US1821416A - Method of and apparatus for picture transmission - Google Patents

Description

E. BELIN 1,821,416

METHOD OF AND APPARATUS FOR PICTURE TRANSMISSION Sept. 1, I931.

I I I x0 I] MMQWOOUM Original Filed Sept. 3. 1924 III 1' the frequency or both of a carrier current.

Patented Sept. 1, 1931 UNITED STA s YOFFICE Enou'nnn- Burnt, on ree s, FRANCE METHOD OF AND APPARATUS FOR PICTURE TRANSMISSION Original application filed september 3, 1924, Serialli 'o. 735,605, patented September 13, 1927, No. 1,642,837. Divided and this application filed. January 26, 1926. Serial No. 83,930. i

This application is a division of my United States application Serial No. 735,605, filed September ,3, 1924:, patented September 13, 1927, No. 1,642,637..

, The. invention relates of pictures, and more particularly to the radio transmission of pictures which are composed in whole or in part of infinite gradations of light and shade between max imum and minimum illumination. In a -co-, pending application it has been pointed out that such a method of transmission is applicable to both. line drawings, manuscripts, and the like which may be described as having highflcontrast and photographs, lithographs and thellike, which have relatively low contrasts:between-adjacent portions.

The condition of any'given portion of a photographic picture is a direct index of the degree of illumination of the corresponding portion of the object photographed and .may be'expressed I mathematically as a function thereof and varying proportionately thereto; that is, the picturemay vary either in relative translucency at the point in question, or in relative thickness; if a gelatine coating be employed. This rela- 1 the illumination may therefore, be expressed by a current which varies, in amplitude proportionately therewith.- If successive points of the. picture be explored by a translating apparatus, the current resulting. may be used to modulate by action either uponthe potential of a direct current, or the amplitude, or

Nhile this resulting variable current: is somewhat like a telephone current in-that it is irregular and in' effect covers a very current variations are very different from those used in other forms of signaling such as telephony, telegraphy and the transmis sion of pictures by points or ,dots, .in that the variations of the present form of variable current are non-periodic, that. is,; n,ot periodic, oscillatory or'cyclic as thecase of; soundwaves or telephone currents produced by sound waves. a

In the system of facsimile telegraphy,

to the transmission 7 y it is desired to broad band, it is to be understood that such described in my, U. S. Patent No. 915,154,

transmission is effected by the slight differences in level of the surface of a relief photograph or the like. These differences in level, by their action upon a variable resist-1 ance, vary the intensity of a weak current passing through the resistance proportionally to such differences .in level, and therefore, according to the differences of light and shade of the photograph or the like to be transmitted, This Weak varying current w must be suitably amplified before it acts upon the wireless transmitting apparatus proper. The amplifier employed for this purpose is of the resistance type and has no condensers or, transformers through which 55 the varying continuous current in the circuit mustpass; the successively. amplified currentsonly var win amplitude progressively and faithfully follow the diiferences in level of the surface explored. I A

It is likewise possible to employ a translucent positive or negative picture having relative gradations ,oflight and shade, and to produce therefrom a varying current which faithfully follows in amplitude the lights and shades, of the picture, and then at the receiving end to obtain from this current a photographic positive ornegative.

This invention comprises a transmitting stationat which is located means for gena0 crating a direct ora carrier wave current, and apparatus adapted to impose upon such currentinodulations which area function of the relative light or shade of the picture transmit; and a receiving station at which is an apparatus adapted to receive the modulated current from the transmitting station, and to produce abeam whose luminosity varies as a function of the modulations of such current, which serves to. translate these modulations into photographic effects. v p v I ,In the parent application heretofore mentioned, thatform of my invention is claimed in which successive points of the picture to be transmittedare explored byan electric translating device "to produce a direct "current ,varying in amplitude in accordance with the-intensity of the light emitted from the successive points oft'he picture, This 100.

varying current is then amplified and employed to modulate a carrier current in both amplitude and frequency. The receiving apparatus comprises a heterodyne receiver in which a locally generated Wave is combined or heterodyned with the received car rier wave to produce beat waves which vary both in amplitude and frequency. In the recording or printing apparatus, which is that set forth in the aforementioned patent, reception of pictures to produce a range of light and shade takes place by the aid of an oscillograph, traversed by the emergent beam from a lamp and shutter device responsive to the transmitted current, and it will be easily understood that an oscillograph, by reason of its low inertia, is Very sensitive to the variations in frequency of the received current, much more so than to the variations in intensity of the current.

In the system of this application the ex ploring or translating device is employed to modulate the amplitude of a musical wave of given frequency by a suitable relief scanning means, the variations of which are a function of the intensity of the light emitted from successive points of the picture. .This modulated low frequency wave is then employed to modulate in turn a high frequency carrier wave. The receiving apparatus comprises an ordinary detector to derive the modulated low-frequency currents from the carrier wave'and'a recorder or printer which varies the intensity of the printing beam in accordance with the variation in amplitude of the low frequency wave. 7

The transmitting and receiving apparatus are synchronized with respect to each other by ways and means well known in the art. Since such means form no part of the present inve'ntion,-they are not shown nor described in detail. I

The preferred form of this apparatus has been found in practice to give excellent results where the communication between the two stations was established through the natural media; but obviously the system is likewise applicable to work along intervening metallic or other conductors as well.

he accompanying drawings set for diagrammatically means of accomplishing the invention, and

Figure 1 is a schematic representation of the apparatus employed at the transmitting station.

Figure 2 is a diagram indicating the apparatus employed at the receiving station.

Fig. 8 is a diagrammatic illustration of the recorder or printer employed at the receiving station.

In Figure 1, E indicates an oscillator for producing an electric current or wave of musical frequency (for example, 600 cycles). This oscillator is of a well known type, having plate and grid inductances 20 and 21,

plate battery 22 and a regulating plate condenser 23.

A microphone M is connected across the plate inductance 20 by means of a variable contact, and the primary winding of transformer 24 is connected in parallel with microphone M. Thismicrophone is acted upon in accordance with the varying level of the surface explored, in the manner disclosed in my U. S. Patent No. 915,154. Its resistance changes in exact accordance with such variations and affects the current supplied to the primary of transformer 24. The final result is that the recording of transformer 24 has induced therein a low frequency current modulated in amplitude in accordance with the variation in intensity of light emitted from successive points of the picture. This current is applied to the grid and filament of an amplifying tube A; and by its potential creates corresponding and amplified variations in the potential across the plate circuit resistance 5, from the plate battery 4. These variations are in turn amplified by the second tube B and succeeding tubes if any, with resistance coupling indicated at 8 and biasing battery at 6. It will be understood that any suitable number of these tubes may be employed, until the resultant current is sufiicient to serve for modulation. In practice, such an amplifier of three or four properly regulated stages is suflicient to modulate a transmitting system of several hundred watts when the resistance of the variable resistora microphone buttononly varied a few ohms (equivalent to three or four watts at most) under the pressures; this represents very feeble variations of the grid potential for the first tube.

The resistance 8 placed in the plate circuit of the last amplifying stage is connected between the filament and the grid of a group of tubes one of which is shown at C, termed absorption tubes, whose filament plate resistance is also varied. Biasing batteries 9 are placed in the grid circuits of the tubes so as to obtain suitable modulation which is made as proportional as is possible. The filament plate circuit of tube C includes the inductance coil 14. The oscillating or control valve D is connected to deliver into this latter circuit high frequency oscillations by means of the grid inductance 10 in electromagnetic relation to the portion of coil 14 utilized as a plate inductance, with grid leak 12 and condenser 11, plate condenser 15, and plate battery 13. Since the internal resistance of the absorption tubes varies with the current from the microphone, the output from these tubes must vary with the relative illumination of the original object.

The apparatus employed at the receiving station is indicated in Figs. 2 and 3, and

consists simply of a detector for deriving the modulated low frequency wave from the received carrier wave, and a recorder operated by the low frequency wave to vary the intensity of the printing beam in accordance with the variation in amplitude of the low frequency wave. Such printing or recording apparatus is preferably in the form of an oscillating oscillograph or galvanometer operated by the modulated low frequency current to cause the printing beam to oscillate at varying amplitude over an absorbing screen 51 in accordance with the amplitude of the low frequency current. The screen is graduated from the center to its outer edge to allow different amounts of light from the beam to pass. A condensing lens 52 is arranged behind the screen and concentrates the light passed by the screen upon the printing surface 53. A convergent fixed luminous bundle of rays are projecte on the galvanometer mirror 54 from a suitable source 55, and the rays are reflected ontothe printing surface 53 through the screen 51 and lens 52, the printing surface being suitably carried by a rotatable cylinder 56 having a translating movement. The cylinder is enclosed in a dark room or container 57 having an opening 58 adapted to be closed by a diagram 59. This type of apparatus is well known and is shown in my U. S. Patent No. 915,154.

Instead of modulating the amplitude of the low frequency wave, as described above,

the frequency of this wave may be modu lated in the same manner as described in the parent application.

While I have shown a particular system for modulating a carrier wave by the modulated low frequency wave, it is to be understood that other and well known modulating systems may be used for the same purpose, i. e. for modulating a carrier wave by the modulated low frequency wave, without departing from the spirit of the invention.

I claim: I

1. A modulating system for effecting the transmission of non-periodic variations from a relief record, comprising an audion tube oscillator having a plate circuit coil and a grid oscircuit inductance 0011, said cillator being adjusted to produce oscillations of a relatively low frequency, an amlifier for aperiodic variations, a transformer having its primary winding coupled to said plate circuit coil and its secondary winding connected to the input circuit of said amplifier, a non-periodic micro hone connected in shunt of the primary W111 ing of the transformer and arranged to, explore the said relief record totranslate variations in relief thereof into corresponding variations in resistance of the microphone, a second audion tube oscillator having a 65 plate circuit inductance coil, and an absorption audion. tube having its input circuit connected to the output circuit of said amplifier and its output or absorption circuit connected in shunt of the plate circuit inductance coil of said second oscillator, said second oscillator being adjusted to produce oscillations of a relatively high or radio freuency..

2. The method of transmitting irregular and non-oscillatory or non-cyclic current variations, which consists in modulating the same onto an oscillatory carrier current 0 an audible frequency or a low frequency capable of affecting mechanically responsive means, modulating the low frequency carrier current onto a carrier current 0 radio frequency, transmitting said radio carrier current by radiation, receiving and demodulating the radio carrier current to obtain the low frequency carrier current and using the low frequency carrier current to directly affect a mechanically responsive device.

8. The method of transmitting picture modulations consisting of non-oscillatory electrical variations, on a radio carrier wave to a mechanically operated light varying means which method comprises generating waves of a frequency sufficiently low to actuate the mechanical means in unison therewith, modulating the low frequency waves with the picture modulations, and modulating said low frequency wave onto the radio wave.

4. The method of transmitting, by radiation, non-oscillatory or non-cyclic current variations incapable of substantially affecting either inductive or capacitive reactances, or of being transferred through an electromagnetic transformer; which consists in generating intermediate low frequency waves of a frequency higher than the rate of variation of said current variations and sufficiently low to directly affect mechanical translating means, modulating said intermediate waves with said current variations, generating radio frequency carrier waves, and modulating said radio waves with said intermediate waves.

In testimony whereof I affix my signature.

DDOUARD BELIN.

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