US2387608A - Electronic scanning device for television - Google Patents

Description

Oct. 23,1945. A. P. PAUMIER 2,387,698

' ELECTRONIC SCANNING DEVICE FOR TELEVISION Y Filed May 6, 1939 Andre Raul $0im ar INVE'N O Patented Oct. 23, 1945 ELECTRONIC SCANNIN G ."DEVICE FOR TELEVISION 'Andr'Paul Paumier, Sccaux,'France; vestd in the Alien Property Custodian "fapplicationMay 6, 1939,--Serial No; 272,073

In; France May 12, 1938 connected with the manner in which theiphoto-l -eleo'tric'mosaic plate is scanned with the cathoderay scanning beam. Various methods have' hithertobeen proposed for compensating or .lcor'r'e'ct- -ingithe marks :inz questionfstarting in g'eneral :from aidevelopment of'the f parasiticmodulation function in' 'MacLaurins progression which is stopped atiits second Forlthird term; and ex perimentally adjusting-the numerical 'values and the phases of the tiand t terma' t'representing the :time, which1 are: produced by' appropriate: generators.

This correction requires accurate -adjustments which have tov be re adjusted'ifromtime to time, and only gives partially satisfactory results. The present invention relates to a'method of correcti'on-a'which isquitedifierent and the success of which has been provedl=by experience. It essen- =tially consists in the use-of: armagnetic correcting field of relativelys'tsmall'i amplitude; the a'ction of which may be assumed tobe exerted on the very soft-secondary lfiparas'itic) electrons'Whiah cause themarks' as has been suggested. The direction of-said magnetic fieldhas to be'substantiallypar- --allel'vvith thecathode raylbeampf the icono- -scope-and inclinedfr'elatively' to the surface -'of --the scanningscreen.

"These conditions are set' forth in detail in-the ensuing description taken with reference to the accompanying "drawinglwhich shows by way of example an embodiment of a device according to the invention.

In the drawing, a scanning tube called iconoscope is shown. Said tube l, the actual construction of which is not a part of the invention, essentially comprises a screen 2 and a cathoderay oscillograph 3. The screen 2 is formed by a metal collecting plate which is separated from a mosaic of photo-electric elements by an insulating plate. On said screen is projected the image to be scanned 4 by means of an optical system 5. The oscillograph essentially comprises a cathode 6, a grid 7, a first anode 8 and a second anode 9, and also means I 0 for causing the oathode-ray beam to deviate in two directions at right angles, so as to scan the screen 2. It is of course understood that" this description -of-the: tube I is only given by-tway =of example in Border tolsillus- 5 trate the present inventionand asa reference to "the arrangement of :-the F tubes --called iconoscopes to; which the present invention. relates;

EXperience has shown that byimodi-fying a con- :tinuous magnetic field, for example by means of av coil surrounding the head of the iconoscope, 'it was possible to compensateimore or less "the marks-of the picture OfWhiCh mentionwas made "above. The compensating action-is completedpr a direction of the field that makes an ang-le--.of about with the-plane-of the mosaic plate, or approximately parallel-with the axisof the cathode-ray oscillog-raph; this compensation becomes zero;fora fieldparallel with the: plane of the mosaic plate. Finally it is only exerted on values .of the. brilliance of. the picture which .are..n'ot too highfin fact, when said brilliance increases, theintensity of the compensating field .haslto be increased,- and this quickly leads to values which interfere with the. s'canning of the mosaic plate. By (way of a .nbn-limitati've example fforian iconoscope wherein the. accelerating Voltage, of the scanning beamwas of the ordr"of'1,'00O',v. and for a picture'illumination'of betweeni'l5and luxes, a compensating field of theorderof 1 'gauss proved "satisfactory. Said'field' may be createdby a coil llwhich is suitably'arranged about the iconosco'pe'and-is supplied by a device 12 which supplies "it "with the necessary current. Satisfactory results are also obtained with an alternating magnetic field of appropriate form and -'frequency, -orwith-a field which is-a discontinuous function of Y thetime, for example which isof suitable intensity at certain instants" or during" certainver'y 'short intervalsgand is Zero "outside saidintervals, the -irequ'e'nc'y of thefield being in this case preferably 1 connected to the periodicity of the scanning, for example by controlling the device I2 by means of the same source of frequency which control the scanning device Hi.

What I claim is:

1.. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, means for creating inside the transmitting tube a magnetic field of small intensity relatively to the other fields existing in the tube, the direction of which is substantially parallel with the electron beam and is inclined relatively to said screen,

whereby parasitic modulation of the image pro- Jected on said mosaic screen is prevented.

2. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an

insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, a coil surrounding said tube, the axis of said coil being substantially parallel with the electron beam of the tube and inclined relatively to said screen, and means for sending an electric current through said coil, whereby a magnetic field hood of the screen, the axis of said coil being substantially parallel with the axis of the tube and inclined relatively to said screen, and means for sending an electric current through said coil, whereby a magnetic field directed to said screen is created inside the tube, which field prevents parasitic modulation of the image projected on said screen.

4. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, means for creating inside the transmitting tube a continuous magnetic field of small intensity relatively to the other fields existing in the tube,

the direction of which is substantially parallel with the electron beam and is inclined relatively to said screen, whereby parasitic modulation of the image projected on said mosaic screen is prevented.

5. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate p ing the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, means for creating inside the transmitting tube an alternating magnetic field of small intensity relatively to the other fields existing in the tube, the direction of which is substantially parallel with the electron beam and is inclined relatively to saidscreen, whereby parasitic modulation of the image projected on said mosaic screen is prevented.

6. A television transmitting tube comprising a mosaic screen formed by a conducting collecting a means for creating inside the transmitting tube a discontinuous magnetic field of small intensity relatively to the other fields existing in the tube, the direction of which is substantially parallel with the electron beam and is inclined relatively to said screen, whereby parasitic modulation of the image projected on said mosaic screen is prevented.

7. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, a coil surrounding said tube, the axis of said coil being substantially parallel with the electron beam of the tube and inclined relatively to said screen, and means for sending a continuous electric current through said coil, whereb a magnetic field is created inside the tube which prevents parasitic modulation of the image projected on said screen.

8. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, a coil surrounding said tube, the axis of said coil being substantially parallel with the electron beam of the tube and inclined relatively to said screen, and means for sending an alternating electric current through said coil, whereby a magnetic field is created inside the tube which prevents parasitic modulation of the image projected on said screen. 7

9. A television transmitting tube comprising a mosaic screen formed by a conducting collecting surface, a mosaic of photo-electric elements, an insulating plate separating the latter from said surface, an electron gun, and deflecting means for scanning said screen by the electron beam, a coil surrounding said tube, the axis of said coil being substantially parallel with the electron beam of the tube and inclined relatively to said screen, and means for sending a discontinuous electric current through said coil, whereby a magnetic field is created inside the tube which prevents parasitic modulation of the image projected on said screen.

ANDRE PAUL PAUMIER.

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