JP2020109956A - Imaging apparatus - Google Patents

Abstract

To provide an imaging apparatus that simultaneously performs visible light imaging and near-infrared light imaging without using an infrared cut filter, suppresses an increase in the thickness of an antireflection film, and exhibits excellent durability and antireflection properties under high temperature and high humidity environments.SOLUTION: In an imaging apparatus, a dual bandpass filter DBPF is provided in an imaging sensor or an imaging lens, and has a transmission characteristic in a visible light band, a cutoff characteristic in a first wavelength band adjacent to the long wavelength side of the visible light band, and a transmission characteristic in a second wavelength band which is a part within the first wavelength band. An antireflection film is formed on the surface of the imaging lens, and its spectral characteristics are low reflectance characteristics in the visible light band, high reflectance characteristics in the first wavelength band adjacent to the long wavelength side of the visible light band, and low reflectance characteristics in a third wavelength band which is a part of the first wavelength band. The third wavelength band of the antireflection film is included in the second wavelength band of the dual bandpass filter.SELECTED DRAWING: Figure 11

Description

The present invention relates to an image pickup device.

An imaging device such as a surveillance camera that performs both visible light imaging and infrared light imaging is known. A photodiode, which is a light receiving part of an image sensor such as a CCD sensor or a CMOS sensor, can receive light in the near-infrared wavelength band of about 1300 nm. Therefore, an imaging device using these image sensors can image in the infrared band. It is possible in principle to do so.

Since the wavelength band in which human visibility is high is 400 nm to 700 nm, when near-infrared light is detected by the image sensor, the image will appear reddish to human eyes. Therefore, when shooting in a bright place such as daytime or indoors, an infrared cut filter (IRCF) that blocks light in the infrared band is provided in front of the image sensor in order to match the sensitivity of the image sensor with the human visual sensitivity. It is necessary to remove light having a wavelength of 700 nm or more. Further, at the time of shooting at night or in a dark place, it is necessary to perform shooting without providing an infrared cut filter.

As such an image pickup device, an image pickup device in which an infrared cut filter is manually attached and detached and an image pickup device in which an infrared cut filter is automatically inserted and removed are known. Further, Patent Document 1 discloses an imaging device that does not require insertion and removal of an infrared cut filter. The image pickup apparatus according to Patent Document 1 uses an optical filter having a characteristic of transmitting light in the visible light band and light in the near-infrared band near 950 nm, thereby performing imaging in the visible light band and the infrared band. Has been realized. In other words, the optical filter is a dual bandpass filter (DBPF) that enables both visible light imaging and infrared light imaging.

In addition, there is an image pickup apparatus in which a lens unit in which a plurality of lenses are arranged along an axial direction is used inside a cylindrical lens barrel, and this lens unit causes factors such as ghost and flare. In order to reduce the reflection of light on the lens surface, the antireflection film (AR coat) is formed on the lens surface (for example, see Patent Document 2). This antireflection film is formed so as to reduce reflection of light in the visible light band.

Japanese Patent No. 5009395 JP, 2017-151451, A

By the way, the film thickness of the antireflection film depends on the wavelength of the light to be antireflection, and the wider the wavelength band of the light is, the thicker the total number of antireflection films is. The film tends to be formed thick. In order to enable visible light photography and near infrared photography, an antireflection film (wide band AR coat) is used so as to reduce reflection of light in the visible light range to the near infrared range (about 400 nm to about 1000 nm). When it is formed on the surface of a plastic lens, in order to keep the reflectance below a predetermined value (for example, 0.5%) from the visible light band to the near infrared band, it is necessary to use, for example, an antireflection film as a multilayer film of 29 layers is there. FIG. 16 is a diagram showing details of an antireflection film composed of 29 layers. As shown in FIG. 16, the total film thickness of the wide band AR coat is about 1400 nm. FIG. 13 is a graph showing the relationship between the wavelength (horizontal axis) and the single-sided reflectance (vertical axis), and the characteristic curve L1 in the figure shows the case where the wide band AR coat is formed on the plastic lens. is there. As can be seen from this characteristic curve L1, in this wide band AR coat of 29 layers, the reflectance is 0.5% or less in the section where the wavelength is from about 400 nm to about 1000 nm.

When the wide band AR coat is formed on the surface of the plastic lens, since the film thickness becomes thick, when the plastic lens is deformed due to thermal expansion, the wide band AR coat is easily subjected to stress due to the deformation. Therefore, the plastic lens may be deformed at a high temperature to cause cracks in the wide band AR coat, and the function as the antireflection film may be impaired. In addition, as the film thickness increases, the reflectance of light with a large incident angle to the lens increases compared to the case where the film thickness is thin (incident angle dependency deteriorates), and the function as an antireflection film is impaired. May be Therefore, it is difficult to simultaneously perform visible light imaging and near infrared imaging while forming an antireflection film (AR coat) to suppress light reflection on the lens surface.

The present invention has been made in view of the above circumstances, and is capable of simultaneously performing visible light imaging and near-infrared light imaging without using an infrared cut filter, and reflecting on the lens surface. It is an object of the present invention to provide an imaging device in which an anti-reflection film can exhibit excellent durability and antireflection characteristics under a high temperature/high temperature and high humidity environment while suppressing an increase in the film thickness.

In order to solve the above-mentioned problems, the imaging device of the present invention is configured such that an imaging sensor main body in which a light receiving element is arranged for each pixel, a plurality of visible light color regions, and an infrared light region are imaged in a predetermined arrangement. An image sensor including a color filter arranged corresponding to the light receiving element of the sensor body, an optical system having a lens for forming an image on the image sensor, and provided in either the image sensor or the optical system. A second wavelength band having a transmission characteristic in the visible light band, a high reflectance characteristic in a first wavelength band adjacent to the long wavelength side of the visible light band, and a part of the first wavelength band. An optical filter having a transmission characteristic in the wavelength band, based on the signal output from the image sensor, performs a process of subtracting the signal of the infrared light component from the signal of each color component of the visible light, a visible image Signal processing means for outputting a signal and an infrared image signal, and an antireflection film having a spectral characteristic is formed on the surface of the lens, and the spectral characteristic has a low reflectance characteristic in the visible light band. And having a high reflectance characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and a low reflectance characteristic in the third wavelength band which is a part of the first wavelength band. And the third wavelength band is included in the second wavelength band of the optical filter. The antireflection film does not have to be formed on all the lenses that form the optical system, and may be formed on at least some of the lenses. In particular, it is preferable that the antireflection film is formed on a resin lens of the lenses forming the optical system, but it may be formed on a glass lens.

According to such a configuration, the optical filter has a transmission characteristic in the visible light band, has a cutoff characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and is in the first wavelength band. Has a transmission characteristic in the second wavelength band, which is a part of the lens, and an antireflection film having a spectral characteristic is formed on the surface of the lens. The spectral characteristic has a low reflectance in the visible light band. The first wavelength band adjacent to the long wavelength side of the visible light band has a high reflectance property, and the third wavelength band that is a part of the first wavelength band has a low reflectance property. And the third wavelength band is included in the second wavelength band of the optical filter. Therefore, the infrared light component included in the visible light component of each color that passes through each color region of the color filter is an infrared component that passes through the third wavelength band of the antireflection film and the second wavelength band of the optical filter. It becomes a light component. Further, the infrared light component that passes through the infrared light region of the color filter becomes the infrared light component that passes through the third wavelength band of the antireflection film and the second wavelength band of the optical filter. As described above, the wavelength range of the infrared light component included in visible light is limited by limiting the wavelength range of the antireflection film (third wavelength band) and the DBPF (second wavelength band). It is possible to remove the infrared light component from the visible light component of each color. Therefore, it becomes possible to more accurately remove the infrared light component contained in the visible light component of each color, and obtain the same visible image as when the infrared cut filter is used without using the infrared cut filter. be able to. Thereby, visible light imaging and near infrared light imaging can be performed at the same time without using an infrared cut filter. Further, since the antireflection film formed on the surface of the lens is configured to have the above-mentioned spectral characteristics, the antireflection film can be a thin film. That is, the antireflection film of the present invention has a high reflectance characteristic region without reducing the reflectance to 0.5% or less over a wide wavelength range of about 400 nm to about 1000 nm like the 29-layer wideband AR coat described above. The low reflectance characteristic region is provided in a limited manner by dividing the visible light band and the third wavelength band with a space between them (the low reflectance characteristic region (the antireflection characteristic region is partially included only in a region actually required). ) Is assigned), the total film thickness can be significantly reduced (total film thickness is 800 nm or less). In this case, in particular, the antireflection film has a low reflectance property of 95% or more in the visible light band and a low reflectance property of 95% or more in the third wavelength band, It is preferable to have high reflectance properties with a transmittance of less than 95% between these two bands that have low reflectance properties. As described above, if the antireflection film can be formed into a thin film, it is possible to prevent the problems such as the occurrence of cracks and the deterioration of the incident angle dependency that occur when the thickness of the antireflection film is large. As a result, the function of the antireflection film is not impaired, and it is possible to suppress the occurrence of problems caused by the reflection of light on the lens surface.

The visible light band is a wavelength band of about 400 nm to about 700 nm. The first wavelength band is a wavelength band of about 700 nm or more as a near infrared wavelength band. The second wavelength band is, for example, a wavelength band of about 800 nm to about 1100 nm, or a wavelength band included in this wavelength band. The third wavelength band is, for example, a wavelength band of about 930 nm to about 980 nm.

In addition, since the image pickup is performed using a color filter including an infrared light region with one image sensor, there is no deviation in the shooting range between the visible image and the infrared image. Each pixel of the pixel and the infrared image correspond to each other. Therefore, it is not necessary to correct the positional deviation between the two unlike the case of using two image pickup elements.

In the above configuration of the present invention, the second wavelength band of the optical filter is included in a fourth wavelength band in which the transmittances of respective color regions of the color filter are close to each other on the longer wavelength side than the visible light band. It is characterized by

According to such a configuration, the second wavelength band of the optical filter is included in the fourth wavelength band in which the transmittances of the respective color regions of the color filter are substantially similar to each other. The transmittance of light passing through the second wavelength band (third wavelength band of the antireflection film) and passing through each color region of the color filter is substantially the same in each color region. Further, since the wavelength band whose transmittance greatly differs in each color region of the color filter overlaps with the wavelength band between the visible light band and the second wavelength band in the optical filter, which has a cutoff characteristic, Light in a wavelength band having a large difference in transmittance between regions does not pass through the optical filter, and only light in a wavelength band having a similar transmittance in the region of each color of the color filter passes through the optical filter on the infrared side. Thereby, the signal of the infrared light component can be more accurately removed from the signal of each color component of the visible light, and the visible image in which the influence of the infrared light transmitted through the second wavelength band of the optical filter is suppressed. Can be obtained.

Further, in the above configuration of the present invention, in the fourth wavelength band of the color filter, a difference in transmittance between regions of respective colors is 10% or less.

According to such a configuration, in the fourth wavelength band, the difference in transmittance between the regions of the respective colors is within 10%, so that a visible image by infrared light that passes through the second wavelength band of the optical filter is obtained. The image processing that suppresses the influence on the image becomes easier, and the color reproducibility can be improved.

The composition of the antireflection film may be various, but as a suitable example for realizing the above-mentioned spectral characteristics, the first film formed of a material having the first refractive index and the first refractive index are used. And a second film formed of a material having a high second refractive index are alternately laminated, and the material forming the first film contains SiO ₂ as a main component to form the second film. An antireflection film whose material is ZrO ₂ or Ta ₂ O ₅ as a main component can be mentioned.

Further, in addition to the above, the present inventors show how the internal stress of each layer (each film) constituting the antireflection film having a multilayer structure affects the durability of the film under high temperature and high temperature and high humidity environments. In a laminated structure in which films of a low refractive index material and films of a high refractive index material are alternately laminated, the internal stress of both the low refractive index material film and the high refractive index material film is 0 to To maintain a stress form exhibiting a compressive stress of 50 MPa, in other words, the melting points of the low-refractive index material film and the high-refractive index material film are both 2100° C. or lower, and the low-refractive index material film and the high-refractive index material film. It has been found that when the Young's modulus of each film is 110 MPa or less, the antireflection film exhibits excellent durability under a high temperature environment and a high temperature and high humidity environment. Hereinafter, this will be specifically described.

First of all, as shown in the table of FIG. 17, SiO having a refractive index of 1.54 is provided on a resin lens having a refractive index of 1.54 with a thickness of 26.33 nm, and further refraction is performed thereon. rate is ZrO ₂ of 2.00 (melting point 2700 ° C.; Young's modulus 210 MPa) SiO ₂ (melting point 1700 ° C.) with 1.42 refractive index lower than that of ZrO ₂ Toko and the formed by laminating alternately laminated structure ( The thickness is 6.75 nm (ZrO ₂ ), 14.28 nm (SiO ₂ ), 33.76 nm (ZrO ₂ ), 9.52 nm (SiO ₂ ), 76.30 nm (ZrO ₂ ), 85.69 nm (from the bottom layer in order). When the antireflection film having SiO ₂ )) (a laminated structure of 7 layers in total) was optimized by a predetermined simulation at a predetermined light incident angle, the spectral characteristic diagram of FIG. 13 (one-sided reflectance of the antireflection film) was obtained. (%) and the incident light wavelength (nm), the spectral characteristic curve L2 shown in the spectral characteristic diagram) was obtained.

As can be seen from the spectral characteristic curve L2, this antireflection film formed by alternately laminating a film of a low refractive index material (SiO ₂ ) and a film of a high refractive index material (ZrO ₂ ) has a prescribed wide wavelength band. At (400 nm to 700 nm), the desired low reflectance condition (reflectance of 1.5 or less) can be almost satisfied, but as described above, the internal stress of the SiO ₂ film exhibits a compressive stress and the internal stress of the ZrO ₂ film Since the stress shows high tensile stress and the tensile stress becomes too strong for the entire film (the internal stress of the entire film is biased to one side), the lens may be exposed to a high temperature environment such as during a high temperature test. When expanded, it cannot withstand the deformation and cracks may occur on the surface (surface of the antireflection film). The cracks thus generated cause a ghost phenomenon and adversely affect the optical characteristics.

The generation of cracks due to such uneven distribution of internal stress can be prevented to some extent by reducing the number of laminated films to reduce the stress of the entire film. However, in such an antireflection film, the reflectance was not completely less than 1.5 within the specified incident wavelength range (400 nm to 700 nm). That is, the reflectance is increased as a whole, and the spectral characteristics are deteriorated.

Therefore, the present inventors have focused on the internal stress of each layer (each film) that constitutes the laminated structure of the antireflection film formed by alternately laminating a film of a low refractive index material and a film of a high refractive index material, As a result of trial and error involving various tests, while satisfying a desired low reflectance condition in a wide wavelength band (specifically, for example, in a prescribed wide wavelength band (400 nm to 700 nm), a desired low reflectance condition (reflection (The ratio is 1.5 or less) Even if the number of laminated layers that can almost satisfy the requirement), cracks and swelling of the film cannot occur (the film can follow stress changes under high temperature environment and high temperature and high humidity environment). ) The stress morphology was determined. That is, when the internal stresses of the low refractive index material film and the high refractive index material film both maintain a compressive stress of 0 to 50 MPa at room temperature, specifically, for example, such stress mode Adopting a material that can realize the above as a low-refractive index material and a high-refractive index material, and setting the film forming conditions to reduce the internal stress (compressive stress) of each layer (each film) to 0 to 50 MPa as necessary. Then, the present inventors have confirmed that excellent film durability can be obtained in a high temperature and high humidity environment. In this case, the difference in the internal stress (compressive stress) between the layers forming the laminated structure is suppressed as low as possible, and the compressive stress distribution over the entire laminated structure is smoothed as much as possible (or the entire antireflection film has low stress). It is desirable to change).

As an example, a material having a lower internal stress than ZrO ₂ or Ta ₂ O ₅ (softer and lower melting point than ZrO ₂ or Ta ₂ O ₅ ) such as Nb ₂ TiO ₇ is used as a high refractive index material (or a high refractive index material). Adopted as the main component). Since Nb ₂ TiO ₇ has a low melting point (melting point of about 1490° C.) and a low Young's modulus (Young's modulus of about 100 MPa), it has high followability with base materials such as resin lenses even at high temperatures. Further, a mixed material of SiO ₂ and Al ₂ O ₃ which is denser and more heat resistant than SiO ₂ (melting point is about 2000° C.) is adopted as the low refractive index material (or the main component of the low refractive index material). By adding Al ₂ O ₃ to SiO ₂ , it is possible to obtain not only a hard but also a dense crystal structure, and the adhesion to a base material such as a high refractive index layer or a resin lens that is made of an adjacent high refractive index material. Of the high refractive index layer and the lens substrate adjacent to each other at high temperature can be improved. Then, by combining these high-refractive index material and low-refractive index material, a stress mode in which the internal stress of both the low-refractive index material film and the high-refractive index material film exhibits a compressive stress of 0 to 50 MPa is realized. (The melting points of the low refractive index material film and the high refractive index material film are both 2100° C. or less, and the Young's modulus of the low refractive index material film and the high refractive index material film are both 110 MPa or less. Thus, it is possible to realize a stress mode in which the internal stress of the low refractive index material film and the high refractive index material film both show a compressive stress of 0 to 50 MPa). Further, the setting of the film forming conditions such that the internal stress (compressive stress) of each layer (each film) is reduced to 0 to 50 MPa may be performed by controlling the oxygen introduction amount, or a laminated structure is formed. When each layer is formed by using the ion assist method or the plasma assist method, it may be performed by controlling parameters of such assist process (for example, gas flow rate, irradiation time, applied output, etc.).

In the above configuration, the antireflection film is provided, for example, by vapor deposition within at least the optically effective range (effective diameter) of the lens. In the above structure, the antireflection film may have another film interposed between the first film and the second film that are alternately laminated. Further, in the above structure, the film-coated lens with the antireflection film may be made of glass or resin. However, as described above, since this antireflection film has a property of excellent heat resistance that can follow the thermal deformation of the lens, it is particularly suitable for a resin lens that easily expands and contracts due to temperature change. Further, in the above structure, the antireflection film may be provided not only on the surface of the lens facing the object side but also on the back surface of the lens facing the image side.

According to the present invention, visible light imaging and near infrared light imaging can be performed at the same time without using an infrared cut filter, and an antireflection film formed on the lens surface can suppress high temperature while suppressing increase in film thickness. / It is possible to provide an imaging device that can exhibit excellent durability and antireflection characteristics in a high temperature and high humidity environment.

It is a schematic block diagram of the imaging device which concerns on embodiment of this invention. FIG. 3 is a diagram for explaining an array pattern of color filters having an infrared region, similarly. 7 is a graph showing a transmittance spectrum of R and G regions of the color filter. 9 is a graph showing a transmittance spectrum of B and IR regions of the color filter. 9 is a graph showing a DBPF transmittance spectrum. 9 is a graph showing the transmittance spectra of the color filter and DBPF. FIG. 3 is a diagram for explaining the imaging lens of the same. FIG. 5 is a table showing detailed data of the laminated structure of the antireflection film. FIG. 9 is a spectral characteristic diagram (wavelength-single-sided reflectance diagram) of the antireflection film having the laminated structure of FIG. 8. FIG. 9 is a spectral characteristic diagram (wavelength-transmittance diagram) of the antireflection film having the laminated structure of FIG. 8. 9 is a graph showing the transmittance spectra of the DBPF, the color filter and the antireflection film. FIG. 9 is a table showing detailed data of a laminated structure of a high heat resistant antireflection film according to a modified example having a 15-layer structure similar to FIG. 8. FIG. 18 is a spectral characteristic diagram (wavelength-single-sided reflectance diagram) of the antireflection film having the laminated structure of each of FIGS. 8, 16 and 17. FIG. 13 is a spectral characteristic diagram (wavelength-single-sided reflectance diagram) of the antireflection film having the laminated structure of FIGS. 8 and 12. FIG. 13 is a spectral characteristic diagram (wavelength-transmittance diagram) of the antireflection film having the laminated structure of FIGS. 8 and 12. It is a table showing the detailed data of the laminated structure of the wide band AR coat. FIG. 11 is a table showing detailed data of a laminated structure of a conventional seven-layer antireflection film.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a camera 110 used in the image pickup apparatus 100 includes a DBPF 111 as an optical filter, an image pickup lens 10 as an optical system for image pickup, an image pickup sensor 115 including a color filter 113 and a sensor body 114. , A signal processing unit (signal processing means) 116 that processes an output signal from the image sensor 115. The signal processing unit 116 also outputs a color visible image signal 121 and an infrared image signal 122.

The image sensor (image sensor) 115 is, for example, red (R), green (corresponding to each pixel (each light receiving element) of the sensor main body 114, which is a CCD (Charge Coupled Device) image sensor, and the sensor main body 114). G), blue (B), and infrared (IR) regions (color filters) are provided with color filters 113 arranged in a predetermined arrangement.

In the CCD image sensor as the sensor body 114, a photodiode as a light receiving element is arranged in each pixel. Note that the sensor body 114 may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor instead of the CCD image sensor.

A Bayer array color filter that has red (R), green (G), and blue (B) regions but does not have an infrared (IR) region has a basic pattern of 4×horizontal. It has 16 areas of 4, 8 areas are G areas, 4 areas are R areas, and 4 areas are B areas. On the other hand, in the color filter 113 according to the present embodiment, as shown in FIG. 2, four out of eight G regions in the Bayer array are IR regions, and R regions are There are 4 areas, 4 areas of G, 4 areas of B, and 4 areas of IR. Each region of R, G, and B has a transmittance peak in the wavelength range of each color and has transparency in the near-infrared wavelength region. Therefore, in FIG. The region of R+IR, G is defined as “G+IR”, and the region of B is defined as “B+IR”. The color filter including the IR region is not limited to the color filter 113 shown in FIG. 2, and color filters of various arrangements can be used. However, it is necessary to include both the region of each color of visible light and the region of IR. The color filter may be configured as follows. That is, in the basic arrangement of 4 rows and 4 columns, the color filter includes four G areas, four C areas, eight C areas, R areas, and B areas among four kinds of areas of R, G, B, and C. Two regions may be arranged, and regions of the same type may be arranged so as not to be adjacent to each other in the row direction and the column direction. At this time, eight C areas are arranged in a checkered pattern. Here, C indicates a transparent state as a clear region, and basically has a transmission characteristic from the visible light band to the near infrared wavelength band. In the visible light band, C=R+G+B. Note that C that is clear can be called white light, that is, white (W) because three colors of RGB are transmitted, and C=W=R+G+B. Therefore, C corresponds to the amount of light in almost the entire wavelength band of the visible light band.

The transmittance spectra of the R region, G region, and B region of the color filter 113 are as shown in the graphs of FIGS. 3 and 4. FIG. 3 shows transmittance spectra in the R region and G region of the color filter 113, and FIG. 4 shows transmittance spectra in the B region and IR region of the color filter 113. There is. 3 and 4, the vertical axis represents the transmittance and the horizontal axis represents the wavelength. The wavelength (horizontal axis) range in the graphs of FIGS. 3 and 4 includes the visible light band and a part of the near infrared band, and is 300 nm to 1100 nm.

FIG. 3A shows the transmittance spectrum in the R region.
As indicated by R (dotted line) in the graph, the R region has a maximum transmittance at a wavelength of 600 nm, and the long wavelength side thereof is in a state where the transmittance is maintained at a maximum even when the wavelength exceeds 1000 nm. Has become.

FIG. 3B shows the transmittance spectrum in the G region.
As shown in G (two-dot chain line) of the graph, the G region has a peak of transmittance maximum at a wavelength of about 540 nm and a transmittance minimum at a wavelength of about 620 nm on the long wavelength side. There is a part that becomes. In addition, the long wavelength side tends to increase from the minimum transmittance portion, and the transmittance becomes approximately maximum at about 850 nm. On the longer wavelength side, the transmittance is in the maximum state even if it exceeds 1000 nm.

FIG. 4A shows the transmittance spectrum of the region B.
As shown by B (broken line) in the graph, the region B has a peak at which the transmittance is maximum at a wavelength of about 460 nm and has a minimum transmittance at a wavelength of about 630 nm on the long wavelength side. There is a part that becomes. On the longer wavelength side, there is an increasing tendency, and the transmittance is approximately maximum at about 860 nm, and on the longer wavelength side, the transmittance is approximately maximum even if it exceeds 1000 nm.

FIG. 4B shows the transmittance spectrum in the IR region.
As shown in the IR (dashed-dotted line) of the graph, the IR region blocks light on the short wavelength side from about 780 nm, blocks light on the long wavelength side from about 1020 nm, and transmits a portion of about 820 nm to 920 nm. The rate is almost the maximum.

3 and 4, 1.0 on the vertical axis (transmittance) does not mean that 100% of light is transmitted, but indicates the maximum transmittance of the color filter 113, for example.

The transmittance spectrum of DBPF111 is as shown in the graph of FIG. The DBPF 111 has a transmission characteristic in the visible light band, a cutoff characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and a second wavelength band that is a part of the first wavelength band. It is an optical filter having transmission characteristics. The infrared light passing through the second wavelength band of the DBPF 111 will pass through the IR region (FIG. 4B) of the color filter 113.
The visible light band is a wavelength band of about 400 nm to about 700 nm. Further, the first wavelength band is a wavelength band of about 700 nm or more as a near infrared wavelength band. The second wavelength band is, for example, a wavelength band of about 800 nm to about 1100 nm, or a wavelength band included in this wavelength band, and in FIG. 5, a wavelength band of about 830 nm to about 970 nm. Has become.

Further, as shown in FIG. 1, when the DBPF 111 is provided between the image pickup lens 10 and the image pickup sensor 115 including the color filter 113, even if the DBPF 111 is provided on the image side of the image pickup lens 10, the image pickup by the image pickup sensor 115 is performed. It may be provided on the lens 10 side. Further, the DBPF 111 may be provided on the object side of the imaging lens 10.
As shown in FIG. 5, the DBPF 111 is shown as DBPF(IR) at a visible light band indicated as DBPF(VR) and at a position on the long wavelength side of the visible light band and slightly away from the visible light band. The transmittance is high in two bands, that is, a part of the infrared band. The DBPF (VR), which has a high transmittance in the visible light band, has a wavelength band of about 370 nm to about 700 nm. Further, the DBPF (IR) as a band (second wavelength band) having a high transmittance in the infrared band is a wavelength band of about 830 nm to about 970 nm, as described above.

FIG. 6 is a graph showing the transmittance spectra of the color filter 113 and the DBPF 111. That is, it is a graph in which FIGS. 3, 4, and 5 are overlapped.
The relationship between the transmittance spectrum of each region of the color filter 113 and the transmittance spectrum of the DBPF 111 is defined as follows. That is, in the DBPF (IR) that transmits infrared light in the transmittance spectrum of the DBPF 111, the R region, the G region, and the B region all have substantially maximum transmittances, and the transmittances are substantially the same in each region. Is included in the wavelength band A (the fourth wavelength band). The DBPF (IR) is included in the wavelength band B (fifth wavelength band) where the transmittance is substantially maximum in the IR region. The wavelength band A is, for example, a wavelength band of about 820 nm or more. The wavelength band B is, for example, a wavelength band of about 790 nm to about 990 nm.

In the wavelength band A in which the R, G, and B regions have substantially the same transmittance, it is preferable that the transmittance difference between the regions is 10% or less. Further, in the wavelength band C (sixth wavelength band) on the shorter wavelength side of the wavelength band A, the transmittance is lower in the G region and the B region than in the R region where the transmittance is substantially maximum. .. The wavelength band C is, for example, a wavelength band of about 700 nm to about 820 nm.

As shown in FIG. 6, a portion having a difference in transmittance between the R, G, and B regions is a portion in the DBPF 111 having a high transmittance in the visible light band, DBPF(VR), and a portion in the infrared band. It corresponds to a portion where the transmittance is minimal (a portion where light is substantially blocked) between the high-reflectance portion and DBPF (IR). In other words, the DBPF 111 blocks light in the wavelength band in which the difference in transmittance between the R, G, and B regions becomes large on the infrared side, and the R, G, and B regions on the longer wavelength side than the wavelength band. Of the wavelength band (wavelength band A) in which the transmittance is substantially maximum and the transmittances are substantially the same.

In the present embodiment, the DBPF 111 used in place of the infrared cut filter has a region that transmits light not only in the visible light band but also in the second wavelength band on the infrared side. At this time, the light having been transmitted through the second wavelength band is affected, but the second wavelength band of the DBPF 111 does not transmit the light of the portions having different transmittances in the R, G, and B regions, Only the light in the wavelength band in which the transmittance of each region is substantially the maximum and the transmittance is substantially the same is transmitted. Further, in the second wavelength band of the DBPF 111, the light having the maximum transmittance in the IR region is transmitted. Here, assuming that the R, G, B, and IR regions are respectively provided in four pixels that are extremely close to each other and are irradiated with substantially the same light, in the second wavelength band, the R region, Light passes through the G region, the B region, and the IR region in substantially the same manner. As the infrared-side light, approximately the same amount of light is emitted in each region including the IR as the photo of the pixel of the sensor body 114. It will lead to a diode. That is, the amount of light that passes through the second wavelength band on the infrared side of the light that passes through the R, G, and B regions is the same as the amount of light that passes through the IR region.

Therefore, the output signal of the sensor main body 114 (R pixel, G pixel, B pixel) that receives the light that has passed through the R, G, and B regions and the sensor main body 114 (that receives the light that has passed through the IR region ( The difference from the output signal of the IR pixel) becomes the output signal of each visible light portion of R, G, B from which the light on the infrared side that has passed through each R, G, B region is removed.

As shown in the pattern (FIG. 2) of the color filter 113, any one region of R, G, B, and IR is arranged for each pixel of the sensor body 114. When the amount of light of each color with which each pixel is irradiated is different, for example, the brightness of each color of each pixel is obtained using a known interpolation method (interpolation method) in each pixel, and the interpolated pixel The difference between the R, G, and B luminances and the IR luminance similarly interpolated can be set as the R, G, and B luminances, respectively. The image processing method for removing the infrared light component from the brightness of each color of R, G, B is not limited to this, and finally the brightness of each color of R, G, B passes through the second wavelength band. Any method may be used as long as it can remove the influence of light. Whichever method is used, the DBPF 111 cuts off light in a portion where the difference in transmittance between the R, G, and B regions on the infrared side is larger than a predetermined ratio (for example, 10%). , The processing for removing the influence of infrared light becomes easy.

When infrared light photography is used as nighttime photography, infrared light illumination is required. The transmittance spectrum of the DBPF 111 is determined in consideration of the transmittance spectrum of each region of R, G, B, and IR and the light of infrared light illumination, for example, the emission spectrum of the infrared light LED for illumination.

According to the imaging device 100, the second wavelength band that transmits light on the infrared side of the DBPF 111 is on the infrared side of each region of R, G, B, and IR, and the transmittance of each region is approximately the maximum. It is included in the wavelength band A in which the transmittance of the region is substantially the same, and is included in the wavelength band B in which the transmittance of the IR region is approximately maximum. In other words, on the longer wavelength side than the visible light band, the transmittance of each region of R, G, B (each filter) is substantially maximum only in the region of R, and the transmittance of the regions of G, B is approximately maximum. However, the light of the portions where the transmittances of the R, G, and B regions are not substantially the same but are different are cut by the DBPF 111.

If the infrared side transmittances in each of the R, G, B, and IR regions are all substantially the same, and the light passing through the second wavelength band is irradiated with the same amount of light, the R, G, B, and IR The amount of transmitted light in the area becomes the same. Therefore, the color correction process is performed easily and accurately based on the signals output from the pixels corresponding to the R, G, and B regions, and the second wavelength band of the DBPF 111 is passed during color imaging. It is possible to obtain a visible image in which the influence of infrared light is suppressed. This makes it possible to easily and accurately perform image processing that removes the effects of infrared light, and as with conventional infrared light cut filters, a visible image (color image) with excellent color reproducibility. Can be obtained.

Further, by making the second wavelength band of the DBPF 111 correspond to the peak of the emission spectrum of the infrared light illumination included in the wavelength band A and the wavelength band B, the light of the infrared light illumination is efficiently used, and By narrowing the width of the second wavelength band, it is possible to reduce the influence of infrared light passing through the second wavelength band during color photography.

When the DBPF 111 is used, the processing performed by the signal processing unit 116, that is, the processing (correction) of subtracting the value of the IR signal from the value of each of the RGB signals output from the image sensor 115 has higher accuracy. For example, the light receiving components of the R, G, and B pixels of the image sensor 115 are in a state in which IR components are added to the components of each color, as shown below.

R pixel R+IR
G pixel G+IR
B pixel B+IR
IR pixel IR

Therefore, as shown below, IR correction is performed by removing the IR component from the light receiving components of the R, G, and B pixels.

R pixel (R pixel output)-(IR pixel output)=(R+IR)-IR=R
G pixel (G pixel output)-(IR pixel output)=(G+IR)-IR=G
B pixel (B pixel output)-(IR pixel output)=(B+IR)-IR=B
As a result, the IR component that transmits the DBPF 111 and the color filter 113 can be removed from the area of each color other than the IR of the color filter 113.

Further, the signal processing unit 116 performs processing such as synchronization processing (interpolation processing), gamma correction, white balance, and RGB matrix correction. The signal processing unit 116 outputs a visible image signal 121 composed of RGB signals from which an IR component has been removed and an infrared image signal 122 composed of an IR signal.

The imaging lens 10 constitutes an optical system that forms an image on the imaging sensor 115. In the present embodiment, even if the visible image and the infrared image are picked up by the group of imaging lenses 10, both the visible image and the infrared image are in a substantially focused state. The imaging lens 10 having the following structure is used.

As shown in FIG. 7, the imaging lens 10 includes, in order from the object side to the image side, a first lens 11 having negative power, a second lens 12 having negative power, and a third lens having positive power. 13 and a fourth lens 14 having a positive power. A diaphragm 15 is arranged between the third lens 13 and the fourth lens 14, and a plate glass 16 is arranged on the image side of the fourth lens 14. The image plane I1 is at a position separated from the plate glass 16 by a predetermined distance. The fourth lens 14 is a cemented lens and includes an object side lens 17 having negative power and an image side lens 18 having positive power. The object-side lens 17 and the image-side lens 18 are bonded to each other with a resin adhesive, and a resin adhesive layer B1 is formed between the object-side lens 17 and the image-side lens 18.

The first lens 11 constituting the imaging lens 10 is a glass lens, and the second lens 12, the third lens 13 and the fourth lens 14 are resin lenses (plastic lenses). Next, the antireflection film formed on the surfaces of the first lens 11, the second lens 12, the third lens 13, and the fourth lens will be described.

The antireflection film is a transparent thin film formed on the surface of the material to reduce the reflection of light on the surface of the material. For example, in a single-layer thin film, when the refractive index of the substance is n0, the refractive index of the thin film is n1, and the refractive index of the outer medium is n2, the condition of n0>n1>n2 (or n0<n1<n2) is satisfied. When the thickness of the thin film is d, the reflectance is minimum when the optical thickness n1d of the thin film is ¼ wavelength, and the refractive index of the thin film is n1=(n0·n2)1/2. The value of the minimum reflectance becomes 0 when the following is satisfied. Further, in the case of further reducing the reflection of light on the surface of the substance, a multilayer antireflection film (multilayer film) is used.

The antireflection film has an AR coat. The AR coat is formed by a vacuum vapor deposition method or the like. As a material for the AR coat, for example, MgF2, SiO2, Ta2O5, ZrO2, or the like is used. Further, as a method other than the vacuum deposition method for forming the AR coat, there is a wet method, for example, a method of applying a fluororesin-based material is known. The AR coat is not limited to those described above, and various AR coats can be used, but those formed by vapor deposition and having high hardness are preferable.

In the present embodiment, the AR coat as the antireflection film is formed on the surface (at least the effective diameter portion) of the first lens 11 to the fourth lens 14. This AR coat has a spectral characteristic. Hereinafter, an AR coat having a spectral characteristic is referred to as a spectral AR coat. The spectral characteristic is a property of reducing reflection of light in the visible light band and part of light in the near-infrared light band and transmitting the light. Since the spectral AR coat is an AR coat with a DBPF function having the same function as the DBPF 111, it can be made thinner than the wideband AR coat.

FIG. 8 is a diagram for explaining each layer forming the spectral AR coat. As shown in FIG. 8, the spectral AR coat is composed of 15 layers, and the total film thickness is about 740 nm. Specifically, the spectral AR coat is composed of a first film made of a material having a first refractive index and a second film made of a material having a second refractive index higher than the first refractive index. Film is alternately laminated, the material forming the first film contains SiO ₂ as a main component, and the material forming the second film contains ZrO ₂ or Ta ₂ O ₅ as a main component. .. More specifically, SiO having a refractive index of 1.60 is formed with a thickness of 35.78 nm on a resin lens having a refractive index of 1.54, and ZrO ₂ having a refractive index of 2.05 is further provided thereon. or _Ta 2 _{O 5} Toko of ZrO ₂ or _Ta 2 _{O 5} formed by laminating a SiO ₂ alternately having a refractive index of 1.41 lower than the laminated structure (in order thickness from the lower layer 10.15Nm (ZrO ₂ Or Ta ₂ O ₅ ), 45.17 nm (SiO ₂ ), 31.55 nm (ZrO ₂ or Ta ₂ O ₅ ), 56.16 nm (SiO ₂ ), 23.15 nm (ZrO ₂ or Ta ₂ O ₅ ), 114 0.04 nm (SiO ₂ ), 6.22 nm (ZrO ₂ or Ta ₂ O ₅ ), 100.64 nm (SiO ₂ ), 28.99 nm (ZrO ₂ or Ta ₂ O ₅ ), 31.89 nm (SiO ₂ ), 92 .14 nm (ZrO ₂ or Ta ₂ O ₅ ), 14.10 nm (SiO ₂ ), 41.98 nm (ZrO ₂ or Ta ₂ O ₅ ), 108.63 nm (SiO ₂ ).

FIG. 9 is a graph showing the relationship between the wavelength (horizontal axis) and the single-sided reflectance (vertical axis) when the spectral AR coat is formed on the surface of the lens (plastic lens). As shown in FIG. 9, in the spectral characteristic curve L3 of this spectral AR coat, the reflectance is 0.5% or less in the section where the wavelength is from about 420 nm to about 720 nm. Further, the reflectance is 0.5% or less in the section where the wavelength is from about 930 nm to about 980 nm. Although the reflectance is set to 0.5% or less in design, it may be set to 1% or less as a product.

FIG. 10 is a graph showing the relationship between the wavelength (horizontal axis) and the transmittance (vertical axis) when the spectral AR coat is formed on the surface of the lens (plastic lens). As shown in the figure, in the spectral characteristic curve L3' of this spectral AR coat, the transmittance is about 99% in the section where the wavelength is from about 420 nm to about 720 nm. Further, the transmittance is about 99% or more in the section where the wavelength is from about 930 nm to about 980 nm (third wavelength band). However, the spectral AR coat (including a high heat resistant AR coat described later) preferably has a low reflectance property of 95% or more in the visible light band and has a transmittance in the third wavelength band. It suffices to have a low reflectance characteristic of 95% or more and have a high reflectance characteristic of a transmittance of less than 95% between these two bands having the low reflectance characteristic.

FIG. 11 is a graph showing the transmittance spectra of the DBPF 111, the color filter 113, and the spectral AR coat. In other words, it is a graph in which the transmittance spectrum (thick line) of the spectral AR coat is further added to the graph of FIG.
The spectral AR coat has a low reflectance characteristic in the visible light band, a high reflectance characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and has a part in the first wavelength band. It has a low reflectance characteristic in a certain third wavelength band (about 930 nm to about 980 nm), and this third wavelength band is included in the second wavelength band of the DBPF 111. In addition, in FIG. 11, the second wavelength band is a wavelength band of about 810 nm to about 1000 nm.

Even when the antireflection film (spectral AR coat) is formed on the surface of the lens, the antireflection film (spectral AR coat) uses the DBPF 111 because the third wavelength band is included in the second wavelength band. It does not interfere with visible light photography and infrared light photography. That is, even when the spectral AR coat is formed on the surface of the lens, visible light imaging and near infrared light imaging using the DBPF 111 can be performed.

At this time, the spectral AR coat has a smaller film thickness than the wide band AR coat, and the total film thickness thereof is about 740 nm. In other words, the total film thickness of the spectral AR coat is about half the total film thickness of the wide band AR coat. This is because the spectral AR coat does not reduce the reflectance to 0.5% or less over a wide wavelength range of about 400 nm to about 1000 nm like the 29-layer wideband AR coat described above, and the high reflectance characteristic region is not covered. The low reflectance characteristic region is limitedly provided by being divided between the visible light band and the third wavelength band (the low reflectance characteristic region (antireflection characteristic region) is partially provided only in an actually required region). This is because they are assigned). This is also apparent from FIG. 13 in which the spectral characteristic curve L3 of the spectral AR coat shown in FIG. 9 is superimposed on the above-mentioned spectral characteristic curves L1 and L2.

If the total film thickness can be greatly reduced in this way, even when the plastic lens is deformed due to thermal expansion, the spectral AR coat is not cracked and the function as the antireflection film is not impaired. Further, the reflectance of light having a large incident angle does not increase (incident angle dependency is deteriorated), and the function as the antireflection film is not impaired.

This has an antireflection film (spectral AR coating) formed on the lens surface, suppresses the occurrence of problems due to the reflection of light on the lens surface, and allows visible light without using an infrared cut filter. It is possible to provide the imaging device 100 capable of simultaneously performing imaging and near-infrared light imaging.

In FIG. 12, a 15-layer structure is formed similarly to the spectral AR coat of FIG. 8, but an antireflection film (high heat-resistant AR coat with a DBPF function) having higher heat resistance and capable of further reducing the total film thickness is shown. A laminated structure is shown. As shown in the figure, this high heat resistant antireflection film is formed on a resin lens having a refractive index of 1.54, and has a film of a low refractive index material (first film) and a film of a high refractive index material (second film). And a film) are alternately laminated to form a laminated structure. In this case, the antireflection film is made of Nb ₂ TiO ₇ (melting point of about 1490° C.; Young's modulus of about 100 MPa), which is a material having lower internal stress (softer than ZrO _{2 and} lower melting point) than ZrO ₂ described above. A mixed material of SiO ₂ and Al ₂ O ₃ , which is adopted as a refractive index material (or a main component of a high refractive index material) and is more dense and heat resistant than SiO ₂ (melting point: about 2000° C.; Young's modulus: 110 MPa or less) ) Is adopted as the low refractive index material (or the main component of the low refractive index material), the internal stress of the low refractive index material film and the high refractive index material film both show compressive stress of 0 to 50 MPa. (The melting points of the low refractive index material film and the high refractive index material film are both 2100° C. or less, and the Young's modulus of the low refractive index material film and the high refractive index material film are both 110 MPa or less. By doing so, a stress mode in which the internal stress of both the low refractive index material film and the high refractive index material film exhibits a compressive stress of 0 to 50 MPa is realized). In this case, the film forming conditions may be set so that the internal stress (compressive stress) of each layer (each film) is further reduced within the range of 0 to 50 MPa. The setting of such film forming conditions may be performed, for example, by controlling the amount of oxygen introduced, or when each layer forming the laminated structure is formed by using an ion assist method or a plasma assist method, It may be performed by controlling the parameters of such an assist process (eg, gas flow rate, irradiation time, applied power, etc.).

More specifically, as shown in FIG. 12, the laminated structure of the antireflection film has a thickness of 33.84 nm of SiO having a refractive index of 1.64 on a resin lens having a refractive index of 1.54. Furthermore, Nb ₂ TiO ₇ having a refractive index of 2.13 and a mixed material of SiO ₂ and Al ₂ O ₃ having a refractive index of 1.43 lower than the Nb ₂ TiO ₇ are alternately provided thereon. Layered structure formed by stacking layers (thicknesses from the bottom are 7.35 nm (Nb ₂ TiO ₇ ), 45.65 nm (SiO ₂ +Al ₂ O ₃ ), 28.49 nm (Nb ₂ TiO ₇ ), 54.83 nm (SiO 2 ₂ +Al ₂ O ₃ ), 20.98 nm (Nb ₂ TiO ₇ ), 112.54 nm (SiO ₂ +Al ₂ O ₃ ), 5.98 nm (Nb ₂ TiO ₇ ), 97.94 nm (SiO ₂ +Al ₂ O ₃ ). , 27.13 nm (Nb ₂ TiO ₇ ), 31.67 nm (SiO ₂ +Al ₂ O ₃ ), 88.15 nm (Nb ₂ TiO ₇ ), 11.39 nm (SiO ₂ +Al ₂ O ₃ ), 41.11 nm (Nb ₂ TiO ₇ ), 105.21 nm (SiO ₂ +Al ₂ O ₃ )) and is formed by vapor deposition.

When the antireflection film having a laminated structure of such a total of 15 layers was optimized by a predetermined simulation at a predetermined light incident angle, the spectral characteristic diagram of FIG. 14 (one-sided reflectance (%) of the antireflection film) was obtained. And the incident light wavelength (nm), the spectral characteristic curve L4 shown in FIG. 15 and the spectral characteristic diagram of FIG. 15 (the transmittance (%) of the antireflection film and the incident light wavelength (nm)) The spectral characteristic curve L4′ shown in the spectral characteristic diagram of FIG. FIGS. 14 and 15 also show the spectral characteristic curves L3 and L3′ shown in FIGS. 9 and 10 of the above-described spectral AR coat of FIG. 8 in an overlapping manner, but as is clear from these figures, This antireflection film formed by alternately stacking first films of a mixed material of SiO ₂ and Al ₂ O ₃ as a low refractive index material and _second films of Nb ₂ TiO ₇ as a high refractive index material. 8 has almost the same spectral characteristics as the above-mentioned spectral AR coat of FIG. 8, but cracks and swelling and bulging phenomena of the film did not occur under a high temperature environment and a high temperature and high humidity environment. That is, the above-mentioned laminated structure has realized a stress mode in which the film can flexibly follow stress changes under high temperature environment and high temperature and high humidity environment.

In the present embodiment, the film stress of the antireflection film forming the laminated structure is measured and calculated as follows.
1. A single layer of any vapor deposition material is formed on a flat substrate such as a silicon wafer with little warpage.
2. To stabilize the film, leave it at room temperature for 2 weeks after film formation, and after 2 weeks, measure the change in the radius of curvature of the film surface before and after film formation in a room temperature environment. calculate.
^{_{σ f = [E s t s}} 2 / (1-V s) 6t f] × [1 / R 1 -1 / R 0] ··· ( Formula)
Here, the Young's modulus of sigma _f is the film stress (internal stress), E _s is the substrate (lens), t _s is the thickness of the substrate, V _s is Poisson's ratio of the substrate, t _f is the film on the substrate thickness , R ₀ is the radius of curvature of the substrate before film formation, and R ₁ is the radius of curvature of the film and lens after film formation. In this case, the radii of curvature of the film and the lens are the radii of curvature of the lenses after vapor deposition.

Although one embodiment of the present invention has been described above, the present invention can be variously modified and implemented without departing from the scope of the invention. For example, in the present invention, the configuration and arrangement form of the imaging lens, the optical filter, the sensor body, etc. are not limited to the above-described embodiment. Further, the high heat resistant antireflection film may be formed on the lens in any form as long as it has the above-mentioned function. Further, some or all of the above-described embodiments may be combined without departing from the scope of the present invention, or a part of the configuration may be omitted from one of the above-described embodiments. Good.

10 Imaging lens (optical system)
111 DBPF (optical filter)
113 Color Filter 114 Image Sensor Main Body 115 Image Sensor 116 Signal Processor (Signal Processor)
121 visible image signal 122 infrared image signal

Claims (10)

An image sensor main body in which a light receiving element is arranged for each pixel, and a color filter in which a plurality of visible light color regions and infrared light regions are arranged in a predetermined arrangement corresponding to the light receiving element of the image sensor main body An image sensor including
An optical system having a lens for forming an image on the image sensor,
The first sensor is provided in either the image sensor or the optical system, has a transmission characteristic in a visible light band, and has a cutoff characteristic in a first wavelength band adjacent to a long wavelength side of the visible light band. An optical filter having a transmission characteristic in a second wavelength band which is a part of the wavelength band of
Signal processing for performing a process of subtracting the infrared light component signal from the respective color component signal of the visible light based on a signal output from the image sensor, and outputting a visible image signal and an infrared image signal And means
An antireflection film having a spectral characteristic is formed on the surface of the lens, and the spectral characteristic has a low reflectance characteristic in the visible light band and is adjacent to the long wavelength side of the visible light band. 1 has a high reflectance characteristic in a wavelength band, has a low reflectance characteristic in a third wavelength band that is a part of the first wavelength band, and the third wavelength band is An image pickup apparatus, which is included in the second wavelength band. The antireflection film has a low reflectance characteristic of 95% or more in the visible light band and a low reflectance characteristic of 95% or more in the third wavelength band, and has a low reflectance. The image pickup apparatus according to claim 1, wherein the image pickup device has a high reflectance characteristic with a transmittance of less than 95% between these two bands having the rate characteristic. The image pickup device according to claim 1, wherein the antireflection film is formed on at least a resin lens of the lenses forming the optical system. The second wavelength band of the optical filter is included in a fourth wavelength band in which transmittances of respective color regions of the color filter are similar to each other on a longer wavelength side than the visible light band. The image pickup apparatus according to claim 1. The imaging device according to claim 4, wherein in the fourth wavelength band of the color filter, a difference in transmittance between regions of respective colors is 10% or less. The antireflection film includes a first film formed of a material having a first refractive index and a second film formed of a material having a second refractive index higher than the first refractive index. It is formed by alternately stacking, and the material forming the first film has SiO ₂ as a main component, and the material forming the second film has ZrO ₂ or Ta ₂ O ₅ as a main component. The image pickup apparatus according to claim 1, wherein The antireflection film includes a first film formed of a material having a first refractive index and a second film formed of a material having a second refractive index higher than the first refractive index. It is formed by alternately laminating, and the internal stress of each of the first film and the second film exhibits a compressive stress of 0 to 50 MPa, and the internal stress of any one of claims 1 to 5 is characterized. Imaging device. The antireflection film includes a first film formed of a material having a first refractive index and a second film formed of a material having a second refractive index higher than the first refractive index. The first film and the second film each have a melting point of 2100° C. or less, and the Young's modulus of each of the first film and the second film is 110 MPa or less. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is provided. The material for forming the first film contains a mixed material of SiO ₂ and Al ₂ O ₃ as a main component, and the material for forming the second film contains Nb ₂ TiO ₇ as a main component. The image pickup apparatus according to claim 7. The imaging device according to claim 1, wherein the total thickness of the antireflection film is 800 nm or less.

Images