JP2004042220A - Lens centering method, lens processing method, and lens - Google Patents

Abstract

To efficiently and stably center a lens in a lens centering machine.
A surface and a surface of a lens are held at low pressure by bell holders and rotated at high speed to center the lens. After the completion of such centering, the rotational speed is reduced and the side peripheral surface of the lens W is processed into a perfect circle by the grindstone 5. The difficulty of centering and the friction between the bell holders 1 and 2 are predicted based on the centering coefficient and the surface roughness based on the shape of the lens W, and the centering rotation speed, centering time, and lens holding force at the time of centering are predicted. By controlling the centering conditions such as the above, efficiency and stabilization of the centering action are achieved.
[Selection diagram] Fig. 1

Description

ここで、Ｄ１、Ｄ２：レンズ保持具外径（ｍｍ）
Ｒ１、Ｒ２：レンズ両面の曲率半径（ｍｍ）
±：両凸および両凹レンズの場合は＋、メニスカスレンズの場合は−
【００１２】
心出し係数および面粗さに基づいてレンズを複数のグループに分類するとよい。
【００１３】
レンズ挟持力を９．８Ｎ以上、９８Ｎ以下に制御するとよい。
【００１４】
心出し回転数を２０００ｒｐｍ以下に制御するとよい。
【００１５】
心出し時間を３０秒以下に制御するとよい。
【００１６】
心出し係数が０．７以下であるとよい。
【００１７】
レンズの球面部の面粗さが１０μｍ以下であるとよい。
【００１８】
【作用】
ベルクランプ方式のレンズ心取加工機において、レンズを低圧挟持してレンズ軸まわりに回転させるレンズ心出しを効率よく安定して行なうために、レンズ形状による心出し難易度を示す心出し係数を求める。この心出し係数によって、各レンズの心出しの難易度を予測するとともに、レンズ保持具との間の摩擦をレンズの面粗さによって推測し、被加工レンズのための適正な心出し条件を設定して心出しを行なう。
【００１９】
例えば、上記のように予測された心出しの難易度と面粗さに基づいてレンズを複数のグループに分類し、各グループごとに心出し回転数、心出し時間および心出し時のレンズ挟持力のうちの少なくとも１つの適正値を設定する。
【００２０】
レンズ形状や面粗さに合わせて適正な心出し条件で心出しを行なうことで、低圧クランプ時の安定性を高めるとともに心出し効率を向上させる。これによって、レンズ加工コストの低減に貢献できる。
【００２１】
また、低圧クランプ時の圧力制御のための制御ユニット等を省略することで、装置コストも低減できる。
【００２２】
なお、心出し回転数は、レンズ軸の軸受等の耐久性を考慮して、できる限り低速回転が望ましい。
【００２３】
また、心出し時間は、加工コストの観点から、短時間である方がよい。
【００２４】
【発明の実施の形態】
本発明の実施の形態を図面に基づいて説明する。
【００２５】
図１は、一実施の形態に用いるレンズ心出しクランプ装置を備えたレンズ心取加工機を示すもので、これは、図示中央の固定側ベルホルダ１にレンズＷを吸着して仮保持し、第１の回転駆動部３によってレンズ保持具であるベルホルダ１、２を低速回転させながら、可動側ベルホルダ２を下方へ移動させて、固定側ベルホルダ１と可動側ベルホルダ２との間にレンズＷを挟持する過程で可動側ベルホルダ２のレンズ当接部２ａとレンズＷの接触点に作用する接線力等を利用して、各ベルホルダ１、２のレンズ当接部１ａ、２ａに対してレンズＷを滑らせることで初期の心出しを行ない、続いて、レンズＷの吸着を解除して、両ベルホルダ１、２の間にレンズＷを９．８Ｎ以上、９８Ｎ以下のレンズ挟持力（クランプ力）で挟持した状態で、第２の回転駆動部７によって、両ベルホルダ１、２を予め設定された心出し時間高速回転させることで心出しを完了するように構成されている。
【００２６】
この高速回転による心出し時間は、一定時間高速回転させた後に停止し、再び一定時間高速回転させる場合は、初期の高速回転開始から最後の高速回転完了迄とする。
【００２７】
レンズ挟持力については、上記の範囲を拡大すれば、心出しの条件は拡大するが、装置のコスト高となる。
【００２８】
固定側ベルホルダ１は、中空部１１ａを有するスピンドル１１と一体的に結合され、スピンドル１１の軸受１２によって回転自在に支持されている。スピンドル１１の中空部１１ａは、ニップル１１ｂによって図示しない真空源に接続され、固定側ベルホルダ１のレンズ当接部１ａにレンズＷを吸着するための真空吸着力を発生させる。
【００２９】
また、可動側ベルホルダ２は、スピンドル２１の一端にこれと一体的に結合され、スピンドル２１は軸受２２によって回転自在に支持されている。
【００３０】
両ベルホルダ１、２を回転させる第１の回転駆動部３は、モータ３０の駆動を電磁クラッチ３０ａの作動により、固定側ベルホルダ１のスピンドル１１に伝達する回転軸３２およびギア列３３、３４と可動側ベルホルダ２のスピンドル２１に伝達するギア列３５、３６に連結自在である。
【００３１】
第１の回転駆動部３によるベルホルダ１、２の回転数は、１００ｒｐｍ以下の低速回転で任意に制御され、砥石５によってレンズＷの外周部（側周面）等を研削するセンタリング工程（心取加工）に用いられる。
【００３２】
砥石５は、不図示の回転源より、砥石スピンドル５１に回転を伝達し、回転できる構成とする。
【００３３】
加工時の砥石周速度は、３５ｍ／秒以下で制御を可能としている。
【００３４】
また、砥石５は、スピンドル１１、２１に対し、平行に移動する機構５３を有する不図示の軸方向スライドユニットと垂直に移動する機構５２を有する不図示の送りスライドユニットに連結され、レンズＷの側周面等を研削する。
【００３５】
両ベルホルダ１、２を回転させる第２の回転駆動部７は、モータ７０の駆動を電磁クラッチ７０ａの作動により、固定側ベルホルダ１のスピンドル１１に伝達する回転軸３２およびギア列３３、３４と可動側ベルホルダ２のスピンドル２１に伝達するギア列３５、３６に連結自在である。
【００３６】
第２の回転駆動部７によるベルホルダ１、２の回転数は、２０００ｒｐｍ以下の範囲で任意に制御され、前述のように両ベルホルダ１、２を高速回転させて自動クランプによるレンズ心出しを行なう工程に用いる。
【００３７】
また、第２の回転駆動部７は、不図示のタイマーにて、３０秒以下で任意に作動時間の設定を可能とする。
【００３８】
可動側ベルホルダ２を軸方向へ移動させる軸方向駆動部４は、可動側ベルホルダ２の軸中心を加圧し、移動させるもので、可動側ベルホルダ２の回転中心と軸方向駆動部４の駆動軸を合致させたピストン４１を有するシリンダ４２と、中心押圧治具４３、４４、フレキシブルジョイント４５、シリンダ４２の移動検出用センサ４６等を有する。
【００３９】
シリンダ４２は、不図示の本体ベース上に支持され、上記のようにシリンダ４２の軸中心と可動側ベルホルダ２の軸中心は、同一直線上に配設され、中心押圧治具４３、シリンダ４２のピストン４１に連結され、中心押圧治具４３は、フレキシブルジョイント４５に連結され、可動側ベルホルダ２のスピンドル２１にも連結される。
【００４０】
シリンダ４２の移動検出センサ４６は、シリンダ４２のハウジングに配設され、レンズＷに可動側ベルホルダ２が到達したことを検出するセンサであり、レンズＷまでの移動距離が変化した場合、移動検出センサ４６は、シリンダ４２のハウジングの軸方向に移動できるように構成されている。
【００４１】
シリンダ４２は、不図示の加圧方向切り換え弁を経由して、低圧挟持のための低圧レギュレータと高圧挟持のための高圧レギュレータに接続自在である。加圧方向切り換え弁は、可動側ベルホルダ２の下方向への軸移動と上方向への軸移動に用いる。
【００４２】
高圧レギュレータとの接続は、レンズＷの側周面の研削時等であり、低圧レギュレータとの接続は、レンズＷを吸着した固定側ベルホルダ１に向かって可動側ベルホルダ２を軸方向に移動させ、自動クランプによるレンズ心出しにおいて両ベルホルダ１、２を高速回転させる工程で行なう。
【００４３】
砥石５の駆動部は、前述のように、不図示の心取加工機の支持台ベースの上面に配設された不図示の軸方向スライドユニット、送りスライドユニット、砥石スピンドル５１等を備えている。
【００４４】
砥石５によってレンズＷの側周面を研削するエリアには、不図示の研削液供給ユニットにより、研削液を供給する。
【００４５】
カバー８は、砥石５、可動側ベルホルダ２、固定側ベルホルダ１を覆うもので、軸方向スライドユニット、送りスライドユニットに研削液が飛散しない構造とする。また、研削液のカバー８は、砥石スピンドル５１と接する部位は、送りスライドユニット、軸方向スライドユニットによって砥石５が自在に作動可能な構成とする。なお、カバー８には、研削液排水口８０が配設される。
【００４６】
加えて、固定側ベルホルダ１のスピンドル１１に連結し、円錐状の固定側ベルホルダのスピンドルカバー１３を配備した構成とする。
【００４７】
また、軸受２２の外周に隣接する位置に円筒状の可動側ベルホルダ２のスピンドルカバー２３を配備した構成とする。
【００４８】
可動側ベルホルダ２のスピンドルカバー２３は、内面側に多穴を有し、前記多穴に空気を供給できる構造を有し、さらに不図示の空気の供給源より、軸受２２の円周部に空気を噴出する機能を有する。
【００４９】
砥石５としては、例えば、円盤状の円筒部等に砥粒（ダイヤモンド）を保持したダイヤモンド砥石が用いられる。
【００５０】
前述のようにベルホルダによるレンズの吸着を解除したうえで、両ベルホルダ間にレンズを低圧挟持した状態で高速回転させて心出しを行なう心出し工程の効率化と信頼性の向上のために、まずレンズ形状による心出しの難易度を表わす心出し係数と、レンズの球面部の面粗さに基づいて２次元的にレンズを分類し、各グループごとに適正な心出し条件を求めておく。
【００５１】
レンズ形状による心出し係数は、レンズのＡ面とＢ面の球面部の曲率半径およびレンズ保持具（ベルホルダ）の外径とを用いて、以下のように凸レンズ、凹レンズ、メニスカスレンズごとに求めた係数である。すなわち、レンズＡ面のレンズ保持具外径と曲率半径の比とレンズＢ面のレンズ保持具外径と曲率半径の比をレンズの形状により加算または、減算させたものの絶対値である。
【００５２】
【数３】

Ｄ１、Ｄ２：ベルホルダ外径（ｍｍ）
Ｒ１、Ｒ２：レンズのＡ面、Ｂ面の曲率半径（ｍｍ）
±：両凸および両凹レンズの場合は＋、メニスカスレンズの場合は−
【００５３】
上記の係数の値が大きい程、心出しが容易であり、係数値が小さい程、心出しが難しい。
【００５４】
また、レンズのＡ面とＢ面の球面部の面粗さについては、レンズの側周面の真円加工が、大きく分けて粗研削、精研削または研磨後のいずれかであり、どの工程を完了したかでレンズ両面の面粗さが異なり、ベルホルダとの摩擦係数が異なることで心出し作用が影響を受ける。
【００５５】
そこで、レンズ形状による心出し係数とレンズの面粗さにより、レンズを２次元的に複数のグループに分類し、各グループごとに心出し回転数、心出し時間、心出し時のレンズ挟持力をそれぞれ適正化する。
【００５６】
例えば、心出し係数については、最小０より、最大０．７までを６段階に区分けし、面粗さについては、１０μｍ以下で４段階に区分けし、各グループごとに心出し条件を検討・評価し、適正値を求めた。その結果を末尾の表１ないし表６に示す。
【００５７】
表１の心出し係数０．０２以下のレンズでは、ベルクランプ方式の心出しは、機械精度の向上等を行なえば可能であるが、装置および加工コストが高くなる。一般的なレンズは、外周をほぼ均一に研削することで、光学偏心５分以内を得ることが可能であるから、機械心出しは不要とし、レンズの組み込み時の調整を実施することでトータルコストの抑制が可能である。
【００５８】
具体的には、レンズのＡ面とＢ面の面粗さに関係なく、レンズ挟持力を、９．８Ｎ〜９８Ｎに設定して、外周をほぼ均一に研削することで、光学偏心５分以内を得ることができた。
【００５９】
レンズ挟持力が、９．８Ｎ未満の場合はレンズを挟持しきれず、レンズが動くため、外周をほぼ均一に研削する位置にクランプができない。また、レンズ挟持力が、９８Ｎを超える場合は、固定側ベルホルダまたは、可動側ベルホルダにて、レンズにキズを与え、外観不良となるおそれがある。
【００６０】
表２の心出し係数０．０２を超え、０．０７以下のレンズでは、心出し時のレンズ挟持力は、９．８Ｎ以上で、上限はレンズの面粗さによって異なる。心出し時のレンズ挟持力が、９．８Ｎ未満の場合、心出し時の回転にて作用する遠心力およびレンズの自重にて、心出し位置での挟持が困難である。また、心出し時のレンズ挟持力の使用可能な上限は、面粗さが粗くなるに従って低くなる。
【００６１】
すなわち、面粗さが粗くなると、レンズとベルホルダの摩擦が大となり、心出しの再現性が悪くなり、光学偏心の品質が安定しない。
【００６２】
なお、同じ面粗さでのレンズ挟持力の許容範囲は、レンズの材質の違いによって異なっており、固定側ベルホルダまたは可動側ベルホルダによって、レンズにキズを与え、外観不良となるのを防ぐため、軟質材のレンズの挟持力は、許容範囲内で弱く、硬質材のレンズの挟持力は、許容範囲内で強く設定する。
【００６３】
心出し回転数は、５００ｒｐｍから２０００ｒｐｍの間での設定であるが、面粗さが粗くなるに従い、レンズとベルホルダの摩擦が大となり、心出し性が劣るため、面粗さが粗くなるに従って速い回転数を設定する。
【００６４】
表２の設定より遅い回転数を設定した場合、心出しの再現性が悪くなり、光学偏心の品質が安定しない。また、設定より速い回転数を設定した場合は、心出し時に作用する遠心力により、ベルホルダの磨耗および損傷を早め、ベルホルダの寿命が短くなり、レンズへのキズによる外観不良や、光学偏心劣化を招く。
【００６５】
心出し時間は、５秒から３０秒の間での設定であるが、面粗さが粗くなるに従い、レンズとベルホルダの摩擦が大となり、心出しの再現性が悪くなり、光学偏心の品質が安定しない。
【００６６】
表２の設定より短い時間を設定した場合、心出しの再現性が悪くなり、光学偏心の品質が安定しない。また、設定より長い時間を設定した場合、ベルホルダを高速で回転させている時間が長いため、ベルホルダの磨耗および損傷を早め、ベルホルダの寿命が短くなり、レンズへのキズによる外観不良や、光学偏心劣化を招く。
【００６７】
なお、表２から表６において、心出し係数が大となるに従って心出しが容易であることが解る。
【００６８】
表３から表６では、いずれも、表２の場合と同様に、心出し時のレンズ挟持力は、９．８Ｎ以上で、レンズの面粗さによって、上限が異なる。心出し時のレンズ挟持力が、９．８Ｎ未満の場合、心出し時の回転にて作用する遠心力およびレンズの自重にて、心出し位置での挟持が困難である。また、心出し時のレンズ挟持力の使用可能な上限は、面粗さが粗くなるに従い、レンズとベルホルダの摩擦が大となり、心出しの再現性が悪くなり、光学偏心の品質が安定しない。
【００６９】
同じ面粗さにてレンズ挟持力の許容範囲は、レンズの材質の違いにより異なる。すなわち、固定側ベルホルダまたは、可動側ベルホルダにて、レンズにキズを与え、外観不良となるのを防ぐため、レンズが軟質材である場合の挟持力は、許容範囲内で弱く、レンズが硬質材である場合の挟持力は、許容範囲内で強く設定する。
【００７０】
心出し回転数は、心出しが容易なレンズ程、遅い回転で心出しが可能である。面粗さが粗くなるに従い、レンズとベルホルダの摩擦が大となり、心出し性が劣るため、面粗さが粗くなるに従って速い回転数に設定する。
【００７１】
表３は、心出し係数が０．０７を超え、０．１０以下のレンズの心出し条件を示す。
【００７２】
表４は、心出し係数が０．１０を超え、０．１５以下のレンズの心出し条件を示す。
【００７３】
表５は、心出し係数が０．１５を超え、０．３０以下のレンズの心出し条件を示す。
【００７４】
表６は、心出し係数が０．３０を超え、０．７０以下のレンズの心出し条件を示す。
【００７５】
表３から表６の設定より遅い回転数を設定した場合、心出しの再現性が悪くなり、光学偏心の品質が安定しない。また、設定より速い回転数を設定した場合、心出し時に作用する遠心力により、ベルホルダの磨耗および損傷を早め、ベルホルダの寿命が短くなり、レンズへのキズによる外観不良または、光学偏心劣化となった。
【００７６】
心出し時間も同様に、心出しが容易なレンズ程、短い時間で心出しが可能である。
【００７７】
また、面粗さが粗くなるに従い、レンズとベルホルダの摩擦が大となり、心出しの再現性が悪くなり、光学偏心の品質が安定しない。
【００７８】
表３から表６の設定より短い時間を設定した場合、心出しの再現性が悪くなり、光学偏心の品質が安定しない。設定より長い時間を設定した場合、ベルホルダを高速で回転させている時間が長いため、ベルホルダの磨耗および損傷を早め、ベルホルダの寿命が短くなり、レンズへのキズによる外観不良または、光学偏心不良となった。
【００７９】
【表１】

【００８０】
【表２】

【００８１】
【表３】

【００８２】
【表４】

【００８３】
【表５】

【００８４】
【表６】

【００８５】
【発明の効果】
本発明は、上述のとおり構成されているので、次に記載する効果を奏する。
【００８６】
Ａ面とＢ面の２面を有するレンズの真円加工を行なうためのレンズ心出し方法において、レンズ形状による心出し難易度を示す心出し係数とレンズ両面の面粗さに基づいて、心出し回転数、心出し時間、心出し時のレンズ挟持力のうちの少なくとも１つを制御することで、レンズの心出しを効率よく安定して行なうことができる。その結果、レンズの心取加工コストを大幅に削減できる。
【００８７】
また、レンズ心出し時のレンズ挟持力を低圧で微細に制御する圧力制御ユニット等の省略により、装置コストも低減できる。
【００８８】
このようにして、レンズの製造コストの削減に貢献できる。
【図面の簡単な説明】
【図１】レンズ心取加工機のレンズ心出しクランプ装置を示す模式図である。
【符号の説明】
１　　固定側ベルホルダ
２　　可動側ベルホルダ
３　　第１の回転駆動部
４　　軸方向駆動部
５　　砥石
７　　第２の回転駆動部
８　　カバー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lens centering machine for rounding a side peripheral surface of a lens having two surfaces A and B, in which the centering of a lens by a bell clamp method is efficiently and stably performed, and a lens manufacturing cost. The present invention relates to a lens centering method, a lens processing method, and a lens that can contribute to reduction of the lens.
[0002]
[Prior art]
Conventionally, in a manufacturing process of a lens which is an optical element, in a centering process (centering process) for centering a lens having spherical portions on both surfaces (A surface and B surface), the lens is clamped at a low pressure. There is known a lens processing method in which after centering is performed by rotating a lens axis at high speed, switching to a high-pressure clamp is performed, and high-precision centering without variation is performed while rotating the lens axis at low speed. (See JP-A-48-48140).
[0003]
In the above prior art, when performing centering by clamping the lens at low pressure and sliding the lens, even if the actuator of the clamp is at a low pressure, the clamping force at the time of centering, that is, the lens holding force increases, and the centering action is performed. Tends to decrease.
[0004]
More specifically, in a structure in which the pressure of an actuator, for example, a cylinder is applied to a lens via a regulator to clamp the lens, even if the cylinder pressure is small, if the inner diameter of the cylinder is large, the clamping at the time of lens centering is performed. The force increases, which may reduce the centering efficiency or prevent centering.
[0005]
Therefore, when the lens is clamped at low pressure and the lens is centered by high-speed rotation, a pressure control unit or the like for controlling the clamping force at low pressure is required.
[0006]
Japanese Patent Application Laid-Open No. 58-160051 discloses a centering method in which a lens is held at low pressure and low speed while rotating a cup-shaped lens holder, and then the lens is pressed at high pressure. In this case, too, the lens tends to be unstable when the lens is clamped at a low pressure, and a control unit for controlling the clamping force at the time of centering is required as described above.
[0007]
Further, Japanese Patent Application Laid-Open No. 50-1492 discloses a method of reducing the friction between a lens holder and a lens to be processed by flowing a fluid into one or both of the lens holders. ing.
[0008]
[Problems to be solved by the invention]
According to the above conventional technique, as described above, it is necessary to add a control unit for clamping at a low pressure for centering, a pipe for supplying a fluid for reducing friction, and the like, thereby increasing the cost of the apparatus. There is an unsolved problem.
[0009]
The present invention has been made in view of the above-mentioned unresolved problems of the related art, and has a centering condition by a low-pressure clamp by optimizing the centering condition in accordance with the shape of a lens in a lens centering machine. It is an object of the present invention to provide a lens centering method, a lens processing method, and a lens capable of efficiently and stably performing the above-mentioned operations and greatly reducing equipment costs and processing costs for manufacturing a lens.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a lens centering method according to the present invention is characterized in that, in a step of processing a side peripheral surface of a lens having spherical portions on both surfaces into a perfect circle, the spherical portion of the lens is reduced in pressure by a pair of lens holders. A lens centering method for pinching and rotating around a lens axis to perform centering, wherein a centering coefficient indicating a degree of difficulty of centering is obtained according to the shape of the lens, and the centering coefficient and the spherical portion are determined. Characterized in that at least one of the centering rotation speed, centering time, and lens holding force at the time of centering is controlled based on the surface roughness.
[0011]
The centering coefficient may be obtained by the following equation.
(Equation 2)

Here, D1, D2: lens holder outer diameter (mm)
R1, R2: radius of curvature of both surfaces of lens (mm)
±: + for biconvex and biconcave lenses,-for meniscus lenses
[0012]
The lenses may be classified into a plurality of groups based on the centering coefficient and the surface roughness.
[0013]
It is preferable to control the lens holding force to be 9.8N or more and 98N or less.
[0014]
The centering rotation speed is preferably controlled to 2000 rpm or less.
[0015]
The centering time is preferably controlled to 30 seconds or less.
[0016]
The centering coefficient is preferably 0.7 or less.
[0017]
The surface roughness of the spherical portion of the lens is preferably 10 μm or less.
[0018]
[Action]
In a bell-clamp type lens centering machine, in order to efficiently and stably perform lens centering in which a lens is held at a low pressure and rotated around a lens axis, a centering coefficient indicating a degree of centering difficulty according to a lens shape is obtained. . The centering coefficient predicts the degree of difficulty of centering each lens, estimates the friction between the lens holder and the lens surface roughness, and sets the appropriate centering conditions for the lens to be processed. And centering.
[0019]
For example, the lenses are classified into a plurality of groups based on the degree of difficulty and the surface roughness of the centering predicted as described above, and the centering rotation speed, the centering time, and the lens holding force at the time of centering are classified into each group. At least one appropriate value is set.
[0020]
By performing centering under appropriate centering conditions in accordance with the lens shape and surface roughness, stability during low-pressure clamping is improved and centering efficiency is improved. This can contribute to a reduction in lens processing cost.
[0021]
Further, by omitting a control unit and the like for pressure control at the time of low-pressure clamping, the apparatus cost can be reduced.
[0022]
The centering rotation speed is preferably as low as possible in consideration of the durability of the lens shaft bearing and the like.
[0023]
The centering time is preferably short from the viewpoint of processing cost.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 shows a lens centering machine provided with a lens centering clamp device used in one embodiment, which temporarily holds a lens W by adsorbing a lens W to a fixed-side bell holder 1 in the center of the drawing. The movable side bell holder 2 is moved downward while the bell holders 1 and 2 as lens holders are rotated at a low speed by the rotation drive unit 1 so that the lens W is sandwiched between the fixed side bell holder 1 and the movable side bell holder 2. In the process, the lens W is slid with respect to the lens contact portions 1a, 2a of the bell holders 1, 2 by utilizing a tangential force or the like acting on the contact point between the lens contact portion 2a of the movable side bell holder 2 and the lens W. The center of the lens W is released by releasing the lens W, and the lens W is released between the bell holders 1 and 2 with a lens clamping force (clamping force) of 9.8 N or more and 98 N or less. In the state By the rotary drive unit 7 is configured so as to complete the centering by causing the centering time high-speed rotation that is set both Beruhoruda 1,2 advance.
[0026]
The centering time by the high-speed rotation is stopped after the high-speed rotation for a certain time, and when the high-speed rotation is performed again for a certain time, it is from the start of the initial high-speed rotation to the completion of the last high-speed rotation.
[0027]
As for the lens holding force, if the above range is increased, the centering condition is increased, but the cost of the apparatus is increased.
[0028]
The fixed-side bell holder 1 is integrally connected to a spindle 11 having a hollow portion 11a, and is rotatably supported by a bearing 12 of the spindle 11. The hollow portion 11a of the spindle 11 is connected to a vacuum source (not shown) by a nipple 11b, and generates a vacuum suction force for suctioning the lens W to the lens contact portion 1a of the fixed-side bell holder 1.
[0029]
The movable-side bell holder 2 is integrally connected to one end of a spindle 21, and the spindle 21 is rotatably supported by a bearing 22.
[0030]
The first rotation drive unit 3 that rotates the bell holders 1 and 2 is movable with the rotation shaft 32 and the gear trains 33 and 34 that transmit the drive of the motor 30 to the spindle 11 of the fixed-side bell holder 1 by the operation of the electromagnetic clutch 30a. It is freely connectable to gear trains 35 and 36 that transmit to the spindle 21 of the side bell holder 2.
[0031]
The number of rotations of the bell holders 1 and 2 by the first rotation drive unit 3 is arbitrarily controlled at a low speed of 100 rpm or less, and a centering step (centering) of grinding the outer peripheral portion (side peripheral surface) of the lens W with the grindstone 5 is performed. Processing).
[0032]
The grindstone 5 is configured to be able to rotate by transmitting rotation to a grindstone spindle 51 from a rotation source (not shown).
[0033]
The grinding wheel peripheral speed during processing can be controlled at 35 m / sec or less.
[0034]
The grindstone 5 is connected to an axial slide unit (not shown) having a mechanism 53 for moving parallel to the spindles 11 and 21 and a feed slide unit (not shown) having a mechanism 52 for moving vertically. Grind the side surface.
[0035]
The second rotation driving unit 7 that rotates the bell holders 1 and 2 is movable with the rotation shaft 32 and the gear trains 33 and 34 that transmit the drive of the motor 70 to the spindle 11 of the fixed-side bell holder 1 by the operation of the electromagnetic clutch 70a. It is freely connectable to gear trains 35 and 36 that transmit to the spindle 21 of the side bell holder 2.
[0036]
The number of rotations of the bell holders 1 and 2 by the second rotation driving unit 7 is arbitrarily controlled within a range of 2000 rpm or less, and the step of rotating the bell holders 1 and 2 at high speed and centering the lens by automatic clamping as described above. Used for
[0037]
In addition, the second rotation drive unit 7 can set an operation time arbitrarily in 30 seconds or less by a timer (not shown).
[0038]
The axial drive unit 4 for moving the movable bell holder 2 in the axial direction presses and moves the axial center of the movable bell holder 2, and moves the rotation center of the movable bell holder 2 and the drive shaft of the axial drive unit 4. It includes a cylinder 42 having a matched piston 41, center pressing jigs 43 and 44, a flexible joint 45, a sensor 46 for detecting movement of the cylinder 42, and the like.
[0039]
The cylinder 42 is supported on a main body base (not shown). As described above, the axis center of the cylinder 42 and the axis center of the movable-side bell holder 2 are arranged on the same straight line. The center pressing jig 43 is connected to the flexible joint 45, and is also connected to the spindle 21 of the movable bell holder 2.
[0040]
The movement detection sensor 46 of the cylinder 42 is a sensor that is provided in the housing of the cylinder 42 and detects that the movable-side bell holder 2 has reached the lens W. When the movement distance to the lens W changes, the movement detection sensor 46 46 is configured to be movable in the axial direction of the housing of the cylinder 42.
[0041]
The cylinder 42 can be connected to a low-pressure regulator for low-pressure clamping and a high-pressure regulator for high-pressure clamping via a pressure direction switching valve (not shown). The pressurizing direction switching valve is used for the downward axial movement and the upward axial movement of the movable-side bell holder 2.
[0042]
The connection with the high-pressure regulator is at the time of grinding the side peripheral surface of the lens W, and the connection with the low-pressure regulator moves the movable-side bell holder 2 in the axial direction toward the fixed-side bell holder 1 on which the lens W is sucked. This is performed in a step of rotating both bell holders 1 and 2 at high speed in lens centering by automatic clamping.
[0043]
As described above, the drive unit of the grindstone 5 includes the axial slide unit (not shown), the feed slide unit, the grindstone spindle 51, and the like, which are disposed on the upper surface of the support base of the centering machine (not shown). .
[0044]
A grinding fluid is supplied by an unillustrated grinding fluid supply unit to an area where the side peripheral surface of the lens W is ground by the grindstone 5.
[0045]
The cover 8 covers the grindstone 5, the movable-side bell holder 2, and the fixed-side bell holder 1, and has a structure in which the grinding fluid is not scattered on the axial slide unit and the feed slide unit. The portion of the grinding fluid cover 8 that is in contact with the grinding wheel spindle 51 is configured so that the grinding wheel 5 can be freely operated by a feed slide unit and an axial slide unit. The cover 8 is provided with a grinding fluid drain port 80.
[0046]
In addition, it is configured to be connected to the spindle 11 of the fixed-side bell holder 1 and to provide a spindle cover 13 of the conical fixed-side bell holder.
[0047]
Further, the spindle cover 23 of the cylindrical movable-side bell holder 2 is provided at a position adjacent to the outer periphery of the bearing 22.
[0048]
The spindle cover 23 of the movable-side bell holder 2 has a multi-hole on the inner surface side, has a structure capable of supplying air to the multi-hole, and further supplies air to a circumferential portion of the bearing 22 from an air supply source (not shown). It has the function of spouting.
[0049]
As the grindstone 5, for example, a diamond grindstone in which abrasive grains (diamonds) are held in a disk-shaped cylindrical portion or the like is used.
[0050]
After releasing the lens by the bell holder as described above, the centering process of rotating the lens at high speed while holding the lens between both bell holders at high speed to improve the efficiency and reliability of the centering process is firstly performed. The lenses are two-dimensionally classified based on the centering coefficient indicating the degree of difficulty of centering by the lens shape and the surface roughness of the spherical portion of the lens, and an appropriate centering condition is obtained for each group.
[0051]
The centering coefficient according to the lens shape was determined for each of the convex lens, the concave lens, and the meniscus lens using the radius of curvature of the spherical portion of the A surface and the B surface of the lens and the outer diameter of the lens holder (bell holder) as follows. It is a coefficient. That is, the absolute value is obtained by adding or subtracting the ratio of the outer diameter of the lens holder to the radius of curvature of the lens A surface and the ratio of the outer diameter of the lens holder to the radius of curvature of the lens B surface according to the shape of the lens.
[0052]
[Equation 3]

D1, D2: Bell holder outer diameter (mm)
R1, R2: radius of curvature of surface A and surface B of lens (mm)
±: + for biconvex and biconcave lenses,-for meniscus lenses
[0053]
The larger the value of the coefficient is, the easier the centering is, and the smaller the coefficient value is, the more difficult the centering is.
[0054]
Regarding the surface roughness of the spherical surfaces of the lens A surface and the surface B, the roundness processing of the side peripheral surface of the lens is roughly divided into any of rough grinding, fine grinding, and after polishing. Depending on the completion, the surface roughness of both surfaces of the lens differs, and the centering action is affected by the difference in the coefficient of friction with the bell holder.
[0055]
Therefore, the lenses are two-dimensionally classified into a plurality of groups based on the centering coefficient and the surface roughness of the lens, and the centering rotation speed, centering time, and lens holding force at the time of centering are determined for each group. Optimize each.
[0056]
For example, the centering coefficient is divided into 6 stages from the minimum 0 to the maximum 0.7, and the surface roughness is divided into 4 stages at 10 μm or less, and the centering condition is examined and evaluated for each group. Then, an appropriate value was obtained. The results are shown in Tables 1 to 6 at the end.
[0057]
For lenses having a centering coefficient of 0.02 or less in Table 1, bell-clamp centering can be performed by improving the mechanical accuracy, but the equipment and processing costs increase. For general lenses, optical eccentricity within 5 minutes can be obtained by grinding the outer circumference almost uniformly. Therefore, mechanical centering is not required, and adjustment when the lens is assembled is performed to reduce total cost. Can be suppressed.
[0058]
Specifically, irrespective of the surface roughness of the A surface and the B surface of the lens, the lens holding force is set to 9.8 N to 98 N and the outer periphery is almost uniformly ground, so that the optical eccentricity is within 5 minutes. Could be obtained.
[0059]
If the lens clamping force is less than 9.8 N, the lens cannot be clamped completely and the lens moves, so that the clamp cannot be performed at a position where the outer periphery is almost uniformly ground. If the lens holding force exceeds 98 N, the lens may be damaged by the fixed-side bell holder or the movable-side bell holder, resulting in poor appearance.
[0060]
For lenses having a centering coefficient exceeding 0.02 and not exceeding 0.07 in Table 2, the lens holding force at the time of centering is 9.8 N or more, and the upper limit varies depending on the surface roughness of the lens. If the lens holding force at the time of centering is less than 9.8 N, it is difficult to hold the lens at the centering position due to the centrifugal force acting upon rotation at the time of centering and the weight of the lens. The usable upper limit of the lens holding force at the time of centering decreases as the surface roughness increases.
[0061]
That is, when the surface roughness becomes rough, the friction between the lens and the bell holder becomes large, the reproducibility of centering becomes poor, and the quality of optical eccentricity becomes unstable.
[0062]
The allowable range of the lens clamping force with the same surface roughness differs depending on the material of the lens, and in order to prevent the lens from being damaged by the fixed-side bell holder or the movable-side bell holder, and to prevent the appearance from being poor, The holding force of the soft material lens is set to be weak within an allowable range, and the holding force of the hard material lens is set to be strong within the allowable range.
[0063]
The centering rotation speed is set between 500 rpm and 2000 rpm, but as the surface roughness increases, the friction between the lens and the bell holder increases, and the centering property deteriorates. Therefore, the centering rotation speed increases as the surface roughness increases. Set the number of revolutions.
[0064]
When a rotation speed lower than the setting in Table 2 is set, reproducibility of centering becomes poor, and the quality of optical eccentricity is not stable. Also, if the rotation speed is set higher than the setting, the centrifugal force acting at the time of centering accelerates the wear and damage of the bell holder, shortens the life of the bell holder, and causes poor appearance due to scratches on the lens and deterioration of optical eccentricity. Invite.
[0065]
The centering time is set between 5 seconds and 30 seconds. As the surface roughness increases, the friction between the lens and the bell holder increases, the reproducibility of centering deteriorates, and the quality of optical eccentricity decreases. Not stable.
[0066]
If a time shorter than the setting in Table 2 is set, the reproducibility of centering will be poor, and the quality of optical eccentricity will not be stable. Also, if the time is set longer than the setting, the time for rotating the bell holder at high speed is long, so that the bell holder is worn and damaged earlier, the life of the bell holder is shortened, the appearance of the lens is poor due to scratches, and the optical eccentricity is reduced. It causes deterioration.
[0067]
In Tables 2 to 6, it is understood that the centering becomes easier as the centering coefficient increases.
[0068]
In each of Tables 3 to 6, similarly to Table 2, the lens holding force at the time of centering is 9.8 N or more, and the upper limit differs depending on the surface roughness of the lens. If the lens holding force at the time of centering is less than 9.8 N, it is difficult to hold the lens at the centering position due to the centrifugal force acting upon rotation at the time of centering and the weight of the lens. In addition, the upper limit of the use of the lens holding force at the time of centering is such that as the surface roughness increases, the friction between the lens and the bell holder increases, the reproducibility of centering deteriorates, and the quality of optical eccentricity becomes unstable.
[0069]
The allowable range of the lens holding force at the same surface roughness differs depending on the material of the lens. That is, in order to prevent the lens from being scratched by the fixed-side bell holder or the movable-side bell holder and resulting in poor appearance, the holding force when the lens is a soft material is weak within an allowable range, and the lens is hard material. Is set to be strong within the allowable range.
[0070]
As for the centering rotation speed, the centering can be performed with a slower rotation as the lens is easier to center. As the surface roughness increases, the friction between the lens and the bell holder increases, and the centering property deteriorates. Therefore, the rotation speed is set to a higher value as the surface roughness increases.
[0071]
Table 3 shows the centering conditions for lenses having a centering coefficient of more than 0.07 and not more than 0.10.
[0072]
Table 4 shows the centering conditions for lenses having a centering coefficient exceeding 0.10 and not more than 0.15.
[0073]
Table 5 shows the centering conditions for lenses having a centering coefficient of more than 0.15 and not more than 0.30.
[0074]
Table 6 shows the centering conditions for lenses having a centering coefficient of more than 0.30 and 0.70 or less.
[0075]
When the rotation speed is set slower than the settings in Tables 3 to 6, the reproducibility of the centering is deteriorated, and the quality of the optical eccentricity is not stabilized. Also, if the rotation speed is set higher than the setting, the centrifugal force acting at the time of centering accelerates the wear and damage of the bell holder, shortens the life of the bell holder, and causes poor appearance due to scratches on the lens or deterioration of optical eccentricity. Was.
[0076]
Similarly, the centering time of a lens that is easy to center can be reduced in a short time.
[0077]
Further, as the surface roughness increases, the friction between the lens and the bell holder increases, the reproducibility of centering deteriorates, and the quality of optical eccentricity becomes unstable.
[0078]
When a time shorter than the settings in Tables 3 to 6 is set, the reproducibility of centering deteriorates, and the quality of optical eccentricity is not stable. If the time is set longer than the setting, the time for rotating the bell holder at high speed is long, so that the bell holder wears and damages faster, the life of the bell holder is shortened, and the appearance of the lens due to scratches on the lens or poor optical eccentricity may occur. became.
[0079]
[Table 1]

[0080]
[Table 2]

[0081]
[Table 3]

[0082]
[Table 4]

[0083]
[Table 5]

[0084]
[Table 6]

[0085]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
[0086]
In a lens centering method for performing a perfect circular processing of a lens having two surfaces A and B, centering is performed based on a centering coefficient indicating a degree of difficulty of centering by a lens shape and surface roughness of both surfaces of the lens. By controlling at least one of the rotation speed, the centering time, and the lens holding force at the time of centering, the centering of the lens can be performed efficiently and stably. As a result, the cost of centering the lens can be significantly reduced.
[0087]
Further, the cost of the apparatus can be reduced by omitting a pressure control unit or the like for finely controlling the lens holding force at the time of lens centering at a low pressure.
[0088]
In this way, it is possible to contribute to a reduction in the manufacturing cost of the lens.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a lens centering clamp device of a lens centering machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed-side bell holder 2 Movable-side bell holder 3 First rotation drive unit 4 Axial drive unit 5 Grinding stone 7 Second rotation drive unit 8 Cover

Claims (10)

In the step of processing the side peripheral surface of a lens having a spherical portion on both surfaces into a perfect circle, a lens center for holding the spherical portion of the lens at a low pressure by a pair of lens holders and rotating the lens around a lens axis to perform centering. A centering method that determines a centering difficulty according to the shape of the lens, and performs centering rotation during the centering based on the centering coefficient and the surface roughness of the spherical portion. A lens centering method comprising controlling at least one of the number, centering time, and lens holding force. 2. The lens centering method according to claim 1, wherein the centering coefficient is obtained by the following equation.

Here, D1, D2: outer diameter (mm) of a lens holder for holding both surfaces of the lens.
R1, R2: radius of curvature of both surfaces of lens (mm)
±: + for a biconvex or biconcave lens,-for a meniscus lens 3. The lens centering method according to claim 1, wherein the lenses are classified into a plurality of groups based on the centering coefficient and the surface roughness. 4. The lens centering method according to claim 1, wherein the lens holding force is controlled to be 9.8 N or more and 98 N or less. 5. The lens centering method according to claim 1, wherein the centering rotation speed is controlled to 2000 rpm or less. 6. A lens centering method according to claim 1, wherein the centering time is controlled to 30 seconds or less. 7. The method according to claim 1, wherein the centering coefficient is 0.7 or less. 8. The lens centering method according to claim 1, wherein a surface roughness of a spherical portion of the lens is 10 [mu] m or less. A lens centered by the lens centering method according to any one of claims 1 to 8, and a side peripheral surface is processed into a perfect circle. 9. A lens processing method comprising: centering a lens by the lens centering method according to claim 1; and centering the side peripheral surface of the lens.

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