Detection device

Abstract

This detection device includes a light source, a plurality of optical sensors, and a control circuit for calculating a value based on the outputs of the plurality of optical sensors. The control circuit individually performs processing on values corresponding to the output of each of the plurality of optical sensors, such processing involving multiplying a value corresponding to the outputs of the optical sensors by a coefficient.

Description

Detection device

[0001] The present disclosure relates to a detection device.

[0002] BACKGROUND ART There is known a detection device that detects a fingertip plethysmogram of a person using a light source that irradiates light onto the finger and a photodetector that receives the light from the light source (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-187539

[0004] The output of an optical sensor can be larger than the output that should be obtained due to the unintentional generation of unwanted components such as noise. For this reason, conventional configurations that simply use the output of the photodetector with the highest light intensity among multiple photodetectors do not provide sufficient accuracy in the output that indicates the result of irradiating light on a human finger.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a detection device that makes it easier to ensure detection accuracy.

[0006] A detection device according to one aspect of the present disclosure comprises a light source, a plurality of optical sensors, and a control circuit that calculates a value based on the output of the plurality of optical sensors, and the control circuit individually multiplies the value corresponding to the output of the optical sensor by a coefficient for each of the values ​​corresponding to the output of the plurality of optical sensors.

[0007] FIG. 1 is an external view showing a detection device according to an embodiment. FIG. 2 is a diagram showing the internal structure of the detection device shown in FIG. 1. FIG. 3 is a diagram showing a cross section taken along line XX' in FIG. 2. FIG. 4 is a diagram explaining an example of how to use the detection device 100. FIG. 5 is a block diagram showing an example of the internal configuration of the control circuit 10. FIG. 6 is a schematic circuit diagram showing the configuration of an output system for an electrical signal from an optical sensor. FIG. 7 is a flowchart showing the process flow for deriving vital signs. FIG. 8 is a flowchart showing the process flow included in the process of step S1. FIG. 9 is a schematic diagram showing a mechanism for obtaining an optical sensor output corresponding to a pulse rate using reflected light from a green LED. FIG. 10 is a graph showing an outline of a method for detecting a pulse rate based on the magnitude of the optical sensor output. FIG. 11 is a graph showing the relationship between blood oxygen concentration and the absorption coefficient of red light and near-infrared light due to hemoglobin (Hb). FIG. 12 is a flowchart showing the process flow for deriving vital signs according to a third embodiment. FIG. 13 is a flowchart showing the process flow for deriving vital signs according to the third embodiment. Fig. 14 is a diagram showing the internal structure of a detection device employed in embodiment 4. Fig. 15 is a flowchart showing the flow of processing related to the derivation of vital values ​​performed in embodiment 4. Fig. 16 is a flowchart showing the flow of processing related to the derivation of vital values ​​performed in modified example 1 of embodiment 4. Fig. 17 is a diagram showing the concept of the difference between vital values ​​V1 and V2. Fig. 18 is a flowchart showing the process flow related to the derivation of vital values ​​performed in modified example 2 of embodiment 4. Fig. 19 is a diagram showing the concept of the difference between difference values ​​N5 and N6.

[0008] Each embodiment of the present disclosure will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present disclosure. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0009] (Embodiment 1) Fig. 1 is an external view showing a detection device according to embodiment 1. In Fig. 1, detection device 100 has a shape of a finger ring. Detection device 100 has a hollow portion 200. A finger can be inserted into hollow portion 200 of detection device 100. In other words, a user of detection device 100 can wear detection device 100 on one finger (for example, finger 301 of a human HM in Fig. 4 described later).

[0010] In FIG. 1 , the detection device 100 has an inner surface portion 1, an outer surface portion 2, and a side surface portion 3. As shown in FIG. 4 , which will be described later, when the detection device 100 is worn on a finger 301, the inner surface portion 1 comes into contact with the finger. That is, the inner surface portion 1 has an inner surface 110 for coming into contact with the worn finger. The inside of the inner surface 110 is a hollow portion 200 through which the finger 301 can be inserted. The outer surface portion 2 is provided outside the inner surface portion 1. If a line passing through the center of the hollow portion 200 is defined as a center line J, the inner surface portion 1 and the outer surface portion 2 are cylindrical members with the center line J as their central axis. The side surface portion 3 is a plate-like member extending along a plane intersecting (e.g., perpendicular to) the center line J and is an annular member centered on the center line J. Note that the side surface portion 3 does not necessarily have to be completely perpendicular to the center line J, as long as it is provided so as to be able to form the housing of the detection device 100 together with the inner surface portion 1 and the outer surface portion 2.

[0011] Hereinafter, unless otherwise specified, the term "diameter" refers to the diameter of a circle centered on the center line J. The term "radial direction" refers to the direction along the diameter of a circle centered on the center line J.

[0012] Fig. 2 is a diagram showing the internal structure of the detection device 100 of Fig. 1. Fig. 2 is a diagram showing a cross section of the detection device 100 of Fig. 1 cut along a plane perpendicular to the center line J. Fig. 2 shows a cross section of the detection device 100 cut along a plane passing through the midpoint in the length direction of the outer surface part 2 along the center line J. Fig. 3 is a diagram showing a cross section cut along line XX' in Fig. 2.

[0013] The diameter of the outer surface portion 2, centered on the center line J, is larger than the diameter of the inner surface portion 1, centered on the center line J. The inner diameter of the ring of the side surface portion 3 corresponds to the diameter of the inner surface portion 1. The outer diameter of the ring of the side surface portion 3 corresponds to the diameter of the outer surface portion 2. As shown in FIG. 3 , which will be described later, two side surface portions 3 are provided facing each other with the inner surface portion 1 and the outer surface portion 2 sandwiched therebetween, and are joined to the inner surface portion 1 on the inner circumferential side and to the outer surface portion 2 on the outer circumferential side. The inner surface portion 1, outer surface portion 2, and two side surface portions 3 joined in this manner give the outer shape of the detection device 100 a ring-like shape, as shown in FIG. 1 . In other words, the inner surface portion 1, outer surface portion 2, and two side surface portions 3 form the housing of the ring-shaped detection device 100.

[0014] 2 , the detection device 100 includes an LED driver 5, a first optical sensor 61, a second optical sensor 62, a third optical sensor 63, a fourth optical sensor 64, a short-range wireless communication driver 7, a battery 8, a coil 9, a control circuit 10, a red LED (Light Emitting Diode) 51, a near-infrared LED 52, and a green LED 53. These components are provided outside the inner surface portion 1 and inside the outer surface portion 2, i.e., between the inner surface portion 1 and the outer surface portion 2. These components are mounted on a flexible substrate 20. These components can exchange signals with each other via the flexible substrate 20.

[0015] Hereinafter, the term "light source 50" encompasses the red LED 51, the near-infrared LED 52, and the green LED 53. The term "optical sensor 60" encompasses the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64 (see FIG. 5).

[0016] The flexible substrate 20 has an annular shape centered on the center line J. The flexible substrate 20 is provided so as to fit along the inner circumferential surface of the outer surface portion 2. The radial positional relationship between the inner surface portion 1, the flexible substrate 20, and the outer surface portion 2 is as follows, from the center toward the outside, with the center line J as the center: inner surface portion 1, flexible substrate 20, outer surface portion 2. Furthermore, the configuration mounted on the flexible substrate 20 is located radially outward from the inner surface portion 1 and radially inward from the flexible substrate 20.

[0017] The red LED 51 outputs red light. The near-infrared LED 52 outputs near-infrared light. The green LED 53 outputs green light. That is, the detection device 100 has light sources provided outside the inner surface portion 1 and inside the outer surface portion 2 (between the inner surface portion 1 and the outer surface portion 2). The LED driver 5 drives the red LED 51, the near-infrared LED 52, and the green LED 53 to emit light.

[0018] The red LED 51 is a light source that emits red light. The near-infrared LED 52 is a light source that emits near-infrared light. The green LED 53 is a light source that emits green light. The optical axes of the light emitted from the red LED 51, near-infrared LED 52, and green LED 53 are directed toward the center line J. The inner surface 1 is a translucent material, and the light emitted from the red LED 51, near-infrared LED 52, and green LED 53 can pass through the inner surface 1. Therefore, when a finger 301 is present in the hollow portion 200, the light emitted from the red LED 51, near-infrared LED 52, and green LED 53 is reflected and scattered by the finger 301. The light reflected and scattered in this manner can be detected by the optical sensor 60. In other words, the optical sensor 60 is positioned so as to detect the light emitted from the red LED 51, near-infrared LED 52, and green LED 53 and reflected and scattered. The outer surface portion 2 and the side surface portion 3 are members that block light.

[0019] As a specific example, the inner surface portion 1 of the first embodiment is made of a translucent resin. The outer surface portion 2 and the side surface portion 3 are made of a non-translucent metal, a non-translucent alloy, a non-translucent metal compound, or a non-translucent resin. The compositions of the inner surface portion 1, the outer surface portion 2, and the side surface portion 3 are not limited to these, and other materials that can be used in terms of translucency and strength as a housing may be used.

[0020] The optical sensor 60 receives as input light output from the red LED 51, near-infrared LED 52, and green LED 53 that has passed through the finger inserted in the hollow portion 200. The optical sensor 60 detects changes in the intensity of the input light. The optical sensor 60 is, for example, an organic photodiode (OPD) and outputs an electrical signal in response to the irradiated light. That is, in the first embodiment, the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64 are each an OPD. Of course, the optical sensor 60 may be an optical sensor using a method other than an OPD.

[0021] Regarding the positional relationship between the light source 50 and the optical sensor 60 in the circumferential direction along the inner circumferential surface of the flexible substrate 20, two of the first optical sensor 61, second optical sensor 62, third optical sensor 63, and fourth optical sensor 64 are located on one circumferential side of the light source 50, and the other two are located on the other circumferential side of the light source 50. In the first embodiment, as shown in Fig. 2 , the first optical sensor 61, second optical sensor 62, green LED 53, red LED 51, near-infrared LED 52, third optical sensor 63, and fourth optical sensor 64 are arranged in this order from one circumferential side to the other. The direction from one circumferential side to the other here refers to the counterclockwise direction in Fig. 2 , which is a direction starting from the first optical sensor 61.

[0022] In the first embodiment, when one of the red LED 51, the near-infrared LED 52, and the green LED 53 is lit, the other two are not lit. When the red LED 51 is lit and the near-infrared LED 52 and the green LED 53 are not lit, red light that has passed through the finger is input to the optical sensor 60. When the near-infrared LED 52 is lit and the red LED 51 and the green LED 53 are not lit, near-infrared light that has passed through the finger is input to the optical sensor 60. When the green LED 53 is lit and the red LED 51 and the near-infrared LED 52 are not lit, green light that has passed through the finger is input to the optical sensor 60.

[0023] The short-range wireless communication driver 7 has an antenna (not shown). The short-range wireless communication driver 7 transmits and receives signals between the detection device 100 and other devices. The short-range wireless communication driver 7 can transmit data measured by each part of the detection device 100 to other devices. The short-range wireless communication driver 7 can also receive data transmitted by other devices.

[0024] The battery 8 supplies power to each component of the detection device 100. The battery 8 is, for example, a lithium ion battery. The battery driver 81 controls the battery 8. The battery 8 is charged by the battery driver 81.

[0025] The coil 9 is a charging coil for charging the battery 8. The coil 9 has a winding wound along the outer periphery of the inner surface portion 1, outside the inner surface portion 1 and inside the outer surface portion 2 (between the inner surface portion 1 and the outer surface portion 2). As described below, an induced current flows through the coil 9 based on an applied magnetic field. The coil 9 includes a coil 91 and a coil 92. As shown in FIG. 3 , the coils 91 and 92 are each wound along the outer periphery of the inner surface portion 1. The coil 91 is provided on one end of the outer surface portion 2 along the center line J, and the coil 92 is provided on the other end of the outer surface portion 2 along the center line J. The coils 91 and 92 are connected in parallel to the battery driver 81. Therefore, the battery 8 can be charged by the induced current flowing through either the coil 91 or the coil 92. The windings of the coils 91 and 92 are each coated to maintain insulation. A portion of the radially outer region of the coil 9 defines a cutout portion 9a where the flexible substrate 20 is not provided. This makes contactless charging by the coil 9 more efficient.

[0026] The control circuit 10 controls each part of the detection device 100. The control circuit 10 is, for example, an integrated circuit (IC) such as a microcontroller. The control circuit 10 may also be, for example, a programmable logic device (PLD) such as a field programmable gate array (FPGA).

[0027] Fig. 4 is a diagram illustrating an example of how to use the detection device 100. As shown in Fig. 4, the detection device 100 is worn on a finger 301 of a hand 300 of a human HM. The detection device 100 performs various operations to derive vital values ​​of the human HM.

[0028] Fig. 5 is a block diagram showing an example of the internal configuration of control circuit 10. As shown in Fig. 5, control circuit 10 of this example has an optical pulse wave measurement circuit 14, memory 15, communication circuit 16, power supply circuit 17, and CPU (Central Processor Unit) 18. These are connected by bus B, and can exchange data with each other via bus B.

[0029] The optical pulse wave measuring circuit 14 is connected to the LED driver 5 and the optical sensor 60. The optical pulse wave measuring circuit 14 amplifies and digitizes the analog output of the optical sensor 60 and stores the digitized output in the memory 15.

[0030] The memory 15 is a storage unit that stores various types of data. The memory 15 may include, for example, a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), etc.

[0031] The communication circuit 16 is connected to the short-range wireless communication driver 7. The communication circuit 16 transmits measurement results and the like to an external device. The external device is, for example, a mobile terminal such as a smartphone or tablet held by a user of the detection device 100. Mobile terminals such as smartphones and tablets have a display screen. By displaying data from the detection device 100 on the screen, the user of the detection device 100 can check the data received from the detection device 100.

[0032] The power supply circuit 17 is connected to a battery driver 81. The power supply circuit 17 controls charging of the battery 8 and supplies power from the battery 8 to each component.

[0033] The CPU 18 is a control unit that controls each unit in the control circuit 10. The CPU 18 executes a predetermined program to measure or calculate biological information such as pulse wave velocity, blood pressure, and pulse frequency.

[0034] 6 is a schematic circuit diagram showing a configuration related to an output system of an electrical signal from the optical sensor 60. In the first embodiment, a first system 501 and a second system 502 are provided. As shown in FIG. 6, the first optical sensor 61 and the third optical sensor 63 are included in the first system 501. The second optical sensor 62 and the fourth optical sensor 64 are included in the second system 502.

[0035] The first system 501 includes a switch 1211, an amplifier 1221, a converter 1231, and a first memory 151. The second system 502 includes a switch 1212, an amplifier 1222, a converter 1232, and a second memory 152.

[0036] The switches 1211 and 1212 are switches that connect one of the two optical sensors to an amplifier circuit and disconnect the other from the amplifier circuit. The switches 1211 and 1212 are provided to be switchable between one state and the other. For example, the switch 1211 is provided to be switchable between a state in which the output from the first optical sensor 61 is transmitted to the switch 1211 and a state in which the output from the third optical sensor 63 is transmitted to the switch 1211. The switch 1212 is provided to be switchable between a state in which the output from the second optical sensor 62 is transmitted to the switch 1212 and a state in which the output from the fourth optical sensor 64 is transmitted to the switch 1212.

[0037] The amplifiers 1221 and 1222 are circuits that function as amplifiers (AMP: AMPlifier) ​​that amplify the outputs transmitted from the optical sensors. The converters 1231 and 1232 are analog-to-digital converters (ADC: Analog to Digital Converters) that convert the analog signals amplified by the amplifier circuits into digital signals. The first memory 151 and the second memory 152 are storage circuits that store the digital signals output from the ADCs.

[0038] In the first embodiment, the phrase "values ​​corresponding to the output of the optical sensors" refers to values ​​obtained by amplifying the outputs of the optical sensors, such as the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64, using amplifiers, such as the amplifiers 1221 and 1222, and converting the outputs into digital data using analog-to-digital conversion circuits, such as the converters 1231 and 1232. In other words, the digitalized values ​​indicate the strength of the outputs of the optical sensors depending on whether the values ​​are large or small. Note that amplification of the outputs of the optical sensors by the amplifiers 1221 and 1222 is not essential and can be omitted.

[0039] The first optical sensor 61 and the third optical sensor 63 are connected to the amplifier 1221 via a switch 1211. The amplifier 1221 is connected to the first memory 151 via a converter 1231. The second optical sensor 62 and the fourth optical sensor 64 are connected to the amplifier 1222 via a switch 1212. The amplifier 1222 is connected to the first memory 151 via a converter 1232. Note that on the opposite side of the switch 1211 across the first optical sensor 61 and the third optical sensor 63 and on the opposite side of the switch 1212 across the second optical sensor 62 and the fourth optical sensor 64, a configuration indicating a reference potential GND (for example, a reference potential electrode, etc.) is provided, and is connected to the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64.

[0040] The configuration shown in FIG. 6 is included in the control circuit 10. As shown in FIG. 5, the control circuit 10 includes an optical pulse wave measurement circuit 14, a memory 15, and the like. The optical pulse wave measurement circuit 14 includes switches 1211 and 1212, amplifiers 1221 and 1222, and converters 1231 and 1232. The first memory 151 and the second memory 152 may be provided as cache memories within the optical pulse wave measurement circuit 14 or may be provided as components included in the memory 15. Regardless of the configuration of the first memory 151 and the second memory 152, the first memory 151 and the second memory 152 are included in the control circuit 10, and the data stored in the first memory 151 and the second memory 152 is also stored in the memory 15. Digital data generated in response to the outputs of the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64 is stored in the memory 15 and referenced during processing by the CPU 18. The CPU 18 performs various processes related to the derivation of vital values. The flow of the processes related to the derivation of vital values ​​will be described below with reference to FIGS.

[0041] 7 is a flowchart showing the flow of processing related to the derivation of vital values. First, outputs from a plurality of sensors are acquired (step S1).

[0042] 8 is a flowchart showing the flow of processing included in the processing of step S1. The processing of step S1 includes processing of steps S11, S12, S13, S14, and S15. The processing of steps S12, S13, S14, and S15 may be performed in any order. The processing of steps S12, S13, S14, and S15 include the digitization processing by the optical pulse wave measurement circuit 14 described above.

[0043] The processing of step S11 turns on any one of the light sources, the red LED 51, the near-infrared LED 52, or the green LED 53. Specifically, the CPU 18 outputs a command to the light source 50 to turn on any one of the light sources, the red LED 51, the near-infrared LED 52, or the green LED 53. In response to the command, the light source 50 turns on any one of the light sources, the red LED 51, the near-infrared LED 52, or the green LED 53. In the processing of step S12, the output of the first optical sensor 61 is acquired as output PD1. In the processing of step S13, the output of the second optical sensor 62 is acquired as output PD2. In the processing of step S14, the output of the third optical sensor 63 is acquired as output PD3. In the processing of step S15, the output of the fourth optical sensor 64 is acquired as output PD4. The outputs from the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64 are digitized via the circuit configuration described with reference to Fig. 6 to become data that can be referenced by the CPU 18. By acquiring this data, the CPU 18 performs the processes of steps S12, S13, S14, and S15. Note that the outputs PD1, PD2, PD3, and PD4 are values ​​that indicate the strength of the output.

[0044] 7, after processing step S1, the CPU 18 calculates values ​​N1, N2, N3, and N4 (step S2). N1 is the value obtained by multiplying output PD1 by weighting coefficient a. N2 is the value obtained by multiplying output PD2 by weighting coefficient b. N3 is the value obtained by multiplying output PD3 by weighting coefficient c. N4 is the value obtained by multiplying output PD4 by weighting coefficient d.

[0045] In this manner, the control circuit 10 including the CPU 18 multiplies the value corresponding to the output of each of the optical sensors 60 (e.g., the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64) by coefficients (e.g., a, b, c, and d), individually for each of the values ​​corresponding to the output of the optical sensors. Therefore, the control circuit 10 including the optical pulse wave measurement circuit 14 and the CPU 18 functions as a control circuit that calculates values ​​based on the outputs of the optical sensors. As described above, the optical pulse wave measurement circuit 14 generates a "value corresponding to the optical sensor output." The CPU 18 calculates a value based on the outputs of the optical sensors by performing arithmetic processing, including multiplying the "value corresponding to the optical sensor output" by a coefficient. Note that a, b, c, and d are arbitrary weighting coefficients, reflecting predetermined real numbers. In the first embodiment, for example, a = b = c = d = 1, but this is not limited thereto.

[0046] After the process of step S2, the CPU 18 calculates a measurement value N by adding together the values ​​N1, N2, N3, and N4 (step S3).

[0047] The CPU 18 generates a data array in which the measurement values ​​N obtained through the processes of steps S1 to S3 are arranged in chronological order (step S4). That is, the acquisition of outputs from the multiple sensors through the process of step S1 is performed multiple times over a fixed period of time (e.g., one minute). The processes of steps S2 and S3 are also performed multiple times according to the number of times step S1 is performed. The CPU 18 generates a data array in the process of step S4 in which the values ​​of the measurement values ​​N generated through each of the multiple processes of step S3 are arranged in chronological order. The fixed period of time is not limited to one minute and can be changed as appropriate. However, if the fixed period of time is one minute, the pulse rate can be expressed in beats per minute (bpm).

[0048] The CPU 18 derives vital values ​​from the data sequence generated in step S4 (step S5). The vital values ​​derived in the first embodiment include a value indicating the pulse rate and a blood oxygen concentration (SpO ２The mechanisms for deriving these vital values ​​will be explained below.

[0049] 9 is a schematic diagram showing a mechanism for obtaining an output of optical sensor 60 corresponding to the pulse rate from reflected light from green LED 53. Irradiation light 531, which is light emitted from green LED 53, is irradiated onto irradiation area 530 through artery 410, through which blood flows in finger 301, and a portion of the light is reflected as reflected light 532 by biological tissue in finger 301, including artery 410, and enters optical sensor 60. Optical sensor 60 detects the reflected light 532 thus generated.

[0050] As shown in FIG. 9 , non-dilated portions 411 and dilated portions 412 occur in the artery 410. The non-dilated portions 411 and dilated portions 412 occur in response to blood being pumped into the artery 410 by the pulsation of the heart. That is, the non-dilated portions 411 and dilated portions 412 occur in response to the pulsation. Therefore, while the state of the artery 410 within the irradiation range 530 in FIG. 9 is the non-dilated portion 411, there are also times when the state of the artery 410 within the irradiation range 530 becomes the dilated portion 412. The number of times the dilated portion 412 occurs at the same location within a certain period of time is referred to as the pulse rate or heart rate. The value indicating the pulse rate among the above-mentioned vital values ​​is the same as the pulse rate.

[0051] FIG. 10 is a graph schematically illustrating a method for detecting a pulse based on the magnitude of the output of the optical sensor 60. The vertical axis of FIG. 10 represents the strength of the output of the optical sensor 60, and the horizontal axis represents the passage of time. Photoplethysmography (PPG) is used to detect the pulse. Even at the same location (e.g., the irradiation area 530) in the artery 410, the volume of blood flowing through the location differs between when the non-dilated portion 411 occurs and when the dilated portion 412 occurs. This difference in blood volume is reflected in the degree of reflected light 532. In other words, the output of the optical sensor 60 obtained by continuing the process of irradiating the irradiation area 530 with irradiation light 531 and detecting the degree of reflected light 532 with the optical sensor 60 for a certain period of time indicates the number of dilated portions 412 that occurred during that period.

[0052] Specifically, the non-expandable portions 411 and the expanded portions 412 alternate periodically in response to the heartbeat. Therefore, the output of the optical sensor 60 also exhibits a periodic pattern of strength and weakness, as shown in Fig. 10, in response to the periodic occurrence of the non-expandable portions 411 and the expanded portions 412. Based on the number of occurrences of characteristic outputs that periodically occur in this pattern, the number of outputs indicating the number of expanded portions 412, i.e., the pulse rate, can be determined.

[0053] In FIG. 10 , the minimum output obtained immediately before the output of the optical sensor 60 suddenly rises is treated as a characteristic output, and timings T1, T2, T3, T4, and T5 at which such characteristic output occurs are particularly shown. The artery 410 in the irradiation range 530, which was a non-dilated portion 411 at timing T1, becomes a dilated portion 412 over time (represented as time R1) in response to pulsation, and then returns to the non-dilated portion 411. At timing T2, the state of the artery 410 has returned to the non-dilated portion 411. That is, during time R1, the artery 410 pulses once. Subsequently, using a similar concept, the artery 410 pulses once during time R2, transitions to the dilated portion 412, and at timing T3, the state of the artery 410 returns to the non-dilated portion 411. Furthermore, during time R3, the artery 410 pulses once, transitions to the dilated portion 412, and at timing T4, the state of the artery 410 returns to the non-dilated portion 411. During time R4, artery 410 pulses once, passes through the state of dilated portion 412, and at timing T5, the state of artery 410 returns to the non-dilated portion 411. In this way, based on the number of occurrences of the characteristic output included in the output of optical sensor 60, the number of outputs indicating the number of dilated portions 412, i.e., the pulse rate, can be determined.

[0054] When obtaining the output of the optical sensor 60 for the purpose of obtaining the pulse rate, such as in a PPG, green light is more likely to obtain the light reflected from the artery 410 in the finger 301 than red light or near-infrared light. Therefore, when obtaining a value indicating the pulse rate among the vital signs, green light, i.e., light from the green LED 53, is used.

[0055] 11 is a graph showing the relationship between blood oxygen concentration and the absorption coefficient of hemoglobin (Hb) for red light and near-infrared light. In FIG. 11, the position on the horizontal axis where dashed line F1 is located indicates the absorption coefficient of red light from the red LED 51. Furthermore, the position on the horizontal axis where dashed line F2 is located indicates the absorption coefficient of near-infrared light from the near-infrared LED 52.

[0056] Red blood cells in the blood contain hemoglobin, which is bound to oxygen to form oxyhemoglobin (HbO ２ The absorption coefficients of red light and near-infrared light differ between hemoglobin in a state of oxygen-free hemoglobin (Hb) and hemoglobin in a state of oxygen-free hemoglobin (Hb). Specifically, as shown in FIG. 11 , hemoglobin has a higher absorption coefficient for red light and a lower absorption coefficient for near-infrared light than oxyhemoglobin. By utilizing these properties of hemoglobin and oxyhemoglobin, the blood oxygen concentration can be measured. Specifically, when red light from red LED 51 is irradiated onto finger 301, the intensity of light scattered by blood passing through artery 410 in finger 301 and detected by optical sensor 60, and when red light from near-infrared LED 52 is irradiated onto finger 301, the intensity of light scattered by blood and detected by optical sensor 60 depend on the ratio of hemoglobin to oxyhemoglobin in the blood. Therefore, the blood oxygen concentration can be determined by performing at least one of a step (first step) of turning on the red LED 51 and detecting scattered light with the optical sensor 60, and a step (second step) of turning on the near-infrared LED 52 and detecting scattered light with the optical sensor 60. In the first embodiment, both the first step and the second step are performed.

[0057] As described with reference to FIG. 10 , artery 410 pulsates. Therefore, when detecting red light and near-infrared light, changes occur in response to changes in blood flow rate, which corresponds to the pulsation state at the location where the light is irradiated, such as in irradiation area 530. Meanwhile, the ratio between the detection levels of red light and near-infrared light within a very small time difference, which is nearly identical, conforms to the dashed lines F1 and F2 described with reference to FIG. 11 . Therefore, the blood oxygen concentration can be determined without any problems. Furthermore, the pulse rate can also be derived based on the red light and near-infrared light, based on the changes in response to such changes in blood flow rate. In the first embodiment, green light is used to determine the pulse rate in order to achieve a more accurate pulse rate determination.

[0058] When a value indicating the pulse rate is derived as a vital value in the processing of step S5, the light source that is turned on in response to the processing of step S11 is the green LED 53. Furthermore, when a value indicating the pulse rate is derived as a vital value in the processing of step S5, the light sources that are turned on in response to the processing of step S11 are the red LED 51 and the near-infrared LED 52. However, the red LED 51 and the near-infrared LED 52 are not turned on simultaneously, and a data array based on the value of the measurement value N obtained when the red LED 51 is turned on and a data array based on the value of the measurement value N obtained when the near-infrared LED 52 is turned on are generated separately.

[0059] As described above, according to the first embodiment, a detection device (e.g., the detection device 100) includes a light source (e.g., the light source 50), a plurality of optical sensors (e.g., the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64), and a control circuit (e.g., the control circuit 10) that calculates values ​​based on the outputs of the plurality of optical sensors. The control circuit individually multiplies the value corresponding to the output of each of the plurality of optical sensors by a coefficient (e.g., a, b, c, or d). This allows the output of each of the plurality of optical sensors to be arbitrarily adjusted according to the degree of light detection. For example, if there is no particular problem with the degree of light detection of each of the plurality of optical sensors, a = b = c = d = 1 may be used, as described in the first embodiment. Furthermore, if it is desirable to apply a larger gain to the outputs of some of the plurality of optical sensors, the coefficient of the value corresponding to the outputs of the some can be made larger than 1. Furthermore, if the outputs of some of the plurality of optical sensors are excessive, the coefficient of the value corresponding to the outputs of the some can be made smaller than 1. In this way, according to the embodiment, the output of each of the multiple optical sensors can be adjusted arbitrarily according to the coefficient settings. Being able to adjust the output arbitrarily in this way makes it easier to prevent excessive output from reaching a plateau or output from being too weak, making it difficult to detect light. Therefore, it becomes easier to ensure detection accuracy.

[0060] Furthermore, in the embodiment, values ​​corresponding to the outputs of the multiple optical sensors are individually multiplied by coefficients, and the sum is then averaged. This makes it easier to reduce the influence of the outputs of some optical sensors, even if the outputs of the some optical sensors deviate from the outputs of the other optical sensors. Therefore, it becomes easier to ensure detection accuracy.

[0061] Furthermore, since the optical sensor 60 is an OPD, i.e., an organic photodiode, the detection device 100 can be made lighter and cheaper to manufacture than an inorganic photodiode. Furthermore, from the viewpoint of mounting on a curved surface such as the inner peripheral surface of the flexible substrate 20, an organic photodiode can be more flexibly arranged and is easier to mount than an inorganic photodiode.

[0062] Furthermore, since the light source (e.g., light source 50), the plurality of optical sensors (e.g., first optical sensor 61, second optical sensor 62, third optical sensor 63, fourth optical sensor 64), and control circuit (e.g., control circuit 10) are stored in a ring-shaped housing, the detection device 100 can be easily worn on the finger 301 of a human HM.

[0063] Second Embodiment Hereinafter, a second embodiment, which differs in part from the first embodiment, will be described with reference to FIG.

[0064] FIG. 12 is a flowchart showing the flow of processing related to the derivation of vital values ​​performed in the second embodiment. In the second embodiment, after the processing of step S1 described in the first embodiment with reference to FIGS. 7 and 8, the processing of step S7 is performed. In the processing of step S7, it is determined whether the light source turned on in the processing of step S11 included in the processing of step S1 is the green LED 53. If the light source turned on in the processing of step S11 is the green LED 53 (step S7; Yes), the CPU 18 sets the weighting coefficients a and d to 0 and the weighting coefficients b and c to 1 (step S8). If the light source turned on in the processing of step S11 is the green LED 53 (step S7; Yes), the CPU 18 sets the weighting coefficients a and d to 1 and the weighting coefficients b and c to 0 (step S9). After the processing of step S8 or step S9, the processing from step S2 described in the embodiment with reference to FIG. 7 is performed.

[0065] As described above, in the second embodiment, when the light source turned on in the process of step S11 is the green LED 53, the weighting coefficients a and d are set to 0 and the weighting coefficients b and c are set to 1. This is equivalent to using the outputs of the second optical sensor 62 and the third optical sensor 63 to detect green light, while disabling the outputs of the first optical sensor 61 and the fourth optical sensor 64. This is because, when detecting pulsation using the green light reflected by the artery 410 (reflected light 532), the second optical sensor 62 and the third optical sensor 63, which are located closer to the green LED 53 than the first optical sensor 61 and the fourth optical sensor 64, are more advantageous in terms of detection accuracy.

[0066] 2 , of the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64, the second optical sensor 62 is closest to the green LED 53, and the fourth optical sensor 64 is the farthest. When the green LED 53 is lit, the coefficient (b) corresponding to the output of the second optical sensor 62 (output PD2) is 1, and the coefficient (d) corresponding to the output of the fourth optical sensor 64 (output PD4) is 0. Therefore, among the coefficients (e.g., a, b, c, and d) by which the value corresponding to the output from the optical sensor 60 in response to the lighting of the green LED 53 is multiplied, the coefficient (b) by which the value corresponding to the output from the second optical sensor 62, which is closest to the green LED 53, is larger than the coefficient (d) by which the value corresponding to the output from the fourth optical sensor 64, which is farthest from the green LED 53, is multiplied.

[0067] Furthermore, in the second embodiment, if the light source turned on in the processing of step S11 is not the green LED 53, i.e., if it is the red LED 51 or the near-infrared LED 52, the weighting coefficients a and d are set to 1 and the weighting coefficients b and c are set to 0. This is equivalent to using the outputs of the first optical sensor 61 and the fourth optical sensor 64 to detect red light and near-infrared light, while disabling the outputs of the second optical sensor 62 and the third optical sensor 63. This is because, when detecting the blood oxygen concentration using scattered red light and near-infrared light by the blood in the artery 410, the first optical sensors 61 and 61, which are located farther from the green LED 53 than the second optical sensors 62 and 63, are more advantageous in terms of detection accuracy.

[0068] 2 , of the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64, the one closest to the near-infrared LED 52 is the third optical sensor 63, and the one furthest from it is the first optical sensor 61. Of the first optical sensor 61, the second optical sensor 62, the third optical sensor 63, and the fourth optical sensor 64, the one closest to the red LED 51 is the second optical sensor 62 or the third optical sensor 63, and the one furthest from it is the first optical sensor 61 or the fourth optical sensor 64. When the red LED 51 or the near-infrared LED 52 is lit, the coefficient (a) corresponding to the output of the third optical sensor 63 (output PD3) is 0, and the coefficient (c) corresponding to the output of the first optical sensor 61 (output PD1) is 1. Therefore, among the coefficients (e.g., a, b, c, d) by which the value corresponding to the output from the optical sensor 60 in response to the lighting of the red LED 51 or the near-infrared LED 52 is multiplied, the coefficient (a) by which the value corresponding to the output from the second optical sensor 62, which is closest to the green LED 53, is smaller than the coefficient (c) by which the value corresponding to the output from the fourth optical sensor 64, which is farthest from the green LED 53.

[0069] As described above, except for the points specifically mentioned, the second embodiment is the same as the first embodiment. According to the second embodiment, the light source 50 has a green light source (e.g., green LED 53) that emits green light, and at least one of a red light source (e.g., red LED 51) that emits red light, and an infrared light source (e.g., near-infrared LED 52) that emits infrared light, and the multiple optical sensors include two or more sensors (e.g., a first optical sensor 61, a second optical sensor 62, a third optical sensor 63, and a fourth optical sensor 64) that are at different distances from the green light source, and among the coefficients (e.g., a, b, c, d) by which values ​​corresponding to outputs from the multiple optical sensors in response to the green light source being turned on are multiplied, the coefficient (b) by which the value corresponding to the output from the optical sensor (e.g., the second optical sensor 62) that is closest to the green light source is multiplied is larger than the coefficient (d) by which the value corresponding to the output from the optical sensor (e.g., the fourth optical sensor 64) that is farthest from the green light source is multiplied, thereby enabling the optical sensor that is closest to the green light source to be used more efficiently in detecting light from the green light source. The intended use of such an optical sensor is advantageous in detecting reflected light of, for example, green light.

[0070] Furthermore, the multiple optical sensors are four optical sensors (first optical sensor 61, second optical sensor 62, third optical sensor 63, fourth optical sensor 64), and the coefficients (b, c) multiplied by the values ​​corresponding to the outputs from the two optical sensors (second optical sensor 62, third optical sensor 63) that are relatively close to the green light source (e.g., green LED 53) are 1, while the coefficients (a, d) multiplied by the values ​​corresponding to the outputs from the optical sensors (first optical sensor 61, fourth optical sensor 64) that are relatively far from the green light source are 0, thereby making it easier to set coefficients that more efficiently utilize the optical sensors that are closest to the green light source.

[0071] Furthermore, the light source 50 includes at least one of a green light source (e.g., green LED 53) that emits green light, a red light source (e.g., red LED 51) that emits red light, and an infrared light source (e.g., near-infrared LED 52) that emits infrared light, and the multiple optical sensors include two or more sensors (e.g., first optical sensor 61, second optical sensor 62, third optical sensor 63, and fourth optical sensor 64) that are located at different distances from the green light source, and among the coefficients multiplied by values ​​corresponding to outputs from the multiple optical sensors in response to lighting of one of the sensors, a coefficient (e.g., c) multiplied by a value corresponding to an output from the optical sensor (e.g., third optical sensor 63) that is closest to the one of the sensors is smaller than a coefficient (e.g., a) multiplied by a value corresponding to an output from the optical sensor (e.g., first optical sensor 61) that is farthest from the one of the sensors, thereby enabling the optical sensor that is farthest from the one of the sensors to be more efficiently used in detecting light from the one of the sensors. The intended use of such optical sensors is advantageous, for example, in detecting scattered red light or infrared light.

[0072] Furthermore, the multiple optical sensors are four optical sensors (first optical sensor 61, second optical sensor 62, third optical sensor 63, fourth optical sensor 64), and the coefficients (b, c) multiplied by the values ​​corresponding to the outputs from two optical sensors (e.g., second optical sensor 62, third optical sensor 63) that are relatively close to at least one of a red light source that emits red light (e.g., red LED 51) and an infrared light source that emits infrared light (e.g., near-infrared LED 52) are 0, and the coefficients (a, d) multiplied by the values ​​corresponding to the outputs from the optical sensors (first optical sensor 61, fourth optical sensor 64) that are relatively far from one of the red light source and the infrared light source that emits infrared light are 1, thereby making it easier to set coefficients that more efficiently utilize the optical sensor that is farthest from one of the red light source and the infrared light source.

[0073] Third Embodiment Hereinafter, a third embodiment, which differs in part from the first and second embodiments, will be described with reference to FIG.

[0074] 13 is a flowchart showing the flow of processing related to the derivation of vital values ​​performed in embodiment 3. In embodiment 3, processing in steps S21 and S22 is performed instead of the processing in step S3 in embodiment 1.

[0075] In the process of step S21, the CPU 18 excludes the minimum and maximum values ​​of the values ​​N1, N2, N3, and N4 calculated in the process of step S2. For example, if the magnitude relationship among the values ​​N1, N2, N3, and N4 satisfies N1>N2>N3>N4, the maximum value N1 and the minimum value N4 are excluded.

[0076] In the process of step S22, the two values ​​not excluded in the process of step S21 are added together to obtain the measurement value N. After the process of step S22, the process proceeds to the process of step S4. In the process of step S4 in the third embodiment, the measurement value N that forms the basis of the data array is the measurement value N obtained in the process of step S22.

[0077] Except for the above-mentioned points, embodiment 3 is similar to embodiment 1. According to embodiment 3, the multiple optical sensors include four or more optical sensors (e.g., first optical sensor 61, second optical sensor 62, third optical sensor 63, and fourth optical sensor 64), and a control circuit (e.g., control circuit 10) calculates the average of the four or more values ​​corresponding to the outputs of the multiple optical sensors, excluding the maximum and minimum values, divided by the number of the multiple optical sensors (e.g., 4) minus 2 (e.g., 4 - 2 = 2), as the light measurement value (e.g., measurement value N) of the multiple optical sensors. Even if at least one of the maximum and minimum values ​​generates an output that is an outlier that deviates from the originally intended optical sensor output, the influence of the maximum and minimum values ​​can be suppressed. Therefore, detection accuracy can be more easily ensured.

[0078] (Modifications of Embodiments 1 and 3) In Embodiments 1 and 3, the values ​​of the weighting coefficients a and d may be greater than the values ​​of the weighting coefficients b and c. Specifically, a = d = 2 and b = c = 1 may be used. The first optical sensor 61 and the fourth optical sensor 64 are located farther from the light source 50 than the second optical sensor 62 and the third optical sensor 63. Therefore, the first optical sensor 61 and the fourth optical sensor 64 tend to detect weaker light intensities than the second optical sensor 62 and the third optical sensor 63. Therefore, in order to correct this tendency, the values ​​of the weighting coefficients a and d may be greater than the values ​​of the weighting coefficients b and c.

[0079] In this configuration, where the multiple optical sensors include two or more sensors (e.g., first optical sensor 61, second optical sensor 62, third optical sensor 63, and fourth optical sensor 64) that are located at different distances from a light source (e.g., light source 50), the coefficient (b or c) by which the value corresponding to the output from the optical sensor (e.g., second optical sensor 62 or third optical sensor 63) closest to the light source is multiplied may be smaller than the coefficient (a or d) by which the value corresponding to the output from the optical sensor (e.g., first optical sensor 61 or fourth optical sensor 64) farthest from the light source is multiplied. This makes it easier to treat the outputs of the multiple sensors more equally. In other words, the coefficient makes it easier to treat the outputs of the multiple sensors equally.

[0080] Fourth Embodiment Hereinafter, a fourth embodiment, which differs in part from the first, second, and third embodiments in processing, will be described with reference to FIGS. 14 and 15. FIG.

[0081] Fig. 14 is a diagram showing the internal structure of the detection device employed in embodiment 4. As shown in Fig. 14, in embodiment 4, in addition to the configuration of the detection device 100 of embodiment 1, a light-shielding portion 65 and a light-shielding portion 66 are further provided. The light-shielding portion 65 and the light-shielding portion 66 are light-shielding bodies. The light-shielding portion 65 and the light-shielding portion 66 block light emitted from the red LED 51, the near-infrared LED 52, and the green LED 53, as well as reflected light and scattered light thereof. The light-shielding portion 65 covers the light detection surface of the first optical sensor 61. The light-shielding portion 66 covers the light detection surface of the fourth optical sensor 64.

[0082] Therefore, in the fourth embodiment, the second optical sensor 62 and the third optical sensor 63 correspond to a first type of optical sensor that is capable of detecting light emitted from the light source 50. Furthermore, the first optical sensor 61 and the fourth optical sensor 64 correspond to a second type of optical sensor that is covered with a light-shielding layer that blocks the light emitted from the light source 50.

[0083] 15 is a flowchart showing the flow of processing related to derivation of vital values ​​performed in embodiment 4. In embodiment 4, processing in steps S31 and S32 is performed instead of processing in steps S3 and S4 in embodiment 1.

[0084] In the process of step S31, the CPU 18 calculates a difference value N5 by subtracting the value N1 from the value N2, and calculates a difference value N6 by subtracting the value N4 from the value N3.

[0085] Here, the difference values ​​N5 and N6 correspond to values ​​(difference values) obtained by subtracting the value corresponding to the output of the second-type optical sensor from the value corresponding to the output of the first-type optical sensor. The second optical sensor 62 and the first optical sensor 61, which are the output sources of the values ​​N2 and N1, respectively, from which the difference value N5 is calculated, constitute a pair of optical sensors including a first-type optical sensor and a second-type optical sensor. The third optical sensor 63 and the fourth optical sensor 64, which are the output sources of the values ​​N3 and N4, respectively, from which the difference value N6 is calculated, constitute a pair of optical sensors including a first-type optical sensor and a second-type optical sensor. Therefore, in the fourth embodiment, two pairs of optical sensors, each including a first-type optical sensor and a second-type optical sensor, are provided.

[0086] In the process of step S32, the CPU 18 generates at least one of a data array in which the difference values ​​N5 are arranged in chronological order and a data array in which the difference values ​​N6 are arranged in chronological order. The process of step S32 is similar to the process of step S4, except that the subject of the time-series data is at least one of the difference values ​​N5 and N6, rather than the measurement value N.

[0087] In the fourth embodiment, the light-shielding portion 65 covers the light detection surface of the first optical sensor 61, preventing the first optical sensor 61 from detecting light from the light source 50. In other words, the output of the first optical sensor 61 is an output when no light is detected. This means that an output when an optical sensor, such as the first optical sensor 61 or the second optical sensor 62, cannot detect light can be obtained from the first optical sensor 61 at any timing, regardless of the lighting state of the light source 50. If the output when an optical sensor cannot detect light is defined as a reference output, the first optical sensor 61 can be said to be a sensor that can obtain a reference output. For the same reason, the fourth optical sensor 64, which is provided with the light-shielding portion 66, can also be said to be a sensor that can obtain a reference output.

[0088] Furthermore, in the process of step S31, the difference value N5 is the value obtained by subtracting the value N1 from the value N2. Here, the values ​​N2 and N1 are values ​​calculated in the process of step S2. The value N2 is the output PD2, i.e., a value corresponding to the output of the second optical sensor 62 obtained in the process of step S13. The value N1 is the output PD1, i.e., a value corresponding to the output of the first optical sensor 61 obtained in the process of step S13. As described above, the first optical sensor 61 can be considered to be a sensor that obtains a reference output. From these facts, the difference value N5, which is the value obtained by subtracting the value N1 from the value N2, can be interpreted as the value obtained by subtracting the value corresponding to the reference output from the value corresponding to the output of the second optical sensor 62. This means that the difference value N5 can be calculated as the value obtained by subtracting the "output when the optical sensor cannot detect light" from the "output of the optical sensor that detects light when it is present and generates an output corresponding to the intensity of the detected light." For example, if the second optical sensor 62 cannot detect any light at all (case 1), the output of the second optical sensor 62 in case 1 should be substantially the same as the output of the first optical sensor 61, which cannot detect light regardless of the presence or absence of light. Therefore, the difference value N5 in case 1 should be substantially zero. On the other hand, if the second optical sensor 62 detects light (case 2), the output of the second optical sensor 62 in case 2 should be significantly different from the output of the first optical sensor 61, which cannot detect light regardless of the presence or absence of light. Therefore, the difference value N5 in case 2 is significantly greater than zero. In this way, by shielding the first optical sensor 61 with the light-shielding portion 65 and calculating the difference value N5, it is possible to more accurately determine whether the optical sensor detected any light or no light at all. For the same reason, by shielding the fourth optical sensor 64 with the light-shielding portion 66 and calculating the difference value N6, it is possible to more accurately determine whether the optical sensor detected any light or no light at all.

[0089] Except for the points noted above, embodiment 4 is similar to embodiment 1. According to embodiment 4, the multiple optical sensors include first-type optical sensors (e.g., second optical sensor 62, third optical sensor 63) that are capable of detecting light emitted from a light source (e.g., light source 50), and second-type optical sensors (e.g., first optical sensor 61, fourth optical sensor 64) that are covered with light-shielding layers (e.g., light-shielding portions 65, 66) that block the light emitted from the light source, and a control circuit (e.g., control circuit 10) calculates light measurement values ​​(e.g., difference value N5, difference value N6) from the multiple optical sensors based on values ​​obtained by subtracting values ​​corresponding to the outputs of the second-type optical sensors from values ​​corresponding to the outputs of the first-type optical sensors, thereby making it possible to more accurately determine whether the first-type optical sensors detected any light or no light at all.

[0090] A modified example of the fourth embodiment in which the process of step S32 in the fourth embodiment is replaced with a more specific process will be described below.

[0091] 16 is a flowchart showing the flow of processing related to derivation of vital values ​​performed in Modification 1 of Embodiment 4. In Modification 1 of Embodiment 4, instead of the processing of step S32 in Embodiment 4, processing of step S41, processing of step S42, processing of step S43, processing of step S44, or processing of step S45 is performed.

[0092] In the process of step S41, the CPU 18 generates both a data array in which the difference values ​​N5 are arranged in chronological order and a data array in which the difference values ​​N6 are arranged in chronological order. In other words, in the process of step S31 in the fourth embodiment, at least one of a data array in which the difference values ​​N5 are arranged in chronological order and a data array in which the difference values ​​N6 are arranged in chronological order is generated, but in the first modification of the fourth embodiment, both are always generated in the process of step S41.

[0093] In the process of step S42, the CPU 18 derives a vital value from the data array of difference value N5 generated in the process of step S41, and also derives a vital value from the data array of difference value N6. That is, the same process as the process of step S5 is performed on each of the data array of difference value N5 and the data array of difference value N6. Here, the CPU 18 sets the vital value derived from the data array of difference value N5 as vital value V1, and the vital value derived from the data array of difference value N6 as vital value V2.

[0094] In step S43, it is determined whether the difference between the vital values ​​V1 and V2 derived in step S42 is within a predetermined range. Here, the concept of the difference between the vital values ​​V1 and V2 will be described with reference to FIG. 17.

[0095] Fig. 17 is a diagram showing the concept of the difference between vital value V1 and vital value V2. Fig. 17 and Fig. 19, which will be described later, show the concept when the vital value is a value indicating the pulse rate. When a value indicating the pulse rate is derived as the vital value, the data array from which the vital value is derived simultaneously indicates the duration and wave height of the pulse.

[0096] The time length here refers to the length of time from the start of one pulse to the end of that pulse. The timing at which a pulse ends is the timing at which the next pulse begins. For example, in FIG. 17 , the pulse that started at time T11 for both vital value V1 and vital value V2 ends at time T12, and the duration of that pulse is time R11 for vital value V1 and time R21 for vital value V2. The pulse that started at time T12 ends at time T13, and the duration of that pulse is time R12 for vital value V1 and time R22 for vital value V2. The pulse that started at time T13 ends at time T14, and the duration of that pulse is time R13 for vital value V1 and time R23 for vital value V2. The pulsation that started at timing T14 ends at timing T15, and the duration of the pulsation is the duration of time R14 for vital value V1 and the duration of time R24 for vital value V2.

[0097] The wave height here is generated by the difference in sensor output due to the alternating intensity of the reflected light 532 in response to the alternating non-expanded portions 411 and expanded portions 412 of the artery 410 (see FIG. 9 ) in the irradiation range 530. In FIG. 17 , the wave heights of the pulsations occurring between timing T11 and timing T12 are individually shown as a wave height PA1 of the vital value V1 and a wave height PA2 of the vital value V2. The wave height PA1 is the difference between the peak Pe and the bottom Bt of the pulsations occurring during the time R11 from timing T11 to timing T12 for the vital value V1. The wave height PA2 is the difference between the peak Pe and the bottom Bt of the pulsations occurring during the time R21 from timing T11 to timing T12 for the vital value V2. While FIG. 17 illustrates the wave heights only for the pulsations occurring between timing T11 and timing T12, the wave heights of other pulsations can also be determined from the data array in a similar manner.

[0098] The CPU 18 compares the duration and wave height of the pulsation indicated by the vital value V1 with the duration and wave height of the pulsation indicated by the vital value V2, and determines whether the difference is within a predetermined range. As a specific example, the CPU 18 calculates the average duration and average wave height of multiple pulsations that occurred within a certain period of time, separately for the vital value V1 and the vital value V2.

[0099] The CPU 18 compares the average duration of pulsation of the vital value V1 (first average) with the average duration of pulsation of the vital value V2 (second average). If one of the first average and the second average is set to 100%, the CPU 18 determines whether the other falls within a predetermined range (e.g., ±10%), and if so, determines that the difference between the vital value V1 and the vital value V2 falls within a predetermined range.

[0100] The CPU 18 also compares the average pulse height of the vital value V1 (third average) with the average pulse height of the vital value V2 (fourth average). The CPU 18 determines whether the third average or the fourth average falls within a predetermined range (e.g., ±10%) when one of the third average and the fourth average is 100%. If the other falls within the predetermined range, the CPU 18 determines that the difference between the vital value V1 and the vital value V2 falls within the predetermined range. If the CPU 18 determines that the difference between the vital value V1 and the vital value V2 falls within the predetermined range in terms of both the duration and the pulse height, the CPU 18 determines in step S43 that the difference between the vital value V1 and the vital value V2 falls within the predetermined range (step S43; Yes). If not, the CPU 18 determines that the difference between the vital value V1 and the vital value V2 does not fall within the predetermined range (step S43; No).

[0101] In the above example, multiple averages of pulses are calculated, such as the first average, the second average, the third average, and the fourth average, and then the average calculated from the vital value V1 is compared with the average calculated from the vital value V2. However, the comparison method is not limited to this. For example, instead of calculating an average, the duration and wave height of pulses indicated by the vital value V1 and the vital value V2 that occur at substantially the same time may be compared individually. In this case, the duration and wave height may be compared for a portion of the sampled pulses among the multiple pulses, or the duration and wave height may be compared for all of the multiple pulses. Furthermore, when comparing the duration (or wave height) of the pulse indicated by vital value V1 with the duration (or wave height) of the pulse indicated by vital value V2, if one is set to a 100% value and the other is within a predetermined percentage (for example, ±10%) of the pulses that make up a predetermined percentage or more (for example, 70% or more) of all the pulses compared, it may be determined that the difference between vital value V1 and vital value V2 is within a predetermined degree.

[0102] If it is determined in the process of step S43 that the difference between vital value V1 and vital value V2 is within a predetermined range (step S43; Yes), the CPU 18 calculates the average of vital value V1 and vital value V2 ((V1 + V2) / 2) as vital value V (step S44). Referring to FIG. 17, vital value V1 has a waveform with a data arrangement intermediate between vital value V1 and vital value V2. If vital value V1 and vital value V2 are completely identical, vital value V will be the same as vital value V1 and vital value V2.

[0103] If it is determined in step S43 that the difference between vital values ​​V1 and V2 is not within a predetermined range (step S43; No), data interpolation is performed (step S45). A specific interpolation method for the data interpolation is to calculate a predicted value based on data from at least two past time points (points), and if the difference between the predicted value and the average of vital values ​​V1 and V2 is within a predetermined range, the predicted value is adopted. If the difference is outside the predetermined range, the vital value closest to the predicted value is selected from vital values ​​V1 and V2. As an example of a specific method for calculating the predicted value, linear approximation is used. If vital values ​​V at the two most recent time points (t1, t2) are y1 and y2, and the vital value V at the time point (t3) to which the predicted value is applied is y3, then y3 is calculated using the following formula (1): y3 = ((y2 - y1) / (t2 - t1)) (t3 - t1) + y1 (1)

[0104] In the first modification of the fourth embodiment, after the processing of step S44 or the processing of step S45, the processing proceeds to step S5. As described above, the first modification of the fourth embodiment is the same as the fourth embodiment, except for the points noted otherwise.

[0105] 18 is a flowchart showing the flow of processing related to derivation of vital values ​​performed in Modification 2 of Embodiment 4. In Modification 2 of Embodiment 4, instead of the processing of step S32 in Embodiment 4, the processing of step S51, the processing of step S52 or step S53, and the processing of step S4 described with reference to FIG.

[0106] In the process of step S51, it is determined whether the difference between the difference value N5 and the difference value N6 calculated in the process of step S31 is within a predetermined range. Here, the concept of the difference between the difference value N5 and the difference value N6 will be described with reference to FIG.

[0107] 19 is a diagram illustrating the concept of the difference between the difference value N5 and the difference value N6. As described in the first modification of the fourth embodiment with reference to FIG. 17, the vital value V1 and the vital value V2, which are the data arrays of the difference value N5 and the difference value N6, respectively, can be depicted as waveforms indicating a pulse. Therefore, the difference value N5 and the difference value N6 can be considered to be "part of a data set that can be expressed as a waveform indicating a pulse by arranging the data in a time series."

[0108] In the second modification of the fourth embodiment, the CPU 18 compares the difference values ​​N5 and N6 calculated based on the output of the optical sensor 60 at a certain timing. That is, for the difference values ​​N5 and N6 compared in the process of step S51, the outputs PD1 and PD2 that form the basis of the difference value N5 and the outputs PD3 and PD4 that form the basis of the difference value N6 are outputs that are output at the same timing.

[0109] 19 illustrates timings T21, T22, T23, and T24 as examples of timings compared in the processing of step S51. In the example shown in FIG. 19, the CPU 18 compares difference value N51, which is the value of difference value N5 at timing T21, with difference value N61, which is the value of difference value N6 at timing T21. The CPU 18 compares difference value N52, which is the value of difference value N5 at timing T22, with difference value N62, which is the value of difference value N6 at timing T22. The CPU 18 compares difference value N53, which is the value of difference value N5 at timing T23, with difference value N63, which is the value of difference value N6 at timing T23. The CPU 18 compares difference value N54, which is the value of difference value N5 at timing T24, with difference value N64, which is the value of difference value N6 at timing T24.

[0110] The CPU 18 determines whether the difference between the difference values ​​N5 and N6 at a certain timing falls within a predetermined range (e.g., ±10%) when one of the difference values ​​N5 and N6 is 100%. If the other falls within a predetermined range, the CPU 18 determines that the difference between the difference values ​​N5 and N6 at that timing falls within a predetermined range. Furthermore, the CPU 18 determines that the difference between the difference values ​​N5 and N6 falls within a predetermined range if, among the difference values ​​N5 and N6 compared within a certain period of time during which the output of the optical sensor 60 is continuously acquired when deriving a value indicating the pulse, the difference between the difference values ​​N5 and N6 falls within a predetermined range if the difference between the difference values ​​N5 and N6 falls within a predetermined range (e.g., 70% or more) of all the values ​​compared (step S51; Yes). Here, "all compared" may include the results of comparison between all difference values ​​N5 and N6 obtained within a certain period of time, or may be composed of the results of comparison between difference values ​​N5 and N6 at certain timings sampled within a certain period of time, such as timings T21, T22, T23, and T24 described with reference to Figure 19.

[0111] If the process of step S51 determines that the difference between difference values ​​N5 and N6 is within a predetermined range (step S51; Yes), the CPU 18 calculates the average of difference values ​​N5 and N6 ((N5 + N6) / 2) as the measured value N (step S52). If the process of step S51 determines that the difference between difference values ​​N5 and N6 is not within the predetermined range (step S51; No), data interpolation is performed (step S53). A specific interpolation method for the data interpolation process involves calculating a predicted value based on data from at least two past points in time. If the difference between the average of difference values ​​N5 and N6 and the predicted value is within a predetermined range, the predicted value is adopted. If the difference is outside the predetermined range, the vital value closest to the predicted value is selected from difference values ​​N5 and N6. As an example of a specific method for calculating the predicted value, when a calculation based on linear approximation is adopted, if the measurement values ​​N at the two most recent time points (t4, t5) are y4 and y5, and the measurement value N at the time point (t6) to which the predicted value is applied is y6, then y6 is calculated as in the following equation (2): y6=((y5-y4) / (t5-t4))(t6-t4)+y1... (2)

[0112] In the second modification of the fourth embodiment, after the processing of step S52 or the processing of step S53, the processing proceeds to step S4. The measurement value N in the processing of step S4 performed here is the measurement value N calculated in the processing of step S52 or the processing of step S53. After the processing of step S4, the processing proceeds to step S5, as in the first embodiment. As described above, the second modification of the fourth embodiment is the same as the fourth embodiment, except for the points noted otherwise.

[0113] According to the fourth embodiment and its modified example, two sets of optical sensors each including the above-mentioned first type optical sensor and second type optical sensor are provided, thereby ensuring the accuracy of detection using the output of each of the two sets of optical sensors.

[0114] Furthermore, the control circuit (control circuit 10) calculates, for each pair of two optical sensors, a difference value (difference value N5, difference value N6) obtained by subtracting the value corresponding to the output of the second-type optical sensor from the value corresponding to the output of the first-type optical sensor, and if the difference between the difference value (difference value N5) of one pair of two optical sensors and the difference value (difference value N6) of the other pair of two optical sensors is within a predetermined range, calculates the average of the difference values ​​of the two pairs of two optical sensors as the light measurement value of the multiple optical sensors. This makes it possible to more accurately determine whether the first-type optical sensor detected even a small amount of light or no light at all, and further ensures the accuracy of the output of the pair of two optical sensors by comparing the difference values ​​corresponding to the outputs of each pair of two optical sensors. This makes it easier to ensure detection accuracy.

[0115] It should be noted that both red light and near-infrared light are not required to determine the blood oxygen concentration; only one of them is possible. Therefore, it is sufficient for the detection device 100 to have at least one of the red LED 51 and the near-infrared LED 52 among the light sources 50, and the other is not necessary. However, in each of the above-described embodiments, both the red LED 51 and the near-infrared LED 52 are provided and used for the purpose of determining the blood oxygen concentration with higher accuracy.

[0116] Furthermore, the number of optical sensors is not limited to four. For example, two may be used, such as only the first optical sensor 61 and the second optical sensor 62, or only the third optical sensor 63 and the fourth optical sensor 64. Of course, the number of optical sensors may be three or five or more. The coefficients of the multiple optical sensors are not limited to four, a, b, c, and d, but are individually set for the multiple optical sensors provided in the detection device. Therefore, if the optical sensors are, for example, only the first optical sensor 61 and the second optical sensor 62, only the coefficients a and b are sufficient.

[0117] The light source 50 is not limited to an LED. For example, it may be an organic light-emitting diode (OLED). Alternatively, the light source 50 may be another light-emitting element that functions in the same manner as the red LED 51, near-infrared LED 52, and green LED 53 of the embodiment.

[0118] Furthermore, in each embodiment and its modified examples, the inner surface 1 is made of a light-transmitting material, which allows light from the light source 50 to be irradiated onto the hollow portion 200 and light to be detected by the light sensor 60, but this may be achieved by other methods. For example, a member having openings at positions corresponding to the light source 50 and the light sensor 60 on the inner circumferential surface of a ring-shaped housing and constituting a non-light-transmitting inner circumferential surface may be used.

[0119] Furthermore, other effects and advantages brought about by the aspects described in this embodiment that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present disclosure.

[0120] 10 Control circuit 50 Light source 51 Red LED 52 Near-infrared LED 53 Green LED 60 Optical sensor 61 First optical sensor 62 Second optical sensor 63 Third optical sensor 64 Fourth optical sensor 100 Detecting device

Claims

1. A detection device comprising: a light source; a plurality of optical sensors; and a control circuit that calculates a value based on the output of the plurality of optical sensors, wherein the control circuit individually multiplies a value corresponding to the output of the optical sensor by a coefficient for each of the values ​​corresponding to the output of the plurality of optical sensors.

2. The detection device according to claim 1, wherein the light source comprises a green light source that emits green light, and at least one of a red light source that emits red light and an infrared light source that emits infrared light, the plurality of optical sensors includes two or more sensors having different distances from the green light source, and among the coefficients by which values ​​corresponding to outputs from the plurality of optical sensors in response to the green light source being turned on are multiplied, a coefficient by which a value corresponding to an output from an optical sensor that is closest to the green light source is larger than a coefficient by which a value corresponding to an output from an optical sensor that is farthest from the green light source is multiplied.

3. The detection device according to claim 2, wherein the plurality of optical sensors are four optical sensors, and a coefficient multiplied by which a value corresponding to an output from two optical sensors that are relatively close to the green light source is 1, and a coefficient multiplied by which a value corresponding to an output from an optical sensor that is relatively far from the green light source is 0.

4. A detection device as described in claim 1 or 2, wherein the light source has at least one of a green light source that emits green light, a red light source that emits red light, and an infrared light source that emits infrared light, the multiple optical sensors include two or more sensors having different distances from one of the sensors, and among the coefficients by which the value corresponding to the output from the multiple optical sensors in response to the lighting of one of the sensors is multiplied, a coefficient by which the value corresponding to the output from the optical sensor that is closest to the one of the sensors is smaller than a coefficient by which the value corresponding to the output from the optical sensor that is farthest from the one of the sensors is multiplied.

5. The detection device according to claim 4, wherein the plurality of optical sensors are four optical sensors, and a coefficient by which a value corresponding to an output from two optical sensors that are relatively close to one of the sensors is multiplied is 0, and a coefficient by which a value corresponding to an output from an optical sensor that is relatively far from the one of the sensors is multiplied is 1.

6. The detection device according to claim 1, wherein the plurality of optical sensors include two or more sensors having different distances from the light source, and among the coefficients by which values ​​corresponding to outputs from the plurality of optical sensors in response to the illumination of the light source are multiplied, a coefficient by which a value corresponding to an output from an optical sensor having a closest distance to the light source is multiplied is smaller than a coefficient by which a value corresponding to an output from an optical sensor having a furthest distance from the light source is multiplied.

7. A detection device as claimed in claim 1 or 6, wherein the plurality of optical sensors includes four or more optical sensors, and the control circuit calculates, as the light measurement value of the plurality of optical sensors, an average value obtained by dividing the sum of four or more values ​​corresponding to the output of each of the plurality of optical sensors, excluding the maximum and minimum values, by the number of the plurality of optical sensors minus 2.

8. The detection device described in claim 1, wherein the plurality of optical sensors include a first optical sensor arranged to be able to detect light emitted from the light source, and a second optical sensor covered with a light-shielding layer that blocks the light emitted from the light source, and the control circuit calculates the light measurement value of the plurality of optical sensors based on a value corresponding to the output of the first optical sensor minus a value corresponding to the output of the second optical sensor.

9. The detection device according to claim 8, wherein two sets of optical sensors each including the first optical sensor and the second optical sensor are provided.

10. The detection device described in claim 9, wherein the control circuit calculates a difference value for each of the two optical sensor sets by subtracting a value corresponding to the output of the second optical sensor from a value corresponding to the output of the first optical sensor, and when a difference between the difference value of one of the two optical sensor sets and the difference value of the other of the two optical sensor sets is within a predetermined range, calculates an average value of the difference values ​​of both of the two optical sensor sets as a light measurement value by the multiple optical sensors.

11. The detection device according to claim 1 or 2, wherein the optical sensor is an organic photodiode.

12. The detection device according to claim 1 or 2, wherein the light source, the plurality of optical sensors and the control circuit are housed in a ring-shaped housing.

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