JPS6113204B2

JPS6113204B2 -

Info

Publication number: JPS6113204B2
Application number: JP6390676A
Authority: JP
Inventors: Hideo Yokota
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1976-06-01
Filing date: 1976-06-01
Publication date: 1986-04-12
Also published as: JPS52146620A

Description

【発明の詳細な説明】[Detailed description of the invention]

本発明は口径比Ｆ＝１：1.8、画角2w＝44゜以
上を充し得るレンズであつて、一眼レフレツクス
カメラ用として充分なバツク・フオーカスを持つ
た６枚構成のガウス型レンズに関するものであ
る。一眼レフレツクスカメラ用の標準レンズとして
最も適しているガウス型レンズは、その高性能化
とコスト低減の為のさまざまな改良がなされて来
た。その方策の一つとして、絞り直前の貼合せレ
ンズを分離する事でコマ収差及びフレアーの改善
を計り、且つ絞りより後方の正レンズに比較して
屈折力を弱くし得る処の絞りより前側の正レンズ
に屈折率の低い硝種を使えるので安価で加工性を
良好にし得る事は良く知られているところであ
る。しかしながらこの構成のレンズは、第１図に描
く如く子午像面がｗ＝16゜以上の画角で急激に負
方向に湾曲する傾向を持つので、周辺画角に於け
る子午結像性能を確保する為に中間画角での子午
像面を近軸像面に一致させなければならず、その
為大きな非点収差を生ずるものである。本発明は前述の構成のレンズの更なる性能向上
を計り、ことに非点収差の改良を目的としてい
る。後に数値を記載する本発明のレンズは第２図
第４図に図示の５群６枚構成で、物体側より順に
第１群と第２群は凸面を物体側に向けた正メニス
カス単レンズ、第３群は凹面を像側に向けた負メ
ニスカス単レンズ、第４群は凹面を物体側に向け
た負メニスカスレンズで、両凹単レンズと両凸単
レンズを順に貼合せて成り、第５群は曲率大なる
面を像側に向けた両凸正レンズであつて、第３群
と第４群の間に絞りを有し、 ri……物体側より順次レンズ面の曲率半径 di……物体側より順次軸上のレンズ厚もしくは
空気間隔 Ni……物体側より順次レンズのｄ線に対する
屈折率 Vi……物体側より順次レンズのアツベ数ｆ………レンズ全系の焦点距離とした時、 0.28f＜｜r₇｜＜0.33f …(a) −0.017f＜（d₃＋d₄＋d₅）−
（d₇＋d₈）＜0.017f…(b) 1.62＜N₁ …(c) 1.62＜N₂＜1.68 …(d) 1.68＜N₆ …(e) を満たすガウス型レンズに於いて以下の条件を満
足する事を特徴とする。 0.63f＜r₄＜0.75f …(1) 0.95f＜r₅＜1.2f …(2) 0.2＜ｒ_１／ｒ_２＜0.23 …(3) 1.1f＜｜r₁₁｜＜1.2f …(4) 0.27f＜r₆＜0.28f …(5) 1.72＜N₅ …(6) 28＜V₃＜32 …(7) 以上の記載のうち、(a)〜(e)の条件は本発明の対
象としている種類のレンズに固有の性質とも云え
るもので、その意味では必ずしも新規な条件では
ないが、収差補正上からは重要であり、条件(1)〜
(7)との共働で目的を達成している。以下に各条件の有効性を説明する。本発明に係る構成のガウス型レンズは、第４及
び第５レンズ面に於て極めて強い収差補正作用を
有するので、それらの面の曲率半径の設定には特
に留意しなければならない。第(1)及び第(2)の条件
は両面の適切な範囲を示すもので、第(1)式の上限
値を越えると球面収差は逆傾向の球面収差とのバ
ランス上から見て補正不足となり、下限値を越え
ると中間画角に於ける輪帯の外向性コマ収差が発
生し、又第(2)式の上限値を越えると中間画角での
フレアーが増大し、下限値を越えると非点収差が
補正不足となる。一方、第２群と第３群とを分離した事に起因す
る画周辺での子午像面の湾曲は、第１，第５，第
６レンズにNd＝1.75以上の高屈折率硝子を使用
する事によつて軽減されるがコスト高を招く。そ
こでこの手法を避けて、第１群の曲率半径の比
r₁／r₂を0.2＜r₁／r₂として周辺での子午像面湾曲
の補正を計るものであるが、上記の補正方法では
球面収差の発生を招く恐れがあるから、その上限
値をr₁／r₂＜0.23に限定し、且つ第５群後面の曲
率半径r₁₁を1.1f＜｜r₁₁｜として第５群で発生す
る球面収差を抑える事でＦ＝１：1.8以上の口径
比を得るものである。即ち第(3)条件の式の下限値を越えると画面周辺
の子午像面湾曲が著るしくなり、上限値を越える
と球面収差が補正不足となる。又第(4)条件の下限
値を越えると球面収差が補正不足となり、上限値
を越えると第５群前面の曲率半径を小さくする必
要から負の歪曲収差が増大する。ガウス型レンズ特有の絞り前後の強い発散面は
球面収差及びコマ収差の補正に対してもその作用
は大きい。第(5)条件そして第(a)条件はそれらの面
の曲率半径の適切な範囲を示すもので、第(5)条件
の上限値を越えると中間画角に於ける内向性コマ
収差が増大し、下限値を越えると輪帯の球面収差
が補正過剰となる。又第(a)条件の上限値を越える
とペツツバール和が増大して球欠像面湾曲が過大
となり、下限値を越えると中間から周辺画角での
フレアーが増大する。第(b)条件は第(3)条件に示す如く、第５群後面の
曲率半径が1.1f＜｜r₁₁｜＜1.2fなる領域に於いて
歪曲収差の補正を可能ならしむるもので、その下
限値を越えると負の歪曲収差の補正が困難とな
り、上限値を越えるとバツクフオーカスが短くな
つて一眼レフレツクスカメラ用として不適とな
る。第(6)条件、第(c)条件、第(d)条件、第(e)条件は正
レンズの硝種の選定に於る最適範囲を示し、各式
とも下限値を越えるとペツツバール和が悪化する
と共に球面収差の補正が因難となる。しかし第２レンズの屈折率N₂については非点
収差の補正の為、第(d)条件の上限値が必要で、そ
の上限値を越えると非点収差の補正が不足する。第(7)条件は第(1)条件、第(2)条件、第(5)条件によ
つて限定された曲率半径の範囲内の第２群及び第
３群に於て色収差の補正を良好に行う為に必要な
条件で、その上限値を越えると軸上色収差の補正
が不足し、下限値を越えると軸上色収差の補正が
過大となる。以下に実施例を記載するが、第２図は実施例１
に対応し、第４図は実施例２に対応する。実施例１焦点距離ｆ＝100 バツクフオーカス＝70.0 The present invention relates to a six-element Gaussian lens that can satisfy an aperture ratio of F = 1:1.8 and an angle of view of 2W = 44 degrees or more, and has sufficient back focus for single-lens reflex cameras. It is something. The Gaussian lens, which is most suitable as a standard lens for single-lens reflex cameras, has undergone various improvements to improve its performance and reduce costs. One of the measures is to improve comatic aberration and flare by separating the bonded lens just before the aperture, and to improve the refractive power of the lens in front of the aperture, where the refractive power can be weakened compared to the positive lens behind the aperture. It is well known that since a glass type with a low refractive index can be used for a positive lens, it can be made at low cost and with good workability. However, with this lens configuration, as shown in Figure 1, the meridional image plane tends to curve sharply in the negative direction at angles of view of w = 16° or more, so the meridional imaging performance at peripheral angles of view is ensured. In order to do this, the meridional image plane at an intermediate angle of view must be made to coincide with the paraxial image plane, which results in large astigmatism. The present invention aims to further improve the performance of the lens configured as described above, and in particular aims to improve astigmatism. The lens of the present invention, the numerical values of which will be described later, has a configuration of 6 elements in 5 groups as shown in FIGS. 2 and 4, and in order from the object side, the first and second groups are positive meniscus single lenses with convex surfaces facing the object side, The third group is a negative meniscus single lens with the concave surface facing the image side, the fourth group is a negative meniscus lens with the concave surface facing the object side, and is made up of a biconcave single lens and a double convex single lens laminated in order. The group is a biconvex positive lens with the surface with large curvature facing the image side, and has an aperture between the third and fourth groups, ri...the radius of curvature of the lens surface di... Lens thickness or air spacing on the axis sequentially from the object side Ni...Refractive index for the d-line of the lens sequentially from the object side Vi...... Atsube number of the lens sequentially from the object side f......When taken as the focal length of the entire lens system , 0.28f＜｜ _r7 ｜＜0.33f…(a) −0.017f＜( _d3 + _d4 + _d5 )−
(d ₇ + d ₈ )<0.017f…(b) 1.62<N ₁ …(c) 1.62<N ₂ <1.68…(d) 1.68<N ₆ …(e) The following conditions are satisfied for a Gaussian lens that satisfies It is characterized by satisfying the following. 0.63f＜r ₄ ＜0.75f …(1) 0.95f＜r ₅ ＜1.2f …(2) 0.2＜r ₁ /r ₂ ＜0.23 …(3) 1.1f＜｜r ₁₁ ｜＜1.2f …(4) ) 0.27f< _r6 <0.28f...(5) 1.72< _N5 ...(6) 28< _V3 <32...(7) Among the above descriptions, conditions (a) to (e) are applicable to the present invention. This can be said to be a property unique to the type of lens in question, and in that sense it is not necessarily a new condition, but it is important from the perspective of aberration correction, and conditions (1) to
(7) Achieves the purpose by working together with. The effectiveness of each condition will be explained below. Since the Gaussian lens configured according to the present invention has an extremely strong aberration correcting effect on the fourth and fifth lens surfaces, particular care must be taken in setting the radius of curvature of these surfaces. Conditions (1) and (2) indicate appropriate ranges for both surfaces; if the upper limit of equation (1) is exceeded, spherical aberration is insufficiently corrected in terms of balance with spherical aberration, which has the opposite tendency. When the lower limit value is exceeded, annular extroverted coma aberration occurs at intermediate angles of view, and when the upper limit value of equation (2) is exceeded, flare at intermediate angles of view increases, exceeding the lower limit value. This results in undercorrection of astigmatism. On the other hand, the curvature of the meridian image plane around the image caused by separating the second and third groups requires the use of high refractive index glass with Nd=1.75 or higher for the first, fifth, and sixth lenses. Although this can be alleviated by doing so, it also increases costs. Therefore, by avoiding this method, the ratio of the radius of curvature of the first group is
The method is to correct the meridional field curvature at the periphery by setting r ₁ /r ₂ to 0.2<r ₁ /r ₂ , but since the above correction method may cause spherical aberration, the upper limit value must be set. By limiting r ₁ /r ₂ <0.23 and setting the radius of curvature r ₁₁ of the rear surface of the fifth group to 1.1f < | r ₁₁ | to suppress the spherical aberration occurring in the fifth group, an aperture of F=1:1.8 or more can be achieved. It is to obtain the ratio. That is, when the lower limit of the equation (3) is exceeded, the meridional field curvature at the periphery of the screen becomes significant, and when the upper limit is exceeded, the spherical aberration becomes insufficiently corrected. Moreover, if the lower limit of condition (4) is exceeded, spherical aberration will be insufficiently corrected, and if the upper limit is exceeded, negative distortion will increase due to the need to reduce the radius of curvature of the front surface of the fifth group. The strong diverging surfaces before and after the aperture, which are unique to Gaussian lenses, have a large effect on correcting spherical aberration and coma aberration. Conditions (5) and (a) indicate the appropriate range of the radius of curvature of these surfaces; if the upper limit of condition (5) is exceeded, inward coma aberration increases at intermediate angles of view. However, when the lower limit is exceeded, the spherical aberration of the annular zone becomes overcorrected. Moreover, when the upper limit of condition (a) is exceeded, the Petzval sum increases and the field curvature becomes excessive, and when the lower limit is exceeded, flare at intermediate to peripheral angles of view increases. Condition (b), as shown in condition (3), makes it possible to correct distortion in the region where the radius of curvature of the rear surface of the fifth group is 1.1f<|r ₁₁ |<1.2f, If the lower limit value is exceeded, it becomes difficult to correct negative distortion aberration, and if the upper limit value is exceeded, the back focus becomes short, making it unsuitable for single-lens reflex cameras. Conditions (6), (c), (d), and (e) indicate the optimal range for selecting the glass type of the positive lens, and for each formula, if the lower limit is exceeded, the Petzval sum worsens. At the same time, correction of spherical aberration becomes a problem. However, for the refractive index N ₂ of the second lens, an upper limit value of condition (d) is required for astigmatism correction, and if the upper limit value is exceeded, the astigmatism correction will be insufficient. Condition (7) provides good correction of chromatic aberration in the second and third groups within the radius of curvature limited by conditions (1), (2), and (5). If the upper limit is exceeded, the correction of longitudinal chromatic aberration will be insufficient, and if the lower limit is exceeded, the correction of longitudinal chromatic aberration will be excessive. Examples are described below, and Figure 2 shows Example 1.
, and FIG. 4 corresponds to the second embodiment. Example 1 Focal length f=100 Back focus=70.0

【表】【table】

【表】実施例２焦点距離ｆ＝100 バツクフオーカス＝69.8【table】 Example 2 Focal length f = 100 Back focus = 69.8

【表】【table】

【表】如上の実施例１の球面収差・非点収差・歪曲収
差・横収差を第３図に示し、実施例２については
第５図に示す。[Table] Spherical aberration, astigmatism, distortion aberration, and lateral aberration of Example 1 are shown in FIG. 3, and Example 2 is shown in FIG. 5.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は周知のガウス型レンズの非点収差図。
第２図は本発明の実施例１に対応するレンズ断面
図で、第３図はその諸収差図である。第４図は実
施例２に対応するレンズ断面図で、第５図はその
諸収差図である。図中でｒはレンズ面の曲率半
径、ｄはレンズの肉厚もしくは面間隔。 FIG. 1 is an astigmatism diagram of a well-known Gaussian lens.
FIG. 2 is a sectional view of a lens corresponding to Example 1 of the present invention, and FIG. 3 is a diagram of various aberrations thereof. FIG. 4 is a sectional view of a lens corresponding to Example 2, and FIG. 5 is a diagram of various aberrations thereof. In the figure, r is the radius of curvature of the lens surface, and d is the lens thickness or surface spacing.

Claims

【特許請求の範囲】１物体側から順に第１群と第２群は凸面を物体
側に向けた正メニスカス単レンズ、第３群は凹面
を像側に向けた負メニスカス単レンズ、第４群は
負と正単レンズを貼合せ且つ凹面を物体側へ向け
た負メニスカスレンズ、第５群は曲率大なる面を
像側へ向けた両凸単レンズとし、第３群と第４群
の間に絞りを有して、riを物体側より順次のレン
ズ面の曲率半径、diを物体側より順次のレンズ厚
もしくは空気間隔、Niを物体側より順次の単レ
ンズのｄ線に対する屈折率、Viを物体側より順
次の単レンズのアツベ数、ｆを全系の焦点距離と
し、 0.28f＜｜r₇｜＜0.33f −0.017f＜（d₃＋d₄＋d₅）−（d₇＋d₈）＜0.017f 1.62＜N₁ 1.62＜N₂＜1.68 1.68＜N₆ を満足する５群６枚構成のレンズに於いて、 0.63f＜r₄＜0.75f 0.95f＜r₅＜1.2f 0.2＜ｒ_１／ｒ_２＜0.23 1.1f＜｜r₁₁｜＜1.2f 0.27f＜r₆＜0.28f 1.72＜N₅ 28＜V₃＜32 である事を特徴とするガウス型レンズ。[Claims] 1. In order from the object side, the first and second groups are a positive meniscus single lens with a convex surface facing the object side, the third group is a negative meniscus single lens with a concave surface facing the image side, and the fourth group is a negative meniscus single lens with a concave surface facing the image side. is a negative meniscus lens made by laminating negative and positive single lenses with the concave surface facing the object side, and the fifth group is a biconvex single lens with the surface with large curvature facing the image side, between the third and fourth groups. ri is the radius of curvature of the lens surface sequentially from the object side, di is the lens thickness or air gap sequentially from the object side, Ni is the refractive index for the d-line of the single lens sequentially from the object side, Vi Let be the Atsube number of the single lens sequentially from the object side, f be the focal length of the entire system, and 0.28f<|r ₇ |<0.33f −0.017f<(d ₃ +d ₄ +d ₅ )−(d ₇ +d ₈ ) <0.017f 1.62<N ₁ 1.62<N ₂ <1.68 1.68<N In a lens with 6 elements in 5 groups that satisfies ₆ , 0.63f<r ₄ <0.75f 0.95f<r ₅ <1.2f 0.2<r ₁ /r ₂ <0.23 1.1f<|r ₁₁ |<1.2f 0.27f<r ₆ <0.28f 1.72<N ₅ 28<V ₃ <32 A Gaussian lens.