JP2004184826A - Objective lens for immersion microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apochromat class objective lens for an immersion microscope whose numerical aperture attains about 1.2, and which hardly causes distortion of an image surface and has an intermediate magnification (about 50). <P>SOLUTION: The objective lens OL for the immersion microscope is constituted of a 1st lens group G1, a 2nd lens group G2, a 3rd lens group G3 having a positive refractive power as a whole, a 4th lens group G4 having a positive refractive power as a whole, a 5th lens group G5, a 6th lens group G6, a 7th lens group G7 and an 8th lens group G8 in this order from the object side, and is constituted to satisfy the following conditional expressions (1), (2) and (3) respectively. In the respective conditional expressions, (1) is ¾r<SB>112</SB>¾<2*d<SB>11</SB>, (2) is n<SB>1i</SB>>1.7 and (3) is ν<SB>2P</SB>>65, ν<SB>3P</SB>>65, ν<SB>4P</SB>>65, ν<SB>5P</SB>>65 and ν<SB>6P</SB>>65. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

（条件対応値）
（１）｜ｒ_１１２｜＝１．４４２
（２）ｎ_１ｉ＝１．７５５０００
（３）ν_２Ｐ＝８２．５１６
ν_３Ｐ＝８２．５１６
ν_４Ｐ＝７１．３１２， ９５．２４７
ν_５Ｐ＝９５．２４７
ν_６Ｐ＝９５．２４７
【００３６】
このように第１実施例では、作動距離Ｗ．Ｄ．が０．２７ｍｍと長くすることができ、また、上記条件式（１）〜（３）は全て満たされていることが分かる。
【００３７】
図２〜６は、第１実施例において、補正環を調整したときのレンズ間隔のポジションＰＯＳ１〜５に対応した諸収差図を表している。各収差図において、ＮＡは開口数を、ｙは像高を示しており、また、ｄはｄ線（５８７．６ｎｍ）の光線を、ＣはＣ線（６５６．３ｎｍ）の光線を、ＦはＦ線（４８６．１ｎｍ）の光線を、ｇはｇ線（４３５．８ｎｍ）の光線をそれぞれ示している。また、非点収差では、実線はサジタル像面を示し、破線はメリジオナル像面を示している。以上の収差図の説明は、他の実施例においても同様である。
【００３８】
以上の各収差図から明らかなように、本実施例では補正環の効果により各ポジションとも諸収差が良好に補正されていることが分かる。
【００３９】
（第２実施例）
下の表２に、本第２実施例における各レンズの諸元を示す。表２における面番号１〜２９は本第２実施例に係る水浸系顕微鏡用対物レンズＯＬに関するものであり、それぞれ図７における符号１〜２９に対応する。
【００４０】
なお、本第２実施例に係る水浸系顕微鏡用対物レンズＯＬにおいても補正環を有して構成されており、補正環使用時のレンズ間隔について、ｄ２はカバーガラスの厚さを、ｄ３はカバーガラスのレンズ側の面（面番号３）から第１レンズ群Ｇ１を構成するレンズＬ２１の物体側の面（面番号４）までの光軸上の距離を、ｄ８は第２レンズ群Ｇ２を構成するレンズＬ２３の物体側の面（面番号８）から第３レンズ群Ｇ３を構成するレンズＬ２４の物体側の面（面番号９）までの光軸上の距離を、ｄ２５は第７レンズ群Ｇ７を構成するレンズＬ３５の像側の面（面番号２５）から第８レンズ群Ｇ８を構成するレンズＬ３６の物体側の面（面番号２６）までの光軸上の距離を表しており、また、それぞれに対してポジションＰＯＳ１〜５まで変化させた場合を示している。
【００４１】
【表２】
ｆ＝３．３
Ｎ．Ａ．＝１．２
β＝−６０
Ｗ．Ｄ．＝０．２７

（条件対応値）
（１）｜ｒ_１１２｜＝１．４４２
（２）ｎ_１ｉ＝１．７５５０００
（３）ν_２Ｐ＝８２．５１６
ν_３Ｐ＝８２．５１６
ν_４Ｐ＝７１．３１２， ９５．２４７
ν_５Ｐ＝９５．２４７
ν_６Ｐ＝９５．２４７
【００４２】このように第２実施例では、作動距離Ｗ．Ｄ．が０．２７ｍｍと長くすることができ、また、上記条件式（１）〜（３）は全て満たされていることが分かる。
【００４３】図８〜１２は、第２実施例において、補正環を調整したときのレンズ間隔ＰＯＳ１〜５に対応した諸収差図を表している。以上の各収差図から明らかなように、本実施例では補正環の効果により各ポジションとも諸収差が良好に補正されていることが分かる。
【００４４】
なお、上述の第１及び２の実施例においては、蛍光観察用途として使用可能なレンズの硝材選択を行っている。また、第１及び２の実施例共に、周辺光量を多く取り入れても収差を良好に補正している。本第１及び２の実施例においては、最大像高の７割程度の画角で中心画角の９５％程度の光量を入れても収差の補正は良好である。
【００４５】
以上に説明した水浸系顕微鏡用対物レンズＯＬは、無限遠補正型であるため、例えば、図１３に示す結像レンズＩＬとともに使用される。この結像レンズＩＬは、物体側から順に両凸レンズＬ４１と両凹レンズＬ４２との接合レンズと、両凸レンズＬ４３と両凹レンズＬ４４との接合レンズとから構成される。この結像レンズＩＬを構成する各レンズの諸元を下の表３に示す。なお、表３における面番号１〜６は結像レンズＩＬに関するものであり、それぞれ図１３における符号１〜６に対応する。
【００４６】
【表３】

【００４７】
【発明の効果】
以上の説明から明らかなように、本発明に係る水浸系顕微鏡用対物レンズによれば、開口数が１．２に達し、倍率が５０倍程度で、像面歪曲の少ないアポクロマート級の水浸系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の実施例に係る水浸系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の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ１にあるときの諸収差図である。
【図３】本発明の第１の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ２にあるときの諸収差図である。
【図４】本発明の第１の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ３にあるときの諸収差図である。
【図５】本発明の第１の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ４にあるときの諸収差図である。
【図６】本発明の第１の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ５にあるときの諸収差図である。
【図７】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズの構成を示す断面図である。
【図８】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ１にあるときの諸収差図である。
【図９】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ２にあるときの諸収差図である。
【図１０】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ３にあるときの諸収差図である。
【図１１】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ４にあるときの諸収差図である。
【図１２】本発明の第２の実施例に係る水浸系顕微鏡用対物レンズにおいて補正環がＰＯＳ５にあるときの諸収差図である。
【図１３】本発明に係る水浸系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 水浸系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
Ｇ５ 第５レンズ群
Ｇ６ 第６レンズ群
Ｇ７ 第７レンズ群
Ｇ８ 第８レンズ群[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apochromat-class objective lens for a water immersion microscope having a medium magnification (about 50 times) and a numerical aperture of about 1.2.
[0002]
[Prior art]
As an apochromat-class microscope objective lens having a magnification of about 50 times, for example, one disclosed in Patent Document 1 is known.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 10-330444
[Problems to be solved by the invention]
By the way, the lens disclosed in Patent Literature 1 is a lens that realizes apochromat-class achromatization with a relatively small number of lenses, but has a slightly smaller numerical aperture of 1.15, and has some dissatisfaction with the resolution. There is a problem that the lens configuration is designed to have a relatively large image field distortion.
[0005]
The present invention has been made in view of the above-described problems, and is an apochromat-class water of a medium magnification (about 50 times), which is a water immersion system, has a numerical aperture of about 1.2, and has a small image surface distortion. An object of the present invention is to provide an immersion microscope objective lens.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, an objective lens for a water immersion microscope according to the present invention includes, in order from the object side, a plano-convex lens having a flat surface facing the object side and a meniscus having a positive refractive power having a concave surface facing the object side. A first lens group having a cemented lens in which the lenses are cemented, a second lens group consisting of one lens having a positive refractive power, a lens having a negative refractive power, and having a positive refractive power A third lens group having a cemented lens having a positive refractive power as a whole by bonding the lenses, a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power And a cemented lens in which a lens having a negative refractive power and a lens having a positive refractive power are cemented. Fifth lens group, and at least A sixth lens group having a cemented lens in which two lenses of a lens having a positive refractive power and a lens having a negative refractive power are cemented; and a lens having at least a positive refractive power and a negative refractive power. A seventh lens group having a cemented meniscus lens having two lenses cemented and having a strong concave surface facing the image side, and a lens having at least a positive refractive power and a lens having a negative refractive power. And an eighth lens group having a cemented meniscus lens having two lenses cemented and having a strong concave surface facing the object side. Then, one of the cemented surfaces of the cemented lens including the three lenses constituting the fourth lens group has a positive refractive power, and the other surface has a negative refractive power. Furthermore, when the radius of curvature of the cemented surface of the cemented lens forming the first lens group is r _112, and the distance on the optical axis from the object to the cemented surface of the cemented lens constituting the first lens group is d ₁₁ , Assuming that the condition represented by the expression | r ₁₁₂ | <2 * d ₁₁ is satisfied and the refractive index of the lens located on the image side among the lenses constituting the first lens group is n _1i , the expression n _1i > 1 .7 are satisfied, the Abbe number of the lens having a positive refractive power in the second lens group is ν _2P, and the Abbe number of the lens having a positive refractive power in the third lens group is ν. _3P , the Abbe number of the lens having a positive refractive power in the fourth lens group is ν _4P , the Abbe number of the lens having a positive refractive power in the fifth lens group is ν _5P, and the when of the Abbe number of the positive lens having a refractive power and [nu _6P, wherein [nu _It is configured to satisfy the conditions represented by _2P > 65, _ν3P > 65, _ν4P > 65, _ν5P > 65, _ν6P > 65.
[0007]
The objective lens for a water immersion microscope according to the present invention transmits at least 30% of ultraviolet light of about 365 nm as excitation light for fluorescence observation, and observes weak fluorescence emitted from a sample by this excitation light. It is preferable that the glass materials of the lenses constituting the first to eighth lens groups are selected and arranged so that the fluorescence emitted from the lenses constituting the first to eighth lens groups by the excitation light does not adversely affect the observation.
[0008]
Further, it is preferable that at least one lens group among the first to eighth lens groups moves along the optical axis to correct an aberration generated due to a difference in cover glass thickness.
[0009]
In addition, it is preferable that the cemented meniscus lens of both or any one of the seventh lens unit and the eighth lens unit is configured by joining three lenses.
[0010]
Further, it is preferable that the first to eighth lens groups are configured to have a light amount of 90% or more of the center image height and to perform aberration correction even when the image height is about 70% of the maximum image height.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 and 7 are configuration diagrams of an objective lens OL for a water immersion microscope corresponding to the first and second embodiments of the present invention, respectively. In any of the embodiments, the first lens group includes, in order from the object side, a cemented lens of a plano-convex lens having a flat surface facing the object side and a meniscus lens having a positive refractive power and having a concave surface facing the object side. G1, a second lens group G2 including one lens having a positive refractive power, and a lens having a negative refractive power and a lens having a positive refractive power are joined to have a positive refractive power as a whole. A third lens group G3 having a cemented lens, a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power are sequentially joined to have a positive refractive power as a whole. A fourth lens group G4 having a cemented lens; a fifth lens group G5 having a cemented lens in which a lens having a negative refractive power and a lens having a positive refractive power are cemented; Lens with refractive power and negative A sixth lens group G6 having a cemented lens obtained by cementing two lenses having a refractive power, and at least two lenses having a lens having a positive refractive power and a lens having a negative refractive power are cemented. A seventh lens group G7 having a cemented meniscus lens and a cemented meniscus lens having at least two lenses of a lens having a positive refractive power and a lens having a negative refractive power. And a lens group G8.
[0012]
In the objective lens OL for a water immersion microscope according to the first embodiment shown in FIG. 1, in order from the object side, the first lens group G1 has a plano-convex lens L1 having a plane facing the object side and a concave surface facing the object side. The second lens group G2 is composed of a positive meniscus lens L3 having a concave surface facing the object side, and the third lens group G3 is composed of a biconcave lens L4 and a biconvex lens L5. The fourth lens group G4 is composed of a cemented lens of a biconvex lens L6, a biconcave lens L7, and a biconvex lens L8, and the fifth lens group G5 is a negative meniscus lens L9 having a convex surface facing the object side and a biconvex lens L10. The sixth lens group G6 is a cemented lens of a positive meniscus lens L11 having a convex surface facing the object side, a biconvex lens L12, and a biconcave lens L13. The seventh lens group G7 is composed of a cemented meniscus lens composed of a biconvex lens L14, a negative meniscus lens L15 having a concave surface facing the object side, and a biconcave lens L16. The eighth lens group G8 is composed of a biconcave lens L17 and a biconvex lens L18. And a cemented meniscus lens.
[0013]
In the objective lens OL for a water immersion microscope according to the second embodiment shown in FIG. 7, the first lens group G1 has, in order from the object side, a plano-convex lens L21 having a plane facing the object side and a concave surface facing the object side. The second lens group G2 is composed of a positive meniscus lens L23 having a concave surface facing the object side, and the third lens group G3 is composed of a cemented lens of a biconcave lens L24 and a biconvex lens L25. The fourth lens group G4 includes a cemented lens of a biconvex lens L26, a biconcave lens L27, and a biconvex lens L28. The fifth lens group G5 includes a negative meniscus lens L29 having a convex surface facing the object side and a biconvex lens L30. The sixth lens group G6 includes a positive meniscus lens L31 having a convex surface facing the object side, a biconvex lens L32, and a biconcave lens L33. The seventh lens group G7 is composed of a cemented meniscus lens composed of a biconvex lens L36 and a biconcave lens L37. The eighth lens group G8 is composed of a biconcave lens L36, a biconvex lens L37, and a concave surface facing the object side. It is composed of a meniscus lens joined with the meniscus lens L38.
[0014]
Generally, in an objective lens having a large magnification of about 50 times and a high numerical aperture, such as the objective lens OL for a water immersion microscope according to the present invention, the curvature of the lens group closest to the object on the image side is non-invasive. By satisfying the condition, a positive refractive power is obtained without spherical aberration. The positive refracting power obtained by the lens having this configuration is extremely large, and is an essential configuration for efficiently obtaining magnification without aberrations.
[0015]
The first lens group G1 of the objective lens OL for a water immersion microscope according to the present invention is a cemented lens of a plano-convex lens having a flat surface facing the object side and a positive meniscus lens having a concave surface facing the object side. By setting the curvature of the surface to a non-idling condition or a condition close thereto, the configuration is such that a positive refractive power is obtained while suppressing spherical aberration. Further, by making the radius of curvature of the cemented surface of the cemented lens constituting the first lens group G1 relatively small so as to satisfy the following conditional expression (1), the Petzval sum is reduced and the field curvature is reduced. Contributes to the correction of In other words, when the radius of curvature is larger than the conditional expression (1), it becomes difficult to correct the image surface distortion. At the same time, by satisfying the following conditional expression (2), a large refractive power can be obtained without causing aberration as much as possible.
[0016]
(Equation 1)
| R ₁₁₂ | <2 * d ₁₁ (1)
n _1i > 1.7 (2)
However,
r ₁₁₂ : radius of curvature of the cemented surface of the cemented lens forming the first lens group G1 d ₁₁ : distance on the optical axis from the object to the cemented surface of the cemented lens constituting the first lens group n _1i : first lens group Refractive index of lens located on the image side among lenses constituting G1
The second lens group G2 and the third lens group G3 serve to convert the divergent light beam into a convergent light beam following the first lens group G1. However, if a lens having a positive refractive power is simply arranged, the spherical aberration is reduced. And coma aberration occurs. Of these various aberrations, for the lower coma, it is effective to perform this correction with the lens group closer to the object, but it is necessary to arrange a surface with a negative refractive power to correct the aberration. Is contrary to the role of converting a light beam into convergent light.
[0018]
In order to balance these, the second lens group G2 is a single lens having a positive power, and the third lens group G3 is a cemented lens having a cemented surface having a negative refractive power as a whole and having a positive refractive power as a whole. Lens. Thereby, while the divergent light beam is converted into a convergent light beam by the positive refractive power of the second lens group G2 and the third lens group G3 as a whole, the joining surface of the third lens group G3 having the negative refractive power allows The lower coma aberration is corrected relatively on the object side of the objective lens.
[0019]
By the way, in an objective lens such as the objective lens OL for a water immersion microscope according to the present invention, generation of high-order aberration is inevitable, and correction of this high-order aberration is achieved by balancing it. That is, the fourth lens group G4 is configured by a cemented lens of three lenses, and the three lenses are configured such that the refractive power is positive, negative, and positive in order to obtain a positive refractive power as a whole. Then, of the two bonding surfaces obtained by bonding the three lenses, one surface is configured to have a positive refractive power, and the other surface is configured to have a negative refractive power. As a result, high-order aberrations are balanced to enable aberration correction.
[0020]
Here, if the correction is performed by providing a cemented surface having a positive refractive power in another cemented lens, the number of lenses may increase in some cases. Also, among the light rays transmitted through the fourth lens group G4, the light rays having a large numerical aperture pass away from the optical axis, and therefore have an effect of correcting higher-order aberrations without having an extremely tight radius of curvature. And the burden of manufacturing is reduced. Further, when three lenses are joined, they are advantageous in terms of correcting chromatic aberration since they have excellent secondary dispersion characteristics.
[0021]
In the fifth lens group G5, among rays emitted from the fourth lens group G4, rays having a high numerical aperture pass away from the optical axis. Therefore, by using the fifth lens group G5 as a cemented lens, the spherical surface continues. The aberration is corrected, and the coma is also corrected.
[0022]
The sixth lens group G6 is a cemented lens composed of three lenses, and has a configuration advantageous for correcting chromatic aberration. The sixth lens group G6 can be composed of a cemented lens composed of two lenses. However, a cemented lens composed of three lenses is effective in improving chromatic aberration (secondary dispersion) and has two lenses. If the same effect is obtained by using a cemented lens made of a lens, the radius of curvature of the cemented surface becomes smaller, which makes production difficult and may increase the cost.
[0023]
In order to better correct chromatic aberration, lenses having a positive refractive power among the lenses constituting the second to sixth lens groups G2 to G6 are configured to satisfy the following conditional expression (3). Is preferred.
[0024]
(Equation 2)
ν _2P > 65, ν _3P > 65, ν _4P > 65, ν _5P > 65, ν _6P > 65 (3)
However,
ν _2P : Abbe number of a lens having a positive refractive power in the second lens group G2 ν _3P : Abbe number of a lens having a positive refractive power in the third lens group G3 ν _4P : in the fourth lens group G4 Abbe number ν _5P of a lens having a positive refractive power: Abbe number ν _6P of a lens having a positive refractive power in the fifth lens group G5: Abbe number of a lens having a positive refractive power in the sixth lens group G6. [0025]
The seventh lens group G7 and the eighth lens group G8 have a so-called Gaussian configuration in which concave surfaces having a small radius of curvature of the cemented meniscus lens are arranged so as to face each other. It contributes to distortion correction.
[0026]
In the seventh lens group G7 and the eighth lens group G8, the contribution to the upper coma beam is large, and particularly in the objective lens OL for a water immersion microscope according to the present invention, which is configured so that the vignetting of the peripheral light beam is reduced. The contribution is great. Therefore, for example, when the seventh lens group G7 is a cemented lens in which three lenses are cemented, the aberration correction effect on each cemented surface is expected to be more than that of an objective lens having relatively large vignette. Can be. Similarly, the eighth lens group G8 may be a cemented lens composed of three lenses, or the seventh lens group G7 and the eighth lens group G8 may be cemented lenses composed of three lenses. A similar effect can be expected.
[0027]
In the objective lens OL for a water immersion microscope according to the present invention, by moving some of the first to eighth lens groups G1 to G8 along the optical axis, so-called aberration correction due to cover glass thickness is corrected. It is possible to construct a correction ring. With a water immersion objective lens, the difference in the refractive index between the water in which the sample is immersed and the cover glass is large, and the aberration fluctuation due to the difference in the thickness of the cover glass used is large. It is more advantageous.
[0028]
Further, in the first and second embodiments according to the present invention, in any case, the moving lens group corresponding to the correction ring is the lens group after the third lens group G3. The third lens group G3 and subsequent lens groups are composed of cemented lenses as described above. Therefore, by using a cemented lens, it is possible to suppress aberrations generated by these lens groups due to movement.
[0029]
In the objective lens OL for a water immersion microscope according to the present invention, the first lens group G1 is configured to satisfy the conditional expression (2) so as to obtain a large refractive index. It is designed to be. Therefore, even if the image height is about 70% of the maximum image height, it has a light amount of 90% or more of the central image height and realizes aberration correction.
[0030]
Further, in the objective lens OL for a water immersion microscope according to the present invention, since the glass material is set in consideration of the transmittance of ultraviolet light of about 365 nm, the excitation light for fluorescence observation is transmitted by about 30% or more. In addition, fluorescence (auto-fluorescence) hardly occurs in the lens due to the excitation light, and it can be used for fluorescence observation. When such a glass material is selected, the range of selection of the lens configuration and the like is narrowed and the degree of freedom in design is limited. However, the above-described configuration enables aberration correction and the like.
[0031]
By configuring the objective lens OL for a water immersion microscope according to the present invention so as to satisfy the above-described conditions, the numerical aperture is about 1.2, the image surface distortion is small, and the medium magnification (about 50 times) is used. Apochromat-class water immersion system having a small vignetting of the peripheral angle of view, a correction of aberrations, and a transmittance of ultraviolet light (about 365 nm) required for fluorescence observation of about 30% or more. The microscope objective lens OL can be obtained.
[0032]
【Example】
Hereinafter, specific examples of the objective lens for a water immersion microscope according to the present invention will be described. The following two examples correspond to the objective lenses OL for immersion microscopes according to the above-described first and second embodiments, respectively. Therefore, the lens configuration diagrams of the first and second embodiments ( 1 and 7) show the lens configuration of the first and second embodiments below, respectively.
[0033]
(First embodiment)
Table 1 below shows data of each lens in the first example. Surface numbers 1 to 29 in Table 1 relate to the objective lens OL for a water immersion microscope according to the first embodiment, and correspond to reference numerals 1 to 29 in FIG. F in Table 1 denotes a focal length; A. Is the numerical aperture, β is the magnification, W. D. Denotes the working distance (the distance on the optical axis from the object plane to the most object-side surface of the lenses constituting the first lens group G1). Further, r is the radius of curvature of the lens, d is the distance between the lens surfaces, nd is the refractive index for the d-line, νd is the Abbe number for the d-line, and these signs are also used in other embodiments. The same is true. The focal length f, the radius of curvature r, the surface distance d, the working distance W. D. Unless otherwise specified, "mm" is generally used for other units of length, but the unit is limited to "mm" because the same optical performance can be obtained even if the optical system is enlarged or reduced proportionally. Instead, other suitable units can be used.
[0034]
The objective lens OL for a water immersion microscope according to the first embodiment is configured to have a correction ring. Regarding the lens interval when the correction ring is used, d2 is the thickness of the cover glass, and d3 is the cover. The distance on the optical axis from the lens-side surface (surface number 3) of the glass to the object-side surface (surface number 4) of the lens L1 forming the first lens group G1, and d8 forms the second lens group G2. D26 is the distance on the optical axis from the object-side surface (surface number 8) of the lens L3 to the object-side surface (surface number 9) of the lens L4 constituting the third lens group G3, and d26 is the seventh lens group G7. And the distance on the optical axis from the image-side surface (surface number 26) of the lens L16 that constitutes the second lens group G8 to the object-side surface (surface number 27) of the lens L17 that constitutes the eighth lens group G8. Shown when the position is changed from POS1 to POS5 for each There.
[0035]
[Table 1]
f = 3.3
N. A. = 1.2
β = −60
W. D. = 0.27

(Conditional value)
(1) | r ₁₁₂ | = 1.442
(2) n _1i = 1.755000
(3) ν _2P = 82.516
ν _3P = 82.516
ν _4P = 71.312, 95.247
ν _5P = 95.247
ν _6P = 95.247
[0036]
Thus, in the first embodiment, the working distance W. D. Can be made as long as 0.27 mm, and it can be seen that all of the conditional expressions (1) to (3) are satisfied.
[0037]
2 to 6 show various aberration diagrams corresponding to the lens spacing positions POS1 to POS5 when the correction ring is adjusted in the first embodiment. In each aberration diagram, NA indicates a numerical aperture, y indicates an image height, d indicates a ray of d-line (587.6 nm), C indicates a ray of C-line (656.3 nm), and F indicates a ray of C-line (656.3 nm). F indicates a light ray of 486.1 nm, and g indicates a light ray of g line (435.8 nm). In the astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. The above description of the aberration diagrams is the same in the other embodiments.
[0038]
As is clear from the above-described aberration diagrams, in this embodiment, it is understood that various aberrations are satisfactorily corrected at each position by the effect of the correction ring.
[0039]
(Second embodiment)
Table 2 below shows the data of each lens in the second example. Surface numbers 1 to 29 in Table 2 relate to the objective lens OL for a water immersion microscope according to the second embodiment, and correspond to reference numerals 1 to 29 in FIG. 7, respectively.
[0040]
The objective lens OL for a water immersion microscope according to the second embodiment is also configured to have a correction ring. Regarding the lens interval when the correction ring is used, d2 represents the thickness of the cover glass, and d3 represents the thickness of the cover glass. The distance on the optical axis from the lens-side surface (surface number 3) of the cover glass to the object-side surface (surface number 4) of the lens L21 constituting the first lens group G1, and d8 is the second lens group G2. The distance on the optical axis from the object-side surface (surface number 8) of the lens L23 to the object-side surface (surface number 9) of the lens L24 forming the third lens group G3, and d25 is the seventh lens group. The distance on the optical axis from the image-side surface (surface number 25) of the lens L35 forming the G7 to the object-side surface (surface number 26) of the lens L36 forming the eighth lens group G8 is shown. , Changed for each position POS1-5 Shows the case was.
[0041]
[Table 2]
f = 3.3
N. A. = 1.2
β = −60
W. D. = 0.27

(Conditional value)
(1) | r ₁₁₂ | = 1.442
(2) n _1i = 1.755000
(3) ν _2P = 82.516
ν _3P = 82.516
ν _4P = 71.312, 95.247
ν _5P = 95.247
ν _6P = 95.247
As described above, in the second embodiment, the working distance W. D. Can be made as long as 0.27 mm, and it can be seen that all of the conditional expressions (1) to (3) are satisfied.
FIGS. 8 to 12 show various aberration diagrams corresponding to the lens intervals POS1 to POS5 when the correction ring is adjusted in the second embodiment. As is clear from the above-described aberration diagrams, in this embodiment, it is understood that various aberrations are satisfactorily corrected at each position by the effect of the correction ring.
[0044]
In the above-described first and second embodiments, a glass material for a lens that can be used for fluorescence observation is selected. Also, in both the first and second embodiments, aberrations are satisfactorily corrected even when a large amount of peripheral light is introduced. In the first and second embodiments, aberration correction is good even when a light amount of about 95% of the central angle of view is applied at an angle of view of about 70% of the maximum image height.
[0045]
The objective lens OL for a water immersion microscope described above is of the infinity-correction type, and is therefore used, for example, 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 L41 and a biconcave lens L42, and a cemented lens of a biconvex lens L43 and a biconcave lens L44. Table 3 below shows the specifications of each lens constituting the imaging lens IL. The surface numbers 1 to 6 in Table 3 relate to the imaging lens IL, and correspond to the reference numerals 1 to 6 in FIG.
[0046]
[Table 3]

[0047]
【The invention's effect】
As apparent from the above description, according to the objective lens for a water immersion microscope according to the present invention, the numerical aperture reaches 1.2, the magnification is about 50 times, and the apochromat-class water immersion with little image field distortion is achieved. An objective lens for a system microscope can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of an objective lens for a water immersion microscope according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating various aberrations when the correction ring is located at POS1 in the objective lens for a water immersion microscope according to the first example of the present invention.
FIG. 3 is a diagram illustrating various aberrations when the correction ring is located at POS2 in the objective lens for a water immersion microscope according to the first example of the present invention.
FIG. 4 is a diagram illustrating various aberrations when the correction ring is located at POS3 in the objective lens for a water immersion microscope according to the first example of the present invention.
FIG. 5 is a diagram illustrating various aberrations when the correction ring is at the POS 4 in the objective lens for a water immersion microscope according to the first example of the present invention.
FIG. 6 is a diagram illustrating various aberrations when the correction ring is at the POS 5 in the objective lens for a water immersion microscope according to the first example of the present invention.
FIG. 7 is a sectional view showing a configuration of an objective lens for a water immersion microscope according to a second embodiment of the present invention.
FIG. 8 is a diagram of various aberrations when the correction ring is at POS1 in the objective lens for a water immersion microscope according to the second embodiment of the present invention.
FIG. 9 is a diagram illustrating various aberrations when the correction ring is located at POS2 in the objective lens for a water immersion microscope according to the second example of the present invention.
FIG. 10 is a diagram illustrating various aberrations when the correction ring is located at POS3 in the objective lens for a water immersion microscope according to the second example of the present invention.
FIG. 11 is a diagram illustrating various aberrations when the correction ring is located at POS4 in the objective lens for a water immersion microscope according to the second example of the present invention.
FIG. 12 is a diagram illustrating various aberrations when the correction ring is at the POS 5 in the objective lens for a water immersion microscope according to the second example of the present invention.
FIG. 13 is a sectional view showing a configuration of an imaging lens used in combination with the objective lens for a water immersion microscope according to the present invention.
[Explanation of symbols]
OL Object lens for immersion microscope G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group G7 Seventh lens group G8 Eighth lens group

Claims (5)

In order from the object side,
A first lens group including a cemented lens formed by joining a plano-convex lens having a flat surface toward the object side and a meniscus lens having a positive refractive power and having a concave surface facing the object side;
A second lens group including one lens having a positive refractive power;
A third lens group comprising a cemented lens having a positive refractive power as a whole by joining a lens having a negative refractive power and a lens having a positive refractive power;
A fourth lens group having a cemented lens having a positive refractive power as a whole by sequentially joining a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power,
A fifth lens group including a cemented lens obtained by cementing a lens having a negative refractive power and a lens having a positive refractive power;
A sixth lens group including a cemented lens obtained by cementing at least two lenses of a lens having a positive refractive power and a lens having a negative refractive power;
A seventh lens group including a cemented meniscus lens having at least two lenses, a lens having a positive refractive power and a lens having a negative refractive power, and having a strong concave surface facing the image side;
An eighth lens group comprising a cemented meniscus lens having at least two lenses, a lens having a positive refractive power and a lens having a negative refractive power, cemented and having a strong concave surface facing the object side; In immersion microscope objectives,
One surface of a cemented surface of the cemented lens including the three lenses constituting the fourth lens group has a positive refractive power, and the other surface has a negative refractive power;
The radius of curvature of the cemented surface of the cemented lens constituting the first lens group and r _112, the distance on the optical axis from the object to the joint surface of the cemented lens constituting the first lens group and a d ₁₁ Then, the following expression | r ₁₁₂ | <2 * d ₁₁ (1)
Satisfies the condition represented by
_Assuming that the refractive index of the lens located on the image side among the lenses constituting the first lens group is n _1i , the following equation: n _1i > 1.7 (2)
Satisfies the condition represented by
The Abbe number of the lens having a positive refractive power in the second lens group is ν _2P, and the Abbe number of the lens having a positive refractive power in the third lens group is ν _3P. The Abbe number of a lens having a positive refractive power of ν _4P , the Abbe number of a lens having a positive refractive power in the fifth lens group is ν _5P, and the positive refractive power of the sixth lens group is Assuming that the Abbe number of the lens has ν _6P , the following expressions ν _2P > 65, ν _3P > 65, ν _4P > 65, ν _5P > 65, ν _6P > 65 (3)
An objective lens for a water immersion microscope, which satisfies the condition represented by: About 30% or more of ultraviolet light of about 365 nm is transmitted as excitation light for fluorescence observation,
When observing the weak fluorescence emitted from the sample by the excitation light, the first to eighth lenses are so arranged that the fluorescence emitted from the lenses constituting the first to eighth lens groups by the excitation light does not adversely affect the observation. 2. The objective lens for a water immersion microscope according to claim 1, wherein a glass material of a lens constituting the group is selected and arranged. The apparatus according to claim 1, wherein at least one of the first to eighth lens groups moves along an optical axis to correct an aberration caused by a difference in cover glass thickness. 3. The objective lens for a water immersion microscope according to 1 or 2. 4. The lens according to claim 1, wherein the cemented meniscus lens of at least one of the seventh lens group and the eighth lens group is configured by joining three lenses. 5. Objective lens for water immersion microscope. The first to eighth lens groups are configured to have a light amount of 90% or more of the center image height and to perform aberration correction even when the image height is about 70% of the maximum image height. Item 5. The objective lens for a water immersion microscope according to any one of Items 1 to 4.

Images