A self-modulation correlation imaging system based on dynamic scattering medium

Abstract

The present invention discloses a self-modulated correlation imaging system based on dynamic scattering medium, wherein the laser passes through a beam expansion and collimation device, passes through a transparent glass groove containing a random flow scattering medium to form a dynamic speckle, and the dynamic speckle passes through an adjustable aperture and is divided into two identical light beams by a beam splitter prism: one of which is collected by a CCD array detector, called a reference light path; the other light passes through the same distance as the reference light path, acts on the object to be measured, and is received by a point detector through a 4f lens system, called a signal light path; the speckle array information collected by the CCD and the object light intensity information collected by the point detector are correlated and calculated, and a reconstructed image of the target object to be measured is obtained. The present invention closely combines the correlation imaging technology with the light path environment medium, fully and directly utilizes the interference of the imaging environment on the light source signal to reconstruct the image, and has important significance for imaging scattering media such as underwater, water fog, and smoke.

Description

Technical Field

[0001] The invention belongs to the technical field of optical equipment, and in particular relates to a self-modulation correlation imaging system based on dynamic scattering medium. Background Art

[0002] Unlike traditional optical imaging, which requires the use of array detectors to obtain image information of the object to be measured, correlation imaging obtains the image of the object by using the light field intensity correlation operation of two light beams. The two light beams are the signal beam and the reference beam. The signal beam is received by the bucket detector without spatial resolution after passing through the object. The reference beam is used as a measurement matrix and does not pass through the object. After freely propagating in space, it is received by the array detector with spatial resolution. The image of the object can be obtained by correlating the information collected by the bucket detector and the detector with spatial capabilities. Since only the light intensity information of the object is collected during the imaging process, the light intensity collected by the bucket detector can resist adverse conditions that affect imaging, such as atmospheric turbulence, water mist, and poor light brightness, so correlation imaging can be used in many extreme environments. Compared with traditional imaging, correlation imaging can also achieve single-pixel imaging and lens-free imaging, which has attracted widespread attention in recent years.

[0003] When laser passes through scattering materials or particles suspended in a medium, speckles will appear. This is because when light propagates, it is affected by molecules or atoms in the propagation medium, which changes its light intensity distribution, polarization state or frequency, and then causes scattering. In real life, optical imaging is used everywhere, and the scattering phenomenon caused by light passing through scattering media leads to poor imaging or even no imaging. For example, space observation and remote sensing mapping cannot be carried out underwater, in water fog, in smoke, etc., which brings many changes to people's lives. Therefore, the research on imaging under scattering media is of great significance to improving people's lives and social progress.

[0004] The traditional correlation imaging system based on pseudothermal light is a light source emitted by a helium-neon laser. After passing through the beam expansion and collimation system, it passes through the slowly rotating frosted glass. The rotating frosted glass scatters the coherent light beam to produce a pseudothermal light source with a distribution similar to that of a real thermal light source. It is divided into a signal light path and a reference light path through a beam splitter prism. The transmissive object is located on the signal light path. After the light beam passes through the target, the light intensity information is measured by a barrel detector. A CCD detector is placed on the reference light path to measure the spatial distribution information of the light field. The data of the two light paths are correlated and calculated to obtain the image information of the target object.

[0005] With the continuous development of environmental detection and development, the requirements for laser imaging technology in scattering media environments such as water, water mist, and smoke are constantly increasing. Correlation imaging is expected to play an important role in the field of scattering medium detection due to its high resolution and anti-scattering and anti-turbulence characteristics. In a scattering medium environment, the correlation imaging system is affected by both scattering characteristics and turbulence. The research on correlation imaging of scattering media and turbulent environments is still in its initial stage. At present, more explorations are focused on image reconstruction and image quality improvement of the correlation imaging system in scattering media.

[0006] In summary, the existing imaging scheme of the correlation imaging system in the scattering medium aims to eliminate the influence of the scattering medium by changing the optical path or imaging algorithm. In the correlation imaging calculation process, a random light energy distribution that changes with time is required. The traditional method mainly uses three methods to achieve the spatial distribution of light intensity that changes randomly with time: ① by adding a moving frosted glass piece to the optical path; ② adding a DMD modulator or a liquid crystal spatial light modulator to the optical path to dynamically and randomly modulate the spatial distribution of light intensity; ③ controlling the illumination mode of the illumination light source (usually an array light source) to achieve random distribution of light energy in space over time. These systems for achieving random spatial distribution of light intensity that changes randomly over time will increase the complexity and cost of the system.

[0007] The researchers added scattering media to the signal optical path and the reference optical path to explore the objective laws, but ignored the property that the scattering medium itself can modulate the light source. Summary of the invention

[0008] In view of the above, the present invention provides a self-modulated correlation imaging system based on dynamic scattering media, which combines the existing imaging optical path and algorithm to realize the application of correlation imaging in an environment full of scattering media without modulating the light source. It can overcome the influence of the scattering medium on the correlation imaging system and use the characteristics of the scattering medium to generate dynamic speckle to directly realize correlation imaging.

[0009] A self-modulation correlation imaging system based on dynamic scattering medium includes an optical unit and an electrical unit, wherein the optical unit includes a helium-neon laser, a beam expansion and collimation component, a transparent glass groove filled with a scattering medium, an adjustable aperture, a beam splitter prism, and a converging light collecting component, and the electrical unit includes a point detector, a CCD array detector, and a host computer, and the target object to be measured is arranged between the beam splitter prism and the converging light collecting component, wherein:

[0010] The helium-neon laser is used to generate continuous laser light;

[0011] The beam expansion and collimation component is used to perform beam expansion and collimation processing on the laser;

[0012] The transparent glass groove is used to scatter the beam after expansion and collimation to form random dynamic speckles;

[0013] The adjustable diaphragm is used to adjust the lateral size of the dynamic speckle;

[0014] The beam splitter prism is used to split the dynamic speckle adjusted by the adjustable iris into two identical beams of light, one of which will be irradiated onto the target object to be measured, and the other beam of light will be used as a reference light path;

[0015] The converging and light-collecting component is used to converge the light beam passing through the target object to be measured;

[0016] The point detector is used to detect the intensity fluctuation information of the light beam after it passes through the target object to be measured and converges;

[0017] The CCD array detector is used to detect the light field spatial distribution information of the reference light path;

[0018] The host computer is used to control the synchronous information collection of the point detector and the CCD array detector, and pre-process the information collected by both, and then perform correlation calculations and image reconstruction based on the information, so as to obtain a reconstructed image of the target object to be measured.

[0019] Furthermore, the helium-neon laser is a gas laser using neutral atomic gases helium and neon as working materials, and outputs continuous laser light in a continuous excitation mode.

[0020] Furthermore, the beam expansion and collimation component is realized by a combination of a beam expander and a converging lens, the adjustable iris is realized by a manual iris variable aperture or an optical light blocker, the beam splitter is realized by a beam splitter prism or an optical splitter, and the converging and light collecting component is realized by a lens or a combination of a lens and a filter.

[0021] Furthermore, the transparent glass groove is filled with scattering media such as corundum turbid liquid, glass sand turbid liquid, water mist, smoke, milk, etc. to scatter the light beam.

[0022] Furthermore, the point detector adopts a Geiger mode avalanche diode or an enhanced charge coupled device, and the CCD array detector adopts a Geiger mode avalanche diode array or an enhanced charge coupled device array.

[0023] Furthermore, the distance L1 between the beam splitter prism and the target object to be measured and the distance L2 between the beam splitter prism and the CCD array detector need to satisfy L1=L2.

[0024] Furthermore, the distance L1 between the beam splitter prism and the target object to be measured and the distance L2 between the beam splitter prism and the CCD array detector must satisfy |L1-L2|<L, where L is the longitudinal coherence length of the light field obtained after the laser passes through the beam expansion and collimation component and the transparent glass groove.

[0025] Furthermore, the host computer controls the synchronous collection of information from the point detector and the CCD array detector to control the number and duration of each collection, and preprocesses and records the collected information, and then performs correlation operations and image reconstruction based on this information to obtain a reconstructed image of the target object to be measured. The algorithm used can be a traditional correlation imaging algorithm, a normalized correlation imaging algorithm, a differential correlation imaging algorithm, a pseudo-inverse algorithm, a compressed sensing algorithm, or a binarization correlation imaging algorithm.

[0026] The present invention takes into account that the scattering medium itself has a random modulation effect on the spatial distribution of light intensity in the scattering medium correlation imaging, and makes full use of the random modulation of the scattering medium itself on the illumination light source, eliminating the moving ground glass, spatial light modulator or array light source modulation components required in the traditional correlation imaging system, which can greatly simplify the measurement system, reduce the hardware complexity and cost of the system, and is more conducive to the application and promotion of correlation imaging technology in smoke space scattering environment and underwater scattering medium. Specifically, the present invention has the following beneficial technical effects:

[0027] 1. The present invention utilizes the characteristics of scattering media to form dynamic speckles, which can realize correlation imaging and solve the problem of interference of scattering media on the correlation imaging system that needs to be solved in the existing scattering medium correlation imaging.

[0028] 2. The present invention directly utilizes the disturbance of light sources in environmental conditions such as underwater, water mist, and smoke to achieve imaging, thereby simplifying the imaging system.

[0029] 3. Compared with the existing pseudothermal optical correlation imaging, the random speckle array generated by the present invention has uniform fluctuations, which is beneficial to improving the image quality of the correlation imaging system.

[0030] 4. The self-modulation correlation imaging system based on dynamic scattering media of the present invention can be widely used in scattering media such as underwater, water mist, and smoke, and is of great significance to the development of imaging fields such as environmental detection and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the self-modulation correlation imaging system of the present invention.

[0032] Figure 2 It is the speckle pattern collected by the CCD array detector in the system of the present invention.

[0033] Figure 3 This is a light intensity fluctuation information diagram of the random speckle collected by the point detector in the system of the present invention acting on the target object to be measured.

[0034] Figure 1Middle: 1—He-Ne laser, 2—beam expansion and collimation component, 3—transparent glass groove filled with scattering medium, 4—adjustable aperture, 5—beam splitter prism, 6—target object to be measured, 7—converging and collecting component, 8—point detector, 9—CCD array detector, 10—host computer. DETAILED DESCRIPTION

[0035] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] The present invention is based on Glauber coherence theory and applies the first-order cross-correlation function:

[0037]

[0038] Where: x s and x r is the lateral position coordinate of each plane of the signal path and the reference path, E s (x s ) and E r (x r ) represents the complex amplitude of the light wave in the output plane of the signal path and the reference path, <> represents the statistical average, and * represents the complex conjugate.

[0039] The second-order mutual interference function can be expressed as:

[0040] G (2) (x s ,x r )= <I(x s )> <I(x r )>+|G (1) (x s ,x r )| 2

[0041] Where: I(x s ) and I(x r ) represents the light field intensity of the output plane of the signal path and the reference path. The light field intensity at different positions in the thermal light field space is not completely independent, and the correlation characteristics at different positions are given by |G (1) (x s ,x r ) 2 It is also the key information to restore the image of the object to be tested.

[0042] When G (1) (x s ,x r )=0, that is<I(x1)I(x2)> =<I(x1)><I(x2)> , indicating that the two different spatial positions of the thermal light source light field are completely unrelated; when When G (1) (x s ,x r ) is equal to other values, it means that the second-order cross-correlation function contains first-order coherence information and can be used to restore the image of the object to be measured.

[0043] Based on the above second-order cross-correlation principle, such as Figure 1 As shown, the present invention provides a self-modulation correlation imaging system based on dynamic scattering medium, which includes an optical unit, an electrical unit and a computational correlation imaging application; wherein the optical unit includes a helium-neon laser 1, a beam expansion and collimation component 2, a transparent glass groove filled with a scattering medium 3, an adjustable aperture 4, a beam splitter prism 5, a target object to be measured 6, and a converging light collecting component 7; the electrical unit includes a point detector 8, a CCD array detector 9, and a host computer 10; the computational correlation imaging application installed in the host computer 10 includes a reference light path speckle pattern processing module, a signal light path object light intensity processing module and a correlation operation imaging module.

[0044] The helium-neon laser 1 is used as the light source of the imaging system. It adopts a gas laser with neutral atomic gases helium and neon as working materials and outputs continuous laser in a continuous excitation mode.

[0045] The beam expansion and collimation component 2 is used to expand and collimate the light source, and it adopts a combination of a beam expander and a converging lens.

[0046] The transparent glass tank 3 is used for scattering the light beam, and is a transparent glass tank filled with materials such as corundum turbid liquid, glass sand turbid liquid, water mist, smoke, milk, etc.

[0047] The adjustable iris 4 is used to change the lateral size of the light source, and adopts a manual iris variable aperture or an optical light blocker.

[0048] The beam splitter prism 5 is used to split the scattered light source into two identical beams, which can be achieved by using a device with optical beam splitting capability including a beam splitter prism or an optical splitter.

[0049] The converging light collecting component 7 is used to collect the light signal transmitted through the target object 6 to be measured onto the point detector 8, and it can be a lens or a combination of a lens and a filter.

[0050] The point detector 8 is used to detect the intensity fluctuation information of the optical signal passing through the target object 6 to be detected, and is implemented by a Geiger mode avalanche diode or an enhanced charge coupled device.

[0051] The CCD array detector 9 is used to detect the spatial distribution information of the light field of the reference light path, and can adopt a Geiger mode avalanche diode array or an enhanced charge coupled device array.

[0052] The distance L1 between the beam splitter prism 5 and the target object 6 to be measured and the distance L2 between the beam splitter prism 5 and the CCD array detector 9 must satisfy L1=L2 or |L1-L2|<L, where L is the longitudinal coherence length of the light field obtained after the laser passes through the beam expansion and collimation component 2 and the transparent glass groove 3.

[0053] The host computer 10 is used to control the point detector 8 and the CCD array detector 9 to collect signals, and control the number and duration of each collection. At the same time, the host computer 10 records and preprocesses the intensity fluctuation information of the signal light path for the point detector 8, and records and preprocesses the spatial distribution information of the reference light path for the CCD array detector 9.

[0054] In addition, the host computer 10 can use any one of the following algorithms to achieve image reconstruction, such as traditional correlation imaging algorithm, normalized correlation imaging algorithm, differential correlation imaging algorithm, pseudo-inverse algorithm, compressed sensing algorithm, and binarization correlation imaging algorithm.

[0055] The imaging principle of the system of the present invention is as follows: the light emitted from the helium-neon laser 1 is processed by the beam expansion and collimation component 2, and then passes through the transparent glass groove 3 filled with a scattering medium to form a random dynamic speckle. The lateral size of the light source signal is controlled by the adjustable aperture 4, and is divided into two identical beams of light by the beam splitter prism 5, one of which is irradiated onto the target object 6 to be measured, and the light passing through the target object 6 to be measured will be converged by the converging light collecting component 7 to the point detector 8, and the point detector 8 outputs the intensity fluctuation information of the signal light path passing through the target object to be measured and provides it to the host computer 10; the other beam of light is irradiated onto the CCD array detector 9, and the CCD array detector 9 outputs the light field spatial distribution information of the reference light path and provides it to the host computer 10, and the host computer 10 pre-processes the information, and at the same time controls the synchronous acquisition of the point detector 8 and the CCD array detector 9 signals, and performs correlation operation according to the pre-processed information to reconstruct the image, and obtains the reconstructed image of the target object 6 to be measured.

[0056] The specific working process of the self-modulation correlation imaging system of the present invention is as follows:

[0057] (1) Steps for obtaining optical signals:

[0058] The light emitted from the HeNe laser 1 is processed by the beam expansion and collimation component 2, and then passes through the transparent glass groove 3 filled with scattering medium to form random dynamic speckles. The lateral size of the light source signal is controlled by the adjustable aperture 4, and is divided into two identical beams by the beam splitter prism 5; one of the beams is irradiated onto the target object 6 to be measured, and the light passing through the target object 6 to be measured will be converged by the converging light collecting component 7 to the point detector 8, and the point detector 8 outputs the intensity fluctuation information of the signal light path passing through the target object to be measured, such as Figure 3 Another beam of light is irradiated onto the CCD array detector 9, and the CCD array detector 9 outputs the light field spatial distribution information of the reference light path, such as Figure 2 shown.

[0059] (2) Steps for array detector control and synchronization:

[0060] The host computer 10 controls the entire dynamic random speckle correlation imaging system based on the scattering medium, including the working control and synchronization signal transmission of the point detector 8 and the CCD array detector 9, to ensure that the point detector 8 and the CCD array detector 9 collect signals synchronously, and the host computer 10 controls the two array detectors to obtain the same number of detection results at the same time.

[0061] (3) Correlation imaging image reconstruction steps:

[0062] The acquisition results of the point detector 8 and the CCD array detector 9 are all stored in the host computer 10 , and the host computer 10 performs correlation operation on the acquired data by using the second-order cross-correlation function principle to reconstruct the image of the target object 6 to be measured.

[0063] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art to the present invention based on the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A self-modulation correlation imaging system based on dynamic scattering medium, characterized in that: It includes an optical unit and an electrical unit. The optical unit includes a helium-neon laser, a beam expansion and collimation component, a transparent glass groove filled with a scattering medium, an adjustable aperture, a beam splitter prism, and a converging and light-collecting component. The electrical unit includes a point detector, a CCD array detector, and a host computer. The target object to be measured is arranged between the beam splitter prism and the converging and light-collecting component, wherein: The helium-neon laser is used to generate continuous laser light; The beam expansion and collimation component is used to perform beam expansion and collimation processing on the laser; The transparent glass groove is used to scatter the beam after expansion and collimation to form random dynamic speckles; The adjustable diaphragm is used to adjust the lateral size of the dynamic speckle; The beam splitter prism is used to split the dynamic speckle adjusted by the adjustable iris into two identical beams of light, one of which will be irradiated onto the target object to be measured, and the other beam of light will be used as a reference light path; The converging and light-collecting component is used to converge the light beam passing through the target object to be measured; The point detector is used to detect the intensity fluctuation information of the light beam after it passes through the target object to be measured and converges; The CCD array detector is used to detect the light field spatial distribution information of the reference light path; The host computer is used to control the synchronous information collection of the point detector and the CCD array detector, and pre-process the information collected by both, and then perform correlation calculations and image reconstruction based on the information, so as to obtain a reconstructed image of the target object to be measured.

2. The self-modulation correlation imaging system according to claim 1, characterized in that: The helium-neon laser uses a gas laser with neutral atomic gases helium and neon as working materials, and outputs continuous laser light in a continuous excitation mode.

3. The self-modulation correlation imaging system according to claim 1, characterized in that: The beam expansion and collimation component is realized by combining a beam expander and a converging lens, the adjustable iris is realized by a manual iris variable aperture or an optical light blocker, the beam splitter is realized by a beam splitter prism or an optical splitter, and the converging light collecting component is realized by a lens or a combination of a lens and a filter.

4. The self-modulation correlation imaging system according to claim 1, characterized in that: The transparent glass tank is filled with scattering media including corundum turbid liquid, glass sand turbid liquid, water mist, smoke, and milk to scatter the light beam.

5. The self-modulation correlation imaging system according to claim 1, characterized in that: The point detector adopts a Geiger mode avalanche diode or an enhanced charge coupled device, and the CCD array detector adopts a Geiger mode avalanche diode array or an enhanced charge coupled device array.

6. The self-modulation correlation imaging system according to claim 1, characterized in that: The distance L1 between the beam splitter prism and the target object to be measured and the distance L2 between the beam splitter prism and the CCD array detector must satisfy L1=L2.

7. The self-modulation correlation imaging system according to claim 1, characterized in that: The distance L1 between the beam splitter prism and the target object to be measured and the distance L2 between the beam splitter prism and the CCD array detector must satisfy |L1-L2|<L, where L is the longitudinal coherence length of the light field obtained after the laser passes through the beam expansion and collimation component and the transparent glass groove.

8. The self-modulation correlation imaging system according to claim 1, characterized in that: The host computer controls the synchronous collection of information from the point detector and the CCD array detector to control the number and duration of each collection, and preprocesses and records the collected information, and then performs correlation operations and image reconstruction based on the information to obtain a reconstructed image of the target object to be measured. The algorithms used are traditional correlation imaging algorithm, normalized correlation imaging algorithm, differential correlation imaging algorithm, pseudo-inverse algorithm, compressed sensing algorithm or binarization correlation imaging algorithm.

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