US2462569A

US2462569A - Television receiving tube with storage properties

Info

Publication number: US2462569A
Application number: US696151A
Authority: US
Inventors: George C Sziklai
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1946-09-11
Filing date: 1946-09-11
Publication date: 1949-02-22
Anticipated expiration: 1966-02-22

Description

eh 1949- I e. c. SZlKLAl 2,462,569

TELEVISION RECEIVING TUBE WITH STORAGE PROPERTIES Filed Sept 11, 1946 Zhmentor Gttomeg Patented Feb. 22, 1949 UNITED STATES KENT OFFICE TELEVISION RECEIVING TUBE WITH STORAGE PROPERTIES Delaware Application September 11, 1946, Serial No. 696,151

4 Claims.

This invention relates to reproducing tubes for television reception.

In present type of reproducing tubes the cathode ray beam of the gun scans the fluorescent screen point by point. Since the beam must be focused into a small spot the beam current is limited. High energy is required at the screen for bright pictures and this means that the electrons must be accelerated to very high velocities to provide the landing energy. This requires strong deflecting fields to scan the beam over the screen which increases the deflection power input and thereby the expense of operation. Also, the beam remains on the picture element only for a very short interval thus saturating the light output of the phosphor in that short interval and permitting it to idle over the larger portion of the picture scanning time.

It is the object of this invention to provide a television reproducing tube that may be operated at low scanning velocity with increased light output at the screen.

Another object of the invention is to provide an electron relay for energizing the fluorescent screen.

Another object is to provide storing means whereby the light output of a fluorescent reproducing tube is greatly increased.

Still another object is to provide a television reproducing tube having low deflection power requirements.

Other objects of the invention will appear in the following description, reference being had to the drawing in which:

Fig. 1 is a section of a cathode ray tube illustrating the principles of the invention; and

Fig. 2 diagrammatically illustrates in elevation the auxiliary electron producing means.

Referring to Fig. l, the evacuated envelope l contains the usual gun G having a cathode 2, the heater not being shown, grid or control electrode 3 and first anode l, the latter two electrodes having small apertures for defining the beam B. The wall coating 5, or equivalent anode, accelerates the beam at relatively low velocity, a few hundred volts, to the target 5 of non-fluorescent material such as thin semiconducting glass as described in the application of Albert Rose filed November 28, 1945, Serial No. 631,441. The electro-magnetic deflecting unit I scans the beam over the target 6 and the beam bombards secondary electrons from the elemental areas in proportion to its intensity. The secondary electrons are collected by the screen 8 which is in out-of-focus position. The

electrons are focused by the axial magnetic field produced by the coil 9. The deflecting unit consists of two coils producing electro-magnetic fields at right angles to each other and to the field of coil 9. The scanning of the beam B over the thin glass target 6 produces a charge image proportional to the charge image in the target of the pick-up tube at the transmitter as will be understood by those skilled in the art.

A plurality of circular auxiliary cathodes IO, M, l2, and it, four being shown by way of example, produce a copious supply of electrons that are projected toward the back surface of the target 6 through the action of electron mirrors M, l5, l6 and El and screen mesh electrode l8. These electron mirrors are anodes having negative potentials relative to the target. The auxiliary cathodes and mirrors need not be circular as they may be linear or of other shape and may extend parallel to the target in any direction. but in out-of-focus position. The mirror electrodes may be connected together and to a negative potential terminal relative to the cathodes which also are shown connected together. The screen mesh l8 may be connected to a potential terminal sufiiciently positive to accelerate the electrons emitted by the cathodes toward the rear surface of target 6. The auxiliary cathodes, mirror and screen are placed as close as practical to the target 6 without placing them in focus. Fluorescent screen is may be placed on the inside surface of the envelope. Wall coating 59, or equivalent electrode, accelerates to high velocity at screen 18 those electrons from the auxiliary cathodes not landing on the target 6 as will later be explained.

The accelerating velocity of electrode l9 may be made as high as desired, say 15,000 volts, as the deflecting field or unit I is screened therefrom.

The operation of my improved reproducing tube may be explained as follows:

Since my improved tube reverses the picture, the incoming signals will be reversed in their application to the gun grid 3 so as to produce a positive on screen 18. The signal modulated beam B scans the front surface of target 6 and produces a charge image thereon. The potential pattern on the rear surface causes the electrons from the auxiliary cathodes to land in proportion thereto until the target becomes negative and the remainder of the auxiliary electrons are accelerated at high velocity to the fluorescent screen I8 where a greatly intensified image of the scene picked up at the transmitter is reproduced. The auxiliary electrons are 1anding on the rear surface of target 6 through substantially all of the frame scanning time for the whitest areas thereof (blackest at the transmitter) and electrons are likewise reflected from the target over substantially all of the frame scanning time for the darkest areas so that in effect storage of the light is produced and much brighter images can be produced with low power deflection of the beam.

The glass target 6 is sufficiently conducting to permit the auxiliary electrons landing thereon to pass through the target and discharge the charge image during a frame time as disclosed in saidRose application.

Electrostatic deflection and focusing may be used if desired and various other changes may be made without departing from the spirit of the invention.

What I claim as new is:

1. A television reproducing tube comprising an envelope containing a cathode ray beam gun, an imperforate target, means for producing a field for scanning the beam from said gun over one side of said target to produce a charge image thereon, a fluorescent screen spaced from the other side of the target, an auxiliary source of electrons between said screen and said target, an anode for projecting part of the electrons emitted by said auxiliary source onto the other surface of said target in proportion to the charge image thereon, and an electrode for accelerating the remainder of the electrons from said auxiliary source to bombard said screen.

2. A television reproducing tube comprising an envelope containing a cathode ray beam gun, a semi-conducting target means for producing a field for scanning the beam from said gun over one side of said target to produce a charge image thereon, a fluorescent screen spaced from the other side of said target, an auxiliary source of electrons between said screen and said target, an anode for projecting part of the electrons 4 from said source onto the other surface of said target in proportion to the charge image thereon, to discharge said image by conduction therethrough, and an additional anode for accelerating the remainder of the electrons from said auxiliary source to bombard said screen.

3. A television reproducing tube comprising an envelope containing a cathode ray beam'gun, a semi-conducting target, means for producing a field for scanning the beam from said gun over one side of said target, a fluorescent screen spaced from the opposite side of said target, a plurality of spaced cathodes between the screen and said other side of the target, a screen anode between the cathodes and said other side of the target, and an additional anode for producing an aclcelerating field between said plurality of cathodes and said screen.

4. A television reproducing tube comprising an envelope containing a cathode ray beam tube, a semi-conducting target, means for producing a field for scanning the beam from said gun over one side of said target, a fluorescent screen spaced from the opposite side of said target, a plurality of spaced cathodes between the screen and said other side of the target, electron mirrors adjacent said spaced cathodes at the side remote from said target, a screen anode between the cathodes and said other side of the target, and an additional anode for producing an accelerating field between said plurality of cathodes and said screen.

GEORGE C. SZIKLAI.

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

UNITED STATES PATENTS Number Name Date 2,055,174 Kwartin Sept. 22, 1936 2,179,205 Toulon Nov. 7, 1939 2,250,721 Moller July 29, 1941