JP2004045452A - Optical multilayer film and optical element - Google Patents

Abstract

An optical multilayer film and an optical element having a low transmittance in a specific wavelength region are provided. In particular, the present invention provides an optical multilayer film and an optical element that realize an optical multilayer film that reflects light in the green wavelength band and transmits light in the blue and red wavelength bands with a relatively small number of layers.
An optical multilayer film that determines an actual film thickness based on a basic structure that defines a basic film thickness and a layer structure of each layer. Basic configuration, the design wavelength as lambda _0, an optical film thickness 7λ _0/32 and first thin film group composed of a single layer or alternating layers of a single layer or 7Ramuda of 7λ _{0/16 0/32} and 7λ _0/16 a second thin film group consisting of alternating layers of, among the three film group and the third thin film group consisting of alternating layers of a single layer or 7λ _0/32 and 7λ _0/8 of 7λ _0/8, 2 kinds And five or more thin film groups, and the thin film groups composed of a single layer are not adjacent to each other. However, the division of the basic configuration is determined by the priority order of the third, second, and first thin film groups.
[Selection diagram] Fig. 1

Description

【００２４】
更に、図３に、この時の透過率特性を示す。横軸は波長、縦軸は透過率を示す。図３において、点線３３ＴＳ２３は空気側から入射角３３度、層数２３層のＳ成分透過率特性を示し、実線４５ＴＳ２３は空気側から入射角４５度、層数２３層のＳ成分透過率特性を示し、破線５７ＴＳ２３は空気側から入射角５７度、層数２３層のＳ成分透過率特性を示す。
【００２５】
本実施例においては、４５度入射の時、４３０〜４８０ｎｍの範囲で平均９８．９％の高透過率、５１０〜５７０ｎｍの範囲で平均２．２％の低透過率、６００〜６５０ｎｍの範囲で平均９８．８％の高透過率が得られた。又、角度特性を半値波長巾（３３度の時の短波長側の半値波長と５７度の時の長波長側の半値波長の差を示し、緑成分の明るさに対応）で示すと、約４９ｎｍであった。共に実用上問題無い特性が得られた。
【００２６】
表１の結果から分かるように、本実施例の膜の特徴は、（１）全薄膜群の総光学膜厚の実施膜厚が基本膜厚の約１．０倍であり、（２）第１薄膜群の総光学膜厚の実施膜厚が基本膜厚の約１．７３倍であり、（３）第２、第３薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．８８倍であり、（４）　２つの７λ_０／３２層とそれに挟まれた１つの７λ_０／８層との計３層（３層基本構成）からなる第３薄膜群において、実施膜厚が約４．２λ_０／４〜６．０λ_０／４の範囲であり、（５）　７λ_０／３２層の単層（単層基本構成）からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第３薄膜群とそれに隣接する２つの第１薄膜群の３群の合計の実施膜厚が約７．３λ_０／４〜７．５λ_０／４の範囲であり、（６）単層基本構成からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第１薄膜群とそれに隣接する２つの第３薄膜群の３群の合計の実施膜厚が約１１．７λ_０／４を満たしていることである。
【００２７】
＜実施例２＞
実施例１と同様にして、第１薄膜群をＴａ_２Ｏ_５膜、第２薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜、第３薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜で構成し、１１群からなる緑反射トリミングフィルターをＢＫ７基板上に真空蒸着法により形成した。表２に、各薄膜群を含む基本構成の基本膜厚、及び透過率改善のための調整後の実施膜厚を示す。但し、使用入射角は０度である。
【００２８】
更に、図４に、この時の透過率特性を示す。図４において、実線０Ｔ２３は空気側から入射角０度、層数２３層の透過率特性を示す。
【００２９】
本実施例においては、０度入射の時、４３０〜４８０ｎｍの範囲で平均９７．４％の高透過率、５１０〜５７０ｎｍの範囲で平均２．９％の低透過率、６００〜６５０ｎｍの範囲で平均９８．３％の高透過率が得られ、実用上問題無い特性であった。
【００３０】
更に、本実施例２の０度入射フィルターと実施例１の４５度入射フィルターを組み合わせる事により、コントラストを向上させる事が出来た。即ち、４５度入射フィルターの後に０度入射フィルターを設置する事により、入射角度に依存する不要な光（図３において、入射角３３度の時の約５００〜５１５ｎｍの透過光、及び入射角５７度の時の約５６５〜５８０ｎｍの透過光）をカットする事が出来た。この時の特性を図４に示す。図４において、０Ｔ２３＊３３Ｔｓは入射角３３度と０度で透過したＳ成分を示し、０Ｔ２３＊５７Ｔｓは入射角５７度と１２度で透過したＳ成分を示す。
【００３１】
【表２】

【００３２】
表２の結果から分かるように、本実施例の膜の特徴は、（１）全薄膜群の総光学膜厚が実施膜厚が基本膜厚の約０．９８倍であり、（２）第１薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．７６倍であり、（３）第２、第３薄膜群の総光学膜厚の実施膜厚が基本膜厚の約１．０２倍であり、（４）３層基本構成からなる第３薄膜群において、実施膜厚が約４．８λ_０／４〜５．９λ_０／４の範囲であり、（５）単層基本構成からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第３薄膜群とそれに隣接する２つの第１薄膜群の３群の合計の実施膜厚が約６．５λ_０／４〜６．８λ_０／４の範囲であり、（６）単層基本構成からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第１薄膜群とそれに隣接する２つの第３薄膜群の３群の合計の実施膜厚が約１２．０λ_０／４を満たしていることである。
【００３３】
＜実施例３＞
実施例１と同様にして、第１薄膜群をＴｉＯ_２膜、第２薄膜群をＡｌ_２Ｏ_３膜とＴｉＯ_２膜、第３薄膜群をＡｌ_２Ｏ_３膜とＴｉＯ_２膜で構成し、１１群からなる緑反射トリミングフィルターをＢＫ７基板上に真空蒸着法により形成した。表３に、各薄膜群を含む基本構成の光学膜厚、及び透過率改善のための調整後の実施した光学膜厚を示す。但し、表３において、ＴｉはＴｉＯ_２膜（５８８ｎｍでの屈折率２．３０）、ＡはＡｌ_２Ｏ_３膜（５８８ｎｍでの屈折率１．６３）を示す。
【００３４】
更に、図５に、この時の透過率特性を示す。図５において、点線３３ＴＳ２３は空気側から入射角３３度、層数２３層のＳ成分透過率特性を示し、実線４５ＴＳ２３は空気側から入射角４５度、層数２３層のＳ成分透過率特性を示し、破線５７ＴＳ２３は空気側から入射角５７度、層数２３層のＳ成分透過率特性を示す。
【００３５】
【表３】
表３

【００３６】
本実施例においては、４５度入射の時、４３０〜４８０ｎｍの範囲で平均９８．１％の高透過率、５１０〜５７０ｎｍの範囲で平均２．０％の低透過率、６００〜６５０ｎｍの範囲で平均９８．８％の高透過率が得られた。又、角度特性を半値波長巾で示すと、約５０ｎｍであつた。共に実用上問題無い特性が得られた。
【００３７】
表３において、第３薄膜群を構成する１層目のＡｌ_２Ｏ_３膜の実施膜厚が０となっている。しかし、これは透過率改善のための調整後、基板に接する層として全体特性の上から０が好ましいという事であり、基本構成（第３群の基本膜厚合計は約５．２５／４λ_０）を逸脱するものではない。
【００３８】
表３の結果からわかるように、本実施例の膜の特徴は、（１）全薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．９７倍であり、（２）第１薄膜群の総光学膜厚の実施膜厚が基本膜厚の合計の約０．８７倍であり、（３）第２、第３薄膜群の総光学膜厚の実施膜厚が基本膜厚の合計の約０．９８倍であり、（４）　３層基本構成からなる第３薄膜群において、実施膜厚が約４．６λ_０／４〜６．１λ_０／４の範囲であり、（５）　単層基本構成からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第３薄膜群とそれに隣接する２つの第１薄膜群の３群の合計の実施膜厚が約６．９λ_０／４〜７．０λ_０／４の範囲であり、（６）　単層基本構成からなる第１薄膜群と３層基本構成からなる第３薄膜群において、１つの第１薄膜群とそれに隣接する２つの第３薄膜群の３群の合計の実施膜厚が約１２．６λ_０／４を満たしていることである。
【００３９】
＜実施例４＞
第２薄膜群を単層のＴａ_２Ｏ_５膜、第３薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜で構成し、５群からなる緑反射トリミングフィルターをＢＫ７基板上に真空蒸着法により形成した。表４に、基板側からの各薄膜群を含む基本構成の光学膜厚、及び透過率改善のための調整後の実施した光学膜厚を示す。使用入射角は４５度である。
【００４０】
【表４】
表４

【００４１】
更に、図６に、この時の透過率特性を示す。図６において、点線３３ＴＳ１５は空気側から入射角３３度、層数１５層のＳ成分透過率特性を示し、実線４５ＴＳ１５は空気側から入射角４５度、層数１５層のＳ成分透過率特性を示し、破線５７ＴＳ１５は空気側から入射角５７度、層数１５層のＳ成分透過率特性を示す。
【００４２】
本実施例においては、４５度入射の時、４３０〜４８０ｎｍの範囲で平均９４．７％の高透過率、５１０〜５７０ｎｍの範囲で平均６．１％の低透過率、６００〜６５０ｎｍの範囲で平均９７．１％の高透過率が得られた。緑領域のモレ透過光がやや多いが、実用上は問題無かった。又、角度特性を半値波長巾で示すと、実施例１と同様約４９ｎｍであつた。
表４において、第２の第３薄膜群は５層目〜１１層目までの交互層で構成されるが、第３薄膜群は必ずしも該３層基本構成で構成されるものではない。
表４の結果からわかるように、本実施例の膜の特徴は、（１）全薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．９３倍であり、（２）第２、第３薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．９３であることである。
【００４３】
＜実施例５＞
実施例２と同様にして、第１薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜、第２薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜、第３薄膜群をＳｉＯ_２膜とＴａ_２Ｏ_５膜で構成し、７群からなる緑反射トリミングフィルターをＢＫ７基板上に真空蒸着法により形成した。表５に、各薄膜群を含む基本構成の光学膜厚、及び透過率改善のための調整後の実施膜厚を示す。但し、使用入射角は０度である。更に、図７に、この時の透過率特性を示す。
【００４４】
【表５】
表５

【００４５】
図７において、実線０Ｔ２５は空気側から入射角０度、層数２５層の透過率特性を示す。本実施例においては、０度入射の時、４３０〜４８０ｎｍの範囲で平均９７．５％の高透過率、５１０〜５７０ｎｍの範囲で平均３．７％の低透過率、６００〜６５０ｎｍの範囲で平均９８．５％の高透過率が得られ、実用上問題無い特性であった。
【００４６】
表５の結果から分かるように、本実施例の膜の特徴は、（１）全薄膜群の総光学膜厚の実施膜厚が基本膜厚の約１．０１倍であり、（２）第１薄膜群の総光学膜厚の実施膜厚が基本膜厚の約１．２１倍であり、（３）第２、第３薄膜群の総光学膜厚の実施膜厚が基本膜厚の約０．８８倍であり、（４）３層基本構成からなる第３薄膜群において、実施膜厚が約４．６λ_０／４〜５．０λ_０／４の範囲であることである。
【００４７】
次に、本発明の比較対照として、本発明とは異なる基本構成の比較例を示した。
【００４８】
＜比較例１＞
Ｔａ_２Ｏ_５膜とＳｉＯ_２膜のλ_０／４の交互層を基本に、高屈折率膜と低屈折率膜の光学膜厚比を換えて多層膜をＢＫ７基板上に形成し、緑反射、青赤透過トリミングフィルターを得た。表６に、透過率改善のための調整後の実施膜厚を基板側から第１層の光学膜厚を示す。使用入射角は４５度である。
【００４９】
表６において、１、２層目と２５〜２８層目は青、赤領域の透過率（リップル）改善のための調整層であり、３〜２４層目までが緑領域で高反射率を得るための交互層である。交互層の基本構成は１：１であるが、反射帯の半値波長巾を満たすためには約１．７：０．３程度の膜厚比の交互層が好ましいことがわかる。
【００５０】
【表６】

【００５１】
更に、図８に、この時の透過率特性を示す。図８において、点線３３ＴＳ２８は空気側から入射角３３度、層数２８層のＳ成分透過率特性を示し、実線４５ＴＳ２８は空気側から入射角４５度、層数２８層のＳ成分透過率特性を示し、破線５７ＴＳ２８は空気側から入射角５７度、層数２８層のＳ成分透過率特性を示す。
【００５２】
本比較例においては、４５度入射の時、４３０〜４８０ｎｍの範囲で平均９１．４％の高透過率、５１０〜５７０ｎｍの範囲で平均３．２％の低透過率、６００〜６５０ｎｍの範囲で平均９５．５％の高透過率が得られた。又、角度特性を半値波長巾で示すと、約４９ｎｍであった。角度特性は本実施例と同等であるが、透過率特性では劣り、青、赤領域で明るさが不足する結果となり実用上問題であった。
【００５３】
＜比較例２＞
比較例１の青、赤領域の透過率を改善するため、約１．７：０．３程度の膜厚比の交互層を基本に膜厚調整して、多層膜をＢＫ７基板上に同様に形成し、緑反射、青赤透過トリミングフィルターを得た。表７に、透過率改善のための調整後の実施した基板側からの光学膜厚を示す。使用入射角は４５度である。
【００５４】
【表７】

【００５５】
更に、図９に、この時の透過率特性を示す。図９において、点線３３ＴＳ３０は空気側から入射角３３度、層数３０層のＳ成分透過率特性を示し、実線４５ＴＳ３０は空気側から入射角４５度、層数３０層のＳ成分透過率特性を示し、破線５７ＴＳ３０は空気側から入射角５７度、層数３０層のＳ成分透過率特性を示す。
【００５６】
本比較例においては、４５度入射の時、４３０〜４８０ｎｍの範囲で平均９９．０％の高透過率、５１０〜５７０ｎｍの範囲で平均２．１％の低透過率、６００〜６５０ｎｍの範囲で平均９８．８％の高透過率が得られた。又、角度特性を半値波長巾で示すと、約４９ｎｍであつた。角度特性、透過率特性は本実施例と同等であるが、層数が多く、製造上好ましくなかった。
【００５７】
＜比較例３＞
特公昭６０−０３８６８３の図４に示される１１層特性のものを実施例１と同様にして形成した。但し、第１薄膜群をＳｉＯ_２膜とＺｒＯ_２膜、第２薄膜群をＳｉＯ_２膜とＺｒＯ_２膜とし、設計波長λ_０は５４０ｎｍ、使用入射角は０度とした。第１薄膜群はλ_０／４の交互層であり、第２薄膜群は４λ_０／４−２λ_０／４−４λ_０／４の基本構成である。この基本構成膜厚の時の特性を図１０に示す。図１０において、実線０Ｔ１１は空気側から入射角０度、層数１１層の透過率特性を示す。
図１０から、４３０〜４８０ｎｍの範囲の高透過率、６００〜６５０ｎｍの範囲の高透過率が得られず、本比較例の構成では、緑反射トリミングフィルターとして実用に適しない。
【００５８】
＜液晶プロジェクターの実施例＞
次に、本実施形態の光学多層膜を用いたトリミングフィルターを有する液晶プロジェクターの実施例を示す
図１１は本実施形態の光学多層膜を用いたトリミングフィルターを有する液晶プロジェクターの図である。図１１において、１０１は光源、１０２は偏光板、１０３は本実施形態の光学多層膜を用いた、緑波長帯域の光（Ｇ）を反射し、青波長帯域の光（Ｂ）と赤波長帯域の光（Ｒ）を透過するトリミングフィルターである。１０４ａ、は青色光の偏光方向を９０度変換し、赤色光の偏光方向は変換しない第１の色選択性位相差板、１０４ｂは青色光の偏光方向は変換せずに、赤色光の偏光方向を９０度変換する第２の色選択性位相差板、１０５ａ、１０５ｂ、１０５ｃは夫々Ｐ偏光を透過し、Ｓ偏光を反射する第１、第２及び第３の偏光ビームスプリッタである。１０６Ｒ、１０６Ｇ、１０６Ｂは夫々入射した光を反射するとともに画像変調する赤用の反射型液晶表示素子、緑用の反射型液晶表示素子、青用の反射型液晶表示素子である。１０８は投射レンズである。
【００５９】
光源１０１から出射した無偏光の光は、偏光板１０２によって直線偏光（Ｓ偏光）とされ、トリミングフィルター１０３に入射する。トリミングフィルター１０３によって、緑色光は反射されるが、青色光と赤色光は透過する。これにより、緑色光と青、赤色光とが色分解される。
【００６０】
緑色光は第１の偏光ビームスプリッタ１０５ａで反射して緑用の反射型液晶表示素子１０６Ｇに入射する。一方、トリミングフィルター１０３を透過した青色光と赤色光は第１の色選択性位相差板１０４ａに入射して、ここで青色光の偏光方向のみが９０度回転させられＰ偏光となる。
【００６１】
第２の偏光ビームスプリッタ１０５ｂは、Ｐ偏光である青色光を透過し、Ｓ偏光である赤色光を反射することでこれらを色分解し、青色光および赤色光はそれぞれ青用の反射型液晶表示素子１０６Ｂ及び赤用の反射型液晶表示素子１０６Ｒ入射する。
【００６２】
緑用の反射型液晶表示素子１０６Ｇで変調された光のうちＰ偏光成分は第１の偏光ビームスプリッタ１０５ａを透過し、第３の偏光ビームスプリッタ１０５ｃも透過して投影光となる。
【００６３】
青用の反射型液晶表示素子１０６Ｂで変調された光のうちＳ偏光成分は第２の偏光ビームスプリッタ１０５ｂで反射し、第２の色選択性位相差板１０４ｂを透過し、第３の偏光ビームスプリッタ１０５ｃで反射して、投影光となる。
【００６４】
赤用の反射型液晶表示素子１０６Ｒで変調された光のうちＰ偏光成分は第２の偏光ビームスプリッタ１０５ｂを透過し、第２の色選択性位相差板１０４ｂによって偏光方向が９０度回転し、Ｐ偏光となり、第３の偏光ビームスプリッタ１０５ｃで反射して、投影光となる。第３の偏光ビームスプリッタ１０５ｃで１つに合成された緑色光と青色光と赤色光は、投射レンズ１０８より投射されることによってカラー画像を表示する。
【００６５】
本実施例の液晶プロジェクターは、本実施形態の光学多層膜を用いることによって、少ない層数で緑色光を反射し、青、赤色光を透過するトリミングフィルターを実現している。
【００６６】
【発明の効果】
本発明により、比較的少ない層数で、特定波長域で透過率が低くなる光学多層膜を実現することが可能となった。
【図面の簡単な説明】
【図１】本発明の概略を示す図である
【図２】薄膜群の切り分け方を示す図である
【図３】本発明の実施例１の光学多層膜の透過率特性を示す図である
【図４】本発明の実施例２の光学多層膜の透過率特性を示す図である
【図５】本発明の実施例３の光学多層膜の透過率特性を示す図である
【図６】本発明の実施例４の光学多層膜の透過率特性を示す図である
【図７】本発明の実施例５の光学多層膜の透過率特性を示す図である
【図８】本発明の比較例１の光学多層膜の透過率特性を示す図である
【図９】本発明の比較例２の光学多層膜の透過率特性を示す図である
【図１０】本発明の比較例３の光学多層膜の透過率特性を示す図である
【図１１】本実施形態のトリミングフィルターを有する液晶プロジェクターの図である[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical multilayer film and an optical element. In particular, the present invention relates to an optical multilayer film used for a color separation (synthesis) optical system such as a liquid crystal projector, and more particularly to a trimming filter that reflects light in a green wavelength band and transmits light in a blue and red wavelength band.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 2001-154152 discloses that a color separation (synthesis) optical system such as a liquid crystal projector is formed by combining a polarization beam splitter and an optical element (color-selective phase difference plate) that converts a polarization direction in a specific wavelength range. It is known in the gazette.
[0003]
The color-selective phase difference plate can separate the light in that wavelength range by changing the polarization direction in a specific wavelength range and combining it with a polarizing beam splitter. It is difficult to separate light with good purity. For example, if the P-polarized light consisting of green light and red light having a continuous wavelength band is converted only to red light into S-polarized light by a color-selective phase difference plate, and green light and red light are separated by a polarizing beam splitter, the green light is converted to green light. It is difficult to separate light of a wavelength band between light and red light with high purity.
[0004]
Therefore, if green light is separated by a trimming filter using an optical multilayer film, and then blue and red light are separated (combined) by a color-selective retardation plate, the wavelength bands of blue light and red light are far apart. There is an advantage that blue and red light are easily separated (combined). Here, the trimming filter is an optical element having an optical multilayer film that reflects light in a specific wavelength range and transmits light in other wavelength ranges.
[0005]
As a method for obtaining a film having green light separation characteristics, λ ₀ A method is known in which a multilayer film is formed on a substrate by changing the optical film thickness ratio of a high refractive index film and a low refractive index film on the basis of an alternating layer of / 4 to obtain green reflection and blue-red transmission characteristics. .
[0006]
Japanese Patent Publication No. Sho 60-038683 proposes an example of a trimming filter which does not have green reflection and blue-red transmission characteristics but divides light in the blue, green and red wavelength bands as main components. In this example, the design wavelength is λ ₀ , The optical film thickness λ ₀ A first thin film group consisting of alternating layers of / 4 and 2λ ₀ / 4 and 4λ ₀ A configuration including four or more groups of two thin film groups of a second thin film group composed of alternating layers of / 4 is disclosed.
[0007]
As a method for obtaining a film having green light separation characteristics, λ ₀ A method is known in which a multilayer film is formed on a substrate by changing the optical film thickness ratio of a high refractive index film and a low refractive index film on the basis of an alternating layer of / 4 to obtain green reflection and blue-red transmission characteristics. .
[0008]
[Problems to be solved by the invention]
However, λ ₀ In a configuration in which a multilayer film is formed by changing the optical thickness ratio of the high refractive index film and the low refractive index film based on the alternating layers of / 4, the number of layers tends to increase in order to obtain desired characteristics. Was.
[0009]
Further, the trimming filter disclosed in Japanese Patent Publication No. 60-038683, which is a prior example, divides the light so that light of each wavelength band of blue, green, and red is a main component, but a wavelength range in which a high transmittance of each component can be obtained. Was narrow, and a high transmittance in the range of 430 to 480 nm and a high transmittance in the range of 600 to 650 nm could not be obtained. Also, a low transmittance in the green transmission band was not obtained.
[0010]
An object of the present invention is to provide a novel optical multilayer film having a low transmittance in a specific wavelength region such as a green wavelength band in view of the above conventional example.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the optical multilayer film of the present invention is an optical multilayer film in which the actual film thickness is determined based on the basic configuration in which the basic thickness and the layer configuration of each layer are determined. To λ ₀ , Optical film thickness 7λ ₀ / 32, a first thin film group consisting of a single layer or alternate layers, and 7λ ₀ / 16 single layer or 7λ ₀ / 32 and 7λ ₀ / 16 and a second thin film group composed of alternating layers ₀ / 8 single layer or 7λ ₀ / 32 and 7λ ₀ And at least five thin film groups of at least two types among the three thin film groups of the third thin film group composed of alternating layers of / 8, and the thin film groups composed of a single layer are not adjacent to each other. .
[0012]
In the basic configuration, the division of each thin film group is determined by the priority of the third thin film group, the second thin film group, and the first thin film group.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The green reflection trimming filter of the liquid crystal projector needs characteristics in consideration of the spectral characteristics of the light source lamp. That is, high transmittance in the range of 430 to 480 nm, low transmittance in the range of 510 to 570 nm, and high transmittance in the range of 600 to 650 nm are required. However, the specific wavelength range, that is, the wavelength range of the high transmission range is not necessarily the fixed value described above, and varies depending on desired characteristics, such as a specific wavelength range of 500 to 600 nm depending on the specification.
[0014]
The trimming filter according to the present embodiment that achieves the above characteristics has a configuration in which a multilayer film in which a plurality of thin films having different optical film thicknesses are stacked is formed on a substrate. The film forming method may be a vacuum deposition method, a sputtering method or any other thin film forming method. Further, the substrate may be any substrate such as a glass substrate, a plastic substrate, or a crystal substrate.
[0015]
As shown in FIG. 1, the multilayer film first sets a center wavelength of a specific wavelength region having desired characteristics to a design wavelength λ. ₀ As a basic configuration, the optical thickness of each layer is determined. Next, the optical thickness of each layer of the basic configuration is adjusted to improve the transmittance. This adjustment is to change the basic film thickness, which is the optical film thickness of each layer of the basic structure, in order to obtain desired characteristics. The film thickness of each layer after the adjustment is referred to as an actual film thickness with respect to the basic film thickness. For example, even if the basic configuration is the same, the actual film thickness will be different if the wavelength range of the desired specific wavelength region is different depending on the specification, or if the used incident angle (the assumed incident angle of light) is different. The conversion from the basic film thickness to the actual film thickness is performed by a known calculation method.
[0016]
The basic configuration is composed of a plurality of thin film groups. The thin film group is a group of thin films composed of one layer or a plurality of layers classified according to the optical film thickness. (In the case of a single layer, it is not strictly a group, but here it is assumed that only one layer is included in the group.) There are three types of thin film groups: the first thin film group, the second thin film group, and the third thin film group . Design wavelength λ ₀ And the first thin film group has an optical film thickness of 7λ. ₀ / 32 (= ndcos θ, n is a refractive index, d is a geometric film thickness, θ is a refraction angle) is a thin film group in which one or a plurality of layers are laminated.
[0017]
The second thin film group is 7λ ₀ / 16 single layer or 7λ ₀ / 16 layer and 7λ ₀ / 32 layers are alternately laminated.
[0018]
The third thin film group is 7λ ₀ / 8 single layer or 7λ ₀ / 8 layer and 7λ ₀ / 32 layers are alternately laminated.
[0019]
In addition, the group is divided into the third, second, and first thin film groups in order of priority, and the number of layers is maximized from the thin film group having the highest priority without departing from the definition of the group. To Further, the thin film groups composed of a single layer do not contact each other continuously. That is, it is assumed that there is a basic structure 2a on the substrate 1 as shown in FIG. When the thin film group is separated based only on the definitions of the first and second thin film groups, the basic configuration 2a becomes 7λ ₀ / 2 first thin film group consisting of a single layer and 7λ ₀ The second thin film group consisting of a single layer of / 16 layer can be taken into three thin film groups in total, and 7λ ₀ / 16 layer and 7λ ₀ / 32 layers are alternately laminated to form one second thin film group. However, since the thin film group is divided in the third, second, and first order as described above, the basic configuration 2a is the second one of the second thin film groups. Assuming that the basic structure 2b is present on the substrate 1 as shown in FIG. 2B, the group is separated from the third group, and two third thin film groups of three layers and 7λ ₀ One thin film group consisting of a single layer of / 32 layers is formed.
[0020]
The present invention achieves desired characteristics by adopting a basic configuration having at least two thin film groups of at least two of the three types of thin film groups.
[0021]
【Example】
Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.
[0022]
<Example 1>
The first thin film group is a single-layer Ta ₂ O ₅ Film and the second thin film group are made of SiO ₂ Membrane and Ta ₂ O ₅ Film and third thin film group ₂ Membrane and Ta ₂ O ₅ A green reflection trimming filter composed of films and composed of 11 groups was formed on a BK7 substrate by a vacuum evaporation method. Table 1 shows the basic film thickness of the basic configuration including each thin film group having the substrate side as the first layer, and the practical film thickness after adjustment for improving transmittance. However, in Table 1, the design wavelength λ ₀ Is 534 nm and the film thickness is λ. ₀ / 4, where Ta is Ta ₂ O ₅ Film (refractive index 2.15 at 588 nm), S is SiO ₂ The film (refractive index at 588 nm 1.46) is shown. The used incident angle is 45 degrees.
[0023]
[Table 1]

[0024]
FIG. 3 shows the transmittance characteristics at this time. The horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance. In FIG. 3, a dotted line 33TS23 indicates the incident angle of 33 degrees from the air side and the S component transmittance characteristics of the 23 layers, and the solid line 45TS23 indicates the incident angle of 45 degrees from the air side and the S component transmittance characteristics of the 23 layers. The broken line 57TS23 indicates the S component transmittance characteristic of 23 layers with an incident angle of 57 degrees from the air side.
[0025]
In this embodiment, at 45 ° incidence, a high transmittance of 98.9% on average in the range of 430 to 480 nm, a low transmittance of 2.2% on average in the range of 510 to 570 nm, and a transmittance of 2.2% on average in the range of 600 to 650 nm. A high transmittance of 98.8% on average was obtained. In addition, when the angle characteristic is represented by a half-value wavelength width (indicating the difference between the half-value wavelength at the short wavelength side at 33 degrees and the half-value wavelength at the long wavelength side at 57 degrees and corresponding to the brightness of the green component), It was 49 nm. In both cases, characteristics having no practical problems were obtained.
[0026]
As can be seen from the results in Table 1, the characteristics of the film of the present embodiment are as follows: (1) the total optical film thickness of all thin film groups is about 1.0 times the basic film thickness; The actual film thickness of the total optical thickness of one thin film group is about 1.73 times the basic film thickness, and (3) the actual film thickness of the total optical film thickness of the second and third thin film groups is about 1.7 times of the basic film thickness. 0.88 times, and (4) two 7λ ₀ / 32 layer and one 7λ sandwiched between ₀ In the third thin film group consisting of a total of three layers (basic configuration of three layers) of / 8 layers, the actual film thickness is about 4.2λ. ₀ / 4 to 6.0λ ₀ / 4, and (5) 7λ ₀ In the first thin film group consisting of a / 32-layer single layer (basic single-layer structure) and the third thin film group consisting of a three-layer basic structure, three groups of one third thin film group and two adjacent first thin film groups Is about 7.3λ ₀ / 4 to 7.5λ ₀ (6) In the first thin film group consisting of a single-layer basic structure and the third thin film group consisting of a three-layer basic structure, one first thin film group and two third thin film groups adjacent to the first thin film group The total film thickness of the three groups is about 11.7λ ₀ / 4 is satisfied.
[0027]
<Example 2>
In the same manner as in Example 1, the first thin film group was formed of Ta. ₂ O ₅ Film and the second thin film group are made of SiO ₂ Membrane and Ta ₂ O ₅ Film and third thin film group ₂ Membrane and Ta ₂ O ₅ A green reflection trimming filter composed of films and composed of 11 groups was formed on a BK7 substrate by a vacuum evaporation method. Table 2 shows the basic film thickness of the basic structure including each thin film group and the practical film thickness after adjustment for improving transmittance. However, the used incident angle is 0 degree.
[0028]
FIG. 4 shows the transmittance characteristics at this time. In FIG. 4, a solid line 0T23 indicates the transmittance characteristics of the 23 layers with an incident angle of 0 ° from the air side.
[0029]
In this embodiment, at 0 degree incidence, a high transmittance of 97.4% on average in the range of 430 to 480 nm, a low transmittance of 2.9% on average in the range of 510 to 570 nm, and a range of 2.9% on average of 600 to 650 nm. A high transmittance of 98.3% on average was obtained, which was a characteristic having no practical problem.
[0030]
Further, by combining the 0-degree incident filter of the second embodiment and the 45-degree incident filter of the first embodiment, the contrast could be improved. That is, by installing a 0-degree incident filter after the 45-degree incident filter, unnecessary light depending on the incident angle (in FIG. 3, transmitted light of about 500 to 515 nm at an incident angle of 33 degrees, and incident angle 57). At about 565-580 nm). FIG. 4 shows the characteristics at this time. In FIG. 4, 0T23 * 33Ts indicates an S component transmitted at an incident angle of 33 degrees and 0 degrees, and 0T23 * 57Ts indicates an S component transmitted at an incident angle of 57 degrees and 12 degrees.
[0031]
[Table 2]

[0032]
As can be seen from the results in Table 2, the characteristics of the film of this example are as follows: (1) the total optical film thickness of all the thin film groups is about 0.98 times the basic film thickness; The actual film thickness of the total optical thickness of one thin film group is about 0.76 times the basic film thickness, and (3) the actual film thickness of the total optical film thickness of the second and third thin film groups is about 0.7% of the basic film thickness. (4) In the third thin film group having the three-layer basic structure, the practical film thickness is about 4.8λ. ₀ / 4 to 5.9λ ₀ (5) In the first thin film group having a single-layer basic structure and the third thin film group having a three-layer basic structure, one third thin film group and two first thin film groups adjacent thereto are included. The total film thickness of the three groups is about 6.5λ ₀ / 4 to 6.8λ ₀ (6) In the first thin film group consisting of a single-layer basic structure and the third thin film group consisting of a three-layer basic structure, one first thin film group and two third thin film groups adjacent to the first thin film group The total film thickness of the three groups is about 12.0λ ₀ / 4 is satisfied.
[0033]
<Example 3>
In the same manner as in Example 1, the first thin film group was formed of TiO. ₂ Film, the second thin film group is Al ₂ O ₃ Film and TiO ₂ Film, third thin film group is Al ₂ O ₃ Film and TiO ₂ A green reflection trimming filter composed of films and composed of 11 groups was formed on a BK7 substrate by a vacuum evaporation method. Table 3 shows the optical film thickness of the basic configuration including each thin film group and the optical film thickness after adjustment for improving transmittance. However, in Table 3, Ti is TiO ₂ Film (refractive index at 588 nm 2.30), A is Al ₂ O ₃ The film (refractive index at 588 nm 1.63) is shown.
[0034]
FIG. 5 shows the transmittance characteristics at this time. In FIG. 5, the dotted line 33TS23 shows the incident angle of 33 degrees from the air side and the S component transmittance characteristics of the 23 layers, and the solid line 45TS23 shows the incident angle of 45 degrees from the air side and the S component transmittance characteristics of the 23 layers. The broken line 57TS23 indicates the S component transmittance characteristic of the 23 layers with an incident angle of 57 degrees from the air side.
[0035]
[Table 3]
Table 3

[0036]
In this embodiment, at 45 ° incidence, high transmittance of 98.1% on average in the range of 430 to 480 nm, low transmittance of 2.0% on average in the range of 510 to 570 nm, and in the range of 600 to 650 nm. A high transmittance of 98.8% on average was obtained. In addition, the angular characteristic was about 50 nm when represented by a half-value wavelength width. In both cases, characteristics having no practical problems were obtained.
[0037]
In Table 3, the first layer of Al constituting the third thin film group ₂ O ₃ The actual film thickness of the film is 0. However, this means that after adjustment for improving transmittance, the layer in contact with the substrate is preferably 0 in terms of overall characteristics, and the basic structure (the total basic film thickness of the third group is about 5.25 / 4λ). ₀ ).
[0038]
As can be seen from the results in Table 3, the characteristics of the film of this example are as follows: (1) the total optical film thickness of all thin film groups is about 0.97 times the basic film thickness; The actual thickness of the total optical thickness of one thin film group is about 0.87 times the sum of the basic thicknesses. (3) The actual thickness of the total optical thickness of the second and third thin film groups is the basic thickness. (4) In the third thin film group having the three-layer basic structure, the actual film thickness is about 4.6λ. ₀ / 4 to 6.1λ ₀ (5) In the first thin film group consisting of the single-layer basic structure and the third thin film group consisting of the three-layer basic structure, one third thin film group and two first thin film groups adjacent thereto are formed. The total film thickness of the three groups is about 6.9λ ₀ / 4 to 7.0λ ₀ (6) In the first thin film group consisting of a single-layer basic structure and the third thin film group consisting of a three-layer basic structure, one first thin film group and two third thin film groups adjacent to the first thin film group The total film thickness of the three groups is about 12.6λ ₀ / 4 is satisfied.
[0039]
<Example 4>
The second thin film group is formed of a single-layer Ta ₂ O ₅ Film and third thin film group ₂ Membrane and Ta ₂ O ₅ A five-group green reflection trimming filter composed of a film was formed on a BK7 substrate by a vacuum evaporation method. Table 4 shows the optical film thickness of the basic configuration including each thin film group from the substrate side and the optical film thickness after adjustment for improving transmittance. The used incident angle is 45 degrees.
[0040]
[Table 4]
Table 4

[0041]
FIG. 6 shows the transmittance characteristics at this time. In FIG. 6, a dotted line 33TS15 indicates the incident angle of 33 degrees from the air side and the S component transmittance characteristics of the 15 layers, and the solid line 45TS15 indicates the incident angle of 45 degrees from the air side and the S component transmittance characteristics of the 15 layers. The broken line 57TS15 shows the S component transmittance characteristics of the 15 layers with an incident angle of 57 degrees from the air side.
[0042]
In this embodiment, at 45 ° incidence, a high transmittance of 94.7% on average in the range of 430 to 480 nm, a low transmittance of 6.1% on average in the range of 510 to 570 nm, and a range of 600 to 650 nm in an average of 6.1%. An average high transmittance of 97.1% was obtained. Although there was a little more light transmitted through the green region, there was no problem in practical use. In addition, when the angle characteristics were expressed by a half-value wavelength width, it was about 49 nm as in Example 1.
In Table 4, the second third thin film group is composed of the fifth to eleventh alternate layers, but the third thin film group is not necessarily composed of the three-layer basic structure.
As can be seen from the results shown in Table 4, the characteristics of the film of this example are as follows: (1) the total optical film thickness of all thin film groups is about 0.93 times the basic film thickness; Second, the practical film thickness of the total optical film thickness of the third thin film group is about 0.93 of the basic film thickness.
[0043]
<Example 5>
In the same manner as in Example 2, the first thin film group is formed of SiO ₂ Membrane and Ta ₂ O ₅ Film and the second thin film group are made of SiO ₂ Membrane and Ta ₂ O ₅ Film and third thin film group ₂ Membrane and Ta ₂ O ₅ A green reflection trimming filter composed of a film and composed of seven groups was formed on a BK7 substrate by a vacuum evaporation method. Table 5 shows the optical film thickness of the basic configuration including each thin film group and the practical film thickness after adjustment for improving transmittance. However, the used incident angle is 0 degree. FIG. 7 shows the transmittance characteristics at this time.
[0044]
[Table 5]
Table 5

[0045]
In FIG. 7, a solid line 0T25 shows the transmittance characteristics of the 25 layers with an incident angle of 0 ° from the air side. In this embodiment, at 0 degree incidence, a high transmittance of 97.5% on average in the range of 430-480 nm, a low transmittance of 3.7% on average in the range of 510-570 nm, and a low transmittance of 600-650 nm on average. A high transmittance of 98.5% on average was obtained, and the characteristics were practically no problem.
[0046]
As can be seen from the results in Table 5, the characteristics of the film of this example are as follows: (1) the total optical film thickness of all thin film groups is about 1.01 times the basic film thickness; The actual film thickness of the total optical thickness of one thin film group is about 1.21 times the basic film thickness, and (3) the actual film thickness of the total optical film thickness of the second and third thin film groups is about 1.2 times the basic film thickness. (4) In the third thin film group having the three-layer basic structure, the actual film thickness is about 4.6λ. ₀ / 4 to 5.0λ ₀ / 4.
[0047]
Next, as a comparative example of the present invention, a comparative example having a basic configuration different from the present invention is shown.
[0048]
<Comparative Example 1>
Ta ₂ O ₅ Film and SiO ₂ Λ of the membrane ₀ A multilayer film was formed on a BK7 substrate by changing the optical film thickness ratio between the high refractive index film and the low refractive index film on the basis of the alternating layer of / 4 to obtain a green reflection and blue red transmission trimming filter. Table 6 shows the optical film thickness of the first layer from the substrate side after adjustment for improving transmittance. The used incident angle is 45 degrees.
[0049]
In Table 6, the first and second layers and the 25th to 28th layers are adjustment layers for improving transmittance (ripple) in the blue and red regions, and the third to 24th layers obtain high reflectance in the green region. For the alternating layers. Although the basic structure of the alternating layers is 1: 1, it can be seen that an alternating layer having a thickness ratio of about 1.7: 0.3 is preferable in order to satisfy the half-value wavelength width of the reflection band.
[0050]
[Table 6]

[0051]
FIG. 8 shows transmittance characteristics at this time. In FIG. 8, a dotted line 33TS28 shows an S component transmittance characteristic of an incident angle of 33 degrees from the air side and 28 layers, and a solid line 45TS28 shows an incident angle of 45 degrees from the air side and an S component transmittance characteristic of 28 layers. The dashed line 57TS28 shows the S component transmittance characteristics of an incident angle of 57 degrees from the air side and 28 layers.
[0052]
In this comparative example, at 45 degrees incidence, a high transmittance of 91.4% on average in the range of 430 to 480 nm, a low transmittance of 3.2% on average in the range of 510 to 570 nm, and a range of 600 to 650 nm in average. An average high transmittance of 95.5% was obtained. In addition, when the angle characteristics were represented by a half-value wavelength width, it was about 49 nm. Although the angle characteristics are the same as those of this embodiment, the transmittance characteristics are inferior, and the brightness is insufficient in the blue and red regions, which is a practical problem.
[0053]
<Comparative Example 2>
In order to improve the transmittance in the blue and red regions of Comparative Example 1, the film thickness was adjusted on the basis of the alternating layers having a film thickness ratio of about 1.7: 0.3, and the multilayer film was similarly formed on the BK7 substrate. A green reflection and blue-red transmission trimming filter was obtained. Table 7 shows the optical film thickness from the substrate side after the adjustment for improving the transmittance. The used incident angle is 45 degrees.
[0054]
[Table 7]

[0055]
FIG. 9 shows the transmittance characteristics at this time. In FIG. 9, a dotted line 33TS30 indicates an incident angle of 33 degrees from the air side and S component transmittance characteristics of 30 layers, and a solid line 45TS30 indicates an incident angle of 45 degrees from the air side and S component transmittance characteristics of 30 layers. The broken line 57TS30 indicates the S component transmittance characteristics of the 30 layers with an incident angle of 57 degrees from the air side.
[0056]
In this comparative example, at 45 degrees incidence, high transmittance of 99.0% on average in the range of 430 to 480 nm, low transmittance of 2.1% on average in the range of 510 to 570 nm, and in the range of 600 to 650 nm. A high transmittance of 98.8% on average was obtained. In addition, when the angle characteristics were expressed in terms of the half-value wavelength width, it was about 49 nm. Although the angle characteristics and the transmittance characteristics were the same as those of the present example, the number of layers was large, which was not preferable in production.
[0057]
<Comparative Example 3>
An 11-layer film having the characteristics shown in FIG. 4 of JP-B-60-036833 was formed in the same manner as in Example 1. However, the first thin film group is made of SiO ₂ Membrane and ZrO ₂ Film and the second thin film group are made of SiO ₂ Membrane and ZrO ₂ Film and design wavelength λ ₀ Was 540 nm and the used incident angle was 0 degree. The first thin film group is λ ₀ / 4 alternating layers, and the second thin film group is 4λ ₀ / 4-2λ ₀ / 4-4λ ₀ / 4. FIG. 10 shows the characteristics at the time of this basic constituent film thickness. In FIG. 10, the solid line 0T11 indicates the transmittance characteristics of the 11 layers from the air side at an incident angle of 0 °.
From FIG. 10, a high transmittance in the range of 430 to 480 nm and a high transmittance in the range of 600 to 650 nm cannot be obtained, and the configuration of this comparative example is not suitable for practical use as a green reflection trimming filter.
[0058]
<Example of liquid crystal projector>
Next, an example of a liquid crystal projector having a trimming filter using the optical multilayer film of the present embodiment will be described.
FIG. 11 is a diagram of a liquid crystal projector having a trimming filter using the optical multilayer film of the present embodiment. In FIG. 11, reference numeral 101 denotes a light source, 102 denotes a polarizing plate, and 103 denotes light (G) in the green wavelength band using the optical multilayer film of the present embodiment, and light (B) in the blue wavelength band and light in the red wavelength band. Is a trimming filter that transmits light (R). Reference numeral 104a denotes a first color-selective phase difference plate that converts the polarization direction of blue light by 90 degrees and does not change the polarization direction of red light, and 104b denotes the polarization direction of red light without changing the polarization direction of blue light. Is a first, second, and third polarizing beam splitters that transmit P-polarized light and reflect S-polarized light, respectively. Reference numerals 106R, 106G, and 106B denote a reflective liquid crystal display element for red, a green reflective liquid crystal display element, and a blue reflective liquid crystal display element, respectively, which reflect incident light and image-modulate. 108 is a projection lens.
[0059]
Non-polarized light emitted from the light source 101 is converted into linearly polarized light (S-polarized light) by the polarizing plate 102 and enters the trimming filter 103. The trimming filter 103 reflects green light, but transmits blue light and red light. Thus, the green light, the blue light, and the red light are color-separated.
[0060]
The green light is reflected by the first polarizing beam splitter 105a and enters the green reflective liquid crystal display element 106G. On the other hand, the blue light and the red light transmitted through the trimming filter 103 are incident on the first color-selective phase difference plate 104a, where only the polarization direction of the blue light is rotated by 90 degrees to be P-polarized light.
[0061]
The second polarization beam splitter 105b transmits blue light that is p-polarized light and color-separates red light that is s-polarized light by reflecting the red light. The blue light and the red light are each a reflective liquid crystal display for blue. The light enters the element 106B and the reflective liquid crystal display element 106R for red.
[0062]
The P-polarized light component of the light modulated by the green reflective liquid crystal display element 106G passes through the first polarizing beam splitter 105a, and also passes through the third polarizing beam splitter 105c to become projection light.
[0063]
The S-polarized light component of the light modulated by the blue reflective liquid crystal display element 106B is reflected by the second polarizing beam splitter 105b, passes through the second color-selective phase difference plate 104b, and becomes the third polarized light beam. The light is reflected by the splitter 105c and becomes projection light.
[0064]
The P-polarized light component of the light modulated by the red reflective liquid crystal display element 106R passes through the second polarization beam splitter 105b, and the polarization direction is rotated by 90 degrees by the second color-selective phase difference plate 104b. The light becomes P-polarized light, is reflected by the third polarizing beam splitter 105c, and becomes projection light. The green light, the blue light, and the red light combined into one by the third polarizing beam splitter 105c are projected from the projection lens 108 to display a color image.
[0065]
The liquid crystal projector of the present embodiment realizes a trimming filter that reflects green light and transmits blue and red light with a small number of layers by using the optical multilayer film of the present embodiment.
[0066]
【The invention's effect】
According to the present invention, it is possible to realize an optical multilayer film having a low transmittance in a specific wavelength region with a relatively small number of layers.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the present invention.
FIG. 2 is a diagram showing a method of dividing a thin film group.
FIG. 3 is a diagram illustrating transmittance characteristics of the optical multilayer film according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating transmittance characteristics of an optical multilayer film according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating transmittance characteristics of an optical multilayer film according to a third embodiment of the present invention.
FIG. 6 is a diagram illustrating transmittance characteristics of an optical multilayer film according to Example 4 of the present invention.
FIG. 7 is a diagram illustrating transmittance characteristics of an optical multilayer film according to a fifth embodiment of the present invention.
FIG. 8 is a diagram showing transmittance characteristics of the optical multilayer film of Comparative Example 1 of the present invention.
FIG. 9 is a diagram showing transmittance characteristics of an optical multilayer film of Comparative Example 2 of the present invention.
FIG. 10 is a diagram showing transmittance characteristics of an optical multilayer film of Comparative Example 3 of the present invention.
FIG. 11 is a diagram of a liquid crystal projector having a trimming filter according to the present embodiment.

Claims (13)

An optical multilayer film which defines the actual film thickness based on the basic structure that defines the basic thickness and layer structure of each layer, when the basic configuration in which the lambda ₀ the design wavelength, the optical thickness 7λ _0/32 a first thin film group composed of a single layer or alternating layers of a second thin film group consisting of alternating layers of a single layer or 7λ _0/32 and 7λ _0/16 of 7λ _0/16, a single layer of 7λ _0/8 or 7λ _0/32 and 7λ _0/8 of the three thin-film group and the third thin film group consisting of alternating layers of, comprising at least two kinds of the thin film group 5 or group, and a thin film group to each other consisting of a single layer Are not adjacent to each other.
However, in the basic configuration, the division of each thin film group is determined by the priority order of the third thin film group, the second thin film group, and the first thin film group. 2. The optical multilayer film according to claim 1, wherein the actual total optical thickness of all thin film groups is in a range of 0.9 to 1.05 times the total optical thickness of the basic film thickness. The actual total optical thickness of the first thin film group is 0.7 to 1.8 times the total optical thickness of the first thin film group in the basic configuration. Optical multilayer film. The sum of the actual total optical thicknesses of the second thin film group and the third thin film group is 0.9 to 0.9 of the sum of the total optical thicknesses of the second thin film group and the third thin film group of the basic thickness. 3. The optical multilayer film according to claim 2, wherein the ratio is 1.05 times. The basic configuration, two 7λ _0/32 layer and the optical multilayer film according to claim 1, further comprising a second thin film group having three layers of one 7λ _0/16 layers. Optical multilayer film according to claim 5, wherein the 7λ _0/16 layer is more high refractive index film refractive index of 2.0. The basic configuration, two 7λ _0/32 layer and the optical multilayer film according to claim 1, further comprising a third thin film group having three layers of one 7λ _0/8 layers. Optical multilayer film according to claim 7, wherein the 7λ _0/8 layers is more high refractive index film refractive index of 2.0. The actual sum of the optical thickness of the third layer of the third thin film group consisting of three layers, the optical multilayer film according to claim 7, wherein the range of 4λ ₀ /4~6.5λ _0/4 . From the basic configuration has a third membrane group consisting 7λ _0/32 the three layers and the first thin film group composed of a single layer of the third thin film group consisting of three layers and two of the single layer adjacent thereto optical multilayer film according to claim 9, wherein the actual sum of the optical thickness of the three films groups the first thin film group is characterized by a range of 6.0λ ₀ /4~8.0λ _0/4 composed . From the basic configuration has a third membrane group consisting of the three layers and the first thin film group composed of a single layer of 7λ _0/32, the first thin film group composed of a single layer and two of said three layers adjacent thereto optical multilayer film according to claim 9, wherein the actual sum of the optical thickness of the three thin-film group and the third thin film group is characterized by a range of 11.0λ ₀ /4~13.0λ _0/4 composed . An optical element comprising the optical multilayer film according to claim 1 formed on a substrate. The method for designing an optical multilayer film includes a step of setting a basic configuration in which a basic thickness and a layer configuration of each layer are determined, and a step of determining an actual film thickness based on the basic configuration. alternate when the wavelength is lambda _0, the first thin film group composed of a single layer or alternating layers of optical thickness 7λ _0/32, a single layer or 7λ _0/32 and 7λ _0/16 of 7λ _0/16 a second thin film group of layers, of the three thin-film group and the third thin film group consisting of alternating layers of a single layer or 7λ _0/32 and 7λ _0/8 of 7λ _0/8, at least two kinds of thin films A method for designing an optical multilayer film, comprising five or more groups, and wherein thin film groups each having a single layer are not adjacent to each other.
However, in the basic configuration, the division of each thin film group is determined by the priority order of the third thin film group, the second thin film group, and the first thin film group.

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