CN112415096B - Super-resolution photoacoustic imaging system and method based on saturable absorption effect - Google Patents
Super-resolution photoacoustic imaging system and method based on saturable absorption effect Download PDFInfo
- Publication number
- CN112415096B CN112415096B CN202011227123.0A CN202011227123A CN112415096B CN 112415096 B CN112415096 B CN 112415096B CN 202011227123 A CN202011227123 A CN 202011227123A CN 112415096 B CN112415096 B CN 112415096B
- Authority
- CN
- China
- Prior art keywords
- beam splitting
- laser
- reflector
- super
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0654—Imaging
- G01N29/0681—Imaging by acoustic microscopy, e.g. scanning acoustic microscopy
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Optics & Photonics (AREA)
- Acoustics & Sound (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
Abstract
The invention discloses a super-resolution photoacoustic imaging system and method based on a saturation absorption effect, wherein the system comprises a laser emitting module, a laser beam splitting/combining module and a signal acquisition/scanning imaging module; the laser beam splitting/combining module comprises a first beam splitting sheet, a first reflector, a chopper, a second reflector, a second beam splitting sheet, an optical delay unit and a vortex glass sheet, wherein the first beam splitting sheet, the first reflector, the chopper, the second reflector and the second beam splitting sheet are sequentially connected to form a first optical branch, and the first beam splitting sheet, the optical delay unit, the vortex glass sheet and the second beam splitting sheet are sequentially connected to form a second optical branch; the first beam splitting sheet is connected with the laser emission module, and the second beam splitting sheet is connected with the signal acquisition/scanning imaging module. The invention can realize the super-resolution photoacoustic imaging of the target object, not only can realize the super-resolution microscopy of a non-fluorophore, but also can not damage an imaging sample, thereby ensuring the authenticity of structural imaging and functional imaging.
Description
Technical Field
The invention relates to a super-resolution photoacoustic imaging system and method based on a saturation absorption effect, and belongs to the technical field of signal modulation and demodulation and photoacoustic microscopic imaging.
Background
Microscopy has played a key role in life sciences since boarding the historical arena. Optical microscopy, particularly fluorescence microscopy, allows the study of the three-dimensional structure of cells and biological tissues and the visualization of specific biomolecules with high specificity through fluorescent labeling, which is the advantage that microscopy is widely used in the fields of biology, medicine, and the like. However, the presence of optical diffraction limits causes the microscope to blur the image of objects with spatial features smaller than half the detection wavelength. In the last two decades, super-resolution microscopy has been vigorously developed, and various super-resolution microscopy technologies based on different principles have been developed to overcome diffraction limit. Optical microscopy contrast results from scattering and fluorescence, it is not possible to image non-radiative absorption contrast with sufficient sensitivity, and fluorescent labeling requires a laborious staining procedure. Most molecules, especially those in biological tissues, absorb photons of a particular wavelength and generate heat through non-radiative relaxation, while only a few species of molecules produce intense radiation, such as fluorescence. Thus, with optical absorption as a contrast, a wider variety of molecules can be imaged and microscopy extended to a wider range of applications. The advent of Photoacoustic Imaging (PAI) technology has made absorption contrast Imaging possible.
Photoacoustic imaging is a new biomedical imaging method developed in recent years, both non-invasive and non-ionizing. When pulsed laser light is irradiated into biological tissue, the light-absorbing domain of the tissue will generate an ultrasonic signal, and such an ultrasonic signal generated by light excitation is called a photoacoustic signal. The photoacoustic signal generated by the biological tissue carries the light absorption characteristic information of the tissue, and the light absorption distribution image in the tissue can be reconstructed by detecting the photoacoustic signal. In general, in photoacoustic imaging, a pulse laser is required to irradiate an imaging region (in particular, in thermoacoustic imaging, irradiation with a pulse laser of a radio frequency is used). A portion of the absorbed optical energy will be converted to thermal energy causing thermoelastic expansion of nearby tissue, resulting in a broad band (megahertz) ultrasound emission. This ultrasound can be detected with ultrasound transducers, and unlike ultrasound imaging, photoacoustic imaging exploits the differences in absorption properties of different components in the body. Photoacoustic imaging combines the advantages of the high contrast feature of optical imaging and the high penetration depth feature of ultrasound imaging, avoids the effects of light scattering in principle, and can provide high resolution and high contrast tissue imaging. Photoacoustic imaging has been developed in a striding manner in terms of detection mode, identification function parameters, technical solutions, and feasible applications.
In the traditional photoacoustic imaging, the optical absorption contrast of tissues is utilized to detect the amplitude intensity of photoacoustic signals and reconstruct the optical absorption distribution of an absorber. However, like wide-field optical microscopes, the lateral resolution of optical resolution photoacoustic microscopes (OR-PAM) is also limited by optical diffraction. Therefore, realizing the absorption contrast imaging with ultrahigh resolution becomes a significant and urgent challenge in the current super-resolution field.
Disclosure of Invention
The invention aims to provide a super-resolution photoacoustic imaging system based on a saturated absorption effect, which is a novel super-resolution microscopic technology based on a photoacoustic effect and a fluorescence-free mark, breaks through the optical diffraction limit of the existing photoacoustic microscopic technology, can realize super-resolution photoacoustic imaging on a target object, can specifically realize unmarked super-resolution photoacoustic imaging on a saturated absorption substance, can realize the super-resolution microscopy of a non-fluorophore, cannot damage an imaging sample, and ensures the authenticity of structural imaging and functional imaging.
The invention also aims to provide a super-resolution photoacoustic imaging method based on the saturated absorption effect.
The purpose of the invention can be achieved by adopting the following technical scheme:
a super-resolution photoacoustic imaging system based on a saturation absorption effect comprises a laser emitting module, a laser beam splitting/combining module and a signal acquisition/scanning imaging module;
the laser beam splitting/combining module comprises a first beam splitting sheet, a first reflector, a chopper, a second reflector, a second beam splitting sheet, an optical delay unit and a vortex glass sheet, wherein the first beam splitting sheet, the first reflector, the chopper, the second reflector and the second beam splitting sheet are sequentially connected to form a first optical branch, and the first beam splitting sheet, the optical delay unit, the vortex glass sheet and the second beam splitting sheet are sequentially connected to form a second optical branch; the laser emission module is connected with the first beam splitting sheet, and the second beam splitting sheet is connected with the signal acquisition/scanning imaging module.
Furthermore, the optical delay unit comprises a third reflector, a retroreflector, a one-dimensional translation guide rail and a fourth reflector, the first beam splitter, the third reflector, the retroreflector, the fourth reflector, the vortex glass sheet and the second beam splitter are sequentially connected to form a second optical branch, and the retroreflector is mounted on the one-dimensional translation guide rail.
Furthermore, the laser emission module comprises a short pulse laser, a first lens and a second lens, and the short pulse laser, the first lens, the second lens and the first beam splitting sheet are connected in sequence.
Further, the laser emission module further comprises a pinhole disposed at a confocal point of the first lens and the second lens.
Furthermore, the signal acquisition/scanning imaging module comprises a fifth reflector, an objective lens, an ultrasonic probe, a scanning translation stage, a preamplifier, a lock-in amplifier and an experimental machine, wherein the second beam splitter, the fifth reflector, the objective lens, the ultrasonic probe, the preamplifier, the lock-in amplifier and the experimental machine are sequentially connected, and the ultrasonic probe is arranged on the scanning translation stage and used for converting the photoacoustic signal into an electrical signal.
Further, the signal acquisition/scanning imaging module further comprises a filter, and the filter is arranged between the ultrasonic probe and the preamplifier.
Furthermore, a sample, a glass slide and a cover glass are placed on the ultrasonic probe, the sample is clamped between the glass slide and the cover glass, and an ultrasonic coupling liquid is coated between the glass slide and the ultrasonic probe.
The other purpose of the invention can be achieved by adopting the following technical scheme:
a super-resolution photoacoustic imaging method based on a saturable absorption effect, the method comprising:
in the laser emission module, a short pulse laser generates a laser beam, and the laser beam passes through a first lens, a pinhole and a second lens in sequence to carry out spatial filtering, collimation and beam expansion on the laser beam so as to obtain a Gaussian beam;
the Gaussian beam enters a laser beam splitting/combining module, is split into two beams of laser by a first beam splitting sheet, passes through a first optical branch and is subjected to intensity modulation by a chopper to form a modulated Gaussian beam; another laser beam passes through a second optical branch and is converted into a Laguerre-Gaussian mode beam by a vortex slide; the two light beams with different modes are converged into one beam by the second beam splitting sheet;
the converged light beam enters a signal acquisition/scanning imaging module, is focused by an objective lens and irradiates a sample, excites a photoacoustic signal, is converted into an electric signal by an ultrasonic probe, is subjected to voltage amplification through a preamplifier, and then sends the amplified photoacoustic signal to a detection signal input end of a phase-locked amplifier; meanwhile, a reference signal input end of the phase-locked amplifier receives a TTL signal with the same frequency as the modulation frequency of the chopper, and the phase-locked amplifier extracts a photoacoustic signal amplitude corresponding to the modulation frequency of the chopper;
in a test machine of a signal acquisition/scanning imaging module, acquiring a signal demodulated by a phase-locked amplifier and storing the signal in the test machine, and controlling a scanning translation stage to perform two-dimensional plane scanning on a sample in the horizontal plane direction; and after the scanning translation stage moves by one step and experiences time delay matched with the integration time of the lock-in amplifier, acquiring a signal demodulated by the lock-in amplifier once, wherein the photoacoustic signal acquired in the two-dimensional plane scanning area corresponds to the sample excitation position coordinate one by one.
Further, in the second optical branch, the optical delay unit controls the time difference of the two different modes of light pulse irradiating the sample, so that the light beam in the Laguerre-Gaussian mode is firstly incident on the surface of the sample, and before the particles in the excited state relax to the ground state, the modulated Gaussian light beam is then incident on the surface of the sample.
Further, the lateral resolution of the super-resolution photoacoustic imaging is calculated as follows:
NA is the numerical aperture of the imaging objective, NA ═ nsin θ, and ζ is a saturation factor, which represents the ratio of Laguerre-Gaussian intensity to saturated intensity.
Compared with the prior art, the invention has the following beneficial effects:
1. the laser beam splitting/combining module can be composed of two optical branches, namely a first optical branch and a second optical branch, firstly, laser emitted by a laser emitting module is divided into two beams of laser, one beam of laser passes through the first optical branch and is modulated by the intensity of a chopper to form a modulated Gaussian beam, the other beam of laser passes through the second optical branch and is converted into a Laguerre-Gaussian mode beam due to the phase delay effect of a vortex glass, the time difference of the two different modes of light pulse irradiating a sample is well controlled by an optical delay unit, so that the Laguerre-Gaussian mode beam is firstly incident on the surface of the sample, and the modulated Gaussian beam is incident on the surface of the sample before particles in an excited state relax to a ground state; the two modes of light are combined and then coaxially propagate, therefore, the focal points are coincident, the imaging sample needs to have the saturated absorption property, due to the saturated absorption effect, a sample area (hollow annular area) under the irradiation of the Laguerre-Gaussian mode light beam generates saturated absorption, when the modulated Gaussian light beam is incident to the sample, only the central part of the Gaussian light beam is absorbed by the sample, most of the Gaussian light beam except the central small area is hardly absorbed by the sample and transmitted out, so that the signal of the signal acquisition/scanning imaging module is only the photoacoustic signal generated by the central part of the modulated Gaussian light beam, the optical diffraction limit can be broken in the transverse direction, compared with the traditional photoacoustic imaging technology, the resolution is limited by the optical imaging diffraction limit, and the traditional photoacoustic imaging is broken by the limitation of the optical diffraction limit, the information extraction capability of the traditional photoacoustic imaging is enriched and expanded.
2. The invention can avoid the fluorescent marking of the biological sample, not only can realize the super-resolution microscopy of a non-fluorophore, but also has the advantages of nondestructiveness and ensures the authenticity of structural imaging and functional imaging. The invention also provides the possibility of fluorescence labeling-free super-resolution microscopic imaging of a living body or in vivo. The invention can show great advantages in clinical detection and medical imaging.
3. The invention has the potential to be popularized to the optical frontier and the medical field, and the invention can exert the real value of a novel microscope, thereby being tightly combined with the current scientific development trend and making contributions to material detection, clinical diagnosis and medical imaging.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a super-resolution photoacoustic imaging system based on a saturable absorption effect according to an embodiment of the present invention.
Fig. 2 is a schematic diagram illustrating the principle of improving the imaging resolution of the super-resolution photoacoustic imaging system based on the saturable absorption effect according to the embodiment of the present invention.
Fig. 3 is a schematic diagram of a photoacoustic image obtained in this embodiment.
Fig. 4 is a schematic diagram of conventional photoacoustic imaging.
The device comprises a 1-short pulse laser, a 2-first lens, a 3-pinhole, a 4-second lens, a 5-first beam splitter, a 6-first reflector, a 7-chopper, an 8-second reflector, a 9-second beam splitter, a 10-third reflector, an 11-retroreflector, a 12-one-dimensional translation guide rail, a 13-fourth reflector, a 14-vortex glass slide, a 15-fifth reflector, a 16-objective, a 17-sample, an 18-glass slide, a 19-ultrasonic coupling liquid, a 20-ultrasonic probe, a 21-scanning translation table, a 22-filter, a 23-preamplifier, a 24-phase-locked amplifier and a 25-experiment machine.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The embodiments are to be understood in conjunction with the appended drawings, which are included merely for purposes of illustration of specific embodiments in which the invention may be practiced and which are not intended to limit the invention. In the present invention, directional terms such as "up", "down", "front", "back", "left", "right", "inner", "outer", "side", etc. refer to directions of the attached drawings. Accordingly, the directional terms used are used for explanation and understanding of the present invention, and are not used for limiting the present invention.
Example (b):
as shown in fig. 1, the present embodiment provides a super-resolution photoacoustic imaging system based on the saturation absorption effect, which includes a laser emitting module, a laser splitting/combining module, and a signal collecting/scanning imaging module.
The laser emitting module is used for generating high-quality large-diameter collimation Gaussian beams and comprises a short pulse laser, a first lens 2 and a second lens 4, the short pulse laser 1, the first lens 2 and the second lens 4 are sequentially connected, the short pulse laser 1 is used for generating laser beams, and the first lens 2 and the second lens 4 are combined to collimate and expand the laser beams generated by the short pulse laser 1.
Further, the laser emission module may further include a pinhole 3, the pinhole 3 is disposed at a confocal position of the first lens 2 and the second lens 4, that is, the short pulse laser 1, the first lens 2, the pinhole 3 and the second lens 4 are sequentially connected, and the pinhole 3 performs spatial filtering on the laser generated by the short pulse laser 1 to obtain a clean gaussian beam with uniform spatial distribution.
The structure of the laser beam splitting/combining module is similar to that of a Mach-Zehnder interferometer, the laser beam splitting/combining module is used for splitting a light beam emitted by the laser emitting module into two beams and comprises a first beam splitter 5, a first reflector 6, a chopper 7, a second reflector 8, a second beam splitter 9, an optical delay unit and a vortex glass slide 14, the vortex glass slide 14 is arranged between the optical delay unit and the second beam splitter 9, the first beam splitter 5, the first reflector 6, the chopper 7, the second reflector 8 and the second beam splitter 9 are sequentially connected to form a first optical branch, and the first beam splitter 5, the optical delay unit, the vortex glass slide 14 and the second beam splitter 9 are sequentially connected to form a second optical branch; the laser emission module is connected with the first beam splitter 5, namely the short pulse laser 1, the first lens 2, the pinhole 3, the second lens 4 and the first beam splitter 5 are sequentially connected, a light beam emitted by the laser emission module is split into two laser beams by the first beam splitter 5, one laser beam passes through the first optical branch and is modulated in intensity by the chopper 7 to form a modulated Gaussian beam, the other laser beam passes through the second optical branch, the laser beam is converted into a Laguerre-Gaussian mode light beam due to the phase delay effect of the vortex glass 14, and the Laguerre-Gaussian mode light beam is a Laguerre-Gaussian mode light beam with a doughnut shape and then is converged into one beam on the second beam splitter 9.
In this embodiment, the optical delay unit is used to irradiate two different modes of light pulses to a sample successively at a fixed time difference, and includes a third reflector 10, a retroreflector 11, a one-dimensional translation guide rail 12, and a fourth reflector 13, where the first beam splitter 5, the third reflector 10, the retroreflector 11, the fourth reflector 13, the vortex glass 14, and the second beam splitter 9 are connected in sequence to form a second optical branch, the retroreflector 11 in this embodiment is a pyramid prism, and is mounted on the one-dimensional translation guide rail 12, and the retroreflector 11 is used to make the reflected light and the incident light completely parallel in the process of moving the retroreflector 11 through the one-dimensional translation guide rail 12.
The optical delay unit enables two different modes of light pulses to irradiate a sample successively at a fixed time difference, and the optical delay unit specifically comprises the following steps: the optical delay unit well controls the time difference of the light pulses in two different modes irradiating a sample, so that the Laguerre-Gaussian beam is firstly incident on the surface of the sample, and before the particles in the excited state relax to the ground state, the modulated Gaussian beam is incident on the surface of the sample; the two modes of light beams are coaxially transmitted after being combined, therefore, the focal points are overlapped, an imaging sample needs to have the property of saturated absorption, due to the saturated absorption effect, a sample area (hollow annular area) under the irradiation of the Laguerre-Gaussian mode light beam generates saturated absorption, when the modulated Gaussian light beam is incident to the sample, only the central part of the Gaussian light beam is absorbed by the sample, and most of the Gaussian light beam except the central small area is hardly absorbed by the sample and is transmitted out.
The signal acquisition/scanning imaging module comprises a fifth reflector 15, an objective lens 16, an ultrasonic probe 20, a scanning translation table 21, a preamplifier 23, a lock-in amplifier 24 and an experimental machine 25, wherein the ultrasonic probe 20 is arranged on the scanning translation table 21, the scanning translation table 21 can be a two-dimensional scanning platform driven by a stepping motor, and the second beam splitter 9 is connected with the signal acquisition/scanning imaging module, namely the second beam splitter 9, the fifth reflector 15, the objective lens 16, the ultrasonic probe 20, the preamplifier 23, the lock-in amplifier 24 and the experimental machine 25 are sequentially connected.
Further, the signal acquisition/scanning imaging module may further include a filter 22, the filter 22 is disposed between the ultrasound probe 20 and the preamplifier 22, that is, the second beam splitter 9, the fifth mirror 15, the objective lens 16, the ultrasound probe 20, the filter 22, the preamplifier 23, the lock-in amplifier 24 and the experiment machine 25, and the filter 22 is capable of filtering high-frequency noise outside the bandwidth of the ultrasound probe 20.
Further, a sample 17, a glass slide 18 and a cover glass are placed on the ultrasonic probe 20, the sample 17 is sandwiched between the glass slide 18 and the cover glass, the sample 17 is adsorbed on the glass slide 18 by van der waals force, the glass slide 18 is attached to the ultrasonic probe 20, an ultrasonic coupling liquid 19 is coated between the glass slide 18 and the ultrasonic probe, the ultrasonic coupling liquid 19 is filled to match acoustic impedance and effectively reduce acoustic attenuation, and the scanning translation stage 21 drives the ultrasonic probe 20 and the glass slide 18 attached to the ultrasonic probe 20 to realize two-dimensional plane scanning of the sample 17.
In this embodiment, the ultrasonic probe 20, the filter 22, the preamplifier 23, the lock-in amplifier 24 and the experimental machine 25 constitute a signal acquisition portion of the signal acquisition/scanning imaging module, the ultrasonic probe 20 can convert a photoacoustic signal into an electrical signal, specifically, the photoacoustic signal excited by the piezoelectric effect is converted into the electrical signal, then most of white gaussian noise is filtered by the filter 22, and after voltage amplification is performed by the preamplifier 23, an amplitude corresponding to the modulation frequency of the chopper 7 is extracted by the lock-in amplifier 24, and an effective photoacoustic signal extracted by the lock-in amplifier 24 is transmitted to the experimental machine 25 through the GPIB communication control port, wherein the signal extracted by the lock-in amplifier 24 is only a photoacoustic signal generated by the central portion of the modulated gaussian beam, so that the optical diffraction limit can be broken through in the transverse direction.
In this embodiment, the experiment machine 25 may adopt a computer, which includes a LabVIEW data acquisition and scanning control program and an MATLAB program for image reconstruction, acquires data transmitted from a GPIB communication control port by using the LabVIEW program, and may control the stepping motor to drive the scanning translation stage 21, and move the sample 17 point by point at equal intervals, so as to implement two-dimensional scanning of the sample 17; the objective lens 16 is a focusing objective lens with a numerical aperture of 0.25; the ultrasonic probe 20 adopts a high-frequency ultrasonic probe, is in the shape of a cylinder with the diameter of 11.2mm and the height of 16mm, and has the main frequency of 50MHz and the bandwidth of 80 percent; the phase-locked amplifier adopts SR 830; in this embodiment, the short pulse laser 1 is a femtosecond laser, the wavelength of the emitted pulse laser is 517nm, the pulse width is 490fs, the repetition frequency of the short pulse laser 1 itself is adjustable between 25kHz and 5MHz, and the repetition frequency is set to 300kHz in this embodiment.
In this embodiment, the super-resolution photoacoustic imaging system based on the saturable absorption effect of this embodiment may further include a bracket assembly for fixing and supporting the first lens 2, the second lens 4, the pinhole 3, the vortex glass 14, the first beam splitter 5, the second beam splitter 9, the chopper 7, the first reflector 6, the second reflector 8, the third reflector 10, the fourth reflector 13, the fifth reflector 15, the retro-reflector 11, the objective lens 16, the glass slide 18, the ultrasonic probe 20, and the scan translation stage 21, wherein the one-dimensional translation stage supporting the scan translation stage 21 is height-adjustable, so as to adjust the distance between the sample 17 and the objective lens 16.
The principle of improving the imaging resolution of the super-resolution photoacoustic imaging system based on the saturation absorption effect in this embodiment is, as shown in fig. 2, that if the light intensity of the Laguerre-Gaussian mode light beam is much less than the saturation light intensity I S The quantity of photons absorbed by a sample area under the irradiation of the Laguerre-Gaussian mode light beam is in direct proportion to the light intensity, and the spatial distribution curve of the photon absorption quantity is consistent with the light intensity distribution of the Laguerre-Gaussian mode light beam; when the incident light intensity is increased to a certain degree, the saturation of the molecular spontaneous absorption leads to the broadening of the space distribution curve of the photon absorption amount to the center and two sides, so that the central inclination angle of the space distribution curve of the photon absorption amount becomes steep, and the method has the advantages of simple structure, low cost and high efficiencyThe absorption amount of the sample to the Gaussian light is greatly reduced, the spontaneous absorption caused by the Gaussian light is mainly concentrated in the central region of the Gaussian light beam, i.e. the Gaussian light absorption amount distribution curve becomes quite narrow, and the resolution of the super-resolution photoacoustic imaging based on the saturation absorption effect is defined as the full width at half maximum of a narrow Gaussian line compressed due to the saturation absorption of the Laguerre-Gaussian mode light beam.
For molecules located at the center of the ring under Laguerre-Gaussian mode beam irradiation, the laser intensity is less than I S The photoacoustic signal linearly changes along with the light intensity of the Gaussian beam, so that the modulation depth of the photoacoustic signal is the maximum; on the ring band, molecules absorb a large amount of Laguerre-Gaussian mode beams, the molecules are strongly saturated, and the absorption of the Gaussian light arriving later is weak, resulting in a small modulation depth of the photoacoustic signal on the ring band.
In the present embodiment, the lateral resolution of the super-resolution photoacoustic imaging based on the saturation absorption effect is calculated as follows:
the numerical aperture of the imaging objective lens is NA, the NA is nsin theta, zeta is a saturation factor and represents the ratio of Laguerre-Gaussian light intensity to saturation light intensity, the larger the light intensity of the Laguerre-Gaussian mode light beam is, the larger the saturation factor is, the more obvious the saturation absorption effect is, and the stronger the transverse resolution capability is.
The embodiment also provides a super-resolution photoacoustic imaging method based on the saturable absorption effect, which comprises the following steps:
and S1, in the laser emission module, the short pulse laser 1 generates a laser beam, and the laser beam passes through the first lens 2, the pinhole 3 and the second lens 4 in sequence to perform spatial filtering, collimation and beam expansion on the laser beam to obtain a Gaussian beam.
S2, enabling the Gaussian beam to enter a laser beam splitting/combining module, splitting the Gaussian beam into two beams of laser by a first beam splitting sheet 5, and carrying out intensity modulation on one beam of laser by a chopper 7 through a first optical branch to form a modulated Gaussian beam; the other laser beam passes through a second optical branch and is converted into a Laguerre-Gaussian mode beam by the vortex slide 14; the two light beams of different modes are converged into one beam by the second beam splitter 9.
S3, enabling the converged light beam to enter a signal acquisition/scanning imaging module, focusing the light beam by an objective lens 16 to irradiate a sample 17, exciting a photoacoustic signal, converting the photoacoustic signal into an electric signal by an ultrasonic probe 20, performing voltage amplification by a preamplifier 23, and sending the amplified photoacoustic signal to a detection signal input end of a phase-locked amplifier 24; meanwhile, the reference signal input end of the phase-locked amplifier 24 receives a TTL signal with the same frequency as the modulation frequency of the chopper, and the phase-locked amplifier 24 extracts the photoacoustic signal amplitude corresponding to the modulation frequency of the chopper.
S4, in the experimental machine 25 of the signal acquisition/scanning imaging module, acquiring the signal demodulated by the phase-locked amplifier by using a LabVIEW program and storing the signal in the experimental machine 25, wherein the LabVIEW program controls the scanning translation table 21 to perform two-dimensional plane scanning on the sample 17 in the horizontal plane direction; after the scanning translation stage 21 moves one step, the signal demodulated by the lock-in amplifier 24 is collected once after the time delay matched with the integration time of the lock-in amplifier 24, and the photoacoustic signal collected in the two-dimensional plane scanning area corresponds to the excitation position coordinate of the sample 17 one by one.
The embodiment pairs MoS through the above steps 2 After the flaky crystal is scanned, the obtained photoacoustic image is shown in fig. 3, while the traditional photoacoustic imaging is shown in fig. 4, so that the limitation of the traditional photoacoustic microscopic imaging on the optical diffraction limit is broken, and the information extraction capability of the traditional photoacoustic imaging is enriched and expanded.
In summary, the laser beam splitting/combining module of the present invention may be composed of two optical branches, which are respectively a first optical branch and a second optical branch, wherein the laser beam emitted by the laser emission module is first split into two laser beams, one laser beam passes through the first optical branch and is modulated by the chopper intensity to form a modulated Gaussian beam, the other laser beam passes through the second optical branch and is converted into a Laguerre-Gaussian mode beam due to the phase delay of the vortex glass, and the optical delay unit controls the time difference between the two different modes of light pulse irradiation on the sample, so that the Laguerre-Gaussian mode beam is firstly incident on the surface of the sample, and before the excited particles relax to the ground state, the modulated Gaussian beam is then incident on the surface of the sample; the two modes of light are combined and then coaxially propagate, therefore, the focal points are coincident, the imaging sample needs to have the saturated absorption property, due to the saturated absorption effect, a sample area (hollow annular area) under the irradiation of the Laguerre-Gaussian mode light beam generates saturated absorption, when the modulated Gaussian light beam is incident to the sample, only the central part of the Gaussian light beam is absorbed by the sample, most of the Gaussian light beam except the central small area is hardly absorbed by the sample and transmitted out, so that the signal of the signal acquisition/scanning imaging module is only the photoacoustic signal generated by the central part of the modulated Gaussian light beam, the optical diffraction limit can be broken in the transverse direction, compared with the traditional photoacoustic imaging technology, the resolution is limited by the optical imaging diffraction limit, and the traditional photoacoustic imaging is broken by the limitation of the optical diffraction limit, the information extraction capability of the traditional photoacoustic imaging is enriched and expanded.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the scope of the present invention.
Claims (7)
1. A super-resolution photoacoustic imaging system based on a saturation absorption effect is characterized by comprising a laser emitting module, a laser beam splitting/combining module and a signal acquisition/scanning imaging module;
the laser beam splitting/combining module comprises a first beam splitting piece, a first reflector, a chopper, a second reflector, a second beam splitting piece, an optical delay unit and a vortex glass sheet, wherein the first beam splitting piece, the first reflector, the chopper, the second reflector and the second beam splitting piece are sequentially connected to form a first optical branch, and the first beam splitting piece, the optical delay unit, the vortex glass sheet and the second beam splitting piece are sequentially connected to form a second optical branch; the laser emission module is connected with the first beam splitting sheet, and the second beam splitting sheet is connected with the signal acquisition/scanning imaging module;
the laser emission module comprises a short pulse laser, a first lens, a second lens and a pinhole, wherein the short pulse laser, the first lens, the second lens and the first beam splitting piece are sequentially connected, and the pinhole is arranged at the confocal position of the first lens and the second lens.
2. The super-resolution photoacoustic imaging system according to claim 1, wherein the optical delay unit comprises a third reflector, a retroreflector, a one-dimensional translation guide rail and a fourth reflector, the first beam splitter, the third reflector, the retroreflector, the fourth reflector, the vortex glass sheet and the second beam splitter are sequentially connected to form a second optical branch, and the retroreflector is mounted on the one-dimensional translation guide rail.
3. The super-resolution photoacoustic imaging system according to any one of claims 1 to 2, wherein the signal acquisition/scanning imaging module comprises a fifth mirror, an objective lens, an ultrasonic probe, a scanning translation stage, a preamplifier, a lock-in amplifier and an experimental machine, the second beam splitter, the fifth mirror, the objective lens, the ultrasonic probe, the preamplifier, the lock-in amplifier and the experimental machine are connected in sequence, and the ultrasonic probe is arranged on the scanning translation stage and used for converting the photoacoustic signals into electrical signals.
4. The super resolution photoacoustic imaging system of claim 3, wherein the signal acquisition/scanning imaging module further comprises a filter disposed between the ultrasound probe and the preamplifier.
5. The super-resolution photoacoustic imaging system of claim 3, wherein the ultrasound probe has a sample, a glass slide and a cover slip placed thereon, the sample is sandwiched between the glass slide and the cover slip, and an ultrasound coupling liquid is coated between the glass slide and the ultrasound probe.
6. A super-resolution photoacoustic imaging method based on the saturation absorption effect, which is realized based on the super-resolution photoacoustic imaging system of any one of claims 3 to 5, wherein the method comprises:
in the laser emission module, a short pulse laser generates a laser beam, and the laser beam passes through a first lens, a pinhole and a second lens in sequence to carry out spatial filtering, collimation and beam expansion on the laser beam so as to obtain a Gaussian beam;
the Gaussian beam enters a laser beam splitting/combining module, is split into two beams of laser by a first beam splitting sheet, and is subjected to intensity modulation by a chopper after passing through a first optical branch to form a modulated Gaussian beam; another laser beam passes through a second optical branch and is converted into a Laguerre-Gaussian mode beam by a vortex slide; the two light beams with different modes are converged into one beam by the second beam splitting sheet; in the second optical branch, the optical delay unit well controls the time difference of the light pulses in two different modes irradiating the sample, so that the Laguerre-Gaussian mode light beam is firstly incident on the surface of the sample, and before the particles in the excited state relax to the ground state, the modulated Gaussian beam is incident on the surface of the sample;
the converged light beam enters a signal acquisition/scanning imaging module, is focused by an objective lens and irradiates a sample, excites a photoacoustic signal, is converted into an electric signal by an ultrasonic probe, is subjected to voltage amplification through a preamplifier, and then sends the amplified photoacoustic signal to a detection signal input end of a phase-locked amplifier; meanwhile, a reference signal input end of the phase-locked amplifier receives a TTL signal with the same frequency as the modulation frequency of the chopper, and the phase-locked amplifier extracts a photoacoustic signal amplitude corresponding to the modulation frequency of the chopper;
in a test machine of a signal acquisition/scanning imaging module, acquiring a signal demodulated by a phase-locked amplifier and storing the signal in the test machine, and controlling a scanning translation stage to perform two-dimensional plane scanning on a sample in the horizontal plane direction; and after the scanning translation stage moves by one step and experiences time delay matched with the integration time of the lock-in amplifier, acquiring a signal demodulated by the lock-in amplifier once, wherein the photoacoustic signal acquired in the two-dimensional plane scanning area corresponds to the sample excitation position coordinate one by one.
7. The method of claim 6, wherein the lateral resolution of the super-resolution photoacoustic imaging is calculated as follows:
NA is the numerical aperture of the imaging objective, NA ═ nsin θ, and ζ is a saturation factor, which represents the ratio of Laguerre-Gaussian intensity to saturated intensity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011227123.0A CN112415096B (en) | 2020-11-06 | 2020-11-06 | Super-resolution photoacoustic imaging system and method based on saturable absorption effect |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011227123.0A CN112415096B (en) | 2020-11-06 | 2020-11-06 | Super-resolution photoacoustic imaging system and method based on saturable absorption effect |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112415096A CN112415096A (en) | 2021-02-26 |
| CN112415096B true CN112415096B (en) | 2022-09-16 |
Family
ID=74827083
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011227123.0A Active CN112415096B (en) | 2020-11-06 | 2020-11-06 | Super-resolution photoacoustic imaging system and method based on saturable absorption effect |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112415096B (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014011403A1 (en) * | 2012-07-11 | 2014-01-16 | The University Of Connecticut | Dual-modality endoscope, method of manufacture, and use thereof |
| US9618445B2 (en) * | 2013-12-09 | 2017-04-11 | National Taiwan University | Optical microscopy systems based on photoacoustic imaging |
| US11768182B2 (en) * | 2019-04-26 | 2023-09-26 | Arizona Board Of Regents On Behalf Of Arizona State University | Photoacoustic and optical microscopy combiner and method of generating a photoacoustic image of a sample |
| CN110755042B (en) * | 2019-10-21 | 2021-01-01 | 华中科技大学 | Time pulse light sheet tomography method and system for realizing large-volume high-resolution |
-
2020
- 2020-11-06 CN CN202011227123.0A patent/CN112415096B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN112415096A (en) | 2021-02-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US11029287B2 (en) | Multi-focus optical-resolution photoacoustic microscopy with ultrasonic array detection | |
| US9618445B2 (en) | Optical microscopy systems based on photoacoustic imaging | |
| US8454512B2 (en) | Confocal photoacoustic microscopy with optical lateral resolution | |
| US7346387B1 (en) | Methods for improved selectivity in photo-activation and detection of molecular diagnostic agents | |
| WO2021077708A1 (en) | Method and system for achieving large-volume and high-resolution time pulse light film tomography imaging | |
| CN106124469A (en) | A kind of photoacoustic imaging and optical imagery multi-modal fusion imaging system | |
| WO2007088709A1 (en) | 3d acoustic imaging device and 3d acoustic imaging method | |
| CN112240880B (en) | Super-resolution stimulated Raman microscopic imaging method and device for realizing near resonance enhancement | |
| CN103018171B (en) | Wide-frequency-band optical-acoustic and fluorescent double-imaging device without energy converter and detection method thereof | |
| Zhang et al. | An ellipsoidal focused ultrasound transducer for extend-focus photoacoustic microscopy | |
| CN112415096B (en) | Super-resolution photoacoustic imaging system and method based on saturable absorption effect | |
| JP2013113804A (en) | Photoacoustic microscope | |
| CN110584612B (en) | Optical microscope system for imaging blood vessels | |
| van Raaij et al. | Femtosecond photoacoustics: integrated two-photon fluorescence and photoacoustic microscopy | |
| He et al. | In vivo imaging of a single erythrocyte with high-resolution photoacoustic microscopy | |
| CN114010152B (en) | Blood brain barrier damage assessment device and method based on dual-wavelength photoacoustic microscopy imaging | |
| CN114098637B (en) | Large-view-field photoacoustic microscopic imaging device and method | |
| Liu et al. | Continuous wave laser excitation based portable optoacoustic imaging system for melanoma detection | |
| CN112535531B (en) | Biological tissue welding effect detection device | |
| CN211131008U (en) | Multi-mode breast tumor imaging device based on multi-spectral ultrasonic modulation | |
| US20090114859A1 (en) | Use of ZnO Nanocrystals For Imaging and Therapy | |
| Shintate et al. | High-speed optical resolution photoacoustic microscopy with a MEMS scanner: Novel and simple distortion correction method | |
| Kim et al. | High-speed wide-field photoacoustic microscopy with enhanced sensitivity | |
| CN116879180A (en) | Photoacoustic microimaging system and method based on radial polarization modulation beam focusing | |
| Chen et al. | 2D photoacoustic scanning imaging with a single pulsed laser diode excitation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |