Ultraviolet light irradiation device and ultraviolet light irradiation method

Abstract

Provided are an ultraviolet light irradiation device and an ultraviolet light irradiation method capable of efficiently irradiating a local region with ultraviolet light.　The ultraviolet light irradiation device includes: a laser light source that emits first light the main light-emission wavelength of which belongs to a wavelength range longer than 400 nm; an optical system that reduces the divergence angle of the first light emitted from the laser light source; a nonlinear optical crystal element into which the first light transmitted through the optical system is incident, which converts the first light into second light the main light-emission wavelength of which belongs to a wavelength range of 200 to 235 nm, and which emits the second light; and a first storage unit in which at least the optical system and the nonlinear optical crystal element are disposed, and which forms a closed space for isolating the optical system and the nonlinear optical crystal element from an external space. The first storage unit includes, in one part of a lateral surface thereof, a light emission part that transmits the second light and emits the same to the outside.

Description

Ultraviolet light irradiation device and ultraviolet light irradiation method

[0001] The present invention relates to an ultraviolet light irradiation device and an ultraviolet light irradiation method.

[0002] Conventionally, a technique for inactivating bacteria or viruses in air using ultraviolet light emitted by an excimer lamp or the like has been studied (see, for example, Patent Document 1 below). In this specification, the term "inactivation" is used to refer to the concept of killing at least a portion of bacteria or viruses or reducing their infectivity.

[0003] JP 2023-69060 A

[0004] The inactivation of bacteria or viruses is required not only in a space but also in a wide range of areas. For example, there are cases where bacteria or viruses need to be inactivated in a localized area, such as the surface of human skin or the oral cavity. However, the device disclosed in Patent Document 1 is designed to irradiate ultraviolet light from a light irradiation window provided in the housing, so the ultraviolet light is irradiated over a fairly wide area. Therefore, there is room for improvement in inactivating bacteria or viruses in a localized area.

[0005] Specifically, to irradiate a localized area with ultraviolet light, it is assumed that the light irradiation window of the ultraviolet light irradiation device is brought close to the area to be irradiated. However, application of a high-frequency voltage is required to turn on the excimer lamp. Since the step-up transformer that generates the high-frequency voltage has a certain volume, the ultraviolet light irradiation device tends to become large, and it is not easy to bring the irradiation window of the ultraviolet light irradiation device close to the area to be irradiated.

[0006] One possible solution to this problem is to use an LED that emits ultraviolet light instead of an excimer lamp, thereby making the device relatively small. However, at present, LEDs that emit ultraviolet light have the problem of low luminous efficiency relative to the power input, making it unrealistic to use an LED as an ultraviolet light source.

[0007] There is a known wavelength conversion technology that uses a nonlinear optical crystal element to convert the energy of incident light through a nonlinear optical phenomenon to obtain light with a shorter wavelength. Specifically, by irradiating a laser beam emitted from a laser light source onto a nonlinear optical crystal element, it is possible to obtain light with half the wavelength of the laser beam (also called the "second harmonic") or one-third the wavelength (also called the "third harmonic").

[0008] It is easy to design a small nonlinear optical crystal element. Therefore, by using a laser light source and a nonlinear optical crystal element to obtain ultraviolet light, it is easy to bring the nonlinear optical crystal element close to the irradiation target area, and ultraviolet light can be suitably irradiated onto a local area.

[0009] However, when the inventors considered generating ultraviolet light using a laser light source and a nonlinear optical crystal element and irradiating a local area with the ultraviolet light, they encountered the problem that the nonlinear optical crystal element was prone to deterioration, making it impossible to irradiate ultraviolet light efficiently.

[0010] In view of the above circumstances, an object of the present invention is to provide an ultraviolet light irradiation device and an ultraviolet light irradiation method that can efficiently irradiate a local region with ultraviolet light.

[0011] The ultraviolet light irradiation device according to the present invention comprises: a laser light source that emits first light having a dominant wavelength that falls within a range of wavelengths longer than 400 nm; an optical system that reduces the divergence angle of the first light emitted from the laser light source; a nonlinear optical crystal element that receives the first light that has passed through the optical system and converts the first light into second light having a dominant wavelength that falls within a range of 200 nm to 235 nm and emits the second light; and a first container that contains at least the optical system and the nonlinear optical crystal element and forms a closed space that isolates the optical system and the nonlinear optical crystal element from an external space, wherein the first container has a light emission portion at a part of its side surface that transmits the second light and emits it to the outside.

[0012] In this specification, the term "dominant wavelength" refers to a wavelength range that exhibits a light intensity of 40% or more of the highest light intensity (peak intensity) in an emission spectrum obtained by decomposing light intensity by wavelength. Typically, the dominant wavelength includes the wavelength that exhibits the peak intensity (peak wavelength).

[0013] A laser light source is a light source capable of emitting coherent light. Examples of laser light sources that can be used include semiconductor lasers (laser diodes), solid-state lasers such as YAG lasers, gas lasers such as CO lasers, and gas lasers such as organic dye lasers. From the viewpoint of facilitating the construction of a compact device, semiconductor lasers are preferred.

[0014] Ultraviolet light (corresponding to "second light") is obtained by wavelength conversion of laser light (corresponding to "first light") emitted by a laser light source using a nonlinear optical crystal element. Since the illuminance of ultraviolet light decreases as the distance it travels increases, in order to efficiently irradiate the irradiation target area with ultraviolet light, it is preferable to bring the irradiation target area and the nonlinear optical crystal element as close as possible. With the above configuration, the position of the nonlinear optical crystal element relative to the irradiation target area can be easily designed as long as the laser light is incident. Therefore, even if the irradiation target area is a localized area, it is easy to bring the nonlinear optical crystal element close to the area.

[0015] The inventors have considered the reason why the phenomenon of deterioration of the nonlinear optical crystal element occurs when ultraviolet light is generated using a laser light source and a nonlinear optical crystal element and the ultraviolet light is irradiated onto a local area as follows.

[0016] Since most nonlinear optical crystal elements have the property of degrading and decreasing in conversion efficiency when exposed to moisture in the air, when ultraviolet light is irradiated onto a local region, the nonlinear optical crystal element comes into contact with the atmosphere of the local region, which is thought to cause the nonlinear optical crystal element to deteriorate and decrease in efficiency of generating ultraviolet light. Furthermore, when the irradiation target region and the nonlinear optical crystal element are brought close to each other, it is thought that the nonlinear optical crystal element becomes more susceptible to the influence of the atmosphere of the irradiation target region, which makes it more likely to deteriorate. In particular, local regions are expected to be high-humidity environments such as the oral cavity or abdominal cavity of the human body, and in such high-humidity environments, the effects of degradation of the nonlinear optical crystal element are expected to be more pronounced.

[0017] In contrast, with the above configuration, the nonlinear optical crystal element is placed in the closed space defined by the first housing section. This prevents deterioration of the nonlinear optical crystal element due to contact between the nonlinear optical crystal element and the atmosphere in the irradiation target area. By preventing deterioration of the nonlinear optical crystal element, the output of the ultraviolet light irradiation device is less likely to decrease, allowing for efficient irradiation of ultraviolet light.

[0018] Examples of localized areas include the surface of the skin of an animal (including a human body). Other examples include areas inside an animal's body, such as the oral cavity, nasal cavity, abdominal cavity, etc. Furthermore, ultraviolet light may be irradiated onto small areas that are difficult for humans to reach, such as drains in sinks.

[0019] In the ultraviolet light irradiation device, the nonlinear optical crystal element may be disposed in a space that is hermetically sealed from an external space.

[0020] For example, areas inside an animal's body, such as the oral cavity, tend to be in a high-humidity environment due to the presence of bodily fluids. According to the above configuration, even in such a high-humidity environment, deterioration of the nonlinear optical crystal element can be more effectively suppressed, and ultraviolet light can be efficiently irradiated. Specific examples of configurations in which the nonlinear optical crystal element is disposed in an airtightly sealed space will be described later.

[0021] The ultraviolet light irradiation device may have a protective film that covers a surface of the nonlinear optical crystal element and transmits the first light and the second light.

[0022] According to the above configuration, the nonlinear optical crystal element is disposed in the enclosed space formed by the protective film. That is, the nonlinear optical crystal element is covered not only by the first housing portion but also by the protective film, which further effectively prevents the nonlinear optical crystal element from coming into contact with the external atmosphere.

[0023] The ultraviolet light irradiation device further includes a second storage section that is disposed in the closed space formed by the first storage section and has a light-transmitting section on a part of its side that transmits the second light, wherein the second storage section has the optical system, the nonlinear optical crystal element, and the laser light source disposed therein and isolates the optical system, the nonlinear optical crystal element, and the laser light source from the space outside the second storage section within the closed space, and the light-transmitting section may be disposed between the nonlinear optical crystal element and the light-emitting section in the direction of propagation of the second light.

[0024] According to the above-mentioned configuration, the nonlinear optical crystal element is doubly enclosed by the first and second housing portions, which is preferable because it more firmly prevents the nonlinear optical crystal element from coming into contact with the external atmosphere.

[0025] The ultraviolet light irradiation device may include: a laser unit equipped with the laser light source; an optical fiber connected to the laser unit and guiding the first light emitted by the laser light source into the first housing portion; a connection portion provided at a portion of a side surface of the first housing portion and to which the optical fiber is connected; and a sealing portion that seals the connection portion.

[0026] According to the above configuration, the laser unit equipped with the laser light source and the first housing portion having the light emitting portion are configured separately. This makes it easier to configure the first housing portion compact. As a result, it becomes easier to bring the first housing portion closer to the local area, and ultraviolet light can be irradiated more efficiently.

[0027] It is assumed that connecting the first housing and the optical fiber makes it easier for the outside atmosphere to enter the first housing through the connection. In contrast, with the above configuration, the space between the optical fiber and the first housing is sealed by a sealing section. This makes it difficult for outside air to enter the first housing, and suppresses deterioration of the nonlinear optical crystal element due to contact with the air.

[0028] In the ultraviolet light irradiation device, the distance from the nonlinear optical crystal element to the light emitting portion may be shorter than the distance from the laser light source to the nonlinear optical crystal element along the path along which at least one of the first light and the second light travels.

[0029] Since the second light, which is ultraviolet light, is more likely to attenuate than the first light, which is laser light with a longer wavelength than the ultraviolet light, it is preferable that the path along which the first light travels be longer than the path along which the second light travels between the laser light source and the light emitting unit.

[0030] Furthermore, from the viewpoint of arranging the nonlinear optical crystal element as close as possible to the light emitting portion and obtaining the second light, which is ultraviolet light, near the light emitting portion, the distance between the nonlinear optical crystal element and the light emitting portion in the direction in which the light emitting portion emits the second light may be within 10 cm.

[0031] The light emitting portion may be made of a material that exhibits diffusivity with respect to the second light.

[0032] As described above, the nonlinear optical crystal element converts the laser light to obtain the second light, which is ultraviolet light, and the second light, like the first light, is highly directional. While the second light is suitable for irradiating a localized area, it is also conceivable that the second light should be irradiated over a wider area within the localized area. With the above configuration, the second light is diffused at the light emitting portion, thereby expanding the irradiation area of ​​the second light.

[0033] The ultraviolet light irradiation device may include a diffusing member made of a material that exhibits diffusibility with respect to the second light, the diffusing member being configured to be attachable to the light emitting portion.

[0034] It is more preferable that the irradiation range of the ultraviolet light can be changed depending on the irradiation target area. According to the above configuration, it is possible to easily switch whether or not the second light is diffused in the light emitting unit. Specific examples will be described later.

[0035] The ultraviolet light irradiation device includes a holding member that holds the nonlinear optical crystal element while connecting the nonlinear optical crystal element to the inner wall of the first storage section, and the holding member may be made of one or more materials selected from the group consisting of copper, silver, aluminum, and brass.

[0036] The nonlinear optical crystal element does not convert all of the incident laser light into ultraviolet light, but rather converts a portion of the incident laser light into heat. In other words, the nonlinear optical crystal element generates heat when irradiated with laser light. From the viewpoint of preventing the nonlinear optical crystal element from deteriorating due to the effects of this heat, it is preferable that the holding member that comes into contact with the nonlinear optical crystal element be made of a material with high thermal conductivity, such as copper, silver, aluminum, or brass.

[0037] In the ultraviolet light irradiation device, the light emitting portion may have a maximum width of 20 mm or less when viewed from a direction opposite to a direction in which the light emitting portion emits the second light.

[0038] According to the above configuration, it is easy to insert the light emitting unit into a narrow area such as the oral cavity or abdominal cavity, thereby enabling more efficient irradiation of a local area with ultraviolet light.

[0039] The light emitting unit may be configured to be inserted into a body of an animal and to be able to irradiate the second light into the body.

[0040] The ultraviolet light irradiation method according to the present invention is characterized by comprising: a step (a) of making a first light having a dominant wavelength longer than 400 nm incident on a nonlinear optical crystal element disposed in a closed space to obtain a second light having a dominant wavelength in the range of 200 nm to 235 nm; and a step (b) of irradiating an irradiation target area with the second light emitted from the closed space.

[0041] According to the above method, the nonlinear optical crystal element is disposed in a closed space, which prevents the nonlinear optical crystal element from being deteriorated by the atmosphere surrounding the irradiation target area, thereby enabling the ultraviolet light obtained from the nonlinear optical crystal element to be efficiently irradiated onto the irradiation target area.

[0042] The step (b) may be a step of irradiating the irradiation target region inside the animal's body with the second light.

[0043] Furthermore, the step (a) may be a step of irradiating the first light onto the nonlinear optical crystal element disposed in a hermetically sealed space.

[0044] By disposing the nonlinear optical crystal element in a hermetically sealed space, it is possible to irradiate the nonlinear optical crystal element with ultraviolet light while more firmly suppressing deterioration of the nonlinear optical crystal element.

[0045] The step (a) may include generating the second light in the vicinity of the irradiation target area.

[0046] To generate the second light, i.e., ultraviolet light, near the target irradiation area, it is preferable to bring a nonlinear optical crystal element close to the target irradiation area. However, when the nonlinear optical crystal element is brought close to the target irradiation area, it is thought that the nonlinear optical crystal element is easily deteriorated by the atmosphere surrounding the target irradiation area. In contrast, in the above method, the nonlinear optical crystal element is placed in a closed space, so that deterioration of the nonlinear optical crystal element is suppressed even when the nonlinear optical crystal element is brought close to the target irradiation area.

[0047] According to the present invention, an ultraviolet light irradiation device and an ultraviolet light irradiation method are provided that can efficiently irradiate a local region with ultraviolet light.

[0048] 1A is a cross-sectional view showing a schematic structure of an ultraviolet light irradiation device; FIG. 1B is a view showing a state in which the cylindrical body part and the light output part of FIG. 1A are disassembled; FIG. 1C is a view of the ultraviolet light irradiation device according to FIG. 1A as seen from the light output part side; FIG. 1D is a cross-sectional view showing a schematic configuration example of an ultraviolet light irradiation device according to a second embodiment, following FIG. 1A; FIG. 1E is a view showing another configuration example of an ultraviolet light irradiation device; FIG. 4 is a view of the ultraviolet light irradiation device according to FIG. 4 as seen from the light output part side; FIG. 1D is a cross-sectional view showing a schematic configuration example of an ultraviolet light irradiation device according to a third embodiment, following FIG. 1A; FIG. 6 is an enlarged view showing in more detail the configuration of the connection part of the ultraviolet light irradiation device according to FIG. 6; FIG. 7 is a cross-sectional view showing a modified example of the light output part; FIG. 8 is a cross-sectional view showing another modified example of the light output part; FIG. 9 is a cross-sectional view showing a modified example of the storage part; FIG. 11 is a cross-sectional view showing another modified example of the storage part; FIG. 12 is a cross-sectional view showing a modified example of an ultraviolet light irradiation device.

[0049] Embodiments of an ultraviolet light irradiation device and an ultraviolet light irradiation method according to the present invention will be described with reference to the accompanying drawings. Note that the drawings are schematic illustrations, and the dimensional ratios in the drawings do not necessarily correspond to the actual dimensional ratios. Furthermore, the dimensional ratios between the drawings do not necessarily correspond to each other.

[0050] 1A and 1B are cross-sectional views showing a schematic structure of an ultraviolet light irradiation device, with some elements shown in block diagrams. In the following figures, an X-Y-Z coordinate system consisting of mutually orthogonal X, Y, and Z directions is referred to as appropriate.

[0051] In the following description, when a positive or negative direction is to be distinguished from the positive or negative direction, the direction is described with a positive or negative sign, such as "+X direction" and "-X direction." When a direction is to be described without distinguishing between positive and negative directions, the direction is simply described as "X direction." In other words, in this specification, when simply described as "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction.

[0052] The ultraviolet light irradiation device 1 inactivates bacteria and viruses that may be present in the irradiation target area W1 by irradiating the irradiation target area W1 with ultraviolet light U1. Below, the configuration of the ultraviolet light irradiation device 1 will be described, and then an ultraviolet light irradiation method that can be performed by the ultraviolet light irradiation device 1 will be described.

[0053] As shown in FIG. 1A, the ultraviolet light irradiation device 1 includes a laser light source 2, an optical system 3, a nonlinear optical crystal element 4 (hereinafter referred to as an “NLO element 4” for convenience), a power supply unit 5, and a housing unit 6.

[0054] The housing 6 is composed of a cylindrical portion 7 and a light-emitting portion 8. In FIG. 1B, the cylindrical portion 7 and the light-emitting portion 8 are shown disassembled to facilitate understanding. As shown in FIG. 1B, the cylindrical portion 7 has an opening 10 on the end surface on the +X side. The light-emitting portion 8 covers the opening 10 and transmits ultraviolet light U1 emitted by the NLO element 4 (described later) to emit the light to the outside. The housing 6 forms a closed space S1 with the cylindrical portion 7 and the light-emitting portion 8. The laser light source 2, the optical system 3, the NLO element 4, and the power supply unit 5 are arranged in the closed space S1 and are isolated from the external space.

[0055] The light emitting unit 8 is made of a material that transmits the ultraviolet light U1, and a more specific example is made of a fluorine-based resin such as PTFE (polytetrafluoroethylene) or a glass material such as quartz glass. When the ultraviolet light irradiation device 1 is used to irradiate a predetermined location inside an animal's body with ultraviolet light U1 to inactivate bacteria or viruses, the irradiation target region W1 in FIG. 1A is a region inside the animal's body. In such a case, it is preferable to make the light emitting unit 8 out of a flexible material such as a fluorine-based resin in order to reduce physical impact on the body.

[0056] Other examples of flexible materials that can be used include fluorine-based resins such as PCTFE (polychlorotrifluoroethylene), ETFE (ethylene tetrafluoroethylene), PFA (perfluoroalkoxyalkane), PVDF (polyvinylidene fluoride), and FEP (perfluoroethylene propene copolymer), as well as PP (polypropylene), PE (polyethylene), PVA (polyvinyl alcohol), PVC (polyvinyl chloride), COC (cyclic olefin copolymer), and silicone resin. These materials have the property that they become transparent to ultraviolet light when made thinner, and the thickness is, for example, 0.01 mm to 1 mm.

[0057] The cylindrical body 7 is preferably made of a material that is resistant to the ultraviolet light U1, such as a metal material such as aluminum, stainless steel, or brass. The metal material typically has a water vapor permeability of 2 or less, and is suitable for making the enclosed space S1 a space that is airtightly sealed from the outside, as will be described later. Furthermore, from the viewpoint of low water vapor permeability, the cylindrical body 7 may be made of a resin material such as PP or PE.

[0058] The cylindrical portion 7 may also be formed from a member made of the above-mentioned metal material and a member made of the above-mentioned resin material. In this case, it is preferable to use a film such as a fluorine-based resin such as PTFE, a biaxially oriented PP film, or a silica-deposited film at the joint between the members.

[0059] The storage section 6 corresponds to the "first storage section."

[0060] In this embodiment, the laser light source 2 is a semiconductor laser that emits laser light L1 whose dominant wavelength is in the range of wavelengths longer than 400 nm. The laser light L1 corresponds to the "first light." More preferably, the dominant wavelength of the laser light L1 is 400 nm to 460 nm.

[0061] A semiconductor laser can operate on a relatively small voltage, for example, about 1 V to 5 V. Therefore, if a semiconductor laser is used as the laser light source 2, it becomes easier to configure the cylindrical unit 7 more compactly, which is preferable. Also, it becomes possible to configure the power supply unit 5 using a battery, for example.

[0062] The NLO element 4 converts part of the energy of the incident laser light L1 by a nonlinear optical phenomenon to generate ultraviolet light U1. The NLO element 4 may be made of, for example, BBO (BaB2O4) crystal, CLBO (CsLiBO) crystal, or the like. 10 ) crystal, or AlN crystal having a polarity inversion structure, etc. can be used. In this embodiment, the NLO element 4 generates ultraviolet light U1 as the second harmonic of the laser light L1. The ultraviolet light U1 corresponds to the "second light."

[0063] From the viewpoint of suppressing the effects of irradiation on the human body, it is preferable that the dominant wavelength of the ultraviolet light U1 be in the range of 200 nm to 235 nm. Furthermore, it is more preferable that the dominant wavelength of the ultraviolet light U1 be in the range of 200 nm to 230 nm. It is optional for the ultraviolet light U1 to be the second harmonic of the laser light L1. For example, the ultraviolet light U1 may be obtained by generating a harmonic higher than the second harmonic by wavelength conversion using multiple NLO elements 4. The configuration of the NLO elements 4 can be adjusted appropriately depending on the wavelength of the laser light L1.

[0064] The power supply unit 5 is a means for supplying power to the laser light source 2, and may be a battery or a circuit unit for generating the current required for the laser light source 2 to emit light from a commercial power source.

[0065] The optical system 3 guides the laser light L1 emitted from the laser light source 2 to the NLO element 4. The optical system 3 includes, for example, a collimator lens 3a that converts the laser light L1 emitted from the laser light source 2 into parallel light, and a condenser lens 3b that condenses the laser light L1 that has passed through the collimator lens 3a onto the NLO element 4.

[0066] Although the laser light L1 emitted by the laser light source 2 is more directional than light emitted by, for example, an LED, in order for the NLO element 4 to efficiently convert the laser light L1 into ultraviolet light U1, it is necessary to make as small as possible the range in which the laser light L1 is incident on the NLO element 4. In view of this, the optical system 3 guides the laser light L1 to the NLO element 4 while reducing the divergence angle of the laser light L1.

[0067] The NLO elements 4 made of the materials listed above are all hygroscopic and therefore susceptible to deterioration when in contact with the external atmosphere. In particular, when the irradiation target area W1 is an area expected to be in a high-humidity environment, such as the oral cavity, contact between this atmosphere and the NLO elements 4 may accelerate deterioration of the NLO elements 4. In contrast, in the ultraviolet light irradiation device 1 of this embodiment, the NLO elements 4 are disposed within the enclosed space S1, which makes it difficult for the atmosphere outside the ultraviolet light irradiation device 1 to come into contact with the NLO elements 4, thereby suppressing the progression of deterioration of the NLO elements 4.

[0068] In particular, when ultraviolet light U1 is irradiated onto an irradiation target area W1 in a high-humidity environment such as the oral cavity or abdominal cavity, it is preferable that the closed space S1 be a space that is airtightly sealed from the outside, from the viewpoint of suppressing deterioration of the NLO element 4. As an example, by constructing the cylindrical portion 7 from the aforementioned material with low water vapor permeability and covering the opening 10 of the cylindrical portion 7 with the light emitting portion 8, the housing portion 6 forms the closed space S1, and the closed space S1 can be made into a space that is airtightly sealed from the outside space.

[0069] In this case, it is preferable that the light emitting portion 8 be made of a material with low water vapor permeability, such as a fluorine-based resin or a glass material such as quartz glass, from the same viewpoint as that of the cylindrical portion 7. In particular, PTFE is a suitable material because it has low water vapor permeability and is easy to process.

[0070] The method for verifying whether the closed space S1 is airtightly sealed from the outside space will be described later.

[0071] FIG. 2 is a diagram of the ultraviolet light irradiation device 1 shown in FIG. 1A as viewed from the light output unit 8 side. For convenience of illustration, the light output unit 8 is shown in a see-through manner in FIG. 1A and FIG. 2. As shown in FIGS. 1A and 2, the NLO element 4 is supported by a holding member 9 that connects the inner wall 7a of the cylindrical portion 7 and the NLO element 4. For example, the NLO element 4 is fixed to the holding member 9 by adhesives (9a, 9b). More specifically, the adhesive 9a bonds the -Z side surface of the NLO element 4 to the -Y side surface of the holding member 9, and the adhesive 9b bonds the -Y side surface of the NLO element 4 to the -Z side surface of the holding member 9. Cytop (registered trademark), for example, can be used as the adhesives (9a, 9b).

[0072] The NLO element 4 generates heat when the laser light L1 is incident on it. To prevent the heat from deteriorating the NLO element 4, the holding member 9 is preferably made of a material with high thermal conductivity. Examples of such materials include metal materials such as copper, silver, aluminum, and brass.

[0073] 1A and 2, the NLO element 4 has a rectangular parallelepiped shape and typically emits ultraviolet light U1 in the longitudinal direction thereof. As shown in Fig. 2, the NLO element 4 contacts the holding member 9 on the +Z side and the +Y side.

[0074] It is assumed that the NLO element 4 and the holding member 9 will thermally expand due to the heat generated by the NLO element 4. If the thermal expansion coefficient of the holding member 9 is greater than that of the NLO element 4, stress due to the thermal expansion of the holding member 9 will be applied to the NLO element 4. If the NLO element 4 contacts the holding member 9 on both side surfaces in the Z direction and both side surfaces in the Y direction, the stress on the NLO element 4 will be greater. In light of this, it is preferable that, as shown in Figure 2, two intersecting side surfaces, consisting of the +Z side surface and the +Y side surface, contact the holding member 9, and that the other, -Z side surface and -Y side surface are open surfaces that do not contact the holding member 9.

[0075] 2, adhesive 9a is shown as being in contact with a partial area of ​​the -Z side surface of NLO element 4, but adhesive 9a may be disposed so as to cover the -Z side surface of NLO element 4. The same applies to adhesive 9b and the -Y side surface of NLO element 4. Also, adhesives 9a and 9b may be in contact with each other and integrated.

[0076] The holding member 9 may support the NLO element 4, the collimator lens 3 a, and the condenser lens 3 b. Alternatively, a plurality of holding members 9 may be arranged, with each holding member 9 supporting the NLO element 4, the collimator lens 3 a, and the condenser lens 3 b, respectively.

[0077] 1A schematically illustrates the propagation of laser light L1 and ultraviolet light U1. As shown in FIG. 1A, a laser light source 2 is driven by power supplied from a power supply unit 5, and laser light L1 is incident on an NLO element 4 via an optical system 3. The NLO element 4 emits ultraviolet light U1 in response to the incidence of laser light L1. In this way, the process of making laser light L1 incident on the NLO element 4 arranged in the enclosed space S1 and obtaining ultraviolet light U1 corresponds to step (a).

[0078] The ultraviolet light U1 emitted from the NLO element 4 is transmitted through the light emitting portion 8 and then irradiated onto the irradiation target area W1. In this manner, the step of irradiating the irradiation target area W1 with the ultraviolet light U1 corresponds to step (b).

[0079] 1A, the distance D2 from the NLO element 4 to the light output unit 8 is preferably shorter than the distance D1 from the laser light source 2 to the NLO element 4 in the direction of the optical axes of the laser light L1 and the ultraviolet light U1. In other words, the NLO element 4 is preferably positioned closer to the light output unit 8 than the midpoint of the path along which at least one of the laser light L1 and the ultraviolet light U1 travels.

[0080] Furthermore, from the viewpoint of making it difficult for the ultraviolet light U1 to be attenuated before it enters the light emitting portion 8, it is preferable that the NLO element 4 be disposed in the vicinity of the light emitting portion 8. Specifically, the distance D2 is preferably within 10 cm, more preferably within 5 cm, and particularly preferably within 1 cm, with respect to the direction in which the NLO element 4 emits the ultraviolet light U1.

[0081] Furthermore, in order to prevent the ultraviolet light U1 emitted from the light emitting unit 8 from attenuating before reaching the irradiation target area W1, it is preferable to position the light emitting unit 8 as close as possible to the irradiation target area W1. For example, if the irradiation target area W1 is inside an animal's body, such as the oral cavity, the ultraviolet light U1 is irradiated with the light emitting unit 8 inserted into the oral cavity or placed close to the entrance of the oral cavity. In this manner, it is preferable to generate the ultraviolet light U1 near the irradiation target area W1. Note that "near the irradiation target area W1" may refer to a range within 5 cm of the irradiation target area W1. Preferably, the distance is within 3 cm, and more preferably within 1 cm.

[0082] When the NLO element 4 is placed near the light emitting portion 8 and the light emitting portion 8 is brought close to the irradiation target area W1, it is thought that the NLO element 4 will be more susceptible to the influence of the atmosphere in the irradiation target area W1. However, as described above, since the NLO element 4 is placed in the enclosed space S1, deterioration of the NLO element 4 due to the influence of the atmosphere is suppressed.

[0083] Furthermore, in order to irradiate a wider range of the irradiation target area W1 with the ultraviolet light U1 while bringing the light emitting unit 8 closer to the irradiation target area W1, the light emitting unit 8 may be made to have diffusibility with respect to the ultraviolet light U1. In this case, it is preferable to make the light emitting unit 8 from a fluorine-based resin such as PTFE. Figure 1A schematically illustrates how the ultraviolet light U1 is diffused and transmitted through the light emitting unit 8.

[0084] Furthermore, from the viewpoint of making it easier to insert the light-emitting portion 8 into a narrow space such as the oral cavity, the maximum width R1 of the light-emitting portion 8 when viewed from the direction opposite to the direction in which the light-emitting portion 8 emits the ultraviolet light U1 is preferably 20 mm or less, and more preferably 10 mm or less (see Figure 2).

[0085] Next, we will explain a method for verifying whether the space in which the NLO element 4 is arranged in the ultraviolet light irradiation device 1 is hermetically sealed from the external space. Below, we will explain this method by dividing it into steps 1 to 5.

[0086] (Step 1) First, prepare the ultraviolet light irradiation device 1 to be verified, and also prepare an identical ultraviolet light irradiation device 1. Hereinafter, to distinguish between the two, the former will be referred to as the "target sample" and the latter as the "standard sample."

[0087] (Step 2) The illuminance of the ultraviolet light U1 emitted from each of the target sample and the standard sample is measured using an illuminance meter disposed at a predetermined distance from the light emitting unit 8.

[0088] Hereinafter, for convenience, the illuminance of the target sample measured in step 2 will be referred to as "initial illuminance A1," and the illuminance of the standard sample will be referred to as "initial illuminance B1."

[0089] (Step 3) Next, the target sample is placed in a condensation environment, i.e., an environment where the relative humidity is adjusted to approximately 100%. The standard sample is also placed in an environment where the relative humidity is adjusted to 20% or less. The samples are then left in this state for 30 days. A thermo-hygrostat can be used, for example, to adjust the relative humidity.

[0090] (Step 4) Then, after removing the target sample and the standard sample, the illuminance of the ultraviolet light U1 emitted from each of the target sample and the standard sample is measured under the same conditions as those for measuring the illuminance in step 2. For convenience, the illuminance of the target sample measured in step 4 is referred to as "illuminance A2," and the illuminance of the standard sample is referred to as "illuminance B2."

[0091] (Step 5) Finally, the rate of decrease A3 of the illuminance A2 relative to the initial illuminance A1 and the rate of decrease B3 of the illuminance B2 relative to the initial illuminance B1 are derived.

[0092] In step 3, the target sample is placed in a more humid environment than the control sample, which is likely to result in more significant deterioration of the NLO element 4. However, if the NLO element 4 is placed in an airtightly sealed space, it is likely that the decrease rates A3 and B3 will be equivalent. In other words, if the decrease rate A3 is equal to or less than the decrease rate B3, it can be said that the NLO element 4 is airtightly sealed in the ultraviolet light irradiation device 1.

[0093] Second Embodiment Next, a second embodiment of the ultraviolet light irradiation device 1 will be described, focusing on differences from the first embodiment. Fig. 3 is a cross-sectional view schematically illustrating an example of the configuration of the ultraviolet light irradiation device 1 according to the second embodiment, following Fig. 1A.

[0094] As shown in Fig. 3, the ultraviolet light irradiation device 1 has a storage unit 16 arranged in a closed space S1 (not shown in Fig. 3, see Fig. 1A) formed by the storage unit 6. The storage unit 16 is composed of a cylindrical portion 17 having an opening (not shown) on an end face relating to the +X side, and a light transmitting portion 18 that covers the opening and transmits ultraviolet light U1. The storage unit 16 corresponds to the "second storage unit."

[0095] The housing 16 forms a closed space S2 with the cylindrical portion 17 and the light transmitting portion 18. The laser light source 2, the optical system 3, the NLO element 4, and the power supply unit 5 are arranged in the closed space S2 and are isolated from a space S11 outside the housing 16 in the closed space S1 formed by the housing 6.

[0096] The closed space S2 is covered by the housing portion 16 in addition to the housing portion 6, and is therefore a space that is more tightly isolated from the external space than the space S11. In other words, the closed space S2 is a space that is more airtight from the external space than the space S11. By disposing the NLO element 4 in the closed space S2, the NLO element 4 is more firmly prevented from being deteriorated by the atmosphere outside the housing portion 6.

[0097] 3, the light transmitting portion 18 is disposed between the NLO element 4 and the light emitting portion 8 in the traveling direction of the ultraviolet light U1. The ultraviolet light U1 is emitted to the outside from the light emitting portion 8 via the light transmitting portion 18. In this embodiment, from the viewpoint of suppressing the ultraviolet light U1 from diffusing when passing through the light transmitting portion 18, it is preferable that the light transmitting portion 18 be made of a glass material such as quartz glass.

[0098] Regarding the fact that the NLO element 4 is held on the inner wall 17a of the cylindrical portion 17 via the holding member 9, the same discussion as that described with reference to Figure 2 can be made by replacing "cylindrical portion 7" with "cylindrical portion 17" and "inner wall 7a" with "inner wall 17a."

[0099] The same discussion as for the cylindrical portion 7 can be applied to the materials that can be used to form the cylindrical portion 17 .

[0100] According to the second embodiment, the NLO element 4 is disposed in a space that is more airtightly sealed from the external space, thereby more effectively suppressing deterioration of the NLO element 4 due to moisture absorption, etc. This embodiment is suitable for irradiating ultraviolet light U1 onto an irradiation target area W1 in a high-humidity environment such as the oral cavity or abdominal cavity.

[0101] [Third Embodiment] In this embodiment, similar to the second embodiment, an NLO element 4 is disposed in a space that is hermetically sealed from the external space. Fig. 4 is a cross-sectional view showing a schematic configuration example of an ultraviolet light irradiation device 1 according to the third embodiment, following Fig. 1A. Fig. 5 is a view of the ultraviolet light irradiation device according to Fig. 4 as seen from the light output unit 8 side.

[0102] 4 and 5, by disposing a protective film 12 on the surface of the NLO element 4, the NLO element 4 can be disposed within the space formed by the protective film 12. This space is covered by the protective film 12 and the housing 6, and is therefore more tightly isolated from the external space than the closed space S1. In other words, the space formed by the protective film 12 is more airtight than the closed space S1 from the external space. This more firmly prevents the NLO element 4 from being deteriorated by the atmosphere outside the housing 6.

[0103] The protective film 12 is transparent to both the laser light L1 and the ultraviolet light U1. Examples of materials that can be used to form the protective film 12 include MgF2, HfO2, and Ta2O5.

[0104] [Fourth embodiment] Next, a fourth embodiment of the ultraviolet light irradiation device according to the present invention will be described, focusing on differences from the first embodiment. Fig. 6 is a cross-sectional view schematically illustrating an example of the configuration of an ultraviolet light irradiation device 1 according to the fourth embodiment, following Fig. 1A. Note that Fig. 6 simplifies the illustration of an optical fiber 30 and a sealing portion 32, which will be described later, and this configuration will be described in detail with reference to Fig. 7.

[0105] As shown in FIG. 6, this embodiment differs from the first embodiment in that it includes a laser unit 20 that is equipped with a laser light source 2 and a power supply unit 5, and an optical fiber 30 that guides laser light L1 from the laser unit 20 to the storage unit 6.

[0106] The laser unit 20 includes therein a collimator lens 21 and a condenser lens 22. The collimator lens 21 and the condenser lens 22 guide the laser light L1 emitted from the laser light source 2 to the optical fiber 30.

[0107] 6 , the ultraviolet light irradiation device 1 has a connection part 31 into which the optical fiber 30 is inserted and connected to the side surface of the cylindrical part 7 on the −X side, and a sealing part 32 that seals the connection part 31. The optical fiber 30 guides the incident laser light L1 into the accommodation part 6.

[0108] From the viewpoint of increasing the illuminance of the ultraviolet light U1 emitted from the light emitting portion 8, it is preferable to increase the intensity of the laser light L1 incident on the NLO element 4. Here, in order to increase the intensity of the laser light L1, it is conceivable to increase the output of the laser light source 2, but in this case, the laser light source 2 and the power supply unit 5 tend to become larger. In contrast, according to this embodiment, the laser unit 20 equipped with the laser light source 2 and the housing portion 6 having the light emitting portion 8 are configured separately. This makes it easy to increase the output of the laser light source 2 while configuring the housing portion 6 to be compact.

[0109] Furthermore, since the laser unit 20 and the housing 6 are configured as separate bodies, it is easy to design the laser unit 20. The laser light source 2 may be a semiconductor laser, a solid-state laser, a liquid laser, or a gas laser. The configuration of the laser light source 2 can be selected appropriately depending on, for example, the required output of the laser light L1.

[0110] Furthermore, the laser light L1 has a dominant wavelength in the range longer than 400 nm. Therefore, compared to the ultraviolet light U1, the laser light L1 is less likely to attenuate when propagating through the optical fiber 30. Therefore, as shown in Fig. 6, it is preferable to guide the laser light L1 through the optical fiber 30 and then input the laser light L1 to the NLO element 4 to obtain the ultraviolet light U1.

[0111] Fig. 7 is an enlarged view showing in more detail the configuration of the connection portion 31 of the ultraviolet light irradiation device 1 shown in Fig. 6. The configurations of the sealing portion 32 and the optical fiber 30 will be described with reference to Fig. 7.

[0112] As shown in Fig. 7, the sealing portion 32 is composed of a ring-shaped sealing member 33 disposed between the cylindrical portion 7 and the optical fiber 30, and a fixing member 34 that fixes the optical fiber 30 in a predetermined position. As an example, the sealing member 33 is an O-ring made of a rubber material such as nitrile rubber, silicone rubber, or fluororubber. The fixing member 34 is, for example, cylindrical and has a spiral groove 34a on its inner circumferential surface. The fixing member 34 is integrated with the cylindrical portion 7 by, for example, welding. The fixing member 34 and the cylindrical portion 7 can be joined together by any method.

[0113] 7, the optical fiber 30 has a propagation portion 35, a coating portion 36, and a connecting portion 37. The propagation portion 35 includes a core layer and a cladding layer, and propagates the incident laser light L1. The coating portion 36 is made of, for example, silicone resin, and coats the propagation portion 35.

[0114] The connecting portion 37 is disposed around the covering portion 36 and has a spiral groove 37a on the outer circumferential surface thereof. The groove 37a is adapted to engage with the groove 34a of the fixing member 34.

[0115] When the connecting portion 37 is inserted into the fixing member 34 via the spiral grooves (34a, 37a), the sealing member 33 comes into contact with the optical fiber 30 and the cylindrical portion 7. As a result, the sealing portion 32 seals the connection portion 31.

[0116] If a sealing member 33 such as an O-ring is not provided when the optical fiber 30 is inserted into the connection portion 31, it is expected that the external atmosphere will enter the housing portion 6 through a small gap that exists between the connection portion 31 and the optical fiber 30. In contrast, as described with reference to Fig. 7, by sealing the connection portion 31 with the sealing portion 32, a closed space S1 can be formed within the housing portion 6. This allows the laser unit 20 and the housing portion 6 to be configured as separate entities, while the NLO element 4 can be disposed within the closed space S1, thereby suppressing deterioration of the NLO element 4.

[0117] Furthermore, the sealing portion 32 seals the connection portion 31, thereby suppressing a decrease in the airtightness of the storage portion 6 caused by connecting the optical fiber 30 to the storage portion 6. In other words, this embodiment is also suitable for the case where the closed space S1 is a space that is airtightly sealed from the outside.

[0118] The configuration of the sealing portion 32 shown in FIG. 7 is an example, and the configuration of the sealing portion 32 is arbitrary as long as it can seal the connection portion 31 .

[0119] 6, as described with reference to Fig. 4, a protective film 12 may be disposed on the surface of the NLO element 4. This allows the NLO element 4 to be disposed in a space that is hermetically sealed from the external space, with the laser unit 20 and the housing 6 configured as separate bodies.

[0120] 6 and 7, when the airtightness of the space in which the NLO element 4 is disposed is verified by the above-described method, the optical fiber 30 may be removed from the laser unit 20 as appropriate if the housing 6 is placed in a predetermined humidity environment. Furthermore, during this verification, it is preferable to suppress the effects of deterioration of the optical fiber 30 caused by placing the optical fiber 30 in a predetermined humidity environment. Therefore, the optical fiber 30 may be replaced with one of the same specifications as the optical fiber 30 as appropriate during this verification.

[0121] [Modifications] Modifications of the ultraviolet light irradiation device 1 will be described below.

[0122] 8A is a cross-sectional view showing a modified example of the light emitting portion 8. From the viewpoint of making it easier to insert the light emitting portion 8 into a narrow space, the light emitting portion 8 may have a shape in which the outer diameter gradually decreases toward the +X side.

[0123] <2> Also, Fig. 8B is a cross-sectional view showing another modified example of the light emitting portion 8. As shown in Fig. 8B , the light emitting portion 8 may be configured to cover the opening 10 (not shown in Fig. 8B , see Fig. 1B ) while being in contact with the outer wall 7b of the cylindrical portion 7 in the Z direction. By having the light emitting portion 8 in contact with the outer wall 7b, it becomes less likely that a gap will be formed between the light emitting portion 8 and the outer wall 7b, making it easier to form the closed space S1.

[0124] <3> Fig. 9 is a cross-sectional view showing a modified example of the storage unit 6. In order to facilitate irradiation of the ultraviolet light U1 to the irradiation target area W1 in a narrow area such as the oral cavity, the storage unit 6 may include a light guide unit 25, as shown in Fig. 9 .

[0125] 9 , the light guide 25 has a curved shape and connects the cylindrical body 7 and the light output section 8 to guide the ultraviolet light U1. The inner surface of the light guide 25 is made to reflect the ultraviolet light U1, so that the ultraviolet light U1 is guided to the light output section 8. The light guide 25 can be made of a metal material such as aluminum or stainless steel. A reflective film made of the above-mentioned metal material may be formed on the inner surface of the light guide 25, or a reflective member 26 that reflects the ultraviolet light U1 may be disposed inside the light guide 25.

[0126] 10 is a cross-sectional view showing another modified example of the housing section 6. Fig. 10 shows an example in which the laser light L1 is guided to the light guide section 25 via the optical fiber 30 described with reference to Fig. 6. Note that the laser unit 20 and the optical system 3 are omitted from Fig. 10. As shown in Fig. 10, a reflecting member 26 and an NLO element 4 may be disposed within the light guide section 25.

[0127] The reflecting member 26 has a reflecting surface that reflects the laser light L1. The reflecting member 26 may be made of a metal material such as aluminum or stainless steel, or may be made of a member having a reflective film made of the above metal material. Alternatively, the reflecting member 26 may be made of a glass material such as quartz glass, and the laser light L1 may be guided by total reflection.

[0128] As shown in Figure 10, by changing the direction of travel of the laser light L1 using the reflecting member 26 and making the laser light L1 incident on the NLO element 4 arranged at the tip side of the light-guiding section 25, ultraviolet light U1 can be obtained as close as possible to the light emitting section 8.

[0129] From the viewpoint of preventing the ultraviolet light U1 from being attenuated or diverged due to reflection by the reflecting member 26, it is preferable to configure the laser light L1 to be incident on the reflecting member 26 and the reflected light to be incident on the NLO element 4, as shown in FIG. 10.

[0130] 9 and 10, ultraviolet light U1 can be efficiently irradiated onto an irradiation target area W1 in the oral cavity by inserting the light emitting unit 8 into the oral cavity. Furthermore, for example, during dental treatment, a cleaning solution is appropriately supplied into the oral cavity. By arranging the NLO element 4 on the tip side of the light guiding unit 25, it is possible to expect the cleaning solution to cool the NLO element 4, which is preferable.

[0131] <4> It is preferable that the irradiation range of the ultraviolet light U1 can be changed depending on the range of the irradiation target region W1. Fig. 11 is a cross-sectional view showing a modified example of the ultraviolet light irradiation device 1. As shown in Fig. 11, the ultraviolet light irradiation device 1 has a diffusing member 40 on the +X side of the light output unit 8. The diffusing member 40 is made of a material that exhibits diffusibility with respect to the ultraviolet light U1. An example of such a material is a fluorine-based resin such as PTFE.

[0132] 11 , by attaching a diffusing member 40 to the light emitting unit 8, the ultraviolet light U1 is diffused, and as a result, the irradiation range of the ultraviolet light U1 is changed. The diffusing member 40 is preferably configured to be detachable from the light emitting unit 8. By switching between a state in which the diffusing member 40 is attached to the light emitting unit 8 and a state in which the diffusing member 40 is detached, the irradiation range of the ultraviolet light U1 can be easily changed.

[0133] As an example, the diffusing member 40 is configured to be slidable by an arbitrary sliding mechanism, and configured to switch the attachment state with respect to the light emitting unit 8. More specifically, the ultraviolet light irradiation device 1 may include an electric motor (not shown) arranged at the operator's hand and a shaft (not shown) connecting the electric motor and the diffusing member 40, and the attachment state of the diffusing member 40 with respect to the light emitting unit 8 may be switched by sliding the diffusing member 40 by moving the shaft driven by the electric motor.

[0134] The electric motor may be controlled by an electric signal or a switch located at the operator's hand, which is preferable because it allows the irradiation range of the ultraviolet light U1 to be easily changed.

[0135] The diffusion member 40 may be configured to be attachable to the light output unit 8 by a method such as screwing. In other words, the means for switching the attachment state of the diffusion member 40 to the light output unit 8 is not limited to the above and may be any means.

[0136] 4 and 5 show an example in which the protective film 12 covers the NLO element 4 from the viewpoint of arranging the NLO element 4 in an airtightly sealed space, but the present invention does not exclude a configuration in which the protective film 12 is arranged on one side of the NLO element 4. For example, a configuration in which the protective film 12 is arranged on both the side surface of the NLO element 4 on the -Y side and the side surface of the NLO element 4 on the -Z side may also be used.

[0137] <6> The ultraviolet light irradiation device 1 can be incorporated into medical equipment such as an endoscope. For example, a light emitting unit 8 can be provided at the tip of an endoscope inserted into the abdominal cavity, and the NLO element 4 can be placed inside the scope. By guiding laser light L1 to the NLO element 4 via an optical fiber built into the scope, ultraviolet light U1 can be suitably irradiated onto the irradiation target area W1 while observing the abdominal cavity. During treatment, an irrigation fluid such as physiological saline is appropriately supplied from the tip of the scope. By placing the NLO element 4 at the tip of the scope, the NLO element 4 can also be expected to be cooled by the irrigation fluid.

[0138] <7> In the above description, the cylindrical body 7 is made of a material with low water vapor permeability. However, the material of the cylindrical body 7 is not limited to the above. Similarly, the material of the light emitting portion 8 is not limited to the above. In other words, the material of the housing portion 6 is arbitrary as long as the housing portion 6 can form an enclosed space.

[0139] The method for verifying the airtightness of the space in which the NLO element 4 is placed, such as the housing portion 6, is as described above.

[0140] <8> The above-described embodiments and modifications can be implemented in appropriate combinations.

[0141] REFERENCE SIGNS LIST 1: Ultraviolet light irradiation device 2: Laser light source 3: Optical system 3a: Collimator lens 3b: Condenser lens 4: Nonlinear optical crystal element 5: Power supply unit 6: Housing unit 7: Cylinder unit 8: Light emitting unit 9: Holding member 12: Protective film 16: Housing unit 17: Cylinder unit 18: Light transmitting unit 20: Laser unit 21: Collimator lens 22: Condenser lens 25: Light guiding unit 26: Reflecting member 30: Optical fiber 31: Connection unit 32: Sealing unit 33: Sealing member 34: Fixing member 34a, 37a: Groove 35: Propagation unit 36: Covering unit 37: Coupling unit 40: Diffusion material

Claims

1. An ultraviolet light irradiation device comprising: a laser light source that emits a first light having a dominant wavelength in the range longer than 400 nm; an optical system that reduces the divergence angle of the first light emitted from said laser light source; a nonlinear optical crystal element that receives the first light that has passed through said optical system and converts the first light into a second light having a dominant wavelength in the range of 200 nm to 235 nm and emits the second light; and a first container that forms a closed space that isolates said optical system and said nonlinear optical crystal element from an external space, wherein said first container has a light exit portion at a portion of a side surface that transmits the second light and emits it to the outside.

2. The ultraviolet light irradiation device according to claim 1, wherein the nonlinear optical crystal element is disposed in a space that is hermetically sealed from the outside space.

3. The ultraviolet light irradiation device according to claim 2, further comprising a protective film covering the surface of said nonlinear optical crystal element and transmitting said first light and said second light.

4. The ultraviolet light irradiation device of claim 2, further comprising a second storage section disposed in the closed space formed by the first storage section and having a light-transmitting section at a portion of a side surface through which the second light passes, wherein the second storage section has the optical system, the nonlinear optical crystal element, and the laser light source disposed therein and isolates the optical system, the nonlinear optical crystal element, and the laser light source from the space outside the second storage section within the closed space, and wherein the light-transmitting section is disposed between the nonlinear optical crystal element and the light emitting section in the direction of propagation of the second light.

5. An ultraviolet light irradiation device as described in claim 1 or 2, characterized in comprising: a laser unit equipped with the laser light source; an optical fiber connected to the laser unit and guiding the first light emitted by the laser light source into the first storage section; a connection section provided at a portion of a side surface of the first storage section and to which the optical fiber is connected; and a sealing section that seals the connection section.

6. An ultraviolet light irradiation device as described in claim 1 or 2, characterized in that, with respect to the path along which at least one of the first light and the second light travels, the distance from the nonlinear optical crystal element to the light emission section is shorter than the distance from the laser light source to the nonlinear optical crystal element.

7. An ultraviolet light irradiation device as described in claim 1 or 2, characterized in that the distance between the nonlinear optical crystal element and the light emitting section in the direction in which the light emitting section emits the second light is within 10 cm.

8. The ultraviolet light irradiation device according to claim 1 or 2, wherein the light emitting section is made of a material that exhibits diffusivity with respect to the second light.

9. The ultraviolet light irradiation device according to claim 1 or 2, further comprising a diffusion member made of a material that exhibits diffusivity with respect to the second light and configured to be attachable to the light emitting portion.

10. An ultraviolet light irradiation device as described in claim 1 or 2, further comprising a holding member for holding the nonlinear optical crystal element in a state in which the nonlinear optical crystal element is in communication with the inner wall of the first storage section, the holding member being made of one or more materials selected from the group consisting of copper, silver, aluminum, and brass.

11. An ultraviolet light irradiation device as described in claim 1 or 2, characterized in that the maximum width of the light emitting portion is 20 mm or less when the light emitting portion is viewed from the direction opposite to the direction in which the light emitting portion emits the second light.

12. An ultraviolet light irradiation device as described in claim 1 or 2, characterized in that the light emitting unit is configured to be inserted into the body of an animal and to be able to irradiate the second light into the body.

13. A method for irradiating ultraviolet light, comprising: a step (a) of making a first light having a dominant wavelength in the range longer than 400 nm incident on a nonlinear optical crystal element placed in a closed space to obtain a second light having a dominant wavelength in the range of 200 nm to 235 nm; and a step (b) of irradiating an irradiation target area with the second light emitted from the closed space.

14. The ultraviolet light irradiation method according to claim 13, wherein step (b) is a step of irradiating the irradiation target area inside the animal's body with the second light.

15. The ultraviolet light irradiation method according to claim 13 or 14, characterized in that the step (a) is a step of irradiating the first light onto the nonlinear optical crystal element arranged in a hermetically sealed space.

16. The ultraviolet light irradiation method according to claim 13 or 14, wherein step (a) includes a step of generating the second light in the vicinity of the irradiation target area.

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