JP4239519B2

JP4239519B2 - Progressive power lens, presbyopia glasses and lens design method

Info

Publication number: JP4239519B2
Application number: JP2002238488A
Authority: JP
Inventors: 朗小松; 優江川; 一寿加藤; 唯之加賀
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2002-03-27
Filing date: 2002-08-19
Publication date: 2009-03-18
Anticipated expiration: 2022-08-19
Also published as: JP2004004436A

Description

【０００１】
【発明の属する技術分野】
本発明は、像の揺れ・歪みを改善し、光学性能を向上させた累進屈折力レンズ、それをフレームに組み込んだ老視用眼鏡及びレンズの設計方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
主に遠距離の物体を見る時に使用する遠用部と、主に近距離の物体を見る時に使用する近用部と、遠用部と近用部との間に連続的に度数が変化する累進帯とを備える累進屈折面を有する累進屈折力レンズには、累進屈折面形状の設計に依らず、近用側方部に像の歪みやボケを生じる領域があり、使用者の装用感低下を招いていた。この光学的な欠陥は、累進屈折面を採用している以上必然的に生じるものであり、本質的にゼロにすることは困難である。従来からこの欠点を解消するために様々な取リ組みがなされてきている。
【０００３】
その一つとして、眼鏡レンズの外面側又は内面側のどちらか一方に設けられていた累進面を両側に設けることによって光学性能を向上させる両面累進レンズのアイデアが、ＷＯ９７／１９３８３と特開２０００−２４９９９２号公報に開示されている。
【０００４】
ＷＯ９７／１９３８３では、レンズの加入度をＡｄｄとした時、外面（第１面）の面加入度Ａ１が、
―（Ｌ・Ｎ／Ｔ）Ａｄｄ＜Ａ１＜Ａｄｄ
を満たす両面累進レンズについて記載されている。但し、Ｌは頂間距離、Ｎはレンズの屈折率、Ｔはレンズの中心厚である。しかし、ＷＯ９７／１９３８３では、両面累進レンズの概念を提案しているが、それぞれの累進面の設計内容については述べられていない。
【０００５】
特開２０００−２４９９９２号公報では、内面（第２面）がリグレッシブ面となる場合、つまり、内面の面加入度Ａ２が、Ａ２＜０となる場合について述べられている。この時、外面の面加入度Ａ１は、Ａｄｄ＜Ａ１となる。さらに、特開２０００−２４９９９２号公報では、外面のプログレッシブ面（面加入度Ａ１がプラス）をソフト設計、内面のリグレッシブ面をハード設計にすることによって、外面・内面で発生する非点収差を相殺し、レンズとしての収差量を低減させるアイデアが開示されている。
【０００６】
しかし、本発明者が詳細に検討したところ、このレンズ構成では、装用感の良い眼鏡レンズは得られないことが判明した。即ち、非点収差が相殺される領域は、レンズ面の中の限られた範囲でしかなく、それ以外の領域では、片面累進面のレンズよりもむしろ大きな非点収差が残される。また、非点収差量の変化が大きいので、像の歪みも局所的に大きくなり、装用感を大きく損なう状態となってしまう。
【０００７】
本発明は、上記事情に鑑みてなされたもので、累進屈折力レンズに必然的に生じる像の歪みやボケを減少させ、装用感を向上させることができる累進屈折力レンズを提供することを目的とする。
【０００８】
また、本発明は、かかる累進屈折力レンズをフレームに組み込んだ老視用眼鏡を提供することを目的とする。
【０００９】
更に、本発明は、優れた装用感を有する累進屈折力レンズの設計方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
累進屈折力レンズの累進面は、古くは外面側に形成されていたが、その累進面を内面側に形成することによって、飛躍的に光学性能が向上することが判明した。この内面累進レンズの理論を応用し、さらに光学性能を向上させるために、本発明においては、外面と内面の両方に累進屈折面を形成した両面累進レンズとすると共に、外面の平均面屈折力を遠用部から近用部にかけて連続的に減少するように設定している。
【００１１】
このような両面累進レンズの外面の平均面屈折力の変化をマイナスとする、即ち外面の面加入度をマイナスとすることにより、近用部の倍率差を小さくして、歪みを減少させることができる。
【００１２】
また、レンズの両面に累進屈折面を設ける場合、両面の累進設計をほぼ同じとすることにより、不自然な揺れ・歪みが生じず光学性能が向上することを見い出した。
【００１３】
さらに、両面累進の効果を発揮するためには、外面の遠用部中心における平均面屈折力ＰＦ１（Ｄ）と、外面の近用部中心における平均面屈折力ＰＮ１（Ｄ）の差（Ａ１＝ＰＮ１−ＰＦ１）がある程度の大きさが必要であるし、又あまり差が有りすぎると、レンズの外観上好ましくない。このため、Ａ１の値が、−ＰＦ１−１０．０＜Ａ１＜−０．２５（Ｄ）の範囲内にあることが好ましい。
【００１４】
また、両面累進レンズでは、外面と内面のそれぞれに累進屈折面が形成されるため、これらの累進屈折面の遠用部視野範囲相互、近用部視野範囲相互及び累進帯相互が重なって見えることによって装用感が向上する。そのため、レンズによる屈折を考慮して、内面の累進屈折面を外面の累進屈折面よりもフィッティングポイント寄りにすることが好ましい。
【００１５】
従って、本発明の累進屈折力レンズは、主に遠距離の物体を見る時に使用する遠用部と、主に近距離の物体を見る時に使用する近用部と、前記遠用部と前記近用部との間に連続的に度数が変化する累進帯とを備える累進屈折面を有する累進屈折力レンズにおいて、物体側の屈折面を第１面、使用者側の屈折面を第２面としたとき、前記第１面及び第２面の両方が累進屈折面に形成され、かつ、前記第１面の平均面屈折力が、前記遠用部から前記近用部にかけて連続的に減少し、前記第１面の前記遠用部中心における平均面屈折力ＰＦ１（Ｄ）と前記第１面の近用部中心における平均面屈折力ＰＮ１（Ｄ）の差を面加入度Ａ１（＝ＰＮ１−ＰＦ１）とし、前記第１面の任意の点における平均面屈折力Ｐ１とＰＦ１との差をＡ１で割った値をＳ１とし、Ｓ１＝（Ｐ１−ＰＦ１）／Ａ１前記第２面の前記遠用部中心における平均面屈折力ＰＦ２（Ｄ）と前記第２面の前記近用部中心における平均面屈折力ＰＮ２（Ｄ）の差を面加入度Ａ２（ＰＮ２−ＰＦ２）とし、前記第１面の点に対応する前記第２面上の点における平均面屈折力Ｐ２と前記ＰＦ２との差をＡ２で割った値をＳ２としたとき、Ｓ２＝（Ｐ２−ＰＦ２）／Ａ２レンズ面上の中心から４０ｍｍの範囲内で、│Ｓ１−Ｓ２│≦０．２５であることを特徴とする。但し、累進屈折面上のある点における平均面屈折力Ｐ（Ｄ）は、その点における曲率の最大値Ｃｍａｘ（１／ｍ）、曲率の最小値Ｃｍｉｎ（１／ｍ）と、累進屈折面より物体側にある媒質の屈折率Ｎ１と使用者側にある媒質の屈折率Ｎ２を用いて、Ｐ＝（Ｎ２−Ｎ１）（Ｃｍａｘ＋Ｃｍｉｎ）／２で定義される。
【００１７】
本発明の累進屈折力レンズは、前記第１面の前記遠用部中心における平均面屈折力をＰＦ１（Ｄ）、前記第１面の前記近用部中心における平均面屈折力をＰＮ１（Ｄ）とし、前記第１面の面加入度Ａ１をＡ１＝ＰＮ１−ＰＦ１とすると、−ＰＦ１−１０．０＜Ａ１＜−０．２５（Ｄ）であることが好ましい。
【００１８】
本発明の累進屈折力レンズは、前記第２面の前記遠用部中心点を通るレンズの光軸との平行線が、前記第１面の前記遠用部中心点を通るレンズの光軸との平行線に対し、同じ位置か又はフィッティングポイント寄りの位置にあり、前記第２面の前記近用部中心点を通るレンズの光軸との平行線が、前記第１面の前記近用部中心点を通るレンズの光軸との平行線に対し、同じ位置か又はフィッティングポイント寄りの位置にあることが好ましい。
【００１９】
本発明の老視用眼鏡は、前述のいずれかに記載の累進屈折力レンズを玉型加工し、フレームに組み込んだことが好ましい。
【００２０】
本発明の累進屈折力レンズの設計方法は、主に遠距離の物体を見る時に使用する遠用部と、主に近距離の物体を見る時に使用する近用部と、前記遠用部と前記近用部との間に連続的に度数が変化する累進帯とを備える累進屈折面を有する累進屈折力レンズの設計方法であって、物体側の屈折面を第１面、使用者側の屈折面を第２面としたとき、前記第１面及び第２面の両方を累進屈折面に形成し、かつ、前記第１面の平均面屈折力を、前記遠用部から前記近用部にかけて連続的に減少させ、前記第１面の前記遠用部中心における平均面屈折力ＰＦ１（Ｄ）と前記第１面の近用部中心における平均面屈折力ＰＮ１（Ｄ）の差を面加入度Ａ１（＝ＰＮ１−ＰＦ１）とし、前記第１面の任意の点における平均面屈折力Ｐ１とＰＦ１との差をＡ１で割った値をＳ１とし、Ｓ１＝（Ｐ１−ＰＦ１）／Ａ１前記第２面の前記遠用部中心における平均面屈折力ＰＦ２（Ｄ）と前記第２面の前記近用部中心における平均面屈折力ＰＮ２（Ｄ）の差を面加入度Ａ２（ＰＮ２−ＰＦ２）とし、前記第１面の点に対応する前記第２面上の点における平均面屈折力Ｐ２と前記ＰＦ２との差をＡ２で割った値をＳ２としたとき、Ｓ２＝（Ｐ２−ＰＦ２）／Ａ２レンズ面上の中心から４０ｍｍの範囲内で、│Ｓ１−Ｓ２│≦０．２５に設計することを特徴とする。但し、累進屈折面上のある点における平均面屈折力Ｐ（Ｄ）は、その点における曲率の最大値Ｃｍａｘ（１／ｍ）、曲率の最小値Ｃｍｉｎ（１／ｍ）と、累進屈折面より物体側にある媒質の屈折率Ｎ１と使用者側にある媒質の屈折率Ｎ２を用いて、Ｐ＝（Ｎ２−Ｎ１）（Ｃｍａｘ＋Ｃｍｉｎ）／２で定義される。
【００２２】
【発明の実施の形態】
以下、本発明の実施の形態について説明するが、本発明は以下の実施の形態に限定されるものではない。
【００２３】
累進屈折力レンズは、主に遠距離の物体を見る時に使用する遠用部と、主に近距離の物体を見る時に使用する近用部と、遠用部と近用部との間に連続的に度数が変化する累進帯とを備える累進屈折面を有する。累進屈折力レンズには、外面（第１面）にのみ累進屈折面を設けた外面累進レンズ、内面（第２面）にのみ累進屈折面を設けた内面累進レンズ、外面と内面の両面に累進屈折面を設けた両面累進レンズの３種類が存在する。
【００２４】
かかる累進屈折力レンズでは、近用側方部に必然的に像の揺れ・歪みを生じる領域がある。これは、遠用部と近用部でレンズの度数が異なるために、見かけの像の大きさが異なることに起因している。像の歪みを抑えるためには、遠用部と近用部の像が、なるべく同じ大きさになれば良い。像の見かけの倍率（ＳＭ：Spectacle Magnification）は、近軸量を使って次式で表される。
【００２５】
ＳＭ＝Ｍｓ×Ｍｐ・・・（１）
Ｍｓ＝１／（１−ｔＤ／ｎ）：シェイプファクタ−
Ｍｐ＝１／（１−ＬＰ）：パワ−ファクタ−
ｔ：レンズの厚さ（ｍ）、ｎ：屈折率、Ｄ：外面の面屈折力（ディオプトリー：Ｄ）、Ｌ：レンズから瞳までの距離（ｍ）、Ｐ：レンズの度数（ディオプトリー：Ｄ）
【００２６】
遠用部の倍率と近用部の倍率を上式に従って計算し、その差を求めれば、側方部の歪みの程度が推察出来る。同じ度数、同じ加入度、ほぼ同じレンズ形状の外面累進レンズ、内面累進レンズ、両面累進レンズを比較した場合、遠用部と近用部のＭｐの差は、それぞれのレンズで皆同じである。これに対し、Ｍｓの値は、どの面に累進面が有るかによって、変わってくる。外面累進レンズでは、第１面（外面）の平均面屈折力が遠用部から近用部にかけて増加しているため、Ｍｓの値は、近用部で増加する。これに対し、内面累進レンズでは、第１面に球面を使用するため、平均面屈折力は遠用部でも近用部でも同じであり、Ｍｓの値も一定である。
【００２７】
本発明による両面累進レンズでは、第１面（外面）の平均面屈折力Ｐ（Ｄ）が、遠用部から近用部にかけて連続的に減少している（リグレッシブ面）。これとは逆に、第２面（内面）の平均面屈折力は、遠用部から近用部にかけて連続的に増加している（プログレッシブ面）。これにより、Ｍｓの値も減少する。従って、本発明の両面累進レンズは内面累進レンズよりもさらに揺れ・歪みを低減させ、光学性能を向上させることが出来る。
【００２８】
但し、累進曲面上のある点における平均面屈折力Ｐ（Ｄ）は、その点における曲率の最大値Ｃｍａｘ（１／ｍ）、曲率の最小値Ｃｍｉｎ（１／ｍ）と、曲面より物体側にある媒質の屈折率Ｎ１と使用者側にある媒質の屈折率Ｎ２を用いて、Ｐ＝（Ｎ２−Ｎ１）（Ｃｍａｘ＋Ｃｍｉｎ）／２で定義される。曲率は、その曲率中心が、面より使用者側に有る時に正、物体側に有る時に負の符号をとる。従って、眼鏡レンズがメニスカス形状をしている場合には、平均曲率（Ｃｍａｘ＋Ｃｍｉｎ）／２は、正の値となる。第１面であれば、面より物体側の媒質は空気なので、Ｎ１が１．０、Ｎ２がレンズ素材の屈折率になるので、Ｐの値は正になる。これに対し、第２面では、Ｎ１がレンズ素材の屈折率になり、Ｎ２が１．０になるので、Ｐの値は、負になる。
【００２９】
図１は、外面累進レンズ、内面累進レンズ、本発明の両面累進レンズのそれぞれの遠用部と近用部の倍率比を示すグラフである。本発明の両面累進レンズは、従来の外面累進レンズ・内面累進レンズよりも倍率差が小さく、歪みが少なくなっていることが認められる。
【００３０】
さらに、両面累進レンズの場合、第１面と第２面の両方に累進屈折面を形成するため、設計の自由度が高い。累進面設計が、装用感を左右する大きな要因である。累進面設計には、様々な要素が考えられるが、大きく分けると、明視域の広さを優先したハ−ド設計と歪みの低減を優先したソフト設計とがある。どの様な累進面設計が選択されるかは、使用者の好みや用途によって変わってくるが、両面累進レンズの場合、異なる性格の累進面設計を組み合わせると、非点収差や像の歪みが不自然になり、装用感が非常に悪くなることが判明した。特開２０００−２４９９９２号公報では、第１面と第２面で発生する非点収差を相殺させ、収差量を低減させる目的で、加入度の少ないハ−ド設計と加入度の大きいソフト設計を組み合わせている。しかし、この場合、累進面上の１点を考えれば非点収差は相殺されるのだが、それ以外の場所に大きな非点収差が残ってしまう。そして残った非点収差の分布は従来の累進レンズとは大きく異なるため、像の歪みも非常に不自然になる。しかも、明視域の広さは、加入度の大きいソフト設計面によって制限されてしまうため、同じ加入度数の従来設計の外面累進レンズよりも狭くなる。
【００３１】
このように両面累進レンズの場合、第１面と第２面の累進設計がなるべく相似している方が良い。そのためには、両方の面の平均面屈折力分布が相似している事が望ましい。具体的には、第１面の任意の点における平均面屈折力Ｐ１と遠用部中心における平均面屈折力ＰＦ１との差を第１面の加入度Ａ１で割った値をＳ１とし、同様に第１面の点に対応する第２面上の点における平均面屈折力Ｐ２と遠用部中心における平均面屈折力ＰＦ２との差を第２面の加入度Ａ２で割った値をＳ２とする。つまり、式で表現すると、Ｓ１＝（Ｐ１−ＰＦ１）／Ａ１、Ｓ２＝（Ｐ２−ＰＦ２）／Ａ２である。この時、累進面のタイプや面の加入度数に依らず、Ｓ１及びＳ２の値は、遠用中心点において０となり、近用中心点において１となり、それ以外の場所では、その間の値を取る。第１面と第２面の累進設計が相似しているためには、Ｓ１とＳ２の値が近い事が必要で、具体的には、レン

５以内、好ましくは０．１５以内、更に好ましくは０．１０以内、最も好ましくは０．０５以内であることが望ましい。
【００３２】
また、両面累進の効果を発揮するためには、外面の遠用部中心における平均面屈折力ＰＦ１（Ｄ）と、外面の近用部中心における平均面屈折力ＰＮ１（Ｄ）の差（Ａ１＝ＰＮ１−ＰＦ１）、即ち加入度がある程度の大きさが必要であるし、又あまり差が有りすぎると、レンズの外観上好ましくない。このため、加入度Ａ１の値が、
−ＰＦ１−１０．０＜Ａ１＜−０．２５（Ｄ）
の範囲内にあることが好ましい。
【００３３】
更に、両面累進レンズは、レンズの第１面と第２面の両方に累進屈折面が設けられていることから、これらの累進屈折面の遠用部視野範囲相互、近用部視野範囲相互及び累進帯相互が重なって見えることによって装用感が向上する。図２に示すように、フィッティングポイントＦＰから離れた点では、眼に入射する光線Ｌ１はレンズ１０の中を斜めに通過する。そのため、第１面１１と第２面１２の累進設計が近似している場合、光軸との平行線Ｌ２を基準にして両面の累進屈折面を設けると、第１面１１と第２面１２の累進屈折面の遠用部視野範囲相互、近用部視野範囲相互及び累進帯相互が光学的にずれてしまい、装用感が悪くなる。このため、第２面１２の遠用部中心点と近用部中心点ＮＰとを対向する第１面の遠用部中心点と近用部中心点に対して光線の傾きを考慮してフィッティングポイント寄りの位置の図示しない遠用部中心点と近用部中心点ＮＰ’に設けることが望ましい。
【００３４】
このような両面累進レンズのレンズ面形状の設計方法としては、次の（１）〜（３）の条件を満たすように設計することが好ましい。但し、下記（２）と（３）の順序は入れ替え可能である。
【００３５】
（１）物体側の屈折面を第１面、使用者側の屈折面を第２面としたとき、レンズの両方の屈折面を累進屈折面として、第１面の面加入度Ａ１をマイナスとし、第２面の面加入度Ａ２をＡ２＝Ａｄｄ−Ａ１とする。但し、Ａｄｄはレンズの加入度数である。
（２）第２面の遠用部中心点を通るレンズの光軸との平行線が、第１面の遠用部中心点を通るレンズの光軸との平行線に対し、同じ位置か又はフィッティングポイント寄りの位置にする。
（３）第２面の近用部中心点を通るレンズの光軸との平行線が、第１面の近用部中心点を通るレンズの光軸との平行線に対し、同じ位置か又はフィッティングポイント寄りの位置にする。
【００３６】
以下に実際の設計例を参照しながら本発明を説明する。ただし、この設計例はほんの一例に過ぎず、本発明がこの例に限定されるものでは無い。
【００３７】
【実施例】
球面度数０．０、乱視度数０．０、加入度２．０Ｄのレンズを、従来の方法と本発明による方法でそれぞれ構成した。実施例は、本発明に基づく両面累進レンズであり、第１面が面加入度−１．０Ｄであり、面平均屈折力が遠用部から近用部にかけて連続的に減少しているリグレッシブ累進面、第２面が面加入度＋３．０Ｄのプログレッシブ累進面である。従来例１は、従来の外面累進レンズであり、第１面が面加入度＋２．０Ｄの累進面、第２面が球面である。従来例２は、従来の内面累進レンズであり、第１面が球面、第２面が面加入度＋２．０Ｄの累進面である。従来例３は、特開２０００−２４９９９２号公報に基づく従来例の両面累進レンズであり、第１面が面加入度＋３．０Ｄのプログレッシブ累進面、第２面が面加入度−１．０Ｄのリグレッシブ累進面である。
【００３８】
実施例の両面累進レンズの第１面の面形状の座標値を図３に、第２面の面形状の座標値を図４にそれぞれ示す。面形状の座標軸は、第１面の最も凸になっている点を原点として光軸と直交する面の水平方向をｘ軸、垂直方向をｙ軸、光軸と平行なｚ軸であり、ｚ軸は眼球側がプラスになっている。
【００３９】
遠用部と近用部のそれぞれの像倍率を求め、それらの差を外面累進を基準にし

例の両面累進レンズの中心点から１０ｍｍ下の水平線上の第１面と第２面の平均面屈折力分布のグラフを示す。図６に、従来例３の両面累進レンズのレンズ中心から１０ｍｍ下の水平線上の第１面と第２面の平均面屈折力分布のグラフを示す。実施例の両面累進レンズの第１面の面収差分布を図７に、第２面の面収差分布を図８に、第１面と第２面の透過収差分布を図９に示す。従来例３の両面累進レンズの第１面の面収差分布を図１０に、第２面の面収差分布を図１１に、第１面と第２面の透過収差分布を図１２に示す。
【００４０】
【表１】

【００４１】
遠用部と近用部の倍率の差は、実施例では、０．０２９３、従来例１では０．０３５０、従来例２では、０．０３１２、従来例３では、０．０３６９となっている。従来例１を基準にして、従来例２では、１０．９％の改善、実施例では、１６．２％の改善となっているが、従来例３では、５．４％の悪化となっている。これは、従来例３と実施例の両方とも両面累進レンズであるが、第１面の平均面屈折力の変化Ａ１が従来例３ではプラスであるのに対し、実施例ではマイナスであることが原因である。近用部の倍率差を小さくして、歪みを減少させるためには、第１面の平均面屈折力の変化がマイナスであることが必要である。
【００４２】
また、レンズを透して見た時の最大収差量は、実施例で２．４１Ｄ、従来例１で２．５２Ｄ、従来例２で２．４６Ｄと、同程度の量であるのに対し、従来例３では、３．５２Ｄと多くなっている。
【００４３】
図５に示すように、実施例の両面累進レンズの第１面のＳ１と第２面のＳ２と

面の累進屈折面と第２面の累進屈折面とは設計が近似していることが認められる。
【００４４】

値は０．２９である。第１面の累進屈折面と第２面の累進屈折面の設計が異なることが認められる。図１２に示した従来例３の透過収差図から、近用部の側方に不自然な収差領域が出来てしまうことが判る。これに対し、図９に示した実施例の透過収差図から、本発明の両面累進レンズは自然な収差分布になっていることが判る。不自然な収差分布が生じてしまう原因は、従来例３では、１面にソフト設計の累進面、２面にハ−ド設計の累進面を用いており、１面と２面の面収差分布が整合しておらず、うまく打ち消し合わない所が生じてしまうことにある。これを解決するためには、本発明の両面累進レンズのように、両面の平均面屈折力分布が相似していることが必要である。
【００４５】
【発明の効果】
本発明の累進屈折力レンズは、累進屈折力レンズに必然的に生じる像の歪みやボケを減少させ、装用感を向上させることができる。
【００４６】
本発明の老視用眼鏡は、かかる累進屈折力レンズを用いているため、装用感に優れる。
【００４７】
本発明のレンズの設計方法によれば、装用感に優れる両面累進レンズを設計することができる。
【図面の簡単な説明】
【図１】外面累進レンズ、内面累進レンズ、両面累進レンズのそれぞれの遠用部に対する近用部の倍率を示すグラフである。
【図２】眼鏡レンズによる屈折により外面と内面との間に光軸との平行線を基準にするとずれが生じることを説明する概念図である。
【図３】実施例の両面累進レンズの第１面の面形状を示す座標値である。
【図４】実施例の両面累進レンズの第２面の面形状を示す座標値である。
【図５】実施例の両面累進レンズの面平均屈折力の分布を示すグラフである。
【図６】従来例３の両面累進レンズの面平均屈折力の分布を示すグラフである。
【図７】実施例の両面累進レンズの第１面の面収差分布図である。
【図８】実施例の両面累進レンズの第２面の面収差分布図である。
【図９】実施例の両面累進レンズの透過収差分布図である。
【図１０】従来例３の両面累進レンズの第１面の面収差分布図である。
【図１１】従来例３の両面累進レンズの第２面の面収差分布図である。
【図１２】従来例３の両面累進レンズの透過収差分布図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a progressive power lens with improved image performance and improved optical performance, presbyopic glasses incorporating the same into a frame, and a lens design method.
[0002]
[Prior art and problems to be solved by the invention]
The frequency changes continuously between the distance portion used mainly when viewing objects at a long distance, the near portion used mainly when looking at objects at a short distance, and the distance portion and the near portion. A progressive-power lens with a progressive-refraction surface with a progressive zone has a region that causes image distortion and blurring in the near side, regardless of the design of the progressive-refraction surface, reducing the user's wearing feeling Was invited. This optical defect is inevitably generated as long as the progressive refractive surface is used, and is essentially difficult to reduce to zero. Conventionally, various approaches have been made to eliminate this drawback.
[0003]
As one of them, the idea of a double-sided progressive lens that improves optical performance by providing a progressive surface provided on either the outer surface side or the inner surface side of a spectacle lens on both sides is disclosed in WO97 / 19383 and JP2000-2000-A. This is disclosed in Japanese Patent No. 249992.
[0004]
In WO97 / 19383, when the addition of the lens is Add, the surface addition A1 of the outer surface (first surface) is
− (L · N / T) Add <A1 <Add
It describes a double-sided progressive lens that satisfies Where L is the apex distance, N is the refractive index of the lens, and T is the center thickness of the lens. However, WO97 / 19383 proposes the concept of a double-sided progressive lens, but does not describe the design contents of each progressive surface.
[0005]
Japanese Patent Laid-Open No. 2000-249992 describes a case where the inner surface (second surface) is a regressive surface, that is, a case where the surface addition A2 of the inner surface satisfies A2 <0. At this time, the surface addition degree A1 of the outer surface becomes Add <A1. Further, in Japanese Patent Application Laid-Open No. 2000-249992, astigmatism generated on the outer surface and the inner surface can be reduced by making the outer progressive surface (the surface addition A1 is positive) a soft design and the inner progressive surface a hard design. The idea of canceling out and reducing the amount of aberration as a lens is disclosed.
[0006]
However, as a result of detailed studies by the present inventor, it has been found that a spectacle lens having a good wearing feeling cannot be obtained with this lens configuration. That is, the region where astigmatism is canceled out is only a limited range in the lens surface, and in other regions, a large astigmatism is left rather than a single-sided progressive surface lens. In addition, since the amount of astigmatism changes greatly, the distortion of the image also increases locally, resulting in a state where the feeling of wearing is greatly impaired.
[0007]
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a progressive power lens capable of reducing image distortion and blur that inevitably occur in a progressive power lens and improving wearing feeling. And
[0008]
It is another object of the present invention to provide presbyopia glasses in which such a progressive power lens is incorporated in a frame.
[0009]
Furthermore, an object of the present invention is to provide a method for designing a progressive-power lens having an excellent wearing feeling.
[0010]
[Means for Solving the Problems]
In the past, the progressive surface of the progressive-power lens was formed on the outer surface side, but it has been found that the optical performance is dramatically improved by forming the progressive surface on the inner surface side. In order to apply this inner surface progressive lens theory and further improve the optical performance, in the present invention, a double-sided progressive lens is formed with a progressive refractive surface on both the outer surface and the inner surface, and the average surface refractive power of the outer surface is increased. The distance is set to decrease continuously from the distance portion to the near portion.
[0011]
By making the change in the average surface refractive power of the outer surface of such a double-sided progressive lens negative, that is, by making the surface addition of the outer surface negative, the magnification difference in the near portion can be reduced and distortion can be reduced. it can.
[0012]
In addition, when providing progressive refracting surfaces on both sides of the lens, it has been found that by making the progressive design on both sides almost the same, optical performance is improved without causing unnatural shaking and distortion.
[0013]
Further, in order to exert the effect of progressive progression on both sides, the difference between the average surface power PF1 (D) at the center of the distance portion on the outer surface and the average surface power PN1 (D) at the center of the near portion on the outer surface (A1 = PN1-PF1) needs to have a certain size, and if there is too much difference, it is not preferable in terms of the appearance of the lens. For this reason, it is preferable that the value of A1 exists in the range of -PF1-10.0 <A1 <-0.25 (D).
[0014]
In addition, since a progressive refracting surface is formed on each of the outer surface and the inner surface of the double-sided progressive lens, the distance viewing range, the near viewing range, and the progressive bands of these progressive refracting surfaces appear to overlap each other. This improves the feeling of wearing. Therefore, in consideration of refraction by the lens, it is preferable that the progressive refracting surface on the inner surface is closer to the fitting point than the progressive refracting surface on the outer surface.
[0015]
Therefore, the progressive-power lens of the present invention mainly includes a distance portion used when viewing an object at a long distance, a near portion used mainly when viewing an object at a short distance, the distance portion, and the near portion. In a progressive-power lens having a progressive addition surface having a progressive zone whose power continuously changes between the object portion and the use portion, the object side refractive surface is the first surface, and the user side refractive surface is the second surface. Then, both the first surface and the second surface are formed as progressive refracting surfaces, and the average surface refractive power of the first surface continuously decreases from the distance portion to the near portion , The difference between the average surface refractive power PF1 (D) at the center of the distance portion of the first surface and the average surface power PN1 (D) at the center of the near portion of the first surface is defined as a surface addition A1 (= PN1−PF1). ), And a value obtained by dividing the difference between the average surface refractive powers P1 and PF1 at an arbitrary point on the first surface by A1 is S1. S1 = (P1−PF1) / A1 Average surface refractive power PF2 (D) at the distance portion center of the second surface and average surface power PN2 (D) at the near portion center of the second surface Is the surface addition power A2 (PN2-PF2), and the value obtained by dividing the difference between the average surface refractive power P2 and the PF2 at the point on the second surface corresponding to the point on the first surface by A2 is S2. S2 = (P2-PF2) / A2 Within a range of 40 mm from the center on the lens surface, | S1-S2 | ≦ 0.25. However, the average surface refractive power P (D) at a certain point on the progressive refraction surface is expressed by the maximum curvature value Cmax (1 / m), the minimum curvature value Cmin (1 / m) at that point, and the progressive refraction surface. Using the refractive index N1 of the medium on the object side and the refractive index N2 of the medium on the user side, P = (N2−N1) (Cmax + Cmin) / 2.
[0017]
In the progressive-power lens of the present invention, the average surface refractive power at the center of the distance portion of the first surface is PF1 (D), and the average surface power at the center of the near portion of the first surface is PN1 (D). When the surface addition A1 of the first surface is A1 = PN1-PF1, it is preferable that -PF1-10.0 <A1 <-0.25 (D) .
[0018]
In the progressive-power lens according to the present invention, a parallel line with the optical axis of the lens passing through the distance portion center point of the second surface is an optical axis of the lens passing through the distance portion center point of the first surface. The parallel line with the optical axis of the lens passing through the center of the near part of the second surface is the same position or near the fitting point with respect to the parallel line of the first surface. It is preferable to be at the same position or a position closer to the fitting point with respect to a parallel line with the optical axis of the lens passing through the center point .
[0019]
In the presbyopic glasses of the present invention , it is preferable that the progressive-power lens described in any of the foregoing is processed into a target lens shape and incorporated into a frame .
[0020]
The progressive power lens design method of the present invention includes a distance portion mainly used when viewing an object at a long distance, a near portion mainly used when viewing an object at a short distance, the distance portion, A progressive power lens design method having a progressive addition surface having a progressive zone whose power changes continuously with a near portion, wherein the object side refractive surface is the first surface and the user side refraction is When the surface is the second surface, both the first surface and the second surface are formed as progressive refractive surfaces, and the average surface refractive power of the first surface is extended from the distance portion to the near portion. The difference between the average surface refractive power PF1 (D) at the center of the distance portion of the first surface and the average surface power PN1 (D) at the center of the near portion of the first surface is decreased continuously. A1 (= PN1−PF1), and the difference between the average surface power P1 and PF1 at any point on the first surface is divided by A1. S1 = (P1−PF1) / A1 Average surface power PF2 (D) at the center of the distance portion of the second surface and average surface power of the second surface at the center of the near portion The difference in PN2 (D) is defined as a surface addition A2 (PN2-PF2), and the difference between the average surface power P2 and the PF2 at a point on the second surface corresponding to the point on the first surface is divided by A2. S2 = (P2−PF2) / A2 where 40 mm from the center on the lens surface, and | S1−S2 | ≦ 0.25 is designed. However, the average surface refractive power P (D) at a certain point on the progressive refraction surface is expressed by the maximum curvature value Cmax (1 / m), the minimum curvature value Cmin (1 / m) at that point, and the progressive refraction surface. Using the refractive index N1 of the medium on the object side and the refractive index N2 of the medium on the user side, P = (N2−N1) (Cmax + Cmin) / 2 .
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.
[0023]
The progressive power lens is a continuous distance between the distance portion and the near portion, and the distance portion used mainly when viewing an object at a long distance, the near portion mainly used when looking at an object at a short distance, and the distance portion. A progressive refracting surface having a progressive zone of varying power. Progressive power lenses include an outer surface progressive lens with a progressive refractive surface only on the outer surface (first surface), an inner surface progressive lens with a progressive refractive surface only on the inner surface (second surface), and progressive on both the outer and inner surfaces. There are three types of double-sided progressive lenses provided with a refractive surface.
[0024]
In such a progressive-power lens, there is a region that inevitably causes image shaking and distortion at the near side portion. This is because the size of the apparent image is different because the lens power is different between the distance portion and the near portion. In order to suppress the distortion of the image, the images of the distance portion and the near portion should be as large as possible. The apparent magnification of the image (SM: Spectacle Magnification) is expressed by the following equation using the paraxial amount.
[0025]
SM = Ms × Mp (1)
Ms = 1 / (1-tD / n): Shape factor-
Mp = 1 / (1-LP): Power factor
t: lens thickness (m), n: refractive index, D: outer surface refractive power (diopter: D), L: distance from lens to pupil (m), P: lens power (dioptre: D)
[0026]
If the magnification of the distance portion and the magnification of the near portion are calculated according to the above formula and the difference is obtained, the degree of distortion of the side portion can be inferred. When comparing an outer surface progressive lens, an inner surface progressive lens, and a double-sided progressive lens having the same power, the same addition, and substantially the same lens shape, the difference in Mp between the distance portion and the near portion is the same for each lens. On the other hand, the value of Ms varies depending on which surface has the progressive surface. In the outer surface progressive lens, since the average surface refractive power of the first surface (outer surface) increases from the distance portion to the near portion, the value of Ms increases in the near portion. On the other hand, since the inner surface progressive lens uses a spherical surface for the first surface, the average surface refractive power is the same in both the distance portion and the near portion, and the value of Ms is also constant.
[0027]
In the double-sided progressive lens according to the present invention, the average surface refractive power P (D) of the first surface (outer surface) continuously decreases from the distance portion to the near portion (regressive surface). In contrast, the average surface refractive power of the second surface (inner surface) continuously increases from the distance portion to the near portion (progressive surface). As a result, the value of Ms also decreases. Therefore, the double-sided progressive lens of the present invention can further reduce the shaking and distortion and improve the optical performance as compared with the inner surface progressive lens.
[0028]
However, the average surface refractive power P (D) at a certain point on the progressive curved surface has a maximum value Cmax (1 / m) of curvature at that point, a minimum value Cmin (1 / m) of curvature, and the object side from the curved surface. Using a refractive index N1 of a certain medium and a refractive index N2 of a medium on the user side, P = (N2−N1) (Cmax + Cmin) / 2. The curvature has a positive sign when the center of curvature is on the user side from the surface and a negative sign when the center is on the object side. Therefore, when the spectacle lens has a meniscus shape, the average curvature (Cmax + Cmin) / 2 is a positive value. In the case of the first surface, since the medium on the object side from the surface is air, N1 is 1.0 and N2 is the refractive index of the lens material, so the value of P is positive. On the other hand, on the second surface, N1 is the refractive index of the lens material and N2 is 1.0, so the value of P is negative.
[0029]
FIG. 1 is a graph showing the magnification ratio of the distance portion and the near portion of the outer surface progressive lens, the inner surface progressive lens, and the double-sided progressive lens of the present invention. It is recognized that the double-sided progressive lens of the present invention has a smaller magnification difference and less distortion than the conventional outer surface progressive lens and inner surface progressive lens.
[0030]
Furthermore, in the case of a double-sided progressive lens, since progressive refracting surfaces are formed on both the first surface and the second surface, the degree of freedom in design is high. Progressive surface design is a major factor that affects wearing comfort. There are various factors in the progressive surface design, but broadly divided into hard design that prioritizes the area of clear vision and soft design that prioritizes distortion reduction. The type of progressive surface design that is selected depends on the user's preference and application, but in the case of a double-sided progressive lens, astigmatism and image distortion can be reduced by combining progressive surface designs with different characteristics. It turned out to be natural and the feeling of wearing became very bad. In Japanese Patent Laid-Open No. 2000-249992, a hard design with a small addition and a soft design with a large addition are used for the purpose of canceling astigmatism generated on the first surface and the second surface and reducing the amount of aberration. Combined. However, in this case, astigmatism is canceled if one point on the progressive surface is considered, but large astigmatism remains in other places. Since the distribution of the remaining astigmatism is significantly different from that of the conventional progressive lens, the image distortion becomes very unnatural. In addition, since the width of the clear vision area is limited by the soft design surface having a large addition power, it becomes narrower than the conventional progressive surface outer lens having the same addition power.
[0031]
Thus, in the case of a double-sided progressive lens, it is preferable that the progressive design of the first surface and the second surface be as similar as possible. For this purpose, it is desirable that the average surface refractive power distributions of both surfaces are similar. Specifically, a value obtained by dividing the difference between the average surface power P1 at an arbitrary point on the first surface and the average surface power PF1 at the center of the distance portion by the addition power A1 of the first surface is S1, and similarly A value obtained by dividing the difference between the average surface power P2 at the point on the second surface corresponding to the point on the first surface and the average surface power PF2 at the center of the distance portion by the addition A2 of the second surface is S2. . That is, when expressed by an expression, S1 = (P1-PF1) / A1 and S2 = (P2-PF2) / A2. At this time, regardless of the type of progressive surface and the addition power of the surface, the values of S1 and S2 are 0 at the distance center point, 1 at the near center point, and take values between them at other locations. . In order for the progressive design of the first surface and the second surface to be similar, the values of S1 and S2 must be close.

It is desirable that it is within 5, preferably within 0.15, more preferably within 0.10, and most preferably within 0.05.
[0032]
Further, in order to exert the effect of progressive progression on both sides, the difference between the average surface power PF1 (D) at the center of the distance portion on the outer surface and the average surface power PN1 (D) at the center of the near portion on the outer surface (A1 = PN1-PF1), that is, the addition needs to have a certain degree of magnitude, and if there is too much difference, it is not preferable in terms of the appearance of the lens. Therefore, the value of the addition A1 is
-PF1-10.0 <A1 <-0.25 (D)
It is preferable to be within the range.
[0033]
Further, since the double-sided progressive lens is provided with progressive refracting surfaces on both the first surface and the second surface of the lens, the distance portion visual field range, the near portion visual range range and Wearing feeling is improved by the progressive zones appearing to overlap each other. As shown in FIG. 2, at a point away from the fitting point FP, the light beam L <b> 1 incident on the eye passes through the lens 10 obliquely. For this reason, when the progressive design of the first surface 11 and the second surface 12 is approximate, providing the progressive refracting surfaces on both sides with reference to the parallel line L2 to the optical axis, the first surface 11 and the second surface 12 Accordingly, the far field areas of the progressive refracting surfaces, the near area fields of view, and the progressive bands are optically shifted from each other, and the feeling of wearing becomes worse. For this reason, fitting is performed in consideration of the inclination of the light rays with respect to the distance-point center point and the near-point center point of the first surface that face the distance-point center point of the second surface 12 and the near-point center point NP. It is desirable to provide at a distance portion center point (not shown) and a near portion center point NP ′ that are close to the point.
[0034]
As a design method of the lens surface shape of such a double-sided progressive lens, it is preferable to design so as to satisfy the following conditions (1) to (3). However, the order of (2) and (3) below can be interchanged.
[0035]
(1) When the object-side refracting surface is the first surface and the user-side refracting surface is the second surface, both refractive surfaces of the lens are progressive refracting surfaces, and the surface addition power A1 of the first surface is negative. The surface addition A2 of the second surface is A2 = Add−A1. Where Add is the addition power of the lens.
(2) The parallel line with the optical axis of the lens passing through the distance point center point of the second surface is at the same position as the parallel line with the optical axis of the lens passing through the distance point center point of the first surface, or Set the position closer to the fitting point.
(3) The parallel line with the optical axis of the lens passing through the near-point center point of the second surface is the same position as the parallel line with the optical axis of the lens passing through the near-point center point of the first surface, or Set the position closer to the fitting point.
[0036]
The present invention will be described below with reference to actual design examples. However, this design example is only an example, and the present invention is not limited to this example.
[0037]
【Example】
Lenses having a spherical power of 0.0, an astigmatism power of 0.0, and an addition power of 2.0D were constructed by the conventional method and the method according to the present invention, respectively. The embodiment is a double-sided progressive lens according to the present invention, wherein the first surface has a surface addition power of −1.0 D, and the surface average refractive power continuously decreases from the distance portion to the near portion. The progressive surface and the second surface are progressive progressive surfaces with a surface addition of + 3.0D. Conventional Example 1 is a conventional outer surface progressive lens, where the first surface is a progressive surface with a surface addition of + 2.0D, and the second surface is a spherical surface. Conventional Example 2 is a conventional inner surface progressive lens, in which the first surface is a spherical surface and the second surface is a progressive surface with a surface addition of + 2.0D. Conventional Example 3 is a conventional double-sided progressive lens based on Japanese Patent Application Laid-Open No. 2000-249992, where the first surface has a progressive progressive surface with a surface addition of + 3.0D, and the second surface has a surface addition of -1.0D. It is a progressive progressive surface.
[0038]
FIG. 3 shows coordinate values of the surface shape of the first surface of the double-sided progressive lens of the embodiment, and FIG. 4 shows coordinate values of the surface shape of the second surface. The coordinate axis of the surface shape is the z axis parallel to the optical axis, the horizontal direction of the surface perpendicular to the optical axis is the x axis, the vertical direction is the y axis, and the z axis is parallel to the optical axis. The axis is positive on the eyeball side.
[0039]
Obtain the image magnification of each of the distance and near-use parts, and use the difference between them as the basis of the outer surface progression.

The graph of the average surface refractive power distribution of the 1st surface and the 2nd surface on the horizontal line 10 mm below from the center point of the double-sided progressive lens of an example is shown. FIG. 6 shows a graph of the average surface power distribution of the first surface and the second surface on the horizontal line 10 mm below the lens center of the double-sided progressive lens of Conventional Example 3. FIG. 7 shows the surface aberration distribution of the first surface of the double-sided progressive lens of the example, FIG. 8 shows the surface aberration distribution of the second surface, and FIG. 9 shows the transmission aberration distribution of the first surface and the second surface. The surface aberration distribution of the first surface of the double-sided progressive lens of Conventional Example 3 is shown in FIG. 10, the surface aberration distribution of the second surface is shown in FIG. 11, and the transmission aberration distribution of the first surface and the second surface is shown in FIG.
[0040]
[Table 1]

[0041]
The difference in magnification between the distance portion and the near portion is 0.0293 in the embodiment, 0.0350 in the conventional example 1, 0.0312 in the conventional example 2, and 0.0369 in the conventional example 3. . Based on the conventional example 1, the improvement in the conventional example 2 is 10.9%, and in the example, the improvement is 16.2%, but in the conventional example 3, the deterioration is 5.4%. Yes. This is a double-sided progressive lens in both the conventional example 3 and the example, but the change A1 in the average surface refractive power of the first surface is positive in the conventional example 3, whereas it is negative in the example. Responsible. In order to reduce the magnification difference in the near portion and reduce the distortion, it is necessary that the change in the average surface refractive power of the first surface is negative.
[0042]
The maximum amount of aberration when viewed through the lens is 2.41D in the example, 2.52D in the conventional example 1, and 2.46D in the conventional example 2. In Conventional Example 3, it is as large as 3.52D.
[0043]
As shown in FIG. 5, S1 of the first surface and S2 of the second surface of the double-sided progressive lens of Example

It can be seen that the progressive refracting surface of the surface and the progressive refracting surface of the second surface are close in design.
[0044]

The value is 0.29. It can be seen that the design of the progressive refractive surface of the first surface and the progressive refractive surface of the second surface are different. From the transmission aberration diagram of Conventional Example 3 shown in FIG. 12, it can be seen that an unnatural aberration region is formed on the side of the near portion. In contrast, the transmission aberration diagram of the embodiment shown in FIG. 9 shows that the double-sided progressive lens of the present invention has a natural aberration distribution. The reason why the unnatural aberration distribution occurs is that, in the conventional example 3, the progressive surface of the soft design is used for one surface, and the progressive surface of the hard design is used for two surfaces. Are inconsistent, and there is a place where they do not cancel each other well. In order to solve this, like the double-sided progressive lens of the present invention, it is necessary that the average surface power distribution on both sides is similar.
[0045]
【The invention's effect】
The progressive-power lens of the present invention can reduce image distortion and blur that inevitably occur in the progressive-power lens, and can improve wearing feeling.
[0046]
Since the presbyopic glasses of the present invention use such a progressive power lens, they are excellent in wearing feeling.
[0047]
According to the lens designing method of the present invention, it is possible to design a double-sided progressive lens with excellent wearing feeling.
[Brief description of the drawings]
FIG. 1 is a graph showing the magnification of a near portion with respect to a distance portion of each of an outer surface progressive lens, an inner surface progressive lens, and a double-sided progressive lens.
FIG. 2 is a conceptual diagram for explaining that a shift occurs between an outer surface and an inner surface based on a parallel line with an optical axis due to refraction by a spectacle lens.
FIG. 3 is a coordinate value showing the surface shape of the first surface of the double-sided progressive lens of Example.
FIG. 4 is a coordinate value showing the surface shape of the second surface of the double-sided progressive lens of Example.
FIG. 5 is a graph showing a distribution of surface average refractive power of a double-sided progressive lens according to an example.
6 is a graph showing a distribution of surface average refractive power of a double-sided progressive lens according to Conventional Example 3. FIG.
FIG. 7 is a surface aberration distribution diagram of the first surface of the double-sided progressive lens of Example.
FIG. 8 is a surface aberration distribution diagram of the second surface of the double-sided progressive lens of Example.
FIG. 9 is a transmission aberration distribution diagram of the double-sided progressive lens of Example.
10 is a surface aberration distribution diagram of a first surface of a double-sided progressive lens of Conventional Example 3. FIG.
11 is a surface aberration distribution diagram of the second surface of the double-sided progressive lens of Conventional Example 3. FIG.
12 is a transmission aberration distribution diagram of the double-sided progressive lens of Conventional Example 3. FIG.

Claims

The distance between the distance portion used mainly when viewing an object at a long distance, the near portion used mainly when viewing an object at a short distance, and the distance portion between the distance portion and the near portion. In a progressive power lens having a progressive refractive surface with a progressive zone that varies,
When the object-side refractive surface is the first surface and the user-side refractive surface is the second surface, both the first surface and the second surface are formed as progressive refractive surfaces,
And the average surface refractive power of the first surface continuously decreases from the distance portion to the near portion ,
The difference between the average surface refractive power PF1 (D) at the center of the distance portion of the first surface and the average surface power PN1 (D) at the center of the near portion of the first surface is defined as a surface addition A1 (= PN1−PF1). )age,
A value obtained by dividing the difference between the average surface power P1 and PF1 at an arbitrary point on the first surface by A1 is S1,
S1 = (P1-PF1) / A1
The difference between the average surface power PF2 (D) at the center of the distance portion of the second surface and the average surface power PN2 (D) at the center of the near portion of the second surface is expressed as a surface addition A2 (PN2-PF2). )age,
When the value obtained by dividing the difference between the average surface refractive power P2 and the PF2 at the point on the second surface corresponding to the point on the first surface by A2 is S2,
S2 = (P2-PF2) / A2
Within a range of 40 mm from the center on the lens surface,
│S1-S2│ ≦ 0.25
A progressive-power lens characterized by that.
However, the average surface refractive power P (D) at a certain point on the progressive refraction surface is expressed by the maximum curvature value Cmax (1 / m), the minimum curvature value Cmin (1 / m) at that point, and the progressive refraction surface. Using the refractive index N1 of the medium on the object side and the refractive index N2 of the medium on the user side,
P = (N2-N1) (Cmax + Cmin) / 2
Defined by

The progressive-power lens according to claim 1,
The average surface refractive power at the center of the distance portion of the first surface is PF1 (D), and the average surface power at the center of the near portion of the first surface is PN1 (D). If the degree A1 is A1 = PN1-PF1 ,
-PF1-10.0 <A1 <-0.25 (D)
Progressive-power lens, characterized in that it.

The progressive-power lens according to claim 1 or 2,
Is the parallel line with the optical axis of the lens passing through the central point of the distance portion of the second surface the same position as the parallel line with the optical axis of the lens passing through the central point of the distance portion of the first surface? Or near the fitting point,
Is the parallel line with the optical axis of the lens passing through the near-point center point of the second surface the same position as the parallel line with the optical axis of the lens passing through the near-point center point of the first surface? Or a progressive-power lens characterized by being located closer to the fitting point .

Presbyopic glasses, wherein the progressive-power lens according to any one of claims 1 to 3 is processed into a target lens shape and incorporated into a frame.

The distance between the distance portion used mainly when viewing an object at a long distance, the near portion used mainly when viewing an object at a short distance, and the distance portion between the distance portion and the near portion. A progressive power lens design method having a progressive addition surface with a progressive zone that varies,
  When the object-side refractive surface is the first surface and the user-side refractive surface is the second surface, both the first surface and the second surface are formed as progressive refractive surfaces,
  And the average surface refractive power of the first surface is continuously decreased from the distance portion to the near portion,
  Average surface refractive power PF1 (D) at the center of the distance portion of the first surface and the near portion of the first surface The difference in average surface refractive power PN1 (D) at the center is defined as a plane addition power A1 (= PN1-PF1),
  A value obtained by dividing the difference between the average surface power P1 and PF1 at an arbitrary point on the first surface by A1 is S1,
  S1 = (P1-PF1) / A1
  The difference between the average surface power PF2 (D) at the center of the distance portion of the second surface and the average surface power PN2 (D) at the center of the near portion of the second surface is expressed as a surface addition A2 (PN2-PF2). )age,
  When the value obtained by dividing the difference between the average surface refractive power P2 and the PF2 at the point on the second surface corresponding to the point on the first surface by A2 is S2,
  S2 = (P2-PF2) / A2
Within a range of 40 mm from the center on the lens surface,
  │S1-S2│ ≦ 0.25
Design method for progressive-power lens,
  However, the average surface refractive power P (D) at a certain point on the progressive refraction surface is expressed by the maximum curvature value Cmax (1 / m), the minimum curvature value Cmin (1 / m) at that point, and the progressive refraction surface. Using the refractive index N1 of the medium on the object side and the refractive index N2 of the medium on the user side,
  P = (N2-N1) (Cmax + Cmin) / 2
Defined by