US2415311A - Cathode-ray tube projector - Google Patents

Description

Feb. 4, 1947. c. s. SZEGHO CATHODE R AY TUBE PROJECTOR Filed Dec. 23, 1944 w J mi F m & 7 M $0 Y M ATTORNEY Patented Feb. 4, 1947 'lf'A'lES PATENT OFFICE GATHODlE-RAY TUBE PROJECTOR Constantin S. Szcgho, Chicago, 111., assignor to The Rauland Corporation, Chicago, Ill., a corporation of Illinois 3 Claims.

This invention relates to new and useful improvements in cathode ray tube projectors of the kind employed in large screen television receivers. This is a division of my application Serial No. 442,835, filed May 13, 1942.

The object of the invention is to increase the light output of projectors using a mirror optic, such as the Schmidt camera. (James G. Baker: The solid-glass Schmidt camera and a family of flat-field cameras, equivalent in performance to the Schmidt camera. Proceedings of American Philosophical Society, vol. 82, No. 3, April 30, 1940.)

In the Schmidt camera type of projector a cathode ray tube having fluorescent material deposited on a transparent support, usually a wall of the cathode ray tube, is located between a large diameter spherical mirror and a correcting plate. The light is first produced at the cathode or back side of the surface of the fluorescent powder and then passes through the powder to emerge from the front surface contacting with the transparent support, usually the end Wall of the tube. The electrons impinge on the back side surface of the layer. The outside surface faces the spherical mirror. In such back surface projection much of the light is lost by absorption in the fluorescent layer.

In accordance with the present invention, the light output of the projector is increased by providing a front surface projection cathode ray tube between the mirror and the correcting plate of a Schmidt camera type of optical system.

In the drawing:

Fig. 1 is a diagrammatic illustration of one embodiment of this invention; and

Figs. 2 and 3 illustrate two methods for assembling the tube of Fig. 1.

An embodiment is illustrated in Fig. 1 in which 2! is an evacuated glass envelope having a neck 22. The neck encloses an electron gun 23 and vertical and horizontal deflecting plates 2 The bell-shaped main chamber of the envelope 21 contains a disc 25 of aluminum having a thickness of approximately 5 microns. The disc is curved and has its convex surface coated with a layer of fluorescent material 26. The curved end wall 21 of the envelope 2! is parallel with the adjacent coated aluminum disc 25 and faces a spherical mirror 28. The neck 22 of the tube projects through a central opening in a correcting plate 28. The mirror 28 and plate 29 constitute a Schmidt camera type of optic, the radius of curvature of the disc 25 being the focal length of the optic.

High voltage electrons produced by the gun 23 will pierce the aluminum member 25 and penetrate the fluorescent layer 26 to cause the eXcitation of its outside surface near the window 21 which will allow substantially all the light from the fluorescent screen to reach the mirror 28. At the customary anode voltage of approximately 50,000 volts, the energy loss of electrons going through such aluminum disc is only about 5%. No negative charge will be present to slow down the electrons which can, therefore, penetrate to a suflicient depth into the fluorescent layer 26 to produce the necessary light effects.

If the space between the spherical mirror and the correcting plate is filled with a liquid of high refraction index the light output of this arrangement can be further increased by a factor which is the square of the refraction index. Instead of filling the space with an immersion liquid this space can be filled with solid material such as glass or plastic. In this case the spherical mirror and the correcting surface will preferably constitute the end faces of the solid.

Figs. 2 and 3 show two arrangements for assembling the tube structure schematically illustrated in Fig. 1. In Fig. 2, the curved aluminum disc 25 is mounted on wires 30 connected with the anode structure 3! in the neck 32 of a glass envelope. The body of the envelope 33 is cylindrical, the end of which may be closed by a flat glass window 34 during which operation the anode structure with the fluorescent screen is withdrawn towards the cathode. In the structure shown in Fig. 3, the aluminum disc 25 is supported 0n wires 35 which are sealed into the wall of cylinder 36, one end of which is closed off by a flat window 31; the other open end may be joined to the neck portion 38 of the tube at such a distance from the aluminum member that it wil1 not be damaged. What I claim is:

1. In combination, a fluorescent layer, a layer of conducting material in contact therewith, an electron gun emitting electrons which penetrate through said conducting layer into said fluorescent layer, a mirror for reflecting 1ight emanating and emerging from the exposed surface of said fluorescent layer, and a correcting plate in the path of the light rays reflected by said mirror.

2. In combination, a fluorescent layer, a layer of conducting material therefor, an electron gun emitting electrons which penetrate through said conducting layer into said fluorescent layer, an evacuated envelope having a transparent end wall parallel with said conducting layer and through 3 which said fluorescent layer is visible and a neck enclosing said gun, a mirror for reflecting light emanating and emerging from the exposed surface of said fluorescent layer, and a correcting plate in the path of the light rays reflected by said mirror.

3. In combination, a fluorescent layer, a convex layer of conducting material therefor, an electron gun emitting electrons which penetrate through said conducting layer into said fluorescent layer, an evacuated envelope having a transparent end made parallel with said conducting layer and adjacent thereto and a neck opposite said conducting layer and symmetrically positioned with re spect thereto, said neck enclosing said gun, a Spherical mirror for reflecting light emanating and emerging from the exposed surface of said fluorescent layer, and a correcting plate in the path of the light rays reflected by said mirror, and having a central aperture through which said neck pro- J'ects.

CONSTANTIN S. SZEGHO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,336,134 Szegho Dec. 7, 1943 2,298,808 Ramberg Oct. 13, 1942 2,295,779 Epstein Sept. 15, 1942

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