JP2016116947A - Pulse wave signal processing device and pulse wave measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique that enables stable extraction of an AC component regardless of a measurement part.SOLUTION: A pulse wave signal processing device has a first light reception unit that receives a reflected light of light emitted from a light emission part that emits light toward the measurement part, where pulse waves are measured, and outputs a first signal according to an amount of the received light, and a second light reception unit that receives the reflected light of the light emitted from the light emission part and outputs a second signal according to the amount of the received light. Each of the first light reception unit and the second light reception unit is provided at a position where a ratio between the AC component and a DC component contained in the second signal is smaller than the ratio between these components contained in the first signal. A light reception amount of each of the first light reception unit and the second light reception unit is adjusted so as to satisfy a condition for the DC component of the second signal to have magnitude equal to or smaller than magnitude of the DC component of the first signal. An amplification unit amplifies a differential signal (l3) between a first signal (l1) outputted from the first light reception part and a second signal (l2) outputted from the second light reception part, and outputs the AC component.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pulse wave signal processing device and a pulse wave measuring device.

  As a method for detecting a pulse wave in a living body, particularly a human body, a pulse wave measuring method using photoelectric conversion has been used. This method emits light of a wavelength that is easily absorbed by blood from a light emitting element such as a light emitting diode, and after passing through the living body or entering the living body, the back scattered light emitted to the outside by scattering by tissue in the living body is a photodiode. A pulse wave is detected by receiving light by a light receiving element such as a phototransistor and converting it into an electric signal. In Patent Document 1 below, when measuring the oxygen saturation level of arterial blood in a living body, an optical sensor is attached to the body surface such as the forehead and fingers where the density of peripheral blood vessels in the living body is relatively high, thereby improving the accuracy of measuring oxygen saturation level. A technique for setting the distance between the light source and the optical sensor is disclosed. Specifically, the following Patent Document 1 discloses a ratio of an AC component (AC component) and a DC component (DC component) of a signal output from the optical sensor (hereinafter referred to as an AC / DC ratio) depending on the distance between the light source and the optical sensor. Is utilized, and a photosensor is disposed at a position where the AC / DC ratio is the highest, so that the direct current component not representing the pulse wave is reduced as much as possible.

JP-A-10-216115

By the way, the AC / DC ratio not only changes according to the distance between the light source and the optical sensor, but also varies depending on the part of the living body to which the optical sensor is attached as shown in FIG. As shown in this figure, a finger having a relatively high density of peripheral blood vessels in the living body has a large AC / DC ratio and a high ratio of AC components representing pulse waves contained in the backscattered light. On the other hand, the wrist and upper arm, which have a relatively low density of peripheral blood vessels in the living body, have a smaller AC / DC ratio than fingers, and the ratio of AC components contained in the backscattered light is small. The signal output from the optical sensor is amplified in the subsequent amplification circuit and only the AC component is extracted. However, when the AC / DC ratio is small, the amplification circuit may be saturated due to the DC component and the AC component may not be extracted. is there. Also, when measuring a pulse wave at a measurement site such as a wrist with a small AC / DC ratio, if the light receiving area of the light receiving element is increased or the power of the light source is increased in order to obtain more AC components, the entire output signal is Since it becomes large, the amplifier circuit becomes saturated as described above, and the AC component cannot be extracted.
The present invention provides a technique capable of stably extracting an AC component regardless of a measurement site.

  A pulse wave signal processing apparatus according to the present invention emits light to a measurement site for measuring pulse waves, and receives a reflected light of light emitted from the light emitting unit and outputs a first signal corresponding to the amount of received light A first light receiving section that receives the reflected light of the light emitted from the light emitting section and outputs a second signal corresponding to the amount of light received, and the first light output from the first light receiving section. An amplifying unit that amplifies a differential signal between the signal and the second signal output from the second light receiving unit and outputs an alternating current component, and the first light receiving unit and the second light receiving unit include the second light receiving unit and the second light receiving unit. Provided at a position where the ratio of the AC component to the DC component of the signal is smaller than the ratio of the first signal, and satisfies the condition that the DC component of the second signal is less than or equal to the magnitude of the DC component of the first signal. As described above, the amount of received light is adjusted. According to this structure, the technique which extracts an alternating current component stably irrespective of a measurement site | part is provided.

  In the pulse wave signal processing device according to the present invention, in the pulse wave signal processing device, the first light receiving unit and the second light receiving unit have light receiving surfaces having different light receiving areas so as to satisfy the condition. It is characterized by. According to this configuration, it is possible to easily adjust the amount of received light as compared to the case of adjusting the amount of received light using another member.

  The pulse wave signal processing device according to the present invention is the above pulse wave signal processing device, wherein the first light receiving unit or the second light receiving unit includes a filter that suppresses transmission of the reflected light so as to satisfy the condition. It is provided on the light receiving surface. According to this configuration, the received light amount can be adjusted without being restricted by the space in the apparatus as compared with the case where the received light amount is adjusted by the light receiving area.

  Further, the pulse wave signal processing device according to the present invention is provided corresponding to the plurality of light emitting units, and a plurality of light emitting units that emit light of different wavelengths to the measurement site for measuring the pulse wave. A first light receiving unit that receives reflected light of the emitted light and outputs a first signal corresponding to the amount of received light; and a second signal that receives reflected light of the light emitted from the light emitting unit and that corresponds to the amount of received light. A plurality of light receiving units each having a second light receiving unit to output, the first signal of the plurality of light receiving units, and the difference signal between the first signal and the second signal output from the second light receiving unit. An amplification unit that amplifies and outputs an alternating current component, and the first light receiving unit and the second light receiving unit of the light receiving unit corresponding to each of the light emitting units, for each wavelength of light emitted by the light emitting unit, The ratio of the AC component and the DC component included in the second signal is smaller than the ratio of the first signal. The amount of received light is adjusted so that the direct current component of the second signal is less than or equal to the magnitude of the direct current component of the first signal. It arrange | positions in the position which does not interfere with light. According to this configuration, the AC component can be stably extracted for each wavelength regardless of the measurement site.

  Also, the pulse wave measuring device according to the present invention is any one of the pulse wave signal processing devices described above, and pulse wave output means for outputting information indicating the pulse wave based on the AC component output from the pulse wave signal processing device. It is characterized by providing. According to this configuration, the AC component can be stably extracted regardless of the measurement site.

It is a figure showing an example of composition of a pulse wave measuring device concerning an embodiment. It is a figure which shows the circuit structural example of the light-receiving part in the embodiment, and the amplifier. It is a figure showing the relationship between the distance of the light emitting element and light receiving element in the case of red light, and AC / DC ratio. It is a figure showing the optical path of the reflected light from a measurement site | part. It is a figure which shows the operation | movement flow of the pulse wave measuring device which concerns on embodiment. (A) is a figure showing the relationship between the distance of the light emitting element and light receiving element in the case of infrared light, and AC / DC ratio. (B) is a figure showing the relationship between the distance of the light emitting element and light receiving element in the case of green light, and AC / DC ratio. It is a figure which shows the example of arrangement | positioning of the light emission part in the modification (4), and a light-receiving part. It is a figure which shows the circuit structural example of the light-receiving part in a modification (5), and an amplifier. It is a figure which shows the circuit structural example of the light-receiving part in a modification (6), and an amplifier. It is a figure which shows the example of arrangement | positioning of the light emission part in the modification (7), and a light-receiving part. It is a figure which shows the relationship between a measurement site | part and AC / DC ratio in the case of red light.

  FIG. 1 is a diagram illustrating a configuration example of a pulse wave measurement device according to the present embodiment. In FIG. 1, a pulse wave measuring device 1 includes a light emitting unit 10, a light receiving unit 11 (first light receiving unit 11a, second light receiving unit 11b), an amplification unit 12, an A / D (ANALOG / DIGITAL) conversion unit 13, and a control unit. 14, an operation unit 15, and a display unit 16. The pulse wave measuring device 1 irradiates a measurement site for measuring the pulse wave of the living body 2 with light, receives backscattered light (reflected light) reflected at the measurement site, and based on the amount of received light, the pulse wave is received. A pulse wave signal indicating a wave is output. Each configuration will be described below.

  The light emitting unit 10 includes a light emitting element such as an LED (Light Emitting Diode) that emits light having a wavelength of red light, and the light emitting element has a light emission peak wavelength in a range of 600 to 780 nm (preferably 625 nm). It is configured. The light emitting unit 10 emits light toward the wrist of the living body 2 that is a measurement site under the control of the control unit 14 described later.

  Next, the light receiving unit 11 and the amplifying unit 12 will be described. FIG. 2 shows a circuit configuration of the light receiving unit 11 and the amplification unit 12 in the present embodiment. The first light receiving unit 11a and the second light receiving unit 11b include light receiving elements 111 and 112 such as photodiodes that receive light having a wavelength of red light. The light receiving element 111 and the light receiving element 112 are provided at different distances from the light emitting element, and the light receiving element 112 is configured to have a light receiving area smaller than that of the light receiving element 111. As shown in FIG. 2, in this embodiment, the anode of the light receiving element 111 of the first light receiving unit 11a and the cathode of the light receiving element 112 of the second light receiving unit 11b are connected in series, and the anode of the light receiving element 111 and the light receiving element are connected. The cathode connection point p 1 is connected to the input terminal of the amplifier 12. When the light receiving element 111 and the light receiving element 112 receive reflected light of the light emitted by the light emitting element of the light emitting unit 10, a current I1 corresponding to the amount of light received by the light receiving element 111 flows in the direction of the arrow, and the amount of light received by the light receiving element 112 is increased. A corresponding current I2 flows in the direction of the arrow. At a connection point p1 between the light receiving element 111 and the light receiving element 112, a current I3 obtained by subtracting the current I2 from the current I1 flows in the arrow direction.

  Here, the point that the ratio (AC / DC ratio) between the AC component and the DC component included in the signal output from the light receiving element differs according to the distance between the light emitting element and the light receiving element will be described. FIG. 3 shows the relationship between the distance from the center of the light emitting element that emits light of the wavelength of red light and the AC / DC ratio. FIG. 4 is a schematic diagram showing an optical path of light received by the light receiving elements X and Y having different distances from the light emitting element. The light emitting element emits light having a wavelength of red light, and the light receiving elements X and Y have the same characteristics as the light receiving elements 111 and 112 and have a light receiving area of the same level.

As shown in FIG. 4, in the light receiving element X having a distance L1 from the light emitting element, backscattered light from a portion close to the epidermis where the blood vessel density is relatively small is from a portion close to the dermis where the blood vessel density is relatively large. Is received more than the backscattered light. In the light receiving element Y whose distance from the light emitting element is L2, the backscattered light from the portion close to the dermis is received more than the backscattered light from the portion close to the epidermis. Backscattered light from a portion close to the epidermis contains more DC components that do not represent pulse waves than AC components that represent pulse waves, and backscattered light from portions close to the dermis has more AC components than DC components. included. In addition, more reflected light reaches the light receiving element X closer to the light emitting element than the light receiving element Y. Therefore, the magnitude relationship between the AC / DC ratio and the AC / DC ratio included in the signals output from the light receiving element X and the light receiving element Y is as follows.
AC component: light receiving element X> light receiving element Y
DC component: light receiving element X >> light receiving element Y
AC / DC ratio: light receiving element X <light receiving element Y

  That is, as shown in FIG. 3, in the case of light having a wavelength of red light, the AC / DC ratio increases as the distance between the light emitting element and the light receiving element approaches L2, and the AC / DC ratio decreases with the distance L2 as a boundary. Has characteristics. When a signal having a large DC component, such as the light receiving element X, is input to the first stage amplifier circuit, it becomes saturated and no AC component is extracted. In this embodiment, an AC / DC ratio that varies depending on the distance from the light emitting element is used. In addition, the DC component is reduced before being input to the first stage amplifier circuit. Specifically, the light receiving element 111 is provided at a position where the distance from the light emitting element is L2, and the light receiving element 112 is provided at a position where the distance from the light emitting element is L1 (<L2). That is, the light-scattering element 112 is arranged to receive the back-scattered light that has passed through the light path shorter than the optical path in the living body 2 of the back-scattered light reaching the light-receiving element 111. With this arrangement, the AC / DC ratio of the current signal of the second light receiving unit 11b (hereinafter referred to as the second signal) is the AC / DC ratio of the current signal of the first light receiving unit 11a (hereinafter referred to as the first signal). Smaller than.

  In addition, the light receiving area of the light receiving element 112 is configured to be smaller than the light receiving element 111 so that the DC component of the light receiving element 112 is approximately the same as the DC component of the light receiving element 111. By configuring in this way, a second signal that includes a DC component of the same degree as the DC component of the first signal and has an AC / DC ratio smaller than the first signal is output from the light receiving element 112, and at the connection point p1, A difference signal representing the difference between the AC component and the DC component of the first signal and the second signal is output. The AC component included in the difference signal is smaller than the AC component of the first signal, but the DC component can be smaller than the DC components of the first signal and the second signal. That is, when the AC component and the DC component included in the first signal and the second signal are defined as (AC1, DC1) and (AC2, DC2), the first signal and the second signal are DC1 ≧ DC2, AC1 / DC1. > The condition of AC2 / DC2 is satisfied.

  Next, the amplification unit 12 will be described. As shown in FIG. 2, the amplifying unit 12 includes a resistor 121, a first amplifying circuit 122 composed of an NPN transistor, a capacitor 123, and a second amplifying circuit 124. In the first amplifier circuit 122, the current I3 of the differential signal input to the base flows through the resistor 121, and an output voltage V (I3 × hfe × R) including an AC component and a DC component is output at the output point p2. The capacitor 123 removes the DC component Vdc of the output voltage V, and the AC component Vac is output to the second amplifier circuit 124. The second amplifier circuit 124 is composed of an inverting amplifier circuit, and amplifies the AC component Vac from the capacitor 123 and outputs it to the output terminal.

  Returning to FIG. 1, the description will be continued. The A / D conversion unit 13 quantizes the voltage signal output from the amplification unit 12 based on a predetermined sampling frequency. The control unit 14 includes a CPU (Central Processing Unit), a memory (ROM (Read Only Memory), and a RAM (Random Access Memory)), and the CPU executes a control program stored in the ROM, so that the control unit 14 Specifically, the control unit 14 controls the display unit 16 to display information indicating a pulse wave based on the voltage value output from the A / D conversion unit 13. Has a switch and an operation key for accepting an operation from the user, and outputs an operation signal indicating the content operated by the user to the control unit 14. The display unit 16 includes a liquid crystal display, and the control unit 14 Under the control, various images such as information indicating the instructed pulse wave are displayed.

(Operation example)
FIG. 5 is an operation flowchart of the pulse wave measuring device 1. The user performs an operation to instruct the start of pulse wave measurement via the operation unit 15 when starting measurement of the pulse wave. The control unit 14 receives an operation for instructing the start of pulse wave measurement from the operation unit 15 (step S11), starts the pulse wave measurement by controlling the light emitting unit 10, and outputs the first signal output from the light receiving unit 11. And signal processing is performed on the difference signal of the second signal (step S12).

  Specifically, the control unit 14 outputs a current signal indicating a certain light intensity to the light emitting unit 10 to irradiate the measurement site with light from the light emitting unit 10, and the first light receiving unit 11a and the second light receiving unit 11b. To receive the reflected light of the light and output a first signal and a second signal indicating a current corresponding to the amount of light received. The difference signal including the difference between the AC component and the DC component of the first signal output from the first light receiving unit 11a and the second signal output from the second light receiving unit 11b is input to the first amplification circuit 122 of the amplification unit 12. The In the first amplifier circuit 122, the differential signal is amplified, converted into a voltage signal, and input to the capacitor 123. The DC signal is removed from the voltage signal input to the capacitor 123, and the AC component is input to the second amplifier circuit 124. The second amplifier circuit 124 amplifies the input AC component voltage signal and outputs it to the A / D converter 13.

  The A / D converter 13 outputs a voltage value obtained by quantizing the voltage signal of the AC component representing the pulse wave input from the amplifier 12 to the controller 14 (step S13). The control unit 14 uses the time interval of the peak of the waveform based on the voltage value output from the A / D conversion unit 13 as the pulse interval, the frequency of appearance of the peak every predetermined time as the pulse rate, and the pulse interval as information indicating the pulse wave The pulse rate is output to the display unit 16 (step S14).

  In the embodiment described above, the light receiving element 111 and the light receiving element 112 are arranged so that the AC / DC ratios of the current signals output from the light receiving element 111 of the first light receiving unit 11a and the light receiving element 112 of the second light receiving unit 11b are different. Therefore, a difference signal having a DC component smaller than the DC components of the first signal and the second signal is input to the first amplifier circuit 122. As a result, the saturation state of the first amplifier circuit 122 caused by the DC component is suppressed, the first amplifier circuit 122 can be stably operated, and an AC component is not output during pulse wave measurement. Can be made difficult to occur.

<Modification>
The present invention is not limited to the above-described embodiment, and may be carried out by being modified as follows. Further, the following modifications may be combined.

(1) In the above-described embodiment, the light receiving element 111 of the first light receiving unit 11a is disposed at the distance L2 (FIG. 3) from the light emitting element where the AC / DC ratio of red light has a peak value, and the second light receiving unit. Although the example in which the light receiving element 112 of 11b is arranged at the position of L1 smaller than the distance L2 has been described, the light receiving element 112 may be arranged at a position of distance L3 (L3> L2) from the light emitting element. In short, it is only necessary that the light receiving element 111 and the light receiving element 112 are arranged so that the AC / DC ratio of the light received by the light receiving element 111 and the light receiving element 112 is different. In this case, since the amount of light received by the light receiving element 112 is smaller than that of the light receiving element 111, the light receiving area of the light receiving element 112 is smaller than that of the light receiving element 111 so that the DC components of the light receiving element 111 and the light receiving element 112 are approximately the same. You may comprise large.

(2) In the above-described embodiment, an example in which light having a wavelength of red light is emitted from the light emitting element has been described. However, infrared light or green light may be used. Since the AC / DC ratio in the case of infrared light has a peak value as shown in FIG. 6A as in the case of red light, the light receiving element 111 and the light receiving element are received at each position described in the embodiment and (1) above. The element 112 may be disposed. In the case of green light having no AC / DC ratio peak value as shown in FIG. 6B, the distance L2 has a high AC / DC ratio and the distance L1 has a lower AC / DC ratio. What is necessary is just to arrange | position the light receiving element 111 and the light receiving element 112, respectively.

(3) In the above-described embodiment, the example in which the light receiving area of the light receiving element 112 is configured to be small so that the DC components are approximately the same has been described. However, for example, optical that suppresses light transmission on the light receiving surface of the light receiving element 112. A filter may be provided to adjust the amount of received light. Further, as illustrated in the modification example (1), when the light receiving element 112 is arranged at a position farther from the light receiving element 111 than the light emitting element, the optical filter is provided on the light receiving surface of the light receiving element 111. The amount of received light may be adjusted.

(4) In the above-described embodiment, the example in which the measurement site is irradiated with light of one wavelength and the reflected light is received has been described. However, the measurement site is irradiated with light of a plurality of wavelengths, and the reflected light of each wavelength. May be configured to receive light. FIG. 7 shows the arrangement of the light emitting / receiving units corresponding to each wavelength in this case. The light receiving / emitting unit A includes a light emitting unit 100 having a light emitting element that emits light having a wavelength of red light, and a first light receiving unit 101 and a second light receiving unit 102 having a light receiving element that receives the reflected light. The light emitting / receiving unit B includes a light emitting unit 200 having a light emitting element that emits light having a wavelength of infrared light, and a first light receiving unit 201 and a second light receiving unit 202 having a light receiving element that receives the reflected light. The light emitting / receiving unit C includes a light emitting unit 300 having a light emitting element that emits light having a wavelength of green light, and a first light receiving unit 301 and a second light receiving unit 302 having a light receiving element that receives the reflected light.

  The light receiving elements of the second light receiving units 102, 202, and 302 are arranged at positions farther from the light emitting elements than the light receiving elements of the first light receiving units 101, 201, and 301, that is, at positions where the AC / DC ratio is higher. Yes. In addition, each of the light receiving elements of the first light receiving units 101, 201, and 301 is configured to have a small light receiving area so as to be approximately the same as the DC component of the first signal output from the corresponding second light receiving unit. That is, the amount of received light is adjusted so that the first signal and the second signal of each wavelength satisfy the conditions of AC2 / DC2> AC1 / DC1 and DC2 ≧ DC1. And each 1st light-receiving part and each 2nd light-receiving part of light-receiving / emitting part A, light-receiving / emitting part B, and light-receiving / emitting part C are arranged outside each light-emitting part so that the light of each wavelength may not interfere. . By comprising in this way, a pulse wave can be measured using the light of a some wavelength.

  In this case, each light emitting section may be made to emit light alternately every certain time, or light of each wavelength may be irradiated simultaneously from each light emitting section. In the latter case, the amplification unit 12 and the A / D conversion unit 13 may be provided for each light emitting / receiving unit. The first light receiving unit and the second light receiving unit receive the reflected light, and the first light receiving unit and the second light receiving unit output the first signal and the second signal corresponding to the amount of received light to the corresponding amplification unit 12. Then, each amplifying unit 12 extracts and amplifies the AC component of each wavelength, and outputs it to the corresponding A / D converter 13. In the present modification, an example in which light having three wavelengths is irradiated and received is described, but the present invention is not limited to this as long as light having two or more wavelengths is irradiated and received.

(5) In the above-described embodiment, the first amplifier circuit 122 may be configured by the current-voltage conversion circuit 125 shown in FIG. In this figure, the current-voltage conversion circuit 125 has an operational amplifier 125a and a feedback resistor 125b. The positive terminal of the operational amplifier 125 a of the current-voltage conversion circuit 125 is grounded, and the negative terminal of the operational amplifier 125 a is connected to the connection point P 1 between the light receiving element 111 and the light receiving element 112. When the difference signal between the first signal and the second signal output from the light receiving element 111 and the light receiving element 112 is input to the negative terminal of the operational amplifier 125a, the current-voltage conversion circuit 125 converts the difference signal into a voltage signal and inverts it. Amplify and output. The voltage signal output from the current-voltage conversion circuit 125 has its DC component removed by the capacitor 123, and the AC component is input to the second amplifier circuit 124 and amplified.

(6) In the above-described embodiment, the example in which the difference signal between the first signal and the second signal is input to the first amplifier circuit 122 has been described. For example, as illustrated in FIG. The anode of 112 may be connected to a differential amplifier circuit combined with an NPN transistor, and a voltage signal obtained by amplifying the difference between the first signal and the second signal input in the differential amplifier circuit may be output. In this case, the light receiving element 111 and the light receiving element 112 adjust the distance from the light emitting element and the light receiving area so as to satisfy the conditions of AC1 / DC1> AC2 / DC2, DC1 ≧ DC2. In addition, a resistor connected to the ground is provided on the anode side of the light receiving element 112, and the amounts of light received by the light receiving element 111 and the light receiving element 112 are adjusted so that the DC components of the light receiving element 112 and the light receiving element 111 are approximately the same. May be.

(7) In the above-described embodiment, the example in which the light emitting element of the light emitting unit 10 and the light receiving elements 111 and 112 of the first light receiving unit 11a and the second light receiving unit 11b are arranged side by side on the same plane has been described. For example, an arrangement as shown in FIG. 10 may be used as long as the positions of the first and second signals output from the element 111 and the light receiving element 112 are different from each other in the AC / DC ratio, that is, the optical path lengths in the measurement region are different. Good. FIG. 10 is a diagram illustrating a cross section of the light receiving and emitting unit in the present modification. In this example, the light receiving element 111 and the light receiving element 112 are provided so that the light receiving surface is in the upward direction in the figure on one surface of each transparent substrate 23 that transmits light, and the light collecting unit that covers the light receiving elements 111 and 112. 21 and 22 are provided. Reflective mirrors are provided on the inner surfaces of the light collecting portions 21 and 22. The light emitting element 20 is provided on the other surface of the transparent substrate 23 provided with the light receiving element 112, and light is emitted from the light emitting element 20 in the direction of the arrow in the figure. Supports 24 are provided at both ends of each transparent substrate 23 on which the light receiving elements 111 and 112 are not provided. Through the support 24, a member 25 such as glass that transmits light provided above the living body 2 is provided. A space K is provided between the transparent substrates 23. In this example, the light receiving element 111 is configured such that the AC / DC ratio of the light receiving element 111 is larger than that of the light receiving element 112 that is close to the light emitting element 20, and each light receiving amount is changed by changing the size and the radius of curvature of the light collecting portions 21 and 22. Has been adjusted. The light emitted from the light emitting element 20 passes through the member 25 from the space K and enters the living body 2, is reflected inside the living body 2, passes through the member 25, the space K, and the transparent substrate 23, and collects the light. , 22 are reflected by the inner surfaces of the light receiving elements 111 and 112, respectively.

(8) In the above-described embodiment, the pulse wave measurement device has been described as an example. However, the pulse wave signal processing device including the light emitting unit 10, the light receiving unit 11, and the amplification unit 12, the A / D conversion unit 13, and the control unit. The control device including at least 14 may be configured separately, and the pulse wave signal processing device and the control device may be connected by wired or wireless communication. In this case, the control device acquires an AC component signal output from the amplification unit 12 of the pulse wave signal processing device, and displays information indicating the pulse wave based on the acquired AC component signal, such as an external display device. You may comprise so that it may output to.

  DESCRIPTION OF SYMBOLS 1 ... Pulse wave measuring device 10, 100 ... Light emission part, 11 ... Light receiving part, 11a, 101, 201, 301 ... 1st light receiving part, 11b, 102, 202, 302 ... 2nd light-receiving part, 12 ... Amplification part, 13 ... A / D conversion part, 14 ... Control part, 15 ... Operation part, 16 ... Display part, 111, 112 ... Light reception Elements 121, resistors, 122, first amplifier circuit, 123, capacitor, 124, second amplifier circuit, 125, current-voltage conversion circuit, 125a, operational amplifier, 125b,. -Feedback resistor, A, B, C ... Light emitting / receiving section.

Claims (5)

A light emitting unit that emits light to a measurement site for measuring a pulse wave;
A first light receiving unit that receives reflected light of the light emitted from the light emitting unit and outputs a first signal corresponding to the amount of received light;
A second light receiving unit that receives reflected light of the light emitted from the light emitting unit and outputs a second signal corresponding to the amount of received light;
An amplification unit that amplifies a differential signal between the first signal output from the first light receiving unit and the second signal output from the second light receiving unit and outputs an AC component;
The first light receiving unit and the second light receiving unit are provided at a position where the ratio of the AC component to the DC component of the second signal is smaller than the ratio of the first signal, and the DC component of the second signal is The received light amount is adjusted so as to satisfy a condition that is equal to or less than the magnitude of the DC component of the first signal.   2. The pulse wave signal processing apparatus according to claim 1, wherein the first light receiving unit and the second light receiving unit have light receiving surfaces having different light receiving areas so as to satisfy the condition.   2. The pulse wave signal according to claim 1, wherein the first light receiving unit or the second light receiving unit is provided with a filter on the light receiving surface for suppressing transmission of the reflected light so as to satisfy the condition. Processing equipment. A plurality of light emitting units that emit light of different wavelengths to the measurement site for measuring the pulse wave;
A first light-receiving unit that is provided corresponding to the plurality of light-emitting units, receives reflected light of light emitted from the light-emitting unit, and outputs a first signal corresponding to the amount of received light; and light emitted from the light-emitting unit A plurality of light receiving parts having a second light receiving part that receives the reflected light of the first light and outputs a second signal according to the amount of light received;
An amplification unit that amplifies each differential signal of the first signal and the second signal output from the first light receiving unit and the second light receiving unit of the plurality of light receiving units and outputs an AC component;
The first light receiving unit and the second light receiving unit of the light receiving unit corresponding to each of the light emitting units have an AC component and a DC component included in the second signal for each wavelength of light emitted by the light emitting unit. The light receiving amount is adjusted so that the ratio is smaller than the ratio of the first signal, and the direct current component of the second signal is less than or equal to the magnitude of the direct current component of the first signal. The pulse wave signal processing device is characterized in that each pair of the light receiving units is arranged at a position where light of each wavelength does not interfere. The pulse wave signal processing device according to any one of claims 1 to 4,
A pulse wave measuring device comprising: pulse wave output means for outputting information indicating a pulse wave based on an alternating current component output from the pulse wave signal processing device.

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