US 3731129 A
A color receiving tube having a maximum deflection angle of greater than 90 DEG disposed close to phosphorescent surface, the perforations of the mask being formed as slits arranged in vertical rows, and an electron gun assembly comprised by three unit electron guns disposed in-line on a common horizontal plane. The deflecting portion of the tube, around which is disposed a deflecting device, is formed as a funnel whose cross-sectional configuration gradually varies from that similar to the configuration of the reproduced image to circular.
Claims available in
Description (OCR text may contain errors)
llnited States Patent 1 Tsuneta et al.
I  RECTANGULAR COLOR TUBE WITH FUNNEL SECTION CHANGING FROM RECTANGULAR TO CIRCULAR Inventors: Asahide Tsuneta, Kawasaki-shi; Yasuo Ohta; Makoto lkegaki, both of Fukaya-shi, Saitama-ken, all of Japan Tokyo Shibaura Kawasaki-shi, Japan Filed: Oct. 28, 1970 Appl. No; 84,809
 Assignee: Electric Co.,
 Foreign Application Priority Data Nov. 4, l969 Japan ..44/87632 US. Cl. ..3l3/64, 313/855, 313/92 B Int. Cl ..H0lj 29/00, HOlj 29/06, HOlj 31/20 Field of Search ..3l3/855, 64, 92 B References Cited UNITED STATES PATENTS 3,652,895 3/1972 Tsuneta et al ..3l3/92 B 1 3,73Lil29 1 May 1, 1973 2,764,628 9/1956 Bambara ..3l3/85 S 3,5l7,242 6/1970 Pappadis ..3i3/70 C FOREIGN PATENTS OR APPLICATIONS 656,682 8/l95l Great Britain ..3l3/64 Primary ExaminerRobert Segal Att0rney-Flynn & Frishauf  ABSTRACT A color receiving tube having a maximum deflection angle of greater than 90 disposed close to phosphorescent surface, the perforations of the mask being formed as slits arranged in vertical rows, and an electron gun assembly comprised by three unit electron guns disposed in-line on a common horizontal plane. The deflecting portion of the tube, around which is disposed a deflecting device, is formed as a funnel whose cross-sectional configuration gradually varies from that similar to the configuration of the reproduced image to circular.
1 Claim, 17 Drawing Figures PATENTEU MY 1 sum 1 or 3 PRIOR ART F l G. 2
PRIOR ART PATENIEDHA-Y 11975 f 3,731,129
I sum 2 OF 3 F l 6.50 FIG.5E
F C F|G.6D mass 'FIG.6B
PATENTEDHAY 1 ms sum 3 [1r 3 FIG.7
RECTANGULAR COLOR TUBE wmr FUNNEL SECTION CHANGING FROM RECTANGULAR To CIRCULA BACKGROUND OF THE INVENTION This invention relates to a color television receiving tube and more particularly to a color television receiving tube having a maximum deflection angle greater than 90 and utilizing a mask having perforations in the form of slits for passing electron beams and is suitable for wide angle deflection.
Especially in, color television receivers it is desired to decrease the depth or the distance between the front and rear of the receiver cabinet. To satisfy this requirement it is essential to construct the color television receiving tube as a wide angle type. However, it is necessary to solve various problems such as increase in the diagonal misconvergence, increase in the deflection power and creation of the neck shadow. It is also necessary tomake easy adjustment of the convergence, and to improve the brightness and clearness of the reproduced image.
In certain types of prior color receiving tubes, it has been difficult to solve these problems. In order to have a better understanding of the invention, the reason why it is difficult to increase the deflection angle is described by outlining the conventional construction of a prior art color receiving tube. With reference first to FIG. 1 of the accompanying drawings which shows a typical prior art color receiving tube including a phosphorescent surface mounted on the inner surface of a face plate la, a plurality of trios of dots 2 of three types of phosphorus emanating different colors are arranged on the inner surface of the face plate as a plurality of equilateral triangles. A funnel 3a is provided with its opening sealed to the periphery of the face plate In and with its reduced diameter portion joined to a neck 6a containing a deflecting portion a surrounded by a deflecting device 4a. An electron gun assembly comprising a plurality of electron gun units 7a which are disposed at the apices of an equilateral triangle is disposed in the neck 6a. In front of the phosphorescent surface is mounted a shadow mask 9a provided with a plurality of circular perforations 8 for transmitting electron beams. Three electron beams 10 emitted from the electron gun assembly are deflected by the deflection magnetic field produced produced by a deflecting device 40 and converged in a perforation by means of a convergence adjuster 11 contained in the neck to pass through one of the perforations 8 so as to reproduce an image free from color mismatch. Each of the electron beams from the electron gun unit is shifted in the direction of an arrow 13 (FIG. 2) by adjusting the intensity of the field between pole pieces of the convergence adjuster 11.
In the color receiving tube having the construction described above, in order to vary the deflection angle from 90 to 1 10, it is necessary to increase about 2.2 times the quantity of convergence adjustment. Moreover, the degree of asymmetry of the convergence of the electron beams with respect to the tube axis which is caused by the shift of the deflection center increases'by a factor of 1.5 with respect to that of 90- deflection. In order to properly correct the convergence of the electron beams at the peripheral edge of the shadow mask, an adjusting current synchronized 5 justment. With this method of adjustment, while it is possible to provide a perfect convergence along the horizontal axis (direction of the horizontal. scanning) and along the vertical axis (direction of the vertical 0 scanning) of the receiving tube, there are some portions along diagonals of the shadow mask in which perfect convergence adjustment is not possible, thus causing color mismatch. The degree of misconvergence along the diagonals (diagonal misconvergence) can be reduced to about 0.5 mm in a conventional deflection tube. However, where the deflection angle is increased to l 10", the degree of diagonal misconvergence increases to about 2.5 mm which is too large for practical color receiving tubes.
Increased deflection angle requires larger deflection power so that it is necessary to reduce the diameter of neck 60 to prevent this increase in the deflection power. However, inasmuch as the electron beams 10 travel along paths about 5 mm spaced apart from the tube axis and along the inner wall of the neck 6, if one tries to increase the deflection angle, with the conventional cross-sectional construction of the deflecting portion the electron beams 10 will collide upon the inner wall thereof, thus causing non-luminous portions or the so-called neck shadow at the ends of diagonals of the fluorescent surface where the electron beams do not reach. Where the cross-sectional configuration of the deflecting portion 5a is circular as in the conventional design, the tendency of forming the neck shadow is increased as the diameter of the neck 6a is reduced. For this reason, it is necessary to increase the diameter of neck 6a in order to increase the deflection angle. However, an increase of the diameter requires larger deflection power. For this reason, with receiving tubes of conventional construction, it has been extremely difficultto increase the deflection angle without increasing the deflection power.
Accordingly, it is an object of this invention to provide an improved wide deflection angle color receiving tube which can decrease the diagonal misconvergence, does not increase the convergence power, does not generate the neck shadow, can increase the deflection angle and can reproduce clear images.
SUMMARY OF THE INVENTION According to this invention there is provided a color receiving tube comprising a face plate; a fluorescent surface provided on the inner surface of the face plate and including a plurality of trios of fluorescent or phosphorescent materials emanating different colors; a funnel section having a larger peripheral portion sealed to the periphery of the face plate, a deflecting portion connected to the larger peripheral portion, and a neck connected to the deflecting portion; a deflecting device surrounding the deflecting portion; an electron gun assembly including three in-line electron gun units and contained in the neck; and a perforated mask disposed close to the fluorescent face, wherein the deflecting portion takes the form of a funnel whose cross-sectional configuration gradually varies from a shape similar to that of the image reproduced on the face plate to circular, and the mask is provided with a plurality of slits.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view, partly in section, of a prior art color receiving tube having a shadow mask provided with circular perforations for transmitting electron beams;
FIG. 2 is an enlarged sectional view of an electron beam convergence adjusting device utilized in the prior art color receiving tube shown in FIG. 1;
FIG. 3 is a perspective view, partly in section, of one embodiment of the color receiving tube of the present invention;
FIG. 4 is a side view of the color receiving tube shown in FIG. 3',
FIGS. 5A to SE show sectional views of the face plate, funnel and the deflection portion taken along lines 5A5A to 5E5E (FIG. 4) respectively;
FIGS. 63 to 6E show another example of sectional views of the deflecting portion of the tube of the present invention;
FIG. 7 shows the arrangement of the slit shaped perforations for the electron beams of the shadow mask shown in FIG. 3;
FIG. 8 shows the arrangement of thecircular perforations for the electron beams of the shadow mask utilized in the prior art tube of FIG. 1;
FIG. 9 shows the arrangements of the electron gun units shown in FIG. 3 (solid lines) and of the electron guns shown in FIG. 1 (dotted lines); and
FIG. 10 shows a modified arrangement of the electron gun units shown in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIG. 3 of the accompanying drawings, an envelope of the receiving tube is shown as comprising a rectangular dish shaped panel 1 having a horizontal length H and a vertical length V of a ratio of approximately 4 3, and a funnel 3. The reduced diameter portion of the funnel comprises a cylindrical neck 6 within which is disposed an electron gun assembly 16 including three unit electron guns 7 arranged side by side (in-line) in a common horizontal plane. Also a portion 17 of a convergence device is contained for adjusting the convergence of three electron beams emitted from respective electron gun units. Deflecting portion 5 of the envelope is adjacent to neck 6 and in the form of a funnel gradually flaring outwardly from the neck. A deflecting device 4 is mounted on the outside of deflecting portion 5 to deflect electron beams 10 in the horizontal and vertical directions. As shown in FIG. 5B, the cross-sectional configuration of the large diameter portion of the deflecting portion is substantially rectangular similar to that of the image displayed on the face plate or panel 1. The cross-sectional configuration gradually varies to circular as shown in FIG. SE successively through smaller rectangular (FIG. 5B), elliptical (FIG. 5C) and oval (FIG. 5D) shapes. Thus the configuration of the deflection portion is generally frustoconical. A shadow mask 9 is disposed in front of panel 1 adjacent to the phosphorescent surface. As shown in FIG. 7, the shadow mask is provided with a plurality of slit shaped (generally rectangular) perforations 18, each having a length l and a width d, for transmitting the electron beams. These slits are arranged in parallel vertical rows, with a horizontal pitch ofp and a vertical spacing of g. If desired the gaps g may be eliminated and the slits may be arranged in parallel horizontal rows.
In the construction shown in FIG. 7, perforations of adjacent rows are dephased gradually, but if desired they may be aligned in the horizontal direction. However, the dephased arrangement shown in FIG. 7 is generally preferred for the reason to be described hereinafter. A phosphorescent surface 22 is mounted on the inner surface of face plate 1 and is provided with a plurality of trios of stripe-shaped phosphorescent elements 20 for emanating three different colors, each stripe of the fluorescent material corresponding to each slit 18 of the shadow mask 9. These stripes of phosphorescent materials may be continuous, if desired.
The three electron beams 10 are deflected in the horizontal and vertical directions by the magnetic field generated by the deflecting device 4, converged in the perforations 18 of the shadow mask 9 and are then caused to impinge upon the trios of phosphors 20 to reproduce an image. Convergence of the electron beams is adjusted by the convergence device 17.
Since respective unit electron guns 7 of the electron gun assembly 16 are arranged in a common horizontal plane the convergence can be more readily adjusted than by the prior method of adjustment. Especially, the dynamic convergence adjustment can be provided only by the horizontal component so that the adjustment is easier than in the prior electron gun assembly wherein the electron gun units are disposed at apices of an equilateral triangle. By adopting a deflecting device 4 suitable for this arrangement the convergence characteristics can be improved, thus decreasing the degree of the diagonal convergence. In other words, even in the case of a tube of 1 10 deflection angle, it is possible to decrease the diagonal convergence to about 0.5 mm in the same manner as in the conventional tube of deflection angle.
However, since three unit electron guns 7 are arranged side by side in a common horizontal plane, if they were constructed to have the same dimensions as conventional electron gun units 7a arranged in a unilateral triangle it is necessary to increase the diameter of the neck 6. As diagrammatically shown in FIG..9, even if the diameter of the the electron gun unit 7 is decreased to have a permissible lower limit of the electron gun characteristics, the width of the assembly is still larger than one side of the prior art triangular arrangement. As a result, with the arrangement of the electron gun units according to this invention, electron beams from two outside guns pass through paths close to the inner surface of the neck. If the deflecting portion 5a were constructed in the form of a frustum of a cone as in the conventional tube, the beams would collide upon the tube wall to form the neck shadow. On the other hand, an increase in the diameter of the deflecting portion 5a for the purpose of preventing the neck shadow results in increasing the deflection power.
Generally, the display surface of a receiving tube is in the form of a rectangle having a ratio of horizontal length H to vertical length V of approximately 4 3, for
example, so that the extent of the electron beams at the deflecting portion is also a smaller rectangle similar to the display surface. Accordingly, the electron beams are most liable to contact with the inner wall of the deflecting portion in the diagonal direction of the rectangle. However, in the novel receiving tube, since the cross-sectional configuration of the deflecting portion 5 where the deflection angle of the electron beams is largest is rectangular similar to the extent of the electron beams, it is possible to perfectly, prevent creation of the undesirable neck shadow.
Let us now consider the deflection power required for the novel receiving tube. If the cross-sectional configuration of the deflection portion were circular as in the conventional design, it is necessary to produce deflection fields larger than that actually required in the horizontal and vertical directions so that it is necessary to pass large deflection current through the deflection device. However, in the novel receiving tube, as the deflecting device 4 is shaped to conform to the outer configuration of the deflecting portion 5 it is possible to decrease the deflection current by D.C.
component required for forming an excessively large deflection field.
Although in the electron gun assembly 16 wherein three unit electron guns are arranged side by side in a common plane, reduction in the diameter of the electron gun units greatly increases the spherical aberration of the electronic lens to render it difficult to reproduce clear images, slit shaped perforations 18 obliterate this difficulty. More particularly, the novel receiving tube having shadow mask 9 provided with vertical rows of slit shaped perforations 18 can greatly improve the percentage of transmission of the electron beams while maintaining a comparable degree of landing allowance as the conventional receiving tube utilizing a shadow mask provided with circular perforations, as shown in FIG. 1. Moreover, the quantity of information transmitted to the face plate through the shadow mask can be increased. These two improvements are sufficient to compensate for the deterioration of the focusing of the electron beams due to the above described increase in the spherical aberration so as to reproduce clear images of high quality.
Following is a theoretical consideration for the reason why the novel cathode ray tube utilizing the slitted mask can increase the quantity of information over conventional cathode ray tubes utilizing shadow masks having circular perforations. More particularly, as the spacing between picture elements formed by the shadow mask is considerably larger than the special resolution determined by the electron beams, the correlation between respective picture elements can be neglected. Accordingly, the relationship among the quantized level number L of the contrast of the picture elements, the number of picture elements N and the quantity of information I transmitted to the display surface by the electron beams is expressed by the following equation I=NlogL.
For example, where a shadow mask shown in FIG. 7 is used having perforations each having dimensions of length i= 0.90 mm, width d 0.13 mm, spacing between vertically adjacent slits g 0.15 mm, and
horizontal pitch of rows p 0.60 mm, each slit shaped perforation can accommodate 2.5 to 3 electron beam spots so that the total number of the picture elements N is expressed as follows:
N= 3.98S to 4.75s
where S represents the surface area of the display surface.
On the other hand, in a conventional shadow mask 9a having circular perforations 8, each having a diameter r= 0.24 mm, and being arranged as shown in FIG. 8 with a pitch P 0.56 mm, as each perforation can accommodate only one electron beam spot, the total number of the picture elements N 3.718. For this reason, the quantity of information transmitted through shadow mask 9 having slit shaped perforations 18 is larger than that through shadow mask 9a having circular perforations by about 25 to 35 percent.
While the shadow mask having slit shaped perforations can reproduce brighter images, gaps g between vertically adjacent perforations often cause Moire fringes in the reproduced image. However, it was found that such Moire fringes can be prevented when corresponding slits in respective rows are shifted vertically or dephased along straight lines inclined with respect to the horizontal. Such Moire fringes can also be prevented by associating a wobbling device (not shown) with the deflecting device 4 or by placing the wobbling device between the deflecting device 4 and the electron gun assembly 16, said wobbling device oscillating at a frequency higher than the horizontal scanning frequency applied to the deflecting device 4 for causing the electron beams to scan horizontally while oscillating in the vertical scanning direction with a small amplitude.
In this manner, according to this invention, there are provided a shadow mask with slit shaped perforations, three unit electron guns arranged side by side in a common horizontal plane, and a funnel shaped deflecting portion having a cross-sectional configuration substantially similar to that of the image reproduced on the face plate so that it is possible to provide an improved wide deflection angle color receiving tube in which it is possible to readily adjust the convergence, can reduce misconvergence, does not create neck shadows, and can reproduce clear and bright images with lower deflection power.
It is to be understood that the invention can be modified in various ways. For example, asshown in FIG. 10 an isosceles triangular arrangement 16' of three unit electron guns is also possible wherein two unit electron guns are disposed in. the horizontal scanning direction with a center distance of D whereas a third unit electron gun is disposed on a normal passing through the center of a line interconnecting the centers of the first two guns at a height of h D/2. The first embodiment may be considered as a particular case wherein h 0.
According to experiments it has been found that the extent of the diagonal misconver'gence produced by the isosceles triangular arrangement 16' of the unit electron guns is less than one-third of that of the equilateral arrangement shown in the prior art tube of FIG. ll. Even when h %D, in the deflection tube embodying this invention the diagonal misconvergence is about 0.8 mm which is comparable with that of thev conventional 90 deflection tube. Such low values of diagonal misconvergence are permissible. With a modified electron gun assembly 16 shown in FIG. 10 it is possible to increase about 10 percent the outer diameter of the unit electron gun 7 with respect to that of the first embodiment wherein three electron guns are arranged side by side in a common horizontal plane so that it is possible to decrease the spherical aberration. The construction and operation of the other components of the receiving tube including the modified electron gun assembly are identical to those of the first embodiment.
While in the above described embodiment the deflection portion was shown in the form of a frustum of a pyramid whose cross-sectional configuration varies from rectangular to circular through oval, the crosssectional configuration may vary from oval to circular as shown in FIGS. 6B to 6E.
In addition to the shadow mask type of color receiving tube, the invention is also applicable to other types of color receiving tubes.
What we claim is:
l. A color receiving tube having a maximum deflection angle greater than 90, comprising:
a face plate section for producing a rectangular shaped image;
a phosphorescent surface provided on the inner surface of said face plate section and including a plurality of electron sensitive phosphors arranged in a regular pattern;
a funnel section having a wider peripheral portion sealed to the periphery of said face plate section, and a deflection portion whose cross-sectional configuration gradually varies from a rectangular shape substantially similar to that of the rectangular image produced on said face plate section to a circular shape both internally and externally;
a circular cylindrical neck portion connected to said circular shaped end opening of said deflection portion;
an electron gun assembly including three electron