US2560585A - Cathode-ray signal to voltage translating devices - Google Patents

Description

B. M MYLLAN July 17, 1951 CATHODE RAY SIGNAL TO VOLTAGE TRANSLATING DEVICE Filed April 6, 1948 FIG. I

SWITCH cmcu/r compoz.

ourpur C ODING 8 CYCLING CIRCUIT INPU 7' BEAM POS/ TIO/V lNVEA/TOR 13. Mc M/LLA/V Arrow/5P Patented July 17, 1951 2,56058'5' CATHODE-RAY SIGNAfi-TO'VOLTKGE TRANSLATING DEVICE s- Bell Telephone Laboratories, mcd iiiratea', New

York; N; Y., a corporation of New York Application April-6, 1948,-=Serial-No ."19,299

90mins (c1. sie e-i This invention relates to cathode ray devices aii'dlmo're particularly to -such devices ofj'the general type disclosed in the: application Serial No 14,014, filed March 10} I948, of J Pierce', Cl E; Shannon and J Tukey, .fortranslating. signals into accurately, reproducible voltages.

*In devicesot thegeneral type to which this in e ntionflpertains the beam of a: cathode ray device is deflected: accordance with signals to be t anslated end the potential across-the beam-defleeting element,.. for exampledeflector plates is precisely and automatically adjusted byactionof afeedbaele-circuiti between the beam target and the deflecting.v element, so that-each input gnalof amplitude: within a prescribed range is translated; into an output voltage across the defleeting: element-' of fixed and preassign'ed -ampli- 't'udes This output-voltage may be utilized tocon trol the beam deflection in one or moreassociated' cathode rayrdevices.

Qnex generalobjec-t otthis invention to im: p'ro' e.-cathode my translatingzfdevices o'f the 'type' e'described More specifically; obj eats: of this inventionare worm e part, =to facilitate: thectmvrsion ot s gnals into voltages of prescribed amnlit'iide="aiid tibwifilfllfOV' the ai-ccuracy? of resolutionof signals into voltages.

in}: one illustrative embodiment of this invention -acathode ray discl iarge device comprises a;-

secondaryelectron emissive' target; a': collectorelectrode for receiving;secondary'elec'trons eina nating from the target, an electron gun for 'pro jec-ting; an ele'ctron beam against the "ta;rget ,-aiid deflection means: for example deflector plates, efiective-when'energized-to deflect the beam A- f'dback' one: dimensionalong; the": ttrrg'get'; coupling: is provided f between 1 the collectoi elee trodea-nd deflection-means for COIlflI-Glllh'glthgde:

fi'ectingdvpotential inacordance' with' th'e position ofth'eibeam In accordance with one feature of this m'vm tion; means are-providedfor selectivelyfestablish any? oneot: 2; plurality? of paths for flow" of secondary electrons fromthe targetto 'the col-lee tor electrode, 7 accordancemitn the-ultimately desired beam; position; whereby the feedbackcoupling .i s efiectiv'e onlyt when-the beam' is- -a'tor immediate-proximity,tome-desired position More-specifically, accordance; with one featureofi this invention, a plurality of" parallel members; extending; norm-e1 to the direction" ofbeem -defie-cticn;jareproviad' a'djacen tthe target eltliddetb dfin aI -IQWOf- PQWS'OFWi'Xi'dbW? through which' secondary; electrons from the target-may pass to the collector electrode. Each openingor window iscontrollable to permitor prevent passage of secondary electrons there-- through,- by control of the potential ofthe two parallelmembers-bounding the window. Furthermore,1 eac-h openingor window correspondsto a respectiveone of-a pluralityof possible beam po-' sitions and,- consequent1y,- isassociated with a respective output voltage across the" deflection means.

Inaccordance withanothet feature of this in-' vention; the severalwindow bounding= members are associated electrically in groups so that any openingzor window"ma-y be opene'd to 1::ermi-t-p'as-' sage of se'condaryelectrons by application we of an appropriatepotential to'two of'the'groups'; This permits selectiveindividual openingof the win dows by. application of potentials to the groups in 'acc'ordarice with a" preassigried code: v y

In accordance with a; further feature-'of the in; vention-,'-. deflection oi the'-beani in response to Sig-m1 is -efi'e'eted solely by operation of the fee 1" back 01 c'uit. Ingone": spi'acific ernbodiine'nt; the" mpli-fy:suchfidevices and apparaitus of which it? Mantis-"directed initially bejiond one end df'tli'e eielo'iv theb sm defie'cteutowaru uiew do to a theiethr ugh; concomitantly witfi th moubrt'o the beam; thefconcritiatio' 1 lattei may be 'inCFeaSe'dso that during" t finala'djustinent of the beain'po'sition} the beaiii iSSHai'pIvfocfisSedF p v The invention a q the above notedan'd" oui r f retui es tuereof Fig is apeispective view' 'illustratingtthe-con sti 'ii'c'ti and association of-the target el'eetrode and? window defining elements Rfiiiilg DYJW t0 th drawing; th cathode rai device illustrated in Fig. 1 comprises an evacuated enclosing vessel 20 at one end of which an electron gun is mounted. For simplicity of illustration, the gun is shown as comprising an indirectly heated cathode 2I and a cylindrical focus control electrode 22. Mounted at the other end of the vessel is a secondary electron emissive target electrode 23', which may be'a plate the surface of which toward the electron gun is coated with a material having a secondary electron emission coefiicient of greater than unity. A cylindrical or rectangular frame-like collector electrode 24 is positioned opposite and in axial alignment with the target 23. Between the gun and collector electrode are a pair of parallel deflector plates 25.

Flow of secondary electrons from the target electrode 23 to the collector electrode 24 is subject to selective control by an assembly of a plurality of electrically individual, parallel plates or strips of electrically conductive material which extend normal to the target electrode and define a group of substantially identical windows between thetarget and collector electrodes. In the specific device shown, eleven plates or strips I to II, inclusive, forming ten windows are .provided. Adjacent plates or strips are spaced a distance somewhat greater than the diameter ofthe focussed beam projected from the electron gun and all the strips are positioned immediately adjacent the-target electrode 23.

The operation of the plates or strips will be understood from the following considerations. The electron beam from the un upon impinging upon the target causes the release of secondary electrons. These electrons, if the plates or strips were absent, would flow tothe collec-.

tor electrode 24. However, these plates or strips, depending upon the potential thereof relative to the target electrode 23, serve to either permit or prevent passage of the secondary electrons to the collector electrode. Consider any pair of adjacent strips. If the potential of either strip or of both strips in this pair is substantially different from that of the target electrode, secondary electrons cannot pass through the {space or window bounded by this pair. For example, if --either strip or both strips of this pair are highly positive relative to the target, secondary electrons will be collected by the strip or strips. If either or both strips are highly negative relative to the target, secondary electrons emanating from the target will be repelled thereto. If, however, two adjacent strips or plates are at substantially the same potential as the target, these together with the target bound a substantially field free region through which secondary electrons canpass to the collector electrode 24. Thus, by proper energization of the strips or plates any window may be opened to permit flow of secondary electrons therethrough, while all other windows are, in efi'ect, closed and passage of secondary electrons is prevented.

It is evident that individual excitation of the multiplicity of plates or strips to effect selective control of the windows would entail use of 'a large number of leading-in conductors. In accordance with one feature of this invention, the number of such conductors requisite is substantially minimized. In the specific device shown in Fig. 1, the plates or strips are grouped in accordance with a two out of five code with five leading-in conductors A to E, inclusive. The specific connections are illustrated clearly in Fig. 3 wherein the lettered circles designate the leading-in conductors and the numbers adjacent a these circles designate the plates or strips con nected to the respective conductor.

It is evident from inspection of Figs. 1 and 3, that application of a potential substantially equal to that of the target electrode to any two of the conductors A to E will result in opening of only one of the windows to permit passage of secondary electrons. For example, if the proper potential is applied to conductors A and C, strips I, 6, II, 3 and I will be energized. Of these, only strips 6 and 1 are adjacent, and, consequently only the window bounded by these two strips will be opened. Similarly, if the potential is applied to conductors A and D, strips I, 6, II, 4 and ID are energized and only the window bounded by strips II] .and II will be opened. Thus, any one of the windows may be ,opened alone by application of the requisite potential to the two conductors connected to the strips bounding that window.

Although in the specific embodiment illustrated in Fig. 1 eleven strips forming ten windows are included, a different number may be employed. The grouping of the strips with the leading-in conductors to enable selective opening of any window by energization of two conductors will be in accordance with the following. If the number of windows w can be expressed generally as k(27c+1) where is is a whole number, then (2k+1) leading-in conductors will'be required. Let the vertices of a polygon having (2Ic+1) sides represent the conductors. Draw all possible chords of the polygon. Clearly, each chord represents a possible-combination of two out of (Zk-I-l). Connect the linear graph the nodes of which are the vertices of the polygon tered intraversing the path until the sequence is closed by connecting strip (10+ 1 to the starting conductor.

The process above outlined may be illustrated by reference to Fig. 3. Start at conductor A. The unicursal path then is traced over the vertices in the order A, B, C, D, E, A, C, E, B, D, A, and

the strips are connected to the conductors in the,

manner heretofore described and as indicated in the figure.

If the number of windows w is not of the form k(2k+'1),- where k is a whole number, a similarprocess of connecting the strips to the leading-in conductors is employed. Specifically, the smallest number w1 larger than 10 which is expressed inthe form k(2lc+1) is selected. The process I above set forth is then followed for the number 101 of windows. After the first (w+ strips,

bounding w windows have been accounted for,-

the construction is stopped. The connections thus indicated are employedfor the strips bound ing the desired w; windows.

The selective openingof the windows is utilized to control the positionof the electronbeam'and thereby the voltage appearing across the deflector plates 25. As shown in Fig. 1, the collector electrode 24 is maintained positive with respect; to the target electrode 23, as by batteries ,26 and 2'1, and is connected in .feedbacl; relation tov the. deflector plates25 by vvay of an 'amplifler 2.8.x.

vielso connected between the plates is a source vAssume that a potential is impressed between thedeflector plates 25 and that the beam is fo- -;cnssed, i. .e. that it is .of a diameter somewhat *lessthan the spacing between adjacent plates or strips. 1 If the feed back circuit .through theamil lifier 28 "were open, the beam deflection would I belinearly proportional to the deflecting voltage 'sdthat the beam position versus deflecting potentiahgraph would be a straight 45-degree line :asrOX Y Z inFig. .2. However, if the feedback :circuit :through the amplifier 28 is closed, the

graph is altered. Consider the case where a po- ;tentialzhaving a value between P3 and P5, such as to cause the bear to pass through the window between plates or strips 3 and (his applied between the deflector plates 25, and the strips -3 and dare at the potential such that secondary electrons flow from the target through the window noted to thecollector electrode. Assume that the amplifier .is so poled that the potential compo- .nent .due thereto impressed between the plates .25 .is :additive with respect to that due to the "source 2.9. Then, if the beam moved across the Windowiin question, the potential between the deflector plates would vary as illustrated by the curved part XMY of the graph in Fig.2.

Some pointsbetween M and Y, however, representfstable beam positions whereas points between .X and M are unstable beam positions. Thiswill-beapparent from a consideration of the relationship involved. If the beam is centered. at aposition corresponding to a point, say midway between M and Y, and the deflecting forces thereon are somehow disturbed so that the beam wouldmove .to the right, in Fig. 2, it is evident from this figure that such movement would result in -a decrease in the deflecting potential. Hence, the beam would :return to .its initial position. Similarly, if the :beam were disturbed and moved to the left, the deflecting potential would increase so :that the beam would return to its initial position. For points between X andM, however, a disturbance of the beam would result in a change in the deflecting potential of such sign asto'move the beam in the direction initiated by the disturbance. For example, if the beam were deflected to .a position near and to the right of that corersponding to point X, it would not be in equilibrium, for a slightm'ove to the right would result in an increase in the deflecting potential and consequently a further motion of the beam to the right.

Hence, it will be seen that for an applied potential between P3 and P4 between the deflector plates 25, the beam will come to rest at a position corresponding to a point between M and Y. .Now, inasmuchpas each beam position corresponds to a certain potential between the deflector plates, it will be appreciated that for an applied potential in the relatively large range between P3 and P4, theresulting potential appearing across the deflector plates will be within a much narrower range. The exact extent of the latter range will be determined by the amplitude of the feedback. In general, the greater the feedback the smaller is the range of resulting potential. In a well de- ;signed:.system, the potential appearing between the deflector plates may be constant within :1: one per cent for a range of applied deflecting potentials varying by of the order of ten per cent.

In one manner of operation of the apparatus illustrated in Fig. 1, the input is in theform .of pulses. Each pulse is resolved .into a potential of corresponding amplitude applied to the deflector plates 25 by way of the deflector circuit 29. .Also at the circuit 32, each pulse is coded to operate the .switch 3|) whereby theproper plates-or strips are energized .to open the window corresponding to the pulse amplitude. By virtue of the feedback action heretofore described, the beam position is adjusted automatically and the corresponding potential is established across the deflector plates 25. In other words, each input pulse is resolved into an output potential of amplitude determined'by .the amplitude of the input pulse.

In anothermanner of operation of the apparatus, feedback alone is utilized to produce'a deflecting potential across the deflector plates .25.. In this case, initially the beam is directed to .one end, e. .g. the lower, of the array of strips :andis somewhat .defooussed so that it is spread .over the target 23 but is sufficiently forcussed .thatany motion :of the beam toward an open window causes an increase in the secondary emission. The .input, then, comprises code groups of two pulses each. For each group, a corresponding window is opened and as a result secondar electrons flow to the collector electrode and a deflecting potential is produced across the deflector plates 25. Consequently, the beam movestoward the open window and the secondary electron current and, hence, the efiective deflecting potential increases. Thus, thebeam is moved to the open window and adjusts itself to equilibriumposition thereby to produce a potential, of amplitude corresponding to the input pulse group, across "the deflector plates.

Advantageously, concomitantly with the deflection of the beam .in response to an input pulse group, the focus control is operated to increase the beam concentration whereby the final adjust ment of beam position is obtained with the beam sharply focussed, i. e. is of a diameter somewhat less than the spacing between adjacent strips. Such focus control ma be effected, for example, by triggering of an RC circuit controlling the potential of the electrode 22, upon application of each input pulse group to the circuit 32.

Although specific embodiments of the invention have been shown and described, it will be understood, of course, that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the-appended claims.

What is claimed is:

1. Electron discharge apparatus comprising a secondary electron'emissive target, means opposite one face of said target defining a row of windows, means for projecting an electron stream against said one face of said target, a collector electrode opposite said one face, means for do fleeting said. stream along said row of windows, a feedback coupling from said collector electrode to said deflecting means and input means connected to said window defining means for en-. ergizing said window defining means to selectively open said windows individually for passage therethrough of secondary electrons from said target to said collector electrode.

7 2. Electron discharge apparatus comprising a secondary electron emissive target, means for projecting an electron stream against one face of said target, a collector electrode opposite said face, a plurality of electrode members adjacent said face and spaced to define a row of openings each of which is bounded by two adjacent electrode members, means for deflecting said stream in the direction to pass along said row of openings, a feedback coupling between said collector electrode and said deflecting means, and input means connected to said electrode members for selectively biasing any two adjacent electrode members at such prescribed potential relative to said target and collector electrode as to permit passage of secondary electrons from said target through the opening bounded thereby, to said collector electrode.

3. Electron discharge apparatus in accordance with claim 2 wherein there are lc(2k+1) openings, It being a whole number, and wherein said biasing means comprises meansconnecting said members electrically into (27c+1) groups in such manner that upon application of said prescribed potential to any two groups only one pair of adjacent electrode members will be at said potential.

4. Electron discharge apparatus comprising a target one face of which has a secondary electron emission coeflicient greater than unity, an electron gun for projecting an electron stream against said one face, a collector electrode opposite said one face, a plurality of parallel strip electrodes between said target and said collector electrode and defining a row of Windows, each window being defined b two adjacent strip electrodes, means for deflecting said stream in the direction along said row of windows, a feedback coupling between said collector electrode and said deflecting means, and input means connected to said strip electrodes for energizing said strip electrodes to selectively open any one of said windows for passage of secondary electrons from said target to said collector electrode.

1 5. Electron discharge apparatus in accordance with claim 4 wherein said energizing means comprises means connecting said strip electrodes into groups wherein no two adjacent strip electrodes are in the same group and said strip electrodes are arranged such that when a prescribed potential is applied to any two of said groups only one pair of adjacent strip electrodes is brought to said potential.

6. Electron discharge apparatus comprising a secondary electron emissive target, means for projecting an electron stream against one face of said target, a collector electrode opposite said face, means for deflecting said stream in one direction along said face, and means for resolving signals applied to said deflecting means into one of a number of potentials across said deflecting means, each of said potentials corresponding to a respective range of signals, each resolving means comprising electrode means adjacent said target and defining a row of windows arrayed in said direction, there being one window for each range of signals, means for selectively energizing said electrode means concomitantly with the application of each signal to said deflecting means to open only the window corresponding to the range in which the signal lies, thereby to permit passage of secondary electrons from said target to said collector electrode through the opened window, and a feedback coupling from said collector electrode to said deflecting means.

7. Electron discharge apparatus comprising a secondary electron emissive target, means for projecting an electron stream against one face of said target, a collector electrode opposite said face, a plurality of members adjacent said face and defining a row of windows for passage of secondary electrons from said target to said collector electrode, each window being bounded by a respective pair of adjacent members, means for deflecting said stream in the direction of said row, a feedback coupling between said collector electrode and said deflecting means, means for selectively biasing any pair of adjacent members at a potential relative to said target and collector electrode to permit passage of secondary electrons from said target to said collector electrode through the window bounded by the biased adjacent members, and means for controlling said stream to vary the focussing thereof, during the period of biasing of any pair of adjacent members, so that at the beginning of said period the stream passes through all of said windows and at the end of said period said stream is substantially focussed upon the window, bounded by the adjacent biased members.

8. Electron discharge apparatus comprising a secondary electron emissive target, means for projecting an electron stream against one face of said target, a collector electrode opposite said face, a plurality of members adjacent said face and defining a row of windows for passage of secondary electrons from said target to said collector electrode, each window being bounded by a respective pair of adjacent members, means for deflecting said stream in the direction of said row, a feedback coupling between said collector electrode and said deflecting means, means for controlling the focus of said stream, means connecting said members in interleaved groups such that upon application of potential pulses to any two groups only one pair of adjacent members will be energized, means for selectively applying to any two of said groups a potential such as to permit passage of secondary electrons from said target to said collector electrode through the window bounded by the two adjacent members energized, and means for energizing said focus controlling means so that initially said beam-is spread over said target and is brought to a sharp focus upon said window concomitantly with the application of said potential.

9. Electron discharge apparatus in accordance with claim 8 wherein there are k(2k+1) winclows, k being a whole number, and said members are connected into (2lc+1) groups.

BROCKWAY McMILLAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Rajchman Jan. 17, 1950

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