WO2023110668A1 - Sensor assembly for an optical vital sign sensor - Google Patents

Abstract

The invention relates to a sensor assembly (1) for use in an optical vital sign sensor, comprising at least one light source (2) and at least one photodetector (3). The light source (2) comprises at least one light-emitting chip (13, 23, 24, 25), and the chip (13, 23, 24, 25) and the photodetector (3) are mutually spaced in a transverse direction (RQ), wherein the chip (13, 23, 24, 25) has a length (L1) and a width (B1), and the length (L1) of the chip (13, 23, 24, 25) is greater than its width (B1).

Description

SENSOR ARRANGEMENT FOR AN OPTICAL VITAL SIGNS SENSOR

The present invention relates to a sensor arrangement for use in an optical vital sign sensor, comprising at least one light source and at least one photodetector, the light source and photodetector being spaced apart from one another in a transverse direction, and an optical vital sign sensor having such a sensor arrangement.

Vital sign sensors are sensors that can be placed on the skin of a human or animal as the user and optionally together with electronics measure or determine vital signs of the human or animal in question. For example, the heartbeat, the heartbeat frequency or the pulse of the human or animal can be measured by the vital sign sensor as a vital sign. The basic measurement method is also known as photoplethysmography (PPG) and is based on the fact that blood-filled arteries are an optical medium that absorbs, transmits and reflects different amounts of light intensity, depending on the amount (volume) of blood and oxygen saturation. The amount of blood fluctuates with each pressure surge as the arteries dilate. The optical properties of the blood also change with the oxygen saturation of the hemoglobin, so that pulse and oxygen saturation can be measured optically as a result.

Such vital sign sensors include a light source such as a light emitting diode (LED) that emits light into a user's skin. The emitted light is scattered in the skin and at least partially absorbed by the blood. Some of the light exits the skin and can be captured by a photodetector. The amount of light detected by the photodetector can be an indication of the blood volume in a user's skin. For example, a vital sign sensor can measure blood flow in the dermis and subcutaneous tissue of the skin by measuring absorption monitor at a specific wavelength. If the blood volume changes due to the pulsing heart, the scattered light returning from the user's skin also changes. Therefore, a pulse of a user in his skin and thus the heart rate can be determined by monitoring the detected light signal by means of the photodetector. In addition, blood components such as oxygen-containing or oxygen-poor hemoglobin and oxygen saturation can be determined.

In applications for monitoring vital parameters, a strong dependence of the modulation depth or alternatively the so-called perfusion index on the distance between the light source and the photodetector is observed. Generally speaking, the measurement of vital parameters is all the more sensitive, the greater the distance between the emitter and the detector. A possible reason lies in a lower cross-talk between emitter and detector, which is reduced with a larger distance between emitter and detector. This is particularly true for red and infrared wavelengths, which are important for measuring blood oxygenation. To a certain extent, however, this also applies to green wavelengths. At the same time, however, the number of photons that reach a detector decreases exponentially with distance, i.e. the distance between emitter and detector, roughly in accordance with the Beer-Lambert law. There is therefore a fundamental conflict of objectives between a sufficiently high sensitivity, which increases with distance, and the signal strength of the light emitted by the emitter and detected by the detector, which decreases with distance. The optimum distance between the emitter and the detector should therefore be selected, at which the signal measured by the detector is still strong enough and the sensitivity is high enough at the same time.

To overcome this trade-off, the amount of light emitted by a light source could be increased to to compensate for losses associated with increasing the distance between the emitter and detector. This can e.g. B. done by increasing both the emission area and the absolute current through an LED, so that the current density , i. H . the amount of current divided by the active area remains approximately constant. However, this would increase the overall size of the entire arrangement and increase its power consumption, so that other components such as power supply, driver stages and the like would have to be designed to be more powerful.

It is therefore an object of the invention to specify a sensor arrangement which avoids at least some of the disadvantages mentioned above.

This object is achieved by a sensor arrangement and an optical vital sign sensor according to the independent claims. Preferred embodiments of the invention are specified in the dependent claims.

The above object is achieved in particular by a sensor arrangement for use in an optical vital sign sensor, comprising at least one light source and at least one photodetector. The light source, for example a photodiode, includes a radiation or light-emitting chip. The chip and the photodetector are spaced from each other in a transverse direction. A length of the chip is greater than its width. The chip can, for example, have an essentially rectangular shape, each with a length and a width, and accordingly cannot have a square shape, whereas the photodetector can have a square shape.

The chip can be a semiconductor component, for example. Due to the shape of the chip or of the semiconductor, in some embodiments, a current density of the chips or . of the emitting semiconductor material are kept constant because a cross-sectional area of the chip can be kept constant, with a small width and large length of the chip component. It is therefore possible to provide the same brightness with the same total current. In other words, the shape of the chip according to the invention allows the chip to be very efficient because the current density can be kept constant and at the same time one dimension in a relevant direction, namely the transverse direction, can be made very small.

In some embodiments, the chip has a shape where its width is very small compared to its length. For example, a ratio of the width to the length of a chip can be equal to or greater than 1:1. 5 ; 1 : 2 ; 1 : 2 . be 5 or 1:3. Under certain circumstances, a length of the chip can have more than 4, 5, 6, 7, 8, 9, 10, 15 or 20 times the value of a width of the chip. In some exemplary embodiments, the shape of the chip can make it possible for a radiation field or illumination field to be generated that has a very homogeneous area. Optimally, the photodetector is arranged so that it overlaps with the homogeneous area of the radiation field.

Additionally or alternatively, in some exemplary embodiments, the width of the chip has a value that lies in a value range having a minimum value of 50 μm, 100 μm, 500 μm, 1 mm, 1.5 mm or 2 mm and/or a maximum value of 2mm, 3mm, 5mm or larger. Under certain circumstances, the shape of the chip approximated to a line can result in all beams emitted by the chip having a similarly long path to the photodetector in the transverse direction. The benefit of the effect can be increased, for example, if the photodetector is also only narrow. With a light source that includes a chip or semiconductor as a package, one would not be able to achieve these small dimensions of 50 μm, for example. In some embodiments, the chip and the photodetector are spaced apart from each other in the lateral direction by a maximum value corresponding to the width of the chip. This can correspond, for example, to an absolute value of at most 50 μm. In addition or as an alternative, the chip and the photodetector can have a minimum distance of 0 in the transverse direction. 5 x the width of the chip. In some embodiments, this can provide an overall light source with a very small width and all rays have a similar path to the detector. In some exemplary embodiments, a good compromise between signal noise and physical size of the vital sign sensor can be achieved as a result. The distance can be measured, for example, from a directly adjacent edge of the chip to a directly adjacent edge of the photodetector in the transverse direction, for example an edge that is perpendicular to the transverse direction and parallel to a longitudinal dimension of the chip. Alternatively, the distance can also be measured, for example, from a center line of the chip to a center line of the photodetector.

The longitudinal side of the light source can run at a distance from and in particular parallel to an adjacent side of the photodetector. In particular, the light source can be arranged at a distance from the photodetector in such a way that a longitudinal side of the light source runs adjacent to one side of the photodetector and in particular runs adjacent and parallel to one side of the photodetector.

The invention can make it possible to maintain the optimum distance between the emitter, i.e. the chip, and the detector, and thus the relationship between distance and sensitivity mentioned at the outset, at which the signal measured by the detector is still strong enough and the sensitivity is simultaneously sufficiently high . According to the emission surface of Light source enlarged without integrating over a larger distance range, but maintaining a specific, well-defined distance between the light source and the photodetector (emitter and detector). There remains an emitting area, e.g. B. the active area of an LED, which is constant in the direction perpendicular to a dividing line between light source and photodetector, but can grow linearly in the direction parallel to the dividing line to reach the maximum current density and current. In particular, the emission surface of the light source is thus enlarged in the longitudinal direction, ie parallel to the dividing line. This is true for all wavelengths, but especially for the red and IR wavelengths, where the sensitivity is more or less a linear function of the distance between the emitter and the detector.

In some exemplary embodiments, the length of the light source and thus the length of the chip deviates from a length of the photodetector by a value that is preferably less than 10, 5 or 2 times a width B1 of the chip. The dimension in the direction of the dividing line is understood here as length. The light source and the photodetector are preferably arranged parallel to one another with respect to a longitudinal axis as a dividing line. In other words, the two components are always at the same distance along their greatest extent. The photodetector and the chip are preferably arranged in such a way that the photodetector is arranged so that it completely overlaps the chip in the longitudinal direction. The light source and photodetector widths are preferably unequal. In particular, the width of the light source is smaller than the width of the photodetector. The dimension in the direction perpendicular to the dividing line is understood here as width.

The light source and the photodetector are designed as discrete components or as integrated components. For example, the light source and the photodetector on one be arranged on a common carrier substrate, or the light source and the photodetector are each arranged on separate carrier substrates.

In one embodiment of the invention, the light source comprises at least one light-emitting diode. In one embodiment of the invention, the photodetector comprises at least one photodiode. The light source, on the other hand, can also include a plurality of light-emitting diodes or, for example, by means of an array, in particular a pixelated array, composed of a plurality of light-emitting diodes. Likewise, the photodetector can include a plurality of photodiodes or, for example, be formed by an array, in particular a pixelated array, of a plurality of photodiodes.

In one embodiment of the invention, the light source comprises a green and/or an infrared (TR) and/or a red light-emitting diode. Depending on the vital function to be measured (heart rate, oxygen saturation, etc.), different wavelengths of the light used are advantageous. The green light-emitting diode preferably has a smaller distance to the photodetector than the red light-emitting diode and the IR light-emitting diode. Since green light is more strongly absorbed in the skin, this measure increases the light yield at the photodiode and allows more precise measurements of the vital functions.

In one embodiment of the invention, the light source comprises at least one light-emitting diode that is embedded in a potting material. This protects the light-emitting diode and its contacts from environmental influences. In one embodiment of the invention, the potting material is free of scattering particles. Because the chip already has the required expansion, a casting compound that is free of stray particles can be used. The radiating surface is then determined solely by the shape and dimensions of the chip. In one embodiment of the invention, the light source comprises at least one light-emitting diode which is embedded in a conversion material, or the encapsulation material has converter particles. As a result, a blue light-emitting diode can be used in particular, the light from which is converted into green light or light of a different color, for example.

In one embodiment of the invention, the light source has a smaller width than the photodetector. The overall size of the sensor arrangement can thus be reduced, particularly in the case of high-intensity light-emitting diodes.

Additionally or alternatively, the chip can be designed to emit green light. In some exemplary embodiments, the chip is additionally or alternatively designed to emit IR radiation. In some exemplary embodiments, the sensor arrangement also has a chip which is designed to emit red light. In this way, all the colors required for different vital functions are arranged in an elongated light source, which helps to further reduce the dimensions of a vital function sensor.

In some embodiments, the chip that is designed to emit green light is arranged at a smaller distance from the photodetector than the chip that is designed to emit red light and/or the chip that is designed to emit IR to emit radiation. For example, the chip that is designed to emit IR radiation can also be arranged at a smaller distance from the photodetector than the chip that is designed to emit red light. In some exemplary embodiments, the photodiode can thus be imagined as a package in which a long, narrow red chip is placed very closely next to a long, narrow IR chip. This would mean advantages for a SPO2 measurement, for example, because then practically at the same position and essentially in the same distance the tissue can be illuminated with red and IR light.

In embodiments, the light source can have a plurality of light-emitting diodes arranged next to one another in the longitudinal direction of the light source instead of an elongated single light-emitting diode. The plurality of light-emitting diodes arranged next to one another in the longitudinal direction of the light source can be rectangular or square and, taken together, result in a rectangular light source with a greater length than width.

In some exemplary embodiments of the invention, the light-emitting diode or light-emitting diodes and/or the photodiode or photodiodes are each arranged on a substrate. The substrate preferably has a cavity or a frame forming a cavity, in which the light-emitting diode or light-emitting diodes and/or the photodiode or photodiodes are each arranged. In particular, the frame can be designed in such a way that it protrudes beyond the light-emitting diode or light-emitting diodes and/or the photodiode or photodiodes in the direction perpendicular to the substrate.

The cavity or the frame forming the cavity can be filled, for example, with a particularly transparent casting material, in which the light-emitting diode(s) is/are embedded. This protects the light-emitting diode and its contacts from environmental influences. The potting material can be free of stray particles, for example. As an alternative or in addition to this, the encapsulation material can also include, for example, conversion particles, such as phosphor particles, by means of which the light emitted by a light-emitting diode embedded in the encapsulation material can be converted into light of a different wavelength.

In some embodiments includes or consists of the cavity or. the frame forming the cavity preferably an opaque material with high diffuse reflectivity for the light used. This can ensure that a direct beam path between the light-emitting diode or the light-emitting diodes and/or the photodiode or the photodiodes is interrupted.

In some exemplary embodiments, the chip is in direct contact with a gas that is also in contact with other components of the sensor arrangement. Because the chip is not cast in a casting material in some exemplary embodiments, but is surrounded by the gas at least in sections, it can determine a radiating surface solely through its size and smaller dimensions can be achieved than in variants with a package. The other components can be, for example, the light source, the detector, a housing, the vital sign sensor or an interior thereof. The gas can be, for example, ambient air, nitrogen or the like. The gas can, for example, be in contact with an environment in which the vital sign sensor is located or be separate from this environment. The sensor arrangement can possibly have a protective plate, which is designed and arranged in order to protect the chip, which is free of encapsulation compound, from mechanical damage. The protective plate can be arranged, for example, at a distance, filled with the gas, from the surface of the chip that is emitting for the measurement. The protective plate can be designed to protect the chip from mechanical damage and transparent to the radiation emitted by the chip. For this purpose, the sensor arrangement can have, for example, at least one or a plurality of spacers, which are arranged and designed to fix the protective plate at a distance from the chip. The chip is preferably in direct contact with the gas, at least with its surface that emits the radiation for the measurement. For example, the chip being in direct contact with the gas may mean that there is no other material or medium between the Semiconductor material of the chip and the gas is arranged. This can advantageously be the case for at least part of the surface of the chip, for example for more than 95%, 90%, 80%, 50%, 40% or 30% of a surface of the chip which emits the radiation for the measurement case . The surface that emits the radiation for the measurement can be, for example, a surface of the chip that faces a user's skin when it is being worn correctly.

The problem mentioned at the outset is also solved by an optical vital sign sensor, configured to measure or determine vital signs of a user, comprising a sensor arrangement according to the invention.

Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawings. Schematically show:

FIG. 1 shows a schematic representation of a sensor arrangement of a vital sign sensor;

FIG. 2 shows a schematic representation of a further sensor arrangement of a vital sign sensor;

FIG. 3 shows a basic sketch of a top view of a sensor arrangement according to the prior art as a comparative example;

FIG. 4 shows a basic sketch of a top view of a sensor arrangement according to an exemplary embodiment of the invention;

Figures 5- 6 a schematic representation of a top view and a schematic representation of a transverse Section of a light source as a comparative example;

FIGS. 7-8 show a schematic representation of a plan view and a schematic representation of a cross section of a light source for use in a sensor arrangement according to an embodiment;

FIGS. 9-10 show a schematic representation of a plan view and a schematic representation of a cross section of a light source as a comparative example;

FIG. 11 shows a schematic representation of a top view of a sensor arrangement according to a further exemplary embodiment;

FIG. 12 shows a schematic representation of a plan view of a sensor arrangement according to a further exemplary embodiment according to some aspects of the proposed principle, in which the light source and the photodetector are arranged on a common substrate;

FIG. 13 shows a schematic representation of a cross section of FIG.

The following embodiments and examples show various aspects and their combinations according to the proposed principle. The embodiments and examples are not always to scale. Likewise, various elements can be enlarged or reduced in order to emphasize individual aspects. It goes without saying that the individual aspects and features of the embodiments and examples shown in the figures can easily be combined with one another can be, without thereby affecting the principle of the invention. Some aspects exhibit a regular structure or shape. It should be noted that minor deviations from the ideal shape can occur in practice, without however contradicting the inventive idea.

In addition, the individual figures, features and aspects are not necessarily of the correct size, nor are the proportions between the individual elements necessarily correct. Some aspects and features are highlighted by enlarging them. However, terms such as "above", "above", "below", "below", "greater", "smaller" and the like are correctly represented with respect to the elements in the figures. It is thus possible to derive such relationships between the elements using the illustrations.

FIG. 1 schematically shows a sensor arrangement 1 of a vital sign sensor, which comprises a light source 2 and a photodetector 3 . The sensor arrangement 1 is placed on the skin 4 of a user. The electrical wiring of light source 2 and photodetector 3 and other assemblies or components such as evaluation electronics, power supply, display or communication means are not shown to simplify the illustration, since understanding the invention essentially depends on the sensor arrangement 1 .

The light 5 emitted by the light source 2 , for example a light-emitting diode (LED ), propagates in the skin 4 . The skin 4 is shown here in a schematically simplified manner, comprising a second skin layer (dermis) 6 with many blood vessels lying under a first skin layer (epidermis) with few or no blood vessels, as well as further layers 7 lying deeper and also carrying blood. The light source 2 and the photodetector 3 are spaced from each other in a transverse direction RQ. The light 5 becomes part absorbed by the blood in the blood vessels of the deeper layers 7 , partly backscattered. The more blood interacts with the light 5, the more light 5 is absorbed. As a result, less backscattered light 5 reaches the photodetector 3, which is designed as a photodiode, for example, and the signal generated by the photodiode becomes smaller.

After every heartbeat, a pulse wave occurs in the blood vessels and the amount of blood increases for a short time. At this moment, the photodetector 3 generates a smaller electric signal compared to a time point after the pulse wave. With every heartbeat, the cycle starts all over again. The periodic change in the signal output by the photodetector 3 is detected by downstream electronics. From this, the electronics calculate the heart rate, for example.

The light source 2 designed as an LED can, for example, emit red, green or IR light 5 which is coupled directly into the skin 4 . Two possible propagation paths A and B from the light source 2 to the photodetector 3 are shown in FIG. Path A is caused by scattering of the light 5 in the upper layers of the skin, which are less than 1 mm deep below the skin surface. Path B results from a scattering of the light 5 in deeper skin layers that are at least 1 mm below the skin surface.

The density of blood vessels in the upper layers of the skin is significantly lower than inside the skin. Therefore, only the light 5 that penetrates deeper into the skin 4 and then reaches the photodetector 3 contains the information about the heart rate. However, the amount of light 5 that contains this information is only a small fraction of the total amount of light falling on the photodetector 3 . The position of the sensor arrangement 1 relative to the skin 4 can change when the user moves. The ratios between the light quantities of the two light paths A and B mentioned above change in particular. In addition, a change in position can result in the vital sign sensor 1 being located directly opposite a large blood vessel for a short time, which causes a very strongly modulated signal. Assuming that the vital sign sensor 1 moves shortly thereafter creating an air gap between the vital sign sensor 1 and the skin 4 , the modulated signal will decrease , but the light reflected from the skin surface will produce a very strong unmodulated signal . Such artefacts caused by movement (English: motion artefacts) disturb the evaluation algorithm and lead to an inaccurate measurement of the heart rate.

FIG. 2 shows an alternative exemplary embodiment of a sensor arrangement 1 . This comprises a photodetector on which a light source 2 is arranged on both sides spaced apart in a transverse direction RQ. The mode of operation corresponds to the sensor arrangement 1 illustrated with reference to the exemplary embodiment in FIG. However, by using a plurality of light sources 2, the area of the skin irradiated with light can be enlarged here, so that overall the illuminance can be increased and the measurement accuracy can be reduced by reducing the artefacts shown above.

The effect of the sensor arrangement 1 according to the invention is explained with reference to FIGS. FIG. 3 shows a basic sketch of a plan view of a sensor arrangement according to the prior art as a comparative example with a small square light source 2 and a larger square photodetector 3 . For easier understanding, reference symbols are used as for the description of the solution according to the invention. As previously explained, the light scattered back from the skin is scattered like this depending on the distance from the light source 2 that a ring-shaped light field 8 results, in which the illuminance decreases radially outwards. As a result, different illuminance levels occur on the photodetector 3 at locations Q1, Q2 and Q3 which are at the same distance from the edge of the light source 2 facing the photodiode 3.

FIG. 4 shows a basic sketch of a sensor arrangement 1 according to the invention in a plan view.

The sensor arrangement 1 for use in an optical vital sign sensor, comprising at least one light source 2 and at least one photodetector 2 . The light source 2, for example a photodiode, comprises a radiation or light-emitting chip as shown in FIG. 4 is denoted by reference numerals 13 , 23 , 24 and 25 . The chips 23, 24 and 25 are used for FIGS. 11 described in more detail. In the following, for the chip of FIG. 4 only reference numeral 13 is used for the sake of simplicity. The chip 13 and the photodetector 3 are arranged spaced apart from one another in a transverse direction RQ, the chip 13 having a substantially rectangular shape each having a length LI and a width Bl, the length LI of the chip 13 being greater than its width Bl .

The chip 13 is the semiconductor component of the light source 2 which emits the radiation, for example red light, green light or IR radiation. In addition to the chip 13, the light source 2 can also include other components, for example components that are designed to be non-emitting. Such components can be, for example, power connections, wire bonds, pads and/or the like, as shown in FIG. 11 and will be described in more detail later on the basis of these. A perpendicular distance A to the photodiode 3 is constant along the length LI of the chip. The elongated design of the chip 13 in the top view results in an approximately oval light field 9 in which the illuminance also decreases radially outwards, but along a parallel to the side surface of the light source 2 and the chip 13, i.e. along the length LI is essentially constant, so that points P1, P2 and P3, which have the same distance to an edge of the photodiode 3 facing the light source 2, on the photodiode 3 are approximately the same

have illuminance.

Figures 5 and 6 show schematic representations of a comparative example in contrast to an embodiment according to the invention. Figure 5 shows a top view of a light source 2 comprising two approximately rectangular or. square light emitting diodes 10 arranged in a cavity of a substrate 12 . The cavity or a frame forming the cavity projects beyond the light-emitting diodes 10 in a direction perpendicular to the substrate 12 . In addition, the light-emitting diodes 10 are embedded in a potting material 11 in the cavity, with the potting material 11 being in particular planar with an upper edge of the cavity or the frame forming the cavity completes.

For this purpose, several small LEDs are arranged in a row. The distance between the LEDs is so small that a continuous light distribution in the skin is guaranteed. The two light-emitting diodes 10 shown in FIGS. 5 and 6 are arranged on a base area with a length L and a width B, the length L being greater than the width B. The length of the line and the number of LEDs is chosen so that the entire length of the detector is evenly illuminated. As can be seen from the side view in FIG. 6, the light-emitting diodes 10 are completely encased by the potting material 11 . The several small LEDs can also have a different shape, for example a round, oval or polygonal shape. FIGS. 7 and 8 show a further exemplary embodiment of a light source 2 according to the invention. In this second exemplary embodiment, a light-emitting diode has the chip 13 which has a rectangular shape with a length L1 and a width B1, the length L being greater than the width B. The long side of the light-emitting diode with the chip 13 is designed to be the same as or close to the length of the detector in order to ensure homogeneous illumination of the entire length of the detector. As can be seen from the side view in FIG. 8, the light-emitting diode with the chip 13 is also arranged in a cavity on a substrate 12 in the exemplary embodiment in FIG. 7 and is completely surrounded by potting material 11 . The light-emitting diode with the chip 13 can also have an oval or elliptical shape, for example, with the oval or elliptical shape having a greater extent in a longitudinal direction than in a direction perpendicular thereto. Non-emitting components of the light-emitting diode with the chip 13 are shown in FIGS. 7 and 8 not shown.

Figures 9 and 10 show schematic representations of a comparative example in contrast to an embodiment according to the invention. FIG. 9 shows a light source 2 . A light emitting diode 14 has a square shape and is arranged in a cavity on a substrate 12 . In addition, the light-emitting diode 14 is encapsulated in a transparent potting material 11 which contains scattering particles 15 on the inside. The height of the transparent encapsulation and the concentration of the scattering particles 15 are selected in such a way that the entire area of the cavity emits the light homogeneously. The emission surface of the light source accordingly has a length L and a width B, the length L being greater than the width B. Alternatively, a blue light-emitting diode can also be used and corresponding converter particles can be introduced into the potting material 11 . The LED accordingly emits blue light, and a diffuser material (in the potting material) comprising con- verter particles, causes the blue light to be converted into the green light required for PPG measurement.

Due to the scattering particles 15, the entire substrate 12 of FIGS. 9 and 10 acts like a large light source 2 with a length L and a width B, the length L being greater than the width B.

FIG. 11 shows a further exemplary embodiment of the invention as a sketch in a plan view. The light source 2 is arranged in the transverse direction RQ to the detector 3 and here comprises a plurality of light-emitting diodes of different colors. , The light source 2 comprises a green light-emitting diode 16 , an infrared light-emitting diode 17 and a red light-emitting diode 18 .

The green light-emitting diode 16, which is designed to emit green light, includes a chip 23 as an emitting component. The chip 23 has a width B1 _λ and a length LI, the length LI being greater than the width B1 _λ . In addition to the chip 23 , the green light-emitting diode 16 also has other non-emitting components, namely two pads 26 and 28 . These are each arranged along the length LI outside of the chip 23 and on opposite sides of the chip 23 . In the transverse direction RQ, the pads 26 and 28 are arranged within the width _B1A of the chip 23 . Pads 26 and 28 are used to contact chip 23 via connections 27 and 29 . Pads 26 and 28 are gold pads. In other exemplary embodiments, the pads can also be made from a different material.

The infrared light-emitting diode 17, which is designed to emit IR radiation, includes a chip 24 as the emitting component. The chip 24 has a width B 1 _B smaller than a length LI and smaller than a width B 1 _λ of the chip 23 designed to emit green light. Similar to the light-emitting diode 16, the light-emitting diode 17 also includes non-emitting components. This is one Pad 30 and a connection 31 which is arranged and constructed analogously to the pad 26 and connection 27 . On the opposite side of the chip 24 there is a connection 32 of a different design. Contact is made here from behind. Terminal 32 is also located outside of an extent of chip 24 along its length LI and transversely within width B _1B of chip 24 .

The light-emitting diode 18, which is designed to emit red light, includes a chip 25 as an emitting component. The chip 25 has a width Bl _c that is smaller than a length LI and smaller than a width B1 _λ of the chip 23 designed to emit green light. Similar to the light-emitting diode 17, the light-emitting diode 18 also includes non-emitting components. This involves a pad 33 and a connection 34 which is arranged and constructed analogously to the pad 30 and connection 31 . A connection 35 of a different design is arranged on the opposite side of the chip 25 . Contact is made here from behind. Also the terminal 35 is located outside an extension of the chip 25 along its length LI and transversely inside the width Blc of the chip 25 .

All the light-emitting diodes 16 , 17 and 18 are therefore arranged on a common side of the photodetector 3 in the transverse direction RQ at a distance from it. The green light-emitting diode 16 with the chip 23 is arranged closest to the photodetector 3, the infrared light-emitting diode 17 with the chip 24 is arranged further away than the green light-emitting diode 16 and the red light-emitting diode 18 with the chip 25 is in turn further away from the Photodetector 3 arranged as the infrared light-emitting diode 17 . The infrared radiation from the infrared light-emitting diodes 17 and the red light from the red light-emitting diode 18 have a greater range in the skin 4 than the green light from the green light-emitting diode 17, hence the arrangement selected here. In one embodiment, the sensor arrangement then has at least the IR light source and the light source, which is designed to emit red light. If the chips each have a width Bl of 50 pm and are spaced apart by 50 pm in the RQ direction, a very narrow overall width of the combination of 150 pm can be achieved. This results in an advantageous distance to the detector, which can be advantageous above all for SPO2 measurements, for example for determining blood oxygen.

However, the illustrated arrangement of the green 16, infrared 17 and red 18 light-emitting diodes is only an example here and can be interchanged depending on the application. Likewise, the light source can additionally include further light-emitting diodes for emitting a different light or the same light. In addition, in the exemplary embodiment in FIG. 11, the non-emitting components are arranged outside of the dimensions specified for the chip. In other exemplary embodiments that are not shown, non-emitting components can also be arranged within the dimensions specified for the chip. Of course, in other exemplary embodiments, the chips can be contacted in a different way and/or the chips can have other widths, for example the chips that are designed to emit red or green light can also have a greater width than the chip which is designed to emit IR radiation.

In the case shown, the infrared light-emitting diode 17 with the chip 23 and the red light-emitting diode 18 with the chip 25 are arranged in a separate cavity, so that the light they emit does not impair the function of the green-light-emitting light-emitting diode.

FIGS. 12 and 13 show a basic sketch of an exemplary embodiment of a sensor arrangement 1 according to the invention, in which the light source 2 with the chip 13 and the photodetector 3 are arranged on a common substrate. Instead of Chips 13, one of the chips 23, 24, or 25 can also be installed. FIG. 12 shows a top view and FIG. 13 shows a cross section through the sensor arrangement 1 . The substrate 19 comprises a substrate base 20 for accommodating and contacting the light source 2 and the photodetector 3 as well as walls 21 running perpendicularly thereto, so that a cup-shaped cavity 22 each results for the light source 2 and the photodetector 3 . The cup-shaped cavities 22 are each filled with a casting material 11 that is free of stray particles and/or can include converter particles. As in the previous exemplary embodiments, the length LI of the chip 13 and thus also the length L of the light source 2 is greater than the width Bl of the light source 2 . The length 1 of the photodetector 3 is essentially equal to the length L of the light source 2 . In contrast, the width b of the photodetector 13 and thus also the total area of the photodetector 13 is greater than that of the light source 2 .

The light source (emitter) according to the invention can, as shown for example in FIGS. 5 to 11, be designed as a discrete component in different variants. The embodiments are based on LED chips that are placed on a substrate inside a cavity. The cavity or a frame forming the cavity consists of an opaque material with a high diffuse reflectivity for the light used. This ensures that the direct optical path between the emitter and the detector is interrupted in order to increase the signal-to-noise ratio of the signal detected by the detector. The substrate ensures the electrical contacting of the LED chips with soldering pads for later installation in the optical vital sign sensor. The LED is protected from the environment by a transparent encapsulation (encapsulation).

As shown in Figures 12 and 13, the light source (emitter) and the detector, however, can also be arranged on a common substrate, and thus an integrated inventive sensor module or form an integrated sensor arrangement according to the invention.

The same geometric arrangements can be used for sensors that work with multiple wavelengths (e.g. for blood oxygen or skin moisture measurements). Each emitter can be implemented according to the exemplary embodiments described above, any combinations of different implementations being possible. There can be a single cavity for emitters of single wavelengths, or multiple emitters of different wavelengths can be combined in one cavity.

If a blue LED and a converter material are used for green light emission, the LEDs of other wavelengths can be accommodated in the same cavity: the light from e.g. B. R and IR LEDs is not converted, only scattered by the converter particles. This ensures a homogeneous light emission of each wavelength (green, red and IR) over the entire surface of the cavity without additional diffuser particles or separate cavities.

REFERENCE LIST

1 sensor arrangement

2 light source

3 photodetector

4 skin

5 light

6 dermis

7 deeper blood-bearing layers of skin

8 ring-shaped light field (comparative example)

9 light field

10 light emitting diode

11 potting material

12 substrate

13 light-emitting diode chip

14 LED

15 scatter particles

16 green light-emitting diode

17 IR LED

18 red light-emitting diode

19 substrate

20 substrate bottom

21 wall

22 cavity

23 chip of the light-emitting diode

24 chip of the light-emitting diode

25 chip of the light-emitting diode

26 gold pad

27 power connector

28 gold pad

29 power connector

30 gold pad

31 power connector

32 connection

33 gold pad

34 power connector 35 connection

L length light source

B Wide light source

LI length chip Bl width chip

1 Photodiode length b Photodiode width

RQ cross direction

Claims

- 26 - PATENT CLAIMS Sensor arrangement (1) for use in an optical vital sign sensor, comprising at least one light source (2) and at least one photodetector (3), wherein the light source (2) comprises at least one radiation-emitting chip (13, 23, 24, 25), wherein the radiation-emitting chip (13, 23, 24, 25) and the photodetector (3) in a transverse direction (RQ) spaced apart are arranged, characterized in that the chip (13, 23, 24, 25) has a shape with a length LI and a width Bl, the length LI of the chip (13, 23, 24, 25) being greater than the width Bl. Sensor arrangement according to Claim 1, characterized in that the width Bl and the length LI of the chip (13, 23, 24, 25) have a ratio B1:L1 h 1:2. Sensor arrangement according to one of the preceding claims, characterized in that the width Bl of the chip (13, 23, 24, 25) has a value from a value range with a minimum value of 50 pm and/or a maximum value of 2 mm. Sensor arrangement according to one of the preceding claims, characterized in that the chip (13, 23, 24, 25) and the photodetector (3) are arranged spaced apart from one another in a transverse direction (RQ) by a maximum value 1 x the width Bl of the chip and /or that the chip (13, 23, 24, 25) and the photodetector (3) in a transverse direction (RQ) at least are arranged spaced apart from one another by a value 0.5 x width Bl. Sensor arrangement according to one of the preceding claims, characterized in that the chip (13, 23, 24, 25) and the photodetector (3) are arranged parallel to one another with respect to a longitudinal axis. Sensor arrangement according to one of the preceding claims, characterized in that the chip (23) is designed to emit green light and/or that the chip (24) is designed to emit IR radiation and/or that the chip (25 ) , is designed to emit red light. Sensor arrangement according to Claim 6, characterized in that the chip (23) which is designed to emit green light is at a smaller distance from the photodetector (3) than the chip (25) which is designed to emit red light and / or the chip (24), which is designed to emit IR radiation. Sensor arrangement according to one of the preceding claims, characterized in that the chip (13, 23, 24, 25) in a stray particle-free potting material (11) is embedded. Sensor arrangement according to one of Claims 1 to 7, characterized in that the chip (13, 23, 24, 25) is at least partially in direct contact with a gas which is also in contact with other components of the sensor arrangement. Optical vital signs sensor configured to measure or determine a user's vital signs to comprising a sensor arrangement according to one of the preceding claims 1 to 9.