US2855530A - Convergence means - Google Patents

Description

0 F HAMANN CONVERGENCE MEANS Filed March 29, 1956 Oct. 7, 1958 INVENTOR.

OMER F. HAMANN.

ATTORNEY United States Patent O CONVERGENCE MEANS Omer F. Hamann, San Diego, Calif., assignor to General Dynamics Corporation, Rochester, N. Y., a corporation of Delaware Application March 29, 1956, Serial No. 574,726

2 Claims. (Cl. 313-77) This invention relates generally to a componentfor utilization with a cathode ray tube, and more particularly, to an improved convergence means.

Convergence means are utilized in many cathode ray tube constructions to effect various desired electromagnetic fields to influence or control an electron beam generated by the cathode ray tube. One type of such cathode ray tube utilizing convergence means is a cathode ray display tube such as is shown and described in the copending application of Joseph T. McNaney et al., Serial No. 507,856, now Patent No. 2,824,250, and my copending application Serial No. 507,902, both assigned to the common assignee hereof, wherein the convergence means is utilized to effect desired focusing and imaging actions upon character shaped beams. In the prior art, it has been found necessary to provide a plurality of mechanical controls to eifect a proper alignment of the convergence means about the neck of the cathode ray tube,

as is exemplified in Serial No. 507,856. Because of the inherent geometry of the tube, the adjustments to the convergence means must generally be made at or near the means itself and at some distance from the screen. The person adjusting the tube therefore generally does not have a first-hand view of the screen and can only see the reflection of the display by means of mirrors to evaluate the images of the display. The convergence means includes a main convergence coil which is of an electromagnetic type and designed with predetermined electro-optical properties. The convergence coil is designed to effect desired beam focus, imaging and convergence of the electron beam according to predetermined conditions within the cathode ray tube. The coil, generally, is utilized in the display tubes not only to redirect the path of the electron beam to a convergence or cross over point along the electrooptical axis, but also to achieve predetermined imaging characteristics of the cross section of the beam upon the target. As is taught in my copending application Serial No. 507,902, proper imaging of the cross section of the electron beam necessitates predetermined electrical spacing relationships between the electrical center or axis of the convergence coil, the beam, and the electrical or electro-optical axis of the tube.

It has been found necessary to provide about 5 of motion to the convergence coil to properly adjust it about the neck of a display tube, for example. It will there fore be seen that it is important, both initially and during operation of the display tube, to effect adjustments of the electrical axis of the convergence coil from time to time to maintain the required parameters. The mechanical adjusting needed to effect adjustment of the convergence coil so that the axis thereof was generally coaxial with the electro-optical axis consisted of mechanical adjustments to effect vertical translation, horizontal translation, pitch, yaw and translation along the electro-optical.

axis of the tube. One of the objects of this invention ICC is to reduce the mechanical adjustments to a single translation adjustment along the optical axis of the tube and an adjustment to maintain the electrical axis of the coil substantially coaxial with the electro-optical axis of the tube.

The present invention overcomes these disadvantages by eliminating the complex mechanical adjustments. The invention utilizes the convergence coil as taught in my copending application Serial No. 507,902 as the basic component. The coil is disposed adpacent and substantialy symmetrically with the cathode ray tube. About the convergence coil is disposed a plurality of auxiliary windings which produce electromagnetic deflecting fields substantially orthogonal with the electrical axis of the coil. The deflecting windings are utilized to compensate for misalignment of the tube elements, to compensate for effects of stray direct current fields and to further compensate for small mechanical misadjustments of the convergence coil itself.

It is another object of this invention to provide a substantially electrically alignable convergence means for cathode ray tubes.

It is another object of this invention to provide a new and improved convergence means which may be electrically adjusted from a remote position to effect its proper alignment.

It is another object of this invention to provide a new and improved convergence means which may be simply and easily mounted about the neck of a cathode ray tube.

It is another object of the present invention to provide a convergence means whose mount assembly is of reduced complexity and cost.

It is another object of this invention to provide a new and improved convergence means which permits utilization of shielding structure of reduced complexity and cost.

It is another object of this invention to provide a new and improved convergence means whose alignment adjustments can be made with great ease by a substantially inexperienced operator.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawings, in which:

Figure 1 is a view of a portion of a cathode ray tube in perspective embodying the invention;

Figure 2 is a view in perspective of a convergence means, with cut-away sections, embodying the invention;

Figure 3 is a view in cross-section along line IIIIII of Figure 2;

Figure 4 is a schematic representation of a circuitry which may be used to effect the necessary alignment adjustments in the convergence means.

Figure 1 shows generally a portion of a cathode ray tube 10, which may be of any known type, but is shown here as a cathode ray display tube such as is exemplified in the aforementioned copending applications Serial Nos. 507,856 and 507,902. At one end of the tube 10 is positioned a beam generating means 11 which provides and projects an electron beam 12 generally along a predetermined electro-optical or electrical axis 13 of the tube 10 for impingement upon a target 14, such as a fluorescent screen. Intermediate the generating means 11 and target 14 is positioned a selection means 15, which may be of any known deflection plate or yoke design, but is shown as a pair of vertical and a pair of horizontal electrostatic deflection plates. The selection means 15 is used to position the beam both horizontally and vertically to a desired portion of a matrix 18 whereby desired characters formed in the matrix are illuminated. The matrix 18 is positioned generally intermediate the target 14 andthe selection means 15.

Intermediate the matrix 18 and the target 14 and positioned about the neck of the tube 10 is a convergence means 19. The convergence means 19 acts through its electromagnetic field to effect predetermined control, such as convergence and imaging, upon the electron beam 12 after the beam leaves the matrix 18. A positioning means 20, located generally intermediate the convergence means 19 and target 14 effects predetermined positioning deflection upon the beam 12 to position the beam crosssection on the target 14 at any desired position.

As is taught in my prior application, it is important to direct the electron beam 12 along predetermined paths and further to effect predetermined convergence, focusing and imaging actions upon the cross section of the electron beam. To accomplish this result the electrical axis of the convergence means and the electro-optical axis of the tube 10 must be oriented to a substantially common axis along which the electron beam may be projected. Proper alignment of the electron beam with the convergence means has been found to require at least of angular motion and some translatory motion of the convergence means whereby the convergence means is properly adjusted about the neck of the tube to effect the desired orientation. Such orientation of the convergence means effects control of the beam in vertical translation, horizontal translation, pitch, yaw and translation along the electrical or electro-optical axis 13 of the tube 10.

The convergence means 19, shown in greater detail in Figures 2 and 3, includes two pair of deflection windings or coil units 22, 23, 24 and 25 which are disposed adjacent and may be disposed generally about a main convergence coil 26. The coils may be formed in any known manner and are shown here as a wound coil,-

namely, main convergence coil 26 and four printed circuit coils 22, 23, 24 and 25. However, it should be expressly understood that the deflection coils 22, 23, 24 and 25 may also be of a wound coil construction rather than a printed circuit construction and still fall within the present invention. The deflection windings or coils 22, 23, 24 and 25 are shown as preferably each of a semi-cylindrical shape and disposed with another to form substantially a cylindrical shape. Coils 22, 23, 24 and 25 are substantially symmetrically disposed about the main convergence coil 26, and act to set up horizontal and vertical deflecting fields generally perpendicular to electrical axis 27 of the main coil 26. The deflecting fields set up by the windings 22, 23, 24 and 25 may be utilized to effect vertical and horizontal translation, pitch and yaw, and a slight translation along the electro-optical axis 13 of the tube 10.

Coils 22 and 23 are shown disposed about main coil 26 and disposed 180 apart from each other with their concavities facing each other. Coil 22 and 23 are connected together electrically as shown schematically in Figure 4. Coils 24 and 25 are rotated 90 from the position of coils 22, 23 and are likewise disposed 180 apart from each other with their concavities facing each other and series connected. Therefore, coils 22 and 23 and coils 24 and 25 are positioned in orthogonal relationship to one another to effect respectively vertical and horizontal deflecting fields which are substantially perpendicular to the field of the main convergence coil 26;

In addition, a pair of trim windings 30, 31, which may be of any known construction but are shown here as coils of conductors, are used on either end of the main convergence coil 26 to effect additional control upon field generated by the main convergence coil 26.

It has been found by experimentation that the deflecting currents necessary in the coils 22, 23 and coils 24, 25 to effect desired alignment of the electro-optical a s 13 and the electrical axis 27 of the main convergence coil 26 is a rather small current on the order of 30 milliamperes. It is possible, therefore, by utilizing a circuitry, for example, as is shown in Figure 4, where a power supply 37 of known construction, furnishes power to the circuit. A main potentiometer 38 regulates the power to the circuit. A plurality of cross connected potentiometers 39 are utilized to permit adjustment in windings 22, 23 and 24, 25 to effect the various desired vertical and horizontal translations, pitch and yaw and to provide slight translation along the electro-optical axis 13 of the tube 10. Utilization of the instant invention also increases the sharpness and clarity of the resulting display upon the target 14 of the tube 10.

The convergence coil 26 carrying the deflection coils may be simply symmetrically mounted about the neck of the tube 10, as shown in Figure l, by any known means of directly mounting the coil on the neck of the tube, but is shown in the preferred embodimentas being accomplished by clamping with clamps 33, 34 of aplastic insert 35 the coil 26 directly to the neck of the tube 10. It is therefore possible as the coil 26 is completely independent of the tube shielding, to reduce the complexity of the shield necessary to effect shielding of the coil and to eliminate the various complicated shield movements needed heretofor to adjust the coil mechanically. Therefore, the various alignment adjustments of the electron beam to compensate for tube element misalignments, stray magnetic fields and minor mechanical misadjustments of the convergence coil may all be accomplished in a straight forward manner by a single operator at the tube screen by varying selectively potentiometers 38 and 39. Further, considerable reduction in cost is effected by elimination of the complex mechanical adjustments and suspensions. The improvement in the tube shielding likewise is of considerable advantage in that the shield need no longer be movable and may now be directly applied above the coil to shield against stray electromagnetic fields.

The particular embodiment of the invention illustrated and described herein is illustrative only and the invention includes such other modifications and equivalents as may readily appear to those skilled in the art within the scope of the appended claims.

I claim:

1. In a cathode ray display tube construction wherein an electron beam is generated and projected along an axis toward a target, a beam shaping member is disposed in the path of the beam to effect a desired cross sectional shaping upon the beam and an electromagnetic convergence means is electromagnetically coupled with said beam, the improvements in said convergence means comprising a main convergence coil having an electrical axis when energized, deflection windings substantially encircling said convergence coil for producing variable intensity fields substantially orthogonal with said electrical axis when energized, said fields being capable of displacing said electrical axis in response to the intensity of said fields to cause coaxial alignment of said axis with said electrical axis.

2. In a cathode ray display tube construction wherein an electron beam is generated and projected along an axis toward a target, a beam shaping member is disposed in the path of the beam to effect a desired cross sectional shaping upon the beam and an electromagnetic convergence means is electromagnetically coupled with said beam, the improvements in said convergence means comprising a main convergence coil having an electrical axis when energized, four windings orthogonally disposed about and adjacent said convergence coil, said coil and said WindingvbeingsYmTfimaHyFW with respect to one another, said windings when energized having a field capable of adjustment to effect displacement of said electrical axis coaxial with said axis.

(References on following page) 6 References Cited in the file of this patent 2,692,355 Sickles et a1. Oct. 19, 1954 2,719,249 Friend Sept. 28, 1955 2151530 E E STATES PATENT; 21 1939 2,793,311 Thomas May 21, 1957 us a ar. 2,167,379 Tolson July 25, 1939 5 OTHER REFERENCES 2,414,925 Buckbee Jan. 28, 1947 Martin: Printed Crossed-Field Deflecting Coils, T ele- 2,539,492 Smyth Jan. 30, 1951 Tech and Electronic Industries, December 1954, pages 2,653,262 Bowman Sept. 22, 1953 82, 83, 140 and 141.

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