JPH04163509A - Endoscope object optical system - Google Patents
Endoscope object optical systemInfo
- Publication number
- JPH04163509A JPH04163509A JP2288444A JP28844490A JPH04163509A JP H04163509 A JPH04163509 A JP H04163509A JP 2288444 A JP2288444 A JP 2288444A JP 28844490 A JP28844490 A JP 28844490A JP H04163509 A JPH04163509 A JP H04163509A
- Authority
- JP
- Japan
- Prior art keywords
- optical system
- aspherical surface
- image
- aspherical
- order
- 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.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 61
- 230000004075 alteration Effects 0.000 description 34
- 201000009310 astigmatism Diseases 0.000 description 25
- 206010010071 Coma Diseases 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 238000003384 imaging method Methods 0.000 description 6
- 210000001747 pupil Anatomy 0.000 description 5
- 238000012937 correction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 101800000244 Allatostatin-3 Proteins 0.000 description 3
- 101800000240 Allatostatin-5 Proteins 0.000 description 3
- 239000008186 active pharmaceutical agent Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 2
- 235000017304 Ruaghas Nutrition 0.000 description 1
- 241000554738 Rusa Species 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- RTIXKCRFFJGDFG-UHFFFAOYSA-N chrysin Chemical compound C=1C(O)=CC(O)=C(C(C=2)=O)C=1OC=2C1=CC=CC=C1 RTIXKCRFFJGDFG-UHFFFAOYSA-N 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000006059 cover glass Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Endoscopes (AREA)
- Instruments For Viewing The Inside Of Hollow Bodies (AREA)
- Lenses (AREA)
Abstract
Description
【発明の詳細な説明】
(産業上の利用分野]
本発明は、主として工業用として使用される管内観察用
内視対物光学系に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an endoscopic objective optical system for observing inside a tube, which is mainly used for industrial purposes.
従来、内視鏡光学系の観察対象物の形状は、平面である
ことを想定している。また撮像面も平面である。そのた
め内視鏡対物光学系は、物体平面に対して共役の結像面
がほぼ平面になるように補正されている。つまり軸外の
結像性能を向上させるために非点隔差を小さくし、かつ
像面湾曲がなくなるような光学設計がなされてきた。し
たがって物体側が平面に近い状態、つまり撮像面の中心
付近と周辺に対応する物体平面までの距離がほぼ等しい
状態であれば良好な画像が得られた。Conventionally, it has been assumed that the shape of an object to be observed by an endoscope optical system is a plane. Further, the imaging surface is also a flat surface. Therefore, the objective optical system of the endoscope is corrected so that the imaging plane conjugate to the object plane is approximately flat. In other words, in order to improve off-axis imaging performance, optical designs have been made to reduce astigmatism and eliminate field curvature. Therefore, good images were obtained when the object side was close to a flat surface, that is, when the distances from the center of the imaging surface to the object plane corresponding to the periphery were approximately equal.
また、主に工業用内視鏡の分野では、水道管や土管など
の管状物体の内面検査に内視鏡対物光学系が用いられて
いる。管状物体を観察する場合、−度により多くの情報
を得ることや、管内面に対して出来るだけ垂直に近い状
態で観察できることが重要であるため、対物光学系の広
角化が望まれる。Furthermore, mainly in the field of industrial endoscopes, endoscope objective optical systems are used to inspect the inner surfaces of tubular objects such as water pipes and clay pipes. When observing a tubular object, it is important to obtain more information in -degrees and to be able to observe the object as close to perpendicular to the inner surface of the tube as possible, so a wide-angle objective optical system is desired.
しかし物体面が管状の場合、像面中心付近と周辺に対応
する物体平面までの距離に違いが出る。However, if the object plane is tubular, there will be a difference in the distance between the center of the image plane and the object plane corresponding to the periphery.
例えば物体平面からスコープの先端までの距離をし、管
の内径をφとし、対物光学系の半画角をωとすると次の
ように表わせる。For example, if the distance from the object plane to the tip of the scope is φ, the inner diameter of the tube is φ, and the half angle of view of the objective optical system is ω, then it can be expressed as follows.
tan ω
ただしEは対物光学系の入射瞳距離である。上の式から
入射瞳位置から物体までの距離L−Eは、管の内径φに
比例し、対物光学系の半画角ωのタンジェントに反比例
することがわかる。第9図は画角と物体距離りとの関係
を示す略図で、対物光学系の画角がω1からω2へと広
がれば広がるほど像面周辺での物体距離がり、からL2
へと近点寄りになる。そのために従来の対物光学系では
、特に細径の管の観察の場合、像面中心付近を無限遠点
にピントを合わせると、被写界深度から近点側がはずれ
、像面周辺でピントが合わないと云う不具合があった。tan ω where E is the entrance pupil distance of the objective optical system. From the above equation, it can be seen that the distance LE from the entrance pupil position to the object is proportional to the inner diameter φ of the tube and inversely proportional to the tangent of the half angle of view ω of the objective optical system. Fig. 9 is a schematic diagram showing the relationship between the angle of view and the object distance. As the angle of view of the objective optical system widens from ω1 to ω2, the object distance around the image plane increases, and from L2
It approaches periapsis. For this reason, with conventional objective optical systems, especially when observing small-diameter tubes, when focusing near the center of the image plane to infinity, the near point side deviates from the depth of field, and the focus is adjusted around the image plane. There was a problem that it wasn't there.
またこの不具合を解消するための手段として被写界深度
をより深くすることが考えられるが、その場合、Fナン
バーが大になるよう絞らなければならず光学系が暗くな
る。Further, as a means to solve this problem, it may be possible to make the depth of field deeper, but in that case, the aperture must be stopped so that the F number becomes large, and the optical system becomes dark.
〔発明が解決しようとする課題]
本発明は、固体撮像素子又はイメージガイドを用いた内
視鏡光学系で、管状物体を観察した時像面中心付近から
周辺までピントが合いかつFナンバーの小さい明るい光
学系を提供することを目的とするものである。[Problems to be Solved by the Invention] The present invention is an endoscope optical system using a solid-state image sensor or an image guide, which is in focus from near the center of the image plane to the periphery when observing a tubular object, and has a small F-number. The purpose is to provide a bright optical system.
本発明の内視鏡光学系は、物体側より順に負の屈折力を
有する第1群と正の屈折力を有する第2群と、第2群の
後に配置された明るさ絞りと、正の屈折力を有する後群
とからなり、光学系中に少なくとも1面非球面を有する
もので、次の条件(1)。The endoscope optical system of the present invention includes, in order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, an aperture stop placed after the second group, and a positive refractive power. and a rear group having refractive power, and has at least one aspherical surface in the optical system, and the following condition (1) is met.
(2)、 (3)を満足することを特徴としている。It is characterized by satisfying (2) and (3).
(1) P −f >0.1
(2) Ei (n=−+ n=) <0(3)
Aj (nj−+−n=) >Qで表わされる光学系
のペッツバール和、fは光学系の焦点距離、E8は光学
系中の任意の非球面で軸外主光線が最も高い位置を含む
非球面iの4次の非球面係数、ni−+ 、n=は前記
非球面iの物体側および像側の媒質の屈折率、AJは光
学系中の非球面jで6次以上の中の少なくとも一つの非
球面係数、nj−1r njは上記非球面jの物体側
および像側の媒質の屈折率である。(1) P −f >0.1 (2) Ei (n=-+ n=) <0(3)
Aj (nj-+-n=) > Petzval sum of the optical system expressed by Q, f is the focal length of the optical system, and E8 is an arbitrary aspherical surface in the optical system that includes the highest position of the off-axis principal ray. The fourth-order aspherical coefficient of the spherical surface i, ni-+, n= is the refractive index of the medium on the object side and the image side of the aspherical surface i, and AJ is the refractive index of the aspherical surface j in the optical system of at least the sixth-order or higher order. One aspheric coefficient, nj-1r nj, is the refractive index of the medium on the object side and image side of the aspheric surface j.
前記の構成のレンズ系で物体平面からスコープ先端まで
の距離をし、対物光学系の前側焦点距離をfr最終面か
らガウス像面までの距離をSKとすると近軸的には次の
関係が成立つ。In the lens system with the above configuration, let the distance from the object plane to the tip of the scope be the front focal length of the objective optical system, and let the distance from the final surface to the Gaussian image plane be SK, then the following relationship holds true paraxially: One.
(L十fr ) (SK fa )= f”
(iii)ここでSl[fgは無限遠物点の結像位置と
近接物点の結像位置との差を表わすが、本発明では一つ
の管状物体を観察する場合でも画角に応じて物体距離が
異なる。そのためSK fiは画角毎に異なる値を持
ち、各画角におけるガウス像面と実像面とのずれを°表
わすことになる。このずれ量(sK−fs )が観察す
る管の内径φと対物光学系の画角ωによって変化するこ
とは明らかである。(L1fr) (SKfa)=f”
(iii) Here, Sl[fg represents the difference between the imaging position of an object point at infinity and the imaging position of a nearby object point, but in the present invention, even when observing a single tubular object, the object Distances are different. Therefore, SK fi has a different value for each angle of view, and represents the deviation between the Gaussian image plane and the real image plane at each angle of view. It is clear that this amount of deviation (sK-fs) changes depending on the inner diameter φ of the tube to be observed and the angle of view ω of the objective optical system.
任意の径φ1の管において、対物レンズの中心(無限遠
物点)での合焦位置から周辺部のそれぞれの画角での物
体面からスコープの先端までの距離りに対応する、各像
高での最終面からガウス像面までの距離SKをつないだ
管内面に共役な像面形状の概略図を第10図に示しであ
る。ここ・で簡単のためfr’fs+=o、f=1とし
ている。For a tube of arbitrary diameter φ1, each image height corresponds to the distance from the in-focus position at the center of the objective lens (object point at infinity) to the object plane at each angle of view at the periphery to the tip of the scope. FIG. 10 shows a schematic diagram of the image surface shape conjugate to the inner surface of the tube, which connects the distance SK from the final surface to the Gaussian image surface. Here, for simplicity, it is assumed that fr'fs+=o and f=1.
光学系で観察すべき物体が管状の場合、第10図に示す
ように、物体距離の変化によりガウス像面は、正の像面
湾曲を示すことになる。この現象による画質の劣化を防
ぐためには、光学系自体に負の像面湾曲を持たせて、前
記の正の像面湾曲をキャンセルすればよい。When the object to be observed with the optical system is tubular, the Gaussian image plane exhibits positive field curvature due to changes in the object distance, as shown in FIG. In order to prevent the image quality from deteriorating due to this phenomenon, the optical system itself should have a negative curvature of field to cancel the positive curvature of field.
実際の対物光学系の像面ば、3次収差の領域では像面が
球面になり、その曲率は、ペッツバールの和Pで次の式
で表わされる。The image surface of an actual objective optical system becomes a spherical surface in the region of third-order aberration, and its curvature is expressed by the Petzval sum P as shown below.
このPの値が正のときは、像面ば、光学系に向かって凹
である。又像面湾曲による対物光学系中心(無限遠物点
)での合焦位置から周辺部での合焦点位置までのずれ量
ΔSKは次の式で与えられま
ただしIは最大像高である。When the value of P is positive, the image surface is concave toward the optical system. Further, the amount of deviation ΔSK from the in-focus position at the center of the objective optical system (object point at infinity) to the in-focus position at the periphery due to field curvature is given by the following equation, where I is the maximum image height.
以上のことから、ペッツバール和Pを正にすることによ
り負の像面湾曲を持たせることができる。From the above, by making the Petzval sum P positive, it is possible to provide a negative curvature of field.
又Pの値が大きければ大きい程ΔSKの絶対値が大にな
り、負の像面湾曲が大きくなり、これにより周辺像面に
共役な物体距離を短くすることができる。つまりより細
径の管で中心から周辺までピントが合う範囲が広がる。Furthermore, the larger the value of P, the larger the absolute value of ΔSK, and the larger the negative curvature of field, thereby making it possible to shorten the object distance conjugate to the peripheral image plane. In other words, the narrower diameter tube expands the range of focus from the center to the periphery.
以上のことから、ペッツバール和Pを正にする必要があ
り、これを実現する具体的な手段として凹の作用の面で
は、その面での軸外主光線との交点を高くかつ高屈折率
の硝材を用いればよい。また凸の作用の面では、逆に軸
外主光線との交点を低くしかつ低い屈折率の硝材を用い
ればよい。即ち、絞り近傍の前側では像面に向って凸面
を向けた正レンズ群を又絞りの後側近傍には物体側に凸
面を向けた正レンズ群を配置することが望ましい。更に
外径の極めて細いスコープ用の対物光学系としては、全
系の焦点距離で規格化したペッツバール和を前述のよう
に条件(1)を満足することにより、無限遠での合焦位
置から周辺部での合焦位置までの大きなずれ量ΔSKを
十分補正出来る。つまり条件(1)を満足しないとずれ
量を補正出来ない。From the above, it is necessary to make the Petzval sum P positive, and as a concrete means to achieve this, in terms of concave action, the intersection with the off-axis principal ray on that surface is made high and has a high refractive index. Glass material may be used. In terms of the effect of the convexity, conversely, it is sufficient to lower the point of intersection with the off-axis chief ray and to use a glass material with a low refractive index. That is, it is desirable to arrange a positive lens group with a convex surface facing the image plane on the front side near the diaphragm, and a positive lens group with a convex surface facing the object side near the back side of the diaphragm. Furthermore, as an objective optical system for a scope with an extremely narrow outer diameter, the Petzval sum normalized by the focal length of the entire system satisfies condition (1) as described above, so that the distance from the focal point at infinity to the peripheral The large amount of deviation ΔSK up to the in-focus position can be sufficiently corrected. In other words, the amount of deviation cannot be corrected unless condition (1) is satisfied.
しかしペッツバール和Pを極端に大きくすると、光学系
の凸の作用が強くなりすぎて、球面収差やコマ収差の発
生量が大になり、実用上問題が生ずる。つまりペッツバ
ール和をある程度で押え球面収差やコマ収差を小さく抑
えるために非球面を設けて負の像面湾曲の発生を増加さ
せる必要がある。However, if the Petzval sum P becomes extremely large, the effect of the convexity of the optical system becomes too strong, and the amount of spherical aberration and comatic aberration generated becomes large, causing a practical problem. In other words, it is necessary to increase the occurrence of negative field curvature by providing an aspherical surface in order to suppress the Petzval sum to a certain extent and to suppress spherical aberration and coma aberration.
そして更に前記の条件(2)、 (3)を満足させる必
要がある。一般に非球面は次の式にて表わすことが出来
る。Furthermore, it is necessary to satisfy the above-mentioned conditions (2) and (3). Generally, an aspherical surface can be expressed by the following formula.
ここでx、 y光軸をy軸にとって像の方向を正方向
にとり、y軸を面と光軸との交点を原点としてy軸に直
交した方向にとった座標の値、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は非球面の形状をあ
られすパラメーター、B。Here, the x, y optical axis is taken as the y-axis, the direction of the image is taken in the positive direction, and the y-axis is the coordinate value taken in the direction orthogonal to the y-axis with the intersection of the plane and the optical axis as the origin, and C is the vicinity of the optical axis. is the reciprocal of the radius of curvature of the circle that touches this aspherical surface, P is a parameter that determines the shape of the aspherical surface, and B is the parameter that defines the shape of the aspherical surface.
E、 F、 G・・・は夫々2次、4次、6次、8次
・・・の非球面係数である。E, F, G... are second-order, fourth-order, sixth-order, eighth-order, etc. aspherical coefficients, respectively.
P=1でB、E、F、G、・・・がすべて0の場合は上
記式は球面を表わす。When P=1 and B, E, F, G, . . . are all 0, the above equation represents a spherical surface.
またザイデルの収差係数を次の式(ii)、(iii)
のように定義する。物体距離をOB、マージナル光線の
開口数をNA、第1面より物体側の媒質の屈折率をno
とした時、近軸光線の第1面における光線高H0が
NA
Ho =OBx −
O
にて決まる。In addition, Seidel's aberration coefficient can be calculated using the following equations (ii) and (iii).
Define it like this. The object distance is OB, the numerical aperture of the marginal ray is NA, and the refractive index of the medium on the object side from the first surface is no.
When, the ray height H0 of the paraxial ray on the first surface is determined by NA Ho = OBx - O.
メリジオナル光線(X=O)に対して
ΔY = (SA3)π3+(0MA3)V1π2+
(3(AST3)+(PTZ3)) y2T+(oIs
3)y3+ (sas)T!5+ (CMA5) yu
4+ (TOBSA) マzP+ (ELCMA)”−
Y曙2+ (5(AST5)+(PTZ5)) V’T
+(o rs5)V’ ±(SA7) H7・・・・・
・・・・ (ii )サジタル光線(Y=O)に対して
ΔZ = (SA3)H’ + ((AST3) +
(PTZ3) ) Z”)l+(SA5)TiS+(S
OBSA)72W3+ ((AST5) +(PTZ5
) ) ’Z’lT+ (SA7)π7・・・(iii
)上記の式(ii)はメリディオナル光線に対して近軸
像点(収差がない時の像点)と実際の像点とのずれをΔ
Yとしたもので、Yは最大像高で規格化した像面におけ
る近軸主光線の入射位置、Hは瞳面における瞳径で規格
化したマージナル光線の入射位置である。またSA3.
SA5. SA7は夫々3次、5次、7次の球面
収差、0MA3. CMA5ハ夫々3次、lのタンジェ
ンシャルコマ、AST3. AST5は夫々3次、5次
の非点収差、PTZ3. PTZ5は夫々3次、5次の
ペッツバール和、0153. DIS5は夫々3次、5
次の歪曲収差、TOBSAは5次の斜方向のタンジェン
シャル球面収差、ELC?IAは5次の楕円コマ、5O
BSAは5次の斜方向のサジタル球面収差である。For meridional ray (X=O) ΔY = (SA3)π3+(0MA3)V1π2+
(3(AST3)+(PTZ3)) y2T+(oIs
3)y3+ (sas)T! 5+ (CMA5) yu
4+ (TOBSA) MazP+ (ELCMA)”-
Y Akebono 2+ (5(AST5)+(PTZ5)) V'T
+ (or rs5) V' ± (SA7) H7...
...... (ii) For sagittal ray (Y=O) ΔZ = (SA3)H' + ((AST3) +
(PTZ3) ) Z”)l+(SA5)TiS+(S
OBSA)72W3+ ((AST5) +(PTZ5
) ) 'Z'lT+ (SA7)π7...(iii
) The above equation (ii) calculates the deviation between the paraxial image point (the image point when there is no aberration) and the actual image point with respect to the meridional ray by Δ
where Y is the incident position of the paraxial principal ray on the image plane normalized by the maximum image height, and H is the incident position of the marginal ray on the pupil plane normalized by the pupil diameter. Also SA3.
SA5. SA7 has 3rd, 5th, and 7th order spherical aberrations, 0MA3. CMA5 is each 3rd order, l tangential coma, AST3. AST5 is 3rd and 5th order astigmatism, PTZ3. PTZ5 is the third-order and fifth-order Petzval sum, respectively, 0153. DIS5 is 3rd and 5th respectively
The next distortion aberration, TOBSA, is the fifth-order oblique tangential spherical aberration, ELC? IA is a 5th order elliptical top, 5O
BSA is a fifth-order oblique sagittal spherical aberration.
以後、非球面の式のうち、P=1.B=Oと置き換えた
式で説明する。Hereinafter, among the aspherical equations, P=1. This will be explained using a formula in which B=O.
非球面により生ずる球面収差ΔIi、コマ収差ΔIIi
、非点収差Δ■、および像面湾曲Δ■、は、4次の非球
面係数E、を用いて次のように表わすことが出来る。Spherical aberration ΔIi and coma aberration ΔIIi caused by aspherical surfaces
, astigmatism Δ■, and field curvature Δ■ can be expressed using the fourth-order aspheric coefficient E as follows.
ただしh□、巳は、夫々1面における近軸マージナル光
線および近軸主光線、nl−1r niは非球面の物
体側および像側の媒質の屈折率である。Here, h□ and 庳 are the paraxial marginal ray and paraxial principal ray in one surface, respectively, and nl-1rni is the refractive index of the medium on the object side and image side of the aspheric surface.
式(iv)より3次の像面湾曲係数Δ■、は非球面係数
Δ■、に等しいことがわかる。またレンズ全系のうちで
球面収差、コマ収差量をあまり変えずに像面湾曲を最適
化するために用いる非球面を配置する位置は、近軸マー
ジナル光線高り、が低くかつ近軸主光線高[の高い位置
が良いことがわかる。この非球面は、絞りの前後どちら
でもよい。ただし負の像面湾曲を発生させるためにΔ■
〈0すなわち条件(2)を満足する必要がある。しかじ
式(iiL (ji)から子午像面湾曲ΔMと球欠像面
湾曲の変化量ΔSがΔM:S=3:1となる。From equation (iv), it can be seen that the third-order field curvature coefficient Δ■ is equal to the aspheric coefficient Δ■. In addition, in the entire lens system, the aspheric surface used to optimize the field curvature without changing much the amount of spherical aberration and coma should be placed at a position where the paraxial marginal ray height is low and the paraxial principal ray height is low. It can be seen that a high position is good. This aspherical surface may be located either before or after the aperture. However, in order to generate negative field curvature, Δ■
<0, that is, condition (2) must be satisfied. From the Kajiji equation (iiL (ji)), the amount of change ΔS between the meridional field curvature ΔM and the truncated field curvature becomes ΔM:S=3:1.
非点収差に限らず一般に収差は、物体距離に依存して値
が変化する。したがって例えば、ある物体距離に対して
非点収差が0となるように設計したものでも、物体距離
が変化すれば収差が発生する。The value of not only astigmatism but also aberration in general changes depending on the object distance. Therefore, for example, even if the astigmatism is designed to be zero for a certain object distance, aberrations will occur if the object distance changes.
第11図は、物体距離無限大に対して非点収差が0にな
るように補正された光学系に対して、物体距離が変化し
た時に非点収差が、どのようになるかを示した図である
。つまりこの図においてSk。Figure 11 shows how the astigmatism changes when the object distance changes for an optical system that has been corrected so that the astigmatism becomes 0 for an infinite object distance. It is. In other words, in this figure, Sk.
が物体距離無限大に対するガウス像面である。物体距離
が近くなるとそれに応じてガウス像面の位置は右側に移
動する。それと同時に非点収差が発生し、その大きさは
第11図において、ΔDM、、 △DS、、 ΔD
M、、ΔDSzで表わされるような値になる。is the Gaussian image plane for infinite object distance. As the object distance becomes closer, the position of the Gaussian image plane moves to the right. At the same time, astigmatism occurs, and its magnitude is shown in Figure 11 as ΔDM, ΔDS, ΔD
The value is expressed as M, .DELTA.DSz.
本発明の光学系は、観察対象物が管状物体なので、第9
図に示すように物体距離りと像高(画角2ω)との間に
特定の関係を有する。つまり物体距離が無限遠(ガラス
像面の位置は第11図のSk、)となるのは、光軸上(
画角が0°)だけである。In the optical system of the present invention, since the object to be observed is a tubular object,
As shown in the figure, there is a specific relationship between the object distance and the image height (angle of view 2ω). In other words, the object distance is infinite (the position of the glass image plane is Sk in Fig. 11) because it is on the optical axis (
The angle of view is 0°).
そしてガウス像面の位置がSklとなるような物体距離
では、像高は0.5だけとなり、又ガウス像面の位置が
Skzとなるような物体距離は、最大像高の点だけであ
る。したがって、物体距離無限大に対して非点収差が0
である光学系を用いて管内面を結像させると第11図に
符号a、bで示すような大きく傾いた像面になり、しか
も像高が高くなるにつれて非点収差が大になり像面aと
bの差が非常に大きくなる。これでは光軸に垂直な像面
上では、鮮鋭な像を得ることは出来ない。At an object distance such that the position of the Gaussian image plane is Skl, the image height is only 0.5, and an object distance such that the position of the Gaussian image plane is Skz is only at the point of maximum image height. Therefore, the astigmatism is 0 for infinite object distance.
When an image is formed on the inner surface of the tube using an optical system, the image plane becomes greatly tilted as shown by symbols a and b in Fig. 11. Furthermore, as the image height increases, astigmatism increases and the image plane The difference between a and b becomes very large. In this case, it is not possible to obtain a sharp image on an image plane perpendicular to the optical axis.
次に第12図をもとに像面形状がどのような形状であれ
ば管状物体内を観察するのに最適であるかを調べる。Next, based on FIG. 12, it is investigated what shape the image plane should be optimal for observing the inside of the tubular object.
第12図において原点(縦軸)は特定の物体距離に対す
るガウス像面であり、S□′は、像高0.5の位置に対
するガウス像面、SKI’は像高が最大の位置に対する
ガウス像面の位置を夫々示している。最大像高に対する
像面ば、第12図において、実線Aにて示すように湾曲
しており、最大像高においてちょうど特定物体距離のガ
ウス像面上に乗る。尚ここでは非点収差がないのでΔD
MとΔDSとは重なっている。又像高0.5となる位置
では、物体距離が遠くなるので、ガウス像面はS Kl
′となるが、物体距離が変化するので非点収差が発生し
、像面ばΔMとΔSとに分れ図において実線と破線のよ
うになるが像面湾曲の程度が小さくなるため像高0.5
の位置では、像点は特定の物体距離に対するガウス像面
よりは左側に来る。In Fig. 12, the origin (vertical axis) is the Gaussian image plane for a specific object distance, S□' is the Gaussian image plane for the position of image height 0.5, and SKI' is the Gaussian image plane for the position where the image height is maximum. The position of each surface is shown. The image plane with respect to the maximum image height is curved as shown by the solid line A in FIG. 12, and lies exactly on the Gaussian image plane at the specific object distance at the maximum image height. In addition, since there is no astigmatism here, ΔD
M and ΔDS overlap. Also, at the position where the image height is 0.5, the object distance becomes long, so the Gaussian image plane becomes S Kl
' However, as the object distance changes, astigmatism occurs, and the image plane is divided into ΔM and ΔS, as shown by the solid line and broken line in the figure, but the degree of field curvature is reduced, so the image height is 0. .5
At the position , the image point is to the left of the Gaussian image plane for a particular object distance.
各像高に関して同様の考察をすると、結局、最大像高に
おいて像点がガウス像面上に乗るようにするためには中
間の像高では像面がプラス側に曲がり、図面に破線al
、b/にて示すようになる。Considering the same for each image height, in order for the image point to be on the Gaussian image plane at the maximum image height, the image plane curves to the plus side at the intermediate image height, and the broken line al
, b/.
つまり管状物体を平らな像面に鮮鋭に結像させるために
は、中間の像高において非点収差を小さくすると共にプ
ラス側への像面の膨らみが小さくなるように中間像高で
の像面湾曲を大きくする必要がある。In other words, in order to form a sharp image of a tubular object on a flat image surface, it is necessary to reduce astigmatism at an intermediate image height and to reduce the bulge of the image surface toward the positive side. It is necessary to increase the curvature.
ここで負の像面湾曲を発生させ、かつ最大像高でDM>
DSを満足させることは、3次の収差係数の領域だけで
像面をマイナス方向にしか倒せないため無理である。そ
のためDM>DSを満足させるには、6次以上の非球面
係数により高次の収差を発生させる必がある。Here, negative field curvature is generated and DM> at the maximum image height
It is impossible to satisfy DS because the image plane can only be tilted in the negative direction in the region of the third-order aberration coefficient. Therefore, in order to satisfy DM>DS, it is necessary to generate high-order aberrations using aspherical coefficients of the sixth order or higher.
本発明では、光学系中の任意の面jに非球面を設け、そ
の非球面の6次以上の非球面係数AJが前記の条件(3
)を満足する必要があり、それによってDM>DSを満
足させることが可能になる。In the present invention, an aspherical surface is provided on any surface j in the optical system, and the aspherical coefficient AJ of the sixth or higher order of the aspherical surface satisfies the above condition (3
), which makes it possible to satisfy DM>DS.
以上のように、本発明の光学系は、前述のレンズ構成で
条件(3)を満足するもので、管状物体を観察する時に
Fナンバーを小さくしても像面中心から周辺までピント
が合う。As described above, the optical system of the present invention satisfies condition (3) with the lens configuration described above, and when observing a tubular object, even if the F number is small, the image plane is in focus from the center to the periphery.
次に本発明の内視鏡対物光学系の各実施例を示す。 Next, embodiments of the endoscope objective optical system of the present invention will be described.
実施例1
f =1.000 F15.883
rl=■
d 、 =0.2419 n 、 =1.88300
v 、 =40.78r z = 0 、9602
d 、=0.4155
r z = 1 、7738
a、=0.9676 n2=1.62004 シ、=
36.25r 、=−1,6352(非球面)
d、=0.3134
rs=(1)(絞り)
d5=0.0538
rb”(1)
d 6=0.8064 n 3=1.5200093
=74.0Or?=■
d 、=0.0538
r s=2.6493
d −=0.5119 n 、=1.60311 v
、=60.7Or 、 =−0,9326
d 、=0.1613 n s=1.83350
v 5=21.0Or +o=−2.4172
d、。=0.3822
r 、、=1.7017 (非球面)
d、、=0.4301 n、=1.58913
シ、=60.97f Iz=OO
d 1z=1.0053 n 、=1.54814
v ?=45.78r、3=oO
d Iz=0.2150 n s=1.51633
v −=64.15r、4=CD
非球面係数
(第4面)
P =1.0000、B=0、E =0.19480X
10弓F =0.15602X10−’
(第11面)
P =1.0000. B = OlE = 0.58
992 X 10− ’F=−0.71753X10−
’、 G=0.18454X10月H=0.37635
X10−”
P −f =0.425>0.2
E、=E、。Example 1 f = 1.000 F15.883 rl = ■ d , = 0.2419 n , = 1.88300
v , =40.78r z = 0 ,9602 d ,=0.4155 r z = 1 ,7738 a, =0.9676 n2=1.62004 ci, =
36.25r, = -1,6352 (aspherical surface) d, = 0.3134 rs = (1) (aperture) d5 = 0.0538 rb” (1) d 6 = 0.8064 n 3 = 1.5200093
=74.0Or? = ■ d , = 0.0538 r s = 2.6493 d - = 0.5119 n , = 1.60311 v
, =60.7Or, =-0,9326 d, =0.1613 ns=1.83350
v5=21.0Or+o=-2.4172d,. =0.3822 r,, =1.7017 (aspherical surface) d,, =0.4301 n, =1.58913
, = 60.97f Iz = OO d 1z = 1.0053 n , = 1.54814
v? =45.78r, 3=oO d Iz=0.2150 n s=1.51633
v −=64.15r, 4=CD Aspheric coefficient (4th surface) P =1.0000, B=0, E =0.19480X
10 bow F = 0.15602X10-' (11th surface) P = 1.0000. B=OlE=0.58
992 X 10- 'F=-0.71753X10-
', G=0.18454XOctober H=0.37635
X10-” P −f =0.425>0.2 E, =E,.
Ell (nlo−n11) =−0,0348<
OA、=F、。Ell (nlo-n11) =-0,0348<
OA,=F,.
F II (n 10− n 11) =0.04
23> 01 / f 、、+=0.519<0.84
実施例2
f=1.ooo F15.970
r、=(1)
d、−0,2466n、=1.88300 シ、=40
.78r 2=0.7414 (非球面)
a 、=0.2555
r z = 1 、2894
d、=0.9865 n、=1.61293 y2=
37.00r 4=−1,5203
d、=0.3625
r、=cc+(絞り)
ds−0,0987
r6=ω
d −=0.8221 n−=1.52000 v
3=74.0Or?=■
d 、=0.0548
r s=2.1299 (非球面)
d 、=0.5684 n 、=1.60881
v 、=58.94r q =−1,0252
d、=0.1644 n、=1.83350 v5
=21.0Or1゜=−2,5986
a 、、=0.3897
r口=1.6936
d、、=0.4385 n、=1.51633 シ
、=64.15r、2=o。F II (n10-n11) =0.04
23>01/f,,+=0.519<0.84
Example 2 f=1. ooo F15.970 r, = (1) d, -0,2466n, = 1.88300 shi, = 40
.. 78r 2 = 0.7414 (aspherical surface) a , = 0.2555 r z = 1 , 2894 d, = 0.9865 n, = 1.61293 y2 =
37.00r 4=-1,5203 d,=0.3625 r,=cc+(aperture) ds-0,0987 r6=ω d-=0.8221 n-=1.52000 v
3=74.0Or? = ■ d , = 0.0548 r s = 2.1299 (aspherical surface) d , = 0.5684 n , = 1.60881
v, = 58.94 r q = -1,0252 d, = 0.1644 n, = 1.83350 v5
=21.0Or1゜=-2,5986 a,,=0.3897 r mouth=1.6936 d,,=0.4385 n,=1.51633 ci,=64.15r,2=o.
a、2=1.0249 n、=1.54814 シ
、=45.78r、、Wo。a,2=1.0249 n,=1.54814 ci,=45.78r,,Wo.
a、、=0.2192 n、=1.51633 シ
、=64.157.4mCD
非球面係数
(第2面)
p=i、oooo、B=0、E =−0,14788F
=−0,29841、G =0.17800xlOH
=−0,39878X 10
(第8面)
P=1.0O00、B=O1E = 0.90927
X 10−2F =−0,11166、G =0.36
380xlO−’H=0.15261
P −f =0.392>0.2
E; −Ez、 Ee
Ez(n+ nz)=−0,131<OE 8 (n
7− n R) =−0,0055< 0AJ=F。a,, = 0.2192 n, = 1.51633 c, = 64.157.4mCD Aspheric coefficient (second surface) p = i, oooo, B = 0, E = -0, 14788F
=-0,29841, G =0.17800xlOH
=-0,39878X 10 (8th surface) P=1.0O00, B=O1E = 0.90927
X 10-2F = -0,11166, G = 0.36
380xlO-'H=0.15261 P-f=0.392>0.2 E; -Ez, Ee Ez(n+nz)=-0,131<OE 8 (n
7-nR) =-0,0055<0AJ=F.
F s (n 7− n’s) =−o、o6so>
OI / f **=0.887/1.661 =0
.534 <0.84実施例3
f=1.000 F15.924
rl=ω
d 、=0.2320 n + =1.88300
v 1=40.78rz=0.9746
d 2=0.5108
r:+=1.5949
d 3=0.9795 n −=1.64769 v
z=33.8゜r 、 =−1,8036
d 4=0.0515
rs=’o(絞り)
d 、= 0.0928
r6=■
a、=0.7733 nz=1.52000 シ=
=74.o。F s (n 7 - n's) = -o, o6so>
OI/f**=0.887/1.661 =0
.. 534 <0.84 Example 3 f=1.000 F15.924 rl=ω d , =0.2320 n + =1.88300
v 1 = 40.78 rz = 0.9746 d 2 = 0.5108 r: + = 1.5949 d 3 = 0.9795 n - = 1.64769 v
z=33.8゜r, =-1,8036 d4=0.0515 rs='o (aperture) d,=0.0928 r6=■ a,=0.7733 nz=1.52000 si=
=74. o.
ri ;■
d 、=0..0515
r a=3.2850 (非球面)
d e=0.5050 n 4=1.58913
v 4=60.97r q =−0,8202
d 、=0.1547 n s=1.83350
v 、=21.0Or +o=−2.0710
a 、 o = 0.3665
rlI=1.5013(非球面)
d、、=0.4124 n+、=1.48749
シ、、=70.2Or +z”’ω
d l2=0.9640 n 7=1.54814
シ、=45.78r I:l=ω
d ++=0.2062 n s=1.51633
V 5=64.15r148ω
非球面係数
(第8面)
P =1.0OOO1B=O1E =−0,11800
F=0.12590X10. G=−0,37467
X10H=0.41332X10
(第11面)
P =1.0000、B=O1E=0.19860F
−−0,31207、G=0.17388H=−0,3
2791X10−’
P −f =0.432>0.2
E、=E、。ri;■d,=0. .. 0515 r a=3.2850 (aspherical surface) d e=0.5050 n 4=1.58913
v4=60.97rq=-0,8202d,=0.1547ns=1.83350
v, = 21.0Or +o = -2.0710 a, o = 0.3665 rlI = 1.5013 (aspherical surface) d,, = 0.4124 n+, = 1.48749
,,=70.2Or +z”'ω d l2=0.9640 n 7=1.54814
,=45.78r I:l=ω d ++=0.2062 n s=1.51633
V 5 = 64.15r148ω Aspheric coefficient (8th surface) P = 1.0OOO1B = O1E = -0,11800
F=0.12590X10. G=-0,37467
X10H=0.41332X10 (11th surface) P=1.0000, B=O1E=0.19860F
--0,31207, G=0.17388H=-0,3
2791X10-' P −f =0.432>0.2 E, =E,.
Elf (nlo−n+1) =−0,0968<OA
、=F、。Elf (nlo-n+1) =-0,0968<OA
,=F,.
F II (n 10− n II) =0.15
21> 01 / f y+=0.8506/1.79
6ミ0.474<0.84実施例4
f =1.OOOF15.965
r 1 °ω
d 、 =0.2546 n 、 =1.88300
v + =40.78rz=1.0155
dz−0,7001
r3=1.8330
d 3=1.0186 n 2=1.63636
v z=35.37r 、 =−1,9586
d、=0.0566
rs=ω(絞り)
ds=0.1019
rb=■
d 、=0.8489 n 3=1.52000
v 、=74.0Or?=(1)
d、=0.0566
r g=3.4958 (非球面)
d s=0.5535 n 4=1.61700
v a=62.79r、=−0,8880
d*=0.1698 n5=1.83350 ν5
=21.0゜r +o=−2,5177
d、、=0.4024
r + + = 1.6440 (非球面)d、、=0
.4527 n、=1.48749 シ、=70.
2Or 、2=CO
d 、2=1.0582 n 、=1.54814
v 、=45.78rll°a)
a、、=0.2138 n5=1.51633 シ
e=64.15r、4=■
非球面係数
(第8面)
P =1.0O00、B=O1E =−0,91116
X 10伺F =0.77178 、G =−0,19
639xlOH= 0.18610 X 10
(第11面)
P =1.0000、B=O1E =0.14781F
=−0,20068、G=0.10186H=−0,
18679X 10− ’
P −f =0.356>0.2
E i −E II
Ez (nIo n++) =−0,0721<OA
、=F、。F II (n 10 - n II) = 0.15
21>01/f y+=0.8506/1.79
6 mi 0.474<0.84 Example 4 f =1. OOOF15.965 r 1 °ω d , =0.2546 n , =1.88300
v + =40.78rz=1.0155 dz-0,7001 r3=1.8330 d3=1.0186 n2=1.63636
v z = 35.37 r , = -1,9586 d , = 0.0566 rs = ω (aperture) ds = 0.1019 rb = ■ d , = 0.8489 n 3 = 1.52000
v,=74.0Or? = (1) d, = 0.0566 r g = 3.4958 (aspherical surface) d s = 0.5535 n 4 = 1.61700
v a=62.79r,=-0,8880 d*=0.1698 n5=1.83350 ν5
=21.0゜r +o=-2,5177 d,, =0.4024 r + + = 1.6440 (Aspherical surface) d,, =0
.. 4527 n, = 1.48749 ci, = 70.
2Or, 2=COd, 2=1.0582 n,=1.54814
v , =45.78rll°a) a,, =0.2138 n5 = 1.51633 She = 64.15r, 4 = ■ Aspheric coefficient (8th surface) P = 1.0O00, B = O1E = - 0,91116
X 10 times F = 0.77178, G = -0,19
639xlOH = 0.18610 x 10 (11th surface) P = 1.0000, B = O1E = 0.14781F
=-0,20068,G=0.10186H=-0,
18679
,=F,.
F ++ (n +o n ++) =0.0978
> OI / f 、、=0.91/1.964=0.
463<0.84ただしrl+r2+ ・・・はレンズ
各面の曲率半径、d、、d2.・・・は各レンズの肉厚
およびレンズ間隔、nI + nz + ・・・は各
レンズの屈折率、ν、。F ++ (n + o n ++) =0.0978
>OI/f,,=0.91/1.964=0.
463<0.84 where rl+r2+ ... is the radius of curvature of each lens surface, d,, d2. ... is the thickness of each lens and the lens interval, nI + nz + ... is the refractive index of each lens, ν.
ν2.・・・は各レンズのアツベ数である。ν2. ... is the Atsube number of each lens.
これらの実施例は、次の条件(4)、 (5)を満足す
る。These Examples satisfy the following conditions (4) and (5).
(4) fil fil + l fzl <5f(
5) 0.3<l f、l/l fzl<1.5ただ
しflは絞りより前にある発散レンズ群の焦点距離、f
2は絞りより前にある収斂レンズ群である。(4) fil fil + l fzl <5f(
5) 0.3<l f, l/l fzl<1.5, where fl is the focal length of the diverging lens group in front of the aperture, f
2 is a convergent lens group located in front of the aperture.
上記条件(4)の上限を越えると絞りの前のレンズ群の
前長が長くなり好ましくない。また条件(4)の下限を
越えると絞りの前の収斂レンズ群の各々の屈折力が非常
に強くなるので全長を短くすることは出来るが、発散レ
ンズ群、収斂レンズ群で発生する収差が大きくなりすぎ
て絞りの前でのレンズ群で発生する収差を小さくするこ
とが出来ない。If the upper limit of the above condition (4) is exceeded, the front length of the lens group in front of the diaphragm becomes long, which is undesirable. Furthermore, if the lower limit of condition (4) is exceeded, the refractive power of each of the converging lens groups in front of the aperture becomes very strong, so the total length can be shortened, but the aberrations generated in the diverging and converging lens groups become large. This is too much and it is not possible to reduce the aberrations generated in the lens group in front of the aperture.
この条件(1)を満足するとき、絞りの前の発散レンズ
群の屈折力に対する収斂レンズ群の屈折力が強すぎると
、発散レンズ群で発生する正の球面収差より収斂レンズ
群で発生する負の球面収差が大きくなりすぎるため球面
収差を絞りの後のレンズ群で補正出来なくなる。逆に発
散レンズ群の屈折力が収斂レンズ群の屈折力より強すぎ
ると、発散レンズ群で発生する負のコマ収差を収斂レン
ズ群で充分補正できない。When this condition (1) is satisfied, if the refractive power of the converging lens group is too strong compared to the refractive power of the diverging lens group in front of the aperture, the negative spherical aberration generated in the converging lens group will be greater than the positive spherical aberration generated in the diverging lens group. Since the spherical aberration becomes too large, it becomes impossible to correct the spherical aberration with the lens group after the aperture. On the other hand, if the refractive power of the diverging lens group is too strong than the refractive power of the converging lens group, the negative coma that occurs in the diverging lens group cannot be sufficiently corrected by the converging lens group.
したがって、収差を良好に補正するためには、絞りの前
の発散レンズ群と絞より前の収斂レンズ群との屈折力の
比をある範囲内に収めることが必要である。これを規定
したのが条件(5)である。Therefore, in order to properly correct aberrations, it is necessary to keep the ratio of refractive power between the diverging lens group in front of the aperture and the converging lens group in front of the aperture within a certain range. Condition (5) stipulates this.
この条件(5)の下限を越えると球面収差が悪化し、又
上限を越えるとコマ収差が悪化し、いずれも補正が困難
になる。If the lower limit of this condition (5) is exceeded, spherical aberration worsens, and if the upper limit is exceeded, coma aberration worsens, both of which become difficult to correct.
実施例1は、第1図に示す構成で、物体側より順に像側
に凹面を有する負レンズの第1群L+ と、像側に凸面
を有する正レンズの第2群L2と、絞りSと、固体撮像
素子(COD)に近赤外領域の光が入射するのを防ぐた
めの色温度補正フィルタF+ と、軸外の倍率の色収差
を補正するためにアツベ数の大きい材料よりなる正レン
ズとアッペ数の小さい材料よりなる負のメニスカスレン
ズとを貼合わせ全体として正の屈折力を有する接合色消
レンズの第3群L3と、物体側に凸面を向けた正のフィ
ールドレンズの第4群L4と、モアレおよび擬色の発生
を防止するために高周波成分をカットする光学的ローパ
スフィルターF2と、CCDカバーガラスCとを配置し
たものである。Embodiment 1 has the configuration shown in FIG. 1, and includes, in order from the object side, a first group L+ of negative lenses having a concave surface on the image side, a second group L2 of positive lenses having a convex surface on the image side, and an aperture S. , a color temperature correction filter F+ to prevent near-infrared light from entering the solid-state image sensor (COD), and a positive lens made of a material with a large Abbe number to correct off-axis chromatic aberration of magnification. A third group L3 of a cemented achromatic lens which has a positive refractive power as a whole by laminating a negative meniscus lens made of a material with a small Appe number, and a fourth group L4 of a positive field lens with a convex surface facing the object side. , an optical low-pass filter F2 that cuts high frequency components in order to prevent the occurrence of moiré and false color, and a CCD cover glass C.
更にフィールドレンズL4の凸の面が条件(2)。Furthermore, the condition (2) is that the field lens L4 has a convex surface.
(3)を満足する形状の非球面として像面湾曲の補正を
行なっている。The field curvature is corrected using an aspherical surface having a shape that satisfies (3).
この実施例1は、画角が約120°の広角な内視鏡対物
光学系である。文明るさ絞りSより後ろの後群の収斂系
における色温度補正フィルターF。Embodiment 1 is a wide-angle endoscope objective optical system with an angle of view of approximately 120°. Color temperature correction filter F in the convergence system of the rear group behind the Bunmei Rusa aperture S.
が吸収フィルターであるとき軸外での入射光の入射角が
大きい(約40°以上)と軸上光線との光路差が大きく
なり、軸上に比べて周辺での赤側の波長の光の分光透過
率がおちる。その影響で画面周辺で多少青みがかる等の
問題が生ずる。またCCD受光素子の前にR,G、B等
のモザイクカラーフィルターが設けられている同時代C
CDにおいては、受光素子への入射角度が大きいと色む
らを起こしやすい欠点がある。そのためCCDに入射す
る各像高での主光線がCCDに対してほぼ垂直に入射す
るようにしなければならない。つまり対物光学系として
は、瞳位置がほぼ無限遠になるテレセンドリンク光学系
が望まれる。When is an absorption filter, if the angle of incidence of the off-axis incident light is large (approximately 40 degrees or more), the optical path difference with the on-axis ray becomes large, and the red wavelength light at the periphery becomes larger compared to on-axis. Spectral transmittance decreases. This causes problems such as a slight bluish tinge around the screen. Also, the same era C had mosaic color filters such as R, G, and B installed in front of the CCD light receiving element.
CDs have the disadvantage that color unevenness tends to occur when the angle of incidence on the light receiving element is large. Therefore, it is necessary to make the chief rays incident on the CCD at each image height almost perpendicular to the CCD. In other words, as an objective optical system, a telescopic link optical system in which the pupil position is almost infinite is desired.
この実施例1では、像高■に対するフィルターF、より
も後方のレンズL、、L、の合成焦点距離f34を長く
して、フィルターF+への入射角を小さくしている。基
本的には以下の式を満足することが好ましい。In Example 1, the composite focal length f34 of the lenses L, . Basically, it is preferable to satisfy the following formula.
1 / f 34< tan40°=0.84又実施例
1は、絞りSの前の凸の面を非球面にして主として球面
収差、コマ収差の補正を行なっている。絞りの直前の面
は、近軸マージナル光線高り、は大きく近軸主光線高は
小さいので、この面を非球面にすると、式(ix)から
3次の非点収差係数は小さく出来、球面収差係数および
コマ収差係数は太き(出来るため球面収差、コマ収差の
補正にとって都合がよい。尚Fナンバーの大きな光学系
では、球面でも差しつかえないことは明らかである。
。1/f34<tan40°=0.84 In the first embodiment, the convex surface in front of the diaphragm S is made an aspherical surface to mainly correct spherical aberration and coma aberration. The surface just in front of the aperture has a large paraxial marginal ray height and a small paraxial principal ray height, so if this surface is made aspherical, the third-order astigmatism coefficient can be reduced from equation (ix), and it becomes a spherical surface. The aberration coefficient and coma aberration coefficient are large (thick), which is convenient for correcting spherical aberration and coma aberration.It is clear that a spherical surface can be used in an optical system with a large F number.
.
この実施例1の光学系を用いて管状物体面を観察した時
の非点収差を第5図に示しである。この時物体距離に相
当する管の内径は、条件としては厳しい管を設定し内径
約8mとした。FIG. 5 shows astigmatism when observing a tubular object surface using the optical system of Example 1. At this time, the inner diameter of the tube, which corresponds to the object distance, was set to be approximately 8 m under strict conditions.
比較のために同一画角でペッツバール和がほぼ零である
第13図に示す特開昭62−173415号の実施例7
の非点収差曲線を第14図に示す。For comparison, Example 7 of JP-A-62-173415 is shown in FIG. 13 where the Petzval sum is almost zero at the same angle of view.
The astigmatism curve of is shown in FIG.
第5図と第14図とを比較すれば明らかなように、前記
従来例の光学系は像面が極端にプラス方向に傾いている
のに対して、この実施例1の光学系は、中心から周辺ま
で像面がフラットである。As is clear from a comparison between FIG. 5 and FIG. 14, in the optical system of the conventional example, the image plane is tilted extremely in the positive direction, whereas in the optical system of this embodiment 1, the image plane is tilted at the center. The image plane is flat from the center to the periphery.
実施例2は、第2図に示す構成で、負レンズL、の像側
の面と接合レンズL3の物体側の面が非球面である。こ
れら非球面は、いずれも近軸主光線高のそれ程高くない
ところに設けられているため、いずれも一方の面だけで
は像面湾曲の補正量が小さい、そのために両非球面合わ
せて像面湾曲の補正を行なっている。Example 2 has the configuration shown in FIG. 2, in which the image-side surface of the negative lens L and the object-side surface of the cemented lens L3 are aspherical. These aspheric surfaces are all located at locations where the height of the paraxial chief ray is not so high, so the amount of correction for field curvature is small when only one surface is used, so the field curvature of both aspheric surfaces combined Corrections are being made.
この実施例3の非点収差は、第6図に示す通りである。The astigmatism of Example 3 is as shown in FIG.
実施例3は、第3図に示す構成で接合レンズL3の物体
側の面と接合レンズL4の物体側の面の2面が非球面で
ある。これら非球面は、2面とも絞りSよりも像側に配
置されている。実施例3の非点収差は、第7図に示す通
りである。Example 3 has the configuration shown in FIG. 3, and two surfaces, the object-side surface of the cemented lens L3 and the object-side surface of the cemented lens L4, are aspherical. Both of these aspherical surfaces are arranged closer to the image side than the aperture S. The astigmatism of Example 3 is as shown in FIG.
実施例4は、第4図に示す構成で、実施例3と同じ構成
で画角を更に広< L 140°にして、より広い範囲
の観察を可能にした光学系である。Example 4 has the configuration shown in FIG. 4, and is an optical system having the same configuration as Example 3, but with a wider angle of view <L 140°, making it possible to observe a wider range.
この実施例4の非点収差は、第8図に示す通りである。The astigmatism of Example 4 is as shown in FIG.
本発明の管内観察用内視鏡光学系は、管状物体を観察し
たとき像面中心付近から周辺までピントが合いかつ明る
い光学系である。The endoscopic optical system for intraductal observation of the present invention is an optical system that is bright and in focus from the vicinity of the center of the image plane to the periphery when observing a tubular object.
第1図乃至第4図は本発明の実施例1乃至実施例4の断
面図、第5図乃至第8図は実施例1乃至実施例4の非点
収差曲線図、第9図は管内観察時の画角と物体距離の関
係を示す図、第10図は従来の光学系での管内観察時の
像面形状を示す図、第11図、第12図は物点距離の変
化に対する非点収差の状況を示す図、第13図は従来の
内視鏡対物レンズの断面図、第14図は上記従来例の非
点収差曲線図である。
出願人 オリンパス光学工業株式会社代理人
向 寛 −
第2図
第3図
第9図
第10図
U 駕笈鴇
第5図
非点収差
第7図
第6図
非点収差
第8図
非点収差Figures 1 to 4 are cross-sectional views of Examples 1 to 4 of the present invention, Figures 5 to 8 are astigmatism curve diagrams of Examples 1 to 4, and Figure 9 is an observation inside the tube. Figure 10 is a diagram showing the image plane shape when observing inside a tube with a conventional optical system. Figures 11 and 12 are astigmatism diagrams for changes in object distance. FIG. 13 is a cross-sectional view of a conventional endoscope objective lens, and FIG. 14 is an astigmatism curve diagram of the conventional example. Applicant Olympus Optical Industry Co., Ltd. Agent
Hiroshi Mukai - Figure 2 Figure 3 Figure 9 Figure 10 U Palette Figure 5 Astigmatism Figure 7 Figure 6 Astigmatism Figure 8 Astigmatism
Claims (1)
折力を有する第2群と、第2群の直後に配置された明る
さ絞りと、正の屈折力を有する後群とよりなり、少なく
とも1面の非球面を有し、下記の条件(1)、(2)、
(3)を満足する内視鏡対物光学系。 (1)P・f>0.1 (2)E_i(n_i_−_1−n_i)<0 (3)A_j(n_j_−_1−n_j)>0 ただしfは対物光学系の焦点距離、Dは対物光学系のペ
ッツバール和、E_iは非球面のうち主光線が最も高い
位置を含む非球面の4次の非球面係数、n_i_−_1
、n_iは上記非球面の物体側および像側の媒質の屈折
率、A_jは6次以上のうちの少なくとも一つの非球面
係数、n_j_−_1、n_jは夫々上記非球面の物体
側および像側の屈折率である。[Claims] In order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, an aperture stop disposed immediately after the second group, and a positive refractive power. It consists of a rear group having force, has at least one aspherical surface, and has the following conditions (1), (2),
An endoscope objective optical system that satisfies (3). (1) P・f>0.1 (2) E_i (n_i_-_1-n_i)<0 (3) A_j(n_j_-_1-n_j)>0 where f is the focal length of the objective optical system, and D is the objective optical system. The Petzval sum of the system, E_i is the fourth-order aspherical coefficient of the aspherical surface including the highest position of the principal ray, n_i_−_1
, n_i is the refractive index of the medium on the object side and image side of the aspherical surface, A_j is at least one aspherical coefficient of the sixth order or higher, and n_j_−_1, n_j are the refractive index of the medium on the object side and image side of the aspherical surface, respectively. It is the refractive index.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2288444A JPH04163509A (en) | 1990-10-29 | 1990-10-29 | Endoscope object optical system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2288444A JPH04163509A (en) | 1990-10-29 | 1990-10-29 | Endoscope object optical system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH04163509A true JPH04163509A (en) | 1992-06-09 |
Family
ID=17730292
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2288444A Pending JPH04163509A (en) | 1990-10-29 | 1990-10-29 | Endoscope object optical system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH04163509A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1020188A (en) * | 1996-07-03 | 1998-01-23 | Asahi Optical Co Ltd | Photographing lens |
DE10311416B4 (en) * | 2003-03-13 | 2005-12-01 | Wente / Thiedig Gmbh | Optical test device for hollow bodies and method for optical testing of hollow bodies |
JP2010181767A (en) * | 2009-02-09 | 2010-08-19 | Japan Aerospace Exploration Agency | Lens with dof curved by field curvature, and method of using the same |
CN108957702A (en) * | 2018-08-14 | 2018-12-07 | 瑞声科技(新加坡)有限公司 | Camera optical camera lens |
CN108957696A (en) * | 2018-08-14 | 2018-12-07 | 瑞声科技(新加坡)有限公司 | Camera optical camera lens |
JP2020151497A (en) * | 2017-03-17 | 2020-09-24 | 株式会社モリタ製作所 | Three-dimensional scanner |
-
1990
- 1990-10-29 JP JP2288444A patent/JPH04163509A/en active Pending
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1020188A (en) * | 1996-07-03 | 1998-01-23 | Asahi Optical Co Ltd | Photographing lens |
DE10311416B4 (en) * | 2003-03-13 | 2005-12-01 | Wente / Thiedig Gmbh | Optical test device for hollow bodies and method for optical testing of hollow bodies |
JP2010181767A (en) * | 2009-02-09 | 2010-08-19 | Japan Aerospace Exploration Agency | Lens with dof curved by field curvature, and method of using the same |
JP2020151497A (en) * | 2017-03-17 | 2020-09-24 | 株式会社モリタ製作所 | Three-dimensional scanner |
CN108957702A (en) * | 2018-08-14 | 2018-12-07 | 瑞声科技(新加坡)有限公司 | Camera optical camera lens |
CN108957696A (en) * | 2018-08-14 | 2018-12-07 | 瑞声科技(新加坡)有限公司 | Camera optical camera lens |
CN108957696B (en) * | 2018-08-14 | 2020-12-11 | 瑞声光学解决方案私人有限公司 | Image pickup optical lens |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP3547103B2 (en) | Wide-angle imaging lens | |
JPS6046410B2 (en) | endoscope objective lens | |
JPS63291019A (en) | Endoscope objective | |
JPH0827429B2 (en) | Objective lens for endoscope | |
JPH07294808A (en) | Image forming lens | |
JP4929902B2 (en) | Single focus lens and imaging apparatus having the same | |
JP4997845B2 (en) | Viewfinder optical system and optical apparatus having the same | |
JPH04151116A (en) | Kepler type zoom finder optical system | |
JPH04163509A (en) | Endoscope object optical system | |
JPH05341185A (en) | Objective optical system for endoscope | |
JPH11174345A (en) | Wide visual field ocular | |
JPH0876033A (en) | Aspherical eyepiece | |
JPH07113952A (en) | Optical system for infrared ray | |
JPH0954259A (en) | Eyepiece lens | |
JPH052134A (en) | Keplerian type zoom finder optical system | |
CN107402446A (en) | A kind of pre-objective of endoscope | |
JPH041713A (en) | Endscope objective optical system for intratube observation | |
JP2855849B2 (en) | Kepler-type zoom finder optical system | |
JPH0574806B2 (en) | ||
JPS6381309A (en) | Photographing lens having long back-focal distance | |
JP4366619B2 (en) | Telephoto conversion lens | |
JPS6180214A (en) | Zoom lens constituted of two groups | |
JPH0792385A (en) | Objective lens for endoscope | |
JPH11109258A (en) | Ocular optical system for diopter variable finder | |
JP3259521B2 (en) | Eyepiece |