US1790491A - Television scanning system - Google Patents

Description

Jamo 27, 1931. T. A. SMITH TELEVISION SCANNING SYSTEM Filed Aprili, 1929 2 sheets-sheet 1 ra rece/vs@ f A` SMITH ips 5mm@ 3 mi- 2751931. r. A. sMm-l f TELEVISION scAHNING SYSTEM Filec April 1, 1929 2 Sheets-Sheet` 2 SMT/OMAR Y ,4l/16901? INVENTOR TA BY() ATTORNEY atented Jan. 27, 1931 UNITED "STATES PATENT OFFICE THEoDoRE A. SMITH, oF RInGEwoo-D, NEW'. JERsEY,Ass1GNoR "ro Ramo CORPORA- 'rIoN oF AMERIQA, A CORPORATION OFDELAWARE TELEVISION SGANNING- SYSTEM The present invention relates to television systems, and, particularly, to a methodand means by Which thetelevision subject may rality of built-up horizontal or vertical lines.-`

be scanned or analyzed and then reproduced on aV screen or the like.

It has heretofore been the custom intelevision systems of the type most common, such as in the rotating disk or mirror disk, or-

drum scanning and reproducing systems, to scan the field by means of a number of successive parallel lines formed from a series of points of light traced across the field. Such scanning action breaks the picture or subject to be transmitted or reproduced into a number of divisions, usually horizontal, although a vertical division is also of the same general type. With this typeoi system a spot of`light is caused tomove horizontally or vertically across the field or subject from one' edge to the other, and then to move once more across the field or subject' along a: parallel line adjustedto but lower than or to the right orv left from the previous line. This action is then repeated untilthe complete field or subject has been scanned or analyzed by a plu# Such action is repeated at a rate of at least .16 times per second in order that the complete subject may be scanned at a rate corresponding to the persistency of vision of the human eye vso as to produce the effect of an -optical illusion in which the 'entire picture appears `to be simultaneously projected .upon the screen, although, in reality, successive points and lines are projected, but

each'point or line is repeated at a rate'corl responding to the persistency'of vision.

With a system of the above described type objection has been found in the fact that in the case of horizontalscanning any diagonal lines appearing in the subject are reproduced as stepped lines, and curved lines are reproduced at the receiver as a jagged line of the average curvature of the original line. Another objection resides in the fact that although the received picture may be transmitted and reproduced in its entirety by a rate greater than the repetition necessary to produce the optical illusion of a continuous ly moving picture, or, at a rate at least equal the fact that the picture has tothe persistency of vision, Aa pronounced flicker appears. This is apparently due to n,ot been pro. jected upon the screen in its entlretybut was built up of successive elements, and, because picture is being scanned and reproduced,the human eye fails to retain the image of the lower portion of the picture and this latter portion, therefore, appears dark. This dark v band at the opposite portion of the picture from that which is being scanned appears to travel up and down or across the screen, and thus causes an annoying flicker when a person-views the received image.

vention,`I have sought to develop a method and means for substantially eliminating the4 undesirable flicker from received television images. 4 if y A.

Asa `further object of my invention, I have sought to 'develop 'a method and means by which a television subject may be scanned or analyzed, and then reproduced in a sequential manner along paths bearing an angular relationship to each other so asto reduce flicker to asubstantial degree. y l

' 'Still a urtherobject of 'my invention vis to provide a method andmeans by which a` television Subj ect may be scanned and then reproduced so that diagonal or curved lines in the original subject may be free from any substantial distortion and .will not appear as stepped lines.

Still other objects of my invention are' to produce a method and means for scanning and reproducing television subjects which is simple in its construction and arrangement of parts, a system which is easily operated, readily installed, conveniently set up, substantially foolproof in its operation, and eiicient in its use.

Still other and ancillary objects of my invention will at once become apparent and suggest themselves to those skilled in the art matically and conventionally represent a 100 .55 of the fact that While the upper part of the i Therefore', as a principal object of this in- ,to which the invention has'been drected'by system for either scanning oi reproducing a television subject according to my novel method of scanning and reproducing along different paths in a sequential manner.

y the accompanying drawings, Fig. 1 represents a suitable means for scanning in a vertical direction, and Fig. 2 represents a suitable means for scanning in an angular direction to that shown by Fig. 1, or along lines in a horizontal direction.

Fig. 3 shows the system of Figs. 1 and 2 combined into a single figure, wherein for the position shown the light from the source will be caused to trace a vertical path upon the picture screen, while for the horizontal path which will be traced upon further rotation of the scanning element, the assumed path is shown by dotted lines. Fig. 4 graphically represents the relationship between the series of lines produced by each of the fixed reflecting ,systems cooperating with the rotatable scanning element.

More particularly, my invention has been directed to a system 'in which the scanning action takes place in a sequential manner hy alternating between horizontal and vertical lines of scanning so that the successive lines by which the picture is analyzed will be at right angles to each other. although it is to he recognized that where desired, and without departing from the basic principles of my invention, the angle which successive scanning actions bear to each other may vary within wide degrees, and may be at any angle suitably chosen.

Thus, to describe, for purpose, of illustration, the system as one in which the picture is'lirst analyzed along horizontal lines, then along vertical lines, and then analyzed again and again by repeating this process, the human eye is unable to distinguish the particular direction of reproducing each of the separate pictures on account of their rapidity, and the resultant picture appears as a combinationl of the two distinct types of scanning motion. The produced picture may appear to be broken up into small squares in- 'stead of lines, but the division between squares will be much dimmer than those between the lines, and therefore less objectionable; and further, the stepped effect is substantially reduced because of the fact that it is entirely different for the two types of scanning, and the combination of the two types of scanning neutralizes the distortions in each direction and the combined picture appears more natural than that produced along either of the component lines of scanning. Further than this, it is possible to 'reduce the flicker to a material extent hecause of the changing in direction of the moving band and because of the 4kfact that the flicker frequency would be substantially changed.

To refer now more particularly to the ac- "mirrors forming the portion 5 of the drum are so tilted and stepped that .they reflect light beams downwardly from the disk or drum along adjacent parallel paths.

The drum disk 1 may be mounted in any convenient manner upon a spindle 7, for eX- ample, and rotated from any-desired type of prime mover (not shown), for example, a synchronous motor wh'ose rotation is controlled by incoming television signals of the general type described and claimed in my copending application, Serial ift-322,704, filed November 30, 1928, and driven in the direction indicated by the arrow appearing on the drum disk.

' As shown, the arrangement has been particularly directed to a television reproducing system, wherein, incoming television signals vare arranged to illuminate 4the glow lamp 9 so as to produce a glow therein. The light from the lamp 9 is then directed by means of a lens system 11 so as to project itself as a point source on the drum disk 1 at a point 1 3, for example, as shown. It is preferable, although not essential, to provide a glow lamp in which the illumination therefrom is as a point source so that it may be more readily focused as a point source upon the individual mirrors forming the series 3 or 5 of the drum disk 1. As the drum disk 1 is rotated in the direction shown by the arrow, the point of light focused thereon by means ofthe lenssystem 11 is caused to travel across the-mirror, and thus, due to the change in angular position of each adjacent mirror, the light beam from the glow lamp o'r other appropriate source is reflected along different paths.

As shown particularly in connection with Fig. 1 of the drawings, the light beams issuing from the glow lamp source 9 have been shown as directed against the set of mirrors 3 so as to be reflected in an upward direction from the disk 1 so as to travel along a path 15, for example, where they will impinge upon a stationary mirror 17 and trace paths thereacross in a direction indicated by the arrow. From the mirrors 17, the light is again reflected along a path generally designated as 19, and is projected upon a second stationary mirror 21 from which it is rellected along a path 23, for example, so as to trace lines in a vertical direction upon the screen 25 in a direction thereacross shown by the arrow, so that over half of a revolution v of the disk 1, a completel picture of the teleby the arrow.

vision subject is built up upon the screen 25 in a vertical manner, so that consecutive lines of reproduction are parallel to 'each other and extend across the screen 25 in the direc# tionvshown by the single line 27' indicating the'manner in-which the picture is lbuiltup.

N ow referring more particularly to Fig. 2, after the disk or d rum 1 has turned through a half revolution .so as to bring the light beams issuing from the glow lamp 9 upon the set of mirrors 5, the light beams-are reflected from the mirror surface of the disk 1 along a path generallydesignated as 29' to a stationary mirror 31A arranged below the drum disk 1. The stationary mirror 31 is .tilted at an appropriate angle so that light beams reflected therefrom along a path 33, for example, will trace horizontal paths 35 across the screen 25 in the direction as shown It is thus seen' thatthe 'stationary mirrors 17, 2 1 and 31 must be fixed andappropriately located so that the an le of tilting thereof is such that all light refected from the mirror surfaces composing groups of mirrors 3 and5 upon the drum 1 will'eventually-be projected as a point lsource upon the screen 25. Thus, as the drum 1 is rotated, the lines by which the picture is reproduced will sequentially or alternately and successively be composed of groups of horizontally extending lines due to the reflection of the group of mirrors 5, and vertically extending parallel lines due to the reflection of the group of mirrors 3 upon the drum disk 1.

Afterthe picture is horizontally scanned or reproduced the vertical scanning and re production is repeated. A f

As has been shown, the drum disk 1 is composed of two distinct sets of mirrors, 3 and 5, and each of these sets of mirrors may preferably be of such a number that the complete picture will be reproduced therefrom, and' supposing, for example, that a fifty line picture were' to be desired, the' drum 1 should carry about its periphery one hundred distinct mirror surfaces. This-number of mirrors would be-divided into two groups, 3 and 5, wherein, the fifty mirrors of group 3 should'all be arranged to reflect light in an upward direction, for example, from the disk, and the fifty mirrors of group 5 should be arranged to reflect light in a downward direction from the drum. It is thus apparent that by utilizing a scheme of the type herein described, it is possible also to reduce the speed of rotation of the disk member by fifty percent, although due to the increase in the number of mirrors about the periphery of the disk, the peripheral speed of the disk must be increased over that of a disk having a smaller number of mirrors.

According to the above description, the system has been described Vseparately as to the vertical and horizontal scanning as produced respectively by the arrangements of Figs.` l and 2, but it should be understood lvthat both of. the arrangements of Figs.1 and 2 are-operating in a sequential manner, and the 'system as a whole has further been schematically-shown by-Fig. 3, wherein the con- -trolled light source is in the position of the disk shown adapted to produce a vertical line upon thescreen, whereas, upon further rotation of the disk, so thatthe light from' the source 9'reaches the mirror surface 5, horizontal'lines will be produced upon the screen, as shown by the dotted line paths 29 and 33, which are respectively directed and reflected 'to and from the stationary mirror surface 31.

The vertical and horizontal vpaths of reproduction are Aconventionally illustrated by Fig..4, wherein thelines 27, 27show the vertical scanning paths, while the lines35, 35

show the horizontal scanning paths which occur after the picture has been rebuilt completely along vertical paths, and-then continue until the picture has been reproduced completely along horizontal paths., at which time the verticalscanning is repeated. Y

It will also be apparent that a scheme of the type herein described may also be readily applied to a lens disk or drum without materially changing theconstruction and arrangement of parts, and I, therefore, desire to make all such modifications and changes as may readily suggest themselves to those skilled in the art to which the invention re- Vlates, provided, of course, such modifications and changes fall fairly within the spirit and scope-of the invention as defined in the hereinafter appended claims.

Having now described my invention, what .Y

I claim and desire to secure Y by Letters Patent is the following:

- 1. In a television system, a mirror disk and;

associated reflector system cooperating with one portion of the said mirror disk for scan ning and reproducing a television subjectV along a parallel set direction across the subject, a second reflector system cooperating with the second portion of said mirror disk for scanning andreproducing the same subject along a second set of parallel lines extending at an angular direction to said first named .set of scanning and reproducing lines, and means operable upon each half revolution of said disk for cyclically changing. from one to the other of said sets of scanning' and reproducing lines ata rate commensurate with the persistency of vision.

of lines extending in one 2, In a television system, a screen for re-A producing a television subject, a rotary scanningelement and a reflector system cooperating with a portion thereof for illuminating said screen along series of parallel. aths eX- tending transverse thereto, a secon reflector system cooperating with the second portion of said rotary scanning element for illuminating said screen at a later period of time along a set of parallel lines extending longitudinally thereof, and means dependent upon the rate of revolution of said rotary scanning element for alternately and successively changing from one to the other of said paths of illumination at a rate equal to that necessary to effectively maintain the impression that all of said lines are being continuously illuminated.

3. In a television system, a scanning and reproducingr disk, a plurality of sets of fixed reflecting bodies associated with said disk, a light sourcejor projecting light upon said disk, and means provided by said disk for tracing on said reflecting bodies a plurality of parallel paths of an intensity corresponding to the intensity of light and shadow on a picture subj ect, and means provided by said disk for cyclically shifting the said parallelly projected lines of lillumination from one to the other of said reflecting bodies at periods when light values corresponding to the entire television subject have been projected upon each of said mirrors.

4. In a television system, a scanning and reproducing disk, a plurality of sets of oppositely tilted mirrors about the periphery thereof, said mirrors being arranged in sets for alternately and successively projecting light impinging thereon in an upward and downward direction from the plane of said disk, whereby light impinging upon said disk may be caused to trace a pair of paths each composed of a group of parallelly extending lines extending at an angular direction with respect to each other.

5. In a television system, a scanninv and reproducing disk, a plurality of sets oiJ mirrors arranged about the periphery of said disk, one of said sets of mirrors being arranged to deliect light impinging thereon along a set of parallel lines upwardly from the plane of said disk, and the other of said sets of mirrors being arranged to project light downwardly from the plane of said disk along a setof parallelly extending lines, a mirror surface positioned above said disk along the path of reected light beams therefrom, a screen, means associated with said mirror for tracing paths of illumination upon said screen in a direction extending vertical thereof, a mirror arranged beneath said disk for tracing paths of illumina-tion upon said screen in a. horizontal direction, and means for rotating said disk and changing from one toanother of said paths at a rate commensurate with the persistency of vision.

G. A television system for scanning and reproducing television subjects including a light source, a rotating disk arranged in the path ofsaid light, a plurality of sets of mirrors arrangedabout the periphery of said disk, one of said sets of mirrors being arranged to continuously project the light imarranged to pro] disk for cyclically 'pinging upon the periphery thereof alonga set of parallel lines in a plane above said disk, and the other of said sets of mirrors -ect the light impinging thereon along a set of parallel lines in a plane beneath said disk, a screen for reproducing a television image, a mirror positioned beneath said disk for reiecting the light projected thereon from said disk as a plurality ot' sets of parallel lines and tracing the same across said screen as a set of parallel lines horizontally thereof, a mirror positioned above said disk for reflecting the light beams projected as parallel paths of light upwardly from said disk, and a second diagonally positioned mirror associated with said last named mirror for tracing the light beams projected upwardly' from said disk as a set of parallelly extending. lines vertically uponl said screen, and means provided by the rotation of said changing from one to the other of said sets of parallel lines of reproduction at a rate commensurate with the persiste'ncy of vision.

7. ln a television system, a screen for reproducing a television image, a scanning and reproducing disk, a light source for projecting light upon said disk, a plurality of sets of mirrors arranged about the periphery ot' said disk, one of said sets of mirrors being arranged to deflect light impinging thereon along a set of parallel lines upwardly from the plane of said disk, and the other of said sets of mirrors being arranged to project light downwardly from the plane of said disk along a set of parallelly extending lines, a mirror surfacepositioned above said disk along the path of reflected light beams therefrom, means associated with said mirror for tracing parallel paths of light upon said screen in a direction extending vertical thereof, a mirror arranged beneath said disk for ltracing parallel paths of light upon said screen in a horizontal direction, and means Jfor rotating said disk and changing from one to another of said paths at a rate commensurate with the persistency of vision.

8. A. system for scanning and reproducing television subjects including a source of illamination, a rotating disk arranged in the path of said illumination,'a plurality of sets of mirrors arranged about the periphery of said disk, one of said sets of mirrors being arranged to continuously project the light ilnpinging thereupon along a set of parallel lines upwardly from said disk, and the other of said sets of mirrors arranged to project the light impinging thereon along a set of parallel lines downwardly from said disk, a screen for reproducing a television image, means positioned beneath said disk for reiecting the light projected in one direction from said disk and cause said light to focus on said screen to' trace a set of parallelly extending lines horizontally of said screen,

means positioned above said disk for rellecting the light beams projected in a second direction from said disk and cause said light to. focus on said screen to trace a set of parallelly extending lines vertically upon' said screen, and means provided by the rotation of said disk for cyclically changing from one to the other of said sets of parallel lines at a rateV commensurate with the lperistency of vision. 9. In a television system, a rotary scanning and reproducing element and a plurality of V sets of reilecting systems cooperating there'- with for causing diierent portions of said rotary scanning element to trace light paths bearing Van angular relationship to each other.

10.",In'a television system, a scanning and reproducing elementrhaving a set of upwardly tilted mirrors and a set of downwardly y zoftilt'ed mirrors about the periphery thereof for projecting light impinging thereon in an upward and downward directionfrom the plane of said disk, and a plurality of fixed reliecting systems cooperating therewith whereby'light impinging upon said disk may be caused to trace alternately a pair of paths each composed of'a group of parallelly extending lines each extending at an angular direction with respect to each other.

THEODORE 'A. SMITH.

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