US2373114A - Television film recording and projection - Google Patents

Description

April 10, 1945. T. T. GoLDsMlTH, JR

TELEVISION FILM RECORDING AND PROJECTION Filed June 21, 1941 2 Sheets-Sheet 1 .Qll fr@ April 10, 1945. T. T. GOLDSMITH, JR 2,373,114

TELEVISION FILM RECORDING AND PROJECTION Filed June 2l, 1941 2 Sheets-Sheet 2 E s fd N Il' l\\ Q l M INVENTOR.

ATTORNY Patented Apr. l0, 1945 TELEVISION FILM RECORDING AND PROJ ECTION Thomas T. Goldsmith, Jr., Cedar signor to Allen B. D Passaic, N. J., a corp u Mont Laboratories, oration of Delaware Grove, N. J., ar-

Inc.,

Application June Z1, 194i, Serial No. 399,055

11 Claims.

This invention relates to the production of television programs in large size on motion picture screens. With the system employed herein, incoming electrical signals are converted into the corresponding lights and shades of a picture on a cathode-ray tube. In carrying out this invention pictures are reproduced as negative images on a cathode-ray tube. IIhen a motion picture camera is used to record the series of pictures directly on positive stock film. This film is developed rapidly and can be projected promptly in standard motion picture theatre projecting equipment, resulting in large screen reproduction of television.

In this way the necessity for reproduction of the television picture on a tube which in itself is of suillciently intense brilliance to allow direct projection, is avoided. The cathode-ray tube is bright enough to provide for recording on an inexpensive grade of motion picture film although this brilliance is far less than that requiredrfor direct projection, say on a screen 30 feet in size. Consequently the life of the cathode-ray tube and associated equipment is much longer than in the case of direct projection and also the equipment is much less costly.

There are many advantages in this intermediate film method of obtaining large screen projected television pictures. By recording on film it is possible to use standard projection equipment with its inherently high brilliance provided by the highly developed projection arc lights. By use of the intermediate film, the program may be edited before showing if desired. Also, repeat programs are available and the programs may be scheduled at will so as not to interrupt the continuity of the theater feature programs for example.

In carrying out the invention a television receiver, which may be of conventional form for accepting the composite video and synchronizing signals either from a transmission line or over the air, may be used. The picture goes through a conventional receiving circuit to be monitored in its positive polarity in the standard way. At a point along the amplifier circuit the composite synchronizing and video signals are fed to the circuit that is necessary to invert the polarity of the picture. This circuit may take the form, for example, of an additional video amplifier stage, or it may consist of a reversed polarity detector circuit when used with radio frequency transmisvolts for acceleration. This bright negative picture is photographed on positive nlm and after a rapid developing process the iilm may be immediately thereafter passed through a motion picture projector to provide a direct positive picture on the conventional theatre screen.

A particular feature of the invention is the provision in the equipment which drives the bright blue cathode-ray tube, for producing locally such signals as are necessary to blank out the white return lines which would otherwise be produced on this inverted television picture. This local blanking generator may, for example, consist of a set of saw-tooth generators operating at horizontal and vertical scanning frequencies and controlled ing signals, followed by suitable blanking signal shaping circuits of the type described in Camp- 'bell Patent 2,207,048.

Another feature of this invention is the use of automatic direct current leveling circuits feeding the cathode-ray tube which maintain the proper voltage relations between the locally generated blanking signals and the incoming picture signals. In the conventional receiver producing a positive picture the pedestal `level of the composite signal determines black for the However, with the present invention this pedestal level determines the maximum white of the picture since the picture signals are inverted. A diode tube is inserted to maintain this white level at a constant brilliance so that the incoming picture signals always Work toward the black from this fixed point. For example, this diode may be placed in the circuit at the grid of the cathode-ray tube. An additional diode direct current leveling circuit is preferably employed to control the operating range for the locally generating blanking. In one embodiment of the invention this locally generated blanking may be applied to the cathode of the cathode-ray tube with its direct current level control adjustable in a manner to providel for change in average brilliance of the tube. These blanking signals are of square pulse shape and must have a minimum amplitude which is as high or higher than the total peak to peak amplitude of the incoming composite picture signal.

If the blanking signal is higher in amplitude there will be no harm done. In practice the blanking signal is continuously 'produced at a level higher than any possible peak picture sig nal. Consequently the use of the direct current leveling diode always regulates the level of the picture interval of this square pulse blanking by the incoming synchroniz-A signal so that this interval corresponds to xed brilliance level and the other level oi the blanking signal may fall Where it will. With the direct current leveling diode the actual amplitude 'as well as the width of the blanking may vary from time to time Without harm since the active.

-may be assembled and connected in carrying out this invention; and

Fig. 2 is a similar diagram on a larger scale j showing more details of certain components and some additional elements.

In the drawings, reference character I indi.. cates a television receiver for an input signal through connection 2 either to a transmission line or through the air. The receiver delivers a composite television signal 3 of conventional polarity which may be monitored on a cathode-ray tube I in the usual way. This composite signal 3 is delivered to a one stage ampliiier 4 which inverts the picture signal as shown. at 6. This inverted signal is passed through a direct current inserter 5 which controls the reference level from which the modulation occurs and yields the Wave form 6 which is opposite in polarity to the conventional wave form 3. The wave form 6 is delivered by means of connection 1 to the grid 48 of the bright cathode-ray tube 8, thus providing the grid modulation to this tube 8 for producing a bright reversed polarity television picture on the screen of this tube. In. one embodiment ofthe invention this cathode-ray tube 8 has a blue screen with a high accelerating voltage so that it produces light which is most actinic even for inexpensive grades of motion picture film.

The television receiver I delivers a horizontal sawtooth wave form by means of connection I I to the monitor cathode-ray tube Ill, to the cathoderay tube 8 and to the horizontal blanking generator I2. The receiver I also delivers a vertical sawtooth wave form by means of connection I3 to the tube I0, to the tube 8, and the vertical blanking generator I4. The horizontal blanking generator I2 and the vertical blanking generator I4 may consist; for example, of circuitsof the type described in the Campbell Patent 2,207,048.

The square wave form blanking pulses from generators l2 and I4 are suitably mixed in the blanking mixer I1 and after passage through a direct current inserter 25 the blanking signals are applied by means of connection 26 to the cathode 41 of the cathode-ray tube 8.

The above described blanking signals which are represented by wave form I8 serve to annul the standard blanking which is an integral portion of wave form 6 and therefore prevent the visible appearance of the return lines in the process of scanning the cathode-ray tube 8. This wave form I8 represents the signal on conductor 26.

The motion picture camera 21 records the reversed polarity pictures which appear on the screen oi tube 8, using positive stock film 28. This nlm may be of an inexpensive grade since the blue light from tube 8 is of suicient brilliance for direct recording on the positive stock. Use of the negative or reversed polarity picture on tube 8 and positive stock film in the camera 21 makes it feasible to develop only one ilm, thus saving the conventional step of initial recording on a negative illm and production of a positive therefrom. The positive lm 28 is immediately thereafter passed through equipment 29 of the known sort for rapid development, xing and drying of the film in the well-known way. This developing process can be accomplished in a minute or less, so that the film is almost immediately ready for projection after reception of the picture on tube 8.

The positive developed film is then passed into the motion picture projector 30 where the conventional arc light 3l is directed by a condensing lens 32 through the nlm gate and the picture is focused by the lens 33 on the conventional theater screen 34 in the well-known manner.

Some of the details of Fig. 1 are shown on a larger scale in Fig. 2. This Fig. 2 shows particularly, more in detail, the circuits for direct current level control of both the picture signals and the locally generated blanking signals. It also shows an additional tube in parallel with the cathode-ray tube which combines the two signals in the same way they are combined in the cathode-ray tube 8 but in a manner so that the resulting signal appears across a load resistor for monitoring on an oscillograph.

The wave form 35 represents the composite television 'picture signal .which is ready to be applied to the grid of the cathode-ray tube 8 exl cept that it has not yet passed through the direct currentlevel control circuits. The wave form 35 represents the signal which is present on the lead 40 and at the lead 48 this wave form has no particular relation between its average voltage level indicated by the dotted line 36 and its blanking level represented by the pedestal height shown at 39. There is no necessary denite relation between the dotted line 36 and the level 39 up to this point, because condenser coupling might have been employed in earlier amplifier stages which would make the level of the dotted line 36 vary with respect to the pedestal 39, depending upon the composition of the picture. The signal 35 is passed through the condenser 4I to a diode tube 42 which is so connected as to provide direct current insertion to control the pedestal level 39 at a iixed voltage relation for the grid 48 ofthe cathode-ray tube 8. The resistor 44 between tube 42 and lead 1 is of low resistance value, yet sufficiently high in resistance so that the synchronizing peaks 31 on the composite wave form are practically ignored; consequently the signal appears on the plate 43 of the diode 42 as though the pedestal level 39 were essentially iiat from the beginning to the end of the blanking interval. A high resistance leak 45 is placed across the diode 42 so that the voltages may return to normal after momentary unusual surges. The condenser 4I tends to apply signals to the plate 43 going positive and negative with respect to the dotted line 36. However, upon an attempt to drive the plate 43 positive with respect to the cathode 46, the tube 42 will conduct current and establish a bias voltage on the con-y denser 4I so that no subsequent signals can go more positive than the cathode 46. The reference voltage level indicated by the dotted line 38 is established in this way, and the television signals are maintained always negative with reference to this line 38, except for the synchronizing peaks 31, and the pedestal 39 level is caused to assume the xed voltage of the dotted line 38 to maintain the proper brilliance setting of the grid 48 in the cathode-ray tube 8. In this way the receiver automatically varies the absolute brilliance of the received picture when the transmitter sends one line, for example, which is essentially bright on a standard picture of positive polarity, as shown in the ilrst section of wave form 6, and a subsequent line which is essentially dark in a standard picture of positive polarit as shown in the second section of wave form 6. It is to be understood that the cathode-ray tube 8 must reproduce this picture in negative polarity and therefore this direct current inserting diode accomplishes the re.. sult of maintaining a direct current level represented byline 38 for maximum white with means for modulating always toward black trom this level, whereas the conventional tube with a picture oi' positive polarity has a direct current inserter for maintaining a constant black level with facilities for modulating toward the white.

The connector 49 carries the locally generated blanking signals from the blanking mixer I1 and introduces these signals through the coupling condenser to the cathode 52 of the direct current insertion diode 53. The plate 54 of this diode is returned to a bias voltage supply by means of the potentiometer 51. The condenser 55 is employed to prevent signal voltage from appearing across the potentiometer 51. The high resistance 56 shunts the diode and enables the circuit to return to its operating range automatically after an abnormal surge may have appeared. By means of the potentiometer 51 the absolute value of the direct current voltage may be set independent of lincoming signals and this potentiometer serves as the brightness control of the cathode-ray tube 8. 'l he vacuum tube 58 is connected as a cathode follower stage to pass the blanking signals without inversion of polarity but with reduction of source impedance. The blanking signals are applied from the direct current inserting diode 53 to the grid 59 of this tube. The cathode 68 is connected directly to the cathode 41 of the cathode-ray tube 8. The resistance 6| in the cathode circuit of tube 58 is of low value so as to transmit the blanking Wave forms without distortion and so that changes in current in the cathode-ray tube 8 will not cause an appreciable change in the direct current level control circuit. The blanking wave form 63 represents the signal on the conductor 49 and would represent the signal at the grid 59 after passage through the condenser lii if it were not for the direct current inserting diode 53. The dotted line 62 represents the average level above and below which the signal swings positively and negatively. 'Thus the voltage diierence between this average level 62 and the level of the picture interval 61 of the blanking signal would depend upon the relative r areas indicated in the shaded portion 64 and the cross hatched portion 65 of the wave form 63. By use of the direct current inserting diode 53 the wave form 66 results and is applied to the grid 53. Here the dotted line 68 becomes the reference level for the direct current in the blanking circuit. This level 68 is actually determined by the potential of the plate 54 and may be varied by means of the potentiometer 51 so as to change the brightness of the cathode-ray tube 8. However, the picture interval 61 of the blanking signal represents the most negative excursion of the blanking signal, and by means of the diode 53 this tendency of the cathode 52 to go negative causes the tube 53 to conduct and charge condenser 5i so that the picture interval level 61 always coincides with the dotted line 68, even if the wave form 63 should be changed in amplitude or width. For example, the shaded area 64 might be increased by widening of the blanking pulse which would cause the wave form 63 to shift with respect to the level 62, causing a change in brilliance of the cathode-ray tube 8. Itis necessary that the portion 64 of the wave form 63 be a square impulse for blanking, which starts slightly before the standard blanking signal in the wave form 35 and ceases slightly after this standard blanking interval ceases so that the entire blanking and synchronizing signal of the incoming television wave form may be completely suppressed. Since it may be necessary to alter the width of the region 64 and it may be desirable to change the amplitude oi the wave form 63, the direct current inserting diode 53 is available for providing automatic means for controlling the output level of this signal so that the critical level 61 is always maintained at its proper value.

A vacuum tube 10 may be connected in parallel with the cathode-ray tube 8 for the purpose of providing monitoring of the combination signal resulting from the two signals applied to the grid 48 and the cathode 41 of the cathode-ray tube 8. The combination signal appears on the cathoderay tube screen of the tube 8 as changes in brilliance, but for adequate control of these signals it is desirable to produce and monitor the resulting wave form of the combination, Therefore the grid 1I of tube 10 is connected directly to the grid 48 0f tube 8. The cathode T2 of tube 10 is connected to the cathode 41 of tube 8. The plate 13 of tube 10 thus carries a current which is characteristic of both signals applied to tube 8. A voltage develops across the plate load resistor 14 which represents this combined signal. It may be applied by means of a selector switch 16 to an oscillagraph 18 so that the wave form will appear on the cathode-ray tube 19 of the oscillagraph for monitoring purposes. The selector switch 15 also makes provision for monitoring the signal B6 through the connection 8B and for monitoring the signal 6 through the connection 8i, thus providing monitoring of either of the signals independently. The switch 1B may also be used to monitor other points in the circuit if desired by use of the lead 82.

Other means for direct current insertion may be employed, such as using the conducting action of a positive swinging grid of a cathode-ray tube or the grid of some tube in an earlier amplitying stage in the known ways.

Also, it may be desirable to produce the negative polarity pictures on the cathode-ray tube l screen by simply using the signal normally fed to the grid of a cathode-ray tube for producing a positive polarity and connecting this signal instead to the cathode of the cathode-ray tube. 'I'hen the blanking signals can be applied to the grid of the cathode-ray tube. This will require less changing of the actual video circuits used in conventional reception.

The particular embodiments of the invention which are shown herein have been explained in considerable detail for purposes of making the invention clearly understood, but there are other ways of carrying out the invention.

For instance, the picture and synchronizing wave form may be mixed with the locally generated blanking signals in a tube ahead of the cathode-ray tube, using direct current leveling on each channel, with direct coupling between such a stage and the cathode-ray tube.

The accompanying sound for the television may be recorded on the same lm with the picture, displaced the conventional distance from the corresponding picture frames so as to synchronize in standard motion picture projectors.

What is claimed is:

1. In a device of the character described, means for receiving television pictures and recording them on film, comprising a cathode-ray tube having a screen and means for producing pictures in negative polarity upon said screen from a received signal of positive polarity, and blanking means to suppress the normal return blanking components in the received television signal.

2. In a device of the character described, means for receiving television pictures and recording them on iilm, comprising a cathoderay tube having a screen and means for producing pictures in negative polarity upon said screen from a received signal of positive polarity, and a camera for recording said pictures on lm.

3. In a device of the character described, means for receiving television pictures and recording them on film, comprising a cathoderay tube having a screen and means for producing pictures in negative polarity upon said screen from a received signal of positive polarity, a camera for recording said pictures on film, and means for quickly developing said film and means for projecting said-film upon a screen.

4. In a television system having synchronizing signals combined with picture signals, means controlled by said synchronizing signals for producing blanking signals, means to apply said picture signals to the grid of a cathode-ray tube in polarity which produces negative pictures on the screen of said tube from received pictures of positive polarity, and means to apply said blanking signals to the cathode of said tube.

5. In a television receiving system, means for producing pictures of inverted polarity on a cathode-ray tube screen from received picture signals of positive polarity, means for recording said pictures on lm with photographic reversal of polarity, and means for projecting on a screen the resulting pictures of positive polarity.

Patent No; 2,575,111

6. In a device of the character described, means for receiving television pictures and recording them'on film, comprising a cathoderay tube having a screen and means for producing pictures in negative polarity upon said screen from a received signal of positive polarity, a direct current inserting diode for maintaining a. direct current level for maximum White on said tube, and means for modulating always toward black from-this level.

7. In the process of producing television programs, lthe steps which comprise producing a negative visible television picture from received signals of positivepolarity and photographing said picture.

8. In the process of producing television programs, the steps which comprise receiving television picture signals in positive polarity from transmissions of positive polarity, linverting the polarity thereof and photographing the pictures thereby produced.

9. In the process of producing television programs, the steps which comprise receiving television picture signals in positive polarity from transmissions of positive polarity, inverting the polarity thereof and photographing the pictures thereby produced and projecting the photograped pictures on an enlarged scale.

10. In the process of producing television programs, the steps which comprise receiving television picture signals in positive polarity from transmissions of positive polarity, inverting the polarity thereof and photographing upon a moving prepared surface the pictures thereby produced. l

11. In the process of producing television pro- THOMAS T. GOLDSMITH, JR.

April io, 19Li5.

THOMAS T. GOIDSMITH, JR.

It is hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 1, first column, line 55, for "invented" read inverted; line 59, secondcolumn,

for "generating" read -generated--g and that the said Letters l-tent should be read with this correction therein that the same may `conform to the record of the case in the Patent Office.

signed mi sealed this 19th day of June, A. D. isililj.

( Seal) Leslie Frazer Acting Commissioner of Patents.

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