Visual tactile sensor fused with optical waveguide and preparation method of visual tactile sensor

Abstract

The invention discloses a visual tactile sensor fused with an optical waveguide and a preparation method thereof, and belongs to the technical field of intelligent tactile sensing. The visual tactile sensor comprises a fixed shell, and the top end of the fixed shell is open; the composite tactile sensing layer is arranged at the opening position of the fixed shell, and the composite tactile sensing layer is sequentially composed of a shading layer, a reflecting layer, a red-green spaced fluorescent layer, an elastic deformation layer and a supporting layer from top to bottom; and the optical lighting and sensing component comprises a blue LED light bar, an array light intensity sensor and a camera, the blue LED light bar and the array light intensity sensor are arranged on the two corresponding sides of the composite touch sensing layer respectively, and the camera is arranged at the bottom in the fixed shell. Through fusion of rapid and stable light intensity detection characteristics of optical waveguide sensing and pressure distribution detection capability of the visual tactile sensor, high-resolution space and texture identification and high-sensitivity mechanical response detection are simultaneously realized in a single sensor architecture.

Description

Technical Field

[0001] This invention belongs to the field of intelligent tactile sensing technology, specifically relating to a visual tactile sensor integrating optical waveguides and its fabrication method. Background Technology

[0002] Tactile sensors are a key component of intelligent robots, human-computer interaction, and medical devices. Among them, optical tactile sensors have become an important solution for robot tactile perception due to their high sensitivity, resistance to electromagnetic interference, and ability to be designed flexibly. The fusion optical tactile sensor involved in this invention is closest to two existing technologies: image recognition-based visual tactile sensors and optical waveguide-based optical sensors. Visual tactile sensors have high resolution and can intuitively present texture and contact patterns, but they are easily affected by external lighting and are insufficient for detecting minute forces and deep deformations. Optical waveguide sensors are sensitive to mechanical response and have high stability, making them suitable for detecting contact intensity and distribution, but they are difficult to provide high-resolution spatial position and texture information, and have limited ability to resolve complex multi-point tactile scenes.

[0003] Patent application number 202310057168.5 pertains to the design of a tactile sensor based on a flexible waveguide array. This technology discloses a prosthetic finger for fingertip tactile perception based on a flexible waveguide array, comprising an interlocking finger body and fingertip. A sensor composed of force-sensitive and temperature-sensitive units is embedded in the fingertip. The force-sensitive units are arranged with flexible waveguides, intersecting perpendicularly in pairs, with contacts joined at the intersections. The temperature-sensitive unit is disposed on the outer layer of the force-sensitive unit, with an MXene temperature-sensitive layer embedded on its surface. This invention achieves 2*2 quasi-distributed tactile force detection through a flexible waveguide array encapsulation structure, enabling the collection of more fingertip tactile perception information. It realizes quasi-distributed fingertip pressure sensing detection, and on this basis, achieves active perception of object contours, hardness, slippage, and temperature, as well as tactile perception of touch trajectory recognition, object dragging, and simple object roughness comparison. Compared to the existing technology that detects only one tactile force, this technology offers stronger tactile perception capabilities. Its core lies in utilizing a 2×2 distributed array, with the entire system packaged in PDMS. Four-color LEDs are coupled to each waveguide, and the distinction between each contact point and the reading of mechanical information are achieved by using spectral peaks. Its limitations are that the spatial resolution and multi-point concurrency capability are constrained by the array density; the sensing mechanism mainly relies on the loss modulation caused by the deformation of light intensity in the waveguide along the propagation path, and it does not provide a high-resolution imaging channel; the system's functionality relies on multi-color light coupling and spectral readout links, and the overall structure needs to maintain precise matching between waveguide convergence and connectors. These characteristics together limit its scalability in larger-scale, higher-resolution fingertip tactile imaging scenarios.

[0004] Patent application number 202510824840.8 pertains to the design of a visual-tactile sensor. This technology discloses a visual-tactile sensor module for a robot end effector. The visual-tactile sensor includes a housing, an elastomer, a light-transmitting plate, and a camera, a light source, and a light-diffusing plate disposed within the housing. The elastomer is connected to the front surface of the light-transmitting plate, which is embedded in the front end of the housing. The elastomer protrudes from the front surface of the housing. The light-transmitting plate is made of a light-transmitting material. One end of the light-diffusing plate corresponds to the light source, and the other end corresponds to the side of the light-transmitting plate. The light-transmitting plate is used to transmit light from the side to the front surface of the light-transmitting plate. This allows for more uniform light illumination on the surface of the elastomer connected to the front surface of the light-transmitting plate, effectively improving the uniformity of the internal light source's supplementary illumination, thereby improving the imaging quality, accuracy, and stability of the elastomer. Its core feature is that the light emitted from the light source is transformed into a uniform surface light source through a light-diffusing plate, enters from the side of the light-transmitting plate, and is uniformly emitted from the front surface after internal conduction, thereby improving the imaging quality and measurement accuracy of elastic body deformation images. Its limitations lie in the lack of a direct, quantitative mechanical readout channel; in complex multi-point contact or dynamic slippage, image features are prone to overlap or ambiguity; its imaging quality is highly dependent on internal supplementary lighting and illumination uniformity, and is easily affected by ambient light. Furthermore, it is difficult to simultaneously achieve high sensitivity and high frequency response in mechanical detection and deep strain sensing.

[0005] Therefore, there is a need for a visual-tactile sensor that integrates optical waveguides and its fabrication method to solve the above problems. Summary of the Invention

[0006] To address the aforementioned issues, namely how to overcome the performance limitations of single optical tactile sensing technology and realize a tactile sensor that combines image spatial resolution, high response speed, and high-sensitivity mechanical detection, this invention provides a visual tactile sensor integrating optical waveguides and its fabrication method.

[0007] This invention provides a visual-tactile sensor integrating optical waveguides, comprising: A fixed housing, wherein the top of the fixed housing is open; A composite tactile sensing layer is disposed at the opening of the fixed outer shell. The composite tactile sensing layer consists of, from top to bottom, a light-shielding layer, a reflective layer, a red-green alternating fluorescent layer, an elastic deformation layer, and a support layer. The optical illumination and sensing components include a blue LED light strip, an array light intensity sensor, and a camera. The blue LED light strip and the array light intensity sensor are respectively disposed on opposite sides of the composite tactile sensing layer, and the camera is disposed at the bottom of the fixed housing.

[0008] Preferably, the light-shielding layer is a thin film made of silicone doped with black pigment.

[0009] Preferably, the reflective layer is a thin film made of silicone doped with aluminum powder and aluminum foil.

[0010] Preferably, the fluorescent layer is made by mixing red and green fluorescent powders with silica gel.

[0011] Preferably, the elastic deformation layer is a soft and elastic transparent layer made of polydimethylsiloxane.

[0012] Preferably, the support layer is a transparent flexible substrate made of polydimethylsiloxane.

[0013] Preferably, the composite tactile sensing layer further includes glass, which is disposed below the support layer, and the glass is transparent.

[0014] Preferably, the composite tactile sensing layer further includes a light-filtering film disposed below the glass, and the light-filtering film is orange-yellow in color.

[0015] Preferably, the blue LED light strip is flush with the elastic deformation layer, and the array light intensity sensor is flush with the elastic deformation layer.

[0016] This invention also provides a method for fabricating a visual-tactile sensor integrating an optical waveguide, comprising the following steps: S1: Printing and preparing the striped mold; S2: Preparation of spaced fluorescent stripes: Mix silica gel and green phosphor at a mass ratio of 2:1, stir evenly and remove bubbles, then pour into a striped mold, smooth the surface and let it stand for complete curing. Then, remove excess silica gel at every interval of one stripe. Mix silica gel and red phosphor at a mass ratio of 2:1, stir evenly and remove bubbles, then pour into a striped mold, smooth and remove excess silica gel, and let it cure completely, thus obtaining a fluorescent layer with alternating green and red stripes. S3: Preparation of reflective layer: Mix silicone with aluminum powder and aluminum foil in a mass ratio of 400:20:3, stir evenly and degas, then pour into the mold of fluorescent stripes to form a 0.5mm thick reflective layer. Cover the upper surface of the mold with glass and wait for it to fully cure, thus making the glass, reflective layer and fluorescent stripes into one piece. S4: Preparation of elastic deformation layer: Remove the previously prepared reflective layer with spaced fluorescent stripes along with the glass, make a dam on the side, mix the A phase and B phase of PDMS at a mass ratio of 20:1, stir thoroughly and degas for 30 minutes, pour the PDMS mixed solution into the spaced fluorescent stripes to form a 2mm thick transparent elastic layer. S5: Preparation of support layer: Based on the preparation in step S4, a dam is made on the side. The A phase and B phase of PDMS are mixed in a mass ratio of 2:1. After stirring thoroughly, the bubbles are degassed for 30 minutes. The PDMS mixed solution is poured onto the elastic deformation layer, and glass is covered on the surface and an orange-yellow filter film is attached. It is left to cure for 48 hours to form a 2mm thick integrated transparent support layer. S6: Preparation of the light-shielding layer: Remove the prepared composite silicone from the glass connected to the reflective layer, mix the silicone with the black color paste in a mass ratio of 20:1, stir evenly to remove bubbles, and then use a brush to coat a thin layer of light-shielding layer on the surface of the reflective layer. S7: Assembly: Assemble the camera, blue LED light strip, array light intensity sensor and fixed shell with the composite tactile sensing layer prepared in step S6 to complete the fabrication of the fused optical waveguide visual tactile sensor.

[0017] The beneficial effects of this invention are as follows: 1. This invention integrates the fast and stable light intensity detection characteristics of optical waveguide sensing with the pressure distribution detection capability of visual-tactile sensors, thereby achieving high-resolution spatial and texture recognition and high-sensitivity mechanical response detection within a single sensor architecture.

[0018] 2. Compared with the original optical waveguide sensor that can only detect pressure at a single point, the present invention can output a two-dimensional pressure distribution image of the contact area. At the same time, based on the high-precision light intensity detection characteristics of optical waveguide sensing, the force sensing range and accuracy are effectively improved.

[0019] 3. Through structural integration, this invention can reuse the light propagation layer and illumination system based on two optical principles, thereby improving the compactness of the structure.

[0020] 4. In addition to the robot grasping and micro-manipulation force feedback scenarios covered by the original two types of sensors, this invention, due to its combination of pressure distribution, high response speed and fine texture, and force perception, can be further applied to robot dynamic operation, precision assembly, medical rehabilitation and human-computer interaction scenarios. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the isometric structure of the present invention; Figure 2 This is a schematic diagram of the exploded structure of the composite tactile sensing layer of the present invention; Figure 3 This is a schematic diagram of the exploded structure of the present invention; Figure 4 This is a schematic diagram of the half-section structure of the present invention.

[0022] In the picture: 1. Composite tactile sensing layer; 11. Light-shielding layer; 12. Reflective layer; 13. Fluorescent layer; 14. Elastic deformation layer; 15. Support layer; 16. Glass; 17. Filter film; 2. Fixed shell; 3. Blue LED light strip; 4. Array light intensity sensor; 5. Camera. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] like Figures 1-4 As shown, this embodiment discloses a visual-tactile sensor integrating optical waveguides, including a fixed housing 2 with an opening at the top; a composite tactile sensing layer 1 disposed at the opening of the fixed housing 2, the composite tactile sensing layer 1 consisting of a light-shielding layer 11, a reflective layer 12, a red-green alternating fluorescent layer 13, an elastic deformation layer 14, and a support layer 15 from top to bottom; and optical illumination and sensing components, including a blue LED light strip 3, an array light intensity sensor 4, and a camera 5, the blue LED light strip 3 and the array light intensity sensor 4 respectively disposed on corresponding sides of the composite tactile sensing layer 1, and the camera 5 disposed at the bottom inside the fixed housing 2.

[0025] like Figure 2 As shown, the light-shielding layer 11 is a thin film made of silicone doped with black pigment. The light-shielding layer 11 is used to isolate ambient light interference.

[0026] like Figure 2 As shown, the reflective layer 12 is a thin film made of silicone doped with aluminum powder and aluminum foil. The reflective layer 12 is used to provide high-contrast visual texture features and for internal reflection of the waveguide.

[0027] like Figure 2 As shown, the fluorescent layer 13 is made of red and green fluorescent powder mixed with silica gel. The red and green alternating fluorescent layer 13 is used to provide striped markings for visual and tactile perception and to form a tri-color light source in the striped areas under blue light illumination.

[0028] like Figure 2 As shown, the elastic deformable layer 14 is a soft and elastic transparent layer made of polydimethylsiloxane (PDMS). The elastic deformable layer 14 is used to transmit contact, force and texture information of the object surface, and also for the propagation of optical signals of the optical waveguide through total internal reflection within its interior.

[0029] like Figure 2As shown, the support layer 15 is a rigid yet flexible transparent substrate made of polydimethylsiloxane (PDMS). The support layer 15 can provide support for the structure.

[0030] like Figure 2 As shown, the composite tactile sensing layer 1 also includes glass 16, which is disposed below the support layer 15. Glass 16 is transparent glass. Glass 16 can provide rigid, non-deformable support and fixation for the composite tactile sensing layer 1.

[0031] like Figure 2 As shown, the composite tactile sensing layer 1 also includes a light-filtering film 17, which is disposed below the glass 16 and is orange-yellow in color. The orange-yellow light-filtering film 17 can filter out excessively strong blue light for visual-tactile sensing, thereby providing a soft light source for visual-tactile sensing.

[0032] like Figure 1 and Figure 3 As shown, the blue LED strip 3 is fixed to the side of the composite tactile sensing layer 1 and is flush with the elastic deformation layer 14. The light source illuminates the interior of the tactile sensing layer 1 perpendicularly to the elastic deformation layer 14, providing tri-color illumination for the visual tactile sensor in conjunction with the red and green alternating fluorescent layer 13, and also serving as the light source for the optical waveguide sensor. The array light intensity sensor 4 is fixed to the side of the composite tactile sensing layer 1 away from the blue LED strip 3 and is flush with the elastic deformation layer 14. The array light intensity sensor 4 directly receives the light intensity of the blue LED strip 3 after it passes through the elastic deformation layer 14. When the elastic deformation layer 14 undergoes local deformation due to external force, the array light intensity sensor 4 at the corresponding position will detect a significant attenuation of light intensity.

[0033] The composite tactile sensing layer 1 is the core component of the tactile sensor; it is the area that directly contacts the environment, undergoes deformation, and converts the deformation into light signals. For example... Figure 1 As shown, the fixed outer shell 2 is a cuboid, housing a composite tactile sensing layer 1, a blue LED light strip 3, an array light intensity sensor 4, and a camera 5. The camera 5 is responsible for capturing images of the tactile sensing layer, thereby analyzing contact, force, and texture information.

[0034] This embodiment also discloses a method for fabricating a visual-tactile sensor integrating an optical waveguide, comprising the following steps: S1: Printing and preparing the striped mold; S2: Preparation of the spaced fluorescent layer: Mix silica gel and green phosphor at a mass ratio of 2:1, stir evenly and degas, then pour into a striped mold, scrape the surface and let it stand for complete curing. Then, remove the excess silica gel every other strip. Mix silica gel and red phosphor at a mass ratio of 2:1, stir evenly and degas, then pour into a striped mold, scrape the surface to remove excess silica gel and wait for it to completely cure, thus obtaining a fluorescent layer with green-red alternating arrangement. S3: Preparation of reflective layer: Mix silicone with aluminum powder and aluminum foil in a mass ratio of 400:20:3, stir evenly and degas, then pour into the mold of fluorescent stripes to form a 0.5mm thick reflective layer. Cover the upper surface of the mold with glass and wait for it to fully cure, thus making the glass, reflective layer and fluorescent layer into one piece. S4: Preparation of elastic deformation layer: Remove the previously prepared reflective layer with red and green spaced fluorescent layer along with the glass, make a dam on the side, mix the A phase and B phase of polydimethylsiloxane at a mass ratio of 20:1, stir thoroughly and degas for 30 minutes, pour the polydimethylsiloxane mixed solution into the space of the fluorescent layer to form a 2mm thick transparent elastic layer. S5: Preparation of support layer: Based on the preparation in step S4, a dam is made on the side. The A phase and B phase of polydimethylsiloxane are mixed in a mass ratio of 2:1. After stirring thoroughly, the bubbles are degassed for 30 minutes. The polydimethylsiloxane mixture is poured onto the elastic deformation layer, and glass is covered on the surface and an orange-yellow filter film is attached. It is left to cure for 48 hours to form a 2mm thick integrated transparent support layer. S6: Preparation of the light-shielding layer: Remove the prepared composite silicone from the glass connected to the reflective layer, mix the silicone with the black color paste in a mass ratio of 20:1, stir evenly to remove bubbles, and then use a brush to coat a thin layer of light-shielding layer on the surface of the reflective layer. S7: Assembly: Assemble the camera, blue LED light strip, array light intensity sensor and fixed shell with the composite tactile sensing layer prepared in step S6 to complete the fabrication of the fused optical waveguide visual tactile sensor.

[0035] The known applications of this invention include, but are not limited to: high-precision force perception and shape recognition in grasping or manipulating intelligent robots; human-computer interaction devices that provide immersive tactile feedback in virtual reality (VR) and augmented reality (AR); multi-dimensional tactile perception in scenarios such as flexible assembly, grasping of small parts and detection of surface defects; and as an information collection platform for robot skill learning.

[0036] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A visual-tactile sensor integrating optical waveguides, characterized in that, include: A fixed outer casing (2) has an opening at its top; The composite tactile sensing layer (1) is disposed at the opening of the fixed shell (2). The composite tactile sensing layer (1) is composed of a light-shielding layer (11), a reflective layer (12), a red-green alternating fluorescent layer (13), an elastic deformation layer (14), and a support layer (15) from top to bottom. The optical lighting and sensing components include a blue LED light strip (3), an array light intensity sensor (4), and a camera (5). The blue LED light strip (3) and the array light intensity sensor (4) are respectively disposed on opposite sides of the composite tactile sensing layer (1), and the camera (5) is disposed at the bottom inside the fixed housing (2).

2. The visual-tactile sensor integrating optical waveguides according to claim 1, characterized in that, The light-shielding layer (11) is a thin film made of silicone doped with black pigment.

3. The visual-tactile sensor integrating optical waveguides according to claim 1, characterized in that, The reflective layer (12) is a thin film made of silicone doped with aluminum powder and aluminum foil.

4. A visual-tactile sensor integrating an optical waveguide according to claim 1, characterized in that, The fluorescent layer (13) is made of red or green fluorescent powder mixed with silica gel.

5. A visual-tactile sensor integrating an optical waveguide according to claim 1, characterized in that, The elastic deformation layer (14) is a soft and elastic transparent layer made of polydimethylsiloxane.

6. A visual-tactile sensor integrating an optical waveguide according to claim 1, characterized in that, The support layer (15) is a transparent flexible substrate made of polydimethylsiloxane.

7. A visual-tactile sensor integrating optical waveguides according to claim 1, characterized in that, The composite tactile sensing layer (1) also includes glass (16), which is disposed below the support layer (15) and is transparent.

8. A visual-tactile sensor integrating an optical waveguide according to claim 7, characterized in that, The composite tactile sensing layer (1) also includes a light filter film (17), which is disposed below the glass (16) and is orange-yellow in color.

9. A visual-tactile sensor integrating an optical waveguide according to claim 1, characterized in that, The blue LED light strip (3) is flush with the elastic deformation layer (14), and the array light intensity sensor (4) is flush with the elastic deformation layer (14).

10. A method for fabricating a visual-tactile sensor integrating optical waveguides, characterized in that, The preparation of the visual-tactile sensor according to any one of claims 1-9 comprises the following steps: S1: Printing and preparing the striped mold; S2: Preparation of the spaced fluorescent layer: Mix silica gel and green phosphor at a mass ratio of 2:1, stir evenly and degas, then pour into a striped mold, scrape the surface and let it stand for complete curing. Then, remove the excess silica gel every other strip. Mix silica gel and red phosphor at a mass ratio of 2:1, stir evenly and degas, then pour into a striped mold, scrape the surface to remove excess silica gel and wait for it to completely cure, thus obtaining a fluorescent layer with green-red alternating arrangement. S3: Preparation of reflective layer: Mix silicone with aluminum powder and aluminum foil in a mass ratio of 400:20:3, stir evenly and degas, then pour into the mold of fluorescent stripes to form a 0.5mm thick reflective layer. Cover the upper surface of the mold with glass and wait for it to fully cure, thus making the glass, reflective layer and fluorescent layer into one piece. S4: Preparation of elastic deformation layer: Remove the previously prepared reflective layer with red and green spaced fluorescent layer along with the glass, make a dam on the side, mix the A phase and B phase of polydimethylsiloxane at a mass ratio of 20:1, stir thoroughly and degas for 30 minutes, pour the polydimethylsiloxane mixed solution into the space of the fluorescent layer to form a 2mm thick transparent elastic layer. S5: Preparation of support layer: Based on the preparation in step S4, a dam is made on the side. The A phase and B phase of polydimethylsiloxane are mixed in a mass ratio of 2:

1. After stirring thoroughly, the bubbles are degassed for 30 minutes. The polydimethylsiloxane mixture is poured onto the elastic deformation layer, and glass is covered on the surface and an orange-yellow filter film is attached. It is left to cure for 48 hours to form a 2mm thick integrated transparent support layer. S6: Preparation of the light-shielding layer: Remove the prepared composite silicone from the glass connected to the reflective layer, mix the silicone with the black color paste in a mass ratio of 20:1, stir evenly to remove bubbles, and then use a brush to coat a thin layer of light-shielding layer on the surface of the reflective layer. S7: Assembly: Assemble the camera, blue LED light strip, array light intensity sensor and fixed shell with the composite tactile sensing layer prepared in step S6 to complete the fabrication of the fused optical waveguide visual tactile sensor.

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