JP2005160641A - Pulse wave detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse wave detector highly precisely detecting a pulse wave by removing the effect of a sunlight. <P>SOLUTION: A pulse wave sensor 3 is used by being fixed to an arm or the like of a human body and, as shown in Fig. (a), provided with an infrared LED 21 and a green LED 23 as light emitting elements and a photodiode 25 as a light receiving element. A light shielding plate 31 is disposed to cover the end face of a light transmission plate. The light shielding plate 31 employs a material having such a flexible characteristic as being in contact with the skin without any clearance, when a pulse wave sensor 3 is fixed to the arm or the like of the human body. The surface in the side of the light shielding plate 31 being in contact with the skin, is painted with a light-absorbing color. Projecting parts 33 are disposed on the light shielding plate 31 (refer to Fig. (b)) surrounding the light transmission plate 29. It is sufficient that if only the projecting part 33 has a height of producing a depression on the skin, when fixing the pulse wave sensor on the arm or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pulse wave detection device that detects a pulse wave of a living body using a light emitting element and a light receiving element.

In recent years, portable devices that support regular exercise such as a pedometer and calorie consumption meter have been used for the purpose of preventing lifestyle-related diseases. In order to judge this momentum more accurately, it is effective to measure the pulse rate. For this reason, an optical pulse wave sensor using a light absorption characteristic by a blood component is often used. This optical pulse wave sensor includes a light emitting element and a light receiving element, and is configured to irradiate light from the light emitting element toward the human body and receive the reflected light by the light receiving element. To detect the pulse wave. As this optical pulse wave sensor, for example, a pulse wave sensor constituted by a light emitting element and a light receiving element is fixed between the base of the human index finger and the second finger joint by a sensor fixing band. The thing is known (for example, refer patent document 1).
No. 97/037588

  However, when the optical pulse wave sensor is used outdoors, sunlight noise becomes a big problem. That is, when sunlight is incident on the pulse wave sensor outdoors, there is a problem that the pulse wave component that should be detected is buried in the sunlight noise and the pulse wave cannot be detected with high accuracy.

  This invention is made | formed in view of such a problem, and it aims at providing the pulse wave detection apparatus which removes the influence of sunlight and detects a pulse wave accurately.

  The pulse wave detection device according to claim 1, which is made to achieve the object, is fixed in contact with the skin of a living body, the light emitting means irradiates light to the living body, and the light receiving means includes: A pulse wave of the living body is detected by receiving the reflected light of the light emitted from the light emitting means through the light transmitting plate. The pulse wave detection device includes a light shielding plate that covers the end face of the translucent plate and shields light. The light shielding plate receives light irradiated from the outside of the pulse wave detection device via the skin of the living body. To prevent the light receiving means from receiving the light.

For this reason, the influence of the light irradiated from the outside can be removed and a pulse wave can be detected accurately.
By the way, as shown in FIG. 6 (a), the light received from the outside of the pulse wave detecting device (hereinafter also referred to as external light) is received by the light receiving means through the skin of the living body. Examples include propagation on the surface and inside the skin. Among these, the propagation on the skin surface is such that external light enters through a gap formed between the light shielding plate and the living body skin, and reaches the light receiving means while repeatedly reflecting between the light shielding plate and the living body skin. It is.

In order to suppress the propagation of the skin surface, the pulse wave detection device according to claim 1 may be configured as described in any one of claims 2 to 5.
That is, in the pulse wave detection device according to claim 1, as described in claim 2, it is preferable that the material of the light shielding plate has a property of absorbing light.

  According to the pulse wave detection device configured in this way, when external light incident from the gap formed between the light shielding plate and the skin of the living body hits the light shielding plate, the external light is absorbed by the light shielding plate, It is possible to suppress external light from being received by the light receiving means.

Further, in the pulse wave detection device according to claim 1 or 2, as described in claim 3, the outer surface of the light shielding plate is preferably painted with a color that absorbs light.
According to the pulse wave detection device configured as described above, when external light incident from a gap formed between the light shielding plate and the skin of the living body hits the light shielding plate, the external light is absorbed by the painted portion. Therefore, external light can be suppressed from being received by the light receiving means.

  Further, in the pulse wave detection device according to any one of claims 1 to 3, as described in claim 4, the material of the light shielding plate is obtained when the pulse wave detection device is fixed to the skin of the living body. In addition, it is preferable that the outer surface of the light-shielding plate has a characteristic that is flexible enough to contact the skin of the living body without any gap.

According to the pulse wave detection device configured as described above, a gap that causes external light to enter is not formed, and therefore it is possible to suppress external light from being received by the light receiving means.
Further, in the pulse wave detection device according to any one of claims 1 to 4, it is assumed that the outer surface is not a mirror surface on the outer surface of the light shielding plate as described in claim 5. It is advisable to form irregularities to the extent that they can be formed.

  According to the pulse wave detection device configured in this way, when external light incident from a gap formed between the light shielding plate and the skin of the living body hits the light shielding plate, the external light is scattered in all directions. It can suppress that light is received by the light receiving means.

On the other hand, propagation within the skin is such that external light passes through the inside of the skin and reaches the light receiving means, as shown in FIG.
In order to suppress propagation within the skin, the pulse wave detection device according to any one of claims 1 to 5, wherein the pulse wave detection device is applied to the skin of the living body as described in claim 6. It is good to provide the light-shielding convex part which produces a hollow in this skin when it fixes on the said outer surface of the said light-shielding plate.

  According to the pulse wave detection device configured in this way, the light-shielding convex portion stands on the path of the external light propagating inside the skin when the light-shielding convex portion presses the skin to such an extent that a dent is formed in the skin. In addition, the external light hitting the light-shielding convex portion is scattered in all directions, and the external light can be prevented from being received by the light receiving means.

  Further, in the pulse wave detection device according to claim 6, further, as described in claim 7, the material of the light-shielding convex portion is obtained when the pulse wave detection device is fixed to the skin of the living body. It is preferable that the light-shielding convex portion has such a flexible characteristic as to contact with the living body skin without any gap.

  According to the pulse wave detection device configured as described above, a gap that causes external light to enter is not formed between the light shielding convex portion and the skin of the living body, so that the external light is received by the light receiving means. Can be further suppressed.

Further, in the pulse wave detection device according to claim 6 or 7, as described in claim 8, the light-shielding convex portion may be arranged so as to surround the light transmitting plate. .
According to the pulse wave detection device configured as described above, the light-shielding convex portion is reliably arranged on the path until the external light propagating inside the skin reaches the light-receiving means, so that the external light is received by the light-receiving means. This can be further suppressed.

Further, in the pulse wave detection device according to an eighth aspect of the present invention, it is preferable that a plurality of the light shielding convex portions are arranged as in the ninth aspect of the present invention.
According to the pulse wave detecting device configured in this way, many light-shielding convex portions are arranged on the path until the external light propagating inside the skin reaches the light receiving means, and the external light is received by the light receiving means. Can be further suppressed from being received.

  By the way, in the case where the arrangement interval between the light-shielding protrusions matches an integer multiple of the frequency of the external light, even if the light-shielding protrusions are arranged on the path of the external light, the outside that propagates inside the skin The light may pass without hitting the light-shielding convex portion.

  For this reason, in the pulse wave detection device according to claim 9, as described in claim 10, the plurality of light-shielding convex portions are arranged so that the arrangement interval between them is random. Good.

  According to the pulse wave detection device configured as described above, the light-shielding convex portion whose arrangement interval does not match the integral multiple of the frequency of the external light is reliably arranged on the path of the external light propagating through the skin. Therefore, it can suppress that external light is received by the light-receiving means.

  Further, in the pulse wave detection device according to any one of claims 8 to 10, further, as described in claim 11, the light shielding convex portion is configured by a protrusion having a start end portion and a termination end portion. It is good to do so.

  According to the pulse wave detection device configured as described above, the air in the gap between the pulse wave detection device and the skin of the living body and the pulse wave detection via the gap formed between the ends of the protrusions. Air outside the device can circulate through a gap formed between the ends of the ridges.

That is, it is possible to suppress the stuffiness that tends to occur at the portion where the pulse wave detection device and the skin are in close contact.
Further, in the pulse wave detection device according to claim 11, further, as described in claim 12, among the plurality of light shielding convex portions, the light shielding convex portion disposed at a position farthest from the light transmitting plate. It is preferable that at least one light-shielding convex portion is arranged on a straight line connecting the gap formed between the end portions of the ridges constituting the light-transmitting plate and the translucent plate.

  According to the pulse wave detecting device configured as described above, the external light incident from the gap formed between the end portions of the protrusions constituting the light-shielding convex portions arranged at the positions farthest from the light transmitting plate. Since the light-shielding convex portion is arranged on the path, it is possible to suppress external light from being received by the light receiving means.

  By the way, the pulse wave detection device according to claims 1 to 12 detects the pulse wave with high accuracy by suppressing external light from being received by the light receiving means. As described, external light detection means for detecting external light irradiated from the outside of the pulse wave detection device and received by the light receiving means, and outputting an external light reception signal corresponding to the amount of received external light; And a pulse wave detecting means for detecting a pulse wave of the living body based on the external light receiving signal and the light receiving signal when the light emitting means emits light.

  According to the pulse wave detection device configured as described above, the external light detection means detects the external light received by the light receiving means and outputs an external light reception signal corresponding to the amount of received external light to detect the pulse wave. The means detects the pulse wave of the living body based on the external light reception signal and the light reception signal when the light emitting means emits light.

  That is, since the pulse wave of the living body can be detected in consideration of the part caused by the external light in the light reception signal when the light emitting means irradiates the light, the influence of the light irradiated from the outside is removed and the accuracy is improved. The pulse wave can be detected well.

In addition, as described in claim 13, the external light detection means and the pulse wave detection means described in claim 14 may be included in the pulse wave detection device described in claims 1-12.
Moreover, in the pulse wave detection device according to claim 13 or 14, as described in claim 15, the pulse wave detection means is based on a difference signal obtained by subtracting the external light reception signal from the light reception signal. The pulse wave may be detected.

According to the pulse wave detection device configured as described above, a signal from which the influence of external light is removed can be obtained by a simple calculation of subtracting the external light reception signal from the light reception signal.
Further, in the pulse wave detection device according to any one of claims 13 to 15, the light received by the light receiving means when the light emitting means is not irradiating light is usually external light. As described, the external light detecting means may detect the external light when the light emitting means stops emitting light.

According to the pulse wave detection device configured in this way, it is possible to detect external light without being affected by the light emitted from the light emitting means.
Further, in the pulse wave detection device according to claim 16, as described in claim 17, the light-emitting means emits light intermittently, and the external light detection means is turned on each time the light-emitting means stops emitting light. The external light may be detected.

  According to the pulse wave detection device configured as described above, the external light incident on the light receiving unit is detected from the previous light emission to the current light emission until the light emission unit emits the current light. The influence of incident external light can be accurately removed.

Embodiments of the present invention will be described below with reference to the drawings.
First, a pulse wave detection device 1 to which the pulse wave detection device of the present invention is applied will be described with reference to FIG.
The pulse wave detection device 1 of the present embodiment is a device that detects the pulse rate of a human body. As shown in FIG. 1, the pulse wave detection device 1 includes an infrared LED 21 and a green LED 23 as light emitting elements, and a photodiode (PD) as a light receiving element. A drive circuit 5 for driving the pulse wave sensor 3 by outputting a drive signal for irradiating light at different timings to the pulse wave sensor 3 provided with 25, the infrared LED 21 and the green LED 23, and It comprises a data processing device 7 that processes a signal from the pulse wave sensor 3 and controls the drive circuit 5. The drive circuit 5 and the data processing device 7 are accommodated in the casing of the pulse wave detection device main body 9.

  First, the configuration of the pulse wave sensor 3 will be described with reference to FIG. 2A is a cross-sectional view showing the configuration of the pulse wave sensor 3, and FIG. 2B is a plan view of the pulse wave sensor 3 viewed from the side in contact with the skin. Note that FIG. 2A shows a cross-section taken along the line AA in FIG.

  The pulse wave sensor 3 is used by being fixed to a human arm or the like. As shown in FIG. 2A, an infrared LED 21 that emits infrared light having a wavelength of about 940 nm and a green color of about 520 nm are used. It is an optical reflective sensor that includes a green LED 23 that emits light and a PD 25 that receives light and outputs a signal (light reception signal) corresponding to the amount of light received.

  The infrared LED 21, the green LED 23, and the PD 25 are arranged in parallel on the bottom 27 of the casing 20 of the pulse wave sensor 3 so that the infrared LED 21 and the green LED 23 are positioned on the left and right sides of the PD 25. A human body can be irradiated with infrared light or green light through a transparent plate 29. Further, a light shielding plate 31 that shields light is disposed so as to cover the end face of the light transmitting plate 29. The light shielding plate 31 is made of a material having such a flexible property that the light shielding plate 31 comes into contact with the skin without any gap when the pulse wave sensor 3 is fixed to a human arm or the like. Is preferred. The surface of the light shielding plate 31 that comes into contact with the skin is painted in a color that absorbs light (for example, black). In addition, although the light shielding plate 31 and the housing | casing 20 show a different thing in the figure, it is good also as a structure which has the same function as the light shielding plate 31 by processing the housing | casing 20. FIG.

  On the light shielding plate 31, the convex portion 33 is disposed so as to surround the light transmitting plate 29 in a triple manner. Although triple is used here, it may be single, double, or four or more. Moreover, the height of the convex part 33 should just be a height of the grade which produces a dent in skin, when the pulse wave sensor 3 is fixed to a human body arm etc., for example, it is good to set it as about 0.3 mm. As will be described later in detail, the convex portion 33 is for preventing external light from being received by the PD 25. Furthermore, the convex part 33 is comprised by the some protrusion which has a start end part and a termination | terminus part, and the space | gap 35 for the prevention of a dampness is formed between the edge parts of a protrusion. Further, the arrangement intervals of the convex portions 33 arranged in triplicate (for example, the intervals S1 and S2 in FIG. 2B) are not equal but random. The convex portion 33 is made of a material having such a flexible characteristic that the convex portion 33 comes into contact with the skin without a gap when the pulse wave sensor 3 is fixed to a human arm or the like. Is preferred. In addition, although the convex part 33 and the light shielding plate 31 and the housing | casing 20 show a different thing in the figure, it is good also as a structure which has the same function as the convex part 33 and the light shielding plate 31 by processing the housing | casing 20. FIG.

  Furthermore, on the line segment (for example, line segment BB) connecting the gap (for example, the gap 35a) formed in the convex portion 33 arranged at the position farthest from the translucent plate 29 and the translucent plate 29, At least one convex portion 33 is arranged.

  In the pulse wave sensor 3 configured as described above, first, as shown in FIG. 1, the pulse wave sensor 3 is fixed by bringing a translucent plate 29 and a light shielding plate 31 into contact with, for example, the skin of a human arm. Thereafter, the infrared LED 21 and the green LED 23 alternately irradiate infrared light and green light toward the human body, respectively, and the PD 25 receives the reflected light of this light. Then, the PD 25 outputs the change in the amount of received light as a light reception signal (for example, a voltage signal) to the data processing device 7.

  In addition, the light irradiated to the human body from the infrared LED 21 and the green LED 23 is absorbed by hemoglobin in the blood flowing through the capillary arteries when a part of the light passes through the inside of the human body. Light is reflected and scattered by capillaries. At this time, since the amount of hemoglobin in the capillary artery changes in a wave manner due to blood pulsation, the light absorbed in the hemoglobin also changes in a wave manner. That is, according to blood pulsation, the amount of received light that is reflected by the capillary artery and detected by the PD 25 changes.

Therefore, information on the pulse wave is obtained from the light reception signal output by the PD 25 (corresponding to the reflected light of the light emitted from the infrared LED 21 or the green LED 23).
The reason why the infrared LED 21 and the green LED 23 are used to detect the pulse wave will be described below.

  As shown in FIG. 5, the received light signal output from the PD 25 includes a signal (pulse wave component) indicating a pulse wave reflected by the capillary artery and a reflected wave component (reflected wave component) reflected from the skin surface or other than the capillary artery. ) And both components are included. When this received light signal is subjected to frequency analysis, it is mainly separated into a pulse component synchronized with the heartbeat, a body motion component synchronized with the body motion, and a substantially direct current component (which is a reflected wave component excluding the body motion component). .

  Among these, the direct current component is a light amount change (hereinafter referred to as noise A) accompanying a blood flow change due to expansion and contraction of a blood vessel, a skin surface scattered light amount change (hereinafter referred to as noise B) due to a shift of the pulse wave sensor 3, This is caused by a change in the amount of light (sunlight or the like) incident from the outside of the pulse wave sensor 3 and is cut by the detection circuit 11 by a method described later.

  As for the pulse component and the body motion component, the light absorption characteristics of infrared light and green light are different. In the light reception signal output from the PD 25 when the green LED 23 is caused to emit light, the pulse component and the body motion component are either Is obtained at a signal level that can be extracted, but in the light receiving signal output by the PD 25 when the infrared LED 21 is caused to emit light, the pulse component is very small compared to the body motion component, and only the body motion component is extracted. Obtained with possible signal levels.

  That is, a light reception signal (including a pulse component and a body motion component) output by the PD 25 when the green LED 23 emits light, and a light reception signal (including only the body motion component) output by the PD 25 when the infrared LED 21 emits light. By comparing these, only the pulse component can be extracted.

Incidentally, light from the outside of the pulse wave sensor 3 such as sunlight (hereinafter also referred to as external light) propagates on the skin surface or inside the skin and enters the PD 25.
Among these, a part of the external light propagating on the skin surface is absorbed by the surface of the light shielding plate 31 coated with a light absorbing color, as shown in FIG. 6B.

Further, the light shielding plate 31 (in close contact with the skin) prevents the formation of a gap that causes external light incidence.
Further, with respect to the external light propagating through the skin, the convex portion 33 formed on the surface of the light shielding plate 31 presses the skin, so that the external light propagating through the skin as shown in FIG. Since the convex portion 33 stands on the path, external light hitting the convex portion 33 is scattered.

These suppress external light from reaching the PD 25.
Next, the data processing device 7 amplifies the received light signal obtained from the pulse wave sensor 3, and a micro that performs various arithmetic processing such as pulse wave detection by processing the signal from the detection circuit 11. A computer (hereinafter referred to as a microcomputer) 13 is provided.

  As shown in FIG. 3, the detection circuit 11 includes an amplifying unit 41 that amplifies the received light signal obtained from the pulse wave sensor 3, and a correcting unit that outputs a DC component signal corresponding to the DC component to the amplifying unit 41. 43.

  Among these, the amplification unit 41 is configured around the operational amplifier OP1. The non-inverting input terminal (+) of the operational amplifier OP1 receives a light reception signal from the pulse wave sensor 3 through the resistor R2, and is grounded through the resistor R1. Further, the inverting input terminal (−) of the operational amplifier OP1 is connected to the output terminal of the operational amplifier OP1 through the resistor R3, while the DC component signal from the correction unit 43 is input through the resistor R4. The output terminal of the operational amplifier OP1 is connected to an A / D port PAD1 of a 10-bit A / D converter 13d described later. Further, the light reception signal from the pulse wave sensor 3 is also input to an A / D port PAD2 of the A / D converter 13d described later. The resistance value of the resistor R1 is set to be equal to the resistor R3, and the resistance value of the resistor R2 is set to be equal to the resistor R4. The resistance values of the resistors R1 to R4 are set so that the amplification degree of the operational amplifier OP1 is, for example, {(resistance value of R1) / (resistance value of R2)} = 1000.

The amplifier 41 configured as described above amplifies and outputs a signal obtained by cutting the voltage value of the DC component signal from the voltage value of the received light signal.
That is, among the light emitted from the infrared LED 21 and the green LED 23, only a small amount of light is absorbed by the hemoglobin, and the change of the pulse component appearing in the received light signal is thereby changed in the A / D converter 13d provided in the microcomputer 13. Amplification is required to enable detection. In this embodiment, amplification of about 1000 times is necessary.

  Further, since the change in the DC component is several to several hundred times larger than the change in the pulse component, if the DC component is amplified without subtracting the DC component from the received light signal, the amplified signal can be input to the A / D converter 13d. The upper limit of voltage is exceeded. For this reason, amplification is performed after the direct current component is subtracted from the received light signal.

  Next, the correction unit 43 is configured around the operational amplifier OP2 and the voltage dividing resistors R9 and R10. A D / A port PDA2 of a 10-bit D / A converter 13e described later is grounded via voltage dividing resistors R9 and R10. Further, the non-inverting input terminal (+) of the operational amplifier OP2 receives a signal from a D / A port PDA1 of a D / A converter 13e described later through a resistor R6 and is grounded through a resistor R5. ing. Further, the inverting input terminal (−) of the operational amplifier OP2 is connected to the connection point between the voltage dividing resistors R9 and R10 via the resistor R8, and is connected to the output terminal of the operational amplifier OP2 via the resistor R7. . The resistance value of the resistor R5 is set to be equal to the resistor R7, and the resistance value of the resistor R6 is set to be equal to the resistor R8. The resistance values of the resistors R5 to R8 are set so that the amplification degree of the operational amplifier OP2 is, for example, {(resistance value of R5) / (resistance value of R6)} = 1. Further, the resistance values of the voltage dividing resistors R9 and R10 are set to be, for example, “(resistance value of resistor R9) / (resistance value of resistor R10) = 1024”.

  In the correction unit 43 configured as described above, a signal obtained by multiplying the voltage value (V2) of the analog signal output from the D / A port PDA2 by (1/1024) is input to the inverting input terminal (−) of the operational amplifier OP2. In addition, a signal having a voltage value (V1) equal to the analog signal output from the D / A port PDA1 is input to the non-inverting input terminal (+) of the operational amplifier OP2. An analog signal having a voltage value of −V2 / 1024) is output.

  That is, the resolution of the voltage value of the analog signal output from the output terminal of the operational amplifier OP2 is 1024 times the resolution of the voltage value of the analog signal output from the D / A port PDA2.

  That is, by using two 10-bit D / A ports, an analog signal having a resolution of 20 bits is output. Then, an analog signal of voltage value V1 from D / A port PDA1 and a voltage value V2 from D / A port PDA2 so that the value of (V1-V2 / 1024) matches the voltage value of the DC component signal. The analog signal is output.

  Therefore, in the D / A port PDA2, when the voltage value of the analog signal to be output is changed by 1 bit of the minimum resolution, a signal exceeding the input voltage width of the A / D port PAD1 is input to the A / D port PAD1. Can be prevented. That is, for example, the input voltage width of the 10-bit A / D port PAD1 is 3V, the output voltage width of the 10-bit D / A port PDA1 is 3V, and only the D / A port PDA1 is used for the DC component signal. Assuming that the corresponding analog signal is output, if the minimum voltage change of the analog signal output from the D / A port PDA1 is 3 mV and the amplification factor of the operational amplifier OP1 is 1000 times as described above, the DC component signal The output change of the operational amplifier OP1 due to the 3 mV voltage change is 3V. That is, the output voltage of the operational amplifier OP1 exceeds the input voltage width of the A / D port PAD1 due to the voltage change of several bits of the DC component signal output from the D / A port PDA1.

  In contrast, in this embodiment, an analog signal having a resolution of 20 bits is output as a DC component signal. Therefore, when the output voltage width is 3 V, the minimum voltage change is about 3 μV, and the minimum voltage change The output change of the operational amplifier OP1 due to is about 3 mV. That is, the output voltage of the operational amplifier OP1 does not exceed the input voltage width of the A / D port PAD1 when the voltage changes for several bits of the DC component signals output from the D / A ports PDA1 and PDA2.

  The detection circuit 11 configured as described above amplifies the received light signal with the voltage value of the DC component signal as an offset while adjusting the voltage value of the DC component signal according to the analog signal from the D / A converter 13e. And output to the A / D converter 13d.

  Next, as shown in FIG. 1, the microcomputer 13 is provided with a CPU 13a that executes processing based on a predetermined processing program, a ROM 13b that stores various control programs, and various memories that store various data. RAM 13c, an A / D converter 13d that converts the voltage value of the analog signal into a 10-bit digital value, a D / A converter 13e that converts the 10-bit digital data generated by the CPU 13a into an analog signal, An input / output port 13f having a plurality of input ports for inputting various digital signals and a plurality of output ports for outputting various digital signals is provided.

  As shown in FIG. 1, the A / D converter 13d includes A / D ports PAD1 and PAD2 to which analog signals are input, and the D / A converter 13e is a D / A port that outputs analog signals. PDA1 and PDA2 are provided. Further, as shown in FIG. 1, the input / output port 13f includes an output port PO1, and a drive circuit 7 is connected to the output port PO1.

  In the microcomputer 13 configured as described above, the CPU 13a outputs the signal of the component corresponding to the noise A and the noise B in the DC component signal and the signal of the component corresponding to the external light. Each process is performed individually.

First, a process for outputting a signal of a component corresponding to the noise A and the noise B will be described.
The frequency of the voltage fluctuation of the received light signal caused by the noise A and the noise B is sufficiently lower than the pulse component, and the voltage fluctuation caused by these noises is small in a short time. For this reason, the CPU 13a analyzes the voltage fluctuation of the received light signal within the predetermined time every predetermined time range (for example, 10 seconds), thereby calculating the voltage fluctuation due to the noise A and the noise B at the present time. It adjusts with respect to the output value of D / A port PDA1, PDA2. As a result, a DC component signal corresponding to the noise A and the noise B is output from the correction unit 43. That is, the voltage value of the DC component signal is adjusted every predetermined time.

  Next, external light adjustment processing for outputting a component signal corresponding to external light (hereinafter referred to as an external light reception signal) will be described with reference to FIG. FIG. 4 is a flowchart showing the external light adjustment process. This external light adjustment process is a process that is repeatedly executed, for example, every time the infrared LED 21 and the green LED 23 are irradiated while the CPU 13a is activated (power ON).

  In this external light adjustment process, the CPU 13a first acquires the voltage value data of the signal input to the A / D port PAD2 in S10. Thereafter, in S20, it is determined whether or not the voltage value data acquired in S10 is the same value as the voltage value data acquired from the A / D port PAD2 last time. If it is determined that the values are the same (S20: YES), the process proceeds to S50. On the other hand, if it is determined that they are not the same value (S20: NO), the process proceeds to S30.

  Then, when the process proceeds to S30, the fluctuation amount of the voltage output from the D / A ports PDA1 and PDA2 is calculated based on the voltage value of the difference between the voltage value data acquired in S10 and the voltage value acquired last time. In S40, the voltage fluctuation calculated in S30 is adjusted with respect to the current output values of the D / A ports PDA1 and PDA2. Thereafter, the process proceeds to S50.

In S50, the green LED 23 is caused to emit light, and the voltage value data of the signal input to the A / D port PAD1 is acquired.
Further, in S60, the infrared LED 21 is caused to emit light and the voltage value data of the signal input to the A / D port PAD1 is acquired, and the external light adjustment process is terminated.

  In other words, in the external light adjustment processing, the light reception signal from the PD 25 when the infrared LED 21 and the green LED 23 are not emitting light is regarded as the external light reception signal, and the D / A port PDA1, in accordance with the voltage value of this light reception signal. The voltage value of the analog signal output from the PDA 2 is adjusted.

  In the pulse wave detection device 1 of the present embodiment configured as described above, immediately before the green LED 23 emits light, the light received by the PD 25 is detected as an external light reception signal (S10), and the external light reception signal is output (S20 to S20). S40). Thereafter, light is emitted in the order of the green LED 23 → the infrared LED 21, the light receiving signal output from the PD 25 when the green LED 23 or the infrared LED 21 emits light and the external light receiving signal are differentiated in the amplifying unit 41, and the difference signal is obtained. A pulse wave is detected by (S50-S60).

  For this reason, since the pulse wave of the human body can be detected in consideration of the portion caused by the external light in the received light signal when the infrared LED 21 or the green LED 23 irradiates light, the influence of the external light is removed and the accuracy is improved. A pulse wave can be detected.

Further, a signal from which the influence of external light is removed can be obtained by a simple calculation of subtracting the external light reception signal from the light reception signal.
Further, since the external light reception signal is detected when the infrared LED 21 and the green LED 23 stop emitting light, the external light can be detected without being affected by the light emitted from the infrared LED 21 or the green LED 23.

  Further, since the external light reception signal is detected immediately before the green LED 23 emits light, the influence of external light incident on the PD 25 when the infrared LED 21 and the green LED 23 emit light can be accurately removed. At this time, the light emission order of the green LED 23 and the infrared LED 21 may be from either.

  The pulse wave detection device 1 of the present embodiment is used in a state where the pulse wave sensor 3 is fixed to the human skin, and the surface of the light shielding plate 31 on the side in contact with the skin is painted with a color that absorbs light. Therefore, when external light incident from a gap formed between the light shielding plate 31 and the skin hits the light shielding plate, the external light is absorbed by the light shielding plate 31 and the external light is prevented from being received by the PD 25. it can.

  In addition, since a plurality of convex portions 33 are arranged on the surface of the light shielding plate 31 on the side in contact with the skin so as to surround the translucent plate 29, the convex portion projects on the path of external light propagating through the skin. The part 33 stands up and the external light striking the convex part 33 is scattered in all directions, and the external light can be suppressed from being received by the PD 25. As the number of convex portions 33 increases, more convex portions 33 are arranged on the path until external light propagating inside the skin reaches PD 25, and external light is received by PD 25. Can be suppressed.

  In addition, since the plurality of convex portions 33 are arranged so that the mutual arrangement interval is random, they do not coincide with an integer multiple of the frequency of the external light on the path of the external light propagating through the skin. Since the convex portions 33 having the arrangement interval are reliably arranged, it is possible to suppress external light from being received by the PD 25.

  Moreover, since the convex part 33 is comprised by the protrusion which has a start end part and a termination | terminus part, it is between the pulse wave sensor 3 and skin via the space | gap 35 formed between the edge parts of a protrusion. The air in the gap and the air outside the pulse wave sensor 3 can circulate. That is, it is possible to suppress the stuffiness that tends to occur at the portion where the pulse wave sensor 3 and the skin are in close contact.

  Moreover, in the convex part 33 arrange | positioned in the position most distant from the translucent board 29, on the line segment (line segment BB) which connects the space | gap 35a formed between the edge parts, and the translucent board 29. Since at least one convex portion 33 is arranged, it is possible to suppress the external light from being received by the PD 25 even when external light is incident from the gap 35a.

  In addition, the material of the light shielding plate 31 and the convex portion 33 is silicon having such a flexible characteristic that the light shielding plate 31 and the convex portion 33 are in contact with the skin without a gap when the pulse wave sensor 3 is fixed to the human skin. The material is used. For this reason, a gap that causes external light to enter is not formed, and external light can be suppressed from being received by the PD 25.

  In the embodiment described above, the infrared LED 21 and the green LED 23 are the light emitting means in the present invention, the PD 25 is the light receiving means in the present invention, the convex portion 33 is the light shielding convex portion in the present invention, and the processing and correction unit of S10 to S40 in FIG. 43 is an external light detection means in the present invention, and the processing of S50 to S60 in FIG. 4 and the amplification unit 41 are pulse wave detection means in the present invention.

As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
For example, in the above embodiment, the surface of the light shielding plate 31 on the side in contact with the skin is painted with a color that absorbs light. However, the light shielding plate 31 may be made of a material that absorbs light (for example, resin or rubber). In this way, when the external light incident from the gap formed between the light shielding plate 31 and the skin hits the light shielding plate, the external light is absorbed by the light shielding plate 31, so that the external light is received by the PD 25. This can be suppressed.

  Further, on the surface of the light shielding plate 31 on the side in contact with the skin, rough irregularities may be formed to such an extent that this surface can be regarded as not a mirror surface. In this way, when external light incident from the gap formed between the light shielding plate 31 and the skin hits the light shielding plate 31, the external light is scattered in all directions, so that the external light is received by the PD 25. Can be suppressed.

  Moreover, in the said embodiment, although shown about the case where sunlight injects as external light, if it is the light which injects from the exterior of the pulse wave sensor 3, it is applicable even if it is other than sunlight. For example, it may be light emitted from a fluorescent lamp.

  Moreover, in the said embodiment, the silicon material was used as a material of the light-shielding plate 31 and the convex part 33. FIG. However, when the pulse wave sensor 3 is fixed to a human arm or the like, a material other than a silicon material may be used as long as it has such a flexible characteristic as to contact the skin without any gap. For example, rubber, cloth, or gel-like solid material may be used.

Moreover, in the said embodiment, although the light-shielding plate 31 and the convex part 33 were shown as a structure different from the housing | casing 20, you may integrally form with the same member so that the same effect may be brought about.
Moreover, in the said embodiment, what the space | gap 35 was formed in the convex part 33 was shown. However, the convex portion 33 may have an annular shape, that is, a shape without the gap 35.

Explanatory drawing which shows the main structures of the pulse wave detection apparatus 1. FIG. An explanatory view showing the composition of pulse wave sensor 3. FIG. FIG. 3 is a circuit diagram showing a configuration of a detection circuit 11. The flowchart which shows the procedure of an external light adjustment process. An explanatory view showing a light reception signal obtained by pulse wave sensor 3. FIG. Explanatory drawing which shows skin surface propagation of external light and skin internal propagation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pulse wave detection apparatus, 3 ... Pulse wave sensor, 5 ... Drive circuit, 7 ... Data processing apparatus, 9 ... Pulse wave detection apparatus main body, 11 ... Detection circuit, 13 ... Microcomputer, 13a ... CPU, 13b ... ROM, 13c ... RAM, 13d ... A / D converter, 13e ... D / A converter, 13f ... input / output port, 20 ... housing, 21 ... infrared LED, 23 ... green LED, 25 ... PD, 27 ... bottom, 29 ... translucent plate, 31 ... light-shielding plate, 33 ... convex part, 35 ... gap, 41 ... amplifying part, 43 ... correction part, OP1, OP2 ... op amp, PAD1, PAD2 ... A / D port, PDA1, PDA2 ... D / A port, PO1 ... output port, R1-R10 ... resistor.

Claims (17)

A light emitting means for irradiating the living body with light;
A light receiving means for receiving at least reflected light of the light emitted from the light emitting means;
A translucent plate disposed on the light irradiation side of the light emitting means and transmitting light;
A light-shielding plate that covers an end surface of the light-transmitting plate and shields light;
The outer surface of the light-transmitting plate and the light-shielding plate opposite to the side where the light-emitting means and the light-receiving means are located is brought into contact with the skin of the living body to fix the device, A pulse wave detection device for detecting a pulse wave of the living body,
The light shielding plate is configured to prevent light irradiated from the outside of the pulse wave detection device from being received by the light receiving means through the skin of the living body.
A pulse wave detection device characterized by that. The pulse wave detection device according to claim 1, wherein a material of the light shielding plate has a characteristic of absorbing light. The pulse wave detection device according to claim 1 or 2, wherein the outer surface of the light shielding plate is painted in a color that absorbs light. The material of the light shielding plate has such a characteristic that the outer surface of the light shielding plate comes into contact with the skin of the living body without any gap when the pulse wave detecting device is fixed to the skin of the living body. The pulse wave detection device according to any one of claims 1 to 3. The pulse according to any one of claims 1 to 4, wherein irregularities are formed on the outer surface of the light shielding plate so that the outer surface can be regarded as not a mirror surface. Wave detector. The light-shielding convex part which produces a dent on the skin when the pulse wave detection device is fixed to the skin of the living body is provided on the outer surface of the light-shielding plate. The pulse wave detection device according to 1. The material of the light-shielding convex part has a characteristic that is flexible enough to allow the light-shielding convex part to come into contact with the skin of the living body without any gap when the pulse wave detection device is fixed to the skin of the living body. The pulse wave detection device according to claim 6. The pulse wave detection device according to claim 6, wherein the light shielding convex portion is disposed so as to surround the light transmitting plate. The pulse wave detection device according to claim 8, wherein a plurality of the light shielding convex portions are arranged. The pulse wave detection device according to claim 9, wherein the plurality of light-shielding convex portions are arranged such that the arrangement interval between them is random. The pulse wave detection device according to claim 8, wherein the light-shielding convex portion is configured by a protrusion having a start end portion and a termination end portion. On the straight line connecting the light-transmitting plate and the gap formed between the ends of the protrusions constituting the light-shielding convex portion disposed at the position farthest from the light-transmitting plate among the plurality of light-shielding convex portions. The pulse wave detection device according to claim 11, wherein at least one light-shielding convex portion is disposed. The light receiving means outputs a light reception signal corresponding to the amount of received light,
An external light detecting means for detecting external light irradiated from the outside of the pulse wave detecting device and received by the light receiving means, and outputting an external light receiving signal corresponding to the amount of received light of the external light;
Pulse wave detection means for detecting a pulse wave of the living body based on the external light reception signal and the light reception signal when the light emitting means emits light;
Comprising
The pulse wave detection device according to any one of claims 1 to 12, wherein the device is a pulse wave detection device. A light emitting means for irradiating the living body with light;
A light receiving means for receiving at least reflected light of the light emitted from the light emitting means and outputting a light reception signal corresponding to the amount of received light;
An external light detecting means for detecting external light irradiated from the outside of the pulse wave detecting device and received by the light receiving means, and outputting an external light receiving signal corresponding to the amount of received light of the external light;
Pulse wave detection means for detecting a pulse wave of the living body based on the external light reception signal and the light reception signal when the light emitting means emits light;
A pulse wave detection device comprising: The pulse wave detection means detects the pulse wave based on a difference signal obtained by subtracting the external light reception signal from the light reception signal;
The pulse wave detection device according to claim 13 or claim 14, characterized by the above. 16. The pulse wave detection device according to claim 13, wherein the external light detection unit detects the external light when the light emitting unit stops light emission. The light emitting means emits light intermittently,
The external light detecting means detects the external light every time the light emitting means stops emitting light.
The pulse wave detection device according to claim 16.

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