Optical element

Abstract

To provide a technique capable of inspecting a region sandwiched between a plurality of light-shielding films in a light transmission direction.SOLUTION: An optical element has a transmission region transmitting a part of first light, when being viewed from a transmission direction of the first light, and a light-shielding region shielding other part of the first light. The optical element has a plurality of light-shielding films forming the light-shielding region, at intervals in the transmission direction of the first light. The transmission region has both a transmission rate (T1) of the first light, and a transmission rate (T2) of second light having a wavelength different from that of the first light, which are higher than those of the light-shielding region. The light-shielding region has a region where the plurality of light-shielding films overlaps each other, when being viewed from the transmission direction of the first light. The light-shielding region has (T2 / T1) of 100 or more, in a region where the most light-shielding films overlap each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical element.

Background Art

[0002] The optical unit described in Patent Document 1 includes a transparent first substrate, a transparent second substrate, and a diaphragm formed of a black resin that fills the periphery of a convex portion between the first substrate and the second substrate. The first substrate and the second substrate are a transparent glass substrate or a transparent resin substrate. The optical unit described in Patent Document 1 includes a second diaphragm having the same configuration as the diaphragm. The second diaphragm is also formed of a black resin.

[0003] Patent Document 2 describes a resin material that blocks visible light and transmits infrared light.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, as described in Patent Document 1, an optical element having a plurality of light-shielding films spaced apart in the light transmission direction is known. The optical element has a region where the plurality of light-shielding films overlap when viewed from the light transmission direction. This region is sandwiched between the plurality of light-shielding films. Therefore, it is difficult for inspection light to reach this region, and it has been difficult to inspect for defects. Defects include, for example, cracks.

[0006] One embodiment of the present disclosure provides a technique capable of inspecting a region sandwiched between a plurality of light-shielding films in the light transmission direction.

Means for Solving the Problems

[0007] An optical element according to one aspect of the present disclosure has a transmission region that transmits a part of the first light and a light-shielding region that blocks another part of the first light when viewed from the transmission direction of the first light. The optical element has a plurality of light-shielding films that form the light-shielding region at intervals in the transmission direction of the first light. The transmission region has a higher transmittance (T1) of the first light and a higher transmittance (T2) of a second light having a wavelength different from that of the first light than the light-shielding region. The light-shielding region has a region where a plurality of the light-shielding films overlap when viewed from the transmission direction of the first light. In the region where the most of the light-shielding films overlap, (T2 / T1) is 100 or more.

Advantages of the Invention

[0008] According to one aspect of the present disclosure, since (T2 / T1) is 100 or more in the region where the most of the light-shielding films overlap, it is possible to inspect a region sandwiched between a plurality of regions in the light transmission direction using the second light.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments for implementing the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted. In the specification, "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value. The numerical range includes the rounded range.

[0011] Referring to FIG. 1, an optical element 10 according to an embodiment will be described. In FIG. 1(B), the arrow direction indicates the transmission direction of the first light LB1. Note that the transmission direction of the first light LB1 may be the direction opposite to the arrow direction. The transmission direction of the first light LB1 is perpendicular to the main surfaces of the light shielding films 11A and 11B in the present embodiment, but may be an oblique direction with respect to the main surfaces of the light shielding films 11A and 11B. The first light LB1 is, for example, visible light. The optical element 10 is used, for example, in the optical system of an imaging device. Note that the first light LB1 is visible light in the present embodiment, but may be ultraviolet light or infrared light.

[0012] As shown in FIG. 1(A), when viewed from the transmission direction of the first light LB1, the optical element 10 includes a transmission region A1 that transmits a part of the first light LB1 and a light shielding region A2 that blocks another part of the first light LB1, and shapes, for example, the shape of the first light LB1. As shown in FIG. 1(B), the optical element 10 includes light shielding films 11A and 11B that form the light shielding region A2, and transparent members 12A, 12B, and 12C that form the transmission region A1. The light shielding region A2 is a region where at least one of the light shielding films 11A and 11B is provided. The transmission region A1 is a region where no light shielding films 11A and 11B are provided at all.

[0013] The light shielding region A2 has a region where a plurality of light shielding films 11A and 11B overlap when viewed from the transmission direction of the first light LB1 in at least a part (the whole in the present embodiment). The plurality of light shielding films 11A and 11B are provided at intervals in the transmission direction of the first light LB1. Therefore, as shown in FIG. 1(B), there is a region A3 sandwiched between the plurality of light shielding films 11A and 11B in the transmission direction of the first light LB1. The region A3 will be hereinafter also referred to as the inspection region A3.

[0014] The inspection area A3 is difficult for the light of the first light LB1 to reach from either side (for example, the upper side and the lower side in FIG. 1(B)) of the optical element 10, and it is difficult to inspect for defects caused by the first light LB1. The defects include, for example, cracks. Therefore, the inspection area A3 is inspected with the second light LB2. The second light LB2 has a wavelength different from that of the first light LB1. The combination of the first light LB1 and the second light LB2 is not particularly limited. For example, the first light LB1 is visible light and the second light LB2 is infrared light.

[0015] When the first light LB1 is visible light and the second light LB2 is infrared light, the transmittance (T1) of the first light LB1 is the average transmittance in the range of 400 nm to 700 nm, and the transmittance (T2) of the second light LB2 is the average transmittance in a desired wavelength range of 50 nm or more within the range of 800 nm to 2500 nm. In this specification, the transmittance is the external transmittance. The light-emitting element and the light-receiving element used for measuring T1 and T2 are arranged with the optical element 10 interposed therebetween. T1 and T2 are measured, for example, in a direction perpendicular to the main surfaces of the light-shielding films 11A and 11B, respectively.

[0016] As described above, the inspection area A3 is inspected with the second light LB2. When inspecting the inspection area A3, the light-emitting element and the light-receiving element of the second light LB2 may be arranged with the optical element 10 interposed therebetween, or may be arranged on one side of the optical element 10. In the former case, the inspection area A3 is inspected with the transmitted light. In the latter case, the inspection area A3 is inspected with the reflected light. In both the former case and the latter case, the number of times the second light LB2 passes through the light-shielding film is about the same (for example, 2 times). Therefore, in both the former case and the latter case, the rate of attenuation of the second light LB2 due to passing through the light-shielding film is about the same.

[0017] Note that in the transmission region A1, the transmittance (T1) of the first light LB1 and the transmittance (T2) of the second light LB2 are both higher than those in the light-shielding region A2. Therefore, the transmission region A1 can be inspected with both the first light LB1 and the second light LB2. Although not shown, in the light-shielding region A2, the region where the plurality of light-shielding films 11A and 11B do not overlap can also be inspected with both the first light LB1 and the second light LB2, similar to the transmission region A1. This is because if the region where the plurality of light-shielding films 11A and 11B do not overlap in the light-shielding region A2 is inspected with reflected light, the inspection light does not need to pass through the light-shielding film.

[0018] Hereinafter, the region where the largest number of the light-shielding films 11A and 11B overlap in the light-shielding region A2 is referred to as the most-overlapped region. When viewed from the transmission direction of the first light LB1, the most-overlapped region is the entire light-shielding region A2 in the present embodiment, but it may also be a part of the light-shielding region A2. In the most-overlapped region, if (T2 / T1) is 100 or more, the transmittance of the second light LB2 is high, and the inspection region A3 can be inspected with the second light LB2.

[0019] (T2 / T1) in the most-overlapped region is preferably 100 or more, more preferably 1000 or more, and even more preferably 5000 or more. From the viewpoint of the inspection accuracy of the inspection region A3, the larger (T2 / T1) in the most-overlapped region is, the more preferable it is. The upper limit value of (T2 / T1) in the most-overlapped region is not particularly limited, but when the number of light-shielding films is 3 or less, (T2 / T1) in the most-overlapped region may be 1,000,000,000 or less from the viewpoint of feasibility.

[0020] Note that in the entire light-shielding region A2, in order to ensure the light-shielding property of the first light LB1, the transmittance (T1) of the first light LB1 is preferably 1.0% or less, and more preferably 0.1% or less. Also, in the entire light-shielding region A2, in order to ensure the light-transmitting property of the second light LB2, the transmittance (T2) of the second light LB2 is preferably 5.0% or more, and more preferably 10% or more.

[0021] When the plurality of light-shielding films 11A and 11B are each measured for transmittance alone, it is preferable that the transmittance (T1) of the first light LB1 is 1.0% or less and the transmittance (T2) of the second light LB2 is 10% or more. Further, when the plurality of light-shielding films 11A and 11B are each measured for transmittance alone, it is more preferable that the transmittance (T1) of the first light LB1 is 0.5% or less and the transmittance (T2) of the second light LB2 is 20% or more.

[0022] The plurality of light-shielding films 11A and 11B are each formed of glass or resin. However, the resin has a greater change in optical properties due to temperature changes than glass. Therefore, the plurality of light-shielding films 11A and 11B are preferably each formed of glass. The glass is not particularly limited, but is, for example, black glass containing 3.0% by mass or more of Fe2O3. If the Fe2O3 content is 3.0% by mass or more, the transmittance difference between the first light LB1 and the second light LB2 is large.

[0023] An example of the transmittance spectrum of the light-shielding film composed of black glass is shown in FIG. 4. In FIG. 4, the black glass is aluminosilicate glass, the Fe2O3 content is 7.7% by mass, the average transmittance at a wavelength of 400 nm to 700 nm is 0.1%, and the average transmittance at a wavelength of 800 nm to 850 nm is 10.2%. The light-shielding film shown in FIG. 4 can shield the first light LB1 and transmit the second light LB2, and the inspection region A3 can be inspected.

[0024] From the viewpoint of ensuring the desired transmittance, the Fe2O3 content of the black glass is preferably 3.0% by mass or more, more preferably 4.5% by mass or more, and still more preferably 6.0% by mass or more. From the viewpoint of suppressing devitrification of the glass, the Fe2O3 content of the black glass is preferably 14.0% by mass or less, more preferably 12.0% by mass or less, and still more preferably 10.0% by mass or less.

[0025] The black glass contains, for example, in terms of mass% based on oxides, 50% to 75% of SiO2, 5% to 20% of Al2O3, 0% to 20% of Na2O, 0% to 20% of K2O, 0% to 15% of MgO, 0% to 20% of CaO, 10% to 20% of B2O3, 0% to 20% of ΣRO (R is Mg, Ca, Sr, Ba, Zn), 0% to 5% of ZrO2, 3.0% to 14% of Fe2O3, 0% to 2% of CoO or Co3O4, and may contain 0% to 0.5% of SO3. ΣRO is the total content of MgO, CaO, SrO, BaO, and ZnO.

[0026] The black glass may contain at least one selected from V2O5, CrO, MnO, CuO, MoO3, and CeO2 as long as the coloring is not impaired. The total content of V2O5, CrO, MnO, CuO, MoO3, and CeO2 is preferably 0% to 3%, more preferably 0% to 1% in terms of mass% based on oxides.

[0027] The black glass may contain at least one selected from SO3, Sb2O3, SnO, Cl, and F as a fining agent as long as the coloring is not impaired. The total content of SO3, Sb2O3, SnO, Cl, and F is preferably 0% to 1%, more preferably 0% to 0.5% in terms of mass% based on oxides.

[0028] An example of the transmittance spectrum of a light-shielding film formed by firing a paste containing a transparent glass powder and a black pigment instead of the black glass is shown in FIG. 5. In FIG. 5, a composite oxide of copper and chromium was used as the black pigment. In this case, the average transmittance at a wavelength of 400 nm to 700 nm was 0.50%, and the average transmittance at a wavelength of 800 nm to 850 nm was 1.02%. The light-shielding film shown in FIG. 5 shields both the first light LB1 and the second light LB2, making it difficult to inspect the inspection area A3.

[0029] Note that the light-shielding films 11A and 11B may each be formed of a resin. As long as they can block the first light LB1 and transmit the second light LB2, for example, the resin described in Patent Document 2 can be used. Further, the light-shielding films 11A and 11B may each be formed of a multilayer film having wavelength selectivity. The multilayer film may alternately have a high refractive index layer and a low refractive index layer. By adjusting the thickness and refractive index of each layer, the first light LB1 can be blocked and the second light LB2 can be transmitted.

[0030] As shown in FIG. 1(B), the transparent members 12A and 12B are provided with the light-shielding film 11A interposed therebetween in the light-shielding region A2 and are continuously in contact with each other in the transmission region A1. In the transmission region A1, nothing needs to exist between the transparent members 12A and 12B. The transparent members 12A and 12B are joined at least in the transmission region A1. The joint surface preferably has a flat surface. If the joint surface has a flat surface, the transparent members 12A and 12B can be uniformly pressed against each other and uniformly joined in the transmission region A1. Note that the transparent member 12A and the light-shielding film 11A may be joined. Also, the transparent member 12B and the light-shielding film 11A may be joined.

[0031] Similarly, the transparent members 12B and 12C are provided with the light-shielding film 11B interposed therebetween in the light-shielding region A2 and are continuously in contact with each other in the transmission region A1. In the transmission region A1, nothing needs to exist between the transparent members 12B and 12C. The transparent members 12B and 12C are joined in the transmission region A1. The joint surface preferably has a flat surface. If the joint surface has a flat surface, the transparent members 12B and 12C can be uniformly pressed against each other and uniformly joined in the transmission region A1. Note that the transparent member 12B and the light-shielding film 11B may be joined. Also, the transparent member 12C and the light-shielding film 11B may be joined.

[0032] The plurality of transparent members 12A, 12B, and 12C are each formed of glass or resin. However, the resin has a greater change in optical properties due to temperature changes compared to glass. Therefore, it is preferable that the plurality of transparent members 12A, 12B, and 12C are each formed of glass. The glass is not particularly limited, and examples thereof include soda-lime glass, alkali-free glass, chemically strengthened glass, borosilicate glass, or lanthanum borate-based glass. The plurality of transparent members 12A, 12B, and 12C may be composed of different glasses, but from the viewpoint of the durability of the optical element 10 against temperature changes, it is preferable that they are composed of the same glass.

[0033] The plurality of light-shielding films 11A, 11B and the plurality of transparent members 12A, 12B, 12C are each preferably formed of glass. If all the members constituting the optical element 10 are formed of glass, the stress caused by the difference in thermal expansion between the members can be reduced, and the durability against temperature changes can be improved.

[0034] Next, a method for manufacturing the optical element 10 having the above configuration will be described. The optical element 10 includes, for example, the transparent member 12A, the light-shielding film 11A, the transparent member 12B, the light-shielding film 11B, and the transparent member 12C in this order. A concave portion is formed on one side of the transparent member 12A, and the light-shielding film 11A is embedded in the concave portion. The light-shielding film 11A and the transparent member 12A are processed to be flush. Then, the transparent member 12A and the transparent member 12B are joined face to face. Also, a concave portion is formed on one side of the transparent member 12B, and the light-shielding film 11B is embedded in the concave portion. The light-shielding film 11B and the transparent member 12B are processed to be flush. Then, the transparent member 12B and the transparent member 12C are joined face to face.

[0035] For example, the joining of glasses may include, in this order, modifying the surface of the glass by plasma treatment, imparting OH groups to the modified surface, overlapping the glasses with the surfaces having the imparted OH groups facing each other, and heat-treating the overlapped glasses. The imparting of OH groups is performed by supplying pure water or water vapor. The glasses are bonded by hydrogen bonds between the OH groups, covalent bonds formed by dehydration condensation after the formation of hydrogen bonds, or van der Waals forces between the glass surfaces.

[0036] Alternatively, the joining of glasses may include, in this order, treating the surface of the glass with an alkaline detergent, washing the surface treated with the alkaline detergent with pure water, overlapping the glasses with the surfaces washed with pure water facing each other, and heat-treating the overlapped glasses. Here, treating the surface of the glass with an alkaline detergent may be omitted.

[0037] Also, the joining of glasses may include welding the glasses. The welding temperature is set to a temperature equal to or higher than the glass transition point of the glass. During welding, the glasses may be pressed and crimped together. Also, during welding, the glass may be thermally deformed. When the glass is thermally deformed, it is also possible to omit the processing before joining.

[0038] Next, with reference to FIG. 2, the optical element 10 according to the first modification will be described. Hereinafter, the differences from the above-described embodiment will be mainly described. The optical element 10 may have a light-shielding film exposed to the outside on at least one of its surfaces. The light-shielding film 11A is provided on one surface of the optical element 10 and is exposed to the outside. The light-shielding film 11B is provided on the opposite surface of the optical element 10 and is exposed to the outside.

[0039] However, it is preferable that the plurality of light-shielding films 11A and 11B are each sandwiched between a plurality of transparent members 12A, 12B, and 12C in the transmission direction of the first light LB1 as shown in FIG. 1. That is, the plurality of light-shielding films 11A and 11B are preferably not exposed on both sides of the optical element 10 and are provided inside the optical element 10. The light-shielding films 11A and 11B can be protected by the transparent members 12A, 12B, and 12C.

[0040] Next, with reference to FIG. 3, the optical element 10 according to the second modification will be described. Hereinafter, the differences from the above-described embodiment will be mainly described. The optical element 10 includes a light-shielding film 11A, a transparent member 12A, a transparent member 12B, a light-shielding film 11B, a transparent member 12C, and a light-shielding film 11C in this order. The transparent members 12A, 12B, and 12C are not in continuous contact in the transmission region A1.

[0041] The transparent members 12A, 12B, and 12C are separated from each other in the transmission region A1. Therefore, the transparent members 12A, 12B, and 12C can have lens surfaces on at least one (all in FIG. 3) of the plurality of surfaces facing each other. That is, the optical element 10 can have a lens surface inside thereof. The lens surface may be a convex curved surface or a concave curved surface. The lens surface refracts the first light LB1.

[0042] The optical element 10 may have a lens surface exposed to the outside on at least one of its surfaces. The optical element 10 shown in FIG. 3 has lens surfaces exposed to the outside on both of its surfaces. The lens surface may be a convex curved surface or a concave curved surface. The lens surface refracts the first light LB1. Note that the optical element 10 shown in FIG. 1 or FIG. 2 does not have lens surfaces exposed to the outside on both of its surfaces, but may have them on at least one of its surfaces.

[0043] As described above, the optical element according to the present disclosure has been described, but the present disclosure is not limited to the above-described embodiment and the like. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope described in the claims. Naturally, they also belong to the technical scope of the present disclosure.

Description of Reference Numerals

[0044] 10 Optical element 11A, 11B Light-shielding films 12A, 12B, 12C Transparent members A1 Transmission region A2 Light-shielding region A3 Inspection region LB1 First light LB2 Second light

Claims

1. An optical element having a transmission region that transmits a part of the first light and a light-shielding region that blocks another part of the first light when viewed from the transmission direction of the first light, wherein a plurality of light-shielding films forming the light-shielding region are provided at intervals in the transmission direction of the first light, wherein the transmission region has a higher transmittance of the first light (T1) and a higher transmittance of a second light having a wavelength different from that of the first light (T2) than the light-shielding region, wherein the light-shielding region has a region where a plurality of the light-shielding films overlap when viewed from the transmission direction of the first light, wherein the optical element has (T2 / T1) of 100 or more in a region where the most light-shielding films overlap.

2. The first light is visible light, and the transmittance (T1) of the first light is an average transmittance at 400 nm to 700 nm, wherein the second light is infrared light, and the transmittance (T2) of the second light is an average transmittance in a desired wavelength range of 50 nm or more within the range of 800 nm to 2500 nm. The optical element according to claim 1.

3. In the optical element according to claim 1 or 2, each of the plurality of light-shielding films is sandwiched between a plurality of transparent members in the transmission direction of the first light.

4. In the optical element according to claim 3, each of the plurality of transparent members is formed of glass or resin.

5. In the optical element according to claim 3, each of the plurality of transparent members is formed of glass.

6. Each of the plurality of light-shielding films is formed of black glass containing 3.0 mass% or more of Fe ２ O ３ The optical element according to claim 1 or 2, wherein the optical element is formed of black glass containing 3.0 mass% or more of Fe

7. Each of the plurality of light-shielding films is sandwiched between a plurality of transparent members in the transmission direction of the first light, and each of the plurality of transparent members is formed of glass. Each of the plurality of light-shielding films is formed of black glass containing 3.0 mass% or more of Fe ２ O ３ The optical element according to claim 1 or 2

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