JPS58201228A - Exposure device for forming phosphor screen of color picture tube - Google Patents

Abstract

PURPOSE:To correct stripe meandering of a phosphor by making at least one side of a negative meniscus lens into an approximate spherical surface to eliminate of a difference of the panel destinations of rays emitted from both ends of a linear light source. CONSTITUTION:In an exposure device, an orientation filter 24, a landing correction lens 25 and a negative meniscus lens 26 are respectively arranged between a shadow mask 23 supported facing to the inside of a panel 22 in order from the shadow mask side 23 so that the optical axis may pass the center of a linear light source. The meniscus lens is formed so as to be the approximately spherical faces 33 and 34 as shown by broken lines.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an exposure apparatus for forming a fluorescent surface of a shadow mask type color receiving tube having a striped fluorescent surface.

Technical Background of the Invention and Problems Thereof Color picture tubes are generally of a type that is composed of a combination of a shadow mask having a large number of slit-like openings and a striped phosphor. The striped phosphors of such a color picture tube are formed by an exposure method through slit-like openings in a shadow mask. Here, the slit-like openings of the shadow mask are arranged along the vertical line of the color picture tube, and a large number of such vertical arrangements are arranged in the horizontal direction. Therefore, when exposure is performed using a normal exposure device, a meandering phenomenon of the phosphor stripes occurs in the periphery of the color picture tube, particularly near the corners, as shown in FIG. This meandering phenomenon becomes more pronounced in larger tubes, and as a result, it impairs the beam landing characteristics and causes deterioration in color purity. There was a rainbow like this.

In order to prevent the line phenomenon, it is necessary to modify the curvature of the mask or the arrangement of slit holes, or to use a correction means such as a hole corresponding to the exposure apparatus.

For example, US Pat. No. 4,078,239 discloses an exposure apparatus using a negative meniscus lens as shown in FIG. The exposure device al) in Figure 2 shows a cross section of the plane parallel to the horizontal line of the panel. Between the long line light source (goods), from the shadow mask (to) side, an alignment filter (2), a landing correction lens (to), and a negative meniscus lens (c) are installed so that the optical axis passes through the center of the line light source. Both sides of this negative meniscus lens are completely spherical and are rotationally symmetrical with respect to the optical axis.If this negative meniscus lens is designed optimally, the light will be emitted from the center of the linear light source and After passing through the negative meniscus lens, all the rays that reach the inner surface proceed as if they were emitted from a position that is a certain distance from the actual center position, and are also a stripe. There is a possibility that meandering can be corrected to some extent.

Incidentally, the amount of stripe meandering that occurs when an appropriate correction means is not used depends mainly on the curvature of the panel and shadow mask in the stripe direction and the curved shape of the landing correction lens. The curved shape of the landing correction lens reflects the electron beam deflection characteristics of the corresponding deflection yoke. Therefore, if the negative meniscus lens having the perfect spherical surface is used, it is possible to correct the stripe meandering, but there is a limit to the amount of correction. Therefore, depending on the curvature of the panel and shadow mask and the curved shape of the correction lens, the negative meniscus lens may not be able to sufficiently correct stripe meandering.

OBJECTS OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks of fog light apparatuses using negative meniscus lenses and to provide an exposure apparatus capable of correcting sufficiently large stripe meandering.

Summary of the Invention The present invention corrects the stripe meandering of the phosphor by eliminating the difference in the panel arrival points of nine rays emitted from both ends of the linear light source by making at least one surface of the negative meniscus lens an approximate spherical surface5. , Embodiment of the Invention An embodiment of the exposure apparatus of the present invention will be described below using one example.

FIG. 3 shows a cross-sectional shape including the optical axis of the negative meniscus lens in the exposure apparatus shown in FIG. It is formed to have an approximate spherical surface α and C4) shown in FIG. Here, in the case of a perfect spherical surface, for example, the inner spherical radius RCII)ti19■, the outer spherical radius R
(To) Fi35■, center thickness 3.2m. FIG. 4 shows the curve of the inner or outer surface of the lens in the cross-sectional view of FIG. 3, together with coordinate axes. That is, it shows the relationship when the height fr of a perpendicular to the optical axis -1 from a point on the curved surface with respect to the two optical axes is expressed by the solid line perfect spherical surface (4a is shown by the following equation).

r snow 2 Z=R(1-(1-(-) l)...(1
) Approximate spherical surfaces (to) and (b) indicated by broken lines in FIG. 3, and approximate spherical surfaces indicated by broken lines in FIG. 4 are expressed by the following equations. That is, +1) 0 of the expression
When the second term t<X->'' is subjected to Taylor expansion and the fourth term is expanded, the formula +1) becomes as follows.

FIG. 5(a) shows numerically calculated meandering correction characteristics near the screen corners of the 92 types of q negative meniscus lenses shown in FIG. 3. The solid line (51) is the solid line C(fi
, @ are the characteristics of a negative meniscus lens consisting of a perfect spherical surface, and the broken line (5z) is the broken line (c) in Figure 3.

(b) Characteristics of the negative meniscus lens used in the exposure apparatus of the present invention. The model is a 19 inch-90 deflection tube, with only a negative meniscus lens placed between a 20 inch long line light source and a panel mask.

Assuming t-, after the light beams emitted from both ends of the linear light source pass through the same point on the mask, thifc "I" in the panel
For the stripe of each arrival point when ll M, pair (
(The difference in vertical position is calculated by changing the position of the negative meniscus lens with respect to the light source. Here, the lens X position is
The distance between the intersection of the lens inner surface and the optical axis and the light source (/i distance).

Figure 5 (mountain) is an example of calculating the vertical direction 4X'tf11 with respect to the stripe of the screen arrival point after the light rays emitted from each position on the linear light source pass through the same point on the mask, It is based on the arrival position of the light beam emitted from the center of the linear light source.

The meandering amount can be estimated based on the difference in the screen arrival points of the light beams emitted from both ends of the linear light source. In other words, it can be said that the greater the difference in the arrival points, the greater the meandering, and if the difference disappears, the meandering also disappears. As can be seen from the solid line (51) in Fig. 5(a), a negative meniscus lens is formed by a perfect spherical surface.

In this case, the correction amount has a certain maximum point and is not corrected beyond that point.The meandering correction characteristic of the negative meniscus lens using the perfect spherical surface changes depending on the inner surface R1 outer surface R and center thickness, but as shown in FIG. (The shape characteristic tendency of the solid line (51) in i3 is generally preserved.Also, the correction amount increases by making the inner surface R smaller, but this negative meniscus lens is ,
Since all the light rays reaching the effective surface of the screen must pass through, the inner surface R cannot be made smaller than a certain limit determined by the length of the linear light source. As can be seen from the above, the meandering correction ability of a negative meniscus lens made of a perfect spherical surface has a certain limit, so
Depending on the picture tube, sufficient correction may not be possible. The solid line (51) in FIG. 5 (&) is also not completely corrected. On the other hand, Figure 5 (&) Break 4
1i! As can be seen from (52), according to the negative meniscus lens of the present invention, a sufficient amount of correction can be obtained.

The principle of meandering correction using the above negative meniscus lens is the coma aberration of the lens. Therefore, when designing a negative meniscus lens, it is necessary to obtain an appropriate coma aberration, but if you also consider the design of the landing correction lens (c), a negative meniscus lens will produce σ rays when they reach the inner surface of the panel. It is also desirable to have the effect of lifting the line light source toward the panel by a distance equal to the center position ti under equal constraints, that is, to minimize the spherical aberration of the lens.3 If this is done, the negative meniscus lens The design and the design of the landing correction lens can be separated, which facilitates the design of the correction lens system. .

FIG. 6 shows the spherical aberration (change in the amount of elevation Δp at the center of the light source) of the negative meniscus of the present invention shown by the broken line in FIG. This is what I calculated. As described above, the spherical aberration of the skin has almost no effect on the landing characteristics of #1.

In the lens indicated by the broken line in FIG. 3, which is an example of a negative meniscus lens used in the exposure apparatus of the present invention, both the inner and outer surfaces are approximately spherical. The deviation is small. Therefore, the outer surface may be a perfect spherical surface. In addition, in the above example, the approximate spherical surface is nine curved surfaces that have up to the fourth term of the Taylor expansion of the curved surface equation of a perfect spherical surface, but the curved surface equation of the negative meniscus lens of the present invention is limited to this approximation method As described above, the negative meniscus lens applied to the exposure apparatus of the present invention is designed to have no influence on the landing characteristics and to have sufficient stripe meandering correction ability. You can do that. Therefore, according to the exposure apparatus of the present invention, it is possible to prevent deterioration of purity due to stripe meandering in any picture tube.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged schematic diagram of a nozzle for showing stripe meandering, Fig. 2 is a schematic sectional view showing an exposure apparatus using a conventional perfect spherical negative meniscus lens, and Fig. 3 is a schematic diagram of a conventional An enlarged partial cross-sectional view comparing a perfect spherical surface and an approximately straight negative meniscus lens of the present invention, FIG. 4 is a curve diagram showing the coordinate system for expressing the lens curved surface formula, and FIG. A characteristic diagram showing the correction characteristics. Figure 5(b) shows an example of the relationship between the light rays on the light source and the arrival point on the screen. Figure 6 shows the spherical surface of the negative meniscus lens of the present invention. FIG. 3 is a characteristic diagram showing aberration characteristics. (20... Exposure device (c)... Panel (to)... Shadow mask @... Light distribution filter (to)
... Landing correction lens ... Negative meniscus lens (foundation) ... Linear light source (31), 03. (40...Curved surface of perfect spherical negative meniscus lens (to), (b), (b)...Curved surface of approximate spherical negative meniscus lens (51)...Correction characteristics of stripe meandering of perfect spherical meniscus lens (52) ... Compensation lF characteristics of stripe meandering of an approximate spherical negative meniscus lens (61) ... Spherical aberration characteristics of an approximate spherical negative meniscus lens (7317) Agent: Patent attorney Noriyuki Chika (and 1 other person) Figure 2 Figure 3 Room 4
5 Figure (b) Figure 6

Claims (1)

[Scope of Claims] ■) A panel on which striped phosphors are formed, a shadow mask having a large number of slit-like openings and supported inside the panel, and disposed opposite to this shadow mask. a linear light source, a landing correction lens disposed between the shadow mask and the linear light source, and a negative meniscus lens disposed between the linear light source and the correction lens; An exposure device for forming a fluorescent surface of a color picture tube, characterized in that at least one surface of a meniscus lens is formed of an approximate spherical surface. 2) For the radius R of the corresponding spherical surface of one concave curved surface of a negative meniscus lens, the length of the perpendicular from a point on the curved surface to the optical axis is 11, and the distance from the plane tangent to the optical axis of the curved surface is 2 2. The exposure device for forming a color picture tube fluorescent surface according to claim 1, wherein the exposure device is expressed by the following curved surface formula: ~lr'' 1. r4 1 r@22R+8 R3+16RI.