CN100451677C - High spectrum full polarization imaging remote sensing system - Google Patents

Abstract

The remote sensing system is composed of imaging lens, linear phase delay LCVR, acousto-optic tunable filter plate AOTF, focal plane array, electronic controller, image collection card, and computer. Being kernel part of whole remote sensing system, the computer is in use for controlling frequency of control signal applied to AOTF so as to change wavelength of light beam passing through AOTF, and obtain image of object in the wavelength. Also, the computer is in use for controlling value of voltage applied to LCVR so as to change linear phase delay LCVR. Moreover, the computer collects image information of object to be measured, and carries out process for the collected image. In wider wavelength range, the invention possesses capability of detecting high spectrum and polarization characteristics corresponding to scale of object image cell.

Description

High spectrum full polarization imaging remote sensing system

Technical field

The present invention relates to a kind of high spectrum full polarization imaging remote sensing system spaceborne, airborne and ground remote sensing of the earth and survey of deep space that is used for.

Background technology

High light spectrum image-forming is owing to have closely, continuously, can write down the feature of the spectrum of measured object and spatial information simultaneously and is widely used.But along with the development of high light spectrum image-forming technology and people further requirement to remote sensing technology, the high light spectrum image-forming technology has run into great challenge, at first be: (1) is owing to be subjected to the restriction of factors such as spectral resolution, atural object structure, noise, atmospheric environment, the phenomenon of " the different spectrum of jljl " and " with the spectrum foreign matter " often appears in high-spectral data, make it be difficult to accurately chemical constitution, composition and the quantity of the various materials of identification, even misjudgment phenomenon occurs; (2) the high light spectrum image-forming technology is powerless to problems such as cloud and aerocolloidal grain diameter measurements; (3) under the dark target in ground, dark background or the wide-angle low-light (level) situation, the picture contrast that high-spectrum remote-sensing obtains is too poor, is difficult to identify target.The high light spectrum image-forming detection system is surveyed the electromagnetic vector ripple of clutter reflections with the mode of scalar, a detected intensity information, thus cause a large amount of useful informations to be lost.

And by electromagnetic character as can be known, any target in earth surface and the atmosphere all can produce the feature polarization by their self properties and the decision of optics philosophy in the process of reflection, scattering and transmission and emission electromagnetic radiation.The different objects or the different conditions of same object (roughness for example. the physicochemical property of voidage, water cut, constituent material etc.) produce different polarizations, many objects all have own unique polarization characteristic, are containing the various information of object in the polarization characteristic.Compare with unpolarized measurement, polarimetry can obtain the clarification of objective information that are easy to distinguish more, can provide new information for the remote sensing target, and particularly low to reflection strength contrast surface utilizes polarization data also can discern effectively.Therefore polarization characteristic just provides new information source for remote sensing technology.

Therefore, spectral information and polarization information combination are just become the new research boom of present remote sensing technology, be subjected to the close attention of each big power.400 multiple images that U.S. NASA uses STS-51A to photograph are analyzed the polarization image of targets such as cloud, atmosphere, ocean, and analysis result shows that polarization state all is extremely valuable information for the different terrain object of identification, atmosphere, cloud layer etc.The spaceborne polarization that has dropped at present actual use is in respect of the earth polarization by reflection side amount instrument (POLDER) of France's development and the earth observation scanning polarimeter (EOSP) of U.S.'s development, although these two load are the partial polarization characteristic of Measuring Object in limited several wave bands just, its data of passing back show that polarization remote sensing has huge potential using value.The Air Force Research Laboratory is developed variable phase delay, infrared Fourier conversion spectrum polarimeter (VRFTSP).The AUS laboratory utilizes the spectrum polarizing imager to carry out the measurement of the polarization spectrum information of meadow, road, automobile, utilizes the polarization difference image to discern artificial target.Japan Airlines survey the airborne LCTF high light spectrum image-forming polarimeter that center JAXA utilizes its development, according to the detection of spectral information and polarization angle information monitoring river, lake water pollution etc.The variation that studies show that rock ore deposit polarized radiation of Britain University of Leicester is relevant with its tenor and suffered hydrocarbon pollution level.The polarization spectrum data that people such as the D.F.Huber of Carnegie Mellon Univ USA utilize the spectrum polarizing imager to record are applied to military system Target Recognition and machine vision traffic system.

Find out from present domestic and international research, polarization remote sensing has demonstrated powerful detectivity, but the spectral band of present polarization spectrum detection system is all narrower, spectral resolution is very low, the category that all belongs to multispectral polarization technology, high spectrum full polarization detection system are also located hand generalities conceptual phase.On the mechanism understanding of polarization remote sensing, also just draw some as the conclusion of degree of polarization with the simple qualitative or quantitative property of variations such as target property, search angle, place, sun altitude.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of high spectrum full polarization imaging remote sensing system is provided, this system has in visible and wavelength coverage that near infrared is big, the high spectrum of while detection of a target pixel yardstick correspondence and the ability of polarization characteristic.

Technical solution of the present invention: high spectrum full polarization imaging remote sensing system, its characteristics are to comprise following part:

Imaging lens is positioned at whole remote sensing system foremost, is used for that measured target is imaged in focal plane array and lists;

Linear phase delayer LCVR is positioned at the back of imaging lens, and linear phase delayer and acousto-optic tunable filter plate constitute the polarimetry assembly of the function with 4 full stokes components of detectable target;

Acousto-optic tunable filter plate AOTF is positioned at the back of linear phase delayer, is used for the spectrum beam split function of remote sensing system, links to each other with computer by serial by control circuit;

Control circuit is used to change the frequency values of the signal that is added in acousto-optic tunable filter plate AOTF, thereby realizes the spectrum beam split function of AOTF, and one end and acousto-optic tunable filter plate AOTF join, and the other end links to each other with computer by serial or USB interface;

Focal plane arrays (FPA) is electrooptical device, is used for the light radiation intensity of measured target is converted to electric signal, and the electric signal of its output is sent into computing machine via Computer I/O card;

Electronic controller is used to control the magnitude of voltage that is added in linear phase delayer LCVR, thereby changes the phase-delay value of LCVR, and one end and linear phase delayer LCVR join, and the other end links to each other with computer by serial or USB interface;

Image pick-up card is used for the signal after the focal plane arrays (FPA) opto-electronic conversion is sent into computing machine, and it is inserted in the PCI slot of calculating;

Computing machine is the core component of whole remote sensing system, is used to control be added in the control signal frequency that AOTF goes up control signal, thereby changes the wavelength by the light of AOTF, obtains the image of target at this wavelength place, has realized the imaging spectral detecting function of system; Control simultaneously is added in the magnitude of voltage of LCVR, thereby changes the phase-delay value of LCVR; Gather the measured target picture signal, and institute's images acquired is handled, realized polarimetry.

Principle of work of the present invention is: the spectral measurement function of system uses acousto-optic tunable filter as beam splitter, be added in the frequency that AOTF goes up control signal by computer control, thereby change wavelength by the light of AOTF, obtain the image of target at this wavelength place, order changes the control signal frequency, the target that sequence is gathered the different wave length place obtains data cube, promptly gets the spectral information of target, has realized the imaging spectral detecting function of system.The polarimetry assembly is by two voltage-controlled variable liquid crystal phase delay device LCVR, with and subsequent the linear polarization function of acousto-optic tunable filter constitute, the direction of adjusting acousto-optic tunable filter only allows horizontal polarization light pass through, length of delay by the computer control phase delay device, 4 groups of different phase-delay value images acquired are set obtain 4 image intensity value, obtain a system of linear equations, utilize inverse matrix to obtain 4 component I of full Stokes Stokes vector, Q, the value of U and V.

The present invention compares with existing Detection Techniques has following advantage:

(1) because phase delay device LCVR and AOTF are combined effectively, the therefore high spectrum full polarization target data of detectable pixel yardstick correspondence can be from the polarization information evaluating objects characteristic of spectrum dimension.

(2) owing to use acousto-optic tunable filter plate AOTF, wave band can be tuning at random, and wavelength coverage can be selected arbitrarily, reduces data redundancy, improve remotely-sensed data transmission time and processing time greatly, solve the contradictory problems that serious data blast of present remote sensing field and information are hungered and thirst.

(3) LCVR and AOTF do not have machinery to move by Electronic Control, have therefore improved system's detection accuracy, detection time and reliability greatly.

Description of drawings

Fig. 1 is that system of the present invention forms theory diagram;

Fig. 2 is the work synoptic diagram of acousto-optic tunable filter plate AOTF of the present invention;

Fig. 3 is that wave vector of the present invention is at TeO ₂Interaction principle figure among the AOTF;

Fig. 4 is that AOTF wavelength of the present invention is selected schematic diagram;

Fig. 5 is the contrast figure of AOTF inner structure of the present invention and light vector and ultrasonic vector;

Fig. 6 is a linear phase delayer LCVR structural drawing of the present invention;

Fig. 7 is a computer control process flow diagram of the present invention.

Embodiment

As shown in Figure 1, the present invention includes imaging lens, LCVR, AOTF, focal plane arrays (FPA), electronic controller, image pick-up card and computing machine, the picture signal of focal plane arrays (FPA) output is sent into computing machine through image pick-up card, the electronic controller of LCVR links to each other with computer by serial or USB interface, the control circuit of AOTF also links to each other with computer by serial, computer control is added in the signal frequency that AOTF goes up control circuit, thereby change wavelength by the light of AOTF, obtain the image of target at this wavelength place, order changes the control signal frequency, the target that sequence is gathered the different wave length place obtains data cube, promptly gets the spectral information of target, realizes.The polarimetry assembly is by two voltage-controlled variable liquid crystal phase delay device LCVR, with and subsequent the linear polarization function of acousto-optic tunable filter constitute, the plane of polarization direction of adjusting acousto-optic tunable filter only allows horizontal polarization light pass through.Length of delay by the computer control phase delay device, 4 groups of different phase-delay value images acquired are set obtain 4 image intensity value, thereby obtain a system of linear equations, utilize inverse matrix to obtain 4 component I of Stokes vector, Q, the value of U and V can realize high spectrum full polarization imaging remote sensing function.

As shown in Figure 2, the principle of work of acousto-optic tunable filter plate AOTF is that light beam and ultrasound wave are interacted in transparent medium.AOTF forms by piezoelectric transducer with along the double refraction single-shaft crystal of suitably direction cutting, comes the drive pressure electric transducer to make to conduct in the crystal ultrasound wave, ultrasound wave to make the refractive index generating period variation of crystals by control signal.This ultrasound wave is formed the ultrasonic phase grating of row, has only the light wave of specific wavelength can satisfy specific momentum matching condition and diffraction takes place in the feasible light wave that incides in the birefringece crystal.Can change the wavelength coverage of passing through rapidly by the frequency AOTF that changes control signal, at extremely short time interscan overall optical spectral limit.

This acousto-optic interaction not only just has the effect of the light of selecting single wavelength, and it also selects the diffraction polarized state of light simultaneously.The AOTF crystal medium makes the natural light of incident be divided into two bundles (o light and e light), their polarization direction quadrature, and velocity of propagation is different with direction.Be illustrated in figure 2 as a typical A OTF fundamental diagram, when a branch of natural light with incident angle θ _iBe directly incident in the crystal of AOTF, diffraction just may take place in the light that this light beam medium wavelength satisfies formula (1) condition.

${\stackrel{r}{k}}_d={\stackrel{r}{k}}_a\±{\stackrel{r}{k}}_i---\left(1\right)$

Wherein

For being respectively diffraction light and incident light vector;

Be ultrasonic vector.

$\left|{\stackrel{r}{k}}_i\right|=\frac{2\mathrm{\π}{n}_i}{\mathrm{\λ}},$ $\left|{\stackrel{r}{k}}_d\right|=\frac{2\mathrm{\π}{n}_d}{\mathrm{\λ}},$ $\left|{\stackrel{r}{k}}_a\right|=\frac{2\mathrm{\πf}}{V}---\left(2\right)$

λ is an optical wavelength in the formula; F is a ultrasonic frequency; V is that sound wave is in intracrystalline velocity of propagation; n _i, n _dBe respectively the refractive index of incident light and diffraction light, they satisfy following relation:

$\frac{1}{n_i^2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20051008692600121.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&theta;}}_i}{{\mathrm{\&eta;}}_o^2}+\frac{{\sin }^2{\mathrm{\&theta;}}_i}{n_e^2}---\left(3\right)$

Fig. 3 is TeO ₂The wavelength vector ellipsoid of the birefringece crystal of AOTF, the incident light vector

At ultrasonic vector

Effect under, become the orthogonal o optical diffraction of polarization state light k _d ^oWith e optical diffraction light k _d ^eBlock e optical diffraction light k _d ^eThe small part light of diffraction does not take place, and then emergent light is and has the very linearly polarized light of narrow bandwidth.

The AOTF wavelength is selected principle as shown in Figure 4, and the light that contains different wave length is injected AOTF, when the ultrasound wave vector is

The time, the diffraction light vector that satisfies the momentum matching condition has only Therefore just having only wavelength is λ ₁Light pass AOTF, the rest may be inferred, when the ultrasound wave vector is

The time, the diffraction light vector that satisfies the momentum matching condition has only

Therefore also just having only wavelength is λ _nLight pass AOTF.Like this, AOTF has just played the effect of beam split filtering.

As shown in Figure 5, if light vector spirogram and ultrasonic polar plot and the non-AOTF of acoustic optic interaction in the same way structural drawing are put together, and corresponding equal angular, can intuitively obtain the principle of acousto-optic interaction, and the angle corresponding relation between each vector wherein.

In the AOTF structural drawing, adjusted the angle of exit plane especially, can make the light wave generation diffraction of different wave length like this after, though the angle of diffraction difference, but the outgoing direction of light is identical, thereby has effectively reduced longitudinal aberration between the pairing image of different wave length.

Computer control is added in the frequency that AOTF goes up the control signal of control circuit, thereby changes the wavelength by the light of AOTF, obtains the image of target at this wavelength place, has realized the imaging spectral detecting function of system.

As shown in Figure 6, the linear filtering face LP that had of variable liquid crystal phase delay device LCVR of the present invention and AOTF itself constitutes the polarimetry function.The both sides up and down of LCVR are two glass plates that borosilicate or fused silica material are made, glass plate is separated from the escapement at two ends separately at a distance of several microns, middle filling liquid crystal LC, liquid crystal is through the flour milling polyimide PI of interior surfaces of glass alignment, make liquid crystal parallel with glass plate, when light passes through LCVR, be divided into o light and e light, if making alive not, because the incorgruous characteristic of liquid crystal, o light and e light phase difference by LCVR differ maximum, differ λ/2, if apply certain voltage on glass plate, then certain inclination takes place in liquid crystal, the phase differential that o light and the e light by LCVR differs 0～λ/2.The electrode of LCVR is transparent electroconductive indium tin oxide electrode ITO.The stationary shaft direction of LCVR becomes an angle in 0 degree～180 degree scopes with the plane of polarization LP direction of AOTF.The plane of polarization direction of adjusting AOTF only allows horizontal polarization light pass through.The electronic control device of LCVR is the accurate stabilized voltage supply of high precision, and is identical with general voltage source principle.

Characterize transmitted light with the Muller matrix operation by the plane of polarization LP of AOTF.The available Stokes vector S of light of coming out from LP ₀=(LP) (VR) s _iRepresent, wherein S _i=(I, Q, U, V) represent (unknown) input Stokes vector by conventional symbols, that is I is the light intensity of polarized light not, Q is that horizontal linear polarization subtracts perpendicular linear polarization, U is that 45 ° of linear polarizations subtract 135 ° of linear polarizations, and V is the difference that right-hand circular polarization subtracts Left-hand circular polarization.

In order to find 4 components of input Stokes vector, 4 groups of different phase-delay value images acquired are set obtain 4 I ₀Value obtains a system of linear equations, utilizes S _iInverting S _i=(B) ^-1I ₀Obtain four 4 components of incident light, wherein (B) row is corresponding to variable I in top each equation of 4 pairs of length of delays (δ, Δ), Q, the coefficient of U and V.

AOTF not only has wavelength selection function, also has polarization characteristic, and the light of only fair single polarization direction passes through, and therefore can only detect the reflected light on the target single direction.After the AOTF front adds LCVR, LCVR can change the target polarization direction, voltage by control LCVR changes the target reflection polarization state of light, just may detect the reflective light intensity on the target different polarization direction, therefore, linear phase delayer LCVR can not only realize polarimetry, can also remedy the defective that AOTF can only survey the single direction polarized light.

The Control Software process flow diagram of computing machine of the present invention as shown in Figure 7, the phase-delay value that LCVR at first is set all is 0 °, change the RF frequency of AOTF, make it begin progressively to scan up to finishing wavelength from initial wavelength location, obtain the image of target, thereby realized the imaging spectral detecting function of system at this wavelength place; Change the phase-delay value of LCVR then successively, the RF frequency that changes AOTF makes it in whole wavelength coverage interscan images acquired, obtains in the scape image arbitrary pixel at 4 I of each wavelength ₀Value is separated the high spectrum Stokes of the target polarized component value that system of linear equations just can get 4 pixel yardstick correspondences, thereby is finished the high spectrum full polarization property detection of a scape image.

Claims (3)

1, high spectrum full polarization imaging remote sensing system is characterized in that comprising following part:

Imaging lens is positioned at whole remote sensing system foremost, is used for that measured target is imaged in focal plane array and lists;

Linear phase delayer LCVR is positioned at the back of imaging lens, and linear phase delayer and acousto-optic tunable filter plate constitute the polarimetry assembly of the function with 4 full stokes components of detectable target;

Acousto-optic tunable filter plate AOTF is positioned at the back of linear phase delayer, is used to realize spectrum beam split function, links to each other with computer by serial by control circuit;

Control circuit is used to change the frequency values of the signal that is added in acousto-optic tunable filter plate AOTF, thereby realizes the spectrum beam split function of AOTF, and one end and acousto-optic tunable filter plate AOTF join, and the other end links to each other with computer by serial or USB interface;

Focal plane arrays (FPA) is electrooptical device, is used for the light radiation intensity of measured target is converted to electric signal, and the electric signal of its output is sent into computing machine via Computer I/O card;

Electronic controller is used to control the magnitude of voltage that is added in linear phase delayer LCVR, thereby changes the phase-delay value of LCVR, and one end and linear phase delayer LCVR join, and the other end links to each other with computer by serial or USB interface;

Image pick-up card is used for the signal after the focal plane arrays (FPA) opto-electronic conversion is sent into computing machine, and it is inserted in the PCI slot of calculating;

Computing machine is the core component of whole remote sensing system, is used to control be added in the control signal frequency that AOTF goes up control signal, thereby changes the wavelength by the light of AOTF, obtains the image of target at this wavelength place, has realized the imaging spectral detecting function of system; Control simultaneously is added in the magnitude of voltage of LCVR, thereby changes the phase-delay value of LCVR; Gather the measured target picture signal, and institute's images acquired is handled, realized polarimetry.

2, high spectrum full polarization imaging remote sensing system according to claim 1, it is characterized in that: described linear phase delayer is by two glass plates making for borosilicate or fused silica material up and down, filling liquid crystal LC in the middle of two glass plates, liquid crystal LC makes liquid crystal parallel with glass plate through the flour milling polyimide PI of interior surfaces of glass alignment.

3, high spectrum full polarization imaging remote sensing system according to claim 1 is characterized in that: described linear phase delayer LCVR stationary shaft direction becomes an angle in 0 degree～180 degree scopes with the plane of polarization LP direction of AOTF.

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