JP2004262734A - Method of forming optical lens and metal mold for optical lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an optical lens and a metal mold for the optical lens by which the center of a 1st surface of the optical lens does not deviate from the center of a 2nd surface in forming the optical lens (for example, an objective lens) using an optical glass base material. <P>SOLUTION: In the formation of the optical lens 1 by butting a 1st lens transfer surface 21e formed at the end part of a cylindrical part 21c of a 1st core 21 to a 2nd lens transferring surface 31e formed at the end part of a cylindrical part 31c of a second core 31, a plurality of ball bearings 34 are moved to be integrated with a retainer 33 of a ball bearing body BB along the inner peripheral surface of a bottom hole 30e of the metal mold 30 to the side where the 1st and the 2nd cores are butted to each other in accordance with the inserting action of the spherical optical glass based material 23 into the ball bearing body BB of the 1st core 21 placed on the 1st lens transfer surface 21e. Simultaneously the plurality of ball bearings 34 are elastically displaced in the diameter direction of the 2nd core to give pre-load to each cylindrical part of the 1st and 2nd ball bearings to eliminate the clearance for sliding between respective cylindrical parts of the 1 st and 2nd cores for the plurality of ball bearings. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

また、対物レンズ１及び超高密度光ディスク２の設計値の一例を下記の表２に示す。
【００３４】
【表２】

また、対物レンズ１の第１面１ａの非球面係数の一例を下記の表３に示す。
【００３５】
【表３】

また、対物レンズ１の第２面１ｂの非球面係数の一例を下記の表４に示す。
【００３６】
【表４】

そして、上記のように対物レンズ１の各値を設定して設計した時に、理論上でのコマ収差，色収差を押さえることができるもの、成形時に対物レンズ１の第１面１ａの中心と、第２面１ｂの中心との位置ズレ量（偏心量）は光学レンズ用金型の構造形態により左右される。ここで、超高密度光ディスク２の信号面２ｂが１層構造の場合に、上記した位置ズレ量（偏心量）は設計上で±３μｍ以下が要求されており、更に、ここでの図示を省略するものの超高密度光ディスク２の信号面が第１信号面と、この第１信号面から僅かの間隔を隔てた第２信号面とからなる２層構造の場合もあり、この２層構造の場合に上記した位置ズレ量（偏心量）は設計上で±１μｍ以下が要求されている。
【００３７】
上記した位置ズレ量（偏心量）の要求に伴って、本発明に係る光学レンズの成形方法及び光学レンズ用金型について以下説明する。
【００３８】
＜第１実施例＞
図２は本発明に係る第１実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図、
図３は本発明に係る第１実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図、
図４は本発明に係る第１実施例において、図２及び図３に示したボールべアリング体と、第１コア（下コア）と、第２コア（上コア）とをそれぞれ示した斜視図、
図５は本発明に係る第１実施例において、第２金型の有底孔内に嵌め込んだボールべアリング体のリテーナーに支持した複数のボールべアリングに沿って第１コアを挿入した際に、第１コアの移動量と最下部のボールべアリングの移動量とを説明するために模式的に示した図である。
【００３９】
図２及び図３に示した如く、本発明に係る第１実施例の光学レンズ用金型１０Ａは、主として光学ガラス素材を用いて少なくとも一つの面が非球面を有する光学レンズ（例えば、対物レンズ）を成形するにあたって、光学レンズの第１面の中心と、第２面の中心とが位置ズレすることなく成形できるように構成されているものである。
【００４０】
即ち、図２に示した如く、本発明に係る第１実施例の光学レンズ用金型１０Ａでは、第１金型（下型）２０に固着させた第１コア（下コア）２１の円筒部２１ｃの上端部２１ｄに非球面を有して形成した第１レンズ転写面２１ｅと、第２金型（下型）３０に固着させた第２コア（上コア）３１の円筒部３１ｃの下端部３１ｄに非球面を有して形成した第２レンズ転写面３１ｅとを同一中心軸上で互いに離間して対向させ、且つ、光学レンズ１の成形時に第２金型３０の有底孔３０ｅ内に嵌め込んだ円筒状のボールべアリング体ＢＢのリテーナー３３に支持した複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させて第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に予圧をかけることで、複数のボールべアリング３４への第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの摺動用スキマを無くすように成したものである。そして、成形前の初期状態時に、第１コア２１を第２コア３１の下方で待機させ、一方、成形時には第１コア２１を第２コア３１に対して第１，第２金型２０，３０間に設けた不図示のガイドシャフトにより位置決めしながら上動させて第１，第２金型２０，３０同士を合体可能に構成したものである。
【００４１】
尚、この第１実施例では、第１金型（下型）２０を可動側とし、且つ、第２金型（上型）３０を固定側として以下説明するものの、第１金型２０を固定側とし、第２金型３０を可動側とすることで、第２金型３０を第１金型２０に向けて下動させても良いものである。
【００４２】
まず、上記した第１金型２０は、下面２０ａ側に大径な鍔部２０ｂが形成され、且つ、鍔部２０ｂの上方に鍔部２０ｂより小径な円筒部２０ｃが同心的に上方に向かって短尺に形成されている。また、第１金型２０の円筒部２０ｃの上面２０ｄの中心部に有底孔２０ｅが穿設されている。
【００４３】
また、第１金型２０に穿設した有底孔２０ｅ内に、第１コア２１の下面２１ａ側に形成した鍔部２１ｂがクリアランスなく嵌め込まれて、第１コア２１の下面２１ａを第１金型２０の下面２０ａ側からネジ２２により第１金型２０に対して固着している。
【００４４】
また、第１コア２１は、下面２１ａ側に形成した鍔部２１ｂの上方に円筒部２１ｃが、鍔部２１ｂより小径な軸径Ｄ２で寸法精度良く第２金型３０側に向かって長尺に形成されていると共に、この円筒部２１ｃの上端部２１ｄのコーナーを僅かにＲ取り又は面取りし、且つ、上端部２１ｄの中心部に第１レンズ転写面２１ｅが所定の厚みを持って凹状に形成されている。この第１コア２１の第１レンズ転写面２１ｅは、超硬合金又はセラミックスなど硬質耐熱材を用いて、研削加工を施した上で光学ガラス素材２３が付着しないように耐摩耗性のある表面処理を行って、レンズ設計仕様に合わせた非球面となるように仕上げられている。この際、第１コア２１の第１レンズ転写面２１ｅは、成形前に質量を管理しながら予め真球に研磨加工を施した球状の光学ガラス素材２３が載置されると共に、成形時に先に図１を用いて説明した対物レンズ１の第１面１ａを転写するためのものである。
【００４５】
次に、上記した第２金型３０は、上面３０ａ側に大径な鍔部３０ｂが形成され、この下方に鍔部３０ｂより小径な円筒部３０ｃが鍔部３０ｂに対して同心的に第１金型２０側に向かって長尺に形成されていると共に、円筒部３０ｃの中心部に下面３０ｄから鍔部３０ｂに向かって有底孔３０ｅが寸法精度良く長尺に穿設されている。
【００４６】
また、第２金型３０に穿設した有底孔３０ｅ内の上方部位に、第２コア３１の上面３１ａ側に形成した鍔部３１ｂがクリアランスなく嵌め込まれて、第２コア３１の上面３１ａを第２金型３０の上面３０ａ側からネジ３２により第２金型３０に対して固着している。
【００４７】
また、第２コア３１は、上面３１ａ側に形成した鍔部３１ｂの下方に円筒部３１ｃが、鍔部３１ｂより小径で且つ第１コア２１の円筒部２１ｃと同径な軸径Ｄ２で寸法精度良く形成されていると共に、第２金型３０の有底孔３０ｅの長さの略半分程度の長さで有底孔３０ｅに対して同心的に第１金型２０側に向かって形成されている。また、第２コア３１の円筒部３１ｃの下端部３１ｄのコーナーを僅かにＲ取り又は面取りをし、且つ、下端部３１ｄの中心に第２レンズ転写面３１ｅが凹状に形成されている。この第２コア３１の第２レンズ転写面３１ｅも、超硬合金又はセラミックスなど硬質耐熱材を用いて、研削加工を施した上で光学ガラス素材２３が付着しないように耐摩耗性のある表面処理を行って、レンズ設計仕様に合わせた非球面となるように仕上げられている。この際、第２コア３１の第２レンズ転写面３１ｅは、成形時に先に図１を用いて説明した対物レンズ１の第２面１ｂを転写するためのものである。
【００４８】
また、第２金型３０に穿設した有底孔３０ｅ内には、予圧付加部材となる円筒状のボールべアリング体ＢＢが嵌め込まれている。このボールべアリング体ＢＢは、第１実施例の要部を構成するものであり、円筒状のリテーナー３３の周面に沿ってボール径Ｄ３に形成した複数のボールべアリング３４が支持されていると共に、リテーナー３３の周面の内周側と外周側とに各ボールべアリング３４の一部を回転可能に露出させた状態で、複数のボールべアリング３４が第２金型３０に穿設した有底孔３０ｅの内周面に沿って転動可能に嵌め込まれている。
【００４９】
そして、成形前の初期状態時に、ボールべアリング体ＢＢはリテーナー３３の上端側に支持したボールべアリング３４のいくつかを第２コア３１の円筒部３１ｃのうちで下端部３１ｄ側の外周面に添接させると共に、リテーナー３３の下端部をリテーナー支持板３５に当接させて、リテーナー３３の下端側に位置する残りのボールべアリング３４に対して第１コア２１の円筒部２１ｃの挿入を許容している。
【００５０】
ここで、図４に示した如く、ボールべアリング体ＢＢは、リテーナー３３及び複数のボールべアリング３４に対して成形時の金型温度に対して耐熱性を有する材料を用いている。更に、ボールべアリング体ＢＢは、複数のボールべアリング３４を円筒状のリテーナー３３の周面に沿って支持させる際に、複数のボールべアリング３４をリテーナー３３の軸方向に対して所定の角度傾斜した傾斜列に沿って配列させている。これにより、第１コア２１の円筒部２１ｃ及び第２コア３１の円筒部３１ｃを両端側から挿入した時に、リテーナー３３の内周側及び外周側に露出した複数のボールべアリング３４が第２金型３０に穿設した有底孔３０ｅの内周面及び第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に略均等の間隔で接することができるようになっている。
【００５１】
また、図５に示した如く、成形開始時に、第２金型３０の有底孔３０ｅ内に嵌め込んだボールべアリング体ＢＢ内に第１コア２１を挿入した時に、第１コア２１の円筒部２１ｃの上端部２１ｄがリテーナー３３に支持した複数のボールべアリング３４のうちで最下部のボールべアリング３４に当接した位置を起点位置とすると、この場合、第２金型３０の有底孔３０ｅの内周面は最下部のボールべアリング３４は勿論のこと残り複数のボールべアリング３４に対して転動用の固定壁として機能し、且つ、第１コア２１の円筒部２１ｃの上端部２１ｄが最下部のボールべアリング３４に当接した起点位置から最下部のボールべアリング３４が矢印方向に回転を始め、その後、第１コア２１の円筒部２１ｃに添接しながら回転を続けるので、動滑車の原理と同様に、第１コア２１の挿入動作に伴って第１コア２１の円筒部２１ｃの上端部２１ｄが起点位置から第２コア３１の円筒部３１ｃの下端部３１ｄに突き当たるまでの移動量をＭ１とした時に、最下部のボールべアリング３４の移動量Ｍ２は上記した第１コア２１の移動量Ｍ１の１／２以下となり、即ち、Ｍ２≦Ｍ１／２が成立する。
【００５２】
そして、図２に示したように、対物レンズ１の成形開始時に、第１コア２１を第２コア３１側（矢印Ｓ１側）に向かって上動させ、第１コア２１の円筒部２１ｃを第２金型３０の有底孔３０ｅ内に嵌め込んだボールべアリング体ＢＢ内に挿入する動作に伴って、リテーナー３３と一体に複数のボールべアリング３４が、第２金型３０の有底孔３０ｅの内周面及び第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに沿って第１，第２コア２１，３１の円筒部２１ｃ，３１ｃを突き合わせた側に上動し、且つ、第２コア３１の円筒部３１ｃの下端部３１ｄに第１コア２１の円筒部２１ｃの上端部２１ｄを突き合わせた時には、図３に示したように、複数のボールべアリング３４が第２コア３１の円筒部３１ｃの外周面及び第１コア２１の円筒部２１ｃの外周面に添接する。
【００５３】
この際、図３に示したように、リテーナー３３に支持した複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させることにより、第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに予圧（プリロード）を加えている。
【００５４】
より具体的には、第２金型３０に穿設した有底孔３０ｅの孔径をＤ１とし、且つ、第１コア２１の円筒部２１ｃの軸径及び第２コア３１の円筒部３１ｃの軸径をＤ２とし、ボールべアリング３５のボール径をＤ３とした時に、ボールべアリング３５に対して第１，第２コア２１，３１の径方向に弾性変位内で予圧をかけることで、Ｄ１＜Ｄ２＋２×Ｄ３が成立することになるので、複数のボールべアリング３５を第１，第２コア２１，３１の径方向に弾性変位させて第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに予圧を付加し、複数のボールべアリング３５と第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面との間で摺動用クリアランスが全く生じない状態となる。
【００５５】
これにより、対物レンズ１の成形時に、第１コア２１に形成した第１レンズ転写面２１ｅの中心と、第２コア３１に形成した第２レンズ転写面３１ｅの中心とが位置ズレしないようになっている。
【００５６】
ここで、上記のように構成した第１実施例の光学レンズ用金型１０Ａを用いて先に図１を用いて説明した対物レンズ１を成形する動作について、図１及び図２を併用しながら新な図６を用いて説明する。
【００５７】
図６は第１実施例の光学レンズの成形方法を説明するための動作フロー図である。
【００５８】
図６に示した如く、ステップＳ１０では、光学レンズ用金型１０Ａの初期状態時に、第１金型２０に固着させた第１コア２１を、第２金型３０に固着させた第２コア３１の下方で待機させている。
【００５９】
次に、ステップＳ１１では、第１コア２１に形成した第１レンズ転写面２１ｅ上に予め研磨加工を施した球状の光学ガラス素材２３を載置する。
【００６０】
次に、ステップＳ１２では、光学ガラス素材２３を第１レンズ転写面２１ｅ上に載置した状態で第１コア２１を上動させ、この第１コア２１の円筒部２１ｃを第２金型３０の有底孔２０ｄ内に嵌め込んだボールべアリング体ＢＢのリテーナー３３に支持した複数のボールべアリング３４に沿って挿入する。
【００６１】
次に、ステップＳ１３では、ヒータ又は遠赤外線などの不図示の加熱手段により光学ガラス素材２３のガラス軟化点温度まで第１，第２コア２１，３１を昇温させて光学ガラス素材２３を軟化させながら、第１コア２１の円筒部２１ｃの上端部２１ｄが第２コア３１の円筒部３１ｃの下端部３１ｄに突き当たるまで第１コア２１を上動させると図３に示した状態に至る。この際、第１コア２１の起点位置からの移動量Ｍ１（図５）に伴って、複数のボールべアリング３４がリテーナー３３と一体に移動量Ｍ２≦Ｍ１／２（図５）だけ第２金型３０の有底孔３０の内周面及び第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに沿って上動し、言い換えると、複数のボールべアリング３４は第１，第２コア２１，３１の円筒部２１ｃ，３１ｃを突き合わせた側に移動して、複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させることにより第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に予圧（プリロード）を加えている。
【００６２】
次に、ステップＳ１４では、第１コア２１の円筒部２１ｃの上端部２１ｄを第２コア３１の円筒部３１ｃの上端部３１ｄに突き合わせた後に、第１コア２１に形成した第１レンズ転写面２１ｅと、第２コア３１に形成した第２レンズ転写面３１ｅとの間で光学ガラス素材２３が軟化した状態となる。
【００６３】
次に、ステップＳ１５では、第１，第２コア２１，３１を不図示の冷却手段で冷却すると対物レンズ１が成形され、この際、第１コア２１の第１レンズ転写面２１ｅで対物レンズ１の第１面１ａ（図１）が非球面として転写され、且つ、第２コア３１の第２レンズ転写面３１ｅで対物レンズ１の第２面１ｂ（図１）も非球面として転写される。
【００６４】
次に、ステップＳ１６では、第１コア２１を下動させて初期状態まで戻し、対物レンズ１を取り出す。この時、第１コア２１の下動に伴って、複数のボールべアリング３４を支持したリテーナー３３は元の初期状態まで下動する。
【００６５】
上記の動作工程中で、複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させて第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に予圧（プリロード）を加えているために、複数のボールべアリング３４への第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの摺動用クリアランスが全く生じない状態となるために、第１コア２１に形成した第１レンズ転写面２１ｅの中心と、第２コア３１に形成した第２レンズ転写面３１ｅの中心とが位置ズレしない。この結果、成形した対物レンズ１の第１面１ａ（図１）の中心と第２面１ｂ（図１）の中心とが位置ズレしないで位置ズレ量（偏心量）を±１μｍ以下に抑えることができ、これにより上記した対物レンズ１は信号面が１層構造の超高密度光ディスク２（図１）は勿論のこと、信号面が２層構造の超高密度光ディスク（図示せず）にも対応可能となる。
【００６６】
次に、本発明に係る第１実施例を一部変形させた変形例について図７を用いて簡略に説明する。
【００６７】
図７は本発明に係る第１実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【００６８】
尚、説明の都合上、先に第１実施例で示した構成部材と同一構成部材に対しては同一の符号を付して図示のみとし、且つ、第１実施例と異なる構成部材に新たな符号を付す共に、この変形例では第１実施例と異なる点を中心に説明する。
【００６９】
図７に示した如く、本発明に係る第１実施例を一部変形させた変形例の光学レンズ用金型１０Ｂは、第１金型（下型）２０の一部が第１実施例に対して異なっており、第２金型（上型）３０は第１実施例と同じである。
【００７０】
この変形例では、第１金型２０に第１コア２１を固着させずに、第１コア２１を第１金型２０の軸中心に対して直角の方向に移動可能に取り付けている。
【００７１】
即ち、第１金型２０の上面２０ｄの中心部に、第１コア２１の鍔部２１ｂの径より僅かに大径の有底孔２０ｆが穿設されている。
【００７２】
また、第１コア２１の下面２１ａの中心部に円錐状凹部２１ｆが形成され、この円錐状凹部２１ｆ内と第１金型２０の有底孔２０ｆの底面との間にスチールボール２４を介挿することで、第１コア２１の円筒部２１ｃをこの軸方向に対して直角方向に移動自在に支持している。
【００７３】
また、第１金型２０の上面２０ｄに、第１コア２１の円筒部２１ｃが進入するための逃げ孔２５ａを貫通させた押さえ板２５を取り付けることで、第１コア２１の鍔部２１ｂが第１金型２０の有底孔２０ｆ内から脱落したり、又は、第１コア２１が傾倒することを防止している。
【００７４】
従って、第１コア２１の円筒部２１ｃを、第２金型３０の有底孔３０ｅ内に嵌め込んだボールべアリング体ＢＢのリテーナー３３に支持した複数のボールべアリング３４に沿って挿入する場合に、第１コア２１の円筒部２１ｃの上端部２１ｄのコーナーを僅かにＲ取り又は面取りした部位がリテーナー３３内又は最下部のボールべアリング３４に添接する動作に伴って、第１コア２１の鍔部２１ｂがスチールボール２４を介して左右方向（矢印方向）に移動することで第１コア２１の円筒部２１ｃの第２コア３１の円筒部３１ｃへの芯だしが容易になるものである。
【００７５】
＜第２実施例＞
図８は本発明に係る第２実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図、
図９は本発明に係る第２実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図である。
【００７６】
図８及び図９に示した如く、本発明に係る第２実施例の光学レンズ用金型４０Ａも、主として光学ガラス素材を用いて少なくとも一つの面が非球面を有する光学レンズ（例えば、対物レンズ）を成形するにあたって、光学レンズの第１面の中心と、第２面の中心とが位置ズレすることなく成形できるように構成されているものである。
【００７７】
この第２実施例の光学レンズ用金型４０Ａでは、第１実施例と異なって、第１金型（下型）２０に固着させた第１コア（下コア）２１の円筒部２１ｃの上端部２１ｄに非球面を有して形成した第１レンズ転写面２１ｅと、第２金型（下型）３０の有底孔３０ｅ内で圧縮バネ４２を介して上下動可能に支持され且つ薄肉リング状スリーブ４１の孔４１ａ内に嵌め込んだ第２コア（上コア）３１の円筒部３１ｃの下端部３１ｄに非球面を有して形成した第２レンズ転写面３１ｅとを同一中心軸上で互いに離間して対向させ、且つ、光学レンズ１の成形時に第２金型３０の有底孔３０ｅ内に嵌め込んだ円筒状のボールべアリング体ＢＢのリテーナー３３に支持した複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させて薄肉リング状スリーブ４１を介してこの薄肉リング状スリーブ４１内に挿入した第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に予圧をかけることで、薄肉リング状スリーブ４１の孔４１ａ内への第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの摺動用スキマを無くすように成したものである。そして、成形前の初期状態時に、第１コア２１を薄肉リング状スリーブ４１の下方で待機させ、一方、成形時には第１コア２１を第２コア３１に対して第１，第２金型２０，３０間に設けた不図示のガイドシャフトにより位置決めしながら上動させて第１，第２金型２０，３０同士を合体可能に構成したものである。
【００７８】
上記に伴って、第２金型（上型）３０の構造が第１実施例に対して一部改良されているものの、第１金型（下型）２０の構造は第１実施例と同じであるので、説明の都合上、第１実施例と同じ機能を有する構成部材に対して同一の符号を付して適宜説明し、且つ、第１実施例と異なる構成部材に新たな符号を付す共に、この第２実施例では第１実施例と異なる点を中心に説明する。
【００７９】
まず、図９に示したように、第１金型２０は、第１実施例と同様に、下面２０ａ側に形成した鍔部２０ｂと、この鍔部２０ｂの上方に鍔部２０ｂより小径に形成した円筒部２０ｃと、円筒部２０ｃの上面２０ｄの中心部に形成した有底孔２０ｅとからなり、有底孔２０ｅ内に第１コア２１の下面２１ａ側に形成した鍔部２１ｂがクリアランスなく嵌め込まれて、第１コア２１がネジ２２により第１金型２０に固着されている。
【００８０】
また、第１コア２１は、第１実施例と同様に、下面２１ａ側に形成した鍔部２１ｂと、この鍔部２１ｂの上方に鍔部２１ｂより小径で長尺に形成した円筒部２１ｃと、円筒部２１ｃの上端部２１ｄの中心部に光学ガラス素材２３（図８）を載置すると共に所定の厚みで非球面を有して形成した第１レンズ転写面２１ｅとからなっている。
【００８１】
次に、図８及び図９に示したように、第２金型３０は、上面３０ａ側に大径な鍔部３０ｂが形成され、この下方に鍔部３０ｂより小径な円筒部３０ｃが鍔部３０ｂに対して同心的に第１金型２０側に向かって第１実施例よりも長尺に形成されていると共に、円筒部３０ｃの中心部に下面３０ｄから鍔部３０ｂに向かって有底孔３０ｅが寸法精度良く第１実施例よりも長尺に穿設されている。
【００８２】
また、第２金型３０に穿設した有底孔３０ｅ内には、第１実施例と異なって、第２コア３１が第２金型３０に固着されずに、薄肉リング状スリーブ４１の孔４１ａ内に第２コア３１の円筒部３１ｃを嵌め込んだ状態で第２コア３１が圧縮バネ４２を介して上下動可能に支持されている。
【００８３】
また、第２コア３１は、上面３１ａ側に第２金型３０の有底孔３０ｅの孔径よりも一回り小径に形成した鍔部３１ｂと、この鍔部３１ｂの下方に鍔部３１ｂよりも小径で且つ第１コア２１と同径で長尺に形成した円筒部３１ｃと、円筒部３１ｃの下端部３１ｄの中心部に非球面を有して形成した第２レンズ転写面３１ｅとが第１実施例と略同じ構成であるものの、第２コア３１の円筒部３１ｃの外周面にこの円筒部３１ｃの長さよりも略倍の長さに形成した薄肉リング状スリーブ４１が嵌め込まれていると共に、第２コア３１の上面３１ａと第２金型３０の有底孔３０ｅ内の天面との間に介装した圧縮バネ４２を支持するための凹孔３１ｆが穿設されている点が第１実施例に対して異なっている。
【００８４】
この際、薄肉リング状スリーブ４１は、弾性変位可能な燐青銅などを用いて薄肉リング状に貫通して第２コア３１の円筒部３１ｃの長さの略倍の長さで長尺に形成され、孔４１ａ内の上方側の約半分の長さ部位に第２コア３１の円筒部３１ｃが予め嵌め込まれ、且つ、孔４１ａ内の下方側の約半分の長さ部位は第１コア２１の円筒部２１ｃの挿入が許容されるようになっている。
【００８５】
また、第２金型３０の有底孔３０ｅの内周面と、薄肉リング状スリーブ４１の外周面４１ｂとの間にボールべアリング体ＢＢが嵌め込まれている。このボールべアリング体ＢＢは、第１実施例と同様に構成されており、円筒状のリテーナー３３の周面に沿って複数のボールべアリング３４が支持されている。この第２実施例では、薄肉リング状スリーブ４１と、円筒状のボールべアリング体ＢＢとで予圧付加部材が構成されている。そして、複数のボールべアリング３４を第２コア３１の径方向に弾性変位させることにより薄肉リング状スリーブ４１を介して孔４１ａ内に嵌め込まれた第２コア３１の円筒部３１ｃに予圧が付加されているので、孔４１ａに対して円筒部３１ｃが略圧入状態となっている。
【００８６】
上記したボールべアリング体ＢＢのリテーナー３３に支持した複数のボールべアリング３４は、後述するように、薄肉リング状スリーブ４１の孔４１ａ内に第１コア２１の円筒部２１ｃが挿入された時に第１コア２１と一体に薄肉リング状スリーブ４１が第２金型３０の有底孔３０ｅ内の天面側に向かって上動する動作に伴って、薄肉リング状スリーブ４１の移動量の１／２以下上動しながら複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させることにより薄肉リング状スリーブ４１を介して第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに予圧を付加するものである。
【００８７】
また、第２金型３０の円筒部３０ｃの下面３０ｃに、薄肉リング状スリーブ４１の進入を許容するための逃げ孔３５ａを穿設したリテーナー支持板３５が取り付けられている。
【００８８】
そして、成形前の初期状態では、図８に示したように、第２金型３０の有底孔３０ｅ内に介装した圧縮バネ４２の付勢力により第２コア３１の円筒部３１ｃを嵌め込んだ薄肉リング状スリーブ４１が第１金型２０側に押圧されて薄肉リング状スリーブ４１の下端部４１ｄが第２金型３０の有底孔３０ｅの外に突出して第１コア２１の円筒部２１ｃの挿入を待機している。
【００８９】
また、成形前の初期状態では、薄肉リング状スリーブ４１の下動に伴ってリテーナー３３は下端部がリテーナー支持板３５に当接し、且つ、上端部が薄肉リング状スリーブ４１の鍔部４１ｃに当接している。更に、薄肉リング状スリーブ４１に嵌め込んだ第２コア３１の円筒部３１ｃの下端部３１ｄは、リテーナ３３に支持した複数のボールべアリング３４のうちで最下部のボールべアリング３４の近傍に位置している。
【００９０】
次に、ここで、上記のように構成した第２実施例の光学レンズ用金型４０Ａを用いて先に図１を用いて説明した対物レンズ１を成形する動作について、図８及び図９を併用しながら新な図１０を用いて説明する。
【００９１】
図１０は第２実施例の光学レンズの成形方法を説明するための動作フロー図である。
【００９２】
図１０に示した如く、ステップＳ２０では、光学レンズ用金型４０Ａの初期状態時に、第１金型２０に固着させた第１コア２１を、第２金型３０の有底孔３０ｅ内で圧縮バネ４２の付勢力により第１金型２０側に移動し且つ第２コア３１の円筒部３１ｃを嵌め込んだ薄肉リング状スリーブ４１の下方で待機させている。
【００９３】
次に、ステップＳ２１では、第１コア２１に形成した第１レンズ転写面２１ｅ上に予め研磨加工を施した球状の光学ガラス素材２３を載置する。
【００９４】
次に、ステップＳ２２では、光学ガラス素材２３を第１レンズ転写面２１ｅ上に載置した状態で第１コア２１を上動させ、この第１コア２１の円筒部２１ｃを薄肉リング状スリーブ４１の孔４１ａ内に挿入して、第１コア２１の円筒部２１ｃの上端部２１ｄを第２コア３１の円筒部３１ｃの下端部３１ｄに突き当てると図９に示した状態に至る。この際、薄肉リング状スリーブ４１の孔４１ａ内で第１コア２１の円筒部２１ｃと第２コア３１の円筒部３１ｃとを突き合わせた時に、内部が密閉状態となるために、例えば第１コア２１の円筒部２１ｃの側面に０．０５ｍｍ程度のガス逃げ溝（図示せず）を設けている。
【００９５】
次に、ステップＳ２３では、ヒータ又は遠赤外線などの不図示の加熱手段により光学ガラス素材２３のガラス軟化点温度まで第１，第２コア２１，３１を昇温させて光学ガラス素材２３を軟化させながら、第１コア２１の上動に伴って第２コア３１を嵌め込んだ薄肉リング状スリーブ４１が圧縮バネ４２の付勢力に抗して第２金型３０の有底孔３０ｅ内の天面側に向かって上動し、薄肉リング状スリーブ４１の鍔部４１ｃが第２金型３０の有底孔３０ｅ内の天面に当接する。そして、薄肉リング状スリーブ４１の移動量に伴って、リテーナー３３と一体に複数のボールべアリング３４が上記した移動料の１／２以下だけ第２金型３０の有底孔３０の内周面及び第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に沿って上動し、言い換えると、複数のボールべアリング３４は第１，第２コア２１，３１の円筒部２１ｃ，３１ｃを突き合わせた側に移動して、複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させることにより薄肉リング状スリーブ４１を介して第１，第２コア２１，３１の円筒部２１ｃ，３１ｃに予圧（プリロード）を加えている。
【００９６】
次に、ステップＳ２４では、第１コア２１の円筒部２１ｃの上端部２１ｄを第２コア３１の円筒部３１ｃの上端部３１ｄに突き合わせた後に、第１コア２１に形成した第１レンズ転写面２１ｅと、第２コア３１に形成した第２レンズ転写面３１ｅとの間で光学ガラス素材２３が軟化した状態となる。
【００９７】
次に、ステップＳ２５では、第１，第２コア２１，３１を不図示の冷却手段で冷却すると対物レンズ１が成形され、この際、第１コア２１の第１レンズ転写面２１ｅで対物レンズ１の第１面１ａ（図１）が非球面として転写され、且つ、第２コア３１の第２レンズ転写面３１ｅで対物レンズ１の第２面１ｂ（図１）も非球面として転写される。
【００９８】
次に、ステップＳ２６では、第１コア２１を下動させて初期状態まで戻し、対物レンズ１を取り出す。この時、圧縮バネ４２の付勢力により第２コア３１を嵌め込んだ薄肉リング状スリーブ４１が下動し、これに伴って複数のボールべアリング３４を支持したリテーナー３３は元の初期状態まで下動する。
【００９９】
上記の動作工程中で、複数のボールべアリング３４を第１，第２コア２１，３１の径方向に弾性変位させて薄肉リング状スリーブ４１を介して第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの外周面に予圧（プリロード）を加えているために、薄肉リング状スリーブ４１の孔４１ａ内への第１，第２コア２１，３１の円筒部２１ｃ，３１ｃの摺動用クリアランスが全く生じない状態となるために、第１コア２１に形成した第１レンズ転写面２１ｅの中心と、第２コア３１に形成した第２レンズ転写面３１ｅの中心とが位置ズレしない。この結果、成形した対物レンズ１の第１面１ａ（図１）の中心と、第２面１ｂ（図１）の中心とが位置ズレしないで位置ズレ量（偏心量）を±１μｍ以下に抑えることができる。更に、第１実施例と異なって、薄肉リング状スリーブ４１を用いることで、第１，第２コア２１，３１の円筒部２１ｃ，３１ｃをボールべアリング体ＢＢ内に挿入する時に、複数のボールべアリング３４に第１，第２コア２１，３１の円筒部２１ｃ，３１ｃが直接添接することがなくなるので、複数のボールべアリング３４を傷つけることがなく、更に、複数のボールべアリング３４に光学ガラス素材２３のカケラなどが付着することもなくなるなどの改善を図ることができる。
【０１００】
次に、本発明に係る第２実施例を一部変形させた変形例について図１１を用いて簡略に説明する。
【０１０１】
図１１は本発明に係る第２実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【０１０２】
図１１に示した如く、本発明に係る第２実施例を一部変形させた変形例の光学レンズ用金型４０Ｂは、第１金型（下型）２０の一部が第２実施例に対して異なっており、第２金型（上型）３０は第２実施例と同じである。
【０１０３】
この変形例では、第１金型２０に第１コア２１を固着させずに、第１コア２１を第１金型２０の軸中心に対して直角の方向に移動可能に取り付けている。
【０１０４】
即ち、第１金型２０の上面２０ｄの中心部に、第１コア２１の鍔部２１ｂの径より僅かに大径の有底孔２０ｆが穿設されている。
【０１０５】
また、第１コア２１の下面２１ａの中心部に円錐状凹部２１ｆが形成され、この円錐状凹部２１ｆ内と第１金型２０の有底孔２０ｆの底面との間にスチールボール２４を介挿することで、第１コア２１の円筒部２１ｃをこの軸方向に対して直角方向に移動自在に支持している。
【０１０６】
また、第１金型２０の上面２０ｄに、第１コア２１の円筒部２１ｃが進入するための逃げ孔２５ａを貫通させた押さえ板２５を取り付けることで、第１コア２１の鍔部２１ｂが第１金型２０の有底孔２０ｆ内から脱落したり、又は、第１コア２１が傾倒することを防止している。
【０１０７】
従って、第１コア２１の円筒部２１ｃを、第２コア３１を嵌め込んだ薄肉リング状スリーブ４１の孔４１ａ内に挿入する場合に、第１コア２１の円筒部２１ｃの上端部２１ｄのコーナーを僅かにＲ取り又は面取りした部位が薄肉リング状スリーブ４１の孔４１ａ内に添接する動作に伴って、第１コア２１の鍔部２１ｂがスチールボール２４を介して左右方向（矢印方向）に移動することで第１コア２１の円筒部２１ｃの第２コア３１の円筒部３１ｃへの芯だしが容易になるものである。
【０１０８】
＜第３実施例＞
図１２は本発明に係る第３実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図、
図１３は本発明に係る第３実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図、
図１４は図１２及び図１３に示した円錐状コレットを示した斜視図である。
【０１０９】
図１２及び図１３に示した如く、本発明に係る第２実施例の光学レンズ用金型５０Ａも、主として光学ガラス素材を用いて少なくとも一つの面が非球面を有する光学レンズ（例えば、対物レンズ）を成形するにあたって、光学レンズの第１面の中心と、第２面の中心とが位置ズレすることなく成形できるように構成されているものである。
【０１１０】
この第３実施例の光学レンズ用金型５０Ａでは、第１金型（下型）６０に固着させた第１コア（下コア）６６の円筒部６６ｃの上端部６６ｄに非球面を有して形成した第１レンズ転写面６６ｅと、第２金型（下型）７０に固着させ且つ薄肉リング状スリーブ７１の孔７１ａ内に嵌め込んだ第２コア（上コア）７２の円筒部７２ｃの下端部７２ｄに非球面を有して形成した第２レンズ転写面７２ｅとを同一中心軸上で互いに離間して対向させ、且つ、薄肉リング状スリーブ７１の外周面７１ｂに第１，第２コア６６，７２の径方向に弾性変位可能な円錐状コレット７４を嵌め込んで、光学レンズ１の成形時に円錐状コレット７４をコレット締め上げ部材７５で第１，第２コア６６，７２の径方向に締め上げながら薄肉リング状スリーブ７１を介してこの薄肉リング状スリーブ７の孔７１ａ内に挿入した第１，第２コア６６，７２の円筒部６６ｃ，７２ｃの外周面に予圧をかけることで、薄肉リング状スリーブ７１の孔７１ａ内への第１，第２コア６６，７２の円筒部６６ｃ，７２ｃの摺動用スキマを無くすように成したものである。そして、成形前の初期状態時に、第１コア６６を第２コア７２を嵌め込んだ薄肉リング状スリーブ７１の下方で待機させ、一方、成形時には第１コア６６を第２コア７２に対して第１，第２金型６０，７０間に設けた不図示のガイドシャフトにより位置決めしながら上動させて第１，第２金型６０，７０同士を合体可能に構成したものである。可能に構成したものである。
【０１１１】
まず、図１２に示したように、第１金型６０は、大径ベース６１の上面６１ａ上に小径ベース６２の下面６２ａが分離可能に同心的に積層されて、使用時に図示しない締結手段により両ベース６１，６２が一体化されている。
【０１１２】
また、大径ベース６１の上面６１ａの中心部には大径有底孔６１ｂが穿設されており、この大径ベース６１の外周側から空気又はオイルを挿脱するための挿脱孔６１ｃが大径有底孔６１ｂに連通して穿設されている。
【０１１３】
また、大径ベース６１の大径有底孔６１ｂ内には、Ｏリング６３を外周に嵌着したピストン６４が空気圧又は油圧により上下動可能に嵌め込まれており、且つ、ピストン６４上に押し棒６５が円周に沿って複数本植設されて、複数の押し棒６５が小径ベース６２に穿設した複数の貫通孔６２ｄ内に上下動可能に進入している。この際、ピストン６４上に植設した複数本の押し棒６５は、後述する第２金型７０内に設けたコレット締め上げ部材７５に対して接離自在になっている。
【０１１４】
また、小径ベース６２の上面６２ｂの中心部に有底孔６２ｃが穿設されており、この有底孔６２ｃ内に第１コア６６の下面６６ａ側に形成した鍔部６６ｂがクリアランスなく嵌め込まれて、第１コア６６の下面６６ａを小径ベース６２の下面６２ｂ側からネジ６７により小径ベース６２に対して固着している。
【０１１５】
また、第１コア６６は、下面６６ａ側に形成した鍔部６６ｂと、この鍔部６６ｂの上方に鍔部６６ｂより小径で長尺に形成した円筒部６６ｃと、円筒部６６ｃの上端部６６ｄの中心部に光学ガラス素材２３を載置すると共に所定の厚みで非球面を有して形成した第１レンズ転写面６６ｅとからなっている。
【０１１６】
次に、第２金型７０は、上面７０ａ側に大径な鍔部７０ｂが形成され、この下方に鍔部７０ｂより小径な円筒部７０ｃが鍔部７０ｂに対して同心的に第１金型６０側に向かって長尺に形成されていると共に、円筒部７０ｃの中心部に下面７０ｄから鍔部７０ｂに向かって大径有底孔７０ｅと小径有底孔７０ｆとが階段状に同心的に穿設されている。
【０１１７】
また、第２金型７０の小径有底孔７０ｆ内には、薄肉リング状スリーブ７１の孔７１ａ内に嵌め込んだ第２コア７２の上面７２ａ側に形成した鍔部７２ｂがクリアランスなく嵌め込まれて、第２コア７２の上面７２ａを第２金型７０の上面７０ａ側からネジ７３により第２金型７０に対して固着している。
【０１１８】
また、第２コア７２は、上面７２ａ側に形成した鍔部７２ｂと、この鍔部７２ｂの下方に鍔部７２ｂよりも小径で且つ第１コア６６の円筒部６６ｃと同径で長尺に形成された円筒部７２ｃと、円筒部７２ｃの下端部７２ｄの中心部に非球面を有して形成した第２レンズ転写面７２ｅとからなっており、円筒部７２ｃの外周面にこの円筒部７２ｃの長さよりも長尺に形成した薄肉リング状スリーブ７１が上端を第２コア７２の鍔部７２ｂに当接させて嵌め込まれており、且つ、薄肉リング状スリーブ７１の下端は後述する落下防止板７６に当接している。
【０１１９】
この際、薄肉リング状スリーブ７１は、弾性変位可能な燐青銅などを用いて薄肉リング状に貫通して第２コア７２の円筒部７２の長さよりも略倍の長さに形成され、孔７１ａ内の上方側の約半分の長さ部位に第２コア７２の円筒部７２ｃが予め嵌め込まれ、且つ、孔７１ａ内の下方側の約半分の長さ部位は第１コア７２の円筒部７２ｃの挿入が許容されるようになっている。
【０１２０】
また、薄肉リング状スリーブ７１の外周面７１ｂは、弾性変位可能な燐青銅などを用いて円錐状に形成した円錐状コレット７４の中央貫通孔７４ａ内に嵌め込まれている。この際、円錐状コレット７４は、第２金型とは別体で着脱自在に形成されている。
【０１２１】
上記した円錐状コレット７４は、図１４に示した如く、上面７４ｃ側及び下面７４ｄ側から第２スリット７４ｅ及び第１スリット７４ｆを円錐状外周面７４ｂに沿って交互に複数箇所形成することで、円錐状コレット７４の円錐状外周面７４ｂが第１，第２コア６６，７２の径方向に弾性変位可能になっている。
【０１２２】
図１２に戻り、円錐状コレット７４の円錐状外周面７４ｂは、この円錐状外周面７４に沿って上下動可能に設けたコレット締め上げ部材７５の中央円錐孔７５ａ内に嵌め込まれており、この第３実施例では、薄肉リング状スリーブ７１と、円錐状コレット７４と、コレット締め上げ部材７５とで予圧付加部材が構成されている。
【０１２３】
また、第２金型７０の円筒部７０ｃの下面７０ｄに取り付けた落下防止板７６によって薄肉リング状スリーブ７１及び円錐状コレット７４並びにコレット締め上げ部材７５が下方に落下することを防止されている。この際、落下防止板７６の中心部に貫通して穿接した逃げ孔７６ａは第１コア６６の円筒部６６ｃの挿入を許容し、且つ、中周部位に穿接した複数の逃げ孔７６ｂは第１金型６０側に設けた複数の押し棒６５の挿入を許容している。
【０１２４】
そして、成形前の初期状態では、第２金型７０の大径有底孔７０ｅ内で、円錐状コレット７４の円錐状外周面７４ｂに嵌め込んだコレット締め上げ部材７５の下面７５ｂは落下防止板７６上に当接していると共に、第２コア７２を嵌め込んだ薄肉リング状スリーブ７１が第１コア６６の円筒部６６ｃの挿入を待機している。
【０１２５】
また、成形前の初期状態では、第１金型６０側に設けたピストン６４上に植設した複数の押し棒６５は下降している。
【０１２６】
ここで、上記のように構成した第３実施例の光学レンズ用金型５０Ａを用いて先に図１を用いて説明した対物レンズ１を成形する動作について、図１２及び図１３を併用しながら新な図１５を用いて説明する。
【０１２７】
図１５は第３実施例の光学レンズの成形方法を説明するための動作フロー図である。
【０１２８】
図１５に示した如く、ステップＳ３０では、光学レンズ用金型５０Ａの初期状態時に、第１金型６０の小径ベース６２に固着させた第１コア６６を、第２金型７０に固着させた第２コア７２の円筒部７２ｃを嵌め込んだ薄肉リング状スリーブ７１の下方で待機させている。
【０１２９】
次に、ステップＳ３１では、第１コア６６に形成した第１レンズ転写面６６ｅ上に予め研磨加工を施した球状の光学ガラス素材２３を載置する。
【０１３０】
次に、ステップＳ３２では、光学ガラス素材２３を第１レンズ転写面６６ｅ上に載置した状態で第１コア６６を上動させ、この第１コア６６の円筒部６６ｃを薄肉リング状スリーブ７１の孔７１ａ内に挿入して、第１コア６６の円筒部６６ｃの上端部６６ｄを第２コア７２の円筒部７２ｃの下端部７２ｄに突き当てると図１３に示した状態に至る。この際、薄肉リング状スリーブ７１の孔７１ａ内で第１コア６６の円筒部６６ｃと第２コア７２の円筒部７２ｃとを突き合わせた時に、内部が密閉状態となるために、例えば第１コア６６の円筒部６６ｃの側面に０．０５ｍｍ程度のガス逃げ溝（図示せず）を設けている。
【０１３１】
次に、ステップＳ３３では、ヒータ又は遠赤外線などの不図示の加熱手段により光学ガラス素材２３のガラス軟化点温度まで第１，第２コア６６，７２を昇温させて光学ガラス素材２３を軟化させながら、第１コア６６の上動に伴ってピストン６４を介して押し棒６５を上動させ、この押し棒６５でコレット締め上げ部材７５を円錐状コレット７４の円錐状外周面７４ｂに沿って押し上げながら円錐状コレット７４の円錐状外周面７４ｂを第１，第２コア６６，７２の径方向に締め上げることで、円錐状コレット７４の中央貫通孔７４ａ内に嵌め込んだ薄肉リング状スリーブ７１を介して第１，第２コア６６，７２の円筒部６６ｃ，７２ｃに予圧（プリロード）を加えている。
【０１３２】
次に、ステップＳ３４では、第１コア６６の円筒部６６ｃの上端部６６ｄを第２コア７２の円筒部７２ｃの上端部７２ｄに突き合わせた後に、第１コア６６に形成した第１レンズ転写面６６ｅと、第２コア７２に形成した第２レンズ転写面７２ｅと間で光学ガラス素材２３が軟化した状態となる。
【０１３３】
次に、ステップＳ３５では、第１，第２コア６６，７２を不図示の冷却手段で冷却すると対物レンズ１が成形され、この際、第１コア６６の第１レンズ転写面６６ｅで対物レンズ１の第１面１ａ（図１）が非球面として転写され、且つ、第２コア７２の第２レンズ転写面７２ｅで対物レンズ１の第２面１ｂ（図１）も非球面として転写される。
【０１３４】
次に、ステップＳ３６では、第１コア６６を下動させて初期状態まで戻し、対物レンズ１を取り出す。この時、ピストン６４を介して押し棒６５を下動してコレット締め上げ部材７５から離間させている。
【０１３５】
上記の動作工程中で、コレット締め上げ部材７５を円錐状コレット７４の円錐状外周面７４ｂに沿って押し上げながら円錐状コレット７４を第１，第２コア６６，７２の径方向に締め上げることで、薄肉リング状スリーブ７１を介して第１，第２コア６６，７２の円筒部６６ｃ，７２ｃの外周面に予圧（プリロード）を加えているために、薄肉リング状スリーブ７１の孔７１ａ内への第１，第２コア６６，７２の円筒部６６ｃ，７２ｃの摺動用クリアランスが全く生じない状態となるために、第１コア６６に形成した第１レンズ転写面６６ｅの中心と、第２コア７２に形成した第２レンズ転写面７２ｅの中心とが位置ズレしない。この結果、成形した対物レンズ１の第１面１ａ（図１）の中心と第２面１ｂ（図１）の中心とが位置ズレしないで位置ズレ量（偏心量）を±１μｍ以下に抑えることができる。更に、第１，第２実施例と異なって、高価なボールべアリング体ＢＢを用いていないので、光学レンズ用金型５０Ａを安価に作製できる。
【０１３６】
次に、本発明に係る第３実施例を一部変形させた変形例について図１６を用いて簡略に説明する。
【０１３７】
図１６は本発明に係る第３実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【０１３８】
図１６に示した如く、本発明に係る第３実施例を一部変形させた変形例の光学レンズ用金型５０Ｂは、第１金型（下型）６０の一部が第３実施例に対して異なっており、第２金型（上型）７０は第３実施例と同じである。
【０１３９】
この変形例では、第１金型６０の小径ベース６２に第１コア６６を固着させずに、第１コア６６を小径ベース６２の軸中心に対して直角の方向に移動可能に取り付けている。
【０１４０】
即ち、第１金型６０の小径ベース６２の上面６２ｂの中心部に、第１コア６６の鍔部６６ｂの径より僅かに大径の有底孔６２ｅが穿設されている。
【０１４１】
また、第１コア６６の下面６６ａの中心部に円錐状凹部６６ｆが形成され、この円錐状凹部６６ｆ内と小径ベース６２の有底孔６２ｅの底面との間にスチールボール６８を介挿することで、第１コア６６の円筒部６６ｃをこの軸方向に対して直角方向に移動自在に支持している。
【０１４２】
また、小径ベース６２の上面６２ｂに、第１コア６６の円筒部６６ｃが進入するための逃げ孔６９ａ及び複数の押し棒６５が進入するための逃げ孔６９ｂを貫通させた押さえ板６９を取り付けることで、第１コア６６の鍔部６６ｂが小径ベース６２の有底孔６２ｅ内から脱落したり、又は、第１コア６６が傾倒することを防止している。
【０１４３】
従って、第１コア６６の円筒部６６ｃを、第２コア７２を嵌め込んだ薄肉リング状スリーブ７１の孔７１ａ内に挿入する場合に、第１コア６６の円筒部６６ｃの上端部６６ｄのコーナーを僅かにＲ取り又は面取りした部位が薄肉リング状スリーブ７１の孔７１ａ内に添接する動作に伴って、第１コア６６の鍔部６６ｂがスチールボール６８を介して左右方向（矢印方向）に移動することで第１コア６６の円筒部６６ｃの第２コア７２の円筒部７２ｃへの芯だしが容易になるものである。
【０１４４】
【発明の効果】
以上詳述した本発明に係る光学レンズの成形方法及び光学レンズ用金型によると、光学レンズの第１面を転写するために第１コアの円筒部の端部に形成した第１レンズ転写面と、光学レンズの第２面を転写するために第１コアの円筒部と同径な第２コアの円筒部の端部に形成した第２レンズ転写面とを同一中心軸上で互いに対向させて、第２コアの円筒部を嵌め込み且つ第１，第２コアの径方向に弾性変位可能な予圧付加部材内に第１コアの円筒部を挿入し、予圧付加部材内で第２コアの円筒部の端部に第１コアの円筒部の端部を突き合わせた際に、予圧付加部材を第１，第２コアの径方向に弾性変位させて第１，第２コアの各円筒部に予圧を付加することで、予圧付加部材内への第１，第２コアの各円筒部の摺動用クリアランスを無くし、これにより、第１コアに形成した第１レンズ転写面の中心と、第２コアに形成した第２レンズ転写面の中心とが位置ズレしない。この結果、成形した光学レンズ（対物レンズ）の第１面の中心と第２面の中心とが位置ズレしないで位置ズレ量（偏心量）を±１μｍ以下に抑えることができる。これにより、光学レンズを例えば超高密度光ディスク用の対物レンズとして成形した場合に、成形した対物レンズの第１面の中心と第２面１ｂの中心との位置ズレ量（偏心量）を±１μｍ以下に抑えることで、信号面が１層構造の超高密度光ディスクは勿論のこと、信号面が２層構造の超高密度光ディスクにも対応可能となる。
【０１４５】
この際、上記した予圧付加部材は、請求項３に記載したように、円筒状のリテーナーの周面に沿って複数のボールベアリングを支持したボールベアリング体を用い、複数のボールベアリングを互いに突き合わせた第１，第２コアの各円筒部に直接添接させ、且つ、複数のボールベアリングを第１，第２コアの径方向に弾性変位させて第１，第２コアの各円筒部に予圧を付加する構造でも良い。
【０１４６】
また、上記した予圧付加部材は、請求項４に記載したように、薄肉リング状スリーブと、円筒状のリテーナーの周面に沿って複数のボールベアリングを支持したボールベアリング体とを用い、薄肉リング状スリーブの孔内で第１，第２コアの各円筒部を突き合わせた際に、複数のボールベアリングを薄肉リング状スリーブの外周面に添接させ、且つ、複数のボールベアリングを第１，第２コアの径方向に弾性変位させて薄肉リング状スリーブを介して第１，第２コアの各円筒部に予圧を付加する構造でも良い。
【０１４７】
また、上記した予圧付加部材は、請求項５に記載したように、薄肉リング状スリーブと、円錐状コレットと、コレット締め上げ部材とを用い、薄肉リング状スリーブの外周部に第１，第２コアの径方向に弾性変位可能な円錐状コレットを嵌め込むと共に、円錐状コレットの円錐状外周面に沿ってコレット締め上げ部材を移動可能に設けて、薄肉リング状スリーブの孔内で第１，第２コアの各円筒部を突き合わせた際に、コレット締め上げ部材で円錐状コレットを第１，第２コアの径方向に締め上げて、薄肉リング状スリーブを介して第１，第２コアの各円筒部に予圧を付加する構造でも良い。
【図面の簡単な説明】
【図１】本発明に係る光学レンズの成形方法及び光学レンズ用金型を適用して成形される光学レンズを説明するための図である。
【図２】本発明に係る第１実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図である。
【図３】本発明に係る第１実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図である。
【図４】本発明に係る第１実施例において、図２及び図３に示したボールべアリング体と、第１コア（下コア）と、第２コア（上コア）とをそれぞれ示した斜視図である。
【図５】本発明に係る第１実施例において、第２金型の有底孔内に嵌め込んだボールべアリング体のリテーナーに支持した複数のボールべアリングに沿って第１コアを挿入した際に、第１コアの移動量と最下部のボールべアリングの移動量とを説明するために模式的に示した図である。
【図６】第１実施例の光学レンズの成形方法を説明するための動作フロー図である。
【図７】本発明に係る第１実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【図８】本発明に係る第２実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図である。
【図９】本発明に係る第２実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図である。
【図１０】第２実施例の光学レンズの成形方法を説明するための動作フロー図である。
【図１１】本発明に係る第２実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【図１２】本発明に係る第３実施例の光学レンズの成形方法及び光学レンズ用金型を説明するために、第１金型（下型）と第２金型（上型）とを分離させた成形前の状態を模式的に示した縦断面図である。
【図１３】本発明に係る第３実施例において、第１金型と第２金型とを合体させて光学レンズを成形する状態を模式的に示した縦断面図である。
【図１４】図１２及び図１３に示した円錐状コレットを示した斜視図である。
【図１５】第３実施例の光学レンズの成形方法を説明するための動作フロー図である。
【図１６】本発明に係る第３実施例を一部変形させた変形例において、第１金型と第２金型とを合体させて対物レンズを成形する状態を模式的に示した縦断面図である。
【図１７】従来例における光学レンズの成形金型の構造を示す模式図である。
【図１８】従来例において、成形完了時での光学レンズの成形金型の状態図である。
【符号の説明】
１…光学レンズ（対物レンズ）、１ａ…第１面１ａ、１ｂ…第２面、
２…超高密度光ディスク、２ａ…レーザービーム入射面、２ｂ…信号面、
１０Ａ…第１実施例の光学レンズ用金型、
１０Ｂ…第１実施例を一部変形させた変形例の光学レンズ用金型、
２０…第１金型（下型）、２０ａ…下面、２０ｂ…鍔部、２０ｃ…円筒部、
２０ｄ…上面、２０ｅ…有底孔、２０ｆ…有底孔、
２１…第１コア（下コア）、２１ａ…下面、２１ｂ…鍔部、２１ｃ…円筒部、
２１ｄ…上端部、２１ｅ…第１レンズ転写面、
２３…球状の光学ガラス素材、２４…スチールボール、２５…押さえ板、
３０…第２金型（上型）、３０ａ…上面、３０ｂ…鍔部、３０ｃ…円筒部、
３０ｄ…下面、３０ｅ…有底孔、
３１…第２コア（上コア）、３１ａ…上面、３１ｂ…鍔部、３１ｃ…円筒部、
３１ｄ…下端部、３１ｅ…第２レンズ転写面、
３３…リテーナー、３４…ボールべアリング、
３５…リテーナー支持板、
４０Ａ…第２実施例の光学レンズ用金型、
４０Ｂ…第２実施例を一部変形させた変形例の光学レンズ用金型、
４１…薄肉リング状スリーブ、４１ａ…孔、４１ｂ…外周面、
４２…圧縮バネ、
５０Ａ…第２実施例の光学レンズ用金型、
５０Ｂ…第２実施例を一部変形させた変形例の光学レンズ用金型、
６０…第１金型（下型）、
６１…大径ベース、６１ａ…上面、６１ｂ…大径有底孔、６１ｃ…挿脱孔、
６２…小径ベース、６２ａ…下面、６２ｂ…上面、６２ｃ…有底孔、
６３…Ｏリング、６４…ピストン、６５…押し棒、
６６…第１コア（下コア）、６６ａ…下面、６６ｂ…鍔部、６６ｃ…円筒部、
６６ｄ…上端部、６６ｅ…第１レンズ転写面、
６８…スチールボール、６９…押さえ板、
７０…第２金型（上型）、７０ａ…上面、７０ｂ…鍔部、７０ｃ…円筒部、
７０ｄ…下面、７０ｅ…大径有底孔、７ｆ…小径有底孔、
７１…薄肉リング状スリーブ、７１ａ…孔、７１ｂ…外周面、
７２…第２コア（上コア）、７２ａ…上面、７２ｂ…鍔部、７２ｃ…円筒部、
７２ｄ…下端部、７２ｅ…第２レンズ転写面、
７４…円錐状コレット、７４ａ…中央貫通孔、７４ｂ…円錐状外周面、
７４ｃ…上面、７４ｄ…下面、７４ｅ…第１スリット、７４ｆ…第２スリット、 ７５…コレット締め上げ部材、７５ａ…中央円錐孔、
７６…落下防止板、
ＢＢ…ボールべアリング体。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of forming an optical lens that does not shift the center of the first surface and the center of the second surface of the optical lens when forming an optical lens (for example, an objective lens) using an optical glass material. The present invention relates to a mold for an optical lens.
[0002]
[Prior art]
In general, an optical disc records information signals such as video information, audio information, and computer data at a high density on spirally or concentrically formed tracks on a disc-shaped disc substrate, and records recorded tracks. It is frequently used because a desired track can be accessed at high speed during reproduction.
[0003]
CDs (Compact Discs) and DVDs (Digital Versatile Discs) are already commercially available as optical discs of this type, but recently, in order to further increase the density of the optical discs, information signals are more commonly used than CDs and DVDs. 2. Description of the Related Art Ultra-high-density optical disks capable of recording and / or reproducing at an ultra-high density have been actively developed.
[0004]
Along with this, a next-generation optical pickup for recording and / or reproducing an ultra-high-density optical disk is also being developed. ) Is focused with an objective lens of 0.75 or more to obtain a blue laser beam, and this blue laser beam is an ultra-high-density optical disc whose thickness from the laser beam incident surface to the signal surface is about 0.1 mm to 0.15 mm. Recording and / or reproduction by irradiating the lens with a single lens type objective lens having at least one aspherical surface using an optical glass material as an objective lens for a next-generation optical pickup ( For example, see Patent Document 1).
[0005]
There is also a molding die that can stably mold a high-precision optical lens using an optical lens material without polishing (for example, see Patent Document 2).
[0006]
[Patent Document 1]
JP-A-2003-5032 (pages 9 to 10, FIG. 3)
[0007]
[Patent Document 2]
JP 2001-270724 A (Pages 4 to 5, FIGS. 1 and 2)
FIG. 17 is a schematic view showing the structure of a molding die for an optical lens in a conventional example.
FIG. 18 is a state diagram of a molding die of an optical lens when molding is completed in a conventional example.
[0008]
The molding die 100 for an optical lens in the conventional example shown in FIGS. 17 and 18 is disclosed in the above-mentioned Patent Document 2 (Japanese Patent Laid-Open No. 2001-270724). This will be described briefly.
[0009]
As shown in FIG. 17, a molding die 100 for an optical lens in a conventional example employs a structure in which a lower die 101 and an upper die 102 are inserted into a sliding hole 103a of a body die 103.
[0010]
First, the molding part of the lower mold 101 includes a first optical effective surface molding part 101a which is ultra-precisionly machined in a concave shape to form the first surface of the optical lens as an aspherical surface or a spherical surface, and a lens. The outer peripheral restriction forming part 101b serving as a forming part for holding the holder, the outer peripheral play forming part 101c for the space (cavity) provided for holding the excess optical lens material 104, and the thickness of the optical lens are set to a predetermined value. An annular convex portion 101d for regulating to a value is formed concentrically. In a non-molded portion of the lower die 101, a flange flange portion 101e for positioning the lower die 101 with respect to the body die 103 is formed.
[0011]
Next, a second optical effective surface forming portion 102a, which is concavely ultra-precision-processed to form the second surface of the optical lens, and an annular convex portion 101d of the lower die 101 are formed in the forming portion of the upper mold 102. Is formed concentrically with the annular flat portion 102b which abuts the optical lens and regulates the thickness of the optical lens to a predetermined value. In a non-molded portion of the upper mold 102, a flange flange 102c for moving the upper mold 102 up and down with respect to the body mold 103 is formed.
[0012]
When the optical lens is molded using the optical lens molding die 100 having the above configuration, the spherical optical lens material 104 is placed on the first optically effective surface molding portion 101a of the lower mold 101. At this time, the spherical optical lens material 104 is preliminarily formed on a ball-polished glass having a diameter of φ3.32 mm using, for example, fluorophosphate glass (glass transition point: Tg 340 ° C., glass sag point: At 410 ° C.). I have.
[0013]
Further, the upper mold 102 is inserted into the sliding hole 103a of the body mold 103 from above, and the second optically effective surface forming portion 102a of the upper mold 102 is brought into contact with the optical lens material 104, and the upper mold 102 is heated and pressurized. When the annular flat portion 102b of the lower die 101 comes into contact with the annular convex portion 101d of the lower mold 101, the state shown in FIG. In the state shown in FIG. 18, the optical lens material 104 is melted and deformed to be formed as an optical lens 105. After cooling, the shapes of the first surface 105a and the second surface 105b of the optical lens 105 are the same as those of the first optical effective surface forming portion 101a of the lower mold 101 and the second optical effective surface forming portion 102a of the upper mold 102, respectively. It is disclosed that the transferred lens can secure the thickness of the optical lens 105 at the time of design and does not require finish polishing, so that coma aberration in the optical lens performance can be reduced.
[0014]
[Problems to be solved by the invention]
By the way, if the optical lens molding die 100 in the above-described conventional example is used, the first optical effective surface molding portion 101a of the lower die 101 and the annular convex portion 101d for regulating the lens thickness can be simultaneously precision-processed. Although it is possible to improve the mold accuracy and reduce the coma aberration in the optical lens performance, when the lower mold 101 and the upper mold 102 are inserted into the sliding hole 103a of the body mold 103 and slid, the sliding clearance ( (Not shown)). In addition, in the molding die 100 for an optical lens, the dimension of the above-mentioned sliding clearance changes even by a high mold temperature.
[0015]
At this time, a phenomenon occurs in which the lower die 101 and the upper die 102 are displaced due to rattling due to the above-mentioned sliding clearance.
[0016]
As a result, the center of the first optically effective surface forming portion 101a of the lower die 101 and the center of the second optically effective surface forming portion 102a of the upper die 102 are displaced, and the first surface 105a of the optical lens 105 is formed after the molding. And the center of the second surface 105b are displaced from each other, which causes problems such as a decrease in optical lens performance.
[0017]
In particular, as described above, an objective lens for an ultra-high-density optical disc that records and / or reproduces using a blue laser beam having a wavelength of about 400 nm has higher dimensional accuracy than an objective lens for a CD or a DVD. In the objective lens (not shown) disclosed in Patent Document 1 described above, the first surface and the second surface are both formed as aspherical surfaces, so that the center of the first surface and the second surface If there is a positional deviation from the center, coma or chromatic aberration occurs, which affects the recording and / or reproduction of an ultra-high density optical disc.
[0018]
Therefore, when molding an optical lens (for example, an objective lens) having at least one surface having an aspherical surface using an optical glass material, an optical lens that does not shift the center of the first surface and the center of the second surface of the optical lens. A lens molding method and an optical lens mold are desired.
[0019]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and a first invention is a first lens transfer surface formed at an end of a cylindrical portion of a first core for transferring a first surface of an optical lens; In order to transfer the second surface of the optical lens, the cylindrical portion of the first core and the second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter are separated from each other on the same central axis. Facing each other,
Placing a spherical optical glass material on the first lens transfer surface of the first core;
After placing a spherical optical glass material on the first lens transfer surface of the first core, a preload applying member which fits the cylindrical portion of the second core and is elastically displaceable in the radial direction of the first and second cores. When the cylindrical portion of the first core is inserted into the inside and the end of the cylindrical portion of the first core abuts against the end of the cylindrical portion of the second core in the preload applying member, the preload applying member Is elastically displaced in the radial direction of the first and second cores to apply a preload to each cylindrical portion of the first and second cores, so that the first and second cores are inserted into the preload applying member. Removing the sliding clearance of each cylindrical part;
Forming the optical lens by softening the optical glass material between the first and second lens transfer surfaces and then cooling the optical glass material to form the optical lens.
[0020]
According to a second aspect of the present invention, a first lens transfer surface formed at an end of a cylindrical portion of a first core for transferring a first surface of an optical lens and a second lens transfer surface for transferring the second surface of the optical lens are provided. The cylindrical portion of the first core and a second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter are spaced apart from each other on the same central axis, and are opposed to each other. After placing the spherical optical glass material on the one-lens transfer surface, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is placed on the first core. An optical lens mold for molding the optical lens by cooling after softening between the second lens transfer surfaces,
A first mold to which the first core is attached;
A second mold in which the second core is mounted in a bottomed hole of a cylindrical portion,
The first and second cores are mounted in the bottomed hole of the second mold so as to be elastically displaceable in the radial direction, the cylindrical portion of the second core is fitted on one end side, and the first portion is mounted on the other end side. A preload applying member that allows insertion of the cylindrical portion of the core,
At the time of molding, a cylindrical portion of the first core in which the spherical optical glass material is placed on the first lens transfer surface is inserted from the other end side of the preload applying member, and the second portion is inserted into the preload applying member. When the cylindrical portion of the first core is brought into contact with the cylindrical portion of the two cores, the preload applying member is elastically displaced in the radial direction of the first and second cores, and the respective cylindrical portions of the first and second cores are displaced. A mold for an optical lens, wherein a clearance for sliding each of the cylindrical portions of the first and second cores into the preload applying member is eliminated by applying a preload to the mold.
[0021]
In a third aspect, a first lens transfer surface formed at an end of a cylindrical portion of a first core for transferring a first surface of an optical lens and a second lens transfer surface for transferring the second surface of the optical lens are provided. The cylindrical portion of the first core and a second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter are spaced apart from each other on the same central axis, and are opposed to each other. After placing the spherical optical glass material on the one-lens transfer surface, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is placed on the first core. An optical lens mold for molding the optical lens by cooling after softening between the second lens transfer surfaces,
A first mold to which the first core is attached;
A second mold in which the second core is mounted in a bottomed hole of a cylindrical portion,
A portion of each of the ball bearings is rotatably exposed on the inner and outer peripheral sides of a cylindrical retainer supporting a plurality of ball bearings, and the portion along the inner peripheral surface of the bottomed hole of the second mold. A plurality of the ball bearings are rollably fitted, and at the initial state before molding, some of the ball bearings on one end side of the retainer are in contact with the cylindrical portion of the second core. A ball bearing body that allows the cylindrical portion of the first core to be inserted into the remaining ball bearings located on the side.
At the time of molding, a plurality of the ball bearings are integrated with a retainer along with an operation of inserting the first core, in which the spherical optical glass material is placed on the first lens transfer surface, into the ball bearing body. Along the inner peripheral surface of the bottomed hole of the second mold and the respective cylindrical portions of the first and second cores, it moves to the side where the respective cylindrical portions of the first and second cores abut, and a plurality of the ball bearings. Is elastically displaced in the radial direction of the first and second cores, and a preload is applied to each cylindrical portion of the first and second cores, so that the first and second cores are applied to a plurality of ball bearings. A mold for an optical lens, wherein a sliding clearance of each cylindrical portion is eliminated.
[0022]
According to a fourth aspect of the present invention, a first lens transfer surface formed at an end of a cylindrical portion of a first core for transferring a first surface of an optical lens, and a second lens transfer surface for transferring the second surface of the optical lens. The cylindrical portion of the first core and a second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter are spaced apart from each other on the same central axis, and are opposed to each other. After placing the spherical optical glass material on the one-lens transfer surface, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is placed on the first core. An optical lens mold for molding the optical lens by cooling after softening between the second lens transfer surfaces,
A first mold to which the first core is attached;
The second core is formed to penetrate a hole longer than the length of the cylindrical portion, and the cylindrical portion of the second core is fitted into the hole at one end, and the second core is inserted into the hole at the other end. A thin-walled ring-shaped sleeve that allows insertion of a one-core cylindrical portion;
In the bottomed hole of the cylindrical portion, a compression spring is interposed between the top surface of the bottomed hole and one end surface of the second core in which the thin ring-shaped sleeve is fitted. The second core is integrated with the thin ring sleeve in a state where the other end side of the thin ring sleeve in which the second core is fitted by the urging force of the compression spring is projected from the bottomed hole. A second mold movably mounted in the bottomed hole,
A portion of each of the ball bearings is rotatably exposed on the inner and outer peripheral sides of a cylindrical retainer supporting a plurality of ball bearings, and the portion along the inner peripheral surface of the bottomed hole of the second mold. A ball bearing body in which a plurality of the ball bearings are rollably fitted, and a plurality of the ball bearings are in contact with an outer peripheral surface of the thin ring-shaped sleeve;
At the time of molding, the cylindrical portion of the first core, on which the spherical optical glass material is placed on the first lens transfer surface, is inserted into a hole on the other end side of the thin ring-shaped sleeve. The thin ring-shaped sleeve moves toward the top surface inside the bottomed hole of the second mold against the compression spring while abutting the cylindrical portion of the first core against the cylindrical portion of the second core. With the operation, the plurality of ball bearings are integrally formed with the retainer along the inner peripheral surface of the bottomed hole of the second mold and the outer peripheral surface of the thin ring-shaped sleeve. Each of the cylinders of the first and second cores is moved to the side where the cylindrical portions abut, and the plurality of ball bearings are elastically displaced in the radial direction of the first and second cores via the thin ring-shaped sleeve. By applying preload to the part, the thin ring shape The first to leave a hole, an optical lens mold, characterized in that eliminating the sliding clearance the cylindrical portion of the second core.
[0023]
According to a fifth aspect of the present invention, a first lens transfer surface formed at an end of a cylindrical portion of a first core for transferring a first surface of an optical lens and a second lens transfer surface for transferring the second surface of the optical lens are provided. The cylindrical portion of the first core and a second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter are spaced apart from each other on the same central axis, and are opposed to each other. After placing the spherical optical glass material on the one-lens transfer surface, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is placed on the first core. An optical lens mold for molding the optical lens by cooling after softening between the second lens transfer surfaces,
A first mold to which the first core is attached;
The second core is formed to penetrate a hole longer than the length of the cylindrical portion, and the cylindrical portion of the second core is fitted into the hole at one end, and the second core is inserted into the hole at the other end. A thin-walled ring-shaped sleeve that allows insertion of a one-core cylindrical portion;
A second mold in which the second core fitted into the thin ring-shaped sleeve is mounted in a bottomed hole of a cylindrical portion;
The outer peripheral portion of the thin ring-shaped sleeve, which is provided in the bottomed hole of the second mold and in which the second core is fitted, is fitted in the central through hole, and the conical outer peripheral surface is formed in the first, first and second holes. A conical collet formed to be elastically displaceable in the radial direction of the second core;
The conical collet is fitted into the conical outer peripheral surface of the conical collet in the bottomed hole of the second mold, and is pushed along the conical outer peripheral surface of the conical collet by a push-up means provided on the first die side. With a moving collet tightening member,
At the time of molding, the cylindrical portion of the first core, on which the spherical optical glass material is placed on the first lens transfer surface, is inserted into a hole on the other end side of the thin ring-shaped sleeve. When the cylindrical portions of the first and second cores are abutted, the conical outer peripheral surface of the conical collet is pushed up by the lifting means along the outer peripheral surface of the conical collet while pushing up the collet tightening member. By radially tightening the first and second cores and applying a preload to each of the cylindrical portions of the first and second cores via the thin ring-shaped sleeve, the inside of the hole of the thin ring-shaped sleeve is increased. A mold for an optical lens, wherein a clearance for sliding each cylindrical portion of the first and second cores is eliminated.
[0024]
Furthermore, a sixth invention provides the optical lens mold according to any one of the second to fifth inventions described above,
The first core is movably mounted on the first mold in a direction perpendicular to an axial direction, and the cylindrical portion of the first core is moved along with the insertion operation of the first core. An optical lens mold characterized in that it can be centered with respect to a cylindrical portion.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a molding method of an optical lens and a mold for an optical lens according to the present invention will be described in detail in the order of <first embodiment> to <third embodiment> with reference to FIGS. .
[0026]
Before describing an optical lens molding method and an optical lens mold according to the present invention, design specifications of an optical lens molded by applying the method will be described first.
[0027]
FIG. 1 is a diagram for explaining an optical lens formed by applying an optical lens molding method and an optical lens mold according to the present invention.
[0028]
As shown in FIG. 1, an optical lens 1 molded by applying an optical lens molding method and an optical lens mold according to the present invention is an ultra-high-density optical disk using a blue laser beam having a wavelength of about 400 nm. 2 was developed as an objective lens for recording and / or reproducing.
[0029]
The optical lens (hereinafter, referred to as an objective lens) 1 has an aspherical first surface 1a and a second surface 1b that are opposed to each other using an optical glass material (for example, NBF1 manufactured by Hoya Glass Co., Ltd.). A single lens having a numerical aperture (NA) of 0.75 or more.
[0030]
Here, the objective lens 1 converts the blue laser beam La having a wavelength of about 400 nm from the first surface 1a into the ultra-high-density optical disc by entering and refracting the blue laser beam La from the first surface 1a. The laser beam is incident from the second laser beam incident surface 2a to form an image on the signal surface 2a. At this time, the thickness of the ultrahigh-density optical disk 2 from the laser beam incident surface 2a to the signal surface 2b is set to about 0.1 mm to 0.15 mm.
[0031]
When the first surface 1a and the second surface 1b of the objective lens 1 are formed as aspherical surfaces, the aspherical surface is represented by using the following polynomial.
Z = CY²/ (1+ (1- (1 + K) C)²Y²) × 0.5) + aY⁴+ BY⁶+ CY⁸+ DY¹⁰+ EY¹²+ FY¹⁴
Here, Z is the distance from the apex of each surface 1a, 1b, C is the curvature of the respective surfaces 1a, 1b (1 / radius of curvature), Y is the height from the optical axis, K is the conic constant, and a to f are Fourth to fourteenth aspherical coefficients. For example, a corresponds to a coefficient of the fourth power of Y.
[0032]
Here, an example of specifications of the objective lens 1 and the ultra-high density optical disc 2 is shown in Table 1 below.
[0033]
[Table 1]

Table 2 below shows an example of design values of the objective lens 1 and the ultra-high density optical disc 2.
[0034]
[Table 2]

Table 3 below shows an example of the aspheric coefficient of the first surface 1a of the objective lens 1.
[0035]
[Table 3]

Table 4 below shows an example of the aspheric coefficient of the second surface 1b of the objective lens 1.
[0036]
[Table 4]

When the values of the objective lens 1 are set and designed as described above, it is possible to suppress the theoretical coma aberration and chromatic aberration. In addition, the center of the first surface 1a of the objective lens 1 and the The amount of positional deviation (the amount of eccentricity) from the center of the two surfaces 1b depends on the structure of the optical lens mold. Here, when the signal surface 2b of the ultra-high density optical disk 2 has a single-layer structure, the above-mentioned positional deviation (eccentricity) is required to be ± 3 μm or less in design, and is not shown here. However, the signal surface of the ultra-high-density optical disk 2 may have a two-layer structure composed of a first signal surface and a second signal surface separated from the first signal surface by a small distance. The above-mentioned positional deviation amount (eccentric amount) is required to be ± 1 μm or less in design.
[0037]
The method for forming an optical lens and the mold for an optical lens according to the present invention will be described below in accordance with the above-mentioned requirement for the amount of displacement (eccentricity).
[0038]
<First embodiment>
FIG. 2 illustrates a method of molding an optical lens and a mold for an optical lens according to a first embodiment of the present invention, in which a first mold (lower mold) and a second mold (upper mold) are separated. Longitudinal sectional view schematically showing the state before molding,
FIG. 3 is a longitudinal sectional view schematically showing a state where an optical lens is formed by combining a first mold and a second mold in the first embodiment according to the present invention;
FIG. 4 is a perspective view showing the ball bearing shown in FIGS. 2 and 3, a first core (lower core), and a second core (upper core) in the first embodiment according to the present invention. ,
FIG. 5 shows the first embodiment according to the present invention, in which the first core is inserted along a plurality of ball bearings supported by a retainer of a ball bearing body fitted in the bottomed hole of the second mold. FIG. 7 is a diagram schematically illustrating a movement amount of a first core and a movement amount of a lowermost ball bearing.
[0039]
As shown in FIGS. 2 and 3, the optical lens mold 10A according to the first embodiment of the present invention mainly includes an optical lens (for example, an objective lens) having at least one aspheric surface using an optical glass material. ) Is formed so that the center of the first surface of the optical lens and the center of the second surface can be formed without displacement.
[0040]
That is, as shown in FIG. 2, in the optical lens mold 10A of the first embodiment according to the present invention, the cylindrical portion of the first core (lower core) 21 fixed to the first mold (lower mold) 20. A first lens transfer surface 21e formed with an aspheric surface on an upper end 21d of the upper end 21c, and a lower end of a cylindrical portion 31c of a second core (upper core) 31 fixed to a second mold (lower mold) 30. A second lens transfer surface 31e formed with an aspheric surface on 31d is opposed to and spaced apart from each other on the same central axis, and is inserted into the bottomed hole 30e of the second mold 30 when the optical lens 1 is formed. The first and second cores 21 and 31 are elastically displaced in a radial direction of the first and second cores 21 and 31 by a plurality of ball bearings 34 supported by a retainer 33 of the fitted cylindrical ball bearing body BB. By applying a preload to the outer peripheral surfaces of the cylindrical portions 21c and 31c, First to bearings 34, cylindrical portion 21c of the second core 21 and 31, in which form so as to eliminate the sliding clearance 31c. Then, in the initial state before molding, the first core 21 is made to stand by below the second core 31, while the first core 21 is moved relative to the second core 31 by the first and second dies 20, 30 during molding. The first and second molds 20 and 30 are configured to be moved upward while being positioned by a guide shaft (not shown) provided therebetween.
[0041]
In the first embodiment, the first mold (lower mold) 20 is set as a movable side, and the second mold (upper mold) 30 is set as a fixed side. The second mold 30 may be moved downward toward the first mold 20 by setting the second mold 30 to the movable side.
[0042]
First, in the first mold 20 described above, a large-diameter flange portion 20b is formed on the lower surface 20a side, and a cylindrical portion 20c having a smaller diameter than the flange portion 20b is concentrically upward above the flange portion 20b. It is formed short. A bottomed hole 20e is formed in the center of the upper surface 20d of the cylindrical portion 20c of the first mold 20.
[0043]
In addition, a flange 21b formed on the lower surface 21a side of the first core 21 is fitted without clearance into a bottomed hole 20e formed in the first mold 20, and the lower surface 21a of the first core 21 is fixed to the first metal. It is fixed to the first mold 20 by screws 22 from the lower surface 20a side of the mold 20.
[0044]
In addition, the first core 21 has a cylindrical portion 21c formed above the flange portion 21b formed on the lower surface 21a side with a shaft diameter D2 smaller than the flange portion 21b and having a long dimension toward the second mold 30 with good dimensional accuracy. While being formed, the corner of the upper end 21d of the cylindrical portion 21c is slightly rounded or chamfered, and the first lens transfer surface 21e is formed in a concave shape with a predetermined thickness at the center of the upper end 21d. Have been. The first lens transfer surface 21e of the first core 21 is ground using a hard heat-resistant material such as cemented carbide or ceramics, and is subjected to a surface treatment with wear resistance so that the optical glass material 23 does not adhere. To achieve an aspheric surface that meets the lens design specifications. At this time, the first lens transfer surface 21e of the first core 21 is placed on the spherical optical glass material 23, which has been previously polished to a true sphere while controlling the mass before molding, and is first placed at the time of molding. This is for transferring the first surface 1a of the objective lens 1 described with reference to FIG.
[0045]
Next, in the above-mentioned second mold 30, a large-diameter flange portion 30b is formed on the upper surface 30a side, and a cylindrical portion 30c having a smaller diameter than the flange portion 30b is provided below the first die concentrically with the flange portion 30b. A long hole 30e is formed in the center of the cylindrical portion 30c from the lower surface 30d to the flange 30b with a high dimensional accuracy.
[0046]
Further, a flange portion 31b formed on the upper surface 31a side of the second core 31 is fitted without clearance into an upper portion inside the bottomed hole 30e formed in the second mold 30, and the upper surface 31a of the second core 31 is removed. The second mold 30 is fixed to the second mold 30 by screws 32 from the upper surface 30a side.
[0047]
Further, the second core 31 has a cylindrical portion 31c below the flange portion 31b formed on the upper surface 31a side, and has a shaft diameter D2 having a smaller diameter than the flange portion 31b and the same diameter as the cylindrical portion 21c of the first core 21, and has dimensional accuracy. While being formed well, it is formed toward the first mold 20 side concentrically with the bottomed hole 30e with a length of about half the length of the bottomed hole 30e of the second mold 30. I have. The corner of the lower end 31d of the cylindrical portion 31c of the second core 31 is slightly rounded or chamfered, and the second lens transfer surface 31e is formed in a concave shape at the center of the lower end 31d. The second lens transfer surface 31e of the second core 31 is also subjected to a grinding process using a hard heat-resistant material such as a cemented carbide or ceramics, and then subjected to a grinding-resistant surface treatment so that the optical glass material 23 does not adhere. To achieve an aspheric surface that meets the lens design specifications. At this time, the second lens transfer surface 31e of the second core 31 transfers the second surface 1b of the objective lens 1 described above with reference to FIG. 1 during molding.
[0048]
A cylindrical ball bearing body BB serving as a preload applying member is fitted in a bottomed hole 30e formed in the second mold 30. The ball bearing body BB constitutes a main part of the first embodiment, and supports a plurality of ball bearings 34 having a ball diameter D3 along the peripheral surface of the cylindrical retainer 33. At the same time, a plurality of ball bearings 34 are bored in the second mold 30 in a state where a part of each ball bearing 34 is rotatably exposed on the inner peripheral side and the outer peripheral side of the peripheral surface of the retainer 33. It is rollably fitted along the inner peripheral surface of the bottomed hole 30e.
[0049]
Then, in the initial state before molding, the ball bearing body BB has some of the ball bearings 34 supported on the upper end side of the retainer 33 on the outer peripheral surface of the cylindrical portion 31c of the second core 31 on the lower end portion 31d side. At the same time, the lower end of the retainer 33 is brought into contact with the retainer support plate 35 to allow the insertion of the cylindrical portion 21c of the first core 21 into the remaining ball bearing 34 located at the lower end of the retainer 33. are doing.
[0050]
Here, as shown in FIG. 4, the ball bearing body BB is made of a material having heat resistance with respect to the mold temperature at the time of molding the retainer 33 and the plurality of ball bearings. Further, when supporting the plurality of ball bearings 34 along the peripheral surface of the cylindrical retainer 33, the ball bearing body BB holds the plurality of ball bearings 34 at a predetermined angle with respect to the axial direction of the retainer 33. They are arranged along an inclined row. Thereby, when the cylindrical portion 21c of the first core 21 and the cylindrical portion 31c of the second core 31 are inserted from both ends, the plurality of ball bearings 34 exposed on the inner and outer peripheral sides of the retainer 33 are formed by the second metal. The inner peripheral surface of the bottomed hole 30e formed in the mold 30 and the outer peripheral surfaces of the cylindrical portions 21c, 31c of the first and second cores 21, 31 can be contacted at substantially equal intervals.
[0051]
As shown in FIG. 5, when the first core 21 is inserted into the ball bearing body BB fitted in the bottomed hole 30e of the second mold 30 at the start of molding, the cylindrical shape of the first core 21 is reduced. If the position where the upper end 21d of the portion 21c abuts on the lowermost ball bearing 34 among the plurality of ball bearings 34 supported by the retainer 33 is defined as the starting position, in this case, the bottom of the second mold 30 is closed. The inner peripheral surface of the hole 30e functions as a fixed wall for rolling with respect to the remaining ball bearings 34 as well as the lowermost ball bearings 34, and the upper end of the cylindrical portion 21c of the first core 21. Since the lowermost ball bearing 34 starts rotating in the direction of the arrow from the starting position where 21d abuts on the lowermost ball bearing 34, and then continues to rotate while being in contact with the cylindrical portion 21c of the first core 21, Running Similarly to the principle of the above, the amount of movement from the start position of the upper end 21d of the cylindrical portion 21c of the first core 21 to the lower end 31d of the cylindrical portion 31c of the second core 31 with the insertion operation of the first core 21. Is M1, the moving amount M2 of the lowermost ball bearing 34 is equal to or less than 1/2 of the moving amount M1 of the first core 21, that is, M2 ≦ M1 / 2.
[0052]
Then, as shown in FIG. 2, at the start of molding of the objective lens 1, the first core 21 is moved upward toward the second core 31 (arrow S1 side), and the cylindrical portion 21c of the first core 21 is moved to the second position. With the operation of being inserted into the ball bearing body BB fitted into the bottomed hole 30e of the second mold 30, a plurality of ball bearings 34 are integrally formed with the retainer 33 and the bottomed hole of the second mold 30. Along the inner peripheral surface of 30e and the cylindrical portions 21c and 31c of the first and second cores 21 and 31, move upward to the side where the cylindrical portions 21c and 31c of the first and second cores 21 and 31 abut, and When the upper end 21d of the cylindrical portion 21c of the first core 21 abuts against the lower end 31d of the cylindrical portion 31c of the second core 31, as shown in FIG. Outer peripheral surface of cylindrical portion 31c and cylindrical portion of first core 21 To bears against the outer peripheral surface of the 1c.
[0053]
At this time, as shown in FIG. 3, the plurality of ball bearings 34 supported by the retainer 33 are elastically displaced in the radial direction of the first and second cores 21 and 31, so that the first and second cores 21 and 31 are moved. A preload (preload) is applied to the cylindrical portions 21c, 31c of the 31.
[0054]
More specifically, the hole diameter of the bottomed hole 30e formed in the second mold 30 is D1, and the shaft diameter of the cylindrical portion 21c of the first core 21 and the shaft diameter of the cylindrical portion 31c of the second core 31. Is set to D2, and when the ball diameter of the ball bearing 35 is set to D3, by applying a preload to the ball bearing 35 in the radial direction of the first and second cores 21 and 31 within the elastic displacement, D1 <D2 + 2 Since × D3 is satisfied, the plurality of ball bearings 35 are elastically displaced in the radial direction of the first and second cores 21 and 31, and are attached to the cylindrical portions 21c and 31c of the first and second cores 21 and 31. A preload is applied, so that there is no sliding clearance between the plurality of ball bearings 35 and the outer peripheral surfaces of the cylindrical portions 21c, 31c of the first and second cores 21, 31.
[0055]
Thus, when the objective lens 1 is molded, the center of the first lens transfer surface 21e formed on the first core 21 and the center of the second lens transfer surface 31e formed on the second core 31 do not shift. ing.
[0056]
Here, the operation of molding the objective lens 1 described above with reference to FIG. 1 using the optical lens mold 10A of the first embodiment configured as described above will be described with reference to FIGS. This will be described with reference to a new FIG.
[0057]
FIG. 6 is an operation flowchart for explaining the method of molding the optical lens of the first embodiment.
[0058]
As shown in FIG. 6, in the step S10, in the initial state of the optical lens mold 10A, the first core 21 fixed to the first mold 20 is replaced with the second core 31 fixed to the second mold 30. Is waiting below.
[0059]
Next, in step S11, a spherical optical glass material 23 that has been polished in advance is placed on the first lens transfer surface 21e formed on the first core 21.
[0060]
Next, in step S12, the first core 21 is moved upward while the optical glass material 23 is placed on the first lens transfer surface 21e, and the cylindrical portion 21c of the first core 21 is The ball bearing BB is inserted along the plurality of ball bearings 34 supported by the retainer 33 of the ball bearing BB fitted in the bottomed hole 20d.
[0061]
Next, in step S13, the first and second cores 21 and 31 are heated to a glass softening point temperature of the optical glass material 23 by a heater or a heating means (not shown) such as far infrared rays to soften the optical glass material 23. When the first core 21 is moved upward until the upper end 21d of the cylindrical portion 21c of the first core 21 abuts on the lower end 31d of the cylindrical portion 31c of the second core 31, the state shown in FIG. At this time, with the movement amount M1 (FIG. 5) of the first core 21 from the starting position, the plurality of ball bearings 34 are integrally formed with the retainer 33 by the movement amount M2 ≦ M1 / 2 (FIG. 5). It moves upward along the inner peripheral surface of the bottomed hole 30 of the mold 30 and the cylindrical portions 21c and 31c of the first and second cores 21 and 31, in other words, the plurality of ball bearings 34 are formed by the first and second cores. The first and second cores 21 and 31 are moved to the side where the cylindrical portions 21c and 31c abut, and the plurality of ball bearings 34 are elastically displaced in the radial direction of the first and second cores 21 and 31. , 31 are preloaded on the outer peripheral surfaces of the cylindrical portions 21c, 31c.
[0062]
Next, in step S14, after the upper end 21d of the cylindrical portion 21c of the first core 21 abuts against the upper end 31d of the cylindrical portion 31c of the second core 31, the first lens transfer surface 21e formed on the first core 21 is formed. Then, the optical glass material 23 is in a softened state between the first lens 31 and the second lens transfer surface 31e formed on the second core 31.
[0063]
Next, in step S15, when the first and second cores 21 and 31 are cooled by a cooling means (not shown), the objective lens 1 is formed. At this time, the objective lens 1 is formed on the first lens transfer surface 21e of the first core 21. The first surface 1a (FIG. 1) is transferred as an aspheric surface, and the second surface 1b (FIG. 1) of the objective lens 1 is also transferred as an aspheric surface on the second lens transfer surface 31e of the second core 31.
[0064]
Next, in step S16, the first core 21 is moved down to return to the initial state, and the objective lens 1 is taken out. At this time, as the first core 21 moves down, the retainer 33 supporting the plurality of ball bearings 34 moves down to the original initial state.
[0065]
In the above-described operation process, the plurality of ball bearings 34 are elastically displaced in the radial direction of the first and second cores 21 and 31 so that the outer surfaces of the cylindrical portions 21c and 31c of the first and second cores 21 and 31 are moved. Since the preload is applied, the clearance for sliding the cylindrical portions 21c and 31c of the first and second cores 21 and 31 to the plurality of ball bearings 34 does not occur at all. The center of the first lens transfer surface 21e formed on the core 21 does not deviate from the center of the second lens transfer surface 31e formed on the second core 31. As a result, the center of the first surface 1a (FIG. 1) of the molded objective lens 1 and the center of the second surface 1b (FIG. 1) are not misaligned and the amount of misalignment (eccentricity) is suppressed to ± 1 μm or less. Accordingly, the objective lens 1 described above can be used not only for an ultra-high-density optical disk 2 having a single-layer signal surface (FIG. 1) but also for an ultra-high-density optical disk having a dual-layer signal surface (not shown). It becomes possible to correspond.
[0066]
Next, a modified example in which the first embodiment according to the present invention is partially modified will be briefly described with reference to FIG.
[0067]
FIG. 7 is a longitudinal sectional view schematically showing a state in which a first mold and a second mold are combined to form an objective lens in a modified example in which the first embodiment according to the present invention is partially modified. It is.
[0068]
For convenience of explanation, the same components as those shown in the first embodiment are denoted by the same reference numerals and are only shown in the drawings, and components different from those of the first embodiment are newly added. In this modified example, the points different from the first embodiment will be mainly described.
[0069]
As shown in FIG. 7, a mold 10B for an optical lens according to a modified example in which the first embodiment according to the present invention is partially modified, a part of the first mold (lower mold) 20 is the same as that of the first embodiment. The second mold (upper mold) 30 is the same as that of the first embodiment.
[0070]
In this modification, the first core 21 is attached movably in a direction perpendicular to the axis center of the first mold 20 without fixing the first core 21 to the first mold 20.
[0071]
That is, a bottomed hole 20f slightly larger in diameter than the diameter of the flange portion 21b of the first core 21 is formed in the center of the upper surface 20d of the first mold 20.
[0072]
A conical recess 21f is formed in the center of the lower surface 21a of the first core 21. A steel ball 24 is inserted between the inside of the conical recess 21f and the bottom surface of the bottomed hole 20f of the first mold 20. By doing so, the cylindrical portion 21c of the first core 21 is movably supported in a direction perpendicular to the axial direction.
[0073]
Further, by attaching a pressing plate 25 having an escape hole 25a through which the cylindrical portion 21c of the first core 21 penetrates to the upper surface 20d of the first mold 20, the flange portion 21b of the first core 21 is moved to the second position. This prevents the mold 20 from falling out of the bottomed hole 20f or the first core 21 from tilting.
[0074]
Therefore, when the cylindrical portion 21c of the first core 21 is inserted along the plurality of ball bearings 34 supported by the retainer 33 of the ball bearing body BB fitted into the bottomed hole 30e of the second mold 30. In addition, with the operation of slightly rounding or chamfering the corner of the upper end 21 d of the cylindrical portion 21 c of the first core 21 in the retainer 33 or the lowermost ball bearing 34, the first core 21 By moving the flange 21b in the left-right direction (the direction of the arrow) via the steel ball 24, the centering of the cylindrical portion 21c of the first core 21 to the cylindrical portion 31c of the second core 31 is facilitated.
[0075]
<Second embodiment>
FIG. 8 illustrates a method of forming an optical lens and a mold for an optical lens according to a second embodiment of the present invention by separating a first mold (lower mold) and a second mold (upper mold). Longitudinal sectional view schematically showing the state before molding,
FIG. 9 is a longitudinal sectional view schematically showing a state in which an optical lens is formed by combining a first mold and a second mold in the second embodiment according to the present invention.
[0076]
As shown in FIGS. 8 and 9, the mold 40A for an optical lens according to the second embodiment of the present invention is also an optical lens mainly made of an optical glass material and having at least one surface having an aspherical surface (for example, an objective lens). ) Is formed so that the center of the first surface of the optical lens and the center of the second surface can be formed without displacement.
[0077]
In the mold 40A for an optical lens of the second embodiment, unlike the first embodiment, the upper end of the cylindrical portion 21c of the first core (lower core) 21 fixed to the first mold (lower die) 20. A first lens transfer surface 21e formed with an aspherical surface on 21d, and a thin ring shape supported vertically movably through a compression spring 42 in a bottomed hole 30e of a second mold (lower mold) 30 via a compression spring 42. A second lens transfer surface 31e having an aspheric surface at the lower end 31d of the cylindrical portion 31c of the second core (upper core) 31 fitted in the hole 41a of the sleeve 41 is separated from each other on the same central axis. And a plurality of ball bearings 34 supported by a retainer 33 of a cylindrical ball bearing body BB fitted into the bottomed hole 30e of the second mold 30 at the time of molding the optical lens 1. 1, by elastically displacing the second cores 21 and 31 in the radial direction By applying a preload to the outer peripheral surfaces of the cylindrical portions 21c and 31c of the first and second cores 21 and 31 inserted into the thin ring-shaped sleeve 41 via the thick ring-shaped sleeve 41, the holes of the thin ring-shaped sleeve 41 are formed. The sliding gap between the cylindrical portions 21c and 31c of the first and second cores 21 and 31 in the inside 41a is eliminated. Then, in an initial state before molding, the first core 21 is made to stand by below the thin ring-shaped sleeve 41, while, at the time of molding, the first core 21 is moved relative to the second core 31 by the first and second molds 20, 20. The first and second molds 20 and 30 are configured to be moved upward while being positioned by a guide shaft (not shown) provided between the first and second molds 30.
[0078]
As described above, although the structure of the second mold (upper mold) 30 is partially improved from that of the first embodiment, the structure of the first mold (lower mold) 20 is the same as that of the first embodiment. Therefore, for convenience of explanation, components having the same functions as in the first embodiment are denoted by the same reference numerals and will be described as appropriate, and components different from those in the first embodiment will be denoted by new reference numerals. In both cases, the description of the second embodiment will focus on the differences from the first embodiment.
[0079]
First, as shown in FIG. 9, the first mold 20 has a flange 20b formed on the lower surface 20a side and a smaller diameter than the flange 20b above the flange 20b, as in the first embodiment. A cylindrical portion 20c and a bottomed hole 20e formed at the center of the upper surface 20d of the cylindrical portion 20c. A flange portion 21b formed on the lower surface 21a side of the first core 21 is fitted into the bottomed hole 20e without clearance. Then, the first core 21 is fixed to the first mold 20 with the screw 22.
[0080]
Further, the first core 21 has a flange 21b formed on the lower surface 21a side, and a cylindrical portion 21c formed longer and smaller in diameter than the flange 21b above the flange 21b, as in the first embodiment. An optical glass material 23 (FIG. 8) is placed at the center of the upper end 21d of the cylindrical portion 21c, and the first lens transfer surface 21e is formed to have an aspheric surface with a predetermined thickness.
[0081]
Next, as shown in FIGS. 8 and 9, the second mold 30 has a large-diameter flange portion 30b formed on the upper surface 30a side, and a cylindrical portion 30c having a smaller diameter than the flange portion 30b is formed below the second metal mold 30. It is formed longer than the first embodiment concentrically with respect to the first die 20 side with respect to the first mold 20 side, and has a bottomed hole at the center of the cylindrical portion 30c from the lower surface 30d toward the flange portion 30b. 30e is pierced longer than the first embodiment with high dimensional accuracy.
[0082]
Further, unlike the first embodiment, the second core 31 is not fixed to the second mold 30 and the hole of the thin ring-shaped sleeve 41 is provided in the bottomed hole 30e formed in the second mold 30. The second core 31 is vertically movably supported via a compression spring 42 in a state where the cylindrical portion 31c of the second core 31 is fitted into the inside 41a.
[0083]
In addition, the second core 31 has a flange 31b formed on the upper surface 31a side and having a diameter slightly smaller than the diameter of the bottomed hole 30e of the second mold 30, and a smaller diameter than the flange 31b below the flange 31b. And a second lens transfer surface 31e formed with an aspheric surface at the center of the lower end 31d of the cylindrical portion 31c. Although the configuration is substantially the same as that of the example, a thin ring-shaped sleeve 41 formed to have a length substantially twice as long as the length of the cylindrical portion 31c is fitted on the outer peripheral surface of the cylindrical portion 31c of the second core 31. The first embodiment is characterized in that a concave hole 31f for supporting a compression spring 42 interposed between the upper surface 31a of the two-core 31 and the top surface in the bottomed hole 30e of the second mold 30 is formed. Different for the example.
[0084]
At this time, the thin ring-shaped sleeve 41 is penetrated in a thin ring shape using an elastically displaceable phosphor bronze or the like, and is formed to have a length almost twice as long as the length of the cylindrical portion 31c of the second core 31. The cylindrical portion 31c of the second core 31 is previously fitted into the upper half length portion of the hole 41a, and the lower half length portion of the first core 21 is inside the hole 41a. The insertion of the portion 21c is allowed.
[0085]
A ball bearing BB is fitted between the inner peripheral surface of the bottomed hole 30 e of the second mold 30 and the outer peripheral surface 41 b of the thin ring-shaped sleeve 41. This ball bearing body BB has the same configuration as that of the first embodiment, and a plurality of ball bearings 34 are supported along the peripheral surface of a cylindrical retainer 33. In the second embodiment, a preload applying member is constituted by a thin ring-shaped sleeve 41 and a cylindrical ball bearing body BB. The preload is applied to the cylindrical portion 31c of the second core 31 fitted into the hole 41a via the thin ring-shaped sleeve 41 by elastically displacing the plurality of ball bearings 34 in the radial direction of the second core 31. Therefore, the cylindrical portion 31c is substantially press-fitted into the hole 41a.
[0086]
As described later, the plurality of ball bearings 34 supported by the retainer 33 of the ball bearing body BB are in a state in which the cylindrical portion 21c of the first core 21 is inserted into the hole 41a of the thin ring-shaped sleeve 41, as described later. With the operation of moving the thin ring-shaped sleeve 41 integrally with the one core 21 toward the top surface side in the bottomed hole 30 e of the second mold 30, the moving amount of the thin ring-shaped sleeve 41 is １ ／. In the following, the plurality of ball bearings 34 are elastically displaced in the radial direction of the first and second cores 21 and 31 while moving upward, so that the cylindrical portions of the first and second cores 21 and 31 are interposed via the thin ring-shaped sleeve 41. A preload is applied to 21c and 31c.
[0087]
A retainer support plate 35 having an escape hole 35a for allowing the thin ring-shaped sleeve 41 to enter is attached to the lower surface 30c of the cylindrical portion 30c of the second mold 30.
[0088]
Then, in the initial state before molding, as shown in FIG. 8, the cylindrical portion 31c of the second core 31 is fitted by the urging force of the compression spring 42 interposed in the bottomed hole 30e of the second mold 30. The thin ring-shaped sleeve 41 is pressed toward the first mold 20, and the lower end 41 d of the thin ring-shaped sleeve 41 protrudes out of the bottomed hole 30 e of the second mold 30 and the cylindrical portion 21 c of the first core 21. Waiting for insertion.
[0089]
In the initial state before molding, the lower end of the retainer 33 contacts the retainer support plate 35 and the upper end of the retainer 33 contacts the flange 41c of the thin ring sleeve 41 as the thin ring sleeve 41 moves downward. In contact. Further, the lower end 31 d of the cylindrical portion 31 c of the second core 31 fitted in the thin ring-shaped sleeve 41 is located near the lowermost ball bearing 34 among the plurality of ball bearings 34 supported by the retainer 33. are doing.
[0090]
Next, the operation of molding the objective lens 1 described above with reference to FIG. 1 using the optical lens mold 40A of the second embodiment configured as described above will be described with reference to FIGS. This will be described with reference to a new FIG.
[0091]
FIG. 10 is an operation flowchart for explaining the optical lens forming method of the second embodiment.
[0092]
As shown in FIG. 10, in step S20, in the initial state of the optical lens mold 40A, the first core 21 fixed to the first mold 20 is compressed in the bottomed hole 30e of the second mold 30. The urging force of the spring 42 moves to the first mold 20 side and waits below the thin ring-shaped sleeve 41 in which the cylindrical portion 31c of the second core 31 is fitted.
[0093]
Next, in step S21, a spherical optical glass material 23 that has been polished in advance is placed on the first lens transfer surface 21e formed on the first core 21.
[0094]
Next, in step S22, the first core 21 is moved upward while the optical glass material 23 is placed on the first lens transfer surface 21e, and the cylindrical portion 21c of the first core 21 is placed on the thin ring-shaped sleeve 41. When inserted into the hole 41a and the upper end 21d of the cylindrical portion 21c of the first core 21 abuts against the lower end 31d of the cylindrical portion 31c of the second core 31, the state shown in FIG. 9 is reached. At this time, when the cylindrical portion 21c of the first core 21 and the cylindrical portion 31c of the second core 31 abut against each other in the hole 41a of the thin ring-shaped sleeve 41, the inside is closed. A gas escape groove (not shown) of about 0.05 mm is provided on the side surface of the cylindrical portion 21c.
[0095]
Next, in step S23, the first and second cores 21 and 31 are heated to a glass softening point temperature of the optical glass material 23 by a heater or a heating means (not shown) such as far infrared rays to soften the optical glass material 23. Meanwhile, the thin ring-shaped sleeve 41 in which the second core 31 is fitted with the upward movement of the first core 21 resists the urging force of the compression spring 42 and the top surface in the bottomed hole 30 e of the second mold 30. Then, the flange 41c of the thin ring-shaped sleeve 41 comes into contact with the top surface in the bottomed hole 30e of the second mold 30. In accordance with the amount of movement of the thin ring-shaped sleeve 41, the plurality of ball bearings 34 are integrally formed with the retainer 33 so that the inner peripheral surface of the bottomed hole 30 of the second mold 30 is 以下 or less of the above moving charge. In addition, the ball bearings 34 move upward along the outer peripheral surfaces of the cylindrical portions 21c and 31c of the first and second cores 21 and 31, in other words, the plurality of ball bearings 34 are attached to the cylindrical portions 21c and 31c of the first and second cores 21 and 31. By moving the plurality of ball bearings 34 in the radial direction of the first and second cores 21 and 31 by moving the ball bearings 31c to the side where they abut, the first and second cores 21 through the thin ring-shaped sleeve 41. , 31 have a preload applied to the cylindrical portions 21c, 31c.
[0096]
Next, in step S24, after the upper end 21d of the cylindrical portion 21c of the first core 21 abuts against the upper end 31d of the cylindrical portion 31c of the second core 31, the first lens transfer surface 21e formed on the first core 21 is formed. Then, the optical glass material 23 is in a softened state between the first lens 31 and the second lens transfer surface 31e formed on the second core 31.
[0097]
Next, in step S25, when the first and second cores 21 and 31 are cooled by a cooling means (not shown), the objective lens 1 is formed. At this time, the objective lens 1 is placed on the first lens transfer surface 21e of the first core 21. The first surface 1a (FIG. 1) is transferred as an aspheric surface, and the second surface 1b (FIG. 1) of the objective lens 1 is also transferred as an aspheric surface on the second lens transfer surface 31e of the second core 31.
[0098]
Next, in step S26, the first core 21 is moved down to return to the initial state, and the objective lens 1 is taken out. At this time, the thin ring-shaped sleeve 41 in which the second core 31 is fitted moves down by the urging force of the compression spring 42, and accordingly, the retainer 33 supporting the plurality of ball bearings 34 moves down to the original initial state. Move.
[0099]
In the above-described operation process, the plurality of ball bearings 34 are elastically displaced in the radial direction of the first and second cores 21 and 31, and the cylinders of the first and second cores 21 and 31 are moved through the thin ring-shaped sleeve 41. Since a preload is applied to the outer peripheral surfaces of the portions 21c and 31c, the clearance for sliding the cylindrical portions 21c and 31c of the first and second cores 21 and 31 into the hole 41a of the thin ring-shaped sleeve 41 is reduced. Since the state does not occur at all, the center of the first lens transfer surface 21e formed on the first core 21 and the center of the second lens transfer surface 31e formed on the second core 31 do not shift. As a result, the center of the first surface 1a (FIG. 1) of the molded objective lens 1 and the center of the second surface 1b (FIG. 1) are not misaligned, and the amount of misalignment (eccentricity) is suppressed to ± 1 μm or less. be able to. Further, unlike the first embodiment, by using the thin ring-shaped sleeve 41, when inserting the cylindrical portions 21c and 31c of the first and second cores 21 and 31 into the ball bearing body BB, a plurality of balls are used. Since the cylindrical portions 21c and 31c of the first and second cores 21 and 31 do not directly contact the bearing 34, the plurality of ball bearings 34 are not damaged. It is possible to improve the glass material 23, for example, to prevent the glass material 23 from sticking.
[0100]
Next, a modified example in which the second embodiment according to the present invention is partially modified will be briefly described with reference to FIG.
[0101]
FIG. 11 is a longitudinal sectional view schematically showing a state in which a first mold and a second mold are combined to form an objective lens in a modified example in which the second embodiment according to the present invention is partially modified. It is.
[0102]
As shown in FIG. 11, a mold 40B for an optical lens according to a modified example in which the second embodiment according to the present invention is partially modified, a part of the first mold (lower mold) 20 is changed to the second embodiment. The second mold (upper mold) 30 is the same as that of the second embodiment.
[0103]
In this modification, the first core 21 is attached movably in a direction perpendicular to the axis center of the first mold 20 without fixing the first core 21 to the first mold 20.
[0104]
That is, a bottomed hole 20f slightly larger in diameter than the diameter of the flange portion 21b of the first core 21 is formed in the center of the upper surface 20d of the first mold 20.
[0105]
A conical recess 21f is formed in the center of the lower surface 21a of the first core 21. A steel ball 24 is inserted between the inside of the conical recess 21f and the bottom surface of the bottomed hole 20f of the first mold 20. By doing so, the cylindrical portion 21c of the first core 21 is movably supported in a direction perpendicular to the axial direction.
[0106]
Further, by attaching a pressing plate 25 having an escape hole 25a through which the cylindrical portion 21c of the first core 21 penetrates to the upper surface 20d of the first mold 20, the flange portion 21b of the first core 21 is moved to the second position. This prevents the mold 20 from falling out of the bottomed hole 20f or the first core 21 from tilting.
[0107]
Therefore, when inserting the cylindrical portion 21c of the first core 21 into the hole 41a of the thin ring-shaped sleeve 41 in which the second core 31 is fitted, the corner of the upper end portion 21d of the cylindrical portion 21c of the first core 21 is As the slightly rounded or chamfered portion comes into contact with the hole 41a of the thin ring-shaped sleeve 41, the flange portion 21b of the first core 21 moves in the left-right direction (the direction of the arrow) via the steel ball 24. This facilitates centering of the cylindrical portion 21c of the first core 21 on the cylindrical portion 31c of the second core 31.
[0108]
<Third embodiment>
FIG. 12 illustrates a method of forming an optical lens and a mold for an optical lens according to a third embodiment of the present invention, in which a first mold (lower mold) and a second mold (upper mold) are separated. Longitudinal sectional view schematically showing the state before molding,
FIG. 13 is a longitudinal sectional view schematically showing a state where an optical lens is formed by combining a first mold and a second mold in the third embodiment according to the present invention;
FIG. 14 is a perspective view showing the conical collet shown in FIGS. 12 and 13.
[0109]
As shown in FIGS. 12 and 13, the optical lens mold 50A according to the second embodiment of the present invention also includes an optical lens (for example, an objective lens) having at least one aspheric surface mainly using an optical glass material. ) Is formed so that the center of the first surface of the optical lens and the center of the second surface can be formed without displacement.
[0110]
In the optical lens mold 50A of the third embodiment, the upper end 66d of the cylindrical portion 66c of the first core (lower core) 66 fixed to the first mold (lower mold) 60 has an aspheric surface. The formed first lens transfer surface 66e and the lower end of the cylindrical portion 72c of the second core (upper core) 72 fixed to the second mold (lower mold) 70 and fitted in the hole 71a of the thin ring-shaped sleeve 71. A second lens transfer surface 72e formed with an aspherical surface in the portion 72d is opposed to and spaced apart from each other on the same central axis, and the first and second cores 66 are formed on the outer peripheral surface 71b of the thin ring-shaped sleeve 71. , 72 which are elastically displaceable in the radial direction, and which are constricted in the radial direction of the first and second cores 66, 72 by the collet tightening member 75 when the optical lens 1 is formed. Raise through thin ring-shaped sleeve 71 By applying a preload to the outer peripheral surfaces of the cylindrical portions 66c, 72c of the first and second cores 66, 72 inserted into the holes 71a of the lever-shaped thin sleeve 7, the holes 71a of the thin ring-shaped sleeve 71 are inserted into the holes 71a. The sliding gap between the cylindrical portions 66c and 72c of the first and second cores 66 and 72 is eliminated. Then, in an initial state before molding, the first core 66 is made to stand by below the thin ring-shaped sleeve 71 in which the second core 72 is fitted. The first and second molds 60 and 70 are moved upward while being positioned by a guide shaft (not shown) provided between the first and second molds 60 and 70 so that the first and second molds 60 and 70 can be combined. It is configured to be possible.
[0111]
First, as shown in FIG. 12, in the first mold 60, a lower surface 62a of a small-diameter base 62 is concentrically laminated on an upper surface 61a of a large-diameter base 61 so as to be separable, and is used by a fastening means (not shown) during use. Both bases 61 and 62 are integrated.
[0112]
A large-diameter bottomed hole 61b is formed in the center of the upper surface 61a of the large-diameter base 61, and an insertion hole 61c for inserting or removing air or oil from the outer peripheral side of the large-diameter base 61 is provided. It is drilled in communication with the large-diameter bottomed hole 61b.
[0113]
A piston 64 having an O-ring 63 fitted on its outer periphery is fitted into the large-diameter bottomed hole 61b of the large-diameter base 61 so as to be vertically movable by pneumatic or hydraulic pressure. A plurality of push rods 65 are implanted along the circumference, and a plurality of push rods 65 are vertically movably inserted into a plurality of through holes 62d formed in the small diameter base 62. At this time, the plurality of push rods 65 implanted on the piston 64 can freely contact and separate from a collet tightening member 75 provided in a second mold 70 described later.
[0114]
A bottomed hole 62c is formed in the center of the upper surface 62b of the small-diameter base 62, and a flange 66b formed on the lower surface 66a side of the first core 66 is fitted into the bottomed hole 62c without clearance. The lower surface 66a of the first core 66 is fixed to the small-diameter base 62 by screws 67 from the lower surface 62b side of the small-diameter base 62.
[0115]
The first core 66 includes a flange 66b formed on the lower surface 66a side, a cylindrical portion 66c formed with a smaller diameter and longer than the flange 66b above the flange 66b, and an upper end 66d of the cylindrical portion 66c. An optical glass material 23 is placed at the center and a first lens transfer surface 66e formed to have an aspheric surface with a predetermined thickness.
[0116]
Next, in the second mold 70, a large-diameter flange portion 70b is formed on the upper surface 70a side, and a cylindrical portion 70c having a smaller diameter than the flange portion 70b is formed concentrically with the flange portion 70b. A large-diameter bottomed hole 70e and a small-diameter bottomed hole 70f are concentrically formed stepwise from the lower surface 70d toward the flange 70b in the center of the cylindrical portion 70c. Has been drilled.
[0117]
In the small-diameter bottomed hole 70f of the second mold 70, a flange 72b formed on the upper surface 72a side of the second core 72 fitted in the hole 71a of the thin ring-shaped sleeve 71 is fitted without clearance. The upper surface 72a of the second core 72 is fixed to the second mold 70 by screws 73 from the upper surface 70a side of the second mold 70.
[0118]
The second core 72 is formed with a flange 72b formed on the upper surface 72a side, and has a smaller diameter below the flange 72b than the flange 72b and has the same diameter as the cylindrical portion 66c of the first core 66 and is long. And a second lens transfer surface 72e formed with an aspheric surface at the center of the lower end 72d of the cylindrical portion 72c. The outer peripheral surface of the cylindrical portion 72c A thin ring-shaped sleeve 71 formed longer than the length is fitted with its upper end in contact with the flange portion 72b of the second core 72, and a lower end of the thin ring-shaped sleeve 71 is provided with a fall prevention plate 76 described later. Is in contact with
[0119]
At this time, the thin ring-shaped sleeve 71 penetrates in a thin ring shape using an elastically displaceable phosphor bronze or the like and is formed to have a length substantially twice as long as the length of the cylindrical portion 72 of the second core 72, and the hole 71a The cylindrical portion 72c of the second core 72 is fitted in advance into the upper half of the cylindrical portion 72c, and the lower half of the cylindrical portion 72c of the first core 72 in the hole 71a. Insertion is allowed.
[0120]
The outer peripheral surface 71b of the thin ring-shaped sleeve 71 is fitted into a central through hole 74a of a conical collet 74 formed in a conical shape using phosphor bronze that can be elastically displaced. At this time, the conical collet 74 is detachably formed separately from the second mold.
[0121]
As shown in FIG. 14, the above-mentioned conical collet 74 is formed by alternately forming a plurality of second slits 74e and first slits 74f along the conical outer peripheral surface 74b from the upper surface 74c side and the lower surface 74d side. The conical outer peripheral surface 74b of the conical collet 74 is elastically displaceable in the radial direction of the first and second cores 66 and 72.
[0122]
Returning to FIG. 12, the conical outer peripheral surface 74b of the conical collet 74 is fitted into a central conical hole 75a of a collet tightening member 75 provided to be vertically movable along the conical outer peripheral surface 74. In the third embodiment, a thin-ringed sleeve 71, a conical collet 74, and a collet tightening member 75 constitute a preload applying member.
[0123]
Further, the thin ring-shaped sleeve 71, the conical collet 74, and the collet tightening member 75 are prevented from falling downward by the fall prevention plate 76 attached to the lower surface 70d of the cylindrical portion 70c of the second mold 70. At this time, the escape hole 76a penetrating and contacting the center of the fall prevention plate 76 allows the insertion of the cylindrical portion 66c of the first core 66, and the plurality of escape holes 76b penetrating the middle peripheral portion are Insertion of a plurality of push rods 65 provided on the first mold 60 side is allowed.
[0124]
In the initial state before molding, the lower surface 75b of the collet tightening member 75 fitted into the conical outer peripheral surface 74b of the conical collet 74 in the large-diameter bottomed hole 70e of the second mold 70 is provided with a fall prevention plate. The thin ring-shaped sleeve 71 in which the second core 72 is fitted is awaiting the insertion of the cylindrical portion 66c of the first core 66.
[0125]
In the initial state before molding, the plurality of push rods 65 implanted on the piston 64 provided on the first mold 60 side are lowered.
[0126]
Here, the operation of molding the objective lens 1 described above with reference to FIG. 1 using the optical lens mold 50A of the third embodiment configured as described above will be described with reference to FIGS. 12 and 13. This will be described with reference to a new FIG.
[0127]
FIG. 15 is an operation flowchart for explaining the optical lens forming method of the third embodiment.
[0128]
As shown in FIG. 15, in step S30, the first core 66 fixed to the small-diameter base 62 of the first mold 60 was fixed to the second mold 70 in the initial state of the optical lens mold 50A. The second core 72 is on standby below the thin ring-shaped sleeve 71 in which the cylindrical portion 72c of the second core 72 is fitted.
[0129]
Next, in step S31, the spherical optical glass material 23 that has been polished in advance is placed on the first lens transfer surface 66e formed on the first core 66.
[0130]
Next, in step S32, the first core 66 is moved upward while the optical glass material 23 is placed on the first lens transfer surface 66e, and the cylindrical portion 66c of the first core 66 is When inserted into the hole 71a and the upper end 66d of the cylindrical portion 66c of the first core 66 abuts against the lower end 72d of the cylindrical portion 72c of the second core 72, the state shown in FIG. 13 is reached. At this time, when the cylindrical portion 66c of the first core 66 and the cylindrical portion 72c of the second core 72 abut against each other in the hole 71a of the thin ring-shaped sleeve 71, the inside becomes a sealed state. A gas escape groove (not shown) of about 0.05 mm is provided on the side surface of the cylindrical portion 66c.
[0131]
Next, in step S33, the first and second cores 66 and 72 are heated to the glass softening point temperature of the optical glass material 23 by a heater or a heating means (not shown) such as far infrared rays to soften the optical glass material 23. While pushing up the first core 66, the push rod 65 is moved upward via the piston 64, and the collet tightening member 75 is pushed up by the push rod 65 along the conical outer peripheral surface 74 b of the conical collet 74. While thinning the conical outer peripheral surface 74b of the conical collet 74 in the radial direction of the first and second cores 66 and 72, the thin ring-shaped sleeve 71 fitted in the central through-hole 74a of the conical collet 74 is formed. A preload is applied to the cylindrical portions 66c, 72c of the first and second cores 66, 72 through the intermediary of the preload.
[0132]
Next, in step S34, after the upper end 66d of the cylindrical portion 66c of the first core 66 abuts against the upper end 72d of the cylindrical portion 72c of the second core 72, the first lens transfer surface 66e formed on the first core 66 is formed. Then, the optical glass material 23 is in a softened state between the second lens transfer surface 72 e formed on the second core 72.
[0133]
Next, in step S35, when the first and second cores 66 and 72 are cooled by a cooling means (not shown), the objective lens 1 is formed. At this time, the objective lens 1 is placed on the first lens transfer surface 66e of the first core 66. The first surface 1a (FIG. 1) is transferred as an aspheric surface, and the second surface 1b (FIG. 1) of the objective lens 1 is also transferred as an aspheric surface on the second lens transfer surface 72e of the second core 72.
[0134]
Next, in step S36, the first core 66 is moved down to return to the initial state, and the objective lens 1 is taken out. At this time, the push rod 65 is moved downward through the piston 64 to separate the push rod 65 from the collet tightening member 75.
[0135]
In the above operation process, the conical collet 74 is pressed up in the radial direction of the first and second cores 66 and 72 while the collet tightening member 75 is pushed up along the conical outer peripheral surface 74b of the conical collet 74. Since the preload is applied to the outer peripheral surfaces of the cylindrical portions 66c and 72c of the first and second cores 66 and 72 via the thin ring-shaped sleeve 71, the thin ring-shaped sleeve 71 is inserted into the hole 71a. The center of the first lens transfer surface 66e formed on the first core 66 and the second core 72 are formed so that no sliding clearance is generated between the cylindrical portions 66c and 72c of the first and second cores 66 and 72. Does not deviate from the center of the second lens transfer surface 72e. As a result, the center of the first surface 1a (FIG. 1) of the molded objective lens 1 and the center of the second surface 1b (FIG. 1) are not misaligned and the amount of misalignment (eccentricity) is suppressed to ± 1 μm or less. Can be. Further, unlike the first and second embodiments, since the expensive ball bearing body BB is not used, the optical lens mold 50A can be manufactured at low cost.
[0136]
Next, a modified example in which the third embodiment according to the present invention is partially modified will be briefly described with reference to FIG.
[0137]
FIG. 16 is a longitudinal sectional view schematically showing a state in which an objective lens is formed by combining a first mold and a second mold in a modification in which the third embodiment according to the present invention is partially modified. It is.
[0138]
As shown in FIG. 16, a mold 50 </ b> B for an optical lens according to a modified example in which the third embodiment according to the present invention is partially modified, a part of a first mold (lower mold) 60 is the same as that of the third embodiment. The second mold (upper mold) 70 is the same as that of the third embodiment.
[0139]
In this modified example, the first core 66 is attached to the small-diameter base 62 of the first mold 60 without being fixed to the small-diameter base 62 so as to be movable in a direction perpendicular to the axial center of the small-diameter base 62.
[0140]
That is, a bottomed hole 62 e having a diameter slightly larger than the diameter of the flange 66 b of the first core 66 is formed in the center of the upper surface 62 b of the small diameter base 62 of the first mold 60.
[0141]
A conical recess 66f is formed at the center of the lower surface 66a of the first core 66, and a steel ball 68 is inserted between the inside of the conical recess 66f and the bottom surface of the bottomed hole 62e of the small-diameter base 62. Thus, the cylindrical portion 66c of the first core 66 is movably supported in a direction perpendicular to the axial direction.
[0142]
In addition, a holding plate 69 having an escape hole 69a through which the cylindrical portion 66c of the first core 66 enters and an escape hole 69b through which the plurality of push rods 65 enter is attached to the upper surface 62b of the small diameter base 62. Thus, the flange 66b of the first core 66 is prevented from dropping out of the bottomed hole 62e of the small diameter base 62, or the first core 66 is prevented from tilting.
[0143]
Therefore, when the cylindrical portion 66c of the first core 66 is inserted into the hole 71a of the thin ring-shaped sleeve 71 in which the second core 72 is fitted, the corner of the upper end portion 66d of the cylindrical portion 66c of the first core 66 is set. As the slightly rounded or chamfered portion comes into contact with the hole 71a of the thin ring-shaped sleeve 71, the flange portion 66b of the first core 66 moves in the left-right direction (the direction of the arrow) via the steel ball 68. This facilitates centering of the cylindrical portion 66c of the first core 66 on the cylindrical portion 72c of the second core 72.
[0144]
【The invention's effect】
According to the optical lens molding method and the optical lens mold described in detail above, the first lens transfer surface formed on the end of the cylindrical portion of the first core for transferring the first surface of the optical lens. And a second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter as the cylindrical portion of the first core for transferring the second surface of the optical lens on the same central axis. Then, the cylindrical portion of the first core is inserted into the preload applying member capable of elastically displacing in the radial direction of the first and second cores by fitting the cylindrical portion of the second core into the cylindrical portion of the second core within the preload applying member. When the end of the cylindrical portion of the first core is abutted against the end of the portion, the preload applying member is elastically displaced in the radial direction of the first and second cores to preload the cylindrical portion of the first and second cores. To eliminate the sliding clearance of each cylindrical portion of the first and second cores into the preload applying member, Les by a center of the first lens transfer surface formed on the first core, and the center of the second lens transfer surface formed in the second core is not displaced. As a result, the amount of misalignment (the amount of eccentricity) of the center of the first surface and the center of the second surface of the molded optical lens (objective lens) can be suppressed to ± 1 μm or less without misalignment. Thus, when the optical lens is molded as, for example, an objective lens for an ultra-high-density optical disk, the positional deviation (eccentricity) between the center of the first surface and the center of the second surface 1b of the molded objective lens is ± 1 μm. By suppressing the thickness below, it is possible to cope with not only an ultra-high-density optical disk having a single-layer signal surface but also an ultra-high-density optical disk having a two-layer signal surface.
[0145]
At this time, the preload applying member uses a ball bearing body that supports a plurality of ball bearings along the peripheral surface of the cylindrical retainer, and abuts the plurality of ball bearings with each other. A preload is applied to each cylindrical portion of the first and second cores by directly contacting each cylindrical portion of the first and second cores and elastically displacing a plurality of ball bearings in the radial direction of the first and second cores. An additional structure may be used.
[0146]
The above-described preload applying member uses a thin ring-shaped sleeve and a ball bearing body that supports a plurality of ball bearings along a peripheral surface of a cylindrical retainer. When the cylindrical portions of the first and second cores abut against each other in the hole of the sleeve, a plurality of ball bearings are brought into contact with the outer peripheral surface of the thin ring-shaped sleeve, and the plurality of ball bearings are attached to the first and second cores. A structure in which a preload is applied to each cylindrical portion of the first and second cores via a thin ring-shaped sleeve by elastically displacing in the radial direction of the two cores may be used.
[0147]
The above-mentioned preload applying member uses a thin ring-shaped sleeve, a conical collet, and a collet tightening member as described in claim 5, and includes first and second outer circumferential portions of the thin ring-shaped sleeve. A conical collet that can be elastically displaced in the radial direction of the core is fitted therein, and a collet tightening member is movably provided along the conical outer peripheral surface of the conical collet. When the cylindrical portions of the second core are abutted against each other, the conical collet is tightened in the radial direction of the first and second cores by a collet tightening member, and the first and second cores are fastened via a thin ring-shaped sleeve. A structure in which a preload is applied to each cylindrical portion may be used.
[Brief description of the drawings]
FIG. 1 is a view for explaining an optical lens formed by applying an optical lens molding method and an optical lens mold according to the present invention.
FIG. 2 is a diagram illustrating a first mold (lower mold) and a second mold (upper mold) in order to explain a molding method of an optical lens and a mold for an optical lens according to a first embodiment of the present invention; FIG. 3 is a longitudinal sectional view schematically showing a state before molding.
FIG. 3 is a longitudinal sectional view schematically showing a state where an optical lens is formed by combining a first mold and a second mold in the first embodiment of the present invention.
FIG. 4 is a perspective view showing the ball bearing shown in FIGS. 2 and 3, a first core (lower core), and a second core (upper core) in the first embodiment of the present invention. FIG.
FIG. 5 is a perspective view of the first embodiment of the present invention, in which the first core is inserted along a plurality of ball bearings supported by a retainer of a ball bearing body fitted into the bottomed hole of the second mold. FIG. 4 is a diagram schematically illustrating a movement amount of a first core and a movement amount of a lowermost ball bearing.
FIG. 6 is an operation flowchart for explaining a method of molding the optical lens of the first embodiment.
FIG. 7 is a longitudinal sectional view schematically showing a state in which a first mold and a second mold are combined to form an objective lens in a modified example in which the first embodiment according to the present invention is partially modified. FIG.
FIG. 8 is a view illustrating a method of molding an optical lens and a mold for an optical lens according to a second embodiment of the present invention, in which a first mold (lower mold) and a second mold (upper mold) are separated. FIG. 3 is a longitudinal sectional view schematically showing a state before molding.
FIG. 9 is a longitudinal sectional view schematically showing a state in which an optical lens is formed by combining a first mold and a second mold in the second embodiment according to the present invention.
FIG. 10 is an operation flowchart for explaining a method of molding an optical lens according to a second embodiment.
FIG. 11 is a longitudinal sectional view schematically showing a state in which a first mold and a second mold are combined to form an objective lens in a modified example in which the second embodiment according to the present invention is partially modified. FIG.
FIG. 12 shows a first mold (lower mold) and a second mold (upper mold) separated for explaining the optical lens molding method and the optical lens mold of the third embodiment according to the present invention. FIG. 3 is a longitudinal sectional view schematically showing a state before molding.
FIG. 13 is a longitudinal sectional view schematically showing a state in which an optical lens is formed by combining a first mold and a second mold in a third embodiment according to the present invention.
FIG. 14 is a perspective view showing the conical collet shown in FIGS. 12 and 13;
FIG. 15 is an operation flowchart for explaining a method of molding an optical lens according to a third embodiment.
FIG. 16 is a longitudinal sectional view schematically showing a state in which a first mold and a second mold are combined to form an objective lens in a modification in which the third embodiment according to the present invention is partially modified. FIG.
FIG. 17 is a schematic view showing the structure of a molding die for an optical lens in a conventional example.
FIG. 18 is a state diagram of a molding die of an optical lens at the time of completion of molding in a conventional example.
[Explanation of symbols]
1 optical lens (objective lens), 1a first surface 1a, 1b second surface,
2 ... Ultra high density optical disk, 2a ... Laser beam incident surface, 2b ... Signal surface,
10A: mold for optical lens of first embodiment,
10B—a mold for an optical lens according to a modified example in which the first embodiment is partially modified;
20: first mold (lower mold), 20a: lower surface, 20b: flange portion, 20c: cylindrical portion,
20d: upper surface, 20e: bottomed hole, 20f: bottomed hole,
21: first core (lower core), 21a: lower surface, 21b: flange, 21c: cylindrical portion,
21d: upper end, 21e: first lens transfer surface,
23: spherical optical glass material, 24: steel ball, 25: holding plate,
Reference numeral 30: second mold (upper die), 30a: upper surface, 30b: flange portion, 30c: cylindrical portion,
30d: lower surface, 30e: bottomed hole,
31: second core (upper core), 31a: upper surface, 31b: flange, 31c: cylindrical portion,
31d: lower end, 31e: second lens transfer surface,
33: retainer, 34: ball bearing,
35 ... retainer support plate,
40A: mold for optical lens of second embodiment,
40B ... a mold for an optical lens according to a modified example obtained by partially modifying the second embodiment;
41: thin ring-shaped sleeve, 41a: hole, 41b: outer peripheral surface,
42 ... compression spring,
50A: mold for optical lens of second embodiment,
50B... An optical lens mold of a modification obtained by partially modifying the second embodiment;
60: first mold (lower mold),
61: Large diameter base, 61a: Upper surface, 61b: Large diameter bottomed hole, 61c: Insertion / removal hole,
62: small diameter base, 62a: lower surface, 62b: upper surface, 62c: bottomed hole,
63 ... O-ring, 64 ... piston, 65 ... push rod,
66: first core (lower core), 66a: lower surface, 66b: flange portion, 66c: cylindrical portion,
66d: upper end, 66e: first lens transfer surface,
68 ... steel ball, 69 ... holding plate,
70: second mold (upper mold), 70a: upper surface, 70b: flange portion, 70c: cylindrical portion,
70d: bottom surface, 70e: large diameter bottomed hole, 7f: small diameter bottomed hole,
71 ... thin ring-shaped sleeve, 71 a ... hole, 71 b ... outer peripheral surface,
72: second core (upper core), 72a: upper surface, 72b: flange portion, 72c: cylindrical portion,
72d: lower end, 72e: second lens transfer surface,
74: conical collet, 74a: central through hole, 74b: conical outer peripheral surface,
74c: upper surface, 74d: lower surface, 74e: first slit, 74f: second slit, 75: collet tightening member, 75a: central conical hole,
76: Fall prevention plate,
BB: Ball bearing body.

Claims (6)

A first lens transfer surface formed at an end of the cylindrical portion of the first core for transferring the first surface of the optical lens; and a cylindrical portion of the first core for transferring the second surface of the optical lens. Causing a second lens transfer surface formed at an end of the cylindrical portion of the second core having the same diameter to face and be spaced apart from each other on the same central axis;
Placing a spherical optical glass material on the first lens transfer surface of the first core;
After placing a spherical optical glass material on the first lens transfer surface of the first core, a preload applying member which fits the cylindrical portion of the second core and is elastically displaceable in the radial direction of the first and second cores. When the cylindrical portion of the first core is inserted into the inside and the end of the cylindrical portion of the first core abuts against the end of the cylindrical portion of the second core in the preload applying member, the preload applying member Is elastically displaced in the radial direction of the first and second cores to apply a preload to each cylindrical portion of the first and second cores, so that the first and second cores are inserted into the preload applying member. Removing the sliding clearance of each cylindrical part;
Forming the optical lens by cooling the optical glass material between the first and second lens transfer surfaces and then cooling the optical glass material. A first lens transfer surface formed at an end of the cylindrical portion of the first core for transferring the first surface of the optical lens; and a cylindrical portion of the first core for transferring the second surface of the optical lens. A second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter is opposed to and separated from each other on the same central axis, and a spherical surface is formed on the first lens transfer surface of the first core. After placing the optical glass material, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is moved between the first and second lens transfer surfaces. In an optical lens mold for forming the optical lens by cooling after softening,
A first mold to which the first core is attached;
A second mold in which the second core is mounted in a bottomed hole of a cylindrical portion,
The first and second cores are mounted in the bottomed hole of the second mold so as to be elastically displaceable in the radial direction, the cylindrical portion of the second core is fitted on one end side, and the first portion is mounted on the other end side. A preload applying member that allows insertion of the cylindrical portion of the core,
At the time of molding, the cylindrical portion of the first core in which the spherical optical glass material is placed on the first lens transfer surface is inserted from the other end side of the preload applying member, and the second portion is inserted into the preload applying member. When the cylindrical portion of the first core is brought into contact with the cylindrical portion of the two cores, the preload applying member is elastically displaced in the radial direction of the first and second cores, and the respective cylindrical portions of the first and second cores are displaced. A mold for an optical lens, wherein a clearance for sliding each of the cylindrical portions of the first and second cores into the preload applying member is eliminated by applying a preload to the mold. A first lens transfer surface formed at an end of the cylindrical portion of the first core for transferring the first surface of the optical lens; and a cylindrical portion of the first core for transferring the second surface of the optical lens. A second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter is opposed to and separated from each other on the same central axis, and a spherical surface is formed on the first lens transfer surface of the first core. After placing the optical glass material, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is moved between the first and second lens transfer surfaces. In an optical lens mold for forming the optical lens by cooling after softening,
A first mold to which the first core is attached;
A second mold in which the second core is mounted in a bottomed hole of a cylindrical portion,
A portion of each of the ball bearings is rotatably exposed on the inner and outer peripheral sides of a cylindrical retainer supporting a plurality of ball bearings, and the portion along the inner peripheral surface of the bottomed hole of the second mold. A plurality of the ball bearings are rollably fitted, and at the initial state before molding, some of the ball bearings on one end side of the retainer are in contact with the cylindrical portion of the second core. A ball bearing body that allows the cylindrical portion of the first core to be inserted into the remaining ball bearings located on the side.
At the time of molding, a plurality of the ball bearings are integrated with a retainer along with an operation of inserting the first core, in which the spherical optical glass material is placed on the first lens transfer surface, into the ball bearing body. Along the inner peripheral surface of the bottomed hole of the second mold and the respective cylindrical portions of the first and second cores, it moves to the side where the respective cylindrical portions of the first and second cores abut, and a plurality of the ball bearings. Is elastically displaced in the radial direction of the first and second cores, and a preload is applied to each cylindrical portion of the first and second cores. A mold for an optical lens, wherein a sliding clearance of each cylindrical portion is eliminated. A first lens transfer surface formed at an end of the cylindrical portion of the first core for transferring the first surface of the optical lens; and a cylindrical portion of the first core for transferring the second surface of the optical lens. A second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter is opposed to and separated from each other on the same central axis, and a spherical surface is formed on the first lens transfer surface of the first core. After placing the optical glass material, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is moved between the first and second lens transfer surfaces. In an optical lens mold for forming the optical lens by cooling after softening,
A first mold to which the first core is attached;
The second core is formed to penetrate a hole longer than the length of the cylindrical portion, and the cylindrical portion of the second core is fitted into the hole at one end, and the second core is inserted into the hole at the other end. A thin-walled ring-shaped sleeve that allows insertion of a one-core cylindrical portion;
In the bottomed hole of the cylindrical portion, a compression spring is interposed between the top surface of the bottomed hole and one end surface of the second core in which the thin ring-shaped sleeve is fitted. The second core is integrated with the thin ring sleeve in a state where the other end side of the thin ring sleeve in which the second core is fitted by the urging force of the compression spring is projected from the bottomed hole. A second mold movably mounted in the bottomed hole,
A portion of each of the ball bearings is rotatably exposed on the inner and outer peripheral sides of a cylindrical retainer supporting a plurality of ball bearings, and the portion along the inner peripheral surface of the bottomed hole of the second mold. A ball bearing body in which a plurality of the ball bearings are rollably fitted, and a plurality of the ball bearings are in contact with an outer peripheral surface of the thin ring-shaped sleeve;
At the time of molding, the cylindrical portion of the first core, on which the spherical optical glass material is placed on the first lens transfer surface, is inserted into a hole on the other end side of the thin ring-shaped sleeve. The thin ring-shaped sleeve moves toward the top surface inside the bottomed hole of the second mold against the compression spring while abutting the cylindrical portion of the first core against the cylindrical portion of the second core. With the operation, the plurality of ball bearings are integrally formed with the retainer along the inner peripheral surface of the bottomed hole of the second mold and the outer peripheral surface of the thin ring-shaped sleeve. Each of the cylinders of the first and second cores is moved to the side where the cylindrical portions abut, and the plurality of ball bearings are elastically displaced in the radial direction of the first and second cores via the thin ring-shaped sleeve. By applying preload to the part, the thin ring shape The first to leave a hole, an optical lens mold, characterized in that eliminating the sliding clearance the cylindrical portion of the second core. A first lens transfer surface formed at an end of the cylindrical portion of the first core for transferring the first surface of the optical lens; and a cylindrical portion of the first core for transferring the second surface of the optical lens. A second lens transfer surface formed at the end of the cylindrical portion of the second core having the same diameter is opposed to and separated from each other on the same central axis, and a spherical surface is formed on the first lens transfer surface of the first core. After placing the optical glass material, the end of the cylindrical portion of the first core is abutted against the end of the cylindrical portion of the second core, and the optical glass material is moved between the first and second lens transfer surfaces. In an optical lens mold for forming the optical lens by cooling after softening,
A first mold to which the first core is attached;
The second core is formed to penetrate a hole longer than the length of the cylindrical portion, and the cylindrical portion of the second core is fitted into the hole at one end, and the second core is inserted into the hole at the other end. A thin-walled ring-shaped sleeve that allows insertion of a one-core cylindrical portion;
A second mold in which the second core fitted into the thin ring-shaped sleeve is mounted in a bottomed hole of a cylindrical portion;
The outer peripheral portion of the thin ring-shaped sleeve, which is provided in the bottomed hole of the second mold and in which the second core is fitted, is fitted in the central through hole, and the conical outer peripheral surface is formed in the first, first and second holes. A conical collet formed to be elastically displaceable in the radial direction of the second core;
The conical collet is fitted into the conical outer peripheral surface of the conical collet in the bottomed hole of the second mold, and is pushed along the conical outer peripheral surface of the conical collet by a push-up means provided on the first die side. With a moving collet tightening member,
At the time of molding, the cylindrical portion of the first core, in which the spherical optical glass material is placed on the first lens transfer surface, is inserted into a hole on the other end side of the thin ring-shaped sleeve. When the cylindrical portions of the first and second cores are abutted, the conical outer peripheral surface of the conical collet is pushed up by the lifting means along the outer peripheral surface of the conical collet while pushing up the collet tightening member. By radially tightening the first and second cores and applying a preload to each of the cylindrical portions of the first and second cores via the thin ring-shaped sleeve, the inside of the hole of the thin ring-shaped sleeve is reduced. A mold for an optical lens, wherein a clearance for sliding each cylindrical portion of the first and second cores is eliminated. The mold for an optical lens according to any one of claims 2 to 5,
The first core is movably mounted on the first mold in a direction perpendicular to the axial direction, and the cylindrical portion of the first core is moved along with the insertion operation of the first core. A mold for an optical lens, wherein the mold can be centered on a cylindrical portion.

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