Photoacoustic microscopic imaging device and method based on photoacoustic confocal multi-depth polymerization

Abstract

The invention discloses a photoacoustic microscopic imaging device and method based on photoacoustic confocal multi-depth polymerization. The imaging device comprises a laser emission module, a photoacoustic confocal multi-depth configuration module and a system control and signal processing module. Light beams emitted by the laser emission module form a plurality of optical focuses at different depth positions on a biological sample through the photoacoustic confocal multi-depth configuration module, and a multi-source photoacoustic signal is excited; the combined structure of the hollow transducer and the photoacoustic coupler enables multiple paths of photoacoustic signals to realize photoacoustic confocal, the detection sensitivity and the imaging signal-to-noise ratio are improved, the structure is compact, the operation is flexible, and the practicability in related fields is improved; according to the method, multiple paths of signals are independently reconstructed and imaged, and a high-resolution and high-contrast imaging result is obtained through focus information extraction and fusion, so that the depth of field of photoacoustic imaging can be improved, and high-sensitivity uniform high-resolution imaging can be realized in a relatively large depth range.

Description

Technical Field

[0001] The present invention relates to the field of photoacoustic imaging technology and devices, and in particular to a photoacoustic microscopic imaging device and an imaging method based on photoacoustic confocal multi-depth polymerization. Background Art

[0002] Photoacoustic imaging combines the advantages of the high contrast characteristics of optical imaging and the deep penetration characteristics of ultrasonic imaging, achieving high-resolution, high-contrast imaging of deep tissues in living bodies. It can provide detailed information about the structure and function of biological tissues and shows great development prospects in the field of biomedical imaging.

[0003] The design of the photoacoustic imaging system mainly includes two parts: ultrasound probe design and optical system design. The design of the ultrasound probe is usually optimized at a certain focal depth, with the highest spatial resolution and imaging signal-to-noise ratio at the acoustic focus. When leaving the acoustic focus, the ultrasound beam expands, resulting in a sharp drop in spatial resolution and imaging signal-to-noise ratio. The laser focus spot size in the optical system design will also affect the imaging resolution. A smaller spot size can obtain higher-resolution photoacoustic imaging, and the overlap of the optical focus and the acoustic focus can further improve the detection sensitivity and imaging signal-to-noise ratio. Therefore, high-resolution photoacoustic imaging requires that the imaging surface has a high degree of flatness.

[0004] However, when imaging actual biological samples, such as the mouse cerebral cortex, the imaging surface is required to have a certain height difference, and a single raster scan cannot achieve focused imaging of structures at different heights, resulting in low imaging resolution. In order to solve this problem, some fast focusing and extended depth of field imaging systems have been proposed. The patent application with application number CN201810927962.X discloses a fast focusing system and method for photoacoustic microscopy. The invention uses the sample signal position and image clarity reflected in the photoacoustic B-type scanning diagram in the photoacoustic signal to continuously and automatically adjust the distance between the sample and the ultrasonic probe, so as to automatically and quickly adjust the sample to the focal plane of the laser beam, but the disadvantage is that it requires iterative search for the best focusing position, complex calculations and slow imaging speed. The patent application with application number CN202210694584.1 discloses a photoacoustic microscopy imaging system based on a high-speed focuser. The invention controls the displacement of the double-cemented lens by moving a fast linear motor, and then adjusts the focal position of the light beam, thereby improving the signal-to-noise ratio and resolution of the image. However, the disadvantage is that the photoacoustic confocality is not considered, which will cause the detection sensitivity to decrease when adjusting the focal position of the light beam. The patent application with application number CN201910048137.7 discloses a photoacoustic endoscope device and imaging method based on Bessel light extended focal depth, which can well achieve high and uniform image resolution and contrast within a certain range, while improving the detection sensitivity. However, the disadvantage is that the artifacts generated by the side lobes affect the resolution and the focal depth extension is limited. Summary of the invention

[0005] The main purpose of the present invention is to overcome at least one of the shortcomings and deficiencies of the prior art, and to propose a photoacoustic microscopic imaging device based on photoacoustic confocal multi-depth polymerization. The present invention forms multiple photoacoustic confocal planes in the depth direction through a multi-channel configuration, and the imaging process does not require multiple adjustments to the position of the focal plane, and there is no positioning error. When applied to the field of microscopic imaging of biological samples, it can maintain high-speed and high-resolution imaging within a certain depth range, and the image resolution is more uniform and the imaging signal-to-noise ratio is higher.

[0006] Another object of the present invention is to provide an imaging method using the above-mentioned photoacoustic microscopy imaging device. The present invention applies photoacoustic confocal multi-depth polymerization to the field of photoacoustic microscopy imaging for the first time, and realizes high-resolution and efficient photoacoustic microscopy imaging by extracting focus information and fusing imaging of imaging results on different focal planes. Especially when performing microscopy imaging on non-planar biological samples, it can maintain uniform high resolution within a larger depth range and has a higher imaging signal-to-noise ratio.

[0007] In order to achieve the above first purpose, the present invention adopts the following technical solutions:

[0008] A photoacoustic microscopic imaging device based on photoacoustic confocal multi-depth polymerization, including a laser emission module, a photoacoustic confocal multi-depth configuration module, and a system control and signal processing module;

[0009] The laser emission module is used to generate multiple light beams with different time delays;

[0010] The photoacoustic confocal multi-depth configuration module is used to convert the multi-path light beams into multi-path coaxial light beams, form multiple light focal points for irradiating the sample to be tested in the depth direction and generate multi-source photoacoustic signals;

[0011] The multi-source photoacoustic signals are transmitted to the system control and signal processing module for data processing, image reconstruction, and focus information extraction and fusion imaging. The system control and signal processing module is also responsible for controlling the laser triggering in the laser emission module.

[0012] Preferably, the laser emission module includes a pulse laser, a neutral density filter, a fiber coupler, and a fiber bundle, which are arranged in sequence. The fiber bundle includes multiple optical fibers and is used to output multiple light beams with different time delays. During operation, the laser is emitted from the pulse laser, passes through the neutral density filter, and enters the fiber coupler. The neutral density filter is used to adjust the light intensity (the rotation axis of the filter is perpendicular to the direction of the light path and is firmly installed. The light intensity is adjusted by rotating the filter); one end of the fiber bundle is connected to the fiber coupler, which is used to adjust the output energy ratio of the fiber bundle. The other end is fixed at different heights to output multiple light beams.

[0013] Preferably, the pulse laser outputs laser light with a wavelength of 532 nm.

[0014] Preferably, the optical fiber bundle includes three optical fibers, and the optical fiber coupler adjusts the output energy of the three optical fibers in the optical fiber bundle in a proportional manner, and the energy ratio of the optical fiber bundle is 37%:31%:32%.

[0015] Preferably, the system control and signal processing module includes an amplifier, a low-pass filter and a host computer arranged in sequence; the signal received from the photoacoustic confocal multi-depth configuration module is input into the system control and signal processing module via the amplifier, and the host computer is also used to control the pulse laser. The received signal is amplified by the amplifier, filtered by the low-pass filter and stored in the host computer, which performs signal processing and fuses the image through image reconstruction and focus information extraction.

[0016] Preferably, the optical fiber bundle comprises n optical fibers, which are used to output n optical beams with different time delays;

[0017] The photoacoustic confocal multi-depth configuration module includes a reflecting prism, n double-glued lenses, n-1 cubic beam splitters, and a multi-channel photoacoustic signal receiver. The reflecting prism, n-1 cubic beam splitters, and the multi-channel photoacoustic signal receiver are arranged in sequence, and the reflecting prism, n-1 cubic beam splitters, and the n double-glued lenses are arranged one by one opposite to each other, and the output ends of the n optical fibers are arranged one by one opposite to the n double-glued lenses.

[0018] Preferably, the multi-channel photoacoustic signal receiver includes a focusing lens, a prism group, a planar transducer, an acoustic lens and n-1 hollow transducers, the focusing lens is located on the side wall of the prism group, the planar transducer is located on the top of the prism group, the bottom surface of the acoustic lens is a curved surface, the acoustic lens and the n-1 hollow transducers are located below the prism group, the n-1 hollow transducers are nested with each other, and the acoustic lens is nested in the innermost hollow transducer.

[0019] Preferably, the multi-channel photoacoustic signal receiver further comprises a linear displacement stage for driving the multi-channel photoacoustic signal receiver to adjust its position.

[0020] Preferably, the system control and signal processing module is also responsible for controlling the laser triggering in the laser emission module and the movement of the linear translation stage.

[0021] Preferably, the linear translation stage comprises three single-axis stepper motors and adopts open-loop control.

[0022] Preferably, the hollow transducer comprises a hollow cylindrical backing layer and an annular high-frequency piezoelectric element, and the annular high-frequency piezoelectric element is fitted on the concave surface at the bottom of the hollow cylindrical backing layer.

[0023] Preferably, the backing layer of the hollow cylinder is made of epoxy resin material, and the annular high-frequency piezoelectric element is made of PVDF material to focus and receive the photoacoustic signal.

[0024] Preferably, the planar transducer is made of piezoelectric ceramic material, bonded to the prism group by epoxy resin, and receives the photoacoustic signal passing through the acoustic lens.

[0025] Preferably, the optical fiber bundle includes three optical fibers, the photoacoustic confocal multi-depth configuration module is provided with three double-cemented lenses, defined as a first double-cemented lens, a second double-cemented lens, and a third double-cemented lens, and two cubic beam splitters are provided, defined as a first cubic beam splitter and a second cubic beam splitter, and the multi-channel photoacoustic signal receiver is provided with two hollow transducers, defined as a first hollow transducer and a second hollow transducer, and the first beam of light passes through the first double-cemented lens after coming out of the optical fiber, is reflected at the reflecting prism, and passes through the first cubic beam splitter and the second cubic beam splitter to form a first coaxial light; the second beam of light comes out of the optical fiber After coming in, it enters the second double-glued lens, passes through the first cubic beam splitter and the second cubic beam splitter to form the second coaxial light; the third beam of light comes out of the optical fiber and enters the third double-glued lens, passes through the second cubic beam splitter to form the third coaxial light; the three coaxial light beams finally pass through the focusing lens, prism group, and acoustic lens to form three optical focal points at different depths, which are irradiated on the sample to be tested to generate photoacoustic signals; the acoustic lens is nested in the first hollow transducer, and the first hollow transducer is nested in the second hollow transducer. The acoustic lens, the first hollow transducer, and the second hollow transducer are respectively focused on three different optical focal points to achieve photoacoustic confocality. The first hollow transducer and the second hollow transducer focus on receiving the photoacoustic signal, and the planar transducer uses the acoustic lens to receive the photoacoustic signal. The photoacoustic signal is received by the corresponding transducer and converted into three electrical signals.

[0026] Preferably, the reflective prism is silver-coated, and the average reflectivity is greater than 97%; the beam splitting ratio of the first cubic beam splitter is 50%:50%; and the beam splitting ratio of the second cubic beam splitter is 70%:30%.

[0027] Preferably, the prism group includes two prisms, which are bonded together by UV-curing glue, wherein the lower prism is aluminum-coated, and the acoustic lens, the first hollow transducer and the second hollow transducer are fixed to the prism group by epoxy resin.

[0028] Preferably, the radius of the arc surface of the acoustic lens is given by the formula R=f(c g -c w ) / c g Sure.

[0029] Preferably, the host computer also controls the pulse laser to emit laser pulses, collect data and control the movement of the linear translation stage.

[0030] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0031] The photoacoustic microscopic imaging method based on photoacoustic confocal multi-depth polymerization includes the following steps:

[0032] A photoacoustic microscopic imaging method based on photoacoustic confocal multi-depth polymerization, the method comprising the steps of:

[0033] Excitation: Generate multiple beams with different time delays through the laser emission module;

[0034] Multiple light beams enter the photoacoustic confocal multi-depth configuration module, forming light focal points at different depths, which are irradiated on the sample to be tested to stimulate multi-source photoacoustic signals;

[0035] Data acquisition: The multi-source photoacoustic signals generated by the sample to be tested are detected by the hollow transducer and the planar transducer. The received photoacoustic signals are converted into multi-channel electrical signals for transmission, and are stored in the host computer after amplification and filtering.

[0036] Image reconstruction: The host computer reconstructs the collected multi-channel electrical signals separately, extracts and fuses the focus information of the multiple photoacoustic images obtained, and completes the high-resolution reconstruction of the photoacoustic images.

[0037] Preferably, the host computer emits laser pulses, collects data and controls the movement of the linear translation stage, and utilizes the movement of the linear translation stage to implement raster scanning to acquire full-width photoacoustic data.

[0038] Preferably, the step of extracting and fusing focus information of the multiple photoacoustic images obtained by processing comprises:

[0039] Convert multiple photoacoustic images into matrix data and extract the focus information of the images;

[0040] The weight distribution of the winner-takes-all strategy is performed according to the focal information of the image;

[0041] High-resolution and high-contrast photoacoustic images are obtained through weighted superposition and fusion.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] (1) The present invention adopts a photoacoustic confocal multi-depth aggregation method to perform photoacoustic imaging with extended depth of field through multiple photoacoustic confocal points in the depth direction. It does not require known height change information of biological structures to complete uniform high-resolution imaging over a large range in the depth direction, and the imaging signal-to-noise ratio is relatively high.

[0044] (2) The present invention adopts a multi-focus information extraction fusion reconstruction method with fast processing speed and high precision, thus achieving high-speed and high-sensitivity detection.

[0045] (3) The photoacoustic microscopy imaging device provided by the present invention has a simple and compact structure, a small size, and is flexible to operate. It does not require repeated adjustment of the focus position and has high positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic structural diagram of a photoacoustic microscopy imaging device provided in an embodiment of the present invention;

[0047] Figure 2 Schematic diagram of the nested structure of the hollow transducer in the embodiment of the present invention;

[0048] Figure 3 is a schematic diagram of a multi-focus information extraction, fusion and reconstruction method in an embodiment of the present invention;

[0049] Among them, 1-laser emission module; 101-pulse laser; 102-neutral density filter; 103-fiber coupler; 104-fiber bundle; 2-photoacoustic confocal multi-depth configuration module; 201-first double glued lens; 202-second double glued lens; 203-third double glued lens; 204-reflecting prism; 205-first cube beam splitter; 206-second cube beam splitter; 207-focusing lens; 208-prism group; 209-acoustic lens; 210-water tank; 211-first hollow transducer; 212-second hollow transducer; 213-planar transducer; 214-linear translation stage; 3-system control and signal processing module; 301-amplifier; 302-low-pass filter, 303-host computer. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with embodiments and drawings.

[0051] like Figure 1As shown, a photoacoustic microscopic imaging device based on photoacoustic confocal multi-depth polymerization provided by the present invention includes a laser emission module 1, a photoacoustic confocal multi-depth configuration module 2 and a system control and signal processing module 3.

[0052] The laser emission module 1 is used to generate the multi-path light beams required by the system. After being emitted from the optical fiber, the multi-path light beams enter the photoacoustic confocal multi-depth configuration module 2. After passing through the focusing lens group and the reflecting prism or the cube beam splitter, the multi-path light beams become multi-path coaxial light beams, forming multiple light foci in the depth direction to illuminate the sample to be tested and generate multi-source photoacoustic signals. The multi-channel photoacoustic signal receiver in the photoacoustic confocal multi-depth configuration module 2 realizes photoacoustic signal reception with high detection sensitivity through the photoacoustic confocal configuration. The multi-channel photoacoustic signal (multi-source photoacoustic signal) is transmitted to the system control and signal processing module 3 for data processing, image reconstruction, and focus information extraction and fusion imaging. The system control and signal processing module 3 is also responsible for controlling the laser triggering in the laser emission module 1 and the movement of the linear translation stage in the photoacoustic confocal multi-depth configuration module 2.

[0053] The system control and signal processing module 3 includes an amplifier 301, a low-pass filter 302 and a host computer 303. The laser emission module 1 includes a pulse laser 101, a neutral density filter 102, a fiber coupler 103 and a fiber bundle 104 arranged in sequence; the laser is emitted from the pulse laser 101, passes through the neutral density filter 102 and enters the fiber coupler 103; multiple light beams with different time delays are output through the fiber bundle 104 and enter the photoacoustic confocal multi-depth configuration module 2, and the host computer 303 is connected to the pulse laser 101. In one embodiment of the present invention, the host computer 303 can control the repetition frequency, output power and wavelength of the pulse laser 101. The output laser passes through the neutral density filter 102 for light intensity attenuation adjustment, enters the fiber coupler 103 and then enters the fiber bundle 104. The other ends of the fiber bundle 104 are respectively fixed at different heights, and the length of each optical fiber in the fiber bundle 104 is different, so that multiple light beams with different time delays are output.

[0054] In one embodiment of the present invention, the number of optical fibers in the optical fiber bundle 104 is 3, that is, 3 light beams with different time delays are output through the optical fiber bundle 104. The following description is based on the output of 3 light beams. It can be understood that in other embodiments, the number of optical fibers in the optical fiber bundle 104 can also be set to other values.

[0055] The photoacoustic confocal multi-depth configuration module 2 includes a first double-cemented lens 201, a second double-cemented lens 202, a third double-cemented lens 203, a reflecting prism 204, a first cubic beam splitter 205, a second cubic beam splitter 206 and a multi-channel photoacoustic signal receiver. The reflecting prism 204, the first cubic beam splitter 205, the second cubic beam splitter 206 and the multi-channel photoacoustic signal receiver are arranged in sequence. The first double-cemented lens 201 is arranged opposite to the reflecting prism 204, the second double-cemented lens 202 is arranged opposite to the first cubic beam splitter 205, and the third double-cemented lens 203 is arranged opposite to the second cubic beam splitter 206. The multi-channel photoacoustic signal receiver includes a planar transducer 213, a focusing lens 207, a prism group 208, an acoustic lens 209, a first The hollow transducer 211, the second hollow transducer 212 and the linear translation stage 214, the focusing lens 207 are located on the side wall of the prism group 208 and opposite to the second cubic beam splitter 206, the planar transducer 213 is located at the top of the prism group 208, the acoustic lens 209, the first hollow transducer 211, and the second hollow transducer 212 are located at the bottom of the prism group 208, and the acoustic lens 209 is nested in the first hollow transducer 211, and the first hollow transducer 211 is nested in the second hollow transducer 212, the focusing positions of the acoustic lens 209, the first hollow transducer 211 and the second hollow transducer 212 respectively coincide with the optical foci at three different depth positions formed by the multi-path light beams to achieve photoacoustic confocality, and the linear translation stage 214 is used to drive the multi-channel photoacoustic signal receiver to move.

[0056] During operation, the first beam of light output by the optical fiber bundle 104 passes through the first double-cemented lens 201 after coming out of the optical fiber, is reflected at the reflecting prism 204, and then passes through the first cubic beam splitter 205 and the second cubic beam splitter 206 in sequence to form a first beam of coaxial light; the second beam of light enters the second double-cemented lens 202 after coming out of the optical fiber, and then passes through the first cubic beam splitter 205 and the second cubic beam splitter 206 in sequence to form a second beam of coaxial light; the third beam of light enters the third double-cemented lens 203 after coming out of the optical fiber, and passes through the second cubic beam splitter 206 to form a third beam of coaxial light; the three beams of coaxial light finally pass through the focusing lens 207, the prism group 208, and the acoustic lens 209 in sequence to form three optical foci (since the height distance between the position where each beam of light emerges from the optical fiber and the double-cemented lens is different, the three optical foci formed are located at different depths), and are irradiated onto the sample to be tested to generate a photoacoustic signal.

[0057] The light focus formed by the light beam through the first double-cemented lens 201 coincides with the focusing position of the acoustic lens 209, the light focus formed by the light beam through the second double-cemented lens 202 coincides with the focusing position of the first hollow transducer 211, and the light focus formed by the light beam through the third double-cemented lens 203 coincides with the focusing position of the second hollow transducer 212, thereby achieving photoacoustic confocality and improving detection sensitivity.

[0058] In other embodiments, when the number of optical fibers in the optical fiber bundle 104 is other numbers, it is necessary to adjust the number of optical fibers in the optical fiber bundle to be consistent with the required number of light focal points, increase the cubic beam splitters accordingly and adjust the splitting ratio of each beam splitter, and increase the number of nested hollow transducers accordingly to always ensure photoacoustic confocality. For example, assuming that the number of optical fibers in the optical fiber bundle 104 is n, the number of double-cemented lenses is n, the number of cubic beam splitters is n-1, and the number of hollow transducers is n-1. The reflecting prism and n-1 beam splitters are arranged in sequence, and the reflecting prism, n-1 beam splitters and the correspondingly arranged double-cemented lenses are arranged one by one relative to each other.

[0059] In one embodiment of the present invention, the energy ratio of the optical fiber bundle 104 is 37%:31%:32%, the reflecting prism 204 is silver-coated, the average reflectivity is greater than 97%, the splitting ratio of the first cubic beam splitter 205 is 50%:50%, and the splitting ratio of the second cubic beam splitter 206 is 70%:30%, thereby ensuring that the laser energy used to excite the multi-source photoacoustic signal is basically consistent.

[0060] The first hollow transducer 211 and the second hollow transducer 212 directly focus the received photoacoustic signal, and the planar transducer 213 receives the photoacoustic signal after focusing using the acoustic lens 209. The photoacoustic signal is received by different transducers and converted into three-way electrical signals, which are processed by the amplifier 301 and the low-pass filter 302 and stored in the host computer 303. In one embodiment of the present invention, the amplifier 301 amplifies the signal by 48dB, the cutoff frequency of the low-pass filter 302 is 70MHz, and the host computer 303 collects the signal at a frequency of 200MHz, with a sampling accuracy of 14 bits. The host computer 303 simultaneously controls the linear translation stage to perform scanning motion, and after the entire imaging area is scanned, signal processing and image reconstruction are performed in the host computer 303, and the trigger signal for data acquisition is sent by the host computer 303.

[0061] See also Figure 2In one embodiment of the present invention, the first hollow transducer 211 and the second hollow transducer 212 both include a hollow cylindrical backing layer 2111 and an annular high-frequency piezoelectric element 2112 , and the annular high-frequency piezoelectric element 2112 is attached to the concave surface at the bottom of the hollow cylindrical backing layer 2111 . The acoustic lens 209 is nested in the center hole of the first hollow transducer 211, and the first hollow transducer 211 is nested in the center hole of the second hollow transducer 212. The bottom surface of the acoustic lens 209 is an arc surface, and the upper surfaces of the acoustic lens 209, the first hollow transducer 211 and the second hollow transducer 212 are flush. The upper surfaces of the acoustic lens 209, the first hollow transducer 211 and the second hollow transducer 212 are fixedly connected to the prism group 208 through epoxy resin, and the planar transducer 213 is bonded to the top of the prism group 208 through epoxy resin to receive the photoacoustic signal passing through the acoustic lens 209. The focusing lens 207 is located on the side wall of the prism group 208.

[0062] In some embodiments of the present invention, the focal length of the acoustic lens 209 is 5.54 mm, the focal length of the first hollow transducer 211 is 5.79 mm, the focal length of the second hollow transducer 212 is 6.04 mm, the hollow cylinder backing layer is made of epoxy resin material, the annular high-frequency piezoelectric element is made of PVDF material, and the planar transducer 213 is made of piezoelectric ceramic material. The radius of the arc surface of the acoustic lens 209 is given by the formula R=f(c g -c w ) / c g Determine, f is the focal length of the acoustic lens, c g is the speed of sound in the acoustic lens material, c w is the acoustic velocity of the coupled material.

[0063] In one embodiment of the present invention, the prism assembly 208 is obtained by bonding the inclined surfaces of two prisms relative to each other.

[0064] In one embodiment of the present invention, a photoacoustic microscopy imaging method based on photoacoustic confocal multi-depth polymerization is also provided, comprising the following steps:

[0065] (1) The biological sample is fixed in the water tank 210, and the photoacoustic confocal multi-depth polymerization photoacoustic microscopy imaging device is started. The pulse laser 101 emits a short pulse laser of 532 nm to form three light focal points in the depth direction of the biological sample.

[0066] (2) The host computer 303 controls the linear translation stage to perform raster scanning. The photoacoustic signals generated by the excitation are received by the two hollow transducers and the planar transducer and converted into three electrical signals. The signals are then transmitted to the amplifier 301 and the filter 302 through the acquisition signal line. After being amplified and filtered, the signals are transmitted to the host computer 301 for storage and processing.

[0067] (3) The host computer 303 independently reconstructs the three signals through programming, and uses the existing photoacoustic signal processing method to process the data to obtain three photoacoustic signal images.

[0068] (4) The three photoacoustic signal reconstruction images are converted into matrix data I1, I2, I3, and the focus information of the image is extracted by the focus extraction function F GLV get:

[0069]

[0070] Where u is the average grayscale of the image, N is the number of pixels in the two-dimensional neighborhood window, and I (x,y) is the matrix data of the reconstructed image, x is the column-wise position index of the matrix data, and y is the row-wise position index of the matrix data.

[0071] Extract results based on focus information Perform weight distribution for the winner-takes-all strategy, such as Then k1(x, y) = 1, k2(x, y) = 0, k3(x, y) = 0, k is the weight matrix; finally, the high-resolution and high-contrast photoacoustic image PI is obtained by weight superposition fusion. The fusion process is as follows: Figure 2 shown.

[0072]

[0073] The device and method provided by the aforementioned embodiments of the present invention can improve the depth of field of photoacoustic imaging, can achieve high-sensitivity uniform high-resolution imaging within a large depth range, and at the same time have a high imaging signal-to-noise ratio, are highly adaptable to biological samples with different complex structures, and can be widely used in the field of biomedical imaging.

[0074] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A photoacoustic microscopic imaging device based on photoacoustic confocal multi-depth polymerization, characterized in that: It includes laser emission module, photoacoustic confocal multi-depth configuration module, system control and signal processing module; The laser emission module is used to generate multiple light beams with different time delays; The photoacoustic confocal multi-depth configuration module is used to convert the multi-path light beams into multi-path coaxial light beams, form multiple light focal points for irradiating the sample to be tested in the depth direction and generate multi-source photoacoustic signals; The multi-source photoacoustic signals are transmitted to the system control and signal processing module for data processing, image reconstruction, and focus information extraction and fusion imaging. The system control and signal processing module is also responsible for controlling the laser triggering in the laser emission module.

2. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 1, characterized in that: The laser emission module (1) comprises a pulse laser (101), a neutral density filter (102), a fiber coupler (103) and a fiber bundle (104) which are arranged in sequence; the fiber bundle (104) comprises a plurality of optical fibers and is used to output multiple light beams with different time delays.

3. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 2, characterized in that: The system control and signal processing module (3) comprises an amplifier (301), a low-pass filter (302) and a host computer (303) which are arranged in sequence; the signal received from the photoacoustic confocal multi-depth configuration module is input into the system control and signal processing module (3) via the amplifier (301), and the host computer (303) is also used to control the pulse laser (101).

4. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 1, characterized in that: The optical fiber bundle (104) comprises n optical fibers, and is used to output n optical beams with different time delays; The photoacoustic confocal multi-depth configuration module (2) comprises a reflection prism, n double-glued lenses, n-1 cubic beam splitters, and a multi-channel photoacoustic signal receiver. The reflection prism, n-1 cubic beam splitters, and the multi-channel photoacoustic signal receiver are arranged in sequence, and the reflection prism, n-1 cubic beam splitters, and the n double-glued lenses are arranged one by one opposite to each other, and the output ends of the n optical fibers are arranged one by one opposite to the n double-glued lenses.

5. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 4, characterized in that: The multi-channel photoacoustic signal receiver comprises a focusing lens (207), a prism group (208), a planar transducer (213), an acoustic lens (209) and n-1 hollow transducers, wherein the focusing lens (207) is located on the side wall of the prism group (208), the planar transducer (213) is located on the top of the prism group (208), the bottom surface of the acoustic lens (209) is a curved surface, the acoustic lens (209) and the n-1 hollow transducers are located below the prism group (208), the n-1 hollow transducers are nested with each other, and the acoustic lens (209) is nested in the innermost hollow transducer.

6. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 5, characterized in that: The multi-channel photoacoustic signal receiver also includes a linear displacement stage (214) for driving the multi-channel photoacoustic signal receiver to adjust its position.

7. The photoacoustic microscopy imaging device based on photoacoustic confocal multi-depth polymerization according to claim 5, characterized in that: The hollow transducer comprises a hollow cylindrical backing layer and an annular high-frequency piezoelectric element, wherein the annular high-frequency piezoelectric element is arranged on the concave surface at the bottom of the hollow cylindrical backing layer.

8. A photoacoustic microscopic imaging device based on photoacoustic confocal multi-depth polymerization according to any one of claims 5 to 7, characterized in that: The optical fiber bundle (104) includes three optical fibers; the photoacoustic confocal multi-depth configuration module (2) is provided with three double-cemented lenses, which are defined as a first double-cemented lens (201), a second double-cemented lens (202), and a third double-cemented lens (203); two cubic beam splitters are provided, which are defined as a first cubic beam splitter (205) and a second cubic beam splitter (206); the multi-channel photoacoustic signal receiver is provided with two hollow transducers, which are defined as a first hollow transducer (211) and a second hollow transducer (212); after a first beam of light comes out of the optical fiber, it passes through the first double-cemented lens (201), is reflected by a reflection prism (204), and passes through the first cubic beam splitter (205) and the second cubic beam splitter (206) to form a first beam of coaxial light; After the second beam of light comes out of the optical fiber, it enters the second double-cemented lens (202), passes through the first cubic beam splitter (205) and the second cubic beam splitter (206), and forms a second beam of coaxial light; after the third beam of light comes out of the optical fiber, it enters the third double-cemented lens (203), passes through the second cubic beam splitter (206), and forms a third beam of coaxial light; the three beams of coaxial light finally pass through the focusing lens (207), the prism group (208), and the acoustic lens (209) to form three optical focal points at different depths, and the optical focal points can be irradiated on the sample to be tested, so that it generates a photoacoustic signal; the acoustic lens (20 9) The first hollow transducer (211) is nested in the first hollow transducer (211), and the first hollow transducer (211) is nested in the second hollow transducer (212). The focusing positions of the acoustic lens (209), the first hollow transducer (211), and the second hollow transducer (212) respectively coincide with the light focal points at three different depth positions to achieve photoacoustic confocality. The first hollow transducer (211) and the second hollow transducer (212) focus on receiving photoacoustic signals, and the planar transducer (213) uses the acoustic lens (209) to receive photoacoustic signals. After being received by different transducers, the photoacoustic signals are converted into three electrical signals.

9. A photoacoustic microscopy imaging method based on photoacoustic confocal multi-depth polymerization, characterized in that: Using the device of claim 5, the method comprises the steps of: Generate multiple light beams with different time delays through a laser emission module; The multiple light beams enter the photoacoustic confocal multi-depth configuration module (2), forming light focal points at different depths, and irradiating the sample to be tested to stimulate multi-source photoacoustic signals; The multi-source photoacoustic signals generated by the excited sample to be tested are detected by the hollow transducer and the planar transducer, and the received photoacoustic signals are converted into multi-channel electrical signals for transmission to the system control and signal processing module; The system control and signal processing module reconstructs the collected multi-channel electrical signals separately, extracts and fuses the focus information of the multiple photoacoustic images obtained, and completes the high-resolution reconstruction of the photoacoustic images.

10. The photoacoustic microscopy imaging method based on photoacoustic confocal multi-depth polymerization according to claim 9, characterized in that: The step of extracting and fusing focus information from the multiple photoacoustic images obtained by processing comprises: Convert multiple photoacoustic images into matrix data and extract the focus information of the images; The weight distribution of the winner-takes-all strategy is performed according to the focal information of the image; High-resolution and high-contrast photoacoustic images are obtained through weighted superposition and fusion.

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