US2025027A - Television system and apparatus - Google Patents

Description

Dec. 24, 1935. H, R N E 2,025,027

TELEVISION SYSTEM AND APPARATUS Filed March 6, 1933 2 SheetsSheet l r v V U.

INVENTOR f araldfiflanla,

E L N O D P H TELEVISION SYSTEM AND APPARATUS Filed March 6, 1931) 2 Sheets-Sheet 2 INVENTOR fiaraldflfiamj Patented Dec. 24, 1935 UNITED STATES ATENT OFFIQE Harold P. Donle, Meriden, Conn, assignor to Radio Inventions, Inc., a corporation of New York Application March 6, 1930, Serial No. 433,670

6 Claims.

The invention relates to improvements in television and comprises a method and apparatus for producing an image of greater detail than the usual scanning methods allow and therefore of better quality.

An object of this invention is the production of greater image detail without requiring radical or costly changes in the dimensions or speed of a given television apparatus.

Another object of this invention is to produce virtual optical apertures of slit-like form in moving elements such as discs or drums as used in scanning, without the expensive and elaborate mechanical processes involved in the accurate production and alignment of such apertures, as for example by punching or cutting as heretofore practiced.

Another object of my invention is to allow the actual physical slits employed in scanning members to be of such width as to be readily formed by ordinary mechanical modes of working the materials used in these scanning members, and yet have the optical slit resultant from the use of my invention of much narrower width than the physical slits, and allow this width to beadjusted at will.

Another object of my invention is to produce the average view in better apparent detail than possible with equi-dimensional elements of scanning and the same maximum frequency transmission requirements.

Another object of my invention as used at a transmitter is to secure a more nearly correct analysis so that better reproduction will take place even with ordinary equi-dimensional scanning elements at the receiver.

Other objects and advantages of this invention will appear from the following specification:

In the accompanying drawings Fig. 1 is a plan view of one form of transmitting device for scanning motion picture film, embodying this invention.

Fig. 2 illustrates diagrammatically the elementary picture areas produced by a scanning device such as the ordinary Nipkow disc, with round scanning apertures.

Fig. 3 shows the elementary areas produced by a scanner with square apertures and ordinary low detail.

Fig. 4 is a diagrammatic representation of the approximate elementary areas produced by one form of my invention, illustrating the high detail in the horizontal dimension, as compared with Figs. 2 and 3.

Fig. 5 is an elevation detail of the scanning aperture arrangement of Fig. 1, showing coacting apertures.

Fig. 6 shows in perspective a single optical slot as produced by this invention.

Fig. '7 shows in perspective a scanning aperture 5 defined in two dimensions, as produced by one form of this apparatus, the parts being disassembled to more clearly illustrate their mutual relationship.

Fig. 8 shows the shape of the optical aperture produced by the device of Fig. 7.

It is a Well known and fundamental principle of television scanning that the smaller the size of the individual element, the better detail the resultant reproduced image will have. Certain l5 structural, optical, and electrical difficulties have limited the practically feasible minimum size of an element, and it has hitherto been the practice to keep the detail the same in both dimensions, i. e., to use either round or square apertures.

I have discovered that an increase of detail in one dimension only is attended by an apparent improvement in detail throughout the image,

. and that the psychological phenomena involved cause the apperception of an image of improved quality without analyzing its dimensional limitations. In fact, by an apparent psychological compensatory transfer of values, some highly exceptional image, such as the figure with radial lines of uniform width used in ordinary optometric measurements, is necessary in order for the mental apperception of the received image to evoke any reaction in the observer of dimensional inequality of degree of detail. Since such geometrical figures, or their equivalents, rarely enter into images to be customarily transmitted, the validity of the invention remains unimpugned in regard to its application to the television transmission of ordinary object matter.

By the use of my invention I have made it a simple matter to increase the number of elemental areas in one dimension of the picture without radical change of apparatus designed for low detail scanning,

I have devised means to readily and economi- 'cally secure a virtual scanning aperture of the small width necessary to accomplish the purpose of high detail, without having recourse to the expensive and difficult mechanical production of such an actual aperture with the desired degree 59 of accuracy of dimensions and placement.

I have devised methods of combining the narrow virtual apertures of my invention with devices giving lower detail scanning, so that a combination of both degrees of detail is readily available, thus taking advantage of the psychological effects above mentioned.

I have found that for most characters of images to be transmitted the best result is to be obtained by making the detail greatest in the horizontal dimension, but do not limit the invention to high detail in either dimension, or in one dimension only;

I accordingly provide a slitted'scanning member in which the slit is so narrow that one dimension of the elementary scanning area is of smaller magnitude than the other dimension.

One method of providing such a narrow slit consists in the use of two slitted members with the slits superposed but with one offset to a degree so that the virtual slit may be as narrow as described.

In Fig. 1 the driving motor I has its shaft 2 connected by a coupling 3 to shaft 4, which rotates in bearings 9 and I2. A composite scanning disc made up of two members or sections In and II combined as hereinafter indicated, is coupled at I3 to shaft 4. This shaft bears a worm 5 engaging with a gear 6 upon a shaft I4. Upon shaft I4 is a chain sprocket connected by a chain 8 with another chain sprocket I5. This sprocket bears also on its shaft I6, film sprocket I1 and its motion is transmitted through spring belt l8 to film reel I9. The film 20 unreels from reel 2| which releases it under slight tension'and passes over guide 22 and through edge guides 32, continuously passing by a stationary slot 23 in a screen 33 supported on a bracket 34, is propelled by film sprocket I! and is rewound upon reel I9. A lamp 25 with'a luminous source 24, has its divergent rays 26 passing through a condenser system 21, whence they emerge as convergent rays 28 and are interrupted in a predetermined fashion by scanning disc III, II so as to scan in one dimension the image on the film which is being simultaneously scanned, usually at a slow rate,

The luminous result of this a housing 3|.

Virtual slits 40 (Fig. 5) in the compmite disc pass by the stationary slit 23. The film moves horizontally through guides 32, by the stationary slit 23.

In Fig. 6 a fragmentary view of the edge of the composite scanning disc shows it made up of disc I0 and disc II which bears respectively the wide slits 4| and 42, so positioned relative to one another that their overlap or common optical opening 40 constitutes the virtual narrow slit of this invention. 'The actual slits 4| and 42 are readily made, due to their width, and readily positioned with respect to the other slits on the same disc. The two discs I0 and II may be identical except that Il may be mounted upon the collar I3 of Fig. 1 by a series of screws I3 in holes II, accuratelydetermining its placement, and the second disc I0 may have mounting slots I0 instead of holes, allowing its angular advancement or retardation in respect tothe first disc. This angular displacement is usually determined upon before operation of the apparatus and the discs then firmly fastened by screws I3 in the desired angular relationship, in respect to one another and the common shaft rotating them.

Fig. '7 illustrates a mode of securing a composite scanning disc which shall scan an image in both dimensions. It is apparent that such a device is applicable to Fig. 1 only if the stationary slit 23 of this figure is omitted and the film operated so that each separate picture thereof remains stationary for the length of time required for such scanning.

This form of my invention is especially suited for the scanning of ordinary three dimensional scenes, not previously optically enregistered into a series of two dimensional views, such as motion picture film, and also to reproduce for purposes of visual viewing or projection, the images transmitted by such a device as Fig. 1, or other type of television transmitter. In this fragmentary disrupted view of the edge of the composite scanning disc, discs I0 and II, with slits 4| and 42, are the same as formerly described, and have be- 16 tween them the disc 50, which is of the ordinary Nipkow type. Holes 43 and 44 represent the first and last members of a spirally disposed series of holes in disc 50. 7

These three discs may obviously be assemble in any order, as long as the two slits cooperate to form a virtual narrow slit and the holes in disc 50 cooperate with this virtual slit, so thatv the slit bisects the circular aperture.

It is evident from Figs. 7 and 8 that-such narrow virtual apertures will appear in a spiral formation as the composite disc revolves, thus scan ning an image in two dimensions without auxiliary scanning apertures in any member other than the composite disc. .30"

image from a similar transmitter or from any transmitter giving proper spacing between successive scannings, by appropriate change of parts such as the substitution of a light reproducing source as customarily used in television receivers, v for the light source 24 shown in this figure, the to elimination of the light-sensitive cell and proper shielding of the film from light other than that passing thru the scanning apertures.

It is possible to use mechanical devices for changing the angularrelationship of the two discs making up the composite scanning disc, while these discs are in motion, similar to the device shown in my copending application 425,785 filed Feb. 4, 1930. This device will allow the width of the virtual optical slit to be changed while in operation, according to the available or desired relationship between the degree of detail and other factors entering into consideration, such as degree of illumination, frequency width of channels of communication and other variables.

A similar phase shifting device can be applied to the composite disc of Figs. 7 and 8, with corresponding results. 7

Synchronization between transmitter and receiver can be obtained in any of the usual ways, or by the method described in my copending application 322,360 filed Nov. 28, 1928.

Framing of the received image may be accomplished by many methods. Rotation of the field of the driving motor, or change of angular relationship of the entire rotating disc, as a whole with respect to the driving shaft, by mechanical means as mentioned supra are two possible methods. It is also possible to produce a r-eduplicated image with the disc of Fig. 7, by making the spiral of holes of more than one convolution, and to select the single image desired, by a movable aperture, substantially in accordance with the principles set forth in my above mentioned copending application #a25,785.

Other modes of construction of the rotating member can be used. For example a composite rotating hollow drum, made up of two drums with sets of Wide slits overlapping to produce a set of narrow virtual optical slits can be used in conjunction with a fixed stationary slit for motion picture film transmission. A composite drum consisting of two slitted drums .as just described and a third drum with helically disposed circular apertures can be used as the sole scanning member.

Apertures of square cross section can be substituted for the round holes in any of the foregoing devices. This invention can be readily applied to scanning systems using two moving members, such as the one outlined in my copending application #425,785.

To secure more perfect parallelism of the sides of the virtual slit, the actual physical slits producing this aforesaid virtual slit may have their sides tapered to an appropriate degree and in an appropriate direction to oifset the error due to the radial character of their lateral boundary lines, which error results in a trapezoidal figure, instead of .a true parallelogram. This error is usually so slight, however, that its correction is unnecessary.

To facilitate clear illustration, the thickness of the component discs has been shown in the drawings as greater relative to the other dimensions, than it would be in practice. Actually the discs would be as thin as consistent with mechanical strength and rigidity.

While not confining this improvement to any definite ratios of elementary unit size in the two dimensions, yet its advantages become most marked when this ratio exceeds two to one, and a ratio as high as ten to one has been employed. The upper limit of this ratio is partially determined by the maintenance of a satisfactory relationship between the light transmitted through an elementary optical unit, and the photo electric cell response. This in turn is related to the intensity of the light source and the sensitivity of the light cell. Likewise, considerations of the frequency transmission characteristics of the communication channel or channels employed, the electrical characteristics of the amplifying systems and other terminal apparatus, all enter into the choice of a suitable ratio, and in general set an upper feasible limit for this ratio in any given case.

Wherever the foregoing explanations and descriptions of my invention are illustrated by actual sizes and details of apparatus as employed in experimental use, such details are not to be considered as in any Way limiting the scope of my invention, which consists broadly in the employment of elementary scanning areas of a different mensuration in two dimensions, and in the method of securing the relatively smaller optical apertures needed for the lesser of said two dimensions by the proper superposition of physical apertures having a size great enough to permit of their economical and easy production.

I claim:

1. A television scanning device including a moving scanning member, said member having a spirally disposed series of optical openings therein,

said openings being defined in one dimension by two parts fixed with relation to one another having slits, the slits in one part cooperating with the slits in the other part to define an optical aperture, and being defined in the other dimension by a part fixed with relation to the other two previously mentioned parts having a spirally disposed series of openings cooperating with said optical apertures resultant from said parts having slits, in order to produce said series of spirally disposed optical openings suited to scan an image by the rotation of the scanning member.

2. Television scanning apparatus, including a member having a slit for determining the vertical dimension of an elemental scanning area, said slit being in motion relative to the image to be scanned, and a member having a series of slits of substantially uniform width not more than half the optical width in their smallest dimension of the width of the smallest dimension of the first mentioned slit, for determining the horizontal dimension of said elemental scanning area, said series of slits being in motion relative to the image to be scanned, in a direction substantially at right angles to the direction of motion of the first mentioned slit.

3. Television transmitting apparatus for use with motion picture film carrying successive images tobe transmitted, including means for moving said film at a substantially constant speed, a first member having a fixed slit positioned substantially at right angles to the direction of motion of said film and acting to delimit one dimension of an elementary scanning area, a second member having a slit positioned substantially parallel to the direction of motion of said film and acting to delimit the other dimension of an elementary scanning area, means for moving said second slitted member at a rate proportional to the velocity of said moving film and so that the slit therein optically intersects said fixed slit, said moving slit having its smallest dimension not more than one half the Width of the smallest dimension of said fixed slit, the ratio of the widths of said two slits remaining substantially constant throughout the transmission process.

4. A television scanner including means for moving a motion picture film at a uniform rate of speed so as to produce a series of moving I images to be scanned, an optical screen having therein a slit past which said images move and acting to limit one dimension of an elementary scanning area in the direction of motion of said images, a second optical screen having therein a slit acting to limit the other dimension of an elementary scanning area, said second slit limiting the other dimension of said scanning area to a value not more than one half its first mentioned dimension, and means for moving the slit in said second screen transversely of the slit in said first screen and at a rate of speed proportional to the speed of said film.

5. A television scanning system including two discrete scanning members, means for producing relative motion between both of said members and an image to be scanned so as to scan said image in two substantially perpendicular dimensions at two different rates of speed, optical means limiting the width of an elementary scanning area in the direction of more rapid scanning to a width not more than one half the width of said area in the direction of slower scanning, one of said scanning members giving substantially complete scanning in one dimension and the other scanning member giving subment of said film, so as to scan said film in said transverse direction, means for scanning said film in the other direction and optical means for delimiting an elementary scanning area to a substantially rectangular form, one of whose dlmen- 5 sions is at least twice as great as the other.

HAROLD P. DONLE.

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