US1768874A - Television system - Google Patents

Television system Download PDF

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Publication number
US1768874A
US1768874A US201315A US20131527A US1768874A US 1768874 A US1768874 A US 1768874A US 201315 A US201315 A US 201315A US 20131527 A US20131527 A US 20131527A US 1768874 A US1768874 A US 1768874A
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US
United States
Prior art keywords
frequency
tube
light
variation
modulation
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US201315A
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English (en)
Inventor
Jr William H Whitten
Thaddeus R Goldsborough
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Westinghouse Electric Corp
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Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL27303D priority Critical patent/NL27303C/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US201315A priority patent/US1768874A/en
Application granted granted Critical
Publication of US1768874A publication Critical patent/US1768874A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/04—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier
    • H04N7/045—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier the carrier being frequency modulated
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/36—Angle modulation by means of light-sensitive element

Definitions

  • This invention relates to systems for producing images of pictures or other objects at distances therefrom. It is applicable both to television systems and to systems for the transmission of pictures.
  • sufiiciently broad tuning to cause it to respond to a definite portion of the frequency range of said modulation.
  • a super-regenerative vacuum-tube device In practicing our invention, we employ a super-regenerative vacuum-tube device.
  • a device of this character produces oscillations of a relatively constant frequency but the oscillations are interrupted periodically at a frequency known as the variation frequency. The period of such interruptions is dependent upon, among other things, the value of the grid-leak resistance.
  • the variation frequency may be made to represent the light. We impress this variation frequency as a modulation upon a carrier-current system and the light is thus represented by the frequency of the modulation.
  • each controlling the brightness of a light source we ohtain a number of changes in intensity of the light which, although not forming a continuous gradation of light, can reproduce the picture satisfactorily.
  • Figure 1 is a apparatus at diagram of the circuits and the sending station, and diagram of the circuits and apparatus at the receiving statio he view to be in Fig. 1 by the arrow 1.
  • a moving object a stationary object or a picture of an object.
  • he optical system including the lens 2 and prisms 3 and 4 and t e screen 5, is constructed in accordance with the dlSClOSlllB ill copendin I I l A t l 6 ll m0 St l. 1 .lm in mu g electric device 8. description and the accompanying drawings, 1;
  • the usual means for con tion frequency of the supe; vice comprise a grid condd h Va by a'grid-leak resistor 19.
  • Ii a-tj e resistor 19 is in parallel wsh he variatioent i herefore, changes With the illunh t lf the device 8.
  • he vacuum-tube 21 is connected totube 23, in the usual to modulator, and the tube 23 th source 22 of plate-current ener pedance is provided in the lead from the positive side of the source 22 to t e common connection for the plates of the tubes 21 and 23.
  • Each tuned circuit includes sufficient resistance to make it of broad tuning which may be a resistor 59 or the resistance of the inassigned to WVestinghouseElectric and Mandudtor or the losses in the condenser. Points of opposite potential in each of said tuned circuits are connected to opposed electrodes of a respective frequency-responsive relay 61 of the type described in the co-pending, joint application of A. M. Skellet and V. K. Zwory-. kin, filed January 3,- 1927, Serial No. 158,668,
  • Each of these relays includes a piezo-electric crystal 62 between said two electrodes.
  • Each relay also includes a third electrode connected to the grid of an associated vacuum tube.
  • the potential impressed from the resonant circuits upon thefrequency-responsive relays is preferably supplemented by a source of direct-current potential. This is indicated upon the drawing by a battery .63 and a resistance connected thereto. The battery and resistance are shunted about a condenser'64 by means of which the alternating potential from the resonant circuit is transmitted.
  • the first of the said tuned circuits is associated with a vacuum tube 7 0, the plate-filament connection of which is in shunt to a portion 71 of a resistor 72.
  • the vacuum tube 7 3 associated with the-next tuned circuit has its plate-filament connection in shunt to a portion of the resistor 72, including the portion 71' and an additionalportion.
  • 74/ -The vacuum tube 75, associated with the third of said tuned circuits, has its plate-filament connection in shunt with the whole of said resistor 72.
  • the resistor 72 is in succession'swith a light source 76 which is, preferably,.of the neon glow-tube type, although any light source which is responsive to potential changes, giving a corresponding intensity for each impressed potential, is suitable.
  • the resistor 72 and light source 76 in-series are supplied ment.
  • grid-controlled glow-discharge tubes such' as are disclosed in the application of D. D. Knowles, filed November 19, 1926, Serial No. 149,290,'as-
  • the frequency of said alternatingcurrent source should be at least as high as, and preferably higher than, would correspond to the shortest period during which-the lightis expected to continue at any one intensity.
  • the light from the source 76 impinges upon a screen. 81, preferably supplied with an ori-' fice 82, which constitutes practically a oint source of light.. If desired, instead 0 the orifice 82 .being completely transparent, it
  • the resistor 7 2 may be filled with translucent material of such anoptical density that the light which passes through it at the time when all of the resistor 7 2 is present in the circuit of the light source 76 will be insuflicient to affect a photographic plate or be visible upon a screen in the receiving device.
  • the receiving device comprises any desired system for optically associating the point-source 8 2 oflight'at any moment with 'that pointin the reproduction which correspondsto the point in the image 6 of the ob ject 1 in register with the orifice 7 at that mo-'
  • the reproducing optical system is of the same type as the optical system at the sending station and, consequently, two rotating prisms 83 and 84 and a lens 85 are shown on the drawing.
  • The-screen 8'6 cooperating with the optical system, is intended to represent either the ground glass in a receiver of the camera type, the wall or screen in a moving picture exhibition hall, a photographic plate or any other suitable or known reproduction surface.
  • the-image of theview 1 is produced upon the screen 5 and moved over the'screen.
  • the motion is such that the points of the image come, in 'turn,
  • this is accomplished by rotating the two prisms 3 and 4, one at a somewhat greater speed than the other.
  • every point of the image is brought into regin synchronism with the optical system in Fig. 1 by any suitable or well-known means; for example, the energy delivered from the sending station may have a peculiar modulation imparted to it each time that the moving optical system passes through a certain posi-. tion and such modulation may be caused to control the optical system at the receiving station, bringing it into said characteristic position each time that the peculiar modulation arrives.
  • the spot of light moving on the screen 86 must so vary in intensity that at each moment the brightness of the spot on the screen 86 corresponds to the illumination of the photocell 8. It is not necessary, however, that this correspondence be a proportionality and, in the system here disclosed, instead of a proportionality, the spot upon the screen 86 will have one of a relatively small number of intensities, that one which corresponds most nearly to the brightness of the illumination of the photocell
  • the tube 10 will produce oscillations of a frequency determined by the tuning of the circuit 16-17, but not continuously. Instead 5 frequency are of being continuous, these oscillations are in-- terrupted at the variation frequency. As the illuminationof the photocell 8 changes, the combined resistance of the photocell and the resistor 19 in parallel changes, with the result that the super-regenerative device changes its variation frequency.
  • the coupling between the feedback coil 14 and the grid-coil 16 must be close enough to give to the device a strong tendency to oscillate.
  • the oscillations produced in the tube 10 pass readily through the condenser 15. They are prevented from passing through the bat- .tery 11 by the radio-frequency choke coil 12.
  • the oscillations generated by the tube 10 must be higher than this in order that the variation period may contain a sufficient number of oscillation cycles for the action to be positive and dependable.
  • the average value of the plate current is increased when the tube is delivering oscillations and diminished when it is not. Consequently, the potential across the condenser 15 has a periodic change at the variation frequency in addition to the oscillations generated at the higher frequency.
  • the coupling between the tube 10 and the tube 21 may be a transformer of moderately broad tuning. It should transmit readily the (changeable) variation frequency, but should not transmit the oscillations generated by the tube 10 and, of course, would not transmit direct current. If, instead of such transformer, the coupling illustrated in Fig. 1 is used, the tuned circuit 3132 prevents the transmission of the oscillation frequency but will permit the transmission of the variation frequency.
  • the condenser 33 is of suflicient capacity to readily transmit the variation frequency.
  • the condenser 15 is of such small capacity as to present a large reactance to the variation frequency, whereby a large potential difference of this frequency is available to be transferred by the coupling.
  • the tube 21 acts as an amplifier for, the variation frequency and also as a modulator for the tube 23.
  • the circuit 2425 should present a large impedance to the variation. frequency, in order that the most effective modulation may be obtained.
  • the maximum impedance would be obtained by, a circuit which was sharply tuned to the variation frequency, but, as the, variation frequency changes throughout a substantial range and the impedance of the circuit 24-25 must be large over all of this range, the tuning of this circuitis broadened by the introduction of.
  • Oscillations generated'by the tube 23 are prevented from'reaching the battery 22 by the radio-frequency choke coil '27.
  • these oscillations are of afrequency corresponding to some or 3.0 meters wave length, because radiation of this wave length obtains very certain control over great distanc'es.
  • the wave length chosen, whether it-is as short as stated or not, should be short enough for a suflicient number of cycles of the carrier frequency to be included within one cycle of the variation frequency. It'is preferable, but not necessary, that the carrier frequency differ substantially from the frequency of the oscillations generated in the tube 10.
  • Theoscillations generated in the tube 23 are modulated by the action of the tube 21,
  • the output circuit of the tube 23 includes the usual tuned circuit 37 for storing the energy and. the usual reactive connection to the antennaby means of which the storedenergy may be radiated.
  • the received energy after being amplified, ifnecessary, is impressed upon the detectortube 52 and the pptput current thereof includes the modula- 10I1S.
  • the photocell 8 When a bright portion of the image 6 is in registry with the orifice '7, the photocell 8 is brightly illuminated. It, therefore, becomes conductive. The combined resistance of the photocell and the resistor 19 is low, andthe variation frequency will, therefore, be high. The corresponding frequency in the output of the detector tube 52 will be high and will, therefore, come within the range to which the circuit 57 is responsive. The inclusion of the resistor 59 in this circuit, by broadening the tuning, will cause it to'be responsive not only to one maximum illumination of the photo cell 8 but to all illuminations from the most intense down to a certain limit. Thus, all portions of the view at which the light-intensity is strong are-correlated to the-circuit 57.
  • the battery 63 impressesacross the crystal 62 a potential which is less than the ionizing potential of the gas in the tube 61.
  • an additional potential is impressed across the crystal 62 which, with the potential from the battery 63, is suflicient to cause the tube 61 to become operative.
  • the range throughout which the response will occur is thus enlarged by the effect of the battery. It is preferable that the range of frequency over which any one tube, 73, for
  • the tube7 5 becomes operative, with the consequence that the whole of the resistor 72 is short-'circuited and the full potential of the source 77 is impressed tube 61 associated upon the lamp 76.
  • the couplin'g 57 is eifec tive at the highest portion of the frequency range; It, therefore, responds when the hotocell 8 is most brightly illuminated. onsequently, the light source 76 is brightest 'when the brightest portion of the image is in registry with the orifice 7.
  • the photocell 8 When a dimly illuminated portion of the view 1 is optically associated with the orifice 7, the photocell 8 will be dimly illuminated, the variation frequency will, therefore, be slow and, the circuit 55 will respond.
  • the photocell 8 When a very dim or a perfectly dark portion of the image 6 is in registry with the orifice 7, the photocell 8 will be non-conductive; the variatlon frequency of the super-regenerative tube will be determined by the resistor 19; the modulation in the output will be slow, and the frequency in the plate circuit of the tube 52 will be too low for even the circuit 55' to be responsive thereto. Consequently, no part of the resistor 72 will be short-circuited, and the lamp 76 will either shine so dimly that a barely perceptible result is present upon the screen 86, or, if the lamp 76, under' these circumstances, is too dim to' penetrate the translucent medium in the orifice 82, the corresponding portion on the screen 86 may be completely dark.
  • the correspondence between the brilliancy in the image 6 and that in the image upon the screen 86 may, if desired, be reversed by re versing the order of the connections between the several tubes 61 and the corresponding portions of the resistor 72. This is of use when the screen 86, instead of being adapted for direct viewing, is a photographic plate and it is desired to produce a positive instead of a negative upon the developed plate.
  • a greater number of degrees of variation may be supplied by providing a larger number of tuned circuits, more sharply tuned, and a corresponding number of tubes whlch each shunt a ortion of the resistor 72.
  • the apparatus does not require any very great exactness of adjustment. 'If,'from any accident, theaverage variation frequency of the tube 10 changes, the tuned circuits at the receiving station may beadjusted to correspond.- If:
  • a highfrequency oscillation generator in a view-transmission system, a highfrequency oscillation generator, a super -regenerative vacuum-tube device, means con: trolled by illumination for altering the variation frequency of said device, means for impressing on said high-frequency oscillations a modulation having a frequency equal to said variation frequency and a device responsive to said modulation in accordance with the frequency thereof.
  • a big frequency oscillation generator In a view-transmission system, a big frequency oscillation generator, a super-regenerative vacuum-tube device, means controlled by illumination for altering the variation frequency of said device, means for impressing'on said high-frequency oscillations a modulation having a frequency equal to said variation frequency and a plurality of frequency-selective responsive devices together covering the frequency range of said modulation.
  • a highfrequency oscillation generator 9. super-regenerative vacuum-tube device, means controlled by illumination for altering the variation frequency of said device, means for impressing on said high-frequency oscillations a modulation havinga frequency equal to said variation frequency and a plurality of frequency-selective responsive devices together covering the frequency range of said modulation, and a light-source controlled by said devices.
  • a sending device comprising means for producinghigh-frequency energy modulated by a modulation of varying frequency, illuminationcontrolled means forcontrolling the fre quency of said modulation, a receiving device comprising a plurality of frequencyselectlve devices each responsive to a range of frequencies overlapping the range of the next, the combined range of said devices covering the whole range of said modulation and a light-source the intensity of which is controlled by said devices.
  • a sending station comprising means for delivering high-frequency energy modulated at a frequency corresponding to illumination
  • a receiving station comprising a light-source having a brilliancy corresponding to the potential impressed thereon, a plurality of differently tuned frequency-responsive devices, means controlled thereby for impressing respectively different potentials on said lightsource and means for delivering to said tuned devices energy of a frequency determined by said modulation, whereby the brilliancy of said light-source will be determined by said illumination.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)
US201315A 1927-06-25 1927-06-25 Television system Expired - Lifetime US1768874A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NL27303D NL27303C (enrdf_load_stackoverflow) 1927-06-25
US201315A US1768874A (en) 1927-06-25 1927-06-25 Television system

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US1768874A true US1768874A (en) 1930-07-01

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238157A (en) * 1978-02-03 1980-12-09 Ernst Leitz Wetzlar Gmbh Process and arrangement for the alignment of imaging systems

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238157A (en) * 1978-02-03 1980-12-09 Ernst Leitz Wetzlar Gmbh Process and arrangement for the alignment of imaging systems

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Publication number Publication date
NL27303C (enrdf_load_stackoverflow)

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