JP2004004742A - Small imaging lens, imaging unit and mobile terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small imaging lens which is made into smaller size and capable of satisfactorily correcting aberration even though the lens is simply constituted of two lenses, and to provide an imaging unit and a mobile terminal using the small imaging lens. <P>SOLUTION: The imaging lens is constituted of an aperture diaphragm S, a first lens L1 having a positive refractive power and whose convex faces the image side, and a second meniscus lens L2 whose concave faces the object side in this order from the object side, and the first lens L1 and the second lens L2 have at least one aspherical surface, respectively, and the imaging lens satisfies prescribed conditions, then, the small imaging lens which is made into smaller size and capable of satisfactorily correcting the aberration can be obtained, irrespective of the simple constitution that the imaging lens is constituted of two lenses. <P>COPYRIGHT: (C)2004,JPO

Description

【００２８】
図１は、本発明の実施例１〜５にかかる小型の撮像レンズの代表的な断面図であり、図中Ｌ１は第１レンズ、Ｌ２は第２レンズ、Ｓは開口絞りを示す。
【００２９】
（実施例１）
実施例１のレンズデータを表１、２に示す。本実施例ではＬ／２Ｙ＝１．２１である。尚、これより示すレンズデータ内において、１０のべき乗数（例えば、２．５×１０^−０３）を、Ｅ（例えば、２．５×Ｅ−０３）を用いて表している。
【表１】

【表２】

【００３０】
図２は、実施例１の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０１％以下である。また、第２レンズは、ポリカーボネイト系のプラスチック材料で形成され。飽和吸水率は０．４％である。
【００３１】
（実施例２）
実施例２のレンズデータを表３、４に示す。本実施例ではＬ／２Ｙ＝１．２２である。
【表３】

【表４】

【００３２】
図３は、実施例２の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０１％以下である。また、第２レンズは、ポリカーボネイト系のプラスチック材料で形成され、飽和吸水率は０．４％である。
【００３３】
（実施例３）
実施例３のレンズデータを表５、６に示す。本実施例ではＬ／２Ｙ＝１．２８である。
【表５】

【表６】

【００３４】
図４は、実施例３の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０ｌ％以下である。また、第２レンズは、ポリカーボネイト系のプラスチック材料で形成され、飽和吸水率は０．４％である。
【００３５】
（実施例４）
実施例４のレンズデータを表７、８に示す。本実施例ではＬ／２Ｙ＝１．２２である。
【表７】

【表８】

【００３６】
図５は、実施例４の小型の撮像レンズにかかる収差図（球曲収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０１％以下である。また、第２レンズは、ポリエステル系のプラスチック材料で形成され、飽和吸水率は０．７％である。
【００３７】
（実施例５）
実施例５のレンズデータを表９、１０に示す。本実施例ではＬ／２Ｙ＝１．２３である。
【表９】

【表１０】

【００３８】
図６は、実施例５の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０１％以下である。また、第２レンズは、ポリカーポネイト系のプラスチック材料で形成され、飽和吸水率は０．４％である。
【００３９】
（実施例６）
実施例６のレンズデータを表１１、１２に示す。本実施例ではＬ／２Ｙ＝１．２５である。
【表１１】

【表１２】

【００４０】
図７は、実施例６の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズは、ポリオレフィン系のプラスチック材料から形成され、飽和吸水率は０．０ｌ％以下である。また、第２レンズは、ポリカーボネイト系のプラスチック材料で形成され、飽和吸水率は０．４％である。
【００４１】
（実施例７）
実施例７のレンズデータを表１３，１４に示す。本実施例では、Ｌ／２Ｙ＝１．３４である。図１２は実施例７にかかる小型の撮像レンズの断面図であり、図中Ｌ１は第１レンズ、Ｌ２は第２レンズ、Ｓは開口絞りを示す。図１３は、実施例７の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。本実施例においては、第１レンズはポリオレフィン系のプラスチック材料から形成され、飽和吸水率０．０１％以下である。また、第２レンズはポリカ一ボネイト系のプラスチック材料で形成され、飽和吸水率は０．４％である。なお、本実施例は最も像側に、赤外線カットフィルタおよび固体撮像素子のシールガラス相当の平行平板を配置した設計例である。
【表１３】

【表１４】

【００４２】
各条件式に対応する各実施例の値を表１５に示す。
【表１５】

【００４３】
なお、上述した実施例は、像側光束のテレセントリック特性については必ずしも十分な設計にはなっていない。テレセントリック特性とは、各像点に対する光束の主光線が、撮像レンズ最終面を射出した後、光軸とほぼ平行になることをいい、換言すれば光学系の射出瞳位置が像面から十分離れることである。テレセントリック特性が悪くなると、光束が固体撮像素子に対し斜めより入射し、画面周辺部において実質的な開口効率が減少する現象（シェーディング）が生じ、周辺光量不足を招くこととなる。しかし、最近の技術では、固体撮像素子の色フィルタやマイクロレンズアレイの配列の見直し等によって、前述のシェーディング現象を軽減することができるようになってきている。従って、本実施例は、テレセントリック特性の要求が緩和された分について、より小型化を目指した設計例となっている。
【００４４】
図８は、上述の実施例にかかる小型の撮像レンズを用いた撮像ユニットの実施の形態を示す断面図である。図９は、かかる撮像ユニットの斜視図である。図１０は、かかる撮像ユニットに用いる固体撮像素子の上面図である。図１１は、小型の撮像レンズの下面図である。本実施の形態の撮像ユニット５０は、光電変換部５１ａを備えた固体撮像素子５１と、固体撮像素子５１の光電変換部５１ａに被写体像を結像させる上述の実施例の撮像レンズ（光学部材１９）と、固体撮像素子５１を保持すると共に電気信号の送受を行う外部接続用端子を有する基板５２と、物体側からの光入射用の開口部５ｃを有し遮光性部材からなる筐体４と、が一体的に形成された撮像ユニットであって、撮像ユニット５０の光学部材１９の光軸方向の高さｈが１０ｍｍ以下となっている。
【００４５】
図８において、光学部材１９は、それぞれ透明なプラスチック材料からなる像側撮像レンズ部材１と物体側撮像レンズ部材９とから構成されている。像側撮像レンズ部材１は、図８に示すように、略中空円筒状の脚部１ｃと、脚部１ｃの一部としてその下端に形成された４つの当接部１ｄと、脚部１ｃの上端周囲に形成された段部１ｅと、撮像レンズ部１ａ（図１のＬ２に相当）と、像側撮像レンズ部材１の上端周囲に形成されたリング部１ｆとから一体的に形成されている。尚、図１１に示すように、像側撮像レンズ部材１の当接部１ｄは、略中空円筒状の脚部１ｃの下面から突出する４つの先細円柱形状を有している。
【００４６】
又、図８において、撮像レンズ部１ａの上部には、遮光性のある素材からなり、周辺光束を規制する絞りとしての開口３ａを有する遮光マスク３が配置されている。
【００４７】
リング部１ｆの内周面に嵌合し、且つリング部１ｆの上面である当接面１ｇに当接するようにして、物体側撮像レンズ部材９が配置されている。物体側撮像レンズ部材９は、リング部１ｆの上方に位置するフランジ部９ｂと、中央に形成された正撮像レンズ部９ａ（図１のＬ１に相当）と、以下に述べる突起９ｃと、リング部１ｆに嵌合するリング部９ｄとから構成されている。
【００４８】
物体側撮像レンズ部材９のフランジ部９ｂの下面には、当接面１ｇに対向するようにして、等間隔で３カ所（３カ所以上であれば何カ所でも良い）に形成された先細の突起９ｃが形成されている。像側撮像レンズ部材１に対し、遮光マスク３を嵌め込んだ後、当接面１ｇに接着剤Ｂを塗布して、上方から物体側撮像レンズ部材９を押圧すると、突起９ｃは当接面１ｇに当接し、接着剤Ｂは突起９ｃの周囲に逃げ、その状態で固着する。
【００４９】
突起９ｃがなければ、像側撮像レンズ部材１と物体側撮像レンズ部材９とは面当たりすることになるが、かかる場合、当接面間に接着剤Ｂが介在し、像側撮像レンズ部材１と物体側撮像レンズ部材９の間隔が不適切になる恐れがある。これに対し、本実施の形態によれば、突起９ｃの先細形状によって、接着剤Ｂの存在に関わらず当接面１ｇにしっかりと当接させることができるため、突起９ｃの突出量を適切な値とすることで、像側撮像レンズ部材１と物体側撮像レンズ部材９の間隔を精度良く規定でき、それにより大量生産時の撮像レンズ全系としての結像位置や諸収差のばらつきを抑えることができる。
【００５０】
更に、本実施の形態では遮光マスク３は、物体側撮像レンズ部材９と当接しておらず、周辺光束を規制する絞りとしてのみ機能しているが、物体側撮像レンズ部材９に当接させることで、突起９ｃの代わりに、撮像レンズ部１ａ、９ａの撮像レンズ間距離を規制するスペーサとして機能させることもできる。
【００５１】
像側撮像レンズ部材１のリング部１ｆの内周面と、物体側撮像レンズ部材９のフランジ部９ｂから下方に突出するリング部９ｄの外周面とは、互いに同径であり且つ光軸に平行になっているので、かかる面同士が係合することにより、撮像レンズ部１ａ、９ａの光軸直交方向の位置決めを行うことができ、それらの光軸を容易に一致させることができる。
【００５２】
光学部材１９の外側には、遮光性のある素材からなる鏡枠４が配置されている。鏡枠４は、図９から明らかなように、角柱状の下部４ａと、円筒状の上部４ｂとを設けている。下部４ａの下端は、基板５２上に当接し、接着剤Ｂにより固着されている。図８において、下部４ａの上面は、隔壁４ｃにより周辺側が覆われており、隔壁４ｃの円形内周面には、光学部材１９の脚部１ｃが密着的に嵌合している。従って、基板５２と鏡枠４とを、例えば自動組立機に備えられた光学センサ（不図示）などを用いて、隔壁４ｃの円形開口部中心と、後述する固体撮像素子５１の光電変換部５１ａの中心を一致させるように位置決め配置し、その後光学部材１９を上部より挿入するだけで、後述する固体撮像素子５１の光電変換部５１ａに対して撮像レンズ部１ａ及び正撮像レンズ部９ａを、光軸直交方向に精度良く位置決めすることができる。
【００５３】
基板５２は、その一平面上で固体撮像素子５１及び筐体５３を支持する支持平板５２ａと、支持平板５２ａの背面（固体撮像素子５１と反対側の面）にその一端部が接続されたフレキシブル基板５２ｂとを備えている。支持平板５２ａは、表裏面に設けられた多数の信号伝達用パッドを有しており、その一平面側で前述したイメージセンサ５１のワイヤＷと接続され、背面側でフレキシブル基板５２ｂと接続されている。フレキシブル基板５２ｂは、上記の如くその一端部が支持平板５２ａと接続され、その他端部に設けられた外部出力端子５４（図９）を介して支持平板５２ａと外部回路（例えば、撮像ユニットを実装した上位装置が有する制御回路）とを接続し、外部回路から固体撮像素子５１を駆動するための電圧やクロック信号の供給を受けたり、また、デジタルＹＵＶ信号を外部回路へ出力したりすることを可能とする。さらに、フレキシブル基板５２ｂの長手方向の中間部が可撓性又は変形性を備え、その変形により、支持平板５２ａに対して外部出力端子の向きや配置に自由度を与えている。
【００５４】
鏡枠４の上部４ｂの上端には、中央の嵌合部５ａと、内周側と外周側において上面より低くなった接着部５ｂと、嵌合部５ａの下方に向かって突出し内径が段々と縮径する縮径部５ｃとを有し、遮光性のある素材からなる保持部材５が取り付けられている。尚、縮径部５ｃは、撮像レンズ全系のＦナンバーを規制する開口絞り（図１のＳに相当する）である。嵌合部５ａには、赤外線吸収特性を有する素材からなるフィルタ７が嵌合配置されている。保持部材５の接着部５ｂに接着剤Ｂを充填した後、薄い遮光シート８を上面に載置することで、フィルタ７と、遮光シート８と、保持部材５とを同時に鏡枠４に取り付けることができる。
【００５５】
図８において、保持部材５と、光学部材１９の段部１ｅとの間には、コイルばねからなる弾性手段６が配置され、保持部材５が鏡枠４に取り付けられることで弾性変形し、その弾性力により、光学部材１９を図８中、下方に向かって押圧している。よって、保持部材５からの力は、鏡枠４を介して基板５２には伝達されるものの、直接、固体撮像素子５１に伝達されることがなく、固体撮像素子５１の保護という観点から好ましい。また、弾性力については、コイルバネ６の線径・巻数などを選択することにより、適切に管理することができる。
【００５６】
図１０において、固体撮像素子５１は、ＣＭＯＳ型イメージセンサからなる。矩形薄板状の固体撮像素子５１の下面は、基板５２の上面に取り付けられている。固体撮像素子５１の上面中央には、画素が２次元的に配列された光電変換部５１ａが形成されており、その周囲には、固体撮像素子５１の内部であって且つ内側に信号処理回路が構成されている周囲面５１ｂが形成されている。薄い側面に直交するように交差した周囲面５１ｂの外縁近傍には、多数のパッド５１ｃが配置されている。外部接続用端子であるパッド５１ｃは、図８に示すごとくワイヤＷを介して、基板５２に接続されている。固体撮像素子５１は、光電変換部５１ａからの電気信号を画像信号等に変換し、これらの信号をパッド５１ｃ及びワイヤＷを介して、基板５２の所定の回路に出力できるようになっている。
【００５７】
更に、光学部材１９の当接部１ｄは、図１１に示すように、脚部１ｃの下端から先細円柱状に突出し脚部１ｃの一部を構成してなる。本実施の形態においては、図１０で点線に示すように、固体撮像素子５１の周囲面５１ｂにおいて、パッド５１ｃの内側に、当接部１ｄのみが当接した状態で光学部材１９が配置されることとなる。ここで、周囲面５１ｂの裏側（図８で下面側）には、固体撮像素子の不図示の信号処理回路が設けられているが、当接部１ｄの当接により信号の処理には影響が及ばないようになっている。
【００５８】
本実施の形態によれば、当接部１ｄが、固体撮像素子５１の周囲面５１ｂに当接した状態で、光学部材１９の段部１ｅの下面と、鏡枠４の下部４ａの隔壁４ｃとの間には、スキマΔが形成されるようになっているので、撮像レンズ部１ａと固体撮像素子５１の光電変換部５１ａとの距離（即ち光軸方向の位置決め）は、脚部１ｃの長さにより精度良く設定されるようになっている。従って、脚部１ｃ（当接部１ｄを含む）の寸法精度を管理することで、撮像レンズ全系としての合焦位置に関する調整を不要とできる。
【００５９】
又、光学部材１９をプラスチック材料で構成しているので、温度変化時の撮像レンズ部１ａ、９ａの屈折率変化に基づく合焦位置のずれを低減することも可能である。すなわち、プラスチックレンズは温度が上昇するにつれて、撮像レンズの屈折率が下がり、撮像レンズ全系の合焦位置が撮像レンズから離れる方向に変化する。一方、脚部１ｃは温度上昇により伸びるため、合焦位置ずれの低減効果がある。尚、本実施の形態の光学部材１９は、比重が比較的軽いプラスチック材料からなるので、同一体積でもガラスに比べて軽量であり、かつ衝撃吸収特性に優れるため、撮像ユニットを誤って落としたような場合でも、固体撮像素子５１の破損を極力抑制できるという利点がある。
【００６０】
本実施の形態においては、鏡枠４が基板５２に接着されており、他の２ヶ所の接着部とあわせて、撮像ユニットの外部に対して、異物が侵入しないよう密封された状態に維持されるため、固体撮像素子５１の光電変換部５１ａに対する異物の悪影響を排除することができる。これらに用いる接着剤は、防湿性を有するのが好ましい。これにより、湿気の侵入による固体撮像素子やパッドの表面劣化を防ぐことができる。
【００６１】
上述した撮像ユニット５０の使用態様について説明する。図１４は、撮像ユニット５０を備えた携帯端末或いは撮像装置としての携帯電話機１００の正面図（Ａ）及び背面図（Ｂ）であり、図１５は、携帯電話機１００の制御ブロック図である。
【００６２】
撮像ユニット５０は、例えば筐体４の物体側端面が携帯電話機１００の背面（液晶表示部側を正面とする）に設けられ、液晶表示部の下方に相当する位置に配設される。そして、撮像ユニット５０の外部接続端子５４は、携帯電話機１００の制御部１０１と接続され、それにより輝度信号や色差信号等の画像信号が制御部１０１側に出力可能となる。
【００６３】
一方、携帯電話機１００は、図１５に示すように、各部を統括的に制御すると共に、各処理に応じたブログラムを実行する制御部（ＣＰＵ）１０１と、番号等をキーにより支持入力するための入力部６０と、所定のデータの他に撮像した映像等を表示する表示部７０と、外部サーバとの間の各種情報通信を実現するための無線通信部８０と、携帯電話機１００のシステムプログラムや各種処理プログラム及び端末ＩＤ等の必要な諸デ―タを記憶している記憶部（ＲＯＭ）９１と、制御部１０１によって実行される各種処理プログラムやデータ、若しくは処理データ、或いは撮像ユニット５０により撮像データ等を一時的に格納する作業領域として用いられる及び―時記憶部（ＲＡＭ）９２とを備えている。
【００６４】
そして、撮像ユニット５０から入力された画像信号は、上記携帯電話機１００の制御系により、記憶部９２に記憶されたり、或いは表示部７０で表示され、さらには、無線通信部８０を介して映像情報として外部に送信される。
【００６５】
以上、本発明を実施例を参照して説明してきたが、本発明は上記実施例に限定して解釈されるべきではなく、適宜変更・改良が可能であることはもちろんである。例えば、本実施例の小型撮像レンズは、レンズと固体撮像素子光電変換部の間に、ローパスフィルタを配置しない設計例であるが、必要に応じてローパスフィルタを配置してもよい。
【００６６】
【発明の効果】
以上述べた本発明によれば、レンズ枚数が２枚という簡略な構成にもかかわらず、より小型で収差の良好に補正された小型の撮像レンズ、撮像ユニット及び携帯端末を提供することができる。
【図面の簡単な説明】
【図１】本発明にかかる小型の撮像レンズの代表的な断面図である。
【図２】実施例１の小型の撮像レンズにかかる収差図である。
【図３】実施例２の小型の撮像レンズにかかる収差図である。
【図４】実施例３の小型の撮像レンズにかかる収差図である。
【図５】実施例４の小型の撮像レンズにかかる収差図である。
【図６】実施例５の小型の撮像レンズにかかる収差図である。
【図７】実施例６の小型の撮像レンズにかかる収差図である。
【図８】上述の実施例にかかる小型の撮像レンズを用いた撮像ユニットの実施の形態を示す断面図である。
【図９】実施の形態にかかる撮像ユニットの斜視図である。
【図１０】実施の形態にかかる撮像ユニットに用いる固体撮像素子の上面図である。
【図１１】実施の形態にかかる小型の撮像レンズの下面図である。
【図１２】実施例７にかかる小型の撮像レンズの断面図である。
【図１３】実施例７の小型の撮像レンズにかかる収差図（球面収差、非点収差、歪曲収差、メリディオナルコマ収差）である。
【図１４】撮像ユニット５０を備えた携帯端末或いは撮像装置としての携帯電話機１００の正面図（Ａ）及び背面図（Ｂ）である。
【図１５】携帯電話機１００の制御ブロック図である。
【符号の説明】
１　像側撮像レンズ部材
３　遮光マスク
４　鏡枠
５　保持部材
６　コイルばね
７　フィルタ
８　遮光シート
９　物体側撮像レンズ部材
１９　光学部材
５０　撮像ユニット
５１　固体撮像素子
５２　基板
Ｌ１　第１レンズ
Ｌ２　第２レンズ
Ｓ　開口絞り[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a small-sized imaging lens suitable for an imaging unit using a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, an imaging unit using the same, and a portable terminal.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as an imaging device using a solid-state imaging device such as a CCD (Charged Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor becomes higher in performance and miniaturized, a mobile phone equipped with the imaging device has been developed. Personal computers are becoming popular. Further, there is an increasing demand for further miniaturization of imaging lenses mounted on these imaging devices.
[0003]
As an imaging lens for such an application, a two-lens configuration lens that can achieve higher performance than a single lens is generally suitable, and a first lens having a negative refractive power, an aperture, and a positive refraction in order from the object side. 2. Description of the Related Art A retrofocus type imaging lens including a second lens having power is known. The imaging lens having such a configuration is disclosed in Patent Documents 1 and 2, for example.
[Patent Document 1]
JP-A-2000-32489
[Patent Document 2]
JP 2001-183578 A
[0004]
[Problems to be solved by the invention]
However, although this type of imaging lens is suitable for widening the angle of view, on the other hand, the back focus tends to be long, and the entire length of the imaging lens (on the optical axis from the most object side surface of the entire imaging lens system to the image side focal point). However, in an imaging lens in which an aperture stop is arranged closest to the object side, it is difficult to shorten the distance (the distance on the optical axis from the aperture stop to the image-side focal point).
[0005]
The present invention has been made in view of such a problem, and despite a simple configuration having two lenses, a small-sized imaging lens having a smaller size and a good correction of aberrations. It is an object of the present invention to provide an imaging unit and a mobile terminal that have been used.
[0006]
Here, as a measure of a small imaging lens, the present invention aims at miniaturization at a level satisfying the following expression. By satisfying this range, the overall length of the imaging lens can be shortened and the outer diameter of the imaging lens can be reduced synergistically. This makes it possible to reduce the size and weight of the entire imaging unit.
L / 2Y <1.50 (5)
However,
L: distance on the optical axis from the aperture stop to the image-side focal point
2Y: Effective screen diagonal length
[0007]
The image-side focal point refers to an image point when a parallel ray parallel to the optical axis enters the lens. When a parallel plate is disposed between the most image-side surface of the lens and the image-side focal position, the parallel plate portion has an air-equivalent length.
[0008]
[Means for Solving the Problems]
2. The small-sized imaging lens according to claim 1, wherein, in order from the object side, an aperture stop, a first lens having a positive refractive power with a convex surface facing the image side, and a second meniscus lens having a concave surface facing the object side. Wherein each of the first lens and the second lens has at least one aspheric surface, and satisfies the following conditional expression.
0.50 <f1 / f <0.80 (1)
0.30 <(R2 + R1) / (R1-R2) <1.20 (2)
However,
fl: focal length of the first lens
f: focal length of the entire imaging lens system
R1: radius of curvature of the object side surface of the first lens
R2: radius of curvature of the image side surface of the first lens
[0009]
In order to obtain a small and well-corrected imaging lens, the basic configuration of the present invention is that the aperture stop is arranged closest to the object side, and the convex surface having a larger refractive power than the object side surface faces the image side. And the second lens having the meniscus shape with the concave surface facing the object side.
[0010]
By arranging the aperture stop closest to the object side and providing the image side surface of the positive first lens with a large positive refractive power, the exit pupil position can be kept away from the image plane. As a result, the principal ray of the light beam emitted from the final lens surface enters the solid-state imaging device at an angle close to perpendicular, that is, the image-side telecentric characteristics required for the imaging lens used in the solid-state imaging device can be sufficiently secured, The shading phenomenon in the peripheral portion of the screen can be reduced. In addition, various aberrations are corrected well by giving a large negative refractive power to the object side surface of the second lens.
[0011]
Further, by using at least one aspheric surface for each of the first lens and the second lens, it is possible to perform better aberration correction. The use of an aspheric surface for the first positive lens is effective in correcting spherical aberration and coma. On the other hand, since the second lens is disposed farthest from the aperture stop and closest to the image, there is a difference in the passing height between the on-axis light flux and the off-axis light flux at the periphery of the screen, and by using an aspheric surface, Various aberrations at the periphery of the screen, such as field curvature and distortion, can be favorably corrected.
[0012]
[Explanation of conditional expression (1)]
Conditional expression (1) is a condition for appropriately setting the refractive power of the first lens. When the value f1 / f exceeds the lower limit, the positive refractive power of the first lens does not become excessively large, and high-order spherical aberration, coma, and magnification that occur on the image side surface of the first lens. Chromatic aberration can be reduced. On the other hand, when the value f1 / f is below the upper limit, the positive refractive power of the first lens can be appropriately secured, and the overall length of the imaging lens can be reduced.
[0013]
[Explanation of conditional expression (2)]
Conditional expression (2) is to appropriately set the shape factor of the positive first lens based on conditional expression (1). When the value (R2 + R1) / (R1-R2) exceeds the lower limit, the positive refractive power of the first lens is mainly carried on the image-side surface, and the image-side telecentric characteristic of the entire imaging lens system is reduced. It becomes easy to secure. When the value is below the upper limit, the radius of curvature of the image side surface of the first lens does not become extremely small, so that the back focus of the entire imaging lens system is easily secured, and the workability of the first lens is improved. It is also preferable from the viewpoint of. The following range is more preferable.
0.40 <(R2 + R1) / (R1-R2) <0.90 (2 ')
[0014]
According to a second aspect of the present invention, there is provided a small-sized imaging lens which satisfies the following conditional expression.
−0.50 <R3 / ((N2-1) · f) <− 0.10 (3)
However,
R3: radius of curvature of the object side surface of the second lens
N2: refractive index of the second lens with respect to d-line
f: focal length of the entire imaging lens system
[0015]
[Explanation of conditional expression (3)]
Conditional expression (3) is a condition for facilitating the correction of the curvature of field and making the image plane flat by appropriately setting the negative refractive power of the object side surface of the second lens. Here, since the focal length of the second lens object side surface is calculated by R3 / (N2-1) using the radius of curvature (R3) and the refractive index (N2) of the second lens, the conditional expression (2) Is an expression representing the ratio of the focal length of the second lens object side surface to the focal length of the entire imaging lens system.
[0016]
When the value R3 / ((N2-1) .f) exceeds the lower limit of conditional expression (3), the negative refracting power on the object side surface of the second lens does not become excessively large, and the coma flare of the off-axis light flux. In addition, the occurrence of pincushion-type distortion can be suppressed, and good image quality can be obtained. On the other hand, when the value is below the upper limit, the negative refractive power of the object side surface of the second lens can be maintained, so that the positive Betzval sum is reduced and the correction of the curvature of field becomes easy. Further, chromatic aberration of magnification occurring on the image side surface of the first lens can be satisfactorily corrected. The following range is more preferable.
−0.40 <R3 / ((N2-1) · f) <− 0.20 (3 ′)
[0017]
According to a third aspect of the present invention, there is provided a small-sized imaging lens according to the first or second aspect, wherein the following conditional expression is satisfied.
25.0 <ν1−ν2 (4)
However,
ν1: Abbe number of the first lens
ν2: Abbe number of the second lens
[0018]
[Explanation of conditional expression (4)]
Conditional expression (4) is a condition for correcting chromatic aberration in the positive first lens and the negative second lens. When the value ν1−ν2 exceeds the lower limit, axial chromatic aberration and lateral chromatic aberration are corrected in a well-balanced manner. can do.
[0019]
A small imaging lens according to a fourth aspect is the small imaging lens according to any one of the first to third aspects, wherein the first lens and the second lens are formed of a plastic material. And Here, being formed from a plastic material includes a case where the surface of the plastic material is subjected to coating treatment for the purpose of preventing reflection and improving the surface hardness, using the plastic material as a base material. The same applies to all descriptions in this specification.
[0020]
In recent years, in order to reduce the size of the entire imaging unit, even a solid-state imaging device having the same number of pixels has a small pixel pitch, and as a result, a light receiving unit (photoelectric conversion unit) having a small screen size has been developed. I have. Such an imaging lens for a solid-state imaging device having a small screen size requires a short focal length of the entire system in order to secure the same angle of view. turn into. Therefore, it becomes difficult to process glass lenses manufactured by polishing. Therefore, by configuring the first lens and the second lens with plastic lenses manufactured by, for example, injection molding, mass production is possible even with an imaging lens having a small radius of curvature or outer diameter. In addition, since it is easy to make an aspheric surface, it is advantageous in correcting aberration. Here, a glass mold lens can be used as an imaging lens that can be manufactured relatively easily even with a small diameter lens, but it can be said that a plastic lens is more suitable for mass production with reduced manufacturing costs.
[0021]
A small imaging lens according to a fifth aspect is the small imaging lens according to the fourth aspect, wherein the first lens and the second lens are formed of a plastic material having a saturated water absorption of 0.7% or less. It is characterized by having.
[0022]
Plastic lenses have a higher saturated water absorption than glass lenses, so if there is a sudden change in humidity, a non-uniform distribution of the water absorption will occur transiently, and the refractive index will not be uniform and good imaging performance will be obtained. Tends to disappear. Therefore, by using a material having a saturated water absorption of a plastic lens of 0.7% or less for the first lens and the second lens, it is possible to suppress performance degradation of a small-sized imaging lens due to a change in humidity.
[0023]
The imaging unit according to any one of claims 1 to 5, wherein the imaging unit according to claim 6, wherein a solid-state imaging device including a photoelectric conversion unit and a subject image are formed on the photoelectric conversion unit of the solid-state imaging device. A lens, a substrate having an external connection terminal for holding the solid-state imaging device and transmitting and receiving an electric signal, and a housing made of a light-shielding member having an opening for light incidence from the object side are integrally formed. A height of the imaging unit in an optical axis direction of the imaging lens is 10 mm or less.
[0024]
According to the present invention, by using the imaging lens of claims 1 to 5, it is possible to obtain an imaging unit having advantages such as smaller size and higher image quality. In addition, the "opening portion for light incidence" is not necessarily limited to one that forms a space such as a hole, but refers to a portion where a region that can transmit incident light from the object side is formed. Further, “the height of the imaging unit in the optical axis direction of the imaging lens is equal to or less than 10 mm” means the entire length of the imaging unit having all the above-described configurations along the optical axis direction. Therefore, for example, when the housing is provided on the front surface of the board and the electronic components and the like are mounted on the back of the board, the electronic components protruding on the back from the front end portion on the object side of the housing. This also includes the case where the distance to the tip of is less than 10 [mm].
[0025]
In the portable terminal according to the seventh aspect, by mounting the imaging unit according to the sixth aspect, it is possible to obtain a smaller portable terminal capable of performing high-quality imaging.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the small-sized imaging lens according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments, and the symbols used in each embodiment are as follows.
f: focal length of the entire imaging lens system
fB: Back focus
F: F number
2Y: Effective screen diagonal length
R: radius of curvature
D: Shaft upper surface interval
Nd: refractive index of the imaging lens material with respect to d-line
νd: Abbe number of imaging lens material
[0027]
In each embodiment, the shape of the aspheric surface is such that, in a rectangular coordinate system in which the vertex of the surface is the origin and the optical axis direction is the X axis, the vertex curvature is C, the conic constant is K, and the i-th order aspheric coefficient is Ai. It is represented by the following “Equation 1”.
(Equation 1)

[0028]
FIG. 1 is a typical sectional view of a small imaging lens according to Examples 1 to 5 of the present invention. In the drawing, L1 denotes a first lens, L2 denotes a second lens, and S denotes an aperture stop.
[0029]
(Example 1)
Tables 1 and 2 show lens data of Example 1. In this embodiment, L / 2Y = 1.21. Incidentally, in the lens data shown below, a power of 10 (for example, 2.5 × 10 ⁻⁰³ ) Is represented using E (for example, 2.5 × E-03).
[Table 1]

[Table 2]

[0030]
FIG. 2 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of the first embodiment. In this embodiment, the first lens is formed of a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is made of a polycarbonate-based plastic material. The saturated water absorption is 0.4%.
[0031]
(Example 2)
Tables 3 and 4 show lens data of Example 2. In this embodiment, L / 2Y = 1.22.
[Table 3]

[Table 4]

[0032]
FIG. 3 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of the second embodiment. In this embodiment, the first lens is formed of a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is formed of a polycarbonate-based plastic material, and has a saturated water absorption of 0.4%.
[0033]
(Example 3)
Tables 5 and 6 show lens data of Example 3. In this embodiment, L / 2Y = 1.28.
[Table 5]

[Table 6]

[0034]
FIG. 4 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of the third embodiment. In this embodiment, the first lens is formed from a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is formed of a polycarbonate-based plastic material, and has a saturated water absorption of 0.4%.
[0035]
(Example 4)
Tables 7 and 8 show lens data of Example 4. In this embodiment, L / 2Y = 1.22.
[Table 7]

[Table 8]

[0036]
FIG. 5 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of the fourth embodiment. In this embodiment, the first lens is formed of a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is formed of a polyester-based plastic material, and has a saturated water absorption of 0.7%.
[0037]
(Example 5)
Tables 9 and 10 show lens data of Example 5. In this embodiment, L / 2Y = 1.23.
[Table 9]

[Table 10]

[0038]
FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small-sized imaging lens of the fifth embodiment. In this embodiment, the first lens is formed of a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is formed of a polycarbonate-based plastic material, and has a saturated water absorption of 0.4%.
[0039]
(Example 6)
Tables 11 and 12 show lens data of Example 6. In this embodiment, L / 2Y = 1.25.
[Table 11]

[Table 12]

[0040]
FIG. 7 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of the sixth embodiment. In this embodiment, the first lens is formed from a polyolefin-based plastic material, and has a saturated water absorption of 0.01% or less. The second lens is formed of a polycarbonate-based plastic material, and has a saturated water absorption of 0.4%.
[0041]
(Example 7)
Tables 13 and 14 show lens data of the seventh embodiment. In the present embodiment, L / 2Y = 1.34. FIG. 12 is a cross-sectional view of a small imaging lens according to the seventh embodiment. In the drawing, L1 denotes a first lens, L2 denotes a second lens, and S denotes an aperture stop. FIG. 13 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small-sized imaging lens of the seventh embodiment. In this embodiment, the first lens is formed of a polyolefin-based plastic material and has a saturated water absorption of 0.01% or less. The second lens is made of a polycarbonate-based plastic material, and has a saturated water absorption of 0.4%. This embodiment is a design example in which an infrared cut filter and a parallel flat plate equivalent to a seal glass of a solid-state imaging device are arranged closest to the image side.
[Table 13]

[Table 14]

[0042]
Table 15 shows values of the examples corresponding to the conditional expressions.
[Table 15]

[0043]
In the above-described embodiment, the telecentric characteristic of the image-side light beam is not always sufficiently designed. The telecentric characteristic means that the principal ray of the luminous flux for each image point becomes almost parallel to the optical axis after exiting the final surface of the imaging lens. In other words, the exit pupil position of the optical system is sufficiently separated from the image plane. That is. When the telecentric characteristic is deteriorated, a light beam is obliquely incident on the solid-state imaging device, causing a phenomenon (shading) in which the aperture efficiency is substantially reduced in a peripheral portion of the screen, and the peripheral light amount becomes insufficient. However, in the recent technology, the shading phenomenon described above can be reduced by reviewing the arrangement of the color filters and the microlens array of the solid-state imaging device. Therefore, the present embodiment is a design example aiming at further miniaturization for the part where the requirement of the telecentric characteristic is relaxed.
[0044]
FIG. 8 is a cross-sectional view illustrating an embodiment of an imaging unit using the small imaging lens according to the above-described example. FIG. 9 is a perspective view of such an imaging unit. FIG. 10 is a top view of a solid-state imaging device used in such an imaging unit. FIG. 11 is a bottom view of a small imaging lens. The imaging unit 50 according to the present embodiment includes the solid-state imaging device 51 including the photoelectric conversion unit 51a and the imaging lens (the optical member 19) according to the above-described example that forms a subject image on the photoelectric conversion unit 51a of the solid-state imaging device 51. ), A substrate 52 having an external connection terminal for holding the solid-state imaging element 51 and transmitting and receiving an electric signal, and a housing 4 made of a light shielding member and having an opening 5c for light incidence from the object side. Are integrally formed, and the height h of the optical member 19 of the imaging unit 50 in the optical axis direction is 10 mm or less.
[0045]
8, the optical member 19 includes an image-side imaging lens member 1 and an object-side imaging lens member 9 each made of a transparent plastic material. As shown in FIG. 8, the image-side imaging lens member 1 includes a substantially hollow cylindrical leg 1c, four abutting portions 1d formed at a lower end of the leg 1c as a part of the leg 1c, and a leg 1c. A step portion 1e formed around the upper end, an imaging lens portion 1a (corresponding to L2 in FIG. 1), and a ring portion 1f formed around the upper end of the image-side imaging lens member 1 are integrally formed. . As shown in FIG. 11, the contact portion 1d of the image-side imaging lens member 1 has four tapered cylindrical shapes protruding from the lower surface of the substantially hollow cylindrical leg 1c.
[0046]
In FIG. 8, a light-shielding mask 3 made of a material having a light-shielding property and having an opening 3a as a stop for restricting a peripheral light beam is disposed above the imaging lens unit 1a.
[0047]
The object-side imaging lens member 9 is arranged so as to fit on the inner peripheral surface of the ring portion 1f and abut on the contact surface 1g, which is the upper surface of the ring portion 1f. The object side imaging lens member 9 includes a flange portion 9b located above the ring portion 1f, a positive imaging lens portion 9a (corresponding to L1 in FIG. 1) formed at the center, a projection 9c described below, and a ring portion. 1f.
[0048]
On the lower surface of the flange portion 9b of the object side imaging lens member 9, tapered projections formed at three places (any number of places are possible if there are three or more places) at equal intervals so as to face the contact surface 1g. 9c is formed. After the light-shielding mask 3 is fitted into the image-side imaging lens member 1, an adhesive B is applied to the contact surface 1 g and the object-side imaging lens member 9 is pressed from above. , And the adhesive B escapes around the protrusion 9c and is fixed in that state.
[0049]
If the projection 9c is not provided, the image-side imaging lens member 1 and the object-side imaging lens member 9 come into contact with each other. In such a case, the adhesive B is interposed between the contact surfaces, and The distance between the object side imaging lens member 9 may be inappropriate. On the other hand, according to the present embodiment, the tapered shape of the projection 9c allows the projection 9c to be firmly in contact with the contact surface 1g regardless of the presence of the adhesive B. By setting the value, the distance between the image-side imaging lens member 1 and the object-side imaging lens member 9 can be accurately defined, thereby suppressing variations in the imaging position and various aberrations of the entire imaging lens system during mass production. Can be.
[0050]
Further, in the present embodiment, the light-shielding mask 3 does not abut on the object-side imaging lens member 9 and functions only as a diaphragm for restricting a peripheral light beam. Thus, instead of the projection 9c, the spacer can function as a spacer that regulates the distance between the imaging lenses of the imaging lens portions 1a and 9a.
[0051]
The inner peripheral surface of the ring portion 1f of the image-side imaging lens member 1 and the outer peripheral surface of the ring portion 9d protruding downward from the flange portion 9b of the object-side imaging lens member 9 have the same diameter and are parallel to the optical axis. By engaging these surfaces, the imaging lens portions 1a and 9a can be positioned in the direction orthogonal to the optical axis, and their optical axes can be easily matched.
[0052]
Outside the optical member 19, the lens frame 4 made of a light-shielding material is arranged. As is clear from FIG. 9, the lens frame 4 is provided with a prismatic lower part 4a and a cylindrical upper part 4b. The lower end of the lower portion 4a abuts on the substrate 52 and is fixed by the adhesive B. In FIG. 8, the upper surface of the lower portion 4a is covered on the peripheral side by a partition 4c, and the leg 1c of the optical member 19 is fitted tightly on the circular inner peripheral surface of the partition 4c. Therefore, the center of the circular opening of the partition wall 4c and the photoelectric conversion unit 51a of the solid-state imaging device 51 described below are formed by using the optical sensor (not shown) or the like provided in the automatic assembling machine. By simply inserting the optical member 19 from above, the imaging lens unit 1a and the positive imaging lens unit 9a are moved with respect to the photoelectric conversion unit 51a of the solid-state imaging device 51 described later. Positioning can be accurately performed in the direction perpendicular to the axis.
[0053]
The substrate 52 has a support plate 52a that supports the solid-state imaging device 51 and the housing 53 on one plane, and a flexible plate having one end connected to the back surface (the surface opposite to the solid-state imaging device 51) of the support plate 52a. And a substrate 52b. The support plate 52a has a large number of signal transmission pads provided on the front and back surfaces, and is connected to the wire W of the image sensor 51 on one plane side and to the flexible substrate 52b on the back side. I have. One end of the flexible substrate 52b is connected to the support plate 52a as described above, and the support plate 52a and an external circuit (for example, an image pickup unit is mounted) via the external output terminal 54 (FIG. 9) provided at the other end. And a supply of a voltage and a clock signal for driving the solid-state imaging device 51 from an external circuit, and outputting a digital YUV signal to the external circuit. Make it possible. Further, the intermediate portion in the longitudinal direction of the flexible substrate 52b has flexibility or deformability, and the deformation gives flexibility to the direction and arrangement of the external output terminals with respect to the support plate 52a.
[0054]
At the upper end of the upper portion 4b of the lens frame 4, a central fitting portion 5a, an adhesive portion 5b lower than the upper surface on the inner peripheral side and the outer peripheral side, and an inner diameter protruding downward from the fitting portion 5a are gradually increased. A holding member 5 having a reduced diameter portion 5c for reducing the diameter and made of a light-shielding material is attached. The reduced diameter portion 5c is an aperture stop (corresponding to S in FIG. 1) that regulates the F number of the entire imaging lens system. A filter 7 made of a material having infrared absorption characteristics is fitted to the fitting portion 5a. After the adhesive portion B of the holding member 5 is filled with the adhesive B, the thin light shielding sheet 8 is placed on the upper surface, so that the filter 7, the light shielding sheet 8 and the holding member 5 are simultaneously attached to the lens frame 4. Can be.
[0055]
In FIG. 8, an elastic means 6 composed of a coil spring is disposed between the holding member 5 and the step 1 e of the optical member 19, and the holding member 5 is elastically deformed by being attached to the lens frame 4. The optical member 19 is pressed downward in FIG. 8 by the elastic force. Therefore, although the force from the holding member 5 is transmitted to the substrate 52 via the lens frame 4, it is not directly transmitted to the solid-state imaging device 51, which is preferable from the viewpoint of protection of the solid-state imaging device 51. In addition, the elastic force can be appropriately managed by selecting the wire diameter, the number of turns, and the like of the coil spring 6.
[0056]
In FIG. 10, the solid-state imaging device 51 is composed of a CMOS image sensor. The lower surface of the thin rectangular solid-state imaging element 51 is attached to the upper surface of the substrate 52. At the center of the upper surface of the solid-state imaging device 51, a photoelectric conversion unit 51a in which pixels are two-dimensionally arranged is formed, and a signal processing circuit inside and inside the solid-state imaging device 51 is formed around the photoelectric conversion unit 51a. The configured peripheral surface 51b is formed. A large number of pads 51c are arranged near the outer edge of the peripheral surface 51b crossing the thin side surface at right angles. The pad 51c serving as an external connection terminal is connected to the substrate 52 via a wire W as shown in FIG. The solid-state imaging device 51 converts an electric signal from the photoelectric conversion unit 51a into an image signal or the like, and can output these signals to a predetermined circuit of the substrate 52 via the pad 51c and the wire W.
[0057]
Further, as shown in FIG. 11, the contact portion 1d of the optical member 19 protrudes from the lower end of the leg 1c in a tapered cylindrical shape, and forms a part of the leg 1c. In the present embodiment, as shown by the dotted line in FIG. 10, the optical member 19 is arranged on the peripheral surface 51b of the solid-state imaging device 51 inside the pad 51c with only the contact portion 1d contacting. It will be. Here, a signal processing circuit (not shown) of the solid-state imaging device is provided on the back side (the lower side in FIG. 8) of the peripheral surface 51b, but the contact of the contact portion 1d affects the signal processing. It has become inaccessible.
[0058]
According to the present embodiment, when the contact portion 1d is in contact with the peripheral surface 51b of the solid-state imaging device 51, the lower surface of the step portion 1e of the optical member 19 and the partition wall 4c of the lower portion 4a of the lens frame 4 are connected. Between them, the distance between the imaging lens unit 1a and the photoelectric conversion unit 51a of the solid-state imaging device 51 (that is, the positioning in the optical axis direction) is longer than the length of the leg 1c. Therefore, it is set with high accuracy. Therefore, by controlling the dimensional accuracy of the leg 1c (including the contact portion 1d), it is not necessary to adjust the focusing position of the entire imaging lens system.
[0059]
Further, since the optical member 19 is made of a plastic material, it is possible to reduce the shift of the focus position based on the change in the refractive index of the imaging lens units 1a and 9a when the temperature changes. That is, as the temperature of the plastic lens increases, the refractive index of the imaging lens decreases, and the focal position of the entire imaging lens system changes in a direction away from the imaging lens. On the other hand, since the leg portion 1c extends due to the temperature rise, there is an effect of reducing the focus position shift. Since the optical member 19 of the present embodiment is made of a plastic material having a relatively low specific gravity, it is lighter than glass even with the same volume, and has excellent shock absorption characteristics. Even in such a case, there is an advantage that damage to the solid-state imaging device 51 can be suppressed as much as possible.
[0060]
In the present embodiment, the lens frame 4 is adhered to the substrate 52 and, together with the other two adhesion portions, is maintained in a sealed state so that foreign matter does not enter the outside of the imaging unit. Therefore, it is possible to eliminate adverse effects of foreign matter on the photoelectric conversion unit 51a of the solid-state imaging device 51. It is preferable that the adhesives used for these have moisture-proof properties. As a result, surface deterioration of the solid-state imaging device and the pad due to invasion of moisture can be prevented.
[0061]
A usage mode of the above-described imaging unit 50 will be described. FIG. 14 is a front view (A) and a rear view (B) of a mobile phone 100 as a mobile terminal or an imaging device provided with the imaging unit 50, and FIG. 15 is a control block diagram of the mobile phone 100.
[0062]
The imaging unit 50 has, for example, an object-side end face of the housing 4 provided on the back surface of the mobile phone 100 (the liquid crystal display unit side is the front), and is disposed at a position corresponding to a position below the liquid crystal display unit. The external connection terminal 54 of the imaging unit 50 is connected to the control unit 101 of the mobile phone 100, so that an image signal such as a luminance signal and a color difference signal can be output to the control unit 101.
[0063]
On the other hand, as shown in FIG. 15, the mobile phone 100 controls the respective units in a centralized manner, and also supports a controller (CPU) 101 that executes a program corresponding to each process and supports and inputs a number and the like using keys. Input unit 60, a display unit 70 for displaying captured images in addition to predetermined data, a wireless communication unit 80 for realizing various types of information communication with an external server, and a system program for the mobile phone 100. Storage unit (ROM) 91 that stores necessary data such as terminal IDs and various processing programs, and various processing programs and data to be executed by the control unit 101, or processing data, or the imaging unit 50. A temporary storage unit (RAM) 92 is used as a work area for temporarily storing image data and the like.
[0064]
Then, the image signal input from the imaging unit 50 is stored in the storage unit 92 or displayed on the display unit 70 by the control system of the mobile phone 100, and further, the video information is transmitted via the wireless communication unit 80. Sent to the outside.
[0065]
As described above, the present invention has been described with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and it is needless to say that modifications and improvements can be made as appropriate. For example, the small imaging lens of this embodiment is a design example in which a low-pass filter is not arranged between the lens and the solid-state imaging device photoelectric conversion unit, but a low-pass filter may be arranged as necessary.
[0066]
【The invention's effect】
According to the present invention described above, it is possible to provide a small-sized imaging lens, an imaging unit, and a mobile terminal, which are smaller and have excellent aberrations, despite the simple configuration of two lenses.
[Brief description of the drawings]
FIG. 1 is a typical sectional view of a small imaging lens according to the present invention.
FIG. 2 is an aberration diagram of the small-sized imaging lens according to the first embodiment.
FIG. 3 is an aberration diagram of the small-sized imaging lens according to the second embodiment.
FIG. 4 is an aberration diagram of the small-sized imaging lens according to the third embodiment.
FIG. 5 is an aberration diagram of the small-sized imaging lens according to the fourth embodiment.
FIG. 6 is an aberration diagram of the small-sized imaging lens according to the fifth embodiment.
FIG. 7 is an aberration diagram of the small-sized imaging lens of the sixth embodiment.
FIG. 8 is a cross-sectional view illustrating an embodiment of an imaging unit using a small-sized imaging lens according to the above-described embodiment.
FIG. 9 is a perspective view of the imaging unit according to the embodiment;
FIG. 10 is a top view of the solid-state imaging device used in the imaging unit according to the embodiment;
FIG. 11 is a bottom view of the small imaging lens according to the embodiment;
FIG. 12 is a sectional view of a small imaging lens according to a seventh embodiment;
13 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the small imaging lens of Example 7. FIG.
FIGS. 14A and 14B are a front view (A) and a rear view (B) of a mobile phone 100 as a mobile terminal or an imaging device including the imaging unit 50. FIGS.
15 is a control block diagram of the mobile phone 100. FIG.
[Explanation of symbols]
1 Image side imaging lens member
3 Shading mask
4 mirror frame
5 Holding member
6 Coil spring
7 Filter
8 Shading sheet
9 Object side imaging lens member
19 Optical components
50 Imaging unit
51 Solid-state image sensor
52 substrate
L1 First lens
L2 Second lens
S aperture stop

Claims (7)

An aperture stop, a first lens having a positive refractive power with a convex surface facing the image side, and a meniscus-shaped second lens with a concave surface facing the object side are arranged in order from the object side. Each of the lenses has at least one aspherical surface, and satisfies the following conditional expression.
0.50 <f1 / f <0.80 (1)
0.30 <(R2 + R1) / (R1-R2) <1.20 (2)
However,
fl: focal length of the first lens f: focal length of the entire lens system R1: radius of curvature of the object side surface of the first lens R2: radius of curvature of the image side surface of the first lens The compact imaging lens according to claim 1, wherein the following conditional expression is satisfied.
−0.50 <R3 / ((N2-1) · f) <− 0.10 (3)
However,
R3: radius of curvature N2 of the object side surface of the second lens N2: refractive index f of d-line of the second lens f: focal length of the entire lens system The compact imaging lens according to claim 1, wherein the following conditional expression is satisfied.
25.0 <ν1−ν2 (4)
However,
ν1: Abbe number of the first lens ν2: Abbe number of the second lens The small imaging lens according to any one of claims 1 to 3, wherein the first lens and the second lens are formed of a plastic material. The small imaging lens according to claim 4, wherein the first lens and the second lens are formed of a plastic material having a saturated water absorption of 0.7% or less. A solid-state imaging device having a photoelectric conversion unit,
The imaging lens according to any one of claims 1 to 5, wherein a subject image is formed on the photoelectric conversion unit of the solid-state imaging device.
A substrate having an external connection terminal for transmitting and receiving an electric signal while holding the solid-state imaging device,
An imaging unit in which a housing having an opening for light incidence from the object side and made of a light-shielding member is integrally formed,
The height of the imaging unit in the direction of the optical axis of the imaging lens is 10 [mm] or less. A mobile terminal comprising the imaging unit according to claim 6.

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