Patent Publication Number: US-2023138688-A1

Title: Photo-acoustic sensor device and photo-acoustic sensing method of the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application Nos. 10-2021-0148589, filed on Nov. 2, 2021, and 10-2022-0084133, filed on Jul. 8, 2022, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure herein relates to a sensor device and a sensing method of the same, and more particularly, to a photo-acoustic sensor device and a photo-acoustic sensing method of the same. 
     In general, photo-acoustic sensor devices may measure a change in a composition ratio of a material contained in a light absorber by measuring a change in an ultrasonic signal generated when light is absorbed by the light absorber. Furthermore, photo-acoustic sensor devices may perform gas concentration measurement, non-invasive living body measurement, and non-invasive blood glucose measurement. Such photo-acoustic sensor devices are widely used in high-sensitivity measurement technology. However, photo-acoustic sensor devices may have a limitation such as a requirement of precision control according to a temperature change. 
     SUMMARY 
     The present disclosure provides a photo-acoustic sensor device and a photo-acoustic sensing method of the same, which are capable of removing or minimizing photo-acoustic noise due to a temperature change. 
     The present disclosure provides a photo-acoustic sensing method. The sensing method includes providing a source light in a subject and receiving an ultrasonic wave generated in the subject by the source light. Here, the source light may have a wavelength of 900 nm to 3000 nm in a near-infrared band. 
     According to an example, the source light may include a first source light; and a second source light having a wavelength that is different from the wavelength of the second source light. 
     According to an example, the first source light may have a first wavelength of a range of 1400 nm to 1500 nm. 
     According to an example, the first wavelength of the first source light may further have a range of 1800 nm to 2500 nm. 
     According to an example, the second source light may have a second wavelength of a range of 1500 nm to 1800 nm. 
     According to an example, the second wavelength of the second source light may further have a range of 1400 nm or less. 
     According to an example, the ultrasonic wave may include: a first ultrasonic wave generated by the first source light; and a second ultrasonic wave generated by the second source light. 
     According to an example, the first ultrasonic wave may be obtained as a reference signal including a noise value, and the second ultrasonic wave may be obtained as a detection signal including a measurement value. 
     According to an example, the method may further include obtaining an absorption coefficient value by removing the noise value from the measurement value. 
     According to an example, the method may further include obtaining a blood glucose value by comparing the absorption coefficient value with a reference value. 
     A photo-acoustic sensor device according to an example of the inventive concept includes: a light source configured to provide a source light to a subject; a detector configured to receive an ultrasonic wave generated in the subject by the source light; and a control unit configured to determine whether the subject is normal by comparing a detection signal of the ultrasonic wave with a reference signal. Here, the light source generates the source light having a wavelength of 900 nm to 3000 nm in a near-infrared band. 
     According to an example, the source light may include a first source light; and a second source light having a wavelength that is different from the wavelength of the second source light. 
     According to an example, the first source light may have a first wavelength of a range of 1400 nm to 1500 nm. 
     According to an example, the first wavelength of the first source light may further have a range of 1800 nm to 2500 nm. 
     According to an example, the second source light may have a second wavelength of a range of 1500 nm to 1800 nm. 
     According to an example, the second wavelength of the second source light may further have a range of 1400 nm or less. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the inventive concept and, together with the description, serve to explain principles of the inventive concept. In the drawings: 
         FIG.  1    is a block diagram of a photo-acoustic sensor device according to the inventive concept; 
         FIG.  2    is a graph illustrating sensitivity according to an absorption coefficient of the subject of  FIG.  1   ; 
         FIG.  3    is a graph illustrating an absorption coefficient of water according to the wavelength of the source light of  FIG.  1   ; 
         FIG.  4    is a cross-sectional view of a photo-acoustic sensor device according to the inventive concept; 
         FIG.  5    is a cross-sectional view of a photo-acoustic sensor device according to the inventive concept; and 
         FIG.  6    is a flowchart illustrating a photo-acoustic sensing method of a photo-acoustic sensor device according to the inventive concept. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the inventive concept will now be described in detail with reference to the accompanying drawings. The advantages and features of embodiments of the inventive concept, and methods for achieving the advantages and features will be apparent from the embodiments described in detail below with reference to the accompanying drawings. However, the inventive concept may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art, and the inventive concept is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. 
     The terminology used herein is not for delimiting the embodiments of the inventive concept but for describing the embodiments of the inventive concept. The terms of a singular form may include plural forms unless otherwise specified. It will be further understood that the terms “includes”, “including”, “comprises”, and/or “comprising”, when used in this description, specify the presence of stated elements, steps, operations, and/or components, but do not preclude the presence or addition of one or more other elements, steps, operations, and/or components. Reference numerals, which are presented in the order of description, are provided according to the embodiments and are thus not necessarily limited to the order. 
       FIG.  1    illustrates an example of a photo-acoustic sensor device  100  according to the inventive concept. 
     Referring to  FIG.  1   , the photo-acoustic sensor device  100  of an embodiment of the inventive concept may be a photo-acoustic-based sensor device. According to an example, the photo-acoustic sensor device  100  may include light sources  10 , detectors  20 , and a control unit  40 . The light sources  10  may generate an ultrasonic wave  16  by providing a source light  12  to a subject  44 . The light sources  10  each may include a laser, a laser diode, or a light-emitting diode. The source light  12  may include a first source light  11  and a second source light  13  according to a wavelength thereof. Similarly, the ultrasonic wave  16  may include a first ultrasonic wave  15  and a second ultrasonic wave  17  according to a wavelength thereof. The subject  44  may include human skin tissue. A support body  42  may be in contact with the subject  44  and transfer the ultrasonic wave  16  to the detectors  20 . The support body  42  may include a solid polymer. The detectors  20  may receive the ultrasonic wave  16  to generate a detection signal. The detectors  20  each may include a piezoelectric sensor, but an embodiment of the inventive concept is not limited thereto. The control unit  40  may calculate a value of glucose concentration in the subject  44  by comparing the detection signal with a reference signal, but an embodiment of the inventive concept is not limited to measuring the concentration of glucose. Furthermore, the control unit  40  may determine whether the subject  44  has a disease, but an embodiment of the inventive concept is not limited thereto. The control unit  40  may detect a temperature of the support body  42  and the subject  44 . 
       FIG.  2    shows sensitivity according to an absorption coefficient of the subject  44 . 
     Referring to  FIG.  2   , the subject  44  may generate the ultrasonic wave  16  with an absorption coefficient that changes according to the wavelength of the source light  12 . A magnitude and characteristic of the generated ultrasonic wave  16  are determined by the absorption coefficient or the wavelength of the source light  12 . For example, the wavelength of the source light  12  having an absorption coefficient of greater than 2000/m has sensitivity of a desensitization range  46  in which an ultrasonic characteristic change is small, and may be used as the first source light  11  for generating the reference signal. The wavelength of the source light  12  having an absorption coefficient of less than 2000/m has sensitivity of a sensitization range  48  in which an ultrasonic characteristic change is significant, and may be used as the second source light  13  for generating the detection signal. 
       FIG.  3    shows an absorption coefficient of water according to the wavelength of the source light  12  of  FIG.  1   . 
     Referring to  FIGS.  1  to  3   , the source light  12 , which generates the reference signal and the detection signal, may include near-infrared light having a wavelength of about 900 nm to about 3000 nm. 
     According to an embodiment, the first source light  11  having an absorption coefficient of the desensitization range  46  may have a first wavelength λ 1 . For example, the first wavelength Ai may be about 1400 nm to about 1500 nm. The first wavelength λ 1  may have a peak of about 1450 nm. Alternatively, the first wavelength λ 1  may be about 1800 nm to about 2500 nm. The first wavelength λ 1  may have a peak of about 1950 nm. 
     According to an embodiment, the second source light  13  having an absorption coefficient of the sensitization range  48  may have a second wavelength λ 2 . For example, the second wavelength λ 2  may be about 1500 nm to about 1800 nm. Alternatively, the second wavelength λ 2  may be about 1400 nm or less. 
     The first source light  11  and the second source light  13  may respectively generate the first ultrasonic wave  15  and the second ultrasonic wave  17  in the subject  44 . A magnitude and characteristic of the generated first ultrasonic wave  15  and second ultrasonic wave  17  may be affected not only by the absorption coefficient of the subject  44  but also by a size of the subject  44 , a characteristic of the support body  42 , and a characteristic of the detector  20 . Since the magnitude and characteristic of the first ultrasonic wave  15  are unsusceptible to a change in the absorption coefficient of the subject  44 , a measurement signal of the first ultrasonic wave  15  may be used as a reference signal for correcting a signal change due to a change in the size of the subject  44 , the characteristic of the support body  42 , and the characteristic of the detector  20 . That is, the reference signal of the first ultrasonic wave  15  may be obtained as noise or a noise value. 
     On the contrary, since the magnitude and characteristic of the second ultrasonic wave  17  generated by the second source light  13  having a wavelength corresponding to the sensitization range  48  are susceptible to a change in the absorption coefficient, a measurement signal of the second ultrasonic wave  17  may be used as a detection signal for measuring an absorption coefficient value of the subject  44 . The detection signal of the second ultrasonic wave  17  may be obtained as a measurement value. 
     A change in the characteristic of the second ultrasonic wave  17  due to the subject  44 , the support body  42 , and the detector  20  may be similar to the change in the characteristic of the first ultrasonic wave  15 . The control unit  40  may precisely extract the absorption coefficient of the subject  44  without being influenced by external noise by using the first ultrasonic wave  15  as the reference signal and the second ultrasonic wave  17  as the detection signal. The control unit  40  may obtain an absorption coefficient value using a signal magnitude change, phase difference change, or the like of the reference signal and the detection signal. That is, the control unit  40  may obtain the absorption coefficient value by removing a noise value of the reference signal from the measurement value of the detection signal. Furthermore, the control unit  40  may obtain a blood glucose value by comparing the absorption coefficient value with the reference value. The control unit  40  may include a program for calculating a changed absorption coefficient as a blood glucose value, but an embodiment of the inventive concept is not limited thereto. 
       FIG.  4    illustrates an example of a photo-acoustic sensor device  100  according to the inventive concept. 
     Referring to  FIG.  4   , the photo-acoustic sensor device  100  may further include an optical switch  50  and an optical coupler. The optical switch  50  may be provided between the light sources  10  and the subject  44 . The optical switch  50  may switch the first source light  11  and the second source light  13 . The detector  20  may be provided on one side of the subject  44  and the support body  42  opposing the optical switch  50 . The light sources  10 , the subject  44 , the support body  42 , and the control unit  40  may be configured in the same manner as illustrated in  FIG.  1   . 
       FIG.  5    illustrates an example of a photo-acoustic sensor device  100  according to the inventive concept. 
     Referring to  FIG.  5   , the optical switch  50  of the photo-acoustic sensor device  100  may be provided at a front end of the light sources  10 . The optical switch  50  may switch the first source light  11  and the second source light  13  provided to the light sources  10 . In the case where the light sources  10  include an optical fiber laser, the optical switch  50  may switch pump lights. The light sources  10 , the subject  44 , the support body  42 , the detector  20 , and the control unit  40  may be configured in the same manner as illustrated in  FIGS.  1  and  4   . 
     A photo-acoustic sensing method of the photo-acoustic sensor device  100  of the inventive concept configured as above is described below. 
       FIG.  6    illustrates a photo-acoustic sensing method of a photo-acoustic sensor device  100  according to the inventive concept. 
     Referring to  FIGS.  1  and  6   , the light sources  10  provide the first source light  11  and the second source light  13  to the subject  44  (S 10 ). The first source light  11  and the second source light  13  may be absorbed in the subject  44  so as to respectively generate the first ultrasonic wave  15  and the second ultrasonic wave  17 . The first source light  11  may have an absorption coefficient or wavelength corresponding to the desensitization range  46 , and the second source light  13  may have an absorption coefficient or wavelength corresponding to the sensitization range  48 . The first source light  11  and the second source light  13  may include near-infrared light having a wavelength of about 900 nm to about 3000 nm. The first source light  11  may have a first wavelength λ 1  of about 1400 nm to about 1500 nm or about 1800 nm to about 2500 nm. The second source light  13  may have a second wavelength λ 2  of about 1500 nm to about 1800 nm or about 1400 nm or less. The first ultrasonic wave  15  and the second ultrasonic wave  17  may be transferred to the detector  20  through the support body  42 . 
     Next, the detector  20  receives the first ultrasonic wave  15  and the second ultrasonic wave  17  (S 20 ). The detector  20  may generate a reference signal and a detection signal by receiving the first ultrasonic wave  15  and the second ultrasonic wave  17 . The reference signal and the detection signal may be obtained as a measurement value and a noise value. 
     Next, the control unit  40  obtains an absorption coefficient value by removing the noise value extracted by the first ultrasonic wave  15  from the measurement value extracted by the second ultrasonic wave  17  (S 30 ). 
     Furthermore, the control unit  40  obtains a blood glucose value by comparing the absorption coefficient value with a reference value (S 40 ). The absorption coefficient value may be quantitatively determined according to the reference value. 
     Although not illustrated, the control unit  40  may use the absorption coefficient value and the reference value to determine whether the subject  44  has diabetes, but an embodiment of the inventive concept is not limited thereto. 
     As described above, a photo-acoustic sensor device and a photo-acoustic sensing method of the same according to an embodiment of the inventive concept may remove or minimize photo-acoustic noise using an ultrasonic wave generated by a source light having a first wavelength of about 1400 nm to about 1500 nm or about 1800 nm to about 2500 nm in a near-infrared band, which is unsusceptible to an external environment. 
     Although the embodiments of the present invention have been described, it is understood that the present invention should not be limited to these embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.