Optical element, optical unit for camera, and method for manufacturing optical element

Abstract

Provided is a technique capable of improving the quality of an antireflection film continuously formed over both a first surface of a transparent substrate and a second surface of a light shielding film. This optical element comprises: a transparent substrate having a first surface and a recessed part formed in a portion of the first surface; a light shielding film provided in the recessed part, having no step with respect to the first surface, and having a second surface formed continuously with the first surface; and an antireflection film formed continuously over both the first surface and the second surface.

Description

Optical element, optical unit for camera, and method for manufacturing an optical element

[0001] This disclosure relates to an optical element, an optical unit for a camera, and a method for manufacturing an optical element.

[0002] The optical element described in Patent Document 1 comprises a transparent substrate, a light-shielding film formed in a frame shape on the surface of the transparent substrate, and an anti-reflective film formed to cover the light-shielding film and the opening of the light-shielding film. The optical element transmits light incident on the region of the opening of the light-shielding film while suppressing reflection. The optical element blocks light incident on the region of the light-shielding film while suppressing reflection.

[0003] Japanese Patent Publication No. 2016-92388

[0004] The light-shielding film described in Patent Document 1 is formed on the surface of a transparent substrate, creating a step between it and the surface of the transparent substrate. The thickness of the anti-reflective film varies at this step. As a result, the function of the anti-reflective film can be impaired.

[0005] One embodiment of the present disclosure provides a technology that can improve the quality of an anti-reflective film that is continuously formed over both a first surface of a transparent substrate and a second surface of a light-shielding film.

[0006] An optical element according to one embodiment of the present disclosure comprises a transparent substrate having a first surface and a recess formed in a part of the first surface; a light-shielding film provided in the recess and having a second surface that is formed continuously with respect to the first surface without any step difference; and an anti-reflective film that is formed continuously over both the first surface and the second surface.

[0007] An optical element according to another embodiment of the present disclosure comprises a transparent substrate having a first surface and including a first glass, and a light-shielding film having a second glass and provided on at least a portion of the first surface, wherein the first glass and the second glass have the same composition, and the light-shielding film is a sintered body of the second glass and a pigment.

[0008] An optical unit for a camera according to one embodiment of the present disclosure is a camera optical unit comprising an optical system for imaging light onto a camera sensor, wherein the optical system has the optical element.

[0009] A method for manufacturing an optical element according to one embodiment of the present disclosure includes the step of providing a light-shielding film including a second glass on at least a portion of the first surface of a transparent substrate including a first glass, wherein the first glass and the second glass have the same composition, and in the step of providing the light-shielding film, the second glass and a pigment are sintered to form the light-shielding film.

[0010] According to one embodiment of the present disclosure, the quality of an anti-reflective film that is continuously formed over both the first surface of a transparent substrate and the second surface of a light-shielding film can be improved.

[0011] Figure 1 is a cross-sectional view showing an optical unit for a camera according to one embodiment. Figure 2 is a cross-sectional view showing a modified example of Figure 1. Figure 3(A) is a plan view of an optical element according to one embodiment, and Figure 3(B) is a cross-sectional view of an optical element according to one embodiment. Figure 4(A) is a plan view showing a first example of a transmission region and a light-shielding region, Figure 4(B) is a plan view showing a second example of a transmission region and a light-shielding region, Figure 4(C) is a plan view showing a third example of a transmission region and a light-shielding region, and Figure 4(D) is a plan view showing a fourth example of a transmission region and a light-shielding region. Figure 5(A) is a plan view showing a fifth example of a transmission region and a light-shielding region, Figure 5(B) is a plan view showing a sixth example of a transmission region and a light-shielding region, and Figure 5(C) is a plan view showing a seventh example of a transmission region and a light-shielding region. Figure 6(A) is a cross-sectional view showing an example of a tapered portion, and Figure 6(B) is a graph showing an example of the change in transmittance in the tapered portion. Figure 7 is a flowchart showing a method for manufacturing an optical element according to one embodiment. Figure 8(A) is a cross-sectional view showing an example of S101, Figure 8(B) is a cross-sectional view showing an example of S102, Figure 8(C) is a cross-sectional view showing an example of S103, and Figure 8(D) is a cross-sectional view showing an example of S104. Figure 9 is a flowchart showing a method for manufacturing an optical element according to the first modified example. Figure 10(A) is a cross-sectional view showing an example of S111, and Figure 10(B) is a cross-sectional view showing an example of S112. Figure 11 is a flowchart showing a method for manufacturing an optical element according to the second modified example. Figure 12(A) is a cross-sectional view showing an example of S121, and Figure 12(B) is a cross-sectional view showing an example of S122. Figure 13 is a cross-sectional view showing a method for manufacturing an optical element according to the third modified example. Figure 14(A) is a perspective view showing an example of the arrangement of a rectangular prism-shaped transparent substrate and a light-shielding film, Figure 14(B) is a perspective view showing a modified version of Figure 14(A), and Figure 14(C) is a perspective view showing another modified version of Figure 14(A). Figure 15(A) is a cross-sectional view showing an example of the height difference between the first and second surfaces, and Figure 15(B) is a cross-sectional view showing another example of the height difference between the first and second surfaces. Figure 16 is a cross-sectional view showing an example of the structure of an anti-reflective coating. Figure 17 is a table showing an example of the physical properties of each dielectric layer constituting the anti-reflective coating. Figure 18 is a table showing an example of the relationship between Δnd and ΔRmax. Figure 19 is a cross-sectional view showing an example of a light-shielding coating in which the extinction coefficient changes in the direction of light propagation.Figure 20 is a table showing a list of reflectances of optical elements with different light-shielding film materials. Figure 21(A) is a perspective view showing an example of the arrangement of a triangular prism-shaped transparent substrate and a light-shielding film, Figure 21(B) is a perspective view showing a modified example of Figure 21(A), and Figure 21(C) is a perspective view showing another modified example of Figure 21(A). Figure 22 is a cross-sectional view of an optical element according to another embodiment. Figure 23 is a cross-sectional view of an optical element according to another embodiment. Figure 24 is a cross-sectional view showing a method for manufacturing an optical element according to a fourth modified example. Figure 25 is a cross-sectional view showing a method for manufacturing an optical element according to a fifth modified example. Figure 26 is a cross-sectional view showing a method for manufacturing an optical element according to a sixth modified example. Figure 27 is a cross-sectional view showing a method for manufacturing an optical element according to a seventh modified example.

[0012] The embodiments for implementing this disclosure will be described below with reference to the drawings. In each drawing, identical or similar components will be denoted by the same reference numeral, and their descriptions may be omitted. In the specification, the "~" indicating a numerical range means that the numbers written before and after it are included as the lower and upper limits. The numerical range includes the rounded range.

[0013] Referring to Figure 1, an optical unit 2 for a camera according to one embodiment will be described. The optical unit 2 for a camera includes an optical system 3. The optical system 3 forms an image of light LB onto the camera sensor 5. The optical system 3 has optical elements 10. The optical elements 10 are, for example, apertures. The number and position of the optical elements 10 are not particularly limited. The number of optical elements 10 may be two as shown in Figure 1, one as shown in Figure 2, or three or more, although these are not shown. Light LB passes through the optical elements 10 and lenses 90 and reaches the camera sensor 5. The number and position of lenses 90 are not particularly limited. The optical elements 10 may be, for example, optical filters or prisms.

[0014] An optical element 10 according to one embodiment will be described with reference to Figures 3(A) and 3(B). The optical element 10 comprises a transparent substrate 20, a light-shielding film 30, and an anti-reflective film 40. The transparent substrate 20 has a first surface 21 and a recess 22 formed on a part of the first surface 21. The light-shielding film 30 is provided on the recess 22 and has a second surface 31 that is formed continuously with the first surface 21 without any step difference. The anti-reflective film 40 is formed continuously over both the first surface 21 and the second surface 31. In this embodiment, the first surface 21 and the second surface 31 are planar, but they may be curved as will be described later. In the optical element according to this disclosure, the anti-reflective film 40 is not an essential component and may not be provided.

[0015] In Figures 3(A) and 3(B), the transparent substrate 20 is plate-shaped, but the shape of the transparent substrate 20 is not particularly limited and may be a rectangular prism or a triangular prism. The first surface 21 of the transparent substrate 20 is, for example, the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20. However, the first surface 21 of the transparent substrate 20 may also be the surface on which light LB is incident from the outside to the inside of the transparent substrate 20. Alternatively, the first surface 21 of the transparent substrate 20 may also be the surface on which light LB is reflected from the inside to the inside of the transparent substrate 20.

[0016] As shown in Figure 3(A), when viewed from a first direction perpendicular to the first surface 21 of the transparent substrate 20 (hereinafter simply referred to as the "first direction"), the optical element 10 comprises a transmission region A1 that transmits a portion of the light LB of a desired wavelength and a light-shielding region A2 that blocks another portion of the light LB. The transmission region A1 is formed on the first surface 21 excluding the recess 22, and the light-shielding region A2 is formed on the second surface 31. The optical element 10 shapes the light LB using the light-shielding region A2. In Figure 3(A), A3 is the boundary line between the transmission region A1 and the light-shielding region A2, that is, the boundary line between the first surface 21 and the second surface 31.

[0017] Viewed from a first direction, the shape of the optical element 10 is rectangular, as shown in Figure 3(A). The rectangle includes a square. Light-shielding regions A2 may be provided along all four sides of the rectangle. However, as shown in Figures 4(A) to 4(C), light-shielding regions A2 may be provided along one, two, or three sides of the rectangle. As shown in Figure 4(D), one transparent region A1 may be provided in a rectangular shape, a light-shielding region A2 may be provided in a rectangular frame shape surrounding the transparent region A1, and another transparent region A1 may be provided in a rectangular frame shape surrounding the light-shielding region A2. As shown in Figure 5(A), a light-shielding region A2 may be provided in a rectangular shape, and a transparent region A1 may be provided in a rectangular frame shape surrounding the light-shielding region A2. As shown in Figures 4(D) and 5(A), the light-shielding regions A2 may be provided at a distance from the periphery of the optical element 10. Furthermore, as shown in Figures 5(B) and 5(C), the shape of the transparent region A1 may be a circle or other shape besides a rectangle.

[0018] Furthermore, the shape of the optical element 10 is not limited to a rectangular shape when viewed from the first direction. When viewed from the first direction, the shape of the optical element 10 may be circular, for example, as shown in Figure 5(B). As shown in Figure 5(B), the transparent region A1 may be provided in a circular shape, and the light-shielding region A2 may be provided in a ring shape so as to surround the transparent region A1. Furthermore, the arrangement of the transparent region A1 and the light-shielding region A2 may be reversed, with the light-shielding region A2 provided in a circular shape and the transparent region A1 provided in a ring shape so as to surround the light-shielding region A2.

[0019] The transparent substrate 20 contains only a material that transmits visible light, such as the first glass. The composition of the glass is measured by SEM-EDX. The transparent substrate 20 can also be formed from resin.

[0020] Generally, glass exhibits less change in optical properties (e.g., refractive index and extinction coefficient) due to temperature changes compared to resin. If the material of the transparent substrate 20 is the first glass, then the change in optical properties of the transparent substrate 20 due to temperature changes is small. The first glass is not particularly limited, but examples include soda-lime glass, borosilicate glass, aluminosilicate glass, lead glass, optical glass, synthetic quartz glass, or crystallized glass.

[0021] As described above, the transparent substrate 20 has a first surface 21 and a recess 22 formed in a part of the first surface 21. The recess 22 is also called a cavity. A light-shielding film 30 is embedded in the recess 22. The recess 22 may be formed by machining, etching, or thermoforming before embedding the light-shielding film 30, or it may be formed by thermal deformation when embedding the light-shielding film 30, as will be described later.

[0022] As described above, the light-shielding film 30 is provided in the recess 22 and has a second surface 31 that is formed continuously with the first surface 21 without any step difference. Here, "no step difference" means that, as shown in Figures 15(A) and 15(B), the height difference ΔH between the first surface 21 and the second surface 31 is less than 30 nm in the range A4 of 10 μm or less from the boundary line A3 when viewed from the first direction. The height difference ΔH is measured in a direction perpendicular to the first surface 21. The height difference ΔH is measured with a white light interferometer. It is preferable that the first surface 21 and the second surface 31 are completely on the same plane, and it is preferable that the height difference ΔH in range A4 is 0 nm.

[0023] In this embodiment, the first surface 21 and the second surface 31 are planar, but they may be curved. If the first surface 21 and the second surface 31 are curved, the height difference ΔH between the first surface 21 and the second surface 31 after removing their respective curved components should be 30 nm. The curved components are represented by the following formulas (1) to (5).

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] In equations (1) to (5) above, (r, θ) is the polar coordinate on the reference plane, z(r, θ) is the height of the curved surface component from the reference plane, and z ０ (r, θ) is the height from the reference plane of the first surface 21 or the second surface 31 before the curved surface component is removed. z(r, θ) and z ０(r, θ) is a value determined depending on r and θ. z ０ (r, θ) is measured with a white interferometer. n is a natural number from 0 to k, k is 2. When n is even, m is only an even number in the range from -n to +n. When n is odd, m is only an odd number in the range from -n to +n. j is an index indicating the combination of n and k, a ｎｍ is a coefficient. As is clear from the above formula (4), as a method of expressing the combination of two indices n and m by one index j, a notation using Fringe is used. The above formula (2) is a Zernike polynomial. Since the Zernike polynomial is an orthogonal polynomial, the coefficient a ｎｍ can be obtained by the above formula (5).

[0030] If there is no step on the boundary line A3 between the first surface 21 and the second surface 31 and the first surface 21 and the second surface 31 are continuously formed, there is no variation in the film thickness of the antireflection film 40 in the vicinity of the boundary line A3, and there is no deterioration in the antireflection function of the antireflection film 40 in the vicinity of the boundary line A3. Therefore, the quality of the antireflection film 40 can be improved.

[0031] Even if the first surface 21 and the second surface 31 are curved surfaces, if ΔH is 30 nm or less, there is no variation in the film thickness of the antireflection film 40 in the vicinity of the boundary line A3, and there is no deterioration in the antireflection function of the antireflection film 40 in the vicinity of the boundary line A3. If a film forming machine equipped with a planetary rotation mechanism is used, even if the first surface 21 and the second surface 31 are curved surfaces, it is possible to form a film with a uniform film thickness.

[0032] The light shielding film 30 includes, for example, the second glass. The content of the second glass in the light shielding film 30 is 50% by volume or more, more preferably 70% by volume or more, and still more preferably 80% by volume or more. Also, the content of the second glass in the transparent substrate 20 may be 100% by volume or less.

[0033] Generally, glass exhibits less change in optical properties (e.g., refractive index and extinction coefficient) due to temperature changes compared to resin. If the content of the second glass in the light-shielding film 30 is 50 volume percent or more, the change in the optical properties of the light-shielding film 30 due to temperature changes will be small. The light-shielding film 30 may be partially crystallized. The light-shielding film 30 can also be formed from resin.

[0034] It is preferable that the transparent substrate 20 contains only the first glass and the light-shielding film 30 contains the second glass. This reduces the difference in the coefficients of linear expansion between the transparent substrate 20 and the light-shielding film 30, thereby reducing the generation of stress due to temperature changes. The first glass and the second glass may have the same composition or different compositions, but from the viewpoint of stress reduction, it is preferable that they have the same composition. When the first glass and the second glass have the same composition, the second glass is transparent.

[0035] The light-shielding film 30 is preferably a sintered body of the second glass and a pigment. The light-shielding film 30 contains the pigment dispersed within the second glass. When the light-shielding film 30 contains the pigment dispersed within the second glass, when measuring the composition of the second glass, the composition of the glass should be measured while avoiding the pigment. If the second glass is colored, the light-shielding film 30 may be a sintered body of the second glass and a pigment. Here, if the pigment in the light-shielding film 30 does not solid dissolve in the second glass and can be observed as particles, it can be determined that the light-shielding film 30 is a sintered body of the second glass and a pigment.

[0036] The pigment is, for example, a black pigment. Preferably, the pigment is an inorganic pigment. Inorganic pigments are, for example, metal oxides, metals, or carbon-based materials. Preferably, the metal oxide is a metal oxide containing at least one of copper, chromium, manganese, iron, cobalt, or titanium. The carbon-based material is graphite or carbon black. Graphite is crystalline, while carbon black is amorphous. Carbon black is more preferable as the carbon-based material in terms of particle size control and color tone. The light-shielding film 30 may contain multiple types of pigments to adjust the wavelength dependence of the light LB transmittance.

[0037] The second glass is, for example, SiO ２It is glass, bismuth-based glass, or vanadium-based glass having a main component. The bismuth-based glass contains Bi ２ O ３ . The vanadium-based glass contains V ２ O ５ . Compared with bismuth-based glass and vanadium-based glass, the glass having SiO ２ as the main component tends to have a low refractive index. Also, the second glass may be a lanthanum borate-based glass. The "main component" in this specification means the component contained the most among the components, and preferably 50% by mass or more.

[0038] The light-shielding film 30 is obtained, for example, by firing a glass paste containing glass powder of the second glass. The glass powder is also called glass frit. The glass paste may contain a pigment in addition to the glass powder. Also, the glass paste may contain additives other than the glass powder and the pigment, and may contain, for example, a resin binder. The resin binder is removed before firing the glass paste.

[0039] Incidentally, the second glass may be black glass. Black glass means that the glass itself is black, and the coloring component is metal ions dissolved in the glass rather than a pigment dispersed in the glass. When the second glass is black glass and the light-shielding film 30 does not contain a pigment, the light-shielding film 30 may be obtained by processing the block of the second glass.

[0040] As shown in FIG. 6(B), it is preferable that the light-shielding film 30 has a lower transmittance of the light LB in the second direction orthogonal to the second surface 31 as the distance L from the boundary line A3 is farther at at least a part (preferably the whole) of the boundary line A3 between the first surface 21 and the second surface 31. Compared with the case where the transmittance of the light LB changes discontinuously at the boundary line A3, diffraction of the light LB can be suppressed and generation of stray light can be suppressed.

[0041] As shown in Figure 6(A), the light-shielding film 30 preferably has a tapered portion 34. The tapered portion 34 is provided on at least a part (preferably the entire) of the boundary line A3. The tapered portion 34 is in contact with the boundary line A3, and its thickness increases as the distance L from the boundary line A3 increases. As a result, as shown in Figure 6(B), the transmittance of light LB decreases as the distance L from the boundary line A3 increases.

[0042] The light-shielding film 30 may have a constant-thickness portion 33. If the light-shielding film 30 has a tapered portion 34, the constant-thickness portion 33 is positioned further from the boundary line A3 than the tapered portion 34. The transmittance of light LB in the constant-thickness portion 33 is preferably 0.1% or less. The transmission of light LB can be sufficiently suppressed in the constant-thickness portion 33. The thickness of the constant-thickness portion 33 is preferably 1 μm or more in order to suppress the transmittance of light LB in the constant-thickness portion 33 to 0.1% or less.

[0043] Although not shown in the figures, the light-shielding film 30 may have a density gradient portion instead of the tapered portion 34. The density gradient portion is provided on at least a part (preferably the entire) of the boundary line A3. The density gradient portion is in contact with the boundary line A3, and the concentration of the coloring component increases as the distance L from the boundary line A3 increases. The coloring component is, for example, a pigment. Note that the coloring component may be a metal ion that is solid-dissolved in the glass, rather than a pigment dispersed in the glass.

[0044] As described above, the density gradient section is in contact with boundary line A3, and the concentration of the coloring component increases as the distance L from boundary line A3 increases. As a result, the transmittance of light LB decreases as the distance L from boundary line A3 increases. Unlike the tapered section 34, the thickness of the density gradient section may be constant regardless of the distance L from boundary line A3. However, similar to the tapered section 34, the thickness of the density gradient section may increase as the distance L from boundary line A3 increases.

[0045] A method for manufacturing an optical element 10 according to one embodiment will be described with reference to Figures 7 and 8. As shown in Figure 7, the manufacturing method includes, for example, steps S101 to S104. However, the manufacturing method does not have to include all of steps S101 to S104. For example, when manufacturing optical elements 10 one by one, step S104 may be omitted. The manufacturing method may also include steps other than steps S101 to S104.

[0046] Step S101 includes preparing a transparent substrate 20, for example, as shown in Figure 8(A). The transparent substrate 20 has a first surface 21 and recesses 22 formed on a part of the first surface 21. The recesses 22 are arranged, for example, in a grid pattern.

[0047] Step S102 includes forming a light-shielding film 30, for example, as shown in Figure 8(B). The light-shielding film 30 is obtained, for example, by applying glass paste, degreasing, and firing. In order to suppress deformation of the transparent substrate 20 during sintering, it is preferable that the bending point of the transparent substrate 20 is higher than the softening point of the light-shielding film 30. The light-shielding film 30 is filled into the recesses 22 of the transparent substrate 20. If the light-shielding film 30 does not completely fill the recesses 22 of the transparent substrate 20 and covers the first surface 21 of the transparent substrate 20, the light-shielding film 30 is polished or etched, for example, so that the first surface 21 is exposed.

[0048] Step S103 includes forming an anti-reflective coating 40, for example, as shown in Figure 8(C). The anti-reflective coating 40 is formed by a PVD (Physical Vapor Deposition) method such as sputtering or a CVD (Chemical Vapor Deposition) method. The anti-reflective coating 40 is formed over both the first surface 21 and the second surface 31, which are formed continuously without any steps. Since there is no step at the boundary line A3 between the first surface 21 and the second surface 31, there is no variation in the thickness of the anti-reflective coating 40 near the boundary line A3, and there is no decrease in the anti-reflective function of the anti-reflective coating 40 near the boundary line A3.

[0049] Step S104 includes cutting the assembled body obtained in step S103 into a plurality of optical elements 10, as shown in Figure 8(D), for example. The cutting includes, for example, blade cutting or laser cutting.

[0050] Incidentally, during heat treatment such as step S103, the refractive index of the glass may change, and internal stress may occur, resulting in birefringence. Therefore, after step S103, the bonded body obtained in step S103 may be heated and slowly cooled (so-called annealing).

[0051] Annealing restores the refractive index of the glass to a desired value and removes internal stresses, thereby eliminating birefringence. Annealing may be performed before or after step S104. However, it is preferable to perform annealing before step S104 because dimensional changes may occur due to annealing.

[0052] A method for manufacturing the optical element 10 according to the first modified example will be described with reference to Figures 9 to 10. As shown in Figure 9, the manufacturing method may include steps S111 to S112. Step S111 involves applying glass paste 30A to the first surface 21 of the transparent substrate 20 and degreasing it, as shown in Figure 10(A). The glass paste 30A may contain transparent glass powder and pigment, or it may contain black glass powder.

[0053] Step S112 involves sintering the glass paste 30A and pressing the sintered light-shielding film 30 onto the heated first surface 21 of the transparent substrate 20 using a press machine 80 or the like. The first surface 21 of the transparent substrate 20 undergoes thermal deformation, forming a recess 22 on the first surface 21, and the light-shielding film 30 fills the recess 22. It is preferable to press the light-shielding film 30 with the press machine 80 or the like while the transparent substrate 20 is fitted into a mold (not shown) to suppress unintended thermal deformation of the transparent substrate 20. After step S112, at least one of the first surface 21 and the second surface 31 may be polished to remove the step difference between the first surface 21 and the second surface 31, or to reduce the surface roughness.

[0054] Steps S111 to S112 of this modified example are preferably applied when the first glass constituting the transparent substrate 20 and the second glass constituting the light-shielding film 30 have similar softening points. The first glass and the second glass may have the same composition. When the second glass is transparent, the glass paste 30A contains a pigment in addition to the glass powder of the second glass.

[0055] Referring to Figures 11 to 12, a method for manufacturing the optical element 10 according to the second modified example will be described. As shown in Figure 11, the manufacturing method may include steps S121 to S122. Step S121 involves placing a light-shielding film 30, which has been pre-processed into a desired shape, onto the first surface 21 of the transparent substrate 20, as shown in Figure 12(A). The light-shielding film 30 may be made from a block of black glass, a sintered body of transparent glass powder and pigment, or a sintered body of black glass powder. The processing method may be machining, molding, or etching.

[0056] Step S122 involves pressing the light-shielding film 30 onto the first surface 21 of the heated transparent substrate 20 using a press machine 80 or the like. The first surface 21 of the transparent substrate 20 is thermally deformed, forming a recess 22 on the first surface 21, and the light-shielding film 30 fills the recess 22. It is preferable to press the light-shielding film 30 with the press machine 80 or the like while the transparent substrate 20 is fitted into a mold (not shown) to suppress unintended thermal deformation of the transparent substrate 20. After step S122, at least one of the first surface 21 and the second surface 31 may be polished to remove the step difference between the first surface 21 and the second surface 31, or to reduce the surface roughness.

[0057] Steps S121 to S122 of this modified example are preferably applied when the glass transition point of the second glass constituting the light-shielding film 30 is higher than the bending point of the first glass constituting the transparent substrate 20. If the glass transition point of the second glass is higher than the bending point of the first glass, deformation of the light-shielding film 30 can be suppressed when the light-shielding film 30 is pressed with a press or the like.

[0058] Referring to Figure 13, a method for manufacturing the optical element 10 according to a third modified example will be described. In this modified example, after forming a light-shielding film 30 in a recess 22 of the first surface 21 of the transparent substrate 20, a second light-shielding film 50 is formed in a second recess 24 of the third surface 23 of the transparent substrate 20, as shown in Figure 13. The second light-shielding film 50 is provided in the second recess 24 and has a fourth surface 51 that is formed continuously with the third surface 23 without any step difference.

[0059] The third surface 23 of the transparent substrate 20 is a surface with a different orientation from the first surface 21. In this modified example, the third surface 23 is a surface perpendicular to the first surface 21. In this modified example, the third surface 23 is a cross-section. The third surface 23 may be a surface facing the opposite direction to the first surface 21, or a surface parallel to the first surface 21. Furthermore, the third surface 23 may be a surface inclined with respect to the first surface 21.

[0060] The second light-shielding film 50 is formed in the same manner as the light-shielding film 30. For example, the second light-shielding film 50 is pressed onto the third surface 23 of the heated transparent substrate 20 using a press machine 80 or the like. At this time, glass paste that has been degreased in advance may be sintered. The third surface 23 of the transparent substrate 20 is thermally deformed, a second recess 24 is formed on the third surface 23, and the second light-shielding film 50 is filled into the second recess 24. In order to suppress unintended thermal deformation of the transparent substrate 20, it is preferable to press the light-shielding film 30 with a press machine 80 or the like while the transparent substrate 20 is fitted into the mold 81.

[0061] Although not shown in the diagram, after the formation of the second light-shielding film 50, a second anti-reflective film is continuously formed over both the third surface 23 and the fourth surface 51. The second anti-reflective film is formed in the same manner as the anti-reflective film 40. If there is no step at the boundary between the third surface 23 and the fourth surface 51, and the third surface 23 and the fourth surface 51 are formed continuously, there will be no variation in the thickness of the second anti-reflective film near the boundary, and there will be no decrease in the anti-reflective function of the second anti-reflective film near the boundary. Therefore, the quality of the second anti-reflective film can be improved.

[0062] Referring to Figure 14, an example of the arrangement of the transparent substrate 20 and the light-shielding film 30 will be described. In Figure 14, the anti-reflective film 40 is formed on the first surface 21 and the third surface 23, and not on the other surfaces (side surfaces 26, 27, 28, and 29). The structure of the anti-reflective film 40 is the same as the anti-reflective film 40 related to the optical element 10 according to the above-described embodiment, and will not be depicted in the drawings described hereafter. The transparent substrate 20 may be rectangular prism-shaped and has a first surface 21 and a third surface 23. The first surface 21 is the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20. The third surface 23 is the surface on which light LB is incident from the outside to the inside of the transparent substrate 20, and is parallel to the first surface 21. The transparent substrate 20 further has side surfaces 26, 27, 28, and 29. Side surfaces 26, 27, 28, and 29 are perpendicular to the first surface 21 and the third surface 23.

[0063] As shown in Figures 14(A), 14(B), and 14(C), a light-shielding film 30 is formed on at least the first surface 21. Preferably, the light-shielding film 30 is formed in a frame shape along the periphery of the first surface 21. In this embodiment, the first surface 21 is the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20, as described above, but it may also be the surface on which light LB is incident from the outside to the inside of the transparent substrate 20.

[0064] As shown in Figure 14(A), a light-shielding film may not be formed on the third surface 23 and the sides 26, 27, 28, and 29. However, as shown in Figure 14(B), a second light-shielding film 50 may be formed on the third surface 23. The second light-shielding film 50 is preferably formed in a frame shape along the periphery of the third surface 23. Also, as shown in Figure 14(C), a third light-shielding film 60 may be formed over the entire surface 26, 27, 28, and 29. The third light-shielding film 60 is formed in the same manner as the light-shielding film 30 and the second light-shielding film 50.

[0065] As described later, the anti-reflective film 40 is formed across the first surface 21 of the transparent substrate 20 and the second surface 31 of the light-shielding film 30. It is preferable that the difference in refractive index between the transparent substrate 20 and the light-shielding film 30 is small so that the function of the anti-reflective film 40 is exhibited on both the first surface 21 and the second surface 31.

[0066] When the refractive index difference between the transparent substrate 20 and the light-shielding film 30 is small, the reflectance of light incident on the light-shielding film 30 from the transparent substrate 20 can be reduced. In particular, when the transparent substrate 20 is a first glass and the light-shielding film 30 is a sintered body of a second glass and a pigment, and the compositions of the first glass and the second glass are the same, the refractive index difference between the transparent substrate 20 and the light-shielding film 30 can be made almost zero. As a result, the reflectance of light incident on the light-shielding film 30 from the transparent substrate 20 can be significantly reduced, and stray light can be suppressed.

[0067] Similarly, it is preferable that the refractive index difference between the transparent substrate 20 and the second light-shielding film 50 is small. Furthermore, it is preferable that the refractive index difference between the transparent substrate 20 and the third light-shielding film 60 is small.

[0068] Referring to Figure 16, an example of the structure of the anti-reflective film 40 will be described. The anti-reflective film 40 is formed across the first surface 21 of the transparent substrate 20 and the second surface 31 of the light-shielding film 30. The anti-reflective film 40 has, for example, a plurality (e.g., two) dielectric layers 41, 42 with different refractive indices, which are alternately repeated. Although not shown, the anti-reflective film 40 may have three or more dielectric layers with different refractive indices, which are repeated. Even if the anti-reflective film 40 is a dielectric multilayer film, according to the technology of this disclosure, there is no variation in the thickness of the anti-reflective film 40, and there is no decrease in the anti-reflective function of the anti-reflective film 40 near the boundary line A3. Therefore, the quality of the anti-reflective film 40 can be improved.

[0069] The anti-reflective coating 40 may prevent the reflection of either light LB incident from the outside to the inside of the optical element 10 or light LB emitted from the inside to the outside of the optical element 10. The anti-reflective coating 40 can prevent the reflection of light LB in both the forward and reverse directions with the same structure. The anti-reflective coating 40 can prevent the reflection of stray light.

[0070] The anti-reflective film 40 is composed of a dielectric multilayer film in which two or more dielectric layers are stacked, for example, a low refractive index dielectric layer, a medium refractive index dielectric layer, and a high refractive index dielectric layer. The high refractive index layer preferably has a refractive index of 1.6 or higher, and more preferably 2.2 to 2.5. As the material for the high refractive index layer, for example, Ta ２ O ５ , TiO ２ ,TiO,Nb２ O ５ Examples include the intermediate refractive layer, which preferably has a refractive index of 1.6 or more and less than 2.2. Examples of materials for the intermediate refractive layer include ZrO ２ Nb ２ O ５ Al ２ O ３ , HfO ２ Examples include: The low refractive index layer preferably has a refractive index of less than 1.6, and more preferably 1.45 or more and less than 1.55. Examples of materials for the low refractive index layer include SiO ２ , SiOxNy, MgF ２ These are some examples.

[0071] The arithmetic mean roughness Ra of the surface of the anti-reflective coating 40 is preferably about the same as the arithmetic mean roughness Ra of the first surface 21 of the transparent substrate 20. Specifically, the arithmetic mean roughness Ra of the surface of the anti-reflective coating 40 is preferably 0 nm to 10 nm, and more preferably 0 nm to 5 nm. The arithmetic mean roughness Ra is measured in accordance with JIS B 0601:2013.

[0072] Referring to Figure 17, an example of the physical properties of each dielectric layer constituting the anti-reflective film 40 will be described. In Figure 17, the numbers indicate which dielectric layer it is, counting from the transparent substrate 20. 1st SiO ２ The layer is closest to the transparent substrate 20, and the 9th SiO ２ The layer is furthest from the transparent substrate 20. The physical properties of each dielectric layer constituting the anti-reflective film 40 were designed so that the average reflectance of the anti-reflective film 40 at wavelengths of 400 to 800 nm is minimized when the refractive index of the transparent substrate 20 at the d line is 1.694.

[0073] Referring to Figure 18, an example of the relationship between Δnd and ΔRmax will be explained. Δnd is the difference (nd2-nd1) between the refractive index nd1 of the transparent substrate 20 at the d line and the refractive index nd2 of the light-shielding film 30 at the d line. Note that nd1 is 1.694 as shown in Figure 17. ΔRmax is the maximum value of the reflectance difference ΔR (ΔR = |R1-R2|) calculated for each wavelength from 400 to 800 nm, for the reflectance R1 (%) of the portion formed on the first surface 21 of the anti-reflective film 40 and the reflectance R2 (%) of the portion formed on the second surface 31 of the anti-reflective film 40. The reflectance for each wavelength from 400 to 800 nm is measured using a microspectrometer. For example, the USPM-RU-W manufactured by Evident Co., Ltd. is used as a microspectrometer. During measurement, a 10x objective lens is used, and the reflectance of the object under test is measured using the amount of reflected light on the BK7 glass mirror surface as a reference. On the second surface 31, as on the first surface 21, a low reflectance is obtained, preferably with a ΔRmax of 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less.

[0074] Referring to Figure 19, an example of a light-shielding film 30 in which the extinction coefficient changes in the direction of light LB propagation will be described. Preferably, the extinction coefficient of the light-shielding film 30 increases as the depth from the second surface 31 increases. The extinction coefficient can be adjusted by the concentration of coloring components such as pigments. It is more preferable that the extinction coefficient of the light-shielding film 30 increases as the depth from the second surface 31 increases, and then decreases.

[0075] For example, the light-shielding film 30 has a first layer 35 and a second layer 36 having different extinction coefficients. The first layer 35 has a lower extinction coefficient than the second layer 36. The first layer 35 forms the second surface 31 of the light-shielding film 30. The first layer 35 can reduce the extinction coefficient of the second surface 31 and suppress the reflection of light on the second surface 31. In addition, the second layer 36 can sufficiently reduce the transmittance. The light-shielding film 30 may have the first layer 35, the second layer 36, and the third layer 37 in this order. The third layer 37 has a lower extinction coefficient than the second layer 36.

[0076] It is preferable that the constant-thickness portion 33 of the light-shielding film 30 has a first layer 35 and a second layer 36. It is preferable that the tapered portion 34 of the light-shielding film 30 has a uniform extinction coefficient overall, and preferably has a lower extinction coefficient than the second layer 36. The tapered portion 34 may have an extinction coefficient similar to that of the first layer 35 of the constant-thickness portion 33. This reduces the extinction coefficient of the tapered portion 34, mitigates changes in internal transmittance near the boundary line A3, and reduces the generation of diffracted light.

[0077] Other embodiments will be described below. Note that matters common to the optical element and the method for manufacturing the optical element according to the above-described embodiment will be omitted from the explanation.

[0078] An optical element according to another embodiment comprises a transparent substrate having a first surface and including a first glass, and a light-shielding film having at least a portion of the first surface and including a second glass. The first glass and the second glass have the same composition. The light-shielding film is a sintered body of the second glass and a pigment. Furthermore, as described above, it is preferable that the second glass has the same composition as the first glass. As described above, the pigment can be an inorganic pigment, such as a metal oxide, metal, or carbon-based material.

[0079] The material of the light-shielding film will be described with reference to Figure 20. The reflectance shown in Figure 20 is the average value of the reflectance of the light-shielding film for light of each wavelength from 400 to 800 nm. Here, the reflectance for each wavelength in the range of 400 to 800 nm was measured using the same method as the reflectance measurement method described above. Here, Example 1 in Figure 20 is a comparative example, in which the light-shielding film was formed from resin. In Example 2, the light-shielding film was formed from a sintered body of a second glass with the same composition as the first glass and a metal oxide pigment, and in Example 3, the light-shielding film was formed from a sintered body of a second glass with the same composition as the first glass and a carbon pigment.

[0080] As shown in Figure 20, in Examples 2 and 3, where the light-shielding film was made of a sintered body of the second glass and pigment, the reflectivity of the light-shielding film was reduced compared to Example 1, where the light-shielding film was made of resin. Therefore, it can be seen that making the light-shielding film of a sintered body of the second glass and pigment is preferable from the viewpoint of reducing the reflectivity of the light-shielding film.

[0081] In this embodiment, it is not necessary to provide a transparent region A1 in the optical element. That is, the light-shielding film may be provided on the entire first surface of the transparent substrate.

[0082] Another embodiment of the optical element is a prism that includes a surface to which light is incident (incident surface) and a surface to which light is emitted (exit surface). Referring to Figure 21, an example of the arrangement of a transparent substrate 20 and a light-shielding film 30 as an optical element (prism) according to another embodiment will be described. In Figure 21, the anti-reflective film 40 is formed on the first surface 21 and the third surface 23, and not on the other surfaces (reflective surface 25 and side surfaces 26, 27). The structure of the anti-reflective film 40 is the same as the anti-reflective film 40 related to the optical element 10 according to the above-described embodiment, and will not be depicted in the drawings described thereafter. The transparent substrate 20 may be triangular prism-shaped and has a first surface 21 and a third surface 23. The first surface 21 is the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20. The third surface 23 is the surface on which light LB is incident from the outside to the inside of the transparent substrate 20, and is perpendicular to the first surface 21. The transparent substrate 20 further has a reflective surface 25 and side surfaces 26 and 27. The reflective surface 25 is a surface that bends the optical path of light LB by total internal reflection. The angle between the reflective surface 25 and the first surface 21, and the angle between the reflective surface 25 and the third surface 23 are acute angles. The side surfaces 26 and 27 are surfaces perpendicular to the first surface 21, the third surface 23, and the reflective surface 25.

[0083] As shown in Figures 21(A), 21(B), and 21(C), a light-shielding film 30 is formed on at least the first surface 21. Preferably, the light-shielding film 30 is formed in a frame shape along the periphery of the first surface 21. In this embodiment, the first surface 21 is the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20, as described above, but it may also be the surface on which light LB is incident from the outside to the inside of the transparent substrate 20.

[0084] As shown in Figure 21(A), a light-shielding film may not be formed on the third surface 23, the reflective surface 25, and the side surfaces 26 and 27. However, as shown in Figure 21(B), a second light-shielding film 50 may be formed on the third surface 23. Preferably, the second light-shielding film 50 is formed in a frame shape along the periphery of the third surface 23. Also, as shown in Figure 21(C), a third light-shielding film 60 may be formed over the entire surface surfaces 26, 27, 28, and 29. The third light-shielding film 60 is formed in the same manner as the light-shielding film 30 and the second light-shielding film 50.

[0085] Referring to Figure 22, an optical element according to another embodiment will be described. The first surface of the transparent substrate 20 has a chamfered portion 22A in addition to the recess 22 formed in a part of the first surface 21. That is, the transparent substrate 20 has a shape in which the edges of the rectangular optical element 10 are chamfered when viewed from the first direction.

[0086] The light-shielding film 30 is provided on the recess 22 and the chamfered portion 22A, and has a second surface 31 that is seamless with the first surface 21 and is formed continuously with the first surface 21. As shown in Figure 22, it is preferable that the light-shielding film 30 has a chamfered covering portion 38. The chamfered covering portion 38 is provided on at least a part (preferably the whole) of the chamfered portion 22A. The thickness of the chamfered covering portion 38 is the same as the thickness of the constant-thickness portion 33, but this is merely an example.

[0087] Referring to Figure 23, an optical element according to another embodiment will be described. As shown in Figure 23, even when the optical element is a prism, it is preferable to provide a chamfered portion 22A on a part of the first surface 21 and a chamfered covering portion 38 of the light-shielding film 30 that covers the chamfered portion 22A. Here, in the optical element according to Figure 23, it is even more preferable that a chamfered portion 22B is provided on the surface connecting the third surface 23 and the reflective surface 25, and a second light-shielding film 50 that covers the chamfered portion 22B is provided. The optical element is triangular prism-shaped in Figure 23, but is not limited to this, and may be polygonal prism-shaped, such as a pentagonal prism. The first surface 21 of the transparent substrate 20 is, for example, the surface on which light LB is emitted from the inside of the transparent substrate 20 to the outside, the third surface 23 of the transparent substrate 20 is, for example, the surface on which light LB is incident from the outside of the transparent substrate 20 to the inside, and the reflective surface 25 of the transparent substrate is, for example, the surface on which light LB is reflected inside the transparent substrate 20. However, the first surface 21 of the transparent substrate 20 may be the surface on which light LB is incident from the outside to the inside of the transparent substrate 20, and the third surface 23 of the transparent substrate 20 may be the surface on which light LB is emitted from the inside to the outside of the transparent substrate 20.

[0088] Referring to Figure 24, a method for manufacturing the optical element 10 according to the fourth modified example will be described. The method for manufacturing the optical element shown in Figure 24 includes steps S101, S102, and S104 shown in Figure 7.

[0089] Step S101 includes preparing a transparent substrate 20, for example, as shown in Figure 24(A). The transparent substrate 20 has a first surface 21 and recesses 22 and chamfered portions 22A formed on a part of the first surface 21. The recesses 22 and chamfered portions 22A are arranged, for example, in a grid pattern. In the example of Figure 24, the chamfered portions 22A are provided by providing grooves along the center of the width of the recesses 22.

[0090] Step S102 includes forming a light-shielding film 30, for example, as shown in Figure 24(B). The light-shielding film 30 is obtained by applying glass paste, degreasing, and firing. The details of the method for obtaining the light-shielding film 30 are the same as those described in step S102 above.

[0091] Step S104 includes cutting the assembled body obtained in step S103 into a plurality of optical elements 10, as shown in Figure 24(C), for example. The cutting includes, for example, blade cutting or laser cutting.

[0092] Step S104 further includes shaping the joined body after cutting it, for example as shown in Figure 24(D). The shaping is, for example, chamfering the edges of the cut surface. This makes it possible to manufacture an optical element having a chamfered covering portion 38 provided on the chamfered portion 22A.

[0093] Referring to Figure 25, a fifth modified example of a method for manufacturing the optical element 10 will be described. The method for manufacturing the optical element shown in Figure 25 includes steps S111, S112, and S104 shown in Figure 9.

[0094] Step S111 involves applying glass pastes 30A and 50A to the first surface 21 of the transparent substrate 20, as shown in Figure 25(A), and then degreasing it. Glass paste 30A is applied to the upper surface of the transparent substrate 20, and glass paste 50A is applied to the lower surface of the transparent substrate 20. This allows for the formation of a light-shielding film 30 from the glass paste 30A and a second light-shielding film 50 from the glass paste 50A.

[0095] In step S112, for example as shown in Figure 25(B), the glass pastes 30A and 50A are sintered, and the sintered light-shielding film 30 and the second light-shielding film 50 are pressed onto the first surface 21 of the heated transparent substrate 20 using a press machine 80 or the like. The first surface 21 of the transparent substrate 20 is thermally deformed, forming a recess 22 on the first surface 21, and the light-shielding film 30 is filled into the recess 22. Here, as shown in Figure 25B, the transparent substrate 20 side of the press machine 80 is provided with linear or grid-shaped protrusions 82. This allows for the formation of a chamfered portion 22A and results in a joined body with grooves. As shown in Figure 25(C), these grooves, along the grooves formed by the protrusions 82, serve as guides for the cutting line in step S104.

[0096] Step S104 includes cutting the bonded body obtained in step S112 into a plurality of optical elements 10, as shown in Figure 25(C), for example. More specifically, as shown in Figure 25(C), the bonded body is cut along the groove formed by the protrusion 82 in the thickness direction of the transparent substrate 20.

[0097] Step S104 further includes shaping the joined body after cutting it, for example as shown in Figure 25(D). Shaping involves, for example, cutting and polishing the transparent substrate 20 to form a reflective surface 25. This makes it possible to manufacture an optical element having a chamfered covering portion 38 provided on the chamfered portion 22A and a second light-shielding film 50.

[0098] Referring to Figure 26, a method for manufacturing the optical element 10 according to the sixth modified example will be described. The method for manufacturing the optical element shown in Figure 26 includes, for example, the step of forming a light-shielding film 30 on both sides of a transparent substrate 20, as shown in Figure 25(A), and step S104. Here, the step of forming a light-shielding film 30 on both sides of the transparent substrate 20 may be either steps S101 and S102 shown in Figure 7, or steps S111 and S112 shown in Figure 9.

[0099] Step S104 includes cutting the bonded body obtained in step S103 into a plurality of optical elements 10, as shown in Figures 26(B) and 26(C), for example. More specifically, first, as shown in Figure 26(B), the bonded body is cut along the thickness direction of the transparent substrate 20, and then, as shown in Figure 26(C), the cut bonded body is fixed to a cutting jig 80A and cut along a direction intersecting the thickness direction of the transparent substrate 20, and then polished. This makes it possible to manufacture optical elements 10 having a reflective surface 25 while suppressing the amount of transparent substrate 20 that is removed and not used as an optical element 10.

[0100] In step S104, for example as shown in Figure 26(D), the edges of the reflective surface 25 are chamfered after the joint is cut. This makes it possible to manufacture an optical element having a chamfered portion 22B.

[0101] Referring to Figure 27, a method for manufacturing the optical element 10 according to the seventh modified example will be described. The method for manufacturing the optical element shown in Figure 27 includes steps S111, S112, and S104 shown in Figure 9.

[0102] Step S111 involves applying glass paste 30A to the first surface 21 of the transparent substrate 20 and degreasing it, for example, as shown in Figure 27(A). The glass paste 30A is applied to both the upper and lower surfaces of the transparent substrate 20. This allows the light-shielding film 30 and the second light-shielding film 50 to be formed from the glass paste 30A.

[0103] Step S112 involves, for example, sintering the glass paste 30A as shown in Figure 27(B), and pressing the sintered light-shielding film 30 onto the first surface 21 of the heated transparent substrate 20 using a press machine 80 or the like. The first surface 21 of the transparent substrate 20 is thermally deformed, forming a recess 22 on the first surface 21, and the light-shielding film 30 fills the recess 22. Here, as shown in Figure 27B, the transparent substrate 20 side of the press machine 80 is provided with linear or grid-shaped protrusions 82 and a second protrusion 83. This allows for the formation of chamfered portions 22A and 22B, and a joined body with grooves is obtained. As shown in Figure 27(C), these grooves serve as guides for the cutting line in step S104.

[0104] Step S104 includes cutting the bonded body obtained in step S112 into a plurality of optical elements 10, as shown in Figure 27(C), for example. More specifically, step S104 includes cutting the bonded body along the groove formed by the protrusion 82 in the thickness direction of the transparent substrate 20, and cutting the bonded body along the groove formed by the second protrusion 83 in a direction intersecting the thickness direction of the transparent substrate 20, as shown in Figure 26(C). This produces a prism with the top surface of the transparent substrate 20 at the time of manufacture on the first surface, and a prism with the bottom surface of the transparent substrate at the time of manufacture on the first surface. Therefore, it is possible to manufacture optical elements 10 having a reflective surface 25 while suppressing the amount of transparent substrate 20 that is not used as an optical element 10 and is removed.

[0105] Step S104 further includes shaping the joined body after cutting it, for example as shown in Figure 27(D). Shaping involves, for example, cutting and polishing the transparent substrate 20 to form a reflective surface 25. This makes it possible to manufacture an optical element having a chamfered covering portion 38 provided on the chamfered portion 22A and a second light-shielding film 50.

[0106] The optical element, camera optical unit, and method for manufacturing the optical element described above have been explained, but this disclosure is not limited to the embodiments described above. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These also naturally fall within the technical scope of this disclosure.

[0107] For example, in the method for manufacturing an optical element according to the fourth to seventh modified examples shown in Figures 24 to 27, an anti-reflective film may be formed during any of the steps after the formation of the light-shielding film.

[0108] 2 Camera optical unit 3 Optical system 5 Camera sensor 10 Optical element 20 Transparent substrate 21 First surface 22 Recess 30 Light-shielding film 31 Second surface

Claims

1. An optical element comprising: a transparent substrate having a first surface and a recess formed in a part of the first surface; a light-shielding film provided in the recess and having a second surface that is seamless with respect to the first surface and is formed continuously with respect to the first surface; and an anti-reflective film that is formed continuously across both the first surface and the second surface.

2. The optical element according to claim 1, wherein the maximum value ΔRmax of the difference ΔR (ΔR = |R1 - R2|) calculated for each wavelength from 400 to 800 nm between the reflectance R1 (%) of the portion formed on the first surface of the anti-reflective film and the reflectance R2 (%) of the portion formed on the second surface of the anti-reflective film is 1% or less.

3. The optical element according to claim 1, wherein the transparent substrate includes a first glass.

4. The optical element according to claim 1, wherein the light-shielding film includes a second glass.

5. The optical element according to claim 1, wherein the light-shielding film is a sintered body of a second glass and a pigment, and the pigment includes a carbon-based material.

6. The optical element according to claim 1, wherein the light-shielding film is a sintered body of a second glass and a pigment, and the pigment includes a metal oxide containing at least one of copper, chromium, manganese, iron, cobalt, and titanium.

7. The optical element according to claim 1, wherein the transparent substrate includes a first glass and the light-shielding film includes a second glass.

8. The optical element according to claim 7, wherein the first glass and the second glass have the same composition, and the light-shielding film is a sintered body of the second glass and a pigment.

9. The optical element according to claim 1, wherein the light-shielding film has a lower transmittance in a second direction perpendicular to the second surface as the distance from the boundary line between the first surface and the second surface increases, at least in part of the boundary line between the first surface and the second surface.

10. The optical element according to claim 1, wherein the extinction coefficient of the light-shielding film increases as the depth from the second surface increases.

11. The optical element according to claim 1, wherein the first surface and the second surface are planar.

12. The optical element according to claim 1, wherein the first surface and the second surface are curved surfaces.

13. An optical element comprising: a transparent substrate having a first surface and including a first glass; and a light-shielding film having a second glass and provided on at least a portion of the first surface, wherein the first glass and the second glass have the same composition, and the light-shielding film is a sintered body of the second glass and a pigment.

14. The optical element according to claim 13, wherein the light-shielding film includes a carbon-based material as the pigment.

15. The optical element according to claim 13, wherein the light-shielding film contains a metal oxide as the pigment, comprising at least one of copper, chromium, manganese, iron, cobalt, and titanium.

16. An optical unit for a camera, comprising an optical system for imaging light onto a camera sensor, wherein the optical system has an optical element as described in any one of claims 1 to 15.

17. An optical element according to any one of claims 1 to 15, which is a prism having a surface into which light is incident and a surface from which the light is emitted.

18. A method for manufacturing an optical element, comprising the step of providing a light-shielding film containing a second glass on at least a portion of the first surface of a transparent substrate containing a first glass, wherein the first glass and the second glass have the same composition, and in the step of providing the light-shielding film, the second glass and a pigment are sintered to form the light-shielding film.

19. The method for manufacturing an optical element according to claim 18, wherein in the step of providing the light-shielding film, the light-shielding film is formed on at least a portion of the upper surface and at least a portion of the lower surface included in the first surface.

Images