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

Abstract

The present invention provides an optical element unit with high environmental resistance and positional accuracy, a method for manufacturing the optical element unit, and an optical instrument. [Solution] An optical element unit comprising a first optical element and a second optical element, wherein the first optical element and the second optical element are joined via a joint formed by solid-state bonding of inorganic material between the peripheral edge of the first optical element and the peripheral edge of the second optical element, and a hollow portion is provided inside the peripheral edges between the joined first optical element and the second optical element.

Description

[Technical Field]

[0001] This disclosure relates to an optical element unit that combines multiple optical elements. [Background technology]

[0002] Optical element units, which integrate multiple optical elements such as lenses, mirrors, filters, and sensors, are widely used in cameras, telescopes, microscopes, cameras in portable electronic products, and image sensor modules. To improve the imaging performance of these optical element units, high positional accuracy is required when assembling the optical elements into a single unit.

[0003] Patent Document 1 describes an image sensor module in which, in order to perform high-precision imaging control and obtain images of excellent quality, multiple spacers are provided between the bonding layers when bonding lenses or when bonding lenses to an image sensor chip, thereby improving positional accuracy.

[0004] Patent Document 2 discloses a method for manufacturing an optical element unit in which two or more transparent resin lenses are bonded together, in which at least one transparent resin lens contains an infrared absorbing agent, and infrared light is irradiated onto the joint to weld and bond it to the other lens. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-195167 [Patent Document 2] Japanese Patent Publication No. 2005-292441 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Conventional lens bonding methods had issues in terms of environmental resistance and optical properties. [Means for solving the problem]

[0007] The purpose of this disclosure is to provide an optical element unit that has high environmental resistance and good optical properties.

[0008] An optical element unit as one embodiment of the present disclosure, which is a means for solving the above problems, is an optical element unit including a first optical element and a second optical element, wherein the first optical element and the second optical element are joined via a joint formed by solid-state bonding of inorganic material between the peripheral edge of the first optical element and the peripheral edge of the second optical element, and a hollow portion is provided inside the peripheral edges between the joined first optical element and the second optical element.

[0009] Furthermore, one embodiment of the present disclosure is a method for manufacturing an optical element unit, which involves joining a first optical element and a second optical element at their respective peripheral edges, comprising the steps of: preparing a first optical element and a second optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one of the joining surfaces of the first optical element and the second optical element; and joining the prepared first optical element and second optical element at their peripheral edges such that a hollow portion is provided between the first optical element and the second optical element on the inside of the peripheral edge.

[0010] Furthermore, one embodiment of the present disclosure is a method for manufacturing an optical element unit, comprising the steps of: preparing a first optical element, a second optical element, and a third optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one joining side surface of the first optical element and the second optical element, and another inorganic layer is provided in a region including the peripheral edge of at least one joining side surface of the second optical element and the third optical element; and joining the prepared first optical element, second optical element, and third optical element at their respective peripheral edges such that a hollow portion is provided between the first optical element and the second optical element, and further between the second optical element and the third optical element. Furthermore, an optical device as one aspect of the present disclosure includes a plurality of optical components, including the optical element unit, and a holding component for holding the plurality of optical components. [Effects of the Invention]

[0011] This disclosure provides a technology that is advantageous for realizing an optical element unit with high environmental resistance and good optical properties. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of the optical element unit relating to this disclosure. [Figure 2] (a) A schematic diagram showing an example of an inorganic film for bonding optical elements in this disclosure; (b) A cross-sectional view showing an example of an optical element unit in this disclosure; (c) A schematic diagram showing an inorganic film of an optical element unit in this disclosure; (d) A schematic diagram showing another example of an inorganic film for bonding optical elements in this disclosure; (e) A cross-sectional view showing another example of an optical element unit in this disclosure; and (f) A schematic diagram showing an inorganic film of an optical element unit of another example in this disclosure. [Figure 3] This is a schematic diagram of an optical element unit including an anti-reflective coating according to the present disclosure. [Figure 4] Cross-sectional SEM image of an optical element unit bonded with an inorganic film according to the present disclosure. [Figure 5] Schematic diagram of a vacuum film-forming apparatus in the present disclosure. [Figure 6] Schematic diagram of a bonding apparatus in the present disclosure. [Figure 7] Schematic diagram of a vacuum film-forming and bonding apparatus in the present disclosure. [Figure 8] Schematic diagram showing an example of an optical device according to the present disclosure.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In the following description and drawings, common configurations across multiple drawings are denoted with common reference numerals. Therefore, common configurations will be described by referring to multiple drawings mutually, and descriptions of configurations with common reference numerals will be omitted as appropriate.

[0014] In bonding using an adhesive, shrinkage occurs when the adhesive cures, making it difficult to achieve positional accuracy. Also, when used in a harsh environment such as a high-temperature and high-humidity environment or in an environment with large temperature and humidity changes, in addition to moisture absorption and drying of the adhesive, the thickness of the adhesive layer changes due to deterioration and alteration. Further, when welding a lens with infrared rays, the influence of environmental changes is smaller compared to the case of using an adhesive, but when welding, the lens melts, causing deformation at that time and a slight misalignment when melting and bonding. Therefore, it is difficult to achieve positional accuracy less than the order of μm. Also, since the optical element is limited to a resin material that absorbs infrared rays, it is difficult to select an optical system.

[0015] The optical element unit according to this disclosure includes a first optical element and a second optical element, wherein the first optical element and the second optical element are joined via a joint formed by solid-phase bonding of inorganic material between the peripheral edge of the first optical element and the peripheral edge of the second optical element, and a hollow portion is provided inside the peripheral edges between the joined first optical element and the second optical element. Furthermore, the optical element unit according to this disclosure may further include a third optical element, wherein the second optical element and the third optical element may be joined via a joint formed by solid-phase bonding of other inorganic material between the peripheral edge of the second optical element and the peripheral edge of the third optical element. In this case, another hollow portion may be provided inside the peripheral edges between the joined second optical element and the third optical element. That is, the optical element unit according to this disclosure may include three or more optical elements.

[0016] Figure 1 shows a schematic cross-sectional view of the optical element unit 100 according to this embodiment. The optical element unit 100 consists of two or more optical elements, and the example shown in Figure 1 shows an example of an optical element unit 100 consisting of optical elements 101a, 101b, 101c, 101d, and 101e. Optical elements 101a and 101b are bonded together via a joint 102a formed by solid-state bonding of inorganic material between the periphery of the optically effective area of ​​optical element 101a and the periphery of the optically effective area of ​​optical element 101b. Similarly, optical elements 101b and 101c, optical element 101c and 101d, and optical element 101d and 101e are bonded together via joints 102b, 102c, and 102d formed on the periphery of each optical element. In this example, optical elements 101a and 101b may be designated as the first and second optical elements, or any other adjacent optical elements may be designated as the first and second optical elements. Furthermore, any optical element adjacent to any second optical element may be designated as the third optical element. In this case, the joints 102a, 102b, 102c, and 102d may be solid-state bonding of glass, for example, if the optical elements are glass lenses.

[0017] Furthermore, optical elements 101a and 101b have a hollow portion 103a between them, with at least a portion of it separated except for the joint (periphery). Similarly, optical elements 101b and 101c, optical elements 101c and 101d, and optical elements 101d and 101e also have hollow portions 103b, 103c, and 103d. In this example, hollow portions 103a, 103b, 103c, and 103d are provided at the optical axis position of the optical element unit 100.

[0018] Furthermore, the hollow sections 103a, 103b, 103c, and 103d, which are covered by the optical elements 101a, 101b, 101c, 101d, and 101e, are maintained at a lower humidity than the atmospheric environment (the space outside the optical element unit). Specifically, the absolute humidity by weight of the hollow sections can be set to 2 g / kg or less.

[0019] The joint can be an inorganic film formed by solid-state bonding between an inorganic layer provided on the periphery of the first optical element and an inorganic layer provided on the periphery of the second optical element. Here, the state of being joined is different from a state where the inorganic layers of the two optical elements with inorganic layers attached are merely in surface contact with each other. The state of being joined means, for example, that when a force is applied to separate the first optical element (e.g., optical element 101a) and the second optical element (e.g., optical element 101b), they have an adhesive strength that prevents them from being separated by a force of at least 0.05 N (5 g). As an evaluation method, the joined first optical element can be suspended, and a weight can be attached to the second optical element and suspended from it to check whether the two joined optical elements can be separated. Another simple evaluation method is to check that the optical element unit can be held as a whole (each optical element does not fall apart) using only the optical element unit without the optical elements or the lens barrel for holding the optical element unit.

[0020] The joint can be located at the periphery of the first optical element and the second optical element, in a region that is not the optically effective area. When the joint is an inorganic film formed by solid-state bonding of inorganic layers provided at the periphery of each optical element as described above, the inorganic film can include at least one selected from the group consisting of metal films, oxide films, nitride films, and fluoride films. Dielectric films (insulating films), such as oxide films, nitride films, and fluoride films, are particularly suitable because they have high melting points, high heat resistance, and low coefficients of thermal expansion, resulting in higher environmental resistance and smaller displacement compared to metal films. Dielectric films are also suitable because they form stronger covalent or ionic bonds compared to metallic bonds, and they have high oxygen and moisture barrier properties. The dielectric film may contain at least one selected from SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, AlN, Si3N4, and SiOC. Using an oxide containing carbon atoms or hydrogen atoms as the dielectric film is more preferable because it facilitates bonding between films at the junction interface via the carbon atoms. Figures 2(a) and 2(d) show schematic diagrams of an optical element with an inorganic film formed on it, viewed from the optical axis direction, and Figures 2(b) and 2(e) show cross-sectional views of the optical element joined by the inorganic film. Figures 2(c) and 2(f) show enlarged views of the junction. First, using Figures 2(a) and 2(b), the inorganic film formation region for joining optical elements 201a and 201b will be explained. The peripheral portion 203 of the optical element represents the outer peripheral portion of the optically effective area 202 through which light is transmitted to the optical element. Here, as one embodiment of the inorganic film 204 used to join two optical elements, as shown in Figures 2(a) and (b), the inorganic film 204 (shown by a wave pattern) is formed on the entire surface of the outer peripheral portion 203 of the optically effective area 202 and joined to form an optical element unit 200. The joining portion is explained in Figure 2(c). The inorganic film 204 is formed by joining the solid phases of the inorganic layer 206a on the optical element 201a and the inorganic layer 206b on the optical element 201b.Unlike bonding using liquid-phase materials such as adhesives or solder, inorganic films are solid materials, and therefore the distance of the bonded portion (the distance between the first optical element and the second optical element) bonded via the inorganic film 204 is determined by the total thickness of the inorganic layers 206a and 206b and is kept constant. The bonding surface does not need to have the same surface area as the inorganic layer 206a on optical element 201a and the inorganic layer 206b on optical element 201b, as long as the predetermined bonding strength is ensured. Another embodiment is described in Figures 2(d) and (e). Regarding the inorganic film formation region for bonding optical elements 211a and 211b, an inorganic film 214 (shown by a wave pattern) may be formed on a portion of the peripheral edge 213 outside the optically effective area 212 of the optical element to form an optical element unit 210. The bonded portion is described in Figure 2(f). The inorganic film 214 may be formed in a form where a portion of the film surface is joined, such as the inorganic layer 216a on the optical element 211a and the inorganic layer 216b on the optical element 211b. As shown in Figures 2(c) and 2(f), a void may exist between the inorganic layer 216a on the optical element 211a and the inorganic layer 216b on the optical element 211b. Also, as shown in Figures 2(c) and 2(f), a void may exist between the inorganic layer 216a on the optical element 211a and the optical element 211b, and a void may exist between the inorganic layer 216b on the optical element 211b and the optical element 211a. Alternatively, an inorganic layer may be formed over the entire surface of the optical elements to be joined, and then joined only through the periphery. However, in all embodiments, the first optical element and the second optical element are closed off by the joining portion (inorganic film), forming a hollow portion covered by the two optical elements and isolated from the external space. Here, areas where light unintended by the original optical design is transmitted due to scattering or multiple reflections between optical elements are not defined as the optically effective area. The thickness of the bonding portion (inorganic film) can be 0.1 nm or more and less than 1 μm. The materials of the first and second optical elements are not limited. Whether they are made of the same material or different materials, bonding can be achieved by forming an inorganic layer on the surface of the optical elements and bonding them via the inorganic film.

[0021] By making the humidity in the hollow sections 205 and 215 lower than that of the external space around the optical element units 200 and 210, condensation can be suppressed. This also suppresses the deterioration of the inorganic films 204 and 214 at the joints and the optical elements 201a, 201b, 211a, and 211b due to the effects of moisture, and also suppresses the decrease in imaging performance due to moisture absorption. Furthermore, the pressure in the hollow sections 205 and 215 can be lower than atmospheric pressure (e.g., 101325 Pa), and it is preferable to have a pressure below atmospheric pressure (e.g., 101325 Pa). A higher vacuum can reduce the absolute humidity by gravity, which has the effect of lowering the saturated water vapor pressure, and is advantageous in suppressing condensation. In addition, an external force due to atmospheric pressure is applied to the entire circumference of the optical element units 200 and 210, which strengthens the bonding between the optical elements and allows for sealing. Furthermore, it is preferable from the viewpoint of suppressing condensation that the pressure in the hollow sections be 1 / 10 or less of atmospheric pressure (e.g., 101325 Pa). The pressure in the hollow sections 205 and 215 should be such that the external force resulting from the pressure difference with the pressure in the external space surrounding the optical element units 200 and 210 is less than or equal to the external force that does not cause deformation of the optical element units 200 and 210. The pressure in the hollow sections should be, for example, 1 × 10⁻⁶. -6 It can be set to Pa or higher.

[0022] For example, if you want to set the pressure of the hollow section to between 10 Pa and atmospheric pressure, the following method can be considered. Use a rotary pump or dry pump as a vacuum pump to evacuate the chamber containing the optical elements to be joined to a vacuum of several Pa. Then, stop the vacuum pump and gradually increase the pressure by supplying CDA (clean dry air) or nitrogen gas while monitoring the pressure with a Pirani vacuum gauge or similar. For example, if you want to set the pressure of the hollow section to 100 Pa, stop the gas supply when the pressure reaches 100 Pa and join the optical elements together. -6 If you want to reduce the pressure to less than 10 Pa, use a rotary pump or dry pump as a vacuum pump to evacuate to a few Pa, and then use a cryopump that can adsorb moisture to further reduce the pressure to 10 Pa. -6The system is evacuated to a vacuum of Pa. Then, the vacuum pump is stopped, and while monitoring the pressure with an ion gauge or similar device, clean dry air (CDA) or nitrogen gas is introduced while controlling the flow rate with a mass flow controller to gradually increase the pressure. For example, if the pressure in the hollow section is to be 1 Pa, the gas supply should be stopped once the pressure reaches 1 Pa, and the optical elements should be joined together.

[0023] The optical element unit according to this disclosure may have an anti-reflective coating between the joint and at least one of the first optical element and the second optical element. In the outer (periphery) areas 203 and 213 of the optically effective area as explained in Figure 2, light unintended in the original optical design may be incident on the inorganic film 204 and inorganic film 214 due to scattering and multiple reflections between optical elements. In this case, the light may be reflected by the inorganic film 204 and inorganic film 214, causing adverse effects such as flare and ghosting at the image plane. Therefore, it is desirable to form an anti-reflective coating between the inorganic film 204 and the optical elements 201a and 201b to suppress flare and ghosting caused by light reflected by the inorganic film.

[0024] Figure 3 shows a schematic diagram of a cross-section of the joint of an optical element unit including an anti-reflective coating. In the optical element unit 300 shown in Figure 3, an anti-reflective coating 303a is formed between the optical element 301a and the inorganic film 302, and an anti-reflective coating 303b is formed between the optical element 301b and the inorganic film 302. This configuration suppresses the reflection of light between the optical element and the inorganic film, thereby suppressing the generation of flare and ghosting. Alternatively, the joint may extend between the hollow portion and at least one of the first optical element and the second optical element, functioning as an anti-reflective coating in the optical path. The inorganic film 302 may also function as part or all of the anti-reflective coating 303a or the anti-reflective coating 303b. Alternatively, it may form either the anti-reflective coating 303a or the anti-reflective coating 303b. Furthermore, a dielectric film is preferred as the anti-reflective film, and when the anti-reflective film also serves as the junction, a dielectric film with low light absorption is preferred as the junction (inorganic film), including SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, Si3N4, SiOC, and compounds or mixtures thereof.

[0025] A manufacturing method for an optical element unit according to this disclosure is a method for manufacturing an optical element unit by joining a first optical element and a second optical element at their respective peripheral edges, comprising the steps of: preparing a first optical element and a second optical element, each having an inorganic layer provided in a region including the peripheral edge of at least one of the joining surfaces of the first optical element and the second optical element; and joining the prepared first optical element and second optical element at their peripheral edges such that a hollow portion is provided between the first optical element and the second optical element on the inside of the peripheral edge. The joining step can be performed in a vacuum (below atmospheric pressure (101325 Pa)). Furthermore, the hollow portion can be manufactured to have a lower humidity than the atmospheric environment. Furthermore, the method for manufacturing an optical element according to this disclosure may include the steps of: arranging a first optical element and a second optical element in an apparatus; and forming an inorganic layer in a region including the peripheral edges of the arranged first optical element and second optical element. Furthermore, the present disclosure provides a method for manufacturing an optical element unit, comprising the steps of: preparing a first optical element, a second optical element, and a third optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one joining side of the first optical element and the second optical element, and another inorganic layer is provided in a region including the peripheral edge of at least one joining side of the second optical element and the third optical element; and joining the prepared first optical element, second optical element, and third optical element at their respective peripheral edges, such that a hollow portion is provided inside the peripheral edge between the first optical element and the second optical element, and further between the second optical element and the third optical element.

[0026] This document describes an example of a manufacturing apparatus and method for manufacturing optical element units in a low-humidity (low-pressure) environment. Figure 5(a) shows a schematic diagram of a vacuum deposition apparatus. The vacuum deposition apparatus 500 consists of a deposition chamber 501, a vacuum pump 502, an evaporation source 503, an assist source 504, and an optical element holding mechanism 505. Two or more optical elements 506, including optical elements 506a and 506b, are held in the optical element holding mechanism 505 and are subjected to 10° by the vacuum pump 502. -5 ~10 -4The system is evacuated to approximately Pa. After evacuating, the evaporation source 503 is heated by an electron beam or resistance heating to evaporate the film material 508, and an inorganic layer is formed on the optical elements 506a and 506b with assistance from ions 509 emitted from the assist source 504. To form the inorganic layer for bonding to the periphery of the optically effective area, the deposition is carried out while shielding with shielding plates 507 (507a, 507b). Figure 5(b) shows a top view of the optical element 506 and the shielding plate 507. By installing the shielding plate 507 so as to cover the center of the optical element 506, the center of the optical element can be shielded, and an inorganic layer can be formed on the periphery of the optically effective area of ​​the optical element 506. In this embodiment, Cr was deposited on a synthetic quartz substrate as an inorganic layer on the optical element 506 in the order of 5 nm and Au in the order of 10 nm. After film deposition, the deposition chamber 501 is vented to return to atmospheric pressure, and then the optical element 506 with the inorganic layer deposited is removed.

[0027] After removing the optical element 506, which has an inorganic layer deposited on it, from the vacuum deposition apparatus 500, bonding is performed using a bonding apparatus 600 for bonding multiple optical elements together.

[0028] The bonding apparatus will be explained using Figures 6(a) and 6(b). Figure 6(a) is a schematic diagram showing a cross-section of the bonding apparatus 600, and (b) is a schematic diagram showing a view from above. In Figure 6(b), heaters, electrodes, etc. are omitted from the illustration for ease of understanding. The bonding apparatus 600 consists of a bonding chamber 601, a preparation chamber 602, and a gate valve 603. The bonding chamber 601 is maintained in an environment where a vacuum of several tens of Pa to several hundreds of Pa is constantly maintained by a vacuum pump 604a. First, two or more optical elements to be bonded are placed in the preparation chamber 602. Next, the preparation chamber 602 is evacuated by a vacuum pump 604b. Once the environments of the bonding chamber 601 and the preparation chamber 602 are roughly the same, the gate valve 603 is opened, and the optical elements prepared in the preparation chamber 602 are transferred one by one to the bonding chamber 601 using a transfer hand 605. After transferring to the bonding chamber 601, the gate valve 603 is closed. Then, Ar gas is supplied to the bonding chamber 601 from the Ar gas supply line 608, and a voltage is applied to the electrode 610 to generate plasma, thereby performing a surface activation treatment on the inorganic layer 607a formed on the optical element 607 that has been transferred to the bonding chamber 601. Depending on the material of the inorganic layer 607a, the optical element 607 may also be heated to about 150°C to 200°C using the heater 611 to increase the bonding strength.

[0029] Once the surface treatment of optical element 607 is complete, the voltage applied to electrode 610 is stopped, and the supply of Ar gas from Ar gas supply line 608 is stopped. The gate valve 603 is opened again, and the other optical element to be joined, 606, is transported from preparation chamber 602 to joining chamber 601 using transport hand 605. Optical element 606 is placed on top of optical element 607, which has been transported and surface activated first, and the crimping arm 612 is lowered to join the two optical elements 606 and 607. After that, the gate valve 603 is closed, and the next optical element is similarly surface activated and transported to joining chamber 601 and joined with crimping arm 612. This process is repeated, thereby joining optical element units consisting of two or more optical elements. By using the above joining apparatus 600, it is possible to manufacture optical element units in which the first optical element and the second optical element are joined at their respective peripheries via an inorganic layer 607a, with the hollow portion 607b between the optical elements at or below atmospheric pressure. The pressure and humidity in the hollow section 607b can also be adjusted by stopping the vacuum pump 604a and supplying nitrogen from the nitrogen gas supply line 609 while only adjusting the opening of the exhaust line just before joining the optical elements.

[0030] Next, a manufacturing apparatus and method that integrates the formation of an inorganic layer and the bonding of optical element units will be described. Figures 7(a) and 7(b) show schematic diagrams of a vacuum deposition bonding apparatus that integrates a vacuum deposition apparatus and a bonding apparatus. The vacuum deposition bonding apparatus 700 consists of a deposition chamber 701, a bonding chamber 702, and a gate valve 703. The deposition chamber 701 is maintained in an environment that is constantly kept under vacuum at several Pa to several tens of Pa by a vacuum pump 704a. First, two or more undeposited optical elements 706 to be bonded are placed in the bonding chamber 702. Next, the bonding chamber 702 is evacuated by a vacuum pump 704b. Once the environments of the deposition chamber 701 and the bonding chamber 702 are roughly equal, the gate valve 703 is opened, and the undeposited optical elements 706 prepared in the bonding chamber 702 are transferred one by one to the deposition chamber 701 using a transfer hand 705. After sequentially transferring all undeposited optical elements 706 to the optical element holder 708 in the deposition chamber 701, the gate valve 703 is closed. The deposition chamber 701 is an ALD deposition apparatus, and gases 710 such as raw material gas and oxidizer are supplied from the gas supply line 709. In this example, only one gas supply line is shown, but the raw material gas supply line and the oxidizing gas supply line that supplies the oxidizing agent are usually configured as two separate lines to prevent the raw material gas and oxidizing gas from reacting in the piping and depositing a film inside the piping. For example, using SAM24 as the raw material gas and a high-concentration ozone of 85% or more as the oxidizing agent, an SiO2 film can be deposited on the entire surface of the optical element at a substrate temperature of 75°C. In the ALD deposition method, one atomic layer is deposited in a cycle consisting of four steps: raw material gas supply, purging, oxidizing gas supply, and purging. This cycle is repeated to deposit a 10 nm SiO2 film as an inorganic layer 707a on the substrate. For this substrate, for example, ZEONEX (trademark) can be used. After film deposition, the gate valve 703 is opened, and the optical elements with the inorganic layer 707a deposited are stacked one by one into the bonding chamber 702 using the transport hand 705. After all the deposited optical elements 707 have been transported, the gate valve is closed, the crimping arm 712 is lowered, and the optical elements 707 are bonded together in a vacuum at room temperature.

[0031] By using the vacuum deposition bonding apparatus 700 described above, an optical element unit can be manufactured in which a first optical element and a second optical element are bonded together via solid-state bonding of inorganic material formed on their respective peripheries, while the hollow section is at or below atmospheric pressure. The pressure and humidity in the hollow section 707b can also be adjusted by stopping the vacuum pump 704b and supplying nitrogen from the nitrogen gas supply line 711 while only adjusting the opening of the exhaust line just before bonding each optical element.

[0032] [Other embodiments] It should be noted that this disclosure is not limited to the embodiments and examples described above, and many modifications are possible within the technical concept of this disclosure.

[0033] This disclosure is broadly applicable to coatings of optical elements, including lenses, filters, mirrors, prisms, image sensors, and displays. Furthermore, it can be used in various optical devices such as cameras, interchangeable lenses, and portable electronic devices that are equipped with an optical element unit. The optical devices according to this disclosure may have the optical unit according to this disclosure. These optical devices may be equipped with a holding component (lens barrel) that holds the multiple optical components in addition to the optical elements. By providing the optical element unit according to this disclosure, imaging performance can be improved and environmental resistance can be enhanced. Figure 8 is a schematic diagram showing an example of an optical device according to this disclosure. Camera 800 has a main body 801, an interchangeable lens 802, and an optical element unit 803 according to this disclosure.

[0034] The embodiments described above can be modified as appropriate without departing from the technical concept. For example, multiple embodiments can be combined. Furthermore, some aspects of at least one embodiment can be deleted or replaced. Furthermore, new aspects can be added to at least one embodiment.

[0035] Furthermore, the disclosures in this specification include not only what is explicitly stated herein, but also all matters that can be understood from this specification and the drawings attached thereto. In addition, the disclosures in this specification include the complement of the individual concepts described herein. That is, if this specification states, for example, "A is B," then even if the description of the case where "A is not B" is omitted, this specification can be said to disclose the case where "A is not B." This is because the statement "A is B" presupposes that the case where "A is not B" is being considered. [Examples]

[0036] [Examples 1-3, Comparative Examples 1 and 2] Examples 1 to 3 based on the embodiments of this disclosure will be described. Three types of optical element units were prepared by depositing SiO2 as an inorganic layer of 10 nm on the periphery of two synthetic quartz optical elements by vacuum deposition, and then joining them while varying the humidity and pressure of the hollow space inside the periphery. Specifically, when joining in atmospheric pressure, the optical elements were placed in a constant temperature and humidity chamber where the temperature and humidity could be kept constant, stabilized for a certain period of time, and then joined together to achieve the desired humidity in the hollow space. When joining in a vacuum, the optical elements to be joined were placed in a chamber connected to a vacuum pump, and the chamber was evacuated using the vacuum pump to create a vacuum. During pressure adjustment, the vacuum pump was stopped, and while monitoring the pressure with a vacuum gauge, the flow rate was controlled with a flow meter, and CDA (clean dry air) or nitrogen gas was introduced. When the pressure on the vacuum gauge reached a predetermined pressure, the gas supply was stopped, and the optical elements were joined. This resulted in obtaining an optical element unit having a hollow space with the desired humidity and pressure. Vacuum deposition was performed using a Synchron BMC850, as is commonly done, by evaporating SiO2 granules placed in a crucible as an evaporation source with an electron beam, and then depositing a film on the periphery of the optical element using a shielding plate while ion-assisted with Ar gas and O2 gas.

[0037] As comparative examples, two optical element units each having a hollow portion in which the peripheral portions of two synthetic quartz were joined with an epoxy-based adhesive to a thickness of about 2 μm were prepared.

[0038] Regarding the humidity and pressure in the hollow portion of the joined optical element unit, the presence and relative amounts of N2, O2, and H2O were evaluated from the intensity at the Raman wavelength by applying light of the third harmonic of a YAG laser with a wavelength of 355 nm from the outside and measuring the Raman scattered light. Table 1 shows the wavelengths and relative intensities of Raman scattering during irradiation with laser light of wavelength 355 nm. MR, I H2O 、I N2 represent the absolute humidity by weight (g / kg) of the hollow portion, the Raman intensities of H2O and N2, and MR0, I 0-H2O 、I 0-N2 represent the absolute humidity by weight (g / kg) outside each optical element unit, the Raman intensities of H2O and N2, respectively. Regarding the pressure, the correlation between the intensity at the Raman wavelength of N2 and the pressure obtained with a Pirani vacuum gauge was obtained and calibrated, and the pressure value calculated from the Raman intensity of N2 was used.

Equation

[0039] [Table 1]

[0040] As an evaluation of the bonded optical element units, a high-temperature and high-humidity test was conducted using an ESPEC SH-642 environmental tester under conditions of 70°C, 80% humidity, and 50 hours, and the changes in appearance were evaluated. Units without bleeding at the joint were classified as A, and those with bleeding were considered to have misalignment and were classified as C. In addition, the temperature difference at which condensation occurred when rapidly cooled from room temperature (25°C) was evaluated, and units with a temperature of 60°C or higher were classified as A, units with a temperature between 30°C and 60°C were classified as B, and units with a temperature below 30°C were classified as C. Table 2 shows the bonding agent, bonding thickness, weight of the hollow portion, absolute humidity and pressure, and evaluation results for the optical elements manufactured in Examples 1 to 3 and Comparative Examples 1 and 2.

[0041] [Table 2]

[0042] From the results of Examples 1 to 3 and Comparative Examples 1 and 2, it can be seen that optical element units bonded via an inorganic film performed without problems in high temperature and high humidity tests, and that those with low humidity and low pressure in the hollow section could suppress condensation over a wide temperature range.

[0043] Although synthetic quartz was used as the glass material for the optical element, it is not limited to this; any glass, resin lens, or film capable of forming a solid-phase bond with inorganic materials may be used. Furthermore, different types of glass may be used for the optical elements being bonded.

[0044] Furthermore, if the bonding portion is provided on the surface of the optical element and is located only outside (at the periphery) of the optically effective area through which light is transmitted to the optical element, it may be made of a light-absorbing material. The bonding portion (inorganic film) that joins the two optical elements is not limited to those described in the examples, and may be a metallic film such as Au, Pt, Ag, Ti, Al, W, or Si; an oxide film such as Al2O3, SiO2, SiOx, MgO, Y2O3, ZrO2, or Nb2O5; a nitride film such as AlN, Si3N4, or TiN; or a fluoride film such as AlF3, MgF2, or LaF3.

[0045] [Examples 4-7 and Comparative Example 3] Examples 4 to 7 and Comparative Example 3 based on the embodiments of this disclosure will be described. Al2O3 was deposited as an inorganic layer on the periphery of two synthetic quartz sheets by atomic layer deposition (ALD) and then joined together. A Samco AD-1 was used as the atomic layer deposition apparatus, with trimethylaluminum (TMA) as the raw material gas and H2O as the oxidizing agent. The raw material gas was supplied for 20 ms, purged for 10 s, the oxidizing agent was supplied for 20 ms, and purged for 10 s, for 1 cycle, 100 cycles, 1000 cycles, 4000 cycles, and 5000 cycles to deposit the film.

[0046] [Table 3]

[0047] Figure 4 shows a cross-sectional SEM image of Example 7, in which two optical elements are joined with an inorganic film. Cross-sectional SEM observation was performed by cutting the optical element unit with an isomed, polishing the cross-section, and then observing it with a GeminiSEM560 at an acceleration voltage of 1kV. In Figure 4, 400 represents an optical element unit in which two optical elements are joined via an inorganic film. In this example, optical elements 401a and 401b, which are synthetic silica lenses, were used as the two optical elements, and the thickness of the bonding material of the optical element unit joined via an Al2O3 film as the inorganic film 402 was evaluated to be 232 nm. The thickness and bonding state were evaluated in the same manner for the other examples and comparative examples. To evaluate the bonding state, one optical element was suspended from each optical element unit, and a weight was placed so that a force of 0.05 N was applied to the other optical element. Those that did not peel apart were given an A rating, and those that peeled apart were given a C rating.

[0048] The surface roughness of the inorganic layer was evaluated using an atomic force microscope (AFM). As shown in Examples 4 to 7, it can be confirmed that good bonding is possible if the surface roughness is less than 1 nm.

[0049] Furthermore, if the inorganic film thickness is 2 atomic layers or more (0.2 nm or more), the optical elements can be bonded well. It is desirable that the surface roughness of the two optical elements 401a and 401b to be bonded, and the surface roughness of the inorganic layer formed on optical elements 401a and 401b, be small. When the surface roughness is small, the surfaces of the two optical elements 401a and 401b make proper contact when bonding them, so the bonding surface area increases and the bonding strength increases. In order to ensure sufficient bonding strength, it is desirable that the surface roughness of optical elements 401a and 401b with the inorganic layer attached be sufficiently small. Surface roughness Ra < 1 nm is desirable, and Ra < 0.5 nm is even more preferable. Generally, as the thickness of the inorganic layer deposited on the optical element increases, the surface roughness increases. For this reason, it is desirable that the thickness of the inorganic film 402 be less than 1 μm.

[0050] This embodiment includes the following configurations and methods. (Composition 1) In an optical element unit including a first optical element and a second optical element, The first optical element and the second optical element are joined together via a joint formed by solid-state bonding of inorganic material between the peripheral edge of the first optical element and the peripheral edge of the second optical element. An optical element unit characterized in that a hollow portion is provided inside the peripheral edge between the joined first optical element and the second optical element. (Configuration 2) The optical element unit according to configuration 1, characterized in that the bonding portion is an inorganic film formed by solid-phase bonding of an inorganic layer provided on the peripheral edge of the first optical element and an inorganic layer provided on the peripheral edge of the second optical element. (Composition 3) The optical element unit according to configuration 2, characterized in that the inorganic film includes at least one selected from the group consisting of a metal film, an oxide film, a nitride film, and a fluoride film. (Composition 4) The optical element unit according to configuration 2, characterized in that the inorganic film is a dielectric film. (Composition 5) The optical element unit according to claim 4, characterized in that the dielectric film includes at least one selected from the group consisting of an oxide film, a nitride film, and a fluoride film. (Composition 6) The optical element unit according to configuration 5, characterized in that the oxide film contains carbon atoms and hydrogen atoms. (Composition 7) The optical element unit according to configuration 4, characterized in that the dielectric film includes at least one selected from SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, AlN, Si3N4, and SiOC. (Composition 8) The optical element unit according to any one of configurations 1 to 7, characterized in that the hollow portion has lower humidity than the atmospheric environment. (Composition 9) The optical element unit according to any one of configurations 1 to 8, characterized in that the joint portion is provided in a region that is not an optically effective area, which is the peripheral portion of the first optical element and the second optical element. (Composition 10) The optical element unit according to any one of configurations 1 to 9, wherein the hollow portion is provided at the optical axis position of the optical element unit. (Composition 11) The optical element unit according to any one of configurations 1 to 10, characterized in that the hollow portion has a weight absolute humidity of 2 g / kg or less. (Composition 12) The optical element unit according to any one of configurations 1 to 11, characterized in that a dielectric film is provided between the joint and at least one of the first optical element and the second optical element. (Composition 13) The optical element unit according to any one of configurations 1 to 12, characterized in that the joint portion extends between the hollow portion and at least one of the first optical element and the second optical element. (Composition 14) The optical element unit according to any one of configurations 1 to 13, characterized in that the thickness of the bonding portion is 0.1 nm or more and less than 1 μm. (Composition 15) The optical element unit according to any one of configurations 1 to 14, characterized in that the hollow portion is at a pressure below atmospheric pressure. (Composition 16) The optical element unit further comprises a third optical element, The optical element unit according to any one of configurations 1 to 15, characterized in that the second optical element and the third optical element are joined via a joint formed by solid-phase bonding of other inorganic materials between the peripheral edge of the second optical element and the peripheral edge of the third optical element. (Composition 17) The optical element unit according to configuration 16, characterized in that another hollow portion is provided inside the peripheral portion between the joined second optical element and the third optical element. (Method 18) A method for manufacturing an optical element unit, comprising joining a first optical element and a second optical element at their respective peripheral edges, A step of preparing the first optical element and the second optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one of the joining surfaces of the first optical element and the second optical element, The process involves joining the prepared first optical element and the second optical element by joining their peripheral edges such that a hollow portion is provided on the inside of the peripheral edge between the first optical element and the second optical element. A method for manufacturing an optical element unit, characterized by having the following features. (Method 19) The method for manufacturing an optical element unit according to method 18, characterized in that the bonding step is performed in a vacuum. (Method 20) The method for manufacturing an optical element unit according to method 18 or 19, characterized in that the hollow portion has lower humidity than the atmospheric environment. (Method 21) The aforementioned preparation steps are: The process involves arranging the first optical element and the second optical element within the apparatus, A step of forming the inorganic layer in a region including the peripheral edges of the arranged first optical element and second optical element, A method for manufacturing an optical element unit according to any one of methods 18 to 20, characterized by having the following: (Method 22) A method for manufacturing an optical element unit, comprising joining a first optical element, a second optical element, and a third optical element at their respective peripheral edges, A step of preparing the first optical element, the second optical element, and the third optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one joining surface of the first optical element and the second optical element, and another inorganic layer is provided in a region including the peripheral edge of at least one joining surface of the second optical element and the third optical element, The process involves joining the prepared first optical element, second optical element, and third optical element such that a hollow portion is provided on the inside of the peripheral edge between the first optical element and the second optical element, and between the second optical element and the third optical element. A method for manufacturing an optical element unit, characterized by having the following features. (Composition 23) Multiple optical components including an optical element unit as described in any of configurations 1 to 17, An optical device characterized by having a holding component for holding the plurality of optical components. [Explanation of Symbols]

[0051] 100...Optical element unit 101a, 101b, 101c, 101d, 101e... Optical elements 102a, 102b, 102c, 102d...junction 103a, 103b, 103c, 103d...Hollow part 200, 210... Optical element unit 201a, 201b, 211a, 211b... Optical elements 202, 212... Optical effective area, 203, 213... Peripheral area 204, 214... Inorganic films 206a, 206b, 216a, 216b...Inorganic layer 300... Optical element unit 301a, 301b... Optical elements 302... Inorganic film 303a, 303b...Anti-reflective coating 400... Optical element unit 401a, 401b... Optical elements 402... Inorganic film 500...Vacuum deposition equipment 501...Deposition chamber 502... Vacuum pump 503... Evaporation source 504... Assist source 505... Optical element holding mechanism 506...Optical elements 507...Shielding plate 508...Membrane materials 509...Assist Ion 600...Joining equipment 601...Joining chamber 602...Preparation room 603...Gate valve 604... Vacuum pump 605... Conveyor Hand 606, 607... Optical elements 608···Ar gas supply line 609... Nitrogen gas supply line 610...electrode 611... Heater 612... Crimping Arm 700...Vacuum film forming bonding equipment 701...Deposition chamber 702...Joining chamber 703...Gate valve 704... Vacuum pump 705... Conveyor Hand 706, 707... Optical elements 708... Optical element holder 709... Gas supply line 710...gas 711... Nitrogen gas supply line 712... Crimping Arm

Claims

1. In an optical element unit including a first optical element and a second optical element, The first optical element and the second optical element are joined together via a joint formed by solid-state bonding of inorganic material between the peripheral edge of the first optical element and the peripheral edge of the second optical element. An optical element unit characterized in that a hollow portion is provided inside the peripheral edge between the joined first optical element and the second optical element.

2. The optical element unit according to claim 1, characterized in that the bonding portion is an inorganic film formed by solid-phase bonding of an inorganic layer provided on the peripheral edge of the first optical element and an inorganic layer provided on the peripheral edge of the second optical element.

3. The optical element unit according to claim 2, characterized in that the inorganic film includes at least one selected from the group consisting of a metal film, an oxide film, a nitride film, and a fluoride film.

4. The optical element unit according to claim 2, characterized in that the inorganic film is a dielectric film.

5. The optical element unit according to claim 4, characterized in that the dielectric film includes at least one selected from the group consisting of an oxide film, a nitride film, and a fluoride film.

6. The optical element unit according to claim 5, characterized in that the oxide film contains carbon atoms and hydrogen atoms.

7. The dielectric film is SiO ２ , Al ２ O ３ , Nb ２ O ５ , Ta ２ O ５ , HfO ２ , MgO, Y ２ O ３ , ZrO ２ , ZnO, MgF ２ , AlF ３ , AlN, Si ３ N ４ The optical element unit according to claim 4, characterized in that it contains at least one selected from SiO, Al ２ O ３ , Nb ２ O ５ , Ta ２ O ５ , HfO ２ , MgO, Y ２ O ３ , ZrO ２ , ZnO, MgF ２ , AlF ３ , AlN, Si ３ N ４ , and SiOC.

8. The optical element unit according to claim 1, characterized in that the hollow portion has lower humidity than the atmospheric environment.

9. The optical element unit according to claim 1, characterized in that the joint portion is provided in a region that is not an optically effective area, which is the peripheral portion of the first optical element and the second optical element.

10. The optical element unit according to claim 1, wherein the hollow portion is provided at the optical axis position of the optical element unit.

11. The optical element unit according to claim 1, characterized in that the hollow portion has a weight absolute humidity of 2 g / kg or less.

12. The optical element unit according to claim 1, characterized in that a dielectric film is provided between the joint and at least one of the first optical element and the second optical element.

13. The optical element unit according to claim 1, characterized in that the joint portion extends between the hollow portion and at least one of the first optical element and the second optical element.

14. The optical element unit according to claim 1, characterized in that the thickness of the bonding portion is 0.1 nm or more and less than 1 μm.

15. The optical element unit according to claim 1, characterized in that the hollow portion is at a pressure below atmospheric pressure.

16. The optical element unit further comprises a third optical element, The optical element unit according to claim 1, characterized in that the second optical element and the third optical element are joined via a joint formed by solid-state bonding of other inorganic materials between the peripheral edge of the second optical element and the peripheral edge of the third optical element.

17. The optical element unit according to claim 16, characterized in that another hollow portion is provided inside the peripheral portion between the joined second optical element and the third optical element.

18. A method for manufacturing an optical element unit, comprising joining a first optical element and a second optical element at their respective peripheral edges, A step of preparing the first optical element and the second optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one of the joining surfaces of the first optical element and the second optical element, The process involves joining the prepared first optical element and the second optical element by joining their peripheral edges such that a hollow portion is provided on the inside of the peripheral edge between the first optical element and the second optical element, A method for manufacturing an optical element unit, characterized by having the following features.

19. The method for manufacturing an optical element unit according to claim 18, characterized in that the bonding step is performed in a vacuum.

20. The method for manufacturing an optical element unit according to claim 18, characterized in that the hollow portion has lower humidity than the atmospheric environment.

21. The aforementioned preparation steps are: The process involves arranging the first optical element and the second optical element within the apparatus, A step of forming the inorganic layer in a region including the peripheral edges of the arranged first optical element and second optical element, A method for manufacturing an optical element unit according to claim 18, characterized by having the following features.

22. A method for manufacturing an optical element unit, comprising joining a first optical element, a second optical element, and a third optical element at their respective peripheral edges, A step of preparing the first optical element, the second optical element, and the third optical element, wherein an inorganic layer is provided in a region including the peripheral edge of at least one joining surface of the first optical element and the second optical element, and another inorganic layer is provided in a region including the peripheral edge of at least one joining surface of the second optical element and the third optical element, The process involves joining the prepared first optical element, second optical element, and third optical element such that a hollow portion is provided on the inside of the peripheral edge between the first optical element and the second optical element, and between the second optical element and the third optical element. A method for manufacturing an optical element unit, characterized by having the following features.

23. A plurality of optical components including the optical element unit described in any one of claims 1 to 17, An optical device characterized by having a holding component for holding the plurality of optical components.

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