Patent Application
20180113022
This disclosure relates to an integrated circuit for sensor applications.
Optoelectronic sensors can be realized as an optoelectrical component with a light source, a photosensitive detector and a control circuit. Light emitted from the light source hits a sample intended for examination. Light reflected and/or scattered from the sample can be detected with the photosensitive detector and evaluated for signals due to processes within the sample. To decrease the size of the optoelectronic sensor, the photosensitive detector and the control circuit may be implemented within an application-specific integrated circuit. An optoelectronic sensor like this may be used as a biosensor.
It could therefore be helpful to provide an improved integrated circuit, an optoelectronic sensor with such an integrated circuit and a method of operation of such a sensor.
We provide an integrated circuit for sensor applications including a plurality of photosensitive areas on a top side, capable of measuring incident light, thereby creating a signal; and a processing unit adapted to evaluate the signal measured by the photosensitive areas.
We also provide a sensor including 1) the integrated circuit for sensor applications including a plurality of photosensitive areas on a top side, capable of measuring incident light, thereby creating a signal, and a processing unit adapted to evaluate the signal measured by the photosensitive areas, 2) a housing with a first cavity and a second cavity, and 3) a barrier located between the first cavity and the second cavity, wherein the integrated circuit is located within the first cavity, the top side of the integrated circuit faces upwardly, and a light source is located within the second cavity.
We further provide a method of operating a sensor, wherein the sensor includes a light source and an integrated circuit with photosensitive areas, and the integrated circuit includes a control circuit to control the light source, including operating the light source with a periodical increase and decrease of the power of the emitted light, exhibiting an operating frequency, and filtering the signal measured by the photosensitive areas of the integrated circuit using the operating frequency.
We also further provide a method of operating a sensor including obtaining an AC portion and a DC portion of a signal measured by photosensitive areas of an integrated circuit of the sensor, and ignoring the signal measured by one of the photosensitive areas if the AC portion of the photosensitive area compared to the DC portion decreases below a pre-set value.
An integrated circuit comprises a plurality of photosensitive areas on a top side of the integrated circuit, capable of measuring incident light, thus creating a signal and a processing unit capable of evaluating the signal measured by the photosensitive areas. Integrating photosensitive areas into an integrated circuit generally leads to smaller active areas of the photosensitive areas compared to the approach of a sensor with an external photosensitive detector. The smaller active areas may be covered with a disturbing element during measurements, for instance by a human hair during a measurement of blood chemistry or heart rate when used as a biosensor or by dust particles during a measurement of environmental data. With the use of a plurality of photosensitive areas on top of the integrated circuit, a signal is still obtainable even if a photosensitive area is covered by a disturbing element.
The processing unit of the integrated circuit may be capable of evaluating the signal of every photosensitive area individually. Thus, the signal quality can be increased, as it is possible to detect if a photosensitive area is covered and thus not working properly. The signal of the photosensitive area not working properly can be neglected, increasing the signal quality.
A control circuit for an external light source may also be part of the integrated circuit. Thus, the external light source can be controlled with the integrated circuit, simplifying the design of the sensor using the integrated circuit as a component.
The top side may comprise a reflective area outside the photosensitive areas. Therefore, stray light not hitting the photosensitive areas may be reflected from the reflective area and after that by other areas of the sensor, increasing the chance that the reflected light finally hits the photosensitive areas of the integrated circuit.
The integrated circuit may be rectangular and two photosensitive areas are located at opposite corners of the integrated circuit. Therefore, the photosensitive areas are not easily covered by a single disturbing element, allowing for a measurement even if one single photosensitive area is covered by the disturbing element.
In the rectangular integrated circuit, four photosensitive areas may be located at four corners of the integrated circuit. This further decreases the probability that all photosensitive areas are covered by a disturbing element each, thus further increasing the signal quality of the sensor using such an integrated circuit.
A fifth photosensitive area may be located at a middle portion of the integrated circuit. This further decreases the probability of a disturbing element covering all photosensitive areas of the integrated circuit.
The area of a photosensitive area may be 0.16 square millimeters or less and the area of the integrated circuit is 1 square millimeter or less. With these sizes, integrated circuits with a small package size are possible, allowing for small sizes of the corresponding sensor.
A sensor comprises an integrated circuit, a housing with a first cavity and a second cavity and a light source. A barrier is located between the first cavity and the second cavity. The integrated circuit is located within the first cavity of the housing, wherein the top side of the integrated circuit faces upward. The light source is located within the second cavity of the housing. Due to the barrier between the cavities, light emitted from the light source does not reach the photosensitive areas of the integrated circuit directly. A sample set on top of the housing covering the cavities leads to scattering of the light emitted from the light source dependent on activity within the sample. For instance, a tissue may be the sample. The amount of light scattered towards the photosensitive areas may change periodically due to a change in an amount of blood within the tissue due to the blood circulation. The frequency of the change corresponds to a heart rate of the blood circulation.
The integrated circuit may particularly be capable of evaluating the signals of the photosensitive areas individually, comprise a control circuit for the external light source, comprise a reflective area at the top side, be of one of the previously described shapes or sizes or exhibit a combination of the aforementioned attributes.
The sensor housing may comprise a third cavity with another light source located within the third cavity. Therefore, processes detectable with light of different wavelengths can be detected.
The first cavity may comprise a reflective surface outside a location of the integrated circuit. This is particularly useful if the integrated circuit comprises a reflective area as well and enhances the probability of light scattered by the tissue to reach the photosensitive areas.
In a method of operating a sensor with a light source and an integrated circuit with photosensitive areas, in which the integrated circuit comprises a control circuit to control the light source, the light source is operated with a periodical increase and decrease of the power of the emitted light. Therefore, the light source exhibits an operating frequency. The signal measured by the photosensitive areas of the integrated circuit is filtered using the operating frequency as filtering frequency. With this approach, the operating frequency is used to pre-set a bandpass filter, thus increasing the signal quality.
In a method of operating a sensor, an AC portion and a DC portion of a signal measured by photosensitive areas of an integrated circuit of the sensor is obtained. The signal measured by one of the photosensitive areas is neglected if the AC portion of the photosensitive area compared to the DC portion decreases below a pre-set value. Therefore, the signal of a photosensitive area irradiated with ambient light not intended for the measurement, which is overpowering compared to the light used for measuring and thus leading to a large DC portion of the signal obtained, may be neglected to increase the signal quality.
In the method of operation, a signal indicating a measurement failure due to the large DC portion compared to the AC portion may be displayed to indicate the immission of stray ambient light.
The above described properties, features and advantages as well as the method of obtaining them, will be more clearly understandable in the context of the following description of the examples, which are explained in more detail in the context of the figures.
A reflective area 160 is located at the top side 102. The reflective area 160 is located outside the photosensitive areas 110. Incident light not reaching the photosensitive areas 110 then may be reflected by the top side 102 of the housing 101. If the integrated circuit 100 is placed within a sensor, which also comprises reflective surfaces, the reflected light may reach the photosensitive areas 110 after several reflections at the reflective surfaces. A reflective area 160 may also be arranged on the top side 102 of the integrated circuits 100 of
The shape of the housing 101 of
In one example the processing unit 120 is capable of evaluating the signal of every photosensitive area 110 individually. If a photosensitive area 110 is covered by a disturbing element, for instance a human hair during a biosensing operation, the signal of the covered photosensitive area may be neglected, increasing the overall signal quality.
In one example, the integrated circuit 100 comprises a control unit 150 indicated with a dashed line in
The area of the photosensitive areas 110 may be 0.16 square millimeters or less. The area of the photosensitive areas 110 may be, for instance, as small as 0.01 square millimeters. The area of the integrated circuit 100 is 1 square millimeter or less. With these sizes, a plurality of photosensitive areas 110 can be implemented within the integrated circuit 100. Furthermore, the remaining area of the integrated circuit 100 is sufficient for the processing unit 120, the optional control circuit 150 and the interconnections needed to electrically connect the photosensitive areas 110, the processing unit 120 and the optional control circuit 150.
A top side 215 of the housing, from which the cavities 211, 212 formed, may be placed on a sample intended to measure a signal. The first cavity 211 comprises the integrated circuit 110 described in
Within the first cavity 211, the sensor 200 comprises a reflective surface 216. This may be used additionally to a reflective area on the top side 102 of the integrated circuit 100. Incident light not reaching the photosensitive areas 110 may then be reflected at the reflective surfaces 216 and/or the top side 102, including multiple reflections, and finally reach the photosensitive areas 110 of the integrated circuit 100. It is possible to arrange reflective surfaces 216 in the first cavity 211 of
The light sources 220, 221 may be light emitting diodes or diode lasers.
For a blood oxygen and heart rate sensor as sensor 200, the light source 220 may emit green light with a wavelength of around 570 nanometers and the other light source 221 may emit red light with a wavelength of around 660 nanometers. With a wavelength of 570 nanometers, within an absorption band of hemoglobin, a heart rate can be obtained by evaluating the strayed light of a wavelength of 570 nanometers, as the intensity of the strayed light increases when less hemoglobin molecules and thus less blood is available within the sample measured. The signal at 570 nanometers thus increases and decreases proportionally to the heart rate. At 660 nanometers, absorption of hemoglobin is dependent on the oxygen content of the blood. Thus, this wavelength is suitable for blood oxygen measurements.
In a method of operating a sensor 200 with a light source 220 and an integrated circuit 100 with photosensitive areas 110, in which the integrated circuit 100 comprises a control circuit 150 to control the light source 220, the light source 220 is operated with a periodical increase and decrease of the power of the emitted light. Therefore, the light source 220 exhibits an operating frequency. The signal measured by the photosensitive areas 110 of the integrated circuit 100 is filtered using the operating frequency as filtering frequency. With this approach, the operating frequency is used to pre-set a bandpass filter, thus increasing the signal quality.
If the sensor 200 comprises another light source 221, as shown in
If a blood oxygen content and a heart rate are to be measured with a sensor 200 with a light source with a wavelength of 570 nanometers and another light source 221 with a wavelength of 660 nanometers, the light source 220 may be operated with a first operating frequency of for instance 300 Hertz. The other light source may be operated with a second operating frequency of for instance 500 Hertz. The first operating frequency and the second operating frequency need to differ, and should not be factors of each other. Furthermore, the operating frequencies should differ from the expected heart rate, which is in the range of below 1 to 3 Hertz. The signal obtained by the photosensitive areas 110 is split and filtered with two bandpass filters of the first operating frequency of 300 Hertz and the second operating frequency of 500 Hertz to separate the signal of the heart rate obtained with the light emitted from the light source 220 and the signal of the blood oxygen content obtained with the light emitted from the other light source 221.
In a method of operating a sensor 200 an AC portion and a DC portion of a signal measured by photosensitive areas 110 of an integrated circuit 100 of the sensor 200 is obtained and wherein the signal measured by one of the photosensitive areas 110 is neglected if the AC portion of the photosensitive area 110 compared to the DC portion decreases below a pre-set value. Therefore, the signal of a photosensitive area 110 irradiated with ambient light not intended for the measurement, which is overpowering compared to the light used for the measuring and thus leading to a large DC portion of the signal obtained, may be neglected to increase the signal quality.
In one example of the method of operation, a signal indicating a measurement failure due to the large DC portion compared to the AC portion is displayed to indicate the immission of stray ambient light.
Although our integrated circuit was described and illustrated in more detail using preferred examples, this disclosure is not limited to the examples. Examples may be derived by those skilled in the art from the described examples without departing from the scope of the appended claims.
