JP2910022B2 - Circular light 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 ring-shaped concave mirror, a convex mirror or a plane mirror having a circular opening (hereinafter referred to as an inner diameter) at a central portion, and more particularly to a large ring-shaped lightweight reflector having an outer diameter of 300 mm or more.

[0002]

2. Description of the Related Art Conventionally, a reflecting mirror has been used for focusing and diffusing electromagnetic waves and light such as sunlight, astronomical light, laser light, and microwaves. This type of reflecting mirror is located on the optical axis of the reflecting mirror. The presence of an incident light source makes it possible to obtain a focused and diffused light with high precision symmetrical to the optical axis.Therefore, a Cassegrain-shaped ring-shaped reflection primary mirror having a circular opening in the center through which a light beam can pass, and In many cases, a reflection type optical system including a facing secondary mirror is used. When such an optical device is used as an optical device such as an astronomical telescope or a laser beam, more luminous flux must be focused and diffused in order to increase efficiency. Typically 300mm to 3000mm in diameter, and even 10m
The above has been required. In addition, as the size of the reflector is increased in applications such as a moving laser reflection system and an astronomical light observation system, in particular, as the size of the reflector increases, conflicting characteristics such as a reduction in the weight of the moving optical system have been required.

[0003] In these large-diameter circular reflectors, swelling or the like occurs due to subtle changes in the volume of the reflector material due to the radiation of reflected light beams or changes in environmental temperature. In addition, since the reflecting mirror is formed by forming a metal vapor-deposited film as an optical reflecting layer on a surface of an optically polished material by a CVD method at 300 to 1000 ° C., a surface change due to heat or the like may deteriorate the performance of the reflecting mirror. There is a risk of lowering. For this reason, in the conventional apparatus, the reflection mirror is often formed using quartz glass or a low-expansion recrystallized glass having a small change accompanying a volume change such as thermal expansion, but such a material is used. Even if the change due to heat is suppressed, the reflecting mirror is supported on an operating support and can be freely rotated in an arbitrary direction. A change in posture, such as a change in the support angle, due to the weight of the reflecting mirror itself causes distortion on the mirror surface, which causes a problem of deterioration in performance.

In order to eliminate such disadvantages, the present applicant has
In the conventional holeless reflector, the reflector base has a surface having a transparent quartz glass mirror surface forming layer on the surface, and the holding layer holding the layer has a total pore volume of 30% of the total pore volume contained therein.
%, And has proposed a lightweight reflector base comprising a quartz glass porous foam layer having an apparent density of 0.1 to 1.2 g / cm ³ containing closed cells of 0.1% or more. (JP-A-5-609
09)

[0005]

However, unlike the above-mentioned reflector having no circular opening in the central portion, in the case of a circular reflector, particularly a circular reflector having an outer diameter of 300 mm or more, the mirror surface is particularly oriented. The closer you get to the vertical,
Concentrated load is likely to be applied around the central circular opening, and even if the concentrated load is reduced by the porous foam, the larger the outer diameter is, the larger the expanded diameter becomes,
Distortion and mirror surface deformation are likely to occur at the center.

Accordingly, the present invention fills the inside with a porous silica glass body to reduce the concentrated load generated around the central circular opening as much as possible even if the weight is reduced. It is an object of the present invention to provide a ring-shaped lightweight reflecting mirror that can reduce the distortion to the extent that distortion and mirror deformation do not occur.

[0007]

According to the present invention, in order to achieve the technical object, the invention according to claim 1 has a circular opening (hereinafter referred to as an inner diameter) at a central portion and an outer diameter of 300 mm or more. In a certain ring-shaped reflecting mirror, a holding layer made of a porous quartz glass body having a circular inner diameter in the center and having an apparent density of 0.1 to 0.5 g / cm ³ is formed, and a mirror surface of the holding layer is formed. The entire surface including the inner side and the inner peripheral side is covered with a transparent quartz glass layer having a predetermined thickness, and the quartz glass porous body constituting the holding body layer is separated from a pore capable of communicating with 80% or more of the pore pore volume. In this case, there is provided a penetrating means which reaches a gap portion which can communicate with a part of the quartz glass layer. In this case, as described in claim 2, the inner diameter of the holding body layer is set to 1/3 or less of the outer diameter, and a predetermined thickness at least higher than the holding body layer on the inner circumferential surface side of the inner diameter. It is preferable to form one or a plurality of circular reinforcing layers, and to set the thickness of the entire circular reinforcing layer to 4% to 10% of the radius of the inner diameter. Further, as described in claim 3, all the voids inside the quartz glass coating layer including the voids of the porous quartz glass constituting the holding layer are depressurized with respect to the atmospheric pressure in a temperature range of at least 1300 ° C or lower. It is good to configure below.

[0008]

According to this technical means, the holding body layer contains a large number of pores, so that the weight can be reduced and the transparent layer on the surface is supported from below through the pores. a number of mesh member connected is that with respect to all directions in order will be located having a substantially equal three-dimensional resistance strength, further 0.1 to apparent density of the carrier layer in the present invention The mesh density of the developed lattice structure is increased by adjusting the ratio between voids and members by setting the range to 0.5 g / cm ³ . However, apparent density is 0.1g
If it is less than / cm ³ , the wall thickness of the mesh member forming the three-dimensional lattice structure cannot be sufficiently obtained, and the strength of the holding layer for supporting the transparent quartz glass layer on the surface side, that is, the mirror surface forming layer is insufficient. , Cannot withstand the polishing pressure of the mirror surface. In the case of a conventional reflector having a non-Cassegrain structure having no circular opening, no problem occurs up to an apparent density of 1.2 g / cm ^3. It has been experimentally confirmed that when the weight is more than 0.5 g / cm ^{3, the} outer periphery of the reflecting mirror is distorted due to its own mechanical weight.

However, even if the above configuration is adopted, it is unavoidable that a concentrated load is generated in the circular opening. Therefore, the present invention provides an inner diameter of the ring-shaped reflecting mirror which is 1 /
It is set to 3 or less, and while dispersing the force on the holding body layer side, a circular opening, that is, a circular reinforcing layer having a predetermined thickness at a higher density than the holding body layer is formed at least on the inner peripheral side of the inner diameter of the holding body layer. Dispersion of concentrated stress is achieved. Also, the inner circumference
The thickness of the entire circular reinforcing layer on the side is 4% to 10% of the radius of the inner diameter.
% Is set. In the present invention, this is
The thickness of the entire stiffener is greater than 10% of the radius of the inner diameter
And the effect of reducing the weight of the entire reflector decreases,
Increases as the Ikyo distortion of the outer periphery can not be ignored, also the inner
If it is set smaller than 4% of the radius of the diameter, the reinforcing effect itself is not
In addition, distortion and mirror deformation occur around the circular opening in the center.
It will be easier.

In the present invention, the circular reinforcing layer on the inner peripheral side of the inner diameter of the holder layer is a porous silica glass body having a higher density than the holder layer, and the density increases from low to high as going from the outside to the inside. By using the reinforcing layer, the stress can be effectively dispersed. Further, since the entire surface including the mirror side and the inner peripheral side of the holding layer is covered with a transparent quartz glass layer having a predetermined thickness, the holding layer is 80% of the pore void volume.
In the case of the configuration of the communicating porous quartz glass body including the communicable voids as described above, by forming a penetration means such as a through hole reaching a communicable void portion in a part of the quartz glass coating layer, the reflection is achieved. The pressure inside and outside the mirror can be made the same, and the mirror surface displacement can be reduced with respect to a change in pressure or a change in temperature outside. In addition, since the entire surface is covered, the holding member is so arranged that the pressure inside the reflecting mirror does not change and the reflecting surface does not change even when the temperature changes in the CVD process for forming the reflecting film as described above. All voids inside the quartz glass coating layer including voids such as closed cells or interconnected pores of a quartz glass porous body composed of closed cells or foams composed of open cells constituting the layer are brought to atmospheric pressure in a temperature range of at least 1300 ° C or less. On the other hand, it is preferable that the pressure is reduced.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, 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, unless otherwise specified. Absent.

First, an embodiment of the present invention will be described with reference to FIG. 1 while explaining a process of manufacturing a ring-shaped flat mirror having an outer diameter of 1000 mm.
A description will be given based on (A) and (B). About 300 hydroxyl groups
A silicon dioxide powder having a particle size of 20 μm or less containing about ppm is molded and sintered at a temperature of about 1400 ° C. to have a diameter of 1200 m.
m was manufactured. Next, this sintered body is
After heating and reacting in an ammonia atmosphere at a temperature of 0 ° C. to ammonia, the mixture was further heated in a reduced-pressure atmosphere at a temperature of 1700 ° C. for 1 hour, fused, and foamed by releasing gas to obtain a foam.

Next, this is cut to have a diameter of 1000
After forming a disc-shaped porous foam member having a thickness of 800 mm and a thickness of 800 mm, the center circular opening is 300 mm and 400 mm.
Each plurality forming a circular ring-type discs, each flat surface mirror base 11
To manufacture. The substrate 11 made of the porous foam member
Was 0.4 g / cm ³ in apparent density, and the ratio of contained closed cells to the total pore volume was about 70%. The content of the closed cells can be easily determined by measuring the apparent density of the member and the density of the silicon dioxide glass itself constituting the member, and from the volume of the interconnected pores obtained by immersing the original foam member in a liquid. can get.

Next, the inner edge diameter of the base 11 is about 4
An annular lid-shaped cover body 12 having a plane mirror surface portion and an outer edge portion which is smaller by mm and has the same outer diameter as the base body 11 is formed of a transparent glass material. The cover body 12 is formed such that the outer edge side thickness 1b and the mirror surface thickness 1c are set to 8 mm, and the inner edge side thickness 1a is set to 2 mm, 4 mm, 13 mm and 20 mm, respectively. Next, a ring-shaped disk-shaped upper plate 1 having the same outer diameter as the projected plane shape of the cover body 12
Prepare 3

As shown in FIG. 1 (B), the furnace mounting surface 20 is formed in a flat shape according to the shape of the flat mirror surface portion.
Above, after placing the cover body 12 in the space Sa 19 placed toward upward opening, after the silicon dioxide fine powder 14 is about 1mm about intervening thickness over its entire inner surface,
The base 11 is fitted, the upper surface and the inner edge gap are filled with fine silicon dioxide powder 14 , and the upper plate 13 is placed on the upper surface. Then, the disc-shaped carbon weight 15 was placed on the upper surface of the upper plate 13 and heat-welding was integrated in a reduced-pressure atmosphere at a temperature of about 1300 ° C. or more. The weight 15
Thus, the height of the cover body 12 is set slightly lower than the height of the base body 11 in anticipation of the amount of compression. In this operation, the silicon dioxide fine powder 14 interposed between the cover body 12 and the upper plate 13 and the base body 11 contracts during the welding and integration, and foams with the transparent quartz glass of the cover body 12 and the like. The base 11 consisting of the body was completely integrated, and the other layer thickness disappeared except for the sintered layer of about 2 mm thickness at the inner edge. Further, in order to examine the density of the sintered layer and the quartz glass layer remaining at the inner edge, each part was cut out with a diamond cutter after all the tests, and the apparent density was examined. / Cm ³ and the quartz glass layer was 2.2 g / cm ³ . The silicon dioxide fine powder 14 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, after the mirror surface of the planar mirror body with holes obtained as described above is polished to a flat surface,
An aluminum deposition film is formed by a CVD method at 0 ° C., and an optical reflection layer 16 is formed. The plane mirror 1 thus obtained
As shown in FIG. 3, after being supported by an aluminum support frame 18 via a silicone rubber layer 17 on the outer periphery, the attitude of the support frame is changed to a vertical state, and the mirror surface displacement in each state is interfered. Investigated by total.

From the observation of the interference fringes, it was found that the inner diameter of the support layer was 4
In the case of 00 mm (greater than 1/3 of the inner / outer diameter ratio), a large displacement was observed on the entire mirror surface near the circular opening 2 and the inner diameter was 3 mm.
00 mm (inner / outer diameter ratio is 1/3 or less), and the sum of the sintered layer thickness and the high-density reinforcing layer of the inner edge side quartz glass thickness is set to 4 mm (less than 4% of the radius of the inner diameter of the holding layer). , A small local displacement is seen near the inner peripheral portion of the circular opening 2. On the other hand, the inner diameter of the holder layer is 300 mm (inner / outer radius ratio is 1/3 or less), and the total of the high-density reinforcing layer composed of the sintered layer thickness and the inner edge side quartz glass thickness is 22 mm (radius of the inner diameter of the holder layer). In the case where the inner diameter is set to be larger than 10%, a small local displacement, which is considered to be caused by its own weight, is seen on the lower mirror surface of the outer peripheral portion of the plane mirror, but the inner diameter is 300 mm (inner / outer diameter ratio is 1/3 or less).
In the case where the total of the high-density reinforcing layer composed of the thickness of the sintered layer and the thickness of the quartz glass on the inner edge side is set to 6 mm and 15 mm (10% or less and 4% or more of the radius of the inner diameter of the holding body layer), In each case, no displacement was observed, and the most desirable results were obtained.

Next, using a silicon dioxide powder containing about 200 ppm of hydroxyl groups and having a particle size of about 50 μm, using a foam having a density set to 0.8 g / cm ³ in the same manner as in the above embodiment, using an outer diameter of After manufacturing a substrate 11 having a thickness of 1000 mm and an inner diameter of 300 mm, a plane mirror 1 is manufactured using the cover body 12 having a thickness of about 2 mm on the inner edge and a thickness of 13 mm on the inner edge. As a result, a test similar to that described above was conducted, and it was confirmed that a large displacement considered to be caused by its own weight occurred on the lower mirror surface of the outer peripheral portion of the plane mirror. Therefore, as apparent from the present examples, it can be understood that it is better to set the apparent density of the support layer in the range of 0.1 to 0.5 g / cm ³ .

Next, another embodiment using a communicating foam for the base 11 will be described. First, the inner diameter is 1000mm
In a slightly larger carbon crucible, finely divided quartz glass powder by thermal vapor synthesis is preliminarily mixed with 850 ° C ammonia gas +
Filled after heat treatment for about 4 hours in a nitrogen gas atmosphere, and 1600 ° C. in a reduced pressure atmosphere (10 ⁻¹ to 10 ⁻² torr).
The quartz glass fine powder is fused and foamed by heating at 石英 1700 ° C. for 2 hours to obtain a quartz glass foam composed of many closed cells. Then, the quartz glass foam obtained by the above-described method is immersed in a 20% hydrofluoric acid solution for about 10 minutes, so that the foam is broken while the thin film between closed cells in the foam is broken. It is made up of pores of interconnected communicating bubbles that have settled therein and communicated with each other after complete sedimentation, and have a pore volume of 80% or more of the pore volume, including residual closed cells, and have an apparent density of 0.1 to 0.1%. A 5 g / cm ³ porous quartz glass body is obtained. FIG. 2A shows closed cells.
(B) shows the state of communicating bubbles.

From the porous quartz glass thus obtained, the inner diameter of 300 m, which was the most desirable condition of the above embodiment, was obtained.
m, after the outer diameter was fabricated base 11 of the holding body layer of 1000 mm, the outer side wall thickness 1b and specular portion thickness 1c and sets to 8 mm, the embodiments et similarly to the inner edge 2mm thickness of about Sintered layer can be formed and inner edge side thickness 1a is 13mm
Using the cover member 12 set as described above, heat-welding and integration are performed in a reduced-pressure atmosphere at a temperature of about 1300 ° C. or more, and grinding, mirror polishing, and formation of a metal deposition layer are performed in the same manner as in the above examples. When a mirror was manufactured and subjected to the same test as above, no displacement of the mirror surface was observed.

According to this embodiment, the holding body layer is formed of a porous quartz glass body which is a foam of open cells, but the open cells of the porous body are at least 1300 ° C.
Since the pressure is reduced in the following temperature range, even if the holder layer is heated via the mirror surface layer with a high-power laser beam or the like, thermal expansion of the internal residual gas does not occur, which is preferable. 3, the small holes 13a are formed in a part of the transparent glass layers 12, 13 surrounding the substrate 11, specifically, in the circular plate 13 on the back side of the mirror surface layer, as shown in FIG. Even if the holes are pierced, the same action as the above-mentioned vacuum communication bubbles can be produced.

[0022]

As described above, according to the present invention, even when the inside is filled with a porous silica glass body and the weight is reduced, the concentrated load generated in the central circular opening is relieved as much as possible and the concentrated load is generated again. However, it is possible to provide a ring-shaped reflecting mirror capable of reducing the distortion to such an extent that no distortion or mirror surface deformation occurs.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a manufacturing process of the present invention.

FIGS. 2A and 2B show a state of bubbles as a holding layer, and FIGS. 2A and 2B show a state of closed cells; FIGS.

FIG. 3 is a cross-sectional view of a donut-shaped lens according to an embodiment of the present invention using a base having open cells.

[Explanation of symbols]

11 flat mirror base (holding body layer) 12 cover body 13 upper plate 1a inner edge side thickness 1b outer edge side thickness

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-60909 (JP, A) Tokuyo Sho 56-500688 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 5/08-5/10

Claims (3)

(57) [Claims] 1. An annular reflector having a circular opening (hereinafter referred to as an inner diameter) in the center and an outer diameter of 300 mm or more, wherein the apparent density is 0.1 to 0.5 g having a circular inner diameter in the center.
/ Cm ^3, a holding layer made of a porous quartz glass body was formed, and the entire surface including the mirror side and the inner diameter inner side of the holding layer was formed.
The surface is covered with a transparent quartz glass layer having a predetermined thickness, and the porous quartz glass body constituting the holding body layer is covered with pores.
80% or more of the volume is formed of a communicable void, and the quartz
Penetrating hand that reaches a gap that can communicate with a part of the glass layer
A ring-shaped lightweight reflector with a step . 2. The method according to claim 1, wherein the inner diameter of said holding body layer is 1 / l of the outer diameter.
3 or less, and forming one or more circular reinforcing layers having a predetermined thickness at a higher density than at least the holding body layer on the inner peripheral surface side of the inner diameter, and setting the entire thickness of the circular reinforcing layer to the radius of the inner diameter. 4
The light-weight circular mirror according to claim 1 , characterized in that the ratio is set to 10% to 10%. Wherein it is constructed in vacuo the atmospheric pressure at a temperature range of at least 1300 ° C. all voids inside the quartz glass coating layer containing voids porous silica glass body constituting the holding body layer The light reflector according to claim 1, characterized in that: