OPTICAL SENSOR

Abstract

An optical sensor (100) for detecting a heart rate and / or a blood oxygen content, comprising a light source (105) having at least one light-emitting semiconductor chip (110) and emitting electromagnetic radiation with three different wavelength ranges, wherein a first wavelength range comprises green light, a second wavelength range comprises red light, and a third wavelength range comprises infrared radiation, wherein the sensor (100) has three light detectors (131, 132, 133), wherein the three light detectors (131, 132, 133) each have a filter (141, 142, 143) for electromagnetic radiation, wherein a first filter (141) is transparent to light of the first wavelength range and opaque to light of the second wavelength range and the infrared radiation of the third wavelength range,a second filter (142) is transparent to light of the second wavelength range and opaque to light of the first wavelength range and the infrared radiation of the third wavelength range, and a third filter (143) is transparent to the infrared radiation of the third wavelength range and opaque to light of the first and second wavelength ranges, wherein the light-emitting semiconductor chip (110) has an emission wavelength of less than 570 nanometers and the light source (105) has a conversion phosphor (120), wherein the conversion phosphor (120) converts the light of the semiconductor chip (110) into electromagnetic radiation with the first wavelength range, the second wavelength range, and the third wavelength range, and wherein the conversion phosphor (120) has a matrix material with three different narrow-band phosphors,where the emission wavelengths of the phosphors lie within the three wavelength ranges.,

Description

[0001] The invention relates to an optical sensor for detecting a heart rate and / or a blood oxygen content.

[0002] Optical sensors for detecting heart rate and / or blood oxygen levels can be created by shining light from an LED onto the skin. The light is scattered by the tissue beneath the skin, and the intensity of the scattered light can be measured with a photodetector. Part of the incident light is absorbed by hemoglobin molecules in the blood. Driven by the heart, blood is pumped through the veins; the amount of blood in a vein is not constant but pulsates at the same frequency as the heart rate. As a result, the amount of blood in the vein fluctuates with the heart rate, as does the amount of available hemoglobin. Depending on whether there is a lot or a little hemoglobin in the vein, more or less of the light from the LED is absorbed by the hemoglobin. The intensity of the scattered light therefore also changes with the heart rate.This changing intensity can be detected by the photodetector. The heart rate can be determined from the change in the photodetector's photocurrent. Such an optical heart rate sensor is known from DE 10 2008 022 920 B4.

[0003] An object of the invention is to provide an improved optical sensor for determining heart rate, which is also suitable for optionally determining blood oxygen content.

[0004] This object is achieved with the optical sensor of claim 1.

[0005] An optical sensor for detecting a heart rate and / or a blood oxygen level has a light source containing at least one light-emitting semiconductor chip. The light source emits electromagnetic radiation with three different wavelength ranges, wherein a first wavelength range comprises green light, a second wavelength range comprises red light, and a third wavelength range comprises infrared radiation. In addition, the sensor has three light detectors, each having a filter for electromagnetic radiation. A first filter on a first light detector is transparent to light of the first wavelength range and opaque to light of the second and infrared radiation of the third wavelength range. A second filter of the second light detector is transparent to light of the second wavelength range and opaque to light of the first and infrared radiation of the third wavelength range.A third filter of a third light detector is transparent to infrared radiation of the third wavelength range and opaque to light of the first and second wavelength ranges. The light-emitting semiconductor chip has an emission wavelength of less than 570 nanometers. The light source has a conversion phosphor, wherein the conversion phosphor converts the light of the semiconductor chip into electromagnetic radiation with the first wavelength range, the second wavelength range, and the third wavelength range. The conversion phosphor has a matrix material with three different narrowband phosphors, wherein the emission wavelengths of the phosphors lie within the three wavelength ranges. Narrowband means that the half-width of an emission peak of the phosphor is less than 40 nanometers.The green light of the first wavelength range makes it possible to measure heart rate using the optical sensor. The red light of the second wavelength range and the infrared radiation of the third wavelength range are suitable for measuring blood oxygen levels using the optical sensor. By using three light detectors with three filters, each of which transmits one of the three wavelength ranges and is opaque to the other two wavelength ranges, three measurements can be carried out in parallel in the three wavelength ranges. It is advantageous to operate the light source in pulsed mode so that less energy is required than in continuous operation. By using the three light detectors with the three filters, it is possible to measure both heart rate and blood oxygen levels simultaneously using a single pulse from the light source.

[0006] The conversion phosphor, which comprises three narrow-band phosphors in a matrix material, is easy to manufacture and enables a simple structure of the optical sensor. By using narrow-band phosphors, the wavelengths suitable for measuring heart rate and blood oxygen levels are used. As little light as possible is generated within the phosphor that lies outside the desired wavelength ranges, so that the required light output of the light-emitting semiconductor chip can be reduced. This leads to power savings. In addition, only a small proportion of light unsuitable for measuring heart rate or blood oxygen levels is generated, thus reducing the amount of stray light. Furthermore, less light is irradiated onto the skin, meaning less unusable energy is transferred from the optical sensor to the skin, making the optical sensor more skin-friendly.

[0007] In one embodiment, the conversion phosphor comprises quantum dots. Quantum dots are well suited as conversion phosphors because, on the one hand, they can be easily configured to absorb the light from the semiconductor chip.

[0008] Furthermore, they can be configured to emit light in a narrow wavelength range. In particular, by choosing quantum dots as the conversion phosphor, it is possible to create a light source that exhibits narrowband emission of light in the first and second wavelength ranges and infrared radiation in the third wavelength range. In particular, it is possible to configure the light source so that the three wavelength ranges do not overlap.

[0009] To generate the light in the first wavelength range, cadmium selenide or indium phosphide quantum dots with a first quantum dot size can be used. The light in the second wavelength range can also be generated using cadmium selenide or indium phosphide quantum dots with a second quantum dot size, where the second size is larger than the first size. The infrared radiation in the third wavelength range can be generated using indium arsenide, lead selenide, or copper indium phosphide quantum dots.

[0010] In one embodiment, at least one filter is an interference filter. Interference filters are filters consisting of layers with different refractive indices. By appropriately selecting the refractive indices and layer thicknesses, a filter can be created that has a very narrowband transmission curve. Interference filters can, in particular, be used to provide filters for light detectors that almost completely transmit electromagnetic radiation in one wavelength range and almost completely suppress electromagnetic radiation in the other two wavelength ranges.

[0011] In one embodiment, the green light has a wavelength between 530 and 610 nanometers, the red light has a wavelength between 620 and 700 nanometers, and the infrared radiation has a wavelength greater than 800 nanometers. These three wavelength ranges are particularly well suited for use in an optical sensor, in particular for determining heart rate and / or blood oxygen levels.

[0012] When generating converted light at the wavelengths mentioned using quantum dots, the materials described below are conceivable. For the green light in the first wavelength range, with a wavelength of around 570 nanometers, cadmium selenide quantum dots with a diameter between 3.0 and 3.5 nanometers can be used. Alternatively, indium phosphide quantum dots with a diameter between 1.8 and 2.2 nanometers can be used for the green light.

[0013] For the red light of the second wavelength range, with a wavelength of around 660 nanometers, cadmium selenide quantum dots with a diameter between 7.5 and 8.5 nanometers can be used. Alternatively, indium phosphide quantum dots with a diameter between 2.8 and 3.2 nanometers can be used for the green light.

[0014] For infrared radiation in the third wavelength range with a wavelength greater than 800 nanometers, indium arsenide quantum dots with a diameter between 3.0 and 6.0 nanometers are possible. Alternatively, for infrared radiation in the third wavelength range with a wavelength greater than 800 nanometers, lead selenide quantum dots with a diameter greater than 5.0 nanometers can be used. Another alternative for infrared radiation in the third wavelength range with a wavelength greater than 800 nanometers is the use of copper indium phosphide quantum dots with a diameter between 2.5 and 5.8 nanometers.

[0015] In one embodiment, the optical sensor comprises an electronic circuit configured to evaluate signals from the light detectors and to supply voltage to the light source. This allows for the creation of an integrated component with small dimensions that requires only connections for a supply voltage and a data interface.

[0016] In one embodiment, the power supply of the light source can be operated in a pulsed mode. The circuit for evaluating the signals from the light detectors is configured to take these pulses into account. Pulsed operation of the light source can produce an optical sensor with lower energy consumption than an optical sensor in which the light source is operated continuously. The pulses can be taken into account, for example, by filtering at the pulse frequency. This improves signal evaluation.

[0017] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings. In each case, in a schematic representation Fig. 1 an optical sensor with light source and three light detectors; Fig. 2 an optical sensor with three semiconductor chips, a conversion phosphor, and three light detectors; Fig. 3 an optical sensor with a semiconductor chip, a conversion phosphor, and three light detectors; Fig. 4 to 6 different arrangement options for the three light detectors; Fig. 7 to 9 different embodiments of the light source with conversion phosphor; and Fig. 10 an optical sensor with an electronic circuit.

[0018] Fig. 1 shows a cross-section through an optical sensor 100. The optical sensor 100 has a housing 101. The housing 101 can, for example, be an injection-molded part made of plastic. It is also possible for the housing 101 to be made of a different material. The housing 101 has a first recess 102 and a second recess 103. Between the two recesses 102, 103 there is a web 104 made of the material of the housing 101. The two recesses 102, 103 are therefore separated from each other by the web 104. A semiconductor chip 110 is mounted in the first recess 102. The semiconductor chip 110 in the first recess 102 and the adjacent parts of the housing 101 form a light source 105. The light source 105 is configured to emit electromagnetic radiation with three different wavelength ranges.In particular, the semiconductor chip 110 is configured to emit electromagnetic radiation with three different wavelength ranges. A first wavelength range comprises green light, a second wavelength range comprises red light, and a third wavelength range comprises infrared radiation. Three light detectors 131, 132, 133 are mounted in the second recess 103, each light detector having a filter 141, 142, 143. The first filter 141 is mounted on the first light detector 131 and configured to transmit light of the first wavelength range and to block light of the second and third wavelength ranges. The second filter 142 is mounted on the second light detector 132 and configured to transmit electromagnetic radiation of the second wavelength range and to block electromagnetic radiation of the first and third wavelength ranges.The third filter 143 is mounted on the third light detector 133 and is configured to transmit electromagnetic radiation of the third wavelength range and not to transmit electromagnetic radiation of the first and second wavelength ranges.

[0019] "Transmitting" means that at least 85%, preferably at least 90%, particularly preferably at least 95%, and especially preferably at least 98% of the light in the wavelength range under consideration passes through the corresponding filter. "Not transmitting" means that a maximum of 10%, preferably a maximum of 5%, particularly preferably a maximum of 2%, and especially preferably a maximum of 1% of the light in the wavelength range under consideration passes through the corresponding filter.

[0020] The optical sensor 100 is configured to be placed on a body part or on a surface of a human body part. The electromagnetic radiation from the light source 105 is reflected or scattered within the tissue of the body part. The scattered light can be detected by the three light detectors 131, 132, 133. The signal in the three light detectors 131, 132, 133 changes depending on the heart rate and / or blood oxygen content within the body part.

[0021] Fig. Figure 2 shows a cross section through another optical sensor 100. The optical sensor 100 has a housing 101, a first recess 102, a second recess 103, and a web 104 between the two recesses 102, 103. In the second recess 103, three light detectors 131, 132, 133 with associated filters 141, 142, 143 are arranged, similar to Fig. 1. Three semiconductor chips 111, 112, 113 are arranged in the first recess 102. The first semiconductor chip 111 emits light with a wavelength of less than 570 nanometers. A second semiconductor chip 112 emits red light, and a third semiconductor chip 113 emits infrared radiation. The first recess 102 is filled with a conversion phosphor 120. This conversion phosphor converts the light from the first semiconductor chip into green light of the first wavelength range and is transparent to the light from the second semiconductor chip 112 and the infrared radiation from the third semiconductor chip 113. The conversion phosphor 120 can consist of phosphor particles in a matrix material. However, other conversion phosphors are also conceivable. The three semiconductor chips 111, 112, 113, the conversion phosphor 120 and the adjacent parts of the housing 101 form the light source 105.

[0022] Fig. 3 shows a further cross section through an optical sensor 100, which essentially corresponds to the optical sensor of the Fig. 1. In this case, the first recess 102 of the housing 101 is filled with a conversion phosphor 120. This conversion phosphor 120 converts the light from the semiconductor chip 110, which has an emission wavelength of less than 570 nanometers, into green light of the first wavelength range, red light of the second wavelength range, and infrared radiation of the third wavelength range. The conversion phosphor 120 is thus configured to absorb the light from the semiconductor chip 110 and emit electromagnetic radiation in three wavelength ranges. The conversion phosphor 120 comprises a matrix material with three different, narrowband phosphors, wherein the emission wavelengths of the phosphors lie within the three wavelength ranges. The phosphors can, for example, each comprise a phosphor whose converted light is narrowband.

[0023] The optical sensors 100 of the Fig. 1 to 3 therefore differ in the area of ​​the light source 105. The second recess 103 and the light detectors and filters located therein are for all three optical sensors of the Fig. 1 to 3 identical.

[0024] Fig. Figure 4 shows a plan view of an optical sensor 100. A housing 101 has a first recess 102 and a second recess 103. The two recesses 102, 103 are separated from each other by a web 104. A semiconductor chip 110 is arranged in the first recess 102. The first recess 102 with the semiconductor chip 110 and the adjacent parts of the housing 101 in turn forms the light source 105. The light source 105 can be analogous to one of the light sources 105 of the Fig. 1 to 3. Three light detectors are located in the second recess 103, with a first light detector 131 having the shortest distance from the light source 105, a second light detector 132 having a greater distance from the light source 105 than the first light detector 131, and a third light detector 133 having the greatest distance from the light source 105. A first filter 141 is arranged on the first light detector 131. A second filter 142 is arranged on the second light detector 132. A third filter 143 is arranged on the third light detector 133. The first filter 141 is permeable to green light of a first wavelength range. The second filter 142 is permeable to red light of a second wavelength range, and the third filter 143 is permeable to infrared radiation of a third wavelength range. The filters 141, 142, 143 are opaque to the other wavelength ranges.The detection of infrared radiation occurs furthest from the light source, while the detection of green light occurs closest to the light source.

[0025] Fig. 5 shows a plan view of a further embodiment of an optical sensor 100. A housing 101 also has a first recess 102 and a second recess 103. Within the first recess 102, one of the light sources 105 of the Fig. 1 to 3. In the second recess 103, three light detectors 131, 132, 133 with three associated filters 141, 142, 143 are arranged, wherein light detectors 131, 132, 133 and filters 141, 142, 143 have the same properties as in Fig. 4. The light detectors 131, 132, 133 and filters 141, 142, 143 have an elongated shape and are arranged in the second recess 103 such that they are each equidistant from the light source 105. In comparison to Fig. 4, the light detectors 131, 132, 133 and filters 141, 142, 143 are arranged rotated by 90 degrees.

[0026] Fig. Figure 6 shows a top view of another embodiment of an optical sensor 100. A housing 101 has a first recess 102 and a second recess 103. Within the first recess 102, a light source 105 is arranged, analogous to one of the light sources 105 of the Fig. 1 to 3. Three light detectors 131, 132, 133 with associated filters 141, 142, 143 are arranged in the second recess 103. The first light detector 131 with the first filter 141 is arranged on the side of the second recess 103 facing the light source 105. The second light detector 132 and the third light detector 133 with the associated filters 142, 143 are arranged rotated by 90 degrees relative to the first light detector 131, so that the distance of the second light detector 132 and the third light detector 133 from the light source is the same, but greater than the distance of the first light detector 131 from the light source 105. The light detectors 131, 132, 133 and the filters 141, 142, 143 correspond to the light detectors and filters of the Fig. 1 to 5.

[0027] Fig. Figure 7 shows a cross section through another light source 105, which is suitable to be part of the optical sensor 100. The light source of the Fig. 7 essentially corresponds to the light source of the Fig. 3. A housing 101 has a first recess 102 in which a semiconductor chip 110 with an emission wavelength of less than 570 nanometers is arranged. The first recess 102 is filled with a conversion phosphor 120, wherein the conversion phosphor 120 corresponds to the conversion phosphor of the Fig. 3. A protective layer 121 is arranged above the conversion phosphor 120, which seals the first recess 102 and the conversion phosphor 120 so that environmental influences cannot affect the conversion phosphor 120.

[0028] Fig. Figure 8 shows another example of a light source 105 for an optical sensor. A semiconductor chip 110 having an emission wavelength of less than 570 nanometers is arranged in a first recess 102 of a housing 101. A conversion phosphor 120 is arranged in the form of a platelet directly on the semiconductor chip 110. Semiconductor chip 110 and conversion phosphor 120 are encapsulated with a protective layer 121. The conversion phosphor 120, in turn, corresponds to the conversion phosphor of the Fig. 7.

[0029] Fig. 9 shows a further example of a light source 105. A semiconductor chip 110 is arranged in a first recess 102 of a housing 101, wherein the semiconductor chip 110 has an emission wavelength of less than 570 nanometers. The first recess 102 is covered with a glass plate 122. Above the glass plate 122 is a spacer 123, which is placed on the glass plate 122. Above the spacer 123 is another glass plate 122. The spacer 123 and the two glass plates 122 form a cavity into which the conversion phosphor 120 is introduced. The conversion phosphor 120 is thereby separated from the environment by the two glass plates 122 and the spacer 123, and is therefore arranged within the space defined by the two glass plates 122 and the spacer 123.

[0030] The three light sources 105 of the Fig. 7 to 9 can each be connected to the three arrangements of the filters 131, 132, 133 of the Fig. 4 to 6 can be combined.

[0031] In one embodiment, the conversion phosphor comprises 120 quantum dots. Quantum dots are particularly suitable as a conversion phosphor because they have a narrowband emission characteristic. In this case, narrowband means that the half-width of the emission peak is 30 to 40 nanometers. The green light of the first wavelength range has its maximum intensity at a wavelength of 570 nanometers. The red light of the second wavelength range has a maximum intensity at 660 nanometers, and the infrared radiation has a maximum wavelength greater than 800 nanometers. Due to the quantum dots and the resulting conversion phosphor with a narrow half-width, it is possible for the green light, the red light, and the infrared radiation to have three separate peaks and not overlap.

[0032] In one embodiment, a filter 141, 142, 143 is an interference filter. Interference filters consist of various layers with different refractive indices. By appropriately selecting the layer thicknesses and refractive indices of the layers, a filter can be created that has a steep slope at a specific wavelength. This means that a filter that is more than 90% transmissive at a first wavelength is opaque to light of the second wavelength at a second wavelength that differs from the first wavelength by only a few nanometers, in particular less than 10 nanometers.

[0033] The combination of a conversion phosphor 120, consisting of quantum dots, and filters 141, 142, 143, which are designed as interference filters, results in a particularly advantageous embodiment of the optical sensor 100.

[0034] In one embodiment, the green light has a wavelength between 530 and 610 nanometers, with a maximum intensity of 670 nanometers. The red light has a wavelength between 620 and 700 nanometers, with a maximum intensity of 660 nanometers. The infrared radiation has a wavelength greater than 800 nanometers. An optical sensor with the aforementioned wavelength ranges for green, red light, and infrared radiation is possible using quantum dots as the conversion phosphor 120 and interference filters as filters 141, 142, 143.

[0035] Fig. 1 to 9 do not show any connections of the semiconductor chips 110, 111, 112, 113 or the light detectors 131, 132, 133. These can be provided by a person skilled in the art within the housing 101.

[0036] Fig. 10 shows a cross section through a further embodiment of an optical sensor 100, wherein the optical sensor 100 is substantially similar to the optical sensor 100 of the Fig. 3. An electronic circuit 150 is arranged below the housing 101. The electronic circuit 150 is configured to supply voltage to the semiconductor chip 110 and to evaluate the signals from the three light detectors 131, 132, 133. For this purpose, the electronic circuit 150 has a controller for a semiconductor chip 154, which is connected to the semiconductor chip 110 via electrical lines 151. The electronic circuit 150 also has a connection for a voltage supply 153, which is connected to the controller for the semiconductor chip 154 ​​via an electrical line 152. In addition, the electronic circuit 150 has evaluation electronics 156, which are connected to the three light detectors 131, 132, 133 via electrical lines 155. The evaluation electronics 156 is connected to a data interface 158 via a data line 157. Also in Fig.10, but optionally, is a data line between the controller 154 for the semiconductor chip and the evaluation electronics 156. The optical sensor 100 thus has a voltage supply 153 and a data interface 158 as external connections, and is otherwise controlled by the electronic circuit 150.

[0037] In one embodiment, the controller 154 is configured to operate the semiconductor chip 110 in a pulsed manner. The evaluation electronics 156 are configured to receive information about the pulses via the data line 159 and to take this information into account when evaluating the signals from the light detectors 131, 132, 133. LIST OF REFERENCE SYMBOLS 100 Optical Sensor 101 housings 102 First recess 103 Second recess 104 jetty 105 Light source 110 semiconductor chips 111 First semiconductor chip 112 Second semiconductor chip 113 Third semiconductor chip 120 conversion fluorescent 121 protective layer 122 glass plates 123 spacers 131 First light detector 132 Second light detector 133 Third light detector 141 First filter 142 Second filter 143 Third filter 150 Electrical circuit 151 Electrical line 152 Electrical line 153 Connection for a power supply 154 Controller for a semiconductor chip 155 Electrical line 156 Evaluation electronics 157 Data line 158 Data interface 159 Data line

Claims

[1] An optical sensor (100) for detecting a heart rate and / or a blood oxygen content, comprising a light source (105) having at least one light-emitting semiconductor chip (110) and emitting electromagnetic radiation with three different wavelength ranges, wherein a first wavelength range comprises green light, a second wavelength range comprises red light, and a third wavelength range comprises infrared radiation, wherein the sensor (100) has three light detectors (131, 132, 133), wherein the three light detectors (131, 132, 133) each have a filter (141, 142, 143) for electromagnetic radiation, wherein a first filter (141) is transparent to light of the first wavelength range and opaque to light of the second wavelength range and the infrared radiation of the third wavelength range,a second filter (142) is transparent to light of the second wavelength range and opaque to light of the first wavelength range and the infrared radiation of the third wavelength range, and a third filter (143) is transparent to the infrared radiation of the third wavelength range and opaque to light of the first and second wavelength ranges, wherein the light-emitting semiconductor chip (110) has an emission wavelength of less than 570 nanometers and the light source (105) has a conversion phosphor (120), wherein the conversion phosphor (120) converts the light of the semiconductor chip (110) into electromagnetic radiation with the first wavelength range, the second wavelength range, and the third wavelength range, and wherein the conversion phosphor (120) has a matrix material with three different narrow-band phosphors,where the emission wavelengths of the phosphors lie within the three wavelength ranges., [2] The optical sensor (100) of claim 1, wherein the conversion phosphor (120) comprises quantum dots. [3] The optical sensor of claim 2, wherein the conversion phosphor (120) comprises cadmium selenide quantum dots having a diameter between 3.0 and 3.5 nanometers or indium phosphide quantum dots having a diameter between 1.8 and 2.2 nanometers, wherein the conversion phosphor additionally comprises cadmium selenide quantum dots having a diameter between 7.5 and 8.5 nanometers or indium phosphide quantum dots having a diameter between 2.8 and 3.2 nanometers, wherein the conversion phosphor (120) comprises indium arsenide quantum dots having a diameter between 3.0 and 6.0 nanometers or lead selenide quantum dots having a diameter greater than 5.0 nanometers or copper indium phosphide quantum dots having a diameter between 2.5 and 5.8 nanometers. [4] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the green light of the first wavelength range comprises cadmium selenide quantum dots with a diameter between 3.0 and 3.5 nanometers. [5] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the green light of the first wavelength range comprises indium phosphide quantum dots with a diameter between 1.8 and 2.2 nanometers. [6] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the red light of the second wavelength range comprises cadmium selenide quantum dots with a diameter between 7.5 and 8.5 nanometers. [7] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the green light of the first wavelength range comprises indium phosphide quantum dots with a diameter between 2.8 and 3.2 nanometers. [8] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the infrared radiation of the third wavelength range comprises indium arsenide quantum dots with a diameter between 3.0 and 6.0 nanometers. [9] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the infrared radiation of the third wavelength range comprises lead selenide quantum dots with a diameter greater than 5.0 nanometers. [10] Optical sensor according to claim 2, wherein the conversion phosphor (120) for generating the infrared radiation of the third wavelength range comprises copper indium phosphide quantum dots with a diameter between 2.5 and 5.8 nanometers. [11] Optical sensor (100) according to one of the preceding claims, wherein at least one filter (141, 142, 143) is an interference filter. [12] Optical sensor (100) according to one of the preceding claims, wherein the green light has a wavelength between 530 and 610 nanometers, the red light has a wavelength between 620 and 700 nanometers and the infrared radiation has a wavelength greater than 800 nanometers. [13] Optical sensor (100) according to one of the preceding claims, comprising an electronic circuit (150) which is arranged to evaluate signals from the light detectors (131, 132, 133) and to supply voltage to the light source (105). [14] Optical sensor (100) according to claim 13, wherein the voltage supply of the light source (105) can be operated in a pulsed manner and the circuit (150) for evaluating the signals of the light detectors (131, 132, 133) is arranged to take the pulses into account.

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