Optical filter and optical hair removal device comprising same

Abstract

To provide an optical filter for an optical hair removal device with which it is possible to reduce discomfort caused by heat and pain felt on skin by a person being treated while maintaining a hair removal function.SOLUTION: This optical filter for an optical hair removal device is disposed in an optical path of light emitted from a xenon tube, the optical filter being characterized by having an average transmittance of 70% or less in a wavelength band of 800-1000 nm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical filter used in an optical hair removal device that performs hair removal by irradiating the skin surface of a subject with light emitted from a xenon tube, and to an optical hair removal device equipped with the same. [Background technology]

[0002] In recent years, photoepilation devices that irradiate the skin surface of a patient with light to remove hair have been put into practical use. These photoepilation devices are equipped with a xenon tube, and irradiate the skin surface with pulsed light from the xenon tube to promote hair removal. The light from the xenon tube is absorbed by the hair roots and melanin around the hair roots and converted into thermal energy, which damages tissues such as the hair roots, hair papilla, and hair matrix cells (for example, Patent Document 1).

[0003] For example, Patent Document 1 describes an optical hair removal treatment device that includes a light-emitting lamp, a reflective filter that reflects light with a wavelength shorter than a predetermined wavelength of the light emitted by the light-emitting lamp, and an absorptive filter that absorbs light with a wavelength shorter than the predetermined wavelength that has passed through the reflective filter. In this optical hair removal treatment device, when light with a wavelength ineffective for hair removal (wavelength of 530 nm or less) is irradiated, the patient may feel hot due to radiant heat. Therefore, the reflective filter is used to reflect light with a wavelength shorter than the predetermined wavelength that is ineffective for hair removal, including ultraviolet light, and then the absorptive filter absorbs light with a wavelength shorter than the predetermined wavelength that has been irradiated at a large angle of incidence and passed through the reflective filter, thereby obtaining light with a wavelength effective for hair removal (600 nm to 800 nm). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-81826 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the configuration described in Patent Document 1, light with wavelengths of 530 nm or less that is unnecessary for hair removal (i.e., light in the high-energy ultraviolet region) is removed, so that the temperature rise of the patient's skin can be suppressed to some extent. However, even with conventional photo-epilation devices that are designed to deal with ultraviolet light, patients still sometimes complain of heat or pain, and further improvements are needed.

[0006] The present invention has been made in consideration of these circumstances, and its purpose is to provide an optical filter for an optical hair removal device that can further reduce the discomfort felt by the patient due to heat and pain on the skin while maintaining hair removal function, and to provide an optical hair removal device equipped with such an optical filter. [Means for solving the problem]

[0007] In order to achieve the above object, the inventors have conducted extensive research and found that the cause of patients' complaints of heat and pain is not only light in the ultraviolet region, but also a strong peak in the near-infrared region (wavelength band: 800 to 1000 nm) contained in the light emitted from the xenon tube. The present invention was made based on this finding.

[0008] That is, the optical filter of the present invention is an optical filter for an optical hair removal device that is placed in the optical path of light emitted from a xenon tube, and is characterized by having an average transmittance of 70% or less in the wavelength band of 800 to 1000 nm.

[0009] With this configuration, the strong peak in the near-infrared region (wavelength band: 800 to 1000 nm) contained in the light emitted from the xenon tube is suppressed, further reducing the heat and pain felt by the patient.

[0010] The optical filter preferably includes a substrate made of glass having a transmittance of 90% or more in the wavelength range of 500 to 750 nm, and a dielectric multilayer film formed on at least one of the main surfaces of the substrate. In this case, the substrate is preferably made of quartz glass or optical glass.

[0011] It is also preferable that the dielectric multilayer film includes an infrared cut film that reflects infrared rays, and in this case, it is also preferable that the dielectric multilayer film further includes an anti-reflection film that prevents reflection of visible light.

[0012] It is also preferable that the dielectric multilayer film further includes an ultraviolet cut film that reflects ultraviolet rays.

[0013] The optical filter preferably includes a substrate made of glass that absorbs ultraviolet light and a dielectric multilayer film formed on at least one major surface of the substrate, and the substrate preferably absorbs light with a wavelength of 500 nm or less. It is also preferable that the dielectric multilayer film includes an infrared cut film that reflects or absorbs infrared rays. It is also preferable that the dielectric multilayer film further includes an anti-reflection film that prevents reflection of visible light.

[0014] Furthermore, the dielectric multilayer film is preferably formed by alternately laminating low-refractive index dielectric films made of a material with a refractive index of 1.1 to 1.5 and high-refractive index dielectric films made of a material with a refractive index of 2.0 to 2.5.

[0015] From another perspective, the optical hair removal device of the present invention is an optical hair removal device that performs hair removal by irradiating light onto the skin surface of a subject, and is characterized in that it comprises a xenon tube that emits light and an optical filter that is placed in the optical path of the light emitted from the xenon tube, and the optical filter has an average transmittance of 70% or less in the wavelength band of 800 to 1000 nm.

[0016] From yet another perspective, the optical filter of the present invention is an optical filter for a photoepilation device that is arranged in the optical path of light emitted from a xenon tube, and is characterized in that the average transmittance in the wavelength band of 800 to 1000 nm is lower than the average transmittance in the wavelength band of 500 to 750 nm. In this case, the difference between the average transmittance in the wavelength band of 800 to 1000 nm and the average transmittance in the wavelength band of 500 to 750 nm is preferably 30% or more, and more preferably 50% or more. [Effects of the Invention]

[0017] As described above, the present invention provides an optical filter for a photo-epilation device that can reduce discomfort caused by heat and pain felt by the patient's skin while maintaining the hair removal function, and also provides a photo-epilation device equipped with such an optical filter. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a photo-epilation device including an optical filter according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of an optical filter according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a graph showing the spectral intensity (light intensity) of light emitted from a xenon tube of an optical hair removal device including an optical filter according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the spectral transmittance characteristics of the glass substrate of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 5] FIG. 5 is a diagram showing the spectral transmittance characteristics of the first dielectric multilayer film (infrared cut film) of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 6] FIG. 6 is a diagram showing the spectral transmittance characteristics of the second dielectric multilayer film (ultraviolet cut film) of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 7]FIG. 7 is a graph showing the spectral intensity (light intensity) of light emitted from the photo-epilation device including the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 8] FIG. 8 is a diagram for explaining an experiment to confirm the effect of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 9] FIG. 9 is a diagram illustrating the results of an experiment to confirm the effect of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. [Figure 10] FIG. 10 is a diagram for explaining the analysis results of the results of FIG. [Figure 11] FIG. 11 is a diagram illustrating the configuration of an optical filter according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0020] (First embodiment) FIG. 1 is a diagram illustrating the configuration of a photo-epilation device 1 equipped with an optical filter 52 according to a first embodiment of the present invention. Also, FIG. 2 is a diagram illustrating the configuration of the optical filter 52 of this embodiment, with FIG. 2(a) being a plan view and FIG. 2(b) being a longitudinal cross-sectional view. As shown in FIGS. 1 and 2, the photo-epilation device 1 is a photo-epilation device that performs a hair removal process by irradiating the skin surface of a subject with light emitted from a xenon tube. Also, the optical filter 52 is an optical filter for a photo-epilation device that is attached to the tip (front surface) of the photo-epilation device 1 (i.e., positioned in the optical path of the light) and reduces the amount of light in a specific wavelength band that transmits through it.

[0021] As shown in Figure 1, the optical hair removal device 1 is a device that is placed on the skin S of a patient to perform hair removal treatment, and is equipped with a housing 11, a power supply unit 20, a control circuit 30, a light source unit 40, an optical filter 52, etc.

[0022] The housing 11 is a case member that covers the power supply unit 20, control circuit 30, light source unit 40, optical filter 52, etc., and a guide surface 12 that comes into contact with the skin S of the patient is formed at the tip (the lowest end in Figure 1).

[0023] The power supply unit 20 is a device that supplies power to the control circuit 30 and the light source unit 40, and is connected to an external power supply (not shown) (for example, an AC / DC converter circuit) to generate the power required to drive the control circuit 30 and the light source unit 40. In another embodiment, the power supply unit 20 may include a battery that can be charged by an external power supply.

[0024] The control circuit 30 is an electronic circuit that controls the xenon tube 41 of the light source unit 40, and controls the xenon tube 41 in accordance with instructions from a user interface (not shown) to control the amount of light emitted from the xenon tube 41.

[0025] The light source unit 40 includes a xenon tube 41 and a reflecting mirror 42 arranged to cover the xenon tube 41, and emits light emitted from the xenon tube 41 and light reflected from the reflecting mirror 42 toward the skin S of the patient. Note that, for example, an elliptical mirror or the like is used as the reflecting mirror 42.

[0026] The optical filter 52 is a component that is arranged in the optical path of the light emitted from the light source unit 40 and the light reflected from the reflecting mirror 42 to reduce the amount of light that passes through a specific wavelength band, and is fixed to the tip of the housing 11.

[0027] As shown in Figure 2, the optical filter 52 of this embodiment has a rectangular plate-like appearance (e.g., 30 mm (horizontal) x 40 mm (vertical), thickness: 1 mm), and is composed of a glass substrate 52a (substrate), a first dielectric multilayer film 52b formed on one main surface of the glass substrate 52a (the upper surface in Figure 2(b)), and a second dielectric multilayer film 52c formed on the other main surface of the glass substrate 52a (the lower surface in Figure 2(b)).

[0028] [Glass substrate] The glass substrate 52a of this embodiment is a member made of glass (for example, quartz glass, optical glass, etc.) that can transmit light from the xenon tube 41. The thickness of the glass substrate 52a of this embodiment is not particularly limited, but from the viewpoint of achieving size and weight reduction while maintaining strength, it is preferably in the range of 0.5 to 3.0 mm, more preferably 0.5 to 1.5 mm, and even more preferably 0.5 to 1.0 mm. The glass substrate 52a of this embodiment is configured so as to have an average transmittance of at least 90% or more in the wavelength range of 500 to 750 nm.

[0029] [First dielectric multilayer film] The first dielectric multilayer film 52b of this embodiment is, for example, an infrared cut film that reflects infrared rays contained in the light from the xenon tube 41, and is an optical thin film that has the function of reducing light in a wavelength band of 800 to 1000 nm so that the average transmittance is 70% or less. In other words, the first dielectric multilayer film 52b functions as a notch filter with a stop band of 800 to 1000 nm. The first dielectric multilayer film 52b is formed by alternately laminating, by vapor deposition or the like, low-refractive index dielectric films made of a material having a refractive index of 1.1 to 1.5 (e.g., SiO2) and high-refractive index dielectric films made of a material having a refractive index of 2.0 to 2.5 (e.g., TiO2).

[0030] [Second dielectric multilayer film] The second dielectric multilayer film 52c of this embodiment is, for example, an ultraviolet-cutting film that reflects ultraviolet rays contained in the light from the xenon tube 41, and is an optical thin film that has the function of reducing ultraviolet rays and light with a wavelength of 500 nm or less, which is a relatively short-wavelength visible light component that does not contribute to hair removal, to an average transmittance of 1% or less. In other words, the second dielectric multilayer film 52c functions as a high-pass filter that cuts off light with a wavelength of 500 nm or less (cutoff wavelength: approximately 530 nm). The second dielectric multilayer film 52c is formed by alternately laminating, by vapor deposition or the like, low-refractive index dielectric films made of a material having a refractive index of 1.1 to 1.5 (e.g., SiO2, MgF2, etc.) and high-refractive index dielectric films made of a material having a refractive index of 2.0 to 2.5 (e.g., ZrO2, Ta2O5, TiO2, Nb2O5, etc.).

[0031] As described above, the optical filter 52 of this embodiment has a first dielectric multilayer film 52b on one main surface (the upper surface in FIG. 2(b)) of the glass substrate 52a, and a second dielectric multilayer film 52c on the other main surface (the lower surface in FIG. 2(b)) of the glass substrate 52a. Therefore, when light from the light source unit 40 enters the optical filter 52, a portion of the light in the wavelength range of 800 to 1000 nm is reflected toward the light source unit 40 without passing through the optical filter 52, and light with a wavelength of 500 nm or less is reflected toward the light source unit 40 without passing through the optical filter 52. All of the light in the wavelength range of 500 to 800 nm, a portion of the light in the wavelength range of 800 to 1000 nm (i.e., reduced near-infrared light), and all of the light in the wavelength range of 1000 nm or more are transmitted through the optical filter 52 and are irradiated onto the skin S of the treatment recipient.

[0032] Fig. 3 is a graph showing the spectral intensity (light intensity) of the light emitted from the xenon tube 41 of the light source unit 40, with the horizontal axis representing wavelength (nm) and the vertical axis representing spectral intensity (au: arbitrary unit). As shown in Fig. 3, the light emitted from the xenon tube 41 contains a wide range of wavelength components, from the ultraviolet range UV to the infrared range IR. Generally, light in the wavelength band of 500 to 800 nm in the visible light range VR is the light that contributes to hair removal, and ultraviolet light with a wavelength of 500 nm or less and relatively short-wavelength visible light are considered to be high-energy light that causes the patient to feel heat, pain, etc. Therefore, conventional optical hair removal devices are configured to cut off light with wavelengths of 500 nm or less, and emit light in the visible light range VR with a wavelength band of 500 to 800 nm, as well as light in the near-infrared range NIR (wavelength band: 800 to 1000 nm) and the infrared range IR (wavelength band: 1000 nm or more).

[0033] However, with conventional optical hair removal devices, patients still sometimes complain of heat or pain. After extensive research into the cause of this, the inventors discovered that the strong peak in the near-infrared region NIR (wavelength band: 800-1000 nm) contained in the light emitted from the xenon tube 41 is the cause of the heat and pain felt by the patient. This is thought to be because the absorption wavelength range of water is 900 to 1050 nm, the absorption wavelength range of fat is 880 to 980 nm, and the absorption wavelength range of blood is 800 to 1050 nm, and therefore the water, fat, and blood around the skin S absorb strong light in the near-infrared region NIR (wavelength band: 800 to 1000 nm).

[0034] Therefore, in order to solve this problem, in this embodiment, a first dielectric multilayer film 52b is formed on the optical filter 52, and light in the wavelength band of 800 to 1000 nm is reduced from the light emitted from the xenon tube 41.

[0035] The optical filter 52 of this embodiment will be further described below with reference to Examples 1 to 3, but the present invention is not limited to the following Examples.

[0036] [1. Selection of glass substrate 52a] (Examples 1 to 3) Optical glass (BK7, thickness 1.0 mm) manufactured by HOYA Corporation was selected as the glass substrate 52a in Examples 1 to 3. Fig. 4 is a diagram showing the spectral transmittance curves of the glass substrate 52a in Examples 1 to 3. In Fig. 4, the horizontal axis represents wavelength (nm) and the vertical axis represents transmittance (%).

[0037] [2. Formation of the first dielectric multilayer film] Example 1 On one surface of the glass substrate 52a, 34 layers of SiO2 films (low refractive index dielectric films) and TiO2 films (high refractive index dielectric films) were alternately stacked by vacuum deposition to form a first dielectric multilayer film 52b (infrared cut film) so that the average transmittance of the optical filter 52 in the wavelength band of 800 to 1000 nm was approximately 1%. Example 2 On one surface of the glass substrate 52a, 44 layers of SiO2 films (low refractive index dielectric films) and TiO2 films (high refractive index dielectric films) were alternately stacked by vacuum deposition to form a first dielectric multilayer film 52b (infrared cut film) so that the average transmittance of the wavelength band of the optical filter 52: 800 to 1000 nm was approximately 20%. Example 3 On one surface of the glass substrate 52a, 26 layers of SiO2 films (low refractive index dielectric films) and TiO2 films (high refractive index dielectric films) were alternately stacked by vacuum deposition to form a first dielectric multilayer film 52b (infrared cut film) so that the average transmittance of the optical filter 52 in the wavelength band of 800 to 1000 nm was approximately 50%. Fig. 5 is a diagram showing the spectral transmittance curves of the first dielectric multilayer film 52b (infrared cut film) of Examples 1 to 3. The horizontal axis of Fig. 5 represents wavelength (nm), and the vertical axis represents transmittance (%). [3. Formation of the second dielectric multilayer film] (Examples 1 to 3) By using a vacuum deposition method, 34 layers of SiO2 films (low refractive index dielectric films) and TiO2 films (high refractive index dielectric films) were alternately stacked, and a second dielectric multilayer film 52c (ultraviolet cut film) was formed so that the average transmittance of the glass substrate 52a for wavelengths of 500 nm or less was approximately 0%, thereby obtaining the optical filters 52 of Examples 1 to 3. Fig. 6 is a diagram showing the spectral transmittance curves of the second dielectric multilayer film 52c (ultraviolet cut film) of Examples 1 to 3. The horizontal axis of Fig. 6 represents wavelength (nm), and the vertical axis represents transmittance (%).

[0038] FIG. 7 is a graph showing the spectral intensity (light intensity) of light emitted from the xenon tube 41 after passing through the optical filter 52 of each of Examples 1 to 3, where the horizontal axis of FIG. 7 is wavelength (nm) and the vertical axis is spectral intensity (au: arbitrary unit). Comparing Figures 3 and 7, it can be seen that when light emitted from the xenon tube 41 passes through the optical filter 52 of each of Examples 1 to 3, ultraviolet rays with wavelengths of 500 nm or less and relatively short wavelength visible light are cut, and light in the near-infrared range NIR (wavelength band: 800 to 1000 nm) is changed depending on the configuration of the first dielectric multilayer film 52b (infrared cut film) of each of Examples 1 to 3. In addition, in FIG. 7, when the vertical axis is converted into transmittance, the average transmittance in the wavelength band of 500 to 750 nm of the optical filters 52 of Examples 1 to 3 was all 94%. That is, in the optical filter 52 of Example 1, the difference between the average transmittance in the wavelength band of 800 to 1000 nm: approximately 1% and the average transmittance in the wavelength band of 500 to 750 nm: 94% was 93%. In the optical filter 52 of Example 2, the difference between the average transmittance of approximately 20% in the wavelength band of 800 to 1000 nm and the average transmittance of 94% in the wavelength band of 500 to 750 nm was 74%. In the optical filter 52 of Example 3, the difference between the average transmittance of approximately 50% in the wavelength band of 800 to 1000 nm and the average transmittance of 94% in the wavelength band of 500 to 750 nm was 44%. Thus, in the optical filters 52 of Examples 1 to 3, it is desirable that the difference between the average transmittance in the wavelength band of 800 to 1000 nm and the average transmittance in the wavelength band of 500 to 750 nm be 30% or more, and it is even more desirable that it be 50% or more. The average transmittance of the optical filter 52 in each of Examples 1 to 3 in the wavelength band of 500 to 750 nm is preferably closer to 100%, more preferably 90% or more, and even more preferably 95% or more.

[0039] [Effectiveness verification experiment] 8 and 9 are diagrams showing the effects confirmation experiments conducted by the present inventors to evaluate the optical filters 52 of Examples 1 to 3 and the results thereof, with Fig. 8 being a diagram explaining the experimental model (experimental environment) of the effects confirmation experiments, and Fig. 9 being a diagram showing the effects of the optical filters 52 of Examples 1 to 3 on each skin sample P. Note that the horizontal axis of Fig. 9 represents each skin sample P, and the vertical axis represents the temperature rise ΔT (°C).

[0040] 8, in the effect confirmation experiment, a paper skin sample P simulating the color of skin S was placed on a thermocouple (K type) 210, and a photoepilation device 1 equipped with an optical filter 52 of each of Examples 1 to 3 was placed on top of the skin sample P, and light from the photoepilation device 1 was irradiated onto the skin sample P. Then, the temperature change of the skin sample P when irradiated with light from the photoepilation device 1 was measured with a data logger (NR-TH08 manufactured by Keyence Corporation) 200, and the data was collected with a PC (personal computer) 100, and the temperature rise of the skin sample P (temperature rise ΔT (°C)) was calculated. As the skin sample P, a color chart was used that imitated the color of human skin: "Fair ochre," "Normal ochre," "Dark ochre," "Fair natural," "Normal natural," "Dark natural," "White pink," and "Normal pink." The experiment to confirm the effect shown in Figure 8 was conducted by sequentially changing these (Figure 9). In addition, in the effect confirmation experiment of Figure 8, as comparative examples, an optical hair removal device (Comparative Example 1) having only a glass substrate 52a (without the first dielectric multilayer film 52b and the second dielectric multilayer film 52c formed) and an optical hair removal device (Comparative Example 2) not having an optical filter 52 were prepared, and the effect confirmation experiment of Figure 8 was also performed on these (Figure 9).

[0041] As shown in Figure 9, the temperature rise ΔT varies depending on the color of the skin sample P because the absorption of light (especially light in the near-infrared region NIR) from the optical hair removal device 1 differs. However, it can be seen that the optical filter 52 of Examples 1 to 3 reduces the temperature rise ΔT of the skin sample P. Furthermore, when comparing Comparative Example 2 with Examples 1 to 3, it can be seen that with the optical filter 52 of this embodiment (Examples 1 to 3), the first dielectric multilayer film 52b reduces light in the wavelength band of 800 to 1000 nm, and therefore the temperature rise ΔT decreases by approximately 10 to 30°C. As described above, it was found that the optical filter 52 of this embodiment (Examples 1 to 3) can suppress a rise in temperature of the skin S of the patient.

[0042] FIG. 10 is an analysis result of the results of FIG. 9, and is a graph showing the relationship between the temperature rise ΔT (°C) and the average transmittance (%) in the wavelength band of 800 to 1000 nm (i.e., the relationship with the optical filters 52 of Examples 1 to 3) when the skin sample P is "Ocher fair skin" and "Natural normal skin." As shown in Figure 10, when the skin sample P has an "ochre-colored" skin, the temperature rise ΔT (22.30°C) of the skin sample P when the average transmittance in the wavelength band of 800 to 1000 nm is approximately 1% (i.e., when the optical filter 52 of Example 1 is used), the temperature rise ΔT (27.52°C) of the skin sample P when the average transmittance in the wavelength band of 800 to 1000 nm is approximately 20% (i.e., when the optical filter 52 of Example 2 is used), and the temperature rise ΔT (36.03°C) of the skin sample P when the average transmittance in the wavelength band of 800 to 1000 nm is approximately 50% (i.e., when the optical filter 52 of Example 3 is used) are plotted. It was found that these are in a proportional relationship (y = 0.2806x + 21.976), and that the temperature rise ΔT of the skin sample P increases as the average transmittance in the wavelength band of 800 to 1000 nm increases. Furthermore, when the skin sample P is "natural normal," the temperature rise ΔT (28.47°C) of the skin sample P when the average transmittance in the wavelength band: 800 to 1000 nm is approximately 1% (i.e., when the optical filter 52 of Example 1 is used), the temperature rise ΔT (33.65°C) of the skin sample P when the average transmittance in the wavelength band: 800 to 1000 nm is approximately 20% (i.e., when the optical filter 52 of Example 2 is used), and the temperature rise ΔT (38.12°C) of the skin sample P when the average transmittance in the wavelength band: 800 to 1000 nm is approximately 50% (i.e., when the optical filter 52 of Example 3 is used) are plotted, and it was found that these are in a proportional relationship (y = 0.1926x + 28.853), and that the temperature rise ΔT of the skin sample P increases as the average transmittance in the wavelength band: 800 to 1000 nm increases.

[0043] Thus, the results of FIG. 10 show that as the average transmittance in the wavelength band of 800 to 1000 nm increases, the temperature of the skin S of the patient increases. The inventors focused on this point and discovered that by keeping the average transmittance in the wavelength band of 800 to 1000 nm low, it is possible to suppress the temperature rise of the patient's skin S and reduce discomfort caused by heat and pain. More specifically, when the temperature of the skin S is raised to 60°C, the cells in the bulge region are sufficiently destroyed and hair is removed, but when the temperature of the skin S rises above 70-75°C, damage to the skin S begins, causing uncomfortable heat and pain. Therefore, the normal temperature of the skin S is assumed to be 32°C, and the allowable temperature rise ΔT is set to 38-43°C or less. 10, the optical filter 52 is formed with a first dielectric multilayer film 52b so that the average transmittance in the wavelength range of 800 to 1000 nm is 70% or less. It is more preferable to configure the average transmittance in the wavelength range of 800 to 1000 nm to be 50% or less.

[0044] The above is a description of the embodiment of the present invention, but the present invention is not limited to the configuration of the above embodiment, and various modifications are possible within the scope of the technical concept thereof.

[0045] For example, the optical filter 52 of the present embodiment (Examples 1 to 3) has been described as having a first dielectric multilayer film 52b (infrared cut film) that reflects infrared rays and a second dielectric multilayer film 52c (ultraviolet cut film) that reflects ultraviolet rays, but is not necessarily limited to this configuration, and instead of the first dielectric multilayer film 52b and the second dielectric multilayer film 52c, a resin layer containing an absorbing dye may be formed to absorb infrared rays and ultraviolet rays. In this case, the resin layer may be formed by a spin coating method, a dipping method, or the like. Furthermore, instead of the second dielectric multilayer film 52c (ultraviolet cut film), or in addition to the first dielectric multilayer film 52b (infrared cut film) and the second dielectric multilayer film 52c (ultraviolet cut film), an anti-reflection film that prevents reflection of light in the visible light range VR (wavelength band: 500 to 800 nm) may be provided.

[0046] (Second embodiment) 11 is a longitudinal cross-sectional view illustrating the configuration of an optical filter 52A according to a second embodiment of the present invention. As shown in FIG. 11, the optical filter 52A of this embodiment differs from the optical filter 52 of the first embodiment in that it includes a sharp-cut filter 52a1 (substrate) instead of the glass substrate 52a, and an anti-reflection film (third dielectric multilayer film 52d) instead of the ultraviolet-cut film (second dielectric multilayer film 52c).

[0047] The sharp cut filter 52a1 is a member that reflects or absorbs ultraviolet light and relatively short wavelength visible light with a wavelength of 500 nm or less that is included in the light from the xenon tube 41, and is made of, for example, borosilicate glass.

[0048] The anti-reflection film (third dielectric multilayer film 52d) is an optical thin film that functions to prevent light in the visible light range VR (wavelength band: 500 to 800 nm) emitted from the xenon tube 41 from being reflected at the interface with the sharp cut filter 52a1.

[0049] According to the configuration of this embodiment, the sharp cut filter 52a1 cuts off light with a wavelength of 500 nm or less, and therefore, the same effects as those of the optical filter 52 of the first embodiment can be obtained. Furthermore, the anti-reflection film (third dielectric multilayer film 52d) allows light in the visible light range VR (wavelength band: 500 to 800 nm) emitted from the xenon tube 41 to be emitted without being reflected at the interface with the sharp cut filter 52a1, thereby increasing the transmittance of the visible light range VR (wavelength band: 500 to 800 nm) (i.e., increasing the spectral intensity (light intensity)).

[0050] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0051] 1: Light hair removal device 11: Housing 12: Guide surface 20: Power supply section 30: Control circuit 40: Light source section 41: Xenon tube 42: Reflective mirror 52: Optical filter 52A: Optical filter 52a: Glass substrate 52a1: Sharp cut filter 52b: First dielectric multilayer film 52c: Second dielectric multilayer film 52d: Third dielectric multilayer film

Claims

1. An optical filter for a photoepilation device, which is disposed in an optical path of light emitted from a xenon tube, The average transmittance in the wavelength range of 800 to 1000 nm is 70% or less. An optical filter characterized by:

2. The optical filter according to claim 1, characterized in that the optical filter comprises a substrate made of glass having a transmittance of 90% or more in the wavelength range of 500 to 750 nm, and a dielectric multilayer film formed on at least one of the main surfaces of the substrate.

3. 3. The optical filter according to claim 2, wherein the substrate is made of quartz glass or optical glass.

4. 3. The optical filter according to claim 2, wherein the dielectric multilayer film includes an infrared cut film that reflects infrared rays.

5. 5. The optical filter according to claim 4, wherein the dielectric multilayer film further includes an anti-reflection film that prevents reflection of visible light.

6. 5. The optical filter according to claim 4, wherein the dielectric multilayer film further includes an ultraviolet-cutting film that reflects ultraviolet rays.

7. 2. The optical filter according to claim 1, wherein the optical filter comprises a substrate made of glass that absorbs ultraviolet light, and a dielectric multilayer film formed on at least one main surface of the substrate.

8. 8. The optical filter according to claim 7, wherein the substrate absorbs light having a wavelength of 500 nm or less.

9. 8. The optical filter according to claim 7, wherein the dielectric multilayer film includes an infrared cut film that reflects or absorbs infrared rays.

10. 10. The optical filter according to claim 9, wherein the dielectric multilayer film further includes an anti-reflection film that prevents reflection of visible light.

11. The optical filter according to any one of claims 2 to 7, characterized in that the dielectric multilayer film is formed by alternately stacking low-refractive index dielectric films made of a material having a refractive index of 1.1 to 1.5 and high-refractive index dielectric films made of a material having a refractive index of 2.0 to 2.

5.

12. A photo-hair removal device that performs hair removal by irradiating light onto the skin surface of a subject, a xenon tube that emits the light; an optical filter disposed in the optical path of the light emitted from the xenon tube; Equipped with The optical filter has an average transmittance of 70% or less in the wavelength range of 800 to 1000 nm. A photoepilation device characterized by:

13. An optical filter for a photoepilation device, which is disposed in an optical path of light emitted from a xenon tube, The average transmittance in the wavelength range of 800 to 1000 nm is lower than the average transmittance in the wavelength range of 500 to 750 nm An optical filter characterized by:

14. The difference between the average transmittance in the wavelength band of 800 to 1000 nm and the average transmittance in the wavelength band of 500 to 750 nm is 30% or more.

14. The optical filter according to claim 13.

15. The difference between the average transmittance in the wavelength band of 800 to 1000 nm and the average transmittance in the wavelength band of 500 to 750 nm is 50% or more.

14. The optical filter according to claim 13.

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