TWI526767B - Optical filter module and optical filter system - Google Patents

Description

Optical filter module and optical filter system

The invention relates to an optical filter module and an optical filter system.

In the optical system of an electronic camera represented by a general video camera and a digital still camera, a combined optical system, an infrared occlusion filter, and an optical low-pass filter are sequentially disposed from the object side along the optical axis. An imaging element such as a CCD (Charge Coupled Device) or a MOS (Metal Oxide Semiconductor) (see, for example, Patent Document 1). Furthermore, the imaging element here has a sensitivity characteristic of light in a wavelength band that is wider than light (visible light) in the wavelength band visible to the human eye. To this end, in addition to visible light, it also responds to light in the infrared or ultraviolet range.

The human eye responds to light at a wavelength in the range of 400 to 620 nm in the dark, and responds to light at a wavelength in the range of 420 nm to 700 nm. On the other hand, for example, in a CCD, light having a wavelength of 400 to 700 nm is responded to with high sensitivity, and light having a wavelength of less than 400 nm and light having a wavelength exceeding 700 nm are also responded.

For this reason, in the imaging device described in Patent Document 1 to be described later, an infrared ray blocking filter is provided in addition to the CCD of the imaging element, so that the light in the infrared light region does not reach the imaging element, and an image of the image close to the human eye is obtained. .

Moreover, in the prior optical filter, in order to maximize the transmittance of the visible field visible to the human eye, the application can be reduced on the main surface of the optical filter. The anti-reflection film (AR coating) of the reflection of light in the field of view is a general filter structure.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-209510

However, in the imaging device, in addition to a general video camera and a digital still camera, there is also an imaging device used for other purposes such as a surveillance camera that is different from normal photography.

For example, in a surveillance camera, it is necessary to perform surveillance photography under squint at night, not only during the daytime. In the sneak peek, since the photograph is in a state in which the human eye cannot see it, the camera in which the normal visible field is set to the photographing range cannot be photographed under scotopic vision. For this reason, the photographic recording system in the illuminating state is performed by using the light in the infrared light field. However, the imaging device described in Patent Document 1 is provided with an infrared ray blocking filter that blocks the light in the infrared light field. Used for squint photography.

Here, in order to solve the above problems, an object of the present invention is to provide an optical filter module and an optical filter system that can perform photographing not only during daylight when natural light enters, but also under dark vision such as nighttime.

In order to achieve the above object, an optical filter module according to the present invention is provided in an image pickup device, and is capable of switching an optical filter module in which a plurality of filters are arranged, wherein the plurality of filters transmit visible light and at least interrupt infrared rays. a first filter and a second filter that passes only infrared rays; the first filter and the second filter are selectively switchable, and the first filter indicates a wavelength band of 400 nm to 550 nm. The transmittance at the wavelength is the maximum value, the transmittance at a wavelength of 700 nm is less than 5%, and the second filter indicates the maximum transmittance at a wavelength in the wavelength band of 860 nm or more, 830 nm. The transmittance in the wavelength is less than 5% of the light transmission property.

According to the invention, since the first filter and the second filter are arranged to be selectively switchable, photographing can be performed not only during daylight when natural light enters, but also under squint at night or the like. Specifically, the first filter is disposed during daylight hours, and the second filter is disposed in a dark state, and photographing can be performed not only during daylight hours but also under dark vision such as nighttime. In particular, since the daytime photography can be performed in a state where the visible light is transmitted and at least the first filter of the infrared ray is interrupted, a more natural imaging image close to the human eye can be obtained during the day. Further, since night photography can be performed in a state in which only the second filter of the infrared rays is present, there is no overexposure due to partial incidence of natural light in the visible region during night photography, and it is possible to obtain more stable. A vivid portrait of infrared photography.

In the above configuration, the second filter may be configured to block other regions of the infrared rays only by a predetermined band set in advance by infrared rays.

At this time, in addition to the above-described effects, the second filter blocks the other bands of the infrared rays only by the specific band set in advance by the infrared rays, so that the photography under scotopic effect can be more excellent.

In the above configuration, the first filter is provided to absorb infrared rays. The infrared absorber and the infrared reflector that reflects infrared rays may also be used.

In this case, in addition to the above-described effects, the first filter includes an infrared absorber that absorbs infrared rays and an infrared reflector that reflects infrared rays, thereby suppressing ghosts and spots while improving color realism. Therefore, the photography during the day can have a better effect.

In the above configuration, the infrared absorber is a light transmission characteristic in which a transmittance in a wavelength band of 620 nm to 660 nm is 50%; and the infrared reflector is a wavelength in a wavelength band of 670 nm to 690 nm. The light transmittance of the medium transmittance is 50%; the combination of the infrared absorber and the infrared reflector indicates that the transmittance in the wavelength band of 620 nm to 660 nm is 50%, and the transmittance in the wavelength of 700 nm is not Light transmission characteristics of 5% or more are also available.

In this case, the first filter includes the infrared absorber and the infrared reflector, and the infrared absorber indicates a light transmission characteristic in which a transmittance in a wavelength band of 620 nm to 660 nm is 50%, and the infrared reflector indicates a light transmission characteristic in which a transmittance in a wavelength band of 670 nm to 690 nm is 50%, and a combination of the infrared absorber and the infrared reflector indicates a transmittance in a wavelength band of 620 nm to 660 nm. 50%, the transmittance of the wavelength of 700 nm is less than 5%. Therefore, by combining the above-mentioned infrared absorber and the above-mentioned infrared reflector, it is possible to obtain a slow reduction in transmittance from the visible pre-covered infrared light field, 700 nm. The transmittance in the wavelength is about 0%, which is close to the sensitivity characteristic of the human eye.

In the infrared absorber, the infrared absorber having a light transmission characteristic of a wavelength of 50% in a wavelength band of 620 nm to 660 nm is used, and for example, has a light transmission property as shown by L11 in Fig. 10 . In the infrared absorbing glass, the point at which the transmittance is about 0% (less than 5%) is 700 nm by combining the infrared absorbing effect of the infrared ray absorbing body on the infrared ray reflecting body. Therefore, the first filter of the present invention is compared with the conventional infrared ray interrupting filter formed of the infrared absorbing glass having the light transmitting property shown by L12 of Fig. 10, in the visible region, especially at 600 nm to 700 nm. The wavelength band maintains high transmittance. In other words, it is possible to transmit a sufficient amount of red light (light having a wavelength of 600 nm to 700 nm) that can be sensed by the imaging element of the imaging device while blocking infrared rays having a wavelength of more than 700 nm. Therefore, the first filter of the present invention is applied to the infrared ray blocking filter of the imaging device, and the sensitivity of the red color of the imaging element can be eliminated, and the image captured by the imaging device can easily become a dark image. The shortcomings.

Further, in the first filter, the infrared reflector is combined with the infrared absorber to suppress the amount of light reflected by the infrared reflector. Therefore, it is possible to suppress the occurrence of ghosting due to reflection of the light of the infrared reflector.

Further, the thickness of the infrared absorbing glass having a light transmitting property indicated by L11 in Fig. 10 having a transmittance of 50% at a wavelength of 640 nm is as shown by L12 of Fig. 10 used as a conventional infrared ray blocking filter. The transmittance of the infrared absorbing glass of the light transmitting property is less than or equal to half of the thickness of the infrared absorbing glass, and the light transmittance of the wavelength of the wavelength range of 620 to 660 nm which is the first filter of the present invention is 50%. The infrared absorber can be made thinner than the infrared cut filter formed of the conventional infrared absorbing glass having the light transmitting property shown by L12 in Fig. 10 . Therefore, according to the first filter of the present invention, it is possible to provide a visible light having a thickness equal to or thinner than that of the conventional infrared ray interrupting filter formed of only the infrared absorbing body, and to sufficiently transmit the visible light of the red light to block the infrared ray. And in the visible field, an infrared ray blocking filter having a light transmission property close to the human eye.

Further, in order to achieve the above object, the optical filter system according to the present invention is provided with a combined optical system that emits light from the outside, at least in order from the external object side along the optical axis, and is switchable. The optical filter module of the filter, the optical filter, and the optical filter system of the imaging device of the imaging element are characterized in that the plurality of filters transmit visible light, at least the first filter that blocks infrared rays, and only passes infrared rays. a second filter; the first filter and the second filter are selectively switchable to the optical axis, and the first filter is a wavelength in a wavelength band of 400 nm to 550 nm. The transmittance is the maximum value, the transmittance at a wavelength of 700 nm is less than 5%, and the second filter is a wavelength at a wavelength in the wavelength band of 860 nm or more, and the wavelength is 830 nm. The transmittance is a light transmission characteristic of less than 5%.

According to the present invention, since either one of the first filter and the second filter is selectively switchable to the optical axis, it can be performed not only during daylight when natural light enters but also during night vision such as nighttime. photography. Specifically, the first filter is disposed on the optical axis during daylight hours, and the second filter is disposed on the optical axis in a dark state, not only during daylight hours but also under night vision. Photography is also possible. In particular, since the daytime photography can be performed in a state where the visible light is transmitted and at least the first filter of the infrared ray is interrupted, a more natural imaging image close to the human eye can be obtained during the day. Further, since night photography can be performed in a state in which only the second filter of the infrared rays is present, there is no overexposure due to partial incidence of natural light in the visible region during night photography, and it is possible to obtain more stable. A vivid portrait of infrared photography.

In the above configuration, the second filter may be configured to block other regions of the infrared rays only by a predetermined band set in advance by infrared rays.

At this time, in addition to the above-described effects, the second filter blocks the other bands of the infrared rays only by the specific band set in advance by the infrared rays, so that the photography under scotopic effect can be more excellent.

In the above configuration, the first filter may include an infrared absorber that absorbs infrared rays and an infrared reflector that reflects infrared rays.

In this case, in addition to the above-described effects, since the first filter includes an infrared absorber that absorbs infrared rays and an infrared reflector that reflects infrared rays, it is possible to suppress ghosting and light spots while improving color realism. Make daytime photography a better result.

In the above configuration, the infrared absorber is a light transmission characteristic in which a transmittance in a wavelength band of 620 nm to 660 nm is 50%; and the infrared reflector is a wavelength in a wavelength band of 670 nm to 690 nm. The light transmittance of the medium transmittance is 50%; the combination of the infrared absorber and the infrared reflector indicates that the transmittance in the wavelength band of 620 nm to 660 nm is 50%, and the transmittance in the wavelength of 700 nm is not Light transmission characteristics of 5% or more are also available.

In this case, the first filter includes the infrared absorber and the infrared reflector, and the infrared absorber indicates a light transmission characteristic in which a transmittance in a wavelength band of 620 nm to 660 nm is 50%, and the infrared reflector indicates a light transmission characteristic having a transmittance of 50% in a wavelength band of 670 nm to 690 nm, and a combination of the infrared absorber and the infrared reflector indicates a wavelength band of 620 nm to 660 nm The transmittance in the wavelength is 50%, and the transmittance in the wavelength of 700 nm is less than 5%. Therefore, by combining the above-mentioned infrared absorber and the infrared reflector, it is possible to obtain an infrared light field from the visible region, and the transmittance is slow. The ground reduction is a transmittance of about 0% in the wavelength of 700 nm which is close to the sensitivity characteristic of the human eye.

In the infrared absorber, the infrared absorber having a light transmission characteristic of a wavelength of 50% in a wavelength band of 620 nm to 660 nm is used, and for example, has a light transmission property as shown by L11 in Fig. 10 . In the infrared absorbing glass, the point at which the transmittance is about 0% (less than 5%) is 700 nm by combining the infrared absorbing effect of the infrared absorbing body in the infrared ray reflecting body. Therefore, the first filter of the present invention is compared with the conventional infrared ray interrupting filter formed of the infrared absorbing glass having the light transmitting property shown by L12 of Fig. 10, in the visible region, especially at 600 nm to 700 nm. The wavelength band maintains high transmittance. In other words, it is possible to transmit a sufficient amount of red light (light having a wavelength of 600 nm to 700 nm) that can be sensed by the imaging element of the imaging device while blocking infrared rays having a wavelength of more than 700 nm. Therefore, the first filter of the present invention is applied to the infrared ray blocking filter of the imaging device, and the sensitivity of the red color of the imaging element can be eliminated, and the image captured by the imaging device can easily become a dark image. The shortcomings.

Further, in the first filter, the infrared reflector is combined with the infrared absorber to suppress the amount of light reflected by the infrared reflector. Therefore, it is possible to suppress the occurrence of ghosting due to reflection of the light of the infrared reflector.

Further, the thickness of the infrared absorbing glass having a light transmitting property indicated by L11 in Fig. 10 having a transmittance of 50% at a wavelength of 640 nm is as shown by L12 of Fig. 10 used as a conventional infrared ray blocking filter. The transmittance of the infrared absorbing glass of the light transmitting property is less than or equal to half of the thickness of the infrared absorbing glass, and the light transmittance of the wavelength of the wavelength range of 620 to 660 nm which is the first filter of the present invention is 50%. The infrared absorber can be made thinner than the infrared cut filter formed of the conventional infrared absorbing glass having the light transmitting property shown by L12 in Fig. 10 . For this reason, according to the first filter of the present invention, it is possible to provide a visible light which is sufficiently transmitted through the same thickness or a thin thickness as the previous infrared ray interrupting filter composed of only the infrared absorbing body, and is occluded. Infrared, and in the visible field, has an infrared blocking filter that is close to the light transmission characteristics of the human eye.

Further, in the above-described configuration of the present invention, the infrared ray absorbing system indicates a light transmittance of a transmittance of 10% to 40% at a wavelength of 700 nm, and the infrared reflection system indicates a transmittance of less than 15% at a wavelength of 700 nm. Light characteristics are also available.

In this case, the infrared absorber having a light transmittance of 10% to 40% in a wavelength of 700 nm and the infrared absorber having a light transmission characteristic of a wavelength of less than 15% in a wavelength of 700 nm are used. In combination, high transmittance is surely obtained in the wavelength band of the visible light of red (600 nm to 700 nm).

Further, in the above configuration of the present invention, the infrared reflection system has a light transmittance of 90% or more in a wavelength band of 430 nm to 650 nm. Features are also available.

At this time, since the light transmission characteristic of the light transmitting property of the infrared absorbing body in the wavelength band of 430 nm to 650 nm is obtained, the infrared light domain is covered from the visible region, and the transmittance is slowly decreased, and the transmission at a wavelength of 700 nm can be obtained. The rate becomes a light transmission characteristic of 0% close to the sensitivity characteristic of the human eye, and in addition, high transmittance can be surely obtained in the visible region, particularly in the wavelength band of visible light of red (600 nm to 700 nm).

According to the present invention, photographing can be performed not only during the day when natural light enters, but also under dark vision such as at night.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment>

In the imaging device 1 of the present embodiment, as shown in FIG. 1, a lens 2 that is coupled to an optical system that emits light from the outside is disposed at least along the optical axis 11 from the external object side, and is switchable. The optical filter module 3 of the complex filter (refer to the later description), the optical filter 8 which is an OLPF, and the imaging element 9.

The optical filter module 3 is provided with a first filter 4 that transmits visible light, at least blocks infrared rays, and a second filter 7 that passes only infrared rays. The Any one of the first filter 4 and the second filter 7 is selectively switched to the optical axis 11 by a known switching means (not shown). Specifically, the first filter 4 is placed on the optical axis 11 when natural light such as daylight enters, and the second filter 7 is placed on the optical axis 11 in the dark view such as at night. In addition, when the second filter 7 is disposed on the optical axis 11, light from an LED (not shown) having a peak wavelength of 850 to 900 nm (in the present embodiment, 870 nm) is irradiated to the subject. body. In the present embodiment, the definition of the daytime is a state in which the illuminance exceeds 4001x, and the definition at night is a condition in which the illuminance is 400x1 or less. Furthermore, the 400x1 system is an example here, and the daytime and nighttime illumination can be freely set by the practitioner. Alternatively, only the nighttime definition may be made, and the illuminance of the definition that deviates from the nighttime may be determined as daytime, or only during the daytime, and the illuminance of the definition deviating from the daytime may be determined as nighttime. In other words, the first filter 4 and the second filter 7 may be switched in accordance with the set illuminance based on the illuminance reference.

Moreover, since the optical filter module 3 includes the first filter 4, the optical filter 8 which is an OLPF does not form an infrared ray interrupting filter, and only two wavelength bands (visible field and infrared light field) are prevented. The reflection preventing film 81 of the single layer in which the light is reflected is formed on both main faces. In the present embodiment, only the single-layer anti-reflection film 81 is formed on the both main surfaces of the optical filter 8. However, the present invention is not limited thereto, and an anti-reflection film capable of preventing reflection of light of a specific wavelength is formed. can.

According to the imaging device 1 shown in FIG. 1, the lens 2, the first filter 4, the optical filter 8, and the imaging element 9 are sequentially disposed from the external subject side along the optical axis 11 during the daytime. By arranging the first filter 4 on the optical axis In the structure of 11, the imaging device 1 (optical filter module 3) has the light transmission characteristics shown in FIG. On the other hand, at night, the lens 2, the second filter 7, the optical filter 8, and the imaging element 9 are sequentially disposed along the optical axis 11 from the external subject side. The imaging device 1 (optical filter module 3) has the light transmission characteristics shown in FIG. 5 by the structure in which the second filter 7 is disposed on the optical axis 11.

As described above, according to the imaging apparatus shown in FIG. 1, since either the first filter 4 and the second filter 7 are selectively switched and arranged on the optical axis 11, in the visible region, sensitivity characteristics close to the human eye can be obtained. The spectral characteristic, and can transmit the light of the desired band of the infrared light domain. As a result, according to the image pickup apparatus 1 shown in FIG. 1, it is possible to appropriately perform photographing during the day when the infrared rays are blocked, and photographing under the dark vision such as nighttime only by infrared rays. That is, photographing can be performed not only during the day when natural light enters, but also under squint at night. Specifically, the first filter 4 is switched between the optical axis 11 during the daytime, and the second filter 7 is switched to the optical axis 11 in the dark state, not only during the day, but also at nighttime. Photography can also be performed underneath. In particular, since the daytime photography can be performed in a state where the visible light is transmitted and at least the first filter 4 that blocks the infrared rays is interposed, a more natural image capturing image close to the human eye can be obtained during the day. Further, since night photography can be performed in a state in which only the second filter 7 of infrared rays is present, there is no possibility that overexposure occurs due to partial injection of natural light in the visible region in night photography, and it is possible to obtain more stable. A vivid portrait of infrared photography.

Next, the optical filter module 3 will be described with reference to FIGS. 1 to 7 . In the optical filter module 3, a first filter 4 and a second filter are provided 7 and a known switching means (not shown).

As shown in Figs. 2 and 3, the first filter 4 is composed of an infrared absorber 5 that transmits visible light and absorbs infrared rays, and an infrared reflector 6 that transmits visible light and reflects infrared rays.

The infrared absorber 5 is formed by forming an anti-reflection film 54 (AR coating) on one main surface 52 of the infrared absorbing glass 51.

As the infrared absorbing glass 51, a blue glass in which a dye such as copper ions is dispersed is used, for example, a square thin plate glass having a thickness of 0.2 mm to 1.2 mm.

Further, the anti-reflection film 54 is formed on the main surface 52 of the infrared absorbing glass 51 by a vacuum deposition apparatus (not shown) to form a single layer made of MgF ₂ by vacuum deposition. A multilayer film made of Al ₂ O ₂ and ZrO ₂ and MgF ₂ , or a film of a multilayer film made of TiO ₂ and SiO ₂ . In addition, the anti-reflection film 54 is subjected to a vapor deposition operation while monitoring the film thickness, and when the predetermined film thickness is reached, the gate (not shown) provided in the vicinity of the vapor deposition source (not shown) is turned off, and the evaporation is stopped. The deposition of the plating material is carried out.

The infrared absorber 5 is a light transmission characteristic in which the transmittance in the wavelength band of 620 nm to 660 nm is 50%, and the transmittance in the wavelength of 700 nm is 10% to 40%. Further, in the light transmission characteristics of the infrared absorber 5, the transmittance is 90% or more of the wavelength in the wavelength band of 400 nm to 550 nm.

The infrared reflector 6 is formed by forming an infrared reflecting film 64 on one main surface 62 of the transparent substrate 61.

As the transparent substrate 61, a colorless transparent glass that transmits visible light and infrared rays, for example, a square thin plate glass having a thickness of 0.2 mm to 1.0 mm is used.

As shown in FIG. 4, the infrared reflecting film 64 is a multilayer film in which a first film 65 made of a high refractive index material and a second film 66 made of a low refractive index material are alternately laminated. Further, in this embodiment, TiO _{2 is} used for the first film 65, SiO _{2 is} used for the second film 66, TiO _{2 is} odd layer, and SiO _{2 is} even layer, but the odd layer is SiO ₂ and the even layer is TiO _{2 is} also available.

As a method of manufacturing the infrared reflecting film 64, TiO ₂ and SiO _{2 are} alternately vacuum-deposited by a known vacuum vapor deposition apparatus (not shown) on one main surface 62 of the transparent substrate 61 to form an infrared ray shown in FIG. A method of reflecting the film 64. In addition, the film thickness adjustment of the first film 65 and the second film 66 is performed while monitoring the film thickness, and when the film thickness is reached, the gate provided in the vicinity of the vapor deposition source (not shown) is closed. (not shown) or the like, the vapor deposition of the vapor deposition material (TiO ₂ , SiO ₂ ) is stopped.

Further, as shown in FIG. 4, the infrared reflecting film 64 is composed of a plurality of layers defined in order from the one main surface 62 side of the transparent substrate 61, and is composed of one layer, two layers, and three layers in the present embodiment. . Each of the first, second, and third layers is formed by laminating a first film 65 and a second film 66. The thickness of each of the first layer, the second layer, and the third layer is different depending on the optical film thickness of the first film 65 and the second film 66. In addition, the optical film thickness here is calculated|required by the following Formula 1.

[Formula 1] Nd = d × N × 4 / λ (Nd: optical film thickness, d: physical film thickness, N: refractive index, λ: center wavelength)

In the present embodiment, the infrared ray reflector 6 has a transmittance of 90% or more in a wavelength band of 430 nm to 650 nm, and a transmittance of 50% in a wavelength band of 660 nm to 690 nm, at 700 nm. The number of layers of the infrared reflector 64 and the optical film thickness of each layer are appropriately adjusted so that the transmittance in the wavelength is less than 15%.

The first filter 4 composed of the infrared absorber 5 and the infrared reflector 6 has a thickness of, for example, 0.4 mm to 1.6 mm. In other words, the thickness of the infrared absorbing glass 51 constituting the infrared absorbing glass 5 and the thickness of the transparent substrate 61 constituting the infrared ray reflector 6 are appropriately adjusted so that the total thickness of the infrared absorbing body 5 and the infrared ray reflector 6 is, for example, 0.4 mm. 1.6mm.

Then, the first filter 4 is a combination of the light-transmitting characteristics of the infrared absorber 5 and the infrared reflector 6, and indicates that the transmittance in the wavelength band of 400 nm to 550 nm becomes the maximum value, and the wavelength of 620 nm to 660 nm. The transmittance in the wavelength in the band is 50%, and the transmittance in the wavelength of 700 nm is less than 5%.

The first filter 4 formed by the above-described structure includes the infrared absorbing body 5 that absorbs infrared rays and the infrared ray reflecting body 6 that reflects infrared rays, thereby suppressing ghost images and light spots, and also improving color realism. Degree, so it can make the daytime photography have a better effect.

Further, as shown in Figs. 5 and 6, the second filter 7 blocks the visible region only by a predetermined band (in the present embodiment, a half value of 850 nm or more) set in advance by infrared rays. Further, in the second filter 7, an LED (not shown) having a peak wavelength of light of 850 to 900 nm (in the present embodiment, 870 nm) is provided, and when the second filter 7 is disposed on the optical axis 11, Light from the LED is illuminated to the subject. As described above, the second filter 7 is a filter dedicated to photography in a dark view, and is not intended to be used for visual observation such as daytime, and cannot be visually photographed. Further, the present invention is not limited to this embodiment, and it is also possible to adopt a structure that is only close to a specific band of 870 nm. At this time, better scotopic photography for removing noise can be performed.

The second filter 7 blocks another region of the infrared ray on the main surface of the transparent substrate 71 in order to pass only a specific band set in advance by infrared rays (corresponding to the wavelength of the light beam irradiated from the LED in the present embodiment). 72 forms infrared rays through the coating 74 (IR through the coating). Further, an anti-reflection film 77 is formed on the other main surface 73 of the second filter 7. The anti-reflection film 77 is formed on the other main surface 73 of the second filter 7 by a vacuum vapor deposition apparatus (not shown) to form a single layer made of MgF ₂ and made of Al _{2 .} A multilayer film of O ₂ and ZrO ₂ and MgF ₂ , or a film of a multilayer film made of TiO ₂ and SiO ₂ . According to the second filter 7, since only the specific band set in advance by the infrared rays (corresponding to the wavelength of the light irradiated from the LED in the present embodiment) is blocked, the other bands of the infrared rays are blocked, and the photography can be performed under scotopic vision. Have a better effect.

As the transparent substrate 71, the use of transmitted visible light and infrared rays is used. The transparent glass is, for example, a square thin plate glass having a thickness of 0.4 mm to 1.6 mm.

As shown in Fig. 7, the infrared ray-passing coating 74 is a multilayer film in which a first film 75 made of a high refractive index material and a second film 76 made of a low refractive index material are alternately laminated. Further, in this embodiment, TiO _{2 is} used for the first film 75, SiO _{2 is} used for the second film 76, TiO _{2 is} odd layer, and SiO _{2 is} even layer, but the odd layer is SiO ₂ and the even layer is TiO _{2 is} also available.

As a method of manufacturing the infrared ray-passing coating 74, TiO ₂ and SiO _{2 are} alternately vacuum-deposited by a known vacuum vapor deposition apparatus (not shown) on a principal surface 72 of the transparent substrate 71 to form a layer as shown in FIG. The method of infrared rays passing through the coating 74. In addition, the film thickness adjustment of the first film 75 and the second film 76 is performed while monitoring the film thickness, and when the predetermined film thickness is reached, the gate provided in the vicinity of the vapor deposition source (not shown) is closed. (not shown) or the like, the vapor deposition of the vapor deposition material (TiO ₂ , SiO ₂ ) is stopped.

Further, the infrared ray-passing coating layer 74 is composed of a plurality of layers defined in order from the one main surface 72 side of the transparent substrate 71 as shown in Fig. 7, and in the present embodiment, one layer, two layers, and three layers are used. Composition. Each of the first, second, and third layers is formed by laminating the first film 75 and the second film 76. Since the optical film thicknesses of the first film 75 and the second film 76 which are laminated are different, the thicknesses of the respective layers of one layer, two layers, and three layers are also different. Here, the optical film thickness is determined by the above calculation formula 1.

In this embodiment, the second filter has a wavelength of 860 nm. The transmittance of the band is 90% or more, the transmittance is 50% at a wavelength in the wavelength band of 850 nm, and the transmittance is less than 15% at a wavelength of 840 nm, and the infrared ray passing through the coating is appropriately adjusted. The number of layers of 74 and the optical film thickness of each layer.

Such a second filter 7 has a thickness of, for example, 0.4 mm to 1.6 mm.

Then, the second filter 7 has a light transmission characteristic of the infrared ray through the coating layer 74, and indicates that the transmittance in the wavelength band of 860 nm or more becomes the maximum value, and the transmittance becomes the wavelength in the wavelength band of 850 nm. 50%, light transmittance at a wavelength of 830 nm of less than 5%.

Next, the wavelength characteristics of the first filter 4 and the second filter 5 were actually measured, and the results and structures were disclosed as an example in FIG. 8 and Tables 1 and 2.

- Regarding the first filter 4 of the embodiment

In the first filter 4 of the present embodiment, as the infrared absorbing glass 51, a glass plate in which a blue glass such as a copper ion is dispersed is used, and a glass plate having a thickness of 0.8 mm and a refractive index of about 1.5 in the N atmosphere is used. Then, on one main surface 52 of the infrared absorbing glass 51, an Al ₂ O ₃ film having a refractive index of 1.6 in N atmosphere, a ZrO ₂ film having a refractive index of 2.0 in N atmosphere, and a refractive index in N atmosphere are In the order of the MgF ₂ film of 1.4, each film constituting the anti-reflection film 54 is formed by vacuum deposition to obtain an infrared absorber 5.

This infrared absorbing body 5 has a light transmitting property as L1 of FIG. Further, in this embodiment, the incident angle of the light is set to 0 degrees, that is, the light is incident perpendicularly.

As shown in Fig. 8, the infrared absorbing glass 51 indicates that the transmittance in the wavelength band of 400 nm to 550 nm is 90% or more, the transmittance in the wavelength band of 550 nm to 700 nm is reduced, and the wavelength is 50% in the wavelength of about 640 nm. The transmittance at a wavelength of 700 nm becomes a light transmission characteristic of about 17%.

As the transparent substrate 61 of the infrared reflector 6, a glass plate having a refractive index of 1.5 in the atmosphere of N and a thickness of 0.3 mm was used. Further, as the first film 65 constituting the infrared ray reflection film 64, TiO ₂ having a refractive index of 2.30 in N atmosphere is used, and as the second film 66, SiO ₂ having a refractive index of 1.46 in N atmosphere is used. The wavelength is 688 nm.

The main surface 62 of the transparent substrate 61 is formed by the method of manufacturing the infrared reflecting film 64 in which the optical thickness of each of the first film 65 and the second film 66 is 40 layers as shown in Table 1 The first film 65 and the second film 66 are laminated (the first film 65) to obtain the infrared reflecting film 6.

Table 1 shows the composition of the infrared reflecting film 64 of the first filter 4 and the optical film thickness of each film (the first film 65 and the second film 66).

This infrared ray reflector 6 has a light transmitting property as L2 of FIG. That is, the light transmission property of the infrared ray reflection film 64 indicates that the transmittance is about 100% in the wavelength band of 395 nm to 670 nm (including the wavelength band of the wavelength band of 430 nm to 650 nm), and the wavelength exceeds about 670 nm. The transmittance is drastically reduced, and the transmittance is about 50% at a wavelength of about 680 nm, and the transmittance at a wavelength of 700 nm is about 4%.

Then, as shown in Fig. 8, the first filter 4 of the embodiment having a thickness of 1.1 mm is obtained by the other main surface 53 of the infrared absorbing glass 51 and then the other main surface 63 of the transparent substrate 61.

The first filter 4 has a light transmitting property as shown by L3 in Fig. 8 in which the light transmitting characteristics of the infrared ray absorbing body 5 and the infrared ray reflecting body 6 are combined. That is, the first filter 4 of the embodiment shows that the transmittance in the wavelength band of 400 nm to 550 nm is 90% or more, the transmittance in the wavelength band of 550 nm to 700 nm is reduced, and the transmittance is in the wavelength of about 640 nm. The transmittance was 50%, and the transmittance was about 0% at a wavelength of 700 nm.

In the first filter 4 of the present embodiment, the combination of the infrared absorber 5 and the infrared reflector 6 can be obtained at 400 nm to 550 nm, as shown by the light transmission characteristics of the first filter 4 of the embodiment. The transmittance in the wavelength band is 90% or more, the transmittance is 50% in the wavelength range of 620 nm to 660 nm, and the transmittance is about 0% in the wavelength of 700 nm (less than 5). %) light transmission characteristics. that is, It is possible to obtain a light transmission characteristic in which the infrared light domain is covered from the visible region, the transmittance is slowly decreased, and the transmittance at a wavelength of 700 nm is about 0% which is close to the sensitivity characteristic of the human eye.

The comparison between the light transmission characteristic L3 of the first filter 4 of the embodiment shown in FIG. 8 and the light transmission characteristic L4 of the previous infrared cut filter will be more specifically described.

The conventional infrared ray blocking filter having the light transmitting property shown by L4 in Fig. 8 is composed of an infrared absorbing body in which an antireflection film is formed on both surfaces of the infrared absorbing glass. In the conventional infrared ray interrupting filter, the thickness of the infrared absorbing glass which is an infrared absorbing body is set to 1.6 mm, and the point at which the transmittance becomes 0% is 700 nm.

On the other hand, in the first filter 4 of the embodiment, half thickness of the previous infrared ray blocking filter (infrared absorbing body) indicating the light transmitting property of L4 is used, and in the visible region, especially 600 nm to 700 nm. In the wavelength band, the infrared absorber 5 having a higher transmittance than the previous infrared cut filter, that is, the infrared absorber 5 showing the light transmission characteristics indicated by L1, combines the infrared reflector 6 and The point at which the transmittance became 0% was set to 700 nm.

Therefore, the light transmission characteristic L3 of the first filter 4 of the embodiment is in the visible light region, particularly in the wavelength band of 600 nm to 700 nm, which is compared with the light transmission characteristic L4 of the previous infrared ray interrupt filter. Higher transmittance. Further, in the light transmission characteristic L3 of the first filter 4 of the embodiment, the light transmittance at a wavelength of 700 nm is closer to 0% than the light transmission characteristic L4 of the previous infrared ray interrupt filter.

Specifically, in the light transmission characteristic L4 of the conventional infrared ray interrupting filter, the transmittance at a wavelength of 600 nm is about 55%, the transmittance at a wavelength of about 605 nm is 50%, and the transmittance at a wavelength of 675 nm. It became about 7.5%, and the transmittance became about 3% at a wavelength of 700 nm.

On the other hand, in the light transmission characteristic L3 of the first filter 4 of the embodiment, the transmittance at a wavelength of 600 nm is about 75%, and the transmittance at a wavelength of about 640 nm is 50%, and the wavelength is 675 nm. The transmittance was about 20%, and the transmittance was about 0% at a wavelength of 700 nm.

Thus, the light transmission characteristic L3 of the first filter 4 of the embodiment is in the wavelength band of 600 nm to 700 nm, especially in the wavelength band of 600 nm to 675 nm, compared with the light transmission characteristic L4 of the previous infrared ray interrupt filter. The transmittance is high and the transmittance at a wavelength of 700 nm is close to 0%. In other words, in the first filter 4 of the embodiment, it is understood that the visible light of red having a wavelength of 600 nm to 700 nm can be sufficiently transmitted while sufficiently blocking infrared rays exceeding 700 nm. Therefore, when the first filter 4 of the embodiment is mounted on the imaging device, the image sensor 9 can be used to image the image in comparison with the color which is strong in red in the past, and the image in the dark can be brightened. Camera.

In the first filter 4 of the present embodiment, the infrared absorber 6 is combined with the infrared absorber 5 to suppress the amount of light reflected by the infrared reflector 6. For this reason, occurrence of ghosting due to reflection of light rays of the infrared ray reflector 6 can be suppressed.

Further, the infrared reflector 6 is configured to attract infrared rays so that the half wavelength of the first filter 4 closely matches the half wavelength of the infrared absorber 5 The half-wavelength light of the body 5 indicates a transmittance of 90% or more. Therefore, the infrared ray interrupting filter has a light-transmitting property of the infrared absorbing body 5 which is gradually reduced in transmittance at a wavelength of 550 nm to 700 nm and is close to the sensitivity characteristic of the human eye. Characteristics, light transmission characteristics close to the sensitivity characteristics of the human eye can be obtained.

Further, in the first filter 4 of the embodiment, the infrared ray absorbing body 5 can be configured to have a thickness thinner than the previous infrared ray shielding filter having the light transmitting property indicated by L4. For this reason, the thickness of the first filter 4 can be set to be the same as or smaller than the previous infrared occlusion filter.

- Regarding the second filter 7 of the embodiment -

In the second filter 7 of the present embodiment, as the transparent substrate 71, a glass plate having a refractive index of 1.5 and a thickness of 1.1 mm in N atmosphere was used. Further, as the first film 75 constituting the infrared ray-passing coating layer 74, TiO ₂ having a refractive index of 2.30 in N atmosphere is used, and as the second film 76, SiO ₂ having a refractive index of 1.46 in N atmosphere is used. The center wavelength is 720 nm.

The main surface 72 of the transparent substrate 71 is formed by the method for producing the infrared ray-passing coating 74 composed of the 48 layers of the first film 75 and the second film 76, which are the 48 layers shown in Table 2, The first film 75 and the second film 76 are formed (layered) to obtain the second filter 7.

Table 2 shows the composition of the second filter 7 and the optical film thickness of each of the films (the first film 75 and the second film 76). This second filter 7 has a light transmitting property as shown in FIG. Further, an anti-reflection film 77 is formed on the other main surface 73 of the transparent substrate 71.

Further, in the above-described embodiment, the first filter 4 and the second filter 7 and the switching means (not shown) are provided in the optical filter module 3. However, the present invention is not limited thereto, and the module is not limited thereto. The first filter 4 and the second filter 7 and the switching means (not shown) may be directly provided in the optical filter system shown in FIG. 9 of the imaging device 1 to be constructed.

Further, the glass plate is used as the transparent substrate 61. However, the glass plate is not limited thereto, and may be, for example, a crystal plate. Further, the transparent substrate 61 may be a birefringent plate, and a birefringent plate composed of a plurality of sheets may be used. Further, the crystal plate and the glass plate may be combined to form the transparent substrate 61.

Further, in the embodiment, TiO _{2 is} used for the first film 65. However, the first film 65 is not limited thereto, and the first film 65 may be made of a high refractive material. For example, ZrO ₂ , TaO ₂ , Nb ₂ O ₂ or the like may be used. can. Further, SiO _{2 is} used for the second film 66. However, the second film 66 is not limited thereto, and the second film 66 may be made of a low refractive material. For example, MgF ₂ or the like may be used.

In the imaging device, the infrared absorber 5 is disposed closer to the lens 2 than the infrared reflector 6, but the present invention is not limited thereto. In other words, the first filter 4 may be disposed such that the infrared ray reflector 6 is located closer to the lens 2 than the infrared absorbing body 5.

For example, in the imaging device, since the first filter 4 is disposed such that the infrared absorber 5 is positioned on the lens 2 side, the infrared absorber 5 can absorb the light reflected by the infrared reflector 6, as compared with The arrangement in which the infrared ray reflector 6 is disposed on the side of the lens 2 can reduce the amount of light scattered by the infrared ray reflector 6 and scattered on the lens 2, and can suppress the occurrence of ghost images. On the other hand, in the case where the first filter 4 is disposed such that the infrared ray reflector 6 is positioned on the side of the lens 2, the infrared ray reflector 6 is disposed in comparison with the case where the infrared absorbing body 5 is disposed on the lens 2 side. Specifically, the distance between the foreign matter generated in the infrared reflector 6 and the imaging element 9 during the manufacturing process is reduced, so that deterioration of the image due to foreign matter can be suppressed.

Further, in the embodiment, the infrared absorbing body 5 is used for forming the anti-reflection film 54 on one main surface 52 or both main surfaces 51 and 52 of the infrared absorbing glass 51. However, the infrared absorbing body 5 in the present invention is It is not limited to this. For example, when the refractive index in the atmosphere of the infrared absorbing glass 51 is almost the same as the refractive index of the atmosphere, the anti-reflection film 54 may not be formed. In other words, as the infrared absorber, an infrared absorbing glass in which an antireflection film is not formed may be used.

Further, in the embodiment, the infrared reflecting body 6 is used to form the infrared reflecting film 64 on one main surface 62 of the transparent substrate 61 on the other main surface 53 of the infrared absorbing glass 51. However, in the present invention, The infrared reflector 6 is not limited to this. For example, as the infrared reflector, an infrared reflection film formed on the surface of the infrared absorbing glass may be used. At this time, the optical filter module and the optical filter system can be easily performed. Miniaturization and switching mechanism simplification and power saving.

That is, in the embodiment, the infrared reflecting film 64 is formed on one main surface 62 of the transparent substrate 61 on the other main surface 53 of the infrared absorbing glass 51, but on the other main surface 53 of the infrared absorbing glass 51, The infrared ray reflection film 64 which is an infrared absorber can also be formed directly. As described above, when the infrared reflecting film 64 is directly formed on the other main surface 53 of the infrared absorbing glass 51, the first filter 4 can be made thinner.

Furthermore, the present invention may be embodied in other various forms without departing from the spirit and scope of the invention. For this reason, the above-described embodiments and examples are merely illustrative and are not to be construed as limiting. The scope of the present invention is disclosed by the scope of the claims, and is not limited by the description herein. Further, all modifications and variations of the scope of the invention are intended to be within the scope of the invention.

In addition, this application claims priority based on Japanese Patent Application No. 2011-018751 filed in Japan on January 31, 2011. In light of the above, all of its contents are incorporated in the present application.

[Industry use possibility]

The present invention is applicable to an optical filter used in an image pickup apparatus.

1‧‧‧ camera

11‧‧‧ optical axis

2‧‧‧ lens

3‧‧‧Optical filter module

4‧‧‧1st filter

5‧‧‧Infrared absorber

51‧‧‧Infrared absorption glass

52,53‧‧‧Main face

54‧‧‧Anti-reflection film

6‧‧‧Infrared reflector

61‧‧‧Transparent substrate

62,63‧‧‧Main face

64‧‧‧Infrared reflective film

65‧‧‧1st film

66‧‧‧2nd film

7‧‧‧2nd filter

71‧‧‧Transparent substrate

72, 73‧‧‧ main face

74‧‧‧Infrared through coating

75‧‧‧1st film

76‧‧‧2nd film

77‧‧‧Anti-reflection film

8‧‧‧Optical filter

81‧‧‧Anti-reflection film

9‧‧‧Photographic components

Fig. 1 is a schematic view showing a schematic configuration of an image pickup apparatus according to an embodiment.

[Fig. 2] Fig. 2 is a view showing the light transmission of the first filter of the embodiment. Sexual figure.

Fig. 3 is a schematic view showing a schematic structure of a first filter according to an embodiment.

Fig. 4 is a partially enlarged view showing a schematic structure of an infrared reflector of a first filter of the embodiment.

Fig. 5 is a view showing light transmission characteristics of a second filter of the embodiment.

Fig. 6 is a schematic view showing a schematic structure of a second filter of the embodiment.

Fig. 7 is a partially enlarged view showing a schematic structure of an infrared ray transmitting body of a second filter of the embodiment.

Fig. 8 is a view showing light transmission characteristics of an infrared ray interrupting filter according to an embodiment.

FIG. 9 is a schematic view showing a schematic configuration of an image pickup apparatus according to another embodiment.

Fig. 10 is a view showing the light transmission characteristics of the infrared absorbing glass.

1‧‧‧ camera

2‧‧‧ lens

3‧‧‧Optical filter module

4‧‧‧1st filter

7‧‧‧2nd filter

8‧‧‧Optical filter

9‧‧‧Photographic components

11‧‧‧ optical axis

81‧‧‧Anti-reflection film

Claims (8)

An optical filter module is disposed on an imaging device and is capable of switching an optical filter module configured with a plurality of filters, wherein the plurality of filters transmit visible light, at least intercepts the first filter of infrared rays, and only a second filter that passes through the infrared ray; the first filter and the second filter are selectively switchable, and the first filter indicates a maximum transmittance at a wavelength in a wavelength band of 400 nm to 550 nm. The transmittance at a wavelength of 700 nm is less than 5%, and the second filter indicates a maximum transmittance at a wavelength in a wavelength band of 860 nm or more, and a transmittance at a wavelength of 830 nm is not satisfied. 5% light transmission. The optical filter module according to claim 1, wherein the second filter blocks another region of the infrared ray only by a predetermined band set in advance by infrared rays. The optical filter module according to the first or second aspect of the invention, wherein the first filter includes an infrared absorber that absorbs infrared rays and an infrared reflector that reflects infrared rays. The optical filter module according to claim 3, wherein the infrared absorber is a light transmission characteristic having a transmittance of 50% in a wavelength band of 620 nm to 660 nm; The infrared reflector is a light transmission characteristic having a transmittance of 50% in a wavelength band of 670 nm to 690 nm; and a combination of the infrared absorber and the infrared reflector indicates a wavelength band of 620 nm to 660 nm. The transmittance in the wavelength at the wavelength is 50%, and the transmittance at a wavelength of 700 nm is less than 5%. An optical filter system is provided with an optical system that emits light from the outside, an optical filter module that can switch between a plurality of filters, and an optical system, which are disposed from the outside of the object side along the optical axis. An optical filter system for an image pickup device of a filter or an image sensor, wherein the plurality of filters transmit visible light, at least a first filter that blocks infrared rays, and a second filter that passes only infrared rays; and the first filter One of the mirror and the second filter is selectively switchable to the optical axis, and the first filter indicates a maximum transmittance at a wavelength in a wavelength band of 400 nm to 550 nm, and a wavelength of 700 nm. The transmittance is a light transmission characteristic of less than 5%, and the second filter indicates a transmittance at a wavelength in a wavelength band of 860 nm or more, and a transmittance at a wavelength of 830 nm of less than 5%. characteristic. The optical filter system according to claim 5, wherein the second filter blocks another region of the infrared ray only by a predetermined band set in advance by infrared rays. An optical filter system as recited in claim 5 or 6, wherein The first filter includes an infrared absorber that absorbs infrared rays and an infrared reflector that reflects infrared rays. The optical filter system according to the seventh aspect of the invention, wherein the infrared absorber is a light transmission characteristic having a transmittance of 50% in a wavelength band of 620 nm to 660 nm; and the infrared reflector; The light transmission characteristic of the wavelength in the wavelength band of 670 nm to 690 nm is 50%; and the combination of the infrared absorber and the infrared reflector means that the wavelength in the wavelength band of 620 nm to 660 nm is transmitted. The transmittance is 50%, and the transmittance at a wavelength of 700 nm is less than 5%.