# US 4,400,649 A · Color picture tube having an improved expanded focus lens type inline electron gun

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- Number: US 4,400,649 A
- Document ID: US4400649A
- Status: Granted
- Kind: A
- Application number: 06/282,231
- Filed: 1981-07-10
- Granted: 1983-08-23
- Earliest claimed: 1981-07-10
- Assignees: RCA Corporation
- Inventors: Hsing-Yao Chen
- Web page: https://patentgrep.com/patent/US4400649A

## CPC

- H01J 29/503: {Three or more guns, the axes of which lay in a common plane}
- H01J 29/62: Electrostatic lenses
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

An improved color picture tube has an inline electron gun for generating and directing three electron beams, a center beam and two side beams, along coplanar paths toward a screen of the tube. The gun includes a main focus lens for focusing the electron beams. The main focus lens is formed by two spaced electrode members each having three separate inline apertures therein. Each electrode also includes a peripheral rim. The peripheral rims of the two electrodes face each other. The apertured portion of each electrode is within a recess set back from the rim. The width of the recess in at least one of the electrodes is wider at the center beam path than at the side beam paths, measured perpendicular to the plane containing the electron beam paths.

## Claims

### Claim 1

In a color picture tube having an inline electron gun for generating and directing three electron beams, a center beam and two side beams, along coplanar paths toward a screen of said tube, said gun including a main focus lens for focusing said electron beams, the main focus lens being formed by two spaced electrode members each having three separate inline apertures therein, each electrode also including a peripheral rim, the peripheral rims of the two electrodes facing each other, and the apertured portion of each electrode being within a recess set back from the rim, the improvement comprising
the width of the recess in at least one of the electrodes being wider at the center beam path than at the side beam paths, measured perpendicular to the plane containing the electron beam paths.

### Claim 2 (depends on 1)

The tube as defined in claim 1, including the center aperture of the three separate inline apertures in said at least one electrode having a smaller diameter than the side apertures.

### Claim 3 (depends on 2)

The tube as defined in claim 2, wherein in said at least one electrode the ratio of the diameter of the center aperture to the diameter of the side apertures approximately equals the ratio of the width of the recess at the side beam paths to the width of the recess at the center beam path.