JP2884555B2 - Lightweight reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reflector, and more particularly, to a large diameter light reflector.

[0002]

2. Description of the Related Art Conventionally, a lightweight reflector has been used to collect electromagnetic waves and light such as sunlight, laser light, and microwaves. This kind of lightweight reflector is provided on the optical axis. A convex mirror or another reflecting mirror or the like can be opposed so as to be able to face, and the light incident from the outside is received by the convex mirror and reflected by the light weight reflecting mirror to enable accurate light collection. Therefore, in order to accurately guide the incident light to the convex mirror, this type of apparatus uses a doughnut-shaped light reflector having a Cassegrain structure in which the center of the light reflector is circularly opened. When such a device is used as an astronomical telescope or a laser condensing device, in order to obtain high light-collecting efficiency and high light-receiving efficiency, the size of the lightweight reflector is increased, and more specifically, the diameter is 300 to 3000 mm, and more specifically, 10 m.
The above has been required.

[0003] In these large donut-type lightweight reflectors, mirror surface undulation or the like is generated due to subtle volume change of the plate material due to the radiation of the condensed beam or a change in environmental temperature. Further, the lightweight reflector has a metal polishing film as an optical reflection layer formed on the surface of a glass polishing material having a predetermined curvature.
Since it is formed by the CVD method at a temperature of up to 800 ° C., the thermal deformation or the like may lower the performance of the lightweight reflector. For this reason, in the conventional apparatus, the lightweight reflector is often formed by using silica glass having a small thermal deformation rate. However, even when the thermal deformation is suppressed by using such silica glass, the lightweight reflector is not used. in order in which freely rotate operation in any direction is supported on the support base for the operation, as the said light amount reflector is large in size, the change of the support angle of the own weight of the reflection mirror itself A change in the posture causes a mirror surface distortion, which causes a problem of deterioration in performance.

In order to eliminate such disadvantages, the present applicant has
In conventional non-donut-type lightweight reflectors and reflectors, the reflector base has a surface having a transparent silica glass mirror surface forming layer on its surface, and a holding layer holding the layer has a total pore contained therein. Contains closed cells of 30% or more of the volume,
A lightweight reflector comprising a silica glass porous foam layer having an apparent density of 0.1 to 1.2 g / cm ³ has been proposed. (JP-A-5-60909)

[0005]

Unlike lightweight reflector not be have a circular opening in the center of, however the [0005], a donut type light reflector, in particular toroidal outer diameter of 300mm or more light reflectors, particularly attitude The closer the mirror surface is to the vertical, the more the concentrated load is likely to be applied to the central circular opening, and the larger the outer shape becomes, the more the concentrated load is applied, and the more the external shape becomes larger, the more likely the central portion is distorted or mirror-shaped. .
However, in the prior art, the porous foam is often formed by integral molding using a crucible. For this reason, the larger the outer diameter of the lightweight reflector, the larger the crucible for molding the same. As a result, it is impossible to form a light-weight reflector having a large diameter of 1 m or more.

[0006] The present invention fills the silica glass porous body at the inner portion, this even if Matatatoe concentrated load while missed as much as possible concentrated load caused circular opening in the central portion even when reduce the weight It is an object of the present invention to provide a donut-type lightweight reflector that can be reduced to the extent that distortion and mirror surface deformation do not occur. Another object of the present invention is to provide a lightweight reflector which can be easily formed even with a large-diameter lightweight reflector of 1 m or more, and even 10 m or more.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above technical object, the present invention first provides a doughnut-type lightweight reflecting mirror with an inner diameter and a holding layer made of a porous silica glass body together with at least the mirror side. The point is that it 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 a Cassegrain light reflector. The transparent silica glass layer on the inner diameter side and the transparent on the outer diameter side are divided as the holder layer is divided in the radial direction.
A point in which a plurality of ribs made of a transparent silica glass material are formed in the radial direction to continuously connect the silica glass layers, and preferably, as shown in FIG. 1, a pair of radially extending radially extending from the inner diameter side or the outer diameter side with a predetermined inner angle. Ribs 19 and transparent silica glass arc-shaped pieces 17 and 18 having an outer diameter or an inner diameter sandwiched between the pair of ribs 19, and the inside thereof is filled with a porous silica glass body 16 (hereinafter, referred to as a segment base). It is characterized in that the generally triangular segments 10 are connected in a donut shape. Note that the present invention is not only lightweight reflector of the Cassegrain structure, said is also applicable to conventional light reflectors, Therefore, in the invention of claim 3, wherein, as to divide said holding body layer in the radial direction The present invention proposes a technique in which a plurality of ribs 19 made of a transparent silica glass material that connects the transparent silica glass layers on the outer diameter side are formed in the radial direction.

[0008]

According to the technical means, the holding body layer 16 is provided.
In addition, since a large number of air bubbles are included, weight reduction is achieved, and a large number of mesh members connecting the transparent layer on the surface are located through the air bubbles. The point having a three-dimensional resistance strength equal to
Since the ribs 19 are provided so as to divide the mirror 6 in the radial direction, the strength is increased by the ribs 19, and no problem occurs in the strength even when the size of the lightweight reflector is increased. In this case, when the substantially triangular segments 10 are connected in a donut shape, the effect is further amplified because the triangle is the strongest in terms of strength. In addition, the present invention allows the holding member layer 16, that is, the foam to be molded in segment units, so that the holding member layer 16 needs to be correspondingly enlarged even when a large lightweight reflector is manufactured. And its manufacture is easy.

In this case, the apparent density of the foam of the holding body layer 16 is 0.1 to 0.1 in the case of a lightweight reflector having a Cassegrain structure.
It is preferable to set the range to 0.5 g / cm ³ to increase the mesh density. In the case of a Cassegrain light reflector, the thickness on the inner diameter side is preferably set to be smaller than the thickness on the outer diameter side, and the thickness of the inner diameter is preferably set to 5% or more of the radius of the inner diameter. . Further, the foam constituting the holding body layer 16 may be formed into any of closed cells or open cells,
Good to the case of forming by open cells are formed by open cells placed under reduced pressure, when more preferably that covers the entire surface of the holding body layer 16 of a transparent silica glass layer having a predetermined thickness, the transparent vitreous silica It is preferable to form through-holes 20 reaching communication bubbles in a part of the layer 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, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

An embodiment of a donut-type lightweight reflector will be described with reference to FIG. First, in a crucible made of carbon, a high-purity amorphous silica glass fine powder having a thermal impurity content of 0.5 ppm or less is prepared in advance by 850.
℃ within ammonia gas and nitrogen gas atmosphere filling the silica glass fine powder was heat-treated for about 2 hours, reduced pressure atmosphere (1
0 ^-2 tor) was heated for 2 hours at 1,650 to 1,700 ° C. in fusing foaming said silica glass fine powder, many consisting closed cell density 0.1 to 0.4 g / cm ³ of silica glass foam Get. In order to obtain an open-celled foam, the silica glass foam obtained as described above is treated with hydrofluoric acid 20
% And 80% water for about 10 min, the thin film between the closed cells is settled while being ruptured, and after completely immersed, a silica glass interconnected foam in which the cells communicate with each other is obtained.

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

Next, a triangular lid-shaped segment cover body 12 having an edge having the same outer shape as the base body 16 is formed of a transparent silica glass material. The cover body 12 has an outer edge and a bottom.
The surface thickness is set to 5 mm and the thickness on the inner edge side is 5 m
Set to m. Next, a donut disk-shaped mirror plate which is press-formed to a predetermined curvature according to the mirror surface shape of the lightweight reflecting mirror is manufactured, and is cut into a triangular shape according to the segment 10 to form a mirror surface segment 13.

After the segment cover body 12 is mounted on the furnace mounting surface (not shown) with the opening facing upward, silica fine powder is interposed about 1 mm in thickness over the entire inner surface. The base 16 is fitted, and the mirror surface segment 13 is further placed on the upper surface of the base 16 via fine silica powder.
Then, in a state where a carbon weight (not shown) projecting at a predetermined curvature according to the mirror surface shape is mounted on the upper surface of the mirror surface segment 13, heat welding and integration are performed in a reduced pressure atmosphere at a temperature of about 1400 ° C. Since the foam of the base 16 is compressed by the weight, the height of the segment cover body 12 is set slightly lower than the height of the base 16 in anticipation of the compression amount.
In this operation, the silica fine powder interposed between the segment cover body 12 and the mirror surface segment 13 and the base 16 shrinks during the welding and integration, and the transparent silica glass and the porous foam of the cover body 12 and the like are shrunk. The substrate 16 was completely integrated, and the layer thickness had disappeared. The silica fine powder obtained by burning and oxidizing and decomposing silicon tetrachloride with an oxyhydrogen flame was used after adjusting the particle size to 5 μm or less.

Next, the segments 10 obtained as described above are assembled into a donut shape as shown in FIG. 1, and the connecting surfaces of the ribs 19 are welded together to form a single piece. Is ground and polished to form a predetermined curvature surface. Then, 400-800 ° C. CVD is applied to the mirror surface of the lightweight reflecting mirror body.
An aluminum reflective film is formed by a method, and an optical reflection layer is formed. In the case where the segment base 16 is formed of open-cell foam instead of closed cells as described above, the segment 10 can be formed under reduced pressure by forming the segment 10 in a vacuum state. Therefore, even if the inside of the holding body layer 16 is heated via the mirror surface layer, thermal expansion or the like does not occur, which is preferable. Incidentally, FIG. 2 without taking the configuration of the
A segment cover surrounding the base 16 as shown in FIG.
Even if the small holes 20 are pierced in the body 12 , the same function as the above-described reduced-pressure communication bubble can be performed.

[0016]

According to the present invention as described above, since each segment is formed of a foam containing many bubbles,
The weight reduction is achieved, and the strength is increased by the ribs 19 formed in a continuous manner. Even if the weight of the light reflecting mirror is increased, no problem occurs in the strength. In this case, if a substantially triangular segment is connected in a donut shape,
The effect is further amplified because the triangle is the strongest in intensity. In addition, since the present invention allows the foam to be molded in segment units, it is not necessary to increase the size of the holding layer 16 correspondingly even in the case of manufacturing a large-sized lightweight reflecting mirror. Can be easily manufactured even with a lightweight reflecting mirror of about 10 m. And so on.

[Brief description of the drawings]

FIG. 1 shows a donut-type lightweight reflecting mirror according to an embodiment of the present invention, wherein (A) is an overall perspective view, (B) is a transverse sectional view,
(C) shows a longitudinal sectional view.

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

[Description of Signs] 1 Donut type lightweight reflector 10 segment 16 silica glass porous body 17 silica glass arc-shaped piece 18 silica glass arc-shaped piece 19 rib

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-60909 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 5/08-5/10

Claims (3)

(57) [Claims] 1. A donut-type lightweight reflecting mirror in which a transparent silica glass layer having a predetermined thickness is coated on at least a mirror surface side and an inner diameter and an outer diameter side of a holding layer made of a porous silica glass body. toroidal lightweight, characterized in that the body layer of transparent silica glass ribs continuously provided a transparent silica glass layers of the transparent vitreous silica layer and the outer diameter side of the inner diameter side as divided into radially and a plurality of radially formed Reflector. 2. A silica inside it and an outer diameter or the inner diameter side of the transparent silica glass arches sandwiched between a pair of ribs and said pair of ribs which extend radially with a predetermined interior angle than than or outer diameter inner diameter side 2. The donut-shaped light reflector according to claim 1, wherein substantially triangular segments filled with a porous glass body are connected in a donut shape. 3. A lightweight reflecting mirror comprising at least a mirror surface side and an outer diameter side of a holding layer made of a porous silica glass body covered with a transparent silica glass layer having a predetermined thickness. Transparent on the outer diameter side as if divided into
A lightweight reflecting mirror comprising a plurality of ribs made of a transparent silica glass material connected in a continuous manner between silica glass layers and formed in a radial direction.