Infrared cut filter, infrared cut lens, and camera module

Abstract

Provided are an infrared cut filter (10), an infrared cut lens (20), and a camera module (100). The camera module (100) includes the infrared cut filter and the infrared cut lens, which can suppress a decrease in transmittance of high-wavelength region visible light in a monochrome filter and obtain a high light amount. The infrared cut filter (10) or the infrared cut lens (20) transmits light having a wavelength of 400 nm to 750 nm, wherein the wavelength at which the transmittance is 50% is in the range of 700 nm to 750 nm.

Description

Technical Field

[0001] This invention relates to an infrared cut-off filter and an infrared cut-off lens, and more specifically, to an infrared cut-off filter and an infrared cut-off lens for a camera module. Background Technology

[0002] Optical imaging systems using imaging elements employ optical lenses and optical components that collect light, such as optical films that transmit light within a predetermined wavelength range but not light within other wavelength ranges. For example, complementary metal-oxide-semiconductor (CMOS) sensors are used as imaging elements. CMOS sensors are mainly divided into color sensors and monochrome sensors. Color sensors are primarily RGB sensors, while monochrome sensors represent grayscale. Color filters are placed on color sensors. By using color filters, visible light with wavelengths suitable for the red, green, and blue (RGB) wavelength range of the imaging element can be selectively transmitted, while visible light in other wavelength ranges can be absorbed. However, this results in a reduction in light intensity. For example, in the case of an RGGB Bayer array, the light intensity becomes one-quarter. On the other hand, because monochrome sensors have a large amount of incident light, they have higher resolution and more information than color sensors.

[0003] Furthermore, an infrared cut-off filter, which confines the light incident on the imaging element to the wavelength range perceptible to the human eye (the visible wavelength range), is placed between the optical lens and the image sensor. This infrared cut-off filter is used to block the transmission of infrared light with wavelengths longer than the visible wavelength range. In an infrared cut-off filter, the transmittance profile varies with the angle of incidence. When the width of the infrared cut-off filter is increased, color sensors experience color deviation problems, resulting in color degradation in the captured image. On the other hand, since monochrome sensors do not initially represent images in color, there is no color deviation problem. However, monochrome filters, which are typically used to cut off infrared light, have the problem of reducing the transmittance of visible light in the high wavelength region. Summary of the Invention

[0004] The purpose of this invention is to provide an infrared cut-off filter, an infrared cut-off lens, and a camera module including the infrared cut-off filter and the infrared cut-off lens. The infrared cut-off filter and the infrared cut-off lens can reduce the decrease in transmittance of visible light in the high wavelength region of a monochromatic filter and obtain high light intensity.

[0005] The infrared cut-off filter of the present invention transmits light with a wavelength of 400 nm to 750 nm, wherein the wavelength with a transmittance of 50% is in the range of 700 nm to 750 nm.

[0006] Preferably, the infrared cut-off filter according to the present invention comprises a filter film and an infrared cut-off film formed on the filter film. Preferably, the infrared cut-off film comprises Ta2O5 and SiO2 or TiO2 and SiO2.

[0007] In addition, the filter film includes organic materials with specific spectral absorption characteristics in order to achieve the desired wavelength cutoff.

[0008] The infrared cutoff lens of the present invention transmits light with a wavelength of 400nm to 750nm, wherein the wavelength with a transmittance of 50% is in the range of 700nm to 750nm.

[0009] Preferably, the infrared cutoff lens according to the present invention includes a lens and an infrared cutoff film formed on the lens.

[0010] The camera module according to the present invention includes an infrared cutoff filter or an infrared cutoff lens.

[0011] The present invention will be further described in detail below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention and are for illustrative purposes only. Attached Figure Description

[0012] The invention can be better understood through the following detailed description of non-limiting embodiments of the invention, and by referring to the accompanying drawings, wherein:

[0013] Figure 1 A diagram of an imaging device using an infrared cutoff filter provided in an embodiment of the present invention is shown;

[0014] Figure 2 A graph showing the transmission characteristics of a conventional infrared cut-off filter and an infrared cut-off filter provided in an embodiment of the present invention is shown.

[0015] Figure 3 A diagram showing the transmission characteristics of an infrared cutoff filter provided in the first embodiment of the present invention is shown;

[0016] Figure 4 A graph showing the transmission characteristics of an infrared cutoff lens provided in the second embodiment of the present invention is shown;

[0017] Figure 5 A diagram showing the transmission characteristics of an infrared cutoff lens provided by a variant of the second embodiment of the present invention is illustrated.

[0018] Figure 6 This is a diagram showing the transmission characteristics of the infrared cutoff filter provided in the third embodiment of the present invention;

[0019] Figure 7 This is a diagram showing the reflection characteristics of the infrared cutoff filter provided in the third embodiment of the present invention;

[0020] Figure 8 This is a diagram showing the transmission characteristics of a camera module using a conventional infrared cut-off filter and a camera module using an infrared cut-off lens provided in the second embodiment of the present invention.

[0021] Figure 9 This is a diagram showing the transmission characteristics in a camera module using the infrared cutoff filter provided in the third embodiment of the present invention. Detailed Implementation

[0022] In this document, unless otherwise stated, when defining the positional relationship between one component and another component, the terms "above" and "below" include cases where another component is located between components, and cases where one component is directly above or directly below another component.

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described below with reference to the accompanying drawings.

[0024] (First Embodiment) Figure 1 A diagram is shown for explaining an imaging device 100 using the infrared cutoff filter 10 provided in the first embodiment of the present invention. (See diagram for reference.) Figure 1 As shown, the imaging device 100 includes an imaging lens 20, an infrared cutoff filter 10, and an imaging element 30. Although the imaging lens 20... Figure 1 While described as a single lens, it typically comprises multiple lenses. The imaging element 30 can be a semiconductor solid-state imaging element, such as a CCD or CMOS. The infrared cut-off filter 10 includes a transparent substrate 12, an infrared reflective layer 14 formed on one surface of the transparent substrate 12, and an infrared absorbent layer 16 formed on another surface of the transparent substrate 12. The infrared cut-off film 10 is configured such that the infrared reflective layer 14 faces the imaging lens 20, and the infrared absorbent layer 16 faces the imaging element 30.

[0025] For example, the transparent substrate 12 can be a plate-shaped body with a thickness of about 0.1 mm to 0.3 mm. There are no particular limitations on the material forming the transparent substrate 12, as long as it can transmit visible light; for example, it can be glass. Since glass substrates are inexpensive, they are preferred in terms of cost. Furthermore, blue glass can be used as the transparent substrate 12. Alternatively, synthetic resin films or synthetic resin substrates, such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), and polyimide (PI), can be used as the transparent substrate 12.

[0026] As described above, an infrared reflective layer (IR coating) 14 is formed on the surface of the transparent substrate 12 and serves as a light incident surface. The infrared reflective layer 14 transmits visible light and reflects infrared light. The infrared reflective layer 14 can be formed from a dielectric multilayer film consisting of stacked dielectric films with different refractive indices. By controlling the refractive index and thickness of each layer, the optical properties of the dielectric multilayer film, such as spectral transmittance characteristics, can be freely designed. For example, the infrared reflective layer 14 can be alternating layers of titanium oxide (TiO2) and silicon oxide (SiO2) with different refractive indices deposited on the transparent substrate 12. As a vapor deposition method, ion-beam assisted deposition (IAD) is preferred, which forms the film at a relatively low temperature. In addition to TiO2 and SiO2, dielectrics such as MgF2, Al2O3, MgO, ZrO2, Nb2O5, and Ta2O5 can also be used as materials for the dielectric multilayer film.

[0027] As described above, an infrared absorption layer (AR coating) 16 is formed on another surface of the transparent substrate 12 and serves as a light-absorbing surface. The infrared absorption layer 16 transmits visible light and absorbs infrared light. The infrared absorption layer 16 has the functions of suppressing reflection, increasing transmitted light, and suppressing ghosting. Light entering the infrared cutoff filter 10 passes through the infrared reflective layer 14 and the transparent substrate 12, and then enters the infrared absorption layer 16. Therefore, the infrared absorption layer 16 absorbs infrared light that is not blocked by the infrared reflective layer 14 and the transparent substrate 12.

[0028] For example, the infrared absorbing layer 16 is formed by applying a solution containing an adhesive resin and then drying and curing the coating, wherein a substance (absorbing substance) having an absorption peak at a wavelength within a specific range is dispersed in the solution. For example, the adhesive resin used to form the infrared absorbing layer 16 is an acrylic resin, polystyrene resin, polyurethane resin, fluororesin, polycarbonate resin, polyimide resin, polyamide resin, polyolefin resin, silicone resin, or epoxy resin. These resins can be formed from a single monomer, an oligomer, or a polymer, or by combining two or more monomers, oligomers, or polymers. For example, the thickness of the infrared absorbing layer 16 is from 1 μm to 200 μm.

[0029] Figure 2 A graph showing the transmission characteristics of a conventional infrared cut-off filter and an infrared cut-off filter provided in an embodiment of the present invention is shown. From Figure 2It is clear that conventional infrared cut-off filters can block infrared light, but exhibit a significant decrease in transmittance in the high wavelength region of visible light (approximately 550 nm to 780 nm). On the other hand, the transmittance curve of the infrared cut-off filter provided in the embodiments of the present invention shows a substantially rectangular transmission region. The infrared cut-off filter provided in the embodiments of the present invention transmits visible light over a wide wavelength range, thus achieving a higher light intensity than conventional infrared cut-off filters. For example, when using the infrared cut-off film provided in the embodiments of the present invention, the light intensity is approximately 1.28 times that of using a conventional infrared cut-off film.

[0030] (Second Embodiment) The infrared cutoff lens provided in the second embodiment of the present invention is characterized in that an infrared reflective layer 14 is disposed on the surface of any one of the plurality of lenses forming the imaging lens 20. Quartz glass, polycarbonate (PC), cyclic olefin copolymer (COC), etc., can be used as the imaging lens 20. Polycarbonate (PC) is superior to cyclic olefin copolymer (COC) because it has good heat resistance. For the material to deposit the infrared reflective layer on the lens, the surface of the lens is preferably flat. Using this configuration, a... Figure 2 The transmission characteristics are shown.

[0031] (Third Embodiment) The infrared cutoff film provided in the third embodiment of the present invention is characterized in that the transparent substrate 12 comprises an organic material having specific spectral absorption characteristics in order to achieve the desired wavelength cutoff. Even with this configuration, better transmission characteristics than conventional infrared cutoff filters can be obtained.

[0032] Embodiments of the present invention will be described below.

[0033] (First Example) An infrared reflective film consisting of alternating layers of TiO2 and SiO2 films was formed on the main surface of a transparent glass substrate (manufactured by Schott, product name: D263) made of borosilicate glass with a thickness of 0.21 mm by ion-beam assisted deposition (IAD). This produced the infrared reflective layer 14 of the first example. The thickness of the infrared reflective layer 14 of the first example is 5 μm.

[0034] Next, an organic dye (selected from one or more organic dyes of anthocyanin, squaric acid, phthalocyanine, and diammonium ketone) is mixed with methyl ethyl ketone (MEK) as a solvent, and polyvinyl butyral (PVB) is added to achieve a solid content ratio of 99% by weight. The mixture is then stirred for 2 hours to obtain a coating liquid. The organic dye has an absorption peak at wavelengths of 700 nm to 750 nm, absorbs very little in the visible region, and is soluble in methyl ethyl ketone (MEK). The coating liquid is applied to another main surface of a transparent glass substrate by spin coating to form a coating film. This coating film is exposed to 140°C for 0.5 hours to dry and cure, forming an absorption film. This produces the infrared absorption layer 16 of the first example. The thickness of the infrared absorption layer 14 of the first example is 3 μm.

[0035] Figure 3 A graph showing the transmission characteristics of the infrared cutoff filter provided in Example 1 of the present invention is illustrated. Figure 3 In the diagram, the solid line represents the transmittance curve when the incident angle of light on the infrared cutoff filter is 0°, and the dashed line represents the transmittance curve when the incident angle is 30°. It can be seen that high transmittance is achieved across a wide wavelength range of visible light (approximately 400 nm to 750 nm) under all conditions. Furthermore, it can be observed that the wavelength with a transmittance of 50% is in the range of approximately 700 nm to 750 nm.

[0036] (Second Example) An infrared reflective film consisting of alternating layers of TiO2 and SiO2 films is formed on the main surface of a lens made of quartz glass (manufactured by Schott) with a thickness of 0.21 mm by ion-beam assisted deposition (IAD). This produces the infrared reflective layer 14 provided in the second example. The thickness of the infrared reflective layer 14 provided in the second example is 5 μm.

[0037] Figure 4 This is a diagram illustrating the transmission characteristics of the infrared cutoff lens provided in the second example of the present invention. Figure 4 In the diagram, the solid line represents the transmittance curve when the incident angle of light on the infrared cutoff lens is 0°, and the dashed line represents the transmittance curve when the incident angle is 30°. It can be seen that high transmittance is achieved in all cases across a wide wavelength range of visible light (approximately 400 nm to 750 nm). Furthermore, it can be observed that the wavelength with a transmittance of 50% is in the range of approximately 700 nm to 750 nm.

[0038] Next, two modified examples of the second example are shown. Modified example 1 is an infrared cutoff lens prepared by the same method as the second example, except that Ta2O5 and SiO2 are used instead of TiO2 and SiO2. Furthermore, modified example 2 is an infrared cutoff lens prepared by the same method as modified example 1, except that the thickness of the infrared reflective layer 14 is changed.

[0039] Figure 5 This is a diagram showing the transmission characteristics of the infrared cutoff lens provided in Examples 1 and 2. Figure 5 Example 1 illustrates the transmission characteristics of a modified infrared cutoff lens provided in Example 1. Figure 5 Example 2 illustrates the transmission characteristics of the infrared cutoff lens provided in Example 2. For comparison, a second example is shown (…). Figure 5 The transmission characteristics of the infrared cutoff lens provided in "Example 3" and its application in conventional smartphones ( Figure 5 The transmission characteristics of the infrared cutoff lens in a "conventional smartphone" are shown. In particular, it can be seen that high transmittance is obtained in a wide wavelength range of visible light in modified Example 1 ("Example 1"). Furthermore, it can be seen that the wavelength with a transmittance of 50% is in the range of approximately 700 nm to 750 nm.

[0040] (Third Example) An infrared cutoff film is prepared by incorporating an organic material with specific spectral absorption characteristics to achieve a cutoff to the desired wavelength in a transparent glass substrate (manufactured by Schott AG, product name: D263) made of borosilicate glass with a thickness of 0.21 mm. This organic material is a cyclic olefin resin with excellent heat resistance, transparency, and processability.

[0041] Next, an organic dye (selected from one or more organic dyes of anthocyanin, squaric acid, phthalocyanine, and diammonium ketone) is mixed with methyl ethyl ketone (MEK) as a solvent, and polyvinyl butyral (PVB) is added to achieve a solid content ratio of 99% by weight. The mixture is then stirred for 2 hours to obtain a coating liquid. The organic dye has an absorption peak at wavelengths of 700 nm to 750 nm, absorbs very little in the visible region, and is soluble in methyl ethyl ketone (MEK). The coating liquid is applied to another main surface of a transparent glass substrate by spin coating to form a coating film. This coating film is exposed to 140°C for 0.5 hours to dry and cure, forming an absorption film. This produces the infrared absorption layer 16 of the third example. The thickness of the infrared absorption layer 14 of the third example is 3 μm.

[0042] Figure 6 A graph showing the transmission characteristics of the infrared cutoff filter provided in the third example is shown. Figure 7 A graph showing the reflection characteristics of the infrared cutoff film provided in the third example is shown. Figure 6 In the diagram, the solid line represents the transmittance curve when the incident angle of light on the infrared cutoff filter is 0°, and the dashed line represents the transmittance curve when the incident angle is 30°. Furthermore, in... Figure 7 In the diagram, the solid line represents the reflectance curve when the incident angle of light on the infrared cutoff filter is 0°, and the dashed line represents the reflectance curve when the incident angle is 30°. From Figure 6 It can be seen that high transmittance is achieved in all cases across a wide wavelength range of visible light (approximately 400 nm to 750 nm). Furthermore, it can be observed that wavelengths with 50% transmittance are in the range of approximately 700 nm to 750 nm.

[0043] (Fourth example) Figure 8 A graph showing the transmission characteristics of a camera module using a conventional infrared cut-off filter and a camera module using an infrared cut-off lens provided in the second example of the present invention is illustrated. From Figure 8 As can be seen, in the camera module using a conventional infrared cutoff filter, the transmission characteristics drop sharply starting from a wavelength of approximately 550 nm. On the other hand, in the camera module using the infrared cutoff lens of the second example, it can be seen that higher transmittance can be obtained over a wider visible light range compared to the camera module using a conventional infrared cutoff filter.

[0044] (Fifth Example) Figure 9 A graph showing the transmission characteristics in a camera module using the infrared cutoff filter provided in the third example of the present invention is illustrated. Figure 9 In the diagram, the solid line represents the transmittance curve when the incident angle of light on the infrared cutoff filter is 0°, and the dashed line represents the transmittance curve when the incident angle is 30°. From Figure 9 As can be seen, compared with camera modules using conventional monochrome filters, camera modules using the infrared cut-off filter provided in the third example have higher transmittance over a wider wavelength range of visible light.

[0045] This invention can be used in camera modules, particularly in camera modules for smartphones.

Claims

1. A camera module, characterized in that, It includes an imaging lens, an infrared cut-off filter, and an imaging element, wherein the imaging element is a monochrome sensor; The infrared cut-off filter transmits light with wavelengths from 400 nm to 750 nm, wherein the wavelength with a transmittance of 50% is in the range of 700 nm to 750 nm. The infrared cut-off filter includes a transparent substrate, an infrared reflective layer, and an infrared absorber layer. The infrared reflective layer is disposed on one side of the transparent substrate, and the infrared reflective layer is disposed on the other side of the transparent substrate. The infrared reflective layer is used to transmit visible light and reflect infrared light, and has a thickness of 5 μm. The transparent substrate or the infrared absorption layer includes an organic material having an absorption peak at a wavelength of 700 nm to 750 nm, the organic material being used to transmit visible light and absorb infrared light.

2. The camera module according to claim 1, characterized in that, The infrared reflective layer comprises alternating layers of Ta2O5 and SiO2 or alternating layers of TiO2 and SiO2.

3. The camera module according to claim 1 or 2, characterized in that, The thickness of the infrared absorption layer is from 1 μm to 200 μm.

Images