JPS62125301A - Optical filter - Google Patents

Abstract

PURPOSE:To improve the performance of an optical filter and to reduce the production cost of the filter by forming a vapor deposition layer as the outermost surface layer to have a two-layered structure having distribution of compsn. and refractive index in the direction of the film thickness. CONSTITUTION:A glass layer 6 formed as the outermost surface layer of multilayered film is formed by vapor-deposition SiO2 in a same cell without introducing reactive gas continuously. The refractive index of the glass layer 6 obtd. in this stage is n 1.50-1.53 and the compsn. of the glass is expressed by SiOx (where x=1.5-<2.0). The film thickness of the glass layer 6 is regulated to ca. 1mum with the purpose for preventing deterioration of optical properties of the filter. Further, SiO is vapor-deposited by resistance heating vapor- deposition forming SiO film having optical film thickness corresponding to 1/2 wavelength on the outermost surface layer (glass layer 6) with the purpose for obtd. reflection reducing effect. The refractive index of the reflection reducing layer 7 is n 1.80-1.85.

Description

【発明の詳細な説明】 〔発明の利用分野〕 本発明は、光合分波機能を有する光学フィルタ、特に誘
電体多層膜により構成された干渉膜フィルタに関するも
のである。DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical filter having an optical multiplexing and demultiplexing function, and particularly to an interference film filter constructed of a dielectric multilayer film.

〔発明の背景〕[Background of the invention]

誘電体多層薄膜で構成される光学フィルタは。 Optical filters are composed of dielectric multilayer thin films.

一般的に光学用ガラス基板トに蒸着、スパッタなどによ
って高屈折率膜と低屈折率膜を交互に規則的に積層した
構造で、各層の膜厚は光の波長をλとするとλ／４とす
るものが基本的である。Generally, it has a structure in which high refractive index films and low refractive index films are regularly stacked alternately on an optical glass substrate by vapor deposition, sputtering, etc., and the film thickness of each layer is λ/4, where λ is the wavelength of light. What you do is basic.

この時、高屈折率膜物質としては、　ＺｎＳ　、　Ｔｉ
Ｑ２など、低屈折率膜物質としてはＭｇＦ２．５ｉ０２
などが適用されている。At this time, as the high refractive index film material, ZnS, Ti
As a low refractive index film material such as Q2, MgF2.5i02
etc. are applied.

従来技術における光学フィルタは第３図に示すとと（、
ガラス基板１上に高屈折率膜および低屈折率膜を交互に
規則的に積層した後、安定な光学特性を得る手段として
最外表面層上に接着剤４によりガラス基板５を設け、誘
電体多層膜をガラス基板１，５ではさむ構成として光学
的な対称性を与えて特性の安定化を計るものであった。The optical filter in the prior art is shown in Figure 3.
After high refractive index films and low refractive index films are alternately and regularly laminated on a glass substrate 1, a glass substrate 5 is provided on the outermost surface layer with an adhesive 4 as a means of obtaining stable optical properties, and a dielectric The multilayer film was sandwiched between glass substrates 1 and 5 to provide optical symmetry and stabilize the characteristics.

接着剤４はその上に形成されるガラス１基板５の屈折率
とほぼ同等の値を持つ透明体が使用されるが、この接着
には高精度な平担性が要求され作業性が極めて悪（、ま
た耐環境性および吸収（損失）など製造、特性上の問題
がありコスト低減を阻む要因であった。これらの解決策
として例えば特開昭５９−６０４０７号では、ガラス基
板５の接着の代わりに最外表面層上に高屈折率物質と低
屈折率物質の中間的な屈折率を有する材料として窒化硅
素（Ｓｉ３Ｎ４）を形成し透過特性の改善を計るシミュ
レーシ層ン結果を記述しているが透過域にリップルが残
っておりその効果は充分なものではない。The adhesive 4 used is a transparent material whose refractive index is almost the same as the refractive index of the glass 1 substrate 5 formed on it, but this adhesive requires highly accurate flatness and is extremely difficult to work with. (Also, there were manufacturing and characteristic problems such as environmental resistance and absorption (loss), which were factors that hindered cost reduction.As a solution to these problems, for example, in Japanese Patent Application Laid-Open No. 59-60407, the bonding of the glass substrate 5 was Instead, silicon nitride (Si3N4) is formed on the outermost surface layer as a material with a refractive index intermediate between a high refractive index material and a low refractive index material, and the results of a simulation layer are described to improve the transmission characteristics. However, ripples remain in the transmission range, and the effect is not sufficient.

〔発明の目的〕[Purpose of the invention]

本発明の目的は前記した従来技術における欠点をな（し
光学特性の安定な構造を有する光学フィルタを提供する
ことにある。SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of the prior art described above and to provide an optical filter having a structure with stable optical characteristics.

〔発明の概要〕[Summary of the invention]

本発明におけるフィルタ構造は、光学用ガラス基板上に
形成される多層膜として高屈折率物質としてＴｉ０２（
ｎ　＝　２３　）低屈折率物質として５ｉＯ２１（ｎ　
＝　１．４６　）を各層ＩＡ波長相当の膜厚で順次規則
的に積層した状態で、この時光学用ガラス基板上の第１
層膜と、最上層に形成される物質は同一なる物質の構成
となる。さらに引続いて従来技術釦おける第２のガラス
基板の接着形成に代わる層として光学用ガラス基板と同
等の屈折率を有する酸化硅素（ＳｉＯｘ）を積層し、対
称性を有する構造とした。さらにフィルタの特性を高安
定なものとするため反射防止効果を与える目的として最
外表面層上に酸化硅素（Ｓｉｎ）を１／２波長相当の膜
厚に同一真空槽内で連続的に形成した。The filter structure in the present invention is a multilayer film formed on an optical glass substrate as a high refractive index material such as Ti02 (
n = 23) 5iO21 (n = 23) as a low refractive index material
= 1.46) were sequentially and regularly laminated with a film thickness equivalent to the IA wavelength for each layer, and at this time, the first layer on the optical glass substrate was
The layer film and the substance formed on the top layer are made of the same substance. Furthermore, silicon oxide (SiOx) having a refractive index equivalent to that of the optical glass substrate was laminated as a layer to replace the adhesion of the second glass substrate in the conventional button, thereby creating a symmetrical structure. Furthermore, in order to make the filter characteristics highly stable, silicon oxide (Sin) was continuously formed on the outermost surface layer to a thickness equivalent to 1/2 wavelength in the same vacuum chamber in order to provide an antireflection effect. .

〔発明の実施例〕[Embodiments of the invention]

以下１本発明の具体的な実施例を第１図および第２図で
説明する。光学用ガラス基板ｌとしては硼硅酸系ガラス
（屈折率ｎ　＝　１．５２　）を使用し、その上に形成
する高屈折率膜ＴｉＯ２２と、低屈折率膜５ｉ０２３を
交互に積層する構造は従来技術と同様であり、実施例で
はこれらの物質の形。A specific embodiment of the present invention will be described below with reference to FIGS. 1 and 2. As the optical glass substrate l, borosilicate glass (refractive index n = 1.52) is used, and the structure in which high refractive index films TiO22 and low refractive index films 5i023 are alternately laminated is conventional. Similar to technology and examples of the form of these substances.

成は電子ビーム蒸着で行い、さらに同一槽内に■ 抵抗加熱蒸着機能を併せ持つ蒸着装置を適用した。あら
かじめ洗浄された光学用ガラス基板ｌ上に形成される多
層膜（Ｔｉ０ｚ　、　５ｉＯｚ　）の形成条件の一例を
示す。The formation was carried out by electron beam evaporation, and in the same tank, a evaporation device that also has a resistance heating evaporation function was used. An example of conditions for forming a multilayer film (Ti0z, 5iOz) formed on an optical glass substrate l that has been cleaned in advance will be shown.

真空槽内をあらかじめ２　ｘ　１（ｊ”６（Ｔｏｒｒ）
以下に排気した状態で加速電圧６（Ｋｖ）のもとに、各
層・の形成には反応性ガスとして酸素を微量導入し。The inside of the vacuum chamber is 2 x 1 (j”6 (Torr)
A trace amount of oxygen was introduced as a reactive gas to form each layer under an accelerating voltage of 6 (Kv) in the following evacuated state.

蒸着材料との反応を促進させ安定な膜質を得た。Stable film quality was obtained by promoting the reaction with the vapor deposition material.

この条件で得られた各々の膜の屈折率はＴｒＯｚキ２．
３０　、５ｉ０２中１．４６であり、形成された各層の
膜厚はＩＡ波長相当の光学的膜厚を基本とし、製作する
フィルタの種類によって層構造は異なるが一部１／２波
長相当の膜厚も含まれる。この多層膜の最外表面層に形
成するガラス層６は、同１一槽内で連続的に反応性ガス
を導入しない状態で酸化硅素（，５ｉＯｚ）を蒸着材料
として形成した。５この時得られたガラス層６の屈折率
はｎ中１．５０〜１．５３であり組成的にはＳ　ｉｏｘ
　（ｘ　＝　１．５〜＜　２．０　）で示される。この
ガラス層６の膜厚はフィルタの光学特性が低下しないよ
うに１μｍ穆度に形成した。The refractive index of each film obtained under these conditions was TrOzki2.
30, 1.46 in 5i02, and the film thickness of each formed layer is basically an optical film thickness equivalent to an IA wavelength, and the layer structure differs depending on the type of filter manufactured, but some are films equivalent to 1/2 wavelength. It also includes thickness. The glass layer 6 formed on the outermost surface layer of this multilayer film was formed using silicon oxide (.5 iOz) as a vapor deposition material in the same tank without continuously introducing a reactive gas. 5 The refractive index of the glass layer 6 obtained at this time is 1.50 to 1.53 in n, and the composition is Siox
(x = 1.5~<2.0). The glass layer 6 was formed to have a thickness of 1 μm so as not to deteriorate the optical characteristics of the filter.

さらに最外表面層（ガラス層６）上に反射防止効果を得
る目的として一酸化硅素（Ｓｉｌ）を蒸着材料として抵
抗加熱蒸着により１／２波長相当の光学的膜厚を形成し
た。この反射防止層７の屈折率はｎ中１．８０〜１．８
５である。Furthermore, in order to obtain an antireflection effect on the outermost surface layer (glass layer 6), an optical film thickness equivalent to 1/2 wavelength was formed by resistance heating vapor deposition using silicon monoxide (Sil) as a vapor deposition material. The refractive index of this antireflection layer 7 is 1.80 to 1.8 in n.
It is 5.

以上の構造から成る光学フィルタの分光透過特性の特性
例を第２図に示す。フィルタの構造は特定波長域のみ透
過域を持つ帯域通過フィルタの測定例である。実施例に
よる構造を持つフィルタの特性曲線はＡ、従来技術にお
ける特性曲線がＢである。FIG. 2 shows an example of the spectral transmission characteristics of the optical filter having the above structure. The structure of the filter is a measurement example of a bandpass filter that has a transmission band only in a specific wavelength range. The characteristic curve of the filter having the structure according to the embodiment is A, and the characteristic curve of the conventional technique is B.

本発明の実施例によるフィルタの透過ピークは従来技術
に比べて１〜１．５％の上昇を示し、透過損失としては
約０．０５　（ｄＲ’）の向上である。The transmission peak of the filter according to the embodiment of the present invention is increased by 1 to 1.5% compared to the prior art, and the transmission loss is improved by about 0.05 (dR').

〔発明の効果〕〔Effect of the invention〕

以上のように本発明の構造を有する光学フィルタはフィ
ルタ性能の向上が計れるのみならず。As described above, the optical filter having the structure of the present invention not only has improved filter performance.

従来技術におけるガラス基板の接合等に対して。For bonding of glass substrates in conventional technology.

同一槽内で連続的に形成するため製造歩留りの向上、さ
らには製品コストの低減にも効果が大きい。Because they are formed continuously in the same tank, they are highly effective in improving manufacturing yields and further reducing product costs.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の一実施例の光学フィルタの概略断面図
、第２図は本発明における光学フイルタの分光透過特性
の測定線図、第３図は従来技術はおける光学フィルタの
概略断面図である。 ｌ・・・光学ガラス基板、　　２・・誘電体高屈折率膜
１．３・・・誘電体低屈折率膜、４・・・接着剤。 ５・・・ガラス基板、　　　　６・・・表面ガラス層。 ７・・・反射防止層。Fig. 1 is a schematic cross-sectional view of an optical filter according to an embodiment of the present invention, Fig. 2 is a measurement diagram of the spectral transmission characteristics of the optical filter according to the present invention, and Fig. 3 is a schematic cross-sectional view of an optical filter according to the prior art. It is. l... Optical glass substrate, 2... Dielectric high refractive index film 1.3... Dielectric low refractive index film, 4... Adhesive. 5...Glass substrate, 6...Surface glass layer. 7...Antireflection layer.

Claims (1)

【特許請求の範囲】[Claims] １、光学ガラス基板上に被着形成された誘電体多層膜を
有する光学フィルタにおいて、最外表面層となる被着層
が膜厚深さ方向に組成および屈折率の分布を持った２層
構造より成ることを特徴とする光学フィルタ。1. In an optical filter having a dielectric multilayer film deposited on an optical glass substrate, the outermost surface layer has a two-layer structure with a composition and refractive index distribution in the depth direction. An optical filter characterized by comprising: