JP3206930B2 - Endoscope objective lens - Google Patents
Endoscope objective lensInfo
- Publication number
- JP3206930B2 JP3206930B2 JP13530491A JP13530491A JP3206930B2 JP 3206930 B2 JP3206930 B2 JP 3206930B2 JP 13530491 A JP13530491 A JP 13530491A JP 13530491 A JP13530491 A JP 13530491A JP 3206930 B2 JP3206930 B2 JP 3206930B2
- Authority
- JP
- Japan
- Prior art keywords
- lens
- image
- objective lens
- aberration
- curvature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Instruments For Viewing The Inside Of Hollow Bodies (AREA)
- Lenses (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、３枚の簡単な構成の内
視鏡の広角な対物レンズに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-angle objective lens of an endoscope having three simple structures.
【０００２】[0002]
【従来の技術】従来、内視鏡の広角な対物レンズは、特
開平２−２９３７０９号公報等に示されるように多数の
レンズを用いて構成されており、主に絞りが負のパワー
を持つ第１レンズ群と正のパワーを持つ第２レンズ群の
間に位置し、絞りの後方に接合レンズが配置されてい
る。それは、視野角が広くなるに伴って、第１レンズ群
で発生する諸収差を絞り以降に配置されているレンズ群
で良好に補正するためである。特に倍率色収差を補正す
るために上記のように接合レンズを配置している。2. Description of the Related Art Conventionally, a wide-angle objective lens of an endoscope is constituted by using a large number of lenses as disclosed in Japanese Patent Application Laid-Open No. 2-293709, and the diaphragm mainly has a negative power. A cemented lens is disposed between the first lens group and the second lens group having a positive power, and is arranged behind the stop. This is because various aberrations generated in the first lens group are favorably corrected by the lens groups arranged after the stop as the viewing angle increases. In particular, a cemented lens is arranged as described above to correct lateral chromatic aberration.
【０００３】しかしながら、上記のような対物レンズ
は、レンズの枚数が多く構成が複雑であるために高価に
ならざるを得ない。However, such an objective lens has to be expensive because the number of lenses is large and the configuration is complicated.
【０００４】また、レンズ枚数を減らして比較的簡単な
構成にしようとすると、各レンズのパワーが相対的に増
大し、それに伴って諸収差が増大するのでこの収差を抑
えるために全長を伸ばさなければならず内視鏡において
要求されるコンパクト性を持つことが出来ない。In order to reduce the number of lenses to achieve a relatively simple configuration, the power of each lens relatively increases, and various aberrations increase accordingly. Therefore, the total length must be increased to suppress these aberrations. The endoscope cannot have the required compactness.
【０００５】又絞りより後方の接合レンズを単レンズで
構成すると倍率の色収差を十分良好に補正できない。例
えば特開平２−２０８６１７号公報には、比較的広角で
簡単な構成をもつ対物レンズの発明が記載されている。
その視野角は、７０°程度であり、この光学系を用い
て、更に広角（８０°〜１４０°）な対物レンズを構成
しようとすると、収差が十分良好に補正できない。特に
特開平２−２０８６１７号公報の実施例の中に単レンズ
３枚で構成されている対物レンズがあり、この実施例
は、各レンズで発生する倍率の色収差の方向が同じであ
り、そのため色収差は厳密には補正されていない。If the cemented lens behind the stop is constituted by a single lens, chromatic aberration of magnification cannot be sufficiently corrected. For example, JP-A-2-208617 discloses an invention of an objective lens having a relatively wide angle and a simple configuration.
The viewing angle is about 70 °. If this optical system is used to form an objective lens having a wider angle (80 ° to 140 °), aberration cannot be sufficiently corrected. In particular, an embodiment disclosed in Japanese Patent Application Laid-Open No. 2-208617 includes an objective lens composed of three single lenses. In this embodiment, the directions of the chromatic aberration of magnification generated by each lens are the same, and therefore, the chromatic aberration is reduced. Is not strictly corrected.
【０００６】[0006]
【発明が解決しようとする課題】本発明の目的は、安価
で構成が簡単であり、色収差を含めて収差が良好に補正
されている対物レンズを提供することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens which is inexpensive, has a simple structure, and in which aberrations including chromatic aberration are well corrected.
【０００７】[0007]
【問題点を解決するための手段】本発明の内視鏡対物レ
ンズは、物体側より順に、負のパワーを有する第１レン
ズと正のパワーを有する第２レンズと第３レンズとの単
レンズ３枚からなり、絞りが第２レンズから像面までの
間に配置される。An endoscope objective lens according to the present invention comprises, in order from the object side, a single lens comprising a first lens having a negative power, a second lens having a positive power, and a third lens. It is composed of three lenses, and the stop is arranged between the second lens and the image plane.
【０００８】上記構成のレンズ系で更に次の条件
（１），（２）を満足することが望ましい。 （１）５＞｜ｆ1 ／ｆ2 ｜＞0.03 （２）ｄ／ｆ＜５ ただし、ｆ1 ，ｆ2 は夫々第１レンズおよび第２レンズ
の焦点距離、ｆは全系の焦点距離、ｄは第２レンズと第
３レンズの間の主点間距離である。It is desirable that the lens system having the above configuration further satisfies the following conditions (1) and (2). (1) 5> | f1 / f2 |> 0.03 (2) d / f <5 where f1 and f2 are the focal lengths of the first and second lenses, respectively, f is the focal length of the entire system, and d is the second. This is the distance between principal points between the lens and the third lens.
【０００９】本発明の対物レンズは、前記の構成で、絞
りを第２レンズから像面までの間のいずれかに配置する
ものである。即ち後に示す実施例１，２，６のように、
絞りを第３レンズの像側の面から像面までの間に配置す
るか、実施例３〜５，７〜１２のように絞りを第２レン
ズの像側の面から第３レンズの物体側の面の間に配置し
たものである。In the objective lens according to the present invention, the stop is arranged at any position between the second lens and the image plane. That is, as in Examples 1, 2, and 6 described below,
The stop is disposed between the image side surface of the third lens and the image surface, or the stop is moved from the image side surface of the second lens to the object side of the third lens as in Examples 3 to 5 and 7 to 12. It is arranged between the surfaces of.
【００１０】このように絞りを配置することにより、絞
りより物体側に正のパワーをもつレンズを少なくとも１
枚配置することになり、負のパワーをもつ第１レンズで
発生する倍率の色収差を上記の正のパワーをもつレンズ
でこの収差を補正する方向に発生させて倍率の色収差を
除去し、これによって倍率の色収差を補正するために従
来設けられていた接合レンズが不要になり、レンズ系を
簡単な構成になし得るようにした。By arranging the aperture in this manner, at least one lens having a positive power is located closer to the object side than the aperture.
The chromatic aberration of magnification generated by the first lens having negative power is generated in the direction of correcting the aberration by the lens having positive power, thereby removing chromatic aberration of magnification. The cemented lens conventionally provided to correct the chromatic aberration of magnification is no longer necessary, and the lens system can have a simple configuration.
【００１１】また倍率の色収差以外の諸収差も、各レン
ズのパワー配分を適切に選びながら面の向きを収差の補
正に最適な向きにして収差を良好に補正している。In addition, various aberrations other than chromatic aberration of magnification are favorably corrected by appropriately selecting the power distribution of each lens and by setting the direction of the surface to an optimum direction for correcting the aberration.
【００１２】また実施例１，２のように、第１レンズの
像側の面の曲率中心が面の像側にある曲率のきつい面で
あり、視野角が広くなるに伴ってこの面での非点収差や
コマ収差が増大する。そのため正のパワーを有する第２
レンズと第３レンズで第１レンズで発生する収差を打消
す方向の非点収差，コマ収差を発生させてレンズ系全体
でほぼ０になるようにしている。Further, as in Embodiments 1 and 2, the center of curvature of the image-side surface of the first lens is a surface having a sharp curvature located on the image side of the surface. Astigmatism and coma increase. Therefore the second with positive power
The lens and the third lens generate astigmatism and coma in the direction of canceling out the aberration generated in the first lens so that the entire lens system becomes almost zero.
【００１３】このとき、第２レンズは絞りから十分離れ
ているので主光線の光線高が高い。そこで第２レンズの
像側の面の曲率中心が物体側になるようにして第１レン
ズで発生する収差と逆方向に発生する収差により、非点
収差を補正している。At this time, the height of the principal ray is high because the second lens is sufficiently far from the stop. Therefore, the astigmatism is corrected by the aberration generated in the opposite direction to the aberration generated in the first lens so that the center of curvature of the image side surface of the second lens is on the object side.
【００１４】また、第３レンズの像側の面の曲率中心を
面の物体側に位置せしめることによって第２レンズと共
に第１レンズの像側の面で発生するコマ収差を補正して
いる。Further, by positioning the center of curvature of the image-side surface of the third lens on the object side of the surface, coma aberration generated on the image-side surface of the first lens together with the second lens is corrected.
【００１５】又実施例３〜５のように、絞りを第２レン
ズと第３レンズの間に配置し、しかも実施例１，２より
も絞りが第２レンズに近い場合、第２レンズの像側の面
での第１レンズの像側の面で発生する非点収差を補正す
る作用が小さくなる。更に第３レンズは絞りの後方に位
置するので、この第３レンズで発生する非点収差は、第
１レンズでの収差の発生方向と同じ向きであるのでレン
ズ系全体の非点収差の補正が難しい。When the stop is disposed between the second lens and the third lens as in Embodiments 3 to 5, and the stop is closer to the second lens than in Embodiments 1 and 2, the image of the second lens is formed. The effect of correcting astigmatism occurring on the image side surface of the first lens on the side surface is reduced. Further, since the third lens is located behind the stop, the astigmatism generated by the third lens is in the same direction as the direction in which the aberration is generated by the first lens. difficult.
【００１６】第１レンズを通過する主光線が第１レンズ
の像側の面のほぼ曲率中心に向かうように配置すること
によって第１レンズの像側の面で発生する非点収差の発
生量を抑えるようにし、第２レンズの物体側の面の曲率
中心と第３レンズの像側の面の曲率中心が夫々絞りの方
向になるようにし、しかも両面をほぼ対称に配置するこ
とによって、第２レンズの非点収差の補正効果の減少と
合わせてレンズ系全体の非点収差を良好に補正してい
る。By arranging the principal ray passing through the first lens so as to be substantially directed toward the center of curvature of the image-side surface of the first lens, the amount of astigmatism generated on the image-side surface of the first lens can be reduced. The second lens is arranged such that the center of curvature of the object-side surface of the second lens and the center of curvature of the image-side surface of the third lens are in the direction of the stop, and that both surfaces are arranged substantially symmetrically. The astigmatism of the entire lens system is satisfactorily corrected together with the reduction of the astigmatism correction effect of the lens.
【００１７】またコマ収差の補正も、主光線が第２レン
ズの物体側の面にほぼ垂直に入射するようにその曲率を
選んで第２レンズの物体側の面で発生するコマ収差を抑
え、更に第２レンズの像側の面の曲率中心位置を適当に
調整することによってレンズ系全体のコマ収差を補正し
ている。In the correction of coma aberration, the curvature is selected so that the principal ray is incident on the object side surface of the second lens almost perpendicularly, and the coma aberration generated on the object side surface of the second lens is suppressed. Further, by appropriately adjusting the center of curvature of the image-side surface of the second lens, coma of the entire lens system is corrected.
【００１８】このとき、第３レンズは、コマ収差，非点
収差が発生しにくい形状にするために、特に像側の面を
その曲率中心が物体側に位置するようにした。このよう
にしてコマ収差の対称性が得られる。尚全体として像面
湾曲は僅かに残存する。At this time, in order to make the third lens a shape in which coma and astigmatism hardly occur, the surface on the image side is particularly arranged such that its center of curvature is located on the object side. In this way, the symmetry of coma can be obtained. The curvature of field slightly remains as a whole.
【００１９】本発明は、以上のように構成すると共に前
記の条件（１），（２）を満足するようにして発明の目
的を達成するようにした。The present invention is configured as described above and attains the object of the invention by satisfying the above conditions (1) and (2).
【００２０】前述のような構成の本発明の内視鏡対物レ
ンズは、アフォーカルな第１レンズと第２レンズとより
なる前群と、正のパワーを有する単レンズの第３レンズ
からなる後群とにて構成されていると考えられる。した
がって、レンズ系の全長Ｌは次の式で表わされる。 Ｌ≡｜ｆ2|−｜ｆ1|＋ｄ＋｜ｆ3| ただしｆ3 は第３レンズの焦点距離である。The endoscope objective lens according to the present invention having the above-described configuration has a front group including an afocal first lens and a second lens, and a rear group including a single lens having a positive power and a third lens. It is considered to be composed of groups. Therefore, the total length L of the lens system is represented by the following equation. L≡ | f2 | − | f1 | + d + | f3 | where f3 is the focal length of the third lens.
【００２１】いま｜ｆ1/ｆ2 ｜≡αとおくと、レンズ系
全系の焦点距離ｆは、ｆ≡α・ｆ3 と表わされるから、
レンズ系の全長Ｌは、次のように書き換えられる。 Ｌ≡｜ｆ2|−｜α・ｆ2|＋ｄ＋ｆ／｜α｜ この式からわかるように、αの値があまり小さいと、レ
ンズ系の全長をあまり短く出来ない。又αの値があまり
大であると第３レンズの焦点距離が小さくなって第３レ
ンズの収差補正作用が大きくなり過ぎて、レンズ系全体
の収差補正が難しくなる。When | f1 / f2 | ≡α is set, the focal length f of the entire lens system is expressed as f≡α · f3.
The overall length L of the lens system can be rewritten as follows. L≡ | f2 | − | α · f2 | + d + f / | α | As can be seen from this equation, if the value of α is too small, the overall length of the lens system cannot be reduced too much. On the other hand, if the value of α is too large, the focal length of the third lens becomes too small, and the aberration correcting action of the third lens becomes too large, making it difficult to correct the aberration of the entire lens system.
【００２２】以上のような理由から設けられたのが条件
（１）である。The condition (1) is provided for the above reason.
【００２３】尚絞りを絞った場合で、ＣＣＤ等の画素が
あらい場合は、条件（１）の上限は５まで許される。又
レンズ系にフィルターを多数挿入して光学特性を向上さ
せる場合、条件（１）の下限は０．０３としても、多少
コンパクト性はそこなわれるが実用上使用に耐え得る。When the aperture is stopped down and there are no pixels such as CCDs, the upper limit of the condition (1) is allowed up to 5. When a large number of filters are inserted into the lens system to improve the optical characteristics, even if the lower limit of the condition (1) is set to 0.03, the compactness is somewhat degraded, but it can be practically used.
【００２４】次に第２レンズと第３レンズの間の主点間
隔ｄを定めたのが条件（２）である。このｄの値が大に
なり上限を越えるとレンズ系の全長が長くなり好ましく
ない。Next, the condition (2) defines the principal point distance d between the second lens and the third lens. If the value of d becomes large and exceeds the upper limit, the overall length of the lens system becomes undesirably long.
【００２５】更に本発明の内視鏡対物レンズは、少なく
とも１面の非球面を最適な位置に配置することによって
諸収差を良好に補正するようにした。Further, in the endoscope objective lens according to the present invention, at least one aspherical surface is arranged at an optimum position to correct various aberrations well.
【００２６】特にＦナンバーを小にして比較的明るいレ
ンズにする場合、球面収差およびコマ収差の発生が増大
するが、これを補正するためには非球面を設ける必要が
あり、この非球面が次の条件（３）を満足することが望
ましい。 （３）｜ｈc/ｈm ｜＜２ ただし、ｈc は最大光線高の軸外主光線の光線高、ｈm
は軸上マージナル光線の光線高である。In particular, when a relatively bright F-number lens is used to make the lens relatively bright, the occurrence of spherical aberration and coma increase. However, it is necessary to provide an aspheric surface in order to correct the aberration. It is desirable that the condition (3) is satisfied. (3) | hc / hm | <2 where hc is the ray height of the off-axis principal ray having the maximum ray height, hm
Is the ray height of the axial marginal ray.
【００２７】この条件（３）は、非球面の位置での軸上
マージナル光線の光線高に対する軸外主光線の光線高の
比を規定したもので、上記のように非球面により主とし
て球面収差とコマ収差とを補正するために必要な条件で
ある。The condition (3) defines the ratio of the ray height of the off-axis principal ray to the ray height of the axial marginal ray at the position of the aspherical surface. This is a condition necessary for correcting coma.
【００２８】この場合、球面収差とコマ収差とを補正す
るための非球面の形状は、非球面が凸面の場合光軸から
遠くなるほど曲率が緩くなるような形状であり、又凹面
の場合光軸から遠くなるほど曲率が強くなるような形状
である。つまり上記形状の非球面によれば、光線高の高
いところを通過する光線に対して球面レンズ系ではマイ
ナス側に大きく発生する球面収差，コマ収差を抑えるこ
とが出来る。In this case, the shape of the aspherical surface for correcting the spherical aberration and the coma aberration is such that when the aspherical surface is convex, the curvature becomes gentler as the distance from the optical axis increases, and when the aspherical surface is concave, the optical axis decreases. The shape is such that the curvature increases as the distance increases. In other words, according to the aspherical surface having the above-mentioned shape, it is possible to suppress the spherical aberration and the coma which are largely generated on the minus side in the spherical lens system with respect to the light beam passing through a place where the light beam height is high.
【００２９】[0029]
【実施例】次に本発明の内視鏡対物レンズの実施例を示
す。 実施例１ ｆ＝1.000 ，Ｆ/4.290，２ω＝116 ° ｒ1 ＝∞ ｄ1 ＝0.5500 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝0.9454 ｄ2 ＝1.2300 ｒ3 ＝4.0175 ｄ3 ＝0.8600 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝-2.6882 ｄ4 ＝0.4000 ｒ5 ＝33.6773 ｄ5 ＝1.0300 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ6 ＝-2.3068 ｄ6 ＝0.0200 ｒ7 ＝∞（絞り） ｄ7 ＝0.5600 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ8＝∞ ｄ8 ＝0.0300 ｒ9＝∞ ｄ9＝0.3600 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ10＝∞ ｄ10＝0.8000 ｒ11＝∞ ｄ11＝0.9400 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ12＝∞ ｜ｆ1/ｆ2 | ＝0.55 ，ｄ／ｆ＝1.16 実施例２ ｆ＝0.965 ，Ｆ/3.993，２ω＝135 ° ｒ1 ＝∞ ｄ1 ＝0.3738 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝1.0287 ｄ2 ＝1.0469 ｒ3 ＝4.6383 ｄ3 ＝1.0510 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝-6.1647 ｄ4 ＝0.6367 ｒ5 ＝3.2550 ｄ5 ＝0.5606 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ6 ＝-2.2529 ｄ6 ＝0.0184 ｒ7 ＝∞（絞り） ｄ7 ＝0.6181 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ8 ＝∞ ｄ8 ＝0.0280 ｒ9＝∞ ｄ9 ＝0.3988 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ10＝∞ ｄ10＝0.7774 ｒ11＝∞ ｄ11＝0.9970 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ12＝∞ ｜ｆ1/ｆ2 |＝0.371 ，ｄ／ｆ＝1.19 実施例３ ｆ＝1.000 ，Ｆ/4.300，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.3284 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝1.0635 ｄ2 ＝0.8128 ｒ3 ＝1.7391 ｄ3 ＝0.8210 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝-7.8275 ｄ4 ＝0.4105 ｒ5 ＝∞（絞り） ｄ5 ＝0.0246 ｒ6 ＝6.2260 ｄ6 ＝0.5114 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ7 ＝-1.7509 ｄ7 ＝0.0162 ｒ８＝∞ ｄ8＝0.5090 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ９＝∞ ｄ9＝0.0246 ｒ10＝∞ ｄ10＝0.3284 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ11＝∞ ｄ11＝0.3801 ｒ12＝∞ ｄ12＝0.8210 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ ｜ｆ1/ｆ2 |＝0.717 ，ｄ／ｆ＝1.04 実施例４ ｆ＝1.001 ，Ｆ/3.833，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.4984 ｎ1 ＝1.88300 ν1＝40.78 ｒ2 ＝1.2048 ｄ2 ＝0.5708 ｒ3 ＝∞ ｄ3 ＝0.6431 ｎ2 ＝1.51633 ν2 ＝64.15 ｒ4 ＝∞ ｄ4 ＝0.0322 ｒ5 ＝1.3000 ｄ5 ＝0.7464 ｎ3 ＝1.51728 ν3 ＝69.56 ｒ6 ＝-3.0866 ｄ6 ＝0.2912 ｒ7 ＝∞（絞り） ｄ7 ＝0.9419 ｎ4 ＝1.51728 ν4 ＝69.56 ｒ8 ＝-1.0736 ｄ8 ＝0.5266 ｒ9＝∞ ｄ9＝1.6077 ｎ5 ＝1.51633 ν5 ＝64.15 ｒ10＝∞ ｜ｆ1/ｆ2 |＝0.727 ，ｄ／ｆ＝1.28 実施例５ ｆ＝1.000 ，Ｆ/4.243，２ω＝100° ｒ1 ＝∞ ｄ1 ＝0.3320 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝1.0944 ｄ2 ＝0.8216 ｒ3 ＝1.4850 ｄ3 ＝0.8299 ｎ2 ＝1.83400 ν2 ＝37.16 ｒ4 ＝-4.8373 ｄ4 ＝0.3734 ｒ5 ＝∞（絞り） ｄ5 ＝0.1826 ｒ6 ＝11.1197 ｄ6 ＝0.5228 ｎ3 ＝1.81600 ν3 ＝46.62 ｒ7 ＝-2.0380 ｄ7 ＝0.0166 ｒ8 ＝∞ ｄ8 ＝0.5145 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ9 ＝∞ ｄ9 ＝0.0249 ｒ10＝∞ ｄ10＝0.3320 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ11＝∞ ｄ11＝0.1411 ｒ12＝∞ ｄ12＝0.8299 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ ｜ｆ1/ｆ2 |＝0.855 ，ｄ／ｆ＝1.17 実施例６ ｆ＝1.001 ，Ｆ/2.796，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.5000 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝0.9742 ｄ2 ＝1.1200 ｒ3 ＝1.3171 ｄ3 ＝0.7000 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝3.3918 ｄ4 ＝0.2400 ｒ5 ＝5.4887（非球面） ｄ5 ＝0.4900 ｎ3 ＝1.75500 ν3 ＝52.33 ｒ6 ＝-1.7388 ｄ6 ＝0.0200 ｒ7 ＝∞（絞り） ｄ7 ＝0.5000 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ8＝∞ ｄ8 ＝0.0200 ｒ9＝∞ ｄ9＝0.3300 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ10＝∞ ｄ10＝0.7500 ｒ11＝∞ ｄ11＝0.8200 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ12＝∞ 非球面係数 Ｐ＝1.0000，Ｅ＝-0.22281，Ｆ＝-0.12062×10-1，Ｇ＝-0.54320×10-1 ｜ｆ1/ｆ2 |＝0.52 ，ｄ／ｆ＝0.036 ，｜ｈc/ｈm ｜＝0.37 実施例７ ｆ＝1.000 ，Ｆ/2.536，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.3234 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝0.9210 ｄ2 ＝0.8003 ｒ3＝1.2745 ｄ3 ＝0.8084 ｎ2 ＝1.80518 ν2 ＝25.43 ｒ4＝7.4446 ｄ4 ＝0.4042 ｒ5 ＝∞（絞り） ｄ5 ＝0.0243 ｒ6＝1.2714 ｄ6 ＝0.5012 ｎ3 ＝1.77250 ν3 ＝49.66 ｒ7＝91.2505 （非球面）ｄ7 ＝0.1617 ｒ8 ＝∞ ｄ8 ＝0.5012 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ9 ＝∞ ｄ9 ＝0.0243 ｒ10＝∞ ｄ10＝0.3234 ｎ5 ＝1.52287 ν5＝59.89 ｒ11＝∞ ｄ11＝0.2183 ｒ12＝∞ ｄ12＝0.8084 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ 非球面係数 Ｐ＝1.0000，Ｅ＝0.28326 ｜ｆ1/ｆ2 |＝0.58 ，ｄ／ｆ＝1.05 ，｜ｈc/ｈm ｜＝0.48 実施例８ ｆ＝1.000 ，Ｆ/2.808，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.3167 ｎ1 ＝1.88300 ν1＝40.78 ｒ2 ＝0.9520 ｄ2 ＝0.7852 ｒ3 ＝1.3451 ｄ3 ＝0.8320 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝8.2060（非球面） ｄ4 ＝0.4819 ｒ5 ＝∞（絞り） ｄ5 ＝0.0238 ｒ6 ＝1.8507（非球面） ｄ6 ＝0.4933 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ7 ＝-3.1601 ｄ7 ＝0.0156 ｒ8 ＝∞ ｄ8＝0.4909 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ9 ＝∞ ｄ9 ＝0.0238 ｒ10＝∞ ｄ10＝0.3167 ｎ5 ＝1.52287 ν5＝59.89 ｒ11＝∞ ｄ11＝0.8234 ｒ12＝∞ ｄ12＝0.7918 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ 非球面係数 （第４面）Ｐ＝1.0000，Ｅ＝0.53786 ×10-2 （第６面）Ｐ＝1.0000，Ｅ＝-0.12945 ｜ｆ1/ｆ2 |＝0.626 ，ｄ／ｆ＝1.12，｜ｈc/ｈm ｜＝0.82 ，0.04 実施例９ ｆ＝1.000 ，Ｆ/2.743，２ω＝100 ° ｒ1 ＝∞ ｄ1 ＝0.3276 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝0.8369 ｄ2 ＝0.8190 ｒ3＝1.1527 ｄ3 ＝0.8190 ｎ2 ＝1.80100 ν2 ＝34.97 ｒ4＝-6.3773 （非球面）ｄ4 ＝0.1556 ｒ5 ＝∞（絞り） ｄ5＝0.1802 ｒ6 ＝2.4229（非球面） ｄ6 ＝0.5160 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ7 ＝-16.6121 ｄ7 ＝0.0164 ｒ8 ＝∞ ｄ8 ＝0.5078 ｎ4 ＝1.52000 ν4 ＝74.00 ｒ9＝∞ ｄ9 ＝0.0246 ｒ10＝∞ ｄ10＝0.3276 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ11＝∞ ｄ11＝0.2457 ｒ12＝∞ ｄ12＝0.8190 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ 非球面係数 （第４面）Ｐ＝1.0000，Ｅ＝0.24824×10-1 （第６面）Ｐ＝1.0000，Ｅ＝-0.26080 ｜ｆ1/ｆ2 |＝0.74 ，ｄ／ｆ＝0.775 ，｜ｈc/ｈm ｜＝0.245 ，0.31 実 施例１０ ｆ＝1.000 ，Ｆ/2.881，２ω＝100 ° ｒ1＝∞ ｄ1 ＝0.2865 ｎ1 ＝1.88300 ν1 ＝40.78 ｒ2 ＝1.1064 （非球面）ｄ2 ＝0.7092 ｒ3 ＝1.4467 （非球面）ｄ3 ＝0.7163 ｎ2 ＝1.88300 ν2 ＝40.78 ｒ4 ＝-1.9231 ｄ4 ＝0.3582 ｒ5 ＝∞（絞り） ｄ5 ＝0.0215 ｒ6 ＝5.5434 ｄ6 ＝0.4441 ｎ3 ＝1.72916 ν3 ＝54.68 ｒ7 ＝-2.4913 ｄ7 ＝0.0143 ｒ8 ＝∞ ｄ8 ＝0.4441 ｎ4＝1.52000 ν4 ＝74.00 ｒ9 ＝∞ ｄ9 ＝0.0215 ｒ10＝∞ ｄ10＝0.2865 ｎ5 ＝1.52287 ν5 ＝59.89 ｒ11＝∞ ｄ11＝0.3510 ｒ12＝∞ ｄ12＝0.7163 ｎ6 ＝1.51633 ν6 ＝64.15 ｒ13＝∞ 非球面係数 （第２面）Ｐ＝1.0000，Ｂ＝-0.59647×10-1，Ｅ＝0.20602 Ｆ＝0.41050 ，Ｇ＝0.16288 （第３面）Ｐ＝1.0000，Ｂ＝-0.19702，Ｅ＝-0.13203×10-1 Ｆ＝0.72757 ×10-1，Ｇ＝-0.14645 ｜ｆ1/ｆ2 |＝0.98 ，ｄ／ｆ＝0.71，｜ｈc/ｈm ｜＝2.9 ，1.2 ただしｒ1 ，ｒ2 ，・・・ は各レンズの屈折率の曲率
半径、ｄ1 ，ｄ2 ，・・・は各レンズの肉厚およびレン
ズ間隔、ｎ1 ，ｎ2 ，・・・ は各レンズの屈折率、ν1
，ν2 ，・・・ は各レンズのアッベ数である。Next, an embodiment of an endoscope objective lens according to the present invention will be described. Example 1 f = 1.000, F / 4.290, 2ω = 116 ° r1 = ∞d1 = 0.5500 n1 = 1.88300 ν1 = 40.78 r2 = 0.9454 d2 = 1.200300 r3 = 4.0175 d3 = 0.8600 n2 = 1.88300 ν2 = 40.782.64 = 0.4000 r5 = 33.6773 d5 = 1.0300 n3 = 1.72916 ν3 = 54.68 r6 = -2.3068 d6 = 0.0200 r7 = ∞ (aperture) d7 = 0.5600 n4 = 1.52000 ν4 = 74.00 r8 = ∞ d8 = 0.0300 r9 = ∞300 = 9300 1.52287 ν5 = 59.89 r10 = ∞ d10 = 0.8000 r11 = ｄ d11 = 0.9400 n6 = 1.51633 ν6 = 64.15 r12 = ∞ | f1 / f2 | = 0.55, d / f = 1.16 Example 2 f = 0.965, F / 3.993, 2ω = 135 ° r1 = ∞ d1 = 0.3738 n1 = 1.88300 v1 = 40.78 r2 = 1.0287 d2 = 1.0469 r3 = 4.6383 d3 = 1.0510 n2 = 1.88300 v2 = 40.78 r4 = -6.1647 d4 = 0.6367 55 = 0.6367 5 = 54.68 r6 = -2.2529 d6 = 0.0184 r7 = ∞ (aperture) d7 = 0.6181 n4 = 1.52000 ν4 = 74.00 r 8 = ∞ d8 = 0.0280 r9 = ｄ d9 = 0.3988 n5 = 1.52287 ν5 = 59.89 r10 = ｄ d10 = 0.7774 r11 = ｄ d11 = 0.9970 n6 = 1.51633 ν6 = 64.15 r12 = ｜ f1 / f2 | = 0.371, d / f = 1.19 Example 3 f = 1.000, F / 4.300, 2ω = 100 ° r1 = ∞d1 = 0.3284 n1 = 1.88300 ν1 = 40.78 r2 = 1.0635 d2 = 0.8128 r3 = 1.7391 d3 = 0.8210 n2 = 1.88300-ν2 = 40.78 7.8275 d4 = 0.4105 r5 = ∞ (aperture) d5 = 0.0246 r6 = 6.2260 d6 = 0.5114 n3 = 1.72916 ν3 = 54.68 r7 = -1.7509 d7 = 0.0162 r8 = ∞ d8 = 0.5090 n4 = 1.52000 ν4 = 94.0 = 74.00 r10 = ∞d10 = 0.3284 n5 = 1.52287 ν5 = 59.89 r11 = ∞d11 = 0.3801 r12 = ∞d12 = 0.8210 n6 = 1.51633 ν6 = 64.15 r13 = ∞ | f1 / f2 | = 0.717, d / f = 1.04 Example 4f = 1.001, F / 3.833, 2ω = 100 ° r1 = ∞ d1 = 0.4984 n1 = 1.88300 ν1 = 40.78 r2 = 1.04848 d2 = 0.5708 r3 Ｄ d3 = 0.6431 n2 = 1.51633 ν2 = 64.15 r4 = ∞ d4 = 0.0322 r5 = 1.3000 d5 = 0.7464 n3 = 1.51728 ν3 = 69.56 r6 = -3.0866 d6 = 0.2912 r7 = 0.9 = 0.94 419 d7 r8 = -1.0736 d8 = 0.5266 r9 = ∞d9 = 1.6077 n5 = 1.51633 ν5 = 64.15 r10 = ∞ | f1 / f2 | = 0.727, d / f = 1.28 Example 5 f = 1.000, F / 4.243, 2ω = 100 ° r1 = ∞ d1 = 0.3320 n1 = 1.88300 v1 = 40.78 r2 = 1.0944 d2 = 0.8216 r3 = 1.4850 d3 = 0.8299 n2 = 1.83400 v2 = 37.16 r4 = -4.8373 d4 = 0.3734 r5 = 6 = 6. = 0.5228 n3 = 1.81600 v3 = 46.62 r7 = -2.0380 d7 = 0.0166 r8 = ∞ d8 = 0.5145 n4 = 1.52000 v4 = 74.00 r9 = ∞ d9 = 0.0249 r10 = ∞ d10 = 0.3320 n5 = 11259 895 = 1.52287 v5 0.1411 r12 = ｄ d12 = 0.8299 n6 = 1.51633 ν6 = 64.15 r13 = ｜ | f1 / f2 | = 0.855, d f = 1.17 Example 6 f = 1.001, F / 2.796, 2ω = 100 ° r1 = ∞d1 = 0.5000 n1 = 1.88300 ν1 = 40.78 r2 = 0.9742 d2 = 1.1200 r3 = 1.3171 d3 = 0.000 n2 = 1.88300 ν2 = 40.78 3.3918 d4 = 0.2400 r5 = 5.4887 (aspherical surface) d5 = 0.4900 n3 = 1.75500 v3 = 52.33 r6 = -1.7388 d6 = 0.0200 r7 = ∞ (aperture) d7 = 0.5000 n4 = 1.52000 ν4 = 74.00 r8 = 200 d8 = 200 d8 ∞ d9 = 0.3300 n5 = 1.52287 ν5 = 59.89 r10 = ∞ d10 = 0.7500 r11 = ∞ d11 = 0.8200 n6 = 1.51633 ν6 = 64.15 r12 = ∞ aspherical coefficient P = 1.0000, E = -0.22281, F = -0.12062 × 10 - 1 , G = -0.54320 × 10 -1 | f1 / f2 | = 0.52, d / f = 0.036, | hc / hm | = 0.37 Example 7 f = 1.000, F / 2.536, 2ω = 100 ° r1 = ∞d1 = 0.3234 n1 = 1.88300 v1 = 40.78 r2 = 0.9210 d2 = 0.8003 r3 = 1.2745 d3 = 0.8084 n2 = 1.805518 v2 = 25.43 r4 = 7.4446 d4 = 0.4042 r5 = ∞ D5 = 0.0243 r6 = 1.2714 d6 = 0.5012 n3 = 1.77250 ν3 = 49.66 r7 = 91.2505 (aspherical surface) d7 = 0.1617 r8 = ｄ d8 = 0.5012 n4 = 1.52000 ν4 = 74.00 r9 = 10 d9 = 0.0243 = 0.0243 0.3234 n5 = 1.52287 ν5 = 59.89 r11 = ｄ d11 = 0.2183 r12 = ｄ d12 = 0.8084 n6 = 1.51633 ν6 = 64.15 r13 = ∞ Aspherical surface coefficient P = 1.0000, E = 0.28326 | f1 / f2 | = 0.58, d / f = 1.05, | hc / hm | = 0.48 Example 8 f = 1.000, F / 2.808, 2ω = 100 ° r1 = ∞d1 = 0.3167 n1 = 1.88300 v1 = 40.78 r2 = 0.9520 d2 = 0.7852 r3 = 1.3451 d3 = 0.8320 n2 = 1.88300 v2 = 40.78 r4 = 8.2060 (aspheric surface) d4 = 0.4819 r5 = ∞ (aperture) d5 = 0.0238 r6 = 1.8507 (aspheric surface) d6 = 0.4933 n3 = 1.72916 v3 = 54.68 r7 = -3.1601 d7 = 0.0156 r8 = 0.4909 n4 = 1.52000 v4 = 74.00 r9 = ∞ d9 = 0.0238 r10 = ∞ d10 = 0.3167 n5 = 1.52287 v5 = 59.89 r 11 = ∞ d11 = 0.8234 r12 = ｄ d12 = 0.7918 n6 = 1.51633 ν6 = 64.15 r13 = ∞ Aspheric coefficient (4th surface) P = 1.0000, E = 0.53786 × 10 -2 (6th surface) P = 1.0000, E = -0.12945 | f1 / f2 | = 0.626, d / f = 1.12, | hc / hm | = 0.82, 0.04 Example 9 f = 1.000, F / 2.743, 2ω = 100 ° r1 = ∞d1 = 0.3276 n1 = 1.88300 v1 = 40.78 r2 = 0.8369 d2 = 0.8190 r3 = 1.1527 d3 = 0.8190 n2 = 1.80100 v2 = 34.97 r4 = -6.3773 (aspherical surface) d4 = 0.1556 r5 = ∞ (aperture) d5 = 0.1802 r6 = 2.4229 (aspherical surface) d6 0.5160 n3 = 1.72916 v3 = 54.68 r7 = -16.6121 d7 = 0.0164 r8 = ∞d8 = 0.5078 n4 = 1.52000 v4 = 74.00 r9 = ∞d9 = 0.0246 r10 = ∞d10 = 0.3276 n5 = 1.5259 11.5 r12 = ∞d12 = 0.8190 n6 = 1.51633 ν6 = 64.15 r13 = ∞ Aspheric coefficient (4th surface) P = 1.0000, E = 0.24824 × 10 -1 (6th surface) P = 1.0000, E = -0.26080 | f1 / f2 | = 0.74, d / f = 0.775, | hc / hm | = 0.245, 0.3 1 real施例1 0 f = 1.000, F / 2.881,2ω = 100 ° r1 = ∞ d1 = 0.2865 n1 = 1.88300 v1 = 40.78 r2 = 1.1064 (aspherical surface) d2 = 0.7092 r3 = 1.4467 (aspherical surface) d3 = 0.7163 n2 = 1.88300 v2 = 40.78 r4 = -1.9231 d4 = 0.3582 r5 = 6 = 0.0 (aperture) = 5.5434 d6 = 0.4441 n3 = 1.72916 v3 = 54.68 r7 = -2.4913 d7 = 0.0143 r8 = ∞ d8 = 0.4441 n4 = 1.52000 v4 = 74.00 r9 = ∞ d9 = 0.0215 r10 = ∞d10 = 0.2865 n5 n5 Ｄ d11 = 0.3510 r12 = ∞ d12 = 0.7163 n6 = 1.51633 ν6 = 64.15 r13 = ∞ Aspherical surface coefficient (second surface) P = 1.0000, B = -0.59647 × 10 -1 , E = 0.20602 F = 0.41050, G = 0.16288 (Third surface) P = 1.0000, B = -0.19702, E = -0.13203 × 10 −1 F = 0.27557 × 10 −1 , G = −0.14645 | f1 / f2 | = 0.98, d / f = 0.71, | hc / h m | = 2.9, 1.2 where r1, r2,... are the radii of curvature of the refractive indices of each lens, d1, d2,... are the thicknesses and lens intervals of each lens, and n1, n2,. Refractive index of lens, ν1
, Ν2, ... are Abbe numbers of each lens.
【００３０】上記実施例中、実施例１〜５は、球面のみ
で構成されたレンズ系であり、又実施例６〜１２は適当
な位置に少なくとも１面の非球面を設け、Ｆナンバーを
小にした比較的明るいレンズ系とした。これら実施例で
用いる非球面の形状は、光軸をｘ軸に取り像の方向を正
とし、面と光軸の交点を原点とし、ｘ軸と直交する方向
をｙ軸とした時、以下の式で表される。 ここで、Ｃは光軸近傍でこの非球面と接する円の曲率半
径の逆数、Ｐは円錐定数、Ｂ，Ｅ，Ｆ，Ｇは夫々２，
４，６，８次の非球面係数である。In the above embodiments, Embodiments 1 to 5 are lens systems constituted only by spherical surfaces, and Embodiments 6 to 12 are provided with at least one aspherical surface at an appropriate position to reduce the F-number. A relatively bright lens system. The shape of the aspherical surface used in these embodiments is as follows when the optical axis is taken as the x-axis, the direction of the image is taken as positive, the intersection of the surface and the optical axis is taken as the origin, and the direction orthogonal to the x-axis is taken as the y-axis. It is expressed by an equation. Here, C is the reciprocal of the radius of curvature of the circle in contact with the aspheric surface near the optical axis, P is the conic constant, B, E, F, and G are 2, respectively.
Fourth, sixth, and eighth order aspherical coefficients.
【００３１】実施例１，２は、夫々図１，２に示す構成
で絞りを第３レンズより像側に配置している。In the first and second embodiments, the diaphragm is arranged on the image side of the third lens with the configuration shown in FIGS.
【００３２】上記のようなタイプのレンズ系は、第１レ
ンズでの収差の発生方向と第２，第３レンズでの収差の
発生方向とが基本的に異なることにより、広角な視野を
確保しつつ倍率の色収差をはじめその他の諸収差の補正
をなし得たものである。A lens system of the type described above secures a wide-angle field of view because the direction in which aberration occurs in the first lens and the direction in which aberration occurs in the second and third lenses are basically different. In addition, it is possible to correct various aberrations including chromatic aberration of magnification.
【００３３】尚図中Ｆ１は観察上不要な赤外光を吸収す
る赤外カットフィルター、Ｆ２は観察に不要なレーザー
光を遮断するＹＡＧフィルター、Ｆ３は固体撮像素子の
カバーガラスである。In the figure, F1 is an infrared cut filter that absorbs infrared light unnecessary for observation, F2 is a YAG filter that blocks laser light unnecessary for observation, and F3 is a cover glass of the solid-state imaging device.
【００３４】実施例３，４，５は夫々図３，図４，図５
に示す構成で、絞りを第２レンズの像側の面から第３レ
ンズの物体側の面までの間に配置したレンズタイプであ
る。Embodiments 3, 4 and 5 correspond to FIGS. 3, 4 and 5, respectively.
Is a lens type in which the stop is arranged between the image-side surface of the second lens and the object-side surface of the third lens.
【００３５】このタイプのレンズ系は、実施例１，２に
示すタイプのレンズ系に比べると、絞りの位置が物体側
に近づいている。そのため第１レンズに入射する主光線
の光線高をより低くすることが出来、対物レンズの細径
化には都合のよい構成である。In this type of lens system, the position of the diaphragm is closer to the object side as compared with the lens systems of the first and second embodiments. Therefore, the height of the chief ray incident on the first lens can be further reduced, which is a convenient configuration for reducing the diameter of the objective lens.
【００３６】実施例６は、図６に示す構成で、絞りを第
３レンズより像側に配置したもので、又第３レンズの物
体側の面を非球面にしたレンズ系である。この非球面の
形状は、光軸から離れるにしたがってその曲率が緩くな
るもので周辺においては凹の作用を有している凸面であ
る。この面は光軸付近では凸の作用を有しているが周辺
部では凹の作用を有している。そのため中間のＮＡをも
った光束に対しては、収差の発生を抑える効果を有して
おり、周辺光束に対しては、凹の作用を有していて収差
の発生方向の符号が逆の収差補正効果を有している。Embodiment 6 is a lens system having the configuration shown in FIG. 6 in which the stop is arranged on the image side of the third lens, and the object-side surface of the third lens is aspherical. The shape of this aspheric surface is such that its curvature becomes gentler as the distance from the optical axis increases, and it is a convex surface having a concave effect on the periphery. This surface has a convex action near the optical axis, but has a concave action near the optical axis. Therefore, it has the effect of suppressing the occurrence of aberrations for a light beam having an intermediate NA, and has a concave effect on the peripheral light beam, and the sign of the direction in which the aberration is generated has the opposite sign. It has a correction effect.
【００３７】実施例７，８，１２は、夫々図７，図８，
図１２に示す構成で、絞りを第３レンズの物体側の面に
近接させたもので、又いずれも適切な位置に非球面を設
けている。Embodiments 7, 8, and 12 correspond to FIGS. 7, 8,
In the configuration shown in FIG. 12, the stop is brought close to the object-side surface of the third lens, and an aspheric surface is provided at an appropriate position in each case.
【００３８】実施例７は、第３レンズの像側の面に曲率
が光軸から離れるにしたがって緩くなり周辺においては
凹の作用を有する凸面である非球面を設けた。この面
は、光軸近傍では凸の作用、中間のＮＡでは緩い凸の作
用、周辺では凹の作用を有しており、中間のＮＡをもっ
た光束に対しては、球面収差、コマ収差の発生を抑えて
いる。また第１レンズで発生した収差を第２レンズで補
正し更に残存する収差を第３レンズの上記非球面の周辺
部の凹面で補正している。In the seventh embodiment, an aspheric surface is provided on the image-side surface of the third lens, the curvature of which becomes gentler as the distance from the optical axis increases, and the periphery has a concave function. This surface has a convex action near the optical axis, a loose convex action at an intermediate NA, and a concave action at the periphery. For a light flux having an intermediate NA, spherical aberration and coma The occurrence is suppressed. Further, the aberration generated by the first lens is corrected by the second lens, and the remaining aberration is corrected by the concave surface at the peripheral portion of the aspheric surface of the third lens.
【００３９】実施例８は、第２レンズの像側の面と第３
レンズの物体側の面に夫々非球面を設けている。第２レ
ンズの像側の面の非球面形状は、光軸から離れるにした
がって曲率が強くなる凹面であり、又第３レンズの物体
側の非球面は、光軸から離れるにしたがって曲率が緩く
なる凸面である。In the eighth embodiment, the image-side surface of the second lens and the third lens
Aspheric surfaces are provided on the object-side surfaces of the lenses. The aspherical shape of the image-side surface of the second lens is a concave surface whose curvature increases as the distance from the optical axis increases, and the curvature of the object-side aspherical surface of the third lens decreases as the distance from the optical axis increases. It is convex.
【００４０】以上のような形状の非球面を二つ設けるこ
とによってこの二つの面に球面収差とコマ収差の補正作
用をうまく分割し、比較的無理のない非球面形状で加工
しやすいレンズで収差を良好に補正し得るようにした。By providing two aspherical surfaces having the above-described shapes, the correcting action of the spherical aberration and the coma aberration can be divided well between these two surfaces, and the lens can be easily processed with a comparatively reasonable aspherical shape. Can be corrected well.
【００４１】実施例９は図９に示す構成で、絞りを第２
レンズと第３レンズのほぼ中間に配置し、第２レンズの
像側の面と第３レンズの物体側の面に夫々非球面を設け
たものである。The ninth embodiment has the configuration shown in FIG.
The lens is disposed almost in the middle between the lens and the third lens, and an aspheric surface is provided on each of the image-side surface of the second lens and the object-side surface of the third lens.
【００４２】第２レンズの像側の面の非球面形状は、光
軸から離れるにしたがって曲率が緩くなる凸面であり、
第３レンズの物体側の面の非球面は、光軸から離れるに
したがって曲率が緩くなる凸面である。The aspherical shape of the image-side surface of the second lens is a convex surface whose curvature becomes gentler as the distance from the optical axis increases.
The aspherical surface on the object side of the third lens is a convex surface whose curvature becomes gentler as the distance from the optical axis increases.
【００４３】[0043]
【００４４】[0044]
【００４５】[0045]
【００４６】[0046]
【００４７】[0047]
【００４８】[0048]
【００４９】[0049]
【００５０】[0050]
【００５１】実施例１０は、実施例３のレンズ系を大口
径化したもので、第１レンズの像側の面と第２レンズの
物体側の面を夫々非球面にした。[0051] Example 1 0 is obtained by a large aperture of the lens system of Example 3 was the surface on the object side of the image side surface and the second lens of the first lens respectively aspherical.
【００５２】第１レンズの像側の面を、光軸から離れる
にしたがって曲率が強くなる凹面の非球面とし又第２レ
ンズの物体側の面を光軸から離れるにしたがって曲率が
緩くなる凸面の非球面にした。The image-side surface of the first lens is a concave aspheric surface whose curvature increases as the distance from the optical axis increases, and the convex surface decreases in curvature as the object-side surface of the second lens moves away from the optical axis. Aspherical.
【００５３】ここで第１レンズの像側の面は、主光線の
光線高とマージナル光線の光線高との比が２．９：１で
あり、非球面の設置範囲を規定した条件（３）を満足し
ない。しかし、この比率が示すように、第１レンズの像
側の面では、主光線の光線高が高いので上記のような非
球面形状をもたせ、光軸から離れるほど主光線を屈曲さ
せるようにして、実施例３では補正しきれなかった像面
湾曲も良好に補正している。また条件（３）を満足する
非球面をもう１面設けて球面収差、コマ収差の補正も行
なっている。Here, on the image-side surface of the first lens, the ratio of the height of the principal ray to the height of the marginal ray is 2.9: 1, and the condition (3) that defines the installation range of the aspheric surface Not satisfied. However, as the ratio indicates, on the image-side surface of the first lens, the ray height of the principal ray is high, so that the aspherical shape is provided as described above, and the principal ray is bent as the distance from the optical axis increases. Also, the curvature of field, which could not be completely corrected in the third embodiment, is corrected well. Further, another spherical surface that satisfies the condition (3) is provided to correct spherical aberration and coma.
【００５４】[0054]
【発明の効果】本発明は、負のパワーの第１レンズと正
のパワーの第２、第３レンズの単レンズ３枚で、絞りを
第２レンズから像面までの間に配置することにより絞り
の前に少なくとも１枚正のパワーのレンズが来るように
して、第１レンズで発生する倍率の色収差をはじめとす
る諸収差を良好に補正されしかもコンパクトな内視鏡対
物レンズを実現したものである。更に上記レンズ系で、
適宜位置に非球面を１面以上設ければ明るい大口径の対
物レンズになし得る。According to the present invention, the first lens having negative power and the second and third lenses having positive power are composed of three single lenses, and the diaphragm is arranged between the second lens and the image plane. A compact endoscope objective lens in which at least one lens with positive power comes before the stop, and various aberrations such as chromatic aberration of magnification generated in the first lens are satisfactorily corrected. It is. Furthermore, with the above lens system,
If at least one aspherical surface is provided at an appropriate position, a bright large-diameter objective lens can be obtained.
【図１】本発明の実施例１の断面図FIG. 1 is a sectional view of a first embodiment of the present invention.
【図２】本発明の実施例２の断面図FIG. 2 is a sectional view of a second embodiment of the present invention.
【図３】本発明の実施例３の断面図FIG. 3 is a sectional view of a third embodiment of the present invention.
【図４】本発明の実施例４の断面図FIG. 4 is a sectional view of a fourth embodiment of the present invention.
【図５】本発明の実施例５の断面図FIG. 5 is a sectional view of a fifth embodiment of the present invention.
【図６】本発明の実施例６の断面図FIG. 6 is a sectional view of a sixth embodiment of the present invention.
【図７】本発明の実施例７の断面図FIG. 7 is a sectional view of a seventh embodiment of the present invention.
【図８】本発明の実施例８の断面図FIG. 8 is a sectional view of Embodiment 8 of the present invention.
【図９】本発明の実施例９の断面図FIG. 9 is a sectional view of Embodiment 9 of the present invention.
【図１０】断面図FIG. 10 is a cross-sectional view
【図１１】断面図FIG. 11 is a cross-sectional view
【図１２】本発明の実施例１０の断面図Sectional view of an embodiment 1 0 of the present invention; FIG
【図１３】本発明の実施例１の収差曲線図FIG. 13 is an aberration curve diagram according to the first embodiment of the present invention.
【図１４】本発明の実施例２の収差曲線図FIG. 14 is an aberration curve diagram according to the second embodiment of the present invention.
【図１５】本発明の実施例３の収差曲線図FIG. 15 is an aberration curve diagram according to the third embodiment of the present invention.
【図１６】本発明の実施例４の収差曲線図FIG. 16 is an aberration curve diagram according to the fourth embodiment of the present invention.
【図１７】本発明の実施例５の収差曲線図FIG. 17 is an aberration curve diagram according to the fifth embodiment of the present invention.
【図１８】本発明の実施例６の収差曲線図FIG. 18 is an aberration curve diagram according to the sixth embodiment of the present invention.
【図１９】本発明の実施例７の収差曲線図FIG. 19 is an aberration curve diagram of the seventh embodiment of the present invention.
【図２０】本発明の実施例８の収差曲線図FIG. 20 is an aberration curve diagram of the eighth embodiment of the present invention.
【図２１】本発明の実施例９の収差曲線図FIG. 21 is an aberration curve diagram of the ninth embodiment of the present invention.
【図２２】収差曲線図[Figure 22] yield difference curves
【図２３】収差曲線図[23] yield difference curves
【図２４】本発明の実施例１０の収差曲線図[Figure 24] aberration curves of Example 1 0 of the present invention
Claims (4)
１レンズと、正の屈折力を有する第２レンズと、正の屈
折力を有する第３レンズとよりなる３枚構成の対物レン
ズで、絞りが上記第２レンズから像面までの間に配置さ
れ、次の条件（１）を満足することを特徴とする内視鏡
対物レンズ。（１）0.99＞｜ｆ1 ／ｆ2 ｜＞0.37 ただし、ｆ1，ｆ2 は夫々第１レンズおよび第２レンズ
の焦点距離である。 1. An objective lens having a three-element structure including a first lens having a negative refractive power, a second lens having a positive refractive power, and a third lens having a positive refractive power, in order from the object side. in the diaphragm is disposed between the image plane from said second lens, an endoscope objective lens, characterized that you satisfy the following condition (1). (1) 0.99> | f1 / f2 |> 0.37 where f1 and f2 are the first lens and the second lens, respectively.
Is the focal length.
とする請求項１の内視鏡対物レンズ。 （ ２）ｄ／ｆ＜５ ただし、ｆは全系の焦点距離、ｄは第２レンズと第３レ
ンズの間の主点間距離である。Wherein the endoscope objective lens according to claim 1, characterized by satisfying the conditions of the following matters (2). ( 2) d / f <5 where f is the focal length of the entire system, and d is the distance between principal points between the second lens and the third lens.
該像側の面よりも像側に位置し、上記第３レンズの像側
の面の曲率中心は該像側の面よりも物体側に位置するこ
とを特徴とする請求項１又は２の内視鏡対物レンズ。3. The center of curvature of the image-side surface of the first lens is located closer to the image than the image-side surface, and the center of curvature of the image-side surface of the third lens is closer to the image-side surface. 3. The endoscope objective lens according to claim 1, wherein the objective lens is also located on the object side.
面を有することを特徴とする請求項２又は３の内視鏡対
物レンズ。 （３）｜ｈc/ｈm ｜＜２ ただし、ｈc は最大光線高の軸外主光線の光線高、ｈm
は軸上マージナル光線の光線高である。4. The endoscope objective lens according to claim 2, wherein the objective lens has an aspherical surface in a range satisfying the following condition (3). (3) | hc / hm | <2 where hc is the ray height of the off-axis principal ray having the maximum ray height, hm
Is the ray height of the axial marginal ray.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13530491A JP3206930B2 (en) | 1991-05-13 | 1991-05-13 | Endoscope objective lens |
| US07/845,944 US5223982A (en) | 1991-03-05 | 1992-03-04 | Objective lens system for endoscopes |
| US08/236,680 US5436767A (en) | 1991-03-05 | 1994-05-02 | Objective lens system for endoscopes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13530491A JP3206930B2 (en) | 1991-05-13 | 1991-05-13 | Endoscope objective lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05107470A JPH05107470A (en) | 1993-04-30 |
| JP3206930B2 true JP3206930B2 (en) | 2001-09-10 |
Family
ID=15148586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13530491A Expired - Lifetime JP3206930B2 (en) | 1991-03-05 | 1991-05-13 | Endoscope objective lens |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3206930B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1903369A1 (en) | 2006-09-19 | 2008-03-26 | Fujinon Corporation | Imaging lens and camera system including the same lens |
| US7436605B2 (en) | 2006-09-29 | 2008-10-14 | Fujinon Corporation | Imaging lens and camera apparatus |
| KR102416272B1 (en) * | 2020-06-11 | 2022-07-01 | 안성호 | Mattress having dissimilar hardness |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09269450A (en) * | 1996-03-29 | 1997-10-14 | Olympus Optical Co Ltd | Objective lens for endoscope |
| JP3723637B2 (en) * | 1996-07-03 | 2005-12-07 | ペンタックス株式会社 | Shooting lens |
| JPH10170821A (en) * | 1996-12-16 | 1998-06-26 | Olympus Optical Co Ltd | Objective lens for endoscope |
| JP4229754B2 (en) * | 2003-05-15 | 2009-02-25 | オリンパス株式会社 | Objective lens and endoscope using the same |
| JP4681921B2 (en) | 2005-03-30 | 2011-05-11 | Ｈｏｙａ株式会社 | Endoscope objective lens system |
| WO2011027622A1 (en) * | 2009-09-01 | 2011-03-10 | オリンパスメディカルシステムズ株式会社 | Objective optical system |
| CN107942477A (en) | 2013-02-19 | 2018-04-20 | 株式会社尼康 | Optical system and Optical devices |
| JP6160112B2 (en) * | 2013-02-19 | 2017-07-12 | 株式会社ニコン | Optical system and optical equipment |
| KR101429899B1 (en) * | 2013-04-10 | 2014-08-13 | 주식회사 세코닉스 | Compact type wide angle lens system |
| JP6286663B2 (en) * | 2014-01-15 | 2018-03-07 | パナソニックＩｐマネジメント株式会社 | Wide-angle lens system, camera |
| WO2017068726A1 (en) * | 2015-10-23 | 2017-04-27 | オリンパス株式会社 | Imaging device and optical device provided with same |
| WO2021166027A1 (en) * | 2020-02-17 | 2021-08-26 | オリンパス株式会社 | Objective optical system, imaging device, and endoscope |
| US11832791B2 (en) * | 2021-09-17 | 2023-12-05 | Altek Biotechnology Corporation | Optical imaging lens assembly and endoscopic optical device |
-
1991
- 1991-05-13 JP JP13530491A patent/JP3206930B2/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1903369A1 (en) | 2006-09-19 | 2008-03-26 | Fujinon Corporation | Imaging lens and camera system including the same lens |
| US7813056B2 (en) | 2006-09-19 | 2010-10-12 | Fujinon Corporation | Imaging lens and camera system including the same lens |
| US7436605B2 (en) | 2006-09-29 | 2008-10-14 | Fujinon Corporation | Imaging lens and camera apparatus |
| KR102416272B1 (en) * | 2020-06-11 | 2022-07-01 | 안성호 | Mattress having dissimilar hardness |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05107470A (en) | 1993-04-30 |
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