US1789686A

US1789686A - Light-chopping disk

Info

Publication number: US1789686A
Application number: US349076A
Authority: US
Inventors: Ranger Richard Howland
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1929-03-22
Filing date: 1929-03-22
Publication date: 1931-01-20
Anticipated expiration: 1948-01-20
Also published as: GB340886A

Description

Jan. 20, 1931. R H, RANGER 1,789,686

LIGHT cuorrme .DISKH Filed March 22'; 1929, 2 Sheets-Sheet 1 f Y avweuto'c W) woman a. RANGER To'rmgsmnea a: I 7

Ja .2o, 1931. R. H. RANGER 1,789,686 IGHT SHOPPING DISK Filed March 22;, 1 s2s 2 Sh e ds-Sheet 2 RRRRRRRRRRRRR ER Patented Jan. 20, 1931 UNITED STATES RICHARD HOWLAND RANGER, or NEWARK, New JERSEY, ASSIGNOR T0 RADIO coR- PATENT, OFFICE! PORATION OF AMERICA, A CORPORATION OF DELAWARE monr-cnorrme isk Application filed March 22, 1929. Serial No. 349,076.

The present invention relates to a method and means for controlling light and is especially adapted to the transmission of pictures, and the like, for facsimile and television work. By the term pictures, "of course, I

i 1928, it has, so far as I know, been hereinbe fore the custom in the art to which the invention relates to chop. light projected through or reflected from the picture surface,

which is to be transmitted prior'to the time that the varying lightintensities corresponding to the intensity of light and shadow on elemental areas of a picture surface are directed upon a photo cell for the purpose of .modulating a transmitter. It has been customary in arrangements of this type to produce this chopping action by'means of rotat-' ing disks and the likewhich are provided about their periphery with a series of holes or slots through which the light may pass, but, in an arrangement of thistype, inherent objections always prevail in that half of the light was of'necessity lostdue to the chopping action, and because of the fact that it is impossible to perforatea disk so that'the entire amount of light available can be used. Therefore, as in the abovenamed copending application, it is an object of my present invention to provide a meanswhereby the objectionable features occasioned by wasting substantially half of the available light are avoided. e I

Still a further object of my invention is to provide a system wherein the light, prior to the time when it is directed to the photoelectric element, may be .chopped so as to produce a definite tone frequency or even carrier frequencyupon the photo cell, and

since substantially no part of the available light is wasted duringthe time. of transmission,'cons-idferable increase in efficiency is available. I 7

Still another object of myinvention is to produce. an arrangement for chopping the light reflected from or directed through a picture surface prior to the time when it reaches a photo cell, in which it is possible with slight modifications to produce efiicient multiplex transmission so as to substantially increase the speed oftransmission as well as the efficiency thereof.

Still another object of my invention is to produce a disk having thereon a seriesof rismatic surfaces for alternately deflecting 5 ight along two or more distinct paths for. producing the chopping action.

Still another object of my invention is to product a light chopping arrangement wherein substantially all of the light directed to the chopping element may be utilized, and wherein substantially no light is absorbed by the chopping element.

Still another ob ect of thepresent invention is to provide a means-for, chopping light 75.

issuing from'a picture surface prior to'the time when such light reaches the photo cell, which is; simple'in its construction and arrangement, a choppingmeans whichis inexpensive to manufacture, convenient to install,

readily: operated, and which may bedriven by wellknown types of A. C. or D. C. motors or by an air driventurbinafor example.

Other and. ancillary objects of-the present invention will become apparent to those 8.

skilled in the art to which it relates a readmg, of the following specification taken in connection with the accompanying drawings forming' a part of my present disclosure, and

illustrating in aconventional manner the in,-

vention in its preferred form, both as applied to ordinary transmission and to multiplex transmission.

Fig. 1 of the drawings represents a chopping disk provided with V-shaped chopping grooves for use with the ordinary existing types of transmission apparatus;

Fig. 2 represents conventionally the manner in which the light is directed to one or another of a pair of parallelly connected photoelectric elements, according to the rotation of the disk as shown by Fig. 1;

Fig. 3 represents a modification of the ar rangement disclosed by Fig. 1, wherein a disk suitable for multiplex transmission has been shown; and,

Fig. 4 is a view on a reduced scale taken on the line H of Fig. 3 showing the light passing through all of the different prismatic surfaces of the multiplex chopping disk of Fi 3.

Flow referring particularly to Fig. 1 of the drawin s, I have provided a disk 1 which is prefera ly formed from plate glass, cut to form a circular element capable of rotation about any given aXis 3. About the periphery of the disk 1, I have arranged a series of V- shaped grooves generally designated 5, which are cut into the disk at such an angle that the sides thereof extend at substantially 45 degrees to the normal bisecting line of the V-shaped grooves. The V-shaped grooves are arranged to form prismatic surfaces having different light deflecting properties, as is apparent from the showing in Fig. 2.

As shown by Fig. 2, light from a source 7 may be projected through any desired system, such as a lens 9 to a picture surface 11, and supposing that the reflection type of transmitter is used, the light which is reflected from the picturesurface 11 in accordance with the intensity of light and shadow thereon will be reflected and directed by means of a sec- 0nd lens system 13 to the disk surface 1. The amount of light which is reflected, of course, is dependent upon the intensity of li ht and shadow on the picture surface 11, an where the picture surface is substantially black, practically the entire amount of light projected in the source 7 will be absorbed, but for high lights on the picture surface 11, substantially the entire amount of available light will be reflected through the lens 13 upon an adjustable diaphragm 14 of the general type disclosed in my copending application Serial No. 321,821, filed November 26, 1928, from which it is projected as a light band of a predetermined width to the disk surface 1, and then projected upon the V-shaped grooves 5. As shown by Fig. 2, the light reflected from the surface 11 is focused by means of lens 13 as a point source upon the diaphragm l4 and then directed to the side 15 of the V- shaped grooves 5 from which it is deflected along a path 16 through the disk, and after passing beyond the disk 1 is deflected along a path 17 to a photoelectric element 19.

As the disk 1 is rotated in the direction shown by the arrow, the light reflected from the surface 11, and reaching the disk through diaphragm 1 1, will be projected upon the side 21 of the V-shaped grooves 5 on the disk member 1, and will be then deflected through disk 1 along a path 22, and after passing beyond the disk 1 is deflected along apath 23 as shown by dotted lines to a second photoelectric cell 25. As the angle of inclination of the V-shaped grooves 5 remains substantially the same for the entire length thereof, the path at which the light beam projected upon the grooves 5 will be deflected remains substantially the same while the disk is rotated, so that a. light beam originally reaching a point 27 will always be deflected along the same path until the disk is rotated to the point where the light beam reaches the point 29, whence the path of deflection will change to the path corresponding to 23 and will remain constant until the disk has travelled so that the point traced by the reflected light from the picture surface 11 reaching the disk 1 through the diaphragm lt corresponds to the point 31 where the path of the deflected beam will again change to the path indicated as 1?, and the process will be repeated. However, in order that the output energy of the photo cells may appear as a true sine wave, it is advisable that the light spot traced on the disk may have some appreciable width and thus illuminate both photo cells simultaneously at periods when the light is either at the top or bottom of the various V-shaped grooves 5.

It is, of course, recognized that the rate at which the light beams travel along the paths 17 or 23 to reach the photo cells 19 or 25 is dependent upon the speed of rotation of the disk member 1, and, of course, the faster the disk rotates the higher the frequency of the chopped light upon the photo cells will appear.

Associated with the photo cells 19 and 25, I have provided the

usual biasing batteries

27 and 29, and the

resistors

31 and 33, each connected to a common point 35, connectin to a like-element of each of the photo cells 19 and 25.

As was disclosed by patent to Nicholson, No. 1,470,696, and also by Patent No. 1,656,338, issued to me on January 17, 1928, light intensities reaching the photoelectric elements produce variable potential drops across the resistors associated therewith, and thus control the potential on the

grid electrodes

37 or 39 of the amplifiers 11 and -13. The

amplifiers

41 and 13 are supplied with plate potential from a common source 45, and each of the output circuits are connected in push-pull fashion by means of transformers -17 and 19 with a second pair of amplifiers o with a circuit 57 connecting with a transmitter of'the usual type.

As light of a greater or lesser intensity reaches the photoelectric elements19or'25, it

produces therein currents whose strength is varied in accordance with this particular amount of light, and thus the potential drop across the

resistors

31 or 33 is continuously changing, and, consequently, the output from the vacuum tube amplifiers 11 or 43 i continuously changing, but, since either of the photo cells 19 or 25 is continuously subjected to light intensity, there is never a total absence of output energy from the

amplifiers

41 or 43. Thus, considerable increase in transmission efficiency is occasioned. The effect of the chopping action of the disk is inherent in the system since the rate of chopping is the same at both photo cells, and each cell is subjected alternately andsuccessively, or in a sequential manner, to'the light reflected from the picture surface 11 at a rate corresponding to the chosen tone or carrier frequency. I I j I I Now referring to the arrangement disclosed by. Fig. 8, I have provided a similar disk 1 provided with a plurality of concentrically arranged V-shaped grooves generally designated as A, B and G extending circumferentially thereabouts. Since the disk of the type shown by Fig. 3 is to be adapted to multiplex communication systems, the pitch of each of the V-shaped grooves forming the series A, B or C is arranged different, and as has been shown in the present instance, merely by way ofexample, the series A may bearranged so that there are 94 V-shaped grooves inthis path, the series B may be provided with 104 V-shaped grooves, and the series C with 114. V-shaped grooves. It is, of course, to be recognized that these values suggested are in no way limiting, although they have been found in practice to be desirable, but other values such as, for example, 70, 90 and 110, or other chosen values may be substituted for the number of grooves in each separate path. i i i As was disclosed in connection with Fig. 1,

eachof the individual V-shaped grooves 5 I is provided with similar sloping

sides

21 and 15, each extending at substantially 15 degrees to the normal bisecting line of the V- shaped groove so as to deflect lightin a manner similar to that shown and explained in connection with the arrangement of Fig. 2.

As has been above disclosed, light from a source 7 may be projected by means of a lens member 9 so as to produce on a picturesurface 11 three distinct paths of illumination 59, 61 and 63, supposing that a three channel multiplex arrangement is to be provided, although, of course, it is to be recognized that the system is in no way limited to 3 channels but may be increased to any desired number, for example,j10'to 20 channels, or more or less,depending, of course, upon the number of separate paths of 'V-shaped grooves extending "circumferentiallyabout the disk 1.

As was explained in connection with Fig. 2, lightreflected from the picture surface 11 is then projected by means of a lens system 65' so as to focus through a. similar diaphragm 11 as'three distinctpoints 67, 69 and 71 upon the respective channels A, B and C of the disk-1 rotating about the spindle 73, and will then be projected to one or the other of the photoelectric elements. 19

or 25. I

As shown, I have provided in connection with a multiplex arrangement of this character an elongated photoelectric cell 19 which extends for a distance equal to the width of the three channels A, B and C, or for a greater distance for a greater number of channels, and this cell will alternately and successively be subjected in a sequential manner to light passing'through the portions A, B and C of the disk 1. As has been V shaped groove than that shown as being projected from theside 15 of each of the grooves. in thismanner, the cells 19 or 25 will receive light from each of the channel A, B and Q at a frequency depending upon the speed of rotation of the disk and the num' ber of separate V-shaped grooves in each path, and will produce in an output circuit, not shown but similarto the circuit 57, energy proportionate to the light intensity projected upon each of the individual paths. While the invention has herein been ex plained principally in regard to its application to radio transmission systems, it is also to be recognized that the same is applicable to wire line transmission or wired radio trans mission, and the term radio transmission systems, as herein used, should therefore be regarded in a generic sense as including all types of communication and not limited to radio alone.

In addition, while a reflection type of transmitter has been particularly described,

has been described in connection with one of its preferred forms, that certain modifica-c tions and changes may readily be made, and I believe I am entitled to make allsuch modifications and changes as would readily suggest themselves to those skilled in the art to which the invention relates provided that such changes fall fairly within the spirit and scope of the invention as defined by the hereinafter appended claims.

Having now described my invention, what I claim and desire to secure by Letters Patent is the. following:

1., In a picture transmitting system, a source of light for illuminatinga picture; surface, a disk having a plurality of prism surfaces about its periphery and so arranged as to alternately and successively deflect the light from said picture in two directions, and a pair of photoelectric elements successively and alternately subjected to illumination by mid deflected light beams.

El In a multiplex communication system, a light chopping disk having a plurality of concentric prismatic surfaces thereabouts, each of said prismatic surfaces being composed of portions having successive and alternate deflecting properties, whereby light directed thereagainst is successively and alternately deflected along a plurality of different paths.

3, A light chopping disk for communication systems actuated in accordance with varying light intensities comprising a circular light transparent surface, and a plurality of V-shaped grooves extending in a radial direction about the entire periphery thereof. whereby the deflecting properties of adjacent sides of the said V-shaped grooves are such that the light beams are deflected alternately and successively along different paths during the rotation of said disk.

4. In communication systems actuated in accordance with varying light intensities reaching a photo cell, a light source arranged to project the issuing light beams along a predetermined path, a transparent disk arranged so that its periphery falls at the focus point of said projected light, a plurality of V-shaped grooves extending radially from the periphery of said disk about the entire circumference thereof, means for rotating said disk, and means provided by said V- shaped grooves for alternately and successively projecting the. light focused thereon along two paths bearing an angular relation ship with respect to each other.

In a communication system utilizing varying light intensities impinging upon a light sensitive element for modulation there of, a light chopping disk having a plurality of V-shaped grooves each of a different pitch extending concentrically with respect to the center of rotation thereof, a light source, a subject for transmission, means for project ing the light from said source upon said subject and reflecting the unabsorbed light therefrom to said disk, a. pair of photo cells arranged behind said disk, and means provided by said disk for sequentially subjecting each of said photo cells to said reflected light at a plurality of different rates.

6-, In a communication system utilizing varying intensities of light impinging upon alight sensitve element for modulation thereof, a light chopping disk having a plurality of V-shaped grooves each of a different pitch extending concentrically with, respect to the center of rotation thereof, a. light source, a. subject for transmission, means for projecting light from said source upon said subject and reflecting the unabsorbed light therefrom as a plurality of light beams to the in dividu-al V-shaped grooves of said disk, a. pairof photoelectric elements arranged behind said disk, means for rotating said disk, and means provided by the rotation of said disk for sequentially subjecting each of said photoelectric elements to reflected light. from said subjects at a plurality of different frequencies and producing therefrom a plurality of different tone frequency outputs from said photoelectric elements.

'7. In a picture transmission system, a subject for transmission, source of light for illuminating said subject, a. chopping disk provided, with V-shaped grooves extending about the periphery thereof, each of said grooves having sloping sides of substantially the same inclination throughout the entire slope, means for rotating said disk, a pair of photoelectric elements arranged behind said disk and in they path of reflected light pass ing through the said grooves in said disk, and means provided by the rotation of said disk for subjectingeach of said photoelectric elements to the lightreflected from, said subject-in a sequential manner and producing in said photoelectric elements frequencies corresponding to the chopping frequency of said light.

8. A light chopping disk comprising a plurality' of prismatic surfaces arranged about its periphery in such a manner thatv light reaching the periphery of the disk is alternately and successively deflected along a pair of paths bearing an angular relationship to each other.

9.. A light, chopping disk having a plurality of prismatic surfaces about the periphery thereof so arranged that light reaching the periphery of the disk is aiternately deflectedduring rotation of the disk along a pair of paths bearing an angular relationship. to each other.

1 0. A light chopping disk having a plurahty of concentric prismatic surfaces thereabout and so arranged that each of the said prismatic surfaces is composed of portions havingsuccessive and alternate light deflect ingproperties.

11. A light chopping disk comprisng a plurality of V-shaped grooves extending about the periphery thereof and so arranged that opposite sides of the said V-shaped ,pitch grooves have alternate light deflecting properties.

12. A light chopping disk comprising a plurality of concentrically arranged paths each of which include a plurality of V-shaped grooves so arranged that opposite sides of the said V-shaped v grooves have alternate light deflecting properties and wherein each of the plurality of concentrically arranged paths have V-shaped grooves of different RICHARD HOWLAND RANGER.