JPS5860642A - Preparation of focusing glass - Google Patents

Abstract

PURPOSE:To prepare a light focusing glass having improved detecting precision of achievement of exact focusing by a simple process, by sprinkling sand on the surface of transparent flat sheet so that fine unevenness is formed on it, corroding the uneven surface chemically so that the protrusion parts of the uneven surface are made into hemispherical surfaces. CONSTITUTION:Sand is sprinkled on the surface 11a of the flat transparent sheet glass 11 so that a great number of the fine unevenness 11b and 11c are formed on the surface 11a. The sheet glass 11 is immersed in a chemical corrosive agent containing fluorine, etc. The tops of the protrusion parts 11b are corroded, and every protrusion part is changed into the hemispherical protrusion part 11b'. The sheet glass 11 thus processed constitutes a focusing glass by itsel. Or, a mold is made by using a sheet glass member having the hemispherical protrusions 11b' as an original form, and a focusing glass is prepared from a transparent plastic plate using the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a light-transmitting focusing plate used in a single-lens reflex camera or the like.

The conventional manufacturing method for focusing plates used in papermaking is to sand the metal surface to form fine irregularities on the metal surface, and then plate the metal surface to form a gold plate. Form a mold.

This mold was then pressed against a heated plastic plate to transfer the fine irregularities of the mold onto the surface of the plastic plate. The plastic plate molded in this way was used as a focusing plate. However, the focusing plate manufactured in this way has a cross-sectional shape as shown in FIG.
A large proportion of the light reflected from the quick return mirror (not shown) was diffused at a large angle R#1 with respect to the vertical direction ZK of the focus plate 1. Therefore, pentaprism 2
The light guided to the eyepiece through the snow, i.e. at a relatively small angle with respect to the vertical direction ZK. In the method of manufacturing a pointless plate, it is possible to make the grain size of the sand grain finer to make the finder screen brighter, but if you use K in this way, it will be formed on the focus plate both when the focus is on and when it is not. The blur of the subject image does not change, resulting in a focus plate with poor focus detection accuracy.

Therefore, in recent years, a focusing plate has been proposed in JP-A-53-42726, in which the cross section of the numerous irregularities formed on the focusing plate surface is formed into a continuous curved surface as shown in FIG.

Since the cross section of the recesses and recesses 31 in this focusing plate 3 is a curved surface, the incident light is at a large angle of 0 with respect to the vertical direction ZK of the focusing plate 3.
1, the proportion of light that is diffused is small and the proportion of light that is guided to the eyepiece is large. Therefore, the finder screen becomes brighter.

The object image formed on the focus plate can have the desired blurring change depending on whether it is in focus or not, and the focus detection accuracy is good. However, this focusing plate 3 had the disadvantage that the manufacturing method was complicated as described below.The manufacturing method will be described below.First, a speckle pattern is formed on a dry plate, and this pattern is transferred to the dry plate. Print and expose.

This dry plate is then processed and washed with water. This dry plate is then bleached and washed again with water. Furthermore, by performing a fixing process on this dry plate and washing it with water again, a dry plate having irregularities corresponding to the speckle pattern on its surface is completed. The thus-produced dry plate is processed into a prototype to make a mold, and this mold is pressed onto a heated plastic plate in the same manner as described above, and the unevenness 3a corresponding to the speckle pattern shown in Fig. 2 is formed.
A focusing plate 3 having the following characteristics was obtained.

However, although this focusing plate manufacturing method is easy and can produce a focusing plate with good focus detection accuracy, the process from printing and exposing the speckle pattern on a dry plate to obtaining the focusing plate is complicated (and also complicated). However, if we look at the process up to forming the irregularities on the mold prototype, that is, the dry plate, the process is complicated, a dark room is required, and there are problems with the characteristics of the photosensitive agent. However, due to the conditions of the bleaching treatment, there are disadvantages such as difficulty in controlling the unevenness to the desired level.

A first object of the present invention is to provide a method for manufacturing a focusing plate that is bright and has good focus detection accuracy, and in which the process to obtain the focusing plate is very simple.

A second object of the present invention is to provide a method for manufacturing a focusing plate that is bright and has good focus detection accuracy, and in which the steps up to obtaining a mold prototype are very simple.
Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 is a diagram illustrating the manufacturing process of the first SJ embodiment of the present invention. First, a flat transparent glass plate 11 as shown in FIG. 3 is prepared.

Next, the surface 11m of the glass plate 110 is sanded to form countless fine irregularities 11b and 11a on the surface 11m. FIG. 3(b) shows a cross section of the glass plate after sanding. What materials should be used for the ceramics and sanding, as long as they can create countless unevenness as mentioned above?(...) After this, the glass plate 11 is immersed in a chemical caustic agent containing hydrofluoric acid, etc. After sanding. The glass plate surface 111 has an acute cross section as shown in FIG. 3(b), but when it is immersed in a chemical corrosive agent, the tips of the convex portions 11b are corroded, and each convex portion is as shown in FIG. It becomes a hemispherical convex part 11b' as shown in (C). When the glass plate is immersed in a chemical corrosive agent, uniform chemical corrosion can be achieved by letting the glass plate work in the solution. The glass plate 11 is processed in this way, and this glass plate 11 itself constitutes a focusing plate.

Although the protrusion 11b' has been described as having a "hemispherical shape," it is not necessary that the protrusion 11b' be a "hemisphere" in the strict sense. In the present invention, "hemispherical" includes the case where the shape is not the same as one half when the sphere is accurately divided into halves on one plane, and the curvature of the convex portion 11b' matches the curvature of the sphere. In other words, in the present invention, the shape of the convex portion 11b' is similar to the shape of the divided sphere when the sphere is divided by one plane (including the case of dividing into equal parts and unequal parts). It has been explained that the convex portion 11b' is "hemispherical" in this sense.

Next, a second embodiment of the present invention will be described. FIG. 4 is a diagram illustrating the manufacturing process of the second embodiment. This example is shown in Figure 3 (
This is a book in which a mold is made using a plate-like member having a hemispherical convex portion 11b' on the surface manufactured by , ) as a prototype, and an elifocusing plate is manufactured using this mold.

In this example, a plate member having the same shape as that shown in FIG. 3(C) is obtained through the steps shown in FIGS. 3(a) and 3(b). In this example, a case where the plate-like member is made of a glass plate will be explained.
In addition to glass plates, this plate-like member may be constructed of hard and brittle materials such as ceramic plates and single crystal silicon plates.

Next, as shown in FIG. 4(1), a metal film 12 such as silver is attached to the surface 111 of the glass plate 11 on which the irregularities have been formed in this manner. This attachment of the metal film 12 is to enable overlaying by the next electroforming method. Then, overlaying is performed on the metal film 12 by electroforming. This state is shown in Figure 4 (b
) K is shown. From the state of the same figure, electroformed metal 1s and glass plate 1
1 and melt the metal film 12 attached to the electroformed metal surface, the uneven surface 11 of the glass surface 11m shown in FIG.
an uneven surface 13b having a shape complementary to b' and 11c';
13a is formed on the electroformed metal surface. The cross section of the mold molded in this way is shown in FIG. 4 (+1).

When this mold 13 is pressed against a heated transparent plastic plate 14, the unevenness of the mold surface is transferred to the surface of the plastic plate 14, and the focusing plate 1 whose cross section is the same as that shown in FIG. 3(e)
4 is obtained.

Figure 4 (d) shows the cross-sectional shape of the focus plate 14 obtained in this way.

Next, a third embodiment of the present invention will be described. FIG. 5 is a diagram illustrating the manufacturing process of the third embodiment. In this embodiment, as in the second embodiment, a mold is made using the plate-like member shown in FIG.

In this embodiment, similar to the second embodiment, a case will be described in which the plate member shown in FIG. 3(e) is made of a glass plate.

In this example, the third
A glass plate 11 having the shape shown in Figure (C) is obtained, but the second step is to make a mold using this glass plate as a prototype.
This is different from the example. This point will be explained in detail below. Third
In this embodiment, as shown in FIG. 5(&), a silicon film 15 is deposited as a mold release agent on the surface 11m of a glass plate 110 having the shape shown in FIG. 3(C). Then, an aluminum protective film 1B is deposited thereon as shown in FIG. 5(b). Then, as shown in FIG. 5(,), epoxy resin 1T is further applied. Thermosetting resins with adhesive properties other than epoxy resins may also be used. The support member 18 made of glass or metal is placed on the epoxy resin 1T as shown in FIG. Membrane 1
6 is integrated. Figure 5 shows the state in which the support member 18, epoxy resin 17, and aluminum protective film 16 have been separated from the glass plate 11, and the aluminum 16 has been melted.
). Of course, materials other than queen silicone and aluminum may be used as the mold release agent and eyelid retaining film. The uneven surfaces 17b and 17e have shapes complementary to the uneven surfaces 11b' and 11c' formed on the surface of the glass plate 110 in FIG. 3(e).Then, the uneven surfaces 17b
, 17e, a metal film 19 made of silver or the like is deposited as shown in FIG. 5(f), and overlay is applied thereon by electroforming as shown in FIG. 5(g). If the electroformed metal 20 and the epoxy resin 1T are separated from the state shown in FIG. 5(g) and the metal 19 attached to the surface of the electroformed metal is melted, this surface 20 &
An uneven surface 20b having the same shape as the glass surface 11 in figure (e),
It becomes 20a. A cross-sectional view of the mold formed in this manner is shown in FIG. 5(h). When this mold 20 is pressed against the heated transparent plastic plate 21, an uneven surface 21b having a shape complementary to the uneven surfaces 11b' and llc' shown in FIG.
, 21C is obtained. FIG. 50) is a sectional view of the reticle thus obtained.

T! 1. In the second and third embodiments described so far, various films 12, 15, 16, 19 are formed during the process from the prototype shown in FIG. 3(C) to the mold 13.20. Needless to say, these films have a small and uniform thickness so that the transferred uneven shape does not collapse.

In addition, in the second and third embodiments, this was achieved by pressing a heated plastic plate onto the mold 13.20;
A plastic focusing plate may be made by pressing plastic powder onto 3.20 and applying heat to this powder. Furthermore, the mold 1 is made by injection molding the molten plastic.
3. At 20, press 1 to make a focusing plate.

Focus plate 11, [4,
21 has a hemispherical convex or concave surface (
・In other words, the convex or concave portion has a curved surface.
・As a result, it becomes a bright focus plate like the conventional example shown in Fig. 2, and by appropriately selecting conditions such as grain size, the sand cover has a bokeh that corresponds to the focus, that is, focus detection. It is possible to obtain a focusing plate with good accuracy.

In this way, the present invention obtains a focus plate that is bright and has good focus detection accuracy, but has hemispherical convex portions adjacent to each other (Fig. 3(a), Fig. 1s4(d)). , or because the contact parts of adjacent hemispherical recesses (see Figure 5 (1)) have relatively acute angles, when an interchangeable lens with a large F number is attached, these acute angle parts may become sunspots. There is a risk that it will appear on the finder screen. The following improved example solves these drawbacks.

First of all, Figure 6@6 will be explained using the first example, and Figure 8g3 (
A partially enlarged cross-section of the glass plate shown in c) is shown, with a transparent organic substance or silicone oil applied to the uneven surface.

With this structure, the contact portions of the adjacent hemispherical convex portions, that is, the lower ends of the concave portions 11C′ are filled with the resin or oil, and a gentle curve is formed due to the surface tension of the resin or oil. .Therefore, the sixth
A focusing plate 11 having a cross-sectional shape as shown in FIG. 3(b) can be obtained. A focusing plate with this shape has no acute angles, so it is recommended to use interchangeable lenses with a large F number (even if there is a concave part 1).
The bottom edge of 1c' will not appear as a black dot on the finder screen.

Furthermore, if the viscosity of the resin or oil filled in the recesses 11C' is low, a flat surface 11d is formed between each convex part as shown in FIG.

In the second and third embodiments, the glass plate 11 obtained in FIG. 6(b) may be used as a prototype instead of the glass plate in FIG. 3(c), and a mold may be made. In this way, it is possible to create a reticle without sunspots.

In the case of the second embodiment, the focusing plate 14 made in FIG.
It has the same shape as in Figure (b), and no black dots appear.

Next, a specific example will be shown in which a focusing plate is manufactured by the manufacturing method of the second embodiment.

In the first specific example, the glass plate 11 shown in FIG.
Using 200 mesh carborundum (material name), sanding was carried out for about 15 minutes to form the uneven surface 11b, 1 as shown in Fig. 3(b).
I got 1e. Then, this glass plate was immersed in a chemical corrosive agent containing hydrogen fluoride for about 5 minutes while being moved to obtain corroded surfaces 11b' and lle' as shown in FIG. 3(c). The diffusion characteristics of the reticle 14 obtained through the subsequent steps shown in FIG. 4 are as shown in FIG. 8(1).

In the second example, Sunakake changed only the particle size of the material to 1,500 mesh, and otherwise made the focusing plate 14 under exactly the same conditions as the first example.

The diffusion characteristics of this focusing plate are as shown in FIG. 8(2).

In the third example, only the particle size was changed to φ2000 mesh, and the focus plate 14 was manufactured under the same conditions as the first and second examples. The diffusion characteristics of this focus plate are as shown in FIG. 8(3).

Figure 8 shows the diffusion characteristic diagram of the focus plate, and the horizontal axis is Figure 4 (d
), take the angle θ with respect to the vertical direction ZK of the reticle,
The vertical axis represents the diffuse transmittance ■θ at the angle θ. In the same figure, (4) shows the diffusion characteristics of the conventional reticle shown in FIG. 1 for consideration.

FIG. 9 shows curved features exaggerated in order to explain the difference between the diffusion characteristics of the reticle according to the present invention shown in FIG. 8 and those of the conventional reticle shown in the figure. In Figure 9, (5) corresponds to (1), (2), and (3) in Figure 8,
(6) corresponds to (4) in FIG. Qualitatively, the area A of the portion surrounded by the vertical axis ■6, the horizontal axis θ, and the characteristic curve (5) in Fig. 9 is the axis! 0, θ, and the area B of the area surrounded by the characteristic curve (6) (A-B), respectively, the amount of light incident on the focusing plate (-the amount of light guided from the quick return mirror in the case of an eye reflex camera) ). Therefore, if the amount of light incident on each focusing plate is equal, in the conventional system, most of the light is diffused at a large angle θ from the vertical direction of the focusing plate. This is indicated by B' in the figure. - In the case of an eye reflex camera, the light actually guided from the focus plate to the pentaprism is at most 0 to 30', so in conventional cameras, the amount of light is lost by the amount of light corresponding to the area of part B'. t~・The viewfinder screen is darkened by the amount of B', which is a shame. In other words, it becomes so dark that it becomes a focusing plate. The focusing plate obtained according to the present invention is tilted at a large angle of 0 as shown in the figure, and there is no light that is diffused.

There is no light loss corresponding to part B'. Therefore, it becomes a bright focus plate.

We also investigated how much the focus plates obtained in the first, second, and third specific examples change their blurring characteristics as the focus position changes.

When the subject was in focus, a clear image of the subject could be formed on the focal plate, and as the subject was out of focus, the desired amount of blur could be obtained. Therefore, it was found that each focusing plate described in the above specific example had a good focus detection accuracy of .degree.

In the above-mentioned embodiment, the process from the prototype shown in FIG. 3(c) to the manufacturing of the deaf for reticle manufacturing shown in FIGS. 4(C) and 5(h) will be explained. However, even in the conventional example of manufacturing the focusing plate shown in FIG. 2, this process can be carried out in various ways and there is no difference between the two and the present invention described above.
.

It goes without saying that the focusing plate of the present invention can be widely used in single-lens reflex cameras, cine cameras, video cameras, etc.

Furthermore, in the embodiment, a case where the above-mentioned unevenness is provided on the entire surface of one side of the reticle is explained, but the present invention can also be applied to a case where such an unevenness is provided on a part of the reticle at: )°C.

As described in detail above, according to the present invention, it is possible to obtain a focusing plate that is bright and has good focus detection accuracy by a very simple manufacturing method.

Further, according to the present invention, a prototype having fine irregularities on the surface is made, a mold for manufacturing a focusing plate is made from this prototype, and a mold is used to manufacture a focusing plate that is bright and has good focus detection accuracy. In this case, the process to create the prototype is very simple.There is no need for a dark room, and there are few chemical factors, so it is easy to control the uneven shape of the prototype.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a focusing plate as a first conventional example, FIG. 2 is a partial cross-sectional view of a focusing plate as a second conventional example, and FIG.
The figure shows a process diagram of the first embodiment of the present invention, FIG. 4 a process diagram of the second embodiment, FIG. 5 a process diagram of the third embodiment, and FIG. 7 is a partial sectional view showing an improved example similar to that in FIG. 6, FIG. 8 is a diffusion characteristic diagram of a specific example, and FIG. 9 is a schematic diagram for explaining the diffusion characteristics of a specific example. be. Figure 1 Figure 2 Figure 5

Claims (1)

[Scope of Claims] 1. A first step of applying sand to the surface of a transparent glass plate to create fine irregularities on the surface; a second step of making the portion hemispherical, and forming the glass plate itself as a focusing plate. 2. The method according to claim #I1, which comprises a third step of filling the concave and convex portions with a transparent material after the second step. Production method. 3. A method for manufacturing a focusing plate, in which a stage is made by replicating a master mold with a finely uneven surface, and a focusing plate is molded into the replicated mold. a first step of applying sand to the surface to create minute irregularities on the surface; and a second step of applying sand to the surface to make the convex portions of the irregularities into a hemispherical shape. A method for manufacturing a focusing plate, characterized in that the uneven surface produced by papermaking in the second step is used as the master model. and a third step of filling the bottoms of the recesses of the uneven surface machined in the second step with a transparent substance, and the uneven surface with the recesses filled is used as the master. A method for manufacturing a focusing plate.