Electronic devices, systems, control methods and programs

Abstract

The aim is to reduce power consumption when determining sleep status using a light-emitting unit. [Solution] The control unit of the electronic device determines whether the subject has fallen asleep based on acceleration data, which is biological information acquired without emitting light from the light-emitting unit. If it determines that the subject has fallen asleep, it starts emitting light from the LED and starts determining the sleep state based on the detection result of the PPG sensor.

Description

Technical Field

[0001] The present invention relates to an electronic device, a system, a control method, and a program.

Background Art

[0002] Conventionally, a technique for acquiring a biological signal and determining a sleep state based on the acquired biological signal has been known (see, for example, Patent Document 1). As the determination of the sleep state based on the biological signal, for example, there is one using a photoplethysmography (PPG) sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the determination of the sleep state using a PPG sensor, since it is necessary to turn on a light-emitting part such as an LED (Light Emitting Diode) until it is determined that the subject has entered the sleep state, there is a problem that the power consumption is large.

[0005] An object of the present invention is to reduce the power consumption in the determination of the sleep state using a light-emitting part.

Means for Solving the Problems

[0006] In order to solve the above problems, an electronic device according to the present invention is an electronic device that controls a light-emitting part used for determining the sleep state of a subject, and determines whether or not the subject has fallen asleep based on the biological information of the subject acquired without causing the light-emitting part to emit light, and when it is determined that the subject has fallen asleep, includes a control part that controls the light-emitting part to start emitting light for determining the sleep state.

Effects of the Invention

[0007] According to the present invention, it is possible to reduce power consumption when determining sleep states using a light-emitting unit. [Brief explanation of the drawing]

[0008] [Figure 1] Block diagram showing examples of electronic device configurations. [Figure 2] This figure shows the relationship between changes in sleep stages and changes in the acceleration spectrogram. [Figure 3] (a) is a graph extracted from the spectrogram at time A in Figure 2, (b) is a graph extracted from the spectrogram at time B in Figure 2, (c) is a graph extracted from the spectrogram at time D in Figure 2, and (d) is a graph extracted from the spectrogram at time E in Figure 2. [Figure 4] This figure shows the maximum and minimum power values ​​in the 0.2Hz to 0.5Hz range. [Figure 5] This flowchart shows the flow of the sleep onset determination process A performed by the control unit in Figure 1 in the first embodiment. [Figure 6] In the second embodiment, this is a flowchart showing the flow of the sleep onset determination process B performed by the control unit in Figure 1. [Figure 7] In the third embodiment, this is a flowchart showing the flow of the awakening determination process performed by the control unit in Figure 1. [Figure 8] This is a diagram showing an example configuration of a sleep analysis system. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described below with reference to the drawings. However, the embodiments described below are subject to various technically preferred limitations for carrying out the present invention. Therefore, the technical scope of the present invention is not limited to the embodiments and illustrated examples below.

[0010] (First embodiment) First, an example of the configuration of the electronic device 1 in the first embodiment of the present invention will be described. The electronic device 1 is a wearable device worn on the arm of a user (subject). The electronic device 1 is equipped with an information processing function for processing information related to sleep and a light emission control function for controlling the light emission unit used for information processing. As shown in Figure 1, it is composed of a control unit 11, a storage unit 12, an operation unit 13, a display unit 14, a sensor unit 15, a timing unit 16, a communication unit 17, and a battery 18, and each unit is connected via a bus 19.

[0011] The control unit 11 is a processor equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), etc., which controls each part of the electronic device 1. The CPU of the control unit 11 reads a specified program from the system program and various processing programs stored in the memory unit 12, loads it into RAM, and executes various processes in cooperation with the loaded program. The control unit 11 functions as a sleep state determination unit, a sleep onset determination unit, and a control unit according to the present invention.

[0012] The control unit 11 may have multiple CPUs. The multiple CPUs may then execute the multiple processes performed by the control unit 11 in this embodiment. In this case, the multiple CPUs may be involved in common processes, or they may independently execute different processes in parallel.

[0013] The storage unit 12 is composed of non-volatile memory or the like, and stores programs, data, etc. The storage unit 12 is not limited to being built into the electronic device 1, but may also include an external recording medium that can be attached to or removed from the electronic device 1. The storage unit 12 stores, for example, the system program of the electronic device 1, programs for executing various processes including the sleep onset determination process A described later, etc.

[0014] The operation unit 13 detects operations by the user and outputs a signal corresponding to the detected operation to the control unit 11. For example, the operation unit 13 includes push button switches and the like, and outputs signals corresponding to these operations to the control unit 11. Further, the operation unit 13 may include a touch panel.

[0015] The display unit 14 is constituted by a display device such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode), for example, and performs display based on the control operation of the control unit 11.

[0016] The sensor unit 15 is a sensor that acquires biological information. The sensor unit 15 is configured to include a PPG sensor 151 (optical sensor) and an acceleration sensor 152 (biological information acquisition unit). The PPG sensor 151 includes an LED (light emitting unit) 151a and a light receiving unit 151b, irradiates light on the skin with the LED 151a, detects the reflected light with the light receiving unit 151b, and outputs the detection result to the control unit 11. The acceleration sensor 152 detects the acceleration in the three-axis directions as the body movement of the user and outputs the detected value (acceleration data) to the control unit 11.

[0017] The timekeeping unit 16 includes an oscillation circuit, a frequency division circuit, a timekeeping circuit, etc., keeps track of the current date and time, and outputs the result of the timekeeping to the control unit 11.

[0018] The communication unit 17 performs communication control for communicating with an external device.

[0019] The battery 18 is a primary battery or a rechargeable secondary battery, and supplies power to each part of the electronic device 1.

[0020] Next, the operation of the electronic device 1 in this embodiment will be described. In conventional electronic devices that determine the user's sleep state using detection results from a PPG sensor, it was necessary to keep the LED of the PPG sensor constantly lit and continuously acquire the detection results of the PPG sensor while the sleep stage analysis mode, which is a mode for determining the sleep state, was set to ON, because it was unknown when the user would fall asleep. However, keeping the LED constantly lit consumes a lot of power. Therefore, in the electronic device 1 in this embodiment, with the LED 151a turned off, sleep onset is determined using an acceleration sensor 152 that acquires the user's biometric information without emitting light from the LED or other light-emitting parts. When it is determined that the user has fallen asleep, the LED 151a is turned on and the system switches to determining the sleep state based on the detection results of the PPG sensor 151.

[0021] Here, we will explain the changes in sleep stages and the changes in the acceleration spectrogram. The upper part of Figure 2 shows the results of determining a sleep stage for a subject by measuring the electroencephalogram (EEG), which is the main factor in determining sleep stages, using an electroencephalograph (EEG). Here, sleep stages are defined as four stages: wake, REM sleep, light sleep, and deep sleep. The lower part of Figure 2 shows the spectrogram of the low-frequency band (0Hz to 1.5Hz) obtained by calculating the L2 norm of the XYZ 3-axis acceleration (acceleration data) acquired at a sampling frequency of 32Hz from an acceleration sensor attached to the arm of the same subject during the same period as the upper part, and then performing a Fast Fourier Transform (FFT) with an analysis window width of 4096 samples. In the spectrogram in the lower part of Figure 2, the closer to black, the lower the power, and the closer to white, the higher the power.

[0022] The upper part of Figure 2 shows that the light sleep phase (light) begins at time C (around 23:15) and progresses to the deepest sleep phase (deep) around midnight. Then, REM sleep occurs around 0:50, and this cycle is repeated several times before waking up at time F (around 6:30). The spectrogram in the lower part of Figure 2 shows that the power of each frequency band decreases from position B in the figure, just before time C when the light sleep phase (light) begins.

[0023] Figures 3(a) to 3(d) are excerpts of the spectrograms from Figure 2 at time points A, B, D, and E, respectively, with the horizontal axis representing frequency and the vertical axis representing power. As shown in Figure 3(a), at time A, just before falling asleep, the power is high across all frequency bands. This is because it is just before drowsiness begins and there are small movements of the arms.

[0024] At time B, just before falling asleep, the power values ​​are generally low, as shown in Figure 3(b). This is because the arm movement has almost stopped as the person begins to doze off. On the other hand, the power values ​​around 0.4 Hz and its harmonic components are slightly higher than those of other frequency bands. 0.4 Hz corresponds to a period of 2.5 seconds, which corresponds to the respiratory cycle, indicating that slight body movement components due to breathing are being detected by the accelerometer attached to the arm through the bedding and the human body. The fact that the slight body movement components due to breathing have become apparent as the arm movement has almost stopped. Normally, the respiratory component during sleep has a period of about 5 seconds (0.2 Hz) to 2 seconds (0.5 Hz), and it is thought that if the presence or absence of a peak in this frequency band can be distinguished, it will be possible to determine whether or not the person has begun to doze off, i.e., to determine when they have fallen asleep.

[0025] At time D in the light sleep (Light), as shown in Figure 3(c), the power values ​​of the 0.3Hz frequency and its harmonics are slightly higher. 0.3Hz corresponds to a period of 3.3 seconds, indicating that the respiratory cycle is slightly slower compared to time B. This suggests that the individual has progressed from a drowsy period to full sleep, and the respiratory cycle has lengthened.

[0026] At awakening time E, as shown in Figure 3(d), the power value is almost the same as at time A, and is slightly higher than at time A across all frequencies. The large power output is due to the start of operation accompanying awakening.

[0027] As described above, if a peak in the 0.2Hz to 0.5Hz range of the spectrogram can be detected at each time point, sleep onset can be determined. However, the base value in this frequency range contains noise due to the conditions shown below, making it difficult to detect the presence or absence of peaks using simple thresholding or differentiation (first-order, second-order). • Conditions of the sleeping environment (other vibrations entering the bedroom, etc.) • Condition of bedding • The state in which the device is attached to the arm • Individual differences in the degree of body movement due to breathing

[0028] Therefore, in the first embodiment, when the sleep stage analysis mode is set to ON by the operation of the operation unit 13, the control unit 11 of the electronic device 1 turns off the LED 151a and starts the sleep onset determination process A shown in Figure 5. As shown in Figure 4, it observes the ratio of the max (corresponding to the peak) power value and the min (corresponding to the base) power value in the 0.2Hz to 0.5Hz band, and when a sufficiently large ratio is obtained, it is determined that a peak due to respiration has been detected, i.e., that the user has fallen asleep. If the control unit 11 determines that the user has fallen asleep for a predetermined number of consecutive times, it determines that the user has fallen asleep. When it is determined that the user has fallen asleep, the control unit 11 starts the LED 151a to emit light and starts sensing with the PPG 151. The sleep onset determination process A will be described below with reference to Figure 5.

[0029] As shown in Figure 5, first, the control unit 11 initializes the variable count to 0 (step S1). At this time, the user is wearing the electronic device 1 on their wrist or elsewhere, and the LED 151a is turned off. The variable count is used to count the number of times that the user has been continuously judged to be in a state of temporary sleep.

[0030] Next, the control unit 11 starts the process of having the acceleration sensor 152 measure at a sampling frequency of approximately 20 Hz to acquire acceleration data, and storing the acquired acceleration data in the LIFO (Last In, First Out) acceleration memory (RAM) (step S2). Measurement and storage of acceleration data by the acceleration sensor 152 continues until it is determined that count is equal to or greater than a predetermined threshold TH2. The sampling frequency is not particularly limited.

[0031] Next, the control unit 11 determines whether or not n seconds' worth of acceleration data (where n is a positive number) has been stored in the acceleration memory (step S3). If it determines that n seconds' worth of acceleration data has not been stored in the acceleration memory (step S3; NO), the control unit 11 returns to step S3.

[0032] If the control unit 11 determines that n seconds of acceleration data has been stored in the acceleration memory (step S3; YES), it acquires the acceleration data for the most recent n seconds, performs a Fourier transform (FFT), and calculates the power spectrum (step S4). For example, the control unit 11 calculates the L2 norm of the XYZ 3-axis acceleration (acceleration data) acquired at a sampling frequency of 32 Hz, and then performs an FFT with an analysis window width of 4096 samples. Note that the sampling frequency and analysis window width are not limited to the above; for example, if a slight decrease in bed entry detection accuracy is acceptable, a sampling frequency of 8 Hz and an analysis window width of 1024 can be used.

[0033] Next, the control unit 11 obtains the maximum and minimum power values ​​(max) and (min) in a specific frequency band (0.2Hz to 0.5Hz band) corresponding to the breathing frequency during sleep (step S5). Next, the control unit 11 determines whether max / min exceeds a predetermined threshold TH1 (first threshold) (step S6). If it determines that max / min exceeds the predetermined threshold TH1, the control unit 11 determines that the user has fallen asleep. It is also conceivable that if max / min exceeds the predetermined threshold TH1, the user could immediately determine that they have fallen asleep. However, in this embodiment, in order to determine that the user has fallen asleep with accuracy, the threshold TH1 is set lower, and the user is determined to have fallen asleep only after max / min has exceeded the threshold TH1 for a predetermined number of consecutive times (TH2 times).

[0034] If max / min exceeds the threshold TH1 (step S6; YES), the control unit 11 determines that it is a temporary sleep state, increments count (step S7), and proceeds to step S9. If max / min does not exceed the threshold TH1 (step S6; NO), the control unit 11 sets count to 0 (step S8) and proceeds to step S9.

[0035] In step S9, the control unit 11 determines whether the count has reached TH2 a predetermined number of times (step S9). If it determines that the count has not reached TH2 a predetermined number of times (step S9; NO), the control unit 11 returns to step S3.

[0036] If the control unit 11 determines that Count has reached a predetermined number of TH2 counts (step S9; YES), it determines that the user has fallen asleep (step S10), illuminates the LED 151a to start detection by the PPG sensor 151, starts the sleep state determination process based on the detection result of the PPG sensor 151 (step S11), and ends the sleep determination process A.

[0037] The control unit 11 calculates the Peak-to-peak Interval (PPI) from the waveform of the detected value output by the PPG sensor 151 and outputs it to the sleep state determination process. The sleep state determination process determines the sleep state (sleep stage) based on the PPI. The method for determining the sleep state based on the PPI is well known, so its explanation is omitted.

[0038] If the control unit 11 determines that the user has woken up based on the sleep state determination process using the detection results of the PPG sensor 151, it turns off the LED 151a and restarts the sleep onset determination process A described above. While the sleep stage analysis mode is ON, the control unit 11 repeats the process of transitioning to the sleep state determination process based on the detection results of the PPG sensor 151 if it determines that the user has fallen asleep in the sleep onset determination process A described above, and transitioning back to the sleep onset determination process A if it determines that the user has woken up. Therefore, since the LED 151a is not illuminated until the user falls asleep, power consumption during sleep state determination can be reduced.

[0039] (Second embodiment) The second embodiment of the present invention will now be described. As shown in Figure 2, when comparing the changes in sleep stages with the changes in the acceleration spectrogram, it can be seen that when the sleep stage is wakeful, the power values ​​of the acceleration spectrogram are high across all frequency bands, and after falling asleep, the power values ​​of the acceleration spectrogram are low across all frequency bands. This is thought to be because there is a lot of movement when awake, but during sleep, only movement due to breathing is detected. Therefore, in the second embodiment, an example will be described in which it is determined whether or not a person has fallen asleep based on whether or not the cumulative value of the power values ​​across the entire frequency range remains below a predetermined threshold TH3 (second threshold) for a certain period of time.

[0040] The configuration of the electronic device 1 in the second embodiment is the same as that described in the first embodiment, so the explanation will be used as a reference, and the sleep onset determination process B, which is performed by the control unit 11 in the second embodiment, will be described below with reference to Figure 6. The sleep onset determination process B is a process that is performed in place of the sleep onset determination process A in the first embodiment.

[0041] As shown in Figure 6, in the sleep onset determination process B, the control unit 11 first executes the processes in steps S21 to S24. The processes in steps S21 to S24 are the same as steps S1 to S4 of the sleep onset determination process A, so the explanation will be based on that.

[0042] In step S25, the control unit 11 calculates the integrated value of the power values ​​across the entire frequency range of the power spectrum for n seconds (step S25). The control unit 11 then determines whether the calculated integrated value is below a predetermined threshold TH3 (step S26). If it is determined that the calculated integrated value is below the predetermined threshold TH3 (step S26; YES), the control unit 11 determines that the user has fallen asleep and increments count (step S27), then proceeds to step S9. If it is determined that the calculated integrated value is not below the predetermined threshold TH3 (step S26; NO), the control unit 11 sets count to 0 (step S28), then proceeds to step S29.

[0043] In step S29, the control unit 11 determines whether the count has reached TH2 a predetermined number of times (step S29). If it determines that the count has not reached TH2 a predetermined number of times (step S29; NO), the control unit 11 returns to step S23.

[0044] If the control unit determines that Count has reached a predetermined number of TH2 counts (step S29; YES), the control unit determines that the user has fallen asleep (step S30), illuminates the LED 151a which had been off since step S21, starts detection by the PPG sensor 151, starts the sleep state determination process based on the detection result of the PPG sensor 151 (step S31), and ends the sleep determination process B.

[0045] If the control unit 11 determines that the user has woken up based on the sleep state determination process using the detection results of the PPG sensor 151, it turns off the LED 151a and restarts the sleep onset determination process B described above. While the sleep stage analysis mode is ON, the control unit 11 repeats the process of transitioning to the sleep state determination process based on the detection results of the PPG sensor 151 if the sleep onset determination process B determines that the user has fallen asleep, and transitioning back to the sleep onset determination process B if the user is determined to have woken up. Therefore, since the LED 151a is not illuminated until the user falls asleep, power consumption during sleep state determination can be reduced.

[0046] (Third embodiment) A third embodiment of the present invention will now be described. In the first and second embodiments, while the sleep stage analysis mode is ON, the control unit 11, when it determines that the user has fallen asleep in the sleep onset determination process A or sleep onset determination process B described above, proceeds to the sleep state determination process based on the detection result of the PPG sensor 151, and when it determines in the sleep state determination process that the user has woken up, it restarts the sleep onset determination process, and repeats this operation. On the other hand, after proceeding to the sleep state determination process, the control unit 11 may execute the wakefulness determination process shown in Figure 7.

[0047] As explained in the second embodiment, when the sleep stage is wakeful, the power values ​​of the acceleration spectrogram are high across all frequency bands, and after falling asleep, the power values ​​of the acceleration spectrogram are low across all frequency bands. Therefore, in the wakefulness determination process, it is determined whether the user has woken up based on whether the cumulative value of the power values ​​across the entire frequency range exceeds a predetermined threshold TH4 (TH4≧TH3). The wakefulness determination process will be explained below with reference to Figure 7.

[0048] In the awakening determination process, the control unit 11 first executes the processes in steps S41 to S44. The processes in steps S41 to S44 are the same as steps S1 to S4 of the sleep onset determination process A, so the explanation will be based on that. Note that in the awakening determination process, count is a variable that stores the number of times the patient was determined to be temporarily awake.

[0049] In step S45, the control unit 11 calculates the integrated value of the power values ​​over the entire frequency range of the power spectrum for n seconds (step S45). The control unit 11 then determines whether the calculated integrated value exceeds a predetermined threshold TH4 (step S46). If it determines that the calculated integrated value exceeds the predetermined threshold TH4 (step S46; YES), the control unit 11 determines that it is a false awakening, increments count (step S47), and proceeds to step S49. If it determines that the calculated integrated value does not exceed the predetermined threshold TH4 (step S46; NO), the control unit 11 sets count to 0 (step S48) and proceeds to step S49.

[0050] In step S49, the control unit 11 determines whether the count has reached TH2 a predetermined number of times (step S49). If it determines that the count has not reached TH2 a predetermined number of times (step S49; NO), the control unit 11 returns to step S43.

[0051] If the control unit 11 determines that Count has reached TH2 a predetermined number of times (step S49; YES), it determines that the user has woken up (step S50), turns off the LED 151a which had been lit to determine the sleep stage because the user had been asleep until immediately before, starts the sleep onset determination process (sleep onset determination process A or sleep onset determination process B) (step S51), and ends the wake-up determination process.

[0052] Thus, the arousal determination process can determine whether the user is awake or not based on acceleration data. In the second and third embodiments, the determination of whether the subject has fallen asleep or woken up is made based on the integrated value of the power values ​​across the entire frequency range of the calculated power spectrum, but the frequency range to which the integrated value is calculated does not necessarily have to be the entire frequency range.

[0053] As explained above, the control unit 11 of the electronic device 1 determines whether the user (subject) has fallen asleep based on the acceleration data measured by the acceleration sensor 152. If it determines that the subject has fallen asleep, it starts the LED 151a to emit light and starts determining the sleep state based on the detection result of the PPG sensor 151. Therefore, since the LED 151a does not emit light until the user falls asleep, power consumption during sleep state determination can be reduced.

[0054] Furthermore, the control unit 11 acquires acceleration data indicating the subject's movement as biological information of the subject, calculates a power spectrum from the acquired acceleration data, and determines whether or not the subject has fallen asleep based on the power spectrum. For example, the control unit 11 repeatedly acquires acceleration data to calculate the power spectrum, calculates the ratio of the maximum and minimum power values ​​in a specific frequency band related to the respiratory component during sleep, and determines that the subject has fallen asleep if the ratio exceeds the threshold TH1 for a predetermined number of consecutive times. Therefore, it is possible to accurately determine whether the subject has fallen asleep without illuminating the LED 151a.

[0055] Furthermore, the control unit 11 repeatedly acquires acceleration data from the acceleration sensor 152 to calculate the power spectrum, calculates the cumulative value of the calculated power values, and determines that the subject has fallen asleep if the cumulative value falls below the second threshold for a predetermined number of consecutive times. Therefore, it is possible to accurately determine when the subject has fallen asleep without illuminating the LED 151a.

[0056] Furthermore, since the acceleration sensor 152, which serves as a biological information acquisition unit, is provided in the electronic device 1, the electronic device 1 alone can determine when a subject has fallen asleep.

[0057] Furthermore, when the control unit 11 determines that the subject has transitioned from sleep to wakefulness based on the detection results of the PPG sensor 151, it controls the LED 151a, which was emitting light, to turn off and restarts the process of determining whether or not the subject has fallen asleep. Therefore, if the subject wakes up from sleep, the system automatically switches to sleep onset determination without using the LED 151a, thus reducing power consumption during sleep state determination.

[0058] Furthermore, when the control unit 11 determines that the subject has fallen asleep, it starts a process to determine whether the subject has transitioned from sleep to wakefulness based on acceleration data from the acceleration sensor 152. If it determines that the subject has transitioned to wakefulness, it turns off the lit LED 151a and restarts the process of determining whether the subject has fallen asleep. Therefore, when the subject wakes up from sleep, the system automatically switches to sleep detection without using the LED 151a, thus reducing power consumption in sleep state detection.

[0059] The descriptions in the above embodiments are merely preferred examples of embodiments relating to the electronic device, sleep state determination method, and program of the present invention, and are not limited thereto.

[0060] For example, in the above embodiment, the electronic device 1 is equipped with an acceleration sensor 151 as a biological information acquisition unit, and the control unit 11 of the electronic device 1 has the functions of the sleep onset determination unit, sleep state determination unit, and control unit of the present invention. As a modified example, as shown in Figure 8, the electronic device 1 is connected to the electronic device 2 to constitute a sleep state determination system, and some or all of the functions of the sleep onset determination unit, sleep state determination unit, and control unit of the present invention may be performed by the electronic device 2 instead of the electronic device 1. That is, the sleep onset determination unit, sleep state determination unit, and control unit of the present invention may be provided in a device outside the electronic device 1 which is equipped with a sensor unit 15 including a biological information acquisition unit. As the electronic device 2, for example, a smartphone, a tablet PC, or a PC (Personal Computer) can be applied. Furthermore, a first electronic device equipped with a light-emitting unit used for processing information related to sleep, a second electronic device that processes information related to sleep, such as sleep state determination, and a third electronic device that controls the light-emitting unit of the first electronic device based on the sleep state determination result of the second electronic device may be separate entities.

[0061] For example, when the sleep stage analysis mode is set to ON, electronic device 2 executes the sleep onset determination process described above, receives acceleration data as biometric information from electronic device 1, and determines when the user has fallen asleep. If it determines that the user has fallen asleep, electronic device 2 transmits this information to electronic device 1, whose LED 151a is off, and electronic device 1, upon receiving the information, starts sensing by illuminating the LED 151a using the PPG sensor 151a and executes the sleep state determination process. Alternatively, electronic device 2 may acquire the detection result of the PPG sensor 151a or PPI data from electronic device 1 and execute the sleep state determination process. This further reduces the power consumption of electronic device 1.

[0062] Furthermore, although the above embodiment was described using the case where the biological information acquisition unit is an acceleration sensor 152 as an example, the biological information acquisition unit is not limited to an acceleration sensor as long as it does not have a light-emitting part such as an LED. For example, a sensor that detects pressure changes may be used to acquire body vibration as biological information, and biological information may be acquired based on the acquired body vibration. Alternatively, biological information may be acquired by a load sensor based on the change in the user's center of gravity position (body movement). In addition, by providing a microphone instead of a pressure sensor, biological information may be acquired based on the sound picked up by the microphone. In addition, biological information may be acquired based on the displacement of the body or bedding using microwaves or laser speckles. The sensor for acquiring biological information may be provided in the electronic device 1 worn by the user, or it may be provided in bedding such as a bed. Note that the light-emitting part is not limited to an LED, and may be a discharge tube or light bulb as long as it can be housed in the electronic device 1.

[0063] Furthermore, although the above embodiment was described using the example of an electronic device 1 being a wearable device attached to the user's (subject's) arm, the electronic device 1 may also be mounted on the ear, fingertip, or ankle, where biometric information such as pulse rate can be easily acquired.

[0064] Furthermore, while the above description discloses examples using semiconductor memory, HDDs, etc., as computer-readable media for the program according to the present invention, the invention is not limited to these examples. Other computer-readable media include portable recording media such as CD-ROMs. Carrier waves can also be used as a medium for providing data for the program according to the present invention via a communication line.

[0065] Although embodiments and modifications of the present invention have been described above, the scope of the present invention is not limited to the embodiments and modifications described above, but includes the scope of the invention as described in the claims and its equivalents. [Explanation of Symbols]

[0066] 1 Electronic device, 11 Control unit, 15 Sensor unit, 151 PPG sensor, 151a LED, 151b Light receiving unit, 152 Acceleration sensor

Claims

1. An electronic device that controls a light-emitting part used to determine the sleep state of a subject, Based on the subject's biological information acquired without emitting light from the light-emitting unit, it is determined whether or not the subject has fallen asleep. When it is determined that the subject has fallen asleep, the system controls the light-emitting unit to start emitting light in order to determine the sleep state. An electronic device equipped with a control unit.

2. The control unit, The system acquires acceleration data indicating the subject's movement as biological information of the subject, calculates a power spectrum from the acquired acceleration data, and determines whether or not the subject has fallen asleep based on the power spectrum. The electronic device according to claim 1.

3. The control unit, The acceleration data is repeatedly acquired to calculate the power spectrum, the ratio of the maximum and minimum power values ​​in a specific frequency band related to respiratory components during sleep is calculated, and if it is determined that the ratio exceeds a first threshold for a predetermined number of consecutive times, it is determined that the subject has fallen asleep. The electronic device according to claim 2.

4. The control unit, The acceleration data is repeatedly acquired to calculate the power spectrum, the cumulative value of the calculated power values ​​is calculated, and if it is determined that the cumulative value falls below the second threshold for a predetermined number of consecutive times, it is determined that the subject has fallen asleep. The electronic device according to claim 2.

5. The system includes a biological information acquisition unit that acquires the biological information of the subject. The electronic device according to claim 1.

6. The control unit, If the sleep state is determined based on the detection results of the optical sensor, and it is determined that the subject has transitioned from sleep to wakefulness, the light-emitting part that was emitting light is controlled to turn off, and the process of determining whether or not the subject has fallen asleep is restarted. The electronic device according to claim 1.

7. The control unit, When it is determined that the subject has fallen asleep, the system starts a process to determine whether the subject has transitioned from sleep to wakefulness based on the subject's biological information acquired without emitting light from the light-emitting unit. When it is determined that the subject has transitioned to wakefulness, the system turns off the light-emitting unit that was emitting light and restarts the process to determine whether the subject has fallen asleep. The electronic device according to claim 1.

8. A sleep state determination unit that uses the light emitted from the light-emitting part to determine the sleep state of the subject, A biological information acquisition unit that acquires the subject's biological information without emitting light from the light-emitting unit, A sleep onset determination unit determines whether or not the subject has fallen asleep based on the subject's biological information acquired by the biological information acquisition unit, When it is determined that the subject has fallen asleep, the control unit causes the light-emitting unit to start emitting light in order to have the sleep state determination unit determine the sleep state, A system equipped with these features.

9. A control method for controlling the emission of light from a light-emitting part used to determine the sleep state of a subject, A biological information acquisition step in which biological information of the subject is acquired without emitting light from the light-emitting unit, A sleep onset determination step, which determines whether or not the subject has fallen asleep based on the subject's biological information obtained in the biological information acquisition step, A control step in which, when it is determined that the subject has fallen asleep, the light-emitting unit starts emitting light in order to determine the sleep state, A control method including

10. The computer in the electronic device that controls the light-emitting part used to determine the sleep state of the subject, Based on the subject's biological information acquired without emitting light from the light-emitting unit, it is determined whether or not the subject has fallen asleep. When it is determined that the subject has fallen asleep, the system controls the light-emitting unit to start emitting light in order to determine the sleep state. A program to enable it to function as a control unit.

Images