US2199066A - Electro-optical method and apparatus - Google Patents

Description

April 30, 1940. P. BERNsTElN ELECTRO-OPTICAL METHOD AND APPARATUS Filed Feb. 2l, 1959 .mwN

INVENTOR L Aww/, w,

ATTORNEY Patented'v y.

PATENT ""oFFlca Emerso-or'rlcAnMarnop AND APPARATUS Philip Bernstein, Brooklyn, N. Y., assignor to Press Wireless, Inc., Chicago, lll., a corporation of Delaware Application February 21, 1939, Serial No. 25"!,620

8 Claims.

This invention relates to electro-optical systems and more particularlyto systems for controlling the frequency and amplitude of alternating current signalling waves. v

A principal object of the invention is to provide an improved form of frequency doubling and power level control systems.

Another principal object is to provide a novel form of level control forwave signalling systems l generally.

A feature of the invention` relates to an improved method of converting electrical signalling voltages of one frequency to a voltage of a different frequency by using an oscillating cathodel ray beam.

Another feature relates to a frequency doubling system employing an oscillating cathoderay beam having means to limit the amplitude of the doubled frequency.

A further feature relates to a system of electrooptical conversion employing anoscillatory deilectable cathode-ray beam wherein the level of the converted impulses is rendered substantially independent of the amplitude of the beam oscillation.

A further feature relates to a method of employing conventional cathode-ray tube apparatus as a frequency converter in conjunction` with a graded light filter to compensate for uneq'ual amplitudes of oscillation of the cathode-ray beam.

A still further feature relates to the novel organization, arrangement and relativelocation andinterconnection of parts which constitute an improved signal converter.

Other features and advantages noi'l specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.4

In the electrical communication arts, it is often highly desirable to convert a signal WaveV of a given frequency into a wave of a multiple or harmonic frequency, or into a wave wherein the successive wave portions are displaced by regularly recurrent periods. It is also advantageous in such systems to be able to limit the power output of the system by providing a suitable form of A. vV. C. or level control. These features are especiallyrusefulin radio communication systems where the effects of level variations in the carrier are to be overcome or compensated for. While therefore the present invention is susceptible of application to any signalling system wherein carrier frequency waves are employed, it is particularly useful in overcoming the effects of (Cl. Z50-20) fading, by providing an improved form of level control for the received signals.

In the drawing,

Fig. 1 is a schematic diagram of a portion of a wave signalling system embodying features of the invention.

Fig. 21s an end view of the cathode-ray tubeof Fig. l.

Referring to the drawing which shows by Way of example one preferred embodiment of the invention,'only those parts of a typical radio signalling system are shown to enable vthe inventive concept to be fully understood, and parts and lconnections which are well-kown to those familiar with the radio art are omitted. The numeral I represents any well-known form of cathode-ray tube whether of the highly evacuated or gaslled type. n provided in the usual manner with an electron gun 3 of known construction for developing a focussed beam of electrons, whereby the screen.A end of the tube is impinged upon by the focussed beam. Associated with the gun 2 are the usual deflecting systems comprising for example a pair of horizontal deflector plates 4, 5, and a pair of vertical defiector plates 6; l. The enlarged flattened end of the tube' which is usually referred to as the screen is provided on its inner surface with any Well-known form of coating Which fluoresces under impact of the cathode-ray beam from gun 3. Any well-known form of second anode may be employed to accelerate the beam electrons from the gun toward the screen, and if desired the funnel-shaped part of the tube may have its interior surface coated with conducting material for this purpose. The fluorescent screen may be either of the floating typeor it may be electrically connected to a suitable potential as is well-known in the cathode-ray tube art.

The signal to be converted is applied to the inputterminals 8, 9. Terminal 8 is connected directly to deflector plate 1, and terminal 9 is connected to deflector plate 6 through a -beam biassing network consisting of the series resistor I0 which is shunted by the by-pass condenser I I, and the two resistors I2, I3. The biassing battery Il is also adjustably connected to resistor IIJ to bias the cathode-ray beam so that normally it strikes approximately the central part of the screen. Likewise the plates 4, 5, are connected to a biassing network comprising the resistors I4, I5, I6, and the biassing battery I1 adjustably connected to resistance I4. By means of the two biassing networks therefore, the cathode-ray beam normally stays in one position which is 'I'he neck portion 2 of the tube is I approximately on the axis of the tube, although as will be obvious, the normal position may be any other desired position. Consequently, when a signalling wave, such for example as an alternating current carrier wave, is impressed upon l terminals 8, 8, the beam is caused to oscillate so that it traces a linear path along a central vertical line of the tube screen.

Mounted adjacent the screen end of tube I, along the vertical central portion thereof as shown in Fig. 2, is a light filter or light wedge I8 of graded transparency from its lower edge I8 to its upper edge 20. Also mounted in vertical alignment with member I8 is an opaque strip 2i, the upper edge 22 of which is slightly spaced from the adjacent edge I3 of strip I8, thus deflning a gap 23 of a gap-width approximately the same as the vertical dimension of the cathode-ray beam where it strikes the screen. If desired, the strips I8 and 2| may be cemented or otherwise fas-` tened to the end of tube I or in certain cases they may be in the form of coatings or the. glass of the tube itself may be treated to provide the requisite transparency or opaqueness.

Mounted in optical alignment with the gap 23 is a lens system 24 which images upon a light sensitive cell 25, the light of the iluorescent screen which passes through gap 23. The cell 25 is provided with any suitable coupling circuit 26 whereby it is coupled to the amplifier tube 21. Also mounted in optical alignment with the strip I8 is a lens system 28 which images the light passed by the strip I8 on another light sensitive cell 29 which is provided with a suitable coupling circuit 30 for coupling to the amplifier tube 3|. The output of amplier tube 3| is applied through a conventional resistance coupling arrangement as shown, to the rectier tube 32 and the rectied output of tube 32 produces a corresponding potential drop across the resistor 33. Resistor 33 is connected in series with another resistor 3l and a suitable grid bias battery to the grid 35 of tube 21 the resistor 33 is a common load resistor for the cathodes of tube 32 and for the control grid 35 of tube 21 whereby the gainof course, that suitable potentials are applied to,

the various electrodes of tube 2,1. For example the control-grid 'may be biassed by the biassing arrangement Il to a potential of approximately -3 volts; the grids 38 and 39 may be connected to a positive potential of the order of 100 volts; the anode 42 may be connected to a positive potential of the o'rder of 250 volts although it will be understood that these voltages are merely typical. With this arrangement therefore, the

'iiuorescent light signals which are picked up by the cell 25 are converted into potentials which are impressed on grid 31 and result in corresponding amplified voltages across the output resistor 33 :I'he level or gain of the Voutput of tube 21 is controlled by the negative potential on grid 35 which in turn is determined by the voltage drop across resistor 33. Aspointed out above. the voltage drop across resistor 33 is determined by the signal picked up by the iight sensitive cell 23. It will be obvious therefore. that the gain of the tube 21 will depend 'upon the amplitude o! oscillation of the cathode-ray beam. Thus, if the beam has its minimum amplitude,v it does not go beyond the relatively dense portion of the strip I8 with the result that a predetermined negative potential is applied to grid 35. As the amplitude of the cathode-ray beam oscillation increases, a correspondingly greater amount o! light is passed by the strip I8 resulting in a corresponding decrease in the negative grid biassing potential on the gain control grid 35.

So long as the amplitude of the cathode-ray beam remains constant, the output level of tube 21 likewise remains constant. However, each time that the beam traverses the gap 23, an impulse is produced in the output of tube 21. Consequently, for each complete cycle of input signal applied to terminals 8` and 8, the cathode-ray beam traverses the gap 23 twice, thus doubling the frequency of the signal in the output of tube 21 as compared with the frequency of the signal impressed on terminals 8 and 8.

Since the cathode-ray beam is not subjected to any intensity control, the luminescent spot remains of substantially constant intensity. However, when the amplitude of oscillation of the beam is increased, the velocity of the beam across the gap 23 is likewise increased which reduces the duration of the impulses in the output circuit of tube 21 with a corresponding decrease in the power output of the tube. On the other hand, for smaller amplitudes the power output of tube 21 would tend to correspondingly increase. 'Ihe purpose of the graded density strip I8 and the cell 29 together with the tubes 3I and 32 is to compensate for this tendency to change in level of the output of amplifier 21. The density lter I8 as above described is so constructed as to efiect a variation in light intensity to cell 23 which is in direct relation to the amplitude of the beam oscillation. -However, the greater this amplitude of oscillation, the greater is the amount of current rectified by tube 32 which acts as above described as a "volume expander for the output of tube 21, by decreasing the negative bias on 35 in direct relation to the amplitude of the cathode-ray beam oscillation and correspondingly increasing the gain and power output of tube 21. By properly designing the density iilter as regards its density gradations from one end to the other, a linear power output can be produced for the entire system.- Consequently, the output of amplifier -21 can then be set at any desired value and will remain. substantially xed regardless of the variation in level of the waves applied to terminals 8 and 9. l

While one specific embodiment of the invention has been disclosed herein, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention. For example,

while the cathode-ray beam is shown as being.'

oscillated by electrostatic deector means, it will y be understood that the beam may be deilected by magnetic means or by a combination of magnetic and electrostatic means. For example, the horizontal plates l and 5 may be replaced by a suitable electromagnet for biassing the beam to its central position and the vertical deflection of the beam under control of the signals may be done by the electrostatic plates 6 and 1. Fur- 1| 'the beam, it will be understood of course, that any well-known form of modulatingy electrode such as a grid may be provided in connection with the electron gun so as to modulate the intensity of the beam. Thus, for example, a carrier current may be applied to the terminals-8, 9, and modulating potential signals may be applied to the control-grid or modulating-grid in the tube 2. Furthermore, while the disclosure relates to the doubling of an input frequency by using one aperture, a plurality of apertures may be employed to produce any harmonic of the input frequency. Likewise, while the description is based upon a linear traverse of the Acathoderay beam, it will be understood that the beam may be caused to traverse any fixed path, e. g., circular or elliptical or any other shape path well-known in the cathode-ray art so long as the beam traverses one or more apertures and is provided with a graded density member for producing a compensating signal in proportion to the amplitude of the beam movement.`

What I claim is:

l. The metliod of wave signalling systems which includes the steps of electro-optically converting electric signal waves into other electric signal waves of a multiple frequency, and electrooptically producing under control of the first waves a level control signal for the converted waves.

2. In a wave signalling system, means to de velop a deflectable beam, electro-optical means for producing electric signals under control of said beam, and electro-optical means for producing level control signals for said electric signals.

3. In a wave signalling system, means to develop a beam of electrons, means to oscillate said beam under control of input signals, means controlled by said beamv for producing electric signais of a frequency different from said input signals, and means controlled by the amplitude of the beam oscillations'for controlling the level of the second-mentioned signals.

4. A wave signalling system according to claim 3 in which the means for producing said signals of different frequency includes a fluorescent screen upon which the beam impinges and an aperture and light sensitive cell, the cell being energized by the fluorescence of said screen through said aperture.

5. A wave signallingsystem according to claim 3 in which the means for controlling the level v of the said second signals includes a graded density member and a light sensitive cell, the cell being mounted so as to be energized by said beam through said graded density member.

6. A frequency converter for wave signals which includes a cathode-ray tube having means to develop a cathode-ray beam and means to defiect the beam in accordance with input signals; a fluorescent screen upon which the beam impinges; a light sensitive cell mounted so as to be energized only when a predetermined area of said screen is fluorescent; another light sensitive cell; and means between said other cell and screen for energizing said other cell in proportion to the amplitude of thebeam oscillations.

7. A frequency converter and power limiter for wave signalling systems comprising a cathoderay tube, means to deflect the cathode-ray beam along a predetermined path under control of input signals, electro-optical means controlled by the beam for producing output signals having a frequency which is a multiple ofthe input signals,

electro-optical means controlled by the beam amplitude for rproducing level control signals, an amplifier for said output signals, and a gain `control circuit for controlling the level of said amplifier, said gain control circuit being controlled by said level control signals.

8. A frequency multiplier and power limiting device for wave signalling systems comprising a cathode-ray tube having a fluorescent screen. a

-light aperture adjacent said screen, a graded density member also mounted adjacent said screen, and a pair of light sensitive cells, one in optical alignment with the said aperture and the other in optical alignment with said graded density member.

PHILIP BERNSTEIN.

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