Force sensor and measurement method

Abstract

To provide a force sensor which enables tri-axial force measurement and in-plane force distribution measurement, and to provide a force sensor which enables moment computation.SOLUTION: A force sensor configured to three-dimensionally capture an image of a pattern on a surface of a plate through a prism and analyze a displacement thereof is provided, as well as a force measurement method. Further, a force sensor configured to three-dimensionally capture an image of a pattern on a surface of a plate through a polygon mirror or four prisms and analyze a displacement thereof is provided, as well as a force and moment measurement method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a force sensor and a measurement method using the same. [Background technology]

[0002] Conventional force sensors include force plates and pressure sensor sheets. These are used, for example, to measure the reaction force of the human sole. Measuring the reaction force of the human sole is important in, for example, sports science, development of prosthetic limbs and orthotics, rehabilitation, robotics, etc.

[0003] As an example of a conventional force sensor, for example, Patent Document 1 describes a force plate equipped with force sensors at the four corners. This force plate detects force with a triaxial load cell installed at the four corners of the plate, and can measure the total force of the sole reaction force of each pressure and shear force. However, the spatial resolution of this force plate was not necessarily sufficient. Even if this force plate is used to measure the distribution of force, there are large restrictions in terms of structure and signal processing, and it is impossible or difficult to make an array of about 10 x 10 pieces required for distribution measurement. In addition, there is an array-shaped pressure sensor sheet as a means of measuring the sole reaction force, but while this can measure the pressure distribution, there is a problem that it cannot measure the shear force, which is important for bringing about human movement, in principle. Force measurement in the shear direction is important in sports science, prosthetic limbs, development of orthotics, rehabilitation, robotics, etc.

[0004] Patent document 2 describes a balance training device. Patent documents 3 and 4 describe a balance training system. Patent document 5 describes a displacement measuring device and a displacement measuring method, which can measure the displacement of a measurement point while reflecting the displacement of the imaging device itself.

[0005] In sports science and in the development of prosthetics and orthotics, there is a strong demand for force plates with high spatial resolution that can measure not only the total force but also the force distribution on the sole of the foot. Therefore, force plate elements that can be made into small arrays are required.

[0006] In recent years, as part of the robotics industry, research on microrobots that explore narrow spaces has been active, and there are many points to learn about the dynamics of leg-based movements, such as the stability and maneuverable running and jumping of small insects. For this reason, the biomechanics of small insect movements have attracted attention. In the past, many studies of small insects have sought to determine the force from the movement trajectory captured by a video camera, but since the weight of each part of the body cannot be accurately determined from the video alone, it was necessary to make assumptions such as a constant body density when converting to force. In addition, when the sole reaction force of the legs and the flying force of the wings occur simultaneously, such as during takeoff, the video alone becomes an indefinite problem, and it is not possible to determine the amount of either force. Regarding insects, attempts have been made to measure the sole reaction force using force sensors, but most of the objects measured are large insects such as cockroaches. This is because conventional force sensors measure forces on the order of mN to N, and it is difficult to measure forces below mN, which are thought to be generated by small insects such as butterflies. Therefore, there was a need for a small, highly sensitive force plate for measuring the reaction force of the soles of small insects. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-003275 A (Patent No. 7106065) [Patent Document 2] JP 2020-146330 A (Patent No. 7081540) [Patent Document 3] Patent Publication No. 2022-032091 [Patent Document 4] JP 2022-038343 A [Patent Document 5] JP 2023-128044 A Summary of the Invention [Problem to be solved by the invention]

[0008] In one embodiment, the present invention aims to provide a force sensor capable of measuring three-axis forces and in-plane force distribution. In another embodiment, the present invention aims to provide a force sensor that can be miniaturized.

[0009] Moreover, in one embodiment, an object of the present invention is to provide a force sensor capable of measuring six-axis forces and measuring in-plane force distribution. [Means for solving the problem]

[0010] As a result of extensive research into solving the above problems, the inventors have discovered that, as an example, the above problems can be at least partially solved by imaging a pattern on the surface of a measurement object via an optical element that enables light to be measured simultaneously from two or more directions and analyzing the displacement, and have completed the present invention, which incorporates this as one embodiment.

[0011] Furthermore, the present inventors have conducted intensive research to solve the above-mentioned problems related to small insects. A non-contact sensor element such as a laser displacement meter has been used as a sensor element to realize a force plate with unprecedented high sensitivity. On the other hand, when increasing the axis to be measured with a force plate using a non-contact sensor element, the number of sensor elements is required according to the number of axes as in the past, and the system becomes complicated. Therefore, the present inventors have conducted further research, and as a result, as an example, the present inventors have found that the above-mentioned problem can be at least partially solved by imaging four patterns on the surface of the measurement object through a polygon mirror and analyzing the displacement, and have completed the present invention that includes this as one embodiment. The present inventors have also found that the above-mentioned problem can be at least partially solved by imaging four patterns on the surface of the measurement object through four optical elements that enable light to be measured simultaneously from two or more directions and analyzing the displacement, and have completed the present invention that includes this as one embodiment.

[0012] The present invention includes the following embodiments. [1] A force sensor comprising: (i) a plate; (ii) a spring portion; (iii) an optical element that enables light to be measured from two or more directions simultaneously; and (iv) an imaging portion, said plate having a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; The force sensor, wherein the imaging unit is positioned so as to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions. [2] The force sensor according to embodiment 1, wherein the optical element that enables simultaneous measurement of light from two or more directions is a prism. [3] The force sensor according to embodiment 1, further comprising (v) a mirror between (iii) an optical element that enables simultaneous measurement of light from two or more directions, and (iv) an imaging unit. [4] Further, (vi) a computer is provided, the computer having an algorithm or software capable of analyzing the displacement of a pattern on the surface of the plate imaged by an imaging unit through an optical element that enables the light to be measured simultaneously from two or more directions, and calculating the force applied to the plate from the spring constant of the spring unit and the displacement of the pattern, or The force sensor of embodiment 1, further connected to a computer, the computer having an algorithm or software capable of analyzing the displacement of a pattern applied to the surface of the plate imaged by an imaging unit via an optical element that enables the light to be measured simultaneously from two or more directions, and calculating the force applied to the plate from the spring constant of the spring unit and the displacement of the pattern. [5] A force sensor array comprising two or more sets of (i) plates, (ii) spring parts, and (iii) optical elements that can simultaneously measure light from two or more directions, each set corresponding to each plate, and further comprising (iv) an imaging part, Each of said plates has a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; The imaging unit is arranged to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions. The array of force sensors. [6] The array of force sensors of embodiment 5, wherein the optical element that enables light to be measured simultaneously from two or more directions is a prism. [7] An array of force sensors as described in embodiment 5, further comprising (v) a mirror between (iii) an optical element that enables light to be measured from two or more directions simultaneously, and (iv) an imaging unit. [8] Further, (vi) a computer is provided, the computer having an algorithm or software capable of analyzing the displacement of the pattern on the surface of each plate imaged by the imaging unit through an optical element that enables the light to be measured from two or more directions simultaneously, and calculating the force applied to each plate from the spring constant of the spring unit and the displacement of the pattern, and measuring the distribution of the force applied to each plate, or Further, the device is connected to a computer, and the computer has an algorithm or software that can analyze the displacement of the pattern on the surface of each plate, which is imaged by the imaging unit through an optical element that enables the light to be measured from two or more directions simultaneously, calculate the force applied to each plate from the spring constant of the spring unit and the displacement of the pattern, and measure the distribution of the force applied to each plate. 6. An array of force sensors as described in embodiment 5. [9] (i) a step of capturing an image of a pattern on a surface of a plate placed on a spring part capable of exerting elastic forces in the x, y, and z directions, using an imaging unit via an optical element that enables light to be measured simultaneously from two or more directions, at a first point in time before a force is applied to the plate and at a second point in time when a force is applied to the plate; (ii) superimposing the pattern applied on the surface of the plate at the first time point and the pattern applied on the surface of the plate at the second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; and (iii) calculating the force applied to the plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; Methods for measuring force, including:

[10] The method of embodiment 9, wherein the optical element that enables light to be measured simultaneously from two or more directions is a prism.

[11] The method according to embodiment 9, wherein a mirror is disposed between the imaging unit and an optical element that enables light to be measured simultaneously from two or more directions.

[12] The method of embodiment 9, wherein steps (ii) and (iii) are performed by a computer, algorithm, or software.

[13] Using an array of force sensors including two or more sets of plates, spring parts capable of exerting elastic forces in the x, y, and z directions corresponding to each plate, and optical elements capable of simultaneously measuring light corresponding to each plate from two or more directions, (i) capturing an image of the pattern formed on the surface of each plate by an imaging unit via an optical element that enables light corresponding to each plate to be measured simultaneously from two or more directions at a first time point before a force is applied to the array and at a second time point when a force is applied to the array; (ii) for each plate, superimposing a pattern applied on the surface of the plate at a first time point and a pattern applied on the surface of the plate at a second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; (iii) calculating the force applied to each plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; and (iv) measuring the distribution of forces applied to the array of force sensors. Methods for measuring force, including:

[14] The method of embodiment 13, wherein the optical element that enables light to be measured simultaneously from two or more directions is a prism.

[15] The method according to embodiment 13, wherein a mirror is disposed between an optical element that enables light to be measured simultaneously from two or more directions and the imaging unit.

[16] The method of embodiment 13, wherein steps (ii), (iii), and (iv) are performed by a computer, algorithm, or software.

[17] A force sensor comprising: (i) a plate; (ii) a spring portion; (iii) an optical element that enables light to be measured simultaneously from two or more directions; and (iv) an imaging portion, said plate having a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; the imaging unit is arranged to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions; The pattern is applied as four patterns on the top, bottom, left, and right of the position where the measurement object is placed on the force sensor, (I) the optical element that enables the (iii) light to be measured from two or more directions simultaneously is a polygon mirror, and a mirror is disposed directly below each of the four patterns; When the polygon mirror is imaged by the imaging unit, each of the four patterns can be imaged from two or more directions via the polygon mirror, or (II) the optical element (iii) that enables light to be measured from two or more directions simultaneously is four prisms, each prism being fixed directly below the four patterns, When the imaging unit images each prism, the four patterns can be imaged from two or more directions through each prism. Force sensor for 6-axis measurement.

[18] The force sensor according to embodiment 17, further comprising (v) a mirror between (iii) an optical element that enables simultaneous measurement of light from two or more directions, and (iv) an imaging unit.

[19] Further, (vi) the apparatus has a computer, the computer having an algorithm or software capable of analyzing the displacement of a pattern on the surface of the plate imaged by an imaging unit through an optical element that enables the light to be measured from two or more directions simultaneously, and calculating the force and moment applied to the plate from the spring constant of the spring unit and the displacement of the pattern, or Further, the device is connected to a computer, and the computer has an algorithm or software that can analyze the displacement of the pattern on the surface of the plate imaged by the imaging unit through an optical element that enables the light to be measured simultaneously from two or more directions, and calculate the force and moment applied to the plate from the spring constant of the spring unit and the displacement of the pattern. 18. A force sensor as described in embodiment 17.

[20] (i) a step of capturing images of four patterns on a surface of a plate placed on a spring part capable of exerting elastic forces in the x, y, and z directions, by an imaging unit through one polygon mirror or four prisms, at a first point in time before a force is applied to the plate and at a second point in time when a force is applied to the plate; However, when the four patterns are imaged through one polygon mirror, four mirrors are disposed between the polygon mirror and the four patterns, so that the imaging unit can image the four patterns through the one polygon mirror, or When the four patterns are imaged through four prisms, one prism is disposed directly below each of the four patterns, so that the imaging unit can image the four patterns through the four prisms; (ii) superimposing the pattern applied on the surface of the plate at the first time point and the pattern applied on the surface of the plate at the second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; and (iii) calculating the force and moment applied to the plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; Methods for measuring force, including:

[21] The method of embodiment 20, wherein an additional mirror is disposed between the one polygon mirror or the four prisms and the imaging unit.

[22] The method of embodiment 20, wherein steps (ii) and (iii) are performed by a computer, algorithm, or software. Effect of the Invention

[0013] In one embodiment, the present invention has an effect of being able to measure not only in-plane displacement of the plate but also out-of-plane displacement.In one embodiment, the present invention has an effect of being able to miniaturize the force sensor. [Brief description of the drawings]

[0014] [Figure 1] 1 is an overall view of a force sensor according to the present invention. [Diagram 2] This shows the principle of the sampling moiré method. When the pattern 2 in the upper left and the pattern 2 in the lower left are overlapped, the moiré fringes 2' appear as shown on the right. A small displacement of the pattern 2 can be converted into a large displacement of the moiré fringes 2'. [Diagram 3] This shows the displacement of (lattice) pattern 2 when the plate is displaced. Plate 1 is shown in A. The arrow indicates the direction of the applied force. Pattern 2 is imaged by imaging unit 5 in B. When a vertical force is applied to plate 1, pattern 2 is also displaced vertically. [Figure 4] This shows the displacement of (lattice) pattern 2 when the plate is displaced. A shows plate 1. The arrow indicates the direction of the applied force. B shows pattern 2 imaged by imaging unit 5. When a lateral force is applied to plate 1, pattern 2 also displaces laterally. [Diagram 5] This shows the displacement of the (lattice) pattern 2 when the plate is displaced. A shows the plate 1. The arrow indicates the direction of the applied force. B shows the pattern 2 imaged by the imaging unit 5. When a load is applied to the vertical surface of the plate 1, the (lattice) patterns 2 move toward or away from each other. [Figure 6] A photograph of the spring structure is shown. [Figure 7]The figure shows a configuration in which a plate 1 is placed on top of a spring portion 7, an optical element 3 (prism) that enables light to be measured from two or more directions simultaneously is placed below the spring portion 7, and a jig 8 is placed below these. A pattern 2 is applied to the underside of the plate 1, and is not shown in the figure. [Figure 8] The photograph shows an arrangement of an imaging unit 5, a lens 9, a mirror 4, a light emitting unit 10, an optical element 3 (prism) that enables light to be measured from two or more directions simultaneously, a spring unit 7, and a plate 1. [Figure 9] This is a photograph of pattern 2 when a weight is placed on plate 1. The left grid moves to the right (+), and the right grid moves to the left (-). [Figure 10] The displacement data (raw data) of the grid pattern on the left is shown. [Figure 11] The displacement data for pattern 2 on the left is shown, low-pass filtered at 10 Hz. [Figure 12] The displacement data (raw data) of the grid pattern on the right is shown. [Figure 13] The displacement data for the right (grid) pattern 2 is shown, low-pass filtered at 10 Hz. [Figure 14] The following shows the results of a Comsol simulation when a vertical downward load of 1N is applied to the spring. [Figure 15] The following shows the results of a Comsol simulation when a vertical downward load of 1N is applied to the spring. [Figure 16] 1 shows an array of force sensors. [Figure 17] A force sensor using a polygon mirror is shown. [Figure 18] FIG. 2 is a diagram showing the polygon mirror as viewed from directly below. [Figure 19] FIG. 1 is a schematic diagram of a force sensor using a polygon mirror. [Figure 20] The movement of the pattern in the camera image is shown as the plate is moved in the x direction. [Figure 21] The movement of the pattern in the camera image is shown as the plate is moved in the y direction. [Figure 22]The movement of the pattern in the camera image is shown as the plate is moved in the z direction. [Diagram 23] A conceptual diagram of what happens when a three-axis force and a three-axis moment are applied to a plate is shown. The four patterns observed through the polygon mirror are defined as CP1 to CP4. [Figure 24] This shows the movement of the pattern when Fx is added to the plate. When Fx is added, all patterns move to the right. [Diagram 25] This shows the movement of the pattern when Fy is added to the plate. When Fy is added, all the patterns move up. [Figure 26] This shows the movement of the patterns when Fz is applied to the plate. When Fz is applied, all the patterns move away from each other. [Figure 27] This shows the pattern shift when Mx is added to the plate. When Mx is added, CP1 and CP3 move upward, while CP2 and CP4 remain almost unchanged. [Figure 28] This shows the shift in the pattern when My is added to the plate. When My is added, CP2 and CP4 move to the left, while CP1 and CP3 barely change. [Figure 29] The figure shows the movement of the pattern when Mz is added to the plate. When Mz is added, CP2 and CP4, and CP1 and CP3 move in opposite directions (CP2 and CP4 move counterclockwise when viewed from below the plate, and CP1 and CP3 move counterclockwise when viewed from below the plate). [Diagram 30] A force sensor with four prisms arranged is shown. [Diagram 31] FIG. 1 is a schematic diagram of a force sensor using a prism. [Diagram 32] The movement of the pattern in the camera image is shown as the plate is moved in the x direction. [Diagram 33] The movement of the pattern in the camera image is shown as the plate is moved in the y direction. [Diagram 34] The movement of the pattern in the camera image is shown as the plate is moved in the z direction. [Diagram 35]A conceptual diagram of the plate when three-axial forces and three-axial moments are applied is shown below. The four pattern pairs observed through the prism are defined as CP1 to CP4. [Diagram 36] This shows the movement of the patterns when Fx is added to the plate. When Fx is added, all pattern pairs move to the right. [Figure 37] This shows the movement of the patterns when Fy is added to the plate. When Fy is added, all pattern pairs move up. [Figure 38] This shows the movement of the patterns when Fz is applied to the plate. When Fz is applied, all pairs of patterns move closer to each other. [Figure 39] This shows the movement of the pattern when Mx is added to the plate. When Mx is added, CP1 and CP3 move toward and away from each other, respectively, while CP2 and CP4 hardly change at all. [Diagram 40] This shows the shift in the pattern when My is added to the plate. When My is added, CP2 and CP4 move toward and away from the plate, respectively, while CP1 and CP3 remain almost unchanged. [Diagram 41] The movement of the pattern when Mz is added to the plate is shown. When Mz is added, the pairs move in the same direction, but CP2 and CP4, and CP1 and CP3 move in opposite directions (CP2 and CP4 move counterclockwise when viewed from below the plate, and CP1 and CP3 move counterclockwise when viewed from below the plate). [Diagram 42] A photograph of the prototype force plate is shown. [Diagram 43] This is a camera image of a pattern (Pattern 2). [Diagram 44] These are the measurement results using sampling moiré. [Diagram 45] The movement of the pattern (grating) in the camera image is shown as the plate is moved in the x-direction. [Diagram 46] The movement of the pattern in the camera image is shown as the plate is moved in the y direction. [Figure 47] The movement of the pattern in the camera image is shown as the plate is moved in the z direction. [Figure 48] A conceptual diagram of the plate when three-axial forces and three-axial moments are applied is shown below. The four pattern pairs observed through the prism are defined as CP1 to CP4. [Figure 49] This shows the movement of the patterns when Fx is added to the plate. When Fx is added, all pattern pairs move to the right. [Figure 50] This shows the movement of the patterns when Fy is added to the plate. When Fy is added, all pattern pairs move up. [Figure 51] This shows the movement of the patterns when Fz is applied to the plate. When Fz is applied, all pairs of patterns move closer to each other. [Figure 52] This shows the movement of the pattern when Mx is added to the plate. When Mx is added, CP1 and CP3 move toward and away from each other, respectively, while CP2 and CP4 hardly change at all. [Diagram 53] This shows the shift in the pattern when My is added to the plate. When My is added, CP2 and CP4 move toward and away from the plate, respectively, while CP1 and CP3 remain almost unchanged. [Figure 54] The movement of the pattern when Mz is added to the plate is shown. When Mz is added, the pairs move in the same direction, but CP2 and CP4, and CP1 and CP3 move in opposite directions (CP2 and CP4 move counterclockwise when viewed from below the plate, and CP1 and CP3 move counterclockwise when viewed from below the plate). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will now be described in detail with reference to the drawings.

[0016] FIG. 1 shows the basic principle of the present invention. A pattern 2 is applied to the surface of a plate 1 (the surface facing downward in FIG. 1) to be measured in advance. Next, the pattern 2 on the surface of the plate is imaged by an imaging unit 5 through an optical element 3 that allows light to be measured simultaneously from two or more directions. First, the pattern 2 is imaged in a state where no force is applied to the plate 1. Next, a force is applied to the plate 1 to image the pattern 2 and analyze the displacement. This makes it possible to measure displacement not only in the plane but also in the out-of-plane direction. In some cases, a mirror 4 may be disposed between the imaging unit 5 and the optical element 3 that allows light to be measured simultaneously from two or more directions. In this specification, for convenience of explanation, the measurement object is a plate, but the measurement object may have any shape. Also, although the spring portion 7 is omitted in FIG. 1, a spring portion 7 may be disposed between the plate 1 and the optical element 3 that allows light to be measured simultaneously from two or more directions.

[0017] The pattern 2 on the surface of the plate 1 may be referred to as a grating in this specification. A grating is a collection of identical, parallel, elongated elements arranged at regular intervals. In one embodiment, the grating includes one type of identical, parallel, elongated elements. In another embodiment, the grating includes two types of identical, parallel, elongated elements. In this case, the second type of elongated elements may be perpendicular to the first type of elongated elements or may intersect at an angle. When two elements are perpendicular to each other, this may be referred to as a lattice pattern, grid, or mesh in this specification.

[0018] In some embodiments, the elongated elements are straight lines. In other embodiments, the elongated elements are regular wavy lines, such as, but not limited to, sine waves, square waves, triangular waves, sawtooth waves, and combinations thereof.

[0019] When a force is applied to the plate 1, the plate 1 is distorted. In the present invention, this is captured as a displacement d of the pattern 2 imaged by the imaging unit 5. In other words, by converting the displacement of the pattern 2 when a force is applied to the plate 1 into the displacement of the moiré fringes 2', it becomes possible to measure the in-plane displacement with higher precision even if the displacement of the pattern 2 is minute.

[0020] In one embodiment, the displacement of the pattern 2 can be analyzed by a sampling moiré method. The sampling moiré method is a method of measuring the displacement of a measurement object by attaching a pattern having elongated elements with a known interval to the measurement object and photographing the pattern with a camera. In the sampling moiré method, the displacement can be measured with high accuracy by using moiré fringes that are generated by superimposing the photographed patterns before and after deformation. The moiré fringes referred to here are stripe patterns that are generated due to a shift in the period of a regular pattern. An outline of the sampling moiré method and moiré fringes are shown in FIG. 2. By using the sampling moiré method, the displacement of each plate 1 can be resolved to 1 / 1000 of the interval (grating pitch) of the elements of the pattern and detected with high accuracy. For details of the sampling moiré method, see, for example, References 1 and 2. In another embodiment, the displacement of the pattern 2 can be analyzed by holographic interferometry, reference light interference fringe measurement, shearing interference fringe measurement, or the like.

[0021] The imaging unit 5 may be a camera, an optical camera, a camera having a CCD image sensor, or a digital camera. Cameras for the sampling moiré method are also commercially available, such as, but not limited to, sampling moiré camera DSMC-100A (Kyowa Electric Industry Co., Ltd.) and DSMC-100A-2M1 (Kyowa Electric Industry Co., Ltd.). Analysis of the moiré fringes may be performed by algorithms or software, such as, but not limited to, commercially available sampling moiré offline analysis software DSMC-10A (Kyowa Electric Industry Co., Ltd.).

[0022] The optical element 3 that allows light to be measured from two or more directions simultaneously includes, but is not limited to, a prism. Any shape of optical element may be used as long as light can be measured from two or more directions simultaneously. Examples of prisms include, but are not limited to, a triangular prism, an Amici prism, a Pellin-Broca prism, an Abbe prism, a Fery prism, and a Porro prism. Examples of materials of the optical element 3 that allows light to be measured from two or more directions simultaneously include, but are not limited to, glass, quartz, organic glass, transparent plastic, diamond, or other transparent materials.

[0023] The principle of the displacement of the pattern 2 with respect to the displacement of the plate 1 is shown in Figures 3, 4, and 5. A case will be described in which a triangular prism is used as the optical element 3 that enables simultaneous measurement of light from two or more directions. The in-plane direction of the plate, which is the direction perpendicular to the triangular surface of the triangular prism, is defined as the x direction. When a force is applied from the x direction, both of the patterns 2 move in the x direction. When the plate is displaced by d in the x direction, the two images of the patterns 2 are displaced by the same amount d in the x direction. The in-plane direction of the plate parallel to the triangular surface of the prism is defined as the y direction. When a force is applied from the y direction, both of the patterns 2 move in the y direction. When the plate is displaced by d in the y direction, the two images of the patterns 2 are displaced by d / (√2) in the y direction. The direction perpendicular to the plate surface is defined as the z direction. When a force is applied from the z direction, the patterns 2 move closer to each other or move away from each other. When the plate is displaced by d in the z direction, the two images of the patterns 2 are displaced by ±d / (√2) in opposite directions in the y direction. The displacement in three directions can be measured using the sampling moiré method, and the displacement can be converted to force by multiplying the spring constant in each direction.

[0024] In one embodiment, the present invention provides a force sensor. In this specification, the force sensor may be referred to as a displacement measurement system. This force sensor includes an optical element 3 that allows light to be measured from two or more directions simultaneously. The force sensor of the present invention may include a mirror 4 in some cases. Unless otherwise specified, in this specification, the pattern 2 on the plate 1 is considered to be a part of the force sensor. In a specific limited embodiment, the pattern 2 on the plate 1 is not a part of the force sensor, but the force sensor can be used in combination with a pattern previously applied to the plate 1. Unless otherwise specified, in this specification, the imaging unit 5 is considered to be a part of the force sensor. In a specific limited embodiment, the imaging unit 5 is not a part of the force sensor, but the force sensor can be used in combination with an imaging unit (e.g., a camera).

[0025] The force sensor may be connected to a computer 6. The computer 6 may have an algorithm or software for analyzing the moiré fringes 2'. The algorithm or software may be stored in a memory or storage medium, and the memory or storage medium may be stored in the computer 6. The force sensor may be directly connected to the computer 6, or may be indirectly connected to the computer 6. An indirect connection includes a remote connection via a communication means. For example, the force sensor may transmit imaging data by a conventional communication means (transmission means), and the transmitted data may be received by the computer 6 by a reception means. In one embodiment, the computer 6 is not a part of the force sensor, but the force sensor may be connected to the computer 6 to measure the force. In another embodiment, the computer 6 is a part of the force sensor. A force sensor including the computer 6 may be referred to as a force sensor system in this specification.

[0026] The force sensor may have a spring portion 7. Unless otherwise specified, in the force sensor, the spring portion 7 is arranged so as to exert an elastic force when a force is applied to the plate 1. The spring portion 7 may have any shape. In one embodiment, the spring portion 7 has a shape having elastic forces in three axial directions. In this case, in the force sensor, the spring portion 7 is arranged so as to exert an elastic force in three axial directions when a force is applied to the plate 1. The three axial directions here refer to two directions within the plane of the plate (x direction, y direction) and a direction outside the plane (z direction).

[0027] In one embodiment, the present invention provides a force sensor array in which two or more sets of an optical element 3 that allows light to be measured from two or more directions simultaneously, a spring portion 7, and a plate 1 having a pattern 2 are arranged in an array. In one embodiment, a computer 6 is not part of the force sensor array, but the force sensor array can be connected to the computer 6 to measure forces and further measure the distribution of forces. In another embodiment, the computer 6 is part of the force sensor array. A force sensor array including a computer 6 may be referred to as a force sensor array system in this specification.

[0028] In one embodiment, in the force sensor array, each plate has a pattern, and an optical element that allows one light to be measured from two or more directions simultaneously is arranged for one plate. However, it is not necessary to image each optical element with a separate imaging unit. In other words, the pattern of each plate can be imaged through an optical element that allows light to be measured from two or more directions simultaneously by one common imaging unit. The force sensor array may have two or more sets of optical elements that allow light to be measured from two or more directions simultaneously and plates with patterns, for example, n×m (where n and m are natural numbers of 2 or more), for example, 10×10, 20×20, 30×30, 40×40, 50×50, 100×100, 8×16, 16×32, 32×64, for example, 64×128, but is not limited thereto. An example of the array is shown in FIG. 16. By adjusting the height (z direction) of the mirrors for each prism, all of the lattice patterns can be captured within the camera's field of view, making it possible to measure the three-axis forces of all of the plates that make up the array with high sensitivity and high speed.

[0029] In one embodiment, the computer 6 has an algorithm or software capable of analyzing the displacement of the pattern 2 on the surface of the plate 1 captured by the imaging unit 5 through the optical element 3 that allows the light to be measured from two or more directions simultaneously, and calculating the force applied to the plate 1 from the spring constant of the spring unit 7 and the displacement of the pattern 2. In another embodiment, the computer 6 has an algorithm or software capable of analyzing the displacement of the pattern 2 on the surface of each plate 1 included in the two or more sets captured by the imaging unit 5 through the optical element 3 that allows the light to be measured from two or more directions simultaneously, and calculating the force applied to each plate 1 from the spring constant of the spring unit 7 and the displacement of the pattern 2, and measuring the distribution of the force applied to each plate 1 included in the two or more sets. In one embodiment, the analysis and the calculation of the force applied to the plate 1 can be performed by an algorithm or software. In one embodiment, the analysis, the calculation of the force applied to each plate 1, and the measurement of the force distribution can be performed by an algorithm or software. In one embodiment, the analysis of the displacement of the pattern 2 imprinted on the surface of the plate 1 can be performed by a sampling Moiré method.

[0030] The sampling moiré method is known to have applications at construction sites, such as measuring the strain on pillars and bridges (References 1, 2, etc.). When the object to be measured is large, multiple patterns are often attached to the object and measurements are performed. However, capturing images of multiple patterns requires a long shooting distance. This also narrows the angle of view and reduces the resolution. Therefore, these conventional methods are not suitable for miniaturization.

[0031] In the present invention, one pattern 2 is imaged by an imaging unit 5 via an optical element 3 that allows light to be measured from two or more directions simultaneously, thereby obtaining two or more images, for example, two images, from one pattern 2. Then, the displacement of the pattern 2 in the two images is analyzed by an analysis method such as the sampling moiré method. This makes it possible to miniaturize the entire system. It also makes it possible to avoid narrowing of the angle of view and a decrease in resolution.

[0032] The present invention will be described more specifically in the following embodiments, but the present invention is not limited thereto.

[0033] When a 50 kg person walks, the reaction force on the sole of the foot in the direction of gravity is expected to be about 0.6 kN. Therefore, taking into account the safety factor and assuming that the entire reaction force is applied to one plate element, the maximum measurable force can be designed to be about 1 kN. In order to measure within the elastic range of the spring even when the maximum force is applied, we will assume that the z-direction displacement is 1 mm for a force of 1 kN, that is, the spring constant is 10 6 If you design a spring of N / m, and use a grating pattern with a pitch of 1 mm, you can resolve it to 1 / 1000 of the pitch, giving you a force resolution of 1 N.

[0034] A spring structure with a hole in the center and a spiral cut on the outside was created as the spring section 7. A photograph of the spring structure is shown in Fig. 6. Fig. 7 shows a configuration in which a plate 1 is placed on top of the spring section 7, a triangular prism is placed below the spring section 7 as the optical element 3 that enables light to be measured from two or more directions simultaneously, and a jig 8 is placed below these. Here, a triangular prism with an inclination angle of about 45 degrees is used. A pattern 2 is applied to the underside of the plate 1. When the pattern applied to the underside of the plate is viewed from the bottom up through the prism, the pattern can be viewed in three dimensions.

[0035] A photograph of the device with a single plate 1 is shown in Figure 8. Weights of 100, 50, 20, 10, 5, 2, and 1 g are placed on plate 1 in order, and the displacement of the pattern is measured. A photograph of pattern 2 when the weights are placed on plate 1 is shown in Figure 9. The left pattern 2 moves to the right, and the right pattern 2 moves to the left. The pitch of the (lattice) pattern 2 is 0.2 mm. The displacement data (raw data) of the left (lattice) pattern 2 is shown in Figure 10. The displacement of the left (lattice) pattern 2 shows a positive value. The result of applying a 10 Hz low-pass filter to this is shown in Figure 11. Similarly, the displacement data (raw data) of the right (lattice) pattern 2 is shown in Figure 12. The displacement of the right (lattice) pattern 2 shows a negative value. The result of applying a 10 Hz low-pass filter to this is shown in Figure 13. The imaged lattice displacement was about 0.645 times the original lattice displacement.

[0036] Next, we used Comsol to simulate the spring structure we created. The experimental results when a vertically downward load of 1N was applied are shown in Figures 14 and 15. In addition, the table below shows a comparison of the experimental and simulation values ​​when a 100g weight was placed on the structure.

[0037] [Table 1]

[0038] Comparing the experimental values ​​with the simulation values, the experimental values ​​are considered to be reasonable.

[0039] The force plate we created can be easily miniaturized. By arranging the miniaturized force plates in an array, we can measure not only the three axes but also the force distribution.

[0040] The differences between the force sensor of the present invention and conventional force plates and pressure sensor sheets are shown in the table below.

[0041] [Table 2]

[0042] The force sensor of the present invention can measure shear force and pressure. In addition, the force sensor of the present invention can increase spatial resolution and measure pressure distribution by measuring an area of ​​40 cm x 20 cm, the same size as a conventional force plate, with an array of 16 x 8 2.5 cm x 2.5 cm square plates.

[0043] <Additional embodiment 1> <6-axis load cell using polygon mirror> In one embodiment, the present invention provides a six-axis load cell using a polygon mirror. Figures 17, 18, and 19 show conceptual diagrams of the six-axis load cell of the present invention. This six-axis load cell has a structure in which the plate 1 to be measured is supported on all four sides by mechanical spring parts 7, and furthermore, the back surface of the plate 1 (the lower surface in Figure 17) has a fine pattern 2 on all four sides. A mirror 4' is placed directly below each lattice pattern, and a polygon mirror 3' is installed directly below the center of the plate 1. The pattern 2 on the surface of the plate is imaged by the imaging unit through the polygon mirror 3'. First, the pattern 2 is imaged in a state where no force is applied to the plate 1. Next, a force is applied to the plate 1 to image the pattern 2, and the displacement is analyzed. This makes it possible to measure displacement not only in the plane but also in the out-of-plane direction. Although the imaging unit is not shown in the figures, a mirror 4 may be placed between the imaging unit and the polygon mirror 3'. In addition, the mirror 4 that can be placed between the imaging unit and the polygon mirror 3' is different from the four mirrors 4' between the polygon mirror 3' and each pattern 2. In this specification, for convenience of explanation, the measurement object is a plate, but the measurement object may have any shape. In addition, although a spring portion 7 is shown in Fig. 17, the shape of the spring portion 7 is not limited to that shown in the figure. In addition, although a lattice pattern is shown as pattern 2 in Figs. 17, 18, and 19, the pattern is not limited to this.

[0044] The minute displacement of each pattern caused by the force and moment applied to the plate is observed through a polygon mirror with one camera (Figure 18). The polygon mirror allows each pattern to be observed at an inclination angle of 40 to 50 degrees, for example 45 degrees, making it possible to measure displacement not only in the in-plane direction but also in the out-of-plane direction. The displacement of the four patterns captured up, down, left and right within the camera's field of view is analyzed using the sampling moiré method. The sampling moiré method is capable of detection with a high resolution of less than 1 / 1000 of the grid pitch, making it possible to realize a small, highly sensitive 6-axis load cell, which was previously difficult to achieve.

[0045] The measurement principles for the in-plane and out-of-plane directions are as follows. Focusing on the two patterns on the yz cross section, as shown in Figure 19, the camera captures the two faces of the polygon mirror, and the mirror is tilted at an angle of 22.5 degrees, so that the patterns are observed from directions tilted at ±45 degrees in the y direction. For ease of understanding, the left side is shown in gray and the right side in black. When the pattern (pattern 2) is displaced in the x direction, the lattices on the two faces move in the same x direction by the same displacement (Figure 20). When the pattern is displaced in the y direction, the lattices on the two faces move in the same y direction by 1 / √2 the displacement (Figure 21). When the pattern is displaced in the z direction, the lattices on the two faces move in the opposite y direction by 1 / √2 the displacement (Figure 22). Therefore, by analyzing the images captured on the two faces using the sampling moiré method, it is possible to measure the displacement in three directions. In other words, if the amount of movement of the pattern is (x, y, z), and the amount of movement in the planar direction of the two faces captured by the camera through the polygon mirror is (x1, y1) and (x2, y2), then

number

number

[0046] Using this measurement principle, the four patterns can be used to detect six-axis forces and moments with good independence. Figure 23 shows a conceptual diagram when three-axis forces and three-axis moments are applied to the plate. The four patterns observed through the polygon mirror are defined as CP1 to CP4. When Fx is applied, all the patterns move to the right (Figure 24). Similarly, when Fy is applied, all the patterns move upward (Figure 25). On the other hand, when Fz is applied, the patterns move away from each other (Figure 26). When Mx is applied, both CP1 and CP3 move upward, and CP2 and CP4 change very little (Figure 27). Similarly, when My is applied, CP2 and CP4 move to the left, and CP1 and CP3 change very little (Figure 28). When Mz is applied, CP2 and CP4, and CP1 and CP3 move in the opposite directions (CP2 and CP4 move counterclockwise when viewed from below the plate, and CP1 and CP3 move counterclockwise when viewed from below the plate) (Figure 29). In other words, if the force and moment applied to the plate are (Fx, Fy, Fz, Mx, My, Mz), and the amounts of movement of CP1 to CP4 in the planar direction are (x1, y1), (x2, y2), (x3, y3), and (x4, y4), then:

number

[0047] <Additional embodiment 2> <6-axis load cell using 4 prisms> In one embodiment, the present invention provides a six-axis load cell using four prisms. Figures 30 and 31 show conceptual diagrams of another six-axis load cell of the present invention. In this six-axis load cell, the plate 1, which is the object of measurement, is supported on all four sides by mechanical spring parts 7. The spring structure deforms in each of the x, y, and z directions. Furthermore, on the back surface of the plate 1 (the lower surface in Figure 30), patterns 2 are applied at four points between the spring parts 7 of the plate, and optical elements 3 (prisms) that enable light to be measured simultaneously from two or more directions are fixed directly below the patterns. A camera is set up so that each pattern can be captured through the prism. First, the pattern 2 is captured in a state where no force is applied to the plate 1. Next, a force is applied to the plate 1 to capture the pattern 2, and the displacement is analyzed. This makes it possible to measure displacement not only in the in-plane direction, but also in the out-of-plane direction. For convenience of explanation, the object of measurement is a plate, but the object of measurement may have any shape. Also, although the spring parts 7 are shown in Figure 30, the shape of the spring parts 7 is not limited to that shown in the figure. Although a lattice pattern is shown as pattern 2 in Figs. 30 and 31, the pattern is not limited to this. Focusing on one pattern, as shown in Fig. 31, the two faces of the prism are captured by the camera, and due to refraction of the prism, the pattern is observed from a direction tilted by ±45 degrees in the y direction. When the pattern is displaced in the x direction, the lattices on the two faces move in the same x direction by the same displacement (Fig. 32). When the pattern is displaced in the y direction, the lattices on the two faces move in the same y direction by a magnitude of 1 / √2 of the displacement (Fig. 33). When the pattern is displaced in the z direction, the lattices on the two faces move in the opposite y direction by a magnitude of 1 / √2 of the displacement (Fig. 34). Therefore, by analyzing the images captured on the two faces using the sampling moiré method, it is possible to measure the displacement in three directions. In other words, if the amount of movement of the pattern is (x, y, z) and the amount of movement in the planar direction of the two faces captured by the camera through the prism is (x1, y1) and (x2, y2), then

number

number

[0048] Using this measurement principle, by arranging patterns and prisms in four locations, it is possible to detect six-axis forces and moments with good independence. Figure 35 shows a conceptual diagram when three-axis forces and three-axis moments are applied to the plate. The pattern pairs observed through each prism are defined as CP1 to CP4. When Fx is applied, all pattern pairs move to the right (Figure 36). Similarly, when Fy is applied, all pattern pairs move upward (Figure 37). On the other hand, when Fz is applied, each pair moves toward each other (Figure 38). When Mx is applied, CP1 and CP3 move toward and away from each other, respectively, and CP2 and CP4 hardly change (Figure 39). Similarly, when My is applied, CP2 and CP4 move toward and away from each other, respectively, and CP1 and CP3 hardly change (Figure 40). When Mz is applied, they move in the same direction as a pair, but CP2 and CP4, and CP1 and CP3 move in opposite directions (CP2 and CP4 move counterclockwise when viewed from below the plate, and CP1 and CP3 move counterclockwise when viewed from below the plate) (Figure 41). In other words, if the force and moment applied to the plate are (Fx, Fy, Fz, Mx, My, Mz), and the amounts of movement of the pairs CP1 to CP4 in the planar direction are (x1, y1), (x2, y2), (x3, y3), (x4, y4), (x5, y5), (x6, y6), (x7, y7), and (x8, y8), then

number

[0049] Based on the above design guidelines, we design and manufacture a force plate for measuring the butterfly, Butterfly. Simulation (COMSOL Multiphysics) is used for the design, and the plate structure including the coil is manufactured by a 3D printer or machine processing. The dimensions of the plate can be, for example, 40 mm × 40 mm, and the spring constant in each of the x, y, and z directions can be designed to be on the order of 100 N / m. For the pattern, we use a film mask of MEMS (Micro Electro Mechanical Systems) that can draw lines with a width of 0.1 mm or less with high precision. For the prism, we can use a right-angle prism made of N-SF11 glass with a refractive index of 1.785, which theoretically has an inclination angle of 41 degrees, close to 45 degrees, or its equivalent. We place the prism directly under the force plate, and construct a setup so that the camera can capture the image from the side through a mirror. We use a high-speed camera that can observe the pattern in high resolution as the camera, and a telecentric lens to observe with parallel light. The camera image is analyzed using analysis software (DSMC-10A, Kyowa Denki) or its equivalent.

[0050] Figure 42 shows a photograph of a plate element prototyped to confirm the principle. The plate structure was prototyped by machining, and a 25 mm × 25 mm plate was supported by a spring structure that deforms in three axial directions. A pattern with a 0.2 mm pitch was placed in the center of the back surface of the plate, and a prism was placed directly below it. When weights ranging from 100 g to 1 g were placed on the plate, the left and right patterns moved in opposite directions as in the theory, and the displacement was calculated linearly with respect to the weight of the weight by the sampling moiré method from the camera images captured at 100 Hz (Figures 43 and 44). The noise level when no weight was placed on the plate was calculated to be 0.07 μm, which is less than 1 / 2000 for a grid pitch of 0.2 mm. Therefore, focusing on Fz, a resolution of 1 / 30000 for the range was achieved. Since sufficient resolution was obtained with this setup, it was demonstrated that a 6-axis load cell based on the above principle can be realized.

[0051] A 6-axis load cell is a sensor that can simultaneously measure six degrees of freedom (three forces: forces in the x, y, and z directions, and three moments: torque around the x, y, and z axes). Unlike typical 1-axis or 3-axis load cells, it can accurately measure forces and moments in multiple directions simultaneously. Conventional 6-axis load cells measure forces and moments in each axis direction by combining and arranging multiple strain gauges. Each strain gauge detects minute deformations caused by external forces or torques applied to the sensor and converts the amount of deformation into an electrical signal. The force and moment of each axis are calculated by analyzing this signal. Basically, it is possible to separate forces from different directions and measure torques, so it is possible to capture the action of complex forces. In recent years, in the fields of medical engineering and precision engineering, where high-precision measurements are required, there is a demand for load cells with a resolution of the order of several centimeters and sub-mN order for mechanical feedback of manipulators. However, to meet these demands, the dimensions and measurement area are too small to build a sensor using the conventional method using a strain gauge, and the size is too large to fabricate a piezoresistive sensor using MEMS microfabrication technology. For example, high-precision products on the order of sub-mN have already been realized for load cells with only one axis. However, it has been considered difficult to realize a six-axis sensor because the sensor structure is complex and three-dimensional. In this context, the inventors have invented an optical detection method using the sampling moiré method, and have been able to build a mechanical structure and a sensor element that detects the six-axis directions separately. This makes it possible to realize a load cell with unprecedented high performance in the sub-mN order range.

[0052] <Additional embodiment 3> <6-axis load cell using grating as pattern> In the above-mentioned 6-axis load cell using a polygon mirror and the 6-axis load cell using four prisms, the pattern is not limited to a lattice pattern, and for example, a line pattern (grating) shown in Figs. 45 to 54 can also be used. [Industrial Applicability]

[0053] By introducing a revolutionary measurement principle to the force plate, the present invention realizes an unprecedented triaxial force measurement method that enables the analysis of the mechanical mechanism of human movement with high spatiotemporal resolution. This invention makes it possible to measure not only the three axes but also the force distribution. In other words, this invention makes it possible to measure not only the total force but also the force distribution on the sole of the foot. This can contribute to sports instruction, elucidation of the movement mechanisms of living organisms, and improvement of the quality of rehabilitation.

[0054] Furthermore, the present invention makes it possible to measure the plantar reaction force in six axial directions. This leads to elucidation of various measurement targets in the field of biomechanics. Furthermore, by arranging multiple force plates, it is possible to realize a force plate array that can measure not only the resultant plantar reaction force but also the distribution of the plantar reaction force of each leg. The measurement targets of the present invention are not limited to butterflies, but also include small butterflies, ants, spiders, etc. By developing force plates tailored to each target, it is possible to comprehensively evaluate the plantar reaction force during the movement of insects and small animals.

[0055] References 1. Tuladhar et al., Buildings 2022, 12(11), 1778 2. Nakajima et al., Mem. Grad. Eng. Univ. Fukui, Vol. 66(March 2018)

[0056] All documents mentioned herein are hereby incorporated by reference in their entirety. [Explanation of symbols]

[0057] 1 Plate 2. Pattern 2' Moire fringes 3. Optical elements that enable simultaneous measurement of light from two or more directions 3' Polygon mirror 4. Mirror 4' Mirror 5. Imaging unit 6. Computers 7 Spring section 8. Jig 9 Lenses 10 Light emitting unit

Claims

1. A force sensor comprising: (i) a plate; (ii) a spring portion; (iii) an optical element that enables light to be measured from two or more directions simultaneously; and (iv) an imaging portion, said plate having a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; The force sensor, wherein the imaging unit is positioned so as to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions.

2. 2. The force sensor according to claim 1, wherein the optical element that enables light to be measured simultaneously from two or more directions is a prism.

3. 2. The force sensor according to claim 1, further comprising: (v) a mirror between (iii) an optical element that enables simultaneous measurement of light from two or more directions and (iv) the imaging unit.

4. Further, (vi) a computer is provided, the computer having an algorithm or software capable of analyzing the displacement of the pattern on the surface of the plate imaged by the imaging unit through an optical element that enables the light to be measured simultaneously from two or more directions, and calculating the force applied to the plate from the spring constant of the spring unit and the displacement of the pattern, or Further, the device is connected to a computer, and the computer has an algorithm or software that can analyze the displacement of the pattern on the surface of the plate imaged by the imaging unit through an optical element that enables the light to be measured simultaneously from two or more directions, and calculate the force applied to the plate from the spring constant of the spring unit and the displacement of the pattern. The force sensor according to claim 1 .

5. An array of force sensors comprising two or more sets of (i) plates, (ii) spring parts, and (iii) optical elements capable of simultaneously measuring light from two or more directions, each set corresponding to each plate, and further comprising (iv) an imaging part, Each of said plates has a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; The imaging unit is arranged to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions. The array of force sensors.

6. 6. The force sensor array of claim 5, wherein the optical element that allows light to be measured from two or more directions simultaneously is a prism.

7. 6. The force sensor array according to claim 5, further comprising: (v) a mirror between (iii) an optical element that enables light to be measured from two or more directions simultaneously and (iv) an imaging unit.

8. Further, (vi) a computer is provided, the computer having an algorithm or software capable of analyzing the displacement of the pattern on the surface of each plate imaged by the imaging unit through an optical element that enables the light to be measured from two or more directions simultaneously, and calculating the force applied to each plate from the spring constant of the spring unit and the displacement of the pattern, and measuring the distribution of the force applied to each plate, or Further, the device is connected to a computer, and the computer has an algorithm or software that can analyze the displacement of the pattern on the surface of each plate, which is imaged by the imaging unit through an optical element that enables the light to be measured from two or more directions simultaneously, calculate the force applied to each plate from the spring constant of the spring unit and the displacement of the pattern, and measure the distribution of the force applied to each plate.

6. An array of force sensors as claimed in claim 5.

9. (i) a step of capturing an image of a pattern on a surface of a plate placed on a spring portion capable of exerting elastic forces in the x, y, and z directions, by an imaging unit via an optical element that enables light to be measured simultaneously from two or more directions, at a first point in time before a force is applied to the plate and at a second point in time when a force is applied to the plate; (ii) superimposing the pattern applied on the surface of the plate at the first time point and the pattern applied on the surface of the plate at the second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; and (iii) calculating the force applied to the plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; Methods for measuring force, including:

10. 10. The method of claim 9, wherein the optical element that allows light to be measured from two or more directions simultaneously is a prism.

11. The method according to claim 9 , wherein a mirror is disposed between the imaging unit and an optical element that enables light to be measured simultaneously from two or more directions.

12. 10. The method of claim 9, wherein steps (ii) and (iii) are performed by a computer, algorithm, or software.

13. A force sensor array including two or more sets of plates, spring parts capable of exerting elastic forces in the x, y, and z directions corresponding to each plate, and optical elements capable of simultaneously measuring light corresponding to each plate from two or more directions, (i) capturing an image of the pattern formed on the surface of each plate by an imaging unit via an optical element that enables light corresponding to each plate to be measured simultaneously from two or more directions at a first time point before a force is applied to the array and at a second time point when a force is applied to the array; (ii) for each plate, superimposing a pattern applied on the surface of the plate at a first time point and a pattern applied on the surface of the plate at a second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; (iii) calculating the force applied to each plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; and (iv) measuring the distribution of forces applied to the array of force sensors. Methods for measuring force, including:

14. 14. The method of claim 13, wherein the optical element that allows light to be measured from two or more directions simultaneously is a prism.

15. The method according to claim 13 , wherein a mirror is disposed between the imaging unit and an optical element that enables light to be measured simultaneously from two or more directions.

16. 14. The method of claim 13, wherein steps (ii), (iii), and (iv) are performed by a computer, algorithm, or software.

17. A force sensor comprising: (i) a plate; (ii) a spring portion; (iii) an optical element that enables light to be measured from two or more directions simultaneously; and (iv) an imaging portion, said plate having a pattern on its surface; the spring portion is disposed so as to exert elastic forces in x, y, and z directions when a force is applied to the plate; the imaging unit is arranged to image the pattern on the plate from two or more directions via an optical element that enables the light to be measured simultaneously from two or more directions; The pattern is provided as four patterns on the top, bottom, left, and right of the position where the measurement object is placed on the force sensor, (I) the optical element that enables the (iii) light to be measured from two or more directions simultaneously is a polygon mirror, and a mirror is disposed directly below each of the four patterns; When the polygon mirror is imaged by the imaging unit, each of the four patterns can be imaged from two or more directions via the polygon mirror, or (II) the optical element (iii) that enables light to be measured from two or more directions simultaneously is four prisms, each prism being fixed directly below the four patterns, When the imaging unit images each prism, the four patterns can be imaged from two or more directions through each prism. Force sensor for 6-axis measurement.

18. 18. The force sensor according to claim 17, further comprising: (v) a mirror between (iii) an optical element that enables simultaneous measurement of light from two or more directions and (iv) the imaging unit.

19. Further, (vi) a computer is provided, the computer having an algorithm or software capable of analyzing the displacement of the pattern applied to the surface of the plate, the image of which is captured by the image capturing unit through an optical element that enables the light to be measured from two or more directions simultaneously, and calculating the force and moment applied to the plate from the spring constant of the spring unit and the displacement of the pattern, or Further, the device is connected to a computer, and the computer has an algorithm or software that can analyze the displacement of the pattern on the surface of the plate imaged by the imaging unit through an optical element that enables the light to be measured simultaneously from two or more directions, and calculate the force and moment applied to the plate from the spring constant of the spring unit and the displacement of the pattern.

20. A force sensor as claimed in claim 17.

20. (i) a step of capturing images of four patterns on a surface of a plate placed on a spring portion capable of exerting elastic forces in the x, y, and z directions by an imaging unit via one polygon mirror or four prisms at a first point in time before a force is applied to the plate and at a second point in time when a force is applied to the plate; However, when the four patterns are imaged through one polygon mirror, four mirrors are disposed between the polygon mirror and the four patterns, so that the imaging unit can image the four patterns through the one polygon mirror, or When the four patterns are imaged through four prisms, one prism is disposed directly below each of the four patterns, so that the four patterns can be imaged by the imaging unit through the four prisms; (ii) superimposing the pattern applied on the surface of the plate at the first time point and the pattern applied on the surface of the plate at the second time point, and analyzing the displacement of the pattern applied on the surface of the plate between the first time point and the second time point; and (iii) calculating the force and moment applied to the plate from the displacement of the pattern between the first time point and the second time point and the spring constant of the spring portion; Methods for measuring force, including:

21. The method according to claim 20, further comprising disposing a further mirror between the one polygon mirror or the four prisms and the imaging section.

22. 21. The method of claim 20, wherein steps (ii) and (iii) are performed by a computer, algorithm, or software.

Images