Light-emitting device and sensing system

Abstract

To support accurate measurement of oxygen saturation, etc.SOLUTION: A light emitting device 2 for emitting output light L includes a light emitting element 20 for emitting primary light L1 and a wavelength conversion body for converting at least part of the primary light L1 to a secondary light L2. The output light L includes at least part of the secondary light L2. Light intensity of the output light L is a predetermined value or more over an entire wavelength range of 750-900 nm. The ratio of the light intensity of the output light L in 900 nm to the light intensity of the output light L in 750 nm is 0.2 or more and less than 3.0. The spectral visibility of the output light L is 0.1-10 lm / W.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a light-emitting device and a sensing system. [Background technology]

[0002] Patent Document 1 discloses a beam-emitting optoelectronic device that is provided in a spectrometer used for analyzing organic substances, etc. The optoelectronic device includes a conversion material that converts a primary beam emitted from a semiconductor chip into a secondary beam having a wavelength between 700 nm and 2000 nm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 174236 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a light-emitting device and a sensing system that can support highly accurate measurements of oxygen saturation and the like. [Means for solving the problem]

[0005] A light emitting device according to one aspect of the present invention is a light emitting device that emits output light, and includes a light emitting element that emits primary light and a wavelength converter that converts at least a portion of the primary light into secondary light. The output light includes at least a portion of the secondary light. The light intensity of the output light is equal to or greater than a predetermined value over the entire wavelength range of 750 nm to 900 nm. The ratio of the light intensity of the output light at 900 nm to the light intensity of the output light at 750 nm is equal to or greater than 0.2 and less than 3.0. The spectral luminosity of the output light is equal to or greater than 0.1 lm / W and equal to or less than 10 lm / W.

[0006] A sensing system according to one aspect of the present invention includes the light emitting device according to the above aspect and a detection device that detects reflected light of the output light. [Effects of the Invention]

[0007] According to the present invention, it is possible to support highly accurate measurements of oxygen saturation and the like. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of the appearance of a light irradiation device including a light emitting device according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the light emitting device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of the spectrum of output light from the light emitting device according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing another example of the spectrum of the output light from the light emitting device according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of the light emitting device according to the second embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the spectrum of output light from the light emitting device according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing another example of the spectrum of the output light from the light emitting device according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating a configuration of a sensing system according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a light-emitting device and a sensing system according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, component arrangements and connection forms, steps, and step orders shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components not recited in the independent claims will be described as optional components.

[0010] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0011] Furthermore, in this specification, terms indicating the relationship between elements, terms indicating the shape of elements, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0012] (Embodiment 1) [composition] First, the configuration of the light emitting device according to the first embodiment will be described with reference to FIGS.

[0013] Fig. 1 is a perspective view showing an example of the appearance of a light irradiation device 1 including a light emitting device according to the present embodiment. Fig. 2 is a cross-sectional view of a light emitting device 2 according to the present embodiment.

[0014] The light irradiation device 1 shown in FIG. 1 is, for example, a spotlight, and includes a light emitting device 2 shown in FIG. 2. The light irradiation device 1 includes the light emitting device 2, a housing that houses the light emitting device 2, and an optical system such as a lens that transmits light emitted from the light emitting device 2. The light irradiation device 1 is fixed to a duct rail or the like installed on a ceiling. The light irradiation device 1 receives power supplied from a power supply device such as a commercial power source, and irradiates output light L (see FIG. 2) emitted by the light emitting device 2 using the power. The light irradiation device 1 may also be a downlight, ceiling light, pendant light, wall light, or floor light.

[0015] The light emitting device 2 emits output light L. The output light L includes primary light L1 and secondary light L2. In other words, the output light L is a composite light of the primary light L1 and the secondary light L2. The primary light L1 is visible light, such as blue light. The secondary light L2 is near-infrared light. The specific spectrum of the output light L will be described later.

[0016] As shown in FIG. 2, the light emitting device 2 includes a substrate 10, a light emitting element 20, a wavelength converter layer 30 including a wavelength converter, and a dam material 40.

[0017] The substrate 10 is a mounting substrate for mounting the light-emitting elements 20. The substrate 10 is provided with metal wiring (not shown) for supplying power to the plurality of light-emitting elements 20. The substrate 10 is, for example, a ceramic substrate made of ceramic, a resin substrate made of resin, or an insulating substrate such as a glass substrate. Alternatively, the substrate 10 may be a metal-based substrate (metal substrate) in which a metal plate is coated with an insulating film.

[0018] The light emitting element 20 emits primary light L1. The light emitting element 20 is, for example, an LED (Light Emitting Diode) chip, and is mounted on the substrate 10. The light emitting element 20 is, for example, a blue LED chip whose central wavelength (peak wavelength of the emission spectrum) is in the range of 430 nm to 495 nm. For example, the light emitting element 20 is a blue LED chip that emits blue light with a peak wavelength of approximately 440 nm as the primary light L1.

[0019] The output energy of the primary light L1 per light-emitting element 20 is, for example, 5 mW or more, but may also be 10 mW or more, or 30 mW or more. The total output energy of the primary light L1 from all the light-emitting elements 20 included in the light-emitting device 2 is, for example, 100 mW or more. The total output energy of the primary light L1 may be 1 W or more, 1.2 W or more, 5 W or more, or 10 W or more. As the output energy of the primary light L1 increases, the output energy of the secondary light L2 also increases.

[0020] The wavelength converter layer 30 includes a wavelength converter that converts at least a part of the primary light L1 into secondary light L2. The wavelength converter layer 30 includes, for example, a resin layer in which the wavelength converter is dispersed. The resin layer is translucent to visible light and near-infrared light. For example, the resin layer is formed using a silicone resin, but is not limited to this.

[0021] In this embodiment, the wavelength converter includes one or more types of phosphors. At least one of the one or more types of phosphors is a near-infrared phosphor that emits near-infrared light. That is, the secondary light L2 includes light in the near-infrared band.

[0022] The near-infrared phosphor may be, for example, a phosphor having a peak fluorescence intensity within a wavelength range of 780 nm or more and less than 2500 nm, preferably 800 nm or more and less than 2500 nm. This allows the output light L to contain an infrared light component that is invisible to the human eye. In this case, the primary light L1 absorbed by the near-infrared phosphor may be light (e.g., blue light) that exhibits a maximum intensity within the wavelength range of visible light of 380 nm or more and less than 700 nm.

[0023] In addition, a phosphor having a peak of fluorescent intensity in a wavelength range of less than 780 nm can also be used as a near-infrared phosphor, as long as it emits light with fluorescent intensity at least within a wavelength range of 780 nm or more and less than 2500 nm.

[0024] As the near-infrared phosphor, a phosphor that is activated with at least one of rare earth ions and transition metal ions and emits fluorescence containing a near-infrared light component can be used. 3+ ,EU 2+ , Ho 3+ , Er 3+ , Tm 3+ and Yb 3+ The transition metal ion is at least one selected from the group consisting of Ti 3+ , V 4+ , Cr 4+ , V 3+ , Cr 3+ , V 2+ , Mn 4+ , Fe 3+ , Co 3+ , Co 2+ and Ni 2+ The near-infrared phosphor may contain the above-mentioned ions as a luminescent center and at least one of oxide, sulfide, nitride, halide, oxysulfide, oxynitride, and oxyhalide as a host.

[0025] In this embodiment, the near-infrared phosphor is, for example, Cr 3+ It is possible to use a phosphor containing the above. This makes it possible to easily realize a near-infrared phosphor that has the property of absorbing visible light, particularly blue or red light, and converting it into near-infrared light components. In addition, it is easy to change the light absorption peak wavelength and / or fluorescence peak wavelength depending on the type of host, which is advantageous in changing the excitation spectrum shape and / or fluorescence spectrum shape.

[0026] Cr absorbs blue or red light and converts it into near-infrared fluorescent components. 3+ Many activated phosphors are known, which not only broadens the range of choices for the light emitting element 20 but also makes it easy to change the fluorescence peak wavelength of the secondary light L2, which is advantageous for controlling the spectral distribution of the output light L.

[0027] For example, a near-infrared phosphor has a garnet-type crystal structure and contains Cr 3+It is possible to use a composite oxide phosphor activated with Cr. 3+ The activated garnet phosphor is, for example, at least one of a rare earth aluminum garnet phosphor and a rare earth gallium garnet phosphor. 3+ The activated garnet phosphor is, for example, Y3Al2(AlO4)3:Cr 3+ , La3Al2(AlO4)3:Cr 3+ , Gd3Al2(AlO4)3:Cr 3+ , Y3Ga2(AlO4)3:Cr 3+ , La3Ga2(AlO4)3:Cr 3+ , Gd3Ga2(AlO4)3:Cr 3+ , Y3Sc2(AlO4)3:Cr 3+ , La3Sc2(AlO4)3:Cr 3+ , Gd3Sc2(AlO4)3:Cr 3+ , Y3Ga2(GaO4)3:Cr 3+ , La3Ga2(GaO4)3:Cr 3+ , (Gd,La)3Ga2(GaO4)3:Cr 3+ , Gd3Ga2(GaO4)3:Cr 3+ , Y3Sc2(GaO4)3:Cr 3+ , La3Sc2(GaO4)3:Cr 3+ , Gd3Sc2(GaO4)3:Cr 3+ , and (Gd,La)3(Ga,Sc)2(GaO4)3:Cr 3+ At least one selected from the group consisting of Cr 3+ The activated garnet phosphor may be a solid solution containing these phosphors as end members.

[0028] In addition, near-infrared phosphors that have crystal structures other than garnet type are also available. 3+ Cr having a crystal structure other than the garnet type may be used. 3+ Since activated phosphors tend to have a peak fluorescence intensity in the wavelength range of 820 nm or more, it is possible to provide a light emitting device that emits light that can measure oxygen saturation and the like with high accuracy.

[0029] Such near-infrared phosphors have high durability against high output. The higher the output energy of the excitation light (primary light L1), the more heat is generated during wavelength conversion by the near-infrared phosphor, resulting in a rise in temperature. The above-mentioned near-infrared phosphors are resistant to deterioration at high temperatures and can efficiently convert the high-output energy primary light L1 into secondary light L2.

[0030] The output energy of the secondary light L2 emitted by the wavelength converter layer 30 is, for example, 10 mW or more. The output energy of the secondary light L2 may be 100 mW or more, 1 W or more, 5 W or more, or 10 W or more. The greater the output energy of the secondary light L2, the more accurate the measurement of vital signs such as oxygen saturation can be.

[0031] In the present embodiment, an example is shown in which the wavelength converter layer 30 is arranged to collectively seal a plurality of light emitting elements 20, but the present invention is not limited to this. The wavelength converter layer 30 may be arranged separately for each of one or more light emitting elements 20. When a wavelength converter layer 30 is provided for each light emitting element 20, the output energy of the secondary light L2 emitted from each wavelength converter layer 30 is, for example, 5 mW or more. Alternatively, the output energy of the secondary light L2 emitted from each wavelength converter layer 30 may be 10 mW or more, or may be 30 mW or more.

[0032] The dam member 40 is a member provided on the substrate 10 to block the wavelength converter layer 30. In this embodiment, the dam member 40 is provided in a ring shape so as to surround the periphery of the wavelength converter layer 30. Note that the dam member 40 does not necessarily have to be provided.

[0033] The dam material 40 is formed using, for example, an insulating thermosetting resin or a thermoplastic resin, etc. Specifically, the dam material 40 may be made of a silicone resin, a phenolic resin, an epoxy resin, etc.

[0034] The light-emitting device 2 configured as described above emits output light L including near-infrared light. The output light L including near-infrared light can be used to measure (non-contact sensing) vital signs such as oxygen saturation in human blood and pulse wave. For example, oxygen saturation is measured by utilizing the absorption of light by hemoglobin in the blood. Specifically, hemoglobin bound to oxygen (HbO2) and hemoglobin separated from oxygen (Hb) have different absorbance curves, which represent the absorbance at each wavelength. For example, at and around 750 nm, the absorbance of Hb is greater than that of HbO2. Furthermore, at and around 900 nm, the absorbance of HbO2 is greater than that of Hb.

[0035] Therefore, by irradiating the device with output light L containing these two wavelengths, receiving the light reflected from the blood vessels, and calculating the ratio of the intensities of the received light, it is possible to calculate the ratio of Hb to HbO2, i.e., oxygen saturation. Similarly, by detecting temporal fluctuations in arterial blood, it is also possible to measure pulse waves. By irradiating light with sufficient intensity, the effects of noise and other factors can be suppressed, improving the accuracy of measuring vital signs such as oxygen saturation and pulse waves.

[0036] [Output light spectrum] Next, the spectrum of the output light L will be described with reference to FIGS.

[0037] 3 and 4 are diagrams each showing an example of the spectrum of output light L from light emitting device 2 according to this embodiment. In each diagram, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents emission intensity.

[0038] 3 and 4 show the spectrum of output light L emitted by a light emitting device 2 equipped with the same type of blue LED chip as the light emitting element 20. The blue LED chip emits blue light having a peak wavelength of approximately 450 nm and a half-width of approximately 15 nm as primary light L1. In this embodiment, since the output light L includes the primary light L1, a peak of light intensity exists in the blue wavelength band, as shown in FIGS.

[0039] The light emitting device 2 emitting the output light L shown in Fig. 3 and the light emitting device 2 emitting the output light L shown in Fig. 4 differ in the type of wavelength converter included. Specifically, the light emitting device 2 emitting the output light L shown in Fig. 3 includes a wavelength converter of (Ga,Sc)2O3:Cr 3+ and Gd3Ga2(GaO4)3:Cr 3+ The light emitting device 2 emitting the output light L shown in FIG. 4 contains (Ga,Sc)2O3:Cr as a wavelength converter. 3+ The wavelength converter is dispersed in the silicone resin. As shown in Figures 3 and 4, a peak corresponding to the secondary light L2 emitted by the wavelength converter exists in the near-infrared wavelength band.

[0040] In this embodiment, the output light L (secondary light L2) has a light intensity equal to or greater than a predetermined value over the entire wavelength range of 750 nm to 900 nm. In other words, the output light L contains a broad near-infrared component.

[0041] The predetermined value is, for example, 0.05 times or more the peak intensity. The predetermined value may be 0.1 times or more, 0.2 times or more, 0.3 times or more, 0.4 times or more, or 0.5 times or more the peak intensity. The peak intensity is the intensity of the maximum peak contained in the wavelength range of 750 nm to 900 nm. The larger the predetermined value, the greater the intensity of the near-infrared light component contained in the output light L, thereby improving the measurement accuracy of oxygen saturation, etc.

[0042] For example, a photoreceiver (photodetector) is used for measurement, and even if the characteristics of this photoreceiver change, it is possible to suppress a decrease in measurement accuracy. In other words, since strict measurement conditions are not required for the characteristics of the photoreceiver, the light-emitting device 2 can be applied to a highly versatile sensing system.

[0043] In this embodiment, the ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm is equal to or greater than 0.2 and less than 3.0. The ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm may be 1.0. This simplifies signal processing because it is not necessary to consider the intensity difference between each wavelength. Alternatively, the ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm may be equal to or greater than 0.2 and less than 1.0, or may be greater than 1.0 and less than 3.0. A desired spectrum can be achieved by adjusting the type and compounding ratio of the wavelength converter depending on the object to be measured.

[0044] For example, in the example shown in Figure 3, the peak wavelength of the secondary light L2 is approximately 810 nm. If the light intensity at this peak wavelength (i.e., peak intensity) is 1, the light intensity at 750 nm is approximately 0.74, and the light intensity at 900 nm is approximately 0.54. In other words, the light intensity at 900 nm is smaller than the light intensity at 750 nm. Specifically, the ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm is approximately 0.73.

[0045] 4, the peak wavelength of the secondary light L2 is approximately 830 nm. If the light intensity at this peak wavelength is 1, the light intensity at 750 nm is approximately 0.22, and the light intensity at 900 nm is approximately 0.66. In other words, the light intensity at 900 nm is greater than the light intensity at 750 nm. Specifically, the ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm is approximately 3.0.

[0046] In this embodiment, the spectral luminous efficiency of the output light L is 0.1 lm / W or more and 10 lm / W or less. The spectral luminous efficiency is a value with wavelength λ as a variable, and is expressed as K(λ). The spectral luminous efficiency K(λ) is expressed by the following equation (1).

[0047] (1) K(λ)=KmV(λ)

[0048] V(λ) is the relative luminous efficiency, specifically, the photopic luminous efficiency, Km=638 lm / W.

[0049] Spectral luminosity K(λ) corresponds to the coefficient for converting physical light intensity into psychophysical brightness. If the spectral density of light intensity is e(λ), the brightness perceived by the human eye, f(λ), is expressed by the following equation (2) using spectral luminosity K(λ).

[0050] (2) f(λ)=K(λ)e(λ)

[0051] If the spectral luminous efficiency K(λ) is too high, it will have a significant impact on the spatial design. That is, the impact of the visible light component from the light-emitting device 2 will be so great that it may give people an impression that is different from that of existing illuminated spaces. On the other hand, if the spectral luminous efficiency K(λ) is too small, the visible light component from the light-emitting device 2 will be so small that it will be impossible to visually confirm whether the light-emitting device 2 is emitting light. In the light-emitting device 2 according to this embodiment, the spectral luminous efficiency K(λ) is 0.1 lm / W or more and 10 lm / W or less, so that it is possible to visually confirm the light emission while minimizing the impact on the spatial design.

[0052] Depending on the lighting environment of the space, even if the spectral luminous efficiency K(λ) is 0.1 lm / W or more and 10 lm / W or less, it may not be possible to visually determine whether the light emitting device 2 is emitting light or not. Therefore, the spectral luminous efficiency K(λ) may be 0.1 lm / W or more and 20 lm / W or less, or may be 0.1 lm / W or more and 30 lm / W or less.

[0053] [Effects, etc.] As described above, the light emitting device 2 according to the present embodiment is a light emitting device that emits output light L and includes a light emitting element 20 that emits primary light L1 and a wavelength converter that converts at least a portion of the primary light L1 into secondary light L2. The output light L includes at least a portion of the secondary light L2. The light intensity of the output light L is equal to or greater than a predetermined value over the entire wavelength range of 750 nm to 900 nm. The ratio of the light intensity of the output light L at 900 nm to the light intensity of the output light L at 750 nm is equal to or greater than 0.2 and less than 3.0. The spectral luminosity of the output light L is equal to or greater than 0.1 lm / W and equal to or less than 10 lm / W.

[0054] This enables highly accurate measurements of oxygen saturation and other conditions to be supported. Specifically, because the output light L has high light intensity across the entire wavelength range of 750 nm to 900 nm, a decrease in measurement accuracy can be suppressed even if the characteristics of the light receiver change. In other words, because strict measurement conditions are not required for the characteristics of the light receiver, the light-emitting device 2 can be applied to highly versatile sensing systems. Furthermore, because the spectral luminous efficiency K(λ) is 0.1 lm / W or more and 10 lm / W or less, the light emission can be confirmed visually while minimizing the impact on spatial design.

[0055] Furthermore, for example, the wavelength converter may include two or more types of phosphors.

[0056] This allows the spectrum of the secondary light L2 to be easily adjusted by using multiple types of phosphors, and it is possible to obtain the spectrum of the secondary light L2 that is optimal for the measurement target and / or measurement environment, for example.

[0057] In addition, for example, at least one of the two or more phosphors may be Cr 3+ It is a near-infrared phosphor comprising:

[0058] This makes it possible to realize a wavelength converter that is less susceptible to deterioration at high temperatures. Therefore, the output energy of the primary light L1, which is excitation light, can be utilized, and the desired output light L can be emitted with high efficiency. Furthermore, since the output energy of the primary light L1 from one light-emitting element 20 can be increased, the number of light-emitting elements 20 can be reduced. This makes it possible to reduce the size of the light-emitting device 2.

[0059] Furthermore, for example, the output energy of the secondary light L2 may be 100 mW or more.

[0060] This makes it possible to increase the intensity of near-infrared light, thereby improving the accuracy of measurements such as oxygen saturation.

[0061] (Embodiment 2) Next, a second embodiment will be described.

[0062] The light emitting device according to embodiment 2 differs from embodiment 1 in that it includes a filter. The following description will focus on the differences from embodiment 1, and descriptions of commonalities will be omitted or simplified.

[0063] 5 is a cross-sectional view of a light emitting device 3 according to this embodiment. The light emitting device 3 shown in FIG. 5 includes a filter 50 in addition to the configuration of the light emitting device 2 shown in FIG.

[0064] The filter 50 absorbs or reflects at least a portion of at least one of the primary light L1 and the secondary light L2. In this embodiment, the filter 50 is a visible light cut filter that absorbs or reflects almost all of the primary light L1 and the visible light component of the secondary light L2. Therefore, the output light L emitted through the filter 50 does not contain the primary light L1 and has almost the same spectrum as the secondary light L2.

[0065] The filter 50 includes, for example, an absorbing pigment dispersed within a substrate such as resin or glass. Alternatively, the filter 50 includes a reflective film formed on the surface of the substrate that reflects visible light components. The reflective film may be, for example, a dielectric multilayer film. There are no particular limitations on the configuration of the filter 50 as long as it can suppress transmission of the target wavelength component.

[0066] In the example shown in FIG. 5, the filter 50 is disposed apart from the wavelength converting layer 30, but the wavelength converting layer 30 and the filter 50 may be in contact with each other.

[0067] Next, the spectrum of the output light L emitted by the light emitting device 3 will be described with reference to FIGS.

[0068] 6 and 7 are diagrams each showing an example of the spectrum of output light L from light emitting device 3 according to this embodiment. In each diagram, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents emission intensity.

[0069] The spectrum of the output light L shown in Fig. 6 is the spectrum of the light after the output light L shown in Fig. 3 has passed through the filter 50. That is, the light emitting device 3 emitting the output light L shown in Fig. 6 contains (Ga,Sc)2O3:Cr as a wavelength converter, as in the case of Fig. 3. 3+ and Gd3Ga2(GaO4)3:Cr 3+ and in a volume ratio of 4:6.

[0070] 7 is the spectrum of the output light L shown in FIG. 4 after it has passed through the filter 50. That is, the light emitting device 3 emitting the output light L shown in FIG. 7 uses (Ga,Sc)2O3:Cr as a wavelength converter, as in the case of FIG. 3+ Contains only

[0071] 6 and 7, output light L that has passed through filter 50 does not substantially contain light in the wavelength range of 400 nm to 700 nm. Output light L contains a small amount of visible light components in the range of 700 nm to 750 nm. By including a small amount of visible light components (here, red light), it becomes easier to visually confirm the light emitted by light-emitting device 3.

[0072] As described above, the light emitting device 3 according to this embodiment includes the filter 50 that absorbs or reflects at least a portion of at least one of the primary light L1 and the secondary light L2.

[0073] This allows the visible light component contained in the output light L to be sufficiently reduced, thereby minimizing the impact on spatial design. Even if the light-emitting device 3 is installed in a general environment such as a living space, rather than in a specialized environment such as a laboratory, the existing lighting environment can be left unchanged. Therefore, it becomes possible to measure vital signs such as a person's oxygen saturation or pulse wave on a daily basis in the living space. Measurement of vital signs using near-infrared light can be performed non-contact, so it does not interfere with daily life and can be performed without the person being aware of the measurement and without any burden.

[0074] The filter 50 may absorb or reflect only the primary light L1. In this case, the output light L includes a visible light component (e.g., red light of about 700 nm) contained in the secondary light L2. That is, when the light emitting device 3 is emitting light, not only near-infrared light but also red light visible to humans is emitted. This makes it easier to visually confirm the light emission of the light emitting device 3.

[0075] (Embodiment 3) Next, a third embodiment will be described.

[0076] The sensing system according to embodiment 3 includes the light emitting device according to embodiment 1 or 2. The following description will focus on the differences from embodiment 1 or 2, and the description of the commonalities will be omitted or simplified.

[0077] FIG. 8 is a diagram showing the configuration of a sensing system 100 according to this embodiment.

[0078] 8 measures characteristic values ​​of an object 101. The object 101 is, for example, a living organism such as a human. The sensing system 100 measures vital signs such as oxygen saturation or pulse wave of the human in a non-contact manner.

[0079] 8, the sensing system 100 includes a light emitting device 2 and a detection device 102. Note that the sensing system 100 may include the light emitting device 3 according to the second embodiment instead of the light emitting device 2.

[0080] The detection device 102 detects reflected light Lr of the output light L emitted from the light emitting device 2. The reflected light Lr is light that is generated when the object 101 reflects the output light L.

[0081] As described above, when measuring oxygen saturation or pulse waves, light of multiple wavelengths included in the near-infrared band is used. Therefore, the detection device 102 includes, for example, a photodetector capable of receiving light of multiple wavelengths. The photodetector outputs an electrical signal corresponding to the intensity of the received reflected light Lr.

[0082] The photodetector may be, for example, a quantum photodetector that detects the charge generated when light is incident on a semiconductor PN junction. Specifically, the photodetector may be a photodiode, a phototransistor, a photo integrated circuit (IC), a charge coupled device (CCD) image sensor, or a complementary metal oxide semiconductor (CMOS) image sensor. Other photodetectors may include a thermal photodetector that detects changes in electrical properties caused by a temperature rise due to heat generated when light is received, or an infrared film that is sensitive to light. Examples of thermal photodetectors that may be used include a thermopile that utilizes the thermoelectric effect and a pyroelectric element that utilizes the pyroelectric effect.

[0083] The detection device 102 includes a signal processing circuit (not shown) that processes the electrical signal output from the photodetector. The signal processing circuit calculates the ratio between the intensities of the reflected light Lr of two wavelengths received by the photodetector, thereby calculating the ratio between Hb and HbO2, i.e., the oxygen saturation level. Alternatively, the signal processing circuit may calculate the pulse wave.

[0084] As described above, the sensing system 100 according to this embodiment includes the light emitting device 2 and the detection device 102 that detects the reflected light Lr of the output light L.

[0085] This allows oxygen saturation, pulse wave, etc. to be measured with high accuracy.

[0086] Furthermore, since the sensing system 100 has little impact on spatial design, the light-emitting device 2 can be placed in the living space. Therefore, people can measure oxygen saturation and other parameters unconsciously while living their daily lives without consciously performing the measurements. In this way, a sensing system 100 that is highly convenient for users can be realized.

[0087] (others) The light emitting device and sensing system according to the present invention have been described above based on the above-mentioned embodiment, but the present invention is not limited to the above-mentioned embodiment.

[0088] For example, different types of phosphors may be dispersed and mixed in one wavelength converter layer 30, or each phosphor may be provided in a separate layer. For example, the wavelength converter layer 30 may have a laminated structure of multiple resin layers, with different types of phosphors dispersed in each resin layer. The primary light L1 from the light emitting element 20 passes through multiple types of phosphors in order and is converted into secondary light L2, thereby improving conversion efficiency. For example, if the secondary light L2 from a first type of phosphor is absorbed by a second type of phosphor, the first type of phosphor is arranged after the second type of phosphor in the order of passage of the primary light L1. This allows the secondary light L2 emitted from the first type of phosphor to be emitted to the outside without being absorbed by the second type of phosphor.

[0089] Furthermore, for example, the light emitting device may include a sintered wavelength converter instead of the wavelength converter dispersed in the resin. Specifically, the light emitting device may include a sintered body of phosphor particles (ceramic phosphor).

[0090] Furthermore, for example, in the above embodiment, a COB (Chip On Board) type light emitting device in which an LED chip is directly mounted on a substrate has been described, but this is not limiting. For example, the light emitting device may include an SMD (Surface Mount Device) type light emitting element.

[0091] The SMD light emitting element may include an LED chip, a package having a recess for accommodating the LED chip, a resin layer filling the recess, and a wavelength converter dispersed in the resin layer. In other words, the wavelength converter may be provided as a part of the SMD light emitting element.

[0092] Furthermore, the light-emitting element does not have to be a blue LED. For example, the light-emitting element may be a purple LED, an ultraviolet LED, or a red LED. That is, the primary light L1 does not have to be blue light, but may be purple light, ultraviolet light, or red light.

[0093] Furthermore, the light-emitting element does not have to be an LED, and may be, for example, a laser element or an organic EL (Electroluminescence) element.

[0094] Furthermore, for example, the light-emitting device may be used for purposes other than measuring vital signs such as oxygen saturation or pulse wave, etc. For example, the light-emitting device may be used as a gas sensor or distance sensor that uses infrared light, or as a surveillance camera.

[0095] In addition, the present invention also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions of each embodiment within the scope of the present invention. [Explanation of symbols]

[0096] 2, 3 Light-emitting device 20 Light-emitting element 30 Wavelength conversion layer 50 filters 100 Sensing System 102 Detection device L output light L1 primary light L2 secondary light Lr reflected light

Claims

1. A light emitting device that emits output light, comprising: a light-emitting element that emits primary light; a wavelength converter that converts at least a part of the primary light into secondary light, the output light includes at least a portion of the secondary light, the light intensity of the output light is equal to or greater than a predetermined value over the entire wavelength range of 750 nm to 900 nm, a ratio of the light intensity of the output light at 900 nm to the light intensity of the output light at 750 nm is equal to or greater than 0.2 and less than 3.0; the spectral luminosity of the output light is 0.1 lm / W or more and 10 lm / W or less; The light emitting device is used for a spotlight, a downlight, a ceiling light, a pendant light, a wall light or a floor light. Light-emitting device.

2. further comprising a filter that absorbs or reflects at least a portion of at least one of the primary light and the secondary light; The light emitting device according to claim 1 .

3. The wavelength converter includes two or more types of phosphors. The light emitting device according to claim 1 or 2.

4. At least one of the two or more phosphors is Cr ３＋ is a near-infrared phosphor comprising The light emitting device according to claim 3 .

5. The output energy of the secondary light is 100 mW or more. The light emitting device according to any one of claims 1 to 4.

6. The light emitting device according to any one of claims 1 to 5, a detection device that detects reflected light of the output light, Sensing system.

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