JP2001318301A - Optical member supporting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly maintain the geometrical positional relation of an optical member regardless of temperature change by making the supporting structure of the optical member of an optical system light in weight and simple. SOLUTION: A main mirror 1 which is the optical member is supported by a main mirror supporting part 2 and is coupled with a main mirror base 3. Three frame supporting members 4 are radially extended from the optical axis center or the main mirror 1 by a uniform angle at the main mirror base 3, and a sub-mirror frame 6 is attached at a position opposed to the main mirror 1 through a V-shaped frame 5 fixed by the frame supporting member 4. A sub-mirror 8 is fixed so as to be opposed to the main mirror through a sub- mirror supporting member 7 at the sub-mirror frame 6. The coefficients of the linear expansion of the main mirror base 3, the frame 5 and the sub-mirror frame 6 are equally set as αa=αc=αd, and also the coefficient αb of linear expansion of the frame supporting member 4 is set as αb>αa. Though the temperature change is caused and a change is caused in the dimension of each member, the length and the coefficient of linear expansion of each member are selected so that the change is not caused in an optical distance between the main mirror 1 and the sub-mirror 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member supporting device capable of exhibiting stable optical performance, for example, with respect to the positional relationship between a primary mirror and a secondary mirror even under a severe thermal environment. It is.

[0002]

2. Description of the Related Art In a conventional optical system such as a reflection telescope, a primary mirror and a secondary mirror are held via a cylindrical or tripod-shaped structural member to maintain a geometric positional relationship between the optical members.

[0003]

However, in the above-mentioned conventional example, the temperature environment used in observation equipment and optical communication optical systems mounted on artificial satellites and the like often changes remarkably, and the structure , The optical distance changes with the above-described temperature change, and it is difficult to maintain the optical performance for a long time.

When the curvature of the optical member itself changes with the above-mentioned temperature change and the focus position needs to be corrected, the optical distance is changed with the above-mentioned temperature change to correct the focus position. However, with a single material configuration, it is difficult to obtain a correction amount suitable for maintaining the optical performance because the change in the optical distance depends on the linear expansion coefficient of the material.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical member supporting apparatus capable of reducing the weight and simplification of a supporting structure of an optical member of an optical system and maintaining a constant geometrical positional relationship between optical members regardless of a temperature change. It is in.

Another object of the present invention is to correct the movement of the focal point caused by the change in the optical member itself by adjusting the amount of change in the optical distance of the support structure, thereby maintaining a stable optical performance. It is to provide a device.

[0007]

According to the present invention, there is provided an optical member supporting apparatus for achieving the above object, wherein the first and second optical members are maintained in a geometrical positional relationship.
An apparatus for supporting the optical member, comprising: a first supporting means for supporting the first optical member and having a plurality of leg members extending radially with respect to the optical axis center of the first optical member; And second support means having a plurality of frames for supporting the second optical member and connecting to the distal ends of the legs of the first support member, wherein the first and second support members are provided. Are characterized by having different linear expansion coefficients and selecting a member size that keeps the geometrical positional relationship constant even when a temperature change occurs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 is a perspective view, in which a primary mirror 1 as an optical member is supported by a primary mirror support 2 and is coupled to a primary mirror base 3. On the primary mirror base 3, three frame supporting members 4 are radially extended from the center of the optical axis of the primary mirror 1 at an equal angle, and via a V-shaped frame 5 fixed to the tip of the frame supporting member 4, A sub mirror frame 6 is mounted at a position facing the main mirror 1. That is, V of frame 5
The U-shaped branch is connected to the frame support member 4, and two ends of the frame 5 are connected to the secondary mirror frame 6.
A sub-mirror 8 is fixed to the sub-mirror frame 6 so as to face the main mirror 1 via a sub-mirror support 7, and a lens barrel 9 for a relay optical system is provided at the center of the main mirror 1. And is connected to the primary mirror base 3. The linear expansion coefficient of the frame support member 4 is different from the linear expansion coefficients of the other members. The plurality of holes on the back surface of the primary mirror 1 are lightened for weight reduction.

In this embodiment, a flexible member having a spring property is used in the vicinity of each joint of the frame 5, so that the influence of the deformation of the main part of the frame 5 and the deformation of other members is reduced. Not to be. Although the frame 5 is a V-shaped member, the frame 5 may be formed of two members having the same length and the same linear expansion coefficient.

FIG. 2 is a schematic view of the present embodiment, showing dimensions required for calculation. The primary mirror base 3 has a linear expansion coefficient α _a
The distance from the optical axis center of the primary mirror 1 to the joint of the frame support member 4 is a. The frame support member 4 has a linear expansion coefficient α _b , and the distance from the joint with the primary mirror base 3 to the joint with the frame 5 is b. The frame 5 has a linear expansion coefficient α _c and a length c. The secondary mirror frame 6 has a triangular shape, and has a linear expansion coefficient α _d and a side length d.
The optical distance between the primary mirror 1 and the secondary mirror 8 is H, and e, f,
g, h1, and h2 are auxiliary dimensions.

In this embodiment, the linear expansion coefficients of the primary mirror base 3, the frame 5, and the secondary mirror frame 6 are equal to α _a = α _c.
= The α _d, is α _b> α _a. The linear expansion coefficients are all positive values.

From the configuration of this embodiment shown in FIG. 2, the following relationships are established for the dimensions of each part. H = (h2 ² -i ² ) ^1/2 where i = (a + b) -e = (a + b) -3 ^1/2 d /
^{6 h2 = (c 2 -d 2} /4) ^1/2. In summary ^{this, H = [{3c 2 -3} (a + b) 2 +3 1/2 d (a + b) -
d ² } / 3] ^1/2 .

Here, when a temperature change T occurs, each member undergoes a dimensional change accompanying this temperature change. The dimensions of each member after the dimensional change are referred to as dimensions a ′ of the primary mirror base 3,
If the dimension b ′ of the frame support member 4, the dimension c ′ of the frame 5, and the length d ′ of the sub mirror frame 6, the following equation is obtained. a ′ = a (1 + α _a T) b ′ = b (1 + α _b T) c ′ = c (1 + α _c T) = c (1 + α _a T) d ′ = d (1 + α _d T) = d (1 + α _a T)

Further, assuming that the optical distance after the dimensional change of each member is H ′, it is calculated by the following equation. H ′ = [{3c ′ ² −3 (a ′ + b ′) ² +3 ^1/2 d ′ (a ′ +
b ′) − d ′ ² } / 3] ^1/2 At this time, if the length and the linear expansion coefficient of each member are selected so that H = H ′, the optical distance H can be obtained even if a temperature change occurs.
Does not change.

For example, when b and c are unknowns and the equation is rearranged for b, the following is obtained. Ab ² + Bb + C = 0, where A = 2T (α _c −α _b ) + T ² (α _c ² −α _b ² ) B = 2a {T (2α _c −α _a −α _b ) + T ² (α _c ² − α
_a α _b )｝ − ^31/2 d {T (2α _c −α _b −α _d ) + T ² (α _c ²
−α _a α _d )｝ / 3 C = a ² {(2T (α _c −α _a ) + T ² (α _c ² −α _a ² )} − 3
^1/2 ad {T (2α _c −α _a −α _d ) + T ² (α _c ² −α
_a α _d )｝ / 3-d ² {2T (α _c −α _d ) + T ² (α _c ² −
α _d ² )｝ / 3-H ² (2α _c T + α _c ² T ² ) Here, when the equation is solved in consideration of A <0, b = ｛− B− (B ² -4AC) ^{1 / 2} ｝ / (2A).

Now, a titanium alloy (linear expansion coefficient α _b = 8.80 · 10 ⁻⁶ [/ K]) is used for the frame supporting member 4, and an invar alloy is used for the primary mirror base 3, the frame 5, and the secondary mirror frame 6. (Linear expansion coefficient α _a = α _c = α _d = 1.20 · 10
^-6 [/ K]).
Optical distance H = 300.00 [mm], primary mirror base 3 has a =
120.00 [mm], d = 50.00 for the secondary mirror frame 6
[mm]. Further, the temperature difference T is set to 50.00 [K].

At this time, according to the above equations, b = 77.582 [mm] for the frame supporting member 4 and c =
352.375 [mm], and the assumed temperature difference T50.
At 0 [K], the optical distance is substantially constant irrespective of this temperature change. A slight change in the optical distance H due to fine adjustment of the dimensions, for example, a change in the optical distance H at a temperature difference T50.0 [K]. It is also possible for the volume to be several μm.

Next, with the combination and dimensions shown here,
If a material having a larger linear expansion coefficient is used for the frame support member 4, a change in the direction in which the optical distance H becomes shorter with an increase in temperature can be caused. The correction of the focal position can be applied to the case where the optical distance should be shortened with an increase in temperature due to a change in the curvature of the optical member itself. For example, the dimensions are the same as above, and an aluminum alloy (linear expansion coefficient α _b = 22.
0 ^-6 [/ K]), the temperature difference T = 50.0
The change amount of the optical distance H is -31.7 μm with respect to [K].
Becomes

Conversely, a change in the curvature of the optical member itself, etc.
Correction of the focal position as the temperature rises
If it should be longer, use the combination shown here.
Therefore, the frame supporting member 4 has a smaller linear expansion than that of the present embodiment.
If a material with a tension coefficient is used,
Causes a change in the direction in which the optical distance H becomes longer.
it can. For example, a CFRP (linear expansion) is
Tension coefficient 2.30 · 10 ^-6[/ K]),
Change in optical distance H with respect to temperature difference T = 50.0 [K]
The amount is +15.4 μm.

Further, the structure of the present embodiment has a shape symmetrical with respect to the optical axis, and the above-described correction relationship holds even if the structure is partially cut out symmetrically with respect to the optical axis. For example, if a temperature change occurs only in a hatched portion shown in FIG.
The above-described correction relationship is established for the portions of the frame support member 4, the frame 5, and the sub mirror frame 6 where the temperature change has occurred,
Portions where no temperature change occurs remain in the original relationship.
Therefore, even if the temperature distribution as shown in FIG.
Does not cause eccentricity and declination with respect to the primary mirror 1.

As described above, depending on the combination of the materials and dimensions of each member, the geometrical positional relationship of the optical system can be made substantially constant even if there is a temperature change, and the optical performance change due to the environmental temperature change can be suppressed. Can be reduced by correcting the optical distance H by the supporting structure. Further, since the supporting method of the optical member is a frame structure, the structure is light and simple.

FIG. 4 is a schematic diagram of the second embodiment. This second embodiment is different from the first embodiment in that the frame 5 is set to 1
The names, materials, and dimensional symbols of each part are the same as in the first embodiment. The secondary mirror frame 6 has a rectangular shape, and the length of one side is d.

From the configuration of this embodiment shown in FIG. 2, the following relationships are established for the dimensions of each part. ^{H = [h 2 - {(} a + b) 2 -d / 2} 2] 1/2 ^{where, h = (c 2 -d 2} /4) ^1/2, and rearranging this, the following expression . ^{H = {(c 2 - (} a + b) 2 + d (a + b) -d 2/2}] 1/2

Here, when the temperature change T occurs, each member undergoes a dimensional change with the temperature change. Assuming that the dimensions of each member after the dimensional change are the dimension a 'of the primary mirror base 3, the dimension b' of the frame support member 4, the dimension c 'of the frame 5, and the length d' of the secondary mirror frame 6, Similarly, it is as follows. a ′ = a (1 + α _a T) b ′ = b (1 + α _b T) c ′ = c (1 + α _c T) = c (1 + α _a T) d ′ = d (1 + α _d T) = d (1 + α _a T)

Assuming that the optical distance after the dimensional change of each member is H ', H' is calculated by the following equation. H ′ = {c ′ ² − (a ′ + b ′) ² + d ′ (a ′ + b ′)
-D ^{'2/2} 1/2} In this case, H = H' Selecting the length and the linear expansion coefficient of each member so that, never optical distance H varies even when the temperature change occurs.

For example, when b and c are unknown numbers and the equation is arranged for b, the following is obtained. Ab ² + Bb + C = 0, where A = 2T (α _c −α _b ) + T ² (α _c ² −α _b ² ) B = 2a ｛T (2α _c −α _a −α _b ) + T ² (α _c ² − α
_a α _b )｝ − d ｛T (2α _c −α _b −α _d ) + T ² (α _c ² −α _b
α _d )｝ C = a ² ｛2T (α _c −α _a ) + T ² (α _c ² −α _a ² )｝ − a
d {T (2α _c −α _a −α _d ) + T ² (α _c ² −α _a α _d )} −
d ² {2T (α _c −α _d ) + T ² (α _c ² −α _d ² )} / 2−H
(2α _c T + α _c ² T ² ) Here, when the equation is solved in consideration of A <0,
The following equation is obtained. ^{b = {- B- (B 2} -4AC) 1/2} / (2A)

Now, a titanium alloy (linear expansion coefficient α _b = 8.80 · 10 ⁻⁶ [/ K]) is used for the frame supporting member 4, and an invar alloy is used for the primary mirror base 3, the frame 5, and the secondary mirror frame 6. (Linear expansion coefficient α _a = α _c = α _d = 1.20 · E ^-6
[/ K]), and the respective dimensions are set as follows: the optical distance H = 300.00 [mm];
120.00 [mm], d = 50.0 for the secondary mirror frame 6
0 [mm]. Further, the temperature difference T is set to 50.0 [K].

At this time, from the above equation, b = 80.816 [mm] for the frame support member 4 and c =
348.621 [mm], and the assumed temperature difference T (5
0.0 [K]), the optical distance H is substantially constant.

[0029]

As described above, in the optical member supporting apparatus according to the present invention, by adjusting and combining the materials and lengths of the respective members, the optical distance can be made substantially constant regardless of the temperature change. Further, when a change in the curvature of the optical member occurs due to a change in the temperature, a shift in the focal position due to the change in the temperature can be corrected by adjusting the optical distance by changing the above combination.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 is a schematic diagram of the first embodiment.

FIG. 3 is a temperature distribution diagram assumed for the optical system of the first embodiment.

FIG. 4 is a schematic diagram of a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary mirror 2 Primary mirror support part 3 Primary mirror base 4 Frame support member 5 Frame 6 Secondary mirror frame 7 Secondary mirror support part 8 Secondary mirror 9 Relay lens barrel

Claims (3)

[Claims] 1. An apparatus for supporting the first and second optical members while maintaining the geometrical positional relationship between the first and second optical members, wherein the first and second optical members are supported and the first and second optical members are supported. First support means having a plurality of leg members extending radially with respect to the optical axis center of the first optical member; and supporting the second optical member and supporting the first optical member. A second support means having a plurality of frames connected to the distal end, wherein the first and second support members have different coefficients of linear expansion so that a geometrical positional relationship is constant even if a temperature change occurs. An optical member supporting device, wherein a member size is selected. 2. The optical member supporting device according to claim 1, wherein said first and second supporting means are connected via a flexible member. 3. The first support member is made of a material having a larger linear expansion coefficient than that of the second optical member.
6. The optical member supporting device according to claim 5.