JPH08315732A - Correcting lens manufacturing mold and correcting lens manufactured thereby as well as its manufacture - Google Patents

Abstract

PURPOSE: To provide such a mold as being capable of easily manufacturing a high-performance correcting lens used when manufacturing the fluorescent screen of a color picture tube. CONSTITUTION: An original mold 1A which has a smooth roughly-curved face is formed on one face of a plate solid material such as a heat-resistant metal, a ceramic and a glass. Then, it is cut at mutually parallel cut positions into a plural of band cut pieces 3C and the direction of these band elements 3C is changed 180 deg. in the original plane for re-arrangement, as the individual orders remain unchanged, to form a mold 1B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for producing a correction lens used when producing a fluorescent screen of a color picture tube, and a correction lens produced thereby.

[0002]

2. Description of the Related Art In manufacturing a color picture tube, the positions of mosaics such as dots and stripes formed on the inner surface of a face plate (panel) and the positional deviation of electron beam projecting points corresponding to each (hereinafter referred to as mislanding Call)
How to reduce this has always been a big issue. For this purpose, a phosphor mosaic is printed on the inner surface of the face plate by photography (called exposure).
When forming, a method of placing a correction lens having a special shape in the path of the printing light beam is generally used. This situation is described, for example, in RCA Review Vol. 16 (1955), pp. 491-497. W. “Improvement in color kin” by Epstein et al.
escapes through optical a
nology ”.

As the correction lens, one having a smooth curved surface having a complicated concavo-convex shape is generally used. However, when the fluorescent surface of the color picture tube in question is a dot type, it is known that it is impossible to obtain perfect mislanding correction over the entire face plate if the surface of the correction lens is limited to a smooth one. There is. This is based on the basic principle of optics, and as long as the above lens surface is limited to a smooth one, it cannot be solved by devising the position and number of surfaces (using a plurality of lenses stacked). . As a countermeasure, a method has been devised in which a lens is divided into two directions orthogonal to each other within the plane, and a plane having discontinuities and small steps is formed on each division line. That is, according to this method, the lens surface is divided into hundreds to several hundreds of small square blocks, and the surface of each block lens does not need to be a curved surface any more. Therefore, an inclined flat surface is used. When this lens is used, the dividing line causes unevenness in illuminance during exposure of the fluorescent screen, and therefore the lens is constantly reciprocated with a small amplitude. The details of such a technique are described in detail in "Discontinuous Surface Lens for Color Picture Tube Manufacturing" by Mr. Yamazaki in the 27th volume of the Television Society (1978), pages 461 to 466.

[0004]

The above conventional discontinuous surface lenses require a large number of divisions because the individual surface elements are flat, and therefore the tools for making them are expensive. There was a drawback.

Further, in the conventional discontinuous surface lens, the dividing lines extend in two directions which are orthogonal to each other. Therefore, in order to eliminate the influence of the dividing lines during use, the reciprocating motion given to the lens is in two directions. It was necessary to prepare a complicated reciprocating mechanism.

Further, in general, in the part of the dividing line, there is a tendency that a problem occurs due to the extraordinary refraction of the exposure line, but this problem is the most at the intersection of one dividing line and the dividing line orthogonal thereto. large. That is, at such intersections, the corners of the protruding lens block are apt to be chipped, which often causes unevenness on the phosphor screen to be burned. Therefore, the yield when manufacturing lenses is poor,
In addition, a considerable amount of labor was required for preliminary tests before use and for maintenance such as cleaning the lens surface. Most of such inconveniences can be considerably improved by making the dividing lines not parallel to each other but only parallel to one direction. However, in this case, the surface of the divided band-shaped lens is theoretically meaningless as a flat surface, and at least one of the surfaces needs to be a curved surface, which is expected to cause great difficulty in manufacturing. As a solution to this problem, a correction lens system is composed of two lenses, a first lens and a second lens, the first lens has a smooth surface, and the second lens has a smooth uneven surface formed on an optical material. Is divided into a plurality of strip-shaped elements by cutting planes parallel to each other, then each strip-shaped element is rearranged in a direction different from the original one without changing the order of adjacent ones. It was For details, see JP-A 2-1.
No. 77232.

By the way, the above-mentioned publication which describes the band-shaped discontinuous surface lens does not specifically describe the manufacturing method thereof so as to be commercially used for manufacturing a color picture tube.
The method described in the text alone has a drawback that the correction lens becomes expensive, and the method of reducing irregular reflection at the adjacent discontinuous portion of the strip-shaped element has not been described so specifically.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a mold capable of producing a correction lens by a simple method.

[0009]

A mold for producing a correction lens according to the present invention forms a smooth concave and convex curved surface on one surface of a plate-shaped solid material such as heat resistant metal, ceramics, glass, and the like. It is formed by cutting a plurality of strip-shaped elements along the cutting plane and rearranging the cut strip-shaped elements by changing their directions by 180 degrees in the original plane without changing the order of each.

Further, after forming a smooth uneven curved surface on one surface of a plate-shaped solid material such as heat-resistant metal, ceramic, glass, etc., this is cut into a plurality of strip-shaped elements by cutting planes parallel to each other, and these are cut. The direction of some of the strip-shaped elements is changed in the original plane by 180 degrees without changing the individual order of the strip-shaped elements.
It is formed by rearranging it again and again. Further, in the above structure, when the strip-shaped elements are rearranged, the mutual positions of the individual strip-shaped elements are displaced in the direction perpendicular to the uneven curved surface. The cut surface forming the band-shaped element is parallel to the short side direction of the fluorescent screen between the color images.

The correction lens according to the present invention has a discontinuous surface produced by these molds.

Further, in the method for manufacturing a correction lens according to the present invention, the correction lens is formed by pressing an optical material made of heated plastic or glass onto the correction lens manufacturing mold or by using the correction lens manufacturing mold as a mold. It is manufactured.

[0013]

According to the mold for producing a correction lens of the present invention, a correction lens having a discontinuous surface can be produced at once by molding, and at the same time, the finished discontinuous surface lens has a discontinuous line on the surface. However, there is no discontinuity in the thick portion of the optical material of the lens body, and there is little extraordinary refraction or irregular reflection of the light beam during exposure, and the unevenness of the fluorescent screen can be reduced.

Further, in the mold according to the present invention, when the cut pieces made of strip-shaped elements are combined, the individual positions of the cut pieces can be displaced in the direction perpendicular to the curved surface, so that the degree of freedom in design is increased, and as a result, The degree of correction of a lens manufactured using this mold can be improved. Further, by making the discontinuous line of the mold parallel to the short side of the phosphor screen, the degree of correction can be improved while minimizing the occurrence of unevenness.

[0015]

【Example】

Example 1. FIG. 1 is a perspective view showing a discontinuous surface lens produced by the mold of the present invention. As will be described later, the optical system of the exposure apparatus for producing a fluorescent screen of a color picture tube has a strip-shaped lens made up of a lens having a smooth surface (simply called a continuous surface lens 2 in the following description) and a strip-shaped element. It is composed of a continuous surface lens (hereinafter simply referred to as discontinuous surface lens 1). Here, although the design method of the continuous surface lens 2 has the following characteristics, the manufacturing method does not have any special characteristics. Therefore, only the discontinuous surface lens 1 is shown in FIG. The discontinuous surface lens 1 is made of a substantially rectangular plate integrally formed of an optical material such as plastic or glass. One surface of this plate is a discontinuous surface 3 as described below. The other surface is generally plane 4. The discontinuity surface 3 generally has a plurality of discontinuity lines 3A, and the discontinuity surface 3 is discontinuous at the discontinuity line 3A, but at other portions, the surface is made smooth. Has been. That is, the discontinuous surface 3 is generally an assembly of smooth belt-shaped curved surfaces. The direction of the discontinuity line 3A is preferably determined in relation to the shape of the panel provided with the fluorescent screen of the color picture tube formed by the correction lens system.

Before entering the detailed description, the relationship of such coordinates will be described with reference to the schematic view of the color picture tube of FIG.
In FIG. 2, reference numeral 100 denotes a panel provided with a fluorescent screen of a color picture tube. The outer shape of the panel 100 is usually similar to that of the phosphor screen, but in general, the horizontal to vertical ratio is 4: 3.
Or it is a rectangle longer than this. In the following description, the normal line standing at the center of the panel is the Z axis, the intersection of the Z axis and the panel is the origin O, and the X axis is defined in the long side direction and the Y axis is defined in the short side direction. Electron guns 101 are arranged facing the panel 100. The electron gun 101 is composed of three element electron guns arranged in a line in the XZ plane. Here, the axis of the central element electron gun is made to coincide with the Z axis, and the electron gun 1
The direction from 01 to the panel 100 is the + Z direction.

Next, the situation in which the phosphor screen mosaic of the color cathode ray tube is printed using the discontinuous surface lens 1 will be described with reference to FIG. In the figure, 50 is a frame of the exposure apparatus main body. A positioning claw 52 is provided on the upper plate 51.
Is attached. When manufacturing the fluorescent screen, the panel 100, which is to be a part of the color picture tube, contacts the positioning claw 52 and is placed at a predetermined position. Although a photosensitizer is applied to the inner surface of the panel 100 and a shadow mask is attached, it is not shown in the drawing. The upper surface plate 51 has a window 53. A lamp house 54 is arranged at an appropriate position on the frame 50, and light rays generated here are concentrated and diverged from a point light source 55 having a small area, and travel toward the panel 100. The point light source 55 diverges the light rays from a substantial point. A discontinuous-surface lens 1 and a continuous-surface lens 2 are placed in the passage of the light ray 200 emitted from the point light source 55 toward the panel 100 to correct the trajectory of the light ray.

The outline of the discontinuous surface lens 1 has been described above, but in the exposure apparatus, the Y direction of the panel 100 is
It is arranged so as to coincide with the direction of the discontinuous line 3A (see the coordinate system in FIG. 1). Here, the discontinuous surface lens 1 includes a frame 5
6 and a link 57 and a driving device 58 connected thereto are configured to constantly reciprocate in the X direction with an appropriate amplitude. In order for the discontinuous surface lens 1 to move only in the X direction, an appropriate slide mechanism is required between the frame 56 and the frame 50, but it is omitted in the figure. The continuous surface lens 2 is fixed to the frame 51 by a frame 59. It should be noted that the reason why the discontinuous surface lens 1 is constantly reciprocated in the X direction is that this lens has a discontinuous line 3A on its surface, but in this portion, the light rays from the point light source 55 are irregularly reflected to cause the panel 100 to move. This is because the irradiation on the inner surface becomes non-uniform, so that this effect is avoided. Now, the light ray 200 that has left the point light source 55 passes through the lenses 1 and 2 and is refracted, and then enters the point P on the panel 100. Inversely, this incident light beam is extended by a straight line, and the point light source 5 having the same height as the point light source 55
A point that intersects with a virtual plane 201 (referred to as an xy plane in the following description) that is parallel to the top plate 51 through 5 is S, and this is referred to as a virtual point light source.

In order to prevent mislanding of the color picture tube, when the point P is arbitrarily set on the panel 100,
It is necessary to provide an ideal position of S point corresponding to this P point, and bring the actual S point to this ideal position. However, it is generally impossible to satisfy this condition on all points on the panel only with a conventional lens having a smooth surface. This issue is discussed in the Television Society Journal Vol. 42, No. 12 (1988), it describes in detail as "About mislanding pattern that can be corrected by a smooth lens". The present invention improves the manufacturing method of the lens by utilizing the fact that the difficulty of correction described above can be greatly improved by using the discontinuous surface lens 1 described above in combination with the continuous surface lens 2. It is intended to bring out its effect further. In the following, an outline of a method of designing both lenses and a method of manufacturing a discontinuous surface lens in consideration of this situation will be described.

In FIG. 3, when an arbitrary point P is considered on the panel 100, if the virtual point light source S corresponding to this P is deviated from its ideal position on the virtual plane 201, mislanding at the point P will occur. Occurs. Therefore, in the following, the deviation of point S from its ideal position will be referred to as mislanding at point P. Mislanding has an x component and ay component. By the way, when considering the mislanding distributed over the entire effective portion of the panel 100, at least one of the x component and the y component can be corrected by a conventionally known smooth correction lens. Therefore,
In FIG. 3, it is assumed that the discontinuous surface lens 1 is not arranged yet, and the y component of mislanding is entirely corrected by the continuous surface lens 2. Since the remaining mislanding in the x direction at this time is a function of the position on the panel,
This is Δx (X, Y). Here, (X, Y) is the coordinates of the position of the point P, which is represented on the panel 100 by the coordinate system determined by FIG. On the other hand, the x component of the original mislanding can be entirely corrected by the continuous surface lens 2. At this time, the remaining mislanding in the y direction is Δy (X, Y).

Correction residual Δ obtained in two ways by the above procedure
The distribution of the magnitudes and the directions of the amounts of x (X, Y) and Δy (X, Y) is irrelevant to the arrangement position of the continuous surface lens 2, and even if the number of smooth lenses is increased, this situation It has been proved from the geometrical optics formula that it cannot be changed. That is, as described above, the problem that an uncorrected amount remains as Δx or Δy is essential as long as a smooth lens is used, and it is impossible to remove both of them simultaneously with a smooth lens. However, each half is corrected and the other half is left, ie 1/2 Δx in the x direction.
The continuous surface lens 2 can realize correction such that correction residuals of 1 / 2Δx (X, Y) are simultaneously generated in the (X, Y) and y directions. Now, it is assumed that the continuous surface lens 2 is designed as such.

Next, consider adding a new second lens. This lens has a thickness T0 at the center x = 0 and y = 0.
Shall have. If such a lens is added to the optical path of the exposure machine, the optical path will change due to the thickness of the material itself and the position of S will move (mislanding correction state will change, even if the surface is not uneven or inclined). Although a problem occurs and the design becomes complicated, it is assumed that the movement of S caused by the total thickness T0 is corrected in advance by the continuous surface lens 2. This is theoretically possible. Now, let's first consider a smooth lens as the second lens. If this lens has 1 correction left
When attempting to correct / 2Δy (X, Y), the correction residue in the x direction increases by 1 / 2Δx (X, Y), and the y direction has already been described in the correction with only the continuous surface lens 2. In this case, the mislanding is completely corrected, and the mislanding correction residual Δx (X, Y) in the x direction is realized. However, now such a smooth lens (however, this second lens is now assumed to be at the position of the discontinuous surface lens 1 in FIG. 3) is intentionally designed. Hereinafter, this lens is referred to as a virtual lens, the lower surface (light source side) is a flat surface, and the upper surface (panel side) is a curved surface. The curved surface has an origin at the center of the upper surface and z = f (x, y). Shall be represented by. Here, the variables (x,
y) is used, but there would be no doubt.

Next, using a suitable solid material, a mold prototype having a curved surface z = f (x, -y) related to the curved surface above is made. This mold prototype is a tool that has the characteristics of a mold master mold for the final use of the lens. It is made by numerically controlling heat-resistant metal, ceramics, glass, etc. that have an appropriate thickness. . This is referred to as a mold prototype 1A in the following description and is shown in FIG. here,
In order to make it easier to understand the relationship between a mold such as a mold prototype and an object (lens) produced by the mold, the coordinate system used for expressing the mold is the same as that used for the virtual lens. That is, it is assumed that the mold material is in the positive direction of z and the curved surface is arranged facing the negative direction of z.
As is apparent from the above relationship, even if the mold prototype 1A is used as it is as a mold, a virtual lens of z = f (x, y) cannot be formed, and a curved surface of z = f (x, -y) is obtained. it can.

Next, the mold prototype 1A is cut along a plurality of planes (hereinafter referred to as discontinuous portions) parallel to the yz plane. In FIG. 4, the dotted line shows this discontinuous portion 3B. The state after this cutting is shown in FIG. Here, for convenience of explanation, each cutting piece 3C is numbered. Here, the number is the one at the positive (plus) end of x, and is sequentially attached as ... Further, the + y and −y ends of each cut piece 3C are marked with + and −, respectively. Next, the directions of these cut pieces 3C are exchanged. At this time, the relationship of (1) ... And the relationship in the x direction are not changed. (2) The relationship between the front and back of the xy plane is not changed. (3) Reverse the directions of + and − with respect to the y direction. Then, the state in which this rearrangement is completed is shown in FIG. This is used as a mold 1B for a discontinuous surface lens. The discontinuous surface lens 1 according to the present embodiment is manufactured by using this mold 1B. That is, the lens-shaped element in which an optical material made of heated plastic or glass is pressed against the mold 1B or the concavities and convexities of the mold 1B are reversed by using the mold 1B as a mold is the discontinuous surface lens 1. At the time of this molding, the surface on the opposite side of the lens is, in principle, a plane parallel to the xy plane (I will not touch on how to make it here,
As described above, the central thickness is T0).

The characteristics of the correction lens used here are determined by the lens thickness at the passage point of each ray and the inclination of the lens curved surface at that point. Here, the inclination is the tangent of the angle between the normal of the surface and the yz plane (inclination in the x direction) and the tangent of the angle between the normal of the surface and the xz plane (inclination in the y direction). These are respectively represented by δf / δx and δf / δy in the case of the above assumed surface. Since the influence of the value T0 at the center can be eliminated as described above, the influence of the difference ΔT = z = f (x, y) from the center becomes a problem. However, if the angle of incidence of the light rays on the lens surface is small (which corresponds to a small deflection angle condition in a color picture tube), this effect can be ignored. Therefore, in the following description, the influence of ΔT will not be considered. Turning now to tilt, at commonly used angles of incidence, the tilt in the x direction is primarily responsible only for correcting mislanding in the x direction and the tilt in the y direction is primarily responsible for correcting mislanding in the y direction. Involved. Therefore, this will be assumed in the following description.

As is clear from the history of its design, this virtual lens is 1 / 2Δy (X, X, Y in the y direction, if the correction state by only the continuous surface lens 2 described above is used as a reference.
Instead of realizing the correction of Y) (reducing the mislanding), it caused an increase of 1 / 2Δx (X, Y) mislanding in the x direction. Summarizing this, the virtual lens having the curved surface of z = f (x, y) is inclined δf / δx in the x direction at the point (x, y).
→ Increase mislanding in the x direction by 1 / 2Δx (X, Y), inclination in the y direction at the (x, y) point δf / δy
→ You can make a diagram of reducing mislanding in the y direction by 1 / 2Δy (X, Y).

Now, the discontinuous surface lens actually used for manufacturing the color picture tube is manufactured as described above. In this case, if the distance between the discontinuous lines 3A is sufficiently small, the inclination of the surface at the point (x, y) on the lens is x,
In the y direction, they are −δf / δx and δf / δy, respectively. As described above, since the mold 1B and the exposure device have the same x direction, if the mold prototype 1A is used as a mold to make a lens, the curved surface of the lens is f
It is clear that it is (x, -y). Comparing the correction characteristic of the discontinuous surface lens 1 having such an inclination with that of the above virtual lens, the correction characteristic in the y direction is the same, but the correction characteristic in the x direction is (x, y ) The inclination in the x direction at point -δf / δx → The formula for reducing the mislanding in the x direction by 1 / 2Δx (X, Y) is established.

That is, the discontinuous surface lens 1 according to the present invention is
It is possible to realize 1 / 2Δx (X, Y) correction in the x direction and simultaneously realize 1 / 2Δy (X, Y) correction in the y direction. However, in the exposure apparatus of FIG. 3, the continuous surface lens 2 has a ½Δx (X, Y) in the x direction and a ½Δ in the y direction.
There was a correction residue of y (X, Y). Therefore, in the combination of the continuous surface lens 2 and the discontinuous surface lens 1, all the mislandings are corrected.

The above description includes some approximations, and the actual discontinuity lens 1 cannot unnecessarily reduce the interval between the discontinuity lines 3A.
The method of the present invention cannot always completely eliminate the correction residue in the conventional smooth lens. However, it has a great effect in practical use, and most of the mislanding, which has been a problem as a correction residual with only a smooth lens, can be removed.

Next, the discontinuous surface lens 1 in this embodiment.
The reason why the discontinuous line 3A is provided in parallel with the y direction will be described.
In the following consideration, the discontinuity line 3A of the discontinuity lens 1 is used.
The distance between the two shall be sufficiently small. In the description of the above-described principle of the correction using the discontinuous surface lens 1 and the continuous surface lens 2, it is neglected that the thickness of the discontinuous surface lens 1 is different between the center and other portions. However, in reality, the thickness is not uniform, and at the point (x, y) there is a difference ΔT from the central portion (both positive and negative are possible). Consider this effect. The influence of the presence of the thickness T0 common to the center over the entire lens is eliminated by the continuous surface lens 2 as described above and can be ignored. Therefore, in the following description, the thickness is simply referred to as ΔT. Now, the slopes δf / δx and δf / δy are mainly related only to the correction in the x and y directions respectively, but the thickness is related to the correction in both the x and y directions if they are affected. Then, the sum of the effects of both the thickness and the inclination is the final correction effect in both the x and y directions.

Considering the point (x, y), this thickness is the same in both the virtual lens and the final discontinuous surface lens 1 (Note: the interval between the discontinuous lines 3A is now sufficiently small. ), Changing the direction of the strip-shaped element of the cut piece (actually, this is reversed at the stage of making a mold, but this will be described below), even if an attempt is made to reverse the direction of correction in the x direction, it is caused by the thickness ΔT. The correction amount does not reverse and remains the same. Therefore, the final correction amount of the lens system described above is y if the influence of the thickness cannot be ignored.
Although almost perfect correction is obtained in the x-direction, it is incomplete in the x-direction. Here, the remaining correction residue is reduced or scattered by redesigning the lens system by changing the ratio in which the correction amount is shared by the continuous surface lens 1 and the discontinuous surface lens 2 (it does not hurt in the y direction. It is possible to some extent to improve the overall characteristics by causing a degree of correction residue. However, even if this process is repeated, there is a limit that no further improvement can be achieved when reaching a certain point. This is because when such a process is repeated, when the direction of the strip-shaped element of the cutting piece is changed to reverse the correction by the tilt, the degree of the correction in the x direction is rather deteriorated depending on the location due to this reversal. . From the viewpoint of correction in the direction in which the discontinuous line 3A extends, the final correction degree is better when the discontinuous line 3A is arranged in parallel with the y direction rather than the x direction. The reason for this has not been elucidated, but the fluorescent screen, and thus the panel 100
The shape of the rectangle long in the direction, the characteristics of the distribution of the correction amount required for the correction lens due to the arrangement of the electron guns 101 in the X direction, and the smooth surface lens (the continuous surface lens 2 in this case) Is considered to have the property of effectively correcting mislanding radially distributed with respect to the center of the phosphor screen.

The direction of the upper discontinuous line 3A is selected as follows.
It is related to the method of making the lens of the present invention. This is because the discontinuous surface lens disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-177232 has a basic structure in which the glass itself constituting the lens is cut, so that the discontinuous surface lens at the boundary surface between adjacent elements is Undesirable refraction and reflection tend to occur, and in order to avoid this effect, the exposure light ray should enter this discontinuity surface as parallel as possible, and the discontinuity line should be parallel to the y direction in relation to the longitudinal direction of the phosphor screen. Has been a problem (cutting in this direction increases the deflection angle in the x direction, increasing the proportion of light rays incident on the discontinuous surface). Therefore, the discontinuous surface lens 1 according to the present invention has the discontinuity line 3A, but this is only on the surface, and most of the material thickness is substantially continuous, which causes a disadvantage in that the light beam obliquely passes. Instead, the discontinuous line 3A can be arranged in a desired direction from the viewpoint of correction.

Example 2. When rearranging the cut pieces 3C to make the mold 1B, the individual cut pieces 3C may be displaced in a direction perpendicular to the curved surface. This can be easily achieved by inserting an appropriate spacer on the side opposite to the curved surface of the cut piece 3C when assembling the mold. As described above, the correction effect of such a correction lens is related to the inclination and the thickness, but even if the discontinuity line 3A is provided on the lens surface,
There remains a relationship between the slope and thickness of each point on the lens. Although the method of the present invention remarkably improves the degree of correction as compared with the correction using only a smooth lens, it is still not a perfect ideal correction. This is because the inclination and thickness of any point on the lens cannot be freely determined, and the relationship that binds them to each other remains. By shifting the curved surface position for each of the cut pieces 3C as in the present embodiment, the degree of freedom is increased to some extent in the relationship between the two. Since the amount of shift can be appropriately selected for each, the correction effect can be further improved.

Example 3. The intervals at which the mold prototype 1A is cut do not have to be equal intervals. Further, there may be a cut piece that does not change its orientation with respect to the coordinate system during rearrangement. For example, as shown in FIG. 6, the cutting interval may be increased in the vicinity of the center (x = 0, y = 0), and the cutting may be made finer at | x |. This is possible because the required correction amount is generally small near the center and the correction amount does not change very rapidly even if the coordinates on the panel change. In such a case, there may be a measure that does not change the direction of only the element including the center. This is because in the case of the cutting method shown in FIG. 6, if the direction of the cutting piece 3D including the widest center is changed according to the rule of FIG. It happens that the existing parts are next to each other after rearrangement. Since the x-coordinates of these two points are distant from each other, when they are adjacent (adjacent to each other), a large step is generated here, which may cause unevenness. In such a case, the direction of only the element including the center may not be changed. In this case, the one before the rearrangement is also next to the same, but in the case of this color picture tube, the structure (and hence the distribution of the correction amount) is basically symmetrical with respect to the top and bottom (X and x axes).
, And have the same thickness, but the problem of step difference is reduced. Of course, the amount of correction may be reduced by such an operation, but since the amount of correction is generally small in the center and around the axis, it may be better to bring in such measures and improve overall characteristics including unevenness depending on the situation. is there.

Example 4. When cutting the mold prototype 1A, the cutting tool must have a certain width, but this causes a phenomenon in which the width of the cut piece to be cut becomes smaller than initially planned. In order to prevent this influence, it is advisable to make the mold prototype 1A large in advance in the width direction of cutting. For example, in the previous embodiment, the shape of the mold prototype 1A, which should have been z = f (x, -y), is z = f (kx, -y), where k <1 and the constant k is the tool number. It should be set considering the width.

The correction lens system described above comprises a combination of a discontinuous surface lens and a continuous surface lens, and the discontinuous surface lens is manufactured by using a mold, but the mold is cut and rearranged as described above. It is also possible to use this as a mold to form a mold, which is called a second working mold, and use it for lens production without using the same as it is for lens production. Therefore, to describe the characteristics of the mold according to the present invention in one word, the completed mold has linear discontinuities parallel to each other, and the parts other than this discontinuity have smooth uneven curved surfaces. When cut and separated at the discontinuous portion and rearranged by changing the direction by 180 degrees in a direction different from the original without changing the order of the individual, the unevenness is formed on both sides of the adjacent strip-shaped element boundary lines. It can be expressed that a shape in which the inclination of the curved surface continuously changes in the direction of the discontinuous portion and the direction orthogonal to the discontinuous portion appears. However, the detailed configuration is not limited to that described above.

Throughout all the examples, the sharing of the correction amount of the continuous surface lens 2 and the discontinuous surface lens 1 is not limited to that already described. For example, in the first embodiment, by the continuous surface lens 2, 1 / 2Δx (X, Y) and 1 / 2Δy (X,
Although it has been stated that the correction residual state of Y) is created and is corrected by the discontinuous surface lens 1, this is not necessarily limited to this, and other correction residual distribution states are first realized, and this is performed. It may be corrected by 1. That is, the distribution of the correction share between the lens 2 having a smooth correction amount and the discontinuous surface lens 1 may be set in any manner, that is, the optimum total characteristic may be aimed for. It goes without saying that the surface of the mold prototype that does not matter now (the surface opposite to the curved surface) should be finished in advance.

[0038]

According to the present invention described above, a correction lens system for producing a fluorescent screen of a color picture tube comprises a combination of a continuous surface lens and a discontinuous surface lens having a discontinuous line,
When making the latter by molding an optical material with a mold, give the shape of this mold a characteristic, make a mold of one discontinuous surface lens, make a mold prototype of one smooth surface, then cut this As a result, the final mold is made by changing the direction of each cut piece without changing the order as a whole, so a correction lens that can realize a color picture tube with less unevenness and mislanding at a relatively low cost. Can be obtained.

Further, in order to manufacture a color picture tube having a rectangular fluorescent screen, a correction lens is manufactured by using a mold in which the direction of the discontinuous line is parallel to the short side of the rectangle, and thereby the degree of unevenness can be reduced. The mislanding correction effect can be improved without deteriorating.

[Brief description of drawings]

FIG. 1 is a perspective view showing a discontinuous surface lens which is a main part of a correction lens system for manufacturing a fluorescent screen of a color picture tube manufactured according to Example 1 of the present invention.

FIG. 2 is a diagram showing a relationship between a panel of a color picture tube and a coordinate system.

FIG. 3 is a side view showing a situation in which the correction lens manufactured according to the present invention is used in a fluorescent screen printing exposure device.

FIG. 4 is a perspective view showing a mold prototype which is a basis of a mold for producing a discontinuous surface lens according to the present invention.

FIG. 5 is a diagram showing a process for producing a mold for producing a discontinuous surface lens according to the present invention from a mold prototype.

FIG. 6 is a plan view showing a mold prototype for producing a mold according to a third embodiment of the present invention.

[Explanation of symbols]

1 discontinuous surface lens, 1A mold prototype, 1B mold, 2 continuous surface lens, 3 discontinuous surface, 3A discontinuous line, 3B discontinuous portion, 3C cut piece, 3D cut piece including center, 4 plane.

Claims (6)

[Claims] 1. A smooth concave-convex curved surface is formed on one surface of a plate-shaped solid material such as heat-resistant metal, ceramics, glass, etc., and this is cut into a plurality of strip-shaped elements by cutting surfaces parallel to each other. A mold for producing a correction lens, characterized in that the band-shaped elements are formed by rearranging and changing the direction by 180 degrees in the original plane without changing the order of each. 2. A smooth solid curved surface is formed on one surface of a plate-shaped solid material such as heat-resistant metal, ceramics, glass, etc., and this is cut into a plurality of strip-shaped elements by cutting surfaces parallel to each other, and these are cut. A mold for producing a correction lens, which is formed by rearranging some of the strip-shaped elements by changing the direction of some of the strip-shaped elements in the original plane by 180 degrees without changing the order of the strip-shaped elements individually. 3. The correction lens according to claim 1, wherein when the strip-shaped elements are rearranged, the mutual positions of the individual strip-shaped elements are displaced in a direction perpendicular to the uneven curved surface. Manufacturing mold. 4. The mold for producing a correction lens according to claim 1, wherein the cut surface is parallel to the short side direction of the fluorescent screen between the color images. 5. A correction lens having a discontinuous surface produced by the correction lens production mold according to claim 1. Description: 6. An optical material made of heated plastic or glass is pressed against the correction lens production mold according to claim 1, or the correction lens production mold is used as a mold. A method of manufacturing a correction lens, which comprises manufacturing a correction lens.