JP2899980B2 - Objective optical system for endoscope - Google Patents
Objective optical system for endoscopeInfo
- Publication number
- JP2899980B2 JP2899980B2 JP2022222A JP2222290A JP2899980B2 JP 2899980 B2 JP2899980 B2 JP 2899980B2 JP 2022222 A JP2022222 A JP 2022222A JP 2222290 A JP2222290 A JP 2222290A JP 2899980 B2 JP2899980 B2 JP 2899980B2
- Authority
- JP
- Japan
- Prior art keywords
- filter
- lens
- optical system
- condition
- endoscope
- 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 - Fee Related
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- Lenses (AREA)
- Instruments For Viewing The Inside Of Hollow Bodies (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、細径電子内視鏡に好適な内視鏡用対物光学
系に関するものである。Description: TECHNICAL FIELD The present invention relates to an objective optical system for an endoscope suitable for a small-diameter electronic endoscope.
［従来の技術］ 内視鏡としては、イメージガイドファイバーを用いた
ファイバースコープが多く用いられているが、先端硬性
部内にCCD等の固体撮像素子を用いたビデオスコープも
多く使用されるようになった。[Prior Art] As an endoscope, a fiberscope using an image guide fiber is widely used, but a videoscope using a solid-state imaging device such as a CCD in a rigid portion at the tip is also often used. Was.
また、最近では撮像素子も小さくなり、それにともな
いスコープの外径も細く出来るようになった。そのた
め、気管支系，泌尿器系のビデオスコープも開発されて
きた。Recently, the image sensor has become smaller, and accordingly, the outer diameter of the scope can be reduced. For this reason, bronchial and urological videoscopes have also been developed.
ビデオスコープにおいては、固体撮像素子が可視光以
外の赤外光にも感度をもつためモニター上に映し出す画
像は、正確な色再現が出来ないので、赤外線を遮断する
ためのフィルターを設ける必要があった。又ビデオスコ
ープを用いて、近赤外から遠赤外のレーザー光による治
療を行なう場合、レーザー光でCCDが飽和しスミアーや
ブリーミングなどによって被検体部分を観察しにくくな
るため、使用するレーザー光の波長を遮断するためのフ
ィルターを光学系中に設けなければならない。In videoscopes, since the solid-state image sensor has sensitivity to infrared light other than visible light, the image projected on the monitor cannot reproduce accurate colors.Therefore, it is necessary to provide a filter to block infrared light. Was. Also, when performing treatment using near-infrared to far-infrared laser light using a videoscope, the CCD becomes saturated with the laser light, making it difficult to observe the subject part due to smearing or bleeding. A filter for blocking the wavelength must be provided in the optical system.
しかし、光学系中に設けられた赤外カットフィルタ
ー、CCDカバーガラス、レーザー光遮断のためのフィル
ター等の厚みは、撮像素子が小さくなり焦点距離が短く
なっても変わらない。そのため焦点距離に対するこれら
フィルターの厚みの空気換算長のしめる割合が大にな
る。However, the thickness of an infrared cut filter, a CCD cover glass, a filter for blocking laser light, and the like provided in the optical system do not change even if the image pickup device becomes smaller and the focal length becomes shorter. Therefore, the ratio of the thickness of these filters to the focal length in terms of the air conversion length becomes large.
光学系中にフィルターを設けた内視鏡対物レンズとし
て、第21図に示すタイプのものが知られている。この第
21図に示す光学系は、通常レトロフォーカスタイプのも
ので、次の関係が成立つ。As an endoscope objective lens provided with a filter in an optical system, a type shown in FIG. 21 is known. This second
The optical system shown in FIG. 21 is usually a retrofocus type, and the following relationship is established.
Ｉ＝fsinθ ただしＩは像高,fは光学系の焦点距離，θは半画角で
ある。I = fsin θ where I is the image height, f is the focal length of the optical system, and θ is the half angle of view.
このタイプのレンズ系で、焦点距離ｆに対する空気換
算長の大きいフィルターf1，f2やカバーガラスｃを配置
し得るようにするためには、レトロ比を大きくしなけれ
ばならない。レンズ系の全長を短く保ったままレトロ比
を大にすると、各群のパワーが強くなり、収差の補正が
困難になる。特に画角を広くしようとすると、焦点距離
は一層小さくなるので、広角化できない。このタイプの
レンズ系は、収差を良好に補正しようとすると、レンズ
枚数が増え、それにともない全長が長くなり、細径用内
視鏡のレンズ系としては好ましくない。In order to be able to arrange filters f 1 and f 2 and a cover glass c having a large air conversion length with respect to the focal length f in this type of lens system, the retro ratio must be increased. If the retro ratio is increased while keeping the overall length of the lens system short, the power of each group becomes strong, and it becomes difficult to correct aberrations. In particular, when trying to widen the angle of view, the focal length is further reduced, so that the angle of view cannot be widened. This type of lens system increases the number of lenses and satisfactorily corrects aberrations, resulting in an increase in the overall length, which is not preferable as a lens system for a small-diameter endoscope.
又吸収型赤外カットフィルターには、通常リン酸系ガ
ラスが用いられる。このリン酸系ガラスは、耐湿度性が
低いため、必ずコーティングして外気と接触しないよう
にする必要がある。このコーティングをほどこしたフィ
ルターは、加工上フィルターの周辺には傷等がつき又は
がれたりすることがあり、その部分が外気に触れて周辺
部から白濁することがある。そのためにフィルターへ入
射する光線の高さを外径に比べ低くする必要がある。し
かし前述のタイプのレンズ系では、２枚のフィルター
f1，f2がCCDカバーガラスＣの直前に配置されているた
めフィルターに入射する光線高は、ほぼ像高と同一かそ
れ以上であり、光学系中の最大の光線高の部分に配置さ
れているために、光線高をフィルター径に対し十分低く
することは出来ない。Phosphate glass is usually used for the absorption type infrared cut filter. Since the phosphate glass has low moisture resistance, it is necessary to always coat the phosphate glass so as not to come into contact with the outside air. The filter provided with this coating may be scratched or peeled off around the filter due to processing, and the portion may come into contact with the outside air and become cloudy from the periphery. Therefore, it is necessary to make the height of the light beam incident on the filter lower than the outer diameter. However, in the above-mentioned type of lens system, two filters
Since f 1 and f 2 are arranged immediately before the CCD cover glass C, the height of the light beam incident on the filter is almost equal to or higher than the image height, and is arranged at the portion of the maximum light height in the optical system. Therefore, the ray height cannot be made sufficiently low with respect to the filter diameter.
［発明が解決しようとする課題］ 本発明は、フィルターに入射する光線高がフィルター
の径に対して十分低く広角で光学系の全長が短くかつ解
像力の良い内視鏡用対物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 provides an objective optical system for an endoscope in which the height of a light beam incident on the filter is sufficiently small with respect to the diameter of the filter, the angle is wide, the total length of the optical system is short, and the resolution is good. The purpose is to do so.
［課題を解決するための手段］ 本発明の対物光学系は、物体側より順に負レズと、明
るさ絞りと、少なくとも一つの正のレンズ群とよりな
り、前記の明るさ絞りの直前に赤外カットフィルター，
レーザー光を遮断するためのフィルターのいずれかを配
置し又明るさ絞りの直後の正のレンズ群よりも後方に他
の一枚のフィルターを配置したもので、次の条件
（１），（２）を満足するようにした。[Means for Solving the Problems] The objective optical system according to the present invention comprises a negative lens, a brightness stop, and at least one positive lens group in order from the object side, and a red lens immediately before the brightness stop. Outside cut filter,
One of filters for blocking laser light is arranged, and another filter is arranged behind the positive lens group immediately after the aperture stop. The following conditions (1) and (2) ).
（１）0.5＜｜f1/f|＜2.0 （２）I/f2＜0.64 ただし、ｆは光学系全系の焦点距離、f1は負レンズの
焦点距離、f2は明るさ絞りより後方の正のレンズ群の合
成焦点距離、Ｉは最大像高である。(1) 0.5 <| f 1 /f|<2.0 (2) I / f 2 <0.64 where f is the focal length of the entire optical system, f 1 is the focal length of the negative lens, and f 2 is from the aperture stop. The composite focal length of the rear positive lens unit, I, is the maximum image height.
本発明の内視鏡用光学系は、以上のような構成にする
ことによってレンズ系の全長が短くフィルターに入射す
る光線高を低くおさえ、高い解像力を得るようにした。The optical system for an endoscope according to the present invention has a configuration as described above, whereby the total length of the lens system is short, the height of light rays incident on the filter is kept low, and a high resolution is obtained.
条件（１）は、明るさ絞りの直前にフィルターを配置
するスペースを設け、全長を規定するためのものであ
る。The condition (1) is to provide a space for disposing a filter immediately before the aperture stop and to define the overall length.
｜f1/f|が条件（１）の下限以下になると負のレンズ
群と正のレンズ群の間隔が短くなり、明るさ絞りの直前
にフィルターを設けることが困難になる。又｜f1/f|が
条件（１）の上限以上になると、負のレンズ群と正のレ
ンズ群の間隔が大になりすぎて、レンズ系の全長も長く
なるため好ましくない。したがってフィルターを光学系
中に設けしかも光学系の全長を短くするためにはこの条
件（１）を満足することが望ましい。When | f 1 / f | is equal to or less than the lower limit of the condition (1), the interval between the negative lens unit and the positive lens unit becomes short, and it becomes difficult to provide a filter immediately before the aperture stop. When | f 1 / f | exceeds the upper limit of the condition (1), the distance between the negative lens unit and the positive lens unit becomes too large, and the overall length of the lens system becomes longer. Therefore, in order to provide the filter in the optical system and to shorten the overall length of the optical system, it is desirable to satisfy the condition (1).
条件（２）は、明るさ絞り直前に設けたフィルターに
入射する軸外主光線の入射角を制限するための条件であ
る。通常干渉型の赤外カットフィルターは、光線の入射
角が40°以上になると赤外域の透過率が急激に高くなり
赤外域の光を遮断することが出来なくなる。又吸収型の
フィルターの場合も、光線の入射角が大になると、像高
の違いにより硝路に差が生じ画面上での色むらの原因に
なる。そのため干渉型，吸収型のいずれのタイプのフィ
ルターを用いる場合でも、フィルターへの入射角を小さ
くする必要がある。The condition (2) is a condition for limiting the incident angle of the off-axis chief ray incident on the filter provided immediately before the aperture stop. When the incident angle of a light beam becomes 40 ° or more, the transmittance of the infrared region of the ordinary interference type infrared cut filter rapidly increases, and it becomes impossible to block the infrared region light. Also, in the case of the absorption type filter, when the incident angle of the light beam is large, the difference in the image height causes a difference in the glass path, which causes color unevenness on the screen. Therefore, it is necessary to reduce the angle of incidence on the filter regardless of whether the filter is of the interference type or the absorption type.
条件（２）において、I/f2の値が、この条件の上限以
上になるとフィルターへの入射角が大きくなり、前記の
ような問題が生じ好ましくない。したがってフィルター
への入射角を小さくするためには、条件（２）を満足す
ることが望ましい。In the condition (2), when the value of I / f 2 is equal to or more than the upper limit of the condition, the incident angle to the filter increases, and the above-described problem occurs, which is not preferable. Therefore, in order to reduce the angle of incidence on the filter, it is desirable to satisfy condition (2).
［実施例］ 次に本発明の内視鏡用光学系の各実施例を示す。Examples Next, examples of the optical system for an endoscope according to the present invention will be described.
実施例１ ｆ＝1,F/6.065,2ω＝96° r1＝∞ d1＝0.4484 n1＝1.51633 ν1＝64.15 r2＝0.6543 d2＝0.3906 r3＝∞ d3＝0.9268 n2＝1.51633 ν2＝64.15 r4＝∞（絞り） d4＝0.1504 r5＝−2.5940 d5＝0.7961 n3＝1.88300 ν3＝40.78 r6＝−1.3698 d6＝0.1495 r7＝2.8985 d7＝0.5105 n4＝1.84666 ν4＝23.78 r8＝1.2075 d8＝1.3163 n5＝1.58913 ν5＝60.97 r9＝−1.9538 d9＝0.1495 r10＝∞ d10＝0.5232 n6＝1.51633 ν6＝64.15 r11＝∞ d11＝0.4683 r12＝∞ d12＝1.4948 n7＝1.51633 ν7＝64.15 r13＝∞ ｜f1/f|＝1.267,I/f2＝0.516,D/f＝1.949 第１フィルター入射角25.3° 実施例２ ｆ＝1,F/5.526,2ω＝120° r1＝∞ d1＝0.5223 n1＝1.51633 ν1＝64.15 r2＝0.6521 d2＝0.4311 r3＝∞ d3＝1.0793 n2＝1.51633 ν2＝64.15 r4＝∞（絞り） d4＝0.1871 r5＝−2.8407 d5＝0.9761 n3＝1.88300 ν3＝40.78 r6＝−1.7120 d6＝0.1742 r7＝2.7683 d7＝0.5818 n4＝1.84666 ν4＝23.78 r8＝1.2503 d8＝1.5320 n5＝1.58913 ν5＝60.97 r9＝−1.9698 d9＝0.1741 r10＝∞ d10＝0.6093 n6＝1.51633 ν6＝64.15 r11＝∞ d11＝0.5223 r12＝∞ d12＝1.7409 n7＝1.51633 ν7＝64.15 r13＝∞ ｜f1/f|＝1.263,I/f2＝0.533,D/f＝2.246 第１フィルター入射角28.4° 実施例３ ｆ＝1,f/3.899,2ω＝101° r1＝∞ d1＝0.4664 n1＝1.88300 ν1＝40.78 r2＝0.7372 d2＝0.5416 r3＝∞ d3＝0.6018 n2＝1.52287 ν2＝59.89 r4＝∞（絞り） d4＝0.1505 r5＝16.9033 d5＝0.8726 n3＝1.72916 ν3＝54.68 r6＝−1.3616 d6＝0.1505 r7＝∞ d7＝0.9328 n4＝1.52000 ν4＝74.00 r8＝∞ d8＝0.5567 r9＝2.3531 d9＝1.1886 n5＝1.60311 ν5＝60.70 r10＝−1.4142 d10＝0.3159 n6＝1.84666 ν6＝23.78 r11＝−4.8145 d11＝0.4514 r12＝∞ d12＝1.5045 n7＝1.51633 ν7＝64.15 r13＝∞ ｜f1/f|＝0.835,I/f2＝0.475 f21／f2＝1.067,f22／f2＝2.365 第１フィルター入射角21.7° 実施例４ ｆ＝1,F/3.870,2ω＝120° r1＝∞ d1＝0.5072 n1＝1.88300 ν1＝40.78 r2＝0.6938 d2＝0.6135 r3＝∞ d3＝0.6763 n2＝1.52287 ν2＝59.89 r4＝∞（絞り） d4＝0.1655 r5＝5.1647 d5＝0.9875 n3＝1.72916 ν3＝54.68 r6＝−1.8356 d6＝0.1836 r7＝∞ d7＝1.0482 n4＝1.52000 ν4＝74.00 r8＝∞ d8＝0.6401 r9＝2.2962 d9＝1.3483 n5＝1.60311 ν5＝60.70 r10＝−1.3264 d10＝0.4923 n6＝1.84666 ν6＝23.78 r11＝−4.0870 d11＝0.5072 r12＝∞ d12＝1.6907 n7＝1.51633 ν7＝64.15 r13＝∞ ｜f1/f|＝0.786,I/f2＝0.447 f21／f2＝0.999,f22／f2＝1.844 第１フィルター入射角22.3° 実施例５ ｆ＝1,F/4.067,2ω＝120.2° r1＝16.8803（非球面） d1＝0.6472 n1＝1.51633 ν1＝64.15 r2＝0.8621 d2＝0.5965 r3＝∞ d3＝1.4574 n2＝1.51633 ν2＝64.15 r4＝∞（絞り） d4＝0.2687 r5＝−3.9741 d5＝1.1815 n3＝1.88300 ν3＝40.78 r6＝−2.0865 d6＝0.2127 r7＝3.6172 d7＝0.2687 n4＝1.84666 ν4＝23.78 r8＝1.5713 d8＝1.7548 n5＝1.58913 ν5＝60.97 r9＝−1.8576（非球面） d9＝0.1221 r10＝∞ d10＝0.7327 n6＝1.51633 ν6＝64.15 r11＝∞ d11＝0.5129 r12＝∞ d12＝1.6486 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.88523×10-2 Ｆ＝0.92065×10-4 （第９面） Ｐ＝1.0000,B＝0,E＝0.28532×10-1 Ｆ＝−0.12887×10-2 ｜f1/f|＝1.784,I/f2＝0.606,D/f＝2.205 f2/f＝1.830,θ/0.64（rad）＝1.636 第１フィルター入射角33.8° 実施例６ ｆ＝1,F/3.890,2ω＝120° r1＝21.4252（非球面） d1＝0.6582 n1＝1.51633 ν1＝64.15 r2＝0.7634 d2＝0.5806 r3＝∞ d3＝1.3603 n2＝1.51633 ν2＝64.15 r4＝∞（絞り） d4＝0.2327 r5＝−1.8851 d5＝1.2486 n3＝1.88300 ν3＝40.78 r6＝−1.9074 d6＝0.1586 r7＝3.3202（非球面） d7＝0.3151 n4＝1.84666 ν4＝23.78 r8＝2.0796 d8＝1.7611 n5＝1.58913 ν5＝60.97 r9＝−2.2592 d9＝0.2194 r10＝∞ d10＝0.7679 n6＝1.51633 ν6＝64.15 r11＝∞ d11＝0.6582 r12＝∞ d12＝2.1426 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.22670×10-1 Ｆ＝−0.71077×10-3 （第７面） Ｐ＝1.0000,B＝0,E＝−0.20373×10-1 Ｆ＝0.15996×10-2 ｜f1/f|＝1.55,I/f2＝0.619,D/f＝2.797 f2/f＝1.849,θ/0.64（rad）＝1.636 第１フィルター入射角36.1° 実施例７ ｆ＝1,F/4.186,2ω＝117.40° r1＝12.9649（非球面） d1＝0.6251 n1＝1.51633 ν1＝64.15 r2＝0.7064 d2＝0.5202 r3＝∞ d3＝1.3014 n2＝1.51633 ν2＝64.15 r4＝∞（絞り） d4＝0.2287 r5＝−4.1941 d5＝1.1762 n3＝1.88300 ν3＝40.78 r6＝−1.8012（非球面） d6＝0.2733 r7＝3.3810 d7＝0.6662 n4＝1.84666 ν4＝23.78 r8＝1.4568 d8＝1.7429 n5＝1.58913 ν5＝60.97 r9＝−2.1536 d9＝0.2084 r10＝∞ d10＝0.5000 n6＝1.51633 ν6＝64.15 r11＝∞ d11＝0.4000 r12＝∞ d12＝1.4000 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.16198×10-1 Ｆ＝−0.13555×10-3 （第６面） Ｐ＝1.0000,B＝0,E＝0.18395×10-1 Ｆ＝−0.51972×10-2 ｜f1/f|＝1.472,I/f2＝0.574,D/f＝1.861 f2/f＝1.833,θ/0.64（rad）＝1.601 第１フィルター入射角32.7° 実施例８ ｆ＝1,F/3.946,2ω＝120° r1＝21.7083（非球面） d1＝0.6811 n1＝1.88300 ν1＝40.78 r2＝0.8528 d2＝0.8649 r3＝∞ d3＝0.9082 n2＝1.52287 ν2＝59.89 r4＝∞（絞り） d4＝0.1864 r5＝13.6166 d5＝1.3061 n3＝1.72916 ν3＝54.68 r6＝−2.5071 d6＝0.1074 r7＝∞ d7＝1.4076 n4＝1.52000 ν4＝74.00 r8＝∞ d8＝0.6826 r9＝2.8757 d9＝1.7932 n5＝1.60311 ν5＝60.70 r10＝−1.9781 d10＝0.5167 n6＝1.84666 ν6＝23.78 r11＝−3.3410（非球面） d11＝0.6811 r12＝∞ d12＝2.2705 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.32789×10-1 Ｆ＝−0.49161×10-2 （第11面） Ｐ＝1.0000,B＝0,E＝0.22862×10-1 Ｆ＝−0.22050×10-2 ｜f1/f|＝0.980,I/f2＝0.444 f21／f2＝1.125,f22／f2＝1.243 f2/f＝2.671,θ/0.64（rad）＝1.636 第１フィルター入射角26.6° 実施例９ ｆ＝1,F/4.042,2ω＝120° r1＝60.9504（非球面） d1＝0.7005 n1＝1.88300 ν1＝40.78 r2＝0.9640 d2＝0.8875 r3＝∞ d3＝0.8929 n2＝1.52287 ν2＝59.89 r4＝∞（絞り） d4＝0.2273 r5＝19.0928 d5＝1.3545 n3＝1.72916 ν3＝54.68 r6＝−2.4303 d6＝0.0962 r7＝∞ d7＝1.3736 n4＝1.52000 ν4＝74.00 r8＝∞ d8＝0.3336 r9＝2.8398（非球面） d9＝1.5085 n5＝1.60311 ν5＝60.70 r10＝−1.6896 d10＝0.4377 n6＝1.84666 ν6＝23.78 r11＝−3.2673 d11＝0.7074 r12＝∞ d12＝2.2115 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.39178×10-1 Ｆ＝−0.57259×10-2 （第９面） Ｐ＝1.0000,B＝0,E＝−0.25386×10-1 Ｆ＝0.42102×10-2 ｜f1/f|＝1.115,I/f2＝0.520 f21／f2＝1.303,f22／f2＝1.503 f2/f＝2.230,θ/0.64（rad）＝1.636 第１フィルター入射角29.5° 実施例10 ｆ＝1,F/4.251,2ω＝120° r1＝7.0860（非球面） d1＝0.6742 n1＝1.88300 ν1＝40.78 r2＝0.7395 d2＝0.8285 r3＝∞ d3＝0.8699 n2＝1.52287 ν2＝59.89 r4＝∞（絞り） d4＝0.2611 r5＝−29.5060 d5＝1.3439 n3＝1.72916 ν3＝54.68 r6＝−1.7847（非球面） d6＝0.1810 r7＝∞ d7＝1.3484 n4＝1.52000 ν4＝74.00 r8＝∞ d8＝0.7682 r9＝3.8053 d9＝1.6352 n5＝1.60311 ν5＝60.70 r10＝−1.6747 d10＝0.3262 n6＝1.84666 ν6＝23.78 r11＝−3.2953 d11＝0.5655 r12＝∞ d12＝2.1748 n7＝1.51633 ν7＝64.15 r13＝∞ 非球面係数 （第１面） Ｐ＝1.0000,B＝0,E＝0.24264×10-1 Ｆ＝−0.83617×10-3 （第６面） Ｐ＝1.0000,B＝0,E＝0.14631×10-1 Ｆ＝−0.72865×10-2 ｜f1/f|＝0.984,I/f2＝0.456 f21／f2＝1.026,f22／f2＝1.605 f2/f＝2.489,θ/0.64（rad）＝1.636 第１フィルター入射角28.2° ただし、r1，r2，…はレンズ各面の曲率半径、d1，
d2，…は各レンズの肉厚および空気間隔、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。Example 1 f = 1, F / 6.065, 2ω = 96 ° r 1 = ∞ d 1 = 0.4484 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.6543 d 2 = 0.3906 r 3 = ∞ d 3 = 0.9268 n 2 = 1.51633 ν 2 = 64.15 r 4 = ∞ (aperture) d 4 = 0.1504 r 5 = -2.5940 d 5 = 0.7961 n 3 = 1.88300 ν 3 = 40.78 r 6 = -1.33698 d 6 = 0.1495 r 7 = 2.9885 d 7 = 0.5105 n 4 = 1.84666 v 4 = 23.78 r 8 = 1.2075 d 8 = 1.3163 n 5 = 1.58913 v 5 = 60.97 r 9 = −1.9538 d 9 = 0.1495 r 10 = ∞ d 10 = 0.5232 n 6 = 1.51633 v 6 = 64.15 r 11 = ∞ d 11 = 0.4683 r 12 = ∞ d 12 = 1.4948 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ | f 1 / f | = 1.267, I / f 2 = 0.516, D / f = 1.949 First Filter incident angle 25.3 ° Example 2 f = 1, F / 5.526, 2ω = 120 ° r 1 = ∞ d 1 = 0.5223 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.6521 d 2 = 0.4311 r 3 = ∞ d 3 = 1.0793 n 2 = 1.51633 ν 2 = 64.15 r 4 = ∞ ( stop) d 4 = 0.1871 r 5 = -2.8407 d 5 = 0.9761 n 3 = 1.88300 ν 3 = 40.78 r 6 = -1.7120 d 6 = 0.1742 r 7 = 2.768 3 d 7 = 0.5818 n 4 = 1.84666 ν 4 = 23.78 r 8 = 1.2503 d 8 = 1.5320 n 5 = 1.58913 ν 5 = 60.97 r 9 = -1.99698 d 9 = 0.1741 r 10 = ∞ d 10 = 0.6093 n 6 = 1.51633 ν 6 = 64.15 r 11 = ∞ d 11 = 0.5223 r 12 = ∞ d 12 = 1.7409 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ | f 1 /f|=1.263,I/f 2 = 0.533, D / f = 2.246 First filter incident angle 28.4 ° Example 3 f = 1, f / 3.899, 2ω = 101 ° r 1 = ∞ d 1 = 0.4664 n 1 = 1.88300 ν 1 = 40.78 r 2 = 0.7372 d 2 = 0.5416 r 3 = ∞ d 3 = 0.6018 n 2 = 1.52287 ν 2 = 59.89 r 4 = ∞ (aperture) d 4 = 0.1505 r 5 = 16.9033 d 5 = 0.8726 n 3 = 1.7916 ν 3 = 54.68 r 6 = -1.3616 d 6 = 0.1505 r 7 = ∞ d 7 = 0.9328 n 4 = 1.52000 ν 4 = 74.00 r 8 = ∞ d 8 = 0.5567 r 9 = 2.3531 d 9 = 1.1886 n 5 = 1.60311 ν 5 = 60.70 r 10 = -1.4142 d 10 = 0.3159 n 6 = 1.84666 v 6 = 23.78 r 11 = −4.8145 d 11 = 0.4514 r 12 = ∞ d 12 = 1.5045 n 7 = 1.51633 v 7 = 64.15 r 13 = ∞ | f 1 /f|=0.835,I/f 2 = 0.4 75 f 21 / f 2 = 1.067 , f 22 / f 2 = 2.365 The first filter incident angle 21.7 ° Example 4 f = 1, F / 3.870,2ω = 120 ° r 1 = ∞ d 1 = 0.5072 n 1 = 1.88300 ν 1 = 40.78 r 2 = 0.6938 d 2 = 0.6135 r 3 = ∞ d 3 = 0.6763 n 2 = 1.52287 ν 2 = 59.89 r 4 = ∞ (aperture) d 4 = 0.1655 r 5 = 5.1647 d 5 = 0.9875 n 3 = 1.72916 ν 3 = 54.68 r 6 = -1.8356 d 6 = 0.1836 r 7 = ∞ d 7 = 1.0482 n 4 = 1.52000 ν 4 = 74.00 r 8 = ∞ d 8 = 0.6401 r 9 = 2.2962 d 9 = 1.3483 n 5 = 1.60311 ν 5 = 60.70 r 10 = -1.3264 d 10 = 0.4923 n 6 = 1.84666 ν 6 = 23.78 r 11 = -4.0870 d 11 = 0.5072 r 12 = ∞ d 12 = 1.6907 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ | F 1 /f|=0.786, I / f 2 = 0.447 f 21 / f 2 = 0.999, f 22 / f 2 = 1.844 First filter incident angle 22.3 ° Example 5 f = 1, F / 4.067, 2ω = 120.2 ° r 1 = 16.8803 (aspherical) d 1 = 0.6472 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.8621 d 2 = 0.5965 r 3 = ∞ d 3 = 1.4574 n 2 = 1.51633 ν 2 = 64.15 r 4 ∞ (stop) d 4 = 0.2687 r 5 = -3.9741 d 5 = 1.1815 n 3 = 1.88300 ν 3 = 40.78 r 6 = -2.0865 d 6 = 0.2127 r 7 = 3.6172 d 7 = 0.2687 n 4 = 1.84666 ν 4 = 23.78 r 8 = 1.5713 d 8 = 1.7548 n 5 = 1.58913 ν 5 = 60.97 r 9 = −1.8576 (aspherical surface) d 9 = 0.1221 r 10 = ∞ d 10 = 0.7327 n 6 = 1.51633 ν 6 = 64.15 r 11 = ∞ d 11 = 0.5129 r 12 = ∞ d 12 = 1.6486 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ aspherical coefficients (first surface) P = 1.0000, B = 0 , E = 0.88523 × 10 -2 F = 0.92065 × 10 -4 (9th surface) P = 1.0000, B = 0, E = 0.28532 × 10 −1 F = −0.12887 × 10 −2 | f 1 /f|=1.784, I / f 2 = 0.606, D / f = 2.205 f 2 /f=1.830, θ / 0.64 (rad) = 1.636 First filter incident angle 33.8 ° Example 6 f = 1, F / 3.890, 2ω = 120 ° r 1 = 21.4252 (aspherical surface) d 1 = 0.6582 n 1 = 1.51633 v 1 = 64.15 r 2 = 0.7634 d 2 = 0.5806 r 3 = ∞ d 3 = 1.3603 n 2 = 1.51633 v 2 = 64.15 r 4 = ∞ (aperture) d 4 = 0.2327 r 5 = -1.8851 d 5 = 1.2486 n 3 = 1.88 300 ν 3 = 40.78 r 6 = -1.9074 d 6 = 0.1586 r 7 = 3.3202 (aspheric surface) d 7 = 0.3151 n 4 = 1.84666 ν 4 = 23.78 r 8 = 2.0796 d 8 = 1.7611 n 5 = 1.58913 ν 5 = 60.97 r 9 = -2.2592 d 9 = 0.2194 r 10 = ∞ d 10 = 0.7679 n 6 = 1.51633 ν 6 = 64.15 r 11 = ∞ d 11 = 0.6582 r 12 = ∞ d 12 = 2.1426 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ Aspherical surface coefficient (first surface) P = 1.0000, B = 0, E = 0.22670 × 10 −1 F = −0.71077 × 10 −3 (seventh surface) P = 1.0000, B = 0, E = − 0.20373 × 10 −1 F = 0.15996 × 10 −2 | f 1 /f|=1.55, I / f 2 = 0.609, D / f = 2.797 f 2 /f=1.949, θ / 0.64 (rad) = 1.636 First Filter incident angle 36.1 ° Example 7 f = 1, F / 4.186, 2ω = 117.40 ° r 1 = 12.9649 (aspherical surface) d 1 = 0.6251 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.7064 d 2 = 0.5202 r 3 = ∞ d 3 = 1.3014 n 2 = 1.51633 ν 2 = 64.15 r 4 = ∞ ( stop) d 4 = 0.2287 r 5 = -4.1941 d 5 = 1.1762 n 3 = 1.88300 ν 3 = 40.78 r 6 = -1.8012 ( aspherical ) d 6 = 0.2733 r 7 = 3.3810 d 7 = 0.6662 n 4 = 1.84666 ν 4 = 23.78 r 8 = 1.4568 d 8 = 1.7429 n 5 = 1.58913 ν 5 = 60.97 r 9 = -2.1536 d 9 = 0.2084 r 10 = ∞ d 10 = 0.5000 n 6 = 1.51633 ν 6 = 64.15 r 11 = ∞ d 11 = 0.4000 r 12 = ∞ d 12 = 1.4000 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ Aspheric coefficient (first surface) P = 1.0000, B = 0, E = 0.16198 × 10 −1 F = −0.13555 × 10 −3 (Sixth surface) P = 1.0000, B = 0, E = 0.18395 × 10 −1 F = −0.51972 × 10 −2 | f 1 /f|=1.472 , I / f 2 = 0.574, D / f = 1.861 f 2 /f=1.833, θ / 0.64 (rad) = 1.601 First filter incident angle 32.7 ° Example 8 f = 1, F / 3.946, 2ω = 120 ° r 1 = 21.7083 (aspherical surface) d 1 = 0.6811 n 1 = 1.88300 ν 1 = 40.78 r 2 = 0.8528 d 2 = 0.8649 r 3 = ∞ d 3 = 0.9082 n 2 = 1.52287 ν 2 = 59.89 r 4 = ∞ ) D 4 = 0.1864 r 5 = 13.6166 d 5 = 1.3061 n 3 = 1.72916 ν 3 = 54.68 r 6 = −2.5071 d 6 = 0.1074 r 7 = ∞ d 7 = 1.4076 n 4 = 1.52000 ν 4 = 74.00 r 8 = ∞ d 8 = 0.6826 r 9 = 2.875 7 d 9 = 1.7932 n 5 = 1.60311 ν 5 = 60.70 r 10 = -1.9781 d 10 = 0.5167 n 6 = 1.84666 ν 6 = 23.78 r 11 = -3.3410 (aspherical surface) d 11 = 0.6811 r 12 = ∞d 12 = 2.2705 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ Aspheric coefficient (first surface) P = 1.0000, B = 0, E = 0.32789 × 10 −1 F = −0.49161 × 10 −2 (11th surface) P = 1.0000, B = 0, E = 0.22862 × 10 -1 F = -0.22050 × 10 -2 | f 1 /f|=0.980,I/f 2 = 0.444 f 21 / f 2 = 1.125, f 22 / f 2 = 1.243 f 2 /f=2.671, θ / 0.64 (rad) = 1.636 First filter incident angle 26.6 ° Example 9 f = 1, F / 4.042, 2ω = 120 ° r 1 = 60.9504 (aspherical surface) d 1 = 0.7005 n 1 = 1.88300 v 1 = 40.78 r 2 = 0.9640 d 2 = 0.8875 r 3 = ∞ d 3 = 0.8929 n 2 = 1.52287 ν 2 = 59.89 r 4 = ∞ (aperture) d 4 = 0.2273 r 5 = 19.0928 d 5 = 1.3545 n 3 = 1.72916 ν 3 = 54.68 r 6 = −2.4303 d 6 = 0.0962 r 7 = ∞ d 7 = 1.3736 n 4 = 1.52000 ν 4 = 74.00 r 8 = ∞ d 8 = 0.3336 r 9 = 2.8398 (aspherical surface) ) D 9 = 1.5085 n 5 = 1. 60311 ν 5 = 60.70 r 10 = -1.6896 d 10 = 0.4377 n 6 = 1.84666 ν 6 = 23.78 r 11 = -3.2673 d 11 = 0.7074 r 12 = ∞ d 12 = 2.2115 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ Aspheric coefficient (first surface) P = 1.0000, B = 0, E = 0.39178 × 10 −1 F = −0.57259 × 10 −2 (9th surface) P = 1.0000, B = 0, E = −0.25386 × 10 -1 F = 0.42102 × 10 -2 | f 1 /f|=1.115,I/f 2 = 0.520 f 21 / f 2 = 1.303, f 22 / f 2 = 1.503 f 2 /f=2.230,θ/0.64 (Rad) = 1.636 First filter incident angle 29.5 ° Example 10 f = 1, F / 4.251, 2ω = 120 ° r 1 = 7.0860 (aspherical surface) d 1 = 0.6742 n 1 = 1.88300 ν 1 = 40.78 r 2 = 0.7395 d 2 = 0.8285 r 3 = ∞ d 3 = 0.8699 n 2 = 1.52287 ν 2 = 59.89 r 4 = ∞ ( stop) d 4 = 0.2611 r 5 = -29.5060 d 5 = 1.3439 n 3 = 1.72916 ν 3 = 54.68 r 6 = -1.7847 (aspherical) d 6 = 0.1810 r 7 = ∞ d 7 = 1.3484 n 4 = 1.52000 ν 4 = 74.00 r 8 = ∞ d 8 = 0.7682 r 9 = 3.8053 d 9 = 1.6352 n 5 = 1.60311 ν 5 = 60.70 r 10 = -1.6747 d 10 = 0.3262 n 6 = 1.84666 ν 6 = 23.78 r 11 = -3.2953 d 11 = 0.5655 r 12 = ∞ d 12 = 2.1748 n 7 = 1.51633 ν 7 = 64.15 r 13 = ∞ aspherical coefficients (first surface) P = 1.0000, B = 0, E = 0.24264 × 10 -1 F = -0.83617 × 10 -3 (Sixth surface) P = 1.0000, B = 0, E = 0.14631 × 10 -1 F = -0.72865 × 10 -2 | F 1 /f|=0.984, I / f 2 = 0.456 f 21 / f 2 = 1.026, f 22 / f 2 = 1.605 f 2 /f=1.489, θ / 0.64 (rad) = 1.636 First filter incident angle 28.2 ° where r 1 , r 2 , ... are the radii of curvature of the respective surfaces of the lens, d 1 ,
d 2, ... is the thickness and air space of the lens, n 1, n 2, ... is the refractive index of each lens, ν 1, ν 2, ... is the Abbe number of each lens.
実施例1,2は、夫々第１図，第２図に示す構成で、明
るさ絞り直前に吸収型の赤外カットフィルターをおき、
レーザー光を遮断するための干渉型のフィルターを接合
レンズの後ろに配置したものである。これらの実施例
は、条件（１），（２）のほかに更に次の条件（３）を
満足するものである。Embodiments 1 and 2 have the configurations shown in FIGS. 1 and 2, respectively, and have an absorption type infrared cut filter placed immediately before the aperture stop.
An interference filter for blocking laser light is arranged behind the cemented lens. These embodiments satisfy the following condition (3) in addition to the conditions (1) and (2).
（３）1.5＜D/f＜3.0 ただしＤは接合レンズの最終面から固体撮像素子まで
の空気換算長、ｆは光学系の焦点距離である。(3) 1.5 <D / f <3.0 where D is the air-equivalent length from the final surface of the cemented lens to the solid-state imaging device, and f is the focal length of the optical system.
この条件（３）は、接合レンズの後ろにフィルターを
配置するための間隔を規定したもので、レンズ系の全長
を短く保った状態でD/fの値が条件（３）の下限以下に
なるとフィルターを置くのに十分な間隔がとれなくな
り、各面のパワーが強くなって収差補正が困難になる。
D/fの値が条件（３）の上限以上になると、レンズと固
体撮像素子との間の間隔が長くなりすぎ、レンズ系の全
長も長くなり好ましくない。The condition (3) defines an interval for disposing a filter behind the cemented lens, and when the value of D / f falls below the lower limit of the condition (3) while keeping the overall length of the lens system short. Sufficient spacing is not provided for placing the filter, and the power of each surface is increased, making it difficult to correct aberrations.
If the value of D / f exceeds the upper limit of the condition (3), the distance between the lens and the solid-state imaging device becomes too long, and the overall length of the lens system becomes undesirably long.
これら実施例1,2は、条件（１）〜（３）を満足する
もので、そのうち実施例１はフィルターに入射する軸外
主光線の入射角が前方のフィルターで25.3°、後方のフ
ィルターで5.6°になっており、又吸収型赤外カットフ
ィルター面上での軸外主光線の高さは、固体撮像素子面
上での像高を１とすると、約0.35の高さである。又実施
例２は、フィルターに入射する軸外主光線の入射角が、
前方のフィルターで28.4°、後方のフィルターで2.5°
で、赤外カットフィルターでの軸外主光線の高さは、固
体撮像素子面上での像高を１として約0.4である。The first and second embodiments satisfy the conditions (1) to (3). In the first embodiment, the incident angle of the off-axis chief ray incident on the filter is 25.3 ° in the front filter and is in the rear filter. It is 5.6 °, and the height of the off-axis principal ray on the surface of the absorption type infrared cut filter is about 0.35 when the image height on the surface of the solid-state imaging device is 1. In the second embodiment, the incident angle of the off-axis chief ray incident on the filter is
28.4 ° in front filter, 2.5 ° in rear filter
The height of the off-axis chief ray in the infrared cut filter is about 0.4, where the image height on the solid-state imaging device surface is 1.
以上のようにこれら実施例は、各条件を満足すること
により全長が短く、フィルターへの入射角が小で光線高
を低く出来、収差が良好に補正されている。As described above, in these examples, the overall length is short by satisfying each condition, the incident angle to the filter is small, the ray height can be reduced, and the aberration is satisfactorily corrected.
実施例3,4は、第３図，第４図に示す構成で、明るさ
絞りの直前に干渉型のレーザー光遮断フィルターを置
き、吸収型赤外カットフィルターを正レンズと接合レン
ズとの間に配置してある。Embodiments 3 and 4 have the configuration shown in FIGS. 3 and 4, in which an interference type laser beam cutoff filter is placed immediately before the aperture stop, and an absorption type infrared cut filter is provided between the positive lens and the cemented lens. It is located in.
この実施例は、条件（１），（２）を満足し更に次の
条件（４），（５）を満足している。This embodiment satisfies the conditions (1) and (2) and further satisfies the following conditions (4) and (5).
（４）0.5＜f21／f2＜2.0 （５）0.5＜f22／f2＜3.0 ただしf21は絞り直後の正レンズの焦点距離、f22は赤
外カットフィルター直後の接合レンズの焦点距離であ
る。(4) 0.5 <focus of f 21 / f 2 <2.0 ( 5) 0.5 <f 22 / f 2 <3.0 , however f 21 is squeezed focal length of the positive lens immediately, f 22 is an infrared cut filter immediately after the cemented lens Distance.
条件（４）は、絞りより後方のフィルターや接合レン
ズへ入射する光の光線高を低くするための条件で、この
条件（４）とともに条件（５）を満足せしめることによ
って絞り直後の正レンズと接合レンズの間にフィルター
を配置する際の二つのレンズ群の間隔が規定される。The condition (4) is a condition for lowering the ray height of light incident on a filter or a cemented lens behind the stop, and by satisfying the condition (5) together with the condition (4), the positive lens immediately after the stop is The distance between the two lens groups when the filter is arranged between the cemented lenses is defined.
条件（４）においてf21／f2が条件の上限をこえる
と、後方のフィルターや接合レンズへ入射する光線の光
線高が高くなり、レンズの外径を大にしなければならな
くなり、内視鏡用光学系としては好ましくない。又接合
レンズでの光線高が高くなりコマ収差の補正が困難にな
る。f21／f2がこの条件の下限以下になると絞り直後の
凸レンズのパワーが強くなりすぎ、球面収差が発生して
しまう。If f 21 / f 2 exceeds the upper limit of the condition (4), the height of light rays incident on the rear filter and the cemented lens increases, and the outer diameter of the lens must be increased. It is not preferable as an optical system for use. Also, the ray height at the cemented lens increases, making it difficult to correct coma. If f 21 / f 2 is lower than the lower limit of this condition, the power of the convex lens immediately after the stop becomes too strong, and spherical aberration occurs.
以上のように後方に配置されるフィルターや、接合レ
ンズへの入射光線の高を低くおさえてレンズ系の全長を
短くするためには、条件（４），（５）を満足すること
が望ましい。As described above, it is desirable to satisfy the conditions (4) and (5) in order to keep the height of the light beam incident on the filter disposed at the rear or the cemented lens low and shorten the overall length of the lens system.
実施例3,4は、条件（１），（２），（４），（５）
を満足するもので、そのうち実施例３は、フィルターへ
入射する軸外主光線の入射角が前方に配置されたフィル
ターで21.7°、後方に配置されたフィルターで13.7°で
あり、赤外カットフィルター面上での軸外主光線の光線
高は、固体撮像素子面上での像高を１とすると約0.55の
高さである。In Examples 3 and 4, conditions (1), (2), (4), and (5)
In Example 3, the incident angle of the off-axis chief ray incident on the filter was 21.7 ° in the filter disposed in the front, 13.7 ° in the filter disposed in the rear, and the infrared cut filter The ray height of the off-axis principal ray on the surface is about 0.55 when the image height on the surface of the solid-state image sensor is 1.
実施例４は、フィルターに入射する軸外主光線の入射
角が前方のフィルターで22.3°、後方のフィルターで1
4.9°で、赤外カットフィルター面上での軸外主光線の
光線高が、固体撮像素子面上での像高に対して約0.6の
高さである。In Example 4, the incident angle of the off-axis chief ray incident on the filter was 22.3 ° in the front filter and 1 in the rear filter.
At 4.9 °, the height of the off-axis chief ray on the infrared cut filter surface is about 0.6 with respect to the image height on the solid-state imaging device surface.
以上のように条件（１），（２），（４），（５）を
満足するようにしてレンズ系の全長が短くフィルターへ
の入射角が小で光線高が低く、収差が良好な光学系にす
ることが出来る。As described above, by satisfying the conditions (1), (2), (4), and (5), the optical system has a short overall length of the lens system, a small incident angle to the filter, a low ray height, and a good aberration. Can be a system.
実施例5,6,7は、実施例1,2と同様のレンズタイプであ
って、非球面を２面設けたものである。Embodiments 5, 6, and 7 are the same lens types as those in Embodiments 1 and 2, and have two aspheric surfaces.
又、実施例8,9,10は、実施例3,4と同じレンズタイプ
であって、非球面を２面設けたものである。Further, Examples 8, 9, and 10 are the same lens type as Examples 3 and 4, and have two aspherical surfaces.
以上述べた実施例１〜４は、球面レンズのみからなる
もので、このような構成の内視鏡用対物レンズは、第22
図のように、明るさ絞りＳよりも物体側に位置するレン
ズL1（負レンズ）に入射する主光線Ｐの光軸に対する傾
きθと、レンズL1から出射して明るさ絞りＳより像側に
位置するレンズL2（少なくとも一つの正レンズ群からな
る）に入射する前記主光線Ｐの光軸に対する傾きθ′と
を比較した時、θに対してθ′がかなり小さいことがわ
かる。これは、レンズL1が視野角を広げる負の屈折作用
を持っていることからも明らかである。Embodiments 1 to 4 described above consist only of a spherical lens.
As shown in the figure, the inclination θ of the principal ray P incident on the lens L 1 (negative lens) located on the object side of the aperture stop S with respect to the optical axis, and the light emitted from the lens L 1 and imaged from the aperture stop S Comparing the inclination θ ′ of the principal ray P incident on the lens L 2 (comprising at least one positive lens group) located on the side with respect to the optical axis, it can be seen that θ ′ is considerably smaller than θ. This is evidenced by the lens L 1 has a negative refracting action widening the viewing angle.
このような特徴をもつレンズ系において、θ′が小さ
いことと収差との間には次のような関係があることが一
般に知られている。つまりザイデルの収差でみると、被
写体に対して、像面湾曲，非点収差，歪曲収差は発生量
が少なく、球面収差，コマ収差は比較的大きい。この関
係は第23図に示す通りである。したがって、正の屈折力
を有するレンズL2は、レンズL1との間の瞳を被写体とし
ての球面収差とコマ収差が補正されていればよく、それ
を満足する条件として正弦条件が知られている。正弦条
件は、第22図において、像高をＩ、レンズL2の合成焦点
距離をf2、レンズL2へ入射する主光線Ｐの光軸に対する
傾き角をθ′とすると、主光線Ｐが像面Ｉに垂直に入射
するテレセントリックな光学系の場合、次の式で表わす
ことが出来る。In a lens system having such characteristics, it is generally known that the following relationship exists between a small θ ′ and aberration. That is, in terms of Seidel's aberration, the amount of curvature of field, astigmatism, and distortion is small with respect to the subject, and the spherical aberration and coma are relatively large. This relationship is as shown in FIG. Therefore, the lens L 2 having a positive refractive power, it is sufficient that the spherical aberration and coma aberration of the pupil between the lenses L 1 as a subject is corrected, the sine condition is known as a condition for satisfying it I have. Sine condition, in FIG. 22, when the inclination angle theta 'relative to the optical axis of the principal ray P entering the image height I, a combined focal length of the lens L 2 f 2, the lens L 2, is the principal ray P In the case of a telecentric optical system that is perpendicularly incident on the image plane I, it can be expressed by the following equation.
Ｉ＝f2sinθ′ またレンズL1についても、第22図のように一般的な球
面レンズ１枚用いたとき、明るさ絞りより前側でも正弦
条件はあまりくずれてはいない。したがって、全系の焦
点距離をｆ、レンズL1へ入射する主光線Ｐの光軸に対す
る傾きをθとすると次の式が成立つ。I = f 2 sin θ ′ Also, as for the lens L1, when one general spherical lens is used as shown in FIG. 22, the sine condition is not so shifted even before the aperture stop. Therefore, the focal length of the entire system f, when the inclination θ with respect to the optical axis of the principal ray P entering the lens L 1 have the following formula holds.
Ｉ＝fsinθ 現在用いられている内視鏡用対物レンズは、レンズの
外径やレンズ枚数の制約の上から上記正弦条件をほぼ満
足するものがほとんどである。I = fsinθ Most of the endoscope objective lenses currently used almost satisfy the above-mentioned sine condition due to restrictions on the outer diameter of the lens and the number of lenses.
上記正弦条件を満足すると、第23図に示すように歪曲
収差は、視野角θの増加に伴い急激に増加する傾向にあ
り、その関係は次の式で表わすことが出来る。When the above sine condition is satisfied, the distortion tends to increase rapidly with an increase in the viewing angle θ as shown in FIG. 23, and the relationship can be expressed by the following equation.
DT（θ）＝cosθ−１ ただしDTは、歪曲収差により変形した像の大きさを
ｙ、近軸計算による理想像の大きさをy0とすると次の式
で与えられる。DT (θ) = cosθ-1 except DT is the size of the image deformed by distortion y, is given by the expression When the next the size of the ideal image by paraxial calculation and y 0.
DT＝（ｙ−y0）／y0×100（％） 上記の正弦条件および歪曲収差DT（θ）とθの関係が
成立つとき、通常の内視鏡対物レンズの場合θの増加に
伴って負の歪曲収差（樽型の歪曲収差）が急激に増加す
る。DT = (y−y 0 ) / y 0 × 100 (%) When the above-mentioned sine condition and the relationship between the distortion DT (θ) and θ are satisfied, in the case of a normal endoscope objective lens, as θ increases, As a result, negative distortion (barrel-shaped distortion) sharply increases.
またＩ＝fsinθ型の対物レンズにおいて、θを変化さ
せた時のDT（θ）の値は次の通りである。In an I = fsinθ type objective lens, the value of DT (θ) when θ is changed is as follows.
視野角２θ 80° 100° 120°140° 歪曲収差DT（θ） −23 −36 −50 −66（％） 以上のように、従来の内視鏡対物レンズは、内視鏡対
物レンズとして不可欠である、広角で、テレセントリッ
ク系で、収差が良好に補正されていて、コンパクトであ
るという要件を満足するために正弦条件を満たしている
が、負の歪曲収差が大である。Viewing angle 2θ 80 ° 100 ° 120 ° 140 ° Distortion aberration DT (θ) -23 -36 -50 -66 (%) As described above, the conventional endoscope objective lens is indispensable as the endoscope objective lens. There is a wide angle, telecentric system, which satisfies the sine condition in order to satisfy the requirements of being well-corrected and compact, but has a large negative distortion.
歪曲収差が発生している内視鏡対物レンズは、中心の
像に比べて周辺の像が小さく、歪んでみえる。In an endoscope objective lens in which distortion has occurred, the peripheral image is smaller than the central image, and appears to be distorted.
そのため、このような歪曲収差を有する対物レンズを
例えば工業製品の検査に用いたときは、形状測定や解析
が正確に行なえず、又医療分野においては、同様の理由
から誤診につながるおそれがある。Therefore, when an objective lens having such distortion is used, for example, for inspection of industrial products, shape measurement and analysis cannot be performed accurately, and in the medical field, erroneous diagnosis may occur for the same reason.
又、歪曲収差の少ない、例えば第24図に示すような広
角なカメラレンズでは、次の式が成立つ。For a wide-angle camera lens having little distortion, for example, as shown in FIG. 24, the following equation is satisfied.
Ｉ＝ftanθ このタイプの対物レンズでは、θの値が大になるにつ
れてcos4θの割合で像面の光量が減少する。ところが従
来の内視鏡は負の歪曲収差が大であるために、中心から
周辺まで同じ大きさの物体を比較した場合、中心に対し
て、周辺の像は小さくなり、これが前記のcos4θの割合
いで明るさが減少するものと打消しあい、Ｉ＝fsinθの
場合、θが増加しても中心から周辺まで均一な明るさに
なる。I = ftan θ In this type of objective lens, as the value of θ increases, the amount of light on the image plane decreases at the rate of cos 4 θ. However, since the conventional endoscope has a large negative distortion, when comparing objects of the same size from the center to the periphery, the peripheral image is smaller than the center, which is the cos 4 θ. And the brightness decreases at the rate of I. In the case of I = fsinθ, the brightness becomes uniform from the center to the periphery even if θ increases.
したがって、正弦条件を満足する多くの内視鏡対物レ
ンズは、像の明るさが中心から周辺まで一様であると言
う優れた特徴を有している。しかし、歪曲収差を有する
ので好ましくなく、少なくともＩ＝fsinθ型の対物レン
ズの歪曲収差を、Ｉ＝ｆθ型の値まで小さくすることが
必要である。Therefore, many endoscope objective lenses that satisfy the sine condition have an excellent feature that the brightness of the image is uniform from the center to the periphery. However, it is not preferable because it has distortion, and it is necessary to reduce at least the distortion of the I = fsinθ type objective lens to the value of I = fθ type.
Ｉ＝ｓθ型の対物レンズにおいてθを変化させた時の
DT（θ）の値は次の通りである。When θ is changed in an I = sθ type objective lens,
The values of DT (θ) are as follows.
視野角２θ 80° 100° 120° 140° 歪曲収差DT（θ） −17％−27％−39.5％−55.5％ 実施例５〜10のように非球面を用いる目的は、これま
での実施例１〜４の目的に加えて、視野角が大きいにも
かかわらず、歪曲収差が実用上十分に除去されていて、
かつ像の明るさが中心から周辺までほぼ一様である内視
鏡光学系を提供するためである。Viewing angle 2θ 80 ° 100 ° 120 ° 140 ° Distortion aberration DT (θ) -17% -27% -39.5% -55.5% The purpose of using an aspherical surface as in Examples 5 to 10 is that of the first embodiment. In addition to the objectives of (1) to (4), despite the large viewing angle, distortion has been sufficiently removed for practical use.
This is also to provide an endoscope optical system in which the brightness of the image is substantially uniform from the center to the periphery.
このような目的を達成するために、これら実施例５〜
10は、第25図に示すような光学系において、これに非球
面を導入することによって、次の式（６），（７）を満
足するように構成した。In order to achieve such an object, these Examples 5 to
In the optical system shown in FIG. 25, an aspherical surface is introduced into the optical system as shown in FIG. 25 so as to satisfy the following expressions (6) and (7).
Ｉ＝f2sinθ2 （６） Ｉ＝ｆθ2 （７） 上記の式において式（６）は、球面収差，コマ収差等
を良好に補正するために必要な条件で、明るさ絞りより
後方の正の屈折力を有する正のレンズ群においてなりた
つものである。I = f 2 sin θ 2 (6) I = f θ 2 (7) In the above equation, the equation (6) is a condition necessary for favorably correcting spherical aberration, coma aberration, and the like. This is a positive lens group having a positive refractive power.
したがって明るさ絞りより後方のこれら正のレンズ群
では、θ2の増加に伴って歪曲収差の発生が考えられる
が、θ2は値が小さいので上記収差の発生は問題になら
ない。又式（６）が成立つ光学系では、θ2の増加に関
係なく像の中心から周辺まで明るさが均一になる。Thus in brightness these positive lens group of the rear of the stop, the occurrence of distortion with increasing theta 2 are considered, theta 2 is generated in the aberration because the value is small, no problem. In Matashiki (6) holds an optical system, the brightness is uniform from the center of no image associated with increased theta 2 to the periphery.
式（７）は、Ｉ＝ｆθ型の歪曲収差の少ない光学系に
関して成立つ。Equation (7) holds true for an I = fθ type optical system with little distortion.
実施例５〜10の対物レンズは、瞳位置Ｓより物体側の
負レンズにおいて、Ｉ＝fsinθ1を満足するタイプの従
来の光学系を、上記の明るさ絞りより後方の正のレンズ
群に関する正弦条件Ｉ＝f2sinθ2をくずすことなしに非
球面を用いることにより、Ｉ＝ｆθに変換して歪曲収差
を実用上問題ないレベルに除去すると共に中心から周辺
まで均一な明るさの像を得るようにしたものである。Sine the objective lens in Example 5-10, in the negative lens on the object side of the pupil position S, the conventional optical system of the type which satisfies I = fsinθ 1, regarding the positive lens group of the rear of the aperture stop of the By using an aspheric surface without disturbing the condition I = f 2 sin θ 2 , it is converted to I = fθ to remove distortion to a level that does not cause a practical problem and to obtain an image with uniform brightness from the center to the periphery. It is like that.
一般に非球面は次の式にて表わすことが出来る。 Generally, an aspheric surface can be represented by the following equation.
ここでx,yは光軸をｘ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ｘ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
わすパラメーター、B,E,F,G・・・は夫々２次,4次,6次,
8次・・・の非球面係数である。 Here, x and y are coordinate values obtained by taking the direction of the image in the positive direction with the optical axis as the x-axis and taking the y-axis in the direction orthogonal to the x-axis with the intersection of the plane and the optical axis as the origin. C is the optical axis. The reciprocal of the radius of curvature of the circle in contact with the aspherical surface in the vicinity, P is a parameter representing the shape of the aspherical surface, and B, E, F, G,.
This is the eighth-order aspheric coefficient.
Ｐ＝１でB,E,F,G,・・・がすべて０の場合は、上記式
は球面を表す。If P = 1 and B, E, F, G,... Are all 0, the above equation represents a spherical surface.
実施例５〜９は、条件（１），（２）を満足すると共
に更に次の条件（８）をも満足する。Examples 5 to 9 satisfy the conditions (1) and (2) and also satisfy the following condition (8).
（８）f2/f＞θ（rad）/0.64 尚θは内視鏡対物レンズの半画角である。(8) f 2 /f>θ(rad)/0.64 where θ is the half angle of view of the endoscope objective lens.
条件（８）は、非球面を光学系中に設け、歪曲収差を
補正した時に、明るさ絞りの直前に配置したフィルター
に入射する光線の角度を規定している。The condition (8) defines an angle of a light beam incident on a filter disposed immediately before the aperture stop when the aspherical surface is provided in the optical system and distortion is corrected.
条件（８）において、f2/fがθ/0.64以下になると絞
り直前のフィルターに入射する光線の入射角が大になり
好ましくない。In the condition (8), if f 2 / f is equal to or less than θ / 0.64, the incident angle of the light beam incident on the filter immediately before the stop becomes large, which is not preferable.
以上のように実施例５〜７は、条件（１），（２），
（３），（８）を、又実施例８〜10は条件（１），
（２），（４），（５），（８）を満足することによ
り、全長が短く、フィルターへの入射角が小さくしかも
歪曲収差が実用上十分に除去されており、明るさが中心
から周辺までほぼ一様な画像が得られる。As described above, in Examples 5 to 7, the conditions (1), (2),
(3) and (8), and Examples 8 to 10 are the conditions (1) and (8).
By satisfying (2), (4), (5), and (8), the overall length is short, the angle of incidence on the filter is small, distortion is sufficiently removed in practical use, and brightness is reduced from the center. An almost uniform image can be obtained up to the periphery.
［発明の効果］ 本発明の光学系は、レンズ系の全長が短く、フィルタ
ーに入射する光線高をフィルターの外径に比べて小さく
でき、かつ解像力の良い像の得られるものである。[Effects of the Invention] The optical system of the present invention has a short overall length of the lens system, can reduce the height of light rays incident on the filter as compared with the outer diameter of the filter, and can obtain an image with good resolution.
第１図乃至第10図は夫々本発明の内視鏡用対物光学系の
実施例１乃至実施例10の断面図、第11図乃至第20図は夫
々実施例１乃至実施例10の収差曲線図、第21図は従来の
内視鏡用対物光学系の断面図、第22図は内視鏡対物レン
ズにおける主光線の屈折状況を示す図、第23図は第22図
に示す対物レンズの主光線の傾き角と各収差量の関係の
概要を示す図、第24図は広角カメラレンズの１例を示す
断面図、第25図は実施例５〜10の光学系における主光線
の屈折状況を示す図である。1 to 10 are sectional views of Embodiments 1 to 10 of the objective optical system for an endoscope according to the present invention, and FIGS. 11 to 20 are aberration curves of Embodiments 1 to 10, respectively. FIG. 21, FIG. 21 is a cross-sectional view of a conventional endoscope objective optical system, FIG. 22 is a view showing a refraction state of a principal ray in an endoscope objective lens, and FIG. 23 is a view of the objective lens shown in FIG. FIG. 24 is a diagram showing an outline of the relationship between the tilt angle of the principal ray and each aberration amount, FIG. 24 is a cross-sectional view showing an example of a wide-angle camera lens, and FIG. 25 is a refraction state of the principal ray in the optical systems of Examples 5 to 10 FIG.
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) G02B 9/00 - 17/08 G02B 21/02 - 21/04 G02B 25/00 - 25/04 ──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. 6 , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04
Claims (1)
と、少なくとも一つの正のレンズ群とよりなり、前記明
るさ絞りの直前に赤外カットフィルター、レーザー光を
遮断するためのフィルターのいずれか１枚のフィルター
を配置し、明るさ絞りの直後の正のレンズ群より後ろに
他の１枚のフィルターを配置した光学系で、次の条件
（１）、（２）を満足する内視鏡用対物光学系。 （１）0.5＜｜f1/f|＜2.0 （２）I/f2＜0.64 ただし、ｆは光学系全体の焦点距離、f1は凹レンズの焦
点距離、f2は明るさ絞りより後方の正のレンズ群の合成
焦点距離、Ｉは最大像高である。1. An infrared cut filter or a filter for blocking a laser beam immediately before the aperture stop, comprising a concave lens, a brightness stop, and at least one positive lens group in order from the object side. Or an optical system in which one filter is arranged and another filter is arranged behind the positive lens group immediately after the aperture stop, and the endoscope satisfying the following conditions (1) and (2) Objective optical system for mirror. (1) 0.5 <| f 1 /f|<2.0 (2) I / f 2 <0.64 where f is the focal length of the entire optical system, f 1 is the focal length of the concave lens, and f 2 is the rear of the aperture stop. The composite focal length of the positive lens group, I, is the maximum image height.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022222A JP2899980B2 (en) | 1990-02-02 | 1990-02-02 | Objective optical system for endoscope |
| US07/520,501 US5175650A (en) | 1989-05-09 | 1990-05-08 | Objective lens system for endoscopes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022222A JP2899980B2 (en) | 1990-02-02 | 1990-02-02 | Objective optical system for endoscope |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03229210A JPH03229210A (en) | 1991-10-11 |
| JP2899980B2 true JP2899980B2 (en) | 1999-06-02 |
Family
ID=12076773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2022222A Expired - Fee Related JP2899980B2 (en) | 1989-05-09 | 1990-02-02 | Objective optical system for endoscope |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2899980B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4445647B2 (en) * | 2000-06-30 | 2010-04-07 | オリンパス株式会社 | Objective lens |
| JP2009014947A (en) * | 2007-07-04 | 2009-01-22 | Olympus Imaging Corp | Image-forming optical system and imaging apparatus using the same |
| WO2011070930A1 (en) * | 2009-12-11 | 2011-06-16 | オリンパスメディカルシステムズ株式会社 | Objective optical system |
-
1990
- 1990-02-02 JP JP2022222A patent/JP2899980B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03229210A (en) | 1991-10-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |