Wide-spectrum microscopic system based on Fourier single-pixel simultaneous imaging

Abstract

The invention discloses a broadband spectrum microscopic system based on Fourier single-pixel simultaneous imaging, and relates to the technical field of UVA-near infrared two-region multispectral synchronous imaging. The system comprises a broadband spectrum light source, a microscopic module, a Fourier structured light generation device, a scattering medium homogenization module, a multi-channel narrow-band detector array, a multi-channel data acquisition system and a calculation imaging processing unit. By arranging and combining a plurality of narrow-band single-point detectors and combining the scattering effect of ground glass, efficient synchronous acquisition and space uniform distribution of UVA to near-infrared two-region multispectral signals are realized, and the problems of complex hardware, low time resolution, spectral crosstalk, incomplete view and the like in traditional multispectral imaging are solved. According to the system, the Fourier single-pixel imaging principle is utilized, through the synergistic effect of structured light coding and a single-pixel detector, the view field consistency of multispectral images is ensured on the hardware level, later registration is not needed, meanwhile, the system has high sensitivity, low cost and compactness, and the system is suitable for high-resolution wide-spectrum microscopic imaging in the fields of biomedicine, material science and the like.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a broadband microscopy system based on Fourier single-pixel simultaneous imaging. This system employs a multi-channel narrowband detector array optimized for scattering media to achieve simultaneous microscopic imaging over a wide spectral range in the UVA-near-infrared II region. Background Technology

[0002] Multispectral microscopy has significant applications in biomedicine, materials science, and environmental monitoring. Traditional multispectral microscopy systems primarily employ three technical approaches: 1. Multi-camera synchronous imaging: This method uses a beam splitter to separate incident light by wavelength into different cameras, achieving simultaneous multispectral imaging. This method is complex, bulky, and expensive, and the dispersive characteristics of the optical elements limit the spectral range. 2. Single-camera time-division imaging: This method uses a filter wheel or tunable filter to achieve sequential switching of different wavelengths. This method has low temporal resolution and cannot achieve true simultaneous imaging. 3. Spectral separation single-camera imaging: This method integrates a filter array on the sensor surface to achieve spatial-spectral separation imaging. This method has complex fabrication processes and high channel crosstalk.

[0003] Single-pixel imaging technology, based on compressed sensing theory, achieves image reconstruction through structured illumination and a single-point detector. Its advantages include high spectral resolution, strong anti-interference capability, and applicability to non-visible light bands. However, traditional single-pixel imaging systems suffer from the following problems: low energy efficiency (structured illumination leads to significant waste of light energy); uneven field of view (fixed detector position results in uneven distribution of the received light field); and limited spectral range (a single detector limits the detectable spectral range).

[0004] A comprehensive analysis of existing technologies reveals the following main problems: 1. High system complexity: Multi-camera systems require precise optical path alignment and synchronization control; 2. High cost: High-performance multispectral cameras are expensive; 3. Limited spectral range: Due to limitations in sensor materials, a single system cannot cover a wide spectral range; 4. Insufficient low-light sensitivity: The performance of array sensors degrades significantly in low-light environments; 5. Spatiotemporal resolution contradiction: It is difficult to achieve high temporal resolution and high spatial resolution simultaneously. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention proposes a single-pixel microscopic imaging system integrating a scattering medium and a multi-channel narrowband detector, thereby achieving simultaneous imaging across a wide spectrum. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a broadband microscopy system based on simultaneous Fourier single-pixel imaging, as shown in the attached figure. Figure 1It includes: a broadband light source, a microscopy module, a Fourier structured light generation device, a scattering medium homogenization module, a multi-channel narrowband detector array, a multi-channel data acquisition system, and a computational imaging processing unit.

[0006] The broadband light source employs a supercontinuum laser or a broadband LED array, covering a wide spectral range from UVA (315-400nm) to near-infrared II (1000-1700nm), with a spectral power density of not less than 1mW / nm.

[0007] The microscopic imaging module includes an existing microscopic architecture and a multi-zoom microscope objective, enabling magnified imaging of the sample. The numerical aperture ranges from 0.1 to 1.4, and the magnification is adjustable.

[0008] The Fourier structured light generating device uses a digital micromirror array (DMD) or a spatial light modulator (SLM) to generate a Fourier substrate pattern with a resolution of not less than 1024×768 pixels and a refresh rate of not less than 10kHz.

[0009] The scattering medium homogenization module uses a specially made frosted glass scattering sheet with a thickness of 1-5mm, a surface roughness of Ra0.1-1μm, and an adjustable scattering angle of 30°-60° to achieve a uniform distribution of the light field.

[0010] The multi-channel narrowband detector array includes multiple single-point detectors with different spectral responses, covering the UVA-near-infrared II region. Each detector has a bandwidth of 10-50nm and a response speed of not less than 1MHz.

[0011] The multi-channel data acquisition system uses a high-speed synchronous data acquisition card with a sampling rate of not less than 1MHz, a number of channels of not less than 8, and a dynamic range of greater than 80dB.

[0012] The computational imaging processing unit realizes image reconstruction based on the Fourier transform algorithm, and supports real-time processing and multispectral image fusion.

[0013] The key innovation of this invention compared to existing technologies lies in: 1. Optimization design of scattering medium: Through theoretical analysis and experimental optimization, the key parameters of the scattering medium are determined.

[0014] Scattering angle distribution: obtained using the Lambert scattering model: ,in θ represents the normal scattering intensity, and θ is the scattering angle. Optimization of scattering medium thickness: Based on Mie scattering theory, the relationship between scattering coefficient and thickness is as follows: ,in denoted as scattering coefficient, g as scattering asymmetry parameter, and t as thickness of scattering medium; Surface roughness control: Surface roughness affects scattering characteristics. ,in, Let be the surface roughness, be the wavelength, n be the refractive index, and R be the reflectivity.

[0015] 2. Optimization of multi-channel detector array layout: The detector array layout is optimized using geometric optics principles. Detector position calculation: Based on the scattering angle distribution of the scattering medium, the optimal position of the detector is: ,in Let be the distance from the i-th detector to the optical axis, and d be the distance from the detector to the scattering medium. This represents the corresponding scattering angle.

[0016] Light field uniformity assessment: The uniformity index is used to assess the light field distribution. , where U is the uniformity index, is the standard deviation of light intensity, and I is the average light intensity.

[0017] 3. Fourier Single-Pixel Imaging Algorithm. A four-step phase-shifting Fourier single-pixel imaging algorithm is used for multispectral image reconstruction: for spatial frequencies of... The Fourier basis, the Fourier coefficients are ,in , , , The phases are 0, , , The detector response value recorded at the time.

[0018] Image reconstruction algorithm: Reconstructing images using inverse Fourier transform: .

[0019] Multispectral image fusion: using a weighted fusion algorithm. ,in is the weighting coefficient for the i-th spectral channel, and N is the number of spectral channels.

[0020] In summary, this invention has the following significant advantages: wide spectral coverage (full coverage of the UVA-near-infrared II region with a single system); true simultaneous imaging (multi-channel parallel acquisition with no time difference); high low-light sensitivity (large photosensitive area and high sensitivity of single-point detector); compact system (no need for complex optical path separation system); cost-effectiveness (significantly reduced cost compared to multi-camera systems); and uniform light field (uniform illumination across the entire field of view is achieved through scattering media).

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the broadband microscopy system of the present invention; Figure 2 This is a comparison diagram showing the influence of scattering media on the light field distribution; Figure 3 This is a schematic diagram of the layout of a multi-channel narrowband detector array; Icons: 1-Broadband light source; 2-Reflector; 3-Optical tube lens; 4-Object under test; 5-Objective lens; 6-Beam splitter; 7-Structured light generating device; 8-Scattering medium; 9-Narrowband detector array; 10-Data acquisition device; 11-Computational imaging processing device; 12-Visible light bandpass filter; 13-Eyepiece. Detailed Implementation

[0023] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, describes a single-pixel microscopic imaging system for simultaneous broadband imaging based on the present invention.

[0024] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0025] In this embodiment, the broadband light source 1 is a highly stable LED array light source with an emission wavelength covering the visible to near-infrared band (320-1700nm). The function of the LED array light source is to provide a temporally stable and spatially uniform broadband illumination beam, ensuring that the sample under test is adequately illuminated throughout the entire spectral range. Exemplarily, the LED array light source can be a multi-wavelength LED combination light source, a xenon lamp light source, a halogen tungsten lamp light source, or a supercontinuum laser, etc.

[0026] In this embodiment, the microscope is a compound microscope system with an objective numerical aperture NA of 0.25-0.85 and an adjustable magnification of 10-60×, based on existing microscopic architecture. Its optical system includes an objective lens 5, an eyepiece 13, and an optical tube lens 3. Since the microscopic structural information of the sample needs to be effectively extracted through microscopic magnification, without the magnification of the microscope system, the minute sample feature information cannot be captured by the subsequent optical encoding system, which will affect the final multispectral imaging quality.

[0027] In the broadband microscopy system of this embodiment, on the one hand, the structured light generating device 7 adopts a digital micromirror array device, which can convert a uniform light beam carrying sample microscopic information into structured light with a specific spatial frequency distribution; on the other hand, the digital micromirror array realizes frequency domain encoding of sample images by rapidly switching different Fourier substrate patterns, providing the necessary spatial information modulation for subsequent single-pixel imaging.

[0028] The structure of the digital micromirror array consists of an array of tiltable micromirrors, a driving circuit, and a control chip. The micromirrors are 13.68 μm × 13.68 μm in size, and their tilt angle can be rapidly switched between +12° and -12°. Optionally, the micromirrors can be fabricated on a silicon substrate using standard semiconductor manufacturing processes to achieve high-precision optical modulation.

[0029] Furthermore, the working process of the digital micromirror array is explained. First, according to the preset Fourier substrate pattern sequence, the control chip sends a control signal to the driving circuit; the driving circuit adjusts the tilt angle of each micromirror according to the control signal. Micromirrors at a +12° angle reflect light into the imaging optical path, while micromirrors at a -12° angle reflect light away from the imaging optical path. By precisely controlling the state combination of different micromirrors, Fourier substrate patterns with different spatial frequencies and phases can be generated. The projection time of each substrate pattern is 10-100ms, ensuring that the narrowband detector 9 has sufficient integration time to acquire a stable light intensity signal. In order to obtain complete Fourier spectrum information, the system adopts a four-step phase shifting technique, that is, projecting four substrate patterns with phases of 0, π / 2, π, and 3π / 2 for each spatial frequency.

[0030] In this embodiment, the frosted glass scattering sheet 8 is located on the light output path of the digital micromirror array and is used to homogenize the structured light. The surface roughness of the frosted glass scattering sheet is Ra = 0.1-1.0 μm, and the scattering angle is 5-15°. Its function is to eliminate the spatial coherence in the structured light generated by the digital micromirror array, making the light energy distribution more uniform, and avoiding the problem of narrow field of view and imaging artifacts caused by uneven light intensity, as shown in the attached figure. Figure 2 .

[0031] In this embodiment, the narrowband detector 9 achieves a narrowband response by selecting the photosensitive material of the device or by combining a broadband detector with a narrowband filter. Taking a multi-channel silicon photodiode array equipped with different narrowband filters as an example, the center wavelengths are 450 nm, 530 nm, 620 nm, 780 nm, 1000 nm, and 1550 nm, respectively, with a full width at half maximum (FWHM) of 20 nm. The function of the narrowband filter is to separate the broadband beam into multiple narrowband spectral channels, enabling the system to simultaneously acquire spectral information of the sample at different wavelengths, achieving true multispectral simultaneous imaging. Exemplarily, the narrowband filter can be a dielectric interference filter, a Fabry-Perot filter, or a tunable filter, etc.

[0032] In this embodiment, the layout of the multi-channel narrowband detector array 9 is optimized using geometric optics principles. Multiple arrangement designs are employed to maximize light energy utilization, as shown in the attached figure. Figure 3 .

[0033] In this embodiment, the multi-channel data acquisition card is a 24-bit, 16-channel, 25 kHz high-speed data acquisition system 10, model VKinging VK7016-pro. Since the narrowband detector generates multiple electrical signals simultaneously, using a single-channel acquisition system or an asynchronous multi-channel acquisition system would result in time delays and crosstalk between different spectral channels, thus affecting the synchronization and accuracy of the multispectral images.

[0034] In the broadband microscopy system of this embodiment, the computer 11 and the computing algorithm employ a GPU-based parallel computing Fast Fourier Transform algorithm, which can process multi-channel data and reconstruct multispectral images in real time. The algorithm includes the following steps: First, the raw data for each spectral channel is preprocessed, including dark current correction, gain correction, and noise filtering; then, the Fourier coefficients for each spatial frequency are calculated according to the four-step phase shift principle; finally, a two-dimensional image of each spectral channel is reconstructed through inverse Fourier transform, and the images of multiple spectral channels are merged to comprehensively represent their effective information.

[0035] Optionally, the substrate pattern playback program employs high-precision timing control to ensure synchronization between pattern switching and data acquisition of the digital micromirror array. The program controls the digital micromirror array via a USB interface, with a pattern switching speed of up to 25 kHz, meeting the requirements of high-speed imaging.

[0036] The data acquisition program employs multi-threaded parallel processing technology, capable of processing data streams from up to 16 spectral channels simultaneously. This embodiment selects 6 spectral channels, achieving an acquisition speed of up to 25 kHz, ensuring no valid data is lost. The program also features real-time data caching and error detection functions to guarantee the reliability of data acquisition.

[0037] The image reconstruction program is based on the CUDA parallel computing architecture and leverages the high parallel processing capabilities of the GPU to reconstruct multispectral images in real time. The program employs an optimized FFT algorithm, achieving a reconstruction speed 10-50 times faster than traditional CPU algorithms, with a reconstruction time of less than 100ms for a single frame of a 768 × 768 pixel 6-channel multispectral image.

[0038] For example, taking multispectral microscopic imaging of biological cells as an example, the working process of this embodiment is described in detail: First, a broadband LED array light source 1 emits a uniform illumination beam of 320-1700nm, which illuminates the cell sample 4 on the glass slide; after the cell sample is magnified by a microscope objective system with NA=0.85 and magnification of 60×, the beam carrying the microscopic structure information of the cells is emitted from the microscope output port; the beam is modulated by a digital micromirror array to generate Fourier-based structured light with a specific spatial frequency; the structured light is homogenized by a frosted glass scattering sheet 8 to eliminate spatial coherence; the homogenized structured light is scattered light carrying the spectral information of the cells; a narrowband detector array 9 (6 arrays) simultaneously receives scattered light signals of different wavelengths and generates corresponding electrical signals through photoelectric conversion; a multi-channel data acquisition card 10 simultaneously acquires 6 electrical signals at a sampling rate of 25 kHz; a computer 11 runs a GPU-based fast Fourier transform algorithm to process the acquired data in real time, and finally reconstructs a high-resolution microscopic image of the cells in 6 spectral channels, realizing the simultaneous acquisition of cell structure and spectral information.

[0039] The broadband microscopy system based on Fourier single-pixel simultaneous imaging in this embodiment of the invention achieves high-resolution imaging of the sample's microstructure and obtains spectral information of the sample in multiple spectral channels through spatial light modulation of a digital micromirror array and spectral separation of a multi-channel narrowband detector 9. This system can help develop high-performance, compact multispectral microscopy imaging equipment and has broad application prospects in fields such as biomedicine, materials science, and environmental monitoring.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0041] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A broadband microscopy system based on simultaneous Fourier single-pixel imaging, characterized in that, include: Broadband light source, microscopic module, Fourier structured light generation device, scattering medium homogenization module, multi-channel narrowband detector array, multi-channel data acquisition system and computational imaging processing unit; The broadband light source is used to generate broadband illumination light covering the UVA (315-400nm) to near-infrared II region (1000-1700nm), with a spectral power density of not less than 1mW / nm; The microscopy module includes an existing microscopy architecture and a microscopy objective, enabling magnified imaging of the sample under test. The numerical aperture ranges from 0.25 to 0.85, and the magnification is adjustable. The Fourier structured light generating device is used to modulate the beam output from the microscopic module into Fourier substrate structured light with a specific spatial frequency distribution. The scattering medium homogenization module is used to homogenize the structured light and eliminate spatial coherence. The multi-channel narrowband detector array consists of multiple single-point detectors with different spectral responses, used to synchronously acquire scattered multispectral optical signals and convert them into electrical signals; The multi-channel data acquisition system is used to simultaneously acquire multiple electrical signals; The computational imaging processing unit performs multispectral image reconstruction based on the Fourier transform algorithm.

2. The system according to claim 1, characterized in that, The light source is a supercontinuum laser or a broadband LED array.

3. The system according to claim 1, characterized in that, The Fourier structured light generating device is a digital micromirror array (DMD) or a spatial light modulator (SLM) that generates a Fourier substrate pattern with a resolution of not less than 1024×768 pixels and a refresh rate of not less than 10 kHz.

4. The system according to claim 1, characterized in that, The scattering medium homogenization module uses a frosted glass scattering sheet, the thickness of which is 1-5 mm and the surface roughness is Ra 0.1-1 μm.

5. The system according to claim 1, characterized in that, The multi-channel narrowband detector array includes: UVA band detector (320-400 nm). Visible light band detector (400-700 nm); Near-infrared detector in region I (700-1000 nm); Near-infrared II detector (1000-17000 nm).

6. The system according to claim 5, characterized in that, The narrowband single-point detector is a silicon-based photodiode (Si-PD), an indium gallium arsenide detector (InGaAs), or a lead sulfide detector (PbS).

7. The system according to claim 1, characterized in that, The multi-channel data acquisition system uses a high-speed synchronous data acquisition card with a sampling rate of no less than 25 kHz, no less than 16 channels, and a dynamic range greater than 80 dB.

8. The system according to claim 1, characterized in that, The computational imaging processing unit employs a four-step phase-shift Fourier single-pixel imaging algorithm and performs image reconstruction through GPU parallel computing, supporting real-time processing.

9. The system according to claim 1, characterized in that, The scattering angle distribution of the scattering medium homogenization module matches the layout of the multi-channel narrowband detector array, ensuring that each detector receives the full field of view light signal uniformly.

10. The system according to claim 1, characterized in that, The system uses the Lambert scattering model to optimize the parameters of the scattering medium, determines the thickness of the scattering medium based on the Mie scattering theory, and optimizes the detector array layout through geometric optics principles.

11. The system according to claim 8, characterized in that, The four-step phase-shift Fourier single-pixel imaging algorithm includes: For each spatial frequency, project a base pattern with phases of 0, π / 2, π, and 3π / 2; Calculate the Fourier coefficients: ; Image reconstruction using inverse Fourier transform: ; A weighted fusion algorithm was used to synthesize multispectral images.

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