Millimeter-wave three-dimensional holographic imaging method and system

1. A millimeter-wave three-dimensional holographic imaging method, comprising:

transmitting a continuous frequency wave to a measured human body by using a millimeter-wave antenna array, and receiving an original echo signal S(t, θ, z) reflected back by the measured human body;

performing Fourier transform on the original echo signal along a time direction to obtain a time transformed echo signal S(ω, θ, z) in a frequency domain;

performing two-dimensional Fourier transform on the time transformed echo signal in the frequency domain along an angle θ and a vertical direction z to obtain a spatially transformed echo signal S(ω, ξ, k z ) in a spatial wave number domain;

performing phase compensation on the spatially transformed echo signal to obtain a phase compensated spatially transformed echo signal in the spatial wave number domain;

performing one-dimensional inverse Fourier transform on the phase compensated spatially transformed echo signal after the phase compensation along the θ direction to obtain sampling data in the spatial wave number domain;

performing non-uniform sampling to uniform sampling interpolation on the sampling data in the spatial wave number domain to obtain echo data evenly distributed in the spatial wave number domain;

performing three-dimensional inverse Fourier transform on the echo data evenly distributed in the spatial wave number domain to obtain three-dimensional echo data; and

projecting the three-dimensional echo data in a quasi standard deviation manner to obtain two-dimensional reconstruction data, and to generate a two-dimensional image;

wherein the step of transmitting the continuous frequency wave to the measured human body by using the millimeter-wave antenna array, and receiving the original echo signal S(ω, θ, z) reflected back by the measured human body specifically comprises:

transmitting the continuous frequency wave to the measured human body by using a millimeter-wave antenna array with a cylindrical synthetic aperture, and receiving the original echo signal S(ω, θ, z) reflected back by the measured human body;

wherein the step of performing phase compensation on the spatially transformed echo signal to obtain a phase compensated spatially transformed echo signal in the spatial wave number domain specifically comprises:

multiplying the spatially transformed echo signal S(ω, ξ, k z ) in the spatial wave number domain by a phase compensation factor exp(−j√{square root over (4k r 2 R 2 −ξ 2 )}) to obtain the phase compensated spatially transformed echo signal, wherein R is a scanning radius of the millimeter-wave antenna array with the cylindrical synthetic aperture; and

wherein the step of projecting the three-dimensional image in the quasi standard deviation manner to obtain the two-dimensional reconstructed image specifically comprises:

projecting a scattering intensity signal of the measured target received at each frequency point by the n th antenna in the m th row according to the following standard deviation projection formula:

I

mn

=

1

N

f

⁢

∑

i

=

1

N

f

⁢

(

I

mn

i

-

I

i

_

)

2

;

and

combining I mn obtained by the projection of all antennas in the millimeter-wave antenna array to obtain the two-dimensional reconstructed image,

wherein the continuous frequency wave transmitted to the measured human body by the millimeter-wave antenna array is a stepped frequency continuous wave signal, the number of frequency points is N f , a scattering intensity signal of the measured target received at each frequency point by the n th antenna in the m th row in the millimeter-wave antenna array is I mni and the statistical average value of scattering intensity of millimeter-wave signals at corresponding frequency points by the human body is Ī l .

2. The millimeter-wave three-dimensional holographic imaging method of claim 1 , wherein after projecting the three-dimensional image in the quasi standard deviation manner to obtain the two-dimensional reconstructed image, the method further comprises: identifying whether the measured human body is carrying foreign matter according to the two-dimensional reconstructed image.

3. A millimeter-wave three-dimensional holographic imaging system, comprising:

an echo signal acquisition unit for transmitting a continuous frequency wave to a measured human body by using a millimeter-wave antenna array, and receiving an original echo signal S(t, θ, z) reflected back by the measured human body;

a first Fourier transform unit for performing Fourier transform on the original echo signal along a time direction to obtain a time transformed echo signal S(ω, θ, z) in a frequency domain;

a second Fourier transform unit for performing two-dimensional Fourier transform on the time transformed echo signal in the frequency domain along an angle θ and a vertical direction z to obtain a spatially transformed echo signal S(ω, ξ, k z ) in a spatial wave number domain;

a phase compensation unit for performing phase compensation on the spatially transformed echo signal to obtain a phase compensated spatially transformed echo signal in the spatial wave number domain;

a first inverse Fourier transform unit for performing one-dimensional inverse Fourier transform on the phase compensated spatially transformed echo signal after the phase compensation along the θ direction to obtain sampling data in the spatial wave number domain;

an interpolation unit for performing non-uniform sampling to uniform sampling interpolation on the sampling data in the spatial wave number domain to obtain echo data evenly distributed in the spatial wave number domain;

a second inverse Fourier transform unit for performing three-dimensional inverse Fourier transform on the echo data evenly distributed in the spatial wave number domain to obtain three-dimensional echo data; and

a two-dimensional image reconstruction unit for projecting the three-dimensional echo data in a quasi standard deviation manner to obtain two-dimensional reconstruction data, and generating a two-dimensional reconstructed image;

wherein the echo signal acquisition unit is specifically used for:

transmitting the continuous frequency wave to the measured human body by using a millimeter-wave antenna array with a cylindrical synthetic aperture, and receiving the original echo signal S(ω, θ, z) reflected back by the measured human body;

wherein the phase compensation unit is specifically used for:

multiplying the spatially transformed echo signal S(ω, ξ, k z ) in the spatial wave number domain by a phase compensation factor exp(−j√{square root over (4k r 2 R 2 −ξ 2 )}) to obtain the phase compensated spatially transformed echo signal, wherein R is a scanning radius of the millimeter-wave antenna array with the cylindrical synthetic aperture; and

wherein the two-dimensional image reconstruction unit is specifically used for:

projecting a scattering intensity signal of the measured target received at each frequency point by the n th antenna in the m th row according to the following standard deviation projection formula:

I

mn

=

1

N

f

⁢

∑

i

=

1

N

f

⁢

(

I

mn

i

-

I

i

_

)

2

;

and

combining I mn obtained by the projection of all antennas in the millimeter-wave antenna array to obtain the two-dimensional reconstructed image, wherein the continuous frequency wave transmitted to the measured human body by the millimeter-wave antenna array is a stepped frequency continuous wave signal, the number of frequency points is N f , a scattering intensity signal of the measured target received at each frequency point by the n th antenna in the m th row in the millimeter-wave antenna array is I mni and the statistical average value of scattering intensity of millimeter-wave signals at corresponding frequency points by the human body is Ī l .

4. The millimeter-wave three-dimensional holographic imaging system of claim 3 , further comprising:

a foreign matter identification unit for identifying whether the measured human body is carrying foreign matter according to the two-dimensional reconstructed image.