A Fourier stacking microscopy system based on spatial light modulator

Abstract

The invention belongs to the technical field of microscopic imaging, and discloses a Fourier stack microscopic system based on a spatial light modulator, comprising: an LED light source; a first beam shaping unit, used for shaping the light emitted by the LED light source into a uniform and collimated illumination beam, and irradiating the light beam onto the spatial light modulator; a projection prism, arranged between the first beam shaping unit and the spatial light modulator; a second beam shaping unit, used for shaping the light field modulated by the spatial light modulator into an angled beam, and irradiating the beam onto the surface of a target object; a camera, used for collecting an image of the target object under the illumination of the light beam; a control unit, used for analyzing the image captured by the camera to obtain a super-resolution image; the system can realize the control of the illumination beam angle and realize the effective utilization of the illumination light source energy.

Description

Technical Field

[0001] The invention belongs to the technical field of microscopic imaging, and in particular relates to a Fourier stack microscopic system based on a spatial light modulator. Background Art

[0002] Fourier Ptychographic Microscopy (FPM) is a computational microscopy technique based on phase recovery. It uses the change of illumination angle to expand the frequency bandwidth of the microscope and obtain super-resolution images. The core of FPM lies in phase resolution and image reconstruction. It restores high-resolution amplitude and phase images by superimposing and iteratively optimizing the frequency domain information of multiple low-resolution images. The following is a detailed introduction to the phase resolution and image reconstruction algorithm model in Fourier Ptychographic Microscopy.

[0003] In FPM, the illumination conditions of the sample are changed by adjusting the incident angle of the light source, and a series of low-resolution images are taken. Each image corresponds to the information of the object at a different spatial frequency. By combining these images under different illumination conditions, a super-resolution image can be restored.

[0004] In the process of realizing the present invention, the inventors found that there are at least the following problems in the prior art: in the existing Fourier stack microscopy imaging system, an LED array is used to perform time-sharing illumination and collection of the target, and the imaging position is inaccurate, resulting in poor imaging effect; and an unshaped large-angle LED light source is used, which cannot effectively concentrate the illumination energy on the target surface.

[0005] The above description of the background technology is only for facilitating an in-depth understanding of the technical solution of the present invention (such as the technical means used, the technical problems solved and the technical effects produced), and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention aims to solve the above technical problems at least to a certain extent. To this end, the present invention aims to provide a Fourier stack microscopy system based on a spatial light modulator.

[0007] The technical solution adopted by the present invention is:

[0008] A Fourier stacking microscopy system based on a spatial light modulator, comprising:

[0009] LED light source;

[0010] A first beam shaping unit, used to shape the light emitted by the LED light source into a uniform and collimated illumination beam, and irradiate it onto the spatial light modulator;

[0011] A projection prism is disposed between the first beam shaping unit and the spatial light modulator;

[0012] A second beam shaping unit, used to shape the light field modulated by the spatial light modulator into a beam with an angle, and irradiate the beam onto the surface of the target object;

[0013] A camera, used for collecting an image of a target object under the illumination of the light beam;

[0014] The control unit is used to analyze the image captured by the camera to obtain a super-resolution image.

[0015] Preferably, the control unit analyzes the image using a Fourier stack microscopy analysis algorithm model.

[0016] Preferably, the control unit analyzes the image including:

[0017] Step S1, phase recovery: the phase recovery adopts the Gerchberg-Saxton iteration method or the alternating minimization method;

[0018] Step S2: Image reconstruction:

[0019] The image collected at each illumination angle corresponds to a portion of the sample spectrum, and these partial spectra are spliced ​​into a larger frequency domain through phase recovery and frequency domain limitation;

[0020] As the image spectra at different angles are gradually spliced ​​together, the entire spectrum range continues to expand, and the high-frequency information of the sample is gradually restored;

[0021] After the stitching is completed, the frequency domain information is converted back to the spatial domain through inverse Fourier transform to obtain an updated sample image; the image is constrained according to the known amplitude information of the low-resolution image.

[0022] Preferably, a barrel lens and an objective lens are provided between the camera and the target object.

[0023] Preferably, the LED light source is a white LED or an RBG complex color LED. The spatial light modulator is a DMD spatial light modulator, an LCOS spatial light modulator or a liquid crystal spatial light modulator. The second beam shaping unit is a single lens or a multi-lens lens group.

[0024] The beneficial effects of the present invention are:

[0025] The present invention provides a Fourier stacking microscopy system based on a spatial light modulator, which generates an angled parallel light beam to illuminate a target through an LED light source, a spatial light modulator, and a beam shaping unit, and processes the captured image through a Fourier stacking microscopy analysis algorithm model to achieve super-resolution imaging; the system can control the angle of the illumination beam and achieve effective utilization of the energy of the illumination light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the optical path of the Fourier stack microscopy system based on the spatial light modulator of the present invention.

[0027] In the figure: 1-LED light source; 2-first beam shaping unit; 3-projection prism; 4-spatial light modulator; 5-second beam shaping unit; 6-sample; 7-objective lens; 8-barrel mirror; 9-camera. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention. The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations.

[0029] In the present invention, unless otherwise clearly stipulated and limited, terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal connection of two elements.

[0030] like Figure 1 As shown, a Fourier stack microscopy system based on a spatial light modulator in this embodiment includes an LED light source 1, a first beam shaping unit 2, a projection prism 3, a spatial light modulator 4, a second beam shaping unit 5, an objective lens 7, a barrel lens 8, and a camera 9. The projection prism 3 is arranged between the first beam shaping unit 2 and the spatial light modulator 4, and the first beam shaping unit 2 is used to shape the light emitted by the LED light source 1 into a uniform and collimated illumination beam, and irradiate it onto the spatial light modulator 4 through the projection prism 3.

[0031] The second beam shaping unit 5 is used to shape the light field modulated by the spatial light modulator 4 into a beam with a specific angle, and irradiate it onto the surface of the sample 6. A barrel mirror 8 and an objective lens 7 are provided between the camera 9 and the sample 6. The camera 9 collects the image of the target object under the illumination of the light beam through the barrel mirror 8 and the objective lens 7; the spatial light modulator 4 is encoded to change the imaging angle so that the image of the sample 6 illuminated at multiple angles can be collected. The control unit uses the Fourier stack microscopy analysis algorithm model to analyze the image taken by the camera 9 to obtain a super-resolution image.

[0032] The LED light source 1 is a white LED or an RBG complex color LED; the spatial light modulator 4 is a DMD spatial light modulator, an LCOS spatial light modulator or a liquid crystal spatial light modulator; and the second beam shaping unit 5 is a single lens or a multi-lens lens group.

[0033] The working process of the above-mentioned Fourier stack microscopy system is:

[0034] 1. Shape the light emitted by the LED light source 1 into a uniform and collimated illumination beam, and irradiate it onto the spatial light modulator 4;

[0035] 2. Using the second beam shaping unit 5 to shape the light field modulated by the spatial light modulator 4 into an illumination beam with a specific angle, and irradiate it onto the surface of the sample 6;

[0036] 3. Using camera 9 to collect images under the illumination of the angle light beam;

[0037] 4. Overlap the above steps, changing the imaging angle during the process, so that images illuminated from multiple angles can be collected;

[0038] 5. The control unit uses the Fourier stack microscopy analysis algorithm model to analyze the captured image and obtain the final super-resolution image through calculation.

[0039] The control unit analyzes the image including the following steps:

[0040] Step S1, phase recovery: indirectly recover the phase information of the sample through an iterative reconstruction algorithm in the frequency domain.

[0041] Phase retrieval uses the Gerchberg-Saxton iterative method or the alternating minimization method.

[0042] The Gerchberg-Saxton iteration method includes:

[0043] 1. Initialization: First, extract amplitude information from low-resolution images collected under multi-angle illumination and use it as the initial estimate. The phase part can be initialized to zero or a random value.

[0044] 2. Frequency domain restriction: Perform Fourier transform on the current complex amplitude to obtain the frequency domain representation of the sample; in the frequency domain, only the spectrum information within the frequency range observable under the current illumination angle is retained, and the other parts remain unchanged;

[0045] 3. Update phase information: According to the intensity constraint of the low-resolution image, the updated spectrum information in the frequency domain is converted back to the image space through inverse Fourier transform; in the image space, the intensity of the original image (i.e., the amplitude remains unchanged) is maintained, and the phase information in the complex amplitude is updated;

[0046] 4. Repeated iteration: Repeat the steps of frequency domain restriction and image space constraint, and gradually optimize the phase estimate through multiple iterations until convergence.

[0047] Step S2, image reconstruction: Expand the frequency domain coverage through multi-angle illumination. For each angle of illumination, the spectrum of the object will shift, thereby obtaining information in different frequency regions. By splicing and superimposing the low-resolution image spectra at different angles, the spectrum bandwidth can be gradually expanded and high-frequency details can be restored.

[0048] Image reconstruction includes the following steps:

[0049] Step S21, spectrum stitching: the image collected at each illumination angle corresponds to a part of the sample spectrum, and these partial spectra are stitched into a larger frequency domain through phase recovery and frequency domain limitation;

[0050] Step S22, frequency domain bandwidth expansion: as the image spectra at different angles are gradually spliced, the entire spectrum range is continuously expanded, and the high-frequency information of the sample is gradually restored; this process is equivalent to super-resolution reconstruction, which can break through the diffraction limit of the microscope;

[0051] Step S23, image space constraint: after stitching is completed, the frequency domain information is converted back to the spatial domain by inverse Fourier transform to obtain an updated sample image; the image is constrained according to the known amplitude information of the low-resolution image to ensure that the reconstruction result is consistent with the acquired data.

[0052] After frequency domain expansion and iterative phase recovery, the final image contains not only the low-frequency information in the low-resolution image, but also the high-frequency details restored by multi-angle illumination stitching, thus significantly improving the resolution.

[0053] Since Fourier stack microscopy is an iterative process, error optimization is required to ensure the accuracy of image reconstruction. The control unit also includes error optimization and convergence steps in the process of image analysis.

[0054] The error optimization and convergence steps include:

[0055] Mean square error: Calculate the mean square error between the reconstructed image and the acquired image in the image space, and optimize the estimation of the complex amplitude through methods such as gradient descent;

[0056] Alternating Optimization: By minimizing the error alternately in the frequency domain and the spatial domain, the accuracy of the phase and amplitude is gradually improved until a certain convergence criterion is reached.

[0057] In order to speed up the iteration process, the control unit adopts a local update strategy when parsing the image, that is, only a part of the phase and spectrum is updated each time, rather than a global update. This can significantly reduce the amount of calculation and improve the convergence speed of the algorithm.

[0058] The present invention is not limited to the above-mentioned optional implementation modes. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A Fourier stack microscopy system based on a spatial light modulator, characterized in that: include: LED light source (1); A first beam shaping unit (2) is used to shape the light emitted by the LED light source (1) into a uniform and collimated illumination beam, and irradiate the beam onto the spatial light modulator (4); A projection prism (3) is arranged between the first beam shaping unit (2) and the spatial light modulator (4); A second beam shaping unit (5) is used to shape the light field modulated by the spatial light modulator (4) into a beam with an angle, and irradiate the beam onto the surface of the target object; A camera (9) is used to collect an image of a target object illuminated by the light beam; A control unit is used to analyze the image captured by the camera (9) to obtain a super-resolution image.

2. The Fourier stack microscopy system according to claim 1, characterized in that: The control unit analyzes the image using a Fourier stack microscopy analysis algorithm model.

3. The Fourier stack microscopy system according to claim 1 or 2, characterized in that: The control unit analyzes the image including: Step S1, phase recovery; Step S2: Image reconstruction: The image collected at each illumination angle corresponds to a portion of the sample spectrum, and these partial spectra are spliced ​​into a larger frequency domain through phase recovery and frequency domain limitation; As the image spectra at different angles are gradually spliced ​​together, the entire spectrum range continues to expand, and the high-frequency information of the sample is gradually restored; After the stitching is completed, the frequency domain information is converted back to the spatial domain through inverse Fourier transform to obtain an updated sample image; the image is constrained according to the known amplitude information of the low-resolution image.

4. The Fourier stack microscopy system according to claim 3, characterized in that: The phase recovery adopts the Gerchberg-Saxton iteration method or the alternating minimization method.

5. The Fourier stack microscopy system according to claim 1, characterized in that: A barrel lens (8) and an object lens (7) are provided between the camera (9) and the target object.

6. The Fourier stack microscopy system according to claim 1, characterized in that: The LED light source (1) is a white LED or an RBG multi-color LED.

7. The Fourier stack microscopy system according to claim 1, characterized in that: The spatial light modulator (4) is a DMD spatial light modulator, an LCOS spatial light modulator or a liquid crystal spatial light modulator.

8. The Fourier stack microscopy system according to claim 1, characterized in that: The second beam shaping unit (5) is a single lens or a multi-lens lens group.

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