US2091152A - Oscillograph - Google Patents

Description

Aug. 24, l193.7. .1. T. M. MALPICA OSCILLOGRAPH Filed June 17, 1936 3 Sheets-Sheet l Figi.

EL? a r H Inventor: Jose' T Mlreles Malp|caby 7VZ Ag His Attorney.

Aug. 24, 1937. J. T. M. MALPlc OSC ILLOGRAPH 3 Sheets-Sheet 2 Filed June 1'?, 1936 Inventor:

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Aug. 24, 1 T M MALPICA OSGILLOGRAPH Filed June 17, 1956 3 Sheets-Sheet 3 ITM/emisor A Jose' T. Mreles Malpica/ by 751W 49M is Attorney.'

Patented Aug. 24, i537 oscILLoGaA'rn Jos T. Mreles Malpica, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 17, 1936, Serial No. 85,812

12 Claims.

My invention relates to recording apparatus and concerns particularly oscillographs of the Wpc employing a deflectible beam of radiant energy to produce the record curve.

The principal object of my invention is to provide an arrangement for producing with a cathode ray oscillograph clearly-visible and well-defined permanent record curves of very rapidly varying phenomena, particularly phenomena which are very short in duration and ncnrecurrent.

It is an object of my invention to provide an arrangement for causing the deflections traced on a fluorescent screen to record directly upon a sensitive lm instead of being photographed.

It is an object of my invention to provide a light concentrator for sensitive film oscillographs.

It is also an object of my invention to arrange a cathode ray oscillograph to make relatively long records.

Other and further objects and advantages will become apparent as the description proceeds.

For the observation of extremely high-speed phenomena, cathode ray Oscilloscopes are known in which a beam of radiant energy, impinging on a uorescent screen to make the end of the beam visible, is electrostatically or electromagnetically deflected along transverse axes to trace a curve on the fluorescent screen, which, by

persistence of vision. appears to the eye as a continuous curve. In the case of regular wave forms of alternating quantities or in the case of regularly recurring transients, a record of the phenomena may be made by photographing the curve traced on the fluorescent screen as in photographing any object. However, in the case of isolated transients, which cause the beam to trace the curve on the screen only once, insufilcient light is produced for photography. In carrying out my invention in its preferred form, I do not photograph the fluorescent screen with a camera in the ordinary way but I cause the light spots on the screen to affect the photographic film directly by passing the film as close as possible to the fluorescent screen in order to increase the effect upon the film. In order to prevent either blurring of the film or complete loss of the image by diffusion of the light from the light spots, I may provide a suitable condenser or light concentrator between the wall of the cathode ray tube and the photographic film.

The invention will be understood more readily from the following detailed description when considered in connection with the accompanying drawings and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. In the drawings, Fig. 1 is an end elevation, partially in section, of a film-driving mechanism for a cathode ray oscillograph embodying my in- 5 vention, the cathode ray tube and a portion of the film being removed to present a view' into the film-driving mechanism; Fig. 2 is a side'elevation, partially in section, of the mechanismof Fig. 1, together with the end portion of a cathode` 1C ray tube with a light-concentrating shield; Fig. 3

is a schematic diagram showing the beam deflection in a cathode ray oscillograph; Fig. 4 is a fragmentary enlarged sectional view of a. por tion of the apparatus of Fig. 2 showing a section cut by a plane extending lengthwise through the light-concentrating shield perpendicular to the plane of the paper in Fig. 2; Fig. 5 is an enlargement of a portion of Fig. 2 showing a section of the part of the light shield immediately 2( surrounding the light concentrator; Fig. 6 represents a modification of the apparatus of Fig. 5; Fig. 7 is a graph illustrating a form of curve which may be produced with the apparatus; Fig.

8 is a diagram showing a portion of the glass wall 25 of a cathode ray tube and a fluorescent screen and explaining the diffusion of light from a point on the screen; Fig. 9 is another diagram showing graphically the diffusion and variation in strength of light emanating from a bright spot 3 on the screen; Fig. 10 is a graph illustrating the effect of diffusion in tracing a sine wave; Fig. 11

is a fragmentary sectional view (corresponding to Fig. 5) of a light shield with the openings filled by quartz rods, the section cutting plane 3 being parallel with the direction of travel of the film as in Figs. 2, 5, and 6 Fig. 12 is a fragmentary sectional view of a modified arrangement with lenses embedded in the end Wall of a cathode ray tube, the section cutting plane being per- 4 pendicular to the direction travel of the film as in Fig. 4; Fig. 13 is a fragmentary sectional view of a modified arrangement with quartz tubes inserted in the end wall of the cathode ray tube, the section cutting plane being perpendicular to 4 the direction of travel of the film as in Figs. 4 and 12; Fig. 14 is a fragmentary view of a modified light shield, locking toward the end of the cathode ray tube, for use with stationary instead n of moving films; Fig. 15 is a modification of the arrangement of Fig. 16 with a fabricated structure and Fig. 16 is a` sectional view of a modified construction having a light shield integral with the end wall of a tube. Like reference characg ters are utilized in the drawings to designate like parts throughout.

As is well known, cathode ray oscilloscope tubes are provided with suitable arrangements for generating the rays and focusing them to form a narrow beam. Since my invention does not relate to these arrangements, they need not be illustrated or described. As illustrated in Fig. 3, such a tube I I is provided with suitable means, such as an electromagnetic coil or a pair of electrostatic deflection plates I2, for deflecting a beam between two limits, such as I3 and I4. The end wall I5, which is usually circular, is made convex and lined with a fluorescent screen I5 which produces a momentary spot of light at the points Where the cathode rays impinge. The deflection plates I2 alone deflect the beam within arplane parallel to the paper and substantially intersecting the tube II in accordance with variations in a voltage to be measured which is applied between the plates I2. For. providing a timing axis and deecting beam transversely. a second pair of defiecting plates I'I may be provided in Oscilloscopes in which a curve traced on the fiuorescent screen I6 is to be viewed directly by the human eye. When the phenomenon observed is recurrent and retraces the same curve indefinitely, a record thereof may be obtained by photographing it since, by continued exposure of the photographic film to the curve, enough light may be obtained to affect the film.

However, in accordance with my invention, since I desire to obtain records of nonrecurrent phenomena, the momentary traces of which on the fiuorescent screen cannot ordinarily be successfully photographed, I place a sensitized chart or film I8 against the end wall I5 having the fiuorescent screen I6. Instead of employing the deflection plates I'I to obtain a timing axis for the curve, I cause the film I8, itself, to be moved in a direction perpendicular to the plane of the paper in Figs. 3 and 4 and I permit the cathode ray beam to deflect only in a single plane under the influence of the deflection plates I2.

In order to avoid fogging the film, I provide a shield I9 covering the entire end I5 of the tube II, except for openings in the plane of deflection I3-I4 of the cathode ray beam. For the sake of avoiding blurring or dimming of the record curve by diffusion of the light from the fluorescent screen I6, I provide a light concentrator in the form of a row of perforations 20 in the shield I9. The perforations 20 have their axes perpendicular to the surfaces of the fluorescent screen I6, the tube end wall I5, and the shield I9, and all the axes lie within the plane of defiection I3-I4 of the cathode ray beam. If desired, an `insert 2I, shown enlarged in transverse section in Fig. 5, may be provided in the shield I9 for carrying the openings 20. The insert 2| is of opaque material, the surfaces of the perforations 20 are blackened, and preferably the inner surface of the shield IS is also blackened to minimize stray light.

Since the shield I9 is provided with a row of perforations rather than a continuous slit for the passage of the light rays affecting the sensitive film I8, any curve produced by the oscillograph will appear as a series of dots as illustrated in Fig. 7. This circumstance permits me to provide a convenient way for providing scale divisions on a plain film as the record is being produced. The perforations 20 are properly spaced to product unit graduations and every tenth perforation is of greater diameter to produce larger light spots 22, representing graduations in multiples of ten. Furthermore, the small perforations on either side of the larger perforations are omitted to define a zero line through the larger light spots 23 separated from the rest of the curve by short gaps on either side of the zero line. If desired, either the light spots 22 or 23 may also be made distinguishable by employing openings of a different shape or character.

Any suitable means may be provided for causing the sensitive film I8 to pass along the lightconcentrating shield I8. For example, the film may be carried by two spools 24 and 25 (Figs. 1 and 2), being wound upon the spool 24 and unwound from the spool 25 by the motor 26, driving the spool 24 through suitable gearing 21. The spools 24 and 25 are suitably iournaled within a lightproof box 28 wholly surrounding the end portion of the cathode ray tube I I. A strip spring 29 may be provided for keeping the film I8 compactly rolled on the spools 24 and 25.

The accumulation of static charges by the film I8 is prevented by providing a metallic shield 3l)v electrically connected to the metallic housing 28. A felt cushion 3| and phosphor bronze springs 32 serve to hold the film I8 closely but resiliently against the light-concentrating shield I9 over the perforation 20.

Fig. 8, showing in section, greatly`enlarged,. a portion of the tube end wall I5 and the fluorescent screen I6, illustrates the effect of the glass wall I5 in causing diffusion of the light emitted from a single point 33 on the surface of the fluorescent screen I6 where the light has been generated by a cathodgray impinging upon the screen I6. Owing to refraction of the light rays upon emergence from the glass wall I5, still greater diffusion takes place outside the wall I5 of the tube. In actual practice, the deflecting beam of the cathode ray tube consists of a bundle of cathode rays producing a light spot 34 of finite area on the fluorescent screen I6 (Fig. 9), and the area of this light spot becomes considerably enlarged upon emergence from the glass wall I5.

The curve 35 represents by its distance from the outer surface 35 of the wall I5 the relative intensity of light at various points on the surface 36. At the surface 36, the light spot becomes progressively dimmer toward the edges, owing to greater deviation from normal of the light rays.

In consequence, although a cathode ray beam may actually follow a sharp curve, such as the curve 3l (Fig. 10) a light-sensitive film placed against the surface 36 (Fig. 9) would have a broadly and dimly illuminated band 38, becoming dimmer toward the edges, so that the record curve actually recorded would be both indistinct and lacking definiteness of position. Such disadvantages are overcome, however, by the interposition of my light-concentrating shield I9. Since the perforations 20 are all perpendicular or normal to the fluorescent screen I6 and the perforations are of appreciable length relative to their diameters, only the relatively powerful normally energizing rays are permitted to strike the lm I8 and a distinct definite curve is produced as illustrated in Fig. 7. The perforations 20 provide light paths perpendicular to the screen I6 and so transmit only effective light rays perpendicular to the screen I6 and the end wall of the tube.

For the sake of illustration, I have described my invention in connection with cathode ray tubes producing electron emissions impinging upon a fiuorescent screen to generate light and other rays, such as actinic rays, to which a photographic type of lm is sensitive. It will be understood, however, that my invention is not limited to this precise arrangement and obviously includes'tubes producing other types of radiant energythan cathode rays as well as such tubes 5 or other types of oscillographs in which no uorescent screen is used and the radiation falls directly upon a suitable sensitive chart or film.

I have also obtained successful records employing a relatively thin perforated shield but l obviously greater 'curve sharpness is obtainable with the relatively thick shield I9 since any danger of divergent light rays passing through the shield is eliminated. As an alternative to the arrangement hereinbefore described and illusl trated in detail in Fig. 5, under certain circumstances in order to obtain increased brilliancy. I may employ a light shield having a row of conical openings 39 (as illustrated in Fig. 6) with polished internal walls, the smaller diameter ends 40 of the openings being toward the lm. Such openings serve as reflecting condensers, being substantially equivalent to very deep parabolic mirrors with their apices cut off.

If desired, cylindrical rods of quartz 4I or other material having a high transmission and suitable index of refraction may be tted into the openings 20 of the arrangement of Figs. 2, 4, and 5 to serve as light condensers as illustrated in Fig. 11. The rods 4I may be inserted directly in the shield I9 instead of employing the insert 2 I Condensing lenses 42 might, of course, also be employed, preferably embedded in the surface of the glass wall I5 as illustrated in Fig. 12. By embedding the quartz rods 4I in the glass wall I5, as shown in Fig. 13, a direct non-diffusing path would be provided for the light rays emanat# ing from the fluorescent screen IS.

In case the oscillograph is to be operated with a stationary sensitive film and the timing and measuring axes are obtained by deflecting the beam along transverse paths, the entire working portion of the shield I9 is provided with perforations 2D or with some other form of light transmitting paths perpendicular to its surface. To 45 permit putting the perforations as close together as possible, they may be staggered With centers at the intersection of GO-degree lines as shown in Fig. 14, which represents a fragment of an end view of a modied form of shield I9.

If desired the effective spacing between the light transmitting paths in the shield I9' may be decreased by utilizing hexagonal openings or hexagonal-prism light transmitters placed immediately adjacent as illustrated in Fig. 15. Fig.

55 15 is a fragmentary end view of the shield I9 magnified to show more in detail that light transmitting openings 42 are formed by joining opaque sheet material to produce hexagonal-prismshaped spaces. Such spaces may, if desired, be lled with a suitable light transmitting substance such as a transparent resin which may be melted and poured into the openings and then allowed to cool and harden. A suitable backing plate will, of course, be temporarily used to prevent the liquid from running out of the openings.

' Among the resins which may be used for this purpose are a synthetic resin manufactured by Rohm & Haas Co., Inc., under the trade name Plexiglass and a resin manufactured by the Du Pont de Nemours Co. under the trade na-rne ,Pontalite which I believe to be polymeric esters, largely polymethyl methacrylate. In using such material the liquid monomer, methyl methacrylate may be poured into the openings 42 5 and then polymerized and solidified by heat. I

understand methyl methacrylate to have this formula:

In case the openings 42 are lled, the shield I9' may form a part of the end wall I5 of the tube II and the iiuorescent screen I6 may form a coating on the back of the shield I9'. It will be understood that the shield will be suitably sealed to the remainder of the tube II to form an air-tight envelope as illustrated in Fig. 16.

Instead of lling up the openings in a grid such as shown in Fig. 15, the light shield may be made up by cementing together hexagonal prisms of glass, quartz, transparent resin or other suitable substance to produce a formation such as that appearing in Fig. 15. The side surfaces of the prisms may be sandblasted, etched or otherwise made opaque or an opaque cement may be employed for joining the prisms.

For slow-speed oscillegraphy, the fluorescent screen may be composed of zink silicate but, for high-speed work in order to avoid leaving a blur on the rapidly traveling iilm, I prefer to use a material such as calcium tungstate which is fast acting and does not leave an afterglow.

I have herein shown and particularly described certain embodiments of my invention and certain methods of operation embraced therein for the purpose of explaining its principle and showing its application but it Will be obvious to those skilled in the art that many modications and variations are possible and I aim, therefore, to cover all such modifications and variations as fall within the scope of my invention which is defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A cathode ray oscillograph comprising an evacuated envelope with a uorescent screen on a wall of said envelope, means for deiiecting a cathode ray along a path across said screen in accordance with variations in a measured quantity, a sensitized chart, means for passing said chart along said iiuorescent screen transverse to the path of deection of the cathode ray, a relatively thick opaque shield interposed between said iiuorescent screen and said chart with a row of openings each perpendicular to said screen, and in the path of the cathode ray, and means for shielding said chart from any actinic rays exc'ept such as pass through said openings in said shield.

2. An oscillograph comprising in combination, a fluorescent screen, means for deflecting a beam of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart, means for passing said chart along said iluorescent screen, and a relatively thick opaque shield interposed between said uorescent screen and said chart with a row of openings, each perpendicular to said screen.

3.- An oscillograph comprising in combination, a uorescent screen, means for deflecting a beam of radiant energy across said screen, a sensitized chart, means for passing said chart along said fluorescent screen, and an opaque shield interposed between said fluorescent screen and said chart, said screen having a row of openings in the line of motion of said beam.

4. An oscillograph comprising in combination, means for producing a beam of radiant energy,

means for defiecting said beam substantially in chart parallel to itself in a direction transverse to said plane, and an opaque shield adjacent said 5 chart interposed between said chart and said beam-producing means, said shield having a row /of openings therein with centers in the plane of deflection of said beam.

5. An oscillograph comprising in combination, means for producing a beam of radiant energy, means for deflectlng said beam substantially in a plane, a sensitized chart having a surface transverse to said plane, means for moving said chart parallel to itself in a direction transverse to said l5 plane, and an opaque shield adjacent said chart interposed between said chart and said beamproducing means, said shield having a row of openings therein with centers in the plane of deilection of said beam, said openings being placed at uniform spacings, and including openings diil'erentiated from the remaining openings and spaced at multiples of the spacings of the remaining openings.

6. An oscillograph comprising in combination, a fluorescent screen, means for deiiecting a beam of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart, means for passing said chart along said fluorescent screen, and a relatively thick opaque shield interposed between said uorescent screen and said chart with a row of openings each perpendicular to said screen, said openings being conical with their smaller diameters toward said chart and having their interiors polished.

7. An oscillograph comprising in combination, a fluorescent screen, means fordefiecting a beam of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart adjacent said screen and a relatively thick shield interposed between said fluorescent screen and said chart with a plurality of openings therein perpendicular to said screen.

8. An oscillograph comprising in combination,

a fluorescent screen, means for deiiecting a beam of radiant energy across saidscreen in accordance with variations in a measured quantity, a

sensitized chart adjacent said screen and a rela# of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart adjacent said screen, and a member interposed between said iiuorescent screen and said chart with a plurality oi light transmitting paths having boundaries for diverting light rays not perpendicular to said screen.

l0. An oscillograph comprising in combination a iiuorescent screen, means for deiiecting a beam of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart adjacent said screen, and a member interposed between said fiuorescent screen and said chart with a plurality of lightconcentrating devices providing light transmitting paths perpendicular to said screen.

11. An oscillograph comprising in combination a fluorescent screen, means for deilecting a beam of radiant energy across said screen in accordance with variations in a measured quantity, a sensitized chart adjacent said screen, and a member interposed between said iluorescent 'screen and said chart with a plurality of quartz rods therein perpendicular to said screen.

12. In a radiant-energy-beam oscillograph, means for producing a radiant-energy-beam deflectible within a plane, and a light-concentrating shield for the oscillograph comprising an opaque plate adapted to cover the beam-receiving end of the oscillograph and having a row of openings therein with axes within said plane and perpendicular to said plate.

JOSE T. MIRELES MALPICA.

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