Optical filter and sensing device

Abstract

Provided is an optical filter having a low transmittance for obliquely incident light in a visible region. This optical filter comprises: a first substrate that includes a first upper surface and a first lower surface; a first reflection and scattering part that is provided on the first lower surface of the first substrate, reflects and scatters first light, which is light in at least a partial wavelength band in a visible region, and transmits second light, which is light in at least a partial wavelength band in an infrared region; a filler that is disposed below the first substrate; a second substrate that is disposed below the filler and includes a second upper surface and a second lower surface; and a second reflection and scattering part that is provided on the second upper surface of the second substrate, reflects and scatters the first light, and transmits the second light.

Description

Optical Filter and Sensing Device

[0001] The present disclosure relates to an optical filter and a sensing device.

[0002] For example, Patent Document 1 discloses an optical filter including a reflection scattering part that reflects and scatters light in at least a part of the wavelength band in the visible region and transmits light in at least a part of the wavelength band in the infrared region.

[0003] Japanese Patent No. 6729396

[0004] One aspect of the present disclosure aims to provide an optical filter and a sensing device with a low transmittance for obliquely incident light in the visible region.

[0005] The optical filter according to one aspect of the present disclosure includes a first substrate including a first upper surface and a first lower surface, a first reflection scattering part provided on the first lower surface of the first substrate, which reflects and scatters first light that is light in at least a part of the wavelength band in the visible region and transmits second light that is light in at least a part of the wavelength band in the infrared region, a filler disposed below the first substrate, a second substrate disposed below the filler and including a second upper surface and a second lower surface, and a second reflection scattering part provided on the second upper surface of the second substrate, which reflects and scatters the first light and transmits the second light.

[0006] The optical filter according to one aspect of the present disclosure includes a substrate including a substrate upper surface and a substrate lower surface, a first reflection scattering part provided on the substrate upper surface of the substrate, which reflects and scatters first light that is light in at least a part of the wavelength band in the visible region and transmits second light that is light in at least a part of the wavelength band in the infrared region, a second reflection scattering part provided on the substrate lower surface of the substrate, which reflects and scatters the first light and transmits the second light, a first filler disposed above the substrate, and a second filler disposed below the substrate.

[0007] According to one aspect of the present disclosure, an optical filter and a sensing device with a low transmittance for obliquely incident light in the visible region can be provided.

[0008] This is a schematic top view showing the overall configuration of the optical filter according to the first embodiment. This is a schematic cross-sectional view taken along the line II-II in Figure 1. This is a schematic cross-sectional view showing the behavior of the first light obliquely incident on the optical filter according to the first embodiment. This is a diagram showing an example of the reflectance spectrum of the first multilayer film of the optical filter according to the first embodiment. This is a schematic cross-sectional view showing an optical filter according to a modified example of the first embodiment. This is a schematic cross-sectional view of the optical filter according to the second embodiment. This is a diagram showing a list of the specifications of the substrate and filler material, as well as the optical characteristics, of the optical filters according to each of Examples 1 to 4. This is a diagram showing a list of the specifications of the substrate and filler material, as well as the optical characteristics, of the optical filters according to each of Examples 5 to 8. This is a diagram showing the transmittance when light with a wavelength of 400 nm or more and 1000 nm or less is incident on the optical filters according to Examples 1 to 4 at an incident angle of 0 degrees. This is a diagram showing the transmittance when light with a wavelength of 400 nm or more and 1000 nm or less is incident on the optical filters according to Examples 1 to 4 at an incident angle of 40 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 50 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 60 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 70 degrees. This figure shows the average transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 600 nm is incident. This figure shows the average transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 930 nm to 950 nm is incident. This figure illustrates the slope of the cut-on wavelength in the optical filters according to Examples 1 to 4. This figure shows the evaluation results of the slope of the cut-on wavelength in the optical filters according to Examples 1 to 4. This figure shows the haze characteristics of the optical filter according to Example 1. This figure shows the haze characteristics of the optical filter according to Example 2. This figure shows the haze characteristics of the optical filter according to Example 3. This figure shows the haze characteristics of the optical filter according to Example 4. This figure shows the haze characteristics of the optical filters according to Examples 1 to 4 for visible light.This figure shows the haze characteristics of the optical filters according to Examples 1 to 4 for infrared light. This figure shows L* of the optical filters according to Examples 1 to 4. This figure shows a* and b* of the optical filters according to Examples 1 to 4. This figure shows the color difference between the first surface and the second surface of the optical filters according to Examples 1 to 4.

[0009] The embodiments for implementing this disclosure will be described in detail below with reference to the drawings. However, the embodiments shown below are illustrative examples of optical filters for realizing the technical concept of the embodiments of this disclosure, and are not limited to those shown below. Note that the size, positional relationships, etc. of the components shown in each drawing may be exaggerated for clarity of explanation. In each drawing, the same components are denoted by the same reference numeral, and redundant explanations are omitted as appropriate.

[0010] This specification and the claims may use terms to indicate specific directions or positions (e.g., “up,” “down,” and other terms including these terms). These terms are used solely for clarity to indicate relative directions or positions in the referenced drawings. Furthermore, “up” or “down” are unrelated to the direction of gravity.

[0011] Furthermore, in the diagrams shown below, a Cartesian coordinate system with X, Y, and Z axes may be used to indicate direction. The X, Y, and Z axes are orthogonal to each other. In the X direction along the X axis, the direction the arrow points is denoted as the +X side, and the opposite side of the +X side is denoted as the -X side. In the Y direction along the Y axis, the direction the arrow points is denoted as the +Y side, and the opposite side of the +Y side is denoted as the -Y side. In the Z direction along the Z axis, the direction the arrow points is denoted as the +Z side, and the opposite side of the +Z side is denoted as the -Z side. However, the above directional expressions merely describe the relative positions, orientations, and directions, and do not necessarily correspond to the actual relationships in use.

[0012] In this specification and the claims, “along the direction” may include deviations of up to ±10 degrees from that direction. “Perpendicular” may include deviations of up to ±10 degrees from 90 degrees. “To position” is not limited to direct contact, but also includes indirect positioning, for example, via other members.

[0013] [First Embodiment] <Configuration of the Optical Filter According to the First Embodiment> The configuration of the optical filter according to the first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a schematic top view showing the overall configuration of the optical filter 100 according to the first embodiment. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic cross-sectional view showing the behavior of the first light L10 obliquely incident on the optical filter 100. In Figures 2 and 3, arrows represent parts of the light incident on the optical filter 100, the light transmitted through the optical filter 100, and the light scattered by the optical filter 100.

[0014] As shown in Figures 1 and 2, the optical filter 100 includes a first substrate 1 including a first upper surface 1-1 and a first lower surface 1-2, and a first reflection scattering section 2 provided on the first lower surface 1-2 of the first substrate 1, which reflects and scatters the first light L10 and transmits the second light L20. The optical filter 100 also includes a filler material 3 disposed below the first substrate 1, and a second substrate 4 disposed below the filler material 3, which includes a second upper surface 4-1 and a second lower surface 4-2. Furthermore, the optical filter 100 has a second reflection scattering section 5 provided on the second upper surface 4-1 of the second substrate 4, which reflects and scatters the first light L10 and transmits the second light L20. The first light L10 is light in at least a portion of the wavelength band in the visible region. The second light L20 is light in at least a portion of the wavelength band in the infrared region. The visible region refers to the wavelength band from 360 nm to less than 830 nm. The infrared region refers to the wavelength range from 830 nm to 1 mm.

[0015] The optical filter 100 transmits the second light L20 while reflecting and scattering the first light L10. As a result, when an observer views the optical filter 100 from the upper surface 100-1 side, for example, the -Z side, the light-receiving area of ​​the first light L10 appears to be colored with a color other than black, such as white, and the space on the lower surface 100-2 side, for example, the +Z side, is not observed. The lower surface 100-2 is the surface of the optical filter 100 opposite to the upper surface 100-1.

[0016] The optical filter 100 is used, for example, in an optical device that uses infrared light, as an infrared light transmission window that blocks visible light and transmits infrared light. The optical device can transmit and receive information with an external device using infrared light while improving its design by blocking visible light so that the inside of the optical device is not visible. The coloring observed in the light-receiving area of ​​the first light L10 is not limited to a single color, but may include a combination of multiple colors such as a mottled pattern or camouflage. The upper surface 100-1 side is the incident or outgoing side of the second light L20 in the optical filter 100, and is one of the predetermined incident sides of the first light L10.

[0017] The first substrate 1 and the second substrate 4 can each be made of a material that is transparent to at least the second light L20. Preferably, the light transmittance is 60% or more for a specific light. The first substrate 1 and the second substrate 4 can be made by including glass or resin, etc., that is transparent to at least the second light L20. For example, borosilicate glass can be used for the first substrate 1 and the second substrate 4, respectively. However, the first substrate 1 and the second substrate 4 may be made of different materials.

[0018] The first reflection scattering section 2 and the second reflection scattering section 5 each have the function of reflecting and scattering the first light L10 by a certain percentage or more, and transmitting the second light L20 by a certain percentage or more. Preferably, the first reflection scattering section 2 and the second reflection scattering section 5 each have the function of scattering the first light L10 more than the second light L20.

[0019] In the examples shown in Figures 1 and 2, the function of scattering light by the first reflection scattering section 2 is realized by the first uneven portion 21 and the first multilayer film 22. The first reflection scattering section 2 can scatter the first light L10 by utilizing the reflection phenomenon at the first multilayer film 22 arranged on the first uneven portion 21. However, the function of scattering light by the first reflection scattering section 2 is not limited to the first uneven portion 21 and the first multilayer film 22, and may also be realized by a fine particle-containing resin layer made of a resin containing fine particles, or by a diffraction structure, etc. If the first reflection scattering section 2 has a fine particle-containing resin layer, it can scatter the first light L10 mainly by utilizing the refraction phenomenon at the interface with the fine particles in the binder filler 3. Alternatively, if the first reflection scattering section 2 has a diffraction structure, it can scatter the first light L10 by utilizing the diffraction phenomenon.

[0020] In the examples shown in Figures 1 and 2, the first uneven portion 21 includes a plurality of first recesses 210. The plurality of first recesses 210 are arranged in two dimensions. Specifically, the plurality of first recesses 210 are aligned in a matrix within the first lower surface 1-2 of the first substrate 1 in the X and Y directions, which are two mutually orthogonal directions. Each of the plurality of first recesses 210 has substantially the same spherical shape. By forming a plurality of first recesses 210 on the first lower surface 1-2 of the first substrate 1, the first substrate 1 constitutes a plano-concave lens array. However, each of the plurality of first recesses 210 is not limited to a spherical shape, and may have any concave shape, and may have different shapes from each other. The first uneven portion 21 may include a plurality of convex portions that are convex toward the first lower surface 1-2, and may include both a plurality of recesses and a plurality of convex portions. The multiple recesses or protrusions in the first uneven portion 21 do not necessarily have to be arranged in a matrix at equal intervals. For example, they may be arranged in a triangular pattern, i.e., the multiple recesses or protrusions may be arranged alternately in the X and Y directions, or they may be formed in a random arrangement on the first lower surface 1-2 of the first substrate 1.

[0021] The first multilayer film 22 is a multilayer film arranged on the first uneven portion 21. The first multilayer film 22 can be a dielectric multilayer film, such as the one used for the mirror layer of a dichroic mirror. Details of the configuration of the first multilayer film 22 will be described separately with reference to Table 1.

[0022] In the example shown in Figure 2, the first uneven portion 21 and the first multilayer film 22 are made of different materials and are shown to be in contact with each other. However, for example, a part of the material that makes up the first multilayer film 22 may also make up the first uneven portion 21. That is, the first uneven portion 21 and the first multilayer film 22 may be integrally formed from the same material, for example. The optical filter 100 may have another functional layer between the first uneven portion 21 and the first multilayer film 22, and the first uneven portion 21 and the first multilayer film 22 may not be in contact with each other. If the first uneven portion 21 and the first multilayer film 22 are not in contact, it is preferable that the distance between the first uneven portion 21 and the first multilayer film 22 be short.

[0023] In the examples shown in Figures 1 and 2, the function of scattering light by the second reflection scattering section 5 is realized by the second uneven portion 51 and the second multilayer film 52. The second reflection scattering section 5 can scatter the first light L10 by utilizing the reflection phenomenon at the second multilayer film 52 arranged on the second uneven portion 51. However, the function of scattering light by the second reflection scattering section 5 is not limited to the second uneven portion 51 and the second multilayer film 52, and may also be realized by a fine particle-containing resin layer made of a resin containing fine particles, or by a diffraction structure, etc. If the second reflection scattering section 5 has a fine particle-containing resin layer, it can scatter the first light L10 mainly by utilizing the refraction phenomenon at the interface with the fine particles in the binder filler 3. Alternatively, if the second reflection scattering section 5 has a diffraction structure, it can scatter the first light L10 by utilizing the diffraction phenomenon.

[0024] In the examples shown in Figures 1 and 2, the second uneven portion 51 includes a plurality of second recesses 510. The plurality of second recesses 510 are arranged in two dimensions. Specifically, the plurality of second recesses 510 are aligned in a matrix within the second upper surface 4-1 of the second substrate 4 in the X and Y directions, which are two mutually orthogonal directions. Each of the plurality of second recesses 510 has substantially the same spherical shape. By forming a plurality of second recesses 510 on the second upper surface 4-1 of the second substrate 4, the second substrate 4 constitutes a plano-concave lens array. However, each of the plurality of second recesses 510 is not limited to a spherical shape, but may have any concave shape, and may have different shapes from each other. The second uneven portion 51 may include a plurality of convex portions that are convex toward the second upper surface 4-1, and may include both a plurality of recesses and a plurality of convex portions. The multiple recesses or protrusions in the second uneven portion 51 do not necessarily have to be arranged in a matrix at equal intervals. For example, they may be arranged in a triangular pattern, i.e., the multiple recesses or protrusions may be arranged alternately in the X and Y directions, or they may be formed randomly on the second upper surface 4-1 of the second substrate 4.

[0025] In the example shown in Figure 1, the second recess 510 has the same size as the first recess 210 when viewed from above and is positioned to substantially overlap with the first recess 210. When viewed from above, the second uneven portion 51 substantially overlaps with the first uneven portion 21, and the multiple second recesses 510 overlap in correspondence with the multiple first recesses 210. To show that the second uneven portion 51 substantially overlaps with the first uneven portion 21, the reference numerals for the first uneven portion 21 and the second uneven portion 51 are shown together in Figure 1. Also, to show that the multiple second recesses 510 overlap in correspondence with the multiple first recesses 210, the reference numerals for the first recess 210 and the second recesses 510 are shown together in Figure 1.

[0026] The second multilayer film 52 is a multilayer film arranged on the second uneven portion 51. The second multilayer film 52 can be a dielectric multilayer film, such as the one used for the mirror layer of a dichroic mirror. Details of the configuration of the second multilayer film 52 will be described separately with reference to Table 1.

[0027] In the example shown in Figure 2, the second uneven portion 51 and the second multilayer film 52 are made of different materials and are shown to be in contact with each other. However, for example, a part of the material that makes up the second multilayer film 52 may also make up the second uneven portion 51. That is, the second uneven portion 51 and the second multilayer film 52 may be integrally formed from the same material, for example. The optical filter 100 may have another functional layer between the second uneven portion 51 and the second multilayer film 52, and the second uneven portion 51 and the second multilayer film 52 may not be in contact with each other. If the second uneven portion 51 and the second multilayer film 52 are not in contact, it is preferable that the distance between the second uneven portion 51 and the second multilayer film 52 be short.

[0028] In Figure 1, the first center-to-center distance P-1 represents the distance between the centers of adjacent first recesses 210 in a plurality of first recesses 210 when viewed from above. The second center-to-center distance P-2 represents the distance between the centers of adjacent second recesses 510 in a plurality of second recesses 510 when viewed from above. In the example shown in Figure 1, the first center-to-center distance P-1 and the second center-to-center distance P-2 are equal. Also, the first center-to-center distance P-1 in the X direction is equal to the first center-to-center distance P-1 in the Y direction. The second center-to-center distance P-2 in the X direction is equal to the second center-to-center distance P-2 in the Y direction. However, the first center-to-center distance P-1 and the second center-to-center distance P-2 do not necessarily have to be equal. Also, the first center-to-center distance P-1 in the X direction is not necessarily equal to the first center-to-center distance P-1 in the Y direction. The distance P-2 between the second centers in the X direction and the distance P-2 between the second centers in the Y direction do not necessarily have to be equal.

[0029] The filler 3 is composed of a resin or the like. For example, an ultraviolet light-curing resin can be used for the filler 3. The filler 3 is placed between the first multilayer film 22 and the second multilayer film 52. The filler 3 is placed in each of the multiple first recesses 210 included in the first uneven portion 21 via the first multilayer film 22, and in each of the multiple second recesses 510 included in the second uneven portion 51 via the second multilayer film 52. The first light L10 incident on the optical filter 100 is reflected and scattered at the interface between the first recesses 210 of the first uneven portion 21 and the filler 3, and at the interface between the second recesses 510 of the second uneven portion 51 and the filler 3. In the example shown in Figure 2, the filler 3 has the function of a bonding material that joins the first substrate 1 and the second substrate 4.

[0030] In the example shown in Figure 2, the first light beam L10 and the second light beam L20 each travel downward, for example, towards the +Z side, and are incident perpendicularly on the optical filter 100 from the upper surface 100-1 side. Incidence perpendicular to the optical filter 100 means that the light beam is incident on the upper surface 100-1 along the direction of the normal vector 100n of the upper surface 100-1. From another perspective, incidence perpendicular to the optical filter 100 means that the angle of incidence of the light ray incident on the optical filter 100 is 0 degrees. The angle of incidence is the angle between the normal vector 100n of the upper surface 100-1 on the optical filter 100 and the incident light ray.

[0031] The first light L10 incident on the optical filter 100 from the top surface 100-1 side reaches the first reflection scattering section 2 and is reflected and scattered by the first reflection scattering section 2. The reflected scattered light Ls1 shown in Figure 2 represents a portion of the light reflected and scattered by the second reflection scattering section 5. The first light L10 incident perpendicularly on the optical filter 100 is almost not transmitted through the second reflection scattering section 5. Due to the reflection and scattering of the first light L10, when the optical filter 100 is viewed from the top surface 100-1 side, the light-receiving region of the optical filter 100 appears colored. On the other hand, the second light L20 incident on the optical filter 100 from the top surface 100-1 side is partially scattered by both the first reflection scattering section 2 and the second reflection scattering section 5, but most of it is transmitted through both sections, respectively.

[0032] Figure 3 shows the first light beam L10 obliquely incident on the optical filter 100. Here, oblique incidence means that the light beam is incident on the optical filter 100 at an angle tilted with respect to the normal 100n of the upper surface 100-1 of the optical filter 100. The incidence angle θ in Figure 3 represents the angle of the incident light beam on the optical filter 100 with respect to the normal 100n. When light is incident obliquely, the incidence angle θ is greater than 0 degrees.

[0033] For example, in an optical filter that reflects and scatters a first light L10 and transmits a second light L20, the reflectivity and scattering of the first light L10 that is incident at an oblique angle may decrease. When the reflectivity and scattering decreases, the transmittance of the first light L10 increases, and the space on the opposite side of the optical filter may become visible. When the space on the opposite side of the optical filter becomes visible, the aesthetic appeal of the optical filter decreases. Furthermore, when the space on the opposite side of the optical filter becomes visible, the effect of obscuring the interior of the optical device having the optical filter is impaired, and the aesthetic appeal of the optical device decreases.

[0034] In this embodiment, the optical filter 100 has a first reflection scattering section 2 and a second reflection scattering section 5. For example, the second reflection scattering section 5 is located below the first reflection scattering section 2. As a result, the optical filter 100 can reflect and scatter light that is obliquely incident on the optical filter 100 from the upper surface 100-1 side, passes through the first reflection scattering section 2, and travels downward, using the second reflection scattering section 5. Note that the positional relationship between the first reflection scattering section 2 and the second reflection scattering section 5 is not limited to the second reflection scattering section 5 being located below the first reflection scattering section 2; the first reflection scattering section 2 may be located below the second reflection scattering section 5.

[0035] In the example shown in Figure 3, the optical filter 100 reflects and scatters the transmitted light Lt that passes through the first reflection and scattering section 2 and travels downward from the first light L10 incident on the optical filter 100 from the upper surface 100-1 side at an incident angle θ degrees, using the second reflection and scattering section 5. The reflected and scattered light Ls2 shown in Figure 3 represents the reflected and scattered light of the transmitted light Lt by the second reflection and scattering section 5. By reflecting and scattering the transmitted light Lt with the second reflection and scattering section 5, the transmittance of the first light L10 that is obliquely incident on the optical filter 100 at an incident angle θ is reduced, making it difficult to see through to the lower surface 100-2 side of the optical filter 100, for example, the space on the +Z side. As a result, in this embodiment, an optical filter 100 with low transmittance to obliquely incident visible light can be provided. For example, in an optical device having an optical filter 100, the design can be improved by blocking visible light to make the inside of the optical device invisible, while information can be transmitted and received with an external device using infrared light.

[0036] When light with a wavelength of 400 nm to 600 nm is incident at an incident angle θ, the average value of the transmittance is T_400 - 600(θ). It is more preferable that T_400 - 600(0) ≤ 10% and T_400 - 600(50) ≤ 10%. This makes it possible to further reduce the transmittance of the first light L10 regardless of the incident angle, and to make the space on the opposite side of the optical filter 100 more difficult to see. Furthermore, it is even more preferable that |T_400 - 600(50) - T_400 - 600(0)| ≤ 5%. This makes it possible to further reduce the transmittance of the first light L10 regardless of the incident angle, and to make the space on the opposite side of the optical filter 100 even more difficult to see.

[0037] Preferably, the first reflection scattering portion 2 includes a first uneven portion 21 containing a plurality of first recesses 210, each of which is concave on the first upper surface 1-1 side, and a first multilayer film 22 disposed on the first uneven portion 21. Preferably, the second reflection scattering portion 5 includes a second uneven portion 51, each of which is concave on the second lower surface 4-2 side, and a second multilayer film 52 disposed on the second uneven portion 51. Furthermore, it is preferable that the plurality of first recesses 210 are arranged in two dimensions, the plurality of second recesses 510 are arranged in two dimensions, and the filler 3 is disposed between the first multilayer film 22 and the second multilayer film 52. With this configuration, the first reflection scattering portion 2 with superior reflection scattering performance can be easily manufactured compared to cases where the first reflection scattering portion 2 has a fine particle-containing resin layer or a diffraction structure. Furthermore, the second reflection scattering portion 5 can be easily manufactured compared to cases where the second reflection scattering portion 5 has a fine particle-containing resin layer or a diffraction structure.

[0038] In the optical filter 100, a filler material 3 is placed between the first substrate 1 and the second substrate 4. As a result, the filler material 3 is not exposed to the outside, thus preventing it from peeling off or being damaged from the first substrate 1 and the second substrate 4.

[0039] In the optical filter 100, for example, in Figure 3, when the first light L10 is incident on the optical filter 100 from the bottom surface 100-2 side, the first light L10 is reflected and scattered by the second reflection scattering section 5 and the first reflection scattering section 2. As a result, when the optical filter 100 is viewed from the bottom surface 100-2 side, the light-receiving area of ​​the first light L10 appears to be colored with a color other than black, such as white. In other words, the optical filter 100 appears to be almost the same color whether viewed from the top surface 100-1 side or the bottom surface 100-2 side. As a result, the optical filter 100 can have a nearly uniform color appearance, improving its design aesthetics.

[0040] In the example shown in FIG. 1, the plurality of first recesses 210 are aligned in the X direction and the Y direction orthogonal to each other within the first lower surface 1-2 of the first substrate 1, and the plurality of second recesses 510 are aligned in the X direction and the Y direction with respect to each other within the second upper surface 4-1 of the second substrate 4. In a top view, the average value of the first center-to-center distance P-1 between adjacent first recesses 210 among the plurality of first recesses 210 is preferably 15 μm or more and 150 μm or less. Further, in a top view, the average value of the second center-to-center distance P-2 between adjacent second recesses 510 among the plurality of second recesses 510 is preferably 15 μm or more and 150 μm or less. By satisfying this condition, the transmittance for obliquely incident light in the visible range can be suitably lowered. When the first concavo-convex portion 21 includes a plurality of convex portions, by setting the average value of the first center-to-center distance P-1 between adjacent convex portions among the plurality of convex portions and the average value of the second center-to-center distance P-2 to 15 μm or more and 150 μm or less, respectively, the same effect as described above can be obtained. However, the first center-to-center distance P-1 and the second center-to-center distance P-2 are not limited to 15 μm or more and 150 μm or less, and can be appropriately selected.

[0041] For light having a wavelength of 930 nm or more and 950 nm or less, when the average value of the refractive index of the first substrate 1 and the average value of the refractive index of the second substrate 4 are each n1, and the average value of the refractive index of the filler 3 is n2, it is preferable to satisfy |n1 - n2| ≤ 0.05. By satisfying this condition, the transmittance for obliquely incident light in the visible range can be lowered, and the transmittance for light having a wavelength of 930 nm or more and 950 nm or less can be increased.

[0042] For light having a wavelength of 840 nm or more and 860 nm or less, when the average value of the refractive index of the first substrate 1 and the average value of the refractive index of the second substrate 4 are each n3, and the average value of the refractive index of the filler 3 is n4, it is preferable to satisfy |n3 - n4| ≤ 0.05. By satisfying this condition, the transmittance for obliquely incident light in the visible range can be suitably lowered, and the transmittance for light having a wavelength of 840 nm or more and 860 nm or less can be increased.

[0043] In this embodiment, a first reflection and scattering part 2 is provided on the first lower surface 1-2 of the first substrate 1, and a second reflection and scattering part 5 is provided on the second upper surface 4-1 of the second substrate 4. With this configuration, for example, compared with the case where the first reflection and scattering part 2 is provided on one surface of the first substrate 1 and the second reflection and scattering part 5 is provided on the other surface, the first substrate 1 can be easily manufactured. Also, compared with the case where the first reflection and scattering part 2 is provided on one surface of the second substrate 4 and the second reflection and scattering part 5 is provided on the other surface, the second substrate 4 can be easily manufactured.

[0044] <Details of the First Multilayer Film 22 and the Second Multilayer Film 52> Table 1-1 shows an example of the detailed configuration of the first multilayer film 22 for a wavelength of 940 nm. In the example shown in Table 1, the first multilayer film 22 includes 43 layers. Table 1-1 shows the layer names, materials, and film thicknesses of the 43 layers, as well as the total film thickness of the 43 layers. Note that "for a wavelength of 940 nm" means having the property of transmitting light with a wavelength near 940 nm. An "optical filter for a wavelength of 940 nm" refers to an optical filter having a wavelength of 930 nm or more and 950 nm or less, and having an average transmittance of 75% or more for light incident at an incident angle of 0 degrees. The second multilayer film 52 can have the same configuration as that of the first multilayer film 22 shown in Table 1-1. However, the first multilayer film 22 and the second multilayer film 52 may have different configurations.

[0045]

[0046] FIG. 4 is a diagram showing an example of the reflectance spectrum of the first multilayer film 22 of the optical filter 100 for a wavelength of 940 nm. FIG. 4 shows the simulation results of the reflectance spectrum for light with a wavelength of 400 nm or more and 1000 nm or less incident on the optical filter 100 from the upper surface 100-1. The reflectance spectrum on the vertical axis is the average value of the reflectance spectra for P-polarized light and S-polarized light, respectively. Note that the second multilayer film 52 can also have a reflectance spectrum similar to that of the first multilayer film 22.

[0047] Graph 71 shows the reflectance spectrum when the incident angle θ is 0 degrees. Graph 72 shows the reflectance spectrum when the incident angle θ is 40 degrees. Graph 73 shows the reflectance spectrum when the incident angle θ is 50 degrees. Graph 74 shows the reflectance spectrum when the incident angle θ is 60 degrees. Graph 75 shows the reflectance spectrum when the incident angle θ is 70 degrees.

[0048] As shown in Graph 71, when the incident angle θ is 0 degrees, the reflectance is 80% or more at wavelengths below 940 nm, and 5% or less at wavelengths longer than 940 nm. In other words, the first multilayer film 22 reflects more than 80% of light at wavelengths below 940 nm and transmits more than 95% of light at wavelengths longer than 940 nm.

[0049] As shown in Graphs 72 to 75, when the incident angle θ for oblique incidence is 40 degrees or more, compared to the case where the incident angle θ is 0 degrees, the wavelength range with high reflectivity shifts to the shorter wavelength side of the visible range, and the reflectivity on the longer wavelength side of the visible range decreases, in other words, the transmittance increases. From this, it can be seen that when visible light is incident at an oblique angle, the reflective scattering properties of the first multilayer film 22 decrease, and visible light is more easily transmitted through the first multilayer film 22.

[0050] As described above, the first multilayer film 22 and the second multilayer film 52 individually have high transmittance to obliquely incident visible light. It is difficult to lower the transmittance of the first multilayer film 22 and the second multilayer film 52 to obliquely incident visible light by adjusting the material or film thickness of the multilayer films. In this embodiment, by having the optical filter 100 have the first multilayer film 22 and the second multilayer film 52, the reflectance to visible light can be increased and the transmittance can be lowered.

[0051] Table 1-2 shows an example of the detailed configuration of the first multilayer film 22 for a wavelength of 850 nm. In the example shown in Table 1-2, the first multilayer film 22 contains 43 layers. Table 1-2 shows the layer name, material, and film thickness of each of the 43 layers, as well as the total film thickness of the 43 layers. Note that "for 850 nm" means that it has the property of transmitting light with a wavelength of around 850 nm. An "optical filter for 850 nm" refers to an optical filter with a wavelength of 840 nm to 860 nm and an average transmittance of 75% or more for light incident at an incident angle of 0 degrees. The second multilayer film 52 may have the same configuration as the first multilayer film 22 shown in Table 1-2. However, the first multilayer film 22 and the second multilayer film 52 may have different configurations.

[0052]

[0053] <Method for Manufacturing Optical Filter 100> An example of a method for manufacturing optical filter 100 is described below.

[0054] In the method for manufacturing the optical filter 100, first, the first uneven portion 21 of the first reflection scattering portion 2 is formed on the first lower surface 1-2 of the first substrate 1. Specifically, an Mo mask and a resist mask are deposited on the first lower surface 1-2 of the first substrate 1 in this order. Next, the Mo mask and resist mask on the first lower surface 1-2 of the first substrate 1 are exposed and developed. Subsequently, the Mo mask and resist mask after exposure and development are dry etched. For dry etching, Ar, CF4, O ２ Plasma or the like can be used. Subsequently, after dry etching, wet etching is performed using an acid etching solution or the like. This forms the first uneven portion 21 on the first lower surface 1-2 of the first substrate 1.

[0055] After the first uneven portion 21 is formed, a first multilayer film 22 is deposited on the first uneven portion 21. As a result, a first reflection scattering portion 2 is provided on the first lower surface 1-2 of the first substrate 1.

[0056] Next, the second uneven portion 51 of the second reflection scattering portion 5 is formed on the second upper surface 4-1 of the second substrate 4. The method for forming the second uneven portion 51 is the same as the method for forming the first uneven portion 21 of the first reflection scattering portion 2.

[0057] After the second uneven portion 51 is formed, a second multilayer film 52 is deposited on the second uneven portion 51. As a result, a second reflection scattering portion 5 is provided on the second upper surface 4-1 of the second substrate 4.

[0058] After a first reflection and scattering portion 2 is provided on the first lower surface 1-2 of the first substrate 1, a filler material 3 is placed in the first reflection and scattering portion 2. The filler material 3 is an ultraviolet light-curing resin or the like.

[0059] After placing the filler material 3 in the first reflection scattering portion 2, the second substrate 4 is placed on the filler material 3 such that the second reflection scattering portion 5 is located on the opposite side of the filler material 3 from the first reflection scattering portion 2. The second substrate 4 is positioned relative to the first substrate 1 such that the first lower surface 1-2 of the first substrate 1 and the second upper surface 4-1 of the second substrate 4 face each other via the filler material 3.

[0060] Next, ultraviolet light is irradiated onto the filler material 3 to harden it. As the filler material 3 hardens, the first substrate 1 and the second substrate 4 are joined together via the filler material 3.

[0061] The optical filter 100 can be manufactured in the manner described above.

[0062] The method for manufacturing the optical filter 100 is not limited to the method described above. For example, a second reflection scattering portion 5 may be provided on the second upper surface 4-1 of the second substrate 4, and then a first reflection scattering portion 2 may be provided on the first lower surface 1-2 of the first substrate 1. Alternatively, after placing the filler material 3 on the second reflection scattering portion 5 of the second substrate 4, the first substrate 1 may be placed on the filler material 3 such that the first reflection scattering portion 2 is located on the opposite side of the filler material 3 from the second reflection scattering portion 5.

[0063] A blasting method or the like may be used to form the first uneven portion 21 or the second uneven portion 51. The blasting method is preferable from the viewpoint of efficiently manufacturing the first uneven portion 21 or the second uneven portion 51 which includes at least one of a plurality of randomly arranged recesses and protrusions. On the other hand, the etching method is preferable from the viewpoint of manufacturing the first uneven portion 21 or the second uneven portion 51 which includes at least one of a plurality of recesses and protrusions arranged in a predetermined pattern with high precision.

[0064] <Modification of the First Embodiment> Next, an optical filter according to a modification of the first embodiment will be described. Note that names and reference numerals identical to those used in the previously described embodiments indicate identical or similar components or configurations, and detailed explanations will be omitted as appropriate. This also applies to the embodiments, modifications, and examples described hereafter.

[0065] Figure 5 is a schematic cross-sectional view showing an optical filter 100a according to a modified example of the first embodiment. Figure 5 shows, for example, a cross-section of the optical filter 100a corresponding to the line II-II in Figure 1.

[0066] In this modified example, the first uneven portion 21 includes a convex array in which a plurality of first convex portions 210a are arranged in a matrix in both the X and Y directions. The second uneven portion 51 includes a convex array in which a plurality of second convex portions 510a are arranged in a matrix in both the X and Y directions. These points differentiate it from the optical filter 100 according to the first embodiment.

[0067] The first protrusions 210a and the second protrusions 510a each have, for example, a spherical shape. The first substrate 1 constitutes a plano-convex lens array by forming a plurality of first protrusions 210a on the first lower surface 1-2 of the first substrate 1. The second substrate 4 constitutes a plano-convex lens array by forming a plurality of second protrusions 510a on the second upper surface 4-1 of the second substrate 4. However, the first protrusions 210a and the second protrusions 510a are not limited to a spherical shape and may have any convex shape. The plurality of first protrusions 210a may have different shapes from each other, and the plurality of second protrusions 510a may have different shapes from each other.

[0068] Among the multiple first protrusions 210a included in the first uneven portion 21, the first center-to-center distance P-1 between adjacent first protrusions 210a can be appropriately selected. The shape of the multiple first protrusions 210a can also be appropriately selected. Furthermore, the multiple first protrusions 210a are not limited to a matrix arrangement, but may be formed in a random arrangement. Among the multiple second protrusions 510a, the second center-to-center distance P-2 between adjacent second protrusions 510a can be appropriately selected. The shape of the multiple second protrusions 510a can also be appropriately selected. Furthermore, the multiple second protrusions 510a are not limited to a matrix arrangement, but may be formed in a random arrangement.

[0069] The effects and benefits of the optical filter 100a according to this modified example are the same as those of the optical filter 100 according to the first embodiment. Note that the optical filter 100 according to the first embodiment is not limited to a configuration in which each of the first uneven portion 21 and the second uneven portion 51 includes a convex array, or a configuration in which each of the first uneven portion 21 and the second uneven portion 51 includes a concave array. The optical filter 100 according to the first embodiment may have a configuration in which the first uneven portion 21 includes a convex array and the second uneven portion 51 includes a concave array, or a configuration in which the first uneven portion 21 includes a concave array and the second uneven portion 51 includes a convex array.

[0070] [Second Embodiment] Next, an optical filter according to the second embodiment will be described. Figure 6 is a schematic cross-sectional view of the optical filter 100b according to the second embodiment. Figure 6 shows a cross-section of the optical filter 100b corresponding to the line II-II in Figure 1.

[0071] As shown in Figure 6, the optical filter 100b according to this embodiment includes a substrate 1b including an upper substrate surface 1b-1 and a lower substrate surface 1b-2, and a first reflection and scattering section 2 provided on the upper substrate surface 1b-1 of the substrate 1b, which reflects and scatters the first light L10 and transmits the second light L20. The optical filter 100b also includes a second reflection and scattering section 5 provided on the lower substrate surface 1b-2 of the substrate 1b, which reflects and scatters the first light L10 and transmits the second light L20, a first filler material 3-1 positioned above the substrate 1b, and a second filler material 3-2 positioned below the substrate 1b. The optical filter 100b differs from the optical filter 100 according to the first embodiment in these respects.

[0072] In the example shown in Figure 6, the optical filter 100b includes a first opposing substrate 6 positioned above the first filler material 3-1 and a second opposing substrate 7 positioned below the second filler material 3-2. However, the optical filter 100b does not necessarily have to include the first opposing substrate 6 and the second opposing substrate 7.

[0073] In the example shown in Figure 6, the first reflection scattering portion 2 includes a first uneven portion 21 containing a plurality of first recesses 210, each of which is concave toward the substrate lower surface 1b-2, and a first multilayer film 22 disposed on the first uneven portion 21. The second reflection scattering portion 5 includes a second uneven portion 51, each of which is concave toward the substrate upper surface 1b-1, and a second multilayer film 52 disposed on the second uneven portion 51. The plurality of first recesses 210 are arranged in two dimensions. The plurality of second recesses 510 are arranged in two dimensions. The first filler 3-1 is disposed above the first multilayer film 22. The second filler 3-2 is disposed below the second multilayer film 52.

[0074] The substrate 1b is configured as a biconcave lens array by having a plurality of first recesses 210 formed on the upper surface 1b-1 of the substrate and a plurality of second recesses 510 formed on the lower surface 1b-2 of the substrate.

[0075] The substrate 1b, the first opposing substrate 6, and the second opposing substrate 7 can be made of a material that is transparent to at least the second light L20. The substrate 1b, the first opposing substrate 6, and the second opposing substrate 7 can be made by including glass or resin or the like that is transparent to at least the second light L20. For example, borosilicate glass can be used for the substrate 1b, the first opposing substrate 6, and the second opposing substrate 7.

[0076] The first filler 3-1 and the second filler 3-2 are each composed of a resin or the like. For example, ultraviolet light-curing resins can be used for the first filler 3-1 and the second filler 3-2. The first filler 3-1 is placed in each of the plurality of first recesses 210 contained in the first uneven portion 21 via a first multilayer film 22. The second filler 3-2 is placed in each of the plurality of second recesses 510 contained in the second uneven portion 51 via a second multilayer film 52. The first light L10 incident on the optical filter 100b is reflected and scattered at the interface between the first recesses 210 of the first uneven portion 21 and the first filler 3-1, and at the interface between the second recesses 510 of the second uneven portion 51 and the second filler 3-2. In the example shown in Figure 6, the first filler 3-1 has the function of a bonding material that joins the substrate 1b and the first opposing substrate 6. The second filler 3-2 has the function of a bonding material that joins the substrate 1b and the second opposing substrate 7.

[0077] In this embodiment, a first reflection scattering portion 2 is provided on the upper surface 1b-1 of the substrate 1b, and a second reflection scattering portion 5 is provided on the lower surface 1b-2 of the substrate 1b. This makes the optical filter 100b thinner compared to the case where the first reflection scattering portion 2 is provided on one of the two substrates and the second reflection scattering portion 5 is provided on the other. Furthermore, in this embodiment, since multilayer films can be provided on both sides of the substrate 1b, warping of the optical filter 100b can be suppressed.

[0078] In the example shown in Figure 6, the optical filter 100b further includes a first opposing substrate 6 positioned above the first filler 3-1 and a second opposing substrate 7 positioned below the second filler 3-2. Because the optical filter 100b has the first opposing substrate 6, the first filler 3-1 is not exposed to the outside, thus preventing the first filler 3-1 from peeling off or being damaged from the substrate 1b. Furthermore, because the optical filter 100b has the second opposing substrate 7, the second filler 3-2 is not exposed to the outside, thus preventing the second filler 3-2 from peeling off or being damaged from the substrate 1b.

[0079] In the example shown in Figure 6, the plurality of first recesses 210 are aligned in mutually orthogonal X and Y directions within the upper surface 1b-1 of the substrate 1b, and the plurality of second recesses 510 are aligned in mutually orthogonal X and Y directions within the lower surface 1b-2 of the substrate 1b. In a top view, the average value of the first center distance P-1 between adjacent first recesses 210 is preferably 15 μm or more and 150 μm or less, and in a top view, the average value of the second center distance P-2 between adjacent second recesses 510 is preferably 15 μm or more and 150 μm or less. By satisfying these conditions, the transmittance for obliquely incident visible light can be suitably reduced. If the first uneven portion 21 includes multiple protrusions, the same effect as above can be obtained by setting the average value of the first center-to-center distance P-1 and the average value of the second center-to-center distance P-2 between adjacent protrusions in the multiple protrusions to 15 μm or more and 150 μm or less, respectively. However, the first center-to-center distance P-1 and the second center-to-center distance P-2 are not limited to 15 μm or more and 150 μm or less, but can be selected as appropriate. Also, the first center-to-center distance P-1 and the second center-to-center distance P-2 do not necessarily have to be equal. Also, the first center-to-center distance P-1 in the X direction and the first center-to-center distance P-1 in the Y direction do not necessarily have to be equal. The second center-to-center distance P-2 in the X direction and the second center-to-center distance P-2 in the Y direction do not necessarily have to be equal.

[0080] For light with a wavelength of 930 nm to 950 nm, it is preferable that |n1 - n2| ≤ 0.05 is satisfied, where n1 is the average refractive index of the substrate 1b, and n2 is the average refractive index of the first filler 3-1 and the average refractive index of the second filler 3-2, respectively. Satisfying this condition makes it possible to lower the transmittance for obliquely incident visible light and to increase the transmittance for light with a wavelength of 930 nm to 950 nm.

[0081] For light with a wavelength of 840 nm to 860 nm, it is preferable that |n3 - n4| ≤ 0.05 is satisfied, where n3 is the average refractive index of the substrate 1b, and n4 is the average refractive index of the first filler 3-1 and the average refractive index of the second filler 3-2, respectively. Satisfying this condition allows for a suitably low transmittance for obliquely incident visible light and a high transmittance for light with a wavelength of 840 nm to 860 nm.

[0082] The effects and advantages of the optical filter 100b according to this embodiment, other than those described above, are the same as those of the optical filter 100 according to the first embodiment.

[0083] <Method for Manufacturing Optical Filter 100b> An example of a method for manufacturing the optical filter 100b will be described. Note that explanations of points common to the manufacturing method of the optical filter 100 according to the first embodiment will be omitted as appropriate, and the differences will be explained in detail.

[0084] First, the first uneven portion 21 of the first reflection scattering portion 2 is formed on the upper surface 1b-1 of the substrate 1b. Specifically, a Mo mask and a resist mask are deposited on the upper surface 1b-1 of the substrate 1b in this order. Next, the Mo mask and resist mask on the upper surface 1b-1 of the substrate 1b are exposed and developed. Subsequently, the Mo mask and resist mask after exposure and development are dry etched. For dry etching, Ar, CF4, O ２ Plasma or the like can be used. Subsequently, after dry etching, wet etching is performed using an acid etching solution or the like. This forms the first uneven portion 21 on the upper surface 1b-1 of the substrate 1b.

[0085] After the first uneven portion 21 is formed, a first multilayer film 22 is deposited on the first uneven portion 21. As a result, a first reflection scattering portion 2 is provided on the upper surface 1b-1 of the substrate 1b.

[0086] Next, the second uneven portion 51 of the second reflection scattering portion 5 is formed on the lower surface 1b-2 of the substrate 1b. The method for forming the second uneven portion 51 is the same as the method for forming the first uneven portion 21 of the first reflection scattering portion 2.

[0087] After the second uneven portion 51 is formed, a second multilayer film 52 is deposited on the second uneven portion 51. As a result, a second reflection scattering portion 5 is provided on the lower surface 1b-2 of the substrate 1b.

[0088] After the first reflection scattering portion 2 is provided on the upper surface 1b-1 of the substrate 1b, the first filler material 3-1 is placed on the first reflection scattering portion 2. The first filler material 3-1 is an ultraviolet light curing resin or the like. By placing the first filler material 3-1 so as to fill the irregularities of the first reflection scattering portion 2 with the first filler material 3-1, the upper surface 3-1a of the first filler material 3-1 placed on the first reflection scattering portion 2 is flattened.

[0089] After the second reflection scattering portion 5 is provided on the lower surface 1b-2 of the substrate 1b, the second filler material 3-2 is placed on the second reflection scattering portion 5. The second filler material 3-2 is an ultraviolet light curing resin or the like. By placing the second filler material 3-2 so as to fill the irregularities of the second reflection scattering portion 5 with the second filler material 3-2, the lower surface 3-2a of the second filler material 3-2 placed on the second reflection scattering portion 5 is flattened.

[0090] Next, the first opposing substrate 6 is placed on the upper surface 3-1a of the first filler material 3-1. The second opposing substrate 7 is then placed on the lower surface 3-2a of the second filler material 3-2.

[0091] Next, the first filler 3-1 and the second filler 3-2 are irradiated with ultraviolet light to cure them. When the first filler 3-1 cures, the first opposing substrate 6 and the substrate 1b are joined via the first filler 3-1. When the second filler 3-2 cures, the second opposing substrate 7 and the substrate 1b are joined via the second filler 3-2.

[0092] In this manner, the optical filter 100b can be manufactured.

[0093] The method for manufacturing the optical filter 100b is not limited to the method described above. For example, the second reflection scattering portion 5 may be provided on the lower surface 1b-2 of the substrate 1b, and then the first reflection scattering portion 2 may be provided on the upper surface 1b-1 of the substrate 1b. Alternatively, the second filler material 3-2 may be placed in the second reflection scattering portion 5, and then the first filler material 3-1 may be placed in the first reflection scattering portion 2.

[0094] <Modified Example of the Second Embodiment> Next, an optical filter according to a modified example of the second embodiment will be described.

[0095] Figure 7 is a schematic cross-sectional view showing an optical filter 100c according to a modified example of the second embodiment. Figure 7 shows, for example, a cross-section of the optical filter 100c corresponding to the line II-II in Figure 1.

[0096] In this modified example, the first uneven portion 21 includes a convex array in which a plurality of first convex portions 210a are arranged in a matrix in the X direction and the Y direction, and the second uneven portion 51 includes a convex array in which a plurality of second convex portions 510a are arranged in a matrix in the X direction and the Y direction, which is different from the optical filter 100b according to the second embodiment.

[0097] The first protrusion 210a and the second protrusion 510a each have, for example, a spherical shape. The substrate 1c is configured as a biconvex lens array by having a plurality of first protrusions 210a formed on the upper surface 1c-1 of the substrate and a plurality of second protrusions 510a formed on the lower surface 1c-2 of the substrate.

[0098] The effects and benefits of the optical filter 100c according to this modified example are the same as those of the optical filter 100b according to the second embodiment. Note that the optical filter 100b according to the second embodiment is not limited to a configuration in which each of the first uneven portion 21 and the second uneven portion 51 includes a convex array, or a configuration in which each of the first uneven portion 21 and the second uneven portion 51 includes a concave array. The optical filter 100b according to the second embodiment may have a configuration in which the first uneven portion 21 includes a convex array and the second uneven portion 51 includes a concave array, or a configuration in which the first uneven portion 21 includes a concave array and the second uneven portion 51 includes a convex array.

[0099] [Examples and Comparative Examples] Next, examples and comparative examples will be described. However, this disclosure is not limited to these examples.

[0100] In the examples and comparative examples, optical filters according to each of Examples 1 to 8 were fabricated and evaluated. Examples 1, 2, 5, and 6 are examples. Examples 3, 4, 7, and 8 are comparative examples.

[0101] (Example 1) Example 1 is an optical filter 100 according to the first embodiment for a wavelength of 940 nm. The first multilayer film 22 and the second multilayer film 52 in Example 1 are each the same as those shown in Table 1-1 above.

[0102] (Example 2) Example 2 is an optical filter 100b according to the second embodiment for a wavelength of 940 nm. The first multilayer film 22 and the second multilayer film 52 in Example 2 are each the same as those shown in Table 1-1 above.

[0103] (Example 3) Example 3 is an optical filter that differs from Example 1 in that the first substrate 1 does not have a first reflection scattering portion 2.

[0104] (Example 4) In Example 4, the first substrate 1 does not have a first reflection scattering portion 2, and the second substrate 4 has SiO on the second lower surface 4-2 ２ This optical filter differs from Example 1 in that it has a film.

[0105] (Example 5) Example 5 is an optical filter 100 according to the first embodiment for a wavelength of 850 nm. The first multilayer film 22 and the second multilayer film 52 in Example 5 are each the same as those shown in Table 1-2 above.

[0106] (Example 6) Example 6 is an optical filter 100b according to the second embodiment for a wavelength of 850 nm. The first multilayer film 22 and the second multilayer film 52 in Example 6 each use the configurations shown in Table 1-2 above.

[0107] (Example 7) Example 7 is an optical filter that differs from Example 5 in that the first substrate 1 does not have a first multilayer film 22.

[0108] (Example 8) Example 8 is an optical filter that differs from Example 5 in that the first substrate 1 does not have a first multilayer film 22 and has an SiO2 film on its lower surface 100-2.

[0109] Figure 8 shows a list of the specifications and optical properties of the substrate and filler material for each of Examples 1 to 4. Figure 9 shows a list of the specifications and optical properties of the substrate and filler material for each of Examples 5 to 8.

[0110] In Examples 1, 2, 5, and 6, it is preferable that the average of the absolute values ​​of the radii of curvature of the first uneven portion 21 and the second uneven portion 51 is 20 μm or more and 620 μm or less. In Examples 1, 2, 5, and 6, it is preferable that the average of the sag amounts of the first uneven portion 21 and the second uneven portion 51 is 0.5 μm or more and 21.0 μm or less. In Examples 1, 2, 5, and 6, it is preferable that the average of the maximum inclination angles of the surfaces of the first uneven portion 21 and the second uneven portion 51 is 8 degrees or more and 30 degrees or less.

[0111] <Evaluation Results> The evaluation results for the optical filters in each example are shown below.

[0112] <Transmittance for light with a wavelength of 400 nm to 1000 nm> Referring to Figures 10 to 14, the transmittance when light with a wavelength of 400 nm to 1000 nm is incident on the optical filters according to Examples 1 to 4 will be explained. Figure 10 shows the case when the incident angle is 0 degrees. Figure 11 shows the case when the incident angle is 40 degrees. Figure 12 shows the case when the incident angle is 50 degrees. Figure 13 shows the case when the incident angle is 60 degrees. Figure 14 shows the case when the incident angle is 70 degrees. A UV-Vis-Near-Infrared Spectrophotometer V-770 manufactured by JASCO Corporation was used as the transmittance measuring device.

[0113] As shown in Figure 10, when the angle of incidence was 0 degrees, the transmittance of visible light was 10% or less in all of Examples 1 to 4. As shown in Figures 11 to 14, when the angles of incidence were 40 degrees, 50 degrees, 60 degrees, and 70 degrees, the transmittance of visible light was higher than 10% in Examples 3 and 4. On the other hand, in Examples 1 and 2, the transmittance of visible light was 10% or less even when the angles of incidence were 40 degrees, 50 degrees, 60 degrees, and 70 degrees. From the above, it was found that Examples 1 and 2 have low transmittance for obliquely incident visible light.

[0114] <Average transmittance for light in a specific wavelength range> Next, with reference to Figures 15 and 16, the average transmittance when light in a specific wavelength range is incident on the optical filters according to Examples 1 to 4 will be described. Figure 15 shows the average transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident on the optical filters according to Examples 1 to 4. Figure 16 shows the average transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident on the optical filters according to Examples 1 to 4. A UV-Vis-Near-Infrared Spectrophotometer V-770 manufactured by JASCO Corporation was used to measure the average transmittance.

[0115] As shown in Figure 15, for light with wavelengths between 400 nm and 600 nm, both Example 1 and Example 2 had lower transmittances than both Example 3 and Example 4. In particular, when the incident angle was 40 degrees, 50 degrees, 60 degrees, and 70 degrees, the range of change in transmittance was larger for Examples 3 and Example 4 compared to the case where the incident angle was 0 degrees. In contrast, for Examples 1 and Example 2, the range of change in transmittance was smaller even when the incident angle was 40 degrees, 50 degrees, 60 degrees, and 70 degrees compared to the case where the incident angle was 0 degrees. The transmittances of both Example 1 and Example 2 were lower than the transmittances of both Example 3 and Example 4.

[0116] Table 2 shows a list of average transmittances for each incident angle of optical filters according to Examples 1 to 4 for light with wavelengths between 400 nm and 600 nm.

[0117]

[0118] As shown in Figure 16, the transmittances of each of the examples from Example 1 to Example 4 were approximately the same for light with a wavelength of 930 nm to 950 nm.

[0119] Table 3 shows a list of transmittances for optical filters according to Examples 1 to 4 for light with wavelengths between 930 nm and 950 nm, at incident angles of 0, 40, 50, 60, and 70 degrees. The transmittances for Examples 1 to 4 were 85% or more at an incident angle of 0 degrees, 81% or more at an incident angle of 40 degrees, 75% or more at an incident angle of 50 degrees, 66% or more at an incident angle of 60 degrees, and 51% or more at an incident angle of 70 degrees.

[0120]

[0121] Table 4 shows a list of transmittances for optical filters according to Examples 5 to 8 at incident angles of 0 degrees and 50 degrees, respectively, for light with wavelengths between 840 nm and 860 nm.

[0122]

[0123] When light with a wavelength between 930 nm and 950 nm is incident at an incident angle θ, the average transmittance is defined as T_930-950(θ). From Table 3, in Example 1 and Example 2, T_930-950(0) ≥ 75% and T_930-950(50) ≥ 70%. This indicates that in Example 1 and Example 2, the transmittance is high for light with a wavelength between 930 nm and 950 nm at both incident angles of 0 and 50 degrees.

[0124] When light with a wavelength of 840 nm to 860 nm is incident at an incident angle θ, the average value of the transmittance is defined as T_840-860(θ). From Table 4, in Examples 5 and 6, T_840-860(0) ≥ 75% and T_840-860(50) ≥ 70%. This indicates that Examples 5 and 6 exhibit high transmittance for light with a wavelength of 840 nm to 860 nm at both incident angles of 0 and 50 degrees.

[0125] When light with a wavelength between 930 nm and 950 nm is incident at an incident angle θ, the average transmittance is given by T_930-950(θ). According to Table 3, in Example 1 and Example 2, |T_930-950(50)-T_930-950(0)| ≤ 15%. This indicates that in Example 1 and Example 2, the difference between the transmittance at an incident angle of 50 degrees and the transmittance at an incident angle of 0 degrees is small for light with a wavelength between 930 nm and 950 nm.

[0126] When light with a wavelength of 840 nm to 860 nm is incident at an incident angle θ, the average transmittance is given by T_840-860(θ). According to Table 4, in Examples 5 and 6, |T_840-860(50)-T_840-860(0)| ≤ 15%. This indicates that in Examples 5 and 6, the difference between the transmittance at an incident angle of 50 degrees and the transmittance at an incident angle of 0 degrees is small for light with a wavelength of 840 nm to 860 nm.

[0127] <Cut-on Wavelength Slope> Next, the cut-on wavelength slope in the optical filters according to Examples 1 to 4 will be explained with reference to Figures 17 and 18. Figure 17 is a diagram illustrating the cut-on wavelength slope in the optical filters according to Examples 1 to 4. Figure 18 is a diagram showing the evaluation results of the cut-on wavelength slope in the optical filters according to Examples 1 to 4.

[0128] As shown in Figure 17, in the transmittance spectrum graph, Slope_7030 is defined as the slope of the straight line connecting the portion with a transmittance of 70% and the portion with a transmittance of 30% in the wavelength range of 400 nm to 2000 nm. Figure 17 shows Slope_7030 for each of Examples 1 to 4 when the incident angle is 0 degrees.

[0129] Figure 18 shows the Slope_7030 of each optical filter according to Examples 1 to 4 when the incident angles are 0 degrees, 40 degrees, and 50 degrees.

[0130] Table 5 lists the Slope_7030 for each optical filter according to Examples 1 to 4 when the incident angles are 0 degrees, 40 degrees, and 50 degrees.

[0131]

[0132] From Figures 17 and 18 and Table 5, it can be seen that Slope_7030 in Examples 1 and 2 is larger than Slope_7030 in Examples 3 and 4. The optical filters in Examples 1 and 2 have two multilayer films, a first multilayer film 22 and a second multilayer film 52. The transmittance shape of the entire filter is equivalent to multiplying the transmittance shape of the first multilayer film 22 and the transmittance shape of the second multilayer film 52, so it is considered that Slope_7030 in Examples 1 and 2 is larger than Slope_7030 in Examples 3 and 4.

[0133] From Table 5, in the transmittance spectrum at an incident angle θ degrees, if we define Slope70-30(θ) as the slope of the line connecting the portion with a transmittance of 70% and the portion with a transmittance of 30%, then in Examples 1 and 2, |Slope70-30(0)| ≥ 1.0 and |Slope70-30(50)| ≥ 0.5. This indicates that in Examples 1 and 2, for infrared light, the steepness of the transmittance change with respect to wavelength near the cut-on wavelength is good at incident angles of 0 and 50 degrees.

[0134] <Haze Characteristics> The haze characteristics of the optical filters according to Examples 1 to 4 will be explained with reference to Figures 19 to 24. Figure 19 is a diagram showing the haze characteristics of the optical filter according to Example 1. Figure 20 is a diagram showing the haze characteristics of the optical filter according to Example 2. Figure 21 is a diagram showing the haze characteristics of the optical filter according to Example 3. Figure 22 is a diagram showing the haze characteristics of the optical filter according to Example 4. Figure 23 is a diagram showing the visible region haze characteristics of the optical filters according to Examples 1 to 4. Figure 24 is a diagram showing the infrared region haze characteristics of the optical filters according to Examples 1 to 4.

[0135] Figures 19 to 22 show the total light transmittance Tt (shown by a solid line), the diffuse light transmittance Td (shown by a dashed line), and the haze value Haze (shown by a dashed-dotted line). Figure 23 shows the average haze value for light with wavelengths between 400 nm and 600 nm. Figure 24 shows the average haze value for light with wavelengths between 930 nm and 950 nm. The total light transmittance Tt, diffuse light transmittance Td, and haze value Haze were measured using the HSP-150Vis HSP-150VIR spectroscopic haze meter manufactured by Murakami Color Technology Laboratory.

[0136] Table 6 is a list of average values ​​for total light transmittance Tt, diffuse light transmittance Td, and haze value Haze for light with wavelengths between 400 nm and 600 nm.

[0137]

[0138] Table 7 is a list of the average values ​​of total light transmittance Tt, diffuse light transmittance Td, and haze value Haze for light with wavelengths between 930 nm and 950 nm.

[0139]

[0140] Table 8 is a list of average values ​​for diffuse light transmittance Td and haze value Haze for light with wavelengths between 840 nm and 860 nm.

[0141]

[0142] From Figures 19 to 24 and Table 6, in Examples 1 and 2, the haze value for visible light was 96.43% or higher, and the haze value for infrared light was 5.37% or lower. In Examples 3 and 4, the haze value for visible light was 57.13% or higher, which was lower than in Examples 1 and 2. Also, in Examples 3 and 4, the haze value for infrared light was 3.14% or lower, which was about the same as in Examples 1 and 2.

[0143] From another perspective, as shown in Table 6, if we define the average value of diffuse transmittance for light with wavelengths between 400 nm and 600 nm as Td_400-600, then in Example 1 and Example 2, Td_400-600 ≤ 10%. This indicates that in Example 1 and Example 2, the diffuse light transmittance Td for visible light is low.

[0144] Table 6 shows that if we define Haze_400-600 as the average haze value for light with wavelengths between 400 nm and 600 nm, then in both Example 1 and Example 2, Haze_400-600 ≥ 80%. This indicates that in both Example 1 and Example 2, the haze value (Haze) for visible light is high.

[0145] Table 7 shows that if we define Td_930-950 as the average value of the diffuse transmittance for light with wavelengths between 930 nm and 950 nm, then in Example 1 and Example 2, Td_930-950 ≤ 5%. This indicates that in Example 1 and Example 2, the diffuse transmittance for light with wavelengths between 930 nm and 950 nm is low.

[0146] Table 8 shows that if we define Td_840-860 as the average value of the diffuse transmittance for light with wavelengths between 840 nm and 860 nm, then in Examples 5 and 6, Td_840-860 ≤ 5%. This indicates that in Examples 5 and 6, the diffuse transmittance for light with wavelengths between 840 nm and 860 nm is low.

[0147] Table 7 shows that if we define Haze_930-950 as the average haze value for light with wavelengths between 930 nm and 950 nm, then in Example 1 and Example 2, Haze_930-950 ≤ 10%. This indicates that in Example 1 and Example 2, the haze value for light with wavelengths between 930 nm and 950 nm is low.

[0148] From Table 8, if we define Haze_840-860 as the average haze value for light with wavelengths between 840 nm and 860 nm, then in Examples 5 and 6, Haze_840-860 ≤ 10%. This indicates that in Examples 5 and 6, the haze value for light with wavelengths between 840 nm and 860 nm is low.

[0149] <Color Characteristics> The color characteristics of the optical filters according to Examples 1 to 4 will be described with reference to Figures 25 to 27. Figure 25 shows the L* of the optical filters according to Examples 1 to 4. Figure 26 shows the a* and b* of the optical filters according to Examples 1 to 4. Figure 27 shows the color difference ΔE*ab between the top and bottom surfaces of the optical filters according to Examples 1 to 4. A CM-700d manufactured by Konica Minolta, Inc. was used as the measuring device for L*, a*, and b*.

[0150] Table 9 lists the L*, a*, and b* values ​​for each of the optical filters related to Examples 1 to 4 for a wavelength of 940 nm. In Table 10, "top surface" refers to the top surface 100-1 of the optical filter, and "bottom surface" refers to the bottom surface 100-2 of the optical filter.

[0151]

[0152] Table 10 lists the L*, a*, and b* values ​​for each optical filter related to Examples 5 to 8 for a wavelength of 850 nm. In Table 11, "top surface" refers to the top surface 100-1 of the optical filter, and "bottom surface" refers to the bottom surface 100-2 of the optical filter.

[0153]

[0154] Table 11 is a list of the color differences ΔE*ab for each optical filter related to Examples 1 to 4 for a wavelength of 940 nm. The color difference ΔE*ab was calculated from the following equations (1), (2), (3), and (4). In equation (2), L* (top surface) represents L* of the top surface 100-1 of the optical filter, and L* (bottom surface) represents L* of the bottom surface 100-2 of the optical filter. In equation (3), a* (top surface) represents a* of the top surface 100-1 of the optical filter, and a* (bottom surface) represents a* of the bottom surface 100-2 of the optical filter. In equation (4), b* (top surface) represents b* of the top surface 100-1 of the optical filter, and b* (bottom surface) represents b* of the bottom surface 100-2 of the optical filter. ΔE*ab = [(ΔL*)] ２ + (Δa*) ２ + (Δb*) ２ ] １／２... (1) ΔL*= L* (top surface) - L* (bottom surface) ... (2) Δa*=a* (top surface) - a* (bottom surface) ... (3) Δb*= b* (top surface) - b* (bottom surface) ... (4)

[0155]

[0156] Table 12 is a list of the chromatic differences ΔE*ab for each optical filter from Example 5 to Example 8 for a wavelength of 850 nm. The chromatic differences ΔE*ab were calculated from the above equations (1), (2), (3), and (4).

[0157]

[0158] In this embodiment, it is preferable that L* ≥ 80, -10 ≤ a* ≤ 10, and -10 ≤ b* ≤ 10. In Figures 25 and 26, and Tables 10 and 11, each of Examples 1 to 8 satisfies these conditions. It was found that by satisfying these conditions, each of the optical filters according to Examples 1 to 8 becomes brighter, has a whiter color, and its design is improved.

[0159] In this embodiment, if ΔE*ab is the difference in chromaticity between the chromaticity of the upper surface 100-1 of the optical filter, measured from the upper surface 100-1 side, and the chromaticity of the lower surface 100-2, measured from the lower surface 100-2 side, then it is preferable that ΔE*ab ≤ 5. In Figure 27, Table 12, and Table 13, each of Examples 1 to 8 satisfies this condition. By satisfying this condition, the colors of the upper surface 100-1 and the lower surface 100-2 of the optical filter become almost the same, so the design of the optical filter can be matched when viewed from the upper surface 100-1 side and when viewed from the lower surface 100-2 side.

[0160] Although preferred embodiments have been described in detail above, the embodiments of this disclosure are not limited to those described above, and various modifications and substitutions can be made to the embodiments of this disclosure without departing from the scope of the claims.

[0161] The ordinal numbers, quantities, and other figures used in the description of the embodiments of this disclosure are all illustrative to specifically illustrate the technology of this disclosure, and this disclosure is not limited to the illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of this disclosure, and are not limited to the connection relationships that realize the functions of this disclosure.

[0162] The optical filter according to the embodiment of this disclosure has low transmittance to obliquely incident visible light, thereby improving the aesthetics by blocking visible light and making the inside of the optical device invisible, while allowing information to be transmitted and received with an external device using infrared light. As a result, the optical filter according to the embodiment of this disclosure can be suitably used, for example, as a window material for an optical device. Examples of optical devices include sensing devices such as facial recognition devices or gesture sensors, industrial equipment, and AR (Augmented Reality) / VR (Virtual Reality) devices. Sensing devices are particularly suitable because, by having the optical filter according to the embodiment of this disclosure, they can transmit and receive information with an external device using infrared light while improving their aesthetics.

[0163] This application claims priority based on Japanese Patent Application No. 2024-207122, filed on 28 November 2024, and incorporates all of its disclosures herein.

[0164] 1. First substrate 1b, 1c; Substrate 1b-1, 1c-1; Top substrate 1b-2, 1c-2; Bottom substrate 1-1; Top substrate 1-2; Bottom substrate 1-2; First reflective scattering portion 3; Filler material 3-1; First filler material 3-1a; Top substrate 3-2; Second filler material 3-2a; Bottom substrate 4; Second substrate 4-1; Top substrate 2-2; Bottom substrate 2-5; Second reflective scattering portion 6; First opposing substrate 7; Second opposing substrate 21; First uneven portion 22; First multilayer film 51; Second uneven portion 52; Second multilayer film 71, 72, 73, 74, 75; Gravity 100, 100a, 100b, 100c; Optical field 100-1; Top substrate 100-2; Bottom substrate 100n; Normal 210; First concave portion 210a 1st convex part 510 2nd concave part 510a 2nd convex part L10 1st light L20 2nd light P-1 1st center-to-center distance P-2 2nd center-to-center distance Ls1, Ls2 Reflected scattered light Lt Transmitted light θ Incident angle

Claims

1. An optical filter comprising: a first substrate including a first upper surface and a first lower surface; a first reflection and scattering portion provided on the first lower surface of the first substrate, which reflects and scatters first light, which is light in at least a portion of the wavelength band in the visible region, and transmits second light, which is light in at least a portion of the wavelength band in the infrared region; a filler material disposed below the first substrate; a second substrate disposed below the filler material, which includes a second upper surface and a second lower surface; and a second reflection and scattering portion provided on the second upper surface of the second substrate, which reflects and scatters the first light and transmits the second light.

2. The optical filter according to claim 1, wherein the first reflection and scattering portion includes a first uneven portion comprising at least one of a plurality of first recesses, each concave toward the first upper surface, and a plurality of first protrusions, each convex toward the first lower surface, and a first multilayer film disposed on the first uneven portion, and the second reflection and scattering portion includes a second uneven portion comprising at least one of a plurality of second recesses, each concave toward the second lower surface, and a plurality of second protrusions, each convex toward the second upper surface, and a second multilayer film disposed on the second uneven portion, at least one of the plurality of first recesses and the plurality of first protrusions is arranged in two dimensions, and at least one of the plurality of second recesses and the plurality of second protrusions is arranged in two dimensions, and the filler is disposed between the first multilayer film and the second multilayer film.

3. An optical filter comprising: a substrate including an upper surface and a lower surface; a first reflection and scattering portion provided on the upper surface of the substrate, which reflects and scatters first light, which is light in at least a portion of the wavelength band in the visible region, and transmits second light, which is light in at least a portion of the wavelength band in the infrared region; a second reflection and scattering portion provided on the lower surface of the substrate, which reflects and scatters the first light and transmits the second light; a first filler material disposed above the substrate; and a second filler material disposed below the substrate.

4. The optical filter according to claim 3, wherein the first reflection and scattering portion includes a first uneven portion comprising at least one of a plurality of first recesses, each concave toward the lower surface of the substrate, and a plurality of first protrusions, each convex toward the upper surface of the substrate, and a first multilayer film disposed on the first uneven portion; the second reflection and scattering portion includes a second uneven portion comprising at least one of a plurality of second recesses, each concave toward the upper surface of the substrate, and a plurality of second protrusions, each convex toward the lower surface of the substrate, and a second multilayer film disposed on the second uneven portion, at least one of the plurality of first recesses and the plurality of first protrusions is arranged in two dimensions, at least one of the plurality of second recesses and the plurality of second protrusions is arranged in two dimensions, the first filler is disposed above the first multilayer film, and the second filler is disposed below the second multilayer film.

5. The optical filter according to claim 3, further comprising a first opposing substrate disposed above the first filler and a second opposing substrate disposed below the second filler.

6. The optical filter according to any one of claims 1 to 5, wherein the average value of transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle θ degrees is T_400-600(θ), such that T_400-600(0) ≤ 10% and T_400-600(50) ≤ 10%.

7. An optical filter according to any one of claims 1 to 5, wherein T_930-950(θ) is the average value of transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident at an incident angle θ, and T_840-860(θ) is the average value of transmittance when light with a wavelength of 840 nm or more and 860 nm or less is incident at an incident angle θ, such that T_930-950(0) ≥ 75% and T_930-950(50) ≥ 70%, or T_840-860(0) ≥ 75% and T_840-860(50) ≥ 70%.

8. The optical filter according to any one of claims 1 to 5, wherein the average transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident at an incident angle θ is T_930-950(θ), and the average transmittance when light with a wavelength of 840 nm or more and 860 nm or less is incident at an incident angle θ is T_840-860(θ), such that |T_930-950(50)-T_930-950(0)| ≤ 15%, or |T_840-860(50)-T_840-860(0)| ≤ 15%.

9. The optical filter according to any one of claims 1 to 5, wherein if the average value of the transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle θ degrees is T_400 - 600(θ), then |T_400 - 600(50) - T_400 - 600(0)| ≤ 5%.

10. In the transmittance spectrum at an incident angle θ degrees, if the slope of the line connecting the portion with a transmittance of 70% and the portion with a transmittance of 30% is defined as Slope70-30(θ), then |Slope70-30(0)| ≥ 1.0% / nm and |Slope70-30(50)| ≥ 0.5% / nm, the optical filter according to any one of claims 1 to 5.

11. The optical filter according to any one of claims 1 to 5, wherein the average value of the diffuse transmittance for light with a wavelength of 400 nm or more and 600 nm or less is Td_400 - 600, and Td_400 - 600 ≤ 10%.

12. An optical filter according to any one of claims 1 to 5, wherein the average value of the haze for light with a wavelength of 400 nm or more and 600 nm or less is defined as Haze_400-600, and Haze_400-600 ≥ 80%.

13. An optical filter according to any one of claims 1 to 5, wherein the average value of the diffuse transmittance for light with a wavelength of 930 nm or more and 950 nm or less is Td_930-950, and the average value of the diffuse transmittance for light with a wavelength of 840 nm or more and 860 nm or less is Td_840-860, such that Td_930-950 ≤ 5% or Td_840-860 ≤ 5%.

14. An optical filter according to any one of claims 1 to 5, wherein the average value of the haze for light with a wavelength of 930 nm or more and 950 nm or less is Haze_930-950, and the average value of the haze for light with a wavelength of 840 nm or more and 860 nm or less is Haze_840-860, such that Haze_930-950 ≤ 10% or Haze_840-860 ≤ 10%.

15. An optical filter according to any one of claims 1 to 5, wherein L* ≥ 80, -10 ≤ a* ≤ 10, and -10 ≤ b* ≤ 10.

16. The optical filter according to any one of claims 1 to 5, wherein ΔE*ab is the difference in chromaticity between the chromaticity of the upper surface measured from the upper side of the optical filter and the chromaticity of the lower surface measured from the lower side opposite to the upper surface of the optical filter, and ΔE*ab ≤ 5.

17. In a top view, the average value of the first center distance between adjacent first recesses in the plurality of first recesses, or the average value of the first center distance between adjacent first protrusions in the plurality of first protrusions, is 15 μm or more and 150 μm or less, and in a top view, the average value of the second center distance between adjacent second recesses in the plurality of second recesses, or the average value of the second center distance between adjacent second protrusions in the plurality of second protrusions, is 15 μm or more and 150 μm or less, the optical filter according to claim 2.

18. In a top view, the average value of the first center distance between adjacent first recesses in the plurality of first recesses, or the average value of the first center distance between adjacent first protrusions in the plurality of first protrusions, is 15 μm or more and 150 μm or less, and in a top view, the average value of the second center distance between adjacent second recesses in the plurality of second recesses, or the average value of the second center distance between adjacent second protrusions in the plurality of second protrusions, is 15 μm or more and 150 μm or less, the optical filter according to claim 4.

19. For light with a wavelength of 930 nm to 950 nm, the optical filter according to claim 1 or claim 2 satisfies |n1 - n2| ≤ 0.05, where n1 is the average value of the refractive index of the first substrate and n2 is the average value of the refractive index of the filler.

20. For light with a wavelength of 840 nm or more and 860 nm or less, the optical filter according to claim 1 or claim 2 satisfies |n3 - n4| ≤ 0.05, where n3 is the average value of the refractive index of the first substrate and n4 is the average value of the refractive index of the filler.

21. For light with a wavelength of 930 nm or more and 950 nm or less, the optical filter according to any one of claims 3 to 5, wherein n1 is the average value of the refractive index of the substrate, and n2 is the average value of the refractive index of the first filler and the average value of the refractive index of the second filler, and the condition |n1 - n2| ≤ 0.05 is satisfied.

22. For light with a wavelength of 840 nm or more and 860 nm or less, the optical filter according to any one of claims 3 to 5, wherein n3 is the average value of the refractive index of the substrate, and n4 is the average value of the refractive index of the first filler and the average value of the refractive index of the second filler, and the condition |n3 - n4| ≤ 0.05 is satisfied.

23. An optical filter comprising: a first substrate including a first upper surface and a first lower surface; a first uneven portion provided on the first lower surface of the first substrate, each including at least one of a plurality of first recesses that are concave toward the first upper surface and a plurality of first protrusions that are convex toward the first lower surface; a first multilayer film disposed on the first uneven portion; a filler disposed below the first substrate; a second substrate disposed below the filler, including a second upper surface and a second lower surface; a second uneven portion provided on the second upper surface of the second substrate, each including at least one of a plurality of second recesses that are concave toward the second lower surface and a plurality of second protrusions that are convex toward the second upper surface; and a second multilayer film disposed on the second uneven portion, wherein the filler is disposed between the first multilayer film and the second multilayer film.

24. An optical filter comprising: a substrate including an upper surface and a lower surface; a first uneven surface provided on the upper surface of the substrate and including at least one of a plurality of first recesses, each concave toward the lower surface of the substrate, and a plurality of first protrusions, each convex toward the upper surface of the substrate; a first multilayer film disposed in the first uneven surface; a second uneven surface provided on the lower surface of the substrate and including at least one of a plurality of second recesses, each concave toward the upper surface of the substrate, and a plurality of second protrusions, each convex toward the lower surface of the substrate; a second multilayer film disposed in the second uneven surface; a first filler disposed above the substrate; and a second filler disposed below the substrate.

25. A sensing device having the optical filter described in claim 1 or claim 3.

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