US1966617A - Scanning device - Google Patents

Description

July 17, 1934. G. v. v. DILLE'NBACK, JR 1,966,617

SCANNING DEVICE Filed Oct. 9, 1930 VENTOR BY W7 l ATTO NEYS'.

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Patented M 17.1934

PATET OFFICE SCANNING DEVICE Garrett Vander Veer Dillenback, Jr., Slingerlands, N. Y., assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Application October 9, 1930, Serial No. 487,433

2 Glaims.

This invention relates to electro-optical systems, and with particularity to methods and means for controlling the speed of analyzing and integrating mechanisms.

While the invention is of peculiar adaptability to such systems as picture transmission, television or the like, it will be understood that the invention in its broad aspects is not limited to any particular system, but is capable of use in any situation where a commercial supply is available for furnishing the main driving power" to rid the mechanism to be synchronized and an additional source of constant frequency currents are available for controlling accurate speed of the mechanism.

. The invention is in the nature of an improvement upon the system disclosed in applications Serial Nos. 365,818 and 405,354.

One of the principal objects of the invention is to provide a method of synchronizing transmitte'r'and receiving apparatus such as ordinarily employed in television, picture transmission and similar systems.

Another object of the invention is to provide a system for transmitting and/or reproducing images, visual representations or the like employing a single channel for carrying both the synchronizing and image or picture signals.

Another object of the invention is to provide methods and means for enabling the picture or image currents themselves to be utilized in controlling the synchronism of receiving and transmitting apparatus in television, picture transmission or similar systems.

A feature of the invention relates to a novel drive for rotatable members generally, comprising a variable speed motor, and a synchronous motor, both these motors being relatively simple and-cheap to construct.

*Another feature of the invention relates to a driving mechanism for a member adapted to be moved at an extremely constant rate of speed comprising an eddy current motor and a synchronizing motor.

- Another feature of the invention relates to methods and means for operating an analyzing or synthesizing device such as ordinarily employed in image or picture transmission systems. In accordance with this feature the driving mechanism for the devices is divided into two portions, one adapted to be energized by current derived from a commercial supply and the other adapted to be energized by currents having characteristics corresponding to the speed of a transmitter or a reoeivera A further feature relates to a novel form of synchronizing drive wherein the rotor member is coupled for relative movement to the driving shaft, and is adapted to be energized under control of synchronizing currents.

A still further feature relates to the novel organization and arrangement of elements which go to makeup a simple, cheap, economical and highly accurate television or image reproducing apparatus wherein the image currents themselves are used for synchronizing.

In the drawing Fig. 1 shows in schematic form a system embodying features of the invention;

Figure 2 is a detail view of a modified form of synchronizing device thatmay be used in the system of Fig. 1;

Fig. 3 is an end view of the synchronizing device of Fig. 2.

Referring more particularly to Fig. 1, the numeral 1 represents a scanning device of known construction. This device may take the form of a drum or disc. Thus in Fig. 1 the scanning device is in the form of a thin annular strip of metal, fibre or any other light material provided with a convolution or convolutions of circumferentially spaced scanning elements or openings in the manner well known in the television art. The annular member 1 is fastened in any suitable manner to a circular metal disc 2 of copper, aluminum or other metal suitable for use as the rotor of an eddy current motor. The disc 2 is fastened to a shaft 3 provided with suitable anti-frictional bearings in standards (not shown). Mounted adjacent the opposite faces of the disc 2 are field magnets 4, 5 and 6. Each of the magnets 4, 5 and 6 is adapted to be energized by alternating or pulsating current from a suitable source 7. Thus the source 7 may take the form of commercial alternating supply means, the frequency of which may vary within the usual limits found in such commercial systems. The currents in the windings i, 5 and 6 are displaced in phase'in any manner known to the art, for example by inserting a reactance such as a condenser 8 in the circuit of the magnets 5 or 6. It will be understood of course that this reactance may be variable and may be placed in circuit with the magnet 4 if desired. A suitable rheostat 10 is connected in circuit with the magnets and the source '7 to control the asynchronous speed of the disc 2. The devices 2, i, 5 and 6 thus form in effect a variable speed motor of the eddy current type, the asynchronous speed of which may be controlled by means of the current control device lo.

Mounted adjacent the scan n member 1 is 2 suitable light trcnslcting device 11 which take the form. of a neon lamp provided with a suitable adjustable mask to illuminate the soon ning field of the member 1.

For a detail description of this portion of the apparatus, reference may be had to the cpplice= tion of G. V. Dillenbech, J12, Serial No. lessee. Removably attached to one end oi the shaft 3 is esynchronizing rotor 12 in the form of etoothed wheel such ordinarily employed in lnfiour or Phonic wheel motors. Mounted edjecent the wheel 12 is e.- i'ield magnet 13 provided with e. winding 14 adapted to be energized by currents received from the t nsrnittt time.

As described. dc ii in ction Serial No. 385,818, end as now well lmovn'i in television sys-= teins, the image or picturecinrcnts have a: char acteristic frequency which. is determined by the speed of the scenuing mechanism at the trens= mitter. Thus if amotion picture film is being scanned at the rate of 15 pictures per second and the scanning device is provided with 48 scanning elements, then the picture currents in addition to being modulated according to the image chenecteristics also have an inherent characteristic of 720 cycles per second.

In accordance with the present invention it is proposed to employ this characteristic frequency to energize the field 13. Thus es illustrated in Fig. 1, the numeral, 15 represents e transmitting station of known construction capable of tronsmitting image or picture currents having a characteristic frequency related to the speed of the transmitting analyzer. The numeral 18 represents any suitable transmission channel such as a. radio or wired lined channel. In the case of radio transmission the channel 16 feeds into a suitable detecting or demodulatlng apparatus 17. The output of the device 17 is further amplified in a suitable amplifier 18 and applied to the reproducing device 11.

Another portion of the output passes through a filter 19 and is amplified in the device 20. The amplified filtered output is then impressed upon the winding 14 and controls the synchronous speed of the member 12 and consequently of the shaft 3. In the case above assumed, namely with 48 lines per picture, 15 pictures per second the. output of the device 17 will have a characteristic component of 720 cycles per second and preferably, therefore, the device 19 may be an electrical network designed to pass currents having a. frequency in the neighborhood of 720 cycles per second. Furthermore, if desired the amplifier 20 may be a tuned amplifier having its maximum transmitting efilciency in the range of 720 cycles per second. I

From the foregoing description it will be seen that the main driving power for the device 1 is derived from the commercial supply '1 through the intermediary of the members 2, 4, 5 and 6. while the synchronous speed thereof is controlled by the device 12. It will be obvious therefore that if the transmitter or analyzing mechanism should vary in speed that the characteristic picture frequency will also vary and consequently the device 1 will be kept continuously in step'wlth the transmitter. It will be obvious that the filter 19 and the amplifier 20 may be made adjustable if deslred,so as to allow for the variation range of the transmitter. If the receiving apparatus shown in Fig. 1 is to be synchronized at a. different frequency then the synchronizing rotor 12 will be replaced with a. rotor corresponding to the synchronizing frequency and similarly the members i end 20 will be adjusted or replaced by the corresponding networks.

While the invention is described above as applied to one lmown type of television system, it will be understood that the invention is not liml thereto. Thus for example the characteristic frequency or modulation of the picture frequencies may be produced in the manner de scribed in Patent 1,694,065 to C. F. Jenkins, granted December 4, 1928. It has been found that the driving shaft 3 may be brought into synclnonism more expeditiously and maintained in szmchronism over a relatively wide synchroraising frequency range if the synclnonlzing rotor 12 is resiliently coupled to the shaft 3.

Thus as shown in Fig. 2 the shaft 3 is pro vided with a threaded end to receive a shoulder screw 21. The synchronizing rotor 12 is mounted loosely for rotation on the shoulder end of the screw 21 and is coupled to the shaft 3 by c coil spring 22. It has beenfound that this type of coupling between the rotor and shaft is necessary where the transmitting apparatus and the synchronizing currents vary over 2. comparatively wide range. It will be obvious, of course, that the manner of coupling the rotor 12 to shaft 3 as shown in Figs. 2 and 3 is merely illustrative, and that any other equivalent resilient connection between the rotor and shaft may be provided.

While specific apparatus and arrangements have been described hereine'bove, it will be understood that the invention is not limited thereto, since broadly the invention is capable of use in any situation where the main driving power for a. driving member is derived from commercial supply mains and the member is synchronized by currents transmitted from s. distance.

Changes and modifications other than those hereinsbove mentioned may be made without departing from the spirit and scope of the lnvention. For example, while an ordinary or undamped spring coupling is provided between shaft 3 and rotor 12, it is preferred, particularly where there is very little friction in the bearing, to provide additional damping means for the free vibrations of the spring. Any well known means for dampening the free vibrations of the spring coupling may be employed, for example hydraulic or mechanical friction members may be employed.

It is also contemplated to employ a. coupling of the type ordinarily referred to in the printing telegraph art with a. mercury flywheel coupllng, in which case the spring coupling may be eliminated entirely, or reliance may be placed, if desired, upon both the spring coupling and the mercury flywheel.

It will also be obvious from the foregoing disclosure that instead of providing the flexible or resilient coupling between the synchronizing rotor and the shaft, the said rotor may be rigidly fastened to the shaft and the resilient coupling provided between the scamiing disc and its shaft.

What is claimed is:

1. In a device of the character described the combination of a, driven shaft, a television scanning device attached at one end of said shaft and having a portion serving as the rotor of an eddy current motor, means for driving said shaft and device by eddy current action on said portion of said disc, said shaft being threaded at its other and free end, a. shoulder screw adapted to be threaded into said threaded free end of said shaft, 9. synchronizing rotor loosely mounted for rotation on the shoulder end of said sm'ew. and a 1 a member adapted to be threaded into the threaded end of said shaft, a synchronizing rotor loosely mounted on said member for rotation thereon, and a spring having one end thereof secured to said rotor and the other end thereof secured to said shaft for coupling said rotor and shaft together.

GARRETT VANDER VEER DILLENBACK, J R.

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