Near-infrared light-emitting device, spectroscopic device, and spectroscopic method

Abstract

In the near-infrared light-emitting device (100), the spectral distribution of output light (20) has a light component of fluorescent light from a phosphor in the wavelength range of at least 600 nm and less than 980 nm, and the center of gravity of the spectral distribution of wavelength-converted light by the phosphor is in the wavelength range of at least 700 nm and less than 900 nm. The minimum value of the spectral intensity in the wavelength range of 660 nm or more and less than 900 nm exceeds 50% of the maximum value, and in the spectral distribution, the light intensity of the spectral distribution of the wavelength-converted light gradually decreases as the wavelength becomes shorter from 600 nm and gradually decreases as the wavelength becomes longer from 980 nm.

Description

Technical Field

[0001] The present invention relates to a near-infrared light emitting device, a spectroscopic device and a spectroscopic method. Background Art

[0002] Conventionally, near-infrared light-emitting devices that emit both visible and near-infrared light components are known. These devices, for example, allow for the evaluation of illuminated objects using both the sensitivity characteristics of a detector and human vision. These devices, in turn, facilitate the evaluation of the quality of objects by both the machine and human eyes, using the machine's vision to aid in the detection of foreign objects that would be easily missed by the human eye alone.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2022 / 176596 Summary of the Invention

[0006] However, while conventional near-infrared light emitting devices can perform rough assessments such as foreign matter detection in both human and machine vision, they have difficulty evaluating factors that determine the market value of the goods being inspected. For example, for inspected items such as fruits and vegetables, it is difficult to evaluate factors that determine market value, such as the presence of spoilage, sugar content, acidity, maturity, and moisture content. Therefore, there is a demand for improved devices that can accurately evaluate these factors.

[0007] The present invention has been made in view of the problems of the prior art and has the object of providing a near-infrared light emitting device suitable for evaluating factors determining the market value of an inspection object, and a spectroscopic device and spectroscopic method using the device.

[0008] To address the above-mentioned issues, the near-infrared light-emitting device of the present invention comprises a solid-state light-emitting element and a wavelength converter containing a phosphor, and emits output light. The spectral distribution of the output light includes a light component derived from the fluorescence of the phosphor at least within a wavelength range of 600 nm to less than 980 nm. The center of gravity of the spectral distribution of the wavelength-converted light based on the phosphor is within a wavelength range of 700 nm to less than 900 nm. The center of gravity is the wavelength at which the integral value of the light intensity of the spectral distribution of the wavelength-converted light, summed from 525 nm toward the longer wavelength side, equals the integral value of the light intensity from 1100 nm toward the shorter wavelength side, for every 1 nm interval of the wavelength-converted light. The minimum value of the spectral intensity within the wavelength range of 660 nm to less than 900 nm exceeds 50% of the maximum value. In the spectral distribution, the light intensity of the wavelength-converted light gradually decreases as the wavelength decreases from 600 nm.

[0009] The spectroscopic device according to an aspect of the present invention includes a near-infrared light emitting device, and irradiates an inspection object with output light emitted by the near-infrared light emitting device.

[0010] The spectroscopic method according to the embodiment of the present invention utilizes a near-infrared light emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram showing an example of a near-infrared light-emitting device according to one embodiment.

[0012] Figure 2 This is a diagram showing an example of spectral distribution of output light output by the near-infrared light-emitting device of Example 1.

[0013] Figure 3 is Figure 2 Added the integral value I S , integral value I L and the spectral distribution of the center of gravity.

[0014] Figure 4 This is a diagram showing an example of a near-infrared light-emitting device according to another embodiment.

[0015] Figure 5 This is a diagram showing an example of a near-infrared light-emitting device according to another embodiment.

[0016] Figure 6 This is a schematic diagram showing an example of a spectroscopic device according to one embodiment.

[0017] Figure 7 This is a schematic diagram showing an example of a spectroscopic device according to another embodiment.

[0018] Figure 8 This is a diagram showing an example of spectral distribution of output light output by the near-infrared light-emitting device of Example 2. DETAILED DESCRIPTION

[0019] The near-infrared light emitting device, spectroscopic device, and spectroscopic method according to the present embodiment are described in detail below using the accompanying drawings. It should be noted that the dimensional ratios in the drawings are sometimes exaggerated for convenience of description and differ from the actual ratios.

[0020] [Near-infrared light-emitting device]

[0021] First, the near-infrared light-emitting device 100 of this embodiment will be described. Figure 1 FIG is a diagram showing an example of a near-infrared light emitting device according to one embodiment. Figure 1 As shown, the near-infrared light emitting device 100 includes a solid-state light emitting element 1 and a wavelength converter 2. The near-infrared light emitting device 100 is configured to emit output light 20. Figure 2This diagram shows an example of the spectral distribution of output light 20 from the near-infrared light-emitting device 100 according to one embodiment. It should be noted that, unless otherwise specified, in this specification, fluorescence and output light 20 are emitted when the temperature of the phosphor or wavelength converter 2 is 30°C.

[0022] Solid-state light-emitting element 1 is an element that converts electricity into light. When powered, it converts the supplied electrical energy into light energy. The converted light energy is then emitted from the light extraction surface as output light 20. Representative examples of solid-state light-emitting element 1 include light-emitting diodes (LEDs) and laser diodes (LDs).

[0023] The wavelength converter 2 is a wavelength conversion element that, upon receiving light, converts it into light with a longer wavelength. Specifically, it receives high-energy photons, converts them into low-energy photons, and outputs them. The wavelength converter 2 includes a phosphor. The phosphor may include an inorganic phosphor containing fluorescent ions added to an inorganic compound. The wavelength converter 2 may also be a resin fluorescent film, a fluorescent ceramic, or a composite. The composite may include at least one of a resin fluorescent film and a fluorescent ceramic. The wavelength converter 2 may contain at least 95% by mass, at least 99% by mass, or even 100% by mass of an inorganic compound. A wavelength converter 2 with a higher proportion of inorganic compound exhibits superior thermal conductivity, thereby improving heat dissipation.

[0024] Resin fluorescent films can also be made by dispersing granular phosphors in a resin. For example, a resin fluorescent film can be formed by curing a phosphor paste obtained by mixing a resin and a powdered phosphor. Translucent resins can be used as the resin, such as silicone resins. Fluorescent ceramics can also be formed by molding phosphors. Fluorescent ceramics can be formed, for example, by pressurizing and heating phosphor raw materials or phosphor powders to cause them to react and sinter.

[0025] The near-infrared light-emitting device 100 can also be configured so that the primary light 10 emitted by the solid-state light-emitting element 1 illuminates at least the wavelength converter 2. With this configuration, the phosphor contained in the wavelength converter 2 absorbs the primary light 10 and converts it into light with a longer wavelength than the primary light 10. The wavelength-converted light, which is the long-wavelength light after wavelength conversion, is then emitted from the wavelength converter 2. Furthermore, the primary light 10 not absorbed by the phosphor passes through the wavelength converter 2 and is emitted from the wavelength converter 2 together with the wavelength-converted light. The primary light 10 and the wavelength-converted light emitted from the wavelength converter 2 are then output as light components constituting the output light 20 of the near-infrared light-emitting device 100.

[0026] The wavelength converter 2 may be arranged with a gap relative to the solid-state light-emitting element 1, or may be arranged in contact with the solid-state light-emitting element 1. When the wavelength converter 2 is arranged in contact with the solid-state light-emitting element 1, the heat generated by the wavelength converter 2 can be conducted through the solid-state light-emitting element 1.

[0027] It should be noted that the spectral distribution of the wavelength-converted light can be varied depending on the type and combination of phosphors. Furthermore, by varying the concentration of the phosphors contained in the wavelength converter 2 or the thickness of the wavelength converter 2, the intensity ratio between the primary light 10 emitted from the wavelength converter 2 and the wavelength-converted light can be varied. The wavelength converter 2 can contain both visible light phosphors and near-infrared phosphors.

[0028] The visible light phosphor emits visible fluorescence 22 having a maximum fluorescence intensity within the visible light wavelength range. The visible light phosphor can be at least one selected from the group consisting of a green phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 490 nm to less than 570 nm, a yellow phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 570 nm to less than 585 nm, an orange phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 585 nm to less than 620 nm, and a red phosphor that emits light having a maximum fluorescence intensity within a wavelength range of 620 nm to less than 780 nm. This allows for adjustment of the spectral distribution of the visible fluorescence component. Therefore, the visible fluorescence component of the output light 20 emitted from the near-infrared light-emitting device 100 can be adjusted according to the intended use.

[0029] The visible light phosphor may be selected from Ce 3+ Activated garnet phosphor, with Eu 2+ Activated alkaline earth metal nitride silicates and Eu 2+ At least one phosphor selected from the group consisting of activated alkaline earth metal nitride aluminum silicate. These visible light phosphors have a high practical performance as LED lighting. Therefore, these visible light phosphors are not only easily available but also provide reliability and ease of use for the near-infrared light emitting device 100.

[0030] As Ce 3+ Activated garnet phosphors include, for example, those of the general formula RE3Al2(AlO4)3:Ce 3+ The phosphor shown, Ca3Sc2(SiO4)3:Ce 3+ 、Y3Ga2(AlO4)3:Ce 3+and their solid solutions. In the above general formula, RE represents a rare earth element, for example, at least one rare earth element selected from Sc, Y, La, Tb, Gd and Lu. 3+ Specific examples of the phosphors represented include Lu3Al2(AlO4)3:Ce 3+ 、Y3Al2(AlO4)3:Ce 3+ (YAG) and (Y,Gd)3Al2(AlO4)3:Ce 3+ )wait.

[0031] As Eu 2+ Activated alkaline earth metal nitride silicates, for example Sr2Si5N8:Eu 2+ 、Ca2Si5N8:Eu 2+ and their solid solutions, etc.

[0032] By Eu 2+ Examples of activated alkaline earth metal nitride aluminum silicates include those of the general formula MAlSiN3:Eu 2+ In the above general formula, M represents magnesium or alkaline earth metal, for example, at least one metal element selected from Mg, Ca, Sr and Ba. Specifically, as the phosphor 2+ Activated alkaline earth metal nitride aluminum silicate, for example, CaAlSiN3:Eu 2+ (CASN), SrAlSiN3:Eu 2+ 、(Sr、Ca)AlSiN3:Eu 2+ (SCASN) and their solid solutions, etc.

[0033] Among them, the visible light phosphor preferably includes at least one phosphor selected from YAG, CASN, and SCASN.

[0034] The near-infrared phosphor emits near-infrared fluorescence 21 having a maximum fluorescence intensity within the near-infrared wavelength range. When irradiated with excitation light, the near-infrared phosphor emits near-infrared fluorescence 21 having a maximum fluorescence intensity within the near-infrared wavelength range. The near-infrared fluorescence 21 may also have a spectral intensity across at least the entire wavelength range of 700 nm to 1000 nm. This spectral distribution is suitable for detecting the characteristic absorption bands of the stretching vibrations of NH, CH, and OH using spectrometry.

[0035] The near-infrared fluorescence 21 may also have a maximum fluorescence intensity within a wavelength range of 800 nm or more and less than 900 nm. Such near-infrared fluorescence 21 can be obtained by, for example, using LiGa5O8:Cr 3+It emits light from near-infrared phosphors and similar near-infrared phosphors. Therefore, it becomes a Ce-like material used in LED lighting. 3+ Activated garnet phosphor and Eu 2+ The near-infrared light emitting device 100 is advantageous in that it is combined with a visible light phosphor having low temperature quenching, such as an activated alkaline earth metal nitride aluminum silicate phosphor, to form the wavelength converter 2. The near-infrared fluorescence 21 preferably has a maximum fluorescence intensity within a wavelength range of 800 nm to 860 nm.

[0036] The half-value width of the spectrum having the maximum fluorescence intensity of the near-infrared fluorescence 21 is preferably greater than 180 nm. Therefore, even without using multiple near-infrared phosphors, a near-infrared light component having a spectral distribution in a wide wavelength range of 700 to 1000 nm can be obtained using only one near-infrared phosphor.

[0037] The near-infrared phosphor can be formed by adding at least chromium ions that function as fluorescent ions to the crystals of an inorganic compound having the same spinel-type crystal structure as the compound LiGa5O8. Whether or not the compound has the same spinel-type crystal structure as the compound LiGa5O8 can be determined by measuring the X-ray diffraction pattern using an X-ray diffraction method. Specifically, the XRD pattern of the near-infrared phosphor is substantially the same as the XRD pattern of the compound LiGa5O8 registered in the ICSD (registration number: 33716).

[0038] The above crystal may contain at least one of an alkali metal of the first group, an element of the thirteenth group, and scandium, and oxygen. 1-x Cr x When )5O8 represents a near-infrared phosphor, A mainly contains an alkali metal, and D mainly contains at least one of a Group 13 element and scandium. It should be noted that D may also mainly contain a Group 13 element.

[0039] It should be noted that "A mainly contains an alkali metal" means that A contains 75 mol% or more of the alkali metal. A may contain 90 mol% or more of the alkali metal, 95 mol% or more, or even 100 mol%. Furthermore, "D mainly contains at least one of a Group 13 element and scandium" means that D contains 75 mol% or more of the at least one of the Group 13 element and scandium. D may contain 90 mol% or more of the at least one of the Group 13 element and scandium, 95 mol% or more, or even 100 mol%.

[0040] The alkali metal is preferably at least one element selected from the group consisting of Li, Na, K, Rb and Cs, more preferably at least one of Li and K. The Group 13 element is preferably at least one element selected from Al, Ga and In, more preferably Ga.

[0041] The above crystals preferably have less alkali metals than the stoichiometric composition. That is, relative to the stoichiometric composition, A(D 1- x Cr x )5O8, preferably with a composition lacking element A. This is a method of using a crystal with chemical properties similar to LiGa5O8 as a near-infrared phosphor. Therefore, it is expected that the same as LiGa5O8:Cr 3+ The unique fluorescence characteristics of near-infrared phosphors are similar to those of near-infrared phosphors. When applied to spectroscopy, high-precision non-destructive measurements can be expected.

[0042] The near-infrared phosphor is preferably composed of the general formula A y (D 1-x Cr x )5O8 represents that A contains an alkali metal as a main component, D contains at least one of a Group 13 element and scandium as a main component, and y is less than 1. When y is less than 1, a near-infrared phosphor with a small proportion of the luminescent component of the bright line can be obtained. y is more preferably less than 0.90, further preferably less than 0.85, and particularly preferably less than 0.83. In addition, y is preferably greater than or equal to 0.70. When y is greater than or equal to 0.70, a heterogeneous β-Ga2O3:Cr 3+ The phosphor is less likely to coexist, making it easier to obtain desired unique fluorescent properties. y is more preferably 0.75 or greater, and even more preferably 0.77 or greater.

[0043] The crystal preferably contains LiGa5O8 as a main component, with a portion of Ga being substituted by Cr. Here, "the crystal contains LiGa5O8 as a main component" means that the crystal contains 75 mol% or more of LiGa5O8, preferably 90 mol% or more.

[0044] Here, the general formula LiGa5O8:Cr 3+ The phosphor represented by (hereinafter referred to as LiGa5O8:Cr 3+ Phosphor) is a deep red phosphor that emits a bright line of deep red fluorescent components with a maximum fluorescence intensity around 715 to 720 nm. 3+ The fluorescent properties of the phosphor were evaluated and it was found that it can function as a near-infrared phosphor when tested under specific mixing conditions and synthesis conditions. 3+ There are examples of phosphors that exhibit the following unique fluorescence characteristics as near-infrared phosphors.

[0045] (1) It has a maximum fluorescence intensity (fluorescence peak) in a wavelength range of 800 nm to 900 nm, such as around 830 nm.

[0046] (2) It has a fluorescent component in a wide wavelength range of 700 to 1000 nm.

[0047] (3) The fluorescence spectrum is ultra-broad, with the half-value width of the spectrum with the maximum fluorescence intensity exceeding 180 nm.

[0048] (4) Temperature quenching is very small (the maximum fluorescence intensity at a phosphor temperature of 150°C is more than 90% of the maximum fluorescence intensity at 30°C).

[0049] (5) The wavelength conversion efficiency (internal quantum efficiency) of converting absorbed visible light components into near-infrared light components exceeds 80% even for prototypes in the early stages of development.

[0050] The near-infrared fluorescence 21 or near-infrared fluorescence component may also have a sharp peak in the wavelength range of 710 nm to 730 nm. Although the reason is not clear, the LiGa5O8:Cr 3+ In the fluorescence spectrum of the near-infrared phosphor, such a peak is generally confirmed. That is, the near-infrared phosphor that emits fluorescence with such a peak is sometimes extremely poorly quenched by temperature. On the other hand, the near-infrared fluorescence 21 or the near-infrared fluorescence component may not have a peak in the wavelength range of 710 nm to 730 nm. Alternatively, even if the near-infrared fluorescence 21 or the near-infrared fluorescence component has a peak, the maximum fluorescence intensity in the wavelength range of 800 nm to 860 nm is set to 1. NIR , set the maximum intensity of the peak to I DR In the case of DR Less than I NIR Here, the peak refers to a sharp peak near 720nm. For example, when the spectral distribution is set to spectral data every 1nm, the spectral data changes by more than 7% / nm within the above wavelength range. It should be noted that I DR Can be less than I NIR 1.25 times, less than 1.0 times, and less than 0.8 times.

[0051] like Figure 2As shown, the spectral distribution of the output light 20 of the near-infrared light-emitting device 100 includes a light component derived from the fluorescence of the phosphor at least within the wavelength range of 600 nm to less than 980 nm. Furthermore, the minimum value of the spectral intensity within the wavelength range of 660 nm to less than 900 nm exceeds 50% of the maximum value. The minimum value of the spectral intensity within the wavelength range of 660 nm to less than 940 nm may also exceed 50% of the maximum value. The spectral distribution of the output light 20 preferably includes a light component derived from the fluorescence of the phosphor at least throughout the entire wavelength range of 600 nm to less than 980 nm.

[0052] like Figure 3 As shown in FIG. 1 , in the spectral distribution on the longer wavelength side than 525 nm, the center of gravity of the spectral distribution of the wavelength-converted light by the phosphor is in the wavelength range of 700 nm to less than 900 nm. The center of gravity is the integral value I obtained by adding the light intensity of the spectral distribution of the wavelength-converted light every 1 nm from 525 nm toward the longer wavelength side. S The integral value I obtained by adding from 1100 nm to the shorter wavelength side L become equal wavelengths. For example, Figure 3 In the case of spectral distribution, the center of gravity is Figure 3 The integral value Is and the integral value I L The value of 813nm is substantially equal to that of 813nm. S and the integral value I L The wavelengths may be substantially equal within a range of error. The center of gravity is preferably within a wavelength range of 750 nm to less than 850 nm, more preferably 770 nm to less than 830 nm.

[0053] It should be noted that, in a preferred embodiment, the minimum value of the spectral intensity within the range of the fluorescence peak wavelength of the solid-state light-emitting element 1 and below 900nm is less than 3% of the maximum value of the spectral intensity, and more preferably less than 1%. The minimum value of the spectral intensity is located within the wavelength range of the fluorescence peak wavelength of the solid-state light-emitting element 1 and below 600nm, and in particular, within the wavelength range of 500nm and below 550nm. Figure 2 and Figure 3 In the example shown, the peak fluorescence wavelength of the solid-state light-emitting element 1 is 460 nm. This spectral distribution of light components suppresses the output of light components not required for quality evaluation of inspection objects such as fruits and vegetables. Consequently, the near-infrared light-emitting device 100 efficiently utilizes input power and exhibits excellent efficiency in converting electricity into light, facilitating high output and the resulting high-precision quality evaluation.

[0054] like Figure 3As shown, in the spectral distribution, the light intensity of the spectral distribution of the wavelength-converted light may also gradually decrease as the wavelength becomes shorter from 600nm. That is, the output light 20 has a spectral distribution in which the light components having an intensity of at least a certain degree are concentrated without omission among the red light components and near-infrared light components with wavelengths above 600nm. Therefore, the near-infrared light-emitting device 100 can efficiently emit the output light 20 containing the red light components and the near-infrared light components. It may also gradually decrease as the wavelength becomes longer from 980nm. That is, the output light 20 has a spectral distribution in which the light components having an intensity of at least a certain degree are concentrated without omission among the red light components and near-infrared light components with wavelengths below 980nm. Therefore, the near-infrared light-emitting device 100 can efficiently emit the output light 20 containing the red light components and the near-infrared light components.

[0055] For example, the spoilage of onions can be determined by spectroscopy using light components ranging from 660 to 950 nm, the maturity and moisture content of tomatoes at 620 to 950 nm, and the sugar content and acidity of fruits and vegetables at 780 to 830 nm. Therefore, by having such a spectral distribution of light components, the near-infrared light emitting device 100 can emit output light 20 suitable for quality evaluation, such as determining the market value of inspection objects such as fruits and vegetables. Furthermore, by having such a spectral distribution of light components, the output of light components not required for quality evaluation of inspection objects such as fruits and vegetables can be suppressed. Consequently, the near-infrared light emitting device 100 can efficiently utilize input power, achieve excellent efficiency in converting electricity into light, and facilitate high output and the resulting high-precision quality evaluation.

[0056] The light component having a spectral distribution within a wavelength range of more than 600 nm and less than 980 nm may be a light component from the electron energy transition of the fluorescent ions of at least any one of Eu ions and Cr ions. These ions emit red fluorescence or near-infrared fluorescence with a wide spectral half-width and relatively small intensity variation relative to the wavelength. In addition, red phosphors and near-infrared phosphors containing these ions are also easy to supply or synthesize. Therefore, by utilizing conventional Eu ion-activated red phosphors and Cr ion-activated near-infrared phosphors, it is possible to obtain output light 20 having light components concentrated in the desired red to near-infrared wavelength region and with small intensity variation, which is also suitable for industrial production. It should be noted that Eu ions may be, for example, Eu 2+ Cr ions can be, for example, Cr 3+ and Cr 4+ At least any one of .

[0057] like Figure 4As shown, the near-infrared light emitting device 100 may also include a lens 3. The lens 3 may also be a collimating lens. The lens 3 may also be arranged to transmit the wavelength-converted light emitted from the wavelength converter 2. In addition to the wavelength-converted light, the lens 3 may also transmit the output light 20.

[0058] like Figure 4 As shown, the output light 20 is outputted through the lens 3, and the lens 3 can also collimate the wavelength-converted light emitted by the wavelength converter 2. According to this method, the wavelength converter 2 outputs the wavelength-converted light emitted as diffused light as collimated light (parallel light). Therefore, it is suitable for constructing an evaluation system that evaluates an inspection object by irradiating the output light 20 from a distance without bringing the near-infrared light-emitting device 100 close. It should be noted that the distance between the surface of the inspection object, which is the irradiated object, and the light output portion of the near-infrared light-emitting device 100 can be greater than 1 cm and less than 1 m, can be greater than 5 cm and less than 50 cm, and can be greater than 10 cm and less than 50 cm.

[0059] like Figure 4 As shown, the light incident surface of the lens 3 can be arranged to cover the entire light exit surface of the wavelength converter 2. According to this structure, almost all of the wavelength-converted light emitted from the wavelength converter 2 is incident on the light incident surface of the lens 3, which is suitable for converting the light emitted from the wavelength converter 2 into collimated light. Figure 4 As shown, the light incident surface of the lens 3 may also have a planar portion, and the arrangement may be such that the wavelength-converted light is incident on the planar portion. Furthermore, the light exit surface of the wavelength converter 2 may also have a planar portion. Furthermore, the planar portion of the light incident surface of the lens 3 and the planar portion of the light exit surface of the wavelength converter 2 may be parallel. The two planar portions may be arranged parallel to each other with a gap therebetween, or they may be arranged so that their planar portions are in contact.

[0060] The wavelength converter 2 is also preferably arranged in surface contact with the main light extraction surface of the solid-state light-emitting element 1. This is because the heat generated by the wavelength converter 2 can be conducted through the solid-state light-emitting element 1. For example, when the solid-state light-emitting element 1 and the wavelength converter 2, as well as the wavelength converter 2 and the lens 3, are arranged in surface contact, the heat from the wavelength converter 2 can also be conducted to the lens 3 for dissipation.

[0061] The shape of the wavelength converter 2 is not particularly limited and can, for example, be plate-shaped. If the wavelength converter 2 is plate-shaped, the thickness of the wavelength converter 2 can be, for example, 50 μm or greater and less than 500 μm. A thin plate-shaped wavelength converter 2 reduces the proportion of wavelength-converted light leaking from the sides of the wavelength converter 2, thereby increasing the proportion of light incident on the light incident surface of the lens 3. This advantageous configuration results in high-quality coherent light output. It should be noted that the thickness of the wavelength converter 2 is preferably 80 μm or greater and less than 300 μm.

[0062] The wavelength converter 2 can also be arranged to rotate. Figure 5 As shown, the solid-state light-emitting element 1 can also emit primary light 10, which is then irradiated onto a rotating wavelength converter 2. With this configuration, the location where the primary light 10 irradiates the wavelength converter 2 changes over time. Consequently, the wavelength converter 2, whose temperature rises due to irradiation with the primary light 10, moves to a location where it is not irradiated by the primary light 10, during which time the wavelength converter 2 cools. Consequently, even when the wavelength converter 2 is irradiated with high-energy-density primary light 10, the temperature rise of the wavelength converter 2 can be suppressed, allowing the near-infrared light-emitting device 100 to emit high-output output light 20. The wavelength converter 2 can also be mounted on a rotatable wheel.

[0063] It should be noted that Figure 4 It is a transmission type. Figure 5 This is a so-called reflective near-infrared light-emitting device 100. In a transmissive type, primary light 10 that strikes the wavelength converter 2 passes through the wavelength converter 2 and is output as output light 20 along with the converted wavelength light. In a reflective type, primary light 10 that strikes the wavelength converter 2 is reflected by the wavelength converter 2 and is output as output light 20 including the converted wavelength light.

[0064] In the reflective type, it is preferred to use Figure 5 The optical element 4 shown, called a dichroic mirror, has the characteristic of transmitting light of a specific wavelength and reflecting light of other wavelengths. When the optical element 4 transmits the primary light 10 and reflects the wavelength-converted light, not only can the primary light 10 be efficiently and uniformly irradiated onto the wavelength converter 2, but the wavelength-converted light can also be output at an angle, such as perpendicular to the irradiation direction of the primary light 10. This allows for greater flexibility in the structural design of the near-infrared light-emitting device 100.

[0065] [Spectroscopic Device and Spectroscopic Method]

[0066] Next, use Figure 6 and Figure 7 The spectroscopic device 200 and the spectroscopic method of this embodiment will be described. The spectroscopic device 200 is, for example, a near-infrared spectroscopic device. The spectroscopic method is, for example, near-infrared spectroscopic method. Figure 6 Schematic diagram showing an example of a transmission-type spectroscopic device 200 . Figure 7 Schematic diagram showing an example of a reflective spectroscopic device 200. Figure 6 and Figure 7 As shown, the spectroscopic device 200 includes the near-infrared light emitting device 100. That is, the spectroscopic device 200 relates to spectrometry using the near-infrared light emitting device 100. The spectroscopic device 200 irradiates the inspection object 5 with the output light 20 emitted by the near-infrared light emitting device 100.

[0067] like Figure 6 As shown, the transmission-type spectrometer 200 includes a near-infrared light emitting device 100 and a spectrometer 6. An inspection object 5 is arranged between the near-infrared light emitting device 100 and the spectrometer 6. The near-infrared light emitting device 100 is configured to emit output light 20. The inspection object 5 is arranged so as to be irradiated with the output light 20. The spectrometer 6 is configured to receive the transmitted light 11, particularly the near-infrared transmitted light, which is transmitted through the interior of the inspection object 5, of the output light 20 irradiated onto the inspection object 5. The spectrometer 6 detects and spectrometers the transmitted light 11. The spectrometer 6 may be, for example, a near-infrared spectrometer. The spectrometer 200 may also be an inspection device. The inspection device may also analyze the data obtained by the spectrometer 6. The inspection device may also include an analysis unit (not shown) that performs an analysis on inspection items such as the internal state and quality of the inspection object 5 or a quality judgment. The analysis unit may include a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The CPU may also read the program and reference data stored in the ROM and perform information processing related to the analysis of the inspection items according to the program.

[0068] like Figure 7 As shown, the reflective spectroscopic device 200 also includes the near-infrared light emitting device 100 and the spectrometer 6. However, in the reflective spectroscopic device 200, the spectrometer 6 is configured to receive reflected light 12, particularly near-infrared reflected light, from the output light 20 irradiated onto the inspection object 5. Other points are the same as those of the transmissive spectroscopic device 200, and therefore their description is omitted.

[0069] The reflective spectrometer 200 may also include a reflective member (not shown), such as a metal plate, particularly a near-infrared reflective member. If the near-infrared fluorescent component of the output light 20 that has passed through the inspection object 5 is reflected by the reflective member and then re-transmitted into the inspection object 5, near-infrared spectroscopic data unique to the inspection object 5 can be readily obtained, even if the inspection object 5 is, for example, a liquid.

[0070] It should be noted that the transmitted light 11 and reflected light 12 only need to contain near-infrared fluorescent components, but may also contain red fluorescent components. Depending on the form of the inspection object 5, a visible fluorescent component may also be transmitted. In the case of a method that reflects visible light components, the visible light components can be separated and utilized for, for example, visual inspection of the inspection object 5.

[0071] The inspection object 5 may be food, for example. It should be noted that "food" is a general term for items consumed by humans, such as ingredients for lunch boxes, grains, fruits, vegetables, meat, fish, processed foods, and beverages.

[0072] The purpose of the spectrometer 200 is not particularly limited. The inspection object 5 may be, for example, a fruit or vegetable, or a food other than a fruit or vegetable, such as a general term for food items consumed by humans, such as ingredients in a lunch box, grains, meat, fish, processed foods, and beverages. The spectrometer 200 may also be, for example, an evaluation device for inspection objects such as fruits and vegetables. For example, light suitable for evaluating the decay, maturity, sugar content, acidity, and water content of fruits and vegetables is irradiated onto fruits and vegetables, thereby becoming a spectrometer 200 that is advantageous for precision inspections such as determining the market value of inspection objects such as fruits and vegetables. The spectrometer 200 may also be used as a foreign matter inspection device for inspecting whether the inspection object 5 contains foreign matter.

[0073] As described above, spectrometer 200 includes near-infrared light emitting device 100. Furthermore, spectrometry utilizes near-infrared light emitting device 100. Output light 20 emitted by near-infrared light emitting device 100 is then irradiated onto the inspection object. Near-infrared light emitting device 100 concentrates red and near-infrared light components within the wavelength range of 600 nm to less than 980 nm, more preferably 660 nm to less than 940 nm, and even more preferably 660 nm to less than 900 nm. Furthermore, light components with relatively small intensity variations are irradiated onto the inspection object. For example, spectrometry can be used to determine the spoilage of onions using light components in the range of 660 to 950 nm, the ripeness and moisture content of tomatoes using light components in the range of 620 to 950 nm, and the sugar content and acidity of fruits and vegetables using light components in the range of 780 to 830 nm. Therefore, spectrometer 200 and spectrometry are suitable for high-precision evaluation of inspection objects such as fruits and vegetables. Fruits and vegetables are sometimes collectively referred to as fruits and vegetables.

[0074] It should be noted that in the above embodiments, unless otherwise specified, the spectra of the spectral distribution of the output light 20, near-infrared fluorescence 21, and visible fluorescence 22 may also be spectra obtained when the primary light 10 (excitation light) has a wavelength of 450 nm. Furthermore, unless otherwise specified, the above spectra may also be spectra at 30°C. Specifically, the above spectra may be spectra obtained when the temperature of the phosphor or wavelength converter is 30°C.

[0075] Example

[0076] Hereinafter, the present embodiment will be described in more detail with reference to Examples and Comparative Examples, but the present embodiment is not limited to these Examples. It should be noted that evaluation was performed at 30° C. unless otherwise specified.

[0077] The near-infrared light-emitting device in the examples utilizes three self-produced near-infrared phosphors. Therefore, this section describes the synthesis of these near-infrared phosphors and their evaluation results. First, common considerations for synthesizing and evaluating near-infrared phosphors are explained, followed by the evaluation results of the synthesized near-infrared phosphors.

[0078] (Preparation of phosphor raw materials)

[0079] In the production of the near-infrared phosphor, the following compound powders were used as raw materials.

[0080] Lithium carbonate (Li2CO3): Purity 2N, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0081] Gallium oxide (Ga2O3): Purity 4N, manufactured by Asia Physical Materials Co., Ltd.

[0082] Gadolinium oxide (Gd2O3): Purity 4N, manufactured by Shin-Etsu Chemical Co., Ltd.

[0083] Scandium oxide (Sc2O3): Purity 4N, manufactured by Shin-Etsu Chemical Co., Ltd.

[0084] Chromium oxide (Cr2O3): Purity 3N, manufactured by Kojundo Chemical Research Institute Co., Ltd.

[0085] (Preparation and Synthesis of Phosphors)

[0086] The oxide phosphors were synthesized using a solid phase reaction preparation method. Specifically, three near-infrared phosphors having the following feed compositions were synthesized.

[0087] 1) LGO:Li(Ga 0.97 Cr 0.03 )5O8

[0088] 2) GGG:Gd3(Ga 0.925 Cr0.075 )2(GaO4)3

[0089] 3)GSO:(Ga 0.59 Sc 0.40 Cr 0.01 )2O3

[0090] The above raw materials are weighed and mixed in a manner to form the above-mentioned feed composition, that is, in a manner to form the ratio of the metal elements in the above-mentioned feed composition. For example, in the above-mentioned LGO, the ratio of the metal elements in the feed composition is set to an atomic ratio of Li:Ga:Cr of 1.00:4.85:0.15. Then, a planetary ball mill (manufactured by Fritsch) is used to wet-mix the prepared raw materials, and the dried powder is used as a mixed raw material. The above-mentioned mixed raw material is transferred to an alumina crucible with a lid and fired in the atmosphere or in a weak reducing atmosphere for 4 hours using a box-type electric furnace. It should be noted that the firing temperature of LGO is 1500°C, the firing temperature of GGG is 1600°C, and the firing temperature of GSO is 1400°C. Then, the fired product obtained by firing is lightly crushed to prepare a phosphor sample.

[0091] (Evaluation of Phosphor Crystals)

[0092] The X-ray diffraction patterns of the compounds that make up the phosphor samples were examined using an X-ray diffraction apparatus (manufactured by Rigaku Corporation). The results showed that all X-ray diffraction patterns were primarily composed of the desired compounds (i.e., LiGa5O8, Gd3Ga2(GaO4)3, or (Ga,Sc)2O3). This indicates that a phosphor with a crystalline phase substantially identical to that of LiGa5O8, Gd3Ga2(GaO4)3, or (Ga,Sc)2O3 can be synthesized.

[0093] It should be noted that the composition of the LGO phosphor sample was investigated using an inductively coupled plasma emission spectrometer (manufactured by Thermo Fisher Scientific Co., Ltd.). 0.81 (Ga 0.75 Cr 0.03 )5O 8-α , relative to the feed composition (Li(Ga 0.97 Cr 0.03 )5O8), a Li-poor composition in which the Li deficiency is 15 atomic % or more (less than 30%).

[0094] (Evaluation of fluorescence characteristics)

[0095] While omitting detailed explanation, the following results describe the fluorescence characteristics of each phosphor when excited at an excitation wavelength of 450 nm using an absolute PL quantum yield measurement device (manufactured by Hamamatsu Photonics Co., Ltd.). Note that FWHM is the half-value width of the spectrum at the fluorescence peak wavelength (maximum fluorescence intensity).

[0096] 1) LGO:

[0097] Fluorescence peak wavelength: 833nm

[0098] Fluorescence spectrum shape: wide

[0099] FWHM: 207nm

[0100] Internal quantum efficiency: 85%

[0101] Light absorption rate: 63%

[0102] 2) GGG:

[0103] Fluorescence peak wavelength: 731nm

[0104] Fluorescence spectrum shape: wide

[0105] FWHM: 96nm

[0106] Internal quantum efficiency: >95%

[0107] Light absorption rate: 48%

[0108] 3)GSO:

[0109] Fluorescence peak wavelength: 823nm

[0110] Fluorescence spectrum shape: wide

[0111] FWHM: 147nm

[0112] Internal quantum efficiency: 92%

[0113] Light absorption rate: 41%

[0114] In this embodiment, the self-made near-infrared phosphor and the commercially available red phosphor are used.

[0115] (Example 1)

[0116] Using the following 1) to 4) components, a Figure 1 A near-infrared light-emitting device (wavelength conversion-type light-emitting device) comprising a solid-state light-emitting element and a wavelength converter as shown.

[0117] 1) Solid-state light-emitting devices

[0118] High-power blue LED (measured peak wavelength: 460 nm) (Product number: SMBB450H-1100, Otsuka Opto Semiconductor Co., Ltd.)

[0119] 2) Wavelength conversion body

[0120] 2-1) CaAlSiN3:Eu 2+ (CASN) Red phosphor (fluorescence peak wavelength: 651 nm) (Mitsubishi Chemical Corporation)

[0121] 2-2) LiGa5O8:Cr 3+ (LGO) Near-infrared phosphor (fluorescence peak wavelength: 833 nm) (manufactured by the above method)

[0122] 2-3) Two-component mixed thermosetting silicone resin (sealing material for LED, product name: KER-2600A / B, Shin-Etsu Chemical Co., Ltd.)

[0123] (Production of wavelength conversion body)

[0124] The wavelength conversion body is produced by laminating the first wavelength conversion body (one sheet of CASN red phosphor sheet) and the second wavelength conversion body (two sheets of LGO near-infrared phosphor sheet) produced as follows.

[0125] (Production of the first wavelength conversion body)

[0126] 0.68 g of CASN red phosphor and silicone resins (1 g of KER-2600A and 1 g of KER-2600B) are mixed using a stirring and defoaming device, and further defoamed. The stirring and defoaming device is manufactured by THINKY Corporation, product name: Awa Toriren Taro (registered trademark), model: ARE-310. In addition, the rotation speed of the stirring and defoaming device is about 2000 rpm, and the treatment is carried out for 3 minutes. Thus, a phosphor paste containing CASN red phosphor and silicone resin is prepared. Using a dispenser (model: ML-5000XII, manufactured by Musashi Engineering Co., Ltd.), the obtained phosphor paste is dropped into a frame with a height of about 140 μm. Then, the phosphor paste is heated in the air at 150 °C for 2 hours to be cured. Thus, a resin phosphor film with a thickness of about 130 μm (CASN red phosphor sheet: 10 mm long × 10 mm wide) is formed, and the first wavelength conversion body is obtained.

[0127] (Production of the second wavelength conversion body)

[0128] First, 0.40 g of LGO near-infrared phosphor and silicone resin (1 g of KER-2600A and 1 g of KER-2600B) were mixed with the first wavelength converter using a stirring and degassing device, and further degassed. In this way, a phosphor paste containing LGO near-infrared phosphor and silicone resin was prepared. Using the above-mentioned dispenser, the obtained phosphor paste was dripped into a frame with a height of about 320 μm. Then, the phosphor paste was heated in an atmosphere at 150°C for 2 hours to cure it. In this way, a resin phosphor film with a thickness of about 300 μm (LGO near-infrared phosphor sheet: 10 mm long × 10 mm wide) was formed to obtain a second wavelength converter.

[0129] (Fabrication of Near-Infrared Light-Emitting Device)

[0130] A near-infrared light emitting device was manufactured by placing a phosphor sheet on the main light extraction surface of the blue LED so that the blue LED faced the second wavelength converter of the stacked wavelength converters.

[0131] The luminous characteristics of the obtained near-infrared light-emitting device were evaluated. When a current of 10 mA (2.6 V) flows through the blue LED chip, blue light is emitted from the blue LED chip as primary light. Then, a part of it is converted into a near-infrared fluorescent component by the second wavelength converter. Furthermore, a part of the primary light that has passed through the second wavelength converter is converted into red light as a visible fluorescent component by the first wavelength converter. Then, a mixed light containing blue light as primary light, a near-infrared fluorescent component and a visible fluorescent component is emitted from the near-infrared light-emitting device as output light. For reference, the appearance of the output light is purple light, which is a light of a hue that is not regarded as white light. It should be noted that purple light is regarded as light based on the additive mixing of the blue light component of the primary light and the red light component of the near-infrared fluorescent component and the visible fluorescent component.

[0132] Figure 2 : shows the spectral distribution of the output light emitted from the near-infrared light emitting device of this embodiment. Figure 2 As can be seen, the spectral distribution of the output light is composed of a light component of the wavelength-converted light from the phosphor and a light component 10A from the primary light. The light component of the wavelength-converted light from the phosphor includes a light component 20A from the near-infrared phosphor contained in the second wavelength converter and a light component 20B from the visible light phosphor contained in the first wavelength converter.

[0133] like Figure 3As shown in the figure, the center of gravity of the wavelength-converted light from the phosphor (i.e., the light components of near-infrared fluorescent component 20A and visible fluorescent component 20B, excluding light component 10A from the primary light) in this spectral distribution was found to be 813 nm. Furthermore, the spectral intensity within the wavelength range of 660 nm to less than 900 nm exhibited a spectral distribution with a minimum value near 710 nm and a maximum value near 719 nm (or near 835 nm), with the minimum value being 54% of the maximum value.

[0134] It should be noted that Figure 3 It can be seen that in the spectral distribution, the light intensity gradually decreases as the wavelength becomes shorter from 600 nm, and gradually decreases as the wavelength becomes longer from 980 nm.

[0135] Depend on Figure 3 As can be seen, according to this example, by combining the LGO phosphor, a near-infrared phosphor, and the CASN red phosphor, a visible light phosphor, a near-infrared light emitting device is produced that emits output light with a spectral distribution suitable for, for example, evaluating factors determining the market value of inspected objects such as fruits and vegetables. Specifically, the spectral distribution of the output light includes a light component derived from the fluorescence of the phosphor at least within the wavelength range of 600 nm to less than 980 nm, and the center of gravity of the spectral distribution of wavelength-converted light derived from the phosphor is within the wavelength range of 700 nm to less than 900 nm. Furthermore, the minimum value of the spectral intensity within the wavelength range of 660 nm to less than 900 nm exceeds 50% of the maximum value.

[0136] (Example 2)

[0137] The following 1) to 5) components are used to form Figure 5 The near-infrared light-emitting device (wavelength conversion-type light-emitting device) of Example 2 is composed of a solid-state light-emitting element and a wavelength converter. It should be noted that the solid-state light-emitting element is a blue laser diode (measured peak wavelength: 453 nm), and the wavelength converter is a resin phosphor film containing the aforementioned CASN red phosphor, the aforementioned GGG near-infrared phosphor, and the aforementioned GSO near-infrared phosphor.

[0138] 1) Blue laser diode (measured peak wavelength: 453 nm) (manufactured by OSRAM Opto Semiconductors)

[0139] 2) CASN red phosphor (Mitsubishi Chemical Corporation)

[0140] 3) GGG near-infrared phosphor (self-made)

[0141] 4) GSO near-infrared phosphor (self-made)

[0142] 5) Thermosetting silicone resin (Product name: KJR-9032, Shin-Etsu Chemical Co., Ltd.)

[0143] Then, a wavelength converter and a near-infrared light-emitting device were produced as follows.

[0144] First, a wavelength converter made of three phosphors and a silicone resin was produced according to the following steps. 4g of silicone resin, 0.600g of CASN red phosphor, 2.76g of GGG near-infrared phosphor, and 8.57g of GSO near-infrared phosphor were placed in a cylindrical plastic container. Then, they were mixed using a rotary mixer to prepare a phosphor paste. The phosphor paste was applied to a wheel substrate (outer diameter: 65mm, raw material: MIRO SILVER) using a screen printer. Then, a curing oven was used to heat the mixture at 150°C to produce a phosphor wheel having a volume ratio (vol%) of 58.6:4.4:8.7:28.3 of silicone resin: CASN: GGG: GSO. The thickness of the phosphor film was 45μm.

[0145] The phosphor wheel thus produced was rotated, and the laser diode was driven to irradiate with laser light (primary light) under the following conditions.

[0146] 1) Fluorescent wheel speed: 10800 rpm

[0147] 2) LD driving conditions: 90V-2.0A

[0148] 3) Laser irradiation power of fluorescent film: 54W

[0149] 4) Irradiation spot size diameter: Φ1.5mm (design value)

[0150] As a result, the phosphor wheel's fluorescent film (wavelength converter) absorbs a portion of the laser light, converting its wavelength into near-infrared and visible fluorescent components. The laser light not absorbed by the wavelength converter is then reflected and, along with the wavelength-converted near-infrared and visible fluorescent components, forms output light, which is then emitted from the near-infrared light-emitting device. The output light appears to be violet, similar to that in Example 1, and has a hue that cannot be considered white.

[0151] Figure 8 : shows the spectral distribution of the output light emitted from the near-infrared light emitting device of Example 2. Figure 8 It can be seen that the spectral distribution of the output light is composed of the light component of the wavelength converted light from the phosphor (i.e., the near-infrared fluorescent component 20A and the visible fluorescent component 20B from the near-infrared phosphor and the visible light phosphor contained in the wavelength converter) and the light component 10A from the primary light.

[0152] like Figure 8 As shown in the figure, the center of gravity of the wavelength-converted light from the phosphor (i.e., the light components of near-infrared fluorescent component 20A and visible fluorescent component 20B, excluding light component 10A from the primary light) in this spectral distribution was found to be 790 nm. Furthermore, the spectral intensity within the wavelength range of 660 nm to less than 900 nm exhibited a spectral distribution with a minimum value near 900 nm and a maximum value near 805 nm, with the minimum value being 52% of the maximum value.

[0153] It should be noted that Figure 8 It can be seen that, in the spectral distribution, taking noise into account, the light intensity substantially decreases as the wavelength becomes shorter from 600 nm, and gradually decreases as the wavelength becomes longer from 980 nm.

[0154] In the near-infrared light emitting device of this example, a combination of GGG near-infrared phosphor and GSO near-infrared phosphor as near-infrared phosphors and CASN red phosphor as visible light phosphor is used. Figure 8 As can be seen, this example provides a near-infrared light-emitting device that emits output light with a spectral distribution suitable for evaluating factors determining the market value of inspected objects such as fruits and vegetables. Specifically, the spectral distribution of the output light includes a light component derived from the fluorescent light of the phosphor at least within the wavelength range of 600 nm to less than 980 nm, and the center of gravity of the spectral distribution of the wavelength-converted light derived from the phosphor is within the wavelength range of 700 nm to less than 900 nm. Furthermore, the minimum value of the spectral intensity within the wavelength range of 660 nm to less than 900 nm exceeds 50% of the maximum value.

[0155] In this way, a near-infrared light emitting device can be constructed that is suitable as a determining factor for evaluating the market value of inspection objects such as fruits and vegetables.

[0156] (Note)

[0157] The following technology is disclosed based on the description of the above embodiments.

[0158] (Technology 1) A near-infrared light-emitting device comprising a solid-state light-emitting element and a wavelength converter containing a phosphor, emitting output light, wherein the spectral distribution of the output light has a light component of fluorescence from the phosphor at least in a wavelength range of 600 nm to less than 980 nm, the center of gravity of the spectral distribution of the wavelength-converted light based on the phosphor is in a wavelength range of 700 nm to less than 900 nm, the center of gravity being a wavelength at which an integral value obtained by adding the light intensity of the spectral distribution of the wavelength-converted light every 1 nm from 525 nm toward the long wavelength side and an integral value obtained by adding the light intensity from 1100 nm toward the short wavelength side become equal, the minimum value of the spectral intensity in the wavelength range of 660 nm to less than 900 nm exceeds 50% of the maximum value, and in the spectral distribution, the light intensity of the spectral distribution of the wavelength-converted light gradually decreases as the wavelength becomes shorter from 600 nm.

[0159] This structure concentrates the light components within the wavelength range of 600nm to less than 980nm, focusing on red and near-infrared components. Furthermore, the output of these light components exhibits minimal intensity variation. Therefore, the near-infrared light-emitting device can produce light suitable for evaluating the spoilage, sugar content, acidity, maturity, and moisture content of fruits and vegetables, for example. Therefore, the near-infrared light-emitting device is suitable for evaluating factors that determine the market value of an object under inspection.

[0160] (Technique 2) The near-infrared light-emitting device according to Technique 1, wherein the spectral distribution gradually decreases in light intensity as the wavelength increases from 980 nm. This structure provides a spectral distribution in which the output light is concentrated in all red light components with wavelengths below 980 nm and near-infrared light components, each with a certain intensity or greater. Consequently, the light-emitting device can efficiently emit output light containing both red and near-infrared components.

[0161] (Technique 3) The near-infrared light-emitting device according to Technique 1 or 2, wherein the light component having a spectral distribution within the wavelength range of 600 nm to less than 980 nm originates from the electron energy transition of the fluorescent ions of at least one of Eu ions and Cr ions. Utilizing conventional Eu ion-activated red phosphors and Cr ion-activated near-infrared phosphors, it is possible to obtain output light with red and near-infrared components concentrated within the wavelength range of 600 nm to less than 980 nm, and with minimal intensity variation. Therefore, the near-infrared light-emitting device is suitable for industrial production.

[0162] (Technique 4) The near-infrared light-emitting device according to any one of Techniques 1 to 3, wherein the output light is output through a lens, and the lens collimates the wavelength-converted light emitted by the wavelength converter. With this configuration, the light emitted by the wavelength converter as diffused light is output as collimated light (parallel light). This allows evaluation of the inspection object by irradiating the device with near-infrared light from a distance without bringing the near-infrared light-emitting device close to the device.

[0163] (Technique 5) The near-infrared light-emitting device according to Technique 4, wherein the light incident surface of the lens is arranged to entirely cover the light exit surface of the wavelength converter. With this configuration, a large amount of wavelength-converted light enters the light incident surface of the lens. Consequently, the near-infrared light-emitting device is suitable for converting light emitted from the wavelength converter into collimated light.

[0164] (Technique 6) A near-infrared light-emitting device according to any one of Techniques 1 to 5, wherein the solid-state light-emitting element emits primary light, and the primary light is irradiated onto the rotating wavelength converter. According to this structure, the location where the wavelength converter is irradiated with the primary light changes position over time. Therefore, the wavelength converter, whose temperature rises due to irradiation with the primary light, moves to a position where it is not irradiated with the primary light, during which time the wavelength converter is cooled. Therefore, even if the wavelength converter is irradiated with primary light of high energy density, the temperature rise of the wavelength converter can be suppressed, and the near-infrared light-emitting device can emit high-output output light.

[0165] (Technique 7) The near-infrared light-emitting device according to any one of Techniques 1 to 6, wherein the wavelength converter is plate-shaped and has a thickness of 50 μm or greater and less than 500 μm. This structure reduces the thickness of the wavelength converter, thereby reducing the proportion of wavelength-converted light leaking from the sides of the wavelength converter and increasing the proportion of light incident on the light incident surface of the lens. Consequently, the near-infrared light-emitting device can output high-quality coherent light.

[0166] (Technique 8) A spectrometer comprising the near-infrared light emitting device described in any one of Techniques 1 to 7, irradiating an inspection object with the output light emitted by the near-infrared light emitting device. With this configuration, the light components are concentrated within the wavelength range of 600 nm to less than 980 nm, with red and near-infrared components irradiating the object with relatively small variations in intensity. Therefore, the spectrometer is suitable for evaluating the spoilage, sugar content, acidity, maturity, and moisture content of fruits and vegetables, for example.

[0167] (Technique 9) The spectrometer according to Technique 8 is an inspection device. With this configuration, the spectrometer irradiates the inspection object with light suitable for precise evaluation of the inspection object. Therefore, the spectrometer is useful for precise inspections such as determining the market value of the inspection object.

[0168] (Technique 10) A spectroscopic method utilizing the near-infrared light emitting device described in any one of Techniques 1 to 7. This configuration concentrates the light components, including red and near-infrared components, within the wavelength range of 600 nm to less than 980 nm. Furthermore, the light components with relatively small intensity variations are irradiated onto the object. Therefore, spectroscopic methods are suitable for evaluating the spoilage, sugar content, acidity, maturity, and moisture content of fruits and vegetables, for example.

[0169] The entire contents of Japanese Tokugan Application No. 2023-010889 (filing date: January 27, 2023) are incorporated herein by reference.

[0170] As mentioned above, although this embodiment was demonstrated, this embodiment is not limited to these, Various deformation|transformation is possible within the range of the summary of this embodiment.

[0171] Industrial applicability

[0172] According to the present disclosure, a near-infrared light emitting device, a spectroscopic device, and a spectroscopic method suitable for evaluating factors determining the market value of an inspection object can be provided.

[0173] Description of Reference Numerals

[0174] 1Solid-state light-emitting element

[0175] 2Wavelength converter

[0176] 3 lenses

[0177] 5Inspection objects

[0178] 10 One Light

[0179] 20 Output Light

[0180] 100 Near-infrared light-emitting device

[0181] 200 Spectrometer

Claims

1. A near-infrared light emitting device comprising a solid-state light emitting element and a wavelength converter containing a phosphor, emitting output light, The spectral distribution of the output light includes a light component derived from the fluorescence of the phosphor at least in a wavelength range of 600 nm to less than 980 nm. The center of gravity of the spectral distribution of the wavelength-converted light of the phosphor is within a wavelength range of 700 nm to less than 900 nm. The center of gravity is a wavelength at which an integrated value obtained by adding the light intensity of the spectral distribution of the wavelength-converted light every 1 nm from 525 nm toward the longer wavelength side and an integrated value obtained by adding the light intensity from 1100 nm toward the shorter wavelength side become equal. The minimum value of the spectral intensity in the wavelength range of 660nm to less than 900nm exceeds 50% of the maximum value, In the spectral distribution, the light intensity of the spectral distribution of the wavelength-converted light gradually decreases as the wavelength becomes shorter from 600 nm.

2. The near-infrared light emitting device according to claim 1, wherein In the above-described spectral distribution, the light intensity gradually decreases as the wavelength becomes longer from 980 nm.

3. The near-infrared light emitting device according to claim 1 or 2, wherein: The light component having a spectral distribution within a wavelength range of 600 nm to less than 980 nm is derived from electron energy transition of fluorescent ions of at least one of Eu ions and Cr ions.

4. The near-infrared light emitting device according to any one of claims 1 to 3, wherein The output light is outputted through a lens, and the lens collimates the wavelength-converted light emitted from the wavelength converter.

5. The near-infrared light emitting device according to claim 4, wherein The light incident surface of the lens is arranged to cover the entire light exit surface of the wavelength converter.

6. The near-infrared light emitting device according to any one of claims 1 to 5, wherein The solid-state light emitting element emits primary light, and the primary light is irradiated onto the rotating wavelength converter.

7. The near-infrared light emitting device according to any one of claims 1 to 6, wherein The wavelength converter is in a plate shape, and has a thickness of 50 μm or more and less than 500 μm. 8 . A spectroscopic device comprising the near-infrared light emitting device according to claim 1 , wherein an inspection object is irradiated with the output light emitted by the near-infrared light emitting device. The spectroscopic device according to claim 8 , which is an inspection device. 10 . A spectroscopic method using the near-infrared light emitting device according to claim 1 .

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