JP7582462B2 - Pulse wave measuring device - Google Patents

Description

The present invention relates to a pulse wave measuring device that has a built-in pulse wave sensor and measures a person's pulse wave.

Conventionally, an example of this type of pulse wave measuring device is a wrist-worn measuring device as disclosed in Japanese Patent Application Laid-Open No. 2003-233696.

This arm-worn measurement device includes a pulse detector, electrodes for detecting electrocardiograms that come into contact with a fingertip placed on the pulse detector, and a finger restricting portion for restricting the orientation of the fingertip relative to the pulse detector and the electrodes. The finger restricting portion is made up of a tip-side protrusion that restricts the position of the tip side of the fingertip by contacting the tip-side protrusion, and side protrusions that restrict the position of both sides of the fingertip by contacting both sides of the fingertip.

JP 2002-165768 A

However, in the arm-worn measuring device disclosed in the above-mentioned conventional patent document 1, as shown in Fig. 1(a), for a person whose fingertip 4 is narrower than the distance between the side protrusions 3, 3 provided on the surface of the housing 2 incorporating the pulse detector 1, the fingertip 4 moves between the side protrusions 3, 3, and the fingertip 4 moves to one side in the width direction between the side protrusions 3, 3. Therefore, the protective glass 5 of the pulse detector 1 may not be completely covered by the pad of the fingertip 4, and the protective glass 5 may be partially exposed. In this case, if the size of the gap formed in the exposed part of the protective glass 5 changes due to vibration or the like, the amount of light incident on the light receiving element of the pulse detector 1 through the gap changes, causing noise in the photoelectric pulse wave measurement and distorting the waveform of the photoelectric pulse wave measured by the pulse detector 1.

1(b), for a person whose fingertip 4 is wider than the distance between the side projections 3, 3, the fingertip 4 may not completely fit between the side projections 3, 3, and may float without touching the protective glass 5. Also, as shown in FIG. 1(c), if the tip side projection 6 that regulates the position of the tip side of the fingertip 4 is high, the fingertip 4 may float without touching the protective glass 5 even when the fingertip is placed against the tip side projection 6 from side A of the tip side projection 6. If the fingertip 4 floats even slightly from the protective glass 5 in this way, the pulse wave cannot be accurately measured by the pulse detector 1.

The present invention has been made to solve such problems,
A pulse wave sensor for measuring a pulse wave;
A housing having a built-in pulse wave sensor;
A pulse wave measuring device is configured by providing a protrusion on the surface of the housing around the pulse wave sensor that sandwiches the pulse wave sensor, the protrusion having a width smaller than the width of the sensing part of the pulse wave sensor and the width of the finger held over the pulse wave sensor, an outer shape larger than the distance between the tactile points of the skin on the pad of the finger held over the pulse wave sensor, and a height higher than the thickness of the epidermis layer of the skin on the pad of the finger and the same as or lower than the combined thickness of the epidermis layer and dermis layer of the skin on the pad of the finger , the protrusion being arranged in a direction along the longitudinal direction of the finger and protruding like a protrusion at an interval smaller than the length of the distal phalanx and larger than the two-point discrimination threshold of the skin on the pad of the finger, and allowing the fingertip of the touching finger to sense whether or not the pad of the fingertip is in close contact with the surface of the housing that covers the pulse wave sensor .

In order to stably measure the pulse wave, it is necessary for the pad of the fingertip to be in close contact with the surface of the housing that covers the pulse wave sensor. However, in the conventional pulse wave measuring device, the fingertip is simply guided and restricted to the sensor position by the finger restriction unit, and the pulse wave measurer does not recognize whether the pad of the fingertip touches the sensor position and whether it is in close contact with the surface of the housing that covers the pulse wave sensor. However, according to the present configuration, the pulse wave sensor is located between protrusions that are spaced apart from each other by a distance smaller than the length of the distal phalange of the finger held over the pulse wave sensor, and the position of the fingertip is recognized by the sensation of the fingertip touching the protrusions. Therefore, the pulse wave measurer can confirm and recognize whether the fingertip is in the sensor position and the pad of the fingertip is in close contact with the surface of the housing that covers the pulse wave sensor. This reduces the possibility that the fingertip will not touch the surface of the housing that covers the pulse wave sensor and will float away, as in the conventional case.

Furthermore, according to this configuration, the fingertip is positioned not by the outline of the finger but by placing the pad of the fingertip between the protrusions, so it can be done regardless of the thickness of the fingertip. Therefore, unlike the conventional case, when a thin fingertip touches the surface of the housing covering the pulse wave sensor in a biased manner with respect to the sensor position, the fingertip does not completely cover the pulse wave sensor, leaving a part of it exposed and creating a gap, and when a thick fingertip does not adhere closely to the surface of the housing covering the pulse wave sensor, it does not float.

In addition, since the pulse wave measurement person recognizes the protrusions by their outer contours, if the width of the protrusions is large, there is a possibility that the recognized position of the protrusions will deviate from the sensor position, but in this configuration, the width of the protrusions is smaller than the width of the sensing part of the pulse wave sensor, so the effect of the position deviation is small. Also, since the interval between the protrusions is smaller than the length of the distal phalanges of the fingers held over the pulse wave sensor, the positions of the distant protrusions can be clearly recognized by simultaneously touching each of the protrusions with the pads of the fingers of the distal phalanges, which have a sensitive sense of touch.

For this reason, according to the present invention, the possibility that the fingertip cannot completely cover the pulse wave sensor or that it floats away from the pulse wave sensor as in the conventional case is reduced, and a pulse wave measuring device can be provided that enables the person measuring the pulse wave to place their fingertip in close contact with the sensor position themselves and accurately measure the pulse wave without distortion.

1A and 1B are diagrams illustrating problems with a conventional pulse wave measuring device. 1 is a diagram showing a pulse wave measuring device according to a first embodiment of the present invention. 3A to 3C are diagrams illustrating a state in which the pulse wave measuring device according to the first embodiment is in close contact with a finger. 3A to 3C are diagrams illustrating the directivity angles of a light emitting element and a light receiving element in a pulse wave sensor constituting a pulse wave measuring device according to the first embodiment. 10A to 10C are diagrams illustrating measurement points of finger dimensions that are referenced in determining the dimensions of protrusions and the like that constitute the pulse wave measuring device according to each embodiment. FIG. 4 is a diagram showing a pulse wave measuring device according to a second embodiment of the present invention. 13A and 13B are diagrams illustrating a state in which a pulse wave measuring device according to a second embodiment is in close contact with a finger. FIG. 11 is a diagram showing a pulse wave measuring device according to a third embodiment of the present invention. 13A and 13B are diagrams illustrating a state in which a pulse wave measuring device according to a third embodiment is in close contact with a finger.

Next, an embodiment of the pulse wave measuring device of the present invention will be described.

Fig. 2(a) is a plan view of a pulse wave measuring device 11A according to a first embodiment of the present invention, and Fig. 2(b) is a cross-sectional view of the pulse wave measuring device 11A cut along line II in Fig. 2(a) and viewed from the direction of the arrows. In this embodiment, the pulse wave measuring device 11A is described as being incorporated into a smartphone, but it can also be incorporated into a mobile phone, a smart watch, a portable or stationary (installed) game machine, a pulse oximeter, a blood pressure estimation device that measures pulse waves, a blood glucose level estimation device, and a fatigue stress measurement device.

Pulse wave measuring device 11A is configured to include a pulse wave sensor 12, a housing 13, a protective cover 14, and protruding protrusions 15, 15. Housing 13 is the housing of a smartphone in which pulse wave measuring device 11A is incorporated, and contains pulse wave sensor 12. Pulse wave sensor 12 is configured from a photoelectric pulse wave sensor that has an LED (light emitting diode) 12a as a light emitting element in a light emitting section and a PD (photodiode) 12b as a light receiving element in a light receiving section, and measures the pulse wave.

In this embodiment, a photoelectric pulse wave sensor is used as the pulse wave sensor 12, but a piezoelectric pulse wave sensor can also be used. However, when the pulse wave sensor 12 is a piezoelectric pulse wave sensor, there may be no protective cover covering the pulse wave sensor 12, and the pulse wave sensor 12 may be exposed. If the protective cover is soft, such as a resin film, the pulse wave sensor 12 may be covered with the protective cover, but if the protective cover is hard, the pulse wave sensor 12 must be exposed because the pulse wave cannot be detected. In addition, the light-emitting element of the light-emitting unit and the light-receiving element of the light-receiving unit constituting the sensing unit of the pulse wave measuring device 11A are not limited to the LED 12a and the PD 12b, and a semiconductor laser such as a VCSEL (Viccell) may be used as the light-emitting element, and a phototransistor may be used as the light-receiving element. In addition, the camera and flash built into the smartphone may be regarded as the light-receiving element and the light-emitting element of the photoelectric pulse wave sensor, respectively, to configure the pulse wave sensor 12.

The light-emitting section is an area where light is emitted by the LED 12a, and the light-receiving section is an area where light can be received by the PD 12b, and each is surrounded by a light-shielding wall 12c. The light-emitting element usually emits pulsed light at about 10 to 1000 Hz. The pulse wave sensor 12 converts the light received by the light-receiving element into an electrical signal, which is then amplified, filtered, and AD-converted. The AD-converted digital signal is sampled in accordance with the light-emitting timing of the light-emitting element. The sampled digital signal is sent to the MCU of the smartphone in which the pulse wave sensor 12 is built.

The MCU obtains a pulse waveform (PPG waveform) based on the input digital signal, and obtains information such as pulse rate, autonomic nerve function, oxygen saturation, blood pressure, and blood glucose level from the obtained PPG waveform. In order to calculate oxygen saturation, a PPG waveform measured with light-emitting elements of multiple wavelengths such as red light and near-infrared light is required. In addition, a clean PPG waveform is required to calculate autonomic nerve function, blood pressure, and blood glucose level. In particular, calculation of blood pressure and blood glucose level is performed using the phenomenon in which the PPG waveform changes minutely due to changes in blood pressure and blood glucose level, so a PPG waveform with a good S/N ratio and no distortion is required.

Although one LED 12a and one PD 12b are shown in the figure, a light emitting element and a light receiving element may be configured with a plurality of each. The light emitting element may be configured with a plurality of LEDs with different emission wavelengths. Typical emission wavelengths are green, which is highly absorbed by living organisms, red, which is often used in pulse oximeters, and near-infrared wavelengths.

The LED 12a and the PD 12b are usually sealed with a transparent resin. Since light that does not pass through the skin and directly enters the PD 12b from the LED 12a significantly reduces the light receiving sensitivity, a light shielding wall 12c is formed between the LED 12a and the PD 12b. Since the pulse wave sensor 12 is touched by fingers, the light emitting section and the light receiving section are covered with a transparent protective cover 14 made of glass, acrylic, polycarbonate, etc. to prevent dirt from adhering, to be waterproof, and to prevent wear. The protective cover 14 is provided on the surface of the housing 13 that covers the built-in pulse wave sensor 12, but may be omitted.

The protrusions 15, 15 are provided in pairs on the surface of the housing 13 around the pulse wave sensor 12, sandwiching the pulse wave sensor 12, and are substantially hemispherical in shape, each having a width w equal to or smaller than the width W1 of the sensing portion of the pulse wave sensor 12. As shown in Figs. 3(a) and 3(b), the protrusions 15, 15 have a width w smaller than the width W2 of the finger 16 held over the pulse wave sensor 12, and as shown in Fig. 3(c), protrude at an interval L2 smaller than the length L1 of the distal part of the finger 16. This interval L2 is the distance between the highest points of the protrusions 15, 15. The protrusions 15, 15 are arranged along the longitudinal direction of the finger 16 to be measured, as shown in Fig. 2(a). The light emitting unit and the light receiving unit are arranged along the direction in which the protrusions 15, 15 are arranged in Fig. 2, but may be arranged in a direction perpendicular to the direction in which the protrusions 15, 15 are arranged.

3(a) and 3(b) are cross-sectional views of pulse wave measuring device 11A on which finger 16 is placed, as viewed from the tip side of finger 16, and Fig. 3(c) is a vertical cross-sectional view of pulse wave measuring device 11A on which finger 16 is placed. In Fig. 3, parts that are the same as or correspond to those in Fig. 2 are given the same reference numerals and their description will be omitted.

In addition, in this embodiment, the finger 16 is described as an index finger, but the finger 16 is not limited to an index finger and may be another finger. The shape of the protrusions 15, 15 may be a cone or a triangular pyramid, but it is preferable to round the corners of the protrusions so that the finger 16 does not feel pain when pressed with the finger 16. The shape may be a cylinder or a rectangular parallelepiped, but if the side surface is nearly vertical and angular, the fingertip may get caught and the pad of the finger 16 may float above the pulse wave sensor 12, so it is preferable that the side surface of the protrusions 15, 15 is inclined rather than vertical.

The protrusions 15, 15 have a height h that is higher than the thickness of the epidermis layer of the skin on the pad of the finger 16 and is equal to or lower than the sum of the thicknesses of the epidermis layer and dermis layer of the skin on the pad of the finger 16. The protrusions 15, 15 have an outer shape with a width w or length L (see FIG. 2(a)) that is larger than the distance between the tactile points of the skin on the pad of the finger 16, and are provided with a distance L2 that is larger than the two-point discrimination threshold of the skin on the pad of the finger 16. The protrusions 15, 15 are arranged outside the directivity angle θ of the photoelectric pulse wave sensor 12 as shown in FIG. 4. FIG. 4 is a vertical cross-sectional view of the pulse wave measuring device 11A showing the directivity angle θ. The angle at which the intensity of the light emitted from the LED 12a of the light-emitting unit is half of the maximum (usually the light-emitting center) is generally called the directivity angle. The angle at which the sensitivity of the light incident on the PD 12b of the light-receiving unit is half of the maximum (usually the light-receiving center) is also called the directivity angle.

If the protrusions 15, 15 are present within the directivity angle θ, the light reflected and scattered by the protrusions 15, 15 will directly enter the PD 12b without passing through the skin of the finger 16, reducing the sensitivity of the photoplethysmographic sensor 12. Therefore, the protrusions 15, 15 are arranged so as not to be within the directivity angle θ. However, since the light intensity is only reduced to half at the directivity angle θ, it is desirable to arrange the protrusions 15, 15 away from the edges of the light-emitting unit and the light-receiving unit so as not to enter the angle at which the light intensity is close to 0. If the directivity angle θ is large, stray light, which is light that enters the PD 12b directly from the LED 12a without passing through the skin of the finger 16, and disturbance light are more likely to enter the PD 12b, which may reduce the S/N ratio of the pulse wave measurement signal. In order to reduce the amount of stray light and disturbance light incident on PD 12b, it is effective to reduce the opening area of the light-emitting section and the light-receiving section or to form a lens at the opening of the light-emitting section and the light-receiving section, but this results in a decrease in the amount of light emitted by the light-emitting element and an increase in the thickness of the pulse wave sensor 12.

When measuring the pulse wave at the tip of the index finger 16, the suitable sizes of the light-emitting unit and the light-receiving unit are a width and length each within the range of 1 to 10 mm, and preferably within the range of 2 to 6 mm. If the size of the light-emitting unit and the light-receiving unit are larger than this, they will not be covered by the pad of the finger 16, causing light leakage from the LED 12a of the light-emitting unit and ambient light to enter the PD 12b of the light-receiving unit, resulting in a decrease in the S/N ratio of the pulse wave measurement signal. Conversely, if the size of the light-emitting unit and the light-receiving unit are smaller than this, the amount of light emitted by the LED 12a and the amount of light received by the PD 12b will decrease, also causing a decrease in the S/N ratio of the pulse wave measurement signal.

In addition, the width w of each of the protrusions 15, 15 is set to be smaller than the width W2 of the finger 16 in this embodiment as described above, but the minimum width W2 of the distal part of the index finger 16 of a Japanese person is the minimum width W2 of the distal part of the index finger 16 of a Japanese woman.
), the average value of the width Wa of the distal joint of the second finger (index finger) of Japanese women shown in FIG. 5(a) is 13.8 mm. The minimum value of this second finger distal joint width Wa is 11.7 mm (=13.8-3×0.7) when the dispersion of three times the standard deviation of the statistical data of 0.7 is expected. Therefore, if this second finger distal joint width Wa is the width W2 of the distal phalanx of the index finger 16, the width W2 of the distal phalanx of about 99.7% of Japanese women is 11.7 mm or more. In addition, the width W1 of the sensing part of the pulse wave sensor 12 is preferably 6 mm or less because the width W3 (see FIGS. 3(a) and 3(b)) where the pad of the index finger 16 contacts the pulse wave sensor 12 is smaller than the width W2 of the distal phalanx. Therefore, the width w of each of the protrusions 15, 15 is set smaller than the minimum width W2 of the distal part of the index finger 16, which is 11.7 mm, but is set to 6 mm or less so as to be equal to or smaller than the width W1 of the sensing part.

However, the smaller the size of each of the protrusions 15, 15, the better, and as described above, either the length L or the width w is set to be greater than the distance between tactile points on the skin of the finger 16. The skin density of Merkel's disks and Meissner's corpuscles, which are tactile receptors, is about 30 pieces/ ^cm2 , and the average distance between them is about 2 mm, so either the length L or the width w of the protrusions 15, 15 is set to be greater than 2 mm. Therefore, it is desirable for the width w of each of the protrusions 15, 15 to be 2 to 6 mm.

As described above, the height h of each of the protrusions 15, 15 is set to be higher than the thickness of the epidermis layer of the skin of the finger 16, which is the measurement site, and is set to be 0.2 mm or more since the thickness of the epidermis layer is about 0.2 to 0.3 mm. As described above, the height h of each of the protrusions 15, 15 is set to be the same as or lower than the sum of the thickness of the epidermis layer and dermis layer of the skin of the finger 16, which is the measurement site, and this sum of the thickness varies depending on the site, but is about 2 mm. Therefore, it is desirable for the height h of each of the protrusions 15, 15 to be 0.2 to 2 mm.

In addition, the distance L2 between the protrusions 15, 15 is set to be smaller than the length L1 of the distal phalange of the index finger 16 as described above, but since there is no statistical data on the length of the distal phalange of the index finger in the AIST human body size and shape database, the distal phalange length is considered to be 1/3 of the length of the index finger 16 for which there is length statistical data. The minimum length of the index finger 16 of Japanese people is the minimum for Japanese women. The average value of the length La of the second finger (index finger) of Japanese women shown in FIG. 5(b) is 66.5 mm according to the AIST human body size and shape database. The minimum value of this second finger length La is 56.0 mm (=66.5-3×3.5) when considering a spread of three times the standard deviation of the statistical data of 3.5. If the length L1 of the distal joint of the index finger 16 is 1/3 of the second finger length La, the length L1 of the distal joint of the index finger 16 is 18.7 mm (≈56.0÷3).

Therefore, the distance L2 between the protrusions 15, 15 is set to be smaller than 18.7 mm, but since in reality it is difficult for the fingertip to come into contact with protrusions such as the protrusions 15, 15, a distance of 15 mm or less is appropriate. Also, as described above, the distance L2 between the protrusions 15, 15 is set to be larger than the two-point discrimination threshold, which is the minimum distance at which two points are sensed on the skin, but this two-point discrimination threshold is 2 to 3 mm at the tip of the index finger 16. Therefore, a distance L2 between the protrusions 15, 15 of 3 to 15 mm is appropriate.

Furthermore, the directivity angle θ of the light-emitting section and the light-receiving section in photoplethysmographic sensor 12 varies depending on the structure of the light-emitting section and the light-receiving section, but is suitably about 30° to 60°. Therefore, if the directivity angle θ is 60° and the height h of protrusion 15 is 0.2 mm, then the distance L3 (see FIG. 4) by which protrusions 15, 15 are spaced from each edge of the light-emitting section and the light-receiving section is desirably 0.35 mm (=0.2×tan 60°) or more.

For stable measurement of the pulse wave, it is necessary that the pad of the fingertip of the finger 16 is in close contact with the surface of the housing 13 that covers the pulse wave sensor 12 and that the contact pressure does not fluctuate. In particular, if a gap is formed between the finger 16 and the surface of the housing 13 that covers the pulse wave sensor 12, noise superimposed on the pulse wave measurement signal increases, causing distortion of the pulse wave waveform. Conventional pulse wave measuring devices simply guide and restrict the fingertip to the sensor position using a finger restricting section, and are not configured to allow the person measuring the pulse wave to recognize for themselves whether or not the fingertip is touching the sensor position and the pad of the fingertip is in close contact with the surface of the housing that covers the pulse wave sensor.

However, according to the pulse wave measuring device 11A of this embodiment, the pulse wave sensor 12 is located between the protrusions 15, 15 that are provided at a distance L2 that is smaller than the length L1 of the distal part of the finger 16 held over the pulse wave sensor 12, and the position of the fingertip is recognized by the sensation of the fingertip of the finger 16 touching the protrusions 15, 15. Therefore, the person measuring the pulse wave checks and recognizes for himself whether the fingertip is at the sensor position and the pad of the fingertip is in close contact with the surface of the housing 13 that covers the pulse wave sensor 12. This reduces the possibility that the tip of the finger 16 will float without touching the surface of the housing 13 that covers the pulse wave sensor 12, as in the conventional case.

In addition, according to the pulse wave measuring device 11A of the present embodiment, the fingertip is positioned not by the outline of the finger 16 but by arranging the pad of the fingertip between the protrusions 15, 15, so that the fingertip can be positioned regardless of the thickness of the fingertip. Therefore, as shown in Fig. 1(a) in the conventional case, the thin fingertip 4 touches the pulse wave sensor 1 biasedly with respect to the sensor position, and the fingertip 4 cannot cover the pulse wave sensor 1, and a part of the fingertip is exposed, resulting in a gap. As shown in Fig. 3(a), the fingertip of the thin finger 16 completely covers the pulse wave sensor 12. Also, as shown in Fig. 1(b) in the conventional case, the thick fingertip 4 does not come into contact with the surface of the housing 2 that covers the pulse wave sensor 1 and floats, and as shown in Fig. 3(b), the fingertip of the thick finger 16 comes into contact with the surface of the housing 13.

Furthermore, since the pulse wave measurement person recognizes the protrusions 15, 15 by the outer periphery of each of the protrusions 15, 15, if the width w of each of the protrusions 15, 15 is large, there is a possibility that the recognized position of the protrusions 15, 15 may deviate from the sensor position. However, in the pulse wave measurement device 11A according to this embodiment, the width w of each of the protrusions 15, 15 is equal to or smaller than the width W1 of the sensing portion of the pulse wave sensor 12, so the influence of the positional deviation is small. Furthermore, since the interval L2 between the protrusions 15, 15 is smaller than the length L1 of the distal phalange of the finger 16 held over the pulse wave sensor 12, the distant protrusions 15, 15 can be simultaneously touched with the pad of the distal phalange of the finger 16, which has a sensitive sense of touch, and the position of each protrusion 15, 15 can be clearly recognized.

For this reason, the pulse wave measuring device 11A of the present embodiment reduces the possibility that, as in the conventional case, the fingertip 4 will not completely cover the pulse wave sensor 1 or will float above the surface of the housing 2 covering the pulse wave sensor 1. It is therefore possible to provide a pulse wave measuring device 11A that enables the person measuring the pulse wave to press the tip of their finger 16 against the sensor position themselves and accurately measure the pulse wave without distortion.

Furthermore, when the pad of the finger 16 contacts the surface of the housing 13 that covers the pulse wave sensor 12, if the width w of each of the protrusions 15, 15 is large and the pressing force of the finger 16 against the protrusions 15, 15 is strong, the blood flow of the finger 16 is obstructed along the contours of the protrusions 15, 15. If the width w of the protrusions 15, 15 is larger than the width W2 of the finger, the blood flow is obstructed over the entire width of the finger 16, and the pulse wave cannot be detected on the fingertip side from the protrusions 15, 15. However, according to the pulse wave measuring device 11A of this embodiment, each of the protrusions 15, 15 has a width w smaller than the width W2 of the finger 16, and there are areas on both sides of each of the protrusions 15, 15 where the blood flow is not obstructed, so that the pulse wave can be detected at the fingertip of the finger 16.

In addition, the skin has an epidermis layer and a dermis layer from the surface side, and sensory receptors including tactile receptors are in the dermis layer but not in the epidermis layer. Therefore, in the pulse wave measuring device 11A according to the present embodiment, the protrusions 15, 15 have a height h that is higher than the thickness of the epidermis layer of the skin on the pad of the finger 16, so that when the skin of the fingertip comes into contact with the surface of the housing 13 that covers the pulse wave sensor 12, the protrusions 15, 15 reach the depth of the dermis layer, and the sensory receptors in the dermis layer of the skin of the fingertip can reliably detect that the fingertip is touching the protrusions 15, 15.

Furthermore, if the height h of the protrusions 15, 15 is increased, the pressure applied to the fingertip from the protrusions 15, 15 will be stronger, which will likely cause blockage of blood flow in the fingertip, making it difficult for the pulse wave sensor 12 to detect the pulse wave. In addition, there is a risk that the protrusions 15, 15 will block the fingertip's pad and cause it to float above the pulse wave sensor 12. If the height h of the protrusions 15, 15 is further increased, the protrusions 15, 15 will no longer be embedded in the pad of the fingertip, and the pad of the fingertip will float above the surface of the housing 13 that covers the pulse wave sensor 12. According to the pulse wave measuring device 11A of this embodiment, the protrusions 15, 15 have a height equal to or less than the sum of the thicknesses of the epidermis layer and dermis layer of the skin on the pad of the finger 16, thereby suppressing the above-mentioned adverse effects. Furthermore, since the protrusions 15, 15 have a height that is the same as or less than the combined thickness of the epidermis layer and dermis layer of the skin on the pad of the finger 16, and have a height h that is greater than the thickness of the epidermis layer, it is possible to reliably detect contact with the protrusions 15, 15 at the fingertip of the finger 16 while suppressing the above-mentioned adverse effects.

Furthermore, if the outer shape of each of the protrusions 15, 15 is smaller than the distance between the tactile points of the skin on the pad of the finger 16, there is a risk that the contact of the protrusions 15, 15 with the pad of the finger 16 cannot be detected by the tactile points depending on the position where the protrusions 15, 15 make contact with the pad of the finger 16. However, according to the pulse wave measuring device 11A of this embodiment, the protrusions 15, 15 have outer shapes larger than the distance between the tactile points of the skin on the pad of the finger 16, so that the contact of the protrusions 15, 15 with the finger 16 can be reliably detected by the tactile points of the skin.

Furthermore, if the distance L2 between the protrusions 15, 15 is smaller than the two-point discrimination threshold of the skin on the pad of the finger 16, the person measuring the pulse wave will not be able to feel that the protrusions 15, 15 are spaced apart by the distance L2, and so may not be able to accurately recognize the position of the pulse wave sensor 12. However, according to the pulse wave measuring device 11A of this embodiment, the protrusions 15, 15 are spaced apart by the distance L2 which is larger than the two-point discrimination threshold of the skin on the pad of the finger 16, so the person measuring the pulse wave will be able to feel the distance L2 between the protrusions 15, 15 and correctly recognize the position of the pulse wave sensor 12 located between the protrusions 15, 15.

In addition, according to the pulse wave measuring device 11A of this embodiment, the protrusions 15, 15 are each substantially hemispherical in shape, and the edges at the protruding ends of the protrusions 15, 15 are not angular, so that the protrusions 15, 15 do not prick the finger and cause pain. In addition, if the side surfaces of the protrusions 15, 15 were nearly vertical, there would be a risk that the fingertip would get caught on the protrusions 15, 15 and the pad of the finger 16 would float above the surface of the housing 13 that covers the pulse wave sensor 12, but this does not happen. In addition, since the protrusions 15, 15 are each substantially hemispherical in shape, even if the fingertip is pressed against the protrusions 15, 15 from the side, the fingertip does not get caught on the protrusions 15, 15, and force is unlikely to be applied from the fingertip to the protrusions 15, 15. Furthermore, since the protrusions 15, 15 are frequently touched, if the protrusions 15, 15 have corners they are likely to wear out, but in the pulse wave measuring device 11A according to this embodiment, the protrusions 15, 15 are each substantially hemispherical and have no corners. Therefore, the protrusions 15, 15 are not easily subjected to force and have no corners, so wear can be effectively suppressed.

In the pulse wave measuring device 11A according to the present embodiment, the pulse wave sensor 12 is a photoelectric pulse wave sensor. A photoelectric pulse wave sensor is advantageous in reducing the size of the measuring device compared to a piezoelectric pulse wave sensor or the like, but if the protrusions 15, 15 are present within the directivity angle θ of the photoelectric pulse wave sensor, light scattered by the protrusions 15, 15 returns to the pulse wave sensor 12 and becomes stray light, causing a decrease in the S/N ratio of the pulse wave measurement signal. However, according to the pulse wave measuring device 11A according to the present embodiment, the protrusions 15, 15 are disposed outside the directivity angle θ of the pulse wave sensor 12, so light is not scattered by the protrusions 15, 15 and no stray light is generated. Therefore, the pulse wave measuring device 11A can be reduced in size without causing a decrease in the S/N ratio of the pulse wave measurement signal.

Fig. 6(a) is a plan view of a pulse wave measuring device 11B according to a second embodiment of the present invention, and Fig. 6(b) is a cross-sectional view of the pulse wave measuring device 11B taken along line II-II in Fig. 6(a) and viewed from the direction of the arrows. Fig. 7 is a vertical cross-sectional view of the pulse wave measuring device 11B on which a finger 16 is placed. In Figs. 6 and 7, parts that are the same as or correspond to those in Figs. 2 and 3(c) are given the same reference numerals and their description will be omitted.

In this embodiment, the housing 13 in which the pulse wave measuring device 11B is incorporated is provided with a protective cover 14' that is longer in the longitudinal direction than the protective cover 14 in the pulse wave measuring device 11A, on the surface of the housing 13 that covers the built-in pulse wave sensor 12, and the protrusions 15, 15 in the pulse wave measuring device 11B are provided on the surface of this transparent protective cover 14'. The other configuration of the pulse wave measuring device 11B is similar to that of the pulse wave measuring device 11A of the first embodiment.

In the pulse wave measuring device 11B of the second embodiment, there are no boundaries 17, 17 (see FIG. 2(a)) between the protective cover 14 and the housing 13 in the pulse wave measuring device 11A, and no slight step or gap between the protective cover 14' covering the pulse wave sensor 12 and the protrusions 15, 15. Therefore, in the pulse wave measuring device 11B of the second embodiment, the person measuring the pulse wave can easily and clearly recognize the position of the protrusions 15, 15 without being confused by the boundaries 17, 17, and the same effects as those of the pulse wave measuring device 11A of the first embodiment are achieved.

In this embodiment, a protective cover 14' is provided on the surface of the housing 13 by providing a protective cover 14' on the top of the pulse wave sensor 12, but the protective cover 14' may also be structured to be attached to the housing 13.

Fig. 8(a) is a plan view of a pulse wave measuring device 11C according to a third embodiment of the present invention, and Fig. 8(b) is a cross-sectional view of the pulse wave measuring device 11C taken along line III-III in Fig. 8(a) and viewed from the direction of the arrows. Figs. 9(a) and 9(b) are cross-sectional views of the pulse wave measuring device 11C on which a finger 16 is placed, viewed from the tip side of the finger 16, and Fig. 9(c) is a vertical cross-sectional view of the pulse wave measuring device 11C on which a finger 16 is placed. In Figs. 8 and 9, parts that are the same as or correspond to those in Figs. 2 and 3 are given the same reference numerals and their description will be omitted.

In this embodiment, finger restriction portions 18, 18 are provided for restricting the movement of the finger 16 in a direction perpendicular to the arrangement direction of the protrusions 15', 15'. The finger restriction portions 18, 18 are provided to protrude along the arrangement direction of the protrusions 15', 15', sandwiching both sides of the protrusions 15', 15' provided at a distance L2 with a distance wider than a contact width W3 of the finger 16 with the surface of the housing 13. The distance L2 between the protrusions 15, 15 in the first and second embodiments was the distance between the highest points of the protrusions 15, 15, but in this embodiment, the distance L2 between the protrusions 15', 15' is the distance between the highest points in the center near the pulse wave sensor 12, since the protrusions 15', 15' do not have a single highest point.

Unlike protrusions 15, 15, protrusions 15', 15' are not substantially hemispherical but substantially semicylindrical. In this embodiment, connecting portions 19, 19 are provided between protrusions 15', 15' and finger restriction portions 18, 18, and protrusions 15', 15', finger restriction portions 18, 18 and connecting portions 19, 19 are integrally formed at the same height h on the surface of housing 13. The other configurations of pulse wave measuring device 11C are similar to those of pulse wave measuring device 11A according to the first embodiment.

9B, the distance L4 between the finger restriction portions 18, 18 is set wide so that the finger 16 will not ride up onto the finger restriction portions 18, 18. Therefore, a recess that is recessed to fit the shape of the finger 16 is formed between the finger restriction portions 18, 18, and the position of the finger 16 held over the pulse wave sensor 12 is roughly restricted by this recess.

The maximum width W2 of the distal joint of the index finger 16 of Japanese people is the width W2 of the distal joint of the index finger 16 of Japanese men. According to the AIST human body size and shape database, the average value of the width Wa of the distal joint of the second finger (index finger) of Japanese men shown in FIG. 5(a) is 15.6 mm. The maximum value of this second finger distal joint width Wa is 18.3 mm (= 15.6 + 3 × 0.9) when the dispersion of the statistical data is three times the standard deviation of 0.9. Therefore, if this second finger distal joint width Wa is the width W2 of the distal joint of the index finger 16, the width W2 of the distal joint of the index finger 16 of about 99.7% of Japanese men is 18.3 mm or more.

Therefore, in order to prevent both sides of the finger 16 from climbing onto the finger restriction portions 18, 18 and the pad of the finger 16 from floating above the surface of the housing 13 that covers the pulse wave sensor 12, the distance L4 between the finger restriction portions 18, 18 is set to, for example, 10 mm. When the height h of the finger restriction portions 18, 18 increases, the distance L4 between the finger restriction portions 18, 18 needs to be widened, but in this embodiment, the finger restriction portions 18, 18 are integrated at the same height h as the protrusions 15', 15'. For this reason, the height h of the finger restriction portions 18, 18 is also set to 0.2 to 2 mm, the same as the protrusions 15', 15' which are equal to the protrusions 15, 15, and the distance L4 between the finger restriction portions 18, 18 is set to, for example, 10 mm as described above.

According to pulse wave measuring device 11C of the present embodiment, the movement of finger 16 in a direction perpendicular to the arrangement direction of protrusions 15', 15' is roughly restricted by finger restricting portions 18, 18, and protrusions 15', 15' are arranged at a distance L2 between finger restricting portions 18, 18. Therefore, a person measuring the pulse wave can recognize the rough position of the tip of finger 16 with finger restricting portions 18, 18, and then recognize the exact position of pulse wave sensor 12 with protrusions 15', 15'. This allows the position of pulse wave sensor 12 to be recognized quickly, and provides the same operational effects as those of pulse wave measuring device 11A of the first embodiment.

In the above third embodiment, the protruding portions 15', 15' are described as being substantially semi-cylindrical in shape, but they may be substantially hemispherical in shape like the protruding portions 15, 15 of the first and second embodiments. In this case, the protruding portions 15', 15' are configured to be separated from the connecting portions 19, 19.

In addition, in each of the above embodiments, the protrusions 15, 15, 15', 15' are provided one on each side of the pulse wave sensor 12, but the present invention is not limited to this, and a configuration in which multiple protrusions, for example, two on each side, a total of four, are provided on each side of the pulse wave sensor 12 may be used. In this case, by considering the cluster of multiple protrusions provided on each side of the pulse wave sensor 12 as one, and applying each of the above embodiments, the same effects as those of the above embodiments can be achieved.

11A, 11B, 11C...Pulse wave measuring device 12...Pulse wave sensor 12a...LED (light emitting element)
12b...PD (photodetector)
12c: light-shielding wall 13: housing 14: protective cover 15, 15': protrusion 16: finger (index finger)
17: Boundary 18: Finger restriction portion 19: Connection portion

Claims (5)

A pulse wave sensor for measuring a pulse wave;
A housing that houses the pulse wave sensor;
a protrusion that protrudes in a protruding shape at an interval smaller than the length of the distal phalanx of the finger and larger than the two-point discrimination threshold of the skin on the pad of the finger, the protrusion being disposed in a direction along the longitudinal direction of the finger , and that allows the user to recognize whether the pad of the fingertip is in close contact with the surface of the housing that covers the pulse wave sensor by the sensation of the fingertip of the finger that is touching the surface of the housing . The pulse wave measuring device according to claim 1 , wherein the protruding portion has a substantially hemispherical shape. 3. The pulse wave measuring device according to claim 1, wherein the pulse wave sensor is a photoelectric pulse wave sensor, and the protrusion is disposed outside the beam angle of the photoelectric pulse wave sensor. 3. The pulse wave measuring device according to claim 1, further comprising finger restriction sections that are disposed on both sides of the protrusions disposed at the intervals, at a distance wider than a contact width of the finger with the surface of the housing, protruding in a direction along which the protrusions are arranged, and that restrict movement of the finger in a direction perpendicular to the direction in which the protrusions are arranged. 3. The pulse wave measuring device according to claim 1 , wherein the housing has a transparent protective cover on a surface of the housing that covers the built-in pulse wave sensor, and the protrusion is provided on the surface of the protective cover.

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