An ultrahigh-throughput single-pixel real-time holographic microscopic imaging system

Abstract

The present application relates to the field of optical imaging technology, and in particular to an ultra-high-throughput single-pixel real-time holographic microscopy imaging system. The system includes 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 arranged in sequence along the propagation direction of light. Since 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 spatial frequency modulation performance, and achieves a good effect of natural modulation of the laser beam without the need for pixel-by-pixel structured light modulation as in the prior art. The system of the present application has ultra-high throughput, achieving the technical effects of a small number of measurements, high algorithm complexity, fast imaging speed, simple system optical path structure, strong robustness, and high imaging quality. At the same time, the present application can realize continuous single-pixel holographic microscopy imaging, can be controlled at high speed, and has a good real-time imaging monitoring effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, in particular to a single-pixel real-time holographic microscopic imaging system with ultra-high throughput. BACKGROUND

[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 phase change to refractive index and the absorption specificity of different spectral components. In the visible light spectrum range, imaging technology has made significant progress due to the mature preparation process of silicon-based cameras. 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 spectrum ranges are often inefficient or expensive, which poses a great challenge to imaging in these fields. At this time, single-pixel detectors, compared to 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 image reconstruction by fitting algorithm, the emerging computational imaging technology of single-pixel imaging becomes 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 realizing real-time two-dimensional imaging monitoring) is an important direction for studying macroscopic natural laws and microscopic life mechanisms in dynamic changes.

[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 parallel measurement by a camera, thus requiring two-step cumbersome computational imaging stages: measurement and reconstruction. For measurement, the detection framework of a single pixel requires an excessive number of measurements to compensate for the lack of the number 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 to modulate a single pixel. The higher the pixel requirement, the more times the pixel modulation needs to be performed, which is relatively cumbersome.

[0004] In addition, in the reconstruction process, since the essence of single-pixel imaging is computational solving, the retrieval of imaging information requires solving the optical equation relationship established by the controlled measurement, so the algorithm fitting also needs further time-consuming. Although compressed sensing technology can reduce the excessive number of measurements through prior knowledge, it increases the algorithm complexity, improves the computational burden and time consumption, and the imaging quality is also deteriorated due to the loss of details.

[0005] Obviously, the above-mentioned unachievable imaging parameters and various application, physical measurement end technical scheme bottleneck defects of the existing single-pixel imaging system, resulting in the flux of the single-pixel imaging system is low. Due to the extremely low space-bandwidth-time product, the single-pixel imaging technology has many disadvantages such as multiple measurements, high algorithm complexity, slow imaging speed, complex system optical path, weak robustness, and poor imaging quality, which almost cannot be used in actual biological, chemical, and material applications. At present, there is no effective solution to enable the single-pixel imaging technology to realize clear complex amplitude real-time imaging monitoring in a dynamic changing scene. SUMMARY

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

[0007] Other characteristics and advantages of the present application will become apparent from the following detailed description, or will be learned by practice of the present application.

[0008] According to an aspect of an embodiment of the present application, a super-high-flux single-pixel real-time holographic microscopic imaging system is provided, the system comprising 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 a preset condition to the beam expander lens group;

[0011] The beam expander lens group is configured to perform beam expansion on 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 light beam;

[0014] The second acousto-optic deflector is configured to diffractively modulate 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 beams and the second sub-diffraction light beams.

[0015] The photoelectric conversion unit is configured to convert a 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.

[0016] In an embodiment of the present application, based on the foregoing scheme, the laser pre-modulation unit comprises a laser source, a half-wave plate, a polarization beam splitter, a first mirror and a second mirror 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 mirror and the second mirror in sequence to form the laser beam meeting the preset condition.

[0017] In an embodiment of the present application, based on the foregoing scheme, the beam expander lens group comprises a first lens and a second lens, the first lens and the second lens are arranged at a distance, the laser beam passes through the first lens and the second lens in sequence, and the first lens and the second lens are configured 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 scheme, the system further comprises a diaphragm arranged between the second lens and the first acousto-optic deflector, the diaphragm is configured to adapt the first target laser beam emitted from the second lens 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 scheme, the system further comprises a conversion lens group, the conversion lens group comprises a third lens and a fourth lens arranged in sequence, the third lens and the fourth lens are arranged at a distance in sequence between the first acousto-optic deflector and the second acousto-optic deflector, and the focal length of the third lens and the fourth lens is 125 mm.

[0020] In an embodiment of the present application, based on the foregoing scheme, the imaging lens group comprises a fifth lens and a sixth lens arranged in sequence with a space therebetween, and a to-be-measured sample is further arranged between the fifth lens and the sixth lens, the orthogonal two-dimensional frequency comb pattern passes through the fifth lens and the to-be-measured sample to form an orthogonal two-dimensional frequency comb pattern carrying complex-amplitude light field imaging information, and 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 an embodiment of the present application, based on the foregoing scheme, 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.

[0022] In an embodiment of the present application, based on the foregoing scheme, the photoelectric conversion unit comprises a grating and a photodetector arranged in sequence with a space therebetween, and the coherent light beam is converted into the target electric signal by the light beam and the photodetector, the target electric signal being a time-domain oscillation signal mapped with the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0023] The present application has the beneficial effect that the laser beam output by the laser pre-modulation unit is introduced into the beam expansion lens group, the laser beam is expanded by the beam expansion lens group, and the first target laser beam obtained has good optical performance, so as to facilitate subsequent laser modulation.

[0024] Under the drive of the first preset frequency comb oscillation signal, the first acousto-optic deflector starts to work and performs first preset direction diffraction modulation on the first target laser beam. Similarly, under the drive of the second preset frequency comb oscillation signal, the second acousto-optic deflector starts to work and performs second preset direction diffraction modulation on the modulated light beam. Since the first preset direction and the second preset direction are orthogonal, an orthogonal two-dimensional frequency comb pattern can be generated, so that the two-dimensional frequency comb pattern has good spatial frequency modulation performance and can naturally modulate the laser beam to achieve good effects without the need for pixel-by-pixel structured light modulation as in the prior art.

[0025] By converting the coherent light beams 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 light beams with a two-dimensional plane, reducing the complexity of the calculation during image reconstruction, so that the system provided by the present application has a super-high throughput, achieving the technical effects of less 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 microscopic imaging can be realized, high-speed regulation and control can be performed, and good real-time imaging monitoring effect is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly described below. Obviously, the described drawings are only part of the embodiments of the present application, not all embodiments, and those skilled in the art can obtain other design schemes and drawings according to these drawings without creative labor.

[0027] Figure 1 is a whole block diagram of the system of the present application;

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

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

[0030] Figure 4 is a running logic diagram of the signal acquisition device of the present application. DETAILED DESCRIPTION

[0031] Example implementations are now described with reference to the drawings; however, it should be understood that the example implementations can be practiced in a variety of forms beyond the specific examples set forth in this document. Specifically, the example implementations should not be construed as limited to the examples set forth herein; rather, these example implementations are presented simply to provide a thorough and complete understanding of the example implementations. The example implementations are presented in such detail to allow those skilled in the art to make and use them.

[0032] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the application can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, devices, implementations, and operations have not been shown or described in detail to avoid obscuring aspects of the application.

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

[0034] The flowcharts shown in the drawings are merely exemplary illustrations, and do not necessarily include all contents and operations / steps, nor are they necessarily executed in the order described. For example, some operations / steps can be further decomposed, and some operations / steps can be combined or partially combined, so the actual execution order can be changed according to actual conditions.

[0035] It should be noted that "multiple" referred to herein means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the three cases of A alone, A and B together, and B alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0036] The background of the present application is described in detail as follows:

[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 refractive index to phase change and the absorption specificity of different spectral components. In the visible light spectral range, imaging technology solutions have made significant progress due to the maturity of silicon-based camera preparation technology. However, in the non-visible light spectral 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 spectral ranges are often inefficient or expensive, which poses a great challenge to imaging in these fields. At this time, single-pixel detectors, compared to pixel array detectors, have excellent detection performance in a wide spectral range due to their simple preparation process and strong material substitutability. A related team first brought the similar principle of reconstructing images by single-pixel measurement into people's field of vision, and through the combination of actively regulated structured illumination and computational image reconstruction by fitting algorithms, the emerging computational imaging technology of single-pixel imaging became 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 greatly improving various important imaging parameters (even realizing real-time two-dimensional imaging monitoring) is an important direction for studying macroscopic natural laws and microscopic life mechanisms in dynamic changes.

[0038] But due to the physical structure limitation of single-pixel imaging, the acquisition of computational information requires a serial scanning imaging scheme rather than a parallel measurement of the camera, so a total of two-step cumbersome computational imaging stages are required: measurement and reconstruction. For measurement, the detection frame of a single pixel requires an excessive number of measurements to make up for the lack of the number of detection elements. At this time, the speed of imaging is extremely dependent on the speed of the modulation of the optical field to establish the spatial information relationship, resulting in a low amount of information acquired by single-pixel imaging in unit time, and the imaging measurement speed is very slow. In addition, in the reconstruction process, since the essence of single-pixel imaging is computational solving, the retrieval of imaging information requires solving the optical equation relationship established by the modulation measurement, so the algorithm fitting also needs further time-consuming. Although the compressed sensing technology can reduce the excessive number of measurements through prior knowledge, it will increase the algorithm complexity, improve the computational burden and time-consuming, and the imaging quality will also be poor due to the loss of details.

[0039] For phase imaging, the development of single-pixel holographic imaging system depends on the compatibility of the built-in structured light illumination in the overall framework of single-pixel imaging and holographic imaging, so that the acquisition of complex amplitude information is realized through holographic measurement and phase dimension optical equation solving at the measurement end. Compared with the imaging of pixel array camera, the holographic structure not only needs to build Michelson interference structure for additional interference light path, but also needs to realize more complex multi-step phase shift strategy at the modulation end at the same time of structured light illumination. This makes the modulation structured light need to load multiple patterns on the same substrate, which increases the number of measurements by several times. In addition, the phase modulation limitation of multi-step phase shift also makes the modulation means of high-speed amplitude regulation more complex, which not only greatly improves the complexity of the system, but also seriously reduces the effective number of pixels of imaging, further degrading the imaging quality.

[0040] Obviously, the above-mentioned unachievable imaging parameters and various applications of the existing single-pixel imaging system can be mainly attributed to the technical scheme bottleneck defects of the physical measurement end and the algorithm reconstruction end, resulting in a low spatial bandwidth time product of the single-pixel imaging system flux. Due to the extremely low spatial bandwidth time product of single-pixel imaging technology, the number of measurements is large, the algorithm complexity is high, the imaging speed is slow, the system light path is complex, the robustness is weak, and the imaging quality is poor, which almost cannot be used in actual biological, chemical, and material applications.

[0041] The existing single-pixel holographic imaging cannot realize high-speed regulation and real-time imaging, and the image reconstruction effect is also low. This is because the single-pixel holographic imaging technology is currently severely limited by the physical detection framework and the algorithm reconstruction model, and the extremely low space-bandwidth time product results in many problems such as multiple measurements, high algorithm complexity, slow imaging speed, complex system optical path, weak robustness, and poor imaging quality. At present, there is no effective solution that can enable single-pixel imaging technology to realize high-quality real-time imaging monitoring of dynamic scene under the conditions of special spectral imaging and complex amplitude holography.

[0042] Therefore, the present application provides an ultrahigh-throughput single-pixel real-time holographic microscopic imaging system. The system of the present application mainly improves the measurement stage of single-pixel holographic imaging, provides a quadrature two-dimensional frequency comb pattern, and converts it into a target electrical signal corresponding to the coherent light beam to provide it to the signal acquisition device. The signal acquisition device can perform fast Fourier image reconstruction according to the target electrical signal, reducing the calculation difficulty, and quickly realizing image reconstruction to achieve the purpose of real-time monitoring.

[0043] The implementation details of the technical solutions of the embodiments of the present application are described in detail as follows:

[0044] According to an aspect of an embodiment of the present application, an ultrahigh-throughput single-pixel real-time holographic microscopic imaging system is provided, as shown in Figure 1 、 Figure 2 and Figure 3 . Figure 1 is a schematic diagram of the system of the present application, Figure 2 is a specific structural diagram of the system of the present application, Figure 3 is a schematic diagram of the deflection direction of the acousto-optic deflector.

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

[0046] The mirror 1 is the first mirror described in the present application, the mirror 2 is the second mirror described in the present application, the acousto-optic deflector x is the first acousto-optic deflector having an x direction in the present application, the acousto-optic deflector y is the second acousto-optic deflector having a y direction in the present application, and the lenses 1, 2, 3, 4, 5, and 6 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, respectively. Figure 2 The top view and the front view (elevation view) are shown in Figure 3It is explained that the deflection direction refers to the deflection direction of the laser beam by the acousto-optic deflector, the first preset direction of the first acousto-optic deflector can be x direction, and the second preset direction can be y direction, that is, as shown in Figure 3 The plane formed by the x direction and the y direction is perpendicular to the propagation direction of the light, and the propagation direction of the light 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 along the z direction.

[0047] The ultrahigh-throughput single-pixel real-time holographic microscopic imaging 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 the light;

[0048] 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;

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

[0050] The beam expander lens group is configured to perform beam expansion on 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 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;

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

[0053] After inputting a second preset frequency comb oscillation signal to the second acousto-optic deflector, the second acousto-optic deflector is configured to perform diffraction modulation of the modulated light beam in the second preset direction 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 configured to convert a 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.

[0055] Specifically, the embodiment of the present application introduces the laser beam output by the laser pre-modulation unit into the beam expander lens group, and performs beam expansion on the laser beam through the beam expander lens group, so that the obtained first target laser beam has good optical performance, so as to facilitate subsequent laser modulation.

[0056] Under the driving of the first preset frequency comb oscillation signal, the first acousto-optic deflector starts to work and performs first preset direction diffraction modulation on the first target laser beam. Similarly, under the driving of the second preset frequency comb oscillation signal, the second acousto-optic deflector starts to work and performs second preset direction diffraction modulation on the modulated light beam. Since the first preset direction and the second preset direction are orthogonal, 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 good natural modulation effect can be achieved on the laser beam without performing structured light modulation on each pixel as in the prior art.

[0057] 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 calculation when reconstructing the image, so that the system provided by the present application has super high throughput, achieves less measurement times, high algorithm complexity, fast imaging speed, simple system optical structure, strong robustness, and high imaging quality. At the same time, since the imaging speed of the present application is fast, continuous single-pixel holographic microscopic imaging can be realized, high-speed regulation and control can be performed, and good real-time imaging monitoring effect can be achieved.

[0058] Further, the laser pre-modulation unit comprises a laser source, a half-wave plate, a polarization beam splitter, a first mirror and a second mirror 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 mirror and the second mirror in sequence to form the laser beam meeting the preset condition.

[0059] Reference Figure 2As shown, the specific parameters of the laser source in the laser pre-modulation unit can be set to ~3kHz narrow-bandwidth laser of 1030nm wavelength, that is, a continuous laser, and the continuous laser can select different wavebands as the light source, and the regulated power is 400mW for stable detection. The half-wave plate is adjusted to change the linear polarization direction and ensure that the extinction ratio of linear polarization reaches the maximum, and the light splitting output of the polarization beam splitter can adjust the corresponding laser intensity for different linear polarization directions, and finally ensure the stable linearly polarized light output with high extinction ratio and tunable power. Finally, the laser beam meeting the preset conditions is output, and the preset conditions are that the extinction ratio performance of the polarization beam splitter meets the preset extinction ratio performance requirements, and also has a preset wavelength and a preset frequency, which can be adjusted according to the requirements of the laser source, that is, the output parameters of the aforementioned continuous laser.

[0060] Further, the beam expander lens set 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, the laser beam is expanded by the first lens and the second lens, and the first target laser beam is obtained; the focal length of the first lens is 7.5mm, and the focal length of the second lens is 60mm.

[0061] Specifically, after being guided by the first mirror and the second mirror, the laser beam enters the first lens, is expanded in the beam expander lens set composed of the first lens and the second lens with focal lengths of 7.5mm and 60mm respectively, 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 set and a second acousto-optic deflector.

[0062] Further, the system further includes a diaphragm arranged between the second lens and the first acousto-optic deflector, the diaphragm is used to adapt the first target laser beam emitted from the second lens to the entrance of the first acousto-optic deflector, and the aperture of the diaphragm is 5mm. The conversion lens set 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 125mm.

[0063] Specifically, the first acousto-optic deflector and the second acousto-optic deflector with high bandwidth and high modulation point number are used to realize 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 a conversion lens set with a 125mm focal length of a strict 4f imaging system (that is, the third lens and the fourth lens) is built in the middle.

[0064] First linearly polarized expanded beam source (i.e. the first target laser beam described in the present application) will first pass through the first acousto-optic deflector, and a 5mm diameter input aperture stop 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 sinusoidal oscillation signals (i.e. the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal described in the present application) with a bandwidth of 30MHz will be used as radio frequency driving signals 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 acoustic wave will form 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, and different diffraction beams will carry different frequency modulation components, thus obtaining a modulated beam. After the beam is re-converged by the 4f imaging system (i.e. the third lens and the fourth lens) and passes through the second acousto-optic deflector, it is recorded 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 beam) will be expanded in another dimension (representing the y direction). The sub-diffraction beams with different deflection angles (representing the second sub-diffraction beam) will load new frequency modulation components again, thereby forming a two-dimensional frequency comb light field pattern with x direction and y direction, so as to complete the pattern projection.

[0066] Further, 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.

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

[0068] f(x n ,y m )=f0+f x (x n )-f y (y m )=f0+(f intx -f inty )+(n-m)Δf

[0069] Where n and m are the coordinates of the x direction and the y direction respectively. f0 represents the frequency of the laser, i.e. 1030nm in the embodiment of the present application, f x (x n ) represents the frequency of each first sub-diffraction beam in the x direction, and f y (x m) represents the frequency of each second sub-diffraction beam 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] Further, the imaging lens group comprises a fifth lens and a sixth lens arranged in sequence with a space, and a sample to be measured is arranged between the fifth lens and the sixth lens. The orthogonal two-dimensional frequency comb pattern carries complex-amplitude light field imaging information after passing through the fifth lens and the sample to be measured, and 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. The photoelectric conversion unit comprises a grating and a photoelectric detector arranged in sequence with a space. The coherent light beam is converted into the target electric signal by the grating and the photoelectric detector. The target electric signal is a time-domain oscillation signal corresponding to the first preset frequency comb oscillation signal and the second preset frequency comb oscillation signal.

[0071] Specifically, the diffracted light beam passing through the acousto-optic frequency comb modulation module is projected as an orthogonal two-dimensional frequency comb pattern. After passing through the imaging lens group, the imaging field of view, the imaging resolution, and the imaging light beam quality of the orthogonal two-dimensional frequency comb pattern are further confirmed to meet the actual application place of the subsequent sample to be measured projection (generally, a lens with a focal length of 7.5 mm is used in a high-resolution microscopic scene). After the orthogonal two-dimensional frequency comb pattern passes through the sample to be measured, a series of optical interactions map the special spectral response absorption and refractive index to the amplitude and phase components of the frequency comb light field. The orthogonal two-dimensional frequency comb pattern carrying the complex-amplitude light field imaging information passes through the 50 mm focal length converging lens (i.e., the sixth lens) and the grating for coherent beam combination. Finally, a series of sub-beams (i.e., coherent light beams) after the beam combination realize the time-sequential signal acquisition of single-pixel imaging in the heterodyne holography with different frequency coherence (after passing through the photoelectric detector, a series of time-domain oscillation signals are formed). Finally, the signal acquisition device performs real-time acquisition, and the real-time imaging display is performed in the parallel processing of measurement and fast Fourier transform, so that the single-pixel real-time holographic microscopic imaging with ultra-high throughput is realized, which supports 1,000 frames per second real-time imaging under 80x81 pixel resolution, the lateral resolution is 3.76 μm, the field of view is about 300 μm, and is suitable for real-time dynamic monitoring in high-speed microscopic scenes.

[0072] In summary, the necessary steps in the operation process of the present application mainly include two parts: 1. Design of frequency comb radio frequency signal and driving of acousto-optic crystal; and 2. Real-time data self-referencing collimation and real-time acquisition and reconstruction.

[0073] 1. Design of frequency comb RF signal and driving of acousto-optic crystal

[0074] The probe light (initial laser beam) is generated by a 1030 nm continuous wave laser (bandwidth ~ 3 kHz) and passed through two-stage orthogonal acousto-optic deflector (i.e. the first acousto-optic deflector in x direction and the second acousto-optic deflector in y direction). The driving frequency comb of the first acousto-optic deflector is an 80th order frequency comb of 63-88 MHz with a tooth interval of 256 kHz between the frequency combs; the driving frequency comb of the acousto-optic deflector y is an 81th order frequency comb of 63-88 MHz with a tooth interval of 252 kHz between the frequency combs. Due to the 80th order frequency comb, the first target number is specifically 80, and due to the 81th order frequency comb, the second target number is specifically 81. 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 the implementation of two-dimensional spectral coding by the orthogonal frequency division multiplexing strategy, the unequal sampling between the frequencies makes the spatial frequency one-to-one correspondence, and the relative offset of the frequency combs also eliminates the spectral aliasing effect in the single sideband detection of the coherent direct measurement. The minimum frequency interval of the coherent holography of the final orthogonal two-dimensional frequency comb pattern is 1000 Hz, which can present an integer period measurement form under the 50 MSa / s rate sampling of the signal acquisition device.

[0075] After the setting parameters are completed, specifically, the laser is turned on, the arbitrary waveform generator loaded with the known RF signal frequency comb is turned on, and the electrical signal amplifier is turned on, the start of the acousto-optic frequency comb modulation module can be realized.

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

[0077] The zero-order unmodulated light is reserved as the coaxial reference light by a 50 line pairs / mm grating, and a stable interference reference is established 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 is sampled at a rate of 50 MSa / s by a signal acquisition device. As a whole, the system is running in a superfast continuous mode and will not be interrupted before the pause key of the acquisition card is pressed or the buffer memory of the acquisition card 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 screening of the two-dimensional frequency comb by the fast Fourier transform reconstruction, the image reconstruction time of GPU acceleration is <350 microseconds. At this time, the reconstruction process timing is mainly determined by Figure 4The detailed workflow is shown as follows. Firstly, in order to ensure high-quality complex amplitude imaging reconstruction through scattering medium, pre-processing calibration can be performed for real-time data self-reference collimation, that is, the system first excites a single frame capture mode, in which 1 ms of data acquisition is performed and an initial image is obtained. Considering the efficiency of the fast Fourier transform algorithm, a background without any target object is used as a relative collimation reference, and the required time is about 300 microseconds. After this initial calibration, the data acquisition card will switch to continuous mode for long-term data collection and dynamic buffer data processing. At this time, the data signal is divided into 1 ms intervals in the dynamic buffer for processing. The 1 ms data collection processing state will immediately trigger the parallel operation of the fast Fourier transform. Since data acquisition and image reconstruction are independent and parallel, the operation process of the fast Fourier transform is synchronized with the next frame of real-time acquisition process of the real-time acquisition card, and the operation of the fast Fourier transform and the self-calibration are within 1 ms, and the subsequent reconstruction can be performed without delay in the next imaging cycle. At the same time, the reconstructed image will also be updated in real time for visual demonstration.

[0078] After the parameters are set, specifically after the acousto-optic frequency comb modulation module is started, the programmable data acquisition card control software is opened through the computer terminal and the code is run, that is, the streamlined process synchronization of the fast Fourier reconstruction module and the acousto-optic frequency comb modulation module is realized. Finally, 1,000 frames / s real-time imaging under 80x81 pixel resolution is realized, the lateral resolution is 3.76 μm, the field of view is about 300 μm, and it is suitable for real-time dynamic monitoring in high-speed micro scenes.

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

[0080] It should be understood that the present application is not limited to the precise construction which has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the claims that follow.

Claims

1. An ultra-high-throughput single-pixel real-time holographic microscopy system, characterized in that: The system includes 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 that meets 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 beams having 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 configured to perform diffraction modulation on the modulated light beam in the second preset direction to obtain a second target number of second sub-diffracted light beams having 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; 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. The beam expander lens assembly 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 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; The system further includes a conversion lens group, the conversion lens group including a third lens and a fourth lens arranged in sequence, the third lens and the fourth lens being 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; The imaging lens group includes a fifth lens and a sixth lens 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 passes through the fifth lens and the sample to be measured to form an orthogonal two-dimensional frequency comb pattern carrying complex amplitude light field imaging information, 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.

2. The ultra-high-throughput single-pixel real-time holographic microscopy imaging system according to claim 1, characterized in that: The system further includes an aperture disposed between the second lens and the first AOD, the aperture being configured to allow the first target laser beam emitted from the second lens to fit into an entrance of the first AOD, and the aperture of the aperture being 5 mm.

3. The ultra-high-throughput single-pixel real-time holographic microscopy imaging system according to claim 2, 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.

4. The ultra-high-throughput single-pixel real-time holographic microscopy imaging system according to claim 3, characterized in that: The photoelectric conversion unit includes a grating and a photodetector arranged in sequence at intervals. The coherent light beam is converted into the target electrical signal through the grating 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.

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

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