May 7, 1945- M. R. MILLER 2,399,754

t CATHODE RAY APPARATUS Filed Jari. 9, 1945 Patented ay 7, 1946 2,399,754 carnoDE-RAY APrARA'rUs Merton R. Miller, Evanston, n1., assignmto Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application January 9, 1943, Serial No. 471,906

(Cl. S15-e30) 8 Claims.

This invention relates to a cathode ray apparatus, and more particularly to an apparatus for maintaining a constant beam intensity of cathode rays with varying sizes f patterns.

In many types of oscillographs a change in the dimensions of the cathode ray pattern results in a decrease or increase in the degree of illumination, depending upon whether the dimensions are increased or decreased and therefore an adjustment must be made in the beam intensity to obtain uniform illumination.

An object of the present invention is to provide effective means for varying the cathode ray intensity as the dimensions of the pattern are varied.

In accordance with one embodiment of the invention a portion of the energy provided for del is varied. I

Referring to the drawing a cathode ray oscillograph is shown including a cathode ray tube 5 provided with a fluorescent screen having a band electrode 6 which may be energized positively relative to a cathode 1 by means of a full wave rectier 8 connected to a transformer 9. This rectifier may also provide anode current for tubes II, I2?, I3 and I4 which` are preferably of the tetrode type.

of rectifier 22 is connected to the modulating grid 2l through a pair of resistances 23 and 2li and the cathode is supplied with energy from this circuit through potentiometer resistances 25 and xed resistances 21, 28 and 29. The circuit thus far described is conventional and therefore greater detail of description is'not deemed necessary. In such a circuit the intensity of the beam is adjusted manually by adjusting the potential on the modulating grid through manipulation of the potentiometer resistance 25 or by varying the resistance through a switch arm 3l. Hence, if the beam current is adjusted to a value giving a satisfactory pattern intensity for a small pattern, the pattern intensity will be 'diminished if the pattern is expanded and be too dim. Similarly, if the intensity is set satisfactorily for a large pattern,'the intensity may increase to a value which will burn or seriously decrease the life of the fluorescent phosphor screen when the pattern is contracted. It is, therefore, evident that an increased cathode ray tube life, as

well as increased facility of operation may be'had if the beam'current is controlled automatically the potential on the deflector plates.

A pair of deflector plates vI5 of the cathode ray tube are connected to the anode circuits of tubes II and I2 to impart a vertical deflection along the Y-axis to the cathode ray beam, the grid circuit of tube II being connected to a source of energy to be analyzed. "Similarly, deflector plates I6 are connected to the anode circuits of tubes I3 and le to impart a horizontal deflection along the X-axis of the cathode ray beam, the grid circuit of tube I3 being connected to a source of sweep current.

The cathode ray tube is also provided with a pair of accelerating-electrodes I1 and It and a focusing electrode I9. Energy is supplied to the focusing electrode I9 as well as to a grid or modulating electrode .ZI through a rectier 22 also connected to transformer 9. The anode' circuit so as to maintain constant pattern intensity independent of pattern expansion.

This is accomplished in accordance with the present invention by supplying a potential to the modulating grid which varies in accordance with For this purpose a rectifier 36 is provided having two anodes 31 and 38, one of which is connected through a condenser 39 and resistance 4I to one of the deiiector plates I6, and the other is connected through condenser 42 and resistance 63 to one of the deflector plates I5. The anodes 31 and 38 are bridged by a center tapped resistance B4 serving as the negative output point of the rectiiier. The cathodes 45 of the rectier are connected in parallel and the output of the4 rectifier is connected to a resistance 46 shunted by a condenser 41 in the modulating grid circuit of the cathode ray tube. Thus portions of the voltages on the horizontal and vertical deector plates are rectified, smoothed by condenser 41 and appliedk to the modulating grid 2l to make it more positive for higher deflector plate voltages and less'positive for lower deector plate voltages. The degree of compensation may be controlled by' the values of the resistances M and 43 in the leads to the horizontal and vertical leads.

The circuit just described gives an average compensation for all frequencies to keep the light intensity of the pattern on the screenuniform as the size of the pattern is varied.

While but one embodiment of the invention has been described and illustrated, it will be evident that many changes and modiiications may be made therein without departing from the spirit y in accordance with the size of the pattern.

2. A cathode ray. apparatus comprising a cathode ray tube having deiiector electrodes and a modulating electrode, means for applying a defiecting voltage to said deilector electrode, means for applying a uni-directional voltage to said modulating electrode, a rectifier, means for applying an average portion of said deector voltage to said rectier, and means for applying rectified uni-directional voltage to said modulating electrode.

3.' A cathode ray apparatus comprising a cathode ray tube having deflector electrodes and a modulating electrode, means for applying a deiiecting voltage to said delector-electrode, means for applying a voltage to said modulating electrode, a rectifier, means for applying a portion of said deector voltage to said rectiiier, and means for applying a unidirectional average value of said rectified voltage to said modulating electrode.

4. A cathode ray apparatus comprising a cathode ray tube having deector electrodes and a modulating electrode, means for applying a deiiecting voltage to said deflector electrode, means for applying a Voltage'to said modulating electrode, a rectifier, means for applying a portion of said deiiector voltage to said rectifier, and means for applying a voltage proportional to the average value of said deiiecting voltage from said rectifier to said modulating electrode. I

5. A cathode ray apparatus comprising a cathode ray tube having deector electrodes and a modulating electrode, a rectifier having a pair' of anode's, a condenser connecting each of said rec-- plyinga voltage to said rectifier proportional to a voltage applied to said deiiector electrodes, and means for applying an average uni-directional rectified voltage to said modulating electrode.

7. A cathode ray apparatus comprising a cathode ray tube having horizontal and vertical defiectorelectrodes and a modulating electrode, a full wave rectiiier having two sets of rectifying electrodes, a, condenser connecting,l one of said horizontal deector electrodes to arectier electrode, a condenser connecting one of said vertical deiiector plates to a rectifier electrode, a

Acenter tapped resistance bridging said rectier electrodes to provide a rectied voltage outlet. and means for applying said rectified voltage to said modulating electrode.

8. A cathode ray apparatus comprising a cathode ray tube having horizontal and vertical defiector electrodes and a modulating electrode, a full wave rectiner having two sets of rectifying electrodes, a v'condenser connecting one of said horizontaldeiiector electrodes with one of said rectiner electrodes. a condenser connecting one of said vertical detlector electrodes with another of said rectiiier electrodes, a center tapped resistance bridging said rectifier electrodes to provide a, rectified voltage outlet, a resistance and condenser in parallel connected to said modulating grid, and means for applying a rectiiied voltage from said rectified voltage outlet to 'said parallel resistance and condenser of the modulating electrode.

` MERTON R. MILLER.