Infrared cut filter and imaging device using infrared cut filter

Abstract

The invention provides an infrared cut filter (IRCF) and an imaging device using the infrared cut filter. The infrared cut filter can correspond to the field angle of an ultra-wide angle camera at low cost and can obtain high image quality. An infrared cut filter has a reflection-type filter unit and an absorption-type filter unit, in which the reflection-type filter unit has a TixSiyO multilayer film, the TixSiyO multilayer film is formed by alternately laminating high-refractive-index material layers and low-refractive-index material layers, and the difference in refractive index at a predetermined wavelength between the high-refractive-index material layers and the low-refractive-index material layers is a predetermined value.

Description

Technical Field

[0001] This invention relates to infrared cutoff filters and imaging devices using infrared cutoff filters. Background Technology

[0002] In this century, in the realm of video recording devices, those using solid-state imaging elements (camera sensors), also known as digital video cameras, have become mainstream. Furthermore, personal computers (PCs), tablet PCs, smartphones, and other information and communication devices are becoming increasingly widespread and used in daily life.

[0003] Most of these information communication devices have built-in small camera modules, and there are now high-performance devices with camera elements having a pixel count of over 10 million. Information communication devices, especially smartphones as portable communication devices, have a strong tendency to become thinner and lighter, and the camera modules, as components of these devices, also need to be miniaturized and space-saving.

[0004] Furthermore, for users, smartphones are increasingly becoming the only camera device, so even with smaller camera modules, the demand for better image quality remains strong.

[0005] As a conventional camera module, it is mainly composed of the following components from the outside: a protective glass made of tempered glass or sapphire glass that covers the camera module; a lens unit consisting of an optical lens group that serves as the internal mechanism of the camera device; a lens carrier that holds the lens unit; a magnet bracket that moves the lens unit axially to achieve autofocus; an infrared cutoff filter (IRCF) that blocks light in the infrared region; and an imaging element that receives light incident through the protective glass, the lens unit, and the infrared cutoff filter. The camera module is fixed to a smartphone casing or the like for use (see Patent Document 1).

[0006] As described below, such infrared cut-off filters are gradually becoming one of the key components of compact camera modules (CCMs) used in smartphones and other devices.

[0007] Although CCM uses image sensors such as CCD and CMOS as imaging elements, the tones of the captured images sometimes differ from the actual objects because they are sensitive not only in the visible light region but also in the near-infrared region (>650nm) which is invisible to the human eye.

[0008] Therefore, by setting an infrared cutoff filter in front of the image sensor, which serves as the camera element, infrared light is blocked, thus bringing the subject closer to what the photographer sees.

[0009] On the other hand, with the popularization of smartphones, in order to enhance their appeal, there is also a trend towards compound lenses for camera lenses. In particular, ultra-wide-angle lenses have the advantage of being able to capture wide fields of view, and there are also ultra-wide-angle lenses that can be used for macro (close-up) shooting.

[0010] In this regard, expanding the field of view greatly increases the technical difficulty for optical filters that utilize the interference effect of light.

[0011] In other words, expanding the field of view increases the technical difficulty for optical filters that utilize the interference effect of light.

[0012] That is, the optical characteristics (transmittance, reflectance) of an interferometric filter are determined by refractive index × film thickness × cosθ. When the incident angle θ of light changes, the optical characteristics will change significantly.

[0013] On the other hand, absorption-type optical filters that utilize the inherent light absorption bands of materials have the advantage of being almost independent of the incident angle θ of light, but they have the problem of high transmittance in the visible light region and the lack of absorbing materials (pigments) that can also cut off the high wavelength side.

[0014] Therefore, in infrared cutoff filters (IRCFs), hybrid IRCFs that combine reflective (interferometric) and absorptive filter sections are gradually becoming the mainstream.

[0015] It should be noted that in typical dielectric IRCF, such as Figure 7 As shown, there are disadvantages such as large ripples appearing near the center of the transmission band as the incident angle increases, and the cutoff wavelength shifting towards the shorter wavelength side.

[0016] Figure 7 This is a graph representing the characteristics of a typical dielectric IRCF.

[0017] In such a typical dielectric IRCF, even if the colors at the center of the image are clearly reproduced, as the image moves towards the edges, there may be instances where red becomes less than the actual color, or yellow and green become lighter.

[0018] Therefore, as prior art close to the present invention, infrared cutoff filters (IRCFs) have been proposed to overcome the above-mentioned disadvantages (Patent Documents 2-4).

[0019] Existing technical documents

[0020] Patent documents

[0021] Patent Document 1: Japanese Patent Application Publication No. 2013-153361

[0022] Patent Document 2: Japanese Patent Application Publication No. 2019-120942

[0023] Patent Document 3: WO2014 / 104370

[0024] Patent Document 4: Japanese Patent Application Publication No. 2020-074366

[0025] However, these existing technologies have problems as described below.

[0026] That is, as a first prior art (Patent Document 2), in order to provide a near-infrared cutoff filter that can suppress oblique incident ripples caused by light with high incident angles using fewer optical multilayer films, a near-infrared cutoff filter is proposed, which has a transparent substrate and a first optical multilayer film disposed on at least one main surface of the transparent substrate. The first optical multilayer film is formed by alternating layers of a medium refractive index film with a refractive index of 1.8 or more and 2.21 or less at a wavelength of 500 nm and a low refractive index film with a refractive index of 1.45 or more and 1.49 or less at a wavelength of 500 nm, having a combination unit of medium refractive index film and low refractive index film in a number of 5 or more and 35 or less. As for the first optical multilayer film, the center wavelength of the wavelength range in which the transmission of light incident at 0° is limited is 890 nm or more and 1200 nm or less, and the width of its wavelength range is 100 nm or more and 300 nm or less.

[0027] However, in this first prior art, a design is shown at the medium refractive index layer / low refractive index layer, but there is a problem that the cutoff effect for ultraviolet / near infrared is deteriorated at incident angles above 40°.

[0028] Furthermore, as a second prior art (Patent Document 3), a near-infrared cutoff filter is proposed. To suppress the impact on the image captured by a large incident angle of light towards the near-infrared cutoff filter, the near-infrared cutoff filter comprises the following structure: a substrate that transmits light at least in the visible wavelength range; and a repeatedly laminated film on at least one side of the substrate consisting of a high-refractive-index film H and a low-refractive-index film L (composed of a material with a refractive index at 500 nm lower than that of the high-refractive-index film H), or a repeatedly laminated film consisting of a high-refractive-index film H, a medium-refractive-index film M (composed of a material with a refractive index at 500 nm lower than that of the high-refractive-index film H), and a low-refractive-index film L' (composed of a material with a refractive index at 500 nm lower than that of the medium-refractive-index film M).

[0029] The near-infrared cutoff filter has light transmission characteristics where the reduction rate of average transmittance in the R region, G region, and B region can be calculated using the following formulas (1) to (3), and the difference between the maximum and minimum values ​​is less than 0.05.

[0030] (T(R0)-T(R40)) / T(R0)……(1)

[0031] (T(G0)-T(G40)) / T(G0)……(2)

[0032] (T(B0)-T(B40)) / T(B0)……(3)

[0033] Specifically, the wavelength band from 600nm to 620nm is designated as region R, the wavelength band from 500nm to 560nm as region G, and the wavelength band from 440nm to 480nm as region B.

[0034] The average transmittances of regions R, G, and B under vertical incidence conditions are set as T(R0), T(G0), and T(B0), respectively.

[0035] The average transmittances of regions R, G, and B under a 40° incident condition are defined as T(R40), T(G40), and T(B40), respectively.

[0036] However, in this second prior art, when the incident angle is 45° or higher, there is a problem that the cutoff effect deteriorates in the ultraviolet region and the region above 620 nm.

[0037] In particular, it does not apply to the angle of incidence that is the object of this application.

[0038] Furthermore, as a third prior art (Patent Document 4; the applicant's earlier application), a hybrid IRCF is proposed, which coats an absorbing ink with a wide blocking domain and a transmission band shape close to the relative visibility curve on a glass substrate to form a Ta2O5 / SiO2 multilayer film, thereby ensuring that the outline of the transmission band does not change significantly between the incident angles of 0° and 45°.

[0039] However, in this third prior art, there is a problem with ripples when the incident angle is above 50°. Summary of the Invention

[0040] The present invention addresses the aforementioned problems and aims to provide a camera device that uses an infrared cutoff filter (IRCF) that can meet the field of view of an ultra-wide-angle camera at low cost and achieve high image quality.

[0041] To achieve the aforementioned objective, the infrared cutoff filter of the present invention is an infrared cutoff filter having a reflective filter section and an absorptive filter section, characterized in that the reflective filter section has Ti x Siy O multilayer film, the Ti x Si y The O multilayer film is formed by alternating layers of high-refractive-index material and low-refractive-index material, wherein the difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer is a predetermined value.

[0042] Another feature of the present invention is an imaging device having a lens unit, an infrared cutoff filter, and an image sensor, wherein the infrared cutoff filter has a reflective filter section and an absorptive filter section, and the reflective filter section has Ti x Si y O multilayer film, the Ti x Si y The O multilayer film is formed by alternating layers of high-refractive-index material and low-refractive-index material, wherein the difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer is a predetermined value.

[0043] Invention Effects

[0044] According to the present invention, a camera device using an infrared cutoff filter (IRCF) can be provided, which can meet the field of view of an ultra-wide-angle camera at low cost and obtain high image quality. Attached Figure Description

[0045] Figure 1 This is a configuration diagram of a camera device 1 using the infrared cutoff filter 7 according to an embodiment of the present invention. Figure 1 (a) is a top view of camera device 1. Figure 1 (b) is along Figure 1 (a) is a cross-sectional view of the camera device 1 along line I-I'.

[0046] Figure 2 It is a graph showing the change of refractive index relative to wavelength when three mixed materials with different composition ratios are used as high refractive materials.

[0047] Figure 3 yes Figure 1 (b) shows the cut-out cross-sectional view of the infrared cut-off filter 7.

[0048] Figure 4 It means Figure 3 The graph shows the characteristics of the ink-absorbing layer 28.

[0049] Figure 5 It means Figure 3 The graphs showing the filter characteristics of SWPF sections 21, 23, and 25 are shown. Figure 5 (a) represents the characteristic when the angle of incidence is 0°. Figure 5(b) is the characteristic when the incident angle is 60°.

[0050] Figure 6 It means Figure 3 The table shows the range of mixing ratios of Ti in the first SWPF section to the third SWPF section 21, 23, 25 of the infrared cutoff filter 7 shown.

[0051] Figure 7 This is a graph representing the characteristics of a typical dielectric IRCF.

[0052] Figure 8 This is a graph representing the characteristics of the hybrid IRCF produced by this invention.

[0053] Explanation of reference numerals in the attached figures:

[0054] 1: Camera device; 3: Protective glass; 5: Lens unit;

[0055] 7: Infrared cutoff filter; 9: Image sensor; 11: Lens carrier;

[0056] 13: Magnet support; 21: First SWPF section; 23: Second SWPF section; 25: Third SWPF section; 27: Glass substrate; 28: Ink absorption layer. Detailed Implementation

[0057] Hereinafter, the infrared cutoff filter implementing the present invention and the camera device using the infrared cutoff filter will be described in connection with the accompanying drawings.

[0058] The present invention is characterized in that, in an infrared cutoff filter, an ideal refractive index is calculated by studying the refractive index difference between high-refractive-index and low-refractive-index materials. To achieve this refractive index, multiple layers of Ti are stacked on the absorbent ink layer. x Si y Short-pass filters (SWPFs) with different wavelength regions in the transmission band, composed of multilayer films, are used as infrared cutoff filters.

[0059] Therefore, an infrared cutoff filter that does not produce ripples up to an incident angle of 60° can be achieved. By applying an infrared cutoff filter with such a wide incident angle range to a camera device, the image quality of an ultra-wide-angle camera can be improved.

[0060] Figure 1 This is a configuration diagram of a camera device 1 using the infrared cutoff filter 7 according to an embodiment of the present invention. Figure 1 (a) is a top view of camera device 1. Figure 1 (b) is along Figure 1 (a) is a cross-sectional view of the camera device 1 along line I-I'.

[0061] It should be noted that, in Figure 1 In this embodiment, a camera device having a camera structure that takes into account digital cameras used in information and communication devices such as personal computers (PCs), tablet PCs, and smartphones is described. However, the infrared cut-off filter can also be used in camera structures for other purposes.

[0062] like Figure 1 As shown in (a), the camera device 1 is circular when viewed from the top surface, as... Figure 1 As shown in the cross-sectional view of (b), from top to bottom, there are protective glass 3, lens unit 5, infrared cut-off filter 7 and image sensor 9.

[0063] The lens unit 5 is held by the lens carrier 11, which is housed in the magnet support 13 that allows the lens unit 5 to move axially in order to achieve the autofocus function.

[0064] Next, the infrared cutoff filter 7 will be explained.

[0065] Here, we will first explain the short-wave pass filter (SWPF) that forms the infrared cutoff filter 7.

[0066] As described above, the short-pass filter (SWPF) in the infrared cutoff filter 7 is composed of an absorbing ink layer and Ti. x Si y The structure is a hybrid membrane composed of multiple layers. First, the process of completing this structure will be explained.

[0067] That is, in an infrared cutoff filter, the ideal refractive index is calculated by studying the refractive index difference between high-refractive-index and low-refractive-index materials. To achieve this refractive index, an absorbing ink layer and Ti are used. x Si y Hybrid films composed of multiple layers are used in infrared cutoff filters.

[0068] First, in the past, although ultra-wide-angle cameras, which started as surveillance cameras, were mounted on smartphones, there was a problem of different tones in the center and corners of the image.

[0069] The following phenomena can be cited as a reason for this: as the incident angle of light entering the infrared cutoff filter (IRCF) increases, ripples appear in the transmission band, and the cutoff wavelength shifts towards the shorter wavelength side (see reference). Figure 7 ).

[0070] The applicant achieved an infrared cutoff filter (IRCF) with no significant change in spectral shape up to 45° by using an ink with a low transmittance blocking bandwidth and a high transmittance in the transmission domain. However, when the angle exceeds 50°, ripples in the transmission band are observed, and the ripples increase to about 25% at 60°.

[0071] Therefore, the applicant focused on the fact that ripples are less likely to occur when the difference between high-refractive-index materials and low-refractive-index materials is small, and conducted design research that also included refractive index dispersion. The results showed that high-refractive-index materials with a small refractive index difference in the transmission frequency band and a large difference in the blocking region are preferred.

[0072] Therefore, by setting the mixed material composed of TiO2 and SiO2 as a low-refractive-index material and changing the composition ratio of the two, the spectral changes of the infrared cutoff filter (IRCF) were investigated. The results showed that when using the mixed film of TiO2 (30%) and SiO2 (70%), the ripple was only about 12% even at an incident angle of 60°.

[0073] The present invention is characterized by calculating an ideal refractive index difference that will not produce ripples by studying the refractive index difference between high-refractive-index materials and low-refractive-index materials. To achieve this refractive index, multiple short-pass filters (SWPFs) with different wavelength regions of the transmission band are used, as shown in the following embodiments.

[0074] It should be noted that, in this embodiment, as described below, three shortwave pass filters (SWPFs) are used. However, even with a single shortwave pass filter (SWPF), the ripple is still very strong. The key is to use three shortwave pass filters (SWPFs) with different wavelength regions in the transmission band.

[0075] If multiple short-pass filters (SWPFs) can be used to achieve an infrared cutoff filter (IRCF) with a wide range of incident angles, then the image quality of ultra-wide-angle cameras can be improved dramatically.

[0076] Here, we will explain how an ideal refractive index without ripples can be achieved when using a SWPF composed of three mixed materials with different composition ratios and different wavelength regions of the transmission band, compared to the case of using a single material.

[0077] Figure 2 It is a curve representing the change of refractive index relative to wavelength when three mixed materials with different composition ratios are used as high refractive materials.

[0078] In Figure 2 In the example, TiO2 and Ti are shown as mixed materials. 0.82 Si 0.18 O2, Ti 0.72 Si 0.28O2, Ti 0.3 Si 0.7 The variation of the refractive index of O2 with respect to different wavelengths.

[0079] like Figure 2 As shown, when using mixed materials, wavelength dispersion (the change in refractive index caused by the change in wavelength) becomes more gradual compared to the case where a single material is used.

[0080] It should be noted that, in order to achieve the ideal refractive index without ripples, three TiO2 and SiO2 mixtures with different ratios were used. x Si y The method for adjusting the composition ratio (refractive index) of O multilayer films when used as high refractive index materials will be described later.

[0081] Figure 3 yes Figure 1 (b) shows the cut-out cross-sectional view of the infrared cut-off filter 7.

[0082] Here, as Ti x Si y As an example of a multilayer film, a hybrid film composed of 82% TiO2 and 18% SiO2 is described. Figure 3 The infrared cutoff filter 7 is composed of three short-pass filters (SWPFs).

[0083] like Figure 3 As shown, the infrared cutoff filter 7 has an absorbing ink layer 28 formed on the glass substrate 27. On the absorbing ink layer 28, three short-pass filters (SWPFs) are formed sequentially from the bottom side as Ti. x Si y The first SWPF section 21, the second SWPF section 23, and the third SWPF section 25 of the O multilayer film.

[0084] Here, the ink-absorbing layer 28 has such Figure 4 The characteristics shown by the curve indicate that the spectral shape of the transmission band closely resembles the sensitivity curve of human visual cells, and it possesses the ability to maintain these characteristics at high incident angles.

[0085] That is, in Figure 4 The diagram shows that incident angles of 0°, 15°, 30°, 40°, and 45° all maintain a characteristic close to the sensitivity curve of human visual cells.

[0086] Figure 4 It means Figure 3 The graph shows the characteristics of the ink-absorbing layer 28.

[0087] It should be noted that, in this embodiment, a hybrid absorption filter section is used, which has the following characteristics: Figure 4 The absorbent ink layer 28 with the characteristics shown is not limited to this; blue glass or the like with equivalent characteristics can also be used.

[0088] Then, the shortwave pass filters (SWPF sections) 21, 23, and 25, which are the first to third multilayer film sections, have the function of reflective filter sections, and become a hybrid IRCF composed of the absorbing ink layer 28 and the first to third SWPF sections 21, 23, and 25.

[0089] The first SWPF section 21 is composed of multiple layers ranging from 1 to 37 layers, and is made of Ti as a 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 It is composed of alternating and repeated layers of 21b.

[0090] Then, the second SWPF section 23 is composed of multiple layers of 38 to 67 layers, made of Ti as a 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 layers 23b are stacked alternately, and the third SWPF part 25 is composed of multiple layers of 68 to 93 layers, made of Ti as a low refractive index material. 0.3 Si 0.7 O X The material is composed of alternating and repeated layers of layer 25a and layer 25b, which is a high-refractive-index material, TiO2.

[0091] Thus, the infrared cutoff filter 7, as a multilayer film part, has three short-pass filters composed of a first SWPF section 21, a second SWPF section 23, and a third SWPF section 25.

[0092] It should be noted that, 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 is composed of a low-refractive-index material, Ti. 0.72 Si 0.28 O XLayer 21b and Ti 0.82 Si 0.18 O X Layer 23b and TiO2 layer 25b are composed of high-refractive-index materials.

[0093] Therefore, SWPF sections 21, 23, and 25 are composed of three short-pass filters with different wavelength regions in the transmission band.

[0094] Therefore, Ti, which is a low-refractive-index material, is adjacent to the first SWPF section 21. 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 layers 21b at a specified wavelength of 550 nm is 0.66. That is, Δn 550nm =0.66.

[0095] The applicant conducted a comparative study on the refractive index difference between high-refractive-index materials and low-refractive-index materials, and discovered that the ideal refractive index difference is Δn. 550nm =0.66.

[0096] Therefore, Ti, which is a low-refractive-index material, is adjacent to the first SWPF section 21. 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 at a predetermined wavelength (550 nm in this case) between layers 21b is set as a predetermined value of 0.66.

[0097] Similarly, Ti, which is a low-refractive-index material, will be adjacent to the second SWPF section 23. 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 550 nm between layers 23b is set to a predetermined value of 0.49. In the third SWPF section 25, the adjacent Ti layer is a low-refractive-index material. 0.3 Si 0.7 O X The difference in refractive index at a wavelength of 550 nm between layer 25a and layer 25b, which is a high-refractive-index material TiO2, is a predetermined value of 0.39.

[0098] In the infrared cutoff filter 7 constructed in this way, when the incident angle is 0° to 60°, the following results are obtained: Figure 4 The characteristics of the relationship between wavelength and transmittance are shown.

[0099] Figure 5 It means Figure 3 The graphs showing the filter characteristics of SWPF sections 21, 23, and 25 are shown. Figure 5 (a) represents the characteristic when the angle of incidence is 0°. Figure 5 (b) is the characteristic of the case where the angle of incidence is 60°.

[0100] It should be noted that, in Figure 5 The text also describes a Ti mixing ratio of ±3%, which will be discussed later.

[0101] That is, such as Figure 5 As shown in (a), it can be seen that a transmittance with ripple suppression of about 90% to 100% can be obtained at wavelengths of about 400 nm to 750 nm, and a filter characteristic that cuts off wavelengths of 750 nm to 1100 nm to less than 0% to 5% is obtained in the range of incident angles of 0° to 60°.

[0102] The infrared cutoff filter 7 constructed as described above can achieve a stable transmittance at wavelengths of approximately 400nm to 750nm that are perceptible to humans when the incident angle is 0° to 60°, and can reliably cut off light of other wavelengths. Therefore, if the infrared cutoff filter is used in the camera structure, the field of view of an ultra-wide-angle camera can be met at low cost, and high image quality can be obtained.

[0103] It should be noted that, in this embodiment, Ti x Si y Ti mixing in O multilayer films, for example Figure 6 As in (a), but not limited to, such as Figure 6 As shown in Figure (b) and Figure 6(c), as long as it is within ±3%, the above results can be obtained. Figure 5 The characteristics shown are roughly equivalent.

[0104] Figure 6 It means Figure 3 The table shows the range of mixing ratios of Ti in the first SWPF section to the third SWPF section 21, 23, 25 of the infrared cutoff filter 7 shown.

[0105] That is, since the mixing ratio of Ti in the first SWPF section to the third SWPF section 21, 23, 25 is within the allowable range of ±3%, the first SWPF section 21 is composed of Ti 0.27～0.33 Si 0.73～0.67 O XLayer 21a and Ti 0.69～0.75 Si 0.31～0.25 O X The layers 21b are stacked alternately and repeatedly, and the second SWPF part 23 is composed of Ti. 0.27～0.33 Si 0.73～0.67 O X Layer 23a and Ti 0.79～ 0.85 Si 0.21～0.15 O X The layers 23b are stacked alternately and repeatedly, and the third SWPF part 25 is made of Ti. 0.27～0.33 Si 0.73～0.67 O X The mixed film formed by alternating and repeated stacking of TiO2 layer 25a and TiO2 layer 25b is within the allowable range.

[0106] It should be noted that, in this invention, when forming the infrared cutoff filter 7, in order to achieve an ideal refractive index without ripples, three TiO2 and SiO2 mixtures with different composition ratios are mixed. x Si y When O multilayer films are used as high-refractive-index materials, the composition ratio (refractive index) is adjusted as follows.

[0107] That is, firstly, Ti, which is a high-refractive-index material in the first SWPF section 21 0.72 Si 0.28 O X In layer 21b, while achieving a balance between the ripples of the transmission band and the blocking band (low wavelength side), the Ti is adjusted. 0.72 Si 0.28 O X The thickness n of layer 21b.

[0108] Next, Ti, a high-refractive-index material, is used in the second SWPF section 23. 0.82 Si 0.18 O X In layer 23b, while observing the transmittance and ripple of the blocking region (mid-wavelength side), the Ti was adjusted. 0.82 Si 0.18 O X The thickness of the film in layer 23b is n.

[0109] Finally, in the TiO2 layer 25b, which is a high-refractive-index material in the third SWPF section 25, the film thickness n of the TiO2 layer 25b is adjusted while observing the transmittance and ripples of the blocking region (high wavelength side) (the ink characteristics of the ink-absorbing layer 28 are also considered here).

[0110] In this way, an infrared cutoff filter 7 with an ideal refractive index that does not produce ripples is formed.

[0111] Figure 8 The curve represents the characteristics of the hybrid IRCF produced by this invention.

[0112] like Figure 8 As shown, with Figure 7 Unlike conventional dielectric IRCFs, this exhibits no large ripples near the center of the transmission band as the incident angle increases. Furthermore, the cutoff wavelength does not shift towards shorter wavelengths.

[0113] It should be noted that the film thickness of high-refractive-index materials can also be adjusted using the least squares fitting method.

[0114] It should be noted that the first to third SWPF sections 21, 23, and 25 of the infrared cutoff filter 7 described above can be easily manufactured at low cost by using a film deposition apparatus that can carry at least two types of targets, such as a metal mode sputtering device, and by using a target that simultaneously outputs Si and Ti.

[0115] In this case, by appropriately using the film-forming device as described above to adjust the output ratio of each target, any mixing ratio can be easily obtained at low cost.

[0116] While this embodiment has been described above, the descriptions and drawings that form part of this disclosure should not be construed as limiting. Various embodiments not described herein are also included.

[0117] That is, in this embodiment, three types of SWPF parts are provided, namely the first SWPF part to the third SWPF part 21, 23 and 25, but it is not limited to these. For example, it may be composed of four or more SWPF parts.

[0118] Furthermore, in this embodiment, a hybrid absorption filter section is used, which has the following characteristics: Figure 3 The absorbent ink layer 28 with the characteristics shown is not limited to this; blue glass or the like with equivalent characteristics can also be used.

[0119] 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, Ti in the second SWPF part 23 0.3 Si 0.7 O X Layer 23a and Ti 0.82 Si 0.18 O X Layer 23b, Ti in the third SWPF part 25 0.3 Si 0.7 OX The film thicknesses of layer 25a and TiO2 layer 25b are basically different, but they can also be the same.

[0120] Here, as a basic design, it consists of three SWPF units, and the film thickness of each layer is optimized using the least squares fitting method to make it close to the target spectrum.

[0121] Furthermore, the Ti of the first SWPF part 21 in this embodiment 0.3 Si 0.7 O X Layer 21a and Ti 0.72 Si 0.28 O X Layer 21b, Ti of the second SWPF part 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 part 25 0.3 Si 0.7 O X The refractive indices of layer 25a and TiO2 layer 25b are examples; they can be any value as long as the difference between the refractive indices of the high-refractive-index material and the low-refractive-index material is 0.66.

Claims

1. An infrared cutoff filter, comprising a reflective filter section and an absorptive filter section, characterized in that, The reflective filter section has Ti x Si y O multilayer film, The Ti x Si y O-multilayer films are formed by alternating layers of high-refractive-index material and low-refractive-index material. The difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer at a specified wavelength is a predetermined value.

2. The infrared cutoff filter according to claim 1, characterized in that, A predetermined value of 0.66 is defined as the difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer at a wavelength of 550 nm.

3. The infrared cutoff filter according to claim 1, characterized in that, The absorption filter section is composed of an absorbent ink layer.

4. The infrared cutoff filter according to claim 1, characterized in that, The Ti x Si y The O multilayer film consists of three SWPF sections, namely the first SWPF section, the second SWPF section, and the third SWPF section, which have different wavelength regions in the transmission band.

5. The infrared cutoff filter according to claim 4, characterized in that, The first SWPF section is made of Ti, which is the low refractive index material. 0.27～0.33 Si 0.73～0.67 O X The layer and Ti as the high refractive material 0.69～0.75 Si 0.31～0.25 O X The second SWPF portion is formed by alternating and repeated stacking of layers, and is made of Ti, which is the low-refractive-index material. 0.27～0.33 Si 0.73～0.67 O X The layer and Ti as the high refractive material 0.79～0.85 Si 0.21～0.15 O X The third SWPF portion is composed of alternating and repeated layers, and is made of Ti, which is the low-refractive-index material. 0.27～0.33 Si 0.73～0.67 O X It is formed by alternating and repeated layers of TiO2, which is the high-refractive-index material.

6. The infrared cutoff filter according to claim 4, characterized in that, The first SWPF section is made of Ti, which is the low refractive index material. 0.3 Si 0.7 O X The layer and Ti as the high refractive material 0.72 Si 0.28 O X The second SWPF portion is formed by alternating and repeated stacking of layers, and is made of Ti, which is the low-refractive-index material. 0.3 Si 0.7 O X The layer and Ti as the high refractive material 0.82 Si 0.18 O X The third SWPF portion is composed of alternating and repeated layers, and is made of Ti, which is the low-refractive-index material. 0.3 Si 0.7 O X It is formed by alternating and repeated layers of TiO2, which is the high-refractive-index material.

7. A camera device comprising a lens unit, an infrared cutoff filter, and an image sensor, characterized in that, The infrared cutoff filter has a reflective filter section and an absorptive filter section. The reflective filter section has Ti x Si y O multilayer film, The Ti x Si y O-multilayer films are formed by alternating layers of high-refractive-index material and low-refractive-index material. The difference in refractive index between the high-refractive-index material layer and the low-refractive-index material layer at a specified wavelength is a predetermined value.

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