CN1789933A - Infrared static type high luminous flux Fourier transform imaging spectrometer - Google Patents

Abstract

The invention discloses a static-type Fuliye transformation imaging spectrometer system of airborne station or satellite-borne infrared band, which is characterized by the following: splitting system light through image plane interferometer of triangle optical path; adapting plane-array detecting device and ground sweep to detect the imaging spectrum of ground object. The invention displays good reliability without moving part, which improves the light fineness and system signal-to-noise ratio.

Description

The infrared static type high luminous flux Fourier transform imaging spectrometer

Technical field:

The present invention relates to a kind of imaging spectral instrument system that is used for spaceborne or airborne useful load, be meant the silent oscillation Fourier transform imaging spectrometer system that works in infrared band especially.

Background technology:

The history in existing so far more than 40 year of appearance since first Fourier transform imaging spectrometer sixties in 20th century.At present, index glass sweep type Fourier transform spectrometer technology is very ripe, is widely used in space flight and airborne remote sensing field.Airborne aspect, U.S. jet propulsion laboratory (JPL) at first developed the fourier spectrometer of available Balloon Observation, done to improve after the relevant experiment.Arizona university has begun airborne fourier spectrometer Study on Technology subsequently, developed the small-sized fourier spectrometer that can be used for astronomical sight, this spectrometer is operated in the infrared band of 0.87-5.6um, has adopted IF-3 type interferometer commonly used in the NASA91.5cm flying telescope system.

Spaceborne aspect, I6-T type fourier spectrometer was carried the detection that is used on the USAF satellite atmospheric optical spec in 1962, IRIS-B type fourier spectrometer by the common development of Goddard space research center (GSFC) and TI company is written into space by the Nimbus3 satellite subsequently, it was worked in space for 14 week, obtained a large amount of useful spectroscopic datas, its modified IRIS-D is written into space by the Nimbus4 satellite subsequently.Succeeding in sending up of ATMOS subsequently, FIRAS, IMG, MIPAS proved absolutely that all index glass sweep type fourier spectrometer has become the strong tool of remote sensing.

To the eighties, in order to overcome the shortcoming that exists in the index glass sweep type fourier spectrometer, people begin the silent oscillation fourier spectrometer is studied.Lawrence Livermore National Laboratory has carried out infrared IFT systematic research, and has done relevant simulated experiment.Under the support of USAF, U.S. Florida technical institute, Kestrel company and Pillips laboratory have completed successfully the visible light ultraphotic spectrum Fourier transform imaging spectrometer (FTVHS) that is used for airborne remote sensing, and carried out flight experiment, the FTVHS core component has adopted the trigonometric expression interferometer, and area array CCD is as sensitive detection parts.Hawaii, America university has adopted total reflection Sagnac interferometer to succeed in developing spatial modulation imaging spectrometer SMIFTS (Spatially modulated imaging Fourier transformspectrometer) as core component, this spectrometer has two kinds of operator schemes can make spectrometer be operated in different visible near-infrared and shortwave spectral bands, the research of the optical design aspect of the Fourier transform imaging spectrometer that the international scientific company that uses just is being devoted to high light flux has proposed to utilize the new approaches of improved Mach_Zehnder interferometer as the high light flux silent oscillation Fourier transform imaging spectrometer of image plane interferometer.Successfully be finally inversed by the multispectral image of visible light wave range in the laboratory.

Summary of the invention:

The objective of the invention is to overcome above-mentioned problems of the prior art, a kind of silent oscillation Fourier transform imaging spectrometer system that works in the high light flux of infrared band, movement-less part own is provided.The movement-less part of this system own, can improve the reliability of system greatly, this system has made full use of the advantage of the hyperchannel transmission of fourier spectrometer itself simultaneously, under the situation of high spectral resolution, still can obtain the higher system signal to noise ratio (S/N ratio), solve the low difficult problem of energy under the situation of high spectral resolution.

Technical scheme of the present invention is as follows:

According to a kind of infrared static type high luminous flux Fourier transform imaging spectrometer of the present invention, can be used as airborne or spaceborne imaging load uses, itself has movement-less part, comprise the primary optical system that the light from ground object target passes through, incide on the image plane interferometer, after interfering, image on the detector, behind detector, become electric signal, through photoelectric signal processing circuit, be converted into digital signal through the data transmission interface circuit, by the spectrum picture that obtains meticulous beam split after data storage and the processing module processing, and also has the logic control timing sequence generating circuit, it produces the drive pulse signal of detector and to above-mentioned photoelectric signal processing circuit, data transmission interface circuit and data storage and processing module provide required time sequential pulse signal, characteristics are: described image plane interferometer is the image plane interferometer of trigonometric expression light path, it has removed slit, described detector itself is as field stop, adopted supplementary lens to incide on the beam splitting chip, help improving the luminous flux of the system of entering coming light to become directional light from the incident of object target; This image plane interferometer also adopts the cut mode beam splitting, and the interferogram contrast can not descended because of pixel dimension on the preposition optics focal plane, therefore, adopts big pixel dimension, realizes high light flux; Light beam is the collimation form in interferometer inside, and interferometer light path length is little to the influence of convergent mirror bore, like this, has just used the preposition optics and the collimating mirror of big relative aperture, in order to improve the image planes light intensity; Under the image planes interference mode, the energy of each pixel target will be limited in this pixel, and when being in the auto-correlation maximal value, whole energy of this pixel receiving target can obtain very big output signal-noise ratio; This detector adopts planar array detector spare, and it becomes the image relation with the target area, and whole energy of target are that detector cells is accepted with the form of autocorrelation function, have high optics output quantity, have improved the signal to noise ratio (S/N ratio) of system effectively; Planar array detector also relies on the push-broom type scanning mechanism to obtain the spatial information of two dimension and the spectral information of one dimension simultaneously, if detector array is classified M * N as, spectrum dimension unit number is N, and then each target element is by Continuous Observation N time, and spectral resolving power is limited by the detector cells number only;

Further, described detector is the detector that works in infrared band, and it is positioned on the focal plane of image plane interferometer;

Described logic control timing sequence generating circuit is mainly finished by the FPGA device, has hardware and realizes simply being easy to characteristics such as debugging;

Described data storage and processing module adopt monolithic DSP digital signal processing chip to constitute.

Belong to total inventive concept, the present invention also provides a kind of data processing method of infrared static type high luminous flux Fourier transform imaging, and its data processing step comprises:

(1) unit number of using is the planar array detector of N*M, and N obtains the data of size for the multispectral image of N*M as the scanning dimension, and the data bulk that collects is (2N-1) * M*N, and wherein useful data are N*N*M, and gibberish accounts for 1/2 of raw data greatly.Corresponding to zone in the space, push away inswept journey and collect a series of data, these data are formed the raw data cube; Be expressed as D[i] [j] [k] i=1,2 ... ..N, j=1,2 ..., M, k=1,2, Press corresponding relation: i=N-l+1, j=m, k=n+l-1, have such relation: Ap[n between autocorrelation function cube and the raw data cube] [m] [l]=D[i] [j] [k], i=N-l+1, j=m, k=n+l-1 n, m represent the space dimension, and l represents the spectrum dimension.According to above relation data are rearranged and just to have obtained autocorrelation function intensity data cube;

(2) adopting the Triangula function that autocorrelation function intensity data cube is cut toe handles;

(3) carry out phase correction and Fourier transform:

The interferogram data x (n) of earlier N being ordered is divided into even number set x ₁(n) and odd number group x ₂(n), again with x ₁(n) and x ₂(n) form a sequence of complex numbers y (n)=x ₁(n)+jx ₂(n) Fourier transform of ordering by N/2 obtains Y (k)=X ₁(k)+jX ₂(k), then, ask modular arithmetic, last, try to achieve spectral image data.Because the Fourier transform of x (n) is: $X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{nk}}=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}x\left(2n\right)W_N^{2\mathrm{nk}}+\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}x(2n+1)W_M^{(2n+1)k}$ That is: $X\left(k\right)=X_1\left(k\right)+W_N^k{X}_2\left(k\right)$ 0≤k≤N-1

So as long as the Fourier transform of order by N/2 calculates the Fourier transform that the Fourier transform of y (n) just can calculate x (n) by following formula, the method more than the employing makes carries out counting of Fourier transform and has reduced half, has improved efficient.

Summary is got up, the present invention has movement-less part, luminous flux is big, noise is high, good reliability can realize characteristics such as meticulous beam split, compares the signal to noise ratio (S/N ratio) that can effectively improve system when realizing meticulous beam split with traditional interference type super spectrum imager.

Description of drawings:

Fig. 1 is an image plane interferometer structural representation of the present invention.

Fig. 2 is the image plane interferometer index path among the present invention.

Fig. 3 is the data processing algorithm process flow diagram among the present invention.

Fig. 4 is that the data recombination among the present invention is handled synoptic diagram.

Fig. 5 is the circuit block diagram of known infrared static type high luminous amount Fourier transform imaging spectrometer.

Embodiment:

Providing better embodiment of the present invention according to Fig. 1-Fig. 4 and in conjunction with Fig. 5 below, and described in detail, enabling that architectural feature of the present invention and functional characteristics are described better, but is not to be used for limiting the scope of the invention.

Please join Fig. 1, Fig. 2 and Fig. 5, as shown in the figure, the light that ground object target sends is through inciding behind the primary optical system 1 on the image plane interferometer 2, and the collimating mirror 25 in image plane interferometer 2 becomes collimated light and incides on the beam splitting chip 23 in the image plane interferometer 2.As shown in Figure 2, described collimation incident ray is through becoming two bundles coherent light parallel to each other behind the beam splitting chip 23, the field angle of incident ray is θ, lateral separation between the two bundle coherent lights that are sheared out is l, and the optical path difference when then they are interfered on the image planes at the back focal plane place of convergent mirror is: Δ (θ)=lsin (θ) ≈ lx/f ₃, x is the lateral coordinates (plane of detector 3 is the xy face) of interference point in the formula, f ₃Focal length for convergent mirror.Beam splitter BS (beam splitting chip 23) should be a unlimited thin semi-permeable diaphragm, the position of mirror M 2 can be regarded as with respect to mirror M 1 about the mirror image position translation of BS one distance, d, the horizontal shear capacity that the light of 2 pairs of any visual fields of image plane interferometer this moment produces is all identical, and its value is: $l=\sqrt{2}d,$ The expression that can obtain optical path difference is: $\mathrm{\Δ}\left(y\right)=\sqrt{2}\mathrm{dx}/f_3$ Consequent phasic difference is: $\mathrm{\φ}\left(x\right)=\frac{2\mathrm{\π}}{\mathrm{\λ}}\mathrm{\Δ}\left(x\right)=2\sqrt{2}\mathrm{\πvdx}/f_3,$ If the spectral distribution of object point be B (v), the interference strength that then obtains in image planes is distributed as: $\mathrm{I\Δ}=2\underset{0}{\overset{+\∞}{\∫}}B\left(v\right)\cos \left(2\mathrm{\πv\Δ}\right)\mathrm{dv}$ Interferogram is carried out the spectral information that Fourier transform can obtain the object point target: $B\left(v\right)=\underset{-\∞}{\overset{+\∞}{\∫}}I\left(\mathrm{\Δ}\right)\exp (-j2\mathrm{\πv\Δ})\mathrm{d\Δ},$ After the optical system of image plane interferometer 2 and planar array detector 3 were fixing, the auto-correlation modulation also was stable.

Because the optical system of image plane interferometer 2 itself is symmetrical, autocorrelation function is symmetrically distributed in the both sides of zero optical path difference, therefore adopts bilateral sampling.

Can obtain under the situation of taking into account system function not according to the structure of interferometer 2, spectral resolution obtains by following formula: $\mathrm{\Δ\σ}=F_3/a\sqrt{2}\mathrm{dN},$ A is the unit interval of device, and d is the symmetric position of M1 and the spacing of M2, F ₃Be the focal length of rearmounted lens, N is the maximum number of device cell, and spectrally resolved ability is R=N/2.The zero point that can determine the spectrum coordinate according to the character of sample mode Fourier transform, the N/2 point was corresponding to σ=σ corresponding to σ=0 _MaxPoint, the N/2-N point is the image frequency of spectrum.

As shown in Figure 5, after interference light signal incides on the planar array detector 3, carry out being converted to electric signal after the opto-electronic conversion through photoelectric signal processing circuit 4, electric signal carries out every straight amplification through photosignal modulate circuit 41, filtering, after recovering, direct current is sent to AD and buffer circuit 42 digital quantizations are the data of 14bit, through ping-pong buffer after data interface circuit 5 is sent to data storage and data processing module 6, data storage and data processing module 6 are made up of a slice TMS320C32-60DSP chip and peripheral circuit thereof, dsp chip is handled the data that receive according to the data processing algorithm described in the present invention, handles back acquisition multiband spectrum view data and spreads out of through data transmission interface.The driving pulse of detector 3, AD sampling pulse, buffer circuit 42 control signals and DSP synchronous communication control signal produce by logic control sequence generation module 7, and this module 7 is made up of a slice 20MHz clock module and a slice CycloneFPGA EP1C3T208C and peripheral interlock circuit thereof.

Consult the data processing algorithm that data storage among Fig. 3 and Fig. 4 and Fig. 5 the present invention and data processing module 6 moved and comprise three aspects, 1) data recombination, 2) cut toe and handle 3) phase correction and Fourier transform.Specific implementation method as shown in Figure 3, the process step of data processor 100:

Step 1000, start-up routine carry out firstization, afterwards, execution in step 1001 is carried out data recombination or interference image data, by the data recombination of carrying out shown in Figure 4, specific practice is: corresponding to zone in the space, push away inswept journey and collect a series of data, these data are formed the raw data cube.Be expressed as D[i] [j] [k] i=1,2 ... ..N, j=1,2 ..., M, k=1,2 ...Press corresponding relation: i=N-l+1, j=m, there is such relation in k=n+l-1 between autocorrelation function cube and the raw data cube:

Ap[n] [m] [l]=D[i] [j] [k], i=N-l+1, j=m, k=n+l-1 n, m represent the space dimension, and l represents the spectrum dimension.According to above relation data are rearranged and just to have obtained autocorrelation function intensity data cube, afterwards, execution in step 1002 is cut toe to the interference image data and is handled,

In order to reduce the side-lobe energy leakage that window function produces, adopt triangle (Triangula) function that the image autocorrelation function intensity data cube that obtains is cut toe and handle, the Triangula function is defined as T (x)=D (x) [1-|x|/L], wherein $D\left(x\right)=\left\{\begin{array}{cc}1& \left|x\right|\≤L\\ 0& \left|x\right|>L\end{array}\right..$

Then carry out phase correction and Fourier transform, because asymmetric of the interferogram data of bilateral sampling can make the phase place of the spectroscopic data that obtains change, amplitude spectrum does not change, and adopts the method for directly asking mould to obtain correction to phase place in Fourier transform, promptly

To interferogram carry out Fourier transform and

2. ask the spectrum amplitude,

Because the Fourier transform of the interferogram of bilateral sampling remains the Fourier transform of plural number, imaginary data still must replace with zero.Therefore, the operation efficiency of the phase correction of bilateral sampling still can improve, and execution in step 1003,1004 successively, and 1005,1006 and 1007:

The interferogram data x (n) of a) N being ordered is divided into even number set x ₁(n) and odd number group x ₂(n),

B) with x ₁(n) and x ₂(n) form a sequence of complex numbers y (n)=x ₁(n)+jx ₂(n),

C) Fourier transform of ordering by N/2 obtains Y (k)=X ₁(k)+jX ₂(k),

D) ask mould and

E) obtain spectral image data.

Because the Fourier transform of x (n) is:

$X\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)W_N^{\mathrm{nk}}=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}x\left(2n\right)W_N^{2\mathrm{nk}}+\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}x(2n+1)W_M^{(2n+1)k}$

That is: $X\left(k\right)=X_1\left(k\right)+W_N^k{X}_2\left(k\right)$ 0≤k≤N-1

So as long as the Fourier transform of order by N/2 calculates the Fourier transform that the Fourier transform of y (n) just can calculate x (n) by following formula, the method more than the employing makes carries out counting of Fourier transform and has reduced half, has improved efficient.

The estimation of operand:

Former algorithm: multiplication number of times: 2Nlog ₂N+6N addition number of times: 2Nlog ₂N+2N

Total operand: 4Nlog ₂N+8N

Improve algorithm: multiplication number of times: Nlog ₂N+10N addition number of times: Nlog ₂N+12N

Total operand: Nlog ₂N+22N

Measured result shows that the operation efficiency that improves algorithm is than former algorithm high about 40%.It is simple to ask modeling method software to realize, can save a large amount of time and storer when hardware is realized.

Claims (5)

1, a kind of infrared static type high luminous flux Fourier transform imaging spectrometer, be used for airborne or spaceborne imaging load, itself has movement-less part, comprise the primary optical system (1) that the light from ground object target passes through, incide on the image plane interferometer (2), after interfering, image on the detector (3), behind detector (3), become electric signal, through photoelectric signal processing circuit (4), be converted into digital signal through data transmission interface circuit (5), by the spectrum picture that obtains meticulous beam split after data storage and processing module (6) processing, and the driving arteries and veins signal that produces detector (3); Photoelectric signal processing circuit (4), data transmission interface circuit (5) and data storage and processing module (6) are provided the logic control timing sequence generating circuit (7) of required time sequential pulse signal, be characterised in that, a, described image plane interferometer (2) are the image plane interferometer of trigonometric expression light path, slit and cylindrical mirror have been removed,, and by supplementary lens (25) light that comes from the incident of object target is become directional light and incide on the beam splitting chip (23) as field stop by detector (3) itself; B, adopt the shear constitution beam splitting, and use the preposition optics and the collimating mirror of big relative aperture; C, sensitive detection parts (3) adopt planar array detector and constitute the image relation with the target area, and whole energy of target are that detector cells is accepted with the form of autocorrelation function; D, this planar array detector rely on to push away to sweep and obtain the two-dimentional spatial information and the spectral information of one dimension simultaneously.

2. infrared static type high luminous flux Fourier transform imaging spectrometer according to claim 1 is characterized in that, described detector (3) is positioned on the focal plane of image plane interferometer (2) for working in the detector of infrared band.

3. infrared static type high luminous flux Fourier transform imaging spectrometer according to claim 1 is characterized in that, described logic control timing sequence generating circuit (7) mainly is made of the FPGA device.

4. infrared static type high luminous flux Fourier transform imaging spectrometer according to claim 1 is characterized in that, described data storage and processing module (6) adopt monolithic DSP digital signal processing chip to constitute.

5, a kind of data processing algorithm of infrared static type high luminous flux Fourier transform imaging comprises step:

(1) use the planar array detector of unit number as N*M, N obtains the data of size for the multispectral image of N*M as the scanning dimension, the data bulk of being gathered is (2N-1) * M*N, and wherein useful data are N*N*M, and gibberish accounts for 1/2 of raw data greatly, corresponding to zone in the space, push away inswept journey and collect a series of data, these data are formed the raw data cube, with D[i] [j] [k] expression, i=1,2 ... ..N, j=1,2 ... M, k=1,2 ... press corresponding relation: i=N-l+1, j=m, k=n+l-1, the pass between autocorrelation function cube and the raw data cube is: Ap[n] [m] [l]=D[i] [j] [k], i=N-l+1, j=m, k=n+l-1 n, m represent the space dimension, l represents the spectrum dimension, according to above relation data is rearranged and has obtained autocorrelation function intensity data cube;

(2) adopting the Triangula function that autocorrelation function intensity data cube is cut toe handles;

(3) carry out phase correction and Fourier transform:

The interferogram data x (n) of earlier N being ordered is divided into even number set x ₁(n) and odd number group x ₂(n), again with x ₁(n) and x ₂(n) form a sequence of complex numbers y (n)=x ₁(n)+jx ₂(n), the Fourier transform of ordering by N/2 then obtains Y (k)=X ₁(k)+jX ₂(k), then, ask modular arithmetic, last, obtain spectral image data.

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