Biological sensor

Abstract

To provide a biological sensor which is capable of detecting a motion of each muscle and is easy to attach and constitute.SOLUTION: A biological sensor (100), in use, is mounted on a living body as a subject. The biological sensor includes: a light emitting unit (11) for irradiating a living body with light; a light receiving unit (12) for receiving return light from a muscle of at least a part of the living body; and an output unit (13) for outputting information on the deformation of the muscle of the part on the basis of a detection signal from the light receiving unit corresponding to the received return light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a biosensor, and particularly to the technical field of biosensors that measure the state of a living body using optical technology.

Background Art

[0002] As this type of device, for example, a device that exhibits the muscle strength corresponding to the minimum value of the oxygen saturation in the blood of the muscle of a subject estimated from a correlation table showing the correlation between oxygen saturation and developed muscle strength has been proposed (see Patent Document 1).

[0003] Alternatively, a device that is fixed to the arm of a subject by a wearing band, has a pressing member that changes according to the contraction state of a muscle, and outputs a detection signal corresponding to the movement displacement of the pressing member has been proposed (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technique described in Patent Document 1, since the oxygen saturation that decreases (i.e., a change appears) due to muscle contraction for a certain period is monitored, there is a technical problem that instantaneous muscle contraction cannot be detected. In the technique described in Patent Document 2, since the wearing band is wound around the arm of the subject, for example, a contraction combining the movement of the prime mover and the movement of the antagonist muscle is detected, and there is a technical problem that the contraction of each individual muscle cannot be detected.

[0006] In addition, an electromyograph that measures the potential on the body surface has technical problems in that it requires time and care to attach the sensor, and in addition, a high-precision detection circuit for detecting weak potentials is required.

[0007] The present invention has been made, for example, in view of the above problems, and an object thereof is to provide a biosensor that can detect the movement of individual muscles and is simple to attach and configure.

Means for Solving the Problems

[0008] The biosensor of the present invention is a biosensor that is attached to a living body as a subject in order to solve the above problems, and includes a light emitting unit that irradiates the living body with light, a light receiving unit that receives at least the return light from the muscle of one part of the living body, and an output unit that outputs information regarding the deformation of the muscle of the one part based on a detection signal from the light receiving unit corresponding to the received return light.

[0009] The operation and other advantages of the present invention will become apparent from the following embodiments for implementation.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

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Figure 5

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Figure 7

Embodiments for Carrying Out the Invention

[0011] An embodiment of the biosensor of the present invention will be described.

[0012] The biosensor according to the embodiment is a biosensor worn on a living body as a subject, and includes a light emitting unit that irradiates the living body with light, a light receiving unit that receives at least the return light from the muscle of one part of the living body, and an output unit that outputs information regarding the deformation of the muscle of one part based on the detection signal from the light receiving unit in response to the received return light.

[0013] The biosensor is worn on the living body during its use. Here, the biosensor may be worn on the living body by a dedicated wearing member such as a band, or may be worn on the living body by, for example, a medical paper tape.

[0014] The light emitting unit emits light having a wavelength of, for example, 660 μm to 940 μm (red light to infrared light). Note that the wavelength of the light emitted from the light emitting unit is not limited to the above wavelength, and may be appropriately set according to, for example, the measurement target. The light receiving unit receives at least the return light from the muscle of one part of the living body.

[0015] The output unit including, for example, a memory, a processor, etc. outputs information regarding the deformation of the muscle of one part based on the detection signal from the light receiving unit.

[0016] Specifically, when the muscle of one part contracts, the physical distance between the light emitting unit and the light receiving unit decreases and the muscle pressure increases compared to the case where the muscle is stretched (during relaxation). As a result, when the muscle of one part contracts, the amount of return light received by the light receiving unit increases compared to when the muscle is stretched (that is, the signal level of the detection signal increases).

[0017] Therefore, the output unit outputs, for example, information indicating the signal level of the detection signal as information regarding the deformation of the muscle of one part.

[0018] According to the biosensor according to this embodiment, information regarding the deformation of a muscle is output based on the return light from the muscle of a certain site, so that even an instantaneous change in the muscle of a certain site can be detected. In addition, since the light receiving unit receives the most return light from the muscle closest to the biosensor (here, the muscle of a certain site), the detection signal from the light receiving unit is dominated by the influence of the deformation of the muscle closest to the biosensor. That is, according to the biosensor, only the deformation of the muscle of a certain site can be detected.

[0019] Furthermore, since the biosensor optically detects the deformation of the muscle, the configuration can be simplified and the handling can be facilitated as compared with an electromyograph that measures the weak electric potential on the body surface.

[0020] In one aspect of the biosensor according to this embodiment, the output unit determines that an increase in the signal level of the detection signal is the contraction of the muscle of a certain site.

[0021] According to this aspect, the deformation of the muscle of a certain site can be detected relatively easily, which is very advantageous in practical use.

[0022] In another aspect of the biosensor according to this embodiment, the light emitting unit and the light receiving unit are arranged on a flexible member.

[0023] According to this aspect, the distance between the light emitting unit and the light receiving unit on the member can be kept constant, so that the measurement result by the biosensor can be made reproducible and the biosensor can be easily attached to the living body.

[0024] In another aspect of the biosensor according to this embodiment, it further includes attenuation means for attenuating a signal component having a period longer than a predetermined period included in the detection signal.

[0025] It has been found by the research of the inventors of the present application that the detection signal includes the influence of physiological reactions such as changes in cardiac output. The influence of physiological reactions included in the detection signal (that is, the component related to the physiological reaction of the signal) has a longer period than the fluctuation period of the detection signal caused by muscle changes.

[0026] Therefore, in the present embodiment, the attenuation means attenuates the signal component having a period longer than a predetermined period included in the detection signal. Therefore, according to this aspect, the deformation of the muscle at one site can be preferably detected.

Example

[0027] An example of the biosensor according to the present invention will be described with reference to the drawings. In the following example, it is assumed that the subject is pedaling a bicycle.

[0028] The configuration of the biosensor according to the example will be described with reference to FIG. 1. FIG. 1 is a block diagram showing an outline of the biosensor according to the example.

[0029] In FIG. 1(a), the biosensor 100 includes a light emitting unit 11, a light receiving unit 12, an arithmetic unit 13, and a display unit 14.

[0030] The light emitting unit 11 has a light emitting element such as an LED (Light Emitting Diode). The wavelength of the light emitted from the light emitting unit 11 may be appropriately set according to the measurement object, for example.

[0031] The light receiving unit 12 has a light receiving element such as a PD (Photodioe). The light emitting unit 12 receives at least the return light from the muscle of the measurement object of the living body as the subject. Here, the "return light" typically means the light scattered or reflected by the living body. The light receiving unit 12 outputs a biological signal as the "detection signal according to the received return light" according to the present invention.

[0032] As shown in FIG. 1(b), the arithmetic unit 13 includes a band-pass filter 131 and a normalization unit 132. Details of the operation of the arithmetic unit 13 will be described later.

[0033] Here, the measurement principle of the biological sensor 100 will be described with reference to FIG. 2. FIG. 2 is a diagram for explaining the measurement principle of the biological sensor according to the embodiment.

[0034] In FIG. 2, first, each of the light emitting unit 11 and the light receiving unit 12 of the biological sensor 100 is attached to a site including the muscle to be measured of the subject. Note that each of the light emitting unit 11 and the light receiving unit 12 may not be attached to the skin of the subject directly or via gel or cream, and may be attached from above clothing, for example, clothing that adheres to the skin and allows the movement of the muscle to be measured to appear.

[0035] As shown in FIG. 2(a), it is desirable that each of the light emitting unit 11 and the light receiving unit 12 is disposed on a flexible member (in FIG. 2(b), the flexible member is not shown for convenience of explanation). However, each of the light emitting unit 11 and the light receiving unit 12 does not necessarily have to be disposed on the flexible member. The “flexible member” according to the embodiment is an example of the “member having flexibility” according to the present invention.

[0036] When the muscle contracts, the myosin filament pulls the actin filament closer to the center, and the myosin filament and the actin filament overlap deeply with each other. Therefore, compared with the relaxed state of the muscle, the muscle fibers are densified and the whole muscle changes into a rounded shape (see FIG. 2(b)).

[0037] When the muscle contracts, as shown in FIG. 2, the light emitting unit 11 and the light receiving unit 12 approach each other, and the angle formed by the normal of the light emitting surface of the light emitting unit 11 and the normal of the light receiving surface of the light receiving unit 12 changes (in FIG. 2, it changes from “θ1” to “θ2”). As a result, the optical distance from the light emitting unit 11 to the light receiving unit 12 is shortened. Therefore, the amount of light incident on the light receiving unit 12 among the light emitted from the light emitting unit 11 and scattered or reflected by the muscle to be measured increases.

[0038] In addition, when the muscle contracts, the intramuscular pressure increases and the blood flow to the active muscle is restricted, so the amount of light absorbed by the blood is reduced compared to when the muscle is relaxed. Therefore, when the muscle contracts, the amount of light scattered or reflected by the muscle to be measured increases.

[0039] That is, the amount of light detected by the light receiving unit 12 (i.e., the signal level of the output biological signal) and the change in the muscle to be measured are correlated.

[0040] When the subject is pedaling a bicycle, the muscles of the subject's legs repeatedly contract and relax periodically. When the biological sensor 100 is attached to the subject's leg, the biological signal output from the light receiving unit 12 has a period synchronized with the pedaling, as shown in FIG. 3, for example.

[0041] By the way, the biological signal includes the influence of physiological reactions such as changes in cardiac output. Specifically, as shown in FIG. 4(a), due to the physiological reaction, the entire biological signal fluctuates up and down with a relatively long period. The biological signal shown in FIG. 4 shows fluctuations over about 10 minutes.

[0042] Therefore, in this embodiment, the component caused by the physiological reaction included in the biological signal is attenuated by the band-pass filter 131 (see FIG. 1(b)) of the arithmetic unit 13. As a result, the signal output from the band-pass filter 131 becomes as shown in FIG. 4(b).

[0043] The filtered signal output from the band-pass filter 131 is normalized by the normalization unit 132 (see FIG. 1(b)). Specifically, the normalization unit 132 normalizes the filtered signal with the maximum value of the signal amplitude of the filtered signal as the maximum contraction state of the muscle and the minimum value of the signal amplitude as the non-contraction state of the muscle.

[0044] Subsequently, the normalization unit 132 outputs information indicating the temporal variation of the muscle contraction rate, for example, with the maximum value of the normalized signal being 100% of the muscle contraction rate and the minimum value of the normalized signal being 0% of the muscle contraction rate. Note that the "information indicating the temporal variation of the muscle contraction rate" according to the embodiment is an example of the "information regarding the deformation of the muscle of one part" according to the present invention.

[0045] In this embodiment, the crank angle of the bicycle that the subject is pedaling is detected by the crank angle sensor 20 (for example, a pedaling monitor). The display unit 14 of the biosensor 100 uses the crank angle detected by the crank angle sensor 20 to display, for example, the information indicating the temporal variation of the muscle contraction rate output from the calculation unit 13 in association with the crank angle (see FIG. 5).

[0046] By displaying in this way, the subject and the like can know the transition of the muscle contraction rate during pedaling, which is very advantageous in practical use.

[0047] Further, the biosensor 100 is not limited to the pair of light emitting unit 11 and light receiving unit 12, and may include a plurality of pairs of light emitting units and light receiving units. With this configuration, for example, the transitions of the contraction rates of a plurality of muscles such as the rectus femoris (front of the thigh), biceps femoris (outside of the hamstrings), gluteus maximus (buttocks), semitendinosus (inside of the hamstrings), tibialis anterior (front of the calf), gastrocnemius (rear of the calf), etc., which are used in the pedaling motion of the bicycle, can be detected (see FIG. 6).

[0048] As a result, for example, it is possible to evaluate the proper use of muscles during pedaling, detect an unintentional eccentric contraction (lengthening muscle contraction), etc., which is very advantageous in practical use.

[0049] (Effect of this embodiment) Among the technologies capable of evaluating the operating state of muscles, an electromyograph is cited as the most practical one. Therefore, the measurement results of the biological sensor 100 according to this embodiment are compared with the measurement results by an electromyograph with reference to FIG. 7. The graphs shown in FIG. 7 all show the variation of the muscle contraction rate for one cycle (i.e., for a crank angle of 360 degrees).

[0050] Although the explanation of the principle of the electromyograph is omitted, the electromyograph detects the action potential caused by the command to contract the muscles from the brain. In contrast, as described above, the biological sensor 100 optically detects the changes in the muscles. In other words, the biological sensor 100 detects the result of the change in the muscles. Thus, although the measurement principles of the electromyograph and the biological sensor 100 are different from each other, as shown in FIG. 7, the measurement results for each muscle are highly similar.

[0051] Therefore, it can be said that the measurement results by the biological sensor 100 are reasonable and have a measurement accuracy comparable to that of the electromyograph. That is, like the electromyograph, the biological sensor 100 can measure the instantaneous changes in the muscles for each muscle with high precision.

[0052] However, since the electromyograph measures the action potential of the muscles, it can measure muscle contractions that do not involve muscle deformation, such as isometric contractions. On the other hand, since the biological sensor 100 measures muscle contractions from the change in the amount of received light caused by the change in the muscles, it cannot measure muscle contractions that do not involve muscle deformation.

[0053] Here, in particular, if the light emitting unit 11 and the light receiving unit 12 of the biological sensor 100 can be physically fixed to the site including the muscle to be measured, the changes in the muscle can be measured, and its handling is very easy. In addition, since the biological sensor 100 only needs to be able to detect signals of about the speed at which the subject moves (for example, 10 Hz or less), for example, the circuit configuration and the like can be simplified and miniaturized. For this reason, the biological sensor 100 can suitably measure the state of the muscles in fields where the muscles are actively moved, such as the sports field and the like.

[0054] In the present embodiment, pedaling a bicycle has been taken as an example. However, for relatively simple periodic motions such as jogging or running, the biological sensor 100 can display measurement results as shown in FIGS. 5 to 7.

[0055] The "arithmetic unit 13" and the "band-pass filter 131" according to the embodiment are examples of the "output unit" and the "attenuation means" according to the present invention, respectively.

[0056] The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or idea of the invention that can be read from the claims and the entire specification. A biological sensor accompanied by such a change is also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0057] 11... light emitting unit, 12... light receiving unit, 13... arithmetic unit, 14... display unit, 20... crank angle sensor, 100... biological sensor, 131... band-pass filter, 132... normalization unit

Claims

【Claim 1】 A biosensor to be worn on a living body as a subject, a light emitting unit that irradiates light onto the living body, a light receiving unit that receives at least the return light from the muscle of one part of the living body, and an output unit that outputs information regarding the deformation of the muscle of the one part based on a detection signal from the light receiving unit corresponding to the received return light. The biosensor is characterized by comprising the above.

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