Pressure sensor

Abstract

To provide a pressure sensor with a tactile sense function and a proximity sense function.SOLUTION: A pressure sensor includes: an imaging element; a light reflection layer facing an imaging surface of the imaging element, arranged apart from the imaging element, and having reflection characteristics that change in accordance with pressure; and a light source that emits light to the light reflection layer. The light reflection layer has: a first region which is transparent to light sensed by the imaging element in both of a state where pressure is not applied and a state where pressure is applied, and a second region in which a reflection wavelength changes in the state where pressure is not applied and the state where pressure is applied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure sensor used as a tactile sensor or the like. [Background technology]

[0002] Pressure sensors are used in a variety of fields. For example, there is a growing 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 deformation so that a robot can apply an appropriate force according to the shape, hardness, etc., of an object when grasping it.

[0003] For example, Patent Document 1 describes a contact sensor comprising a block of elastomer illuminated by one or more light sources and having translucency, a reflective coating that covers the elastomer and contains reflective particles that reflect incident light from inside the elastomer, and a light detection mechanism positioned to receive a portion of the reflected light; when an object comes into contact with the reflective coating and pressure is applied, the reflective coating geometrically deforms and the surface normal changes locally, and as a result of this change, the amount of reflected light traveling from the reflective coating to the light detection mechanism changes locally, so that an image-like reflected light showing one or more characteristics of the object exerting pressure is incident on the light detection mechanism. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2011-525284 Summary of the Invention [Problem to be solved by the invention]

[0005] Because tactile sensors cannot detect an object until it comes into contact with it, when used in robotics, for example, there are problems such as the need for a robot to move slowly when trying to grab something, and it being difficult to determine whether it can grab an object at the desired position.

[0006] In contrast, a proximity sensor that can detect when an object surface is in close proximity can detect objects that are not in contact with the sensor. Therefore, for example, in robot applications, the robot can operate relatively quickly when grabbing something, and can grab an object at a more appropriate position.

[0007] However, conventional pressure sensors function as tactile sensors, and none of them function as proximity sensors.

[0008] An object of the present invention is to solve the problems of the conventional technology and to provide a pressure sensor having both a tactile function and a proximity function. [Means for solving the problem]

[0009] In order to solve this problem, the present invention has the following configuration. [1] An image sensor; a light reflective layer whose reflection characteristics change in response to pressure, the light reflective layer being disposed opposite to the imaging surface of the imaging element and spaced apart from the imaging element; A light source that emits light to the light reflecting layer, A pressure sensor comprising an optically reflective layer having a first region that is transparent to light sensed by an imaging element in both an unstressed and stressed state, and a second region whose reflected wavelength changes between an unstressed and stressed state. [2] The pressure sensor according to [1], wherein the light sensed by the imaging element is light having any wavelength in the visible light range. [3] The pressure sensor according to [2], wherein the imaging element is a color two-dimensional sensor. [4] The pressure sensor according to any one of [1] to [3], wherein the light reflecting layer is a liquid crystal layer. [5] The pressure sensor according to [4], wherein the second region is a cholesteric liquid crystal layer. [6] The pressure sensor according to any one of [1] to [5], wherein the second region reflects light that is sensed by the imaging element in both a pressure-free state and a pressure-applied state. [7] The pressure sensor according to any one of [1] to [6], wherein the light reflecting layer has a plurality of second regions, the plurality of second regions being discretely arranged, and the first region being arranged between the plurality of discretely arranged second regions. [8] The pressure sensor according to [7], wherein the light reflecting layer is deformable by stress applied in an in-plane direction, and detects shear stress applied in the in-plane direction by detecting a change in the position of the second region. [9] A pressure sensor according to any one of [1] to [8], which changes the intensity of light emitted from the light source in response to a change in state between a state in which no pressure is applied to the second region and a state in which pressure is applied to the second region.

[10] An optical system for directing light to an image sensor; The pressure sensor according to any one of [1] to [9], which changes a focal position of the optical system in response to a change in state between a state in which no pressure is applied to the second region and a state in which pressure is applied to the second region.

[11] The pressure sensor according to any one of [1] to

[10] , further comprising a black portion disposed on a surface of the light reflecting layer opposite to the imaging element, the black portion being located at a position corresponding to the second region. Effect of the Invention

[0010] According to the present invention, a pressure sensor having a tactile function and a proximity function can be provided. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram conceptually showing an example of a pressure sensor of the present invention. [Diagram 2] FIG. 2 is a plan view of a light reflecting layer of the pressure sensor shown in FIG. [Diagram 3] FIG. 3 is a plan view of a black layer included in the pressure sensor shown in FIG. [Figure 4]FIG. 4 is a conceptual diagram showing an example of a robot arm having a pressure sensor of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining the operation of the pressure sensor of the present invention. [Figure 6] FIG. 6 is a plan view of the light reflecting layer of the pressure sensor shown in FIG. [Figure 7] FIG. 7 is a diagram for explaining the operation of the pressure sensor of the present invention. [Figure 8] FIG. 8 is a plan view of the light reflecting layer of the pressure sensor shown in FIG. [Figure 9] FIG. 9 is a plan view conceptually showing another example of the light reflecting layer of the pressure sensor of the present invention. [Figure 10] FIG. 10 is a diagram for explaining the operation of the pressure sensor of the present invention. [Figure 11] FIG. 11 is a plan view of the light reflecting layer of the pressure sensor shown in FIG. [Figure 12] FIG. 12 is a diagram for explaining the operation of the pressure sensor of the present invention. [Figure 13] FIG. 13 is a plan view of the light reflecting layer of the pressure sensor shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure sensor according to the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

[0013] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, the terms "same" and "identical" are intended to include a generally acceptable margin of error in the technical field.

[0014] In this specification, the bond direction of a divalent group (e.g., -CO-O-, etc.) is not limited unless otherwise specified. For example, when Y is -CO-O- in a compound represented by the formula "XYZ", the compound may be either "XO-CO-Z" or "X-CO-OZ".

[0015] Note that the drawings shown below are all conceptual diagrams for explaining the present invention, and therefore the shapes, thicknesses, sizes, positional relationships, etc. of the components do not necessarily correspond to the actual ones.

[0016] [Pressure sensor] The pressure sensor of the present invention comprises an imaging element and a light reflective layer whose reflection characteristics change in response to pressure, the light reflective layer being disposed opposite to the imaging surface of the imaging element and spaced apart from the imaging element; A light source that emits light to the light reflecting layer, The pressure sensor has a light reflective layer having a first region that is transparent to light sensed by an imaging element in both an unstressed and stressed state, and a second region whose reflected wavelength changes between an unstressed and stressed state.

[0017] FIG. 1 conceptually illustrates an example of a pressure sensor of the present invention.

[0018] The pressure sensor 30 shown in FIG. 1 includes an imaging element 32, a lens 34, a light source 36, a light reflective layer 38, a patterned black layer 40, and a housing 42.

[0019] In the pressure sensor 30, a lens 34 is disposed on the imaging surface side of the imaging element 32, and a laminate of a light reflecting layer 38 and a patterned black layer 40 is disposed on the surface of the lens 34 opposite the imaging element 32. The light reflecting layer 38 and the patterned black layer 40 are sheet-like (plate-like, film-like, layer-like) members. The light source 36 is disposed at a position where it can irradiate light onto the surface of the light reflecting layer 38 on the imaging element 32 side.

[0020] In the pressure sensor 30 of the present invention, the light reflecting layer 38 has a first region 38a that is transparent to the light sensed by the imaging element 32 in both the unpressurized and pressurized states, and a second region 38b whose reflected wavelength changes between the unpressurized and pressurized states. The second region 38b reflects light of a wavelength sensed by the imaging element 32 at least in the pressurized state. The light source 36 emits (irradiates) light of a wavelength reflected by the second region 38b at least in the pressurized state. In the following description, the wavelength (light) reflected by the second region 38b in the pressurized state of the light reflecting layer 38 is also simply referred to as the wavelength (light) reflected by the second region 38b. The light reflected by the second region 38b (light reflecting layer 38) is also referred to as reflected light. The light emitted by the light source 36 is also referred to as measurement light.

[0021] The pressure sensor 30 having such a light reflecting layer 38 can detect an object P that is not in contact with the pressure sensor 30 and exists in the vicinity of the pressure sensor 30 by receiving the light that is reflected by the surface of the object P due to external light and transmitted through the first region 38a with the imaging element 32. That is, the pressure sensor 30 functions as a proximity sensor. Also, the pressure sensor 30 can detect whether or not pressure is applied to the light reflecting layer 38 by receiving the light from the light source 36 reflected by the second region 38b with the imaging element 32. That is, the pressure sensor 30 functions as a tactile sensor. Therefore, the pressure sensor 30 having the light reflecting layer 38 having the first region 38a and the second region 38b is a pressure sensor having a tactile function and a proximity function.

[0022] The operation of the pressure sensor 30, as well as the light reflective layer 38, will be described in more detail below.

[0023] The housing 42 holds the image pickup element 32, the lens 34, the light source 36, the light reflecting layer 38, and the patterned black layer 40 in a predetermined arrangement.

[0024] The housing 42 is, for example, a rectangular parallelepiped. The imaging element 32 is held on the upper wall in the figure with the imaging surface facing the inside of the housing 42. The light reflecting layer 38 is held on the lower wall in the figure, and is disposed so that the patterned black layer 40 laminated on the surface of the light reflecting layer 38 opposite the imaging element 32 is exposed to the outside of the housing 42. The lens 34 is disposed between the imaging element 32 and the light reflecting layer 38. The members in the housing 42 may be held by a known method using a holding member or the like.

[0025] In the pressure sensor 30, there are no limitations on the shape, size, forming material, wall thickness, etc. of the housing 42. Considering the weight, strength, etc. of the pressure sensor 30, suitable forming materials include plastics and metals such as stainless steel and aluminum.

[0026] 1 measures pressure by illuminating measurement light from a light source 36 onto the light reflecting layer 38 and capturing an image of the light reflected from the second region 38b of the light reflecting layer 38 with the imaging element 32, and captures an image of the object P by capturing an image of the light reflected by the object P and transmitted through the first region 38a with the imaging element 32. Therefore, if external environmental light enters the housing 42 from anywhere other than the light reflecting layer 38, this light becomes noise, decreasing the measurement accuracy. For this reason, it is preferable that the housing 42 has a light-blocking property against light in the wavelength range received by the imaging element 32.

[0027] Furthermore, if scattered light inside the housing 42 becomes noise, it is preferable that the inner surface of the housing 42 is capable of absorbing the measurement light emitted by the light source 36, the reflected light from the light reflecting layer 38, and the external light transmitted through the first region 38a. There are no limitations on the method for enabling the inner surface of the housing 42 to absorb the measurement light, the reflected light, and the external light, and known methods such as selecting a material for forming the housing 42 or coating the inner surface of the housing 42 with a light absorbing material can be used.

[0028] As described above, there is no limit to the thickness of the wall of the housing 42, i.e., the plate material constituting the housing 42. Here, the plate material constituting the housing 42 is preferably thicker in terms of the strength of the pressure sensor 30, while it is preferably thinner in terms of reducing the weight and size of the pressure sensor 30. In consideration of this, the thickness of the plate material constituting the housing 42 is preferably 0.05 to 10 mm, and more preferably 0.1 to 5 mm.

[0029] The imaging element 32 is a known imaging element and is disposed with its imaging surface facing the inside of the housing 42, i.e., toward the light reflecting layer 38 side.

[0030] In the pressure sensor of the present invention, the imaging element 32 may be a so-called two-dimensional sensor in which pixels are arranged two-dimensionally, or may be a so-called line sensor in which pixels are arranged in only one row according to the color to be imaged. However, the pressure sensor 30 used for robot applications is required to measure the pressure in a certain area. In consideration of this, the imaging element 32 is preferably a two-dimensional sensor. The imaging element 32 of the pressure sensor 30 shown in FIG. 1 is a two-dimensional sensor.

[0031] In addition, the imaging element 32 senses light of at least a portion of the wavelength range of light that is reflected by the surface of the object P due to external light and passes through the first region 38a of the light reflecting layer 38, and senses light of a wavelength reflected by the second region 38b of the light reflecting layer 38 (light of a wavelength emitted by the light source 36) when pressure is applied to the second region 38b of the light reflecting layer 38.

[0032] The imaging element 32 senses light in at least a part of the wavelength range of light reflected from the surface of the object P and transmitted through the first region 38a, thereby being able to capture an image of the object P located on the surface of the light reflecting layer 38 opposite the imaging element 32. From the viewpoint of capturing an image of the object P, it is preferable that the imaging element 32 senses light of a certain wavelength in the visible light region.

[0033] In addition, there is no particular restriction on the wavelength of the light reflected by the second region 38b that is sensed by the imaging element 32, i.e., the wavelength of the light source 36, and it may be any wavelength in the visible light region, or any wavelength in the ultraviolet light region, near-infrared light region, far-infrared light region, etc.

[0034] The imaging element 32 may be a monochrome sensor that captures a black-and-white image (luminance image), a monochrome sensor that captures a single-color image such as a red image, a green image, and a blue image, a color sensor that captures a two-color image such as a red image and a green image, or a color sensor that captures a full-color image of a red image, a green image, and a blue image. Alternatively, it may be a color sensor that captures at least one of a red image, a green image, and a blue image, and an ultraviolet light image and / or an infrared light image. A color sensor that captures a full-color image is preferably used as the imaging element 32. More preferably, the imaging element 32 is a color two-dimensional sensor in which pixels are arranged two-dimensionally and captures a full-color image.

[0035] Depending on the application of the pressure sensor of the present invention, 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 least in one place between the light source 36 and the light reflecting layer 38 and between the light reflecting layer 38 and the image sensor 32. Such a filter may have wavelength selectivity and transmittance adjusted by a light absorbing material, and may be an interference filter made of a liquid crystal film, a laminated film, or the like, or a polarizing filter.

[0036] In addition, if the second region 38b of the light reflecting layer 38 has wavelength selectivity in reflection like a cholesteric liquid crystal layer described later, when using a monochrome sensor that captures a single-color image or a color sensor that captures a two-color image as the image sensor 32, it is preferable to use a sensor that is sensitive to the wavelength range selectively reflected by the second region 38b of the light reflecting layer 38.

[0037] In the following description, unless otherwise specified, a color sensor refers to a color sensor that captures a full-color image.

[0038] Various known imaging elements can be used as the imaging element 32. As an example of the imaging element 32, a solid-state imaging element is preferably used, and a CCD image sensor using a photodiode formed of silicon and a charge-coupled device for signal transmission, a CMOS image sensor using a CMOS for signal transmission, etc. can be used. In addition to these, an organic thin-film imaging element using an organic semiconductor, an imaging element using other semiconductors, etc. can also be used as the imaging element 32. Among them, a CCD image sensor, a CMOS image sensor, an organic thin-film imaging element, etc. are preferably used.

[0039] There is no limit to the spatial resolution of the imaging element 32, but basically, the higher the resolution, the better. The number of pixels of the imaging element 32 is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 1 million or more. There is no particular upper limit to the number of pixels of the imaging element 32, but considering the energy and time required for image processing, the number of pixels is preferably 10 million or less.

[0040] There is no particular limit to the size of the imaging element 32, but a smaller size is preferable from the viewpoint of miniaturization of the pressure sensor 30, and a larger size is preferable from the viewpoint of high sensitivity and high resolution. 2 is preferable, and 10 to 500 mm 2 is more preferable, 20~400mm 2 is more preferred.

[0041] In a preferred embodiment of the pressure sensor 30, a lens 34 is provided between the image pickup element 32 and the light reflecting layer 38.

[0042] The lens 34 forms an image of the light reflected by the second region of the light reflecting layer 38 on the imaging surface of the image sensor 32. And / or, the lens 34 forms an image of the light reflected by the surface of the object P and transmitted through the first region of the light reflecting layer 38 on the imaging surface of the image sensor 32.

[0043] A known lens can be used as the lens 34. The lens 34 may be a single lens or a lens group made up of a plurality of lenses. The lens 34 is the optical system of the present invention.

[0044] The focal position of the lens 34 (optical system) may be changeable. For example, the focal position of the lens 34 (optical system) may be configured to change in response to a change in state between a state in which no pressure is applied to the second region and a state in which pressure is applied to the second region.

[0045] For example, the focal position of the lens 34 may be variable between a position where the light reflected by the second region of the light reflecting layer 38 is imaged on the imaging surface of the image sensor 32, a position where the light reflected by the surface of the object P and transmitted through the first region of the light reflecting layer 38 is imaged on the imaging surface of the image sensor 32, or infinity. In this case, for example, in a state where no pressure is applied to the second region 38b of the light reflecting layer 38, the focal position of the lens 34 is adjusted to a position where the light reflected by the surface of the object P and transmitted through the first region of the light reflecting layer 38 is imaged on the imaging surface of the image sensor 32 (or infinity), and in a state where pressure is applied to the second region 38b of the light reflecting layer 38, the focal position of the lens 34 can be adjusted to a position where the light reflected by the second region of the light reflecting layer 38 is imaged on the imaging surface of the image sensor 32. As a result, when no pressure is applied to the second region 38b of the light reflecting layer 38, i.e., when the object P is not in contact with the pressure sensor 30, the object P can be imaged more clearly, and when pressure is applied to the second region 38b of the light reflecting layer 38, i.e., when the object P is in contact with the pressure sensor 30, the light reflected by the second region can be imaged more clearly. That is, the accuracy of the proximity sense and the tactile sense can be improved.

[0046] The focal position of the lens 34 can be changed by a known autofocus mechanism.

[0047] The light source 36 emits measurement light for the pressure sensor 30 to measure pressure toward the light reflecting layer 38. That is, the light source emits light of a wavelength reflected by the second region 38b of the light reflecting layer 38 toward the light reflecting layer 38. In the pressure sensor 30 shown in FIG. 1, the light source 36 is provided between the imaging element 32 and the light reflecting layer 38 at a position where the light is not imaged by the imaging element 32, and is provided so that the measurement light is incident on the light reflecting layer 38 from an oblique direction. The position of the light source 36 is not limited thereto, and it is sufficient if the light source 36 can emit the measurement light toward the light reflecting layer 38. However, it is preferable to place the light source 36 at a position that does not block the light reflected by the second region 38b of the light reflecting layer 38 from entering the imaging element 32, and it is also preferable to place the light source 36 at a position that does not block the light transmitted through the first region 38a of the light reflecting layer 38 from entering the imaging element 32.

[0048] There is no limitation on the light source 36, 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 36 include an LED (Light Emitting Diode), an LD (Laser Diode), and a fluorescent lamp.

[0049] The light source 36 may be a white light source as long as it emits light including a wavelength selectively reflected by the second region 38b of the light reflecting layer 38, or may be a light source that emits monochromatic light such as red light, blue light, and green light in a wavelength range selectively reflected by the second region 38b of the light reflecting layer 38, or may be a light source that emits light of multiple colors such as red light and green light. In addition, when the second region 38b of the light reflecting layer 38 reflects invisible light such as infrared light, the light source 36 may be a light source that emits invisible light such as infrared light.

[0050] The pressure sensor 30 shown in Fig. 1 has one light source 36, but is not limited to this. That is, the pressure sensor 30 may have multiple light sources 36. Furthermore, the light source 36 may not be a point light source, but may be a rod-shaped light source (linear light source) such as a fluorescent lamp. Furthermore, when multiple light sources 36 are included, the wavelengths emitted by the light sources 36 may be different from each other.

[0051] When a cholesteric liquid crystal layer is used as the second region 38b of the light reflecting layer 38, the light source 36 may have a circular polarizer so that circularly polarized light selectively reflected by the cholesteric liquid crystal layer is incident on the light reflecting layer 38. An example of the circular polarizer is a circular polarizer made of a linear polarizer and a quarter-wave plate (λ / 4 plate).

[0052] In addition, when the light source 36 is a point light source such as an LED or an LD, the light source 36 may have an optical member that diverges light, such as a convex lens. Alternatively, when the light source 36 is a point light source such as an LED or an LD, the light source 36 may have a mechanism for changing the direction of emitted light so that the emitted light scans the surface of the light reflecting layer 38.

[0053] The light source 36 may adjust the amount of light emitted in response to a change in state between a state where no pressure is applied to the second region 38b and a state where pressure is applied to the second region 38b, so as to change the intensity of the light emitted. For example, when no pressure is applied to the second region 38b, i.e., when the object P is not in contact with the light reflecting layer 38, the amount of light emitted by the light source 36 can be reduced so as not to interfere with the external light reflected on the surface of the object P passing through the first region 38a and being received by the image sensor 32. When pressure is applied to the second region 38b, i.e., when the object P is in contact with the light reflecting layer 38, the amount of light emitted by the light source 36 can be increased so as to suitably detect a change in the spectrum of the light reflected by the second region 38b. It is also preferable to have a mechanism for automatically adjusting the amount of light emitted by the light source 36 in conjunction with the contact detection of the object P based on a change in color of the image captured by the image sensor 32.

[0054] In the pressure sensor 30, a light reflecting layer 38 is provided facing the imaging surface of the imaging element 32. As shown in FIG. 1, the light reflecting layer 38 is disposed at a distance from the imaging element 32, and its reflection characteristics change according to pressure. The light reflecting layer 38 is disposed at a distance from the imaging element 32, meaning that the light reflecting layer 38 is not in direct contact with the imaging element 32. In this case, a substance or state that transmits the light sensed by the imaging element 32 may exist between the light reflecting layer 38 and the imaging element 32, and for example, a gas such as air, nitrogen, or argon, or a resin that transmits the light sensed by the imaging element 32 may exist, or a vacuum state may be used. It is preferable that a gas such as air exists between the light reflecting layer 38 and the imaging element 32.

[0055] FIG. 2 shows a plan view of the light reflecting layer 38, that is, a view seen from the imaging element 32 side in FIG.

[0056] As shown in FIG. 2, the light reflecting layer 38 has a configuration in which a plurality of first regions 38a and a plurality of second regions 38b are alternately arranged in one direction and in a direction perpendicular to the one direction, that is, arranged in a lattice pattern.

[0057] The first region 38a is a region that is transparent to light sensed by the imaging element 32 in both a state where no pressure is applied to the light reflecting layer 38 and a state where pressure is applied to the light reflecting layer 38. For example, when the imaging element 32 senses light with wavelengths in the visible light region, the first region 38a is transparent to light with wavelengths in the visible light region.

[0058] In the present invention, transparency means that the light transmittance for the light of the target wavelength is 30% or more, preferably 60% or more, more preferably 80% or more, and even more preferably 90% or more. The total light transmittance (transmission spectrum) for each wavelength may be determined by a conventionally known method using a spectrophotometer or the like.

[0059] The first region 38a is not limited as long as it is transparent to the light sensed by the imaging element 32 in both a state where pressure is not applied to the light reflective layer 38 and a state where pressure is applied to the light reflective layer 38, and may be made of a transparent resin material, or may be a liquid crystal layer in a non-oriented state, a cholesteric liquid crystal layer whose reflection wavelength is significantly different from the wavelength of light sensed by the imaging element 32, or a uniaxially oriented liquid crystal layer. When the first region 38a is a liquid crystal layer, there is no particular restriction, but a liquid crystal composition similar to the liquid crystal composition used in the second region 38b described later can be used.

[0060] The second region 38b is a region in which the reflected wavelength changes depending on whether pressure is applied or not to the light reflecting layer 38. In a preferred embodiment, the second region 38b has wavelength selectivity in the reflection of light, and the wavelength of light that is selectively reflected changes depending on deformation (compression and expansion) due to pressure.

[0061] In the present invention, "reflecting light of a certain wavelength" means that the light reflectance at the target wavelength is 10% or more, preferably 20% or more, and more preferably 30% or more. The total light reflectance (reflection spectrum) for each wavelength may be determined by a conventionally known method using a spectrophotometer or the like.

[0062] The second region 38b reflects light in the wavelength range emitted by the light source 36 at least in a state where pressure is applied. Furthermore, the second region 38b may reflect light in the wavelength range emitted by the light source 36 in a state where pressure is not applied, or may not reflect light in the wavelength range emitted by the light source 36. When the second region 38b reflects light in the wavelength range emitted by the light source 36 in a state where pressure is not applied, it is only necessary that the wavelength of the light reflected by the second region 38b differs between a state where pressure is applied and a state where pressure is not applied.

[0063] For example, the second region 38b may reflect light having a wavelength in the infrared region when no pressure is applied, and may reflect light having a wavelength in the visible region (e.g., red light) when pressure is applied. Alternatively, the second region 38b may reflect light having different wavelengths in the infrared region when no pressure is applied and when pressure is applied. Alternatively, the second region 38b may reflect light having different wavelengths in the visible region when no pressure is applied and when pressure is applied. For example, the second region 38b may reflect light having a wavelength in the red region when no pressure is applied and may reflect light having a wavelength in the green region when pressure is applied.

[0064] In addition, the wavelength of light reflected by the second region 38b when pressure is applied may be shorter or longer than the wavelength of light reflected by the second region 38b when pressure is not applied. When the second region 38b is made of a cholesteric liquid crystal layer as described below, the helical pitch of the helical structure of the cholesteric liquid crystal phase shortens when pressure is applied, so that the wavelength of light reflected by the second region 38b when pressure is applied becomes shorter than the wavelength of light reflected by the second region 38b when pressure is not applied.

[0065] In addition, if the second region 38b reflects light in the wavelength range emitted by the light source 36 even when no pressure is applied, the image sensor 32 only needs to sense the light of the wavelength reflected by the second region 38b when pressure is applied, and it does not have to sense the light of the wavelength reflected by the second region 38b when pressure is not applied.

[0066] The second region 38b of the light reflecting layer 38 can be of various types as long as the reflected wavelength changes according to pressure. Here, if the second region 38b of the light reflecting layer 38 can obtain a sufficient change in reflected wavelength even with a small deformation, pressure can be measured with high sensitivity. In consideration of this point, the second region 38b is preferably a light reflecting layer that uses Bragg diffraction by regularly arranged scatterers, and a light reflecting layer that uses liquid crystal, etc., in which the wavelength characteristic of reflection (reflection spectrum) changes when subjected to the above-mentioned pressure. In particular, a light reflecting layer that uses liquid crystal is preferable in consideration of both low elasticity (flexibility) that allows sufficient deformation with small pressure and regular arrangement.

[0067] A preferred example of the second region 38b (light reflecting layer) using liquid crystal and having such light reflecting properties is a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase.

[0068] A cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase has a helical structure in which the liquid crystal compounds are spirally rotated and stacked, and the liquid crystal compounds spirally rotate in one turn (360° rotation) and stacked in one helical pitch (helical pitch P), and have a structure in which the helically rotating liquid crystal compounds are stacked in multiple pitches.

[0069] As is well known, cholesteric liquid crystal phases exhibit selective reflection at specific wavelengths. In a typical cholesteric liquid crystal phase, the central wavelength of selective reflection (selective reflection central wavelength λ) depends on the helical pitch (helical pitch P) in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal phase and λ = n x P. Therefore, the selective reflection central wavelength can be adjusted by adjusting this helical pitch. The longer the helical pitch P, the longer the selective reflection central wavelength of the cholesteric liquid crystal phase becomes.

[0070] As described above, the helical pitch P is one pitch (helical period) of the helical structure of the cholesteric liquid crystal phase. In other words, the helical pitch P is one turn of the helix, that is, the length of the helical axis direction in which the director (the long axis direction in the case of rod-shaped liquid crystal) of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°.

[0071] As is well known, cholesteric liquid crystal phases exhibit selective reflection for either left-handed or right-handed circularly polarized light at a specific wavelength. Whether the reflected light is right-handed or left-handed circularly polarized light depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. When the helix of the cholesteric liquid crystal phase is twisted to the right, the cholesteric liquid crystal phase reflects right-handed circularly polarized light, and when the helix is ​​twisted to the left, the cholesteric liquid crystal phase reflects left-handed circularly polarized light.

[0072] For example, in the case of a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light, the helical twist direction of the cholesteric liquid crystal phase is right-handed. The direction of rotation of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and / or the type of chiral agent added.

[0073] Furthermore, the half-width Δλ (nm) of the selective reflection wavelength range (circularly polarized light reflection wavelength range) where the cholesteric liquid crystal phase exhibits selective reflection depends on the Δn and helical pitch P of the cholesteric liquid crystal phase, and follows the relationship Δλ = Δn × P. Therefore, the width of the selective reflection wavelength range can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compounds forming the cholesteric liquid crystal layer, as well as the temperature at which the orientation is fixed.

[0074] Therefore, when a cholesteric liquid crystal layer is used as the second region 38b of the light-reflecting layer 38, the thickness decreases depending on the pressing force applied when the object P comes into contact with it, and the helical pitch P changes accordingly, changing the wavelength range of the light that is selectively reflected.

[0075] As is well known, in a cholesteric liquid crystal layer, the wavelength of selectively reflected light becomes shorter as the angle of incidence of light with respect to the direction perpendicular to the main surface of the cholesteric liquid crystal layer (the normal direction) increases, which is called a short-wave shift (blue shift). Note that the main surface is the maximum surface of the sheet-like material, and is usually both sides in the thickness direction.

[0076] As such a cholesteric liquid crystal layer, various known cholesteric liquid crystal layers can be used as long as they have the low elasticity described above. One example is a cholesteric liquid crystal elastomer film made of a low molecular weight liquid crystal compound, which can be arbitrarily designed in response to force stimuli and can visualize color changes, as introduced in "Nanostructure Control Technology of Molecular Materials: Development into Various Optical Functional Elements (Ritsumeikan University)" in "https: / / www.jst.go.jp / tt / fair / ij2020 / exhibitor / un20200420.html" by the Japan Science and Technology Agency. In addition, a cholesteric liquid crystal film made of a hydroxypropyl cellulose (HPC) derivative, described in "New Pressure Sensing of Cellulose Derivatives with Rubber Elasticity (Furuumi Chiichi, Suzuki Hana, Fukawa Masashi, Tokyo University of Science)" on pages 33 to 38 of the Journal of the Society of Rubber Science and Technology, Vol. 91, No. 2 (2018), can also be used.

[0077] It is also preferable that celluloses are contained in the second region 38b of the light reflecting layer 38. Examples of celluloses include unsubstituted cellulose, and cellulose derivatives or hardened products thereof.

[0078] The term "unsubstituted cellulose" refers to a polymeric compound in which a large number of glucose molecules are polymerized through β-1,4-glycosidic bonds, and in which the hydroxyl groups directly or indirectly bonded to the carbon atoms at the 2nd, 3rd, and 6th positions in the glucose ring of the cellulose are unsubstituted.

[0079] Moreover, the term "cellulose derivative" refers to a cellulose in which the hydroxyl groups that are directly or indirectly bonded to the carbon atoms at the 2-, 3- and 6-positions of the glucose ring are substituted with substituents.

[0080] The cellulose derivative may be a cellulose compound having a polymerizable group (hereinafter, simply referred to as a "specific cellulose compound"). The light reflecting layer 38 may contain a hardened material of the specific cellulose compound (a hardened material formed by polymerization of the polymerizable group of the specific cellulose compound).

[0081] As the cellulose derivative, a specific cellulose compound is preferable which exhibits thermotropic cholesteric liquid crystallinity or lyotropic cholesteric liquid crystallinity, has elasticity, and can have its orientation fixed at the wavelength of Bragg reflection.

[0082] The polymerizable group in the specific cellulose compound is not particularly limited, but is preferably a polymerizable group capable of radical polymerization or cationic polymerization.

[0083] As the radical polymerizable group, a generally known radical polymerizable group can be used, and a suitable one is an acryloyloxy group or a methacryloyloxy group. In this case, it is known that the polymerization rate of the acryloyloxy group is generally fast, and from the viewpoint of improving productivity, the acryloyloxy group is preferred, but the methacryloyloxy group can also be used as the polymerizable group.

[0084] As the cationic polymerizable group, a generally known cationic polymerizable group can be used, specifically, an alicyclic ether group, a cyclic acetal group, a cyclic lactone group, a cyclic thioether group, a spiro orthoester group, and a vinyloxy group can be mentioned. Among them, an alicyclic ether group or a vinyloxy group is preferable, and an epoxy group, an oxetanyl group, or a vinyloxy group is more preferable.

[0085] The specific cellulose compound preferably has a repeating unit represented by the following formula (I).

[0086] Formula (I)

[0087] [ka]

[0088] In the above formula (I), D1, D2 and D3 each independently represent a single bond, or -CO-, -O-, -S-, -C(=S)-, -CR1R2-, -CR3=CR4-, -NR5-, or a divalent linking group consisting of a combination of two or more of these, and R1 to R5 each independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 12 carbon atoms.

[0089] In the above formula (I), SP1, SP2 and SP3 each independently represent a single bond, a linear or branched alkylene group having 1 to 12 carbon atoms, or a divalent linking group in which one or more -CH2- constituting the linear or branched alkylene group having 1 to 12 carbon atoms is replaced with -O-, -S-, -NH-, -N(Q)-, or -CO-, and Q represents a substituent.

[0090] In the above formula (I), L1, L2 and L3 each independently represent a hydrogen atom, a hydroxyl group, or a monovalent organic group, and at least one of L1, L2 and L3 represents a polymerizable group.

[0091] In the above formula (I), examples of the divalent linking group represented by one embodiment of D1, D2, and D3 include -O-CO-, -O-, -C(=S)O-, -CR1R2-, -CR1R2-CR1R2-, -O-CR1R2-, -O-CR1R2-CR1R2-O-CR1R2-CR1R2-, -CO-O-CR1R2-, -O-CO-CR1R2-, -O-CO-NR5-, -O-CO-NR5-CR1R2-CR1R2-, -CO-NR5-CR1R2-CR1R2-, -NR5-CR1R2-, and -CO-NR5-. R1, R2, and R5 each independently represent a hydrogen atom, a hydroxyl group, or an alkyl group having 1 to 12 carbon atoms.

[0092] Among these, any of -O-CO-, -O-, -C(=S)O-, -O-CR1R2-, -O-CR1R2-CR1R2-O-CR1R2-CR1R2-, -CO-O-CR1R2-, -O-CO-CR1R2-, -O-CO-NR5-, -O-CO-NR5-CR1R2-CR1R2-, -CO-NR5-CR1R2-CR1R2- and -CO-NR5- are preferred, and any of -O-CO-, -O-, -O-CO-NR5- and -O-CO-NR5-CR1R2-CR1R2- are more preferred.

[0093] In the above formula (I), examples of the linear or branched alkylene group having 1 to 12 carbon atoms represented by one embodiment of SP1, SP2, and SP3 include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a methylhexylene group, and a heptylene group.

[0094] As described above, SP1 and SP2 may be a divalent linking group in which one or more -CH2- constituting a linear or branched alkylene group having 1 to 12 carbon atoms have been replaced with -O-, -S-, -NH-, -N(Q)-, -CO-, or -O-CO-NH-, and are also preferably a divalent linking group in which one or more -CH2- constituting a linear or branched alkylene group have been replaced with -O- or -O-CO-NH-.

[0095] 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 alkylamide group. Among these, an alkyl group is preferable.

[0096] In the above formula (I), examples of the monovalent organic group represented by L1, L2, and L3 include an alkyl group, an aryl group, and a heteroaryl group.

[0097] The alkyl group may be linear, branched or cyclic, but is preferably linear. The alkyl group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0098] The aryl group may be either monocyclic or polycyclic, but is preferably monocyclic. The aryl group preferably has 6 to 25 carbon atoms, and more preferably has 6 to 10 carbon atoms.

[0099] The heteroaryl group may be a monocyclic or polycyclic ring. The number of heteroatoms constituting the heteroaryl group is preferably 1 to 3. The heteroatoms constituting the heteroaryl group are preferably nitrogen atoms, sulfur atoms, or oxygen atoms. The number of carbon atoms in the heteroaryl group is preferably 6 to 18, and more preferably 6 to 12.

[0100] The alkyl group, aryl group and heteroaryl group may be unsubstituted or may have a substituent.

[0101] In the above formula (I), the polymerizable group represented by at least one of L1, L2 and L3 is not particularly limited, and is preferably a polymerizable group capable of radical polymerization or cationic polymerization.

[0102] As the radical polymerizable group, a generally known radical polymerizable group can be used, and a suitable one is an acryloyloxy group or a methacryloyloxy group.In this case, it is known that the polymerization rate of the acryloyloxy group is generally fast, and from the viewpoint of improving productivity, the acryloyloxy group is preferred, but the methacryloyloxy group can also be used as the polymerizable group.

[0103] As the cationic polymerizable group, a generally known cationic polymerizable group can be used, specifically, an alicyclic ether group, a cyclic acetal group, a cyclic lactone group, a cyclic thioether group, a spiro orthoester group, and a vinyloxy group can be mentioned. Among them, an alicyclic ether group or a vinyloxy group is preferable, and an epoxy group, an oxetanyl group, or a vinyloxy group is more preferable.

[0104] Particularly preferred examples of the polymerizable group include the polymerizable groups represented by any of the following formulas (P-1) to (P-20).

[0105] [ka]

[0106] It is also preferable that the specific cellulose compound has a repeating unit represented by the following formula (II).

[0107] Formula (II)

[0108] [ka]

[0109] In the above formula (II), R1, R2 and R3 each independently represent a hydroxyl group, -O-R4, -(O-CH2-CH(CH3)) m R5 or a polymerizable group. R4 represents a hydrogen atom, -CO-R6, or -CO-NH-R7. R5 represents a hydroxyl group, -OCO-R8, -OCO-NH-R9, or a polymerizable group. R6, R7, R8, and R9 each independently represent an alkyl group or an aryl group which may have a polymerizable group as a substituent, and at least one of R1, R2, and R3 has a polymerizable group. In addition, m represents an integer of 1 to 10.

[0110] Specific examples of the specific cellulose compound include compounds represented by the following formula (III). Specifically, D1, D2 and D3, SP1, SP2 and SP3, and L1, L2 and L3 in the following formula (1) each include compounds having the side chain structures shown in Table 1 below.

[0111] Formula (III)

[0112] [ka]

[0113] [Table 1]

[0114] The cellulose preferably contains a hardened product of a cellulose compound having a polymerizable group and an unsubstituted cellulose compound in terms of controlling flexibility, liquid crystallinity, stability, and the like.

[0115] The molecular weight of the 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, further preferably in the range of 20,000 to 200,000, and particularly preferably in the range of 30,000 to 100,000.

[0116] 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, further preferably in the range of 20,000 to 1,500,000, and particularly preferably in the range of 30,000 to 500,000.

[0117] 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, and even more preferably in the range of 1.3 to 3.0.

[0118] By setting the average molecular weight within this range, it is possible to further improve the moldability of the molded product, etc. Also, by setting the molecular weight distribution within this range, it is possible to further improve the moldability, etc.

[0119] In the present invention, the number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (MWD) can be measured by gel permeation chromatography (GPC). Specifically, they can be determined by using tetrahydrofuran as a solvent, polystyrene gel and a converted molecular weight calibration curve previously obtained from the constituent curve of standard monodisperse polystyrene.

[0120] Even when the second region 38b contains the above-mentioned cellulose, it is preferable that a cholesteric liquid crystal layer is formed.

[0121] From the viewpoint of controlling the wavelength region of reflection, it is preferable that the cellulose exhibits thermotropic liquid crystallinity. When the cellulose exhibits thermotropic liquid crystallinity, it is easy to control the temperature during curing.

[0122] There is no limitation on the thickness of the light reflecting layer 38 (second region 38b), and the film thickness that provides the required light reflecting characteristics and the required low elasticity, i.e., the required amount of film thickness variation, can be set appropriately depending on the material that forms the second region 38b, etc.

[0123] Here, in terms of increasing the reflectance of the measurement light, it is preferable that the second region 38b is thicker. On the other hand, the thicker the second region 38b, the more disadvantageous it is in terms of deformation against pressure and the thickness of the pressure sensor 30. In consideration of this, the thickness of the second region 38b is preferably 0.1 to 500 μm, and more preferably 1 to 100 μm.

[0124] There is no particular limitation on the area ratio between the first region 38a and the second region 38b in the light reflecting layer 38. To achieve both pressure detection using reflected light in the second region 38b, i.e., tactile sensation, and proximity change detection by transmitted light through the first region 38a, i.e., proximity sense, the area of ​​the first region:the area of ​​the second region is preferably 90:10 to 10:90.

[0125] 2, when the first regions 38a and the second regions 38b are arranged in a lattice pattern, the size of each of the first regions 38a and each of the second regions 38b is not particularly limited as long as it is possible to detect pressure (tactile sensation) using reflected light from the second region 38b and to detect proximity changes (proximity sensation) using transmitted light from the first region 38a. The area of ​​each of the first regions 38a and each of the second regions 38b is 100 to 1,000,000 μm 2 It is preferable that the thickness is 2,500 to 250,000 μm. 2 More preferably, the thickness is 10,000 to 90,000 μm. 2 It is even more preferable that:

[0126] The light reflecting layer 38 (second region 38b) has low elasticity such that its thickness changes due to the pressure applied when the object P comes into contact with it. Specifically, the light reflecting layer 38 (second region 38b) has a low elasticity of about 0.05 to 10 MPa, preferably 0.05 to 1 MPa. In the pressure sensor of the present invention, the physical properties of the light reflecting layer 38 (second region 38b) can be appropriately selected outside the above range depending on the pressure measurement target and the configuration of the pressure measurement device. In addition, depending on the size, shape, etc. of the second region 38b and the first region 38a, it is preferable that the first region 38a also has low elasticity from the viewpoint of suppressing the inhibition of the deformation of the second region 38b, and the Young's modulus is preferably 0.05 to 10 MPa, more preferably 0.05 to 1 MPa. Therefore, it is preferable that the light reflecting layer 38 also has low elasticity, and the Young's modulus is preferably 0.05 to 10 MPa, and more preferably 0.05 to 1 MPa.

[0127] <Method of producing light reflective layer> There is no particular limitation on the method for producing the light reflecting layer 38 having the first region 38a and the second region 38b.

[0128] When the first region 38a is a liquid crystal layer, for example, a coating film is formed using a liquid crystal composition containing a liquid crystal compound having a polymerizable group and a chiral agent, and exposed through a photomask having light-transmitting and light-shielding parts corresponding to the arrangement pattern of the first region 38a and the second region 38b of the light-reflecting layer 38, and the state of the liquid crystal compound in the exposed region (region corresponding to the light-transmitting portion) is fixed. At this stage, the liquid crystal compound is not oriented, so the region corresponding to the light-transmitting portion is fixed in a non-oriented state. On the other hand, the region corresponding to the light-shielding portion is not exposed, so the liquid crystal compound remains unfixed. Next, a heat treatment (alignment treatment) is performed to align the liquid crystal compound in the region corresponding to the light-shielding portion into a cholesteric liquid crystal phase, and then at least this region is exposed to light to fix it in the cholesteric liquid crystal phase state. As a result, the area fixed in the non-distributed light state becomes a first area 38a that is transparent to the light sensed by the imaging element 32 in both the unpressurized and pressurized states, and the area fixed in the cholesteric liquid crystal phase state becomes a second area 38b whose reflected wavelength changes in both the unpressurized and pressurized states.

[0129] Next, an example will be described in which the first region 38a is a liquid crystal layer, and is a cholesteric liquid crystal layer that reflects light of a wavelength different from that sensed by the imaging element 32. In the following example, a chiral agent that has a higher helical twisting power (HTP) at a lower temperature is used. First, as an example, a coating film is formed using a liquid crystal composition containing a liquid crystal compound having a polymerizable group and a chiral agent, and exposed to a high temperature through a photomask having light-transmitting and light-shielding parts corresponding to the arrangement pattern of the first region 38a and the second region 38b of the light-reflecting layer 38, and the state of the liquid crystal compound in the exposed region (the region corresponding to the light-transmitting part) is fixed. As a result, the exposed region (the region corresponding to the light-transmitting part) becomes a cholesteric liquid crystal layer having a selective reflection wavelength in, for example, the infrared region. In addition, the region corresponding to the light-shielding part is not exposed, so the liquid crystal compound remains unfixed.

[0130] Next, the film is cooled to room temperature and exposed from the side opposite to the photomask to fix the state of the liquid crystal compound in the area corresponding to the light-shielding portion that was not fixed by the previous exposure. As a result, the liquid crystal compound in the area corresponding to the light-shielding portion becomes a cholesteric liquid crystal layer having a selective reflection wavelength in, for example, a green region. That is, a cholesteric liquid crystal layer having a shorter selective reflection wavelength than the area corresponding to the light-transmitting portion is formed.

[0131] As a result, the region made of the cholesteric liquid crystal layer having a selective reflection wavelength in the infrared region becomes a first region 38a that is transparent to the light sensed by the image sensor 32 in both the unstressed and stressed states, and the region made of the cholesteric liquid crystal layer having a selective reflection wavelength in the green region becomes a second region 38b whose reflection wavelength changes between the unstressed and stressed states.

[0132] As a photomask having light transmitting portions and light blocking portions corresponding to the arrangement pattern of the first regions 38a and second regions 38b of the light reflecting layer 38, a patterned black layer, which will be described later, may be used.

[0133] Furthermore, when the first region 38a is made of a transparent resin material, a plurality of recesses or through-holes may be provided in the resin substrate, a liquid crystal composition may be applied to the recesses or through-holes, and an alignment process and a curing process may be performed to form a cholesteric liquid crystal layer in the plurality of recesses or through-holes.

[0134] The application, alignment and curing of the liquid crystal composition can be performed in the same manner as in the conventional method for forming a cholesteric liquid crystal layer. The processing conditions can be appropriately set according to the type of liquid crystal material and the type of chiral agent used, so that a desired cholesteric liquid crystal layer can be formed.

[0135] Here, when forming the cholesteric liquid crystal layer, an alignment film for aligning the liquid crystal compound is usually formed on the surface of a support such as a resin film, and the cholesteric liquid crystal layer is formed on the surface of this alignment film. Therefore, when the second region 38b is a cholesteric liquid crystal layer and the first region 38a is a liquid crystal layer, the cholesteric liquid crystal layer may be peeled off from the alignment film before use. Alternatively, when the second region 38b is a cholesteric liquid crystal layer and the first region 38a is a liquid crystal layer, the pressure sensor 30 may have the cholesteric liquid crystal layer and the liquid crystal layer layer peeled off from the support, and an alignment film. Alternatively, when the second region 38b is a cholesteric liquid crystal layer and the first region 38a is a liquid crystal layer, the pressure sensor 30 may have the cholesteric liquid crystal layer and the liquid crystal layer layer, an alignment film, and a support.

[0136] When the pressure sensor 30 has an alignment film or a support in addition to the cholesteric liquid crystal layer and the liquid crystal layer as the light reflecting layer 38, the laminate including the cholesteric liquid crystal layer may be disposed so that the layer including the cholesteric liquid crystal layer faces the imaging element 32, or the alignment film and the support may be on the imaging element 32 side. When the alignment film and the support are on the imaging element 32 side, the optical properties such as the transmittance of the alignment film and the support must be appropriately adjusted so as not to prevent all reflected light from entering the imaging element 32. In addition, when the layer including the cholesteric liquid crystal layer faces the imaging element 32, the support can be selected so that the support also serves as the patterned black layer 40 described later, for example.

[0137] Furthermore, when a cholesteric liquid crystal layer is used as the second region 38b, the second region 38b may have two cholesteric liquid crystal layers having the same selective reflection center wavelength and opposite rotation directions of the circularly polarized light that is selectively reflected.

[0138] The second region 38b, in which the wavelength of light selectively reflected changes according to deformation (compression and expansion) caused by pressure, is not limited to an organic cholesteric liquid crystal layer, and various known layers having the above-mentioned low elasticity can be used. One example is the inorganic nanosheet structural color gel (Fukuoka Institute of Technology) made of inorganic nanosheet liquid crystals obtained by exfoliating and dispersing inorganic layered compounds including smectite clay minerals, layered potassium hexaniobate, layered perovskite, and graphite, which is introduced in "https: / / prtimes.jp / main / html / rd / p / 000000012.000047155.html".

[0139] The second region 38b of the light reflecting layer 38 may be made of a wet gel. The wet gel means a solid component having fluidity, and preferably contains a liquid component. In other words, the second region 38b may contain a liquid component.

[0140] When the second region 38b is made of a wet gel, it is possible to achieve a good balance between liquid crystallinity and flexibility that responds to slight pressure.

[0141] The liquid component is not particularly limited, and may be a liquid component in which the material contained therein (particularly, the liquid crystal material) is well dissolved or dispersed. As the liquid component, it is preferable that the component contained in the second region 38b is a liquid component that easily exhibits liquid crystallinity. For example, when the second region 38b contains cellulose, water or an organic solvent is preferably selected as the liquid component.

[0142] In addition, when the second region 38b contains a liquid component, it is preferable to have a mechanism for preventing the liquid component from volatilizing in order to ensure stability. In other words, it is preferable that the light reflecting layer is sealed with a sealant. For example, it is preferable that a sealant or base material that inhibits the volatilization of the liquid component is provided on the top, bottom, and side surfaces of the second region 38b.

[0143] It is desirable to select a material with low moisture permeability as the sealing material or substrate 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.

[0144] In addition, as materials constituting the sealing material or the base material, polyolefin (PO) resins such as homopolymers or copolymers of ethylene, polypropylene, and butene, etc.; amorphous polyolefin resins (APO) such as cyclic polyolefins; polyester resins such as polyethylene terephthalate (PET) and polyethylene 2,6-naphthalate (PEN); polyamide (PA) resins such as nylon 6, nylon 12, and copolymer nylon; polyvinyl alcohol resins such as polyvinyl alcohol (PVA) resin and ethylene-vinyl alcohol copolymer (EVOH); polyimide (PI) resins; polyetherimide (PEI) resins; polysulfone (PS) resins; polyethersulfone (PES) resins; polyetheretherketone (PEEK) resins; polycarbonate (PC) resins; polyvinyl butyrate (PVB) resin; polyarylate (PAR) resin; fluorine-based resins such as ethylene-tetrafluoroethylene copolymer (ETFE), trifluorochloroethylene (PFA), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (FEP), vinylidene fluoride (PVDF), vinyl fluoride (PVF) and perfluoroethylene-perfluoropropylene-perfluorovinyl ether copolymer (EPA); resin compositions made of acrylate compounds having radical reactive unsaturated compounds; resin compositions made of the above acrylate compounds and mercapto compounds having thiol groups; photocurable resins such as resin compositions in which oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate and polyether acrylate are dissolved in polyfunctional acrylate monomers. Furthermore, it is also possible to use as the resin substrate a substrate in which one or more of these materials are laminated by means of lamination, coating, etc. Furthermore, a substrate made of the above-mentioned material and coated with the above-mentioned inorganic thin film and organic thin film can also be used.

[0145] The pressure sensor 30 has a patterned black layer 40 as a light-shielding layer on the surface of the light reflecting layer 38 opposite the imaging element 32. In the present invention, the patterned black layer 40 is provided as a preferred embodiment, but is not an essential component.

[0146] FIG. 3 shows a plan view of the patterned black layer 40, that is, a view seen from the imaging element 32 side in FIG.

[0147] 3, the patterned black layer 40 has a configuration in which a plurality of transmissive portions 40a and a plurality of black portions 40b are alternately arranged in one direction and in a direction perpendicular to the one direction, that is, arranged in a lattice pattern. When viewed from a direction perpendicular to the main surface of the patterned black layer 40, the plurality of transmissive portions 40a have substantially the same shape and size as the first region 38a of the light reflecting layer 38, and are arranged at positions overlapping the first region 38a of the light reflecting layer 38. The plurality of black portions 40b have substantially the same shape and size as the second region 38b of the light reflecting layer 38, and are arranged at positions overlapping the second region 38b of the light reflecting layer 38.

[0148] The transmissive portion 40a is a region that is transparent to light sensed by the imaging element 32. For example, when the imaging element 32 senses light with wavelengths in the visible light region, the transmissive portion 40a is transparent to light with wavelengths in the visible light region.

[0149] The black portion 40b is a region that blocks light sensed by the imaging element 32. For example, when the imaging element 32 senses light with wavelengths in the visible light region, the transmissive portion 40a blocks light with wavelengths in the visible light region.

[0150] In applications where the pressure sensor 30 is used for tactile sensing, such as robot applications, the pressure sensor 30 is used with the patterned black layer 40 facing the object side that is in contact. In the pressure sensor 30, ambient light (external ambient light) from the surroundings and measurement light from the light source 36 that is unnecessarily incident on the object being held may be reflected by the surface of the object and enter the inside of the pressure sensor 30 from the second region 38b of the light reflecting layer 38. If such unwanted light enters the pressure sensor 30 and is measured by the image sensor 32, it becomes noise, which is undesirable as it causes an error in the pressure measurement.

[0151] The patterned black layer 40 is a layer for preventing such unwanted light from entering the inside of the pressure sensor 30 from the second region 38b of the light reflecting layer 38.

[0152] The pressure sensor 30 has a black portion 40b on the surface of the second region 38b of the light reflecting layer 38 opposite the imaging element 32, thereby suppressing unwanted light from passing through the second region 38b and entering the pressure sensor 30, thereby preventing the unwanted light from being sensed by the imaging element 32. This makes it easier for the imaging element 32 to detect changes in the wavelength of light reflected by the second region 38b.

[0153] The black portion 40b of the pattern black layer 40 is not limited, and various layers can be used as long as they can absorb unnecessary light and prevent it from entering the inside of the pressure sensor 30 from the surface of the light reflecting layer 38 opposite to the imaging element 32. As the black portion 40b, various known layers can be used as long as they absorb specific light according to the purpose. Specific examples of the black portion 40b include a black layer using a black material such as carbon black, black paint, and black dye, a light absorbing layer using an organic substance such as an organic pigment that absorbs in the visible range, an inorganic substance such as a metal oxide that absorbs in the visible range, an organic substance that absorbs in the ultraviolet or infrared range, and an inorganic substance that absorbs in the ultraviolet or infrared range. Alternatively, as the black portion 40b, a 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.

[0154] There is no limitation on the thickness of the black portion 40b of the patterned black layer 40, and the thickness may be appropriately set to a value that can prevent unwanted light from entering the inside of the pressure sensor 30 depending on the material that the black portion 40b is made of.

[0155] There is no limitation on the method for forming the patterned black layer 40. As an example, the black portion 40b can be formed by applying a black paint in a pattern on one surface of a transparent resin base material.

[0156] In the pressure sensor 30, the imaging element 32, the light reflecting layer 38, and the patterned black layer 40 are preferably sheet-shaped (plate-shaped, film-shaped, layer-shaped) members, but may be curved or have a three-dimensional shape depending on the application. The imaging element 32, the light reflecting layer 38, and the patterned black layer 40 may have the same size and / or different shape. Furthermore, the imaging element 32, the lens 34, the light reflecting layer 38, and the patterned black layer 40 may be arranged on the same axis or may be arranged offset from each other.

[0157] Although not shown, the imaging element 32 is connected to an image processing device such as a computer. The image processing device stores the relationship between the pressure applied to the second region 38b of the light reflecting layer 38 and the characteristics of the reflected light described above. The image processing device processes and analyzes the image of the light reflecting layer 38 (second region 38b) captured by the imaging element 32, detects the pressure applied to each location of the light reflecting layer 38 (second region 38b), and outputs the pressure distribution applied to the light reflecting layer 38 (second region 38b) by, for example, image display.

[0158] The operation of the pressure sensor 30 of the present invention will now be described.

[0159] As described above, the pressure sensor 30 is used, for example, for tactile sensing in robotic applications. As an example, as shown in FIG. 4, the pressure sensor 30 is attached to the tip of an arm member 48 of a robot arm 46 and used as a tactile sensor and proximity sensor for the robot arm 46.

[0160] As shown in FIG. 4, as an example, in robot applications, the pressure sensor 30 is provided at the tip of at least one of two arm members 48 of a robot arm 46, and is suitably used as a tactile sensor that measures the pressure and pressure distribution applied to the robot arm 46, i.e., object P, when the robot arm 46 grasps or grabs the object P, and as a proximity sensor that detects an object P present in the vicinity.

[0161] In the example shown in FIG. 4, the pressure sensor 30 is attached to the tip of both arm members 48, but this is not limited to this, and the pressure sensor 30 may be attached to the tip of one arm member 48 and no pressure sensor 30 may be attached to the tip of the other arm member 48.

[0162] Furthermore, the shape of the arm member and the mounting position of the pressure sensor are not limited to the shape shown in Fig. 4. In other words, when the pressure sensor of the present invention is used in a robot arm, arms of various shapes can be used, and the sensor can be used appropriately in any location on the arm where it is desired to detect touch and proximity.

[0163] The pressure sensor of the present invention is not limited to being mounted on an arm-type robot as shown in Fig. 4, but can also be used in, for example, a hand-type robot imitating a number of fingers. Furthermore, the pressure sensor of the present invention can be mounted not only on the tips of the arms and hands, but also on various parts (surfaces) of the robot that come into contact with the object P.

[0164] Moreover, the pressure sensor 30 is, for example, connected to an image processing device such as a computer.

[0165] When tactile sensing and proximity sensing of the robot arm 46 are performed by the pressure sensor 30, first, the light source 36 is turned on to allow measurement light to be incident on the light reflecting layer 38. The light source 36 may be turned on under the control of an image processing device to which the pressure sensor 30 is connected, or may be turned on by providing a switch on the housing 42 of the pressure sensor 30. As described above, the amount of light from the light source 36 may be adjusted in response to the detection of pressure by the pressure sensor 30 (contact detection of the object P).

[0166] When the robot arm equipped with the pressure sensor 30 starts to grasp an object, but the pressure sensor 30 is not in contact with the object P, the ambient light reflected from the surface of the object P passes through the transmissive portion 40a of the patterned black layer 40 and the first region 38a of the light reflecting layer 38, and enters the inside of the pressure sensor 30 (housing 42), as shown in Figures 5 and 6. This light is collected and imaged by the lens 34, and enters the imaging element 32.

[0167] On the other hand, in the first region 38a of the light reflecting layer 38, the measurement light emitted by the light source 36 passes through the first region 38a and the transmissive portion 40a of the patterned black layer 40 and is emitted to the outside of the pressure sensor 30. In the second region 38b of the light reflecting layer 38, the measurement light is reflected by the second region 38b, and is collected and imaged by the lens 34 and enters the imaging element 32. Alternatively, the measurement light is not reflected by the second region 38b and is absorbed by the black portion 40b of the patterned black layer 40.

[0168] Therefore, as shown in FIG. 6, the imaging element 32 captures an image of an object P present in the vicinity of the pressure sensor 30 in the area corresponding to the first area 38a, and captures an image of the color of the wavelength reflected by the second area 38b, or a black image, in the area corresponding to the second area 38b.

[0169] The image captured by the imaging element 32 is output to an image processing device and processed. The relationship between the pressure applied to the second region 38b and the image (color (wavelength)) captured by the imaging element 32 is known in advance and stored, for example, in the image processing device, so that information on whether pressure is applied to the light reflecting layer 38, that is, information on whether the object P is in contact with the pressure sensor 30, can be obtained from the region of the captured image corresponding to the second region 38b. In the case of FIG. 6, an image of a color reflected when no pressure is applied to the second region 38b or a black image is obtained in the region corresponding to the second region 38b, so that it can be seen from the image that the object P is not in contact with the pressure sensor 30.

[0170] Moreover, information on the object P can be obtained from a region corresponding to the first region 38a in the image captured by the imaging element 32. Specifically, for example, information such as the size, shape, and color of the object P, and the positional relationship between the object P and the pressure sensor 30 in an in-plane direction (a direction parallel to the main surface of the light reflecting layer 38) can be obtained. Furthermore, if information on the actual size of the object P is known in advance, information on the distance between the object P and the pressure sensor 30 can also be calculated from information on the actual size of the object P and the size of the captured object P.

[0171] Furthermore, while the robot arm is operating, the imaging element 32 continuously captures such images (i.e., captures a video), and, for example, when an object P is approaching the pressure sensor 30 as shown by the arrow in Figure 5, information such as whether or not the object P is approaching can be obtained from the change in size of the object P.

[0172] In this way, since the pressure sensor 30 has a first region 38a in which the light reflective layer 38 is transparent to the light sensed by the imaging element 32, the pressure sensor 30 acts as a proximity sensor that detects an object P at a close distance.

[0173] By providing the pressure sensor 30 with a proximity sensing function, for example, it is possible to fine-tune the position of the robot arm so that the robot arm grasps the object P at an appropriate position based on information on the positional relationship in the in-plane direction between the object P and the pressure sensor 30. Alternatively, for example, based on information on the distance between the object P and the pressure sensor 30, it is possible to slow down the movement of the robot arm just before the robot arm grasps the object P.

[0174] Next, when the robot arm equipped with the pressure sensor 30 grasps an object, that is, when the pressure sensor 30 comes into contact with the object P as shown by the arrow in Figure 7, the second region 38b of the light reflecting layer 38 is pressed by the object P and is deformed (compressed) by this pressure, since the second region 38b of the light reflecting layer 38 is a low-elasticity layer whose thickness changes when it is pressed by the object P.

[0175] 7 and 8, the measurement light emitted by the light source 36 is reflected in the second region 38b of the light reflecting layer 38 in the region (indicated by dots in FIG. 8) in which the second region 38b is in contact with the object P and pressure is applied, and in the region of the second region 38b not in contact with the object P and not pressure is applied, the measurement light is reflected in the other wavelengths. Alternatively, in the region of the second region 38b in which the second region 38b is in contact with the object P and pressure is applied, the measurement light is reflected in at least some wavelengths, and in the region of the second region 38b not in contact with the object P and not pressure is applied, the measurement light is not reflected. The light reflected by the second region 38b is collected and imaged by the lens 34 and enters the imaging element 32.

[0176] Furthermore, in the first region 38 a of the light reflecting layer 38 , the measurement light emitted by the light source 36 passes through the first region 38 a and the transmitting portion 40 a of the patterned black layer 40 , and is emitted to the outside of the pressure sensor 30 .

[0177] On the other hand, the ambient light reflected from the surface of the object P passes through the transmissive portion 40a of the patterned black layer 40 and the first region 38a of the light reflecting layer 38, and enters the inside of the pressure sensor 30 (housing 42). This light is collected and imaged by the lens 34 and enters the imaging element 32.

[0178] Therefore, as shown in FIG. 8, the imaging element 32 captures an image of an object P present in the vicinity of the pressure sensor 30 in the area corresponding to the first area 38a, and captures an image of the color of the wavelength reflected by the second area 38b, or a black image, in the area corresponding to the second area 38b.

[0179] The image captured by the imaging element 32 is output to an image processing device and processed. The relationship between the pressure applied to the second region 38b and the image (color (wavelength)) captured by the imaging element 32 is known in advance and stored, for example, in the image processing device, so that information on whether or not pressure is being applied to the light reflecting layer 38 from the region of the captured image corresponding to the second region 38b, i.e., information on whether or not the object P is in contact with the pressure sensor 30, can be obtained.

[0180] In the case of Fig. 8, in a part of the region corresponding to the second region 38b (region indicated by dots), an image of the color reflected when pressure is applied to the second region 38b is obtained, and in the remaining region corresponding to the second region 38b, an image of the color reflected when pressure is not applied to the second region 38b (or black) is obtained. That is, in the region corresponding to the second region 38b, an image of a different color is obtained between the region where pressure is applied and the region where pressure is not applied. Therefore, it is possible to know from the image that the object P is in contact with the pressure sensor 30 and at what position on the pressure sensor 30 (light reflecting layer 38) the object P is in contact.

[0181] In this way, the pressure sensor 30 functions as a tactile sensor that detects contact with an object P because the light reflective layer 38 has a second region in which the reflected wavelength changes between the no pressure state and the pressure state.

[0182] The pressure sensor 30 having a tactile function can, for example, determine whether or not the robot arm has grasped the object P. Also, it can determine at what position the robot arm is grasping the object P.

[0183] In addition, the pressure applied to the second region 38b of the light reflecting layer 38 varies depending on the shape of the object, etc. For example, in the example shown in Fig. 7, the pressure applied to the second region 38b is the largest at the top point of the object P, and the pressure is smaller at the edge of the region in contact with the object P.

[0184] In the present invention, the reflection characteristics of the second region 38b of the light reflecting layer 38 change in response to pressure. Preferably, the second region 38b of 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.

[0185] Therefore, for example, when the second region 38b of the light reflecting layer 38 is a cholesteric liquid crystal layer, the helical pitch of the cholesteric liquid crystal phase changes and the incident angle of the measurement light with respect to the helical axis also changes due to the change in thickness caused by pressing the object P. As a result, the wavelength of the measurement light selectively reflected by the second region 38b of the light reflecting layer 38, i.e., the wavelength of the reflected light (reflection spectrum), changes depending on the change in thickness caused by pressing the object P and the incident angle of the measurement light.

[0186] Therefore, for example, when the measurement light is white light and the image sensor 32 is a color sensor, the color and density of the image captured by the image sensor 32 will change partially depending on the location that is pressed and the strength of the pressure at each location.

[0187] In addition, when the measurement light is white light or monochromatic light such as red light and green light, and the imaging element 32 is a black and white monochrome sensor (brightness sensor) or a sensor corresponding to monochromatic light, the density (brightness) of the image captured by the imaging element 32 changes partially depending on the places pressed and the strength of the pressure at each place.

[0188] 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 density (brightness) of the image captured by the image sensor 32 changes partially depending on the location that is pressed and the strength of the pressure at each location. In this case, the color of the image captured by the image sensor 32 also changes partially and slightly depending on the relationship between the wavelength range of the measurement light and the wavelength range of the light selectively reflected by the second region 38b of the light reflecting layer 38.

[0189] Here, the state of pressing the second region 38b of the light reflecting layer 38 by the object P, i.e., the state of deformation of the light reflecting layer 38 by the object, differs depending on the applied pressure. As described above, the pressure applied to the second region 38b of the light reflecting layer 38 differs partially depending on the shape of the object P, etc. Therefore, the color of the image captured by the imaging element 32 also changes depending on the shape of the object P to be grasped and the gripping force of the object by the robot arm, etc.

[0190] Therefore, if the relationship between the pressure of the contacting object P and the image (color) captured by the image capture element 32 is known in advance and stored in, for example, an image processing device, it is possible to measure the pressure (pressure distribution) applied to each position of the robot arm 46 (arm member 48) gripping the object P, i.e., the pressure applied to each position of the object P, by matching the color (wavelength) of the area corresponding to the second area 38b of the captured image with the color, i.e., wavelength, corresponding to the pre-stored pressure. Note that image matching may be performed by a known method. The measurement result is displayed, for example, on a display connected to the image processing device.

[0191] In this way, the pressure sensor 30 of the present invention can measure, for example, the pressure (pressure distribution) acting on each position of a robot arm gripping an object P, i.e., perform tactile sensing on the robot arm, by simply knowing in advance the relationship between the pressure caused by the contacting object P and the image captured by the imaging element 32 and storing it, for example, in an image processing device, without performing complex calculations, etc.

[0192] Moreover, the imaging element 32 can usually capture moving images. Therefore, the pressure sensor 30 of the present invention can continuously measure the pressure applied to the robot arm 46 gripping the object P, and can continuously measure the pressure and the fluctuations in pressure distribution, for example, even when the gripping force and the orientation of the object P are changed by manipulating the robot arm 46.

[0193] In addition, in the pressure sensor 30 of the present invention, the image captured by the imaging element 32 can detect not only a change in image density (brightness) according to pressure, but also a change in color (wavelength) according to pressure. In addition, preferably, a space is provided between the light reflecting layer 38 and the imaging element 32, and a lens 34 is disposed between them, so that an image of the second region 38b of the light reflecting layer 38 can be properly formed on the imaging element 32. Therefore, according to the pressure sensor 30 of the present invention, more detailed changes in the captured image can be captured and detected with high image quality, and as a result, pressure distribution can be measured with higher accuracy and higher resolution.

[0194] Due to the advantages of the present invention, particularly in that the captured image can change in color in addition to density according to pressure, enabling measurements with higher accuracy and resolution, it is preferable that the light source 36 in the pressure sensor 30 be a white light source and that the image capture element 32 be a color sensor.

[0195] In measuring pressure using the pressure sensor 30 of the present invention, the light source 36 may emit measurement light continuously or may emit pulsed light.

[0196] Here, in the example shown in Fig. 1 and Fig. 2, the light reflecting layer 38 has a configuration in which the first region 38a and the second region 38b are arranged in a lattice shape, but is not limited to this. For example, the light reflecting layer may have a configuration in which the second regions are arranged discretely, and the first region is arranged between the discretely arranged second regions, or may have a configuration in which the first region is arranged discretely, and the second region is arranged between the discretely arranged first regions. Note that the discrete arrangement of the second regions means that the second regions are arranged in the in-plane direction without contacting each other.

[0197] FIG. 9 is a plan view conceptually showing another example of the light reflecting layer of the pressure sensor of the present invention.

[0198] The light reflecting layer 39 shown in Fig. 9 has a configuration in which the second regions 39b are arranged discretely, and the first regions 39a are arranged between the discretely arranged second regions 39b. Specifically, in a plan view, the light reflecting layer 39 has a plurality of substantially circular second regions 39b arranged at predetermined intervals in one direction and in a direction perpendicular to the one direction. The first regions 39a are filled in the regions between the arranged second regions 39b.

[0199] The first region 39a and the second region 39b are similar to the above-described first region 38a and second region 38b, except that their arrangement and shape are different.

[0200] In FIG. 9, the shape of one second region 39b in a planar view is approximately circular, but this is not limited to this and may be various shapes such as polygonal shapes such as a triangle, a rectangle, a hexagon, or an octagon, an ellipse, or an irregular shape.

[0201] In addition, in FIG. 9, the second regions 39b are arranged at predetermined intervals in one direction and in a direction perpendicular to the one direction, but the present invention is not limited to this. The second regions 39b may be arranged in any manner as long as the tactile function and the proximity function can be appropriately exerted. For example, the arrangement of the second regions 39b may be a staggered arrangement or a random arrangement. The distance between adjacent second regions 39b may be constant or may vary depending on the position.

[0202] The area of ​​one second region 38b is 100 to 1,000,000 μm 2 It is preferable that the thickness is 2,500 to 250,000 μm. 2 More preferably, the thickness is 10,000 to 90,000 μm. 2 It is even more preferable that:

[0203] Furthermore, the distance between adjacent second regions 38b is preferably 0.01 mm to 20 mm, more preferably 0.1 mm to 10 mm, and even more preferably 0.5 mm to 5 mm.

[0204] In addition, in the case of a configuration having a plurality of first regions, the plurality of first regions being discretely arranged, and a second region being arranged between the plurality of discretely arranged first regions, the first region in the description of Figure 9 above can be read as the second region, and the second region can be read as the first region.

[0205] 9, a light reflecting layer 39 having a configuration in which a plurality of second regions 39b are discretely arranged and a first region 39a is arranged between the discretely arranged second regions 39b can detect a stress applied in the in-plane direction (hereinafter also referred to as shear stress) by detecting a change in the position of the second region 39b in the in-plane direction. In the following description, detecting a stress applied in the in-plane direction is also referred to as shear detection.

[0206] This point will be described with reference to Figures 10 to 13. Note that Figures 10 and 12 only show pressure sensor 30 attached to the tip of the arm portion of the robot arm.

[0207] When the robot arm 46 as shown in Fig. 4 grasps the object P in a horizontal direction (see the arrows in Fig. 10), gravity acts in the vertical direction (downward in Fig. 10) on the object P. In this case, if the gripping force of the robot arm 46 is sufficiently large, the object P does not move in the in-plane direction of the light reflecting layer 39, i.e., downward in Fig. 10, as shown in Fig. 10.

[0208] As described above, the light reflecting layer 39 (second region 39b) is a low elastic member that is deformed by the applied pressure, and therefore can be deformed by the applied pressure (stress) even in the in-plane direction.

[0209] Therefore, in the example shown in Fig. 10, the light reflecting layer 39 is deformed by the pressure of the object P, and as shown in Fig. 11, the second regions 39b (39b-1 to 39b-4) at the position where the object P contacts move in the in-plane direction as shown by the arrows from the positions shown by the dashed circles in Fig. 11. The dashed circles in Fig. 11 indicate the positions of the second regions 39b (39b-1 to 39b-4) when no pressure is applied to the light reflecting layer 39. For example, in the examples shown in Figs. 10 and 11, since the object P is spherical, the second regions 39b-1 to 39b-4 at the positions where the object P contacts move outward from the center of the object P in a plan view as shown by the arrows, respectively.

[0210] On the other hand, when the robot arm 46 grasps the object P by pinching it horizontally (see the arrows in Figure 12), if the gripping force of the robot arm 46 is insufficient, the object P will move due to gravity in the in-plane direction of the light reflecting layer 39, i.e., downward in Figure 12, as shown by the white arrow in Figure 12.

[0211] In this case, the second regions 39b (39b-1 to 39b-4) at the position where the object P contacts move in the in-plane direction from the position indicated by the dashed circle in FIG. 13 as indicated by the arrows due to the deformation of the light reflecting layer 39 caused by the pressure of the object P and the movement of the object P in the in-plane direction. That is, so-called shear deformation occurs in the light reflecting layer 39. The dashed circle in FIG. 13 indicates the position of the second regions 39b (39b-1 to 39b-4) in a state where no pressure is applied to the light reflecting layer 39. For example, in the example shown in FIG. 12 and FIG. 13, the object P tries to move in the downward direction in the figure, so that the object P applies a shear stress in the in-plane direction (downward in the figure) to the light reflecting layer 39. Therefore, as shown in FIG. 13, the second regions 39b-1 to 39b-4 at the position where the object P contacts move downward in a plan view as indicated by the arrows.

[0212] Therefore, in a pressure sensor 30 using a light reflecting layer 39 having a configuration as shown in Figure 9, in which the second regions 39b are discretely arranged and the first region 39a is arranged between the discretely arranged second regions 39b, it is possible to know in advance the relationship between the pressure applied in the in-plane direction of the light reflecting layer 39 and the amount of change in the in-plane position of the second regions 39b, and to detect the change in the in-plane position of the second regions 39b from the captured image, thereby detecting the stress applied in the in-plane direction, and also to detect whether the grasped object P is moving in the in-plane direction (detecting displacement).

[0213] The above examples are examples in which the pressure sensor of the present invention is used as a tactile sensor and a proximity sensor at the end of a robot arm, but the pressure sensor of the present invention is not limited to this and can be used for various pressure measurements. As an example, the pressure sensor of the present invention can be exemplified as a touch sensor for a panel, a button, etc. In particular, the pressure sensor of the present invention is suitably used as the tactile sensor and the proximity sensor for the robot described above.

[0214] In the following description, preferred aspects of each component of the pressure sensor 30 used as a tactile sensor and proximity sensor for robots will be described. However, these aspects can also be used in pressure sensors other than the pressure sensor 30 used as a tactile sensor and proximity sensor for robots.

[0215] As described above, the pressure sensor 30 of the present invention is suitable for use as a tactile sensor, a proximity sensor, or the like, in the gripping portion (tip) of the robot arm 46. In such applications, in order to measure pressure with high resolution and precision, it is necessary to align the focus of the image captured by the imaging element 32 with the surface of the light reflecting layer 38. For this purpose, it is necessary to take measures such as bringing the imaging element 32 into contact with or as close as possible to the light reflecting layer 38, or matching the measurement area of ​​the light reflecting layer 38 with the imaging area of ​​the imaging element.

[0216] Here, the pressure sensor 30 used in the tactile sensor and proximity sensor of the robot arm is preferably capable of measuring pressure over a certain area, such as 2×2 cm, 3×3 cm, etc. Therefore, in order to perform proper imaging, the imaging surface of the imaging element 32 must also be the same size. However, the imaging surface of the imaging element is usually about 1×1 cm, and the larger the imaging surface, the more expensive and the greater the power consumption.

[0217] In contrast, in the pressure sensor 30 of the present invention, a space is provided between the imaging element 32 and the light reflecting layer 38, and in a more preferred embodiment, a lens 34 is provided between them. With this configuration, the optical distance required for imaging by the lens 34 is ensured, and the distance between the lens 34, the imaging element 32, and the light reflecting layer 38 can be adjusted, so that the focus of the image captured by the imaging element 32 can be adjusted to the light reflecting layer 38.

[0218] This enables high-quality imaging by the imaging element 32, i.e., enables highly accurate pressure measurement. Furthermore, even if the light reflective layer 38 of the pressure sensor 30 is large, such as 3×3 cm, a normal or small imaging element 32 of about 1×1 cm can be used. In other words, by using the lens 34, it becomes possible to easily configure the device using a general-purpose imaging element 32.

[0219] Furthermore, by selecting the lens 34, it is possible to prevent the distance between the image pickup element 32 and the light reflecting layer 38 from becoming wider than necessary, that is, to prevent the pressure sensor 30 from becoming larger.

[0220] There is no limit to the interval (distance) between the imaging element 32 and the light reflecting layer 38, but considering mounting on a robot or the like, it is preferable for the interval to be short in order to miniaturize the pressure sensor 30. On the other hand, considering the placement of the lens 34 and the miniaturization of the imaging element 32, it is preferable for there to be an optically significant distance.

[0221] Considering this point, the distance between the imaging element 32 and the light reflecting layer 38 is preferably 0.1 to 50 mm, more preferably 1 to 30 mm, and even more preferably 3 to 20 mm.

[0222] Furthermore, taking into consideration the size of the pressure sensor 30, the cost and driving power of the image sensor 32, etc., it is preferable that the area of ​​the imaging surface of the image sensor 32 in the pressure sensor 30 be smaller than the area of ​​the light reflecting layer .

[0223] This point is the same for all pressure sensors of the present invention, including the above-mentioned pressure sensor 30. However, the configuration in which the area of ​​the imaging surface of the imaging element is smaller than the area of ​​the light reflecting layer is merely a preferred embodiment, and the pressure sensor of the present invention may be configured so that the area of ​​the imaging surface is the same as the area of ​​the light reflecting layer, or may be configured so that the area of ​​the imaging surface is larger than the area of ​​the light reflecting layer.

[0224] Although the pressure sensor of the present invention has been described in detail above, the present invention is not limited to the above-described examples, and various improvements and modifications may of course be made without departing from the gist of the present invention. [Industrial Applicability]

[0225] The present invention can be suitably used for various pressure measurements such as tactile sensing in robotics applications. [Explanation of symbols]

[0226] 30 Pressure Sensor 32 Image sensor 34 Lens 36 light source 38, 39 Light reflective layer 38a, 39a 1st area 38b, 39b 2nd area 40 Pattern Black Layer 40a Transparent part 40b Black part 42 Case 46 Robot Arm 48 Arm parts P object

Claims

1. An imaging element; a light reflective layer that is disposed facing an imaging surface of the imaging element and spaced apart from the imaging element, and whose reflection characteristics change in response to pressure; a light source that emits light to the light reflecting layer, A pressure sensor, wherein the light reflective layer has a first region that is transparent to light sensed by the imaging element in both an unstressed and stressed state, and a second region whose reflected wavelength changes between an unstressed and stressed state.

2. The pressure sensor according to claim 1 , wherein the light sensed by the imaging element is light having any wavelength in the visible light region.

3. The pressure sensor according to claim 2 , wherein the imaging element is a color two-dimensional sensor.

4. The pressure sensor according to any one of claims 1 to 3, wherein the light reflective layer is a liquid crystal layer.

5. The pressure sensor of claim 4 , wherein the second region is a cholesteric liquid crystal layer.

6. The pressure sensor according to claim 1 , wherein the second region reflects light sensed by the imaging element in both a no-pressure state and a pressure state.

7. The pressure sensor according to any one of claims 1 to 3, wherein the light reflecting layer has a plurality of the second regions, the plurality of second regions are discretely arranged, and the first region is arranged between the plurality of discretely arranged second regions.

8. The pressure sensor according to claim 7 , wherein the light reflecting layer is deformable by a stress applied in an in-plane direction, and the shear stress applied in the in-plane direction is detected by detecting a change in position of the second region.

9. A pressure sensor as described in any one of claims 1 to 3, which changes the intensity of light emitted from the light source in response to a change in state between a state in which no pressure is applied to the second region and a state in which pressure is applied to the second region.

10. an optical system that causes light to be incident on the imaging element; 4. The pressure sensor according to claim 1, wherein the focal position of the optical system is changed in response to a change in state between a state in which no pressure is applied to the second region and a state in which pressure is applied to the second region.

11. 4. The pressure sensor according to claim 1, further comprising a black portion disposed on a surface of the light reflecting layer opposite to the imaging element, the black portion being located at a position corresponding to the second region.

Images