US2288096A - Television film projector - Google Patents

Description

June 30, 1942. H. R. LUBCKE ETAI.

TELEVISION FILM PROJECTOR Filed July 27, 1940 Patented June 30, 1942 UNITED STATES PATENT f OFFICE TELEVISION FILM PROJECTOR `Harry B. Lubcke, Los Angeles, Willet E. Brown, Santa Anita, and William B. `Klein, Los Angeles, Calif., assignors to Don Lee Broadcasting System, Los Angeles, Calif., a corporation of California Application July 21, 1940, serial No. 341,900' 1 1 claim. (ci. 11s-1.2)

ond with a two to oneinterlace, so that the picture i'leld is scanned every sixtieth of a second, with the result that whatever the phase relationship may be between the motion picture pro-` jector and the television pickup, a change of frame of the film will occur during certain of the television scansions if the ordinary type of motion picture projector be used. The time required for moving the film between successive frames isabout 14% of the frame period, which equals about tn of a second or 35% of one television scanning period. It will thus be seen that with the standard motion picture projector the frame of the iilm will be changed every two and one-half scansions, resulting in a darkening of the field which lasts for about one-third (35%) of thescansion.

The present invention is concerned with the storage type of television pickup tube, typified by the Iconoscope," wherein the signal generated by the scanslon of each point of the picture eld is proportional (to a rst approximation) to the integral of the light which has fallen on that point since it last was scanned. If the ileld has been dark a portion of the time since the last scansion the intensity of the signal will be reduced approximately in proportion to the ratio of the time of darkening to the total time between scansions.

The eld at a television receiver is illuminated only one point at a time, each point being illuminated once in each l/o of a second under present standards, and this rate is itself slow enough to result in a perceptible flicker.l It ls to avoid this ilicker that interlace" is used, alternate lines being scanned in successive scansions, for it has been found that if the rate of flicker of the held as a whole is doubled it becomes imperceptible, the inter-line flicker not being noticed and the eye appreciating only an apparent average illumination. If, however, the intensity of signal differs materially for the successive scansions, as

' it will if the ield has been darkened for nlm changing before one scansion but not before the next in the same repetition period, the value of the interlace is largely lost, andra flicker of a particularly annoying type results.

In the past the problem thus presented has been met in two distinct ways each involving the use of a special type of projector. The first of these methods involves displaying successive frames of the lm for unequal intervals, the rst .frame being exposed during three scansions of the field, while the succeeding frame is exposed during two scansions only, thus retaining the same average illm speed but making the change oi frame occur Veach time in the same epoch of the scanning. The field is illuminated brieiiy between the scansions, which take place while the photosensitive screen is dark.

The second method of solving the problem involves the use of a continuous projector, wherein the film progresses at a constant rate through the projector and the consequent motion of the image is optically compensated so as to hold it in a xed position on the screen. This method can be used either with the storage type or the instantaneous type of television pickup, but the projector is expensive, complicated, and must be manufactured with an extremely high degree of accuracy in order to be satisfactory.

The method of our invention, as above stated. involves the use of a television pickup or camera of the storage type, and among the objects of the invention to provide a method of transmitting motion pictures by television which is applicable to any desired ratio of nlm frame rate to scanning rate; to provide a method to which standard motion picture projectors may be readily adapted; to provide a method which will produce 'ickerless television images irrespective of the frame and scansion rates employed; and to provide a method which greatly decreases the cost and complexity of the equipment used. It is also an object to provide apparatus whereby the method here set forth may be accomplishedI and to provide apparatus with which direct pickup cameras may be used for motion .picture projection with no positional or electrical inversion of the camera.

Our invention possesses numerous other objects and features of advantage, some of which, together with the foregoing, will be set forth in the following description of specic apparatus embodyingk and utilizing our novel method. It is therefore to be understood that our method is applicable to other apparatus, and that .we do not limit ourselves, in any way, to the apparatus of the present application, as we may adopt various other apparatus embodiments, utilizing the method, within the scope of the appended claims.

The instant invention operates through the cooperation of two groups of factors. The first group is dependent upon the nature of vision as it affects the perception of flicker, and in such perception contrast is a primary factor. Flicker (i. e., visible or apparent iiicker), is increased if the variation in intensity of one point from instant to instant is high. It is also increased if the area which is flickering is in immediate proximity to an area which is not, or which is flickering in opposite phase. Sharp definition of the flickering area therefore increases its apparent intensity.

The second group of factors has to do with the operating characteristics of storage type television pickup tubes. These tubes will operate over a definite range of operating conditions. When an optical image is focused upon the sensitive mosaic of the tube the individual droplets or islands of photosensitive material lose electrons, in the initial instant of illumination, proportionally to the illumination, thereby acquiring positive charges. As these charges increase with time the more highly illuminated portions (and therefore the more positive portions) exhibit space charge effects to a greater and greater extent, as a result of which the emission decreases, so that they approach a certain limit of potential. Added to this is the fact that the more positive points attract more strongly any stray electrons which may be in the neighborhood, and this also has the effect of decreasing with time the rate at which these points acquire positive charges. The photosensitive mosaic is scanned by a moving beam or pencil of electrons, which has a twofold effect. First, certain of these electrons neutralize the positive charges which were photoelectrically acquired. Second, there is also a tendency of the scanning beam to knock off secondary electrons, which causes the particles to tend to swing positive rather than negative, the magnitude of these effects being dependent upon the velocity and intensity of the impacting beam and the potential of the electrodes which pick up the electrons knocked off or emitted by photoelectric action. The two effects cooperate to drive the various areas to a definite equilibrium. In practice it is usually the effort to have the scanning beam bring the points scanned to complete equilibrium.

It is an experimental fact, however, that the degree of neutralization of charge obtained in scanning is under the control of the operator, i. e., that it is possible by varying the intensity of the scanning beam to neutralize the stored charges more or less completely, leaving more or less of a residual charge having image characteristics upon the screen. Since it is the neutralization of charge that generates the television signal it would appear obvious that the best picture would be obtainable when the stored charge was completely neutralized. Again, however, it is an experimental fact that if the scanning beam be gradually increased in intensity from zero, the signal will be found to approach a maximum with the charge incompletely neutralized, and after this point is reached relatively large changes in intensity of the scanning beam cause relatively little change in signal intensity.

Another operating feature of these tubes is the fact that the degradation of the image due to the limitation of positive charges in the high lights is reduced by back lighting; i. e., if the 'tion comprises projecting the motion picture to be transmitted upon the screen of a storage type television pickup intermittently as with the conventional type of projector, scanning the screen with an electron beam preferably of minimum vintensity so as to leave a material picture charge upon the screen, and illuminating the screen during the period of occultation of the film by a diffused light which will reduce the contrast in average illumination between the portion of the picture area which is illuminated for the full *frame periodk and that which is scanned after a period of `\oc`cultatlon. Preferably, alsof the occultation is accomplished so as to cut ofi illumination gradually instead of suddenly, making the contrast between those portions which have been occulted and those which have not more gradual, and back lighting is also used to increase the effectiveness of the period during which the screen is fully illuminated by the image as will be more fully set forth later.

From the aspect of apparatus the invention comprises the combination with television pickup equipment of the storage type and a motion picture projector having an intermittent motion for progressing the film and a shutter for occulting this film during its progression, of means to supplying to the screen d-uring occultation a general illumination distributed over the screen which will maintain the average illumination of the picture field sensibly constant.

Referring to the drawing:

Fig. 1 is a lschematic diagram, reduced to lowest terms, showing the essential features of a system embodying our invention.

Fig. 2 is a graphical representation showing the relationship existing between frame frequency, vertical scanning frequency, repetition frequency, and illumination in the system of our invention.

Fig. 3 is a graphical representation of the distribution of illumination over the picture field where conventional apparatus is used.

Figs. 4 and 5 are diagrammatic representations of two forms of shutters adapted for use with this invention.

Fig. 6 is a schematic showing of a modification of the apparatus shown in Fig. 1.

In the diagrammatic representation of Fig. 1 the film l is preferably standard sound-motionpicture film, exposed at the rate of twenty-four frames per second and bearing upon its edge the customary sound track. The major portionvof the projector may be in any conventional form, and is shown as including the usual feed reel 2 on which the film is stored before projection, and from which it is unwound by means of the pulldown sprocket 3, 'to be progressed past the lm gate 4 by a claw or `other intermittent mechanism 5, and thence passed over the takeupvsprocket 1 and through the sound head 9 to be rewound upon the takeup reel l0. The various loops and auxiliary sprockets which are utilized in the conventional projector are used here also, but are not shown since they are completely conventional and would merely complicate the showing.

The nlm is illuminated by an optical system comprising, for example, a lamp I I backed up by a reflector I2, with a condensing lens I3 arranged in accordancewith the usual practice to focus an image of the filament through'the lm gated into the plane of the optical center of a projecting lens Id. Instead of the image being projected directly upon the screen, however, it is inverted deiiected by a first surface mirror I5 through the shutter I'l and onto the inclined screen I9 of a storage type television pickup tube 20. The tube is enclosed within a conventional camera housing 2! which is indicated by the dash lines.

The television camera is entirely conventional and with it are associated the usual deflecting circuits, master pulse and scanning generators, etc., but these are not shown as theyare well known to those skilled in the art and are merely ancillary to the present invention.

The primary diierence between the setup thus described and the combination of a standard motion picture projector and a standard television camera lies in the shutter Il. A preferred form of this shutter is shown in Fig. 4. It differs from the standard shutter in its scimiter shape, the curved edges being provided to cause occultation of the image on the different portions of the screen at slightly different epochs, so that the transition band between occulted andy nonocculted film will not occur in perfectly straight lines across the image and will therefore be less apparent to the eye. This is a 4secondary feature, however, since the important characteristic is that the shutter is translucent or light diffusing rather than either transparent or opaque. This may be accomplished by making the shutter of transparent plastic (e. g., Lucite) and spraying upon it droplets of transparent plastic or lacquer, which, by forming minute lenses,- alter the focal distance and diiiuse the image so as to permit substantially the same amount of light to fall manipulation is necessary in order to transmit upright pictures.

In considering the operation of the device attention rst is directed to Fig. 2 which shows the time sequence of the various events in one half cycle of operation of 'a conventional projector as used with this type of television camera.

The second half cycle differs from the rst only in that the rst scansion therein is of even instead oli-odd unes. Abpve the axis is shown the motion picture sequence, whichstarts with the operation of the pull-down mechanism, lasting 14% of the frame period, during whichportion of the period the shutter occults the light from the lm. With the ordinary, opaque type of shutter there is Ano illumination of the lrnl for this occultation period and hence no storage of image on any part of the screen. At the end of the pull-down time, the screen is, fully illuminated and remains so until the next occultation and pull-down 1&4 of a second later.

Beneath the axis line is shown the sequence of events in the television system. i In this case the scanning of the vfield is assumed to have been completed at the instant that the pull-down starts, and during the first 8% of they scanning period the scanning beam moves from the lower right-hand corner of the picture field back to the upper left-hand corner of the field and then starts to scan the odd numbered lines of the picture eld. When the odd lines have all been scanned the second scanning period begins, 8% thereof again being occupied by the return of the beam, and this time the even numbered lines are scanned.

If the scanning beam has been so adjusted as to neutralize the screen completely the effective charges start to build up from zero the instant theV beam has passed, and'continue to build up during the repetition or double scanning period. Because the eld was dark during the iirst portion of this period, however, it is only when the double period has fully been accomplished after the pull-down that the elements are transmitted at full brilliancy. The relative rate at.

which any point in the iield theoretically acquires its charge is proportional to the slope of curve 2'2, zero during Voccultation and constant between occultations, the actual rate being proportional also, of course, to the intensity of illumination of the individual point. The strength of the signals generated by the scanning of the point at any time tis similarly proportional to the integral of this slope between the limit.: (t-r) and t, where r is the period of repetition, or l@ of a second, the curve representing this integral being illustrated by the curve 23 of Fig. 2, wherein the ordinate at any point representing an instant t is equal to the ordinate of curve 23 at the point t minus its ordinate at (t-r).

If the successive sections of the curve 23 be superimposed, as shown in Fig. 3, it will be seen that the average amount of light falling upon each part of the screen is the same when inte grated over the complete half cycle of the two frames or five scanning periods, but that there are two areas, each occupying about 19% of the effective area of the frame (N1/2% of the total frame period including .the return period) that increase in brightness F11/2% every fth scanning period, or twelve times per second, which causes the annoying icker before mentioned. Between these two areas of bad iiicker there are transition areas, occupying the remainder of the tele'- vision frame, in which the icker changes phase, vbeing reduced to half the intensity and increased to double the frequency half way between the two badly flickering areas.

When, now, the translucent or diffusing shutter of our invention is substituted for the opaque shutter of ordinary practice, the average illumination remains constant throughout and the visible icker is greatly reduced.. Some localized iiicker remains. For those portions of thepicture where illumination is equal to `theaverage the flicker becomes zero, but the darker portions of the picture will now beincreased in brightness during the intervals when they wereformerly de,- creased, whilev in those portions which are above average brightness there will still be van increase operate in addition to the fact that the actual intensity of the flicker has been reduced to about one-half in the case of themost widely varying points. In the case of the shadows these factors include rst,4 the fact that apparent flicker is a function of brightness, and the less the intrinsic brilliancy the less the apparent icker. 'I'he second is the fact that a short period of darkness occurring in a relatively long interval of illiimination is very much less apparent than the ireverse condition.

In the case of the high lights the favorable factor lies in the pickup tube rather than in the eye of the beholder, and resides in the fact that the charges in the high lmhts tend to approach a limiting value and that therefore a slight decrease in illumination during a portion of the scanning period has a very slight eifect upon the strength of the signal is approached.

Itshould be bornev in mind that the diffused illumination during the pull-down period covers the entire eld and not any particular part of the field. Its eiect therefore is merely to raise slightly the average illumination of the field as a whole, thereby slightly decreasing the contrast.

This results only in a slight increase in the D. C. component of the signalQand since practically all television systems provide for some degree of manual background control, even where automatic control is also used, this can readily be compensated for.

While the factors thus far brought out comprise the major step in our invention, it may be made even more eiective by further steps, each constituting a successive approximation toward the absolute elimination of flicker. 'I'he second major step in our method comprises the adjustment of the pickup tube so that the scanning beam is at minimum intensity consistent with approximately maximum signal, i. e., so that a residual image is left upon the screen after each scansion.

Why this should be so may not be apparent.

without a more detailed analysis than is practical here. Qualitatively, however, it may be seen that with the use of the system thus far described those portions ofthe eld which formerly exhibited a flicker in brilliancy will now exhibit what may be termed a dicker in contrast, displaying the greatest amount of contrast in the course of those scansions which with the ordinary system would display the greatest degree of brilliancy. If we assume that one-third of the image strength is left when the area of greatest contrast is scanned, the next scanning of this area/,will result in a signal wherein two-thirds of the charge has been acquired at low contrast and one-third has been left at high contrast, thus increasing the dilerential of contrast of the low contrast scansion by one-third. Conversely, when the high contrast portion is next scanned only two-thirds of the charge will have been acquired at high contrast while the remainder has been acquired at low contrast, and the contrast upon this scansion will be correspondingly re duced. It will bevunderstood that these ngures are a first approximation only, and that the actual increases and decreases in contrast, result from the summation of a geometric series. The effect, however, is to tend to equalize the differences in contrast. It' might be expected that this would result in ghost images in parts of the eld where motion occurs, but actually residual flicker can be substantially neutralized before aaeaoce ghosts become apparent. 'Ihe third step in the series of approximations has already been mentioned, and comprises so occulting the ileld, las by means of the curved shutter blade, that the areas where icker would normally occur are not marked out by clearly defined straight' lines,

where this limiting value y which the eye can readily follow. 'Ihat this actually has the eiect of reducing apparent icker is an empirical fact which will be left to the psychologists for explanation.

Since it will be apparent that the principal, and in fact the only undesirable effect of the system as thus far described is a slight reduction in contrast, it is desirable that the contrast be built up as much as possible, and we have found that the loss can be regained substantially in its entirety by the back lighting before referred to. This is accomplished by means of a lamp 25 mounted in the camera behindv the screen of the pickup tube, where it will illuminate the Walls of the tube without illuminating the screen itself. l

It has been stated above that the illumination of the screen which is used in the elimination of the flicker is the average illumination of the picture iield as a` whole. A more accurate statement would be that the illumination should be the average apparent illumination as determined by the eye. It will be recognized that the shutter I1 being of a diffusing character and also being a solid body, will have a diierent coeiiicient of refraction from the air in which it is operating, and there will be some loss of light due to reflection from its various surfaces, absorption in the passage through it, as well as by its defocusing effect. Experience has shown that this slight decrease in actual illumination below the average is not disadvantageous, in that the light which actually reaches the screen usually approaches more closely to the occular average than where the absolute average illumination is the same. Another method of practicing our invention, wherein the amount of icker neutralizing light is under control, is to substitute for the shutter Il of Fig. 4 the type shown in Fig. 5. In this case shutter Il is also made of transparent material, preferably plastic, the shading upon the blade indicating a mirror deposit upon the surface which graduates in opacity and also in reflecting ability from the edges of the blade toward the center where the heaviest shading is shown, this portion being completely opaque. A lamp 21, backed by a reflector 29 and provide-d with a 1ers so throws a diffused beam of nght y along the path shown by the arrows against the reflecting surface of the shutter and thence onto the sensitive screen I9.' 'I'he lamp 21 is shown as being excited by pure D.C., indicated as supplied from a battery 3|, since it is important that no flicker be present in this illumination, it being understood that any other pure D.C. source may be substituted for the battery. Intensity of illumination may be adjusted by the rheostat 32. The graduated reflecting and occulting surface of the mirror I1 causes the diffuse reflected light from the lamp 30 to increase in intensity in substantially the same time and the same proportion that the image is decreased in intensity by the occulting action of the shutter. As in the case of the curved edges ofthe shutter blades shown in Fig. 4, the gradual occultation makes the transition from occultation to non-occultation and the reverse less distinctly marked, and thus contributes to the results desired. In this case the amount of icker neutralizing light is under the control of the operator, who adjusts the rheoaaeaoae stat 32 until the best results are obtained as determined by eye upon a monitor screen.

Fig. 6 indicates a slight modification of the equipment'shown at the right of Fig. 1. In this case the inverting mirror I is omitted, and the path of the image is direct from the lens I4 (Fig. 1) to the screen I9. In order that the light from the lamp 30' may reach the screen I9, the shutter i'la is mounted at an angle.

In Fig. 6 the pickup tube and the camera are inverted in comparison with the tube in Fig. 1, to indicate symbolically that in this case, since the image is not optically inverted, other means must be used in order that the transmission will appear upright.

Various other modications of the mechanical means used to accomplish the method of this invention will be apparent. It is clear that a large part of the value of the invention may be appreciated even though the shutter I1' be made completely opaque throughout if its surface be reflecting. It will be further apparent that it is not necessary that the shutter control flicker neutralizing illumination, but that this may be done by using a lamp 30 having an instantaneous luminous response and opening and closing its circuit electrically in synchronism with the shutter. Other possible modifications will doubtless suggest themselves to those skilled in the art.

One of these possibilities deserves particular mention, however, and that is the total elimination of the shutter. 'The movement of the film in itself destroys the image, and tends to distribute the illumination uniformly over the screen. With certain types ofy picture, e. g., in pictures where the whole of one side of the field is materially different in illumination from the other, this method may give even better results than those heretofore discussed, since the average is taken for individual strips of the film, rather than for the whole. In other situations,

however, it may result in streaks in the reproduced picture, and therefore it is not our present preference. The fact that it vis usable at all, however, leads to the obvious conclusion that it is not essential that the shutter occult the image for the entire pull-down time and experiment has shown that this is the case, and that, if desired, the shutter which may be of any of the types here discussed, may be made to occult the image, for, say 10% instead of 14% of the pull-down time without introducing perceptible streaks or travel ghosts.

It will also be apparent that the various modiiications shown may be combined. Thus the shutter of Fig. 4 may be used and additional il- K lumination supplied to the screen from the separate source 30, the non-specular reflection from such source onto the screen making up any deficiency in the average illumination caused by reflection from and absorption in the shutter of the light from the film.

In the final analysis we have found that so far as the eye can detect the method and apparatus as here described result in complete elimination of flicker. Examination of the screen under a magnifying glass reveals some residual iiicker, just as the inter-line fiicker can be thus detected even when direct pickup is used. For practical purposes, however, it is entirely satisfactory, and is not only simpler and less expensive than conventional methods, but is less difficult of adjustment, and being applicable to any ratio of frame frequency to scanning frequency, is more flexible.

We claim:

1. The method of television transmission from motion picture film with a pickup device having a photosensitive screen ofthe charge-storing type which comprises the steps of progressing said film intermittently, projecting stationary images of successive frames of said film onto said screen during substantially the whole intervals between such progressions, and illuminating said screen during the periods of movement of said film with substantially the same quantity of light as comprises said images but having different distribution over said screen than the light projected thereon during the image projecting intervals.

2. The method of television transmission from motion picture film with a pickup device having a photosensitive screen of the charge-storing type which comprises the steps of progressing said film intermittently, projecting stationary images of successive frames of said film onto said screen during substantially the whole intervals 'between said progressions, continuing to project illumination from said film onto said screen during the periods of progression, and destroying the image characteristics of said illumination during said periods.

3. The methodr of television transmission from motion picture film with a pickup device having a photosensitive screenl of the charge-storing type which comprises the steps of `progressing said film intermittently, projecting light through said film and onto said screen, focusing said light as an image of a portion of said film upon said screen during substantially the whole intervals between such progressions, gradually destroying said focus immediately before the period of progression of said film, and gradually restoring said focus at the end of said period.

4. The method of television transmission from motion picture film with a pickup device having a photosensitive screen of the charge-storing type which comprises the steps of progressing 1 said film intermittently, projecting light through said film and onto said screen, focusing said light as an image of a portion of said film upon said screen during substantially the whole intervals between such progressions, gradually decreasing the intensity of said image immediately before the period of progression, and maintaining the total illumination of said film substantially constant by general illumination increasing in intensty as the intensity of said image decreases.

5. The method of television transmission'from motion picture film with a pickup device having a photosensitive screen of the charge-storing type which comprises the steps of progressing said nlm intermittently, projecting stationary images of successive frames of said film onto said screen during substantially the whole intervals between such progressions, occulting said imagesat intervals, such occultation occurring non-rectilinearly across said screen and during the periods of progression of said film, and illuminating said screen generally during the periods of said occultation with a quantity of light substantially equal to that forming said images. i

6. In the method as set forth in claim 1, the additional step of scanning said sensitive screen with an electron beam, said beam being of sufficient intensity to remove only partially the.

charges stored by the projection of light thereon.

7. In the method as set forth in claim 1, the step of occulting said images from said screen during said periods of progression, separately generating light during said periods, and illuminating said screen generally with said separately generated light during said periods.

8. llihe method as set forth in claim 1 including the step of illuminating separately the portions of said pickup device adjacent said screen while preventing said illumination from reaching said screen.

9. Television apparatus for the transmission of signals from motion picture film comprising a motion picture projector including means for intermittently progressing a film therethrough, means for illuminating said iilm during substantially the whole intervals between such progressions, a projection lens for forming an image of the illuminated portion of said film, and means for simultaneously destroying said image and for illuminating the plane thereof with substantially the same amount of light differently distributed during the periods of progression of said film.

10. Television apparatus for the transmission of signals from motion picture film comprising a motion picture projector including means for intermittently progressing a film therethrough, means for illuminating said illm during substantially the whole intervals between such progressions, a pickup device of the charge-storing type. a projection lens for forming an image of the illuminated portion of said film upon the photosensitive screen of said pickup device, and a semi-transparent shutter timed with said intermittent means for destroying the image characteristics of the illumination from said Projection lens reaching the plane of said'image during the periods of progression of said lm.

11. Television apparatus for the transmission of signals from motion picture film comprising a motion picture projector including means for intermittently progressing a film therethrough, means for illuminating said film during substantially the whole intervals between such progressions, a pickup device of the charge-storing type, a projection lens for forming an image of the illuminated portion of said film upon the photosensitive screen of said pickup device, and a shutter of transparent material having a. light diffusing surface timed with said intermittent means for destroying the image characteristics of the illumination reaching the plane of said guage during the periods of progression of said i2. Television apparatus for the transmission oi signals from motion picture film comprising a motion picture projector including means for intermittently progressing a film therethrough, means for illuminating said lm during substantially the whole intervals between such progressions, a projection lens for forming an image of the illuminated portion of said film, a shutter of transparent material and having a mirror surface of graduated opacity increasing from the edges oi' said shutter to the center thereof, said intermittent means occulting said image during the periods of progression of said film, a separate source of light, and means for directing light from said source onto said surface at an angle such as to be reflected therefrom onto the plane of said image.

13. Apparatus in accordance with claim 9 including means for inverting the image produced by said projection lens.

14. The combination as set forth in claim 9 including a shutter for occulting said image during the periods of progression of said film, a

separate source of illumination, and means timed with said shutter for directing illumination from said source onto the plane of said image during the periods of occultation only.

l5. In combination, a motion picture projector having intermittent means for progressing a film therethrough, means for illuminating a portion of said film during substantially the whole intervals between such progressions and a projecting lens for forming an image of said illuminatedportion, a television pickup having a photosensitive screen of storage type positioned in the plane of said image, separate means for illuminating said pickup with the exception of said screen, and a shutter on said projector timed in synchronism with said intermittent means, said shutter being formed of transparent material and having a light diffusing surface.

16. Apparatus in accordance with claim 15 wherein said shutter comprises a rotating blade having non-radial edges.

17. Apparatus in accordance with claim 15 wherein said shutter comprises a rotating scimiter-shaped blade.

HARRY R. LUBCKE. 'WILLET H. BROWN. WILLIAM S. KLEIN.

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