CN103744059A - Single-lens optical processor of synthetic aperture laser imaging radar - Google Patents

Abstract

The invention provides a single-lens optical processor of a synthetic aperture laser imaging radar. The single-lens optical processor comprises a transmission-type structure and a reflection-type structure; a liquid crystal spatial light modulator is used for loading a target echo signal of the synthetic aperture laser imaging radar; a single lens is used for realizing focusing and imaging in a distance direction and an azimuth direction; an imaging result is received by virtue of an image receiver; the whole system is automatically controlled by virtue of a system control module. The single-lens optical processor provided by the invention is simple in structure, cost-saving, and easy to integrate, has extensive application prospects in future onboard and satellite-borne synthetic aperture laser imaging radar systems and is a key technical improvement for optical imaging treatment of the synthetic aperture laser imaging radar.

Description

The Single-lens Optical processor of synthetic aperture laser imaging radar

Technical field

The present invention relates to synthetic aperture laser imaging radar, a Single-lens Optical processor for synthetic aperture laser imaging radar particularly, utilize single lens simultaneously realize target echoed signal distance to, orientation to focal imaging, save cost, simple in structure, be easy to integrated.

Background technology

The ultimate principle of synthetic aperture laser imaging radar (SAIL) derives from the synthetic aperture radar (SAR) in microwave region, be external report can be at the remote unique optical imagery Observations Means that obtains centimetre magnitude resolution.Since two thousand two, synthetic aperture laser imaging radar has successively obtained checking [referring to document 1:M.Bashkansky in laboratory, R.L.Lucke, E.Funk, L.J.Rickard, and J.Reintjes, " Two-dimensional synthetic aperture imaging in the optical domain, " Optic Letters, Vol.27, pp1983-1985 (2002), document 2:W.Buell, N.Marechal, J.Buck, R.Dickinson, D.Kozlowski, T.Wright, and S.Beck, " Demonstrations of Synthetic Aperture Imaging Ladar, " Proc.of SPIE Vol.5791pp152-166 (2005), document 3: Zhou Yu, Xu Nan, Luan Zhu, Yan Aimin, Wang Lijuan, Sun Jianfeng, Liu Liren, yardstick dwindles the two-dimensional imaging experiment of Synthetic Aperture Laser Radar, Acta Optica, Vol.31 (9) (2011), document 4: Liu Liren, Zhou Yu, the sub-nanmu of duty, Sun Jianfeng, heavy caliber synthetic aperture laser imaging radar demonstration model and laboratory proofing thereof, Acta Optica, Vol.29 (7): 2030～2032 (2011)], within 2006, the He Nuo lattice company of Raytheon Co. under U.S. national defense advanced project office supports has realized respectively airborne Synthetic Aperture Laser Radar experiment (without any details report) [referring to document 5:J.Ricklin, M.Dierking, S.Fuhrer, B.Schumm, and D.Tomlison, " Synthetic aperture ladar for tactical imaging, " DARPA Strategic Technology Office.].2011, Luo Ma company has realized airborne synthetic aperture laser imaging radar imaging experiment [referring to document 6:Brian W.Krause to the terrain object of 1.6 kms, Joe Buck, Chris Ryan, David Hwang, Piotr Kondratko, Andrew Malm, Andy Gleason " Synthetic Aperture Ladar Flight Demonstration, "].

The echoed signal of initial microwave SAR generally adopts the mode of optics to carry out imaging processing, [referring to document 7:L.J.Cutrona, E.N.Leith, L.J.Porcello et al., " On the application of coherent optical processing techniques to synthetic-aperture radar; " Proc.IEEE54,1026～1032 (1966) .] be accompanied by the raising of digital processing ability, this optical processing method is replaced by digital processing mode to a great extent.The echoed signal of SAIL also mainly adopts digital form to carry out imaging processing equally, now.Yet the demand that the following raising that spaceborne and airborne SAIL image resolution ratio is required and real time imagery are processed, proposes severe challenge to the transmission of digital imaging processor and arithmetic speed.Optical imagery processor can provide noncoherent parallel data processing ability, realize bidimensional Fourier transform truly, shorten data processing time, thereby realize realtime graphic acquisition of information, can provide vital decision information to the navigation of satellite or unmanned plane and orientation, and there is very high dynamic output area, can reduce the requirement to communication system transmitted data amount and transmission bandwidth, can realize integrated, effectively reduce the weight and volume of system, the power consumption of reduction system, therefore the following Data processing tool at synthetic aperture laser imaging radar has great advantage.The optical imagery of Technologies Against Synthetic Aperture laser imaging radar is processed still in the primary research stage both at home and abroad at present, has higher researching value and development space.Formerly technology [referring to document 8: Hou Peipei, Liu Liren, Sun Jianfeng, the sub-nanmu of duty, Zhou Yu, Lu Wei, Wang Lijuan, the optical synthesis aperture laser imaging radar processor based on astigmatism Fourier transform, patent of invention, application number: 201310150460.8; Document 9: Sun Zhiwei, the sub-nanmu of duty, Sun Jianfeng, Zhou Yu, Hou Peipei, Liu Li people, the optical imaging system of synthetic aperture laser imaging radar and optical imaging method, patent of invention, application number: 201310300362.8] a kind of principle scheme of synthetic aperture laser imaging radar proposed, but the focusing that foregoing invention adopts a plurality of lens combinations to realize echoed signal is processed, and system is more complicated, and cost is higher and be difficult for integrated.

Summary of the invention

The technical problem to be solved in the present invention is to propose a kind of Single-lens Optical processor of synthetic aperture laser imaging radar, this optical processor simple in structure, save cost, be easy to integrated, in, satellite-borne synthetic aperture laser imaging radar system airborne in future, having wide practical use, is that the gordian technique that synthetic aperture laser imaging radar optical imagery is processed is improved.

Technical solution of the present invention is as follows:

A kind of Single-lens Optical processor of synthetic aperture laser imaging radar, it is characterized in that its formation comprises system control module, transmission-type LCD space light modulator, the first astigmatic lens and picture receiver, along optical axis direction, be followed successively by described transmission-type LCD space light modulator, the first astigmatic lens and picture receiver, the input end of the transmission-type LCD space light modulator described in the output termination of described system control module, the first input end of described system control module is bonded into the data receiving system of aperture laser imaging radar, the output terminal of the picture receiver described in the second input termination of described system control module, described transmission-type LCD space light modulator, the first astigmatic lens is close to placement, the distance of the first described astigmatic lens is f to focal length _a, orientation is f to focal length _eq1=(f _af _c1)/(f _a+ f _c1), f in formula _c1=f _lc/ λ _c, wherein, f _lcfor described transmission-type LCD space light modulator orientation is to quadratic term phase place radius-of-curvature, λ _cfor the Single-lens Optical processor optical maser wavelength used of described synthetic aperture laser imaging radar, the distance of described picture receiver and described the first astigmatic lens is f _a.

A kind of Single-lens Optical processor of synthetic aperture laser imaging radar, its feature is that its formation comprises system control module, picture receiver, reflection type liquid crystal spatial light modulator, beam splitter and the second astigmatic lens, along optical axis direction, be followed successively by described reflection type liquid crystal spatial light modulator, beam splitter, the second astigmatic lens and picture receiver, the input end of the reflection type liquid crystal spatial light modulator described in the output termination of this system control module, the first input end of described system control module is bonded into the data receiving system of aperture laser imaging radar, the output terminal of the picture receiver described in the second input termination of described system control module, the distance of described reflection type liquid crystal spatial light modulator and the second described astigmatic lens is d, the distance of the second described astigmatic lens is f to focal length _r, orientation is f to focal length _eq2=(f _rf _c2)/(f _r+ f _c2), f in formula _c2=(d-f _lc)/λ _c, the distance of described picture receiver and described the second astigmatic lens is f _r.

Technique effect of the present invention:

The present invention proposes to utilize system control module automatically control the loading of SAIL echoed signal and the reception of imaging results storage and show, without artificial participation, save the processing time, improve treatment effeciency, in addition, adopt single lens simultaneously realize target distance to, orientation to focal imaging, simple in structure, save cost, and be easy to integratedly, in future, in airborne, spaceborne SAIL system, have wide practical use.The gordian technique that is synthetic aperture laser imaging radar echo data optical imagery mode is improved.

Accompanying drawing explanation

Fig. 1 is Single-lens Optical processor embodiment 1 structural representation of synthetic aperture laser imaging radar of the present invention.

Fig. 2 is Single-lens Optical processor embodiment 2 structural representations of synthetic aperture laser imaging radar of the present invention.

Embodiment

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

First refer to Fig. 1, Fig. 1 is the Single-lens Optical processor structure schematic diagram of the embodiment of the present invention 1 reflective synthetic aperture laser imaging radar, the Single-lens Optical processor of reflective synthetic aperture laser imaging radar in the present invention as seen from the figure, its formation comprises: system control module 1, transmission-type LCD space light modulator 2, the first astigmatic lens 3, picture receiver 4, along optical axis direction, be followed successively by described transmission-type LCD space light modulator 2, the first astigmatic lens 3, picture receiver 4, the output terminal 11 of described system control module 1 connects the input end 21 of described transmission-type LCD space light modulator 2, the first input end 12 of described system control module 1 is bonded into the data receiving system of aperture laser imaging radar, the second input end 13 of described system control module 1 connects the output terminal 41 of described picture receiver 4,

Described transmission-type LCD space light modulator 2, the first astigmatic lenses 3 are close to placement, and the distance of the first described astigmatic lens 3 is f to focal length _a, orientation is f to focal length _eq1=(f _af _c1)/(f _a+ f _c1), f in formula _c1=f _lc/ λ _c, wherein, f _lcfor described transmission-type LCD space light modulator 2 orientation are to quadratic term phase place radius-of-curvature, λ _cfor the Single-lens Optical processor optical maser wavelength used of described synthetic aperture laser imaging radar, described picture receiver 4 is f with the distance of the first described astigmatic lens 3 _a.

Refer to Fig. 2, Fig. 2 is the Single-lens Optical processor structure schematic diagram of the embodiment of the present invention 2 transmission-type synthetic aperture laser imaging radars again.The Single-lens Optical processor of transmission-type synthetic aperture laser imaging radar in the present invention as seen from the figure, its formation comprises described system control module 1, picture receiver 4, reflection type liquid crystal spatial light modulator 5, beam splitter 6, the second astigmatic lens 7, along optical axis direction, be followed successively by described reflection type liquid crystal spatial light modulator 5, beam splitter 6, the second astigmatic lens 7, picture receiver 4, the output terminal 11 of this system control module 1 connects the input end 51 of described reflection type liquid crystal spatial light modulator 5, the first input end 12 of described system control module 1 is bonded into the data receiving system of aperture laser imaging radar, the second input end 13 of described system control module 1 connects the output terminal 41 of described picture receiver 4,

Described reflection type liquid crystal spatial light modulator 5 is d with the distance of the second described astigmatic lens 7, and the distance of the second described astigmatic lens is f to focal length _r, orientation is f to focal length _eq2=(f _rf _c2)/(f _r+ f _c2), f in formula _c2=(d-f _lc)/λ _c, described picture receiver 4 is f with the distance of the second described astigmatic lens 7 _r.

Adopt an impact point to explain the imaging processing process of the Single-lens Optical processor of synthetic aperture laser imaging radar of the present invention below.

The emission coefficient of synthetic aperture laser imaging radar is launched chirped chirped pulse laser to investigated impact point, transmitting light wave is by be concerned with heterodyne reception carry out plural number of receiving system after the reflection of above-mentioned impact point, and the echoed signal of the point target of the system control module described in being transferred to is i (t _f, t _sv):

$\begin{array}{c}i(t_f,t_{s}v)=A_k{\sin c}^2\left(\frac{S_x{x}_k}{\mathrm{\λZ}}\right){\sin c}^2\left[\frac{S_y(y_k-t_{s}v)}{\mathrm{\λZ}}\right]\mathrm{rect}\left(\frac{t_f-T_f/2}{T_f}\right)\×\\ \mathrm{rect}\left(\frac{{\mathrm{vt}}_s-B_s/2}{B_s}\right)\exp [j2\mathrm{\π\ρ}\frac{{2\mathrm{\Δz}}_k}{c}{t}_f+j\frac{\mathrm{\π}}{\mathrm{\λR}}{(y_k-t_{s}v)}^2]\end{array}$

Wherein, A _kfor with Laser emission power, local oscillator laser power, optical heterodyne receiving sensitivity, transmit and receive the relevant constant such as optical system structure, free-space optical transmission, target complex index of reflection characteristic.X _k, y _kthe distance that is respectively described impact point is to, orientation to coordinate, t _f, t _sbe respectively distance to fast time, orientation to the slow time, v be radar bearing to movement velocity, B _sfor radar optics toes orientation is to yardstick, the orientation definite with receiving structure by radar emission to directivity function is: sinc ²[S _y(y _k-vt _s)/λ Z], S _yfor radar emission bore orientation is to width, λ is radar emission laser center wavelength, and Z is the distance that radar is put to target's center, sets t _f=0, t _s=0 carries out time, the spatial sampling initial point of Data Collection for radar to impact point, to directivity function, be vertically: sinc ²(S _xx _k/ λ Z), S _xfor radar emission bore is vertically to width, make radar emission bore equate with Receiver aperture here, distance is to time-sampling width T _f, radar emission laser frequency chirp rate is ρ, Δ z _kfor deducting the target radar equivalent distances after reference light brachium, c is the light velocity, and radar optics toes equivalence radius-of-curvature is R=Z/2.

Above formula signal is loaded in LCD space light modulator as its modulating function by data line, setting LCD space light modulator distance is a to width, be positioned at x coordinate axis, load distance to signal, orientation is long for b to width, is positioned at y coordinate axis, load orientation to signal, in signal loading process, distance by radar is to time-sampling coordinate, and orientation is to volume coordinate (t _f, mt _sv) be respectively with the transformational relation of LCD space light modulator volume coordinate (x, y):

$t_f=\frac{T_f}{a}x,t_{s}v=\frac{B_s}{b}y$

After above-mentioned coordinate transform relation, the modulating function being loaded in LCD space light modulator is t (x, y):

$\begin{array}{c}t(x,y)=A_k{\sin c}^2\left(\frac{S_x{x}_k}{\mathrm{\λZ}}\right){\sin c}^2\left[\frac{S_y(y_k-B_{s}y/b)}{\mathrm{\λZ}}\right]\mathrm{rect}\left(\frac{x-a/2}{a}\right)\mathrm{rect}\left(\frac{y-b/2}{b}\right)\\ \exp [j2\mathrm{\π\ρ}\frac{{2\mathrm{\Δz}}_k}{c}\frac{T_f}{a}x+j\frac{\mathrm{\π}}{\mathrm{\λR}}{\left(\frac{B_s}{b}\right)}^2{(\frac{b}{B_s}{y}_k-y)}^2]\end{array}$

For described transmission-type LCD space light modulator, orientation to quadratic term phase place radius-of-curvature is:

$f_{\mathrm{lc}}=\mathrm{\λR}{\left(\frac{b}{B_s}\right)}^2$

The phase transmittance function of the first described astigmatic lens is:

$t_{\mathrm{fir}}(x,y)=\exp (-j\frac{\mathrm{\π}}{{\mathrm{\λ}}_c{f}_a}{x}^2)\exp (-j\frac{\mathrm{\π}}{{\mathrm{\λ}}_c{f}_{\mathrm{eq}1}}{y}^2)$

Plane light wave irradiates described transmission-type LCD space light modulator, and distance is to carrying out Fourier transform after above-mentioned modulating function modulation for transmitted light, and orientation is f to seeing through the described laggard row distance of the first astigmatic lens _afresnel diffraction, the volume coordinate of setting described picture receiver place is (u, v), the imaging complex amplitude signal of the impact point of investigating is herein:

Above formula C (x _k, y _k: u, v) comprise the constant phase factor and constant coefficient in conversion, asterisk represents convolution.The strength information of above-mentioned signal | e (u, v) | ²through described picture receiver, receive and pass back described system control module and store demonstration.

For described reflection type liquid crystal spatial light modulator, orientation to binomial phase place radius-of-curvature is-f _lc, the quadratic term phase place radius-of-curvature while arriving the second described astigmatic lens front surface is d-f _lc, the volume coordinate of setting the second astigmatic lens front surface is (α, β), light field is herein

$\begin{array}{c}{t}^{\′}(\mathrm{\α},\mathrm{\β})=A_k{\sin c}^2\left(\frac{S_x{x}_k}{\mathrm{\λZ}}\right){\sin c}^2\left[\frac{S_y(y_k-B_s\mathrm{\β}/b)}{\mathrm{\λZ}}\right]\mathrm{rect}\left(\frac{\mathrm{\α}-a/2}{a}\right)\mathrm{rect}\left(\frac{\mathrm{\β}-b/2}{b}\right)\\ \exp [j2\mathrm{\π\ρ}\frac{{2\mathrm{\Δz}}_k}{c}\frac{T_f}{a}\mathrm{\α}+j\frac{\mathrm{\π}}{\mathrm{\λ}[d-R{(b/B_s)}^2]}{(\frac{b}{B_s}{y}_s-\mathrm{\β})}^2]\end{array}$

The phase transmittance factor of the second described astigmatic lens is:

$t_{\sec }(x,y)=\exp (-j\frac{\mathrm{\π}}{{\mathrm{\λ}}_c{f}_r}{x}^2)\exp (-j\frac{\mathrm{\π}}{{\mathrm{\λ}}_c{f}_{\mathrm{eq}2}}{y}^2)$

Distance is carried out Fourier transform to the second astigmatic lens by described, and orientation is f to seeing through the laggard row distance of this second astigmatic lens _rfresnel diffraction, the imaging complex amplitude signal of the impact point of investigating forming at described picture receiver place is:

Above formula D (x _k, y _k: u, v) comprise the constant phase factor and constant coefficient in conversion, the strength information of above-mentioned signal in formula | e ' (u, v) | ²through described picture receiver, receive and pass back described system control module and store demonstration.

One embodiment of the present of invention are to process for the focal imaging of the Area Objects 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=1.55 μ m, frequency chirp rate: ρ=1.25 * 10 ¹³hz/s, optics toes size: 22mm * 22mm, radar target centre distance: z=14m, distance is to sampling time width: T _s=40ms, distance is to sample frequency: 2.5MHz, optics toes radius-of-curvature: R=2.6047m, target sizes: 8mm * 40mm, long limit be positioned at orientation to, 45 ° of placements of the relative radar inclination of target minor face, optical processor laser output wavelength used is: λ=632.8nm, the size of reflective pure phase used position LCD space light modulator: a=2.4mm, load distance to pure phase bit data, b=7.7924mm, loads orientation to pure phase bit data, and described LCSLM orientation is f to quadratic term phase place radius-of-curvature _c=200mm, described the second astigmatic lens distance is f to focal length _r=150mm, orientation is to equivalent focal length f _eq2=+∞, the spacing of described reflective LCSLM and described the second astigmatic lens is d=50mm.

The Single-lens Optical processor of synthetic aperture laser imaging radar of the present invention has provided transmission-type and reflective two kinds of structures, proposition utilizes single lens to realize distance to, orientation to focal imaging simultaneously, compare priori technology, simple in structure, save cost, being easy to integratedly, in future, in airborne, spaceborne SAIL system, having wide practical use, is that the gordian technique that SAIL optical imagery is processed is improved.

Claims (2)

1. the Single-lens Optical processor of a synthetic aperture laser imaging radar, be characterised in that its formation comprises system control module (1), transmission-type LCD space light modulator (2), the first astigmatic lens (3) and picture receiver (4), along optical axis direction, be followed successively by described transmission-type LCD space light modulator (2), the first astigmatic lens (3) and picture receiver (4), the output terminal (11) of described system control module (1) connects the input end (21) of described transmission-type LCD space light modulator (2), the first input end (12) of described system control module (1) is bonded into the data receiving system of aperture laser imaging radar, second input end (13) of described system control module (1) connects the output terminal (41) of described picture receiver (4), described transmission-type LCD space light modulator (2) and the first astigmatic lens (3) are close to placement, the distance of described the first astigmatic lens (3) is f to focal length _a, orientation is f to focal length _eq1=(f _af _c1)/(f _a+ f _c1), f in formula _c1=f _lc/ λ _c, wherein, f _lcfor described transmission-type LCD space light modulator (2) orientation is to quadratic term phase place radius-of-curvature, λ _cfor the Single-lens Optical processor optical maser wavelength used of described synthetic aperture laser imaging radar, described picture receiver (4) is f with the distance of described the first astigmatic lens (3) _a.

2. the Single-lens Optical processor of a synthetic aperture laser imaging radar, be characterised in that its formation comprises described system control module (1), picture receiver (4), reflection type liquid crystal spatial light modulator (5), beam splitter (6) and the second astigmatic lens (7), along optical axis direction, be followed successively by described reflection type liquid crystal spatial light modulator (5), beam splitter (6), the second astigmatic lens (7) and picture receiver (4), the output terminal (11) of described system control module (1) connects the input end (51) of described reflection type liquid crystal spatial light modulator (5), the first input end (12) of described system control module (1) is bonded into the data receiving system of aperture laser imaging radar, second input end (13) of described system control module (1) connects the output terminal (41) of described picture receiver (4), described reflection type liquid crystal spatial light modulator (5) is d with the distance of described the second astigmatic lens (7), the distance of the second described astigmatic lens is f to focal length _r, orientation is f to focal length _eq2=(f _rf _c2)/(f _r+ f _c2), f in formula _c2=(d-f _lc)/λ _c, described picture receiver (4) is f with the distance of described the second astigmatic lens (7) _r.