Biometric information detection system, biometric information detection method, and program

Abstract

Provided are a biometric information generation system, a biometric information generation method, and a program, whereby biometric information such as the respiration rate and heart rate of a subject can be accurately measured while suppressing the processing load. On the basis of the measurement results of a load applied to each of a plurality of load sensors specified on the basis of load data, a Doppler sensor selection unit (26) selects at least one Doppler sensor from among a plurality of Doppler sensors having mutually different measurement zones. An operation control unit (30) suppresses the operation of Doppler sensors other than the at least one Doppler sensor that was selected. A biometric information generation unit (40) generates biometric information of the subject on the basis of Doppler data indicating the measurement results of the at least one Doppler sensor that was selected.

Description

Biological information detection system, biological information detection method, and program

[0001] The present invention relates to a biological information detection system, a biological information detection method, and a program, and particularly relates to a system for detecting biological information of a subject based on a Doppler signal.

[0002] Various systems for measuring biological information such as the respiration rate or heart rate of a subject on a bed have been studied. As an example of such a system, Patent Document 1 describes a monitoring device that non-contactedly determines the respiration rate and heart rate of a care recipient on a bed using a microwave Doppler sensor.

[0003] Japanese Patent Application Laid-Open No. 2017-134795

[0004] In the technique described in Patent Document 1, when a subject moves, such as turning over, it may not be possible to accurately measure biological information such as the respiration rate or heart rate of the subject.

[0005] Here, in order to accurately measure biological information even when the subject moves, it may be considered to increase the number of Doppler sensors that operate for measuring biological information.

[0006] However, as the number of Doppler sensors that operate for measuring biological information increases, the processing load of the entire system including these Doppler sensors increases.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a biological information generation system, a biological information generation method, and a program capable of accurately measuring biological information such as the respiration rate and heart rate of a subject while suppressing the processing load.

[0008] (1) The biological information detection system according to the present invention includes: load data acquisition means for acquiring load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person to be measured when the person to be measured is on a bed; Doppler sensor selection means for selecting at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; operation suppression means for suppressing the operation of Doppler sensors other than the selected at least one Doppler sensor; and biological information generation means for generating biological information of the person to be measured based on Doppler data indicating the measurement result of each of the selected at least one Doppler sensor.

[0009] (2) The biological information detection system described in (1) further includes a ratio calculation means that calculates a ratio for each of the plurality of load sensors by dividing the measured load result applied to the load sensor by the total value of the measured load results applied to each of the plurality of load sensors, and the Doppler sensor selection means selects at least one Doppler sensor based on the ratio calculated for each of the plurality of load sensors.

[0010] (3) In the biological information detection system described in (1) or (2), the plurality of Doppler sensors are arranged in a line along the width direction of the bed, and the system further includes a position estimation means for estimating the position of the person to be measured along the width direction of the bed based on the measurement results of the load applied to each of the plurality of load sensors, and the Doppler sensor selection means selects at least one of the Doppler sensors based on the estimated position of the person to be measured.

[0011] (4) A biometric information detection system according to any one of (1) to (3), further comprising a body axis direction estimation means for estimating the body axis direction of the person being measured based on the measurement results of the load applied to each of the plurality of load sensors, wherein the Doppler sensor selection means selects at least one Doppler sensor based on the estimated body axis direction.

[0012] (5) In the biological information detection system described in any of (1) to (4), the load sensor is provided on each of the four legs of the bed.

[0013] (6) In a biological information detection system according to any one of (1) to (5), the Doppler sensor selection means further includes an operation suppression release means that repeatedly performs the selection of the Doppler sensor based on the latest load measurement result, and releases the suppression of the operation of the Doppler sensor that was not selected in the previous selection but is selected in the latest selection, in accordance with the selection of the Doppler sensor based on the latest load measurement result.

[0014] (7) In a biological information detection system according to any one of (1) to (5), the Doppler sensor selection means repeatedly performs the selection of the Doppler sensor based on the latest load measurement result, and the operation suppression means further includes an activation means that, in response to the selection of the Doppler sensor based on the latest load measurement result, stops the Doppler sensor that was selected in the previous selection but is not selected in the latest selection, and activates the Doppler sensor that was not selected in the previous selection but is selected in the latest selection, in response to the selection of the Doppler sensor based on the latest load measurement result.

[0015] (8) A biological information detection system according to any one of (1) to (7), further comprising: a body movement determination means for determining whether or not body movement of the person being measured is occurring based on the magnitude of the fluctuation of the sum of the measured values ​​of the load applied to each of the plurality of load sensors; and a generation suppression means for suppressing the generation of the biological information when it is determined that body movement of the person being measured is occurring.

[0016] (9) The biological information detection system according to any one of (1) to (7) further includes a motion determination means that determines whether or not the subject is moving based on the magnitude of the fluctuation of the sum of the measured values ​​of the load applied to each of the plurality of load sensors, wherein the motion suppression means suppresses the operation of all of the plurality of Doppler sensors when it is determined that the subject is moving.

[0017] (10) In the presence / absence determination system described in any of (1) to (9), the Doppler sensor selection means selects a predetermined number of the Doppler sensors.

[0018] (11) A biological information detection method according to the present invention includes the steps of: acquiring load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person to be measured while the person to be measured is on a bed; selecting at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; suppressing the operation of the Doppler sensors other than the selected at least one Doppler sensor; and generating biological information of the person to be measured based on Doppler data indicating the measurement result of each of the selected at least one Doppler sensor.

[0019] (12) The present invention provides a program for causing a computer to perform the following steps: acquire load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person to be measured while the person to be measured is on a bed; select at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; suppress the operation of the Doppler sensors other than the selected at least one Doppler sensor; and generate biological information of the person to be measured based on the Doppler data indicating the measurement result of each of the selected at least one Doppler sensor. The program may be stored in a computer-readable information storage medium.

[0020] According to the present invention, biological information such as the respiratory rate and heart rate of a subject can be measured with high accuracy while suppressing the processing load.

[0021] This is a configuration diagram of a biological information detection system according to an embodiment of the present invention. This is a plan view of the bed shown in Figure 1. This is a functional block diagram of a signal processing device according to an embodiment of the present invention. This is a flowchart showing an example of the flow of Doppler sensor selection processing performed by a signal processing device according to an embodiment of the present invention. This is a diagram illustrating an example of processing in the Doppler data acquisition unit. This is a flowchart showing an example of the flow of frequency spectrum selection processing performed by a signal processing device according to an embodiment of the present invention. This is a diagram schematically showing an example of aggregate spectrum generation.

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0023] Figure 1 is a configuration diagram of a biological information detection system 1 according to an embodiment of the present invention. As shown in the figure, the biological information detection system 1 includes a signal processing device 10, a Doppler sensor unit 12, and a plurality of load sensors 14. The Doppler sensor unit 12 contains a plurality of Doppler sensors. Here, for example, the Doppler sensor unit 12 is assumed to contain six Doppler sensors (first Doppler sensor to sixth Doppler sensor). Also, as shown in Figure 1, the biological information detection system 1 includes four load sensors 14 (14a to 14d).

[0024] In the example shown in Figure 1, the Doppler sensor unit 12 is mounted on the headboard of the bed 16. Here, the Doppler sensor unit 12 may be mounted symmetrically with respect to the center line L1 of the bed 16 (a line passing through the center in the width direction of the bed 16 and extending in the length direction of the bed 16). Alternatively, multiple Doppler sensors may be mounted perpendicular to the length direction of the bed 16 (the direction along the center line L1 of the bed 16). That is, multiple Doppler sensors may be mounted along the width direction of the bed 16. Alternatively, multiple Doppler sensors may be mounted in a line at equal intervals. Note that the position and orientation of the Doppler sensors are not limited to the examples described above. For example, the Doppler sensors may be mounted on the ceiling. Also, the number of Doppler sensors is not limited to six.

[0025] Each Doppler sensor is positioned to face the longitudinal direction of the bed 16 and emits microwaves in the longitudinal direction of the bed 16. The microwaves are reflected by the chest of the person being measured while they are sleeping on the bed 16, and each Doppler sensor receives the reflected waves. Each Doppler sensor generates a Doppler signal from the reflected waves that indicates the movement of the chest associated with breathing, and outputs Doppler data obtained by digitizing this Doppler signal. The microwaves emitted from each Doppler sensor have slightly different frequencies to prevent interference between them.

[0026] Due to the Doppler effect, the reflected wave is frequency-shifted, and by observing this, the respiratory rate of the person being measured can be obtained. The reflected wave is detected by quadrature detection as a Doppler signal containing an I signal, which is in phase with the transmitted wave, and a Q signal, which is an orthogonal component, and is output to the signal processing device 10 in digital format. The Doppler signal input to the signal processing device 10 is time-series data, showing the amplitude (I component and Q component) at each time point.

[0027] Figure 2 is a plan view of the bed 16 shown in Figure 1. Figure 2 shows the measurement areas 18 (18a to 18f) corresponding to each of the six Doppler sensors. The measurement area 18 of the Doppler sensor may be a substantially rectangular parallelepiped-shaped area in front of the microwave emission direction of the Doppler sensor. The Doppler sensor is configured to accurately detect reflected waves from a person being measured when that person is in the measurement area 18 of the Doppler sensor. Adjacent measurement areas 18 may partially overlap. However, adjacent measurement areas 18 do not necessarily have to overlap.

[0028] The load sensor 14 is positioned below the position of the person being measured when they are on the bed 16. As shown in Figure 1, the load sensor 14 may be provided on each of the four legs of the bed 16. Note that the position and number of load sensors 14 are not limited to those shown in Figure 1.

[0029] Each load sensor 14 then outputs load data indicating the measurement result of the load applied to that load sensor 14.

[0030] The signal processing device 10 may be composed of a known computer, for example, a CPU, memory, input device, and display. The signal processing device 10 generates the respiratory rate of the person being measured based on the Doppler signal output from the Doppler sensor.

[0031] Figure 3 is a functional block diagram of a signal processing device 10 according to an embodiment of the present invention. As shown in the figure, the signal processing device 10 includes a load data acquisition unit 20, a ratio calculation unit 22, a positional body axis estimation unit 24, a Doppler sensor selection unit 26, a body movement determination unit 28, an motion control unit 30, a Doppler data acquisition unit 32, a frequency spectrum generation unit 34, a frequency spectrum selection unit 36, an aggregated spectrum generation unit 38, and a bio-information generation unit 40. These functional blocks are realized by the execution of a signal processing program in the signal processing device 10, which is a computer. This signal processing program may be stored in various computer-readable information storage media such as semiconductor memory and loaded from the media to the signal processing device 10. Alternatively, it may be downloaded to the signal processing device 10 via a data communication line such as the Internet.

[0032] The load data acquisition unit 20 acquires load data indicating the measurement result of the load applied to each of the multiple load sensors 14 located below the position of the person being measured when the person being measured is on the bed 16.

[0033] In the following description, the load data acquisition unit 20 will acquire load data showing the latest load measurement result from each of the four load sensors 14 (load sensors 14a to 14d) at predetermined time intervals. Furthermore, the load measurement timing of the four load sensors 14 will be synchronized.

[0034] The ratio calculation unit 22 calculates, for example, a ratio for each of the multiple load sensors 14 by dividing the measured load result applied to that load sensor 14 by the total measured load result applied to each of the multiple load sensors 14. Hereinafter, the ratio calculated in this manner will be referred to as the load ratio.

[0035] The position axis estimation unit 24 estimates the position of the person being measured along the width direction of the bed 16 based on, for example, the measurement results of the load applied to each of the multiple load sensors 14. The position axis estimation unit 24 may also estimate the position of the person being measured along the width direction of the bed 16 based on the load ratio described above.

[0036] Furthermore, the position axis estimation unit 24 estimates the body axis direction of the person being measured based on the measurement results of the load applied to each of the multiple load sensors 14. The position axis estimation unit 24 may also estimate the body axis direction of the person being measured based on the load ratio described above.

[0037] The Doppler sensor selection unit 26 selects at least one Doppler sensor from among a plurality of Doppler sensors whose measurement regions 18 differ from each other, based on the measurement results of the load applied to each of the plurality of load sensors 14, which are identified based on load data.

[0038] Here, the Doppler sensor selection unit 26 may select at least one Doppler sensor based on the load ratio calculated for each of the multiple load sensors 14. Alternatively, the Doppler sensor selection unit 26 may select at least one Doppler sensor based on the estimated position of the person being measured along the width direction of the bed 16. Alternatively, the Doppler sensor selection unit 26 may select at least one Doppler sensor based on the estimated body axis direction.

[0039] Here, we will explain an example of the flow of the Doppler sensor selection process, which is executed in response to the acquisition of the latest load data, with reference to the flowchart shown in Figure 4.

[0040] First, the ratio calculation unit 22 calculates the load ratio based on the latest load measurement result indicated by the load data (S101). For example, suppose the latest load measurement results from load sensors 14a, 14b, 14c, and 14d are a1, b1, c1, and d1, respectively. In this case, the ratio calculation unit 22 calculates the values ​​of a1 / (a1+b1+c1+d1), b1 / (a1+b1+c1+d1), c1 / (a1+b1+c1+d1), and d1 / (a1+b1+c1+d1) as the load ratio a2 for load sensor 14a, the load ratio b2 for load sensor 14b, the load ratio c2 for load sensor 14c, and the load ratio d2 for load sensor 14d, respectively.

[0041] Then, the position axis estimation unit 24 estimates the position of the person being measured along the width direction of the bed 16 (for example, the position of the person's center of gravity) based on the load ratio calculated in the process shown in S101 (S102). Hereinafter, the position of the person's center of gravity along the width direction of the bed 16 will be referred to as the width direction center of gravity position. The position axis estimation unit 24 calculates a value obtained by, for example, the formula (-a² + b² - c² + d²) as the width direction center of gravity position value. In this case, the range of possible values ​​for the width direction center of gravity position value is between -1 and 1.

[0042] The Doppler sensor selection unit 26 then determines whether the estimated widthwise centroid position is shifted to the left (S103). For example, if the calculated widthwise centroid position value is less than a predetermined value (for example, less than -0.5), it may be determined that the widthwise centroid position is shifted to the left, and if it is greater than or equal to the predetermined value (for example, -0.5 or greater), it may be determined that the widthwise centroid position is not shifted to the left.

[0043] If it is determined that the center of gravity in the width direction is shifted to the left (S103: Y), the Doppler sensor selection unit 26 selects the four Doppler sensors from the left (S104).

[0044] When it is determined that the center of gravity position in the width direction is not shifted to the left (S103: N), the Doppler sensor selection unit 26 determines whether the estimated center of gravity position in the width direction is shifted to the right (S105). Here, for example, when the center of gravity position value in the width direction is equal to or greater than a predetermined value (for example, 0.5 or more), it is determined that the center of gravity position in the width direction is shifted to the right, and when it is less than the predetermined value (for example, less than 0.5), it may be determined that the center of gravity position in the width direction is not shifted to the right.

[0045] When it is determined that the center of gravity position in the width direction is shifted to the right (S105: Y), the Doppler sensor selection unit 26 selects four Doppler sensors from the right (S106).

[0046] When it is determined that the center of gravity position in the width direction is not shifted to the right (S105: N), the body axis estimation unit 24 estimates the body axis direction of the person to be measured (S107). The body axis estimation unit 24 calculates, for example, a value calculated by a mathematical formula with (-a2 + b2 + c2 - d2) as the body axis direction value. In this case, the range of values that the body axis direction value can take is -1 or more and 1 or less.

[0047] Then, the Doppler sensor selection unit 26 determines whether the estimated body axis direction is a direction from the upper left to the lower right (S108). Here, for example, when the body axis direction value is less than a predetermined value (for example, less than -0.5), it is determined that the body axis direction is a direction from the upper left to the lower right, and when it is equal to or greater than the predetermined value (for example, -0.5 or more), it may be determined that the body axis direction is not a direction from the upper left to the lower right.

[0048] When it is determined that the body axis direction is a direction from the upper left to the lower right (S108: Y), the Doppler sensor selection unit 26 selects four Doppler sensors from the left (S104).

[0049] If it is determined that the body axis direction is not from the upper left to the lower right (S108:N), the Doppler sensor selection unit 26 determines whether the estimated body axis direction is from the upper right to the lower left (S109). Here, for example, if the body axis direction value is greater than or equal to a predetermined value (for example, 0.5 or more), it may be determined that the body axis direction is from the upper right to the lower left, and if it is less than the predetermined value (for example, less than 0.5), it may be determined that the body axis direction is not from the upper right to the lower left.

[0050] If it is determined that the body axis direction is from the upper right to the lower left (S109: Y), the Doppler sensor selection unit 26 selects four Doppler sensors from the right (S106).

[0051] If it is determined that the body axis direction is not from the upper right to the lower left (S109:N), the Doppler sensor selection unit 26 selects the four central Doppler sensors (S110).

[0052] As described above, at least one Doppler sensor will be selected. As shown in the processing example above, the Doppler sensor selection unit 26 may select a predetermined number of Doppler sensors (four Doppler sensors in the processing example above).

[0053] In this embodiment, the process shown in Figure 4 may be executed each time the latest load data is acquired. That is, the Doppler sensor selection unit 26 may repeatedly select a Doppler sensor based on the latest load measurement result.

[0054] The body movement determination unit 28 determines, for example, whether or not the subject is moving based on the magnitude of the fluctuation in the sum of the measured loads applied to each of the multiple load sensors 14.

[0055] Here, for example, the body movement determination unit 28 may calculate the sum of the measured loads indicated by each of the load data each load data represents each time load data is acquired. Furthermore, the body movement determination unit 28 may determine whether or not body movement of the person being measured is occurring each time a determination timing occurs that occurs at a time interval longer than the time interval in which load data is acquired.

[0056] Here, the period between two consecutive judgment timings will be called the body movement judgment period. The maximum or minimum value of the total value calculated during a particular body movement judgment period may be specified. The average value of the total value calculated during the body movement judgment period immediately preceding that particular body movement judgment period may also be specified. If the difference between the maximum value specified for the body movement judgment period and the average value specified for the body movement judgment period immediately preceding that particular body movement judgment period is greater than or equal to a predetermined value, it may be determined that body movement of the subject occurred during that body movement judgment time. Alternatively, if the difference between the minimum value specified for the body movement judgment period and the average value specified for the body movement judgment period immediately preceding that particular body movement judgment period is greater than or equal to a predetermined value, it may be determined that body movement of the subject occurred during that body movement judgment time. If none of the above applies, it may be determined that no body movement of the subject occurred during that body movement judgment time. Note that the method for determining whether or not body movement of the subject has occurred is not limited to this method.

[0057] The motion control unit 30 suppresses the operation of Doppler sensors other than at least one Doppler sensor selected by the Doppler sensor selection unit 26. For example, the motion control unit 30 may stop a Doppler sensor that was selected in the previous selection but not in the latest selection, depending on the selection of a Doppler sensor based on the latest load measurement result.

[0058] Furthermore, the motion control unit 30 may release the suppression of the operation of a Doppler sensor that was not selected in the previous selection but is selected in the latest selection, depending on the selection of the Doppler sensor based on the latest load measurement result. For example, the motion control unit 30 may activate a Doppler sensor that was not selected in the previous selection but is selected in the latest selection.

[0059] For example, if the previous selection selected the four Doppler sensors from the left, and the latest selection selected the four Doppler sensors in the center, the motion control unit 30 may activate the second Doppler sensor from the right and deactivate the leftmost Doppler sensor. Alternatively, if the previous selection selected the four Doppler sensors in the center, and the latest selection selected the four Doppler sensors from the left, the motion control unit 30 may activate the leftmost Doppler sensor and deactivate the second Doppler sensor from the right.

[0060] Furthermore, for example, if the four central Doppler sensors were selected in the previous selection and the four rightmost Doppler sensors were selected in the latest selection, the operation control unit 30 may activate the rightmost Doppler sensor and deactivate the second Doppler sensor from the left. Also, if the four rightmost Doppler sensors were selected in the previous selection and the four central Doppler sensors were selected in the latest selection, the operation control unit 30 may activate the second Doppler sensor from the left and deactivate the rightmost Doppler sensor.

[0061] Furthermore, for example, if the previous selection selected the four Doppler sensors from the left and the latest selection selected the four Doppler sensors from the right, the operation control unit 30 may activate the rightmost Doppler sensor and the second Doppler sensor from the right, and deactivate the leftmost Doppler sensor and the second Doppler sensor from the left. Also, if the previous selection selected the four Doppler sensors from the right and the latest selection selected the four Doppler sensors from the left, the operation control unit 30 may activate the leftmost Doppler sensor and the second Doppler sensor from the left, and deactivate the rightmost Doppler sensor and the second Doppler sensor from the right.

[0062] Furthermore, the motion control unit 30 may suppress the operation of all of the multiple Doppler sensors if it determines that the person being measured is moving. For example, the motion control unit 30 may stop all of the Doppler sensors if it determines that the person being measured is moving.

[0063] The Doppler data acquisition unit 32 acquires Doppler data for each of the at least one Doppler sensors selected by the Doppler sensor selection unit 26, showing the measurement results from that Doppler sensor over a certain period of time. Here, the Doppler data acquisition unit 32 may acquire Doppler data from a Doppler sensor that is in operation.

[0064] In the following explanation, we will assume that the Doppler sensor selection unit 26 has selected four Doppler sensors from the left, and that these four Doppler sensors (for example, the first Doppler sensor, the second Doppler sensor, the third Doppler sensor, and the fourth Doppler sensor) are operating.

[0065] The Doppler data acquisition unit 32, for example as shown in Figure 5, extracts a portion of the Doppler data representing the measurement results for each of the Doppler sensors selected by the Doppler sensor selection unit 26 for each of the multiple periods (multiple time windows), showing the measurement results for that period.

[0066] For example, from the first Doppler data acquired from the first Doppler sensor, Doppler data D(1,1), D(2,1), D(3,1), D(4,1), ... showing the measurement results in the first time window, second time window, third time window, fourth time window, ... are extracted. Similarly, from the second Doppler data acquired from the second Doppler sensor, Doppler data D(1,2), D(2,2), D(3,2), D(4,2), ... showing the measurement results in the first time window, second time window, third time window, fourth time window, ... are extracted.

[0067] Similarly, for the third and fourth Doppler sensors, Doppler data showing the measurement results for each time window is extracted. For example, from the third Doppler data acquired from the third Doppler sensor, Doppler data D(1,3), D(2,3), D(3,3), D(4,3), ... showing the measurement results for the first, second, third, fourth, ... time windows are extracted. Also, from the fourth Doppler data acquired from the fourth Doppler sensor, Doppler data D(1,4), D(2,4), D(3,4), D(4,4), ... showing the measurement results for the first, second, third, fourth, ... time windows are extracted.

[0068] Each time window has a fixed length (e.g., 60 seconds), and the start time of each time window is shifted by a predetermined amount of time (for example, 2 seconds). Furthermore, the time windows applied to each of the first, second, and fourth Doppler data are the same. That is, for each of the first, second, and fourth Doppler data, for example, the period corresponding to the first time window is the same, and the period corresponding to the second time window is also the same.

[0069] The frequency spectrum generation unit 34 generates a frequency spectrum for each of the selected Doppler sensors, based on the Doppler data indicating the measurement results from that Doppler sensor.

[0070] The frequency spectrum generation unit 34 converts the input Doppler data into a frequency spectrum by, for example, performing a Fast Fourier Transform (FFT) on the Doppler data. Here, for example, the data for the I signal and the data for the Q signal may each be converted into a frequency spectrum.

[0071] The frequency spectrum selection unit 36 ​​selects, for example, a plurality of frequency spectra from those generated for each selected Doppler sensor, based on the peak frequencies in the frequency spectra generated for each selected Doppler sensor.

[0072] Here, an example of the flow of the frequency spectrum selection process performed by the frequency spectrum selection unit 36 ​​will be explained with reference to the flowchart illustrated in Figure 6. Here, for example, we will explain the process of selecting multiple frequency spectra from the I signal data and Q signal data of four Doppler data D(1,1), D(1,2), D(1,3), and D(1,4) extracted for the first time window.

[0073] First, the frequency spectrum selection unit 36 ​​identifies the peak frequency, which is the frequency of the maximum amplitude in the frequency spectrum generated for the I signal data and Q signal data of each of the four Doppler data D(1,1), D(1,2), D(1,3), and D(1,4), as the respiratory rate corresponding to that frequency spectrum (S201).

[0074] Then, the frequency spectrum selection unit 36 ​​calculates a representative value (in this case, an average value) of the respiratory rate identified in the process shown in S201 (S202).

[0075] Then, the frequency spectrum selection unit 36 ​​checks whether there is a frequency spectrum corresponding to a respiratory rate (i.e., an outlier respiratory rate) whose difference from the representative value calculated in the process shown in S202 is greater than or equal to a predetermined value (for example, 5) (S203).

[0076] If an outlier respiratory rate exists (S203: Y), the frequency spectrum selection unit 36 ​​excludes the frequency spectrum corresponding to the outlier respiratory rate (S204) and returns to the process shown in S202.

[0077] If there are no outlier respiratory rates (S203: N), the process shown in this example is terminated. Note that in the process shown in this example, all frequency spectra may be selected without any frequency spectra being excluded.

[0078] The frequency spectrum that remains after the above process is selected from the frequency spectra generated for the I signal data and Q signal data of each of the four Doppler data extracted for the first time window. The process described above is performed for each of the multiple time windows.

[0079] The aggregated spectrum generation unit 38 generates an aggregated spectrum, for example, based on some or all of the frequency spectra generated for each of the selected Doppler sensors. As shown in Figure 7, with respect to the first time window, the aggregated spectrum (1) may be generated by adding the amplitudes (intensities) of the frequency spectra of the data for the I signal of D(1,1), the Q signal of D(1,1), the I signal of D(1,2), the Q signal of D(1,2), the I signal of D(1,3), the Q signal of D(1,3), ..., the Q signal of D(1,4) for each frequency. The aggregated spectrum (1) corresponds to the aggregated spectrum of the first time window. In this way, the aggregated spectrum generation unit 38 may generate an aggregated spectrum which is the sum of some or all of the frequency spectra generated for each of the multiple Doppler sensors.

[0080] Furthermore, the aggregated spectrum generation unit 38 may generate an aggregated spectrum, which is a frequency spectrum obtained by averaging some or all of the frequency spectra generated for each of the multiple Doppler sensors.

[0081] Furthermore, the aggregated spectrum generation unit 38 may generate an aggregated spectrum based on a plurality of frequency spectra selected by the frequency spectrum selection unit 36. For example, suppose the frequency spectra of the I signal data of D(1,4) and the Q signal data of D(1,4) are excluded, and the other frequency spectra are selected. In this case, an aggregated spectrum (1) may be generated, which is the sum of the frequency spectra of the I signal data of D(1,1), the Q signal data of D(1,1), the I signal data of D(1,2), the Q signal data of D(1,2), the I signal data of D(1,3), and the Q signal data of D(1,3). By doing so, the influence of outliers in the generated aggregated spectrum can be suppressed.

[0082] Figure 7 shows the aggregated spectrum (1), which is the aggregated spectrum of the first time window. Similarly, the aggregated spectrum (2), which is the aggregated spectrum of the second time window, the aggregated spectrum (3), which is the aggregated spectrum of the third time window, and so on are generated.

[0083] The biological information generation unit 40 generates biological information of the subject based on Doppler data showing the measurement results of at least one selected Doppler sensor. The biological information generation unit 40 may also generate biological information of the subject for a given period based on an aggregated spectrum. Here, the biological information generation unit 40 may generate the respiratory rate of the subject for a given period based on the peak frequency in the aggregated spectrum. For example, the frequency of the maximum amplitude in the aggregated spectrum may be identified as the peak frequency. The peak frequency in the aggregated spectrum may then be generated as the respiratory rate.

[0084] Furthermore, the biological information generation unit 40 may identify the maximum amplitude and the second largest amplitude in the aggregated spectrum. The biological information generation unit 40 may then generate an amplitude ratio obtained by dividing the maximum amplitude by the second largest amplitude.

[0085] Furthermore, the biological information generation unit 40 may generate an amplitude ratio for each of the aggregated spectra calculated for a plurality of time windows (for example, a first time window to a 30th time window). The biological information generation unit 40 may then extract aggregated spectra in which the amplitude ratio is equal to or greater than a predetermined threshold (for example, 1.5). The biological information generation unit 40 may then generate the average value of the respiratory rate generated for each of the aggregated spectra in which the amplitude ratio is equal to or greater than a predetermined threshold (for example, 1.5) as the respiratory rate for a period (for example, 1 minute) associated with the plurality of time windows.

[0086] Furthermore, the biological information generation unit 40 may generate a confidence score as the ratio of the number of aggregated spectra whose amplitude ratio is equal to or greater than a predetermined threshold (e.g., 1.5) to the number of aggregated spectra calculated for multiple time windows.

[0087] In this embodiment, the frequency spectrum selection unit 36 ​​does not necessarily have to select a frequency spectrum. The aggregated spectrum generation unit 38 may use all the frequency spectra generated by the frequency spectrum generation unit 34 for a certain period to generate an aggregated spectrum for that period.

[0088] Furthermore, the frequency spectrum selection unit 36 ​​may select frequency spectra on a Doppler sensor basis. That is, the frequency spectrum selection unit 36 ​​may select multiple Doppler sensors from among a plurality of Doppler sensors based on the peak frequencies in the frequency spectra generated for each of the plurality of Doppler sensors. The aggregated spectrum generation unit 38 may then generate an aggregated spectrum based on the frequency spectra generated for each of the selected plurality of Doppler sensors.

[0089] Furthermore, it is not necessary for the data of the I signal and the data of the Q signal to be converted into frequency spectra. For example, the data of a complex signal with the I component as the real part and the Q component as the imaginary part may be converted into a frequency spectrum. Then, an aggregate spectrum may be generated based on that frequency spectrum.

[0090] When measuring a subject's biological information using multiple Doppler sensors, the measurement results obtained from each of these sensors may include some with low accuracy, depending on the subject's position and posture.

[0091] Therefore, if biological information is measured using each of these multiple Doppler sensors, and a representative value such as the average of the measured biological information is used as the biological information value of the person being measured, the biological information value obtained in this way may not be a valid value.

[0092] In this embodiment, as described above, biological information is generated based on the aggregated spectrum. Therefore, according to this embodiment, it is possible to measure the biological information of a subject with greater accuracy compared to the case where a representative value such as the average value of the measured biological information is used as the value of the subject's biological information.

[0093] Furthermore, for example, each Doppler sensor has a different angle relative to the person being measured, so the peak frequencies of the frequency spectra based on the measurement results may differ slightly. However, when multiple Doppler sensors are arranged perpendicular to the length of the bed 16, symmetrically with respect to the center line of the bed 16, or in a line at equal intervals, an aggregate spectrum is generated by appropriately averaging the frequency spectra corresponding to each Doppler sensor. As a result, it becomes possible to measure the biological information of the person being measured with greater accuracy.

[0094] Furthermore, in this embodiment, at least one Doppler sensor is selected based on load data. Then, based on the Doppler data showing the measurement results of each selected Doppler sensor, the subject's biological information is generated. Therefore, in this embodiment, even if the subject moves, such as turning over in bed, the subject's biological information can be measured with high accuracy.

[0095] Furthermore, in this embodiment, the operation of Doppler sensors other than the selected Doppler sensor is suppressed. Therefore, in this embodiment, it is possible to prevent the overall processing load of the system, including these Doppler sensors, from becoming high due to the operation of many Doppler sensors. In particular, by selecting a predetermined number of Doppler sensors, it is possible to keep the overall processing load of the system, including these Doppler sensors, relatively constant.

[0096] As described above, this embodiment makes it possible to accurately measure biological information such as the respiratory rate of a subject while suppressing the processing load.

[0097] Furthermore, if body movement occurs, there is a high probability that the respiratory rate cannot be accurately detected. Therefore, as explained above, if it is determined that the subject is moving, the operation of all multiple Doppler sensors may be suppressed. This reduces the processing load in cases where there is a high probability that the respiratory rate cannot be accurately detected.

[0098] Furthermore, in this embodiment, instead of suppressing the operation of the Doppler sensor when it is determined that the subject is moving, the motion control unit 30 may suppress the generation of biological information by the biological information generation unit 40. For example, if it is determined that the subject is moving, biological information may not be generated. In this case as well, it is possible to reduce the processing load in cases where there is a high possibility that the respiratory rate cannot be accurately detected.

[0099] Furthermore, in this embodiment, the Doppler sensors may be arranged in a line along the length of the bed 16. The position axis estimation unit 24 may estimate the position of the person being measured along the length of the bed 16 based on the measurement results of the load applied to each of the multiple load sensors 14. The Doppler sensor selection unit 26 may select at least one Doppler sensor based on the estimated position of the person being measured.

[0100] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the above description, respiratory rate was generated as the subject's biological information, but heart rate can be generated in the same manner.

[0101] Regarding heart rate, for example, the following processes (1) to (4) may be performed for each of the at least one Doppler sensors selected by the Doppler sensor selection unit 26.

[0102] (1) The Doppler data acquisition unit 32 acquires Doppler data showing the measurement results from the Doppler sensor in each of a plurality of time windows (for example, the first to the 30th time window). (2) The frequency spectrum generation unit 34 generates a frequency spectrum for each of the plurality of time windows based on the acquired Doppler data. (3) The bio-information generation unit 40 identifies the maximum amplitude and the second largest amplitude in the generated frequency spectrum for each of the plurality of time windows, and generates an amplitude ratio by dividing the maximum amplitude by the second largest amplitude. (4) The bio-information generation unit 40 generates a confidence score as the ratio of the number of frequency spectra whose amplitude ratio is equal to or greater than a predetermined threshold (for example, 1.5) to the number of frequency spectra generated for the plurality of time windows.

[0103] The biological information generation unit 40 may then identify the Doppler sensor with the highest reliability value. The biological information generation unit 40 may then identify from the frequency spectra generated by the process described in (2) above for the identified Doppler sensor that have an amplitude ratio of 1.5 or higher. The biological information generation unit 40 may then identify the frequency of the maximum amplitude for each of the frequency spectra whose amplitude ratio is 1.5 or higher. The biological information generation unit 40 may then generate the average value of the maximum amplitude frequencies identified for each of the frequency spectra whose amplitude ratio is 1.5 or higher as the heart rate for a period (1 minute) associated with the plurality of time windows.

Claims

1. A biological information detection system comprising: load data acquisition means for acquiring load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person being measured while the person is lying on a bed; Doppler sensor selection means for selecting at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; operation suppression means for suppressing the operation of Doppler sensors other than the selected at least one Doppler sensor; and biological information generation means for generating biological information of the person being measured based on Doppler data indicating the measurement result of each of the selected at least one Doppler sensor.

2. A biological information detection system according to claim 1, further comprising a ratio calculation means for each of the plurality of load sensors, which calculates a ratio obtained by dividing the measurement result of the load applied to the load sensor by the total value of the measurement results of the load applied to each of the plurality of load sensors, wherein the Doppler sensor selection means selects at least one Doppler sensor based on the ratio calculated for each of the plurality of load sensors.

3. A biological information detection system according to claim 1, wherein the plurality of Doppler sensors are arranged in a line along the width direction of the bed, and further includes a position estimation means for estimating the position of the person to be measured along the width direction of the bed based on the measurement result of the load applied to each of the plurality of load sensors, and the Doppler sensor selection means selects at least one Doppler sensor based on the estimated position of the person to be measured.

4. A biological information detection system according to claim 1, further comprising: a body axis direction estimation means for estimating the body axis direction of a person to be measured based on the measurement results of the load applied to each of the plurality of load sensors, wherein the Doppler sensor selection means selects at least one Doppler sensor based on the estimated body axis direction.

5. A biological information detection system according to claim 1, wherein the load sensor is provided on each of the four legs of the bed.

6. A biological information detection system according to claim 1, wherein the Doppler sensor selection means repeatedly performs the selection of the Doppler sensor based on the latest load measurement result, and the operation suppression release means releases the suppression of the operation of the Doppler sensor that was not selected in the previous selection but is selected in the latest selection, in accordance with the selection of the Doppler sensor based on the latest load measurement result.

7. A biological information detection system according to claim 1, further comprising: a Doppler sensor selection means that repeatedly selects a Doppler sensor based on the latest load measurement result; an operation suppression means that, in response to the selection of a Doppler sensor based on the latest load measurement result, stops a Doppler sensor that was selected in the previous selection but is not selected in the latest selection; and an activation means that, in response to the selection of a Doppler sensor based on the latest load measurement result, activates a Doppler sensor that was not selected in the previous selection but is selected in the latest selection.

8. A biological information detection system according to claim 1, further comprising: a body movement determination means for determining whether or not body movement of the person being measured is occurring based on the magnitude of fluctuation in the sum of the measured values ​​of the load applied to each of the plurality of load sensors; and a generation suppression means for suppressing the generation of the biological information when it is determined that body movement of the person being measured is occurring.

9. A biological information detection system according to claim 1, further comprising: a motion determination means for determining whether or not body movement of the person being measured is occurring based on the magnitude of the fluctuation of the sum of the measured values ​​of the load applied to each of the plurality of load sensors, wherein the motion suppression means suppresses the operation of all of the plurality of Doppler sensors when it is determined that body movement of the person being measured is occurring.

10. A biological information detection system according to claim 1, wherein the Doppler sensor selection means selects a predetermined number of Doppler sensors.

11. A method for detecting biological information, comprising: acquiring load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person being measured while the person is lying on a bed; selecting at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; suppressing the operation of the Doppler sensors other than the selected at least one Doppler sensor; and generating biological information of the person being measured based on Doppler data indicating the measurement result of each of the selected at least one Doppler sensor.

12. A program for causing a computer to perform the following steps: acquiring load data indicating the measurement result of the load applied to each of a plurality of load sensors located below the position of the person being measured while the person is lying on a bed; selecting at least one Doppler sensor from a plurality of Doppler sensors having different measurement areas based on the measurement results of the load applied to each of the plurality of load sensors identified based on the load data; suppressing the operation of the Doppler sensors other than the selected at least one Doppler sensor; and generating biological information of the person being measured based on the Doppler data indicating the measurement result of each of the selected at least one Doppler sensor.

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