JP3617004B2

JP3617004B2 - Double-sided aspherical progressive-power lens

Info

Publication number: JP3617004B2
Application number: JP2002154681A
Authority: JP
Inventors: 明木谷; 吉洋菊池
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2002-05-28
Filing date: 2002-05-28
Publication date: 2005-02-02
Anticipated expiration: 2022-05-28
Also published as: CN101241237A; CN101241237B; JP2003344813A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば、眼鏡用老視用累進屈折力レンズとして用いられるレンズであって、物体側表面である第１の屈折表面と眼球側表面である第２の屈折表面とに分割配分されている累進屈折力作用を備え、前記第１の表面と前記第２の表面とを合わせて処方値に基づいた遠用度数（Ｄｆ）と加入度数（ＡＤＤ）を与える構成となっている両面非球面型累進屈折力レンズに関する。
【０００２】
【従来の技術】
累進屈折力レンズは老視用眼鏡レンズでありながら外見上は容易に老眼鏡と察知されない利点や、遠距離から近距離まで切れ目なく連続的に明視しうる利点などの理由から、一般に広く利用されている。しかしながら、限られたレンズ面積の中に境界線を介入させることなく、遠方を見るための視野と近方を見るための視野、更にはそれらの中間的な距離を見るための視野といった複数の視野を配置する都合から、各々の視野の広さが必ずしも充分ではないことや、主として側方の視野に像の歪みや揺れを感じさせる領域が存在するなど、累進屈折力レンズ特有の欠点があることも広く知られている。
【０００３】
これらの累進屈折力レンズ特有の欠点を改善する目的で古くから様々な提案がなされてきたが、それらの従来の累進屈折力レンズの面構成は、物体側表面に「累進面」を配し、眼球側表面に「球面」や「乱視面」を配した組合せのものが殆どであった。また、これらとは逆に、眼球側表面に「累進作用」を付加させたことを特徴とする累進屈折力レンズとして、１９７０年に仏国ＥｓｓｅｌＯｐｔｉｃａｌＣｏ．（現Ｅｓｓｉｌｏｒ）から発売されたＡｔｏｒａｌＶａｒｉｐｌａｓがある。
【０００４】
また、近年提案された先行技術として、例えば、特許国際公開ＷＯ９７／１９３８２号及びＷＯ９７／１９３８３号公報に記載の技術等などがあり、一般に裏面累進（または凹面累進）と呼ばれている。この近年提案された裏面累進における面構成の主な目的は、必要な加入度数の一部または全部を、物体側表面から眼球側表面に分担させることで、遠用部と近用部の像の倍率差を減らし、像の歪みや揺れを改善しようとするものである。
【０００５】
これらの先行技術のうち、ＷＯ９７／１９３８２号公報に記載のものは、物体側表面を球面や回転対称非球面とすることで「累進作用」を全て消し去り、眼球側表面のみに所定の加入度数を与える「累進面」を付加（融合）させており、また、ＷＯ９７／１９３８３号公報記載のものは、物体側表面の「累進面」における加入度数を所定の値より少なくし、不足分の加入度数を与える「累進面」を裏面側の「球面」や「乱視面」に付加（融合）させた構成となっている。
【０００６】
また、目的や根拠に違いはあるが、眼球側表面に「累進作用」を付加させた記載のある累進屈折力レンズの他の先行技術として、例えば、特公昭４７−２３９４３号公報、特開昭５７−１０１１２号公報、特開平１０−２０６８０５号公報、特開２０００−２１８４６号公報等に記載のものなどがあり、更に、前述のＷＯ９７／１９３８３号公報に記載のものと同様に、レンズの両面に「累進作用」を持たせた先行技術として、例えば、特開２０００−３３８４５２号公報や特開平６−１１８３５３号公報記載のものがある。これらの先行技術の共通点は、必要な加入度数を表裏２面で分担して与えていることである。
【０００７】
【発明が解決しようとする課題】
これらの先行技術の主な目的は、必要な加入度数の一部または全部を、物体側表面から眼球側表面に分担させることで、遠用部と近用部の倍率差を減らし、倍率差による像の歪みや揺れを改善しようとするものである。ところが、それらの改善効果が得られる根拠については明確な記載が少なく、わずかに前記特許国際公開ＷＯ９７／１９３８３号公報（以下、従来技術１という）等において、部分的な記載があるにすぎない。即ち、従来技術１には次のような（１）式〜（３）式に示すレンズ倍率ＳＭの計算式が開示され、レンズ設計の基本評価パラメータとして採用されている。
【０００８】
即ち、従来技術１には、以下のような記載がある。
「レンズの倍率ＳＭは、一般的に次の式で表される。
ＳＭ＝Ｍｐ×Ｍｓ…（１）
ここで、Ｍｐはパワーファクター、また、Ｍｓはシェープファクターと呼ばれる。レンズの眼球側の面の頂点（内側頂点）から眼球までの距離を頂間距離Ｌ、内側頂点の屈折力（内側頂点屈折力）をＰｏ、レンズの中心の厚みをｔ、レンズの屈折率をｎ、レンズの物体側の面のベースカーブ（屈折力）をＰｂとすると以下のように表される。
Ｍｐ＝１／（１−Ｌ×Ｐｏ）…（２）
Ｍｓ＝１／（１−（ｔ×Ｐｂ）／ｎ）…（３）
なお、式（２）および（３）の計算にあたっては、内側頂点屈折力Ｐｏを、ベースカーブＰｂについてはディオプトリ（Ｄ）を、また、距離Ｌおよび厚みをｔについてはメートル（ｍ）をそれぞれ用いる。」
【０００９】
そして、これらのレンズ倍率ＳＭの計算式を用いて遠用部と近用部の倍率の差を算出し、従来技術１ではその倍率差が少ないので、像の歪みや揺れが改善されているとしている。
【００１０】
本願発明者の研究によれば、上記従来技術１においては、その先行技術に比較して一定の効果が認められるが、より高性能のレンズ設計を行なうためには、さらに以下の点を検討する必要のあることが判明した。
ａ．上記従来技術１で用いている基本評価パラメータには、「レンズの眼球側の面の頂点から眼球までの距離Ｌ」と「レンズの中心の厚みｔ」という記載からも明らかなように、本来ならばレンズの中央近傍に対してのみ適用されるべきパラメータが含まれている。即ち、従来技術１の実施例では、レンズの中央近傍にある遠用部に対してのみ適用されるべき基本評価パラメータが、レンズ中心から大きく下方に位置する近用部に対しても適用されていることになるので、それによる誤差の可能性が残る。
【００１１】
ｂ．従来技術１では、上記の他に「レンズの屈折率ｎ」を加えた、５個の基本評価パラメータでレンズの倍率ＳＭが算出されている。しかしながら、実際に度数の付いたレンズを前後に傾けてみればすぐわかるように、像の大きさは「視線とレンズ面との角度」に強く影響されると考えられる。従って、特にレンズ中心から大きく下方に位置する近用部の倍率の算出では、この「視線とレンズ面との角度」を無視出来ないと考えられる。よって、従来技術１のレンズ設計には「視線とレンズ面との角度を考慮することなくレンズの倍率を算出している」ことによる誤差の可能性を有する。
【００１２】
ｃ．従来技術１における「倍率」には、乱視レンズへの応用例の記載以外に方向の概念がないので、例えば、レンズ中心から大きく下方に位置する近用部において起きる「縦方向と横方向との倍率が異なる」といった場合には、これによる誤差の可能性が生ずる。
【００１３】
ｄ．近用部に対する倍率計算を正確に行うには、視標までの距離、即ち「対物距離」が計算ファクターとして追加されねばならないが、従来技術１ではこの「対物距離」について考慮されていないので、それによる誤差の可能性も否定できない。
ｅ．倍率計算において、プリズム作用による影響が考慮されていないので、これによる誤差の可能性もある。
このように、従来技術は、特に、「倍率」の算出をより正確に行うという視点からみると、必ずしも十分でない可能性を有するものである。
【００１４】
本発明は、かかる課題を解決するためになされたものであり、「視線とレンズ面との角度」や「対物距離」による影響を考慮し、像の倍率を正しく算出することにより、遠用部と近用部における像の倍率差を低減し、処方値に対する良好な視力補正と、装用時における歪みの少ない広範囲な有効視野を与える両面非球面型累進屈折力レンズを提供すること目的とする。
【００１５】
更に、物体側表面として「左右対称の半完成品」を用い、受注後に眼球側表面のみを近方視における眼の輻湊作用に対応した左右非対称な曲面として加工することを可能とし、加工時間とコストとを低減させることを可能とする両面非球面型累進屈折力レンズを提供することを目的とするものである。
【００１６】
【課題を解決するための手段】
上述の課題を解決するための手段として、第１の手段は、
物体側表面である第１の屈折表面と、眼球側表面である第２の屈折表面とに分割配分されている累進屈折力作用を備えた両面非球面型累進屈折力レンズであって、
前記第１の屈折表面において、遠用度数測定位置Ｆ１における横方向の表面屈折力及び縦方向の表面屈折力をそれぞれ、ＤＨｆ、ＤＶｆとし、
前記第１の屈折表面において、近用度数測定位置Ｎ１における横方向の表面屈折力及び縦方向の表面屈折力をそれぞれＤＨｎ、ＤＶｎとするとき、
ＤＨｆ＋ＤＨｎ＜ＤＶｆ＋ＤＶｎ、かつ、ＤＨｎ＜ＤＶｎ
となる関係式を満足させると共に、前記第１の屈折表面のＦ１及びＮ１における表面非点収差成分を、前記第２の屈折表面にて相殺し、前記第１と第２の屈折表面とを合わせて処方値に基づいた遠用度数（Ｄｆ）と加入度数（ＡＤＤ）とを与えるようにしたことを特徴とする両面非球面型累進屈折力レンズである。
第２の手段は、
ＤＶｎ−ＤＶｆ＞ＡＤＤ／２、かつ、ＤＨｎ−ＤＨｆ＜ＡＤＤ／２となる関係式を満足することを特徴とする第１の手段にかかる両面非球面型累進屈折力レンズである。
第３の手段は、
前記第１の屈折表面が前記遠用度数測定位置Ｆ１を通る一本の子午線を境に左右対称であり、前記第２の屈折表面が、この第２の屈折表面の遠用度数測定位置Ｆ２を通る一本の子午線を境に左右対称であって、かつ、この第２の屈折表面の近用度数測定位置Ｎ２の配置は所定の距離だけ鼻側に内寄せされており、近方視における眼の輻湊作用に対応していることを特徴とする第１又は第２の手段にかかる両面非球面累進屈折力レンズである。
第４の手段は、
前記第１の屈折表面が、前記遠用度数測定位置Ｆ１を通る一本の子午線を母線とした回転面であり、前記第２の屈折表面が、この第２の屈折表面の遠用度数測定位置Ｆ２を通る一本の子午線を境に左右対称であって、かつ、この第２の屈折表面の近用度数測定位置Ｎ２の配置は所定の距離だけ鼻側に内寄せされており、近方視における眼の輻湊作用に対応していることを特徴とする第１〜第３のいずれかに記載の両面非球面型累進屈折力レンズである。
第５の手段は、
前記第１と第２の屈折表面とを合わせて処方値に基づいた遠用度数（Ｄｆ）と加入度数（ＡＤＤ）とを与える構成とする上で、装用状態における視線とレンズ面とが直交しえないことに起因する非点収差の発生や度数の変化を低減したことを特徴とする第１〜だ４のいずれかの手段にかかる両面非球面型累進屈折力レンズである。
【００１７】
上述の手段は、以下の解明結果に基づいて案出されたものである。以下、図面を参照にしながら説明する。図１は眼鏡レンズ表面の各位置における各種の表面屈折力の説明図、図２は眼球と視線とレンズとの位置関係の説明図、図３−１、図３−２及び図３−３並びに図４−１、図４−２及び図４−３はプリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図、図５−１は累進屈折力レンズの光学的レイアウトの説明図であって累進屈折力レンズを物体側表面から眺めた正面図、図５−２は累進屈折力レンズの光学的レイアウトの説明図であって縦方向の断面を表す側面図、図５−３は累進屈折力レンズの光学的レイアウトの説明図であって横方向の断面を表す立面図、図６は「加入度数」の定義の違いを示す説明図である。なお、これらの図において、符号Ｆは遠用度数測定位置、Ｎは近用度数測定位置、Ｑはプリズム度数測定位置を示す。また、図１等に記した他の符号は、
ＤＶｆ：Ｆを通る縦方向断面曲線の、Ｆにおける表面屈折力
ＤＶｎ：Ｎを通る縦方向断面曲線の、Ｎにおける表面屈折力
ＤＨｆ：Ｆを通る横方向断面曲線の、Ｆにおける表面屈折力
ＤＨｎ：Ｎを通る横方向断面曲線の、Ｎにおける表面屈折力
を表している。さらに、図の屈折表面が物体側表面である第１の屈折表面である場合には全ての符号に添字１を付し、眼球側表面である第２の屈折表面である場合には全ての符号に添字２を付して識別する。
【００１８】
また、符号Ｆ１及びＦ２は物体側表面と眼球側表面の遠用度数測定位置、同様にＮ１及びＮ２は物体側表面と眼球側表面の近用度数測定位置を示す。さらに、Ｅは眼球、Ｃは眼球の回旋中心点、ＳはＣを中心とした参照球面、Ｌｆ及びＬｎはそれぞれ遠用度数測定位置と近用度数測定位置を通る視線である。また、Ｍは正面上方から下方まで両眼視したときの視線が通過する、主注視線と呼ばれる曲線である。そして、Ｆ１、Ｎ１、Ｆ２、Ｎ２、Ｎ３は、「加入度数」の定義によって異なるレンズメーターの開口部を当てる部位を示している。
【００１９】
まず、上記従来技術の（ａ）の課題である「パラメータを近用部に対応させる」ことと、（ｄ）の課題である「対物距離を考慮すること」によって改善した近用部に対応した倍率の計算式は次のようにして求めるようにした。すなわち、Ｍｐをパワーファクター、Ｍｓをシェープファクターとしたとき、像の倍率ＳＭは、
ＳＭ＝Ｍｐ×Ｍｓ…（１’）
で表される。ここで、視標までの対物パワー（ｍ単位で表した対物距離の逆数）をＰｘとし、レンズの近用部における眼球側の面から眼球までの距離をＬ、近用部における屈折力（近用部における内側頂点屈折力）をＰｏ、レンズの近用部における厚みをｔ、レンズの屈折率をｎ、レンズの近用部における物体側の面のベースカーブ（屈折力）をＰｂとすると、以下の関係が成立する。
Ｍｐ＝（１−（Ｌ＋ｔ）Ｐｘ）／（１−Ｌ×Ｐｏ）…（２’）
Ｍｓ＝１／（１−ｔ×（Ｐｘ＋Ｐｂ）／ｎ）…（３’）
【００２０】
これらの式において、各パラメータを遠用部に対応させ、対物距離のパワー表示であるＰｘに対して無限遠に対応した０を代入すると、前述の従来技術１の数式に一致する。即ち、従来技術１において用いられていた数式は、無限遠の対物距離である遠方視専用の数式であったと考えられる。さて、ここで（１’）は、前述の従来技術１の数式と同一であるが、一般に近方視の対物距離は０．３ｍ〜０．４ｍ程度なので、その逆数であるＰｘは−２．５〜−３．０程度の値となる。したがって、（２’）は分子が増えるのでＭｐが増大し、（３’）では分母が増えるのでＭｓが減少する。即ち、近方視におけるシェープファクターＭｓの影響は、従来技術１の計算よりも少ないことがわかる。例えばＰｂ＝−Ｐｘ、即ちレンズの物体側の面のベースカーブ（屈折力）が＋２．５〜＋３．０程度の値である場合にはＭｓ＝１となり、近方視におけるシェープファクターは像の倍率に全く無関係となることが解る。
【００２１】
さて、以上のようにして各パラメータを近用部に対応させ、「対物距離」をも考慮した倍率の計算式を求めることが出来たが、実際の近方視における倍率を算出するには、更に前記従来技術１の（ｂ）の課題である「視線とレンズ面との角度」についても考慮しなければならない。ここで重要なことは「視線とレンズ面との角度」には方向性があるということである。即ち、「視線とレンズ面との角度」を考慮するということは、前記従来技術１の（ｃ）の課題である「像の倍率」の方向性を同時に考慮するということに他ならない。
【００２２】
この観点で前述の（１’）〜（３’）の第１の計算式を見直すと、「視線とレンズ面との角度」が影響する計算ファクターとして近用部における内側頂点屈折力Ｐｏと近用部における物体側の面のベースカーブ（屈折力）Ｐｂがある。ここで、近方視における視線と近用部領域の光軸とのなす角をα、近方視における視線と近用部における物体側表面の法線とのなす角をβとして、よく知られたＭａｒｔｉｎの近似式を用いると、
近用部における縦方向の内側頂点屈折力：
Ｐｏｖ＝Ｐｏ×（１＋Ｓｉｎ２α×４／３）
近用部における横方向の内側頂点屈折力：
Ｐｏｈ＝Ｐｏ×（１＋Ｓｉｎ２α×１／３）
近用部における物体側表面の縦断面屈折力：
Ｐｂｖ＝Ｐｂ×（１＋Ｓｉｎ２β×４／３）
近用部における物体側表面の横断面屈折力：
Ｐｂｈ＝Ｐｂ×（１＋Ｓｉｎ２β×１／３）
となる。このように、角αやβ、及びＰｏやＰｂがゼロでない限り、屈折力やパワーファクター、シェープファクターなどは縦横で異なる値となり、その結果、縦方向と横方向との倍率に差が生じてくるのである。
【００２３】
さて、ここでは「視線の方向に応じて屈折力が変わる」ことを簡単に説明するために近似式を用いたが、実際の光学設計においては厳密な光線追跡計算によってこれらの値を求めることが望ましい。これらの計算方法の非限定例として、たとえば、スネルの法則を用いて視線に沿った光路を計算し、Ｌ、ｔ及び、物体側屈折面から物点までの距離を算出し、次に、この光路に沿って、微分幾何学における第１基本形式、第２基本形式、Ｗｅｉｎｇａｒｔｅｎの式などを用いることによって、物体側屈折面及び、眼球側屈折面における光路上での屈折の影響を考慮にいれた屈折力を計算することが出来る。これらの式や計算方法は極めて古くから公知であり、たとえば公知文献「微分幾何学」（矢野健太郎著（株）朝倉書店発行初版１９４９年）などに記載されているので説明は省略する。
【００２４】
さて、このように厳密な光線追跡計算を行なうことで、前述の（ａ）〜（ｄ）の課題であるＬ、Ｐｏ、ｔ、Ｐｂの４個の計算ファクターについての考慮もなされ、レンズ中心から大きく下方に位置する近用部はもちろん、全ての視線方向において厳密な倍率計算が可能となる。このようにして前述の項目、
近用部における縦方向の内側頂点屈折力：Ｐｏｖ
近用部における横方向の内側頂点屈折力：Ｐｏｈ
近用部における物体側表面の縦断面屈折力：Ｐｂｖ
近用部における物体側表面の横断面屈折力：Ｐｂｈ
について、Ｍａｒｔｉｎの近似式を用いるよりも更に高い精度で求められるのである。
【００２５】
このように、「視線の方向に応じて屈折力が変わる」ことから、前述の像の倍率計算についても、全て視線方向の違いに対応させるべきことも容易に理解されよう。ここで、Ｍｐをパワーファクター、Ｍｓをシェープファクターとし、縦方向についてはｖ、横方向についてはｈの添字を付けて表すと、像の倍率ＳＭについて、前述の（１’）〜（３’）の式は次のように書き換えられる。
ＳＭｖ＝Ｍｐｖ×Ｍｓｖ…（１ｖ’）
ＳＭｈ＝Ｍｐｈ×Ｍｓｈ…（１ｈ’）
Ｍｐｖ＝（１−（Ｌ＋ｔ）Ｐｘ）／（１−Ｌ×Ｐｏｖ）…（２ｖ’）
Ｍｐｈ＝（１−（Ｌ＋ｔ）Ｐｘ）／（１−Ｌ×Ｐｏｈ）…（２ｈ’）
Ｍｓｖ＝１／（１−ｔ×（Ｐｘ＋Ｐｂｖ）／ｎ）…（３ｖ’）
Ｍｓｈ＝１／（１−ｔ×（Ｐｘ＋Ｐｂｈ）／ｎ）…（３ｈ’）
【００２６】
以上のようにして前記従来技術１の（ａ）から（ｄ）までの課題に対応することが出来た。最後に、実際の近方視における倍率を算出する上での前述の（ｅ）の課題である「プリズム作用による影響」について述べる。プリズムそのものにはレンズのような屈折力は存在しないが、プリズムへの光線の入射角度や出射角度によってプリズムの倍率Ｍγが変化する。ここで、図３−１および図４−１の左側の如く、真空中から屈折率ｎの媒質中に入射した光線が媒質表面で屈折する場合の角倍率γを考える。このときの入射角をｉ、屈折角をｒとしたとき、良く知られたＳｎｅｌｌの法則によりｎ＝Ｓｉｎｉ／Ｓｉｎｒである。また、屈折による角倍率γは、γ＝Ｃｏｓｉ／Ｃｏｓｒで表される。ｎ≧１であるから、一般にｉ≧ｒとなりγ≦１となる。ここでγが最大値１となるのはｉ＝ｒ＝０、即ち垂直入射の場合である。また、屈折角ｒがｎ＝１／Ｓｉｎｒとなるとき、γは理論上の最小値 γ＝０となる。このときｉ＝π／２であり、ｒは媒質中から光線が出る場合の全反射の臨界角に等しい。
【００２７】
一方、図３−１および図４−１の右側の如く、屈折率ｎの媒質から真空中に光線が出る場合の角倍率γ’は上記と全く逆となる。即ち、媒質内部から媒質表面で屈折して真空中に光線が出る場合の入射角をｉ’、屈折角をｒ’としたとき、Ｓｎｅｌｌの法則は１／ｎ＝Ｓｉｎｉ’／Ｓｉｎｒ’となり、角倍率はγ’＝Ｃｏｓｉ’／Ｃｏｓｒ’で表される。ｎ≧１であるから、一般にｒ’≧ｉ’となりγ’≧１となる。ここで、γ’が最小値１となるのはｉ’＝ｒ’＝０、即ち垂直入射の場合である。また、入射角ｉ’がｎ＝１／Ｓｉｎｉ’となるとき、γ’は理論上の最大値 γ’＝∞となる。このときｒ’＝π／２であり、ｉ’は媒質中から光線が出る場合の全反射の臨界角に等しい。
【００２８】
図３−３および図４−３の如く、一枚の眼鏡レンズの物体側表面に入射した光線がレンズ内部を通過し、眼球側表面から出射して眼球に到達する場合を考える（以後、説明の簡略化のために簡易的に、空気の屈折率は、真空中と同じ１に近似して考えることとする。）。眼鏡レンズの屈折率をｎ、物体側表面に入射した光線の入射角をｉ、屈折角をｒとし、レンズ内部から眼球側表面に到達した光線の入射角をｉ’、出射した光線の屈折角をｒ’とすると、眼鏡レンズの二つの表面を透過した角倍率Ｍγは前述の２種類の角倍率の積で表わされ、
Ｍγ＝γ×γ’＝（Ｃｏｓｉ×Ｃｏｓｉ’）／（Ｃｏｓｒ×Ｃｏｓｒ’）
となる。これは、レンズ表面の屈折力とは無関係であり、プリズムの倍率として知られている。
【００２９】
ここで、図３−１および図４−１の如く、ｉ＝ｒ’，ｒ＝ｉ’ の場合を考えると、
Ｍγ＝γ×γ’＝１
となり、プリズムを通して見た像の倍率に変化がないことになる。ところが、図３−２の如く、眼鏡レンズの物体側表面に垂直に光線が入射した場合は、
Ｍγ＝γ’＝Ｃｏｓｉ’／Ｃｏｓｒ’≧１
となり、逆に、図４−２の如く、眼鏡レンズの眼球側表面から光線が垂直出射した場合は、
Ｍγ＝γ＝Ｃｏｓｉ／Ｃｏｓｒ≦１
となる。
【００３０】
ここで、重要なことは、これらのプリズムの倍率Ｍγには方向性があるということである。即ち、累進屈折力レンズにおけるプリズムの分布について考えると、度数や処方プリズム値によって異なるのは当然であるが、概してレンズ中央に近い遠方視におけるプリズムは少なく、レンズの下方に位置する近方視における縦方向のプリズムは大きい。従って、プリズムの倍率Ｍγは、特に近方視の縦方向に対して影響が大きいといえる。
【００３１】
さて、累進屈折力レンズのみならず、眼鏡レンズは一般に物体側表面が凸であり、眼球側表面が凹であるメニスカス形状をしており、近方視における視線が下向きであることを考え合わせると、図３−３に示すように、近用部が正の屈折力を有する累進屈折力レンズの近方視は、Ｍγ＝１である図３−１よりもＭγ≧１である図３−２の形状に近く、少なくともＭγ＞１と言える。同様に、図４−３に示すように、近用部が負の屈折力を有する累進屈折力レンズの近方視は、Ｍγ＝１である図４−１よりもＭγ≦１である図４−２の形状に近く、少なくともＭγ＜１と言える。従って、近用部が正の屈折力を有する累進屈折力レンズの近方視ではＭγ＞１であり、近用部が負の屈折力を有する累進屈折力レンズの近方視ではＭγ＜１となる。
【００３２】
前記従来技術１におけるレンズの倍率ＳＭは、前述の如く、パワーファクターＭｐとシェープファクターＭｓとの積としてしか把握されていなかったのに対し、本発明では更にプリズムの倍率Ｍγを掛け合わせて、正しいレンズの倍率を得ようとするものである。
【００３３】
このプリズムによる倍率ＭγをＭｐやＭｓとの対比から「プリズムファクター」と呼ぶことにし、縦方向についてはｖ、横方向についてはｈの添字を付けて表すと、像の倍率ＳＭについて、前述の（１ｖ’）と（１ｈ’）の式は次のように書き換えられる。
ＳＭｖ＝Ｍｐｖ×Ｍｓｖ×Ｍγｖ…（１ｖ″）
ＳＭｈ＝Ｍｐｈ×Ｍｓｈ×Ｍγｈ…（１ｈ″）
なお、これらのＭγｖやＭγｈは、前述の厳密な光線追跡の計算過程において求めることが出来る。これにより、前述の眼鏡の倍率計算におけるプリズム作用による影響の課題を解決することが出来た。
【００３４】
さて、通常の凸面累進屈折力レンズでは、物体側表面の「累進面」の表面屈折力が遠用部＜近用部となっている。これに対して前記従来技術１の累進屈折力レンズでは、物体側表面の「累進面」の表面屈折力を、遠用部＝近用部などとすることで、遠近のシェープファクターの割合を変え、遠近の像の倍率差を減少させることで累進屈折力レンズの像の歪みや揺れを改善しようとするものである。ところが、本願発明における考察では、物体側表面の「累進面」の遠近の表面屈折力差を少なくすることにより、横方向についての遠近の像の倍率差が減少するという利点が生ずるが、縦方向について表面屈折力差を少なくすることには幾つかの問題のあることがわかった。
【００３５】
第１の問題は、縦方向のプリズムファクターＭγｖの影響である。前述の如く縦方向のプリズムファクターＭγｖは、負の屈折力を有する場合にはＭγｖ＜１であり、正の屈折力を有する場合にはＭγｖ＞１となるが、その傾向は縦方向の表面屈折力差を少なくすることによって強められ、近用部の度数が正負いずれの場合にも、裸眼の倍率であるＭγｖ＝１から離れていく。ところが横方向のプリズムファクターＭγｈにはそのような影響はなく、Ｍγｈ＝１のままである。その結果、特に近用部から下方にかけての像の倍率に縦横の差が生じ、本来正方形に見えるべきものが、プラス度数にあって縦長に、マイナス度数にあっては横長に見えてしまうという不都合が生ずる。
【００３６】
第２の問題は、特に近用部の縦方向が正の屈折力を有する場合にのみ起きる問題である。それは縦方向の表面屈折力差を少なくすることによって、近方視における視線とレンズ面との角度が更に斜めとなり、前述の縦方向のパワーファクターＭｐｖが増大し、第１の問題であった縦方向のプリズムファクターＭγｖの増大と２重に作用することにより縦方向の倍率ＳＭｖが増大し、遠近の像の倍率差がかえって増大してしまうという不都合が生ずる。
【００３７】
即ち、物体側表面である累進面の遠近の表面屈折力差を少なくすることは、横方向については利点があるが、縦方向についてはかえって改悪となることが判明した。従って、従来型の凸面累進屈折力レンズにおいて、物体側表面である累進面を縦方向と横方向とに分け、横方向についてのみ遠近の表面屈折力差を少なくすることで、上述の問題を回避することができるのである。
【００３８】
以上述べたように、本願発明の最も大きな特徴は、累進屈折力レンズの累進作用について、レンズの縦方向と横方向とに分割した上で、各々の方向に対して最適な表裏２面の分担比率を定め、一枚の両面非球面型累進屈折力レンズを構成していることにある。例えば極端な例として、縦方向の累進作用は全て物体側表面で与え、横方向の累進作用は全て眼球側表面で与えることも本願発明の範疇である。この場合、レンズの表裏２面は、いずれも片面だけでは通常の累進面として機能しないため、累進面としての加入度数を特定することが出来ない。即ち、表裏いずれの面も累進面ではない累進屈折力レンズとなる。これに対し前述の様々な先行技術は、分担比率に違いはあるものの、いずれも必要な加入度数の「値」を表裏２面に割り当て、各々の加入度数を与える実質的な累進面を想定した上で、必要に応じて乱視面などとの合成面を構成している。即ち、本願発明が前述の先行技術と決定的に異なる点は、方向により異なる累進作用を有した非球面を両面に用いた両面非球面型累進屈折力レンズを構成していることにある。
【００３９】
【発明の実施の形態】
以下、本願発明の実施の形態にかかる両面非球面累進屈折レンズを説明する。なお、以下の説明では、まず、実施の形態にかかる両面非球面累進屈折レンズを得るために用いた設計方法を説明し、次いで、実施の形態にかかる両面非球面累進屈折レンズを説明する。
【００４０】
（レンズ設計の手順）
実施の形態にかかる両面非球面累進屈折レンズの光学設計方法の概略手順は、以下のとおりである。
▲１▼入力情報の設定
▲２▼凸累進屈折力レンズとしての両面設計
▲３▼本願発明の凸面形状への転換とそれに伴う裏面補正
▲４▼透過設計、リスティング則対応設計などに伴う裏面補正
以下、個々の手順をさらに細かいステップに分解して詳述する。
【００４１】
▲１▼入力情報の設定
入力情報は下記の２種類に大別される（光学設計以外は省略）。
▲１▼−１：アイテム固有情報
レンズアイテムに固有のデータである。素材の屈折率Ｎｅ、最小中心肉厚ＣＴｍｉｎ、最小コバ厚ＥＴｍｉｎ、累進面設計パラメータなど。
▲１▼−２：装用者固有情報
遠用度数（球面度数Ｓ、乱視度数Ｃ、乱視軸ＡＸ、プリズム度数Ｐ、プリズム基底方向ＰＡＸなど）、加入度数ＡＤＤ、フレーム形状データ（３次元形状データが望ましい）、フレーム装用データ（前傾角、あおり角など）、頂点間距離、レイアウトデータ（遠用ＰＤ、近用ＣＤ、アイポイント位置など）、その他、眼球に関するデータなど。なお、装用者から指定される累進帯長や加入度数測定方法、近用部内寄せ量などの累進面設計パラメータは装用者固有情報に分類される。
【００４２】
▲２▼凸累進屈折力レンズとしての両面設計
最初に従来型の凸累進屈折力レンズとして、凸面と凹面とに分けて設計する。
▲２▼−１：凸面形状（凸累進面）設計
入力情報として与えられた加入度数ＡＤＤや累進帯長を実現するために、入力情報である累進面設計パラメータに従って従来型の凸累進の面形状を設計する。このステップにおける設計では従来の様々な公知技術を利用することが可能であり、本願発明の設計技術は必要としない。
【００４３】
この方法の具体例として、例えば、まず最初にレンズ面を構成する際の背骨にあたる「主子午線」を設定する方法がある。この「主子午線」は最終的には眼鏡装用者が正面上方（遠方）から下方（近方）まで両眼視したときの視線とレンズ面との交線にあたる「主注視線」とすることが望ましい。ただし、近方視における眼の輻湊作用に対応した近方領域の内寄せなどの対応は、後述するように必ずしもこの「主注視線」の内寄せ配置にて行う必要はない。従って、ここでの「主注視線」はレンズ中央を通過し、レンズ面を左右に分割する縦方向の一本の子午線（主子午線）として定義する。レンズは表裏２面あるので、この「主子午線」もまた表裏２本存在することになる。この「主子午線」はレンズ面に対して垂直に眺めると直線状に見えるが、レンズ面が曲面である場合、一般に３次元空間では曲線となる。
【００４４】
次に、所定の加入度数や累進帯の長さなどの情報をもとに、この「主子午線」に沿った適切な屈折力分布を設定する。この屈折力分布は、レンズの厚みや視線と屈折面との角度などの影響を考慮して、表裏２面に分割設定することも可能であるが、このステップにおける設計では従来型の凸累進の面形状を設計するのであるから、累進作用は全て物体側表面である第１の屈折表面にあるものとする。従って、例えばレンズの表面（物体側表面である第１の屈折表面）の表面屈折力をＤ１とし、レンズの裏面（眼球側表面である第２の屈折表面）の表面屈折力をＤ２としたとき、得られる透過屈折力をＤとすると、一般にＤ≒Ｄ１−Ｄ２として近似的に求めることができる。ただし、Ｄ１とＤ２との組み合わせは、物体側表面が凸であり、眼球側表面が凹であるメニスカス形状であることが望ましい。ここで、Ｄ２は正の値であることに留意されたい。通常、レンズの裏面は凹面であり、表面屈折力としては負の値となるが、本明細書では説明の簡素化の為に正の値とし、Ｄ１から減じて透過屈折力をＤを算出することとする。
【００４５】
この表面屈折力と表面形状との関係式については一般に次の式で定義される
Ｄｎ＝（Ｎ−１）／Ｒ
ここに、Ｄｎ：第ｎ面の表面屈折力（単位：ジオプター）、Ｎ：レンズ素材の屈折率、Ｒ：曲率半径（単位：ｍ）である。従って、表面屈折力の分布を曲率の分布に換算する方法は、上記の関係式を変形した、
１／Ｒ＝Ｄｎ／（Ｎ−１）
を用いる。曲率の分布が得られたことにより、「主子午線」の幾何学的形状が一義的に確定し、レンズ面を構成する際の背骨にあたる「主子午線」が設定されたことになる。
【００４６】
次に、必要となるのは、レンズ面を構成する際の肋骨にあたる「水平方向の断面曲線群」である。これらの「水平方向の断面曲線群」と「主子午線」とが交わる角度は必ずしも直角である必要は無いが、説明を簡単にする為に、ここでは各々の「水平方向の断面曲線」は「主子午線」上で直角に交わるものとする。さらに「主子午線」との交点における「水平方向の断面曲線群」の「横方向の表面屈折力」もまた、必ずしも「主子午線」に沿った「縦方向の表面屈折力」と等しい必要はなく、現に、特許請求の範囲に記載があるように、本願発明は縦方向と横方向についての表面屈折力の違いに立脚している。しかしながらこのステップにおける設計では従来型の凸累進の面形状を設計するのであるから、これらの交点における縦方向と横方向の表面屈折力は等しいものとする。
【００４７】
さて、全ての「水平方向の断面曲線」はこれらの交点における表面屈折力を有する単純な円形曲線とすることも出来るが、様々な従来技術を組込んだ応用も可能である。「水平方向の断面曲線」に沿った表面屈折力分布に関する従来技術例として、例えば、特公昭４９−３５９５の技術がある。これはレンズの中央近傍に一本のほぼ円形形状の「水平方向の断面曲線」を設定し、それより上方に位置する断面曲線は中央から側方にかけて増加する表面屈折力分布を有し、下方に位置する断面曲線は中央から側方にかけて減少する表面屈折力分布を有することを特徴としている。このように、「主子午線」と、その上に無数に並んだ「水平方向の断面曲線群」が、あたかも背骨と肋骨の如くレンズ面を構成することになり、屈折面が確定する。
【００４８】
▲２▼−２：凹面形状（球面または乱視面）設計
入力情報として与えられた遠用度数を実現するために、凹面形状を設計する。遠用度数に乱視度数があれば乱視面となり、無ければ球面となる。このとき、度数に適した中心肉厚ＣＴや凸面と凹面との面相互の傾斜角も同時に設計し、レンズとしての形状を確定する。このステップにおける設計も従来の様々な公知技術を利用することが可能であり、本願発明の設計技術は必要としない。
【００４９】
▲３▼本願発明の凸面形状への転換とそれに伴う裏面補正
入力情報として与えられた遠用度数や加入度数ＡＤＤなどに応じ、従来型の凸累進屈折力レンズから本願発明のレンズとしての形状に転換する。
▲３▼−１：凸面形状（本願発明）設計
入力情報として与えられた遠用度数や加入度数ＡＤＤなどに応じ、従来型の凸累進面から本願発明の凸面形状に転換する。即ち、前述の従来型凸累進のレンズの表面（物体側表面である第１の屈折表面）において、遠用度数測定位置Ｆ１における、横方向の表面屈折力をＤＨｆ、縦方向の表面屈折力をＤＶｆ、近用度数測定位置Ｎ１における、横方向の表面屈折力をＤＨｎ、縦方向の表面屈折力をＤＶｎとするとき、
ＤＨｆ＋ＤＨｎ＜ＤＶｆ＋ＤＶｎ、かつＤＨｎ＜ＤＶｎ
となる関係式を満足させるか、
ＤＶｎ−ＤＶｆ＞ＡＤＤ／２、かつＤＨｎ−ＤＨｆ＜ＡＤＤ／２
となる関係式を満足させる累進屈折力表面とする。このとき、凸面全体の平均的な表面屈折力は変えないで本願発明の凸面形状に変換することが望ましい。例えば、遠用部と近用部との縦横の表面屈折力の総平均値を維持することなどが考えられる。ただし、物体側表面が凸であり、眼球側表面が凹であるメニスカス形状を保つ範囲内であることが望ましい。
【００５０】
▲３▼−２：凹面形状（本願発明）設計
上記▲３▼−１において、従来型の凸累進面から本願発明の凸面形状に転換した際の変形量を、▲２▼−２で設計した凹面形状に加算する。即ち、▲３▼−１のプロセスで加えられたレンズの表面（物体側表面である第１の屈折表面）の変形量を、レンズの裏面（眼球側表面である第２の屈折表面）側にも同じ量だけ加えるのである。この変形はレンズそのものを曲げる「ベンディング」と似ているが、全面に均一な変形ではなく、▲３▼−１に記載した関係式を満足させる表面としていることに留意されたい。なお、これらの裏面補正は本願発明の範疇ではあるが、一次近似的な補正にすぎず、▲４▼の裏面補正を加えることが望ましい。
【００５１】
▲４▼透過設計、リスティング則対応設計、近用部の内寄せ対応設計などに伴う裏面補正
入力情報として課せられた光学的な機能を、装用者が実際に装用した状況において実現するために、▲３▼において得られた本願発明のレンズに対して更に裏面補正を加えることが望ましい。
▲４▼−１：透過設計のための凹面形状（本願発明）設計
透過設計とは、装用者がレンズを実際に装用した状況において本来の光学的な機能を得るための設計方法であり、主として視線とレンズ面とが直交しえないことに起因する非点収差の発生や度数の変化を、除去もしくは低減するための「補正作用」を加える設計方法である。
【００５２】
具体的には前述の如く、視線の方向に応じた厳密な光線追跡計算によって、目的である本来の光学性能との差異を把握し、その差異を打ち消す面補正を実施する。これを繰返すことにより差異を極小化させ、最適な解を得ることが出来る。一般に、目標とする光学性能を有するレンズ形状を直接算出することは極めて困難であり、事実上不可能であることが多い。これは「任意に設定した光学性能を有するレンズ形状」が、実在するとは限らないからである。ところがこれとは逆に「任意に設定したレンズ形状の光学性能」を求めることは比較的容易である。従って、最初に任意の方法で第一次近似の面を仮計算し、その近似面を用いたレンズ形状の光学性能の評価結果に応じて前記設計パラメータを微調整し、レンズ形状を逐次変更して評価ステップに戻り、再評価と再調整を繰り返して目標とする光学性能へ近付けることが可能である。この手法は「最適化」と呼ばれて広く知られている手法の一例である。
【００５３】
▲４▼−２：リスティング則対応設計のための凹面形状（本願発明）設計
我々が周囲を見渡すときの眼球の３次元的な回旋運動は「リスティング則」と呼ばれる規則に則っていることが知られているが、処方度数に乱視度数がある場合、眼鏡レンズの乱視軸を「正面視での眼球の乱視軸」に合わせたとしても、周辺視をした場合には双方の乱視軸が一致しない場合がある。このように周辺視におけるレンズと眼との乱視軸方向が一致しないことに起因する非点収差の発生や度数の変化を、除去もしくは低減するための「補正作用」を、本発明によるレンズの乱視矯正作用を有する側の表面の曲面に加えることが出来る。
【００５４】
具体的には▲４▼−１で用いた「最適化」の方法と同様で、視線の方向に応じた厳密な光線追跡計算によって、目的である本来の光学性能との差異を把握し、その差異を打ち消す面補正を実施する。これを繰返すことにより差異を極小化させ、最適な解を得ることが出来る。
【００５５】
▲４▼−３：近用部の内寄せ対応設計のための凹面形状（本願発明）設計
また、本発明は両面非球面という面構成であるが、本発明の効果を得るにあたり、必ずしも受注後に初めて両面を加工する必要はない。例えば本発明の目的にかなう物体側表面の「半完成品」をあらかじめ準備しておき、受注後にそれらの中から処方度数や上述のカスタムメイド（個別設計）などの目的に適合した物体側表面の「半完成品」を選び、眼球側表面のみを受注後に加工して仕上げることも、コストと加工スピードの点で有益である。
【００５６】
この方法の具体例として、例えば前述▲３▼−１の凸面形状（本願発明）設計において物体側表面を左右対称の「半完成品」としてあらかじめ準備しておき、瞳孔間距離や近方視の対物距離などの個人情報が入力されてから、眼球側表面を目的にかなった左右非対称な曲面として設計することにより、個人情報に対応した近用部の内寄せを行なうことが出来る。
【００５７】
以下、上述の設計方法によって設計した両面非球面累進屈折レンズの実施例を図面を参照にしながら説明する。図７は実施例１、４、５、６と各々の度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表１−１及び表１−２にまとめて示した図、図８は実施例２、７と各々の度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表２−１及び表２−２にまとめて示した図、図９は実施例３とその度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表３−１及び表３−２にまとめて示した図、図１０は実施例１及び実施例２の表面屈折力分布を表すグラフ１−１、１−２、２−１、２−２を示す図、図１１は実施例３の表面屈折力分布を表すグラフ３−１、３−２を示す図、図１２は実施例４〜６の表面屈折力分布を表すグラフ４−１、４−２、５−１、５−２、６−１、６−２を示す図、図１３は実施例７の表面屈折力分布を表すグラフ７−１、７−２を示す図、図１４は従来技術例Ａ，Ｂ，Ｃの表面屈折力分布を表すグラフＡ−１、Ａ−２、Ｂ−１、Ｂ−２、Ｃ−１、Ｃ−２を示す図である。
【００５８】
図１５は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｓｖを示す図、図１６は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｓｈを示す図、図１７は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｐｖを示す図、図１８は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｐｈを示す図、図１９は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍγｖを示す図、図２０は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍγｈを示す図、図２１は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−ＳＭｖを示す図、図２２は実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−ＳＭｈを示す図である。
【００５９】
図２３は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｓｖを示す図、図２４は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｓｈを示す図、図２５は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｐｖを示す図、図２６は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｐｈを示す図、図２７は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍγｖを示す図、図２８は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍγｈを示す図、図２９は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−ＳＭｖを示す図、図３０は実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−ＳＭｈを示す図である。
【００６０】
図３１は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｓｖを示す図、図３２は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｓｈを示す図、図３３は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｐｖを示す図、図３４は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｐｈを示す図、図３５は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍγｖを示す図、図３６は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍγｈを示す図、図３７は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−ＳＭｖを示す図、図３８は実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−ＳＭｈを示す図である。
【００６１】
（実施例１）
図７の表１−１は本発明による実施例１の表面屈折力に関する一覧表である。この実施例１の度数はＳ０．００Ａｄｄ３．００に対応しており、比較のために同度数の３種類の従来技術例を併記してある。なお、従来技術例Ａは物体側表面が累進面である「凸面累進屈折力レンズ」に、従来技術例Ｂは物体側表面と眼球側表面との両方が累進面である「両面累進屈折力レンズ」に、従来技術例Ｃは眼球側表面が累進面である「凹面累進屈折力レンズ」に、それぞれ対応している。また、表１−１で用いた項目の意味は下記の通りである。
ＤＶｆ１：物体側表面の遠用度数測定位置Ｆ１における縦方向の表面屈折力
ＤＨｆ１：物体側表面の遠用度数測定位置Ｆ１における横方向の表面屈折力
ＤＶｎ１：物体側表面の近用度数測定位置Ｎ１における縦方向の表面屈折力
ＤＨｎ１：物体側表面の近用度数測定位置Ｎ１における横方向の表面屈折力
ＤＶｆ２：眼球側表面の遠用度数測定位置Ｆ２における縦方向の表面屈折力
ＤＨｆ２：眼球側表面の遠用度数測定位置Ｆ２における横方向の表面屈折力
ＤＶｎ２：眼球側表面の近用度数測定位置Ｎ２における縦方向の表面屈折力
ＤＨｎ２：眼球側表面の近用度数測定位置Ｎ２における横方向の表面屈折力
【００６２】
図１０のグラフ１−１と１−２とは実施例１の主注視線に沿った表面屈折力分布を表すグラフであり、横軸は向って右側がレンズ上方、左側がレンズ下方を、また、縦軸は表面屈折力を表す。ここで、グラフ１−１は物体側表面に対応し、グラフ１−２は眼球側表面に対応している。また、実線のグラフは主注視線に沿った縦方向の表面屈折力分布を表し、点線のグラフは主注視線に沿った横方向の表面屈折力分布を表す。なお、これらは面構成の基本的な違いを説明するグラフであり、周辺部の非点収差除去のための非球面化や、乱視度数対応のための乱視成分付加などの場合などは省略してある。
【００６３】
さらに、比較のために表１−１に掲げた同度数の３種類の従来技術例の主注視線に沿った表面屈折力分布を表すグラフとして、図１４にグラフＡ−１と２、グラフＢ−１と２、グラフＣ−１と２を併記する。なお、これらのグラフにおける用語の意味は下記の通りである。
Ｆ１：物体側表面の遠用度数測定位置、
Ｆ２：眼球側表面の遠用度数測定位置
Ｎ１：物体側表面の近用度数測定位置、
Ｎ２：眼球側表面の近用度数測定位置
ＣＶ１：物体側表面の主注視線に沿った縦方向の表面屈折力分布を表すグラフ（実線にて表示）
ＣＨ１：物体側表面の主注視線に沿った横方向の表面屈折力分布を表すグラフ（点線にて表示）
ＣＶ２：眼球側表面の主注視線に沿った縦方向の表面屈折力分布を表すグラフ（実線にて表示）
ＣＨ２：眼球側表面の主注視線に沿った横方向の表面屈折力分布を表すグラフ（点線にて表示）
【００６４】
また、これらのグラフのＦ１，Ｎ１，Ｆ２，Ｎ２における表面屈折力は、前記表１−１に対応しており、ＤＶｆ１〜ＤＨｎ２などの用語の意味もまた、前記表１−１の場合と同一である。なお、これらのグラフの中央にある水平方向の一点鎖線は、物体側表面の平均表面屈折力（Ｆ１とＮ１における縦横の表面屈折力の総平均値）を示している。本発明による実施例１と３種類の従来技術例における物体側表面の平均表面屈折力は、いずれも５．５０ジオプターに統一して比較上の公平を期した。
【００６５】
次に、図１５〜図２２に示されるグラフ１−３−で始まる８種類のグラフは、本発明による実施例１のレンズを主注視線に沿って眺めたときの倍率分布を、前述の厳密な倍率計算を行って求めた結果を表すグラフであり、横軸は向って右側がレンズ上方、左側がレンズ下方を、また、縦軸は倍率を表す。図の濃い実線が実施例１であり、薄い鎖線が従来技術例Ａ、濃い鎖線が従来技術例Ｂ、薄い実線が従来技術例Ｃである。以下のこの種のグラフも同じである。なお、公平を期するために、横軸は眼球回旋角を用いて視線の方向ごとの比較が出来るようにすると共に、各グラフの縦軸の倍率の縮尺を合わせた。グラフ１−３−の後に付した符号の意味は、
Ｍｓｖ：縦方向のシェープファクター、
Ｍｓｈ：横方向のシェープファクター
Ｍｐｖ：縦方向のパワーファクター、
Ｍｐｈ：横方向のパワーファクター
Ｍγｖ：縦方向のプリズムファクター、
Ｍγｈ：横方向のプリズムファクター
ＳＭｖ：縦方向の倍率、
ＳＭｈ：横方向の倍率
であり、前述の如く、縦方向の倍率ＳＭｖ及び、横方向の倍率ＳＭｈは、
ＳＭｖ＝Ｍｓｖ×Ｍｐｖ×Ｍγｖ
ＳＭｈ＝Ｍｓｈ×Ｍｐｈ×Ｍγｈ
という関係にある。
【００６６】
なお、実施例１と前記３種類の従来技術例はいずれも、屈折率ｎ＝１．６９９、中心厚ｔ＝３．０ｍｍ、幾何学中心ＧＣでプリズムのない仕様、とした。対物パワー（対物距離の逆数）については、Ｆ１，Ｆ２における対物パワーＰｘ＝０．００ジオプター（無限遠方）、Ｎ１，Ｎ２における対物パワーＰｘ＝２．５０ジオプター（４０ｃｍ）とし、他の位置における対物パワーは主注視線に沿った付加屈折力の比率に２．５０ジオプターを乗じて与えた。また、レンズ後頂点から角膜頂点までの距離Ｌ＝１５．０ｍｍ、角膜頂点から眼球回旋中心までの距離ＣＲ＝１３．０ｍｍとした。眼球回旋角θは眼球回旋中心点Ｃを物体側レンズ表面の幾何学中心ＧＣを通る法線上に置き、この法線と視線が一致したときの回旋角を０度とし、上方を（＋）下方を（−）で表示した。しかる後に、Ｆ１，Ｆ２に対する眼球回旋角θ＝＋３０．０度とし、Ｎ１，Ｎ２に対する眼球回旋角θ＝−１５．０度に統一することにより、累進作用や表面屈折力の分布が表裏いずれの側にあろうとも同一条件で比較できるように配慮した。
【００６７】
図７の表１−２は本発明による実施例１と、比較のために準備した３種類の従来技術例について、特定の視線方向に対する厳密な倍率計算結果の一覧表であり、前述の図２１のグラフ１−３−ＳＭｖ（縦方向の総合倍率）と図２２のグラフ１−３−ＳＭｈ（横方向の総合倍率）に対応している。前述の説明の如く、縦方向と横方向では倍率の値が異なるので、双方の倍率を算出してある。ここで、表１−２の符号が表す意味は以下のとおりである。
ＳＭｖｆ：遠用測定点を通過する視線上の縦方向倍率
ＳＭｖｎ：近用測定点を通過する視線上の縦方向倍率
ＳＭｖｆｎ：縦方向倍率差（ＳＭｖｎ−ＳＭｖｆ）
ＳＭｈｆ：遠用測定点を通過する視線上の横方向倍率
ＳＭｈｎ：近用測定点を通過する視線上の横方向倍率
ＳＭｈｆｎ：横方向倍率差（ＳＭｈｎ−ＳＭｈｆ）
【００６８】
さて、表１−２のＳＭｖｆｎとＳＭｈｆｎ、即ち縦方向倍率差（ＳＭｖｎ−ＳＭｖｆ）と横方向倍率差（ＳＭｈｎ−ＳＭｈｆ）を見てみると、従来技術例Ａが０．１３８０と０．１０１５、Ｂが０．１３６０と０．０９８８、Ｃが０．１３４２と０．０９６１であるのに対し、本発明による実施例１の値は０．１３４２と０．０９５４という低い倍率差に押えられていることがわかる。即ち、本発明による実施例１の遠用部と近用部の倍率差は、従来技術１よりも更に少なくなっているので、像の歪みや揺れについても従来技術１より更に改善されていることがわかる。なお、前述の従来技術１に対応した特許明細書には、倍率を計算をする上で、縦方向や横方向の違いについて全く考慮されていない。ところが、本発明による実施例１に対応した厳密な倍率計算による図２１のグラフ１−３−ＳＭｖ（縦方向の総合倍率）とグラフ図２２の１−３−ＳＭｈ（横方向の総合倍率）を比べるとすぐにわかるように、縦方向と横方向における像の倍率分布は明白に異なっている。また、この違いは主に近用部とその下方（眼球回旋角で−２０°近辺以下）で顕著なことも容易に読取れる。
【００６９】
さて、前述の倍率の計算式、
縦方向の倍率ＳＭｖ＝Ｍｓｖ×Ｍｐｖ×Ｍγｖ
横方向の倍率ＳＭｈ＝Ｍｓｈ×Ｍｐｈ×Ｍγｈ
にあるように、グラフ１−３−ＳＭｖは３つの要素、グラフ１−３−Ｍｓｖとグラフ１−３−Ｍｐｖとグラフ１−３−Ｍγｖの値を掛け合わせて得られ、同様に、グラフ１−３−ＳＭｈは３つの要素、グラフ１−３−Ｍｓｈとグラフ１−３−Ｍｐｈとグラフ１−３−Ｍγｈの値を掛け合わせて得られる。ここで各々の要素の縦方向と横方向を比べると、シェイプファクターであるＭｓｖとＭｓｖには明確な差が見られないが、ＭｐｖとＭｐｈでは近用部より下方（眼球回旋角で−２５°近辺以下）に違いが見られる。また、ＭγｖとＭγｈでは近用部とその下方（眼球回旋角で−１５°近辺以下）に顕著な違いがある。即ち、グラフ１−３−ＳＭｖとグラフ１−３−ＳＭｈの違いの主たる原因は、ＭγｖとＭγｈの違いであり、副次的な原因はＭｐｖとＭｐｈの違いであって、ＭｓｖとＭｓｈには明確な差が見られず、ほとんど無関係であることがわかる。つまり、従来技術１に対応した特許明細書に縦方向や横方向の倍率の違いが見られないのは、倍率の違いの主たる原因であるプリズムファクターＭγｖとＭγｈを全く考慮しておらず、副次的な原因であるパワーファクターＭｐｖとＭｐｈについても対物距離や視線とレンズとの角度を無視しているので差が出ないのである。更に、従来技術１において改善の根拠とされているシェイプファクターＭｓｖとＭｓｈについても、本発明の実施例１で用いた縮尺で見る限り、遠近の倍率差に各例相互の違いが見られない。
【００７０】
なお、従来技術１では「遠用部と近用部の倍率差を減らす」ことで「像の歪みや揺れを少なく出来る」としているが、本発明では更に「縦方向と横方向の倍率差を減らす」ことも「像の歪みや揺れを少なく出来る」効果があると考える。即ち、四角い物が扁平に見えたり、丸い物が楕円形に見えたりすることを避けようとするのである。この視覚的な感覚の向上については「差を減らす」ことより「比率を１に近づける」と捉える方が本質的であろう。ここで重要なのは、四角い物が扁平に見えたり、丸い物が楕円形に見えたりする感覚は「遠近比」ではなく「縦横比」であるということである。即ち、本発明では「遠用部と近用部の倍率差を減らす」ことばかりではなく、更に重要な改善として「縦方向と横方向の倍率差を減らし、倍率比を１に近づける」ことにより「像の歪みや揺れを少なく出来る」という改善効果が得られるのである。なお、これらの傾向は主に近用部より下方（眼球回旋角で−２５°近辺以下）で顕著である。
【００７１】
（実施例２）
図８の表２−１は本発明による実施例２の表面屈折力に関する一覧表である。この実施例２の度数はＳ＋６．００Ａｄｄ３．００に対応しており、比較のために同度数の３種類の従来技術例を併記してある。なお、従来技術例Ａは物体側表面が累進面である「凸面累進屈折力レンズ」に、従来技術例Ｂは物体側表面と眼球側表面との両方が累進面である「両面累進屈折力レンズ」に、従来技術例Ｃは眼球側表面が累進面である「凹面累進屈折力レンズ」に、それぞれ対応している。また、表２−１で用いたＤＶｆ１〜ＤＨｎ２などの用語の意味は、前記表１−１と同一である。グラフ２−１と２は本発明による実施例２の主注視線に沿った表面屈折力分布を表すグラフであり、横軸は向って右側がレンズ上方、左側がレンズ下方を、また、縦軸は表面屈折力を表す。ここでグラフ２−１は物体側表面に対応し、グラフ２−２は眼球側表面に対応している。また、実線のグラフは主注視線に沿った縦方向の表面屈折力分布を表し、点線のグラフは主注視線に沿った横方向の表面屈折力分布を表す。なお、これらは面構成の基本的な違いを説明するグラフであり、周辺部の非点収差除去のための非球面化や、乱視度数対応のための乱視成分付加などの場合などは省略してある。
【００７２】
さらに、比較のために表２−１に掲げた同度数の３種類の従来技術例の主注視線に沿った表面屈折力分布を表すグラフとして、前記実施例１において用いたグラフＡ−１と２、グラフＢ−１と２、グラフＣ−１と２を再び用いる。従って、これらのグラフの用語の意味は前記実施例１と同様であるが、Ｆ１，Ｎ１，Ｆ２，Ｎ２における表面屈折力は、表２−１にも対応しているものとし、また中央にある水平方向の一点鎖線が示す物体側表面の平均表面屈折力も表２−１に対応させる都合から、いずれも１０．５０ジオプターという深いカーブとなっているものとする。
【００７３】
次に、図２３〜図３０に示したグラフ２−３−で始まる８種類のグラフは、本発明による実施例２のレンズを主注視線に沿って眺めたときの倍率分布を、前述の厳密な倍率計算を行って求めた結果を表すグラフである。用語やグラフ２−３−の後に付した符号の意味などは、図の濃い実線が実施例２である以外は、前記実施例１の場合と同様である。なお、実施例２と前記３種類の従来技術例で用いた屈折率や対物パワー、眼球回旋角などは、いずれも前記実施例１の場合と同様としたが、実施例２と前記３種類の従来技術例の度数がＳ＋６．００Ａｄｄ３．００であることから、中心厚ｔだけは６．０ｍｍとして実際の製品に近づけた。
【００７４】
図８の表２−２は本発明による実施例２と、比較のために準備した３種類の従来技術例について、特定の視線方向に対する厳密な倍率計算結果の一覧表であり、前述のグラフ２−３−ＳＭｖ（縦方向の総合倍率）とグラフ２−３−ＳＭｈ（横方向の総合倍率）に対応している。ここで、表２−２の符号が表す意味は前述の表１−２の意味と同様である。
【００７５】
さて、表２−２のＳＭｖｆｎとＳＭｈｆｎ、即ち縦方向倍率差（ＳＭｖｎ−ＳＭｖｆ）と横方向倍率差（ＳＭｈｎ−ＳＭｈｆ）を見てみると、従来技術例Ａが０．２２７５と０．１３２５、Ｂが０．２２７７と０．１２６８、Ｃが０．２２８０と０．１２１０であるのに対し、本発明による実施例２の値は０．２１５１と０．１１９９という低い倍率差に押えられていることがわかる。即ち、本発明による実施例２の遠用部と近用部の倍率差は、従来技術１よりも更に少なくなっているので、像の歪みや揺れについても従来技術１より更に改善されていることがわかる。なお、前述の実施例１と同様に、本発明による実施例２に対応した厳密な倍率計算によるグラフ２−３−ＳＭｖ（縦方向の総合倍率）とグラフ２−３−ＳＭｈ（横方向の総合倍率）を比べるとすぐにわかるように、縦方向と横方向における像の倍率分布は明白に異なっている。
【００７６】
また、この違いは主に中間部から下方（眼球回旋角で−１０°近辺以下）で顕著なことも容易に読取れる。さて、前述の実施例１と同様に、実施例２においてもグラフ２−３−ＳＭｖは３つの要素、グラフ２−３−Ｍｓｖとグラフ２−３−Ｍｐｖとグラフ２−３−Ｍγｖの値を掛け合わせて得られ、同様に、グラフ２−３−ＳＭｈは３つの要素、グラフ２−３−Ｍｓｈとグラフ２−３−Ｍｐｈとグラフ２−３−Ｍγｈの値を掛け合わせて得られる。ここで各々の要素の縦方向と横方向を比べると、シェイプファクターであるＭｓｖとＭｓｖには明確な差が見られないが、ＭｐｖとＭｐｈでは近用部より下方（眼球回旋角で−２０°近辺以下）に違いが見られる。また、ＭγｖとＭγｈでは中間部から下方（眼球回旋角で−１０°近辺以下）に顕著な違いがある。ここで遠用部の上方（眼球回旋角で＋２０°近辺以上）にも差が見られるが、各例による差が出るのは遠用部のかなり上方（眼球回旋角で＋３０°近辺以上）であり、使用頻度も少ないので無視しうる。
【００７７】
即ち、前述の実施例１と同様に、実施例２においても図２９のグラフ２−３−ＳＭｖと図３０のグラフ２−３−ＳＭｈの違いの主たる原因は、ＭγｖとＭγｈの違いであり、副次的な原因はＭｐｖとＭｐｈの違いであって、ＭｓｖとＭｓｈには明確な差が見られず、ほとんど無関係であることがわかる。更に、従来技術１において改善の根拠とされているシェイプファクターＭｓｖとＭｓｈについても、本発明の実施例２で用いた縮尺で見る限り、遠近の倍率差に各例相互の違いが見られない。なお、実施例２においても、前述の実施例１と同様に、「遠用部と近用部の倍率差を減らす」ことばかりではなく、更に重要な改善として「縦方向と横方向の倍率差を減らし、倍率比を１に近づける」ことにより「像の歪みや揺れを少なく出来る」という改善効果が得られている。なお、これらの傾向は主に近用部より下方（眼球回旋角で−２５°近辺以下）で顕著である。
【００７８】
（実施例３）
図９の表３−１は本発明による実施例３の表面屈折力に関する一覧表である。この実施例３の度数はＳ−６．００Ａｄｄ３．００に対応しており、比較のために同度数の３種類の従来技術例を併記してある。なお、従来技術例Ａは物体側表面が累進面である「凸面累進屈折力レンズ」に、従来技術例Ｂは物体側表面と眼球側表面との両方が累進面である「両面累進屈折力レンズ」に、従来技術例Ｃは眼球側表面が累進面である「凹面累進屈折力レンズ」に、それぞれ対応している。また、表３−１で用いたＤＶｆ１〜ＤＨｎ２などの用語の意味は、前記表１−１や表２−１と同一である。
【００７９】
図１１のグラフ３−１と２は本発明による実施例３の主注視線に沿った表面屈折力分布を表すグラフであり、横軸は向って右側がレンズ上方、左側がレンズ下方を、また、縦軸は表面屈折力を表す。ここで、グラフ３−１は物体側表面に対応し、グラフ３−２は眼球側表面に対応している。また、実線のグラフは主注視線に沿った縦方向の表面屈折力分布を表し、点線のグラフは主注視線に沿った横方向の表面屈折力分布を表す。なお、これらは面構成の基本的な違いを説明するグラフであり、周辺部の非点収差除去のための非球面化や、乱視度数対応のための乱視成分付加などの場合などは省略してある。
【００８０】
さらに、比較のために図９の表３−１に掲げた同度数の３種類の従来技術例の主注視線に沿った表面屈折力分布を表すグラフとして、前記実施例１や２において用いたグラフＡ−１と２、グラフＢ−１と２、グラフＣ−１と２を再び用いる。従って、これらのグラフの用語の意味は前記実施例１や２と同様であるが、Ｆ１，Ｎ１，Ｆ２，Ｎ２における表面屈折力は、表３−１にも対応しているものとし、また中央にある水平方向の一点鎖線が示す物体側表面の平均表面屈折力も表３−１に対応させる都合から、いずれも２．５０ジオプターという浅いカーブとなっているものとする。
【００８１】
次に、図３１〜図３８に示したグラフ３−３−で始まる８種類のグラフは、本発明による実施例３のレンズを主注視線に沿って眺めたときの倍率分布を、前述の厳密な倍率計算を行って求めた結果を表すグラフである。用語やグラフ３−３−の後に付した符号の意味などは、図の濃い実線が実施例３である以外は、前記実施例１や２の場合と同様である。なお、実施例３と前記３種類の従来技術例で用いた屈折率や対物パワー、眼球回旋角などは、いずれも前記実施例１や２の場合と同様としたが、実施例３と前記３種類の従来技術例の度数がＳ−６．００Ａｄｄ３．００であることから、中心厚ｔだけは１．０ｍｍとして実際の製品に近づけた。
【００８２】
図９の表３−２は本発明による実施例３と、比較のために準備した３種類の従来技術例について、特定の視線方向に対する厳密な倍率計算結果の一覧表であり、前述のグラフ３−３−ＳＭｖ（縦方向の総合倍率）とグラフ３−３−ＳＭｈ（横方向の総合倍率）に対応している。ここで、表３−２の符号が表す意味は前述の表１−２や表２−２の意味と同様である。
【００８３】
さて、表３−２のＳＭｖｆｎとＳＭｈｆｎ、即ち縦方向倍率差（ＳＭｖｎ−ＳＭｖｆ）と横方向倍率差（ＳＭｈｎ−ＳＭｈｆ）を見てみると、従来技術例Ａが０．０４７５と０．０７７４、Ｂが０．０４１８と０．０７５０、Ｃが０．０３６３と０．０７２７であるのに対し、本発明による実施例２の値は０．０５１２と０．０７２６という値であり、縦方向倍率差は増えているが横方向倍率差は減っていることがわかる。ただし、縦方向倍率差は前述の実施例１や実施例２に比べていずれも１／３乃至１／５といった低い値であり、横方向倍率差がわずかながら減っていることを考え合わせると、本発明による実施例３の遠用部と近用部の倍率差は、従来技術１に比べて大差ないと言える。ところが、本発明による実施例３に対応した厳密な倍率計算によるグラフ３−３−ＳＭｖ（縦方向の総合倍率）とグラフ３−３−ＳＭｈ（横方向の総合倍率）を観察すると、本発明による実施例３は従来例に比べ、特に近用部より下方（眼球回旋角で−２０°近辺以下）における「縦方向の倍率が１より小さくなる傾向」が最も少なく、結果的に「縦横の倍率差」が最も少なくなっており、像の歪みや揺れが従来例よりも改善されている。
【００８４】
なお、図３７のグラフ３−３−ＳＭｖ（縦方向の総合倍率）において、縦方向と横方向における像の倍率分布に顕著な違いが出るのは中間部から下方（眼球回旋角で−１０°近辺以下）と遠用部の上方（眼球回旋角で＋１０°近辺以上）であるが、各例による差が出るのは近用部より下方（眼球回旋角で−２０°近辺以下）と遠用部のやや上方（眼球回旋角で＋２５°近辺以上）である。この内、遠用部のやや上方については使用頻度も少ないので無視しうるが、近用部より下方については使用頻度も多く、無視し得ない。その結果、本発明による実施例３は従来例に比べ、特に近用部より下方（眼球回旋角で−２０°近辺以下）において縦方向の倍率が１に最も近く、その結果「縦横の倍率差」が最も少なくなっており、従来例よりも像の歪みや揺れが改善されているのである。なお、これらの傾向は主に近用部より下方（眼球回旋角で−２５°近辺以下）で顕著である。また、従来技術１において改善の根拠とされているシェイプファクターＭｓｖとＭｓｈについては、本発明の実施例１や実施例２と同様に、実施例３で用いた縮尺で見ても、遠近の倍率差に各例相互の違いが見られない。
【００８５】
（実施例４〜７）
本発明の実施例として、前述の実施例１〜３の他にも特許請求の範囲に記載した範囲内で、様々な表面屈折力の分布の組合わせが可能である。ここで、実施例１と同度数の応用例として実施例４〜６を、また実施例２と同度数の応用例として実施例７を示す。これらの実施例の表面屈折力と特定の視線方向に対する厳密な倍率計算結果の一覧表とグラフを、図７の表１−１、表１−２及び図１２〜図１４のグラフ４−１、グラフ４−２乃至グラフ７−１、グラフ７−２に示す。
【００８６】
（変形例）
更に本発明においては通常の処方値のみならず、これまでレンズメーカーが把握することの少なかった眼鏡装用者の個人的ファクターとして、例えば角膜頂点からレンズ後方頂点までの距離、眼球回旋中心からレンズ後方頂点までの距離、左右眼の不等像視の程度、左右眼の高さの差、最も頻度の高い近方視の対物距離、フレームの前傾角（上下方向）やあおり角（左右方向）、レンズのコバ厚方向に対するヤゲン位置、などを入力情報としてレンズ設計に組み入れることにより、カスタムメイド（個別設計）の要求に応えることも可能である。また、本発明は両面非球面という面構成であるが、本発明の効果を得るにあたり、必ずしも受注後に初めて両面を加工する必要はない。例えば本発明の目的にかなう物体側表面の「半完成品」をあらかじめ準備しておき、受注後にそれらの中から処方度数や上述のカスタムメイド（個別設計）などの目的に適合した物体側表面の「半完成品」を選び、眼球側表面のみを受注後に加工して仕上げることも、コストと加工スピードの点で有益である。
【００８７】
この方法の具体例として、例えば左右対称の物体側表面の「半完成品」をあらかじめ準備することが考えられる。そして近方視における眼の輻湊作用に対応した近用部の内寄せについては、瞳孔間距離や近方視の対物距離などの個人情報に対応し、眼球側表面を目的にかなった左右非対称な曲面とすることで組み入れることが可能である。無論、これらの個人情報は実測ばかりではなく、推定や平均的・標準的な値とするなど、情報の取得や確定手段は様々な場合が考えられるが、それらの手段如何によって本発明が限定されることはない。又、通常の処方値のみならず、前述の個人的ファクターをレンズ設計に組み入れるための光学計算を行なう際に、物体側表面、又は眼球側表面、又は物体側表面と眼球側表面の両方の曲面に於いて、主として視線とレンズ面とが直交しえないことに起因する非点収差の発生や度数の変化を、除去もしくは低減するための「補正作用」を加えることも可能である。
【００８８】
更に、一般に我々が周囲を見渡すときの眼球の３次元的な回旋運動は「リスティング則」と呼ばれる規則に則っていることが知られているが、処方度数に乱視度数がある場合、眼鏡レンズの乱視軸を「正面視での眼球の乱視軸」に合わせたとしても、周辺視をした場合には双方の乱視軸が一致しない場合がある。このように周辺視におけるレンズと眼との乱視軸方向が一致しないことに起因する非点収差の発生や度数の変化を、除去もしくは低減するための「補正作用」を、本発明によるレンズの乱視矯正作用を有する側の表面の曲面に加えることも可能である。
【００８９】
尚、本発明における「所定の加入度数」の定義として、図６の如く、レンズメーターの開口部を物体側表面の遠用度数測定位置Ｆ１と近用度数測定位置Ｎ１に当てて測定した屈折力差とした場合の他に、レンズメーターの開口部を眼球側表面の遠用度数測定位置Ｆ２と近用度数測定位置Ｎ２に当てて測定した屈折力差とした場合、更にはレンズメーターの開口部を眼球側表面の遠用度数測定位置Ｆ２に当てて測定した屈折力と、眼球回旋中心位置を中心として回転させて近用度数測定位置Ｎ２に向けてＮ３で測定した屈折力との差とした場合、また各々の屈折力として特に水平方向の屈折力成分のみを用いた場合などがあり、これらの内のいずれの定義を採用することも可能である。
【００９０】
【発明の効果】
以上詳述したように、本発明によれば、「視線とレンズ面との角度」や「対物距離」による影響を考慮し、像の倍率を正しく算出するようにしたことにより、遠用部と近用部における像の倍率差を低減し、処方値に対する良好な視力補正と、装用時における歪みの少ない広範囲な有効視野を与えることができ、更に、物体側表面として「左右対称の半完成品」を用い、受注後に眼球側表面のみを近方視における眼の輻湊作用に対応した左右非対称な曲面として加工することを可能とし、加工時間とコストとを低減させることを可能とする両面非球面型累進屈折力レンズを得ることができる。
【図面の簡単な説明】
【図１】眼鏡レンズ表面の各位置における各種の表面屈折力の説明図である。
【図２】眼球と視線とレンズとの位置関係の説明図である。
【図３−１】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図３−２】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図３−３】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図４−１】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図４−２】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図４−３】プリズムの倍率Ｍγに関する説明図であってプラスレンズとマイナスレンズによる違いや主としてレンズの下部である近用部を用いて眺めた場合の倍率の違いに関する説明図である。
【図５−１】累進屈折力レンズの光学的レイアウトの説明図であって累進屈折力レンズを物体側表面から眺めた正面図である。
【図５−２】累進屈折力レンズの光学的レイアウトの説明図であって縦方向の断面を表す側面図である。
【図５−３】累進屈折力レンズの光学的レイアウトの説明図であって横方向の断面を表す立面図である。
【図６】「加入度数」の定義の違いを示す説明図である。
【図７】実施例１、４、５、６と各々の度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表１−１及び表１−２にまとめて示した図である。
【図８】実施例２、７と各々の度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表２−１及び表２−２にまとめて示した図である。
【図９】実施例３とその度数に対応した従来技術Ａ，Ｂ，Ｃの「表面屈折力」と「特定の視線方向に対する厳密な倍率計算結果」を表３−１及び表３−２にまとめて示した図である。
【図１０】実施例１及び実施例２の表面屈折力分布を表すグラフ１−１、１−２、２−１、２−２を示す図である。
【図１１】実施例３の表面屈折力分布を表すグラフ３−１、３−２を示す図である。
【図１２】実施例４〜６の表面屈折力分布を表すグラフ４−１、４−２、５−１、５−２、６−１、６−２を示す図である。
【図１３】実施例７の表面屈折力分布を表すグラフ７−１、７−２を示す図である。
【図１４】従来技術例Ａ，Ｂ，Ｃの表面屈折力分布を表すグラフＡ−１、Ａ−２、Ｂ−１、Ｂ−２、Ｃ−１、Ｃ−２を示す図である。
【図１５】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｓｖを示す図である。
【図１６】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｓｈを示す図である。
【図１７】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｐｖを示す図である。
【図１８】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍｐｈを示す図である。
【図１９】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍγｖを示す図である。
【図２０】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−Ｍγｈを示す図である。
【図２１】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−ＳＭｖを示す図である。
【図２２】実施例１とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ１−３−ＳＭｈを示す図である。
【図２３】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｓｖを示す図である。
【図２４】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｓｈを示す図である。
【図２５】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｐｖを示す図である。
【図２６】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍｐｈを示す図である。
【図２７】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍγｖを示す図である。
【図２８】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−Ｍγｈを示す図である。
【図２９】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−ＳＭｖを示す図である。
【図３０】実施例２とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ２−３−ＳＭｈを示す図である。
【図３１】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｓｖを示す図である。
【図３２】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｓｈを示す図である。
【図３３】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｐｖを示す図である。
【図３４】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍｐｈを示す図である。
【図３５】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍγｖを示す図である。
【図３６】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−Ｍγｈを示す図である。
【図３７】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−ＳＭｖを示す図である。
【図３８】実施例３とその度数に対応した３種類の従来例Ａ，Ｂ，Ｃのレンズを主注視線に沿って眺めたときの倍率分布を厳密な倍率計算を行って求めた結果を表すグラフ３−３−ＳＭｈを示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention is, for example, a lens used as a progressive-power lens for presbyopia for spectacles, and is divided and distributed into a first refractive surface that is an object side surface and a second refractive surface that is an eyeball side surface. A double-sided aspherical surface that has a progressive refractive power action and is configured to give a distance power (Df) and an addition power (ADD) based on a prescription value by combining the first surface and the second surface Type progressive power lens.
[0002]
[Prior art]
Progressive-power lenses are generally used widely because they are presbyopic eyeglass lenses that are not easily seen as presbyopia in appearance, and that they can be clearly visible continuously from long to short distances. ing. However, multiple fields of view, such as a field of view for viewing distant and a field of view for viewing near, and a field for viewing intermediate distances without intervening boundaries in a limited lens area There are disadvantages peculiar to progressive-power lenses, such as the fact that the width of each field of view is not always sufficient, and there are areas that cause image distortion and shaking mainly in the side field of view. Is also widely known.
[0003]
Various proposals have been made for a long time for the purpose of improving the disadvantages specific to these progressive-power lenses, but the surface configuration of these conventional progressive-power lenses has a "progressive surface" on the object side surface, Most of the combinations had a “spherical surface” or “astigmatic surface” on the eyeball side surface. On the contrary, as a progressive addition lens characterized by adding a “progressive action” to the eyeball side surface, in 1970, Essel Optical Co. There is an Atoral Variplace sold by (currently Essilor).
[0004]
Further, as a prior art proposed in recent years, there are, for example, the techniques described in International Patent Publications WO97 / 19382 and WO97 / 19383, and the like is generally called back surface progression (or concave surface progression). The main purpose of the surface composition in this recently proposed rear surface progression is to share a part or all of the required addition power from the object side surface to the eyeball side surface, so that the images of the distance portion and the near portion are imaged. It is intended to reduce magnification differences and improve image distortion and shaking.
[0005]
Among these prior arts, the one described in WO97 / 19382 eliminates all of the “progressive action” by making the object side surface spherical or rotationally symmetric aspherical, and a predetermined addition power is applied only to the eyeball side surface. "Progressive surface" is added (fused), and the one described in WO 97/19383 has an additional power on the "progressive surface" on the object side surface that is less than a predetermined value, so The “progressive surface” that gives power is added (fused) to the “spherical surface” and “astigmatism surface” on the back side.
[0006]
In addition, although there are differences in purpose and grounds, other prior arts of progressive-power lenses described in which a “progressive action” is added to the surface of the eyeball are disclosed in, for example, Japanese Patent Publication No. 47-23934 57-10112, JP-A-10-206805, JP-A-2000-21846, and the like. Further, as described in the aforementioned WO97 / 19383, both surfaces of the lens are disclosed. For example, Japanese Patent Application Laid-Open No. 2000-338452 and Japanese Patent Application Laid-Open No. 6-118353 disclose prior art with “progressive action”. The common point of these prior arts is that the required addition power is shared between the two sides.
[0007]
[Problems to be solved by the invention]
The main purpose of these prior arts is to share a part or all of the required addition power from the object side surface to the eyeball side surface, thereby reducing the magnification difference between the distance portion and the near portion, and by the magnification difference. It is intended to improve image distortion and shaking. However, there is little clear description about the grounds for obtaining such improvement effects, and there is only a partial description in the above-mentioned Patent International Publication No. WO97 / 19383 (hereinafter referred to as Prior Art 1). That is, the prior art 1 discloses a formula for calculating the lens magnification SM shown in the following formulas (1) to (3), which is adopted as a basic evaluation parameter for lens design.
[0008]
That is, the prior art 1 has the following description.
“The lens magnification SM is generally expressed by the following equation.
SM = Mp × Ms (1)
Here, Mp is called a power factor, and Ms is called a shape factor. The distance from the vertex of the lens's eyeball side (inner vertex) to the eyeball is the apex distance L, the refractive power of the inner vertex (inner vertex refractive power) is Po, the thickness of the lens center is t, and the refractive index of the lens is When the base curve (refractive power) of the object side surface of the lens is Pb, it is expressed as follows.
Mp = 1 / (1-L × Po) (2)
Ms = 1 / (1− (t × Pb) / n) (3)
In calculating the expressions (2) and (3), the inner vertex power Po is used, the diopter (D) is used for the base curve Pb, and the meter (m) is used for the distance L and the thickness t. . "
[0009]
Then, the difference in magnification between the distance portion and the near portion is calculated using the calculation formula of these lens magnifications SM. Since the magnification difference is small in the prior art 1, the distortion and shaking of the image are improved. Yes.
[0010]
According to the research of the present inventor, the conventional technique 1 has a certain effect as compared with the prior art. However, in order to design a lens with higher performance, the following points are further examined. It turned out to be necessary.
a. The basic evaluation parameters used in the above-mentioned prior art 1 include the “distance L from the apex of the lens on the eyeball side of the lens to the eyeball” and “lens center thickness t”. In other words, parameters that should be applied only to the vicinity of the center of the lens are included. That is, in the example of the prior art 1, the basic evaluation parameter that should be applied only to the distance portion near the center of the lens is also applied to the near portion located substantially below the lens center. As a result, there remains a possibility of error.
[0011]
b. In the prior art 1, the lens magnification SM is calculated with five basic evaluation parameters including “lens refractive index n” in addition to the above. However, it is considered that the size of the image is strongly influenced by the “angle between the line of sight and the lens surface”, as can be readily seen by tilting the lens with the power actually back and forth. Therefore, it is considered that this “angle between the line of sight and the lens surface” cannot be ignored particularly in the calculation of the magnification of the near portion located largely below the lens center. Therefore, the lens design of the prior art 1 has a possibility of error due to “calculating the magnification of the lens without considering the angle between the line of sight and the lens surface”.
[0012]
c. The “magnification” in the prior art 1 has no concept of direction other than the description of the application example to the astigmatic lens. For example, the “magnification between the vertical direction and the horizontal direction that occurs in the near portion located greatly below the lens center”. In the case of “the magnification is different”, there is a possibility of an error due to this.
[0013]
d. In order to accurately calculate the magnification for the near portion, the distance to the target, that is, the “object distance” must be added as a calculation factor. However, in the prior art 1, this “object distance” is not considered. The possibility of error due to this cannot be denied.
e. Since the influence of the prism action is not considered in the magnification calculation, there is a possibility of an error due to this.
In this way, the prior art has a possibility that it is not always sufficient from the viewpoint of more accurately calculating the “magnification”.
[0014]
The present invention has been made to solve such a problem, and by taking into consideration the influence of the “angle between the line of sight and the lens surface” and the “objective distance”, by correctly calculating the magnification of the image, the distance portion It is an object of the present invention to provide a double-sided aspherical progressive-power lens that reduces the difference in magnification of the image in the near portion and provides a good visual acuity correction with respect to the prescription value and a wide effective field of view with little distortion during wearing.
[0015]
Furthermore, it is possible to process only the eyeball side surface as a left-right asymmetric curved surface corresponding to the eye convergence in near vision after receiving an order by using a “right and left symmetrical semi-finished product” as the object side surface. An object of the present invention is to provide a double-sided aspherical progressive-power lens capable of reducing the cost.
[0016]
[Means for Solving the Problems]
As means for solving the above-mentioned problem, the first means is:
A double-sided aspherical progressive-power lens having a progressive-power action divided and distributed into a first refractive surface that is an object-side surface and a second refractive surface that is an eyeball-side surface,
In the first refractive surface, the horizontal surface power and the vertical surface power at the distance power measurement position F1 are DHf and DVf, respectively.
In the first refracting surface, when the horizontal surface power and the vertical surface power at the near power measurement position N1 are DHn and DVn, respectively,
DHf + DHn <DVf + DVn and DHn <DVn
Is satisfied, and the surface astigmatism components at F1 and N1 of the first refractive surface are canceled by the second refractive surface, and the first and second refractive surfaces are combined. Thus, the double-sided aspherical progressive addition lens is characterized in that it gives a distance power (Df) and an addition power (ADD) based on the prescription value.
The second means is
The double-sided aspherical progressive-power lens according to the first means is characterized by satisfying a relational expression of DVn-DVf> ADD / 2 and DHn-DHf <ADD / 2.
The third means is
The first refracting surface is symmetrical with respect to one meridian passing through the distance power measurement position F1, and the second refracting surface defines the distance power measurement position F2 of the second refracting surface. It is symmetrical with respect to a single meridian passing therethrough, and the arrangement of the near power measurement position N2 of the second refractive surface is inwardly aligned to the nose side by a predetermined distance. It is a double-sided aspherical progressive-power lens according to the first or second means, characterized in that it corresponds to the divergent action.
The fourth means is
The first refracting surface is a rotating surface with a meridian passing through the distance power measurement position F1 as a generating line, and the second refracting surface is a distance power measurement position of the second refracting surface. It is symmetrical with respect to one meridian passing through F2, and the arrangement of the near-field power measurement position N2 on the second refractive surface is inset to the nose side by a predetermined distance. The double-sided aspherical progressive-power lens according to any one of the first to third aspects, which corresponds to an eye convergence action in
The fifth means is
In the configuration in which the first and second refractive surfaces are combined to give the distance power (Df) and the addition power (ADD) based on the prescription value, the line of sight in the wearing state and the lens surface are orthogonal to each other. This is a double-sided aspherical progressive-power lens according to any one of the first to fourth aspects, characterized in that the occurrence of astigmatism and the change in power due to failure are reduced.
[0017]
The above-described means has been devised based on the following elucidation results. Hereinafter, description will be given with reference to the drawings. FIG. 1 is an explanatory diagram of various surface refractive powers at each position on the spectacle lens surface, FIG. 2 is an explanatory diagram of a positional relationship between an eyeball, a line of sight, and a lens, FIG. 3-1, FIG. 3-2 and FIG. FIGS. 4A, 4B, and 4C are explanatory diagrams regarding the magnification Mγ of the prism. The magnification when viewing with the difference between the plus lens and the minus lens and the near portion that is mainly the lower part of the lens. FIG. 5A is an explanatory view of the optical layout of the progressive addition lens, FIG. 5B is a front view of the progressive addition lens viewed from the object side surface, and FIG. 5B is an optical view of the progressive addition lens. FIG. 5C is an explanatory view of the optical layout of the progressive-power lens and an elevation view showing the cross section in the lateral direction, and FIG. It is explanatory drawing which shows the difference in the definition of "addition frequency". In these drawings, symbol F indicates a distance power measurement position, N indicates a near power measurement position, and Q indicates a prism power measurement position. In addition, the other symbols shown in FIG.
DVf: Surface power at F of longitudinal section curve through F
DVn: Surface power at N of the longitudinal section curve through N
DHf: Surface power at F of transverse cross section curve through F
DHn: Surface power at N of transverse cross section curve through N
Represents. Furthermore, when the refractive surface in the figure is the first refractive surface that is the object-side surface, the suffix 1 is attached to all symbols, and when the refractive surface is the second refractive surface that is the eyeball-side surface, all symbols Is identified by subscript 2.
[0018]
Symbols F1 and F2 indicate distance power measurement positions on the object side surface and the eyeball side surface, and similarly N1 and N2 indicate near power measurement positions on the object side surface and the eyeball side surface. Further, E is the eyeball, C is the center of rotation of the eyeball, S is the reference spherical surface centered on C, and Lf and Ln are the lines of sight passing through the distance power measurement position and the near power measurement position, respectively. Further, M is a curve called a main gazing line through which the line of sight passes when viewed from both front and below with both eyes. F1, N1, F2, N2, and N3 indicate portions to which different lens meter openings are applied according to the definition of “additional power”.
[0019]
First, it corresponds to the near-use part improved by “corresponding the parameter to the near-use part” which is the problem of the above-mentioned conventional technique (a) and “considering the objective distance” which is the problem of (d). The formula for calculating the magnification was obtained as follows. That is, when Mp is a power factor and Ms is a shape factor, an image magnification SM is
SM = Mp × Ms (1 ′)
It is represented by Here, the objective power to the target (the reciprocal of the objective distance expressed in m) is Px, the distance from the eyeball side surface to the eyeball in the near part of the lens is L, and the refractive power (nearly in the near part). When the inner vertex refractive power at the lens portion is Po, the thickness at the near portion of the lens is t, the refractive index of the lens is n, and the base curve (refractive power) of the object side surface at the near portion of the lens is Pb, The following relationship holds.
Mp = (1− (L + t) Px) / (1−L × Po) (2 ′)
Ms = 1 / (1−t × (Px + Pb) / n) (3 ′)
[0020]
In these equations, if each parameter is made to correspond to the distance portion and 0 corresponding to infinity is substituted for Px which is the power display of the objective distance, the equation of the prior art 1 is matched. That is, it can be considered that the mathematical formula used in the prior art 1 is a special formula for far vision that is an infinite objective distance. Now, (1 ′) is the same as the mathematical formula of the above-mentioned prior art 1, but since the objective distance for near vision is generally about 0.3 m to 0.4 m, the reciprocal Px is −2. It becomes a value of about 5-3.0. Therefore, (2 ′) increases Mp because the numerator increases, and (3 ′) decreases Ms because the denominator increases. That is, it can be seen that the influence of the shape factor Ms in near vision is less than the calculation of the conventional technique 1. For example, when Pb = −Px, that is, when the base curve (refractive power) of the surface on the object side of the lens is a value of about +2.5 to +3.0, Ms = 1, and the shape factor in near vision is the image factor. It turns out that it becomes completely unrelated to the magnification.
[0021]
Now, as described above, each parameter was made to correspond to the near-use part, and a calculation formula for the magnification in consideration of the “object distance” could be obtained, but in order to calculate the magnification in actual near vision, Furthermore, the “angle between the line of sight and the lens surface”, which is the problem of the prior art 1 (b), must be considered. What is important here is that “the angle between the line of sight and the lens surface” has directionality. In other words, taking into account the “angle between the line of sight and the lens surface” is nothing other than taking into account the directionality of the “magnification of image”, which is the problem of the prior art 1 (c).
[0022]
From this point of view, when reexamining the first calculation formulas (1 ′) to (3 ′) described above, the inner vertex power Po in the near portion and the near power are calculated as a calculation factor influenced by the “angle between the line of sight and the lens surface”. There is a base curve (refractive power) Pb of the object side surface in the use portion. Here, the angle between the line of sight in near vision and the optical axis of the near vision area is α, and the angle between the line of sight in near vision and the normal of the object side surface in the near vision area is β. Using Martin's approximation,
Longitudinal inner power in the near direction:
Pov = Po × (1 + Sin2α × 4/3)
Lateral inner vertex power in the near part:
Poh = Po × (1 + Sin2α × 1/3)
Longitudinal cross section refractive power of object side surface at near part:
Pbv = Pb × (1 + Sin2β × 4/3)
Cross-sectional refractive power of the object-side surface at the near portion:
Pbh = Pb × (1 + Sin2β × 1/3)
It becomes. Thus, as long as the angles α and β, and Po and Pb are not zero, the refractive power, power factor, shape factor, and the like are different values in the vertical and horizontal directions. As a result, there is a difference in the magnification between the vertical and horizontal directions. It will come.
[0023]
Here, an approximate expression is used to briefly explain that “the refractive power changes according to the direction of the line of sight”. However, in an actual optical design, these values can be obtained by strict ray tracing calculation. desirable. As non-limiting examples of these calculation methods, for example, the optical path along the line of sight is calculated using Snell's law, and the distances from the object side refractive surface to the object point are calculated, and then By using the first basic form, the second basic form, Weingarten's formula, etc. in differential geometry along the optical path, the influence of refraction on the optical path on the object side refractive surface and the eyeball side refractive surface can be taken into consideration. The refractive power can be calculated. Since these formulas and calculation methods have been known for a very long time, they are described in, for example, the publicly known document “differential geometry” (published by Kentaro Yano (published by Asakura Shoten Co., Ltd., first edition, 1949)), and the description thereof will be omitted.
[0024]
By performing the exact ray tracing calculation in this way, the four calculation factors L, Po, t, and Pb, which are the problems of the above (a) to (d), are taken into consideration. Strict magnification calculation can be performed in all gaze directions as well as the near-use part located greatly below. In this way,
Longitudinal inner vertex power in the near portion: Pov
Lateral inner vertex power in the near portion: Poh
Longitudinal section refractive power of object side surface at near portion: Pbv
Cross-sectional refractive power of object side surface at near portion: Pbh
Is obtained with higher accuracy than using Martin's approximate expression.
[0025]
As described above, since “refractive power changes according to the direction of the line of sight”, it can be easily understood that all the above-described image magnification calculations should correspond to the difference in the direction of the line of sight. Here, when Mp is a power factor, Ms is a shape factor, and v is added to the vertical direction and h is added to the horizontal direction, the above-described (1 ') to (3') are described with respect to the image magnification SM. Can be rewritten as follows.
SMv = Mpv × Msv (1v ′)
SMh = Mph × Msh (1h ′)
Mpv = (1− (L + t) Px) / (1−L × Pov) (2v ′)
Mph = (1− (L + t) Px) / (1−L × Poh) (2h ′)
Msv = 1 / (1−t × (Px + Pbv) / n) (3v ′)
Msh = 1 / (1-t × (Px + Pbh) / n) (3h ′)
[0026]
As described above, the problems (a) to (d) of the prior art 1 can be addressed. Finally, the “influence of the prism action”, which is the above-mentioned problem (e) in calculating the magnification in actual near vision, will be described. The prism itself does not have a refracting power like a lens, but the magnification Mγ of the prism changes depending on the incident angle and exit angle of the light beam to the prism. Here, as shown on the left side of FIG. 3A and FIG. 4A, the angular magnification γ in the case where a light beam incident from a vacuum into a medium having a refractive index n is refracted on the medium surface will be considered. When the incident angle is i and the refraction angle is r, n = Sin i / Sin r according to the well-known Snell's law. The angular magnification γ due to refraction is expressed by γ = Cos i / Cos r. Since n ≧ 1, in general, i ≧ r and γ ≦ 1. Here, γ has a maximum value of 1 when i = r = 0, that is, in the case of normal incidence. Further, when the refraction angle r is n = 1 / Sin r, γ becomes the theoretical minimum value γ = 0. At this time, i = π / 2, and r is equal to the critical angle of total reflection when light rays are emitted from the medium.
[0027]
On the other hand, as shown on the right side of FIGS. 3-1 and 4-1, the angular magnification γ ′ when a light ray is emitted from a medium having a refractive index n into a vacuum is completely opposite to the above. That is, when the incident angle is i ′ and the refraction angle is r ′ when the light beam is refracted from the inside of the medium and is emitted into the vacuum, Snell's law is 1 / n = Sin i ′ / Sin r ′. The angular magnification is represented by γ ′ = Cos i ′ / Cos r ′. Since n ≧ 1, in general, r ′ ≧ i ′ and γ ′ ≧ 1. Here, γ ′ has a minimum value of 1 when i ′ = r ′ = 0, that is, in the case of normal incidence. When the incident angle i ′ is n = 1 / Sin i ′, γ ′ is the theoretical maximum value γ ′ = ∞. At this time, r ′ = π / 2, and i ′ is equal to the critical angle of total reflection when light rays are emitted from the medium.
[0028]
As shown in FIGS. 3-3 and 4-3, a case where a light beam incident on the object side surface of one spectacle lens passes through the inside of the lens, is emitted from the eyeball side surface, and reaches the eyeball (hereinafter described). For the sake of simplicity, the refractive index of air is assumed to be close to 1 as in vacuum). The refractive index of the spectacle lens is n, the incident angle of the light incident on the object side surface is i, the refraction angle is r, the incident angle of the light reaching the eyeball side surface from the inside of the lens is i ′, and the refraction angle of the emitted light. Is r ′, the angular magnification Mγ transmitted through the two surfaces of the spectacle lens is represented by the product of the above-mentioned two types of angular magnifications.
Mγ = γ × γ ′ = (Cos i × Cos i ′) / (Cos r × Cos r ′)
It becomes. This is independent of the refractive power of the lens surface and is known as the magnification of the prism.
[0029]
Here, as shown in FIGS. 3-1 and 4-1, when i = r ′ and r = i ′,
Mγ = γ × γ ′ = 1
Thus, there is no change in the magnification of the image viewed through the prism. However, as shown in FIG. 3-2, when light rays are incident on the object side surface of the spectacle lens perpendicularly,
Mγ = γ ′ = Cos i ′ / Cos r ′ ≧ 1
On the contrary, as shown in FIG. 4B, when a light beam is emitted vertically from the eyeball side surface of the spectacle lens,
Mγ = γ = Cos i / Cos r ≦ 1
It becomes.
[0030]
Here, what is important is that the magnification Mγ of these prisms has directionality. That is, when considering the distribution of the prism in the progressive power lens, it is natural that it varies depending on the power and the prescription prism value, but in general there are few prisms in far vision near the center of the lens, and in near vision located below the lens. The vertical prism is large. Therefore, it can be said that the magnification Mγ of the prism has a great influence on the longitudinal direction of near vision.
[0031]
Considering that not only progressive-power lenses but also spectacle lenses generally have a meniscus shape with a convex surface on the object side and a concave surface on the eyeball side, and the line of sight in near vision is downward. As shown in FIG. 3C, the near vision of the progressive addition lens in which the near portion has a positive refractive power has Mγ ≧ 1 than FIG. 3A in which Mγ = 1. It can be said that at least Mγ> 1. Similarly, as shown in FIG. 4C, the near vision of the progressive addition lens in which the near portion has a negative refractive power has Mγ ≦ 1 as compared to FIG. 4A where Mγ = 1. It is close to the shape of −2, and it can be said that at least Mγ <1. Accordingly, Mγ> 1 in the near vision of the progressive addition lens in which the near portion has a positive refractive power, and Mγ <1 in the near vision of the progressive addition lens in which the near portion has a negative refractive power. Become.
[0032]
The lens magnification SM in the prior art 1 was only known as the product of the power factor Mp and the shape factor Ms as described above, but in the present invention, the magnification Mγ of the prism is further multiplied to obtain the correct value. The lens magnification is to be obtained.
[0033]
The magnification Mγ by the prism is referred to as “prism factor” in comparison with Mp and Ms, and is expressed by subscripting v for the vertical direction and h for the horizontal direction. The expressions 1v ′) and (1h ′) can be rewritten as follows.
SMv = Mpv × Msv × Mγv (1v ″)
SMh = Mph × Msh × Mγh (1h ″)
These Mγv and Mγh can be obtained in the above-described strict ray tracing calculation process. Thereby, the problem of the influence by the prism action in the above-mentioned calculation of the magnification of the glasses could be solved.
[0034]
Now, in a normal convex progressive addition lens, the surface refractive power of the “progressive surface” on the object side surface is the distance portion <the near portion. On the other hand, in the progressive power lens of the prior art 1, the surface refractive power of the “progressive surface” on the object side surface is changed to the distance portion = the near portion, thereby changing the ratio of the shape factor in the distance. The objective is to improve the distortion and shaking of the progressive power lens image by reducing the magnification difference between the near and near images. However, in the consideration in the present invention, by reducing the surface refractive power difference in the perspective of the “progressive surface” on the object side surface, there is an advantage that the difference in magnification of the perspective image in the lateral direction is reduced, but in the vertical direction It has been found that there are several problems in reducing the surface refractive power difference.
[0035]
The first problem is the influence of the vertical prism factor Mγv. As described above, the longitudinal prism factor Mγv is Mγv <1 when it has a negative refractive power and Mγv> 1 when it has a positive refractive power. It is strengthened by reducing the force difference, and moves away from Mγv = 1, which is the magnification of the naked eye, when the power of the near portion is positive or negative. However, the prism factor Mγh in the horizontal direction has no such influence and Mγh = 1. As a result, there is a vertical and horizontal difference in the magnification of the image particularly from the near portion to the lower portion, and what is supposed to be square in the original is in the positive frequency and in the vertical direction, and in the negative frequency, it is in the horizontal direction. Will occur.
[0036]
The second problem is a problem that occurs only when the longitudinal direction of the near portion has a positive refractive power. By reducing the surface refractive power difference in the vertical direction, the angle between the line of sight and the lens surface in near vision becomes further oblique, the vertical power factor Mpv increases, and the vertical problem was the first problem. The increase in the prism factor Mγv in the direction and the double effect increase the vertical magnification SMv, which causes a disadvantage that the magnification difference between the near and near images increases.
[0037]
That is, it has been found that reducing the surface refractive power difference in the near and far sides of the progressive surface, which is the object side surface, has an advantage in the lateral direction, but is rather worse in the longitudinal direction. Therefore, in the conventional convex progressive-power lens, the above-mentioned problem is avoided by dividing the progressive surface, which is the object side surface, into a vertical direction and a horizontal direction, and reducing the difference in near-surface surface refractive power only in the horizontal direction. It can be done.
[0038]
As described above, the greatest feature of the present invention is that the progressive action of the progressive addition lens is divided into the vertical direction and the horizontal direction of the lens, and the optimal two sides of the front and back are divided in each direction. The ratio is determined and one double-sided aspherical progressive-power lens is formed. For example, as an extreme example, it is also within the scope of the present invention that all of the progressive action in the vertical direction is given on the object side surface and all the progressive action in the horizontal direction is given on the eyeball side surface. In this case, since both the front and back surfaces of the lens do not function as normal progressive surfaces only on one side, the addition power as the progressive surface cannot be specified. That is, the front and back surfaces are progressive lenses that are not progressive surfaces. On the other hand, although the above-mentioned various prior arts have different sharing ratios, all of them assign a "value" of the required addition power to the front and back surfaces and assume a substantially progressive surface that gives each addition power. Above, a composite surface with an astigmatism surface or the like is formed as necessary. In other words, the present invention is decisively different from the above-described prior art in that a double-sided aspherical progressive-power lens using aspherical surfaces having a progressive action different depending on directions is used.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a double-sided aspherical progressive refraction lens according to an embodiment of the present invention will be described. In the following description, first, the design method used to obtain the double-sided aspherical progressive-refraction lens according to the embodiment will be described, and then the double-sided aspherical progressive-refraction lens according to the embodiment will be described.
[0040]
(Lens design procedure)
A schematic procedure of the optical design method of the double-sided aspherical progressive-refraction lens according to the embodiment is as follows.
(1) Input information setting
(2) Double-sided design as a convex progressive-power lens
(3) Conversion to the convex shape of the present invention and back surface correction accompanying it
(4) Backside correction due to transmission design, listing rule design, etc.
Hereinafter, each procedure will be described in detail by breaking it down into smaller steps.
[0041]
(1) Input information setting
Input information is roughly classified into the following two types (omitted except for optical design).
(1) -1: Item specific information
This is data specific to the lens item. Refractive index Ne of material, minimum center thickness CTmin, minimum edge thickness ETmin, progressive surface design parameters, etc.
(1) -2: Wearer-specific information
Distance power (spherical power S, astigmatism power C, astigmatism axis AX, prism power P, prism base direction PAX, etc.), addition power ADD, frame shape data (preferably 3D shape data), frame wear data (forward tilt angle, Tilt angle, etc.), distance between vertices, layout data (distance PD, near CD, eye point position, etc.), and other data related to the eyeball. The progressive surface design parameters such as the progressive zone length designated by the wearer, the addition power measurement method, and the near-site inset amount are classified as wearer-specific information.
[0042]
(2) Double-sided design as a convex progressive-power lens
First, a conventional convex progressive addition lens is designed by dividing it into a convex surface and a concave surface.
(2) -1: Convex shape (convex progressive surface) design
In order to realize the addition power ADD and progressive band length given as input information, a conventional convex progressive surface shape is designed according to the progressive surface design parameter as input information. In the design in this step, various conventional known techniques can be used, and the design technique of the present invention is not required.
[0043]
As a specific example of this method, for example, there is a method of setting a “principal meridian” corresponding to the backbone when the lens surface is first configured. This “main meridian” will ultimately be the “main gaze” that is the intersection of the line of sight and the lens surface when the eyeglass wearer sees both eyes from the front upper (far) to the lower (near). desirable. However, it is not always necessary to perform the alignment of the near region corresponding to the eye convergence action in the near vision by the alignment of the “main gaze” as described later. Accordingly, the “main line of sight” here is defined as a single meridian (main meridian) in the vertical direction that passes through the center of the lens and divides the lens surface into left and right. Since there are two front and back lenses, there are also two “main meridians”. This “principal meridian” looks straight when viewed perpendicular to the lens surface, but when the lens surface is a curved surface, it is generally a curve in a three-dimensional space.
[0044]
Next, an appropriate refractive power distribution along the “main meridian” is set based on information such as a predetermined addition power and the length of the progressive zone. This refractive power distribution can be divided into two front and back surfaces in consideration of the influence of the lens thickness and the angle between the line of sight and the refracting surface. Since the surface shape is designed, it is assumed that all the progressive actions are on the first refractive surface which is the object side surface. Therefore, for example, when the surface refractive power of the lens surface (first refractive surface that is the object-side surface) is D1, and the surface refractive power of the rear surface of the lens (second refractive surface that is the eyeball-side surface) is D2. If the transmission power obtained is D, it can be approximately obtained as D≈D1−D2. However, the combination of D1 and D2 is preferably a meniscus shape in which the object-side surface is convex and the eyeball-side surface is concave. Note that D2 is a positive value. Normally, the rear surface of the lens is concave, and the surface refractive power has a negative value. However, in this specification, for simplicity of explanation, a positive value is used, and the transmission refractive power is calculated by subtracting from D1. I will do it.
[0045]
The relational expression between the surface refractive power and the surface shape is generally defined by the following formula.
Dn = (N-1) / R
Here, Dn is the surface refractive power (unit: diopter) of the nth surface, N is the refractive index of the lens material, and R is the radius of curvature (unit: m). Therefore, the method of converting the surface refractive power distribution into the curvature distribution is a modification of the above relational expression.
1 / R = Dn / (N-1)
Is used. By obtaining the distribution of curvature, the geometric shape of the “main meridian” is uniquely determined, and the “main meridian” corresponding to the backbone when the lens surface is constructed is set.
[0046]
Next, what is needed is a “horizontal cross-sectional curve group” that corresponds to the rib when the lens surface is constructed. The angle at which these “horizontal cross section curve group” and “main meridian” intersect is not necessarily a right angle, but for the sake of simplicity, each “horizontal cross section curve” is “ It shall intersect at right angles on the “main meridian”. Furthermore, the “lateral surface power” of the “horizontal section curve group” at the intersection with the “main meridian” does not necessarily have to be equal to the “vertical surface power” along the “main meridian”. Actually, as described in the claims, the present invention is based on the difference in surface refractive power between the vertical direction and the horizontal direction. However, since the conventional convex progressive surface shape is designed in the design in this step, it is assumed that the surface refractive powers in the vertical direction and the horizontal direction at these intersections are equal.
[0047]
Now, all “horizontal cross-sectional curves” can be simple circular curves having surface refractive powers at these intersections, but applications incorporating various conventional techniques are also possible. As a prior art example regarding the surface refractive power distribution along the “horizontal cross section curve”, for example, there is a technique disclosed in Japanese Patent Publication No. 49-3595. This sets a single “circular cross-sectional curve” in the vicinity of the center of the lens, and the cross-sectional curve located above it has a surface refractive power distribution that increases from the center to the side, The cross-sectional curve located at is characterized by having a surface refractive power distribution that decreases from the center to the side. In this way, the “main meridian” and the “horizontal cross-sectional curve group” arranged innumerably thereon constitute a lens surface as if it were a spine and a rib, and the refractive surface is determined.
[0048]
(2) -2: Concave surface (spherical or astigmatic surface) design
In order to realize the distance dioptric power given as input information, a concave shape is designed. If the distance power has an astigmatism power, an astigmatism surface is obtained. At this time, the central thickness CT suitable for the power and the inclination angle between the convex and concave surfaces are also designed at the same time, and the shape as a lens is determined. The design in this step can also use various conventional techniques, and does not require the design technique of the present invention.
[0049]
(3) Conversion to the convex shape of the present invention and back surface correction accompanying it
According to the distance dioptric power or addition power ADD given as input information, the conventional convex progressive addition lens is changed to the shape of the lens of the present invention.
(3) -1: Convex shape (present invention) design
According to the distance power or addition power ADD given as input information, the conventional convex progressive surface is converted to the convex shape of the present invention. That is, on the surface of the above-described conventional convex progressive lens (the first refractive surface that is the object-side surface), the lateral surface refractive power at the distance power measurement position F1 is DHf, and the vertical surface refractive power is When DVf is the near surface power measurement position N1, the horizontal surface power is DHn, and the vertical surface power is DVn.
DHf + DHn <DVf + DVn and DHn <DVn
Or satisfy the relational expression
DVn-DVf> ADD / 2 and DHn-DHf <ADD / 2
A progressive power surface that satisfies the following relational expression. At this time, it is desirable to convert the average surface refractive power of the entire convex surface into the convex shape of the present invention without changing it. For example, it is conceivable to maintain the total average value of the vertical and horizontal surface refractive powers of the distance portion and the near portion. However, it is desirable that the surface on the object side is convex and the meniscus shape in which the eyeball side surface is concave is maintained.
[0050]
(3) -2: Concave surface shape design (invention)
In (3) -1, the amount of deformation when the conventional convex progressive surface is converted to the convex shape of the present invention is added to the concave shape designed in (2) -2. That is, the deformation amount of the lens surface (first refractive surface that is the object-side surface) applied in the process (3) -1 is transferred to the rear surface (second refractive surface that is the eyeball-side surface) side of the lens. Add the same amount. It should be noted that this deformation is similar to “bending” in which the lens itself is bent, but is not a uniform deformation over the entire surface, but a surface that satisfies the relational expression described in (3) -1. These back surface corrections are within the scope of the present invention, but are only linear approximation corrections, and it is desirable to add the back surface correction of (4).
[0051]
(4) Backside correction due to transmission design, listing rule support design, near-centered support design, etc.
In order to realize the optical function imposed as input information in a situation where the wearer actually wears it, it is desirable to further perform back surface correction on the lens of the present invention obtained in (3).
(4) -1: Concave surface shape design for transmission design (present invention)
The transmission design is a design method for obtaining the original optical function in a situation where the wearer actually wears the lens, and mainly the astigmatism caused by the fact that the line of sight and the lens surface cannot be orthogonal to each other. This is a design method for adding a “correcting action” for removing or reducing the occurrence and the change in frequency.
[0052]
Specifically, as described above, the difference from the target original optical performance is grasped by strict ray tracing calculation according to the direction of the line of sight, and surface correction is performed to cancel the difference. By repeating this, the difference can be minimized and an optimal solution can be obtained. In general, it is extremely difficult and often impossible to directly calculate a lens shape having a target optical performance. This is because the “lens shape having arbitrarily set optical performance” does not always exist. However, conversely, it is relatively easy to obtain “optical performance of an arbitrarily set lens shape”. Therefore, the first approximate surface is temporarily calculated by an arbitrary method, the design parameters are finely adjusted according to the evaluation result of the optical performance of the lens shape using the approximate surface, and the lens shape is sequentially changed. Thus, it is possible to return to the evaluation step and repeat the reevaluation and readjustment to approach the target optical performance. This method is an example of a widely known method called “optimization”.
[0053]
(4) -2: Concave surface shape design (invention of the present application) for listing law design
It is known that the three-dimensional rotational movement of the eyeball when we look around is based on a rule called “listing rule”, but if the prescription power has an astigmatic power, the astigmatic axis of the spectacle lens Even if it is adjusted to “the astigmatic axis of the eyeball in front view”, the astigmatic axes may not coincide with each other when peripheral vision is performed. As described above, the “correcting action” for removing or reducing astigmatism and the change in power caused by the astigmatic axis directions of the lens and the eye in peripheral vision are not corrected. It can be added to the curved surface of the surface having the correcting action.
[0054]
Specifically, in the same manner as the “optimization” method used in (4) -1, it is possible to grasp the difference from the intended original optical performance by strict ray tracing calculation according to the direction of the line of sight. Perform surface correction to cancel the difference. By repeating this, the difference can be minimized and an optimal solution can be obtained.
[0055]
(4) -3: Concave surface (invention of the present invention) design for the near-centered design
Further, although the present invention has a surface configuration of double-sided aspherical surfaces, it is not always necessary to process both sides for the first time after receiving an order in order to obtain the effects of the present invention. For example, a “semi-finished product” of the object side surface that meets the object of the present invention is prepared in advance, and after the order is received, the object side surface suitable for the purpose such as the prescription frequency or the above custom-made (individual design) is prepared. It is also advantageous in terms of cost and processing speed to select “semi-finished product” and finish only the eyeball side surface after receiving an order.
[0056]
As a specific example of this method, for example, the object side surface is prepared in advance as a “semi-finished product” that is symmetrical in the convex shape (invention of the present invention) design of {circle around (3)} − 1 described above. After the personal information such as the objective distance is input, the near-side portion corresponding to the personal information can be aligned by designing the eyeball side surface as a right and left asymmetric curved surface.
[0057]
Hereinafter, embodiments of a double-sided aspherical progressive refraction lens designed by the above-described design method will be described with reference to the drawings. FIG. 7 shows “surface refractive power” and “strict magnification calculation results for a specific line-of-sight direction” of the conventional techniques A, B, and C corresponding to Examples 1, 4, 5, and 6, and Table 1-1. FIG. 8 is a table collectively shown in Table 1-2, and FIG. 8 shows “surface refractive power” and “strict magnification with respect to a specific line-of-sight direction” in the conventional techniques A, B, and C corresponding to Examples 2 and 7 and respective frequencies. FIG. 9 is a table summarizing the “calculation results” in Tables 2-1 and 2-2. FIG. 9 is the “surface refractive power” and “specific line of sight” of the prior art A, B, and C corresponding to Example 3 and the frequency. FIG. 10 is a graph in which the strict magnification calculation results with respect to the direction are collectively shown in Tables 3-1 and 3-2. FIGS. 10A and 10B are graphs 1-1 and 1-2 showing the surface refractive power distributions of Example 1 and Example 2. , 2-1 and 2-2 are diagrams, FIG. 11 is a diagram illustrating the graphs 3-1 and 3-2 representing the surface refractive power distribution of Example 3, and FIG. FIGS. 13A and 13B show graphs 4-1, 4-2, 5-1, 5-2, 6-1, and 6-2 representing surface refractive power distributions of FIG. FIGS. 14A and 14B are graphs showing graphs 7-1 and 7-2, and FIGS. 14A and 14B are graphs A-1, A-2, B-1, B-2, and C-1 showing surface refractive power distributions of the related art examples A, B, and C, respectively. , C-2.
[0058]
FIG. 15 shows a result obtained by performing a strict magnification calculation on the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. FIG. 16 is a graph showing a graph 1-3-3-Msv. FIG. 16 shows a strict magnification distribution when the lenses of the three conventional examples A, B, and C corresponding to Example 1 and the frequency thereof are viewed along the main line of sight. FIG. 17 shows a graph 1-3-3-Msh representing the result obtained by performing magnification calculation. FIG. 17 shows the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. FIG. 18 is a diagram showing a graph 1-3-3-Mpv showing the result of strict magnification calculation of the magnification distribution when viewed, FIG. 18 shows Example 1 and three conventional examples A and B corresponding to the frequency , C obtained by strict magnification calculation for the magnification distribution when the lens of C is viewed along the main line of sight. FIG. 19 shows a magnification distribution when the lenses of the conventional example A, B, and C corresponding to Example 1 and the frequency thereof are viewed along the main gazing line. FIG. 20 shows a graph 1-3-3-Mγv showing the result obtained by performing strict magnification calculation. FIG. 20 shows the main gaze of the lenses of Example 1 and three conventional examples A, B, and C corresponding to the frequency. FIG. 21 is a diagram showing a graph 1-3-3-Mγh showing a result obtained by performing strict magnification calculation on the magnification distribution when viewed along the line, and FIG. 21 shows Example 1 and three types of conventional examples A corresponding to the frequency. , B, and C show a graph 1-3-3-SMv showing the result of performing a strict magnification calculation of the magnification distribution when viewing the lens along the main gazing line. FIG. Magnification when viewing the lenses of three conventional examples A, B, and C corresponding to the frequency along the main line of sight It is a diagram showing a graph 1-3-SMh representing results of cloth obtained by performing accurate magnification calculations.
[0059]
FIG. 23 shows a result obtained by carrying out a strict magnification calculation when observing the magnification distribution of Example 2 and the three types of conventional lenses A, B, and C corresponding to the power along the main line of sight. FIG. 24 shows a graph 2-3-3-Msv. FIG. 24 shows the strict magnification distribution when the lenses of the conventional example A, B, and C corresponding to Example 2 and the frequency thereof are viewed along the main line of sight. FIG. 25 shows a graph 2-3-3-Msh representing the result obtained by performing the magnification calculation, and FIG. 25 shows the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. FIG. 26 is a diagram showing a graph 2-3-3-Mpv showing the result of strict magnification calculation of the magnification distribution when viewed, FIG. 26 shows Example 2 and three types of conventional examples A and B corresponding to the frequency , C obtained by strict magnification calculation for the magnification distribution when the lens of C is viewed along the main line of sight. FIG. 27 is a graph showing the graph 2-3-3-Mph, and FIG. 27 shows the magnification distribution when the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the frequency are viewed along the main line of sight. FIG. 28 shows a graph 2-3-3-Mγv showing the result obtained by performing a strict magnification calculation. FIG. 28 shows the main gaze of the lenses of Example 2 and three conventional examples A, B, and C corresponding to the frequency. FIG. 29 is a diagram showing a graph 2-3-3-Mγh showing a result obtained by performing strict magnification calculation on the magnification distribution when viewed along FIG. 29, and FIG. 29 shows Example 2 and three types of conventional examples A corresponding to the frequency , B, and C show a graph 2-3-3-SMv showing the result of performing a strict magnification calculation of the magnification distribution when viewing the lens along the main gazing line. FIG. Magnification when viewing the lenses of three conventional examples A, B, and C corresponding to the frequency along the main line of sight It is a diagram showing a graph 2-3-SMh representing results of cloth obtained by performing accurate magnification calculations.
[0060]
FIG. 31 shows a result obtained by performing a strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. FIG. 32 is a graph showing the graph 3-3-Msv. FIG. 32 shows a strict magnification distribution when the lenses of the three conventional examples A, B, and C corresponding to Example 3 and the frequency thereof are viewed along the main line of sight. FIG. 33 shows a graph 3-3-Msh representing the result obtained by performing the magnification calculation, and FIG. 33 shows the lenses of Example 3 and three conventional examples A, B, and C corresponding to the frequency along the main line of sight. FIG. 34 shows a graph 3-3-Mpv showing the result of strict magnification calculation of the magnification distribution when viewed, FIG. 34 shows Example 3 and three conventional examples A and B corresponding to the frequency , C obtained by strict magnification calculation for the magnification distribution when the lens of C is viewed along the main line of sight. FIG. 35 shows a graph 3-3-Mph representing the magnification distribution when the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the frequency are viewed along the main line of sight. FIG. 36 shows a graph 3-3-Mγv showing a result obtained by performing strict magnification calculation, and FIG. 36 shows the main gaze of the lenses of Example 3 and three conventional examples A, B, and C corresponding to the frequency. FIG. 37 is a diagram showing a graph 3-3-Mγh showing a result obtained by performing a strict magnification calculation of the magnification distribution when viewed along FIG. 37, and FIG. 37 shows Example 3 and three types of conventional examples A corresponding to the frequency , B, and C show a graph 3-3-SMv showing the result of performing a strict magnification calculation of the magnification distribution when viewing the lens along the main gazing line. FIG. Magnification when viewing the lenses of three conventional examples A, B, and C corresponding to the frequency along the main line of sight It is a diagram showing a graph 3-3-SMh representing results of cloth obtained by performing accurate magnification calculations.
[0061]
Example 1
Table 1-1 in FIG. 7 is a list relating to the surface refractive power of Example 1 according to the present invention. The frequency in Example 1 corresponds to S0.00 Add3.00, and three types of prior art examples of the same frequency are shown for comparison. The conventional example A is a “convex progressive-power lens” in which the object-side surface is a progressive surface, and the conventional example B is “double-sided progressive-power lens in which both the object-side surface and the eyeball-side surface are progressive surfaces. The prior art example C corresponds to a “concave progressive addition lens” whose surface on the eyeball side is a progressive surface. Moreover, the meaning of the item used by Table 1-1 is as follows.
DVf1: Longitudinal surface refractive power at the distance power measurement position F1 on the object side surface
DHf1: Surface refractive power in the lateral direction at the distance power measurement position F1 on the object side surface
DVn1: Longitudinal surface refractive power at near power measurement position N1 on the object side surface
DHn1: Surface refractive power in the lateral direction at the near power measurement position N1 on the object side surface
DVf2: Surface refractive power in the vertical direction at the distance power measurement position F2 on the eyeball side surface
DHf2: Surface refractive power in the lateral direction at the distance power measurement position F2 on the eyeball side surface
DVn2: Surface refractive power in the vertical direction at the near power measurement position N2 on the eyeball side surface
DHn2: Surface refractive power in the lateral direction at the near power measurement position N2 on the eyeball side surface
[0062]
Graphs 1-1 and 1-2 in FIG. 10 are graphs showing the surface refractive power distribution along the main line of sight of Example 1, and the horizontal axis is directed to the right side above the lens, the left side below the lens, The vertical axis represents the surface refractive power. Here, the graph 1-1 corresponds to the object side surface, and the graph 1-2 corresponds to the eyeball side surface. The solid line graph represents the vertical surface power distribution along the main gaze line, and the dotted line graph represents the horizontal surface power distribution along the main gaze line. These are graphs that explain the basic differences in surface composition, and are omitted for cases such as making aspherical surfaces to remove astigmatism in the periphery and adding astigmatism components to support astigmatism power. is there.
[0063]
Furthermore, as a graph showing the surface refractive power distribution along the main line of sight of three types of prior art examples of the same power listed in Table 1-1 for comparison, graphs A-1 and 2 and graph B in FIG. -1 and 2 and graphs C-1 and 2 are shown together. The meanings of terms in these graphs are as follows.
F1: Distance power measurement position on the object side surface,
F2: Distance-use power measurement position on the eyeball side surface
N1: Near-use power measurement position on the object side surface,
N2: Near-field power measurement position on the eyeball side surface
CV1: graph representing the surface refractive power distribution in the vertical direction along the main line of sight on the object side surface (shown as a solid line)
CH1: A graph representing the surface refractive power distribution in the lateral direction along the main line of sight on the object side surface (indicated by a dotted line)
CV2: graph representing the surface refractive power distribution in the vertical direction along the main line of sight on the eyeball side surface (shown as a solid line)
CH2: A graph representing the surface refractive power distribution in the lateral direction along the main line of sight on the eyeball side surface (indicated by a dotted line)
[0064]
The surface refractive powers at F1, N1, F2, and N2 in these graphs correspond to those in Table 1-1, and the meanings of terms such as DVf1 to DHn2 are also the same as those in Table 1-1. It is. In addition, the one-dot chain line in the horizontal direction in the center of these graphs indicates the average surface refractive power (total average value of the vertical and horizontal surface refractive powers at F1 and N1) on the object side surface. The average surface refractive power of the object side surface in Example 1 and the three types of prior art examples according to the present invention was unified to 5.50 diopters for fairness in comparison.
[0065]
Next, eight types of graphs beginning with graph 1-3 shown in FIGS. 15 to 22 show the magnification distribution when the lens of Example 1 according to the present invention is viewed along the main line of sight. FIG. 6 is a graph showing results obtained by performing various magnification calculations, in which the horizontal axis faces and the right side is above the lens, the left side is below the lens, and the vertical axis is the magnification. In the figure, the dark solid line is Example 1, the thin chain line is Conventional Example A, the dark chain line is Conventional Example B, and the thin solid line is Conventional Example C. This kind of graph below is the same. For the sake of fairness, the horizontal axis used eyeball rotation angle to enable comparison for each line of sight, and the scale of the vertical axis of each graph was adjusted. The meaning of the reference signs after the graph 1-3 is
Msv: vertical shape factor,
Msh: Shape factor in the horizontal direction
Mpv: Power factor in the vertical direction
Mph: Power factor in the horizontal direction
Mγv: Prism factor in the vertical direction
Mγh: Prism factor in the horizontal direction
SMv: vertical magnification,
SMh: Horizontal magnification
As described above, the vertical magnification SMv and the horizontal magnification SMh are
SMv = Msv × Mpv × Mγv
SMh = Msh × Mph × Mγh
There is a relationship.
[0066]
In addition, both Example 1 and the three types of prior art examples have a refractive index n = 1.699, a center thickness t = 3.0 mm, a geometric center GC, and a specification without a prism. Regarding the objective power (reciprocal of objective distance), the objective power Px at F1 and F2 is 0.00 diopter (infinitely far), the objective power Px at N1 and N2 is 2.50 diopter (40 cm), and objectives at other positions are used. The power was given by multiplying the ratio of the additional refractive power along the main line of sight by 2.50 diopters. Further, the distance L from the rear vertex of the lens to the apex of the cornea was set to 15.0 mm, and the distance CR from the apex of the cornea to the center of eyeball rotation was set to 13.0 mm. As for the eyeball rotation angle θ, the eyeball rotation center point C is placed on a normal line passing through the geometric center GC of the object side lens surface, the rotation angle when the normal line and the line of sight coincide with each other is 0 degree, and the upper direction is (+) downward Is indicated by (−). After that, the eyeball rotation angle θ for F1 and F2 is set to +30.0 degrees, and the eyeball rotation angle θ for N1 and N2 is unified to 15.0 degrees, so that the progressive action and the distribution of the surface refractive power can be reversed. Consideration was given so that comparisons could be made under the same conditions, regardless of the side.
[0067]
Table 1-2 in FIG. 7 is a list of strict magnification calculation results for a specific line-of-sight direction for Example 1 according to the present invention and three types of conventional technology prepared for comparison. Graph 1-3-3-SMv (total magnification in the vertical direction) and Graph 1-3-SMh (total magnification in the horizontal direction) in FIG. As described above, since the magnification values are different in the vertical direction and the horizontal direction, both magnifications are calculated. Here, the meanings represented by the symbols in Table 1-2 are as follows.
SMvf: Longitudinal magnification on line of sight passing through distance measurement point
SMvn: Longitudinal magnification on the line of sight passing through the near measurement point
SMvfn: longitudinal magnification difference (SMvn−SMvf)
SMhf: Lateral magnification on the line of sight passing through the distance measurement point
SMhn: Lateral magnification on the line of sight passing through the near measurement point
SMhfn: Lateral magnification difference (SMhn-SMhf)
[0068]
Now, looking at SMvfn and SMhfn in Table 1-2, ie, the longitudinal magnification difference (SMvn-SMvf) and the lateral magnification difference (SMhn-SMhf), the prior art example A is 0.1380 and 0.1015, Whereas B is 0.1360 and 0.0988 and C is 0.1342 and 0.0961, the value of Example 1 according to the present invention is held down by a low magnification difference of 0.1342 and 0.0954. I understand that. That is, since the magnification difference between the distance portion and the near portion in the first embodiment according to the present invention is further smaller than that in the prior art 1, the distortion and shaking of the image are further improved as compared with the prior art 1. I understand. In the patent specification corresponding to the above-described prior art 1, the difference between the vertical direction and the horizontal direction is not considered at all in calculating the magnification. However, the graph 1-3SMv (total magnification in the vertical direction) in FIG. 21 and the 1-3-3-SMh (total magnification in the horizontal direction) in FIG. 22 by strict magnification calculation corresponding to Example 1 according to the present invention are obtained. As can be readily seen by comparison, the magnification distributions of the images in the vertical and horizontal directions are clearly different. In addition, it can be easily read that this difference is conspicuous mainly in the near portion and below (the eyeball rotation angle is around −20 ° or less).
[0069]
Now, the above-mentioned formula for calculating magnification,
Vertical magnification SMv = Msv × Mpv × Mγv
Horizontal magnification SMh = Msh × Mph × Mγh
Graph 1-3-3-SMv is obtained by multiplying the values of three elements, Graph 1-3-Msv, Graph 1-3-Mpv, and Graph 1-3-Mγv. -3-SMh is obtained by multiplying the values of three elements, graph 1-3-Msh, graph 1-3-Mph, and graph 1-3-Mγh. Here, when the vertical and horizontal directions of each element are compared, there is no clear difference between the shape factors Msv and Msv, but Mpv and Mph are below the near part (−25 ° in the eyeball rotation angle). There is a difference in the vicinity). Further, in Mγv and Mγh, there is a remarkable difference between the near portion and the lower portion (the eyeball rotation angle is around −15 ° or less). That is, the main cause of the difference between the graph 1-3SMv and the graph 1-3-3-SMh is the difference between Mγv and Mγh, and the secondary cause is the difference between Mpv and Mph. It can be seen that there is no clear difference and it is almost irrelevant. In other words, the reason why the vertical and horizontal magnification differences are not observed in the patent specification corresponding to the prior art 1 is that the prism factors Mγv and Mγh, which are the main causes of the magnification differences, are not considered at all. Regarding power factors Mpv and Mph which are the next causes, the objective distance and the angle between the line of sight and the lens are ignored, so there is no difference. Further, regarding the shape factors Msv and Msh, which are grounds for improvement in the prior art 1, as long as the scale factors used in the first embodiment of the present invention are viewed, there is no difference between the examples in the perspective magnification difference.
[0070]
In the prior art 1, “reducing the magnification difference between the distance portion and the near portion” indicates that “the distortion and shaking of the image can be reduced”, but in the present invention, “the magnification difference between the vertical direction and the horizontal direction is further reduced. “Reducing” also has the effect of “reducing image distortion and shaking”. That is, it tries to avoid that a square object looks flat or a round object looks oval. This improvement in visual sensation may be more essential in terms of “making the ratio closer to 1” than “reducing the difference”. What is important here is that the feeling that a square object looks flat or a round object looks oval is not an “perspective ratio” but an “aspect ratio”. That is, in the present invention, not only “reducing the magnification difference between the distance portion and the near portion” but also as an important improvement “by reducing the magnification difference between the vertical direction and the horizontal direction and bringing the magnification ratio closer to 1”. The improvement effect that “the distortion and shaking of the image can be reduced” can be obtained. In addition, these tendencies are conspicuous mainly below the near portion (at an eyeball rotation angle of around −25 ° or less).
[0071]
(Example 2)
Table 2-1 in FIG. 8 is a list relating to the surface refractive power of Example 2 according to the present invention. The frequency in Example 2 corresponds to S + 6.00 Add3.00, and three types of prior art examples of the same frequency are shown for comparison. The conventional example A is a “convex progressive-power lens” in which the object-side surface is a progressive surface, and the conventional example B is “double-sided progressive-power lens in which both the object-side surface and the eyeball-side surface are progressive surfaces. The prior art example C corresponds to a “concave progressive addition lens” whose surface on the eyeball side is a progressive surface. The meanings of terms such as DVf1 to DHn2 used in Table 2-1 are the same as those in Table 1-1. Graphs 2-1 and 2 are graphs showing the surface refractive power distribution along the main line of sight of Example 2 according to the present invention. The horizontal axis faces the right side above the lens, the left side below the lens, and the vertical axis. Represents the surface refractive power. Here, the graph 2-1 corresponds to the object side surface, and the graph 2-2 corresponds to the eyeball side surface. The solid line graph represents the vertical surface power distribution along the main gaze line, and the dotted line graph represents the horizontal surface power distribution along the main gaze line. These are graphs that explain the basic differences in surface composition, and are omitted for cases such as making aspherical surfaces to remove astigmatism in the periphery and adding astigmatism components to support astigmatism power. is there.
[0072]
Further, as a graph representing the surface refractive power distribution along the main line of sight of the three prior art examples of the same power listed in Table 2-1, for comparison, the graph A-1 used in Example 1 and 2, graphs B-1 and 2 and graphs C-1 and 2 are used again. Therefore, the meanings of the terms in these graphs are the same as those in the first embodiment, but the surface refractive powers in F1, N1, F2, and N2 also correspond to Table 2-1, and are in the center. The average surface refractive power of the object-side surface indicated by the one-dot chain line in the horizontal direction is assumed to be a deep curve of 10.50 diopters in order to correspond to Table 2-1.
[0073]
Next, eight types of graphs starting with a graph 2-3 shown in FIGS. 23 to 30 show the magnification distribution when the lens of Example 2 according to the present invention is viewed along the main line of sight. It is a graph showing the result calculated by performing various magnification calculations. The terms and the meanings of the symbols attached after the graph 2-3 are the same as in the case of Example 1 except that the dark solid line in the figure is Example 2. The refractive index, objective power, and eyeball rotation angle used in Example 2 and the three types of prior art examples are the same as those in Example 1, but Example 2 and the three types of prior art are the same. Since the frequency of the prior art example is S + 6.00 Add3.00, only the center thickness t is set to 6.0 mm, which is close to an actual product.
[0074]
Table 2-2 in FIG. 8 is a list of strict magnification calculation results with respect to a specific line-of-sight direction for Example 2 according to the present invention and three types of prior art examples prepared for comparison. It corresponds to −3−SMv (total magnification in the vertical direction) and graph 2-3−SMh (total magnification in the horizontal direction). Here, the meanings represented by the symbols in Table 2-2 are the same as those in Table 1-2.
[0075]
Now, looking at SMvfn and SMhfn in Table 2-2, that is, the longitudinal magnification difference (SMvn-SMvf) and the lateral magnification difference (SMhn-SMhf), the prior art example A is 0.2275 and 0.1325, Whereas B is 0.2277 and 0.1268, and C is 0.2280 and 0.1210, the value of Example 2 according to the present invention is suppressed to a low magnification difference of 0.2151 and 0.1199. I understand that. That is, the magnification difference between the distance portion and the near portion according to the second embodiment of the present invention is further smaller than that of the prior art 1, and therefore image distortion and shaking are further improved compared to the prior art 1. I understand. Similar to the above-described first embodiment, a graph 2-3SMv (total magnification in the vertical direction) and a graph 2-3-3-SMh (total in the horizontal direction) by strict magnification calculation corresponding to the second embodiment according to the present invention. As can be readily seen by comparing (magnification), the magnification distribution of the image in the vertical and horizontal directions is clearly different.
[0076]
In addition, it can be easily read that this difference is conspicuous mainly downward from the middle part (in the vicinity of −10 ° or less in eyeball rotation angle). As in the first embodiment, in the second embodiment, the graph 2-3-SMv has three elements, the values of the graph 2-3-3-Msv, the graph 2-3-3-Mpv, and the graph 2-3-3-Mγv. Similarly, graph 2-3-3-SMh is obtained by multiplying the values of three elements, graph 2-3-3-Msh, graph 2-3-3-Mph, and graph 2-3-3-Mγh. Here, when comparing the vertical and horizontal directions of each element, there is no clear difference between the shape factors Msv and Msv, but Mpv and Mph are below the near part (−20 ° in the eyeball rotation angle). There is a difference in the vicinity). In addition, there is a significant difference between Mγv and Mγh from the middle portion downward (eye rotation angle is around −10 ° or less). Here, a difference is also seen above the distance portion (in the vicinity of + 20 ° or more in the eyeball rotation angle), but the difference in each example is significantly above the distance portion (in the vicinity of + 30 ° or more in the eyeball rotation angle). Yes, it can be ignored because it is used less frequently.
[0077]
That is, in the same manner as in Example 1 described above, also in Example 2, the main cause of the difference between the graph 2-3SMv in FIG. 29 and the graph 2-3-3-SMh in FIG. 30 is the difference between Mγv and Mγh. A secondary cause is the difference between Mpv and Mph, and there is no clear difference between Msv and Msh, indicating that they are almost irrelevant. Further, regarding the shape factors Msv and Msh, which are grounds for improvement in the prior art 1, as long as the scale factors used in the second embodiment of the present invention are viewed, there is no difference between the examples in the perspective magnification difference. In the second embodiment, as in the first embodiment described above, not only “reducing the magnification difference between the distance portion and the near portion” but also as an important improvement “the magnification difference between the vertical direction and the horizontal direction”. By reducing the magnification ratio and bringing the magnification ratio close to 1, an improvement effect of “reducing image distortion and shaking” is obtained. In addition, these tendencies are conspicuous mainly below the near portion (at an eyeball rotation angle of around −25 ° or less).
[0078]
(Example 3)
Table 3-1 in FIG. 9 is a list relating to the surface refractive power of Example 3 according to the present invention. The frequency in Example 3 corresponds to S-6.00 Add3.00, and three types of prior art examples of the same frequency are shown for comparison. The conventional example A is a “convex progressive-power lens” in which the object-side surface is a progressive surface, and the conventional example B is “double-sided progressive-power lens in which both the object-side surface and the eyeball-side surface are progressive surfaces. The prior art example C corresponds to a “concave progressive addition lens” whose surface on the eyeball side is a progressive surface. The meanings of terms such as DVf1 to DHn2 used in Table 3-1 are the same as those in Table 1-1 and Table 2-1.
[0079]
Graphs 3-1 and 2 in FIG. 11 are graphs showing the surface refractive power distribution along the main line of sight of Example 3 according to the present invention. The horizontal axis faces the right side above the lens, the left side below the lens, The vertical axis represents the surface refractive power. Here, the graph 3-1 corresponds to the object side surface, and the graph 3-2 corresponds to the eyeball side surface. The solid line graph represents the vertical surface power distribution along the main gaze line, and the dotted line graph represents the horizontal surface power distribution along the main gaze line. These are graphs that explain the basic differences in surface composition, and are omitted for cases such as making aspherical surfaces to remove astigmatism in the periphery and adding astigmatism components to support astigmatism power. is there.
[0080]
Furthermore, as a graph showing the surface refractive power distribution along the main line of sight of the three prior art examples of the same power listed in Table 3-1 of FIG. 9 for comparison, the graph was used in Examples 1 and 2 described above. Graphs A-1 and 2, Graphs B-1 and 2, and Graphs C-1 and 2 are used again. Accordingly, the meanings of the terms in these graphs are the same as those in the first and second embodiments, but the surface refractive powers at F1, N1, F2, and N2 also correspond to Table 3-1, and It is assumed that the average surface refractive power of the object-side surface indicated by the one-dot chain line in the horizontal direction in FIG.
[0081]
Next, eight types of graphs starting with the graph 3-3 shown in FIGS. 31 to 38 show the magnification distribution when the lens of Example 3 according to the present invention is viewed along the main line of sight. It is a graph showing the result calculated by performing various magnification calculations. The terms and the meanings of the symbols attached after the graph 3-3 are the same as those in the first and second embodiments except that the solid line in the figure is the third embodiment. The refractive index, objective power, eyeball rotation angle, etc. used in Example 3 and the three types of prior art examples are the same as those in Examples 1 and 2, but Examples 3 and 3 Since the frequency of the type of prior art example is S-6.00 Add3.00, only the center thickness t was set to 1.0 mm, which was close to an actual product.
[0082]
Table 3-2 in FIG. 9 is a list of strict magnification calculation results for a specific line-of-sight direction for Example 3 according to the present invention and three types of prior art examples prepared for comparison. It corresponds to -3-SMv (total magnification in the vertical direction) and graph 3-3SMh (total magnification in the horizontal direction). Here, the meanings represented by the symbols in Table 3-2 are the same as those in Tables 1-2 and 2-2.
[0083]
Now, looking at SMvfn and SMhfn in Table 3-2, that is, the longitudinal magnification difference (SMvn-SMvf) and the lateral magnification difference (SMhn-SMhf), the prior art example A is 0.0475 and 0.0774, Whereas B is 0.0418 and 0.0750, and C is 0.0363 and 0.0727, the values of Example 2 according to the present invention are values of 0.0512 and 0.0726. It can be seen that the horizontal magnification difference is decreasing, though increasing. However, considering that the vertical magnification difference is a low value such as 1/3 to 1/5 of both the above-described Example 1 and Example 2 and the lateral magnification difference is slightly reduced, It can be said that the magnification difference between the distance portion and the near portion according to the third embodiment of the present invention is not significantly different from that of the related art 1. However, when observing the graph 3-3-SMv (total magnification in the vertical direction) and the graph 3-3-SMh (total magnification in the horizontal direction) by strict magnification calculation corresponding to Example 3 according to the present invention, it is according to the present invention. Compared with the conventional example, Example 3 has the smallest “vertical magnification tends to be smaller than 1” particularly below the near portion (eye rotation angle of about −20 ° or less). The “difference” is the smallest, and the distortion and shaking of the image are improved compared to the conventional example.
[0084]
Note that in the graph 3-3-SMv (total magnification in the vertical direction) in FIG. 37, the difference in image magnification distribution between the vertical direction and the horizontal direction is downward from the middle part (−10 ° in the eyeball rotation angle). Nearer and below) and above the distance part (eye rotation angle around + 10 ° or more), but the difference in each case is lower than the near part (eye rotation angle around -20 ° or less) and distance use It is slightly above the part (eye rotation angle around + 25 ° or more). Of these, the frequency of use slightly above the distance portion is negligible and can be ignored, but the frequency below the near portion is high and cannot be ignored. As a result, in Example 3 according to the present invention, in comparison with the conventional example, the magnification in the vertical direction is closest to 1 particularly below the near portion (the eye rotation angle is around −20 ° or less). "Is the smallest, and image distortion and shaking are improved compared to the conventional example. In addition, these tendencies are conspicuous mainly below the near portion (at an eyeball rotation angle of around −25 ° or less). In addition, as for the shape factors Msv and Msh, which are grounds for improvement in the prior art 1, as in the case of the first and second embodiments of the present invention, the magnification in the perspective is also seen in the scale used in the third embodiment. There is no difference between the examples.
[0085]
(Examples 4 to 7)
As an embodiment of the present invention, in addition to the first to third embodiments described above, various surface refractive power distribution combinations are possible within the scope described in the claims. Here, Examples 4 to 6 are shown as application examples of the same degree as Example 1, and Example 7 is shown as an application example of the same degree as Example 2. Lists and graphs of strict magnification calculation results for the surface refractive power and specific line-of-sight direction of these examples are shown in Table 1-1, Table 1-2 in FIG. 7, and Graph 4-1 in FIGS. It shows in graph 4-2 thru | or graph 7-1, graph 7-2.
[0086]
(Modification)
Furthermore, in the present invention, not only the normal prescription value but also the personal factor of the spectacle wearer, which has been rarely grasped by the lens manufacturer, for example, the distance from the corneal vertex to the rear vertex of the lens, the center of eyeball rotation to the rear of the lens Distance to the apex, degree of unequal image vision of the left and right eyes, difference in height between the left and right eyes, most frequent near vision objective distance, forward tilt angle (vertical direction) and tilt angle (horizontal direction), By incorporating the bevel position in the edge thickness direction of the lens into the lens design as input information, it is possible to meet custom-made (individual design) requirements. Further, although the present invention has a surface configuration of double-sided aspherical surfaces, it is not always necessary to process both sides for the first time after receiving an order in order to obtain the effects of the present invention. For example, a “semi-finished product” of the object side surface that meets the object of the present invention is prepared in advance, and after the order is received, the object side surface suitable for the purpose such as the prescription frequency or the above custom-made (individual design) is prepared. It is also advantageous in terms of cost and processing speed to select “semi-finished product” and finish only the eyeball side surface after receiving an order.
[0087]
As a specific example of this method, for example, it is conceivable to prepare in advance a “semi-finished product” on a symmetrical object-side surface. And for near vision inset corresponding to the eye convergence effect in near vision, it corresponds to personal information such as interpupillary distance and near vision objective distance, and asymmetrical left and right for the eyeball side surface It can be incorporated by making it a curved surface. Of course, there are various ways of acquiring and determining information, such as estimation and average / standard values, as well as actual measurement of these personal information, but the present invention is limited by such means. Never happen. In addition to normal prescription values, curved surfaces of the object-side surface, or the eyeball-side surface, or both the object-side surface and the eyeball-side surface when performing optical calculations to incorporate the aforementioned personal factors into the lens design In this case, it is also possible to add a “correction action” for removing or reducing astigmatism and the change in power mainly due to the fact that the line of sight and the lens surface cannot be orthogonal.
[0088]
Furthermore, it is generally known that the three-dimensional rotational movement of the eyeball when we look around is based on a rule called “listing rule”, but if the prescription power has an astigmatic power, Even if the astigmatism axis is matched with “the astigmatism axis of the eyeball in front view”, the astigmatism axes may not coincide in peripheral vision. As described above, the “correcting action” for removing or reducing astigmatism and the change in power caused by the astigmatic axis directions of the lens and the eye in peripheral vision are not corrected. It is also possible to add to the curved surface of the surface having the correcting action.
[0089]
The definition of “predetermined addition power” in the present invention is as follows. As shown in FIG. 6, the refractive power measured by applying the aperture of the lens meter to the distance power measurement position F1 and the near power measurement position N1 on the object side surface. In addition to the case of the difference, when the refractive power difference is measured by applying the opening of the lens meter to the distance power measurement position F2 and the near power measurement position N2 on the eyeball side surface, and further, the opening of the lens meter. Is the difference between the refractive power measured by applying to the distance power measurement position F2 on the eyeball side surface and the refractive power measured at N3 toward the near power measurement position N2 by rotating around the center of rotation of the eyeball. In some cases, only the refractive power component in the horizontal direction is used as each refractive power, and any of these definitions can be adopted.
[0090]
【The invention's effect】
As described above in detail, according to the present invention, the magnification of the image is correctly calculated in consideration of the influence of the “angle between the line of sight and the lens surface” and the “objective distance”. It can reduce the magnification difference of the image in the near part, give good vision correction to the prescription value, and provide a wide effective field of view with little distortion at the time of wearing. Can be processed as a left-right asymmetric curved surface corresponding to the eye convergence in near vision after receiving an order, and the processing time and cost can be reduced. Type progressive power lens can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of various surface refractive powers at various positions on a spectacle lens surface.
FIG. 2 is an explanatory diagram of a positional relationship among an eyeball, a line of sight, and a lens.
FIG. 3A is an explanatory diagram regarding a magnification Mγ of a prism, and is an explanatory diagram regarding a difference between a plus lens and a minus lens and a difference in magnification when viewed using a near portion which is mainly a lower portion of the lens.
FIG. 3-2 is an explanatory diagram regarding the magnification Mγ of the prism, and is an explanatory diagram regarding a difference between a plus lens and a minus lens and a difference in magnification when viewed using a near portion, which is mainly a lower portion of the lens.
FIG. 3-3 is an explanatory diagram regarding the magnification Mγ of the prism, and is an explanatory diagram regarding a difference between a plus lens and a minus lens and a difference in magnification when viewed using a near portion, which is mainly a lower portion of the lens.
FIG. 4A is an explanatory diagram regarding the magnification Mγ of the prism, and is an explanatory diagram regarding a difference between a plus lens and a minus lens and a difference in magnification when viewed using a near portion that is mainly a lower portion of the lens.
FIG. 4-2 is an explanatory diagram regarding the magnification Mγ of the prism, and is an explanatory diagram regarding the difference between the plus lens and the minus lens and the difference in magnification when viewed using the near portion, which is mainly the lower part of the lens.
FIG. 4-3 is an explanatory diagram regarding the magnification Mγ of the prism, and is an explanatory diagram regarding the difference between the plus lens and the minus lens and the difference in magnification when viewed using the near portion, which is mainly the lower part of the lens.
FIG. 5A is an explanatory diagram of an optical layout of a progressive-power lens, and is a front view of the progressive-power lens as viewed from the object side surface;
FIG. 5-2 is an explanatory diagram of an optical layout of a progressive-power lens and is a side view showing a cross section in the vertical direction;
FIG. 5-3 is an explanatory view of an optical layout of a progressive-power lens, and an elevation view showing a cross section in a lateral direction.
FIG. 6 is an explanatory diagram showing a difference in definition of “additional power”.
FIG. 7 shows “surface refractive power” and “strict magnification calculation results for a specific line-of-sight direction” of prior art A, B, and C corresponding to Examples 1, 4, 5, and 6, respectively. It is the figure put together in Table 1 and Table 1-2.
FIG. 8 shows the “surface refractive power” and the “strict magnification calculation result for a specific line-of-sight direction” of the conventional techniques A, B, and C corresponding to the respective frequencies in Examples 2 and 7, and Tables 2-1 and 2 FIG.
[Table 9] Table 3-1 and Table 3-2 show “surface refractive power” and “exact magnification calculation result for a specific line-of-sight direction” of the prior art A, B, and C corresponding to Example 3 and the frequency thereof. It is the figure shown collectively.
10 is a graph showing graphs 1-1, 1-2, 2-1, and 2-2 showing surface refractive power distributions of Example 1 and Example 2. FIG.
11 is a graph showing graphs 3-1, 3-2 representing a surface refractive power distribution of Example 3. FIG.
FIG. 12 is a diagram illustrating graphs 4-1, 4-2, 5-1, 5-2, 6-1, and 6-2 representing surface refractive power distributions of Examples 4 to 6;
13 shows graphs 7-1 and 7-2 representing surface refractive power distributions in Example 7. FIG.
FIG. 14 is a diagram showing graphs A-1, A-2, B-1, B-2, C-1, and C-2 representing surface refractive power distributions of Related Art Examples A, B, and C.
FIG. 15 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 1-3-3-Msv to represent.
FIG. 16 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 1-3-3-Msh to represent.
FIG. 17 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 1-3-3-Mpv to represent.
FIG. 18 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 1-3-3-Mph to represent.
FIG. 19 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 1-3-3-M (gamma) v to represent.
FIG. 20 shows the result obtained by performing strict magnification calculation on the magnification distribution when the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the frequency are viewed along the main line of sight. It is a figure which shows the graph 1-3-3-Mγh to represent.
FIG. 21 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 1-3-3-SMv to represent.
FIG. 22 shows the result of strict magnification calculation for the magnification distribution when the lenses of Example 1 and three types of conventional examples A, B, and C corresponding to the frequency are viewed along the main line of sight. It is a figure which shows the graph 1-3-3-SMh to represent.
FIG. 23 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-Msv to represent.
FIG. 24 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-Msh to represent.
FIG. 25 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-Mpv to represent.
FIG. 26 shows results obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-Mph to represent.
FIG. 27 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 2-3-3-M (gamma) v to represent.
FIG. 28 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-Mgammah to represent.
FIG. 29 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-SMv to represent.
FIG. 30 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 2 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 2-3-3-SMh to represent.
FIG. 31 shows the result of strict magnification calculation for the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 3-3-Msv to represent.
FIG. 32 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 3-3-Msh to represent.
FIG. 33 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 3-3-Mpv to represent.
FIG. 34 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 3-3-Mph to represent.
FIG. 35 shows the result obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the frequency along the main line of sight. It is a figure which shows the graph 3-3-M (gamma) v to represent.
FIG. 36 shows results obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 3-3-Mgammah to represent.
FIG. 37 shows results obtained by performing strict magnification calculation on the magnification distribution when viewing the lenses of Example 3 and three types of conventional examples A, B, and C corresponding to the power along the main line of sight. It is a figure which shows the graph 3-3-SMv to represent.
FIG. 38 shows the result of strict magnification calculation for the magnification distribution when Example 3 and three conventional lenses A, B, and C corresponding to the frequency are viewed along the main line of sight. It is a figure which shows graph 3-3-SMh to represent.

Claims

A double-sided aspherical progressive-power lens having a progressive-power action divided and distributed into a first refractive surface that is an object-side surface and a second refractive surface that is an eyeball-side surface,
In the first refractive surface, the horizontal surface power and the vertical surface power at the distance power measurement position F1 are DHf and DVf, respectively.
In the first refracting surface, when the horizontal surface power and the vertical surface power at the near power measurement position N1 are DHn and DVn, respectively,
DHf + DHn <DVf + DVn and DHn <DVn
Satisfying the following relational expression, the surface astigmatism components at F1 and N1 of the first refractive surface are canceled by the second refractive surface, and the first and second refractive surfaces are combined. A double-sided aspherical progressive-power lens characterized by providing a distance power (Df) and an addition power (ADD) based on a prescription value.

2. The double-sided aspherical progressive-power lens according to claim 1, wherein a relational expression of DVn−DVf> ADD / 2 and DHn−DHf <ADD / 2 is satisfied.

The first refracting surface is symmetrical with respect to one meridian passing through the distance power measurement position F1, and the second refracting surface defines the distance power measurement position F2 of the second refracting surface. It is symmetrical with respect to a single meridian passing therethrough, and the arrangement of the near power measurement position N2 of the second refractive surface is inwardly aligned to the nose side by a predetermined distance. The double-sided aspherical progressive-power lens according to claim 1, wherein the double-sided aspherical progressive-power lens is compatible with the converging action.

The first refracting surface is a rotating surface with a meridian passing through the distance power measurement position F1 as a generating line, and the second refracting surface is a distance power measurement position of the second refracting surface. It is symmetrical with respect to one meridian passing through F2, and the arrangement of the near-field power measurement position N2 on the second refractive surface is inset to the nose side by a predetermined distance. The double-sided aspherical progressive-power lens according to any one of claims 1 to 3, wherein the double-sided aspherical progressive-power lens corresponds to the eye convergence effect.

In the configuration in which the first and second refractive surfaces are combined to give the distance power (Df) and the addition power (ADD) based on the prescription value, the line of sight in the wearing state and the lens surface are orthogonal to each other. The double-sided aspherical progressive-power lens according to any one of claims 1 to 4, wherein occurrence of astigmatism and change in power due to failure are reduced.