Light irradiation device

Abstract

The purpose of the present invention is to provide a light irradiation device with which it is possible to cause ultraviolet light to be incident on an eyeball along the visual axis. A light irradiation device 1 includes: ultraviolet light sources 2 that emit light including ultraviolet light; and light guide members 3 made of a material that allows the ultraviolet light emitted from the ultraviolet light sources 2 to propagate therein and that can transmit visible light. The light guide members 3 are disposed so as to be close to the eyeballs, at positions where at least portions thereof cover the front of the eyeballs, and allow the ultraviolet light propagated therein to be emitted from in front front of the eyeballs and enter the eyeballs.

Description

light irradiation device

[0001] The present invention relates to a light irradiation device.

[0002] A wearable device that irradiates the eyeball with ultraviolet light of 360 nm to 400 nm has been proposed for the purpose of suppressing the progression of myopia (see, for example, Patent Document 1).

[0003] Patent No. 6175210 specification

[0004] The device disclosed in Patent Document 1 is a device in which an ultraviolet light source is placed on the rim of a patient's eyeglasses or the brim of a hat, and ultraviolet light emitted from the ultraviolet light source is incident on the eyeball from a corner position that does not obstruct the patient's field of vision. However, because the ultraviolet light from the ultraviolet light source of the device disclosed in Patent Document 1 is incident from a direction that forms a large angle with respect to the visual axis, the ultraviolet light can only be directed at a portion of the retina, making it difficult to effectively suppress the progression of myopia. Therefore, there is a need for a light irradiation device that can direct ultraviolet light into the eyeball along the visual axis.

[0005] A first aspect of the present disclosure is a light irradiation device comprising an ultraviolet light source that emits light including ultraviolet rays, and a light-guiding member that propagates the ultraviolet rays emitted from the ultraviolet light source inside and is made of a material that is capable of transmitting visible light, wherein the light-guiding member is positioned close to the eyeball in a position where at least a portion of the light-guiding member covers the front of the eyeball, and the ultraviolet rays that have propagated inside are emitted from the front of the eyeball and made to enter the eyeball.

[0006] According to this aspect, when light containing ultraviolet light emitted from an ultraviolet light source enters a light-guiding member at least a portion of which is disposed in a position covering the front of the patient's eyeball, the ultraviolet light propagates through the light-guiding member and is emitted from the front of the eyeball toward the eyeball, where it can enter the eyeball. This allows the ultraviolet light to enter in a direction along the visual axis of the eyeball and irradiate the retina near the central region around the fovea centralis within the eyeball. As a result, compared to conventional methods in which ultraviolet light is incident from a direction that forms a large angle with the visual axis, it is possible to irradiate a wider area of ​​the retina and efficiently suppress the progression of myopia.

[0007] Furthermore, since the light guide member is made of a material that can transmit visible light even when it is positioned in a position that covers the front of the eyeball, light from the outside can be incident on the eyeball without being blocked. Therefore, it is possible to suppress the progression of myopia while going about daily life with the light irradiation device worn.

[0008] In the above aspect, the light guide member may be made of a material having a refractive index of 1.8 or less, thereby improving the ultraviolet transmittance of the light guide member, allowing more ultraviolet light incident on the light guide member to be emitted toward the eyeball, and improving the efficiency of ultraviolet light utilization.

[0009] In the above aspect, the light guide member may be made of any one of cycloolefin polymer (COP), cycloolefin copolymer (COC), and acrylic resin, which allows the light guide member to be easily molded and the light irradiation device to be lightweight.

[0010] In the above aspect, the light-guiding member may include a diffraction grating at a position located in front of the eyeball, which diffracts the ultraviolet light propagating through the light-guiding member and outputs it to the outside. This allows the ultraviolet light propagating through the light-guiding member to be diffracted by the diffraction grating and efficiently emitted outside the light-guiding member. Furthermore, because the diffraction grating is formed with fine irregularities, it is possible to prevent refraction of visible light passing through the light-guiding member. Therefore, ultraviolet light can be emitted into the eyeball from in front of the eyeball without substantially obstructing the field of view.

[0011] In the above aspect, the following relational expression may be satisfied: 1.1λ≦P<10λ, where λ is the peak wavelength of the light emitted from the ultraviolet light source, and P is the pitch of the diffraction grating.

[0012] When the diffraction grating pitch is P≧1.1λ, the diffraction grating can generate multiple-order diffracted light. This allows the ultraviolet light emitted from the light-guiding member to be diffracted over a wider range, thereby irradiating a wider area of ​​the retina. If the diffracted light is visible light, multiple-order diffracted light incident on the retina will result in a doubled image. Since ultraviolet light is invisible, generating multiple-order diffracted light can expand the irradiation range of the retina without obstructing the field of view. When the diffraction grating pitch is P≧10λ, the diffraction efficiency is less than 5%, reducing the amount of ultraviolet light emitted from the light-guiding member and the ultraviolet light utilization rate.

[0013] In the above aspect, the diffraction grating may emit diffracted light of multiple orders, thereby diffracting the ultraviolet light emitted from the light-guiding member over a wider range and irradiating a wider area of ​​the retina.

[0014] In the above aspect, the light-guiding member may transmit light having a wavelength of 360 nm or more and 400 nm or less therein. In the above aspect, a filter may be provided between the ultraviolet light source and the light-guiding member to block light having a wavelength longer than 400 nm. This prevents light having a wavelength of 400 nm or more from entering the light-guiding member, thereby reducing the glare felt by the patient by light emitted from the front of the eyeball.

[0015] 1 is a schematic perspective view showing a light irradiation device according to an embodiment of the present invention; FIG. 2 is a longitudinal sectional view showing the principle of the light irradiation device of FIG. 1; FIG. 3 is a longitudinal sectional view showing an example of a diffraction grating provided in a light guide member of the light irradiation device of FIG. 1; FIG. 4 is a schematic view explaining diffraction of light in the diffraction grating of FIG. 3; FIG. 5 is a view showing the intensity of diffracted light when the pitch P of the diffraction grating is 0.7λ; FIG. 6 is a view showing the intensity of diffracted light when the pitch P of the diffraction grating is 1.1λ; FIG. 7 is a view showing the intensity of diffracted light when the pitch P of the diffraction grating is 1.5λ; FIG. 8 is a view showing the intensity of diffracted light when the pitch P of the diffraction grating is 2.5λ; and FIG. 9 is a graph showing the relationship between the pitch P of the diffraction grating and diffraction efficiency. FIG. 10 is a longitudinal sectional view showing a modified example of the light irradiation device of FIG. 2; and FIG. 11 is a longitudinal sectional view showing another modified example of the light irradiation device of FIG. 2.

[0016] A light irradiation device 1 according to an embodiment of the present disclosure will be described below with reference to the drawings. As shown in Fig. 1 , the light irradiation device 1 according to this embodiment is a glasses-type device worn by a subject who wishes to suppress the progression of myopia, and includes an ultraviolet light source 2 and a light-guiding member 3.

[0017] The ultraviolet light source 2 and the light-guiding member 3 are attached to a spectacle frame 4. The spectacle frame 4 includes a pair of temples 5 that the subject wears over both ears, and a rim 6 to which one end of each temple 5 is connected.

[0018] The ultraviolet light source 2 is disposed, for example, at an inner position near one end of a pair of temples 5 of the eyeglass frame 4 that is connected to the rim 6. As shown in Fig. 2, the ultraviolet light source 2 includes, for example, a light source 7 that emits light containing ultraviolet rays with a wavelength of 360 nm or more and 400 nm or less, and a lens 8 that condenses the light from the light source 7.

[0019] The light source 7 is an LD, LED, or the like having an emission peak in the wavelength range of 360 nm to 400 nm. The lens 8 is, for example, a collimating lens, which converts the light emitted from the light source 7 into approximately parallel light and makes the light incident on the light-guiding member 3. The ultraviolet light source 2 is disposed so that an exit port for emitting the approximately parallel light containing ultraviolet light faces the edge of the light-guiding member 3 that is close to the rim 6, and emits the light containing ultraviolet light toward the opposing light-guiding member 3.

[0020] The light-guiding member 3 is a plate-like member placed on the rim 6 of the eyeglass frame 4 at a position where a pair of eyeglass lenses would be placed in normal eyeglasses, and is made of a material with a refractive index of 1.8 or less, such as COP, acrylic resin, cycloolefin copolymer (COC), polystyrene, BK7, i-line glass, LF5, FK5, or fluorite. This allows the light-guiding member 3 to transmit light, including ultraviolet light with a wavelength of 360 nm or more and 400 nm or less, inside, and to transmit visible light.

[0021] Furthermore, it is preferable that the light guide member 3 has a transmittance of 60% / 10 mm or more at a wavelength of 370 nm. Furthermore, by forming the light guide member 3 from, for example, cycloolefin polymer (COP), there are advantages in that it is lightweight and easy to manufacture.

[0022] The light-guiding member 3 also has diffraction gratings 11, 12 in a first region 9 into which light emitted from the ultraviolet light source 2 is incident, and in a second region 10 that is disposed in front of the subject's eyeball A when the light irradiation device 1 is worn. The diffraction grating (input grating) 11 provided in the first region 9 has the function of diffracting light from the ultraviolet light source 2 disposed outside the light-guiding member 3 when it is incident into the light-guiding member 3, and directing the light to propagate within the light-guiding member 3 in a direction approaching the second region 10 by total reflection.

[0023] The diffraction grating (output grating) 12 provided in the second region 10 has the function of diffracting light that has propagated inside the light-guiding member 3 and emitting the light to the outside of the light-guiding member 3. In this embodiment, the output grating 12 has fine irregularities that are repeated at a constant pitch P, as shown in FIG. 3 , for example, and the pitch P satisfies the following conditional expression (1):

[0024] 1.1λ≦P<10λ (1) where λ is the peak wavelength of the light emitted from the light source 7 .

[0025] The operation of the light irradiation device 1 according to this embodiment configured as described above will be described below. A subject who wishes to suppress the progression of myopia places the temples 5 of the eyeglass frame 4 over both ears and positions the rims 6 of the eyeglass frame 4 in front of the eyes. This allows the light irradiation device 1 to be worn with the pair of light guiding members 3 held by the rims 6 of the eyeglass frame 4 positioned close to the eyeballs A in positions where at least a portion of each light guiding member 3 covers the front of each of the left and right eyeballs A. In this state, the second region 10 of the light guiding member 3 is positioned directly in front of both eyeballs A of the subject.

[0026] In this case, the light-guiding member 3 is made of a material that is transmissive to visible light, so that even if it covers the front of the eyeball A, visible light from the outside world can be transmitted in the thickness direction without being obstructed and can be incident on the eyeball A. This allows the subject to see the outside world while wearing the light irradiation device 1, and to carry out daily life without any inconvenience.

[0027] In this state, if the subject wishes to obtain the effect of suppressing the progression of myopia, he or she activates the ultraviolet light source 2, causing the ultraviolet light source 2 to emit light containing ultraviolet light. The light emitted from the emission port of the ultraviolet light source 2 is incident on the light-guiding member 3 arranged opposite the emission port. An input grating 11 is provided in the first region 9 opposite the emission port of the ultraviolet light source 2, so that the light emitted from the ultraviolet light source 2 is diffracted by the input grating 11 when it enters the light-guiding member 3.

[0028] 2, the light diffracted by the input grating 11 is directed in a direction of total reflection inside the light-guiding member 3. As a result, the light incident on the light-guiding member 3 is propagated by repeatedly being totally reflected on the inner surface of the light-guiding member 3, and when it reaches the output grating 12 provided in an area near the center of the light-guiding member 3, it is diffracted and emitted to the outside of the light-guiding member 3.

[0029] In particular, according to this embodiment, the light-guiding member 3 is made of a material having a refractive index of 1.8 or less, and therefore ultraviolet rays can be efficiently propagated within the light-guiding member 3. Furthermore, more ultraviolet rays that enter the light-guiding member 3 can be emitted toward the eyeball A, thereby improving the utilization efficiency of ultraviolet rays.

[0030] Furthermore, since the output grating 12 is provided on the surface of the light-guiding member 3 facing the eyeball A, in the second region 10 located in front of the eyeball A, the light emitted from the light-guiding member 3 is incident on the eyeball A at a small angle with respect to the visual axis. This makes it easier for ultraviolet light to be incident in a direction along the visual axis of the eyeball A, and can be irradiated onto the retina near the central region around the fovea centralis within the eyeball A. As a result, compared to conventional methods in which ultraviolet light is incident from a direction that forms a large angle with respect to the visual axis, it is possible to irradiate ultraviolet light over a wider area of ​​the retina, thereby achieving the effect of efficiently suppressing the progression of myopia.

[0031] Furthermore, because the output grating 12 is formed by minute concaves and convexes, it is possible to prevent refraction of visible light passing through the light-guiding member 3. This has the advantage that ultraviolet light can be emitted into the eyeball A from the front of the eyeball A without interfering with the field of view.

[0032] Furthermore, according to the light irradiation device 1 of this embodiment, the output grating 12 satisfies the formula (1). As a result, as shown in Fig. 4, the output grating 12 can generate multiple orders of diffracted light when diffracting light that has propagated inside the light-guiding member 3 and emitting it toward the eye A.

[0033] When the pitch P of output grating 12 is P<1.1λ, for example, when P=0.7λ, first-order diffracted light is dominant in the light emitted from output grating 12, as shown in the simulation results in Figure 5. The simulation was performed assuming a refractive index n of light-guiding member 3 of 1.533, a wavelength of 380 nm, a slant angle of output grating 12 of 36.5°, and light (incident light) incident at an angle of 42° to 74° relative to output grating 12. When P<1.1λ, the angular range of light emitted from output grating 12 is limited, making it impossible to irradiate a wide area of ​​the retina with ultraviolet light, resulting in a reduced myopia suppression effect.

[0034] In contrast, when P = 1.1λ, second-order diffracted light can be generated in addition to first-order diffracted light, which has the advantage of irradiating a wider area of ​​the retina with ultraviolet light and improving the myopia suppression effect, as shown in the simulation results of Figure 6. Similarly, when P = 1.5λ and when P = 2.5λ, multiple-order diffracted light can be emitted toward the eyeball A, as shown in the simulation results of Figures 7 and 8, respectively.

[0035] Since the density of photoreceptors is higher near the center of the retina, which is the center of the visual field, light can be more efficiently irradiated onto the photoreceptors when the diffraction angle has multiple peaks between -30° and +30° (i.e., a range of 60°). Therefore, when P = 1.1λ, the second-order diffracted light has a lower intensity than the first-order diffracted light, but when P = 1.5λ, the first-order and second-order diffracted light have equivalent intensities, allowing ultraviolet light to be irradiated over a wider range of the retina, greater than 60°. Furthermore, when P = 2.5λ, third-order diffracted light can also be generated in addition to the first-order and second-order diffracted light.

[0036] Specifically, when P = 1.1λ in Fig. 6, the peak of the first-order diffracted light is -24, the peak of the second-order diffracted light is +24, and the interval between the peak wavelengths of the first and second diffracted light is 48. When P = 1.5λ in Fig. 7, the peak of the first-order diffracted light is -35, the peak of the second-order diffracted light is +3, and the interval between the peak wavelengths of the first and second diffracted light is 38. When P = 2.5λ in Fig. 8, the peak of the second-order diffracted light is -23, the peak of the third-order diffracted light is -4, the interval between the peak wavelengths of the second-order diffracted light and the third-order diffracted light is 19, the peak of the third-order diffracted light is -4, the peak of the fourth-order diffracted light is +19, and the interval between the peak wavelengths of the third-order diffracted light and the fourth-order diffracted light is 23. It is preferable to have multiple peaks, and it is even more preferable for the intervals between the peak wavelengths to be narrow. Therefore, when P = 2.5λ, the intervals between the peak wavelengths of each diffracted light can be narrowed to achieve a uniform myopia suppression effect over a wider range of the retina.

[0037] When diffracting light in output grating 12, if multiple-order diffracted light is incident on the retina, double images will appear, so multiple-order diffracted light is not actively generated. However, according to this embodiment, the light diffracted by output grating 12 is ultraviolet light, which is difficult for the retina to perceive, and therefore has the advantage that even if multiple-order diffracted light is generated, the range of illumination on the retina can be expanded without obstructing the field of view.

[0038] Furthermore, if the pitch P of the output grating 12 is P≧10λ, as shown in Figure 9, the diffraction efficiency will be less than 5%, the diffracted light will not spread, the amount of UV light emitted from the light-guiding member 3 will decrease, and the UV utilization rate will decrease, which is undesirable. Furthermore, if a material with high UV transmittance is used as the material for the light-guiding member 3, the refractive index will be low, and therefore it will not normally be possible to irradiate UV light over a wide field of view. In this embodiment, by designing the pitch P of the output grating 12 to be within the range of the above-mentioned formula (1), it is possible to utilize high-order diffracted light and achieve a wide irradiation range.

[0039] As described above, with the light irradiation device 1 according to this embodiment, light containing ultraviolet light is emitted from the front of the eyeball A, so that the light can be incident on the eyeball A along the visual axis of the eyeball A or at a small angle relative to the visual axis. As a result, there is an advantage that ultraviolet light can be irradiated onto a wider area of ​​the retina, improving the myopia suppression effect.

[0040] Conventionally, when light containing ultraviolet light is incident on eyeball A at a large angle relative to the visual axis, the ultraviolet light can only be irradiated onto the retina in an area biased in one direction relative to the fovea, resulting in a low myopia suppression effect. In addition, ultraviolet light is also irradiated onto areas of the face other than eyeball A, causing side effects such as sunburn. However, according to this embodiment, ultraviolet light is incident into eyeball A along the visual axis, making it less likely that such side effects will occur and allowing ultraviolet light to be used effectively.

[0041] Furthermore, since light containing ultraviolet light is incident on the light-guiding member 3 at a position other than in front of the eyeball A and is emitted from the front of the eyeball A, it is not necessary to place the ultraviolet light source 2 in a position that obstructs the field of view. Furthermore, by making the light-guiding member 3 placed close to the front of the eyeball A out of a material that is transmissive to visible light, visibility of the outside world can be ensured.

[0042] Furthermore, by constructing the light-guiding member 3 from a material having a refractive index of 1.8 or more, ultraviolet rays can be efficiently propagated, improving the utilization rate of ultraviolet rays. Also, by emitting multiple-order diffracted light of ultraviolet rays toward the eyeball A, ultraviolet rays can be irradiated over a wider area of ​​the retina, improving the myopia suppression effect.

[0043] In this embodiment, the ultraviolet light source 2 and the light guide member 3 are attached to the eyeglass frame 4 having a pair of temples 5 and a rim 6, but the present invention is not limited to this. For example, a light irradiation device of any shape may be envisioned, such as an eyeglass frame 4 without a rim 6, or an eyeglass-type device without temples 5 and a rim 6.

[0044] Furthermore, although the example has been given in which the light emitted from the ultraviolet light source 2 is directly incident on the light-guiding member 3, instead, as shown in Fig. 10, the light source 7 may be disposed on the proximal end side of the temple 5, and the light may be guided to a position close to the light-guiding member 3 by an optical fiber 13 or a light guide, etc. In the figure, reference numeral 14 denotes a condensing lens that condenses the light from the light source 7 onto the incident end of the optical fiber 13. By disposing the light source 7, which has mass, near the ear of the subject, the light-guiding member 3 side can be prevented from becoming heavy, improving wearability.

[0045] 11, a filter 15 that blocks light with wavelengths longer than 400 nm may be disposed between the ultraviolet light source 2 and the light-guiding member 3. This prevents ultraviolet light with wavelengths longer than 400 nm from entering the light-guiding member 3 and prevents light with wavelengths longer than 400 nm from being emitted from the light-guiding member 3, thereby reducing the glare felt by the patient by light emitted from the front of the eyeball A.

[0046] Furthermore, in this embodiment, the ultraviolet light propagating inside the light-guiding member 3 is emitted from the light-guiding member 3 by the diffraction grating 12 provided in the light-guiding member 3. Alternatively, a structure other than the diffraction grating 12 may be used, for example, fine irregularities having a random pitch and height formed by roughening the surface of the light-guiding member 3. Furthermore, in this embodiment, the light containing ultraviolet light is made incident into the light-guiding member 3 by the input grating 11 provided in the vicinity of the edge of the light-guiding member 3, but instead, the light may be made incident from the edge of the light-guiding member 3.

[0047] REFERENCE SIGNS LIST 1 Light irradiation device 2 Ultraviolet light source 3 Light guide member 11 Diffraction grating (input grating) 12 Diffraction grating (output grating) 15 Filter A Eyeball

Claims

1. A light irradiation device comprising: an ultraviolet light source that emits light including ultraviolet rays; and a light guiding member made of a material that allows the ultraviolet rays emitted from the ultraviolet light source to propagate inside and that is capable of transmitting visible light, wherein the light guiding member is positioned close to the eyeball in a position where at least a portion of the light guiding member covers the front of the eyeball, and the ultraviolet rays that have propagated inside are emitted from the front of the eyeball to enter the eyeball.

2. The light irradiation device according to claim 1, wherein said light guide member is made of a material having a refractive index of 1.8 or less.

3. The light irradiation device according to claim 1 or 2, wherein the light guide member is made of any one of cycloolefin polymer (COP), cycloolefin copolymer (COC), and acrylic resin.

4. The light irradiation device according to claim 1, wherein the light-guiding member is provided with a diffraction grating at a position located in front of the eyeball, which diffracts the ultraviolet light propagated inside and emits it to the outside.

5. The light irradiation device according to claim 4, which satisfies the following relational expression: 1.1λ≦P<10λ, where λ is the peak wavelength of the light emitted from the ultraviolet light source, and P is the pitch of the diffraction grating.

6. The light irradiation device according to claim 4 or 5, wherein the diffraction grating emits multiple orders of diffracted light.

7. The light irradiation device according to claim 1, wherein the light guide member internally propagates light having a wavelength of 360 nm or more and 400 nm or less.

8. The light irradiation device according to claim 7, further comprising a filter between said ultraviolet light source and said light guide member for blocking light with a wavelength longer than 400 nm.

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