JP4352374B2 - Microscope objective lens - Google Patents

Description

【００５５】
【発明の効果】
以上の説明から明らかなように、本発明に係る顕微鏡用対物レンズによれば、接合レンズを用いない単レンズのみの構成でも、収差補正の性能と偏心公差への効きを良好にすることができ、高倍率（４０倍程度以上）で開口数が０．９程度に達し、深紫外波長領域で使用することを目的とした顕微鏡用対物レンズを得ることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例に係る顕微鏡用対物レンズの構成を示す断面図である。
【図２】本発明の第１の実施例に係る顕微鏡用対物レンズの諸収差図である。
【図３】本発明の第２の実施例に係る顕微鏡用対物レンズの構成を示す断面図である。
【図４】本発明の第２の実施例に係る顕微鏡用対物レンズの諸収差図である。
【図５】本発明の第３の実施例に係る顕微鏡用対物レンズの構成を示す断面図である。
【図６】本発明の第３の実施例に係る顕微鏡用対物レンズの諸収差図である。
【図７】本発明に係る顕微鏡用対物レンズと組み合わせて使われる結像レンズの構成を示す断面図である。
【符号の説明】
ＯＬ 顕微鏡用対物レンズ
Ｇ１ 第１レンズ群
Ｇ２ 第２レンズ群
Ｇ３ 第３レンズ群
Ｇ４ 第４レンズ群[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microscope objective lens that has a high magnification (about 40 times or more), a numerical aperture of about 0.9, and is intended for use in the deep ultraviolet wavelength region.
[0002]
[Prior art]
As an objective lens for a microscope intended to be used in the deep ultraviolet wavelength region at a high magnification (about 40 times or more) and a numerical aperture of about 0.9, for example, the one disclosed in Patent Document 1 is used. Are known.
[0003]
[Patent Document 1]
JP 2001-318317 A
[0004]
[Problems to be solved by the invention]
The microscope objective lens disclosed in Patent Document 1 does not include a cemented lens by bonding, and avoids various problems that occur when the adhesive is irradiated with deep ultraviolet light. However, due to the absence of a cemented lens, it is easy to increase the eccentricity tolerance due to an error in the lens shape and the arrangement position (the influence of the error in the lens shape and the arrangement position on the eccentricity tolerance is described in There is a problem that the lens configuration has a burden on manufacturing.
[0005]
The present invention has been made in view of the problems as described above. The effect on the eccentricity tolerance can be relaxed without using a cemented lens, and the numerical aperture is high at a high magnification (about 40 times or more). An object of the present invention is to provide a microscope objective lens that reaches about 9 and is intended for use in the deep ultraviolet wavelength region.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the objective lens for a microscope according to the present invention is such that adjacent lenses are all arranged with an air gap, and the lens configuration is a positive lens with a concave surface facing the object side in order from the object side. A first lens group having a meniscus lens having a refractive power of 1, a second lens group having a single lens having a positive refractive power, and two adjacent lenses having positive and negative refractive powers. When the two adjacent lenses having the same curvature radius sign of the adjacent surfaces are set as one lens set, at least five or more of these lens sets are arranged, and the whole is positive. The third lens group having a refractive power of 4 and the fourth lens group having a negative refractive power as a whole. At this time, when the Abbe number of a lens having a positive refractive power among the two lenses constituting the lens group in the third lens group is ν3P and the Abbe number of a lens having a negative refractive power is ν3N, Satisfy the condition represented by ν3P> ν3N, and let dmin be the center thickness of the lens with the thinnest center thickness among the lenses constituting the third lens group, and the distance between the adjacent surfaces of the two lenses constituting the lens set Is a lens having the maximum effective diameter from the most object side lens among the lenses constituting the third lens group, satisfying the condition expressed by the formula 2 × dmin> dcenter + dedge Placed in the section leading to each The concave lens has an object-side radius of curvature r1a and an image-side radius of curvature r2a, and is disposed in a section from the lens having the maximum effective diameter to the fourth lens group. each When the radius of curvature on the object side of the concave lens is r1b and the radius of curvature on the image side is r2b, All of the respective concave lenses | R1a | <| r2a |, | r1b |> | r2b |, and the third lens group and the fourth lens group have a total lens length (distance from the object surface to the final surface of the objective lens). ), Or the same focal length, whichever is shorter, is configured to be spaced apart by an air interval of 1/6 or more.
[0007]
In the third lens group, a lens set is disposed on the object side and the image side with the lens having the maximum effective diameter interposed therebetween, and is disposed in a section from the lens on the most object side to the lens having the maximum effective diameter. The adjacent surfaces of the two lenses constituting the surface are surfaces having a negative radius of curvature so The adjacent surfaces of the two lenses constituting the lens set arranged in the section from the lens having the maximum effective diameter to the fourth lens group are surfaces having a positive radius of curvature so Preferably, it is configured.
[0008]
At this time, in the third lens group, the lens group disposed in the section from the lens closest to the object side to the lens having the maximum effective diameter is configured by a lens having positive refractive power on the object side, and has the maximum effective diameter. It is preferable that the lens group disposed in the section from the first lens group to the fourth lens group is composed of lenses having negative refractive power on the object side.
[0009]
Further, the third lens group has one or more lens groups each including three lenses having positive, negative, positive and negative refractive power, and the three lenses. Of these, two sets of lenses formed by combining two adjacent lenses are It is preferable to be configured to satisfy the condition expressed by the formula 2 × dmin> dcenter + dedge.
[0010]
Also, the principal ray of the luminous flux emitted from the point intersecting the optical axis on the object plane and the maximum numerical aperture of the luminous flux, and the principal ray of the luminous flux emitted from the maximum object surface height and the maximum numerical aperture in the upper and lower coma rays. It is preferable that the incident angle and the outgoing angle when the light ray enters and exits the second to fourth lens groups are 50 degrees or less, and more preferably, the angle is 45 degrees or less.
[0011]
Further, among the lenses constituting the third lens group, when the maximum value of the ratio of the focal length to the effective diameter of the lens having positive refractive power is Amax and the minimum value is Amin, the expression Amax / Amin <2. It is preferable to be configured so as to satisfy the conditions.
[0012]
Of the lenses constituting the third lens group, when the maximum value of the ratio of the focal length to the effective diameter of the lens having negative refractive power is Bmax and the minimum value is Bmin, the expression Bmax / Bmin <2. It is preferable to be configured so as to satisfy the conditions.
[0013]
Further, when the focal length of the convex lens in the third lens group is f3P and the total focal length of the first to fourth lens groups is fall, the condition expressed by the formula f3P / fall> 6 is satisfied. It is preferable to be configured as described above.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1, 3 and 5 are configuration diagrams of a microscope objective lens OL corresponding to the first to third embodiments of the present invention, respectively, and adjacent lenses are all arranged with an air gap. . In any of the embodiments, in order from the object side, a first lens group G1 having a positive refractive power with a concave surface facing the object side, and a second lens group G2 made up of a single lens having a positive refractive power; When two adjacent lenses are composed of lenses having positive and negative refractive powers, and two lenses having the same curvature radius sign on the adjacent surfaces are used as one lens set, this lens At least five or more groups are arranged, and the third lens group G3 having a positive refractive power as a whole and a fourth lens group G4 having a negative refractive power as a whole.
[0016]
In the microscope objective lens OL according to the first embodiment shown in FIG. 1, in order from the object side, the first lens group G1 includes a positive meniscus lens L1 having a concave surface facing the object side, and the second lens group G2 includes The third lens group G3 includes a positive meniscus lens L2 having a concave surface facing the object side. The third lens group G3 includes a biconvex lens L3 and a negative meniscus lens L4 having a concave surface facing the object side. A lens set consisting of two lenses, L5 and a negative meniscus lens L6 with a concave surface facing the object side, and a lens set consisting of two lenses, a biconvex lens L7 and a negative meniscus lens L8 with a concave surface facing the object side, A lens set consisting of three lenses, a biconvex lens L9, a biconcave lens L10, and a biconvex lens L11, and a lens set consisting of two lenses, a biconcave lens L12 and a biconvex lens L13 A lens set composed of two lenses, a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15, and a lens composed of two lenses, a negative meniscus lens L16 having a convex surface facing the object side and a biconvex lens L17 The fourth lens group G4 includes a positive meniscus lens L18 having a convex surface directed toward the object side and a biconcave lens L19.
[0017]
In the microscope objective lens OL according to the second embodiment shown in FIG. 3, in order from the object side, the first lens group G1 includes a positive meniscus lens L21 having a concave surface directed toward the object side, and the second lens group G2 includes The third lens group G3 is composed of a positive meniscus lens L22 having a concave surface facing the object side, and the third lens group G3 includes a biconvex lens L23 and a negative meniscus lens L24 having a concave surface facing the object side, and a biconvex lens L25. A lens set consisting of two lenses, a negative meniscus lens L26 with a concave surface facing the object side, a lens set consisting of two lenses, a biconvex lens L27 and a negative meniscus lens L28 with a concave surface facing the object side, A lens set comprising three lenses, a convex lens L29, a biconcave lens L30, and a biconvex lens L31, and two lenses, a biconcave lens L32 and a biconvex lens L33 A lens group consisting of two lenses, a negative meniscus lens L34 having a convex surface facing the object side and a biconvex lens L35, and a negative meniscus lens L36 having a convex surface facing the object side and a biconvex lens L37. The fourth lens group G4 includes a positive meniscus lens L38 having a convex surface facing the object side and a biconcave lens L39.
[0018]
In the microscope objective lens OL according to the third embodiment shown in FIG. 5, in order from the object side, the first lens group G1 includes a positive meniscus lens L41 having a concave surface directed toward the object side, and the second lens group G2 includes The third lens group G3 includes a lens set including two lenses, a biconvex lens L43 and a biconcave lens L44, and a positive meniscus lens L45 having a concave surface facing the object side. A lens set consisting of three lenses of a biconvex lens L46, a biconcave lens L47 and a biconvex lens L48, a lens set consisting of three lenses of a biconvex lens L49, a biconcave lens L50 and a biconvex lens L51, and a biconvex lens L52. A lens set consisting of three lenses, a biconcave lens L53 and a biconvex lens L54, a negative meniscus lens L55 with a convex surface facing the object side, and both It consists lens group and consisting of two lenses of a lens L56, the fourth lens group G4 is composed of a positive meniscus lens L57 having a convex surface directed toward the object side biconcave lens L58 Prefecture.
[0019]
In general, the objective lens having a magnification larger than about 40 times, such as the microscope objective lens OL according to the present invention, and the objective lens having a high numerical aperture, the curvature of the image side of the lens group closest to the object is set to be insensitive. By satisfying the above, it is configured to obtain positive refractive power with no aberration for spherical aberration. The positive refracting power obtained with a lens having this configuration is very large, and is an indispensable configuration for efficiently obtaining magnification without aberration.
[0020]
The first lens group G1 of the microscope objective lens OL according to the present invention is a meniscus lens having a positive refractive power with the concave surface facing the object side, and the curvature of the image side surface is a non-playing condition or a condition close thereto. Thus, positive refractive power is obtained while suppressing the occurrence of spherical aberration, and the Petzval sum is reduced by the concave surface on the object side, thereby contributing to correction of field curvature.
[0021]
The second lens group G2 has a structure that earns positive refracting power by disposing a single lens having positive refracting power following the first lens group G1.
[0022]
The third lens group G3 has a positive refractive power as a whole, and converts the divergent light emitted from the second lens group G2 into convergent light. At this time, the observation light (248 ± 3 nm in the embodiment of the present invention) is converted. In order to achromatic the light used for the automatic focusing mechanism and the like, the following conditional expression (1) is satisfied, and the sign of the radius of curvature of the adjacent surface of the adjacent lens is the same, At least five or more lens groups each including two lenses having positive and negative refractive powers that satisfy the following conditional expressions (2) and (3) are arranged. This configuration is necessary to provide an aberration correction effect due to the concave surface at the same time as the achromatization.
[0023]
[Expression 1]
ν3P> ν3N (1)
2 × dmin> dcenter + dedge (2)
| R1a | <| r2a |, | r1b |> | r2b | (3)
However,
ν3P: Abbe number of a lens having positive refractive power among two lenses constituting the lens group in the third lens group G3
ν3N: Abbe number of the lens having negative refractive power among the two lenses constituting the lens group in the third lens group G3
dmin: the center thickness of the thinnest lens among the lenses constituting the third lens group G3
dcenter: the distance between the two lenses constituting the lens group in the third lens group G3
dedge: the edge air space between the two lenses constituting the lens group in the third lens group G3
r1a: radius of curvature of the object side of the concave lens arranged in the section from the most object side lens to the lens having the maximum effective diameter among the lenses constituting the third lens group G3
r2a: radius of curvature on the image side of the concave lens arranged in the section from the most object side lens to the lens having the maximum effective diameter among the lenses constituting the third lens group G3
r1b: radius of curvature on the object side of the concave lens arranged in the section from the lens having the maximum effective diameter to the fourth lens group G4 among the lenses constituting the third lens group G3
r2b: radius of curvature on the image side of the concave lens arranged in the section from the lens having the maximum effective diameter to the fourth lens group G4 among the lenses constituting the third lens group G3
[0024]
In the above-described lens set, in a configuration in which a cemented lens can be used, it is often convenient to configure it as a cemented lens. However, in the microscope objective lens OL according to the present invention, an adhesive necessary for forming the cemented lens is used. In order to cope with various problems caused by irradiating deep ultraviolet light on the surface, no cemented lens is used. However, the above lens group has an effect close to that of a cemented lens in terms of aberration correction, and has a shape close to that of the cemented lens in terms of shape, so that it will be referred to as a “pseudo cemented lens” in the following description. .
[0025]
The fourth lens group G4 has a negative refracting power as a whole, and converts the convergent light emitted from the third lens group G3 into a parallel light beam, and at the same time, mainly contributes to aberration correction of the upper coma light beam. In addition, the fourth lens group G4 is 1/6 or more of the third lens group G3 and the total lens length (distance from the object plane to the final surface of the microscope objective lens OL) or the shorter focal length, whichever is shorter. The air gap of the distance is arranged. Since the objective lens used in the ultraviolet region such as the objective lens has a large decrease in the light amount due to the absorption of the glass material, the decrease in the light amount due to the absorption of the glass material can be suppressed by separating the air interval as described above.
[0026]
By the way, when the cemented lens is replaced with the above-mentioned pseudo cemented lens, if the adhesive for joining the cemented lens is simply peeled off the adjacent surface of the pseudo cemented lens, the incident angle and the exit angle of the light beam There has been a problem that the effect on the eccentricity tolerance becomes sensitive. For this reason, when a pseudo cemented lens is used, the aberration correction performance is improved by suppressing the incident angle and the outgoing angle of the light beam transmitted through the lenses constituting the second to fourth lens groups G2 to G4 to 50 degrees or less. While maintaining, the effect on the eccentricity tolerance can be relaxed. The light beams that pass through the lenses constituting the second to fourth lens groups G2 to G4 include the principal ray of the light beam emitted from the point intersecting the optical axis of the microscope objective lens OL on the object plane and the light beam having the maximum numerical aperture. In addition, the main ray of the luminous flux emitted from the maximum object height of the object surface and the maximum numerical aperture in the upper and lower coma rays are targeted, and the incident angle and the emission angle of this ray are suppressed to 50 degrees or less. Has been.
[0027]
Although it is known that a lens having a surface with a relatively large incident angle and exit angle may have a good correction of aberrations by design, a lens having such a surface is decentered. The effect on tolerance becomes sensitive and the burden on the manufacturing side increases. For this reason, in the microscope objective lens OL that does not use a cemented lens, as described above, the aberration correction performance and the effect on the eccentricity tolerance are better when the lens surface is configured so that the incident angle and the outgoing angle are not increased. There are many cases.
[0028]
For example, in a divergent light beam, a negative lens curvature can reduce the incident angle and the outgoing angle with respect to the lens surface. On the other hand, in the convergent light beam, the incident angle and the outgoing angle with respect to the lens surface can be reduced by making the lens curvature positive. For this reason, as described above, the adjacent surfaces of the pseudo cemented lenses constituting the lens group in the third lens group G3 are configured such that the curvature is negative in the divergent light beam and the curvature is positive in the convergent light beam. Accordingly, the incident angle and the emission angle of the light beam transmitted through the lenses constituting the second to fourth lens groups G2 to G4 can be suppressed to 50 degrees or less, and the effect on the eccentricity tolerance can be relaxed.
[0029]
In order to configure the third lens group G3 as described above, the third lens group G3 is configured when the divergent light beam emitted from the second lens group G2 is converted into convergent light by the third lens group G3. The lens is configured to gradually convert with the lens. For this reason, the concave lens constituting the third lens group G3 satisfies the conditional expression (3), and a lens set is disposed on each of the object side and the image side across the lens having the maximum effective diameter of the third lens group G3. The lens having the maximum effective diameter is configured to have a divergent light beam on the object side and the convergent light beam on the image side, and the lens having the maximum effective diameter is configured to maximize the light beam. As described above, the curvature of the adjacent surface of the lens set composed of the pseudo-junction lens disposed on the object side from the lens having the maximum effective diameter through which the light beam, which is a divergent light beam, is transmitted is made negative, and the convergent light beam is approximately The curvature of the adjacent surface of the lens set composed of the pseudo cemented lens arranged on the image side from the lens having the maximum effective diameter through which the light ray passes is positive.
[0030]
At this time, in the third lens group G3, since the adjacent surface of the lens set disposed on the object side from the lens having the maximum effective diameter has a negative curvature, the two lenses constituting the lens set are arranged on the object side. The adjacent surface of the arranged lens has a positive refractive power, and the adjacent surface of the lens arranged on the image side has a negative refractive power. Therefore, it is more convenient for the lens group disposed on the object side than the lens having the maximum effective diameter to be a pseudo-junction lens in which a lens having a positive refractive power and a lens having a negative refractive power are sequentially disposed from the object side. Is good. Similarly, since the adjacent surface of the lens set disposed on the image side of the lens having the maximum effective diameter has a positive curvature, the adjacent surface of the lens disposed on the object side among the two lenses constituting the lens set. Has a negative refractive power, and the adjacent surface of the lens disposed on the image side has a positive refractive power. Therefore, it is more convenient for the lens group arranged on the image side than the lens having the maximum effective diameter to be a pseudo-junction lens in which a lens having a negative refractive power and a lens having a positive refractive power are sequentially arranged from the object side. Is good.
[0031]
In an optical system that requires achromaticity, achromaticity is achieved by combining the lenses having positive and negative refractive powers that satisfy the conditional expression (1) with a moderately strong refractive power. Therefore, when the arrangement of the two lenses having positive and negative refractive powers constituting the lens group in the third lens group G3 is configured as described above, a lens group using a biconvex lens or a biconcave lens is configured. Therefore, it is easy to increase the refractive power. On the other hand, although it is possible to configure the third lens group G3 by reversing the arrangement of the lenses having positive and negative refractive powers constituting the lens set, the object side of the lens having the maximum effective diameter as described above. When the adjacent surface of the lens set arranged in the lens has a negative curvature and the adjacent surface of the lens set arranged on the image side from the lens having the maximum effective diameter has a positive curvature, two lenses constituting the lens set Both need to be composed of meniscus lenses, which may make it difficult to increase the refractive power of the lens.
[0032]
From the viewpoint of achromaticity, in general, in a cemented lens, a three-piece cemented lens contributes to an improvement in secondary dispersion than a two-piece cemented lens. Therefore, the third lens group G3 includes three lenses having positive, negative, positive and negative refractive powers, and the three lenses satisfy the conditional expression (2). It is preferable to configure as described above. At this time, when a pseudo-joint lens including three lenses is used, there are cases where the concave lens has a biconcave lens whose curvature is reversed between the object side and the image side. In this case as well, if the configuration satisfying the conditional expression (3) is satisfied, the incident angle and the emission angle of the light beam transmitted through the concave lens can be reduced as much as possible, and the effect on the eccentricity tolerance can be suppressed.
[0033]
If a small number of lenses in the lens system have a large refractive power, the lens having the large refractive power often has a large effect on the eccentricity tolerance, and the effect on the eccentricity tolerance is relaxed. From this point of view, it is a configuration to avoid. However, on the other hand, if a lens having a large refractive power is disposed at an appropriate place, it may be advantageous in correcting aberrations. For this reason, when the third lens group G3 is configured to satisfy the following conditional expressions (4) and (5), both the aberration correction performance and the effect on the eccentricity tolerance are good and the balance is good. It can be a lens system. Conversely, if the conditions expressed by the conditional expressions (4) and (5) are exceeded, the effect on the eccentricity tolerance becomes severe, and the burden on the manufacturing surface increases, making it difficult to achieve performance as designed. .
[0034]
[Expression 2]
Amax / Amin <2 (4)
Bmax / Bmin <2 (5)
However,
Amax: maximum value of the ratio (f / D) of the focal length (f) to the effective diameter (D) of the lens having positive refractive power in the third lens group G3
Amin: the minimum value of the ratio (f / D) of the focal length (f) to the effective diameter (D) of the lens having positive refractive power in the third lens group G3
Bmax: Maximum value of the ratio (f / D) of the focal length (f) to the effective diameter (D) of the lens having negative refractive power in the third lens group G3
Bmin: Minimum value of the ratio (f / D) of the focal length (f) to the effective diameter (D) of the lens having negative refractive power in the third lens group G3
[0035]
For the same reason, by limiting the focal length of the convex lens constituting the third lens group G3 and dispersing the positive refractive power so as to satisfy the following conditional expression (6), the positive refractive power is dispersed. It is possible to reduce the effect and to prevent the aberration correction performance from being adversely affected.
[0036]
[Equation 3]
f3P / fall> 6 (6)
However,
f3P: focal length of the convex lens in the third lens group G3
fall: the overall focal length of the microscope objective lens OL
[0037]
In addition, if the on-axis achromatization of a specific single wavelength ray and observation light in the visible region or infrared region is realized, an automatic focusing mechanism using this single wavelength can be realized without offsetting the focus. This is advantageous in construction.
[0038]
By configuring the microscope objective lens OL according to the present invention so as to satisfy the various conditions as described above, even with a single lens configuration that does not use a cemented lens, aberration correction performance and effects on eccentricity tolerance are good. It is possible to obtain a microscope objective lens OL that is intended to be used in the deep ultraviolet wavelength region with a numerical aperture of about 0.9 at a high magnification (about 40 times or more).
[0039]
【Example】
Specific examples of the microscope objective lens according to the present invention will be described below. The three examples shown below correspond to the microscope objective lenses OL according to the first to third embodiments described above, and accordingly, lens configuration diagrams for the first to third embodiments (FIG. 1, 3 and 5) respectively show the lens configurations of the first to third embodiments below.
[0040]
(First embodiment)
Table 1 below shows the specifications of each lens in the first example. Surface numbers 1 to 39 in Table 1 relate to the microscope objective lens OL according to the first example, and correspond to reference numerals 1 to 39 in FIG. Further, “fall” in Table 1 indicates the focal length of the microscope objective lens OL, N.P. A. Is the numerical aperture, β is the magnification, r is the radius of curvature of the lens, d is the distance between the lens surfaces, ν is the Abbe number, and n is the refractive index with respect to the reference ray (248 nm). The same applies to the embodiments. In addition, unless otherwise specified, “mm” is generally used as the unit of length for the focal length fall, the radius of curvature r, the surface interval d, and other lengths listed in all the following specification values. Since equivalent optical performance can be obtained even when proportional expansion or reduction is performed, the unit is not limited to “mm”, and other appropriate units can be used.
[0041]
[Table 1]
fall = 2
N. A. = 0.9
β = −200
Surface number r d v n Lens code
1 ∞ 0.4876 1.000000
(First lens group G1)
2 -2.1033 1.7000 67.85 1.508584 L1
3 -1.7214 0.1000 1.000000
(Second lens group G2)
4 -4.5730 2.7000 95.25 1.468023 L2
5 -3.5517 0.1000 1.000000
(Third lens group G3)
6 23.4773 2.9500 95.25 1.468023 L3
7 -7.4574 0.4500 1.000000
8 -6.4520 1.0000 67.85 1.508584 L4
9 -33.5010 0.1000 1.000000
10 22.8970 3.2000 95.25 1.468023 L5
11 -10.6020 0.5500 1.000000
12 -8.6180 1.0000 67.85 1.508584 L6
13 -58.6520 0.1000 1.000000
14 23.8490 3.3500 95.25 1.468023 L7
15 -14.2404 0.7500 1.000000
16 -10.3350 1.0000 67.85 1.508584 L8
17 -100.7110 0.2000 1.000000
18 21.8499 3.8000 95.25 1.468023 L9
19 -18.1930 0.1000 1.000000
20 -20.1220 1.0000 67.85 1.508584 L10
21 24.2950 0.1000 1.000000
22 20.2670 3.7500 95.25 1.468023 L11
23 -18.7508 0.2000 1.000000
24 -51.5030 1.0000 67.85 1.508584 L12
25 13.0412 0.7500 1.000000
26 18.9700 3.6000 95.25 1.468023 L13
27 -18.9700 0.2000 1.000000
28 1155.1500 1.0000 67.85 1.508584 L14
29 10.5790 0.8000 1.000000
30 15.2012 3.6500 95.25 1.468023 L15
31 -17.6690 0.2000 1.000000
32 75.7050 1.0000 67.85 1.508584 L16
33 8.8814 0.8500 1.000000
34 13.2500 2.9500 95.25 1.468023 L17
35 -32.1830 14.1000 1.000000
(Fourth lens group G4)
36 3.7930 2.9500 95.25 1.468023 L18
37 3.8157 1.4000 1.000000
38 -4.6607 1.0000 67.85 1.508584 L19
39 11.5020 1.000000
(Conditional value)
(1) Between L3 and L4 ν3P = 95.25, ν3N = 67.85
Between L5 and L6 ν3P = 95.25, ν3N = 67.85
Between L7 and L8 ν3P = 95.25, ν3N = 67.85
Between L9 and L10 ν3P = 95.25, ν3N = 67.85
Between L12 and L13 ν3P = 95.25, ν3N = 67.85
Between L14 and L15 ν3P = 95.25, ν3N = 67.85
Between L16 and L17 ν3P = 95.25, ν3N = 67.85
(2) 2 × dmin = 2
Between L3 and L4 dcenter + dedge = 0.67
Between L5 and L6 dcenter + dedge = 0.76
Between L7 and L8 dcenter + dedge = 0.97
Between L9 and L10 dcenter + dedge = 0.33
Between L10-L11 dcenter + dedge = 0.41
Between L12-L13 dcenter + dedge = 0.97
Between L14-L15 dcenter + dedge = 1.02
Between L16 and L17 dcenter + dedge = 1.08
(3) | r1a | <| r2a |
L4 | r1a | = 6.4520, | r2a | = 33.5010
L6 | r1a | = 8.6180, | r2a | = 58.6520
L8 | r1a | = 10.3350, | r2a | = 100.7110
L10 | r1a | = 20.1220, | r2a | = 24.2950
| R1b |> | r2b |
L12 | r1b | = 51.5030, | r2b | = 13.0412
L14 | r1b | = 1155.1500, | r2b | = 10.5790
L16 | r1b | = 75.7050, | r2b | = 8.8814
(4) Amax / Amin = 1.282
(5) Bmax / Bmin = 1.266
(6) L3 f3P / fall = 6.22461485
L5 f3P / fall = 7.98066755
L7 f3P / fall = 9.81654003
L9 f3P / fall = 10.954441636
L11 f3P / fall = 10.75178399
L13 f3P / fall = 10.466638433
L15 f3P / fall = 9.06483122
L17 f3P / fall = 10.25591075
[0042]
Thus, in the first embodiment, it can be seen that all the conditional expressions (1) to (6) are satisfied. Moreover, since 1/6 of the total length of the objective lens is 10.69 and the distance between the third lens group G3 and the fourth lens group G4 is 14.10, the condition regarding the distance between G3 and G4 is also satisfied.
[0043]
FIG. 2 is a diagram showing various aberrations in the first example. In each graph, NA is the numerical aperture, y is the image height, L is a light beam of 248 nm, K is a light beam of 251 nm, and M is a light beam of 245 nm. In astigmatism, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The explanation of the above aberration diagrams is the same in the other examples.
[0044]
As is apparent from the above aberration diagrams, it can be seen that various aberrations are satisfactorily corrected in this example.
[0045]
(Second embodiment)
Table 2 below shows the specifications of each lens in the second example. Surface numbers 1 to 39 in Table 2 relate to the microscope objective lens OL according to the second embodiment, and correspond to reference numerals 1 to 39 in FIG.
[0046]
[Table 2]
fall = 2
N. A. = 0.9
β = −200
Surface number r d v n Lens code
1 ∞ 0.4784 1.000000
(First lens group G1)
2 -2.1033 1.7000 67.85 1.508584 L21
3 -1.6640 0.1000 1.000000
(Second lens group G2)
4 -4.0700 2.6000 95.25 1.468023 L22
5 -3.5517 0.1000 1.000000
(Third lens group G3)
6 26.0490 2.9500 95.25 1.468023 L23
7 -7.2001 0.4500 1.000000
8 -6.2570 1.0000 67.85 1.508584 L24
9 -22.4990 0.1000 1.000000
10 23.6960 3.1500 95.25 1.468023 L25
11 -10.5790 0.5000 1.000000
12 -8.6622 1.0000 67.85 1.508584 L26
13 -56.0280 0.1000 1.000000
14 27.6070 3.3000 95.25 1.468023 L27
15 -13.4200 0.6500 1.000000
16 -10.3350 1.0000 67.85 1.508584 L28
17 -94.4360 0.2000 1.000000
18 21.7880 3.7500 95.25 1.468023 L29
19 -18.4480 0.1000 1.000000
20 -20.9940 1.0000 67.85 1.508584 L30
21 24.3510 0.1500 1.000000
22 19.1698 3.7500 95.25 1.468023 L31
23 -19.1698 0.2000 1.000000
24 -62.0990 1.0000 67.85 1.508584 L32
25 12.4310 0.8000 1.000000
26 19.5970 3.4000 95.25 1.468023 L33
27 -21.0450 0.1500 1.000000
28 394.9230 1.0000 67.85 1.508584 L34
29 10.4840 0.9500 1.000000
30 17.2013 3.7000 95.25 1.468023 L35
31 -14.1957 0.2500 1.000000
32 98.4990 1.0000 67.85 1.508584 L36
33 8.7014 0.8500 1.000000
34 13.0047 2.7500 95.25 1.468023 L37
35 -36.8830 14.4500 1.000000
(Fourth lens group G4)
36 3.8060 2.5000 95.25 1.468023 L38
37 4.8905 1.4500 1.000000
38 -6.1030 1.3500 67.85 1.508584 L39
39 6.1030 1.000000
(Conditional value)
(1) Between L23 and L24 ν3P = 95.25, ν3N = 67.85
Between L25 and L26 ν3P = 95.25, ν3N = 67.85
Between L27 and L28 ν3P = 95.25, ν3N = 67.85
Between L29 and L30 ν3P = 95.25, ν3N = 67.85
Between L32 and L33 ν3P = 95.25, ν3N = 67.85
Between L34 and L35 ν3P = 95.25, ν3N = 67.85
Between L36 and L37 ν3P = 95.25, ν3N = 67.85
(2) 2 × dmin = 2
Between L23 and L24 dcenter + dedge = 0.66
Between L25 and L26 dcenter + dedge = 0.67
Between L27 and L28 dcenter + dedge = 0.86
L29-L30 dcenter + dedge = 0.36
Between L30 and L31 dcenter + dedge = 0.53
Between L32 and L33 dcenter + dedge = 0.98
Between L34 and L35 dcenter + dedge = 1.18
Between L36 and L37 dcenter + dedge = 1.09
(3) | r1a | <| r2a |
L24 | r1a | = 6.2570, | r2a | = 22.4990
L26 | r1a | = 8.6622, | r2a | = 56.0280
L28 | r1a | = 10.3350, | r2a | = 94.4360
L30 | r1a | = 20.9940, | r2a | = 24.3510
| R1b |> | r2b |
L32 | r1b | = 62.0990, | r2b | = 12.4310
L34 | r1b | = 394.9230, | r2b | = 10.4840
L36 | r1b | = 98.4990, | r2b | = 8.7014
(4) Amax / Amin = 1.382
(5) Bmax / Bmin = 1.350
(6) L23 f3P / fall = 6.161777538
L25 f3P / fall = 7.999752212
L27 f3P / fall = 9.833736090
L29 f3P / fall = 10.92814039
L31 f3P / fall = 10.50123383
L33 f3P / fall = 11.06619317
L35 f3P / fall = 8.57739736
L37 f3P / fall = 10.38790069
[0047]
Thus, in the second embodiment, it can be seen that all the conditional expressions (1) to (6) are satisfied. Further, since 1/6 of the total length of the objective lens is 10.65 and the distance between the third lens group G3 and the fourth lens group G4 is 14.45, the condition regarding the distance between G3 and G4 is also satisfied.
[0048]
FIG. 4 shows various aberration diagrams in the second example. As is apparent from the above aberration diagrams, it can be seen that various aberrations are satisfactorily corrected in this example.
[0049]
(Third embodiment)
Table 3 below shows the specifications of each lens in the third example. Surface numbers 1 to 37 in Table 3 relate to the microscope objective lens OL according to the third example, and correspond to reference numerals 1 to 37 in FIG.
[0050]
[Table 3]
fall = 2
N. A. = 0.9
β = −200
Surface number r d v n Lens code
1 ∞ 0.5200 1.000000
(First lens group G1)
2 -1.8620 2.0000 67.85 1.508584 L41
3 -1.9013 0.1250 1.000000
(Second lens group G2)
4 -6.2503 2.3800 95.25 1.468023 L42
5 -3.6261 0.1700 1.000000
(Third lens group G3)
6 22.8989 2.5000 95.25 1.468023 L43
7 -10.0801 0.9850 1.000000
8 -5.8820 1.0000 67.85 1.508584 L44
9 100.7110 0.4600 1.000000
10 -91.1160 3.1000 95.25 1.468023 L45
11 -8.6002 0.2000 1.000000
12 90.0270 3.3000 95.25 1.468023 L46
13 -11.0820 0.2000 1.000000
14 -10.9770 1.0000 67.85 1.508584 L47
15 18.3330 0.2000 1.000000
16 18.7508 3.4000 95.25 1.468023 L48
17 -32.4720 0.2000 1.000000
18 46.7670 3.8000 95.25 1.468023 L49
19 -14.4530 0.2000 1.000000
20 -15.0000 1.0000 67.85 1.508584 L50
21 16.5999 0.2000 1.000000
22 16.8960 3.8000 95.25 1.468023 L51
23 -31.3570 0.2000 1.000000
24 24.3002 3.6500 95.25 1.468023 L52
25 -19.9960 0.2000 1.000000
26 -21.9530 1.0000 67.85 1.508584 L53
27 10.8997 1.3750 1.000000
28 29.1610 3.6000 95.25 1.468023 L54
29 -13.2998 0.1000 1.000000
30 156.8810 1.0000 67.85 1.508584 L55
31 8.7310 0.9200 1.000000
32 14.0305 2.7500 95.25 1.468023 L56
33 -28.2500 12.9600 1.000000
(Fourth lens group G4)
34 3.7092 2.0000 95.25 1.468023 L57
35 3.7450 1.5050 1.000000
36 -6.0906 2.0000 67.85 1.508584 L58
37 9.1997 1.000000
(Conditional value)
(1) Between L43 and L44 ν3P = 95.25, ν3N = 67.85
Between L44 and L45 ν3P = 95.25, ν3N = 67.85
Between L46 and L47 ν3P = 95.25, ν3N = 67.85
Between L47 and L48 ν3P = 95.25, ν3N = 67.85
Between L49 and L50 ν3P = 95.25, ν3N = 67.85
Between L50 and L51 ν3P = 95.25, ν3N = 67.85
Between L52 and L53 ν3P = 95.25, ν3N = 67.85
Between L53 and L54 ν3P = 95.25, ν3N = 67.85
Between L55 and L56 ν3P = 95.25, ν3N = 67.85
(2) 2 × dmin = 2
Between L43 and L44 dcenter + dedge = 1.18
Between L44 and L45 dcenter + dedge = 0.66
Between L46 and L47 dcenter + dedge = 0.40
Between L47 and L48 dcenter + dedge = 0.40
Between L49 and L50 dcenter + dedge = 0.51
Between L50-L51 dcenter + dedge = 0.40
Between L52 and L53 dcenter + dedge = 0.55
Between L53 and L54 dcenter + dedge = 1.58
Between L55 and L56 dcenter + dedge = 1.12
(3) | r1a | <| r2a |
L44 | r1a | = 5.8820, | r2a | = 100.7110
L47 | r1a | = 10.9770, | r2a | = 18.3330
L50 | r1a | = 15.00000, | r2a | = 16.5999
| R1b |> | r2b |
L53 | r1b | = 21.9530, | r2b | = 10.8997
L55 | r1b | = 156.8810, | r2b | = 8.7310
(4) Amax / Amin = 1.195
(5) Bmax / Bmin = 1.606
(6) L43 f3P / fall = 7.61713038
L45 f3P / fall = 9.965597684
L46 f3P / fall = 10.558932679
L48 f3P / fall = 12.88961552
L49 f3P / fall = 11.962214865
L51 f3P / fall = 11.996083960
L52 f3P / fall = 11.996338938
L54 f3P / fall = 9.996956614
L56 f3P / fall = 10.116661318
[0051]
Thus, in the third embodiment, it can be seen that all the conditional expressions (1) to (6) are satisfied. Moreover, since 1/6 of the total length of the objective lens is 10.67 and the distance between the third lens group G3 and the fourth lens group G4 is 12.96, the condition regarding the distance between G3 and G4 is also satisfied.
[0052]
FIG. 6 shows various aberration diagrams in the third example. As is apparent from the above aberration diagrams, it can be seen that various aberrations are satisfactorily corrected in this example. In any of the first to third embodiments, axial achromaticity is also applied to the light beam (770 nm) used for the automatic focusing mechanism or the like.
[0053]
Since the microscope objective lens shown in the first to third embodiments is an infinity correction type, for example, it is used together with the imaging lens IL shown in FIG. The imaging lens IL includes, in order from the object side, a cemented lens of a biconvex lens L61 and a biconcave lens L62, a negative meniscus lens L63 having a concave surface facing the object side, and a positive meniscus lens L64 having a concave surface facing the object side. It consists of a cemented lens. Table 4 below shows the specifications of each lens constituting the imaging lens IL. Note that surface numbers 1 to 6 in Table 4 relate to the imaging lens IL, and correspond to reference numerals 1 to 6 in FIG.
[0054]
[Table 4]

[0055]
【The invention's effect】
As is clear from the above description, according to the microscope objective lens according to the present invention, the performance of aberration correction and the effect on the eccentricity tolerance can be improved even with a single lens configuration that does not use a cemented lens. A microscope objective lens intended to be used in the deep ultraviolet wavelength region can be obtained with a numerical aperture of about 0.9 at a high magnification (about 40 times or more).
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a microscope objective lens according to a first embodiment of the present invention.
FIG. 2 is a diagram showing various aberrations of the microscope objective lens according to the first example of the present invention.
FIG. 3 is a cross-sectional view showing a configuration of a microscope objective lens according to a second example of the present invention.
FIG. 4 is a diagram illustrating all aberrations of the microscope objective lens according to the second example of the present invention.
FIG. 5 is a cross-sectional view showing a configuration of a microscope objective lens according to a third example of the present invention.
FIG. 6 is a diagram of various aberrations of the microscope objective lens according to the third example of the present invention.
FIG. 7 is a cross-sectional view showing a configuration of an imaging lens used in combination with the microscope objective lens according to the present invention.
[Explanation of symbols]
OL microscope objective lens
G1 first lens group
G2 second lens group
G3 Third lens group
G4 4th lens group

Claims (8)

All adjacent lenses are arranged with an air gap, and the configuration of the lenses in order from the object side,
A first lens group having a meniscus lens having a positive refractive power with a concave surface facing the object side;
A second lens group comprising one lens having positive refractive power;
When the two adjacent lenses have positive and negative refractive powers, and the adjacent two lenses having the same sign of the radius of curvature of the adjacent surfaces are used as one lens set, the lens A third lens group having at least five or more groups, and having a positive refractive power as a whole;
A fourth lens group having negative refractive power as a whole,
When the Abbe number of a lens having a positive refractive power among the two lenses constituting the lens group in the third lens group is ν3P and the Abbe number of a lens having a negative refractive power is ν3N,
ν3P> ν3N (1)
Satisfying the condition represented by
Of the lenses constituting the third lens group, the center thickness of the thinnest lens is dmin, the distance between adjacent lenses of the two lenses constituting the lens set is dcenter, and the edge air distance is dedge. Then, the following formula 2 × dmin> dcenter + dedge (2)
Satisfying the condition represented by
Of the lenses constituting the third lens group, the radius of curvature of the object side of each concave lens arranged in the section from the lens closest to the object side to the lens having the maximum effective diameter is r1a, and the radius of curvature of the image side is r2a. and then, the maximum effective diameter of a lens having an object side of each of the concave lens disposed in a section leading to the fourth lens group curvature radius r1b, when the curvature radius of the image side and r2b, the respective concave lens All are expressed by the following expression: | r1a | <| r2a |, | r1b |> | r2b | (3)
Satisfying the condition represented by
The third lens group and the fourth lens group are separated from each other by an air interval of 1/6 or more of the total lens length (distance from the object surface to the final surface of the objective lens) or the same focal length, whichever is shorter. An objective lens for a microscope characterized by being arranged. In the third lens group,
The lens set is arranged on the object side and the image side across the lens having the maximum effective diameter,
Closest surface from the object side of the lens the maximum effective diameter is arranged in a section that leads to a lens having two constituting the lens module lens is constituted by a surface having a negative radius of curvature,
Adjacent surfaces of the two lenses constituting the lens group which is arranged in a section leading to the fourth lens group from the lens having the largest effective diameter is characterized in that it is constituted by a surface having a positive radius of curvature The microscope objective lens according to claim 1. In the third lens group,
The lens set arranged in the section from the lens closest to the object side to the lens having the maximum effective diameter is composed of lenses having a positive refractive power on the object side,
3. The microscope according to claim 2, wherein the lens group disposed in a section from the lens having the maximum effective diameter to the fourth lens group includes a lens having negative refractive power on the object side. Objective lens. The third lens group has at least one lens group composed of three lenses having positive, negative, positive and negative refractive powers, and is formed by combining two adjacent lenses among the three lenses. The objective lens for a microscope according to any one of claims 1 to 3 , wherein the two sets of lenses satisfy the condition represented by the formula (2) according to claim 1.   The principal ray of the luminous flux emitted from the point intersecting the optical axis on the object plane and the ray with the maximum numerical aperture, and the principal ray of the luminous flux emitted from the maximum object height on the object plane and the ray of the maximum numerical aperture in the upper and lower coma rays. 5. The microscope objective lens according to claim 1, wherein an incident angle and an emission angle when passing through the second to fourth lens groups are 50 degrees or less. When the maximum value of the ratio of the focal length to the effective diameter of a lens having positive refractive power among the lenses constituting the third lens group is Amax and the minimum value is Amin,
Amax / Amin <2 (4)
The objective lens for microscopes according to any one of claims 1 to 5, satisfying a condition expressed by: When the maximum value of the ratio of the focal length to the effective diameter of a lens having negative refractive power among the lenses constituting the third lens group is Bmax and the minimum value is Bmin,
Bmax / Bmin <2 (5)
The objective lens for microscopes according to any one of claims 1 to 6, satisfying a condition expressed by: When the focal length of the convex lens in the third lens group is f3P and the total focal length of the first to fourth lens groups is fall,
f3P / fall> 6 (6)
The objective lens for microscopes according to any one of claims 1 to 7, satisfying a condition expressed by:

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