Sensor for detecting a biometric function

Abstract

Sensor (1) for detecting a biometric function, in particular for detecting a pulse or the blood oxygen content of a person, with at least one transmitter (2) which is designed to transmit electromagnetic radiation (13) in a radiation direction (21), with at least one receiver (3) which is designed to receive electromagnetic radiation (14) in a receiving direction (22), wherein the transmitter (2) and the receiver (3) are designed in such a way that the radiation direction (21) of the transmitter (2) is inclined at a fixed angle (23) away from the reception direction (22) of the receiver (3), wherein the angle (23) is between 1° and 60°, in particular between 20° and 40°, wherein the transmitter (2) has a reflector (16), wherein the reflector (16) determines the radiation direction (21) and / or the radiation angle range (24), wherein the reflector (16) has at least partially a parabolic shape, and wherein the transmitter (2) is arranged in a focus of the parabolic shape.

Description

[0001] The invention relates to a sensor for detecting a biometric function and a method for detecting a biometric function.

[0002] Photoplethysmographs are known in the art. These sensors can be used to measure a pulse rate, for example, on a person's wrist or finger, using electromagnetic radiation with the aid of a transmitter and a receiver. These sensors have a poor signal-to-noise ratio.

[0003] WO 2016 / 022 295 A1 describes an optical sensor module for measuring physiological information in which a transmission direction and a reception direction point apart.

[0004] WO 2014 / 054 420 A1 describes a light sensor for detecting the presence of an object with a light emitter and a light detector.

[0005] US 2007 / 0 241 943 A1 describes a reflection-based optical encoder.

[0006] The object of the invention is to provide an improved sensor for detecting a biometric function, in particular for detecting a human pulse or a human blood oxygen level.

[0007] The object of the invention is achieved by the sensor according to patent claim 1 and by the method according to patent claim 12.

[0008] Further embodiments of the sensor or method are specified in the dependent claims.

[0009] One advantage of the sensor described is that the signal-to-noise ratio is improved. This is achieved by arranging a sensor's emission direction at a predetermined angle, particularly an angle between 1 degree and 60 degrees, relative to a receiver's reception direction. Tests have shown that this arrangement can achieve an improved signal-to-noise ratio. For example, for a transmitter-receiver distance of 3-5 mm, good results can be achieved in an angle range between 20 degrees and 40 degrees, particularly in an angle range around 30 degrees.

[0010] In a further embodiment, the sensor has one or more transmitters with a radiation angle range of no more than 40 degrees, in particular no more than 35 degrees or smaller. A smaller radiation angle range also increases the signal-to-noise ratio on the receiver side. Ideally, the light is emitted parallel to the optical axis of the transmitter.

[0011] The transmitter has a reflector, which determines the radiation direction and / or the radiation angle range. Using a reflector allows a desired radiation direction and / or a desired radiation angle range to be determined in a simple and cost-effective manner.

[0012] In a further embodiment, the receiver(s) comprises a reflector, wherein the reflector defines a receiving direction and / or a receiving angle range of the receiver.

[0013] Experiments have shown that a reflector that is at least partially parabolic in shape further improves the sensor. A parabolic reflector can be beneficial for both the transmitter and the receiver.

[0014] In a further embodiment, the transmitter and / or the receiver comprise a lens suitable for defining a radiation direction or a reception direction or a radiation angle range or a reception angle range. In a further embodiment, the radiation can be aligned using a prism.

[0015] In a further embodiment, the transmitter and the receiver are arranged next to each other on one side of a carrier, i.e. housed in one component.

[0016] 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 which Fig. 1 a schematic representation of a sensor, Fig. 2 a schematic representation of a transmitter and a receiver of a sensor, Fig. 3 a perspective top view of a sensor and Fig. 4 a schematic cross-section through the sensor of the Fig. 3 represents.

[0017] Fig. 1 shows a schematic representation of a cross-section through a sensor 1, wherein the sensor 1 has a transmitter 2 and a receiver 3. The transmitter 2 is designed to generate electromagnetic radiation 13 and emit it in a predetermined radiation direction and / or within a predetermined radiation angle range. The transmitter 2 can be designed, for example, as a light-emitting diode or as a laser diode. For example, the radiation emitted by the transmitter 2 can represent green light. Depending on the selected embodiment, the light can also have other wavelengths.

[0018] The receiver 3 is configured to receive reflected electromagnetic radiation 14 in a predetermined receiving direction and / or within a predetermined receiving angle range. The receiver 3 is configured, for example, as a photodiode that converts incident light into an electrical signal. An evaluation unit 12 may be provided for evaluating the electrical signal. This evaluation unit is arranged on the sensor 1 and is electrically connected to the receiver 3.

[0019] A basic principle of sensor 1 is that the electromagnetic radiation 13 of the transmitter 2 is emitted toward a measurement object, for example, a finger 9. The finger 9 has skin, bones 10, arteries 15, veins, and muscles. The electromagnetic radiation 13 penetrates the skin of the finger 9 and is scattered and (partially) absorbed by body cells. The optical properties (scattering / absorption) of blood differ from those of the surrounding body cells. The returned light is modulated by the volume expansion of the artery during a heartbeat.

[0020] At the same time, unmodulated electromagnetic radiation is scattered toward the receiver 3 from other parts of the finger that do not pulsate. The modulated scattered radiation 14 causes a corresponding modulation of the electrical signal of the receiver 3. Thus, a heart rate can be detected based on the present modulation.

[0021] A major portion of the unmodulated reflected radiation is caused by the lower layers of skin and veins. The sensor described above increases the useful signal, i.e., increases the modulated reflected radiation 14.

[0022] In the illustrated embodiment, the transmitter 2 and the receiver 3 are arranged on a common carrier 4. The carrier 4, in turn, is arranged on a printed circuit board 8. In addition, a wall 7 is provided between the transmitter 2 and the receiver 3, which wall prevents direct irradiation of the receiver 3 by the transmitter 2. Furthermore, the transmitter 2 and the receiver 3 are surrounded by a housing 5 in a ring shape. In addition, a cover 6 is applied to the housing 5 and to the wall 7. The cover 6 is permeable to the electromagnetic radiation 13 and the reflected electromagnetic radiation 14. Depending on the selected embodiment, the cover 6 can be made of glass, for example. The finger 9 rests directly on the cover 6 for a measurement, for example. This establishes a defined distance between the transmitter 2 and the finger 9 and between the receiver 3 and the finger 9.

[0023] Experiments have shown that an increase in the useful signal can be achieved by arranging a radiation direction of the transmitter 2 at a predetermined angle relative to a reception direction of the receiver 3. The angle can be between 1 degree and 60 degrees, in particular between 20 degrees and 40 degrees. Furthermore, the angle can be in a range of around 30 degrees.

[0024] Fig. 2 shows a schematic representation of the transmitter 2 with a radiation direction 21. Also shown schematically is the receiver 3 with a reception direction 22. In the example shown, the radiation direction 21 is arranged at an angle 23 of 30 degrees away from the reception direction 22. As already explained, instead of the angle 23 of 30 degrees, another angular range between 1 degree and 60 degrees, in particular between 20 degrees and 40 degrees, can be provided. The radiation direction 21 defines a center of a radiation angle range 24. The reception direction 22 defines a center of a reception angle range 25. The radiation angle range 24 determines the angular range in which a significant intensity of the electromagnetic radiation 13 is emitted.

[0025] For example, a value greater than 10% of the maximum intensity can be assumed to be the essential intensity. Tests have shown that the useful signal is further enhanced when the radiation angle range of the transmitter 2 is less than 40 degrees, in particular less than 35 degrees or even smaller. With increasing parallel radiation of the electromagnetic wave 13, i.e., with decreasing radiation angle from the transmitter 2, a gradual increase in the intensity of the useful signal is detected on the side of the receiver 3.

[0026] Both for a precise determination of the radiation direction 21 of the transmitter 2 and for a precise determination of the reception direction 22 of the receiver 3, reflectors 16, 17 as well as lenses 18, 19 can be used ( Fig. 1). Depending on the selected embodiment, either a lens or a reflector can be provided to define a radiation direction and / or a radiation angle range. Furthermore, either a reflector or a lens can be provided to define a reception direction and / or a reception angle range of the receiver. Depending on the selected embodiment, the lens can be designed, for example, as a prism.

[0027] When designing the reflectors 16, 17, it has been shown that a parabolic shape increases the useful signal for both the transmitter 2 and the receiver 3. The parabolic shape of the reflector allows for the electromagnetic radiation 13 from the transmitter 2 to be emitted as parallel as possible. Furthermore, a parabolic reflector 17 can increase the useful signal for the receiver 3. The parabolic shape of the reflector enables narrow-angle beam shaping, ideally parallel beam shaping.

[0028] Fig. Figure 3 shows an embodiment of a sensor 1, wherein a transmitter 2 and a receiver 3 are provided. The transmitter 3 is arranged in a first recess 31 of a material 20. The receiver 3 is arranged in a second recess 32 of the material 20. In the illustrated embodiment, the side walls of the first and second recesses 31, 32 are designed as reflectors 16, 17 with a corresponding coating, in particular with a corresponding metallic coating. Furthermore, the walls of the first and second recesses 31, 32 have a parabolic shape in the illustrated embodiment.

[0029] Fig. 4 shows a cross section through the arrangement of the Fig. 3. Thus, the wall of the first recess 31 is formed in the form of a first reflector 16, which has a parabolic shape. Furthermore, the wall of the second recess 32 is formed in the form of a second reflector 17, which has the shape of a parabolic reflector. The material 20 can, for example, comprise a plastic material. Furthermore, the sensor 1 can be manufactured, for example, using mid-LED technology.

[0030] Furthermore, in Fig.4 shows the emission direction 21 of the first reflector 16 and the reception direction 22 of the second reflector 17. The emission direction 21 and the reception direction 22 are arranged inclined away from one another by a predetermined angle 23. As already explained, the predetermined angle can be in the range between 1 degree and 60 degrees, in particular between 20 degrees and 40 degrees, for example around 30 degrees. In this embodiment too, the emission direction and / or the reception direction are defined by a center, i.e. a center axis of a emission region, and by a center, i.e. a center slot of a reception region. Depending on the selected embodiment, the second reflector 17 can be omitted from the receiver 3.

[0031] Depending on the chosen embodiment, the sensor, which represents a photoplethysmograph, can also be designed as a combined component, with the transmitter and receiver located in the same component. Furthermore, the sensor can be constructed from several discrete components.

[0032] The determination of the emission direction and / or the reception direction can be achieved by a correspondingly tilted arrangement of the reflector relative to a surface of the carrier 4, in particular a chip surface. In addition, the corresponding alignment of the emission direction and / or the reception direction can be realized by a correspondingly tilted lens. In addition, a transmitter or a receiver can be arranged offset relative to a lens or a reflector. Furthermore, a prism or a prism array can be provided above the transmitter and / or the receiver 3 for the corresponding determination of the emission direction and / or the reception direction. In addition, the emission angle range and the emission direction of the transmitter and / or the reception angle range and the reception direction of the receiver can be determined by corresponding reflectors.

[0033] Furthermore, experiments have shown that the longer the wavelength of the electromagnetic radiation 13 emitted by the transmitter 2, the smaller the angle 23 can be in order to achieve an increase in the useful signal, in particular an optimization of the useful signal.

[0034] When using a reflector in the form of a parabolic reflector, the receiver and / or the transmitter are preferably arranged in the focus of the parabolic reflector.

[0035] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. LIST OF REFERENCE SYMBOLS 1 sensor 2 channels 3 recipients 4 carriers 5 housings 6 Cover 7 Wall 8 circuit board 9 fingers 10 bones 12 Evaluation unit 13 electromagnetic radiation 14 reflected radiation 15 Artery 16 first reflector 17 second reflector 18 first lens 19 second lens 20 materials 21 Beam direction 22 Reception direction 23 angles 24 beam angle range 25 reception angle range 31 first recess 32 second recess

Claims

[1] Sensor (1) for detecting a biometric function, in particular for detecting a pulse or the blood oxygen content of a person, with at least one transmitter (2) which is designed to transmit electromagnetic radiation (13) in a radiation direction (21), with at least one receiver (3) which is designed to receive electromagnetic radiation (14) in a receiving direction (22), wherein the transmitter (2) and the receiver (3) are designed in such a way that the radiation direction (21) of the transmitter (2) is inclined at a fixed angle (23) away from the reception direction (22) of the receiver (3), wherein the angle (23) is between 1° and 60°, in particular between 20° and 40°, wherein the transmitter (2) has a reflector (16), wherein the reflector (16) determines the radiation direction (21) and / or the radiation angle range (24), wherein the reflector (16) has at least partially a parabolic shape, and wherein the transmitter (2) is arranged in a focus of the parabolic shape. [2] Sensor according to claim 1, wherein the transmitter (2) has a radiation angle range (24) of 40° or less, in particular of 35° or less. [3] Sensor according to one of the preceding claims, wherein the receiver (3) has a reflector (17), wherein the reflector (17) of the receiver (3) defines a receiving direction (22) and / or a receiving angle range (25). [4] Sensor according to claim 3, wherein the reflector (17) of the receiver (3) has at least partially a parabolic shape, and wherein the receiver (3) is arranged in a focus of the parabolic shape. [5] Sensor according to one of the preceding claims, wherein the transmitter (2) and / or the receiver (3) has a lens (18, 19) for beam guidance. [6] Sensor according to claim 5, wherein the lens (18, 19) is designed as a prism. [7] Sensor according to one of the preceding claims, wherein the transmitter (2) and the receiver (3) are arranged side by side on one side of a carrier (4). [8] Sensor according to one of the preceding claims, wherein the radiation direction (21) is defined by a center of a radiation area. [9] Sensor according to one of the preceding claims, wherein the receiving direction (22) is defined by a center of a receiving area (24). [10] Sensor according to one of the preceding claims, wherein the transmitter (2) and the receiver (3) are arranged on a common carrier (4), wherein the emission direction (21) and / or the reception direction (22) is determined by a tilted arrangement of a reflector (16, 17) relative to a surface of the carrier (4). [11] Sensor according to one of the preceding claims, wherein the transmitter (2) and the receiver (3) are arranged on a common carrier (4), wherein the emission direction (21) and / or the reception direction (22) is determined by a tilted arrangement of a lens (18, 19) relative to a surface of the carrier (4). [12] Method for detecting a biometric function, in particular for detecting a pulse or the blood oxygen content of a person, wherein an electromagnetic radiation (13) is transmitted in a radiation direction (21) by a transmitter (2), wherein a reflected electromagnetic radiation (14) is received in a receiving direction (22) by a receiver (3), wherein the transmitter (2) and the receiver (3) are designed in such a way that the radiation direction (21) of the transmitter (2) is inclined at a fixed angle (23) away from the reception direction (22) of the receiver (3), wherein the angle (23) is between 1° and 60°, in particular between 20° and 40°, wherein the transmitter (2) has a reflector (16), wherein the reflector (16) determines the radiation direction (21) and / or the radiation angle range (24), wherein the reflector (16) has at least partially a parabolic shape, and wherein the transmitter (2) is arranged in a focus of the parabolic shape.

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