Ultrahigh-flux single-pixel real-time holographic microscopic imaging system

Abstract

The invention relates to the technical field of optical imaging, in particular to an ultrahigh-flux single-pixel real-time holographic microscopic imaging system. The system comprises a laser pre-modulation unit, and a beam expanding lens group, a first acousto-optic deflector, a conversion lens group, a second acousto-optic deflector and a photoelectric conversion unit which are sequentially arranged along the propagation direction of light. Because the first preset direction is orthogonal to the second preset direction, an orthogonal two-dimensional frequency comb pattern can be generated, so that the two-dimensional frequency comb pattern has good performance of spatial frequency modulation and achieves a good effect of natural modulation on a laser beam, and structured light modulation is not required to be performed pixel by pixel in the prior art. The system provided by the invention has the technical effects of ultrahigh flux, few measurement times, high algorithm complexity, high imaging speed, simple system light path structure, strong robustness and high imaging quality. And meanwhile, continuous single-pixel holographic microscopic imaging can be realized, high-speed regulation and control can be performed, and a good real-time imaging monitoring effect is achieved.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and particularly to a single-pixel real-time holographic microscopy imaging system with ultra-high throughput. Background Art

[0002] In the field of modern optical imaging, optical imaging technology can clearly display some rare physical phenomena and material characteristics through the sensitivity of refractive index to phase change and the absorption specificity of different spectral components. In the visible light spectrum range, imaging technology solutions have made significant progress due to the maturity of silicon-based phase mechanism preparation technology. However, in the non-visible light spectrum range, such as terahertz, mid-infrared, near-infrared, ultraviolet, and X-ray spectra, the development of traditional pixel array detection cameras is still in its infancy. Therefore, cameras in these non-visible light spectra are often inefficient or expensive, which poses a huge challenge to imaging in these fields. At this time, single-pixel detectors - compared with pixel array detectors - have excellent detection performance in a wide range of spectra due to their simple preparation process and strong material substitutability. Through the combination of actively controlled structured illumination and computational image reconstruction using fitting algorithms, the emerging computational imaging technology of single-pixel imaging has become an alternative imaging solution to replace pixel array detectors, with potential advantages for special spectral imaging and complex amplitude holographic imaging. Therefore, realizing single-pixel holographic imaging and significantly improving various important imaging parameters (even achieving real-time two-dimensional imaging monitoring) is an important direction for studying the macroscopic natural laws and microscopic life mechanisms during dynamic change processes.

[0003] However, due to the physical structure limitations of single-pixel imaging, the acquisition of computational information requires a serial scanning imaging scheme rather than the parallel measurement of a camera. Therefore, two cumbersome computational imaging stages are required: measurement and reconstruction. For measurement, the detection framework of a single pixel requires an excessive number of measurements to make up for the shortage of detection elements. In existing measurement methods, a spatial light modulator is usually required to perform structured light illumination and interact with the sample to be measured for single-pixel modulation. The higher the pixel requirements, the more times of pixel modulation are required, and this method appears to be rather cumbersome.

[0004] In addition, during the reconstruction process, since the essence of single-pixel imaging is computational solution, the retrieval of imaging information requires solving the optical equation relationship established by the control measurement. Therefore, algorithm fitting also requires further time consumption. Although compressive sensing technology can reduce the excessive number of measurements through prior knowledge, it will increase the algorithm complexity, improve the computational burden and time consumption, and the imaging quality will also deteriorate due to the loss of details.

[0005] Obviously, the above-mentioned unachievable imaging parameters and various applications existing in the existing single-pixel imaging system, as well as the bottleneck defects in the technical solutions at the physical measurement end, result in extremely low flux - spatial bandwidth time of the single-pixel imaging system. Due to the extremely low spatial bandwidth time product of the single-pixel imaging technology, there are many adverse factors such as a large number of measurement times, high algorithm complexity, slow imaging speed, complex system optical path, weak robustness, and poor imaging quality, making it almost impossible to be used in actual biological, chemical, and material applications. Currently, there is no effective solution to enable the single-pixel imaging technology to achieve real-time imaging monitoring of clear complex amplitude in a dynamically changing scene. Summary of the Invention

[0006] The present application provides a single-pixel real-time holographic microscopy imaging system with ultra-high flux to solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or create conditions.

[0007] Other features and advantages of the present application will become apparent through the following detailed description, or be learned in part through the practice of the present application.

[0008] According to one aspect of the embodiments of the present application, a single-pixel real-time holographic microscopy imaging system with ultra-high flux is provided. The system includes a laser pre-modulation unit, and a beam expander lens group, a first acousto-optic deflector, a conversion lens group, a second acousto-optic deflector, and a photoelectric conversion unit arranged in sequence along the propagation direction of light.

[0009] The deflection direction of the first acousto-optic deflector is a first preset direction, and the deflection direction of the second acousto-optic deflector is a second preset direction, and the first preset direction is orthogonal to the second preset direction.

[0010] The laser pre-modulation unit is configured to input a laser beam meeting preset conditions to the beam expander lens group.

[0011] The beam expander lens group is configured to expand the laser beam to obtain a first target laser beam.

[0012] After inputting a first preset frequency comb oscillation signal to the first acousto-optic deflector, the first acousto-optic deflector is configured to perform diffraction modulation of the first target laser beam in the first preset direction to obtain a first target number of first sub-diffraction beams having the first preset direction.

[0013] The conversion lens group is configured to converge each of the first sub-diffraction beams to obtain a modulated beam.

[0014] After inputting the second preset frequency comb oscillation signal to the second acousto-optic deflector, the second acousto-optic deflector is configured to perform diffraction modulation on the modulated light beam in the second preset direction to obtain a second target number of second sub-diffraction light beams having the second preset direction, and output an orthogonal two-dimensional frequency comb pattern formed by the first sub-diffraction light beam and the second sub-diffraction light beam;

[0015] The photoelectric conversion unit is configured to convert the coherent light beam obtained according to the orthogonal two-dimensional frequency comb pattern into a target electrical signal, and transmit the target electrical signal to the signal acquisition device.

[0016] In an embodiment of the present application, based on the foregoing solution, the laser pre-modulation unit includes a laser source, a half-wave plate, a polarization beam splitter, a first reflector, and a second reflector arranged in sequence. The laser source is configured to generate an initial laser beam, and the initial laser beam passes through the half-wave plate, the polarization beam splitter, the first reflector, and the second reflector in sequence to form the laser beam that meets the preset conditions.

[0017] In an embodiment of the present application, based on the foregoing solution, the beam expander lens group includes a first lens and a second lens. The first lens and the second lens are spaced apart. The laser beam passes through the first lens and the second lens in sequence, and the first lens and the second lens are used to expand the laser beam to obtain the first target laser beam; the focal length of the first lens is 7.5 mm, and the focal length of the second lens is 60 mm.

[0018] In an embodiment of the present application, based on the foregoing solution, the system further includes a diaphragm disposed between the second lens and the first acousto-optic deflector. The diaphragm is configured to make the first target laser beam emitted from the second lens adapt to the entrance of the first acousto-optic deflector, and the aperture of the diaphragm is 5 mm.

[0019] In an embodiment of the present application, based on the foregoing solution, the system further includes a conversion lens group. The conversion lens group includes a third lens and a fourth lens arranged in sequence. The third lens and the fourth lens are sequentially spaced apart between the first acousto-optic deflector and the second acousto-optic deflector, and the focal lengths of the third lens and the fourth lens are both 125 mm.

[0020] In one embodiment of the present application, based on the foregoing solution, the imaging lens group includes a fifth lens and a sixth lens arranged at intervals in sequence. A sample to be measured is also arranged between the fifth lens and the sixth lens. The orthogonal two-dimensional frequency comb pattern forms an orthogonal two-dimensional frequency comb pattern carrying complex amplitude light field imaging information after passing through the fifth lens and the sample to be measured, and the orthogonal two-dimensional frequency comb pattern of the complex amplitude light field imaging information is converged into the coherent light beam by the sixth lens; the focal length of the fifth lens is 15 mm, and the focal length of the sixth lens is 50 mm.

[0021] In one embodiment of the present application, based on the foregoing solution, the difference between the first target quantity and the second target quantity is one, so that there is an asymmetric relationship between the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0022] In one embodiment of the present application, based on the foregoing solution, the photoelectric conversion unit includes a grating and a photodetector arranged at intervals in sequence. The coherent light beam is converted into the target electrical signal after passing through the light beam and the photodetector, and the target electrical signal is a time-domain oscillation signal mapped to the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0023] The beneficial effect of the present application is that the laser beam output by the laser pre-modulation unit is introduced into the beam expander lens group, and the laser beam is expanded by the beam expander lens group to obtain a first target laser beam with good optical performance, which is convenient for subsequent laser modulation.

[0024] Driven by the first preset frequency comb oscillation signal, the first acousto-optic deflector starts to work and performs diffraction modulation on the first target laser beam in a first preset direction. Similarly, driven by the second preset frequency comb oscillation signal, the second acousto-optic deflector starts to work and performs diffraction modulation on the modulated light beam in a second preset direction. Since the first preset direction is orthogonal to the second preset direction, an orthogonal two-dimensional frequency comb pattern can be generated therefrom, so that the two-dimensional frequency comb pattern has good performance of spatial frequency modulation, and can achieve a good effect of natural modulation on the laser beam, without the need to perform structured light modulation on each pixel as in the prior art.

[0025] By converting the coherent light beam obtained according to the orthogonal two-dimensional frequency comb pattern into a target electrical signal and transmitting the target electrical signal to a signal acquisition device, the signal acquisition device can directly modulate the coherent light beam with a two-dimensional plane, reducing the complexity of calculations during image reconstruction, enabling the system provided by the present application to have ultra-high throughput, achieving technical effects such as fewer measurement times, high algorithm complexity, fast imaging speed, simple system optical path structure, strong robustness, and high imaging quality. At the same time, due to the fast imaging speed of the present application, continuous single-pixel holographic microscopy imaging can be realized, high-speed regulation can be performed, and good real-time imaging monitoring effects can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly describe the drawings required for the description of the embodiments. Obviously, the described drawings are only a part of the embodiments of the present application, rather than all embodiments. Those skilled in the art can also obtain other design solutions and drawings based on these drawings without creative efforts.

[0027] Figure 1 It is the overall block diagram of the system of the present application;

[0028] Figure 2 It is the specific structure diagram of the system of the present application;

[0029] Figure 3 It is the schematic diagram of the deflection direction of the acousto-optic deflector;

[0030] Figure 4 It is the operation logic diagram of the signal acquisition device of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Now, the exemplary embodiments will be described more comprehensively with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art.

[0032] In addition, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to give a full understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of the present application.

[0033] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or micro-control node devices.

[0034] The flowcharts shown in the accompanying drawings are merely illustrative and not necessarily include all the content and operations / steps, nor are they necessarily executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0035] It should be noted that: "a plurality of" mentioned in this article refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0036] The following is a detailed introduction to the background technology of this application:

[0037] In the field of modern optical imaging, optical imaging technology can clearly display some rare physical phenomena and material characteristics through the sensitivity of phase change to refractive index and the absorption specificity of different spectral components. In the visible light spectrum range, imaging technology solutions have made significant progress due to the maturity of silicon-based phase mechanism preparation technology. However, in the non-visible light spectrum range, such as terahertz, mid-infrared, near-infrared, ultraviolet, and X-ray spectra, the development of traditional pixel array detection cameras is still in its infancy. Therefore, cameras in these non-visible light spectra are often inefficient or expensive, which poses a huge challenge to imaging in these fields. At this time, single-pixel detectors - compared with pixel array detectors - have excellent detection performance in a wide spectral range due to their simple preparation process and strong material replaceability. A related team first brought the similar principle of single-pixel measurement for reconstructing images into people's vision. Through the combination of actively controlled structured illumination and computational image reconstruction using fitting algorithms, the emerging computational imaging technology of single-pixel imaging has become an alternative imaging solution to replace pixel array detectors, with potential advantages for special spectral imaging and complex amplitude holographic imaging. Therefore, realizing single-pixel holographic imaging and significantly improving various important imaging parameters (and even realizing real-time two-dimensional imaging monitoring) is an important direction for studying the macroscopic natural laws and microscopic life mechanisms in the process of dynamic changes.

[0038] However, due to the physical structure limitations of single-pixel imaging, the acquisition of computational information requires a serial scanning imaging scheme rather than the parallel measurement of a camera. Therefore, a total of two cumbersome computational imaging stages are required: measurement and reconstruction. For measurement, the detection framework of a single pixel requires an excessive number of measurements to make up for the shortage of the number of detection elements. At this time, the imaging speed is extremely dependent on the speed of establishing the spatial information relationship by modulating the optical field at the modulation end, resulting in an extremely low amount of information obtained by single-pixel imaging per unit time and a very slow imaging measurement speed. In addition, during the reconstruction process, since the essence of single-pixel imaging is computational solution, the retrieval of imaging information requires solving the optical equation relationship established by the modulation measurement. Therefore, algorithm fitting also requires further time consumption. Although compressive sensing technology can reduce the excessive number of measurements through prior knowledge, it will increase the algorithm complexity, improve the computational burden and time consumption, and the imaging quality will also deteriorate due to the loss of details.

[0039] For phase imaging, the development of a single-pixel holographic imaging system depends on the compatibility between the structured light illumination built into the overall framework of single-pixel imaging and holographic imaging, so as to obtain complex amplitude information through holographic measurement and the solution of optical equations in the phase dimension at the measurement end. However, compared with the imaging of a pixel array camera, the holographic structure not only requires an additional interference optical path to construct a Michelson interference structure, but also requires a more complex multi-step phase shift strategy at the modulation end while illuminating with structured light for the recovery of the phase information of the optical field measurement. This makes it necessary to load patterns multiple times under the same basis for the modulated structured light, increasing the required number of measurements several times. In addition, the phase modulation limitation of multi-step phase shift also makes the modulation means of high-speed amplitude control more complex, not only greatly increasing the complexity of the system, but also severely reducing the effective number of pixels of the imaging, further deteriorating the imaging quality.

[0040] Obviously, the above-mentioned unachievable imaging parameters and various applications existing in the existing single-pixel imaging system can be mainly attributed to the bottleneck defects of the technical solutions at the physical measurement end and the algorithm reconstruction end, resulting in an extremely low throughput - spatial bandwidth time of the single-pixel imaging system. Due to the extremely low spatial bandwidth time product of single-pixel imaging technology, there are many adverse factors such as a large number of measurements, high algorithm complexity, slow imaging speed, complex system optical path, weak robustness, and poor imaging quality, making it almost impossible to be used in actual biological, chemical, and material applications.

[0041] Existing single-pixel holographic imaging cannot achieve high-speed regulation and real-time imaging, and the image reconstruction effect is also low. This is because the single-pixel holographic imaging technology currently has severe limitations in the physical detection framework and the algorithm reconstruction model. The extremely low spatio-temporal bandwidth product leads to many problems such as a large number of measurement times, high algorithm complexity, slow imaging speed, complex system optical path, weak robustness, and poor imaging quality. Currently, there is no effective solution to enable the single-pixel imaging technology to achieve high-quality complex amplitude real-time imaging monitoring of dynamic changing scenes under the conditions of special spectral imaging and complex amplitude holography.

[0042] Therefore, the present application provides a single-pixel real-time holographic microscopy imaging system with ultra-high throughput. The system of the present application mainly improves the measurement stage of single-pixel holographic imaging, provides an orthogonal two-dimensional frequency comb pattern, and converts it into a target electrical signal corresponding to a coherent light beam to be provided to the signal acquisition device, so that the signal acquisition device can perform fast Fourier image reconstruction according to the target electrical signal, reducing the computational difficulty and enabling fast image reconstruction, thereby achieving the purpose of real-time monitoring.

[0043] The implementation details of the technical solution of the embodiments of the present application are elaborated in detail below:

[0044] According to one aspect of the embodiments of the present application, a single-pixel real-time holographic microscopy imaging system with ultra-high throughput is provided, as shown in Figure 1 、 Figure 2 and Figure 3 . Figure 1 is the overall block diagram of the system of the present application, Figure 2 is the specific structural diagram of the system of the present application, Figure 3 is the schematic diagram of the deflection direction of the acousto-optic deflector.

[0045] The following explains Figure 2 and Figure 3 :

[0046] Mirror 1 is the first mirror described in the present application, Mirror 2 is the second mirror described in the present application, acousto-optic deflector x is the first acousto-optic deflector with the x direction in the present application, acousto-optic deflector y is the second acousto-optic deflector with the y direction in the present application, and Lens 1, Lens 2, Lens 3, Lens 4, Lens 5, and Lens 6 respectively correspond to the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens described in the present application. Figure 2 shows the top view and the front view (front elevation). In the perspective of the top view, the x direction is longitudinal, and in the perspective of the front view, the y direction is longitudinal. Therefore, it can be combined with Figure 3For explanation, the deflection direction refers to the deflection direction of the acousto-optic deflector for the laser beam. The first preset direction of the first acousto-optic deflector can specifically be the x direction, and the second preset direction can specifically be the y direction, that is, the x direction and the y direction marked as shown in Figure 3 The x direction and the y direction form a plane perpendicular to the light propagation direction, and the light propagation direction is the z direction. Among them, the beam expander lens group, the first acousto-optic deflector, the conversion lens group, the second acousto-optic deflector, and the photoelectric conversion unit are sequentially arranged at intervals along the z direction.

[0047] The ultra-high-throughput single-pixel real-time holographic microscopy system includes a laser pre-modulation unit and a beam expander lens group, a first acousto-optic deflector, a conversion lens group, a second acousto-optic deflector, and a photoelectric conversion unit that are sequentially arranged along the light propagation direction;

[0048] The deflection direction of the first acousto-optic deflector is the first preset direction, the deflection direction of the second acousto-optic deflector is the second preset direction, and the first preset direction is orthogonal to the second preset direction;

[0049] The laser pre-modulation unit is used to input a laser beam meeting preset conditions to the beam expander lens group;

[0050] The beam expander lens group is used to expand the laser beam to obtain a first target laser beam;

[0051] After inputting a first preset frequency comb oscillation signal to the first acousto-optic deflector, the first acousto-optic deflector is used to perform diffraction modulation in the first preset direction on the first target laser beam to obtain a first target number of first sub-diffraction beams having the first preset direction;

[0052] The conversion lens group is used to converge each of the first sub-diffraction beams to obtain a modulated beam;

[0053] After inputting a second preset frequency comb oscillation signal to the second acousto-optic deflector, the second acousto-optic deflector is used to perform diffraction modulation in the second preset direction on the modulated beam to obtain a second target number of second sub-diffraction beams having the second preset direction, and output an orthogonal two-dimensional frequency comb pattern formed by the first sub-diffraction beams and the second sub-diffraction beams;

[0054] The photoelectric conversion unit is used to convert the coherent beam obtained according to the orthogonal two-dimensional frequency comb pattern into a target electrical signal and transmit the target electrical signal to the signal acquisition device.

[0055] Specifically, in the embodiments of the present application, the laser beam output by the laser pre-modulation unit is introduced into the beam expander lens group, and the beam expander lens group expands the laser beam, and the obtained first target laser beam has good optical performance, so as to facilitate subsequent laser modulation.

[0056] Driven by the first preset frequency comb oscillation signal, the first acousto-optic deflector starts to work and performs diffraction modulation on the first target laser beam in the first preset direction. Similarly, driven by the second preset frequency comb oscillation signal, the second acousto-optic deflector starts to work and performs diffraction modulation on the modulated beam in the second preset direction. Since the first preset direction is orthogonal to the second preset direction, an orthogonal two-dimensional frequency comb pattern can be generated, enabling the two-dimensional frequency comb pattern to have good performance in spatial frequency modulation, achieving a good effect of natural modulation on the laser beam, without the need for structured light modulation pixel by pixel as in the prior art.

[0057] By converting the coherent beam obtained according to the orthogonal two-dimensional frequency comb pattern into a target electrical signal and transmitting the target electrical signal to the signal acquisition device, the signal acquisition device can directly modulate the coherent beam with a two-dimensional plane, reducing the complexity of calculation during image reconstruction, making the system provided by the present application have ultra-high throughput, achieving technical effects such as fewer measurement times, high algorithm complexity, fast imaging speed, simple system optical path structure, strong robustness, and high imaging quality. At the same time, due to the fast imaging speed of the present application, continuous single-pixel holographic microscopy imaging can be realized, high-speed regulation can be performed, and a good real-time imaging monitoring effect can be obtained.

[0058] Further, the laser pre-modulation unit includes a laser source, a half-wave plate, a polarization beam splitter, a first reflector, and a second reflector arranged in sequence. The laser source is used to generate an initial laser beam, and the initial laser beam passes through the half-wave plate, the polarization beam splitter, the first reflector, and the second reflector in sequence to form the laser beam that meets the preset conditions.

[0059] Refer to Figure 2As shown, the specific parameters of the laser source in the laser pre-modulation unit can be set to a narrow-bandwidth laser with a wavelength of 1030 nm and a frequency of ~3 kHz, that is, a continuous laser. The continuous laser can select different wavelength bands as the light source, and its adjustable power is 400 mW for stable detection. The linear polarization direction is adjusted by a half-wave plate to change the linear polarization direction and ensure that the extinction ratio of the linear polarization reaches the maximum. The splitting output of the polarization beam splitter can adjust the corresponding laser intensity for different linear polarization directions. Finally, a highly extinction-ratio stable linearly polarized light output with adjustable power is ensured. Finally, a laser beam that meets the preset conditions is output. The preset conditions are that the extinction ratio performance of the polarization beam splitter meets the preset extinction ratio performance requirements, and at the same time, it has a preset wavelength and a preset frequency. The preset wavelength and preset frequency can be used to control the laser source according to requirements, that is, the output parameters of the aforementioned continuous laser.

[0060] Further, the beam expander lens group includes a first lens and a second lens. The first lens and the second lens are spaced apart. The laser beam sequentially passes through the first lens and the second lens, and the beam of the laser beam is expanded by the first lens and the second lens to obtain the first target laser beam. The focal length of the first lens is 7.5 mm, and the focal length of the second lens is 60 mm.

[0061] Specifically, after being guided by the first mirror and the second mirror, the laser beam enters the first lens and is beam-expanded in the beam expander lens group composed of the first lens with a focal length of 7.5 mm and the second lens with a focal length of 60 mm, and then reaches the first acousto-optic modulator, that is, enters the acousto-optic frequency comb modulation module. In the embodiment of the present application, the acousto-optic frequency comb modulation module includes a first acousto-optic deflector, a conversion lens group, and a second acousto-optic deflector.

[0062] Further, the system further includes a diaphragm disposed between the second lens and the first acousto-optic deflector. The diaphragm is used to make the first target laser beam emitted from the second lens adapt to the entrance of the first acousto-optic deflector. The aperture of the diaphragm is 5 mm. The conversion lens group includes a third lens and a fourth lens arranged in sequence. The third lens and the fourth lens are sequentially spaced between the first acousto-optic deflector and the second acousto-optic deflector. The focal lengths of the third lens and the fourth lens are both 125 mm.

[0063] Specifically, the first acousto-optic deflector and the second acousto-optic deflector with high bandwidth and high modulation points are used to achieve high-quality acousto-optic frequency comb projection. In the acousto-optic frequency comb modulation module, the main structure is divided into two acousto-optic deflectors with orthogonal arrangement directions for modulation, and in the middle, a conversion lens group with a focal length of 125 mm with a strict 4f imaging system (that is, the third lens and the fourth lens) is built.

[0064] First, the linearly polarized beam expander light source (i.e., the first target laser beam described in this application) will first pass through the first acousto-optic deflector. The input aperture diaphragm with a diameter of 5 mm is used to filter the expanded beam to adapt to the entrance of the first acousto-optic deflector. At this time, a series of frequency comb sine oscillation signals (i.e., the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal described in this application), with a bandwidth of 30 MHz, will be used as the radio frequency drive signal to excite the first acousto-optic deflector and the second acousto-optic deflector. Due to the piezoelectric effect of the acousto-optic deflector, the refractive index change of the excited acoustic wave forms acousto-optic Bragg diffraction.

[0065] The expanded beam (i.e., the first target laser beam) after passing through the first acousto-optic deflector will diffract a series of sub-diffraction beams in the x direction. Different diffraction beams will carry different frequency modulation components, and at this time, the modulated beam is obtained. After the beam passing through the 4f imaging system (i.e., the third lens and the fourth lens) is re-converged and then passes through the second acousto-optic deflector, denoted as the y direction. Therefore, the original series of one-dimensional (representing the x direction) acousto-optic diffraction beams (i.e., the first sub-diffraction beams) will be expanded in another dimension (representing the y direction). The sub-diffraction beams with different deflection angles (representing the second sub-diffraction beams) will be loaded with new frequency modulation components again, thereby forming an optical field pattern with a two-dimensional frequency comb in the x direction and the y direction, and thus completing the pattern projection.

[0066] Furthermore, the difference between the first target quantity and the second target quantity is one, so that there is an asymmetric relationship between the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0067] Specifically, in the signal design of the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal, the teeth of the orthogonal direction are staggered. The destruction of symmetry (i.e., the asymmetric relationship described in this application) will enable the two-dimensional frequency comb to achieve an independent mapping relationship of spatial frequencies. The specific formula design is as follows:

[0068] f(x n ,y m )=f 0 +f x (x n )-f y (y m )=f 0 +(f intx -f inty )+(n - m)Δf

[0069] Where n and m are the coordinates in the x direction and the y direction respectively. f 0 represents the frequency of the laser, that is, 1030 nm in the embodiment of this application, f x (x n) represents the frequencies of the respective first sub-diffraction beams in the x direction, f y (x m ) represents the frequencies of the respective second sub-diffraction beams in the y direction; f intx and f inty respectively represent the starting frequencies of the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal, and Δf represents the frequency interval between the x direction and the y direction.

[0070] Furthermore, the imaging lens group includes a fifth lens and a sixth lens arranged at intervals in sequence. A sample to be measured is also arranged between the fifth lens and the sixth lens. The orthogonal two-dimensional frequency comb pattern forms an orthogonal two-dimensional frequency comb pattern carrying complex amplitude light field imaging information after passing through the fifth lens and the sample to be measured, and the orthogonal two-dimensional frequency comb pattern of the complex amplitude light field imaging information is converged into the coherent beam through the sixth lens; the focal length of the fifth lens is 15 mm, and the focal length of the sixth lens is 50 mm. The photoelectric conversion unit includes a grating and a photodetector arranged at intervals in sequence. The coherent beam is converted into the target electrical signal through the beam and the photodetector, and the target electrical signal is a time-domain oscillation signal mapped to the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0071] Specifically, the projection of the diffraction beam passing through the acousto-optic frequency comb modulation module is called an orthogonal two-dimensional frequency comb pattern. After the orthogonal two-dimensional frequency comb pattern passes through the imaging lens group, its imaging field of view range, imaging resolution, and imaging beam quality will be further confirmed to meet the actual application scenarios of subsequent sample projections to be measured (generally, a lens focal length of 7.5 mm is used in high-resolution microscopic scenarios). After the orthogonal two-dimensional frequency comb pattern then passes through the sample to be measured, a series of optical interactions will map the absorption rate and refractive index of the special spectral response to the amplitude and phase components of the frequency comb light field. The orthogonal two-dimensional frequency comb pattern carrying complex amplitude light field imaging information will be coherently combined with a grating through a converging lens with a focal length of 50 mm (i.e., the sixth lens). The finally combined series of sub-beams (i.e., the coherent beam) will realize the acquisition of the time-series serial signal of single-pixel imaging in heterodyne holography with different frequencies being coherent (after passing through the photodetector, a series of time-domain oscillation signals are formed), and finally, it is collected in real time by the signal acquisition device and presented in a streamlined real-time imaging manner in the parallel processing of measurement and fast Fourier transform, ultimately realizing ultra-high-throughput single-pixel real-time holographic microscopy imaging, achieving real-time imaging at 1,000 frames per second with a resolution of 80×81 pixels, a lateral resolution of 3.76 μm, and a field of view of approximately 300 μm, suitable for real-time dynamic monitoring in high-speed microscopic scenarios.

[0072] In summary, the necessary steps in the operation of this application are mainly divided into two parts, namely: 1. Design of frequency comb radio frequency signals and driving of acousto-optic crystals; 2. Self-referencing collimation of real-time data and real-time acquisition and reconstruction.

[0073] 1. Design of frequency comb radio frequency signals and driving of acousto-optic crystals

[0074] Probe light (initial laser beam) is generated by a 1030 nm continuous wave laser (bandwidth ~ 3 kHz) and passes through two-stage orthogonal acousto-optic deflectors (i.e., the first acousto-optic deflector in the x direction and the second acousto-optic deflector in the y direction). The driving frequency comb of the first acousto-optic deflector is an 80-order frequency comb with a frequency range of 63 - 88 MHz, and the tooth interval between frequency combs is 256 kHz; the driving frequency comb of the acousto-optic deflector y is an 81-order frequency comb with a frequency range of 63 - 88 MHz, and the tooth interval between frequency combs is 252 kHz. Due to the 80-order frequency comb, the specific number of the first target is 80, and due to the 81-order frequency comb, the specific number of the second target is 81. Among them, there is a relative offset of 1000 Hz between the driving frequency combs of the first acousto-optic deflector and the second acousto-optic deflector. After two-dimensional spectral encoding is realized by the orthogonal frequency division multiplexing strategy, the unequal sampling between frequencies enables one-to-one correspondence of spatial frequencies, and the relative offset of the frequency comb also enables single-sideband detection in coherent direct measurement to eliminate the spectral aliasing effect. Finally, the minimum frequency interval of the coherent holography of the orthogonal two-dimensional frequency comb pattern is 1000 Hz, and an integer-period measurement form that can be divided evenly can be presented under the sampling rate of 50 MSa / s of the signal acquisition device.

[0075] After setting the parameters, specifically, turn on the laser, turn on any waveform generator loaded with the known radio frequency signal frequency comb, and turn on the electrical signal amplifier to start the acousto-optic frequency comb modulation module.

[0076] 2. Self-referencing collimation of real-time data and real-time acquisition and reconstruction

[0077] The zero-order unmodulated light is retained by a grating with 50 line pairs / mm as the coaxial reference light to establish a stable interference reference with a series of sub-diffraction beams of the orthogonal two-dimensional frequency comb pattern. The heterodyne holographic time-varying signal is received by a single-pixel photodetector (bandwidth: 150 MHz), and sampled by the signal acquisition device at a rate of 50 MSa / s. Overall, the system operates in an ultrafast continuous mode and will not interrupt until the pause button of the acquisition card is pressed or the memory of the acquisition card buffer is exhausted. First, in the known acousto-optic frequency comb modulation module, the data acquisition time of one frame of imaging signal is 1 ms, and under the addressing and screening of the two-dimensional frequency comb reconstructed by the fast Fourier transform, the image reconstruction time accelerated by the GPU is < 350 microseconds. At this time, the timing of its reconstruction process is mainly determined by Figure 4As shown in the detailed workflow. First, to ensure high-quality complex amplitude imaging reconstruction through the scattering medium, preprocessing calibration can be performed for self-referencing collimation of real-time data. That is, the system first activates the single-frame capture mode, in which 1 ms of data is collected to obtain an initial image. Considering the efficiency of the fast Fourier transform algorithm, a background without any target object is used as a relative collimation reference, which takes about 300 microseconds. After this initial calibration, the data acquisition card switches to the continuous mode for long-term data collection and data processing in the dynamic buffer. At this time, the data signal is segmented into 1-ms intervals and placed in the dynamic buffer for processing. The pending state of each 1-ms data collection immediately triggers the parallel operation of the fast Fourier transform. Since data acquisition and image reconstruction are executed independently and in parallel, the operation process of the fast Fourier transform is synchronized with the next-frame real-time acquisition process of the real-time acquisition card. The operation of the fast Fourier transform and self-calibration are within 1 ms, and subsequent reconstruction can be carried out without delaying the next imaging cycle. At the same time, the reconstructed image will also be updated in real time for visualization demonstration.

[0078] After setting the parameters, specifically after starting the acousto-optic frequency comb modulation module, by opening the programmable data acquisition card control software through the computer terminal and running the code, the streamlined process synchronization between the fast Fourier reconstruction module and the acousto-optic frequency comb modulation module can be achieved. Finally, real-time imaging at 1,000 frames per second with a resolution of 80×81 pixels, a lateral resolution of 3.76 μm, and a field of view of about 300 μm is realized, which is suitable for real-time dynamic monitoring in high-speed microscopic scenarios.

[0079] In addition, the above-mentioned drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, rather than for limiting purposes. It is easy to understand that the processes shown in the above-mentioned drawings do not indicate or limit the chronological order of these processes. Additionally, it is also easy to understand that these processes can be executed synchronously or asynchronously in multiple modules.

[0080] It should be understood that the present application is not limited to the exact structure already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present application is only limited by the appended claims.

Claims

1. An ultra-high throughput single-pixel real-time holographic microscopy imaging system, characterized in that: The system comprises a laser pre-modulation unit and a beam expansion lens group, a first acousto-optic deflector, a conversion lens group, a second acousto-optic deflector, and a photoelectric conversion unit which are sequentially arranged along the propagation direction of light; The deflection direction of the first acousto-optic deflector is a first preset direction, the deflection direction of the second acousto-optic deflector is a second preset direction, and the first preset direction is orthogonal to the second preset direction; The laser pre-modulation unit is used to input a laser beam meeting preset conditions to the beam expansion lens group; The beam expansion lens group is used to expand the laser beam to obtain a first target laser beam; After inputting a first preset frequency comb oscillation signal into the first acousto-optic deflector, the first acousto-optic deflector is used to perform diffraction modulation on the first target laser beam in the first preset direction to obtain a first target number of first sub-diffracted light beams with the first preset direction; The conversion lens group is used to converge each of the first sub-diffracted light beams to obtain a modulated light beam; After inputting a second preset frequency comb oscillation signal into the second acousto-optic deflector, the second acousto-optic deflector is used to perform diffraction modulation on the modulated light beam in the second preset direction, obtain a second target number of second sub-diffracted light beams with the second preset direction, and output an orthogonal two-dimensional frequency comb pattern formed by the first sub-diffracted light beams and the second sub-diffracted light beams; The photoelectric conversion unit is used to convert the coherent light beam obtained according to the orthogonal two-dimensional frequency comb pattern into a target electrical signal, and transmit the target electrical signal to a signal acquisition device.

2. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 1, characterized in that: The laser premodulation unit includes a laser source, a half-wave plate, a polarization beam splitter, a first reflector and a second reflector which are arranged in sequence. The laser source is used to generate an initial laser beam, and the initial laser beam passes through the half-wave plate, the polarization beam splitter, the first reflector and the second reflector in sequence to form the laser beam that meets the preset conditions.

3. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 1, characterized in that: The beam expansion lens group includes a first lens and a second lens, the first lens and the second lens are set at a distance, the laser beam passes through the first lens and the second lens in sequence, and the laser beam is expanded by the first lens and the second lens to obtain the first target laser beam; the focal length of the first lens is 7.5 mm, and the focal length of the second lens is 60 mm.

4. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 3, characterized in that: The system further includes an aperture disposed between the second lens and the first AOD, the aperture being used to adapt the first target laser beam emitted from the second lens to an entrance of the first AOD, and an aperture of the aperture being 5 mm.

5. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 1, characterized in that: The system also includes a conversion lens group, which includes a third lens and a fourth lens arranged in sequence, the third lens and the fourth lens are arranged in sequence and spaced apart between the first acousto-optic deflector and the second acousto-optic deflector, and the focal lengths of the third lens and the fourth lens are both 125 mm.

6. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 5, characterized in that: The imaging lens group includes a fifth lens and a sixth lens which are arranged in sequence at intervals, and a sample to be measured is also arranged between the fifth lens and the sixth lens. The orthogonal two-dimensional frequency comb pattern forms an orthogonal two-dimensional frequency comb pattern carrying complex amplitude light field imaging information through the fifth lens and the sample to be measured, and the orthogonal two-dimensional frequency comb pattern with complex amplitude light field imaging information is converged into the coherent light beam through the sixth lens; the focal length of the fifth lens is 15 mm, and the focal length of the sixth lens is 50 mm.

7. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 6, characterized in that: The difference between the first target number and the second target number is one, so that the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal have an asymmetric relationship.

8. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 7, characterized in that: The photoelectric conversion unit includes a grating and a photodetector that are arranged in sequence at intervals. The coherent light beam is converted into the target electrical signal through the light beam and the photodetector. The target electrical signal is a time domain oscillation signal mapped to the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

9. The ultra-high throughput single-pixel real-time holographic microscopy imaging system according to claim 1, characterized in that: The laser beam under the preset condition is a laser beam with a preset frequency and a preset wavelength.

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