US2254614A - Electro-optical scanning system - Google Patents

Description

Sept. 2, .1941. c. F, MA1-TK; 2,254,614

ELECTRO-OPTICAL scANNING SYSTEM Filed oct. 15, 1937 s sheets-sheet 1 9v i y l 6 F/G. 00

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ELECTRO-OPTICAL SCANNING SYSTEM Filed Oct. l5, 1937 5 Sheets-Sheet 2 /A/L/ENTOR C. E MA TT/(E B UMa/VTM A TTORNEV Sept. 2, 1941. c. F. MA'r'rKE 2,254,614

ELECTRO-OPTICAL scANNING SYSTEM Filed Oct. 15, 1937 5 Sheets-Sheetl 3 INVENTOR By c. f.' MATT/(E ATTORNEY Sept. 2, 1941. c. F. MATTKE ELEGTRO-OPTICAL SCANNING SYSTEM Filed 001'..` 15, 1957 5 Sheets-Sheet 4 A TTOR/VEV Sept.- 2, 1941. c. r-. MATTKE ELECTRO-OPTICAL SCANNING SYSTEM Filed 00T.. l5. 1957 5 Sheets-Sheet 5 WF C.

A TTORNE'V Patented Sept. 2, 1941 ELECTRO-OPTICAL SCANNING SYSTEM Charles F. Mattke, Jackson Heights, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 15, 1937, Serial No. 169,117

8 Claims.

This invention relates to electro-optical systems and more particularly to method and means for effecting television.

An object of the invention is to provide improved television equipment.

In an example of practice illustrative of the invention, scanning of continuously moving motion picture film is effected by means of a rotating scanning disc carrying a ring of lenses. A compact optical unit is employed for producing the picture scanning light beam and the synchronizing light pulses. The synchronizing pulses are produced by light directed through a lens and reflected back through the same lens just prior to the time when that same lens starts to scan a line of the picture. The optical unit is securely bolted to the protecting casing surrounding the disc and comprises a collimating lens, an adjustable aperture, and an annular stop in the picture channel and a double prism with aperture and an objective lens for the synchronizing channel, the optical axis of the synchronizing channel being twice turned through 90 degrees while the optical axis of the picture channel is rectilinear. The lm in its travel is' caused t0 coincide with the plane of the principal foci of the disc lenses at the line of scanning and the picture scanning head is adjustable to effect proper positioning of the nlm. Framing indicating means is provided so that the operator may know by observation when a selected lens is scanning a given line of the picture. This framing indicating means comprises a frame observation gate through which the film passes, a flashing neon lamp for illuminating the portion of the film within this gate at the instant when the lens which is to scan the rst line of a frame starts to scan a line, and a telescope for observing the observation gate, the observation gate being so positioned with respect to the scanning lenses that the distance along the film from the point of scanning to the edge of the observation gate where the film leaves the gate is an integral number of picture frames. The pressure pads which bear against the film to hold it close to the lm guides in the scanning gate are releasable to facilitate threading the lm through the gate. The main lm sprocket which draws the film from the supply reel and feeds it to the takeup reel, and the scanning sprocket which pulls the film through the scanning gate, are driven through shafting and gears from a magnetic clutch on the end of the disc shaft. A fiywheel on the scanning sprocket shaft is driven through a friction coupling in order to relieve strains on the mechanism when the magnetic clutch is suddenly engaged. The lm is pulled through the sound reproducing head by motor-driven friction rollers, the motor circuit being interlocked with the clutch circuit so that the clutch cannot be energized unless the motor circuit has been previously set to energize the m'otor. The light pulses which are produced by the synchronizing optical unit are directed to an electron multiplier which produces corresponding electrical impulses which may be used to control the line sweep circuit of a cathode ray tube television receiver. Since any given lens produces the synchronizing impulse a fraction of a scanning line period before that lens starts to scan a line, a delay network is inserted in the synchronizing channel.

A more detailed description of the invention follows having reference to the accompanying drawings, of which Fig. l is a schematic drawing of film scanning equipment embodying this invention;

Fig. 2 is an elevation of such lm scanning equipment looking toward the scanning dsc from the film side with certain parts cut away or left out;

Fig, 3 is an elevation of the optical unit of this invention, partially in section, and including a portion of the scanning disc and housing;

Fig. 4 is a plan of the optical unit of Fig. 3;

Fig. 5 is a cross-section of the optical unit of Fig. 4 looking in the direction of the arrows 5;

Fig. 6 is an elevation, partly in section, of the p-icture scanning gate showing the adjustable focussing mechanism and the releasable pressure pad:

Fig. 7 is a fragment of Fig. 6 showing the pressure pad in released position;

Fig. 8 is a cross-section of a portion of the mechanism of Fig. 6 looking in the direction of the arrows 8;

Fig. 9 is a cross-section of Fig. 6 looking in the direction of the arrows 9;

Fig. l0 is a face view of a fragment of the scanning disc showing the mounting of the disc lens holders; and

Fig. 11 is an end View of the optical unit looking toward the adjustable aperture.

The same reference characters are used to indicate identical elements in the several figures of the drawings.

Referring now to Fig. 1, film 5 which is to be scanned is drawn from supply reel 6 by lm feed sprocket 1. The film 5 as it comes from sprocket 1 is drawn through framing indicating gate 8 and scanning position 9 by scanning sprocket IIJ. The film 5 as it comes from the scanning sprocket I is drawn through the sound scanning position I I by a pair of motor driven steel friction rollers I 2 and I3 which keep the film taut between sprocket I9 and rollers I2 and I3. The film 5 as it comes from rollers I2 and I3 is fed by feed sprocket 1 to lm take-up reel I4.

Elemental linear transverse portions of film 5 are scanned at the position 9 by a moving spot of light produced by means including rotating scanning disc I5. The outer edge of disc I5 carries 240 lens holders I6 each provided with a pair of plano-convex scanning lenses. 'I'hese lenses are all at the same radial distance from the center of the disc I5. The disc I5 is mounted on a shaft I1 which is driven by a motor I8 in the direction indicated by the arrow. The speed of motor I8 may be controlled by the same tuning fork (not shown) as is used to determine electrical frequencies in other elements of the television system.

The film feed sprocket 1 is driven from shaft I9 through gear and pinion 20, shaft 2I, and gear and pinion 22. The film take-up reel I4 is belt driven from pulley 23 on the shaft of feed sprocket 1 by belt 24 driving pulley 25.

The scanning sprocket I9 is also driven from shaft I9 through gear and pinion 26, shaft 21, and gear and pinion 28. The gear of gear and pinion 28 is coupled to the shaft of scanning sprocket I IJ by flexible coupling 29 of well-known design. Also mounted on the shaft of scanning sprocket I0 is a heavy flywheel 36. This flywheel 30 is driven by friction with the shaft of sprocket I8, the shaft being provided with a conical axle against which a conical bearing in flywheel 30 is pressed by means of a spring (shown in Fig. 2).

The shaft I9 is driven from shaft I1 through magnetic clutch 3I. This clutch 3| comprises portion 32 which is rigidly secured to shaft I1 and an armature 34 exibly connected to shaft I9 in fixed angular relationship with shaft I9 but longitudinally movable to engage the portion 32 on shaft I1. The portion 32 comprises an electromagnet energizable through slip rings 33. The energization of clutch 3I is controlled jointly by a single-pole single-throw switch 35 and the left-hand blade of double-pole singlethrow switch 36. The energizing current is obtained from a llO-volt source of direct current (not shown) connected to terminals 31.

The friction roller I 2 is belt driven by constant speed motor 38 through pulley 39, belt 40, and pulley 4I. The friction roller I3 is spring pressed against the film 5 where it runs over roller I2. This pressure is sufcient to pull the film through the sound gate but not sufficient to injure the film even though the motor 38 is running and turning the roller I2 while the film is stationary due to the clutch 3I being deenergized. The function of the rollers I2 and I3 is to pull through the sound head any film which has passed by the scanning sprocket' I9 and as rapidly as it passes by said sprocket. The motor 38 is energized from a 11G-volt source of alternating current (not shown) connected to terminals 42 through the right-hand blade of switch 36. The motor 38 normally runs so that there is a slight slippage in the forward direction between the roller I2 and the film 5.

The energizing circuits of magnetic clutch 3I and sound motor 38 are interlocked through switches 35 and 36 so the clutch 3| cannot be energized unless motor 38 is running or is ready to start running as soon as the clutch is energized. If this were not so and clutch 3l were energized before motor 38, scanning sprocket Il) would pile up lm ahead of the sound head which rollers I2 and I3 would not take away and film feed sprocket 1 in trying to take film away from rollers I2 and I3 would place such a strain on the film that it would break at guide pin 43. If switch 35 alone is closed the clutch 3l is not energized because its energizing circuit is still open at the left-hand blade of switch 36. If switch 36 is now closed both the clutch 3I and motor 38 are energized simultaneously and normal operation occurs. If switch 36 alone is closed the motor 38 is energized through the right-hand blade and the energizing circuit of clutch 3I is partially completed through the left-hand blade of switch 36. The motor 38 and friction roller I2 start running but no injury to the film results as hereinbefore pointed out. As soon as switch 35 is closed clutch 3| is energized, film is fed to the sound head by sprocket IIJ and taken away from the sound head by sprocket 1 and normal operation occurs. Injury to the film and improper operation of the film moving mechanism are prevented by this interlocking circuit.

The picture line scanning optical system comprises a source of light 44, a spherical lens unit 45, a cylindrical lens 46, an aperture member 41, a collimating lens 48, disc lens units 49 and a highly eiiicient light conductor 50. This optical system has rectilinear axes which are at right angles to the plane of the disc I5 and film 5 at the picture scanning position 9. An image of the aperture in member 41 is formed at the principal focus of each disc lens unit 49 while such unit is in the beam of collimating lens 48 formed by light rays from the source 44. As the disc I5 rotates this image moves across the portion of the film 5 in the scanning gate. The diverging rays from this image, controlled in intensity by the tone values of the scanned portions of the lm 5, are gathered by the light conductor 50 and impressed upon the light sensitive cathode 5I of multistage electron multiplier 52, the output circuit of which is connected to a suitable image current channel. The multiplier 52, shown conventionally, may be of any suitable type known to the art.

'I'he synchronizing optical system comprises a source of light 53, a condensing lens unit 54, a small reflecting prism provided with an elongated aperture adjacent to its incident face, one edge of collimating lens 48 and disc lens unit 49 which is next on the left of the effective line scanning lens unit as viewed in Fig. 1, a plane mirror 56 to direct light rays from disc lens unit 49 back through the same lens unit and collimating lens 48, large reflecting prism 51, objective lens 58, aperture plate 59 and lens 6D. The optical axis of this synchronizing lens system is twice turned through 90 degrees, once by prism 55 and again by prism 51. Each disc lens unit 49 during the course of its movement through the light beam from source 53 forms an image of the aperture on the incident face of prism 55 by light rays reflected by the mirror 56 in the neighborhood of its own optical center and lens 58 forms an image of this image at the aperture plate 59. As this second image at plate 59 sweeps across the aperture in plate 59 the diverging rays passing through the aperture are gathered by lens 60 and directed to the light sensitive cathode 6I of synchronizing multistage electron multiplier 62, the output circuit of which is connected through delay circuit 63 to a suitable picture line synchronizing channel. Multiplier 62, also shown conventionally, may be of any suitable type known to the art.

Since the image on aperture plate 59 sweeps across the aperture very rapidly during normal scanning of the lm an electrical impulse of short duration is produced by the multiplier 62 as each disc lens unit 49 becomes eirective to produce a line synchronizing pulse shortly before it starts the scanning of a picture line. The delay network 63 delays this impulse in time so that it is available in the synchronizing channel just before the line scanning begins. In a specific embodiment of the invention herein disclosed this delay is less than the time required to scan one picture line. In other words, the disc lens unit producing the synchronizing pulse is adjacent to, but following with reference to the direction of rotation of the disc, the disc lens unit then eiective in scanning a picture line. This is made possible by the arrangement of the optical elements in a compact unitary structure and utilizing reflected rays in the synchronizing optical channel.

The delay network 63 effects the major portion of the phase shift of the synchronizing impulses with respect to the image current. Further adjustment of this phase relationship is effected by adjustment of aperture plate 59 to vary the position of the aperture along the path of the moving synchronizing image. f

Frame synchronizing impulses are controlled by circuit closer 64 which comprises an insulating collar 65 rigidly secured to shaft |1 'and provided with a metallic contact bar 66 which conductively connects brushes 61 once during each revolution of the disc l5. The conductors connected to brushes 61 lead to a suitable frame synchronizing channel wherein an impulse of current occurs each time brushes 61 contact bar 66. Brushes 61 and bar 66 are so positioned that the frame scanning impulse occurs just before one of the disc lens units 49 starts to scan a picture line. If this impulse is used to control the frame sweep circuit of a cathode ray television receiver the disc lens unit about to start scanning will scan what will appear as the first line of the received picture. Such disc lens unit will hereinafter be called disc lens No. 1.

In order, therefore, that the picture produced at the cathode ray receiver shall correspond to a complete frame of the motion picture lm it is necessary that disc lens No. 1 scan the leading edge of each frame or preferably the trailing edge of the blank space between frames. An adjustable framing device is therefore provided comprising a roller 68 carried on an arm 69 which is rotatable around a pivot 18. This arm B9 may be fashioned in any desired position by a nut on a threaded stud which extends through a circular slot in fixed support 1|, Roller 68 engages a loop in iilm 5 between scanning sprocket I6 and picture scanning position 9. By rotating arm 69 the length of i-llm between sprocket I8 and scanning position 9 may be changed so that disc lens No. 1 will scan the leading edge of each frame after the energization of clutch 3| which energization starts the motion of the lm 5. The received picture then will be in frame at the cathode ray receiver.

It is desirable that the operator at the transmitter shall be able to ascertain when the adjustment is such that the picture will be in frame without reference to the picture at the receiver. A framing indicating device is therefore provided which comprises the framing indicating gate 8 intermittently illuminated by neon lamp 12 and observed preferably through telescope 13. The neon lamp 12 is energized once during each revolution of the disc l5 by circuit closer 14 which comprises an insulating collar 15 rigidly secured to shaft I1 and provided with a metallic contact bar 16 which conductively connects brushes 11 once during each revolution of disc I5. The circuit closer 14 completes an energizing circuit for neon lamp 12 through condenser 18 which condenser is charged through resistance 82 by current from a 11G-volt source of direct current (not shown) connected to terminals 83. This circuit is closed when disc lens No. 1 starts to scan a picture line and the observing gate 8 is so positioned with respect to the scanning position 9 that a. full frame of the iilm 5 is in the gate 8 when the lead ing edge of a frame is being scanned by disc lens No. 1. If the operator after energizing clutch 3| to start the lm in motion adjusts the roller 68 until a full film frame is seen in nlm gate 8 when looking through telescope 13, he will know that the image currents and both the line and frame synchronizing impulses are in proper phase relationship to produce an image in full frame at the receiver.

This framing indicating device may have other adjustments than that just described depending upon the angular position of circuit closer 14 with respect to disc lens No. 1 and the length of lm between observing gate 8 and scanning position 9. For one such alternative adjustment, for example, an indicator pointer is placed on one side of the observing gate 8 intermediate the topand bottom of the gate, the position of the scanning gate being such that when a full frame of the film is in the gate and the scanning mechanism adjusted so that disc lens No. 1 is scanning the leading edge of another frame, this indicator points to the middle of the frame in the gate. The circuit closer 14 is adjusted to cause neon lamp 12 to flash after disc l5 has turned a half revolution beyond the scanning position of disc lens No. 1. With this adjustment the operator will know that the framing mechanism is properly set to produce images in full frame, if he sees in the observing gate 8 portions of two adjacent frames with the indicator pointing to the leading edge of the incoming frame. The use of such an indicator pointer appears to make possible more rapid framing.

The sound head is of well-known design and is represented schematically by light source 19, objective lens and photoelectric cell 8|. The lens 80 forms an image of the light source 19 or an image of an aperture illuminated by such light source at the sound track on lm 5 and' the transmitted rays energize the photoelectric cell 8|. The output current of cell 8| is connected to a suitable sound channel. The length of lm between the picture scanning position 9 and the sound scanning position is approximately the same as that between the picture taking position and the sound recording position in the sound camera used in making the lm 5. In the adjustment of framing roller 68 this length of film may vary by as much as half a frame length. Such variation has a negligible eilect upon the synchronization of the reproduced picture and accompanying sound eiects.

The arrangement of certain portions of the equipment schematically illustrated in Fig. 1 is further shown in Fig. 2 which is a view in elevation of certain parts of the equipment looking toward the scanning disc from the film side of the disc. The scanning disc I5 rotates within a sheet-iron housing 90 which is rigidly secured to suitable framework (not shown) including the bearings of the shafts I1 and |9 and the main driving motor I8. The film supply reel 6 is mounted in housing 9|, the film feeding out between guide rollers 92 and under guide roller 93 to the upper side of film feed sprocket 1, against which it is held by rollers 94. The takeup reel I4 is mounted in housing 95, the film. feeding into this housing from the lower side f film feed sprocket 1 against which it is held by rollers 96 over guide rollers 91 and H2 and between guide rollers 98.

The roller H2 is mounted on an arm H3 pivoted on a pin H4. A spring H secured to the movable end of arm H3 bears on the edge of casting |03 and tends to push the arm H3 upward. The loop of film between film feed sprocket 1 and rollers 98 is thus of variable length. This variable loop is provided to prevent injury to the film 5 when it is quickly started upon the energization of magnetic clutch 3|. Since the take-up reel I4 is belt-driven from the shaft of sprocket 1, the belt tension being such that there is some slippage, there is a tendency for the reel I4 to come up to speed more slowly than film 5 is fed from sprocket 1 and then with heavy reels to overrun the supply speed of the film suflciently to break the film unless the strain is eased by shortening of the loop against the pressure of spring H5. The friction between the spring H5 and the bearing surface on casting |03 is sufficient to overcome any tendency to oscillate.

As the film feeds from the upper side of sprocket 1 it passes over two guide pins 99 and |00 whereby the plane of the film is turned through 90 degrees and the direction of movement reversed from upward to downward as shown by the arrows. After leaving pin |00 the film passes into framing indicating gate 8 where it may be observed in aperture I0| which is an opening the size of a motion picture frame. The neon lamp 'I2 which is positioned back of this aperture and the observing telescope 13 which is positioned in front thereof are not shown in this View. Immediately below gate 0 is the picture scanning gate housing |02 which is located at picture scanning position 9. This housing |02 and lthe framing indicating gate 8 are secured to a supporting casting |03 which is bolted to the disc housing 90. The light conductor 50 is shown in cross-section.

As the film passes from the picture scanning gate housing |02 it passes over framing roller 68 to scanning sprocket I0. In Fig. 2 framing roller 68 with its supporting mechanisms is shown somewhat above its normal position behind scanning sprocket |0 for clearness of illustration. Film sprocket I0 is rigidly secured to shaft |04 which extends through and serves as an axle for the gear of gear and pinion 28 and the driving portion of flexible coupling 29. The flywheel 30 has a conical bearing which is journaled on conical axle |05 secured on the end of shaft |04. Flywheel 30 is forced against the axle |05 by a coiled spring |06, the outer end of which is held by collar |01, also rigidly secured to the shaft |04. This friction coupling between the flywheel 30 and the shaft |04 permits the flywheel to come up to speed slowly when the shaft is started rapidly and thus obviates destructive strains being placed on the mechanism when the film is started rapidly as in normal operation.

Sound head |08 located at the sound scanning position I| is merely indicated by a block.

'I'he gears of gears and pinions 20 and 26 of Fig. 1 are preferably constructed as a single gear |09 as shown in Fig. 2, the respective pinions meshing with this gear on opposite sides thereof. Space is thereby conserved and the equipment can be made more compact.

The shafts 2| and 21 are provided with universal couplings H0 and III, respectively.

Further details of the compact unitary optical arrangement for picture line scanning and synchronizing light pulse production are shown in Figs. 3, 4 and 5. Source of light 53, condensing lens unit 54, aperture plate 59, lens 60 and light sensitive cathode 6I of electron multiplier 62 are omitted from Fig. 4. This compact arrangement of the optical elements makes it possible Ato use each disc lens unit 49 during operation to first produce a synchronizing pulse and then, within less than a line scanning period, to start the scanning of a line. The delay necessary in the synchronizing channel is reduced to a minimum without introducing deleterious interference between the picture scanning optical channel and the synchronizing optical channel.

This unitary optical arrangement comprises a casting |20 having a conical bore |2| at one end and a cylindrical bore |22 at the other. Within the cylindrical bore |22 a circular tube |23 is inserted in any suitable manner, as by sweating At the larger end of the casting |20 a flange |24 is provided. A cylindrical recess |25 is provided in the open end of flange |24 which constitutes a seat for collimating lens 48, a soft paper gasket |28 being placed between the lens and its seat. A ring |21 fastened to the face of flange |24 by .three screws |28 retains the lens 48 in fixed position. The gasket |26 also extends between the ring |21 and the lens 48.

At the open end of the tube |23 the aperture member 41 is located. This member 41 comprises a cup-shaped member I 29 secured to another cupshaped member |30, bottom to bottom. There are central apertures in the bottoms of both cupshaped members |29 and |30. The sides of member |30 slide inside of tube I 23. Three lugs I 3| extend from the sides of member |30 and enter corresponding slots in the end of tube |23. Member I 30 may be moved longitudinally with respect to tube |23 by knurled, internally threaded rings |32 and 33 which cooperate with the threads on tube |23. The lugs |3I may be clamped between rings |32 and |33 to maintain a fixed relationship between member |30 and tube |23. Within the cup-shaped member |29 are two adjustable jaws |34 and |35, controlled by knurled screws |36 and |31, respectively. Jaws |34 and |35 are provided with overlapping V-shaped notches as shown in Fig. 11. A square aperture is formed between jaws |34 and |35. The size of this aperture, as well as its position transversely of tube |23, are determined by the position of jaws |34 and |35. The aperture in member 41 is thus adjusted to proper size and positioned in the axis of collimating lens 48 by the adjustment of screws |36 and |31 while it is positioned at the principal focus of lens 48 by the adjustment of rings 32 and |33. By changing the angle of the V-shaped notches in jaws |34 and |35 other shapes of apertures may be obtained.

' d This unitary optical arrangement is bolted to the disc housing 90 by screws |38 passing through flange |24 and ring |21 into the side of housing 90. A hole is cut in housing 90 about the same size as the hole in the ring |21. The optical axis of collimating lens 48 is approximately the same distance from the center of disc as are the optical axes of disc lens units 49.

The synchronizing light source 53 and condensing lens unit 54 are supported from casting |20 by bracket |39 which is bolted to the end of casting |20 by studs |40 and to the condensing lens unit 54 by bolt 4|. 'Ihe condensing lens unit 54 comprises two plano-convex lenses |42 Iand |43 and a stop |44. Stop |44 `has a circular aperture so as to limit the divergence of the beam passing through aperture |45 on the incident face of small prism 55 to prevent interference with the picture scanning beam.

Prisms 55 and 51 and lens 58 are mounted in a holder |46 which is bolted to the ange |24 of casting |20. The prism 55 is cemented to prism 51 by Canada balsam so that light rays are not deviated in passing through the adjacent faces of these prisms. The prisms 55 and 51 are set at an angle, as shown in Figs. 4 and 5, to compensate for the bending of the optical axes of disc lens units 49 Ias they pass through the edge of collimating lens 48. In order to provide space for the prism holder |46, a portion of the casting |20 is cut away. AS a further means of preventing interference between the picture scanning and synchronizing optical channels, an opaque screen |41 is provided adjacent to one of the ends of prisms 55 and 51 and portion |48 of lens 58 which extends beyond screen |41 is painted black.

In a hole in the disc housing 90 opposite collimating lens 48 is a casting |03 which supports the picture scanning gate and the synchronizing mirror 56. This casting is secured to the housing 90 by screws. The picture scanning gate guides the lm 5 and holds one end of the light conductor 50 in the position shown in Fig. 4. A piece of transparent glass is placed over an opening in casting |03 between the film 5 and disc lens units 49 to permit the picture scanning rays to reach the lm 5 without leaving a physical opening in the disc housing.

The inside surfaces of casting |20 and tube |23 A.

are painted black to minimize reection. The picture scanning beam is prevented from impinging 'on these surfaces by a removable stop |49 which is inserted in a transverse slot in the side of tube |23 between the aperture in member 41 and collimating lens 48. The aperture in this stop |49 is large enough to so fill collimating lens 48 with light rays from the aperture in member 41 that disc lens units 49 are completely lled with light when in the picture line scanning position. Each lens disc unit 49 is provided with a stop |50, the aperture in which is about one-half the diameter of the lens of this unit. By stopping down these lenses a more uniform size of scanning spot is obtained since small variations in the distance between the emulsion of lm 5 and the disc lens units 49 have less effect on the size of the scanning spot.

In order to facilitate adjustment of the picture scanning optical system, movable mirror |60 and a ground glass screen |6| are provided. This mirror |60 may be slid up between guides |62 to intercept the light beam from the aperture in member 41 and direct it to screen |6I. The size and location of the spot on screen |6| give an indication of the size and position of the spot which will be formed on collimating lens 48 when the mirror is lowered out of the path of the beam. The screen |6| and mirror |60 are mounted in a housing |63 which is secured to tube |23 by screws |64.

In operation, the aperture in member 41 is illuminated by light rays from source 44, the source being imaged on the aperture by lenses 45 and 46, as shown in Fig. 1. The cylindrical lens 46 is used because the light source 44 is longer in the horizontal direction than in the vertical. By using lens 46 the image is substantially compressed in a horizontal direction, resulting in a more intense illumination of the aperture in member 41. The rays passing through the aperture in member 41 and through the aperture in stop |49 are collimated by lens 48. As the disc lens units 49 travel across this beam the rays passing through units 49 are brought to a focus in the plane of the principal foci of these units which is in the plane of the emulsion of film 5 for minimum size of scanning spot. By this arrangement a reduced image of the aperture in member 41 is formed on the film 5 at the scanning position 9. This spot travels transversely across the lm 5 as each lens disc unit 49 becomes effective for picture line scanning. At the same time a beam of light from synchronizing source 53 is -condensed on aperture |45 by condensing lens unit 54. The rays which pass through aperture |45, form, after reection by small prism 55, passage through the edge of collimating lens 48 and reiiection by mirror 56, an image of the aperture |45 at approximately the center of disc lens unit 49 following the lens disc unit then effective for picture line scanning. The rays passing from the image |65 are reected by large prism 51 to lens 58 which lens forms an image of image |65 `at aperture plate 59. As disc lens unit 49, which is elective for producing the synchronizing pulse, moves with the disc |5 following the lens unit 49 which is effective for picture scanning, the synchronizing image on aperture plate 59 moves upward perpendicularly to the plane of the paper in Fig. 3. When it crosses the aperture in plate 59 a pulse of light energizes cathode 6l of electron multiplier 62 to produce an electrical synchronizing impulse. The aperture in plate 59 is so positioned that this impulse occurs when the picture line then being scanned is about half scanned.

In Fig. 3 the boundary rays of the synchronizing light beams are indicated by dot and dash lines. The path of one typical ray passing through the center of aperture |45 and, therefore, the center of image |65 is indicated by dotted lines. The arrows on these ray lines indicate the direction of propagation of the rays. 'Ihe optical axis of one of the disc lens units 49 in one position showing how it is bent in passing through the edge of collimating lens 48 is indicated by the dotted line with arrows in Fig. 4.

This compact unitary optical arrangement makes it possible to use the same disc lens unit 49 for producing a synchronizing pulse and later scanning a picture line the reproduction of which is partially controlled by said synchronizing pulse. This result is effected with negligible interference between the picture line scanning and synchronizing optical systems and requires delaying the synchronizing electrical impulses less than the period required for scanning a picture line.

The lens holders I6 for disc lens units 49 are L-shaped members in section, as shown in Fig. 3. The two plano-convex lenses of each lens unit 49 are seated in a hole which extends lengthwise through the shorter leg of lens holder I6. The longer leg is bolted to the outer edge of disc I by machine screws |66 and accurately positioned by pins |61. The relative positions of the lens holders I6 on the face of disc |5 are shown in Fig. 10. The space |68 between the holders |6, after they have been mounted on the disc I5, is filled with Krackno in order to prevent light from lens 48 passing between holders I6 to the lm 5 and light conductor 50 and also to minimize air friction when the disc I5 is rotating in the housing 90. Only one lens holder I6 is shown in Fig. 3 for clearness of illustration.

Further details of the picture scanning gate are illustrated in Figs. 6, '7, 8 and 9. The 'casting |03 is shown secured to housing 90 by machine screws |10, one only of which is shown. The relative location of one disc lens unit 49 and the boundaries of the other disc lens units are indicated by dotted lines within the housing 90. Lens ring |21 and a portion of the ange |24 of casting |20 is shown attached' to the opposite side of housing 90. Within the aperture in casting |03, through which the picture is scanned, a piece of transparent glass |1| is secured.

The picture scanning gate comprises an adjustable plate |12, the upper end of which is bent to form a channel which fits over two eccentric cylindrical cams |13. These cams are integral with an axle |98 extending therebetween, which axle is mounted on and secured to a shaft |14, which is supported by bearings |15 in the legs of a shallow U-shaped member |16. The shaft |14 with the cams |13 may be r-otated by the lever |11, which is secured to the end of shaft |14. The plate |12 with cams |13 and their mounting elements constitutes an adjustable support |18 for the lm gate and associated elements. This support |18 is mounted on casting 03 by a threepoint suspension. One point of this suspension is the machine screw |19, which passes through a hole in the base of U-shaped member |16, into a threaded hole in casting |03. The other two points of suspension are pivot screws |80 and |8| located near the sides and at the lower end of plate |12, the conical pivot ends of which seat in recesses in screws |82 set in casting |03. The upper portion of pivot screw |80 is broken away in order to show pivot screw |8| situated behind it. The pivot screws |80 and |8| are held in their seats by coiled spring |83 and machine screw |84. The screw |84 passes through a hole in plate |12 and is threaded into a hole in casting |03.

In order to allow space for threading the lm 5 over the curved film guide |85, a portion of plate |12 is cut away. At the rear of plate |12 there is secured a lip |86 which is integral with plate |81. Plate |81 serves as a support for the framing indicating gate 8, the film guide 85, the guide wings |88 and |89 for light conductor 50, and the guide and support blocks |90 and |9I, which in turn support jaws |92 and |93 respectively for determining the transverse portion of film 5 which is scanned. Jaw |93 is secured to block |9| in fixed position by screw |94. Jaw |92 is adjustable by means of screw |95 and is held against block |90 by spring |96. 'Ihe adjustment of jaw |92 determines where the scanning of the picture line begins and so makes it possible to vary the period between line scannings.

The light conductor 50 is wrapped in blac paper 200 and inserted in a copper tube 20| of rectangular cross-section. The end 202 of light conductor 50 which is nearer the film 5 extends beyond the copper tube 20| and paper 200, as indicated by dotted lines in Fig. 6. The corresponding end of the copper tube 20| is inserted between support blocks |90 and |9I, a felt pad 204 being provided between the support blocks and the tube. The clearance between the support blocks and the tube is such that the tube may be easily removed if desired.

It is thus seen that the film 5 which is threaded and runs over film guide |85 may be moved toward or away from disc lens units 49 by rotating cam handle |11 and cams |13, thereby moving plate |12 around the points of pivot screws |80 and |8|. 'Ihe emulsion on the nlm 5 may thus be brought into coincidence with the principal foci of disc lens units 49. By adjusting pivot screws and |8| the plane of the lm 5 at the scanning position 9 may be positioned parallel to the path of the principal foci of disc lens units 49 as the disc I5 rotates. The picture scanning spot, therefore, remains of constant size at the nlm emulsion as the spot travels across the lm 5 during normal scanning operation.

The film 5 is held against the upper part of the film guide by releasable pressure pad 205, the lm being drawn against the lower part of film guide |85 by lm sprocket I0, which pulls the film through the picture scanning gate over framing roller 68. This pad 205 is supported from plate |12 by bracket 206. The operating mechanism for pad 205 includes a spring 201 which exerts pressure on the back side of pad 205, tending to force it against the film guide |85. The rotatable shaft |99 supported in a bearing member 208 secured to plate |12 is provided with a pin 209 which when the shaft is rotated in a counter-clockwise direction by handle 2|0 forces down the left-hand end of lever 2||, which is pvoted at point 2|2. The right-hand end of lever 2| I, by means of a hooked connection with pressure pad 205, pulls the pad away from the film guide |85 against the pressure of spring 201. The pad 205 is shown in retracted position in Fig. '7. The shaft |99 is stopped in the releasing position by stop-pin 2|4 contacting with stop 2 I3.

The housing 2|5 for neon lamp 12 is secured to frame indicating gate 8, a film guide plate 2|6 being located between the housing 2|5 and the gate 8. This plate 2|6 has turned-up portions 2| 1 above the nlm and a turned-down portion 2 I8 on either side of the film 5 to guide the lm centrally in the gate. The gate 8 also has a turned-down portion 2|9 below the film Where the nlm enters the gate. The aperture in the gate 8, which is the size of a film picture frame, is indicated by dotted lines.

The mounting of the synchronizing mirror 56 is further illustrated in Fig. 9. This mirror 56 backed by a piece of soft cardboard 226 and a metallic plate 225 ts into an aperture in casting I 03. Plate 225 is fastened to the casting |03 with screws. By removing the plate 225, the mirror 56 may easily be removed and cleaned.

In a specic embodiment of the invention which has been operating satisfactorily in a television system producing images from ordinary sound motion picture film at the rate of twenty-four frames per second, scanning disc I5 carries 240 lens disc units 49 on 7A; inch centers. The centers of the disc lens units 49, therefore, are approximately 331/2 inches from the center of the disc I 5, the disc ydiameter without the lens holders I6 being slightly less than 66 inches. The lenses of the lens disc units 49 are slightly less than 3A inch in diameter and are stopped down to inch. The relative dimensions of the apparatus elements are shown rather accurately in Figs. 3 to 11, inclusive, certain of the elements being exaggerated in size for the sake of clearness. For best results the aperture in aperture member 4l is a square 30 mils cn each side and the image of the aperture formed at the emulsion of film 5 is a square -3 mils on each side. The synchronizing aperture |45 on small prism 55 is a rectangle 1A; inch by al; inch. Disc l5 rotates twenty-four times per second producing 5,760 line synchronizing light pulses per second. Since each synchronizing pulse is produced prior to the time when it is used to initiate a line scanning at the receiver by a period less than one-half of a line scanning period it is only necessary to delay the electrical synchronizing impulses less than 1 divided by 11,520 parts of a second. Because of the novel construction of the unitary optical arrangement of this invention, such a small delay is made possible without introducing troublesome interference between the picture line scanning and synchronizing optical channels.

What is claimed is:

1. An optical device for producing recurring impulses of radiant energy of short duration, comprising a source of light, means to illuminate a small aperture, a movable lens, a reflector in the path of light rays from said aperture through said lens for reflecting rays back through said lens, said aperture, lens and reflector being so located that an image of said aperture is formed outside the plane of said aperture by reflected rays, means to move said lens past said aperture and ref-lector periodically, and means to utilize the rays from said image only While said lens is traversing a small portion of its path between said aperture and reflector.

2. A synchronizing optical system for television comprising a rotatable television scanning disc having a circle of lens-equipped apertures, an aperture so located that the axes of the lenses on the -disc pass therethrough as the disc rotates and at a point on the axis outside the principal focus, a plane mirror parallel to the plane of the disc also intercepted by the axes of said lenses when the axes intercept said aperture on the side of the disc opposite to said aperture and in the neighborhood of the principal foci of said lenses, a second aperture, and means to form an image at said second aperture of the image of said first aperture formed by said lenses with rays from any lens reflected back through the same lens.

3. A scanning system comprising a rotating disc carrying a plurality of lenses angularly spaced around said disc, an optical system on a rectilinear axis comprising a source of light for directing image scanning light through said lenses in succession, and another optical system comprising a second source of light having axes in part parallel to the axis of said image scanning optical system and in part transverse thereto also directing light through said lenses in succession.

4. A method of effecting proper framing of television images which comprises scanning an object field in a succession of elemental areas, introducing a succession of views of the object into the object field, observing a view while occupying an observing area outside the object field,

illuminating the view to be observed by a flash of light occurring when a given elemental area of the object field is being scanned and so spacing the observed View and the scanned View physically that at the instant the flash occurs the elemental area of the observed view corresponding to the given elemental area being scanned of the scanned view occupies the same relative position in the observed field as the scanned elemental area occupies in the scanned field.

5. A scanning arrangement for television for motion picture lm comprising a scanning gate, a frame-viewing gate, means to illuminate the lm in said viewing gate at the instant that a given elemental area is being scanned in the scanning gate, means to drive the lm through both gates with a fixed length of film between said gates, means to position said scanning gate and said film gate so that when said given elemental area is being scanned and the flash of light occurs the corresponding elemental area of the frame in the viewing gate occupies the corresponding position in the viewing gate, and means to adjust the length of film between the driving means and said gates so that a full frame appears in the viewing gate when the flash occurs.

6. An optical device comprising a tubular support, a collimating lens seated in one end of said support, an aperture forming member at the other end of said support, means to position said aperture at the principal focus of said collimating lens, a pair of reflecting prisms of unequal size having a non-reflecting face of the smaller prism cemented to the reflecting face of the larger prism, and the reflecting faces positioned at right angles to one another, means to mount said prisms in an opening in the side of said tubular support adjacent one edge of said collimating lens so that a light ray incident on the reflecting face of said smaller prism at an angle of incidence of 45 degrees is reflected through the cemented portions of said prisms to the face of said collimating lens near one edge thereof, and means in said tubular support to prevent light rays entering through said aperture from impinging upon said prisms.

7. An optical device comprising a tubular support, a collimating lens seated in one end of said support, an aperture forming member at the other end of said support, means to position said aperture at the principal focus of said collimating lens, a pair of reflecting prisms of unequal size having a non-reflecting face of the smaller prism cemented to the reflecting face of the larger prism, and the reflecting faces positioned at right angles to one another, means to mount said prisms in an opening in the side of said tubular support adjacent one edge of said collimating lens so that a light ray incident on the reflecting face of said smaller prism at an angle of incidence of 45 de'- grees is reflected through the cemented portions of said prisms to the face of said collimating lens near one edge thereof, means in said tubular support to prevent light rays entering said aperture from impinging upon said prisms, and means to move a succession of lenses past said collimating lens, said movable lenses being of such size and so positioned that in pairs they receive at given positions light rays simultaneously from said collimating lens, the rays passing to one lens of said pair from said aperture and the rays passing to the other lens of said pair from said smaller prism.

8. A framing indicating device for a motion picture scanner comprising a rotatable scanning disc having a plurality of scanning apertures, means to move a motion picture film past said disc so that one frame of said lm is completely scanned for each revolution of said disc, a viewing gate positioned a fixed distance from said scanning position measured along said lm, means to illuminate the lm in said viewing gate at the instant that a given aperture is effective for scanning, and means in said gate which coincides with a characteristic mark on each frame of the lm at the instant when said viewing gate is illuminated and the lm is in frame for scanning.

CHARLES F. MATTKE.

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