to be effective upon the various cells throughout the duration of a line t, with the con sequence that the picture signals or impulses, which in themselves are several times stronger, ues only by the variable or gain-controlled indi vidual ampli?ers provided at points further along in the system. The high speed switch free from inertia which is required both at the sending as well as at the receiving end according to this invention, which switch during the length of a line t picks up the transmission values of all elementary areas con secutively, may be of varied and different forms of construction. At the transmitter end of the system it is possible to cause an intense pencil of light of constant value to pass at a suitable rate of speed over a series of p many photoelectric switch cells which are conjugated to the p many scanning cells of the picture line or strip, i. e., the switches are suitably united with the output ends of the ampli?ers controlled thereby so that by becoming transmissive or conductive for cur rent as the pencil of light impinges thereon, vol 40 ume regulated or “dosed” voltage impulses which are proportional to the different brightness values of the p many picture elements along the line or strip of the picture result. These sequential con trol impulses act through a series resistance com mon to all of the 10 many discharge paths upon 45 the control grid of an electron tube which con— stitutes the input of the transmitter ampli?er. The releasing or scanning light ray pencil could be shifted over the lines by the agency of a mirror wheel arrangement of a kind known in the 50 earlier art. Other ways and means of operating a system of this type include substituting in the transmit ter apparatus a cathode ray pencil for the light ray pencil. This cathode ray pencil or beam, by 55 the aid of ways and means known in the prior art, is rotationally swept over a circular sequence or bank of circuit-making or closing contacts, the number of these latter equally the number p of elementary areas of the picture line. In a fundamentally similar manner the switching ar rangement, as hereinbefore described, causes the 60 conversion of the subsequently ampli?ed poten tials simultaneously created by the luminous ac tions in the 10 many scanning cells into a time 65 sequence of impulses to control the television transmitter. The switch action of the cathode ray pencil and photoelectric release action could also be combined in such a manner that the luminescence 70 produced by the influence of the impinging elec— trons in a phosphorescent surface is caused to act upon a bank or row of photocells disposed opposite the said screen. The preferable plan 75 2,109,198 is to guide the cathode ray pencil which is pref-. erably of constant and stable intensity along a circular path, it, of course, being the plan also that the photoelectric cells are to be disposed along the ensuing luminous track. However, only a few of the conceivable and possible ways and means adapted to insure high speed scanning or pick-up of line values have been mentioned in what precedes. In other 10 schemes for instance, the p many switch photo electric cells, or the p many switch contacts of the cathode ray tube could be replaced by p many blocked electron tubes operated from the anode end by the ampli?ed photocell potentials. In such a case the control grids of the electron tubes 3 Upon the switch photocells, in the direction of the arrows a, b, c", d . . . r is caused to impinge the constant light ?ux of the optical change~ over switch in such a way that the excita tion propagating in the sense of the horizontal C1 arrow A returns cyclically at a periodicity t, that is the length of a line of scanning. The photo electrical discharge current impulses consecu tively recurring at like time intervals t/p and being of variable amplitude flow through the joint 10 resistance l5 and the return lead it, and the drop of potential caused across the resistance 15 controls the input tube It of the ampli?er in the transmitter (not shown). In a modi?ed form of the arrangement shown 15 would have impressed thereon in time sequence by Fig. 2, the switch photocells l’, 2', 3’, etc., brief unlocking positive voltage impulses. This might be accomplished, for instance, by the aid have been replaced. by the closing paths of a ro of a surge or traveling wave whose transit time 20 along the p many control grids is equal to t, and whose periodic production is synchronized with the picture resolution or scanning. If the electron tubes are equipped with two multiplica tively acting control grids, as would be the case with the usual form of hexode tube, then the p many second control grids, in the presence of constant plate potential, may be fed directly or through ampli?ers, with the “brightness poten tials” created by the 11: many scanning cells. 150 These will then govern the intensity prevailing at any given instant of the plate current impulse being ampli?ed at the same time in accordance with the ampli?er function of the tube incidental to the switch process, whereas the p many ?rst tating cathode ray pencil 25, while the arrange ment of the input of the transmitter ampli?er, that is, the part comprising the conductor l3, 20 the resistor l5 and the tube It, has remained unaltered. In this ?gure the numerals 9, H), ll, 52 . . . again denote the output resistances of the amplifiers 5, 6, ‘l, 8 . . . (not again shown by Fig. 2) across which the photoelectrically con 25 trolled brightness voltages of a line of elementary areas or picture points result. The free ends of the resistances are united with the 10 many elec trodes ll, l6, l9, 29 . . . of the cathode ray tube‘ to which are coordinated p many grid-like coop site the former. These systems act like p many Faraday cages, the interior spaces of which are rendered conductive sequentially by the cathode ray pencil 25 penetrating therein. Each of these 35 grids merely ful?ll the function of opening and closing or blocking the discharge path. All of individual cells incidentally sets up a surge or the discharge current surges exercise a control ling action through a joint series resistance upon impulse of current, the intensity of which is a function of the fall of potential prevailing at a the input tube of the transmitter ampli?er. The given instant across the resistance (9, I0, ll, 40 tube arrangement as here described, however, is 30 erating electrodes 2!, 22, 23, 24 . . . placed oppo 52 . . .) coordinated thereto. 40 Having thus described the invention, what is capable of a great many modi?cations in accord ance with rules and laws known in the art. The re-conversion at the receiving end of the is the following: sequence of impulses sent from the transmitter end into a time parallel control of 110 many chan translating elements positioned in line formation, 45 nels, fundamentally speaking, is accomplishable an ampli?er system connected with each. of said in accordance with the same scheme as at the elements, said ampli?ers each having a time con stant circuit associated therewith in the order of the time duration of each scanning line, a load circuit, and an inertialess high speed switching 50 sending end. In the receiver system a switch pencil which is modulated in its intensity by the electrical signals corresponds to the switch pencil of constant intensity at the transmitter end. Reference may now be had more speci?cally to the forms of the invention exempli?ed and schematically illustrated by Figs. 1 and 2 of the drawing. Considering ?rst Fig. 1, the pick-up photoelectric cells are indicated at l, 2, 3, 4 . . . p. The varying light intensities of the projected picture line or strip are caused to im pinge on these cells in the direction of the ar iii) rows. The numerals 5, 6, ‘l, 8, etc., indicate the p many separately‘ regulable ampli?ers, while numerals 9, 10, ll, l2, etc., represent resistances whose voltage fall is governed by the excitation of the cells l, 2, 3, ll . . . , while additional ca pacities, shown in dotted outline, if desired, may be shunted in relation to these resistances 9, Hi, II, it . . . In the case of Fig. 1, the assumption is made that the high speed scanning of line values is eiTected by the aid of light. For this purpose, claimed and desired to secure by Letters Patent 1. In a television system, a plurality of light device for sequentially connecting each ampli?er with the load circuit. 2. In a television system, a plurality of light translating elements positioned in line formation, an ampli?er system connected with each of said 55 elements, each of said ampli?er systems having a time constant circuit associated therewith in the order of the time duration of each scanning line of the subject of which an electro-optical representation is to be produced, a load circuit, a 60 second light translating element serially con nected with each of said ?rst-named light trans lating elements, and an inertialess high speed switching device for sequentially connecting each 65 ampli?er with the load circuit. 3. The television system claimed in claim 2 wherein said inertialess high speed switching de the free ends of the resistances 9, 16, ll, l2 . . . vice consists of a light ray pencil caused to sweep across said second-named light translating ele 70 ments. 4. The television system claimed in claim 1, with single-pole through-connection are united with the p many switch photocells L8, 2’, 3', vice consists of a cathode ray tube. 4' . . . 10' whose active cathodes are placed op posite the anodes connected together by lead l3. wherein said inertialess high speed switching de— 5. A television transmission system comprising a plurality of light translating elements positioned 75 4- 2,109,193 in line formation, an ampli?er system connected with each of said elements, a time constant circuit associated with each of said ampli?er systems having a time constant in the order of the time duration of each scanning line, a load circuit, a second light translating element connected in series with each of said amplifying devices and the load circuit, said second-named light trans lating elements being arranged in a closed cir cular path, and an electronic‘ tube for sequen~ tially illuminating each of said second-named light translating elements for connecting the ?rst-named light translating elements and the shielded ampli?ers in sequence With the load circuit. AUGUST KAROLUS.