US1805848A - Method and means for scanning - Google Patents

Description

May 19, 1931. u. A. sANABRl v1,805,843

METHOD AND MEANS FOR scANNIN'G Filed June 7. 1929 2 'Sheets-Sheet 2 y v l0 /z Ff@ 4. w?

f c /0 g L /7-277 Y l' f 'H UL/.Sf/LJAr/Am /N VENTO/2 Pf6. 5. By @2f/Azz ATTORNEY Patented Maly 19, 19,31r

l aura sar s 1 rar 1*,a15isA LISES A, SANABBIA, FA LOUISVILLE, KENTCKY, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO WESTERN TELEVISION CORPORATION, 0F CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE METHOD AND ivrnensron scAivNING Appiicatim sied :rune 7, ieee. serial ingesamt.l

My invention relates to apparatus for broadcastingy and receivingk visual images and pictures and more particularly to a novel scanning device and method for analyzing the image or Object Which is desired to be transmitted and received'either by Wireless or vvii'ed television.

Heretofcre methods employed for scanning or covering a picture surface have used T a-rotating or'other movable member provided with suitable analyzing elements for controlling pencils of light adapted tc sweep over the image or picture surface from one of its sides to the other and in succession from top to bottom or vice versa, once for each revolution or complete cycle. v i

Obviously, such scanning methods cause the picture surface to betraversed by a series of light pencils Which sweepover the picture surface in successive vadjacent ,paths With the result that successive scan lines or paths have practically thel saine shading characteristics in other than certain geometrical images, and since electrical impulses given off lor controlled by the photo-electric cells, so placed as tc receive the light changes from the image being transmitted,y derive their Wave form lcharacteristics from the shading of the image, it is obvious that successive electrical impulses will possess similar Wave shape and frequency characteristics corresponding tothe shading,characteristics of said image. y

It is Well known that all electrical circuits exhibiting selective frequency characteristics possess a certain amount of electrical inertia, that is any certa-in Wave form must be repeated a certain number of times in order for this inertia to be overcome and the transient to disappear, thus permittiiig'the signal to reach. an optimum, y

When the above system of scanning is utilized, similar Wave forms are repeated several times, thereby giving effectual duration sufficient to overcome said inertia 'and permit the'signals to buildup suiiiciently to affect the selective qualities vof an electrical circuit having selective frequency characteristics.L This buildingv up of signal frequency causes undesirable interference due to the Widening ofthe so-called side-bands.

I propose to eleminate this objectionable interference caused by the side-baiids by interposing dissimilar Wave forms so that no particular Wave form Will be repeated a sufficient number of times to overcome the inertiaof the' circuit having selective fre-4 quency characteristics, therefore, a signalis not permitted te build up to sucient strength to be a factor Within' the range of practical perceptibility.

@ne method of accomplishing this inter.-V

position of frequencies is to provide a scanning -disc having analyzing elements ar'- ranged sc that-successive elements of rota'- tion do not kscan adjacent segments of the image. In other Words, they proba-bility is that the successive lines of scanning Will possess vastly dierent shading characteristics. Itl follows that the electrical Wave shapes generated byy the photo-electric cells, when',

'and no one Wave shape will have suiificient duration te give rise tc audible side-band interference, thereby eliminating all interfereence Withinthe limits of practical perceptibility.'v

lit is an object of my inventionhto obtain e the foregoing by using a scanning member having its analyzing elements so arranged that for each complete cycle a plurality of ycoarse scans of the image are made. These coarsescans being odset from one lanother `in such a manner that their combined effect for each complete cycle is aline scan.

`eo y A further object-cfiny inventioniis to provide a method of iinage'transmission Which Will scan. or cover the image or picture surfacev to be transmitted with a plurality of light pencils adapted to traverse the picture sur` face in a plurality of adjacent paths but With.

successive .light pencils traversing the picture surface innen-adj acent paths.

y A further object of my invention is to provide aV novel, comparativelyjsimple andiefz inra l fective method and apparatus whereby the definition of the image is materially increased without necessitating a corresponding increase in the light impulse frequency, or, conversely, whereby the light impulse frequency and resulting elect-rical frequency are decreased without a corresponding decrease in definition.

Another object is to provide a method for rapidly covering the area of the object or picture to be transmitted within the time of persistence of vision, that is, twelve to sii:- teen times per second without involving too high a speed and which will reduce the flicker at both the transmitting and receiving stations.

A further object of this invention is to provide a rotating scanning disc having a series of apertures or analyzing openings each situated at a different distance from the center of rotation and arranged in more than one spiral.

My invention will be better understood from the following description taken in connection wit-h the accompanying drawings and its scope will be pointed out in the appended claims. n

Referring to the drawings, Figure l is a plan view of my improved scanning disc; Figure 2 is a diagrammatic slretch illustrating the manner in which the image or picture field is scanned or analyzed and composed or built up; Figure 3 shows another disc embodying my invention; Figures l and 5 are sketches showing the radial arrangement of the apertures; Figure 6 shows a perforated ribbon or band; and Figure .7 is a schematic drawing showing one way of carrying out my method.

The scanning disc shown in Figure l comprises a disc lO of some suitable material such as aluminum having` holes ll near its center for mounting to any suitable driving` means such as an electric motor (not shown) for rotation about center O. Scanning or analyzing apertures l2 are formed, by dr'llingl or otherwise, near the periphery of the disc l0. For convenience, l have illustrated a disc having only fifteen aper tures, although l prefer to use a greater number, as for instance forty-live, but since the principle is the same regardless of the number of apertures used, a disc having fteeny apertures will suffice for the purpose of giving a complete description and disclosure of my invention. The apertures 12 are equally spaced angularly which, in the present case of fifteen apertures, is twenty-f0ur degrees (24) and are arranged inthe form of three spirals. Each aperture 12 is located a different distance from the center O of the disc lO.

A description of a method of layout for a fifteen hole disc will best describe the exact arrangement of the apertures l2 on the disc 10. First of all fifteen equallu spaced radii r are inscribed on the disc 10. rlhen fifteen equi-spaced concentric circles c are drawn having as their` center the center of rotation O of the disc 10. The distances between the concentric circles c should equal or be less than the diameter of the apertures l2 which are to be formed.

rEhe intersections of the radii r and the con centric circles c determine the centers of the apertures 12 which are located in the following manner Starting with spiral l an aperture l2 is formed at the intersection of the radial line r and the outmost circle c. Going clockwise twenty-four degree Q24?) another aperture is formed at the intersection v of a radial line r and the fourth circle c counting towards the center O. This process is repeated for the remaining three apertures l2 of spiral l so that each aperture of rotation is radially spaced from the proceeding aperture by the distance between three of the concentric circles c which is the distance between adjacent circles times the number of spirals. 'lille apertures in spiral ll are located or situated in the same way except that the first aperture l2 of the spiral ll is located on the intersection of its radial line r and the second concentric circle c counting towards the center O. The same applies to spiral lll which has its first aperture located on the third circle c counting from the outmost circle towards the center (l.

From this it is observed that the first aperture l2 in spiral ll is radially spaced from the first aperture l2 in spiral l by the distance between adjacent circles c.

For a more complete understanding of the exact arrangement of the apertures l2 in the various spirals reference is made to Figur-es l and 5 in which the radial lines r have been rotated about the center 0 to bring the apertures l2 into close proximity with one another. From the arrangement of the apertures l2 it can be seen that the apertures l2 in spiral l will coarsely scan the entire image or picture field and that spirals ll and lll will also coarsely scan the entire ima-ge or picture field in succession. Due to the fact that no two of t ie apertures l2 scan the saine elements of the image or picture field, it is evident that the combined effect cf the three coarse scans is to give a line scan or detailed analysis of the entire image or picture field for each revolution of the scanning dise i0.

his combining of coarse scans to build up a ne scan is illustrated in Figure 2 in which A indicates the elements of the image or picture which are analyzed by spiral l and B and C indicate the element-s analyzed by spirals ll and lll respectively. For each revolution of the scanning dise l-O the coarse Ascans of spirals l, ll and lll .are interposed to form the fine or complete scan represented by D.

lt is obvious that my invent-ion may take 'il O agr CSX

various forms suc-h as shown in Figure 3 Where a six spiral disc is represented in Whichsome of the spirals alternate, that is, scanv from bottoni to top While the other spirals scan from top to bottom. is in the case of the three spiral disc the coarse scans of each spiral fit together to form a fine or complete scan.

lNithout changing my method the .apertures may be formed ina ribbon or band as .shown in Figure 6 in which the apertures are arranged in a series of groups so that each group will coarsely scan the image .and the resultant of all the groups will form a. fine scan in the same manner as a disc made in accordance with my invention as above described.

In Figure 7 the disc l0 having apertures l2 made in accordance With my invention is w intended to be rotated between a source of light L and a picture surface S shown edge on.

IVhen the aperture l2 is infront of the light L the pencil of light strikes the picture surface S near the top, as shown in full line; When some other aperture l2 is in position the pencil of light strikes the picture surface S near the bottom, as indicated by thebrolrenV line; when other apertures come into position the light pencils strike in different positions between these extremes. y

It Will readily be understood that upon rotating my improved disc that light pencils Will travel across the picture surface from side to side; While thearrangement of the apertures in more than one spirall causes successive light pencils to traverse the picture surface in non-adjacent paths, the adjacent paths being traversed by non-successive light pencils. p

In reception the light source L is van illuminant modulated in accordance With the received signals and the image is built up on the surface S in the same sequence in which it vvas analyzed for transmission, that is, a series of coarse scans interposed to form a fine scan. This building up of the entire imager simultaneously does avvay with the' crawling effect observed When a single spiral disc is used and reduces flicker in the received image.

While I have shown the analyzing elements to be small round holes or apertures'my iny vention is not limited there-to, but obviously includes the use of apertures having any other shape such as square or oval and also includes" the use of lenses, prisms and mirrors which are Well known in the art since all are equally adapted to my improved method of scanning.

I have found in using a scanning device made in accordance with this invention for the transmission and reception of images or pictures that for the same speed of scanning and the same number of apertures the fidelity and definition of reception lis far better than when using the spiral.

I have also found Withthe'use of my improved scanning method that it is possible-to transmit and receive half-tone images having satisfactory definition and fidelity vvithy out exceeding the broadcast band perceptibly.

I believe that the interposition of frequencies as above explained, obtainable by m factor Which enables me to transmit and receive half-tone images'vvitliout using a band of frequencies greater than required for firstclass voice and music broadcasting. Y

Whilc I have described a particular embodiment of my invention, and -certain apparatus for carrying out my method, it will be obvious to those skilled in the art that various ordinary disc-,having a single y* novel method of scanning, is the controlling disc provided With aY plurality of apertures arranged in more than one spiral and sol positioned that each aperture describes a separate circularvpath about the center of rotation.

2. InV apparatus of the class described an optical analyzing .unit comprising a rotating disc provided With a series of yapertures arranged in a plurality of spirals to svveep over an image and so arranged that theapertures in each spiral make a complete coarse scanof the image offset' from that of theV other spirals.

3. A rotating scanning disc .provided with a plurality of apertures each vsituatedk at a diiferent distancel from the center of rotation and so arranged that the distance from the i center of rotation of successive apertures of rotation differ more than that ofV some nonsuccessive apertures of rotation.

iio

.4. A rotatingscanning disc provided With a series yoffanalyzing elements eacli situated a different distance from the center of rota- I tion and arranged in more than one spiral.

6. In an apparatus ofthe class described alyzing elements arranged to svveep over an image in non-adjacent parallel paths.

7. In combination, a stationary picture surface, a stationary` light translating element, a rotatable disc interposed between said surface and said element, said disc being pro-y an optical analyzing unit comprising a movf ing member provided With a plurality of anvided with a plurality of apertures so arranged that upon rotation of the disc the apertures pass successively betvveen said surface and said element and successive images of the light translating element traverse the picture surface by non-adjacent parallel paths.

8. A scanning disc provided with a plurality of apertures arranged cn a plurality of spirals in such a manner that any aperture on one spiral appears on a radius equal to the radius of the corresponding aperture on any other spiral, plus or minus an integral nu1nber of aperture diameters.

9. A scanning disc provided With a plurality of apertures arranged on a plurality of spirals in such a manner that successive apertures of rotation are radially displaced from each other by a distance greater than the diameter of an aperture.

l0. A rotating scanning disc provided With a plurality 01"' analyzing elements each analyzing element being located on a single circle of a series of concentric circles7 said concentric circles being equi-spaced apart frein each other and said analyzing elements being so arranged that successive analyzing elements of rotation lie upon non-adjacent circles.

ll. A rotating scanning disc provided with a plurality of apertures situated cn equispaced concentric circles having a common center coinciding with the center of rotation of the discA and so arranged that successive apertures of rotation lie on non-adj acent circles.

l2. A scanning disc having a center of rotation and provided With a plurality of apertures spaced angularly near the periphery thereof and arranged in such a manner that `successive apertures of rotation are radially displaced from each other by a distance greater than the diameter of any one aperture. Y

13. In a television receiver an illuminant adapted to be modulated in accordance With incoming signals7 scanning means for coinposing an image from said signals compris ing a disc having a plurality of analyzing elements so arranged that upon rotation of the disc the successive analyzing elements of rotation follow nen-adjacent paths.`

In testimony whereof I have aiiXed my signature.

ULISES A. SANABRIA.

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