Method for removing EMI noise from photoacoustic sensing signal and photoacoustic sensing apparatus using same

Abstract

A method of removing EMI noise from a photoacoustic sensing signal and a photoacoustic sensing apparatus employing the same are provided. A photoacoustic sensing apparatus includes: a light source that directs an optical signal toward an analyte; a photoacoustic sensor receiving ultrasonic waves generated from the analyte and generating a photoacoustic sensor signal; and a signal processing device controlling to guide the optical signal to the analyte and to remove electromagnetic interference (EMI) noise from the photoacoustic sensor signal to generate a photoacoustic signal. A photoacoustic sensing method includes: providing a first control signal to an optical switch connected to a light source to block or transmit an optical signal; generating a mixed signal including a photoacoustic signal and a first EMI noise when the optical switch transmits the optical signal, and generating a second EMI noise when the optical switch blocks the optical signal; and removing EMI noise from the photoacoustic sensor signal based on the mixed signal and the second EMI noise.

Description

[0001] Cross - reference to related applications This application claims the priority of Korean Patent Application No. 10 - 2023 - 0160579, filed on November 20, 2023, and Korean Patent Application No. 10 - 2024 - 0125373, filed on September 13, 2024, the entire contents of which are incorporated herein by reference in their entirety. Technical field

[0002] Embodiments of the present disclosure relate to a method for removing electromagnetic interference (EMI) noise from photoacoustic sensing signals and a photoacoustic sensing device using the method. Background art

[0003] The photoacoustic effect is a phenomenon in which, when a specific substance absorbs light and its temperature increases, vibrations are transmitted to the surrounding gas due to thermal expansion, thus generating an acoustic signal.

[0004] A photoacoustic sensing device is a device that measures changes in the content or component ratio of a substance to be measured based on the photoacoustic effect.

[0005] For example, a photoacoustic sensing device can measure gas concentration, non - invasively measure biological signals, or non - invasively measure blood glucose levels. Such optical sensing devices widely use high - sensitivity measurement techniques. However, in the case of a non - invasive biological signal measurement sensor in an optical sensing device, the change in the measurement signal is relatively small, resulting in a problem that the measurement signal is distorted by minute noises such as electromagnetic interference (EMI). Summary of the invention

[0006] The present invention aims to provide a device for removing electromagnetic interference (EMI) noise and a photoacoustic sensing device using the device, wherein the device for removing electromagnetic interference (EMI) noise can compensate for the EMI noise of an external device or a signal processing circuit to improve the measurement accuracy of photoacoustic signals.

[0007] Even weak EMI noise may cause distortion of the measurement signal of a photoacoustic sensing device. Therefore, it is difficult to ensure the measurement accuracy of a photoacoustic sensing device. In particular, in the case of a non - invasive sensor (such as a non - invasive blood glucose meter), the measurement signal changes subtly as the amount of the substance to be measured changes. Therefore, EMI noise may have a significant impact on the measured value of the sensor. The present invention aims to improve the measurement accuracy of photoacoustic signals by measuring EMI noise and compensating the measurement signal of the sensor based on the measurement result.

[0008] More specifically, the present invention aims to provide a method for improving the measurement accuracy of a sensor system by extracting only the EMI noise component of the sensor system when the sensor system is operating and using the extracted component to compensate the photoacoustic measurement signal, and a photoacoustic sensing device employing the method. The EMI noise comes from various sources, such as the circuit for generating the light source signal of the sensor system, the signal processing circuit for detecting the received signal, external devices, etc. The EMI noise emitted from these various sources can be detected by the receiving circuit device of the photoacoustic sensing device according to the present invention, and the photoacoustic sensing device detects such EMI noise and uses the detected noise to compensate the signal received from the analyte, so that the physical quantity to be measured can be measured more accurately.

[0009] The technical objectives of the present invention are not limited to those described above, and based on the following description, other objectives not described above will become apparent to those of ordinary skill in the art.

[0010] According to an embodiment of the present invention, there is provided a photoacoustic sensing device including: a light source that directs an optical signal to an analyte; a photoacoustic sensor that, when the optical signal is directed, receives ultrasonic waves generated from the analyte and generates a photoacoustic sensor signal; and a signal processing device that sends a first control signal to an optical switch connected to the light source to control the directing of the optical signal to the analyte, and uses the first control signal to extract a photoacoustic signal from which electromagnetic interference (EMI) noise has been removed from the photoacoustic sensor signal, wherein the photoacoustic sensor signal is generated when the optical signal is directed to the analyte.

[0011] In an embodiment of the present invention, the signal processing device may generate a first clock signal and send the generated first clock signal to the light source, and the light source may modulate the intensity of the optical signal according to a specific frequency determined by the first clock signal.

[0012] In an embodiment of the present invention, the first control signal may be a signal for turning the optical switch on / off.

[0013] In an embodiment of the present invention, the signal processing device may classify the photoacoustic sensor signal into a mixed signal of a photoacoustic signal and a first EMI noise and one of second EMI noises based on the first control signal, and analyze the mixed signal and the second EMI noise to estimate information about the photoacoustic signal.

[0014] In an embodiment of the present invention, the signal processing device may include: a switch controller that sends a first control signal to an optical switch to control directing an optical signal to an analyte; an analog-to-digital converter (ADC) that converts a photoacoustic sensor signal into a digital signal; a selector that classifies the digital signal into one of a mixed signal of a photoacoustic signal and a first EMI noise and a second EMI noise based on a second control signal of the switch controller; and a processor that analyzes the mixed signal and the second EMI noise to estimate information about the photoacoustic signal.

[0015] In an embodiment of the present invention, the second control signal may be a signal synchronized with the first control signal.

[0016] In an embodiment of the present invention, when the first control signal is a control signal for setting the optical switch to an on state, the mixed signal may be a digital signal.

[0017] In an embodiment of the present invention, when the first control signal is a control signal for setting the optical switch to an off state, the second EMI noise may be a digital signal.

[0018] In an embodiment of the present invention, the signal processing device may further include a signal generator that sends a first clock signal to a light source so that the light source can modulate the intensity of the optical signal according to a specific frequency.

[0019] In an embodiment of the present invention, the signal processing device may further include a lock-in amplifier that receives a photoacoustic sensor signal from a photoacoustic sensor, receives a second clock signal synchronized with the first clock signal from the signal generator, and detects a signal according to a specific frequency from the photoacoustic sensor signal based on the second clock signal. In this case, the ADC may convert the signal according to the specific frequency into a digital signal and send the digital signal to the selector.

[0020] The information about the photoacoustic signal may include amplitude and phase or x component and y component.

[0021] In an embodiment of the present invention, the processor may detect the mixed signal and the second EMI noise by dividing each of the mixed signal and the second EMI noise into an x component and a y component, and estimate information about the photoacoustic signal based on the difference between the x component of the mixed signal and the x component of the second EMI noise and the difference between the y component of the mixed signal and the y component of the second EMI noise.

[0022] According to an embodiment of the present invention, there is provided a signal processing device for removing EMI noise from a photoacoustic sensor signal, wherein the photoacoustic sensor signal is generated by a photoacoustic sensor based on an ultrasonic signal generated from an analyte to which an optical signal is directed.

[0023] The signal processing device may include: a switch controller that sends a first control signal to an optical switch connected to a light source to control directing an optical signal to an analyte; an ADC that converts a photoacoustic sensor signal into a digital signal; a selector that classifies the digital signal into one of a mixed signal of a photoacoustic signal and a first EMI noise and a second EMI noise based on a second control signal of the switch controller; and a processor that analyzes the mixed signal and the second EMI noise to estimate the amplitude and phase of the photoacoustic signal.

[0024] In an embodiment of the present invention, the second control signal may be a signal synchronized with the first control signal.

[0025] In an embodiment of the present invention, when the first control signal may be a control signal that can set the optical switch to an on state, the mixed signal may be a digital signal.

[0026] In an embodiment of the present invention, when the first control signal may be a control signal that can set the optical switch to an off state, the second EMI noise may be a digital signal.

[0027] In an embodiment of the present invention, the signal processing device may further include a signal generator that can send a first clock signal to the light source so that the light source can modulate the intensity of the optical signal according to a specific frequency.

[0028] In an embodiment of the present invention, the signal processing device may further include a lock-in amplifier that can receive a photoacoustic sensor signal from the photoacoustic sensor, receive a second clock signal synchronized with the first clock signal from the signal generator, and detect a signal according to a specific frequency from the photoacoustic sensor signal based on the second clock signal. In this case, the ADC can convert the signal according to the specific frequency into a digital signal and send the digital signal to the selector.

[0029] In an embodiment of the present invention, the processor may detect the mixed signal and the second EMI noise by dividing each of the mixed signal and the second EMI noise into an x component and a y component, and estimate the amplitude and phase of the photoacoustic signal based on the difference between the x component of the mixed signal and the x component of the second EMI noise and the difference between the y component of the mixed signal and the y component of the second EMI noise.

[0030] According to an embodiment of the present invention, there is provided a photoacoustic sensing method for removing EMI noise from a photoacoustic sensor signal, wherein the photoacoustic sensor signal is generated by a photoacoustic sensor based on an ultrasonic signal generated from an analyte to which an optical signal is directed.

[0031] The photoacoustic sensing method may include: sending a first control signal from a switch controller to an optical switch connected to a light source, the first control signal being configured to set the optical switch to an off state such that an optical signal emitted from the light source toward an analyte is blocked; converting a photoacoustic sensor signal generated by a photoacoustic sensor into a first digital signal by an analog-to-digital converter (ADC); receiving, by a selector, a second control signal synchronized with the first control signal from the switch controller, and classifying the first digital signal as a second EMI noise based on the second control signal and sending the second EMI noise to a processor; sending a first clock signal to the light source by a signal generator to perform control such that the light source modulates the intensity of the optical signal according to a specific frequency, and sending a second clock signal synchronized with the first clock signal to a lock-in amplifier; sending a first control signal from the switch controller to the optical switch, the first control signal being configured to set the optical switch to an on state such that the light source directs the optical signal toward the analyte; receiving, by the lock-in amplifier, the photoacoustic sensor signal from the photoacoustic sensor, and detecting a signal according to the specific frequency from the photoacoustic sensor signal based on the second clock signal; converting the signal detected by the lock-in amplifier into a second digital signal by the ADC and sending the second digital signal to the selector; receiving, by the selector, a second control signal synchronized with the first control signal from the switch controller, and classifying the second digital signal as a mixed signal of a photoacoustic signal and a first EMI noise based on the second control signal and sending the mixed signal to the processor; and estimating the photoacoustic signal by the processor based on the second EMI noise and the mixed signal.

[0032] In an embodiment of the present invention, estimating the photoacoustic signal by the processor may include: analyzing the second EMI noise by the processor to derive an x component and a y component of the second EMI noise; analyzing the mixed signal to derive an x component and a y component of the mixed signal; and calculating an amplitude and a phase of the photoacoustic signal based on the x component and the y component of the second EMI noise and the x component and the y component of the mixed signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] By referring to the accompanying drawings and describing in detail some embodiments of the present disclosure, the above and other objects, features, and advantages of various embodiments of the present disclosure will become more apparent to those of ordinary skill in the art, where: Figure 1 is a block diagram showing the configuration of a photoacoustic sensing device according to a first embodiment of the present disclosure; Figure 2 is a block diagram showing the configuration of a photoacoustic sensing device according to a second embodiment of the present disclosure; Figure 3 is a block diagram showing the configuration of a photoacoustic sensing device according to a third embodiment of the present disclosure; Figure 4A and Figure 4BIt is a diagram for describing a method of obtaining components of a photoacoustic signal based on mixed signals and EMI noise; Figure 5A and Figure 5B It is a graph showing the result of measuring EMI noise; Figure 6 It is a flowchart for describing a photoacoustic sensing method according to an embodiment of the present disclosure. Detailed Description of the Invention

[0034] Hereinafter, with reference to the detailed description of the following embodiments in conjunction with the accompanying drawings, the advantages and features of various embodiments of the present disclosure and the ways to implement them will become apparent. However, the embodiments of the present disclosure are not limited to such embodiments and can be implemented in various forms.

[0035] The terms used herein are for helping to describe and understand the embodiments and are not intended to limit the scope and embodiments of the present disclosure. It should be understood that unless otherwise clearly specified in the context, the singular form also includes the plural form. The terms "comprising", "comprising of", "containing" and / or "containing of" used herein specify the presence of the described features, integers, steps, operations, elements, components and / or their combinations, and do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations.

[0036] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be called a second element, and vice versa.

[0037] It should be understood that when a first element is referred to as "connected" or "coupled" to a second element, the first element may be directly connected or coupled to the second element, or there may be an intermediate element between them. On the contrary, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intermediate element between them. Other words used to describe the relationship between elements (i.e., "between" and "directly between", "adjacent" and "directly adjacent", etc.) should be interpreted in a similar manner.

[0038] In the description of the embodiments of the present disclosure, when it is determined that the detailed description of the related art may unnecessarily obscure the gist of these embodiments, the detailed description may be omitted for the sake of brevity.

[0039] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. For a better understanding of the present disclosure, the same reference numerals are used to refer to the same elements in the description of the drawings.

[0040] Figure 1is a block diagram showing the configuration of a photoacoustic sensing device according to a first embodiment of the present disclosure.

[0041] The photoacoustic sensing device 10-1 is a device that guides an optical signal 20 to an analyte 31, detects ultrasonic waves 40 generated from the analyte 31 by a photoacoustic sensor 230 to generate a photoacoustic sensor signal 50, and extracts a photoacoustic signal 80 based on the photoacoustic sensor signal 50.

[0042] The photoacoustic sensing device 10-1 may be affected by various types of EMI noise. Therefore, the photoacoustic sensing device 10-1 not only detects the photoacoustic signal as a detection target but also detects a mixed signal 60 that is a combination of the photoacoustic signal and EMI noise.

[0043] In this specification, the EMI noise included in the mixed signal 60 is referred to as first EMI noise 62, and the EMI noise detected separately from the photoacoustic signal 61 is referred to as second EMI noise 70.

[0044] EMI noise has various sources. For example, there may be EMI noise 71 generated from a signal generator 110 for driving an optical element 211, EMI noise 72 generated from the photoacoustic sensor 230, EMI noise 73 generated in the environment of the photoacoustic sensing device 10-1 (such as an external device 90), and the like.

[0045] Therefore, the photoacoustic sensor signal 50 output by the photoacoustic sensor 230 is generally a mixed signal 60 that combines the photoacoustic signal 61 and the first EMI noise 62 and may be a distorted measurement signal.

[0046] The above details regarding the occurrence and influence of EMI noise also apply to Figure 2 the shown photoacoustic sensing device 10-2 or Figure 3 the shown photoacoustic sensing device 10-3.

[0047] The photoacoustic sensing device 10-1 according to an embodiment of the present disclosure may operate in the order of the following operations S1 to S3.

[0048] First, the photoacoustic sensing device 10-1 measures the second EMI noise 70 (S1). Then, the photoacoustic sensing device 10-1 measures the mixed signal 60 of the photoacoustic signal 61 and the first EMI noise 62 (S2). Then, the photoacoustic sensing device 10-1 subtracts the second EMI noise 70 from the mixed signal 60, thereby generating the undistorted photoacoustic signal 80 with minimized EMI noise influence (S3). In operation S1, the photoacoustic sensing device 10-1 blocks the optical signal 20 guided to the photoabsorber 30, and at the same time operates all components included in the photoacoustic sensing device 10-1 to obtain the second EMI noise 70. The second EMI noise 70 is a measurement signal that combines the EMI noise 71 generated from the light source 210, the EMI noise 72 generated from the photoacoustic sensor 230, and the EMI noise 73 generated in the environment including the external device 90.

[0049] Referring Figure 1 , the photoacoustic sensing device 10-1 according to an embodiment of the present disclosure includes a signal processing device 100-1, a light source 210, an optical switch 221, and a photoacoustic sensor 230. The signal processing device 100-1 according to an embodiment of the present disclosure includes an analog-to-digital converter (ADC) 130, a switch controller 140, a selector 150, and a processor 160. In some embodiments, the signal processing device 100-1 may further include a signal generator 110.

[0050] Provided Figure 1 the photoacoustic sensing device 10-1 and the signal processing device 100-1 shown in Figure 1 , and the components of the photoacoustic sensing device 10-1 and the signal processing device 100-1 according to an embodiment of the present disclosure are not limited to

[0051] the embodiments shown in

[0052] In Figure 1 the embodiments of

[0053] The optical element 211 is an element that generates light. For example, the optical element 211 may be a laser, a laser diode (LD), or a light emitting diode (LED). The signal generator 110 uses a current signal or a voltage signal to adjust the intensity of the optical signal 20 generated from the optical element 211.

[0054] The waveform of the optical signal 20 output from the light source 210 is determined according to the output signal of the signal generator 110. When the optical switch 221 is turned on (closed), the optical signal 20 output from the light source 210 reaches the photoabsorber 30, and the analyte 31 included in the photoabsorber 30 generates an ultrasonic wave 40 due to the influence of the optical signal 20.

[0055] The optical switch 221 is an element that blocks or transmits the optical signal 20, and is controlled by the switch controller 140 of the signal processing device 100-1. The optical switch 221 allows the optical signal 20 to be transmitted to the photoabsorber 30 when it is turned on (closed), and blocks the optical signal 20 from being transmitted to the photoabsorber 30 when it is turned off (opened).

[0056] By measuring the changes in the magnitude and phase of the ultrasonic wave 40, the type, concentration, and amount of the analyte 31 included in the photoabsorber 30 can be analyzed. For example, the photoabsorber 30 may be the skin tissue of a human body, and the analyte 31 may be glucose that constitutes blood sugar. However, the photoabsorber 30 and the analyte 31 are not limited to the above examples and may vary according to the embodiments of the present disclosure.

[0057] The photoacoustic sensor 230 receives the ultrasonic wave 40 generated from the analyte 31 to generate a photoacoustic sensor signal 50, and provides the photoacoustic sensor signal 50, which is an electrical signal, to the ADC 130 included in the signal processing device 100-1. The ADC 130 converts the photoacoustic sensor signal 50 into a digital signal and provides the digital signal to the selector 150.

[0058] The photoacoustic sensor 230 may include an ultrasonic element that converts the received ultrasonic wave 40 into an electrical signal, and a signal amplifier that amplifies the converted electrical signal. That is, the photoacoustic sensor 230 can convert the ultrasonic wave 40 generated from the analyte 31 into an electrical signal and amplify the electrical signal. For example, the ultrasonic element may include a piezoelectric sensor. However, the embodiments of the present disclosure are not limited to the configuration of the above ultrasonic element.

[0059] As described above, the photoacoustic sensing device 10-1 generates a first EMI noise 62 and a second EMI noise 70, and is affected by the first EMI noise 62 and the second EMI noise 70. Therefore, the photoacoustic sensor signal 50 output by the photoacoustic sensor 230 may be a mixed signal 60 of a photoacoustic signal 61 originating from the analyte 31 and the first EMI noise 62.

[0060] The first EMI noise 62 or the second EMI noise 70 may include at least one of the EMI noise 71 from the signal generator 110, the EMI noise from the light source 210, or the EMI noise 72 generated by the photoacoustic sensor 230. As used herein, including in the claims, the "or" used in a list of items ended with a phrase such as "at least one of...", "one or more of...", or "one or two of..." indicates an inclusive list, such that for example, a list of at least one of A, B, or C indicates A or B or C or AB or AC or BC or ABC (i.e., A and B and C). For example, the EMI noise 72 may be generated by a signal processing board included in the photoacoustic sensor 230, which includes an ultrasonic element (or an electrical signal converter), a signal amplifier, and a power supply. Additionally, the EMI noise 73 generated in the environment of the photoacoustic sensing device 10-1 (such as the external device 90) may also affect the photoacoustic sensor signal 50.

[0061] Hereinafter, the EMI noise compensation mechanism of the photoacoustic sensing device 10-1 will be described. In an embodiment, the signal processing device 100-1 controls the optical signal 20 to be directed to the analyte 31 and removes the EMI noise from the photoacoustic sensor signal 50 to generate the photoacoustic signal 80.

[0062] The signal processing device 100-1 blocks the optical switch 221 through the switch controller 140 so that the optical signal 20 emitted from the light source 210 is not transmitted to the light absorber 30, thereby measuring the second EMI noise 70. That is, the optical switch 221 has the function of transmitting or blocking the optical signal 20 to the light absorber 30 under the control of the switch controller 140.

[0063] The switch controller 140 may generate a first control signal and provide the first control signal indicating a first state (e.g., an off state) to the optical switch 221 so that the optical switch 221 does not transmit the optical signal 20 to the light absorber 30, and in this case, the photoacoustic sensor signal 50 output from the photoacoustic sensor 230 corresponds to the second EMI noise 70. For example, when the first control signal sets the optical switch 221 to the off state, the ADC 130 outputs the second EMI noise 70 as a digital signal.

[0064] In addition, the switch controller 140 may send a first control signal indicating a second state (e.g., on state) to the optical switch 221, such that the optical switch 221 transmits the optical signal 20 to the photoabsorber 30, and in this case, the photoacoustic sensor signal 50 output from the photoacoustic sensor 230 corresponds to a mixed signal 60 of a photoacoustic signal 61 and a first EMI noise 62. For example, when the first control signal sets the optical switch 221 to the on state, the ADC 130 outputs the mixed signal 60 as a digital signal.

[0065] The selector 150 receives the photoacoustic sensor signal 50 from the photoacoustic sensor 230, classifies the photoacoustic sensor signal 50 into the mixed signal 60 or a second EMI noise 70 based on a second control signal of the switch controller 140, and sends the classified photoacoustic sensor signal 50 to the processor 160. For example, the selector 150 receives a digital signal corresponding to the photoacoustic sensor signal 50 and classifies the digital signal into one of the mixed signal and the second EMI noise 70 based on the second control signal of the switch controller 140.

[0066] When the selector 150 is synchronized with the optical switch 221, the selector 150 may distinguish the photoacoustic sensor signal 50 into the mixed signal 60 and the second EMI noise 70. That is, when the control signal sent from the switch controller 140 to the optical switch 221 is referred to as a "first control signal" and the control signal sent from the switch controller 140 to the selector 150 is referred to as a "second control signal", the switch controller 140 may synchronize the first control signal and the second control signal such that the selector 150 may classify the photoacoustic sensor signal 50 into one of the mixed signal 60 and the second EMI noise 70. For example, the switch controller 140 may synchronize the first control signal for turning on (off) the optical switch 221 with the second control signal that allows the selector 150 to classify the photoacoustic sensor signal 50 into the second EMI noise 70, thereby allowing the photoacoustic sensor signal 50 to be classified into the second EMI noise 70. In addition, the switch controller 140 may synchronize the first control signal for closing (on) the optical switch 221 with the second control signal that allows the selector 150 to classify the photoacoustic sensor signal 50 into the mixed signal 60, thereby allowing the photoacoustic sensor signal 50 to be classified into the mixed signal 60.

[0067] For example, the selector 150 may be a demultiplexer (DeMUX). Additionally, for example, the selector 150 may be controlled by a software program. However, embodiments of the present disclosure are not limited to the configuration and control method of the selector 150.

[0068] Selector 150 sends the classification signal to processor 160, and processor 160 can remove the second EMI noise 70 from the mixed signal 60 to generate a photoacoustic signal 80. That is, processor 160 generates the photoacoustic signal 80 through the differential operation of the mixed signal 60 and the second EMI noise 70. Processor 160 can be a digital signal processor. The smaller the difference between the time points when the mixed signal 60 and the second EMI noise 70 are measured, the more similar the first EMI noise 62 and the second EMI noise 70 may be. In this way, the signal processing device 100-1 can extract the photoacoustic signal 80 originating from the analyte 31 while minimizing the influence of the first EMI noise 62. That is, the photoacoustic signal 80 generated by processor 160 is a signal substantially free of the first EMI noise 62 or a signal with a significantly reduced influence of the first EMI noise 62.

[0069] Figure 2 is a block diagram showing the configuration of a photoacoustic sensing device according to a second embodiment of the present disclosure. Figure 2 The photoacoustic sensing device 10-2 shown in is an example of a photoacoustic sensing device implemented using a lock-in amplifier (LIA).

[0070] Refer to Figure 2 , the photoacoustic sensing device 10-2 according to an embodiment of the present disclosure includes a signal processing device 100-2, a light source 210, an optical switch 221, and a photoacoustic sensor 230. The signal processing device 100-2 according to an embodiment of the present disclosure includes a signal generator 110, a lock-in amplifier 120, an ADC 130, a switch controller 140, a selector 150, and a processor 160.

[0071] Similar to the photoacoustic sensing device 10-1, the photoacoustic sensing device 10-2 also uses the method of modulating the optical signal 20 emitted from the light source 210 by the signal generator 110. The photoacoustic sensing device 10-2 is equipped with lock-in amplification technology and thus has the benefit of accurately detecting microscopic signals.

[0072] The signal generator 110 sends a first clock signal to the light source 210 so that the light source 210 modulates the optical output intensity of the optical signal 20 according to a specific frequency. That is, the optical signal 20 emitted from the light source 210 may have a varying intensity or may alternate between on and off according to the specific frequency provided by the signal generator 110.

[0073] In addition, the signal generator 110 inputs a second clock signal synchronized with the first clock signal into the lock-in amplifier 120, and the lock-in amplifier 120 selectively detects only the signal of a specific frequency component from the photoacoustic sensor signal 50 using the second clock signal. The ADC 130 converts the signal detected by the lock-in amplifier 120 into a digital signal and sends the digital signal to the selector 150.

[0074] In an embodiment of the present disclosure, the lock-in amplifier 120 may output the x and y components of the mixed signal 60 and the second EMI noise 70, or output the amplitude and phase of the mixed signal 60 and the second EMI noise 70. In this case, the processor 160 may calculate the amplitude and phase of the photoacoustic signal 80 based on the x and y components of the mixed signal 60 and the second EMI noise 70, and may calculate the amplitude and phase of the photoacoustic signal 80 based on the amplitude and phase of the mixed signal 60 and the second EMI noise 70.

[0075] Similar to Figure 1 the embodiment of, the switch controller 140 provides a first control signal to the optical switch 221 to control the optical switch 221, and provides a second control signal to the selector 150 to control the selector 150. The switch controller 140 may synchronize the first control signal and the second control signal to allow the selector 150 to classify the digital signal received from the ADC 130 into one of the mixed signal 60 and the second EMI noise 70.

[0076] When the switch controller 140 controls the optical switch 221 to be in the off state, the processor 160 classifies the output signal of the ADC 130 as the second EMI noise 70, and when the switch controller 140 controls the optical switch 221 to be in the on state, the processor 160 classifies the output signal of the ADC 130 as the mixed signal 60. The processor 160 calculates the difference between the mixed signal 60 and the second EMI noise 70 to detect the photoacoustic signal 80.

[0077] Figure 3 is a block diagram showing the configuration of a photoacoustic sensing device according to a third embodiment of the present disclosure.

[0078] Similar to the second embodiment, the third embodiment is an example of a photoacoustic sensing device implemented using a lock-in amplifier, and is different from the second embodiment in that a switch (e.g., an electrical switch) 222 is arranged between the signal generator 110 and the light source 210. In response to the first control signal output from the signal processing device 100-2, the electrical switch 222 transmits the output signal of the signal generator 110 in the signal processing device 100-2 to the light source 210 or blocks the output signal to the light source 210. The switch controller 140 controls the opening and closing of the electrical switch 222. The photoacoustic sensing device 10-3 can apply or block the optical signal 20 to the photoabsorber 30 through this mechanism. That is, the light source 210 generates the optical signal 20 based on the first clock signal input from the signal generator 110 according to the switching control of the electrical switch 222, and the generated optical signal 20 is applied to the photoabsorber 30.

[0079] The method for measuring and compensating the EMI noise of the photoacoustic sensing device 10-3 is basically the same as that of the second embodiment, and therefore, for the sake of brevity, its detailed description is omitted.

[0080] Figure 4A and Figure 4B are diagrams for describing a method for obtaining components of a photoacoustic signal based on a mixed signal and EMI noise. In Figure 4A and Figure 4B , an example of obtaining the difference between the mixed signal 60 and the second EMI noise 70 is shown. The technical details of Figure 4A and Figure 4B can be performed by the photoacoustic sensing device 10-1, the photoacoustic sensing device 10-2, and the photoacoustic sensing device 10-3.

[0081] The mixed signal 60 is a signal that mixes the photoacoustic signal 61 and the first EMI noise 62. Even when the amplitudes of the photoacoustic signal 61 and the first EMI noise 62 are the same at different measurement time points (T1 and T2), when the phases of the photoacoustic signal 61 and the first EMI noise 62 are different, the amplitude and phase of the mixed signal 60 may change. Since the embodiments of the present disclosure estimate the first EMI noise 62 as the second EMI noise 70, when obtaining the components of the photoacoustic signal 80 by obtaining the difference between the mixed signal 60 and the second EMI noise 70, the influence of the phase needs to be considered.

[0082] As Figure 4A shown, when the phase difference between the photoacoustic signal 80 and the second EMI noise 70 is 90 degrees or less, the mixed signal 60 can be measured to be greater than the photoacoustic signal 80, and as Figure 4BAs shown, when the phase difference between the photoacoustic signal 80 and the second EMI noise 70 is 90 degrees or greater, the mixed signal 60 can be measured to be less than the photoacoustic signal 80. Here, it is assumed that the magnitude of the second EMI noise 70 is sufficiently small compared to the magnitude of the photoacoustic signal 80.

[0083] The photoacoustic signal 80 can be extracted by measuring the signal magnitudes (or amplitudes) and phases of the mixed signal 60 and the second EMI noise 70, or by separately measuring the x and y components of the mixed signal 60 and the second EMI noise 70, and the photoacoustic signal 80 with minimized influence of EMI noise can be estimated more precisely.

[0084] In the second and third embodiments, the processor 160 can detect the magnitudes and phases of the mixed signal 60 and the second EMI noise 70 or the x and y components of the mixed signal 60 and the second EMI noise 70 based on the signal generated by the lock-in amplifier 120.

[0085] The processor 160 can detect the signals of the mixed signal 60 and the second EMI noise 70 by separating the signals of the mixed signal 60 and the second EMI noise 70 output by the lock-in amplifier 120 and converted into digital signals by the ADC 130 into x and y components, and can precisely generate the photoacoustic signal 80 with EMI noise compensated and no signal distortion by calculating the amplitude differences of each component. As another example, the processor 160 can also generate the photoacoustic signal 80 by measuring the amplitudes and phases of the mixed signal 60 and the second EMI noise 70 and compensating for the EMI noise.

[0086] Figure 5A and Figure 5B are graphs showing the results of measuring EMI noise.

[0087] The amplitude of the EMI noise can vary according to the type of the light source L1 or L2 (see Figure 5A ). The amplitude (see Figure 5A ) and phase (see Figure 5B ) of the EMI noise change over time. Therefore, in order to precisely measure the photoacoustic signal 80, it is necessary to measure the second EMI noise 70 in a relatively short period.

[0088] The embodiments of the present disclosure have the benefit of improving the measurement accuracy and accuracy of the photoacoustic signal by reducing signal distortion caused by EMI noise.

[0089] Figure 6 is a flowchart for describing a photoacoustic sensing method according to an embodiment of the present disclosure. The photoacoustic sensing method is a method for removing EMI noise from a photoacoustic sensor signal. In other words, the photoacoustic sensing method is a data processing method for estimating a photoacoustic signal generated from an analyte by compensating for EMI noise.

[0090] Referring to Figure 6 , the photoacoustic sensing method according to an embodiment of the present disclosure includes operations S410 to S460. The operations of the photoacoustic sensing method according to an embodiment of the present disclosure are not limited to Figure 6 the embodiments shown in

[0091] For ease of description, it is assumed that Figure 6 the photoacoustic sensing method shown in Figure 2 is performed by the photoacoustic sensing device 10-2 in

[0092] Operation S410 is an operation of setting the optical switch to an off state.

[0093] The switch controller 140 sends a first control signal to the optical switch 221 connected to the light source 210 to set the optical switch 221 to an off state. Accordingly, the optical signal 20 emitted from the light source 210 is blocked, and the optical signal 20 is not directed to the analyte 31.

[0094] In addition, while the switch controller 140 sends the first control signal (off) to the optical switch 221, the switch controller 140 sends a second control signal (off) to the selector 150.

[0095] Operation S420 is an operation of obtaining the x-component and y-component of the EMI noise.

[0096] Since the optical switch 221 is set to an off state, the photoacoustic sensor signal 50 generated by the photoacoustic sensor 230 corresponds to the second EMI noise 70.

[0097] The lock-in amplifier 120 receives the photoacoustic sensor signal 50 from the photoacoustic sensor 230 and receives a second clock signal synchronized with the first clock signal from the signal generator 110. The lock-in amplifier 120 detects a signal according to a specific frequency from the photoacoustic sensor signal 50 based on the second clock signal, where the specific frequency has been applied to the intensity modulation of the optical signal 20.

[0098] The ADC 130 converts the signal detected by the lock-in amplifier 120 into a digital signal and sends the digital signal to the selector 150, and the selector 150 classifies the digital signal as the second EMI noise 70 based on the second control signal of the switch controller 140 and sends the second EMI noise to the processor 160. In other words, the selector 150 can output a digital signal corresponding to the second EMI noise 70 based on the second control signal indicating the first state. For example, the second control signal (e.g., indicating the "off" state) is a signal synchronized with the first control signal.

[0099] The processor 160 can analyze the second EMI noise 70 to derive the x-component Nx and y-component Ny of the second EMI noise 70.

[0100] The operation S430 is an operation of setting the optical switch to the on state.

[0101] The signal generator 110 sends a first clock signal to the light source 210, such that the light source 210 modulates the intensity of the optical signal 20 according to a specific frequency.

[0102] The switch controller 140 sends a first control signal to the optical switch 221 connected to the light source 210 to set the optical switch 221 to the on state. Accordingly, the optical signal 20 emitted from the light source 210 is directed to the analyte 31. The switch controller 140 sends a second control signal (on) to the selector 150 while sending the first control signal (on) to the optical switch 221.

[0103] The operation S440 is an operation of obtaining the x-component and y-component of the mixed signal.

[0104] Since the optical switch 221 is set to the on state, the photoacoustic sensor signal 50 generated by the photoacoustic sensor 230 corresponds to the mixed signal 60.

[0105] The lock-in amplifier 120 receives the photoacoustic sensor signal 50 from the photoacoustic sensor 230 and receives a second clock signal synchronized with the first clock signal from the signal generator 110. The lock-in amplifier 120 detects a signal according to the specific frequency from the photoacoustic sensor signal 50 based on the second clock signal, and the specific frequency has been applied to the intensity modulation of the optical signal 20.

[0106] The ADC 130 converts the signal detected by the lock-in amplifier 120 into a digital signal and sends the digital signal to the selector 150. The selector 150 classifies the digital signal as the mixed signal 60 based on the second control signal of the switch controller 140 and sends the mixed signal to the processor 160. In other words, the selector 150 can output a digital signal corresponding to the mixed signal 60 based on the second control signal indicating the second state. For example, the second control signal (e.g., indicating the "on" state) is a signal synchronized with the first control signal.

[0107] The processor 160 can analyze the mixed signal 60 to derive the x-component Rx and y-component Ry of the mixed signal 60.

[0108] The operation S450 is an operation of calculating the amplitude and phase of the photoacoustic signal.

[0109] The processor 160 estimates the photoacoustic signal 80 based on the mixed signal 60 and the second EMI noise 70.

[0110] The processor 160 may calculate the x-component Rx - Nx and y-component Ry - Ny of the photoacoustic signal 80 based on the x-component Rx and y-component Ry of the mixed signal 60 and the x-component Nx and y-component Ny of the second EMI noise 70, and may use the x-component Rx - Nx and y-component Ry - Ny of the photoacoustic signal 80 to calculate the amplitude and phase of the photoacoustic signal 80. Specifically, the processor 160 may calculate the difference Rx - Nx between the x-component Rx of the mixed signal 60 and the x-component Nx of the second EMI noise 70 and the difference Ry - Ny between the y-component Ry of the mixed signal 60 and the y-component Ny of the second EMI noise 70, so as to use the differences Rx - Nx and Ry - Ny to calculate the amplitude and phase of the photoacoustic signal 80 to estimate information about the photoacoustic signal 80.

[0111] Operation S460 is an operation of estimating information about the analyte.

[0112] The processor 160 may use a pre-stored table, formula, or model to estimate information about the analyte 31, such as type, quantity, and concentration, based on the amplitude and phase of the photoacoustic signal 80.

[0113] The photoacoustic sensing method has been described above with reference to the flowcharts presented in the accompanying drawings. Although the above method has been shown and described as a series of blocks for simplicity, it should be understood that the embodiments of the present disclosure are not limited to the order of the blocks, and some blocks may be executed in an order different from the order shown and described herein or simultaneously with other blocks, and various other branches, processes, and block orders that achieve the same or similar results may be implemented. Additionally, not all of the shown blocks are necessary for implementing the method described herein.

[0114] In addition, in the description with reference to Figure 6 According to an example of an implementation of the present invention, each operation may be further divided into a greater number of sub-operations or combined into a smaller number of operations. Additionally, some operations may not be performed as needed or the order of the operations may be changed. Further, even in the case of omitting content, Figures 1 to 5B the content of Figure 6 may be applied to Figure 6 the content of Figures 1 to 5B In addition,

[0115] In an embodiment, a photoacoustic sensing method for removing electromagnetic interference (EMI) noise from a photoacoustic sensor signal includes: providing a first control signal to an optical switch connected to a light source to block or transmit an optical signal; generating a mixed signal including a photoacoustic signal and a first EMI noise when the optical switch transmits the optical signal, and generating a second EMI noise when the optical switch blocks the optical signal; and removing the EMI noise from the photoacoustic sensor signal based on the mixed signal and the second EMI noise to generate a photoacoustic signal.

[0116] In an embodiment, generating the mixed signal and generating the second EMI noise include converting the photoacoustic sensor signal into a digital signal; receiving a second control signal synchronized with the first control signal; and classifying the digital signal into one of the mixed signal and the second EMI noise based on the second control signal.

[0117] In an embodiment, generating the mixed signal and generating the second EMI noise further include providing a first clock signal to the light source to control the light source to modulate the intensity of the optical signal according to a specific frequency, and providing a second clock signal synchronized with the first clock signal to a lock-in amplifier; receiving, by the lock-in amplifier, the photoacoustic sensor signal from the photoacoustic sensor, and detecting a signal according to the specific frequency from the photoacoustic sensor signal based on the second clock signal; and converting the signal detected by the lock-in amplifier into a digital signal.

[0118] In an embodiment, the method further includes analyzing the mixed signal and the second EMI noise to estimate information about the photoacoustic signal. Analyzing the mixed signal and the second EMI noise includes analyzing the second EMI noise to derive an x component and a y component of the second EMI noise; analyzing the mixed signal to derive an x component and a y component of the mixed signal; and estimating information about the photoacoustic signal based on the x component and the y component of the second EMI noise and the x component and the y component of the mixed signal.

[0119] As is obvious from the above, in various sensor systems, EMI noise may be generated by sensor operation, signal processing circuits, and external devices, thereby affecting the measurement signal and causing errors in the measurement value. In sensor systems that require high-sensitivity and high-accuracy measurements, such as non-invasive biosignal measurement sensors and gas sensors, EMI noise affects measurement accuracy and reliability. Therefore, noise removal and compensation techniques are required for high-sensitivity sensing devices. Embodiments of the present disclosure propose a technique for measuring EMI noise and compensating a signal received from an analyte. Through the disclosed technique, the performance of photoacoustic sensors and various sensing devices including photoacoustic sensors can be improved.

[0120] By way of embodiments of the present disclosure, by solving the problem of low measurement accuracy in non-invasive blood glucose measurement technology, the non-invasive blood glucose measurement technology can be commercialized. In addition, through the technology proposed by the present disclosure, the measurement accuracy and reliability of various existing sensing technologies (such as non-invasive biosignal sensors, gas sensors, etc.) that require ultra-high sensitivity measurement technology can be improved.

[0121] The effects of the present disclosure are not limited to the effects described above, and other effects not described can be understood by those skilled in the art from the above detailed description.

[0122] Although the specific embodiments of the present disclosure have been described in detail as above, those of ordinary skill in the art to which the present disclosure pertains should be able to understand that various modifications and changes can be made.

Claims

1. A photoacoustic sensing device, comprising: a light source, which directs the optical signal toward the analyte; a photoacoustic sensor that receives ultrasonic waves generated from the analyte and generates a photoacoustic sensor signal; as well as A signal processing device controls the optical signal to be directed toward the analyte and removes electromagnetic interference (EMI) noise from the photoacoustic sensor signal to generate a photoacoustic signal.

2. The photoacoustic sensing device of claim 1, wherein: The signal processing device generates a first clock signal and sends the generated first clock signal to the light source; and The light source modulates the intensity of the optical signal according to a specific frequency determined by the first clock signal.

3. The photoacoustic sensing device of claim 1, further comprising: an optical switch, which blocks or transmits the optical signal in response to a first control signal output from the signal processing device, Wherein, when the optical switch transmits the optical signal, the signal processing device generates a mixed signal including the photoacoustic signal and a first EMI noise, and when the optical switch blocks the optical signal, the signal processing device generates a second EMI noise.

4. The photoacoustic sensing device according to claim 3, in, The signal processing device classifies the photoacoustic sensor signal into one of the mixed signal and the second EMI noise based on a first control signal, and analyzes the mixed signal and the second EMI noise to estimate information about the photoacoustic signal.

5. The photoacoustic sensing device of claim 3, wherein: The signal processing device comprises: a switch controller generating a first control signal and a second control signal, and providing the first control signal to the optical switch to control directing the optical signal toward the analyte; an analog-to-digital converter (ADC), converting the photoacoustic sensor signal into a digital signal; a selector that classifies the digital signal into one of the mixed signal and a second EMI noise based on a second control signal of the switch controller; and A processor analyzes the mixed signal and the second EMI noise to estimate information about the photoacoustic signal.

6. The photoacoustic sensing device of claim 5, wherein: The second control signal is synchronized with the first control signal.

7. The photoacoustic sensing device of claim 5, wherein: When the first control signal sets the optical switch to an on state, the ADC outputs the mixed signal, and When the first control signal sets the optical switch to an off state, the ADC outputs a second EMI noise.

8. The photoacoustic sensing device of claim 5, wherein: The signal processing device further includes: a signal generator, which sends a first clock signal to the light source, so that the light source modulates the intensity of the optical signal according to a specific frequency.

9. The photoacoustic sensing device of claim 8, wherein: The signal processing device further includes a lock-in amplifier that receives the photoacoustic sensor signal from the photoacoustic sensor, receives a second clock signal synchronized with the first clock signal from the signal generator, and detects a signal according to the specific frequency from the photoacoustic sensor signal based on the second clock signal, and The ADC converts the signal according to the specific frequency into the digital signal and then provides the digital signal to the selector.

10. The photoacoustic sensing device of claim 5, wherein: The information includes the amplitude and phase of the photoacoustic signal.

11. The photoacoustic sensing device of claim 5, wherein: The processor detects the mixed signal and the second EMI noise by dividing each of the mixed signal and the second EMI noise into an x-component and a y-component, and estimates information about the photoacoustic signal based on a difference between the x-component of the mixed signal and the x-component of the second EMI noise and a difference between the y-component of the mixed signal and the y-component of the second EMI noise.

12. The photoacoustic sensing device of claim 1, further comprising: an electrical switch that blocks or transmits an electrical signal in response to a first control signal output from the signal processing device, Wherein, when the electrical switch transmits the electrical signal, the signal processing device generates a mixed signal including the photoacoustic signal and a first EMI noise, and when the electrical switch blocks the electrical signal, the signal processing device generates a second EMI noise.

13. A signal processing device for removing electromagnetic interference (EMI) noise in a photoacoustic sensor signal, wherein: The photoacoustic sensor signal is generated by the photoacoustic sensor based on an ultrasonic wave signal generated from an analyte to which the optical signal is guided, and the signal processing device includes: a switch controller generating a first control signal and a second control signal, and providing the first control signal to the optical switch to control directing the optical signal toward the analyte; an analog-to-digital converter (ADC), converting the photoacoustic sensor signal into a digital signal; a selector that classifies the digital signal into one of a mixed signal and a second EMI noise based on a second control signal of the switch controller, the mixed signal including the photoacoustic signal and the first EMI noise; and A processor analyzes the mixed signal and the second EMI noise to estimate information of the photoacoustic signal.

14. The signal processing device according to claim 13, wherein: The second control signal is synchronized with the first control signal, and When the first control signal sets the optical switch to an on state, the ADC outputs the mixed signal. When the first control signal sets the optical switch to an off state, the ADC outputs a second EMI noise.

15. The signal processing device according to claim 13, further comprising: a signal generator, which sends a first clock signal to the light source, so that the light source modulates the intensity of the optical signal according to a specific frequency; as well as a lock-in amplifier that receives the photoacoustic sensor signal from the photoacoustic sensor, receives a second clock signal synchronized with the first clock signal from the signal generator, and detects a signal according to the specific frequency from the photoacoustic sensor signal based on the second clock signal, and The ADC converts the signal according to the specific frequency into the digital signal and provides the digital signal to the selector.

16. The signal processing device according to claim 13, wherein: The processor detects the mixed signal and the second EMI noise by dividing each of the mixed signal and the second EMI noise into an x-component and a y-component, and estimates information of the photoacoustic signal based on a difference between the x-component of the mixed signal and the x-component of the second EMI noise and a difference between the y-component of the mixed signal and the y-component of the second EMI noise.

17. A photoacoustic sensing method for removing electromagnetic interference (EMI) noise in a photoacoustic sensor signal, wherein: The photoacoustic sensor signal is generated by a photoacoustic sensor based on an ultrasonic wave signal generated by an analyte to which the optical signal is directed, and the photoacoustic sensing method includes: providing a first control signal to an optical switch connected to the light source to block or transmit the optical signal; When the optical switch transmits the optical signal, a mixed signal including a photoacoustic signal and a first EMI noise is generated, and when the optical switch blocks the optical signal, a second EMI noise is generated; and The EMI noise is removed from the photoacoustic sensor signal based on the mixed signal and the second EMI noise to generate a photoacoustic signal.

18. The method according to claim 17, wherein: Generating the mixed signal and generating the second EMI noise includes: Converting the photoacoustic sensor signal into a digital signal; receiving a second control signal synchronized with the first control signal; and The digital signal is classified into one of the mixed signal and a second EMI noise based on a second control signal.

19. The method according to claim 18, wherein: Generating the mixed signal and generating the second EMI noise further includes: providing a first clock signal to the light source to control the light source to modulate the intensity of the optical signal according to a specific frequency, and providing a second clock signal synchronized with the first clock signal to the lock-in amplifier; receiving the photoacoustic sensor signal from the photoacoustic sensor by the lock-in amplifier, and detecting a signal according to the specific frequency from the photoacoustic sensor signal based on a second clock signal; and The signal detected by the lock-in amplifier is converted into the digital signal.

20. The method of claim 17, further comprising: analyzing the mixed signal and the second EMI noise to estimate information about the photoacoustic signal, Wherein, analyzing the mixed signal and the second EMI noise includes: analyzing the second EMI noise to derive an x-component and a y-component of the second EMI noise; analyzing the mixed signal to derive an x-component and a y-component of the mixed signal; and Information of the photoacoustic signal is estimated based on the x-component and the y-component of the second EMI noise and the x-component and the y-component of the mixed signal.

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