CN101078765B - Laser radar remote sensing polarized imaging system - Google Patents

Abstract

The invention provides a new radar remote-sensing polarization imaging system. It can make use of polarization information of target backward scattered light to carry out radar remote-sensing detection for target and quick real-time polarization degree imaging. The system comprises semiconductor laser, polarization-status generating system, beam expanding system, cassegrain telescope system, polarization-status detecting system, and data collecting and imaging system. The invention realizes polarization degree detection by the polarization-status generating system and the polarization-status detecting system and adopts polarization splitting prism in the polarization-status detecting system to realize a first detection for target polarization degree and real-time imaging.

Description

Laser radar remote sensing polarized imaging system

1. technical field

The invention discloses a kind of laser radar remote sensing polarized imaging system that utilizes polarization information to carry out accurate remote sensing and imaging.Be mainly used in detection, identification and the imaging of man-made target in natural background and complex background in the military system; The fields such as remote sensing of integrated informations such as the kind of vegetation and crops, growth, health in the civilian system.

2. background technology

The conventional laser radar usually utilizes and sends out/and the flight time (apart from parameter), echo strength parameter, target of receiving pulse are to the back scattering waveform parameter of laser pulse and utilize object space angle parameter (3-D imaging system) that scanning angle obtains etc., do not consider the polarization characteristic of target, can not well discern natural target and man-made target; And can not well describe the essence and the intrinsic characteristic of target, survey and there is obvious deficiency aspects such as agricultural, vegetation detection in military target.Polarization characteristic can provide the target more information, and can obtain high-contrast, high-quality image as one of key character of target.There is special ability the laser radar remote sensing polarized aspects such as detection identification that are imaged on vegetative breakdown and hiding military target, it is abundant application to laser intelligence, being the raising of conventional laser radar remote sensing performance and perfect, also is the development trend of laser radar remote sensing simultaneously.

The Egan of New York University has carried out the research of polarization characteristic to C2130 type aircraft, B252 type aircraft and camouflage vehicle respectively at 1999 and 2002.In observing with atmospheric polarization over the ground, the polarization and the directivity instrument (POLDER) of the earth reflectance of the EOS instrument of Nasa (NASA)---earth observation scanning polarimeter (EOSP) and Centre National d'Etudes Spatiales (CNES) development are representative.Their energy measurement I, Q, three Stocks parameters of U.EOSP has 12 channel of polarization, can provide global gasoloid to distribute and characteristics such as the optical thickness of cloud layer and state; And POLDER has three polarimetry passages, in order to measure global ocean water colour, cloud and gasoloid etc.

The CALIPSO satellite of emission on April 28th, 2006, by NASA and Centre National D'etudes Spatiales's cooperative research and development, it is equipped with dual wavelength polarization laser radar and infrared and visible light imaging and passive imaging equipment, can be used for the gasoloid that measuring vertical distributes, the state of cloud, rear orientation light by different wave length can be classified to aerocolloidal size, study global cloud layer distribution situation, and to the influence of global atmosphere.

Anhui Inst. of Optics and Fine Mechanics, Chinese Academy of Sciences has finished " ground multiband polarization CCD camera principle prototype " development under the support of projects such as " 863 ".This model machine adopts the CCD planar array detector of 1024 * 1024 pixels, has 4 to measure passage: 443nm, 555nm, 665nm, 865nm between 400～900nm, and spectral bandwidth is 30～50nm, measures I, Q, three Stocks parameters of U." metre scattering polarization micro-pulse laser radar control method and device " patent of this institute, the patent No. is CN1641339A, be mainly used in the polarization characteristic research of targets such as atmospheric environment, gasoloid, but this system is not owing to there is polarization state to produce system, can only launch the polarization laser of particular state, the complete polarization information of target can not be obtained, the Target Recognition field can not be applied to.

3. summary of the invention

Because traditional laser radar imaging method exists many shortcomings, the laser radar remote sensing polarized imaging that the present invention proposes, be utilize the target rear orientation light polarization information particularly degree of polarization target is surveyed and imaging, obtain the internal feature information of target and high-contrast, high-quality polarization image.

The present invention is the important improvement and the raising of conventional laser radar, adopts following technical scheme:

Invention proposes laser radar remote sensing polarized imaging system as shown in Figure 1: this system mainly is made up of laser instrument, polarization state generation device, Cassegrain telescope receiving system, polarization state pick-up unit, data acquisition process and imaging device.Its core concept is that target is carried out active probe, and the rear orientation light of receiving target extracts the polarization parameter in the rear orientation light and carries out imaging.

In the present invention, system's various piece is described as follows:

(1) lasing light emitter: lasing light emitter is exported continuous laser by semiconductor laser, and produces system by entering polarization state behind the collimation lens collimation.

(2) polarization state produces system: by Glan laser polarization prism, 1/8 wave plate is formed.According to parameter, the angle that Glan laser polarization prism and 1/8 wave plate are rationally regulated in the requirement of system, make laser by polarization state generation system after, obtain determining the polarized light of polarization state.

(3) collimating and beam expanding system: for the detection of a target on a large scale, obtain the image of target complete and accurate, we adopt the collimating and beam expanding system of being made up of two plano-convex collimation lenses, collimating and beam expanding system does not change polarization state of light, and therefore the polarization state of light that incides on the target by collimating and beam expanding system still is the polarization state of light by the output of polarization generation system.And eliminate parasitic light by diaphragm, obtain the higher emergent light of the depth of parallelism.

(4) Cassegrain telescope receiving system: after light incides target, by the rear orientation light of Cassegrain telescope system receiving target.By entering the polarization state detection system of back behind the narrow band pass filter.

(5) polarization state detection system: form by 1/8 wave plate and polarization splitting prism.Native system directly obtains two orthogonal smooth I of polarization state by adopting polarization splitting prism _∥And I _⊥, further to realize the one-shot measurement of degree of polarization according to the degree of polarization computing formula.

(6) data acquisition process and imaging device: form by a twin-channel data collecting card and computing machine.Receive the mutually perpendicular two-beam of exporting by the polarization state detection system of polarization state respectively by data collecting card, according to the computing formula of degree of polarization $p_d=\frac{I_{//}-I_{\⊥}}{I_{//}-I_{\⊥}},$ Carry out data processing by computing machine at last, obtain the degree of polarization image of target.

Main characteristic of the present invention: the polarization information to the target rear orientation light is surveyed, and realizes laser radar remote sensing polarized imaging.

Benefit of the present invention and application prospect: (1) is because the polarization characteristic of target rear orientation light can characterize the intrinsic propesties of target, and can discern man-made target and camouflage target in natural background and the complex background fast and accurately, and obtain the polarization image of high-quality, high-contrast, serve the man-made target in the military system and the accurate identification of camouflaged target.(2) can characterize by the degree of polarization of the rear orientation light of plant in view of information such as the kinds of vegetation, crops, growth, health status, therefore utilize polarization information that the integrated information of vegetation, crops is carried out necessity and the important supplement that remote sensing is the conventional laser radar remote sensing.(3) polarization image of target can be given prominence to the detailed information and the internal feature of target, in the imaging of medical field important application will be arranged.(4) the laser polarization radar remote sensing can provide abundant sensor information in remote sensings such as atmosphere, gasoloid, river are used, to serve aerological sounding; Pollution monitoring such as atmosphere, river.

4. description of drawings

Fig. 1 is a laser polarization radar remote sensing system diagram

5. embodiment

Figure 1 shows that laser polarization radar remote sensing system diagram.The polarization characteristic of target rear orientation light can characterize the essential characteristic and the important parameter characteristic of target; And can effectively discern the man-made target in natural background and complex background.Shown in Figure 1: the wavelength of semiconductor laser (1) is 808nm, by plano-convex collimation lens (2), enter polarization state and produce system (5), polarization state produces system (5) and is made up of Glan laser prism (3) and 1/8 wave plate (4), wherein the angle of the light transmission shaft of Glan laser prism (3) and x axle is-72.385 °, and the fast axle of 1/8 wave plate (4) is 45 ° with the angle of x axle.The Stocks vector that produces system (5) back light by polarization state is: $S_{\mathrm{intagget}}=\left(\begin{array}{c}1\\ -1/\sqrt{3}\\ -1/\sqrt{3}\\ -1/\sqrt{3}\end{array}\right).$ The light that produces system (5) ejaculation from polarization state is incided on the target by catoptron (10) and (11) by collimating and beam expanding system (9), and wherein collimating and beam expanding system is made up of two plano-convex collimation lenses (6,8) and diaphragm (7).The Stocks vector of target rear orientation light is:

$S_{\mathrm{outt}\arg \mathrm{et}}=\left(\begin{array}{c}{M}_{00}\\ -{\mathrm{<figure-callout\; id="11"\; label="M"\; filenames="S071B8417820070802E000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_{11}/\sqrt{3}\\ -{\mathrm{<figure-callout\; id="11"\; label="M"\; filenames="S071B8417820070802E000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_{11}/\sqrt{3}\\ -M_{33}/\sqrt{3}\end{array}\right),$ M wherein ₀₀Be the total scattering coefficient of target, M ₁₁Be the linear polarization coefficient of target, M ₃₃Circular polarization coefficient for target.Rear orientation light by Cassegrain telescope primary mirror (12) receiving target, and enter polarization state detection system (18) by Cassegrain telescope secondary mirror (13) reflection, polarization state detection system (18) is made up of 1/8 wave plate (16) and polarization splitting prism (17), wherein the fast axle of 1/8 wave plate (16) is 45 ° with the angle of x axle, the main shaft of polarization splitting prism with the angle of x axle be-72.385 °, also be that light intensity is respectively by first of the Stocks vector of the mutually perpendicular light of polarization state of polarization splitting prism outgoing:

$I_{//}=1+\frac{1}{3}(2{\mathrm{<figure-callout\; id="11"\; label="M"\; filenames="S071B8417820070802E000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_{11}+M_{33}),$ ? $I_{\&perp;}=1-\frac{1}{3}(2{\mathrm{<figure-callout\; id="11"\; label="M"\; filenames="S071B8417820070802E000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_{11}+M_{33}).$ Receive the light intensity of this two bundles polarization state mutually perpendicular light respectively by CCD (19) and CCD (20), receive the data of gathering by these two CCD by double channel data acquisition card (21), and according to the computing formula of degree of polarization $\mathrm{pd}=\frac{I_{//}-I_{\&perp;}}{I_{//}+I_{\&perp;}}$ By computing machine (22) to data handle, data fusion, obtain the degree of polarization image of target.Realize laser radar remote sensing polarized imaging.

Claims (5)

1. laser radar remote sensing polarized imaging system, utilize the polarization information of target rear orientation light to survey and imaging, this system is mainly by laser transmitting system, the telescope receiving system, the polarization state detection system, and Data Receiving and disposal system four parts composition, the laser radar emission coefficient is mainly by colimated light system, polarization state produces system, collimating and beam expanding system and dioptric system are formed, by the semiconductor laser output wavelength is the laser of 808nm, pass through collimation lens, obtain parallel beam, enter polarization state and produce system, produce the polarized light of particular state, shine target by collimating and beam expanding system and dioptric system, the rear orientation light of target is received by Cassegrain telescope, after entering the polarization state detection system by narrow band pass filter, be divided into the mutually perpendicular two-beam of polarization state, receive by two CCD cameras respectively, send into Computer Processing by the double channel data acquisition card, obtain image simultaneously by degree of polarization and intensity coding, it is characterized in that: polarization state produces system and is made up of Glan laser polarization prism and 1/8 wave plate, Glan laser polarization prism can bear bigger luminous power, and having fabulous polarization characteristic, its extinction ratio can reach 10 ^-6More than, the polarization state detection system is made up of 1/8 wave plate and polarization splitting prism, and polarization splitting prism directly obtains the mutually perpendicular two-beam of polarization state, realizes, fast measurement disposable in real time to the target degree of polarization.

2. laser radar remote sensing polarized imaging system according to claim 1, it is characterized in that: collimating and beam expanding system mainly is made up of two plano-convex lenss and diaphragm, the symmetrical placement of plano-convex lens is suitable for expanding bundle, adds diaphragm between two lens and can eliminate the not round influence to second plano-convex lens of first plano-convex lens focal spot.

3. laser radar remote sensing polarized imaging system according to claim 1, it is characterized in that: dioptric system is by two parallel placements, form with the catoptron at optical axis inclination angle at 45, second catoptron is centered close to the back side of Cassegrain's receiving telescope secondary mirror, be positioned at same optical axis with telescope, help the rear orientation light of telescope receiving target.

4. laser radar remote sensing polarized imaging system according to claim 1, it is characterized in that: Data Receiving and disposal system adopt Cassegrain telescope, rear orientation light to target receives, behind narrow band pass filter, enter the polarization state detection system, the primary mirror of Cassegrain telescope and secondary mirror all are coated with aluminium film, reduce the influence of telescope receiving system to the target scattering light polarization as far as possible; Narrow band pass filter centre wavelength 808nm, the influence of filtering parasitic light.

5. laser radar remote sensing polarized imaging system according to claim 1, it is characterized in that: Data Receiving and disposal system adopt two CCD cameras and a double channel data acquisition card, the data that collect are sent into Computer Processing, two CCD cameras record the strength information of the mutually perpendicular two-beam of described polarization state simultaneously, through data processing, obtain the degree of polarization and the intensity coding image of target respectively.

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