Optical filter and pulsed-light hair removal device comprising same

Abstract

Provided is an optical filter for a pulsed-light 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 pulsed-light hair removal function.　This optical filter for a pulsed-light 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.

Description

Optical filter and photoepilation device equipped with same

[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.

[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 include a xenon tube that irradiates the skin surface with pulsed light 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 (see, for example, Patent Document 1).

[0003] For example, Patent Document 1 describes an optical hair removal device including a light-emitting lamp, a reflective filter that reflects light of a wavelength shorter than a predetermined wavelength of the light emitted by the light-emitting lamp, and an absorption filter that absorbs light of a wavelength shorter than the predetermined wavelength that has passed through the reflective filter. In this optical hair removal device, when light of 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 of a wavelength shorter than the predetermined wavelength that is ineffective for hair removal, including ultraviolet light, and then the absorption filter absorbs light of 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 of a wavelength effective for hair removal (600 nm to 800 nm).

[0004] JP 2022-81826 A

[0005] According to the configuration described in Patent Document 1, light with wavelengths of 530 nm or less (i.e., light in the ultraviolet region with high energy) that is unnecessary for hair removal is removed, so that the temperature rise of the skin of the treatment subject can be suppressed to some extent. However, even with conventional photoepilation devices that deal with light in the ultraviolet region in this way, there are still cases where the treatment subject complains of heat or pain, and further improvement is required.

[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.

[0007] In order to achieve the above object, the inventors have conducted extensive research and discovered 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: 800-1000 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, and in this case, the substrate is preferably made of silica 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. The substrate preferably absorbs light with a wavelength of 500 nm or less. The dielectric multilayer film preferably includes an infrared-cut film that reflects or absorbs infrared light. The dielectric multilayer film preferably further includes an anti-reflection film that prevents reflection of visible light.

[0014] Furthermore, it is desirable that the dielectric multilayer film is formed by alternately stacking 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 disposed in the optical path of light emitted from a xenon tube, and is characterized in that the average transmittance in the 800 to 1000 nm wavelength band is lower than the average transmittance in the 500 to 750 nm wavelength band. In this case, the difference between the average transmittance in the 800 to 1000 nm wavelength band and the average transmittance in the 500 to 750 nm wavelength band is preferably 30% or more, and more preferably 50% or more.

[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.

[0018] FIG. 1 is a diagram illustrating the configuration of an optical hair removal device equipped with an optical filter according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of an optical filter according to a first embodiment of the present invention. FIG. 3 is a graph showing the spectral intensity (light intensity) of light emitted from a xenon tube of an optical hair removal device equipped with an optical filter according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating 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. FIG. 5 is a diagram illustrating 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. FIG. 6 is a diagram illustrating 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. FIG. 7 is a graph showing the spectral intensity (light intensity) of light emitted from an optical hair removal device equipped with an optical filter according to the first embodiment (Examples 1 to 3) of the present invention. FIG. 8 is a diagram illustrating an experiment to confirm the effectiveness of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. FIG. 9 is a diagram illustrating the results of an experiment to confirm the effectiveness of the optical filter according to the first embodiment (Examples 1 to 3) of the present invention. Fig. 10 is a diagram for explaining the analysis results of the results of Fig. 9. Fig. 11 is a diagram for explaining the configuration of an optical filter according to a second embodiment of the present 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 their description will not be repeated.

[0020] (First embodiment) Fig. 1 is a diagram illustrating the configuration of a photoepilation device 1 equipped with an optical filter 52 according to a first embodiment of the present invention. 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 photoepilation device 1 is a photoepilation device that performs hair removal by irradiating the skin surface of a patient with light emitted from a xenon tube. The optical filter 52 is an optical filter for a photoepilation device that is attached to the tip (front surface) of the photoepilation device 1 (i.e., positioned in the optical path of the light) and reduces the amount of light transmitted through a specific wavelength band.

[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 source (e.g., an AC / DC converter circuit) not shown to generate the power necessary 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 source.

[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 that is 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 positioned 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 FIG. 2, the optical filter 52 of this embodiment has an appearance of a rectangular plate (e.g., 30 mm (horizontal) × 40 mm (vertical), thickness: 1 mm), and is composed of a glass substrate 52 a (substrate), a first dielectric multilayer film 52 b formed on one main surface of the glass substrate 52 a (the upper surface in FIG. 2( b)), and a second dielectric multilayer film 52 c formed on the other main surface of the glass substrate 52 a (the lower surface in FIG. 2( b)).

[0028] [Glass Substrate] The glass substrate 52a of this embodiment is a member made of glass (e.g., 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 small size and light weight 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 to have an average transmittance of 90% or more in at least 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 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 deposition or the like using a material with a refractive index of 1.1 to 1.5 (for example, SiO ２ ) and a material with a refractive index of 2.0 to 2.5 (for example, TiO ２ ) and a high refractive index dielectric film made of the material.

[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 deposition or the like using a material with a refractive index of 1.1 to 1.5 (for example, SiO ２ , MgF ２ A low refractive index dielectric film made of a material with a refractive index of 2.0 to 2.5 (e.g., ZrO ２ , Ta ２ O ５ , TiO ２ , Nb ２ O ５ The dielectric film is formed by alternately laminating high refractive index dielectric films made of a material such as a silicon dioxide film, ...

[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. 2B) of the glass substrate 52a, and a second dielectric multilayer film 52c on the other main surface (the lower surface in FIG. 2B) of the glass substrate 52a. Therefore, when light from the light source unit 40 is incident on 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] 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 and relatively short-wavelength visible light with wavelengths of 500 nm or less 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 photoepilation devices, patients still sometimes complain of heat and pain, and the inventors have conducted extensive research into the cause of this, and have found that the strong peak in the near-infrared region (NIR) (wavelength range: 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 due to the fact that the absorption wavelength range of water is 900-1050 nm, the absorption wavelength range of fat is 880-980 nm, and the absorption wavelength range of blood is 800-1050 nm, and therefore the moisture, fat, and blood around the skin S absorb the strong light in the near-infrared region (NIR) (wavelength range: 800-1000 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 First Dielectric Multilayer Film Example 1 SiO 2 was formed on one surface of a glass substrate 52a by vacuum deposition. ２ film (low refractive index dielectric film) and TiO ２ The first dielectric multilayer film 52b (infrared cut film) was formed by alternately laminating 34 layers of a high refractive index dielectric film and a high refractive index dielectric film, so that the average transmittance of the optical filter 52 in the wavelength band of 800 to 1000 nm was approximately 1%. ２ film (low refractive index dielectric film) and TiO ２ The first dielectric multilayer film 52b (infrared cut film) was formed by alternately laminating 44 layers of a high refractive index dielectric film and a high refractive index dielectric film, so that the average transmittance of the optical filter 52 in the wavelength band of 800 to 1000 nm was approximately 20%. ２ film (low refractive index dielectric film) and TiO ２ The first dielectric multilayer film 52b (infrared cut film) was formed by alternately stacking 26 layers of a high refractive index dielectric film and a high refractive index dielectric film, so that the average transmittance of the optical filter 52 in the wavelength band of 800 to 1000 nm was approximately 50%. Figure 5 shows the spectral transmittance curves of the first dielectric multilayer film 52b (infrared cut film) of Examples 1 to 3. In Figure 5, the horizontal axis represents wavelength (nm) and the vertical axis represents transmittance (%). [3. Formation of second dielectric multilayer film] (Examples 1 to 3) SiO ２ film (low refractive index dielectric film) and TiO ２A second dielectric multilayer film 52c (ultraviolet cut film) was formed so that the average transmittance of the glass substrate 52a at wavelengths of 500 nm or less was approximately 0%, thereby obtaining the optical filters 52 of Examples 1 to 3. Figure 6 is a diagram showing the spectral transmittance curves of the second dielectric multilayer film 52c (ultraviolet cut film) of Examples 1 to 3. In Figure 6, the horizontal axis 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. The horizontal axis of FIG. 7 represents wavelength (nm), and the vertical axis represents spectral intensity (au: arbitrary unit). Comparing FIG. 3 with FIG. 7 , it can be seen that when the light emitted from the xenon tube 41 passes through the optical filter 52 of each of Examples 1 to 3, ultraviolet light with wavelengths of 500 nm or less and relatively short-wavelength visible light are cut, while light in the near-infrared region (NIR) (wavelength band: 800 to 1000 nm) is changed depending on the configuration of the first dielectric multilayer film 52b (infrared-cutting film) of each of Examples 1 to 3. Furthermore, when the vertical axis in FIG. 7 is converted to transmittance, the average transmittance of the optical filter 52 of each of Examples 1 to 3 in the wavelength band of 500 to 750 nm was 94%. That is, in the optical filter 52 of Example 1, the difference between the average transmittance of approximately 1% in the 800-1000 nm wavelength band and the average transmittance of 94% in the 500-750 nm wavelength band was 93%. Furthermore, in the optical filter 52 of Example 2, the difference between the average transmittance of approximately 20% in the 800-1000 nm wavelength band and the average transmittance of 94% in the 500-750 nm wavelength band was 74%. Furthermore, in the optical filter 52 of Example 3, the difference between the average transmittance of approximately 50% in the 800-1000 nm wavelength band and the average transmittance of 94% in the 500-750 nm wavelength band was 44%. Thus, in the optical filters 52 of Examples 1 to 3, the difference between the average transmittance in the 800-1000 nm wavelength band and the average transmittance in the 500-750 nm wavelength band is preferably 30% or more, and more preferably 50% or more. The average transmittance of the optical filter 52 in the wavelength band of 500 to 750 nm in each of Examples 1 to 3 is preferably as close to 100%, more preferably 90% or more, and even more preferably 95% or more.

[0039] 8 and 9 are diagrams showing the effects confirmation experiment 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 experiment, 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] As shown in Figure 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 the skin sample P, and light from the photoepilation device 1 was irradiated onto the skin sample P. The temperature change of the skin sample P when irradiated with light from the photoepilation device 1 was measured using a data logger (NR-TH08 manufactured by Keyence Corporation) 200, and data was collected using a PC (personal computer) 100 to determine the temperature rise (temperature rise ΔT (°C)) of the skin sample P. Note that, as the skin sample P, a color chart of "Ocher Fair," "Ocher Normal," "Ocher Dark," "Natural White," "Natural Normal," "Natural Black," "Pink White," and "Pink Normal" was used to simulate human skin colors, and the effect confirmation experiment of Figure 8 was performed by sequentially changing these color charts (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) 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, although the temperature rise ΔT differs depending on the color of the skin sample P due to the difference in absorption of light (particularly light in the near-infrared region NIR) by the photoepilation device 1, the optical filter 52 of Examples 1 to 3 can be seen to reduce 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 the optical filter 52 of this embodiment (Examples 1 to 3) reduces light in the wavelength band: 800 to 1000 nm by the first dielectric multilayer film 52b, thereby reducing the temperature rise ΔT by approximately 10 to 30°C. Thus, it was found that the optical filter 52 of this embodiment (Examples 1 to 3) can suppress the temperature rise of the skin S of the treatment recipient.

[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 fair complexion," 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 of 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 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 (38.12°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. These are found to be in a proportional relationship (y = 0.1926x + 28.853), and it was found 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.

[0043] As described above, the results of FIG. 10 show that the temperature of the recipient's skin S increases as the average transmittance in the 800-1000 nm wavelength band increases. The inventors focused on this point and discovered that by keeping the average transmittance in the 800-1000 nm wavelength band low, it is possible to suppress the temperature rise in the recipient's skin S and reduce discomfort due to heat and pain. More specifically, when the temperature of the skin S is raised to 60°C, cells in the bulge region are sufficiently destroyed and hair removal is achieved. However, when the temperature of the skin S rises to 70-75°C or higher, damage to the skin S begins, causing uncomfortable heat and pain. Therefore, assuming a normal skin temperature of 32°C, the allowable temperature rise ΔT is set to 38-43°C or less. In other words, in this embodiment, based on the results of FIG. 10, the optical filter 52 is formed with a first dielectric multilayer film 52b, which is configured to have an average transmittance of 70% or less in the 800-1000 nm wavelength band. It is more preferable to configure the optical element so that the average transmittance in the wavelength band of 800 to 1000 nm is 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 including a first dielectric multilayer film 52b (infrared-blocking film) that reflects infrared light and a second dielectric multilayer film 52c (ultraviolet-blocking film) that reflects ultraviolet light. However, the present invention is not necessarily limited to this configuration. 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 light and ultraviolet light. 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-blocking film), or in addition to the first dielectric multilayer film 52b (infrared-blocking film) and the second dielectric multilayer film 52c (ultraviolet-blocking 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] 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-cutting 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 wavelengths of 500 nm or less that are 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 wavelengths of 500 nm or less, thereby achieving the same effects as the optical filter 52 of the first embodiment. 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.

[0051] 1: Photoepilation device 11: Housing 12: Guide surface 20: Power supply unit 30: Control circuit 40: Light source unit 41: Xenon tube 42: Reflection 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 that is placed in the optical path of light emitted from a xenon tube, characterized in that the average transmittance in the wavelength band of 800 to 1000 nm is 70% or less.

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

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

5. The optical filter according to claim 4, wherein said dielectric multilayer film further includes an anti-reflection film for preventing reflection of visible light.

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

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

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

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

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

11. An 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 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.

12. An optical hair removal device that performs hair removal by irradiating light onto the skin surface of a subject, comprising: a xenon tube that emits the light; and an optical filter that is placed in the optical path of the light emitted from the xenon tube, wherein the optical filter has an average transmittance of 70% or less in the wavelength band of 800 to 1000 nm.

13. An optical filter for a photoepilation device that is placed in the optical path of light emitted from a xenon tube, 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.

14. The optical filter according to claim 13, wherein 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.

15. The optical filter according to claim 13, wherein 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.

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