JPH0894813A - Light-weight reflection mirror - Google Patents

Abstract

PURPOSE: To provide a light-weight reflection mirror with which even a light- weight reflection mirror having a large diameter such as >=1m, furthermore, >=10m is easily formed. CONSTITUTION: This doughnut-shaped light-weight reflection mirror is constituted by coating at least not only the mirror surface side but the inside diameter and the outside diameter sides of a holding body layer 16 made of a silica glass porous substance with transparent silica glass layers 18 and 17 having specified thickness. Then, plural ribs 19 made of a transparent silica glass material communicating between the glass layer 18 on the inside diameter side and the glass layer 17 on the outside diameter side so that the holding body layer 16 may be divided in a radial direction are formed in the radial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight reflecting mirror, and more particularly to a large donut type lightweight reflecting mirror having a Cassegrain structure having a circular opening (hereinafter referred to as an inner diameter) in a central portion thereof.

[0002]

2. Description of the Related Art Conventionally, a light-weight reflecting mirror has been used to collect electromagnetic waves and light such as sunlight, laser light, and microwaves. With a convex mirror and other reflecting mirrors and the like facing each other, the incident light from the outside is received by the convex mirror and reflected by the lightweight reflecting mirror, thereby enabling accurate light collection. Therefore, in many devices of this type, in order to guide the incident light to the convex mirror with high accuracy, a doughnut-shaped lightweight reflecting mirror having a Cassegrain structure in which the central portion of the lightweight reflecting mirror is circularly opened is used. And when such a device is used as an astronomical telescope or a laser focusing device, in order to obtain a high focusing efficiency and a high light receiving efficiency, the lightweight reflecting mirror is enlarged, and more specifically, the diameter is 300 to 3000 mm, further 10 m.
The above things are being demanded.

In these large donut type lightweight reflecting mirrors, mirror surface waviness occurs due to subtle volume changes of the plate material due to radiation of the focused beam and changes in environmental temperature. In addition, the lightweight reflecting mirror has a metal vapor deposition film as an optical reflecting layer formed on the surface of the glass polishing material formed to have a predetermined curvature.
Since it is formed by the CVD method at ˜800 ° C., the thermal deformation and the like may deteriorate the performance of the lightweight reflecting mirror. Therefore, in the conventional apparatus, the lightweight reflecting mirror is often formed by using silica glass having a small thermal deformation rate, but even if thermal deformation is suppressed by using such silica glass, the lightweight reflecting mirror is Since the light reflector is supported by an operating support table and can be freely rotated in any direction, the weight of the light reflector itself becomes larger, and the weight of the reflector itself causes the posture of the supporting angle to change. Change causes a mirror surface distortion, which causes a problem of performance deterioration.

In order to eliminate such drawbacks, the present applicant has
In conventional non-doughnut type lightweight reflectors, reflectors, etc., the reflector substrate has a surface having a transparent silica glass mirror-forming layer on its surface, and the holding layer holding the layer has all the pores contained inside. Contains 30% or more closed cells by volume,
It proposes a lightweight mirror body consisting of a silica glass porous foam layer having an apparent density of 0.1 to 1.2 g / cm ³ . (JP-A-5-60909)

[0005]

However, unlike the above-described lightweight reflector having a circular opening in the central portion, a donut-type lightweight reflector, particularly a donut-type lightweight reflector having an outer diameter of 300 mm or more, has a particular attitude. Is closer to the vertical, the concentrated load is more likely to be applied to the circular opening in the central portion, and the concentrated load is larger as the outer shape is larger, and distortion or mirror surface deformation is likely to occur in the central portion. In the prior art, however, the porous foam is often integrally formed by using a crucible. Therefore, as the outer diameter of the lightweight reflecting mirror increases, the crucible for forming the same must be enlarged. As a result, it becomes impossible to form a lightweight reflecting mirror having a large diameter of 1 m or more.

Therefore, according to the present invention, even if the inside is filled with a silica glass porous body to reduce the weight, the concentrated load generated in the circular opening in the central portion is released as much as possible and even if the concentrated load is generated, It is an object of the present invention to provide a donut type lightweight reflecting mirror capable of reducing the distortion to the extent that distortion or mirror surface deformation does not occur. Another object of the present invention is to provide a length of 1 m or more, further 10 m.
An object of the present invention is to provide a lightweight reflecting mirror which can be easily formed even with the above-mentioned large-diameter lightweight reflecting mirror.

[0007]

In order to achieve such a technical object, the present invention firstly proposes a doughnut-shaped lightweight reflecting mirror, in which at least the mirror surface side of the holder layer made of a silica glass porous body and the inner diameter and The point is a donut type lightweight reflecting mirror whose outer diameter side is covered with a transparent silica glass layer having a predetermined thickness. Such a structure is novel in the Cassegrain structure lightweight reflecting mirror. A point in which a plurality of ribs made of a transparent silica glass material that continuously connects the transparent silica glass layer on the inner diameter side and the transparent glass layer on the outer diameter side are formed in the radial direction so as to divide the holding body layer in the radial direction and preferably FIG. 1, a pair of ribs 19 radially extending from the inner diameter side or the outer diameter side with a predetermined inner angle and transparent glass arc pieces 17, 18 on the outer diameter or inner diameter side sandwiched between the pair of ribs 19. And a substantially triangular segment 10 having a silica glass porous body 16 (hereinafter referred to as a segment substrate) filled therein is connected in a donut shape. The present invention can be applied not only to the lightweight reflector having the Cassegrain structure, but also to the conventional lightweight reflector. Therefore, in the invention according to claim 3, the holder layer is divided in the radial direction. A technique is proposed in which a plurality of ribs 19 made of a transparent silica glass material are continuously formed between the transparent glass layers on the outer diameter side in the radial direction.

[0008]

According to such technical means, the holder layer 16
Since it contains a large number of bubbles, weight reduction is achieved, and since a large number of mesh members connecting the transparent layers on the surface are located through the bubbles, it is substantially effective in all directions. The point having a three-dimensional resistance strength equal to is as described above, and the present invention further relates to the above-mentioned carrier layer 1.
Since ribs 19 are provided so as to divide 6 in the radial direction, the ribs 19 increase the strength, and even if the lightweight reflecting mirror is upsized, no problem occurs in terms of strength. Further, in this case, when the substantially triangular segments 10 are connected in a donut shape, the above-mentioned effect is further amplified because the triangle has the strongest strength. In addition, according to the present invention, since the holder layer 16, that is, the foam can be molded in segment units, it is necessary to enlarge the holder layer 16 correspondingly even when manufacturing a large-sized lightweight reflecting mirror. It's easy to make.

In this case, the apparent density of the foam of the holder layer 16 is 0.1 to 0.1 in the case of the lightweight reflection mirror having the Cassegrain structure.
It is preferable to set it in the range of 0.5 g / cm ³ to increase the mesh density. Further, in the case of a lightweight reflector having a Cassegrain structure, it is preferable that the wall thickness on the inner diameter side is set to be smaller than the wall thickness on the outer diameter side, and the wall thickness of the inner diameter is set to 5% or more of the radius of the inner diameter. . Furthermore, the foam forming the holder layer 16 may be formed into either closed cells or open cells.
In the case of forming with open cells, it is preferable to form with open cells under reduced pressure, and more preferably, when the entire surface of the holding layer 16 is covered with a transparent silica glass layer having a predetermined thickness, the quartz lath glass layer It is preferable to form the through-holes 20 that reach the communicating bubbles in a part of each of the above in units of individual segments.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, the dimensions, materials, shapes, relative positions and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely examples, unless otherwise specified. Not too much.

An embodiment of the donut type lightweight reflecting mirror will be described with reference to FIG. 2 in the order of manufacturing. First, in a carbon crucible, fine particles of a high-purity amorphous silica glass produced by a hot gas phase method having a metal impurity content of 0.5 ppm or less were previously prepared in advance.
The silica glass fine powder was filled with the quartz glass fine powder heat-treated for about 2 hours in an atmosphere of ammonia gas + nitrogen gas at 50 ° C., and heat-treated for 2 hours at 1650 to 1700 ° C. in a reduced pressure atmosphere (10 −2 tor) to obtain the fine silica glass powder. Fuse and foam,
Density consisting of many closed cells 0.1-0.4g / cm3
To obtain a silica glass foam. When a foam having open cells is obtained, the silica glass foam obtained above is immersed in a solution of 20% hydrofluoric acid and 80% water for about 10 minutes to break the thin film between the closed cells. A silica glass continuous foam in which cells are connected to each other after being precipitated while being opened and completely immersed is obtained.

Then, this is fitted into a donut shape to be manufactured as shown in FIG. 2, and cut into a substantially triangular arc-shaped piece radially extending from the inner diameter side or the outer diameter side with a predetermined internal angle, and the diameter is 1500 mm, A segment substrate 16 made of a disk-shaped porous foam having a height of 800 mm is prepared. The substrate 16 had an apparent density of 0.1 to 0.4 g / cm ³ as described above, and the ratio of the total closed cell volume of the contained closed cells was about 70%. The content of the closed cells is determined by measuring the apparent density of the member and the density of the silica glass itself constituting the member, and the original porous foam member as described above in a solution of 20% hydrofluoric acid and 80% water. It can be easily obtained from the volume of the continuous ventilation hole obtained by immersing in.

Next, a triangular lid-shaped segment cover body 12 having an edge portion having the same outer shape as the base body 16 is formed of a transparent silica glass material. And the cover body 12 is the outer edge side 12
b and the bottom wall thickness 12c are set to 5 mm, and the inner edge side thickness 12a is set to 5 mm. Next, after manufacturing a donut disk-shaped mirror surface plate press-molded to a predetermined curvature in accordance with the mirror surface shape of the light weight reflecting mirror, the donut disk-shaped mirror surface plate
A mirror surface segment 13 is formed by aligning with 0 and cutting into a triangular shape.

After placing the segment cover body 12 on the mounting surface (not shown) in the furnace with the opening facing upward, silica fine powder having a thickness of about 1 mm is inserted over the entire inner surface of the segment cover body 12. The base 16 is fitted, and the mirror surface segment 13 is placed on the upper surface of the base 16 with silica fine powder interposed therebetween.
Then, a carbon weight (not shown), which was convexly formed to have a predetermined curvature in accordance with the mirror surface shape, was placed on the upper surface of the mirror surface segment 13 and integrated by heat welding in a reduced pressure atmosphere at a temperature of about 1400 ° C. Since the foam of the base body 16 is compressed by the weight, the height of the segment cover body 12 is set slightly lower than the height of the base body 16 in consideration of the amount of compression.
In this operation, the silica fine powder interposed between the segment cover body 12 and the mirror surface segment 13 and the base body 16 contracts during the fusion and integration, so that the transparent silica glass such as the cover body 13 and the porous foam body are separated from each other. The base 16 was completely integrated and the layer thickness disappeared. The fine silica powder was obtained by burning and oxidizing and decomposing silicon tetrachloride with an oxyhydrogen flame, and adjusted to 5 μm or less before use.

Next, segment 1 obtained as described above
In No. 0, as shown in FIG. 1, the ribs 19 are assembled into a donut shape and the continuous surfaces of the ribs 19 are welded to be integrated, and then the mirror surface is ground and polished to form a predetermined curvature surface. Then, an aluminum vapor deposition film is formed on the mirror surface of the lightweight reflecting mirror body by a CVD method at 400 to 800 ° C. to form an optical reflecting layer. When the segment substrate 16 is formed of a foam having open cells instead of closed cells as described above, the segment 10 can be formed in a vacuum state to form a reduced pressure segment, and a high-power laser beam is produced. Therefore, even if the inside of the holder layer 16 is heated via the mirror surface layer, thermal expansion does not occur, which is preferable. It should be noted that the configuration shown in FIG.
As shown in, even if the small hole 20 is bored in the cover body segment 13 surrounding the base body 16, the same action as the reduced pressure communication bubble can be performed.

[0016]

[Effect] As described above, according to the present invention, since each segment is formed of a foam containing a large number of bubbles,
In addition to the reduction in weight, the ribs 19 formed by connecting the aggregates increase the strength, so that there is no problem in terms of strength even if the lightweight reflecting mirror is upsized. Also in this case, if the substantially triangular segments are connected in a donut shape,
The effect is further amplified because the triangle is the strongest one. Further, according to the present invention, since the foam can be molded in segment units, it is not necessary to upsize the holder layer 16 correspondingly even when manufacturing a large-sized lightweight reflecting mirror, and it is possible to further increase the length by 1 m or more. Can be easily manufactured with a lightweight reflector of about 10 m. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 shows a doughnut-shaped lens according to an embodiment of the present invention, (A) is an overall perspective view, (B) is a horizontal sectional view, and (C) is a vertical sectional view.

FIG. 2 shows an exploded perspective view of a segment.

[Explanation of symbols]

 19 rib 16 porous body 17 glass arc piece 18 glass arc piece

Front page continuation (72) Inventor Kunio Yoshida 2-2-3-303 Torikano, Settsu City, Osaka Prefecture

Claims (3)

[Claims] 1. A doughnut-shaped lightweight reflecting mirror in which a transparent silica glass layer having a predetermined thickness covers at least the mirror surface side and the inner diameter and outer diameter side of a holder layer made of a silica glass porous body, A donut type lightweight reflection characterized by forming a plurality of ribs made of transparent silica glass in the radial direction that connect the transparent silica glass layer on the inner diameter side and the transparent glass layer on the outer diameter side in a continuous manner as the body layer is divided in the radial direction. mirror 2. Silica glass comprising a pair of ribs extending radially from the inner diameter side or the outer diameter side at a predetermined inner angle and a transparent glass arc piece on the outer diameter or inner diameter side sandwiched between the pair of ribs. The doughnut-shaped lightweight reflecting mirror according to claim 1, wherein substantially triangular-shaped segments filled with a porous body are connected in a donut shape. 3. A lightweight reflecting mirror comprising a holder layer made of a silica glass porous material, at least the mirror surface side and a diameter side of which are covered with a transparent silica glass layer having a predetermined thickness, wherein the holder layer is arranged in a radial direction. A light-weight reflecting mirror characterized in that a plurality of ribs made of a transparent silica glass material that connects the transparent glass layers on the outer diameter side to each other in a divided manner are formed in the radial direction.