US1951781A - System for electrical transmission and reception of pictures, documents, and the like - Google Patents

Description

March 20, 1934. v. YANOUCHEWSKY ,7

SYSTEM FOR ELECTRICAL TRANSMISSION AND RECEPTION OF PICTURES, DOCUMENTS, AND THE LIKE Filed March 20, 1932.

Human //vz//v70/e VlAD/N/R m/voucuswszrr 14 TTORNEYS Patented Mar. 20, 1934 SYSTEM FOR ELECTRICAL TRANSMISSION AND RECEPTION F PICTURES, DOCU- MENTS, AND THE LIKE Vladimir Yanouchewsky, Le Chesnay, France, as-

signor to Etablissements Edouard Belin, Paris,

France, a corporation Application March 20,

of France 1931, Serial No. 524,094

In France March 29, 1930 4 Claims.

My invention relates to devices for identically reproducing a phenomenon A, through intermediary steps B, C, D, etc.

For instance, if A is a luminous point of a vari- 5 able intensity, which is to be identically reproduced at a certain distance, the variations of intensity of this point will be photoelectrically transformed into variations of current, which may be called step B. These variations of current will be transmitted to a receiver, which constitutes step C. Finally, at the receiving station, a phenomenon permitting to transform varia tions of current into luminous variations (step D) will make it possible, under certain conditions, to identically reproduce the original phenomenon A. Obviously, in most cases, the law of variation of intermediate state B as a function of corresponding variations of phenomenon A, the law of variation of intermediate state C as a function of 0 B, and so on, in short the law of variation of the effect with respect to the law of variation of the cause that determines said effect, will not be a linear law.

Be that as it may, if certain laws from cause to effect are not linear (From A to B, from B to C, for instance) and introduce into the successive steps of the reproduction what may be termed a deformation, it Will be necessary that other laws from cause to effect (from C to D and from D to A, for example) should introduce an inverse deformation, if the original phenomenon is to be reproduced.

The object of my invention is to provide means through which certain of these laws can be acted upon in order to compensate for the deformations introduced by other ones.

Although the arrangement that will be hereinafter described could be applied to various possible uses of the detected currents, its application to phototelegraphy will be particularly described, merely by way of example.

In the system for transmitting half-tone pictures, making use of reflected light for exploring the picture, the photoelectric currents that correspond to the black portions of the document are exceedingly feeble and the differences between such currents for very dark portions are very small. On the contrary, the differences are very important between currents corresponding to light shades. In other words, the variation of the photoelectric current as a function of half tints is very different from a linear function. At the receiving station it is very important to so modify the laws of detection that, account being taken of the curves of blackening of the photographic emulsions'that are used, the shades of the original may be accurately reproduced by means of an apparatus transforming electric variations into luminous variations.

For this purpose I amplify the incoming current from the emitting photoelectric amplifier by means of two or more circuits having different characteristics and I provide means for subsequently detecting said current in different manners in each of these circuits.

A particular embodiment of my device will be hereinafter described with reference to the appended drawing, given merely by way of example, and in which Fig. 1 is a diagrammatic view of an electric arrangement adapted to be used in connection with the above mentioned application.

Figs. 2 and 3 are diagrammatic representations of the operation of the tubes by reference to the characteristic curves of the same.

The incoming current is sent into transformer T, then amplified and detected by two separate circuits.

The first one includes T1, T1, T1", and R and will be called circuit 1.

The second one includes T2, T2, T2, and will be called circuit 2.

The two circuits are connected together in Z and in the common circuit (or in another one coupled therewith) is located apparatus E, which serves to transform electric variations into luminous variations. The circuits located before the detecting tubes of each circuit 1 and 2 are arranged in such manner that the alternating amplitude applied to the detectors of circuit 1 may be adjustable and higher than that applied to the detectors of circuit 2.

That difference of amplitude may be obtained for example, by using either an input transformer having several different terminals on its secondary (see the figure) or amplifying tubes having different characteristic or still a supplementary stage of amplification on one of the branches and so on.

The detector or detectors (T1', T1") of circuit 1 on the grids of which is applied a great alternating amplitude are but little polarized. The low value of this polarization makes it possible by operating in the higher portion of the charicteristic, to block the amplifier when the alternating amplitude exceeds a certain value.

The detectors of circuit 2 are normally polar- 1266. and the alternating amplitude applied to their grids is smaller than in circuit 1.

Detection accordingly takes place along the straight parts of the characteristics.

Finally a resistance R having suitable value inserted in the plate circuit of the detectors of circuit 1 makes it possible to regulate the relative action of the two detections of circuit 1 and 2 respectively. Through adjustment of the amplitude at the input terminals of the rectifying tubes of each of the circuits, of the polarization and of the value of R, it is possible to choose the points of the characteristics of the lamps about which said lamps are caused to Work in such manner that the curve of current intensities as a function of the shades may Within certain limits, be modified at will.

As above stated, the example shown is but a particular type of application. This method of modifying the law of detection may be adapted to any other kinds of application for obtaining the best result from the effects received at the input end in order to have them produce at the output end an sheet which is correct with respect to the cause of the effects received at the input end.

What I claim is:

1. In electric systems for identically reproducing a given phenomenon which include for transforming the variations of this phenomenon into variations of an electric current, an arrangement comprising an apparatus for transform" ing variations of an electic current back into variations of the phenomenon to be reproduced two circuits connected in parallel to apparatus, an amplifying tube and a detecting tube in each circuit, the detecting tube of the first circuit being less polarized than that of the second circuit, means for feeding the electric current whose variations correspond to those of the original phenomenon to be reproduced to the grids of the above mentioned amplifying tubes, and means for causing the amplitude of the current fed to the amplifying tube of the first circuit to be greater than that of the current fed to the amplifying tube of the second circuit.

2. In electric systems for identically reproducing a given phenomenon which include means for transforming the variations of this phenomenon into variations of an electric current, an arrangement comprising an apparatus for transforming variations of an electric current back into variations of the phenomenon to be reproduced, two circuits connected in parallel to said apparatus, an amplifying tube and two detecting tubes in each circuit, the detecting tubes of the first circuit being less polarized than those of the second circuit, a transformer for feeding the electric current whose variations correspond to those of the original phenomenon to be reproduced to the grids of the above mentioned amplifying tubes, a plurality of terminals on the secondary of said transformer connected to the amplifying tubes of the two circuits in such manner that the amplitude of the current fed to the first circuit is greater than that of "he current fed to the second circuit.

An arrangement accor to claim 1 further comprising a resistance inserted in the plate circuit of the detecting tube of one of the above named circuits for regulating the relative action of these two circuits on the apparatus for converting variations of the electric circuit into variations of the phenomenon to be reproduced.

t. An arrangement according to claim 2 further characterized in the plates of the two detecting tubes of circuit are connected in parallel to the above named apparatus, and comprising a resistance insered between the plates of the detecting tubes of one circuit and said apparatus for regulating the combined action of the two circuits on said apparatus.

VLADIMIR YANOUCHEW' SKY.

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