WO2023210376A1

WO2023210376A1 - Pressure sensor and robot

Info

Publication number: WO2023210376A1
Application number: PCT/JP2023/014905
Authority: WO
Inventors: 哲朗三ツ井; 陽大石井; 直之師岡; 遼司姫野; 慎一森嶌
Original assignee: 富士フイルム株式会社
Priority date: 2022-04-28
Filing date: 2023-04-12
Publication date: 2023-11-02

Abstract

The present invention addresses the problem of providing a pressure sensor that makes it possible to easily measure pressure such as blood pressure and a robot including the pressure sensor. In order to solve the problem, this pressure sensor comprises an imaging element, a light reflecting layer opposed to an imaging surface and disposed with a space from the imaging element, the light reflecting layer having reflective characteristics that change depending on pressure, and a light source for emitting light that enters the space between the imaging element and the light reflecting layer, and pressure is detected from a change in an image captured by the imaging element when pressure is applied from a side of the light reflecting layer facing away from the imaging element, with the light from the light source entering the space between the imaging element and the light reflecting layer.

Description

Pressure sensors and robots

The present invention relates to a pressure sensor used as a blood pressure sensor, a tactile sensor, etc., and a robot equipped with this pressure sensor.

Pressure sensors are used in various fields.
For example, in recent years, blood pressure has been measured not only in medical facilities but also at home in order to check the state of health and maintain health.
Blood pressure measurement devices usually measure blood pressure by wrapping a blood pressure measurement cuff called a cuff around the arm or wrist, compressing blood vessels, blocking blood flow, and then releasing the pressure. , measured using a method called the oscillometric method.

Here, blood pressure varies depending on the health condition of the subject. Therefore, for example, if there is a possibility of developing a high-risk disease such as cerebrovascular disease or cardiovascular disease, it is preferable to measure blood pressure continuously.

However, in the oscillometric method, it is necessary to cut off blood flow once in order to measure blood pressure, and therefore blood pressure cannot be measured continuously. Furthermore, in the oscillometric method, it takes time and effort to measure blood pressure once, and continuous blood pressure measurement is substantially difficult.
On the other hand, a blood pressure measuring method called tonometry is known as a blood pressure measuring method that can easily and continuously measure blood pressure.
The tonometry method is a blood pressure measurement method in which, for example, a pressure sensor is pressed flat against the radial artery near the body surface of the wrist and the blood pressure is measured every beat.

For example, Patent Document 1 describes a method for generating blood pressure data by processing output signals from a two-dimensional array of photosensitive elements, in which the two-dimensional array of photosensitive elements is placed on the body surface of a subject. and an output signal from one or a set of photosensitive elements; The optical blood pressure sensor generates a two-dimensional image of the subject's body surface during the period in which blood pressure information is being determined about the subject. and digitally processing the two-dimensional image to thereby obtain a two-dimensional array of digital output values, the output values being output values for one or a set of photosensitive elements. , a method for measuring blood pressure by tonometry is disclosed, further comprising applying a calibration relationship to a portion of the array of digital output values corresponding to one or a set of photosensitive elements, thereby obtaining blood pressure data. There is.

Moreover, pressure sensors are used for various purposes other than blood pressure measurement.
For example, there is an increasing demand for pressure sensors in tactile sensing applications such as robotics and input interfaces.
Specifically, in robot applications, it is desirable to constantly detect pressure, contact area, and amount of deformation so that when a robot grasps something, it can apply an appropriate force depending on the shape, hardness, etc. ing. In response to this, for example, Non-Patent Document 1 discloses a system that calculates pressure by measuring the deformation of a membrane when it comes into contact with an object from a captured image.

Special Publication No. 2003-532475

The blood pressure measurement method described in Patent Document 1 mentioned above includes a flexible light-reflecting film, a line light source formed by arranging a plurality of light sources in a line, and a line light source disposed between the light-reflecting surface and the line light source. Blood pressure is measured using a line sensor.

That is, in the blood pressure measurement method described in Patent Document 1, a flexible light-reflecting film is pressed against the radial artery from the body surface of the subject, and measurement light is irradiated from a line light source to the light-reflecting film. Then, the measurement light reflected by the light reflection film is photometered by a line sensor.
Since the light reflecting surface has flexibility, it deforms in response to expansion of the radial artery due to heartbeat. Further, the degree of deformation of the light reflecting surface changes depending on blood pressure. As a result, the intensity of reflected light received by each pixel of the line sensor also changes depending on the blood pressure.
Therefore, blood pressure can be measured by knowing in advance the relationship between blood pressure and the image output by the line sensor.

Therefore, according to the method for measuring blood pressure using tonometry, as described in Patent Document 1, it becomes possible to continuously measure blood pressure for each beat.

Even when considering uses other than blood pressure measurement, it is desired to easily measure pressure. In this case, it is desired that the pressure sensor has a fast response to pressure, a wide pressure measurement range, high accuracy, and the ability to detect the contact area and shape.
Furthermore, for robot applications, for example, it is required that the device be of a size that is easy to install in a required location, that wiring is easy, and that data processing is easy.
For example, the system described in Non-Patent Document 1 has simple wiring and is easy to implement on a robot arm. On the other hand, since this system measures pressure from the deformation of the membrane, special calculation processing is required for pressure measurement.

The object of the present invention is to provide a new pressure sensor that can easily measure pressure, which is used for blood pressure measurement using the tonometry method as described above, tactile sensing in robot applications, etc. The purpose of the present invention is to provide a robot equipped with a tactile sensor.

In order to solve this problem, the present invention has the following configuration.
[1] An image sensor,
a light reflecting layer whose reflection characteristics change according to pressure, the layer facing the imaging surface of the imaging device and disposed apart from the imaging device;
Pressure is detected from changes in the image captured by the image sensor when pressure is applied from the side of the light reflection layer opposite to the image sensor with light entering between the image sensor and the light reflection layer. sensor.
[2] The pressure sensor according to [1], which includes a light guide layer between the image sensor and the light reflection layer.
[3] The pressure sensor according to [1], which includes a light source that enters light between the image sensor and the light reflection layer.
[4] The pressure sensor according to [2], which includes a light source that enters light between the image sensor and the light reflection layer.
[5] The pressure sensor according to [2] or [4], wherein the image sensor and the light guide layer are in contact with each other, and the light reflection layer and the light guide layer are in contact with each other.
[6] The pressure sensor according to any one of [2], [4] and [5], wherein the light guide layer is a resin layer or a glass layer.
[7] The pressure sensor according to any one of [4] to [6], which has a plurality of light sources, and the light sources are arranged so as to sandwich the light guide layer.
[8] The pressure sensor according to any one of [2] and [4] to [7], wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
[9] The pressure sensor according to [1], which has a space between the image sensor and the light reflective layer.
[10] The pressure sensor according to [9], which includes a light source that irradiates the light reflection layer with light.
[11] The pressure sensor according to [9] or [10], which includes a lens between the image sensor and the light reflective layer.
[12] The pressure sensor according to any one of [9] to [11], wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
[13] The pressure sensor according to [1] or [3], wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
[14] The pressure sensor according to any one of [1] to [13], further comprising a light-shielding layer on the side of the light-reflecting layer opposite to the image sensor.
[15] The pressure sensor according to any one of [1] to [14], wherein the light reflecting layer is a cholesteric liquid crystal layer.
[16] The pressure sensor according to any one of [1] to [15], wherein the light reflecting layer contains cellulose.
[17] The pressure sensor according to [16], wherein the cellulose contains a cured product of a cellulose compound having a polymerizable group.
[18] The pressure sensor according to [16] or [17], wherein the cellulose contains an unsubstituted cellulose compound.
[19] The pressure sensor according to any one of [1] to [18], wherein the light reflecting layer is composed of a wet gel.
[20] The pressure sensor according to any one of [1] to [19], wherein the light reflecting layer contains a liquid component.
[21] The pressure sensor according to any one of [1] to [20], wherein the light reflecting layer is sealed with a sealing material.
[22] The pressure sensor according to any one of [1] to [21], wherein the image sensor is a color sensor.
[23] The pressure sensor according to [1] to [22], which is a blood pressure sensor.
[24] The pressure sensor according to any one of [1] to [22], which is a tactile sensor.
[25] A robot equipped with any one of the pressure sensors of [1] to [22] as a tactile sensor.

According to the present invention, there is provided a novel pressure sensor that can easily measure pressure, which is used for blood pressure measurement by tonometry method, tactile detection in robot applications, etc., and a tactile sensor for this pressure sensor. A robot that can be installed as a robot is provided.

FIG. 1 is a diagram conceptually showing an example in which an example of the pressure sensor of the present invention is utilized as a blood pressure sensor. FIG. 2 is a plan view of the blood pressure sensor shown in FIG. 1. FIG. 3 is a diagram conceptually showing an example of a state in which the blood pressure sensor shown in FIG. 1 is attached to a subject. FIG. 4 is a diagram conceptually showing another example in which the pressure sensor of the present invention is used as a blood pressure sensor. FIG. 5 is a diagram conceptually showing another example in which the pressure sensor of the present invention is used as a blood pressure sensor. FIG. 6 is a plan view of the blood pressure sensor shown in FIG. 5. FIG. 7 is a diagram conceptually showing another example of the pressure sensor of the present invention. FIG. 8 is a diagram conceptually showing an example of the use of the pressure sensor shown in FIG. 7.

Hereinafter, the pressure sensor and robot of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits.
In this specification, "same" includes a generally accepted error range in the technical field.

In this specification, the bonding direction of the divalent group (for example, -CO-O-, etc.) described herein is not limited unless otherwise specified. For example, when Y in a compound represented by the formula "X-Y-Z" is -CO-O-, the above compound has the formula "X-O-CO-Z" and "X-CO-O- Z" may be used.

Note that all the figures shown below are conceptual diagrams for explaining the present invention. Therefore, the shape, thickness, size, positional relationship, etc. of each member do not necessarily match the actual one.

FIG. 1 conceptually shows an example in which the pressure sensor of the present invention is used as a blood pressure sensor.
Note that the following explanation is an explanation of an example in which the pressure sensor of the present invention is used as a blood pressure sensor, but the structure and pressure measurement function of the pressure sensor of the present invention are basically similar to the blood pressure sensor described below. The same is true. Therefore, the following description also serves as a description of the pressure sensor of the present invention even if there is no particular description of "pressure sensor."

The blood pressure sensor 10 shown in FIG. 1 includes a substrate 12, an image sensor 14, a light guide layer 16, a light reflection layer 18, a light absorption layer 20 as a light shielding layer, and a light source 24.

FIG. 2 shows a diagram of the blood pressure sensor 10 viewed from the light absorption layer 20 side.
In the blood pressure sensor 10, the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20 are all sheet-like (plate-like, film-like, layer-like) members. In the illustrated example, the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20 have the same rectangular (rectangular) planar shape and are stacked with their outer peripheries aligned. However, depending on the position of the light source 24, the introduced light, etc., the sizes and/or shapes of the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20 may not have to match. Each component may be shifted even if it has the same size and/or shape. Further, the light absorption layer 20 may partially cover the side surface of the light reflection layer 18.
Further, as shown in FIG. 2, three light sources 24 are arranged in the longitudinal direction of the image sensor 14 so as to sandwich the image sensor 14 in the lateral direction.

FIG. 3 conceptually shows a state in which the blood pressure sensor 10 is attached to a blood pressure subject.
The blood pressure sensor 10 is used, for example, in a wristwatch-type blood pressure measurement device, and is fixed inside a band 28 of the blood pressure measurement device.
The blood pressure sensor 10 is attached to a band 28 with the light absorption layer 20 facing the epidermis S of the subject, so that the longitudinal direction of the image sensor 14 crosses the blood vessel to be measured, for example, the radial artery A (see FIG. 2). It is attached to the epidermis S of the wrist of the subject.

Here, as shown in FIG. 3, the blood pressure sensor 10 is attached by pressing the epidermis S of the subject with a constant force so as to press the radial artery A with a constant force.
Therefore, the band 28 of the wristwatch-type blood pressure measuring device is wrapped around the subject's wrist so as to tighten the subject's wrist with a constant force when measuring blood pressure. For example, the blood pressure measurement device has an actuator at the part of the band 28 where the blood pressure sensor 10 is attached, and by lightly tightening the band 28 with the actuator, the band 28 tightens the subject's wrist with a constant force. The blood pressure measuring device thereby presses the radial artery A with the blood pressure sensor 10 with a constant force.
Preferably, the band 28 is provided with a pressure sensor, and the amount by which the band 28 is tightened by the actuator is adjusted according to the pressure measurement result by the pressure sensor so that the tightening force of the band 28 on the wrist becomes a predetermined force.

Here, the blood pressure sensor 10 has a rigidity that does not bend due to the band 28 pressing the epidermis S, that is, pressing the radial artery A.
This rigidity may be ensured, for example, by the rigidity of one or more members of the substrate 12, the image sensor 14, and the light guide layer 16 that constitute the blood pressure sensor 10.
Alternatively, in order to prevent the blood pressure sensor 10 from bending due to the pressure of the epidermis S, the blood pressure sensor 10 may include a high-rigidity plate having the necessary rigidity. Note that this highly rigid plate is provided closer to the substrate 12 than the light reflecting layer 18 . Further, when this high-rigidity plate is provided closer to the light reflection layer 18 than the imaging surface of the image sensor 14, the high-rigidity plate needs to have a light transmittance similar to that of the light guide layer 16.

The actuator and pressure sensor attached to the band 28 are not limited, and various known types can be used.
Examples of the actuator include general-purpose actuators such as a piezo actuator, an electromagnetic actuator, and a servo motor.
In addition, as pressure sensors, general-purpose pressure sensors such as MEMS (Micro Electro Mechanical Systems) pressure sensors, strain gauge pressure sensors, piezoelectric sensors, resistance pressure sensors, capacitance pressure sensors, and photodetection pressure sensors are used. Sensors are available.

Further, the wristwatch-type blood pressure measuring device using the blood pressure sensor 10 may include a display for displaying blood pressure measurement results, etc., and a blood pressure sensor, for example, at a position of the band 28 that is the clock part of the wristwatch, as necessary. 10 (blood pressure measuring device), etc. may be provided. As the operation means, known ones such as a touch panel and a button type operation means can be used. Further, the band 28 may be provided with a battery for driving the blood pressure sensor 10 and the like. In addition, the band 28 is equipped with auxiliary or additional sensors such as optical sensors such as photocapacitance pulse wave (PPG) sensors, electrochemical measurement sensors, and potential measurement sensors for electrocardiogram and electromyography measurements. It's okay.
Alternatively, a wristwatch-type blood pressure measuring device using the blood pressure sensor 10 may connect the substrate 12 of the blood pressure sensor 10 to an external device wirelessly or by wire, and display the blood pressure measurement results on this external device. In this case, the external device may be used as the power supply source, or the external device may assume at least part of the functions of the board 12, which will be described later.
Furthermore, a wristwatch-type blood pressure measuring device using the blood pressure sensor 10 connects the image sensor 14 of the blood pressure sensor 10 and an external device wirelessly or by wire, and processes images captured by the image sensor 14 in the external device. , blood pressure measurement results may be displayed. Also in this case, an external device may be used as the power supply source.

As described above, the blood pressure sensor 10 includes the substrate 12, the image sensor 14, the light guide layer 16, the light reflection layer 18, the light absorption layer 20, and the light source 24.
Three light sources 24 are arranged in the longitudinal direction of the image sensor 14 so as to sandwich the image sensor 14 in the lateral direction. The number and placement locations of the light sources 24 can be adjusted as appropriate.

The board 12 is a known printed wiring board (electronic circuit board).
The board 12 controls the lighting of a light source 24, which will be described later, and performs image processing of an image captured by the image sensor 14.

The image sensor 14 is also a known image sensor.
The image sensor 14 is arranged with its imaging surface (imaging surface) facing away from the substrate 12, that is, toward the light reflective layer 18 side.

In the blood pressure sensor of the present invention, the image sensor 14 may be a so-called area sensor in which pixels are arranged two-dimensionally, or may be a so-called line sensor in which only one row of pixels is arranged according to the color to be imaged.
The image sensor 14 of the blood pressure sensor 10 shown in FIGS. 1 and 2 is an area sensor.

Further, the image sensor 14 may be a monochrome sensor that captures a monochrome image (luminance image), a monochrome sensor that captures monochrome images such as a red image, a green image, and a blue image, or a monochrome sensor that captures monochrome images such as a red image, a green image, and a blue image. A color sensor that captures a two-color image may be used, or a color sensor that captures a full-color image of a red image, a green image, and a blue image may be used. As the image sensor 14, a color sensor that captures a full color image is preferably used.
Furthermore, the wavelengths of the measurement light and the light measured by the sensor can be selected depending on the application of the pressure sensor of the present invention, and for example, near-infrared light, far-infrared light, etc. can also be used. Depending on the wavelength of the light used, the image sensor 14, the light guide layer 16, the light reflection layer 18, the light absorption layer 20, and the light source 24 can be suitably adjusted and selected. Furthermore, depending on the application of the pressure sensor of the present invention, the space between the light source 24 and the light guide layer 16, between the light guide layer 16 and the light reflecting layer 18, and between the light guide layer 16 and the image sensor 14 may be A filter such as an optical filter that passes only a part of the light and a semi-transmissive filter (ND filter) that adjusts the amount of light may be provided at at least one location of the light source. Such a filter may have wavelength selectivity, transmittance, etc. adjusted by a light absorption material, and may be an interference filter made of a liquid crystal film, a laminated film, etc., a polarizing filter, etc.
Note that when the light reflecting layer 18 has wavelength selectivity in reflection like a cholesteric liquid crystal layer described later, a monochrome sensor that captures a monochrome image or a color sensor that captures a two-color image is used as the image sensor 14. In some cases, it is preferable to use a sensor that is sensitive to the wavelength range that is selectively reflected by the light reflecting layer 18.
Regarding the above points, the same applies to the pressure sensor 30 shown in FIG. 7, which will be described later.

In the following description, unless otherwise specified, a color sensor refers to a color sensor that captures a full-color image.

As the image sensor 14, various known image sensors can be used.
As the image sensor 14, a solid-state image sensor is preferably exemplified, and a CCD image sensor that uses a photodiode made of silicon and uses a charge-coupled device for signal transmission, and a CMOS image sensor that uses a CMOS for signal transmission. etc. can be used. In addition to this, an organic thin film image sensor using an organic semiconductor, an image sensor using other semiconductors, etc. can be used as the image sensor 14.
Among these, CCD image sensors, CMOS image sensors, organic thin film image sensors, and the like are preferably used.

Although there is no limit to the spatial resolution of the image sensor 14, it is basically preferable that it be higher.
Specifically, the pixel interval in the image sensor 14 is preferably smaller than the thickness of the radial artery A, preferably 0.5 mm or less, more preferably 0.2 mm or less, and even more preferably 0.1 mm or less.

In the blood pressure sensor 10, a light reflective layer 18 is provided apart from the image sensor 14 and facing the imaging surface of the image sensor 14.
In the illustrated example, as a preferred embodiment, an image sensor 14, a light guide layer 16, and a light reflection layer 18 are stacked with a light guide layer 16, which will be described later, interposed therebetween. That is, in the blood pressure sensor 10, the image sensor 14 and the light guide layer 16 are in contact with each other, and the light guide layer 16 and the light reflection layer 18 are in contact with each other.

The light reflecting layer 18 reflects light emitted from a light source 24, which will be described later.
In the following description, the light emitted by the light source 24 is also referred to as measurement light for convenience, and the measurement light reflected by the light reflection layer 18 is also referred to as reflected light for convenience.

In the present invention, the light-reflecting layer 18 has such low elasticity that its thickness changes depending on the pressure (pulse pressure) caused by the expansion of the radial artery A in response to the heartbeat (see the lower part of FIG. 3). Specifically, the light reflecting layer 18 has a low elasticity with a Young's modulus of about 0.05 to 0.5 MPa. In the pressure sensor of the present invention, the physical properties of the light reflecting layer 18 can be appropriately selected outside the above-mentioned range depending on the object of pressure measurement and the configuration of the pressure measurement device.

Further, the light reflective layer 18 has reflective characteristics that change depending on pressure.
Specifically, in a preferred embodiment, the light reflecting layer 18 has wavelength selectivity in the reflection of light, and changes the wavelength of the light that is selectively reflected in response to deformation (compression and expansion) caused by pressure. changes.
Alternatively, the light reflection layer 18 may have a light reflectance that changes in response to deformation due to pressure. In this case, the light reflecting layer 18 may or may not have wavelength selectivity in light reflection.

Various types of light reflection layer 18 can be used as long as the reflection characteristics change according to pressure. Here, even if the light reflection layer 18 is only slightly deformed, if a sufficient change in reflection characteristics is obtained, blood pressure can be measured with high sensitivity.
Considering this point, the light reflection layer 18 may be a light reflection layer that uses black diffraction due to regularly arranged scatterers, a light reflection layer that uses liquid crystal, etc. A light reflecting layer 18 whose reflection wavelength characteristics (reflection spectrum) change when exposed to light is suitable. In particular, the light reflecting layer 18 using liquid crystal is suitable, considering both low elasticity (flexibility) that can be sufficiently deformed with small pressure and regular alignment.

A preferable example of the light reflecting layer 18 using liquid crystal having such light reflecting characteristics is a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed.

A cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase has a helical structure in which liquid crystal compounds are spirally rotated and stacked, and a structure in which liquid crystal compounds are stacked in a spiral manner by making one rotation (360° rotation). The liquid crystal compound has a structure in which a plurality of pitches of liquid crystal compounds spirally swirled are stacked with one pitch of the spiral (helix pitch P).

As is well known, a cholesteric liquid crystal phase exhibits selective reflection at a specific wavelength.
In a general cholesteric liquid crystal phase, the center wavelength of selective reflection (selective reflection center wavelength λ) depends on the helical pitch (helix pitch P) in the cholesteric liquid crystal phase, and the average refractive index n and λ=n of the cholesteric liquid crystal phase. According to the relationship ×P.
Therefore, by adjusting this helical pitch, the selective reflection center wavelength can be adjusted. The longer the helical pitch P, the longer the selective reflection center wavelength of the cholesteric liquid crystal phase becomes.

Note that, as described above, the helical pitch P is one pitch of the helical structure of the cholesteric liquid crystal phase (the period of the helix). In other words, the helical pitch P is the number of turns of the helix, that is, the direction of the helical axis in which the director of the liquid crystal compound constituting the cholesteric liquid crystal phase (in the case of a rod-like liquid crystal, the long axis direction) rotates 360°. It is the length.

Furthermore, as is well known, the cholesteric liquid crystal phase exhibits selective reflection property for either left or right circularly polarized light at a specific wavelength. Whether the reflected light is right-handed circularly polarized light or left-handed circularly polarized light depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. Selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects right-handed circularly polarized light when the helical twist direction of the cholesteric liquid crystal phase is to the right, and reflects left-handed circularly polarized light when the helical twist direction of the cholesteric liquid crystal phase is to the left.
For example, in the case of a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light, the direction in which the helix of the cholesteric liquid crystal phase is twisted is in the right direction.
Note that the direction of rotation of the cholesteric liquid crystal phase can be controlled by the type of liquid crystal compound forming the cholesteric liquid crystal layer and/or the type of chiral agent added.

In addition, the half-width Δλ (nm) of the selective reflection wavelength range (circularly polarized light reflection wavelength range) in which the cholesteric liquid crystal phase exhibits selective reflection depends on Δn of the cholesteric liquid crystal phase and the helical pitch P, and Δλ=Δn×P. Follow the relationship. Therefore, the width of the selective reflection wavelength range can be controlled by adjusting Δn. Δn can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer, the mixing ratio thereof, and the temperature at which the orientation is fixed.

Therefore, when a cholesteric liquid crystal layer is used as the light reflection layer 18, the thickness becomes thinner according to the pressing force from the radial artery A, and the helical pitch P changes accordingly, so that the light that is selectively reflected becomes thinner. The wavelength range changes.

In addition, as is well known, the cholesteric liquid crystal layer has a so-called short-wavelength structure in which the wavelength of selectively reflected light becomes shorter as the incident angle of light with respect to the direction perpendicular to the main surface of the cholesteric liquid crystal layer (normal direction) becomes larger. A shift (blue shift) occurs. Note that the main surface is the largest surface of the sheet-like material, and usually both surfaces in the thickness direction.

As such a cholesteric liquid crystal layer, various known cholesteric liquid crystal layers can be used as long as they have the above-mentioned low elasticity.
As an example, the National Research and Development Agency Japan Science and Technology Agency's "Nanostructure control technology for molecular materials: Various An example of this is a cholesteric liquid crystal elastomer film made of a low-molecular liquid crystal compound that can be designed to respond to force stimuli and visualize color changes, as introduced in ``Development to Optical Functional Devices'' (Ritsumeikan University). .
Also, "New Pressure Sensing of Cellulose Derivatives with Rubber Elasticity (Tokyo University of Science, Seiichi Furumi, Kana Suzuki, Masashi Fukawa)" on pages 33 to 38 of the Journal of the Japan Rubber Association Vol. 91, No. 2 (2018) Cholesteric liquid crystal films based on hydroxypropylcellulose (HPC) derivatives, as described in , are also available.

It is also preferable that the light-reflecting layer 18 contains cellulose.
Examples of celluloses include unsubstituted cellulose, cellulose derivatives, and cured products thereof.
Note that "unsubstituted cellulose" is a polymer compound in which a large number of glucoses are polymerized through β-1,4-glycosidic bonds, and the carbon atoms at the 2nd, 3rd, and 6th positions in the glucose ring of cellulose are It means that the hydroxyl group bonded directly or indirectly is unsubstituted.
Furthermore, the term "cellulose derivative" refers to one in which the hydroxyl groups directly or indirectly bonded to carbon atoms at the 2nd, 3rd, and 6th positions in the glucose ring of cellulose are substituted with substituents.
Examples of cellulose derivatives include cellulose compounds having a polymerizable group (hereinafter also simply referred to as "specific cellulose compounds"). The light-reflecting layer 18 may include a cured product of a specific cellulose compound (a cured product obtained by polymerizing polymerizable groups of a specific cellulose compound).

The cellulose derivative is preferably a specific cellulose compound that exhibits thermotropic cholesteric liquid crystallinity or lyotropic cholesteric liquid crystallinity, has elasticity, and can be fixed in orientation at the wavelength of Bragg reflection.
The polymerizable group in the specific cellulose compound is not particularly limited, and preferably a polymerizable group capable of radical polymerization or cationic polymerization.
As the radically polymerizable group, generally known radically polymerizable groups can be used, and preferred examples include an acryloyloxy group and a methacryloyloxy group. In this case, it is known that an acryloyloxy group generally has a high polymerization rate, and an acryloyloxy group is preferred from the viewpoint of improving productivity, but a methacryloyloxy group can also be used as a polymerizable group.
As the cationic polymerizable group, generally known cationic polymerizable groups can be used, and specifically, alicyclic ether group, cyclic acetal group, cyclic lactone group, cyclic thioether group, spiro-orthoester group, and , vinyloxy group. Among these, an alicyclic ether group or a vinyloxy group is preferred, and an epoxy group, an oxetanyl group, or a vinyloxy group is more preferred.

It is preferable that the specific cellulose compound has a repeating unit represented by the following formula (I).

Formula (I)

In the above formula (I), D ₁ , D ₂ and D ₃ are each independently a single bond or -CO-, -O-, -S-, -C(=S)-, -CR ₁ R ₂ -, -CR ₃ =CR ₄ -, -NR ₅ -, or a divalent linking group consisting of two or more of these, and R ₁ to R ₅ each independently represent a hydrogen atom, a fluorine atom, Represents an atom or an alkyl group having 1 to 12 carbon atoms.
In the above formula (I), SP ₁ , SP ₂ and SP ₃ each independently represent a single bond, a linear or branched alkylene group having 1 to 12 carbon atoms, or a C 1 to 12 linear or branched alkylene group. 2 in which one or more of -CH ₂ - constituting a linear or branched alkylene group is substituted with -O-, -S-, -NH-, -N(Q)-, or -CO- represents a valent linking group, and Q represents a substituent.
Further, in the above formula (I), L ₁ , L ₂ and L ₃ each independently represent a hydrogen atom, a hydroxyl group, or a monovalent organic group, and at least one of L ₁ , L ₂ and L ₃ One represents a polymerizable group.

In the above formula (I), the divalent linking group represented by one embodiment of D ₁ , D ₂ and D ₃ is, for example, -O-CO-, -O-, -C(=S)O-, - CR ₁ R ₂ -, -CR ₁ R ₂ -CR ₁ R ₂ -, -O-CR ₁ R ₂ -, -O-CR ₁ R ₂ -CR ₁ R ₂ -O-CR ₁ R ₂ -CR ₁ R ₂ -, -CO-O-CR ₁ R ₂ -, -O-CO-CR ₁ R ₂ -, -O-CO-NR ₅ -, -O-CO-NR ₅ -CR ₁ R ₂ -CR ₁ R ₂ -, -CO-NR ₅ -CR ₁ R ₂ -CR ₁ R ₂ -, -NR ₅ -CR ₁ R ₂ -, and -CO-NR ₅ -. R ₁ , R ₂ and R ₅ each independently represent a hydrogen atom, a hydroxyl group, or an alkyl group having 1 to 12 carbon atoms.
Among these, -O-CO-, -O-, -C(=S)O-, -O-CR ₁ R ₂ -, -O-CR ₁ R ₂ -CR ₁ R ₂ -O-CR ₁ R ₂ -CR ₁ R ₂ -, -CO-O-CR ₁ R ₂ -, -O-CO-CR ₁ R ₂ -, -O-CO-NR ₅ -, -O-CO-NR ₅ -CR ₁ R ₂ -CR ₁ R ₂ -, -CO-NR ₅ -CR ₁ R ₂ -CR ₁ R ₂ -, and -CO-NR ₅ -, preferably -O-CO-, -O -, -O-CO-NR ₅ -, and -O-CO-NR ₅ -CR ₁ R ₂ -CR ₁ R ₂ - are more preferred.

In the above formula (I), examples of the linear or branched alkylene group having 1 to 12 carbon atoms represented by one embodiment of SP ₁ , SP ₂ and SP ₃ include a methylene group, an ethylene group, a propylene group, and a butylene group. group, pentylene group, hexylene group, methylhexylene group, and heptylene group.
In addition, as mentioned above, SP ₁ and SP ₂ are such that one or more of -CH ₂ - constituting a linear or branched alkylene group having 1 to 12 carbon atoms is -O-, -S-, -NH -, may be a divalent linking group substituted with -, -N(Q)-, -CO-, or -O-CO-NH-, and constitute a linear or branched alkylene group - It is also preferred that one or more of CH ₂ - is a divalent linking group substituted with -O- or -O-CO-NH-.

Examples of the substituent represented by Q include an alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group, an alkylamino group, and an alkylamido group, and among them, an alkyl group is preferred.

In the above formula (I), examples of the monovalent organic group represented by L ₁ , L ₂ and L ₃ include an alkyl group, an aryl group, and a heteroaryl group.
The alkyl group may be linear, branched or cyclic, but linear is preferred. The number of carbon atoms in the alkyl group is preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10.
Further, the aryl group may be monocyclic or polycyclic, but monocyclic is preferable. The number of carbon atoms in the aryl group is preferably 6 to 25, more preferably 6 to 10.
Further, the heteroaryl group may be monocyclic or polycyclic. The number of heteroatoms constituting the heteroaryl group is preferably 1 to 3. The heteroatom constituting the heteroaryl group is preferably a nitrogen atom, a sulfur atom, or an oxygen atom. The heteroaryl group preferably has 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms.
Further, the alkyl group, aryl group and heteroaryl group may be unsubstituted or may have a substituent.

In the above formula (I), the polymerizable group represented by at least one of L ₁ , L ₂ and L ₃ is not particularly limited, and a polymerizable group capable of radical polymerization or cationic polymerization is preferable.
As the radically polymerizable group, generally known radically polymerizable groups can be used, and preferred examples include an acryloyloxy group and a methacryloyloxy group. In this case, it is known that an acryloyloxy group generally has a high polymerization rate, and an acryloyloxy group is preferred from the viewpoint of improving productivity, but a methacryloyloxy group can also be used as a polymerizable group.
As the cationic polymerizable group, generally known cationic polymerizable groups can be used, and specifically, alicyclic ether group, cyclic acetal group, cyclic lactone group, cyclic thioether group, spiro-orthoester group, and , vinyloxy group. Among these, an alicyclic ether group or a vinyloxy group is preferred, and an epoxy group, an oxetanyl group, or a vinyloxy group is more preferred.
Particularly preferred examples of polymerizable groups include polymerizable groups represented by any of the following formulas (P-1) to (P-20).

It is also preferable that the specific cellulose compound has a repeating unit represented by the following formula (II).

Formula (II)

In the above formula (II), R ₁ , R ₂ and R ₃ are each independently a hydroxyl group, -O-R ₄ , -(O-CH ₂ -CH(CH ₃ )) _m -R ₅ , or Represents a polymerizable group. R ₄ represents a hydrogen atom, -CO-R ₆ or -CO-NH-R ₇ . R ₅ represents a hydroxyl group, -OCO-R ₈ , -OCO-NH-R ₉ or a polymerizable group. R ₆ , R ₇ , R ₈ and R ₉ each independently represent an alkyl group or an aryl group which may have a polymerizable group as a substituent, and R ₁ , R ₂ and R ₃ At least one of them has a polymerizable group.
Further, m represents an integer from 1 to 10.

As the specific cellulose compound, specifically, for example, a compound represented by the following formula (III) is preferably mentioned, and specifically, D ₁ , D ₂ and D ₃ in the following formula (1), Examples of SP ₁ , SP ₂ and SP ₃ , L ₁ , L ₂ and L ₃ include compounds having side chain structures shown in Table 1 below.

Formula (III)

It is preferable that the celluloses contain a cured product of a cellulose compound having a polymerizable group and an unsubstituted cellulose compound from the viewpoint of controlling flexibility, liquid crystallinity, stability, etc.

The molecular weight of cellulose is not particularly limited, but the number average molecular weight (Mn) is preferably in the range of 5,000 to 1,000,000, more preferably in the range of 10,000 to 500,000, and more preferably in the range of 20,000 to 200. A range of ,000 is more preferred, and a range of 30,000 to 100,000 is particularly preferred.
The mass average molecular weight (Mw) is preferably in the range of 7,000 to 5,000,000, more preferably in the range of 15,000 to 2,500,000, and more preferably in the range of 20,000 to 1,500,000. is more preferred, and a range of 30,000 to 500,000 is particularly preferred.
The molecular weight distribution (MWD) is preferably in the range of 1.1 to 5.0, more preferably in the range of 1.2 to 3.5, even more preferably in the range of 1.3 to 3.0.
By setting the average molecular weight within this range, the moldability etc. of the molded article can be further improved. Moreover, by setting the molecular weight distribution within this range, moldability etc. can be further improved.
In the present invention, the number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution (MWD) can be measured using gel permeation chromatography (GPC). Specifically, it can be determined using tetrahydrofuran as a solvent, polystyrene gel, and a reduced molecular weight calibration curve previously determined from the constitutive curve of standard monodisperse polystyrene.

Even when the light-reflecting layer 18 contains the above-mentioned cellulose, it is preferable that a cholesteric liquid crystal layer is formed.
Further, from the viewpoint of controlling the reflected wavelength range, it is preferable that the cellulose exhibits thermotropic liquid crystallinity. When cellulose exhibits thermotropic liquid crystallinity, it is easy to control the temperature during curing.

The cholesteric liquid crystal layer can be formed by a known method. As an example, a coating composition containing a liquid crystal compound, a chiral agent, etc. is prepared, the coating composition is applied to an alignment film, and then the liquid crystal compound is aligned to a cholesteric liquid crystal phase by heating. Thereafter, the coating composition is dried to form a cholesteric liquid crystal layer. Note that the alignment of the liquid crystal compound and the drying of the coating composition may be performed simultaneously.
Further, after drying the coating composition, the liquid crystal compound may be polymerized by irradiation with ultraviolet rays or the like, if necessary.

Here, when forming a cholesteric liquid crystal layer, an alignment film for aligning a liquid crystal compound is usually formed on the surface of a support such as a resin film, and a cholesteric liquid crystal layer is formed on the surface of this alignment film. .
Therefore, when the light reflecting layer 18 is a cholesteric liquid crystal layer, it may be used after being peeled off from the alignment film. Alternatively, when the light reflective layer 18 is a cholesteric liquid crystal layer, the blood pressure sensor 10 may have a cholesteric liquid crystal layer and an alignment film peeled off from the support. Alternatively, when the light reflective layer 18 is a cholesteric liquid crystal layer, the blood pressure sensor 10 may include a cholesteric liquid crystal layer, an alignment film, and a support.
When the blood pressure sensor 10 (pressure sensor of the present invention) includes a cholesteric liquid crystal layer as the light reflection layer 18 and an alignment film or further a support, the cholesteric liquid crystal layer is arranged so that the cholesteric liquid crystal layer faces the image sensor 14. A laminate including a liquid crystal layer may be arranged, or an alignment film and a support may be provided on the image sensor 14 side. When the alignment film and the support are located on the image sensor 14 side, it is necessary to adjust the optical properties such as the transmittance of the alignment film and the support as appropriate so as not to obstruct all of the reflected light from entering the image sensor 14. be. Further, when the cholesteric liquid crystal layer faces the image sensor 14, the support may be selected so that, for example, the support also serves as a light absorption layer 20 (light-shielding layer), which will be described later.

In addition, when a cholesteric liquid crystal layer is used as the light reflection layer 18, the light reflection layer 18 is a two-layer cholesteric liquid crystal layer in which the selective reflection center wavelength is the same and the direction of rotation of the selectively reflected circularly polarized light is opposite. It may have.

The light reflecting layer 18, whose wavelength of selectively reflected light changes according to deformation (compression and expansion) due to pressure, is not limited to an organic cholesteric liquid crystal layer, but may be any layer having the above-mentioned low elasticity. Various known ones can be used.
As an example, inorganic layered compounds containing smectite clay minerals, layered potassium hexaniobate, layered perovskite, and graphite are introduced in "https://prtimes.jp/main/html/rd/p/000000012.000047155.html" An example of this is the inorganic nanosheet structural color gel (Fukuoka Institute of Technology), which is made of inorganic nanosheet liquid crystals obtained by exfoliating and dispersing.

There is no limit to the thickness of the light-reflecting layer 18, and the thickness of the light-reflecting layer 18 should be determined so as to provide the necessary light-reflecting properties and the necessary low elasticity, that is, the necessary amount of change in thickness against expansion pressure of the radial artery A. What is necessary is just to set it suitably according to the formation material of 18, etc.
Here, it is preferable that the light reflection layer 18 be thicker in terms of increasing the reflectance of the measurement light. On the other hand, the thicker the light reflecting layer is, the more disadvantageous it becomes in terms of deformability against pressure and the thickness of the blood pressure sensor 10. Considering this point, the thickness of the light reflecting layer 18 is preferably 0.1 to 500 μm, more preferably 1 to 100 μm.

The light reflecting layer 18 may be made of wet gel.
The above-mentioned wet gel means a fluid solid component, and preferably includes a liquid component.
That is, the light reflecting layer 18 may contain a liquid component.
When the light-reflecting layer 18 is made of wet gel, it is possible to achieve a better balance between liquid crystallinity and flexibility that responds to slight pressure.
The liquid component is not particularly limited, and includes liquid components in which the contained material (especially liquid crystal material) can be well dissolved or dispersed. As for the liquid component, it is preferable that the component contained in the light reflective layer 18 is a liquid component that easily exhibits liquid crystallinity. For example, when the light reflective layer 18 contains cellulose, water or an organic solvent is preferably selected as the liquid component.

Further, when the light-reflecting layer contains a liquid component, in order to ensure stability, it is preferable to have a mechanism that prevents the liquid component from volatilizing. That is, the light reflecting layer is preferably sealed with a sealing material. For example, it is preferable that a sealing material or a base material that inhibits volatilization of the liquid component be provided above, below, and on the side surfaces of the light-reflecting layer.
It is desirable to select a material with low moisture permeability depending on the liquid component. For example, inorganic thin films such as silicon compounds such as aluminum oxide and silicon oxide, organic thin films such as parylene and acrylic resin, and laminated films thereof can be used as the gas barrier film.
In addition, as materials constituting the sealing material or base material, polyolefin (PO) resins such as homopolymers, copolymers, or copolymers of ethylene, polypropylene, and butene; amorphous polyolefin resins such as cyclic polyolefins ( APO): Polyester resins such as polyethylene terephthalate (PET) and polyethylene 2,6-naphthalate (PEN): Polyamide-based (PA) resins such as nylon 6, nylon 12 and copolymerized nylon: Polyvinyl alcohol (PVA) resins and ethylene - Polyvinyl alcohol resin such as vinyl alcohol copolymer (EVOH): Polyimide (PI) resin: Polyetherimide (PEI) resin: Polysulfone (PS) resin: Polyethersulfone (PES) resin: Polyetheretherketone ( PEEK) resin: polycarbonate (PC) resin: polyvinyl butyrate (PVB) resin: polyarylate (PAR) resin: ethylene-tetrafluoroethylene copolymer (ETFE), trifluorochloroethylene (PFA), tetrafluoride Fluororesins such as ethylene-perfluoroalkyl vinyl ether copolymer (FEP), vinylidene fluoride (PVDF), vinyl fluoride (PVF), and perfluoroethylene-perfluoropropylene-perfluorovinylether copolymer (EPA) : Resin composition made of an acrylate compound having a radically reactive unsaturated compound : Resin composition made of the above acrylate compound and a mercapto compound having a thiol group : Oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, and polyether acrylate Examples include photocurable resins such as resin compositions dissolved in polyfunctional acrylate monomers.
Furthermore, it is also possible to use as a resin base material a material in which one or more of these materials are laminated by means such as lamination and coating. Furthermore, a base material made of the above material and coated with the above-mentioned inorganic thin film and organic thin film can also be used.

A light guide layer 16 is provided between the image sensor 14 and the light reflective layer 18. The light guide layer 16 is a member that forms an optical path of measurement light between the image sensor 14 and the light reflection layer 18.
That is, the light guide layer 16 guides the measurement light in the plane direction between the image sensor 14 and the light reflective layer 18, and also fills the gap between the image sensor 14 and the light reflective layer 18, that is, the gap between the image sensor 14 and the light reflective layer 18. This is to maintain an appropriate positional relationship with the Preferably, the light guide layer 16 guides the measurement light to the entire surface of the image sensor 14 and the light reflective layer 18 in the plane direction.

Note that in the present invention, the light guide layer 16 is provided as a preferred embodiment and is not an essential component.
Therefore, when the blood pressure sensor of the present invention does not have a light guide layer, the light source 24 (described later) is placed between the image sensor 14 and the light reflective layer 18 which are provided apart from each other, or toward the image sensor 14. Alternatively, measurement light is irradiated toward the light reflecting layer 18.

In the illustrated blood pressure sensor 10, the light source 24 is arranged so as to make measurement light incident on the end surface of the light guide layer 16, as indicated by the white arrow in the figure.
The measurement light incident on the light guide layer 16 is guided by the light guide layer 16 and travels between the image sensor 14 and the light reflective layer 18 in the plane direction of the image sensor 14 and the light reflective layer 18 .
The measurement light traveling through the light guide layer 16 is transmitted to the image sensor 14 and the image sensor 14 depending on the angle of incidence to the interface between the light guide layer 16 and the image sensor 14 and the interface between the light guide layer 16 and the light reflective layer 18. The light is incident on the light reflecting layer 18.

There is no limit to the light guide layer 16, and various layers can be used as long as it can transmit the measurement light emitted by the light source 24 and the light reflected by the light reflection layer 18. That is, various layers can be used as the light guide layer 16 as long as it serves as an optical path for the measurement light in the surface direction and allows the light reflected by the light reflection layer 18 to pass through in the thickness direction.
Examples of the light guide layer 16 include resin layers made of various resin materials such as acrylic resin, polycarbonate resin, vinyl chloride resin, polyethylene terephthalate resin, cellulose resin, and olefin resin, and glass layers (glass plates). be done.

There is no limit to the thickness of the light guide layer 16, and depending on the configuration of the blood pressure sensor, the material for forming the light guide layer 16, the configuration of the blood pressure sensor, etc., the thickness of the light guide layer 16 may vary depending on the thickness of the light guide layer 16. What is necessary is to appropriately set the thickness that allows the guide.
Note that when the light guide layer 16 is not provided, the gap between the image sensor 14 and the light reflection layer 18 is such that a light source 24 (described later) makes measurement light incident on the entire surface between the image sensor 14 and the light reflection layer 18. The gap that can be formed may be set as appropriate.

The blood pressure sensor 10 has a light absorption layer 20 as a light shielding layer on the surface of the light reflection layer 18 on the side opposite to the image sensor 14.
Note that in the present invention, the light absorption layer 20 is provided as a preferred embodiment and is not an essential component.

As described above, the wristwatch-type blood pressure measuring device is worn on the wrist of the subject with the light absorption layer 20 of the blood pressure sensor 10 facing the epidermis S.

In the blood pressure sensor 10, environmental light incident on the subject's wrist (arm), measurement light from the light source 24, etc. that is incident on the subject's wrist unnecessarily is reflected within the subject's wrist, etc. , may enter the inside of the blood pressure sensor 10 from the light reflecting layer 18 .
If such unnecessary light enters the blood pressure sensor 10 and is measured by the image sensor 14, it becomes noise and causes an error in the measured blood pressure, which is not preferable.

The light absorption layer 20 is a layer for preventing such unnecessary light from entering the blood pressure sensor 10 from the light reflection layer 18.
That is, the blood pressure sensor 10 of the present invention has the light absorption layer 20 on the surface of the light reflection layer 18 opposite to the image sensor 14, thereby making it possible to measure blood pressure with higher precision.

There are no restrictions on the light absorption layer 20, as long as it can absorb unnecessary light and prevent it from entering the blood pressure sensor 10 from the surface of the light reflection layer 18 opposite to the image sensor 14. , various layers are available.
As an example, the light absorption layer 20 may be any of a variety of known layers as long as it absorbs specific light depending on the purpose. Specifically, the light absorption layer 20 includes a black layer using a black material such as carbon black, black paint, and black dye, an organic material such as an organic dye that absorbs in the visible region, and a metal that absorbs in the visible region. Examples include light absorption layers using inorganic materials such as oxides, organic materials that absorb in the ultraviolet or infrared region, and inorganic materials that absorb in the ultraviolet or infrared region.
In addition, in the blood pressure sensor 10 of the present invention, the light-shielding layer for preventing unnecessary light from entering the inside of the blood pressure sensor 10 from the light-reflecting layer 18 is not limited to the light-absorbing layer 20; Various layers are available that can achieve this. For example, metal foil, a light reflecting layer that reflects specific light, a layer that blocks light by reflecting and absorbing light, an optical filter that blocks specific light, etc. can also be used as the light blocking layer.

There is no limit to the thickness of the light absorption layer 20, and a thickness that can prevent unnecessary light from entering the blood pressure sensor 10 may be appropriately set depending on the material of the light absorption layer 20.
In this regard, the same applies to other light shielding layers.

In the blood pressure sensor 10, the light source 24 is arranged so as to sandwich the image sensor 14 in the lateral direction, which is a stacked body having a rectangular planar shape and including the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20. Placed. Further, three light sources 24 are arranged in the longitudinal direction of the above-described laminate.
In the following description, a laminate having a rectangular planar shape and including the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20 is also simply referred to as a "laminate." Furthermore, in the following description, the longitudinal direction and the lateral direction refer to the longitudinal direction and the lateral direction of a rectangle in the planar shape of the stacked body, that is, the image sensor 14.

The light source 24 emits measurement light for the blood pressure sensor 10 to measure blood pressure.
In the blood pressure sensor 10 shown in FIG. 1, the light source 24 is provided so as to sandwich the light guide layer, and as described above, is provided so that the measurement light is incident on the end surface of the light guide layer 16.

The light source 24 is not limited, and various light sources (light emitting elements) can be used as long as they can emit a predetermined measurement light.
Examples of the light source 24 include an LED (Light Emitting Diode), an LD (Laser Diode), and a fluorescent lamp.

The light source 24 may be a white light source, or may be a light source that emits monochromatic light such as red light, blue light, and green light, such as light in a wavelength range that is selectively reflected by the light reflection layer 18. A light source that emits light of multiple colors such as green light may also be used. In addition, when the light source 24 is other than a white light source, it is preferable that the measurement light emitted by the light source 24 includes light in the wavelength range reflected by the light reflection layer 18.
Further, the light source 24 may be a light source that emits invisible light such as infrared light.

Although the illustrated blood pressure sensor 10 has three light sources 24 arranged in the longitudinal direction of the image sensor 14, the present invention is not limited to this.
That is, the number of light sources 24 arranged may be two or less, or four or more, depending on the length of the laminate in the longitudinal direction. Further, the light source 24 may be a rod-shaped light source (linear light source) such as a fluorescent lamp instead of a point light source.
Furthermore, the light source 24 may be provided so as to sandwich the image sensor 14 in the longitudinal direction instead of being provided so as to sandwich the image sensor 14 in the lateral direction.

Note that when a cholesteric liquid crystal layer is used as the light reflection layer 18, the light source 24 may have a circular polarizer so that the circularly polarized light selectively reflected by the cholesteric liquid crystal layer is incident on the light guide layer 16. good. As the circular polarizer, for example, a circular polarizer consisting of a linear polarizer and a quarter wavelength plate (λ/4 plate) is exemplified.
Furthermore, in the blood pressure sensor 10 of the present invention, the light source 24 is provided as a preferred embodiment and is not an essential component. For example, the blood pressure sensor of the present invention does not have a light source, and allows environmental light such as an indoor light and natural light such as sunlight to enter the light guide layer 16, or between the image sensor 14 and the light reflective layer 18. The blood pressure may be measured as described below.

Hereinafter, the pressure sensor of the present invention will be explained in more detail by explaining the functions of the blood pressure sensor 10 and the substrate 12.

As described above with reference to the conceptual diagram of FIG. 3, the blood pressure sensor 10 is used in a wristwatch-type blood pressure measuring device, and is fixed inside the band 28 of the blood pressure measuring device.
The blood pressure measuring device is attached to a band with the light absorption layer 20 side facing the epidermis S of the subject so that the longitudinal direction of the imaging element 14 (laminated body) of the blood pressure sensor 10 crosses the radial artery A (see FIG. 2). 28 is attached to the wrist of the subject. At this time, as shown in FIG. 3, the blood pressure sensor 10 is attached by pressing the epidermis S of the subject with a constant force so as to press the radial artery A with a constant force.

When the blood pressure sensor 10 is attached to the epidermis S (wrist) of the subject, the board 12 turns on the light source 24. In this example, the blood sensor 10 is, for example, a wristwatch-type blood pressure measurement device.
As described above, the light source 24 makes measurement light incident on the end surface of the light guide layer 16. As described above, the measurement light incident on the light guide layer 16 is guided by the light guide layer 16 in the plane direction of the image sensor 14 and the light reflective layer 18, and is directly incident on the image sensor 14, or is directly reflected by the light guide layer 16. The light enters the layer 18 and is reflected, and the reflected light enters the image sensor 14 and is imaged.
An image captured by the image sensor 14 is processed by the substrate 12, for example.

When the heart is in an expanded state, that is, when the blood pressure is low, the radial artery A is in a state responsive to the pressure applied by the blood pressure sensor 10, as conceptually shown in the upper part of FIG.
Therefore, in this state, the measurement light directly incident from the light guide layer 16 and the reflected light reflected by the undeformed flat plate-shaped light reflection layer 18 are incident on the imaging element 14.

On the other hand, when the heart contracts and blood is supplied to the blood vessels, the radial artery A expands due to blood pressure, as conceptually shown in the lower part of FIG.
As described above, the light reflecting layer 18 is a low elastic layer whose thickness changes depending on the pressure (pulse pressure) caused by expansion of the radial artery A in response to heartbeat. Therefore, when the radial artery A expands, the light reflecting layer 18 is pressed by this expansion, and is deformed (compressed) by this pressing. Therefore, when the radial artery A is expanded, the imaging device 14 receives measurement light directly incident from the light guide layer 16 and is reflected by the light reflection layer 18 whose thickness has partially changed due to the pressure applied by the radial artery A. reflected light is incident.

In the present invention, the light reflective layer 18 has reflective characteristics that change depending on pressure. Preferably, the light reflecting layer 18 has wavelength selectivity for reflected light, like a cholesteric liquid crystal layer, and the wavelength of the selectively reflected light changes in response to deformation (compression and expansion) due to pressure.
Therefore, for example, when the light reflection layer 18 is a cholesteric liquid crystal layer, the helical pitch of the cholesteric liquid crystal phase changes due to the change in thickness due to the pressure of the radial artery A, and the incident angle of the measurement light with respect to the helical axis also changes. Change. As a result, the light reflection layer 18 changes in thickness due to the pressure of the radial artery A, and the wavelength of the measurement light that the light reflection layer 18 selectively reflects, that is, the wavelength of the reflected light, depending on the incident angle of the measurement light. The wavelength (reflection spectrum) changes.

Therefore, for example, when the measurement light is white light and the image sensor 14 is a color sensor, the blood pressure is low when the light reflection layer 18 is not pressed by the radial artery A in which the heart is dilated, as shown in the upper row of FIG. In this state and in the state shown in the lower part of FIG. 3 where the heart is contracting and the light reflective layer 18 is pressed by the dilated radial artery A and the blood pressure is high, the color and density of the image captured by the image sensor 14 are different. , partially changing.
In addition, when the measurement light is white light or monochromatic light such as red light and green light, and the image sensor 14 is a black and white monochrome sensor (luminance sensor) or a sensor compatible with monochromatic light, the upper part of FIG. The density (brightness) of the image captured by the image sensor 14 partially changes between a low blood pressure state and a high blood pressure state shown in the lower part of FIG.
Furthermore, when the measurement light is monochromatic light such as red light and green light, and the image sensor 14 is a color sensor, a state in which the blood pressure is low as shown in the upper part of FIG. 3, and a state in which the blood pressure is high as shown in the lower part of FIG. As a result, the density (brightness) of the image captured by the image sensor 14 partially changes. In addition, in this case, due to the relationship between the wavelength range of the measurement light and the wavelength range of the light selectively reflected by the light reflection layer 18, the color tone of the image captured by the image sensor 14 may also be slightly different in some parts. ,Change.

Here, the state of pressing of the light reflective layer 18 by the radial artery A, that is, the state of deformation of the light reflective layer 18 by the radial artery A, differs depending on the amount of expansion of the radial artery A, that is, the blood pressure.
Therefore, if the blood pressure of the radial artery A differs, the image captured by the image sensor 14 also changes depending on the blood pressure.

The present invention utilizes this, and the relationship between the blood pressure of the radial artery A and the image captured by the image sensor 14 is known in advance and stored in, for example, the substrate 12. Alternatively, the light reflecting layer 18 may be designed, controlled, and manufactured so that the image captured by the image sensor 14 becomes a predetermined image that has a correlation with blood pressure.
Then, as described above, by wrapping the band 28 around the wrist of the blood pressure subject, the blood pressure sensor 10 is pressed against the radial artery A, and measurement light is incident on the light guide layer 16 from the light source 24, An image is captured by the image sensor 14. Next, on the board 12, necessary image processing is performed on the image captured by the image sensor 14, and matching is performed between the image captured by the image sensor 14 and an image corresponding to the blood pressure stored in advance. Thereby, the subject's blood pressure can be measured. Note that image matching may be performed using a known method.

The blood pressure measurement results are displayed on a display provided on the band 28, for example.
Alternatively, the blood pressure measurement result or the image captured by the image sensor 14 is transmitted from the board 12 to an external device wirelessly or by wire, and the blood pressure measurement result is displayed on the external device. In this case, at least a part of the image processing such as matching performed by the substrate 12 may be performed by an external device.

That is, according to the blood pressure sensor 10 (pressure sensor) of the present invention, blood pressure can be easily measured by simply wrapping the band 28 of a wristwatch-type pressure measuring device around the wrist of a blood pressure test subject, for example. .
Further, the image sensor 14 can normally capture moving images. Therefore, the blood pressure sensor 10 of the present invention is capable of continuously measuring blood pressure, for example, continuously measuring the maximum value of blood pressure for each beat, and continuously outputting and observing fluctuations in blood pressure.
In addition, the blood pressure sensor 10 of the present invention detects an image captured by the image sensor by changing not only the image density (brightness) according to the blood pressure but also the color (wavelength) according to the blood pressure. be able to. Therefore, according to the blood pressure sensor 10 of the present invention, more detailed changes in captured images can be detected, and as a result, blood pressure can be measured with higher precision and higher resolution.
Furthermore, in the blood pressure sensor 10 of the present invention, all of the laminates except the image sensor 14 are formed by laminating film-like members. Therefore, the first blood pressure sensor 10 can be made thin and can continuously measure blood pressure with less burden on the subject.

The advantage of the present invention is that the color of the captured image according to the blood pressure can be changed in addition to the density, making it possible to measure blood pressure with higher accuracy and resolution. Preferably, the image sensor 14 is a color sensor.

Note that the above example is an example of measuring the systolic blood pressure, but when measuring the diastolic blood pressure, for example, the pressure of tightening by the band 28 of the blood pressure measuring device is changed, and the blood pressure sensor 10 detects pulsation. It is also possible to detect the pressure that is no longer possible.

In measuring blood pressure using the blood pressure sensor 10 of the present invention, the light source 24 may emit measuring light continuously or may emit pulsed light.
By using the measurement light emitted by the light source 24 as pulsed light and making the emission period higher than the body movement period of the subject, for example, by filter cutting using a low-pass filter, the influence of body movement on blood pressure measurement results can be reduced. This allows for more accurate blood pressure measurements.

Although the blood pressure sensor 10 shown in FIGS. 1 and 2 makes measurement light incident on the end face of the light guide layer 16, the present invention is not limited to this.
For example, as in a blood pressure sensor 10a conceptually shown in FIG. By irradiating measurement light from the light source 24 onto a region not covered by the light reflection layer 18, the measurement light may be incident on the light guide layer 16 and guided in the surface direction.
In this example as well, by arranging the light sources 24 to sandwich the light guide layer 16, the measurement light emitted by the light sources 24 passes through the light guide layer 16 in the thickness direction and directly enters the image sensor 14. can be prevented from happening.

Further, as described above, the blood pressure sensor of the present invention can also use a line sensor instead of an area sensor as an imaging element.
An example is conceptually shown in FIGS. 5 and 6. Note that FIG. 5 and FIG. 6 are views of the blood pressure sensor viewed from the same direction as FIG. 1 and FIG. 2, respectively.

As shown in FIGS. 5 and 6, the blood pressure sensor 10b is provided with a light source 24 so as to sandwich the line sensor 14L in the lateral direction. Also in the illustrated example, the measurement light from the light source 24 is incident on the end surface of the light guide layer 16.
Further, the blood pressure sensor 10b is attached to and pressed on the subject's wrist so that the longitudinal direction of the line sensor 14L crosses the radial artery A, as conceptually shown in FIG.

In the blood pressure sensor 10 of the present invention, in order to accurately measure blood pressure, the longitudinal direction of the image sensor 14 (line sensor 14L) and the light reflection layer 18 must cross a blood vessel to be measured, such as the radial artery A. It needs to be as long as possible. However, on the other hand, it is preferable for the blood pressure sensor 10 to be small.
Considering this point, the length in the longitudinal direction of the image sensor 14 and the light reflection layer 18 is preferably 10 mm or more, and more preferably 20 mm or more. Specifically, the length of the image sensor 14 and the light reflective layer 18 in the longitudinal direction is preferably 10 to 100 mm, more preferably 20 to 40 mm.

Furthermore, in the blood pressure sensor of the present invention, in order to measure blood pressure with higher precision, it is preferable to supply measurement light to a region corresponding to the entire surface of the image sensor.
In this respect, a line sensor is more advantageous than an area sensor as an image sensor.
However, on the other hand, an area sensor is more advantageous than a line sensor in that the change in the image captured by the image sensor depending on the blood pressure can be more clearly seen.
However, in consideration of supplying the measurement light to a region corresponding to the entire surface of the image sensor, the length of the image sensor 14 in the lateral direction is preferably 5 mm or less.

In each of the blood pressure sensors described above, a light source 24 is provided so as to sandwich the image sensor 14 (line sensor 14L), and measurement light is incident on both sides of the image sensor 14.
However, the present invention is not limited to this, and the light sources 24 may be arranged (arranged) only on one side without sandwiching the image sensor 14.
In order to facilitate the supply of measurement light to the area corresponding to the entire surface of the image sensor as described above, in the blood pressure sensor of the present invention, the light source 24 is provided so as to sandwich the image sensor 14, as in the blood pressure sensor in the illustrated example. It is preferable that the measurement light be incident on both sides of the image sensor 14.

Further, in the above example, the laminate of the blood pressure sensor has a rectangular planar shape, but the present invention is not limited to this, and the laminate can have a planar shape other than circular, elliptical, square, and rectangular. Various shapes are available, such as polygons.
Furthermore, in the blood pressure sensor of the present invention, the planar shape and size of the image sensor 14, the light guide layer 16, the light reflection layer 18, and the light absorption layer 20 may be different from each other. However, it is preferable that the light reflective layer 18 be provided so as to cover the entire imaging surface of the image sensor 14. Further, the light absorption layer 20 is preferably provided so as to cover the entire surface of the light reflection layer 18 on the side opposite to the image sensor 14.

Although the above example is an example in which the pressure sensor of the present invention is used as a blood pressure sensor, the pressure sensor of the present invention is not limited to this and can be used for various pressure measurements.
Examples include a tactile sensor at the tip of a robot's arm, a touch sensor on a panel, a button, and the like.
Among them, the pressure sensor of the present invention is suitably used for the above-mentioned blood pressure sensor and a tactile sensor for robots.

FIG. 7 conceptually shows another example of the pressure sensor of the present invention.
For example, as conceptually shown in FIG. 8, this pressure sensor 30 is provided at one tip of an arm member 48 in a robot arm 46 in a robot application, and is used when the robot arm 46 grips or grasps an object. , is suitably used as a tactile sensor that measures pressure and pressure distribution applied to a robot arm, that is, an object.
Note that the shape of the arm member and the mounting position of the pressure sensor are not limited to the shape shown in FIG. 8. That is, when the pressure sensor of the present invention is used in a robot arm, arms of various shapes can be used, and it can be used as appropriate in the location where it is desired to detect a tactile sensation on the arm.
Further, the pressure sensor of the present invention is not limited to being mounted on an arm-type robot as shown in FIG. 8, but can also be used, for example, on a hand-type robot imitating a plurality of fingers. Furthermore, the pressure sensor of the present invention can be mounted not only on the tips of arms and hands, but also on various parts (surfaces) of the robot that come into contact with objects.
Thus, a robot using the pressure sensor of the present invention as a tactile sensor is a robot of the present invention.

The pressure sensor 30 shown in FIG. 7 includes an image sensor 32, a lens 34, a light source 36, a light reflection layer 38, a light absorption layer 40 as a light shielding layer, and a housing 42.
In the pressure sensor 30, the same image sensor 32, light source 36, light reflection layer 38, and light absorption layer 40 as in the blood pressure sensor 10 described above can be used. In the following description, preferred embodiments of each member in the pressure sensor 30 used as a tactile sensor for robot applications will be described. However, these aspects can also be used in pressure sensors of the present invention other than the pressure sensor 30 used as a tactile sensor of a robot.

The pressure sensor 30 shown in FIG. 7 is configured by incorporating an image sensor 32, a lens 34, a light source 36, a light reflection layer 38, and a light absorption layer 40 into a housing 42.
The housing 42 is, for example, a rectangular parallelepiped. The image sensor 32 is held on the upper wall surface in the figure with its imaging surface facing inside the casing 42 . Further, the light reflecting layer 38 is held on the lower wall surface in the figure, and a light absorbing layer 40 is laminated on the outer surface side of the light reflecting layer 38.
Each member in the housing 42 may be held by a known method using a holding member or the like.

As an example, the pressure sensor 30 shown in FIG. 7 has a housing 42 fixed to the tip of an arm member 48 of a robot arm 46 with the imaging element 32 side facing the arm member 48, as shown in FIG. 8 described above. and used.
When the robot arm 46 grips an object, pressure from the object is applied to the light reflective layer 38 via the light absorbing layer 40 .
Similar to the blood pressure sensor 10 described above, the light reflection characteristics of the light reflection layer 38, particularly the reflection wavelength (reflection spectrum), change depending on the pressure applied to the light reflection layer 38. The pressure sensor 30 measures the pressure distribution applied to the light reflective layer 38 , that is, the gripped object, from the light reflected by the light reflective layer 38 by capturing an image of the light reflective layer 38 with the image sensor 32 .
That is, by capturing an image of part or all of the light reflective layer 38 with the image sensor 32 and detecting the reflected light, it is possible to detect a location on the light reflective layer 38 where pressure is applied. Similar to the blood pressure sensor 10 described above, the light reflection characteristics of the light reflection layer 38 change depending on the pressure. Therefore, the change in the light reflection characteristics when a prescribed pressure is applied is measured in advance, and the relationship between the pressure applied to the light reflection layer 38 and the characteristics of the reflected light, for example, the pressure applied to the light reflection layer 38 and the wavelength of the reflected light, is measured. Understand the relationship between By using this relationship, the pressure applied to each location on the light reflective layer 38 can be measured from the reflected light at each location on the light reflective layer 38.

In the pressure sensor 30, there are no restrictions on the shape, size, forming material, wall thickness, etc. of the housing 42.
Here, considering the weight and strength of the pressure sensor 30, suitable examples of the forming material include plastic, and metals such as stainless steel and aluminum.
Further, the pressure sensor 30 shown in FIG. 7 measures pressure by making measurement light from a light source 36 enter the light reflection layer 38 and capturing an image of the reflected light from the light reflection layer 38 with the imaging element 32. Therefore, when external environmental light enters the housing 42, this light becomes noise, reducing measurement accuracy. Therefore, it is preferable that the housing 42 has a light shielding property against light in the wavelength range measured by the image sensor 32.
Furthermore, if the scattered light inside the housing 42 becomes noise, it is preferable that the inner surface of the housing 42 be able to absorb the measurement light emitted by the light source 36 and the reflected light from the light reflection layer 38. Note that there are no restrictions on the method of making the inner surface of the casing 42 absorb the measurement light and the reflected light, such as selecting the material for forming the casing 42, coating the inner surface of the casing 42 with a light absorbing material, etc. Known methods are available.
As described above, there is no limit to the thickness of the wall of the casing 42, that is, the thickness of the plate material that constitutes the casing 42. Here, the plate material constituting the casing 42 is preferably thicker in terms of strength of the pressure sensor 30, while thinner is preferable in terms of reducing the weight and size of the pressure sensor 30. Considering this point, the thickness of the plate material constituting the housing 42 is preferably 0.05 to 10 mm, more preferably 0.1 to 5 mm.

In the pressure sensor 30, the image sensor 32, the light reflection layer 38, and the light absorption layer 40 are preferably all sheet-like (plate-like, film-like, layered) members, but may be curved or three-dimensional depending on the application. It may have a similar shape.
Moreover, the size and/or shape of the image sensor 32, the light reflection layer 38, and the light absorption layer 40 may be the same or different.
Further, the image sensor 32, the lens 34, the light reflecting layer 38, and the light absorbing layer 40 may be arranged on the same axis or may be staggered.

Although not shown, the image sensor 32 is connected to an image processing device such as a computer.
The image processing device stores the above-described relationship between the pressure applied to the light reflection layer 38 and the characteristics of reflected light. The image processing device processes and analyzes the image of the light reflective layer 38 captured by the image sensor 32, detects the pressure applied to each location of the light reflective layer 38, and detects the pressure applied to the light reflective layer 38 by, for example, displaying the image. Output pressure distribution.

In the pressure sensor 30 shown in FIG. 7, the image sensor 32 is similar to the image sensor 14 in the blood pressure sensor 10 described above, and the known image sensor described above can be used.

Further, like the image sensor 14 in the blood pressure sensor 10, the image sensor 32 may be an area sensor or a line sensor. However, the pressure sensor 30 used for robot applications is required to measure pressure in a certain area. Considering this point, it is preferable that the image sensor 32 is an area sensor.
Note that the type of sensor such as monochrome or color, measurement light wavelength, various filters, etc. are the same as those of the image sensor 14 in the blood pressure sensor 10, as described above.

Although there is no limit to the spatial resolution of the image sensor 32, a higher resolution is basically preferable. The number of pixels of the image sensor 32 is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 1,000,000 or more.
Although there is no particular upper limit to the number of pixels of the image sensor 32, considering that image processing requires energy and time, the number of pixels is preferably 10 million or less.

Although there is no particular restriction on the size of the image sensor 32, a smaller size is preferable from the viewpoint of downsizing the pressure sensor 30, and a larger size is preferable from the viewpoint of high sensitivity and high resolution.
The size of the image sensor 32 is preferably 1 to 1000 mm ² , more preferably 10 to 500 mm ² , and even more preferably 20 to 400 mm ² .

In the pressure sensor 30, a light reflective layer 38 is provided apart from the image sensor 32 and facing the imaging surface of the image sensor 32.
That is, in the pressure sensor 30 used as a tactile sensor in a robot arm or the like, a space is preferably provided between the image sensor 32 and the light reflective layer 38. This point will be explained in detail later.

The light reflection layer 38 reflects measurement light emitted from a light source 36, which will be described later.
This light reflection layer 38 also has a reflection characteristic that changes depending on the pressure, and is similar to the light reflection layer 18 of the blood pressure sensor 10 described above. Therefore, the above description of the light reflective layer 18 of the blood pressure sensor 10 also serves as a description of the light reflective layer 38 of the pressure sensor 30.

In the pressure sensor 30, the image sensor 32 is arranged with its imaging surface (light receiving surface) facing the light reflective layer 38 side.
Moreover, in the pressure sensor 30, a space is provided between the image sensor 32 and the light reflection layer 38 as a preferable aspect, and a lens 34 is provided between the two as a more preferable aspect. That is, in the pressure sensor 30, as a preferred embodiment, the image sensor 32 and the light reflection layer 38 are arranged apart from each other, and as a more preferred embodiment, the lens 34 is provided between them.

As described above, the pressure sensor 30 shown in FIG. 7 is suitably used as a tactile sensor or the like in the gripping portion (tip) of the robot arm 46.
In such applications, in order to accurately measure pressure with high resolution, it is necessary to focus the image taken by the image sensor 32 on the surface of the light reflective layer 38. To this end, countermeasures are required, such as bringing the image sensor 32 and the light reflection layer 38 into contact with each other or as close as possible to each other, and making the measurement area of the light reflection layer 38 coincide with the imaging area of the image sensor.
Here, it is preferable that the pressure sensor 30 used as a tactile sensor of a robot arm or the like is capable of measuring pressure in a certain area, such as 2×2 cm or 3×3 cm, for example. Therefore, in order to perform proper imaging, the imaging surfaces of the imaging elements 32 must also be of the same size.
However, the imaging surface of an image sensor is usually about 1×1 cm, and the larger the imaging surface, the more expensive it is and the more power it consumes.

On the other hand, in the pressure sensor 30 of the present invention, there is a space between the image sensor 32 and the light reflecting layer 38, and in a more preferred embodiment, a lens 34 is provided between the two.
By having such a configuration, the optical distance necessary for image formation by the lens 34 is ensured, and the distance between the lens 34, the image sensor 32, and the light reflection layer 38 is adjusted, so that the image pickup device 32 can take an image. can be focused on the light reflecting layer 38.
This allows the image sensor 32 to capture high-quality images, that is, to measure pressure with high precision. Furthermore, even if the light reflecting layer 38 of the pressure sensor 30 has a large size such as 3×3 cm, a normal or small image sensor 32 of about 1×1 cm can be used. That is, by using the lens 34, it becomes possible to easily configure the apparatus using the general-purpose image sensor 32.
Furthermore, by selecting the lens 34, it is possible to prevent the distance between the image sensor 32 and the light reflection layer 38 from becoming wider than necessary, that is, to prevent the pressure sensor 30 from becoming larger.
Although there is no limit to the interval (distance) between the image sensor 32 and the light reflection layer 38, it is preferable that it be short in order to downsize the pressure sensor 30 in consideration of mounting it on a robot or the like. On the other hand, considering the arrangement of the lens 34 and the miniaturization of the image sensor 32, it is preferable that there be an optically significant distance.
Considering this point, the distance between the image sensor 32 and the light reflective layer 38 is preferably 0.1 to 50 mm, more preferably 1 to 30 mm, and even more preferably 3 to 20 mm.

Furthermore, in consideration of the size of the pressure sensor 30, the cost of the image sensor 32, the driving power, etc., in the pressure sensor 30, it is preferable that the area of the imaging surface of the image sensor 32 is smaller than the area of the light reflective layer 38.
In this regard, the same applies to all pressure sensors of the present invention, including the blood pressure sensor 10 described above. However, the configuration in which the area of the imaging surface of the image sensor is smaller than the area of the light-reflecting layer is only a preferred embodiment, and in the pressure sensor of the present invention, the area of the imaging surface of the image-capturing element is the same as the area of the light-reflecting layer. Alternatively, the area of the imaging surface may be larger than the area of the light reflecting layer.

The pressure sensor 30 has a light absorption layer 40 as a light shielding layer on the surface of the light reflection layer 38 on the side opposite to the image sensor 14 .
Note that in the present invention, the light absorption layer 40 is provided as a preferred embodiment and is not an essential component.

In applications for tactile sensing such as robot applications, the pressure sensor 30 is used with the light absorption layer 40 facing the object to be contacted.
In the pressure sensor 30 , ambient light from the surroundings (external ambient light) and measurement light from the light source 36 that is unnecessarily incident on the object to be gripped are reflected on the object surface and reflected from the light reflecting layer 38 to the pressure sensor 30 . There is a possibility that it may enter the interior.
If such unnecessary light enters the pressure sensor 30 and is measured by the image sensor 32, it becomes noise and causes an error in the measured pressure, which is not preferable.

The light absorption layer 40 is a layer for preventing such unnecessary light from entering the inside of the pressure sensor 30 from the light reflection layer 38.
That is, the pressure sensor 30 of the present invention has the light absorption layer 40 on the surface of the light reflection layer 38 opposite to the image pickup device 32, thereby making it possible to measure pressure with higher precision.

Such a light absorption layer 40 is similar to the light absorption layer 20 of the blood pressure sensor 10 described above, and absorbs unnecessary light and releases pressure from the surface of the light reflection layer 38 opposite to the image sensor 32. Various layers can be used as long as they can prevent light from entering the sensor 30.
Therefore, the light absorption layer 40 that is exemplified for the light absorption layer 20 can be used.

The light source 36 emits measurement light for the pressure sensor 30 to measure pressure.
In the pressure sensor 30 shown in FIG. 7, the light source 36 is provided so that measurement light is incident on the light reflective layer 38.
Note that the light source 36 is the same as the light source 24 of the blood pressure sensor 10 described above except for the incident position of the measurement light. Therefore, the above description of the light source 24 of the blood pressure sensor 10 also serves as a description of the light source 36 of the pressure sensor 30.

Hereinafter, the operation of the pressure sensor 30 of the present invention will be explained.
As described above, the pressure sensor 30 is used for tactile sensing in robot applications, for example, and is attached to the tip of the arm member 48 of the robot arm 46 and used as a tactile sensor for the robot arm 46. Ru.
Moreover, the pressure sensor 30 is connected to an image processing device such as a computer, for example.
When performing tactile sensing of the robot arm 46 using the pressure sensor 30, first, the light source 36 is turned on and measurement light is made incident on the light reflection layer 38. The light source 36 may be turned on by controlling an image processing device to which the pressure sensor 30 is connected, or by providing a switch in the casing 42 of the pressure sensor 30.
The measurement light incident on the light reflective layer 38 is reflected by the light reflective layer 38. The light reflected by the light reflection layer 38 is focused and imaged by the lens 34, and enters the image sensor 32, where it is imaged. Depending on the configuration of the pressure sensor 30, a portion of the measurement light from the light source 36 directly enters the image sensor 32 through the lens 34, and is imaged together with the reflected image from the light reflective layer 38. The image captured by the image sensor 32 is output to the image processing device and processed.

As described above, the light reflective layer 38 is a low elastic layer whose thickness changes depending on the pressure applied by an object. Therefore, when the robot arm to which the pressure sensor 30 is attached performs an operation of grasping an object, the light reflecting layer 38 is pressed by the object, and is deformed (compressed) by this pressing.
Further, the pressure applied to the light reflecting layer 38 differs depending on the shape of the object and the like.

In the present invention, the light reflective layer 38 has reflective characteristics that change depending on pressure. Preferably, the light reflecting layer 38 has wavelength selectivity for reflected light, like a cholesteric liquid crystal layer, and the wavelength of the selectively reflected light changes in response to deformation (compression and expansion) due to pressure.
Therefore, for example, when the light reflection layer 38 is a cholesteric liquid crystal layer, the helical pitch of the cholesteric liquid crystal phase changes due to the change in thickness due to the pressure of an object, and the incident angle of the measurement light with respect to the helical axis also changes. . As a result, the light-reflecting layer 38 has a wavelength of the measurement light selectively reflected by the light-reflection layer 38, that is, a wavelength of the reflected light ( reflection spectrum) changes.

Therefore, for example, if the measurement light is white light and the image sensor 32 is a color sensor, the image captured by the image sensor 32 will depend on the location being pressed and the strength of the pressure at each location. Color and density change locally.
In addition, when the measurement light is white light or monochromatic light such as red light and green light, and the image sensor 32 is a black and white monochrome sensor (luminance sensor) or a sensor compatible with monochromatic light, the pressed location, The density (brightness) of the image captured by the image sensor 32 partially changes depending on the strength of the pressure at each location.
Furthermore, when the measurement light is monochromatic light such as red light and green light, and the image sensor 32 is a color sensor, the image sensor 32 The density (brightness) of the image captured by the camera changes partially. In addition, in this case, due to the relationship between the wavelength range of the measurement light and the wavelength range of the light selectively reflected by the light reflection layer 38, the color tone of the image captured by the image sensor 32 may also be slightly different in some parts. ,Change.

Here, the state in which the light reflection layer 38 is pressed by the object, that is, the state in which the light reflection layer 38 is deformed by the object, differs depending on the applied pressure. Further, as described above, the pressure applied to the light reflecting layer 38 differs depending on the shape of the object and the like.
Therefore, the image captured by the image sensor 32 also changes depending on the shape of the object to be grasped, the force with which the robot arm grasps the object, and the like.

The present invention utilizes this, and the relationship between the pressure caused by the contacting object and the image captured by the image sensor 32 is known in advance and stored in, for example, an image processing device.
Then, for example, as described above, the pressure sensor 30 is attached to the robot arm 46, the object is gripped by the robot arm 46, measurement light is incident on the light reflection layer 38 from the light source 36, and the image sensor 32 Take an image. Next, the captured image is output to an image processing device to perform necessary image processing, and matching is performed between the image captured by the image sensor 32 and the image corresponding to the pressure stored in advance. For example, the color or wavelength of each location in the image captured by the image sensor 32 is matched with the color or wavelength corresponding to the pressure stored in advance. Note that image matching may be performed using a known method.
This makes it possible to measure the pressure (pressure distribution) applied to each position of the robot arm 46 (arm member 48) that grips the object, that is, the pressure at each position of the object.
This measurement result is displayed on a display connected to the image processing device, for example.

As described above, according to the pressure sensor 30 of the present invention, the relationship between the pressure caused by a contacting object and the image captured by the image sensor 32 can be known in advance and stored in, for example, an image processing device. For example, it is possible to measure the pressure (pressure distribution) applied to each position of the robot arm gripping an object, that is, to perform tactile sensing on the robot arm, without performing complicated calculations.
Further, the image sensor 32 can normally capture moving images. Therefore, the pressure sensor 30 of the present invention is capable of continuously measuring the pressure applied to the robot arm 46 gripping an object. For example, even when the robot arm 46 is operated to change the gripping force and the orientation of the object, Pressure and pressure distribution fluctuations can be measured continuously.
In addition, in the pressure sensor 30 of the present invention, the image captured by the image sensor is detected by not only changing the image density (brightness) according to the pressure, but also changing the color (wavelength) according to the pressure. be able to. In addition, preferably, by providing a space between the light-reflecting layer 38 and the image sensor 32 and arranging the lens 34 between them, the light-reflecting layer 38 (image of the light-reflecting layer 38) can be properly adjusted. An image can be formed on the image sensor 32 at the same time. Therefore, according to the pressure sensor 30 of the present invention, more detailed changes in captured images can be captured and detected with high quality, and as a result, pressure distribution can be measured with higher precision and higher resolution.

The advantages of the present invention, particularly in that the pressure sensor 30 is able to change not only the density but also the color of the captured image according to the pressure, making it possible to measure blood pressure with higher precision and resolution. The light source 36 is preferably a white light source, and the image sensor 32 is preferably a color sensor.

In measuring pressure using the pressure sensor 30 of the present invention, the light source 36 may emit measuring light continuously or may emit pulsed light.
The measurement light emitted by the light source 36 is pulsed light, and the emission period is set to a higher frequency than, for example, the vibration period of the measuring object, thereby eliminating the influence of vibration on the pressure measurement results, for example, by filter cutting using a low-pass filter. This allows for more accurate pressure measurements.

Although the pressure sensor and robot of the present invention have been described in detail above, the present invention is not limited to the above-mentioned examples, and various improvements and changes may be made without departing from the gist of the present invention. , of course.

The present invention will be explained in more detail below based on Examples.
The materials, usage amounts, proportions, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the embodiments shown below.

(Synthesis of specific cellulose compound 1)
Specific cellulose compound 1 was synthesized by the procedure described in the scheme below.

Hydroxypropylcellulose (HPC) (manufactured by Wako Pure Chemical Industries, Ltd., product name: Hydroxypropylcellulose 2.0 to 2.9) was dried at 80° C. for 2 hours or more under reduced pressure. 20.0 g of HPC was weighed into a three-necked flask filled with nitrogen, and dissolved in 80 mL of dehydrated acetone with stirring to obtain an HPC solution. 0.40 mL (3.2 mmol) of Karenz AOI (2-isocyanatoethyl acrylate, manufactured by Showa Denko K.K.) was added to the HPC solution at room temperature, and the mixture was reacted at 50° C. for 2 hours. After the reaction was completed, 2 mL of methanol was added to the resulting solution to quench the unreacted substrate. After removing the solvent of the reaction solution using a rotary evaporator, the product was dried under reduced pressure at room temperature (25° C.) for 2 hours or more to obtain a white powder product. The yield of specific cellulose compound 1 was 18.0 g. As a result of measuring the ¹ H-NMR spectrum of the specific cellulose compound 1, the degree of substitution of the acryloyl group to the HPC side chain (hydrogen atom of the hydroxyl group possessed by HPC) was 0.06.

(Synthesis of specific cellulose compound 2)
Hydroxypropylcellulose (HPC) (manufactured by Wako Pure Chemical Industries, Ltd., product name: Hydroxypropylcellulose 2.0 to 2.9) was dried at 80° C. for 2 hours or more under reduced pressure. 20.0 g of HPC was weighed into a three-necked flask filled with nitrogen, and dissolved in 80 mL of dehydrated acetone with stirring to obtain an HPC solution. 0.13 mL (1.1 mmol) of Karenz AOI (2-isocyanatoethyl acrylate, manufactured by Showa Denko K.K.) was added to the HPC solution at room temperature, and the mixture was reacted at 50° C. for 2 hours. After the reaction was completed, 2 mL of methanol was added to the obtained solution to quench the unreacted substrate. After removing the solvent of the reaction solution using a rotary evaporator, the product was dried under reduced pressure at room temperature (25° C.) for 2 hours or more to obtain a white powder product. The yield of specific cellulose compound 2 was 18.0 g. As a result of measuring the ¹ H-NMR spectrum of the specific cellulose compound 2, the degree of substitution of the acryloyl group to the HPC side chain (hydrogen atom of the hydroxyl group possessed by HPC) was 0.02.

(Synthesis of specific cellulose compound 3)
Hydroxypropylcellulose (HPC) (manufactured by Wako Pure Chemical Industries, Ltd., product name: Hydroxypropylcellulose 2.0 to 2.9) was dried at 80° C. for 2 hours or more under reduced pressure. 12.0 g of HPC was weighed into a three-necked flask and dissolved in 40 mL of dehydrated acetone with stirring to obtain an HPC solution. 2.74 ml (0.0285 mol) of 3-chloropropionic acid chloride and 23.1 ml (0.257 mol) of propionyl chloride were added to the HPC solution at room temperature, and the mixture was reacted at room temperature for 8 hours. After the reaction was completed, the obtained solution was diluted by adding 100 mL of ethyl acetate, 24 g of sodium hydrogen carbonate and 100 mL of water were added, and after stirring for 1 hour, a liquid separation operation was performed to remove the aqueous layer. After adding 14 mL of triethylamine to the obtained organic layer and stirring at room temperature for 3 days, 200 mL of ethyl acetate and 200 mL of 1N HCL aqueous solution were added, a liquid separation operation was performed, and the aqueous layer was removed. Furthermore, 200 mL of 15% by mass brine was added to the remaining organic layer, the aqueous layer was removed by separation, and the solvent was removed by drying under reduced pressure at 60° C. to obtain a glutinous specific cellulose compound 3. . Yield was 15.0g. As a result of measuring the ¹ H-NMR spectrum of specific cellulose compound 3, the degree of substitution of the acryloyl group on the HPC side chain (the hydrogen atom of the hydroxyl group that HPC has) is 0.06, and the degree of substitution of the propionyl group is 2.90. Met.

(Manufacture of light reflective layer 1)
Specific cellulose compound 1 (1.52 g), hydroxypropyl cellulose (HPC) (manufactured by Wako Pure Chemical Industries, Ltd., product name: hydroxypropyl cellulose 2.0 to 2.9) (0.51 g), photoinitiator 1 -(4-(2-hydroxyethoxy)-phenyl)-2-hydroxy-methylpropanone (0.015 g) and water (0.96 g) were mixed to prepare a mixed solution 1. The obtained mixed liquid 1 was placed between a polyvinylidene chloride base material (10 μm) and a PET base material (40 μm) so that the thickness was 450 μm. At that time, the polyvinylidene chloride base material and the PET base material are pasted together with a transparent adhesive film (450 μm) made of acrylic resin, and placed so that there is no gap around the mixed liquid 1, so that the surroundings of the mixed liquid 1 are covered with polyvinylidene. It was installed so that it was covered with a vinylidene chloride base material, a PET base material, and a transparent adhesive film made of acrylic resin.
Thereafter, from the PET base material side, it was exposed to light using a high-pressure mercury lamp adjusted to have an illumination intensity of 0.03 W/cm ² in the UV-A region at an exposure amount of 0.03 J/cm ² (UV-A region), and cured. In this way, a light reflective layer 1 was obtained. The light reflecting layer 1 produced in this way has cholesteric liquid crystallinity with a reflection band with a reflectance of about 40% in the green light region (light wavelength 450 to 550 nm), and the color changes from blue to ultraviolet depending on the pressure. It was possible for the color to change in response to minute pressure.

(Manufacture of light reflective layer 3)
Specific cellulose compound 2 (1.52 g), hydroxypropyl cellulose (HPC) (manufactured by Wako Pure Chemical Industries, Ltd., product name: hydroxypropyl cellulose 2.0-2.9) 0.51 g, photoinitiator 1-(4 -(2-hydroxyethoxy)-phenyl)-2-hydroxy-methylpropanone (0.015 g) and water (0.96 g) were mixed to prepare a mixed solution 3. The obtained mixed solution 3 was placed between a polyvinylidene chloride base material (10 μm) and a PET base material (40 μm) so that the thickness was 450 μm. At that time, the polyvinylidene chloride base material and the PET base material are bonded together using a transparent adhesive film (450 μm) made of acrylic resin, and placed so that there is no gap around the mixed liquid 3, so that the surroundings of the mixed liquid 3 are It was installed so that it was covered with a polyvinylidene chloride base material, a PET base material, and a transparent adhesive film made of acrylic resin.
Thereafter, from the PET base material side, it was exposed to light with a high-pressure mercury lamp adjusted so that the illuminance in the UV-A region was 0.03 W/cm ² at an exposure amount of 0.03 J/cm ² (UV-A region) and cured. , a light reflective layer 3 was obtained. The light reflecting layer 3 produced in this way has cholesteric liquid crystallinity with a reflection band with a reflectance of about 40% in the green light region (light wavelength 450 to 550 nm), and the color changes from blue to ultraviolet depending on the pressure. It was possible for the color to change on the skin in response to vascular pressure associated with pulsation.

(Light reflective layer 2, 4 to 11)
Light reflective layers 2, 4 to 11 were produced according to the same procedure as that for light reflective layer 1 or light reflective layer 3, except that the manufacturing conditions for light reflective layers 1 and 3 were changed to those shown in Table 2 below.
The light reflection layers 2, 4 to 9 have cholesteric liquid crystallinity with a reflection band of 40% reflectance in the green light region, and the color changes from blue to ultraviolet region depending on the pressure, and reduces blood vessel pressure associated with pulsation. It was possible for the color to change on the skin as a result of the exposure.
The light-reflecting layer 10 has cholesteric liquid crystallinity with a reflection band in the red region with a reflectance of 40%, and its color changes from green to ultraviolet region depending on the pressure. It was possible to change the color tone.
The light-reflecting layer 11 has cholesteric liquid crystallinity with a reflection band in the blue region with a reflectance of 40%, and its color changes to the ultraviolet region according to pressure, and changes color on the skin in response to vascular pressure associated with pulsation. It was possible to change the taste.

In Table 2, the "Compound 1 (g)" column represents the amount (g) of specific cellulose compound 1 used.
In Table 2, the "Compound 2 (g)" column represents the amount (g) of specific cellulose compound 2 used.
In Table 2, the "HPC (g)" column represents the amount (g) of hydroxypropyl cellulose used.
In Table 2, the "color before pressurization" column indicates the color of the light-reflecting layer before pressurization, which was visually confirmed.

In Table 2, the numerical values in the "responsiveness" column represent the following.
When the produced light-reflecting layer was pressed with a finger and further released, the color change was visually observed and evaluated using the following criteria.
"1": The color (reflection wavelength) changes with very weak pressure.
"2": The color (reflection wavelength) changes in response to slightly weak pressure.
"3": The color (reflection wavelength) changes in response to weak pressure.
"4": The color (reflection wavelength) changes in response to slightly strong pressure.
"5": The color (reflection wavelength) changes in response to strong pressure.

In Table 2, the numerical values in the "operational stability" column represent the following.
The produced light-reflecting layer was pressed with a finger with gentle pressure, and when it was further released, the color change was visually observed and evaluated according to the following criteria.
"1": When pressure is applied to the light reflection layer and then the pressure is reduced to 0, the color returns very quickly to the state before pressure application.
"2": When pressure is applied to the light reflection layer and then the pressure is reduced to 0, the color quickly returns to the state before pressure application.
"3": When pressure is applied to the light reflection layer and then the pressure is reduced to 0, the color returns to the state before pressure application somewhat quickly.
"4": When pressure is applied to the light reflection layer and then the pressure is reduced to 0, the color returns to the state before pressure application rather slowly.
"5": When pressure is applied to the light reflection layer and then the pressure is reduced to 0, the color slowly returns to the state before pressure application.

As shown in Table 2 above, it was confirmed that the light reflective layers 1 to 11 changed color by applying pressure.

(Manufacture of light reflective layer 12)
Dissolve specific cellulose compound 3 (8.6 g) in ethyl acetate (114 g), add dodecyl acrylate (1.3 g) and 2,2-dimethoxy-2-phenylacetophenone (0.3 g), stir, and dissolve. After that, ethyl acetate was removed using an evaporator to prepare a mixed solution 12. After sandwiching the mixed liquid 12 between glass substrates while applying shear, it was exposed and cured with a mercury xenon lamp (exposure amount 1 J/cm ² , illumination intensity 4 mW/cm ² ), and then the liquid crystal film was placed between the glass substrates. The light reflecting layer 12 was obtained by peeling it off. At this time, the film thickness of the liquid crystal film of the light reflective layer 12 was adjusted to 100 μm by controlling the distance between the glass substrates using a spacer when sandwiching them between the glass substrates. The light-reflecting layer 12 produced in this manner has cholesteric liquid crystallinity with a reflection band with a reflectance of about 30% in the green light region (light wavelength 450 to 550 nm), and the color changes from blue to ultraviolet depending on the pressure. It was possible for the color to change in response to minute pressure.

As described above, the light reflective layers 1 to 12 were capable of changing color under pressure.
Next, blood pressure sensors of Examples 1 to 12 were manufactured using these light reflection layers 1 to 12 as the light reflection layer 18 provided in the blood pressure sensor 10 shown in FIG. 1, respectively. It was confirmed that when pressure was applied to the blood pressure sensors of Examples 1 to 12, they exhibited the above-mentioned color change.

Further, pressure sensors of Examples 13 to 24 were manufactured using the light reflection layers 1 to 12 as the light reflection layer 38 provided in the pressure sensor 30 shown in FIG. 7, respectively. It was confirmed that when pressure was applied to the pressure sensors of Examples 13 to 24, the above-mentioned color changes were exhibited.

It can be suitably used for various pressure measurements such as blood pressure measurement and tactile sensing in robot applications.

10, 10a, 10b Blood pressure sensor 12

Substrate

14, 32 Image sensor 14L Line sensor 16

Light guide layer

18, 38

Light reflection layer

20, 40

Light absorption layer

24, 36 Light source 28 Band 30 Pressure sensor 34 Lens 42 Housing 46 Robot arm 48 Arm member A Radial artery S Epidermis

Claims

An image sensor and
a light reflecting layer whose reflection characteristics change depending on pressure, the layer facing the imaging surface of the imaging device and disposed apart from the imaging device;
Pressure is generated from a change in the image captured by the image sensor when pressure is applied from the side of the light reflection layer opposite to the image sensor while light is incident between the image sensor and the light reflection layer. A pressure sensor that detects
The pressure sensor according to claim 1, further comprising a light guide layer between the image sensor and the light reflective layer.
The pressure sensor according to claim 1, further comprising a light source that enters light between the image sensor and the light reflective layer.
The pressure sensor according to claim 2, further comprising a light source that enters light between the image sensor and the light reflective layer.
The pressure sensor according to claim 2 or 4, wherein the image sensor and the light guide layer are in contact with each other, and the light reflection layer and the light guide layer are in contact with each other.
The pressure sensor according to claim 2 or 4, wherein the light guide layer is a resin layer or a glass layer.
The pressure sensor according to claim 4, wherein the pressure sensor has a plurality of light sources, and the light sources are arranged so as to sandwich the light guide layer.
The pressure sensor according to claim 2 or 4, wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
The pressure sensor according to claim 1, further comprising a space between the image sensor and the light reflecting layer.
The pressure sensor according to claim 9, further comprising a light source that irradiates the light reflection layer with light.
The pressure sensor according to claim 9 or 10, further comprising a lens between the image sensor and the light reflective layer.
The pressure sensor according to claim 11, wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
The pressure sensor according to claim 1 or 3, wherein the area of the imaging surface of the image sensor is smaller than the area of the light reflective layer.
The pressure sensor according to claim 2 or 9, further comprising a light-shielding layer on the opposite side of the light-reflecting layer from the image sensor.
The pressure sensor according to claim 2 or 9, wherein the light reflecting layer is a cholesteric liquid crystal layer.
The pressure sensor according to claim 2 or 9, wherein the light reflective layer contains cellulose.
The pressure sensor according to claim 16, wherein the cellulose contains a cured product of a cellulose compound having a polymerizable group.
The pressure sensor according to claim 16, wherein the cellulose contains an unsubstituted cellulose compound.
The pressure sensor according to claim 2 or 9, wherein the light reflecting layer is made of wet gel.
The pressure sensor according to claim 2 or 9, wherein the light reflecting layer contains a liquid component.
The pressure sensor according to claim 2 or 9, wherein the light reflecting layer is sealed with a sealing material.
The pressure sensor according to claim 2 or 9, wherein the image sensor is a color sensor.
The pressure sensor according to claim 2 or 4, which is a blood pressure sensor.
The pressure sensor according to claim 9 or 10, which is a tactile sensor.
A robot equipped with the pressure sensor according to claim 9 or 10 as a tactile sensor.