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

Abstract

The invention relates to an optical element unit, a method for manufacturing the optical element unit, and an optical apparatus. Provided is an optical element unit including a first optical element and a second optical element, in which the first optical element and the second optical element are bonded to each other by interposing a bonding portion formed by solid-phase bonding of an inorganic substance between a peripheral edge portion of the first optical element and a peripheral edge portion of the second optical element, and wherein the optical element unit has a hollow portion formed on an inner side of the peripheral portion between the first optical element and the second optical element joined to each other.

Description

Technical Field

[0001] This disclosure relates to an optical element unit comprising a plurality of optical elements. Background Technology

[0002] Optical element units, which combine and integrate multiple optical elements including lenses, mirrors, filters, and sensors, are widely used in cameras, telescopes, microscopes, and portable electronic products, and even in image sensor modules.

[0003] In recent years, in order to improve the imaging performance of optical element units, it is necessary to unify optical elements with high positional accuracy.

[0004] In Japanese Patent Application Publication No. 2007-195167, in order to perform high-precision imaging control and obtain images of excellent quality in an image sensor module, multiple spacers are provided between the bonding layers to improve positional accuracy when bonding lenses together or bonding lenses to an image sensor chip.

[0005] Japanese Patent Application Publication No. 2005-292441 discloses a method for manufacturing an optical element unit that bonds two or more transparent resin lenses together. The method involves using a lens containing an infrared absorber as at least one of the transparent resin lenses, and irradiating the joint with infrared light to fuse and join the lens with another lens. Summary of the Invention

[0006] This disclosure relates to providing an optical element unit with high environmental resistance and good optical properties.

[0007] To address the aforementioned problems, according to one aspect of this disclosure, an optical element unit is provided, comprising a first optical element and a second optical element, wherein the first optical element and the second optical element are joined together by means of a joint formed by solid-state bonding of an inorganic material between the peripheral portions of the first optical element and the peripheral portions of the second optical element, and wherein the optical element unit has a hollow portion formed inside the peripheral portion between the joined first optical element and the second optical element.

[0008] According to another aspect of this disclosure, a method for manufacturing an optical element unit by joining a first optical element and a second optical element at their peripheral portions is provided. The method includes: preparing a first optical element and a second optical element, wherein an inorganic layer is disposed in a region of a peripheral portion including a joining side surface of at least one of the first optical element and the second optical element; and joining the peripheral portions of the prepared first optical element and the second optical element to form a hollow portion between the first optical element and the second optical element, inside the peripheral portion.

[0009] According to another aspect of this disclosure, a method for manufacturing an optical element unit by joining a first optical element, a second optical element, and a third optical element at their peripheral portions is provided. The method includes: preparing the first optical element, the second optical element, and the third optical element, wherein an inorganic layer is disposed in a region of a peripheral portion including a joining side surface of at least one of the first optical element and the second optical element, and another inorganic layer is disposed in a region of a peripheral portion including a joining side surface of at least one of the second optical element and the third optical element; and joining the peripheral portions of the prepared first optical element, second optical element, and third optical element to form a hollow portion between the first optical element and the second optical element and further between the second optical element and the third optical element, inside the respective peripheral portions.

[0010] According to another aspect of this disclosure, an optical device including the aforementioned optical element unit is provided.

[0011] Referring to the accompanying drawings, the features of this disclosure will become apparent from the following description of embodiments. The following description of embodiments is illustrated by way of example. Attached Figure Description

[0012] Figure 1 This is a schematic cross-sectional view of an optical element unit according to the present disclosure.

[0013] Figure 2A This is a schematic diagram illustrating an example of an inorganic film used for bonding optical elements in this disclosure.

[0014] Figure 2B This is a cross-sectional view used to illustrate an example of an optical element unit according to the present disclosure.

[0015] Figure 2C This is a schematic diagram illustrating an example of an inorganic film for an optical element unit in this disclosure.

[0016] Figure 2D This is a schematic diagram illustrating another example of an inorganic film used for bonding optical elements in this disclosure.

[0017] Figure 2E This is a cross-sectional view used to illustrate another example of an optical element unit according to the present disclosure.

[0018] Figure 2F This is a schematic diagram illustrating another example of an inorganic film for an optical element unit in this disclosure.

[0019] Figure 3 This is a schematic diagram illustrating an optical element unit including an anti-reflective film in this disclosure.

[0020] Figure 4This is a cross-sectional SEM image of an optical element unit obtained by means of inorganic film bonding in this disclosure.

[0021] Figure 5A This is a schematic diagram of the vacuum film-forming equipment disclosed herein.

[0022] Figure 5B This is a top view of the optical element (506) and the shielding plate (507).

[0023] Figure 6A This is a schematic diagram illustrating a cross-section of the joining device in this disclosure.

[0024] Figure 6B This is a schematic diagram illustrating the state of the coupling device in this disclosure as viewed from top.

[0025] Figure 7A This is a schematic diagram illustrating a cross-section of the vacuum film deposition bonding apparatus of this disclosure.

[0026] Figure 7B This is a schematic diagram illustrating the state of the vacuum film deposition bonding apparatus in this disclosure as viewed from above.

[0027] Figure 8 This is a schematic diagram illustrating an example of an optical device according to the present disclosure. Detailed Implementation

[0028] Embodiments of this disclosure are described below with reference to the accompanying drawings. In the following description and drawings, common components in multiple drawings are indicated by the same reference numerals. Therefore, multiple drawings are referenced to each other to describe common components, and descriptions of components indicated by the same reference numerals are appropriately omitted.

[0029] In bonding applications using adhesives, the adhesive shrinks during curing, making it difficult to improve positional accuracy. Furthermore, in harsh environments, such as those with high temperature and humidity, or those with large temperature or humidity variations, the thickness of the adhesive layer changes not only due to the adhesive's moisture absorption and drying, but also due to its deterioration and degradation. Additionally, while the effects of environmental changes are reduced when using infrared fusion lenses compared to adhesive-based bonding, the lens melts during fusion, causing deformation and slight positional shifts during subsequent bonding. Therefore, achieving positional accuracy below the micrometer level is difficult. Moreover, the optical elements are limited to infrared-absorbing resin materials, making the selection of the optical system challenging.

[0030] The optical element unit according to this disclosure includes a first optical element and a second optical element, wherein the first and second optical elements are joined together by means of a joint formed by solid-state bonding of an inorganic material between the peripheral portions of the first and second optical elements, and the optical element unit has a hollow portion formed inside the peripheral portion between the joined first and second optical elements. Furthermore, the optical element unit according to this disclosure may further include a third optical element, and the second and third optical elements may be joined together by means of a joint formed by solid-state bonding of another inorganic material between the peripheral portions of the second and third optical elements. In this case, another hollow portion may be formed inside the peripheral portion between the joined second and third optical elements. That is, the optical element unit according to this disclosure may include three or more optical elements.

[0031] Figure 1 This is a schematic cross-sectional view of the optical element unit 100 according to this embodiment. The optical element unit 100 includes two or more optical elements. Figure 1 An example of an optical element unit 100 including optical elements 101a, 101b, 101c, 101d, and 101e is shown. Optical elements 101a and 101b are bonded together by intervening a joint 102a formed by solid-state bonding of inorganic materials between the peripheral portions of the optically effective regions of optical elements 101a and 101b. Similarly, optical elements 101b and 101c, 101c and 101d, and 101d and 101e are bonded together by intervening joints 102b, 102c, and 102d formed at the peripheral portions of each optical element, respectively. In this example, optical elements 101a and 101b can be used as a first optical element and a second optical element, respectively, or other adjacent optical elements can be used as a first optical element and a second optical element. Furthermore, any optical element adjacent to the second optical element can be used as a third optical element. In this case, the joints 102a, 102b, 102c, and 102d can be solid-state joints between glass elements, for example, when the optical element is a glass lens.

[0032] Furthermore, optical elements 101a and 101b include a hollow portion 103a between them, wherein at least a portion other than the joining portion 102a (peripheral portion) is separate. Similarly, optical elements 101b and 101c, 101c and 101d, and 101d and 101e also include hollow portions 103b, 103c, and 103d, respectively. In this example, the hollow portions 103a, 103b, 103c, and 103d are formed at the optical axis position of the optical element unit 100.

[0033] The hollow portions 103a, 103b, 103c, and 103d covering the optical elements 101a, 101b, 101c, 101d, and 101e maintain a humidity level lower than that of the atmospheric environment (the space outside the optical element unit). Specifically, the hollow portions can be set to have a weight-absolute humidity of less than 2 g / kg.

[0034] The joint can be an inorganic film formed by solid-state bonding between an inorganic layer disposed on the periphery of the first optical element and an inorganic layer disposed on the periphery of the second optical element. The bonding state as used herein is considered different from a state in which the inorganic layers of two optical elements with attached inorganic layers are only in contact with each other on their surfaces. The bonding state refers to a state with such adhesive strength that, for example, when a force is applied to peel off the first optical element (e.g., optical element 101a) and the second optical element (e.g., optical element 101b), the optical elements will not peel off even with a force of at least 0.05 N (5 g). As an evaluation method, the first optical element is suspended while the second optical element is suspended with a weight placed on it. At this time, the two bonded optical elements are checked to see if they have peeled off for evaluation. Furthermore, as another simple evaluation method, it is possible to check whether the optical element units are in a state where they can be held together (the optical elements are not separated) simply by using the optical elements themselves or by using an optical element unit without a lens barrel for holding the optical element unit.

[0035] The bonding portion can be located in a region situated at the periphery of the first and second optical elements and outside the optically effective region. When the bonding portion is an inorganic film formed by solid-state bonding between inorganic layers disposed at the periphery of the respective optical elements as described above, the inorganic film may include at least one selected from the group consisting of metal films, oxide films, nitride films, and fluoride films. In particular, dielectric films (insulator films), represented by oxide films, nitride films, and fluoride films, have high melting points and therefore high heat resistance and a small coefficient of thermal expansion. Therefore, dielectric films (insulator films) are suitable because they have higher environmental resistance and can reduce positional displacement more significantly compared to metal films. Furthermore, dielectric films are also suitable because they are formed by bonding through covalent or ionic bonds with high bond strength, as stronger bonding and higher oxygen and moisture barrier properties can be achieved compared to metallic bonds. The dielectric film may contain at least one of SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, AlN, Si3N4, and SiOC. Furthermore, oxide films containing both carbon and hydrogen atoms are more suitable because such films are more likely to bond at the interface via carbon atom bonding sites. Figure 2A and Figure 2D It is a diagram used to illustrate the state of an inorganic film formed on an optical element as observed from the optical axis direction, and Figure 2B and Figure 2E This is a cross-sectional view of an optical element formed by bonding together the aforementioned inorganic films. Figure 2C and Figure 2F This is an enlarged view used to show the joint. First, refer to... Figure 2A and Figure 2B This describes the formation region of the inorganic film used to bond optical elements 201a and 201b to each other. The peripheral portion 203 of the optical element refers to the peripheral portion outside the optically effective region 202 of the optical element through which light is transmitted. In this case, as... Figure 2A and Figure 2B As shown, as one embodiment of the inorganic film 204 for joining two optical elements together, the optical element unit 200 is formed by forming and joining the inorganic film 204 (represented by a waveform pattern) on the entire surface of the peripheral portion 203 outside the optically effective region 202. Figure 2CThis is an explanatory diagram illustrating the joint. An inorganic film 204 is formed between the inorganic layer 206a on optical element 201a and the inorganic layer 206b on optical element 201b by solid-state bonding. Unlike bonding using liquid-phase materials such as adhesives or solders, the inorganic film is a solid material. Therefore, the distance of the joint (the gap between the first and second optical elements) formed by intervening in the inorganic film 204 is defined by the total film thickness of the inorganic layers 206a and 206b, and is characterized by maintaining a constant distance. Even if the surface areas of the inorganic layer 206a on optical element 201a and the inorganic layer 206b on optical element 201b do not match, only the bonding surfaces need to ensure the predetermined bonding strength described above. Furthermore, Figure 2D and Figure 2E This is an illustrative diagram illustrating another embodiment. The optical element unit 210 can be formed by forming and bonding an inorganic film 214 (represented by a waveform pattern) in a portion of the peripheral portion 213 outside the optically effective region 212 of the optical element in the region of the inorganic film forming region for bonding optical elements 211a and 211b to each other. Figure 2F This is an explanatory diagram illustrating the joint. The inorganic film 214 can be formed such that portions of the film surfaces are bonded to each other, as in the inorganic layer 216a on optical element 211a and the inorganic layer 216b on optical element 211b. Figure 2C and Figure 2F As shown, an air gap may exist between the inorganic layer 216a on optical element 211a and the inorganic layer 216b on optical element 211b. Furthermore, as... Figure 2C and Figure 2F As shown, an air gap may exist between the inorganic layer 216a on optical element 211a and optical element 211b, and an air gap may also exist between the inorganic layer 216b on optical element 211b and optical element 211a. Furthermore, bonding can be achieved through peripheral intervention only, where the inorganic layer is formed over the entire surface of the optical elements to be bonded. However, in any embodiment, it is considered that the first and second optical elements form a hollow portion, which is enclosed by the bonding portion (inorganic film) and covers both optical elements to isolate them from the external space. In this case, the area that transmits light undesired in the original optical design due to scattering or multiple reflections between the optical elements is not defined as the optically effective area. The film thickness of the bonding portion (inorganic film) can be set to be greater than 0.1 nm and less than 1 μm. The first and second optical elements can be formed of any material. Regardless of whether the materials are the same or different, the optical elements can be bonded to each other through the intervention of the inorganic film by forming an inorganic layer on the surface of the optical element.

[0036] By forming the hollow portions 205 and 215 with a humidity level lower than that of the external space of the optical element units 200 and 210, condensation can be suppressed. Furthermore, the degradation of the inorganic films 204 and 214 at the joints and the optical elements 201a, 201b, 211a, and 211b due to moisture absorption can be suppressed, as well as the reduction in imaging performance due to moisture absorption. Additionally, the hollow portions 205 and 215 can be set to have a pressure equal to or less than atmospheric pressure (e.g., 101,325 Pa), preferably less than atmospheric pressure (e.g., 101,325 Pa). A higher vacuum reduces the absolute humidity by weight and has the effect of reducing the saturated water vapor pressure, thus being effective in suppressing condensation. Furthermore, by applying a force from the outside through atmospheric pressure to the entire circumference of each of the optical element units 200 and 210, the optical elements are further joined together, thereby achieving a seal. Furthermore, from the viewpoint of suppressing condensation, it is preferable that the hollow portion has a pressure equal to or less than 1 / 10 of atmospheric pressure (e.g., 101,325 Pa). It is desirable that the pressure of each of the hollow portions 205 and 215 has a pressure difference with the pressure of the external space of each of the optical element units 200 and 210, such that the external force caused by the pressure difference is equal to or less than the external force that would not cause deformation of each of the optical element units 200 and 210. The pressure of the hollow portion can be set, for example, to 1 × 10⁻⁶ Pa. -6 Pa or above.

[0037] For example, when it is desired to set the pressure of the hollow section to be above 10 Pa but below atmospheric pressure, the following method can be considered. A rotary pump or dry pump is used as a vacuum pump, and the interior of the chamber containing the optical elements to be joined is evacuated to a vacuum of several Pascals. Afterward, the vacuum pump is stopped, and while monitoring the pressure using a Pirani vacuum gauge or similar device, the pressure is gradually increased by supplying clean, dry air (CDA) or nitrogen. For example, when it is desired to set the pressure of the hollow section to 100 Pa, the gas supply can be stopped when the pressure reaches 100 Pa, and then the optical elements can be joined together. Furthermore, for example, when it is desired to set the pressure of the hollow section from 10 Pa... -6 When the pressure drops from Pa to less than 10 Pa, after evacuating the chamber to a vacuum of several Pascals using a rotary pump or dry pump, the chamber is further evacuated to 10 Pascals using a cryogenic pump capable of absorbing moisture. -6 A vacuum of Pa is established. The vacuum pump is then stopped, and while monitoring the pressure with an ionization vacuum gauge, the pressure is gradually increased by introducing clean, dry air (CDA) or nitrogen at a minute flow rate controlled by a mass flow controller. For example, when it is desired to set the pressure of the hollow section to 1 Pa, the gas supply can be stopped when the pressure reaches 1 Pa, and then the optical elements can be joined together.

[0038] According to this disclosure, the optical element unit may include an anti-reflective film between the junction and at least one of the first and second optical elements. Furthermore, in reference... Figures 2A to 2F The outer (peripheral) portions 203 and 213 of the described optically effective regions are subject to incident light that is undesirable in the original optical design due to scattering or multiple reflections between optical elements. These situations include light being reflected by the inorganic film 204 or 214, causing adverse effects such as glare and ghosting on the imaging surface. Therefore, it is desirable to form an antireflective film between the inorganic film 204 and the optical element 201a or 201b to suppress glare and ghosting caused by light reflected from the inorganic film.

[0039] Figure 3 This is a schematic diagram illustrating a cross-section of the joint of an optical element unit including an anti-reflective film. Figure 3 In the illustrated optical element unit 300, an antireflective film 303a is formed between the optical element 301a and the inorganic film 302, and an antireflective film 303b is formed between the optical element 301b and the inorganic film 302. With this configuration, light reflected between the optical element and the inorganic film can be suppressed, thereby suppressing glare and ghosting. The junction can extend between the hollow portion and at least one of the first and second optical elements to function as an antireflective film in the optical path. Furthermore, the inorganic film 302 can also serve as part or all of the antireflective film 303a or the antireflective film 303b. Additionally, either the antireflective film 303a or the antireflective film 303b can be formed. Furthermore, the dielectric film is preferably used as an antireflective film, and when the junction is also used as an antireflective film, the junction (inorganic film) is preferably a dielectric film with a small light absorption rate, such as films of SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, Si3N4, SiOC, films of their compounds, or films of mixtures thereof.

[0040] The method for manufacturing 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 peripheral portions, and includes: preparing a first optical element and a second optical element, wherein an inorganic layer is disposed in a region of a peripheral portion including a joining side surface of at least one of the first optical element and the second optical element; and joining the peripheral portions of the prepared first optical element and the second optical element to form a hollow portion between the first optical element and the second optical element, inside the peripheral portion. The joining can be performed in a vacuum (at a pressure less than atmospheric pressure (101,325 Pa)). Furthermore, the optical element unit can be manufactured such that the humidity of the hollow portion is lower than the humidity of the atmospheric environment. In addition, in the method for manufacturing an optical element unit according to this disclosure, the preparation may include: disposing the first optical element and the second optical element in a device; and forming an inorganic layer in a region including the respective peripheral portions of the disposed first optical element and the second optical element.

[0041] Furthermore, the manufacturing method for manufacturing an optical element unit according to this disclosure can be a method for manufacturing an optical element unit by joining a first optical element, a second optical element, and a third optical element at their peripheral portions, and may include: preparing a first optical element, a second optical element, and a third optical element, wherein an inorganic layer is provided in a region of a peripheral portion including a joining side surface of at least one of the first optical element and the second optical element, and another inorganic layer is provided in a region of a peripheral portion including a joining side surface of at least one of the second optical element and the third optical element; and joining the peripheral portions of the prepared first optical element, second optical element, and third optical element to form a hollow portion between the first optical element and the second optical element and further between the second optical element and the third optical element, on the inner side of their respective peripheral portions.

[0042] Examples of manufacturing equipment and methods for manufacturing optical element units in low humidity (low pressure) environments are described. Figure 5A This is a schematic diagram illustrating a vacuum film deposition apparatus. The vacuum film deposition apparatus 500 includes a film deposition chamber 501, a vacuum pump 502, an evaporation source 503, an auxiliary source 504, and an optical element holding mechanism 505. Two or more optical elements 506, including optical elements 506a and 506b, are held by the optical element holding mechanism 505 and are evacuated by the vacuum pump 502 to a vacuum level of approximately 10. -5 Pa to approximately 10 -4Pa. After vacuuming, the evaporation source 503 is heated by electron beam or resistance heating to evaporate the film material 508. With the assistance of ions 509 emitted from the auxiliary source 504, an inorganic layer is formed on each of the optical elements 506a and 506b. In order to form an inorganic layer for bonding at the periphery of the optically effective region, film formation is performed while shielding with shielding plates 507 (507a, 507b). Figure 5B This is a top view of the optical element 506 and the shielding plate 507. When the shielding plate 507 is installed 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 at the periphery of the optically effective area of ​​the optical element 506. In this embodiment, Cr and Au are deposited as inorganic layers as described above on a synthetic quartz substrate used as the optical element 506, with thicknesses of 5 nm and 10 nm, respectively. After film formation, the film formation chamber 501 is vented and the pressure is restored to atmospheric pressure, and then the optical element 506 with the inorganic layer formed thereon is removed.

[0043] After the optical element 506, on which the inorganic layer is formed, is removed from the vacuum film forming apparatus 500, it is joined by a joining apparatus 600 for joining multiple optical elements together.

[0044] refer to Figure 6A and Figure 6B Describe the coupling device. Figure 6A This is a schematic diagram illustrating a cross-section of the joining device 600, and Figure 6B This is a schematic diagram illustrating the state of the engagement device 600 as viewed from above. Figure 6B For ease of understanding, illustrations of heaters and electrodes are omitted. The bonding apparatus 600 includes a bonding chamber 601, a preparation chamber 602, and a gate valve 603. The bonding chamber 601 is maintained in a vacuum environment of tens to hundreds of Pascals by a vacuum pump 604a. First, two or more optical elements to be bonded are mounted in the preparation chamber 602. Next, the preparation chamber 602 is evacuated by a vacuum pump 604b. When the environments of the bonding chamber 601 and the preparation chamber 602 become substantially identical, 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 the transfer 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. This generates plasma to perform surface activation treatment on the inorganic layer 607a formed on the optical element 607 transferred to the bonding chamber 601. Furthermore, depending on the material of the inorganic layer 607a, the optical element 607 can be heated to about 150°C to about 200°C using a heater 611 to enhance the bonding strength.

[0045] After the surface treatment of optical element 607 is completed, the voltage applied to electrode 610 is stopped, and the Ar gas supply from Ar gas supply line 608 is stopped. Gate valve 603 is reopened, and another optical element 606 to be joined is conveyed from preparation chamber 602 to joining chamber 601 using conveyor arm 605. Optical element 606 is stacked on top of the previously conveyed and surface-activated optical element 607, and crimping arm 612 is lowered, so that the two optical elements 606 and 607 are joined together. Thereafter, gate valve 603 is closed, and surface activation is performed similarly. The next optical element is conveyed to joining chamber 601 and joined using crimping arm 612. This operation is repeated to allow joining optical element units comprising two or more optical elements. By using the aforementioned bonding device 600, an optical element unit can be manufactured in which a first optical element and a second optical element are bonded to each other at their periphery through the intervention of an inorganic layer 607a, while the hollow portion 607b between the optical elements is subjected to a pressure equal to or less than atmospheric pressure. The pressure and humidity of the hollow portion 607b can also be regulated by stopping the vacuum pump 604a and supplying nitrogen from the nitrogen supply line 609 immediately before bonding the optical elements, while only adjusting the opening degree of the exhaust line.

[0046] Next, a manufacturing apparatus and manufacturing method integrating the formation of inorganic layers and the bonding of optical element units will be described. Figure 7A and Figure 7BThis is a schematic diagram illustrating a vacuum film deposition and bonding apparatus in which the vacuum film deposition equipment and bonding equipment are integrated. The vacuum film deposition and bonding apparatus 700 includes a film deposition chamber 701, a bonding chamber 702, and a gate valve 703. The film deposition chamber 701 is maintained in a vacuum environment of several to tens of Pascals by a vacuum pump 704a. First, two or more undepositioned optical elements 706 to be bonded are installed in the bonding chamber 702. Next, the bonding chamber 702 is evacuated by a vacuum pump 704b. When the environments of the film deposition chamber 701 and the bonding chamber 702 become substantially identical, the gate valve 703 is opened, and the undepositioned optical elements 706 prepared in the bonding chamber 702 are transferred one by one to the film deposition chamber 701 using a transfer hand 705. After all the undepositioned optical elements 706 have been sequentially transferred to the optical element holding stage 708 in the film deposition chamber 701, the gate valve 703 is closed. The film deposition chamber 701 is an ALD film deposition apparatus, and a gas 710, such as a feed gas or an oxidant, is supplied from the gas supply line 709. In this example, the number of gas supply lines is described as one, but typically the feed gas supply line and the oxidizing gas supply line for supplying the oxidant are separated into two lines to avoid film deposition in the piping due to the reaction between the feed gas and the oxidizing gas in the piping. For example, using SAM24 as the feed gas and using a high concentration of ozone (over 85%) as the oxidant allows a SiO2 film to be formed on the entire surface of the optical element at a substrate temperature of 75°C. In the ALD film deposition method, the four steps of feed gas supply, purging, oxidizing gas supply, and purging are considered as one cycle to form an atomic layer. This cycle is repeated to form a 10 nm thick SiO2 film as an inorganic layer 707a on the substrate. For example, ZEONEX (trademark) can be used as the substrate. After film formation, gate valve 703 is opened, and optical elements, each having an inorganic layer 707a formed thereon, are stacked one by one in bonding chamber 702 using conveyor arm 705. After all the film-formed optical elements 707 have been conveyed, gate valve is closed, and crimping arm 712 is lowered, so that the optical elements 707 are bonded to each other in a vacuum at room temperature.

[0047] By using the vacuum film 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 to each other through solid-phase bonding of inorganic material formed at their peripheries, while the hollow portion is subjected to a pressure equal to or less than atmospheric pressure. The pressure and humidity of the hollow portion 707b can also be regulated by stopping the vacuum pump 704a and supplying nitrogen from the nitrogen supply line 711 immediately before bonding the optical elements, while only adjusting the opening degree of the exhaust line.

[0048] [Other Implementation Plans]

[0049] This disclosure is not limited to the above-described implementation schemes and examples, and many modifications can be made to them within the technical concept of this disclosure.

[0050] This disclosure is broadly applicable to coatings on optical elements such as lenses, filters, mirrors, prisms, imaging elements (image sensors), or display elements (displays). Furthermore, this disclosure is applicable to optical devices that include optical element units, such as various cameras, interchangeable lenses, or portable electronic devices. Optical devices according to this disclosure may include optical element units according to this disclosure. In addition to multiple optical components including optical element units, these optical devices may also include holding components (lens barrels) for holding the multiple optical components. By assembling optical element units according to this disclosure, imaging performance can be improved, and environmental resistance can also be enhanced. Figure 8 This is a schematic diagram illustrating an example of an optical device according to the present disclosure. The camera 800 includes a main body 801, an interchangeable lens 802, and an optical element unit 803 according to the present disclosure.

[0051] Without departing from the technical concept, the above implementation schemes can be appropriately modified. For example, multiple implementation schemes can be combined. Furthermore, a portion of at least one implementation scheme can be deleted or replaced. Additionally, new elements can be added to at least one implementation scheme.

[0052] The disclosure in this specification includes not only what is explicitly stated herein, but also all matters that can be understood from this specification and the accompanying drawings. Furthermore, the disclosure in this specification includes the complementary set of the various concepts described herein. That is, for example, when this specification states "A is B," even if the statement "A is not B" is omitted, it is considered that the statement "A is not B" is disclosed. This is because when "A is B" is stated, the statement "A is not B" is taken into account as a premise.

[0053] [Example]

[0054] [Examples 1-3 and Comparative Examples 1 and 2]

[0055] Embodiments 1 to 3 based on the present disclosure are described. At the periphery of each of two optical elements made of synthetic quartz, a SiO2 film of 10 nm thickness is formed as an inorganic layer by vacuum evaporation. Three types of optical element units were prepared, wherein bonding was performed while varying the humidity and pressure of the hollow portion inside the periphery. Specifically, when bonding was performed at atmospheric pressure, the optical elements were placed in a constant temperature and humidity chamber capable of maintaining constant temperature and humidity for a certain period. The optical elements were then bonded together, resulting in a hollow portion with the desired humidity. When bonding was performed in a vacuum, the optical elements to be bonded were placed in a chamber connected to a vacuum pump, and the interior of the chamber was evacuated to a vacuum by the vacuum pump. During pressure regulation, the vacuum pump was stopped, and clean dry air (CDA) or nitrogen was introduced at a flow rate controlled by a flow meter while the pressure was monitored by a vacuum gauge. After the pressure in the vacuum gauge reached a predetermined pressure, the gas supply was stopped, and the optical elements were bonded together. In this way, an optical element unit comprising a hollow portion with the desired humidity and pressure was obtained. Vacuum evaporation is performed as follows. Using a BMC850 manufactured by SHINCRON CO., LTD., as is the usual procedure, SiO2 particle powder placed in a crucible as an evaporation source is evaporated by an electron beam, and a film is formed on the periphery of the optical element using a shielding plate while ion-assisted deposition using Ar and O2 gases.

[0056] As a comparative example, two types of optical element units were prepared, each comprising a hollow portion obtained by bonding the peripheries of two pieces of synthetic quartz with an epoxy adhesive of approximately 2 μm thickness as the bonding material.

[0057] Regarding the humidity and pressure of the hollow portion of the optical element unit obtained through bonding, a third harmonic light from a YAG laser with a wavelength of 355 nm was applied externally, and Raman scattering was measured. The presence and relative amounts of N2, O2, and H2O were then evaluated based on the intensity of the Raman wavelength. Table 1 shows the Raman scattering wavelengths and relative intensities under 355 nm laser irradiation. In the following expressions, MR, I... H2O and I N2 The values ​​represent the absolute humidity (g / kg) of the hollow section, the Raman intensity of H2O, and the Raman intensity of N2, respectively, and MR0, I 0-H2O and I 0-N2r These represent the absolute humidity (g / kg) of the external weight of the optical element unit, the Raman intensity of H2O, and the Raman intensity of N2, respectively. Regarding pressure, the correlation between the intensity of N2 at its Raman wavelength and the pressure obtained using a Pirani vacuum gauge was acquired and calibrated to obtain the pressure value calculated from the Raman intensity of N2.

[0058]

[0059] Here, the external absolute humidity MR0 is measured as follows. First, the temperature and relative humidity of the external environment are measured using a thermo-hygrometer. Then, the saturated water vapor pressure is obtained from the temperature, and the actual water vapor pressure is calculated from the relative humidity. The saturated water vapor pressure Ps is calculated using the temperature T (°C) and the following Tetens equation.

[0060] Ps=6.1078×10 (7.5T / (T+237.3))

[0061] The water vapor pressure Pv is calculated using the relative humidity RH (%) and the following expression.

[0062] Pv=RH / 100×Ps

[0063] By using Ps and Pv obtained as described above, the molar mass of water vapor Mv (18.01528 g / mol) and the molar mass of dry air M DA (28.966 g / mol), calculate the weight absolute humidity MR0 using the following expression.

[0064] MR0=Mv / M DA ×Pv / (P-Pv)

[0065] In this expression, P represents atmospheric pressure (typically 1,013.25 hPa).

[0066] [Table 1]

[0067]

[0068] As an evaluation of the optical element units obtained through bonding, high-temperature and high-humidity tests were conducted at 70°C, 80% humidity, and 50 hours using an environmental testing machine manufactured by ESPEC CORP., and changes in appearance were evaluated. Optical element units without contamination at the bonding joint were rated A, while those with contamination were considered to have positional misalignment and were rated C. Furthermore, the temperature difference causing condensation during rapid cooling from room temperature (25°C) was evaluated. Cases above 60°C were rated A, cases above 30°C but below 60°C were rated B, and cases below 30°C were rated C. Table 2 shows the bonding material, bonding thickness, absolute humidity and pressure of the hollow portion, and evaluation results for each optical element unit manufactured in Examples 1 to 3 and Comparative Examples 1 and 2.

[0069] [Table 2]

[0070]

[0071] From the results of Examples 1 to 3 and Comparative Examples 1 and 2, it can be understood that the optical element unit obtained by means of the intervention of inorganic film has no problems in high temperature and high humidity tests, and furthermore, when the humidity and pressure of the hollow part are reduced to a low level, condensation can be suppressed over a wide temperature range.

[0072] Synthetic quartz has been used as a glass material for optical elements, but this disclosure is not limited thereto. All glasses, resin lenses, and films on which solid-phase bonds of inorganic materials can be formed can be used. Furthermore, the optical elements to be bonded can be of different glass types.

[0073] Furthermore, when the bonding portion is disposed on the surface of the optical element and only on the outer side (peripheral portion) of the optically effective area through which light transmits through the optical element, the bonding portion can be formed of a light-absorbing material. The bonding portion (inorganic film) used to bond two optical elements is not limited to those described in the embodiments, and can be: a metal film such as Au, Pt, Ag, Ti, Al, W, or Si; or an oxide such as Al2O3, SiO2, or SiO2. x Oxide films of MgO, Y2O3, ZrO2 or Nb2O5; nitride films of AlN, Si3N4 or TiN; and fluoride films of AlF3, MgF2 or LaF3.

[0074] [Examples 4-7 and Comparative Example 3]

[0075] Examples 4 to 7 and Comparative Example 3, based on embodiments of the present disclosure, are described. An Al₂O₃ film was formed as an inorganic layer at the periphery of each of two pieces of synthetic quartz by atomic layer deposition (ALD), and then bonded together. An AD-1 manufactured by SUMCO Corporation was used as the apparatus for the ALD process. Trimethylaluminum (TMA) was used as the feed gas, and H₂O was used as the oxidant. Film formation was performed by continuously performing one cycle of 20 ms feed gas supply, 10 s purging, 20 ms oxidant supply, and 10 s purging, for 100 cycles, 1,000 cycles, 4,000 cycles, and 5,000 cycles.

[0076] [Table 3]

[0077]

[0078] Figure 4 The cross-sectional SEM image of Example 7 is shown, in which two optical elements are bonded to each other by an inorganic film. Cross-sectional SEM observation was performed by equidistantly cutting the optical element units, grinding the cross-section, and then observing the cross-section using a GeminiSEM 560 at an accelerating voltage of 1 kV. Figure 4An optical element unit 400 is shown, in which two optical elements are joined together by the intervention of an inorganic film. In Example 7, optical elements 401a and 401b, which are synthetic quartz lenses, are used as the two optical elements. When evaluating the film thickness of the bonding material of the optical element unit obtained by joining by means of an Al2O3 film as an inorganic film 402, the film thickness is 232 nm. Furthermore, the film thickness and bonding state are evaluated similarly for other embodiments and comparative examples. The bonding state is evaluated by suspending one optical element of each optical element unit and installing a weight to apply a force of 0.05 N to the other optical element. Optical element units that do not peel off after suspension are evaluated as A, and optical element units that peel off after suspension are evaluated as C.

[0079] The surface roughness of the inorganic layer was evaluated using atomic force microscopy (AFM).

[0080] As can be understood from Examples 4 to 7, bonding can be performed satisfactorily when the surface roughness is less than 1 nm.

[0081] Furthermore, when the thickness of the inorganic film is equal to or greater than two atomic layers (equal to or greater than 0.2 nm), the optical elements can be satisfactorily bonded to each other. It is desirable that the surface roughness of each of the two optical elements 401a and 401b to be bonded, as well as the surface roughness of the inorganic layer to be formed on the optical elements 401a and 401b, be small. When the surface roughness becomes smaller, the surfaces of the two optical elements 401a and 401b are neatly in contact with each other when the two optical elements 401a and 401b are bonded to each other, thus increasing the bonding surface area and bonding strength. To ensure sufficient bonding strength, it is desirable that the surface roughness of each of the optical elements 401a and 401b in the state with the inorganic layer attached is sufficiently small. Ideally, the surface roughness is Ra < 1 nm, more preferably Ra < 0.5 nm. Generally, the surface roughness increases as the thickness of the inorganic layer formed on the optical element increases. Therefore, it is desirable that the thickness of the inorganic film 402 is less than 1 μm.

[0082] According to this disclosure, there is a technique that is advantageous in realizing optical element units with high environmental resistance and good optical properties.

[0083] Although this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An optical element unit, comprising a first optical element and a second optical element, The first optical element and the second optical element are joined together by a joint formed by solid-state bonding of inorganic materials between the peripheral portions of the first optical element and the peripheral portions of the second optical element. The optical element unit has a hollow portion formed inside the peripheral portion between the first optical element and the second optical element that are joined together.

2. The optical element unit according to claim 1, wherein the bonding portion is an inorganic film formed by solid-state bonding between an inorganic layer disposed on the periphery of the first optical element and an inorganic layer disposed on the periphery of the second optical element.

3. The optical element unit according to claim 2, wherein the inorganic film comprises at least one selected from the group consisting of metal films, oxide films, nitride films and fluoride films.

4. The optical element unit according to claim 2, wherein the inorganic film comprises a dielectric film.

5. The optical element unit according to claim 4, wherein the dielectric film comprises at least one selected from the group consisting of oxide films, nitride films and fluoride films.

6. The optical element unit according to claim 5, wherein the oxide film comprises carbon atoms and hydrogen atoms.

7. The optical element unit according to claim 4, wherein the dielectric film comprises at least one selected from SiO2, Al2O3, Nb2O5, Ta2O5, HfO2, MgO, Y2O3, ZrO2, ZnO, MgF2, AlF3, AlN, Si3N4, and SiOC.

8. The optical element unit according to claim 1, wherein the humidity of the hollow portion is lower than the humidity of the atmospheric environment.

9. The optical element unit according to claim 1, wherein the joining portion is disposed in the periphery of the first optical element and the periphery of the second optical element and in a region outside the optically effective region.

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

11. The optical element unit according to claim 1, wherein the absolute humidity of the hollow portion is less than 2 g / kg.

12. The optical element unit according to claim 1, further comprising a dielectric film between the junction and at least one of the first optical element and the second optical element.

13. The optical element unit of claim 1, wherein the joining 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, wherein the thickness of the junction is 0.1 nm or more and less than 1 μm.

15. The optical element unit according to claim 1, wherein the hollow portion has a pressure equal to or less than atmospheric pressure.

16. The optical element unit according to claim 1, further comprising a third optical element, The second optical element and the third optical element are joined together by a joint formed by solid-phase bonding of another inorganic material between the peripheral portions of the second optical element and the peripheral portions of the third optical element.

17. The optical element unit according to claim 16, wherein the optical element unit has another hollow portion formed inside the peripheral portion between the second optical element and the third optical element that are joined to each other.

18. A method for manufacturing an optical element unit, comprising joining a first optical element and a second optical element at their peripheral portions to manufacture the optical element unit, the method comprising: The first optical element and the second optical element are fabricated, wherein an inorganic layer is disposed in the region of the peripheral portion including the bonding side surface of at least one of the first optical element and the second optical element; and The peripheral portions of the first optical element and the second optical element are joined together to form a hollow portion between the first optical element and the second optical element, inside the peripheral portion.

19. The method of manufacturing an optical element unit according to claim 18, wherein the bonding is performed in a vacuum.

20. The method for manufacturing an optical element unit according to claim 18, wherein the humidity of the hollow portion is lower than the humidity of the atmospheric environment.

21. The method of manufacturing an optical element unit according to claim 18, wherein the manufacturing process comprises: The first optical element and the second optical element are configured in the device; and An inorganic layer is formed in the region including the respective peripheral portions of the first and second optical elements.

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 peripheral portions to manufacture the optical element unit, the method comprising: The first optical element, the second optical element, and the third optical element are prepared, wherein an inorganic layer is provided in a region of the peripheral portion of the bonding side surface of at least one of the first optical element and the second optical element, and another inorganic layer is provided in a region of the peripheral portion of the bonding side surface of at least one of the second optical element and the third optical element. and The peripheral portions of the prepared first optical element, second optical element and third optical element are joined together to form a hollow portion between the first optical element and the second optical element and further between the second optical element and the third optical element, inside the respective peripheral portions.

23. An optical device comprising an optical element unit according to any one of claims 1 to 17.

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