JP5190691B2 - Microscope objective lens - Google Patents

Microscope objective lens Download PDF

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Publication number
JP5190691B2
JP5190691B2 JP2008231955A JP2008231955A JP5190691B2 JP 5190691 B2 JP5190691 B2 JP 5190691B2 JP 2008231955 A JP2008231955 A JP 2008231955A JP 2008231955 A JP2008231955 A JP 2008231955A JP 5190691 B2 JP5190691 B2 JP 5190691B2
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lens
lens group
diffractive optical
line
refractive index
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JP2010066445A5 (en
JP2010066445A (en
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妙子 渡士
晶子 宮川
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Nikon Corp
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Nikon Corp
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Priority to JP2008231955A priority Critical patent/JP5190691B2/en
Application filed by Nikon Corp filed Critical Nikon Corp
Priority to CN201310088645.0A priority patent/CN103235405B/en
Priority to EP16186957.3A priority patent/EP3128355B1/en
Priority to CN201310088382.3A priority patent/CN103235404B/en
Priority to PCT/JP2009/057161 priority patent/WO2009125778A1/en
Priority to EP09729761.8A priority patent/EP2264506B1/en
Priority to CN200980112811.8A priority patent/CN101999090B/en
Publication of JP2010066445A publication Critical patent/JP2010066445A/en
Priority to US12/889,783 priority patent/US8958154B2/en
Publication of JP2010066445A5 publication Critical patent/JP2010066445A5/ja
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Priority to US14/586,004 priority patent/US9158102B2/en
Priority to US14/585,976 priority patent/US9134520B2/en
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Description

本発明は、顕微鏡対物レンズに関する。   The present invention relates to a microscope objective lens.

従来の顕微鏡対物レンズは、諸収差の中でも色収差を良好に補正するために多数の接合レンズを必要とし、また、２次スペクトルを補正するのに異常分散ガラスを用いる必要があったため、高価にならざるを得なかった。近年、高倍率・高開口数で、接合レンズや異常分散ガラスを多用することなく諸収差、特に２次スペクトルまで含めた色収差を補正できる回折光学素子（ＤＯＥ）を用いたレンズ系が提案されている（例えば、特許文献１参照）。
特開平６−３３１８９８号公報 Conventional microscope objective lenses require a large number of cemented lenses to satisfactorily correct chromatic aberration among various aberrations, and it is necessary to use anomalous dispersion glass to correct the secondary spectrum. I had to. In recent years, a lens system using a diffractive optical element (DOE) has been proposed that can correct various aberrations, particularly chromatic aberration including the secondary spectrum, without using a cemented lens or anomalous dispersion glass with a high magnification and a high numerical aperture. (For example, refer to Patent Document 1).
JP-A-6-331898

しかしながら、このような回折光学素子を用いたレンズ系では、回折光学素子で色収差を補正できても、高倍率・高開口数では高画角でのコマ収差の補正が困難となり、視野周辺部での像性能が低いという課題があった。   However, in a lens system using such a diffractive optical element, even if chromatic aberration can be corrected by the diffractive optical element, it is difficult to correct coma at a high angle of view at a high magnification and a high numerical aperture. There was a problem that the image performance of the image was low.

本発明は、このような課題に鑑みてなされたものであり、２次スペクトルまで含めて十分な色収差の補正がされ、且つ、十分な視野範囲で、諸収差が良好に補正され、さらに、長作動距離を有する顕微鏡対物レンズを提供することを目的とする。   The present invention has been made in view of such a problem. The chromatic aberration is sufficiently corrected including the secondary spectrum, and various aberrations are satisfactorily corrected in a sufficient visual field range. It is an object to provide a microscope objective having a working distance.

前記課題を解決するために、本発明に係る顕微鏡対物レンズは、物体側から順に、正の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群と、負の屈折力を有する第３レンズ群と、を有し、第１レンズ群は、最も物体側に位置し負の屈折力を有するレンズ面を含む正レンズ成分と、少なくとも１つ以上の、合成で正の屈折力を有する接合レンズ成分と有し、第２レンズ群は、異なる光学材料からなる２つの回折素子要素を接合し、当該接合面に回折格子溝が形成された回折光学面を有する回折光学素子と、少なくとも１つ以上の接合レンズ成分とを有し、第３レンズ群は、少なくとも１つ以上の合成で負の屈折力を有する色補正レンズ成分を有し、且つ、当該第３レンズ群の最も像側のレンズ面が、像側に凹面を向けて配置されて構成されている。そして、第１レンズ群に設けられた正レンズ成分の負の屈折力を有するレンズ面の曲率半径をＲとし、当該負の屈折力を有するレンズ面の物体側の媒質のｄ線に対する屈折率をｎ１、像側の媒質のｄ線に対する屈折率をｎ２とし、負の屈折力を有するレンズ面の頂点から物体までの光軸上の距離をｄ０としたとき、次式
｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜ ＜ ０．０１
の条件を満足し、全系の焦点距離をｆとし、回折光学面を通る最大画角に対応する光束の主光線の光軸からの高さをｈとしたとき、次式
０．０５ ＜ ｜ｈ／ｆ｜
の条件を満足するように構成される。但し、軸外物点から発する光束の主光線は、軸外物点から射出される光束の中、最も光軸から離れた方向に射出される光線を、軸上物点から射出される最大開口数（ＮＡ）の光線と第１レンズ群内の適宜の面との交点で制限し、最も光軸に近い方向に射出される光線を、軸上物点から射出される最大開口数の光線と第３レンズ群内の適宜の面との交点で制限したとき、当該光束の中心光線とする。 In order to solve the above problems, a microscope objective lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a negative refractive power. A first lens group having a positive lens component including a lens surface located closest to the object side and having a negative refractive power, and at least one combined positive refraction. includes a cemented lens component having a power, the second lens group includes a diffractive optical element having different joining two diffractive element formed of the optical material, the diffractive optical surface of the diffraction grating grooves on the cemented surface is formed At least one cemented lens component, and the third lens group has at least one color correction lens component having a negative refractive power in combination, and the third lens group is the most of the third lens group. The lens surface on the image side is placed with the concave surface facing the image side. It is configured Te. The radius of curvature of the lens surface having negative refractive power of the positive lens component provided in the first lens group is R, and the refractive index with respect to d-line of the medium on the object side of the lens surface having negative refractive power is defined as When n1, the refractive index of the medium on the image side with respect to the d-line is n2, and the distance on the optical axis from the apex of the lens surface having negative refractive power to the object is d0, the following expression | (n2-n1) / (R · d0) | <0.01
When the focal length of the entire system is f and the height from the optical axis of the principal ray of the light beam corresponding to the maximum angle of view passing through the diffractive optical surface is h, the following expression 0.05 <| h / f |
It is configured to satisfy the following conditions. However, the chief ray of the light beam emitted from the off-axis object point is the maximum light beam emitted from the on-axis object point, the light beam emitted from the off-axis object point in the direction farthest from the optical axis. The light beam emitted in the direction closest to the optical axis is defined as the light beam with the maximum numerical aperture emitted from the on-axis object point. When restricted at the intersection with an appropriate surface in the third lens group, it is set as the central ray of the luminous flux.

このような顕微鏡対物レンズは、全系の焦点距離をｆとし、第１レンズ群と第２レンズ群との合成焦点距離をｆ１２としたとき、次式
１．５ ≦ ｜ｆ１２／ｆ｜ ≦ ４
の条件を満足し、全系の焦点距離をｆとし、第３レンズ群の焦点距離をｆ３としたとき、次式
１ ≦ ｜ｆ３／ｆ｜ ≦ ３．５
の条件を満足することが好ましい。 In such a microscope objective lens, when the focal length of the entire system is f and the combined focal length of the first lens group and the second lens group is f12, the following formula 1.5 ≦ | f12 / f | ≦ 4
When the focal length of the entire system is f and the focal length of the third lens group is f3, the following expression 1 ≦ | f3 / f | ≦ 3.5 is satisfied.
It is preferable to satisfy the following conditions.

また、このような顕微鏡対物レンズは、全系の焦点距離をｆとし、第２レンズ群の焦点距離をｆ２としたとき、次式
５ ≦ ｜ｆ２／ｆ｜
の条件を満足することが好ましい。 Further, in such a microscope objective lens, when the focal length of the entire system is f and the focal length of the second lens group is f2, the following formula 5 ≦ | f2 / f |
It is preferable to satisfy the following conditions.

また、このような顕微鏡対物レンズは、回折光学素子における回折光学面の回折格子溝の数をＮとし、当該回折光学面の有効半径をＨとしたとき、次式
２ ≦ Ｎ／Ｈ ≦ １０
の条件を満足することが好ましい。但し、有効半径Ｈは、軸上物点から射出される最大開口数の光線及び、軸外物点から射出される光束の中、最も光軸から離れた方向に射出される光線を、軸上物点から射出される最大開口数の光線と第１レンズ群内の適宜の面との交点で制限し、最も光軸に近い方向に射出される光線を、軸上物点から射出される最大開口数の光線と第３レンズ群内の適宜の面との交点で制限したときに決まる当該光束の最外側の光線で決定される。 Further, in such a microscope objective lens, when the number of diffraction grating grooves of the diffractive optical surface in the diffractive optical element is N and the effective radius of the diffractive optical surface is H, the following formula 2 ≦ N / H ≦ 10
It is preferable to satisfy the following conditions. However, the effective radius H is defined as the light beam having the maximum numerical aperture emitted from the on-axis object point and the light beam emitted from the off-axis object point in the direction farthest from the optical axis. The maximum ray emitted from the object point on the axis is limited by the intersection of the ray with the maximum numerical aperture emitted from the object point and an appropriate surface in the first lens group, and the ray emitted in the direction closest to the optical axis is emitted from the object point on the axis. It is determined by the outermost ray of the luminous flux determined when the beam is limited by the intersection of the ray having the numerical aperture and an appropriate surface in the third lens group.

さらに、このような顕微鏡対物レンズは、回折光学素子中の２つの回折素子要素のうち、屈折率が低くアッベ数が小さい方の回折素子要素の材料のｄ線に対する屈折率をｎｄ１、Ｆ線に対する屈折率をｎＦ１、Ｃ線に対する屈折率をｎＣ１とし、回折光学素子中の２つの回折素子要素のうち、屈折率が高くアッベ数が大きい方の回折素子要素の材料のｄ線に対する屈折率をｎｄ２、Ｆ線に対する屈折率をｎＦ２、Ｃ線に対する屈折率をｎＣ２としたとき、次式
ｎｄ１ ≦ １．５４
０．０１４５ ≦ ｎＦ１−ｎＣ１
１．５５ ≦ ｎｄ２
ｎＦ２−ｎＣ２ ≦ ０．０１３
の条件を満足することが好ましい。 Further, such a microscope objective lens has a refractive index with respect to the d-line of the material of the diffractive element having the lower refractive index and the smaller Abbe number of the two diffractive element elements in the diffractive optical element. The refractive index is nF1, the refractive index with respect to the C-line is nC1, and the refractive index with respect to the d-line of the material of the diffractive element element having the higher refractive index and the larger Abbe number among the two diffractive element elements in the diffractive optical element is nd2. When the refractive index for the F line is nF2, and the refractive index for the C line is nC2, the following formula nd1 ≦ 1.54
0.0145 ≦ nF1-nC1
1.55 ≤ nd2
nF2-nC2 ≦ 0.013
It is preferable to satisfy the following conditions.

本発明に係る顕微鏡対物レンズを以上のように構成すると、十分な色収差の補正がされ、且つ、視野が十分な範囲での諸収差が良好に補正され、さらに、長作動距離を有する顕微鏡対物レンズを提供することができる。   When the microscope objective lens according to the present invention is configured as described above, the chromatic aberration is sufficiently corrected, various aberrations in a sufficient field of view are well corrected, and the microscope objective lens has a long working distance. Can be provided.

以下、本発明の好ましい実施形態について図面を参照して説明する。まず、図１を用いて、本実施の形態に係る顕微鏡対物レンズの構成について説明する。この顕微鏡対物レンズＯＬは、物体側から順に、正の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２と、負の屈折力を有する第３レンズ群Ｇ３とを有して構成される。   Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the configuration of the microscope objective lens according to the present embodiment will be described with reference to FIG. The microscope objective lens OL includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. It is comprised.

このような顕微鏡対物レンズＯＬにおいて、第１レンズ群Ｇ１は、物体からの発散光束を平行光束へと近づけるためのレンズ群であり、そのため、負の屈折力を有するレンズ面を含む正レンズ成分（例えば、図１における正メニスカスレンズＬ１）と、正レンズと負レンズとを接合してなる少なくとも１つ以上の色消しレンズ成分（図１における接合レンズＣＬ１１）とを有して構成される。なお、正レンズ成分は、単レンズで構成しても良いし、接合レンズで構成しても良い。ここで、正レンズ成分に含まれる負の屈折力を有するレンズ面（例えば、図１における第１面）の曲率半径をＲとし、当該レンズ面の物体側の媒質のｄ線に対する屈折率をｎ１、像側の媒質のｄ線に対する屈折率をｎ２とし、物体から当該レンズ面（例えば、図１における最も物体側にあるレンズ面である第１面）の頂点までの光軸上の距離をｄ０としたとき、次の条件式（１）を満足する。   In such a microscope objective lens OL, the first lens group G1 is a lens group for bringing a divergent light beam from an object closer to a parallel light beam. Therefore, a positive lens component (including a lens surface having negative refractive power) ( For example, the positive meniscus lens L1) in FIG. 1 and at least one achromatic lens component (a cemented lens CL11 in FIG. 1) formed by cementing a positive lens and a negative lens are configured. The positive lens component may be composed of a single lens or a cemented lens. Here, the radius of curvature of a lens surface having negative refractive power included in the positive lens component (for example, the first surface in FIG. 1) is R, and the refractive index with respect to the d-line of the medium on the object side of the lens surface is n1. The refractive index with respect to the d-line of the medium on the image side is n2, and the distance on the optical axis from the object to the apex of the lens surface (for example, the first surface that is the lens surface closest to the object in FIG. 1) is d0. The following conditional expression (1) is satisfied.

｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜ ＜ ０．０１ （１） | (N2-n1) / (R · d0) | <0.01 (1)

この条件式（１）は、第１レンズ群Ｇ１に設けられた上述の正レンズ成分に含まれる前記負の屈折力を有するレンズ面の屈折力を規定するものであり、この条件式（１）の上限値を上回ると、ペッツバール和の補正が困難となり、高画角までの像面平坦性を確保することが困難になる。さらに十分に長い作動距離を確保できなくなる。なお、さらに好ましくは、条件式（１）の上限値を０．００８とすれば、ペッツバール和の補正をより良好とできる。   This conditional expression (1) defines the refractive power of the lens surface having the negative refractive power included in the above-mentioned positive lens component provided in the first lens group G1, and this conditional expression (1) If the upper limit is exceeded, it is difficult to correct the Petzval sum, and it becomes difficult to ensure image plane flatness up to a high angle of view. Furthermore, a sufficiently long working distance cannot be secured. More preferably, if the upper limit value of conditional expression (1) is 0.008, the Petzval sum can be corrected more favorably.

また、第２レンズ群Ｇ２は、第１レンズ群Ｇ１から出射した略平行光束を受けて、球面収差や色収差を補正するためのレンズ群であり、特に色収差を補正するために、回折光学素子ＧＤが設けられている。回折光学素子ＧＤは、１ｍｍあたり数本から数百本の細かい溝状またはスリット状の格子構造が同心円状に形成された回折光学面Ｄを備え、この回折光学面Ｄに入射した光を格子ピッチ（回折格子溝の間隔）と入射光の波長によって定まる方向へ回折する性質を有している。また、回折光学素子ＧＤ（回折光学面Ｄ）は、負の分散値（本願の実施例ではアッベ数＝−３．４５３）を有し、分散が大きく、また異常分散性（本願の実施例では部分分散比（ｎｇ−ｎＦ）／（ｎＦ−ｎＣ）＝０．２９５６）が強いため、強力な色収差補正能力を有している。光学ガラスのアッベ数は、通常３０〜８０程度であるが、回折光学素子のアッベ数は負の値を持っている。換言すると、回折光学素子ＧＤの回折光学面Ｄは分散特性が通常のガラス（屈折光学素子）とは逆で光の波長が短くなるに伴い屈折率が小さくなり、長い波長の光ほど大きく曲がる性質を有している。そのため、通常の屈折光学素子と組み合わせることにより、大きな色消し効果が得られる。したがって回折光学素子ＧＤを利用することで、色収差を良好に補正することが可能になる。   The second lens group G2 is a lens group that receives the substantially parallel light beam emitted from the first lens group G1 and corrects spherical aberration and chromatic aberration. In particular, the diffractive optical element GD is used to correct chromatic aberration. Is provided. The diffractive optical element GD includes a diffractive optical surface D in which several to hundreds of fine groove-shaped or slit-shaped grating structures are formed concentrically per 1 mm, and the light incident on the diffractive optical surface D is grating pitch It has the property of diffracting in a direction determined by the (grating groove interval) and the wavelength of incident light. The diffractive optical element GD (diffractive optical surface D) has a negative dispersion value (Abbe number = −3.453 in the embodiment of the present application), large dispersion, and anomalous dispersion (in the embodiment of the present application). Since the partial dispersion ratio (ng−nF) / (nF−nC) = 0.2956) is strong, it has a strong ability to correct chromatic aberration. The Abbe number of the optical glass is usually about 30 to 80, but the Abbe number of the diffractive optical element has a negative value. In other words, the diffractive optical surface D of the diffractive optical element GD has a dispersion characteristic that is opposite to that of normal glass (refractive optical element), and the refractive index decreases as the wavelength of light becomes shorter. have. Therefore, a large achromatic effect can be obtained by combining with an ordinary refractive optical element. Therefore, chromatic aberration can be favorably corrected by using the diffractive optical element GD.

本実施の形態における回折光学素子ＧＤは、異なる光学材料からなる２つの回折素子要素（例えば、図１の場合、光学部材Ｌ６，Ｌ７）を接合し、その接合面に回折格子溝を設けて回折光学面Ｄを構成している、いわゆる「密着複層型回折光学素子」である。そのため、この回折光学素子は、ｇ線からＣ線を含む広波長域において回折効率を高くすることができる。したがって、本実施の形態に係る顕微鏡対物レンズＯＬは広波長域において利用することが可能となる。なお、回折効率は、透過型の回折光学素子において１次回折光を利用する場合、入射強度Ｉ０と一次回折光の強度Ｉ１との割合η（＝Ｉ１／Ｉ０×１００［％］）を示す。   The diffractive optical element GD in the present embodiment joins two diffractive element elements (for example, optical members L6 and L7 in the case of FIG. 1) made of different optical materials, and diffracts by providing a diffraction grating groove on the joint surface. This is a so-called “contact multilayer diffractive optical element” constituting the optical surface D. Therefore, this diffractive optical element can increase the diffraction efficiency in a wide wavelength region including g-line to C-line. Therefore, the microscope objective lens OL according to the present embodiment can be used in a wide wavelength range. The diffraction efficiency indicates the ratio η (= I1 / I0 × 100 [%]) between the incident intensity I0 and the intensity I1 of the first-order diffracted light when the first-order diffracted light is used in the transmission type diffractive optical element.

また、密着複層型回折光学素子は、回折格子溝が形成された２つの回折素子要素をこの回折格子溝同士が対向するように近接配置してなるいわゆる分離複層型回折光学素子に比べて製造工程を簡素化することができるため、量産効率がよく、また光線の入射角に対する回折効率が良いという長所を備えている。したがって、密着複層型回折光学素子を利用した本実施の形態に係る顕微鏡対物レンズＯＬでは、製造が容易となり、また回折効率も良くなる。   In addition, the contact multilayer diffractive optical element is compared to a so-called separated multilayer diffractive optical element in which two diffraction element elements formed with diffraction grating grooves are arranged close to each other so that the diffraction grating grooves face each other. Since the manufacturing process can be simplified, it has the advantages of high mass production efficiency and good diffraction efficiency with respect to the incident angle of light. Therefore, the microscope objective lens OL according to the present embodiment using the multi-contact diffractive optical element is easy to manufacture and improves the diffraction efficiency.

ここで、この顕微鏡対物レンズＯＬの全系の焦点距離をｆとし、回折光学面Ｄ（図１における第１０面）を通る最大画角に対応する光束の主光線の光軸からの高さをｈとしたとき、この回折光学素子ＧＤは、次の条件式（２）を満足する位置に配置される。   Here, let f be the focal length of the entire system of the microscope objective lens OL, and let the height from the optical axis of the principal ray of the light beam corresponding to the maximum field angle passing through the diffractive optical surface D (the tenth surface in FIG. 1). When h, the diffractive optical element GD is disposed at a position that satisfies the following conditional expression (2).

０．０５ ＜ ｜ｈ／ｆ｜ （２） 0.05 <| h / f | (2)

但し、この図１の顕微鏡レンズＯＬにおいて、軸外物点から発する光束の主光線を、軸外物点から射出される光束の中、最も光軸から離れた方向に射出される光線を、軸上物点から射出される最大開口数の光線と第１レンズ群Ｇ１内のレンズＬ１の物体側の面との交点で制限し、最も光軸に近い方向に射出される光線を、軸上物点から射出される最大開口数の光線と第３レンズ群Ｇ３内のレンズＬ１２の像側の面との交点で制限し、軸外光束を決め、当該軸外光束の中心光線として決めている。   However, in the microscope lens OL of FIG. 1, the principal ray of the light beam emitted from the off-axis object point is changed to the light ray emitted in the direction farthest from the optical axis among the light beams emitted from the off-axis object point. The light beam having the maximum numerical aperture emitted from the upper object point is limited by the intersection of the object side surface of the lens L1 in the first lens group G1, and the light beam emitted in the direction closest to the optical axis is The light beam having the maximum numerical aperture emitted from the point is limited by the intersection of the image side surface of the lens L12 in the third lens group G3, the off-axis light beam is determined, and the center light beam of the off-axis light beam is determined.

回折光学素子ＧＤを、この条件式（２）を満足する位置に配置することにより、この回折光学素子ＧＤの色収差補正能力を、軸上色収差の補正だけでなく倍率色収差の補正にも効果を持たせることができる。なお、この回折光学素子ＧＤの回折格子溝の最小ピッチが小さくなってしまわないように、１次の色消しをこの第２レンズ群Ｇ２の屈折レンズで、ある程度行う必要がある。そのため、この第２レンズ群Ｇ２には、正レンズと負レンズとを接合してなる色消しレンズ成分（例えば、図１における接合レンズ成分ＣＬ２１）を少なくとも１つ以上設けることが必要である。   By disposing the diffractive optical element GD at a position that satisfies the conditional expression (2), the chromatic aberration correcting ability of the diffractive optical element GD is effective not only for correcting axial chromatic aberration but also for correcting lateral chromatic aberration. Can be made. In order to prevent the minimum pitch of the diffraction grating grooves of the diffractive optical element GD from becoming small, it is necessary to perform the first order achromaticity to some extent with the refractive lens of the second lens group G2. For this reason, it is necessary to provide at least one achromatic lens component (for example, a cemented lens component CL21 in FIG. 1) formed by cementing a positive lens and a negative lens in the second lens group G2.

第３レンズ群Ｇ３は、第２レンズ群Ｇ２を出射した収斂光束を略平行光束にするレンズ群である。この第３レンズ群Ｇ３は、負の屈折力を有する色補正レンズ成分（例えば、図１における正メニスカスレンズＬ１１及び両凹レンズＬ１２からなる接合レンズ成分ＣＬ３１）を少なくとも１つ有して構成されている。さらに、この第３レンズ群Ｇ３の最も像側に配置されるレンズの像側の面（例えば、図１における第１８面）は、像側に凹形状に形成されている。第３レンズ群Ｇ３へ入射する光束は、第１レンズ群Ｇ１及び第２レンズ群Ｇ２が正の屈折力を持っているため収斂光束となっている。第３レンズ群Ｇ３は、かかる収斂光束を受け、球面収差やコマ収差の発生を抑えつつ平行光束に変換する役割を担う。第３レンズ群Ｇ３の最も像側の面は、第３レンズ群Ｇ３の負の屈折力の多くの部分を担う面であり、この面を像側に凹の面で構成することにより、収斂光線の当該最終面に対する入射角を小さく構成でき、特に高次のコマ収差等の発生を的確に抑えることが可能となる。なお、この色補正レンズ要素は、接合レンズとしてだけでなく、色収差補正能力を大きく低下させない程度の空気間隔を空けて配置した複数のレンズで構成しても良い。   The third lens group G3 is a lens group that converts the convergent light beam emitted from the second lens group G2 into a substantially parallel light beam. The third lens group G3 includes at least one color correction lens component having a negative refractive power (for example, a cemented lens component CL31 including a positive meniscus lens L11 and a biconcave lens L12 in FIG. 1). . Further, the image side surface (for example, the 18th surface in FIG. 1) of the lens disposed closest to the image side in the third lens group G3 is formed in a concave shape on the image side. The light beam incident on the third lens group G3 is a convergent light beam because the first lens group G1 and the second lens group G2 have positive refractive power. The third lens group G3 plays a role of receiving such a convergent light beam and converting it into a parallel light beam while suppressing the occurrence of spherical aberration and coma aberration. The most image-side surface of the third lens group G3 is a surface that bears a large part of the negative refractive power of the third lens group G3. By constructing this surface as a concave surface on the image side, convergent light rays The incident angle with respect to the final surface can be made small, and in particular, the occurrence of higher-order coma and the like can be suppressed accurately. In addition, this color correction lens element may be constituted not only as a cemented lens but also by a plurality of lenses arranged with an air interval so as not to greatly reduce the chromatic aberration correction capability.

さらに、この顕微鏡対物レンズＯＬは、全系の焦点距離をｆとし、第１レンズ群Ｇ１と第２レンズ群Ｇ２との合成焦点距離をｆ１２としたとき、次の条件式（３）を満足することが望ましい。   Furthermore, this microscope objective lens OL satisfies the following conditional expression (3), where f is the focal length of the entire system and f12 is the combined focal length of the first lens group G1 and the second lens group G2. It is desirable.

１．５ ≦ ｜ｆ１２／ｆ｜ ≦ ４ （３） 1.5 ≦ | f12 / f | ≦ 4 (3)

条件式（３）は、十分な作動距離を確保しながら十分な開口数を確保するための条件である。この条件式（３）の下限値を下回ると、全系の焦点距離ｆに比べ、第１及び第２レンズ群Ｇ１，Ｇ２の合成焦点距離ｆ１２が短くなり、開口数の確保が困難になるとともに、球面収差の補正が困難になる。反対に、条件式（３）の上限値を上回ると、全系の焦点距離ｆに比べ、第１及び第２レンズ群Ｇ１，Ｇ２の合成焦点距離ｆ１２が長くなり、光線の収束が十分でなくなることで全長が長くなる傾向になるとともに、高画角での諸収差や、色収差の二次スペクトルの補正が困難となる。   Conditional expression (3) is a condition for securing a sufficient numerical aperture while ensuring a sufficient working distance. If the lower limit of conditional expression (3) is not reached, the combined focal length f12 of the first and second lens groups G1 and G2 becomes shorter than the focal length f of the entire system, and it becomes difficult to ensure the numerical aperture. This makes it difficult to correct spherical aberration. On the contrary, if the upper limit value of conditional expression (3) is exceeded, the combined focal length f12 of the first and second lens groups G1 and G2 becomes longer than the focal length f of the entire system, and the convergence of the light beam becomes insufficient. As a result, the overall length tends to be long, and it becomes difficult to correct various aberrations at high angles of view and the secondary spectrum of chromatic aberration.

また、この顕微鏡対物レンズＯＬは、全系の焦点距離をｆとし、第３レンズ群Ｇ３の焦点距離をｆ３としたとき、次の条件式（４）を満足することが望ましい。   The microscope objective lens OL preferably satisfies the following conditional expression (4), where f is the focal length of the entire system and f3 is the focal length of the third lens group G3.

１ ≦ ｜ｆ３／ｆ｜ ≦ ３．５ （４） 1 ≦ | f3 / f | ≦ 3.5 (4)

条件式（４）は、色による変化も含めた球面収差を良好に補正し、さらに十分な視野を確保するための条件である。この条件式（４）の下限値を下回ると、全系の焦点距離ｆに比べ、第３レンズ群Ｇ３の焦点距離ｆ３が短くなり、色毎に球面収差のばらつきが出るとともに、高次の曲がりが発生する。反対に、条件式（４）の上限値を上回ると、全系の焦点距離ｆに比べ、第３レンズ群Ｇ３の焦点距離ｆ３が長くなり、球面収差の補正が不足になるとともに、結像性能の良い十分な視野を確保することが困難となる。   Conditional expression (4) is a condition for satisfactorily correcting spherical aberration including changes due to color and ensuring a sufficient field of view. If the lower limit of conditional expression (4) is not reached, the focal length f3 of the third lens group G3 becomes shorter than the focal length f of the entire system, and variations in spherical aberration occur for each color, as well as higher-order bending. Occurs. On the other hand, if the upper limit value of conditional expression (4) is exceeded, the focal length f3 of the third lens group G3 becomes longer than the focal length f of the entire system, and correction of spherical aberration becomes insufficient, and imaging performance is increased. It is difficult to secure a good field of view.

ところで、回折光学素子ＧＤは、回折格子溝の厚さを持っているため、わずかな入射角の変化でも回折効率が大きく変化する。すなわち、回折光学面Ｄに対する入射角が大きくなると、回折効率が著しく低下し、ブレ−ズされていない次数の光線がフレアとなって表れてしまう。そこで、この顕微鏡対物レンズＯＬは、全系の焦点距離をｆとし、第２レンズ群Ｇ２の焦点距離をｆ２としたとき、次の条件式（５）を満足することが望ましい。   By the way, since the diffractive optical element GD has the thickness of the diffraction grating groove, the diffraction efficiency changes greatly even with a slight change in incident angle. That is, when the incident angle with respect to the diffractive optical surface D is increased, the diffraction efficiency is remarkably lowered, and the light beam of the order that is not blazed appears as flare. Therefore, it is desirable that the microscope objective lens OL satisfies the following conditional expression (5), where f is the focal length of the entire system and f2 is the focal length of the second lens group G2.

５ ≦ ｜ｆ２／ｆ｜ （５） 5 ≦ | f2 / f | (5)

条件式（５）は、パワー配分を使って回折光学素子ＧＤへの入射角を制御するための条件である。この条件式（５）の下限値を下回ると、全系の焦点距離ｆに比べ、第２レンズ群Ｇ２の焦点距離ｆ２が短くなり、この第２レンズ群Ｇ２内での光線の屈折角が大きくなり、回折光学素子ＧＤへの入射角が大きくなってしまう。また、上述の条件式（３）で、全系の焦点距離ｆに対する第１及び第２レンズ群Ｇ１，Ｇ２の合成焦点距離ｆ１２の範囲を規定しているため、この条件式（５）の下限値を下回ると、第１レンズ群Ｇ１のパワーが弱くなって第１レンズ群Ｇ１から発生する収差が減り、第２レンズ群Ｇ２での収差、特に球面収差の発生が大きくなり、第１レンズ群Ｇ１と第２レンズ群Ｇ２との収差のバランスをとるのが困難となる。   Conditional expression (5) is a condition for controlling the incident angle to the diffractive optical element GD using power distribution. If the lower limit value of conditional expression (5) is not reached, the focal length f2 of the second lens group G2 becomes shorter than the focal length f of the entire system, and the refraction angle of the light beam in the second lens group G2 is large. Thus, the incident angle to the diffractive optical element GD is increased. In addition, since the conditional expression (3) defines the range of the combined focal length f12 of the first and second lens groups G1 and G2 with respect to the focal length f of the entire system, the lower limit of the conditional expression (5) If the value is below the value, the power of the first lens group G1 becomes weak, the aberration generated from the first lens group G1 decreases, the aberration in the second lens group G2, particularly the generation of spherical aberration, increases, and the first lens group It becomes difficult to balance the aberration between G1 and the second lens group G2.

また、この顕微鏡対物レンズＯＬは、回折光学素子ＧＤにおける回折光学面Ｄの回折格子溝の数をＮとし、この回折光学面Ｄの有効半径をＨとしたとき、次の条件式（６）を満足することが望ましい。   Further, in this microscope objective lens OL, when the number of diffraction grating grooves of the diffractive optical surface D in the diffractive optical element GD is N and the effective radius of the diffractive optical surface D is H, the following conditional expression (6) is satisfied. It is desirable to be satisfied.

２ ≦ Ｎ／Ｈ ≦ １０ （６） 2 ≦ N / H ≦ 10 (6)

但し、この図１の顕微鏡対物レンズＯＬにおいて、有効半径Ｈは、軸上物点から射出される最大開口数の光線及び、軸外物点から射出される光束の中、最も光軸から離れた方向に射出される光線を、軸上物点から射出される最大開口数の光線と第１レンズ群Ｇ１内のレンズＬ１の物体側の面との交点で制限し、最も光軸に近い方向に射出される光線を、軸上物点から射出される最大開口数の光線と第３レンズ群Ｇ３内のレンズＬ１２の像側の面との交点で制限したときに決まる当該光束の最外側の光線で決定される。   However, in the microscope objective lens OL of FIG. 1, the effective radius H is farthest from the optical axis among the light beams having the maximum numerical aperture emitted from the on-axis object point and the light beams emitted from the off-axis object point. The light beam emitted in the direction is limited by the intersection of the light beam having the maximum numerical aperture emitted from the on-axis object point and the object-side surface of the lens L1 in the first lens group G1, and is in the direction closest to the optical axis. The outermost ray of the luminous flux determined when the emitted ray is limited by the intersection of the ray having the maximum numerical aperture emitted from the on-axis object point and the image side surface of the lens L12 in the third lens group G3. Determined by

条件式（６）は、回折光学面Ｄの回折格子溝の数Ｎと有効半径Ｈの適切な範囲を規定する条件式である。この条件式（６）の下限値を下回ると、軸上色収差はｄ線とｇ線で色消しした際に、Ｃ線とＦ線で色消し不足となる（二次スペクトル）。一方、条件式（６）の上限値を上回ると、軸上色収差はｄ線とｇ線で色消しした際に、Ｃ線とＦ線で色消し過剰となる（二次スペクトル）。また、回折光学素子ＧＤに形成された回折格子溝の最小ピッチ幅が小さくなり、製造上の精度を確保するのが困難となる。   Conditional expression (6) is a conditional expression that defines an appropriate range of the number N of diffraction grating grooves and the effective radius H of the diffractive optical surface D. If the lower limit of conditional expression (6) is not reached, axial chromatic aberration will be insufficiently achromatic in the C-line and F-line when achromatic in the d-line and g-line (secondary spectrum). On the other hand, if the upper limit of conditional expression (6) is exceeded, axial chromatic aberration will be excessively achromatic in the C-line and F-line when achromatic in the d-line and g-line (secondary spectrum). Further, the minimum pitch width of the diffraction grating grooves formed in the diffractive optical element GD becomes small, and it becomes difficult to ensure manufacturing accuracy.

さらに、この顕微鏡対物レンズＯＬは、回折光学素子ＧＤ中の２つの回折素子要素のうち、屈折率が低くアッベ数が小さい方の回折素子要素の材料のｄ線に対する屈折率をｎｄ１、Ｆ線に対する屈折率をｎＦ１、Ｃ線に対する屈折率をｎＣ１とし、回折光学素子中の２つの回折素子要素のうち、屈折率が高くアッベ数が大きい方の回折素子要素の材料のｄ線に対する屈折率をｎｄ２、Ｆ線に対する屈折率をｎＦ２、Ｃ線に対する屈折率をｎＣ２としたとき、次の条件式（７）〜（１０）を満足することが望ましい。   Further, this microscope objective lens OL has a refractive index with respect to the d-line of the material of the diffractive element having the lower refractive index and the smaller Abbe number of the two diffractive element elements in the diffractive optical element GD. The refractive index is nF1, the refractive index with respect to the C-line is nC1, and the refractive index with respect to the d-line of the material of the diffractive element element having the higher refractive index and the larger Abbe number is nd2 When the refractive index for the F-line is nF2 and the refractive index for the C-line is nC2, it is desirable that the following conditional expressions (7) to (10) are satisfied.

ｎｄ１ ≦ １．５４ （７）
０．０１４５ ≦ ｎＦ１−ｎＣ１ （８）
１．５５ ≦ ｎｄ２ （９）
ｎＦ２−ｎＣ２ ≦ ０．０１３ （１０） nd1 ≦ 1.54 (7)
0.0145 ≦ nF1-nC1 (8)
1.55 ≦ nd2 (9)
nF2-nC2 ≦ 0.013 (10)

条件式（７）〜（１０）は、回折光学素子ＧＤを構成する２つの回折素子要素の材質の屈折率と、Ｆ線及びＣ線に対する分散（ｎＦ−ｎＣ）をそれぞれ規定するものである。これらの条件式を満足することで、より良い性能で異なる２つの回折素子要素を密着接合させて回折光学面Ｄを形成することができ、これにより、ｇ線からＣ線までの広波長域において９０％以上の回折効率を実現することができる。なお、このような光学材料としての樹脂の例としては、例えば特願２００４−３６７６０７号公報、特願２００５−２３７５７３号公報等に記載されている。各条件式（７）〜（１０）の上限値または下限値を超えると、本実施の形態に係る色消しレンズ系における回折光学素子ＧＤは、広波長域において９０％以上の回折効率を得ることが困難になり、密着複層型回折光学素子の利点を維持することが困難になってしまう。   Conditional expressions (7) to (10) respectively define the refractive indexes of the materials of the two diffractive element elements constituting the diffractive optical element GD, and the dispersion (nF-nC) with respect to the F line and the C line. By satisfying these conditional expressions, it is possible to form a diffractive optical surface D by tightly bonding two different diffractive element elements with better performance, and thereby in a wide wavelength range from g-line to C-line. A diffraction efficiency of 90% or more can be realized. In addition, as an example of resin as such an optical material, it describes in Japanese Patent Application No. 2004-367607, Japanese Patent Application No. 2005-237573, etc., for example. When the upper limit value or lower limit value of the conditional expressions (7) to (10) is exceeded, the diffractive optical element GD in the achromatic lens system according to the present embodiment obtains a diffraction efficiency of 90% or more in a wide wavelength region. It becomes difficult to maintain the advantages of the contact multilayer diffractive optical element.

以下に、本実施の形態に係る顕微鏡対物レンズＯＬの４つの実施例を示すが、各実施例において、回折光学素子ＧＤに形成された回折光学面Ｄの位相差は、通常の屈折率と後述する非球面式（１１）とを用いて行う超高屈折率法により計算した。超高屈折率法とは、非球面形状と回折光学面の格子ピッチとの間の一定の等価関係を利用するものであり、本実施例においては、回折光学面Ｄを超高屈折率法のデータとして、すなわち、後述する非球面式（１１）及びその係数により示している。なお、本実施例では収差特性の算出対象として、ｄ線、Ｃ線、Ｆ線及びｇ線を選んでいる。本実施例において用いられたこれらｄ線、Ｃ線、Ｆ線及びｇ線の波長と、各スペクトル線に対して設定した超高屈折率法の計算に用いるための屈折率の値を次の表１に示す。   In the following, four examples of the microscope objective lens OL according to the present embodiment are shown. In each example, the phase difference of the diffractive optical surface D formed on the diffractive optical element GD is equal to the normal refractive index and will be described later. It calculated by the ultrahigh refractive index method performed using the aspherical surface formula (11). The ultrahigh refractive index method uses a certain equivalent relationship between the aspherical shape and the grating pitch of the diffractive optical surface. In this embodiment, the diffractive optical surface D is replaced by the ultrahigh refractive index method. As data, that is, an aspherical expression (11) described later and its coefficient. In this embodiment, d-line, C-line, F-line and g-line are selected as the calculation target of the aberration characteristics. The wavelengths of these d-line, C-line, F-line and g-line used in this example and the refractive index values used for calculation of the ultrahigh refractive index method set for each spectral line are shown in the following table. It is shown in 1.

（表１）
波長 屈折率（超高屈折率法による）
ｄ線 587.562ｎｍ 10001.0000
Ｃ線 656.273ｎｍ 11170.4255
Ｆ線 486.133ｎｍ 8274.7311
ｇ線 435.835ｎｍ 7418.6853 (Table 1)
Wavelength Refractive index
d-line 587.562nm 10001.0000
C line 656.273nm 11170.4255
F line 486.133nm 8274.7311
g-line 435.835nm 7418.6853

各実施例において、非球面は、光軸に垂直な方向の高さをｙとし、高さｙにおける各非球面の頂点の接平面から各非球面までの光軸に沿った距離（サグ量）をＳ（ｙ）とし、基準球面の曲率半径（頂点曲率半径）をｒとし、円錐定数をκとし、ｎ次の非球面係数をＡnとしたとき、以下の式（１１）で表される。なお、以降の実施例において、「Ｅ−ｎ」は「×１０-n」を示す。 In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature (vertex radius of curvature) of the reference sphere, k is the conic constant, and An is the nth-order aspheric coefficient, and is expressed by the following equation (11). In the following examples, “E−n” indicates “× 10 −n ”.

Ｓ（ｙ）＝（ｙ2／ｒ）／｛１＋（１−κ×ｙ2／ｒ2）1/2｝
＋Ａ2×ｙ2＋Ａ4×ｙ4＋Ａ6×ｙ6＋Ａ8×ｙ8＋Ａ10×ｙ10 （１１） S (y) = (y 2 / r) / {1+ (1−κ × y 2 / r 2 ) 1/2 }
+ A2 × y 2 + A4 × y4 + A6 × y 6 + A8 × y 8 + A10 × y 10 (11)

なお、各実施例において、回折光学面が形成されたレンズ面には、表中の面番号の右側に＊印を付しており、非球面式（１１）は、この回折光学面の性能の諸元を示している。   In each example, the lens surface on which the diffractive optical surface is formed is marked with an asterisk (*) on the right side of the surface number in the table, and the aspherical expression (11) indicates the performance of the diffractive optical surface. The specifications are shown.

また、以下の各実施例における顕微鏡対物レンズＯＬ１〜ＯＬ４は、無限遠補正型のものであり、図９に示す構成であって、表２に示す諸元を有する結像レンズＩＬとともに使用される。なお、この表２において、第１欄ｍは物体側からの各光学面の番号を、第２欄ｒは各光学面の曲率半径を、第３欄ｄは各光学面から次の光学面までの光軸上の距離を、第４欄ｎｄはｄ線に対する屈折率を、そして、第５欄νｄはアッベ数をそれぞれ示している。ここで、空気の屈折率1.00000は省略してある。この諸元表の説明は以降の実施例においても同様である。   In addition, the microscope objective lenses OL1 to OL4 in each of the following examples are of the infinity correction type, have the configuration shown in FIG. 9, and are used together with the imaging lens IL having the specifications shown in Table 2. . In Table 2, the first column m is the number of each optical surface from the object side, the second column r is the radius of curvature of each optical surface, and the third column d is from each optical surface to the next optical surface. , The fourth column nd indicates the refractive index with respect to the d-line, and the fifth column νd indicates the Abbe number. Here, the refractive index of air of 1.0000 is omitted. The description of the specification table is the same in the following embodiments.

（表２）
ｍ ｒ ｄ ｎｄ νｄ
1 75.043 5.10 1.62280 57.03
2 -75.043 2.00 1.74950 35.19
3 1600.580 7.50
4 50.256 5.10 1.66755 41.96
5 -84.541 1.80 1.61266 44.40
6 36.911 (Table 2)
m r d nd νd
1 75.043 5.10 1.62280 57.03
2 -75.043 2.00 1.74950 35.19
3 1600.580 7.50
4 50.256 5.10 1.66755 41.96
5 -84.541 1.80 1.61266 44.40
6 36.911

なお、この結像レンズＩＬは、物体側から順に、両凸レンズＬ２１と両凹レンズＬ２２とを接合した接合レンズ、及び、両凸レンズＬ２３と両凹レンズＬ２４とを接合した接合レンズから構成される。   The imaging lens IL includes a cemented lens in which a biconvex lens L21 and a biconcave lens L22 are cemented in order from the object side, and a cemented lens in which a biconvex lens L23 and a biconcave lens L24 are cemented.

［第１実施例］
上述の説明で用いた図１は、第１実施例に係る顕微鏡対物レンズＯＬ１を示している。この顕微鏡対物レンズＯＬ１は、乾燥系の対物レンズであって、物体側より順に、正の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２と、負の屈折力を有する第３レンズ群Ｇ３とから構成される。第１レンズ群Ｇ１は、物体側より順に、物体側に凹面を向けた正メニスカスレンズＬ１、両凸レンズＬ２と物体側に凹面を向けた負メニスカスレンズＬ３とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ１１とから構成される。また、第２レンズ群Ｇ２は、物体側から順に、物体側に凸面を向けた負メニスカスレンズＬ４と回折光学面Ｄを含み物体側に凸面を向けた正メニスカスレンズ形状の回折光学素子ＧＤ、及び、両凸レンズＬ９と両凹レンズＬ１０とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２１から構成される。さらに、第３レンズ群Ｇ３は、物体側から順に、物体側に凹面を向けた正メニスカスレンズＬ１１と両凹レンズＬ１２とを接合した接合レンズ成分ＣＬ３１から構成される。このように、この第１実施例においては、第３レンズ群Ｇ３を構成する色補正レンズ成分ＣＬ３１は、２つのレンズを接合した接合レンズ成分として構成されている。 [First embodiment]
FIG. 1 used in the above description shows a microscope objective lens OL1 according to the first embodiment. The microscope objective lens OL1 is a dry objective lens, and in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative refraction. And a third lens group G3 having power. The first lens group G1, in order from the object side, is a cemented lens component (achromatic lens) in which a positive meniscus lens L1 having a concave surface facing the object side, a biconvex lens L2, and a negative meniscus lens L3 having a concave surface facing the object side are cemented. Component) CL11. The second lens group G2 includes, in order from the object side, a negative meniscus lens L4 having a convex surface facing the object side and a diffractive optical surface D, and a diffractive optical element GD having a positive meniscus lens shape having a convex surface facing the object side, and And a cemented lens component (achromatic lens component) CL21 formed by cementing the biconvex lens L9 and the biconcave lens L10. Further, the third lens group G3 includes a cemented lens component CL31 in which a positive meniscus lens L11 having a concave surface directed toward the object side and a biconcave lens L12 are cemented in order from the object side. As described above, in the first embodiment, the color correction lens component CL31 constituting the third lens group G3 is configured as a cemented lens component in which two lenses are cemented.

また、回折光学素子ＧＤは、物体側に凸面を向けた平凸レンズＬ５、それぞれ異なる樹脂材料から形成された２個の光学部材Ｌ６，Ｌ７、及び、像側に凹面を向けた平凹レンズＬ８がこの順で接合され、光学部材Ｌ６，Ｌ７の接合面に回折格子溝（回折光学面Ｄ）が形成されている。すなわち、この回折光学素子ＧＤは、密着複層型の回折光学素子である。   The diffractive optical element GD includes a plano-convex lens L5 having a convex surface facing the object side, two optical members L6 and L7 made of different resin materials, and a plano-concave lens L8 having a concave surface facing the image side. The diffraction grating grooves (diffractive optical surfaces D) are formed on the bonded surfaces of the optical members L6 and L7. That is, the diffractive optical element GD is a contact multilayer diffractive optical element.

このように図１に示した第１実施例に係る顕微鏡対物レンズＯＬ１の諸元を表３に示す。なお、この表３において、ｆは顕微鏡対物レンズＯＬ１の全系の焦点距離を、ＮＡは開口数を、βは倍率をそれぞれ示している。また、ｄ０は標本から最も物体側にある最初のレンズ（レンズＬ１）の最も物体側に位置し、負の屈折力を有するレンズ面（第１面）の頂点までの光軸上の距離を示している。ここで、この負の屈折力を有するレンズ面は、この第１実施例を含む以降の実施例において、第１面である。また、ｈは回折光学面Ｄを通る最大画角に対応する光束の主光線の光軸からの高さを示し、ｆ１は第１レンズ群Ｇ１の焦点距離を示し、ｆ２は第２レンズ群Ｇ２の焦点距離を示し、ｆ１２は第１及び第２レンズ群Ｇ１，Ｇ２の合成焦点距離を示し、ｆ３は第３レンズ群Ｇ３の焦点距離を示し、Ｎは回折光学素子ＧＤにおける回折光学面Ｄの回折格子溝の数を示し、Ｈは、この回折光学面の有効半径を示す。また、前述の如く、本第１実施例における軸外主光線及び有効径を決める軸外光束を制限するレンズ面は、正メニスカスレンズＬ１の物体側の面（第１面）と両凹レンズＬ１２の像側の面（第１８面）である。   Table 3 shows the specifications of the microscope objective lens OL1 according to the first example shown in FIG. In Table 3, f represents the focal length of the entire microscope objective lens OL1, NA represents the numerical aperture, and β represents the magnification. D0 indicates the distance on the optical axis from the sample to the apex of the lens surface (first surface) which is located closest to the object side of the first lens (lens L1) closest to the object side and has negative refractive power. ing. Here, the lens surface having negative refractive power is the first surface in the following embodiments including the first embodiment. Further, h represents the height from the optical axis of the principal ray of the light beam corresponding to the maximum field angle passing through the diffractive optical surface D, f1 represents the focal length of the first lens group G1, and f2 represents the second lens group G2. F12 represents the combined focal length of the first and second lens groups G1 and G2, f3 represents the focal length of the third lens group G3, and N represents the diffractive optical surface D of the diffractive optical element GD. The number of diffraction grating grooves is indicated, and H indicates the effective radius of the diffractive optical surface. As described above, the lens surface for limiting the off-axis principal ray and the off-axis light beam that determines the effective diameter in the first embodiment is the object side surface (first surface) of the positive meniscus lens L1 and the biconcave lens L12. This is the image side surface (18th surface).

また、第１欄ｍに示す各光学面の番号（右の＊は回折光学面として形成されているレンズ面を示す）は、図１に示した面番号１〜１８に対応している。また、第２欄ｒにおいて、曲率半径0.000は平面を示している。また、回折光学面の場合は、第２欄ｒにベースとなる非球面の基準となる球面の曲率半径を示し、超高屈折率法に用いるデータは非球面データとして諸元表内に示している。さらに、この表３には、上記条件式（１）〜（１０）に対応する値、すなわち、条件対応値も示している。これらの諸元表の説明は、以降の実施例においても同様である。   The numbers of the optical surfaces shown in the first column m (* on the right indicate the lens surfaces formed as diffractive optical surfaces) correspond to the surface numbers 1 to 18 shown in FIG. In the second column r, the curvature radius 0.000 indicates a plane. In the case of a diffractive optical surface, the second column r indicates the radius of curvature of the spherical surface that serves as a reference for the base aspherical surface, and the data used for the ultrahigh refractive index method is indicated in the specification table as aspherical data. Yes. Further, Table 3 also shows values corresponding to the conditional expressions (1) to (10), that is, condition corresponding values. The description of these specification tables is the same in the following examples.

なお、以下の全ての諸元において掲載される曲率半径ｒ、面間隔ｄ、全系の焦点距離ｆその他長さの単位は、特記の無い場合、一般に「ｍｍ」が使われるが、光学系は比例拡大又は比例縮小しても同等の光学性能が得られるので、単位は「ｍｍ」に限定されることはなく、他の適当な単位を用いることもできる。   Unless otherwise specified, “mm” is generally used as the unit of the radius of curvature r, the surface interval d, the focal length f of the entire system, and other lengths that are listed in all the following specifications. Since the same optical performance can be obtained even when proportional expansion or reduction is performed, the unit is not limited to “mm”, and other appropriate units may be used.

（表３）
ｆ＝10.076
ＮＡ＝0.35
β＝20x
ｄ０＝25.95
ｈ＝0.54
ｆ１＝23.106
ｆ２＝52.842
ｆ１２＝16.215
ｆ３＝-12.744
Ｎ＝39
Ｈ＝9.11

ｍ ｒ ｄ ｎｄ νｄ
1 -100.000 3.00 1.75500 52.29
2 -22.783 0.20
3 46.962 4.70 1.49782 82.52
4 -25.699 1.20 1.71736 29.52
5 -44.046 0.20
6 26.111 1.30 1.75692 31.59
7 16.131 4.10 1.49782 82.52
8 0.000 0.20 1.55690 50.17
9 0.000 0.00 10001.00000 -3.45
10* 0.000 0.20 1.52760 34.71
11 0.000 2.00 1.51680 64.12
12 316.639 0.20
13 20.449 3.80 1.49782 82.52
14 -58.825 1.40 1.72342 37.94
15 46.452 12.00
16 -35.297 2.00 1.84666 23.78
17 -9.400 1.00 1.72916 54.66
18 11.185

回折光学面データ
第１０面 κ＝1.0000 Ａ2＝-2.77779E-08 Ａ4＝5.65073E-14
Ａ6＝-2.12592E-16 Ａ8＝-1.96429E-19 Ａ10＝0.00000E+00

条件対応値
（１）｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜＝0.00029
（２）｜ｈ／ｆ｜＝ 0.05
（３）｜ｆ１２／ｆ｜＝ 1.61
（４）｜ｆ３／ｆ｜＝ 1.27
（５）｜ｆ２／ｆ｜＝ 5.24
（６）Ｎ／Ｈ＝ 4.28
（７）ｎｄ１＝ 1.52760
（８）ｎＦ１−ｎＣ１＝ 0.015
（９）ｎｄ２＝ 1.55690
（１０）ｎＦ２−ｎＣ２＝ 0.011 (Table 3)
f = 10.076
NA = 0.35
β = 20x
d0 = 25.95
h = 0.54
f1 = 23.106
f2 = 52.842
f12 = 16.215
f3 = -12.744
N = 39
H = 9.11

m r d nd νd
1 -100.000 3.00 1.75500 52.29
2 -22.783 0.20
3 46.962 4.70 1.49782 82.52
4 -25.699 1.20 1.71736 29.52
5 -44.046 0.20
6 26.111 1.30 1.75692 31.59
7 16.131 4.10 1.49782 82.52
8 0.000 0.20 1.55690 50.17
9 0.000 0.00 10001.00000 -3.45
10 * 0.000 0.20 1.52760 34.71
11 0.000 2.00 1.51680 64.12
12 316.639 0.20
13 20.449 3.80 1.49782 82.52
14 -58.825 1.40 1.72342 37.94
15 46.452 12.00
16 -35.297 2.00 1.84666 23.78
17 -9.400 1.00 1.72916 54.66
18 11.185

Diffraction optical surface data 10th surface κ = 1.0000 A2 = -2.77779E-08 A4 = 5.65073E-14
A6 = -2.12592E-16 A8 = -1.96429E-19 A10 = 0.000000 + 00

Condition corresponding value (1) | (n2-n1) / (R · d0) | = 0.00029
(2) | h / f | = 0.05
(3) | f12 / f | = 1.61
(4) | f3 / f | = 1.27
(5) | f2 / f | = 5.24
(6) N / H = 4.28
(7) nd1 = 1.52760
(8) nF1-nC1 = 0.015
(9) nd2 = 1.55690
(10) nF2-nC2 = 0.011

なお、表３に示した条件対応値のうち、条件式（１）は、第１面の曲率半径Ｒとその前後の媒質のｄ線に対する屈折率ｎ１，ｎ２とから算出された値である。また、条件式（７），（８）は第１０面の値に相当し、条件式（９），（１０）は第８面の値に相当する。このように、第１実施例では上記条件式（１）〜（１０）は全て満たされていることが分かる。図２に、この第１実施例におけるｄ線、Ｃ線、Ｆ線及びｇ線の光線に対する球面収差、非点収差、倍率色収差、及び、コマ収差の諸収差図を示す。これらの収差図のうち、球面収差図は開口数ＮＡに対する収差量を示し、非点収差図及び倍率色収差は像高Ｙに対する収差量を示し、コマ収差図は、像高Ｙが１２．４ｍｍのとき、９．０ｍｍのとき、６．０ｍｍのとき、及び、０ｍｍのときの収差量を示している。また、球面収差図、倍率色収差図及びコマ収差図において、実線はｄ線を示し、点線はＣ線を示し、一点鎖線はＦ線を示し、二点鎖線はｇ線を示している。さらに、非点収差図において、実線は各波長に対するサジタル像面を示し、破線は各波長に対するメリジオナル像面を示している。これらの諸収差図の説明は以降の実施例においても同様である。この図２に示す各収差図から明らかなように、第１実施例では諸収差が良好に補正され、優れた結像性能が確保されていることがわかる。   Of the condition corresponding values shown in Table 3, conditional expression (1) is a value calculated from the curvature radius R of the first surface and the refractive indexes n1 and n2 with respect to the d-line of the medium before and after the first surface. Conditional expressions (7) and (8) correspond to values on the tenth surface, and conditional expressions (9) and (10) correspond to values on the eighth surface. Thus, it can be seen that all the conditional expressions (1) to (10) are satisfied in the first embodiment. FIG. 2 shows various aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, and coma aberration for the d-line, C-line, F-line, and g-line rays in the first embodiment. Among these aberration diagrams, the spherical aberration diagram shows the aberration amount with respect to the numerical aperture NA, the astigmatism diagram and the lateral chromatic aberration show the aberration amount with respect to the image height Y, and the coma aberration diagram shows that the image height Y is 12.4 mm. In this case, the aberration amount is shown at 9.0 mm, 6.0 mm, and 0 mm. In the spherical aberration diagram, the lateral chromatic aberration diagram, and the coma aberration diagram, the solid line indicates the d line, the dotted line indicates the C line, the alternate long and short dash line indicates the F line, and the alternate long and two short dashes line indicates the g line. Further, in the astigmatism diagram, the solid line indicates the sagittal image plane for each wavelength, and the broken line indicates the meridional image plane for each wavelength. The explanation of these aberration diagrams is the same in the following examples. As is apparent from the respective aberration diagrams shown in FIG. 2, it is understood that various aberrations are corrected well and excellent imaging performance is secured in the first embodiment.

［第２実施例］
次に、第２実施例として、図３に示す顕微鏡対物レンズＯＬ２について説明する。この図３に示す顕微鏡対物レンズＯＬ２も、乾燥系の対物レンズであって、物体側より順に、正の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２と、負の屈折力を有する第３レンズ群Ｇ３とから構成される。第１レンズ群Ｇ１は、物体側より順に、物体側に凹面を向けた正メニスカスレンズＬ１、及び、両凸レンズＬ２と物体側に凹面を向けた負メニスカスレンズＬ３とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ１１から構成される。また、第２レンズ群Ｇ２は、物体側から順に、両凸レンズＬ４と、両凹レンズＬ５と、回折光学面Ｄを含む両凸レンズ形状の回折光学素子ＧＤとを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２１、及び、物体側に凸面を向けた負メニスカスレンズＬ１０と両凸レンズＬ１１と両凹レンズＬ１２とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２２で構成される。さらに、第３レンズ群Ｇ３は、物体側から順に、物体側に凹面を向けた正メニスカスレンズＬ１３と両凹レンズＬ１４とを接合した接合レンズ成分ＣＬ３１から構成される。このように、この第２実施例においては、第３レンズ群Ｇ３を構成する色補正レンズ成分ＣＬ３１は、２つのレンズを接合した接合レンズ成分として構成されている。また、本第２実施例における軸外主光線及び有効径を決める軸外光束を制限するレンズ面は、正メニスカスレンズＬ１の像側の面（第２面）と正メニスカスレンズＬ１３の物体側の面（第１８面）である。 [Second Embodiment]
Next, as a second embodiment, a microscope objective lens OL2 shown in FIG. 3 will be described. The microscope objective lens OL2 shown in FIG. 3 is also a dry objective lens, and in order from the object side, a first lens group G1 having a positive refractive power, and a second lens group G2 having a positive refractive power. And a third lens group G3 having negative refractive power. The first lens group G1, in order from the object side, is a cemented lens component (color) in which a positive meniscus lens L1 having a concave surface facing the object side and a biconvex lens L2 and a negative meniscus lens L3 having a concave surface facing the object side are cemented. Erasing lens component) CL11. The second lens group G2 includes, in order from the object side, a cemented lens component (achromatic lens component) in which a biconvex lens L4, a biconcave lens L5, and a biconvex lens-shaped diffractive optical element GD including the diffractive optical surface D are cemented. ) CL21, and a cemented lens component (achromatic lens component) CL22 obtained by cementing a negative meniscus lens L10 having a convex surface toward the object side, a biconvex lens L11, and a biconcave lens L12. Further, the third lens group G3 includes a cemented lens component CL31 in which a positive meniscus lens L13 having a concave surface directed toward the object side and a biconcave lens L14 are cemented in order from the object side. Thus, in the second embodiment, the color correction lens component CL31 constituting the third lens group G3 is configured as a cemented lens component in which two lenses are cemented. In the second embodiment, the lens surfaces for limiting the off-axis principal ray and the off-axis light beam that determines the effective diameter are the image side surface (second surface) of the positive meniscus lens L1 and the object side of the positive meniscus lens L13. This is the surface (18th surface).

また、この第２実施例に係る回折光学素子ＧＤも密着複層型の回折光学素子であって、物体側に凸面を向けた平凸レンズＬ６、それぞれ異なる樹脂材料から形成された２個の光学部材Ｌ７，Ｌ８、及び、像側に凸面を向けた平凸レンズＬ９がこの順で接合され、光学部材Ｌ７，Ｌ８の接合面に回折格子溝（回折光学面Ｄ）が形成されている。   Further, the diffractive optical element GD according to the second embodiment is also a close-contact multilayer diffractive optical element, which is a plano-convex lens L6 having a convex surface facing the object side, and two optical members formed from different resin materials. L7 and L8 and a plano-convex lens L9 having a convex surface facing the image side are joined in this order, and a diffraction grating groove (diffractive optical surface D) is formed on the joint surface of the optical members L7 and L8.

この図３に示した第２実施例に係る顕微鏡対物レンズＯＬ２の諸元を表４に示す。なお、表４に示す面番号は図３に示した面番号１〜２０と一致している。   Table 4 shows the specifications of the microscope objective lens OL2 according to the second example shown in FIG. In addition, the surface number shown in Table 4 corresponds with the surface numbers 1-20 shown in FIG.

（表４）
ｆ＝4.005
ＮＡ＝0.45
β＝50x
ｄ０＝17.83
ｈ＝0.54
ｆ１＝19.146
ｆ２＝51.432
ｆ１２＝12.025
ｆ３＝-7.889
Ｎ＝25
Ｈ＝8.25

ｍ ｒ ｄ ｎｄ νｄ
1 -57.300 3.00 1.77250 49.62
2 -17.338 0.20
3 86.481 3.50 1.60300 65.47
4 -27.000 1.20 1.62374 47.04
5 -41.645 0.20
6 20.575 5.20 1.43385 95.25
7 -26.714 1.00 1.61340 44.27
8 14.002 5.00 1.59240 68.33
9 0.000 0.20 1.55690 50.17
10 0.000 0.00 10001.00000 -3.45
11* 0.000 0.20 1.52760 34.71
12 0.000 2.00 1.60300 65.47
13 -46.301 0.20
14 13.584 1.50 1.62374 47.04
15 7.271 6.00 1.43385 95.25
16 -16.966 1.00 1.74950 35.27
17 35.143 12.90
18 -12.687 1.70 1.80810 22.76
19 -4.450 0.80 1.60300 65.47
20 5.751

回折光学面データ
第１１面 κ＝1.0000 Ａ2＝-2.12762E-08 Ａ4＝6.05843E-14
Ａ6＝-1.82066E-16 Ａ8＝-1.96429E-19 Ａ10＝0.00000E+00

条件対応値
（１）｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜＝0.00076
（２）｜ｈ／ｆ｜＝0.14
（３）｜ｆ１２／ｆ｜＝3.00
（４）｜ｆ３／ｆ｜＝1.97
（５）｜ｆ２／ｆ｜＝12.84
（６）Ｎ／Ｈ＝3.03
（７）ｎｄ１＝1.52760
（８）ｎＦ１−ｎＣ１＝0.015
（９）ｎｄ２＝1.55690
（１０）ｎＦ２−ｎＣ２＝0.011 (Table 4)
f = 4.005
NA = 0.45
β = 50x
d0 = 17.83
h = 0.54
f1 = 19.146
f2 = 51.432
f12 = 12.025
f3 = -7.889
N = 25
H = 8.25

m r d nd νd
1 -57.300 3.00 1.77250 49.62
2 -17.338 0.20
3 86.481 3.50 1.60300 65.47
4 -27.000 1.20 1.62374 47.04
5 -41.645 0.20
6 20.575 5.20 1.43385 95.25
7 -26.714 1.00 1.61340 44.27
8 14.002 5.00 1.59240 68.33
9 0.000 0.20 1.55690 50.17
10 0.000 0.00 10001.00000 -3.45
11 * 0.000 0.20 1.52760 34.71
12 0.000 2.00 1.60300 65.47
13 -46.301 0.20
14 13.584 1.50 1.62374 47.04
15 7.271 6.00 1.43385 95.25
16 -16.966 1.00 1.74950 35.27
17 35.143 12.90
18 -12.687 1.70 1.80810 22.76
19 -4.450 0.80 1.60300 65.47
20 5.751

Diffraction optical surface data 11th surface κ = 1.0000 A2 = -2.12762E-08 A4 = 6.05843E-14
A6 = -1.82066E-16 A8 = -1.96429E-19 A10 = 0.000000 + 00

Condition corresponding value (1) | (n2-n1) / (R · d0) | = 0.00076
(2) | h / f | = 0.14
(3) | f12 / f | = 3.00
(4) | f3 / f | = 1.97
(5) | f2 / f | = 12.84
(6) N / H = 3.03
(7) nd1 = 1.52760
(8) nF1-nC1 = 0.015
(9) nd2 = 1.55690
(10) nF2-nC2 = 0.011

なお、表４に示した条件対応値のうち、条件式（１）は、第１面の曲率半径Ｒとその前後の媒質のｄ線に対する屈折率ｎ１，ｎ２とから算出された値である。また、条件式（７），（８）は第１１面の値に相当し、条件式（９），（１０）は第９面の値に相当する。このように、第２実施例では上記条件式（１）〜（１０）は全て満たされていることが分かる。図４にこの第２実施例に係る顕微鏡対物レンズＯＬ２の球面収差、非点収差、倍率色収差及びコマ収差の諸収差図を示す。なお、この図４に示すコマ収差図は、像高Ｙが１２．５ｍｍのとき、９．０ｍｍのとき、６．０ｍｍのとき、及び、０ｍｍのときの収差量を示している。この各収差図から明らかなように、この第２実施例でも、収差が良好に補正され、優れた結像性能が確保されていることが分かる。   Of the condition corresponding values shown in Table 4, conditional expression (1) is a value calculated from the curvature radius R of the first surface and the refractive indices n1 and n2 with respect to the d-line of the medium before and after the first surface. Conditional expressions (7) and (8) correspond to the values of the eleventh surface, and conditional expressions (9) and (10) correspond to the values of the ninth surface. Thus, it can be seen that all the conditional expressions (1) to (10) are satisfied in the second embodiment. FIG. 4 shows various aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, and coma aberration of the microscope objective lens OL2 according to the second example. The coma aberration diagram shown in FIG. 4 shows the amount of aberration when the image height Y is 12.5 mm, when it is 9.0 mm, when it is 6.0 mm, and when it is 0 mm. As is apparent from the respective aberration diagrams, it is understood that the aberration is corrected well and excellent imaging performance is ensured also in the second embodiment.

［第３実施例］
次に、第３実施例として、図５に示す顕微鏡対物レンズＯＬ３について説明する。この図５に示す顕微鏡対物レンズＯＬ３も、乾燥系の対物レンズであって、物体側より順に、正の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２と、負の屈折力を有する第３レンズ群Ｇ３とから構成される。第１レンズ群Ｇ１は、物体側より順に、物体側に凹面を向けた正メニスカスレンズＬ１、物体側に凹面を向けた正メニスカスレンズＬ２、及び、両凸レンズＬ３と物体側に凹面を向けた負メニスカスレンズＬ４とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ１１から構成される。また、第２レンズ群Ｇ２は、物体側から順に、回折光学面Ｄを含む両凸レンズ形状の回折光学素子ＧＤと両凹レンズＬ９と物体側に凸面を向けた正メニスカスレンズＬ１０とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２１、両凸レンズＬ１１と両凹レンズＬ１２とを接合した接合レンズＣＬ２２、及び、物体面側に凸面を向けた負メニスカスレンズＬ１３と両凸レンズＬ１４と両凹レンズＬ１５とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２３で構成される。さらに、第３レンズ群Ｇ３は、物体側から順に、両凹レンズＬ１６と両凸レンズＬ１７と両凹レンズＬ１８とを接合した接合レンズ群ＣＬ３１から構成される。このように、この第３実施例においては、第３レンズ群Ｇ３を構成する色補正レンズ成分ＣＬ３１は、３つのレンズを接合した接合レンズ成分として構成されている。また、本第３実施例における軸外主光線及び有効径を決める軸外光束を制限するレンズ面は、正メニスカスレンズＬ１の像側の面（第２面）と両凹レンズＬ１６の物体側の面（第２３面）である。 [Third embodiment]
Next, a microscope objective lens OL3 shown in FIG. 5 will be described as a third embodiment. The microscope objective lens OL3 shown in FIG. 5 is also a dry objective lens, and in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a positive refractive power. And a third lens group G3 having negative refractive power. The first lens group G1, in order from the object side, is a positive meniscus lens L1 having a concave surface directed toward the object side, a positive meniscus lens L2 having a concave surface directed toward the object side, and a negative lens having a concave surface directed toward the object side from the biconvex lens L3. It is composed of a cemented lens component (achromatic lens component) CL11 cemented with the meniscus lens L4. The second lens group G2 is a cemented lens in which, in order from the object side, a biconvex lens-shaped diffractive optical element GD including the diffractive optical surface D, a biconcave lens L9, and a positive meniscus lens L10 having a convex surface facing the object side are cemented. Component (achromatic lens component) CL21, a cemented lens CL22 in which the biconvex lens L11 and the biconcave lens L12 are cemented, and a negative meniscus lens L13 having a convex surface facing the object surface, a biconvex lens L14, and a biconcave lens L15 are cemented. It is composed of a cemented lens component (achromatic lens component) CL23. Further, the third lens group G3 includes a cemented lens group CL31 in which a biconcave lens L16, a biconvex lens L17, and a biconcave lens L18 are cemented in order from the object side. Thus, in the third embodiment, the color correction lens component CL31 constituting the third lens group G3 is configured as a cemented lens component in which three lenses are cemented. Further, the lens surfaces for limiting the off-axis principal ray and the off-axis light beam that determines the effective diameter in the third embodiment are the image side surface (second surface) of the positive meniscus lens L1 and the object side surface of the biconcave lens L16. (23rd surface).

また、この第３実施例に係る回折光学素子ＧＤも密着複層型の回折光学素子であって、物体側に凸面を向けた平凸レンズＬ５、それぞれ異なる樹脂材料から形成された２個の光学部材Ｌ６，Ｌ７、及び、像側に凸面を向けた平凸レンズＬ８がこの順で接合され、光学部材Ｌ６，Ｌ７の接合面に回折格子溝（回折光学面Ｄ）が形成されている。   Further, the diffractive optical element GD according to the third embodiment is also a close-contact multilayer diffractive optical element, a plano-convex lens L5 having a convex surface facing the object side, and two optical members formed from different resin materials, respectively. L6 and L7 and a plano-convex lens L8 having a convex surface facing the image side are joined in this order, and a diffraction grating groove (diffractive optical surface D) is formed on the joint surface of the optical members L6 and L7.

この図５に示した第３実施例に係る顕微鏡対物レンズＯＬ３の諸元を表５に示す。なお、表５に示す面番号は図５に示した面番号１〜２６と一致している。   Table 5 shows the specifications of the microscope objective lens OL3 according to the third example shown in FIG. In addition, the surface number shown in Table 5 corresponds with the surface numbers 1-26 shown in FIG.

（表５）
ｆ＝2.003
ＮＡ＝0.7
β＝100x
ｄ０＝8.824
ｈ＝0.84
ｆ１＝12.897
ｆ２＝117.192
ｆ１２＝7.192
ｆ３＝-6.687
Ｎ＝43
Ｈ＝10.04

ｍ ｒ ｄ ｎｄ νｄ
1 -12.140 3.05 1.78800 47.38
2 -8.907 0.10
3 -35.273 3.65 1.49782 82.52
4 -15.323 0.10
5 37.000 5.80 1.49782 82.52
6 -19.000 1.40 1.61340 44.26
7 -28.903 0.10
8 28.628 3.00 1.60300 65.47
9 0.000 0.20 1.55690 50.17
10 0.000 0.00 10001.00000 -3.45
11* 0.000 0.20 1.52760 34.71
12 0.000 3.20 1.49782 82.52
13 -27.000 1.20 1.61340 44.27
14 17.614 5.00 1.49782 82.52
15 2747.644 0.20
16 20.683 4.70 1.49782 82.52
17 -29.639 1.00 1.67270 32.11
18 110.800 0.20
19 12.594 1.65 1.72047 34.71
20 5.909 5.30 1.49782 82.52
21 -13.696 1.00 1.61340 44.27
22 11.538 10.50
23 -7.015 0.80 1.71300 53.89
24 5.609 2.00 1.80518 25.43
25 -3.931 0.70 1.61340 44.26
26 5.858

回折光学面データ
第１１面 κ＝1.0000 Ａ2＝-2.50000E-08 Ａ4＝6.08882E-14
Ａ6＝-2.46978E-16 Ａ8＝-1.96414E-19 Ａ10＝0.00000E+00

条件対応値
（１）｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜＝0.0074
（２）｜ｈ／ｆ｜＝0.42
（３）｜ｆ１２／ｆ｜＝3.59
（４）｜ｆ３／ｆ｜＝3.34
（５）｜ｆ２／ｆ｜＝58.51
（６）Ｎ／Ｈ＝4.28
（７）ｎｄ１＝1.52760
（８）ｎＦ１−ｎＣ１＝0.015
（９）ｎｄ２＝1.55690
（１０）ｎＦ２−ｎＣ２＝0.011 (Table 5)
f = 2.003
NA = 0.7
β = 100x
d0 = 8.824
h = 0.84
f1 = 12.897
f2 = 117.192
f12 = 7.192
f3 = -6.687
N = 43
H = 10.04

m r d nd νd
1 -12.140 3.05 1.78800 47.38
2 -8.907 0.10
3 -35.273 3.65 1.49782 82.52
4 -15.323 0.10
5 37.000 5.80 1.49782 82.52
6 -19.000 1.40 1.61340 44.26
7 -28.903 0.10
8 28.628 3.00 1.60300 65.47
9 0.000 0.20 1.55690 50.17
10 0.000 0.00 10001.00000 -3.45
11 * 0.000 0.20 1.52760 34.71
12 0.000 3.20 1.49782 82.52
13 -27.000 1.20 1.61340 44.27
14 17.614 5.00 1.49782 82.52
15 2747.644 0.20
16 20.683 4.70 1.49782 82.52
17 -29.639 1.00 1.67270 32.11
18 110.800 0.20
19 12.594 1.65 1.72047 34.71
20 5.909 5.30 1.49782 82.52
21 -13.696 1.00 1.61340 44.27
22 11.538 10.50
23 -7.015 0.80 1.71300 53.89
24 5.609 2.00 1.80518 25.43
25 -3.931 0.70 1.61340 44.26
26 5.858

Diffraction optical surface data 11th surface κ = 1.0000 A2 = -2.50000E-08 A4 = 6.08882E-14
A6 = -2.46978E-16 A8 = -1.96414E-19 A10 = 0.000000 + 00

Condition corresponding value (1) | (n2−n1) / (R · d0) | = 0.004
(2) | h / f | = 0.42
(3) | f12 / f | = 3.59
(4) | f3 / f | = 3.34
(5) | f2 / f | = 58.51
(6) N / H = 4.28
(7) nd1 = 1.52760
(8) nF1-nC1 = 0.015
(9) nd2 = 1.55690
(10) nF2-nC2 = 0.011

なお、表５に示した条件対応値のうち、条件式（１）は、第１面の曲率半径Ｒとその前後の媒質のｄ線に対する屈折率ｎ１，ｎ２とから算出された値である。また、条件式（７），（８）は第１１面の値に相当し、条件式（９），（１０）は第９面の値に相当する。このように、第３実施例では上記条件式（１）〜（１０）は全て満たされていることが分かる。図６にこの第３実施例に係る顕微鏡対物レンズＯＬ３の球面収差、非点収差、倍率色収差及びコマ収差の諸収差図を示す。なお、この図６に示すコマ収差図は、像高Ｙが１２．５ｍｍのとき、９．０ｍｍのとき、６．０ｍｍのとき、及び、０ｍｍのときの収差量を示している。この各収差図から明らかなように、この第３実施例でも、収差が良好に補正され、優れた結像性能が確保されていることが分かる。   Of the condition corresponding values shown in Table 5, the conditional expression (1) is a value calculated from the curvature radius R of the first surface and the refractive indexes n1 and n2 with respect to the d-line of the medium before and after the first surface. Conditional expressions (7) and (8) correspond to the values of the eleventh surface, and conditional expressions (9) and (10) correspond to the values of the ninth surface. Thus, it can be seen that all the conditional expressions (1) to (10) are satisfied in the third embodiment. FIG. 6 is a diagram showing various aberrations of spherical aberration, astigmatism, lateral chromatic aberration, and coma aberration of the microscope objective lens OL3 according to the third example. The coma aberration diagram shown in FIG. 6 shows the amount of aberration when the image height Y is 12.5 mm, when it is 9.0 mm, when it is 6.0 mm, and when it is 0 mm. As is apparent from the respective aberration diagrams, it is understood that aberrations are corrected well and excellent imaging performance is secured in this third embodiment.

［第４実施例］
最後に、第４実施例として、図７に示す顕微鏡対物レンズＯＬ４について説明する。この図７に示す顕微鏡対物レンズＯＬ４も、乾燥系の対物レンズであって、物体側より順に、正の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２と、負の屈折力を有する第３レンズ群Ｇ３とから構成される。第１レンズ群Ｇ１は、物体側より順に、物体側に凹面を向けた正メニスカスレンズＬ１、両凸レンズＬ２と物体側に凹面を向けた負メニスカスレンズＬ３とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ１１から構成される。また、第２レンズ群Ｇ２は、物体側から順に、両凸レンズＬ４と両凹レンズＬ５と両凸レンズＬ６とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２１、回折光学面Ｄを含む平板形状の回折光学素子ＧＤ、及び、物体側に凸面を向けた負メニスカスレンズＬ１１と両凸レンズＬ１２と両凹レンズＬ１３とを接合した接合レンズ成分（色消しレンズ成分）ＣＬ２２から構成される。さらに、第３レンズ群Ｇ３は、物体側から順に、物体側に凹面を向けた正メニスカスレンズＬ１４と両凹レンズＬ１５とを接合した接合レンズ成分ＣＬ３１から構成される。このように、この第４実施例においては、第３レンズ群Ｇ３を構成する色補正レンズ成分ＣＬ３１は、２つのレンズを接合した接合レンズ成分として構成されている。また、本第４実施例における軸外主光線及び有効径を決める軸外光束を制限するレンズ面は、正メニスカスレンズＬ１の像側の面（第２面）と正メニスカスレンズＬ１４の物体側の面（第２０面）である。 [Fourth embodiment]
Finally, as a fourth embodiment, a microscope objective lens OL4 shown in FIG. 7 will be described. The microscope objective lens OL4 shown in FIG. 7 is also a dry objective lens, and in order from the object side, a first lens group G1 having a positive refractive power, and a second lens group G2 having a positive refractive power. And a third lens group G3 having negative refractive power. The first lens group G1, in order from the object side, is a cemented lens component (achromatic lens) in which a positive meniscus lens L1 having a concave surface facing the object side, a biconvex lens L2, and a negative meniscus lens L3 having a concave surface facing the object side are cemented. Component) CL11. The second lens group G2 includes, in order from the object side, a cemented lens component (achromatic lens component) CL21 obtained by cementing the biconvex lens L4, the biconcave lens L5, and the biconvex lens L6, and a diffractive optical surface D. An optical element GD and a cemented lens component (achromatic lens component) CL22 formed by cementing a negative meniscus lens L11 having a convex surface toward the object side, a biconvex lens L12, and a biconcave lens L13 are configured. Further, the third lens group G3 includes a cemented lens component CL31 in which a positive meniscus lens L14 having a concave surface directed toward the object side and a biconcave lens L15 are cemented in order from the object side. Thus, in the fourth embodiment, the color correction lens component CL31 constituting the third lens group G3 is configured as a cemented lens component in which two lenses are cemented. Further, the lens surfaces for limiting the off-axis principal ray and the off-axis light beam that determines the effective diameter in the fourth embodiment are the image side surface (second surface) of the positive meniscus lens L1 and the object side of the positive meniscus lens L14. It is a surface (20th surface).

また、この第４実施例に係る回折光学素子ＧＤも密着複層型の回折光学素子であって、平板状の光学ガラスＬ７、それぞれ異なる樹脂材料から形成された平板状の２個の光学部材Ｌ８，Ｌ９、及び、平板状の光学ガラスＬ１０がこの順で接合され、光学部材Ｌ８，Ｌ９の接合面に回折格子溝（回折光学面Ｄ）が形成されている。   Further, the diffractive optical element GD according to the fourth embodiment is also a close-contact diffractive optical element, and is a flat optical glass L7 and two flat optical members L8 formed from different resin materials. , L9 and the flat optical glass L10 are joined in this order, and a diffraction grating groove (diffractive optical surface D) is formed on the joining surface of the optical members L8, L9.

この図７に示した第４実施例に係る顕微鏡対物レンズＯＬ４の諸元を表６に示す。また、表６に示す面番号は図７に示した面番号１〜２２と一致している。   Table 6 shows the specifications of the microscope objective lens OL4 according to the fourth example shown in FIG. Further, the surface numbers shown in Table 6 coincide with the surface numbers 1 to 22 shown in FIG.

（表６）
ｆ＝ 4.014
ＮＡ＝ 0.45
β＝50x
ｄ０＝ 17.83
ｈ＝0.48
ｆ１＝ 18.136
ｆ２＝ 74.682
ｆ１２＝11.633
ｆ３＝ -8.683
Ｎ＝61
Ｈ＝7.6

ｍ ｒ ｄ ｎｄ νｄ
1 -57.300 3.00 1.80440 39.57
2 -17.390 0.20
3 71.472 3.50 1.60300 65.47
4 -24.538 1.20 1.62004 36.24
5 -39.899 0.20
6 30.223 5.20 1.60300 65.47
7 -19.420 1.00 1.64769 33.79
8 26.032 4.50 1.60300 65.47
9 -200.000 0.30
10 0.000 1.00 1.51680 64.12
11 0.000 0.20 1.55690 50.17
12 0.000 0.00 10001.00000 -3.45
13* 0.000 0.20 1.52760 34.71
14 0.000 1.50 1.51680 64.12
15 0.000 0.30
16 15.092 1.50 1.67003 47.25
17 7.250 6.00 1.49782 82.52
18 -14.111 1.00 1.71700 47.93
19 28.782 12.50
20 -14.824 1.80 1.80518 25.43
21 -4.550 1.85 1.60300 65.47
22 5.911

回折光学面データ
第１３面 κ＝1.0000 Ａ2＝-6.24941E-08 Ａ4＝1.04769E-13
Ａ6＝-1.68555E-16 Ａ8＝-1.96387E-19 Ａ10＝0.00000E+00

条件対応値
（１）｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜＝0.00079
（２）｜ｈ／ｆ｜＝0.12
（３）｜ｆ１２／ｆ｜＝2.90
（４）｜ｆ３／ｆ｜＝2.16
（５）｜ｆ２／ｆ｜＝18.61
（６）Ｎ／Ｈ＝8.03
（７）ｎｄ１＝1.52760
（８）ｎＦ１−ｎＣ１＝0.015
（９）ｎｄ２＝1.55690
（１０）ｎＦ２−ｎＣ２＝0.011 (Table 6)
f = 4.014
NA = 0.45
β = 50x
d0 = 17.83
h = 0.48
f1 = 18.136
f2 = 74.682
f12 = 11.633
f3 = −8.683
N = 61
H = 7.6

m r d nd νd
1 -57.300 3.00 1.80440 39.57
2 -17.390 0.20
3 71.472 3.50 1.60300 65.47
4 -24.538 1.20 1.62004 36.24
5 -39.899 0.20
6 30.223 5.20 1.60300 65.47
7 -19.420 1.00 1.64769 33.79
8 26.032 4.50 1.60300 65.47
9 -200.000 0.30
10 0.000 1.00 1.51680 64.12
11 0.000 0.20 1.55690 50.17
12 0.000 0.00 10001.00000 -3.45
13 * 0.000 0.20 1.52760 34.71
14 0.000 1.50 1.51680 64.12
15 0.000 0.30
16 15.092 1.50 1.67003 47.25
17 7.250 6.00 1.49782 82.52
18 -14.111 1.00 1.71700 47.93
19 28.782 12.50
20 -14.824 1.80 1.80518 25.43
21 -4.550 1.85 1.60300 65.47
22 5.911

Diffraction optical surface data 13th surface κ = 1.0000 A2 = -6.24941E-08 A4 = 1.04769E-13
A6 = -1.68555E-16 A8 = -1.96387E-19 A10 = 0.000000 + 00

Condition corresponding value (1) | (n2-n1) / (R · d0) | = 0.00079
(2) | h / f | = 0.12
(3) | f12 / f | = 2.90
(4) | f3 / f | = 2.16
(5) | f2 / f | = 18.61
(6) N / H = 8.03
(7) nd1 = 1.52760
(8) nF1-nC1 = 0.015
(9) nd2 = 1.55690
(10) nF2-nC2 = 0.011

なお、表６に示した条件対応値のうち、条件式（１）は、第１面の曲率半径Ｒとその前後の媒質のｄ線に対する屈折率ｎ１，ｎ２とから算出された値である。また、条件式（７），（８）は第１３面の値に相当し、条件式（９），（１０）は第１１面の値に相当する。このように、第４実施例では上記条件式（１）〜（１０）は全て満たされていることが分かる。図８にこの第４実施例に係る顕微鏡対物レンズＯＬ４の球面収差、非点収差、倍率色収差及びコマ収差の諸収差図を示す。なお、この図８に示すコマ収差図は、像高Ｙが１２．５ｍｍのとき、９．０ｍｍのとき、６．０ｍｍのとき、及び、０ｍｍのときの収差量を示している。この各収差図から明らかなように、この第４実施例でも、収差が良好に補正され、優れた結像性能が確保されていることが分かる。   Of the condition corresponding values shown in Table 6, conditional expression (1) is a value calculated from the curvature radius R of the first surface and the refractive indexes n1 and n2 with respect to the d-line of the medium before and after the first surface. Conditional expressions (7) and (8) correspond to values on the thirteenth surface, and conditional expressions (9) and (10) correspond to values on the eleventh surface. Thus, it can be seen that all the conditional expressions (1) to (10) are satisfied in the fourth embodiment. FIG. 8 is a diagram showing various aberrations of spherical aberration, astigmatism, lateral chromatic aberration, and coma aberration of the microscope objective lens OL4 according to the fourth example. The coma aberration diagram shown in FIG. 8 shows the amount of aberration when the image height Y is 12.5 mm, when it is 9.0 mm, when it is 6.0 mm, and when it is 0 mm. As is apparent from the respective aberration diagrams, it is understood that aberrations are corrected well and excellent imaging performance is secured in the fourth embodiment.

第１実施例に係る顕微鏡対物レンズのレンズ構成図である。It is a lens block diagram of the microscope objective lens which concerns on 1st Example. 上記第１実施例に係る顕微鏡対物レンズの諸収差図である。FIG. 6 is a diagram illustrating various aberrations of the microscope objective lens according to the first example. 第２実施例に係る顕微鏡対物レンズのレンズ構成図である。It is a lens block diagram of the microscope objective lens which concerns on 2nd Example. 上記第２実施例に係る顕微鏡対物レンズの諸収差図である。FIG. 5 is an aberration diagram of the microscope objective lens according to the second example. 第３実施例に係る顕微鏡対物レンズのレンズ構成図である。It is a lens block diagram of the microscope objective lens which concerns on 3rd Example. 上記第３実施例に係る顕微鏡対物レンズの諸収差図である。FIG. 10 is a diagram illustrating all aberrations of the microscope objective lens according to the third example. 第４実施例に係る顕微鏡対物レンズのレンズ構成図である。It is a lens block diagram of the microscope objective lens which concerns on 4th Example. 上記第４実施例に係る顕微鏡対物レンズの諸収差図である。It is various aberrational figures of the microscope objective lens which concerns on the said 4th Example. 上記顕微鏡対物レンズとともに用いられる結像レンズのレンズ構成図である。It is a lens block diagram of the imaging lens used with the said microscope objective lens.

符号の説明Explanation of symbols

ＯＬ（ＯＬ１〜ＯＬ４） 顕微鏡対物レンズ
Ｇ１ 第１レンズ群 Ｇ２ 第２レンズ群 Ｇ３ 第３レンズ群
ＧＤ 回折光学素子 OL (OL1 to OL4) Microscope objective lens G1 First lens group G2 Second lens group G3 Third lens group GD Diffractive optical element

Claims (5)

物体側から順に、
正の屈折力を有する第１レンズ群と、
正の屈折力を有する第２レンズ群と、
負の屈折力を有する第３レンズ群と、を有し、
前記第１レンズ群は、最も物体側に位置し負の屈折力を有するレンズ面を含む正レンズ成分と、少なくとも１つ以上の、合成で正の屈折力を有する接合レンズ成分とを有し、
前記第２レンズ群は、異なる光学材料からなる２つの回折素子要素を接合し、当該接合面に回折格子溝が形成された回折光学面を有する回折光学素子と、少なくとも１つ以上の接合レンズ成分とを有し、
前記第３レンズ群は、少なくとも１つ以上の合成で負の屈折力を有する色補正レンズ成分を有し、且つ、当該第３レンズ群の最も像側のレンズ面が、像側に凹面を向けて配置されており、
前記第１レンズ群に設けられた前記正レンズ成分の前記負の屈折力を有するレンズ面の曲率半径をＲとし、当該負の屈折力を有するレンズ面の物体側の媒質のｄ線に対する屈折率をｎ１、像側の媒質のｄ線に対する屈折率をｎ２とし、前記負の屈折力を有するレンズ面の頂点から物体までの光軸上の距離をｄ０としたとき、次式
｜（ｎ２−ｎ１）／（Ｒ・ｄ０）｜ ＜ ０．０１
の条件を満足し、
全系の焦点距離をｆとし、前記回折光学面を通る最大画角に対応する光束の主光線の光軸からの高さをｈとしたとき、次式
０．０５ ＜ ｜ｈ／ｆ｜
の条件を満足するように構成された顕微鏡対物レンズ。 From the object side,
A first lens group having a positive refractive power;
A second lens group having a positive refractive power;
A third lens group having negative refractive power,
The first lens group includes a positive lens component including a lens surface located closest to the object side and having a negative refractive power, and at least one cemented lens component having a combined positive refractive power ,
The second lens group includes a diffractive optical element having a diffractive optical surface in which two diffractive element elements made of different optical materials are bonded and a diffraction grating groove is formed on the bonded surface, and at least one bonded lens component. And
The third lens group has at least one color correction lens component having a negative refractive power in combination, and the lens surface closest to the image side of the third lens group faces a concave surface toward the image side. Arranged,
The radius of curvature of the lens surface having negative refractive power of the positive lens component provided in the first lens group is R, and the refractive index with respect to d-line of the medium on the object side of the lens surface having negative refractive power. Is n1, the refractive index for the d-line of the medium on the image side is n2, and the distance on the optical axis from the apex of the lens surface having the negative refractive power to the object is d0, the following expression | (n2-n1 ) / (R · d0) | <0.01
Satisfy the conditions of
When the focal length of the entire system is f and the height from the optical axis of the principal ray of the light beam corresponding to the maximum field angle passing through the diffractive optical surface is h, the following formula 0.05 <| h / f |
Microscope objective lens configured to satisfy the following conditions. 全系の焦点距離をｆとし、前記第１レンズ群と前記第２レンズ群との合成焦点距離をｆ１２としたとき、次式
１．５ ≦ ｜ｆ１２／ｆ｜ ≦ ４
の条件を満足し、
全系の焦点距離をｆとし、前記第３レンズ群の焦点距離をｆ３としたとき、次式
１ ≦ ｜ｆ３／ｆ｜ ≦ ３．５
の条件を満足する請求項１に記載の顕微鏡対物レンズ。 When the focal length of the entire system is f and the combined focal length of the first lens group and the second lens group is f12, the following formula 1.5 ≦ | f12 / f | ≦ 4
Satisfy the conditions of
When the focal length of the entire system is f and the focal length of the third lens group is f3, the following expression 1 ≦ | f3 / f | ≦ 3.5
The microscope objective lens according to claim 1, which satisfies the following condition. 全系の焦点距離をｆとし、前記第２レンズ群の焦点距離をｆ２としたとき、次式
５ ≦ ｜ｆ２／ｆ｜
の条件を満足する請求項１または２に記載の顕微鏡対物レンズ。 When the focal length of the entire system is f and the focal length of the second lens group is f2, the following formula 5 ≦ | f2 / f |
The microscope objective lens according to claim 1 or 2, which satisfies the following condition. 前記回折光学素子における前記回折光学面の回折格子溝の数をＮとし、当該回折光学面の有効半径をＨとしたとき、次式
２ ≦ Ｎ／Ｈ ≦ １０
の条件を満足する請求項１〜３いずれか一項に記載の顕微鏡対物レンズ。 When the number of diffraction grating grooves on the diffractive optical surface in the diffractive optical element is N and the effective radius of the diffractive optical surface is H, the following formula 2 ≦ N / H ≦ 10
The microscope objective lens as described in any one of Claims 1-3 which satisfy | fills these conditions. 前記回折光学素子中の前記２つの回折素子要素のうち、屈折率が低くアッベ数が小さい方の前記回折素子要素の材料のｄ線に対する屈折率をｎｄ１、Ｆ線に対する屈折率をｎＦ１、Ｃ線に対する屈折率をｎＣ１とし、前記回折光学素子中の前記２つの回折素子要素のうち、屈折率が高くアッベ数が大きい方の前記回折素子要素の材料のｄ線に対する屈折率をｎｄ２、Ｆ線に対する屈折率をｎＦ２、Ｃ線に対する屈折率をｎＣ２としたとき、次式
ｎｄ１ ≦ １．５４
０．０１４５ ≦ ｎＦ１−ｎＣ１
１．５５ ≦ ｎｄ２
ｎＦ２−ｎＣ２ ≦ ０．０１３
の条件を満足する請求項１〜４いずれか一項に記載の顕微鏡対物レンズ。 Of the two diffractive element elements in the diffractive optical element, the refractive index for the d-line of the material of the diffractive element element having the lower refractive index and the smaller Abbe number is nd1, the refractive index for the F line is nF1, and the C line. The refractive index with respect to the d-line of the material of the diffractive element element having the higher refractive index and the larger Abbe number among the two diffractive element elements in the diffractive optical element with respect to nd2 and F-line is nC1. When the refractive index is nF2 and the refractive index for the C-line is nC2, the following formula nd1 ≦ 1.54
0.0145 ≦ nF1-nC1
1.55 ≤ nd2
nF2-nC2 ≦ 0.013
The microscope objective lens as described in any one of Claims 1-4 which satisfies these conditions.
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EP16186957.3A EP3128355B1 (en) 2008-04-11 2009-04-08 Microscope objective lens
CN201310088382.3A CN103235404B (en) 2008-04-11 2009-04-08 Micro objective
PCT/JP2009/057161 WO2009125778A1 (en) 2008-04-11 2009-04-08 Microscope objective lens
EP09729761.8A EP2264506B1 (en) 2008-04-11 2009-04-08 Microscope objective lens
CN200980112811.8A CN101999090B (en) 2008-04-11 2009-04-08 Microscope objective lens
CN201310088645.0A CN103235405B (en) 2008-04-11 2009-04-08 Microscope objective lens
US12/889,783 US8958154B2 (en) 2008-04-11 2010-09-24 Microscope objective lens including a diffractive optical element
US14/586,004 US9158102B2 (en) 2008-04-11 2014-12-30 Microscope objective lens including a first lens group with a positive refractive power, a second lens group, and a third lens group having a negative refractive power
US14/585,976 US9134520B2 (en) 2008-04-11 2014-12-30 Microscope objective lens including a first lens group with a positive refractive power, a second lens group with a positive refractive power, and a third lens group having a negative refractive power

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