US2248559A - Scanning disk for television transmission - Google Patents

Description

y 3, 1941- K. SCHLESINGER 2248559 SCANNING DISK FOR TELEVISION TRANSMISSION Original Filed June 5, 1936 KSheets-Sheet 1 In ve mor:

i 1941- K. SCHLESINGER 2.248.559 SCANNING DISK FOR TELEVISION TRANSMISSION Original Filed June 5, 1936 3 Sheets-Sheet 2 Jm/en/Ur: MUM

J 8, 19419 K. SCHLESINGER 248,59

SCANNING DISK FOR TELEVISION TRANSMISSION Original Filed June 5, 1936 3 Sheets-Sheet 5 Patented July 8, 1941 SCANNING DISK FOR TELEVISION TRANSMISSION Kurt Schlesinger, Berlin, Germany, assignor, by

mesne assignments, to Loewe Radio, Inc., a corporation of New York Original application June 5, 1936, Serial No.

83,705, now PatentNo. 2,227,006, dated December 31, 1940. Divided and this application July 26, 1938, Serial No. 221,318. In Germany June 7- Claims.

In the earlier application Ser. No. 36,008/35.

the. applicant has described a method which permits the scanning of a continuously moved film according to the interlaced line-group method. This method is based on the use of a scanning disk having a spiral of apertures of several turns, whereby the number of turns is equal to the number of groups of lines of which an image is composed. In the case of a film moved at the rate of 25 images per second and of two part images there was used, for example, a disk having a spiral of two turns of which each turn had half the height of the film image and was rotating at 50 revolutions per second, in such fashion that the apparent radial movement of the image points was opposite to the apparent radial movement of the projected film image,

In the present application there is retained the essence of the idea disclosed in the cited earlier application. the present case a disk having, for example, a

spiral of two coherent turns, whereby the image holes follow up radially in a direction opposite to the movement of the projected film image. The difference between the two methods resides in the production of the line displacement. If, in the manner described in the earlier application, there is employed an even number of image holes, for example 2x 120, on the spiral aperture disk,

a line displacement can only be obtained at the.

receiving station if upon the reception the relaxation oscillations commences and ends upon each second relaxation period to theextent of'the width of one line higher or lower than the preceding period. The vertical relaxation oscillation must perform in addition .to the normal Scanning movement a rocking movement of the height of a line width, i. e. the so-called line jump. In order to produce this line jump at the receiving station it was necessary to transmit from the sending end image-change impulses, of which each second one was produced by a line period earlier or later respectively as compared with an exactly isochronous sequence. It was accordingly necessary to transmit the image-change signals in the form of a group each comprising two anisochronous part-impulses. represents an increased load on the vertical relaxation apparatus of the receiver, as the same must perform the relaxation with exactness in alteration between two pairs of limits. ,It is the subject matter of the present invention todepart from the method employing the anisochronousv image-change signals and to operate; with purely isochronous image-change signals without the There is also employed in This method necessity for any line-jump, and does not require to perform anything beyond that called for in the case of television with simple standard of scanning.

The fundamental idea concerning the fact that, in the case of two part-images, a line displacement occurs automatically when an odd number oflines are employed, is already known. These arrangements provide to scan of one film image one line-group and of the next film image the second line group or use an interruptedly moved film whilst the present invention concerns a continuously moved film.

The novel features which I believe to be charabout.

Fig. 5 serves to explain an operation of a spiral disk of several turns, whilst Fig. 6 shows an arrangement of producing synchronisation impulses, to which further reference is made in the following paragraphs.

' In particulars referring to Fig. 1 an image area having three lines is scanned in two groups of lines, so that accordingly each group of lines comprises one and a half lines. The first group of lines comprises the lines in and (12, the second group of lines the lines in and b2. It is to be recognized that the group of lines I) is disposed in the intermediate spaces of the group of lines a without it being necessary for the vertical Screen apparatus to depart from the two limiting points; 0, the upper edge of the image, and d, the lower edge of the image. An oscillation of this kind between two fixed lines of limitation can be The number of lines is fractional in respect of each part-image.

In Fig. 2 there is shown a scanning disk suitable for the transmission of 239 full lines. The sectional area on to which the film image is projected is designated 2. The same is formed by two radii 3 and 4, which are taken through the holes I and 239, the two extreme image holes of a two turns spiral. The spiral is an Archimedian spiral running continuously from number I to number 239 without interruption and without irregularities. The angle a between two subsequent radii of a disk of this kind is represented in the case of 2 holes by This angle amounts for example in the case of a disk having 239 holes to 3 45". A transmission with a disk of this kind will be performed with advantage in conjunction with the so-called self-synchronising image point method. If the disk, viewed from the projection light source, rotates clockwise, as shown in Fig. 2, each image element must traverse a starting line 5 at the edge of the image on the left hand side. This is accentuated in relation to the image by particularly bright lighting and provides the line synchronisation signal with excess of amplitude. For sorting out the two image-point spirals there is combined with the disk according to Fig. 2 a spiral diaphragm, which is designated 6 in Fig. 2 and rotates in the same direction at half the velocity. In practice the disk rotates for example at 6000 R. P. M. and the diaphragm 6 at 3000 R. P. M. The diaphragm may rotate in the plane of an intermediate air image for avoiding loss of light or lack of sharpness.

In addition to the line synchronisation, which is effected by the starting line, there is also required an image-change synchronisation. This is obtained by a single synchronisation slot 1. This synchronisation slot cuts a projection 5' of the starting line 5, which may be regulated by means of a shiftable gap, so that the intensity of both synchronizing signals is equal. The image-change slot 1, on each occasion when it passes through the starting line 5', is freed up to the photo-cell. For this purpose the shading diaphragm 6 is furnished with two openings 8 and 9 which are generously dimensioned in the peripheral direction. The length of the slot 1 determines the duration of darkening of the vertical return line. I It has been found that in the television art a duration of the return amounting to 1% is fully adequate. 1 may accordingly have the length of 1-3 line periods.

To explain the manner in which the decomposition of the image is brought about there is also provided Fig. 3. In Fig. 3 there is to be seen in what manner the reproduction of the original film passes over the decomposing points of the disk and both sections move one against the other. The movement of the film image 6 is divided into 7 phases. The image moves evenly from the bottom towards the top and the image holes of the disk move at the same rate but in opposition from the top towards the bottom. The disk contains seven holes and decomposes the film into 2 3.5 lines. In phase a there operates the hole 4. Up to the phase I) it has scanned the topmost line I of the reproduction of the film. At phase b there commences the hole 5, and up to phase 0 it has scanned the line 3. In phase 0 there commences the hole 6 which up to phase d has scanned the line 5. In phase (Z the lowermost hole I scans line I of the original. It does not complete this, however, but moves away from the original image at the lower edge after completion of a halfline. At this moment there requires to commence the image-change impulse. The commencement of the image change signal is entered as 1. By reason of the jump in the disk section from the hole 1 to the following hole I there is initiated the scanning of, the second group of lines.

The hole I passes during e over the line 2, which was free. The hole 2 passes during I over the line 4, which was previously free, and in similar fashion the hole 3 scans the line 6 during y. Point 4 is unable to reach the original image, which has now been completely scanned twice, and already commences the scanning of the next image. Phase it accordingly follows on phase a. At this moment, in accordance with the invention, there must commence the second image-change signal 1'. The position of both image-change signals is exactly isochronous. The spacing of the two signals amounts to half the total of all line periods. This condition is satisfied by provision of the synchronisation slot 7 shown in Fig. 2. The end of this slot 1 requires -to pass exactly over the projections 5' of the starting line 5 when the radius of the middle hole passes through the middle of the image area.

In other words, the first scanning of a single film image (or its reproduction on the film gate) begins when its upper end has reached the middle of the film gate, is made by the inner turn of the spiral and is finished when the image covers the gate; now begins the second scanning which is made by the outer turn of the spiral.

It is possible in accordance with the above statements to design other transmission disks for a difierent number of lines and for a different number of part-image transmissions. Principally a single turn spiral is able to perform a scanning for any number of part images, but for placing the high number of holes wanted for good television two turns at least are necessary. The number of complete spiral turns is equal to the number of part-image transmissions if the disk rotates as many times per part-image as image repetitions are desired. The total radial height of all spirals is equal to the height of the reproduction of the film image.

For comparatively large numbers of lines it is advisable to employ scanning disks operating at a higher speed than one revolution per part image. In contraclistinction to the scanning disk described in connection with Fig. 2 which rotates twice for a single image transmission and contains two spiral turns, there is shown in Fig. 4,

an example of a high speed disk having a four turns spiral which rotates four times for each image transmission. In the above example the disk requires to perform 6,000 revolutions per minute. The image holes (I19 or 239) are equally distributed over the four turns of the spiral.

The diaphragm 6 runs at 1,500 revs. This shading diaphragm may be arranged either close to the disk, so that it throws a comparatively sharp shadow on the disk, or it may also be arranged in the plane of an air image of the disk. To explain the second case the plane of the disk is designated 23 in Fig. 5. The film 25 is reproduced sharply on this disk by means of a lens 2 3. By means of an auxiliary lens 25' there is again produced from the image on the disk 23 an air image 25 and in this image plane the said diaphragm 6. Behind this there may be connected the photo-cell I I either in direct fashion or with the interposition of a collimator ID.

The frame synchronisation is eifected by means of a synchronisation slot 1. The slot 1 must commence with the same central angle either with the hole I or with the middle point The slot is uncovered as many times as partimages are to be disposed one over the other. In

the present case the slot is uncovered twice upon four revolutions of the main disk. By reason of the bisecting of the angle a by the middle section point it is accomplished that each part-image is scanned to the extent of one-half of a line period too late as compared with the preceding one, and I a starting line, also be effected by means of a light chopper consisting of a row of slots M (Fig. 4:). In order to obtain the line synchronisation frequency a slot l4 must be provided for each radius taken from an image point to the central point,

and the obtained frequency must be induced in the ratio of 1:11. This frequency reduction is produced preferably by electric means.

In Fig. 6 there is shown an arrangement of this kind. The disk having 4 or 2 spirals and rotating with 6,000 or 3,000 revolutions generates by its apertures M in conjunction with a light source 15, a photo-cell i6 and an amplifier H a control frequency. This is not capable of being employed in direct fashion for synchronisation of the received image. In accordance with the invention it is .passed to a frequency reducer l8. This frequency reducer i8 may consist of a relaxation generator in which a condenser 49 is charged by a resistance 20 with a frequency of A1 or /2 of the aforesaid slot frequency. In the manner Well known per so every second or every fourth period ignites the discharge tube 2|. All remaining changes pass through unutilized. At the transformer 22 an impulse series may accordingly be tapped as sub-harmonic. This may be employed, possibly after filtering, in immediate fashion for synchronisation of the receiver. An advantage of this method is the fact that no rotating screening diaphragm is required.

laced lines rotating twice per image, two being,

the number of part images and having a spiral of 2 points equally distributed over the spiral, 2 being the total number of lines of an image and being an odd one, and a shutter disk rotating once per image for uncovering at once one of said turns.

3. Scanning disk for television transmission for scanning a continuously moved film with interlaced lines rotating at a higher speed than 1) times per image, p being the number of part images, and having a spiral of 2 points equally distributed over the spiral, 2 being the total number of lines of an image, p and 2 having no common factor, and a shutter for uncovering at once one of said turns.

4. Scanning disk for television transmission for scanning a continuously moved film with interlaced lines rotating twice per image, two being the number of part images, and having a spiral of a points equally distributed over the spiral, 2 being the total number of lines of an image, being an odd number, and a shutter for uncovering at once one of said turns.

5. Scanning disk for television transmission for scanning a continuously moved film with interlaced lines rotating p times per image, p being the number of part images, and having a spiral of 2 points equally distributed over the spiral, a being the total number of lines of an image, 12 and 2 having no common factor, and a shutter for uncovering at once one of said turns, said disk being further provided with a special slot for producing one frame change signal per revolution.

6. Scanning disk for television transmission for scanning a continuously moved film With interlaced lines rotating in times per image, 1) being the number of part images, and having a spiral of 2 points equally distributed over the spiral, 2 being the total number of lines of an image, p and 2 having no common factor, a shutter for uncovering at once one of said turns, and means for projecting a small light bundle of great brightness at the margin of the image on. said disk for producing the line change signals when scanned by said holes.

7. Scanning disk for television transmission for scanning a continuously moved film with interlaced lines rotating 10 times per image, 1) being the number of part images, and having a spiral of 2 points equally distributed over the spiral, 2 being the total number of lines of an image, p and 2 having no common factor, said disk being further provided with "a separate rim of 2 slots for producing p impulses per revolution, and a frequency reducer for reducing said 1oz impulses to 2 line synchronizing impulses per image.

KURT SCHLESINGER.

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