Optical sterilization device, and optical sterilization method

Abstract

To provide an optical sterilization device capable of preventing reduction of optical sterilization efficiency at a position distant from a light source.SOLUTION: According to an embodiment, an optical sterilization device comprises: first and second mirrors which are remote from each other and oppose each other; and a light source which emits at least two light beams. The light source and the first and second mirrors are arranged such that at least two light beams emitted from the light source reflect at least once on each of the first mirror and the second mirror. At least two light beams from the light source include a wavelength deactivating microorganisms in fluid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of the present invention relate to an optical sterilization device and an optical sterilization method. [Background technology]

[0002] It is becoming increasingly important to sterilize microorganisms (pathogenic or harmful microorganisms such as fungi, bacteria, and viruses) present in various fluids such as air and water. Conventional methods for sterilization include irradiating the fluid with ultraviolet (UV) light using an ultraviolet light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-214292 [Non-patent literature]

[0004] [Non-Patent Document 1] Andrew G. Buchan, Liang Yang & Kirk D. Atkinson, “Predicting airborne coronavirus inactivation by far-UVC in populated rooms using a high-fidelity coupled radiation-CFD model,” Scientific Reports (2020) 10:19659 [Non-patent document 2] Herriott, Donald; Schulte, Harry (1965). "Folded Optical Delay Lines". Applied Optics 4 (8) Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide an optical sterilization device and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position away from the light source. [Means for solving the problem]

[0006] According to an embodiment, the optical sterilization device includes first and second mirrors spaced apart and facing each other, and a light source emitting at least two light beams. The light source and the first and second mirrors are arranged so that the at least two light beams emitted from the light source are reflected at least once by each of the first and second mirrors. The at least two light beams from the light source include wavelengths that inactivate microorganisms in a fluid. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an optical sterilization device according to a first embodiment. [Figure 2] FIG. 2 is a schematic enlarged view of the light source unit of the optical sterilization device shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an optical sterilization device according to a second modified example of the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an optical sterilization device according to the second embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an optical sterilization device according to the third embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an optical sterilization device according to the fourth embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an optical sterilization device according to a fifth embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an optical sterilization device according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed explanations will be omitted where appropriate.

[0009] In this specification, light is a type of electromagnetic wave, and includes X-rays, ultraviolet light, visible light, infrared light, microwaves, etc. In this embodiment, the light is ultraviolet light, and the central wavelength (peak wavelength) is, for example, 280 nm. However, the light is not limited to this.

[0010] (First embodiment) The optical sterilization device 10 according to this embodiment will be described below with reference to FIGS.

[0011] 1 shows a schematic cross-sectional view of an optical sterilization device 10 according to this embodiment. The optical sterilization device 10 according to this embodiment has a light source unit 12, a first mirror 14, a second mirror 16, and a cylindrical housing 18. An axis passing through the center of the first mirror 14 is defined as an optical axis C. The cross-sectional view in FIG. 1 is taken to be on the xz plane, and the z axis coincides with the optical axis C.

[0012] As shown in FIG. 2, in this embodiment, the light source unit 12 includes a light source 32 that emits ultraviolet light, and an optical element (collimator optical element) 34 that can reduce the divergence angle of the light from the light source 32.

[0013] The light source 32 is assumed to be an LED (Light-Emitting Diode). The LED as the light source 32 emits divergent light. The light source 32 is preferably thermally connected to a heat sink 32a for dissipating heat generated when the light source 32 is turned on. The heat sink 32a is preferably formed of a metal material having high thermal conductivity, such as aluminum. The light source 32 emits at least two light rays having a divergence angle, i.e., a group of light rays. For example, the two light rays from the light source 32 are a first light ray L1 and a second light ray L2. In this case, the angle formed by these light rays L1 and L2 is the divergence angle of the two light rays L1 and L2. The divergence angle of the entire group of light rays is the largest of the divergence angles of the two light rays L1 and L2.

[0014] The at least two light beams L1 and L2 from the light source 32 may have wavelengths that inactivate microorganisms in the fluid. For example, light with a central wavelength of 280 nm is considered to have a high ability to inactivate microorganisms in the fluid.

[0015] Here, the optical element 34 is a collimator optical element capable of reducing the divergence angle of light from the light source 32. The collimator optical element 34 is disposed in the direction of emission of at least two light beams L1 and L2 from the light source 32. The light from the light source 32 can be made closer to parallel light by the collimator optical element 34, which can reduce the divergence angle. This function (action) is called a collimator function (action). Here, a lens is used as the collimator optical element 34. However, this is not a limitation, and the collimator optical element 34 may also be a concave mirror, a gradient index lens, or the like. In other words, the collimator optical element 34 may be any optical element capable of reducing the divergence angle. In FIG. 2, the lens serving as the collimator optical element 34 is schematically depicted as a single lens, but it may also be a lens assembly composed of multiple lenses. Alternatively, the collimator optical element 34 may be a concave mirror, a convex mirror, or a combination thereof.

[0016] The collimator optical element 34 may also be an imaging optical element. An imaging optical element has the function of converging a group of light rays emitted from one point to a conjugate point. This is also called imaging or being shifted to a conjugate point. The plane of conjugate points to which a group of light rays emitted from a sufficiently distant point are shifted by the imaging optical element is called the focal plane of the imaging optical element. A line perpendicular to the focal plane and passing through the center of the imaging optical element is called the optical axis C. In this case, the conjugate image point to which a sufficiently distant object point on this optical axis is shifted is called the focus. On the other hand, a collimator optical element without an imaging function is called a non-imaging optical element. The collimator optical element 34 of this embodiment is, for example, an imaging optical element.

[0017] As shown in Figures 1 and 2, the first mirror 14 and the second mirror 16 are spaced apart and face each other. Both the first mirror 14 and the second mirror 16 have reflective surfaces that reflect ultraviolet light. The reflective surfaces may be flat or curved. The reflectance of the mirrors 14 and 16 may be any value, but is assumed to be 80% here.

[0018] The second mirror 16 has a through-hole 16a formed in the vicinity of its optical axis C. Light from the light source 32 is first collimated by a collimator optical element 34 and then passes through this through-hole 16a. For this reason, for example, the light source 32 and the collimator optical element 34 are disposed in the through-hole 16a of the second mirror 16. When the first mirror 14 is disposed in a position where it reflects at least two light rays L1 and L2 from the light source 32, it is preferable to dispose the second mirror 16 in the vicinity of the light source 32.

[0019] The housing 18 is cylindrical and includes an inlet 18a and an outlet 18b for drawing in a fluid such as air or water. The fluid flows through the housing 18 along the optical axis C from the inlet 18a to the outlet 18b in the direction indicated by the symbol D. The reflectivity of the inner wall of the housing 18 may be any value, but is assumed to be 60% here. That is, the reflectivity of the housing 18 is lower than that of the reflective surfaces of the mirrors 14 and 16. The housing 18 generally has a larger inner wall surface area than the mirrors 14 and 16, so increasing the reflectivity of the inner wall of the housing 18 increases costs. Furthermore, the inner wall of the housing 18 often has a large curvature. Therefore, it is difficult to increase the reflectivity of the inner wall of the housing 18 compared to the mirrors 14 and 16 due to the difficulty of manufacturing. Here, the shape of the inner wall of the housing 18 is assumed to be rotationally symmetric with respect to the optical axis C. However, this is not a limitation, and the shape of the inner wall of the housing 18 may be any value. For example, the inner wall may be translationally symmetric in the direction perpendicular to the plane of the drawing.

[0020] One, several, or all of the light source unit 12, the first mirror 14, and the second mirror 16 may be disposed inside the housing 18 or outside the housing 18.

[0021] Based on the above configuration, the operation of the optical sterilization device 10 according to this embodiment will be described.

[0022] Pathogenic or harmful filamentous fungi, bacteria, viruses, and the like may exist as microorganisms in a fluid. It is known that these can be sterilized by irradiating them with ultraviolet light (see Patent Document 1 and Non-Patent Document 1). The sterilization effect increases with increasing ultraviolet light intensity (brightness or illuminance) and with increasing irradiation time. In other words, the higher the ultraviolet light intensity, the higher the sterilization rate, and the longer the irradiation time, the higher the sterilization rate.

[0023] Consider a case where the first mirror 14 is not present. Light from the light source 32 passes through the through-hole 16a of the second mirror 16 before being reflected by the second mirror 16. At this time, the light traveling from the light source unit 12 along the optical axis C cannot return to the light source unit 12 again.

[0024] On the other hand, by providing the first mirror 14 as in this embodiment, light traveling from the light source unit 12 along the optical axis C can be reflected at least once by the first mirror 14 and travel back to the light source unit 12. Furthermore, light generally travels much faster than the speed of a fluid. In other words, the fluid can be considered to be almost stationary while the light travels through the housing 18. This allows the light to pass through the almost stationary fluid twice, once on its outward journey and once on its return journey. This means that the residence time of light in the fluid, which can be considered to be almost stationary compared to the speed of light, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light on the fluid between the light source 32 and the first mirror 14 can be increased. This allows the optical sterilization device 10 according to this embodiment to have the effect of increasing sterilization efficiency.

[0025] Consider the case where there is no second mirror 16. In this case, when light traveling along the optical axis C from the light source unit 12 is reflected by the first mirror 14 and returns to the light source unit 12, it is either absorbed by the light source unit 12 or the heat sink 32a, or is emitted outside the housing 18.

[0026] On the other hand, by providing the second mirror 16 as in the optical sterilization device 10 of this embodiment, light reflected by the first mirror 14 and returning to the light source unit 12 can be reflected back to the first mirror 14. Therefore, the second mirror 16 reflects the light reflected from the first mirror 14 at least once. Furthermore, light is generally much faster than the speed of a fluid. In other words, the fluid can be considered to be almost stationary while the light travels through the housing 18. This allows the light to pass through the fluid, which can be considered to be almost stationary compared to the speed of light, three times. In other words, the residence time of the light in the fluid, which can be considered to be almost stationary compared to the speed of light, can be increased. In this way, by repeatedly reflecting the light beams L1 and L2 between the mirrors 14 and 16, the optical sterilization device 10 is provided, which can prevent a decrease in optical sterilization efficiency at positions away from the light source 32. In other words, by using the optical sterilization device 10 according to this embodiment, it is possible to lengthen the time for which light is irradiated onto the light source 32 and the fluid between the second mirror 16 and the first mirror 14. As a result, the optical sterilization device 10 according to this embodiment has the advantage of being able to improve the sterilization efficiency of the fluid between the mirrors 14 and 16.

[0027] The above description is similar for each of the light rays L1 and L2. Here, for example, the amount of sterilization can be increased by simultaneously irradiating the light ray L2 as well as the light source 32 of the optical sterilization device 10 compared to irradiating only the light ray L1. Similarly, the amount of sterilization can be increased by simultaneously irradiating the light ray L1 as well as the light source 32 of the optical sterilization device 10 compared to irradiating only the light ray L2. In other words, there is an effect that sterilization efficiency can be improved by emitting the light rays L1 and L2.

[0028] Therefore, the optical sterilization method of this embodiment includes emitting at least two light beams L1 and L2 from a light source 32, the light beams including wavelengths that inactivate microorganisms in a fluid, emitting the at least two light beams L1 and L2 to one of at least two first mirrors 14 and second mirrors 16 that are spaced apart from each other and facing each other, and reflecting the at least two light beams L1 and L2 at least once by each of the first mirror 14 and the second mirror 16, i.e., two or more times in total.

[0029] For example, if the fluid is air or water, light can pass through the fluid, which can be considered to be almost stationary compared to the speed of light, not just three times but many times, depending on the light transmittance through the fluid, the reflectivity of the mirrors 14 and 16, the distance between the mirrors 14 and 16, etc. This allows for more uniform sterilization of the entire fluid between the mirrors 14 and 16. Therefore, the optical sterilization device 10 according to this embodiment can prevent a decrease in the sterilization efficiency of light away from the light source 32.

[0030] Next, consider the case where the collimator optical element 34 is not present. In this case, because the light emitted from the LED serving as the light source 32 is divergent, most of the light rays L1 and L2 reach the inner surface of the housing 18 and are reflected there. Then, most of the light rays L1 and L2 are repeatedly reflected on the inner surface of the housing 18, travel along the optical axis C, and exit the housing 18 or are reflected by the first mirror 14. Due to this reflection on the inner surface of the housing 18, the intensity of the light rays L1 and L2 gradually decreases in proportion to the power of the reflectivity. In other words, most of the light rays L1 and L2 have an intensity equal to the reflectivity raised to the power of the number of reflections. As a result, most of the light rays L1 and L2 are significantly attenuated in intensity before exiting the housing 18 or being reflected by the first mirror 14. However, some of the light from the light source 32 is emitted without being reflected by the housing 18.

[0031] On the other hand, when the collimator optical element 34 is provided as in this embodiment, the divergence angle of the divergent light from the LED serving as the light source 32 can be reduced. This reduces the number of times that the light rays L1 and L2 are reflected by the inner circumferential surface of the housing 18, compared to when the collimator optical element 34 is not provided. In other words, the attenuation of the intensity of the light rays L1 and L2 can be suppressed by providing the collimator optical element 34. This has the effect of increasing the proportion of the light rays L1 and L2 that continue to reflect between the mirrors 14 and 16 while suppressing the attenuation of the intensity of the light rays L1 and L2, thereby improving the sterilization rate of the fluid.

[0032] Generally, the greater the intensity of ultraviolet light, the higher the sterilization efficiency. According to the optical sterilization device 10 of this embodiment, the light from the light source 32 does not dissipate immediately, and the light intensity does not weaken even when the light source 32 is farther away, thereby improving the sterilization efficiency of the fluid.

[0033] According to this embodiment, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position distant from the light source 32.

[0034] In this embodiment, an example using two mirrors, the first mirror 14 and the second mirror 16, has been described, but it goes without saying that, for example, the inner peripheral surface of the housing 18 may be a mirror. Therefore, the number of mirrors may be three or more.

[0035] The optical sterilization device 10 according to this embodiment has been described as an example in which the housing 18 is used. If the light source unit 12, the first mirror 14, and the second mirror 16 are provided, the housing 18 is not necessarily required.

[0036] (First Modification) The light source unit 12 of the optical sterilization device 10 according to a modified example of this embodiment may not have the collimator optical element 34, and the light source 32 may be a laser light source (not shown). The laser light source 32 may be, for example, a semiconductor laser (laser diode, LD) that emits ultraviolet light. By using the laser beams L1 and L2 from the laser light source 32, it is possible to emit a group of beams with a small divergence angle that includes the beams L1 and L2. However, by providing an additional collimator optical element 34 in the path of the laser beams L1 and L2, the divergence angle can be further reduced, the intensity of the beams L1 and L2 can be increased, and the sterilization efficiency of the fluid between the mirrors 14 and 16 can be further improved.

[0037] According to this modification, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at positions distant from the light source 32.

[0038] (Second Modification) In an optical sterilization device 10 according to a modified example of this embodiment, a porous material 40, for example, a ceramic material (base material) carrying a photocatalytic material such as titanium oxide, may be disposed between the reflective surface of the first mirror 14 and the reflective surface of the second mirror 16. In the example shown in Fig. 3, for example, the porous material 40 is supported by the housing 18. The porous material 40 is formed, for example, in a circular ring shape.

[0039] In this case, it is preferable that the LED or laser light source serving as light source 32 irradiates ultraviolet light (UV-A) with a peak wavelength of 300 nm or more and 450 nm or less, as well as ultraviolet light (UV-C) with a peak wavelength of 280 nm, which directly sterilizes the fluid by irradiating it with light rays L1 and L2. For this reason, it is preferable that multiple types of LED or laser light sources be used as light source 32.

[0040] Irradiation of UV-A light on the surface of the photocatalytic material of the porous material 40 generates active oxygen and OH radicals. If the fluid is air, the photocatalytic material decomposes bacteria, viruses, and odorous substances contained in the air passing through it into water and carbon dioxide, suppressing the activity of viruses and bacteria. Therefore, when UV-A light is irradiated onto the surface of the photocatalytic material of the porous material 40, the optical sterilization device 10 exerts a sterilization and deodorization effect.

[0041] Instead of disposing the annular porous material 40 at a position between the reflective surfaces of the first mirror 14 and the second mirror 16, away from the reflective surfaces of the first mirror 14 and the second mirror 16, the porous material 40 carrying a photocatalytic material such as titanium oxide may be disposed on part of the reflective surface of the first mirror 14 and / or part of the reflective surface of the second mirror 16. In this case, it is preferable that part of the reflective surface of the first mirror 14 and part of the reflective surface of the second mirror 16 have an area (for example, a mirror surface) with a higher reflectivity than the porous material 40.

[0042] For this reason, the porous material 40 is in any event disposed between the first and second mirrors 14,16.

[0043] This modification provides an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position distant from the light source 32. Furthermore, the light from the light source 32 can exert a deodorizing effect on the fluid.

[0044] (Second embodiment) An optical sterilization device 10 according to the second embodiment will be described below with reference to Fig. 4. This embodiment is a modification of the first embodiment including various modifications, and the same components as those described in the first embodiment or components having the same functions are assigned the same reference numerals as much as possible, and detailed descriptions thereof will be omitted.

[0045] 4 shows a schematic cross-sectional view of the optical sterilization device 10 according to this embodiment. The light source unit 12 according to this embodiment includes a light source 32 and a collimator optical element .

[0046] The light source 32 is an LED that emits ultraviolet light. The LED emits diverging light. The LED is thermally connected to a heat sink 32a to dissipate heat generated when the LED is turned on. A second mirror 16 is placed between the heat sink 32a and the light source 32. The second mirror 16 transfers heat from the light source 32 to the heat sink 32a. The second mirror 16 may be a metal mirror made of aluminum, which has high thermal conductivity. Alternatively, the second mirror 16 may be a thermally conductive dielectric multilayer film or a thin, thermally conductive substrate with a reflective coating.

[0047] In this embodiment, there are at least two or more LEDs serving as the light source 32. All of these are thermally connected to the heat sink 32a via the second mirror 16.

[0048] The light from the light source 32 can be made closer to parallel light by a collimator optical element 36 that can reduce the divergence angle. In this embodiment, the collimator optical element 36 is a fly's eye lens. However, this is not limiting and the collimator optical element 36 may also be a lenticular lens or a microlens array. In other words, any optical element that has at least two optical elements that require lens action arranged adjacent to each other may be used. Each light source 32 is arranged so as to face each lens surface of the fly's eye lens 36.

[0049] Based on the above configuration, the operation of the optical sterilization device 10 according to this embodiment will be described.

[0050] In this embodiment, the light beams L1 and L2 from the light source unit 12 and the mirrors 14 and 16 allow the light to pass through the fluid, which can be considered to be substantially stationary compared to the speed of light, three or more times. In other words, by using the optical sterilization device 10 according to this embodiment, the residence time of light in the fluid, which can be considered to be substantially stationary compared to the speed of light between the mirrors 14 and 16, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light to the fluid, which can be considered to be substantially stationary compared to the speed of light between the mirrors 14 and 16, can be increased. As a result, the optical sterilization device 10 according to this embodiment has the effect of increasing the sterilization efficiency.

[0051] Consider a case where the fly-eye lens 36 is not present. In this case, the light emitted from the LED serving as the light source 32 is divergent light, so most of the light rays reach the inner surface of the housing 18 and are reflected. Then, while repeatedly reflecting, they travel along the optical axis C and exit through the outlet 18b of the housing 18 or are reflected by the first mirror 14. Due to this reflection on the inner surface of the housing 18, the intensity of the light rays L1 and L2 gradually decreases in proportion to the power of the reflectivity. In other words, the intensity of most of the light rays L1 and L2 is reduced by the reflectivity multiplied by the number of reflections. As a result, most of the light rays are significantly attenuated in intensity before exiting the housing 18 or being reflected by the first mirror 14. However, some of the light from the light source 32 is emitted without being reflected by the housing 18.

[0052] On the other hand, when the fly-eye lens 36 is provided as in this embodiment, the divergence angle of the divergent light from the LED serving as the light source 32 can be reduced. This reduces the number of times that the light rays L1 and L2 are reflected by the inner circumferential surface of the housing 18, compared to when the fly-eye lens 36 is not provided. In other words, the attenuation of the intensity of the light rays L1 and L2 can be suppressed by providing the fly-eye lens 36. This means that the proportion of the light rays L1 and L2 that continue to reflect between the mirrors 14 and 16 can be increased while suppressing the attenuation of the intensity of the light rays L1 and L2, thereby increasing the sterilization rate of the fluid. By using the fly-eye lens 36, divergent light from at least two light sources 32 can be simultaneously converted into parallel light, compared to when a single lens is used. In other words, the number of light sources 32 can be increased to two or more, while the light sources 32 can be made closer to parallel light along the optical axis C. In other words, the fly-eye lens 36 can perform a collimator function for the light beams L1 and L2 emitted from the light-emitting surfaces of each light source 32. On the other hand, when a single lens is used, the light source 32 must be positioned on the optical axis C of the lens in order to generate parallel light traveling along the optical axis C. Furthermore, by using the fly-eye lens 36, the light sources 32 can be positioned apart from each other in a direction intersecting the light irradiation direction. At least two light-emitting surfaces of the light sources 32 for the light beams L1 and L2 are spaced apart from each other. The fly-eye lens 36, which is a collimator optical element, faces the light-emitting surfaces of the light sources 32. In other words, heat from each light source 32 can be dispersed, thereby reducing the temperature rise of the light source unit 12.

[0053] The above description is similar for each of the light rays L1 and L2. Here, for example, the amount of sterilization can be increased by simultaneously irradiating the light ray L2 as well as the light source 32 of the optical sterilization device 10 compared to irradiating only the light ray L1. Similarly, the amount of sterilization can be increased by simultaneously irradiating the light ray L1 as well as the light source 32 of the optical sterilization device 10 compared to irradiating only the light ray L2. In other words, there is an effect that sterilization efficiency can be improved by emitting the light rays L1 and L2.

[0054] According to this embodiment, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position distant from the light source 32.

[0055] (Third embodiment) The optical sterilization device 10 according to this embodiment will be described below with reference to Fig. 5. This embodiment is a modification of the first embodiment, including various modifications, and the second embodiment. In the description of this embodiment, the same components as those described in the first and second embodiments or components having the same functions are assigned the same reference numerals as much as possible, and detailed description thereof will be omitted.

[0056] FIG. 5 shows a schematic cross-sectional view of an optical sterilization device 10 according to this embodiment. The optical sterilization device 10 according to this embodiment includes a light source unit 12, a first mirror 14, a second mirror 16, a housing 18, a first fan (air blower) 22, and a second fan (air blower) 24. An axis passing through the center of the first mirror 14 is defined as an optical axis C. The cross-sectional view shown in FIG. 5 is taken on an xz plane, and the z axis coincides with the optical axis C. In this embodiment, the optical axis C of the first mirror 14 and the optical axis C of the second mirror 16 coincide. However, this is not a limitation, and the optical axes C of the two mirrors may be misaligned.

[0057] The inner wall of the housing 18 has a constricted portion 18c between the inlet 18a and the outlet 18b that narrows the fluid flow path (cross-sectional area) compared to at least one of the inlet 18a and the outlet 18b. In this embodiment, the constricted portion 18c between the inlet 18a and the outlet 18b that narrows the fluid flow path (cross-sectional area) compared to both of the inlet 18a and the outlet 18b. Therefore, the cross-sectional area of ​​the fluid flow path of the housing 18 gradually narrows from the inlet 18a side toward the constricted portion 18c, and gradually widens from the constricted portion 18c toward the outlet 18b side. It is preferable that the constricted portion 18c be located approximately in the center between the inlet 18a and the outlet 18b.

[0058] In this embodiment, the first fan 22 is located close to the light source unit 12 and the second mirror 16, and the second fan 24 is located close to the first mirror 14. The first mirror 14 is located near the axis of symmetry of the rotating part of the second fan 24. The second mirror 16 is located near the axis of symmetry of the rotating part of the first fan 22. However, the positions of the first fan 22 and the second fan 24 may be interchanged.

[0059] The first fan 22 draws fluid into the housing 18, and the second fan 24 exhausts the fluid from the housing 18. However, this is not limited to this, and the roles of the two fans may be reversed. In other words, the first fan 22 may exhaust fluid, and the second fan 24 may draw fluid. The first fan 22 and the second fan 24 may be, for example, axial fans, and their swirl sections are axially symmetric, with their respective axes of symmetry coinciding with the optical axis C. However, this is not limited to this, and the first fan 22 and the second fan 24 may have axes of symmetry that are offset from the optical axis C. Furthermore, the fans 22 and 24 are not necessarily limited to axial fans, and any type of fan that can advect a fluid, such as a centrifugal fan, may be used.

[0060] Here, the light source section 12 will be described as an example using the light source 32 and collimator optical element 34 described in the first embodiment, but the light source 32 and optical element 36 described in the second embodiment may also be used.

[0061] The first mirror 14 and the second mirror 16 have reflective surfaces that reflect ultraviolet light. Both reflective surfaces are curved. The curved surfaces may have a radius of curvature larger than the distance between the two mirrors 14 and 16 (i.e., a small curvature) (see Non-Patent Document 2). By using such a radius of curvature, the light beams L1 and L2 can travel back and forth between the two mirrors 14 and 16 multiple times. In this embodiment, at least two light beams (or beams) L1 and L2 travel back and forth simultaneously. This allows the light beam illuminance at the cross section of the fluid to be increased compared to traveling back and forth with a single light beam (or beam).

[0062] On the other hand, a conventional technique is known in which a single light ray (or beam) is sent back and forth, and the attenuation rate is calculated from the intensity ratio before and after the round trip, thereby determining the concentration of an absorbing medium in a fluid. In this case, if multiple light rays are sent back and forth simultaneously, it becomes difficult to distinguish the light rays, so the light ray (or beam) must be limited to one.

[0063] The second mirror 16 has a through-hole 16a formed in the vicinity of the optical axis C. Light from the light source 32 is first collimated by the collimator optical element 34 and then passes through this through-hole 16a.

[0064] Based on the above configuration, the operation of the optical sterilization device 10 according to this embodiment will be described.

[0065] In this embodiment, too, the light beams L1 and L2 from the light source unit 12 and the mirrors 14 and 16 allow the light to pass through the fluid, which can be considered to be almost stationary compared to the speed of light, three or more times. In other words, the residence time of the light in the fluid, which can be considered to be almost stationary compared to the speed of light, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of the light to the fluid between the light source 32 and the second mirror 16 and the first mirror 14 can be increased. As a result, the optical sterilization device 10 according to this embodiment has the effect of increasing the sterilization efficiency.

[0066] The first mirror 14 and the second mirror 16 are disposed near the rotation axes of the second fan 24 and the first fan 22, respectively. When an object is disposed in the region near the rotation axes of the fans 22 and 24, the closer the distance between the fan 22 and 24 and the object, the less likely it is that the object will interfere with the fluid advection caused by the fans 22 and 24. In other words, an increase in pressure loss due to the object can be prevented. As a result, for example, by disposing the first mirror 14 relative to the second fan 24 in the region near the rotation axis of the second fan 24, it is possible to prevent fluid pressure loss. Similarly, by disposing the second mirror 16 relative to the first fan 22 in the region near the rotation axis of the first fan 22, it is possible to prevent fluid pressure loss. The reflective surfaces of the first mirror 14 and the second mirror 16 both have curvature. The radius of curvature of these mirrors 14 and 16 is larger (i.e., the curvature is small) than the distance between the two mirrors 14 and 16. This allows light beams L1 and L2 arriving at the first mirror 14 from the light source 32 to travel back and forth between the first mirror 14 and the second mirror 16 multiple times, as is known (see Non-Patent Document 2). In this embodiment, at least two light beams (the first light beam L1 and the second light beam L2) from the light source 32 simultaneously travel back and forth between the first mirror 14 and the second mirror 16 multiple times. This has the effect of increasing the illuminance on the cross section of the fluid compared to traveling back and forth with a single light beam.

[0067] By increasing the divergence angle of the light beams that travel from the light source 32 through the optical element 34 to the first mirror 14 so that the light beams reach the entire reflective surface of the first mirror 14, it is possible to increase the spatial region within the fluid through which the light beams travel back and forth, thereby improving the efficiency of sterilization.

[0068] In this embodiment, the fans 22 and 24 are axial fans. It is generally known that the larger the diameter of an axial fan, the higher the flow rate. When the flow rate is constant, the larger the flow rate becomes, and the larger the amount of bacteria that can be removed per unit time becomes. Therefore, the larger the diameter of an axial fan, the more the flow rate efficiency improves, and at the same time, a synergistic effect can be expected in which the bacteria removal capacity also improves.

[0069] It is known that an axial flow fan generates a swirling flow, which increases the residence time of the fluid within the housing 18. This increases the irradiation time of ultraviolet light from the light source 32, which has the effect of improving the sterilization ability.

[0070] In this embodiment, the inner wall of the housing 18 has a constricted structure near the center of the first fan 22 and the second fan 24. This has the effect of ensuring that the fluid passes through the group of light rays. In other words, it is possible to reduce the area of ​​the fluid that passes through the housing 18 without being irradiated by the light rays.

[0071] 5, constricted portion 18c is shown as the region with the smallest cross-sectional area compared to the inlet and outlet sides of the fluid on the inner wall of housing 18. Housing 18 may have a structure in which the inlet side is large, then narrows as it is constricted, and the outlet remains as narrow as the constricted portion.

[0072] The flow rate of a fluid is given by "flow rate divided by the cross-sectional area of ​​the flow path" of the housing. For example, for a given flow rate, the flow rate will be slower in the area of ​​the housing 18 where the cross-sectional area of ​​the flow path is larger, and faster in the area of ​​the housing 18 where the cross-sectional area of ​​the flow path is smaller. By using the constricted portion 18c according to this embodiment to change the cross-sectional area of ​​the flow path within the housing 18 in the direction indicated by the symbol D, the flow rate of the fluid can be appropriately changed.

[0073] By simultaneously using the first fan 22 and the second fan 24 to advect the fluid, a large flow rate can be achieved even when the pressure loss of the fluid is high within the housing 18. In this embodiment, the first fan 22 and the second fan 24 are arranged at a distance from each other, but they may also be arranged adjacent to each other. In this case, both fans perform either the intake or exhaust function.

[0074] The heat sink 32a is disposed near the first fan 22. This promotes heat dissipation from the heat sink 32a by the fluid circulated by the fan 22. This allows the power input to the light source 32 to be increased, which has the effect of increasing the light intensity and enhancing the sterilization capability.

[0075] According to this embodiment, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position distant from the light source 32.

[0076] (Variation) The surface of the propeller of the rotating part of the first fan 22 or the second fan 24 may be coated with a reflective coating that reflects ultraviolet light. Alternatively, the propeller of the rotating part may be made of a material that reflects ultraviolet light. This allows the light that reaches the propeller to be reflected and reflected back and forth within the fluid, thereby lengthening the time the light stays in the fluid and improving the sterilization ability.

[0077] (Fourth embodiment) The optical sterilization device 10 according to this embodiment will be described below with reference to Fig. 6. This embodiment is a modification of the first, second, and third embodiments, including their respective modifications. In the description of this embodiment, the same components as those described in the first, second, and third embodiments or components having the same functions as those described in the first, second, and third embodiments will be assigned the same reference numerals as much as possible, and detailed description will be omitted.

[0078] FIG. 6 shows a schematic cross-sectional view of the optical sterilization device 10 according to this embodiment.

[0079] The optical sterilization device 10 according to this embodiment includes a light source unit 12, a first mirror 14, a second mirror 16, a housing 18, and a first fan (blower) 22. The axis passing through the center of the first mirror 14 is defined as the optical axis C. The cross-sectional view of FIG. 6 is assumed to be on the xz plane, and the z axis coincides with the optical axis C. In this embodiment, the optical axis C of the second mirror 16 coincides with the optical axis C of the first mirror 14. However, this is not a limitation, and the optical axes C of the two may be offset. Furthermore, in this embodiment, the second mirror 16 is a flat mirror. Therefore, the optical axis C of the second mirror 16 may be set in any direction as long as it is perpendicular to the flat mirror.

[0080] The first fan 22 draws fluid into the housing 18 through the intake port 18a of the housing 18 and discharges the fluid from the exhaust port 18b of the housing 18. However, this is not limited to this, and the roles may be reversed. In other words, the first fan 22 may also have the role of discharging the fluid. In this case, the fluid is drawn in from the end (exhaust port 18b) of the housing 18 that faces the first fan 22. The first fan 22 is an axial fan, and its rotating part is axially symmetric, with the axis of symmetry coinciding with the optical axis C. However, this is not limited to this, and the axis of symmetry may be offset from the optical axis C. Furthermore, the fan 22 is not necessarily limited to an axial fan, and any fan that can advect a fluid, such as a centrifugal fan, may be used.

[0081] The light source 32 is an LED that emits ultraviolet light. The LED emits diverging light. The LED is thermally connected to a heat sink 32a to dissipate heat generated when the LED is turned on. A second mirror 16 is placed between the heat sink 32a and the light source 32. The second mirror 16 transfers heat from the light source 32 to the heat sink 32a. The second mirror 16 may be a metal mirror made of aluminum, for example. Alternatively, it may be a thermally conductive dielectric multilayer film or a thin thermally conductive substrate with a reflective coating.

[0082] The first mirror 14 and the second mirror 16 have reflective surfaces that reflect ultraviolet light. The reflective surface of the first mirror 14 is curved. This curved surface is concave and has a radius of curvature. Therefore, the first mirror 14 has a focal point F. The light source 32 is preferably positioned at or near this focal point F.

[0083] The second mirror 16 has a through-hole 16a formed in the vicinity of the optical axis C. Light from the light source 32 passes through this through-hole 16a.

[0084] Based on the above configuration, the operation of the optical sterilization device 10 according to this embodiment will be described.

[0085] Light emitted from the light source 32 passes through the through-hole 16a of the second mirror 16 and reaches the first mirror 14. The light is then reflected by the first mirror 14 and collimated along the optical axis C, becoming parallel light. This collimation occurs because the light source 32 is positioned at the focal point F of the first mirror 14. By providing the first mirror 14 as in this embodiment, the light from the light source 32 is reflected by the first mirror 14 and travels back to the light source 32. Since the light is collimated along the optical axis C, it is possible to prevent the light from being reflected by the housing 18 and losing its intensity. Furthermore, light generally travels much faster than the speed of a fluid. In other words, the fluid can be considered to be nearly stationary while the light travels through the housing 18. This allows light to pass through a fluid that can be considered to be nearly stationary compared to the speed of light twice, once on its outward and return journeys. This means that the residence time of light in a fluid that can be considered to be nearly stationary compared to the speed of light can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, it is possible to lengthen the time that light is irradiated onto the fluid between the light source 32 and the first mirror 14. As a result, the optical sterilization device 10 according to this embodiment has the effect of increasing sterilization efficiency.

[0086] Consider the case where there is no second mirror 16. In this case, when light traveling along the optical axis C from the light source 32 is reflected by the first mirror 14 and returns to the light source 32, it is either absorbed by the light source 32 or the heat sink, or emitted outside the housing 18.

[0087] On the other hand, by providing the second mirror 16 as in this embodiment, light reflected by the first mirror 14 and returning to the light source 32 can be reflected back to the first mirror 14. Furthermore, light generally travels much faster than the speed of a fluid. That is, the fluid can be considered to be nearly stationary while the light travels through the housing 18. This allows light to pass through the fluid, which can be considered to be nearly stationary compared to the speed of light, three times. This means that the residence time of light in the fluid, which can be considered to be nearly stationary compared to the speed of light, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light to the fluid between the light source 32, the second mirror 16, and the first mirror 14 can be increased. This allows the optical sterilization device 10 according to this embodiment to have the effect of increasing sterilization efficiency.

[0088] The second mirror 16 is disposed near the rotation axis of the first fan 22. When an object is disposed in the area near the rotation axis of the fan 22, the closer the distance between the fan 22 and the object, the less likely it is that the object will interfere with the advection of fluid by the fan 22. In other words, it is possible to prevent an increase in pressure loss due to the object. Therefore, by disposing the second mirror 16 with respect to the first fan 22 in the area near the rotation axis of the fan 22, it is possible to prevent pressure loss from occurring.

[0089] By increasing the divergence angle of the light beams reaching the first mirror 14 from the light source 32 so that the light beams reach the entire reflective surface of the first mirror 14, it is possible to increase the spatial region within the fluid through which the light beams travel back and forth, thereby improving the efficiency of sterilization.

[0090] In this embodiment, the fan 22 is an axial fan. It is known that the larger the diameter of the fan 22, the more the flow efficiency of the axial fan generally improves. When the flow rate is constant, the greater the flow rate, the greater the amount of bacteria that can be removed per unit time. Therefore, the larger the diameter of the axial fan, the more the flow efficiency improves, and at the same time, a synergistic effect can be expected in which the bacteria removal capacity also improves.

[0091] It is known that an axial flow fan generates a swirling flow, which increases the residence time of the fluid inside the housing 18. This increases the irradiation time of the ultraviolet rays, which has the effect of improving the sterilization ability.

[0092] The heat sink 32a is disposed near the first fan 22. This promotes heat dissipation from the heat sink 32a by the fluid circulated by the fan 22. This allows the power input to the light source 32 to be increased, which has the effect of increasing the light intensity and enhancing the sterilization capability.

[0093] According to this embodiment, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position distant from the light source 32.

[0094] (Fifth embodiment) The optical sterilization device 10 according to this embodiment will be described below with reference to Fig. 7. This embodiment is a modification of the first to fourth embodiments, including each of the modifications. In the description of this embodiment, the same components as those described in the first to fourth embodiments or components having the same functions as those described in the first to fourth embodiments will be assigned the same reference numerals as much as possible, and detailed description will be omitted.

[0095] FIG. 7 shows a schematic cross-sectional view of the optical sterilization device 10 according to this embodiment.

[0096] The optical sterilization device 10 according to this embodiment includes a light source unit 12, a first mirror 14, a second mirror 16, a housing 18, a first fan (air blower) 22, and a light guide 26. An axis passing through the center of the first mirror 14 is defined as an optical axis C. The cross-sectional view shown in FIG. 7 is on the xz plane, and the z axis coincides with the optical axis C. In this embodiment, the optical axis C of the second mirror 16 and the optical axis C of the first mirror 14 coincide. However, this is not a limitation, and the optical axes C of the two mirrors may be misaligned.

[0097] The first fan 22 draws in fluid and expels it from the housing 18. However, this is not a limitation, and the roles may be reversed. In other words, the first fan 22 may also have the role of expelling fluid. In this case, the fluid is drawn in from the end of the housing 18 facing the first fan 22. The first fan 22 is an axial fan, and its swirl section is symmetrical about an axis, with the axis of symmetry coinciding with the optical axis C. However, this is not a limitation, and the axis of symmetry may be offset from the optical axis C. Furthermore, the fan 22 is not necessarily limited to an axial fan, and any fan that can advect a fluid, such as a centrifugal fan, may be used.

[0098] In this embodiment, the light source unit 12 is provided on the exhaust port 18b side of the housing 18, not on the intake port 18a side. The light source 32 of the light source unit 12 is an LED that emits ultraviolet light. The light source 32 emits diverging light. The light source 32 emits a group of light rays with a divergence angle. The light source 32 is also thermally connected to a heat sink 32a for dissipating heat generated when the light source is turned on.

[0099] The first mirror 14 and the second mirror 16 have reflective surfaces that reflect ultraviolet light. The reflective surfaces of the first mirror 14 and the second mirror 16 are curved. The curved surfaces of the first mirror 14 and the second mirror 16 are concave (concave mirrors) and have a radius of curvature. Therefore, the first mirror 14 and the second mirror 16 each have a focal point F.

[0100] Light from the light emitting surface of the light source 32 immediately enters one end of the light guide 26 and exits from the other end of the light guide 26. This exit end is located at the focal point F of the first mirror 14.

[0101] The light guide 26 guides light using total internal reflection. In this case, the light guide 26 can be transparent to light (ultraviolet rays). The material of the light guide 26 may be, for example, ultraviolet-transmitting glass or ultraviolet-transmitting resin. However, this is not a limitation, and the light guide 26 may also use specular reflection or be opaque to light (ultraviolet rays).

[0102] For example, let us assume that two light rays from the light source 32 are a first light ray L1 and a second light ray L2. The angle formed by these light rays L1 and L2 emitted from the end of the light guide 26 is the divergence angle of the two light rays L1 and L2. The divergence angle of the entire light ray group is the largest of the divergence angles of the two light rays L1 and L2.

[0103] Based on the above configuration, the operation of the optical sterilization device 10 according to this embodiment will be described.

[0104] Light emitted from the light source 32 passes through the light guide 26 and reaches the focal point F of the first mirror 14. The light emitted from focal point F is then reflected by the first mirror 14 and collimated along the optical axis C, becoming parallel light. This collimation occurs because the exit end of the light guide 26 is located at the focal point F of the first mirror 14. By providing the light guide 26 and the first mirror 14 in this embodiment, the light from the light source 32 is reflected by the first mirror 14 and travels to the second mirror 16. Since the light is collimated along the optical axis C, the light beams traveling toward the inner surface of the housing 18 are suppressed, preventing the light beams L1 and L2 from being reflected by the inner surface of the housing 18 and attenuating their intensity. Furthermore, light generally travels much faster than the velocity of a fluid. In other words, the fluid can be considered to be substantially stationary while the light travels through the housing 18. As a result, light can pass through the fluid, which can be considered to be substantially stationary compared to the speed of light, twice, once on the outward and once on the return path, between the exit end of the light guide 26 and the first mirror 14. In other words, the residence time of light in the fluid, which can be considered to be substantially stationary compared to the speed of light, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light onto the fluid between the light source 32 and the first mirror 14 can be extended. As a result, the optical sterilization device 10 according to this embodiment has the effect of increasing sterilization efficiency.

[0105] The light guide 26 is transparent to light (ultraviolet light), and therefore has the effect of not blocking light passing through the fluid.

[0106] Consider a case where the second mirror 16 is not provided. In this case, light traveling from the light source 32 along the optical axis C is reflected by the first mirror 14 and emitted, for example, outside the housing 18. On the other hand, by providing the second mirror 16 as in this embodiment, the light reflected by the first mirror 14 and collimated toward the second mirror 16 can be reflected back to the first mirror 14. Furthermore, light is generally much faster than the speed of a fluid. In other words, the fluid can be considered to be nearly stationary while the light travels through the housing 18. This allows light to pass twice through a fluid that can be considered to be nearly stationary compared to the speed of light. In other words, the residence time of light in a fluid that can be considered to be nearly stationary compared to the speed of light can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light to the fluid between the first mirror 14 and the second mirror 16 can be increased. As a result, the optical sterilization device 10 according to this embodiment has the effect of increasing sterilization efficiency.

[0107] In this embodiment, there is no need to provide the through-hole 16a in the second mirror 16, so it is possible to reduce the proportion of light that leaks to the outside of the housing 18 through the through-hole 16a, which has the effect of improving the sterilization ability.

[0108] The second mirror 16 is disposed near the rotation axis of the first fan 22. When an object is disposed in the area near the rotation axis of the fan 22, the closer the distance between the fan 22 and the object, the less likely it is that the object will interfere with the advection of fluid by the fan 22. In other words, it is possible to prevent an increase in pressure loss due to the object. Therefore, by disposing the second mirror 16 with respect to the first fan 22 in the area near the rotation axis of the fan 22, it is possible to prevent pressure loss from occurring.

[0109] By increasing the divergence angle of the light beams reaching the first mirror 14 from the exit end of the light guide 26 so that the light beams reach the entire reflective surface of the first mirror 14, it is possible to increase the spatial region within the fluid through which the light beams travel back and forth. This can be achieved, for example, by roughening the surface of the exit end, which has the effect of improving the efficiency of sterilization.

[0110] In this embodiment, the fan 22 is an axial fan. It is known that the larger the diameter of the fan 22, the more the flow efficiency of the axial fan generally improves. When the flow rate is constant, the greater the flow rate, the greater the amount of bacteria that can be removed per unit time. Therefore, the larger the diameter of the axial fan, the more the flow efficiency improves, and at the same time, a synergistic effect can be expected in which the bacteria removal capacity also improves.

[0111] The axial flow fan 22 is known to generate a swirling flow, which increases the residence time of the fluid inside the housing 18. This increases the irradiation time of the ultraviolet rays, which has the effect of improving the sterilization ability.

[0112] The heat sink 32a is disposed at or near the outlet 18b of the housing 18 through which the fluid is discharged. This promotes heat dissipation from the heat sink 32a. This also has the effect of increasing the power input to the light source 32, increasing the light intensity, and improving sterilization capability.

[0113] (Variation) As shown in FIG. 8, a method may be adopted in which the light source 32 is disposed not near the first mirror 14 but far from the first mirror 14, and the light is guided to the focal point of the first mirror 14 by a light guide.

[0114] 8 is an example in which the light source unit 12 is arranged on the inlet 18a side of the housing 18. That is, the light source 32 of the light source unit 12 is arranged near the second mirror 16. The incident end of the light guide 26 is arranged on the light emitting surface of the light source 32. The light guide 26 extends through the through hole 16a of the second mirror 16 toward the first mirror 14. The exit end of the light guide 26 is arranged at the focal point F of the first mirror 14.

[0115] The light source section 12 and the light guide 26 may be formed in this manner.

[0116] Based on the above configuration, the operation of the optical sterilization device 10 according to this modified example will be described.

[0117] Light emitted from the light source 32 passes through the light guide 26 and reaches the focal point F of the first mirror 14. The light emitted from the focal point F is then reflected by the first mirror 14 and collimated along the optical axis C to become parallel light. This collimation occurs because the exit end of the light guide 26 is located at the focal point F of the first mirror 14. As described above, by providing the light guide 26 and the first mirror 14 as in this modification, the light from the light source 32 can be reflected by the first mirror 14 and travel to the second mirror 16. At this time, because the light is collimated along the optical axis C, it is possible to prevent the light from being reflected by the inner surface of the housing 18 and the intensity of the light beams L1 and L2 from being attenuated. Furthermore, by arranging the light guide 26 parallel to the optical axis C, it is possible to prevent the parallel light beams L1 and L2 from being blocked by the light guide 26. Furthermore, light generally travels much faster than the speed of a fluid. In other words, the fluid can be considered to be almost stationary while the light travels through the housing 18. This allows the light to pass through the fluid, which can be considered to be almost stationary compared to the speed of light, twice, once on the outward journey and once on the return journey, between the exit end of the light guide 26 and the first mirror 14. This means that the residence time of the light in the fluid, which can be considered to be almost stationary compared to the speed of light, can be increased. In other words, by using the optical sterilization device 10 according to this embodiment, the irradiation time of light onto the fluid can be extended. This allows the optical sterilization device 10 according to this embodiment to have the effect of increasing the sterilization efficiency.

[0118] According to at least one of the embodiments described above, it is possible to provide an optical sterilization device 10 and an optical sterilization method that can prevent a decrease in optical sterilization efficiency at a position away from the light source 32.

[0119] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0120] 10...optical sterilization device, 12...light source unit, 14...first mirror, 16...second mirror, 16a...through hole, 18...housing, 18a...inlet, 18b...outlet, 18c...constriction portion, 22...first fan, 24...second fan, 26...light guide, 32...light source, 32a...heat sink, 34, 36...collimator optical element, 40...porous material, L1, L2...light beam.

Claims

1. first and second mirrors spaced apart and facing each other; a light source emitting at least two light beams; Assume that it is equipped with the light source and the first and second mirrors are arranged such that the at least two light beams emitted from the light source are reflected at least once by each of the first mirror and the second mirror; the at least two light beams from the light source include wavelengths that inactivate microorganisms in a fluid; Optical sterilization device.

2. The light source is a laser light source. The optical sterilization device according to claim 1 .

3. a collimator optical element in the direction of emission of the at least two light beams from the light source; The optical sterilization device according to claim 1 or 2.

4. the light source comprises at least two spaced apart light emitting surfaces; The collimator optical elements face each light-emitting surface. The optical sterilization device according to claim 3 .

5. At least one of the first and second mirrors is a concave mirror; The optical sterilization device according to claim 1 or 2.

6. a light guide that guides light from the light source to a focal point of the concave mirror or its vicinity and emits the light; The optical sterilization device according to claim 5 .

7. an inlet and an outlet for the fluid; at least one fan that generates a flow of the fluid, located near at least one of the intake port and the exhaust port; Assume that it is equipped with The first mirror or the second mirror is disposed near a rotation axis of the fan. The optical sterilization device according to claim 1 or 2.

8. When the first mirror is positioned to reflect the at least two light beams from the light source, disposing the second mirror in proximity to the light source; The optical sterilization device according to claim 7 .

9. a cylindrical housing having the inlet and outlet for the fluid; an inner wall of the housing having a constricted portion between the inlet and the outlet that narrows the flow path of the fluid more than at least one of the inlet and the outlet; The optical sterilization device according to claim 7 .

10. A through hole is provided in the second mirror, The light from the light source is configured to pass through the through hole before being reflected by the second mirror. The optical sterilization device according to claim 1 or 2.

11. The light source emits ultraviolet light including light with a peak wavelength of 280 nm. The optical sterilization device according to claim 1 or 2.

12. a porous material carrying a photocatalytic material is disposed between the first and second mirrors; The optical sterilization device according to claim 1 or 2.

13. emitting at least two light beams from a light source, the light beams including wavelengths that inactivate microorganisms in the fluid; emitting the at least two light beams to one of a first and a second mirror spaced apart and facing each other, and reflecting the at least two light beams at least once by each of the first and second mirrors; An optical sterilization method comprising:

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