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

Abstract

Provided are a biological information generation system, a biological information generation method, and a program that make it possible to accurately measure biological information such as the respiration rate and heart rate of a subject. A Doppler sensor control unit (30) controls the position of a Doppler sensor (15) such that the Doppler sensor (15) is disposed at one of a plurality of predetermined candidate positions. A reliability calculation unit (36) calculates, for at least one candidate position, the reliability of biological information obtained from Doppler data indicating a measurement result measured by the Doppler sensor (15) disposed at the candidate position, on the basis of the Doppler data. A determination unit (38) determines the measurement position from among the plurality of candidate positions on the basis of the reliability calculated for the at least one candidate position. The biological information generation unit (40) repeatedly executes processing for generating biological information of the measurement subject on the basis of Doppler data indicating a measurement result measured by the Doppler sensor (15) disposed at the measurement position.

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 more particularly 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 respiratory rate or heart rate of a person in bed have been studied. As an example of such a system, Patent Document 1 describes a sensor system that senses biological information in a non-contact manner using multiple Doppler sensors attached to the bed. Furthermore, Patent Document 2 describes a monitoring system that determines whether the breathing or pulse rate deviates from normal based on information acquired from Doppler sensors placed under the bed or on the ceiling.

[0003] JP 2020-18861 A JP 2020-113016 A

[0004] In the technologies described in Patent Documents 1 and 2, the Doppler sensor is fixed, so depending on the position and posture of the person being measured, it may not be possible to accurately measure the person's biological information, such as respiratory rate and heart rate.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a biometric information detection system, a biometric information detection method, and a program that can accurately measure biometric information such as the respiratory rate and heart rate of a subject.

[0006] (1) The biometric information detection system of the present invention includes a Doppler sensor control means for controlling the position of the Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; a reliability calculation means for calculating, for at least one of the candidate positions, the reliability of the biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor placed at the candidate position; a measurement position determination means for determining a measurement position from among the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and a biometric information generation means for repeatedly executing a process of generating biometric information of the subject based on the Doppler data indicating the measurement results by the Doppler sensor placed at the measurement position.

[0007] (2) In the biometric information detection system described in (1), the system may further include a measurement condition determination means for determining whether the calculated reliability satisfies a given measurement condition, and the measurement condition determination means may determine whether the calculated reliability satisfies the measurement condition, and the Doppler sensor control means may move the Doppler sensor to another candidate position if the calculated reliability does not satisfy the measurement condition, repeated until the calculated reliability satisfies the measurement condition, and the measurement position determination means may determine the candidate position where the calculated reliability satisfies the measurement condition as the measurement position.

[0008] (3) In the biometric information detection system described in (1), the reliability calculation means may calculate the reliability for each of all the candidate positions, and the measurement position determination means may determine the candidate position with the highest calculated reliability as the measurement position.

[0009] (4) In a biometric information detection system described in any of (1) to (3), the system may further include a change condition determination means for determining whether the reliability of the latest biometric information generated satisfies a given change condition when the process of generating the biometric information of the subject is repeatedly executed, and the Doppler sensor control means may change the position of the Doppler sensor in response to the reliability of the latest biometric information satisfying the change condition.

[0010] (5) In the biometric information detection system described in any one of (1) to (3), for each of a plurality of Doppler sensors, a plurality of candidate positions associated with the Doppler sensor are predetermined, the Doppler sensor control means controls the position of each of the plurality of Doppler sensors so that the Doppler sensor is placed at one of the plurality of candidate positions associated with the Doppler sensor, the measurement position determination means determines a measurement Doppler sensor from among the plurality of Doppler sensors and determines the measurement position from among the plurality of candidate positions associated with the measurement Doppler sensor, and the biometric information generation means may repeatedly perform a process of generating the biometric information based on Doppler data indicating the measurement results by the measurement Doppler sensor placed at the measurement position.

[0011] (6) In the biometric information detection system described in (5), when the process of generating the biometric information of the subject is repeatedly executed, the system may further include a change condition determination means for determining whether the reliability of the latest generated biometric information satisfies a given change condition, and when the reliability of the latest biometric information satisfies the change condition, the measurement position determination means may redetermine the measurement Doppler sensor from among the plurality of Doppler sensors and redetermine the measurement position from among the plurality of candidate positions associated with the measurement Doppler sensor, and after the measurement Doppler sensor and the measurement position have been redetermined, the biometric information generation means may repeatedly execute the process of generating the biometric information based on Doppler data indicating the measurement results by the redetermined measurement Doppler sensor placed at the redetermined measurement position.

[0012] (7) In the bioinformation detection system described in (6), the measurement position determination means may determine a heart rate Doppler sensor from among the plurality of Doppler sensors and determine a heart rate measurement position from among the plurality of candidate positions associated with the heart rate Doppler sensor, the measurement position determination means may determine a respiratory Doppler sensor from among the plurality of Doppler sensors and determine a respiratory measurement position from among the plurality of candidate positions associated with the respiratory Doppler sensor, the respiratory Doppler sensor being a Doppler sensor different from the heart rate Doppler sensor, the bioinformation generation means may repeatedly execute a process of generating a heart rate of the person being measured based on Doppler data indicating a measurement result by the heart rate Doppler sensor placed at the heart rate measurement position, and the bioinformation generation means may repeatedly execute a process of generating a respiratory rate of the person being measured based on Doppler data indicating a measurement result by the respiratory Doppler sensor placed at the respiratory measurement position.

[0013] (8) The biological information detection system according to (7), further comprising a heartbeat measurement change condition determination means for determining whether the reliability of the latest generated heart rate satisfies a given heartbeat measurement change condition, and a respiration measurement change condition determination means for determining whether the reliability of the latest generated respiration rate satisfies a given respiration measurement change condition, wherein the measurement position determination means, when the reliability of the latest heart rate satisfies the heartbeat measurement change condition, redetermines the heartbeat Doppler sensor from among Doppler sensors other than the respiratory Doppler sensor, and redetermines the heartbeat measurement position from among the plurality of candidate positions associated with the heartbeat Doppler sensor, and when the reliability of the latest respiration rate satisfies the respiration measurement change condition, the measurement position determination means, when the reliability of the latest respiration rate satisfies the respiration measurement change condition, redetermines the heartbeat Doppler sensor from among Doppler sensors other than the respiratory Doppler sensor, The respiratory Doppler sensor may be redetermined from among Doppler sensors other than a cardiac Doppler sensor, and the respiratory measurement position may be redetermined from among the plurality of candidate positions associated with the respiratory Doppler sensor, and after the cardiac Doppler sensor and the cardiac measurement position have been redetermined, the biometric information generating means may repeatedly execute a process of generating the heart rate based on Doppler data indicating a measurement result by the redetermined cardiac Doppler sensor placed at the redetermined cardiac measurement position, and after the respiratory Doppler sensor and the cardiac measurement position have been redetermined, the biometric information generating means may repeatedly execute a process of generating the respiratory rate based on Doppler data indicating a measurement result by the redetermined cardiac Doppler sensor placed at the redetermined cardiac measurement position.

[0014] (9) In the biometric information detection system described in any one of (5) to (8), the system may further include a Doppler sensor selection means for selecting multiple of the multiple Doppler sensors based on the position of the subject, and the measurement position determination means may determine the measurement Doppler sensor from the selected multiple Doppler sensors.

[0015] (10) In the biometric information detection system described in any one of (1) to (9), the Doppler sensor control means controls the orientation of the Doppler sensor so that one of a plurality of predetermined candidate directions becomes the microwave emission direction, the reliability calculation means calculates the reliability of the biometric information obtained from the Doppler data for at least one of the candidate directions based on Doppler data indicating the measurement results by the Doppler sensor emitting microwaves in the candidate direction, and the biometric information generation means may further include a measurement direction determination means for determining a measurement direction from among the plurality of candidate directions based on the reliability calculated for at least one of the candidate directions, and the biometric information generation means may generate the biometric information of the subject based on the Doppler data indicating the measurement results by the Doppler sensor controlled so that the microwave emission direction becomes the measurement direction.

[0016] (11) In the biometric information detection system described in any one of (1) to (10), the Doppler sensor control means controls the Doppler sensor so that one of a plurality of predetermined candidate polarization plane directions becomes the emission polarization plane direction of the microwave, the reliability calculation means calculates the reliability of the biometric information obtained from the Doppler data for at least one of the candidate polarization plane directions based on Doppler data indicating the measurement results by the Doppler sensor that emits microwaves with the candidate polarization plane direction as the emission polarization plane direction, and the biometric information generation means may further include a measured polarization plane direction determination means that determines a measured polarization plane direction from among the plurality of candidate polarization plane directions based on the reliability calculated for at least one of the candidate polarization plane directions, and the biometric information generation means may generate the biometric information of the subject based on the Doppler data indicating the measurement results by the Doppler sensor that is controlled so that the measured polarization plane direction becomes the emission polarization plane direction of the microwave.

[0017] (12) In the biometric information detection system described in any of (1) to (11), the system may further include a body movement determination means for determining whether or not the subject is moving, and the biometric information generation means may suppress the generation of the biometric information in response to determining that the subject is moving, and may resume the generation of the biometric information in response to determining that the subject is not moving in a situation in which the generation of the biometric information is suppressed.

[0018] (13) In the bioinformation detection system described in any one of (1) to (12), the system may further include a frequency spectrum generating means for generating a frequency spectrum based on the Doppler data, and the reliability calculating means may calculate the reliability as the amplitude ratio between the largest peak and the second largest peak contained in the frequency spectrum.

[0019] (14) The biometric information detection method of the present invention includes the steps of: controlling the position of a Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; calculating, for at least one of the candidate positions, the reliability of the biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor placed at the candidate position; determining a measurement position from among the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and repeatedly executing a process to generate biometric information of the subject based on the Doppler data indicating the measurement results by the Doppler sensor placed at the measurement position.

[0020] (15) A program according to the present invention causes a computer to execute the following steps: controlling the position of a Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; calculating, for at least one of the candidate positions, based on Doppler data indicating a measurement result by the Doppler sensor placed at the candidate position, a reliability of bioinformation obtained from the Doppler data; determining a measurement position from the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and repeatedly executing a process of generating bioinformation of a subject based on the Doppler data indicating a measurement result by the Doppler sensor placed at the measurement position. This program may be stored in a computer-readable information storage medium.

[0021] According to the present invention, it is possible to accurately measure biological information such as the respiratory rate and heart rate of a subject.

[0022] FIG. 1 is a configuration diagram of a biological information detection system according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing an example of a Doppler sensor shown in FIG. 1. FIG. 3 is a diagram schematically showing an example of a Doppler sensor shown in FIG. 1. FIG. 4 is a diagram schematically showing an example of a Doppler sensor shown in FIG. 1. FIG. 5 is a diagram schematically showing an example of a Doppler sensor shown in FIG. 1. FIG. 6 is a diagram schematically showing an example of a Doppler sensor shown in FIG. 1. FIG. 7 is a functional block diagram of a computer according to an embodiment of the present invention. FIG. 8 is a diagram showing an example of a frequency spectrum. FIG. 9 is a diagram showing an example of estimation of the position of a subject. FIG. 10 is a flow chart showing an example of a processing flow performed by a computer according to an embodiment of the present invention. FIG. 11 is a flow chart showing an example of a processing flow performed by a computer according to an embodiment of the present invention.

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0024] FIG. 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 computer 10, a Doppler sensor unit 12, and a plurality of load sensors 14. The Doppler sensor unit 12 includes a plurality of Doppler sensors 15 (see FIGS. 2A to 2F). Here, for example, the Doppler sensor unit 12 includes six Doppler sensors 15. The biological information detection system 1 also includes four load sensors 14 (14a to 14d). In this embodiment, a ball screw 18 is attached to the headboard of a bed 16, and the Doppler sensors 15 are supported by the ball screw 18 (see FIGS. 2A to 2F).

[0025] In this embodiment, the ball screw 18 is disposed so as to extend in the vertical direction along the headboard surface of the bed 16. The Doppler sensor 15 is movable along the headboard surface of the bed 16. That is, the Doppler sensor 15 is movable in the vertical direction along the extension direction of the ball screw 18. Note that the vertical direction along the headboard surface may be substantially vertical.

[0026] In this embodiment, for example, one of the Doppler sensors 15 emits microwaves toward the heart of a person being measured who is sleeping in bed 16. The microwaves are reflected by the person's heart, and the reflected waves are received by each Doppler sensor 15. The Doppler sensor 15 then generates a Doppler signal from the reflected waves that indicates the movement of the heart associated with the heartbeat, and outputs Doppler data that is a digital version of this Doppler signal. The reflected waves are frequency shifted due to the Doppler effect, and the heart rate of the person being measured can be obtained by observing this.

[0027] Furthermore, one of the Doppler sensors 15 emits microwaves toward the chest of the person being measured who is sleeping in bed 16. The microwaves are reflected by the chest of the person being measured, and the reflected waves are received by each Doppler sensor 15. The Doppler sensor 15 then generates a Doppler signal from the reflected waves that indicates chest movement associated with breathing, and outputs Doppler data that is digitized from this Doppler signal. The reflected waves are frequency shifted due to the Doppler effect, and by observing this, the respiratory rate of the person being measured can be obtained.

[0028] The reflected wave is detected by quadrature detection as a Doppler signal including an I signal, which is an in-phase component with the transmitted wave, and a Q signal, which is a quadrature component, and is output in digital form to computer 10. The Doppler signal input to computer 10 is time-series data, and indicates the amplitude (I component and Q component) at each time.

[0029] In this embodiment, the Doppler sensor 15 that measures the heart rate and the Doppler sensor 15 that measures the respiratory rate may be separate, or the Doppler sensor 15 that measures the heart rate and the respiratory rate may be the same Doppler sensor 15. For example, if, based on the measurement results of a certain Doppler sensor 15, the heart rate is accurately measured in a predetermined frequency range associated with the heart rate (e.g., around 1.25 Hz) and the respiratory rate is accurately measured in a predetermined frequency range associated with the respiratory rate (e.g., around 0.3 Hz), then both the heart rate and the respiratory rate may be measured by the Doppler sensor 15.

[0030] The load sensor 14 is positioned below the position of the person being measured when the person is on the bed 16. As shown in Fig. 1, a load sensor 14 may be provided on each of the four legs of the bed 16. Each load sensor 14 outputs load data indicating the measurement result of the load acting on the load sensor 14.

[0031] The computer 10 may be configured as a known computer including, for example, a CPU, a memory, an input device, and a display. The computer 10 generates biological information of the subject (here, for example, heart rate and respiratory rate) based on the Doppler signal output from the Doppler sensor 15.

[0032] The biometric information detection system 1 according to this embodiment also includes 18 stepping motors 20 that operate in accordance with control signals received from the computer 10. Six of the 18 stepping motors 20, or stepping motors 20a, are connected to different ball screws 18. The stepping motors 20a connected to the ball screws 18 control the rotation of the ball screws 18, thereby moving the Doppler sensor 15 in the vertical direction. Six of the 18 stepping motors 20, or stepping motors 20b, are provided on the housing of the Doppler sensor 15. The stepping motors 20b provided on the housing of the Doppler sensor 15 control the rotation of the Doppler sensor 15 in one direction (e.g., the vertical direction). Six of the 18 stepping motors 20, or stepping motors 20c, are connected to antennas provided in the Doppler sensor 15. The stepping motors 20c connected to the antennas are capable of controlling the orientation of the antennas.

[0033] 3 is a functional block diagram of a computer 10 according to an embodiment of the present invention. As shown in the figure, the computer 10 includes a Doppler sensor control unit 30, a Doppler data acquisition unit 32, a frequency spectrum generation unit 34, a reliability calculation unit 36, a determination unit 38, a biometric information generation unit 40, a biometric information storage unit 42, a change condition determination unit 44, a load data acquisition unit 46, a body movement determination unit 48, a subject position estimation unit 50, and a Doppler sensor selection unit 52. These functional blocks are implemented by executing a signal processing program and a control program in the computer 10. The signal processing program and the control program may be stored in various computer-readable information storage media such as semiconductor memory and loaded into the computer 10 from the medium. Alternatively, they may be downloaded to the computer 10 via a data communication line such as the Internet.

[0034] The Doppler sensor control unit 30 controls the position of the Doppler sensor 15 so that the Doppler sensor 15 is placed at one of a plurality of predetermined candidate positions, for example.

[0035] Here, for each of the multiple (for example, six) Doppler sensors 15, multiple candidate positions associated with the Doppler sensor 15 may be determined in advance.

[0036] The Doppler sensor control unit 30 may then control the position of each of the multiple Doppler sensors 15 so that the Doppler sensor 15 is positioned at one of multiple candidate positions associated with the Doppler sensor 15.

[0037] For example, the Doppler sensor control unit 30 outputs a control signal to the stepping motor 20a connected to the ball screw 18, in accordance with a target position of the Doppler sensor 15 connected to the ball screw 18. Then, the stepping motor 20a rotates in accordance with the control signal, causing the ball screw 18 to rotate, and as a result, the Doppler sensor 15 may be positioned at the target position.

[0038] For example, a plurality of candidate positions may be predetermined at 5-centimeter intervals along the extension direction (e.g., the vertical direction) of the ball screw 18. The Doppler sensor 15 may then be placed at any of the candidate positions set at 5-centimeter intervals.

[0039] Alternatively, a predetermined number of heights (e.g., three), such as a first height, a second height, and a third height, may be determined in order from the highest to the lowest. In this case, the position at the first height, the position at the second height, and the position at the third height correspond to the plurality of candidate positions, respectively. The position of the Doppler sensor 15 may then be controlled to be one of the first height, the second height, and the third height.

[0040] Fig. 2A shows an example of how the position of the Doppler sensor 15 is controlled to a first height, Fig. 2B shows an example of how the position of the Doppler sensor 15 is controlled to a second height, and Fig. 2C shows an example of how the position of the Doppler sensor 15 is controlled to a third height.

[0041] Here, one of the candidate positions may be set to a height 300 mm above the surface of a mattress placed on the bed 16 .

[0042] In this embodiment, thresholds (for example, upper and lower limits of height) may be set for positions where the Doppler sensor 15 can be placed. The Doppler sensor 15 may then be placed within a range that does not exceed the threshold (a range that is equal to or greater than the lower limit and equal to or less than the upper limit).

[0043] Furthermore, the Doppler sensor control unit 30 may control the orientation of the Doppler sensor 15 so that the microwave emission direction is one of a plurality of predetermined candidate directions.

[0044] Here, for each of the multiple (for example, six) Doppler sensors 15, multiple candidate directions associated with the Doppler sensor 15 may be determined in advance.

[0045] The Doppler sensor control unit 30 may then control the orientation of each of the multiple Doppler sensors 15 so that the microwave emission direction is one of multiple candidate directions associated with that Doppler sensor 15.

[0046] For example, the Doppler sensor control unit 30 outputs a control signal to a stepping motor 20b provided on the housing of the Doppler sensor 15, in accordance with a target emission direction of microwaves from the Doppler sensor 15. Then, the stepping motor 20b may rotate in accordance with the control signal, so that the emission direction of microwaves from the Doppler sensor 15 becomes the target emission direction.

[0047] 2A, 2D, 2E, and 2F, the orientation of the Doppler sensor 15 may be controlled so that the emission direction of microwaves from the Doppler sensor 15 is oriented in any one of the following directions: the front direction (see FIG. 2A), a direction 10 degrees downward from the front direction (see FIG. 2D), a direction 20 degrees downward from the front direction (see FIG. 2E), and a direction 30 degrees downward from the front direction (see FIG. 2F). In this case, the front direction, the direction 10 degrees downward from the front direction, the direction 20 degrees downward from the front direction, and the direction 30 degrees downward from the front direction correspond to the plurality of candidate directions, respectively.

[0048] In addition, the Doppler sensor control unit 30 may control the Doppler sensor 15 so that the polarization plane direction of the emitted microwave (hereinafter referred to as the microwave emission polarization plane direction) is one of a plurality of predetermined candidate polarization plane directions.

[0049] Here, for each of the multiple (for example, six) Doppler sensors 15, multiple candidate polarization plane directions associated with the Doppler sensor 15 may be determined in advance.

[0050] The Doppler sensor control unit 30 may then control the Doppler sensor 15 so that, for each of the multiple Doppler sensors 15, one of the multiple candidate polarization plane directions associated with that Doppler sensor 15 becomes the microwave emission polarization plane direction.

[0051] For example, the Doppler sensor control unit 30 outputs a control signal to the stepping motor 20c connected to the antenna included in the Doppler sensor 15, in accordance with a target direction of the polarization plane of the microwave emitted by the Doppler sensor 15. Then, the stepping motor 20c rotates in accordance with the control signal, thereby rotating the antenna, and as a result, the direction of the polarization plane of the microwave emitted by the Doppler sensor 15 may become the target direction of the polarization plane of the microwave emitted.

[0052] Here, for example, the Doppler sensor 15 may be controlled so that the direction of the output polarization plane is either the horizontal direction (0 degrees) or the vertical direction (90 degrees). In this case, the horizontal direction and the vertical direction correspond to the multiple output polarization plane directions, respectively.

[0053] In this embodiment, for each of the six Doppler sensors 15, the position of the Doppler sensor 15 (height in the above example), the direction in which the microwaves are emitted by the Doppler sensor 15, and the direction of the polarization plane in which the microwaves are emitted by the Doppler sensor 15 can be controlled independently.

[0054] The Doppler data acquisition unit 32 acquires, for each of the six Doppler sensors 15, Doppler data indicating the measurement results of the Doppler sensor 15 over a certain period of time.

[0055] The frequency spectrum generating unit 34 generates a frequency spectrum based on, for example, the Doppler data acquired by the Doppler data acquiring unit 32. An example of the generated frequency spectrum is shown in FIG.

[0056] The frequency spectrum generator 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 I signal data and the Q signal data may each be converted into a frequency spectrum.

[0057] For example, the reliability calculation unit 36 ​​calculates, for at least one candidate position, the reliability of the biological information obtained from the Doppler sensor 15, based on Doppler data indicating the measurement results by the Doppler sensor 15 placed at the candidate position. The reliability calculation unit 36 ​​may calculate, for at least one candidate direction, the reliability of the biological information obtained from the Doppler sensor 15, based on Doppler data indicating the measurement results by the Doppler sensor 15 that emits microwaves in the candidate direction. The reliability calculation unit 36 ​​may calculate, for at least one candidate polarization direction, the reliability of the biological information obtained from the Doppler sensor 15, based on Doppler data indicating the measurement results by the Doppler sensor 15 that emits microwaves with the candidate polarization direction as the emission polarization direction.

[0058] As described above, when each Doppler sensor 15 has three degrees of freedom, namely, position, emission direction, and emission polarization plane direction, when a microwave is emitted from a certain Doppler sensor 15 disposed at a certain position in a certain emission direction and with a certain emission polarization plane direction, a reliability associated with the combination of the Doppler sensor 15, the position, the emission direction, and the emission polarization plane direction may be calculated based on Doppler data indicating the measurement results of the Doppler sensor 15.

[0059] Here, the reliability calculation unit 36 ​​may calculate, for example, the amplitude of the largest peak and the amplitude of the second largest peak included in the frequency spectrum generated based on the Doppler data. In the example of Fig. 4, a largest peak P1 and a second largest peak P2 are shown. The reliability calculation unit 36 ​​may then calculate, as the reliability, the amplitude ratio between the amplitude of the largest peak P1 and the amplitude of the second largest peak P2 included in the frequency spectrum, i.e., the amplitude ratio obtained by dividing the amplitude of the largest peak P1 by the amplitude of the second largest peak P2.

[0060] The determiner 38 determines a measurement position, which is the position of the Doppler sensor 15 when the biometric information is generated, from among the plurality of candidate positions, for example, based on the reliability calculated for at least one candidate position. Here, the determiner 38 may determine a measurement Doppler sensor from among the plurality of Doppler sensors 15, and may also determine a measurement position from among the plurality of candidate positions associated with the measurement Doppler sensor.

[0061] Furthermore, the determiner 38 may determine, from among the plurality of candidate directions, a measurement direction which is the emission direction of the microwave when the biometric information is generated, based on the reliability calculated for at least one candidate direction. Furthermore, the determiner 38 may determine, from among the plurality of candidate polarization directions, a measurement polarization direction which is the emission polarization direction of the microwave when the biometric information is generated, based on the reliability calculated for at least one candidate polarization direction.

[0062] Details of determining the measurement position, measurement direction, and measurement polarization plane direction will be described later.

[0063] In this embodiment, a heart rate Doppler sensor for measuring the heart rate and a respiratory Doppler sensor for measuring the respiratory rate may be determined. Here, as described above, the heart rate Doppler sensor may be the same Doppler sensor 15 as the respiratory Doppler sensor, or may be a Doppler sensor 15 different from the respiratory Doppler sensor.

[0064] Then, a heartbeat measurement position may be determined from among a plurality of candidate positions associated with the cardiac Doppler sensor, a heartbeat measurement direction may be determined from among a plurality of candidate directions associated with the cardiac Doppler sensor, and a heartbeat measurement polarization direction may be determined from among a plurality of candidate directions associated with the cardiac Doppler sensor.

[0065] Then, a respiration measurement position may be determined from among a plurality of candidate positions associated with the respiratory Doppler sensor, a respiration measurement direction may be determined from among a plurality of candidate directions associated with the respiratory Doppler sensor, and a respiration measurement polarization direction may be determined from among a plurality of candidate polarization directions associated with the respiratory Doppler sensor.

[0066] The biological information generating unit 40 generates the biological information of the subject based on, for example, Doppler data indicating the measurement results obtained by the Doppler sensor 15 placed at the measurement position. Here, the biological information generating unit 40 may repeatedly execute the process of generating the biological information of the subject based on the Doppler data indicating the measurement results obtained by the Doppler sensor 15 placed at the measurement position.

[0067] The biological information generating unit 40 may also repeatedly execute a process of generating biological information based on Doppler data indicating the measurement results obtained by a measurement Doppler sensor disposed at a measurement position. For example, the biological information generating unit 40 may repeatedly execute a process of generating the heart rate of the subject based on Doppler data indicating the measurement results obtained by a heart rate Doppler sensor disposed at a heart rate measurement position. The biological information generating unit 40 may also repeatedly execute a process of generating the respiration rate of the subject based on Doppler data indicating the measurement results obtained by a respiratory Doppler sensor disposed at a respiration measurement position.

[0068] For example, depending on the determination of the measurement Doppler sensor, measurement position, measurement direction, and measurement polarization plane direction, the acquisition of Doppler data for a certain period of time, the generation of a frequency spectrum based on the Doppler data, and the generation of biometric information associated with the period based on the frequency spectrum may be repeatedly performed.

[0069] For example, the bioinformation generating unit 40 may identify a spectral peak in a first frequency range (for example, around 0.3 Hz) corresponding to respiration in a frequency spectrum based on Doppler data representing the measurement results obtained by the respiratory Doppler sensor, and calculate the respiration rate from the frequency corresponding to the peak. For example, the bioinformation generating unit 40 may calculate the respiration rate per minute by multiplying the frequency (in Hertz) of the spectral peak by 60.

[0070] Furthermore, the biometric information generating unit 40 may, for example, identify a spectral peak in a second frequency range (for example, around 1.25 Hz) corresponding to the heartbeat in a frequency spectrum based on Doppler data representing the measurement results from the heartbeat Doppler sensor, and calculate the heart rate from the frequency corresponding to the peak. For example, the biometric information generating unit 40 may calculate the heart rate per minute by multiplying the frequency (in Hertz) of the spectral peak by 60.

[0071] The respiratory rate and heart rate calculated in this manner are stored in the biological information storage unit 42. In this manner, the biological information storage unit 42 stores time-series data of the respiratory rate and heart rate.

[0072] For example, in a situation where the process of generating biometric information of the subject is being repeatedly executed, the change condition determination unit 44 determines whether the reliability of the latest generated biometric information satisfies a given change condition.

[0073] Here, it may be determined whether or not the change condition is satisfied for each of the heart rate and the respiratory rate. That is, the change condition determination unit 44 may determine whether or not the reliability of the latest generated heart rate satisfies a given heart rate measurement change condition. Also, the change condition determination unit 44 may determine whether or not the reliability of the latest generated respiratory rate satisfies a given respiration measurement change condition.

[0074] An example of the change condition is that the reliability is equal to or less than a predetermined threshold. Here, the threshold for the heartbeat measurement change condition and the threshold for the respiration measurement change condition may be the same or different.

[0075] Then, depending on whether the reliability of the latest biometric information satisfies the change condition, for example, the determination unit 38 re-determines the measurement position from among a plurality of candidate positions, and the Doppler sensor control unit 30 changes the position of the Doppler sensor 15 to the measurement position re-determined from among the plurality of candidate positions.

[0076] Here, in response to the reliability of the latest biological information satisfying the change condition, the determiner 38 may redetermine the measurement Doppler sensor from among the multiple Doppler sensors 15 and redetermine the measurement position from among the multiple candidate positions associated with the measurement Doppler sensor. In this case, the same Doppler sensor 15 as the measurement Doppler sensor when the reliability of the latest biological information satisfied the change condition may be redetermined as the measurement Doppler sensor, or a Doppler sensor 15 different from the measurement Doppler sensor when the reliability of the latest biological information satisfied the change condition may be redetermined as the measurement Doppler sensor.

[0077] Furthermore, if the reliability of the latest heart rate satisfies the heart rate measurement change condition, a heart rate Doppler sensor may be redetermined from among the Doppler sensors 15 other than the respiratory Doppler sensor, and a heart rate measurement position may be redetermined from among a plurality of candidate positions associated with the heart rate Doppler sensor. In this case, the respiratory Doppler sensor may continue to generate the respiration rate without being changed.

[0078] Furthermore, if the reliability of the latest respiratory rate satisfies the respiratory measurement change condition, the respiratory Doppler sensor may be redetermined from among the Doppler sensors 15 other than the cardiac Doppler sensor, and the respiratory measurement position may be redetermined from among a plurality of candidate positions associated with the respiratory Doppler sensor. In this case, the cardiac Doppler sensor may continue to generate the heart rate without being changed.

[0079] After the position of the Doppler sensor 15 is changed to the redetermined measurement position, the biometric information generating unit 40 may repeatedly execute the process of generating biometric information based on Doppler data indicating the measurement results by the Doppler sensor 15 at the changed measurement position. Here, after the measurement Doppler sensor and measurement position are redetermined, the biometric information generating unit 40 may repeatedly execute the process of generating biometric information based on Doppler data indicating the measurement results by the redetermined measurement Doppler sensor placed at the redetermined measurement position.

[0080] Furthermore, after the heart rate Doppler sensor and the heart rate measurement position are redetermined, a process of generating a heart rate based on Doppler data indicating a measurement result by the redetermined heart rate Doppler sensor placed at the redetermined heart rate measurement position may be repeatedly executed. Furthermore, after the respiratory Doppler sensor and the respiratory measurement position are redetermined, a process of generating a respiratory rate based on Doppler data indicating a measurement result by the redetermined respiratory Doppler sensor placed at the redetermined respiratory measurement position may be repeatedly executed.

[0081] In the above description, the measurement position is redetermined in response to the reliability satisfying the change condition, but the measurement direction and the measurement polarization direction may also be redetermined in a similar manner. Then, the measurement direction may be changed to the redetermined one, and the measurement polarization direction may also be changed to the redetermined one.

[0082] The load data acquisition unit 46 acquires, for example, load data indicating the measurement results of the loads applied to a plurality of (e.g., four) load sensors 14. Here, the load data output from each of the plurality of (e.g., four) load sensors 14 may be acquired at predetermined time intervals.

[0083] The body movement determination unit 48 may determine, for example, whether or not the subject is moving. Here, the body movement determination unit 48 may calculate a total weight based on load data acquired from each of the four load sensors 14 at predetermined time intervals and generate total weight data indicating the calculated total weight. For example, total weight data indicating the sum of the measurement results of the loads applied to each of the four load sensors 14 may be generated. The body movement determination unit 48 may then determine whether or not the subject is moving based on the magnitude of fluctuation in the value indicated by the total weight data. Here, for example, the body movement determination unit 48 may determine whether or not the subject is moving each time a determination timing arrives, which occurs at a time interval longer than the time interval at which the total weight data is generated.

[0084] Here, the period between two consecutive determination timings is referred to as a body movement determination period. The maximum or minimum value of the total weight data generated during a specific body movement determination period may be identified. The average value of the total weight data generated during the body movement determination period immediately preceding the specific body movement determination period may be identified. If the difference between the maximum value identified for the specific body movement determination period and the average value identified for the body movement determination period immediately preceding the specific body movement determination period is equal to or greater than a predetermined value, it may be determined that the subject's body movement has occurred during the body movement determination time. Furthermore, if the difference between the minimum value identified for the specific body movement determination period and the average value identified for the body movement determination period immediately preceding the specific body movement determination period is equal to or greater than a predetermined value, it may be determined that the subject's body movement has occurred during the body movement determination time. If neither of these conditions is met, it may be determined that the subject's body movement has not occurred during the body movement determination time. Note that the method for determining whether the subject's body movement has occurred is not limited to this method.

[0085] Then, in response to determining that the subject is moving, the biological information generating unit 40 may suppress the generation of the biological information. Then, in response to determining that the subject is not moving while the generation of the biological information is being suppressed, the biological information generating unit 40 may resume the generation of the biological information.

[0086] The subject position estimation unit 50 estimates, for example, the position of the subject on the bed 16. The subject position estimation unit 50 may estimate the position of the subject on the bed 16 based on load data acquired from the four load sensors 14 at predetermined time intervals.

[0087] 5, when viewed from above the bed 16 with the headboard of the bed 16 at the top edge, the direction from left to right is the positive X-axis direction, and the direction from top to bottom is the positive Y-axis direction. The coordinates of the centers of the load sensors 14a, 14b, 14c, and 14d are (0,0), (1,0), (0,1), and (1,1), respectively.

[0088] The latest load measurement results obtained by the load sensor 14a, the load sensor 14b, the load sensor 14c, and the load sensor 14d are assumed to be a, b, c, and d, respectively.

[0089] In this case, the coordinate values ​​(x, y) of the subject's position may be calculated using the formulas x = (b + d) / (a ​​+ b + c + d) and y = (c + d) / (a ​​+ b + c + d). Note that the method for estimating the subject's position is not limited to this method.

[0090] The Doppler sensor selection unit 52 selects multiple Doppler sensors 15 based on the subject's position. For example, a predetermined number (e.g., four) of Doppler sensors 15 closest to the subject's estimated position may be selected. When the Doppler sensors 15 are selected, the determination unit 38 may determine the measurement Doppler sensor from the selected multiple Doppler sensors 15. In this case, the reliability calculation unit 36 ​​may calculate the above-mentioned reliability only for the selected multiple Doppler sensors 15.

[0091] An example of the flow of the measurement position determination process will now be described with reference to the flow charts shown in FIGS. 6A and 6B.

[0092] In the process shown in this processing example, it is assumed that each of the six Doppler sensors 15 is placed at a predetermined initial position, which is one of a plurality of candidate positions.

[0093] First, the Doppler data acquisition unit 32 operates each of the six Doppler sensors 15 for a predetermined time period and acquires Doppler data indicating the measurement results of the Doppler sensor 15 for the predetermined time period (S101).

[0094] Then, for each of the six Doppler data acquired in the process shown in S101, the frequency spectrum generating unit 34 generates a frequency spectrum based on the Doppler data (S102).

[0095] Then, the reliability calculation unit 36 ​​calculates the reliability (S103). Here, for each of the six frequency spectra generated in the process shown in S102, the reliability is calculated within a predetermined frequency range associated with the heart rate (for example, within a predetermined frequency range around 1.25 Hz). Hereinafter, the reliability calculated from the frequency spectrum based on the Doppler data indicating the measurement results by the Doppler sensor 15 will be referred to as the reliability corresponding to the Doppler sensor 15.

[0096] The determination unit 38 then determines whether or not a predetermined measurement condition (heart rate measurement condition) is satisfied for each of the six reliabilities calculated in the process shown in S103 (S104). Here, for example, it may be determined whether or not the amplitude ratio, which is the calculated reliability, is greater than a predetermined value.

[0097] Then, the determination unit 38 determines whether there is at least one Doppler sensor 15 corresponding to the reliability that satisfies the heart rate measurement condition (S105).

[0098] If there is one (S105: Y), one of the Doppler sensors 15 corresponding to the reliability that satisfies the heartbeat measurement condition is determined as the heartbeat Doppler sensor, and the candidate position where that heartbeat Doppler sensor is located is determined as the heartbeat measurement position (S106). Here, for example, the Doppler sensor 15 corresponding to the highest reliability (e.g., the largest amplitude ratio) may be determined as the heartbeat Doppler sensor.

[0099] If no body movement exists (S105: N), the body movement determining unit 48 determines whether or not there is body movement, and if it is determined that there is body movement, it waits until it is determined that there is no body movement (S107).

[0100] If it is determined that there is no body movement, the Doppler sensor control unit 30 changes the position of at least one Doppler sensor 15 (S108) and returns to the process shown in S101. In this case, the positions of all Doppler sensors 15 may be changed. In addition, in this case, taking into account that the heart rate tends to be measured more accurately when the Doppler sensor 15 is closer to the subject, the height of the Doppler sensor 15 may be changed downward by 5 centimeters.

[0101] After the heart rate Doppler sensor and the heart rate measurement position are determined in the process shown in S106, the reliability calculation unit 36 ​​calculates the reliability (S109). Here, for example, the reliability is calculated within a predetermined frequency range associated with the respiratory rate (for example, within a predetermined frequency range around 0.3 Hz) for the frequency spectrum based on the Doppler data of the heart rate Doppler sensor generated in the process shown in S102.

[0102] The determination unit 38 then determines whether the reliability calculated in the process of S109 satisfies predetermined measurement conditions (respiration measurement conditions) (S110). For example, the determination may be made based on whether the amplitude ratio, which is the calculated reliability, is greater than a predetermined value. Note that the respiration measurement conditions may be the same as or different from the heart rate measurement conditions.

[0103] If the respiration measurement condition is met (S110: Y), the cardiac Doppler sensor is also determined as the respiratory Doppler sensor, and the candidate position where the respiratory Doppler sensor is located is also determined as the respiration measurement position (S111).Then, the processing shown in this processing example ends.

[0104] If the respiration measurement condition is not satisfied (S110: N), the reliability calculation unit 36 ​​calculates the reliability (S112). Here, for example, for each of the frequency spectra generated in the process shown in S102 for the Doppler sensors 15 other than the cardiac Doppler sensor (e.g., five Doppler sensors 15), the reliability is calculated within a predetermined frequency range associated with the respiration rate.

[0105] The determination unit 38 then determines whether or not predetermined respiration measurement conditions are satisfied for each of the five reliabilities calculated in the process shown in S112 (S113). For example, the determination may be made as to whether the amplitude ratio, which is the calculated reliability, is greater than a predetermined value. As described above, the respiration measurement conditions may be the same as or different from the heart rate measurement conditions. Furthermore, the respiration measurement conditions in the process shown in S110 and the respiration measurement conditions in the process shown in S113 may be the same as or different from each other.

[0106] Then, the determination unit 38 determines whether there is at least one Doppler sensor 15 corresponding to the reliability that satisfies the respiration measurement condition in the process shown in S113 (S114).

[0107] If there is a Doppler sensor 15 (S114: Y), one of the Doppler sensors 15 corresponding to the reliability that satisfies the respiration measurement condition is determined as the respiratory Doppler sensor, and the candidate position where that respiratory Doppler sensor is located is determined as the respiration measurement position (S115). Here, for example, the Doppler sensor 15 corresponding to the highest reliability (e.g., the largest amplitude ratio) may be determined as the respiratory Doppler sensor. Then, the processing shown in this processing example ends.

[0108] If there is no Doppler sensor 15 (S114: N), the Doppler sensor control unit 30 changes the position of at least one of the Doppler sensors 15 other than the heart rate Doppler sensor (S116). In this case, the positions of all of the Doppler sensors 15 other than the heart rate Doppler sensor (e.g., five Doppler sensors 15) may be changed. In this case, taking into account that measuring a wider area tends to enable more accurate measurement of respiration, the height of the Doppler sensor 15 may be changed upward by 5 centimeters.

[0109] Then, the Doppler data acquisition unit 32 operates each of the five Doppler sensors 15 other than the heart rate Doppler sensor for a predetermined period of time and acquires Doppler data indicating the measurement results of the Doppler sensor 15 for that predetermined period of time (S117).

[0110] Then, for each of the five Doppler data acquired in the process shown in S117, the frequency spectrum generating unit 34 generates a frequency spectrum based on the Doppler data (S118).

[0111] Then, the process returns to S112, where the reliability is calculated for each of the frequency spectra generated in the process of S118, for example.

[0112] 6A and 6B , taking into consideration that the heartbeat has a small displacement and is difficult to detect, the heartbeat Doppler sensor and the heartbeat measurement position are determined, and then the respiratory Doppler sensor and the respiratory measurement position are determined. Alternatively, the respiratory Doppler sensor and the respiratory measurement position may be determined first, and then the heartbeat Doppler sensor and the heartbeat measurement position may be determined.

[0113] Furthermore, when the position of the Doppler sensor 15 reaches a threshold value, the Doppler sensor control unit 30 may change the position of the Doppler sensor 15 to the initial position.

[0114] 6A and 6B , determining whether the calculated reliability satisfies the measurement condition and, if the calculated reliability does not satisfy the measurement condition, moving the Doppler sensor 15 to another candidate position may be repeated until the calculated reliability satisfies the measurement condition. Then, the candidate position whose calculated reliability satisfies the measurement condition may be determined as the measurement position.

[0115] In this embodiment, the reliability calculation unit 36 ​​may calculate the reliability for each of all the candidate positions, and the determination unit 38 may determine the candidate position with the highest calculated reliability as the measurement position.

[0116] For example, the reliability calculation unit 36 ​​may calculate the reliability in a round-robin manner for all combinations of the Doppler sensor 15, candidate positions, candidate directions, and candidate polarization directions.

[0117] For example, suppose there are six Doppler sensors 15, three candidate positions (a first height, a second height, and a third height), four candidate directions (a frontal direction, a direction 10 degrees downward from the frontal direction, a direction 20 degrees downward from the frontal direction, and a direction 30 degrees downward from the frontal direction), and two candidate polarization directions (a horizontal direction and a vertical direction). In this case, while performing control by the Doppler sensor control unit 30, the reliability calculation unit 36 ​​may sequentially calculate the reliability for all 144 (6 × 3 × 4 × 2) combinations.

[0118] For example, the Doppler sensor 15, candidate position, candidate direction, and candidate polarization direction in the combination with the highest calculated reliability may be determined as the measurement Doppler sensor, measurement position, measurement direction, and measurement polarization direction, respectively.

[0119] The Doppler sensor control unit 30 may control the measurement Doppler sensor to be positioned at the measurement position and emit microwaves whose polarization plane direction is the measurement polarization plane direction in the measurement direction. The biological information generation unit 40 may then start generating biological information using the measurement Doppler sensor.

[0120] In this case, the combination with the highest calculated reliability for each of the heartbeat and respiration may be determined.The Doppler sensor 15, candidate position, candidate direction, and candidate polarization direction for the combination with the highest reliability for the heartbeat may be determined as the heartbeat Doppler sensor, heartbeat measurement position, heartbeat measurement direction, and heartbeat measurement polarization direction, respectively.Furthermore, the Doppler sensor 15, candidate position, candidate direction, and candidate polarization direction for the combination with the highest reliability for respiration may be determined as the respiratory Doppler sensor, respiration measurement position, respiration measurement direction, and respiration measurement polarization direction, respectively.

[0121] Next, an example of the flow of processing for changing the measurement position, measurement direction, and measurement polarization plane direction will be described with reference to the flow chart shown in FIG.

[0122] In this processing example, each time biometric information of the subject is generated for each of the heart rate and respiratory rate, the change condition determination unit 44 determines whether the reliability of the latest biometric information satisfies a given change condition (S201).

[0123] Here, for example, if it is determined that the respiratory rate satisfies the respiratory measurement change condition (S201: Y), the Doppler sensor control unit 30 changes the respiratory measurement polarization plane direction of the respiratory Doppler sensor (S202).

[0124] Then, the change condition determination unit 44 determines again whether the respiration measurement change condition is satisfied for the respiratory Doppler sensor (S203).

[0125] If the respiration measurement change condition is not satisfied (S203: N), the process returns to S201.

[0126] If the respiration measurement change condition is met (S203: Y), the Doppler sensor control unit 30 initializes the respiration measurement polarization plane direction of the respiratory Doppler sensor (S204). In this processing example, for example, it is assumed that the horizontal direction is pre-defined as the initial value of the respiration measurement polarization plane direction. In this case, the respiration measurement polarization plane direction of the respiratory Doppler sensor is set to the horizontal direction.

[0127] Then, the Doppler sensor control unit 30 changes the respiration measurement direction of the respiratory Doppler sensor (S205). Here, for example, the respiration measurement direction is changed by 10 degrees so that the sensor faces the position of the subject estimated by the subject position estimation unit 50.

[0128] Then, the change condition determination unit 44 determines again whether the respiratory measurement change condition is satisfied for the respiratory Doppler sensor (S206).

[0129] If the respiration measurement change condition is not satisfied (S206: N), the process returns to S201.

[0130] If the respiration measurement change condition is met (S206: Y), the Doppler sensor control unit 30 determines whether the measurement direction has reached a threshold value (for example, a frontal direction or a direction 30 degrees downward from a frontal direction) (S207).

[0131] If the threshold value has not been reached (S207: N), the process returns to S205.

[0132] If the threshold value is reached (S207: Y), the Doppler sensor control unit 30 initializes the respiration measurement direction of the respiratory Doppler sensor (S208). In this processing example, for example, the front direction is assumed to be the default respiration measurement direction. In this case, the respiration measurement direction of the respiratory Doppler sensor is set to the front direction.

[0133] Then, the Doppler sensor control unit 30 changes the respiration measurement position of the respiratory Doppler sensor (S209). Here, for example, the height of the respiratory Doppler sensor may be changed upward by 5 centimeters.

[0134] Then, the change condition determination unit 44 determines again whether the respiration measurement change condition is satisfied for the respiratory Doppler sensor (S210).

[0135] If the respiration measurement change condition is not satisfied (S210: N), the process returns to S201.

[0136] If the respiration measurement change condition is met (S210: Y), the Doppler sensor control unit 30 determines whether the respiration measurement position has reached a threshold value (S211). For example, in this case, it is determined whether the respiration measurement position of the Doppler sensor 15 has reached a predetermined position.

[0137] If the threshold value has not been reached (S211: N), the process returns to S202.

[0138] If the threshold value is reached (S211: Y), the Doppler sensor control unit 30 initializes the respiration measurement position, respiration measurement direction, and respiration measurement polarization direction (S212), and returns to the process shown in S201. Here, for example, the respiration measurement position may be set to a predetermined initial position, the respiration measurement direction may be set to the front direction, and the respiration measurement polarization direction may be set to the horizontal direction.

[0139] In this processing example, in the processing shown in S212, the determination unit 38 may redetermine a respiratory Doppler sensor from among the four Doppler sensors 15 other than the respiratory Doppler sensor and the heart rate Doppler sensor, redetermine a respiratory measurement position from among candidate positions associated with the redetermined respiratory Doppler sensor, redetermine a respiratory measurement direction from among candidate directions associated with the redetermined respiratory Doppler sensor, and redetermine a respiratory measurement polarization direction from among candidate polarization directions associated with the redetermined respiratory Doppler sensor. The redetermining process of the respiratory Doppler sensor, respiratory measurement position, respiratory measurement direction, and respiratory measurement polarization direction may be, for example, the same as the determining process of the respiratory Doppler sensor, respiratory measurement position, respiratory measurement direction, and respiratory measurement polarization direction described above.

[0140] The Doppler sensor control unit 30 may then control the respiratory Doppler sensor to be positioned at the re-determined measurement position, and the respiratory Doppler sensor to emit microwaves in the re-determined measurement direction, with the polarization plane direction of the respiratory Doppler sensor being re-determined.The biological information generation unit 40 may then start generating the respiration rate using the respiratory Doppler sensor.

[0141] Alternatively, the reliability calculation unit 36 ​​may calculate the reliability of all combinations of the Doppler sensor 15, candidate position, candidate direction, and candidate polarization direction for the four Doppler sensors 15 in a brute force manner. Then, the determination unit 38 may redetermine the Doppler sensor 15, candidate position, candidate direction, and candidate polarization direction for the combination with the highest calculated reliability as the respiratory Doppler sensor, respiratory measurement position, respiratory measurement direction, and respiratory measurement polarization direction, respectively.

[0142] If the processing shown in S201 determines that the heart rate satisfies the heart rate measurement change condition, the same processing as described above may be executed to redetermine the heart rate Doppler sensor, heart rate measurement position, heart rate measurement direction, and heart rate measurement polarization plane direction.

[0143] In this embodiment, the measurement position of the Doppler sensor 15 is controllable, and biological information is generated based on Doppler data measured at a measurement position determined based on reliability. Therefore, according to this embodiment, biological information such as the respiratory rate and heart rate of the subject can be measured with high accuracy regardless of the position or posture of the subject.

[0144] In this embodiment, the ball screw 18 does not necessarily extend in the vertical direction, but may extend in the horizontal direction. The Doppler sensor 15 may be movable in a direction other than the vertical direction (for example, the horizontal direction). The Doppler sensor 15 may also be movable in both the vertical and horizontal directions. The Doppler sensor 15 may also be movable in any direction on a given plane.

[0145] In addition, in this embodiment, the Doppler sensor 15 may be movable along a given surface other than the headboard surface of the bed 16. For example, the ball screw 18 may be provided on the wall surface of the room in which the bed 16 is placed. Then, the Doppler sensor 15 may be movable along the wall surface of the room in which the bed 16 is placed.

[0146] The positions and number of the load sensors 14 are not limited to those shown in Fig. 1. Alternatively, an acceleration sensor may be provided on the mattress, and the body movement determination unit 48 may determine whether or not body movement is occurring based on the measurement results of the acceleration sensor.

[0147] Furthermore, the position and orientation of the Doppler sensor 15 are not limited to those described above. For example, the Doppler sensor 15 may be attached to the ceiling.

[0148] Furthermore, the number of Doppler sensors 15 included in the biological information detection system 1 is not limited to six. For example, the number of Doppler sensors 15 included in the biological information detection system 1 may be one.

[0149] Furthermore, the position of the Doppler sensor 15, the emission direction of the microwaves, and the direction of the emission polarization plane of the microwaves do not need to be automatically controlled according to program instructions. For example, a person such as an operator may manually control the position of the Doppler sensor 15, the emission direction of the microwaves, and the direction of the emission polarization plane of the microwaves by inputting operations into the computer 10.

Claims

1. A biometric information detection system comprising: a Doppler sensor control means for controlling the position of a Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; a reliability calculation means for calculating, for at least one of the candidate positions, the reliability of biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor placed at the candidate position; a measurement position determination means for determining a measurement position from among the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and a biometric information generation means for repeatedly performing a process of generating biometric information of a subject based on the Doppler data indicating the measurement results by the Doppler sensor placed at the measurement position.

2. A biological information detection system as defined in claim 1, further comprising a measurement condition determination means for determining whether the calculated reliability satisfies a given measurement condition, wherein the measurement condition determination means determines whether the calculated reliability satisfies the measurement condition, and the Doppler sensor control means moves the Doppler sensor to another candidate position if the calculated reliability does not satisfy the measurement condition, repeated until the calculated reliability satisfies the measurement condition, and the measurement position determination means determines the candidate position where the calculated reliability satisfies the measurement condition as the measurement position.

3. A biometric information detection system as described in claim 1, wherein the reliability calculation means calculates the reliability for each of all of the candidate positions, and the measurement position determination means determines the candidate position with the highest calculated reliability as the measurement position.

4. A biometric information detection system as described in claim 1, further comprising a change condition determination means for determining whether the reliability of the latest generated biometric information satisfies a given change condition when the process of generating the biometric information of the subject is being repeatedly executed, and wherein the Doppler sensor control means changes the position of the Doppler sensor in response to the reliability of the latest biometric information satisfying the change condition.

5. A biometric information detection system as described in claim 1, wherein for each of a plurality of Doppler sensors, a plurality of candidate positions associated with that Doppler sensor are predetermined; the Doppler sensor control means controls the position of each of the plurality of Doppler sensors so that the Doppler sensor is placed at one of the plurality of candidate positions associated with that Doppler sensor; the measurement position determination means determines a measurement Doppler sensor from among the plurality of Doppler sensors and determines the measurement position from among the plurality of candidate positions associated with that measurement Doppler sensor; and the biometric information generation means repeatedly executes a process of generating the biometric information based on Doppler data indicating the measurement results by the measurement Doppler sensor placed at the measurement position.

6. A biometric information detection system as defined in claim 5, further comprising a change condition determination means for determining whether the reliability of the latest generated biometric information satisfies a given change condition when the process of generating the biometric information of the subject is being repeatedly executed, wherein the measurement position determination means, when the reliability of the latest biometric information satisfies the change condition, redetermines the measurement Doppler sensor from among the plurality of Doppler sensors and redetermines the measurement position from among the plurality of candidate positions associated with the measurement Doppler sensor, and after the measurement Doppler sensor and the measurement position have been redetermined, the biometric information generation means repeatedly executes the process of generating the biometric information based on Doppler data indicating the measurement results by the redetermined measurement Doppler sensor placed at the redetermined measurement position.

7. A biological information detection system as defined in claim 6, wherein the measurement position determination means determines a heart rate Doppler sensor from among the plurality of Doppler sensors and determines a heart rate measurement position from among the plurality of candidate positions associated with the heart rate Doppler sensor; the measurement position determination means determines a respiratory Doppler sensor from among the plurality of Doppler sensors and determines a respiratory measurement position from among the plurality of candidate positions associated with the respiratory Doppler sensor; the respiratory Doppler sensor is a Doppler sensor different from the heart rate Doppler sensor; the biological information generation means repeatedly executes a process of generating a heart rate of the person being measured based on Doppler data indicating a measurement result by the heart rate Doppler sensor placed at the heart rate measurement position; and the biological information generation means repeatedly executes a process of generating a respiratory rate of the person being measured based on Doppler data indicating a measurement result by the respiratory Doppler sensor placed at the respiratory measurement position.

8. A biological information detection system according to claim 7, further comprising: a heartbeat measurement change condition determination means for determining whether the reliability of the latest generated heart rate satisfies a given heartbeat measurement change condition; and a respiration measurement change condition determination means for determining whether the reliability of the latest generated respiration rate satisfies a given respiration measurement change condition, wherein the measurement position determination means, when the reliability of the latest heart rate satisfies the heartbeat measurement change condition, redetermines the heartbeat Doppler sensor from among Doppler sensors other than the respiratory Doppler sensor, and redetermines the heartbeat measurement position from among the plurality of candidate positions associated with the heartbeat Doppler sensor, and when the reliability of the latest respiration rate satisfies the respiration measurement change condition, the measurement position determination means, when the reliability of the latest respiration rate satisfies the respiration measurement change condition, redetermines the respiratory Doppler sensor from among Doppler sensors other than the heartbeat Doppler sensor, and redetermines the respiration measurement position from among the plurality of candidate positions associated with the respiratory Doppler sensor. a biometric information generating means for repeatedly executing a process of generating the heart rate based on Doppler data indicating a measurement result by the re-determined heart rate Doppler sensor that is placed at the re-determined heart rate measurement position after the heart rate Doppler sensor and the heart rate measurement position are redetermined, and a biometric information generating means for repeatedly executing a process of generating the respiration rate based on Doppler data indicating a measurement result by the re-determined respiratory Doppler sensor that is placed at the re-determined respiration measurement position after the respiratory Doppler sensor and the respiration measurement position are redetermined.

9. A bioinformation detection system as described in claim 5, further comprising a Doppler sensor selection means for selecting a plurality of the Doppler sensors based on the position of the subject, and wherein the measurement position determination means determines the measurement Doppler sensor from the selected plurality of Doppler sensors.

10. A biometric information detection system as described in claim 1, wherein the Doppler sensor control means controls the orientation of the Doppler sensor so that one of a plurality of predetermined candidate directions becomes the emission direction of the microwave; the reliability calculation means calculates, for at least one of the candidate directions, the reliability of the biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor emitting microwaves in the candidate direction; and the system further includes measurement direction determination means that determines a measurement direction from among the plurality of candidate directions based on the reliability calculated for at least one of the candidate directions; and the biometric information generation means generates biometric information of the subject based on the Doppler data indicating the measurement results by the Doppler sensor, which is controlled so that the emission direction of the microwave becomes the measurement direction.

11. A biometric information detection system as described in claim 1, wherein the Doppler sensor control means controls the Doppler sensor so that one of a plurality of predetermined candidate polarization plane directions becomes the emission polarization plane direction of the microwave; the reliability calculation means calculates, for at least one of the candidate polarization plane directions, the reliability of the biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor that emits microwaves with the candidate polarization plane direction as the emission polarization plane direction; and the biometric information generation means further includes a measured polarization plane direction determination means that determines a measured polarization plane direction from among the plurality of candidate polarization plane directions based on the reliability calculated for at least one of the candidate polarization plane directions; and the biometric information detection system generates biometric information of the subject based on Doppler data indicating the measurement results by the Doppler sensor that is controlled so that the measured polarization plane direction becomes the emission polarization plane direction of the microwave.

12. A biometric information detection system as described in claim 1, further comprising a body movement determination means for determining whether or not the subject is moving, wherein the biometric information generation means suppresses the generation of the biometric information in response to determining that the subject is moving, and resumes the generation of the biometric information in response to determining that the subject is not moving while the generation of the biometric information is suppressed.

13. A biological information detection system as defined in claim 1, further comprising frequency spectrum generation means for generating a frequency spectrum based on the Doppler data, wherein the reliability calculation means calculates the amplitude ratio between the largest peak and the second largest peak contained in the frequency spectrum as the reliability.

14. A method for detecting biological information, comprising: a step of controlling the position of a Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; a step of calculating, for at least one of the candidate positions, the reliability of biological information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor placed at the candidate position; a step of determining a measurement position from among the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and a step of repeatedly performing a process of generating biological information of a subject based on the Doppler data indicating the measurement results by the Doppler sensor placed at the measurement position.

15. A program for causing a computer to execute the steps of: controlling the position of a Doppler sensor so that the Doppler sensor is placed at one of a plurality of predetermined candidate positions; calculating, for at least one of the candidate positions, the reliability of biometric information obtained from the Doppler data based on Doppler data indicating the measurement results by the Doppler sensor placed at the candidate position; determining a measurement position from among the plurality of candidate positions based on the reliability calculated for at least one of the candidate positions; and repeatedly executing a process for generating biometric information of a subject based on Doppler data indicating the measurement results by the Doppler sensor placed at the measurement position.

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