JP5126669B2 - Infrared zoom lens - Google Patents

Infrared zoom lens Download PDF

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JP5126669B2
JP5126669B2 JP2008034221A JP2008034221A JP5126669B2 JP 5126669 B2 JP5126669 B2 JP 5126669B2 JP 2008034221 A JP2008034221 A JP 2008034221A JP 2008034221 A JP2008034221 A JP 2008034221A JP 5126669 B2 JP5126669 B2 JP 5126669B2
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zoom lens
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JP2009192886A (en
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健太 須藤
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/008—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras designed for infrared light
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/144—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only
    • G02B15/1441—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive
    • G02B15/144113—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive arranged +-++

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Description

本発明は、赤外線撮像装置等に好適な赤外線ズームレンズに関する。   The present invention relates to an infrared zoom lens suitable for an infrared imaging device or the like.

赤外光学系は、暗闇などにおいて肉眼では見えない被写体を、赤外線を利用して可視像に変換する赤外線撮像装置等に利用されている。赤外線撮像装置は、赤外光学系と、赤外線検出器（ディテクタ）とから主に構成されている。赤外光学系は、被検物体等から放射される熱、すなわち赤外線を集光し、赤外線検出器の検出面上に結像させている。赤外線検出器（ディテクタ）は、赤外光学系により被検物体等からの赤外線が集光される位置に配置され、検出器面上に複数の受光素子（ＣＣＤ（電荷結合素子））を有している。   Infrared optical systems are used in infrared imaging devices that convert a subject that cannot be seen with the naked eye in the dark or the like into a visible image using infrared rays. An infrared imaging device mainly includes an infrared optical system and an infrared detector (detector). The infrared optical system collects heat radiated from an object to be examined, that is, infrared rays, and forms an image on the detection surface of the infrared detector. An infrared detector (detector) is arranged at a position where infrared rays from an object to be detected are collected by an infrared optical system, and has a plurality of light receiving elements (CCD (charge coupled device)) on the detector surface. ing.

そして、上記のような赤外線撮像装置では、赤外線検出器にて被検物以外から放射される不要な赤外線（例えば、鏡筒の自己放射）の影響を取り除くため、赤外光学系と赤外線検出器との間に、赤外光学系によって集光された赤外線を通過させる開口部を備えたコールドシールドを配置して、検出面の周囲（側方や斜方）からの不要光を遮断するとともに、このコールドシールドと赤外線検出器を低温（ほぼ液体窒素温度）に冷却して、これら自体から放射する赤外線を極力除去する構成となっている。   In the infrared imaging apparatus as described above, an infrared optical system and an infrared detector are used to remove the influence of unnecessary infrared rays (for example, self-radiation of the lens barrel) emitted from other than the test object by the infrared detector. And a cold shield with an opening that allows the infrared light collected by the infrared optical system to pass therethrough, blocking unnecessary light from the surroundings (side and oblique) of the detection surface, The cold shield and the infrared detector are cooled to a low temperature (almost liquid nitrogen temperature) to remove as much infrared rays as possible from the cold shield and the infrared detector.

また、コールドシールドが備えている開口部は、赤外光学系の射出瞳の位置と大きさ（射出瞳の径）が一致するように設計されており、このような状態は一般に「開口整合の取れた状態」と呼ばれている。このように、コールドシールドが赤外光学系の射出瞳と開口整合を取ることにより、赤外線検出器において、赤外光学系の被検物体以外の不要な赤外光を効率良く抑えることができ、被検物体の赤外光のみを取り入れることができるようになっている。   The aperture provided in the cold shield is designed so that the exit pupil position and size (exit pupil diameter) of the infrared optical system coincide with each other. It is called “taken off”. In this way, by taking aperture matching with the exit pupil of the infrared optical system, the cold shield can efficiently suppress unnecessary infrared light other than the test object of the infrared optical system in the infrared detector, Only the infrared light of the test object can be taken in.

しかしながら、上記のような開口整合を取るために、赤外光学系の射出瞳の位置とコールドシールドの開口部とを一致させようとすると、射出瞳が赤外光学系と赤外線検出器との間に置かれることになり、光学系の収差補正が困難になってしまったり、レンズ口径が大きくなってしまったりといった問題があった。このような問題を解決するため、近年、種々の赤外光学系が開示されている（例えば、特許文献１及び２を参照）。   However, if the position of the exit pupil of the infrared optical system is matched with the aperture of the cold shield in order to achieve aperture matching as described above, the exit pupil is located between the infrared optical system and the infrared detector. Therefore, there is a problem that aberration correction of the optical system becomes difficult and the lens aperture becomes large. In order to solve such a problem, various infrared optical systems have been disclosed in recent years (see, for example, Patent Documents 1 and 2).

具体的には、特許文献１に記載の赤外光学系は、物体側より順に、第１〜第５レンズ群からなる５つのレンズ群と、開口絞りとが主に配置され、第４レンズ群及び第５レンズ群は各々少なくとも１つの非球面形状を備えた構成となっている。また、特許文献２に記載の赤外光学系は、物体側より順に、第１および第２レンズ群からなる２つのレンズ群と、開口絞りとが配置され、中間像が第１と第２レンズ群との間に形成される構成となっている。
特開２００２−１４２８３号公報 特開２００７−２６４１９１号公報 Specifically, the infrared optical system described in Patent Document 1 includes, in order from the object side, five lens groups including first to fifth lens groups and an aperture stop, which are mainly arranged, and a fourth lens group. Each of the fifth lens group has at least one aspherical shape. In addition, in the infrared optical system described in Patent Document 2, two lens groups including the first and second lens groups and an aperture stop are arranged in this order from the object side, and the intermediate image is the first and second lenses. It is the structure formed between groups.
JP 2002-14283 A JP 2007-264191 A

ところで、赤外線を透過させる光学材料としては、従来より、ゲルマニウム（Ｇｅ），シリコン（Ｓｉ），硫化亜鉛（ＺｎＳ）などの結晶材料が使われているが、これらの材料は非常に高価であるため、レンズの構成枚数が多いとコストが高くなってしまうといった問題がある。また、レンズの構成枚数が多いと、光学系における透過率の低下が問題となり、赤外線検出器の低感度化や熱雑音の増加を招いてしてしまう。よって、赤外光学系では、最小限のレンズ枚数で構成することが望まれている。   By the way, crystal materials such as germanium (Ge), silicon (Si), and zinc sulfide (ZnS) are conventionally used as optical materials that transmit infrared rays. However, these materials are very expensive. There is a problem that the cost increases when the number of lenses is large. In addition, when the number of lenses is large, a decrease in transmittance in the optical system becomes a problem, leading to a reduction in sensitivity of the infrared detector and an increase in thermal noise. Therefore, it is desired that the infrared optical system be configured with a minimum number of lenses.

しかしながら、特許文献１に開示の赤外光学系では、レンズの構成枚数が多い上に、非球面形状を有するレンズが複数含まれている。上記のように赤外光学系用の光学材料は高価であり、さらに非球面レンズも高価であるため、コスト上不利となってしまう。また、コスト以外の観点からも、レンズの構成枚数が多いと、透過率の減少、フレアの増加、ゴーストの発生、ナルシサスの発生等が考えられ、性能上不利であり、好ましくない。   However, the infrared optical system disclosed in Patent Document 1 includes a large number of lenses and a plurality of lenses having an aspherical shape. As described above, the optical material for the infrared optical system is expensive, and the aspheric lens is also expensive, which is disadvantageous in terms of cost. Also, from a viewpoint other than cost, if the number of lenses is large, a decrease in transmittance, an increase in flare, generation of ghost, generation of narcissus, and the like are considered, which is disadvantageous in terms of performance and is not preferable.

また、特許文献２に開示の赤外光学系では、フォーカシングはレンズ移動により行われているが、焦点距離は変倍レンズの挿脱による切り換え式となっているため、特定の２つの焦点距離しか用いることができない。また、変倍レンズを退避させるスペースが必要であるため、光学系の小型化に不利であり、好ましくない。   In the infrared optical system disclosed in Patent Document 2, focusing is performed by moving the lens. However, since the focal length is a switching type by inserting / removing a variable power lens, there are only two specific focal lengths. Cannot be used. Further, since a space for retracting the zoom lens is required, it is disadvantageous for downsizing the optical system, which is not preferable.

本発明は、このような問題に鑑みてなされたものであり、少ないレンズ枚数で構成しつつも、良好に諸収差を補正し、レンズ口径の小型化を図り、開口整合を取ることができ、さらには焦点距離を連続的に変化させることができる、赤外線ズーム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, and while correcting the various aberrations while configuring with a small number of lenses, it is possible to reduce the lens diameter and achieve aperture matching. Furthermore, it aims at providing the infrared zoom lens which can change a focal distance continuously.

このような目的を達成するため、本発明の赤外線ズームレンズは、全体として正の屈折力を有し、合焦機能と変倍に伴う補償機能を持つ第１レンズ群と、全体として負の屈折力を有し、変倍機能を持つ第２レンズ群と、全体として正の屈折率を有し、中間像を形成する機能を持つ第３レンズ群と、全体として正の屈折率を有し、前記中間像をリレー結像する機能を持つ第４レンズ群と、開口絞りとを有し、前記第１レンズ群は正レンズを含み、前記第３レンズ群は物体側に凸面を向けた正メニスカスレンズを含み、前記第４レンズ群は最も像側のレンズが物体側に凸面を向けたメニスカス形状に形成されており、前記第１レンズ群の前記正レンズのアッベ数をνL1とし、前記第３レンズ群の前記正メニスカスレンズのアッベ数をνL3としたとき、次式νL1＞２νL3の条件を満足することを特徴とする。 In order to achieve such an object, the infrared zoom lens of the present invention has a positive refractive power as a whole, a first lens group having a focusing function and a compensation function accompanying zooming, and a negative refraction as a whole. A second lens group having a variable power function, a third lens group having a positive refractive index as a whole and forming an intermediate image, and a positive refractive index as a whole, A fourth lens group having a function of relay-forming the intermediate image; and an aperture stop; the first lens group includes a positive lens; and the third lens group has a positive meniscus with a convex surface facing the object side. The fourth lens group is formed in a meniscus shape with the most image side lens facing the convex surface on the object side, and the Abbe number of the positive lens of the first lens group is ν L1 . When the Abbe number of the positive meniscus lens in the three lens group is ν L3 The following condition is satisfied: ν L1 > 2ν L3

以上説明したように、本発明によれば、少ないレンズ枚数で構成しつつも、良好に諸収差を補正し、レンズ口径の小型化を図り、開口整合を取ることができ、焦点距離を連続的に変化させることができる、赤外線ズームレンズを提供することができる。   As described above, according to the present invention, while configuring with a small number of lenses, various aberrations can be corrected satisfactorily, the lens diameter can be reduced, aperture alignment can be achieved, and the focal length can be continuously increased. It is possible to provide an infrared zoom lens that can be changed to

以下、本発明の好ましい実施形態について説明する。本発明に係る赤外線ズームレンズは、赤外線撮像装置等に搭載される、物体の像を撮像手段の検出面上に形成する光学系であり、物体側より順に並んだ、全体として正の屈折力を有し、合焦機能と（後述の第２レンズ群による）変倍に伴う補償機能を持つ第１レンズ群と、全体として負の屈折力を有し、変倍機能を持つ第２レンズ群と、全体として正の屈折率を有し、中間像を形成する機能を持つ第３レンズ群と、全体として正の屈折率を有し、前記中間像をリレー結像する機能を持つ第４レンズ群と、開口絞りとを有して構成されている。なお、開口絞りの直前には、撮像素子用窓材として、２枚のゲルマニウム平行平面板が配置されている。   Hereinafter, preferred embodiments of the present invention will be described. An infrared zoom lens according to the present invention is an optical system that forms an image of an object on a detection surface of an image pickup means, which is mounted on an infrared imaging device or the like, and has a positive refractive power as a whole arranged in order from the object side. A first lens group having a focusing function and a compensation function associated with zooming (by a second lens group to be described later), and a second lens group having a negative refractive power as a whole and having a zooming function A third lens group having a positive refractive index as a whole and having a function of forming an intermediate image, and a fourth lens group having a positive refractive index as a whole and having a function of forming a relay image of the intermediate image And an aperture stop. In addition, immediately before the aperture stop, two germanium parallel flat plates are arranged as an image sensor window material.

上記構成の赤外線ズームレンズは、広角端から望遠端へのズーミング時において、第３レンズ群、第４レンズ群及び開口絞りは固定しつつ、第１レンズ群および第２レンズ群は光軸方向に移動可能に構成されており、第２レンズ群を光軸方向に移動させることにより変倍を行うとともに、第１レンズ群を光軸方向に移動させることにより結像位置の補正を行うようになっている。なお、各ズームポジションにおいて、ズーミング時の第１レンズ群と第２レンズ群の位置関係は、第１レンズ群で生じた球面収差を、第２レンズ群で補正するように考慮された上で、決定されている。   In the infrared zoom lens having the above configuration, the third lens group, the fourth lens group, and the aperture stop are fixed while zooming from the wide-angle end to the telephoto end, and the first lens group and the second lens group are arranged in the optical axis direction. It is configured to be movable, and zooming is performed by moving the second lens group in the optical axis direction, and the imaging position is corrected by moving the first lens group in the optical axis direction. ing. In each zoom position, the positional relationship between the first lens group and the second lens group during zooming is considered so that spherical aberration generated in the first lens group is corrected by the second lens group. It has been decided.

なお、第４レンズ群は、最も像側のレンズ（具体的には、後述の第１および第２実施例の第４レンズ群Ｇ４の負メニスカスレンズＬ４３が相当）が、物体側に凸面を向けた比較的曲率半径の小さいメニスカス形状に形成されている。これにより、ペッツバール和の補正を良好に行うことができる。   In the fourth lens group, the most image-side lens (specifically, a negative meniscus lens L43 of a fourth lens group G4 in first and second embodiments described later) has a convex surface directed toward the object side. It is formed in a meniscus shape having a relatively small radius of curvature. As a result, the Petzval sum can be corrected satisfactorily.

また、第１レンズ群は正レンズを含み、第３レンズ群は物体側に凸面を向けた正メニスカスレンズを含み、これらのレンズの間には、第１レンズ群の正レンズのアッベ数をνL1とし、第３レンズ群の正メニスカスレンズのアッベ数をνL3としたとき、次式（１）を満足する関係がある。但し、アッベ数νは、硝材の設計基準波長の屈折率をｎmとし、硝材の設計最短波長の屈折率をｎhとし、硝材の設計最長波長の屈折率をｎlとしたとき、ν＝（ｎm−１）／（ｎh−ｎl）で定義される。 The first lens group includes a positive lens, the third lens group includes a positive meniscus lens having a convex surface directed toward the object side, and the Abbe number of the positive lens of the first lens group is defined as ν between these lenses. When L1 is set and the Abbe number of the positive meniscus lens in the third lens group is set to ν L3 , there is a relationship satisfying the following expression (1). However, the Abbe number [nu, when the refractive index of the design wavelength of the glass material and n m, the refractive index of the design shortest wavelength of the glass material and n h, the refractive index of the design longest wavelength of the glass material was n l, [nu = It is defined by (n m −1) / (n h −n l ).

νL1＞２νL3 …（１） ν L1 > 2ν L3 (1)

通常の色収差補正では、正レンズには低分散（アッベ数は小）の硝材、負レンズには高分散（アッベ数は大）の硝材を使用する。しかしながら、本実施形態においては、第３レンズ群の正メニスカスレンズに、上記条件式（１）を満足するような高分散の硝材（後述の第１実施例ではゲルマニウム、第２実施例では硫化亜鉛）を使用している。以下に、第３レンズ群の正メニスカスレンズ、すなわち正レンズに高分散の硝材を使用した理由について説明する。   In normal chromatic aberration correction, a low-dispersion glass material (small Abbe number) is used for the positive lens, and a high-dispersion glass material (large Abbe number) is used for the negative lens. However, in the present embodiment, the positive meniscus lens of the third lens group is made of a highly dispersed glass material that satisfies the above conditional expression (1) (germanium in the first example described later, zinc sulfide in the second example) ) Is used. The reason for using a high-dispersion glass material for the positive meniscus lens of the third lens group, that is, the positive lens will be described below.

本実施形態の第３レンズ群では、正メニスカスレンズより物体側に位置する負レンズが球面収差とコマ収差の補正に最適な形状となっているために、軸上色収差は補正過剰の状態となり、倍率色収差は補正不足の状態となる。そこで、第３レンズ群の正メニスカスレンズに高分散の硝材を使用し、さらにその形状をアプラナチックレンズに近づけて構成することで、第３レンズ群において（前記負レンズにより行われている）球面収差の補正に与える影響を抑えながらも、軸上色収差と倍率色収差も同時に補正することを可能にしている。その結果、本実施形態に係る赤外線ズームレンズは、良好な結像性能を持ちつつも、レンズの構成枚数を抑えることができるようになっている。   In the third lens group of the present embodiment, since the negative lens located on the object side from the positive meniscus lens has an optimal shape for correcting spherical aberration and coma aberration, axial chromatic aberration is overcorrected, The lateral chromatic aberration is undercorrected. Therefore, a high-dispersion glass material is used for the positive meniscus lens of the third lens group, and the shape thereof is made closer to the aplanatic lens, so that in the third lens group (performed by the negative lens). While suppressing the influence on correction of spherical aberration, it is possible to correct axial chromatic aberration and lateral chromatic aberration at the same time. As a result, the infrared zoom lens according to the present embodiment is capable of suppressing the number of constituent lenses while having good imaging performance.

本実施形態では、開口絞りを本光学系の最も像側に配置することにより、本光学系の射出瞳の位置と開口絞りの位置とを一致させて、開口整合を取ることを可能にしている。さらに、第３レンズ群により中間像を形成することにより、入射瞳の位置を開口絞りより物体側に配置し、本光学系の物体側のレンズ口径を小さくすることを可能にしている。   In the present embodiment, the aperture stop is arranged on the most image side of the optical system, so that the position of the exit pupil of the optical system and the position of the aperture stop can be matched to achieve aperture matching. . Furthermore, by forming an intermediate image with the third lens group, the position of the entrance pupil is arranged closer to the object side than the aperture stop, and the lens aperture on the object side of the present optical system can be reduced.

以下、各実施例を図面に基づいて説明する。まず、表１に、各実施例において本ズームレンズを構成する硝材として用いた、ゲルマニウム、シリコン及び硫化亜鉛の屈折率を示す。表１では、第１実施例に対応する波長３〜５μｍ及び第２実施例に対応する波長８〜１２μｍの赤外光に対する屈折率を示している。   Hereinafter, each embodiment will be described with reference to the drawings. First, Table 1 shows the refractive indexes of germanium, silicon, and zinc sulfide used as glass materials constituting the zoom lens in each example. Table 1 shows the refractive index for infrared light having a wavelength of 3 to 5 μm corresponding to the first embodiment and a wavelength of 8 to 12 μm corresponding to the second embodiment.

（表１）材料別屈折率
３μm ４μm ５μｍ ８μｍ 10μｍ 12μｍ
シリコン 3.43234 3.42541 3.42227
ゲルマニウム 4.04481 4.02448 4.01535 4.00523 4.00316 4.00231
硫化亜鉛 2.22281 2.20016 2.17007 (Table 1) Refractive index by material
3μm 4μm 5μm 8μm 10μm 12μm
Silicon 3.43234 3.42541 3.42227
Germanium 4.04481 4.02448 4.01535 4.00523 4.00316 4.00231
Zinc sulfide 2.22281 2.20016 2.17007

（第１実施例）
第１実施例について、図１〜図８及び表２を用いて説明する。なお、図１には第１実施例に係るレンズ構成図を、図２には本実施例における望遠端状態（Ｔ）から中間焦点距離状態（Ｍ）を経て広角端状態（Ｗ）までの焦点距離状態の変化、すなわちズーミングの際の各レンズ群の移動の様子を示す。また、表２には第１実施例におけるレンズ諸元を示す。 (First embodiment)
1st Example is described using FIGS. 1-8 and Table 2. FIG. FIG. 1 shows a lens configuration diagram according to the first embodiment, and FIG. 2 shows a focus from the telephoto end state (T) to the wide-angle end state (W) through the intermediate focal length state (M) in this embodiment. A change in the distance state, that is, how the lens groups move during zooming is shown. Table 2 shows lens specifications in the first example.

本実施例に係る赤外線ズームレンズは、３〜５μｍの波長域（基準波長４μｍ）に対応したものであり、図１に示すように、物体側より順に並んだ、全体として正の屈折力を有する第１レンズ群Ｇ１と、全体として負の屈折力を有する第２レンズ群Ｇ２と、全体として正の屈折率を有する第３レンズ群Ｇ３と、全体として正の屈折率を有する第４レンズ群Ｇ４と、開口絞りＡＳとから構成されている。開口絞りＡＳの直前には、撮像素子用窓材として２枚のゲルマニウム平行平面板Ｐ１，Ｐ２が配置されている。図中のＩは像面を示しており、不図示の複数の受光素子（ＣＣＤ（電荷結合素子）等）を備えて構成されている。なお、本光学系の射出瞳の位置と開口絞りＡＳの位置とは一致しており、いわゆる開口整合が取れた状態となっている。   The infrared zoom lens according to the present embodiment corresponds to a wavelength region of 3 to 5 μm (reference wavelength 4 μm), and has a positive refractive power as a whole, which is arranged in order from the object side as shown in FIG. The first lens group G1, the second lens group G2 having a negative refractive power as a whole, the third lens group G3 having a positive refractive index as a whole, and the fourth lens group G4 having a positive refractive index as a whole. And an aperture stop AS. Immediately before the aperture stop AS, two germanium parallel flat plates P1 and P2 are arranged as imaging element window materials. In the drawing, I denotes an image plane, and is configured to include a plurality of light receiving elements (CCD (charge coupled device) or the like) not shown. Note that the position of the exit pupil of the present optical system and the position of the aperture stop AS coincide with each other, and so-called aperture alignment is achieved.

第１レンズ群Ｇ１は物体側に凸面を向けた正メニスカスレンズＬ１からなる。第２レンズ群Ｇ２は両凹レンズＬ２からなる。第３レンズ群Ｇ３は、物体側より順に並んだ、両凸レンズＬ３１と、物体側に凹面を向けた負メニスカスレンズＬ３２と、物体側に凸面を向けた正メニスカスレンズＬ３３とからなる。第４レンズ群Ｇ４は、物体側より順に並んだ、物体側に凹面を向けた正メニスカスレンズＬ４１と、物体側に凸面を向けた正メニスカスレンズＬ４２と、物体側に凸面を向けた負メニスカスレンズＬ４３とからなる。   The first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconcave lens L2. The third lens group G3 includes a biconvex lens L31, a negative meniscus lens L32 having a concave surface facing the object side, and a positive meniscus lens L33 having a convex surface facing the object side. The fourth lens group G4 includes a positive meniscus lens L41 having a concave surface directed toward the object side, a positive meniscus lens L42 having a convex surface directed toward the object side, and a negative meniscus lens having a convex surface directed toward the object side. L43.

なお、本実施例では色収差を良好に補正するため、上記ズームレンズを構成する硝材として赤外線を通す分散の異なる２種類の材料を用いて設計している。具体的には、第１レンズ群Ｇ１の正メニスカスレンズＬ１はシリコン、第２レンズ群Ｇ２の両凹レンズＬ２はシリコン、第３レンズ群Ｇ３の両凸レンズＬ３１はシリコン、負メニスカスレンズＬ３２はゲルマニウム、正メニスカスレンズＬ３３はゲルマニウム、第４レンズ群Ｇ４の正メニスカスレンズＬ４１はシリコン、正メニスカスレンズＬ４２はシリコン、負メニスカスレンズＬ４３はゲルマニウムを用いて設計している（表２参照）。   In this embodiment, in order to satisfactorily correct chromatic aberration, the glass material constituting the zoom lens is designed by using two kinds of materials having different dispersions for transmitting infrared rays. Specifically, the positive meniscus lens L1 of the first lens group G1 is silicon, the biconcave lens L2 of the second lens group G2 is silicon, the biconvex lens L31 of the third lens group G3 is silicon, the negative meniscus lens L32 is germanium, and positive. The meniscus lens L33 is designed using germanium, the positive meniscus lens L41 of the fourth lens group G4 is made of silicon, the positive meniscus lens L42 is made of silicon, and the negative meniscus lens L43 is designed using germanium (see Table 2).

そして、赤外線ズームレンズは、図２に示すように、望遠端状態（Ｔ）から広角端状態（Ｗ）へのズーミング（変倍）の際には、第３レンズ群Ｇ３、第４レンズ群Ｇ４及び開口絞りＡＳは固定しつつ、第１レンズ群Ｇ１を（物体側に凸の軌跡にて）光軸に沿って移動させ、第２レンズ群Ｇ２を（直線の軌跡にて）光軸に沿って移動させる。   As shown in FIG. 2, the infrared zoom lens has a third lens group G3 and a fourth lens group G4 during zooming from the telephoto end state (T) to the wide-angle end state (W). While the aperture stop AS is fixed, the first lens group G1 is moved along the optical axis (in a locus convex toward the object side), and the second lens group G2 is along the optical axis (in a straight locus). To move.

このような構成の赤外線ズームレンズでは、被検物体（不図示）から放射される熱すなわち赤外線は、第１レンズ群Ｇ１を通って合焦され、第２レンズ群Ｇ２を通って変倍され、第３レンズ群Ｇ３を通って中間像が形成され、この中間像が第４レンズ群によりリレー結像された後に、開口絞りＡＳを介して像面Ｉ（検出器面）上に集光され、この検出器面Ｉ上に設けられた受光素子（不図示）より受光されるようになっている。   In the infrared zoom lens having such a configuration, heat, that is, infrared rays radiated from an object to be examined (not shown) is focused through the first lens group G1, and is scaled through the second lens group G2. An intermediate image is formed through the third lens group G3, and this intermediate image is relay-formed by the fourth lens group, and then condensed on the image surface I (detector surface) via the aperture stop AS. Light is received from a light receiving element (not shown) provided on the detector surface I.

表２に、第１実施例における赤外線ズームレンズの各レンズの諸元値を示す。表２において、第１欄ｍは物体側からの各光学面の番号（以下、面番号と称する）、第２欄ｒは各光学面の曲率半径、第３欄ｄは各光学面から次の光学面（又は像面Ｉ）までの光軸上の距離（以下、面間隔と称する）、第４欄は硝材名、第５欄は所属するレンズ群を表す。なお、表２の面番号１〜２０は、図１の面番号１〜２０に対応している。   Table 2 shows the specifications of each lens of the infrared zoom lens in the first example. In Table 2, the first column m is the number of each optical surface from the object side (hereinafter referred to as the surface number), the second column r is the radius of curvature of each optical surface, the third column d is from the optical surface to the next The distance on the optical axis to the optical surface (or image surface I) (hereinafter referred to as the surface interval), the fourth column represents the glass material name, and the fifth column represents the lens group to which it belongs. The surface numbers 1 to 20 in Table 2 correspond to the surface numbers 1 to 20 in FIG.

また、表中において、第１レンズ群Ｇ１と第２レンズ群Ｇ２との軸上空気間隔をｄ１とし、第２レンズ群Ｇ２と第３レンズ群Ｇ３との軸上空気間隔をｄ２とし、これらの軸上空気間隔はズーミング（変倍）に際して変化する。また、表２では、ｆは焦点距離、ωは画角（deg．）を示すとともに、上記条件式（１）に対応する値、すなわち条件式対応値も示している。   In the table, the axial air gap between the first lens group G1 and the second lens group G2 is d1, and the axial air gap between the second lens group G2 and the third lens group G3 is d2. The axial air space changes during zooming. In Table 2, f indicates the focal length, ω indicates the angle of view (deg.), And also indicates a value corresponding to the conditional expression (1), that is, a value corresponding to the conditional expression.

表２において、焦点距離ｆ、曲率半径ｒ、面間隔ｄなど、その他の長さの単位は、一般に「ｍｍ」が使われている。但し、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」に限定されることなく、他の適当な単位を用いることが可能である。また、表２において、曲率半径の「0.00000」は平面または開口を示している。以上、諸元値に関する表の説明は、他の実施例においても同様である。   In Table 2, “mm” is generally used as the unit of other lengths such as the focal length f, the radius of curvature r, and the surface interval d. However, since the optical system can obtain the same optical performance even when proportionally enlarged or proportionally reduced, the unit is not limited to “mm”, and other appropriate units can be used. In Table 2, the curvature radius “0.00000” indicates a plane or an opening. The description of the table relating to the specification values is the same in the other examples.

（表２）
波長３〜５μｍ（基準波長４μｍ）
［レンズ諸元］
ｍ ｒ ｄ 硝材名 （レンズ名）レンズ群
１ 188.22268 6.00000 シリコン （Ｌ１ ）Ｇ１
２ 248.24435 (d1)
３ -348.36381 3.50000 シリコン （Ｌ２ ）Ｇ２
４ 488.37708 (d2)
５ 153.20090 6.00000 シリコン （Ｌ３１）Ｇ３
６ -140.87647 1.94960
７ -103.28020 3.00000 ゲルマニウム （Ｌ３２）
８ -486.90118 43.61728
９ 38.14881 4.00000 ゲルマニウム （Ｌ３３）
１０ 41.71549 71.30273
１１ -1273.41645 2.50000 シリコン （Ｌ４１）Ｇ４
１２ -73.37961 0.10000
１３ 18.71103 3.00000 シリコン （Ｌ４２）
１４ 34.89691 1.43373
１５ 38.62777 7.30000 ゲルマニウム （Ｌ４３）
１６ 14.70468 1.88754
１７ 0.00000 2.00000 ゲルマニウム Ｐ１
１８ 0.00000 1.00000
１９ 0.00000 1.00000 ゲルマニウム Ｐ２
２０ 開口絞りAS 30.00000
［ズーミング（変倍）時における可変間隔］
ｆ ω d1 d2
望遠端無限遠 250 4.58 146.33960 5.00000
望遠端近距離１０ｍ 212 4.41 155.40909 5.00000
中間無限遠 140 8.17 97.05323 54.08661
中間近距離１０ｍ 137 7.79 106.32248 54.08661
広角端無限遠 80 14.25 10.00000 80.62113
広角端近距離１０ｍ 81 13.75 19.48489 80.62113
［条件式］
νL1＝２４１
νL3＝１０３
（１）νL1（＝241）＞２νL3（＝2×103＝206） (Table 2)
Wavelength 3-5μm (reference wavelength 4μm)
[Lens specifications]
m r d Glass name (Lens name) Lens group 1 188.22268 6.00000 Silicon (L1) G1
2 248.24435 (d1)
3 -348.36381 3.50000 Silicon (L2) G2
4 488.37708 (d2)
5 153.20090 6.00000 Silicon (L31) G3
6 -140.87647 1.94960
7 -103.28020 3.00000 Germanium (L32)
8 -486.90118 43.61728
9 38.14881 4.00000 Germanium (L33)
10 41.71549 71.30273
11 -1273.41645 2.50000 Silicon (L41) G4
12 -73.37961 0.10000
13 18.71103 3.00000 Silicon (L42)
14 34.89691 1.43373
15 38.62777 7.30000 Germanium (L43)
16 14.70468 1.88754
17 0.00000 2.00000 Germanium P1
18 0.00000 1.00000
19 0.00000 1.00000 Germanium P2
20 Aperture stop AS 30.00000
[Variable interval during zooming]
f ω d1 d2
Telephoto end infinity 250 4.58 146.33960 5.00000
Telephoto end short distance 10m 212 4.41 155.40909 5.00000
Intermediate infinity 140 8.17 97.05323 54.08661
Middle short distance 10m 137 7.79 106.32248 54.08661
Wide angle end infinity 80 14.25 10.00000 80.62113
Short-distance at wide-angle end 10m 81 13.75 19.48489 80.62113
[Conditional expression]
ν L1 = 241
ν L3 = 103
(1) ν L1 (= 241)> 2ν L3 (= 2 × 103 = 206)

表２に示す諸元の表から分かるように、第１実施例に係る赤外線ズームレンズでは、上記条件式（１）を全て満たすことが分かる。   As can be seen from the table of specifications shown in Table 2, it can be seen that the infrared zoom lens according to the first example satisfies all the conditional expressions (1).

図３〜図８は、第１実施例に係る赤外線ズームレンズの横収差図である。図３は望遠端状態における無限遠物点での合焦状態の横収差図、図４は望遠端状態における近距離物点１０ｍでの合焦状態の横収差図、図５は中間焦点距離状態における無限遠物点での合焦状態の横収差図、図６は中間焦点距離状態における近距離物点１０ｍでの合焦状態での横収差図、図７は広角端状態における無限遠物点での合焦状態の横収差図、図８は広角端状態における近距離物点１０ｍでの合焦状態の横収差図をそれぞれ示す。なお、各収差図において、各像高（半画角ω）毎にタンジェンシャル像面及びサジタル像面における収差曲線を示している。また、各収差図において、実線は波長５μｍ、点線は４μｍ、一点鎖線は３μｍの収差曲線をそれぞれ示している。   3 to 8 are lateral aberration diagrams of the infrared zoom lens according to Example 1. FIG. 3 is a lateral aberration diagram in a focused state at an infinite object point in the telephoto end state, FIG. 4 is a lateral aberration diagram in a focused state at a short distance object point 10 m in the telephoto end state, and FIG. 5 is an intermediate focal length state. FIG. 6 is a lateral aberration diagram in the in-focus state at an infinite object point, FIG. 6 is a transverse aberration diagram in the in-focus state at a near object point 10 m in the intermediate focal length state, and FIG. 7 is an infinite object point in the wide-angle end state. FIG. 8 is a lateral aberration diagram in the in-focus state, and FIG. 8 is a lateral aberration diagram in the in-focus state at the short-distance object point 10 m in the wide-angle end state. In each aberration diagram, aberration curves on the tangential image surface and the sagittal image surface are shown for each image height (half angle of view ω). In each aberration diagram, a solid line indicates an aberration curve of a wavelength of 5 μm, a dotted line indicates an aberration curve of 4 μm, and an alternate long and short dash line indicates an aberration curve of 3 μm.

図３〜図８に示す各収差図から明らかであるように、第１実施例の赤外線ズームレンズでは、望遠端状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態、中間焦点距離状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態、及び、広角端状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態において、いずれの場合にも良好に収差補正され、優れた結像性能が確保されていることが分かる。   As apparent from the respective aberration diagrams shown in FIGS. 3 to 8, in the infrared zoom lens of the first embodiment, each focal length state from the infinity object point to the short-distance object point 10 m in the telephoto end state, the intermediate focus Good in each case in each focal length state from infinity object point to 10m near object point in the distance state and each focal distance state from infinity object point to near object point 10m in the wide angle end state It can be seen that aberration correction is performed and excellent imaging performance is secured.

（第２実施例）
第２実施例について、図９〜図１６及び表３を用いて説明する。なお、図９には第２実施例に係るレンズ構成図を、図１０には本実施例における望遠端状態（Ｔ）から中間焦点距離状態（Ｍ）を経て広角端状態（Ｗ）までの焦点距離状態の変化、すなわちズーミングの際の各レンズ群の移動の様子を示す。 (Second embodiment)
A second embodiment will be described with reference to FIGS. 9 to 16 and Table 3. FIG. 9 shows a lens configuration diagram according to the second embodiment, and FIG. 10 shows a focus from the telephoto end state (T) to the wide-angle end state (W) through the intermediate focal length state (M) in this embodiment. A change in the distance state, that is, how the lens groups move during zooming is shown.

本実施例に係る赤外線ズームレンズは、８〜１２μｍの波長域（基準波長１０μｍ）に対応したものであり、図９に示すように、物体側より順に並んだ、全体として正の屈折力を有する第１レンズ群Ｇ１と、全体として負の屈折力を有する第２レンズ群Ｇ２と、全体として正の屈折率を有する第３レンズ群Ｇ３と、全体として正の屈折率を有する第４レンズ群Ｇ４と、開口絞りＡＳとから構成されている。開口絞りＡＳの直前には、撮像素子用窓材として２枚のゲルマニウム平行平面板Ｐ１，Ｐ２が配置されている。図中のＩは像面を示しており、不図示の複数の受光素子（ＣＣＤ（電荷結合素子）等）を備えて構成されている。なお、本光学系の射出瞳の位置と開口絞りＡＳの位置とは一致しており、いわゆる開口整合が取れた状態となっている。   The infrared zoom lens according to the present example corresponds to a wavelength region of 8 to 12 μm (reference wavelength of 10 μm), and has a positive refractive power as a whole arranged in order from the object side as shown in FIG. The first lens group G1, the second lens group G2 having a negative refractive power as a whole, the third lens group G3 having a positive refractive index as a whole, and the fourth lens group G4 having a positive refractive index as a whole. And an aperture stop AS. Immediately before the aperture stop AS, two germanium parallel flat plates P1 and P2 are arranged as imaging element window materials. In the drawing, I denotes an image plane, and is configured to include a plurality of light receiving elements (CCD (charge coupled device) or the like) not shown. Note that the position of the exit pupil of the present optical system and the position of the aperture stop AS coincide with each other, and so-called aperture alignment is achieved.

第１レンズ群Ｇ１は物体側に凸面を向けた正メニスカスレンズＬ１からなる。第２レンズ群Ｇ２は両凹レンズＬ２からなる。第３レンズ群Ｇ３は、物体側より順に並んだ、両凸レンズＬ３１と、物体側に凹面を向けた負メニスカスレンズＬ３２と、物体側に凸面を向けた正メニスカスレンズＬ３３とからなる。第４レンズ群Ｇ４は、物体側より順に並んだ、物体側に凹面を向けた両凸レンズＬ４１と、物体側に凹面を向けた負メニスカスレンズＬ４２と、物体側に凸面を向けた正メニスカスレンズＬ４３とからなる。   The first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconcave lens L2. The third lens group G3 includes a biconvex lens L31, a negative meniscus lens L32 having a concave surface facing the object side, and a positive meniscus lens L33 having a convex surface facing the object side. The fourth lens group G4 includes a biconvex lens L41 having a concave surface facing the object side, a negative meniscus lens L42 having a concave surface facing the object side, and a positive meniscus lens L43 having a convex surface facing the object side. It consists of.

なお、本実施例では色収差を良好に補正するため、上記ズームレンズを構成する硝材として赤外線を通す分散の異なる２種類の材料を用いて設計している。具体的には、第１レンズ群Ｇ１の正メニスカスレンズＬ１はゲルマニウム、第２レンズ群Ｇ２の両凹レンズＬ２はゲルマニウム、第３レンズ群Ｇ３の両凸レンズＬ３１はゲルマニウム、負メニスカスレンズＬ３２は硫化亜鉛、正メニスカスレンズＬ３３は硫化亜鉛、第４レンズ群Ｇ４の両凸レンズＬ４１はゲルマニウム、負メニスカスレンズＬ４２はゲルマニウム、正メニスカスレンズＬ４３はゲルマニウムを用いて設計している（表３参照）。   In this embodiment, in order to satisfactorily correct chromatic aberration, the glass material constituting the zoom lens is designed by using two kinds of materials having different dispersions for transmitting infrared rays. Specifically, the positive meniscus lens L1 of the first lens group G1 is germanium, the biconcave lens L2 of the second lens group G2 is germanium, the biconvex lens L31 of the third lens group G3 is germanium, the negative meniscus lens L32 is zinc sulfide, The positive meniscus lens L33 is designed using zinc sulfide, the biconvex lens L41 of the fourth lens group G4 is made of germanium, the negative meniscus lens L42 is designed using germanium, and the positive meniscus lens L43 is designed using germanium (see Table 3).

そして、赤外線ズームレンズは、図１０に示すように、望遠端状態（Ｔ）から広角端状態（Ｗ）へのズーミング（変倍）の際には、第３レンズ群Ｇ３、第４レンズ群Ｇ４及び開口絞りＡＳは固定しつつ、第１レンズ群Ｇ１を（物体側に凸の軌跡にて）光軸に沿って移動させ、第２レンズ群Ｇ２を（直線の軌跡にて）光軸に沿って移動させる。   As shown in FIG. 10, the infrared zoom lens has a third lens group G3 and a fourth lens group G4 when zooming from the telephoto end state (T) to the wide-angle end state (W). While the aperture stop AS is fixed, the first lens group G1 is moved along the optical axis (in a locus convex toward the object side), and the second lens group G2 is along the optical axis (in a straight locus). To move.

このような構成の赤外線ズームレンズでは、被検物体（不図示）から放射される熱、すなわち赤外線は、第１レンズ群Ｇ１を通って合焦され、第２レンズ群Ｇ２を通って変倍され、第３レンズ群Ｇ３を通って中間像が形成され、この中間像が第４レンズ群によりリレー結像された後に、開口絞りＡＳを介して像面Ｉ（検出器面）上に集光され、この検出器面Ｉ上に設けられた受光素子（不図示）より受光されるようになっている。   In the infrared zoom lens having such a configuration, heat radiated from an object to be examined (not shown), that is, infrared light is focused through the first lens group G1, and is scaled through the second lens group G2. Then, an intermediate image is formed through the third lens group G3, and this intermediate image is relay-formed by the fourth lens group and then condensed on the image plane I (detector surface) through the aperture stop AS. The light is received by a light receiving element (not shown) provided on the detector surface I.

表３に、第２実施例における赤外線ズームレンズの各レンズの諸元値を示す。表３の面番号１〜２０は、図９の面番号１〜２０に対応している。また、表中において、第１レンズ群Ｇ１と第２レンズ群Ｇ２との軸上空気間隔をｄ１とし、第２レンズ群Ｇ２と第３レンズ群Ｇ３との軸上空気間隔をｄ２とし、これらの軸上空気間隔はズーミングに際して変化する。   Table 3 shows the specification values of each lens of the infrared zoom lens in the second example. Surface numbers 1 to 20 in Table 3 correspond to surface numbers 1 to 20 in FIG. In the table, the axial air gap between the first lens group G1 and the second lens group G2 is d1, and the axial air gap between the second lens group G2 and the third lens group G3 is d2. The axial air spacing changes during zooming.

（表３）
波長８〜１２μｍ（基準波長１０μｍ）
［レンズ諸元］
ｍ ｒ ｄ 硝材名 （レンズ名）レンズ群
１ 281.04271 12.00000 ゲルマニウム （Ｌ１ ）Ｇ１
２ 368.40753 (d1)
３ -964.23530 5.00000 ゲルマニウム （Ｌ２ ）Ｇ２
４ 323.04414 (d4)
５ 883.81258 7.00000 ゲルマニウム （Ｌ３１）Ｇ３
６ -241.32699 2.96529
７ -116.48199 4.00000 硫化亜鉛 （Ｌ３２）Ｇ３
８ -369.38897 12.30479
９ 68.65620 7.00000 硫化亜鉛 （Ｌ３３）Ｇ３
１０ 107.13713 150.29094
１１ 2553.75491 7.00000 ゲルマニウム （Ｌ４１）Ｇ４
１２ -124.61165 5.35609
１３ -82.57337 4.50000 ゲルマニウム （Ｌ４２）Ｇ４
１４ -129.72691 0.10000
１５ 42.57893 20.00000 ゲルマニウム （Ｌ４３）Ｇ４
１６ 33.26128 15.72304
１７ 0.00000 2.00000 ゲルマニウム Ｐ１
１８ 0.00000 1.00000
１９ 0.00000 1.00000 ゲルマニウム Ｐ２
２０ (開口絞りAS) 30.00000
［ズーミング（変倍）時における可変間隔］
ｆ ω d1 d2
望遠端無限遠 250 4.58 227.74035 5.00000
望遠端近距離１０ｍ 216 4.29 240.59736 5.00000
中間無限遠 140 8.17 198.58650 81.20892
中間近距離１０ｍ 137 7.31 211.55090 81.20892
広角端無限遠 80 14.25 147.06467 121.92404
広角端近距離１０ｍ 85 13.08 160.43801 121.92404
［条件式］
νL1＝１０２８
νL3＝２３
（１）νL1（＝1028）＞２νL3（＝2×23＝46） (Table 3)
Wavelength 8-12μm (reference wavelength 10μm)
[Lens specifications]
m r d Glass material name (Lens name) Lens group 1 281.04271 12.00000 Germanium (L1) G1
2 368.40753 (d1)
3 -964.23530 5.00000 Germanium (L2) G2
4 323.04414 (d4)
5 883.81258 7.00000 Germanium (L31) G3
6 -241.32699 2.96529
7 -116.48199 4.00000 Zinc sulfide (L32) G3
8 -369.38897 12.30479
9 68.65620 7.00000 Zinc sulfide (L33) G3
10 107.13713 150.29094
11 2553.75491 7.00000 Germanium (L41) G4
12 -124.61165 5.35609
13 -82.57337 4.50000 Germanium (L42) G4
14 -129.72691 0.10000
15 42.57893 20.00000 Germanium (L43) G4
16 33.26128 15.72304
17 0.00000 2.00000 Germanium P1
18 0.00000 1.00000
19 0.00000 1.00000 Germanium P2
20 (Aperture stop AS) 30.00000
[Variable interval during zooming]
f ω d1 d2
Telephoto end infinity 250 4.58 227.74035 5.00000
Telephoto end short distance 10m 216 4.29 240.59736 5.00000
Intermediate infinity 140 8.17 198.58650 81.20892
Middle short distance 10m 137 7.31 211.55090 81.20892
Wide angle end infinity 80 14.25 147.06467 121.92404
Near end of wide angle 10m 85 13.08 160.43801 121.92404
[Conditional expression]
ν L1 = 1028
ν L3 = 23
(1) ν L1 (= 1028)> 2ν L3 (= 2 × 23 = 46)

表３に示す諸元の表から分かるように、第２実施例に係る赤外線ズームレンズでは、上記条件式（１）を全て満たすことが分かる。   As can be seen from the table of specifications shown in Table 3, it can be seen that the infrared zoom lens according to Example 2 satisfies all the conditional expressions (1).

図１１〜図１６は、第２実施例に係る赤外線ズームレンズの横収差図である。図１１は望遠端状態における無限遠物点での合焦状態の横収差図、図１２は望遠端状態における近距離物点１０ｍでの合焦状態の横収差図、図１３は中間焦点距離状態における無限遠物点での合焦状態の横収差図、図１４は中間焦点距離状態における近距離物点１０ｍでの合焦状態での横収差図、図１５は広角端状態における無限遠物点での合焦状態の横収差図、図１６は広角端状態における近距離物点１０ｍでの合焦状態の横収差図をそれぞれ示す。なお、各収差図において、各像高（半画角ω）毎にタンジェンシャル像面及びサジタル像面における収差曲線を示している。また、各収差図において、実線は波長１２μｍ、点線は１０μｍ、一点鎖線は８μｍの収差曲線をそれぞれ示している。   11 to 16 are lateral aberration diagrams of the infrared zoom lens according to Second Example. 11 is a lateral aberration diagram in a focused state at an infinite object point in the telephoto end state, FIG. 12 is a lateral aberration diagram in a focused state at a near object point 10 m in the telephoto end state, and FIG. 13 is an intermediate focal length state. FIG. 14 is a lateral aberration diagram in the in-focus state at the near object point 10m in the intermediate focal length state, and FIG. 15 is an infinite object point in the wide-angle end state. FIG. 16 is a transverse aberration diagram in the in-focus state, and FIG. 16 is a transverse aberration diagram in the in-focus state at the short-distance object point 10 m in the wide-angle end state. In each aberration diagram, aberration curves on the tangential image surface and the sagittal image surface are shown for each image height (half angle of view ω). In each aberration diagram, a solid line indicates an aberration curve having a wavelength of 12 μm, a dotted line indicates 10 μm, and an alternate long and short dash line indicates an aberration curve of 8 μm.

図１１〜図１６に示す各収差図から明らかであるように、本実施例の赤外線ズームレンズでは、望遠端状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態、中間焦点距離状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態、及び、広角端状態における無限遠物点から近距離物点１０ｍまでの各焦点距離状態において、いずれの場合にも良好に収差補正され、優れた結像性能が確保されていることが分かる。   As is apparent from the aberration diagrams shown in FIGS. 11 to 16, in the infrared zoom lens of the present embodiment, each focal length state from the infinity object point to the short-distance object point 10m in the telephoto end state, the intermediate focal length In each case, each focal length state from an infinite object point to a short-distance object point of 10 m in a state and each focal length state from an infinite object point to a short-distance object point in a wide-angle end state are good in any case. It can be seen that the aberration is corrected and excellent imaging performance is secured.

なお、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 addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

第１実施例に係る赤外線ズームレンズのレンズ構成図である。It is a lens block diagram of the infrared zoom lens which concerns on 1st Example. 第１実施例に係る赤外線ズームレンズにおける、望遠端状態（Ｔ）から中間焦点距離状態（Ｍ）を経て広角端状態（Ｗ）までの焦点距離状態の変化、すなわちズーミングの際の各レンズ群の移動の様子を示す図である。In the infrared zoom lens according to the first embodiment, the change in the focal length state from the telephoto end state (T) to the intermediate focal length state (M) to the wide angle end state (W), that is, each lens group during zooming. It is a figure which shows the mode of a movement. 第１実施例に係る赤外線ズームレンズの横収差図である。It is a lateral aberration diagram of the infrared zoom lens according to the first example. 第１実施例に係る赤外線ズームレンズの望遠端状態における無限遠物点での合焦状態の横収差図である。FIG. 6 is a lateral aberration diagram in a focused state at an infinite object point in the telephoto end state of the infrared zoom lens according to Example 1. 第１実施例に係る赤外線ズームレンズの望遠端状態における近距離物点１０ｍでの合焦状態の横収差図である。FIG. 6 is a lateral aberration diagram in a focused state at a short-distance object point of 10 m in the telephoto end state of the infrared zoom lens according to Example 1. 第１実施例に係る赤外線ズームレンズの中間焦点距離状態における無限遠物点での合焦状態の横収差図である。FIG. 6 is a lateral aberration diagram in a focused state at an infinite object point in the intermediate focal length state of the infrared zoom lens according to Example 1. 第１実施例に係る赤外線ズームレンズの中間焦点距離状態における近距離物点１０ｍでの合焦状態での横収差図である。FIG. 6 is a lateral aberration diagram in a focused state at a short-distance object point of 10 m in the intermediate focal length state of the infrared zoom lens according to Example 1. 第１実施例に係る赤外線ズームレンズの広角端状態における無限遠物点での合焦状態の横収差図である。FIG. 6 is a lateral aberration diagram in a focused state at an object point at infinity in the wide-angle end state of the infrared zoom lens according to Example 1. 第２実施例に係る赤外線ズームレンズのレンズ構成図である。It is a lens block diagram of the infrared zoom lens which concerns on 2nd Example. 第２実施例に係る赤外線ズームレンズにおける、望遠端状態（Ｔ）から中間焦点距離状態（Ｍ）を経て広角端状態（Ｗ）までの焦点距離状態の変化、すなわちズーミングの際の各レンズ群の移動の様子を示す図である。In the infrared zoom lens according to the second embodiment, the change in the focal length state from the telephoto end state (T) to the intermediate focal length state (M) to the wide angle end state (W), that is, each lens group during zooming. It is a figure which shows the mode of a movement. 第２実施例に係る赤外線ズームレンズの望遠端状態における無限遠物点での合焦状態の横収差図である。FIG. 10 is a lateral aberration diagram in a focused state at an infinite object point in the telephoto end state of the infrared zoom lens according to Example 2. 第２実施例に係る赤外線ズームレンズの望遠端状態における近距離物点１０ｍでの合焦状態の横収差図である。FIG. 12 is a lateral aberration diagram in a focused state at a short-distance object point of 10 m in the telephoto end state of the infrared zoom lens according to Second Example. 第２実施例に係る赤外線ズームレンズの中間焦点距離状態における無限遠物点での合焦状態の横収差図である。FIG. 10 is a lateral aberration diagram in a focused state at an infinite object point in an intermediate focal length state of the infrared zoom lens according to Example 2. 第２実施例に係る赤外線ズームレンズの中間焦点距離状態における近距離物点１０ｍでの合焦状態での横収差図である。FIG. 12 is a lateral aberration diagram in a focused state at a short-distance object point of 10 m in the intermediate focal length state of the infrared zoom lens according to Second Example. 第２実施例に係る赤外線ズームレンズの広角端状態における無限遠物点での合焦状態の横収差図である。FIG. 12 is a lateral aberration diagram in a focused state at an infinite object point in the wide-angle end state of the infrared zoom lens according to Example 2. 第２実施例に係る赤外線ズームレンズの広角端状態における近距離物点１０ｍでの合焦状態の横収差図である。FIG. 10 is a lateral aberration diagram in a focused state at a short-distance object point of 10 m in the wide-angle end state of the infrared zoom lens according to Example 2.

符号の説明Explanation of symbols

Ｇ１ 第１レンズ群
Ｇ２ 第２レンズ群
Ｇ３ 第３レンズ群
Ｇ４ 第４レンズ群
ＡＳ 開口絞り
Ｉ 像面 G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group AS Aperture stop I Image surface

Claims (5)

物体側より順に並んだ、
全体として正の屈折力を有し、合焦機能と変倍に伴う補償機能を持つ第１レンズ群と、
全体として負の屈折力を有し、変倍機能を持つ第２レンズ群と、
全体として正の屈折率を有し、中間像を形成する機能を持つ第３レンズ群と、
全体として正の屈折率を有し、前記中間像をリレー結像する機能を持つ第４レンズ群と、
開口絞りとを有し、
前記第１レンズ群は正レンズを含み、前記第３レンズ群は物体側に凸面を向けた正メニスカスレンズを含み、前記第４レンズ群は最も像側のレンズが物体側に凸面を向けたメニスカス形状に形成されており、
前記第１レンズ群の前記正レンズのアッベ数をνL1とし、前記第３レンズ群の前記正メニスカスレンズのアッベ数をνL3としたとき、次式
νL1＞２νL3
の条件を満足することを特徴とする赤外線ズームレンズ。 Arranged in order from the object side,
A first lens group having a positive refractive power as a whole and having a focusing function and a compensation function associated with zooming;
A second lens group having a negative refractive power as a whole and having a zooming function;
A third lens group having a positive refractive index as a whole and having a function of forming an intermediate image;
A fourth lens group having a positive refractive index as a whole and having a function of relay-imaging the intermediate image;
An aperture stop,
The first lens group includes a positive lens, the third lens group includes a positive meniscus lens having a convex surface facing the object side, and the fourth lens group has a meniscus having the most image side lens facing the convex surface toward the object side. Formed into a shape,
When the Abbe number of the positive lens of the first lens group is ν L1, and the Abbe number of the positive meniscus lens of the third lens group is ν L3 , the following equation is established: ν L1 > 2ν L3
An infrared zoom lens characterized by satisfying the above conditions. 開口整合を取ることを特徴とする請求項１に記載の赤外線ズームレンズ。   The infrared zoom lens according to claim 1, wherein aperture alignment is achieved. 前記第１〜第４レンズ群はそれぞれ赤外線を通す硝材で構成されていることを特徴とする請求項１または２に記載の赤外線ズームレンズ。   The infrared zoom lens according to claim 1, wherein each of the first to fourth lens groups is made of a glass material that transmits infrared rays. 前記硝材はシリコン、ゲルマニウムおよび硫化亜鉛の少なくとも１つの材料から構成されることを特徴とする請求項３に記載の赤外線ズームレンズ。   4. The infrared zoom lens according to claim 3, wherein the glass material is made of at least one material of silicon, germanium, and zinc sulfide. 広角端から望遠端へのズーミングに際し、前記第１レンズ群および前記第２レンズ群は光軸方向に移動させ、前記第３レンズ群、前記第４レンズ群及び前記開口絞りは固定することを特徴とする請求項１〜４のいずれか一項に記載の赤外線ズームレンズ。   During zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group are moved in the optical axis direction, and the third lens group, the fourth lens group, and the aperture stop are fixed. The infrared zoom lens according to any one of claims 1 to 4.
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CN106154520A (en) * 2016-08-30 2016-11-23 福建福光股份有限公司 Medium-wave infrared turntable optical lens and control method thereof
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