A method and system for correlation imaging through scattering media based on preset scattering media

Abstract

The present invention discloses a method and system for through-scattering medium correlation imaging based on a preset scattering medium, the method comprising the following steps: acquiring a laser beam, and obtaining a pseudothermal light field based on the laser beam; obtaining a detection light field and a reference light field based on the pseudothermal light field; obtaining the light intensity of an object to be measured based on scattering media in an environment and the detection light field; obtaining a speckle light intensity based on a preset scattering medium and the reference light field; and obtaining a reconstructed image of the object to be measured based on the light intensity of the object to be measured and the speckle light intensity. In order to realize through-scattering medium correlation imaging, the present invention proposes a method for through-scattering medium correlation imaging based on a preset scattering medium, which has the characteristics of low cost and low system complexity.

Description

Technical Field

[0001] The present invention belongs to the field of computational imaging technology, and in particular relates to a method and system for imaging through a scattering medium based on a preset scattering medium. Background Art

[0002] Common scattering media in life, such as fog, haze, and dust, will change the propagation path of light, resulting in a decrease in the imaging quality of traditional imaging methods based on the "point-to-point imaging mechanism". Imaging through scattering media plays an important role in remote sensing, medical imaging, imaging in smoke environments, and other scenarios, and has great application potential.

[0003] Among the existing imaging technologies through scattering media, the feedback optimization wavefront method is not very timely and the system is complex; the refocusing technology based on the transmission matrix is ​​complex and has high stability requirements; the speckle autocorrelation imaging technology based on the optical memory effect has a small imaging field of view and is limited by the range of the memory effect of the scattering medium.

[0004] Correlation imaging is a non-local imaging technology. The pseudothermal illumination light field is divided into a detection light field and a reference light field by a beam splitter. The total light intensity of the detection light after interacting with the object through the detection light path is detected by the bucket detector. The reference light field passes through the reference light path, and its light field distribution is recorded by the CCD. After multiple measurements, the measured signal is subjected to a second-order correlation operation to reconstruct the image of the target. This imaging mechanism has the advantage of "imaging away from the object" and provides a new idea for realizing imaging through scattering media.

[0005] Relevant researchers have conducted many explorations in theory and experiment. The results show that compared with traditional imaging, correlation imaging is resistant to the scattering medium between the target object and the barrel detector. However, the scattering medium between the beam splitter and the object will reduce or even lose the correlation between the light field distribution of the detection light field and the reference light field distribution collected by the CCD camera in the reference light path, thereby interfering with the imaging results of correlation imaging. There are many related reports at home and abroad on this issue, but there are some disadvantages. For example, some still need to know the transmission matrix of the scattering medium, and some need to know the prior information such as the shape of the target to be imaged. The currently reported methods have not made good use of the non-local characteristics of correlation imaging. This paper proposes a scheme of "introducing a scattering medium with the same characteristics as that in the detection arm at a position symmetrical to the beam splitter in the reference arm", which realizes the second-order correlation calculation after the preset scattering medium modulates the reference light field, and then realizes correlation imaging through the scattering medium. Summary of the invention

[0006] The present invention discloses a method and system for through-scattering medium correlation imaging based on pre-set scattering medium. Based on the imaging mechanism of non-locality of correlation imaging, a scattering medium with the same scattering characteristics as the scattering medium in the detection light path is preset at a position symmetrical to the beam splitter in the reference light path, and then second-order correlation reconstruction is performed to realize through-scattering medium correlation imaging.

[0007] To achieve the above object, on the one hand, the present invention provides a method for correlation imaging through a scattering medium based on a preset scattering medium, comprising the following steps:

[0008] Acquire a laser beam, and obtain a pseudothermal light field based on the laser beam;

[0009] Based on the pseudothermal light field, obtaining a detection light field and a reference light field;

[0010] Based on the scattering medium in the environment and the detection light field, a scene of the detection light field passing through the scattering medium in the environment is simulated, and the total light intensity passing through the object to be detected is obtained;

[0011] Based on the preset scattering medium and the reference light field, a reference speckle light field is obtained;

[0012] Based on the total light intensity transmitted through the object to be measured and the reference speckle light field, an image of the object to be measured is reconstructed by a second-order correlation algorithm.

[0013] Optionally, the process of obtaining the total light intensity passing through the object to be measured is: after the detection light field passes through the scattering medium in the environment, the object to be measured is illuminated to obtain the total light intensity passing through the object to be measured.

[0014] Optionally, the distribution calculation formula of the total light intensity passing through the object to be measured is:

[0015]

[0016] Optionally, the process of obtaining the reference speckle light field is: after the reference light field passes through the preset scattering medium, the reference speckle light field is obtained.

[0017] Optionally, the calculation formula of the reference speckle light field is:

[0018]

[0019] Optionally, the process of reconstructing the image of the object to be measured is: performing a second-order correlation calculation on the total light intensity passing through the object to be measured and the reference speckle light field to reconstruct the image of the object to be measured.

[0020] Optionally, the second-order correlation calculation formula is:

[0021] H= <a′-<A′》<b′-<B′》。

[0022] On the other hand, the present invention provides a through-scattering medium correlation imaging system based on a preset scattering medium, comprising: a laser, a rotating frosted glass, a beam splitter, a scattering medium in an environment, a preset scattering medium, a barrel detector, a CCD camera and an imaging module;

[0023] The laser is used to generate a laser beam;

[0024] The rotating frosted glass is used to obtain a pseudothermal light field based on the laser beam;

[0025] The beam splitter is used to obtain a detection light field and a reference light field based on the pseudothermal light field;

[0026] The scattering medium in the environment is used to simulate the scene when the detection light field passes through the scattering medium, and after the detection light field after passing through the scattering medium illuminates the object to be measured, the total light intensity passing through the object to be measured is obtained;

[0027] The preset scattering medium is used to obtain a reference speckle light field based on the preset scattering medium and the reference light field;

[0028] The barrel detector is used to detect the total light intensity passing through the object to be tested;

[0029] The CCD camera is used to collect the reference speckle light field;

[0030] The imaging module is used to reconstruct an image of the object to be measured based on the total light intensity transmitted through the object to be measured and the reference speckle light field.

[0031] Compared with the prior art, the technical effects of the present invention are:

[0032] In order to realize through-scattering medium correlation imaging, the present invention proposes a through-scattering medium correlation imaging method based on a preset scattering medium, which has the characteristics of low cost and low system complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0034] Figure 1 It is a schematic diagram of the device for associative imaging described in the present invention.

[0035] Figure 2 It is a schematic diagram of the device when there is a scattering medium between the beam splitter and the object to be measured according to the present invention.

[0036] Figure 3It is a schematic diagram of a device for presetting a scattering medium having the same scattering characteristics as the scattering medium in the detection light path in the reference light path according to the present invention.

[0037] Figure 4 : is a comparison diagram of imaging results. Among them: (a) is the imaging result when there is no scattering medium in the optical path, and the image of the object to be measured can be reconstructed; (b) is the imaging result when there is a scattering medium between the beam splitter and the object, and the image of the object to be measured cannot be reconstructed; (c) is the imaging result under the method described in the present invention, and the image of the object to be measured can be reconstructed. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] Example 1

[0040] In the prior art, such as Figure 1 As shown in the figure, when there is no scattering medium in the optical path, the laser generates a pseudothermal light field after passing through the rotating frosted glass, and then is divided into a detection light field and a reference light field through a beam splitter. After the detection light field illuminates the object to be tested in the detection light path, the total transmitted light intensity value is detected by the barrel detector, and the reference light field is collected by the CCD camera in the reference light path. Assume that the size of the object to be tested H is m×n, and each pixel position is recorded as O(x, y), which can be represented as a column in matrix form:

[0041] H=[O(1,1) O(2,1) ... O(m,n)] T

[0042] The size of the speckle image collected by the CCD camera in the reference light path is also m×n, and the light intensity value at each pixel position is recorded as I R (x, y), the reference light field distribution detected for the kth time can be represented by one row in matrix form:

[0043]

[0044] After the detection light field illuminates the object to be measured, the total light intensity value transmitted is detected by the bucket detector, and the kth measurement result satisfies the following mathematical relationship:

[0045] b (k) =a (k) H

[0046] After K measurements, the light field distribution of all reference light fields collected can be expressed as:

[0047]

[0048] The corresponding bucket detection value collected can be expressed as:

[0049] B=[b (1) b (2) ... b (K) ] T

[0050] Satisfies the mathematical relationship:

[0051] B=AH

[0052] The image matrix of the object to be measured can be solved through the following mathematical operations:

[0053] H=A -1 B

[0054] like Figure 2 As shown in the figure, when there is a scattering medium between the beam splitter and the object, the modulation process of the scattering medium on the light field can be represented by the transmission matrix F of the scattering medium. The laser generates a pseudothermal light field after passing through the rotating frosted glass, which is then divided into a detection light field and a reference light field by the beam splitter. After the detection light field passes through the scattering medium in the detection light path, the light intensity I′ at each pixel position during the kth measurement is T (x,y)=I T (x,y)·F, after K measurements, can be expressed as:

[0055]

[0056] The total intensity of the object to be tested collected by the bucket detector, that is, the bucket detection value is:

[0057] B′=(A·F)H=GH

[0058] After K measurements with the CCD camera, the light field distribution of all reference light fields collected is correlated with the detection value of the bucket, and the reconstructed result is:

[0059] H′=A -1 B′=A -1 GH=FH≠H

[0060] That is, the target object to be measured cannot be reconstructed.

[0061] like Figure 3As shown, the present invention provides a method for correlation imaging through scattering media based on a preset scattering medium, and the method flow is as follows: a laser beam is acquired, and a pseudothermal light field is acquired based on the laser beam; a detection light field and a reference light field are acquired based on the pseudothermal light field; based on the scattering medium in the environment, a scene when the detection light field passes through the scattering medium is simulated, and after the detection light field after passing through the scattering medium illuminates the object to be measured, the total light intensity passing through the object to be measured is acquired; based on the preset scattering medium, the reference light field passes through the preset scattering medium to acquire a reference speckle light field. Based on the total light intensity passing through the object to be measured and the reference speckle light field, the image of the object to be measured is reconstructed by a second-order correlation algorithm.

[0062] Specifically, a scattering medium with the same scattering characteristics as the scattering medium in the detection light path is preset in the reference light path. The modulation of the reference light field by the scattering medium can also be represented by the scattering medium transmission matrix F. After the reference light field passes through the preset scattering medium, the light intensity I′ at each pixel position in the kth measurement is R (x,y)=I R (x, y)·F, after K measurements, can be expressed as A′=AF, that is:

[0063]

[0064] After K measurements with the CCD camera, all the reference speckle light fields collected are correlated with the bucket detection value, and the reconstructed result is:

[0065] H″=A ′-1 B′=A ′-1 ·(A·F)H=(AF) -1 ·(A·F)H=H

[0066] That is, by performing a second-order correlation calculation on the two measured signals: H = <a′-<A′> > <b′-<B′> >The image of the object to be measured can be reconstructed to achieve correlation imaging through penetrating scattering media.

[0067] Example 2

[0068] In the prior art, such as Figure 1 As shown, the schematic diagram of the correlation imaging device includes: 532nm laser, rotating frosted glass, 50:50 beam splitter, CCD camera, hollow double slit of the object to be measured and barrel detector.

[0069] The laser emits a laser that hits the rotating frosted glass to generate a pseudothermal light field, which is divided into two parts by the beam splitter, one part is the detection light field, and the other part is the reference light field. The distance between the object to be measured and the beam splitter is Z1, the distance between the CCD camera and the beam splitter is also Z1, and the detection surface of the barrel detector is close to the object to be measured. After the detection light field propagates a distance of Z1 in the detection light path, it interacts with the object to be measured. After the interaction, the total light intensity value of the light field is detected by the barrel detector. After the reference light field propagates a distance of Z1 in the reference light path, it is collected by the CCD camera. After 780 samplings, the collected signal is subjected to a second-order correlation calculation, and the reconstruction result is as follows Figure 4 (a).

[0070] like Figure 2 As shown in the figure, it is a schematic diagram of the device when there is a scattering medium between the beam splitter and the object to be measured. The distance between the container containing the scattering medium (scattering medium 1) and the beam splitter is Z2. After the detection light field interacts with the scattering medium 1, it interacts with the object to be measured. The total light intensity value after the interaction is detected by the bucket detector. After the reference light field propagates the distance Z1, it is collected by the CCD camera. After 780 samplings, the collected signal is subjected to second-order correlation calculation, and the reconstruction result is as follows Figure 4 (b).

[0071] like Figure 3 As shown, the present invention provides a scattering medium correlation imaging system based on a preset scattering medium, comprising: a 532nm laser, a rotating frosted glass, a 50:50 beam splitter, a scattering medium in the environment, a preset scattering medium module, a hollow double slit of an object to be measured, a barrel detector and a CCD camera;

[0072] When there is a scattering medium between the beam splitter and the object to be measured, the present invention is a schematic diagram of a device for presetting a scattering medium with the same scattering characteristics as the scattering medium in the detection light path in the reference light path. The distance between the container for the pre-set scattering medium 2, that is, the pre-set scattering medium module and the beam splitter is also Z2. After the reference light field interacts with the pre-set scattering medium 2, the light field distribution when it propagates to the position where the CCD image plane is located is collected by the CCD camera. After 780 samplings, the collected signal is subjected to a second-order correlation calculation H= <a′-<A′> > <b′-<B′> >, the reconstruction result is as follows Figure 4 (c), size is 128×128.

[0073] Furthermore, the contrast-to-noise ratio (CNR) and visibility (V) of the reconstruction result are calculated as evaluation indicators. The calculation formula of the contrast-to-noise ratio is:

[0074]

[0075] The formula for calculating visibility is:

[0076]

[0077] Among them, H(x in ) and H(x out ) represent the transmission area and reflection area of ​​the hollow double slits respectively;

[0078] like Figure 4 The following is a comparison of the imaging results. The contrast-to-noise ratio and visibility of the reconstructed results are marked below each image in the form of (CNR, V). Among them: (a) is the imaging result when there is no scattering medium in the optical path, and the image of the object to be measured can be reconstructed; (b) is the imaging result when there is a scattering medium between the beam splitter and the object, and the image of the object to be measured cannot be reconstructed, and the contrast-to-noise ratio and visibility are significantly reduced; (c) is the imaging result under the method described in the present invention, and the image of the object to be measured can be reconstructed, and the contrast-to-noise ratio and visibility are improved compared with (b).

[0079] In order to realize through-scattering medium correlation imaging, the present invention proposes a through-scattering medium correlation imaging method based on a preset scattering medium, which has the characteristics of low cost and low system complexity.

[0080] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for correlation imaging through a scattering medium based on a preset scattering medium, characterized in that: The following steps are involved: Acquire a laser beam, and obtain a pseudothermal light field based on the laser beam; Based on the pseudothermal light field, obtaining a detection light field and a reference light field; Based on the scattering medium in the environment and the detection light field, a scene of the detection light field passing through the scattering medium in the environment is simulated, and the total light intensity passing through the object to be detected is obtained; Based on the preset scattering medium and the reference light field, a reference speckle light field is obtained; Reconstructing an image of the object to be measured by a second-order correlation algorithm based on the total light intensity transmitted through the object to be measured and the reference speckle light field; The process of obtaining the total light intensity passing through the object to be measured is as follows: after the detection light field passes through the scattering medium in the detection light path, the object to be measured is illuminated to obtain the total light intensity passing through the object to be measured; The distribution calculation formula of the total light intensity passing through the object to be measured is: The process of obtaining the reference speckle light field is as follows: after the reference light field passes through the preset scattering medium, the reference speckle light field is obtained; The calculation formula of the reference speckle light field is: The process of reconstructing the image of the object to be measured is: performing a second-order correlation calculation on the total light intensity passing through the object to be measured and the reference speckle light field to reconstruct the image of the object to be measured; The formula for calculating the second-order correlation is: H= <a′-<A′> > <b′-<B′> >, Wherein, H is the object to be measured.

2. A through-scattering medium correlation imaging system based on a preset scattering medium, used to implement the through-scattering medium correlation imaging method based on a preset scattering medium according to claim 1, characterized in that: include: Laser, rotating frosted glass, beam splitter, scattering medium in the environment, preset scattering medium, bucket detector, CCD camera and imaging module; The laser is used to generate a laser beam; The rotating frosted glass is used to obtain a pseudothermal light field based on the laser beam; The beam splitter is used to obtain a detection light field and a reference light field based on the pseudothermal light field; The scattering medium in the environment is used to simulate the scene when the detection light field passes through the scattering medium, and after the detection light field after passing through the scattering medium illuminates the object to be measured, the total light intensity passing through the object to be measured is obtained; The preset scattering medium is used to obtain a reference speckle light field based on the preset scattering medium and the reference light field; The barrel detector is used to detect the total light intensity passing through the object to be tested; The CCD camera is used to collect the reference speckle light field; The imaging module is used to reconstruct an image of the object to be measured through a second-order correlation algorithm based on the total light intensity passing through the object to be measured and the reference speckle light field.

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