Патент USA US2114610код для вставки
April 19, 1938. ‘ ' K. SCHLESINGE'R 2,114,610 TELEVISION TUBE Filed July 21, 1933 7/7Ver7 for: 2,114,610 Patented Apr. 19, 1938 UNITED STA ES PATENT OFFICE 2,114,610 TELEVISION TUBE Kurt Schlesinger, Berlin, Germany Application July 21, 1933, Serial No. 681,466 In Germany July 25, 1932 5 Claims. (Cl. 250—27.5) The object of the invention is a method of pro ducing television images of large size with cath ode ray tubes. It has been found that in the attempt to in 5 crease the size of a television image there is very quickly reached with a given number of lines per image a de?ned limit, above which the image impression, with a given distance of the eye of the observer, noticeably deteriorates. This mo ment occurs when due to enlargement of the current. The size of the image point produced by means of a given electron-optical system is in proportion to the surface of the cathode. Large points with high density of ray current _ may be produced in particularly simple fashion by the use of indirectly heated large-surface cath odes. According to the invention there are em ployed for this purpose more particularly indi rectly heated cathodes, the emissive surface of which possesses the form of a cup, preferably spacing between the lines this spacing between the lines, with a given width of the recording point, is equal to or greater than the lines them selves. On the other hand it is undoubtedly known that open towards the tube space, of a suitable and preferably not excessive diameter. The cup, for example, may have a diameter of 1-5 millimetres, an increase of size with a given intensity of vision tubes having good developed electron-opti light and size of image point always encounters the difficulty that the surface brightness of the image decreases. With a given size of image 20 point it is only possible to proceed beyond this stage by increasing the intensity of the image point, which from a technical point of view is a dif?cult matter. According to the invention two requirements 25 for large total intensity and good psychological effect with a given number of lines are connected up by means of an adapted dimensioning in such a manner that an optimal total effect is obtained. Brie?y the dimensioning consists in that the size 30 of the image point, with constant density of light, i. e., with cathode ray tubes having a constant ray current density per square millimetre, is so selected that the lines are disposed closely to gether. If 2 lines are present and h. is the height 35 of the usual size, the point accordingly requires to be brought to the size h 2 40 This value may naturally be increased to a slight extent; an over-dimensioning of this kind, how ever, is not essentially favourable, because assum ing the image point is substantially square or cir cular the maximum sharpness of the contour 45 capable of being obtained is determined by ex actly the same size, viz., the spacing of the lines. The measure according to the invention of em ploying large points represents for the construc tion of cathode ray tubes a very pleasant simpli? cation. It has been found that a reduction of the image point with a pre-determined size of the source of emission, for example the cathode (or the intermediate diaphragm), is much more difficult than a simultaneous increase in the size of image point and the total strength of the ray 55 10 and be connected with a, say, loop-like heating element, possibly by welding. When using tele- ‘ cal systems (for example, according to the United States Patent No. 2,049,781), which enable the emissive surface to be reproduced on the screen, it is possible in simple fashion to provide the point with a suitable form. ' Thus, for example, it is o possible in accordance with the invention to fur nish the cup cathode with a rectangular emissive surface (the greatest expanse of which may con~ veniently be disposed vertically to the direction of the line), and in this manner to obtain image points of rectangular form, which have been found to be particularly favourable for the method ac cording to the invention. The invention will be more fully understood from the appended drawing, whereof Fig. 1 shows a Braun tube furnished with a cathode according to the invention, while in Fig. 2 an embodiment of the cathode is shown H on a larger scale, and Fig. 3 shows a line-screen according to the in vention. In the drawing l is the bulb of the cathode ray tube, 2 a Weh nelt-cylinder, 3 the cathode, 4, 5 and 6 elements of the electron-optical system, ‘I and 8 de?ecting means and 9 the ?uorescent screen. In Fig. 2, 3 is the cathode body, [0 the heating ?lament, l I the preferably rectangular emis sive body, arranged in a recess of the cathode 45 body; I2 is the preferably earthed heating line. As is shown in Fig. 3, the width of each of the lines I4 is equal to 11 Z 2 being the number of the lines. It is self under stood, that practically no separating lines are to be seen in the image. It is particularly convenient to determine once 2 2,114,610 and for all for a, particular tube the form and size of the image by corresponding selection of the cathode (or an intermediate diaphragm to be reproduced on the screen in place of the cathode) and to dimension accordingly the means deter mining the dimensions of the optical screen, so that the total arrangement is adjusted to a size of image, which may be varied only within very , narrow limits. 10 15 20 39 4.0' 45 50 Naturally, however, it is also possible to vary the size of the image point in other fashion, and trol the intensity of the electron emission from said area, a picture receiving screen, de?ecting means ior producing on said picture receiving screen a line screen having the height of h units and comprising z lines, said de?ecting means comprising means to de?ect the cathode ray in regular periods in the direction in which the height of the line screen is taken, said de?ecting means further ‘comprising means to de?ect the cathode ray in periods of 2/2 the length of the 10 first mentioned periods in a direction perpendic to alter the strength of the ray current accord- _ ular to the ?rst mentioned direction, and an ingly, so that the tube supplies image points of electron optical system acting on the lines of an different size but constant or practically con optical lens for reproducing said area on said stant surface intensity. Tubes of this nature fluorescent screen for producing a light spot hav may readily be employed for the production of ing a heightrof h/z units taken in the same direc images of desired size. The adjustment of the tion in which the height of the line screen is size of the image point may be performed--par taken. ticularly in the case of high-vacuum tubes-by 3. A high vacuum electron discharge tube com suitable adjustment of the electron-optical sys prising an indirectly heated cathode furnished 20 tem (displacement of the focal point in such with an emissive area having the shape of the fashion that the same falls in front of or be light spot to be reproduced, means to control hind the image screen). The adjustment of the the intensity of the electron emission from said strength of the ray current may be e?ected, for area, a picture receiving screen, de?ecting means example, by the application of a suitable con for producing on said picture receiving screen stant grid bias to the intensity control grid of a line screen having the height of h units and‘ the tube. comprising 2 lines, said de?ecting means com. The formation and dimensioning of the image prising means to de?ect the cathode ray in reg point in accordance with the invention is of par ular periods in the direction in which the height ticular importance in connection with a size of of the line screen is taken, said de?ecting means 3 O image of more than approximately 3 x 4 cm. By further comprising means to de?ect the cathode using the method according to the invention it ray in periods of 1/2 the length of the ?rst men is possible, even when employing relatively small tioned periods in a direction perpendicular to the numbers of image points, to produce images of ?rst mentioned direction, and an electron optical large size, which have a considerable strength of system acting on the. lines of an optical lens light and are well recognizable even at a con for reproducing said area on said ?uorescent siderable distance without auxiliary measures of screen sfor producing a light spot having a height any kind, such as projection or the like, and of 11/2 units taken in the same direction ‘in which reveal the maximum sharpness of image which the height of the line screen is taken. is capable of being obtained with the particular 4. In a cathode ray tube more particularly for .40 number of image points concerned. television purposes comprising a picture receiv . I claim: ing screen: the combination comprising an in 1. A high vacuum electron discharge tube com directly heated cathode having in its surface fac prising a thermionic cathode, a control electrode ing said picture receiving surface a recess and surrounding said cathode for controlling the in an emissive substance in said recess, and means .7. tensity of the electron emission from said cath for electron-optically reproducing the area of said ode, an image receiving screen, an electrostatical electron emissive substance on said picture re electron-optical system acting on the lines of an ceiving surface. 7 optical lens, said electron-optical system being 5. In a cathode ray tube more particularly for arranged between said cathode and said screen, television purposes comprising a picture receiv an electrode having an opening of non-circular ing screen: the combination comprising an in shape interposed between said cathode and said electron-optical system, said electron-optical sys directly heated cathode having in its surface at the side thereof facing said picture receivingsur— tem reproducing on said screen said non-circular 55 opening for producing an image point, and means face a recess and anelectron-emissive substance in said recess, the area of said emissive sub for de?ecting said image point in two directions perpendicular to each other for scanning said stance being of non-circular shape, and means electron-optically reproducing the area of said screen. electron emissive substance on said picture re 2. A high vacuum electron discharge tube com rising an electron emissive area having the shape of the light spot to be reproduced, means to con ceiving surface to produce a non-circular image, spot on said picture receiving surface. 60 KURT SCHLESINGER.