US2910532A - Arrangement for projecting televised images on to a large screen - Google Patents

Arrangement for projecting televised images on to a large screen Download PDF

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Publication number
US2910532A
US2910532A US436603A US43660354A US2910532A US 2910532 A US2910532 A US 2910532A US 436603 A US436603 A US 436603A US 43660354 A US43660354 A US 43660354A US 2910532 A US2910532 A US 2910532A
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Prior art keywords
sheet
grid
arrangement
support
modulating
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Expired - Lifetime
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US436603A
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English (en)
Inventor
Auphan Michel
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ELECTRONIQUE SOC GEN
GENERALE D'ELECTRONIQUE Ste
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ELECTRONIQUE SOC GEN
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
    • H04N5/7416—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
    • H04N5/7425—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal the modulator being a dielectric deformable layer controlled by an electron beam, e.g. eidophor projector

Definitions

  • the object of the invention is to provide an arrangement for projecting televised images on to a large screen.
  • This arrangement is of the kind in which the fluorescent screen of the normal type of cathode-ray tube is replaced by a metallic sheet, the function of which is to modulate locally, in association with a suitable optical system, the light emitted from an external source.
  • This metallic sheet or membrane has a refiecting surface and it is in general flat or spherical in the position of rest. It is disposed at a very short distance from an insulating support and, when it is traversed by a pencil of light rays, it charges up the insulating support, especially bysecondary emission. 'Ihe sheet then becomes locally deformed under the effect of electrostatic forces.
  • the optical system usually used is of the kind known under the name of the Toepler optical system which transforms this local deformation into a brilliant spot on the screen.
  • the present invention is more particularly intended to provide improvements both in the mechanical and in the electrical field, to the said modulating sheet and in its conditions of operation.
  • Fig. l shows a possible form of embodiment of the arrangement for projecting televised images on to a large screen, utilising an optical system provided with grids.
  • Figs, 2, 3, 3a, 4 and 5 show different improvements of the light-modulating system in the case in which the cathode-ray tube is of the positive-modulation type.
  • Fig. 6 shows an arrangement in accordance with the invention which is applicable to tubes of the negativemodulation type.
  • Modulation is known as positive for the purposes of the present description, when the maximum intensity of the cathode beam corresponds to the white portions of the image, and is called negative when this maximum intensity corresponds to the black portion.
  • Fig. 7 shows a television arrangement on a large screen With an optical system utilising a spherical modulating sheet which forms a concave mirror in its state of rest.
  • FIG. l An example of a form of construction of the optical system is given in Fig. l, in which T indicates the cathoderay tube and F the modulating reflecting sheet.
  • the sheet F is supposed to have a flat surface in the state of rest.
  • a grid, made up of parallel bars G1 is suitably illuminated from a source S t lrough a condenser C.
  • the arrangement of the lens O1 and the sheet F gives an image of this grid G1 in the plane of a second grid G2.
  • the various component members are arranged in such a way that the images of G1 and G2 interlace exactly, that is to say the image of a full bar of the grid G1 is produced e .t 1C@ in the space separating two bars of G2 and vice-versa.
  • the methods and arrangements in conformity with the present invention enable the light-modulating sheet to assume an undulating form in all the light portions of the televised image, even if the scanning lines are not effectively separated.
  • the desired undulation may be obtained by the various arrangements which follow hereafter, these arrangements all having a common feature comprising the utilisation of a network which influences the deformation of the sheet:
  • the sheet F has alternate thick and thin portions; the bands having the same thickness are at right angles to the chevrons and parallel to the grids. Under the electronic bombardment, the deformation of the sheet varies in accordance with the thickness of the band in question and this causes the production of the desired undulations.
  • the sheet F is of uniform thickness but the chevrons are crenellated.
  • the sheet is much more free to assume deformation between the tops of each tooth, which are here known as supporting strips, than along the lines of these strips. Under the effect of the electronic bombardment, the sheet also assumes an undulating form. It will, of course, be understood that these teeth should not be visible from the side of the support; the material which constitutes the bottoms of these castellations should thus be opaque.
  • the insulating support is again provided with thin parallel strips of a substance, but they are no longer provided with the object of modifying locally its secondary emission.
  • the nature of the substance is such that it confers on the insulating support, at the areas covered by the deposit, a certain superficial conductivity. This conductivity should be sulicient for it to be able to discharge the insulating support in a time which is much less than the duration of an image.
  • Fig. 5 differs from the preceding arrangements by the fact that the chevrons which support the sheet -are parallel and not in this case perpendicular torthe grids G1 and G2 of the Toepler system, but they are built up in a special Way so that they do not produce diffraction of the light in the absence of deformation of the sheet.
  • these chevrons are composed of two substances 1 and 2, the substance 1 is transparent and the substance 2 is preferably metallic, that is to say opaque withpa reflecting surface.
  • the index and the thickness of the substance 1 are so chosen that the optical thickness of the layer 1 is equal to the distance ofthe moving sheet from the support (the optical length is the product of the real length multiplied by the index).
  • the substance 1 is no longer useful, provided that the distance between the sheet S and the support I in the state of rest, is equal to a multiple ofrhalf a wave-length.
  • the chevrons may then be undulating and the sheet may adhere to the entire length of the chevrons; it is thus undulating in its state of rest (or it may have a castellated shape).
  • the chevrons are perpendicular to the bars of the grids G1 and G2, as in the rst systems described, but the sheet, in its state of rest, corresponds to the maximum of white.
  • it adheres to the insulating support and, in consequence, becomes flat everywhere it is visible, that is to say between the chevrons.
  • the areas which are thus stuck together will therefore correspond to the black part of the image.
  • the mosaic does not need to have a plane surface; it may, in particular, be spherical or it may represent an optically-defined surface.
  • One application, in accordance with the invention, of spherical modulating sheets consists in the elimination of the lens O1 of the optical equipment.
  • the mosaic which is then a concave mirror, gives directly an image of the grid G1 on the grid G2 (see Fig. 7).
  • the presence of an electric held in the vicinity of the sheet facilitates its deformation under the effect of the electronic bombardment.
  • this electric field As far as the direction of this electric field is concerned, several cases may be considered:
  • the electric field must prevent all secondary electrons from leaving the support and passing through the moving sheet; in this case, the sheet must be charged to a potential higher than that of the metallisation of the tube.
  • this property may be applied to a new method of wiping out the mosaic, which avoids the use of a slightly conductive support.
  • the mosaic is obliterated during the return of each line.
  • the potential of the sheet is brought hack to a kvalue equal to that of the metallisation of the tube.
  • the cathode-ray is not cut off during the return-lines but is brought back to a state of constant current; it is, furthermore, slightly deflected towards the base of the image. lt will thus be understood that'it will obliterate, in the areas which are to be restored, the line or the few lines which follow.
  • a positive modulation may be used in the case of the mosaics described with reference to Fig. 6.
  • the potential of the metallisation is the same as that of the sheet and during the return-line, the potential of the rnetallisationl is less than that of the sheet, so that during each return-line the sheet re-adheres to the support over the bombarded areas.
  • a new improvement in the arrangements suggested consist in placing a grid in front of the mosaic, arranged as shown in Fig. 1.
  • the object sought for is different, and there is no need for the grid to be stretched so close to the mosaic.
  • its wires will then be as line as possible so as to intercept as little as possible of the electron ow.
  • This grid may also be replaced by a metallic membrane stretched over a frame, on the condition that it is line enough not to interfere with the passage of the electrons.
  • the electric field is applied by establishing a difference of potential between the moving sheet F and the grid or the membrane.
  • the grid does not require to be very close to the mosaic and can thus be used with a non-plane mosaic, for example a spherical mosaic.
  • apparatus for the projection of television images utilizing an optical system and a cathode ray tube, said tube having at least a source of electrons adjacent one end thereof and a modulating element adjacent the other end thereof, said modulating element including an insulating support and a thin reflecting metallic sheet held at a short distance from said support, means for sweeping said sheet with a beam of electrons from said source, said sheet being locally deformable in response to the impingement thereon of said beam of electrons, and means interfaced between said sheet and said source of electrons to limit the impingement of said beam to predetermined areas of said sheet.
  • a cathode ray tube for the projection of televised images on a large screen, a modulating element disposed in the position normally occupied by the fluorescent screen in conventional tubes, said modulating element being locally deformable by an electron beam within said tube and an optical system cooperating therewith for locally modulating the light emitted by an auxiliary luminous source, the structure of said modulating element comprising an insulating support, a metallic reflecting sheet held at a short distance from said support, suitable means for supporting said sheet such that normally plane areas become rippled and normally rippled areas become plane upon impingernent thereon of said electronic beam.
  • a modulating element as described in claim 2 including holding bands connecting said reflecting metallic sheet to said insulating support.
  • a modulating element as defined in claim 2 and incorporated in an optical system of the Toepler type comprising a grid disposed on the side of said insulating support opposite to said metallic reccting screen, said grid being parallel to said screen and having its bars parallel to those of the lgrids of said optical system.
  • a structure of a modulating element as dened in claim 2 and incorporated in au optical system of the Toepler type comprising a grid disposed on the opposite side of said metallic reflecting sheet from said insulating support, said grid being parallel to said sheet and having its bars parallel to those of said grids of said optical system, and parallel holding bands connecting said sheet to said insulating support and being perpendicular to said bars of said grids.
  • a structure for a modulating element as defined in claim 2 and incorporated in an optical system of the Toepler type comprising a grid disposed on the opposite side of said metallic reflecting sheet from said insulating support, said grid being parallel to said sheet and having its bars formed on the metallic sheet itself by thickened areas in the form of parallel bands of equal thickness parallel to the bars of said grids of said optical system.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Transforming Electric Information Into Light Information (AREA)
US436603A 1953-06-15 1954-06-14 Arrangement for projecting televised images on to a large screen Expired - Lifetime US2910532A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR334171X 1953-06-15
FR260554X 1954-05-26

Publications (1)

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US2910532A true US2910532A (en) 1959-10-27

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US (1) US2910532A (fr)
CH (1) CH334171A (fr)
GB (1) GB786553A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3137762A (en) * 1960-06-30 1964-06-16 Foerderung Forschung Gmbh Arrangement for amplifying the brightness of an optically formed image
US3233040A (en) * 1962-01-02 1966-02-01 Magnavox Co Electrostrictive display means
US3517126A (en) * 1966-11-17 1970-06-23 Tokyo Shibaura Electric Co Light value image projection system with deformable membrane and thin film target electrode
US3708712A (en) * 1969-09-29 1973-01-02 Rca Corp Intelligence-handling device having means for limiting induced electrostatic potential
US3746911A (en) * 1971-04-13 1973-07-17 Westinghouse Electric Corp Electrostatically deflectable light valves for projection displays
US5493439A (en) * 1992-09-29 1996-02-20 Engle; Craig D. Enhanced surface deformation light modulator

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2510846A (en) * 1945-05-23 1950-06-06 Scophony Corp Television receiving device
GB678307A (en) * 1948-11-30 1952-09-03 Foerderung Forschung Gmbh Improvements in or relating to television apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2510846A (en) * 1945-05-23 1950-06-06 Scophony Corp Television receiving device
GB678307A (en) * 1948-11-30 1952-09-03 Foerderung Forschung Gmbh Improvements in or relating to television apparatus

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3137762A (en) * 1960-06-30 1964-06-16 Foerderung Forschung Gmbh Arrangement for amplifying the brightness of an optically formed image
US3233040A (en) * 1962-01-02 1966-02-01 Magnavox Co Electrostrictive display means
US3517126A (en) * 1966-11-17 1970-06-23 Tokyo Shibaura Electric Co Light value image projection system with deformable membrane and thin film target electrode
US3708712A (en) * 1969-09-29 1973-01-02 Rca Corp Intelligence-handling device having means for limiting induced electrostatic potential
US3746911A (en) * 1971-04-13 1973-07-17 Westinghouse Electric Corp Electrostatically deflectable light valves for projection displays
US5493439A (en) * 1992-09-29 1996-02-20 Engle; Craig D. Enhanced surface deformation light modulator

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Publication number Publication date
GB786553A (en) 1957-11-20
CH334171A (fr) 1958-11-15

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