JP2002071513A - Interferometer for immersion microscope objective and evaluation method of the immersion microscope objective - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interferometer for immersion microscope objective capable of quantitatively and accurately evaluating the immersion microscope objective. SOLUTION: A hemispherical plane and convex lens 12 having a plane 12 and a return spherical surface 12b is arranged facing the objective 10. In this case, an immersion liquid 15 is filled in the gap between the plane 12a and the objective lens 10, focus positions of the plane 12a and the objective 10 coincide and the center of the sphere of the return spherical surface 12b and the focus position also coincide in the arrangement. Detected wave 8 formed with a reference plane plate 4 after passing through the objective 10 is reflected vertically by the return spherical surface 12b to proceed in the reverse direction in the light path. The detected wave 8 having proceeded in the light path interferes with a reference wave 7 and its interference fringe is photographed with a CCD imaging device 6. From the interference pattern state, the performance of the objective 10 can be evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interferometer for evaluating an immersion microscope objective and a method for evaluating the immersion microscope objective.

[0002]

2. Description of the Related Art As a method of evaluating a dry microscope objective lens, not an immersion system, there is a method using an interferometer. FIG. 5 is a diagram for explaining the evaluation method, and shows a schematic configuration of the evaluation device. The optical path of the plane wave 2 from the light source is bent by the beam splitter 5 and is incident on the plane plate 51. A part of the plane wave 2 is reflected by the plane plate 51 to be a reference wave, and the other part is transmitted and enters the objective lens 50 as a test wave. The test wave 8 is collected at the focal point 52 of the objective lens 50 and then vertically reflected by the concave surface (part of the spherical surface) 53 and goes backward in the optical path. As a result, interference fringes occur due to interference between the reference wave reflected by the flat plate 51 and the test wave 8 emitted downward from the objective lens 50 in the figure. The objective lens 50 can be evaluated by imaging and observing the interference fringes with the CCD imaging device 6, that is, by measuring the wavefront aberration.

[0003]

In a microscope using an immersion objective lens, observation is performed by filling an immersion liquid such as oil or water between the objective lens and the specimen. However, in the case of the configuration as shown in FIG. 5, the space between the objective lens 50 and the concave surface 53 cannot be filled with the immersion liquid.
An immersion objective could not be evaluated with such a device. Therefore, as for the immersion objective lens, an inspector observes a sample such as a pinhole or the like having a theoretical resolution close to the theoretical resolution with a microscope, and evaluates the objective lens from observation conditions (such as blur).

An object of the present invention is to provide an interferometer for an immersion microscope objective that can quantitatively and accurately evaluate an immersion microscope objective lens without human judgment, and an immersion microscope objective lens. To provide an evaluation method.

[0005]

An embodiment of the present invention will be described with reference to FIGS. 1 and 4. FIG. (1) Explaining in conjunction with FIG. 1, the interferometer for an immersion microscope objective lens according to the first aspect of the invention forms a reference wave 7 and a test wave 8, and converts the test wave 8 into an immersion microscope objective. A first optical system 4 for entering a lens 10 and a folded spherical surface 1
2b and an immersion liquid 1 between the
5 which are arranged to face each other and emit the test wave 8 transmitted through the objective lens 10 and reflected by the folded spherical surface 12b.
And a detector 6 that detects an interference wave between the test wave 8 and the reference wave 7 reflected by the folded spherical surface 12b.
The objective lens 10 based on the interference wave detected by the detector 6
The above object is achieved by evaluating. (2) The invention according to claim 2 is the interferometer for an immersion microscope objective lens according to claim 1, wherein the second optical system 12 comprises:
A plane 12a disposed at the focal position of the objective lens 10,
This is a hemispherical flat convex lens having a convex spherical surface 12b whose spherical center coincides with the focal position and a lens thickness equal to the radius of curvature of the convex spherical surface 12b. (3) Explaining in connection with FIG. 4, the invention of claim 3 is the interferometer for an immersion microscope objective lens according to claim 1, wherein the second optical system 30 is formed by a plane 30a and a spherical center. It has a convex spherical surface 30b coincident with the focal position, and the lens thickness is equal to the sum of the thickness d of the cover glass used for the immersion microscope and the radius of curvature of the convex spherical surface 30b, and is equal to the refractive index of the cover glass. Hemispherical convex convex lens 3 having high refractive index
It is set to 0. (4) Referring to FIG. 1, in the evaluation method according to the fourth aspect of the present invention, the folded spherical surface 12b disposed between the objective lens 10 and the immersion microscope objective lens 10 with the immersion liquid 15 interposed therebetween. Is reflected, and the objective lens 10 is evaluated based on the interference wave between the reference wave 7 and the test wave 8 reflected by the folded spherical surface 12b.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easier to understand. However, the present invention is not limited to the embodiment.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a view showing one embodiment of an interferometer according to the present invention, and is a schematic configuration diagram of the interferometer. The interferometer 1 is provided with a light source 3 for generating a plane wave 2, a beam splitter 5 for guiding the plane wave 2 from the light source 3 to a reference plane plate 4, and a CCD imaging device 6 for photographing interference fringes. The reference plane plate 4 is a reference plane (Fizeau surface) 4
a, a part of the plane wave 2 from the beam splitter 5 is reflected by the reference plane 4a, and the rest is transmitted through the reference plane 4a. The plane wave 7 reflected by the reference plane 4a is called a reference wave, and the plane wave 8 transmitted through the reference plane 4a is called a test wave. If a polarizing beam splitter and a quarter-wave plate are used instead of the beam splitter 5, no light returns to the light source 3 and the adverse effect on the light source 3 due to the return beam can be prevented.

Reference numeral 9 denotes an adapter for mounting a test lens to which an immersion microscope objective lens 10 as a test lens is fixed. The objective lens 1 is attached to a screw portion 9a formed on the adapter 9.
0 is fixed. The adapter 9 is attached to a support 11 and is adjusted so that the axis of the objective lens 10 and the optical axis of the interferometer 1 coincide with each other when the objective lens 10 is fixed to the screw portion 9a.

Reference numeral 12 denotes a hemispherical hemispherical flat convex lens, which is mounted on an x-stage 13x of the stage 13. The hemispherical flat convex lens 12 has a flat surface 12a and a folded spherical surface 1
2b, and the spherical center of the folded spherical surface 12b is the plane 1
2a. That is, the lens thickness of the hemispherical flat convex lens 12 is equal to the radius of curvature of the folded spherical surface 12b. The hemispherical flat convex lens 12 is disposed such that the flat surface 12 a faces the objective lens 10, and a gap between the flat surface 12 a and the objective lens 10 is filled with the immersion liquid 15. As the immersion liquid 15, the same oil or water as that used in the immersion microscope is used.

The stage 13 comprises an x stage 13x, a y stage 13y and a z stage 13z.
The z stage 13z attached to 1 is a knob 14z
Can be moved up and down along the column 11 by rotating. The y stage 13y provided on the z stage 13z can be moved in the y direction by rotating the knob 14y. Further, the x stage 13x provided on the y stage 13y has a knob 14
By rotating x, it can be moved in the x direction.

Next, the procedure for evaluating the objective lens will be described. First, the objective lens 10 is fixed to the adapter 9, and the hemispherical flat convex lens 12 is placed on the x-stage 13x such that the plane 12a is on the lower side. Next, the z stage 13z is moved up and down, and the z position of the stage 13 is adjusted so that the position of the focal point 16 of the objective lens 10 and the plane 12a of the hemispherical flat convex lens 12 coincide.

When the z position adjustment is completed, the objective lens 1
After filling the gap between 0 and the plane 12a with the immersion liquid 15, the light source 3 emits light with a small beam diameter to adjust the position of the hemispherical flat convex lens 12. On the imaging surface of the CCD imaging device 6, the beam reflected by the reference plane 4a of the reference plane plate 4 and the folded spherical surface 12b of the hemispherical flat convex lens 12 after passing through the reference plane plate 4 and passing through the objective lens 10 are used. The reflected beam is imaged. Then, the x and y positions of the hemispherical flat convex lens 12 are adjusted by the stage 13 so that the two beams coincide with each other. At this time, focus adjustment is also performed by finely adjusting the z position of the stage 13.

When the position of the hemispherical flat convex lens 12 is adjusted, the objective lens 10 is evaluated by emitting a plane wave having a predetermined beam diameter from the light source 3. When the plane wave 2 is incident on the reference plane plate 4 after the optical path is bent by the beam splitter 5, the plane wave 2 is divided into the reference wave 7 and the test wave 8 as described above. The reference wave 7 enters the CCD imaging device 6 via the beam splitter 5. On the other hand, the test wave 8 enters the objective lens 10 after being refracted and transmitted through the reference plane plate 4, enters the hemispherical flat convex lens 12 after passing through the focal point 16 of the objective lens 10. Since the focal point 16 coincides with the spherical center of the hemispherical convex convex lens 12, the test wave 8 is vertically reflected by the folded spherical surface 12 b of the hemispherical convex convex lens 12, travels backward in the optical path, and enters the CCD imaging device 6.

When the reference wave 7 and the test wave 8 are superimposed, interference fringes occur due to interference.
Is imaged. 2A and 2B are diagrams illustrating an example of observation of interference fringes, in which FIG. 2A illustrates interference fringes when the objective lens 10 has aberration, and FIG. 2B illustrates interference fringes when there is no aberration. If the objective lens 10 has no aberration, the interference fringes are parallel as shown in FIG. 2B, but if there is an aberration, FIG.
As shown by a portion 19 of FIG.

When the objective lens 10 is evaluated, its performance is evaluated in comparison with a reference objective lens.
Are related to the objective lens 10 determined to have no difference from the reference one in the visual inspection by pinhole observation. Thus, aberrations that could not be confirmed by visual inspection can be confirmed by using the interferometer according to the present invention, and the performance of the immersion objective lens 10 can be quantitatively and highly accurately evaluated. it can.

<< Modification 1 >> FIG. 3 is a diagram showing a configuration in a case where the immersion type objective lens 20 as a test lens is a finite system (the objective lens in FIG. 1 is called an infinite system). Only parts are shown. In the finite objective lens 20, the test wave 21
It is necessary to make a spherical wave incident, and a Fizeau lens 22 having a Fizeau surface 22a for forming a spherical wave is used instead of the reference plane plate 4 in FIG. Fizeau lens 22
Is that the center of curvature of the Fizeau surface 22a is the test wave (spherical wave) 2
1 divergence center (the luminous flux of the test wave 21 is
(A point that intersects one point when extended in the direction). When the plane wave 2 from the light source 3 (see FIG. 1) is incident on the Fizeau lens 22 via the beam splitter 5, a spherical wave test wave 21 and a reference wave 22 are formed by the Fizeau surface 22a. Other configurations are the same as those of the interferometer shown in FIG.

The test wave 21 incident on the objective lens 20 is collected at the focal point 16, that is, at the spherical center of the hemispherical flat convex lens 12.
The light is vertically reflected at 2b and travels backward in the optical path. The reversed test wave 21 and the reference wave formed by the Fizeau surface 22a are converted to a plane wave and emitted to the beam splitter 5 below the Fizeau lens 22 in the drawing, and interference fringes are formed on the imaging surface of the CCD imaging device 6. Is done.

<< Modification 2 >> FIG. 4 is a view showing a second modification of the interferometer shown in FIG. 1, and is an enlarged view of a hemispherical flat convex lens portion. In the hemispherical convex convex lens 30 shown in FIG. 4, the lens thickness is made larger than the hemispherical convex convex lens 12 shown in FIG. 1 by the thickness d of the cover lens, and is formed of an optical material having the same refractive index as the cover glass. did. That is, if the radius of curvature of the turning spherical surface 30b is R, the lens thickness is set to (R + d).

Usually, when observing with a microscope, the specimen is covered with a cover glass, and an immersion liquid is filled between the cover glass and the objective lens. When the objective lens is evaluated using the hemispherical convex convex lens 12 as shown in FIG. 1, a cover glass is inserted between the hemispherical convex convex lens 12 and the objective lens 10 to measure the wavefront interference. Therefore, workability is poor and reflection on the surface of the cover glass may affect the evaluation.

On the other hand, the hemispherical flat convex lens 30 shown in FIG. 4 has a shape having a cover glass integrally. After passing through the immersion liquid 15, the test wave 8 from the objective lens 10 enters the hemispherical flat convex lens 30 from the plane 30a, and focuses on a position 16 at a distance d from the plane 30a. Since the hemispherical convex convex lens 30 is disposed so that the spherical center coincides with the focal position 16 of the objective lens 10, the test wave 8 entering the hemispherical convex convex lens 30 is vertically reflected by the folded spherical surface 30b and reverses the optical path. Then, the light enters the CCD imaging device 6 (see FIG. 1).

Since the hemispherical flat convex lens 30 has a refractive index equal to that of the cover glass, the refractive index of the immersion liquid 15 is substantially equal, and the test wave 8 is hardly reflected by the plane 30a. Therefore, the influence of the reflected light as described above can be prevented, and workability can be improved because there is no need to provide a separate cover glass.

In the correspondence between the embodiment described above and the elements of the claims, the reference plane plate 4 and the Fizeau lens 22 correspond to the first optical system and the hemispherical flat convex lens 12,
Numeral 30 denotes a second optical system, folded spheres 12b and 30b form convex spheres, and the CCD imaging device 6 constitutes a detector.

[0023]

As described above, according to the present invention,
By filling the immersion liquid between the second optical system having the folded spherical surface and the immersion type objective lens and arranging the immersion liquid to face each other, the test wave transmitted through the objective lens is reflected by the folded spherical surface of the second optical system. To interfere with the reference wave. The performance of the immersion objective lens can be quantitatively and accurately evaluated by detecting interference fringes generated by the interference with the detector.
In particular, in the invention of claim 3, since the lens thickness of the second optical system is set equal to the sum of the thickness of the cover glass and the radius of curvature of the convex spherical surface, the second optical system is evaluated at the time of evaluation. There is no need to insert a cover glass between the
Workability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of an interferometer according to the present invention, and is a schematic configuration diagram of the interferometer.

2A and 2B are diagrams illustrating an example of observation of interference fringes, in which FIG. 2A illustrates interference fringes when the objective lens 10 has aberration;
(B) shows interference fringes when there is no aberration.

FIG. 3 is a diagram for explaining a first modification example, and shows a configuration of an interferometer for a finite immersion type objective lens 20;

FIG. 4 is a diagram illustrating a second modification, and is an enlarged view of a hemispherical flat convex lens portion.

FIG. 5 is a diagram illustrating a method of evaluating a wavefront of a dry microscope objective lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interferometer part 2 Plane wave 3 Light source 4 Reference plane plate 4a Reference plane 6 CCD imaging device 7 Reference wave 8,21 Test wave 9 Adapter 10 Objective lens 12,30 Hemispherical flat convex lens 12a, 30a Plane 12b, 30b Folded spherical surface 13 Stage 15 Immersion liquid 22 Fizeau lens

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F064 AA09 BB04 FF00 GG12 GG22 GG38 GG47 HH03 JJ01 KK01 2G086 HH06 2H087 KA12 LA21 NA00 PA01 PA17 PB01

Claims (4)

[Claims] An immersion liquid between a first optical system that forms a reference wave and a test wave and causes the test wave to be incident on an immersion microscope objective lens, and has a folded spherical surface and the objective lens. And a second optical system that is disposed to face and transmits the objective lens and emits the test wave reflected by the folded sphere, and interference between the test wave reflected by the folded sphere and the reference wave. An interferometer for an immersion microscope objective lens, comprising: a detector for detecting a wave; and evaluating the objective lens based on the interference wave detected by the detector. 2. The immersion microscope objective lens interferometer according to claim 1, wherein the second optical system is configured such that a plane disposed at a focal position of the objective lens and a spherical center are located at the focal position. And a convex spherical surface having the same shape as that of the convex spherical surface, and having a lens thickness equal to the radius of curvature of the convex spherical surface. 3. The interferometer for an immersion microscope objective lens according to claim 1, wherein the second optical system has a convex spherical surface whose plane and sphere coincide with the focal position, and has a lens thickness. Is a hemispherical flat convex lens having a refractive index equal to the sum of the thickness of the cover glass used for the immersion microscope and the radius of curvature of the convex spherical surface, and having the same refractive index as the cover glass. Interferometer for immersion microscope objectives. 4. A test wave transmitted through the objective lens is reflected by a folded spherical surface disposed between the immersion liquid and the immersion microscope objective lens through an immersion liquid, and a reference wave and the reflected wave are reflected by the folded spherical surface. A method for evaluating an objective lens for an immersion microscope, wherein the objective lens is evaluated based on an interference wave with a test wave.