JP3743065B2 - Eyepiece - Google Patents

Description

なる条件を満たす。
但し、ｘ：頂点から光軸方向に測った距離
ｙ：頂点から光軸と垂直に測った距離
Ｃ₀：頂点曲率（Ｃ₀＝１／Ｒ、Ｒ：頂点曲率半径）
κ：円錐定数
Ｃ_2i：第２ｉ（ｉ≧２）次の非球面係数
である。更に第４次の非球面係数Ｃ₄としては、
１×１０^-8＜｜Ｃ₄｜ ‥‥（Ｃ′）
なる条件を満たす。
【０００８】
以下に上記条件（Ｃ）及び（Ｃ′）について説明する。
接眼レンズに非球面を用いた補正板を加えることによって、瞳の収差を補正する場合を考えてみる。図１３に示すように従来の球面レンズよりなる接眼レンズＬ_eのアイポイント側に、非球面形状を有する補正板Ｌ_cを配置し、この補正板Ｌ_cにより接眼レンズＬ_eの瞳収差を補正する。
補正板Ｌ_cの形状が図１４に示されているように、ｑを定数として次の式で表されたとする。
ｘ＝ｑｙ⁴ ‥‥（１）
接線の角度θは（１）式を微分して次のように得られる。
θ＝４ｑｙ³
補正板Ｌ_cの屈折率をｎとし、補正板Ｌ_cの非球面を通過した後の光線Ｒの角度をθ’とし、非球面による光線Ｒの偏角をδとすれば、偏角δは次式で表される。

【０００９】
一方接眼レンズＬ_eによる瞳の収差ΔＳ’は、Ａを定数として３次収差の領域において次のように表される。
ΔＳ’＝Ａｙ² ‥‥（３）
ｙは接眼レンズに入射する光線の高さである。
接眼レンズの瞳の結像における倍率をβとするとΔＳ’は、以下のようにも表せる。
ΔＳ’＝−β²ΔＳ ‥‥（４）
入射瞳までの距離Ｓは接眼レンズの焦点距離に比べて十分大きいとすると、正弦定理により次式が成り立つ。
ΔＳ＝−Ｓ²δ／ｙ＝−４（１−１／ｎ）ｑＳ²ｙ² ‥‥（５）
【００１０】
（５）式を（４）式に代入して（３）式と比較することにより、
Ａ＝４（１−１／ｎ）β²ｑＳ² ‥‥（６）
とすれば（３）式と（４）式が一致することがわかる。歪曲収差は、瞳の収差に伴って減る傾向があるため、（６）式を満足するようなｑを与えれば、全体として瞳の収差、つまり歪曲収差のない接眼レンズを得ることができる。（１）式を書き換えれば、
ｘ＝ｑｙ⁴＝Ａ／（４（１−１／ｎ）β²Ｓ²）・ｙ⁴ ‥‥（７）
となる。また、β＝Ｓ’／Ｓであるから上式は次のように書き換えられる。
ｘ＝Ａ／（４（１−１／ｎ）Ｓ’²）・ｙ⁴ ‥‥（８）
前述のｑは、非球面を表すために一般的に用いられる前記（Ｅ）式におけるｙ⁴の係数Ｃ₄に対応している。
【００１１】
（８）式において、Ｓ’は接眼レンズのアイレリーフであるから、Ｓ’は１０〜３０ｍｍ程度と考えてよい。接眼レンズの構成、入射瞳位置、焦点距離などによって、定数Ａは異なるが、Ｃ₄が前記条件（Ｃ）の範囲にあるようにすれば、一般的な接眼レンズの定数Ａに対して、瞳収差の補正を良好に行うことができる。歪曲収差だけでなく、良好な非点収差の補正も望むならば、前記条件（Ｃ′）をも満たせば良い。
Ｃ₄が条件（Ｃ′）の下限を越えるなら、瞳収差は補正不足となり、逆に条件（Ｃ）の上限を越えると、補正過剰となる。又、上述の説明では補正板Ｌ_cはアイポイント側に置いたが、物体側に置いても同様の結果が得られる。
【００１２】
次に頂点曲率Ｃ₀が０でない、すなわちｙ²の項の係数が０でない場合を考えてみる。非球面形状が次の式で表されたとする。
ｘ＝ｐｙ²＋ｑｙ⁴ ‥‥（９）
上記と同様に接線の角度θと、瞳の収差ΔＳ’は以下のように求められる。

【００１３】
この式における右辺第２項は、頂点曲率Ｃ₀が０である場合のものと同一である。第１項はｙ²を含まない定数項、すなわち頂点曲率Ｃ₀の面による像点の移動を表す項であり、瞳収差の補正には関係ないものである。従って、補正板の形状にｙ²の項（２次曲面）に相当するものが入っても、言い換えれば、補正板が屈折力を持つレンズであっても、瞳収差の補正にはｙ⁴の項のみが影響しているため、Ｃ₄の値が条件（Ｃ）ないしは更に条件（Ｃ′）の範囲にある限り、瞳収差は良好に補正される。
【００１４】
以上の説明では、補正板Ｌ_cの形状としてｙ⁴の項だけを持つ場合、あるいはｙ⁴の次数までを持つ場合について述べたが、これは３次収差の領域においては、ｙ⁴の項のみで完全に瞳収差が補正されるためである。しかし、接眼レンズの画角を広げるほど３次収差の領域から外れるため、ｙ⁴の項のみで表された上述の非球面補正板では瞳収差を完全に補正できなくなる。その場合には補正板Ｌ_cの非球面形状において、前述のｙ⁴の項の他に、更に高次の補正項を付加してやれば良い。
【００１５】
【発明の実施の形態】
本発明による接眼レンズの実施の形態について説明する。図１、図３、図５、図７及び図９に、それぞれ本発明の第１〜第５実施例のレンズ構成図を示す。また図１１に比較例のレンズ構成図を示す。各実施例と比較例は、アイポイント側から順に、１個の正レンズ成分で構成された第１レンズ群Ｇ₁と、正レンズ成分と負レンズ成分との接合レンズ、又は負レンズ成分と正レンズ成分との接合レンズで構成された正屈折力の第２レンズ群Ｇ₂と、正レンズ成分と負レンズ成分との接合レンズで構成された正屈折力又は負屈折力の第３レンズ群Ｇ₃とからなる。
【００１６】
このうち第１実施例、第２実施例、及び第５実施例では、第１レンズ群Ｇ₁の物体側のレンズ面に非球面が用いられている。但し第１実施例と第２実施例では、第２レンズ群Ｇ₂の接合レンズが、アイポイント側から負レンズ成分と正レンズ成分の順に配置されているのに対して、第５実施例では、第２レンズ群Ｇ₂の接合レンズが、アイポイント側から正レンズ成分と負レンズ成分の順に配置されている点で相違する。更に第１実施例では、非球面を含む第１レンズ群Ｇ₁の硝材として、光学ガラスが用いられているのに対し、第２実施例では、第１レンズ群Ｇ₁の硝材として樹脂製の光学材料が用いられている点で相違する。
また第３実施例では、第２レンズ群Ｇ₂の最も物体側のレンズ面に非球面が用いられており、第４実施例では、第３レンズ群Ｇ₂の最も物体側のレンズ面に非球面が用いられている。これに対して比較例では、いずれのレンズ面にも非球面は用いられていない。
【００１７】
以下の表１〜表２に、それぞれ第１〜第５実施例の全体諸元、レンズ諸元及び非球面データを示す。また表６に比較例の全体諸元とレンズ諸元を示す。各表のレンズ諸元において、第１カラムは物体側からのレンズ面の番号、第２カラムｒはレンズ面の曲率半径、第３カラムｄはレンズ面の中心間のレンズ厚又は空気厚、第４カラムｎは屈折率、第５カラムνはアッベ数、第６カラムはレンズ群番号を表す。
レンズ面番号に※印を付したレンズ面は非球面を表し、非球面のレンズ面における曲率半径ｒは、非球面の頂点での曲率半径を表す。いずれの非球面も前記（Ｅ）式においてＮ＝５とした式で表される回転対称非球面である。各表の非球面データにおいて、第１カラムは非球面のレンズ面の番号、第２カラムκは円錐定数、第３カラムＣ₄、Ｃ₆、Ｃ₈及びＣ₁₀は第４次、第６次、第８次及び第１０次の非球面係数を表す。
非球面データ中には、各実施例の前記条件（Ａ₁）又は（Ａ₂）のパラメータの値と、第１、第２及び第５実施例についての条件（Ｂ）のパラメータの値を示す。なお条件（Ｃ）のパラメータの値は、第４次非球面係数Ｃ₄として示されている。
【００１８】
【表１】

【００１９】
【表２】

【００２０】
【表３】

【００２１】
【表４】

【００２２】
【表５】

【００２３】
【表６】

【００２４】
図２、図４、図６、図８及び図１０に、それぞれに第１〜第５実施例の球面収差、非点収差、及び歪曲収差を示す。また図１２に比較例の諸収差を示す。各収差は、アイポイントＥ．Ｐ．側から光線を追跡したときのものである。非点収差図中、破線はメリジオナル像面を表し、実線はサジタル像面を表す。各図中Ｆ_NO.はＦナンバー、ωは見掛け視界の半分を表す。
図２、図４、図６及び図１０と図１２とを比較して見ると、第１、第２、第３及び第５実施例では、レンズ面に周辺での曲率半径が頂点での曲率半径よりも大きくなるような非球面を用いたことによる効果のために、比較例に比べて歪曲収差が大きく改善されていることがわかる。同様に、図８と図１２とを比較して見ると、第４実施例では、レンズ面に周辺での曲率半径が頂点での曲率半径よりも小さくなるような非球面を用いたことによる効果のために、比較例に比べて歪曲収差が大きく改善されていることがわかる。
【００２５】
更に表１〜５と表６とを比較して見ると、球面レンズのみによる比較例の接眼レンズでは、アイレリーフが焦点距離の８０％程度であるが、各実施例ではアイレリーフが焦点距離以上に長くなっていることがわかる。また、この実施例からわかるように硝材は光学ガラス、樹脂製の光学材料のどちらでも構わない。
このように各実施例では非球面を用いることによって、更には各条件（Ａ₁）、（Ａ₂）、（Ｂ）又は（Ｃ）を満たすことによって、歪曲収差を良好に補正することを実現している。また、各実施例では見かけ視界が６０°の場合を示したが、レンズ径が大きくなっても構わなければ、見かけ視界７０°ぐらいまで十分な光学性能を保持することが可能である。
【図面の簡単な説明】
【図１】第１実施例の構成図
【図２】第１実施例の収差図
【図３】第２実施例の構成図
【図４】第２実施例の収差図
【図５】第３実施例の構成図
【図６】第３実施例の収差図
【図７】第４実施例の構成図
【図８】第４実施例の収差図
【図９】第５実施例の構成図
【図１０】第５実施例の収差図
【図１１】比較例の構成図
【図１２】比較例の収差図
【図１３】非球面を用いない接眼レンズに非球面の補正板を付加した構成を示す説明図
【図１４】非球面の補正板を透過する光線を示す説明図
【図１５】非球面形状を表す説明図
【符号の説明】
Ｇ₁…第１レンズ群 Ｇ₂…第２レンズ群
Ｇ₃…第３レンズ群 Ｅ．Ｐ．…アイポイント
※…非球面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an eyepiece used in a telescope, a microscope, and the like.
[0002]
[Problems to be solved by the invention]
With an eyepiece having a wide apparent field of view, it is difficult to sufficiently correct aberrations up to the periphery of the field of view, and it is particularly difficult to correct distortion aberrations.
SUMMARY OF THE INVENTION An object of the present invention is to provide an eyepiece in which, in an eyepiece having a wide apparent field of view, various aberrations such as distortion are well corrected to the periphery of the field of view.
[0003]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problem, that is, in an eyepiece having an apparent field of view of 40 ° or more, a first lens group configured by one positive lens component in order from the eye point side. and G _1, a cemented lens of a positive lens component and a negative lens component, or the negative lens component and the second lens group G ₂ having a positive refractive power composed of a cemented lens of a positive lens component, a positive lens component and a negative lens and a positive refractive power or negative refractive power a third lens group G ₃ Metropolitan of which is composed of a cemented lens of a component, out of the lens surfaces of the lens components, wherein at least one surface is aspherical It is an eyepiece.
[0004]
As the aspherical shape, when the aspherical surface is concave, the radius of curvature at the periphery is smaller than the radius of curvature at the apex, and when the aspherical surface is convex, the radius of curvature at the periphery is the curvature at the apex. It can be formed to be larger than the radius.
By forming in this way, it becomes possible to further correct the distortion, and further, it is possible to secure a sufficiently long distance from the eye relief of the eyepiece lens, that is, the distance from the lens surface closest to the eye point to the eye point.
[0005]
When at least one of the lens surface on the eye point side and the lens surface on the object side of the first lens group G ₁ is an aspherical surface,
0.001 <| d _x /h|<2.0 (A ₁ )
It is formed so as to satisfy the following condition .
However, as shown in FIG.
h: Distance from the optical axis of the incident position of the most off-axis chief ray to the aspheric surface d _x : An aspheric surface at a height h away from the optical axis by a distance h and a mother sphere based on the apex radius of curvature of the aspheric surface , The distance in the optical axis direction.
On the other hand, a lens surface nearest to the object side and nearest to the eye point side of the lens surface of the second lens group G _2, of the most eye point side of the lens surface the most object side lens surface of the third lens group G ₃ When at least one lens surface is aspherical,
0.001 <| d _x /h|<2.0 (A ₂ )
It is formed so as to satisfy the following condition .
Here, in the above formulas (A ₁ ) and (A ₂ ), if the lower limit is not reached, distortion is insufficiently corrected, and if it exceeds the upper limit, distortion is excessively corrected.
In the above formula (A ₁ ), it is preferable to set the upper limit value to 0.84 in order to further correct the distortion aberration, and in the above formula (A ₂ ), the distortion aberration is corrected more satisfactorily. Therefore, it is preferable to set the upper limit value to 0.45.
[0006]
When at least one of the lens surface on the eye point side and the lens surface on the object side of the first lens group G ₁ is an aspherical surface,
(R _b + r _a ) / (r _b −r _a ) <0 (B)
It is preferable to form so as to satisfy the following condition.
However, r _a: a radius of curvature at the top r _b of the lens surface of the first lens group G ₁ of the eye point side: a vertex radius of curvature of the lens surface of the first lens group G ₁ on the object side.
[0007]
The aspheric shape is

Satisfy the following condition.
Where x: distance measured from the vertex in the optical axis direction y: distance measured from the vertex perpendicular to the optical axis C ₀ : vertex curvature (C ₀ = 1 / R, R: vertex curvature radius)
κ: conic constant C _2i : 2nd (i ≧ 2) -order aspheric coefficient. Furthermore, as the fourth-order aspheric coefficient C ₄ ,
1 × 10 ^-8 <| C ₄ | (C ')
Satisfy the following condition.
[0008]
The conditions (C) and (C ′) will be described below.
Consider a case in which the aberration of the pupil is corrected by adding a correction plate using an aspherical surface to the eyepiece. The eye point side of the eyepiece lens L _e made of conventional spherical lenses, as shown in FIG. 13, the correction plate L _c having a non-spherical shape is disposed, corrects the pupil aberrations of the eyepiece L _e The correction plate L _c To do.
Assume that the shape of the correction plate L _c is expressed by the following equation with q as a constant, as shown in FIG.
x = qy ⁴ (1)
The tangent angle θ is obtained as follows by differentiating the equation (1).
θ = 4qy ³
If the refractive index of the correction plate L _c is n, the angle of the light ray R after passing through the aspheric surface of the correction plate L _c is θ ′, and the declination angle of the light ray R by the aspheric surface is δ, the declination angle δ is It is expressed by the following formula.

[0009]
On the other hand eyepiece L _e by pupil aberration [Delta] S 'is in the area of third-order aberration of A as a constant is expressed as follows.
ΔS ′ = Ay ² (3)
y is the height of the light ray incident on the eyepiece.
ΔS ′ can also be expressed as follows, where β is the magnification in image formation of the pupil of the eyepiece.
ΔS ′ = − β ² ΔS (4)
Assuming that the distance S to the entrance pupil is sufficiently larger than the focal length of the eyepiece, the following equation is established by the sine theorem.
ΔS = −S ² δ / y = −4 (1-1 / n) qS ² y ² (5)
[0010]
By substituting equation (5) into equation (4) and comparing with equation (3),
A = 4 (1-1 / n) β ² qS ² (6)
Then, it can be seen that the formulas (3) and (4) match. Since distortion tends to decrease with pupil aberration, an eyepiece without pupil aberration, that is, distortion aberration as a whole, can be obtained by giving q satisfying the equation (6). If we rewrite equation (1)
x = qy ⁴ = A / (4 (1-1 / n) β ² S ² ) · y ⁴ (7)
It becomes. Since β = S ′ / S, the above equation can be rewritten as follows.
x = A / (4 (1-1 / n) S ′ ² ) · y ⁴ (8)
The q described above corresponds to the coefficient C ₄ of y ^{4 in} the equation (E) that is generally used to represent an aspheric surface.
[0011]
In the formula (8), since S ′ is an eye relief of the eyepiece, S ′ may be considered to be about 10 to 30 mm. The constant A varies depending on the configuration of the eyepiece, the entrance pupil position, the focal length, and the like. However, if C ₄ is in the range of the condition (C), the pupil A can be compared with the constant A of the general eyepiece. The aberration can be corrected satisfactorily. If it is desired to correct not only distortion but also astigmatism, the above condition (C ′) should be satisfied.
If C ₄ exceeds the lower limit of the condition (C ′), the pupil aberration is undercorrected. Conversely, if C 4 exceeds the upper limit of the condition (C), the correction is overcorrected. In the above description, the correction plate _Lc is placed on the eye point side, but the same result can be obtained by placing it on the object side.
[0012]
Next, consider a case where the vertex curvature C ₀ is not 0, that is, the coefficient of the term y ² is not 0. Assume that the aspheric shape is expressed by the following equation.
x = py ² + qy ⁴ (9)
Similar to the above, the tangential angle θ and the pupil aberration ΔS ′ are obtained as follows.

[0013]
The second term on the right side in this equation is the same as that when the vertex curvature C ₀ is zero. The first term is a constant term not including y ² , that is, a term representing the movement of the image point by the surface having the vertex curvature C ₀ , and is not related to the correction of pupil aberration. Therefore, even if the correction plate has a shape corresponding to the term y ² (second-order curved surface), in other words, even if the correction plate is a lens having a refractive power, y ⁴ is used to correct pupil aberration. Since only the term affects, as long as the value of C ₄ is within the range of the condition (C) or further the condition (C ′), the pupil aberration is corrected well.
[0014]
In the above description, the case where only the y ⁴ term is used as the shape of the correction plate L _c , or the case where the correction plate L _c has the order up to y ⁴ has been described, but this is only the y ⁴ term in the third-order aberration region. This is because the pupil aberration is completely corrected. However, the larger the angle of view of the eyepiece lens, the more the third-order aberration is deviated, so the above-mentioned aspherical correction plate represented only by the term y ⁴ cannot correct pupil aberration completely. In that case, a higher-order correction term may be added to the aspherical shape of the correction plate L _c in addition to the y ⁴ term described above.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an eyepiece according to the present invention will be described. FIGS. 1, 3, 5, 7, and 9 are lens configuration diagrams of first to fifth embodiments of the present invention, respectively. FIG. 11 shows a lens configuration diagram of a comparative example. In each example and comparative example, in order from the eye point side, the first lens group G ₁ composed of _one positive lens component, a cemented lens of a positive lens component and a negative lens component, or a negative lens component and a positive lens A second lens group G ₂ having a positive refractive power composed of a cemented lens with a lens component, and a third lens group G having a positive refractive power or a negative refractive power composed of a cemented lens of a positive lens component and a negative lens component. It consists of _three .
[0016]
Among the first embodiment, second embodiment, and in the fifth embodiment, aspherical surface is used on the lens surface of the first lens group G ₁ on the object side. However, in the first example and the second example, the cemented lenses of the second lens group G ₂ are arranged in order of the negative lens component and the positive lens component from the eye point side, whereas in the fifth example, The second lens group G _{2 is different in that} the cemented lenses are arranged in the order of the positive lens component and the negative lens component from the eye point side. Further, in the first embodiment, optical glass is used as the glass material of the first lens group G ₁ including an aspherical surface, whereas in the second embodiment, the glass material of the first lens group G ₁ is made of resin. The difference is that an optical material is used.
In the third embodiment, and aspheric surfaces used in the lens surface on the most object side in the second lens group G _2, in the fourth embodiment, the non-lens surface on the most object side of the third lens group G ₂ A spherical surface is used. On the other hand, in the comparative example, no aspherical surface is used for any lens surface.
[0017]
Tables 1 and 2 below show the overall specifications, lens specifications, and aspheric data of the first to fifth examples, respectively. Table 6 shows the overall specifications and lens specifications of the comparative example. In the lens specifications of each table, the first column is the lens surface number from the object side, the second column r is the radius of curvature of the lens surface, the third column d is the lens thickness or air thickness between the centers of the lens surfaces, The fourth column n represents the refractive index, the fifth column ν represents the Abbe number, and the sixth column represents the lens group number.
The lens surface marked with * in the lens surface number represents an aspheric surface, and the curvature radius r of the aspheric lens surface represents the curvature radius at the apex of the aspheric surface. Any aspherical surface is a rotationally symmetric aspherical surface represented by the equation where N = 5 in the equation (E). In the aspheric data in each table, the first column is the number of the aspheric lens surface, the second column κ is the conic constant, and the third columns C ₄ , C ₆ , C ₈ and C ₁₀ are the 4th and 6th orders. , 8th and 10th order aspherical coefficients.
In the aspheric surface data, the parameter value of the condition (A ₁ ) or (A ₂ ) of each embodiment and the parameter value of the condition (B) for the first, second, and fifth embodiments are shown. . Note that the parameter value of the condition (C) is shown as a fourth-order aspheric coefficient C ₄ .
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
[Table 3]

[0021]
[Table 4]

[0022]
[Table 5]

[0023]
[Table 6]

[0024]
2, 4, 6, 8, and 10 show the spherical aberration, astigmatism, and distortion of the first to fifth embodiments, respectively. FIG. 12 shows various aberrations of the comparative example. Each aberration is represented by eye point E.E. P. This is when the ray is traced from the side. In the astigmatism diagram, the broken line represents the meridional image plane, and the solid line represents the sagittal image plane. In each figure, F _NO. Represents the F number, and ω represents half of the apparent field of view.
When comparing FIGS. 2, 4, 6 and 10 with FIG. 12, in the first, second, third and fifth embodiments, the radius of curvature around the lens surface is the curvature at the apex. It can be seen that distortion is greatly improved compared to the comparative example due to the effect of using an aspheric surface that is larger than the radius. Similarly, when comparing FIG. 8 with FIG. 12, in the fourth embodiment, the effect of using an aspherical surface in which the radius of curvature at the periphery is smaller than the radius of curvature at the apex is used for the lens surface. Therefore, it can be seen that the distortion is greatly improved as compared with the comparative example.
[0025]
Further, comparing Tables 1 to 5 with Table 6, in the eyepiece of the comparative example using only the spherical lens, the eye relief is about 80% of the focal length, but in each embodiment, the eye relief is greater than the focal length. It turns out that it is long. Further, as can be seen from this example, the glass material may be either optical glass or resin optical material.
As described above, in each embodiment, it is possible to satisfactorily correct distortion by using an aspheric surface and further satisfying each condition (A ₁ ), (A ₂ ), (B), or (C). is doing. In each embodiment, the apparent field of view is 60 °. However, if the lens diameter can be increased, sufficient optical performance can be maintained up to the apparent field of view of about 70 °.
[Brief description of the drawings]
FIG. 1 is a block diagram of the first embodiment. FIG. 2 is an aberration diagram of the first embodiment. FIG. 3 is a block diagram of the second embodiment. FIG. 4 is an aberration diagram of the second embodiment. FIG. 6 is an aberration diagram of the third embodiment. FIG. 7 is a diagram of an aberration of the fourth embodiment. FIG. 8 is an aberration diagram of the fourth embodiment. FIG. 10 is an aberration diagram of the fifth embodiment. FIG. 11 is a configuration diagram of the comparative example. FIG. 12 is an aberration diagram of the comparative example. FIG. 13 is a configuration in which an aspheric correction plate is added to an eyepiece that does not use an aspheric surface. Explanatory diagram showing FIG. 14 Explanatory diagram showing a light beam transmitted through an aspherical correction plate FIG. 15 Explanatory diagram showing an aspheric shape
G ₁ ... 1st lens group G ₂ ... 2nd lens group G ₃ ... 3rd lens group P. ... eye point * ... aspherical surface

Claims (5)

In an eyepiece with an apparent field of view of 40 ° or more,
In order from the eye point side, the first lens group G ₁ composed of _one positive lens component and a cemented lens composed of a positive lens component and a negative lens component, or a cemented lens composed of a negative lens component and a positive lens component A second lens group G ₂ having a positive refractive power and a third lens group G ₃ having a positive refractive power or a negative refractive power composed of a cemented lens of a positive lens component and a negative lens component.
Wherein one of the lens surfaces of the lens components, an eyepiece, characterized in that at least one surface satisfies the aspherical der is, and the following conditional expression.
0.001 <| d _x /h|<2.0
1 × 10 ⁻⁸ <| C ₄ | <1 × 10 ⁻³
Where h: distance from the optical axis of the incident position of the most off-axis chief ray on the aspheric surface
d _x : distance in the optical axis direction between the aspherical surface at a height separated from the optical axis by the distance h and the base spherical surface based on the vertex curvature radius of the aspherical surface
C ₄ : The distance measured from the apex of the aspherical surface in the optical axis direction is x, the distance measured from the apex perpendicular to the optical axis is y, the vertex curvature is C ₀ , and the conic constant is κ. , The second i (i ≧ 2) _-order aspheric coefficient is C _2i ,

4th-order aspherical coefficient
It is. At least one of the lens surface on the eye point side and the lens surface on the object side of the first lens group G ₁ is the aspheric surface,
When the aspherical surface is concave, the radius of curvature at the periphery is smaller than the radius of curvature at the apex, and when the aspherical surface is convex, the radius of curvature at the periphery is greater than the radius of curvature at the apex. The eyepiece according to claim 1, wherein the eyepiece is large. The radius of curvature at the top of the object-side lens surface and the eye point side of the lens surface of the first lens group G _1, when a r _a and r _b, respectively,
(R _b + r _a ) / (r _b −r _a ) <0
The eyepiece according to claim 2 , wherein the following condition is satisfied. Of the lens surface closest to the eye point and the lens surface closest to the object side of the second lens group G ₂ , and the lens surface closest to the eye point and the lens surface closest to the object side of the third lens group G ₃ , At least one lens surface is the aspheric surface,
When the aspherical surface is concave, the radius of curvature at the periphery is smaller than the radius of curvature at the apex, and when the aspherical surface is convex, the radius of curvature at the periphery is greater than the radius of curvature at the apex. The eyepiece according to claim 1, wherein the eyepiece is large. The first lens group G ₁ including a non-spherical surface, the glass material of the second lens group G ₂ and the third lens group G ₃ is, of claims 1 to 4, characterized in that the optical material made of optical glass or resin The ocular lens of any one of Claims.

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