US1175313A - Transmission of pictures of moving objects. - Google Patents

Description

A. SINDING-LARSEN. y TRANSMISSION OF PICTURES 0F MOVING OBJECTS.

APPLICATION F|LED1uNE1o,1911.

1 1 75, 3 1 3 Patented Mar. 14, 1916.

2 SHEETS-SHEETA l.

Figi.

A. SlNDlNG-LARSEN.

TRANSMISSION OF PICTURES 0F MOVING OBJECTS.

APPLICATION FILED JUNE I0. 19H.

i1, 1 75,3 1 3. Patented Mar. 14, 1916.

2 SHEETS-SHEET 2.

Fig. 7.

""WM/ Qf maw 6 210 ZU@ l A l" L UNITED STATES PATENT OFFICE.

ALF SINDING-LARSEN, OF CHRISTIANIA, NORWAY, ASSIGNOR 0F ONE-HALF T0 JOHAN HENRIK -LABE LUND, OF CHRISTIANIA, VNOIWVAY.

Specification of Letters Patent.

Patented Mar. 14, 1916.

Application led June 10, 1911. Serial No. 632,410.

To all whom t may concern. 'p

Be it known that I, ALF SINDING-LARsEN, a subject of the King of Norway, residing at Christiania, Norway, have invented certain new and useful Improvements in and Relating to the Transmission of Pictures of Moving Gbjects; Vand I do hereby declare that the following is a full, clearA and exact description of the same.

My invention relates to the art of transmitting over long distances pictures of moving objects, and consists in improvements in the method or system as well as in the means and in the combinations of devices for carrying out the invention. In the devices hitherto proposed for transmitting pictures through conductors a principle common to all of them is, that the picture to be transmitted is decomposed into a series of points or elements by devices performing two linear movements perpendicular to each other, said elements being successively transmitted to the receiver, in which, by corresponding linear movements, the pictures are recomposed. This necessitates two absolutely nchronous movements at the transmitter and the receiver. In the graphical transmission of pictures (for instance according to the Korns system) in which the duration of each movement is not limited, it isnot difiicult to establish such synchronism, but in the transmission of moving pictures, where every light point or picture element has to be repeated before the light impression on the eye has ceased, (between one tenth and one hundredth part of a second).which requires a very rapid performance of each single movement, such a motion system is very difficult to accomplish. A prior inventor (British Patent 27570/07) has tried to overcome this difficulty by making use of a picture decomposed in the transmitter, comprising two rotary polyhedral mirrors the axes of which are perpendicular to each other and which rotate at different speeds. The recomposing device in the receiver, however, does not consist'of a similar mirror system with a corresponding motion, scheme. which would have been impracticable on account of the absolute accuracy `rof synchronism necessary), but itis proposed to effect the recomposing of the picture in these systems by means of electrical current impulses, created hv the rotating systems, which impulses vcause synchronous linear movements in oscillographs, especially in the so called Brauns tubes,- known from the scientific study of electrical waves. In other words, in these systems synchronous movements are sought to be established between devices of wholly different natures, a scheme which may be considered practically impossible to realize. The use of polyhedral mirrors for the purpose is moreover, in itself, disadvantageous, as each mirror4 is only partially utilized, the mirrors entering the field of rays successively, and again successively leaving said field. Another drawback is that the picture elements may become intermiXed, as a reflection may take place simultaneously from two surfaces of the polyhedron.

In contradistinction to this old system my invention consists in a system for the transmission over long distances of pictures of moving objects in which an absolutely synchronous motion is practically realized by arranging the transmitter and the receiver in such manner that the movements required for the decomposing devices and those required for the recomposing devices are of the same character.

One important point in my invention isthat the decomposer at the transmitting station and the. recomposer at the receiving station both have a double oscillating motion, that is to say, they perform oscillations in two different planes, and that the synchronism of these oscillations is insured by the action of oscillating bodies having free vibration and kept in motion by a common source of driving force.

Having indicated the nature of my invention as regards the principle employed for enabling me to Secure a synchronous action of the decomposing and the recomposing devices, I shall now explain some examples of how the invention as a whole may be carried out,'andf. describe some of the devices which I have-,made use of. in order to prove the possibility of practically utilizing my invention. An image ofthe object is taken'up by a kind of camera, in which, however, the imagedoes not fall directly upon the rear image surface, or .focal plane, but in which a mirror is mounted between such plane and the object lens, said mirror reflecting .the light to another mirror from which the light finally falls upon the image surface. These two mirrors are associated with tuning forks or like freely vibrating devices, having different frequency of vibrations.Y The axes vso of oscillation of said mirrors may be perpendicular to one another, or form some other angle, While their planes should be parallel when in the middle position. These tuning forks, one of which may have a vibration frequency of N for instance 100 in a second, and the other a frequency of N2 or 10000 in a second, may now be kept in steady motion by means of a suitable electromagnetic arrangement. By means of this device every vpoint of the image formed is in its turn transmitted to one and the same point on the image surface. At this point a light opening is arranged, and immediately behind this opening is the light receiving device which transmits the light to the receiver.

The receiver is constructedv in a manner quite similar to the transmitter. It comprises a device emitting through a small light orifice the light coming from the transmitter, or emitting the light from a local light source, the light given od through the light-orifice varying in intensity in accordance with the simultaneous intensity of the light passing through the light orifice of the transmitter. The variable light po-int thus formed in the receiver is looked upon through a system of reiiectors corresponding to that of the transmitter, and oscillating synchronously with this latter system.

For transmitting the pictures-directly I make use of a. narrow tube Wwith strongly reectino' inner surfaces, which tube is arranged.j with its rear opening behind the light orifice in the transmitter. The tube is preferably made of silver, gold, copper or other metal having a refraction coefficient lower than that of air. The optical system forming the image is arranged in such a manner that the rays forming the individual image points cross one another at a very acute angle. By this Iam enabled to cause the light taken up in the mouth of the tube to be transmitted through the tube without being materially weakened in its. passage to the other end of the tube and vthe image surface ofthe receiver. In order to maintain lrhe greatest possible reiiecting angl',` of the light rays during passage through the tube, the tube should have a very small sectional area and its curves or bends be of the greatest possible radius.

The synchronous movement of the mirrors is effected by coupling in series the electromagnets serving to keep the mirrors moving. The same tube that transmits the light rays may serve as conductor for the electric current. All these oscillating parts may be made to work in a vacuum in order to avoid disturbing noise and possible disadvantages resulting from air damping.

When the transmission'of the picture is effected directly, that is, When the light A'is conducted through reecting tubes, these latter may be kept filled with a gas adapted to preserve the reflecting surface against oxidation, such for instance, as hydrogen. The tube may also be evacuated.

To insure constant andcomplete uniformity between the oscillations of the tuning forks and of the mirrors associated with said forks, I make use of the following -arrangement: The electromagnets actuating the tuning forks in the transmitter and receiver are coupled in series and are thus driven from a common source of current; while the quickly oscillating tuning forks or the magnet armatures mounted upon them are unpo-larized, so that the direction of current in the electroma'gnet having a very soft iron core is of no consequence. The slowly oscillating tuningforks or their armatures are polarized in such a. manner that the direction of oscillation is dependent upon the direction of current in the magnet. A third tuning fork arranged in the transmitter or receiver and having the same frequency of vibration as the abovementioned slowly oscillating ones, serves to control the rotation of a commutator inserted in the battery circuit, which by means of suitable segment arrangement transforms the direct current into alternating current, whose periodicity is in accordance with the periodicity of the slowly oscillating tuning forks. It is obvious that the slowly oscillating, polarized tuning fork arranged in the receiver and transmitter when acted upon by an alternating magnetic field of its own periodicity produced by this alternat- Ying current, is compelled to maintain quite consonant and coincident oscillations. And it is also quite clear that the quickly oscillating tuning forks in the transmitter and receiver which are acted upon by one and the same interrupted current corresponding with their periodicity of oscillation are also compelled to maintain quite coincident oscillation. The rotation controlled by means of said third tuning fork may also vact to directly produce the alternating current necessary, so that a battery may be superiuous. For these arrangementa'as well as for those above-described, other bodies with a free vibration or self-oscillating capacity may be employed, instead of tuning forks. In vthe transmitter and in the receiver an electromagnet may be employed for the purpose of driving both tuning forks. The conductor or conductors emploved for the transmission of pictures may also be used for the purpose of telephoning or transmission of telegrams.

I shall now describe some forms of apparatus used by me in carrying out my invention.

Referring to the drawings, in which like p arts are similarly designated-Figure l is a diagram of motion. Fig. 2 is a side y view of a .transmitter and a receiver illustrating means for carrying out the invention. Fig. 3 is a longitudinal section on an enlarged scale through the transmitter. Fig. 4L is a. detail showing a cross section through one of the mirrors. Figs. 5 and 6 are details. Fig. 7 is a diagrammatic perspective view of a generator for interrupted alternating cur-rents. Fig. 8 is a current diagram. Fig. 9 shows a vmodification of' the mirror arrangement.

Reference being had to Figs. 2-6, T represents the transmitting apparatus and R the receiver; they are supposed to be connected by a reflection tube 5. 1 is the object lens of the receiving station camera, in which is placed two mirrors, 2 and 3; the mirror 2 oscillates very fast on an vaxis perpendicular to the plane of the drawing, while the mirror 3 oscillates more slowly on an axis lying in the said plane and is perpendicular to the axis of oscillation of the mirror 2. By these means the elements of the image formed-by the lens 1 are in succession folle-wing a continuous zigzag line, transferred to the focus of a lens 4 placed in the opening of a reection tube 5, said lens parallelizing the rays which meet the image point. In the receiver two similar mirrors 7 and 6 oscillating synchronously with the mirrors 2 and 3 respectively, thro-w the train of rays emerging from the reflection tube to the eye of the observer as indicated, or to the object lens of a camera o-r projection apparatus. The synchronous vibration of the respective pairs of mirrors is insured by means of the tuning forks and is maintained by means of electromagnets receiving current from the same source; this current may, for one of the pairs of mirrors, be an interrupted current, and for the other pair an alternating current, or it may be simultaneously interrupted and alternating, in which case it is not necessary to have a separate circuit fo-r each pair of mirrors. The breaking or the alternation of the current for each pair of` mirrors correspo-nds with the frequency of the freevibration of the mirrors. This principle of resonant adjustment of the oscillating systems is fo-und to be an absolute condition for obtaining the synchronism necessary for the correct transmission of the pictures; it enables me also to have these movements established with a minimum of power, a fact which is of no little importance. But the greatest advantage of the system is that the synchronism is in this manner self 'adjusting, because if the mirrors are by some outer force brought out of their regular motion, they will immediately, when left to themselves, reassume their synchronous motion. The system therefore enables me to control an unlimited number of stations from a common central. K

In the drawing I have shown two sets of mirrors in each station. I may also make use of any other means for decomposing and recomposing the picture in the manner described. The main feature of this part of the invention being that the oscillatory movements used for the decomposition and recomposition of the picture are tuned so as to be in resonance with the free vibration of the swinging bodies.

The rapidly swinging mirrors 2 and 7 may suitably be driven by interrupted current supplied to electromagnets with unpolarized armatures, and the mirrors 3 and 6 may be driven by alternating current by means of electro-magnets the armatures of which are polarized. If the transmitter and the receiver' are driven by interrupted direct current, and the light transmission is effected by means of the described reflection tubes, it will be seen that only two electricconductors are needed for the transmission of the picture, and as one of these may be the reflection tube and the other the earth, no other connection than the tube is necessary between the two stations. I have found that a tube of an inside diameter of 2 millimeters and an outside diameter of 3 millimeters is Suitable. Instead of tubes I may make use of wires or strings of a material of little light absorbent quality, or of tubes filled with fluids of this nature. In o-rder that as little light as possible shall be absorbed bv the walls of the tube it is preferable that the lens 4 shall have a short focal length. l

The mirror 2 (see Fig. 3) may be made of iron, polished and silver plated on the front face and have its back fixed to a piano string 8 which has a free swing or vibration. The tension of the string is so adjusted that a suitable free vibration frequency is secured by the combined action of the mass of the mirror and the forces of torsion 0f the string. The piano string may be so mounted that it is prevented from having transverse vibration, which latter would disturb the picture. .Y

9 represents an electro-magnet creatinga field'in which: the mirror acts as an armature. The windings of the electro-magnet are connected with an interrupted current circuit the frequency of-which corresponds with the free vibration frequency of theA mirror.

The mirror 3 is pivoted on the pins 10, 10, and on its back is secured a permanent magnet 11, the poles of which extend into the fields created by the alternating current magnets 12, 12. This mirror has arelatively slow vibratory motion, the frequency of which is made to correspond with the frequency of the alternating current by adjustment of its mass and of -a spring, which tends to keep it in its intermediate position.

For generation of an interrupted alternating current suitable for the purpose of my having a distinct free vibration, and 22 a motor-driven commutator giving off current Vto the brushes 23, 24C, connected in series or in parallel With the transmitting and receiving apparatus and rotated, preferably, so as to send current impulses in synchro nism with the free vibration of the suspenders for the mirrors. The commutator 22 is driven by a Weight operatedmotor governed by an escapement mechanism consisting of an escapement Wheel 62 having pins 63 coperating With the detent 64 carried by an arm of tuning fork 60 which is kept in vibration by the magnet 6l. According to the frequency of the interrupter relatively to the number of alternations caused by the commutator, current-curves o-f difterent form Will be obtained. If the frequency of the interruptions is greater than the frequency of the alternations, as supposed in the apparatus above described., the curve will be as shown in Fig. 8. Of course the number of variations in each positive and negative part of the Wave Will be much greater than shown. In order to increase the intensity of the light transmitted there may be arranged tivo or more light-transmitting and light-receiving devices at the transmitter and receiver, respectively, said. devices coperating With each other and transmitting simultaneously dierent points of the picture, either directly .or .indirectly as described; of course care must be taken that the said devices are placed at the same distance and in the same relative position to each other at both stations.

If the transmitter and receiver have great dimensions, it may be unsuitable to use mirrors of the above-described arrangement, be cause the air may have too great a retarding action on mirrors of great dimensions swinging With great velocity. In such a case- I may make use of mirrors formed in sections like Window blinds or louvers, as shown in Fig. 9. The sections, although having a very slight peripheral movement, Will perform the saine Work as a continuous mirror, having the same angular motion. These mirrorsmove on their axes synchronously' and are vibrated by like means as described with respect to mirrors 2 or 3.

Instead of a lens, as shown in Fig. 5, I may use an arrangement such as that shovvn in Fig. 6. The endY of the tube is in this case provided With a mouth piece 14 having a polished conical inner surface. The rays entering the small orifice of this mouth piece Will be repeatedly reflected, so as to finally take a direction about parallel to the axis of the tube. It is preferable that the light rays enter the tube at a slight angle, for example, not over 10.

I claim l. In the method of transmitting pictures of moving objects to a distance, the step which comprises forming an image of the object, breaking up the image into minor elements by oscillating reflectors having a freely vibrating suspension, and maintaining the vibration of said suspension by imparting to said reflectors impulses in phase With the vibration of said suspension.

2. In the method of transmitting pictures of moving objects to a distance, the step Which comprises forming an image of the object, breaking up the image by `double re flection to oscillating reflectors having freely vibrating suspensions, and maintaining the vibration. of said reflectors by imparting impulses thereto substantially in synchronism with the fundamental of the suspension.

3. In the method of transmitting pictures of moving objects, the step Which comprises forming an image, breaking up the image by vdouble reflection first to a rapidly oscila lating reflector vhaving a freely vibrating suspension and thence to a slowly vibrating reflector also having a freely vibrating sus pension, and maintaining the vibration. of said suspensions and reflectors by imparting impulses thereto substantially in synchronism `with their fundamental. n

4l. Mechanism for transmitting moving pictures, comprising a sending station and a receiving station, each station having mirrors to produce double reflection, and a reflecting tube connecting the stations, said mirrors having freely vibrating suspensions and means to produce a magnetic field for each mirror in synchronism With thevibrations of said suspensions.

Mechanism for transmitting moving pictures, comprising a sending station and a receiving station, each station having tWo reflectors vibrating at an angle to .one another, freely vibrating suspensions for said reflectors, and electro-magnetic means to maintain said mirrors in vibration, and means to simultaneously send current impulses to said electro-magnetic means in synchronism with the vibrations of said suspensions..

In testimony that I claim the' foregoing as my invention, I have signed my name in presence of tWo subscribing Witnesses.

Y ALF SINDING-LARSEN.

Witnesses: .f

MARLIN GULoRMsEN, HENRY Bonnnwroii.

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