JP7241859B2 - Slice mirror, area spectroscope, telescope and method for manufacturing slice mirror - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a slice mirror used in an image slicer-type area spectroscope of an astronomical telescope, etc., and a manufacturing method thereof.

Imaging observation and slit spectroscopic observation are typical observation methods of astronomical observation. Imaging observation is a method of obtaining an image of a celestial body, and it is possible to observe two-dimensional spatial information. Slit spectroscopic observation is a method of spectroscopy of light that has passed through an elongated slit, and can observe two-dimensional information of one-dimensional space information and wavelength information. In this way, the conventional observation method could only obtain two-dimensional information.

In recent years, an observation method called field spectroscopy has been rapidly developed in astronomy. Area spectroscopy is an observation method that can simultaneously obtain wavelength information while maintaining spatial two-dimensional information in the field of view.

An optical instrument used to achieve area spectroscopy is called an area spectrometer. An image slicer is a type of area spectroscope, which divides an astronomical object image on a telescope focal plane into a plurality of elongated divided images, arranges the divided images one-dimensionally, and collectively disperses the divided images. In order to perform highly accurate area spectroscopy, the optical members that make up the area spectroscope must be precisely processed and arranged (see Non-Patent Document 1 and Patent Document 1).

Chuji Kirino, Itsuki Sakon, Development of image slicer type infrared spectroscopy unit and ultra-precision processing technology to support it, Journal of the Japan Society for Precision Engineering, Vol.83, No.4, 2017, P309-312

Japanese Unexamined Patent Application Publication No. 2016-2105

The slice mirror of the present disclosure is a slice mirror that divides and reflects an incident image into a plurality of elongated divided images, and is a plurality of flat mirrors having elongated mirror surfaces with different tilts of the mirror axis, and a first surface that is orthogonal to each. and a fixing member having a second surface and a third surface, wherein the plane mirror has a back surface having two opposing long sides and two opposing short sides, and biaxial directions with respect to the back surface. The mirror surface has an inclination, two first side surfaces connected to the long sides, and two second side surfaces connected to the short sides, and the plane mirrors are in contact with each other at the first side surfaces, The first side surfaces of the three plane mirrors abut the first surface, the second side surfaces of all the plane mirrors abut the second surface, and the back surfaces of all the plane mirrors abut the third surface. abutting.

1 is a schematic diagram of an area spectrometer of this embodiment; FIG. It is a schematic diagram of a slice mirror of this embodiment.

The slice mirror, area spectroscope, and telescope of the present disclosure will be described with reference to the drawings, taking an infrared telescope using an image slicer type area spectroscope as an example. FIG. 1 is a schematic diagram showing an example of a surface spectroscope of this embodiment, and FIG. 2 is a schematic diagram showing an example of a slice mirror of this embodiment. A surface spectroscope (hereinafter also simply referred to as a spectroscope) 1 includes an incident side mask (pinhole mask) 3, a slice mirror 2 that divides an incident image into a plurality of elongated divided images, and the divided images are arranged one-dimensionally. The image slicer type area spectroscope 1 includes a pupil mirror 4 for re-forming an image, an exit-side mask (pupil mask) 5, and various mirrors (not shown) arranged on the image optical path.

An image slicer type area spectrometer 1 divides a celestial object image on a focal plane into a plurality of elongated divided images, arranges the divided images one-dimensionally, and disperses the arranged divided images collectively. In order to perform highly accurate area spectroscopy, the optical members that make up the spectroscope 1 must be processed and arranged with high accuracy.

A slice mirror 2 of the present disclosure includes a plurality of plane mirrors 11 and a fixing member 12 for fixing the plurality of plane mirrors 11 .

The plane mirror 11 has an elongated mirror surface 11a and a back surface 11b facing the mirror surface 11a. The back surface 11b has two opposing long sides and two opposing short sides. In one plane mirror 11, the long sides are parallel to each other, and at least one of the short sides is perpendicular to the long side. The shape of such a back surface 11b is, for example, a rectangular shape. The plane mirror 11 has a side surface connecting the mirror surface 11a and the back surface 11b. The side surfaces are composed of two first side surfaces 11c connected to the long sides of the back surface 11b and two second side surfaces 11d connected to the short sides of the back surface 11b. In one plane mirror 11, the first side surfaces 11c are parallel to each other, and at least one of the second side surfaces 11d is perpendicular to the first side surface 11c. The thickness of the plane mirror 11 (the distance between the mirror surface 11a and the back surface 11b) is not particularly limited, but from the standpoint of ease of processing and handling, it is suitable that the thickness is intermediate between the lengths of the long and short sides of the back surface 11b. The short side, long side, and thickness dimensions are, for example, 2.5 mm×40 mm×15 mm.

The fixed member 12 has a first surface 12a, a second surface 12b, and a third surface 12c, which are orthogonal to each other, and contacts the plane mirror 11 at the first surface 12a, the second surface 12b, and the third surface 12c. The fixing member 12 may be a single body, or a plurality (for example, three) of block-shaped parts that constitute the first surface 12a, the second surface 12b, and the third surface 12c are assembled to form the fixing member 12. good too.

A plurality of plane mirrors 11 are stacked such that the first side surfaces 11c are in contact with each other, and the first side surface 11c of one of the plane mirrors 11 is in contact with the first surface 12a of the fixing member 12. As shown in FIG. The second side surfaces 11 d of all plane mirrors 11 are in contact with the second surface 12 b of the fixed member 12 , and the back surfaces 11 b of all the plane mirrors 11 are in contact with the third surface 12 c of the fixed member 12 . The flatness of the back surface 11b, the first side surface 11c, the second side surface 11d, the first surface 12a, the second surface 12b, and the third surface 12c is preferably 1 μm or less.

In order to one-dimensionally arrange the divided images reflected by the mirror surfaces 11a, the respective mirror surfaces 11a of the plurality of plane mirrors 11 have different inclinations in two axial directions with respect to the back surface 11b. Therefore, it is difficult to process and arrange them with high accuracy. Since the slice mirror 2 of the present disclosure has the configuration described above, other surfaces can be processed and arranged with reference to a plane (for example, the back surface 11b) that serves as a reference surface. Therefore, it is possible to provide the field spectroscope 1 and the telescope capable of high-precision measurement with improved processing accuracy and placement accuracy.

The plane mirror 11 has a body portion and a reflecting portion for reflecting incident infrared light. The reflecting portion is arranged on the side of the mirror surface 11a. The surface of the main body on the mirror surface 11a side is also called a mirror surface. The material of the reflecting portion is, for example, gold. An intermediate layer (for example, a chromium layer) may be provided at the interface between the reflecting section and the main body section to improve adhesion.

The observation target of the area spectrometer 1 is infrared light with a wavelength of several micrometers to several hundred micrometers. Infrared telescopes are placed at high altitudes, or in space, to reduce the effects of infrared absorption by the atmosphere. Also, in order to reduce noise due to heat, it is used at extremely low temperatures (for example, 10K or less). Space telescopes used in outer space have the advantage of not being affected by infrared radiation from the ground and the atmosphere, but have various limitations such as weight, size, and mechanical strength. The material of the main body of the plane mirror 11 and the fixing member 12 constituting the slice mirror 2 has a coefficient of thermal expansion within ±1.5×10 ⁻⁶ /K from the operating temperature to room temperature (that is, −1.5×10 ^{− 6} /K or more and 1.5×10 ⁻⁶ /K or less) is desirable. If the main body of the plane mirror 11 and the fixing member 12 are made of a low thermal expansion material, the shape and arrangement of each optical member processed and arranged at room temperature can be maintained even in the temperature environment during use. The spectrometer 1 has high reliability even in a certain use environment or a use environment in which the temperature changes during use.

From the viewpoint of specific rigidity and strength, the main body of the plane mirror 11 and the fixing member 12 are preferably made of ceramics. Examples of low thermal expansion ceramic materials include cordierite ceramics. Cordierite ceramics are ceramics containing cordierite as a main component. Here, the main component means a component that accounts for 60% by mass or more of the total 100% by mass of the components constituting the member. The components constituting the ceramic member may be determined using an X-ray diffraction device (XRD). After identifying the component, the content of each component is determined using an X-ray fluorescence spectrometer (XRF) or an ICP emission spectrometer to determine the content of the elements that make up the component, and converted to the identified component. good.

The shape of the plane mirror 11 when viewed from the front is defined by two first side surfaces 11c and two second side surfaces 11d. When the first side surface 11c and the second side surface 11d are orthogonal to each other, both the shape of the plane mirror 11 when viewed from the front and the shape of the back surface 11b are rectangular.

The surfaces of the flat mirror 11 and the fixed member 12 that come into contact with the other flat mirror 11 (hereinafter referred to as contact surfaces) may both be a single plane. A plurality of protrusions having coplanar faces or vertices may contact each other. As a result, one of the contact surfaces can be formed by planarizing the top surfaces or vertices of the plurality of first protrusions, so that the processing is easier and the processing accuracy is higher than when the entire contact surface is planarized. also higher.

The first side surfaces 11 c of the plane mirrors 11 are in contact with each other, and one of the first side surfaces 11 c is in contact with the first surface 12 a of the fixing member 12 . The plane mirror 11 may have a plurality of first projections with top surfaces or vertices on the same plane on one of the two first side surfaces 11c. If three first protrusions are formed on one first side surface 11c, it is possible to provide three-point support for stability. If the height of the first convex portion is larger than the wavelength of the infrared light to be observed (several μm to several hundred μm), the infrared light enters between the contact surfaces (first side surfaces 11c) and causes noise. It is preferable that the height of the first convex portion is smaller than several times the wavelength of the infrared light to be observed. The height of the first protrusion is preferably 10 μm or less, for example.

The second side surface 11 d of the plane mirror 11 contacts the second surface 12 b of the fixed member 12 , and the rear surface 11 b of the plane mirror 11 contacts the third surface 12 c of the fixed member 12 . The fixing member 12 may have a second protrusion on the second surface 12b that contacts the second side surface 11d of the plane mirror 11, and a third protrusion that contacts the back surface 11b of the plane mirror 11 on the third surface 12c. . At least one second protrusion may be formed on one second side surface 11d, and at least one third protrusion may be formed on one back surface 11b. In particular, if one convex portion is formed on the smaller surface of the second side surface 11d and the rear surface 11b, and two convex portions are formed on the larger surface of the second side surface 11d, it is possible to provide stable three-point support. Since the second convex portion and the third convex portion are formed outside the mirror surface 11a of the plane mirror 11 (outside the image), the height of the second convex portion and the third convex portion is smaller than that of the first convex portion. 0.1 mm to 1.0 mm.

When the second convex portions and the third convex portions adjacent to each other in the direction in which the plane mirrors 11 are stacked are arranged in a zigzag pattern, it is easy to process the respective convex portions. In particular, when flattening individual projections after fixing the fixing member 12, if the projections are arranged in a zigzag pattern, the desired projections can be processed without interfering with other projections. It's easy to do.

The plane mirror 11 and the fixing member 12 are fastened and fixed using fastening members such as bolts. Therefore, the plane mirror 11 and the fixing member 12 have fastening holes. When the first convex portion is annularly arranged around the fastening hole formed in the first side surface 11c of the plane mirror 11, the area to be flattened is compared with the outer diameter of the top surface of the convex portion. Since the target becomes smaller, flatness can be made more easily and with high precision. Similarly, the second protrusion is positioned around the fastening hole formed on the second surface 12b of the fixing member 12, and the third protrusion is positioned around the fastening hole formed on the third surface 12c of the fixing member 12. It is preferable that each of them is formed in a ring around its periphery.

The material of the bolts and washers for fastening the plane mirror 11 and the fixed member 12 is, for example, a metal with a relatively small coefficient of thermal expansion such as an iron-36 wt % nickel alloy (trade name Invar). Also, the material of the coil insert used for fastening with the bolt is, for example, metal such as SUS304.

A method for manufacturing a slice mirror according to the present disclosure will be described below. The manufacturing method of the slice mirror 2 includes a preparatory step of preparing a ceramic member for making the plane mirror 11 and a ceramic member for making the fixed member 12, and processing the surface to be the rear surface 11b of the plane mirror 11 to flatten it. Then, a back surface processing step, a side surface processing step of processing the side surface of the plane mirror 11 so as to be orthogonal to the back surface 11b, and a surface of the plane mirror 11 that will be the mirror surface 11a are inclined with respect to the back surface 11b as desired. , a mirror surface processing step of processing a surface that will become the mirror surface 11a, a reflecting portion forming step of forming a reflecting portion on the processed surface that becomes the mirror surface 11a, and a fixing member 12 that is processed to form a first surface 12a perpendicular to the surface 12a, a second surface 12a A fixing member processing step of forming the second surface 12b and the third surface 12c, and a fixing step of fastening and fixing the plane mirror 11 and the fixing member 12 using a fastening member.

Here, at least in the mirror-finishing step and the reflecting portion forming step, processing and film formation are performed in a state in which the ceramic member is fixed to a dummy member (also called a yatoi). The dummy member is preferably made of the same material as the ceramic member or a material with similar processing characteristics. Furthermore, it is preferable that the ceramic member can be fixed in a pressurized state using a fastening member or the like. A highly accurate slice mirror 2 can be obtained by forming the mirror surface 11a, which requires particularly highly accurate processing, under the same stress as during use. Fixation, processing, and film formation by dummy members may be performed individually for each plane mirror 11, or a plurality of plane mirrors 11 may be collectively fixed to perform processing and film formation.

The mirror surface of the ceramic member, the back surface 11b, the first side surface 11c, and the second side surface 11d of the plane mirror 11, and the first surface 12a, the second surface 12b, and the third surface 12c of the fixing member 12 are processed by a surface grinder, a lapping device, or the like. It can be processed using

The plane mirror 11 and the fixed member 12 may have convex portions (first convex portion, second convex portion, third convex portion) on the contact surfaces. It is preferably formed by blasting or laser processing using a mask of .

The reflecting portion is formed by laminating chromium and gold on the mirror surface of the ceramic member by, for example, sputtering or vapor deposition.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, combinations, etc. are possible without departing from the gist of the present disclosure.

1 Spectroscope (image slicer, area spectroscope)
2 Slice mirror 3 Entrance-side mask 4 Pupil mirror 5 Output-side mask 11 Plane mirror 11a Mirror surface 11b Back surface 11c First side surface 11d Second side surface 12 Fixing member 12a First surface 12b Second surface 12c Third surface

Claims (11)

A slice mirror that divides and reflects an incident image into a plurality of elongated divided images,
a plurality of plane mirrors having elongated mirror surfaces with different inclinations of mirror axes;
a fixing member having a first surface, a second surface, and a third surface, which are orthogonal to each other;
Each of the plurality of plane mirrors has a back surface having two long sides facing each other and two short sides facing each other, the mirror surface inclined in two axial directions with respect to the back surface, and two mirror surfaces connected to the long sides. having two first sides and two second sides connected to the short sides,
The first side surfaces of the plane mirrors are in contact with each other and overlap each other, the first side surface of one plane mirror is in contact with the first surface, and the second side surfaces of all the plane mirrors are the second surfaces. and the back surfaces of all the plane mirrors are in contact with the third surface,
The plane mirror has, on one of the two first side surfaces, a plurality of first projections whose apex surfaces or points are on the same plane, and the height of the first projections is 10 μm or less,
A slice mirror, wherein the plane mirror has a hole for fastening with the fixing member with a bolt, and the first convex portion is annularly arranged around the hole. The plane mirror includes a main body and a reflecting part disposed on the mirror surface side of the main body, and the main body has a low thermal expansion coefficient of ±1.5×10 ⁻⁶ /K or less. 2. The slice mirror of claim 1, made of material. 3. The slice mirror according to claim 2, wherein said low thermal expansion material is cordierite ceramics. 4. The slice mirror according to claim 1, wherein said flat mirror has a rectangular shape in a front view. 2. The plane mirror has a second convex portion at a portion facing each of the plane mirrors on the second surface, and a third convex portion at a portion facing each of the plane mirrors on the third surface. 5. The slice mirror according to any one of 1 to 4 . 6. The slice mirror according to claim 5 , wherein the heights of said second convex portion and said third convex portion are 0.1 to 1.0 mm. 7. The slice mirror according to claim 5 , wherein adjacent second convex portions and adjacent third convex portions are arranged in a zigzag pattern in the stacking direction of the plurality of plane mirrors. 8. The plane mirror has a hole for fastening with the fixing member with a bolt , and at least one of the second convex portion and the third convex portion is annularly arranged around the hole. A slice mirror according to any one of . A field spectrometer comprising the slice mirror according to any one of claims 1 to 8 . A telescope comprising the area spectroscope according to claim 9 . A method for manufacturing a slice mirror according to any one of claims 1 to 8 ,
a mirror surface processing step of polishing the plane mirror while the plane mirror is fixed to a dummy member so that the surface to be the mirror surface has a desired inclination with respect to the back surface;
A method of manufacturing a slice mirror, comprising: forming a reflecting portion on the surface to be the mirror surface in a state where the plane mirror is fixed to the dummy member.

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