US1857329A - ranger - Google Patents

Description

May 10, 1932. R. H. RANGER 1,857,329

PICTURE TRANSMISSION Original Filed April 13, I926 2 Sheets-Sheet l E It ,m Q R.

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[I I 400'" 20o l l l i l l f 0 2 1 1 9. 3 14 INVENTOR RICHARD H. RANGER M ATTORN EY May 10, 1932. R. H. RANGER 1,357,329

PICTURE TRANSMISSION Original Filed April 1926 2 Sheets-Sheet 2 INVENTOR RICHARD H. RANGER dam,

A ORNEY Ill Patented May 10, 1932 UNITED STATES PATENT OFFICE RICHARD H. RANGER, OI NEWARK, NEW JERSEY, ASSIGNOB TO RADIO CORPORATION 01 AMERICA, A OOBPORATION OI DELAWARE PICTURE TRANSMISSION Application med April 18, 1926, Serial). 101,611. Renewed August 13, 1930.

My invention relates to the transmission of pictures over a signaling channel and particularly to refinements in the method thereof.

An object of my invention is to provide an improvement in picture transmission processes.

Another object of my invention is to provide means for increasing the detail of a transmitted icture.

Another oliject of my invention is to produce a picture composed of parallel lines of dots, dashes and spaces in which alternate lines produce an effect of a darker tone than the intermediate lines.

In my copending applications, Serial Nos. 695,17 5 filed February 26, 1924, and 726,235 filed July 16, 1924, I have disclosed two modifications of a process for the transmission of pictures over a signal channel. In these processes, synchronized scanning and reproducing means are provided whereby the lights and shadows of a picture are analyzed by a photo-cell and the total amount of light energy therefrom, along a given narrow line,

- is integrated to,pr0duce a series of current pulses corresponding in spacing, or in both length and spacing, to the mean efi'ective illumination from the picture. pulses are then transmitted over a convenient signal channel and are caused to actuate a pen, moving in synchronism with the scan: ning means of the sender, whereby rows of marks are made upon paper corresponding to the light tones of the original picture. It has been found that excellent reproduction of pictures may be obtained by the process as disclosed in the mentioned applications.

As in the above named applications, the

system is herein described as relating to the transmission or duplication of picturesor thelike. but it is to be understood that the invention is not limited to the transmission of pictures'onlybut any other type of subject matter such as motionpicture films, newspapers, financial statements, fashion plates,

and the like, may be transmitted and are in tended to fall within the scope of the term pictures.

My present invention, however, provides means for making a further improvement in These currenting description when read in connection with the accompanying drawings, wherein:

Figure l is a diagrammatic representation of circuits and apparatus embodying my invention and 4 Figure 2 is a modified form of circuits and apparatus embodying my invention.

Figure 3- is a dlagrammatic representation of the circuits of my hoto modulator of the previously mentione applications with a form of my present invention embodied -there1n.

Figure 4 is a diagrammatic indication of the difference between the product as formerly made and a product of my present invention and,

Figure 5 is a picture reproduced according to my'invention.

Broadly the process of my invention consists in modifying the response of the photocell and amplifier above at the sending apparatus in such wa that atsuccessive intervals the pulses pro uced correspond to, thosewhich would normally be produced from a print having variations in a high light-key rate, and at another instant, variations in a low light-key with respect to the actual'density at the particular point. This in efi'ect is equivalent to varying the length of spaces, or the length of both the spaces and dots,

corresponding to a given light intensity of the print.

In my first indicated embodiment the change in efiective intensity occurs at the end of the line of scanning so that alternate cross lines of the recorded picture are alternately til ' pearance characteristic of the lighter than, and heavier than, the normalline. rovided b m original s stem as revious l disclos l- It is, howgver, obvibus that tli lines gives apicture tone value which is very closely equivalent to the picture tone value of two lines of the former t pe, of recorded picture. It has, however, t e great advantage of giving much more sharply marked out image lines, much better much wider range of tone values. Likewise it tends to obviate the coarsel granular apfirst too strictly regular prints produced by the processes of the above mentioned applications.

The change ma be produced by any convenient means an at any convenient rate of speed. It may be produced by a cyclic change ,in li ht intensity of the scanning light. It

may produced by a small fluctuating light impinging directly upon the photo-cell, or it may be produced by a change in the grid bias of any convenient amplifier triode incorporated in either the transmitting or receiving apparatus. Likewise the change in intensity, which may be called for convenience a bias, may be produced by a potentiometer control upon the grid of an amplifier triode,,which shifts in value by the required amount at the end of each line of scanning under the control of the synchronous scanning-drive mechanism or it may be shifted nonsynchronously by anyconvenient device. A convenient means for providing this bias isshown in Figure 1. A photo-cell 1 is provided and connected to a battery 2 in series with an output resistance 3. Amplifying means as shown in the previously mentioned applications amplifies the photo-cell output through the agency of a triode amplifier 4.

Any convenient grid biasing means for the triode 4 may be provided, such, for instance, as a resistance 5 in the filament su ply leads. A pair of potentiometers 6 and are then connected to the biasing resistance 5 and provision made for setting the contacts thereon to give any desired negative bias to the grid of the triode 4, by way of the photo-cell circuit. Leads'are takenfrom the contacts of the potentiometers 6 and 7 to contacts of a relay8, the tongue of whichis connected to the photo-cell circuit and thereby to the grid of the triode4. The coil of the relay 8 may be energized by any convenient portion of the circuits so that it will swing from one contact to the other at. regular intervals. This interval may be, as above described,-that of the successive cross-wise movements of the scanning means, in which case alternate cross lines. will be predominantly alternately light and heavy asdescribed. The potentiometers may then be adjusted by trial. One, No. 6, for instance, may be set to make the grid somewhat less negative than would normally be done, whereby a heavier current flows in the e heaviness of marking of two such detail and a triode4 under a given illumination of the photo-cell 1. This reduces a relatively greater number of pu ses than normally, and

therefore, a heavier line in the receiving device. T e other otentiometer may then be set to ma e the gr1d somewhat more ne ative thannormally, and in consequence ,un er its control rather less. current will flow thr ugh the triode 4 with a given illumination of the piloto-cell 1, and therefore, a 1i hter line will produced at the recorder. lternation of control of the grid bias between the two potentiometers by the swing of the tongue of the relay 8 then gives the desired alternation between predominantly light and predominantly dark lines in the recorder.

This is conveniently shown by the representation of Figure 4 the upper portion a of which indicates the character of marks produced by my invention as described in the previously mentioned applications while the lower portion 6 indicates the result of my present invention. As indicated, the portion (1 consists of marks which may vary in length and in spacing to vary the tone value of the reflected light, while portion 7) shows marks varying in average density in alternate lines. This representation is purely diagrammatic in character since it has been found impossible to produce by hand a picture of the character produced mechanically by the device of my invention.

s The actual resultproduced by the apparatus of my invention as herein disclosed is shown in Figure 5 which has been transferred to the drawings of this application by photomechanical processes due to the fact that a picture of the type shown by Figure 5 cannot be produced manually. The picture record per se, as an article of manufacture, has been more particularly described, claimed and set forth in applicantsdivisional application Serial No; 338,073, filed Feb. 7, 1929.

The embodiment shown in Figure 1 and above described produces a marked improvement in the character of the reproduced picture. It is, however, rather more regular in its variation between light and dark lines than is desirable.

The embodiment shown in Figure 2 provides a random change from predominantly light, to predominantly dark lines and a change at a higher frequency than the embodiment of Figure 1, so that the change may occur in a random distribution in the course of a marking of a given line.

In this embodiment a photo-cell 1 is provided as beforewith battery 2, output resistance 3 and triode amplifier 4. As before, a grid bias resistance 5 is provided. A potentiometer 9 is provided and connected across the ends of the resistance 5. In parallel with the potentiometer 9 is connected a second potentiometer 11 which is designed to have its contact arm continuously rotated by negative bias which can be furnished by means of a motor 12 or other convenient device. An additional potentiometer 14 is provided and connected betweenthc contacts of the potentiometers 9 and 11 with its own contact connected to the photo-cell circuit and thereby, to the grid of the triode 4.

In the operation of this device the setting of the contact of the potentiometer 9 determines the average grid bias. The rotation of the contact of the potentiometer 11 then causes alternately the maximum, and minimum the biasing resistance 5. These maxima or minima are not, however, impressed di rectly upon the grid of the triode 4,

but are applied to oneterminal of the potentiometer 14, to the other terminal of which is applied the meaneifective bias produced by the potentiometerfi. The bias upon the contact of the potentiometer 14 then fluctuates about the value set by the potentiometer 9 by an amount depending upon the a the potentiometer 14 as will be obvious of in-- value of the drop in the resistance 5, swing of the rotating potentiometer and the setting of spection of the diagrammatic showing.

By either of these means the desired fluctuating marking line density is obtained at the reproducer and the desired improvement in detail and sharpness of outline of the reproduced print occurs.

By Figure 3 of the arrangement herein- .disclosed I have shown the application of the equally simple to combine therewith .the-

showing of Figure 2 or other such modifications of the invention as may readily suggest themselves to those skilled inthe art to which the invention relates.

While I have shown but two embodiments of my invention in the foregoing drawings and de scriptionsit is capable of various modifications' therefrom without departing from the spirit thereof. and it is desired therefore that only such limitations shall be imposed thereon as are required by the priorart or indicated by the appended claims.

I claim as my invention:

1. In combination, an amplifier-devices, means for producing potential changes thereon, and means for producing at time periods of relatively wide separation an abrupt its conta'ct arm to takecurrent.

below the normal bias for producing at said predetermined rate an increase above normal output and a decrease below normal output from the am lifier.

. 2. In combmation, a photo-cell device for.

convertingc'changing light values into-proportionately changing electric currents, an

amplifier device connected with said photocell, means for impressing the output currents from sald hoto-cell upon said amplithrough, and means for intermittently applying to said amplifier device,biasing otentials of two limital values above. and elow the normal biasin otentials for alter nately increasing ant? ecreasing the amphfier response from the normal.

3. The method of reproducing pictures and the like, which comprises the step of intermittently modifying an electriccurrent .the number of such modifications perunitof time being progressively varied according to the light intensity of a unit of the picture to be reproduced, andi'n'dependently cyclically modifying said electric current.

her for controlling the current flow there- 4. A method of reproducing pictures 'and the like which comprises the step of progressively projecting upon a light sensitive element, light from different sections of the picture to be reproduced. and utilizing the changes in said light sensitive element thereby produced to produce intermittent changes in an electric current in a manner to cause the number of said changes per unitof time to vary according to intensity of light falling upon said element, and also cyclically varying the base line value of said electric -5. A method of reproducing pictures and the like which comprises progressively projecting upon a light sensitive cell light from different sections of the picture and utilizing the variations in said cell thereby produced to control an electric current in a manner to variations per unit of time in accordance with light intensities of successive portions of the picture, rythmically varying the effectiveness of light intensities in producing said variations, and suitably reproducing the picture from such variations.

7. A method of expressing variations of light intensity in terms of electric current which comprises translating varying light intensities into current impulses, light inchange in the grid bias to points above and tensities at one end of the scale being represented by impulses of substantially uniform duration separated by periods exceeding in duration thedurationiof said im ulses, and light intensities lying on the ot er end of said scale bein represented b impulses separated by periods of substantia ly uniform duration,- the duration of said impulses exceeding the duration of the separating peri'ods, and cyclically varying the effective response to light values, whereby the impulses are alternately. lighter than, and heavier than, the normal value required to represent said light intensities.

8. A method of representing variations of li ht intensity in terms of electric current which comprises normally producing current im ulses of substantially uniform duration and separated by spacing periods of substantially uniform duration, the duration of the current impulses having a predetermined ratio to the duration of the spacing periods, for a predetermined intensity of light, and varying said ratio in the direction of increase for variations of light intensity in one direction away from-said predetermined value of light. intensity and varylng said ratio in the direction of decrease for variations in light intensity in the other direction from said' predetermined value of light intensity and cyclically varying the degree-of response to J a predetermined light.

9. In apparatus for translating variable light intensities into electric impulses, the combination of means for producing periodic impulses normally of substantially equal duration and separated by periods of substantially equal duration, and the duration of the impulses normally being equal tothe duration of the separating periods, and means for var ing the duration of either of said periods an means cyclically varying the degree of response to a given light value.

10. In apparatus .for translating variable light intensities into electric impulses, the combination of means for producing periodic impulses normally of substantially equal duration and separated by periods of substantially equal duration, and the duration of the impulses normally being equal to the duration of the separatin periods, and means for varying the duration of either of said periods, independently of the other, and means for cyclically varying a response to a given light intensity.

11. In modulating apparatus, the combination of a plurality of means for storing predetermined quantities of electricity, means for supplying electricity to said plurality of means at a predetermined normal rate, and means controlled by light intensity for varying the rate of supply of electricity to one of said storing means independently, and means for cyclically varying the rate of response to said-light intensity of said light controlled means.

tricity to the ot er of said storing means in accordance with variations in intensity of light lyin on the other side of said predetermined ight intensity and means for cyclically varying the controlling efiect of said light intensity.

13. The method of reproducing pictures and the like which comprises activating the photo-electric element in accordance with variations of light and shade of a picture surface, intermittently modifying the potential on an amplifier in accordance with the light reaching the photoelectric element, and abru tly changing the biasing potential applied to said amplifier from oneto another predetermined value for accentuating the current flow therethrough during certain time periods and retarding the current flow therethrough during other time periods.

14; The method of reproducing pictures and the like which com rises intermittently and progressivelymodig'ing an electric current in accordance with the tone intensities of elemental areas of a picture to be reproduced, and" in independently andabruptly which comprises translating the elemental tone intensities of a picture into varying strength electric current impulses, controlling an amplifying system in accordance with the strength of said varying impulses, and

time

abruptly increasing and decreaslng to two predetermined limited values at predeter-- mined time intervals the effect of said first named current impulses upon said amplifying system, I I

16. Amodulating apparatus for facsimile transmission which includes, in combination, means for translating varying intensities of light and shade on a picture surface intovarying strength electric current impulses, means for amplifying said varying strength electric current impulses, and independent means operable at predetermined time intervals for increasing and decreasing abruptly the amplification of said first named electric current impulses to limits above and below normal.

1,7. A photo amplifying system including photo-electric means for translating varying intensities of light and shade on a picture surface to be transmitted into varying strength electric current impulses, an amplifier, means for impressing said varying strength electric current impulses directly upon said amplifier and varying the current output thereof in accordancewith the strength of the current impulses applied thereto, and independent potentiometric means connected with the input of said amplifier for cyclically increasing and decreasing the current output from said amplifier in a predetermined spaced relationship for bringing the amplified current impulses above the normal tone value during certain predetermined periods and below a predetermined tone value at other predetermined A periods.

18. A photo amplifying system including, in combination, a photo-electric cell for trans lating varying intensities of light and shade on elemental areas of a picture surface into varying strength electric current impulses, a vacuum tube amplifying system foramplifying said impulses, means for impressing said impulses upon the input. circuit of said vacuum tube amplifying system and controlling the amplified currents in accordance with the strength of the applied current impulses, a plurality of independent biasing resistances connected with the input of said amplifying system, and means for alternately and cyclically connecting said resistances in the input circuit of said amplifier for increasing and decreasing the current flow through said amplifier so as to cyclically bring the current flow above and below a predetermined value for the particular tone intensity of the picture surface.

19. The method of reproducing pictures which comprises producing electric currents of values proportionate to the intensity of light and shadow of elemental areas of a record surface which is to be reproduced, and

independently and abruptly modifying the electric currents produced for producing during one predetermined time period increased output currents and for producing during like predetermined periods decreased output currents.

20. The method of reproducing pictures which comprises progressively varying the strength of an electric current in accordance.

with the intensity of light and shadow of elemental areas of a picture subject which is to be reproduced, and intermittently and alternately varying independently of the picture to be reproduced the electric currents to increase the current strength to a predetermined value during certain predetermined time periods and to decrease the current strength to a predetermined value i like predetermined time periods.

21. In a double setting system for the reproduction of visible subjects, an amplifier and-intermittentl operable means connected with said ampli er for alternately placing the output energy level therefrom at prede-.

termined points above and below the. norm output energy for impressed input energy.

22. In a double setting system for the reproduction of visible subjects, an amplifier and 23. In a double setting picture reproducing system, an amplifier, an input circuit associated therewith for applying tosaid amplifier varying potentials corresponding to signals for amplification, and intermittently operable means for changing the output energy from said amplifier irrespective of the input energy for producing for predetermined time periods output energy above and below the normal output energy producible from normal amplification for said input energy v 24. In a double setting picture reproducing system, an amplifier, light translating means for converting varying intensities of light and shadow on a'record surface of which an image is to be transmitted into proportionate strength electric current impulses, means for impressing said electric current impulses .upon the mput circuit of said amplifier, and

proportion to preestablished intensities of' light and shadow upon said amplifier, means for causin a response from said amplifier over a pre etermined time period of a value below the normal response for said impressed signals, means for causing a response from i said amplifier during a second similar predetermined time period of a value above the normal response for said impressed impulses, and abruptly operable means for changing the response of said amplifier between said Values above and below the normal output therefrom so as to produce a resulting effective output which is substantially linear.

26. In a system for producing the effect of linear response from a photo tube amplifying system for amplifying currents produced in accordance withwarying changes in light intensity upon elemental sections of a record surface of which an image is to be transmitted,

a light converting element for converting the i a changes in light intensity upon elemental sections of a record surface into psigportionate strength ePectric current impu an am-- plifying system for amplifyi the produced electric current impulses, an means inte'r-, mittently operable at a predeterminedslowly changin rate for chan ing the characteristic curve 0 operation of t e amplifying system between limitlng values above and below the normal operating characteristic whereby the resulting efiective output from theamplifying system is substantially linear.

27 In combination with picture transmitting apparatus, a light translating element, an amplifier, and means operable alternateiiy at predetermined time periods correspon ing tothe time period re uired to scan each line of the picture record y said light translating element for abru tly changing the out ut level of said ampli er to values above an below the normal out ut level.

. 28. In combination wit a picture reproducing system, a light translating 1 element adapted to be move in a line for ne manner relative to a record subject of which an image is to be reproduced for converting lifght values of successive elemental areas 0 the picture into proportionately varied electric current impulses, an amplifier for amplifying said produced electric 'current impulses, and means operable at the end of each line of picture scanning for abru tly changing the output level of said ampli er to a value above or below the normal output level thereof. e

29. The method of reproducing picture records which comprises scanning a record subject by a li ht translating element in a series of parallel lines to produce electric current impulses. of intensities varying in accordance with the intensity ofv light and shadow on successive elemental areas of the record of whichthe electro-optical image is I desired, amplifying the produced electric current impulses, and changing at the end of each line of scanning the normal bias upon the amplifying system between values above and below normal to produce increased contrast and sharpness of detail in a icture record reproduced from the amplifie signalling impulses.

RICHARD H. RANGER.

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