US2109339A - Variable speed television - Google Patents

Description

Feb. 22, 1938. A MCL. NICOLSON 2,109,339

VARIABLE SPEED TELEVISION Filed Feb. 8. 1954 :ELEr* l JR RECEIVER I AMPLIFIER Hulk-j INVENTOR Alexander MLean Nuznlsnn BY M/KQ ATTORN EY Patented Feb. 22, 1938 UNITED STATES PATENT OFFICE VARIABLE SPEED TELEVISION Application February 8, 1934, Serial No. 710,229

'7 Claims.

This invention relates to the transmission of intelligence in the form of visible images with a rapidity suflicient to give the illusion of motion and particularly to such a system employing an. electrodynamic electrical discharge or arc, which is propagated along a predetermined path and modulated in accordance with the light and shade densities of an object or image being transmitted.

There are several different types of systems for the transmission of images, which fundamentally distinguish from one another on the basis of the method of and apparatus for propagating light beam over the object or screen used for observa-- tion. Such systems are well known. such as the mirror drum, disc, cathode ray. and electrodynarnic arc systems, the latter of which are disclosed in my United States Patents Nos. 1,863,278.. issued June 14, 1932 and 1,839,696, issued January 5, 1932. The present are system differs from those disclosed in the patents by the process known as modulation. In the patents the electrical discharge or are is varied in intensity, while in the present invention, modulation occurs by varying the arc speed. Thus a dark spot is created by a relatively high speed motion of the arc, while a bright spot is produced by a relatively slow propagation thereof, the intermediate intensities being produced by intermediate spccds.

An object of the invention is to transmit and reproduce television images.

Another object of the invention is to scan an object and reproduce the images thereof with an eleetrodynamic discharge or are.

A further object of the invention is to reproduce television images with a moving electrical discharge or are whose rate of propagation is varied in accordance with the light and shade densities of the object or image being transmitted. this variation reproducing the image or object.

It is well known that the eye integrates light, within certain limits, similar to that of a photographic film. That is, should light of a definite iz'atensity be projected on the eye within definite time limits, this light will appear brighter. the longer the projection. We have, therefore, a method of modulating a constant intensity light beam to reproduce a television image.

As disclosed in the above-mentioned patents, the electrical discharge is propagated along electrode rails over a definite area. These electrode rails are provided with a source of voltage to produce the arc. Surrounding the electrode rails is a magnetic field which provides a force on the discharge for propagating it along the rails. If the arc length, the electrode voltage and the field strength are maintained constant, the arc will have a constant speed of propagation. Should the field, however, be varied, the speed will also vary correspondingly.

The invention will be more fully understood by reference to the following description read in conjunction with the accompanying drawing in which:

Fig. 1 is a diagrammatic representation of transmitter terminal apparatus, and

Fig. 2 is a similar representation of the receiver apparatus involving the invention.

In Fig. 1 an electrodynamic arc screen. similar to those disclosed in the abovementioned patents. comprises electrode rails 5 and i, a field winding 1, which represents a solenoid or other type of coil of many turns, and a mask 8 with a pinhole or lens 9 therein. The electrode rails 5 and l are energized from a source of direct current potential l2 under control of a rheostat 13, while the field winding 1 is supplied from a source of potential I4 under control 01 a rheostat :5. In this last-mentioned supply circuit is a secondary of a transformer H, the primary of which is com nected to an amplifier Hi. This amplifier receives its input from a photosensitive device 19 posi tioned in the neighborhood of the screen to reccive light variations corresponding to the light and shade densities of an object, such as ll. which is explored with the light beam from the arc screen. The amplifier l8 feeds a transmitter 2! for transmission from an antenna 2 or over wires connected at 23.

The above transmitter operates in a simple manner. An electrical discharge is produced across the electrodes 5 and 6 from the potential source I2 and propagated therealong by the field produced from the source 14. the respective rheostats being adjusted to provide the speed oi prop section which is required to produce the images at a sufficient rate of speed to produce the illusion of motion. As the arc travels along its rails. light therefrom scans the object ll and electrical currents will be set up in the device H), which after a predetermined amount of amplification are impressed upon the transmitter 2|. A portion of the energy from the amplifier i8, however, is returned to the field I for the purpose of synchronizing the electrical discharge on the rails 5 and 6 at the transmitter. This synchronizing system is in accordance with the disclosure in copending application Serial No. 584,797, filed Jan-- uary 5, 1932.

Referring now to the receiver in Fig. 2, the transmitted impulses are received on an antenna 39 or over wire lines to terminals 3| and impressed upon a receiver 32. The detected currents are then amplified in amplifier 34 and impressed upon an output transformer 35. An are system similar to the one in Fig. 1 is employed at the receiver, prime numerals being given to elements corresponding to those in Fig. 1. Now the incoming impulses impressed on the transformer 35 vary the field excitation in accordance with the light and shade densities of the object 0 and thus produce a variation in the rate of propagation of the are along the electrode rails 5 and 6 to produce the image of the object being scanned. A similar variation is set up in the transmitter screen, thus producing the synchronism desired. It is to be understood that the rheostats l3 and I5 must be set to produce substantially the same propagation at the receiver as at the transmitter. Also that the synchronizing variations may have smaller amplitudes than the modulating variations but the proportionalities between them must remain substantially constant. The mask 8 in Fig. 2 may be a ground glass through which the image is viewed directly, or it may have a pinhole or lens similar to that in Fig. 1 and the light projected on a screen for observation.

The above variable speed television system has several advantages over similar systems in which the arc current is varied to produce modulation. The present system requires a minimum of apparatus by eliminating certain synchronizing controls and permits of a greater variation in the accuracy of spacing the electrodes to produce television transmission. There are other advantages in the use of such a system in view of the fact that it requires no mechanically moving elements and is especially adapted for variable speed modulation.

What is claimed is:

1. In a television transmission system, the combination of means for producing a primary light source having a constant intensity at all times, said light source comprising an ionized path, means for immersing said light source in a magnetic field for moving said source, means for projecting the light from said source to an object to be scanned, means for translating the light from said object into electrical currents, means for transmitting said currents to receiving app-arat-us, means at said receiving apparatus for immersing a second light source similar to said first light source in a magnetic field, said second light source having a constant intensity at all times, and means for impressing said received currents on said immersing means for varying the speed of said light source in accordance with the light and shade densities of said object being scanned by the transmitter.

2. In a television system, a combination of a transmitter and a receiver, a plurality of electrode rails at said transmitter supplied by a constant voltage to produce a constant electrical discharge therebetween at all times, means for creating a field in which said discharge is located, means for scanning an object with the light from said discharge, means for translating said light variations into electrical currents, means for transmitting said currents to receiving apparatus comprising a similar electrical discharge system having similar electrode rails and means for creating a field, and means for varying the energy supplied to both of said field creating means for varying the speed of said discharges in accordance with the light and shade densities of said object, the intensity of said discharges remaining constant at all times.

3. In a radio receiving system, a receiving apparatus comprising a plurality of electrodes arranged to form a field of view, a constant energy supply for producing a constant intensity discharge at all times between said electrodes and in a single plane, a field winding producing a field in which said discharge is positioned, an energy supply for said winding, and means for varying said last mentioned energy supply in accordance with the light and shade densities of an image or object, said means including a feed back circuit connected to said field winding.

4. In a radio receiving system, means for receiving electrical currents corresponding to light and shade densities of an object, a plurality of electrode rails, a source of energy having a constant value producing a constant intensity discharge at all times between said rails, and in a single plane, a field winding for producing a field in which said electrode rails are positioned, said :iield being supplied from a constant source of energy, and means for varying the intensity of said field in accordance with the light and shade densities of an image or object to be reproduced.

5. The method of television reception of the image of a scanned object visible with a constant intensity moving electrical discharge movable in a single plane in a magnetic field comprising varying the speed of said moving discharge by varying the strength of said magnetic field in accordance with the light and shade densities of said scanned object to produce dark elements by increasing the speed and producing light elements by decreasing the speed of said discharge in proper proportionalities, the absolute intensity of said discharge remaining constant at all times.

6. The method of television transmission and reception of images of a scanned object with visible moving electrical discharges having constant intensities at all times, comprising scanning said object, obtaining electrical currents characterized by the light and shade densities of said object scanned with one constant intensity electrical discharge and varying the speed of another moving electrical discharge having a constant intensity in accordance with the currents produced with the first discharge while scanning, the absolute intensity of each of said discharges being maintained constant.

7. In a television receiving system, means for producing a primary constant intensity light source, said light source comprising an ionized path, means tending to move said light source at a constant speed over a certain area in a single plane, and means for varying the speed of said source per unit area in accordance with the iight and shade variations of an image to be reproduced while maintaining said light source at a constant absolute intensity at all times.

ALEXANDER MCLEAN NICOLSON.

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