JP2899974B2

JP2899974B2 - Illumination optical system

Info

Publication number: JP2899974B2
Application number: JP7379689A
Authority: JP
Inventors: 彰菊地
Original assignee: Olympus Corp
Current assignee: Olympus Corp
Priority date: 1988-05-17
Filing date: 1989-03-28
Publication date: 1999-06-02
Anticipated expiration: 2014-06-02
Also published as: JPH0250107A

Description

【発明の詳細な説明】［産業上の利用分野］本発明は、面状光源から射出される光を被照射面に向
けて照射する照明光学系で、配光特性の均一性が極めて
良好である照明光学系に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an illumination optical system that irradiates light emitted from a planar light source toward a surface to be illuminated. It relates to a certain illumination optical system.

［従来の技術］例えば光学ファイバー束からなるライトガイドを用い
て光源からの光を所望の位置へ導く場合、ライトガイド
に入射する光のうち軸に平行に入射した光に比較して軸
に対して大きな角度をなして入射した光の方が減衰量が
大きい。そのためライトガイドの射出光は軸に平行に射
出する光に比べ射出角の大きい光が非常に弱く、これを
そのまま被照射面に照射すると照野の中心と周辺の明る
さの差が著しく大きくなりつまり配光特性が悪く観察上
不都合である。[Prior art] For example, when light from a light source is guided to a desired position using a light guide made of an optical fiber bundle, the light incident on the light guide has a smaller axis than the light incident parallel to the axis. Light incident at a large angle has a greater attenuation. For this reason, the light emitted from the light guide has a very large exit angle compared to the light exiting parallel to the axis, and is very weak. That is, the light distribution characteristics are poor, which is inconvenient for observation.

このような欠点を除去するために、従来レンズを用い
て配光特性を改善する試みがなされ、例えば特公昭61−
15401号公報の光学系が知られている。In order to eliminate such defects, attempts have been made to improve the light distribution characteristics using a conventional lens.
An optical system disclosed in Japanese Patent No. 15401 is known.

この従来の照明系は、第４図に示すように光源４の側
に配置された光源側のライトガイド１と硬性鏡５内に配
置された物体側のライトガイド２とを夫々別のライトガ
イドを使用して符号６に示す部分を結像レンズ系７によ
って物体側のライトガイド２の入射端面2a上に結像する
ものである。In this conventional illumination system, as shown in FIG. 4, a light guide 1 on the light source side arranged on the side of the light source 4 and a light guide 2 on the object side arranged in the rigid endoscope 5 are provided separately from each other. Is used to form an image of the portion indicated by reference numeral 6 on the incident end surface 2a of the light guide 2 on the object side by the imaging lens system 7.

ここで、光源側のライトガイド１の出射端面での実験
的に求めた配光特性は、Ｉ（sinθ）＝−asin²θ＋ｂに
て与えられる式においてsinθを変数とする２次曲線に
近似したものになる。ここで、Ｉはライトガイド出射端
における光の強度分布、θはライトガイドより出射する
光の光軸とのなす角、a,bは係数である。Here, the light distribution characteristics experimentally determined at the exit end surface of the light source side of the light guide 1, I (sinθ) = - approximated to a quadratic curve for the sin [theta variable in asin ² theta + given expression by b Become something. Here, I is the intensity distribution of light at the light guide emission end, θ is the angle between the light emitted from the light guide and the optical axis, and a and b are coefficients.

この従来例においては、物体側のライトガイド２へ入
射する光の配光特性を平坦にしかつ配光の範囲を広く
し、更に連結部における光の損失を少なくするために第
１のライトガイド１の出射端面が結像レンズ系７の前側
焦点近傍に、又第２のライトガイド２の入射端面が結像
レンズ系の後側焦点近傍に位置するようにしてある。In this conventional example, the first light guide 1 is used to flatten the light distribution characteristics of light incident on the light guide 2 on the object side, widen the range of light distribution, and further reduce the loss of light at the connecting portion. Are located near the front focal point of the imaging lens system 7, and the entrance end face of the second light guide 2 is located near the rear focal point of the imaging lens system.

この特公昭61−15401号公報に記載されている従来例
は、結像レンズ系として少ない枚数で強い屈折力を有す
る球面レンズを用いているために結像レンズ系の周辺で
の収差の発生が大である。In the conventional example described in Japanese Patent Publication No. 61-15401, since a spherical lens having a strong refractive power with a small number of lenses is used as an imaging lens system, aberrations are generated around the imaging lens system. Is big.

第５図において結像レンズ系の焦点距離をｆ、光源側
のライトガイド１の各オプチカルファイバーから出る光
の光軸とのなす角をθ_１、その光が物体側のライトガイ
ド２へ入射する時の光軸とのなす角をθ_２、夫々のライ
トガイドの端面上のある点におけるライトガイドの中心
からの距離を夫々r₁,r₂とすると次の関係が成立つ。In FIG. 5, the focal length of the imaging lens system is f, the angle between the optical axis of light emitted from each optical fiber of the light guide 1 on the light source side and θ _{1 is} the light, and the light enters the light guide 2 on the object side. Assuming that the angle formed by the optical axis at the time is θ ₂ , and the distance from the center of the light guide at a certain point on the end face of each light guide is r ₁ , r ₂ , the following relationship is established.

f sinθ_１＝r₂ r₁＝f sinθ_２この式において配光特性として横軸にsinθ、縦軸に
照明強度Ｉをとると第６図に示すように比較的均一なも
のになる。f sin θ ₁ = r ₂ r ₁ = f sin θ _{2 In} this equation, when the horizontal axis represents sin θ and the vertical axis represents illumination intensity I, the light distribution characteristics are relatively uniform as shown in FIG.

しかしながら、第６図に示す配光特性を横軸をθに変
換して示すと、sinθによる特性値にcosθが乗ぜられる
ので、第７図に示すようにθが大きい場合には周辺部の
光量が減少し配光特性が悪化するが、目視又は写真撮影
においては実用上問題がない。However, when the light distribution characteristic shown in FIG. 6 is shown by converting the horizontal axis to θ, the characteristic value due to sin θ is multiplied by cos θ. Therefore, when θ is large as shown in FIG. And light distribution characteristics deteriorate, but there is no practical problem in visual observation or photographing.

しかし最近の傾向として内視鏡の接眼部にテレビカメ
ラを接続し、テレビモニター上で観察する場合が増えて
来ている。又内視鏡の先端部に固体撮像素子を組込んだ
電子内視鏡等も増えて来ている。さらに内視鏡は、視野
角の広角化が望まれている。However, as a recent trend, the number of cases where a television camera is connected to an eyepiece of an endoscope and observation is performed on a television monitor is increasing. Also, electronic endoscopes and the like in which a solid-state imaging device is incorporated at the end of the endoscope are increasing. Further, the endoscope is desired to have a wide viewing angle.

このように固体撮像素子を用いてモニター上で観察す
る場合は、従来の観察方法に比べて固体撮像素子のラテ
ィチュードが狭く、視野角100゜以上の広角観察が行な
えるような内視鏡が増えることにより、従来例のように
r₁＝f sinθ_２、r₂＝f sinθ_１を満足するライトガイド
結像レンズ系では十分な配光が得られない。Thus, when observing on a monitor using a solid-state imaging device, the latitude of the solid-state imaging device is narrower than that of the conventional observation method, and endoscopes capable of performing wide-angle observation with a viewing angle of 100 ° or more increase. As a result,
A light guide imaging lens system that satisfies r ₁ = f sin θ ₂ and r ₂ = f sin θ ₁ cannot provide a sufficient light distribution.

又、視野周辺まで良好な配光を得るための照明光学系
として、特開昭62−178207号公報の光学系が知られてい
る。Further, as an illumination optical system for obtaining a good light distribution to the periphery of a visual field, an optical system disclosed in Japanese Patent Application Laid-Open No. Sho 62-178207 is known.

この照明光学系は、光学系から遠方に配置された光源
から射出された光の前記光学系への入射高をｈ、前記光
学系から射出される光線の角度をθとした時、次の式を
満足するように構成されている。The illumination optical system has the following formula, where h is an incident height of light emitted from a light source disposed far from the optical system, and θ is an angle of a light beam emitted from the optical system. It is configured to satisfy.

ｈ≒k tanθ 内視鏡等で用いられる照明光学系は、限られたスペー
ス内において良好な配光と十分な光量が得られるように
する必要がある。しかし前記の特開昭62−178207号公報
に記載された照明光学系は、光源の照射角が約10゜と非
常に狭い範囲では上記の式を満足するが、光源の照射角
が広くなると、軸外の光線に対しては、上記の式を満足
しなくなり、配光が悪くなる。又光源を光学系から遠方
に配置するために光源の照射角を広くすると、レンズの
外径が大きくなり、非常に広いスペースが必要になる。h ≒ k tanθ The illumination optical system used in the endoscope or the like needs to be able to obtain a good light distribution and a sufficient amount of light in a limited space. However, the illumination optical system described in Japanese Patent Application Laid-Open No. 62-178207 satisfies the above expression in a very narrow range where the irradiation angle of the light source is about 10 °, but when the irradiation angle of the light source increases, For off-axis rays, the above expression is no longer satisfied, and the light distribution is poor. Also, if the irradiation angle of the light source is increased in order to dispose the light source far from the optical system, the outer diameter of the lens increases, and a very large space is required.

［発明が解決しようとする課題］本発明は以上の点を考慮し、観察したい視野範囲の中
心から周辺までより均一な配光特性を有する照明光学系
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] In view of the above points, an object of the present invention is to provide an illumination optical system having more uniform light distribution characteristics from the center to the periphery of a viewing range to be observed. .

［課題を解決するための手段］本発明の照明光学系は、f sinθ＝ｒよりも更に光線
高に応じた屈折角の増大の割合が小さいレンズ系を用い
ることによって、周辺光量を増加させ配光特性が一層改
善されるようにしたものである。つまり本発明の照明光
学系は、例えば第１図のように光源からの光を入射端で
受けて射出端面まで伝送する第１のライトガイド１と、
この第１のライトガイド１の射出端面近傍に前側焦点が
位置するように配置された正のレンズ系３と、このレン
ズ系の後側焦点近傍に入射端が位置するように配置され
た第２のライトガイド２とよりなるもので、前記レンズ
系が次の条件（１）を条件（２）の範囲で有効光束断面
積の少なくとも50％以上で満足するものである。[Means for Solving the Problems] The illumination optical system of the present invention uses a lens system in which the rate of increase of the refraction angle according to the ray height is smaller than f sin θ = r, thereby increasing the amount of peripheral light. The light characteristics are further improved. That is, the illumination optical system of the present invention includes a first light guide 1 for receiving light from a light source at an incident end and transmitting the light to an exit end face as shown in FIG. 1, for example.
A positive lens system 3 arranged so that the front focal point is located near the exit end face of the first light guide 1, and a second lens system arranged such that the incident end is located near the rear focal point of this lens system. Wherein the lens system satisfies the following condition (1) at least at least 50% of the effective light beam cross-sectional area within the range of condition (2).

（２）０≦|r₁|≦|f| ただし、r₁は前記第１のライトガイドの射出端面上の
任意の点の光軸からの距離、θは前記の点から光軸に平
行に射出した光線が前記第２のライトガイドの入射端面
に入射する際の光軸とのなす角、ｆは前記レンズ系の焦
点距離である。 (2) 0 ≦ | r ₁ | ≦ | f | where r ₁ is a distance from the optical axis to an arbitrary point on the exit end face of the first light guide, and θ is a distance from the point parallel to the optical axis. The angle f formed with the optical axis when the emitted light beam enters the incident end face of the second light guide, and f is the focal length of the lens system.

レンズ系でf sinθ＝r₁の関係が成立つとすると、次
の関係が得られる。Assuming that the relationship of f sin θ = r ₁ holds in the lens system, the following relationship is obtained.

sinθ＝r₁/f また（ｄθ/dr₁）_r1＝０＝1/f したがって、次の式が成立つ。sinθ = r ₁ / f (Dθ / dr ₁ ) _{r1 = 0} = 1 / f Therefore, the following equation is established.

したがって条件（１）を満足するようにすれば、光線
高r₁の増加に対するθの増加の割合を従来例のものより
も小さくすることが出来、特にr₁の大きいところで小さ
くすることが出来る。このように前記条件（１）を満足
するレンズ系を備えた本発明の照明光学系は、改善され
た良好な配光特性が得られる。 Therefore, if the condition (1) is satisfied, the rate of increase of θ with respect to the increase of the ray height r ₁ can be made smaller than that of the conventional example, and especially at a large r ₁ . As described above, the illumination optical system of the present invention including the lens system that satisfies the condition (1) can obtain improved and favorable light distribution characteristics.

上記条件（１）を満足するレンズ系は、正レンズと負
レンズとを含む２枚以上のレンズを組合わせることによ
って実現出来、それをライトガイド間に配置して配光特
性の良好な照明系を得られる。しかしこの場合、レンズ
系が比較的レンズ枚数の多い複雑なものになる。A lens system that satisfies the above condition (1) can be realized by combining two or more lenses including a positive lens and a negative lens. Can be obtained. However, in this case, the lens system becomes complicated with a relatively large number of lenses.

このレンズ系をより簡単な構成にするためには、少な
くとも一つの正レンズを含むもので、この正レンズに光
軸から周辺部に行くにつれ曲率が徐々にゆるくなる非球
面を導入すればよい。この非球面の式は光軸をｘ軸、光
軸に垂直な方向をｙ軸にとった時の次の式（３）にて近
似される。In order to make this lens system simpler, at least one positive lens should be introduced, and an aspherical surface whose curvature gradually decreases from the optical axis toward the periphery may be introduced into this positive lens. This aspherical expression is approximated by the following expression (3) when the optical axis is the x axis and the direction perpendicular to the optical axis is the y axis.

ただしP,E,F,G・・・は非球面を表わす係数、Ｒは非
球面の光軸上の曲率半径である。 Where P, E, F, G... Are coefficients representing the aspherical surface, and R is the radius of curvature of the aspherical surface on the optical axis.

尚ここでは、y²の項は用いないで上記の第１項とy⁴以
上の項とにて表わした。Note here, expressed in the first term and y ⁴ or more terms of the not uses terms y ^2.

又上記の条件（１）を満足させるための非球面を導入
する場合、第30図に破線にて示すように製作上の誤差に
よる面のうねり等の実線にて示す設計値からのずれがあ
る程度生じてもよい。When an aspherical surface for satisfying the above condition (1) is introduced, a deviation from a design value indicated by a solid line due to a manufacturing error as shown by a broken line in FIG. May occur.

上記のレンズ系を更に少ない枚数にするためには、次
の条件（４）乃至条件（14）のうちの条件（４），
（５），（６）又は条件（４），（６），（７），
（８），（９），（10），（11）又は条件（４），
（６），（８），（９），（12），（13），（14）の組
合わせのうちのいずれかを有効光束が通る部分の面積の
少なくとも50％以上で満足することが好ましい。これに
よって後に示す実施例のようにレンズ系を１枚のレンズ
にて構成することが可能になる。In order to further reduce the number of the above lens systems, the following conditions (4) to (14) must be satisfied.
(5), (6) or conditions (4), (6), (7),
(8), (9), (10), (11) or condition (4),
It is preferable that any one of the combinations of (6), (8), (9), (12), (13), and (14) be satisfied by at least 50% or more of the area of the portion through which the effective light beam passes. . This makes it possible to configure the lens system with one lens as in the embodiment described later.

（４）0.2≦D/f≦３（５）Ｐ＜０（６）｜Δ｜≦|X_max|/2 （７）０≦Ｐ＜１（８）Ｅ≦０（９）Ｆ≧０（10）０≦|E・D^-3|≦１（11）０≦|F・D^-3|≦0.5 （12）Ｐ≧１（13）0.1≦|E・D^-3|≦0.6 （14）０≦|F・D^-3|≦0.1 又条件（５）に示すＰ＜０の場合には、次の各条件を
満足すれば一層好ましい。(4) 0.2 ≦ D / f ≦ 3 (5) P <0 (6) | Δ | ≦ | X _max | / 2 (7) 0 ≦ P <1 (8) E ≦ 0 (9) F ≧ 0 ( 10) 0 ≦ | E · D ^-3 | ≦ 1 (11) 0 ≦ | F · D ^-3 | ≦ 0.5 (12) P ≧ 1 (13) 0.1 ≦ | E · D ^-3 | ≦ 0.6 (14) 0 ≦ | F · D ⁻³ | ≦ 0.1 In the case of P <0 shown in the condition (5), it is more preferable that the following conditions are satisfied.

Ｅ≦０Ｆ≧００≦|E・D^-3|≦1.5 ０≦|F・D^-3|≦１前記のような照明レンズ系の前側焦点位置近傍に光源
側のライトガイド１の出射端面を配設し後側焦点位置近
傍に物体側のライトガイド２の入射側端面を配置して、
本発明の照明光学系を構成する。E ≦ 0 F ≧ 0 0 ≦ | E · D ^-3 | ≦ 1.5 0 ≦ | F · D ^-3 | ≦ 1 The exit end face of the light guide 1 on the light source side near the front focal position of the illumination lens system as described above. And the incident side end face of the light guide 2 on the object side is arranged near the rear focal point position.
The illumination optical system of the present invention is configured.

このような光学系（第１図）において、レンズ系３の
焦点距離をｆ、光源側のライトガイド１の各ファイバー
より出る光が光軸となす角をθ_１、その光線が物体側の
ライトガイド２へ入射する時の光軸とのなす角をθ_２、
夫々のライトガイドの端面上のある点におけるライトガ
イドの中心からの距離を夫々r₁,r₂とする時次の関係が
なりたつ。In such an optical system (FIG. 1), the focal length of the lens system 3 is f, the angle between light emitted from each fiber of the light guide 1 on the light source side and the optical axis is θ ₁ , and the light beam is the light on the object side. The angle formed by the optical axis when entering the guide 2 is θ ₂ ,
When the distances from the center of the light guide at a certain point on the end face of each light guide are r ₁ and r ₂ , respectively, the following relationship is established.

f tanθ_１＝r₂ （ｉ） r₁＝f tanθ_２（ii）これは第１図において光源側のライトガイド１よりθ
_１の角度で出射したすべての光線は、物体側のライトガ
イドの入射端面に集光することを示している。そして同
じ角度で射出した光線は、全て同じ点に集光する。つま
り第１図において光線L₁,L₄,L₇は＋r₂の位置に、光線
L₂,L₅,L₈は０の位置に、光線L₃,L₆,L₉は−r₂の位置に集
まる。また光源側のライトガイドの端面上の同じ位置か
ら射出した光は、全て同じ角度で物体側のライトガイド
の入射端面に入射する。つまり第１図において光線L₁,L
₂,L₃は角−θ_２で、光線L₄,L₅,L₆は０度で、光線L₇,L₈,
L₉は＋θ_２で入射する。f tan θ ₁ = r ₂ (i) r ₁ = f tan θ ₂ (ii) This is obtained from the light guide 1 on the light source side in FIG.
All the rays emitted at an angle of ₁ are converged on the incident end face of the light guide on the object side. Light rays emitted at the same angle are all focused on the same point. That is, in FIG. 1, the rays L ₁ , L ₄ and L ₇ are located at the position of + r ₂ ,
L ₂ , L ₅ , and L ₈ converge at a position of 0, and light beams L ₃ , L ₆ , and L ₉ converge at a position of −r ₂ . Light emitted from the same position on the end face of the light guide on the light source side is all incident on the incident end face of the light guide on the object side at the same angle. That light L _1, L in Figure 1
₂ , L ₃ are angles −θ ₂ , rays L ₄ , L ₅ , L ₆ are 0 degrees, rays L ₇ , L ₈ ,
L ₉ is incident at + theta _2.

次に式（ｉ），（ii）より式（iii）が導びかれる。 Next, equation (iii) is derived from equations (i) and (ii).

tanθ₁tanθ_２＝r₂/r₁＝β′ （iii）この式（iii）から実施例の物体側のライトガイドの
入射端面での強度分布の範囲はr₂＝β′r₁であり、強度
分布の形は光源側のライトガイドの出射側端面の形をＩ
（tanθ）＝−a tan²θ＋ｂと２次近似すると、つまり
第２図の曲線ｂ（曲線ａは実験値）にて表わされるよう
にするとその形を保ったままtanθ_１がr₂に変換された
もの（この変換は光源側のライトガイドから等しいθ_１
で射出した光が物体側ライトガイドの入射端面上で全て
同じ位置r₂に入射することを意味する）であるからＩ（r₂）＝−ar₂ ²＋ｂとなる。そしてr₂＝β′r₁の時式（iv）のようになる。tan θ ₁ tan θ ₂ = r ₂ / r ₁ = β ′ (iii) From this equation (iii), the range of the intensity distribution at the entrance end face of the light guide on the object side of the embodiment is r ₂ = β′r ₁ , The shape of the intensity distribution is the shape of the end face of the light guide on the light source side on the exit side.
When (tan θ) = − a tan ² θ + b is secondarily approximated, that is, when it is represented by a curve b (curve a is an experimental value) in FIG. ₂ , tan θ ₁ is converted to r ₂ while maintaining its shape. (This conversion is equal to θ ₁ from the light guide on the light source side.)
In because the injected light is all on the entrance end surface on the object side light guide means being incident on the same position _{_{r 2) I (r 2)}} = - a ar _{² 2} + b. Then, when r ₂ = β′r ₁ , equation (iv) is obtained.

Ｉ（r₂）＝−ａβ′²r₁ ²＋ｂ＝０（iv）また全光量は単位面積当りの光量を１とすると光源側のライトガイ
ドの出射端でπr₁ ²となるので次の式（ｖ）のようにな
る。 _{I (r 2) = - aβ} '2 r 1 2 + b = 0 (iv) The total light When the light amount per unit area is 1, πr ₁ ² is obtained at the exit end of the light guide on the light source side, so that the following equation (v) is obtained.

式（iv）と式（ｖ）とから次のようになる。 From equation (iv) and equation (v), the following is obtained.

ａ＝2/β′^４×1/r₁ ²、ｂ＝2/β′^２ ∴Ｉ（r₂）＝−2/β′^４・1/r²・r₂ ²＋2/β′^２又配光特性は、光源側のライトガイド１の強度分布が
ｒ＝constantのところでr₁がtanθ_２に変換されるのでt
anθ_２＝constantになる。尚この変換は光源側ライトガ
イドの同じ位置ｒから射出した光が、物体側ライトガイ
ドの入射端面にて全て等しい角θで入射することを意味
する。 ^{a = 2 / β '4 ×} 1 / r 1 2, b = 2 / β' 2 ∴I (r 2) = - 2 / β '4 · 1 / r 2 · r 2 2 + 2 / β' 2 Matahai The light characteristic is such that r ₁ is converted to tan θ ₂ when the intensity distribution of the light guide 1 on the light source side is r = constant.
anθ ₂ = constant. This conversion means that the lights emitted from the same position r of the light source side light guide are all incident on the incident end face of the object side light guide at the same angle θ.

そして配光特性の範囲はtanθ_２＝1/β′tanθ_１であ
る。The range of light distribution characteristics is tanθ _{2 =} ₁ / β'tanθ 1.

今になるようにすると強度Ｉ（r₂）は次のようになる。now Then, the intensity I (r ₂ ) becomes as follows.

Ｉ（r₂）＝−8/r₁ ²・r₂ ²＋４又配光特性の範囲は、次の通りになる。 _{I (r 2) = - 8} / r 1 2 · r 2 2 +4 The range of light distribution characteristic becomes as follows.

これを図示すると第３図（Ａ），（Ｂ），（Ｃ）のよ
うになる。これらの図より明らかなように、本発明の照
明光学系によれば、光源側のライトガイド端面の２次光
源の強度分布並びに配光特性に比べ物体側のライトガイ
ドのそれは大幅に改善される。 This is illustrated in FIGS. 3 (A), (B) and (C). As is clear from these figures, according to the illumination optical system of the present invention, the intensity distribution of the secondary light source on the light guide end face on the light source side and the light distribution characteristics of the light guide on the object side are greatly improved as compared with the light distribution characteristics.

このようなｒ＝tanθ型のレンズ系を形成するために
は、光軸付近の屈折力が強く周辺へ行くにしたがって屈
折力が徐々に弱くなるような非球面が必要である。この
非球面は、主として双曲面に類似した形状をしている。In order to form such an r = tan θ type lens system, an aspherical surface is required in which the refractive power near the optical axis is strong and the refractive power gradually decreases toward the periphery. This aspheric surface has a shape mainly similar to a hyperboloid.

又内視鏡等に、本発明に記載するような照明系を使用
する場合には配光角が最低でも片側30゜以上必要であ
る。これを満たすためには前記の条件の各組合せのうち
の一つを満足することが望ましい。つまり条件（４）乃
至条件（６）の組合せ又は条件（４），（６），（７）
乃至（11）の組合わせ、又は条件（４），（６），
（８），（11），（12）〜（14）の組合わせのうちの一
つを満足することが望ましい。When an illumination system as described in the present invention is used for an endoscope or the like, the light distribution angle must be at least 30 ° on one side. In order to satisfy this, it is desirable to satisfy one of the combinations of the above conditions. That is, a combination of the conditions (4) to (6) or the conditions (4), (6), (7)
Or combinations of (11) or (4), (6),
It is desirable to satisfy one of the combinations of (8), (11), and (12) to (14).

条件（４）を満足しないでｆが大になると、十分な配
光角を得ることが出来なくなり、内視鏡等の照明系とし
ては、適当でない。If f is large without satisfying the condition (4), it becomes impossible to obtain a sufficient light distribution angle, which is not suitable for an illumination system such as an endoscope.

条件（５），（６）、又は条件（６）乃至条件（1
1）、又は条件（６），（９），（８），（12）〜（1
4）は、前掲の非球面の式において、この式がほぼ双曲
面を表わすことを示す条件である。この条件から外れる
とｒ＝ftanθを満足しなくなり配光が悪くなる。Condition (5), (6), or Condition (6) to Condition (1)
1) or conditions (6), (9), (8), (12) to (1)
4) is a condition indicating that, in the above-described aspherical expression, this expression substantially represents a hyperboloid. If the condition is not satisfied, r = ftanθ is not satisfied, and the light distribution deteriorates.

以上の説明は、ライトガイドにて伝送された光を他の
ライトガイドの端面に入射させる場合について述べた。
しかし光源が一定の広さを持つ面光源であり、これを照
明すべき面上にレンズ系を用いて照明する場合にも適用
出来る。そしてこの場合にも照明される面の配光その他
は同様に良好なものである。The above description has described the case where the light transmitted by the light guide is made incident on the end face of another light guide.
However, the light source is a surface light source having a certain width, and the present invention can also be applied to a case where the light source is illuminated on a surface to be illuminated using a lens system. Also in this case, the light distribution on the illuminated surface and the like are similarly good.

［実施例］次に本発明の照明レンズ系の実施例を示す。Example Next, an example of the illumination lens system of the present invention will be described.

実施例１ｆ＝1.451 r₁＝1.6337（非球面）ｄ＝2.1000 ｎ＝1.78472 ν＝25.70 r₂＝−1.6337（非球面）非球面係数（第１面）Ｐ＝−1.0840,E＝０Ｆ＝−0.22498×10^-2,G＝０（第２面）Ｐ＝−1.0840,E＝０Ｆ＝0.22498×10^-2,G＝０ P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例２ｆ＝1.395 r₁＝1.5284（非球面）ｄ＝2.1000 ｎ＝1.78472 ν＝25.70 r₂＝−1.5284（非球面）非球面係数（第１面）Ｐ＝−2.4800,E＝０Ｆ＝0.13488×10^-2,G＝０（第２面）Ｐ＝−2.4800,E＝０Ｆ＝−0.13488×10^-2,G＝０ P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例３ｆ＝1.193 r₁＝1.0455（非球面）ｄ＝2.1000 ｎ＝1.78472 ν＝25.70 r₂＝−1.0455（非球面）非球面係数（第１面）Ｐ＝−4.0008,E＝０Ｆ＝0.19616×10^-2,G＝０（第２面）Ｐ＝−4.0008,E＝０Ｆ＝−0.19616×10^-2,G＝０ P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例４ｆ＝1.102 r₁＝0.9427（非球面）ｄ＝1.9510 ｎ＝1.78472 ν＝25.70 r₂＝−0.9427（非球面）非球面係数（第１面）Ｐ＝−5.5981,E＝0.12574×10^-2 Ｆ＝0.21918×10^-2,G＝−0.10968×10^-6 （第２面）Ｐ＝−5.5981, Ｅ＝−0.12574×10^-2 Ｆ＝−0.21918×10^-2 Ｇ＝0.10968×10^-6 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例５ｆ＝1.170 r₁＝1.5204（非球面）ｄ＝1.7143 ｎ＝1.88300 ν＝40.78 r₂＝−1.5204（非球面）非球面係数（第１面）Ｐ＝−2.8145,E＝０Ｆ＝0.60462×10^-3,G＝０（第２面）Ｐ＝−2.8145,E＝０Ｆ＝−0.60462×10^-3,G＝０ P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例６ｆ＝0.974 r₁＝1.0788（非球面）ｄ＝1.7143 ｎ＝1.88300 ν＝40.78 r₂＝−1.0788（非球面）非球面係数（第１面）Ｐ＝−5.6395,E＝０Ｆ＝0.23377×10^-2,G＝０（第２面）Ｐ＝−5.6395,E＝０Ｆ＝−0.23377×10^-2,G＝０ P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例７ｆ＝1.141 r₁＝1.2767（非球面）ｄ＝2.3000 ｎ＝1.78472 ν＝25.70 r₂＝−0.6241（非球面）非球面係数（第１面）Ｐ＝−2.5679,E＝0.14389×10^-1 Ｆ＝0.21916×10^-2 Ｇ＝−0.10968×10^-6 （第２面）Ｐ＝−10.1148, Ｅ＝0.14898×10^-1 Ｆ＝−0.21926×10^-2 Ｇ＝0.10967×10^-6 P₁/P₂＝0.2541,Δ＝０｜ω_１（Ｄ）／ω_２（Ｄ）｜＝2.154,D＝１実施例８ｆ＝1.111 r₁＝1.1013（非球面）ｄ＝1.9998 ｎ＝1.78472 ν＝25.70 r₂＝−0.8432（非球面）非球面係数（第１面）Ｐ＝−0.6443, Ｅ＝−0.33017×10^-1,F＝0.21916×10^-2 Ｇ＝−0.10968×10^-6 （第２面）Ｐ＝−17.7885, Ｅ＝−0.31311×10^-1 Ｆ＝−0.21931×10^-2 Ｇ＝0.10967×10^-6 P₁/P₂＝0.036,Δ＝０｜ω_１（Ｄ）／ω_２（Ｄ）｜＝1.649,D＝１実施例９ｆ＝1.136 r₁＝1.1601（非球面）ｄ＝2.1764 ｎ＝1.78472 ν＝25.70 r₂＝−0.6745（非球面）非球面係数（第１面）Ｐ＝−1.8617,E＝0.14226×10^-1 Ｆ＝0.21915×10^-2 Ｇ＝−0.10968×10^-6 （第２面）Ｐ＝−13.9993, Ｅ＝0.12040×10^-1 Ｆ＝−0.21925×10^-2 Ｇ＝0.10967×10^-6 P₁/P₂＝0.133,Δ＝０｜ω_１（Ｄ）／ω_２（Ｄ）｜＝3.15,D＝１実施例10 ｆ＝1.069 r₁＝1.2636（非球面）ｄ＝1.8337 ｎ＝1.78472 ν＝25.70 r₂＝−0.9030（非球面）非球面係数（第１面）Ｐ＝−0.9365,E＝0.80216×10^-2 Ｆ＝0.21913×10^-2 Ｇ＝−0.10968×10^-6 （第２面）Ｐ＝−14.9547, Ｅ＝0.18359×10^-1 Ｆ＝−0.21923×10^-2 Ｇ＝0.10967×10^-6 P₁/P₂＝0.063,Δ＝０｜ω_１（Ｄ）／ω_２（Ｄ）｜＝3.778,D＝１実施例11 ｆ＝1.057 r₁＝1.2119（非球面）ｄ＝1.6097 ｎ＝1.78472 ν＝25.70 r₂＝−1.0931（非球面）非球面係数（第１面）Ｐ＝−1.5870,E＝0.23812×10^-1 Ｆ＝0.21914×10^-2 Ｇ＝−0.10968×10^-6 （第２面）Ｐ＝−15.7719, Ｅ＝−0.41582×10^-2 Ｆ＝−0.21923×10^-2 Ｇ＝0.10967×10^-6 P₁/P₂＝0.101,Δ＝０｜ω_１（Ｄ）／ω_２（Ｄ）｜＝2.481,D＝１実施例12 ｆ＝1.170 r₁＝2.5702（非球面） d₁＝1.1600 ｎ＝1.88300 ν_１＝40.78 r₂＝−3.2305（非球面） d₂＝0.0857 r₃＝3.2305（非球面） d₃＝1.1600 n₂＝1.88300 ν_２＝40.78 r₄＝−2.5702（非球面）非球面係数（第１面）Ｐ＝2.5126,E＝−0.76810×10^-1 Ｆ＝0.90435×10^-7,G＝０（第２面）Ｐ＝−8.7600, Ｅ＝−0.22112×10^-1 Ｆ＝−0.67696×10^-6,G＝０（第３面）Ｐ＝−8.7600,E＝0.22112×10^-1 Ｆ＝0.67696×10^-6,G＝０（第４面）Ｐ＝2.5126, Ｅ＝0.76810×10^-1 Ｆ＝−0.90435×10^-7,G＝０実施例13 ｆ＝1.075 r₁＝1.1739（非球面） d₁＝1.6234 n₁＝1.78472 ν_１＝25.76 r₂＝−1.1739（非球面）非球面係数（第１面）Ｐ＝−2.5000, Ｅ＝−0.76732×10^-1 Ｆ＝0.35388×10^-1,G＝−0.45172×10^-7 （第２面）Ｐ＝−2.5000, Ｅ＝0.76732×10^-1 Ｆ＝−0.35388×10^-1,G＝0.45172×10^-7 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例14 ｆ＝1.077 r₁＝1.2822（非球面） d₁＝1.4067 n₁＝1.78472 ν_１＝25.76 r₂＝−1.2822（非球面）非球面係数（第１面）Ｐ＝−0.5000,E＝−0.14713 Ｆ＝0.52671×10^-1,G＝0.87334×10^-8 （第２面）Ｐ＝−0.5000,E＝0.14713 Ｆ＝−0.52671×10^-1,G＝−0.87334×10^-8 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例15 ｆ＝1.077 r₁＝1.2855（非球面） d₁＝1.3991 n₁＝1.78472 ν_１＝25.76 r₂＝−1.2855（非球面）非球面係数（第１面）Ｐ＝0,E＝−0.17484 Ｆ＝0.55298×10^-1,G＝0.17356×10^-7 （第２面）Ｐ＝0,E＝0.17484 Ｆ＝−0.55298×10^-1,G＝−0.17356×10^-7 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例16 ｆ＝1.077 r₁＝1.2942（非球面） d₁＝1.3786 n₁＝1.78472 ν_１＝25.76 r₂＝−1.2942（非球面）非球面係数（第１面）Ｐ＝0.5000,E＝−0.19891 Ｆ＝0.47206×10^-1,G＝−0.48882×10^-8 （第２面）Ｐ＝0.5000,E＝0.19891 Ｆ＝−0.47206×10^-1,G＝0.48882×10^-8 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例17 ｆ＝1.078 r₁＝1.3999（非球面） d₁＝1.0990 n₁＝1.78472 ν_１＝25.76 r₂＝−1.3999（非球面）非球面係数（第１面）Ｐ＝1.0000,E＝−0.17071 Ｆ＝0.11270×10^-1,G＝−0.85546×10^-7 （第２面）Ｐ＝1.0000,E＝0.17071 Ｆ＝−0.11270×10^-1,G＝0.85546×10^-7 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例18 ｆ＝1.079 r₁＝1.5171（非球面） d₁＝0.7215 n₁＝1.78472 ν_１＝25.76 r₂＝−1.5171（非球面）非球面係数（第１面）Ｐ＝1.2000,E＝−0.13557 Ｆ＝−0.24303×10^-2,G＝−0.10944×10^-6 （第２面）Ｐ＝1.2000,E＝0.13557 Ｆ＝0.24303×10^-2,G＝0.10944×10^-6 P₁/P₂＝1,Δ＝0,|ω_１（Ｄ）／ω_２（Ｄ）｜＝１Ｄ＝１実施例19 ｆ＝0.987 r₁＝4.9437（非球面） d₁＝1.0408 n₁＝1.78472 ν_１＝25.76 r₂＝∞ d₂＝0.3934 r₃＝0.7758（非球面） d₃＝1.0417 n₂＝1.78472 ν_２＝25.76 r₄＝∞ 非球面係数（第１面）Ｐ＝1.0053,E＝0.37292×10^-1 Ｆ＝0.55715×10^-4,G＝０（第３面）Ｐ＝−2.3790,E＝0.31172×10^-1 Ｆ＝0.94539×10^-3,G＝０ Δ＝0,D＝１尚上記各実施例の（ｄθ/dr₁）／｛（ｄθ/dr₁）
_r1＝０｝およびの値は次の通りである。Example 1 f = 1.451 r ₁ = 1.6337 (aspherical surface) d = 2.1000 n = 1.84772 ν = 25.70 r ₂ = −1.6337 (aspherical surface) Aspherical surface coefficient (first surface) P = −1.0840, E = 0 F = −0.22498 × 10 ⁻² , G = 0 (second surface) P = −1.0840, E = 0 F = 0.22498 × 10 ⁻² , G = 0 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ ( D) / ω ₂ (D) | = 1 D = 1 Example 2 f = 1.395 r ₁ = 1.5284 (aspherical surface) d = 2.1000 n = 1.8472 ν = 25.70 r ₂ = −1.5284 (aspherical surface) Aspherical surface coefficient ( First surface) P = −2.4800, E = 0 F = 0.13488 × 10 ⁻² , G = 0 (Second surface) P = −2.4800, E = 0 F = −0.13488 × 10 ⁻² , G = 0 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 3 f = 1.193 r ₁ = 1.0455 (aspherical surface) d = 2.1000 n = 1.84742 ν = 25.70 r ₂ = −1.0455 (aspherical surface) Aspherical surface coefficient (first surface) P = −4.008, E = 0 F = 0.19616 × 10 ⁻² , G = 0 (second surface) P = −4.0008, E = 0 ^{F = -0.19616 × 10 -2, G} = _{_{P 1 / P 2 = 1,}} Δ = 0, | ω 1 (D) / ω 2 (D) | = 1 D = 1 Example _{4 f = 1.102 r 1 = 0.9427} ( aspherical) d = 1.9510 n = 1.78472 ν = 25.70 r ₂ = −0.9427 (aspherical surface) Aspherical surface coefficient (first surface) P = −5.5981, E = 0.12574 × 10 ⁻² F = 0.1918 × 10 ⁻² , G = −0.10968 × 10 ⁻⁶ 2) P = −5.5981, E = −0.12574 × 10 ⁻² F = −0.21918 × 10 ⁻² G = 0.10968 × 10 ⁻⁶ P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 5 f = 1.170 r ₁ = 1.5204 (aspherical surface) d = 1.7143 n = 1.88300 ν = 40.78 r ₂ = −1.5204 (aspherical surface) Aspherical surface coefficient (first surface ) P = -2.8145, E = 0 F = 0.60462 × 10 -3, G = 0 ( second surface) P = -2.8145, E = 0 F = -0.60462 × 10 -3, G = 0 P 1 / P 2 = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 6 f = 0.974 r ₁ = 1.0788 (aspherical surface) d = 1.7143 n = 1.88300 ν = 40.78 r ₂ = -1.0788 (Aspherical surface) Aspherical surface coefficient (No. 1) P = -5.6395, E = 0 F = 0.23377 x 10 ^-2 , G = 0 (Second surface) P = -5.6395, E = 0 F = -0.23377 x 10 ^-2 , G = 0 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 7 f = 1.141 r ₁ = 1.2767 (aspherical surface) d = 2.3000 n = 1.84742 ν = 25.70 r ₂ = −0.6241 (aspherical surface) Aspherical surface coefficient (first surface) P = −2.5679, E = 0.14389 × 10 ⁻¹ F = 0.21916 × 10 ⁻² G = −0.10968 × 10 ⁻⁶ (second surface) P = −10.1148, E = 0.14898 × 10 ⁻¹ F = −0.21926 × 10 ⁻² G = 0.10967 × 10 ⁻⁶ P ₁ / P ₂ = 0.2541, Δ = 0 | ω ₁ (D) / ω ₂ (D) | = 2.154, D = 1 Example 8 f = 1.111 r ₁ = 1.113 (aspherical surface) d = 1.9998 n = 1.8472 ν = 25.70 r ₂ = −0.8432 (aspherical surface) Aspherical surface coefficient (first surface) P = −0.6443 , E = −0.33017 × 10 ⁻¹ , F = 0.21916 × 10 ⁻² G = −0.10968 × 10 ⁻⁶ (Second surface) P = −17.7885, E = −0.31311 × 10 ⁻¹ F = −0.21931 × 10 ^{− 2} G = 0.10967 × 10 ^-6 P ₁ / P ₂ = 0.036, Δ = 0 | ω ₁ (D) / ω ₂ (D) | = 1.649, D = 1 Example 9 f = 1.136 r ₁ = 1.1601 (aspheric surface) d = 2.1764 n = 1.84772 ν = 25.70 r ₂ = −0.6745 ( (Aspherical surface) Aspherical surface coefficient (first surface) P = −1.8617, E = 0.12426 × 10 ⁻¹ F = 0.21915 × 10 ⁻² G = −0.10968 × 10 ⁻⁶ (second surface) P = −13.99993, E = 0.12040 × 10 ⁻¹ F = −0.21925 × 10 ⁻² G = 0.10967 × 10 ⁻⁶ P ₁ / P ₂ = 0.133, Δ = 0 | ω ₁ (D) / ω ₂ (D) | = 3.15, D = 1 Example 10 f = 1.0069 r ₁ = 1.2636 (aspherical surface) d = 1.8337 n = 1.84742 ν = 25.70 r ₂ = −0.9030 (aspherical surface) Aspherical surface coefficient (first surface) P = −0.9365, E = 0.80216 × 10 ^-2 F = 0.21913 × 10 ^-2 G = −0.10968 × 10 ⁻⁶ (Second surface) P = −14.9547, E = 0.18359 × 10 ⁻¹ F = −0.21923 × 10 ⁻² G = 0.10967 × 10 ⁻⁶ P ₁ / P ₂ = 0.063, Δ = 0 | ω ₁ (D) / ω ₂ (D) | = 3.778, D = 1 Example 11 f = 1.070 r ₁ = 1.2119 (aspheric surface) d = 1.6097 n = 1.84742 ν = 25.70 r ₂ = -1.0931 (aspherical surface) Aspherical surface coefficient (first surface) P = -1.5870, E = 0.23812 * 10 < ^-1 > F = 0.21914 * 10 ^<-2 > G = -0.10968 * 10 < ^-6 > (second surface) P =- 15.7719, E = −0.41582 × 10 ⁻² F = −0.21923 × 10 ⁻² G = 0.10967 × 10 ⁻⁶ P ₁ / P ₂ = 0.101, Δ = 0 | ω ₁ (D) / ω ₂ (D) | = 2.481, D = 1 Example 12 f = 1.170 r ₁ = 2.5702 (aspherical surface) d ₁ = 1.1600 n = 1.88300 ν ₁ = 40.78 r ₂ = −3.2305 (aspherical surface) d ₂ = 0.0857 r ₃ = 3.2305 (aspherical surface) ) D ₃ = 1.1600 n ₂ = 1.88300 ν ₂ = 40.78 r ₄ = −2.5702 (aspherical surface) Aspherical surface coefficient (first surface) P = 2.5126, E = −0.76810 × 10 ⁻¹ F = 0.90435 × 10 ^-7 , G = 0 (second surface) P = −8.7600, E = −0.22112 × 10 ⁻¹ F = −0.67696 × 10 ^-6 , G = 0 (third surface) P = −8.7600, E = 0.22112 × 10 ⁻¹ F = 0.67696 × 10 ⁻⁶ , G = 0 (Fourth surface) P = 2.5126, E = 0.76810 × 10 ⁻¹ F = −0.90435 × 10 ⁻⁷ , G = 0 Example 13 f = 1.0075 r ₁ = 1.1739 ( Aspherical surface) d ₁ = 1.6234 n ₁ = 1.78472 ν ₁ = 25.76 r ₂ = −1.1739 (aspherical surface) Aspherical surface coefficient (first surface) P = −2.5000, E = −0.76732 × 10 ⁻¹ F = 0.35388 × 10 ⁻¹ , G = −0.45172 × 10 ^-7 (Second surface) P = −2.5000, E = 0.76732 × 10 ⁻¹ F = −0.35388 × 10 ⁻¹ , G = 0.45172 × 10 ^-7 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 14 f = 1.076 r ₁ = 1.82222 (aspheric surface) d ₁ = 1.4067 n ₁ = 1.84772 ν ₁ = 25.76 r ₂ = −1.2822 (aspheric surface) aspherical coefficients (first surface) P = -0.5000, E = -0.14713 F = 0.52671 × 10 -1, G = 0.87334 × 10 -8 ( second surface) P = -0.5000, E = 0.14713 F = -0.52671 × 10 ⁻¹ , G = −0.87334 × 10 ⁻⁸ P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 15 f = 1.0077 r ₁ = 1.2855 (aspheric surface) d ₁ = 1.3991 n ₁ = 1.78472 ν ₁ = 25.76 r ₂ = −1.2855 (aspheric surface) Aspheric coefficient (first surface) P = 0, E = −0.17484 F = 0.55298 × 10 ⁻¹ , G = 0.17356 × 10 ^-7 (second surface) P 0, E = 0.17484 F = -0.55298 × 10 -1, G = -0.17356 × 10 -7 P 1 / P 2 = 1, Δ = 0, | ω 1 (D) / ω 2 (D) | = 1 D = 1 example 16 f = 1.077 r ₁ = 1.2942 _{_{(aspherical) d 1 = 1.3786 n 1 =}} 1.78472 ν 1 = 25.76 r 2 = -1.2942 ( aspherical) aspherical coefficients (first surface) P = 0.5000, E = −0.9891 F = 0.47206 × 10 ⁻¹ , G = −0.48882 × 10 ^-8 (Second surface) P = 0.5000, E = 0.19891 F = −0.47206 × 10 ⁻¹ , G = 0.48882 × 10 ^-8 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 17 f = 1.0078 r ₁ = 1.3999 (aspheric surface) d ₁ = 1.0990 n ₁ = 1.78472 ν ₁ = 25.76 r ₂ = -1.3999 (aspherical surface) Aspherical surface coefficient (first surface) P = 1.0000, E = -0.17071 F = 0.11270 × 10 ^-1 , G = -0.85546 × 10 ^-7 (second surface) P = 1.0000, E = 0.17071 F = -0.11270 x 10 ^-1 , G = 0.85546 x 10 ^-7 P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 example _{18 f = 1.079 r 1 = 1.5171} ( aspherical) d ₁ = .7215 n ₁ = 1.84772 ν ₁ = 25.76 r ₂ = −1.5171 (aspherical surface) Aspherical surface coefficient (first surface) P = 1.2000, E = −0.13557 F = −0.24303 × 10 ⁻² , G = −0.10944 × 10 ^-6 ( Second surface) P = 1.2000, E = 0.13557 F = 0.24303 × 10 ⁻² , G = 0.10944 × 10 ⁻⁶ P ₁ / P ₂ = 1, Δ = 0, | ω ₁ (D) / ω ₂ (D) | = 1 D = 1 Example 19 f = 0.987 r ₁ = 4.9437 (aspheric surface) d ₁ = 1.0408 n ₁ = 1.78472 ν ₁ = 25.76 r ₂ = ∞ d ₂ = 0.3934 r ₃ = 0.7758 (aspheric surface) d ₃ = 1.0417 n ₂ = 1.78472 ν ₂ = 25.76 r ₄ = ∞ Aspherical coefficient (first surface) P = 1.0053, E = 0.32992 × 10 ⁻¹ F = 0.55715 × 10 ^-4 , G = 0 (third surface) P = −2.3790, E = 0.31172 × 10 ⁻¹ F = 0.94539 × 10 ⁻³ , G = 0 Δ = 0, D = 1 Note that (dθ / dr ₁ ) / ｛(dθ / dr ₁ ) in each of the above embodiments.
_{r1 = 0} } and Are as follows.

実施例１ r₁ 0.2 0.4 0.6 0.8 1.0 1.076 I 0.691 0.703 0.739 0.837 1.244 11.914 II 1.010 1.040 1.098 1.199 1.380 1.491 実施例２ r₁ 0.2 0.4 0.6 0.8 1.0 1.133 I 0.711 0.704 0.710 0.746 0.912 5.866 II 1.010 1.044 1.108 1.221 1.434 1.659 実施例３ r₁ 0.2 0.4 0.6 0.8 1.0 1.09 I 0.836 0.846 0.811 0.724 0.815 6.903 II 1.014 1.061 1.157 1.348 1.834 2.460 実施例４ r₁ 0.2 0.4 0.6 0.8 1.0 1.1 1.102 I 0.996 0.954 0.731 0.501 0.435 0.445 0.447 II 1.017 1.073 1.192 1.454 2.38 16.606 実施例５ r₁ 0.2 0.4 0.6 0.8 0.967 I 0.845 0.833 0.850 0.985 8.953 II 1.015 1.064 1.165 1.370 1.776 実施例６ r₁ 0.2 0.4 0.6 0.8 0.974 I 0.993 0.912 0.732 0.560 0.547 II 1.022 1.097 1.269 1.753 実施例７ r₁ 0.2 0.4 0.6 0.8 1 1.140 I 0.911 0.878 0.657 0.462 0.375 0.366 II 1.016 1.068 1.176 1.402 2.077 23.89 実施例８ r₁ 0.2 0.4 0.6 0.8 1.0 1.110 I 0.908 0.865 0.665 0.453 0.405 0.514 II 1.017 1.072 1.188 1.441 2.295 23.574 実施例９ r₁ 0.2 0.4 0.6 0.8 1.0 1.135 I 0.910 0.877 0.657 0.462 0.374 0.360 II 1.016 1.068 1.178 1.408 2.108 23.838 実施例10 r₁ 0.2 0.4 0.6 0.8 1.0 1.068 I 0.912 0.818 0.662 0.508 0.379 0.339 II 1.018 1.078 1.208 1.508 2.829 23.103 実施例11 r₁ 0.2 0.4 0.6 0.8 1.0 1.056 I 0.914 0.802 0.652 0.567 0.596 0.639 II 1.018 1.080 1.215 1.530 3.087 22.995 実施例12 r₁ 0.2 0.4 0.6 0.8 1.0 1.169 I 0.847 0.825 0.796 0.775 0.808 1.754 II 1.015 1.064 1.165 1.37 1.926 24.192 実施例13 r₁ 0.2 0.4 0.6 0.8 1 I 0.974 0.906 0.735 0.452 0.564 II 1.018 1.077 1.205 1.497 2.725 実施例14 r₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.906 0.739 0.446 0.606 II 1.018 1.077 1.204 1.494 2.693 実施例15 r₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.907 0.738 0.446 0.608 II 1.018 1.077 1.204 1.494 2.693 実施例16 r₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.907 0.739 0.445 0.616 II 1.018 1.077 1.204 1.494 2.693 実施例17 r₁ 0.2 0.4 0.6 0.8 1 I 0.978 0.908 0.741 0.438 0.701 II 1.018 1.077 1.204 1.492 2.678 実施例18 r₁ 0.2 0.4 0.6 0.8 1 I 0.98 0.91 0.741 0.437 0.745 II 1.018 1.077 1.203 1.49 2.662 実施例19 r₁ 0.2 0.4 0.6 0.8 0.987 I 0.853 0.628 0.516 0.505 0.546 II 1.021 1.094 1.259 1.707 22.22 ただしＩは（ｄθ/dr₁）／｛（ｄθ/dr₁）_r1＝０｝を
IIはを表わしている。Example 1 r ₁ 0.2 0.4 0.6 0.8 1.0 1.076 I 0.691 0.703 0.739 0.837 1.244 11.914 II 1.010 1.040 1.098 1.199 1.380 1.491 Example 2 r ₁ 0.2 0.4 0.6 0.8 1.0 1.133 I 0.711 0.704 0.710 0.746 0.912 5.866 II 1.010 1.044 1.108 1.221 1.434 1.659 Example 3 r ₁ 0.2 0.4 0.6 0.8 1.0 1.09 I 0.836 0.846 0.811 0.724 0.815 6.903 II 1.014 1.061 1.157 1.348 1.834 2.460 Example 4 r ₁ 0.2 0.4 0.6 0.8 1.0 1.1 1.102 I 0.996 0.954 0.731 0.501 0.435 0.445 0.447 II 1.017 1.073 1.192 1.454 2.38 16.606 Example 5 r ₁ 0.2 0.4 0.6 0.8 0.967 I 0.845 0.833 0.850 0.985 8.953 II 1.015 1.064 1.165 1.370 1.776 Example 6 r ₁ 0.2 0.4 0.6 0.8 0.974 I 0.993 0.912 0.732 0.560 0.547 II 1.022 1.097 1.269 1.753 Example 7 r ₁ 0.2 0.4 0.6 0.8 1 1.140 I 0.911 0.878 0.657 0.462 0.375 0.366 II 1.016 1.068 1.176 1.402 2.077 23.89 Example 8 r ₁ 0.2 0.4 0.6 0.8 1.0 1.110 I 0.908 0.865 0.665 0.453 0.405 0.514 II 1.017 1.072 1.188 1.441 2.295 23.574 Example 9 r ₁ 0.2 0.4 0.6 0.8 1.0 1.135 I 0.910 0.877 0.657 0.462 0.374 0.360 II 1.016 1.068 1.178 1.408 2.108 23.838 Example 10 r ₁ 0.2 0.4 0.6 0.8 1.0 1.068 I 0.912 0.818 0.662 0.508 0.379 0.339 II 1.018 1.078 1.208 1.508 2.829 23.103 Example 11 r ₁ 0.2 0.4 0.6 0.8 1.0 1.056 I 0.914 0.802 0.652 0.567 0.596 0.639 II 1.018 1.080 1.215 1.530 3.087 22.995 Example 12 r ₁ 0.2 0.4 0.6 0.8 1.0 1.169 I 0.847 0.825 0.796 0.775 0.808 1.754 II 1.015 1.064 1.165 1.37 1.926 24.192 Example 13 r ₁ 0.2 0.4 0.6 0.8 1 I 0.974 0.906 0.735 0.452 0.564 II 1.018 1.077 1.205 1.497 2.725 Example 14 r ₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.906 0.739 0.446 0.606 II 1.018 1.077 1.204 1.494 2.693 Example 15 r ₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.907 0.738 0.446 0.608 II 1.018 1.077 1.204 1.494 2.693 Example 16 r ₁ 0.2 0.4 0.6 0.8 1 I 0.977 0.907 0.739 0.445 0.616 II 1.018 1.077 1.204 1.494 2.693 Example 17 r ₁ 0.2 0.4 0.6 0.8 1 I 0.978 0.908 0.741 0.438 0.701 II 1.018 1.077 1.204 1.492 2.678 Example 18 r ₁ 0.2 0.4 0.6 0.8 1 I 0.98 0.91 0.741 0.437 0.745 II 1.018 1.077 1.203 1.49 2.66 2 Example 19 r ₁ 0.2 0.4 0.6 0.8 0.987 I 0.853 0.628 0.516 0.505 0.546 II 1.021 1.094 1.259 1.707 22.22 where I is (dθ / dr ₁ ) / {(dθ / dr ₁ ) _{r1 = 0} }
II Is represented.

上記実施例１乃至実施例19の照明レンズ系は、夫々第
８図乃至第26図に示す通りである。The illumination lens systems of Examples 1 to 19 are as shown in FIGS. 8 to 26, respectively.

これら実施例のうち実施例１乃至実施例６および実施
例13乃至実施例18は等非球面の単レンズで、成形の際、
型が一種類でよく低コストである。Among these examples, Examples 1 to 6 and 13 to 18 are equi-aspherical single lenses.
Only one type is required and the cost is low.

実施例７〜実施例11は非等非球面の単レンズで、性能
が一層向上している。Embodiments 7 to 11 are singular lenses having non-uniform aspheric surfaces, and the performance is further improved.

実施例12および実施例19は２枚の非球面レンズよりな
り１枚のものより性能の向上をはかることが出来る。The twelfth and nineteenth embodiments are composed of two aspherical lenses, and the performance can be improved more than one.

これら実施例に示すような本発明の照明レンズ系は、
条件（４）で規定するようにその焦点距離ｆをある程度
小さくすることが配光を向上させるための条件である。
そのためにはレンズ面の曲率を強くしなければならな
い。しかし物体側のライトガイド２の側に向いた凸面の
曲率を強くしすぎると光源側のライトガイド１から出射
された光が上記凸面の周辺部で全反射し光量の損失等を
生じ配光が悪くなる。これを防いで周辺まで均一な配光
を得るためには次の条件（16），（17）を満足する必要
がある。The illumination lens system of the present invention as shown in these examples,
A condition for improving the light distribution is to reduce the focal length f to some extent as defined by the condition (4).
For that purpose, the curvature of the lens surface must be increased. However, if the curvature of the convex surface facing the light guide 2 on the object side is too strong, the light emitted from the light guide 1 on the light source side is totally reflected at the periphery of the convex surface, causing a loss of light quantity and the like, and the light distribution is reduced. become worse. To prevent this and obtain uniform light distribution to the periphery, the following conditions (16) and (17) must be satisfied.

（16） P₁/P₂≦２（17）｜ω_１（Ｄ）／ω_２（Ｄ）｜≧0.5 ただしP₁,P₂は第１面、第２面の非球面を表わす係数
Ｐ、ω_１（Ｄ）はライトガイド１側に向いた面のライト
ガイド１の半径Ｄの位置における面のＹ軸（光軸に直交
する軸）に対する傾き角、ω_２（Ｄ）はライトガイド２
側に向いた面のライトガイド１の半径Ｄの位置における
面のＹ軸に対する傾き角である。(16) P ₁ / P ₂ ≦ 2 (17) | ω ₁ (D) / ω ₂ (D) | ≧ 0.5 where P ₁ and P ₂ are coefficients P representing the first and second aspheric surfaces, ω ₁ (D) is the inclination angle of the surface facing the light guide 1 with respect to the Y axis (axis orthogonal to the optical axis) at the position of the radius D of the light guide 1, and ω ₂ (D) is the light guide 2
This is the inclination angle of the surface with respect to the Y axis at the position of the radius D of the light guide 1 of the surface facing the side.

条件（16）は第１面と第２面の非球面を表わす係数P₁
とP₂の比率の範囲を定めたものである。光軸に平行に入
射した光は、第１面で屈折するため第２面での入射角が
大になる傾向を有する。したがって第２面を第１面より
凸形状をゆるくしないとレンズ周辺から入射した光が第
２面で全反射され、視野周辺に向かう光が減少する。こ
れを防止するために設けたのが条件（16）である。Condition (16) is a coefficient P ₁ representing the aspheric surface of the first surface and the second surface.
And in which defining a range of the ratio of P _2. Light incident parallel to the optical axis tends to have a large incident angle on the second surface because it is refracted on the first surface. Therefore, if the second surface is not loosened more convexly than the first surface, the light incident from the periphery of the lens is totally reflected by the second surface, and the light traveling toward the periphery of the visual field decreases. The condition (16) is provided to prevent this.

条件（17）は、ライトガイド１の側を向いた面の半径
Ｄの位置における面のｙ軸に対する傾き角がライトガイ
ド２の側を向いた面のライトガイド１の半径Ｄの位置に
おける面のｙ軸に対する傾き角よりも比較的大きいこと
を表わしている。Condition (17) is that the inclination angle of the surface facing the light guide 2 with respect to the y-axis at the position of the radius D of the surface facing the light guide 1 is equal to the inclination angle of the surface at the position of the radius D of the light guide 1 facing the light guide 2. This indicates that the angle is relatively larger than the inclination angle with respect to the y-axis.

これら条件（16），（17）を外れるといずれもライト
ガイド２の側を向いた非球面を含む凸面の周辺部の面の
傾きが比較的大きくなり全反射が発生し光量が低下す
る。If these conditions (16) and (17) are not satisfied, the inclination of the peripheral surface of the convex surface including the aspherical surface facing the light guide 2 becomes relatively large, and total reflection occurs to reduce the amount of light.

以上述べた条件（１）〜条件（17）はライトガイド１
から出射する光束のうちその出射角が比較的光軸に対し
て平行な軸上光線の領域（第１図の光線L₂,L₅,L₈）に関
して規定したものである。Conditions (1) to (17) described above correspond to light guide 1
Are defined with respect to the axial ray regions (light rays L ₂ , L ₅ , L _{8 in} FIG. 1) of the light flux emitted from the optical axis, the exit angle of which is relatively parallel to the optical axis.

ところでライトガイド１から出射する光束は、一般に
光軸に対して30゜程度までの範囲が十分な光量を有す
る。このような軸外光線の領域（第１図の光線L₁,L₃,
L₄,L₆,L₇,L₉）に関しても軸上光線の領域同様に光束が
集光することが望ましい。By the way, the light beam emitted from the light guide 1 generally has a sufficient amount of light in a range up to about 30 ° with respect to the optical axis. Regions of such off-axis rays (the rays L ₁ , L ₃ ,
Regarding L ₄ , L ₆ , L ₇ , and L ₉ ), it is desirable that the light beam be converged similarly to the area of the axial ray.

しかしながら条件（１）〜条件（17）を満足するよう
な双曲面形状では、双曲面の曲率が光軸より周辺部へ行
くにしたがって急激に弱くなるので軸外光線の領域にお
いて光束の集束性が低下し、ライトガイド２への入射光
量が低下する。これを防ぐためには、全反射を生ずるこ
となくかつ軸上光線と軸外光線が透過する位置が比較的
異なるライトガイド１の側を向いた非球面部分を含む凸
面の少なくとも一つの面が光軸から周辺に行くにしたが
って面の曲率が徐々に弱くなる面を含んでおり、かつさ
らに周辺に行くにしたがって面の曲率が徐々に強くなる
面を含んでいることが望ましい。However, in a hyperboloid shape satisfying the conditions (1) to (17), the convergence of the luminous flux in the region of the off-axis light ray is reduced because the curvature of the hyperboloid becomes rapidly weaker toward the periphery from the optical axis. And the amount of light incident on the light guide 2 decreases. To prevent this, at least one of the convex surfaces including the aspherical portion facing the side of the light guide 1 that does not cause total internal reflection and that transmits the on-axis light beam and the off-axis light beam at relatively different positions has an optical axis. It is desirable to include a surface where the curvature of the surface gradually decreases as going from the periphery to the periphery, and further include a surface where the curvature of the surface gradually increases as going toward the periphery.

又実施例19は、レンズの外径が小さく、良好な配光特
性を有している。前記のように、一般にライトガイド
は、大きなNAを有するために、実施例１〜11,13〜18の
非球面単レンズでは、レンズの外径が大きくなり、内視
鏡等の照明光学系としては、不都合なこともある。その
ため、より外径の小さい照明光学系を得るためには、実
施例19のような構成にすることが望ましい。In Example 19, the outer diameter of the lens is small, and the lens has good light distribution characteristics. As described above, in general, the light guide has a large NA, so that the aspherical single lenses of Examples 1 to 11, and 13 to 18 have a large outer diameter of the lens, and are used as an illumination optical system such as an endoscope. May be inconvenient. Therefore, in order to obtain an illumination optical system with a smaller outer diameter, it is desirable to adopt a configuration as in the nineteenth embodiment.

実施例19は、ライトガイド１の射出端面の外周に近い
部分から射出される大きなNAを持った光束が、光軸から
あまり遠ざからないように、第１面を周辺に行くにした
がって徐々に曲率が小さくなる非球面にし、第３面を条
件（１）を満足するようにして、双曲面状の非球面にし
ている。更に単レンズと比較して、実施例19のレンズ系
は、各面で徐々に光線が曲げられるために、全反射等に
よる光量の損失が少ない。In the nineteenth embodiment, the light flux having a large NA emitted from a portion near the outer periphery of the light emitting end surface of the light guide 1 is gradually curved toward the periphery of the first surface so as not to be too far from the optical axis. Is reduced, and the third surface is made a hyperboloid aspherical surface so as to satisfy the condition (1). Further, compared to the single lens, the lens system of Example 19 has a small loss of light amount due to total reflection and the like because light rays are gradually bent on each surface.

第27図は、前述の従来例の結合レンズによるライトガ
イド２の入射端面上の配光特性を示す。又第28図および
第29図は夫々本発明のレンズ系の実施例４および実施例
11の配光特性を示す。FIG. 27 shows the light distribution characteristics on the incident end face of the light guide 2 by the above-described conventional coupling lens. 28 and 29 show Embodiment 4 and Embodiment of the lens system of the present invention, respectively.
11 shows light distribution characteristics.

これら図より明らかなように、本発明の実施例は、従
来例よりも良好な配光が得られることが明らかである。As is clear from these figures, it is clear that the embodiment of the present invention can obtain a better light distribution than the conventional example.

本発明の光学系を、ライトガイドの連続光学系として
用いる場合、光源側ライトガイドの側に配置しても物体
側ライトガイドの側に配置してもよい。又配光特性の異
なるもの複数を交換自在にしてもよい。又本発明で使用
するレンズは、研磨による製作、切削による製作又、高
温高圧下におけるプレス成形によるものいずれでもよ
い。又材料は比較的屈折率の高いものが望ましく、光学
ガラスでも光学結晶でもよい。When the optical system of the present invention is used as a continuous optical system of a light guide, it may be arranged on the light source side light guide side or on the object side light guide side. A plurality of light distribution characteristics may be interchangeable. The lens used in the present invention may be manufactured by polishing, manufactured by cutting, or formed by press molding under high temperature and high pressure. The material is preferably one having a relatively high refractive index, and may be optical glass or optical crystal.

［発明の効果］本発明の照明光学系は、従来例の光学系よりも物体側
のライトガイドの入射端面等の非照明面へ入射する光の
配光特性を角度の大きいところまで平坦にすることが出
来、視野角の大きな内視鏡に用いた場合、特に効果的で
ある。[Effects of the Invention] The illumination optical system of the present invention flattens the light distribution characteristics of light incident on a non-illumination surface such as the incident end face of the light guide on the object side, to a larger angle than the conventional optical system. This is particularly effective when used in an endoscope having a large viewing angle.

又この光学系で用いられる照明レンズ系として非球面
を有する少なくとも一つの正レンズを含む構成にするこ
とによって枚数が少なく、組立構造が簡単になることも
加えて大幅なコストダウンをはかることが出来る。In addition, by using at least one positive lens having an aspherical surface as the illumination lens system used in this optical system, the number of the lenses is reduced, the assembly structure is simplified, and the cost can be significantly reduced. .

尚照明レンズ系に用いる非球面は、多面体近似を用い
て双曲面を近似した形状でもよく、高次の非球面係数を
用いて双曲面様にしたものでもよい。更にフレネルレン
ズ、段付レンズ又、非軸対称非球面レンズ等を用いても
同様の効果が得られる。The aspherical surface used in the illumination lens system may have a shape obtained by approximating a hyperboloid using polyhedral approximation, or may have a hyperboloid-like shape using a higher order aspherical coefficient. Further, similar effects can be obtained by using a Fresnel lens, a stepped lens, a non-axially symmetric aspherical lens, or the like.

[Brief description of the drawings]

第１図は、本発明の光学系の基本構成を示す図、第２図
は物体側ライトガイド端面での強度分布を示す図、第３
図はその配光特性を示す図、第４図，第５図は従来の連
結光学系の構成を示す図、第６図，第７図は上記従来例
の特性を示す図、第８図乃至第26図は本発明のレンズ系
の実施例１乃至実施例19の断面図、第27図は従来例の配
光特性を示す図、第28図，第29図は夫々本発明の実施例
４および実施例11の配光特性を示す図で、第30図は非球
面形状の一例を示す図である。FIG. 1 is a diagram showing a basic configuration of an optical system of the present invention, FIG. 2 is a diagram showing an intensity distribution at an end face of an object-side light guide, and FIG.
4 and 5 show the configuration of a conventional coupling optical system, FIGS. 6 and 7 show the characteristics of the above-mentioned conventional example, and FIGS. FIG. 26 is a sectional view of Examples 1 to 19 of the lens system of the present invention, FIG. 27 is a diagram showing light distribution characteristics of a conventional example, and FIGS. 28 and 29 are Example 4 of the present invention. FIG. 30 shows light distribution characteristics of Example 11 and FIG. 30. FIG. 30 shows an example of an aspherical shape.

Claims

(57) [Claims]

At least one positive lens is included,
In an illumination optical system that irradiates light emitted from a planar light source toward a surface to be irradiated, the positive lens has an optical axis along an x-axis,
When the direction perpendicular to the optical axis is taken on the y-axis, it has an aspheric surface approximated by the following expression (3), and the following conditions (4), (5),
An illumination optical system characterized in that (6) is satisfied by at least 50% or more of an area of a portion through which an effective light beam passes. (4) 0.2 ≦ D / f ≦ 3 (5) P <0 (6) | Δ | ≦ | X _max | / 2 where P, E, F, G... Are coefficients representing an aspherical surface, and R is The radius of curvature on the optical axis of the aspheric surface, D is the distance from the optical axis to the outermost periphery of the planar light source, f is the focal length of the lens system, and Δ is the optical axis between the approximate aspheric surface and the actual aspheric surface. Direction deviation amount,
X _max is the maximum value of | x | represented by equation (3).

2. An illumination optical system for irradiating light emitted from a planar light source toward a surface to be illuminated by a lens system including at least one positive lens, wherein the positive lens has an optical axis of x axis and an optical axis of When the direction perpendicular to is taken on the y-axis, equation (3)
And the following condition (4),
An illumination optical system characterized by satisfying (6), (7), (8), (9), (10), and (11) with at least 50% or more of an area of a portion through which an effective light beam passes. (4) 0.2 ≦ D / f ≦ 3 (6) | Δ | ≦ | X _max | / 2 (7) 0 ≦ P <1 (8) E ≦ 0 (9) F ≧ 0 (10) 0 ≦ | E · D ^-3 | ≦ 1 (11) 0 ≦ | F · D ^-3 | ≦ 0.5 where P, E, F, G... Are coefficients representing an aspheric surface, and R is on the optical axis of the aspheric surface. Radius of curvature, Δ is the distance from the optical axis to the outermost edge of the planar light source, f is the focal length of the lens system, Δ is the amount of deviation between the approximate aspheric surface and the actual aspheric surface in the optical axis direction,
X _max is the maximum value of x represented by Expression (3).

3. An illumination optical system for irradiating light emitted from a planar light source toward a surface to be irradiated by a lens system including at least one positive lens, wherein the positive lens has an optical axis x.
When the direction perpendicular to the optical axis and the optical axis is taken as the y axis, it has an aspheric surface approximated by the equation (3), and further has the following conditions (4) and (4).
(6) An illumination optical system which satisfies (8), (9) and (12) to (14) with at least 50% or more of the area of a portion through which an effective light beam passes. (4) 0.2 ≦ D / f ≦ 3 (6) | Δ | ≦ | X _max | / 2 (8) E ≦ 0 (9) F ≧ 0 (12) P ≧ 0 (13) 0.1 ≦ | E · D ^-3 | ≦ 0.6 (14) 0 ≦ | F · D ^-3 | ≦ 0.1 where P, E, F, G... Are coefficients representing an aspheric surface, and R is a radius of curvature of the aspheric surface on the optical axis. , D is the distance from the optical axis to the outermost edge of the planar light source, f is the focal length of the lens system, Δ is the amount of deviation between the approximate aspheric surface and the actual aspheric surface in the optical axis direction,
X _max is the maximum value of x represented by Expression (3).

4. The illumination optical system according to claim 1, wherein said lens system includes a plurality of aspherical surfaces, and further satisfies conditions (15) and (16). (15) P ₁ / P ₂ ≦ 2 (16) | ω ₁ (D) / ω ₂ (D) | ≧ 0.5 where P ₁ and P ₂ are aspherical surfaces facing the planar light source side and the irradiation surface side, respectively. A coefficient P representing an aspheric surface in the equation (3) of
ω ₁ (D) and ω ₂ (D) are axes passing through the optical axis of the aspheric surface at the outermost peripheral position D of the planar light source facing the planar light source side and the irradiation surface side, respectively, and orthogonal to the optical axis. It is the inclination angle with respect to.

5. The illumination optical system according to claim 2, wherein said lens system includes a plurality of aspherical surfaces, and further satisfies conditions (15) and (16). (15) P ₁ / P ₂ ≦ 2 (16) | ω ₁ (D) / ω ₂ (D) | ≧ 0.5 where P ₁ and P ₂ are aspherical surfaces facing the planar light source side and the irradiation surface side, respectively. A coefficient P representing an aspheric surface in the equation (3) of
ω ₁ (D) and ω ₂ (D) are axes passing through the optical axis of the aspheric surface at the outermost peripheral position D of the planar light source facing the planar light source side and the irradiation surface side, respectively, and orthogonal to the optical axis. It is the inclination angle with respect to.

6. The illumination optical system according to claim 3, wherein said lens system includes a plurality of aspheric surfaces, and further satisfies conditions (15) and (16). (15) P ₁ / P ₂ ≦ 2 (16) | ω ₁ (D) / ω ₂ (D) | ≧ 0.5 where P ₁ and P ₂ are aspherical surfaces facing the planar light source side and the irradiation surface side, respectively. A coefficient P representing an aspheric surface in the equation (3) of
ω ₁ (D) and ω ₂ (D) are axes passing through the optical axis of the aspheric surface at the outermost peripheral position D of the planar light source facing the planar light source side and the irradiation surface side, respectively, and orthogonal to the optical axis. It is the inclination angle with respect to.