US1631963A

US1631963A - Transmission of pictures by electricity

Info

Publication number: US1631963A
Application number: US683632A
Authority: US
Inventors: Herbert E Ives
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1923-12-31
Filing date: 1923-12-31
Publication date: 1927-06-14
Anticipated expiration: 1944-06-14

Description

June ,14 1927.

H. E. was

TRANSIISSION 0F PICTURES BY ELECTRICITY Filed Dec. 31. 1923 Patented June 14, 1927.

UNITED STATES 1,631,963 PATENT OFFICE.

HERBERT E. IvEs, OF NToTAIR, N W JERSEY, .ASSIGNOB To wEsTERN ELEcTRm COMPANY, INCORPORATED, or N w Yo K, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION 01? PICTURES BY ELECTRICITY.

. Application filed December 31, 1923. Serial No. 683,632.

This invention relates to the transmission of pictures by electricity and more particularly to the reproduction of a picture in the form of a dot image.

In the reproduction of a picture from an electric current which varies in accordance with the light characteristis of the original, the picture may be built up of linetraces of varying density, of lines of uniform density and varying width, or of dots of various sizes. Pictures reproduced in the last mentioned manner are similar in appearance to the Ordinary half tone pictures so well known in the printing art. Such pictures have a much less objectionable grain than do pictures consisting ofparallel lines or strips and so are somewhat preferable fromthe standpoint of appearance. A possibly even greater advantage of the dot picture is that it may be used to print directly upon the copper or zinc used by the photo-engraver to make a typographic printing plate. Such use permits the elimination of several copy-, ing Operations which have heretofore been necessary with electrically transmitted, pictures.

An object of this invention is the reproduction of pictures in the form of dotimages in a novel and effective manner.'

In one embodiment of the invention, an

field, in such a manner that current there-' throu h will cause relative movement thereof. paque plates each with a V-shaped edge are mounted on the wires so that the resultant opening is a square whose size varies with the motion of the wires. The wires are mounted at an angle of degrees to the direction of the. trace on the record blank. Intermittent exposure at rcper intervals in order to form dots is e ected by a rotating sectored disc.

The novel features which are characteristic of this invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of Operation, together with otherobjects and advantages will be understood from the following description, having reference to the accompan mg drawing. It will be noted that some 0 the features of the invention are useful in other fields than that of picture transmission as will inafter. a

Fig. 1 illustrates schematically a system for the transmission of pictures by electricity according to this invention including an arrangement for reproducing the picture in the form of a dot image.

Fig. 2 is an enlarged section of one form of a developed record showing the relation of the exposed areas to the opaque shields and movable shields. Fig. 3 is a partial cross-section along the line X-X of Fig. 2 showing the relative positions of the opaque shields and movable wlres.

Referring now to Fig. 1, two rotating 'drums 5 and 6 are mounted on shafts 7 and 8, which are caused to rotate in any suitable manner. As the drums rotate, they are caused to move axially with respect to the shaft. The drum 5 is transparent and has .mounted thereon a transparency 9 of the determined by the tone value of the ele-- mental area of transparency 9 which is opposite the aperture in screen 13 at any given time. The circuit of the photo-electric cell 11 is connected to a modulating device 14, whereby carrier waves from source 15 are modulated and transmitted to the transmissionline L. The modulating device 14 may consist of electron discharge devices as indicated. A suitable arrangement for synchronously rotating the drums 5 and 6 and modulating the carrier waves in accordance with picture currents from the photo-electric cell 11 is disclosed in the copending application of M. B. Long Serial No. 681,347, filed -December 18, 1923.

At the reproducing station, a light valve V controls the amount of light which may pass from a sour e. 16 to efi'ect exposure, of the light sensitive record blank 10. "The light valve V is similar in general arrangement towthe light valve disclosed in a copending application of E. C. Wente Serial appear here- No. 6-': 5,886, filed May 1, 1923. It' consists of two

wires

17 and 18 suspended in a magnetic field which is produced by acoil 19. Mounted on the wire 17 is an opaque shield 20 and on the wire 18 an opaque shield 21, each ofwhich. has a V-shaped notch in one edge. The shape and relative location of the wires and shields are shown more clearly in Figs. 2 and 3.

Under the action of current from the line L, (which current may be translated in any suitable manner in the. electrical apparatus indicated in block 22) the wires are caused to move relatively to each other. The result of such movement is the formation of a square aperture between the opaque. shields varying in size in, accordance with "the. strength of the actuating current. The translating action which takes place within the block 2;. may bea demodulating action as disclosed in the Long application supra, or it may be a simple amplification of the modulated carrier waves. In any event, the adjustment of the movable wires is such that the aperture is either at. its maximum opening or entirely closed when no carrier waves are being received from the line L.

The shields are illuminated by light from the light source 16 which is concentrated by condensing lens 23. The projection lens 24 then forms an image of the aperture between the opaque shields on the record blank whenever a slit in the sectored disc 25 permits the passage of light through an aperture in the screen 26. The sectored disc 25 is rotated at a speed proportional to that of the drum 6 and at such a speed that any desired number of exposures per linear inch of trace may be effected. For a good grade of reproduction, this speed would be such that 50 or 60 exposures per linear inch of trace would .be

'madc. The scctored disc may be driven by means of the gears 27 as shown.

It is to be noted that the movable wires and the sectored disc in Fig. 1 are shown in perspective for the purpose of clearness and simplicity.

. The size of the exposed area on the sensitive record blank 10 is determined by the size of the aperture between the

opaque shields

20 and 21 which inturn is a function .of the current flowing in the conductors 17 t and 18.

Fig. 2 in addition to showing the movable wires and opaque screens shows a section of the developed surface of the record blank 10. This showing is of course greatly enlarged. The paths between the vertical dotdash lines indicate the trace of the. light beam as the drum 6 rotates. The record is in the form of squares of varying size depending upon the relative ti ositions of the movable wlres 17 and 18. he axes of the

wires

17 and 18 are located at an angle of 45 degrees to the direction of the trace of the V-shaped e record, as shown, so that the sides of the dots will be parallel or at right angles to the direction of the trace. Other arrangements may of course be used if desired.

Since the movement of the wires relatively to each other is directly proportional to the current flowing thcretln'ough, the areas of the dots are proportional to the square of the current. For example, it the current is doubled, the area of the aperture and hence of the dot will be quadrupled. This is inherent. in the structure of the. device. In order. therefore, that each dot may be proportional to the density or tone value oi the corresponding elemental area of the transparency 9 of the picture. the picture current. corresponding thereto should vary as the square root. of the light intensity within the photo-electric cell 11. ,This condition may be obtained by any one or more of several adjustments of the apparatus elements of the circuit located between the photo-electric cell 11 and the movable wires of lightvalve V. Such adjustments will be obvious to those skilled in the art. One means for effecting this result, is to use resistance 28 shunted across the circuit extending from the battery 29 and photo-electric cell llto the modulating device 14 the cell being one whose characteristic is such that the photoelectric. current rises rapidly with voltage. This resistance should be large, the absolute value of which is dependent upon characteristics of the photo-electric cell.

It is not necessary that picture current. from the photo-electric cell 11 be transmitted as modulations of a carrier wave but it may be transmitted directly to the light valve V with or without amplification as the requirements of the circuit demand. The sectored disc should preferably be placed as close as convenient to the screen 26, although other positions may be selected.

, The scope of the invention is not to be limited by the specific embodiment shown in the drawing, but only by the appended claims.

What is claimed is:

1. A light valve comprising means to produce a magnetic field of uniform strength, a member having a V-shaped edge located in said field a second member also having a dge suspended in said magnetic field and adapted to move relatively to said first mentioned member so as to form, a square aperture of varylng size.

'2. A light valvecomprising means to produce-a magnetic field of uniform strength, a pair of movable members suspended in said magnetic field and adapted to move relatively to each other, an opaque screen havin" a V-shaped edge mounted on each of sai movable members and adapted to form a square aperture of varying size between said opaque screens.

3. In a system for the transmission of pietures by electricity. a source of picture current varying as a function of the tone values of the elemental areas of a picture to be re produced, an electromagnetic light valve having a conductor movable under the influence of said current, an opaque screen controlled by said conductor for completely defining an aperture, and means to record the size of said aperture.

4. In a system for the transmission of pictures by electricity. a source of picture cur.- rent having characteristics which are a function of the tone values of the elemental areas of a picture to be reproduced, an electromagnetic light valve having conductors movable under the influence of said current. opaque screens having V-shaped edges and controlled by said conductors for completely defining an aperture, and means torecord the size of the said aperture.

5. In a system for the transmission of pietures by electricity, a source of picture current having characteristics which are a function of the tone values of the elemental areas of a pictureto be reproduced, an electromagnetic light valve having conductors movable under the influence of said current, opaque screens having V-shaped edges and controlled by said conductors for completely defining an aperture, means to illuminate said aperture, a movable light sensitive record blank and a sectored disc for intermittently exposing said record blank to said illuminated aperture. 6. In a system for the transmission of pic- I tures by electricity, a source of picture current having characteristics which are a function of the tone values of the elemental areas of a picture to be reproduced, an electromagnetic light valve having conductors movable under the influence of said current, opaque screens having V-shaped edges and controlled by said conductors for completely defining an aperture, means to illuminate said a rture, a movable light sensitive record bank and a sectored disc adapted to successively expose elemental areas of said record blank to light from said illuminated aperture.

7 In a system for the transmission of pictures by electricity. means to produce picture currents, means under the control of said picture currents to produce a beam of light having a cross-sectional area proportional to said picture currents, means sensitive to said beam of light, and means to cause said beam of light to affect said sensitive means intermittently.

8. In an electro-optical system, a source of electric current, means actuated by'current from said source to produce a beam of light having a cross-sectional area proportional to said current. means sensitive to said beam of light, and a disc acting upon said'beam of light to affect vsaid sensitive means intermittently.

9. In a system for the transmission of pictures by electricity, a picture to be transmitted, means to produce picture current, the instantaneous amplitudes of which are proportional to the square roots of the tone values of the elemental areas of the picture. and means including an electromagnetic light valve for reproducing the picture in. the form of a dot image.

10. In a 'stem for the transmission of pictures by ectricity, a picture to be transmitted, means to produce picture current, the instantaneous amplitudes of which are proportional to the square roots of the tone values of the elemental areas of the picture, means including an electromagnetic light valve havin conductors movable under the influence 0 said icture current, opaque screens having .V- aped edges and controlled by said conductors for completely defining an aperture, and light sensitive means to indicate the size of said aperture.

In witness whereof, I hereunto subscribe m name this 26day of December, A. D. 1923.

HERBERT E. IVES.