A fouling detection device and method based on photoacoustic imaging

Abstract

The application discloses a fouling detection device and method based on photoacoustic imaging, wherein the detection device comprises: a sealed cover with at least one transparent surface; a photoacoustic excitation module comprising a laser, an optical fiber bundle and a plurality of micro-fiber collimators; the micro-fiber collimators are integrated in the transparent surface and used for irradiating laser outside the transparent surface to generate a photoacoustic signal; a photoacoustic collection module arranged along the propagation direction of the photoacoustic signal and used for collecting the photoacoustic signal; and a data processing module in communication connection with the photoacoustic collection module and used for calculating the fouling degree outside the transparent surface according to the collected photoacoustic signal. The application adopts nanosecond-level light pulses to improve the detection accuracy; and the laser sequentially traverses the optical fiber, so that the position of fouling can be accurately located, and a reliable basis is provided for fouling removal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underwater detection, and in particular to a fouling detection device and method based on photoacoustic imaging. BACKGROUND

[0002] Marine biofouling on the surface of underwater instruments and equipment usually causes drift of observation signals and data errors, which seriously affects the service life of the instruments and equipment; with the aggravation of fouling, the necessary frequency and cost of manual maintenance also increase sharply. Therefore, timely detection of underwater fouling is necessary for effective removal of fouling and protection of instruments and equipment.

[0003] However, due to the underwater light conditions and the strong scattering, reflection and refraction of light in water, in-situ monitoring of biofouling on the surface of underwater instruments and equipment based on traditional optical detection is difficult to effectively achieve.

[0004] In view of the above, there is a need to design a fouling detection device and method based on photoacoustic imaging to solve the problems in the prior art. SUMMARY

[0005] The present application provides a fouling detection device and method based on photoacoustic imaging, which solves the problem of inaccurate observation signals caused by the difficulty in detecting marine biofouling on the surface of underwater instruments and equipment.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A fouling detection device based on photoacoustic imaging, comprising:

[0008] a sealed cover provided with at least one transparent surface;

[0009] a photoacoustic excitation module comprising a laser, an optical fiber bundle and a plurality of micro-fiber collimators, one end of the optical fiber bundle is connected with the laser through an optical switch, and the other end is connected with a plurality of micro-fiber collimators respectively; the micro-fiber collimators are integrated in the transparent surface for irradiating laser outside the transparent surface to generate photoacoustic signals;

[0010] a photoacoustic acquisition module arranged along the propagation direction of the photoacoustic signals for collecting the photoacoustic signals;

[0011] a data processing module in communication connection with the photoacoustic acquisition module and calculating the degree of fouling outside the transparent surface according to the collected photoacoustic signals.

[0012] In some embodiments of the present application, the micro-fiber collimators are arranged in an array on the transparent surface; the optical switch is used to control the laser to traverse the optical fiber bundle; and the laser emitted by the laser is pulsed laser.

[0013] In some embodiments of the present application, the photoacoustic acquisition module comprises an ultrasonic transducer, a signal amplifier and a data acquisition card connected in sequence; the ultrasonic transducer is arranged in the propagation direction of the photoacoustic signal and used for receiving the photoacoustic signal; the signal amplifier is used for amplifying the photoacoustic signal collected by the ultrasonic transducer and sending the amplified photoacoustic signal to the data acquisition card; and the data acquisition card is used for transmitting the amplified photoacoustic signal to the data processing module.

[0014] In some embodiments of the present application, the data processing module is used for dividing the transparent surface into a plurality of virtual grids, and the plurality of micro-fiber collimators are respectively located in each virtual grid.

[0015] In some embodiments of the present application, the detection method of the fouling detection device comprises the following steps:

[0016] S1, the laser emits pulsed laser, enters the micro-fiber collimator through the optical fiber bundle, and irradiates the transparent surface outside the micro-fiber collimator to generate a photoacoustic signal;

[0017] S2, after the ultrasonic transducer collects the photoacoustic signal in the step S1, the photoacoustic signal enters the data acquisition card through the signal amplifier, and the data acquisition card inputs data to the data processing module;

[0018] S3, the data processing module obtains the amplitude Ai of the photoacoustic signal after pre-processing the data, and then calculates the original amplitude A0i of the photoacoustic signal;

[0019] S4, the data processing module assigns a value to the brightness value of each imaging grid according to the original amplitude A0i in the step S3, and then performs normalization to obtain an initial image, which is the detection result.

[0020] In some embodiments of the present application, the pre-processing in the step S3 comprises filtering and denoising the data in the step S2.

[0021] In some embodiments of the present application, the calculation formula of the original amplitude A0i in the step S3 is:

[0022] ;

[0023] Wherein, α is the ultrasonic attenuation coefficient of seawater, and Li is the distance between the ultrasonic transducer and the micro-fiber collimator.

[0024] In some embodiments of the present application, the following formula is used for normalization processing to obtain normalized data in the step S4 :

[0025] ;

[0026] wherein, is the maximum value of the original amplitude A0i.

[0027] In some embodiments of the present application, the step S4 further comprises converting the normalized data to obtain the initial image; the conversion formula is:

[0028] .

[0029] In some embodiments of the present application, when the number of ultrasonic transducers is multiple, the step S4 further comprises the following steps:

[0030] The data processing module can obtain the detection result after superimposing the initial image corresponding to each ultrasonic transducer.

[0031] The technical scheme of the present application has the following technical effects relative to the prior art:

[0032] The present application uses a sealed cover with a transparent surface, integrates an optical fiber and a collimator thereon, irradiates the transparent surface with laser light, and uses a data processing module to process the photoacoustic signal excited thereby to determine the degree of contamination of the transparent surface; the use of nanosecond-level light pulses makes the light energy in a short time higher, and the ultrasonic transducer can easily detect the photoacoustic signal, thereby improving the accuracy of detection; meanwhile, the array collimator and the optical fiber are integrated on the transparent surface, and the laser light sequentially traverses the optical fiber, so that the imaging obtained by the ultrasonic transducer and the data processing module can accurately locate the position of the contamination, thereby providing a reliable basis for the removal of the contamination.

[0033] In addition, the data processing module inverses the initial amplitude of the photoacoustic signal excited by the contamination according to the extracted amplitude of the photoacoustic signal, and then obtains the accurate degree of contamination. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0035] Figure 1 Fig. 1 is a structural schematic diagram of a contamination detection device shown in the embodiments.

[0036] Figure 2 Fig. 2 is a structural schematic diagram of a sealed cover and a photoacoustic excitation module shown in the embodiments.

[0037] Figure 3 Fig. 3 is an installation schematic diagram of the micro optical fiber collimator and the transparent surface shown in the embodiments.

[0038] 100 - Sealing cover; 110 - Transparent surface; 120 - Virtual grid; 200 - Photoacoustic excitation module; 210 - Laser; 220 - Optical fiber bundle; 230 - Optical switch; 240 - Micro-fiber collimator; 300 - Photoacoustic acquisition module; 310 - Ultrasonic transducer; 320 - Signal amplifier; 330 - Data acquisition card; 400 - Data processing module. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0040] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or detachably connected, or integrally connected. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0041] Embodiment 1

[0042] Referring to Figure 1 and Figure 2 As shown in the drawings, a fouling detection device based on photoacoustic imaging comprises:

[0043] The sealing cover 100 is provided with at least one transparent surface 110;

[0044] The sealing cover 100 can be processed into a photoacoustic sealing cover according to the shape of the underwater instrument, and a sealing cavity is formed inside for placing the underwater instrument to prevent the underwater instrument from contacting with seawater, realize the sealing of the instrument, and facilitate the laser conduction; The fouling attached to the transparent surface 110 can represent the fouling attached to the surface of the underwater instrument; For the transparent surface 110, organic glass can be used as the main material.

[0045] A photoacoustic excitation module 200, comprising a laser 210, an optical fiber bundle 220 and a plurality of micro-fiber collimators 240, one end of the optical fiber bundle 220 is connected with the laser 210 through an optical switch 230, and the other end is connected with the plurality of micro-fiber collimators 240 respectively; the micro-fiber collimators 240 are integrated in the transparent surface 110 for irradiating laser to the outside of the transparent surface 110 to generate a photoacoustic signal.

[0046] Specifically, the laser 210 can be installed at a position above the water surface, and the laser emitted by the laser 210 is connected with the optical switch 230 through an optical fiber, that is, introduced into the optical switch 230, the optical switch 230 can be arranged underwater, and the optical switch 230 controls the order of laser entering the optical fiber bundle 220, thereby determining the order of laser emitted by the micro-fiber collimator 240.

[0047] A photoacoustic collection module 300 arranged along the propagation direction of the photoacoustic signal for collecting the photoacoustic signal;

[0048] A data processing module 400 in communication connection with the photoacoustic collection module 300 and calculating the degree of fouling outside the transparent surface 110 according to the collected photoacoustic signal.

[0049] In some embodiments of the present application, for the transparent surface 110, referring to Figure 3 As shown, the data processing module 400 can divide the transparent surface 110 into a plurality of virtual grids 120, and the plurality of micro-fiber collimators 240 are located in each virtual grid 120 respectively, specifically, the micro-fiber collimator 240 is located at the center of the virtual grid 120, and the micro-fiber collimators 240 are distributed in an array on the transparent surface 110.

[0050] In some embodiments of the present application, a plurality of transparent surfaces 110 can be arranged on the sealing cover 100, and the micro-fiber collimator 240 is integrated on each transparent surface 110, and the photoacoustic collection module 300 is arranged in the emission direction of the micro-fiber collimator 240 on each transparent surface 110, so that the degree of fouling on each transparent surface 110 can be collected and calculated.

[0051] In some embodiments of the present application, for the photoacoustic excitation module 200, the laser emitted by the laser 210 is pulse laser, and the pulse width is ns level (usually 8-10 ns); specifically, the wavelength of the pulse laser is determined by the strongest wavelength band of the light absorption coefficient of the fouling substance, and the commonly used wavelengths are 532 nm, 808 nm and 1064 nm, and the wavelength of the laser can also be selected according to the type of fouling.

[0052] The optical switch 230 is used to control the laser to traverse the fiber bundle 220; the entering sequence can be determined according to requirements, such as linear type, S type, spiral type, etc. When the laser emitted by the micro optical fiber collimator 240 irradiates on the contamination on the transparent surface 110, the contamination material generates a photoacoustic effect, and a photoacoustic signal can be excited.

[0053] In some embodiments of the present application, for the photoacoustic acquisition module 300, the photoacoustic acquisition module 300 comprises an ultrasonic transducer 310, a signal amplifier 320 and a data acquisition card 330 which are sequentially connected in communication; the ultrasonic transducer 310 is arranged in the propagation direction of the photoacoustic signal, and is used to receive the photoacoustic signal; the signal amplifier 320 is used to amplify the photoacoustic signal collected by the ultrasonic transducer 310 and then send it to the data acquisition card 330; the data acquisition card 330 is used to transmit the amplified photoacoustic signal to the data processing module 400.

[0054] In some embodiments of the present application, for the data processing module 400, after receiving the photoacoustic signal sent by the data acquisition card 330, the degree of contamination of the current transparent surface 110 can be obtained by calculation.

[0055] In some embodiments of the present application, the detection method of the contamination detection device comprises the following steps:

[0056] S1, the laser 210 emits pulsed laser, which enters the micro optical fiber collimator 240 through the fiber bundle 220, and irradiates outside the transparent surface by the micro optical fiber collimator 240 to generate a photoacoustic signal;

[0057] S2, after the ultrasonic transducer 310 collects the photoacoustic signal in the step S1, it sequentially receives the photoacoustic signal corresponding to each virtual grid 120, enters the data acquisition card 330 through the signal amplifier 320, and the data acquisition card 330 inputs data to the data processing module 400;

[0058] S3, the data processing module 400 obtains the amplitude Ai of the photoacoustic signal corresponding to each virtual grid after pre-processing the data, and then calculates the original amplitude A0i of the photoacoustic signal;

[0059] Specifically, the data processing module 400 filters and denoises the data in the step S2, that is, performs cross-correlation operation on the laser signal emitted by the laser and the photoacoustic signal collected by the ultrasonic transducer, to obtain the amplitude Ai of the photoacoustic signal;

[0060] The amplitude A of the photoacoustic signal is inversed to the original amplitude A0i of the photoacoustic signal caused by the fouling at the transparent surface 110 where each micro-fiber collimator 240 is located according to the distance Li between each micro-fiber collimator 240 and the ultrasonic transducer 310 and the seawater ultrasonic attenuation coefficient a at the temperature at that time,

[0061] The formula for calculating the original amplitude A0i is:

[0062] ;

[0063] Wherein, the maximum value of the original amplitude A0i is taken as ;

[0064] In the design process of the detection device, the distance Li between each micro-fiber collimator 240 and the ultrasonic transducer 310 has been determined.

[0065] S4, the data processing module assigns a brightness value to each imaging grid according to the original amplitude A0i in step S3, and then normalizes to obtain an initial image, which is the detection result.

[0066] Specifically, the brightness value of each imaging grid is proportional to the amplitude Ai corresponding to it, that is, the original amplitude A0i can be used to represent the brightness value, and then the data processing module 400 uses the following formula to perform normalization processing to obtain normalized data :

[0067] ;

[0068] Wherein, is the maximum value of the original amplitude A0.

[0069] At this point, the initial image formed by the normalized data can display the detection result. Specifically, the stronger the photoacoustic signal, that is, the brighter the initial image, the more serious the fouling degree at the corresponding grid.

[0070] Embodiment 2

[0071] In this embodiment, in order to obtain a picture consistent with the expression habit and normal sense of sight, the step S4 further includes converting the normalized data to obtain the initial image; the conversion formula is:

[0072] .

[0073] The initial image formed by the normalized data can display the detection result. Specifically, the stronger the photoacoustic signal, that is, the darker the initial image, the more serious the fouling degree at the corresponding grid.

[0074] Embodiment 3

[0075] In the embodiment, when the number of the ultrasonic transducers 310 is multiple, the photoacoustic signal excited by the fouling at each virtual grid 120 can be received by the multiple ultrasonic transducers 310; that is, if the number of the ultrasonic transducers 310 is N, the data processing module 400 can obtain N initial images, and the step S4 further includes the following steps:

[0076] The data processing module 400 superimposes the initial images corresponding to each ultrasonic transducer, and the detection result can be obtained after superimposing the N initial images.

[0077] In addition, in the embodiment, because the points with strong photoacoustic signals have the same position in each initial image, the brightest point is rounded up (or rounded), and the obtained number should be the number of the ultrasonic transducers 310 participating in the detection. By using this method, whether the ultrasonic transducer 310 is in a non-working state can be detected; one case is that the ultrasonic transducer 310 is completely broken and cannot collect photoacoustic signals, so that the data in the data acquisition card 330 is empty. Another case is that the ultrasonic transducer 310 is faulty, and meaningless signal sequences are obtained, which can be regarded as white noise. After the normalization processing of the data processing module 400, most points tend to 1, and then after conversion, they tend to zero.

[0078] The technical scheme of the present application has the following technical effects relative to the prior art:

[0079] The present application integrates the optical fiber and the collimator on the sealed cover 100 with the transparent surface 110, irradiates the fouling outside the transparent surface 110 with the laser, and processes the photoacoustic signal excited by the fouling by using the data processing module 400 to determine the fouling degree of the transparent surface 110; the nanosecond-level light pulse has high light energy in a short time, and the ultrasonic transducer 310 can easily detect the photoacoustic signal, thereby improving the detection accuracy; meanwhile, the array collimator and the optical fiber are integrated on the transparent surface 110, the laser sequentially traverses the optical fiber, the imaging obtained by the ultrasonic transducer 310 and the data processing module 400 can accurately locate the position of the fouling, and a reliable basis is provided for the removal of the fouling. In addition, the data processing module 400 inverses the initial amplitude of the photoacoustic signal excited by the fouling according to the extracted amplitude of the photoacoustic signal, and then obtains the accurate fouling degree.

[0080] In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0081] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A detection method of a fouling detection device, characterized by, The fouling detection device comprises: a sealed cover provided with at least one transparent surface; a photoacoustic excitation module comprising a laser, a fiber bundle and a plurality of micro-fiber collimators, one end of the fiber bundle is connected with the laser through an optical switch, and the other end is connected with the plurality of micro-fiber collimators respectively; the micro-fiber collimators are integrated in the transparent surface for irradiating laser outside the transparent surface to generate photoacoustic signals; a photoacoustic collection module arranged along the propagation direction of the photoacoustic signals for collecting the photoacoustic signals; a data processing module in communication connection with the photoacoustic collection module and calculating the degree of fouling outside the transparent surface according to the collected photoacoustic signals; the photoacoustic collection module comprises an ultrasonic transducer, a signal amplifier and a data acquisition card connected in sequence; the ultrasonic transducer is arranged in the propagation direction of the photoacoustic signals for receiving the photoacoustic signals; the signal amplifier is used for amplifying the photoacoustic signals collected by the ultrasonic transducer and sending them to the data acquisition card; the data acquisition card is used for transmitting the amplified photoacoustic signals to the data processing module; the detection method comprises the following steps: S1, the laser emits pulsed laser, which enters the micro-fiber collimator through the fiber bundle, and irradiates outside the transparent surface through the micro-fiber collimator to generate photoacoustic signals; S2, after the ultrasonic transducer collects the photoacoustic signals in step S1, the photoacoustic signals enter the data acquisition card through the signal amplifier, and the data acquisition card inputs data to the data processing module; S3, the data processing module obtains the amplitude Ai of the photoacoustic signal after preprocessing the data, and then calculates the original amplitude A0i of the photoacoustic signal; the calculation formula of the original amplitude A0i is: ； wherein, α is the seawater ultrasonic attenuation coefficient, and Li is the distance between the ultrasonic transducer and the micro-fiber collimator; S4, the data processing module assigns values to the brightness values of each imaging grid according to the original amplitude A0i in step S3, and then normalizes to obtain an initial image, which is the detection result; The normalization data is obtained by using the following formula in the step S4 : ； wherein is the maximum value of the original amplitude A0i.

2. The detection method according to claim 1, characterized in that, the micro-fiber collimators are arranged in an array on the transparent surface; the optical switch is used to control the laser to traverse the fiber bundle; the laser emitted by the laser is pulsed laser.

3. The method of claim 1, wherein, The data processing module is used to divide the transparent surface into a plurality of virtual grids, and the plurality of micro-fiber collimators are respectively located in each virtual grid.

4. The method of claim 1, wherein The preprocessing in step S3 includes filtering and denoising the data in step S2.

5. The method of claim 1, wherein The step S4 further comprises converting the normalized data to obtain the initial image; the conversion formula is: 。 6. The method of claim 1, wherein when the number of ultrasonic transducers is multiple, the step S4 further comprises the following steps: the data processing module superimposes the initial images corresponding to each ultrasonic transducer to obtain the detection result.

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