JP2001074605A - Apparatus for measuring wavefront aberration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus for measuring a wavefront aberration capable of accurately measuring the aberration at a low cost even in a bright optical system having a large NA or an optical system having a solid immersion lens. SOLUTION: The apparatus for measuring a wavefront aberration to measure the aberration of an optical system 12 to be measured comprises a reflecting optical system for reflecting a first luminous flux L12 passed through the system 12 to return the flux L12 to the system 12 and interferes the wavefront of the flux L12 passed through the system 12 after reflecting by the reflecting optical system with a reference wavefront. In this case, the reflecting optical system has a plano-convex lens 13 having a flat surface 13a and a convex spherical surface 13b. The lens 13 is disposed at a center A13 of curvature of the surface 13b, and disposed in a direction in which the surface 13a becomes the optical system 12 side. The surface 13a of the lens 13 is a transmission surface for transmitting the flux L12, and the surface 13b is a reflecting surface for reflecting the flux L12 passed through the surface 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavefront aberration measuring device for measuring a wavefront aberration of an optical system by interference measurement.

[0002]

2. Description of the Related Art Conventionally, a wavefront aberration measuring apparatus for measuring the wavefront aberration of an optical system by interference measurement has been used for accurately evaluating the performance of a highly accurate optical system. Generally, the wavefront of the light beam that has passed through the measured optical system (measured wavefront)
Is deformed according to the aberration of the optical system to be measured. Therefore, the wavefront aberration measuring apparatus causes the measured wavefront to interfere with the reference wavefront, and measures the wavefront aberration of the measured optical system based on the obtained interference fringes.

[0003] Such a wavefront aberration measuring apparatus 20 is shown in FIG.
As shown in FIG. 2, a wavefront interference unit 21 for causing a measured wavefront and a reference wavefront to interfere with each other and a spherical turning mirror 23 are provided on the focal points F21 and F22 of the measured optical system 22, respectively. . The folding mirror 23 is arranged such that its center of curvature A23 coincides with the focal point F22 of the optical system 22 to be measured.

When measuring the wavefront aberration of the measured optical system 22 using the wavefront aberration measuring device 20, a measurement light beam L 21 is emitted from the wavefront interference unit 21 to the measured optical system 22. The measurement light beam L21 is focused on one focal point F21 of the measured optical system 22, and then enters the measured optical system 22. The light beam L22 that has passed through the measured optical system 22 is condensed at the other focal point F22 of the measured optical system 22, then enters the turning mirror 23, and is reflected there. The light beam L23 reflected by the return mirror 23 travels back through the optical path of the light beam L22 and passes through the optical system to be measured 22 again, and further travels backward in the optical path of the light beam L21.
Return to 1.

[0005] The wavefront of the light beam L23 returning to the wavefront interference unit 21 in this manner is deformed in accordance with the aberration of the optical system 22 to be measured. Can be measured.

[0006]

By the way, using the conventional wavefront aberration measuring device 20 described above, NA (ＮＡ sin θ2)
In order to measure a bright optical system having a large NA, it is necessary to prepare a folding mirror 23 having a large NA. In addition to not only increasing the NA of the turning mirror 23, the surface accuracy within the effective diameter B23 of the turning mirror 23 must be kept high. This is because, in the wavefront aberration measuring device 20, the surface accuracy of the folding mirror 23 directly affects the measurement result of the wavefront aberration.

However, it is very difficult to machine the folding mirror 23 having a large NA with high accuracy, and it is also very difficult to inspect the accuracy of the machined surface. Therefore, the wavefront aberration measuring device 20 capable of measuring an optical system having a large NA is very expensive. On the other hand, in the case of an optical system including a solid immersion lens (hereinafter, referred to as “SIL optical system”), the following problem occurs. Incidentally, the SIL optical system has recently been proposed for an optical pickup lens or the like, and has a large NA. Further, some SIL optical systems have an NA exceeding 1.

[0008] Among the SIL optical systems, particularly, NA is 1
In the case of exceeding the value, when the measurement is performed using the wavefront aberration measuring device 20, the measurement light flux is totally reflected at the end face of the solid immersion lens. Therefore, the measurement light beam cannot reach the turning mirror 23. Therefore, the conventional wavefront aberration measuring apparatus 20 cannot measure an SIL optical system whose NA exceeds 1.

In the case of a SIL optical system whose NA does not exceed 1, the measuring beam does not undergo total reflection at the end face of the solid immersion lens.
Can be used to measure the wavefront aberration. However, there is a problem that a light beam reflected on the end face of the solid immersion lens becomes noise and accurate measurement cannot be performed.

For example, if the refractive index of the solid immersion lens is n = 1.5, the amplitude reflectance at the end face of the solid immersion lens is (n-1) / (n + 1) =
A light beam having an amplitude of about 0.2, which is ５ of the light beam L22, is reflected on this surface. Therefore, even if the reflectance of the surface of the turning mirror 23 in FIG. 4 is 1, if the light beam reflected by the end face of the solid immersion lens interferes with the light beam L23, the phase modulation of the light beam L23 received by this will never occur. Not a small one.

In order to reduce the reflection at the end face of the solid immersion lens, it is conceivable to coat this end face with an antireflection film. However, solid immersion lenses are generally very small, and it is difficult to coat an end face with an antireflection film. For this reason, the measurement of the SIL optical system whose NA does not exceed 1 has to be performed without coating the end face of the solid immersion lens.

An object of the present invention is to provide an inexpensive wavefront aberration measuring apparatus capable of measuring wavefront aberration with high accuracy even in an optical system having a large NA and an optical system including a solid immersion lens.

[0013]

According to a first aspect of the present invention, there is provided a reflection optical system which reflects a first light beam having passed through an optical system to be measured and returns the first light beam to the optical system to be measured. A wavefront aberration measuring apparatus for measuring a wavefront aberration of an optical system to be measured by causing a wavefront of a second light beam having passed through an optical system to be measured after reflection and a reference wavefront to interfere with each other. It is composed of a plano-convex lens having a spherical surface. This plano-convex lens is arranged such that the center of curvature of the spherical surface is located on a plane and the plane is on the side of the optical system to be measured. The plane of the plano-convex lens is a transmission surface that transmits the first light beam, and the spherical surface is a reflection surface that reflects the first light beam transmitted through the plane.

In the wavefront aberration measuring apparatus according to the first aspect, the first light beam that has passed through the optical system to be measured transmits through the plane of the plano-convex lens, is reflected by the spherical surface, transmits through the plane again, and returns to the optical system to be measured. . Then, the light flux returned to the measured optical system passes through the measured optical system again. Since the wavefront of the second light beam that has passed through the measured optical system is deformed according to the aberration of the measured optical system, by causing the wavefront of the second light beam to interfere with the reference wavefront, the measured optical system Can be measured.

The first light beam having passed through the optical system to be measured is refracted when passing through the plane of the plano-convex lens. For this reason, the effective diameter of the spherical surface (the area that reflects the first light beam) can be reduced. The invention described in claim 2 is the first invention.
Wherein the center of curvature of the spherical surface of the plano-convex lens coincides with the focal point of the optical system to be measured.

In the wavefront aberration measuring apparatus according to a second aspect, the first light beam having passed through the optical system to be measured is focused on the center of curvature of the spherical surface. Furthermore, the luminous flux reflected by the spherical surface (reflected luminous flux)
Light is collected at the center of curvature of the spherical surface. Since the center of curvature of the spherical surface is on a plane, the focal points of the first light beam and the reflected light beam are located on the plane. Therefore, when the first light beam and the reflected light beam pass through the plane of the plano-convex lens, no aberration occurs.

According to a third aspect of the present invention, in the wavefront aberration measuring apparatus according to the second aspect, a plane of a plano-convex lens is adhered to an end face of a solid immersion lens included in the optical system to be measured. According to the wavefront aberration measuring device of the third aspect, the first light flux can be guided from the end face of the solid immersion lens to the plane of the plano-convex lens. Therefore, the wavefront aberration of the optical system including the solid immersion lens can be measured.

According to a fourth aspect of the present invention, in the wavefront aberration measuring apparatus according to the third aspect, a liquid having a refractive index substantially equal to that of the plano-convex lens is provided between the plane of the plano-convex lens and the end face of the solid immersion lens. , The refractive index n of the plano-convex lens satisfies the condition of “NAmax / n ≦ 1”. Here, NAmax represents the maximum NA of the solid immersion lens.

According to the wavefront aberration measuring device of the fourth aspect, the gap between the plane of the plano-convex lens and the end face of the solid immersion lens is eliminated, and the total reflection at the boundary between the plano-convex lens and the solid immersion lens is reduced. Since this does not occur, the wavefront aberration of the optical system including the solid immersion lens can be accurately measured. In the wavefront aberration measuring apparatus according to the fourth aspect, the position of the end face of the solid immersion lens can be adjusted by forming a minute concave portion for holding the liquid on the plane of the plano-convex lens. Therefore, the center of curvature of the spherical surface of the plano-convex lens can be positioned on the end surface of the solid immersion lens.

In addition, there is provided a reflecting optical system that reflects the first light beam that has passed through the optical system to be measured and returns the first light beam to the optical system to be measured, and that the second light beam that has passed through the optical system to be measured after being reflected by the reflecting optical system. A wavefront aberration measuring device for measuring a wavefront aberration of an optical system to be measured by causing a wavefront and a reference wavefront to interfere with each other, wherein a reflecting optical system is formed by a container having a concave spherical surface at a bottom and a liquid in the container. Constitute. Further, the reflection optical system is configured such that the center of curvature of the spherical surface is located on the liquid surface of the liquid, and is arranged so that the liquid surface is on the side of the measured optical system. In addition, the liquid surface of the liquid is a transmission surface that transmits the first light flux. The spherical surface of the container is a reflecting surface that reflects the first light flux transmitted through the liquid surface.

In this wavefront aberration measuring apparatus, the first light beam that has passed through the optical system to be measured transmits through the liquid surface of the liquid, is reflected by the spherical surface of the container, passes through the liquid surface again, and returns to the optical system to be measured. . Then, the light flux returned to the measured optical system passes through the measured optical system again. Since the wavefront of the second light beam that has passed through the optical system to be measured is deformed according to the aberration of the optical system to be measured, the wavefront of the second light beam and the reference wavefront interfere with each other, so that the optical system to be measured Can be measured.

The first light beam that has passed through the optical system to be measured is refracted when transmitting through the liquid surface of the liquid. For this reason, the effective diameter of the spherical surface of the container (the area that reflects the first light beam) can be reduced.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) First, a first embodiment will be described. The first embodiment corresponds to claims 1 and 2.

The wavefront aberration measuring apparatus 10 according to the first embodiment
As shown in FIG. 1, a wavefront interference unit 11 arranged on one focal point F11 side of the measured optical system 12 and a plano-convex lens 13 arranged on the other focal point F12 side of the measured optical system 12.
It is composed of Although the detailed configuration of the wavefront interfering unit 11 is not shown in FIG. 1, the laser light source and a part of the laser beam are similar to a well-known two-beam interferometer such as a Fizeau interferometer or a Twyman-Green interferometer. (Measurement light flux L
11) is composed of an optical system that focuses the light beam 11) on the focal point F11 of the measured optical system 12, an optical system that generates a reference light beam from another part of the laser light beam, and an optical system that detects interference fringes.

On the other hand, the plano-convex lens 13 has a flat surface 13a and a convex spherical surface 13b, and has a center of curvature A1 of the spherical surface 13b.
3 is an optical element processed so as to be located on the plane 13a. The plano-convex lens 13 is arranged so that the plane 13a is on the side of the optical system 12 to be measured. Further, the plano-convex lens 13 is arranged such that the center of curvature A13 of the spherical surface 13b coincides with the focal point F12 of the optical system 12 to be measured.

The plane 13a of the plano-convex lens 13 is a transmitting surface for transmitting a light beam (measurement light beam L12) that has passed through the optical system 12 to be measured. The spherical surface 1 of the plano-convex lens 13
Reference numeral 3b denotes a reflection surface (concave shape) that reflects the measurement light beam L12 transmitted through the plane 13a. In the wavefront aberration measuring apparatus 10 configured as described above, the measurement light beam L11 emitted from the wavefront interference unit 11 is focused on the focal point F11 of the optical system 12 to be measured.
After being condensed, the light is diverged and enters the optical system under measurement 12.

The measurement light beam L12 that has passed through the measured optical system 12 is condensed at the focal point F12 of the measured optical system 12, and reaches the plane 13a of the plano-convex lens 13 at the same time. 13 is incident. Further, the measurement light beam L12 incident on the plano-convex lens 13 becomes a divergent light beam and travels toward the spherical surface 13b. Measurement light flux L12
Corresponds to the “first light flux” in the claims.

Here, the converging angle of the measurement light beam L12 passing through the optical system under measurement 12 is θo, the divergence angle of the measurement light beam L12 incident on the plano-convex lens 13 is θ1, the plano-convex lens 13
Assuming that the refractive index is N1 and the refractive index of air is No, the relationship between the converging angle θo and the diverging angle θ1 is expressed by the following equation (1) (Snell's law). No × sin (θo) = N1 × sin (θ1) (1) Since the refractive index N1 of the plano-convex lens 13 is larger than the refractive index No of air, the measurement light beam L12 incident on the plano-convex lens 13
Is smaller than the converging angle θo.

As described above, the measurement light beam L12 diverging at the divergence angle θ1 smaller than the converging angle θo and traveling toward the spherical surface 13b reaches the spherical surface 13b and is reflected there. The center of curvature A13 of the spherical surface 13b is located on the plane 13a,
Further, since the light flux coincides with the focal point (F12) of the measurement light flux L12, the light flux (measurement light flux L13) obtained by the reflection on the spherical surface 13b goes backward in the optical path of the measurement light flux L12. That is, the measurement light beam L13 converges on the plane 13
The light is focused at a center of curvature A13 of the spherical surface 13b toward a.

Thereafter, the measurement light beam L13 passes through the plane 13a to become a divergent light beam, and reenters the measured optical system 12. The light beam (measurement light beam L14) that has passed through the measured optical system 12 again travels backward in the optical path of the measured light beam L11, is collected at the focal point F11 of the measured optical system 12, becomes a divergent light beam, and enters the wavefront interference unit 11. I do. The wavefront of the measurement light beam L <b> 14 that has entered the wavefront interference unit 11 is deformed according to the aberration of the measured optical system 12. The measurement light beam L14 corresponds to a “second light beam” in the claims.

In the wavefront interference unit 11, the wavefront of the returning measurement light beam L 14 and the wavefront of the reference light beam (reference wavefront) interfere with each other, and an interference fringe corresponding to the aberration of the optical system 12 to be measured is formed. Therefore, the wavefront aberration of the measured optical system 12 can be measured based on the interference fringes. As described above, according to the wavefront aberration measuring apparatus 10, the plano-convex lens 13
The divergence angle θ1 (corresponding to the converging angle of the measurement light beam L13) of the measurement light beam L12 incident on the inside can be reduced, so that the effective diameter B of the spherical surface 13b that requires high surface accuracy is required.
13 can be made smaller than the conventional effective diameter B23.

Therefore, even when measuring a bright optical system 12 having a large NA (∝ sin θo), the effective diameter B
13 does not need to be large, and the wavefront aberration measuring apparatus 10 can be configured at low cost. Further, the measured optical system 1
The measurement light beam L12 from 2 is a plane 13a of the plano-convex lens 13.
When the light is incident on the flat surface 13a, no aberration occurs due to the incidence of the measurement light beam L12 on the plano-convex lens 13.

When the measured optical system 12 has an aberration, strictly speaking, the measurement light beam L12 is incident on the plano-convex lens 13 to cause an aberration on the plane 13a. However, the measured optical system 12 that performs the aberration measurement using the wavefront aberration measurement device 10 has high accuracy and its aberration is sufficiently small. Therefore, even if an aberration occurs on the plane 13 a of the plano-convex lens 13, it can be said that the aberration does not actually affect the measurement result by the wavefront aberration measurement device 10.

(Second Embodiment) Next, a second embodiment will be described. The second embodiment corresponds to claims 1 to 5. The wavefront aberration measuring device according to the second embodiment is for measuring the wavefront aberration of the measured optical system 12 including the solid immersion lens 14.

For this reason, the wavefront aberration measuring apparatus according to the second embodiment has a wavefront interference section (not shown) and a plano-convex lens 13 similar to those of the above-described wavefront aberration measuring apparatus 10, and also has a structure as shown in FIG. A micro concave portion 15 is provided, and a liquid 16 is held in the fine concave portion 15. Here, the minute concave portion 15 is formed on the plane 13 a of the plano-convex lens 13. The liquid 16 has a refractive index N1 of the plano-convex lens 13.
The one having a refractive index substantially the same as that of (for example, matching oil used in an oil immersion microscope) is used.

Here, the solid immersion lens 14
Is, as shown in FIG. 2B, a spherical incident surface 14a.
And a planar end surface 14b. In the measured optical system 12 including the solid immersion lens 14, the measurement light flux L12 is applied to the end surface 14b of the solid immersion lens.
Collects light. Now, the plano-convex lens 13 is disposed with the liquid 16 interposed between the plano-convex lens 13 and the end face 14 b of the solid immersion lens 14. At this time, the spherical surface 13b of the plano-convex lens 13
Of the solid immersion lens 14
Is adjusted so as to be positioned on the end surface 14b of the lens and coincide with the focal point F12.

As described above, since the end face 14b of the solid immersion lens 14 is brought into close contact with the liquid 16, the measuring light beam L2 can be transmitted to the liquid 16 without being reflected by the end face 14b. Therefore, the first
As in the case of the embodiment, the measurement light beam L12 is reflected by the spherical surface 13b of the plano-convex lens 13 (measurement light beam L13), and passes through the measured optical system 12 including the solid immersion lens 14 again. Then, the wavefront aberration is measured based on the measurement light beam L14 that has passed through the measured optical system 12.

As described above, according to the wavefront aberration measuring apparatus of the second embodiment, whether the NA of the optical system under measurement 12 including the solid immersion lens 14 exceeds 1, or does not exceed 1, Can be accurately measured.

Further, since the refractive index of the liquid 16 filling the space between the end surface 14b of the solid immersion lens 14 and the plano-convex lens 13 is sufficiently close to the refractive index N1 of the plano-convex lens 13,
No aberration occurs when the measurement light beams L12 and L13 pass through the 16 layers of liquid. Even if there is some difference between the refractive index of the liquid 16 and the refractive index N1 of the plano-convex lens 13, if the solid immersion lens 14 and the plano-convex lens 13 are brought into close contact with each other so that the thickness of the liquid 16 layer is sufficiently small, the liquid The aberration generated when the measurement light beams L12 and L13 pass through the 16 layers can be reduced. However, even when the thickness of the liquid 16 layer is made sufficiently small, it is preferable to make the minute concave portion 15 shallow so that the center of curvature A13 of the spherical surface 13 is located on the end surface 14b of the solid immersion lens 14.

Further, in the above-described second embodiment, an example has been described in which the minute concave portion 15 for the liquid 16 is provided on the plane 13a of the plano-convex lens 13, but the minute concave portion 15 can be omitted. When the minute concave portion 15 is omitted, the plano-convex lens 13
The liquid 16 is thinly applied to the flat surface 13a of the lens, and the plano-convex lens 13 and the solid immersion lens 1
4 and the same measurement can be performed.

Also, an example has been described in which the liquid 16 is disposed between the plano-convex lens 13 and the solid immersion lens 14, but the liquid 16 is omitted, and the plane 13a of the plano-convex lens 13 and the end surface 14b of the solid immersion lens 14 are omitted.
The wavefront aberration can be measured even in the case of close contact. In this case, it is preferable that the refractive index N1 of the plano-convex lens 13 satisfies the condition of the following expression (2) (the maximum NA of the solid immersion lens 14 is NAmax). At this time, total reflection at the interface between the plano-convex lens 13 and the solid immersion lens 14 can be avoided.

NAmax / N1 ≦ 1 (3) (Third Embodiment) Next, a third embodiment will be described. The third embodiment corresponds to claim 6.

The wavefront aberration measuring apparatus according to the third embodiment is also for measuring the wavefront aberration of the optical system under measurement 12 including the solid immersion lens 14 (see FIG. 2B). In the wavefront aberration measuring apparatus of the third embodiment, a container 18 is provided instead of the plano-convex lens 13 of the wavefront aberration measuring apparatus 10 as shown in FIG.
The liquid 17 is held in the inside 8.

Here, the bottom of the container 18 has a concave spherical surface 1.
8a. The center of curvature A18 of the spherical surface 18a
Is located on the liquid surface 17 a of the liquid 17. In addition, liquid 1
For 7, one having a relatively large refractive index (for example, matching oil used in an oil immersion microscope) is used. The liquid surface 17a of the liquid 17 is a transmitting surface through which the measurement light beam L12 is transmitted. Also, the spherical surface 18a of the container 18
Is a reflection surface that reflects the measurement light beam L12 transmitted through the liquid surface 17a.

The measured optical system 12 including the solid immersion lens 14 is disposed such that the end face 14 b of the solid immersion lens 14 is in close contact with the liquid surface 17 a of the liquid 17. At this time, the center of curvature A18 of the spherical surface 18a of the container 18 corresponds to the end surface 14 of the solid immersion lens 14.
b and coincides with the focal point F12. As described above, the end face 14b of the solid immersion lens 14 is brought into close contact with the liquid 17, so that the measurement light beam L2 does not reflect on the end face 14b and can be transmitted to the liquid 17 side.

Therefore, similarly to the above-described embodiment, the measurement light beam L12 is reflected by the spherical surface 18a of the container 18 (measurement light beam L13), and the solid immersion lens 14
Again pass through the optical system to be measured 12. Then, the wavefront aberration is measured based on the measurement light beam L14 that has passed through the measured optical system 12. Thus, according to the wavefront aberration measuring device of the third embodiment, the solid immersion lens 14
Even if the NA of the optical system under measurement 12 including
Even when the value does not exceed 1, the wavefront aberration can be accurately measured.

The liquid level 17a of the liquid 17 in the container 18
Is higher than the center of curvature A18 of the spherical surface 18a, but by adjusting the position of the solid immersion lens 14,
The same measurement can be performed by positioning the center of curvature A18 of the spherical surface 18 on the end surface 14b of the solid immersion lens 14.

[0048]

As described above, according to the first to sixth aspects of the present invention, it is possible to accurately measure the wavefront aberration even in an optical system having a large NA and an optical system including a solid immersion lens. It is possible to provide a wavefront aberration measuring device that can be configured at a low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a wavefront aberration measurement device according to a first embodiment.

FIG. 2 is a configuration diagram illustrating a wavefront aberration measurement device according to a second embodiment.

FIG. 3 is a configuration diagram illustrating a wavefront aberration measurement apparatus according to a third embodiment.

FIG. 4 is a configuration diagram showing a conventional wavefront aberration measuring device.

[Explanation of symbols]

 10, 20 Wavefront aberration measuring device 11, 21 Wavefront interference unit 12, 22 Optical system to be measured 13 Plano-convex lens 14 Solid immersion lens 15 Micro concave portion 16, 17 Liquid 18 Container 23 Folding mirror

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[Procedure amendment]

[Submission date] September 1, 1999 (1999.9.1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

(Second Embodiment) Next, a second embodiment will be described. The second embodiment corresponds to claims 1 to 4 . The wavefront aberration measuring device according to the second embodiment is for measuring the wavefront aberration of the measured optical system 12 including the solid immersion lens 14.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction contents]

NAmax / N1 ≦ 1 (3) (Third Embodiment) Next, a third embodiment will be described.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction contents]

[0048]

As described above, according to the first to fourth aspects of the present invention, the wavefront aberration can be accurately measured even in a bright optical system having a large NA or an optical system including a solid immersion lens. It is possible to provide a wavefront aberration measuring device that can be configured at a low cost.

Continued on the front page F term (reference) 2F064 AA11 BB03 CC04 EE09 GG15 GG44 HH03 JJ01 2F065 AA65 BB22 CC21 DD02 DD03 FF51 GG04 HH02 HH13 JJ03 JJ09 JJ26 LL04 LL16 LL19 QQ21 QQ32 2G087 HH06 TA

Claims (4)

[Claims] A reflection optical system that reflects the first light flux that has passed through the optical system to be measured and returns the first light flux to the optical system to be measured, and that has passed through the optical system to be measured after being reflected by the optical system to be measured. A wavefront aberration measuring apparatus for measuring a wavefront aberration of the optical system to be measured by causing a wavefront of a light beam to interfere with a reference wavefront, wherein the reflecting optical system has a flat surface and a convex spherical surface, and the spherical surface. Is formed of a plano-convex lens whose center of curvature is located on the plane, and is arranged so that the plane is on the side of the optical system to be measured. The plane is a transmission surface that transmits the first light flux. The wavefront aberration measuring device, wherein the spherical surface is a reflecting surface that reflects the first light beam transmitted through the plane. 2. The wavefront aberration measuring apparatus according to claim 1, wherein the plano-convex lens is arranged so that a center of curvature of the spherical surface coincides with a focal point of the optical system to be measured. apparatus. 3. The wavefront aberration measuring apparatus according to claim 2, wherein the plano-convex lens is disposed such that the flat surface is in close contact with an end surface of a solid immersion lens included in the optical system to be measured. Wavefront aberration measurement device. 4. The wavefront aberration measuring apparatus according to claim 3, wherein the plano-convex lens is a liquid having a refractive index substantially equal to that of the plano-convex lens between the plane and the end face of the solid immersion lens. When the maximum NA of the solid immersion lens is NAmax, the refractive index n of the plano-convex lens is “NAmax /
A wavefront aberration measuring device satisfying a condition of n ≦ 1.