Sensor that detects a heart rate and/or a blood oxygen content, and method of operating a sensor

A sensor that detects a heart rate and/or a blood oxygen content includes a radiation source and a photodetector, wherein the radiation source includes a light-emitting diode array, the light-emitting diode array includes a plurality of emission regions, the emission regions each include a first light-emitting diode and a second light-emitting diode, the first light-emitting diode includes a first wavelength, the second light-emitting diode includes a second wavelength, and a distance between the first light-emitting diode and the second light-emitting diode within the emission regions is 100 micrometers or less.

TECHNICAL FIELD

This disclosure relates to a sensor that detects a heart rate and/or a blood oxygen content as well as a method of operating such a sensor.

BACKGROUND

Sensors that detect a heart rate and/or a blood oxygen content may be constructed by two radiation sources and a photodetector. One radiation source may detect the heart rate, while a second radiation source may detect the blood oxygen content. Such a sensor may comprise, for example, two light-emitting diodes comprising different wavelengths. In that example, the light-emitting diodes are arranged at a distance such that the radiation emitted by the light-emitting diodes acts on different regions of a blood vessel during the detection of the heart rate and/or the blood oxygen content.

There is nonetheless a need to provide an improved sensor that detects a heart rate and/or a blood oxygen content, and a method of operating such an improved sensor.

SUMMARY

We provide a sensor that detects a heart rate and/or a blood oxygen content, including a radiation source and a photodetector, wherein the radiation source includes a light-emitting diode array, the light-emitting diode array includes a plurality of emission regions, the emission regions each include a first light-emitting diode and a second light-emitting diode, the first light-emitting diode includes a first wavelength, the second light-emitting diode includes a second wavelength, and a distance between the first light-emitting diode and the second light-emitting diode within the emission regions is 100 micrometers or less.

We also provide a method of operating a sensor, wherein the sensor includes a radiation source and a photodetector, the radiation source includes a light-emitting diode array, the light-emitting diode array includes a plurality of emission regions, the emission regions each include a first light-emitting diode and a second light-emitting diode, the first light-emitting diode includes a source of green light, the second light-emitting diode includes an infrared source, the distance between the first light-emitting diode and the second light-emitting diode within the emission regions is a maximum of 100 micrometers, the sensor includes a controller, the controller is configured to operate the first light-emitting diodes and the second light-emitting diodes independently of one another, the first light-emitting diodes and the second light-emitting diodes are each operated with a variable voltage oscillating between zero volts and an operating voltage, the oscillating variable frequency of each light-emitting diode includes a dedicated frequency, the signal of the photodetector is divided into individual components on the basis of the dedicated frequencies, and the individual components are assigned to the light-emitting diodes on the basis of the dedicated frequencies.

LIST OF REFERENCE SIGNS

DETAILED DESCRIPTION

Our sensor that detects a heart rate and/or a blood oxygen content comprises a radiation source and a photodetector. The radiation source comprises a light-emitting diode array comprising a plurality of emission regions. The emission regions each comprise a first light-emitting diode and a second light-emitting diode. The first light-emitting diode comprises a first wavelength, that is to say is configured to emit electromagnetic radiation comprising a first wavelength. The second light-emitting diode comprises a second wavelength, that is to say is configured to emit electromagnetic radiation comprising a second wavelength. Within the emission regions, the distance between the first light-emitting diode and the second light-emitting diode is 100 micrometers or less.

As a result of the distance of a maximum of 100 micrometers, the electromagnetic radiation comprising the first and the second wavelengths is emitted by the radiation source in spatial proximity to one another. Therefore, the probability is high that the light emitted by the first and the second light-emitting diodes within an emission region will penetrate on a similar path into a tissue to be measured and absorptions will take place there at identical molecules within a blood vessel. The measurement accuracy of the sensor that detects a heart rate and/or a blood oxygen content is improved as a result.

The first wavelength may be in the range of 550 to 590 nanometers. The second wavelength may be greater than 800 nanometers. As a result, the first light-emitting diodes emit green light, which is suitable for detecting a heart rate. The second light-emitting diodes emit infrared radiation, which is suitable for determining a blood oxygen content.

The first light-emitting diode may comprise a first conversion element. The second light-emitting diode may comprise a second conversion element. As a result, light comprising a shorter wavelength than the first wavelength may be converted into light of the first wavelength by the first conversion element. Likewise, light comprising a shorter wavelength than the second wavelength may be converted into light of the second wavelength by the second conversion element.

The first and second light-emitting diodes may comprise identical light-emitting diode chips and different conversion elements. Likewise, the first and second light-emitting diodes may comprise different light-emitting diode chips and identical or different conversion elements.

The first conversion element may comprise quantum dots. The second conversion element may comprise quantum dots.

In generating converted light comprising the abovementioned wavelengths by quantum dots, e.g., the materials explained below are possible. For green light of the first wavelength around 570 nanometers, in this example, it is possible to use cadmium selenide quantum dots comprising a diameter of 3.0 to 3.5 nanometers. Alternatively, it is possible to use indium phosphide quantum dots comprising a diameter of 1.8 to 2.2 nanometers for the green light.

Indium arsenide quantum dots comprising a diameter of 3.0 to 6.0 nanometers are possible for the infrared radiation of the second wavelength of greater than 800 nanometers. Alternatively, lead selenide quantum dots comprising a diameter of greater than 5.0 nanometers may be used for the infrared radiation. A further alternative for the infrared radiation is the use of copper indium phosphide quantum dots comprising a diameter of 2.5 to 5.8 nanometers.

The first light-emitting diodes and the second light-emitting diodes may be contacted independently of one another such that each light-emitting diode of the light-emitting diode array is individually drivable. Furthermore, the sensor comprises a controller configured to operate the first and second light-emitting diodes independently of one another. This makes it possible to separate signals of the light-emitting diodes from one another by individual driving of the light-emitting diodes.

The emission regions may comprise a third light-emitting diode, wherein the third light-emitting diode comprises a third wavelength. The third wavelength may be in the range of 640 to 680 nanometers. The third light-emitting diodes thus emit red light. An improved measurement of the blood oxygen content is made possible as a result.

The third light-emitting diode may comprise a third conversion element. The third conversion element may comprise quantum dots.

For the red light in the second wavelength range comprising a wavelength around 660 nanometers, it is possible in this example to use cadmium selenide quantum dots comprising a diameter of 7.5 to 8.5 nanometers. Alternatively, it is possible to use indium phosphide quantum dots comprising a diameter of 2.8 to 3.2 nanometers for the red light.

The photodetector and the radiation source may be arranged within a housing.

The housing may comprise a recess configured to receive a body part. The radiation source and the photodetector may be arranged on different sides of the recess. In this example, the recess may be configured, for example, to receive a finger. By virtue of the fact that radiation source and photodetector are arranged on different sides of the recess, light emitted by the radiation source may pass through the body part located within the recess to the photodetector, wherein absorptions of the radiation relevant to the measurement take place in the body part and the light transmitted through the body part is evaluated by the photodetector. A sensor comprising a good measurement accuracy, in particular for stationary applications, may be achieved as a result.

The housing may comprise a recess, wherein the radiation source and the photodetector are arranged within the recess. The housing may be configured to be arranged on a body part such that the recess faces in the direction of the body part. A flat design of the sensor, in particular for mobile applications, may be achieved as a result.

The light-emitting diode array may comprise a carrier, wherein the light-emitting diodes are arranged in at least four columns and four rows on the carrier. A first column comprises first light-emitting diodes, and a second column comprises second light-emitting diodes. Two emission regions are provided in each row. A space-saving arrangement of the light-emitting diodes and/or of the light-emitting diode array may be achieved as a result.

Third light-emitting diodes may be provided in a third column, wherein the light-emitting diodes may be arranged in at least six columns and at least four rows. As a result, six light-emitting diodes are arranged in each row, in each case three of the light-emitting diodes lying within an emission region.

A sensor that detects a heart rate and/or a blood oxygen content comprising a radiation source and a photodetector, wherein the radiation source comprises a light-emitting diode array comprising a plurality of emission regions, wherein the emission regions each comprise a first light-emitting diode and a second light-emitting diode, wherein the first light-emitting diode comprises a source of green light, the second light-emitting diode comprises an infrared source, and the distance between the first light-emitting diode and the second light-emitting diode within the emission regions is less than 100 micrometers, wherein the sensor comprises a controller, is operated such that the first light-emitting diodes and the second light-emitting diodes are each operated independently of one another with a variable voltage oscillating between zero volts and an operating voltage. In this example, the oscillating variable voltage of each light-emitting diode comprises a dedicated frequency. The signal of the photodetector is divided into individual components on the basis of the dedicated frequencies, wherein the individual components are assigned to the light-emitting diodes on the basis of the dedicated frequencies.

As a result, the light-emitting diodes may be operated and evaluated simultaneously.

The emission regions may comprise third light-emitting diodes that are likewise operated with a variable further voltage oscillating between zero volts and an operating voltage, wherein the further voltage of the third light-emitting diodes in turn comprises a dedicated frequency.

The signal may be divided by Fourier analysis. As a result, a large number of light-emitting diodes of the light-emitting diode array may be operated and evaluated simultaneously.

The above-described properties, features and advantages and the way in which they are achieved will become clearer and more clearly understood in association with the following description of examples explained in greater detail in association with the drawings.

FIG.1shows a plan view of a sensor100. A radiation source110and a photodetector140are arranged on a carrier101. The radiation source110comprises a light-emitting diode array120. The light-emitting diode array120is subdivided into a first emission region121and a second emission region122, wherein the emission regions each comprise a first light-emitting diode131and a second light-emitting diode132. The light-emitting diode array120thus consists of four light-emitting diodes131,132in two emission regions121,122. It is also possible to provide more than two emission regions121,122each comprising a first light-emitting diode131and a second light-emitting diode132.

The distance between the first light-emitting diode131and the second light-emitting diode132within an emission region121,122is in this example 100 micrometers or less. The first light-emitting diodes131comprise a first wavelength, while the second light-emitting diodes comprise a second wavelength, which is different than the first wavelength.

In one example, the first wavelength of the first light-emitting diodes131is in the range of 550 to 590 nanometers. Light comprising the first wavelength is absorbed by the hemoglobin that occurs in human blood. As a result of a fluctuation of the absorption depending on a quantity of blood in a blood vessel, a heart rate may be determined by the first wavelength of the first light-emitting diodes131.

In one example, the second wavelength of the second light-emitting diodes132is greater than 800 nanometers. The infrared radiation of the second wavelength of the second light-emitting diodes132is absorbed by hemoglobin molecules with added oxygen to a greater extent than by hemoglobin molecules without added oxygen. As a result, a blood oxygen content may be measured by the infrared radiation in the second wavelength range of the second light-emitting diodes132.

FIG.2shows a cross section through a sensor100, that substantially corresponds to the sensor100inFIG.1. In this example, the cross section extends through the first emission region121fromFIG.1. In this example, the first light-emitting diode131comprises a first light-emitting diode chip134and a first conversion element137, wherein the first wavelength is generated by virtue of the fact that light comprising a shorter wavelength is emitted by the first light-emitting diode chip134, which light is then converted into light comprising the first wavelength by the first conversion element137. The second light-emitting diode132comprises a second light-emitting diode chip135and a second conversion element138, wherein the second wavelength is generated by virtue of the fact that light comprising a shorter wavelength is emitted by the second light-emitting diode chip135, which light is then converted into radiation comprising the first wavelength by the second conversion element138.

In this example, only the first light-emitting diodes131comprise a first conversion element137and the second light-emitting diodes132consist only of the second light-emitting diode chips135without a second conversion element138and emit the second wavelength. Alternatively, only the second light-emitting diodes132may comprise a second conversion element138, while the first light-emitting diodes131consist only of the first light-emitting diode chips134without a first conversion element137and emit the second wavelength. Furthermore, first light-emitting diode chips134and second light-emitting diode chips135may be different from one another or identical.

By way of example, it is possible for the first light-emitting diode chips134to emit blue light comprising a wavelength of 405 nanometers and for the first conversion element137to convert the blue light into green light comprising a wavelength of 570 nanometers. The second light-emitting diode chips135can then, for example, emit red light comprising a wavelength of 670 nanometers and the second conversion element138can convert the red light into infrared radiation comprising a wavelength of 950 nanometers.

Alternatively, both the first light-emitting diode chips134and the second light-emitting diode chips135can emit green light comprising a wavelength of 570 nanometers. The light of the second light-emitting diode chips135can then be converted into infrared radiation comprising a wavelength of 950 nanometers by the second conversion element138, while the first light-emitting diodes131do not comprise a first conversion element137.

In one example, the first conversion element137comprises quantum dots. In another example, the second conversion element138comprises quantum dots.

For green light of the first wavelength around 570 nanometers, in this example, it is possible to use cadmium selenide quantum dots comprising a diameter of 3.0 to 3.5 nanometers. Alternatively, it is possible to use indium phosphide quantum dots comprising a diameter of 1.8 to 2.2 nanometers for the green light.

Indium arsenide quantum dots comprising a diameter of 3.0 to 6.0 nanometers are possible for the infrared radiation of the second wavelength of greater than 800 nanometers. Alternatively, lead selenide quantum dots comprising a diameter of greater than 5.0 nanometers may be used for the infrared radiation. A further alternative for the infrared radiation is the use of copper indium phosphide quantum dots comprising a diameter of 2.5 to 5.8 nanometers.

FIG.3shows a plan view of a sensor100that substantially corresponds to the sensor100inFIG.1. The radiation source110and the photodetector140are constructed analogously toFIG.1. Furthermore, the carrier101comprises a controller150. The first light-emitting diodes131and the second light-emitting diodes132are each contacted independently of one another such that each light-emitting diode131,132is individually drivable. The controller150is configured to drive and operate the light-emitting diodes individually. Furthermore, the controller150may be configured to evaluate a signal of the photodetector140.

The sensor100may be operated such that the first light-emitting diodes131and the second light-emitting diodes132are each operated independently of one another with a variable voltage oscillating between zero volts and an operating voltage. In this example, the oscillating variable voltage of each light-emitting diode131,132comprises a dedicated frequency. The signal of the photodetector140is divided into individual components on the basis of the dedicated frequencies of the light-emitting diodes131,132, wherein the individual components are assigned to the light-emitting diodes131,132on the basis of the dedicated frequencies. As a result, the light-emitting diodes131,132may be operated and evaluated simultaneously.

The signals may be divided by Fourier analysis in this example.

FIG.4shows a plan view of a further sensor100that substantially corresponds to the sensor100inFIG.1. The light-emitting diode array120of the radiation source110comprises a third light-emitting diode133comprising a third wavelength in each emission region121,122.

In one example, the third wavelength is in the range of 640 to 680 nanometers. Red light of the third wavelength of the third light-emitting diodes133is absorbed by hemoglobin molecules with added oxygen to a lesser extent than by hemoglobin molecules without added oxygen. As a result, measurement of the blood oxygen content may be improved by the red light in the third wavelength range of the third light-emitting diodes133.

The sensor100may be operated such that, in addition to the first light-emitting diodes131and the second light-emitting diodes132, the third light-emitting diodes133are also each operated independently of one another with a variable voltage oscillating between zero volts and an operating voltage. In this example, the oscillating variable voltage of each light-emitting diode131,132,133comprises a dedicated frequency. The signal of the photodetector140is divided into individual components on the basis of the dedicated frequencies of the light-emitting diodes131,132,133, wherein the individual components are assigned to the light-emitting diodes131,132,133on the basis of the dedicated frequencies. As a result, the light-emitting diodes131,132,133may be operated and evaluated simultaneously.

The signals may be divided by Fourier analysis in this example.

FIG.5shows a cross section through the sensor100fromFIG.4. In this example, the first light-emitting diode131comprises a one first light-emitting diode chip134and a first conversion element137, wherein the first wavelength is generated by the fact that light comprising a shorter wavelength is emitted by the first light-emitting diode chip134, which light is then converted into light comprising the first wavelength by the first conversion element137. The second light-emitting diode132comprises a second light-emitting diode chip135and a second conversion element138, wherein the second wavelength is generated by the fact that light comprising a shorter wavelength is emitted by the second light-emitting diode chip135, which light is then converted into radiation comprising the first wavelength by the second conversion element138. In this example, the third light-emitting diode133comprises a third light-emitting diode chip136and a third conversion element139, wherein the third wavelength is generated by the fact that light comprising a shorter wavelength is emitted by the third light-emitting diode chip137, which light is then converted into light comprising the third wavelength by the third conversion element139.

In this example, the third light-emitting diode chips136may emit blue light comprising a wavelength of 405 nanometers that is converted into red light in the third wavelength range by the third conversion element139.

FIG.6shows a cross section through a further sensor100. The sensor100additionally comprises a housing102comprising a recess103, wherein radiation source110and photodetector140are arranged within the recess103on a carrier101. An arrangement of radiation source110and photodetector140within the recess103without a carrier101is likewise possible.

The housing102comprises bearing surfaces104, wherein the housing102may be arranged on a body part such that the housing102with the bearing surfaces104faces in the direction of the body part. Light emitted by the radiation source101may then be scattered and partly absorbed in the body part, wherein the light scattered onto the photodetector140may be evaluated.

A dashed line indicates an upper boundary plane of the recess103located in a plane with the bearing surfaces104. The recess103may be filled with a transparent material up to the upper boundary plane or be closed with a transparent cover.

Analogously toFIG.2, one or two of the conversion elements137,138,139may be absent and the corresponding light-emitting diode chips134,135,136may emit the corresponding light.

FIG.7shows a cross section through a further sensor100comprising a housing102and a recess103of the housing102. The radiation source110and the photodetector140are arranged on different sides of the recess103such that a body part may be received by the recess103. Light emitted by the radiation source110may then transmit through the body part and be partly absorbed in the body part. The transmitted light then impinges on the photodetector140and may be evaluated. In this example, the radiation source110consists of a light-emitting diode array120comprising first light-emitting diodes131and second light-emitting diodes132. The first light-emitting diodes131comprise a first light-emitting diode chip134with a first conversion element137. The second light-emitting diodes132comprise a second light-emitting diode chip135with a second conversion element138.

FIG.8shows a cross section through a further sensor100that substantially corresponds to the sensor100inFIG.7. A transparent material105is additionally arranged within the recess103and surrounds the radiation source110and the photodetector140and thus protects them against environmental influences. In this example, the radiation source110consists of a light-emitting diode array120comprising first light-emitting diodes131, second light-emitting diodes132and third light-emitting diodes133. The first light-emitting diodes131comprise a first light-emitting diode chip134with a first conversion element137. The second light-emitting diodes132comprise a second light-emitting diode chip135with a second conversion element138. The third light-emitting diodes133comprise a third light-emitting diode chip136with a third conversion element139.

Instead of the light-emitting diode arrays120inFIGS.7and8, light-emitting diode chips134,135,136without a corresponding conversion element137,138,139may also be provided or the light-emitting diode chips134,135,136may only partly comprise conversion elements137,138,139.

As a result of the small distance between the first light-emitting diode131and the second light-emitting diode132within an emission region121,122, the light emitted by the first light-emitting diodes131of an emission region121,122comprises a path through the body part similar to that of the light emitted by second light-emitting diodes132of an emission region121,122. As a result, the light of an emission region121,122impinges on the same hemoglobin molecules in most situations, such that the measurement of heart rate and blood oxygen content may be carried out in a spatially resolved manner.

FIGS.9to12each show a plan view of a light-emitting diode array120, which light-emitting diode arrays may likewise be used in the sensors100described above.

InFIG.9, the light-emitting diode array120comprises eight emission regions121,122. The light-emitting diode array consists of sixteen light-emitting diodes131,132in four columns161,162,163,164and four rows167. A first emission region121and a second emission region122each comprising a first light-emitting diode131and a second light-emitting diode132, each arranged in each row167. First light-emitting diodes131are arranged within a first column161, while second light-emitting diodes132are arranged in a second column162. The light-emitting diodes131,132respectively form the first emission regions121. First light-emitting diodes131are arranged within a third column163, while second light-emitting diodes132are in turn arranged in a fourth column164. The light-emitting diodes131,132respectively form the second emission regions122.

The light-emitting diode array120inFIG.10is constructed in a similar manner to the light-emitting diode array120inFIG.9. InFIG.10, however, the order of the first light-emitting diodes131and the second light-emitting diodes132has been interchanged in every second one of the rows167, thus resulting overall in a checkered arrangement of the light-emitting diodes131,132.

InFIG.11, the light-emitting diode array120comprises eight emission regions121,122. The light-emitting diode array consists of twenty-four light-emitting diodes131,132,133in six columns161,162,163,164,165,166and four rows167. A first emission region121and a second emission region122each comprising a first light-emitting diode131, a second light-emitting diode132and a third light-emitting diode are each arranged in each row167. First light-emitting diodes131are arranged within a first column161, while second light-emitting diodes132are arranged in a second column162. Third light-emitting diodes133are arranged in a third column163. The light-emitting diodes131,132,133respectively form the first emission regions121. First light-emitting diodes131are arranged within a fourth column164, while second light-emitting diodes132are in turn arranged in a fifth column165. Third light-emitting diodes133are arranged in a sixth column166. The light-emitting diodes131,132,133respectively form the second emission regions122.

The light-emitting diode array120inFIG.12is constructed in a similar manner to the light-emitting diode array120inFIG.11. In this example, a first light-emitting diode131, a second light-emitting diode132, a third light-emitting diode133and, finally, a first light-emitting diode131are arranged within the first column161. In this example, a second light-emitting diode132, a third light-emitting diode133, a first light-emitting diode131and, finally, a second light-emitting diode132are arranged within the second column162. In this example, a third light-emitting diode133, a first light-emitting diode131, a second light-emitting diode132and, finally, a third light-emitting diode133are arranged within the third column163. The fourth column164corresponds to the first column161, the fifth column165corresponds to the second column162, and the sixth column166corresponds to the third column163.

The light-emitting diodes131,132,133inFIGS.9to12may be constructed from light-emitting diode chips134,135,136with or without a corresponding conversion element137,138,139, analogously to the examples described inFIGS.1to8. Furthermore, the light-emitting diode arrays120inFIGS.9to12may also comprise a larger number of light-emitting diodes131,132,133with an analogous arrangement.

Although our detectors and methods have been more specifically illustrated and described in detail by preferred examples, this disclosure is not restricted by the examples disclosed and other variations may be derived therefrom by those skilled in the art, without departing from the scope of protection of the appended claims.

This application claims priority of DE 10 2017 101 271.0, the subject matter of which is incorporated herein by reference.