JP2000121950A - Optical equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain light-weight optical equipment capable of realizing accurate focusing by largely deforming a reflection mirror without using a direct acting mechanism at a focusing part by elongating and contracting a 1st driving means and moving the focal point of the reflection mirror in accordance with the curvature change of the reflection mirror. SOLUTION: A motor 24 being a 2nd driving means drives to rotate a turntable 22 around a 1st axis. Either side of a piezoelectric element 25 being a 1st driving means is fixed at the end of the reflection mirror 23 and the other side is fixed on the turntable 22. Since the mirror 23 is deformed in a direction A by applying voltage (for instance, applying positive voltage) in a direction where the element 25 is contracted by a power source 29, the focal point of the mirror 23 is moved in a direction C. Since the mirror 23 is deformed in a direction B by applying the voltage (for instance, applying negative voltage) in a direction where the element 25 is elongated, on the contrary, the focal point is moved in a direction D. The operator of this optical equipment obtains a video in focus by adjusting the voltage applied to the element 25 by an adjuster provided in the power source 29 while viewing the video on a CRT 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical instrument such as a large-aperture reflective telescope mounted on an artificial satellite.
In particular, the present invention relates to an optical device that performs focus adjustment.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a configuration example of a conventional reflection type telescope. 1 is a lens barrel, 2 is a parabolic reflecting mirror supported by the lens barrel 1, 3 is a sub-mirror, 4 is an eyepiece support for supporting an eyepiece 5, 5 is an eyepiece, and 6 is an image plane. , 7
Is a linear guide that supports the eyepiece supporting portion 4 so as to be able to translate in the second axial direction (the optical axis direction of the eyepiece 5) with respect to the lens barrel 1, 8 is a motor, and 9 is a rotational force generated by the motor 8. It is converted into a translational force in the second axial direction, and the eyepiece support 4
Gear box for moving the motor in the second axial direction
This is the power supply for driving.

In the reflection type telescope constructed as described above, an image which enters the opening of the lens barrel 1 from, for example, G is reflected by the reflection mirror 2 and the sub-mirror 3 (h) and focuses on it. Through the eyepiece 5 (Le), the image plane 6
(ヲ). For example, when a positive current is applied to the motor 8 by the power supply 10, the eyepiece 5 moves in the direction of the arrow, and when a negative current is applied to the motor 8, the eyepiece 5 moves in the direction of the arrow. The focus adjustment of the reflection type telescope is performed by moving the motor 8 while the operator views the image on the image plane 6.

In a large-diameter reflective telescope or the like, when the temperature environment or attitude changes, the shape of the reflective mirror surface changes and the performance as an imaging system deteriorates. Adaptive control optics for improving the imaging performance by minutely deforming is known, and in some cases it has already been commercialized. For example, a 10-m diameter reflector is divided into hexagons, and a large astronomical telescope in the United States, Kack I, II, or a single 8.3-m-diameter mirror is driven by a motor. A number of springs are known. Also in these examples, focus adjustment was performed by providing a mechanism for linearly moving the eyepiece lens as in the above-described example.

Also, Japanese Patent Laid-Open Publication No. Hei 6-131445, "Full aperture image synthesis using rotary strip aperture surface image measurement"
With a large-sized reflector telescope mounted on a satellite equipped with a parabolic shaped main mirror equipped with a strip-shaped reflector, and by rotating the reflector, a large-diameter reflector was used on the image plane. There is disclosed a reflection type telescope which has the same aperture performance as that described above and can reduce the mass of the reflection mirror. Also in this example, focus adjustment was performed by providing a mechanism for linearly moving the eyepiece lens as in the above-described example.

[0006]

In a conventional optical apparatus such as a reflection type telescope, the focus is adjusted by linearly moving the eyepiece as described above. But,
In order to adjust the focus, it is necessary to move the eyepiece linearly for several mm to several tens cm with high precision feed of several μm or less, and for that purpose, a linear guide with high accuracy with little rattling etc. Was needed. In addition, since many of the general actuators at present are of a rotary type such as a motor, a gearbox or the like is used to convert the rotary motion into a linear motion. Here, in order to finely adjust the focus, a high-precision gear box in which the backlash of the internal gear is small is required. Therefore, the equipment was complicated and expensive.

When the diameter of the reflecting telescope is increased as described above, there is an example in which the mirror surface is minutely deformed using adaptive control optics in order to improve the performance of the imaging system.
Since the parabolic reflecting mirror has high rigidity and deforms only minutely, it is difficult to deform the mirror surface so large that the focus can be adjusted arbitrarily.

[0008] A lightweight reflecting telescope is obtained by rotating the reflecting mirror obtained by cutting the main mirror into a strip as described above. However, focusing is performed by moving the eyepiece linearly as described above. Mechanism such as a linear guide, a motor, and a gear box were required. In space equipment and the like, it is necessary to reduce the weight as much as possible due to the load on the launch rocket. However, it was necessary to reduce the weight of the focus adjustment mechanism to reduce the launch cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional optical equipment, and does not use a direct-acting mechanism in the focus adjustment unit, but largely deforms the reflecting mirror to achieve a high-precision focus. An object of the present invention is to obtain a lightweight optical device that can be adjusted.

[0010]

An optical apparatus according to a first aspect of the present invention comprises a rotary table rotatably supported on a pedestal and a parabolic flat plate, and a reflective surface formed on the concave side of the flat plate. And a central portion of the flat plate is fixed to a rotation axis of the rotary table, and a reflecting mirror for condensing incident light on an image forming surface; and a reflecting mirror having one end fixed to the rotating table and the other end being expanded and contracted. And at least two or more first driving means respectively supporting both ends of the reflecting mirror so as to change the curvature of the reflecting mirror, and a second means for rotating the turntable to form a paraboloid by rotating the reflecting surface. A driving unit; and a focus adjusting unit that expands and contracts the first driving unit and moves a focal point of the reflecting mirror according to a change in curvature of the reflecting mirror.

An optical apparatus according to a second aspect of the present invention is a rotary table rotatably supported on a pedestal, a parabolic flat plate, and a reflective surface formed on the concave side of the flat plate. A central portion is fixed to the rotation axis of the turntable, a reflecting mirror for condensing incident light on an image forming surface, speed detecting means for detecting a rotation speed of the reflecting mirror, and the reflecting surface for rotating the turntable. Driving means for forming a parabolic surface by rotation of the mirror, and changing the rotational speed detected by the speed detecting means to change the curvature of the reflecting mirror, and moving the focal point of the reflecting mirror according to the change in the curvature. And a focus adjusting means for controlling the driving means.

An optical apparatus according to a third aspect of the present invention is a rotary table rotatably supported on a pedestal, a parabolic flat plate, and a reflective surface formed on a concave side of the flat plate, and a convex surface of the flat plate. A reflector having a lower coefficient of thermal expansion than the reflection surface formed on the side thereof, and a central portion of the flat plate fixed to a rotation shaft of the turntable, for condensing incident light on an image forming surface; Temperature changing means for heating or cooling the contactlessly,
Driving means for rotating the turntable to form a paraboloid by rotating the reflecting surface, and changing the temperature of the reflecting mirror by the temperature changing means to change the curvature of the reflecting mirror, and according to the change in the curvature. To move the focal point of the reflector,
A focus adjusting means for controlling the temperature changing means.

An optical apparatus according to a fourth aspect of the present invention has a pedestal having an optical window and maintaining airtightness, a turntable rotatably supported on the pedestal, and a gas having a parabolic shape and enclosed therein. A thin hollow member having a reflecting surface formed on the concave side of the member and having a higher rigidity on the concave side of the member than the convex side, and a central portion of the flat plate fixed to the rotating shaft of the turntable. A reflecting mirror for condensing incident light incident through an optical window on an image forming surface, a driving means for rotating the rotating table to form a paraboloid by rotating the reflecting surface, and a pressure inside the pedestal. A pressure changing means for changing the pressure of the reflecting mirror by changing a pressure in the pedestal by the pressure changing means, and moving a focal point of the reflecting mirror in accordance with the change in the curvature. Focusing means for controlling the It is.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 In the prior art, a light-weight reflecting telescope was obtained by rotating a strip-shaped reflecting mirror. It was done by moving. A linear guide, a motor, and a gear box are required to perform a linear movement with a precision of several mm to several tens of cm, and precise focus adjustment is difficult due to the backlash. Therefore, in the present invention, the rotating strip-shaped reflecting mirror has a small rigidity in the longitudinal direction and is easy to be deformed. If it is slightly deformed, the focal point changes dynamically, and the movable range is small. Is not required,
Using a piezo element (piezoelectric element) capable of precise positioning without being affected by play or the like, the reflecting mirror is deformed to adjust the focus.

FIG. 1 is a configuration diagram showing an optical apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 21 denotes a pedestal installed on an artificial satellite or on the ground, 22 denotes a turntable rotatably supported on the pedestal 21 around a first axis, 23 denotes a turntable 22 supported by a turntable 22, and an aluminum alloy. A reflecting mirror in which a flat plate as a material is curved into a parabolic shape and the concave side is processed into an optical reflecting surface, 24 is a motor as second driving means for rotating the turntable 22 about the first axis, 25 is One is a piezo element as first driving means fixed to the end of the reflecting mirror 23 and the other is fixed to the turntable 22, and 26 is a pedestal 21 and a turntable 2
2, a slip ring for supplying power to the piezo element 25, a bearing 27 for rotatably supporting the turntable 22, a power supply 28 for driving the motor 24,
Is a power supply for driving the piezo element of the piezo element 25, which is a focus adjusting means, 30 is a CCD camera, 31 is an image memory, 32
Denotes a CRT, and the secondary mirror 3 and the eyepiece 5 are the same as in the conventional example. The reflecting mirror 23 has a central portion fixed to the turntable 22 and both ends supported by two piezo elements 25. The first axis is the optical axis.

In the optical apparatus thus configured, incident light is condensed by the reflecting mirror 23 and formed on the image plane 6 on the CCD camera 30 via the eyepiece 5, as in the prior art. On the other hand, in this embodiment, the image formed on the CCD camera 30 by the reflecting mirror 23 is stored in the image memory 31 for one rotation. The video for one rotation stored in the image memory 31 is smoothed by taking a time average and output to the CRT 32. At this time, the turntable 22 is continuously rotated in one direction by the motor 24 at a predetermined number of rotations satisfying a required resolution.

In this embodiment, the focus adjusting means operates as follows. Power supply 29 in the direction in which piezo element 25 contracts
When a voltage is applied (for example, a positive voltage is applied), the reflecting mirror 22 is deformed in the direction A, so that the focal point of the reflecting mirror 22 moves in the direction C. Conversely, when a voltage is applied in the direction in which the piezo element 25 extends (for example, a negative voltage is applied), the reflection mirror 2
Since the lens 2 is deformed in the direction B, the focal point moves in the direction D.
The operator of the optical apparatus adjusts the voltage applied to the piezo element with an adjuster (not shown) provided in the power supply 29 while watching the image on the CRT 32, thereby obtaining a focused image. In the graph of FIG. 2, the relationship between the voltage applied to the piezo element and the focal length is shown. As described above, the focus of an image can be adjusted by changing the voltage and the polarity applied to the piezo element 25. In particular, since the reflecting mirror 22 is formed by bending a flat plate, the rigidity is low with respect to the reflecting surface of the paraboloid, and the reflecting mirror surface can easily undergo large deformation, so that the focus can be adjusted. In addition, a linear motion mechanism using a linear guide, a motor, a gear box, etc. is not required for focus adjustment, and instead a lightweight piezo element is used. Since there is no backlash in the gear box, precise focus adjustment is possible.

Embodiment 2 FIG. 3 is a structural view showing an optical apparatus according to Embodiment 2 of the present invention. FIG. 4B is a detailed side view of a reflecting mirror 42 described below, and FIG. It is a top view. Reference numeral 41 denotes a pedestal, and reference numeral 42 denotes a plate formed by bending a flat plate made of an aluminum alloy into a parabolic shape, and processing the concave side of the flat plate into an optical reflection surface. The reflector 43 is a thin plate rotatably supported by the mirror 43, weights attached to both ends of the reflector 42 in a balanced manner, and 44 is a pedestal 41.
A tachogenerator for detecting the rotation speed of the reflecting mirror 42 with respect to the reference numeral 45; a controller which is a focus adjustment means for detecting the rotation speed of the tachogenerator 44 and controlling the motor 24 so that the rotation speed is arbitrarily set;
5, 6 are the same as in the conventional example, and 24, 27, 28, 30
32 are the same as in the first embodiment.

The optical apparatus thus configured can obtain an image by rotating the reflecting mirror 42 as in the first embodiment. On the other hand, the focus adjusting means of this embodiment operates as follows. When the controller 45 of the motor 24 controls the rotating speed of the reflecting mirror 42 to increase, the reflecting mirror 42 is deformed in the direction A by the centrifugal force applied to the weight 43, so that the focal point of the reflecting mirror 42 moves in the direction C.
Conversely, if the rotation speed is controlled to decrease, the reflection mirror 42
Is restored in the direction b, the focal point moves in the direction d. As described above, the operator of the optical apparatus can adjust the focus of the image by adjusting the rotation speed of the motor with the controller 45 while viewing the image on the CRT 32. After the focus adjustment, the controller 45 controls the rotation speed to be constant, and the focus is kept constant. Therefore, even if the slip ring 26 is not provided as in the first embodiment,
Focus adjustment can be performed without transmitting power to an actuator such as the piezoelectric element 25 provided in the rotating unit. Therefore, there is no need for instantaneous interruption of electric power due to abrasion of the brush in the slip ring or replacement of the brush, thereby improving reliability and extending the life. Further, since a piezo element which consumes a large amount of power compared to the power for continuously driving the motor in one direction is not used, it is possible to reduce the power consumption as compared with the first embodiment.

Third Embodiment FIG. 5 is a structural view showing an optical apparatus according to a third embodiment of the present invention, and FIG. 6 is a detailed view of the reflecting mirror. Reference numeral 61 denotes a pedestal, 62 denotes a reflecting mirror rotatably supported by the bearing 27 around the first axis with respect to the pedestal 61, and a flat plate is bent into a parabolic shape and the concave side is processed into an optical reflecting surface.
Peltier element fixed to 1, 64 is a reflecting surface made of a thin aluminum plate, 65 is made of stainless steel,
A back plate of a reflecting mirror 62 fixed to a reflecting surface 64 by bonding, and 66 is a Peltier element 6 as a focus adjusting means.
Reference numeral 3 denotes a power supply for driving the Peltier element. Reference numerals 3, 5, and 6 are the same as those in the conventional example, and reference numerals 24, 27, 28, and 30 to 32 are the same as those in the first embodiment.

This embodiment is configured as described above.
The focus adjusting means operates as follows. When the voltage and the polarity applied to the Peltier element 63 are changed by the power supply 66, the temperatures of the reflection surface 64 and the back plate 65 constituting the reflection mirror 62 change. When the reflecting mirror 62 is heated, the coefficient of thermal expansion (2
(3.2 × 10 ⁻⁶ / ° C.) is larger than the thermal expansion coefficient of the stainless steel of the back plate 65 (10.1 × 10 ⁻⁶ / ° C.), so that the reflecting mirror 62 is deformed in the direction a. The focal point moves in the direction C. Conversely, when the reflecting mirror 62 is cooled, the reflecting mirror 12 is deformed in the direction B, so that the focal point moves in the two directions. As described above, the operator of the optical apparatus can adjust the focus of the image by adjusting the voltage and the polarity applied to the Peltier element by the Peltier element driving power supply 66 while viewing the image on the CRT 32. Embodiment 1
The focus adjustment can be performed without transmitting the power to the actuator such as the piezoelectric element 25 provided in the rotating unit without providing the slip ring 26 as described in the above. For this reason,
There is no need for instantaneous interruption of power due to brush wear in the slip ring, and no need for brush replacement, thereby improving reliability and extending the life. Furthermore, since it is not necessary to change the number of rotations of the motor, the rotational angular velocity control as in the second embodiment is unnecessary. Note that, even if a member having a higher coefficient of thermal expansion than the reflecting surface 64 is provided as the back plate 65 of the reflecting mirror 62 and a motor is used instead of the Peltier element 63, the focus can be adjusted.

Embodiment 4 FIG. 7 is a configuration diagram showing an optical apparatus according to Embodiment 4 of the present invention. FIG. 8A is a detailed side view of the following reflecting mirror 82, and FIG. FIG. 8 (a) is a detailed view of a cross section ho-ho. 81 is a pedestal whose inside is airtight to the surrounding air, 82 is a material made of aluminum on a plastic surface, and is rotatably supported on the pedestal 81 around the first axis by the bearing 27. A reflecting mirror which is curved into a shape and whose concave side is processed into an optical reflecting surface, 83 is a base 8
An optical window that is fixed to 1 and keeps airtight; 84 is a pump that is pressure changing means for changing the atmospheric pressure inside the pedestal 81;
Reference numeral 85 denotes a through hole formed in the reflecting mirror 82, 86 denotes a plug adhered to both ends of the hole 85, and seals the air inside the hole 85. Reference numerals 3, 5, and 6 denote the same as the conventional example. 2
7, 28, 30 to 32 are the same as in the first embodiment.

This embodiment is configured as described above.
The focus adjusting means operates as follows. When the inside of the pedestal 81 is depressurized by an adjuster (not shown) which is a focus adjusting means provided in the pump 84, the pressure of the air sealed in the hole 85 causes the convex side of the reflecting mirror 82 to have a small thickness and low rigidity. Since the plate is thicker and has a larger elongation than the concave side (reflecting mirror surface side) having high rigidity, the reflecting mirror 82 is deformed in the direction B, and the focal point of the reflecting mirror 82 moves in the two directions. Conversely, when the inside of the pedestal 81 is pressurized, the reflecting mirror 82 is deformed in the direction A, so that the focal point moves in the direction C. As described above, the operator of the optical apparatus sees the image on the CRT 32 and
The focus of the image can be adjusted by changing the internal pressure by the adjuster of the pump 84. Embodiment 1
As described above, the focus can be adjusted without transmitting power to an actuator such as the piezoelectric element 25 provided in the rotating unit without providing the slip ring 26. Therefore, there is no need for instantaneous interruption of electric power due to abrasion of the brush in the slip ring or replacement of the brush, thereby improving reliability and extending the life.
Further, since it is not necessary to change the number of rotations of the motor, it is not necessary to control the rotational angular velocity. Further, since the inside of the pedestal is shielded from the outside air, it is easy to prevent the deterioration of the image quality due to dust or the like.

[0024]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, the reflecting mirror, which forms a parabola by rotating a flat plate, condenses by rotating the reflecting mirror, makes it easy to greatly deform the reflecting mirror surface, and linearly adjusts the focus for focus adjustment. A guide and a gear box are not required, and high-precision focus adjustment without play is possible. Further, the weight of the optical device can be reduced.

According to the second aspect of the present invention, the focus can be adjusted without transmitting power to the rotating unit by the slip ring, and there is no need for instantaneous interruption of power due to abrasion of the brush in the slip ring or replacement of the brush. As a result, the reliability and the service life can be extended. Further, since a piezo element that consumes a large amount of power is not used as compared with the power for continuously driving the motor in one direction, the power consumption can be reduced.

According to the third aspect of the invention, it is possible to adjust the focus without transmitting power to the rotating unit by a slip ring or the like, and it is possible to perform instantaneous interruption of power due to abrasion of the brush in the slip ring and replacement of the brush. It is unnecessary, and the reliability can be improved and the service life can be extended. Further, since it is not necessary to change the number of rotations of the motor, it is not necessary to control the rotational angular velocity.

According to the fourth aspect of the invention, it is possible to adjust the focus without transmitting power to the rotating unit by a slip ring or the like, and it is possible to perform instantaneous interruption of power due to abrasion of the brush in the slip ring and replacement of the brush. It is unnecessary, and the reliability can be improved and the service life can be extended. Further, since it is not necessary to change the number of rotations of the motor, it is not necessary to control the rotational angular velocity. Also,
Since the inside of the pedestal is shut off from the outside air, it is easy to prevent deterioration of the image quality due to dust and the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a voltage applied to a piezo element and a focal length according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a detailed view of a reflecting mirror according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a third embodiment of the present invention.

FIG. 6 is a detailed view of a reflecting mirror according to Embodiment 3 of the present invention.

FIG. 7 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 8 is a detailed view of a reflecting mirror according to a fourth embodiment of the present invention.

FIG. 9 is a configuration example of a conventional general reflection telescope.

[Explanation of symbols]

Reference Signs List 1 lens barrel, 2 reflecting mirror, 3 secondary mirror, 4 eyepiece support section, 5 eyepiece, 6 imaging surface, 7 linear guide,
8 motor, 9 gear box, 10 motor power supply,
21 pedestal, 22 turntable, 23 reflector, 24 motor, 25 piezo element, 26 slip ring, 27
Bearing, 28 Motor power supply, 29 Piezo drive power supply,
30 CCD camera, 31 image memory, 32 CR
T, 41 pedestal, 42 reflector, 43 weight, 44
Tacho generator, 45 controller, 61 pedestal,
62 reflecting mirror, 63 Peltier element, 64 reflecting surface, 6
5 back plate, 66 power supply for Peltier device, 81
Pedestal, 82 reflector, 83 optical window, 84 pump, 8
5 holes, 86 stoppers.

Claims (4)

[Claims] 1. A rotating table rotatably supported on a pedestal, a parabolic flat plate, a reflecting surface formed on the concave side of the flat plate, and the center of the flat plate is formed by the rotating table. A reflecting mirror fixed to a rotating shaft and condensing incident light on an image forming surface; and both ends of the reflecting mirror such that one end is fixed to the rotating table and the curvature of the reflecting mirror is changed by expansion and contraction of the other end. At least two or more first driving means respectively supporting the above, a second driving means for rotating the rotary table to form a paraboloid by rotating the reflecting surface, and expanding and contracting the first driving means An optical apparatus comprising: a focus adjusting unit that moves a focal point of the reflecting mirror according to a change in curvature of the reflecting mirror. 2. A turntable rotatably supported on a pedestal, a parabolic flat plate, wherein a reflective surface is formed on a concave side of the flat plate, and a center portion of the flat plate is the turntable. A reflecting mirror fixed to a rotation axis and condensing incident light on an image forming surface, speed detecting means for detecting a rotation speed of the reflecting mirror, and a paraboloid by rotating the rotating table and rotating the reflecting surface Controlling the driving means so as to change the rotational speed detected by the speed detecting means, change the curvature of the reflecting mirror, and move the focal point of the reflecting mirror according to the change in the curvature. An optical apparatus comprising: 3. A rotating table rotatably supported on a pedestal, a parabolic flat plate, wherein a reflecting surface is formed on the concave side of the flat plate, and the reflecting surface is formed on the convex side of the flat plate by the reflecting surface. A member having a low expansion coefficient is formed, and a central portion of the flat plate is fixed to a rotation axis of the rotating table, and a reflecting mirror for condensing incident light on an image forming surface, and heating or cooling the reflecting mirror in a non-contact manner Temperature changing means, driving means for rotating the turntable to form a paraboloid by rotating the reflecting surface, and changing the temperature of the reflecting mirror by the temperature changing means to change the curvature of the reflecting mirror, An optical apparatus comprising: focus adjusting means for controlling the temperature changing means so as to move the focal point of the reflecting mirror in accordance with the curvature change. 4. A pedestal having an optical window and maintaining airtightness, a turntable rotatably supported on the pedestal, and a thin hollow member having a parabolic shape and containing gas therein. A reflective surface is formed on the concave side of the member, the rigidity of the concave side of the member is made higher than that of the convex side, and the center of the flat plate is fixed to the rotating shaft of the turntable, and the light enters through the optical window. A reflecting mirror that condenses incident light to be focused on an image forming surface, a driving unit that rotates the turntable to form a paraboloid by rotating the reflective surface, and a pressure changing unit that changes the air pressure inside the pedestal, Focus adjusting means for controlling the pressure changing means so as to change the curvature of the reflecting mirror by changing the air pressure in the pedestal by the pressure changing means and to move the focal point of the reflecting mirror according to the change in the curvature. An optical device comprising: