US2435962A

US2435962A - Color television

Info

Publication number: US2435962A
Application number: US366400A
Authority: US
Inventors: Peter C Goldmark; John N Dyer
Original assignee: Columbia Broadcasting System Inc
Current assignee: CBS Broadcasting Inc
Priority date: 1940-11-20
Filing date: 1940-11-20
Publication date: 1948-02-17
Anticipated expiration: 1965-02-17

Description

Feb. 17, 1948.

P. C. GOLDMARK ET AL Filed Nov. 20, 1940 COLOR TELEVISION 4 Sheets-Sheet l INVENTORS Peter 6'. 6 Zdmarl" J Z77 D er 5 2 1 BY 1 y ATTORNEY-5 Feb. 17, 1948.

P. c. GOLDMARK ETAL 5 COLOR TELEVISION Filed Nov. 20, 1940 4 Sheets-Sheet 2 ATTORNEYS Feb. 17, 1948.

Filed NOV. 20, 1940 4 Sheets-Sheet 3 INVENTORS 1762197 6. Goldwar/F J55)? A4 Qyer ATTO RNEYS Feb. 17, 1948.

P. c. GOLDMARK ETAL COLOR TELEVISION Filed Nov. 20, 1940 4 Sheets-Sheet 4 Patented Feb. 17, 1948 2,435,962 'coLoR TELEVISION Peter C. Goldmark, New York. N. Y., and John N. Dyer, Stamford, Conn., assignors to Columbia Broadcasting System, Inc., New York, N. Y., a corporation of New York Application November 20, 1940, Serial No. 366,400

28 Claims.

This invention relates to television, particularly to color television. The invention is especially directed to the provision of direct-pickup apparatus employing a transmitting tube of the storage type, but certain features are also applicable to film scanning. In certain of its aspects the invention is more broadly applicable.

At the present time, tubes of the storage type are commonly used for direct pickup, that is, the scanning of natural object fields either indoors or outdoors, as distinguished from film scanning. Non-storage tubes are suitable for film scanning, where adequate light can usually be obtained, but are usually much less sensitive than storage type tubes and hence are not as satisfactory for direct pickup. Also, at the present time, pictures are transmitted almost exclusively by the interlaced method. Such interlacing has been found advantageous to avoid flicker without excessive frame-scanning speeds.

To televise pictures in color, a number of systems have been suggested. In one type of system an object field is simultaneously scanned by a pIurality of scanning devices in a corresponding plurality of colors. The resulting color signals are transmitted over separate channels to a receiver, Where they are reproduced. In another type of system an object field is successively scanned in a plurality of primary colors and the corresponding signals sent over a single channel to a receiver. Commonly, a single scanning device is employed, and different color aspects of the object field are successively presented to the scanning device, for example, by a rotating tri-chromatic filter disk. This latter type of system is considered preferable since it avoids the difiiculties and complexities of multiple channel transmission and reception.

The use of a storage tube with associated means, such as a tri-chromatic filter disk, for successively presenting difierent color aspects of an object field, gives rise to a serious difficulty when interlaced scanning is employed. It is desirable that successive interlaced field cansions be in different primary colors so that adequate color rendition without flicker may be secured. The systems disclosed in the co-pending application of Peter C. Goldmark, Serial No. 355,840, filed Septemper 7, 1940, have been found advantageous. With such a system, the scanning device will be exposed through one color filter, say the red filter, and one set of interlaced lines scanned. The scanning device will then be xposed through another filter, say the green filter, andv a second set of interlaced lines scanned. The second set of lines, will however, have been exposed to the red image during the previous field scanning period and corresponding charges stored up. Hence, during the scanslon oi the second set of lines, the resulting signal will represent a mixture of red and green aspects. Thus correct color rendition is not obtained.

The present invention is particularly directed to the solution of the foregoing problem, namely, the use of a storage scanning device in a color system employing interlaced scansion where suzcessive interlaced sets of lines represent different colors. However, many features of the invention are more broadly applicable.

In accordance with the invention, instead of scanning different interlaced sets of lines of the scanning or image receiving area (usually a mosaic) of the storage tube during successive field scanning periods, only a single set of lines is scanned. The spacing of the scanned set of lines, however, is the same as the spacing of one set of lines in interlaced scansion, so that the scanned lines are non-contiguous. Then the image on the scanning or image receiving area is displaced between successive scansions by amounts suflicient to cause a plurality of different interlaced sets of lines of the image to successively coincide with the non-contiguous set of lines of the scanning or image receiving area.

For example, assuming a double interlaced pattern composed of A-lines and B-lines, the scanning pattern on the scanning area of the storage device will consist of lines having the separation of, say, the A-lines. The image is projected onto the scanning area and the A-lines scanned. Then the image is displaced by the distance between A-lines and B-lines, which will usually be approximately the width of one line, and the scanning area re-scanned along the same pattern. The resultant signal will correspond to the usual double interlaced scanning pattern. However, since only a single set of lines of the scanning area is scanned, that set of lines will be discharged each field-scanning period and thus prepared for the reception of a differently colored image. Thus the carry-over" of stored charges of one color from one field to the next may be prevented.

Since recharge of elemental area in the storage tube begins immediately after the scanning beam passes, it is desirable that displacement of the image and exposure through the next filter follow the scanning beam with approximate coincidence. Thus, as soon as one line of the scanning area has been scanned for. say, a red signal, the elemental portion of the image coinciding 3 with the scanned line should be shifted by the amount required to produce interlacing and the scanned line exposed through the next color filter. That is, instead of shifting the image as a whole, the image is progressively shifted line by line in substantial synchronism with the low-frequency movement of the scanning beam. Also, exposure through the next color filter takes place progressively in similar manner. Practically. a slight difference in phase may be found permissibie, that is, a scanned line could remain exposed to the same line of the imag and to the same color for a small percentage of the next field period without seriously affecting correct rendition in many cases. Alternatively, the line may be scanned a brief interval after the shift and accompanying exposure to the next color.

' While particularly designed for direct pickup, the invention can also be applied to film scanners using a storage device.

The invention will be better understood by reference to the drawings, which illustrate several specific embodiments, taken in conjunction with the following description thereof, and will be pointed out specifically in the claims.

In the drawings:

Fig. 1 illustrates a specific embodiment of direct-pickup apparatus in accordance with the invention;

Fig. 2 is a front view of the glass disk of Fig. 1 which produces the required displacement optically;

Fig. 3 is a side view of the disk of Fig. 2;

Figs. 4a and 4b illustrate the principles of the displacement produced by the disk of Fig. 2;

Figs. 5a and 5b illustrate the manner in which image displacement produces the effect of interlaced scansion;

Fig. 6 is a diagrammatic plan view of another specific embodiment of direct-pickup apparatus;

Fig. 7 is a diagrammatic front view of the embodiment of Fig. 6;

Fig. 8 is a further modification of the apparatus of Fig. l, in which an intermediate image is employed;

Fig. 9 illustrates a specific embodiment of filmscanning apparatus in accordance with the invention;

Fig. 10 is a detail of the optical image-shifting disk of Fig. 9; and

Fig, 11 illustrates a further specific embodiment of film-scanning apparatus employing electronic image shifting instead of optical shifting.

Referring to Fig. 1, an object field I0 is focused by lens I2 to form an image H at a selected plane, in this case the plane of the scanning or image receiving area l3 of a storage scanning tube It. Any suitable type of storage tube may be employed, as desired. The tube specifically illustrated is of the so-called Orthicon type. having an electron gun l5, horizontal deflecting plates [6, vertical deflecting coils l1 and axial field coil it. The horizontal deflecting plates and vertical deflecting coils are energized by suitable highefrequency and low-frequency sawtooth wave generators, as indicated. In the Orthicon, the scanning area I3 is a translucent mosaic charge-storing target.

Positioned in front of the scanning tube l4, and preferably as close to the image receiving area I3 as convenient, is a disk IQ for optically shifting the position of the image on the mosaic ll. The disk is rotatable about axis by motor 2|, and is provided with a plurality of optically flat glass segments around the periphery thereof, the glass segments having parallel faces in the plane of the disk but being of different thicknesses. The plane of the disk is at an angle with respect to the scanning area (measured in a plane normal to the area and substantially perpendicular to the scanning lines), so that glass plates of different thickness will produce different deflections in a vertical direction of the light rays passing therethrough. Rims, spokes, etc., have been omitted for simplicity of illustration.

The color filters may be combined with the glass elements, as is shown in Fig. 2 or, if desired, the filters could be separate from the disk. For example, a separate rotating tri-chromatic disk could be provided, or other means for successively exposing the mosaic target to different colors of the image.

Referring to Fig, 2, an interlacing disk l9 suitable for double interlacing with three colors is shown. The disk is provided with two series of optically flat glass segments I and 2. respectively, spaced around the periphery of the disk at equal intervals. The faces of the segments are parallel and in the plane of the disk. The segments of series 2, however. are thicker than those of series I. The segments are also colored red, green and blue in sequence around the disk, as indicated by the letters R, G and B. The glass segments may themeselves be colored or, what is more convenient and practical, the filters may be placed over the glass segments. For example, common Wratten gelatine filters may be attached to the glass segments, as by optical cement.

The principles of the relative displacements produced by series I and 2 will be understood by referring to Figs. 4a and 412. A ray of light 22 impinges on a glass plate 23 at an angle a with the normal 24 to the surface. In accordance with well-known principles of optics, in passing through the glass plate the ray of light 22 undergoes a displacement d given by the following formula:

As indicated by the formula, the displacement d is a function of the thickness T of the glass plate, the angle of incidence a, and the index of refraction a. For-a given a and a given angle a, however, the displacement is directly proportional to the thickness T. This is illustrated in Figs. 4a and 4b where a thickness of T gives a displacement one-half that of a thickness T.

Referring now to Figs. 5a and 5b, the manner in which interlacing is produced will be ex plained. Fig. 5b illustrates a conventional douhie-interlaced scanning pattern, composed of a set of lines A interlaced with a set of lines B. For convenience of description, these lines will be understood as representing lines in the light image H on the mosaic, the lightimage being conjugate to the object field Ill. Fig. 5a shows the scanning pattern with which the scanning area 13 of the storage tube I4 is actually scanned. Only one set of lines AB of the mosaic is scanned by the scanning beam. This set of lines has a spacing equal to that of lines A of Fig. 5a (equal to the spacing of lines B), and hence is equal to the spacing of one set of interlaced lines. The lines AB are hence non-contiguous and the set of lines forms a non-interlaced scanning pattern.

The operation of the apparatus is as follows: Disk 19 is rotated at such a speed that successive segments I, 2 traverse the scanning area I! in the low frequency direction at field-scam ning frequency. To accomplish this, the motor 2| is synchronized with the vertical deflection and the ratio of drive between motor and disk properly chosen. For a field frequency of I20 scansions per second, and the [2 segment disk shown, the disk will rotate at 600 R. P. M.

Assume that a red thin section I is traversing the scanning area l3, thus charging all the elemental areas of the scanning area in accordance with the red aspect of the image. Lines AB of the scanning plane are scanned from bottom to top, thus producing an interlaced field scansion which represents the A-lines of the image projected thereon. As lines of the scanning area are scanned they are obscured by the next segment 2, colored green and thicker than I. The diiferencein thickness is so chosen that the image is displaced by the distance required to produce interlacing. In double interlacing the displacement is the distance between interlaced lines of the image, that is,,the distance between adjacent lines A and B of'Fig.'5b. As soon as the red scansion is completed, lines AB of the scanning area are re-scanned from bottom to top during the next field-scanning period. Due to the image displacement produced by the difference in thickness between segments l and 2, the scanned lines AB of the mosaic actually correspond to the B-lines of the image. Thus, full interlaced detail is obtained, even though only one set of lines on the scanning area of the storage tube is scannedfi tlurin successive field-scanning period s. g

It is therefore seen that by repeatedly scanning the set of lines AB during' successive field scanning periods, and by repeatedlyvshifting the image relative to thejsca'nning pattern, a pin-- rality of interlaced sets*of""lines'-of the image and a plurality of color aspects may be scanned. The color aspect scanned is-cyclically changed and the set of lines of the image' which is scanned is cyclically changed. I

The actual shift requiredto produce the interlacing is quite small i'qreaflarge number of lines. Therefore, by" making the thickness- T of segments 2 sufiiciently great; the angled of the disk may be made only afew degrees.

It is advantageous to have'theydisk and-imam" ning beam phased so that the scanning beam and the boundary line between successive seg ments coincide as nearly as possible throughout the scanning period. In such case, as soon as a line has been scanned, and thus discharged, it will be exposed to the next color and to the corresponding line ofthe other set of lines of the image projected thereon.

vIn Fig. 2, due to the fact that a boundary line between two segments I, 2 intercepts the first-sand last lines of the scanning area at an angle,- exact coincidence is not possible. However, the lack ,of coincidence'may be minimized by makingthe disk of large diameter as comlpared to thesize of the scanning area. Since coincidence should be maintained, at least aptwenty-four or even more segments may be employed. For a greater number of segments, the speed of rotation of the disk would be correspondingly reduced.

Even where the disk and scanning beam are not precisely phased to cause color change and the line being scanned to coincide, it is desirable to have the color change effected progressively at substantially the scanning speed so as to expose all areas equally to a given color prior to scanning the respective areas.

For convenience, the interval between immediately successive scanslons of a given line AB may be termed a "scanning interval or that line.

In Fig. 1, diil'erent color aspects of the image and diflerent lines of the image are presented to the lines AB during successive scanning intervals of the lines.

Figs. 2 and 3 illustrate a disk having alternate thick and thin segments. Actually the same result may be obtained by reducing the thickness of the thin sections to zero, that is, having the sections entirely in air, thus simplifying the construction: A corresponding change in thickness of the thick segments would then be made. In such case, sections I may represent merely the thickness of a gelatine color filter. It will be understood that the phrase "transparent segments of different thickness," and similar phrases. as used herein, include the case where some segments are entirely air.

As before stated, instead of attaching the color filters to the glass segments, a separate color filter disk may be employed. In many cases color carry-over from one field to the next may be more detrimental than image carry-over. In such cases the color disk may be made of larger diameter and more sections than the glass disk, so as to follow the scanning beam more accurately. In general, it would be less expensive and involve fewer mechanical difliculties to make a large filter disk than a large glass image-displacing disk, since the latter requires care in construction to accurately align the various segments and to prevent distortion due to rotation, age, etc. It would not be necessary to have the separate filter disk rotate in a plane parallel to that of the glass disk, since the filter disk is not -.required to effect displacement of the image.

The filter disk could be arranged to rotate in a plane parallel to the scanning area I! and preterably close thereto.

The invention may, of course, be used with other than double interlacing. For quadruple interlacing, for example, four series or glass segments of four diflerent thicknesses may be employed to produce the required displacement of the image to produce interlacing. The separation of lines scanned on the mosaic would be that of one set of interlaced lines. If one series is entirely in air, only three thicknesses of glass need be employed. The actual thicknesses will be calculated in accordance with the angle which the disk makes with respect to the scanning area, the index of refraction of the glass, and the actual displacements required to produce the desired "interlacing, as will be understood from the foregoing.

At a receiver, the signals produced by the apparatus of the invention should be reproduced in interlaced form to preserve definition. Under present standards, the transmitted signal is utilized to eflect interlacing at the receiver. At the transmitter, if even-line interlacing were employed. the scanning pattern AB on the scanning area of the storage tube could be produced without interlacing pulses, and the pulses could be subsequently added to the signal wave before it is transmitted. In case of odd-line interlacing, a. rectangular wave of suitable magnitude could be applied to the vertical deflecting circuit of the storage tube in addition to the usual deflecting wave, to remove the interlacing. That is, the sets of lines which would normally be interlaced at the scanning area are artificially paired. It will be understood that any suitable means for scanning a single set of lines of the mosaic may be employed as desired.

Referring now to Figs. 6 and 7, apparatus is illustrated in which the color changeover can be made to coincide quite accurately with the line being scanned. To accomplish this. instead of amxing color filter segments to the image d18- placing disk I9, or employing a separate color filter disk, a filter drum 3i is employed instead. The filter drum is rotatable about the axis 32 by motor 2!, and has a plurality of color filters arranged around the peripheral surface thereof.

work of the drum 3| in any desired manner, as

by strips 34.

One end 35 of the drum 3| is open so as to admit light from lens l2 to the mirror 38. This mirror is positioned so as to reflect light from the lens through the filters to the scanning area I 3 of the storage scanning tube it. In the embodiment illustrated, the mirror is placed at an angle of 45 with the axis of the drum. As the drum rotates, the color aspect of the image It impinging on the lines of the scanning area I3 is progressively changed. By employing a drum of sufiicient diameter,'the progressive change may be made substantially linear with respect to time. For example, if the drum is rotated at a uniform speed, and the radius of the drum is equal to the height of the image on the scanning area It, the speed with which a boundary line between adjacent filters progresses across the scanning area [3 is within one per cent of being linear. Such an error is believed ermissible, but could be decreased by increasing the radius of the drum.

If the color scanning system is such that successive colors are scanned during successive fiield-scanning periods, it is advantageous to select the diameter of the drum and the number of segments such that the boundary line be tween adjacent filters traverses the scanning area l3 at the same speed as the lines are scanned, that is at the speed with which the image is scanned in a vertical direction. To accomplish this. the circumferential distance between the leading edges of adjacent filters may be made equal to the height of the image on the scanning area plus an allowance for the blanking period between successive vertical scansions. If the surface of the drum is not in close proximity to the scanning area, a suitable correction can be made as will be understood. In any case, it is advantageous to have the leading edges of the filters traverse the scanning area at the same speed as the scanning beam so that, by properly phasing the disk with respect .to the low-frequency scanning, the color impinging on the lines of the scanning area is changed substantially asthe lines are scanned. Thus color carryover from one field scansion to the next is substantiaily avoided. The edges of the filter segments will usually be parallel to the drum axis so that the edges are substantially parallel to the scanning lines, the pitch of the latter being very small.

Figs. 6 and 7 show one specific arrangement of filter drum and mirror in the path of light from object field to scanning tube. It will be appreciated that many different arrangements may be devised, and used in place of the one specifically illustrated. Also, the filter segments could be fiat, instead of rounded as shown. For six segments, this would form a drum of hexagonal, rather than circular, cross-section.

The image displacing disk I! may be constructed in accordance with the considerations pointed out in connection with Fig. 1. The various modifications pointed out in connection with Fig. 1 also apply to Fig. 6.

In all the embodiments described herein, adjacent color' filter or image-displacing segments may be separated by an opaque band, if desired, for structural or other reasons.

Referring to Fig. 8, apparatus is shown in which the image-displacing disk and the color filter means may be removed a substantial distance from the scanning area. It is desirable that the line or band along which the color is changed and the image is shifted be sharply focussed on the scanning area. With an Orthlcon, where the mosaic is commonly formed on one end of the tube, and with the long focal length lenses at present employed, the lack of coincidence of glass disk and scannin area is not serious. Where the scanningmg' is so positioned that the glass and color cannot be placed sumciently close, or where the focal length of the objective is so short that lack of coincidence is serious, an intermediate image of the object field may be formed and the glass and color disks placed in or near the plane thereof, the plane of the glass disk being usually at an angle with respect to the plane of the intermediate image. The intermediate image is then focussed onto the storage scanning area by a second lens.

One example where an intermediate image may be desirable is in connection with a storage scanning tube of the so-called "iconoscope" type. As at present constructed, the mosaic of this tube is located at a considerable distance from the window of the tube. Therefore, unless very long focal length lenses are used, the boundary be tween filter segments and between successive image-shifting segments may be considerably defocussed at the plane of the mosaic, or scanning area.

In Fig. 8, the projection lens l2 forms an intermediate image of the object field, and the intel-mediate image is projected by an additional lens 46 to form an image 41 at the mosaic I! of a tube 48 of the iconoscope type. A field lens 49 near the plane of the intermediate image is advantageous, but may be omitted if desired. The image shifting disk I! with associated color filters is placed near the plane of the intermediate image. The modifications shown in previous figures of the drawing, or described hereinbefore, may be employed in connection with the apparatus of Fig. 8. These include the use of a filter drum, the use of separate color and image shifting disks, etc. The operation of the apparatus of Fig. 8 will be apparent in the foregoing.

The image 45 in Fig. 8, and the image II in Figs. 1, 6, etc. will usually be in a fiat plane, since the image-receiving surface of the scanning device will usually be fiat. However, if desired for any reason, curved surfaces and curved image planes may be employed, and it will be understood that the term "plane as used herein may include such curvature.

The principles of image shifting and color changing, in conjunction with the scanning of a non-contiguous set of lines of a scanning area of a storage tube described hereinbefore, may be applied to the scanning of film as well as to the direct scanning of a natural object field. A few specific embodiments will be described, but it will be understood that many other arrangements may be devised for applying the principles of the invention to the scanning of film.

The apparatus described hereinbefore is directly applicable to the scanning of a continuously moving film by employing a projector of the type in which the motion of the film is stopped" so that the projected image remains stationary. The projected image may be made to coincide with the scanning area and the image shifting and color changing effected as described hereinbefore. Or, the film images may be projected to an intermediate plane at which the film images are stationary, and the apparatus described hereinbefore employed in conjunction with the image at the intermediate plane. a

Fig. 9 illustrates film-scanning apparatus employing an intermittently moving film. The film Si is fed through gate 52 by a suitable intermediate film-moving mechanism, preferably driven by the motor 2| so that proper synchronous relationships can be readily maintained. The film is illuminated by a suitable source of light, here shown as an arc 53 and condenser lenses 54. A film-frame image 55 is projected by a suitable projection lens 55 to the image receiving area iii of a storage scanning device l4, here shown as tube of the Orthlcon type. It will be understood that the terms "field" and object field used herein may be applied to the portion of the film projected as well as to a natural physical object field.

Since photoelectric surfaces are commonly sen sitive to infrared, which would adversely affect proper color balance, an infrared filter 51 may be interposed at any convenient point in the path of light from the projection source to the scanning area. Such an infrared filter may of course be employed in the direct pickup devices illustrated in previous figures in the drawings and described hereinbefore.

In film scanning sufilcient light can readily be obtained so as to permit the exposure of the storage scanning area only during the blanking periods between field scansions. Such exposure can readily be accomplished by a suitable flashing shutter 58, constructed in a well known manner, and preferably driven by motor 2i. An image shifting and color changing disk 59 is mounted at a suitable point in the path of light to the scanning area. For trichrornatic double-interlaced scanning, the disk illustrated in Fig. 10 is convenient. This disk is composed of alternate thin glass segments I and thick glass segments 2 spaced around the disk. As before pointed out, the thin glass segments may be eliminated and air spaces employed instead. Successive segments are covered with red, green and blue filters as indicated.

Since the scanning area is exposed to the object field, in this case a film-frame image, only during the blanking period, it is not necessary that the image shifting and color changing be effected progressively as the lines are scanned.

Thus the design and construction of the disk 59 may be quite simple. The number of segments and. speed of rotation should be selected so that the color is changed and the image shifted for successive field-scanning periods. Since the exposure during the blanking period may be made very short. the circumferential length of the filter and glass segments may be made only sufficient to cover the image area during the projection periods. Also, since progressive image shifting and color changing is unnecessary, the boundary between adjacent filters and adjacent image-shifting segments need not be sharply focussed at the plane of the scanning area. Therefore considerable latitude in the positioning of the disk with respect to the scanning area is permitted. For example. it could be placed near the film, if other apparatus leaves sumcient room.

For scanning systems involving a diflerent number of interlaced sets of lines. or a different number of colors. the disk 59 may be changed accordingly, as described .hereinbefore. Also. if the filters are mounted separately from the image displacing segments, for example, on a separate disk. they could be placed at any convenient position in the path of li ht from the projection source to the scanning tube.

If the pickup device were sufiiciently sensitive. a flashing shutter similar to that employed in film scanning could be employed with a direct pickup device. In such case the simpler image-shifting disk could be employed. However, at the present time the required sensitivity has not been attained.

Fig. 11 illustrates apparatus employing electronic image shifting instead of optical image shifting. In this figure a scanning tube is employed of the type in which an electron image is formed in space. The scanning tube 6| comprises a glass envelope having a window 6! on the inner surface of which is deposited as thin photoelectric surface 63. An image of the film is projected onto the photoelectric surface 63 and liberates an electron image. the density of electrons in the various elemental portions of the electron image corresponding to the various intensities of the light image projected onto the photoelectric surface. Hence the projection of the electron image may be considered a continuance oi the projection of the optical image.

The electron image is maintained in focus by suitable means. In the tube here shown, electrostatic focussing rings 84. energized by suitable means not shown, are employed. The electron image is cau"ed to impinge upon the mosaic 55 of the tube, and the mosaic is scanned by a suitable electron beam 68 generated by electron gun I1. Suitable deflecting means are employed for scanning the mosaic in horizontal and vertical direction to scan a non-contiguous set of lines, but are not shown in the drawing for simplicity of illustration. Other means for maintaining the electron image in focus may of course be employed if desired.

A suitable fla hing shutter 58 is employed to project film images to the photoelectric surface 63 during the blanking periods between successive field scansions. A color disk 88 for exposing successive color aspects of the image during .suc-

- cessive field scansions is employed. This'may be fiecting means, here shown as a coil 89 constructed to shift the electron imagein vertical direction, is employed. The image deflecting coil 09 is energized by a suitable generator ii. In the case of double interlacing, the generator may be constructed to supply a rectangular wave of suitable magnitude to effect the desired deflection. For a different number of sets of interlaced lines, the wave should be changed accordingly. For example, in quadruple interlacing the source should be designed to produce four different positions of the electron image. A commutator, or other desired means, may be employed for this purpose.

In the foregoing description of the optical image-shifting disk, the use of glass segments of difierent thickness to produce image shifts of difierent amounts has been explained. From Formula I, however, it will be apparent that segments of the same thickness and different refractive index (a) could be used instead, or a combination of different thicknesses and different refractive indices. Ordinarily it will be advantageous to use glass of the same refractive index and diflerent thickness.

While the apparatus of the invention is especially designed for use with storage devices and intended to solve problems peculiar to storage devices, features of the invention could be employed with non-storage devices if desired.

Many modifications of the invention are of course possible, without departing from the spirit and scope of the invention as defined in the claims. It will be particularly understood that different means may be employed for shifting the image other than those specifically described. Other modifications will be apparent to those skilled in the art. Furthermore, some features of the invention may be employed in systems widely difierent from those specifically described.

Reference is made to application Serial No. 370,008, entitled Television." filed Dec. 13, 1940, by Peter C. Goldmark, in which certain arrangements of color filters in combination with scanning devices in a television system are described and claimed.

We claim:

1. In television apparatus, the combination which comprises means for producing a repeated scanning pattern composed of a set of non-contiguous lines, means for utilizing said scanning pattern to scan a field, and means for repeatedly producing a relative shift between said scanning pattern and said field progressively line by line throughout the field in substantial synchronism with the scanning during a scanning period by amounts sufiicient to cause a plurality of interlaced sets of lines of said field to be scanned by successive scansions of said scanning pattern.

2. In television apparatus, the combination which comprises a storage scanning device,

means associated with said storage scanning device tor producing a repeated non-interlaced scanning pattern composed of a set of non-contiguous lines, means for utilizing said scanning pattern to scan a field, and means for repeatedly producing a relative shift between said scanning pattern and said field progressively line by line throughout the field in substantial synchronism with the scanning during a scanning period by amounts sufllcient to cause a. plurality of interlaced sets of lines of said field to be scanned by successive scansions of said scanning pattern.

3. In television apparatus, the combination which comprises a storage scanning device, means associated with said storage scanning device for repeatedly scanning a set of non-contiguous lines of a selected plane to thereby produce a recurring scanning pattern, means for utilizing said scanning pattern to scan a field, and means intermediate said field and said selected plane for repeatedly producing a relative shift between said field and said selected plane progressively line by line throughout the field in substantial synchronism with the scanning during a scanning period by amounts suflicient to cause a plurality o! interlaced sets of lines of said field to be scanned by repeated scansions of said set of noncontiguous lines of said selected plane.

4. In television transmitting apparatus, the combination which comprises means for forming an image at a selected plane, a scanning device positioned to scan an image in said plane, means associated with said scanning device for repeatedly scanning a set of non-contiguous lines of said plane to thereby scan the set of lines of said image which coincides therewith, and means for repeatedly shifting the image at said plane progressively line by line throughout the image in substantial synchronism with the scanning during a scanning period by amounts sufllcient to cause a plurality of interlaced sets of lines of said image to successively coincide with said set of non-contiguous lines of said plane.

5. In television transmitting apparatus, the combination which comprises means for forming an image at a selected plane, a storage scanning device positioned to scan an image in said plane, means associated with said storage scanning device for repeatedly scanning a set of non-contiguous lines of said plane to thereby scan the set of lines of said image which coincides therewith, and means for repeatedly shifting the image on said scanning area progressively line by line throughout the image in substantial synchronism with the scanning during a scanning period by amounts sumcient to cause a plurality of diflerent interlaced sets of lines of said image to successively coincide with said set of non-contiguous lines of said plane, whereby a plurality of interlaced sets of lines of an image may be scanned by repeatedly scanning a single set of lines 01' said plane.

6. In television transmitting apparatus, the combination which comprises means for forming a light image at a selected plane, a scanning device positioned to scan an image in said plane, means associated with said scanning device for repeatedly scanning a set oi non-contiguous lines of said plane to thereby scan the set of lines 0! said image which coincides therewith,'and a rotatable disk having a plurality oi. transparent segments spaced therearound and positioned so that as the disk rotates said segments are successivel and progressively interposed in the path of the light rays forming said image, said segments being constructed and positioned to produce a shift of the image at said selected plane to a plurality of positions separated by amounts selected to cause a plurality of interlaced sets of lines of said light image to successively coincide with said set of non-contiguous lines of said selected plane.

7. In television transmitting apparatus, the combination which comprises means for forming a light image at a selected plane, a storage scanning device positioned to scan an image in said plane, means associated with said storage scanning device for repeatedlyscanning a set of noncontiguous lines of said plane to thereby scan the set of lines of said image which coincides therewith, and a rotatable disk having a plurality of transparent segments spaced therearound and positioned so that as the disk rotates said segments are successively interposed in the path of the light rays forming said image, each segment being interposed progressively during a scanning period the face of said disk being at an angle to said selected plane measured in a plane normal to said selected plane and substantially perpendicular to said non-contiguous set of lines, the thicknesses and lndices of refraction of said plurality of segments being correlated with said angle so that successive segments shift the image at said selected area. by difierent amounts predetermined to cause a plurality of different interlaced sets of lines of said light image to suecessively coincide with said set of non-contiguous lines of said selected plane, whereby a plurality of interlaced sets of lines of said light image may be scanned by repeatedly scanning a single set oi lines of said selected plane.

8. In color television transmitting apparatus the combination which comprises a storage scanning device, means for successively focussing on an image receiving area of said storage scannin device a plurality of color aspects of an image, means for repeatedly scanning a set of non-contiguous lines of said image receiving area to thereby scan the set of lines of said image which coincides therewith and derive corresponding color signals, and means for successively shifting the image on said image receiving area for successive scansions of said set of non-contiguous lines by amounts sufflcient to cause a plurality of different interlaced sets of lines of said image to successively coincide with said set of non-contiguous lines, said shifting being progressive line by line during a scanning period, in substantial synchronism with the low frequency movement of the scanning beam, whereby a plurality of interlaced sets of lines and a pluralit of color aspects of an image may be scanned by repeatedly scanning a single set of lines of said image receiving area.

9. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for focussing a light image of an object field on an image receiving area of said storage scanning device, means associated with said storage scanning device for repeatedly scanning a set of non-contiguous lines of said image receiving area, color filter means positioned in the path of light to said image receiving area and constructed and adapted to successively expose said image receiving area to a plurality of color aspects of the object field, and image shifting means positioned in the path of light to said image receiving area and constructed and adapted to successively shift the light image impinging on said image receiving area to a plurality of positions, said shift being progressive line by line during a scanning period in substantial synchronism with the low frequency movementof the scanning beam, the distance between said positions being selected to causea plurality of interlaced sets of lines of said light image to successively coincide with said set of non-contiguous lines of the image receiving area.

10. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for iocussing an image onto an image receiving area of said storage scanning device. means for repeatedly scanning a set oi non-contiguous lines of said image receiving area during successive field-scanning periods, color filter means constructed and positioned to cyclically and progressivelychange the color aspect of the image impinging on the lines of said image receiving area from one color to the next of a plurality of colors during successive field-scanning periods, and image shifting means constructed and positioned to cyclically and progressively shift line by line the image impinging on the non-contiguous lines of said image receiving area during successive field-scanning periods in substantial synchronism with the low frequency movement ofthe scanning beam by amounts suillcient to cause a plurality of different interlaced sets of lines of said image to successively coincide with said non-contiguous lines for successive scansions thereof, whereby a plurality of interlaced sets of lines and a plurality of color aspects of an image may be scanned by repeatedly scanning a single set of lines of said image receiving area.

11. In direct pickup color television transmitting apparatus, the combination which comprises a storage scanning device, means for focussing a light image of an object field onto a scannin area of said storage scanning device, means for repeatedly scanning a non-contiguous set of lines of said scanning area during successive fieldscanning periods, color filter means for cylically changing the color aspect of the image projected onto said scanning area from one color to the next of a plurality of colors for successive scansions of the image field, said color filter means being constructed and positioned to change the color impinging on the lines of said scannin area progressively during a field-scanning period, and image shifting means for cyclically and suc cessively shifting the light image projected onto the lines of said set in a direction substantially transverse to the lines by amounts suflicientto cause a plurality of different interlaced sets of lines of said light image to successively coincide with said non-contiguous set of linesfor successive scansions thereof, said image shifting means being constructed and positioned to shift the light image impinging on the non-contiguous lines of the scanning area progressively line by line during a field-scanning period in substantial synchronism with the low frequency movement of the scanning beam.

12. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for iocussing an image of an object field onto an image receiving area of said storage scanning device, means associated with said scanning device for repeatedly scanning a set of non-contiguous lines of said image receiving area during successive field-scanning periods, color filter means for successively presenting a plurality of color aspects of said image to the lines of said set during successive scanning intervals of said lines, said color filter means being constructed and adapted to change progressively the color impinging on the lines of said set substantially as the lines are scanned, and means for successively'shiiting the image on the lines of said set for successive scansions thereof by amounts sumcient to cause a plurality of difierent interlaced sets of lines of said image to successivelycoincide with said set of non-contiguous lines of the image receiving area, said means for shifting the image being constructed and adapted to shift progressively line by line the image impinging on the lines of said image receiving area substantially in synchronism with the low frequency movement of the scanning beam as the lines are scanned.

13. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for focussing a light image of an object field on an image receiving area of said storage scanning device, means associated with said storage scanning device for repeatedly scanning a set of non-contiguous lines of said image receiving area, color filter means positioned in the path of light to said image receiving area and constructed and adapted to successively expose said area to a plurality of color aspects of the object field, and a rotatable disk having a plurality of transparent segments spaced therearound and positioned so that as the disk rotates the segments successively traverse the light rays forming said image in a direction lateral to said lines, said segments being constructed and positioned to produce a shift of the image on said image receiving area to a plurality of positions separated by amounts predetermined to cause a plurality of interlaced sets of lines of said light image to successively coincide with said set of non-contiguous lines of the image receiving area.

14. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for focussing a light image of an object field on an image receiving area of said storage scanning device, means associated with said storage scanning device for repeatedly scanning a set of non-contiguous lines of said image receiving area during successive field-scanning periods, color filter means constructed and positioned to cyclically and progressively change the color aspect of the image impinging on the lines of said image receiving area from one color to the next of a plurality of colors during successive field-scanning periods, and image shifting means comprising a rotatable disk having a plurality of transparent segments spaced therearound and positioned so that as the disk rotates said segments are successively interposed in the path of light forming said image, said segments being constructed and adapted to progressively displace said image to a plurality of positions on the image receiving area separated by amounts selected to cause a plurality of interlaced sets of lines of said light image to successively coincide with said set of non-contiguous lines of the image receiving area.

15. In a color television transmitting apparatus, the combination which comprises a storage scanning device, means for successively focussing onto an image receiving area of said storage scanning device a plurality of color images of an object field, means for repeatedly scanning a non-contiguous set of lines of said image receiving area to thereby scan the set of lines of said images which coincide therewith and derive corresponding color signals, a rotatable disk having a plurality of transparent segments spaced therearound, said disk being positioned in front of said image receiving area so that as the disk rotates said plurality of segments will be successively interposed in the path of the light rays forming an image on the image receiving area, the face of said disk being at an angle to the image receiving area in a plane which is normal to said area and substantially perpendicular to said non-contiguous set of lines, the thicknesses and indices of refraction of said plurality of segments being correlated with said angle so that as the disk rotates successive segments displace the image on said image receiving area by different amounts predetermined to cause a plurality of different interlaced sets of lines of said image to successively coincide with said non-contiguous set of lines, whereby a plurality of interlaced sets of lines and a plurality of color aspects of an image may be scanned by repeatedly scanning a single set of lines of said image receiving area.

16. In color television transmitting apparatus. the combination which comprises a storage scan- 'ning device, means for focussing a light image of an object field on an image receiving area of said storage scanning device, color filter means positioned in the path of light to said image receiving area and constructed and adapted to suecessively expose said image receiving area to a plurality of color aspects of the object field, means associated with said scanning device for repeatedly scanning a non-contiguous set of lines of said image receiving area to thereby scan the set of lines of said image which coincides therewith and derive corresponding color signals, a rotatable disk having a plurality of transparent segments of diflerent thicknesses and plane parallel faces spaced therearound. said disk being positioned in front of said image receiving area so that as the disk rotates said plurality of segments will be successively interposed in the path of the light rays forming said image, the face of said disk being at an angle to the image receiving area in a plane which is normal to said area and substantially perpendicular to said non-contiguous set of lines, the difierent thicknesses of said segments being correlated with said angle so that as the disk rotates successive segments displace the image on said image receiving area by amounts sutlicient to cause a plurality of diflerent interlaced sets of lines of said image to successively coincide with said non-contiguous set of lines of the image receiving area, whereby a plurality of interlaced sets of lines and a plurality of color aspects of an image may be scanned by repeatedly scanning a single set of lines of said image receiving area.

17. In television, the method which comprises producing a repeated non-interlaced scanning pattern composed of a set of non-contiguous lines, utilizing said scanning pattern to scan a field. and producing a repeated relative shift between said scanning pattern and said field progressively line by line throughout the field in substantial synchronism with the scanning during respective scanning periods by amounts sufficient to cause a plurality of interlaced sets of lines of said field to be scanned by successive scansions of said scanning pattern.

18. In television transmission employing a scanning device of the storage type, the method which comprises repeatedly scanning a set of non-contiguous lines of a scanning area associated with said storage scanning device to thereby provide a scanning pattern, utilizing said scanning pattern to scan an object field, and producing a repeated relative shift between said scanning area and said object field progressively line by line throughout the object field in substantial synchronism with the scanning during respective scanning periods by amounts sumcient to cause a plurality of interlaced sets of lines of said field to be scanned by successive scansions of said set of non-contiguous lines.

19. In television transmission employing a scanning device of the storage type, the method which comprises focusing a light image of an object held on an image-receiving area of said storage scanning device, repeatedly scanning a set of non-contiguous lines of said image-receiving area, and optically shifting the light image on said image-receiving area progressivel line by line throughout the image in substantial synchronlsm with the scanning during respective scanning periods by amounts sufllcient to cause a plurality of interlaced sets of lines of said image to successively coincide with said non-contiguous set of lines.

20. In color television transmitting apparatus, the combination which comprises a storage scanning device, means for focusing an image of an object field onto an image receiving area of said storage scanning device, means associated with said scanning device for repeatedly scanning a set of non-contiguous lines of said image receiving area during successive field-scanning periods, and means for successively shiftingthe image on the lines of said set for successive scansions thereof by amounts suflicient to cause a plurality of diilerent interlaced sets of lines of said image to successively coincide with said set of non-contiguous lines of the image receiving area, said means for shifting the image being constructed and adapted to shift progressively line by line throughout the image impinging on the lines of said image receiving area substantially as the lines are scanned and in substantial synchronism with the low frequency movement of the scanning beam.

21. A color television signal-translating system comprising, a cathode-ray tube including a target, means for successively scanning said target with an electron beam in a series of similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, means for changing the color of light associated with each line a given interval after such line is scanned and for maintaining said color associated with said line until said line is next scanned by said beam, means included in said optical means for effectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby efiectively to provide interlacing of the scanning lines of the translated image, and means for blocking the image to each line when changing the color of light and displacing the image associated with each line.

22. A television signal-transmitting system, comprising a cathode-ray tube including a target electrode, means ior successively scanning said target electrode with an electron beam in a series of similar fields of spaced parallel lines, optical means associated with said target electrode for forming thereon an image of the translated television picture, means included in said optical means for effectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby effectively to provide interlacing of the scanning lines of the translated image, and means for deriving a television signal from said target electrode.

23. A television signal-transmitting system, comprising, a cathode-ray tube including a target electrode, means for successively scanning said target electrode with an electron beam in a series or similar fields of spaced parallel lines, optical means associated with said target electrode tor forming thereon an electron image of the translated television picture, means included in said optical means for effectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby efiectively to provide interlacing of the scanning lines of the translated image. and means for deriving a television signal from said target electrode,

24. A television signal-translating system comprising, a cathode-ray tube including a target, means for successively scanning said target with an electron beam in a serie of similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, and means included in said optical means for effectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby eifectively to provide interlacing oi the scanning lines of the translated image.

25. A television signal-translating system comprising, a cathode-ray tube including a target. means for successively scanning said target with an electron beam in a series of similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, means for blocking the image of each line during the interval said line is being scanned, and means included in said optical means for efiectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby eiiectively to provide interlacing of the scanning lines of the translated image.

26. A television signal-translating system comprising, a cathode-ray tube including a target, means for successively scanning said target with an electron beam in a series of similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, and light-retracting means in said optical means for eflectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said beam, thereby efiectively to provide interlacing of the scanning lines of the translated image.

2'7. A television signal-translating system comprising, a, cathode-ray tube including a target, means for successively scanning said target with an electron beam in a series of similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, and means effectively comprising a disc having radial sectors of different refractive indices and moving in a plane inclined with respect to the optical axis 01' said optical means for eflectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for maintaining said image displaced until said line is next scanned by said 19 beam. thereby eii'ectively to provide interlacing or the scanning lines oi the translated picture.

28. A television signal-translating system comprising, a cathode-ray tube including a target, means for successively scanning said target with an electron beam in a series or similar fields of spaced parallel lines, optical means associated with said target for forming an image of the translated television picture, and a disc eii'ectlvely having sectors of diflerent refractive indices and rotating in a plane inclined with respect to the optical axis of said optical means for eflectively displacing the image associated with each line with respect to said scanning lines a given interval after said line is scanned and for main- 15 PETER c. GOLDMARK. 20

JOHN N. DYER.

REFERENCES crrEn The following references are of record in the iiie of this patent:

UNITED STATES PATENTS Number, Name Date 2,186,931 Schlesinger Jan. 9, 1940 2,244,688 Goldsmith et al. June 10, 1941 1,687,193 Bertele Oct. 9, 1928 1,385,325 Jenkins July 19, 1921 FOREIGN PATENTS Number Country Date 494,365 Great Britain Oct. 25, 1938 418,527 Great Britain Oct. 26, 1934 459,400 Great Britain Jan, I, 1937 OTHER REFERENCES Fernseh A. G. for August, 1939, pages 171 to 179. Electronics, Oct. 1940, pages 32 to 84.