WO2016125325A1

WO2016125325A1 - Observation device

Info

Publication number: WO2016125325A1
Application number: PCT/JP2015/070590
Authority: WO
Inventors: 上原　誠
Original assignee: 株式会社目白ゲノッセン
Priority date: 2015-02-05
Filing date: 2015-07-17
Publication date: 2016-08-11

Abstract

Provided is an observation device with which it is possible to observe an object surface of, for example, roughly 24.6x24.6mm, at a resolution of no more than 10 microns and at a large inclination angle which exceeds 45 degrees. An observation device 10 is provided with a light receiving surface 20 and an image forming optical system 30 for forming light from an object surface S into an image on the light receiving surface 20. The image forming optical system 30 includes a concave-surface primary mirror 32, a sub-mirror 34, and a flat extraction mirror 36. The beams of the light from the object surface S are reflected by the concave-surface primary mirror 32, the convex-surface sub-mirror 34, and the concave-surface primary mirror 32, in that order, and thereafter form an image on the light receiving surface 20 via the flat extraction mirror 36. The observation device 10 is provided with the following: a first tilting means which can change the angle α formed by the optical axis L1 of the light traveling from the object surface S towards the concave-surface primary mirror 32 and the perpendicular line N1 of the object surface S; and a second tilting means which can change the angle β formed by the optical axis L2 of the light traveling from the flat extraction mirror 36 towards the light receiving surface 20 and the perpendicular line N2 of the light receiving surface 20.

Description

Observation device

The present invention relates to an observation apparatus.

For example, there is a demand for observing not only the two-dimensional shape of the surface of the printed circuit board but also the three-dimensional shape of the surface of the printed circuit board for defect inspection of the printed circuit board. That is, there is a demand for observing the height of the concavo-convex shape (= the height in the Z-axis direction) on the surface while observing the two-dimensional shape (XY plane shape) of the surface of the printed circuit board.

It is possible to measure the two-dimensional shape of the surface of the printed circuit board by observing the surface of the printed circuit board from directly above. However, in order to obtain information on the height in the Z-axis direction, it is necessary to observe the uneven shape of the substrate surface from an oblique direction. For example, when the substrate surface is observed obliquely, the width of the near side of the observed image is widened and the width of the far side is narrowed. Here, if the center of the observed image is focused, the near side and the far side are not focused, and a clear image cannot be obtained in a portion other than the center. The reason why the near side and the far side are out of focus is that, in a normal optical system, the image plane and the object plane are arranged perpendicular to the optical axis. In order to focus on the entire surface including the near side and the far side, it is necessary to incline the image plane with respect to the optical axis and to satisfy the Scheinproof condition for the image plane and the object plane. Further, in order to observe the near side and the far side with the same width, it is necessary to use an optical system in which both the object side and the image side are telecentric.

The present inventor has already proposed an invention of a measuring apparatus capable of measuring an object plane from an oblique direction (see Patent Document 1). This measuring device uses a 1 × reflection type imaging optical system.

JP 2013-174844 A

By using the Scheinproof principle, the entire object surface observed obliquely can be imaged on the light receiving surface. Most of the conventional optical observation apparatuses using the Scheinproof principle use a refractive lens system. The performance of a conventional optical observation apparatus using a refractive lens system is, for example, as shown in Table 1 below.

As shown in Table 1, there is no optical observation apparatus capable of observing the object surface obliquely with a large inclination angle exceeding 45 degrees and a resolution of 10 microns or less.

Also, when a refractive lens system is used as the imaging optical system of the observation apparatus, there is a problem that the wavelength band of light that can be transmitted through the glass material used for the refractive lens is limited. In this case, there is a problem that it is difficult to apply the observation apparatus to the semiconductor and bio fields.

An object of the present invention is to provide an observation apparatus capable of observing, for example, an object surface of about 24.6 × 24.6 mm with a resolution of 10 microns or less and a large tilt angle exceeding 45 degrees. It is another object of the present invention to provide an observation apparatus in which the wavelength of light used for observing an object surface is not limited.

Means for solving the above problems are the following inventions.
(1) An observation apparatus comprising: a light receiving surface that receives light from an object surface; and an imaging optical system that forms an image of light from the object surface on the light receiving surface;
The imaging optical system includes a concave primary mirror, a convex secondary mirror, and an extraction flat mirror, and reflects a light beam from the object surface in the order of the concave primary mirror, the convex secondary mirror, and the concave primary mirror. After that, it is composed of an equal-magnification reflection type imaging optical system that can form an image on the light receiving surface through the extraction flat mirror,
First tilting means capable of changing an angle α formed by an optical axis of light directed from the object plane toward the concave primary mirror and a perpendicular to the object plane;
An observation apparatus comprising: a second tilting unit capable of changing an angle β formed by an optical axis of light directed from the extraction flat mirror toward the light receiving surface and a perpendicular to the light receiving surface.

(2) comprising control means for controlling the first tilting means and the second tilting means;
The observation device according to (1), wherein the control unit controls the first tilting unit and the second tilting unit so that the angle α and the angle β are equal.

(3) The first tilting means can change the angle α in the range of 0 degrees to 70 degrees,
The observation apparatus according to (1) or (2), wherein the second tilting unit is capable of changing the angle β in a range of 0 degrees to 70 degrees.

(4) The observation apparatus according to any one of (1) to (3), wherein the observation apparatus is a microscope, a spectroscopic ellipsometer, a defect detection apparatus, or a reflectance measurement apparatus.

According to the present invention, for example, an observation apparatus capable of observing an object surface of about 24.6 × 24.6 mm with a resolution of 10 microns or less and a large tilt angle exceeding 45 degrees can be provided. In addition, it is possible to provide an observation apparatus in which the wavelength of light used for observing the object plane is not limited.

It is the front view, top view, and side view of an observation apparatus which make a X axis a rotating shaft. It is the front view, top view, and side view of an observation apparatus which make a Y-axis a rotating shaft. It is a top view of the observation apparatus rotated by 0 ° around the X axis. It is a side view of the observation apparatus rotated by 0 ° around the X axis. It is a front view of the observation apparatus rotated by 0 ° around the X axis. It is a front view of the observation apparatus rotated by 30 degrees around the X axis. It is a front view of the observation apparatus rotated by 60 ° around the X axis. FIG. 6 is a front view of the observation apparatus rotated by −60 ° about the X axis. It is a top view of the observation apparatus rotated by 0 ° around the Y axis. It is a side view of the observation apparatus rotated by 0 ° around the Y axis. It is a front view of the observation apparatus rotated by 0 ° around the Y axis. It is a front view of the observation apparatus rotated by 30 ° around the Y axis. It is a front view of the observation apparatus rotated by 60 ° around the Y axis. FIG. 6 is a front view of the observation apparatus rotated by −30 ° about the Y axis. Furthermore, it is a front view which shows the external appearance of a specific observation apparatus. FIG. 4 is a front view of the observation apparatus rotated by −45 ° about the Y axis. It is a side view of an observation apparatus. The calculation result of the resolution (MTF) when the observation apparatus is rotated by 0 ° about the X axis is shown. The calculation result of the resolution (MTF) when the observation apparatus is rotated ± 30 ° around the X axis is shown. The calculation result of the resolution (MTF) when the observation apparatus is rotated by ± 60 ° about the X axis is shown. The calculation result of the resolution (MTF) when the observation apparatus is rotated by 0 ° about the Y axis is shown. The calculation result of the resolution (MTF) when the observation apparatus is rotated ± 30 ° around the Y axis is shown. The calculation result of the resolution (MTF) when the observation apparatus is rotated by ± 60 ° about the Y axis is shown.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view, a top view, and a side view of an observation apparatus having an X axis as a rotation axis. FIG. 2 is a front view, a top view, and a side view of the observation apparatus with the Y axis as the rotation axis.
As shown in FIGS. 1 and 2, the observation apparatus 10 of the present embodiment forms a light receiving surface 20 for receiving light from the object surface S and an image of light from the object surface S on the light receiving surface 20. The imaging optical system 30 is provided.

In the observation apparatus 10 of the present embodiment, the imaging optical system 30 is configured by an Offner optical system that is one of the equal-magnification reflective imaging optical systems. The imaging optical system 30 is configured by a telecentric optical system.

The observation apparatus 10 of this embodiment may include an illumination optical system (not shown) for irradiating the object surface S with light. The illumination optical system may be configured by a telecentric optical system in accordance with the imaging optical system 30. As the illumination optical system, for example, a Kohler illumination system disclosed in JP2013-174844A can be used.

As shown in FIGS. 1 and 2, the imaging optical system 30 configured by an Offner optical system includes a primary mirror 32 configured by a concave mirror, a secondary mirror 34 configured by a convex mirror, and a lead plane mirror 36. Yes. The light beam from the object surface S is reflected in the order of the primary mirror 32, the secondary mirror 34, the primary mirror 32, and the extraction plane mirror 36, and then forms an image on the light receiving surface 20.

The object surface S and the light receiving surface 20 are in a conjugate relationship of equal magnification in the Offner optical system.
The object plane S is the surface of an object to be observed, for example, the surface of a printed board.
The light receiving surface 20 is a surface on which light from the object surface S forms an image, and is, for example, a light receiving surface of an imaging element such as a two-dimensional CCD.
The secondary mirror 34 is a pupil of the optical system.

Note that a commonly used CCD incorporates a condenser lens called a micro lens and a thick color filter in front of each element in order to increase the light receiving efficiency. However, since a light beam having a large inclination does not reach the light receiving surface of the CCD, it is difficult to collect the light with a micro lens. Therefore, the two-dimensional CCD used for the light receiving surface 20 is preferably a type in which a micro lens or a thick color filter is not incorporated.

As shown in FIGS. 1 and 2, the light flux from the object surface S toward the concave primary mirror 32 is telecentric. The light reflected by the primary mirror 32 is reflected by the convex secondary mirror 34 that also serves as a stop. The light reflected by the secondary mirror 34 is reflected again by the concave primary mirror 32 and becomes telecentric. The light that has become telecentric after being reflected by the main mirror 32 is reflected by the extraction plane mirror 36 and forms an image on the light receiving surface 20 at the same magnification.

The field of view of the object plane S is, for example, 24.6 × 24.6 mm and NA = 0.04.
The field of view of the light receiving surface 20 on which the light from the object surface S forms an equal magnification is, for example, 24.6 × 24.6 mm and NA = 0.04.

FIG. 3 is a top view of the observation apparatus 10 rotated by 0 ° around the X axis. FIG. 4 is a side view of the observation apparatus 10 rotated by 0 ° around the X axis. FIG. 5 is a front view of the observation apparatus 10 rotated by 0 ° around the X axis.
As shown in FIG. 5, in a state where the observation apparatus 10 is rotated by 0 ° about the X axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light from the object plane S toward the main mirror 32 in the YZ plane. Is inclined by 0 ° with respect to (α = 0 °). Further, the perpendicular N2 of the light receiving surface 20 is inclined by 0 ° (β = 0 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 6 is a front view of the observation apparatus 10 rotated by 30 ° about the X axis.
As shown in FIG. 6, in a state where the observation apparatus 10 is rotated by 30 ° about the X axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light traveling from the object plane S toward the main mirror 32 in the YZ plane. Is inclined by 30 ° with respect to (α = 30 °). Further, the perpendicular line N2 of the light receiving surface 20 is inclined by 30 ° (β = 30 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 7 is a front view of the observation apparatus 10 rotated by 60 ° about the X axis.
As shown in FIG. 7, in a state where the observation apparatus 10 is rotated by 60 ° about the X axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light traveling from the object plane S toward the main mirror 32 in the YZ plane. With respect to the angle (α = 60 °). Further, the perpendicular line N2 of the light receiving surface 20 is inclined by 60 ° (β = 60 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 8 is a front view of the observation apparatus 10 rotated by −60 ° about the X axis.
As shown in FIG. 8, when the observation apparatus 10 is rotated by −60 ° about the X axis, the perpendicular line N1 of the object plane S is the optical axis of the light from the object plane S toward the main mirror 32 in the YZ plane. It is inclined by −60 ° with respect to L1 (α = −60 °). The perpendicular line N2 of the light receiving surface 20 is inclined by −60 ° (β = −60 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 9 is a top view of the observation apparatus 10 rotated by 0 ° about the Y axis. FIG. 10 is a side view of the observation apparatus 10 rotated by 0 ° around the Y axis. FIG. 11 is a front view of the observation apparatus 10 rotated by 0 ° around the Y axis.
As shown in FIG. 11, in a state where the observation apparatus 10 is rotated by 0 ° about the Y axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light traveling from the object plane S toward the main mirror 32 in the XZ plane. Is inclined by 0 ° with respect to (α = 0 °). Further, the perpendicular N2 of the light receiving surface 20 is inclined by 0 ° (β = 0 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 12 is a front view of the observation apparatus 10 rotated by 30 ° about the Y axis.
As shown in FIG. 12, in a state where the observation apparatus 10 is rotated by 30 ° about the Y axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light traveling from the object plane S toward the main mirror 32 in the XZ plane. Is inclined by 30 ° with respect to (α = 30 °). Further, the perpendicular line N2 of the light receiving surface 20 is inclined by 30 ° (β = 30 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 13 is a front view of the observation apparatus 10 rotated 60 ° around the Y axis.
As shown in FIG. 13, in a state where the observation apparatus 10 is rotated by 60 ° about the Y axis, the perpendicular line N1 of the object plane S is the optical axis L1 of light traveling from the object plane S toward the main mirror 32 in the XZ plane. With respect to the angle (α = 60 °). Further, the perpendicular line N2 of the light receiving surface 20 is inclined by 60 ° (β = 60 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

FIG. 14 is a front view of the observation apparatus 10 rotated by −30 ° about the Y axis.
As shown in FIG. 14, when the observation apparatus 10 is rotated by −30 ° about the Y axis, the perpendicular line N1 of the object plane S is the optical axis of the light from the object plane S toward the main mirror 32 in the XZ plane. It is inclined by −30 ° with respect to L1 (α = −30 °). Further, the perpendicular N2 of the light receiving surface 20 is inclined by −30 ° (β = −30 °) with respect to the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20.

As described above, the observation apparatus 10 of the present embodiment can rotate around both the X axis and the Y axis. That is, when the object surface S to be observed is located in the XY two-dimensional plane, the lens barrel body that accommodates the primary mirror 32, the secondary mirror 34, and the extraction planar mirror 36 is placed on both the X axis and the Y axis. It can be driven to rotate around the center. In addition, the light receiving surface 20 made of, for example, a CCD image sensor can be freely rotated in accordance with the rotation angle of the lens barrel body. Thereby, it is possible to rotationally drive the barrel main body of the observation apparatus 10 and the light receiving surface 20 so that the object surface S and the light receiving surface 20 satisfy the Scheinproof condition. As a result, even when the object plane S is observed from an oblique direction, it is possible to focus on the entire surface of the object plane S.

FIG. 15 is a front view showing a more specific appearance of the observation apparatus 10. FIG. 17 is a side view of the observation apparatus 10. FIG. 16 is a front view of the observation apparatus 10 rotated by −45 ° about the Y axis.
As shown in FIGS. 15 to 17, the observation apparatus 10 includes a barrel main body 12 that integrally accommodates a primary mirror 32, a secondary mirror 34, and a drawer plane mirror 36 therein. The observation apparatus 10 also includes means for rotationally driving the lens barrel body 12 about the X axis and the Y axis. This driving means is constituted by, for example, a stepping motor or a servo motor. The means for rotationally driving the lens barrel body 12 is not particularly limited, and may be means other than the stepping motor or the servo motor. The means for rotationally driving the lens barrel body 12 corresponds to the “first tilting means” of the present invention.

The observation apparatus 10 includes means for rotationally driving the light receiving surface 20 constituted by, for example, a CCD image sensor. This driving means is constituted by, for example, a stepping motor or a servo motor. The means for rotationally driving the light receiving surface 20 is not particularly limited, and may be means other than a stepping motor or a servo motor. The means for rotationally driving the light receiving surface 20 corresponds to the “second tilting means” of the present invention.

In addition, the observation apparatus 10 controls the means for rotating the lens barrel body 12 (first tilting means) and the means for rotating the light receiving surface 20 (second tilting means), respectively. The control means is provided. The control means can control the rotation angles of the lens barrel body 12 and the light receiving surface 20 by controlling the first tilting means and the second tilting means, respectively. This control means is constituted by, for example, a personal computer. The first tilting means and the control means are electrically connected. The second tilting means and the control means are electrically connected. It is preferable that software for controlling each of the first tilting means and the second control means is installed in the control means.

The first tilting means changes the angle α formed by the optical axis L1 of the light from the object plane S toward the concave primary mirror 32 and the perpendicular N1 of the object plane S by rotating the lens barrel body 12. Is possible. The first tilting means can preferably change the angle α in the range of 0 ° to 70 °.

The second tilting means can change the angle β formed by the optical axis L2 of the light traveling from the extraction flat mirror 36 toward the light receiving surface 20 and the perpendicular N2 of the light receiving surface 20 by rotating the light receiving surface 20. It is. The second tilting means can preferably change the angle β in the range of 0 ° to 70 °.

The control means can control the first tilting means and the second tilting means so that the angle α and the angle β are equal. That is, the inclination angles of the object surface S and the light receiving surface 20 with respect to the optical axis can be controlled so that the object surface S and the light receiving surface 20 satisfy the Scheimpflug condition. Thereby, even when the object surface S is observed from a direction inclined by 60 °, for example, the entire surface of the object surface S can be focused.

As described above, the imaging optical system for imaging light from the object surface S on the light receiving surface 20 is constituted by an Offner optical system which is one of the equal-magnification reflection type imaging optical systems. Such a reflective optical system has an advantage that the wavelength of light used for observation of the object plane S is not limited, unlike a refractive lens. For this reason, since the wavelength of the light used for observation is not restrict | limited, the observation apparatus 10 of this embodiment can be applied to various fields, such as a semiconductor and biotechnology.

The observation apparatus 10 of this embodiment can be applied to a microscope for observing an object plane, for example.
The observation apparatus 10 of this embodiment can be applied to, for example, a spectroscopic ellipsometer, a defect detection apparatus, or a reflectance measurement apparatus.
In addition to these devices, the observation device of the present embodiment has a possibility of being applicable to general optical observation devices.

FIG. 18 shows a calculation result of resolution (MTF) when the observation apparatus of the present embodiment is rotated by 0 ° about the X axis. FIG. 19 shows the calculation result of resolution (MTF) when the observation apparatus of the present embodiment is rotated ± 30 ° about the X axis. FIG. 20 shows the calculation result of resolution (MTF) when the observation apparatus of the present embodiment is rotated ± 60 ° about the X axis. FIG. 21 shows the calculation result of the resolution (MTF) when the observation apparatus of the present embodiment is rotated by 0 ° about the Y axis. FIG. 22 shows the calculation result of resolution (MTF) when the observation apparatus of the present embodiment is rotated ± 30 ° around the Y axis. FIG. 23 shows the calculation result of resolution (MTF) when the observation apparatus of the present embodiment is rotated by ± 60 ° about the Y axis. The resolution (MTF) was calculated in a wavelength region from 250 nm (Weight 1.0) to 800 nm (Weight 1.0), assuming that the dominant wavelength is 550 nm (Weight 1.0). The resolution (MTF) was calculated up to 100 LP / mm (5 μmμL & S).

When the observation apparatus is perpendicular to the XY plane (X axis center and Y axis center rotation angle = 0 °), the object plane and the light receiving plane are symmetric (line symmetric) with respect to the Y axis in the XY projection plane. Not relevant for X axis. In this case, as shown in FIGS. 18 and 21, the MTFs at the center of the light receiving surface and the four corners substantially overlap with the theoretical values.

When the observation apparatus is rotated ± 30 ° and ± 60 ° around the X axis, the object plane and the light receiving plane are symmetric (line symmetric) with respect to the Y axis and asymmetric with respect to the X axis within the XY projection plane. In this case, as shown in FIG. 19 and FIG. 20, the MTF in the X direction of the light receiving surface is almost the same as the rotation angle = 0 °. The MTF in the Y direction of the light receiving surface is cos30 ° = 0.866 lower when the rotation angle is 30 °, and cos60 ° = 0.5 lower when the rotation angle is 60 °, which almost overlaps the theoretical value.

When the observation apparatus is rotated ± 30 ° and ± 60 ° around the Y axis, the object surface and the light receiving surface are asymmetric with respect to both the X axis and the Y axis in the XY projection plane. In this case, as shown in FIGS. 22 and 23, the MTF in the X direction of the light receiving surface is almost the same as the rotation angle = 0 °. The MTF in the Y direction of the light receiving surface is cos30 ° = 0.866 lower when the rotation angle is 30 °, and cos60 ° = 0.5 lower when the rotation angle is 60 °, which almost overlaps the theoretical value.

As shown in FIG. 1, the observation apparatus of the present embodiment can achieve a resolution of almost the theoretical value when the observation apparatus is rotated around the X axis in the YZ plane. In addition, as shown in FIG. 2, the observation apparatus of the present embodiment can achieve a substantially theoretical resolution even when the observation apparatus is rotated around the Y axis in the XZ plane.

In the case where the object plane is placed on the XY plane, an observation apparatus shown in FIG. 1 that can tilt the observation apparatus placed in the Z-axis direction perpendicular to the object plane in the X-axis direction is also conceivable.
When the object plane is placed on the XY plane, an observation apparatus shown in FIG. 2 that can tilt the observation apparatus placed in the Z-axis direction perpendicular to the object plane in the Y-axis direction is also conceivable.
The observation apparatus of this embodiment can observe the object surface from almost all directions.
The observation apparatus of the present embodiment can realize a resolution of almost theoretical value even when the object plane is observed from an oblique direction.

In general, the object plane of the microscope on which the sample is placed moves in the XY directions. The objective lens that requires focusing moves in the Z-axis direction perpendicular to the object plane. That is, the microscope has three drive shafts.
The observation apparatus according to the present embodiment further includes a drive shaft for rotating the observation apparatus about the X axis and a drive shaft for rotating the observation apparatus about the Y axis. That is, the observation apparatus of this embodiment can include five drive shafts. In this case, the observation apparatus of this embodiment may be realized by incorporating a 5-axis robot.

DESCRIPTION OF SYMBOLS 10 Observation apparatus 12 Lens barrel main body 20 Light-receiving surface 30 Imaging optical system 32 Primary mirror 34 Secondary mirror 36 Draw plane mirror L1, L2 Optical axis N1, N2 Perpendicular S Object surface

Claims

An observation apparatus comprising: a light receiving surface that receives light from an object surface; and an imaging optical system that forms an image of light from the object surface on the light receiving surface;
The imaging optical system includes a concave primary mirror, a convex secondary mirror, and an extraction flat mirror, and reflects a light beam from the object surface in the order of the concave primary mirror, the convex secondary mirror, and the concave primary mirror. After that, it is composed of an equal-magnification reflection type imaging optical system that can form an image on the light receiving surface through the extraction flat mirror,
First tilting means capable of changing an angle α formed by an optical axis of light directed from the object plane toward the concave primary mirror and a perpendicular to the object plane;
An observation apparatus comprising: a second tilting unit capable of changing an angle β formed by an optical axis of light directed from the extraction flat mirror toward the light receiving surface and a perpendicular to the light receiving surface.
Control means for controlling the first tilting means and the second tilting means;
The observation apparatus according to claim 1, wherein the control unit controls the first tilting unit and the second tilting unit so that the angle α and the angle β are equal.
The first tilting means can change the angle α in a range of 0 degrees to 70 degrees,
The observation apparatus according to claim 1 or 2, wherein the second tilting means is capable of changing the angle β in a range of 0 degrees to 70 degrees.
The observation apparatus according to any one of claims 1 to 3, wherein the observation apparatus is a microscope, a spectroscopic ellipsometer, a defect detection apparatus, or a reflectance measurement apparatus.