JP2012137650A - Optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter which can reduce occurrence of ghost light and reduce variations in optical characteristics due to moisture absorption from peripheral environment.SOLUTION: A light absorbing structure 3 is formed on a surface of a transparent substrate 2. A near infrared light reflecting structure 4 being as an atmospheric shielding layer is disposed so as to cover an upper surface and a side surface of the light absorbing structure 3. A near infrared light reflecting structure 5 and an ultraviolet light reflecting structure 6 are sequentially laminated on an opposite surface of the transparent substrate 2. At least a part of an absorbing wavelength region of the light absorbing structure 3 is overlapped with an inside of a transition wavelength region from a transmitting wavelength region of the near infrared light reflecting structure 4 to a non-transmitting wavelength region thereof.

Description

  The present invention relates to an optical filter such as an infrared cut filter or an ultraviolet infrared cut filter that restricts transmission of light in a predetermined wavelength region used in an imaging apparatus or the like.

  A solid-state imaging device used in an imaging apparatus such as a video camera may be used in combination with a filter that adjusts optical characteristics such as spectral transmittance in order to correspond to the sensitivity characteristics of the human eye. Specifically, there are a near-infrared cut filter, an ultraviolet cut filter, or an ultraviolet / infrared cut filter in which these are realized by a single filter.

  In order to limit the transmission of light in a desired wavelength region, these filters absorb the material by absorbing the light in the restricted region into the filter base material or apply it on the base material. Yes. In addition, there are some in which two or more kinds of thin films having different refractive indexes are laminated on a base material and reflected by utilizing interference of the thin films.

  These filters have a transmission wavelength region, a non-transmission wavelength region, and a transition wavelength region that transitions from a transmission wavelength region to a non-transmission wavelength region. Since the transition wavelength region that transitions from the transmission wavelength region to the non-transmission wavelength region cannot be set to an ideal 0 nm, for example, the transmittance is ideally 100 → 0% between the transition wavelength regions of about 50 nm, Or it is changed from 0 to 100%.

  The transmission wavelength region is a wavelength region that continuously maintains a transmittance of 80% or more, more preferably 90% or more, and the non-transmission wavelength region is a transmittance of approximately 15% or less, more preferably 5%. % Is a wavelength region that is continuously maintained below 100%.

  In a video camera or the like, in the transition wavelength region described above, a phenomenon occurs in which part of the light transmitted through the optical filter is reflected by the image sensor and reenters the optical filter from the surface side of the image sensor. At this time, in the reflection type optical filter, a part of the re-incident light is reflected again by the optical filter and reaches the image pickup device, so that ghost light is generated and the image may be deteriorated. .

  In a simple way of thinking, the intensity of the ghost light in the optical filter at each wavelength is based on (incident light transmittance) and (incident light reflectance).

  Therefore, for example, in the case of an ultraviolet-infrared cut filter, the intensity of such ghost light becomes maximum near the half-value wavelength on the ultraviolet light side or near the half-value wavelength on the near-infrared light side. Although the influence varies depending on the sensitivity characteristics of the image sensor, the arrangement position of the filter, and the like, in the reflection type infrared cut filter, the ghost light is a phenomenon that always occurs more or less in principle.

  These problems have become apparent with the recent increase in sensitivity of image sensors. In particular, in surveillance cameras that retract the infrared cut filter from the optical path and use light in the near infrared wavelength region, the sensitivity in the near infrared wavelength region is very high, so when using the infrared cut filter in normal mode In addition, such a problem becomes remarkable.

  In order to reduce the above-described ghost light, various methods have been proposed to take measures such as disposing a reflection type optical filter inclined with respect to the optical axis, or forming a thin film on a curved substrate. ing. However, other problems such as an increase in the space on the optical path, an increase in film thickness error in the same optical filter, and a significant reduction in productivity occur.

  Thus, when ghost light becomes a problem, it can be said that an optical filter using an infrared absorbing material is more preferable.

JP 2001-83889 A JP 2004-101956 A JP 2004-354857 A

  Various types of absorption-type infrared cut filters have been proposed. For example, a method of forming a dye by dispersing a dye having a characteristic of absorbing light of a specific wavelength in a resin has been proposed. However, in order to limit the transmittance in the non-transmission wavelength region over the near-infrared wavelength region up to about 700 to 1100 nm or about 1200 nm with only the absorption component, and ideally to approach 0%, The transmittance will be lowered. There is also a problem that a large ripple is generated in the transmission wavelength region.

  In addition, a method of dispersing a metal complex or the like in a substrate such as glass or resin and absorbing light of a specific wavelength has been proposed. However, in such an optical filter, an appropriate thickness is required for the absorption layer, and particularly when an absorbent is dispersed in the substrate, a thickness of about 0.3 to 0.5 mm or more is required. Therefore, it becomes difficult to achieve the demand for thinner and smaller optical filters.

  Therefore, the present applicant has proposed a hybrid type optical filter that combines a near-infrared light reflecting structure made of an inorganic film and a light absorbing structure made of an organic film formed by dispersing a pigment such as a dye in a resin binder. is doing. This hybrid type optical filter has a visible wavelength region that changes from a transmission wavelength region to a non-transmission wavelength region or from a non-transmission wavelength region to a transmission wavelength region of the spectral transmittance characteristic produced by the near-infrared light reflecting structure. Some have a transition wavelength region. In the transition wavelength region, light having a desired wavelength is absorbed by the light absorption structure.

  With such a configuration, good optical characteristics can be obtained, and the reflection ghost caused by the transition wavelength region described above can be reduced, and an optical filter that can be thinned can be obtained.

  However, in general, such a dye is weak against moisture, and even when dispersed in a resin binder, the optical characteristics may change due to moisture absorption from the surrounding environment. Accordingly, there is a need for an optical filter that can reduce changes in optical properties due to moisture and has good environmental resistance.

  Patent Document 1 proposes an optical filter for a plasma display in which a water vapor barrier layer is formed on both surfaces of a substrate as a method for preventing deterioration of a pigment due to moisture. However, with such a configuration, it is extremely difficult to suppress moisture absorption from the end portion on the cross-sectional side of the optical filter.

  Patent Document 2 discloses an optical filter having a structure in which an absorption layer made of a colored resin layer is sealed with a base material and a planarizing layer. Patent Document 3 discloses a resin that attenuates light in a predetermined wavelength region. Optical filters have been proposed in which the layer is covered with a protective layer. However, if a new protective layer is provided for the purpose of a water vapor barrier, the cost will increase significantly.

  An object of the present invention is to provide an optical filter that can eliminate the above-mentioned problems, reduce the generation of ghost light, reduce the change in optical characteristics due to moisture absorption from the surrounding environment, and the like, and can be thinned. There is.

  In order to achieve the above object, an optical filter according to the present invention is formed by laminating a light absorption structure having a predetermined absorption wavelength region and a plurality of inorganic thin films formed on a transparent substrate by a resin layer in which a pigment is dispersed. In an optical filter formed with a near-infrared light reflecting structure that reflects at least a part of the near-infrared wavelength region, transition from a transmission wavelength region that transmits light of the near-infrared light reflection structure to a non-transmission wavelength region At least a part of the absorption wavelength region of the light absorption structure overlaps with the transition wavelength region, and an air shielding layer is provided on the surface of the light absorption structure.

  According to the optical filter of the present invention, the ambient environment can be obtained by covering the light absorbing structure containing a pigment weak to moisture with the atmospheric shielding layer of the near-infrared light reflecting structure or the antireflection structure constituted by the inorganic thin film. Can reduce moisture absorption and also reduce the generation of ghost light.

2 is a configuration diagram of an optical filter according to Embodiment 1. FIG. It is sectional drawing of the principal part. It is a spectral characteristic of a near-infrared light reflection structure, a light absorption structure, and the produced infrared cut filter. It is a graph of the spectral absorptance of a cyanine dye. It is explanatory drawing in the case of forming a light absorption structure into a film on a transparent substrate. It is explanatory drawing of the manufacturing process of an optical filter. It is a block diagram of a modification. FIG. 6 is a configuration diagram of an imaging apparatus according to a second embodiment. FIG. 6 is a configuration diagram of a light amount adjusting device according to a third embodiment.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram of an optical filter including an infrared cut filter 1 according to the first embodiment. A light absorbing structure 3 is formed on the surface of a transparent substrate 2 so as to cover the light absorbing structure 3. A near-infrared light reflecting structure 4 is provided. Further, a near infrared light reflecting structure 5 and an ultraviolet light reflecting structure 6 are sequentially laminated on the opposite surface of the transparent substrate 2, and this optical filter also functions as an ultraviolet and infrared cut filter.

  In addition, although the relationship between the transparent substrate 2, the light absorption structure 3, and the near-infrared light reflection structure 4 differs depending on the film forming method, more accurately, for example, as shown in the cross-sectional view of FIG. Is an air shielding layer covering the upper surface and the end surface of the light absorbing structure 3.

  Note that the spectral characteristics of the near-infrared light reflecting structure 4 and the near-infrared light reflecting structure 5 of the present embodiment have a characteristic of reflecting in the ultraviolet region and the near-infrared region as shown in FIG. ing. The near-infrared light reflecting structure 4 and the near-infrared light reflecting structure 5 have different spectral characteristics, and the reflecting structure 4 does not have a transition wavelength region from a transmission wavelength region to a non-transmission wavelength region. The body 5 has a transition wavelength region. The light absorbing structure 3 has absorption characteristics in the vicinity of the half-value wavelength on the infrared light side formed by the near infrared light reflecting structure 4 and the near infrared light reflecting structure 5. The infrared cut filter 1 is designed to limit the transmission of a part of the desired ultraviolet wavelength region and the near infrared wavelength region, and to have a spectral transmittance characteristic as shown in FIG.

  In Example 1, an Arton (manufactured by JSR, product name) film having a thickness of 0.1 mm is used for the transparent substrate 2. The Arton film has a glass transition point of 100 ° C. or higher, a relatively high flexural modulus of about 3000 MPa, and is selected because it can reduce cracks and waviness of the transparent substrate 2. In this example, Arton, which is a norbornene-based material, was used, but in addition to this, a polyimide-based resin film or the like is also a suitable base material, and is not limited thereto, and PET, PEN, PES, PC, etc. May be used.

  In the infrared cut filter 1 shown in FIG. 1, after the light absorbing structure 3 is formed on the transparent substrate 2, a plurality of inorganic thin film atmospheres are formed by the IAD method so that the light absorbing structure 3 is not directly exposed to the atmosphere. A dielectric film satisfying the role as a shielding layer is laminated, and this is used as the near-infrared light reflecting structure 4. Subsequently, similarly to the near-infrared light reflecting structure 4, a near-infrared light reflecting structure 5 and an ultraviolet light reflecting structure 6 made of an inorganic thin film are sequentially formed on the opposite surface of the transparent substrate 2. At this time, in order to reduce the warpage of the transparent substrate 2, the thin film laminated structure is divided and arranged on both surfaces of the transparent substrate 2. The respective stresses are measured in advance and arranged on both surfaces of the transparent substrate 2. It is desirable to optimize.

  The light absorption structure 3 has a predetermined absorption wavelength region as shown in FIG. The light absorbing structure 3 is prepared by dispersing a cyanine-based infrared absorbing dye in a resin binder made of an acrylic-styrene copolymer resin, and preparing a coating liquid in which the concentration of the dye is adjusted so as to obtain a desired absorption. Is obtained.

  Then, this coating solution is applied in a film form on the transparent substrate 2 by the gravure coating method so as to form a pattern of the light absorption structure 3 as shown in (a) cross-sectional view and (b) plan view of FIG. To do. At this time, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) are mixed in the coating solution, added as a solvent, heated after coating, dried and cured.

  The refractive index of the transparent substrate 2 in light with a wavelength of 589 nm is about 1.52, and the refractive index of the acrylic-styrene copolymer resin is about 1.49, and the difference in refractive index is relatively small with respect to the transparent substrate 2. A coating solution is prepared using the material. The resin binder of the light absorption structure 3 is more preferably one having a small difference in refractive index with the transparent substrate 2. When the light absorption structure 3 is formed on the transparent substrate 2, the resin binder is reduced by reducing the difference in refractive index. The reflection at the interface between the transparent substrate 2 and the resin binder can be reduced. Further, even when the resin binder is thinned to reduce the stress of the resin layer, the influence of the interference effect can be further reduced.

  When the resin of the light-absorbing structure 3 is dried, the stress resulting from the curing shrinkage can be reduced by reducing the thickness of the resin layer. In this case, in order to maintain the desired absorption characteristics, it is necessary to adjust the concentration of the pigment and the coating process. For the same reason, even when a functional film such as an adhesive layer or a stress relaxation layer is inserted between the transparent substrate 2 and the light absorbing structure 3, the transparent substrate 2, the functional film, and the light absorbing structure. Those having a refractive index close to the three are more desirable.

  In Example 1, as an infrared absorbing dye, azo dyes other than cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, diimonium dyes, polymethine dyes, anthraquinone dyes, naphthoquinone dyes, triphenylmethane dyes, aminium dyes, pyrylium dyes, squarylium dyes. You may use pigments, such as a system. Moreover, you may use these in mixture of 2 or more types. However, in consideration of the color reproducibility of the filter, it is preferable that the absorption in the transmission wavelength region is small and the transmittance in the transmission wavelength region changes flatly or continuously.

  If the resin binder has a high transmittance in the visible wavelength region, an acrylic resin, polystyrene resin, cyclic olefin resin, polyester resin, polyurethane resin, fluorine resin, polyimide resin, PC (polycarbonate) resin or the like is used. May be. These resins may be used alone or in combination of two or more, or may be used as a copolymer. The resin binder has compatibility with infrared absorbing dyes, adhesion to the transparent substrate 2, the near-infrared light reflecting structures 4, 5, and the ultraviolet light reflecting structure 6, processes before and after, characteristics required for the optical filter, etc. What is necessary is just to select an optimal thing suitably considering.

  In Example 1, the solvent is not limited to ketones, but hydrocarbons such as cyclohexane and toluene, esters such as methyl acetate and ethyl acetate, ethers such as diethyl ether and tetrahydrofuran, alcohols such as methanol and ethanol. In addition, an amine solvent such as dimethylformamide or water may be appropriately selected in consideration of the solubility and volatility of the pigment and the resin binder so as to obtain an optimum combination as a single substance or a mixture of two or more kinds.

  Further, although the gravure coating method is selected as the film forming method of the light absorbing structure 3, it can be formed by a spray method or the like, and is optimal in consideration of the film thickness, shape, productivity, etc. that satisfy a desired spectrum. A film formation method may be selected. If any curing process is required after the light absorbing structure 3 is formed, not only the thermal curing method but also other active energy rays, for example, visible light, electron beam, plasma, infrared, ultraviolet, etc. may be used. . The irradiation amount of active energy rays should just be the energy amount which hardening of a resin composition advances.

  Moreover, a photoinitiator can also be added as needed. For example, as a photopolymerization initiator, benzophenone, benzyl, 4,4-dimethylaminobenzophenone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, diethoxyacetophenone, benzyldimethyl ketal, 2-hydroxy-2 -Methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, hydrazone, α-acyloxime ester, and the like, but are not limited to these. May be used.

  Examples of the electron beam curing initiator include benzophenone, 2-ethylanthraquinone, 2,4-diethylthioxanthone, methyl orthobenzoylbenzoate, isopropylthioxanthone, diethoxyacetophenone, benzyldimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, benzoin methyl ether. , Benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-phenylphosphine oxide, methylbenzoylformate, 1,7-bisacridinylheptane, 9-phenylacridine However, the present invention is not limited to these and can be used alone or in combination.

  Examples of the thermal polymerization initiator include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxydi. Carbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide, 2,2-azobisisobutyrate Nitrile, 2,2-azobis (2-methylbutyronitrile), 1,1-azobis (cyclohexane-1-carbonyl), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2- Azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2-azobis (2-methylpropionate), 4,4-azobis (4-cyanovaleric acid) and the like, but are not limited to these, and may be used alone or in combination. Good.

  In addition, by adding an antioxidant, it may be possible to reduce the deterioration of the pigment, such as phenol, binderd phenol, amine, binderd amine, sulfur , Phosphoric acid type, phosphorous acid type and the like.

  Each of the near-infrared light reflecting structures 4 and 5 and the ultraviolet light reflecting structure 6 is configured by laminating a plurality of at least two types of inorganic thin films, and the antireflection structure 7 includes at least one type of inorganic thin films. It is comprised by the inorganic thin film.

In the first embodiment, a near-infrared light reflecting structure 4 is formed on the surface on which the light absorption structure 3 is previously formed as shown in FIG. 6A, and thereafter, as shown in FIG. A near-infrared light reflecting structure 5 is formed on the opposite surface of the transparent substrate 2. Finally, as shown in (c), an ultraviolet light reflecting structure 6 is formed on the reflecting structure 5. Such structures 4,5,6 material forming the dielectric film of the inorganic thin film, the TiO ₂ is in the high refractive index material, the low refractive index material using SiO _2, TiO ₂ and SiO _The structure is composed of _two alternating layers.

Although it differs depending on the film forming method, generally Nb ₂ O ₅ , ZrO ₂ , Ta ₂ O ₅ or the like is generally used as a high refractive index material, and MgF ₂ may be used for a low refractive index material. . For reasons of design and film formation, Al ₂ O ₃ or the like, which is an intermediate refractive index material, may be used in some layers, but this is not a limitation, and the optimal combination of materials should be selected appropriately. That's fine.

  When a synthetic resin substrate is used for the transparent substrate 2 and the near-infrared light reflecting structures 4 and 5 and the ultraviolet light reflecting structure 6 are formed, problems due to heat in the film forming process occur. In a synthetic resin substrate having a glass transition point lower than that of a glass substrate, warpage of the transparent substrate 2 due to the difference in linear expansion coefficient between the transparent substrate 2 and the film, and cracks in the film surface due to this warpage are generated. There is a case.

  Therefore, it is necessary to take measures against heat generated during film formation, and a method of selecting a substrate material having a high heat-resistant temperature or performing film formation by a low-temperature process can be considered. In Example 1, a method for removing heat generated in the transparent substrate 2 during film formation by a radiation cooling effect was selected by providing a heat absorption mechanism in the film formation apparatus. At this time, it is necessary to measure in advance the maximum temperature on the transparent substrate 2 reached in the film forming process and select a base material that can withstand the temperature.

  In the first embodiment, considering the stability of the film forming process, a certain allowable value is added to the maximum temperature reached in the experiment, and the glass transition point is used as a parameter for determining the suitability. A material for the transparent substrate 2 having a transition point was selected.

  In addition, since the temperature during film formation is particularly low compared to normal film formation, a process that increases the film density by adding some assistance or film formation with relatively high energy, such as sputtering, is selected. Is more preferable. Specifically, any film forming method capable of relatively accurately controlling the film thickness, such as sputtering, IAD, ion plating, IBS, and cluster deposition, and capable of obtaining a highly reproducible film. The optimal method may be selected as appropriate.

  In the case of a reflection type infrared cut filter formed only of an inorganic thin film, the reference value of the ghost light intensity becomes maximum at the half-wavelength of infrared light. Therefore, the light absorption structure 3 reduces the reflectance to 50% or less by absorbing near the half-wavelength of infrared light included in the transition wavelength region formed by the near-infrared light reflection structures 4 and 5. Reduce the intensity of ghost light.

  Therefore, more preferably, the light absorption structure 3 generally has an absorption wavelength region between wavelengths of 600 to 750 nm, which is a part of the visible wavelength region where the half-wavelength of infrared light is formed. Furthermore, it has the maximum absorption in the wavelength of about 650 to 800 nm including the above-mentioned half-valued wavelength of infrared light among the wavelengths from the visible wavelength region to about 400 to 1200 nm corresponding to the near infrared wavelength region. It is more preferable.

  If the characteristic has an absorption peak at a wavelength shorter than 650 nm, there is a possibility that a part of the transmission wavelength region that is originally required may be largely absorbed. Further, if the characteristic has an absorption peak at a wavelength longer than 800 nm, it is necessary to mix a plurality of dyes in order to obtain sufficient absorption in the transition wavelength region, and ripple in the transmission wavelength region is a problem. Is likely to be. Further, in the case of dealing with the increase in the concentration of the dye, it is possible to reduce the transmittance to the transmission wavelength region or to increase the thickness of the resin layer that forms the light absorption structure 3 as described above. Such stress may be a problem.

  The influence of the ghost light on the image varies depending on the sensitivity characteristic of the image sensor and the arrangement position of the optical filter, in addition to the intensity of the ghost light. However, it is possible to reduce ghost light by reducing the intensity of reflected light by an optical filter or the like in the vicinity of the half-wavelength of infrared light.

  In addition, in the case of a hybrid type filter of an organic film and an inorganic film as in Example 1, considering the absorption by the organic film and the reflection by the inorganic film, the desired wavelength is an infrared light half-value wavelength. It may be necessary to adjust in advance.

  After forming the near-infrared light reflecting structure 4, the near-infrared light reflecting structure 5, and the ultraviolet light reflecting structure 6 as an atmospheric shielding layer so as to cover the light absorption structure 3 on the transparent substrate 2, a desired film is formed. The infrared cut filter 1 is obtained by performing a punching process so as to have the shape shown in FIG. However, in order to avoid the state where the cross-sectional end of the light absorption structure 3 is exposed to the atmosphere as much as possible in the state where the infrared cut filter 1 is completed, the near infrared light reflection structure 4 is a light absorption structure as shown in FIG. It is necessary to punch as a shape larger than 3.

  The produced infrared cut filter 1 was able to obtain spectral characteristics as shown in FIG. In a simple approximation, the standard of the maximum intensity of ghost light with only the near-infrared light reflecting structures 4 and 5 is 25%, whereas the infrared cut filter of this embodiment with the light absorbing structure 3 added thereto. The standard of the maximum intensity of ghost light in the transition wavelength region of 1 is 8% or less.

  As described above, the influence of the ghost light varies depending on various factors such as the sensitivity characteristics of the image sensor. However, in the infrared cut filter 1 manufactured in Example 1, the standard value of the maximum intensity in the transition wavelength region is reduced by 30% or more, and the ghost light has an adverse effect on the image in many optical systems. It can be significantly reduced.

  When the infrared cut filter 1 thus manufactured was subjected to a high-temperature and high-humidity test, when the change in optical characteristics was evaluated with respect to the shift amount of the half-wavelength of infrared light, the average value of several samples was 0.8 nm or less, with a maximum value. A change of 1.2 nm was confirmed.

  On the other hand, a sample in which the positions of the near-infrared light reflecting structure 4 and the light-absorbing structure 3 are interchanged with the above-described infrared cut filter 1 and the film structure of each layer, the film forming process, and the like are completely the same. It produced as a comparative example. In this comparative example sample, since the film thickness was not adjusted to optimize the optical characteristics, a large ripple occurred in the transmission wavelength region, but the half-wavelength of infrared light could be confirmed near the wavelength of 675 nm, and the environmental characteristics were The characteristic which can confirm the difference was obtained. However, when the same high-temperature and high-humidity test was performed on this comparative example sample, it was confirmed that the shift amount of the half-wavelength of infrared light was changed by about 3 nm on the average of several samples and 4 nm on the maximum value. It was done.

  FIG. 7 shows a modification of the first embodiment. The infrared cut filter 1 ′ shown in FIG. 7A also has a function of an ultraviolet and infrared cut filter. On the transparent substrate 2, a light absorbing structure 3, a near infrared light reflecting structure 5 as an air shielding layer, and an ultraviolet light reflecting structure 6 are sequentially laminated. An antireflection structure 7 having a structure is formed.

  In this case, the near-infrared light reflecting structure 5 and the ultraviolet light reflecting structure 6 are provided on the surface of the light absorbing structure 3 as an atmospheric shielding layer. Further, the antireflection structure 7 has a function of balancing the stress with the opposite surface on which the light absorption structure 3, the reflection structure 5, and the reflection structure 6 are arranged.

  In the infrared cut filter 1 ″ of the modified example shown in (b), the light absorption structure 3 is formed on the surface side of the transparent substrate 2, and the antireflection structure 7 is formed on the surface as an air shielding layer. The near-infrared light reflecting structure 5 is formed on the surface.

  When the near-infrared light reflecting structure 5 or the ultraviolet light reflecting structure 6 as the atmospheric shielding layer is formed on the outermost layer, the antireflection function is the reflecting structure 5 or the reflecting structure 6 or the configuration. Is included in both reflecting structures 5 and 6.

  FIG. 8 is a configuration diagram of an imaging apparatus such as a video camera using the infrared cut filter 1 manufactured in the first embodiment. On the optical path, the lens 11, the light quantity diaphragm 12, the lenses 13 to 15, the infrared cut filter 1, and the solid-state image sensor 16 are sequentially arranged. Further, when the infrared cut filter 1 is disposed, the light absorption structure 3 is disposed so as to be closer to the solid-state imaging device 16 with respect to the near-infrared light reflection structure 5 so that ghost light can be further reduced. To do.

  In the light quantity diaphragm 12, a pair of diaphragm blades 18 a and 18 b are movably attached to the diaphragm blade support plate 17. An ND (Neutral Density) filter 19 is attached to the diaphragm blade 18a for the purpose of reducing the amount of light passing through the opening formed by the diaphragm blades 18a and 18b.

  By mounting the infrared cut filter 1 according to the first embodiment on the front surface of the solid-state imaging device 16, an imaging device in which a change in optical characteristics due to moisture such as the ambient atmosphere is significantly reduced can be obtained.

  The infrared cut filter 1 can also be driven to move forward and backward in the optical path. Specifically, the amount of light that has passed through the light amount diaphragm 12 and formed on the solid-state imaging device 16 is determined, and the infrared cut filter 1 is inserted into the optical path. When the amount of light of the incident field is sufficient for normal photographing, the infrared cut filter 1 is caused to enter the optical path by a drive unit (not shown) so as to be applied to the solid-state imaging device 16. When the amount of light is insufficient, the solid-state image sensor 16 is retracted out of the optical path so as not to be applied.

  Depending on the presence or absence of the infrared cut filter 1 in the optical path, an optical path difference may occur in the light beam to be imaged, and the image may deteriorate. In such a case, image deterioration can be sufficiently reduced by inserting a base material made of the same material as the transparent substrate 2 of the infrared cut filter 1 as a dummy.

  The imaging device thus manufactured can significantly reduce the occurrence of ghosts.

  FIG. 9 shows a configuration diagram of a light amount adjusting device suitable for use in a photographing system such as a video camera or a digital still camera. The light amount adjusting device is provided to control the amount of light incident on the solid-state imaging device 16 composed of a CCD or a CMOS sensor. As the field of view becomes brighter, the apertures by the diaphragm blades 18a and 18b are controlled to be narrowed down further. It has a structure that goes on. As a countermeasure against the deterioration of the image performance that occurs in the small aperture state, an ND filter 19 is disposed in the vicinity of the aperture blades 18a and 18b, and the aperture is extremely reduced even if the brightness of the object field is the same. I do not have to.

  Incident light from the object field passes through the light amount diaphragm 12 and reaches the solid-state image sensor 16 so that it is converted into an electrical signal to form an image. The infrared cut filter 1 can be arranged in the light quantity diaphragm device 12, the infrared cut filter 1 can be arranged at the position of the ND filter 19 instead of the ND filter 19, and the diaphragm blade support plate 17. It can also be arranged to be fixed to.

  In this case, although depending on the position where the infrared cut filter 1 is disposed and the mechanical mechanism of the light quantity reduction device 12, it may be assumed that the outer shape required for the infrared cut filter 1 is different, and if an optimum shape is selected. Good. The infrared cut filter 1 having a desired characteristic and shape is manufactured by changing the pattern of the light absorbing structure 3 and the punching shape used at the time of film formation by the same film design and film formation process as in Example 1. Is possible.

  By using the light quantity restricting device 12 manufactured in this way, it is possible to realize an imaging device in which changes in optical characteristics due to moisture such as the ambient atmosphere are reduced. At this time, similarly to the second embodiment, the light absorption structure 3 is disposed on the surface side close to the solid-state imaging device 16 so that the ghost light can be further reduced.

  The light quantity restricting device 12 thus manufactured can significantly reduce the generation of ghost light.

DESCRIPTION OF SYMBOLS 1, 1 ', 1 "Infrared cut filter 2 Transparent substrate 3 Light absorption structure 4, 5 Near-infrared light reflection structure 6 Ultraviolet light reflection structure 7 Antireflection structure 12 Light quantity diaphragm 16 Solid-state image sensor 17 Diaphragm blade Support plate 18a, 18b Aperture blade 19 ND filter

Claims (6)

  A near-infrared light that is formed of a resin layer in which a pigment is dispersed on a transparent substrate and has a predetermined absorption wavelength region and a plurality of inorganic thin films are laminated to reflect at least a part of the near-infrared wavelength region. In the optical filter formed with the light reflecting structure, the absorption wavelength of the light absorbing structure is changed to a transition wavelength region in which the light of the near infrared light reflecting structure is transmitted to a nontransparent wavelength region. An optical filter, wherein at least part of the region overlaps and an air shielding layer is provided on the surface of the light absorption structure.   The optical filter according to claim 1, wherein the atmospheric shielding layer is the near-infrared light reflecting structure or an ultraviolet light reflecting structure in which a plurality of inorganic thin films are laminated.   The optical filter according to claim 1, wherein the optical filter has a function of an infrared cut filter or an ultraviolet infrared cut filter.   An imaging apparatus comprising the optical filter according to any one of claims 1 to 3.   The imaging apparatus according to claim 4, wherein the optical filter has the light absorption structure disposed closer to the imaging element than a near-infrared light reflection structure having the transition wavelength region.   An aperture blade that forms an opening, an optical filter according to any one of claims 1 to 3 that can freely advance and retract into the opening, and a drive unit that drives the optical filter. Light quantity adjustment device.

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