JP6354170B2 - Objective lens - Google Patents
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Description
本発明は、対物レンズに関する。 The present invention relates to an objective lens.
液浸系顕微鏡対物レンズでは、像面湾曲を補正するために、先端レンズに相対的に屈折率の低い平凸レンズを埋め込み、その屈折率の差により接合面に負の屈折力を与え、ペッツバール和を低減させることが公知の技術となっている。このような液浸対物レンズの設計例として、下記の特許文献１がある。 In an immersion microscope objective lens, a plano-convex lens having a relatively low refractive index is embedded in the tip lens in order to correct the curvature of field, and a negative refractive power is given to the cemented surface due to the difference in refractive index. It is a well-known technique to reduce this. As a design example of such an immersion objective lens, there is Patent Document 1 below.
また、紫外線励起による蛍光観察は一般的に行われているため、蛍光観察用対物レンズには紫外線を透過することが要求される。このような油浸対物レンズの設計例として、下記の特許文献２がある。 In addition, since fluorescence observation by ultraviolet excitation is generally performed, the fluorescence observation objective lens is required to transmit ultraviolet light. As a design example of such an oil immersion objective lens, there is Patent Document 2 below.
また最近では、回折光学素子の色収差補正効果が利用されており、このような対物レンズの設計例として、下記の特許文献３がある。
Recently, the chromatic aberration correction effect of a diffractive optical element has been used. As a design example of such an objective lens, there is
紫外線を透過する硝材は限られており、ｄ線に対する屈折率が１．９を超えると、ｉ線近傍からの短波長域では殆ど透過しなくなる。このため、液浸対物レンズの先端の埋め込みレンズには十分な屈折率差を与えることができず、像面湾曲が補正しきれないという問題があった。 Glass materials that transmit ultraviolet rays are limited, and when the refractive index for d-line exceeds 1.9, it hardly transmits in the short wavelength region from the vicinity of i-line. For this reason, there is a problem that a sufficient refractive index difference cannot be given to the embedded lens at the tip of the immersion objective lens, and the curvature of field cannot be corrected completely.
本発明は、このような問題に鑑みてなされたものであり、像面の平坦性を向上させ、視野周辺まで高い解像力を得ることができる、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 problems, and an object of the present invention is to provide an objective lens that can improve the flatness of the image plane and obtain a high resolving power up to the periphery of the field of view.
このような目的を達成するため、本発明に係る対物レンズは、物体側から順に並んだ、正の屈折力を持つ第１レンズ群と、正の屈折力を持つ第２レンズ群と、負の屈折力を持つ第３レンズ群とからなり、前記第１レンズ群は、最も物体側に配置された物体側に平面を向けた平凸レンズと物体側に凹面を向けたメニスカスレンズとの接合正レンズと、このレンズの像側に隣接して配置された像側に凸面を向けたメニスカス形状で正屈折力の単レンズとを有し、前記第２レンズ群は、複数の接合レンズを有し、そのうち最も物体側の接合レンズのいずれかのレンズ面に、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を備え、前記第３レンズ群は、物体側から順に並んだ、像側に凹面を向けた接合メニスカスレンズと、物体側に凹面を向けた接合メニスカスレンズとからなり、以下の条件式（１）〜（３）を満足するとともに、前記第２レンズ群が有する複数の接合レンズのうち、少なくとも２つの接合レンズは、以下の条件式（４）及び（５）を満足する負レンズと正レンズとから構成されている。 In order to achieve such an object, an objective lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a negative lens arranged in order from the object side. and a third lens group having a refractive power, the first lens group includes a cemented positive lens of a meniscus lens having a concave surface on the plano-convex lens and the object side that is planar to the object side, which are arranged closest to the object side And a single lens having a positive refractive power in a meniscus shape with a convex surface facing the image side, which is arranged adjacent to the image side of the lens, and the second lens group has a plurality of cemented lenses, A diffractive optical element having a diffractive optical surface in which two diffractive element elements made of different optical materials are bonded to one of the lens surfaces of the most object side cemented lens and a diffraction grating groove is formed on the cemented surface is provided. The third lens group is arranged in order from the object side. I, a cemented meniscus lens having a concave surface facing the image side and a cemented meniscus lens having a concave surface facing the object side, with satisfying the following conditional expressions (1) to (3), the second lens group Among the plurality of cemented lenses, at least two cemented lenses are composed of a negative lens and a positive lens that satisfy the following conditional expressions (4) and (5).
３．００ ≦ ｆL3／ｆ ≦ １０．００ ・・・ （１）
１．６５ ≦ ｎdL3 ・・・ （２）
４５．０ ≦ νdL3 ・・・ （３）
０．３０ ≦ ｎdn−ｎdp ・・・ （４）
４０．０ ≦ νdp−νdn ・・・ （５）
但し、
ｆL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの焦点距離、
ｆ：全系の焦点距離、
ｎdL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの硝材のｄ線に対する屈折率、
νdL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの硝材のｄ線を基準とするアッベ数、
ｎdn：前記第２レンズ群の前記接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdn：前記第２レンズ群の前記接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdp：前記第２レンズ群の前記接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdp：前記第２レンズ群の前記接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。
3.00 ≤ fL3 / f ≤ 10.00 (1)
1.65 ≦ ndL3 (2)
45.0 ≦ νdL3 (3)
0.30 ≦ ndn−ndp (4)
40.0 ≦ νdp−νdn (5)
However,
fL3: a focal length of a single lens having a positive refractive power in a meniscus shape with a convex surface facing the image side,
f: focal length of the entire system,
ndL3: a refractive index with respect to d-line of a glass material of a single lens having a meniscus shape having a convex surface facing the image side and having a positive refractive power,
νdL3: Abbe number based on the d-line of a single lens glass material having a meniscus shape with a convex surface facing the image side and a positive refractive power ,
ndn: refractive index with respect to d-line of the glass material of the negative lens constituting the cemented lens of the second lens group,
νdn: Abbe number based on the d-line of the glass material of the negative lens constituting the cemented lens of the second lens group,
ndp: refractive index with respect to d-line of the glass material of the positive lens constituting the cemented lens of the second lens group,
νdp: Abbe number based on the d-line of the glass material of the positive lens constituting the cemented lens of the second lens group .
本発明に係る対物レンズにおいて、前記第１レンズ群の前記接合正レンズを構成する物体側に凹面を向けたメニスカスレンズは、次の条件式（６）及び（７）を満足することが好ましい。 In the objective lens according to the present invention, it is preferable that the meniscus lens having a concave surface facing the object side constituting the cemented positive lens of the first lens group satisfies the following conditional expressions (6) and (7) .
１．８０ ≦ ｎdL2 ・・・ （６）
４０．０ ≦ νdL2 ・・・ （７）
但し、
ｎdL2：前記物体側に凹面を向けたメニスカスレンズの硝材のｄ線に対する屈折率、
νdL2：前記物体側に凹面を向けたメニスカスレンズの硝材のｄ線を基準とするアッベ数。
1.80 ≦ ndL2 (6)
40.0 ≦ νdL2 (7)
However,
ndL2: Refractive index with respect to d-line of the glass material of the meniscus lens with the concave surface facing the object side,
νdL2: Abbe number based on the d-line of the glass material of the meniscus lens with the concave surface facing the object side.
本発明に係る対物レンズにおいて、前記第１レンズ群は、最も像側に接合レンズを有し、前記接合レンズは、次の条件式（８）〜（１０）を満足する負レンズと正レンズとから構成されていることが好ましい。 In the objective lens according to the present invention, the first lens group includes a cemented lens closest to the image side, and the cemented lens includes a negative lens and a positive lens that satisfy the following conditional expressions (8) to (10): It is preferable that it is comprised from these.
１．６０ ≦ （ｎdL4＋ｎdL5）／２ ・・・ （８）
｜ｎdL4−ｎdL5｜ ≦ ０．１０ ・・・ （９）
１５．０ ≦ ｜νdL5−νdL4｜ ・・・ （１０）
但し、
ｎdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。
1.60 ≦ (ndL4 + ndL5) / 2 (8)
｜ ndL4−ndL5 | ≦ 0.10 (9)
15.0 ≤ | νdL5−νdL4 | ... (10)
However,
ndL4: refractive index of d-line of the glass material of the negative lens constituting the most image side cemented lens,
νdL4: Abbe number based on the d-line of the glass material of the negative lens constituting the most image side cemented lens,
ndL5: refractive index with respect to d-line of the glass material of the positive lens constituting the most image side cemented lens,
νdL5: Abbe number based on the d-line of the glass material of the positive lens constituting the most image side cemented lens.
本発明に係る対物レンズにおいて、前記第１レンズ群を構成する前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズは、像側面が非球面であることが好ましい。 In the objective lens according to the present invention, it is preferable that the image side surface of the single lens having a meniscus shape having a convex surface facing the image side and constituting the first lens group and having a positive refractive power is an aspherical surface.
本発明に係る対物レンズにおいて、前記第３レンズ群を構成する２つの接合メニスカスレンズは、対向する凹面のうち、少なくとも１面が非球面であることが好ましい。 In the objective lens according to the present invention, it is preferable that at least one of the two cemented meniscus lenses constituting the third lens group is an aspherical surface.
本発明に係る対物レンズにおいて、前記第３レンズ群は、光軸方向に移動可能に構成されていることが好ましい。 In the objective lens according to the present invention, it is preferable that the third lens group is configured to be movable in the optical axis direction.
本発明に係る対物レンズにおいて、前記回折光学素子を構成する２つの回折素子要素は、互いに異なる樹脂からなり、次の条件式（１１）及び（１２）を満足することが好ましい。 In the objective lens according to the present invention, it is preferable that the two diffractive element elements constituting the diffractive optical element are made of different resins and satisfy the following conditional expressions (11) and (12) .
０．０１ ≦ ｎd1−ｎd2 ・・・ （１１）
０．００１５ ≦ ΔｎFC2−ΔｎFC1 ・・・ （１２）
但し、
ｎd1、ｎF1及びｎC1：前記２つの回折素子要素のうち、高屈折率低分散な方の回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率、
ｎd2、ｎF2及びｎC2：前記２つの回折素子要素のうち、低屈折率高分散な方の回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率。
また、ΔｎFC1＝ｎF1−ｎC1、ΔｎFC2＝ｎF2−ｎC2と定義する。
0.01 ≦ nd1−nd2 (11)
0.0015 ≦ ΔnFC2−ΔnFC1 (12)
However,
nd1, nF1, and nC1: Refractive indexes for the d-line, F-line, and C-line of the material of the diffractive element having the higher refractive index and lower dispersion among the two diffractive element elements,
nd2, nF2, and nC2: Refractive indexes for the d-line, F-line, and C-line of the material of the diffractive element having the lower refractive index and higher dispersion among the two diffractive element elements.
Further, ΔnFC1 = nF1-nC1, and ΔnFC2 = nF2-nC2 are defined.
本発明に係る対物レンズにおいて、前記回折光学素子は、主光線が光軸と交わる位置よりも物体側に配置され、次の条件式（１３）を満足することが好ましい。 In the objective lens according to the present invention, it is preferable that the diffractive optical element is disposed on the object side with respect to a position where the principal ray intersects the optical axis and satisfies the following conditional expression (13) .
４．０° ≦ ｜θent| ≦ １２．０° ・・・ （１３）
但し、
θent：物体中心から最大ＮＡとなる光線が前記回折光学素子の空気側面に入射する角度。
4.0 ° ≦ | θent | ≦ 12.0 ° (13)
However,
θent: An angle at which a light beam having a maximum NA from the object center is incident on the air side surface of the diffractive optical element.
本発明に係る対物レンズは、次の条件式（１４）を満足することが好ましい。 The objective lens according to the present invention preferably satisfies the following conditional expression (14) .
１００．００ ≦ ｜ｆdoe／ｆ| ・・・ （１４）
但し、
ｆdoe：前記回折光学素子の焦点距離。
100.00 ≦ | fdoe / f | (14)
However,
fdoe: focal length of the diffractive optical element.
本発明に係る対物レンズは、次の条件式（１５）を満足することが好ましい。 The objective lens according to the present invention preferably satisfies the following conditional expression (15) .
４．００ ≦ ｆG2／ｆ ≦ ２０．００ ・・・ （１５）
但し、
ｆG2：前記第２レンズ群の焦点距離。
4.00 ≦ fG2 / f ≦ 20.00 (15)
However,
fG2: focal length of the second lens group.
本発明によれば、像面の平坦性を向上させ、視野周辺まで高い解像力を得ることができる、対物レンズを提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the objective lens which can improve the flatness of an image surface and can obtain high resolving power to a visual field periphery can be provided.
以下、実施形態について、図面を参照しながら説明する。本実施形態に係る対物レンズＯＬは、図１に示すように、物体側から順に並んだ、正の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、負の屈折力を持つ第３レンズ群Ｇ３とを有して構成される。 Hereinafter, embodiments will be described with reference to the drawings. As shown in FIG. 1, the objective lens OL according to the present embodiment includes a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, arranged in order from the object side, And a third lens group G3 having negative refractive power.
第１レンズ群Ｇ１は、最も物体側に配置された物体側に平面を向けた平凸レンズＬ１と物体側に凹面を向けたメニスカスレンズＬ２との接合正レンズと、このレンズの像側に隣接して配置された像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３とを有する。 The first lens group G1 is adjacent to the image side of a cemented positive lens of a plano-convex lens L1 having a plane facing the object side disposed closest to the object side and a meniscus lens L2 having a concave surface facing the object side. And a single lens L3 having a meniscus shape with a convex surface facing the image side and having a positive refractive power.
最も物体側に平凸レンズＬ１を配置することにより、対物レンズＯＬの先端部を浸液に浸して物体（標本）を観察するときに、該レンズの物体側の面（第１面）内に気泡等が滞留するのを防ぐとともに、諸収差の発生を抑えることができる。また、平凸レンズＬ１が埋め込まれたメニスカスレンズＬ２の像側の凸面の曲率がきつくなると球面収差やコマ収差が発生するため、その像側に隣接して像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３を配置して、前記収差を補正している。 By arranging the plano-convex lens L1 on the most object side, when observing an object (specimen) by immersing the tip of the objective lens OL in immersion liquid, bubbles are formed in the object-side surface (first surface) of the lens. Etc. can be prevented and the occurrence of various aberrations can be suppressed. In addition, when the curvature of the convex surface on the image side of the meniscus lens L2 in which the plano-convex lens L1 is embedded becomes tight, spherical aberration and coma aberration occur. Therefore, a meniscus shape with a convex surface facing the image side adjacent to the image side is positive. A single lens L3 having a refractive power is arranged to correct the aberration.
第２レンズ群Ｇ２は、複数の接合レンズ（図１では、レンズＬ６，Ｌ７からなる接合レンズ、レンズＬ８，Ｌ９からなる接合レンズ、レンズＬ１０，Ｌ１１からなる接合レンズ）を有し、そのうち最も物体側の接合レンズのいずれかのレンズ面（図１では、第１０面）に、異なる光学材料からなる２つの回折素子要素Ｐ１，Ｐ２を接合し、当該接合面（図１では、第１１面）に回折格子溝が形成された回折光学面Ｄを有する回折光学素子ＰＦを備える。 The second lens group G2 has a plurality of cemented lenses (in FIG. 1, a cemented lens composed of the lenses L6 and L7, a cemented lens composed of the lenses L8 and L9, and a cemented lens composed of the lenses L10 and L11). Two diffractive element elements P1 and P2 made of different optical materials are bonded to any lens surface (the tenth surface in FIG. 1) of the side cemented lens, and the cemented surface (the eleventh surface in FIG. 1). Are provided with a diffractive optical element PF having a diffractive optical surface D on which diffraction grating grooves are formed.
本実施形態では、回折光学素子ＰＦは、色収差を補正するために設けられている。回折光学素子ＰＦ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ＰＦ（回折光学面Ｄ）は、負の分散値を有し、分散が大きく、また異常分散性が強いため、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ＰＦ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ＰＦ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。 In the present embodiment, the diffractive optical element PF is provided to correct chromatic aberration. The diffractive optical element PF includes a diffractive optical surface D in which several to several hundreds of fine groove-shaped or slit-shaped grating structures are formed concentrically per 1 mm. It has the property of diffracting in a direction determined by the (grating groove interval) and the wavelength of incident light. In addition, the diffractive optical element PF (diffractive optical surface D) has a negative dispersion value, a large dispersion, and a strong anomalous dispersion, and thus has a strong chromatic aberration correction capability. 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 PF 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 PF.
この回折光学素子ＰＦによって、軸上色収差と倍率色収差を同時に補正するためには、屈折力の配置上、その回折光学面Ｄを、主光線が光軸と交わる位置より物体側に配置する必要がある。主光線が光軸と交わる位置よりも前側（物体側）で、この回折光学素子ＰＦにより軸上色収差と倍率色収差のバランスを取って補正し、主光線が光軸と交わる位置よりも後ろ側で、接合レンズ等により、残った倍率色収差を補正することができるからである。 In order to correct axial chromatic aberration and lateral chromatic aberration at the same time by this diffractive optical element PF, it is necessary to dispose the diffractive optical surface D on the object side from the position where the principal ray intersects the optical axis in terms of the arrangement of refractive power. is there. On the front side (object side) of the position where the chief ray intersects the optical axis, the diffractive optical element PF corrects the balance of axial chromatic aberration and chromatic aberration of magnification and corrects it behind the position where the chief ray intersects the optical axis. This is because the remaining lateral chromatic aberration can be corrected by a cemented lens or the like.
なお、この回折光学素子ＰＦのみで色収差補正を行うと、回折格子溝の最小ピッチが小さくなりすぎ、製造が困難になる。このため、色収差の補正を分担させるべく、第２レンズ群Ｇ２は、複数の接合レンズを有しており、それらは回折光学面Ｄよりも像側に配置されることが好ましい。 If chromatic aberration correction is performed using only the diffractive optical element PF, the minimum pitch of the diffraction grating grooves becomes too small, which makes it difficult to manufacture. For this reason, in order to share correction of chromatic aberration, the second lens group G2 has a plurality of cemented lenses, which are preferably arranged on the image side of the diffractive optical surface D.
本実施形態における回折光学素子ＰＦは、異なる光学材料からなる２つの回折素子要素Ｐ１，Ｐ２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を構成した、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線までの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、本実施形態に係る対物レンズ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 PF in this embodiment is a so-called “adhesive multilayer” in which two diffractive element elements P1 and P2 made of different optical materials are joined, and a diffractive optical groove D is formed on the joined surface to form a diffractive optical surface D. Type diffractive optical element ”. Therefore, this diffractive optical element can increase the diffraction efficiency in a wide wavelength range from the g-line to the C-line. Therefore, the objective lens OL according to the present embodiment can be used in a wide wavelength region. 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、また入射画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形態に係る対物レンズＯＬでは、製造が容易となり、また回折効率が良くなる。 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, the mass production efficiency is good and the diffraction efficiency with respect to the incident angle of view is good. Therefore, the objective lens OL according to the present embodiment using the multi-contact diffractive optical element is easy to manufacture and improves the diffraction efficiency.
第３レンズ群Ｇ３は、物体側から順に並んだ、像側に凹面を向けた接合メニスカスレンズ（図１では、レンズＬ１２，Ｌ１３からなる接合レンズ）と、物体側に凹面を向けた接合メニスカスレンズ（図１では、レンズＬ１４，Ｌ１５からなる接合レンズ）とからなる。この構成により、ペッツバール和を減少させつつ、軸上色収差と倍率色収差とをバランスよく補正することができる。 The third lens group G3 includes a cemented meniscus lens (a cemented lens including lenses L12 and L13 in FIG. 1) and a cemented meniscus lens having a concave surface facing the object side, which are arranged in order from the object side. (In FIG. 1, a cemented lens including lenses L14 and L15). With this configuration, axial chromatic aberration and lateral chromatic aberration can be corrected in a well-balanced manner while reducing Petzval sum.
このように、本実施形態に係る対物レンズＯＬでは、第１レンズ群Ｇ１内に平凸レンズＬ１と物体側に凹面を向けたメニスカスレンズＬ２とを貼り合わせた接合レンズを配置するとともに、第３レンズ群Ｇ３内に互いの凹面が対向するように２つの接合メニスカスレンズを配置したいわゆるガウスタイプの構成をとることにより、ペッツバール和を抑え、像面湾曲を良好に補正することができる。また、第２レンズ群Ｇ２内に複数の接合レンズ及び回折光学素子ＰＦを配置することにより、補正したい波長域において色収差を良好に補正することができる。 As described above, in the objective lens OL according to the present embodiment, the cemented lens in which the plano-convex lens L1 and the meniscus lens L2 with the concave surface facing the object side are bonded in the first lens group G1, and the third lens is arranged. By adopting a so-called Gauss type configuration in which two cemented meniscus lenses are arranged so that their concave surfaces face each other in the group G3, Petzval sum can be suppressed and field curvature can be corrected well. Further, by arranging a plurality of cemented lenses and the diffractive optical element PF in the second lens group G2, chromatic aberration can be favorably corrected in the wavelength region to be corrected.
上記構成のもと、本実施形態に係る対物レンズＯＬは、次の条件式（１）〜（３）を満足する。 Based on the above configuration, the objective lens OL according to the present embodiment satisfies the following conditional expressions (1) to (3).
３．００ ≦ ｆL3／ｆ ≦ １０．００ …（１）
１．６５ ≦ ｎdL3 …（２）
４５．０ ≦ νdL3 …（３）
但し、
ｆL3：像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３の焦点距離、
ｆ：全系の焦点距離、
ｎdL3：像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３の硝材のｄ線に対する屈折率、
νdL3：像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３の硝材のｄ線を基準とするアッベ数。
3.00 ≦ fL3 / f ≦ 10.00 (1)
1.65 ≦ ndL3 (2)
45.0 ≦ νdL3 (3)
However,
fL3: a focal length of a single lens L3 having a meniscus shape having a convex surface facing the image side and having a positive refractive power,
f: focal length of the entire system,
ndL3: refractive index with respect to d-line of the glass material of the single lens L3 having a meniscus shape having a convex surface facing the image side and having a positive refractive power
νdL3: Abbe number based on the d-line of the glass material of the single lens L3 having a meniscus shape having a convex surface facing the image side and having a positive refractive power.
条件式（１）は、第１レンズ群Ｇ１を構成する像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３の適切な焦点距離を制限するものである。条件式（１）の下限値を下回ると、正屈折力の単レンズＬ３の屈折力が強くなりすぎ、球面収差や軸上色収差が増大する。条件式（１）の上限値を上回ると、後群のレンズ径が大きくなりすぎる。また、正屈折力の単レンズＬ３の屈折力が弱くなり、軸上色収差が補正しきれなくなる。 Conditional expression (1) limits the appropriate focal length of the single lens L3 having a meniscus shape with a convex surface facing the image side constituting the first lens group G1 and having a positive refractive power. If the lower limit value of conditional expression (1) is not reached, the refractive power of the single lens L3 having positive refractive power becomes too strong, and spherical aberration and axial chromatic aberration increase. If the upper limit of conditional expression (1) is exceeded, the lens diameter of the rear group becomes too large. In addition, the refractive power of the single lens L3 having a positive refractive power becomes weak, and axial chromatic aberration cannot be corrected.
より効果的に収差補正を行うためには、条件式（１）の下限値を４．００とすることが好ましい。より効果的に収差補正を行うためには、条件式（１）の上限値を８．００とすることが好ましい。 In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (1) to 4.00. In order to perform aberration correction more effectively, it is preferable to set the upper limit of conditional expression (1) to 8.00.
条件式（２）及び（３）は、第１レンズ群Ｇ１を構成する像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３のｄ線に対する屈折率及びアッベ数を制限するものである。条件式（２）の下限値を下回ると、曲率半径が小さくなり、ペッツバール和の増大による像面湾曲や球面収差の補正が困難となる。条件式（３）の下限値を下回ると、軸上色収差や異なる波長による球面収差の補正が困難となる。 Conditional expressions (2) and (3) limit the refractive index and Abbe number for the d-line of the single lens L3 having a meniscus shape with a convex surface facing the image side constituting the first lens group G1 and having a positive refractive power. is there. If the lower limit value of conditional expression (2) is not reached, the radius of curvature becomes small, and it becomes difficult to correct curvature of field and spherical aberration by increasing Petzval sum. If the lower limit of conditional expression (3) is not reached, it will be difficult to correct longitudinal chromatic aberration and spherical aberration due to different wavelengths.
より効果的に収差補正を行うためには、条件式（２）の下限値を１．７０とすることが好ましい。より効果的に収差補正を行うためには、条件式（３）の下限値を５０．０とすることが好ましい。 In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (2) to 1.70. In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (3) to 50.0.
本実施形態に係る対物レンズＯＬは、第２レンズ群Ｇ２が有する複数の接合レンズのうち、少なくとも２つの接合レンズは、次の条件式（４），（５）を満足する負レンズと正レンズとから構成されていることが好ましい。 The objective lens OL according to the present embodiment includes a negative lens and a positive lens satisfying the following conditional expressions (4) and (5) among at least two cemented lenses included in the second lens group G2. It is preferable that it is comprised from these.
０．３０ ≦ ｎdn−ｎdp …（４）
４０．０ ≦ νdp−νdn …（５）
但し、
ｎdn：第２レンズ群Ｇ２の前記接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdn：第２レンズ群Ｇ２の前記接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdp：第２レンズ群Ｇ２の前記接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdp：第２レンズ群Ｇ２の前記接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。
0.30 ≦ ndn−ndp (4)
40.0 ≦ νdp−νdn (5)
However,
ndn: refractive index with respect to d-line of the glass material of the negative lens constituting the cemented lens of the second lens group G2.
νdn: Abbe number based on the d-line of the glass material of the negative lens constituting the cemented lens of the second lens group G2,
ndp: refractive index with respect to d-line of the glass material of the positive lens constituting the cemented lens of the second lens group G2.
νdp: Abbe number based on the d-line of the glass material of the positive lens constituting the cemented lens of the second lens group G2.
条件式（４）及び（５）は、第２レンズ群Ｇ２内に配置された、少なくとも２つの接合レンズ（図１では、レンズＬ８，Ｌ９からなる接合レンズと、レンズＬ１０，Ｌ１１からなる接合レンズ）を構成する、負レンズと正レンズのｄ線に対する屈折率差とアッベ数差を制限するものである。条件式（４）及び条件式（５）の下限値を下回ると、軸上色収差と球面収差の補正が困難となる。 Conditional expressions (4) and (5) indicate that at least two cemented lenses (in FIG. 1, a cemented lens composed of lenses L8 and L9 and a cemented lens composed of lenses L10 and L11) are disposed in the second lens group G2. The refractive index difference and the Abbe number difference with respect to the d-line of the negative lens and the positive lens are limited. If the lower limit value of conditional expression (4) and conditional expression (5) is not reached, it will be difficult to correct axial chromatic aberration and spherical aberration.
より効果的に収差補正を行うためには、条件式（４）の下限値を０．３５とすることが好ましい。より効果的に収差補正を行うためには、条件式（５）の下限値を４５．００とすることが好ましい。 In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (4) to 0.35. In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (5) to 45.00.
本実施形態に係る対物レンズＯＬにおいて、第１レンズ群Ｇ１の接合正レンズを構成する、物体側に凹面を向けたメニスカスレンズＬ２は、次の条件式（６），（７）を満足することが好ましい。 In the objective lens OL according to the present embodiment, the meniscus lens L2 having a concave surface facing the object side and constituting the cemented positive lens of the first lens group G1 satisfies the following conditional expressions (6) and (7). Is preferred.
１．８０ ≦ ｎdL2 …（６）
４０．０ ≦ νdL2 …（７）
但し、
ｎdL2：物体側に凹面を向けたメニスカスレンズＬ２の硝材のｄ線に対する屈折率、
νdL2：物体側に凹面を向けたメニスカスレンズＬ２の硝材のｄ線を基準とするアッベ数。
1.80 ≦ ndL2 (6)
40.0 ≦ νdL2 (7)
However,
ndL2: refractive index with respect to d-line of the glass material of the meniscus lens L2 with the concave surface facing the object side,
νdL2: Abbe number based on the d-line of the glass material of the meniscus lens L2 with the concave surface facing the object side.
条件式（６）及び（７）は、第１レンズ群Ｇ１の接合正レンズを構成する、物体側に凹面を向けたメニスカスレンズＬ２のｄ線に対する屈折率とアッベ数を制限するものである。条件式（６）及び（７）の下限値を下回ると、ペッツバール和と色収差の補正が困難となるだけでなく、硝材の組成上、近紫外域（ｉ線）の透過率を確保することも困難となる。 Conditional expressions (6) and (7) limit the refractive index and the Abbe number for the d-line of the meniscus lens L2 constituting the cemented positive lens of the first lens group G1 and having the concave surface facing the object side. If the lower limit value of conditional expressions (6) and (7) is not reached, correction of Petzval sum and chromatic aberration becomes difficult, and the transmittance in the near-ultraviolet region (i-line) is ensured due to the composition of the glass material. It becomes difficult.
本実施形態に係る対物レンズＯＬにおいて、第１レンズ群Ｇ１は、最も像側に接合レンズ（図１では、レンズＬ４，Ｌ５からなる接合レンズ）を有し、前記接合レンズは、次の条件式（８）〜（１０）を満足する負レンズと正レンズとから構成されていることが好ましい。 In the objective lens OL according to the present embodiment, the first lens group G1 has a cemented lens (a cemented lens including lenses L4 and L5 in FIG. 1) closest to the image side, and the cemented lens has the following conditional expression: It is preferable that the lens is composed of a negative lens and a positive lens that satisfy (8) to (10).
１．６０ ≦ （ｎdL4＋ｎdL5）／２ …（８）
｜ｎdL4−ｎdL5｜ ≦ ０．１０ …（９）
１５．０ ≦ ｜νdL5−νdL4｜ …（１０）
但し、
ｎdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。
1.60 ≦ (ndL4 + ndL5) / 2 (8)
| NdL4−ndL5 | ≦ 0.10 (9)
15.0 ≦ | νdL5−νdL4 | (10)
However,
ndL4: refractive index of d-line of the glass material of the negative lens constituting the most image side cemented lens,
νdL4: Abbe number based on the d-line of the glass material of the negative lens constituting the most image side cemented lens,
ndL5: refractive index with respect to d-line of the glass material of the positive lens constituting the most image side cemented lens,
νdL5: Abbe number based on the d-line of the glass material of the positive lens constituting the most image side cemented lens.
条件式（８），（９）及び（１０）は、第１レンズ群Ｇ１の最も像側に配置された接合レンズを構成する２枚のレンズ（図１では、負レンズＬ４と、正レンズＬ５）のｄ線に対する平均屈折率、屈折率差及びアッベ数差を制限するものである。 Conditional expressions (8), (9), and (10) are expressed by two lenses (a negative lens L4 and a positive lens L5 in FIG. 1) that constitute a cemented lens disposed closest to the image side of the first lens group G1. ) For the d-line, the average refractive index, the refractive index difference, and the Abbe number difference are limited.
条件式（８）の下限値を下回ると、ペッツバール和が大きくなり、像面湾曲の補正が困難となる。より効果的に収差補正を行うためには、条件式（８）の下限値を１．６２とすることが好ましい。 If the lower limit value of conditional expression (8) is not reached, the Petzval sum becomes large and it becomes difficult to correct field curvature. In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (8) to 1.62.
条件式（９）の上限値及び条件式（１０）の下限値を超えると、色収差の補正が困難となる。より効果的に収差補正を行うためには、条件式（９）の上限値を０．０５とすることが好ましい。より効果的に収差補正を行うためには、条件式（１０）の下限値を１８．０とすることが好ましい。 If the upper limit value of conditional expression (9) and the lower limit value of conditional expression (10) are exceeded, it will be difficult to correct chromatic aberration. In order to perform aberration correction more effectively, it is preferable to set the upper limit of conditional expression (9) to 0.05. In order to perform aberration correction more effectively, it is preferable to set the lower limit of conditional expression (10) to 18.0.
本実施形態に係る対物レンズＯＬにおいて、第１レンズ群Ｇ１を構成する、像側に凸面を向けたメニスカス形状で正屈折力の単レンズＬ３は、像側面が非球面であることが好ましい。この構成により、球面収差を良好に補正することができる。 In the objective lens OL according to this embodiment, it is preferable that the image side surface of the single lens L3 having a positive refractive power in the meniscus shape having a convex surface directed to the image side and constituting the first lens group G1 is an aspherical surface. With this configuration, spherical aberration can be corrected satisfactorily.
本実施形態に係る対物レンズＯＬにおいて、第３レンズ群Ｇ３を構成する２つの接合メニスカスレンズ（例えば、図３における、レンズＬ１０，Ｌ１１からなる接合レンズと、レンズＬ１２，Ｌ１３からなる接合レンズ）は、対向する凹面のうち、少なくとも１面（図３では、第１９面）が非球面であることが好ましい。この構成により、コマ収差の発生を良好に抑えることができる。 In the objective lens OL according to the present embodiment, two cemented meniscus lenses (for example, a cemented lens composed of the lenses L10 and L11 and a cemented lens composed of the lenses L12 and L13 in FIG. 3) constituting the third lens group G3 are provided. Of the concave surfaces facing each other, at least one surface (the 19th surface in FIG. 3) is preferably an aspherical surface. With this configuration, the occurrence of coma aberration can be satisfactorily suppressed.
本実施形態に係る対物レンズＯＬにおいて、第３レンズ群Ｇ３は、光軸方向に移動可能に構成されていることが好ましい。これは、カバーガラスと浸液の屈折率は同一ではないため、カバーガラスの厚みにばらつきが生じたり、顕微鏡対物レンズを使用する環境で温度変化が生じたりすると、浸液やレンズに使われる硝材の屈折率変化により収差が変動する。そこで、本実施形態においては、第３レンズ群Ｇ３を光軸方向に移動させることにより、前記のような観察環境に起因して収差が発生した場合でも、諸収差を抑え、良好な結像性能を維持することができるようにしている。 In the objective lens OL according to this embodiment, it is preferable that the third lens group G3 is configured to be movable in the optical axis direction. This is because the refractive index of the cover glass and immersion liquid is not the same, so if the thickness of the cover glass varies or the temperature changes in the environment where the microscope objective lens is used, the glass material used for the immersion liquid and lens The aberration fluctuates due to the refractive index change. Therefore, in the present embodiment, by moving the third lens group G3 in the optical axis direction, even when aberration occurs due to the observation environment as described above, various aberrations are suppressed, and good imaging performance is achieved. To be able to maintain.
本実施形態に係る対物レンズＯＬにおいて、回折光学素子を構成する２つの回折素子要素Ｐ１，Ｐ２は、互いに異なる樹脂からなり、次の条件式（１１）及び（１２）を満足することが好ましい。 In the objective lens OL according to the present embodiment, the two diffractive element elements P1 and P2 constituting the diffractive optical element are preferably made of different resins and satisfy the following conditional expressions (11) and (12).
０．０１ ≦ ｎd1−ｎd2 …（１１）
０．００１５ ≦ ΔｎFC2−ΔｎFC1 …（１２）
但し、
ｎd1、ｎF1及びｎC1：２つの回折素子要素Ｐ１，Ｐ２のうち、高屈折率低分散な方の前記回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率、
ｎd2、ｎF2及びｎC2：前記２つの回折素子要素Ｐ１，Ｐ２のうち、低屈折率高分散な方の前記回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率。
また、ΔｎFC1＝ｎF1−ｎC1、ΔｎFC2＝ｎF2−ｎC2と定義する。
0.01 ≦ nd1−nd2 (11)
0.0015 ≦ ΔnFC2−ΔnFC1 (12)
However,
nd1, nF1, and nC1: Refractive index with respect to d-line, F-line, and C-line of the material of the diffractive element having a higher refractive index and lower dispersion among the two diffractive element elements P1, P2.
nd2, nF2, and nC2: Refractive indexes for the d-line, F-line, and C-line of the material of the diffractive element having the lower refractive index and higher dispersion among the two diffractive element elements P1 and P2.
Further, ΔnFC1 = nF1-nC1, and ΔnFC2 = nF2-nC2 are defined.
条件式（１１）及び（１２）は、第２レンズ群Ｇ２に配置された回折光学素子ＰＦを構成する、回折素子要素Ｐ１，Ｐ２に用いる異なる２つの材料の適切な屈折率と分散の範囲を制限するものである。条件式（１１）及び（１２）を満足することにより、より良い性能で異なる２つの回折素子要素Ｐ１，Ｐ２を密着接合させて回折光学面Ｄを形成することができ、これにより広波長域において高い回折効率を実現することができる。条件式（１１）及び（１２）の下限値を下回ると、２種類の材料の屈折率差が小さくなりすぎて回折格子の高さが大きくなるために回折効率が低下したり、分散の差が小さくなりすぎて広波長域に亘って高い回折効率を維持したりすることができなくなる。なお、２つの回折素子要素にＰ１，Ｐ２に用いる材料は、ｄ線に対する屈折率が１．５以上で、かつ、各素子厚においてｉ線（波長365.015nm）を５０％以上透過する樹脂であることが望ましい。 Conditional expressions (11) and (12) indicate appropriate refractive indexes and dispersion ranges of two different materials used for the diffractive element elements P1 and P2 constituting the diffractive optical element PF arranged in the second lens group G2. It is a limitation. By satisfying conditional expressions (11) and (12), two different diffraction element elements P1 and P2 with better performance can be tightly bonded to form the diffractive optical surface D. High diffraction efficiency can be realized. If the lower limit value of the conditional expressions (11) and (12) is not reached, the difference in refractive index between the two materials becomes too small and the height of the diffraction grating becomes large, so that the diffraction efficiency is lowered or the difference in dispersion is reduced. It becomes too small to maintain high diffraction efficiency over a wide wavelength range. The material used for P1 and P2 for the two diffraction element elements is a resin that has a refractive index of 1.5 or more with respect to the d-line and transmits 50% or more of the i-line (wavelength 365.015 nm) at each element thickness. It is desirable.
本実施形態に係る対物レンズＯＬにおいて、上述したように、光束が回折光学素子ＰＦに入射する光線の角度が大きいと、回折効率が落ちてしまい、設計次数以外の回折光の効率が大きくなってフレアとなる。このため、回折光学素子ＰＦは、主光線と光軸とが交わる位置よりも物体側に配置されるとともに、次の条件式（１３）を満足することが好ましい。 In the objective lens OL according to the present embodiment, as described above, if the angle of the light beam incident on the diffractive optical element PF is large, the diffraction efficiency decreases, and the efficiency of diffracted light other than the designed order increases. It becomes a flare. For this reason, it is preferable that the diffractive optical element PF is disposed on the object side with respect to the position where the principal ray and the optical axis intersect and satisfies the following conditional expression (13).
４．０° ≦ ｜θent| ≦ １２．０° …（１３）
但し、
θent：物体中心から最大ＮＡとなる光線が回折光学素子ＰＦの空気側面に入射する角度。
4.0 ° ≦ | θent | ≦ 12.0 ° (13)
However,
θent: An angle at which a light beam having a maximum NA from the object center is incident on the air side surface of the diffractive optical element PF.
条件式(１３)は、第２レンズ群Ｇ２内に配置される回折光学素子ＰＦに入射する適切な角度を制限するものである。条件式（１３）を満足することにより、回折効率がよく、設計次数以外の回折光の効率が大きくなることを抑え、フレアを良好に防止することができる。条件式（１３）の下限値を下回ると、空気側面での反射によるフレアが増大し、像のコントラストが低下する。条件式（１３）の上限値を上回ると、回折光学素子ＰＦの接合面に形成された回折光学面Ｄに入射する角度が大きくなりすぎて、回折効率の低下による結像性能の劣化を引き起こす。 Conditional expression (13) limits an appropriate angle of incidence on the diffractive optical element PF disposed in the second lens group G2. By satisfying conditional expression (13), the diffraction efficiency is good, the efficiency of diffracted light other than the designed order is prevented from increasing, and flare can be prevented well. If the lower limit of conditional expression (13) is not reached, flare due to reflection on the air side surface increases, and the contrast of the image decreases. If the upper limit value of conditional expression (13) is exceeded, the angle of incidence on the diffractive optical surface D formed on the cemented surface of the diffractive optical element PF becomes too large, causing deterioration in imaging performance due to a decrease in diffraction efficiency.
本実施形態に係る対物レンズＯＬは、次の条件式（１４）を満足することが好ましい。 The objective lens OL according to the present embodiment preferably satisfies the following conditional expression (14).
１００．００ ≦ ｜ｆdoe／ｆ| …（１４）
但し、
ｆdoe：前記回折光学素子の焦点距離。
100.00 ≦ | fdoe / f | (14)
However,
fdoe: focal length of the diffractive optical element.
条件式（１４）は、第２レンズ群Ｇ２内に配置された回折光学素子ＰＦの回折光学面Ｄの適切なパワーを制限するものである。条件式（１４）の下限値を下回ると、回折光学面Ｄのパワーが強くなりすぎて、色収差の補正が困難になるだけでなく、回折格子溝のピッチ幅が小さくなりすぎて、製造が困難となる。 Conditional expression (14) limits the appropriate power of the diffractive optical surface D of the diffractive optical element PF disposed in the second lens group G2. If the lower limit value of conditional expression (14) is not reached, the power of the diffractive optical surface D becomes too strong, making it difficult to correct chromatic aberration, and making the pitch width of the diffraction grating grooves too small to make manufacture difficult. It becomes.
本実施形態に係る対物レンズＯＬは、次の条件式（１５）を満足することが好ましい。 The objective lens OL according to the present embodiment preferably satisfies the following conditional expression (15).
４．００ ≦ ｆG2／ｆ ≦ ２０．００ …（１５）
但し、
ｆG2：第２レンズ群Ｇ２の焦点距離。
4.00 ≦ fG2 / f ≦ 20.00 (15)
However,
fG2: focal length of the second lens group G2.
条件式（１５）は、第２レンズ群Ｇ２の適切な焦点距離を制限するものである。条件式（１５）の下限値を下回ると、第２レンズ群Ｇ２のパワーが強くなりすぎて、結果的に第３レンズ群Ｇ３のパワーも増大し、球面収差やコマ収差が補正過剰となる。条件式（１５）の上限値を上回ると、逆に高次の球面収差やコマ収差が発生し、これらの補正が困難となる。 Conditional expression (15) limits the appropriate focal length of the second lens group G2. If the lower limit of conditional expression (15) is not reached, the power of the second lens group G2 becomes too strong, and as a result, the power of the third lens group G3 also increases, and the spherical aberration and coma aberration are overcorrected. If the upper limit value of conditional expression (15) is exceeded, high-order spherical aberration and coma will occur conversely, making it difficult to correct these.
本実施形態の効果をより確実なものとするために、条件式（１５）の下限値を６．００とすることが好ましい。本実施形態の効果をより確実なものとするために、条件式（１５）の上限値を１５．００とすることが好ましい。 In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (15) to 6.00. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (15) to 15.00.
これより本実施形態に係る各実施例について、図面に基づいて説明する。以下に、表１〜表３を示すが、これらは第１実施例〜第３実施例における各諸元の表である。 Each example according to the present embodiment will be described with reference to the drawings. Tables 1 to 3 are shown below, but these are tables of specifications in the first to third examples.
なお、第１実施例に係る図１に対する各参照符号は、参照符号の桁数の増大による説明の煩雑化を避けるため、実施例ごとに独立して用いている。ゆえに、他の実施例に係る図面と共通の参照符号を付していても、それらは他の実施例とは必ずしも共通の構成ではない。 In addition, each reference code with respect to FIG. 1 according to the first embodiment is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, even if the same reference numerals as those in the drawings according to the other embodiments are given, they are not necessarily in the same configuration as the other embodiments.
表中の［全体諸元］において、βは倍率、ＮＡは開口数、ｆは全系の焦点距離を示す。また、ｄ０は、平行平面板（カバーガラスやガラスシャーレ等）の対物レンズ側の面から、第１レンズ群Ｇ１の最も物体側にあるレンズＬ１の最も物体側のレンズ面までの光軸上の距離を示す。 In [Overall specifications] in the table, β represents a magnification, NA represents a numerical aperture, and f represents a focal length of the entire system. D0 is on the optical axis from the objective lens side surface of the plane parallel plate (cover glass, glass petri dish, etc.) to the most object side lens surface of the lens L1 closest to the object side of the first lens group G1. Indicates distance.
表中の［レンズ諸元］において、面番号は光線の進行する方向に沿った物体側からの光学面の順序、Ｒは各光学面の曲率半径、ｄは各光学面から次の光学面（又は像面）までの光軸上の距離である面間隔、ｎｄは光学部材の材質のｄ線（波長587.5620nm）に対する屈折率、νｄは光学部材の材質のｄ線を基準とするアッベ数をそれぞれ示す。曲率半径の「∞」は平面又は開口を示す。空気の屈折率「1.00000」の記載は省略する。光学面が回折光学面である場合には、面番号に＊Ｄを付す。また、光学面が非球面である場合には、面番号に＊Ａを付し、曲率半径Ｒの欄には近軸曲率半径を示す。 In [Lens Specifications] in the table, the surface number is the order of the optical surfaces from the object side along the light traveling direction, R is the radius of curvature of each optical surface, d is the next optical surface from each optical surface ( Or an optical surface distance to the image surface), nd is a refractive index with respect to the d-line (wavelength 587.5620 nm) of the material of the optical member, and νd is an Abbe number based on the d-line of the material of the optical member. Each is shown. The curvature radius “∞” indicates a plane or an opening. The description of the refractive index “1.00000” of air is omitted. When the optical surface is a diffractive optical surface, * D is added to the surface number. When the optical surface is an aspherical surface, * A is given to the surface number, and the paraxial radius of curvature is shown in the column of the radius of curvature R.
表中の［回折光学面データ］には、［レンズ諸元］に示した回折光学面について、その位相差Φを、次式（ａ）の位相関数Φ（ｈ）で示す。この式（ａ）において、ｈは光軸からの高さ、λは波長、Ｃiは第ｉ次の位相差係数を示す。 In [Diffraction optical surface data] in the table, the phase difference Φ of the diffractive optical surface shown in [Lens specifications] is represented by the phase function Φ (h) of the following equation (a). In this formula (a), h is the height from the optical axis, λ is the wavelength, and Ci is the i-th phase difference coefficient.
Φ（ｈ）＝２π／λ×（Ｃ2×ｈ2＋Ｃ4×ｈ4＋Ｃ6×ｈ6＋Ｃ8×ｈ8） …（ａ） Φ (h) = 2π / λ × (C2 × h 2 + C4 × h 4 + C6 × h 6 + C8 × h 8 ) (a)
表中の［非球面データ］には、［レンズ諸元］に示した非球面について、その形状を次式（ｂ）で示す。この非球面は、回転対称非球面であり、ｚはレンズ面頂点からの光軸方向のサグ量、ｈは光軸からの距離、ｃは曲率（曲率半径ｒの逆数）、Ｋはコーニック定数、Ａiは第ｉ次の非球面係数を示す。「Ｅ-n」は、「×１０-n」を示す。例えば、1.234E-05＝1.234×10-5である。 [Aspherical data] in the table shows the shape of the aspherical surface shown in [Lens Specification] by the following equation (b). This aspherical surface is a rotationally symmetric aspherical surface, z is the amount of sag in the optical axis direction from the apex of the lens surface, h is the distance from the optical axis, c is the curvature (the reciprocal of the radius of curvature r), K is the conic constant, Ai represents the i-th aspherical coefficient. “E-n” indicates “× 10 −n ”. For example, 1.234E-05 = 1.234 × 10 −5 .
表中の［条件式］には、上記の条件式（１）〜（１５）に対応する値を示す。 [Conditional expression] in the table indicates values corresponding to the conditional expressions (1) to (15).
以下、全ての諸元値において、掲載されている焦点距離ｆ、曲率半径Ｒ、面間隔ｄ、その他の長さ等は、特記のない場合一般に「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、これに限られるものではない。また、単位は「mm」に限定されることなく、他の適当な単位を用いることが可能である。 Hereinafter, in all the specification values, “mm” is generally used as the focal length f, radius of curvature R, surface interval d, and other lengths, etc. unless otherwise specified, but the optical system is proportionally enlarged. Alternatively, the same optical performance can be obtained even by proportional reduction, and the present invention is not limited to this. Further, the unit is not limited to “mm”, and other appropriate units can be used.
各実施例に共通する事項として、対物レンズ内に配置される回折光学素子ＰＦは、高屈折率低分散樹脂と、低屈折率高分散樹脂とからなる２つの回折光学素子Ｐ１，Ｐ２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Ｄを有する密着複層型の回折光学素子である。そして、２つの回折光学素子の構成材料には、以下の値の屈折率を有する、異なる２つの紫外線硬化樹脂を用いた。但し、樹脂屈折率は、樹脂硬化後の屈折率を示す。また、それぞれの樹脂に対して、ｎＣはＣ線（波長656.273nm）に対する屈折率、ｎｄはｄ線（波長587.562nm）に対する屈折率、ｎＦはＦ線（波長486.133nm）に対する屈折率、ｎｇはｇ線（波長435.835nm）に対する屈折率を示す。 As a matter common to each embodiment, the diffractive optical element PF disposed in the objective lens is formed by joining two diffractive optical elements P1 and P2 made of a high refractive index and low dispersion resin and a low refractive index and high dispersion resin. This is a contact multilayer diffractive optical element having a diffractive optical surface D in which a diffraction grating groove is formed on the joint surface. As the constituent materials of the two diffractive optical elements, two different ultraviolet curable resins having the following refractive indices were used. However, the resin refractive index indicates the refractive index after the resin is cured. For each resin, nC is the refractive index for the C line (wavelength 656.273 nm), nd is the refractive index for the d line (wavelength 587.562 nm), nF is the refractive index for the F line (wavelength 486.133 nm), and ng is The refractive index with respect to g-line (wavelength: 435.835 nm) is shown.
［樹脂屈折率］
ｎＣ ｎｄ ｎＦ ｎｇ
低屈折率樹脂 1.52330 1.52780 1.53910 1.54910
高屈折率樹脂 1.55380 1.55710 1.56500 1.57130
[Resin refractive index]
nC nd nF ng
Low refractive index resin 1.52330 1.52780 1.53910 1.54910
High refractive index resin 1.55380 1.55710 1.56500 1.57130
これらの樹脂を用いた密着複層型回折光学素子の製造方法は、例えば、欧州特許公開第１８３０２０４号公報、および欧州特許公開第１８３０２０５号公報に記載されている。 A manufacturing method of a contact multilayer diffractive optical element using these resins is described in, for example, European Patent Publication No. 1830204 and European Patent Publication No. 1830205.
ここまでの説明は全ての実施例において共通であり、以下での説明を省略する。 The description so far is common to all the embodiments, and the description below is omitted.
（第１実施例）
第１実施例について、図１，図２及び表１を用いて説明する。第１実施例に係る対物レンズＯＬ（ＯＬ１）は、倍率６０倍、開口数１．４を有する、油浸用超アポクロマート級対物レンズである。
(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. The objective lens OL (OL1) according to the first example is an oil immersion super apochromatic objective lens having a magnification of 60 times and a numerical aperture of 1.4.
図１に示すように、物体側から順に並んだ、正の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、負の屈折力を持つ第３レンズ群Ｇ３とから構成される。 As shown in FIG. 1, 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 having a negative refractive power, which are arranged in order from the object side. G3.
第１レンズ群Ｇ１は、物体側から順に並んだ、物体側に平面を向けた平凸レンズＬ１とこれに貼り合わされた物体側に凹面を向けたメニスカスレンズＬ２とからなる接合正レンズと、像側により屈折力の大きな面（凸面）を向けたメニスカス形状で正屈折力の単レンズＬ３と、両凹形状の負レンズＬ４と両凸形状の正レンズＬ５とを貼り合わせた接合正レンズとから構成される。 The first lens group G1 includes, in order from the object side, a cemented positive lens including a plano-convex lens L1 having a flat surface facing the object side and a meniscus lens L2 having a concave surface facing the object side, which is bonded to the first lens group G1. A meniscus single lens L3 having a positive refractive power with a surface having a large refractive power (convex surface) and a cemented positive lens in which a biconcave negative lens L4 and a biconvex positive lens L5 are bonded together. Is done.
第２レンズ群Ｇ２は、物体側から順に並んだ、平面板ＰＰと像側に凹面を向けた平凹レンズＬ６と両凸形状の正レンズＬ７とを貼り合わせ、平面板ＰＰと平凹レンズＬ６との間に回折光学素子ＰＦを挟み込んでいる接合正レンズと、像側に凹面を向けたメニスカス形状の負レンズＬ８と両凸形状の正レンズＬ９とを貼り合わせた接合正レンズと、両凸形状の正レンズＬ１０と両凹形状の負レンズＬ１１とを貼り合わせた物体側に凸面を向けた接合メニスカスレンズとから構成される。 The second lens group G2 includes a plane plate PP, a plano-concave lens L6 having a concave surface facing the image side, and a biconvex positive lens L7, which are arranged in order from the object side, and are bonded to each other to form the plane plate PP and the plano-concave lens L6. A cemented positive lens having a diffractive optical element PF sandwiched therebetween, a cemented positive lens in which a meniscus negative lens L8 having a concave surface facing the image side and a biconvex positive lens L9 are bonded together; It is composed of a cemented meniscus lens having a convex surface facing the object side, which is formed by bonding a positive lens L10 and a biconcave negative lens L11.
回折光学素子ＰＦは、高屈折率低分散の光学特性を持つ紫外線硬化樹脂と、低屈折率高分散の光学特性を持つ紫外線硬化樹脂とからなる２つの回折光学素子Ｐ１，Ｐ２を接合し、当該接合面（第１１面）に回折格子溝が形成された回折光学面Ｄを有する密着複層型の回折光学素子である。 The diffractive optical element PF joins two diffractive optical elements P1 and P2 made of an ultraviolet curable resin having high refractive index and low dispersion optical characteristics and an ultraviolet curable resin having low refractive index and high dispersion optical characteristics. This is a contact multilayer diffractive optical element having a diffractive optical surface D in which a diffraction grating groove is formed on a bonding surface (11th surface).
第３レンズ群Ｇ３は、物体側から順に並んだ、両凸形状の正レンズＬ１２と両凹形状の負レンズＬ１３との貼り合わせで像側に凹面を向けた接合メニスカスレンズと、両凹形状の負レンズＬ１４と両凸形状の正レンズＬ１５との貼り合わせで物体側に凹面を向けた接合メニスカスレンズとから構成される。 The third lens group G3 includes a cemented meniscus lens having a concave surface facing the image side by bonding a biconvex positive lens L12 and a biconcave negative lens L13, arranged in order from the object side, and a biconcave lens. It is composed of a cemented meniscus lens having a concave surface facing the object side by bonding the negative lens L14 and the biconvex positive lens L15.
第１実施例に係る対物レンズＯＬ１は、浸液として、ｄ線に対する屈折率１．５１４８２、ｄ線を基準とするアッベ数４０．３のオイルを使用し、物体面と第１レンズ群Ｇ１との間に配置される平行平面板（カバーガラスやガラスシャーレ等）として、ｄ線に対する屈折率１．５２４３９、ｄ線を基準とするアッベ数５４．３、厚さｔ＝０．１７mmのものを使用することを前提として設計されている。 The objective lens OL1 according to the first example uses, as immersion liquid, oil having a refractive index of 1.51482 with respect to the d line and an Abbe number of 40.3 with respect to the d line, and the object surface and the first lens group G1. As a plane parallel plate (such as a cover glass or a glass petri dish) disposed between the two, a plate having a refractive index of 1.52439 with respect to the d line, an Abbe number of 54.3 based on the d line, and a thickness t = 0.17 mm is used. It is designed for use.
下記の表１に、第１実施例における各諸元の値を示す。表１における面番号１〜２６が、図１に示すｍ１〜ｍ２６の各光学面に対応している。 Table 1 below shows the values of each item in the first example. Surface numbers 1 to 26 in Table 1 correspond to the optical surfaces m1 to m26 shown in FIG.
（表１）
［全体諸元］
β ＝-60.0
ＮＡ＝ 1.4
ｄ０＝ 0.15
ｆ ＝ 3.338
［レンズ諸元］
面番号 Ｒ ｄ ｎｄ νｄ
1 ∞ 0.600 1.51823 59.0
2 -1.0906 3.450 1.88300 40.8
3 -3.4610 0.100
4 -14.9528 4.362 1.72916 54.7
5 -7.8158 0.150
6 -36.6224 1.000 1.67300 38.2
7 18.2991 8.418 1.64000 60.1
8 -16.7197 0.150
9 ∞ 1.000 1.51633 64.1
10 ∞ 0.100 1.55710 49.7
11*Ｄ ∞ 0.100 1.52780 33.4
12 ∞ 1.000 1.81600 46.6
13 20.6103 9.140 1.49782 82.6
14 -17.6460 0.150
15 39.1799 1.200 1.81600 46.6
16 14.6458 8.173 1.43875 95.0
17 -22.1484 0.150
18 13.1045 5.798 1.43875 95.0
19 -42.6110 1.000 1.81600 46.6
20 18.4512 0.150
21 8.0000 7.000 1.49782 82.6
22 -61.9605 2.910 1.81600 46.6
23 4.9817 3.894
24 -4.9199 1.201 1.60300 65.5
25 46.4100 2.985 1.73800 32.3
26 -7.9684
［回折光学面データ］
第11面
C2 ＝ -2.4461E-04
C4 ＝ 6.0689E-07
C6 ＝ -7.4364E-09
C8 ＝ 1.0320E-11
［条件式］
条件式（１）ｆL3／ｆ ＝5.348
条件式（２）ｎdL3 ＝1.72916
条件式（３）νdL3 ＝54.7
条件式（４）ｎdn−ｎdp ＝0.377
条件式（５）νdp−νdn ＝48.4
条件式（６）ｎdL2 ＝1.88300
条件式（７）νdL2 ＝40.8
条件式（８）（ｎdL4＋ｎdL5）／２ ＝1.6565
条件式（９）｜ｎdL4−ｎdL5｜ ＝0.033
条件式（１０）｜νdL5−νdL4｜ ＝21.9
条件式（１１）ｎd1−ｎd2 ＝0.0293
条件式（１２）ΔｎFC2−ΔｎFC1 ＝0.0046
条件式（１３）｜θent| ＝5.0
条件式（１４）｜ｆdoe／ｆ| ＝612.275
条件式（１５）ｆG2／ｆ ＝11.273
(Table 1)
[Overall specifications]
β = -60.0
NA = 1.4
d0 = 0.15
f = 3.338
[Lens specifications]
Surface number R d nd νd
1 ∞ 0.600 1.51823 59.0
2 -1.0906 3.450 1.88300 40.8
3 -3.4610 0.100
4 -14.9528 4.362 1.72916 54.7
5 -7.8158 0.150
6 -36.6224 1.000 1.67300 38.2
7 18.2991 8.418 1.64000 60.1
8 -16.7197 0.150
9 ∞ 1.000 1.51633 64.1
10 ∞ 0.100 1.55710 49.7
11 * D ∞ 0.100 1.52780 33.4
12 ∞ 1.000 1.81600 46.6
13 20.6103 9.140 1.49782 82.6
14 -17.6460 0.150
15 39.1799 1.200 1.81600 46.6
16 14.6458 8.173 1.43875 95.0
17 -22.1484 0.150
18 13.1045 5.798 1.43875 95.0
19 -42.6110 1.000 1.81600 46.6
20 18.4512 0.150
21 8.0000 7.000 1.49782 82.6
22 -61.9605 2.910 1.81600 46.6
23 4.9817 3.894
24 -4.9199 1.201 1.60300 65.5
25 46.4100 2.985 1.73800 32.3
26 -7.9684
[Diffraction optical surface data]
11th page
C2 = -2.4461E-04
C4 = 6.0689E-07
C6 = -7.4364E-09
C8 = 1.0320E-11
[Conditional expression]
Conditional expression (1) fL3 / f = 5.348
Conditional expression (2) ndL3 = 1.72916
Conditional expression (3) νdL3 = 54.7
Conditional expression (4) ndn-ndp = 0.377
Conditional expression (5) νdp−νdn = 48.4
Conditional expression (6) ndL2 = 1.88300
Conditional expression (7) νdL2 = 40.8
Conditional expression (8) (ndL4 + ndL5) /2=1.6565
Conditional expression (9) | ndL4−ndL5 | = 0.033
Conditional expression (10) | νdL5−νdL4 | = 21.9
Conditional expression (11) nd1−nd2 = 0.0293
Conditional expression (12) ΔnFC2−ΔnFC1 = 0.0046
Conditional expression (13) | θent | = 5.0
Conditional expression (14) | fdoe / f | = 612.275
Conditional expression (15) fG2 / f = 11.273
表１から、本実施例に係る対物レンズＯＬ１は、条件式（１）〜（１５）を満たすことが分かる。 From Table 1, it can be seen that the objective lens OL1 according to the present example satisfies the conditional expressions (1) to (15).
図２は、第１実施例に係る対物レンズＯＬ１の諸収差図（球面収差図、非点収差図、コマ収差図）である。球面収差図及びコマ収差図において、波長852.1100nm（ｓ線）、波長768.1950nm（Ａ´線）、波長656.2790nm、波長587.5620nm（ｄ線）、波長486.1330nm（Ｆ線）、435.8350nm（ｇ線）、波長404.6560nm（ｈ線）の光線に対する収差を示す。非点収差図においては、実線Ｓはサジタル像面を、破線Ｔはタンジェンシャル像面を示す。 FIG. 2 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, coma aberration diagram) of the objective lens OL1 according to the first example. In spherical aberration diagram and coma aberration diagram, wavelength 852.1100nm (s line), wavelength 768.1950nm (A 'line), wavelength 656.2790nm, wavelength 587.5620nm (d line), wavelength 486.1330nm (F line), 435.8350nm (g) Line), and aberrations with respect to light having a wavelength of 404.6560 nm (h line). In the astigmatism diagram, a solid line S indicates a sagittal image plane, and a broken line T indicates a tangential image plane.
図２に示す各収差図から、第１実施例に係る対物レンズＯＬ１は、軸上色収差の補正範囲が通常のアポクロマートよりもはるかに広帯域となるｈ線（波長404.6560nm）からｓ線（波長852.1100nm）までとなっており、開口数１．４、視野数２５において、良好に収差補正されていることが分かる。 From the aberration diagrams shown in FIG. 2, the objective lens OL1 according to the first example shows that the correction range of the axial chromatic aberration is much wider than that of a normal apochromat, from the h-line (wavelength 404.6560 nm) to the s-line (wavelength 852.1100). nm), and it can be seen that aberration correction is satisfactorily corrected at a numerical aperture of 1.4 and a field of view of 25.
（第２実施例）
第２実施例について、図３〜図５及び表２を用いて説明する。第２実施例に係る対物レンズＯＬ（ＯＬ２）は、倍率２５倍、開口数１．１を有する、水浸用超アポクロマート級対物レンズである。
(Second embodiment)
2nd Example is described using FIGS. 3-5 and Table 2. FIG. The objective lens OL (OL2) according to the second example is a super apochromat class objective lens for water immersion having a magnification of 25 times and a numerical aperture of 1.1.
図３に示すように、物体側から順に並んだ、正の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、負の屈折力を持つ第３レンズ群Ｇ３とから構成される。 As shown in FIG. 3, 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 having a negative refractive power, which are arranged in order from the object side. G3.
第１レンズ群Ｇ１は、物体側から順に並んだ、物体側に平面を向けた平凸レンズＬ１とこれに貼り合わされた物体側に凹面を向けたメニスカスレンズＬ２とからなる接合正レンズと、像側により屈折力の大きな面（凸面）を向けたメニスカス形状の正屈折力の単レンズＬ３と、像側に凹面を向けたメニスカス形状の負レンズＬ４と両凸形状の正レンズＬ５とを貼り合わせた接合正レンズとから構成される。 The first lens group G1 includes, in order from the object side, a cemented positive lens including a plano-convex lens L1 having a flat surface facing the object side and a meniscus lens L2 having a concave surface facing the object side, which is bonded to the first lens group G1. Thus, a meniscus single lens L3 having a positive refractive power facing a surface (convex surface) having a large refractive power, a meniscus negative lens L4 having a concave surface facing the image side, and a biconvex positive lens L5 are bonded together. It consists of a cemented positive lens.
第２レンズ群Ｇ２は、物体側から順に並んだ、回折光学素子ＰＦと像側に凹面を向けたメニスカス形状の負レンズＬ６と両凸形状の正レンズＬ７とをこの順で貼り合わせた接合正レンズと、像側に凹面を向けたメニスカス形状の負レンズＬ８と両凸形状の正レンズＬ９とを貼り合わせた接合正レンズとから構成される。 The second lens group G2 includes a diffractive optical element PF arranged in order from the object side, a meniscus negative lens L6 having a concave surface facing the image side, and a biconvex positive lens L7 bonded in this order. The lens includes a cemented positive lens in which a meniscus negative lens L8 having a concave surface facing the image side and a biconvex positive lens L9 are bonded together.
回折光学素子ＰＦは、高屈折率低分散の光学特性を持つ紫外線硬化樹脂と、低屈折率高分散の光学特性を持つ紫外線硬化樹脂とからなる２つの回折光学素子Ｐ１，Ｐ２を接合し、当該接合面（第１０面）に回折格子溝が形成された回折光学面Ｄを有する密着複層型の回折光学素子である。 The diffractive optical element PF joins two diffractive optical elements P1 and P2 made of an ultraviolet curable resin having high refractive index and low dispersion optical characteristics and an ultraviolet curable resin having low refractive index and high dispersion optical characteristics. This is a contact multilayer diffractive optical element having a diffractive optical surface D in which a diffraction grating groove is formed on a joint surface (tenth surface).
第３レンズ群Ｇ３は、物体側から順に並んだ、物体側に凸面を向けた平凸形状の正レンズＬ１０と像側に凹面を向けた平凹形状の負レンズＬ１１との貼り合わせで像側に凹面を向けた接合メニスカスレンズと、物体側に凹面を向けたメニスカス形状の負レンズＬ１２と像側に凸面を向けたメニスカス形状の正レンズＬ１３との貼り合わせで物体側に凹面を向けた接合メニスカスレンズとから構成される。 The third lens group G3 is formed by bonding together a plano-convex positive lens L10 having a convex surface facing the object side and a plano-concave negative lens L11 having a concave surface facing the image side. A cemented meniscus lens with a concave surface facing the surface, a meniscus negative lens L12 with a concave surface facing the object side, and a meniscus positive lens L13 with a convex surface facing the image side are bonded together so that the concave surface faces the object side. It consists of a meniscus lens.
第２実施例に係る対物レンズＯＬ２は、浸液として、ｄ線に対する屈折率１．３３２５５、ｄ線を基準とするアッベ数５５．９の水を使用し、物体面と第１レンズ群Ｇ１との間に配置される平行平面板（カバーガラスやガラスシャーレ等）として、ｄ線に対する屈折率１．５２４３９、ｄ線を基準とするアッベ数５４．３の材料を使用し、厚さｔ＝０〜０．１７mmまでの収差変化に対応できるように設計されている。 The objective lens OL2 according to the second example uses, as immersion liquid, water having a refractive index of 1.33255 with respect to the d-line and an Abbe number of 55.9 with respect to the d-line, and the object surface and the first lens group G1. As a plane parallel plate (cover glass, glass petri dish, etc.) disposed between the two, a material having a refractive index of 1.52439 with respect to the d line and an Abbe number of 54.3 based on the d line is used, and a thickness t = 0 Designed to accommodate aberration changes up to ~ 0.17mm.
下記の表２に、第２実施例における各諸元の値を示す。表２における面番号１〜２２が、図３に示すｍ１〜ｍ２２の各光学面に対応している。 Table 2 below shows the values of each item in the second embodiment. Surface numbers 1 to 22 in Table 2 correspond to the optical surfaces m1 to m22 shown in FIG.
（表２）
［全体諸元］
β ＝-25.0
ＮＡ＝ 1.1
ｄ０＝ 2.00
ｆ ＝ 7.983
［レンズ諸元］
面番号 Ｒ ｄ ｎｄ νｄ
1 ∞ 2.000 1.45850 67.8
2 -3.4600 4.000 1.88300 40.8
3 -6.1546 0.100
4 -24.8585 3.643 1.72916 54.7
5 -13.9338 0.150
6 100.0000 1.000 1.67300 38.2
7 23.4455 8.536 1.43875 95.0
8 -17.7502 0.200
9 150.0000 0.100 1.55710 49.7
10*Ｄ 150.0000 0.100 1.52780 33.4
11 150.0000 1.000 1.83481 42.7
12 31.6286 8.085 1.43875 95.0
13 -21.4630 0.200
14 34.5420 1.000 1.83481 42.7
15 16.4134 7.992 1.43875 95.0
16 -35.8411 d16(可変)
17 11.5969 8.820 1.43875 95.0
18 ∞ 1.000 1.83481 42.7
19 9.6538 7.487
20 -8.4923 1.000 1.69350 50.8
21 -26.6082 4.939 1.73800 32.3
22 -11.4551
［回折光学面データ］
第10面
C2 ＝ -1.5195E-04
C4 ＝ 2.4453E-07
C6 ＝ 6.7127E-10
C8 ＝ -8.1884E-12
［条件式］
条件式（１）ｆL3／ｆ ＝4.775
条件式（２）ｎdL3 ＝1.72916
条件式（３）νdL3 ＝54.7
条件式（４）ｎdn−ｎdp ＝0.377
条件式（５）νdp−νdn ＝48.4
条件式（６）ｎdL2 ＝1.88300
条件式（７）νdL2 ＝40.8
条件式（１１）ｎd1−ｎd2 ＝0.0293
条件式（１２）ΔｎFC2−ΔｎFC1 ＝0.0046
条件式（１３）｜θent| ＝11.691
条件式（１４）｜ｆdoe／ｆ| ＝412.192
条件式（１５）ｆG2／ｆ ＝8.628
(Table 2)
[Overall specifications]
β = -25.0
NA = 1.1
d0 = 2.00
f = 7.983
[Lens specifications]
Surface number R d nd νd
1 ∞ 2.000 1.45850 67.8
2 -3.4600 4.000 1.88300 40.8
3 -6.1546 0.100
4 -24.8585 3.643 1.72916 54.7
5 -13.9338 0.150
6 100.0000 1.000 1.67300 38.2
7 23.4455 8.536 1.43875 95.0
8 -17.7502 0.200
9 150.0000 0.100 1.55710 49.7
10 * D 150.0000 0.100 1.52780 33.4
11 150.0000 1.000 1.83481 42.7
12 31.6286 8.085 1.43875 95.0
13 -21.4630 0.200
14 34.5420 1.000 1.83481 42.7
15 16.4134 7.992 1.43875 95.0
16 -35.8411 d16 (variable)
17 11.5969 8.820 1.43875 95.0
18 ∞ 1.000 1.83481 42.7
19 9.6538 7.487
20 -8.4923 1.000 1.69350 50.8
21 -26.6082 4.939 1.73800 32.3
22 -11.4551
[Diffraction optical surface data]
10th page
C2 = -1.5195E-04
C4 = 2.4453E-07
C6 = 6.7127E-10
C8 = -8.1884E-12
[Conditional expression]
Conditional expression (1) fL3 / f = 4.775
Conditional expression (2) ndL3 = 1.72916
Conditional expression (3) νdL3 = 54.7
Conditional expression (4) ndn-ndp = 0.377
Conditional expression (5) νdp−νdn = 48.4
Conditional expression (6) ndL2 = 1.88300
Conditional expression (7) νdL2 = 40.8
Conditional expression (11) nd1−nd2 = 0.0293
Conditional expression (12) ΔnFC2−ΔnFC1 = 0.0046
Conditional expression (13) | θent | = 11.691
Conditional expression (14) | fdoe / f | = 412.192
Conditional expression (15) fG2 / f = 8.628
表２から、本実施例に係る対物レンズＯＬ２は、条件式（１）〜（７）、（１１）〜（１５）を満たすことが分かる。 From Table 2, it can be seen that the objective lens OL2 according to the present example satisfies the conditional expressions (1) to (7) and (11) to (15).
上記諸元を有する対物レンズＯＬ２は、第３レンズ群Ｇ３を光軸方向に移動させることにより、平行平面板（カバーガラス）の厚さに起因する収差変動を補正できるように構成されている。このため、表２の面間隔ｄ１６は、第３レンズ群Ｇ３のレンズＬ１０〜Ｌ１３の光軸方向の移動によって変化する可変値である。平行平面板を使用しない場合は、面間隔ｄ０＝２．００mm、面間隔ｄ１６＝１．１４６mmとなり、厚さ０．１７mmの平行平面板を使用する場合は、面間隔ｄ０＝１．８９０mm、面間隔ｄ１６＝０．２００mmとなる。 The objective lens OL2 having the above specifications is configured to be able to correct aberration variations caused by the thickness of the plane-parallel plate (cover glass) by moving the third lens group G3 in the optical axis direction. For this reason, the surface interval d16 in Table 2 is a variable value that changes due to the movement of the lenses L10 to L13 of the third lens group G3 in the optical axis direction. When a plane parallel plate is not used, the plane spacing d0 = 2.00 mm and the plane spacing d16 = 1.146 mm. When a plane parallel plate having a thickness of 0.17 mm is used, the plane spacing d0 = 1.890 mm, the plane The distance d16 = 0.200 mm.
図４は、平行平面板の厚さが０mmのときの、第２実施例に係る対物レンズＯＬ２の諸収差図（球面収差図、非点収差図、コマ収差図）である。図５は、平行平面板の厚さが０．１７mmのときの、第２実施例に係る対物レンズＯＬ２の諸収差図（球面収差図、非点収差図、コマ収差図）である。球面収差図及びコマ収差図において、波長1013.9800nm（ｔ線）、波長852.1100nm（ｓ線）、波長768.1950nm（Ａ´線）、波長656.2790nm、波長587.5620nm（ｄ線）、波長486.1330nm（Ｆ線）、波長435.8350nm（ｇ線）、波長404.6560nm（ｈ線）の光線に対する収差を示す。非点収差図においては、実線Ｓは各波長に対するサジタル像面を、破線Ｔは各波長に対するタンジェンシャル像面を示す。 FIG. 4 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, coma aberration diagram) of the objective lens OL2 according to Example 2 when the thickness of the plane-parallel plate is 0 mm. FIG. 5 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, coma aberration diagram) of the objective lens OL2 according to Example 2 when the thickness of the plane parallel plate is 0.17 mm. In spherical aberration diagram and coma aberration diagram, wavelength 1013.9800nm (t line), wavelength 852.1100nm (s line), wavelength 768.1950nm (A 'line), wavelength 656.2790nm, wavelength 587.5620nm (d line), wavelength 486.1330nm ( F-rays), aberrations with respect to light rays having a wavelength of 435.8350 nm (g-line) and a wavelength of 404.6560 nm (h-line). In the astigmatism diagram, a solid line S indicates a sagittal image plane for each wavelength, and a broken line T indicates a tangential image plane for each wavelength.
図４及び図５に示す各収差図から、第２実施例に係る対物レンズＯＬ２は、軸上色収差の補正範囲が通常のアポクロマートよりもはるかに広帯域となるｈ線（波長404.656nm）からｔ線（波長1013.98nm）までとなっており、開口数１．１、視野数２２において、良好に収差補正されていることが分かる。 4 and FIG. 5, the objective lens OL2 according to the second example shows that the correction range of the axial chromatic aberration is much wider than that of a normal apochromat, from the h-line (wavelength 404.656 nm) to the t-line. (Wavelength 1013.98 nm), and it can be seen that aberrations are well corrected at a numerical aperture of 1.1 and a field of view of 22.
（第３実施例）
第３実施例について、図６〜図８及び表３を用いて説明する。第３実施例に係る対物レンズＯＬ（ＯＬ３）は、倍率２５倍、開口数１．１を有する、水浸用超アポクロマート級対物レンズである。
(Third embodiment)
A third embodiment will be described with reference to FIGS. The objective lens OL (OL3) according to the third example is a water immersion super apochromatic objective lens having a magnification of 25 times and a numerical aperture of 1.1.
図６に示すように、物体側から順に並んだ、正の屈折力を持つ第１レンズ群Ｇ１と、正の屈折力を持つ第２レンズ群Ｇ２と、負の屈折力を持つ第３レンズ群Ｇ３とから構成される。 As shown in FIG. 6, 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 having a negative refractive power, which are arranged in order from the object side. G3.
第１レンズ群Ｇ１は、物体側から順に並んだ、物体側に平面を向けた平凸レンズＬ１とこれに貼り合わされた物体側に凹面を向けたメニスカスレンズＬ２とからなる接合正レンズと、像側により屈折力の大きな面（凸面）を向けたメニスカス形状の正屈折力の単レンズＬ３と、像側に凹面を向けたメニスカス形状の負レンズＬ４と両凸形状の正レンズＬ５とを貼り合わせた接合正レンズとから構成される。正屈折力の単レンズＬ３の像側面は、回転対称非球面Ａである。 The first lens group G1 includes, in order from the object side, a cemented positive lens including a plano-convex lens L1 having a flat surface facing the object side and a meniscus lens L2 having a concave surface facing the object side, which is bonded to the first lens group G1. Thus, a meniscus single lens L3 having a positive refractive power facing a surface (convex surface) having a large refractive power, a meniscus negative lens L4 having a concave surface facing the image side, and a biconvex positive lens L5 are bonded together. It consists of a cemented positive lens. The image side surface of the single lens L3 having positive refractive power is a rotationally symmetric aspherical surface A.
第２レンズ群Ｇ２は、物体側から順に並んだ、回折光学素子ＰＦと像側に凹面を向けたメニスカス形状の負レンズＬ６と両凸形状の正レンズＬ７とをこの順で貼り合わせた接合正レンズと、像側に凹面を向けたメニスカス形状の負レンズＬ８と両凸形状の正レンズＬ９とを貼り合わせた接合正レンズとから構成される。 The second lens group G2 includes a diffractive optical element PF arranged in order from the object side, a meniscus negative lens L6 having a concave surface facing the image side, and a biconvex positive lens L7 bonded in this order. The lens includes a cemented positive lens in which a meniscus negative lens L8 having a concave surface facing the image side and a biconvex positive lens L9 are bonded together.
回折光学素子ＰＦは、高屈折率低分散の光学特性を持つ紫外線硬化樹脂と、低屈折率高分散の光学特性を持つ紫外線硬化樹脂とからなる２つの回折光学素子Ｐ１，Ｐ２を接合し、当該接合面（第１０面）に回折格子溝が形成された回折光学面Ｄを有する密着複層型の回折光学素子である。 The diffractive optical element PF joins two diffractive optical elements P1 and P2 made of an ultraviolet curable resin having high refractive index and low dispersion optical characteristics and an ultraviolet curable resin having low refractive index and high dispersion optical characteristics. This is a contact multilayer diffractive optical element having a diffractive optical surface D in which a diffraction grating groove is formed on a joint surface (tenth surface).
第３レンズ群Ｇ３は、物体側から順に並んだ、物体側に凸面を向けた平凸形状の正レンズＬ１０と像側に凹面を向けた平凹形状の負レンズＬ１１との貼り合わせで像側に凹面を向けた接合メニスカスレンズと、物体側に凹面を向けたメニスカス形状の負レンズＬ１２と像側に凸面を向けたメニスカス形状の正レンズＬ１３との貼り合わせで物体側に凹面を向けた接合メニスカスレンズとから構成される。平凹形状の負レンズＬ１１の像側面は、回転対称非球面Ａである。 The third lens group G3 is formed by bonding together a plano-convex positive lens L10 having a convex surface facing the object side and a plano-concave negative lens L11 having a concave surface facing the image side. A cemented meniscus lens with a concave surface facing the surface, a meniscus negative lens L12 with a concave surface facing the object side, and a meniscus positive lens L13 with a convex surface facing the image side are bonded together so that the concave surface faces the object side. It consists of a meniscus lens. The image side surface of the plano-concave negative lens L11 is a rotationally symmetric aspherical surface A.
第３実施例に係る対物レンズＯＬ３は、浸液として、ｄ線に対する屈折率１．３３２５５、ｄ線を基準とするアッベ数５５．９の水を使用し、物体面と第１レンズ群Ｇ１との間に配置される平行平面板（カバーガラスやガラスシャーレ等）として、ｄ線に対する屈折率１．５２４３９、ｄ線を基準とするアッベ数５４．３の材料を使用し、厚さｔ＝０〜０．１７mmまでの収差変化に対応できるように設計されている。 The objective lens OL3 according to the third example uses, as immersion liquid, water having a refractive index of 1.33255 with respect to the d line and an Abbe number of 55.9 with respect to the d line, and the object surface and the first lens group G1. As a plane parallel plate (cover glass, glass petri dish, etc.) disposed between the two, a material having a refractive index of 1.52439 with respect to the d line and an Abbe number of 54.3 based on the d line is used, and a thickness t = 0 Designed to accommodate aberration changes up to ~ 0.17mm.
下記の表３に、第３実施例における各諸元の値を示す。表３における面番号１〜２２が、図６に示すｍ１〜ｍ２２の各光学面に対応している。 Table 3 below shows values of various specifications in the third example. Surface numbers 1 to 22 in Table 3 correspond to the optical surfaces m1 to m22 shown in FIG.
（表３）
［全体諸元］
β ＝-25.0
ＮＡ＝ 1.1
ｄ０＝ 2.00
ｆ ＝ 8.015
［レンズ諸元］
面番号 Ｒ ｄ ｎｄ νｄ
1 ∞ 2.000 1.45850 67.8
2 -3.4600 4.000 1.88300 40.8
3 -6.0299 0.100
4 -39.2991 3.338 1.72916 54.7
5*Ａ -16.4741 0.150
6 326.4133 1.000 1.67300 38.2
7 39.6210 7.472 1.43875 95.0
8 -16.3626 0.200
9 546.4391 0.100 1.55710 49.7
10*Ｄ 546.4391 0.100 1.52780 33.4
11 546.4391 1.000 1.83481 42.7
12 28.6663 8.568 1.43875 95.0
13 -19.1978 0.200
14 29.5454 1.000 1.83481 42.7
15 15.4112 8.401 1.43875 95.0
16 -30.6795 d16(可変)
17 10.6917 7.671 1.43875 95.0
18 ∞ 1.000 1.83481 42.7
19*Ａ 8.6490 8.332
20 -8.4043 1.000 1.69350 50.8
21 -20.0000 5.868 1.73800 32.3
22 -11.7029
［回折光学面データ］
第10面
C2 ＝-1.6669E-04
C4 ＝ 3.3798E-07
C6 ＝-2.2703E-10
C8 ＝-3.6811E-12
［非球面データ］
第5面
K ＝ 0
A4 ＝ 0.179752E-04
A6 ＝ 0.128802E-06
A8 ＝-0.777830E-11
A10＝ 0.581171E-11
第19面
K ＝ 0
A4 ＝-0.302832E-05
A6 ＝-0.547084E-06
A8 ＝ 0.132138E-07
A10＝-0.271115E-09
［条件式］
条件式（１）ｆL3／ｆ ＝4.571
条件式（２）ｎdL3 ＝1.72916
条件式（３）νdL3 ＝54.7
条件式（４）ｎdn−ｎdp ＝0.377
条件式（５）νdp−νdn ＝48.4
条件式（６）ｎdL2 ＝1.88300
条件式（７）νdL2 ＝40.8
条件式（１１）ｎd1−ｎd2 ＝0.0293
条件式（１２）ΔｎFC2−ΔｎFC1 ＝0.0046
条件式（１３）｜θent| ＝7.521
条件式（１４）｜ｆdoe／ｆ| ＝374.232
条件式（１５）ｆG2／ｆ ＝9.970
(Table 3)
[Overall specifications]
β = -25.0
NA = 1.1
d0 = 2.00
f = 8.015
[Lens specifications]
Surface number R d nd νd
1 ∞ 2.000 1.45850 67.8
2 -3.4600 4.000 1.88300 40.8
3 -6.0299 0.100
4 -39.2991 3.338 1.72916 54.7
5 * A -16.4741 0.150
6 326.4133 1.000 1.67300 38.2
7 39.6210 7.472 1.43875 95.0
8 -16.3626 0.200
9 546.4391 0.100 1.55710 49.7
10 * D 546.4391 0.100 1.52780 33.4
11 546.4391 1.000 1.83481 42.7
12 28.6663 8.568 1.43875 95.0
13 -19.1978 0.200
14 29.5454 1.000 1.83481 42.7
15 15.4112 8.401 1.43875 95.0
16 -30.6795 d16 (variable)
17 10.6917 7.671 1.43875 95.0
18 ∞ 1.000 1.83481 42.7
19 * A 8.6490 8.332
20 -8.4043 1.000 1.69350 50.8
21 -20.0000 5.868 1.73800 32.3
22 -11.7029
[Diffraction optical surface data]
10th page
C2 = -1.6669E-04
C4 = 3.3798E-07
C6 = -2.2703E-10
C8 = -3.6811E-12
[Aspherical data]
5th page
K = 0
A4 = 0.179752E-04
A6 = 0.128802E-06
A8 = -0.777830E-11
A10 = 0.581171E-11
19th page
K = 0
A4 = -0.3302832E-05
A6 = -0.547084E-06
A8 = 0.132138E-07
A10 = -0.271115E-09
[Conditional expression]
Conditional expression (1) fL3 / f = 4.571
Conditional expression (2) ndL3 = 1.72916
Conditional expression (3) νdL3 = 54.7
Conditional expression (4) ndn-ndp = 0.377
Conditional expression (5) νdp−νdn = 48.4
Conditional expression (6) ndL2 = 1.88300
Conditional expression (7) νdL2 = 40.8
Conditional expression (11) nd1−nd2 = 0.0293
Conditional expression (12) ΔnFC2−ΔnFC1 = 0.0046
Conditional expression (13) | θent | = 7.521
Conditional expression (14) | fdoe / f | = 374.232
Conditional expression (15) fG2 / f = 9.970
表３から、本実施例に係る対物レンズＯＬ３は、条件式（１）〜（７）、（１１）〜（１５）を満たすことが分かる。 From Table 3, it can be seen that the objective lens OL3 according to the present example satisfies the conditional expressions (1) to (7) and (11) to (15).
上記諸元を有する対物レンズＯＬ３は、第３レンズ群Ｇ３を光軸方向に移動させることにより、平行平面板（カバーガラス）の厚さに起因する収差変動を補正できるように構成されている。このため、表３の面間隔ｄ１６は、第３レンズ群Ｇ３のレンズＬ１０〜Ｌ１３の光軸方向の移動によって変化する可変値である。平行平面板を使用しない場合は、面間隔ｄ０＝２．００mm、面間隔ｄ１６＝１．０００mmとなり、厚さ０．１７mmの平行平面板を使用する場合は、面間隔ｄ０＝１．８９５mm、面間隔ｄ１６＝０．２００mmとなる。 The objective lens OL3 having the above specifications is configured to be able to correct aberration variations caused by the thickness of the plane-parallel plate (cover glass) by moving the third lens group G3 in the optical axis direction. For this reason, the surface interval d16 in Table 3 is a variable value that varies with the movement of the lenses L10 to L13 of the third lens group G3 in the optical axis direction. When the plane parallel plate is not used, the plane interval d0 = 2.00 mm and the plane interval d16 = 1.000 mm. When the plane parallel plate having a thickness of 0.17 mm is used, the plane interval d0 = 1.895 mm, the plane The distance d16 = 0.200 mm.
図７は、平行平面板の厚さが０mmのときの、第３実施例に係る対物レンズＯＬ３の諸収差図（球面収差図、非点収差図、コマ収差図）である。図８は、平行平面板の厚さが０．１７mmのときの、第３実施例に係る対物レンズＯＬ３の諸収差図（球面収差図、非点収差図、コマ収差図）である。球面収差図及びコマ収差図において、波長1013.9800nm（ｔ線）、波長852.1100nm（ｓ線）、波長768.1950nm（Ａ´線）、波長656.2790nm、波長587.5620nm（ｄ線）、波長486.1330nm（Ｆ線）、波長435.8350nm（ｇ線）、波長404.6560nm（ｈ線）、波長365.0150nm（ｉ線）の収差を示す。非点収差図においては、実線Ｓは各波長に対するサジタル像面を、破線Ｔは各波長に対するタンジェンシャル像面を示す。 FIG. 7 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, coma aberration diagram) of the objective lens OL3 according to Example 3 when the thickness of the plane-parallel plate is 0 mm. FIG. 8 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, coma aberration diagram) of the objective lens OL3 according to Example 3 when the thickness of the plane-parallel plate is 0.17 mm. In spherical aberration diagram and coma aberration diagram, wavelength 1013.9800nm (t line), wavelength 852.1100nm (s line), wavelength 768.1950nm (A 'line), wavelength 656.2790nm, wavelength 587.5620nm (d line), wavelength 486.1330nm ( F-line), wavelength 435.8350 nm (g-line), wavelength 404.6560 nm (h-line), and wavelength 365.0150 nm (i-line). In the astigmatism diagram, a solid line S indicates a sagittal image plane for each wavelength, and a broken line T indicates a tangential image plane for each wavelength.
図７及び図８に示す各収差図から、第３実施例に係る対物レンズＯＬ３は、軸上色収差の補正範囲が超アポクロマートであり、第２実施例よりもさらに広帯域となるｉ線（波長365.015nm）からｔ線（波長1013.98nm）までとなっており、開口数１．１、視野数２２において、良好に収差補正されていることが分かる。 From the aberration diagrams shown in FIGS. 7 and 8, the objective lens OL3 according to the third example has an axial chromatic aberration correction range of super apochromat, and an i-line (wavelength 365.015) having a wider bandwidth than that of the second example. nm) to t-line (wavelength 1013.98 nm), and it can be seen that aberrations are well corrected at a numerical aperture of 1.1 and a field of view of 22.
また、本実施例のように、回折光学面や回転対称非球面を適切に配置することにより、球面系のみのレンズ構成では達成できなかった全長や平坦性の仕様の対物レンズが設計可能となる。 In addition, by appropriately arranging the diffractive optical surface and the rotationally symmetric aspherical surface as in the present embodiment, it becomes possible to design an objective lens having a full length or flatness specification that could not be achieved with a lens configuration of only a spherical system. .
なお、第１〜第３実施例に係る対物レンズＯＬ１〜ＯＬ３は、いずれも無限遠補正型であり、図９に示す構成及び表４に示す諸元を有する結像レンズＩＬとともに使用される。結像レンズＩＬは、図９に示すように、物体側から順に並んだ、両凸形状の正レンズＬ２１と両凹形状の負レンズＬ２２との接合レンズと、両凸形状の正レンズＬ２３と両凹形状の負レンズＬ２４との接合レンズとから構成される。 The objective lenses OL1 to OL3 according to the first to third examples are all of the infinity correction type and are used together with the imaging lens IL having the configuration shown in FIG. 9 and the specifications shown in Table 4. As shown in FIG. 9, the imaging lens IL includes a cemented lens of a biconvex positive lens L21 and a biconcave negative lens L22, a biconvex positive lens L23, and both arranged in order from the object side. It is composed of a cemented lens with a concave negative lens L24.
下記の表４に、結像レンズＩＬにおける諸元の値を示す。表４における面番号１〜６が、図９に示すｍ１〜ｍ６の各光学面に対応している。 Table 4 below shows values of specifications in the imaging lens IL. Surface numbers 1 to 6 in Table 4 correspond to the optical surfaces m1 to m6 shown in FIG.
（表４）
面番号 Ｒ ｄ ｎｄ νｄ
1 75.043 5.10 1.62280 57.0
2 -75.043 2.00 1.74950 35.2
3 1600.580 7.50
4 50.256 5.10 1.66755 42.0
5 -84.541 1.80 1.61266 44.4
6 36.911
(Table 4)
Surface number R d nd νd
1 75.043 5.10 1.62280 57.0
2 -75.043 2.00 1.74950 35.2
3 1600.580 7.50
4 50.256 5.10 1.66755 42.0
5 -84.541 1.80 1.61266 44.4
6 36.911
ここまで本発明を分かりやすくするために、実施形態の構成要件を付して説明したが、本発明がこれに限定されるものではないことは言うまでもない。 In order to make the present invention easy to understand, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.
ＯＬ（ＯＬ１〜ＯＬ３） 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
ＰＦ 回折光学素子
Ｄ 回折光学面
Ａ 非球面
OL (OL1 to OL3) Objective lens G1 First lens group G2 Second lens group G3 Third lens group PF Diffraction optical element D Diffraction optical surface A Aspherical surface
Claims (10)
前記第１レンズ群は、最も物体側に配置された物体側に平面を向けた平凸レンズと物体側に凹面を向けたメニスカスレンズとの接合正レンズと、このレンズの像側に隣接して配置された像側に凸面を向けたメニスカス形状で正屈折力の単レンズとを有し、
前記第２レンズ群は、複数の接合レンズを有し、そのうち最も物体側の接合レンズのいずれかのレンズ面に、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を備え、
前記第３レンズ群は、物体側から順に並んだ、像側に凹面を向けた接合メニスカスレンズと、物体側に凹面を向けた接合メニスカスレンズとからなり、
以下の条件式（１）〜（３）を満足するとともに、
前記第２レンズ群が有する複数の接合レンズのうち、少なくとも２つの接合レンズは、以下の条件式（４）及び（５）を満足する負レンズと正レンズとから構成されている、
ことを特徴とする対物レンズ。
３．００ ≦ ｆL3／ｆ ≦ １０．００ ・・・ （１）
１．６５ ≦ ｎdL3 ・・・ （２）
４５．０ ≦ νdL3 ・・・ （３）
０．３０ ≦ ｎdn−ｎdp ・・・ （４）
４０．０ ≦ νdp−νdn ・・・ （５）
但し、
ｆL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの焦点距離、
ｆ：全系の焦点距離、
ｎdL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの硝材のｄ線に対する屈折率、
νdL3：前記像側に凸面を向けたメニスカス形状で正屈折力の単レンズの硝材のｄ線を基準とするアッベ数、
ｎdn：前記第２レンズ群の前記接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdn：前記第２レンズ群の前記接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdp：前記第２レンズ群の前記接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdp：前記第２レンズ群の前記接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。 In order from an object consists of a first lens group having positive refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power,
The first lens group is disposed adjacent to the image side of a cemented positive lens of a plano-convex lens having a plane facing the object side disposed closest to the object side and a meniscus lens having a concave surface facing the object side. A single lens with a positive refractive power in a meniscus shape with a convex surface facing the image side,
The second lens group has a plurality of cemented lenses, of which two diffractive element elements made of different optical materials are cemented to one of the lens surfaces of the most cemented lens on the object side, and a diffraction grating is coupled to the cemented surface. A diffractive optical element having a diffractive optical surface formed with a groove;
The third lens group is composed of a cemented meniscus lens having a concave surface facing the image side and a cemented meniscus lens having a concave surface facing the object side, which are arranged in order from the object side.
While satisfying the following conditional expressions (1) to (3) ,
Of the plurality of cemented lenses of the second lens group, at least two cemented lenses are composed of a negative lens and a positive lens that satisfy the following conditional expressions (4) and (5):
An objective lens characterized by that.
3.00 ≤ fL3 / f ≤ 10.00 (1)
1.65 ≦ ndL3 (2)
45.0 ≦ νdL3 (3)
0.30 ≦ ndn−ndp (4)
40.0 ≦ νdp−νdn (5)
However,
fL3: a focal length of a single lens having a positive refractive power in a meniscus shape with a convex surface facing the image side,
f: focal length of the entire system,
ndL3: a refractive index with respect to d-line of a glass material of a single lens having a meniscus shape having a convex surface facing the image side and having a positive refractive power,
νdL3: Abbe number based on the d-line of a single lens glass material having a meniscus shape with a convex surface facing the image side and a positive refractive power ,
ndn: refractive index with respect to d-line of the glass material of the negative lens constituting the cemented lens of the second lens group,
νdn: Abbe number based on the d-line of the glass material of the negative lens constituting the cemented lens of the second lens group,
ndp: refractive index with respect to d-line of the glass material of the positive lens constituting the cemented lens of the second lens group,
νdp: Abbe number based on the d-line of the glass material of the positive lens constituting the cemented lens of the second lens group .
１．８０ ≦ ｎdL2 ・・・ （６）
４０．０ ≦ νdL2 ・・・ （７）
但し、
ｎdL2：前記物体側に凹面を向けたメニスカスレンズの硝材のｄ線に対する屈折率、
νdL2：前記物体側に凹面を向けたメニスカスレンズの硝材のｄ線を基準とするアッベ数。 2. The objective according to claim 1, wherein the meniscus lens having a concave surface facing the object side constituting the cemented positive lens of the first lens group satisfies the following conditional expressions (6) and (7): lens.
1.80 ≦ ndL2 (6)
40.0 ≦ νdL2 (7)
However,
ndL2: Refractive index with respect to d-line of the glass material of the meniscus lens with the concave surface facing the object side,
νdL2: Abbe number based on the d-line of the glass material of the meniscus lens with the concave surface facing the object side.
前記接合レンズは、以下の条件式（８）〜（１０）を満足する負レンズと正レンズとから構成されていることを特徴とする請求項１または２に記載の対物レンズ。
１．６０ ≦ （ｎdL4＋ｎdL5）／２ ・・・ （８）
｜ｎdL4−ｎdL5｜ ≦ ０．１０ ・・・ （９）
１５．０ ≦ ｜νdL5−νdL4｜ ・・・ （１０）
但し、
ｎdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線に対する屈折率、
νdL4：前記最も像側の接合レンズを構成する負レンズの硝材のｄ線を基準とするアッベ数、
ｎdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線に対する屈折率、
νdL5：前記最も像側の接合レンズを構成する正レンズの硝材のｄ線を基準とするアッベ数。 The first lens group has a cemented lens closest to the image side,
The cemented lens, the following conditional expression (8) - (10) The objective lens of claim 1 or 2, characterized in that it is composed of a negative lens and a positive lens that satisfies a.
1.60 ≦ (ndL4 + ndL5) / 2 (8)
｜ ndL4−ndL5 | ≦ 0.10 (9)
15.0 ≤ | νdL5−νdL4 | ... (10)
However,
ndL4: refractive index of d-line of the glass material of the negative lens constituting the most image side cemented lens,
νdL4: Abbe number based on the d-line of the glass material of the negative lens constituting the most image side cemented lens,
ndL5: refractive index with respect to d-line of the glass material of the positive lens constituting the most image side cemented lens,
νdL5: Abbe number based on the d-line of the glass material of the positive lens constituting the most image side cemented lens.
以下の条件式（１１）及び（１２）を満足することを特徴とする請求項１〜６のいずれか一項に記載の対物レンズ。
０．０１ ≦ ｎd1−ｎd2 ・・・ （１１）
０．００１５ ≦ ΔｎFC2−ΔｎFC1 ・・・ （１２）
但し、
ｎd1、ｎF1及びｎC1：前記２つの回折素子要素のうち、高屈折率低分散な方の回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率、
ｎd2、ｎF2及びｎC2：前記２つの回折素子要素のうち、低屈折率高分散な方の回折素子要素の材料のｄ線、Ｆ線及びＣ線に対する屈折率。
また、ΔｎFC1＝ｎF1−ｎC1、ΔｎFC2＝ｎF2−ｎC2と定義する。 The two diffractive element elements constituting the diffractive optical element are made of different resins,
Following conditional expressions (11) and an objective lens according to any one of claims 1 to 6, characterized by satisfying the (12).
0.01 ≦ nd1−nd2 (11)
0.0015 ≦ ΔnFC2−ΔnFC1 (12)
However,
nd1, nF1, and nC1: Refractive indexes for the d-line, F-line, and C-line of the material of the diffractive element having the higher refractive index and lower dispersion among the two diffractive element elements,
nd2, nF2, and nC2: Refractive indexes for the d-line, F-line, and C-line of the material of the diffractive element having the lower refractive index and higher dispersion among the two diffractive element elements.
Further, ΔnFC1 = nF1-nC1, and ΔnFC2 = nF2-nC2 are defined.
以下の条件式（１３）を満足することを特徴とする請求項１〜７のいずれか一項に記載の対物レンズ。
４．０° ≦ ｜θent| ≦ １２．０° ・・・ （１３）
但し、
θent：物体中心から最大ＮＡとなる光線が前記回折光学素子の空気側面に入射する角度。 The diffractive optical element is disposed closer to the object side than the position where the principal ray intersects the optical axis,
Objective lens according to any one of claims 1 to 7, characterized by satisfying the following conditional expression (13).
4.0 ° ≦ | θent | ≦ 12.0 ° (13)
However,
θent: An angle at which a light beam having a maximum NA from the object center is incident on the air side surface of the diffractive optical element.
１００．００ ≦ ｜ｆdoe／ｆ| ・・・ （１４）
但し、
ｆdoe：前記回折光学素子の焦点距離。 Objective lens according to any one of claims 1-8, characterized by satisfying the following conditional expression (14).
100.00 ≦ | fdoe / f | (14)
However,
fdoe: focal length of the diffractive optical element.
４．００ ≦ ｆG2／ｆ ≦ ２０．００ ・・・ （１５）
但し、
ｆG2：前記第２レンズ群の焦点距離。 Objective lens according to any one of claims 1 to 9, characterized by satisfying the following conditional expression (15).
4.00 ≦ fG2 / f ≦ 20.00 (15)
However,
fG2: focal length of the second lens group.
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