CN103235299A - Optical imaging processing system of synthetic-aperture laser imaging radar - Google Patents

Abstract

The invention relates to an optical imaging processing system of a synthetic-aperture laser imaging radar. The optical imaging processing system comprises a complex value processing unit, a data sampling and phase extraction unit, a laser, a collimating beam expander, a pure phase liquid crystal spatial light modulator, a cylindrical lens, a spherical lens, a CCD (Charge Coupled Device) and a computer. According to the optical imaging processing system, an optical processing mode is utilized to realize aperture synthesizing imaging of a radar detection target. Compared with a traditional digital imaging processing mode, the data processing time is greatly shortened, real-time image acquisition is realized, and the optical imaging processing system is an important technical improvement of the synthetic-aperture laser imaging radar and has a broad application prospect in the airborne and satellite borne synthetic-aperture laser imaging radar system in the future.

Description

Synthetic aperture laser imaging radar optical imagery disposal system

Technical field

The present invention relates to synthetic aperture laser imaging radar, a kind of synthetic aperture laser imaging radar optical imagery disposal system particularly, the mode of utilizing optical imagery to handle realizes the aperture compound imaging of radar illumination target.

Background technology

The principle of synthetic aperture laser imaging radar (SAIL) is taken from the synthetic aperture radar (SAR) principle of RF application, be external report can be at the remote unique optical imagery Observations Means that obtains centimetre magnitude resolution.The emission laser of synthetic aperture laser imaging radar adopts the modulation of namely warbling of optical frequency linear modulation, the photoelectricity heterodyne reception adopts and to go oblique demodulation mode namely to adopt the same emission laser of warbling as heterodyne local oscillator light beam, therefore obtained distance to comprise range information and in the orientation to the echo difference frequency signal that comprises phase history information.On the target face echoed signal phase distance descriscent of each point be with distance to relevant linear term phase place of fast time, the orientation is to being to relevant quadratic term phase place of slow time with the orientation.

Since 2002, synthetic aperture laser imaging radar has successively obtained checking [referring to document 1:M.Bashkansky in the laboratory, R.L.Lucke, E.Funk, L.J.Rickard, andJ.Reintjes, " Two-dimensionalsynthetic apertureimagingintheopticaldomain, " OpticLetters, Vol.27, pp1983-1985 (2002); Document 2:W.Buell, N.Marechal, J.Buck, R.Dickinson, D.Kozlowski, T.Wright, andS.Beck, " DemonstrationsofSyntheticApertureImagingLadar, " Proc.ofSPIEVol.5791pp152-166 (2005); Document 3: Zhou Yu, Xu Nan, Luan Zhu, Yan Aimin, Wang Lijuan, Sun Jianfeng, Liu Liren, yardstick dwindle the two-dimensional imaging experiment of Synthetic Aperture Laser Radar, the optics journal, and Vol.31 (9) (2011); Document 4: Liu Liren, Zhou Yu, the inferior nanmu of duty, Sun Jianfeng, heavy caliber synthetic aperture laser imaging radar demonstration model and laboratory proofing thereof, the optics journal, Vol.29 (7): 2030～2032 (2011)], Raytheon Co. and Nuo Ge company under U.S. national defense advanced project office supports realized respectively that airborne Synthetic Aperture Laser Radar experiment (not having any details report) was [referring to document 5:J.Ricklin, M.Dierking, S.Fuhrer in 2006, B.Schumm, andD.Tomlison, " Synthetic apertureladarfortacticalimaging, " DARPAStrategicTechnologyOffice.].2011, Luo Ma company has realized that to the terrain object at 1.6 kilometers places airborne synthetic aperture laser imaging radar imaging experiment is [referring to document 6:BrianW.Krause, JoeBuck, ChrisRyan, DavidHwang, PiotrKondratko, Andrew Malm, AndyGleason " SyntheticApertureLadarFlightDemonstration, "].

In above-mentioned all relevant reports [referring to document 1,2,3,4,5,6], the imaging processing mode of echoed signal all is the digital imagery processing mode, be about to photoelectricity reception and digitizing echoed signal afterwards and at first carry out Fast Fourier Transform (FFT) realization target range to focal imaging, will adopt the quadratic term matched filtering in space to realize that the orientation of target is to focal imaging apart from the signal behind focal imaging then.This two step has sequencing in time, can not carry out simultaneously, yet, along with the requirement of future raising and the real time imagery of spaceborne and airborne synthetic aperture laser imaging radar imaging resolution being handled, the data volume of radar collection will inevitably increase greatly, and computing and the transmission speed of digital imaging processing mode proposed stern challenge.

Summary of the invention

The technical problem to be solved in the present invention is to propose a kind of optical imagery disposal system of synthetic aperture laser imaging radar, the mode that this optical imagery disposal system utilizes optical imagery to handle realizes the aperture compound imaging to the radar detection target, because the quick and parallel processing capability of optical processing system, make the processing time of radar echo signal shorten greatly with respect to traditional digital processing mode, realizing real time imagery, is that the important technology of synthetic aperture laser imaging radar improves.

Technical solution of the present invention is as follows:

A kind of optical imagery disposal system of synthetic aperture laser imaging radar is characterized in that its formation comprises that complex value processing unit, sampling of data and phase extraction unit, laser instrument, collimator and extender device, pure phase position LCD space light modulator, focal length are f _aCylindrical lens, focal length be f _tSpherical lens, CCD, computing machine, described focal length is f _aThe focal length of cylindrical lens

In the formula, λ _sBe synthetic aperture laser imaging radar emission laser center wavelength, f is synthetic aperture laser imaging radar optics toes equivalence radius-of-curvature, λ is the emission optical maser wavelength of described laser instrument, and b is that LCD space light modulator orientation, described pure phase position is to the phase signal loading direction length of side, B _sFor synthetic aperture laser imaging radar optics toes orientation to length, the described sampling of data of output termination and the phase extraction unit of described complex value processing unit, the first input end of the described pure phase of the output termination position LCD space light modulator of described sampling of data and phase extraction unit, along being described collimator and extender device successively on the primary optical axis of described laser instrument laser output, pure phase position LCD space light modulator, cylindrical lens, spherical lens (7), CCD, computing machine, described pure phase position LCD space light modulator and described cylindrical lens are close to placement, described pure phase position LCD space light modulator distance is parallel with the generatrix direction of described cylindrical lens to the phase signal loading direction, described cylindrical lens is on the front focal plane of described spherical lens, described CCD on the back focal plane of described spherical lens, the described input end and computer of output termination of described CCD;

Described data complex value processing unit carries out the complex value processing to the target echo signal of synthetic aperture laser imaging radar, the target echo signal of the synthetic aperture laser imaging radar after described sampling of data and phase extraction unit are handled described complex value is sampled and phase extraction, form the phase modulated signal of described pure phase position LCD space light modulator, this phase modulated signal is loaded on the described LCD space light modulator via data line;

The laser that is sent by described laser instrument shines described pure phase position LCD space light modulator through the collimator and extender device, carry out imaging processing through described cylindrical lens, spherical lens in this LCD space light modulator after the phase place modulation of described phase modulated signal and form the target picture, this target picture is received by described CCD and is shown by described computing machine.

Technique effect of the present invention:

The mode that the present invention proposes to utilize optical imagery to handle is carried out imaging processing to radar echo signal, at first radar echo signal is carried out pluralization, sampling, phase extraction, the phase signal that extracts is as the phase modulation function of pure phase position LCD space light modulator, laser by laser instrument output shines on the LCD space light modulator of pure phase position through behind the collimator and extender, emergent light passes through cylindrical lens successively, spherical lens is realized the imaging to the radar detection target, and imaging results is received by CCD and shown by computing machine.Because the quick and parallel processing capability of optical processing system makes the processing time of radar echo signal shorten greatly with respect to traditional digital processing mode, realizes real time imagery, be that the important technology of synthetic aperture laser imaging radar improves.

Description of drawings

Fig. 1 is synthetic aperture laser imaging radar optical imagery disposal system structural representation of the present invention.

Fig. 2 is LCD space light modulator volume coordinate synoptic diagram in pure phase position among the present invention.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in further detail, but should limit protection scope of the present invention with this.

See also Fig. 1 earlier, Fig. 1 is synthetic aperture laser imaging radar optical imagery disposal system synoptic diagram of the present invention.As seen from the figure, synthetic aperture laser imaging radar optical imagery disposal system structure of the present invention, its structure comprises: complex value processing unit 1, sampling of data and phase extraction unit 2, laser instrument 3, collimator and extender device 4, pure phase position LCD space light modulator 5, focal length are f _a Cylindrical lens 6, focal length be f _t Spherical lens 7, CCD8, computing machine 9, described focal length is f _aThe focal length of cylindrical lens 6

In the formula, λ _sBe synthetic aperture laser imaging radar emission laser center wavelength, f is synthetic aperture laser imaging radar optics toes equivalence radius-of-curvature, λ is the emission optical maser wavelength of described laser instrument 3, and b is that LCD space light modulator orientation, described pure phase position is to the phase signal loading direction length of side, B _sFor synthetic aperture laser imaging radar optics toes orientation to length, the described sampling of data of output termination and the phase extraction unit 2 of described complex value processing unit 1, the first input end of the described pure phase of the output termination position LCD space light modulator 5 of described sampling of data and phase extraction unit 2, along being described collimator and extender device 4 successively on the primary optical axis of described laser instrument 3 laser output, pure phase position LCD space light modulator 5, cylindrical lens 6, spherical lens 7, CCD8, computing machine 9, described pure phase position LCD space light modulator 5 is close to placement with described cylindrical lens 6, LCD space light modulator 5 distances in described pure phase position are parallel with the generatrix direction of described cylindrical lens 6 to the phase signal loading direction, described cylindrical lens 6 is on the front focal plane of described spherical lens 7, described CCD8 on the back focal plane of described spherical lens 7, the input end of the described computing machine 9 of output termination of described CCD8;

The target echo signal of 1 pair of synthetic aperture laser imaging radar of described data complex value processing unit carries out complex value to be handled, the target echo signal of the synthetic aperture laser imaging radar after the 2 pairs of described complex values in described sampling of data and phase extraction unit are handled is sampled and phase extraction, form the phase modulated signal of described pure phase position LCD space light modulator 5, this phase modulated signal is loaded on the described LCD space light modulator 5 via data line;

The laser that is sent by described laser instrument 3 shines described pure phase position LCD space light modulator 5 through collimator and extender device 4, carry out imaging processing through described cylindrical lens 6, spherical lens 7 in this LCD space light modulator 5 after the phase place modulation of described phase modulated signal and form the target picture, this target picture is received by described CCD8 and is shown by described computing machine 9.

Adopt a point target to explain the processing procedure of synthetic aperture laser imaging radar optical imagery disposal system of the present invention below:

The synthetic aperture laser imaging radar reflecting telescope is launched chirped chirped pulse laser to point target, and by the receiving telescope heterodyne reception that is concerned with, the point target echoed signal that is stored in the computing machine is the emission light wave after point target reflection:

$I(t_f,n{\mathrm{\&Delta;t}}_{s}v)=\cos [2\mathrm{\&pi;\&rho;}{\mathrm{<figure-callout\; id="2"\; label="t\; f"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">t</figure-callout>}}_f\frac{2\mathrm{\&Delta;z}}{c}+\frac{\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}{(y_k-{\mathrm{n\&Delta;t}}_{s}v)}^2]$

In the formula, t _fFor distance by radar to the sampling time coordinate, n is radar emission laser sequence number, △ t _sBe the duration of radar emission pulsatile once, v be radar bearing to stepping rate, ρ is radar emission laser frequency chirp rate, △ z is for introducing the target and the equivalent distances of radar after the local oscillator, f is the equivalent radius-of-curvature of radar optics toes, y _kFor the orientation of impact point on objective plane to coordinate, for the ease of analyzing, following formula has carried out normalized to coefficient.

After the processing of the described plural numberization cell complex of above-mentioned signal process be:

$I^{\&prime;}(t_f,{\mathrm{n\&Delta;t}}_{s}v)=\exp [\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&rho;}{\mathrm{<figure-callout\; id="2"\; label="t\; f"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">t</figure-callout>}}_f\frac{2\mathrm{\&Delta;z}}{c}+j\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;f}}{(y_k-{\mathrm{n\&Delta;t}}_{s}v)}^2]$

Above-mentioned signal through the phase signal of described data sampling and phase extraction processing gained is:

The following formula phase signal is loaded on the LCD space light modulator of described pure phase position as its phase modulation function by data line, see also Fig. 2 again, Fig. 2 is the pure phase position LCD space light modulator volume coordinate synoptic diagram described in the present invention, as seen from the figure, described pure phase position LCD space light modulator is wide to be a, be positioned at the x coordinate axis, respective distances loads to phase signal, long is b, be positioned at the y coordinate axis, corresponding orientation loads to phase signal, and in the phase signal loading procedure, distance by radar is to time-sampling coordinate t _f, the orientation is to volume coordinate (t _f, n △ t _sV) the transformational relation with x, y is respectively:

$t_f=\frac{T_{s}x}{a},{\mathrm{n\&Delta;t}}_{s}v=\frac{B_{s}y}{b}$

In the formula, T _sFor distance by radar to time-sampling width, B _sFor radar optics toes orientation to yardstick.After above-mentioned coordinate transform relation, the phase modulation function that is loaded on the LCD space light modulator of described pure phase position is:

Monochromatic plane wave is sent by described laser instrument, shine on the LCD space light modulator of described pure phase position through behind the described collimator and extender device, make that the incident light wave amplitude is 1, then the outgoing light field of carrying out after the phase place modulation through described pure phase position LCD space light modulator is:

$I_o(x,y)=\exp [\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{2\mathrm{\&Delta;z}{T}_s\mathrm{\&rho;}}{\mathrm{ac}}x+j\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;f}}{\left(\frac{B_s}{b}\right)}^2{(\frac{b}{B_s}{y}_k-y)}^2]$

The focal length of described cylindrical lens is:

Be close to placement with described pure phase position LCD space light modulator, generatrix direction is parallel with x, and then, the phase transmittance function of described cylindrical lens is:

$t\left(y\right)=\exp (-j\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}{f}_a}{y}^2)=\exp [-j\frac{\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}{\left(\frac{B_s}{b}\right)}^2{y}^2]$

Then the light field of the rear surface of described cylindrical lens is:

$I_a(x,y)=I_a(x,y)\&times;t(x,y)$

$=\exp [\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{{2\mathrm{\&Delta;zT}}_s\mathrm{\&rho;}}{\mathrm{ac}}x+j\frac{\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}{\left(\frac{B_s}{b}\right)}^2{(\frac{b}{B_s}{y}_k-y)}^2]\&times;\exp [-j\frac{\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}{\left(\frac{B_s}{b}\right)}^2{y}^2]$

$=\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{{2\mathrm{\&Delta;zT}}_s\mathrm{\&rho;}}{\mathrm{ac}}x\right)\exp (-\frac{2\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}\frac{B_s}{b}{y}_{k}y)\exp \left(j\frac{\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}{y}_k^2\right)$

Described cylindrical lens is on the front focal plane of described spherical lens, and described CCD is in the back meeting of described spherical lens, and then the light field that receives of CCD is the Fourier transform of described cylindrical lens rear surface light field, so the light field that CCD receives is:

$I_i(\mathrm{\&xi;},\mathrm{\&eta;})=\mathrm{fft}\left\{I_a(x,y)\right\}$

$=\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}\begin{array}{c}\left\{\begin{array}{c}\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{{2\mathrm{\&Delta;zT}}_s\mathrm{\&rho;}}{\mathrm{ac}}x\right)\exp (-\frac{2\mathrm{\&pi;}}{{\mathrm{\&lambda;}}_{s}f}\frac{B_s}{b}{y}_{k}y)\&times;\\ \exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{\mathrm{\&xi;}}{\mathrm{\&lambda;}{f}_t}x-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003074227300011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{\mathrm{\&eta;}}{{\mathrm{\&lambda;f}}_t}y)\mathrm{rect}\left(\frac{x}{a}\right)\mathrm{rect}\left(\frac{y}{b}\right)\end{array}\right\}\mathrm{dxdy}\end{array}$

$=\sin c\left(\frac{\mathrm{a\&xi;}}{{\mathrm{\&lambda;f}}_t}\right)*\mathrm{\&delta;}(\frac{\mathrm{\&xi;}}{{\mathrm{\&lambda;f}}_t}-\frac{2{\mathrm{\&Delta;zT}}_s\mathrm{\&rho;}}{\mathrm{ac}})\&times;\sin c\left(\frac{\mathrm{b\&eta;}}{{\mathrm{\&lambda;f}}_t}\right)*\mathrm{\&delta;}(\frac{\mathrm{\&eta;}}{{\mathrm{\&lambda;f}}_t}+\frac{B_s{y}_k}{{\mathrm{\&lambda;}}_s\mathrm{fb}})$

In the formula, it is image planes distances to, orientation to coordinate that ξ, η are respectively plane, CCD place, f _tBe the focal length of described spherical lens, Be respectively Fourier integral distance to, orientation to window function.

Can be got by following formula, for the point target of investigating:

A) become some image distance descriscent coordinate: Distance to resolution is:

B) become the some image aspect to coordinate: The orientation to resolution is:

For each point on the target face, the imaging processing process is identical, and appearance is put on the stack that each impact point becomes a picture and constituted the face picture, by described CCD reception and by described calculating and demonstration.

One embodiment of the present of invention are to handle for the focal imaging of the target echo data of heavy caliber synthetic aperture laser imaging radar demonstration model acquisition, provide the parameter of radar system and target below: radar emission laser center wavelength λ=1.5 μ m, frequency chirp rate: ρ=1.25 * 10 ¹³Hz/s, optics toes size: 22mm * 22mm, radar target centre distance: z=14m, radar bearing are to stepping length: △ t _sV=0.1mm, distance is to sampling time width: T _s=40ms, distance is to sample frequency: 2.5MHz, optics toes radius-of-curvature: f=2.6m, target sizes: 8mm * 40mm, long limit is positioned at the orientation to the 45 ° of placements of tilting of, the relative radar of target minor face, used laser output wavelength is: λ=632.8nm, the size of used pure phase position LCD space light modulator: a=15.36mm, b=8.64mm, the focal length of used cylindrical lens: f _a=952.3mm, the spherical lens focal length is: f _t=500mm.

In synthetic aperture laser imaging radar, the imaging processing mode of traditional radar return data all is the digital processing mode, be about to photoelectricity reception and digitizing echoed signal afterwards and at first carry out Fast Fourier Transform (FFT) realization target range to focal imaging, will adopt the quadratic term matched filtering in space to realize that the orientation of target is to focal imaging apart from the signal behind focal imaging then.This two step has sequencing in time, can not carry out simultaneously, yet, along with the requirement of future raising and the real time imagery of spaceborne and airborne synthetic aperture laser imaging radar imaging resolution being handled, the data volume of radar collection will inevitably increase greatly, and computing and the transmission speed of digital imaging processing mode proposed stern challenge.The mode that the present invention proposes to utilize optical imagery to handle is carried out imaging processing to radar echo signal, at first radar echo signal is carried out pluralization, sampling, phase extraction, the phase signal that extracts is as the phase modulation function of pure phase position LCD space light modulator, laser by laser instrument output shines on the LCD space light modulator of pure phase position through behind the collimator and extender, emergent light passes through cylindrical lens successively, spherical lens is realized the imaging to the radar detection target, and imaging results is received by CCD and shown by computing machine.Because the quick and parallel processing capability of optical processing system, make the processing time of radar echo signal shorten greatly with respect to traditional digital processing mode, realize real time imagery, the important technology that is synthetic aperture laser imaging radar improves, in addition, can provide vital decision information to navigation and the orientation of satellite or unmanned plane, and has a very high dynamic output area, can reduce communication system transmitted data amount and requirements for transmission, can realize integrated, effectively reduce the weight and volume of system, reduce the power consumption of system, tool had great advantage during therefore following data at synthetic aperture laser imaging radar were handled.

Claims (1)

1. the optical imagery disposal system of a synthetic aperture laser imaging radar is characterized in that its formation comprises that complex value processing unit (1), sampling of data and phase extraction unit (2), laser instrument (3), collimator and extender device (4), pure phase position LCD space light modulator (5), focal length are f _aCylindrical lens (6), focal length be f _tSpherical lens (7), CCD(8), computing machine (9), described focal length is f _aThe focal length of cylindrical lens (6)

In the formula, λ _sBe synthetic aperture laser imaging radar emission laser center wavelength, f is synthetic aperture laser imaging radar optics toes equivalence radius-of-curvature, λ is the emission optical maser wavelength of described laser instrument (3), b is that the orientation of described pure phase position LCD space light modulator (5) is to the phase signal loading direction length of side, B _sFor synthetic aperture laser imaging radar optics toes orientation to length, the described sampling of data of output termination of described complex value processing unit (1) and phase extraction unit (2), the first input end of the described pure phase of the output termination position LCD space light modulator (5) of described sampling of data and phase extraction unit (2), along being described collimator and extender device (4) successively on the primary optical axis of described laser instrument (3) laser output, pure phase position LCD space light modulator (5), cylindrical lens (6), spherical lens (7), CCD(8), computing machine (9), described pure phase position LCD space light modulator (5) is close to placement with described cylindrical lens (6), described pure phase position LCD space light modulator (5) distance is parallel with the generatrix direction of described cylindrical lens (6) to the phase signal loading direction, described cylindrical lens (6) is on the front focal plane of described spherical lens (7), the input end of the described computing machine of output termination (9) described CCD(8) on the back focal plane of described spherical lens (7), described CCD(8);

Described data complex value processing unit (1) carries out the complex value processing to the target echo signal of synthetic aperture laser imaging radar, the target echo signal of the synthetic aperture laser imaging radar after handle described complex value described sampling of data and phase extraction unit (2) is sampled and phase extraction, form the phase modulated signal of described pure phase position LCD space light modulator (5), this phase modulated signal is loaded on the described LCD space light modulator (5) via data line;

The laser that is sent by described laser instrument (3) shines described pure phase position LCD space light modulator (5) through collimator and extender device (4), carry out imaging processing through described cylindrical lens (6), spherical lens (7) in this LCD space light modulator (5) after the modulation of the phase place of described phase modulated signal and form the target picture, this target picture is by described CCD(8) receive and shown by described computing machine (9).

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