JP2012137648A - Imaging optical unit - Google Patents

Imaging optical unit Download PDF

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JP2012137648A
JP2012137648A JP2010290429A JP2010290429A JP2012137648A JP 2012137648 A JP2012137648 A JP 2012137648A JP 2010290429 A JP2010290429 A JP 2010290429A JP 2010290429 A JP2010290429 A JP 2010290429A JP 2012137648 A JP2012137648 A JP 2012137648A
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light
infrared
cut filter
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infrared cut
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JP5759717B2 (en
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Yasuhiro Sato
安紘 佐藤
Michio Yanagi
道男 柳
Shinji Uchiyama
真志 内山
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Canon Electronics Inc
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Abstract

PROBLEM TO BE SOLVED: To reduce degradation of image quality by ghost light caused between an infrared cut filter and an imaging element.SOLUTION: A light absorption structure 4 for absorbing light of an infrared half value wavelength of an infrared cut filter 1 is disposed on a surface opposed to an imaging element 5. Thus, light transmitted through the filter 1 and reflected by the imaging element 5 is transmitted through the light absorption structure 4 before reaching a near infrared reflection structure 3 of the filter 1, so that reflection light by the reflection structure 3 can be reduced. The reflection light reflected by the imaging element 5 and reflected by the reflection structure 3 is transmitted through the light absorption structure 4 again before reaching the imaging element 5, so that reflectance by incident light from the imaging element 5 can be reduced.

Description

本発明は、固体撮像素子を用いたビデオカメラ、デジタルスチルカメラ、監視用カメラ等に搭載する撮像光学ユニットに関するものである。   The present invention relates to an imaging optical unit mounted on a video camera, a digital still camera, a surveillance camera, or the like using a solid-state imaging device.

従来から、ビデオカメラ或いはデジタルスチルカメラ等の撮像系には、ＣＣＤ（Charge Coupled Device）やＣＭＯＳ（Complementary Metal Oxide Semiconductor）センサ等から成る撮像素子が用いられている。これらの撮像素子は比較的広い光波長において感度を有しており、可視波長領域の光に加えて近赤外波長領域の光にも感度を有している。しかし、通常のカメラの用途においては、人間の眼に見えない赤外波長領域は不要である。このため、カメラ等の撮像光学系には、撮像素子の入射光側に赤外は跳梁域の光を遮蔽する赤外線カットフィルタを配置し、赤外光が撮像素子に入射することを防いでいる。   Conventionally, imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors have been used in imaging systems such as video cameras and digital still cameras. These image sensors have sensitivity in a relatively wide light wavelength, and also have sensitivity in light in the near-infrared wavelength region in addition to light in the visible wavelength region. However, in an ordinary camera application, an infrared wavelength region that is invisible to the human eye is unnecessary. For this reason, in an imaging optical system such as a camera, an infrared cut filter that shields light in the jump beam region is disposed on the incident light side of the imaging element to prevent infrared light from entering the imaging element. .

赤外線カットフィルタには、赤外線を反射させる反射タイプのものと、赤外線を吸収する吸収タイプのものがある。   Infrared cut filters include a reflective type that reflects infrared rays and an absorption type that absorbs infrared rays.

反射タイプの赤外線カットフィルタは、透明基板上に真空蒸着法やＩＡＤ法、イオンプレーティング法、スパッタ法等によって多層膜を積層することにより作製し光の干渉により反射させている。また、近年においては軽量化や任意形状への加工等の要望に伴い、基板に合成樹脂製のものも用いられている。   The reflection type infrared cut filter is manufactured by laminating a multilayer film on a transparent substrate by vacuum deposition, IAD, ion plating, sputtering, or the like, and is reflected by light interference. Further, in recent years, substrates made of synthetic resin have been used in response to demands for weight reduction and processing into arbitrary shapes.

一方、吸収タイプの赤外線カットフィルタは、金属イオン等により赤外線を吸収させたり、基材となる樹脂中に金属イオンや色素を練り込んだり、透明基板上に赤外線を吸収する色素を塗布することにより作製されている。   On the other hand, an absorption type infrared cut filter absorbs infrared rays by metal ions, kneads metal ions and pigments in a resin as a base material, or applies a pigment that absorbs infrared rays on a transparent substrate. Have been made.

特開２００３−１６１８３１号公報JP 2003-161831 A 特開２０００−７８７０号公報JP 2000-7870 A 特開２００２−３０３７２０号公報JP 2002-303720 A 特開２００２−２８１５１５号公報JP 2002-281515 A 特開２００６−３０１４８９号公報JP 2006-301894A 特開２００８−５１９８５号公報JP 2008-51985 A 特開２００８−１１２０３３号公報JP 2008-112033 A

特許文献１においては、透明基板上に低屈折材料と高屈折材料とを複数積層させることにより近赤外光反射構造体を形成し、所望の分光特性を得る反射タイプの赤外線カットフィルタが開示されている。反射タイプの赤外線カットフィルタは吸収タイプと比較すると薄く作製することができ、更に透過波長領域における透過率が高く、色再現性が良いという利点を有している。   Patent Document 1 discloses a reflection-type infrared cut filter that forms a near-infrared light reflecting structure by laminating a plurality of low-refractive materials and high-refractive materials on a transparent substrate to obtain desired spectral characteristics. ing. The reflection type infrared cut filter can be manufactured thinner than the absorption type, and further has an advantage of high transmittance in the transmission wavelength region and good color reproducibility.

しかし、この反射タイプの赤外線カットフィルタは、光を透過させる透過波長領域と、透過を妨げる不透過波長領域と、透過波長領域から不透過波長領域へと遷移する遷移波長領域を持っている。遷移波長領域は６００〜７５０ｎｍの間の波長において、透過率が５０％となる波長（赤外光半値波長）を有し、その波長における反射率は概ね５０％となる。このため、遷移波長領域の赤外光半値波長の光はゴースト光の原因となり、画質の劣化を引き起こし易い。   However, this reflection type infrared cut filter has a transmission wavelength region that transmits light, a non-transmission wavelength region that prevents transmission, and a transition wavelength region that transitions from the transmission wavelength region to the non-transmission wavelength region. The transition wavelength region has a wavelength (infrared light half-value wavelength) at which the transmittance is 50% at a wavelength between 600 and 750 nm, and the reflectance at that wavelength is approximately 50%. For this reason, infrared half-wavelength light in the transition wavelength region causes ghost light and is likely to cause deterioration in image quality.

赤外線カットフィルタによるゴースト光の強度は、簡易的には（赤外線カットフィルタの分光透過率）・（赤外線カットフィルタの面の分光反射率）で計算された値が目安となる。   The intensity of the ghost light by the infrared cut filter is simply a value calculated by (spectral transmittance of the infrared cut filter) / (spectral reflectance of the surface of the infrared cut filter).

特許文献２においては、基材の樹脂中に銅イオン等を含有させた吸収タイプの赤外線カットフィルタが開示されている。これは銅イオン等の赤外線吸収作用を利用して赤外線カットフィルタを作製し、赤外光半値波長における反射率は小さく、ゴースト光の要因となることはない。しかし、近赤外波長領域の光を十分に吸収させるためには、少なくとも０．３５ｍｍ以上の厚さが必要となり、特に求められている近年の光学系の小型化の要望に相反する。   Patent Document 2 discloses an absorption-type infrared cut filter in which copper ions or the like are contained in a base resin. This produces an infrared cut filter using an infrared absorption action of copper ions or the like, and has a low reflectance at the half-wavelength of infrared light, and does not cause ghost light. However, in order to sufficiently absorb light in the near-infrared wavelength region, a thickness of at least 0.35 mm is required, which is in conflict with the recent demand for miniaturization of optical systems that is particularly required.

特許文献３においては、基板上に色素を塗布した吸収タイプの赤外線カットフィルタが開示されており、近赤外波長領域の光を吸収する色素を樹脂や有機溶媒に分散させた塗布液を用いて作製している。しかし、このように作製された赤外線カットフィルタは特許文献２と同様に、ゴースト光による画質劣化を引き起こすことは殆どないが、色素は可視波長領域の光も若干吸収し、近赤外波長領域において十分に吸収させると可視波長領域の透過率が低下してしまう。   In patent document 3, the absorption type infrared cut filter which apply | coated the pigment | dye on the board | substrate is disclosed, Using the coating liquid which disperse | distributed the pigment | dye which absorbs the light of a near-infrared wavelength range to resin or an organic solvent. I am making it. However, the infrared cut filter produced in this way hardly causes image quality degradation due to ghost light, as in Patent Document 2, but the dye absorbs light in the visible wavelength region slightly, and in the near infrared wavelength region. If it is sufficiently absorbed, the transmittance in the visible wavelength region is lowered.

特許文献４においては、赤外線カットフィルタと撮像素子との間に、赤外線カットフィルタの赤外光半値波長の光を吸収するカラーフィルタを配置した撮像光学系が開示されている。このような構成とすることにより、ゴースト光の発生を著しく低減することは可能であるが、別途にカラーフィルタが必要となり、撮像光学系の大型化や高コスト化を招来する。   Patent Document 4 discloses an imaging optical system in which a color filter that absorbs light of an infrared light half-value wavelength of an infrared cut filter is disposed between the infrared cut filter and the imaging element. With such a configuration, it is possible to significantly reduce the generation of ghost light, but a separate color filter is required, leading to an increase in the size and cost of the imaging optical system.

特許文献５、６はフィルタの薄型化を目的として、干渉膜から成る近赤外光反射構造体と、赤外線を吸収する色素による光吸収構造体を設けたハイブリットタイプの赤外線カットフィルタが開示されている。このような構成とすることにより、４００〜７００ｎｍの波長の可視波長領域における透過率を維持しながら、近赤外波長領域の光を遮蔽する薄型の赤外線カットフィルタを作製することができる。   Patent Documents 5 and 6 disclose, for the purpose of thinning the filter, a hybrid type infrared cut filter provided with a near-infrared light reflecting structure made of an interference film and a light absorbing structure made of a dye that absorbs infrared light. Yes. By setting it as such a structure, the thin infrared cut filter which shields the light of a near-infrared wavelength range can be produced, maintaining the transmittance | permeability in the visible wavelength range of a wavelength of 400-700 nm.

しかし特許文献５、６に示すように、可視波長領域の透過率を高く維持する構成にすると、ゴースト光の主な要因となる６００〜７５０ｎｍの波長に存在する近赤外光反射構造体の赤外光半値波長の光を十分に吸収することができなくなる。そのため、ゴースト光による画質の劣化を大きく改善することは困難である。また特許文献５、６においては、ゴースト光の発生をより低減させる光吸収構造体の配置場所については記載されていない。   However, as shown in Patent Documents 5 and 6, when the transmittance in the visible wavelength region is maintained high, the red of the near-infrared light reflecting structure existing at a wavelength of 600 to 750 nm, which is a main factor of ghost light, It becomes impossible to sufficiently absorb light of half-wavelength of outside light. For this reason, it is difficult to greatly improve image quality degradation due to ghost light. Further, Patent Documents 5 and 6 do not describe the location of the light absorption structure that further reduces the generation of ghost light.

監視カメラ等のように、近赤外波長領域の感度が高い撮像素子を用いる場合には、赤外線カットフィルタに起因するゴースト光が発生し易く、光吸収構造体の配置位置を最適にし、ゴースト光の強度を極力低減することが望まれている。   When using an image sensor with high sensitivity in the near-infrared wavelength region, such as a surveillance camera, ghost light due to the infrared cut filter is likely to be generated, and the arrangement position of the light absorbing structure is optimized, and the ghost light It is desired to reduce the strength of the as much as possible.

本発明の目的は、上述の問題点を解消し、ハイブリットタイプの赤外線カットフィルタにおいて、光吸収構造体の光吸収特性や配置位置等を最適にすることにより、ゴースト光による画質劣化を抑制する撮像光学ユニットを提供することである。   An object of the present invention is to eliminate the above-described problems and optimize the light absorption characteristics and arrangement position of a light absorption structure in a hybrid type infrared cut filter, thereby suppressing image quality deterioration due to ghost light. An optical unit is provided.

上記目的を達成するための本発明に係る撮像光学ユニットは、赤外線カットフィルタと撮像素子とから成り、前記赤外線カットフィルタは、透明基板と近赤外光反射構造体と所定の吸収波長領域を有する光吸収構造体とを有し、前記近赤外光反射構造体は少なくとも６００〜７５０ｎｍの波長の間に透過波長領域から不透過波長領域に遷移する遷移波長領域を有し、前記光吸収構造体の前記吸収波長領域の少なくとも一部は前記遷移波長領域と重なり、前記光吸収構造体は前記遷移波長領域を有する近赤外反射構造体と前記撮像素子との間に配置したことを特徴とする。   In order to achieve the above object, an imaging optical unit according to the present invention includes an infrared cut filter and an image sensor, and the infrared cut filter has a transparent substrate, a near infrared light reflecting structure, and a predetermined absorption wavelength region. The near-infrared light reflecting structure has a transition wavelength region transitioning from a transmission wavelength region to a non-transmission wavelength region between wavelengths of at least 600 to 750 nm, and the light absorption structure At least part of the absorption wavelength region overlaps with the transition wavelength region, and the light absorption structure is disposed between the near-infrared reflective structure having the transition wavelength region and the imaging device. .

本発明に係る撮像光学ユニットによれば、赤外光半値波長を有する近赤外光反射構造体と撮像素子との間に光吸収構造体を配置することにより、赤外光半値波長近辺に高い感度を有する撮像素子を使用しても、ゴースト光による画質劣化を抑制できる。   According to the imaging optical unit according to the present invention, by arranging the light absorption structure between the near-infrared light reflection structure having the half-wavelength of infrared light and the imaging element, the vicinity of the half-wavelength of infrared light is high. Even when an image sensor having sensitivity is used, image quality deterioration due to ghost light can be suppressed.

実施例１の撮像光学ユニットの構成図である。FIG. 2 is a configuration diagram of an imaging optical unit of Example 1. シアニン系の色素の光学特性のグラフ図である。It is a graph of the optical characteristics of a cyanine dye. 監視用カメラに用いられる撮像素子の感度特性のグラフ図である。It is a graph of the sensitivity characteristic of the image sensor used for the surveillance camera. ゴースト光の強度特性のグラフ図である。It is a graph of the intensity characteristic of ghost light. 変形例の撮像光学ユニットの構成図である。It is a block diagram of the imaging optical unit of a modification. 実施例２の撮像光学ユニットの構成図である。FIG. 6 is a configuration diagram of an imaging optical unit of Example 2. ゴースト光の強度特性のグラフ図である。It is a graph of the intensity characteristic of ghost light. 変形例の撮像光学ユニットの構成図である。It is a block diagram of the imaging optical unit of a modification. 実施例３の撮像光学ユニットの構成図である。FIG. 6 is a configuration diagram of an imaging optical unit of Example 3. 近赤外光反射防止構造体の構成図である。It is a block diagram of a near-infrared-light reflection prevention structure. ゴースト光の強度特性のグラフ図である。It is a graph of the intensity characteristic of ghost light. 撮像光学系の構成図である。It is a block diagram of an imaging optical system.

本発明を図示の実施例に基づいて詳細に説明する。   The present invention will be described in detail based on the embodiments shown in the drawings.

図１は実施例１の撮像光学ユニットの構成図を示している。赤外線カットフィルタ１は、透明基板２上に近赤外光反射構造体３、光吸収構造体４を積層した構成とされ、この赤外線カットフィルタ１の光吸収構造体４側の光路上に固体撮像素子５が配置されている。   FIG. 1 is a configuration diagram of an imaging optical unit according to the first embodiment. The infrared cut filter 1 has a configuration in which a near-infrared light reflecting structure 3 and a light absorbing structure 4 are laminated on a transparent substrate 2, and solid-state imaging is performed on the optical path on the light absorbing structure 4 side of the infrared cut filter 1. Element 5 is arranged.

本実施例１において、透明基板２には板厚０．２ｍｍのガラス基板、具体的にはＯＡ−１０Ｇ（日本電気硝子社製、商品名）を用いている。なお、透明基板２はポリカーボネートやＰＥＮ、ポリイミド系等の合成樹脂製基板を用いてもよいが、近赤外光反射構造体３の成膜による熱、水分による分光特性の変化等を考慮すると、耐熱性つまりガラス転移点Ｔｇが高く、吸水率が低いものがより好ましい。   In Example 1, a glass substrate having a thickness of 0.2 mm, specifically OA-10G (trade name, manufactured by Nippon Electric Glass Co., Ltd.) is used for the transparent substrate 2. The transparent substrate 2 may be a substrate made of synthetic resin such as polycarbonate, PEN, or polyimide, but considering the change in spectral characteristics due to heat, moisture, etc. due to the film formation of the near-infrared light reflecting structure 3, It is more preferable that the heat resistance, that is, the glass transition point Tg is high and the water absorption is low.

近赤外光反射構造体３は透明基板２上に、屈折率が異なるＳｉＯ2とＴｉＯ2とを真空蒸着法により複数積層させることにより成膜している。反射構造体３の分光特性はＳｉＯ2とＴｉＯ2の光学膜厚ｎ・ｄ（ｎ：屈折率、ｄ：物理膜厚）により決定する。また、反射構造体３は６００〜７５０ｎｍの波長の間に透過波長領域から不透過波長領域にかけて連続的に透過率が減少する遷移波長領域に、透過率と反射率が共に概ね５０％となる波長（赤外光半値波長）を有している。そして、この反射構造体３は近赤外波長領域の光を遮蔽するように膜設計されている。 The near-infrared light reflecting structure 3 is formed on the transparent substrate 2 by laminating a plurality of SiO 2 and TiO 2 having different refractive indexes by a vacuum deposition method. The spectral characteristics of the reflective structure 3 are determined by the optical film thickness n · d (n: refractive index, d: physical film thickness) of SiO 2 and TiO 2 . The reflection structure 3 has a wavelength at which both the transmittance and the reflectance are approximately 50% in the transition wavelength region where the transmittance continuously decreases from the transmission wavelength region to the non-transmission wavelength region between wavelengths of 600 to 750 nm. (Infrared light half-value wavelength). The reflecting structure 3 is designed as a film so as to shield light in the near infrared wavelength region.

本実施例においては、近赤外光反射構造体３にＳｉＯ2とＴｉＯ2を使用しているが、例えばＭｇＦ2、Ａｌ2Ｏ3、ＭｇＯ、ＺｒＯ2、Ｎｂ2Ｏ5、Ｔａ2Ｏ5等を用いてもよく、所望の分光特性に適した材料を適宜に選択すればよい。また、本実施例において反射構造体３は真空蒸着法により成膜したが、真空蒸着法以外のイオンプレーティング法、イオンアシスト蒸着法、スパッタリング法等の成膜方法によっても成膜が可能であり、目的や条件に最も適した成膜方法を選択すればよい。 In the present embodiment, SiO 2 and TiO 2 are used for the near-infrared light reflecting structure 3. For example, MgF 2 , Al 2 O 3 , MgO, ZrO 2 , Nb 2 O 5 , Ta 2 O 5 are used. May be used, and a material suitable for a desired spectral characteristic may be selected as appropriate. In this embodiment, the reflective structure 3 is formed by a vacuum vapor deposition method, but can also be formed by a film formation method other than the vacuum vapor deposition method, such as an ion plating method, an ion assist vapor deposition method, or a sputtering method. A film formation method most suitable for the purpose and conditions may be selected.

光吸収構造体４は有機溶媒に所定の吸収波長領域を有する染料である色素を樹脂に溶解し、分散させることにより得た塗布溶液を近赤外光反射構造体３上に塗布することにより成膜している。   The light absorbing structure 4 is formed by applying a coating solution obtained by dissolving and dispersing a pigment, which is a dye having a predetermined absorption wavelength region in an organic solvent, onto the near infrared light reflecting structure 3. It is filming.

本実施例においては、光吸収構造体４の色素として、図２に示すような透過率、吸収率の光学特性を有するシアニン系の色素を用い、樹脂にはスチレン系のものを用いている。これらの色素及び樹脂をメチルエチルケトン、メチルイソブチルケトン等のケトン系の混合液から成る有機溶媒に溶解させて塗布液を作製し、この塗布液を近赤外光反射構造体３上にスピンコート法によって塗布する。更に、加熱炉で乾燥させ、溶媒を揮発させることにより光吸収構造体４を成膜する。光吸収構造体４はスピンコート法ではなく、ディップ法、スプレ法、グラビア法、バーコータ法等により成膜してもよい。   In the present embodiment, a cyanine dye having optical characteristics such as transmittance and absorptivity as shown in FIG. 2 is used as the dye of the light absorption structure 4, and a styrene resin is used as the resin. These dyes and resins are dissolved in an organic solvent composed of a ketone mixture such as methyl ethyl ketone and methyl isobutyl ketone to prepare a coating solution, and this coating solution is applied onto the near-infrared light reflecting structure 3 by a spin coating method. Apply. Further, the light absorbing structure 4 is formed by drying in a heating furnace and volatilizing the solvent. The light absorbing structure 4 may be formed by a dip method, a spray method, a gravure method, a bar coater method or the like instead of the spin coating method.

また、色素はシアニン系に限られたものでなく、近赤外波長領域に吸収を有するものであれば、例えばフタロシアニン系、ナフタロシアニン系、ピリリウム系、スクワリリウム系、ポリメチン系、ジイモニウム系、アゾ化合物系、アンスラキノン系等を用いてもよく、或いはこれらを複数ｎお色素を混合して用いてもよい。   In addition, the dye is not limited to cyanine, but may be any one having absorption in the near infrared wavelength region, for example, phthalocyanine, naphthalocyanine, pyrylium, squarylium, polymethine, diimonium, azo compound Or anthraquinone may be used, or these may be used by mixing a plurality of n pigments.

樹脂は可視波長領域において高い透過率を有していれば、スチレン系に限らず、ポリエステル系やアクリル系等の樹脂を用いてもよく、或いは複数の樹脂を混合して用いてもよい。   As long as the resin has high transmittance in the visible wavelength region, the resin is not limited to styrene, and may be a polyester or acrylic resin, or a mixture of a plurality of resins.

更に、有機溶媒はケトン系に限らず、シクロヘキサン等の炭化水素系、酢酸エチル等のエステル系、メチルセロソルブ等のエーテル系、メタノール等のアルコール系、ジメチルホルムアミド等のアミン系有機溶媒を単独又は複数混合したものを使用してもよい。   Furthermore, the organic solvent is not limited to a ketone type, and may be a hydrocarbon type such as cyclohexane, an ester type such as ethyl acetate, an ether type such as methyl cellosolve, an alcohol type such as methanol, or an amine type organic solvent such as dimethylformamide. A mixture may be used.

前述したように、赤外線カットフィルタのゴースト光の強度は、簡易的に（赤外線カットフィルタの分光透過率）・（赤外線カットフィルタの分光反射率）で計算される。近赤外光反射構造体３から成る赤外線カットフィルタでは、透過波長領域から不透過波長領域の遷移する遷移波長領域においてゴースト光の強度は最大となり、概ね２５％となる。   As described above, the intensity of the ghost light of the infrared cut filter is simply calculated by (spectral transmittance of the infrared cut filter) · (spectral reflectance of the infrared cut filter). In the infrared cut filter comprising the near-infrared light reflecting structure 3, the intensity of the ghost light is maximum in the transition wavelength region where the transmission wavelength region transitions to the non-transmission wavelength region, and is approximately 25%.

実用的には、ゴースト光の強度は撮像光学系や撮像素子の感度にもよるが、１５〜１６％程度以下にする必要がある。そのため、例えば強度を１６％以下にまで低減するには、光吸収構造体４を組合わせた場合に、少なくとも透過率４０％、反射率４０％となるようする。従って、光吸収構造体４の吸収波長領域において、少なくともその一部は近赤外光反射構造体３の遷移波長領域に重なり、２０％以上の吸収率を有する特性が求められる。   Practically, the intensity of the ghost light needs to be about 15 to 16% or less although it depends on the sensitivity of the imaging optical system and the imaging device. Therefore, for example, in order to reduce the intensity to 16% or less, when the light absorbing structure 4 is combined, at least the transmittance is 40% and the reflectance is 40%. Therefore, at least part of the absorption wavelength region of the light absorption structure 4 overlaps the transition wavelength region of the near-infrared light reflection structure 3, and a characteristic having an absorption rate of 20% or more is required.

このように、色素、樹脂、有機溶媒の選択は、目的や条件に合わせて最適な組み合わせを適宜選択すればよい。   Thus, the selection of the pigment, resin, and organic solvent may be appropriately selected in accordance with the purpose and conditions.

図３は撮像素子５の赤色、緑色、青色の色ごとの感度特性のグラフ図を示し、例えば監視用カメラに用いる撮像素子５では夜間でも監視できるように、特に赤色に感度の強い特性を有するものを使用することが好ましい。   FIG. 3 is a graph of sensitivity characteristics of the image sensor 5 for each of red, green, and blue colors. For example, the image sensor 5 used in the monitoring camera has a characteristic particularly sensitive to red so that it can be monitored at night. It is preferable to use one.

図４は赤外線カットフィルタと図３に示す特性を有する撮像素子５によって生ずる赤外光半値波長（６６０ｎｍ）付近のゴースト光の強度特性のグラフ図を示している。   FIG. 4 is a graph showing the intensity characteristics of ghost light near the half-wavelength of infrared light (660 nm) generated by the infrared cut filter and the image sensor 5 having the characteristics shown in FIG.

そして、図４のＡに示すように、光吸収構造体４を設けずに近赤外光反射構造体３のみで構成された赤外線カットフィルタを用いた撮像光学ユニットにおけるゴースト光の強度は最大約２４％である。   And as shown to A of FIG. 4, the intensity | strength of the ghost light in the imaging optical unit using the infrared cut filter comprised only by the near-infrared-light reflection structure 3 without providing the light absorption structure 4 is about maximum. 24%.

また、比較例１として、図１に示す赤外線カットフィルタ１の近赤外光反射構造体３と光吸収構造体４との積層順を逆転し、透明基板２上に光吸収構造体４、反射構造体３の順に積層した。このような赤外線カットフィルタを用いた撮像光学ユニットにおいては、図３のＢに示すようにゴースト光の強度は最大約１２．５％の結果が得られた。   Further, as Comparative Example 1, the stacking order of the near-infrared light reflecting structure 3 and the light absorbing structure 4 of the infrared cut filter 1 shown in FIG. 1 is reversed, and the light absorbing structure 4 and the reflection are reflected on the transparent substrate 2. The structures 3 were stacked in this order. In the imaging optical unit using such an infrared cut filter, the maximum ghost light intensity was about 12.5% as shown in FIG. 3B.

これらに対して、本実施例１のように透明基板２上に近赤外光反射構造体３、光吸収構造体４を順次に積層した赤外線カットフィルタ１を用いた撮像光学ユニットでは、図３のＣに示すようにゴースト光の強度は最大約６％となっている。   On the other hand, in the imaging optical unit using the infrared cut filter 1 in which the near-infrared light reflection structure 3 and the light absorption structure 4 are sequentially laminated on the transparent substrate 2 as in the first embodiment, FIG. As shown in C, the intensity of the ghost light is about 6% at the maximum.

本実施例１の赤外線カットフィルタ１は、近赤外光反射構造体３の遷移波長領域の光を吸収する光吸収構造体４を撮像素子５と対向する面に配置する。   In the infrared cut filter 1 of the first embodiment, a light absorbing structure 4 that absorbs light in the transition wavelength region of the near infrared light reflecting structure 3 is disposed on a surface facing the imaging element 5.

これにより、赤外線カットフィルタ１を透過し、撮像素子５によって反射された光が、赤外線カットフィルタ１の近赤外光反射構造体３に到達するまでに光吸収構造体４を通過することにより、反射構造体３による反射光を低減することができる。   Thereby, the light transmitted through the infrared cut filter 1 and reflected by the image sensor 5 passes through the light absorption structure 4 before reaching the near infrared light reflection structure 3 of the infrared cut filter 1. Light reflected by the reflective structure 3 can be reduced.

更に、撮像素子５により反射され、近赤外光反射構造体３において反射された反射光は撮像素子５に到達するまでに、再度光吸収構造体４を通過することとなり、撮像素子５への入射光による撮像素子５からの反射率を低減することができる。   Further, the reflected light reflected by the imaging element 5 and reflected by the near-infrared light reflecting structure 3 passes through the light absorbing structure 4 again before reaching the imaging element 5, The reflectance from the image sensor 5 due to incident light can be reduced.

本実施例１においては、図１に示すような構成としたが、図５（ａ）の変形例に示すように、透明基板２の撮像素子５側の面に光吸収構造体４、反対側の面に近赤外光反射構造体３を成膜してもよい。或いは、図５（ｂ）に示すように、透明基板２の撮像素子５の反対側の面上に光吸収構造体４、反射構造体３を順次に成膜してもよい。つまり、光吸収構造体４を近赤外光反射構造体３と撮像素子５の間に配置するような構造とすればよい。   In the first embodiment, the configuration as shown in FIG. 1 is adopted. However, as shown in the modification of FIG. 5A, the light absorption structure 4 is provided on the surface of the transparent substrate 2 on the imaging element 5 side, and the opposite side. The near-infrared light reflecting structure 3 may be formed on the surface. Alternatively, as shown in FIG. 5B, the light absorption structure 4 and the reflection structure 3 may be sequentially formed on the surface of the transparent substrate 2 opposite to the imaging element 5. That is, a structure in which the light absorption structure 4 is disposed between the near-infrared light reflection structure 3 and the imaging element 5 may be used.

また、複数の光吸収構造体４を設ける場合は、少なくともその１つが近赤外光反射構造体３と撮像素子５との間に配置されていればよい。   Moreover, when providing the some light absorption structure 4, at least one should just be arrange | positioned between the near-infrared-light reflection structure 3 and the image pick-up element 5. FIG.

図６は実施例２の撮像光学ユニットの構成図を示し、透明基板２の撮像素子５と反対側の面に赤外光半値波長の光を遮蔽する近赤外光反射構造体３ａを成膜している。更に、透明基板２の撮像素子５側の面には、光吸収構造体４を成膜し、更に光吸収構造体４上に反射構造体３ａで遮蔽することのできない不透過波長領域の光を遮蔽する近赤外光反射構造体３ｂを成膜している。   FIG. 6 is a configuration diagram of the imaging optical unit of Example 2, and a near-infrared light reflecting structure 3a that shields light having a half-wavelength of infrared light is formed on the surface of the transparent substrate 2 opposite to the imaging element 5. is doing. Further, a light absorption structure 4 is formed on the surface of the transparent substrate 2 on the image pickup element 5 side, and light in an opaque wavelength region that cannot be shielded by the reflection structure 3a on the light absorption structure 4 is further formed. The near-infrared light reflecting structure 3b to be shielded is formed.

透明基板２として合成樹脂フィルム基板、具体的には板厚０．１ｍｍのノルボルネン系樹脂であるＡｒｔｏｎ（ＪＳＲ社製、商品名）を用いている。しかし、可視波長領域において透明性が高ければ、Ａｒｔｏｎに限らず、Ｚｅｏｎｅｘ、Ｚｅｏｎｏｒ（日本ゼオン社製、商品名）、Ｆ１（グンゼ社製、商品名）等の他のノルボルネン系樹脂を使用してもよい。また、ノルボルネン系樹脂以外でもＰＭＭＡ、ＰＣ（ポリカーボネート）、ＰＥＴ、ＰＥＮ、ポリイミド系樹脂等の種々の合成樹脂フィルム基板を使用することもできる。   As the transparent substrate 2, a synthetic resin film substrate, specifically, Arton (trade name, manufactured by JSR), which is a norbornene-based resin having a thickness of 0.1 mm, is used. However, if the transparency in the visible wavelength region is high, not only Arton but also other norbornene resins such as Zeonex, Zeonor (trade name, manufactured by Nippon Zeon Co., Ltd.), F1 (trade name, manufactured by Gunze Co., Ltd.) are used. Also good. In addition to norbornene resins, various synthetic resin film substrates such as PMMA, PC (polycarbonate), PET, PEN, and polyimide resins can also be used.

近赤外光反射構造体３の成膜による熱応力や膜応力、水分による分光の変化を考慮すると、耐熱性つまりガラス転移点Ｔｇが高く、曲げ弾性が大きく、更には吸水率が低いものがより好ましい。これらの条件を考慮するとノルボルネン系樹脂、ポリイミド系樹脂が最も適している材料の１つである。   Considering thermal stress and film stress due to film formation of the near-infrared light reflecting structure 3, and changes in the spectrum due to moisture, the heat resistance, that is, the glass transition point Tg is high, the bending elasticity is high, and the water absorption is low. More preferred. Considering these conditions, norbornene resin and polyimide resin are one of the most suitable materials.

合成樹脂フィルム基板は通常のガラス基板等と比較すると薄く、柔軟性があり、薄型化や任意形状に加工可能という利点を有している。しかし、膜応力等の影響を受け易いため、特許文献７に開示されているように、基板の両面に互いの膜応力を打ち消すように近赤外光反射構造体３を成膜することが好ましい。   A synthetic resin film substrate is thinner and more flexible than a normal glass substrate or the like, and has an advantage that it can be thinned and processed into an arbitrary shape. However, since it is easily affected by film stress or the like, it is preferable to form the near-infrared light reflecting structure 3 on both surfaces of the substrate so as to cancel each other's film stress as disclosed in Patent Document 7. .

図７は本実施例２における撮像光学ユニットの赤外光半値波長（６６０ｎｍ）付近のゴースト光の強度特性のグラフ図を示している。光吸収構造体４を設けずに、近赤外光反射構造体３ａ、３ｂのみで構成された赤外線カットフィルタを用いた撮像光学ユニットにおけるゴースト光の強度は、Ａのように最大約２４％である。   FIG. 7 is a graph showing the intensity characteristics of ghost light in the vicinity of the half-wavelength of infrared light (660 nm) of the imaging optical unit in the second embodiment. The intensity of the ghost light in the imaging optical unit using the infrared cut filter composed only of the near-infrared light reflecting structures 3a and 3b without providing the light absorbing structure 4 is about 24% at the maximum like A. is there.

また、比較例２として、図６に示す近赤外光反射構造体３ａ、３ｂの位置を逆にし、透明基板２の撮像素子５の反対側の面に反射構造体３ｂを成膜し、透明基板２の撮像素子５側の面に光吸収構造体４、反射構造体３ａを成膜した。このような赤外線カットフィルタを用いた撮像光学ユニットにおけるゴースト光の強度は、Ｂのように最大約１２．５％の結果となった。   Further, as Comparative Example 2, the positions of the near-infrared light reflecting structures 3a and 3b shown in FIG. 6 are reversed, and the reflecting structure 3b is formed on the surface of the transparent substrate 2 on the opposite side of the image pickup device 5 to be transparent. The light absorption structure 4 and the reflection structure 3a were formed on the surface of the substrate 2 on the image sensor 5 side. The intensity of the ghost light in the imaging optical unit using such an infrared cut filter was a maximum of about 12.5% as shown in B.

これらに対して、本実施例２における赤外線カットフィルタ１を用いた撮像光学ユニットにおけるゴースト光の強度は、Ｃのように最大約７．５％となっている。   On the other hand, the intensity of the ghost light in the imaging optical unit using the infrared cut filter 1 in the second embodiment is about 7.5% at the maximum like C.

これは、撮像素子５からの赤外光半値波長近辺の反射光に対する赤外線カットフィルタ１の反射は、近赤外光反射構造体３ａによるものが支配的であり、反射構造体３ａに到達するまでに光吸収構造体４で赤外光半値波長の近辺の光を吸収するためである。   This is because the reflection of the infrared cut filter 1 with respect to the reflected light in the vicinity of the half-wavelength of infrared light from the imaging element 5 is predominantly due to the near-infrared light reflecting structure 3a, and reaches the reflecting structure 3a. This is because the light absorbing structure 4 absorbs light in the vicinity of the half-wavelength of infrared light.

本実施例２では、図６に示すような構成としているが、図８（ａ）の変形例に示すように、透明基板２の撮像素子５側の面に近赤外光反射構造体３ｂを成膜し、反対側の面上に光吸収構造体４、近赤外光反射構造体３ａを順次に成膜してもよい。或いは、図８（ｂ）に示すように、透明基板２の撮像素子５側の面上に近赤外光反射構造体３ｂ、光吸収構造体４を順次に成膜し、反対側の面に反射構造体３ａを成膜してもよい。これらの場合においても、比較例２のような反射構造体３ａと撮像素子５との間に、光吸収構造体４が位置しない赤外線カットフィルタと比較すると、ゴースト光の強度を小さくすることができる。   In the second embodiment, the configuration shown in FIG. 6 is used. However, as shown in the modification of FIG. 8A, the near-infrared light reflecting structure 3b is provided on the surface of the transparent substrate 2 on the image sensor 5 side. The light absorbing structure 4 and the near-infrared light reflecting structure 3a may be sequentially formed on the opposite surface. Alternatively, as shown in FIG. 8B, the near-infrared light reflecting structure 3b and the light absorbing structure 4 are sequentially formed on the surface of the transparent substrate 2 on the image pickup device 5 side, and on the opposite surface. The reflective structure 3a may be formed. Even in these cases, the intensity of the ghost light can be reduced as compared with an infrared cut filter in which the light absorption structure 4 is not located between the reflection structure 3a and the imaging element 5 as in Comparative Example 2. .

また、光吸収構造体４を複数構成する場合は、少なくともその１つが近赤外光反射構造体３ａと撮像素子５との間に配置されていればよい。   When a plurality of light absorbing structures 4 are configured, at least one of the light absorbing structures 4 may be disposed between the near-infrared light reflecting structure 3 a and the image sensor 5.

図９は実施例３における撮像光学ユニットの構成図を示しており、図８（ｂ）に示す赤外線カットフィルタ１の撮像素子５側の最表層に、更に反射防止構造体６が成膜されている。反射防止構造体６として、図１０に示すような光の波長よりも短く、突部を撮像素子５側に向けた円錐状の多数の突起体６ａを有するアクリル系の樹脂を使用している。   FIG. 9 shows a configuration diagram of the imaging optical unit in Example 3. Further, an antireflection structure 6 is further formed on the outermost layer on the imaging element 5 side of the infrared cut filter 1 shown in FIG. 8B. Yes. As the antireflection structure 6, an acrylic resin having a plurality of conical protrusions 6 a whose projections are shorter than the wavelength of light as shown in FIG.

円錐状の突起体６ａは最頂部から最底部に向かうにつれて体積が徐々に変化し、それに対応した有効屈折率も突起体６ａの最頂部から最底部に向かい連続的に変化する。そのため、円錐状の突起体６ａに上方から光が入射した場合には、滑らかな有効屈折率分布を有するため急激な屈折率差がなく、反射防止構造体６の表面では光は殆ど反射されることはない。   The volume of the conical protrusion 6a gradually changes from the top to the bottom, and the corresponding effective refractive index also changes continuously from the top to the bottom of the protrusion 6a. Therefore, when light enters the conical protrusion 6a from above, since there is a smooth effective refractive index distribution, there is no abrupt refractive index difference, and almost no light is reflected on the surface of the antireflection structure 6. There is nothing.

本実施例３においては、反射防止構造体６の突起体６ａを円錐状としたが、角錐状の突起体や逆円錐状の凹部を有するものを使用しても、同様の効果が得られる。   In the third embodiment, the protrusion 6a of the antireflection structure 6 has a conical shape, but the same effect can be obtained even when a pyramid-shaped protrusion or an inverted conical recess is used.

この反射防止構造体６は微細凹凸周期構造を形成したモールドを用い、重合性化合物と重合開始剤とを含有する樹脂組成物を充填し、この樹脂組成物を硬化させると共にモールドを剥離することにより成形している。   The antireflection structure 6 uses a mold having a fine uneven periodic structure, is filled with a resin composition containing a polymerizable compound and a polymerization initiator, is cured, and the mold is peeled off. Molding.

本実施例３においては、反射防止構造体６にアクリル系の樹脂を用いたが、光透過率の高いものであればよく、例えばウレタン系樹脂、ポリスチレン系樹脂、オレフィン系樹脂等を用いることができる。   In the third embodiment, an acrylic resin is used for the antireflection structure 6, but any resin having a high light transmittance may be used. For example, a urethane resin, a polystyrene resin, an olefin resin, or the like may be used. it can.

また本実施例３では、反射防止構造体６となる樹脂組成物を熱硬化させたが、樹脂組成物の硬化は他の活性エネルギ線、例えば可視光線、電子線、プラズマ、赤外線、紫外線等を用いてもよい。活性エネルギ線の照射量は、樹脂組成物の硬化が進行するエネルギ量であればよい。また、反射防止構造体６の作製については射出成型法等を用いてもよく、最終的に微細凹凸構造が得られればよい。   In Example 3, the resin composition to be the antireflection structure 6 was thermally cured, but the resin composition was cured by using other active energy rays such as visible light, electron beam, plasma, infrared rays, and ultraviolet rays. It may be used. The irradiation amount of active energy rays should just be the energy amount which hardening of a resin composition advances. Further, for the production of the antireflection structure 6, an injection molding method or the like may be used as long as a fine uneven structure is finally obtained.

反射防止構造体６はアルミナやジルコニア等の酸化物から形成された微細凹凸構造から成るものや、単層或いは複数の薄膜から構成されたものを用いてもよい。反射防止構造体６の作製法としては、例えばアルミニウム化合物や亜鉛化合物等の微細凹凸構造の成分となる材料を有機溶媒に溶解させた塗布溶液を作製し、この塗布溶液を塗布し、室温又は加温して、乾燥或いは熱処理することで得られる。溶液の塗布には、ディッピング法、スピンコート法、スプレー法、印刷法、フローコート法等が用いられる。   The antireflection structure 6 may be made of a fine concavo-convex structure made of an oxide such as alumina or zirconia, or may be made of a single layer or a plurality of thin films. As a method for producing the antireflection structure 6, for example, a coating solution in which a material that is a component of a fine concavo-convex structure such as an aluminum compound or a zinc compound is dissolved in an organic solvent is prepared, and this coating solution is applied at room temperature or under pressure. It is obtained by heating and drying or heat treatment. For applying the solution, a dipping method, a spin coating method, a spray method, a printing method, a flow coating method, or the like is used.

また、単層或いは複数層の薄膜から構成される反射防止構造体６は、単層の場合はＭｇＦ2やＳｉＯ2等の比較的屈折率の低いものを用い、複数層から成る場合は屈折率の異なる薄膜を交互に積層させて得る。成膜法としては真空蒸着法、イオンプレーティング法、イオンアシスト蒸着法、スパッタリング法等が用いられる。 Further, the antireflection structure 6 composed of a single layer or a plurality of layers of thin films uses a relatively low refractive index such as MgF 2 or SiO 2 in the case of a single layer, and the refractive index in the case of a plurality of layers. Obtained by alternately laminating thin films having different thicknesses. As a film forming method, a vacuum deposition method, an ion plating method, an ion assist deposition method, a sputtering method, or the like is used.

図１１は反射防止構造体６の有無による撮像光学ユニットのゴースト光の強度を比較した強度特性のグラフ図であり、反射防止構造体６がないものは図８（ｂ）に示す構成、反射防止構造体６があるものは図９に示す構成としている。   FIG. 11 is a graph of intensity characteristics comparing the intensity of ghost light of the imaging optical unit with and without the antireflection structure 6, and the structure without the antireflection structure 6 is shown in FIG. The structure 6 has a structure shown in FIG.

このグラフ図から、反射防止構造体６を有する撮像光学ユニットの方が、ゴースト光の強度が小さいことが分かる。これは反射防止構造体６により、赤外線カットフィルタ１の撮像素子５側の表面の反射率が小さくなるためである。   From this graph, it can be seen that the imaging optical unit having the antireflection structure 6 has lower ghost light intensity. This is because the reflectance of the surface of the infrared cut filter 1 on the image sensor 5 side is reduced by the antireflection structure 6.

なお、上述の各実施例１、２においても、赤外線カットフィルタ１の撮像素子５側の表面に反射防止構造体６を設けることもできる。   In each of the first and second embodiments, the antireflection structure 6 can be provided on the surface of the infrared cut filter 1 on the image sensor 5 side.

図１２は監視用カメラ等に用いられる撮像光学系を示し、実施例１〜３の撮像光学ユニットが用いられている。光路上に、レンズ１１、光量絞り装置１２、レンズ１３〜１５、赤外線カットフィルタ１、撮像素子５が順次に配列されている。   FIG. 12 shows an image pickup optical system used for a monitoring camera or the like, and the image pickup optical units of Embodiments 1 to 3 are used. On the optical path, the lens 11, the light quantity diaphragm 12, the lenses 13 to 15, the infrared cut filter 1, and the image sensor 5 are sequentially arranged.

光量絞り装置１２では、絞り羽根支持板１６に一対の絞り羽根１７ａ、１７ｂが可動に取り付けられ、開口部の面積を変化させて光量を調節するようにされている。絞り羽根１７ａには、光量を減光することを目的としたＮＤ（Neutral Density）フィルタ１８が取り付けられている。   In the light quantity diaphragm device 12, a pair of diaphragm blades 17a and 17b are movably attached to the diaphragm blade support plate 16, and the light quantity is adjusted by changing the area of the opening. An ND (Neutral Density) filter 18 for reducing the amount of light is attached to the diaphragm blade 17a.

絞り羽根１７ａ、１７ｂ、ＮＤフィルタ１８によって、同じ光量でも、絞りの開口をできるだけ大きく維持できるように入射光量を調節している。これにより、ハンチング現象や光の回折現象等による画質の低下を低減することができる。   The diaphragm blades 17a and 17b and the ND filter 18 adjust the amount of incident light so that the aperture of the diaphragm can be maintained as large as possible even with the same amount of light. As a result, it is possible to reduce deterioration in image quality due to a hunting phenomenon or a light diffraction phenomenon.

また、赤外線カットフィルタ１は制御手段１９の出力によりフィルタ駆動部２０によって光路に対し自在に進退できるようにされ、撮像素子５の特性に合わせて、赤外線の光量を制限し、適正な画像を得ることができるようになっている。   Further, the infrared cut filter 1 can be freely advanced and retracted with respect to the optical path by the filter drive unit 20 according to the output of the control means 19, and the amount of infrared light is limited in accordance with the characteristics of the image sensor 5 to obtain an appropriate image. Be able to.

光量絞り装置１２を透過した光は、赤外線カットフィルタ１に入射するが、被写体が明るいとき、即ち可視光における光量が十分なときは赤外線カットフィルタ１はフィルタ駆動部２０によって撮像光学系の光路上に挿入する。一方、夜間のような被写体が暗いとき、即ち可視光における光量が不十分のときは、赤外線カットフィルタ１はフィルタ駆動部２０によって撮像光学系の光路外に退避させる。   The light that has passed through the light amount diaphragm 12 enters the infrared cut filter 1, but when the subject is bright, that is, when the amount of visible light is sufficient, the infrared cut filter 1 is placed on the optical path of the imaging optical system by the filter drive unit 20. Insert into. On the other hand, when the subject is dark, such as at night, that is, when the amount of visible light is insufficient, the infrared cut filter 1 is retracted out of the optical path of the imaging optical system by the filter driving unit 20.

このとき、実施例１〜３で示した赤外線カットフィルタ１を用いることで、遷移波長領域の赤外光半値波長近辺の光の波長によるゴースト光をより低減できる。   At this time, by using the infrared cut filter 1 shown in the first to third embodiments, it is possible to further reduce ghost light due to the wavelength of light in the vicinity of the half-wavelength of infrared light in the transition wavelength region.

１ 赤外線カットフィルタ
２ 透明基板
３、３ａ、３ｂ 近赤外光反射構造体
４ 光吸収構造体
５ 撮像素子
６ 反射防止構造体
６ａ 突起体
１２ 光量絞り装置
１７ａ、１７ｂ 絞り羽根
１８ ＮＤフィルタ
２０ フィルタ駆動部 DESCRIPTION OF SYMBOLS 1 Infrared cut filter 2 Transparent substrate 3, 3a, 3b Near-infrared light reflection structure 4 Light absorption structure 5 Imaging element 6 Antireflection structure 6a Protrusion 12 Light quantity diaphragm 17a, 17b Diaphragm blade 18 ND filter 20 Filter drive Part

Claims (6)

赤外線カットフィルタと撮像素子とから成り、前記赤外線カットフィルタは、透明基板と近赤外光反射構造体と所定の吸収波長領域を有する光吸収構造体とを有し、前記近赤外光反射構造体は少なくとも６００〜７５０ｎｍの波長の間に透過波長領域から不透過波長領域に遷移する遷移波長領域を有し、前記光吸収構造体の前記吸収波長領域の少なくとも一部は前記遷移波長領域と重なり、前記光吸収構造体は前記遷移波長領域を有する近赤外光反射構造体と前記撮像素子との間に配置したことを特徴とする撮像光学ユニット。   The infrared cut filter comprises an infrared cut filter and an imaging device, and the infrared cut filter includes a transparent substrate, a near infrared light reflection structure, and a light absorption structure having a predetermined absorption wavelength region, and the near infrared light reflection structure. The body has a transition wavelength region that transitions from a transmission wavelength region to a non-transmission wavelength region between wavelengths of at least 600 to 750 nm, and at least a part of the absorption wavelength region of the light absorption structure overlaps the transition wavelength region. The imaging optical unit, wherein the light absorbing structure is disposed between a near infrared light reflecting structure having the transition wavelength region and the imaging element. 前記光吸収構造体は樹脂に色素を分散したものであることを特徴とする請求項１に記載の撮像光学ユニット。   The imaging optical unit according to claim 1, wherein the light absorbing structure is a resin in which a pigment is dispersed. 前記近赤外光反射構造体の前記遷移波長領域内で透過率が略５０％となる波長において、前記光吸収構造体は２０％以上の吸収率を有することを特徴とする請求項１又は２に記載の撮像光学ユニット。   The light absorbing structure has an absorptivity of 20% or more at a wavelength at which the transmittance is approximately 50% within the transition wavelength region of the near infrared light reflecting structure. The imaging optical unit described in 1. 前記赤外線カットフィルタの前記撮像素子側の表層に反射防止構造体を設けたことを特徴とする請求項１〜３の何れか１つの請求項に記載の撮像光学ユニット。   The imaging optical unit according to any one of claims 1 to 3, wherein an antireflection structure is provided on a surface layer on the imaging element side of the infrared cut filter. 前記透明基板は合成樹脂フィルムであることを特徴とする請求項１〜４の何れか１つの請求項に記載の撮像光学ユニット。   The imaging optical unit according to any one of claims 1 to 4, wherein the transparent substrate is a synthetic resin film. 開口部を有する絞り羽根と、請求項１〜５の何れか１つの請求項に記載の撮像光学ユニット、前記赤外線カットフィルタを前記開口部内に自在に進退できるように駆動する駆動部とを有することを特徴とする撮像光学系。   A diaphragm blade having an opening, an imaging optical unit according to any one of claims 1 to 5, and a drive unit that drives the infrared cut filter so that the infrared cut filter can freely move back and forth in the opening. An imaging optical system characterized by the above.
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