US2166399A - Television and like receiver - Google Patents

Description

y 18, 1939- H. M. DOWSETT ET AL 9 TELEVISION AND LIKE RECEIVER Filed Jan. 30, 1936 INVENTOR H. M- DOWSETT R. A DZOW 774$ I ATTORNEY Patented July 18, 1939 UNITED STATES PATENT OFFICE TELEVISION AND LIKE RECEIVER Harry Melville Dowsett,

London, and Robert Cadzow, Argyllshire, England, assignors to Radio Corporation of America, a corporation of Delaware 2 Claims.

This invention relates to television and like receivers' and more particularly to receivers of the kind wherein received pictures are reproduced by means of a cathode ray tube having a fluorescent screen.

The object of the invention is to provide an improved receiving apparatus whereby pictures thus reproduced by means of a relatively small cathode ray tube may be projected efficiently upon a viewing screen sufficiently large to be viewed by a number of persons, e. g. upon a viewing screen 12 or 18 inches square.

According to this invention a television or like reproducer arrangement comprises a cathode ray tube having a fluorescent screen upon which received pictures are built up by a scanning cathode ray beam and the said tube is inserted in an aperture in an optical projection device of substantially larger area than said screen and so positioned and arranged as to collect light from said screen and focus images built up upon said screen upon a viewing screen.

Preferably the optical projection device is a mirror which faces both towards the viewing screen and towards the fluorescent screen of the cathode ray tube, and preferably also, the said fluorescent screen is so constructed as substantially not to pass light so that as much as possible of the light which is generated by the incidence of the cathode ray beam, upon the fluorescent screen is collected by the mirror and projected thereby on to, the viewing screen.

The invention is illustrated in the accompanying drawing which shows schematically one way of carrying it into effect. Referring to the drawing, a television or like receiver comprises a cathode ray tube A including an electron gun (not shown) electrostatic or other cathode ray beam deflecting means (not shown) and a fluorescent screen C upon which the scanning cathode ray beam from the gun is projected. In the construction illustrated the fluorescent screen is in the form of a deposit of fluorescent material on the electron gun side of a flat metal plate which, in use, may be maintained at a positive potential relative to the potential of the electron gun of the tube. The cathode ray tube A is mounted in an aperture in the centre of a spherical parabolic or other suitably shaped reflector surface B which faces both towards the fluorescent side of the fluorescent screen C and a semi-transparent viewing screen D which may consist, for example, of a ground glass sheet. The shape of the reflector and the relative positions of the reflector, the fluorescent screen, and the viewing screen are so chosen that images of the pictures built up upon the fluorescent screen are projected via the reflector on to the viewing screen so as to produce thereon images of desired size; for example, a light spot F on the screen C will give an image E on the screen D. The broken lines in the figure indicate light rays and, for the sake of simplicity in the drawing, the electrodes (other than the screen C) and the circuits therefor are all omitted since they may be as well known per se.

It will be seen that with the illustrated arrangement the light from the fluorescent screen is picked up over a wide angle, so that a large pro portion of the useful light is utilized. Further, since the light utilized is that from the side of the fluorescent screen which faces the electron gun, light transmission losses due to light passing through the fluorescent material of the screen are avoided.

If desired, the glass envelope of the cathode ray tube may be specially shaped in such manner as to avoid distortion thereby of the viewed images, for it will be appreciated that light from the fluorescent screen passes to the mirror via the glass of the cathode ray tube. A preferred arrangement (not illustrated) is one wherein part of the tube envelope is spherical with the fluorescent screen centrally located therein so that light from the screen C to the reflector B passes radially, or nearly radially, through the spherical part of the tube.

Having now described our invention, what we claim is:

1. In a television receiver, a cathode ray tube having an elongated envelope for reconstructing the televised image, a viewing screen member, and a reflector embracing at least partially circumferentially the exterior of the envelope of the tube for reflecting the reconstructed image on to the screen member.

2. Apparatus in accordance with claim 1 wherein said mirror is parabolic in shape.

HARRY MELVILLE DOWSETT. ROBERT CADZOW.

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