Convergence correction method and apparatus for delta-gun colour cathode ray tube displays

Claim 3

A method according to claim 1, characterised in that it comprises the further step of selecting the boundary locations of the coordinate systems such that each equation coefficient is changed only when the variable it multiplies is zero.

Claim 4

A method according to claim 1 or 2, characterised in that it comprises the further step of selecting the coordinate system such that the screen is divided into four equal beam deflecting quadrants (I, II, III, IV) defined by a horizontal x, -x axis and a vertical y, -y axis and defining the equation variables in terms of x and y beam deflections and the coefficients in terms of a, b and c corresponding respectively to the angular position of the blue, green and red guns relative to the x and y axes.

Claim 5

A method according to claim 3, characterised in that the blue gun lies in the plane of the y-axis, the red gun lies in a plane 120 displaced from the blue gun, and the green gun lies in a plane 240 0 displaced from the blue gun, and in that the separate equations are of the form:- wherein a represents adjustable coefficients for converging the blue beam at the symbol location, b represents adjustable coefficients for converging the red beam at the symbol location, and c represents adjustable coefficients for converging the green beam at the symbol location.

Claim 7

A method according to claim 5, characterised in that it comprises the further step of selecting a first colour for two of the symbol elements requiring but two of the guns to produce, and selecting a second colour for the third of the symbol elements requiring one of the two guns and the other of said guns to produce.

Claim 8

Convergence correction apparatus for a delta-gun colour cathode ray tube display having primary signal responsive deflection means for positioning the electron beams of the guns in a primary horizontal and vertical coordinate system of the screen of the tube and convergence correction means for positioning each beam of each gun in a secondary coordinate system peculiar to that gun's location relative to the primary coordinate system, characterised in that the apparatus comprises a. means (10, 11) for supplying signals proportional to the horizontal (x) and vertical (y) deflection signals of the primary deflection means, b. first multiplier means (12, 13) responsive to each of the horizontal and vertical deflection signals for supplying signals respectively proportional to the square thereof, c. second multiplier means (16) responsive to the horizontal and vertical deflection means for supplying a signal proportional to the product thereof. d. first and second switch means (14, 15) responsive to the horizontal and vertical deflection signals for supplying the horizontal and vertical squared signals to each of the beam's convergence correction means dependent upon a predetermined plurality of location of the beams in the primary coordinate system, and e. third switch means (32) responsive to each of the horizontal and vertical deflection means for supplying the product signal to each of the beams convergence correction means dependent upon predetermined plurality of locations of the beams in the primary coordinate system, and f. means (a 11 ...,b 11 ...,c 11 ... ) responsive to each of the signals supplied to each of the beam's convergence correction means for effectively converting each of the signals in the primary coordinate system to corresponding signals in the secondary coordinate system.

Claim 9

Convergence correction apparatus for a delta-gun colour cathode ray tube display having primary signal responsive deflection means for positioning the electron beams of the guns in a primary horizontal and vertical coordinate system of the screen of the tube and convergence correction means for positioning each beam of each gun in a secondary coordinate system peculiar to that gun's location relative to the primary coordinate system, characterised in that the apparatus comprises a. means (10, 11) for supplying signals proportional to the horizontal (x) and vertical (y) deflection signals of the primary deflection means, b. first multiplier means (12, 13) responsive to each of the horizontal and vertical deflection signals for supplying signals respectively proportional to the square thereof, c. second multiplier means (16) responsive to the horizontal and vertical deflection means for supplying a signal proportional to the product thereof. d. first and second switch means (14, 15) responsive to the horizontal and vertical deflection signals for supplying the horizontal and vertical squared signals to each of the beam's convergence correction means dependent upon a predetermined plurality of location of the beams in the primary coordinate system, and e. third switch means (32) responsive to each of the horizontal and vertical deflection means for supplying the product signal to each of the beams convergence correction means dependent upon predetermined plurality of locations of the beams in the primary coordinate system, and f. means (a 11 ...,b 11 ...,c 11 ... ) responsive to each of the signals supplied to each of the beam's convergence correction means for effectively converting each of the signals in the primary coordinate system to corresponding signals in the secondary coordinate system.

Claim 10

Apparatus according to claim 7, characterised in that the means (all...,bll.",cll...) corresponds to each of the predetermined beam locations in the primary coordinate system.

Claim 11

Apparatus according to claim 8, characterised in that the means (a 11 ...,b 11 ...,c 11 ...) comprises means (37, 38, 39) for modifying the magnitude of each of the signals.

Claim 12

Apparatus according to claim 9, characterised in that each of the signal modifying means comprises an impedence means (37, 38, 39).

Claim 13

Apparatus according to any of claims 7 to 10, characterised in that the display screen is rectangular, the primary coordinate system is rectalinear, and the predetermined locations are at the right and left centre upper and lower centre and at each of the corners of the display screen.

Claim 14

A display symbol for use in correcting the convergence of the electron beams of a delta-gun colour cathode ray tube display, characterised in that the delta-gun includes electron beam emitters for exciting, when properly converged, the corresponding blue, red and green phosphor dots of the display screen and located at the apices of an equilateral triangle, and convergence correction electrodes for deflecting each of the beams in a direction normal to the sides of the equilateral triangle, the display symbol comprising three lines of predetermined length relatively oriented to each other so as to form an equilateral triangle, the apices of which correspond to the relative angular positions of the electron guns, two of the lines being generated by the excitation of two of the electron guns and the third of the lines being generated by the excitation of one of said two electron guns and the other of the electron guns.

Claim 15

A display symbol for use in correcting the convergence of the electron beams of a delta-gun colour cathode ray tube display, characterised in that the delta-gun includes electron beam emitters for exciting, when properly converged, the corresponding blue, red and green phosphor dots of the display screen and located at the apices of an equilateral triangle, and convergence correction electrodes for deflecting each of the beams in a direction normal to the sides of the equilateral triangle, the display symbol comprising three lines of predetermined length relatively oriented to each other so as to form an equilateral triangle, the apices of which correspond to the relative angular positions of the electron guns, two of the lines being generated by the excitation of two of the electron guns and the third of the lines being generated by the excitation of one of said two electron guns and the other of the electron guns.

Claim 16

A display symbol according to claim 12, characterised in that the said two lines are generated by exciting the guns corresponding to the red and green dots, and the other line by the excitation of one of the guns corresponding to the red and green dots and the gun corresponding to the blue dot.