Infrared cut filter and imaging device using an infrared cut filter

Abstract

This invention provides an imaging device that uses an infrared cut filter (IRCF) to obtain high image quality at a low cost while supporting the field of view of an ultra-wide-angle camera. [Solution] An infrared cut filter having a reflective filter section and an absorbing filter section, wherein the reflective filter section is Ti x Si y It has an O multilayer film, x Si y The O multilayer film is formed by alternately stacking layers of high-refractive-index material and layers of low-refractive-index material, and the difference in refractive index between the high-refractive-index layer and the low-refractive-index layer at a predetermined wavelength is a predetermined value.

Description

[Technical Field]

[0001] The present invention relates to an infrared cut filter and an imaging device using an infrared cut filter. [Background technology]

[0002] Since the beginning of this century, imaging devices, or cameras, have shifted to digital cameras, which use solid-state image sensors. Furthermore, information and communication devices such as personal computers (PCs), tablet PCs, and smartphones have become widespread and are now used daily. These information and communication devices often incorporate small camera modules, and currently, some feature high-performance image sensors with over 10 million pixels. Information and communication devices, especially mobile communication devices like smartphones, are increasingly becoming thinner and lighter, and their camera modules also need to be miniaturized and space-saving. Furthermore, since smartphones are often the only imaging device for users, there is a strong demand for better image quality even if the camera module becomes smaller.

[0003] Conventional camera modules typically consist of, from the outside in, a cover glass made of tempered glass or sapphire glass that covers the camera module, a lens unit consisting of an optical lens group which is the internal mechanism of the imaging device, a lens carrier that holds the lens unit, a magnetic holder that moves the lens unit axially to realize an autofocus function, an infrared cut filter (IRCF) that cuts out light in the infrared region, and an image sensor that receives light incident through the cover glass, lens unit, and infrared cut filter, and are used fixed in a smartphone casing or the like (see Patent Document 1).

[0004] As will be explained below, these types of infrared cut filters are becoming a key component of compact camera modules (CCMs) used in smartphones and other devices. In CCMs, imaging sensors such as CCDs and CMOS are used as image sensors. However, because they are sensitive not only to the visible range but also to the near-infrared range (>650nm) which is invisible to the human eye, the colors of the captured images sometimes differ from those of the actual object. Therefore, an infrared cut filter is placed in front of the imaging sensor to cut out infrared light, allowing the image to appear closer to the subject being photographed as seen by the photographer.

[0005] Meanwhile, with the increasing popularity of smartphones, there is a growing trend towards multi-lens camera designs to enhance their appeal. In particular, ultra-wide-angle lenses offer the advantage of capturing a wide field of view, and some even allow for macro (close-up) photography. In this regard, widening the field of view significantly increases the technical difficulty for optical filters that utilize the interference effect of light. In other words, widening the field of view increases the technical difficulty for optical filters that utilize the interference effect of light. In other words, the optical properties (transmittance and reflectance) of an interference filter are determined by refractive index × film thickness × cosθ, so the optical properties change significantly when the angle of incidence θ of light changes.

[0006] On the other hand, absorption-type optical filters that use the material's inherent light absorption band have the advantage of being largely independent of the angle of incidence θ of light, but they have the problem that there are no absorbing materials (pigments) that can have high transmittance in the visible range while also being able to cut out high wavelengths. Therefore, currently, hybrid infrared cut filters (IRCFs), which combine a reflective (interference) filter section and an absorptive filter section, are becoming the mainstream choice.

[0007] Furthermore, in typical dielectric IRCFs, as shown in Figure 7, a drawback is that as the incident angle increases, a large ripple appears near the center of the transmission band, and the cutoff wavelength shifts to the shorter wavelength side. Figure 7 is a graph showing the characteristics of a typical dielectric IRCF. With typical dielectric IRCFs, even if the colors in the center of the image are reproduced well, the colors tend to become less red or lighter in the yellow-green range as you move towards the edges. Therefore, conventionally, infrared cut filters (IRCFs) similar to the present invention have been proposed to compensate for the aforementioned shortcomings (Patent Documents 2-4). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2013-153361 [Patent Document 2] Japanese Patent Publication No. 2019-120942 [Patent Document 3] WO2014 / 104370 publication [Patent Document 4] Japanese Patent Publication No. 2020-074366 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] However, these conventional technologies had the following problems. In other words, as the first prior art (Patent Document 2), a near-infrared cut filter has been proposed that can suppress oblique incidence ripple caused by light at a high incidence angle using an optical multilayer film with a relatively small number of layers. This filter comprises a transparent substrate and a first optical multilayer film provided on at least one main surface of the transparent substrate. The first optical multilayer film is made up of alternating layers of a medium refractive index film with a refractive index of 1.8 to 2.21 at a wavelength of 500 nm and a low refractive index film with a refractive index of 1.45 to 1.49 at a wavelength of 500 nm, with a number of combination units of medium refractive index film and low refractive index film between 5 and 35. The first optical multilayer film has a central wavelength of the wavelength range in which the transmission of light incident at 0° is limited, between 890 nm and 1200 nm, and a width of that wavelength range between 100 nm and 300 nm. However, this first conventional technology, while demonstrating a design with a medium refractive index layer / low refractive index layer, had the problem that the UV and near-infrared cutoff became insufficient at incident angles of 40° or more.

[0010] Furthermore, as a second prior art (Patent Document 3), in order to suppress the effect on the captured image when the angle of incidence of light to the near-infrared cut filter is large, the substrate transmits light in the visible wavelength range, and at least one of the substrates is composed of a repeating laminated film consisting of a high refractive index film H and a low refractive index film L (made of a constituent material whose refractive index at a wavelength of 500 nm is smaller than that of the constituent material of the high refractive index film H), or a repeating laminated film consisting of a high refractive index film H, a medium refractive index film M (made of a constituent material whose refractive index at a wavelength of 500 nm is smaller than that of the constituent material of the high refractive index film H) and a low refractive index film L' (made of a constituent material whose refractive index at a wavelength of 500 nm is smaller than that of the constituent material of the medium refractive index film M), The decrease rate of the average transmittance in the R region, G region, and B region is calculated using the following equations (1) to (3), and the difference between the maximum and minimum values ​​is 0.05 or less, indicating that the light transmission characteristics are such that (T(R0)-T(R40)) / T(R0) ···(1) (T(G0)-T(G40)) / T(G0) ···(2) (T(B0)-T(B40)) / T(B0) ···(3) However, the wavelength range of 600-620 nm is defined as the R region, the wavelength range of 500-560 nm as the G region, and the wavelength range of 440-480 nm as the B region. Let T(R0), T(G0), and T(B0) be the average transmittances in the R, G, and B regions, respectively, under normal incidence conditions. A near-infrared cut filter has been proposed in which the average transmittances of the R region, G region, and B region under a 40° incidence condition are defined as T(R40), T(G40), and T(B40), respectively. However, this second conventional technology had a problem in that when the incident angle was 45° or greater, the cutoff in the ultraviolet region and the region above 620nm was not sufficient. In particular, it was not applicable to the incident angle targeted in this application.

[0011] Furthermore, as a third prior art (Patent Document 4; prior application of the applicant of the present application), a hybrid IRCF has been proposed in which the profile of the transmission band does not change significantly between incident angles of 0° and 45°. This is achieved by applying an absorbing ink with a wide stopping zone and a transmission band shape close to the relative luminous efficiency curve to a glass substrate and forming a Ta2O5 / SiO2 multilayer film. However, this third conventional technology had a problem: ripples would appear when the incident angle was 50° or greater.

[0012] This invention was made in view of the aforementioned conventional problems, and aims to provide an imaging device that uses an infrared cut filter (IRCF) that can obtain high image quality corresponding to the field of view of an ultra-wide-angle camera at low cost. [Means for solving the problem]

[0013] To achieve the above objective, the infrared cut filter according to the present invention is an infrared cut filter having a reflective filter portion and an absorbing filter portion, wherein the reflective filter portion is Ti x Si y It has an O multilayer film, and the Ti x Si y The O multilayer film is formed by alternately stacking layers of a high-refractive index material and layers of a low-refractive index material, and the difference in refractive index between the high-refractive index material layer and the low-refractive index material layer is a predetermined value.

[0014] Another feature of the present invention is an imaging device having a lens unit, an infrared cut filter, and an image sensor, wherein the infrared cut filter has a reflective filter portion and an absorptive filter portion, and the reflective filter portion is Ti x Si y It has an O multilayer film, and the Ti x Si y The O multilayer film is formed by alternately stacking layers of high-refractive index material and layers of low-refractive index material, and the difference in refractive index between the high-refractive index material layer and the low-refractive index material layer is a predetermined value. [Effects of the Invention]

[0015] According to the present invention, it becomes possible to provide an imaging device that uses an infrared cut filter (IRCF) that can obtain high image quality corresponding to the field of view of an ultra-wide-angle camera at low cost. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a diagram showing the configuration of an imaging device 1 using an infrared cut filter 7 according to an embodiment of the present invention, where (a) is a plan view of the imaging device 1 and (b) is a cross-sectional view of the imaging device 1 shown in (a) along the line I-I'. [Figure 2] Figure 2 is a graph showing the change in refractive index with respect to wavelength when three mixed materials with different composition ratios are used as high-refractive index materials. [Figure 3] Figure 3 is a cross-sectional view of the infrared cut filter 7 shown in Figure 1(b). [Figure 4] Figure 4 is a graph showing the characteristics of the absorbent ink layer 28 shown in Figure 3. [Figure 5] Figure 5 is a graph showing the filter characteristics of SWPF sections 21, 23, and 25 shown in Figure 3, where (a) is the characteristic when the incident angle is 0° and (b) is the characteristic when the incident angle is 60°. [Figure 6] Figure 6 is a table showing the range of Ti mixing ratios in the first to third SWPF sections 21, 23, and 25 of the infrared cut filter 7 shown in Figure 3. [Figure 7] Figure 7 is a graph showing the characteristics of a typical dielectric IRCF. [Figure 8] Figure 8 is a graph showing the characteristics of the hybrid IRCF fabricated according to the present invention. [Modes for carrying out the invention]

[0017] The infrared cut filter and imaging device using the present invention will be described below with reference to the drawings.

[0018] The feature of the present invention is that in an infrared cut filter, an ideal refractive index is calculated by examining the refractive index difference between a high refractive material and a low refractive material, and in order to realize that refractive index, Ti is added to the absorption ink layer x Si y It is formed of a multilayer film of O and a plurality of short wavelength pass filters (SWPFs) having different wavelength regions in the transmission band are stacked and used for an infrared cut filter As a result, an infrared cut filter in which ripples do not appear up to an incident angle of 60° can be realized, and by applying this infrared cut filter with a wide range of incident angles to an imaging device, the image quality of an ultra-wide angle camera can be improved

[0019] FIG. 1 is a configuration diagram of an imaging device 1 using an infrared cut filter 7 according to an embodiment of the present invention. (a) is a plan view of the imaging device 1, and (b) is a cross-sectional view taken along the line I-I' of the imaging device 1 shown in (a) In FIG. 1, in this embodiment, an imaging device having a camera structure with a digital camera used in information communication devices such as personal computers (PCs), tablet PCs, and smartphones in mind is described, but this infrared cut filter may be used in a camera structure for other applications

[0020] As shown in FIG. 1(a), this imaging device 1 is circular when viewed from above, and as shown in the cross-sectional view of FIG. 1(b), in order from the upper side, it has a cover glass 3, a lens unit 5, an infrared cut filter 7, and an image sensor 9 The lens unit 5 is held by a lens carrier 11, and the lens carrier 11 is housed in a magnet holder 13 that moves the lens unit 5 in the axial direction to realize an autofocus function

[0021] Next, the above-mentioned infrared cut filter 7 will be described Here, first, the short wavelength pass filter (SWPF) forming the infrared cut filter 7 will be described In this infrared cut filter 7, the short-wavelength pass filter (SWPF) consists of an absorbing ink layer and Ti, as described above. x Si y It consists of a hybrid mixed film made up of multiple O films, but first, let me explain how we arrived at this structure. In other words, in an infrared cut filter, the ideal refractive index is calculated by examining the refractive index difference between a high-refractive-index material and a low-refractive-index material, and in order to achieve that refractive index, the absorption ink layer and Ti x Si y A mixed film combining multiple layers is used in the infrared cut filter.

[0022] Firstly, ultra-wide-angle cameras, which originally started as surveillance cameras, have come to be installed in smartphones, but they have had the problem of different colors in the center and corners of the image. The reason given for this was that as the incident angle of light entering the infrared cut filter (IRCF) increases, ripples appear in the transmission band, causing the cut wavelength to shift to shorter wavelengths (see Figure 6).

[0023] The applicant has previously achieved an infrared cut filter (IRCF) with no significant change in spectral shape up to 45° by using an ink with a wide band of low transmittance in the stop zone and high transmittance in the transmit zone. However, beyond 50°, ripple in the transmit zone becomes visible, and at 60°, the ripple increases to about 25%. Therefore, the applicant focused on the fact that ripple is less likely to occur when the difference between high-refractive-index and low-refractive-index materials is small, and proceeded with design studies including refractive index dispersion, and found that a high-refractive-index material with a small refractive index difference in the transmission band and a large difference in the stopband is preferable. Therefore, we used a mixed material consisting of TiO2 and SiO2 as a low-refractive index material and investigated the spectral changes of an infrared cut filter (IRCF) by changing the composition ratio of the two materials. We found that when using a mixed film of TiO2 (30%) and SiO2 (70%), the ripple remained at about 12% even at an incident angle of 60°.

[0024] The distinguishing feature of this invention is that, by examining the refractive index difference between a high-refractive-index material and a low-refractive-index material, an ideal refractive index difference that does not produce ripple is calculated, and in order to achieve that refractive index, multiple short-wavelength pass filters (SWPFs) with different wavelength ranges of the transmission band, as shown in the following embodiments, are used. In this embodiment, as described below, three short-wavelength pass filters (SWPFs) are used. However, using only one SWPF results in strong ripple, so the key point is to use three SWPFs with different transmission wavelength ranges. If an infrared cut filter (IRCF) with a wide range of incident angles can be achieved using multiple short-wavelength pass filters (SWPFs) in this way, it will be possible to dramatically improve the image quality of ultra-wide-angle cameras. Here, we will explain that, compared to using a single material, an ideal refractive index without ripple can be achieved by using a SWPF consisting of three mixed materials with different composition ratios and different wavelength ranges of transmission bands. Figure 2 is a graph showing the change in refractive index with respect to wavelength when three mixed materials with different composition ratios are used as high-refractive index materials. In Figure 2, the mixed material is TiO2, Ti 0.82 Si 0.18 O2, Ti 0.72 Si 0.28 O2, Ti 0.3 Si 0.7 This shows the change in refractive index of O2 with respect to each wavelength. As shown in Figure 2, when a mixed material is used, the wavelength dispersion (change in refractive index due to change in wavelength) becomes more gradual compared to when a single material is used. Furthermore, in order to achieve an ideal refractive index without ripple, three types of TiO2 and SiO2 with different composition ratios were created. x Si y The method for adjusting the composition ratio (refractive index) when using O multilayer films as high refractive index materials will be described later. Figure 3 is a cross-sectional view of the infrared cut filter 7 shown in Figure 1(b). Here, x Si yAs an example of a mixed film consisting of 82% TiO2 and 18% SiO2, an infrared cut filter 7 with a structure consisting of three short-wavelength pass filters (SWPFs) as shown in Figure 3 is described.

[0025] As shown in Figure 3, the infrared cut filter 7 has an absorption ink layer 28 formed on a glass substrate 27, and on top of that, three short-wavelength pass filters (SWPFs) are formed in order from the bottom: Ti x Si y A first SWPF portion 21, a second SWPF portion 23, and a third SWPF portion 25 are formed as a multilayer film. Here, the absorbing ink layer 28 has the characteristics shown in the graph in Figure 4. That is, the spectral shape of the transmission band is close to the human photoreceptor sensitivity curve, and it has the characteristic of being able to maintain its properties even at high incident angles. In other words, Figure 4 shows that the characteristics are similar to the human photoreceptor sensitivity curve at all incident angles of 0°, 15°, 30°, 40°, and 45°. Figure 4 is a graph showing the characteristics of the absorbent ink layer 28 shown in Figure 3. In this embodiment, an absorbent ink layer 28 having the characteristics shown in Figure 4 is used as the hybrid absorbent filter section, but the invention is not limited to this, and blue glass or other materials with equivalent characteristics may be used.

[0026] Furthermore, the first to third multilayer short-wavelength pass filters (SWPF sections) 21, 23, and 25 function as reflective filter sections, and the absorbing ink layer 28 and the first to third SWPF sections 21, 23, and 25 are combined to form a hybrid IRCF. The first SWPF section 21 consists of 1 to 37 layers, with Ti as the low refractive index material. 0.3 Si 0.7 O X Layer 21a and Ti as a high refractive index material 0.72 Si 0.28 O X The layers 21b and 21b are stacked alternately in a repeating manner. The second SWPF section 23 consists of 38 to 67 layers, with Ti as the low refractive index material. 0.3 Si 0.7 O X Layer 23a and Ti as a high refractive index material 0.82 Si 0.18 O X Layer 23b and the third SWPF section 25 are stacked alternately in a repeating manner, and the third SWPF section 25 consists of 68 to 93 layers, with Ti as the low refractive index material. 0.3 Si 0.7 O X Layer 25a and layer 25b of TiO2 as a high refractive index material are alternately and repeatedly laminated.

[0027] Thus, the infrared cut filter 7 has three types of short-wavelength pass filters as multilayer film portions, consisting of a first SWPF section 21, a second SWPF section 23, and a third SWPF section 25. Furthermore, as mentioned above, Ti 0.3 Si 0.7 O X Layer 21a and Ti 0.3 Si 0.7 O X Layer 23a and Ti 0.3 Si 0.7 O X Layer 25a consists of a low refractive index material, Ti 0.72 Si 0.28 O X Layer 21b and Ti 0.82 Si 0.18 O X Layer 23b and layer 25b of TiO2 are made of a high refractive index material.

[0028] As a result, the SWPF sections 21, 23, and 25 consist of three short-wavelength pass filters with different wavelength ranges for transmission.

[0029] Therefore, in the first SWPF section 21, Ti is used as an adjacent low-refractive index material. 0.3 Si 0.7 O X Layer 21a and Ti as a high refractive index material 0.72 Si 0.28 O XThe difference in refractive index between layer 21b and layer 21b at a predetermined wavelength of 550 nm is 0.66. That is, Δn 550nm This equals 0.66. The applicant compared and examined the refractive index difference between a high-refractive index material and a low-refractive index material, and found that the ideal refractive index difference is Δn 550nm We have determined that the answer is 0.66. Therefore, in the first SWPF section 21, Ti is used as an adjacent low-refractive index material. 0.3 Si 0.7 O X Layer 21a and Ti as a high refractive index material 0.72 Si 0.28 O X The difference in refractive index between layer 21b and layer 21b at a predetermined wavelength (in this case, 550 nm) was set to a predetermined value of 0.66. Similarly, in the second SWPF section 23, Ti is used as an adjacent low-refractive index material. 0.3 Si 0.7 O X Layer 23a and Ti as a high refractive index material 0.82 Si 0.18 O X The difference in refractive index at a wavelength of 550 nm between layer 23b and layer 25 is 0.49, which is a predetermined value, and Ti is used as an adjacent low refractive index material in the third SWPF section 25. 0.3 Si 0.7 O X The difference in refractive index at a wavelength of 550 nm between layer 25a and layer 25b of TiO2 as a high refractive index material is set to a predetermined value of 0.39.

[0030] With this configuration, the infrared cut filter 7 obtained the wavelength-to-transmittance relationship characteristics shown in Figure 4 for incident angles from 0° to 60°. Figure 5 is a graph showing the filter characteristics of SWPF sections 21, 23, and 25 shown in Figure 3, where (a) is the characteristic when the incident angle is 0° and (b) is the characteristic when the incident angle is 60°. Note that Figure 5 also shows the case where the Ti mixing ratio is ±3%, which will be discussed later. That is, as shown in Fig. 5(a), a transmittance with a ripple suppression of about 90 - 100% can be obtained at wavelengths of about 400 nm to 750 nm, and filter characteristics that cut wavelengths of 750 nm to 1100 nm to 0 - 5% or less can be obtained within the range of incident angles of 0° to 60°.

[0031] According to the infrared cut filter 7 configured as described above, within the range of incident angles of 0° to 60°, a stable transmittance can be obtained at wavelengths of about 400 nm to 750 nm that can be perceived by humans, and light of other wavelengths can be surely cut. Therefore, if this infrared cut filter is used in a camera structure, it becomes possible to obtain high image quality corresponding to the viewing angle of an ultra-wide-angle camera at low cost.

[0032] Note that in this embodiment, Ti x Si y Although the mixing ratio of Ti in the Ti-Si-O multilayer film is as shown in Fig. 6(a), it is not limited thereto. As shown in Fig. 6(b) and Fig. 6(c), if it is within the range of ±3%, characteristics almost equivalent to those shown in Fig. 3 above can be obtained. Fig. 6 is a table showing the range of the mixing ratio of Ti in the first to third SWPF parts 21, 23, 25 of the infrared cut filter 7 shown in Fig. 3. That is, since the mixing ratio of Ti in the first to third SWPF parts 21, 23, 25 has a tolerance range of ±3%, the first SWPF part 21 has layers 21a of Ti 0.27~0.33 Si 0.73~0.67 O X and layers 21b of Ti 0.69~0.75 Si 0.31~0.25 O X alternately and repeatedly laminated, the second SWPF part 23 has layers 23a of Ti 0.27~0.33 Si 0.73~0.67 O X and layers 23b of Ti 0.79~0.85 Si 0.21~0.15 O X alternately and repeatedly laminated, and the third SWPF part 25 has layers 25a of Ti 0.27~0.33 Si 0.73~0.67 O X and a mixed film in which layers 25b of TiO2 are alternately and repeatedly laminated is within the tolerance range.

[0033] In the present invention, in forming the infrared cut filter 7, in order to realize an ideal refractive index without ripple, three types of Ti with different composition ratios of TiO2 and SiO2 mixed are used. x Si y When using the O multilayer film as the high refractive material, the composition ratio (refractive index) is adjusted as follows. That is, first, in the layer 21b of Ti 0.72 Si 0.28 O X which is the high refractive material in the first SWPF part 21, while taking the balance between the ripple in the transmission band and the stop band (low wavelength side), the film thickness n of the layer 21b of Ti 0.72 Si 0.28 O X is adjusted. Next, in the layer 23b of Ti 0.82 Si 0.18 O X which is the high refractive material in the second SWPF part 23, while looking at the transmittance and ripple in the stop region (medium wavelength side), the film thickness n of the layer 23b of Ti 0.82 Si 0.18 O X is adjusted. Finally, in the layer 25b of TiO2 which is the high refractive material in the third SWPF part 25, while looking at the transmittance and ripple in the stop region (high wavelength side), the film thickness n of the layer 25b of TiO2 is adjusted (here, the ink characteristics of the absorption ink layer 28 are also considered). In this way, an infrared cut filter 7 with an ideal refractive index without ripple is formed. FIG. 8 is a graph showing the characteristics of the hybrid type IRCF fabricated according to the present invention. As shown in FIG. 8, different from the conventional general dielectric IRCF shown in FIG. 7, as the incident angle increases, no large ripple appears near the center of the transmission band. Also, the cut wavelength does not shift to the short wavelength side. Note that the adjustment of the film thickness of the high refractive material may be performed using the least squares fitting method. Furthermore, the first to third SWPF sections 21, 23, and 25 of the infrared cut filter 7 described above can be easily and inexpensively manufactured by simultaneously outputting Si and Ti targets using a film deposition apparatus capable of mounting at least two types of targets, such as a metal mode sputtering apparatus. In this case, by appropriately using the aforementioned film deposition apparatus and adjusting the output ratio of each target, any desired mixing ratio can be easily obtained at low cost.

[0034] Although this embodiment has been described above, the descriptions and drawings that constitute part of this disclosure should not be understood as limiting. Various embodiments not described herein are included. In other words, in this embodiment, three types of SWPF sections 21, 23, and 25 are provided, but the system is not limited to this, and may be composed of four or more types of SWPF sections.

[0035] Furthermore, in this embodiment, an absorbent ink layer 28 having the characteristics shown in Figure 3 is used as the hybrid absorbent filter section, but it is not limited to this, and blue glass or other materials with equivalent characteristics may be used.

[0036] Furthermore, in this embodiment, as described above, Ti in the first SWPF section 21 0.3 Si 0.7 O X Layer 21a and Ti 0.72 Si 0.28 O X Layer 21b and Ti in the second SWPF section 23 0.3 Si 0.7 O X Layer 23a and Ti 0.82 Si 0.18 O X Layer 23b and Ti in the third SWPF section 25 0.3 Si 0.7 O X Although the film thicknesses of layer 25a and the TiO2 layer 25b are fundamentally different, they may also be the same thickness. Here, the basic design consists of three SWPF sections, and the film thickness of each layer is optimized using the least-squares fitting method to approach the target spectrum.

[0037] Furthermore, in this embodiment, the Ti of the first SWPF section 21 0.3 Si 0.7 O X Layer 21a and Ti 0.72 Si 0.28 O X Layer 21b and Ti of the second SWPF section 23 0.3 Si 0.7 O X Layer 23a and Ti 0.82 Si 0.18 O X Layer 23b and Ti of the third SWPF section 25 0.3 Si 0.7 O X The refractive indices of layer 25a and layer 25b of TiO2 are examples only; any value is acceptable as long as the difference in refractive index between the high-refractive-index material and the low-refractive-index material is 0.66. [Explanation of symbols]

[0038] 1...Imaging device, 3...Cover glass, 5...Lens unit, 7...Infrared cut filter, 9...Image sensor, 11...Lens carrier, 13...Magnet holder, 21...First SWPF section, 23...Second SWPF section, 25...Third SWPF section, 27...Glass substrate, 28...Absorbing ink layer

Claims

1. An infrared cut filter having a reflective filter section and an absorbing filter section, wherein the reflective filter section is Ti ｘ Si ｙ It has an O multilayer film, and the Ti ｘ Si ｙ An infrared cut filter in which a multilayer film is formed by alternately stacking layers of a high-refractive-index material and layers of a low-refractive-index material, and the difference in refractive index between the high-refractive-index layer and the low-refractive-index layer at a predetermined wavelength is a predetermined value determined in advance.

2. An infrared cut filter according to claim 1, characterized in that a predetermined value, which is the difference in refractive index at a wavelength of 550 nm between the high refractive index layer and the low refractive index layer, is 0.

66.

3. An infrared cut filter according to claim 1, characterized in that the absorption type filter portion consists of an absorption ink layer.

4. An infrared cut filter according to claim 1, wherein the Ti ｘ Si ｙ A near-infrared cut filter characterized in that the multilayer film consists of three SWPF sections, a first SWPF section, a second SWPF section, and a third SWPF section, each with different wavelength ranges in the transmission band.

5. The infrared cut filter according to claim 4, wherein the first SWPF part is Ti as the low refractive index material ０．２７～０．３３ Si ０．７３～０．６７ O Ｘ layers and layers of Ti as the high refractive index material ０．６９～０．７５ Si ０．３１～０．２５ O Ｘ are alternately and repeatedly laminated, and the second SWPF part is Ti as the low refractive index material ０．２７～０．３３ Si ０．７３～０．６７ O Ｘ layers and layers of Ti as the high refractive index material ０．７９～０．８５ Si ０．２１～０．１５ O Ｘ are alternately and repeatedly laminated, and the third SWPF part is Ti as the low refractive index material ０．２７～０．３３ Si ０．７３～０．６７ O Ｘ layers and layers of TiO2 as the high refractive index material are alternately and repeatedly laminated, characterized in that it is a near-infrared cut filter

6. An infrared cut filter according to claim 4, wherein the first SWPF portion is Ti as the low refractive index material ０．３ Si ０．７ O Ｘ The layer and the Ti as the high refractive index material ０．７２ Si ０．２８ O Ｘ The layers are repeatedly stacked alternately, and the second SWPF portion is made of Ti as the low refractive index material. ０．３ Si ０．７ O Ｘ The layer and the Ti as the high refractive index material ０．８２ Si ０．１８ O Ｘ The layers are repeatedly stacked alternately, and the third SWPF portion is made of Ti as the low refractive index material. ０．３ Si ０．７ O Ｘ A near-infrared cut filter characterized in that a layer of [material name] and a layer of TiO2 as the high refractive index material are alternately and repeatedly laminated.

7. An imaging device comprising a lens unit, an infrared cut filter, and an image sensor, wherein the infrared cut filter has a reflective filter section and an absorbing filter section, and the reflective filter section is Ti ｘ Si ｙ It has an O multilayer film, and the Ti ｘ Si ｙ An imaging device characterized in that a multilayer film is formed by alternately stacking layers of a high-refractive-index material and layers of a low-refractive-index material, and the difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer at a predetermined wavelength is a predetermined value determined in advance.

Images