Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1982-10-01
1984-12-11
Blum, Theodore M.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
H01J 2980
Patent
active
044880936
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to color shadow mask cathode ray tubes.
BACKGROUND ART
When several kinds of information are to be displayed on a cathode ray tube (CRT), a color display helps the operator categorize the information more easily than does a monochrome display. The conventional color shadow mask CRT includes red (R), green (G), and blue (B) phosphors on the back of the faceplate of the CRT. When one or more of these phosphors are irradiated by the electron guns of the CRT, many different colors can be rendered visible on the CRT. However, when using two or more beams to irradiate two or more color phosphors and thereby provide a combined color, the beams are sometimes misconverged. This misconvergence causes a reduction in the quality of the resolution of the display. in order to overcome this problem, these color CRTs are provided with convergence circuits for compensating for this misconvergence. The convergence circuits can be very complex and expensive. Consequently, the conventional color CRTs are not suitable for use with simple color displays, such as logic analyzer displays in which only a few different colors are required. Self-converged CRTs employing red, green and blue phosphors are known, but the amount of possible misconvergence of a display using more than one color is not tolerable.
DISCLOSURE OF INVENTION
According to one aspect of the present invention there is provided a color shadow mask cathode ray tube having a faceplate upon the back of which are deposited arrays of first, second and third phosphors which radiate first, second and third colors respectively when irradiated by electrons, and first, second and third electron guns for providing beams of electrons for irradiating the first, second and third phosphors respectively, the first, second and third colors being such that said third color is produced when said first and second colors are combined.
According to another aspect of the present invention there is provided a method of providing a color display, comprising employing a shadow mask color CRT having a face plate upon the back of which are deposited arrays of first, second and third phosphors which radiate first, second and third colors respectively when irradiated by electrons, said third color also being produced when said first and second colors are combined, and the method also comprising providing first, second and third electron beams for irradiating the first, second and third phosphors respectively, and controlling the first, second and third electron beams to cause the third color to be produced by irradiating the first and second phosphors when the third color is to be displayed in an area adjacent to an area in which the first color is displayed, and to cause the third color to be produced by irradiating the third phosphor when the third color is to be displayed in an area which is separate from areas in which the first color is displayed.
The present invention makes it possible to provide a color logic analyzer display apparatus in which the quality of the characters on the display reflect near perfect convergence, and wherein the use of more than one electron beam at a time is minimized thereby eliminating the need for complex convergence circuits.
Preferably, the first, second and third colors are red, green and yellow respectively and, for the most part, only one color phosphor is irradiated at a time for generation of the display.
Red, green and yellow are high acuity colors, and are therefor inherently suitable for use in an information display. By use of yellow as the third color the advantage is obtained that an area of yellow can be provided within or adjacent a larger area of red by irradiating both the red and green phosphors within that area. There is no convergence problem because it is not necessary that the area of irradiated green phosphors be in registry with an area of irradiated red phosphors. When it is desired to provide an area of yellow which is separate from red and green areas, only the yellow phosphors are irr
REFERENCES:
patent: 3928785 (1975-12-01), Standaart
patent: 4385259 (1983-05-01), Chase et al.
Haines Doug
Kaufman Murlan
Taylor Keith
Blum Theodore M.
Smith-Hill John
Tektronix Inc.
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