US1980150A - Television and like apparatus - Google Patents

Television and like apparatus Download PDF

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Publication number
US1980150A
US1980150A US596254A US59625432A US1980150A US 1980150 A US1980150 A US 1980150A US 596254 A US596254 A US 596254A US 59625432 A US59625432 A US 59625432A US 1980150 A US1980150 A US 1980150A
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United States
Prior art keywords
scanning
station
disc
image
apertures
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Expired - Lifetime
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US596254A
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English (en)
Inventor
Baird John Logie
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Baird Television Ltd
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Baird Television Ltd
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Publication date
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Publication of US1980150A publication Critical patent/US1980150A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/14—Systems for two-way working
    • H04N7/141—Systems for two-way working between two video terminals, e.g. videophone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising

Definitions

  • This invention relates to systems for the electrical transmission of views, scenes, objects, or optical images of the same to a distance, by means of wires, or by radio transmission;
  • 5 more particularly to television or like systems by which two or more persons situated at a distance from each other are enabled to see and hear each other simultaneously or selectively.
  • a disc at each station is provided with two concentric spirals of apertures, lenses, or the like, to serve respectively for transmission and reception.
  • synchronism is judged by the movement or appearance of the image on the receiving screen at either station,
  • the present invention it is proposed to employ only one channel of communication between the stations of a two-way or multiple-way television system, and to transmit intelligence from each station .discontinuously, the quiescent periods during which one of the stations is not transmitting intelligence being employed for the reception of intelligence from the otherstations of a group of co-operating stations of a multiple-way system and this form of transmission is utilized to provide an improved means, as hereinafter described, for obtaining synchronism between two stations, or
  • Figure 1 shows a complete two-way television system.
  • Figure 2 shows the form of scanning disc
  • Figures 3'and 4 show the relativepositions of the discs at the two stations.
  • Figure 5 illustrates the method of applying the image signals to the transmission line to obtain eflicient synchronizing.
  • Figure 6 shows a circuit, the use of which prevents the local image from affecting the local light-relay.
  • FIG. 1 illustrates, by way of example, a twoway television system incorporating a method of maintaining synchronism between co-operating scanning devices at the two stations in accordance with the present invention.
  • each station is provided with a rotary scanning device for the purpose of effecting traversal of an operator thereatand at the same time reconstituting an image for his benefit, according to practice well-known in the art per se.
  • element 2 is a scanning disc mounted upon the shaft of a driving motor 28 and provided with a double series, of apertures, each series conforming to a singleconvolution of a spiral to effect traversal according to practice very well known in the art, but the apertures of one series lying upon radii of the disc mid-way-between the radii upon which the apertures of the other series lie.
  • the radius of the outermost aperture of one series hereinafter referred to as the inner series is substantially less than the radius of the innermost aperture of the other series hereinafter referred to as the outer series.
  • the disc 2 is also shown, in greater detail, in Figure 2.
  • a light source preferably comprising an electric arc, 4, is provided, and co-operates with a condensing lens, 6, to illuminate with substantially even intensityan area 'of the disc 2 through which area pass the apertures of the inner series in ordered sequence during the rotation of the disc.
  • a projecting lens 10 which serves to focus an image of each of the apertures of the inner series in turn upon an operator 8 during the passage of the said aperture across the field on the disc illuminated by the are 4 in co-operation with the lens 6.
  • an element 20 Co-operating with the outer series of apertures in the disc 2 there is an element 20 comprising a glow discharge lamp of type well-known in the art having a flat rectangular cathode substantially' co-extensive in one sense with the pitch of the spiral to which the apertures of the outer series conform, and in the other-with the width, in the direction of motion of the disc 2, of an image to be reconstituted thereby.
  • a glow discharge lamp of type well-known in the art having a flat rectangular cathode substantially' co-extensive in one sense with the pitch of the spiral to which the apertures of the outer series conform, and in the other-with the width, in the direction of motion of the disc 2, of an image to be reconstituted thereby.
  • the glow discharge lamp consists preferably of a neon-filled tube in which the cathode glow is excited at current densities of and above. about 5 milliamperes over substantially the whole of at least one surface of the rectangular cathode.
  • a mask or shield 29 serves appropriately to frame those portions of the inner and outer series'of apertures which are to be' operative in scanning and reconstituting respectively.
  • a laminated toothed rotor of ferro-magnetic material 26 of the phonic wheel type adapted to co-operate with a stator or fixed field winding of any type known in the art.
  • the number of teeth upon the rotor corresponds to and is in a preferred modification of this invention, equal to the number of apertures in one series of apertures in the disc 2: the numbers of apertures in inner and outer series in the disc are, of
  • the disc at each of the co-operating stations is rotated at a speed of about 750 revolutions per minute, and the optical systems, including the are 4, the condensing lens 6 and the projecting lens 10 and their corresponding equivalents at the other station, are adjusted to yield a scanning beam in which the flux of radiation-is as large as possible.
  • the flux should be at least one third of a' lumen, and preferably as high'as two or three lumens.
  • This signal hereinafter referred to as the first image signal, is passed by way of a suitable thermionic amplifier 14 to a channel of communication 16, which may comprise a pair of wires, a radio link, a submarine cable, or any other suitable transfer means.
  • a channel of communication 16 which may comprise a pair of wires, a radio link, a submarine cable, or any other suitable transfer means.
  • the co-operatingstation of the two way system comprising elements respectively the same as and similarly positioned to, those at the station above described. From this co-operating station proceeds a signal (hereinafter referred to as the second image signal) of type similar to that derived at the station described above.
  • the mask or shield 29 is so designed that light can become operative in scanning the operator only for those periods'during which an aperture is within a prescribed portion of its ambit, which portion corresponds to half the distance between successive apertures of the inner series. That is, light is allowed to pass to the scanned area while an aperture is passing across the area 36 shown in Figure 2.
  • the strip-frequency fundamental of the incoming television signals is exactly 180 out of phase with that of the strip frequency of the locally derived signals: If, in addition, it is arrangedby suitably balanced amplification, that the amplitudes of the two components thus superposed 180 out of phase are substantially equal, we have the condition illustrated by the dotted curve of Figure 5c, in which the resultant of the two superposed strip-frequency fundamentals is shown to be a straight line-that is, a sensibly constant potential difference,-substantially Cor incident with the datum line that is, of sensibly zero value.
  • thermionic amplifier 18 to the neon tube 20, and also, by a branch circuit in shunt, to a circuit 24, which comprises a thermionic am-v plifier, preferably incorporating a circuit or circuits tuned approximately to the frequency of that component of the television signals which is numerically equal to the number of strips scanned at each station per second. It is, of course, impossible to obtain sharp tuning at such a low frequency because of the inherent resistance of the inductances employed, but this is an advantage, provided that the filtering action of the tuned circuits is adequate to elide components due to details of the configuration in the pictures transmitted.
  • This circuit 24 yields alternating current power to the field circuit associated with the toothed rotor 26, which, it will be remembered, is provided with thesame number of teeth as there are apertures in one of the spiral series of the disc 2, and therefore The nature of this condimaintains a fixed phase relationship with the locally generated strip. frequency component or v with the corresponding component of the incoming signals.
  • This phaserelatlonship may bereckoned as existing between the locally derived signals and the back electromotive force due to therotation of the rotor near the pole pieces of ,the stator, and its valueis such that maximum current occurs in the field coils, due to the local signals, when the pole-tips of the field are midway between'teeth of the rotor. In operation, therefore, since the strip-frequency components of the two sets of signals mutually annul one another, he controlling torque is exerted by the toothed rotor 26 upon the shaft of the motor 28.
  • Figure 2 shows the form of scanning disc used. This has two sets and 32, of spirally arranged apertures so arranged that when an aperture of one set is in either of the areas '34 or 36 (these areas represent the apertures in the. mask 29) an aperture in the other set is not within the other area. 'At the same time it is arranged that an aperture is always within one of the areas.
  • this type of disc it is clear that single strips of-thetwo operators images-are transmitted alternately but the present invention is not limited to this extent, for example, 'a plurality of strips of each operator's image may be transmitted alternately tor even a complete image or series of complete images may be alternately transmitted provided always. that the speed oi scanning is such that the reconstituted image appears continuous owing to the retentivity of vision.
  • Figure 3 shows the phase relationship that has to be maintained between the ,two scanning discs.
  • the apertures 38, 40 and 42 are on the disc, at (say) the near station and the apertures (shaded in the drawings, in, order to distinguish them) 44, 46 and 48,
  • the image of the operator at the far station will be displaced to the left of the area 34 on the near station disc, and a black band will appear at the other edge of the picture, while at the far station the image of the near operator will be displaced to the right of the area 34 and a black band will appear at the left side of the area 34. If the discs get sufllciently out of phase the image of the far operator will pass, towards the left-hand side,,. right out of the area 34 at the near station leaving a blank space while the image of the near operator will pass right out of the area 34 at the far station by way of the right-hand side.
  • the image signals are applied to the line 50, by means or the transformers 52 and 53, at the near and far stations respectively.
  • I The input terminals .of the valves 54 and 56 situated at,
  • the near and far stations respectively are also connected across the line 5.
  • the grid electrodes of these valves being so biased that the valve 54, is working on the bottom bend of its characteristic while the valve 56, is working on the top bend of its characteristic.
  • the anode circuits of these valves each contain a transformer that feeds the corresponding neon-glow lamp amplifier.
  • signal impulses are put on to the line in such a sense that those from the near station cause the upper conductor shown in the figure (and consequently the grids of the two valves 54 and 56) to become negatively charged relative to the lower conductor and the valve filaments.
  • the result isthat-the impulses create corresponding impulses in theanode circuit of the distant valve 56, buthave no effect on the anode current of thenearvalve 54, since the grid is already negatively biased so that the valve is at the bottom bend of its characteristic.
  • a commutator arranged upon the shaft of the motor drivingthe scanning device,
  • This particular device is eminentlysuitable forf two-way television, one of each'of these devices being placed atthe sending and receiving station and rotated synchronously.
  • spotlight scanning in which a scanning or projection lens is interposed in the path of the scanning rays, the image .reconstituted at the receiver bymeans of a'flat-plate neon tube behind the discmay be reproduced the right way up by choosing the throw of the receiving spiral in the opposite sense to that of the transmitting spiral, so that lateral inversion is obviated.
  • I may also employ apertured or lensed drums or truncated cones for scanning and'for reconstitution.
  • floodlighting instead of spotlighting for scanning the object at each station.
  • An additional advantage of the system of twoway television is that when a single disc is employed with two spirals of apertures, by appropriate arrangement of the maskusually employed tolimit or frame the received picture -for instance, by enlarging its dimension in the direction of rotation of the disc to double that value which is required to expose only the picture received from the opposite station a picture of the observer's own person may be presented to him, side by side (in the case of horizontal scanning) with that of the distant observer.
  • means for maintaining syntony between the scanning mechanisms at the two stations comprising a scanning disc at each station having apertures arranged to give interrupted scanning and a tation of the said scanning discs and fed with a polarizing direct current upon which is superimposed the combined signals generated by scanning with the said discs.
  • a duplex television system consisting intwo of spirally arranged apertures interdigitated to scan groups of strips of the image. Of the observerand to reconstitute groups of stripsof the image of his co-operator alternately; the said light sensitive cell and light. valve being connected to the channel in such a sense that local signals coming from the light sensitive cell and distant signals going to the light valve are out of phase as regards a principal component of their waveforms.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Closed-Circuit Television Systems (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Treatment Of Fiber Materials (AREA)
  • Spinning Or Twisting Of Yarns (AREA)
US596254A 1931-03-04 1932-03-02 Television and like apparatus Expired - Lifetime US1980150A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB6712/31A GB374114A (en) 1931-03-04 1931-03-04 Improvements in or relating to television and like systems

Publications (1)

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US1980150A true US1980150A (en) 1934-11-06

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US596254A Expired - Lifetime US1980150A (en) 1931-03-04 1932-03-02 Television and like apparatus

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US (1) US1980150A (fr)
FR (1) FR743655A (fr)
GB (1) GB374114A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2420198A (en) * 1944-06-20 1947-05-06 Scophony Corp Of America Two-way television communication unit
US2524531A (en) * 1947-04-24 1950-10-03 Ets Edouard Belin Apparatus for transforming halftone documents into a printing weft
US3263027A (en) * 1962-12-11 1966-07-26 Beltrami Aurelio Simultaneous bilateral televideophonic communication systems
US3482040A (en) * 1966-02-11 1969-12-02 John F Brinster Image transmission system
US5202957A (en) * 1990-08-09 1993-04-13 Future Communications Full motion video telephone system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2420198A (en) * 1944-06-20 1947-05-06 Scophony Corp Of America Two-way television communication unit
US2524531A (en) * 1947-04-24 1950-10-03 Ets Edouard Belin Apparatus for transforming halftone documents into a printing weft
US3263027A (en) * 1962-12-11 1966-07-26 Beltrami Aurelio Simultaneous bilateral televideophonic communication systems
US3482040A (en) * 1966-02-11 1969-12-02 John F Brinster Image transmission system
US5202957A (en) * 1990-08-09 1993-04-13 Future Communications Full motion video telephone system

Also Published As

Publication number Publication date
FR743655A (fr) 1933-04-03
GB374114A (en) 1932-06-06

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