JP6692032B2 - Wavelength conversion device and lighting device - Google Patents

Description

  The present invention relates to a wavelength conversion device and a lighting device.

  There is illumination using a solid-state light source such as a laser. In such illumination, white light is produced by irradiating the phosphor with blue light emitted by a solid-state light source. Since the phosphor scatters the yellow light excited by a part of the blue light and the other part of the transmitted blue light, white light in which these are mixed can be created.

  On the other hand, solid-state light sources such as lasers have strong directivity and high energy density. Therefore, when the phosphor is directly irradiated with the blue light emitted from the solid-state light source, the phosphor is heated to a high temperature because a lot of heat is generated in the irradiated region. Since the phosphor has a temperature quenching characteristic that the wavelength conversion efficiency decreases as the temperature rises, it is necessary to suppress the temperature rise of the phosphor.

  Therefore, for example, Patent Document 1 discloses an illuminating device in which a diffusing unit for diffusing light from a solid-state light source is formed on a phosphor layer. According to Patent Document 1, the energy distribution of the light from the solid-state light source is diffused by the diffusing means to prevent energy concentration on the phosphor layer (reduce the heat load) and suppress the temperature rise of the phosphor layer. can do.

JP, 2012-104267, A

  However, in the above-mentioned conventional technique, although the heat load on the phosphor layer can be reduced, there is a problem that a part of the light from the solid-state light source is scattered and lost due to diffusion. That is, the above-mentioned conventional technique has a problem that it is difficult to increase the output of the lighting device.

  The present invention has been made in view of the above problems, and provides a wavelength conversion device capable of achieving high output while reducing the heat load on the phosphor layer, and an illumination device using the same. To aim.

  In order to achieve the above object, the wavelength conversion device according to one embodiment of the present invention includes a light source that emits light of a predetermined wavelength in a wavelength range from ultraviolet light to visible light, and the light source that is incident on an incident surface. An optical member disposed between the light source and the phosphor layer for converting the wavelength of the light, and splitting and separating the light emitted by the light source and making the light incident on the incident surface of the phosphor layer. With.

  In the wavelength conversion device according to one aspect of the present invention, high output can be achieved while reducing the heat load on the phosphor layer.

It is a figure which shows an example of the illuminating device with which the wavelength converter in embodiment is used. It is a figure which shows an example of a structure of the wavelength converter in embodiment. It is a figure which shows the perspective view of a structure of the optical member in an embodiment. FIG. 3B is a diagram showing a top view of the diffractive lens array shown in FIG. 3A. It is a figure which shows the cross section of the optical member in the Z plane of FIG. 3A. It is a figure for demonstrating operation | movement of the wavelength converter in embodiment. It is a figure for demonstrating operation | movement of a comparative example. It is a simulation model figure of the wavelength conversion device in an embodiment. It is a figure which shows the simulation result of the relationship between a 1st-order diffraction efficiency and a grating height. It is a figure which shows an example of a structure of the wavelength converter in a modification. It is sectional drawing of the micro lens array in a modification. FIG. 10 is a top view of the microlens array shown in FIG. 9.

  Hereinafter, embodiments will be described with reference to the drawings. Each of the embodiments shown here shows one specific example of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement and connection form of constituent elements, steps (processes), order of steps, and the like shown in the following embodiments are examples and limit the present invention. is not. Among the constituents in the following embodiments, constituents not described in the independent claims are constituents that can be added arbitrarily. In addition, each drawing is a schematic view and is not necessarily strictly illustrated.

(Embodiment)
[Lighting device]
In the following, first, an illumination device will be described as an example of an applied product in which the wavelength conversion device according to the present embodiment is used.

  FIG. 1 is a diagram showing an example of a lighting device 4 in which the wavelength conversion device 1 according to the present embodiment is used.

  The illumination device 4 shown in FIG. 1 is, for example, an endoscope, a fiberscope, or the like, and includes a wavelength conversion device 1, an optical fiber 2, and a lamp 3.

  The optical fiber 2 is a transmission line that transmits light to a remote place. The optical fiber 2 has a double structure in which a high refractive index core is wrapped with a clad layer having a lower refractive index than the core. Both the core and clad layers are made of quartz glass or plastic that has a very high light transmittance.

  The lamp 3 is used to irradiate the observation target with the light from the wavelength conversion device 1 transmitted through the optical fiber 2. The lamp 3 includes, for example, a stainless fiber coupling, a stainless ferrule, a glass lens, an aluminum holder, and an aluminum outer shell.

  The wavelength conversion device 1 corresponds to a light source means using a laser in the illumination device 4, and makes light enter the optical fiber 2. Hereinafter, the details of the wavelength conversion device 1 will be described.

[Wavelength converter]
FIG. 2 is a diagram showing an example of the configuration of the wavelength conversion device 1 according to the present embodiment.

  As shown in FIG. 2, the wavelength conversion device 1 includes a light source 11, an optical member 12, and a phosphor layer 13.

(Light source 11)
The light source 11 emits light having a predetermined wavelength in a wavelength range from ultraviolet light to visible light. In the present embodiment, the light source 11 is a laser that emits blue light.

(Optical member 12)
FIG. 3A is a diagram showing a perspective view of the configuration of the optical member 12 in the present embodiment. FIG. 3B is a diagram showing a top view of the diffractive lens array 122 shown in FIG. 3A. FIG. 3C is a diagram showing a cross-sectional view of the optical member 12 in the Z plane of FIG. 3A.

  The optical member 12 is disposed between the light source 11 and the phosphor layer 13, divides and separates the light emitted by the light source 11 and makes the light incident on the incident surface of the phosphor layer 13. The optical member 12 superimposes the light emitted from the light source 11 which is divided and separated, into the area of the incident surface of the phosphor layer 13 which is larger than the diameter of the light emitted from the light source 11 around the optical axis of the light source 11. Without incident. The optical member 12 is an example of a microlens array, for example, and includes a base material 121 and a diffractive lens array 122 as shown in FIG. 3A, for example.

  The base material 121 is a base material of the microlens array. A diffractive lens array 122 is formed on the base material 121.

  As a material for forming the base material 121, for example, any material such as glass or plastic can be used. Here, as the glass, for example, soda glass, non-alkali glass, or the like can be used. As the plastic, for example, acrylic resin, polycarbonate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or the like can be used. Further, the material of the base material 121 needs to be selected in consideration of heat resistance. Further, the substrate 121 is preferably transparent without absorption of light, and is preferably made of a material having an extinction coefficient of almost zero.

  The diffractive lens array 122 splits and separates the light emitted from the light source 11, and emits the light toward the incident surface of the phosphor layer 13. The cross-sectional shape of a surface of the diffractive lens array 122 that is perpendicular to the incident surface of the phosphor layer 13 has a sawtooth shape. Further, the diffractive lens array 122 has a plurality of regions in which the saw teeth are arranged in the same direction in the same region and the saw teeth are arranged in different regions in different regions.

  In the present embodiment, an example in which the diffractive lens array 122 has three regions (regions 121a, 121b, 122c) having different alignment directions as shown in FIGS. 3A and 3B is shown. In FIGS. 3A and 3B, in each of the three regions (regions 121a, 121b, 122c) in the same region, there are a plurality of linearly arranged lens arrays, and the plural lens arrays are arranged in the same direction. Here, when the wavelength of the blue light of the light source 11 is, for example, 460 nm, the grating pitch of the plurality of lens arrays is, for example, 5 μm, and the grating height is 1 μm. Further, the cross-sectional shape of the diffractive lens array 122 in the Z plane of FIG. 3A or Z1 of FIG. 3B is a sawtooth shape as shown in FIG. 3C. Here, the Z plane corresponds to a surface perpendicular to the incident surface of the phosphor layer 13. Although the cross-sectional shape of the diffractive lens array 122 in the region 122a is shown in FIG. 3C, the other regions 122b and 122c are similarly saw-toothed. That is, the diffractive lens array 122 corresponds to a so-called blazed diffraction grating. Thereby, the diffractive lens array 122 can increase the first-order diffraction efficiency and reduce the loss of light emitted from the light source 11 (optical loss).

  Further, in the diffractive lens array 122, for example, as shown in the top view of FIG. 3B, the sawtooth arrangement directions in the three regions (region 122a, region 122b, and region 122c) are different. With such a configuration, the diffractive lens array 122 splits and separates the light emitted from the light source 11 into the incident surface of the phosphor layer 13 and makes the incident surface of the phosphor layer 13 incident on the incident surface. Energy concentration can be prevented.

  The material of the diffractive lens array 122 is selected according to the method of forming the diffractive lens array 122, heat resistance, and refractive index. Examples of methods for forming the diffractive lens array 122 include nanoimprinting, printing, photolithography, EB lithography, and particle orientation. As the material of the diffractive lens array 122, when the diffractive lens array 122 is formed by, for example, nanoimprinting or printing, epoxy resin or acrylic resin is selected as the UV curing resin, and polymethylmethacrylate (PMMA) is selected as the thermoplastic resin. do it. The material of the diffractive lens array 122 may be glass or quartz selected in consideration of heat resistance, and the diffractive lens array 122 may be formed by photolithography or EB lithography. Further, the diffractive lens array 122 is preferably formed of a material having a refractive index similar to that of the base material 121 so that light from the base material 121 can easily enter. Further, like the base material 121, the diffractive lens array 122 is preferably transparent without absorption of light, and is preferably made of a material having an extinction coefficient of almost zero.

(Phosphor layer 13)
The phosphor layer 13 produces white light from the blue light emitted from the light source 11, and makes the produced white light enter the optical fiber 2.

  More specifically, the phosphor layer 13 has a function of wavelength converting a part of the light incident from the lower surface (incident surface) shown in FIG. In the present embodiment, the phosphor layer 13 receives the blue light from the light source 11 and emits the yellow light excited by a part of the incident blue light. Further, the phosphor layer 13 emits (transmits) the other part of the incident blue light. Since the blue light and the yellow light are mixed and emitted from the phosphor layer 13, the phosphor layer 13 emits white light.

  The phosphor layer 13 is formed in, for example, a flat plate shape as shown in FIG. The phosphor layer 13 includes a phosphor, and is formed by covering the phosphor with a resin such as silicon or epoxy. Note that the loss associated with wavelength conversion is changed to heat. The heat dissipation of the phosphor layer 13 is very important because the phosphor layer 13 has a temperature extinction characteristic in which the wavelength conversion efficiency decreases as the temperature rises. Although not particularly shown here, it is desirable that the phosphor layer 13 be supported by a heat dissipation plate formed of a material having a high thermal conductivity such as Al. Alternatively, the resin for forming the phosphor layer 13 may be mixed with a material having a high thermal conductivity, for example, an inorganic oxide such as ZnO to enhance the heat dissipation. Further, a minute structure may be provided on the incident surface of the phosphor layer 13 so that light can easily enter the phosphor layer 13 or heat can be easily radiated from the incident surface.

[Operation of wavelength conversion device 1]
Next, the operation of the wavelength conversion device 1 configured as above will be described.

  FIG. 4 is a diagram for explaining the operation of the wavelength conversion device 1 in the present embodiment. FIG. 5 is a diagram for explaining the operation of the comparative example.

  As shown in FIG. 4, the wavelength conversion device 1 according to the present embodiment includes the optical member 12 arranged between the light source 11 and the phosphor layer 13, so that three light beams 11a emitted from the light source 11 ( The light 12a, the light 12b, and the light 12c) can be divided and separated to be emitted toward the incident surface of the phosphor layer 13. In this way, the light 11a of the light source 11 can be split and separated into the light 12a, the light 12b, and the light 12c without being significantly changed, and can be incident on the phosphor layer 13. Further, in the phosphor layer 13, since the divided and separated light (light 12a, light 12b, light 12c) is incident on different regions of the incidence surface, energy concentration on the incidence surface of the phosphor layer 13 is prevented. You can see that it has been prevented. Then, the phosphor layer 13 can respectively generate white light 13e from the light (light 12a, light 12b, light 12c) that has been made incident on different regions of the incident surface.

  As described above, the wavelength conversion device 1 according to the present embodiment can prevent the energy concentration on the incident surface of the phosphor layer 13 and suppress the temperature rise of the phosphor layer 13, so that the light emitted from the light source 11 is lost. The entire amount can be emitted to the phosphor layer 13 without doing so. That is, according to the wavelength conversion device 1 in the present embodiment, even if the energy of the light emitted from the light source 11 is increased, the temperature rise of the phosphor layer 13 can be suppressed, so that high output can be achieved.

  On the other hand, the comparative example shown in FIG. 5 shows the wavelength conversion device 50 not including the optical member 12 of the present embodiment.

  In the wavelength conversion device 50 in the comparative example shown in FIG. 5, the light 11a emitted from the light source 11 is not divided and separated, but is emitted as it is toward one region 52a on the incident surface of the phosphor layer 13, and white light is emitted in the region 52a. Create 52b. However, since the energy of the light 11a is concentrated in one region 52a of the phosphor layer 13, the temperature rise in the region 52a cannot be suppressed. In other words, the more the wavelength conversion device 50 in the comparative example is used, the higher the temperature of the region 52a and the lower the wavelength conversion efficiency. Therefore, it is necessary to reduce the output of the light source 11 in order to reduce the energy of the light 11a. Occurs.

[Operation simulation of wavelength conversion device 1]
Next, an operation simulation of the wavelength conversion device 1 according to the present embodiment will be described.

  FIG. 6 is a simulation model diagram of the wavelength conversion device 1 according to the present embodiment. FIG. 7 is a diagram showing a simulation result of the relationship between the first-order diffraction efficiency and the grating height.

  FIG. 6 shows a simulation model of the cross section of the wavelength conversion device 1 according to the present embodiment in the z plane shown in FIG. In the simulation model shown in FIG. 6, the distance between the light source 11 and the phosphor layer 13 is 5.5 mm, the grating pitch of the diffractive lens array 122 in the region 122 a is 5 μm, and the light 11 a of the light source 11 is diffracted light 12 a. The angle θ (diffraction angle) with the light 11a was set to 5.2 deg. Then, the relationship between the first-order diffraction efficiency and the grating height was simulated using the simulation model shown in FIG. The results are shown in Figure 7. The wavelength of the blue light of the light source 11 is 460 nm. The first-order diffraction efficiency is a value indicating how much of the energy of the light 12a of the light source 11 that is incident light can be extracted as diffracted light.

  As shown in FIG. 7, the first-order diffraction efficiency is 80% or more in the grating height range of 0.8 μm to 1.1 μm, and the first-order diffraction efficiency is 88% when the grating height is around 1.0 μm. .. As a result, in the diffraction type lens array 122, a sawtooth lens array is formed with a grating pitch of 5 μm and a grating height of 1.0 μm, so that the first-order diffraction efficiency can be increased and the loss of light emitted from the light source 11 ( It can be seen that the optical loss) can be reduced.

[Effects, etc.]
As described above, the wavelength conversion device 1 according to the present embodiment includes the optical member between the light source 11 and the phosphor layer 13 for separating and splitting the light incident from the light source 11 by diffraction. This makes it possible to increase the output while reducing the heat load on the phosphor layer 13.

  More specifically, the wavelength conversion device according to one aspect of the present invention includes a light source 11 that emits light of a predetermined wavelength in a wavelength range from ultraviolet light to visible light, and a light source 11 that is incident on an incident surface. An optical member disposed between the light source 11 and the phosphor layer 13 for converting the wavelength of the light of the light source 11, and splitting and separating the light emitted from the light source 11 and making the light incident on the incident surface of the phosphor layer 13. And 12 are provided.

  Thereby, even if the light emitted from the light source 11 is divided and separated and emitted toward the incident surface of the phosphor layer 13, it is possible to prevent energy concentration on the incident surface of the phosphor layer 13. Thereby, even if the energy of the light emitted from the light source 11 is increased, the temperature rise of the phosphor layer 13 can be suppressed, so that the output of the wavelength conversion device 1 can be increased.

  Here, for example, the light emitted by the light source 11 divided and separated by the optical member 12 is overlapped on the area of the incident surface, which is larger than the diameter of the light emitted by the light source 11 centered on the optical axis of the light source 11. It is incident without incident.

  Further, for example, the optical member 12 is a microlens array.

  As a result, the microlens array that diffracts the incident light can reduce the optical loss and increase the output.

  Here, for example, the cross-sectional shape of a plane perpendicular to the incident surface of the microlens array (diffractive lens array 122) is a sawtooth shape.

  Accordingly, since the diffractive lens array 122 corresponds to a so-called blazed diffraction grating, the first-order diffraction efficiency can be increased, the loss of light emitted from the light source 11 (optical loss) can be reduced, and the high wavelength conversion device 1 can be obtained. Output can be achieved.

  Further, for example, the microlens array (diffraction type lens array 122) has a plurality of regions in which the saw teeth are arranged in the same direction in different regions and the saw teeth are arranged in different regions in different regions. Here, for example, the plurality of regions are three regions.

  Thereby, even if the light emitted from the light source 11 is divided and separated and emitted toward the incident surface of the phosphor layer 13, it is possible to prevent energy concentration on the incident surface of the phosphor layer 13. Thereby, even if the energy of the light emitted from the light source 11 is increased, the temperature rise of the phosphor layer 13 can be suppressed, so that the output of the wavelength conversion device 1 can be increased.

(Modification)
The configuration of the wavelength conversion device 1 of the present invention is not limited to that described in the above embodiment. A microlens array having a diffractive lens array different from the diffractive lens array 122 described above may be further provided on the phosphor layer 13. Hereinafter, an example of this case will be described as a modified example.

  FIG. 8: is a figure which shows an example of a structure of the wavelength converter in this modification. FIG. 9 is a cross-sectional view of the microlens array 14 in this modification. FIG. 10 is a top view of the microlens array 14 shown in FIG. The same elements as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

  The microlens array 14 includes a base material 141 and a diffractive lens array 142.

  The base material 141 is a base material of the microlens array 14, and is formed in a flat plate shape. In the present modification, the base material 141 is formed on the phosphor layer 13. A diffractive lens array 142 is formed on the base material 141.

  The material for forming the base material 141 is the same as that of the base material 121, and thus detailed description thereof is omitted. However, the base material 141 is the same as the phosphor material layer 13 so that light from the phosphor material layer 13 can easily enter. It is preferably formed of a material having a refractive index of the order of magnitude. Here, the same degree of refractive index means that the difference in refractive index between them is ± 0.2 or less. Although not particularly shown, the phosphor layer 13 and the base material 141 are preferably bonded by an adhesive layer having a refractive index similar to those of the two. Examples of the material of the adhesive layer include acrylic resin and epoxy resin. The base material 141 and the adhesive layer are preferably transparent without absorption of light, and are preferably formed of a material having an extinction coefficient of almost zero.

  The diffractive lens array 142 emits a part of the light whose wavelength is converted by the phosphor layer 13 and the other part of the light that has passed through the phosphor layer 13 from the emission surface. As shown in FIG. 9, the exit surface of the diffractive lens array 142 is provided with a plurality of diffractive lenses for diffracting and emitting a part of the wavelength-converted light and the other part of the transmitted light. There is. For example, as shown in FIG. 10, the plurality of diffractive lenses are concentrically provided on the exit surface. In the present embodiment, the cross section of the diffractive lens in the plane perpendicular to the exit surface is described as having a sawtooth shape, but the present invention is not limited to this, and may be rectangular, triangular, or hemispherical.

  The plurality of diffractive lenses diffract a part of the blue light wavelength-converted into yellow light by the phosphor layer 13 and the blue light transmitted through the phosphor layer 13 to form a predetermined area of the optical fiber 2. It is provided so as to collect light at the opening. Therefore, the pitch of the plurality of diffractive lenses is different for each predetermined area (zone). Further, the pitch of the plurality of diffractive lenses is narrowed from the center of the diffractive lens array 142 toward the periphery.

  Since the material of the diffractive lens array 142 is the same as that of the diffractive lens array 122, detailed description thereof will be omitted. However, the diffractive lens array 142 is provided with the base material 141 so that the light from the base material 141 can easily enter. It is preferable to use materials having similar refractive indexes. Further, like the base material 141, the diffractive lens array 142 is preferably transparent without absorption of light, and is preferably formed of a material having an extinction coefficient of almost zero.

  The microlens array 14 may be directly formed (integrated) on the phosphor layer 13 so that light easily enters the diffraction lens array 142 from the phosphor layer 13. In this case, the microlens array 14 may be formed of the resin forming the phosphor layer 13, or may be formed of a material having a refractive index similar to that of the phosphor layer 13.

(Other embodiments, etc.)
Needless to say, the above-described embodiment is merely an example, and various changes, additions, omissions, and the like can be made.

  Further, a form realized by arbitrarily combining the constituent elements and functions shown in the above-described embodiment is also included in the scope of the present invention. In addition, it can be realized by making various modifications to the above-described embodiment by those skilled in the art, and by arbitrarily combining the components and functions of each embodiment without departing from the spirit of the present invention. The form is also included in the present invention.

  For example, the present invention includes an illuminating device using the wavelength conversion device 1 in the above embodiment. By using the wavelength conversion device 1 according to the above-described embodiment as a lighting device, it is possible to make the size smaller than a lighting device using an LED light source.

  In addition, in the above-described embodiment and modified examples, the diffractive lens array 122 has been described as having three regions (regions 121a, 121b, 122c) having different alignment directions, for example, as shown in FIGS. 3A and 3B. , But not limited to this. Even if the light emitted from the light source 11 is split and separated and emitted toward the incident surface of the phosphor layer 13, if the energy concentration on the incident surface of the phosphor layer 13 can be prevented, even in two regions. It goes without saying that any number of four areas may be used.

  Further, the size of the diffractive lens array 122 may be larger than the spot diameter of the light of the light source 11, and can take an arbitrary value on condition that the luminous flux of the light emitted by the light source 11 is not changed.

11 light source 12 optical member 13 phosphor layer

Claims (4)

A light source that emits light of a predetermined wavelength in a wavelength range from ultraviolet light to visible light,
A phosphor layer for wavelength-converting the light from the light source that is incident on the incident surface,
The light source and the disposed between the phosphor layer, by dividing and separating the light the light source emitted, Bei example an optical member to be incident on the incident surface of the phosphor layer,
The optical member is a microlens array,
The cross-sectional shape of a plane perpendicular to the incident surface of the microlens array has a sawtooth shape,
The microlens array has a plurality of regions in which the saw teeth are arranged in the same direction in the same region and the saw teeth are arranged in different regions in different regions.
Wavelength converter. The light emitted by the light source, which is divided and separated by the optical member, is incident on the area of the incident surface without overlapping with the area larger than the diameter of the light emitted by the light source around the optical axis of the light source. Will be
The wavelength conversion device according to claim 1. The plurality of regions are three regions,
The wavelength conversion device according to claim 1 . Using a wavelength conversion device according to any one of claims 1 to 3, the lighting device.

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