Fourier lamination imaging phase compensation method for full-view-field vignetting micrograph

Abstract

The invention discloses a Fourier lamination imaging phase compensation method for a full-view-field vignetting micrograph. In the Fourier laminated imaging technology, the local information of the reconstructed phase is lost due to the influence of the vignetting effect. The method comprises the following steps of: firstly, simulating a vignetting effect of phase curvature change caused by illumination delay in a light wave propagation process by introducing a phase factor with adjustable parameters; sequentially performing phase recovery on the images by using an alternating projection algorithm; a phase of a reconstructed high-resolution image is obtained through iterative convergence in a frequency domain, phase compensation is performed on the reconstructed phase by using an accurate conjugate phase, and finally a reconstructed image including compensated phase information is obtained. Therefore, the Fourier lamination imaging phase compensation method for the full-view-field vignetting micrograph can eliminate the problem that the phase of the image cannot be correctly reconstructed due to introduction of the phase curvature, and further improves the image phase reconstruction quality.

Description

(1) Technical field

[0001] The present invention belongs to the field of digital microscopic imaging, and in particular relates to a Fourier stack imaging phase compensation method for full-field vignetting micrographs. (2) Background technology

[0002] Fourier stacking combines the design strategies of synthetic aperture imaging with phase recovery techniques. Its core process involves capturing a series of low-resolution images using an illumination array. These images contain only intensity information, while phase information is lost during the acquisition process. Fourier stacking algorithms are then used to recover the sample's high-resolution phase information from these intensity distributions. Phase recovery is then performed through an iterative process, reconstructing a high-resolution image. This allows software algorithms to improve imaging quality based on existing low-resolution imaging system hardware, offering new possibilities for the development of imaging technology. Furthermore, particularly in the field of observing tiny objects, Fourier stacking can provide an imaging method that eliminates the need for complex optical systems or expensive equipment, making large-field-of-view, high-resolution imaging more accessible and economical.

[0003] Due to the different brightness and instability of the light source generated by the LED, there are different delays in the illumination of the sample. In addition, the aperture limitation of the system causes the image to be half bright and half dark, resulting in vignetting, which affects the phase reconstruction. Some existing hardware systems use the illumination system during the imaging process to obtain higher-quality reconstructed images, but they also have high requirements for system debugging accuracy and few areas for algorithmic improvement, making the reconstruction algorithm very inflexible. Using the algorithm to accurately compensate for the phase can effectively remove the phase loss caused by vignetting in the reconstruction results. (3) Summary of the invention

[0004] The present invention proposes a phase compensation method for Fourier stack imaging of full-field vignetting micrographs, aiming to solve the problem of missing phase information of reconstructed images caused by the vignetting effect in full-field Fourier stack imaging.

[0005] To achieve the above object, the present invention provides a Fourier stack imaging phase compensation method for full-field vignetting micrographs, the method comprising the following steps:

[0006] S1: Set up the digital microscope optical path and use a camera to record the central image of the full field of view;

[0007] S2: A parameter-adjustable phase factor is introduced into the collected central image to simulate the vignetting of phase curvature changes caused by illumination delay during light wave propagation;

[0008] S3: Perform phase recovery on each vignetted image, and then iterate using the images at multiple angles with recovered phases to obtain a high-resolution image containing phase information.

[0009] S4: performing phase compensation on the phase information of the obtained high-resolution image in the frequency domain to obtain complex amplitude information after phase compensation;

[0010] S5: The frequency domain information of the image finally obtained is subjected to an inverse Fourier transform to the spatial domain to obtain a reconstructed image, including the correctly reconstructed phase.

[0011] In the S1, the digital microscope light path is based on the microscope light path under vertical illumination of the calibrated and aligned LED.

[0012] In S2, the object light wave is actually modulated by the phase factor, resulting in the loss of phase information after reconstruction. This phase modulation is related to the propagation direction of the light wave and is usually proportional to the square of the propagation distance in spatial coordinates. The phase factor is expressed as:

[0013]

[0014] where i is the imaginary unit, k is the wave number, is the reference distance from the sample to the lens, x and y are the spatial coordinates, and α and β are the adjustable parameters of the system.

[0015] In S3, the reconstruction after phase recovery includes first performing phase recovery on each vignetted image using an alternating projection algorithm, and then reconstructing the image data using the recovered phase information through an iterative algorithm. It is necessary to perform Fourier transform on the image and iteratively update the complex amplitude of the image. After the iteration, the high-resolution image complex amplitude is obtained, which is expressed as:

[0016]

[0017] Where P(K) is the pupil function, which is related to the system aperture. The spectrum is limited by the finite aperture of the lens, and the sample spectrum is filtered by the pupil.

[0018] In S4, the phase of the reconstructed image is compensated in the frequency domain, and the complex amplitude is expressed as:

[0019]

[0020] in Represents the conjugate matrix for phase compensation to eliminate the influence of phase curvature.

[0021] In S5, the inverse Fourier transform is finally performed to obtain the reconstructed image information, and the formula is:

[0022] I(r)=|F -1 {O′ (KK n )}| 2

[0023] Among them F -1 For the inverse Fourier transform, the square of the modulus value is finally used to obtain the reconstructed image and the compensated phase.

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

[0025] The present invention provides a phase compensation method for Fourier stack imaging of full-field vignetted micrographs. In Fourier stack imaging technology, the vignetting effect causes the loss of local information of the reconstructed phase. The present invention first simulates the vignetting effect of the phase curvature change caused by the illumination delay during the propagation of light waves by introducing a phase factor with adjustable parameters; then performs phase recovery on the image using an alternating projection algorithm; obtains the phase of a reconstructed high-resolution image through iterative convergence in the frequency domain, performs phase compensation on the reconstructed phase using a precise conjugate phase, and finally obtains a reconstructed image including the compensated phase information. Therefore, the phase compensation method for Fourier stack imaging of full-field vignetted micrographs of the present invention can eliminate the phase of the image that cannot be correctly reconstructed due to the introduction of phase curvature, thereby further improving the quality of image phase reconstruction. (IV) Description of the accompanying drawings

[0026] Figure 1 1. It is a schematic diagram of an algorithm flow of a Fourier stack imaging phase compensation method for full-field vignetting micrographs of the present invention;

[0027] Figure 2 Schematic diagram of the phase compensation result of the present invention; (V) Specific implementation methods

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with 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 should not be understood as limiting the present invention.

[0029] See also Figure 1 The present invention provides a Fourier stack imaging phase compensation method for full-field vignetting micrographs, comprising the following steps:

[0030] S1: Set up the digital microscope optical path and use a camera to record the central image of the full field of view.

[0031] S2: A parameter-adjustable phase factor is introduced into the collected central image to simulate the vignetting of phase curvature changes caused by illumination delay during light wave propagation;

[0032] S3: Perform phase recovery on each vignetted image, and then iterate using the images at multiple angles with recovered phases to obtain a high-resolution image containing phase information.

[0033] S4: performing phase compensation on the phase information of the obtained high-resolution image in the frequency domain to obtain complex amplitude information after phase compensation;

[0034] S5: The frequency domain information of the image finally obtained is subjected to an inverse Fourier transform to the spatial domain to obtain a reconstructed image, including the correctly reconstructed phase.

[0035] The following is a further explanation based on the specific implementation steps:

[0036] In step S1 , the digital microscope light path is based on the microscope light path under vertical illumination of the calibrated and aligned LED.

[0037] In step S2, the object light wave is actually modulated by the phase factor, resulting in the loss of phase information after reconstruction. This phase modulation is related to the propagation direction of the light wave and is usually proportional to the square of the propagation distance in spatial coordinates. The phase factor is expressed as:

[0038]

[0039] where i is the imaginary unit, k is the wave number, is the reference distance from the sample to the lens, x and y are the spatial coordinates, and α and β are the adjustable parameters of the system.

[0040] In step S3, the reconstruction after phase recovery includes first performing phase recovery on each vignetted image using an alternating projection algorithm, and then reconstructing the image data using the recovered phase information through an iterative algorithm. This requires Fourier transforming the image and iteratively updating the complex amplitude of the image. After the iteration, the high-resolution image complex amplitude is obtained, which is expressed as:

[0041]

[0042] Where P(K) is the pupil function, which is related to the system aperture. The spectrum is limited by the finite aperture of the lens, and the sample spectrum is filtered by the pupil.

[0043] In step S4, the phase of the reconstructed image is compensated in the frequency domain, and the complex amplitude is expressed as:

[0044]

[0045] in Represents the conjugate matrix for phase compensation to eliminate the influence of phase curvature.

[0046] In step S5, the inverse Fourier transform is finally performed to obtain the reconstructed image information, and the formula is:

[0047] I(r)=|F -1 {O ′ (KK n )}| 2

[0048] Among them F -1 For the inverse Fourier transform, the square of the modulus value is finally used to obtain the reconstructed image and the compensated phase.

[0049] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A Fourier stack imaging phase compensation method for full-field vignetting micrographs, characterized in that: The method comprises the following steps: S1: Set up the digital microscope optical path and use a camera to record the central image of the full field of view; S2: A parameter-adjustable phase factor is introduced into the collected central image to simulate the vignetting of phase curvature changes caused by illumination delay during light wave propagation; S3: Perform phase recovery on each vignetted image, and then iterate using the images at multiple angles with recovered phases to obtain a high-resolution image containing phase information. S4: performing phase compensation on the phase information of the obtained high-resolution image in the frequency domain to obtain complex amplitude information after phase compensation; S5: The frequency domain information of the image finally obtained is subjected to an inverse Fourier transform to the spatial domain to obtain a reconstructed image, including the correctly reconstructed phase.

2. The Fourier stack imaging phase compensation method for full-field vignetting micrographs according to claim 1, characterized in that: In the S1, the digital microscope light path is based on the microscope light path under vertical illumination of the calibrated and aligned LED.

3. The Fourier stack imaging phase compensation method for full-field vignetting micrographs according to claim 1, characterized in that: In S2, the object light wave is actually modulated by the phase factor, resulting in the loss of phase information after reconstruction. This phase modulation is related to the propagation direction of the light wave and is usually proportional to the square of the propagation distance in spatial coordinates. The phase factor is expressed as: where i is the imaginary unit, k is the wave number, is the reference distance from the sample to the lens, x and y are the spatial coordinates, and α and β are the adjustable parameters of the system.

4. The Fourier stack imaging phase compensation method for full-field vignetting micrographs according to claim 1, characterized in that: In S3, the reconstruction after phase recovery includes first performing phase recovery on each vignetted image using an alternating projection algorithm, and then reconstructing the image data using the recovered phase information through an iterative algorithm. It is necessary to perform Fourier transform on the image and iteratively update the complex amplitude of the image. After the iteration, the high-resolution image complex amplitude is obtained, which is expressed as: Where P(K) is the pupil function, which is related to the system aperture. The spectrum is limited by the finite aperture of the lens, and the sample spectrum is filtered by the pupil.

5. The Fourier stack imaging phase compensation method for full-field vignetting micrographs according to claim 1, characterized in that: In S4, the phase of the reconstructed image is compensated in the frequency domain, and the complex amplitude is expressed as: in Represents the conjugate matrix for phase compensation to eliminate the influence of phase curvature.

6. The Fourier stack imaging phase compensation method for full-field vignetting micrographs according to claim 1, characterized in that: In S5, the inverse Fourier transform is finally performed to obtain the reconstructed image information, and the formula is: I(r)=|F -1 {O ′ (K-K n )}| 2 Among them F -1 This is the inverse Fourier transform, and finally the square of the modulus value is used to obtain the reconstructed image and the compensated phase.

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