A non-invasive single-frame wide-spectrum scattering imaging system and imaging method based on sub-region homogenization

Abstract

The application discloses a kind of non-invasive single-frame wide spectrum scattering imaging systems based on sub-region homogenization, including the light source and adjusting module, imaging module and image detection module arranged in sequence;The light source and adjusting module include: wide spectrum light source and optical path collimator arranged in sequence;The imaging module includes: target and scattering medium arranged in sequence;The image detection module includes: detector and data processing terminal arranged in sequence;The detector is electrically connected with the data processing terminal;The light spot formed after the wide spectrum light source passes through optical path collimator covers the target.The application also discloses a kind of non-invasive single-frame wide spectrum scattering imaging method based on sub-region homogenization.The application only needs to detect the speckle image obtained by single-frame exposure of detector, and the target reconstruction under wide spectrum illumination can be realized, with high time resolution, and the reconstruction result has high spatial resolution, so it is strong in universality.

Description

Technical Field

[0001] This invention belongs to the field of scattering imaging and computational imaging technology, specifically relating to a non-invasive single-frame broadband scattering imaging system and imaging method based on sub-region homogenization. Background Technology

[0002] Traditional imaging systems primarily acquire and interpret information from ballistic light. However, this often requires the imaging system to operate in a relatively "clean" environment. In imaging systems, when scattering media are present in the optical path, such as fog, turbid liquids, or biological tissue, the propagation direction of photons and the wavefront phase of the incident light undergo random changes. The proportion of ballistic light decreases rapidly due to scattering, resulting in the detector acquiring a speckle pattern rather than a direct image of the target object. Hidden within this seemingly chaotic speckle pattern is "coded" target information. Extracting the necessary information from the speckle pattern to reconstruct the target object is called scattering imaging. Scattering imaging has significant research value and implications in fields such as military security, biomedicine, and autonomous driving.

[0003] Currently, wavefront modulation (WFS) and deconvolution methods can image targets through scattering media. Wavefront modulation uses phase compensation devices, such as spatial light modulators (SLMs), to correct for phase changes caused by the scattering medium. The corrected optical system can be considered equivalent to a traditional optical system. Deconvolution uses a point light source to obtain the system's point spread function (PSF) in advance. The acquired intensity map is considered to be the result of convolution between the target and the system's PSF. Deconvolution algorithms, such as the Richardson-Lucy algorithm and the Winner filtering algorithm, are used to solve for target information.

[0004] However, both of these methods require prior system calibration. To address this issue, a non-invasive scattering imaging method based on single-frame speckle autocorrelation was proposed. This method can recover the target from a single frame image, offering advantages such as ease of operation, lensless single-lens operation, and high-quality recovery. However, this method requires a narrow spectral width of the light source. As the spectral width of the light source increases, the quality of the target recovery result rapidly deteriorates or even fails to produce an image. Broadband scattering imaging technology based on speckle field polarization common-mode suppression successfully solves the problem of broadband speckle correlation imaging. By utilizing the polarization characteristics of the scattered field, interference in the autocorrelation caused by the broadband light source is suppressed, achieving non-invasive scattering imaging under broadband light sources. However, this method requires the incident light to be linearly polarized and requires the acquisition of speckle patterns at 0°, 45°, 90°, and 135°. Therefore, the non-invasive speckle correlation imaging method cannot be applied to light fields with excessive background noise caused by the spectral width of incoherent white light sources, which limits the application range of non-invasive broadband scattering imaging. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a non-invasive single-frame broadband scattering imaging system and method based on sub-region homogenization. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] A first aspect of the present invention provides a non-invasive single-frame broadband scattering imaging system based on sub-region homogenization, comprising a light source and adjustment module, an imaging module and an image detection module arranged sequentially.

[0007] The light source and adjustment module include: a broadband light source and an optical path collimator arranged sequentially;

[0008] The imaging module includes: a target and a scattering medium arranged sequentially;

[0009] The image detection module includes: a detector and a data processing terminal arranged sequentially;

[0010] The detector is electrically connected to the data processing terminal;

[0011] The broadband light source, after passing through the optical collimator, forms a light spot that covers the target.

[0012] In one embodiment of the present invention, the optical collimator includes: an aperture stop and a collimating lens arranged sequentially.

[0013] In one embodiment of the present invention, the scattering medium is frosted glass;

[0014] The frosted glass has one and only one rough surface.

[0015] In one embodiment of the present invention, the broadband light source has a visible light spectrum.

[0016] In one embodiment of the present invention, the detector is a scientific-grade camera.

[0017] A second aspect of this invention provides a non-invasive single-frame broadband scattering imaging method based on sub-region homogenization, applied to the data processing terminal of the imaging system provided in the first aspect of this invention, characterized by comprising the following steps:

[0018] Obtain the original speckle pattern;

[0019] The original speckle pattern is subjected to sub-region homogenization processing to obtain a reconstructed speckle pattern; wherein the contrast of the reconstructed speckle pattern is greater than that of the original speckle pattern;

[0020] Autocorrelation is performed on the reconstructed speckle pattern to determine the target autocorrelation information;

[0021] Based on the target's self-related information, the target is reconstructed to obtain a target image.

[0022] In one embodiment of the present invention, the step of performing sub-region homogenization processing on the original speckle pattern to obtain a reconstructed speckle pattern includes:

[0023] The original speckle pattern is divided into multiple initial sub-regions;

[0024] Each initial sub-region is subjected to intensity homogenization processing to obtain an intermediate sub-region;

[0025] Multiple intermediate sub-regions are spliced ​​together according to their corresponding positions in the original speckle pattern based on their corresponding initial sub-regions to obtain a spliced ​​speckle pattern.

[0026] The spliced ​​speckle pattern and the original speckle pattern are processed to obtain the reconstructed speckle pattern.

[0027] In one embodiment of the present invention, the step of performing intensity uniformization processing on each of the initial sub-regions to obtain intermediate sub-regions includes:

[0028] Calculate the average intensity value of all pixels in each initial sub-region;

[0029] The average value is used as the intensity value of each pixel in the corresponding initial sub-region to obtain the intermediate sub-region.

[0030] In one embodiment of the present invention, processing the spliced ​​speckle pattern and the original speckle pattern to obtain a reconstructed speckle pattern includes:

[0031] The reconstructed speckle pattern is obtained by dividing the spliced ​​speckle pattern by the original speckle pattern.

[0032] In one embodiment of the present invention, the step of reconstructing the target based on the target autocorrelation information to obtain a target image includes:

[0033] The Fourier amplitude information of the target is determined based on the target's self-related information;

[0034] The Fourier amplitude information of the target is processed by a phase recovery algorithm to obtain the Fourier phase of the target;

[0035] The target image is obtained by performing an inverse Fourier transform on the Fourier phase of the target.

[0036] The beneficial effects of this invention are:

[0037] This invention achieves imaging through randomly scattering media under broadband illumination by utilizing a sub-region homogenization method. Compared with traditional speckle correlation imaging methods, the technique provided by this invention effectively suppresses interference from cross-correlation between different narrow bands caused by broadband illumination, improves speckle contrast, and results in clearer reconstructed image contours, significantly enhancing the reconstruction quality of the target and improving the signal-to-noise ratio and structural similarity of the reconstructed image. It realizes imaging through randomly scattering media under broadband illumination, solving the problem of severe noise or even inability to reconstruct under broadband illumination, improving the signal-to-noise ratio and structural similarity of the reconstructed target image, and expanding the application scope of scattering imaging technology. This invention achieves target reconstruction under broadband illumination without requiring any prior information or narrowband filters, only needing speckle images acquired by a single-frame exposure of the detector. It has high temporal resolution and high spatial resolution, thus possessing strong universality.

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of a non-invasive single-frame broadband scattering imaging system based on sub-region homogenization, provided in an embodiment of the present invention.

[0040] Figure 2 This is a flowchart illustrating another non-invasive single-frame broadband scattering imaging method based on sub-region homogenization provided in an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] A-Light source and adjustment module; B-Imaging module; C-Image detection module; 1-LED broadband light source; 2-Aperture; 3-Collimating lens; 4-Target; 5-Scattering medium; 6-Detector; 7-Computer. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0044] Example 1

[0045] like Figure 1 As shown, a first aspect of the present invention provides a non-invasive single-frame broadband scattering imaging system based on sub-region homogenization, comprising a light source and adjustment module A, an imaging module B, and an image detection module C arranged sequentially.

[0046] The light source and adjustment module A includes a broadband light source and an optical collimator arranged sequentially. The broadband light source has a visible light spectrum; in this embodiment, the broadband light source is an LED broadband light source 1, emitting completely unpolarized light. Preferably, it can be a white LED light source with a bandwidth of 200nm. The optical collimator allows for better matching of the light spot size with the target size.

[0047] Imaging module B includes a target 4 and a scattering medium 5 arranged sequentially. The modulated light beam is scattered by the scattering medium 5, thereby forming a speckle light field. The light spot formed by the broadband light source after passing through the optical collimator covers the target 4. The target 4 is approximately 1.5 mm in size.

[0048] The image detection module C includes a detector 6 and a data processing terminal arranged sequentially. The detector 6 is electrically connected to the data processing terminal. The detector 6 is used to receive speckle patterns carrying target information and with phase modulation. The data processing terminal is a computer 7, used to store and process the speckle patterns received by the detector 6.

[0049] Furthermore, the optical collimator includes: an aperture stop 2 and a collimating lens 3 arranged sequentially. For example... Figure 1 As shown, the LED broadband light source 1, aperture 2, collimating lens 3, target, scattering medium 5, and detector 6 are arranged sequentially. The scattering medium 5 is frosted glass (220-grit ground glass, Edmund); the frosted glass has one and only one rough surface. The detector 6 is a scientific-grade camera.

[0050] The broadband illumination scattering imaging system of this embodiment is simple in structure, highly stable, and inexpensive. The data processing terminal of this embodiment is used to execute the imaging method of Embodiment 2.

[0051] Example 2

[0052] like Figure 2 As shown, a second aspect of the present invention provides a non-invasive single-frame broadband scattering imaging method based on sub-region homogenization. Based on the imaging system of Embodiment 1, the following steps are performed by a data processing terminal:

[0053] Step 10: Obtain the original speckle pattern. The data processing terminal receives the original speckle pattern sent by detector 6.

[0054] Step 20: Perform sub-region homogenization processing on the original speckle pattern to obtain the reconstructed speckle pattern. After processing the low-contrast original speckle pattern, a high-contrast reconstructed speckle pattern is obtained.

[0055] Among them, the contrast of the reconstructed speckle pattern is greater than that of the original speckle pattern.

[0056] The specific steps in this process include steps 21-24:

[0057] Step 21: Divide the original speckle pattern into multiple initial sub-regions.

[0058] Step 22: Perform intensity homogenization on each initial sub-region to obtain the intermediate sub-region.

[0059] Specifically, step 22 includes steps 221-222:

[0060] Step 221: Calculate the average intensity value of all pixels in each initial sub-region. An average intensity value is calculated for each initial sub-region.

[0061] Step 222: The average value is used as the intensity value of each pixel in the corresponding initial sub-region to obtain the intermediate sub-region. In this step, the intensity value of each pixel in the initial sub-region is set to the average value corresponding to that initial sub-region. After performing the same processing on each initial sub-region, multiple processed intermediate sub-regions are finally obtained.

[0062] Step 23: Multiple intermediate sub-regions are stitched together according to their corresponding positions in the original speckle pattern based on their initial sub-regions, resulting in a stitched speckle pattern. In this step, the intermediate sub-regions are stitched together in the order they appear in the original speckle pattern.

[0063] Step 24: Process the spliced ​​speckle pattern and the original speckle pattern to obtain the reconstructed speckle pattern. Specifically, divide the spliced ​​speckle pattern and the original speckle pattern to obtain the reconstructed speckle pattern.

[0064] Step 30: Perform autocorrelation on the reconstructed speckle pattern to determine the target autocorrelation information.

[0065] Specifically, by performing autocorrelation on the reconstructed speckle pattern, the autocorrelation information of the target can be estimated:

[0066]

[0067] in, I represents the reconstructed speckle pattern, and O represents the image of the target. δ is the sum of autocorrelation across all narrowband bands, a peak function. However, its peak value is not 1, but rather depends on the amount of autocorrelation N. λ i and λ j Δλ represents the center wavelength of two different narrow spectrums. i and Δλ j These represent the spectral widths of two different narrow spectra. B sum (λ i ,λ j ,Δλi ,Δλ j ) represents the cross-correlation term between narrowband bands. B represents the background noise term when calculating autocorrelation.

[0068] As can be seen from the above formula, the background noise B of the reconstructed speckle pattern obtained after processing the original speckle pattern through steps 21-24 is small and can be ignored. Therefore, it can be considered that the autocorrelation of the reconstructed speckle pattern is equivalent to the autocorrelation of the target image.

[0069] Step 40: Reconstruct the target image based on its self-correlation information. In this step, the Fourier amplitude of the target is obtained according to Wiener-Khinchin's theorem, and the original target is reconstructed using a phase retrieval algorithm. Specifically, this step includes steps 41-43:

[0070] Step 41: Determine the Fourier amplitude information of the target based on the target's autocorrelation information. According to Wiener-Khinchin's theorem, the Fourier amplitude information |F{O(x,y)}| of the target can be obtained from the target's autocorrelation information:

[0071] F -1 {|F{O(x,y)}| 2}=O(x,y)★O(x,y).

[0072] Step 42: Process the Fourier amplitude information of the target using a phase retrieval algorithm to obtain the Fourier phase of the target. The Fourier phase e of the target is obtained using the phase retrieval algorithm. i2πO(ξ,η) .

[0073] Step 43: Perform an inverse Fourier transform on the Fourier phase of the target to obtain the target image. The target can then be reconstructed using the inverse Fourier transform.

[0074] In this embodiment, imaging through a random scattering medium 5 under broadband illumination is achieved by utilizing a sub-region homogenization processing method. Compared with traditional speckle correlation imaging methods, the technique provided by this invention effectively suppresses the interference of cross-correlation between different narrow bands caused by broadband light sources, improves speckle contrast, and results in clearer reconstructed image contours, greatly enhancing the reconstruction quality of the target and improving the signal-to-noise ratio and structural similarity of the reconstructed image. The imaging method in this embodiment does not require prior information or target location information and only needs to acquire a single frame of speckle pattern, significantly improving the imaging temporal resolution and making it possible to quickly achieve high-resolution scattering imaging under broadband illumination, thus possessing better universality.

[0075] This embodiment solves the problem that the non-invasive speckle correlation imaging method cannot be applied due to the excessive background noise caused by the spectral width of the white light incoherent source. Moreover, the system structure is simple and stable, requiring no prior information or narrowband filter, and no need to acquire multiple speckle patterns, thus realizing single-frame broadband high-resolution imaging through the scattering medium 5.

[0076] Example 3

[0077] This embodiment also provides a method for using a non-invasive single-frame broadband scattering imaging system based on sub-region homogenization, applied to the imaging system of Embodiment 1, including the following steps:

[0078] Step 1: Turn on the LED broadband light source 1.

[0079] Step 2: Align the aperture 2 with the center of the collimating lens 3, and adjust the position so that the light spot completely covers the target 4.

[0080] Step 3: Place the frosted glass at a distance of 460cm from the target.

[0081] Step 4: Place detector 6 12cm away from the frosted glass behind it.

[0082] Step 5: Open the original speckle pattern generated by the receiving system of detector 6, and adjust the position of detector 6 so that the scattered light spot is located at the center of the target surface of detector 6.

[0083] Step six: The imaging method steps in Example 2 are executed by computer 7.

[0084] This embodiment achieves broadband high-resolution transmission through a scattering medium 5 imaging without any prior or reference information under a broadband illumination source such as white LED or natural light, which is inexpensive and readily available, by acquiring a single frame speckle image. This greatly promotes the development of the scattering imaging field and improves the universality of scattering imaging technology.

[0085] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0086] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0087] 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 non-invasive single-frame broadband scattering imaging method based on sub-region homogenization, applied to the data processing terminal of an imaging system, characterized in that, The imaging system includes a light source and adjustment module (A), an imaging module (B), and an image detection module (C) arranged in sequence; the light source and adjustment module (A) includes a broadband light source and an optical collimator arranged in sequence; the imaging module (B) includes a target (4) and a scattering medium (5) arranged in sequence; the image detection module (C) includes a detector (6) and a data processing terminal arranged in sequence; the detector (6) is electrically connected to the data processing terminal; the light spot formed by the broadband light source after passing through the optical collimator covers the target (4); the optical collimator includes an aperture (2) and a collimating lens (3) arranged in sequence; The method includes the following steps: Obtain the original speckle pattern; The original speckle pattern is subjected to sub-region homogenization processing to obtain a reconstructed speckle pattern; wherein the contrast of the reconstructed speckle pattern is greater than that of the original speckle pattern; Autocorrelation is performed on the reconstructed speckle pattern to determine the target autocorrelation information; Target reconstruction is performed based on the target self-related information to obtain the target image; The step of performing sub-region homogenization processing on the original speckle pattern to obtain the reconstructed speckle pattern includes: The original speckle pattern is divided into multiple initial sub-regions; Calculate the average intensity value of all pixels in each initial sub-region; The average value is used as the intensity value of each pixel in the corresponding initial sub-region to obtain the intermediate sub-region; Multiple intermediate sub-regions are spliced ​​together according to their corresponding positions in the original speckle pattern based on their corresponding initial sub-regions to obtain a spliced ​​speckle pattern. The reconstructed speckle pattern is obtained by dividing the spliced ​​speckle pattern by the original speckle pattern.

2. The non-invasive single-frame broadband scattering imaging method based on sub-region homogenization according to claim 1, characterized in that, The step of reconstructing the target image based on the target autocorrelation information includes: The Fourier amplitude information of the target is determined based on the target's self-related information; The Fourier amplitude information of the target is processed by a phase recovery algorithm to obtain the Fourier phase of the target; The target image is obtained by performing an inverse Fourier transform on the Fourier phase of the target.

3. The non-invasive single-frame broadband scattering imaging method based on sub-region homogenization according to claim 1, characterized in that, The scattering medium (5) is frosted glass; The frosted glass has one and only one rough surface.

4. The non-invasive single-frame broadband scattering imaging method based on sub-region homogenization according to claim 1, characterized in that, The broadband light source has a visible light spectrum.

5. The non-invasive single-frame broadband scattering imaging method based on sub-region homogenization according to claim 1, characterized in that, The detector (6) is a scientific-grade camera.

Images