WO2022257174A1 - 基于随机光场空间结构调控的光学成像系统及方法 - Google Patents

基于随机光场空间结构调控的光学成像系统及方法 Download PDF

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WO2022257174A1
WO2022257174A1 PCT/CN2021/101132 CN2021101132W WO2022257174A1 WO 2022257174 A1 WO2022257174 A1 WO 2022257174A1 CN 2021101132 W CN2021101132 W CN 2021101132W WO 2022257174 A1 WO2022257174 A1 WO 2022257174A1
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light
measured
intensity distribution
polarized light
scattering medium
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PCT/CN2021/101132
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English (en)
French (fr)
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陈亚红
彭德明
刘永雷
王飞
蔡阳健
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苏州大学
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Priority to US17/797,685 priority Critical patent/US20230314309A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4795—Scattering, i.e. diffuse reflection spatially resolved investigating of object in scattering medium
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
    • G02B30/10—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images using integral imaging methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4788—Diffraction
    • G01N2021/479—Speckle

Definitions

  • the invention relates to the field of optical technology, in particular to an optical imaging method and system based on random light field spatial structure control.
  • the main technologies include adaptive optical imaging technology, optical coherence tomography technology, multiphoton microscopy and multiphoton microscopy. Spectral photoacoustic tomography, etc.
  • the development and application of these technologies have solved problems in the fields of astronomical imaging, underwater detection, and biological imaging. With the continuous in-depth study of the scattering mechanism, the current scattering imaging technology no longer focuses on separating scattered light to extract ballistic light, but focuses more on the utilization of scattered light.
  • imaging methods through scattering media mainly include wavefront shaping technology and scattering imaging technology based on optical memory effect.
  • the wavefront shaping technology includes three parts: optical phase conjugation, wavefront shaping technology based on feedback optimization and optical transmission matrix technology.
  • Scattering imaging technology based on optical memory effect includes speckle correlation imaging technology and point spread function engineering imaging technology.
  • wavefront shaping technology The focus of wavefront shaping technology is to study the propagation characteristics of light in scattering media, and use mathematical forms to express quantitatively or qualitatively the characteristics of scattering media, laying the foundation for the use of scattering effects.
  • the method of relying on wavefront shaping technology to image through scattering media has the disadvantages of low energy efficiency, complex and time-consuming process, and real-time performance needs to be improved, so it is impossible to observe objects hidden behind scattering media in real time.
  • the essence of scattering imaging technology based on optical memory effect is to make full use of speckle energy and speckle distribution characteristics to perform imaging through scattering media.
  • some researchers have proposed a non-invasive imaging method through the scattering layer.
  • the optical camera can be used to record the speckle after the scattering medium, that is, the light intensity information, and the entire
  • the optical system is regarded as an incoherent system with a spatial translation invariant point spread function (PSF), then the speckle can be written as the convolution form of the target information and the system PSF.
  • PSF spatial translation invariant point spread function
  • this method does not need to measure the prior information of the scattering imaging system. In other words, this method does not need a reference optical path to assist imaging, and does not need to implant a light source behind or inside the scattering medium.
  • the imaging range of the target size is limited by the optical memory effect, and it is impossible to image larger objects.
  • some researchers proposed that by measuring the point spread function of the system, the Lucy-Richardson deconvolution iterative nonlinear restoration method was used to realize imaging through the scattering medium.
  • Some scholars have proposed a speckle imaging method based on the phase diversity applied in astronomical imaging, by obtaining speckle information of multiple different image planes, and jointly estimating the point spread function of the entire scattering optical system without reference. Furthermore, the imaging through the scattering medium is realized by the deconvolution technique.
  • the point spread function engineering imaging technology needs to obtain the point spread function of the system in advance, and its imaging effect depends on the accuracy of the point spread function of the obtained system.
  • the stability of the scattering medium must be ensured, and it is only applicable to static Scattering media imaging.
  • the imaging range is not limited by the optical memory effect, and the point spread function of the entire optical system does not need to be measured.
  • the technical problem to be solved by the present invention is to overcome the defects in the prior art that the imaging efficiency of dynamic objects is low, the imaging range is limited by the optical memory effect, and the point spread function of the entire optical system needs to be measured.
  • the present invention provides an optical imaging system based on random light field spatial structure regulation, including:
  • a scattering component the scattering component is used to use a scattering medium to scatter the light beam transmitted through free space to obtain the light to be measured, wherein the light beam carries the information of the object to be measured;
  • the first beam-splitting polarization component is used to perform beam-splitting polarization processing on the light to be measured, wherein one beam of light to be measured is divided into x-direction polarized light and y-direction polarized light, and the other
  • the light to be measured is combined with the reference light and then divided into polarized light in the x direction and polarized light in the y direction, and the reference light is completely coherent light of the light to be measured;
  • optical measurement component the optical measurement component is used to measure the light intensity distribution of the x-direction polarized light and the y-direction polarized light of the light to be measured, the x-direction polarized light and the y-direction polarized light of the reference light and the light to be measured combined beam
  • a calculation unit the calculation unit is used to obtain the real part and imaginary part of the cross spectral density of the light to be measured according to the light intensity distribution, and use the real part and imaginary part of the cross spectral density to restore the light intensity distribution of the scattering medium , and calculate the light intensity distribution of the scattering medium to obtain the shape and position of the object to be measured.
  • a Fourier lens is further included, and the Fourier lens is arranged between the scattering medium and the first beam splitting polarization component.
  • a first half-wave plate is further included, and the first half-wave plate is disposed between the Fourier lens and the first beam splitting polarization component.
  • the first beam-splitting polarization component includes a first beam-splitting element and a first polarization beam-splitting element, and the first beam-splitting element is arranged on the first half-wave plate and the between the first polarizing beam-splitting elements.
  • the present invention also includes a second beam splitting polarization component connected to the optical measurement component, the second beam splitting polarization component includes a second beam splitting element a, a second beam splitting element b, a second polarization splitting A beam element a, a second polarization beam splitting element b, and a reflective element, the reference light is split by the second beam splitting element a, wherein a beam of reference light and the light to be measured are in the second beam splitting element b Combined beams are combined, and the combined beam is divided into x-direction polarized light and y-direction polarized light by the second polarization beam splitting element a; after another beam of reference light is reflected by the reflective element, the reference beam is separated by the second polarization beam splitting element b The light is divided into x-direction polarized light and y-direction polarized light.
  • the optical measurement component includes a first charge coupler unit, a second charge coupler unit and a third charge coupler unit forming an array structure, the first charge coupler unit, the second charge coupler unit Both the second charge coupler unit and the third charge coupler unit include at least two charge coupler units, wherein the optical path from the uppermost charge coupler unit to the Fourier lens in the first charge coupler unit is equal to the Fourier The focal length of the lens.
  • the optical distances from all the charge-coupler units in the first charge-coupler unit and the second charge-coupler unit to the first beam-splitting element are equal, and the optical distance is equal to the first The optical path from all charge coupler units in the second charge coupler unit and the third charge coupler unit to the second beam splitting element b.
  • the present invention also provides an optical imaging method based on regulation of the spatial structure of the random light field, including:
  • a scattering medium to scatter the light beam transmitted through free space to obtain the light to be measured, wherein the light beam carries the information of the object to be measured;
  • the reference light is the completely coherent light of the light to be measured;
  • the real part and the imaginary part of the cross spectral density of the light to be measured are obtained according to the light intensity distribution, and the light intensity distribution of the scattering medium is restored by using the real part and the imaginary part of the cross spectral density include:
  • ⁇ ... > S represents the spatial average
  • r, r 1 and r 2 represent the coordinates of any point on the observation surface
  • I x (r) represent the x-direction and y-direction polarization of the light to be measured light intensity distribution
  • I x (r) represent the x-direction and y-direction polarization of the reference light
  • the cross-spectral density is used to restore the light intensity distribution p( ⁇ ) of the scattering medium through Fourier transform, where the formula is as follows:
  • ⁇ represents the wavelength of light
  • f represents the focal length of the Fourier lens
  • ⁇ represents the coordinates of any point on the plane where the scattering medium is located
  • i represents the imaginary unit.
  • calculating the light intensity distribution of the scattering medium to obtain the shape and position of the object to be measured includes:
  • the phase recovery algorithm in the Fresnel domain is used to calculate the light intensity distribution of the scattering medium to obtain the shape and position of the object to be measured.
  • the present invention first measures the light intensity distribution of the light to be measured, the light intensity distribution of the combined beam after the light to be measured and the reference light are combined, and the light intensity distribution of the reference light, and obtains the cross spectral density of the light to be measured according to the light intensity distribution
  • the real and imaginary parts of the cross-spectral density are used to restore the light intensity distribution on the surface of the scattering medium, and the light intensity distribution of the scattering medium is calculated to obtain the shape and position of the object to be measured, so that it can be quickly analyzed
  • Imaging of dynamic objects the imaging range is not limited by the optical memory effect, and there is no need to measure the point spread function of the entire optical system.
  • FIG. 1 is a schematic structural diagram of an optical imaging system based on regulation of the spatial structure of a random light field according to the present invention.
  • FIG. 2 is a schematic flow chart of an optical imaging method based on regulation of the spatial structure of a random light field according to the present invention.
  • this embodiment provides an optical imaging system based on regulation of the spatial structure of a random light field.
  • the system includes a scattering component, a first beam splitting polarization component, an optical measurement component 10 and a computing unit 22 .
  • the scattering component is used to use the scattering medium 5 to scatter the light beam transmitted through the free space to obtain the light to be measured, wherein the light beam carries the information of the object 3 to be measured.
  • the scattering medium 5 is preferably frosted glass.
  • the first beam-splitting polarization component is used to split and polarize the light to be measured.
  • One beam of light to be measured is divided into x-direction polarized light and y-direction polarized light, and the other beam to be measured is combined with the reference light and then divided into Polarized light in the x direction and polarized light in the y direction, the reference light is the fully coherent light of the light to be measured.
  • the optical measurement component 10 is used to measure the light intensity distribution of the x-direction polarized light and the y-direction polarized light of the light to be measured, the light intensity distribution of the x-direction polarized light and the y-direction polarized light after the reference light is combined with the light to be measured, and the reference light The light intensity distribution of the x-polarized light and y-polarized light.
  • the calculation unit 22 is used to obtain the real part and the imaginary part of the cross spectral density of the light to be measured according to the light intensity distribution, use the real part and the imaginary part of the cross spectral density to recover the light intensity distribution of the scattering medium 5, and calculate the light intensity distribution of the scattering medium 5
  • the light intensity distribution is calculated to obtain the shape and position of the object 3 to be measured.
  • a Fourier lens 6 is also included, and the Fourier lens 6 is arranged between the scattering medium 5 and the first beam splitting polarization component.
  • the Fourier lens 6 can perform Fourier transform on the light to be measured after passing through the scattering medium 5, thereby improving the coherence of the light field.
  • a first half-wave plate 7 is also included, and the first half-wave plate 7 is arranged between the Fourier lens 6 and the first beam splitting polarization component.
  • the light to be measured passes through the first half-wave plate 7 to obtain linearly polarized light with a polarization direction of 45°.
  • the first beam-splitting polarization component includes a first beam-splitting element 8 and a first polarization beam-splitting element 9 , and the first beam-splitting element 8 is disposed between the first half-wave plate 7 and the first polarization beam-splitting element 9 .
  • the linearly polarized light from the first half-wave plate 7 is split into two by the first beam splitting element 8, and the transmitted beam is split into x-direction polarized light and y-direction polarized light by the first polarized beam splitting element 9 Light.
  • the first beam splitting element 8 may be a beam splitting mirror
  • the first polarizing beam splitting element 9 may be a polarizing beam splitting mirror.
  • the first laser 1 can emit a fully coherent linearly polarized laser, the beam carries the information of the object under test 3, and the beam passes through
  • the first beam expander 2 (which may be a beam expander) expands the beam, and the expanded beam is transmitted to the scattering medium 5 ( Can be frosted glass).
  • the second beam-splitting polarization assembly includes a second beam-splitting element a17, a second beam-splitting element b18, a second polarization beam-splitting element a19, The second polarization beam splitting element b21 and the reflective element 20 .
  • the reference light is split by the second beam splitting element a17, wherein a beam of reference light and the light to be measured are combined at the second beam splitting element b18, and the combined beam is split into x direction by the second polarization beam splitting element a19 Polarized light and polarized light in the y direction; after another beam of reference light is reflected by the reflective element 20, the reference light is divided into polarized light in the x direction and polarized light in the y direction by the second polarization beam splitting element b21.
  • the second beam splitting element a17 and the second beam splitting element b18 may be beam splitters
  • the second polarization beam splitting element a19 and the second polarization beam splitting element b21 may be polarization beam splitters
  • the reflective element 20 may be a reflective mirror.
  • the optical measurement component 10 includes a first charge coupler unit, a second charge coupler unit and a third charge coupler unit forming an array structure.
  • the first charge coupler unit is used to measure the light intensity distribution of the x-direction polarized light and the y-direction polarized light of the light to be measured;
  • the second charge coupler unit is used to measure the x-direction polarized light and The light intensity distribution of the polarized light in the y direction;
  • the third charge coupler unit is used to measure the light intensity distribution of the polarized light in the x direction and the polarized light in the y direction of the reference light.
  • each of the first charge coupler unit, the second charge coupler unit and the third charge coupler unit includes at least two charge coupler units.
  • each charge coupler unit includes two charge coupler units, that is, three charge coupler units have a total of six charge coupler units, and from top to bottom are charge coupler units 101, charge A coupler cell 102 , a charge coupler cell 103 , a charge coupler cell 104 , a charge coupler cell 105 , and a charge coupler cell 106 .
  • the optical distance from the charge coupler unit 101 to the Fourier lens 6 is equal to the focal length of the Fourier lens 6 .
  • the optical paths from the charge coupled unit 101, the charge coupled unit 102, the charge coupled unit 103 and the charge coupled unit 104 to the first beam splitting element 8 are all equal, and the optical path is equal to the charge coupled The optical path from the unit 103, the unit 104, the unit 105, and the unit 106 to the second beam splitting element b18.
  • a second laser 12 is connected to the first laser 1 through the phase-locked loop 11, that is, the phase-locked loop 11, the second laser 12 of the same type as the first laser 1, and the linear polarizer 13 are used to obtain the complete laser light emitted by the first laser 1.
  • Coherent linearly polarized light which serves as a reference light, is used to measure the coherent structure of the light field.
  • the reference light passes through the second half-wave plate 14 to obtain linearly polarized light polarized in the direction of 45°, and then passes through the quarter-wave plate 15 whose fast axis or slow axis is 0° to obtain circularly polarized light, and the circularly polarized light passes through the second expansion
  • the working principle of an optical imaging system based on random light field spatial structure regulation in this embodiment is: the first laser 1 can be a helium-neon laser, and the helium-neon laser emits a complete phase wave with a wavelength of 633nm. Trunk polarized laser, the beam carries the information of the object to be measured, the beam passes through the first beam expander 2 to expand the beam, and the enlarged beam passes through the object to be measured 3 (the object to be measured can move freely up, down, left, and right) and then passes through the free space transmission unit 4 transmitted to the scattering medium 5 (may be frosted glass) to obtain the light to be measured.
  • the scattering medium 5 may be frosted glass
  • the light intensity image will become blurred.
  • the light beam continues to transmit and irradiates on the rotating scattering medium 5 , due to the scattering effect of the scattering medium 5 , the phase information of the light to be measured is lost. If it is necessary to recover the information of the image, we can measure the coherent structure of the light field behind the scattering medium 5 and restore the light intensity distribution information on the surface of the scattering medium 5, so that the phase recovery algorithm in the Fresnel domain can be used to obtain the measured The shape and position of object 3.
  • the light to be measured passes through the first half-wave plate 7 to obtain linearly polarized light with a polarization direction of 45°, and the linearly polarized light passes through the first beam splitting element 8 to split the light beam into two, wherein the transmitted
  • the light to be measured is divided into x-direction polarized light and y-direction polarized light by the first polarization beam splitting element 9, and the charge coupler monomer a and charge coupler monomer b of the optical measurement component 10 are used to measure the light to be measured respectively Light intensity distribution of x-polarized light and y-polarized light.
  • the phase-locked loop 11 uses the phase-locked loop 11, the second laser 12 of the same type as the first laser 1, and the linear polarizer 13 to obtain linearly polarized light that is completely coherent with the laser light emitted by the first laser 1, and the linearly polarized light is used as a reference
  • the light is used to measure the coherent structure of the light field.
  • the reference light passes through the second half-wave plate 14 to obtain linearly polarized light polarized in the direction of 45°, and then passes through the quarter-wave plate 15 whose fast axis or slow axis is 0° to obtain circularly polarized light, and the circularly polarized light passes through the second expansion
  • the beam element 16 expands the beam.
  • the second beam splitting element a17 uses the second beam splitting element a17 to split the reference light into two, wherein the transmitted reference light and the light to be measured are combined at the second beam splitting element b18, and the combined beam is combined by the second polarization beam splitting element a19 Divided into x-direction polarized light and y-direction polarized light, using the charge coupler monomer c and charge coupler monomer d of the optical measurement component 10 to measure the light intensity distribution of the x-direction polarized light and the y-direction polarized light of the combined beam respectively .
  • the reference light reflected by the second beam splitting element a17 is reflected by the reflective element 20
  • the reference light is divided into the x-direction polarized light and the y-directed polarized light by the second polarization beam splitting element b21, and the electric charge of the optical measurement component 10 is used to
  • the coupler unit e and the charge coupler unit f respectively measure the light intensity distribution of the x-direction polarized light and the y-direction polarized light of the reference light.
  • the light intensity distribution information obtained above is sent to the calculation unit 22 , and it is calculated and processed by the calculation unit 22 .
  • Embodiment 2 of the present invention An optical imaging method based on random light field spatial structure regulation provided by Embodiment 2 of the present invention is introduced below.
  • the optical imaging systems regulated by the field space structure can be referred to each other correspondingly.
  • this embodiment provides an optical imaging method based on random light field spatial structure control, including the following steps:
  • S100 Use the scattering medium 5 to scatter the light beam transmitted through free space to obtain the light to be measured, wherein the light beam carries the information of the object to be measured.
  • the light beam carrying the information of the object under test 3 transmitted through free space will lose phase information under the scattering effect of the scattering medium 5. If it is necessary to restore the information of the image, we can measure the coherent structure of the light field behind the scattering medium 5 , and recover the light intensity distribution information on the rear surface of the scattering medium 5, and use the phase recovery algorithm to obtain the shape and position of the object under test 3. In order to make the measurement easier and more accurate, we can add a Fourier lens 6 behind the scattering medium 5, which is used to perform Fourier transform on the light to be measured after passing through the scattering medium 5, so as to improve the coherence of the light field.
  • S200 Perform beam splitting and polarization processing on the light to be measured, wherein one beam of light to be measured is divided into polarized light in the x direction and polarized light in the y direction, and the other beam of light to be measured is combined with the reference light and divided into polarized light in the x direction and y direction Polarized light, the reference light is the completely coherent light of the light to be measured.
  • a phase-locked loop 11 a second laser 12 of the same type as the first laser 1, and a linear polarizer 13 are used to obtain linearly polarized light that is completely coherent with the laser light emitted by the first laser 1, and the linearly polarized light is used as a reference light Used to measure the coherent structure of light fields.
  • the speckle information of the x-direction polarized light and the speckle information of the y-direction polarized light of the light to be measured are respectively measured by using the charge coupler unit a and the charge coupler unit b of the optical measurement component 10, where the speckle The information is the light intensity distribution.
  • S400 Obtain the real part and imaginary part of the cross spectral density of the light to be measured according to the light intensity distribution, use the real part and imaginary part of the cross spectral density to recover the light intensity distribution of the scattering medium 5, and analyze the light intensity distribution of the scattering medium 5 Perform calculations to obtain the shape and position of the object to be measured 3 .
  • phase recovery algorithm in the Fresnel domain can be used to calculate the light intensity distribution of the scattering medium 5 to obtain the shape and position of the object under test 3 .
  • the light intensity image has become blurred, that is, the light field on the front surface of the scattering medium 5 can be expressed as:
  • i represents the imaginary number unit
  • O(v) represents the light field distribution of the object under test 3
  • ⁇ and k represent the wavelength and wave number of light, respectively
  • z represents the transmission distance, that is, the distance between the object under test 3 and the scattering medium 5
  • v and ⁇ represent the coordinates of the cross-section where the object to be measured 3 and the scattering medium 5 are located, respectively.
  • the light field loses the phase information, and the light field is expressed as:
  • E'( ⁇ ) represents the light field distribution on the rear surface of the scattering medium 5, denotes a random phase, which is related to the coordinate ⁇ .
  • the light intensity on the surface of the scattering medium 5 is:
  • the above formula shows that the light intensity distribution on the front and rear surfaces of the scattering medium 5 is the same.
  • the light field on the rear surface of the scattering medium 5 can be characterized by its second-order statistical characteristic cross-spectral density:
  • ⁇ ((7) represents the Dirac ⁇ function
  • ⁇ 1 and ⁇ 2 represent the coordinates of the plane where the scattering medium 5 is located.
  • r, r 1 and r 2 represent the coordinates of any point on the observation surface, and f represents the focal length of the Fourier lens 6.
  • the second-order statistical properties of the light to be measured can be expressed by the cross spectral density function as;
  • E(r) represents the random electric field at point r in space
  • the superscript asterisk represents the complex conjugation
  • the angle brackets represent the ensemble average.
  • a beam of reference light E R (r) is introduced to combine with the light to be measured E(r).
  • two beams of reference light with a phase difference of ⁇ can be obtained by rotating the quarter-wave plate, and the two generated
  • the reference optical path is coherently combined with the light to be measured respectively, and the total random electric fields after combining are:
  • E R1 (r) and E R2 (r) represent the electric fields of the two reference beams, respectively.
  • ⁇ takes a value of 1 or 2
  • I C ⁇ (r) represents the light intensity of the ⁇ th combined beam.
  • the light intensity correlation of the two combined beams is:
  • I R1 (r)
  • 2 and I R2 ( r )
  • R1 (r)+I(r) and I U2 (r) I R2 (r)+I(r) respectively represent the incoherent superposition of the light intensities of the two reference beams and the light to be measured.
  • the phase difference of the two reference light paths can be controlled to obtain the information of the real part and the imaginary part of the cross spectral density, thereby obtaining the amplitude and phase of the cross spectral density of the light to be measured.
  • the light intensity cross-correlation function contains the background item.
  • ⁇ ...> S represents the spatial average. Since the light field is generated by the Fourier system, the ensemble average can be replaced by the spatial average instead of the time average. According to the formula (6), the measured The obtained cross spectral density restores the light intensity distribution p( ⁇ ) on the surface of the scattering medium 5 through Fourier transform.
  • the light intensity distribution p( ⁇ ) on the surface of the scattering medium 5 is known through the above formula, and if the specific distribution of the function of the object under test 3 is to be further obtained, the object under test 3 can be recovered through the phase recovery algorithm. Its specific steps are:
  • ⁇ and k represent the wavelength and wave number of light, respectively
  • z represents the transmission distance, that is, the distance between the initial object to be measured and the scattering medium 5
  • v and ⁇ represent the coordinates of the cross-section where the initial object to be measured and the scattering medium 5 are located, respectively .
  • E' k ( ⁇ ) is transmitted through free space with a distance of -z, and the real part of the obtained light field is taken to obtain O' k (v).
  • the present invention first measures the light intensity distribution of the light to be measured, the light intensity distribution of the combined beam after the light to be measured and the reference light are combined, and the light intensity distribution of the reference light, and obtains the light intensity distribution of the light to be measured according to the light intensity distribution.
  • the real part and the imaginary part of the cross spectral density using the real part and the imaginary part of the cross spectral density to restore the light intensity distribution on the surface of the scattering medium 5, and calculate the light intensity distribution on the surface of the scattering medium 5 to obtain the shape of the object to be measured 3 and position, so that dynamic objects can be quickly imaged, the imaging range is not limited by the optical memory effect, and there is no need to measure the point spread function of the entire optical system.
  • the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.
  • computer-usable storage media including but not limited to disk storage, CD-ROM, optical storage, etc.
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Abstract

一种基于随机光场空间结构调控的光学成像系统，包括散射介质（5）、第一分束偏振组件、光学测量组件（10）和计算单元（22），将传输光进行散射处理得到待测光；将待测光进行分束偏振处理，一束待测光被分为x方向偏振光和y方向偏振光，另一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光；测量待测光、参考光与待测光合束后以及参考光的x方向偏振光和y方向偏振光的光强分布；根据光强分布求得待测光的交叉谱密度的实部和虚部，利用其实部和虚部恢复散射介质（5）表面的光强分布，对散射介质（5）的光强分布进行计算得到待测物的形状和位置。光学成像系统能快速对动态物体进行成像，成像范围不受光学记忆效应的限制，而且无需测量整个光学系统的点扩散函数。

Description

基于随机光场空间结构调控的光学成像系统及方法 技术领域
本发明涉及光学技术领域，尤其是指一种基于随机光场空间结构调控的光学成像方法及系统。
背景技术
随着透过散射介质成像技术的逐渐发展，已经取得了众多突破。目前比较常用的方式是通过抑制散射光，提取从散射介质中透过的弹道光的方式进行弱散射介质成像，主要技术有自适应光学成像技术、光学相干层析技术、多光子显微以及多光谱光声层析等，这些技术的发展和应用，解决了天文成像、水下探测和生物成像等领域的问题。随着对散射机理的不断深入研究，现阶段的散射成像技术已不再侧重于分离散射光提取弹道光，而是更侧重于对散射光的利用。经过对散射光特性的充分研究，实现了从不可恢复隐藏在强散射层后的物体到可恢复散射层后的物体的质的飞跃。特别的是，透过散射介质成像技术不但在显微成像以及超分辨成像方面有着广泛的应用，同样也将在光纤成像、全息成像和光通讯等领域扮演重要的角色。
目前透过散射介质成像方法主要包括波前整形技术和基于光学记忆效应的散射成像技术两大类。其中波前整形技术包括光学相位共辄、基于反馈优化的波前整形技术和光学传输矩阵技术三部分。基于光学记忆效应的散射成像技术，包含散斑相关成像技术和点扩散函数工程成像技术两部分。
波前整形技术的重点在于研究光在散射介质中传播特性，利用数学的形式对散射介质特性进行定量或定性表示，为散射效应的利用奠定了基础。但 是依赖于波前整形技术透过散射介质成像的方法存在能量利用率低，过程复杂且耗时以及实时性有待提高的缺陷，因此无法对隐藏在散射介质后的物体进行实时的观测。
基于光学记忆效应的散射成像技术的本质在于充分利用散斑能量以及散斑分布特点进行透过散射介质成像。其中在散斑相关成像技术中有学者提出无侵入透过散射层成像方法，当目标尺寸在光学记忆效应范围内，即可利用光学相机记录散射介质后的散斑，即光强信息，将整个光学系统视作空间平移不变点扩散函数(PSF)的非相干系统，那么散斑可以写成目标信息与系统点扩散函数的卷积形式。通过对光强自相关运算，便可获取隐藏在散射介质后物体目标的傅里叶振幅信息，进而结合有效的相位恢复算法实现对目标的重建。与波前整形技术相比，该方法无需测量散射成像系统的先验信息，换言之，该方法不需要参考光路辅助成像，无需在散射介质后或者内部植入光源。但是目标尺寸的成像范围受到光学记忆效应的限制，无法对尺寸较大的物体进行成像。另外在扩散函数工程成像技术中有学者提出通过测量系统的点扩散函数，利用Lucy-Richardson去卷积迭代非线性复原方法，实现了透过散射介质成像。还有学者提出借鉴天文成像所应用的相位多样性的散斑成像方法，通过获取多张不同像平面的散斑信息，在无参考的情况下，联合估算获得整个散射光学系统的点扩散函数，进而通过去卷积技术实现了透过散射介质成像。但是点扩散函数工程成像技术都需要提前获取系统的点扩散函数，其成像效果依赖于所获取系统的点扩散函数的准确性，在成像过程中要保证散射介质的稳定性，且仅适用于静态散射介质成像。
综上所述，目前急需一种能够快速对动态物体进行成像、成像范围不受光学记忆效应的限制以及无需测量整个光学系统的点扩散函数的成像系统及其方法。
发明内容
为此，本发明所要解决的技术问题在于克服现有技术中动态物体成像效率低、成像范围受到光学记忆效应的限制以及需要测量整个光学系统的点扩散函数的缺陷。
为解决上述技术问题，本发明提供一种基于随机光场空间结构调控的光学成像系统，包括：
散射组件，所述散射组件用于利用散射介质对经过自由空间传输的光束进行散射处理，得到待测光，其中所述光束携带有待测物信息；
第一分束偏振组件，所述第一分束偏振组件用于对所述待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光，所述参考光为所述待测光的完全相干光；
光学测量组件，所述光学测量组件用于测量所述待测光的x方向偏振光和y方向偏振光的光强分布、所述参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布；
计算单元，所述计算单元用于根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布，并对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置。
在本发明的一个实施例中，还包括傅立叶透镜，所述傅立叶透镜设置于所述散射介质和第一分束偏振组件之间。
在本发明的一个实施例中，还包括第一半波片，所述第一半波片设置于所述傅立叶透镜与所述第一分束偏振组件之间。
在本发明的一个实施例中，所述第一分束偏振组件包括第一分束元件和 第一偏振分束元件，所述第一分束元件设置于所述第一半波片和所述第一偏振分束元件之间。
在本发明的一个实施例中，还包括连接光学测量组件的第二分束偏振组件，所述第二分束偏振组件包括第二分束元件a、第二分束元件b、第二偏振分束元件a、第二偏振分束元件b和反射元件，所述参考光通过所述第二分束元件a进行分束，其中一束参考光和待测光在所述第二分束元件b出进行合束，并通过第二偏振分束元件a将合束光分成x方向偏振光和y方向偏振光；另外一束参考光经过反射元件反射后，通过第二偏振分束元件b将参考光分成x方向偏振光和y方向偏振光。
在本发明的一个实施例中，所述光学测量组件包括构成阵列结构的第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元，所述第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元均包括至少两个电荷耦合器单体，其中第一电荷耦合器单元中的最上方的电荷耦合器单体到傅立叶透镜的光程等于所述傅立叶透镜的焦距。
在本发明的一个实施例中，所述第一电荷耦合器单元和第二电荷耦合器单元中的所有电荷耦合器单体到第一分束元件的光程均相等，且该光程等于第二电荷耦合器单元和第三电荷耦合器单元中的所有电荷耦合器单体到第二分束元件b的光程。
此外，本发明还提供一种基于随机光场空间结构调控的光学成像方法，包括：
利用散射介质对经过自由空间传输的光束进行散射处理，得到待测光，其中所述光束携带有待测物信息；
对所述待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y 方向偏振光，所述参考光为所述待测光的完全相干光；
测量所述待测光的x方向偏振光和y方向偏振光的光强分布、所述参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布；
根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布，并对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置。
在本发明的一个实施例中，根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布包括：
所述待测光的交叉谱密度的实部W'(r 1,r 2)和虚部W”(r 1,r 2)的计算公式如下：
Figure PCTCN2021101132-appb-000001
Figure PCTCN2021101132-appb-000002
式中，< …> S表示空间平均，r、r 1以及r 2表示观察面任意一点的坐标，I x(r)、I y(r)分别表示待测光的x方向和y方向偏振的光强分布，
Figure PCTCN2021101132-appb-000003
分别表示参考光的x方向和y方向偏振的光强分布，
Figure PCTCN2021101132-appb-000004
分别表示参考光与待测光合束之后的合束光的x方向和y方向偏振的光强分布；
根据公式利用交叉谱密度通过傅里叶变换恢复散射介质的光强分布p(ρ)，其中公式如下：
Figure PCTCN2021101132-appb-000005
式中，λ表示光的波长，f表示傅立叶透镜的焦距，ρ表示散射介质所在平面任意一点的坐标，i表示虚数单位。
在本发明的一个实施例中，对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置包括：
利用菲涅尔域中的相位恢复算法对散射介质的光强分布进行运算，得到所述待测物的形状和位置。
本发明的上述技术方案相比现有技术具有以下优点：
本发明首先测得待测光的光强分布、待测光和参考光合束之后的合束光的光强分布以及参考光的光强分布，根据光强分布求得待测光的交叉谱密度的实部和虚部，利用交叉谱密度的实部和虚部恢复散射介质表面的光强分布，并对散射介质的光强分布进行计算，得到待测物的形状和位置，从而能够快速对动态物体进行成像，成像范围不受光学记忆效应的限制，而且无需测量整个光学系统的点扩散函数。
附图说明
为了使本发明的内容更容易被清楚的理解，下面根据本发明的具体实施例并结合附图，对本发明作进一步详细的说明，其中
图1是本发明一种基于随机光场空间结构调控的光学成像系统的结构示意图。
图2是本发明一种基于随机光场空间结构调控的光学成像方法的流程示意图。
附图标记说明：1、第一激光器；2、第一扩束元件；3、待测物；4、自 由空间传输单元；5、散射介质；6、傅立叶透镜；7、第一半波片；8、第一分束元件；9、第一偏振分束元件；10、光学测量组件；11、锁相环；12、第二激光器；13、线偏振片；14、第二半波片；15、四分之一波片；16、第二扩束元件；17、第二分束元件a；18、第二分束元件b；19、第二偏振分束元件a；20、反射元件；21、第二偏振分束元件b；22、计算单元。
具体实施方式
下面结合附图和具体实施例对本发明作进一步说明，以使本领域的技术人员可以更好地理解本发明并能予以实施，但所举实施例不作为对本发明的限定。
实施例一
请参阅图1所示，本实施例提供一种基于随机光场空间结构调控的光学成像系统，系统包括散射组件、第一分束偏振组件、光学测量组件10和计算单元22。
散射组件用于利用散射介质5对经过自由空间传输的光束进行散射处理，得到待测光，其中光束携带有待测物3信息。散射介质5优选毛玻璃。
第一分束偏振组件用于将待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光，参考光为待测光的完全相干光。
光学测量组件10用于测量待测光的x方向偏振光和y方向偏振光的光强分布、参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布。
计算单元22用于根据光强分布求得待测光的交叉谱密度的实部和虚部，利用交叉谱密度的实部和虚部恢复散射介质5的光强分布，并对散射介质5 的光强分布进行计算，得到待测物3的形状和位置。
在本实施例中，还包括傅立叶透镜6，傅立叶透镜6设置于散射介质5和第一分束偏振组件之间。傅立叶透镜6能够对经过散射介质5后的待测光进行傅里叶变换，从而提高光场的相干度。
在本实施例中，还包括第一半波片7，第一半波片7设置于傅立叶透镜6与第一分束偏振组件之间。待测光经过第一半波片7可以得到45°偏振方向的线偏振光。
其中，第一分束偏振组件包括第一分束元件8和第一偏振分束元件9，第一分束元件8设置于第一半波片7和第一偏振分束元件9之间。从第一半波片7出来的线偏振光通过第一分束元件8将光束一分为二，其中透射的光束通过第一偏振分束元件9将光束分为x方向偏振光和y方向偏振光。优选的，第一分束元件8可以是分束镜，第一偏振分束元件9可以是偏振分束镜。
在本实施例中，还包括第一激光器1、第一扩束元件2和自由空间传输单元4，第一激光器1可以发射出完全相干线偏振激光，该光束携带待测物3信息，光束经过第一扩束元件2(可以是扩束镜)使得光束扩大，扩大的光束在经过待测物3(该待测物可以上下左右自由移动)后通过自由空间传输单元4传输至散射介质5(可以是毛玻璃)。
在本实施例中，还包括连接光学测量组件10的第二分束偏振组件，第二分束偏振组件包括第二分束元件a17、第二分束元件b18、第二偏振分束元件a19、第二偏振分束元件b21和反射元件20。参考光通过第二分束元件a17进行分束，其中一束参考光和待测光在第二分束元件b18处进行合束，并通过第二偏振分束元件a19将合束光分成x方向偏振光和y方向偏振光；另外一束参考光经过反射元件20反射后，通过第二偏振分束元件b21将参考光分成x方向偏振光和y方向偏振光。优选的，第二分束元件a17和第二分束元件 b18可以是分束镜，第二偏振分束元件a19和第二偏振分束元件b21可以是偏振分束镜，反射元件20可以是反射镜。
其中，光学测量组件10包括构成阵列结构的第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元。第一电荷耦合器单元用于测量待测光的x方向偏振光和y方向偏振光的光强分布；第二电荷耦合器单元用于测量参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布；第三电荷耦合器单元用于测量参考光的x方向偏振光和y方向偏振光的光强分布。
进一步地，第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元均包括至少两个电荷耦合器单体。优选的，每个电荷耦合器单元均包括两个电荷耦合器单体，即三个电荷耦合器单元总共有六个电荷耦合器单体，从上至下依次为电荷耦合器单体101、电荷耦合器单体102、电荷耦合器单体103、电荷耦合器单体104、电荷耦合器单体105和电荷耦合器单体106。其中电荷耦合器单体101到傅立叶透镜6的光程等于傅立叶透镜6的焦距。
还有，电荷耦合器单体101、电荷耦合器单体102、电荷耦合器单体103和电荷耦合器单体104到第一分束元件8的光程均相等，且该光程等于电荷耦合器单体103、电荷耦合器单体104、电荷耦合器单体105和电荷耦合器单体106到第二分束元件b18的光程。
在本实施例中，还包括第二激光器12、锁相环11、线偏振片13、第二半波片14、四分之一波片15和第二扩束元件16。第二激光器12通过锁相环11连接第一激光器1，即利用锁相环11、与第一激光器1同类型的第二激光器12以及线偏振片13获得与第一激光器1所发射的激光完全相干的线偏振光，该线偏振光作为参考光，其用来测量光场的相干结构。参考光通过第二半波片14可以得到45°方向偏振的线偏振光，再经过快轴或慢轴为0°的四分之 一波片15得到圆偏振光，圆偏振光经过第二扩束元件16(可以是扩束镜)使得光束扩大。
下面对本实施例提供的一种基于随机光场空间结构调控的光学成像系统的工作原理进行阐述。
请继续参阅图1所示，本实施例一种基于随机光场空间结构调控的光学成像系统的工作原理是：第一激光器1可以选用氦氖激光器，氦氖激光器发射出波长为633nm的完全相干线偏振激光，该光束携带待测物信息，光束经过第一扩束元件2使得光束扩大，扩大的光束在经过待测物3(该待测物可以上下左右自由移动)后通过自由空间传输单元4传输至散射介质5(可以是毛玻璃)得到待测光。当光束通过自由空间传输单元4时，由于衍射的影响，光强图像将会变得模糊不清。光束继续传输照射在旋转的散射介质5上，由于散射介质5的散射作用，待测光丢失相位信息。若需要恢复图像的信息，我们可以通过测量散射介质5后光场的相干结构，并恢复出散射介质5后表面的光强分布信息，从而利用菲涅尔域中的相位恢复算法得出待测物3的形状和位置。为了测量简便且更为精准，我们可以在散射介质5后增加一个傅立叶透镜6，其用于对经过散射介质5后的待测光进行傅里叶变换，从而提高光场的相干度。为了便于测量光场的相干结构，待测光经过第一半波片7得到45°偏振方向的线偏振光，该线偏振光通过第一分束元件8将光束一分为二，其中透射的待测光通过第一偏振分束元件9将光束分为x方向偏振光和y方向偏振光，利用光学测量组件10的电荷耦合器单体a和电荷耦合器单体b分别测量待测光的x方向偏振光和y方向偏振光的光强分布。
另一方面，利用锁相环11、与第一激光器1同类型的第二激光器12以及线偏振片13获得与第一激光器1所发射的激光完全相干的线偏振光，该线偏振光作为参考光用来测量光场的相干结构。参考光通过第二半波片14可以得到45°方向偏振的线偏振光，再经过快轴或慢轴为0°的四分之一波片15得 到圆偏振光，圆偏振光经过第二扩束元件16使得光束扩大。再利用第二分束元件a17将参考光一分为二，其中透射的参考光与待测光在第二分束元件b18处合束，合束光利用第二偏振分束元件a19将合束光分为x方向偏振光和y方向偏振光，利用光学测量组件10的电荷耦合器单体c和电荷耦合器单体d分别测量合束光的x方向偏振光和y方向偏振光的光强分布。而从第二分束元件a17所反射的参考光经过反射元件20反射后，利用第二偏振分束元件b21将参考光分为x方向偏振光和y方向偏振光，利用光学测量组件10的电荷耦合器单体e和电荷耦合器单体f分别测量参考光的x方向偏振光和y方向偏振光的光强分布。
最后，将上述得到的光强分布信息发送至计算单元22，并通过计算单元22对其进行运算和处理。
实施例二
下面对本发明实施例二提供的一种基于随机光场空间结构调控的光学成像方法进行介绍，下文描述的一种基于随机光场空间结构调控的光学成像方法与上文描述的一种基于随机光场空间结构调控的光学成像系统可相互对应参照。
请参阅图2所示，本实施例提供一种基于随机光场空间结构调控的光学成像方法，包括如下步骤：
S100：利用散射介质5对经过自由空间传输的光束进行散射处理，得到待测光，其中光束携带有待测物信息。
示例地，经过自由空间传输的携带有待测物3信息的光束在散射介质5的散射作用下会丢失相位信息，若需要恢复图像的信息，我们可以通过测量散射介质5后光场的相干结构，并恢复出散射介质5后表面的光强分布信息，利用相位恢复算法得出待测物3的形状和位置。为了测量简便且更为精准， 我们可以在散射介质5后增加一个傅立叶透镜6，其用于对经过散射介质5后的待测光进行傅里叶变换，从而提高光场的相干度。
S200：对待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光，参考光为待测光的完全相干光。
示例地，利用锁相环11、与第一激光器1同类型的第二激光器12以及线偏振片13获得与第一激光器1所发射的激光完全相干的线偏振光，该线偏振光作为参考光用来测量光场的相干结构。
S300：测量待测光的x方向偏振光和y方向偏振光的光强分布、参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布。
示例地，利用光学测量组件10的电荷耦合器单体a和电荷耦合器单体b分别测量待测光的x方向偏振光的散斑信息和y方向偏振光的散斑信息，这里的散斑信息即为光强分布。
S400：根据光强分布求得待测光的交叉谱密度的实部和虚部，利用交叉谱密度的实部和虚部恢复散射介质5的光强分布，并对散射介质5的光强分布进行计算，得到待测物3的形状和位置。
示例地，可以利用菲涅尔域中的相位恢复算法对散射介质5的光强分布进行运算，得到待测物3的形状和位置。
下面对本实施例提供的一种基于随机光场空间结构调控的光学成像方法的工作原理进行阐述。其工作原理如下：
原理1.随机光场的产生
携带有待测物3信息的光束在自由空间传输单元的传输过程中，由于干涉效应，光强图像已经变得模糊，即散射介质5前表面的光场可表示为：
Figure PCTCN2021101132-appb-000006
式中，i表示虚数单位，O(v)表示待测物3的光场分布，λ和k分别表示光的波长和波数，z表示传输距离，即待测物3与散射介质5的距离，v和ρ分别表示待测物3和散射介质5所在的横截面的坐标。
经过散射介质5的散射作用，光场丢失了相位信息，其光场表示为：
Figure PCTCN2021101132-appb-000007
式中，E'(ρ)表示散射介质5后表面的光场分布，
Figure PCTCN2021101132-appb-000008
表示随机相位，其与坐标ρ有关。
在散射介质5表面的光强为：
p(ρ)＝E*(ρ)E(ρ)＝E*'(ρ)E'(ρ)    (3)
上式表明散射介质5前后表面的光强分布是相同的。
散射介质5后表面的光场可通过其的二阶统计特性交叉谱密度来表征：
Figure PCTCN2021101132-appb-000009
式中，δ(…)表示Diracδ函数，ρ 1和ρ 2表示散射介质5所在平面的坐标。
为了测量简便且更为精准，我们可以在散射介质5后增加一个傅立叶透镜6，对散射介质5后表面的光场进行傅里叶变换，从而提高光场的相干度。光场经过傅立叶透镜6后，得到的是部分相干光束，其交叉谱密度为：
Figure PCTCN2021101132-appb-000010
式中，r、r 1以及r 2表示观察面任意一点的坐标，f表示傅立叶透镜6的焦距。
将公式(4)代入公式(5)，即可建立散射介质5表面的光强分布与观察面的空间相干结构的关系：
Figure PCTCN2021101132-appb-000011
原理2.测量随机光场的空间相干结构
待测光的二阶统计特性(包含其相干性)可以由交叉谱密度函数表示为；
W(r 1,r 2)＝<E *(r 1)E(r 2)>   (7)
式中，E(r)表示在空间r点处的随机电场，上标星号表示复共轭，尖括号表示系综平均。
具体地，引入一束参考光E R(r)与待测光E(r)进行合束，理论上可以通过旋转四分之一波片得到两束相位差为Δφ的参考光，产生的两参考光路分别与待测光相干合束，合束后的总随机电场分别为：
E C1(r)＝E(r)+E R1(r)   (8)
E C2(r)＝E(r)+E R2(r)   (9)
式中，E R1(r)和E R2(r)分别表示两束参考光的电场。
那么合束光的光强为：
I Cυ(r)＝E Cυ(r)E Cυ*(r)   (10)
式中， υ取值为1或2，I Cυ(r)表示第 υ束合束光的光强。
两次合束光的光强强度互关联为：
G C(r 1,r 2)＝<I C1(r 1)I C2(r 2)>     (11)
将公式(8)～(10)代入公式(11)，得到合成场的光强互关联可以表示成如下形式：
Figure PCTCN2021101132-appb-000012
式中，I R1(r)＝|E R1(r)| 2和I R2(r)＝|E R2(r)| 2分别表示两束参考光的光强分布，I U1(r)＝I R1(r)+I(r)与I U2(r)＝I R2(r)+I(r)分别表示两束参考光与待测光的光强非相干叠加。
从上式中，可以发现光强互关联G C(r 1,r 2)与参考光路相位差Δφ有关，且Δφ＝arg[E R2(r)-E R1(r)]，并且待测光的交叉谱密度振幅和相位信息也包含在G C(r 1,r 2)中。例如：当Δφ＝0时，公式中的最后一项中包括了交叉谱密度的实部信息；当
Figure PCTCN2021101132-appb-000013
时，公式中的最后一项中包括了交叉谱密度的虚部信息。
也就是说可以控制两参考光路的相位差来获得交叉谱密度的实部和虚部信息，从而获得待测光的交叉谱密度振幅和相位。
此外，从公式(12)中可以发现光强互关联函数中包含了背景项。为了去除背景项，我们引入参考光与待测光的非相干叠加的光强互相关：
Figure PCTCN2021101132-appb-000014
公式(12)减去公式(13)，可以得到：
Figure PCTCN2021101132-appb-000015
公式(14)中，分别取Δφ分布为0和
Figure PCTCN2021101132-appb-000016
可得交叉谱密度的的实部与虚部：
Figure PCTCN2021101132-appb-000017
Figure PCTCN2021101132-appb-000018
本实施例中，为了测量待测光的交叉谱密度，我们利用偏振分束镜和电荷耦合器单体记录π/4线偏振的部分待测光的x方向和y方向偏振的光强分布I x(r)、I y(r)，此外还记录了圆偏振参考光x方向和y方向偏振的光强分布
Figure PCTCN2021101132-appb-000019
并且记录了参考光与待测光合束之后的合束光的x方向和y方向偏振的光强分布
Figure PCTCN2021101132-appb-000020
通过以上的量，可以恢复交叉谱密度的实部和虚部如下：
Figure PCTCN2021101132-appb-000021
Figure PCTCN2021101132-appb-000022
式中，<…> S表示空间平均，由于该光场是经过傅里叶系统产生的，因此，可以通过空间平均而不是时间平均来替代系综平均，根据公式(6)，即可利用测得的交叉谱密度通过傅里叶变换恢复散射介质5表面的光强分布p(ρ)。
原理3.利用菲涅尔域的相位恢复算恢法复待测物3的形状与位置
通过上式已知散射介质5表面的光强分布p(ρ)，而若要进一步获得待测物3函数的具体分布情况，则可以通过相位恢复算法恢复出待测物3。其具体步骤为:
10、首先假设初始待测物为：
Figure PCTCN2021101132-appb-000023
20、初始待测物经过距离为z的自由空间传输后，其光场为：
Figure PCTCN2021101132-appb-000024
式中，λ和k分别表示光的波长和波数，z表示传输距离，即初始待测物与散射介质5的距离，v和ρ分别表示初始待测物和散射介质5所在的横截面的坐标。
30、获取E k(ρ)的相位为：
θ k(ρ)＝arg[E k(ρ)]   (21)
40、将相位赋给
Figure PCTCN2021101132-appb-000025
得到新的散射介质表面的光场：
Figure PCTCN2021101132-appb-000026
50、E' k(ρ)经过距离为-z的自由空间传输，并对得到的光场取实部获得O' k(v)。
60、根据限制条件对O' k(v)进行有效信息筛选：
Figure PCTCN2021101132-appb-000027
至此，我们得到了新的待测物的函数O k+1(v)，为了获得更为精准的信息，需要循环迭代，也就是重复这六个步骤，可以循环30到80次，对最终得到的新的待测物函数O k+1(v)的实部进行平方，就得到了初始待测物的光强分布，实现了透过散射介质对隐藏在散射介质后的待测物3的成像。
综上，本发明首先测得待测光的光强分布、待测光和参考光合束之后的合束光的光强分布以及参考光的光强分布，根据光强分布求得待测光的交叉谱密度的实部和虚部，利用交叉谱密度的实部和虚部恢复散射介质5表面的光强分布，并对散射介质5表面的光强分布进行计算，得到待测物3的形状和位置，从而能够快速对动态物体进行成像，成像范围不受光学记忆效应的限制，而且无需测量整个光学系统的点扩散函数。
本领域内的技术人员应明白，本申请的实施例可提供为方法、系统、或计算机程序产品。因此，本申请可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且，本申请可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程序产品的形式。
本申请是参照根据本申请实施例的方法、设备(系统)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器，使得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。
这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中，使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品，该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。
这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上，使得在计算机或其他可编程设备上执行一系列操作步骤以产生计算机实现的处理，从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。
显然，上述实施例仅仅是为清楚地说明所作的举例，并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引申出的显而易见的变化或变动仍处于本发明创造的保护范围之中。

Claims (10)

  1. 一种基于随机光场空间结构调控的光学成像系统，其特征在于，包括：
    散射组件，所述散射组件用于利用散射介质对经过自由空间传输的光束进行散射处理，得到待测光，其中所述光束携带有待测物信息；
    第一分束偏振组件，所述第一分束偏振组件用于对所述待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光，所述参考光为所述待测光的完全相干光；
    光学测量组件，所述光学测量组件用于测量所述待测光的x方向偏振光和y方向偏振光的光强分布、所述参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布；
    计算单元，所述计算单元用于根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布，并对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置。
  2. 根据权利要求1所述的基于随机光场空间结构调控的光学成像系统，其特征在于：还包括傅立叶透镜，所述傅立叶透镜设置于所述散射介质和第一分束偏振组件之间。
  3. 根据权利要求2所述的基于随机光场空间结构调控的光学成像系统，其特征在于：还包括第一半波片，所述第一半波片设置于所述傅立叶透镜与所述第一分束偏振组件之间。
  4. 根据权利要求1或3所述的基于随机光场空间结构调控的光学成像系统，其特征在于：所述第一分束偏振组件包括第一分束元件和第一偏振分束元件，所述第一分束元件设置于所述第一半波片和所述第一偏振分束元件之间。
  5. 根据权利要求1所述的基于随机光场空间结构调控的光学成像系统，其特征在于：还包括连接光学测量组件的第二分束偏振组件，所述第二分束偏振组件包括第二分束元件a、第二分束元件b、第二偏振分束元件a、第二偏振分束元件b和反射元件，所述参考光通过所述第二分束元件a进行分束，其中一束参考光和待测光在所述第二分束元件b出进行合束，并通过第二偏振分束元件a将合束光分成x方向偏振光和y方向偏振光；另外一束参考光经过反射元件反射后，通过第二偏振分束元件b将参考光分成x方向偏振光和y方向偏振光。
  6. 根据权利要求1所述的基于随机光场空间结构调控的光学成像系统，其特征在于：所述光学测量组件包括构成阵列结构的第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元，所述第一电荷耦合器单元、第二电荷耦合器单元以及第三电荷耦合器单元均包括至少两个电荷耦合器单体，其中第一电荷耦合器单元中的最上方的电荷耦合器单体到傅立叶透镜的光程等于所述傅立叶透镜的焦距。
  7. 根据权利要求6所述的基于随机光场空间结构调控的光学成像系统，其特征在于：所述第一电荷耦合器单元和第二电荷耦合器单元中的所有电荷耦合器单体到第一分束元件的光程均相等，且该光程等于第二电荷耦合器单元和第三电荷耦合器单元中的所有电荷耦合器单体到第二分束元件b的光程。
  8. 一种基于随机光场空间结构调控的光学成像方法，其特征在于，包括：
    利用散射介质对经过自由空间传输的光束进行散射处理，得到待测光，其中所述光束携带有待测物信息；
    对所述待测光进行分束偏振处理，其中一束待测光被分为x方向偏振光和y方向偏振光，另外一束待测光与参考光合束后被分成x方向偏振光和y方向偏振光，所述参考光为所述待测光的完全相干光；
    测量所述待测光的x方向偏振光和y方向偏振光的光强分布、所述参考光与待测光合束后的x方向偏振光和y方向偏振光的光强分布以及参考光的x方向偏振光和y方向偏振光的光强分布；
    根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布，并对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置。
  9. 根据权利要求8所述的基于随机光场空间结构调控的光学成像方法，其特征在于，根据光强分布求得所述待测光的交叉谱密度的实部和虚部，利用所述交叉谱密度的实部和虚部恢复散射介质的光强分布包括：
    所述待测光的交叉谱密度的实部W'(r 1,r 2)和虚部W”(r 1,r 2)的计算公式如下：
    Figure PCTCN2021101132-appb-100001
    Figure PCTCN2021101132-appb-100002
    式中，< …> S表示空间平均，r、r 1以及r 2表示观察面任意一点的坐标，I x(r)、I y(r)分别表示待测光的x方向和y方向偏振的光强分布，
    Figure PCTCN2021101132-appb-100003
    分别表示参考光的x方向和y方向偏振的光强分布，
    Figure PCTCN2021101132-appb-100004
    分别表示参考光与待测光合束之后的合束光的x方向和y方向偏振的光强分布；
    根据公式利用交叉谱密度通过傅里叶变换恢复散射介质的光强分布p(ρ)，其中公式如下：
    Figure PCTCN2021101132-appb-100005
    式中，λ表示光的波长，f表示傅立叶透镜的焦距，ρ表示散射介质所在平面任意一点的坐标，i表示虚数单位。
  10. 根据权利要求8所述的基于随机光场空间结构调控的光学成像方法，其特征在于：对所述散射介质的光强分布进行计算，得到所述待测物的形状和位置包括：
    利用菲涅尔域中的相位恢复算法对散射介质的光强分布进行运算，得到所述待测物的形状和位置。
PCT/CN2021/101132 2021-06-07 2021-06-21 基于随机光场空间结构调控的光学成像系统及方法 WO2022257174A1 (zh)

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