JP2009265198A - Wavelength filter - Google Patents

Wavelength filter Download PDF

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JP2009265198A
JP2009265198A JP2008111914A JP2008111914A JP2009265198A JP 2009265198 A JP2009265198 A JP 2009265198A JP 2008111914 A JP2008111914 A JP 2008111914A JP 2008111914 A JP2008111914 A JP 2008111914A JP 2009265198 A JP2009265198 A JP 2009265198A
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light
wavelength
phase difference
polarizer
plate
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Kazuyuki Nakasendo
和之 中仙道
Mitsuru Fujita
満 藤田
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Miyazaki Epson Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength variable filter equivalent to a multistage-structured Lyot filter, in which an increase in the length/scale of equipment is suppressed by decreasing the number of components, sharp and narrow-band characteristics of transmitting spectrum can be demonstrated in a wide wavelength band including short wavelength band. <P>SOLUTION: The wavelength filter 31 includes: a Babinet-Soleil phase plate 32 composed of two wedge-shaped birefringence plates 33 and 34 and has a fixed optical thickness between upper side and the lower side principal surfaces; first to fourth polarizers 35 to 38 and upper side reflection mirrors 39 and 40 provided to the upper side principal surface and a lower side reflection mirror 41 provided to the lower side principal surface. Incident light is multiply-reflected between the first to the fourth polarizers and the upper and the lower reflection mirrors, passes through the Babinet-Soleil phase plate, and is emitted. The phase difference between two adjacent polarizers along an optical path inside of the Babinet-Soleil phase plate is set at 2<SP>n-1</SP>×2π (here n: 1 to 3). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、透過する光の波長を特定の値及び／又は範囲に固定して又は可変的に制御するための波長可変フィルタに関する。   The present invention relates to a wavelength tunable filter for controlling or variably controlling the wavelength of transmitted light at a specific value and / or range.

従来、所望の波長領域の光を透過するために様々なバンドパスフィルタが使用されている。例えば、複屈折板を用いて狭帯域の光のみを透過させるバンドパスフィルタとしてリオフィルタが知られている（例えば、特許文献１〜３を参照）。図１８は、リオフィルタの基本的構成を示している。同図に示すように、リオフィルタ１は、透過軸の平行な偏光子２ａ〜２ｄの間にそれぞれ複屈折板３ａ〜３ｃを、それらの結晶光学軸３a1〜３c1が前記偏光子の透過軸２a1〜２d1と４５°をなすように配置する。複屈折板３ａ〜３ｃには、方解石や水晶等の一軸性結晶が用いられ、その厚さｄi は２ｉ−１ｄ（ｉ＝１〜３）、即ちｄ、２ｄ、４ｄとなるように構成される。特許文献１では、リオフィルタが、背面に反射鏡を配設した液晶表示パネルにおいてＲＧＢの三原色の色純度を高くするために、該液晶表示パネルの表面に積層されている。このリオフィルタを構成するプラスチックフィルムは、液晶表示パネルの背面側から反射される光の透過スペクトルのピークがＲＧＢに対応するように、その光学位相差を決定する。 Conventionally, various band-pass filters are used to transmit light in a desired wavelength region. For example, a rio filter is known as a bandpass filter that transmits only narrow-band light using a birefringent plate (see, for example, Patent Documents 1 to 3). FIG. 18 shows a basic configuration of the Rio filter. As shown in the figure, the Rio filter 1 includes birefringent plates 3a to 3c between polarizers 2a to 2d having parallel transmission axes, and crystal optical axes 3a1 to 3c1 are transmission axes 2a1 of the polarizers. Arranged at 45 ° with 2d1. The birefringent plates 3a to 3c are made of uniaxial crystals such as calcite and quartz, and have a thickness di of 2 i-1 d (i = 1 to 3), that is, d, 2d, and 4d. Is done. In Patent Document 1, a rio filter is stacked on the surface of a liquid crystal display panel in order to increase the color purity of the three primary colors of RGB in a liquid crystal display panel having a reflecting mirror on the back. The plastic film constituting the rio filter determines its optical phase difference so that the peak of the transmission spectrum of light reflected from the back side of the liquid crystal display panel corresponds to RGB.

上記リオフィルタは、使用する複屈折板によって透過スペクトルが特定の波長に固定される。そこで、複屈折板に代えて液晶セルを２枚の偏光子の間に挟んだ波長可変型オプティカル・バンドパスフィルタが知られている（例えば、特許文献２，３を参照）。このバンドパスフィルタの構成を図１９に示す。同図において、バンドパスフィルタ１１は、偏光子１２ａ〜１２ｄに挟まれた液晶セル１３ａ〜１３ｃへの印加電圧を適当に設定することにより、透過スペクトル波長を変化させる。特に図１９のバンドパスフィルタは、透過軸１２a1、１２b1を直交させて配置した所謂クロスニコルの偏光子１２ａ、１２ｂ間の液晶セル１３ａと、透過軸１２b1〜１２d1を平行に配置した所謂平行ニコルの偏光子１２ｂ〜１２ｄで挟んだ２枚の液晶セル１３ｂ、１３ｃとを組み合わせることにより、可視領域に残る２つの単色光のうち一方を除去するように構成されている。   The rio filter has its transmission spectrum fixed at a specific wavelength by the birefringent plate used. Therefore, a wavelength tunable optical bandpass filter in which a liquid crystal cell is sandwiched between two polarizers instead of a birefringent plate is known (see, for example, Patent Documents 2 and 3). The configuration of this bandpass filter is shown in FIG. In the figure, the band pass filter 11 changes the transmission spectrum wavelength by appropriately setting the voltage applied to the liquid crystal cells 13a to 13c sandwiched between the polarizers 12a to 12d. In particular, the band-pass filter shown in FIG. 19 is a so-called parallel Nicol liquid crystal cell 13a between so-called crossed Nicols polarizers 12a and 12b arranged so that transmission axes 12a1 and 12b1 are orthogonal to each other, and transmission axes 12b1 to 12d1 arranged in parallel. By combining the two liquid crystal cells 13b and 13c sandwiched between the polarizers 12b to 12d, one of the two monochromatic lights remaining in the visible region is removed.

更に、図１９と同様の構成において、偏光子の間に液晶セルと位相差フィルムとからなる複合層を挟んだ波長可変フィルタが知られている（例えば、特許文献４を参照）。この波長可変フィルタの構成を図２０に示す。同図において、波長可変フィルタ２１は、偏光子２２ａ〜２２ｄに挟まれた各液晶セル２３ａ〜２３ｃにそれぞれ位相差フィルム２４ａ〜２４ｃが重ねて配置されている。この位相差フィルムによって、液晶セルのセル厚を必要最小限に抑え、それによるリタデーション値の減少を補充し、液晶の応答性低下を回避しつつ、狭半値幅の透過率ピークを発生させる。また、液晶セルのセル厚を透過順にｄ、２ｄ、１．５ｄに設定することにより、１つの電圧印加装置を共有して全液晶セルに同じ制御電圧を印加し、透過スペクトルの波長を調整することができる。   Furthermore, a wavelength tunable filter having a configuration similar to that in FIG. 19 is known in which a composite layer composed of a liquid crystal cell and a retardation film is sandwiched between polarizers (see, for example, Patent Document 4). The configuration of this tunable filter is shown in FIG. In the figure, the wavelength tunable filter 21 is configured such that retardation films 24a to 24c are overlapped on liquid crystal cells 23a to 23c sandwiched between polarizers 22a to 22d, respectively. This retardation film suppresses the cell thickness of the liquid crystal cell to the necessary minimum, supplements the decrease in retardation value thereby, and generates a transmittance peak with a narrow half-value width while avoiding a decrease in the response of the liquid crystal. Also, by setting the cell thickness of the liquid crystal cell to d, 2d, and 1.5d in the order of transmission, the same control voltage is applied to all the liquid crystal cells by sharing one voltage application device, and the wavelength of the transmission spectrum is adjusted. be able to.

また、位相差を調整できる位相素子として、バビネソレイユ補償板が知られている（例えば、特許文献５を参照）。バビネソレイユ補償板は、光学軸が平行な２枚の楔状複屈折板からなる複屈折素子とそれらとは光学軸方向が直交する平行平面板とを有し、楔状複屈折板を互いに摺動させて複屈折素子の厚さを調整することにより、位相差を制御することができる。一般にバビネソレイユ補償板は、例えば光磁気記録の再生において楕円偏光を直線偏光に戻したり所望の位相差を与えるため、複屈折層を有する光学材料のギャップ厚を測定するため、液晶表示装置において液晶セルの表示の着色を解消するための位相差補償素子として使用されている（例えば、特許文献６〜８を参照）。   Further, as a phase element that can adjust the phase difference, a Babinet Soleil compensator is known (see, for example, Patent Document 5). The Babinet Soleil compensator has a birefringent element composed of two wedge-shaped birefringent plates whose optical axes are parallel to each other, and a parallel plane plate perpendicular to the optical axis direction, and slides the wedge-shaped birefringent plates relative to each other. Thus, the phase difference can be controlled by adjusting the thickness of the birefringent element. In general, a Babinet Soleil compensator is used in a liquid crystal display device to measure the gap thickness of an optical material having a birefringent layer, for example, to return elliptically polarized light to linearly polarized light or give a desired phase difference in reproducing magneto-optical recording. It is used as a phase difference compensation element for eliminating coloration of cell display (see, for example, Patent Documents 6 to 8).

特許第３０００６６９号公報Japanese Patent No. 3000669 特許第３１０２０１２号公報Japanese Patent No. 3102012 特開２０００−２６７１２７号公報JP 2000-267127 A 特開２００５−１１５２０８号公報JP 2005-115208 A 特開昭６３−１１３８３８号公報JP-A-63-113838 特開平３−４０２５２号公報JP-A-3-40252 特開平９−５０４０号公報Japanese Patent Laid-Open No. 9-5040 実開平４−９０１６号公報Japanese Utility Model Publication 4-9016

しかしながら、液晶セルは、ＩＴＯ（インジウム錫酸化物）膜等での反射により透過光量に損失を生じることに加えて、特に紫外域〜青色の短波長域の光を吸収する性質がある。そのため、上述したように液晶セルを用いた波長可変フィルタは、短波長域での透過率が大幅に低下するという問題がある。   However, the liquid crystal cell has a property of absorbing light in a short wavelength range from ultraviolet to blue in addition to causing a loss in transmitted light amount due to reflection on an ITO (indium tin oxide) film or the like. Therefore, as described above, the wavelength tunable filter using the liquid crystal cell has a problem that the transmittance in a short wavelength region is significantly reduced.

更に、複数の液晶セルへの印加電圧を精密に制御するためには、液晶セル毎に独立した駆動制御回路が必要で、装置全体の構成及び制御が複雑になるという問題を生じる。しかも、液晶セルは、耐熱性が低く、透過波面収差が大きい等の問題がある。また、液晶セルは、その屈折率の印加電圧に対する応答が遅いため、印加電圧を連続的に変化させて透過波長を連続的に変化させることは、実用的に困難な場合がある。   Furthermore, in order to precisely control the voltage applied to the plurality of liquid crystal cells, an independent drive control circuit is required for each liquid crystal cell, which causes a problem that the configuration and control of the entire apparatus are complicated. Moreover, the liquid crystal cell has problems such as low heat resistance and large transmitted wavefront aberration. Moreover, since the liquid crystal cell has a slow response to the applied voltage of the refractive index, it may be practically difficult to continuously change the transmission wavelength by changing the applied voltage continuously.

また、リオフィルタ及び上述した従来の波長可変フィルタは、２つの偏光子及びその間に挟まれた複屈折板又は液晶セル等の位相子を１ブロックとして、これを光路に沿って直列に配置して多段に構成する。そのため、透過スペクトルをより急峻にして狭帯域な透過特性が得られる反面、部品点数が多くなり、フィルタ全体を長大化・大型化させるという問題がある。特に多段構造の可変波長フィルタは、光学的厚さ及び他の仕様の異なる複数の液晶セルが必要になるので、コストが増加する。   In addition, the Rio filter and the above-described conventional wavelength tunable filter have two polarizers and a phase shifter such as a birefringent plate or a liquid crystal cell sandwiched between them as one block, which are arranged in series along the optical path. Configure in multiple stages. For this reason, the transmission spectrum becomes steeper and narrow band transmission characteristics can be obtained, but there is a problem that the number of parts increases and the entire filter becomes longer and larger. In particular, a multi-wavelength variable wavelength filter requires a plurality of liquid crystal cells having different optical thicknesses and other specifications, which increases costs.

更に従来の波長フィルタは、偏光子として位相差フィルムのような吸収型偏光子を使用するので、光学的損失が大きい。これに対し、ワイヤグリット偏光子やフォトニック結晶偏光子、輝度向上フィルム等の反射型偏光子は、一般に低損失かつ広帯域な光学特性を有し、耐熱性に優れた特徴を有する。しかしながら、従来の各光学要素を光路に沿って直列に配置した多段構成の波長フィルタに反射型偏光子を用いると、不要な反射光が生じて迷光となるので、良好な光学特性を得られない。   Furthermore, since the conventional wavelength filter uses an absorptive polarizer such as a retardation film as the polarizer, the optical loss is large. On the other hand, reflective polarizers such as wire grid polarizers, photonic crystal polarizers, and brightness enhancement films generally have low loss and broadband optical characteristics, and are excellent in heat resistance. However, if a reflective polarizer is used in a wavelength filter having a multi-stage configuration in which conventional optical elements are arranged in series along the optical path, unnecessary reflected light is generated and stray light cannot be obtained. .

本願発明者らは、バビネソレイユ補償板が水晶等の透過率が高い材料で形成され、複屈折素子の厚さを機械的に制御して位相差を調整するので、耐熱性が高く、短波長領域でも透過効率が高く、応答性が良い等の特徴に着目した。そして、上述した従来の問題点に鑑み、バビネソレイユ補償板を波長可変フィルタに適用することについて様々な検討を加えた結果、本発明を案出するに至ったものである。   The inventors of the present application have a high heat resistance and a short wavelength because the Babinet Soleil compensator is formed of a material having high transmittance such as quartz and adjusts the phase difference by mechanically controlling the thickness of the birefringent element. We focused on features such as high transmission efficiency and good responsiveness even in the region. In view of the above-described conventional problems, the present invention has been devised as a result of various studies on applying a Babinet Soleil compensation plate to a wavelength tunable filter.

そこで本発明の目的は、部品点数をできる限り少なくしかつ装置全体の長大化・大型化を抑制しつつ、多段構造のリオフィルタと同等に、透過スペクトルが急峻で狭帯域特性を発揮し得ると共に、バビネソレイユ補償板を利用することにより、紫外域〜青色の短波長域を含む広い波長域の光について、より簡単かつ高精度に透過波長を可変制御し得る波長可変フィルタを実現することにある。   Accordingly, an object of the present invention is to reduce the number of parts as much as possible and suppress the increase in the length and size of the entire apparatus, and can exhibit a narrow band characteristic with a sharp transmission spectrum, similar to a multistage rio filter. By using a Babinet Soleil compensator, it is intended to realize a wavelength tunable filter that can variably control the transmission wavelength of light in a wide wavelength range including a short wavelength range from ultraviolet to blue with higher accuracy. .

本発明によれば、上記目的を達成するために、第１主面及び第２主面を有する位相差素子と、その第１主面及び第２主面に設けられた複数の偏光子と反射ミラーとを備え、該位相差素子が、一端から他端に向けて厚さを薄くした楔状をなしかつ互いに対向させて配置した２枚の位相差板からなり、該２枚の位相差板が、位相差素子の厚さを変化させるように相対的に変位可能であり、位相差素子に入射した光が、該位相差素子内部を偏光子と反射ミラーとの間で前記主面の法線方向に関して一定の角度をもって多重反射して透過し、位相差素子から出射する波長可変フィルタが提供される。   According to the present invention, in order to achieve the above object, a retardation element having a first main surface and a second main surface, and a plurality of polarizers and reflections provided on the first main surface and the second main surface The phase difference element is composed of two phase difference plates arranged in a wedge shape with a thickness reduced from one end to the other end and facing each other, the two phase difference plates being The phase difference element is relatively displaceable so as to change the thickness of the phase difference element. Light incident on the phase difference element passes through the phase difference element between the polarizer and the reflection mirror and is normal to the main surface. There is provided a wavelength tunable filter that multiple-reflects and transmits at a certain angle with respect to the direction and emits from the phase difference element.

位相差素子内部を多重反射しながら透過する光の光路に沿って隣接する２つの偏光子間の位相差は、該２つの偏光子間の光路長によって決定され、該位相差に対応して透過スペクトルのピーク波長が設定される。そして、位相差素子は、それを構成する２枚の位相差板、即ち複屈折板を相対的に移動させることにより、第１主面と第２主面間の光学的厚さを変化させて、透過する光の波長を調整することができる。これにより、従来のリオフィルタと同様の構造において、透過スペクトル波長を自在に変化させ得る波長可変フィルタが実現される。   The phase difference between two polarizers adjacent to each other along the optical path of light transmitted through multiple reflections inside the phase difference element is determined by the optical path length between the two polarizers, and is transmitted corresponding to the phase difference. The peak wavelength of the spectrum is set. The retardation element changes the optical thickness between the first principal surface and the second principal surface by relatively moving the two retardation plates constituting the retardation element, that is, the birefringence plate. The wavelength of transmitted light can be adjusted. As a result, a wavelength tunable filter capable of freely changing the transmission spectrum wavelength is realized in the same structure as the conventional rio filter.

また、共通した１つの位相差素子の主面に設ける偏光子の数を増やすことによって、多段構造のリオフィルタと同等の構成が得られるから、部品点数を少なくしかつ装置全体の長大化・大型化を抑制することができる。特に、部品点数が従来よりも格段に減少することにより、製造過程や使用済の廃棄品が及ぼす環境への影響が少なくなるという側面からも、極めて有利である。   In addition, by increasing the number of polarizers provided on the main surface of one common phase difference element, a configuration equivalent to a multistage rio filter can be obtained, so the number of parts is reduced and the overall length and size of the apparatus are increased. Can be suppressed. In particular, it is extremely advantageous from the viewpoint that the influence of the manufacturing process and the used waste product on the environment is reduced by reducing the number of parts much more than before.

更に、水晶等からなる複屈折板を用いた位相差素子は、紫外域〜青色の短波長域でも高い透過率を発揮するので、短波長域を含む広い波長域の光について、透過波長を可変制御し得る波長可変フィルタを実現することができる。しかも、位相差素子は耐熱性が優れているので、液晶セルを用いた従来技術に比して、波長可変フィルタの耐熱性が大幅に向上する。   Furthermore, a retardation element using a birefringent plate made of quartz or the like exhibits high transmittance even in the short wavelength range from ultraviolet to blue, so that the transmission wavelength can be varied for light in a wide wavelength range including the short wavelength range. A tunable filter that can be controlled can be realized. In addition, since the phase difference element is excellent in heat resistance, the heat resistance of the wavelength tunable filter is greatly improved as compared with the conventional technique using a liquid crystal cell.

或る実施例では、位相差素子内部を透過する光の光路に沿って隣接する２つの偏光子間の位相差Γｉが、該光路を透過する光の波長に対してΓｉ＝２ｉ−１×２π、（但し、ｉ＝１〜ｎ、ｎ：２以上の整数）の関係を満足することにより、常に２πの整数倍となるので、従来のリオフィルタと同様の可変バンドパスフィルタとしての透過特性が得られる。 In one embodiment, the phase difference Γ i between two polarizers adjacent to each other along the optical path of light transmitted through the inside of the phase difference element is such that Γ i = 2 i− with respect to the wavelength of light transmitted through the optical path. By satisfying the relationship of 1 × 2π (where i = 1 to n, n: an integer equal to or greater than 2), it is always an integer multiple of 2π. Therefore, as a variable bandpass filter similar to the conventional rio filter, Transmission characteristics are obtained.

ここで更に、位相差素子内部を透過する光の光路に沿って隣接する２つの偏光子間の少なくとも１つの位相差Γｊが、光路を透過する光の波長に対してΓｊ＝２ｊ−１×２π−π、（但し、ｊ＝１〜ｍ、ｍ：自然数）の関係を満足することにより、可変波長域を拡大することができる。 Here, further, at least one phase difference Γ j between two polarizers adjacent to each other along the optical path of light passing through the inside of the phase difference element is such that Γ j = 2 j− with respect to the wavelength of light passing through the optical path. By satisfying the relationship of 1 × 2π−π (where j = 1 to m, m: natural number), the variable wavelength region can be expanded.

更に別の実施例では、位相差素子内部を透過する光の光路に沿って隣接する２つの偏光子が平行ニコル又はクロスニコルの関係に配置されていることにより、従来のリオフィルタと同様の可変バンドパスフィルタとしての透過特性が得られる。   In yet another embodiment, two adjacent polarizers are arranged in a parallel Nicols or crossed Nicols relationship along the optical path of light passing through the inside of the phase difference element. Transmission characteristics as a bandpass filter can be obtained.

或る実施例では、位相差素子への光の入射口と出射口とが互いに異なる主面に設けられることにより、入射光と出射光とをインライン配置することができる。別の実施例では、位相差素子への光の入射口と出射口とが一方の主面に設けられることにより、入射光と出射光とを対向配置することができる。   In one embodiment, the incident light and the light exit to the phase difference element are provided on different main surfaces, so that the incident light and the outgoing light can be arranged in-line. In another embodiment, an incident port and an exit port for light to the phase difference element are provided on one main surface, so that the incident light and the emitted light can be arranged to face each other.

或る実施例では、位相差素子の主面に設けられた偏光子がワイヤグリッド偏光子であると、該偏光子に入射する光をその偏光方向によって選択的に反射できるので、別個の反射手段を追加する必要がなく、部品点数をより少なくできると共に、ｐ偏光及びｓ偏光のいずれについても高い透過率を発揮するので、高い光利用効率を得ることができる。   In one embodiment, when the polarizer provided on the main surface of the phase difference element is a wire grid polarizer, light incident on the polarizer can be selectively reflected according to the polarization direction. In addition, the number of components can be further reduced, and high transmittance can be obtained for both p-polarized light and s-polarized light, so that high light utilization efficiency can be obtained.

別の実施例では、ワイヤグリッド偏光子である全ての偏光子が位相差素子の一方の主面に設けられ、位相差素子の光の出射口が他方の主面に設けられることにより、各偏光子から外部に透過する不要光を所望の出射光から確実に排除することができる。   In another embodiment, all the polarizers which are wire grid polarizers are provided on one main surface of the phase difference element, and the light exit of the phase difference element is provided on the other main surface. Unwanted light transmitted from the child to the outside can be surely excluded from the desired emitted light.

また、或る実施例では、位相差素子の端面に設けられた垂直反射ミラーを更に有し、位相差素子内部を透過する光が垂直反射ミラーにより反射されて逆向きに進行することにより、フィルタ全体を短くして小型化することができる。   In one embodiment, the filter further includes a vertical reflection mirror provided on the end face of the phase difference element, and light transmitted through the phase difference element is reflected by the vertical reflection mirror and travels in the reverse direction. The whole can be shortened and downsized.

別の実施例では、位相差素子を構成する２板の位相差板が、平行平板の一方の面をそのままにして反対側の面を所定の楔角で傾斜加工して形成され、その傾斜面を互いに対向させ、かつ互いに厚さの厚い方の端部と厚さの薄い方の端部とを同じ側にして互違いに配置されることにより、それらを互いに傾斜面に沿って相対的に動かして、位相差素子の光学的厚さを変化させることができる。更に別の実施例では、位相差素子を構成する平行平板の一方の面をそのままにして反対側の面を所定の楔角で傾斜加工して形成され、前記一方の面を互いに対向させ、かつ互いに厚さの厚い方の端部と厚さの薄い方の端部とを同じ側にして互違いに配置される。   In another embodiment, the two retardation plates constituting the retardation element are formed by inclining the opposite surface at a predetermined wedge angle while leaving one surface of the parallel plate as it is. Are arranged in a staggered manner so that the thicker end and the thinner end are on the same side, so that they are relatively aligned with each other along the inclined surface. It can be moved to change the optical thickness of the phase difference element. In yet another embodiment, one surface of the parallel plate constituting the retardation element is left as it is, and the opposite surface is formed by inclining with a predetermined wedge angle, the one surface is opposed to each other, and The thicker end portions and the thinner end portions are arranged on the same side in a staggered manner.

或る実施例では、２枚の位相差板が、それらの結晶光学軸を互いに平行に配置されることにより、透過光をその偏光方向をそのまま維持して透過させることができる。別の実施例では、２枚の位相差板が、それらの結晶光学軸を互いに直交させて配置されることにより、透過光をその偏光方向を９０°回転させて透過させることができる。   In one embodiment, two retardation plates are arranged so that their crystal optical axes are parallel to each other, so that transmitted light can be transmitted while maintaining its polarization direction as it is. In another embodiment, two retardation plates are arranged with their crystal optical axes orthogonal to each other, so that transmitted light can be transmitted with its polarization direction rotated by 90 °.

また或る実施例では、位相差素子が、少なくとも一方の前記位相差板と組み合わせた平行平板の位相差板を更に有することにより、透過光の波長範囲を拡大することができる。   In one embodiment, the retardation element further includes a parallel plate retardation plate combined with at least one of the retardation plates, so that the wavelength range of transmitted light can be expanded.

以下に、添付図面を参照しつつ、本発明による波長可変フィルタの好適な実施例を詳細に説明する。尚、各図において、類似の構成要素には同一又は類似の参照符号を付して表すことにする。   Exemplary embodiments of a tunable filter according to the present invention will be described below in detail with reference to the accompanying drawings. In each drawing, similar components are denoted by the same or similar reference numerals.

図１（Ａ）〜（Ｃ）は、本発明による波長フィルタの第１実施例の構成を概略的に示している。本実施例の波長フィルタ３１は、一定の光学的厚さと該厚さに対する十分な長さとを有する位相子を備える。前記位相子は、バビネソレイユ位相板３２からなる位相差素子であり、同じ楔角θを有する２枚の楔状複屈折板３３，３４を備える。図１（Ｃ）に示すように、本実施例のバビネソレイユ位相板３２は、一方即ち上側の複屈折板３３が楔角θの楔板３３１と平行平板３３２とで構成され、他方即ち下側の複屈折板３４が楔角θの楔板のみで構成される。前記上側複屈折板の楔板３３１及び前記下側複屈折板は、平行平板の複屈折板の一方の面を研磨等により傾斜加工して、その傾斜面と平行平板面のままである反対側の面との間に所定の楔角θを画定するように形成したものである。また、前記上側及び下側複屈折板は水晶で形成され、又は他の類似の光学結晶材料で形成される。 1A to 1C schematically show the configuration of a first embodiment of a wavelength filter according to the present invention. The wavelength filter 31 of the present embodiment includes a phaser having a certain optical thickness and a sufficient length for the thickness. The phase shifter is a phase difference element including a Babinet Soleil phase plate 32 and includes two wedge-shaped birefringence plates 33 and 34 having the same wedge angle θ. As shown in FIG. 1 (C), Babinet Soleil phase plate 32 of this embodiment, whereas or upper birefringent plate 33 is constituted by the wedge plate 33 1 and the parallel plate 33 second wedge angle theta, the other i.e. The lower birefringent plate 34 is composed only of a wedge plate having a wedge angle θ. The upper birefringent plate wedge plate 331 and the lower birefringent plate are oppositely formed by subjecting one surface of the parallel plate birefringent plate to an inclination process by polishing or the like, and the inclined surface remains a parallel plate surface. It is formed so as to define a predetermined wedge angle θ with respect to the side surface. The upper and lower birefringent plates may be made of quartz or other similar optical crystal material.

バビネソレイユ位相板３２は、前記複屈折板が、それらの傾斜面を互いに対向させ、互いに厚さの厚い方の端部と厚さの薄い方の端部とを同じ側にして互違いに配置される。図示しないマイクロメータ等からなるアクチュエータによって、下側の複屈折板３４を前記バビネソレイユ位相板の幅方向に上側の複屈折板３３に関して相対的に動かし、バビネソレイユ位相板３２の光学的厚さを変更して、透過光の波長を調整することができる。複屈折板３３，３４は、対向する傾斜面を互いに接触させかつそれらを摺動させながら、又は対向する傾斜面を互いに空隙を挟んで離隔した状態で、相対的に動かすことができる。添付図面は、説明を分かり易くするために、前記複屈折板の対向する傾斜面を互いに離隔した状態を示している。   In the Babinet Soleil phase plate 32, the birefringent plates are arranged in a staggered manner such that their inclined surfaces face each other and the thicker end and the thinner end are on the same side. Is done. The lower birefringent plate 34 is moved relative to the upper birefringent plate 33 in the width direction of the Babinet Soleil phase plate by an actuator (not shown) such as a micrometer, so that the optical thickness of the Babinet Soleil phase plate 32 is increased. The wavelength of the transmitted light can be adjusted by changing. The birefringent plates 33 and 34 can be relatively moved while the opposed inclined surfaces are brought into contact with each other and slid therebetween, or the opposed inclined surfaces are separated from each other with a gap therebetween. The attached drawings show a state in which the inclined surfaces facing each other of the birefringent plates are separated from each other for easy understanding.

楔板３３１と複屈折板３４とは、光学軸Ｏp1，Ｏp2が同じ向きにかつ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向されている。楔板３３１と平行平板３３２とは、光学軸Ｏp1，Ｏp3が互いに直交するようにかつそれぞれ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向される。 The wedge plate 33 1 and the birefringent plate 34, the optical axis Op1, Op2 are oriented at 45 ° orientation with respect to the length direction of and the Babinet Soleil phase plate in the same direction. The wedge plate 33 1 and the parallel plate 33 2, the optical axis Op1, Op3 is oriented at 45 ° orientation relative to the longitudinal direction of and each of the Babinet Soleil phase plates so as to be perpendicular to each other.

本実施例では、バビネソレイユ位相板３２の上面即ち上側複屈折板３３の上面の一方の端部（図中左側）３３ａ付近を光の入射口とし、かつ他方の端部（図中右側）３３ｂ付近を光の出射口とし、該バビネソレイユ位相板内部を光が図中左から右へ進行するようにする。前記バビネソレイユ位相板の上側主面即ち上側複屈折板３３の上面には、前記光入射口と光出射口との間に第１〜第４偏光子３５〜３８と上側反射ミラー３９，４０とが設けられる。前記バビネソレイユ位相板を透過する光の進行方向に沿って、第１及び第２偏光子３５，３６が連続して配置され、次に上側反射ミラー３９を挟んで第３偏光子３７と、更に上側反射ミラー４０を挟んで第４偏光子３８とが配置される。前記バビネソレイユ位相板の下側主面即ち下側複屈折板３４の下面には、その全面に下側反射ミラー４１が設けられる。   In this embodiment, the vicinity of one end (left side in the figure) 33a of the upper surface of the Babinet Soleil phase plate 32, that is, the upper surface of the upper birefringent plate 33 is used as the light entrance, and the other end (right side in the figure) 33b. The vicinity is used as a light exit, and light travels from the left to the right in the figure inside the Babinet Soleil phase plate. On the upper main surface of the Babinet Soleil phase plate, that is, the upper surface of the upper birefringent plate 33, first to fourth polarizers 35 to 38 and upper reflecting mirrors 39 and 40 are provided between the light incident port and the light emitting port. Is provided. The first and second polarizers 35 and 36 are continuously arranged along the traveling direction of the light transmitted through the Babinet Soleil phase plate, and then the third polarizer 37 with the upper reflection mirror 39 interposed therebetween, and A fourth polarizer 38 is arranged with the upper reflecting mirror 40 in between. A lower reflecting mirror 41 is provided on the lower main surface of the Babinet Soleil phase plate, that is, the lower surface of the lower birefringent plate 34.

第１〜第４偏光子３５〜３８は、ワイヤグリッド偏光子からなる。ワイヤグリッド偏光子は、透明基板の表面に金属細線を周期的に透過波長よりも短い一定の周期で格子状に配列され、格子の周期方向と垂直な振動成分の光を反射し、かつ平行な振動成分の光を透過させるという特性を有する。本実施例では、波長フィルタ３１への入射光Ｌ1と上側複屈折板３３上面の法線とを含む平面（図１（Ｂ）の紙面）に対して垂直な直線偏光をｓ偏光として、図中黒丸点●で、平行な直線偏光をｐ偏光として、図中短い両端矢印で示す。前記第１〜第４偏光子は、その格子をバビネソレイユ位相板３２の長さ方向に整合させて、その周期方向が前記バビネソレイユ位相板の光学軸Ｏp1〜Ｏp3と４５°の角度をなし、かつ前記バビネソレイユ位相板の幅方向と一致するように配向する。前記各偏光子の格子の向きは、図１（Ａ）の平面図において多数の平行な細い横線で、図１（Ｃ）の端面図において多数の平行な細い縦線で表す。   The first to fourth polarizers 35 to 38 are wire grid polarizers. Wire grid polarizers are arranged on a transparent substrate surface in the form of a lattice of metal thin wires periodically with a constant period shorter than the transmission wavelength, reflect the light of vibration components perpendicular to the periodic direction of the lattice, and are parallel to each other It has the characteristic of transmitting light of vibration components. In this embodiment, linearly polarized light perpendicular to a plane including the incident light L1 to the wavelength filter 31 and the normal line on the upper surface of the upper birefringent plate 33 (the paper surface of FIG. 1B) is s-polarized light. A black circle dot ● indicates that the parallel linearly polarized light is p-polarized light and is indicated by a short double-ended arrow in the figure. The first to fourth polarizers have their gratings aligned with the length direction of the Babenesoleil phase plate 32, and the periodic direction forms an angle of 45 ° with the optical axes Op1 to Op3 of the Babenesoleil phase plate. And it orients so that it may correspond with the width direction of the said Babinet Soleil phase plate. The orientation of the grating of each polarizer is represented by a large number of parallel thin horizontal lines in the plan view of FIG. 1A and by a large number of parallel thin vertical lines in the end view of FIG.

前記各偏光子は、入射光をその偏光方向によって透過又は反射するように分光するものであれば、ワイヤグリッド偏光子以外の様々な公知の偏光子を用いることができる。このような偏光子として、例えばフォトニック結晶偏光子、樹脂材料からなる輝度向上フィルム等がある。前記各反射ミラーは、例えばＡｌ，Ａｇ，Ａｕ等の金属膜を前記複屈折板の表面に蒸着等の方法で付着させることにより形成される。また、前記反射ミラーは、誘電体多層膜を積層することにより形成され、所望の直線偏光成分のみを選択的に反射して、他の直線偏光成分を反射しないように構成し、反射による損失をより少なくすることができる。   As each of the polarizers, various known polarizers other than the wire grid polarizer can be used as long as they split the incident light so as to be transmitted or reflected depending on the polarization direction. Examples of such a polarizer include a photonic crystal polarizer and a brightness enhancement film made of a resin material. Each of the reflecting mirrors is formed by attaching a metal film such as Al, Ag, or Au to the surface of the birefringent plate by a method such as vapor deposition. The reflection mirror is formed by laminating dielectric multilayer films, and is configured to selectively reflect only a desired linearly polarized light component and not to reflect other linearly polarized light components. Can be less.

波長フィルタ３１への入射光Ｌ1は、前記光入射口からバビネソレイユ位相板３２を透過し、下側反射ミラー４１により該位相板の主面の法線方向に関して所定の角度φをもって反射される。反射光は第１偏光子３５に入射し、ｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過して、不要光として外部に出射する。ｐ偏光成分は、前記第１偏光子により前記位相板主面の法線方向に関して同じ反射角度φをもって反射され、バビネソレイユ位相板３２の内部を多重反射しながら透過する。隣接する２つの前記偏光子同士は、前記ワイヤグリッド偏光子の格子の周期方向を上述したように配向したことにより、それぞれ透過軸を互いに平行にした平行ニコルの関係に配置されている。   Incident light L1 to the wavelength filter 31 passes through the Babinet Soleil phase plate 32 from the light entrance and is reflected by the lower reflection mirror 41 with a predetermined angle φ with respect to the normal direction of the main surface of the phase plate. The reflected light enters the first polarizer 35 and is split into an s-polarized component and a p-polarized component. The s-polarized light component passes through the first polarizer 35 and is emitted to the outside as unnecessary light. The p-polarized component is reflected by the first polarizer with the same reflection angle φ with respect to the normal direction of the phase plate main surface, and is transmitted through the Babinet Soleil phase plate 32 while being subjected to multiple reflections. The two adjacent polarizers are arranged in a parallel Nicol relationship in which the transmission axes are parallel to each other by aligning the periodic direction of the grating of the wire grid polarizer as described above.

第１偏光子３５から反射したｐ偏光は、バビネソレイユ位相板３２を透過し、その間にｓ偏光に変換され、下側反射ミラー４１により反射されて再び前記バビネソレイユ位相板を透過し、その間に再びｐ偏光に変換され、第２偏光子３６に入射して反射する。次に、前記第２偏光子から反射したｐ偏光は、前記下側反射ミラーと上側反射ミラー３９とにより３度反射されて、前記バビネソレイユ位相板を２度往復透過し、第３偏光子３７に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、ｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、２度繰り返して変換される。前記第３偏光子から反射したｐ偏光は、前記下側反射ミラーと上側反射ミラー４０とにより７度反射されて、前記バビネソレイユ位相板を４度往復透過し、第４偏光子３８に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、同様にｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、４度繰り返して変換される。最後に、前記第４偏光子から反射したｐ偏光は、再び下側反射ミラー４１に反射されて前記バビネソレイユ位相板を一度往復透過し、その間にｐ偏光からｓ偏光に変換され、更にｓ偏光からｐ偏光に戻されて、前記光出射口から外部に出射する。   The p-polarized light reflected from the first polarizer 35 is transmitted through the Babinet Soleil phase plate 32, converted into s-polarized light in the meantime, reflected by the lower reflection mirror 41, and again transmitted through the Babinet Soleil phase plate. The light is again converted to p-polarized light and is incident on the second polarizer 36 and reflected. Next, the p-polarized light reflected from the second polarizer is reflected by the lower reflection mirror and the upper reflection mirror 39 three times, and is transmitted twice through the Babinet Soleil phase plate twice. Is incident and reflected. In the meantime, every time the light passes back and forth through the Babinet Soleil phase plate, p-polarized light is converted twice into s-polarized light, and further from s-polarized light to p-polarized light. The p-polarized light reflected from the third polarizer is reflected seven times by the lower reflection mirror and the upper reflection mirror 40, reciprocates through the Babinet Soleil phase plate four times, and enters the fourth polarizer 38. Reflect. In the meantime, every time the light passes through the Babinet Soleil phase plate, the p-polarized light is similarly converted into s-polarized light, and further converted from s-polarized light to p-polarized light four times. Finally, the p-polarized light reflected from the fourth polarizer is reflected again by the lower reflection mirror 41 and once passes back and forth through the Babinet Soleil phase plate, while being converted from p-polarized light to s-polarized light, and further s-polarized light. Is returned to p-polarized light and emitted to the outside from the light exit port.

バビネソレイユ位相板３２は、その上側及び下側主面間を光が一度透過する間に１８０°の位相差が与えられるように構成される。従って、前記各偏光子は、前記バビネソレイユ位相板内部を進行する光路に沿って隣接する２つの偏光子間、即ち第１偏光子３５と第２偏光子３６間、前記第２偏光子と第３偏光子３７間、及び前記偏光子３７と第４偏光子４０間の位相差が、順に３６０°、７２０°、１４４０°に、即ち２ｎ−１×２π、（ｎ：１〜３）となるように配置される。このように２つの前記偏光子間の位相差が常に２πの整数倍となるので、波長可変フィルタ３１は、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性が得られる。 The Babinet Soleil phase plate 32 is configured such that a phase difference of 180 ° is given while light is once transmitted between its upper and lower main surfaces. Accordingly, each of the polarizers is between two polarizers adjacent to each other along an optical path traveling inside the Babinet Soleil phase plate, that is, between the first polarizer 35 and the second polarizer 36, and between the second polarizer and the first polarizer. The phase differences between the three polarizers 37 and between the polarizer 37 and the fourth polarizer 40 are sequentially 360 °, 720 °, 1440 °, that is, 2 n-1 × 2π, (n: 1 to 3). It is arranged to become. Thus, since the phase difference between the two polarizers is always an integer multiple of 2π, the wavelength variable filter 31 can obtain transmission characteristics as a band-pass filter similar to a conventional rio filter.

別の実施例では、バビネソレイユ位相板３２の前記上側及び下側主面間を光が一度透過する間に与えられる位相差を９０°に設定することができる。その場合、隣接する前記各２つの偏光子間で、前記バビネソレイユ位相板を透過する光の反射回数を２倍にして、所望の位相差が得られるようにする。これにより、波長可変フィルタ３１は、同様に２つの前記偏光子間の位相差を常に２πの整数倍に設定して、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性を得ることができる。   In another embodiment, the phase difference given while light is once transmitted between the upper and lower main surfaces of the Babinet Soleil phase plate 32 can be set to 90 °. In that case, the number of reflections of the light transmitted through the Babinet Soleil phase plate is doubled between the two adjacent polarizers so that a desired phase difference is obtained. As a result, the wavelength tunable filter 31 can similarly set the phase difference between the two polarizers to an integral multiple of 2π to obtain transmission characteristics as a bandpass filter similar to the conventional rio filter. .

本実施例の波長可変フィルタ３１は、前記アクチュエータを駆動することにより、バビネソレイユ位相板３２を透過する光の波長が変化するので、透過スペクトル波長を自在に変化させることができる。特に水晶からなる複屈折板を用いたバビネソレイユ位相板３２は、紫外域〜青色の短波長域でも高い透過率を発揮する。従って、短波長域を含む広い波長域の光について、透過波長を可変制御し得る波長可変フィルタが実現される。しかも、バビネソレイユ位相板は耐熱性が優れているので、液晶セルを用いた従来技術に比して、波長可変フィルタ３１の耐熱性が大幅に向上する。   In the wavelength tunable filter 31 of this embodiment, the wavelength of the light transmitted through the Babinet Soleil phase plate 32 is changed by driving the actuator, so that the transmission spectrum wavelength can be freely changed. In particular, the Babinet Soleil phase plate 32 using a birefringent plate made of quartz exhibits high transmittance even in a short wavelength range from ultraviolet to blue. Therefore, a wavelength tunable filter that can variably control the transmission wavelength of light in a wide wavelength range including a short wavelength range is realized. In addition, since the Babinet Soleil phase plate is excellent in heat resistance, the heat resistance of the wavelength tunable filter 31 is greatly improved as compared with the conventional technique using a liquid crystal cell.

また、本実施例の波長可変フィルタ３１は、このようにバビネソレイユ位相板３２が共通化され、その主面に設けられる偏光子の数に拘わらず、１つだけで済むので、部品点数を大幅に少なくし、かつ装置全体の長大化・大型化を抑制することができる。更に、共通の１つの前記バビネソレイユ位相板の主面に設ける偏光子の数を増やすことによって、より多段構成の波長可変フィルタが得られる。   In addition, the wavelength tunable filter 31 of this embodiment has the same Babinet Soleil phase plate 32 as described above, and only one is required regardless of the number of polarizers provided on the main surface thereof. The increase in length and size of the entire apparatus can be suppressed. Furthermore, by increasing the number of polarizers provided on the main surface of one common Babinet Soleil phase plate, it is possible to obtain a tunable filter having a multistage structure.

図２（Ａ）〜（Ｄ）は、波長可変フィルタ３１の波長特性、即ち透過スペクトルのピークの透過率をシミュレーションした結果を示している。図２（Ａ）〜（Ｄ）は、それぞれバビネソレイユ位相板３２を透過して出射する光の光路に沿って図１（Ｂ）に示す各位置Ｐ１〜Ｐ４における光の波長に関する透過率の変化を示している。ここで、λ０は特定波長即ち入射光の波長であり、λは各位置Ｐ１〜Ｐ４における透過光又は出射光の波長である。同図において、実線は、バビネソレイユ位相板３２の光学的厚さが基準値である場合を、破線は、該バビネソレイユ位相板をその光学的厚さを基準値よりも薄くした場合を表している。 2A to 2D show the results of simulating the wavelength characteristics of the wavelength tunable filter 31, that is, the transmittance of the peak of the transmission spectrum. 2 (A) to 2 (D) show changes in the transmittance with respect to the wavelength of light at each of the positions P1 to P4 shown in FIG. 1 (B) along the optical path of the light transmitted through the Babinet Soleil phase plate 32, respectively. Is shown. Here, λ 0 is a specific wavelength, that is, a wavelength of incident light, and λ is a wavelength of transmitted light or outgoing light at each of the positions P1 to P4. In the figure, the solid line represents the case where the optical thickness of the Babenesoleil phase plate 32 is a reference value, and the broken line represents the case where the optical thickness of the Babenesoleil phase plate is made thinner than the reference value. Yes.

入射後に、第１偏光子３５から反射した後の前記光路の位置Ｐ１では、光の透過率は全波長範囲において５０％一定である（図２（Ａ））。第２偏光子３６から反射した後の前記光路の位置Ｐ２は、最初に隣接する前記偏光子間の透過特性を示し、前記特定波長の整数倍となる波長でピークを有する（図２（Ｂ））。次に隣接する前記偏光子間の透過特性は、前記特定波長の１／２波長の整数倍の波長でピークを有するから、第３偏光子３７から反射した後の前記光路の位置Ｐ３では、これと図２（Ｂ）とを重ね合わせた透過特性を示す（図２（Ｃ））。最後に隣接する前記偏光子間の透過特性は、前記特定波長の１／４波長の整数倍の波長でピークを有するから、バビネソレイユ位相板３２から出射した後の位置Ｐ４では、更にこれを図２（Ｃ）に重ね合わせた透過特性を示す（図２（Ｄ））。   After the incidence, at the position P1 of the optical path after being reflected from the first polarizer 35, the light transmittance is constant by 50% in the entire wavelength range (FIG. 2A). The position P2 of the optical path after being reflected from the second polarizer 36 first shows the transmission characteristics between the adjacent polarizers, and has a peak at a wavelength that is an integral multiple of the specific wavelength (FIG. 2B). ). Next, the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of ½ wavelength of the specific wavelength. Therefore, at the position P3 of the optical path after reflection from the third polarizer 37, And FIG. 2B show the transmission characteristics (FIG. 2C). Finally, since the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of a quarter wavelength of the specific wavelength, this is further illustrated at the position P4 after exiting from the Babinet Soleil phase plate 32. 2 (C) shows the superimposed transmission characteristics (FIG. 2D).

隣接する前記偏光子間の各透過スペクトルのピークは、前記特定波長の整数倍の波長で全て重なるので、波長フィルタ３１は、図２（Ｄ）に示すように、前記特定波長の整数倍で急峻なピークを有する透過特性が得られる。ここで、前記アクチュエータを駆動してバビネソレイユ位相板３２の光学的厚さを変化させると、透過特性は、図２（Ａ）〜（Ｄ）に破線で例示するように、ピーク波長が高波長側又は低波長側にシフトする。   Since the peaks of the transmission spectra between adjacent polarizers all overlap at a wavelength that is an integral multiple of the specific wavelength, the wavelength filter 31 is steep at an integral multiple of the specific wavelength, as shown in FIG. A transmission characteristic having a large peak is obtained. Here, when the actuator is driven to change the optical thickness of the Babenesoleil phase plate 32, the transmission characteristic has a high peak wavelength as illustrated by broken lines in FIGS. 2 (A) to (D). Shift to the side or low wavelength side.

図３（Ａ）〜（Ｃ）は、第１実施例の変形例の構成を概略的に示している。本実施例の波長フィルタ３１１は、光の入射口及び出射口がバビネソレイユ位相板３２の下面即ち下側複屈折板３４の下面の一方の端部（図中左側）３４ａ付近と、他方の端部（図中右側）３４ｂ付近に設けられる点において、第１実施例と異なる。そのため、下側反射ミラー４１１は、前記光の入射口及び出射口の部分を空けて下側複屈折板３４下面に設けられる。他の構成は、図１の波長フィルタ３１と同一であるので、詳細な説明は省略する。 3A to 3C schematically show the configuration of a modification of the first embodiment. Wavelength filter 31 1 of this embodiment, one end portion of the lower surface of the lower surface or lower birefringence plate 34 of the entrance and exit of light Babinet Soleil phase plate 32 and the vicinity (left side in the drawing) 34a, the other It differs from the first embodiment in that it is provided near the end (right side in the figure) 34b. Therefore, the lower side reflection mirror 41 1 is provided on a lower surface below the birefringent plate 34 at a portion of the entrance and exit of the light. Other configurations are the same as those of the wavelength filter 31 of FIG.

波長フィルタ３１１への入射光Ｌ1は、下側複屈折板３４下面の前記光入射口からバビネソレイユ位相板３２を透過して第１偏光子３５に入射し、ｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過して、不要光として外部に出射する。ｐ偏光成分は、前記第１偏光子により前記位相板主面の法線方向に関して同じ反射角度φをもって反射され、図１の実施例について説明したようにバビネソレイユ位相板３２内部を多重反射しながら透過して、最後の第４偏光子３８に入射する。前記第４偏光子から反射したｐ偏光は、前記バビネソレイユ位相板を透過し、その間にｓ偏光に変換されて、下側複屈折板３４下面の前記光出射口から外部に出射する。 Incident light L1 to the wavelength filter 31 1 is first incident on the polarizer 35 passes through the Babinet Soleil phase plate 32 from the lower birefringent plate 34 lower surface of the light entrance, and s-polarized light component and p-polarized light component Spectral. The s-polarized light component passes through the first polarizer 35 and is emitted to the outside as unnecessary light. The p-polarized component is reflected by the first polarizer with the same reflection angle φ with respect to the normal direction of the phase plate main surface, and while being reflected by the inside of the Babinet Soleil phase plate 32 as described in the embodiment of FIG. The light passes through and enters the last fourth polarizer 38. The p-polarized light reflected from the fourth polarizer passes through the Babinet Soleil phase plate, is converted into s-polarized light in the meantime, and exits to the outside from the light exit port on the lower surface of the lower birefringent plate 34.

本実施例では、前記光の出射口が、前記第１〜第４偏光子を配置した上側複屈折板３３とは反対側の下側複屈折板３４下面に設けられる。従って、出射光は、前記各偏光子から外部に出射する不要光から完全に分離され、その混入を確実に防止することができる。   In the present embodiment, the light exit is provided on the lower surface of the lower birefringent plate 34 opposite to the upper birefringent plate 33 on which the first to fourth polarizers are arranged. Therefore, the emitted light is completely separated from the unnecessary light emitted from the respective polarizers to the outside, and the mixing thereof can be reliably prevented.

図４（Ａ）〜（Ｃ）は、第１実施例の別の変形例の構成を概略的に示している。本実施例の波長フィルタ３１２は、光の出射口がバビネソレイユ位相板３２の下面即ち下側複屈折板３４の下面の他方の端部（図中右側）３４ｂ付近に設けられる点において、第１実施例と異なる。そのため、下側反射ミラー４１２は、前記光の出射口の部分を空けて下側複屈折板３４下面に設けられる。他の構成は、図１の波長フィルタ３１と同一であるので、詳細な説明は省略する。 4A to 4C schematically show the configuration of another modification of the first embodiment. Wavelength filter 312 of the present embodiment, the lower surface of the other end portion of the lower surface or lower birefringent plate 34 of the exit of the light Babinet Soleil phase plate 32 in that provided in the vicinity (the right side in the drawing) 34b, a Different from one embodiment. Therefore, the lower side reflection mirror 41 2 are provided on the lower surface under the birefringent plate 34 at a portion of the exit port of the light. Other configurations are the same as those of the wavelength filter 31 of FIG.

波長フィルタ３１２への入射光Ｌ1は、図１の実施例と同様に、上側複屈折板３３上面の前記光入射口からバビネソレイユ位相板３２を透過し、第１偏光子３５によりｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過して、不要光として外部に出射し、ｐ偏光成分は、前記第１偏光子により反射されて前記バビネソレイユ位相板内部を多重反射しながら透過し、最後の第４偏光子３８に入射する。前記第４偏光子から反射したｐ偏光は、前記バビネソレイユ位相板を透過し、その間にｓ偏光に変換されて、下側複屈折板３４下面の前記光出射口から外部に出射する。 Incident light L1 to the wavelength filter 31 2, similar to the embodiment of FIG. 1, it is transmitted through the Babinet Soleil phase plate 32 from the light incident port of the upper birefringent plate 33 upper surface, s-polarized light component by the first polarizer 35 And p-polarized component. The s-polarized light component is transmitted through the first polarizer 35 and emitted to the outside as unnecessary light, and the p-polarized light component is reflected by the first polarizer and transmitted through the Babinet Soleil phase plate while being multiple-reflected, The light enters the last fourth polarizer 38. The p-polarized light reflected from the fourth polarizer passes through the Babinet Soleil phase plate, is converted into s-polarized light in the meantime, and exits to the outside from the light exit port on the lower surface of the lower birefringent plate 34.

本実施例も、前記光の出射口が、前記第１〜第４偏光子を配置した上側複屈折板３３とは反対側の下側複屈折板３４下面に設けられる。従って、出射光は、前記各偏光子から外部に出射する不要光から完全に分離され、その混入を確実に防止することができる。   Also in the present embodiment, the light exit is provided on the lower surface of the lower birefringent plate 34 opposite to the upper birefringent plate 33 on which the first to fourth polarizers are arranged. Therefore, the emitted light is completely separated from the unnecessary light emitted from the respective polarizers to the outside, and the mixing thereof can be reliably prevented.

図５（Ａ）〜（Ｃ）は、第１実施例の更に別の変形例の構成を概略的に示している。本実施例の波長フィルタ３１３は、光の入射口がバビネソレイユ位相板３２の下面即ち下側複屈折板３４の下面の一方の端部（図中左側）３４ａ付近に設けられる点において、第１実施例と異なる。そのため、下側反射ミラー４１３は、前記光の入射口の部分を空けて下側複屈折板３４下面に設けられる。他の構成は、図１の波長フィルタ３１と同一であるので、詳細な説明は省略する。 5A to 5C schematically show the configuration of still another modified example of the first embodiment. Wavelength filter 313 of the present embodiment, one end portion of the lower surface of the lower surface or lower birefringence plate 34 of the entrance of light Babinet Soleil phase plate 32 in that provided in the vicinity (left side in the drawing) 34a, the Different from one embodiment. Therefore, the lower side reflection mirrors 41 3 provided on the lower surface under the birefringent plate 34 at a portion of the entrance of the light. Other configurations are the same as those of the wavelength filter 31 of FIG.

波長フィルタ３１３への入射光Ｌ1は、下側複屈折板３４下面の前記光入射口からバビネソレイユ位相板３２を透過し、第１偏光子３５によりｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過して、不要光として外部に出射し、ｐ偏光成分は、前記第１偏光子により反射されて前記バビネソレイユ位相板内部を多重反射しながら透過し、最後の第４偏光子３８に入射する。前記第４偏光子から反射したｐ偏光は、下側反射ミラー４１３により反射されて前記バビネソレイユ位相板を往復透過し、上側複屈折板３３上面の前記光出射口から外部に出射する。 Incident light L1 to the wavelength filter 31 3, is dispersed from the light incident port of the lower surface the lower birefringent plate 34 passes through the Babinet Soleil phase plate 32, the first polarizer 35 and the s-polarized component and p-polarized light component The The s-polarized light component is transmitted through the first polarizer 35 and emitted to the outside as unnecessary light, and the p-polarized light component is reflected by the first polarizer and transmitted through the Babinet Soleil phase plate while being multiple-reflected, The light enters the last fourth polarizer 38. P-polarized reflected from the fourth polarizer, the Babinet Soleil phase plate reciprocally transmitted is reflected by the lower reflecting mirror 41 3, emitted from the light exit of the upper birefringent plate 33 upper surface to the outside.

図６（Ａ）〜（Ｃ）は、第１実施例の更に別の変形例の構成を概略的に示している。本実施例の波長フィルタ３１４は、図５の変形例において、バビネソレイユ位相板３２上面に配置される第４偏光子４２が、ワイヤグリット偏光子の格子の周期方向を図１の第４偏光子３８のそれと直交する向きに配向した点において、第１実施例と異なる。 6A to 6C schematically show the configuration of still another modification of the first embodiment. Wavelength filter 31 4 of the present embodiment, in the modification of FIG. 5, a fourth polarizer 42 disposed on Babinet Soleil phase plate 32 upper surface, a fourth polarization direction of periodicity of the grating of the wire grid polarizer of FIG. 1 It differs from the first embodiment in that it is oriented in a direction perpendicular to that of the child 38.

波長フィルタ３１４への入射光Ｌ1は、下側複屈折板３４下面の前記光入射口からバビネソレイユ位相板３２を透過し、第１偏光子３５に入射してｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過して、不要光として外部に出射し、ｐ偏光成分は、前記第１偏光子により反射されて前記バビネソレイユ位相板内部を多重反射しながら透過する。下側反射ミラー４１３に反射されて最後の第４偏光子３８に入射したｐ偏光は、そのまま該第４偏光子を透過して外部に出射する。他の構成は、図１の波長フィルタ３１と同一であるので、詳細な説明は省略する。 Incident light L1 to the wavelength filter 31 4, a lower birefringent plate 34 lower surface of the light incident port passes through the Babinet Soleil phase plate 32, s-polarized light component incident on the first polarizer 35 and the p-polarized component Spectral. The s-polarized light component passes through the first polarizer 35 and is emitted to the outside as unnecessary light, and the p-polarized light component is reflected by the first polarizer and passes through the inside of the Babinet Soleil phase plate while being subjected to multiple reflections. P polarized light reflected on the lower side reflection mirrors 41 3 and enters the end of the fourth polarizer 38 is emitted to the outside is transmitted through the fourth polarizer. Other configurations are the same as those of the wavelength filter 31 of FIG.

図７（Ａ）〜（Ｃ）は、第１実施例の更に別の変形例の構成を概略的に示している。本実施例の波長フィルタ３１５は、第１〜第４偏光子３５〜３８及び上側反射ミラー３９，４０が上側の複屈折板３３から分離した別個の部品として、下側反射ミラー４１が下側の複屈折板３４から分離した別個の部品として構成されている点において、第１実施例と異なる。 FIGS. 7A to 7C schematically show the configuration of still another modification of the first embodiment. Wavelength filters 31 5 of the present embodiment, as a separate component first to fourth polarizer 35 to 38 and the upper reflecting mirror 39, 40 is separated from the upper birefringent plate 33, the lower side of the lower side reflection mirrors 41 The second embodiment is different from the first embodiment in that it is configured as a separate part separated from the birefringent plate 34.

これにより、本実施例は、前記第１〜第４偏光子と上側及び下側反射ミラーとに制限されることなく、バビネソレイユ位相板３２の駆動方向を選択することができ、かつ各構成要素を高い自由度をもって設計配置することができる。従って、波長フィルタ３１５への光の入射角、及び前記バビネソレイユ位相板を挟んで前記第１〜第４偏光子及び上側反射ミラーと下側反射ミラーとの反射間隔を、用途、使用条件等に応じて任意に設定することができる。 Thereby, the present embodiment can select the driving direction of the Babinet Soleil phase plate 32 without being limited to the first to fourth polarizers and the upper and lower reflection mirrors, and each component. Can be designed and arranged with a high degree of freedom. Therefore, the incident angle of light into the wavelength filter 31 5, and the reflection distance between the first to fourth polarizers and the upper reflection mirror and the lower side reflection mirror across the Babinet Soleil phase plate, application, use conditions, etc. It can be arbitrarily set according to.

図８（Ａ）〜（Ｃ）は、本発明による波長フィルタの第２実施例の構成を概略的に示している。本実施例の波長フィルタ５１は、ワイヤグリッド偏光子からなる追加の偏光子５２をバビネソレイユ位相板３２の下側複屈折板３４の下面に有する点において、第１実施例と異なる。追加偏光子５２は、前記バビネソレイユ位相板の前記光路に沿って第１偏光子３５の直ぐ上流側に配置される。追加偏光子５２は、ワイヤグリッド偏光子の格子の周期方向が図１の前記偏光子のそれと直交する向きに配向されている。従って、追加偏光子５２と第１偏光子３５とは、クロスニコルの関係に配置される。他の構成は、図１の波長フィルタ３１と同一であるので、詳細な説明は省略する。   FIGS. 8A to 8C schematically show the configuration of the second embodiment of the wavelength filter according to the present invention. The wavelength filter 51 of this embodiment is different from that of the first embodiment in that an additional polarizer 52 made of a wire grid polarizer is provided on the lower surface of the lower birefringent plate 34 of the Babenesoleil phase plate 32. The additional polarizer 52 is disposed immediately upstream of the first polarizer 35 along the optical path of the Babinet Soleil phase plate. The additional polarizer 52 is oriented so that the periodic direction of the grating of the wire grid polarizer is orthogonal to that of the polarizer of FIG. Therefore, the additional polarizer 52 and the first polarizer 35 are arranged in a crossed Nicols relationship. Other configurations are the same as those of the wavelength filter 31 of FIG.

波長フィルタ５１への入射光Ｌ1は、上側複屈折板３３上面の前記光入射口からバビネソレイユ位相板３２を透過し、追加偏光子５２に入射してｓ偏光成分とｐ偏光成分とに分光される。ｐ偏光成分は前記追加偏光子を透過して、不要光として外部に出射する。ｓ偏光成分は、前記追加偏光子により反射されて前記バビネソレイユ位相板内部を多重反射しながら透過する。   Incident light L1 to the wavelength filter 51 passes through the Babinet Soleil phase plate 32 from the light entrance on the upper surface of the upper birefringent plate 33, enters the additional polarizer 52, and is split into an s-polarized component and a p-polarized component. The The p-polarized light component passes through the additional polarizer and is emitted to the outside as unnecessary light. The s-polarized light component is reflected by the additional polarizer and passes through the inside of the Babinet Soleil phase plate with multiple reflections.

追加偏光子５２から反射したｓ偏光は、バビネソレイユ位相板３２を透過し、その間にｐ偏光に変換され、第１偏光子３５に入射して反射する。第１偏光子３５から反射したｐ偏光は、バビネソレイユ位相板３２を透過し、その間にｓ偏光に変換され、下側反射ミラー４１により反射されて再び前記バビネソレイユ位相板を透過し、その間に再びｐ偏光に変換され、第２偏光子３６に入射して反射する。次に、前記第２偏光子から反射したｐ偏光は、前記下側反射ミラーと上側反射ミラー３９とにより３度反射されて、前記バビネソレイユ位相板を２度往復透過し、第３偏光子３７に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、ｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、２度繰り返して変換される。前記第３偏光子から反射したｐ偏光は、前記下側反射ミラーと上側反射ミラー４０とにより７度反射されて、前記バビネソレイユ位相板を４度往復透過し、第４偏光子３８に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、同様にｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、４度繰り返して変換される。最後に、前記第４偏光子から反射したｐ偏光は、再び下側反射ミラー４１に反射されて前記バビネソレイユ位相板を一度往復透過し、その間にｐ偏光からｓ偏光に変換され、更にｓ偏光からｐ偏光に戻されて、前記光出射口から外部に出射する。   The s-polarized light reflected from the additional polarizer 52 passes through the Babinet Soleil phase plate 32, is converted into p-polarized light in the meantime, and enters the first polarizer 35 to be reflected. The p-polarized light reflected from the first polarizer 35 is transmitted through the Babinet Soleil phase plate 32, converted into s-polarized light in the meantime, reflected by the lower reflection mirror 41, and again transmitted through the Babinet Soleil phase plate. The light is again converted to p-polarized light and is incident on the second polarizer 36 and reflected. Next, the p-polarized light reflected from the second polarizer is reflected by the lower reflection mirror and the upper reflection mirror 39 three times, and is transmitted twice through the Babinet Soleil phase plate twice. Is incident and reflected. In the meantime, every time the light passes back and forth through the Babinet Soleil phase plate, p-polarized light is converted twice into s-polarized light, and further from s-polarized light to p-polarized light. The p-polarized light reflected from the third polarizer is reflected seven times by the lower reflection mirror and the upper reflection mirror 40, reciprocates through the Babinet Soleil phase plate four times, and enters the fourth polarizer 38. Reflect. In the meantime, every time the light passes through the Babinet Soleil phase plate, the p-polarized light is similarly converted into s-polarized light, and further converted from s-polarized light to p-polarized light four times. Finally, the p-polarized light reflected from the fourth polarizer is reflected again by the lower reflection mirror 41 and once passes back and forth through the Babinet Soleil phase plate, while being converted from p-polarized light to s-polarized light, and further s-polarized light. Is returned to p-polarized light and emitted to the outside from the light exit port.

上述したように、バビネソレイユ位相板３２は、上側及び下側主面３２ａ，３２ｂ間を光が一度透過する間に１８０°の位相差が与えられる。従って、前記バビネソレイユ位相板内部を進行する光路に沿って最初に隣接する２つの偏光子５２，３５間の位相差は１８０°である。この後段に続いて隣接する各２つの偏光子３５，３６間、３６，３７間、及び３７，４０間の位相差は、順に３６０°、７２０°、１４４０°に、即ち２ｎ−１×２π、（ｎ：１〜３）となるように配置される。 As described above, the Babinet Soleil phase plate 32 is given a phase difference of 180 ° while light is once transmitted between the upper and lower main surfaces 32a and 32b. Therefore, the phase difference between the two polarizers 52 and 35 adjacent to each other along the optical path traveling inside the Babinet Soleil phase plate is 180 °. Subsequent to this subsequent stage, the phase differences between two adjacent polarizers 35, 36, 36, 37, and 37, 40 are sequentially 360 °, 720 °, 1440 °, that is, 2 n−1 × 2π. , (N: 1 to 3).

このように隣接する偏光子間の位相差が２πの整数倍となる波長可変フィルタ５１において、その１つの位相差を１８０°とすることにより、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性が得られ、かつ可変波長域を拡大して広帯域化することができる。別の実施例では、追加偏光子を２つ以上に増やし、かつ各追加偏光子とそれに隣接する前記偏光子間の位相差Γｊが、前記光路を透過する光の波長に対してΓｊ＝２ｊ−１×２π−π、（但し、ｊ＝１〜ｍ、ｍ：自然数）の関係を満足することにより、πの奇数倍となるように構成して、可変波長域をより拡大することができる。 In this way, in the wavelength tunable filter 51 in which the phase difference between adjacent polarizers is an integral multiple of 2π, by setting the one phase difference to 180 °, transmission as a bandpass filter similar to the conventional rio filter is possible. Characteristics can be obtained, and the variable wavelength band can be expanded to widen the band. In another embodiment, the number of additional polarizers is increased to two or more, and the phase difference Γ j between each additional polarizer and the polarizer adjacent to the additional polarizer is Γ j = for the wavelength of light transmitted through the optical path. 2 j−1 × 2π−π (where j = 1 to m, m: natural number) By satisfying the relationship, it is configured to be an odd multiple of π to further expand the variable wavelength range. Can do.

別の実施例では、追加偏光子５２を第４偏光子３８の後段に配置することができる。第４偏光子３８と追加偏光子５２とはクロスニコルの関係に配置され、それらの間の位相差は１８０°である。この場合も、同様に従来のリオフィルタと同様のバンドパスフィルタとしての透過特性が得られ、かつ可変波長域を拡大して広帯域化することができる。   In another embodiment, the additional polarizer 52 can be disposed after the fourth polarizer 38. The fourth polarizer 38 and the additional polarizer 52 are arranged in a crossed Nicols relationship, and the phase difference between them is 180 °. In this case as well, transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained, and the variable wavelength band can be expanded to widen the band.

図９（Ａ）〜（Ｅ）は、波長可変フィルタ５１の波長特性、即ち透過スペクトルのピークの透過率をシミュレーションした結果を示している。図９（Ａ）〜（Ｅ）は、それぞれバビネソレイユ位相板３２を透過して出射する光の光路に沿って図８（Ｂ）に示す各位置Ｐ１〜Ｐ５における光の波長に関する透過率の変化を示している。ここで、λ０は特定波長即ち入射光の波長であり、λは各位置Ｐ１〜Ｐ５における透過光又は出射光の波長である。同図において、実線は、バビネソレイユ位相板３２の光学的厚さが基準値である場合を、破線は、該バビネソレイユ位相板をその光学的厚さを基準値よりも薄くした場合を表している。 9A to 9E show the results of simulating the wavelength characteristics of the wavelength tunable filter 51, that is, the transmittance of the peak of the transmission spectrum. FIGS. 9A to 9E show changes in the transmittance with respect to the wavelength of light at each of the positions P1 to P5 shown in FIG. 8B along the optical path of the light transmitted through the Babinet Soleil phase plate 32 and emitted. Is shown. Here, λ 0 is a specific wavelength, that is, a wavelength of incident light, and λ is a wavelength of transmitted light or outgoing light at each of the positions P1 to P5. In the figure, the solid line represents the case where the optical thickness of the Babenesoleil phase plate 32 is a reference value, and the broken line represents the case where the optical thickness of the Babenesoleil phase plate is made thinner than the reference value. Yes.

入射後に、追加偏光子５２を透過した後の前記光路の位置Ｐ１では、光の透過率は全波長範囲において５０％一定である（図９（Ａ））。第１偏光子３５から反射した後の前記光路の位置Ｐ２では、最初に隣接する前記偏光子間の透過特性を示し、前記特定波長の整数倍となる波長でピークを有する（図９（Ｂ））。次に隣接する前記偏光子間の透過特性は、前記特定波長の１／２波長の整数倍の波長でピークを有するから、第２偏光子３６から反射した後の前記光路の位置Ｐ３では、これと図９（Ｂ）とを重ね合わせた透過特性を示す（図９（Ｃ））。更に次に隣接する前記偏光子間の透過特性は、前記特定波長の１／４波長の整数倍の波長でピークを有するから、第３偏光子３７から反射した後の前記光路の位置Ｐ４では、これを図９（Ｃ）に重ね合わせた透過特性を示す（図９（Ｄ））。最後に隣接する前記偏光子間の透過特性は、前記特定波長の１／８波長の整数倍の波長でピークを有するから、バビネソレイユ位相板３２から出射した後の位置Ｐ５では、これを図９（Ｄ）に重ね合わせた透過特性を示す（図９（Ｅ））。   At the position P1 of the optical path after passing through the additional polarizer 52 after incidence, the light transmittance is constant 50% in the entire wavelength range (FIG. 9A). At the position P2 of the optical path after being reflected from the first polarizer 35, the transmission characteristic between the adjacent polarizers is first shown, and has a peak at a wavelength that is an integral multiple of the specific wavelength (FIG. 9B). ). Next, the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of ½ wavelength of the specific wavelength. Therefore, at the position P3 of the optical path after being reflected from the second polarizer 36, And FIG. 9B show transmission characteristics (FIG. 9C). Further, since the transmission characteristics between the adjacent polarizers have a peak at a wavelength that is an integral multiple of a quarter wavelength of the specific wavelength, at the position P4 of the optical path after being reflected from the third polarizer 37, The transmission characteristics are shown in FIG. 9C (FIG. 9D). Finally, since the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of 1/8 wavelength of the specific wavelength, this is shown in FIG. 9 at position P5 after exiting from the Babenesoleil phase plate 32. FIG. 9D shows the superimposed transmission characteristics (FIG. 9E).

隣接する前記偏光子間の各透過スペクトルのピークは、前記特定波長の整数倍の波長で全て重なるので、波長フィルタ５１は、図９（Ｅ）に示すように、前記特定波長の整数倍で急峻なピークを有する透過特性が得られる。ここで、前記アクチュエータを駆動してバビネソレイユ位相板３２の光学的厚さを変化させると、透過特性は、図９（Ａ）〜（Ｅ）に破線で例示するように、ピーク波長が高波長側又は低波長側にシフトする。   Since the peaks of the transmission spectra between the adjacent polarizers all overlap at a wavelength that is an integral multiple of the specific wavelength, the wavelength filter 51 is steep at an integral multiple of the specific wavelength, as shown in FIG. A transmission characteristic having a large peak is obtained. Here, when the actuator is driven to change the optical thickness of the Babenesoleil phase plate 32, the transmission characteristics have a high peak wavelength as illustrated by broken lines in FIGS. 9 (A) to (E). Shift to the side or low wavelength side.

図１０（Ａ）〜（Ｃ）は、第２実施例の変形例の構成を概略的に示している。本実施例の波長フィルタ５１１は、追加偏光子５２１がバビネソレイユ位相板３２の下側複屈折板３４の下面に前記光路に沿って第２偏光子３６の直ぐ下流側に配置されている点において、第１実施例と異なる。追加偏光子５２１は、ワイヤグリッド偏光子の格子の周期方向が図１の前記偏光子のそれと直交する向きに配向されている。従って、第２偏光子３６と追加偏光子５２１とは、クロスニコルの関係に配置され、それらの間の位相差は１８０°である。追加偏光子５２１の下流側の第３，第４偏光子３７１，３８１は、該追加偏光子と平行ニコルの関係に配置されるように、ワイヤグリッド偏光子の格子の周期方向が図１の前記偏光子のそれと直交する向きに配向される。 FIGS. 10A to 10C schematically show the configuration of a modification of the second embodiment. Wavelength filter 511 of the present embodiment, the additional polarizer 52 1 is disposed immediately downstream of the second polarizer 36 along the optical path on the lower surface of the lower birefringent plate 34 Babinet Soleil phase plate 32 This is different from the first embodiment. Add polarizer 52 1, the periodic direction of the grating of the wire grid polarizer is oriented in a direction perpendicular to that of the polarizer of FIG. Therefore, the second polarizer 36 and the additional polarizer 52 1 is disposed in crossed Nicols relationship, the phase difference between them is 180 °. The third and fourth polarizers 37 1 , 38 1 on the downstream side of the additional polarizer 52 1 are arranged in a parallel Nicols relationship with the additional polarizer so that the periodic direction of the grating of the wire grid polarizer is illustrated. Oriented in a direction perpendicular to that of one of the polarizers.

波長フィルタ５１１への入射光Ｌ1は、上側複屈折板３３上面の前記光入射口からバビネソレイユ位相板３２を透過し、下側反射ミラー４１１により反射されて第１偏光子３５に入射し、ｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子３５を透過し、不要光として外部に出射する。ｐ偏光成分は、前記第１偏光子により前記位相板主面の法線方向に関して同じ反射角度φをもって反射され、バビネソレイユ位相板３２の内部を多重反射しながら透過する。 Incident light L1 to the wavelength filter 51 1 is transmitted through the Babinet Soleil phase plate 32 from the light incident port of the upper birefringent plate 33 upper surface, and enters the first polarizer 35 is reflected by the lower reflecting mirror 41 1 , S-polarized component and p-polarized component. The s-polarized light component passes through the first polarizer 35 and is emitted to the outside as unnecessary light. The p-polarized component is reflected by the first polarizer with the same reflection angle φ with respect to the normal direction of the phase plate main surface, and is transmitted through the Babinet Soleil phase plate 32 while being subjected to multiple reflections.

第１偏光子３５から反射したｐ偏光は、バビネソレイユ位相板３２を透過し、その間にｓ偏光に変換され、下側反射ミラー４１により反射されて再び前記バビネソレイユ位相板を透過し、その間にｐ偏光に変換され、第２偏光子３６に入射して反射する。次に、前記第１偏光子から反射したｐ偏光は、バビネソレイユ位相板３２を透過し、その間にｓ偏光に変換され、追加偏光子５２１に入射する。追加偏光子５２１は、ｓ偏光を反射し、それ以外の光を透過して、不要光として外部に出射する。 The p-polarized light reflected from the first polarizer 35 is transmitted through the Babinet Soleil phase plate 32, converted into s-polarized light in the meantime, reflected by the lower reflection mirror 41, and again transmitted through the Babinet Soleil phase plate. The light is converted into p-polarized light and is incident on the second polarizer 36 and reflected. Then, p-polarized light reflected from said first polarizer is transmitted through the Babinet Soleil phase plate 32, is converted into s-polarized light between them incident to add the polarizer 52 1. Add polarizer 52 1 reflects the s-polarized light, and transmits light of other wavelengths, emitted to the outside as unwanted light.

追加偏光子５２１から反射したｓ偏光は、上側反射ミラー３９１と下側反射ミラー４１２とにより３度反射されて、前記バビネソレイユ位相板を２度往復透過し、第３偏光子３７１に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、ｓ偏光はｐ偏光に、更にｐ偏光からｓ偏光に、２度繰り返して変換される。前記第３偏光子から反射したｓ偏光は、前記上側反射ミラーと下側反射ミラー４１３とにより７度反射されて、前記バビネソレイユ位相板を４度往復透過し、第４偏光子３８１に入射する。その間に前記バビネソレイユ位相板を往復透過する毎に、同様にｓ偏光はｐ偏光に、更にｐ偏光からｓ偏光に、４度繰り返して変換される。第４偏光子３８１は、ｓ偏光を反射し、それ以外の光を透過して、不要光として外部に出射する。第４偏光子３８１から反射したｓ偏光は、前記バビネソレイユ位相板を透過し、その間にｐ偏光に変換されて、前記光出射口から外部に出射する。 S-polarized reflected from the additional polarizer 52 1, is three times reflected by the upper reflecting mirror 39 1 and the lower side reflection mirror 41 2, the Babinet Soleil phase plate twice reciprocating transmission, third polarizer 37 1 Is incident and reflected. In the meantime, every time the light passes back and forth through the Babinet Soleil phase plate, s-polarized light is converted twice into p-polarized light, and further from p-polarized light into s-polarized light. S-polarized reflected from said third polarizer, the are 7 degrees reflected by the upper reflection mirror and the lower side reflection mirror 41 3, the Babinet Soleil phase plate 4 times reciprocally transmits, to the fourth polarizer 38 1 Incident. In the meantime, every time the light passes through the Babinet Soleil phase plate, the s-polarized light is converted to p-polarized light, and further converted from p-polarized light to s-polarized light four times. The fourth polarizer 38 1 reflects the s-polarized light, and transmits light of other wavelengths, emitted to the outside as unwanted light. The 4 s-polarized reflected from the polarizer 38 1 is transmitted through the Babinet Soleil phase plate is converted into the p-polarized light while the emitted to the outside from the light exit opening.

本実施例においても、隣接する偏光子間の位相差が２πの整数倍となる波長可変フィルタ５１１において、その１つの位相差を１８０°とすることにより、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性が得られ、かつ可変波長域を拡大して広帯域化することができる。更に別の実施例では、追加偏光子を２つ以上に増やし、かつ各追加偏光子とそれに隣接する前記偏光子間の位相差Γｊが、前記光路を透過する光の波長に対してΓｊ＝２ｊ−１×２π−π、（但し、ｊ＝１〜ｍ、ｍ：自然数）の関係を満足することにより、πの奇数倍となるように構成して、可変波長域をより拡大することができる。 Also in this embodiment, in the wavelength tunable filter 51 1 the phase difference between the adjacent polarizer is an integral multiple of 2 [pi, by that one of the phase difference and 180 °, conventional Rio filter similar to the bandpass Transmission characteristics as a filter can be obtained, and the variable wavelength range can be expanded to widen the band. In yet another embodiment, increasing the additional polarizer into two or more, and the phase difference gamma j between the polarizer adjacent thereto and each additional polarizer, gamma j with respect to the wavelength of light transmitted through the optical path = 2 j−1 × 2π−π (where j = 1 to m, m: natural number), so that the variable wavelength region is further expanded by being configured to be an odd multiple of π. be able to.

図１１（Ａ）〜（Ｃ）は、本発明による波長フィルタの第３実施例の構成を概略的に示している。本実施例の波長フィルタ６１は、バビネソレイユ位相板６２が上記各実施例よりも短い。バビネソレイユ位相板６２は、上記各実施例と同様に、水晶又は他の類似の光学結晶材料で形成され、同じ楔角θを有する２枚の楔状複屈折板６３，６４を備える。複屈折板６３，６４は、対向する傾斜面を互いに接触させかつそれらを摺動させながら、又は対向する傾斜面を互いに空隙を挟んで離隔した状態で、相対的に動かすことができる。図示しないマイクロメータ等からなるアクチュエータによって、下側の複屈折板６４を幅方向に上側の複屈折板６３に関して相対的に動かし、その光学的厚さを変更することにより、前記バビネソレイユ位相板の透過光の波長を調整することができる。   11A to 11C schematically show the configuration of a third embodiment of the wavelength filter according to the present invention. In the wavelength filter 61 of this embodiment, the Babinet Soleil phase plate 62 is shorter than the above embodiments. Similarly to each of the above embodiments, the Babenesoleil phase plate 62 includes two wedge-shaped birefringent plates 63 and 64 which are made of quartz or other similar optical crystal material and have the same wedge angle θ. The birefringent plates 63 and 64 can be relatively moved while the opposed inclined surfaces are brought into contact with each other and slid therebetween, or the opposed inclined surfaces are separated from each other with a gap therebetween. The lower birefringent plate 64 is moved relative to the upper birefringent plate 63 in the width direction by an actuator composed of a micrometer (not shown), and the optical thickness thereof is changed, so that the Babinet Soleil phase plate can be changed. The wavelength of transmitted light can be adjusted.

図１１（Ｃ）に示すように、バビネソレイユ位相板６２は、一方即ち上側の複屈折板６３が楔角θの楔板６３１と平行平板６３２とで構成され、他方即ち下側の複屈折板６４が楔角θの楔板のみで構成される。楔板６３１と複屈折板６４とは、光学軸Ｏp1，Ｏp2が同じ向きにかつ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向されている。楔板６３１と平行平板６３２とは、光学軸Ｏp1，Ｏp3が互いに直交するようにかつそれぞれ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向される。 As shown in FIG. 11 (C), Babinet Soleil phase plate 62, whereas or upper birefringent plate 63 is constituted by the wedge plate 63 1 and the parallel plate 63 second wedge angle theta, the other i.e. the lower double The refracting plate 64 is composed only of a wedge plate having a wedge angle θ. The wedge plate 63 1 and the birefringent plate 64, the optical axis Op1, Op2 are oriented at 45 ° orientation with respect to the length direction of and the Babinet Soleil phase plate in the same direction. The wedge plate 63 1 and the parallel plate 63 2, the optical axis Op1, Op3 is oriented at 45 ° orientation relative to the longitudinal direction of and each of the Babinet Soleil phase plate so as to be perpendicular to each other.

本実施例では、バビネソレイユ位相板６２の下面及び上面、即ち下側複屈折板６４の下面及び上側複屈折板６３の上面の一方の端部（図中左側）６４ａ，６３ａ付近を光の入射口及び出射口とする。前記バビネソレイユ位相板の上側主面即ち上側複屈折板６３の上面には、第１〜第４偏光子６５〜６８と上側反射ミラー６９とが設けられる。前記光入射口から反対側の端部に向けて、第１、第４及び第２偏光子６５，６８，６６が連続して配置され、次に上側反射ミラー６９を挟んで第３偏光子３７が配置される。前記バビネソレイユ位相板の下側主面即ち下側複屈折板３４の下面には、前記光出射口の部分を空けて、他の部分の全面に下側反射ミラー７０が設けられる。更に本実施例は、バビネソレイユ位相板６２の光入射口とは反対側の端面に垂直反射ミラー７１が設けられている。   In this embodiment, light is incident on the lower and upper surfaces of the Babinet Soleil phase plate 62, that is, near one end (left side in the figure) 64a and 63a of the lower surface of the lower birefringent plate 64 and the upper surface of the upper birefringent plate 63. The mouth and the exit. First to fourth polarizers 65 to 68 and an upper reflecting mirror 69 are provided on the upper main surface of the Babinet Soleil phase plate, that is, the upper surface of the upper birefringent plate 63. First, fourth, and second polarizers 65, 68, 66 are continuously arranged from the light entrance to the opposite end, and then the third polarizer 37 with the upper reflection mirror 69 interposed therebetween. Is placed. On the lower main surface of the Babinet Soleil phase plate, that is, the lower surface of the lower birefringent plate 34, a lower reflection mirror 70 is provided on the entire surface of the other portion with the light exit opening portion therebetween. Further, in this embodiment, a vertical reflection mirror 71 is provided on the end face of the Babinet Soleil phase plate 62 opposite to the light incident port.

第１〜第４偏光子６５〜６８は、ワイヤグリッド偏光子からなる。前記第１〜第４偏光子は、ワイヤグリッド偏光子の格子をバビネソレイユ位相板６２の長さ方向に整合させ、その周期方向が前記バビネソレイユ位相板の光学軸Ｏp1〜Ｏp3と４５°の角度をなし、かつ前記バビネソレイユ位相板の幅方向と一致するように配向する。   The first to fourth polarizers 65 to 68 are wire grid polarizers. The first to fourth polarizers align the grid of the wire grid polarizer with the length direction of the Babenesoleil phase plate 62, and the period direction is an angle of 45 ° with the optical axes Op1 to Op3 of the Babenesoleil phase plate. And oriented so as to coincide with the width direction of the Babinet Soleil phase plate.

波長フィルタ６１への入射光Ｌ1は、下側複屈折板６４下面の前記光入射口からバビネソレイユ位相板６２を透過して第１偏光子６５に入射し、ｓ偏光成分とｐ偏光成分とに分光される。ｓ偏光成分は第１偏光子６５を透過し、不要光として外部に出射する。ｐ偏光成分は、前記第１偏光子により前記位相板の主面の法線方向に関して同じ反射角度φをもって反射され、後述するようにバビネソレイユ位相板６２内部を多重反射しながら透過する。   Incident light L1 to the wavelength filter 61 is transmitted from the light incident port on the lower surface of the lower birefringent plate 64 through the Babinet Soleil phase plate 62 and is incident on the first polarizer 65, where the s-polarized component and p-polarized component are converted. Spectroscopic. The s-polarized light component passes through the first polarizer 65 and is emitted to the outside as unnecessary light. The p-polarized component is reflected by the first polarizer with the same reflection angle φ with respect to the normal direction of the main surface of the phase plate, and passes through the Babinet Soleil phase plate 62 while being multiple-reflected as will be described later.

第１偏光子６５から反射したｐ偏光は、バビネソレイユ位相板６２を透過し、その間にｓ偏光に変換され、下側反射ミラー７０により反射されて再び前記バビネソレイユ位相板を透過し、その間に再びｐ偏光に変換され、第２偏光子７６に入射して反射する。次に、前記第２偏光子から反射したｐ偏光は、前記下側反射ミラーと上側反射ミラー６９とにより３度反射されて、前記バビネソレイユ位相板を２度往復透過し、第３偏光子６７に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、ｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、２度繰り返して変換される。前記第３偏光子から反射したｐ偏光は、前記下側反射ミラーと垂直反射ミラー７１と上側反射ミラー６９とにより８度反射されて、前記バビネソレイユ位相板を４度往復透過し、第４偏光子６８に入射して反射する。その間に前記バビネソレイユ位相板を往復透過する毎に、同様にｐ偏光はｓ偏光に、更にｓ偏光からｐ偏光に、４度繰り返して変換される。最後に、前記第４偏光子から反射したｐ偏光は、再び下側反射ミラー７０に反射されて前記バビネソレイユ位相板を一度往復透過し、その間にｐ偏光からｓ偏光に変換されかつｓ偏光からｐ偏光に戻されて、前記光出射口から外部に出射する。   The p-polarized light reflected from the first polarizer 65 passes through the Babinet Soleil phase plate 62, is converted into s-polarized light in the meantime, is reflected by the lower reflection mirror 70, and passes through the Babinet Soleil phase plate again. The light is again converted to p-polarized light, and enters the second polarizer 76 to be reflected. Next, the p-polarized light reflected from the second polarizer is reflected three times by the lower reflection mirror and the upper reflection mirror 69, and reciprocates twice through the Babinet Soleil phase plate. Is incident and reflected. In the meantime, every time the light passes through the Babinet Soleil phase plate, the p-polarized light is repeatedly converted into s-polarized light, and further from s-polarized light to p-polarized light twice. The p-polarized light reflected from the third polarizer is reflected by the lower reflection mirror, the vertical reflection mirror 71, and the upper reflection mirror 69 by 8 degrees, and is reciprocally transmitted through the Babinet Soleil phase plate by 4 degrees. The light enters the child 68 and is reflected. In the meantime, every time the light passes through the Babinet Soleil phase plate, the p-polarized light is similarly converted into s-polarized light, and further converted from s-polarized light to p-polarized light four times. Finally, the p-polarized light reflected from the fourth polarizer is reflected again by the lower reflecting mirror 70 and once passes back and forth through the Babinet Soleil phase plate, while being converted from p-polarized light to s-polarized light, and from s-polarized light. The light is returned to p-polarized light and is emitted to the outside from the light exit port.

バビネソレイユ位相板６２は、その上側及び下側主面間を光が一度透過する間に１８０°の位相差が与えられるように構成される。従って、前記各偏光子は、前記バビネソレイユ位相板内部を進行する光路に沿って隣接する２つの前記偏光子間の位相差が、順に３６０°、７２０°、１４４０°に、即ち２ｎ−１×２π、（ｎ：１〜３）となるように配置される。このように２つの前記偏光子間の位相差が常に２πの整数倍となるので、波長可変フィルタ３１は、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性が得られる。更に、本実施例は、バビネソレイユ位相板６２を透過する光が前記端面で折り返されて双方向に進行するので、上記各実施例よりも更に部品点数を大幅に少なくでき、かつ特に装置の長さ寸法を小型化することができる。 The Babinet Soleil phase plate 62 is configured such that a phase difference of 180 ° is given while light is once transmitted between its upper and lower main surfaces. Accordingly, each polarizer has a phase difference between two polarizers adjacent to each other along an optical path traveling inside the Babinet Soleil phase plate in order of 360 °, 720 °, and 1440 °, that is, 2 n−1. It arrange | positions so that it may become x2 (pi) and (n: 1-3). Thus, since the phase difference between the two polarizers is always an integer multiple of 2π, the wavelength variable filter 31 can obtain transmission characteristics as a band-pass filter similar to a conventional rio filter. Furthermore, in this embodiment, the light transmitted through the Babinet Soleil phase plate 62 is folded back at the end face and travels in both directions. Therefore, the number of parts can be significantly reduced compared to the above embodiments, and the length of the apparatus is particularly long. The size can be reduced.

別の実施例では、バビネソレイユ位相板６２の前記上側及び下側主面間を光が一度透過する間に与えられる位相差を９０°に設定することができる。その場合、隣接する前記各２つの偏光子間で、前記バビネソレイユ位相板を透過する光の反射回数を２倍にして、所望の位相差が得られるようにする。これにより、波長可変フィルタ６１は、同様に２つの前記偏光子間の位相差を常に２πの整数倍に設定して、従来のリオフィルタと同様のバンドパスフィルタとしての透過特性を得ることができる。   In another embodiment, the phase difference given while light is once transmitted between the upper and lower main surfaces of the Babinet Soleil phase plate 62 can be set to 90 °. In that case, the number of reflections of the light transmitted through the Babinet Soleil phase plate is doubled between the two adjacent polarizers so that a desired phase difference is obtained. As a result, the wavelength tunable filter 61 can similarly set the phase difference between the two polarizers to an integral multiple of 2π to obtain transmission characteristics as a bandpass filter similar to the conventional rio filter. .

また、別の実施例において、波長可変フィルタ６１は、第２実施例の追加偏光子を備えることができる。これにより、同様に、可変波長域を広帯域化することができる。   In another embodiment, the tunable filter 61 may include the additional polarizer of the second embodiment. Thereby, similarly, the variable wavelength region can be widened.

上記各実施例のバビネソレイユ位相板３２，６２は、図１に関連して上述したように、２枚の複屈折板の一方が楔板と平行平板とから構成されている。このように平行平板の複屈折板を組み合わせることによって、バビネソレイユ位相板の位相差を０°から無限大までの広い範囲で自由に設定できるので、透過波長範囲を高い自由度をもって設計することができる。   As described above with reference to FIG. 1, the Babinet Soleil phase plates 32 and 62 of each of the above embodiments are configured such that one of the two birefringent plates is a wedge plate and a parallel plate. By combining parallel birefringent plates in this way, the phase difference of the Babinet Soleil phase plate can be set freely in a wide range from 0 ° to infinity, so the transmission wavelength range can be designed with a high degree of freedom. it can.

別の実施例では、上記実施例と異なる様々な構成のバビネソレイユ位相板を用いることができる。図１２に示すバビネソレイユ位相板３２１は、図１の実施例から平行平板３３２を省略したものである。従って、上側の複屈折板３３は楔板だけで構成される。複屈折板３３，３４の光学軸Ｏp1，Ｏp2は、図１の実施例と同様に、同じ向きにかつ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向されている。この場合、前記第１〜第４偏光子及び前記上側反射ミラーは、楔板の平行平板面３３ｃ上に設けられる。このように２枚の楔板だけでバビネソレイユ位相板を構成することによって、部品点数を最小にし、フィルタ全体の構成を簡単にかつより小型にすることができる。   In another embodiment, various configurations of the Babynet Soleil phase plate different from the above embodiment can be used. 12 is obtained by omitting the parallel plate 332 from the embodiment of FIG. Therefore, the upper birefringent plate 33 is composed only of a wedge plate. The optical axes Op1 and Op2 of the birefringent plates 33 and 34 are oriented in the same direction and at an angle of 45 ° with respect to the length direction of the Babinet Soleil phase plate, as in the embodiment of FIG. In this case, the first to fourth polarizers and the upper reflection mirror are provided on a parallel plate surface 33c of a wedge plate. In this way, by configuring the Babinet Soleil phase plate with only two wedge plates, the number of parts can be minimized, and the overall configuration of the filter can be made simpler and more compact.

図１３に示すバビネソレイユ位相板３２２は、図１の実施例において、両複屈折板３３，３４をそれぞれ上下逆向きにし、上側複屈折板３３の平行平板３３２と下側複屈折板３４の平行平板面３４ｃとを対向させて配置している。楔板３３１及び複屈折板３４の光学軸Ｏp1，Ｏp2は同じ向きにかつ前記バビネソレイユ位相板の長さ方向に対して４５°の向きに配向され、平行平板３３２の光学軸Ｏp3は楔板３３１の光学軸Ｏp1に対して互いに直交するように配向される。この場合、前記第１〜第４偏光子及び前記上側反射ミラーは楔板３３１の傾斜面３３ｄ上に設けられ、前記下側反射ミラーは下側複屈折板３４の傾斜面上に設けられる。本実施例のバビネソレイユ位相板３２２は、位相差を調整する際に、両複屈折板３３，３４をその対向面の面方向と平行に、それらを前記対向面で摺接させた状態でも、より円滑に駆動することができる。   In the embodiment of FIG. 1, the Babinet Soleil phase plate 322 shown in FIG. 13 has both the birefringent plates 33 and 34 turned upside down, and the parallel plate 332 of the upper birefringent plate 33 and the lower birefringent plate 34 are parallel. The flat plate surface 34c is disposed so as to face each other. The optical axes Op1 and Op2 of the wedge plate 331 and the birefringent plate 34 are oriented in the same direction and at an angle of 45 ° with respect to the length direction of the Babinet Soleil phase plate, and the optical axis Op3 of the parallel plate 332 is the wedge plate 331. The optical axes Op1 are oriented so as to be orthogonal to each other. In this case, the first to fourth polarizers and the upper reflecting mirror are provided on the inclined surface 33 d of the wedge plate 331, and the lower reflecting mirror is provided on the inclined surface of the lower birefringent plate 34. Even when the Babinet Soleil phase plate 322 of this embodiment adjusts the phase difference, both the birefringent plates 33 and 34 are parallel to the surface direction of the opposing surface, and are in sliding contact with the opposing surface, It can be driven more smoothly.

図１４に示すバビネソレイユ位相板３２３は、図１３の実施例において、図１２の実施例と同様に平行平板３３２を省略したものである。上側の複屈折板３３は楔板だけで構成され、その平行平板面３３ｃと下側複屈折板３４の平行平板面３４ｃとを対向させて配置される。これにより、バビネソレイユ位相板３２３の位相差を調整する際に、両複屈折板３３，３４をその対向する平行平板面の面方向と平行に、それらを前記平行平板面で摺接させた状態であっても、円滑に駆動できる。更に、２枚の楔板だけでバビネソレイユ位相板を構成することによって、部品点数を最小にし、フィルタ全体の構成を簡単にかつより小型にすることができる。   14 is the same as the embodiment shown in FIG. 12, except that the parallel plate 332 is omitted from the embodiment shown in FIG. The upper birefringent plate 33 is composed only of a wedge plate, and the parallel flat plate surface 33c and the parallel flat plate surface 34c of the lower birefringent plate 34 are arranged to face each other. Thereby, when adjusting the phase difference of the Babinet Soleil phase plate 323, both the birefringent plates 33 and 34 are in sliding contact with the parallel flat plate surface parallel to the surface direction of the opposing parallel flat plate surface. Even so, it can be driven smoothly. Furthermore, by configuring the Babinet Soleil phase plate with only two wedge plates, the number of parts can be minimized, and the overall configuration of the filter can be made simpler and more compact.

図１５に示すバビネソレイユ位相板３２４は、図１３の実施例において、各複屈折板３３，３４が、その傾斜面３３ｄ，３４ｄにそれぞれ同じ楔角θの楔状ガラス板７２，７３を貼り合わせて、平行平板に形成されている。これにより、前記第１〜第４偏光子、前記上側反射ミラー及び下側反射ミラーは、それぞれ平行平板面である楔板７２の上面及び楔板７３の下面に設けられるので、その位置合わせが簡単で製造が容易になる。また、複屈折板３３，３４は、バビネソレイユ位相板３２４の位相差を調整する際に、それらを対向面で摺接させた状態であっても、円滑に駆動できる。   In the embodiment shown in FIG. 13, the birefringent phase plate 324 shown in FIG. 15 has the birefringent plates 33 and 34 bonded to the inclined surfaces 33d and 34d with wedge-shaped glass plates 72 and 73 having the same wedge angle θ. It is formed in a parallel plate. As a result, the first to fourth polarizers, the upper reflection mirror, and the lower reflection mirror are provided on the upper surface of the wedge plate 72 and the lower surface of the wedge plate 73, which are parallel flat surfaces, respectively, so that the alignment is easy. This makes it easy to manufacture. Further, the birefringent plates 33 and 34 can be driven smoothly even when they are in sliding contact with each other when the phase difference of the Babinet Soleil phase plate 324 is adjusted.

図１６に示すバビネソレイユ位相板３２５は、図１５の実施例において、図１２の実施例と同様に上側複屈折板３３から平行平板３３２を省略したものである。これにより、部品点数を少なくし、構成を簡単にすることができる。上側複屈折板３３は、楔板３３１に楔状ガラス板７２を貼り合わせて平行平板に形成され、楔状ガラス板７３を貼り合わせて平行平板に形成した下側複屈折板３４と対向させて配置される。従って、複屈折板３３，３４は、バビネソレイユ位相板３２５の位相差を調整する際に、それらを対向面で摺接させた状態であっても、円滑に駆動できる。   16 is the same as the embodiment of FIG. 12 except that the parallel plate 332 is omitted from the upper birefringent plate 33 in the embodiment of FIG. Thereby, the number of parts can be reduced and the configuration can be simplified. The upper birefringent plate 33 is formed in a parallel plate by bonding a wedge-shaped glass plate 72 to a wedge plate 331, and is disposed to face the lower birefringent plate 34 formed in a parallel plate by bonding a wedge-shaped glass plate 73. The Accordingly, the birefringent plates 33 and 34 can be driven smoothly even when they are in sliding contact with each other when the phase difference of the Babinet Soleil phase plate 325 is adjusted.

図１７に示すバビネソレイユ位相板３２６は、図１２の実施例において、複屈折板３３，３４の光学軸Ｏp1，Ｏp2が、いずれも前記バビネソレイユ位相板の長さ方向と同じ向きに配向されている。一般に複屈折板は、その外周形状に関して光学軸を水平又は垂直な向きに配向すると、特に楔板の加工において製造が簡単になるので有利である。尚、この場合には、複屈折板３３，３４の光学軸の向きに対応して、バビネソレイユ位相板３２６の上側及び下側主面に設けられる偏光子の偏光軸を、図１の実施例の場合から４５°回転させた向きに配向する必要がある。   In the embodiment shown in FIG. 12, the optical axis Op1 and Op2 of the birefringent plates 33 and 34 are all oriented in the same direction as the length direction of the Babenesoleil phase plate. Yes. In general, it is advantageous to orient the optical axis in the horizontal or vertical orientation with respect to the outer peripheral shape of the birefringent plate, since this makes it easy to manufacture especially in processing of a wedge plate. In this case, the polarization axes of the polarizers provided on the upper and lower principal surfaces of the Babinet Soleil phase plate 326 corresponding to the orientations of the optical axes of the birefringent plates 33 and 34 are set as shown in the embodiment of FIG. In this case, it is necessary to orient in the direction rotated by 45 °.

更に別の実施例では、図１５及び図１６の実施例において、複屈折板３３，３４をそれぞれ上下逆向きにし、かつそれらに貼り付けた楔状ガラス板７２，７３同士を対向させた向きに配置することができる。また、これら様々な構成のバビネソレイユ位相板は、図３乃至図８、図１０及び図１１の各実施例についても、同様に適用することができる。   In another embodiment, the birefringent plates 33 and 34 are turned upside down in the embodiment shown in FIGS. 15 and 16, and the wedge-shaped glass plates 72 and 73 attached to them are arranged so as to face each other. can do. Further, these various configurations of the Babinet Soleil phase plate can be similarly applied to the embodiments shown in FIGS. 3 to 8, 10 and 11.

本発明は、上記実施例に限定されるものでなく、その技術的範囲内で様々な変形又は変更を加えて実施することができる。例えば、バビネソレイユ位相板は、従来から公知の様々な形態のものを同様に用いることができる。また、各偏光子及び反射ミラーは、バビネソレイユ位相板主面の上記各実施例以外の様々な位置に配置することができる。更に、前記偏光子及び反射ミラーの数を増やして、より多段の波長可変フィルタを構成することができる。また、バビネソレイユ位相板主面の各偏光子は、吸収型偏光板と反射ミラーとを組み合わせて構成することもできる。   The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, various types of conventionally known various types of Babinet Soleil phase plates can be used as well. In addition, each polarizer and reflection mirror can be arranged at various positions other than the above-described embodiments on the main surface of the Babinet Soleil phase plate. Furthermore, the number of the polarizers and the reflection mirrors can be increased to configure a multistage wavelength tunable filter. In addition, each polarizer on the main surface of the Babinet Soleil phase plate can be configured by combining an absorptive polarizing plate and a reflecting mirror.

（Ａ）図は、本発明による波長可変フィルタの第１実施例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing a first embodiment of a wavelength tunable filter according to the present invention, (B) is a side view showing the traveling direction of light, and (C) is an end face on the incident side. Figure. （Ａ）〜（Ｄ）図はそれぞれ第１実施例の透過特性を示す線図。(A)-(D) are diagrams each showing the transmission characteristics of the first embodiment. （Ａ）図は、第１実施例の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing a modification of the first embodiment, (B) is a side view along the light traveling direction, and (C) is an end view on the incident side. （Ａ）図は、第１実施例の別の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。FIG. 5A is a plan view schematically showing another modification of the first embodiment, FIG. 5B is a side view showing the traveling direction of light, and FIG. 5C is an end view on the incident side. （Ａ）図は、第１実施例の更に別の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing along the traveling direction of light, and (C) is an end view on the incident side. . （Ａ）図は、第１実施例の更に別の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing along the traveling direction of light, and (C) is an end view on the incident side. . （Ａ）図は、第１実施例の更に別の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing along the traveling direction of light, and (C) is an end view on the incident side. . （Ａ）図は、本発明による波長可変フィルタの第２実施例を概略的に示す平面図、（Ｂ）図はその光の進行方向に沿って示す側面図、（Ｃ）図はその入射側の端面図。(A) is a plan view schematically showing a second embodiment of a wavelength tunable filter according to the present invention, (B) is a side view showing the light traveling direction, and (C) is an incident side thereof. End view. （Ａ）〜（Ｅ）図はそれぞれ第２実施例の透過特性を示す線図。(A)-(E) are diagrams each showing the transmission characteristics of the second embodiment. （Ａ）図は、第２実施例の変形例を概略的に示す平面図、（Ｂ）図は光の進行方向に沿って示す側面図、（Ｃ）図は入射側の端面図。(A) is a plan view schematically showing a modification of the second embodiment, (B) is a side view along the light traveling direction, and (C) is an end view on the incident side. （Ａ）図は、本発明による波長可変フィルタの第３実施例を概略的に示す平面図、（Ｂ）図はその光の進行方向に沿って示す側面図、（Ｃ）図はその入射側の端面図。(A) is a plan view schematically showing a third embodiment of a wavelength tunable filter according to the present invention, (B) is a side view showing the light traveling direction, and (C) is an incident side thereof. End view. （Ａ）図は、バビネソレイユ位相板の別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing another embodiment of a Babinet Soleil phase plate, (B) is a plan view thereof. （Ａ）図は、バビネソレイユ位相板の更に別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing still another embodiment of a Babinet Soleil phase plate, and (B) is a plan view thereof. （Ａ）図は、バビネソレイユ位相板の更に別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing still another embodiment of a Babinet Soleil phase plate, and (B) is a plan view thereof. （Ａ）図は、バビネソレイユ位相板の更に別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing still another embodiment of a Babinet Soleil phase plate, and (B) is a plan view thereof. （Ａ）図は、バビネソレイユ位相板の更に別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing still another embodiment of a Babinet Soleil phase plate, and (B) is a plan view thereof. （Ａ）図は、バビネソレイユ位相板の更に別の実施例を示す側面図、（Ｂ）図はその平面図。(A) is a side view showing still another embodiment of a Babinet Soleil phase plate, and (B) is a plan view thereof. リオフィルタの基本的構成を示す図。The figure which shows the basic composition of a Rio filter. 液晶セルを用いた従来例の構成図。The block diagram of the prior art example using a liquid crystal cell. 液晶セルを用いた別の従来例の構成図。The block diagram of another prior art example using a liquid crystal cell.

符号の説明Explanation of symbols

１…リオフィルタ、２ａ〜２ｄ，１２ａ〜１２ｄ，２２ａ〜２２ｄ，３５〜３８，３７１，３８１，５２，５２１，６５〜６８…偏光子、２a1〜２d1，１２a1〜１２d11…透過軸、３ａ〜３ｃ…複屈折板、３a1〜３c1…光学軸、４…光軸、１１…バンドパスフィルタ、１３ａ〜１３ｃ，２３ａ〜２３ｃ，４３…液晶セル、２１，３１，３１１〜３１５，５１，５１１，６１…波長可変フィルタ、２４ａ〜２４ｃ…位相差フィルム、３２，３２１〜３２６，６２…バビネソレイユ位相板、３３，３４，６３，６４…楔状複屈折板、３３１，６３１…楔板、３３２，６３２…平行平板、３３ａ，３３ｂ，３４ａ，３４ｂ，６３ａ，６４ａ…端部、３３ｃ，３４ｃ…平行平板面、３３ｄ，３４ｄ…傾斜面、３９〜４１，３９１，４１１〜４１３，７０，７１…反射ミラー、７２，７３…楔状ガラス板。 1 ... Rio filter, 2a~2d, 12a~12d, 22a~22d, 35~38,37 1, 38 1, 52,52 1, 65~68 ... polarizer, 2A1～2d1,12a1～12d11 ... transmission shaft, 3a to 3c: birefringent plate, 3a1 to 3c1: optical axis, 4 ... optical axis, 11: band pass filter, 13a-13c, 23a-23c, 43 ... liquid crystal cell, 21, 31, 31 1 to 31 5 , 51 , 51 1 , 61 ... wavelength tunable filter, 24a to 24c ... retardation film, 32, 32 1 to 32 6 , 62 ... babynesoleil phase plate, 33, 34, 63, 64 ... wedge-shaped birefringent plate, 33 1 , 63 1 ... wedge plate, 33 2, 63 2 ... parallel plates, 33a, 33b, 34a, 34b , 63a, 64a ... end, 33c, 34c ... parallel plate surfaces, 33d, 34d ... inclined surface, 39～41,39 1 , 41 1 -41 < 3 >, 70,71 ... reflection mirror, 72, 73 ... wedge-shaped glass plate.

Claims (14)

第１主面及び第２主面を有する位相差素子と、前記第１主面及び第２主面に設けられた複数の偏光子と反射ミラーとを備え、
前記位相差素子が、一端から他端に向けて厚さを薄くした楔状をなしかつ互いに対向させて配置した２枚の位相差板からなり、前記２枚の位相差板が、前記位相差素子の厚さを変化させるように相対的に変位可能であり、
前記位相差素子に入射した光が、該位相差素子内部を前記偏光子と前記反射ミラーとの間で前記主面の法線方向に関して一定の角度をもって多重反射して透過し、前記位相差素子から出射することを特徴とする波長可変フィルタ。 A retardation element having a first main surface and a second main surface, and a plurality of polarizers and reflection mirrors provided on the first main surface and the second main surface,
The phase difference element is composed of two phase difference plates arranged in a wedge shape with a thickness reduced from one end to the other end and facing each other, and the two phase difference plates are the phase difference elements. Is relatively displaceable to change the thickness of
The light incident on the phase difference element passes through the phase difference element through multiple reflection at a certain angle with respect to the normal direction of the main surface between the polarizer and the reflection mirror. A wavelength tunable filter that emits light from a light source. 前記位相差素子内部を透過する前記光の光路に沿って隣接する２つの前記偏光子間の位相差Γｉが、前記光路を透過する光の波長に対してΓｉ＝２ｉ−１×２π、（但し、ｉ＝１〜ｎ、ｎ：２以上の整数）の関係を満足することを特徴とする請求項１記載の波長可変フィルタ。 The phase difference Γ i between the two polarizers adjacent to each other along the optical path of the light passing through the inside of the retardation element is Γ i = 2 i−1 × 2π with respect to the wavelength of the light passing through the optical path. The wavelength tunable filter according to claim 1, wherein the following relationship is satisfied: (where i = 1 to n, n: integer of 2 or more). 前記位相差素子内部を透過する前記光の光路に沿って隣接する２つの前記偏光子間の少なくとも１つの位相差Γｊが、前記光路を透過する光の波長に対してΓｊ＝２ｊ−１×２π−π、（但し、ｊ＝１〜ｍ、ｍ：自然数）の関係を満足することを特徴とする請求項２記載の波長可変フィルタ。 At least one phase difference Γ j between two polarizers adjacent to each other along the optical path of the light passing through the inside of the retardation element is Γ j = 2 j− with respect to the wavelength of the light passing through the optical path. The wavelength tunable filter according to claim 2, wherein a relationship of 1 × 2π−π (where j = 1 to m, m: natural number) is satisfied. 前記位相差素子内部を透過する前記光の光路に沿って隣接する２つの前記偏光子が平行ニコル又はクロスニコルの関係に配置されていることを特徴とする請求項１乃至３のいずれか記載の波長可変フィルタ。   The two said polarizers which adjoin along the optical path of the said light which permeate | transmits the inside of said phase difference element are arrange | positioned in the relationship of parallel Nicol or crossed Nicol, The Claim 1 thru | or 3 characterized by the above-mentioned. Tunable filter. 前記位相差素子への前記光の入射口と出射口とが互いに異なる前記主面に設けられることを特徴とする請求項１乃至４のいずれか記載の波長可変フィルタ。   5. The wavelength tunable filter according to claim 1, wherein an entrance and an exit of the light to the phase difference element are provided on the main surfaces different from each other. 6. 前記位相差素子への前記光の入射口と出射口とが一方の前記主面に設けられることを特徴とする請求項１乃至４のいずれか記載の波長可変フィルタ。   The wavelength tunable filter according to claim 1, wherein an entrance and an exit of the light to the phase difference element are provided on one main surface. 前記偏光子がワイヤグリッド偏光子であることを特徴とする請求項１乃至６のいずれか記載の波長可変フィルタ。   The wavelength tunable filter according to claim 1, wherein the polarizer is a wire grid polarizer. 前記偏光子がワイヤグリッド偏光子であり、かつ全ての前記偏光子が前記位相差素子の一方の前記主面に設けられ、前記位相差素子の前記光の出射口が他方の前記主面に設けられることを特徴とする請求項１乃至７のいずれか記載の波長可変フィルタ。   The polarizer is a wire grid polarizer, and all the polarizers are provided on one main surface of the phase difference element, and the light exit of the phase difference element is provided on the other main surface. The wavelength tunable filter according to claim 1, wherein the wavelength tunable filter is provided. 前記位相差素子の端面に設けられた垂直反射ミラーを更に有し、前記位相差素子内部を透過する前記光が前記垂直反射ミラーにより反射されて逆向きに進行することを特徴とする請求項１乃至８のいずれか記載の波長可変フィルタ。   2. The apparatus according to claim 1, further comprising a vertical reflection mirror provided on an end face of the phase difference element, wherein the light transmitted through the phase difference element is reflected by the vertical reflection mirror and travels in the opposite direction. The wavelength tunable filter according to any one of 1 to 8. 前記２板の位相差板が、平行平板の一方の面をそのままにして反対側の面を所定の楔角で傾斜加工して形成され、その傾斜面を互いに対向させ、かつ互いに厚さの厚い方の端部と厚さの薄い方の端部とを同じ側にして互違いに配置されることを特徴とする請求項１乃至９のいずれか記載の波長フィルタ。   The two retardation plates are formed by inclining the opposite surface with a predetermined wedge angle while leaving one surface of the parallel plate as it is, with the inclined surfaces facing each other and having a large thickness. The wavelength filter according to any one of claims 1 to 9, wherein one end portion and the one end portion having a smaller thickness are disposed alternately with the same end portion being the same side. 前記２枚の位相差板が、平行平板の一方の面をそのままにして反対側の面を所定の楔角で傾斜加工して形成され、前記一方の面を互いに対向させ、かつ互いに厚さの厚い方の端部と厚さの薄い方の端部とを同じ側にして互違いに配置されることを特徴とする請求項１乃至９のいずれか記載の波長フィルタ。   The two retardation plates are formed by inclining one surface of a parallel plate while keeping one surface of the parallel plate as it is, with the one surface facing each other and having a thickness of each other. The wavelength filter according to any one of claims 1 to 9, wherein the thicker end portion and the thinner end portion are arranged in a staggered manner on the same side. 前記２枚の位相差板が、それらの結晶光学軸を互いに平行に配置されることを特徴とする請求項１乃至１１のいずれか記載の波長フィルタ。   The wavelength filter according to claim 1, wherein the two retardation plates are arranged such that their crystal optical axes are parallel to each other. 前記２枚の位相差板が、それらの結晶光学軸を互いに直交させて配置されることを特徴とする請求項１乃至１１のいずれか記載の波長フィルタ。   The wavelength filter according to claim 1, wherein the two retardation plates are arranged with their crystal optical axes orthogonal to each other. 前記第１及び第２位相差素子の少なくとも一方が、少なくとも一方の前記位相差板と組み合わせた平行平板の位相差板を更に有することを特徴とする請求項１乃至１３のいずれか記載の波長フィルタ。   The wavelength filter according to any one of claims 1 to 13, wherein at least one of the first and second phase difference elements further includes a parallel plate phase difference plate combined with at least one of the phase difference plates. .
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