CN102944308A - Attitude error correcting method of time-space joint modulation interference imaging spectrometer - Google Patents

Abstract

The invention discloses an attitude error correcting method of a time-space joint modulation interference imaging spectrometer, comprising the following steps: 1. obtaining images containing interested target points through the time-space joint modulation interference imaging spectrometer; 2. resolving elements of exterior orientation according to POS measurement data; 3. building the function relationship between an ideal image space coordinate system and a distorted image space coordinate system; 4. obtaining a position Q' of an interested target point Q in a distorted image plane; 5. obtaining the interference strength of interested target points in distorted images corresponding to one optical path difference; 6. judging if the collection of the distorted images is finished; 7. obtaining complete interference data of the interested target points corresponding to different optical path differences; and 8. obtaining an interested target point spectrum. According to the attitude error correcting method of the time-space joint modulation interference imaging spectrometer disclosed by the invention, the POS data is conducted in the correction link, so that the interference strength data of the interested target points is directly extracted from the distorted image sequence; and then the non-uniform Fourier transform is performed to recover the spectrum, so that the spectrum recovery precision of the targets can be improved.

Description

A kind of space-time unite interferometric modulator imaging spectrometer attitude error rectification method

Technical field

The present invention relates to signal processing technology, belong to the remote sensing image data processing technology field, be specifically related to a kind of space-time unite interferometric modulator imaging spectrometer attitude error rectification method.

Background technology

Space-time unite interferometric modulator imaging spectrometer is as a kind of novel imaging spectrometer, overcome the deficiency of time-modulation type inteference imaging spectrometer poor stability and spatial modulation type inteference imaging spectrometer small throughput, had that spectral resolution is high, signal to noise ratio (S/N ratio) is high, an advantage such as high flux and high stability.The utilization of space-time unite interferometric modulator imaging spectrometer pushes away the mode of sweeping and scans object scene, difference constantly target imaging at the detector diverse location, thereby obtain the complete point interference of impact point, restore the spectrum that produces this target by Fourier transform by point interference again.Because space-time unite interferometric modulator imaging spectrometer obtains the curve of spectrum of culture point must be through the inswept journey that pushes away of full visual field once, in a single day the attitude of carrier changes in pushing away inswept journey, as sidewinder, pitching, driftage etc., will cause the interferogram distortion, restore the real property that the spectrum that just can't reflect the scenery target.In order to realize high-precision spectrum recovering, need the data of obtaining are proofreaied and correct.

The purpose of Image correction in remote sensing is the geometry deformation that changes original image, produces the new images that a width of cloth meets certain map projection or avatars requirement.It is that conversion and grey scale pixel value resample that basic link has pixel coordinate.Pixel coordinate is that conversion can realize by utilizing registration result between ground control point data, attitude parameter, image etc. to set up suitable distorted pattern.The method that grey scale pixel value resamples mainly contains cube convolution interpolation, bilinear interpolation, arest neighbors interpolation.

POS(Position and Orientation System) is position and a range tie that Geographic Reference can directly be provided for photogrammetric measurement.Along with improving constantly of POS data precision, can utilize remote-sensing flatform attitude measurement data to realize active correction.Can obtain the elements of exterior orientation of boat sheet according to the POS measurement data, can set up accordingly the funtcional relationship between fault image space coordinates and ideal image space coordinates, and then realize proofreading and correct.

In prior art, the bearing calibration of spectrum picture is mainly comprised: based on the relevant joint image correcting algorithm relevant with the normalizing eliminate indigestion of phase place.Rotation translation feature according to Fourier transform, by the phase place related function between computed image, utilize FFT to realize the high-precision correction of image sequence rotation distortion, employing realizes the correction of image translation distortion based on the relevant method of normalizing eliminate indigestion, carry out at last point interference nonuniform sampling, Fourier transform recovery spectrum; Or utilize POS data obtain the navigating elements of exterior orientation of sheet, and then the elements of exterior orientation that utilizes gained is set up certain corresponding relation between fault image space and ideal image space (correction space), recycle this corresponding relation and the whole elements in the distortion space are transformed in the correcting image go, realize geometry correction.

Therefore have following shortcoming in the existing spectrum picture alignment technique: be applicable to proofread and correct the attitude of satellite and change the distortion that the imaging spectrometer image is caused, it is inaccurate and can't accurately restore the atural object spectrum information that ground object target point extraction can appear in the correction that changes comparatively violent airborne imaging spectrum instrument image for attitude; Perhaps be applicable to the correction of the color dispersion-type hyperspectral imager PHI image of instantaneous imaging, and space-time unite interferometric modulator imaging spectrometer need to utilize and pushes away the mode of sweeping and obtain the atural object spectrum information, the geological information of the atural object that its image comprises can be proofreaied and correct, interference information is but proofreaied and correct, thereby can't accurately restore the spectrum information of atural object.

Summary of the invention

To the objective of the invention is to improve ground object target spectrum recovering precision in order addressing the above problem, to have proposed a kind of space-time unite interferometric modulator imaging spectrometer attitude error rectification method.

A kind of attitude error rectification method of space-time unite interferometric modulator imaging spectrometer comprises following step:

Step 1: obtain the image that comprises interesting target point, i.e. fault image by space-time unite interferometric modulator imaging spectrometer;

Step 2: resolve elements of exterior orientation according to the POS measurement data;

Step 3: set up the funtcional relationship between desirable image space coordinate system and distorted image space coordinates;

Step 4: obtain interesting target point Q(x _Q, y _Q) position Q ' (x in the distorted image plane _{Q '}', y _{Q '}');

Step 5: obtain the interference strength that interesting target in the fault image is put corresponding a certain optical path difference;

Step 6: judge whether to finish the fault image collection;

Step 7: obtain the complete interference strength data that interesting target is put corresponding different optical path differences;

Step 8: the complete interference strength data communication device of interesting target point is crossed Nonuniform fast Fourier transform restore the spectrum that obtains this interesting target point.

The invention has the advantages that:

(1) the present invention introduces correction link with the POS data, directly extracts the interference strength data of interesting target point from the fault image sequence, carries out Nonuniform fast Fourier transform again and restores spectrum, can improve the spectrum recovering precision of target.

(2) method proposed by the invention all is suitable for for spaceborne, on-board data, effectively overcome single image has been proofreaied and correct the difficult point of proofreading and correct simultaneously geological information and interference information to satisfy, be applicable to the correction of space-time unite interferometric modulator imaging spectrometer attitude error.

Description of drawings

Fig. 1 is coordinate system conversion schematic diagram among the present invention;

Fig. 2 is method flow diagram of the present invention.

Embodiment

The present invention is described in further detail below in conjunction with specific embodiment.

The present invention is a kind of attitude error rectification method of space-time unite interferometric modulator imaging spectrometer, and flow process comprises following step as shown in Figure 2:

Step 1: obtain the image that comprises interesting target point by space-time unite interferometric modulator imaging spectrometer, i.e. the fault image sequence;

Space-time unite interferometric modulator imaging spectrometer is to add interferometer to realize before common photographic system, so, the image that the space-time unite interferometric modulator imaging spectrometer that the present invention adopts obtains no longer is the direct image of target, but the interference image of target, image changes more sharp-pointed along the rail direction.

Determine to gather the quantity A of image according to Shannon's sampling theorem, A represents to gather the quantity of image.For the interesting target point, the corresponding specific optical path difference of each width of cloth image, an A width of cloth image corresponding A different optical path difference;

Restore the curve of spectrum of impact point, need to obtain the abundant interference data of the corresponding different optical path differences of impact point.Required sampling number can be determined according to Shannon's sampling theorem.Thereby need to be from sequence image abundant width of cloth image extracts the gray-scale value of interesting target point, obtains a series of interference strength data that interesting target is put corresponding different optical path differences, thus the complete interference strength data of acquisition target.

Step 2: resolve elements of exterior orientation according to the POS measurement data.

For a width of cloth fault image, obtain elements of exterior orientation, be specially:

The boat sheet foreign side parallactic angle list of elements is levied the photography light beam at the photography dimensional orientation of moment, in order to X _sAxle is the corner system of main shaft when representing, For lateral tilt, ω are that fore and aft tip, κ are the photograph swing angle,

The angle of pitch Φ that ω, κ and POS record, the transformational relation between angle of roll Ω, the crab angle K are:

In the formula: Be expressed as between figure coordinate system (m) and the geocentric coordinate system (E) rotation matrix,

Rotation matrix between expression geocentric coordinate system (E) and the local geographic coordinate system (g),

Represent between local geographic coordinate system (g) and the IMU coordinate system (b) rotation matrix,

Rotation matrix between expression IMU coordinate system (b) and the imaging spectrometer coordinate system (c),

Rotation matrix between expression imaging spectrometer coordinate system (c) and the image space coordinate system (i),

Can determine according to the parameter that POS provides.

Be expressed as figure coordinate system (m) to the rotation matrix between the image space coordinate system coordinate system (i), it is

The function of ω, κ; Represent local geographic coordinate system (g) to the rotation matrix between the IMU coordinate system (b), it is the function of Φ, Ω, K.

Step 3: set up the funtcional relationship between desirable image space coordinate system and distorted image space coordinates.

As shown in Figure 1, owing to changing, the carrying platform attitude causes photographic coordinate system O _S-X _SY _SZ _SSuccessively around its X _sAxle, Y _sAxle, Z _sThe axle anglec of rotation

Behind ω, the κ, desirable image space coordinate system O-XYZ is transformed into distorted image space coordinates O '-X ' Y ' Z ', and the transformational relation between two coordinate systems is

$\left[\begin{array}{c}{X}^{\′}\\ Y^{\′}\\ Z^{\′}\end{array}\right]=R\×\left[\begin{array}{c}X\\ Y\\ Z\end{array}\right]+p---\left(2\right)$

In the formula:

Translation vector

F is focal length, and s is pixel resolution.

Step 4: find the solution interesting target point Q (x _Q, y _Q) position in the distorted image plane.

As shown in Figure 1, O _SBe the photography point, for ideal as putting Q (x in the plane X OY _Q, y _Q), straight line O _sThe intersection point Q ' of Q and distorted image plane X ' O ' Y ' is required.

In the known resonable imagination space coordinates, photography point O _SCoordinate be (0,0 ,-f/s), impact point Q coordinate is (x _Q, y _Q, 0), obtain O according to formula (2) _S, the coordinate of Q in the distorted image space coordinates be followed successively by (x ₁', y ₁', z ₁'), (x ₂', y ₂', z ₂'), therefore straight line O _sThe equation of Q in the distorted image space coordinates is

$\frac{x^{\′}-{x_1}^{\′}}{{x_2}^{\′}-{x_1}^{\′}}=\frac{y^{\′}-{y_1}^{\′}}{{y_2}^{\′}-{y_1}^{\′}}=\frac{z^{\′}-{z_1}^{\′}}{{z_2}^{\′}-{z_1}^{\′}}---\left(3\right)$

The distorted image plane equation is

z′＝0 （4）

Simultaneous formula (3), formula (4) obtain intersection point Q ' coordinate (x _{Q '}', y _{Q '}').

By said process, obtain Q ' (x _{Q '}', y _{Q '}') be the coordinate of interesting target point in the fault image in the step 1.

Step 5: obtain the interference strength that interesting target is put corresponding a certain optical path difference.

Obtain interesting target point Q ' coordinate (x in the fault image in the step 4 _{Q '}', y _{Q '}'), as (x _{Q '}', y _{Q '}') when being integer, obtain the gray-scale value of a fault image Q ' position, be Q ' some interference strength value under a certain optical path difference of correspondence, as (x _{Q '}', y _{Q '}') when being non-integer, adopt the arest neighbors method of interpolation, obtain the gray-scale value of a fault image Q ' position, be Q ' some interference strength value under a certain optical path difference of correspondence;

Q ' point coordinate (the x that obtains in the step 4 _{Q '}', y _{Q '}') might be non-integer, in view of the handled space-time unite interferometric modulator of the present invention imaging spectrometer image with interference fringe, image changes more sharp-pointed along the rail direction, for keep the details of original image as far as possible, adopt the arest neighbors method of interpolation, the gray-scale value that obtains at Q ' also is the interference strength value of the corresponding a certain optical path difference of impact point.

Extract the gray-scale value of impact point a certain width of cloth image correspondence position in the fault image sequence, can obtain impact point corresponding to the interference strength data under some optical path differences (each width of cloth image can only obtain the interference strength of the corresponding a certain optical path difference of target).

Step 6: judge whether to finish the fault image collection.

Judge whether the fault image sampling number reaches A, if reach, enters step 7, otherwise, return step 1, continue to obtain the image that comprises interesting target point by space-time unite interferometric modulator imaging spectrometer.

Step 7: obtain the complete some interference data that interesting target is put corresponding different optical path differences.

Obtain complete some interference strength data of an interesting target point corresponding A different optical path difference.

Step 8: the complete interference strength data communication device of interesting target point is crossed Fourier transform restore the spectrum that obtains this interesting target point.

Because the variations such as the carrying platform attitude sidewinders, pitching, driftage can cause interesting target point interference strength data right and wrong on optical path difference of extracting equally distributed, need to carry out the curve of spectrum of Nonuniform fast Fourier transform recovery impact point.

The interference strength data that interesting target point is complete are carried out Nonuniform fast Fourier transform, and the curve of spectrum after the Fourier transform is the spectrum of impact point.

Claims (1)

1. the attitude error rectification method of a space-time unite interferometric modulator imaging spectrometer is characterized in that, comprises following step:

Step 1: obtain the image that comprises interesting target point, i.e. fault image by space-time unite interferometric modulator imaging spectrometer;

Determine to gather the quantity A of fault image according to Shannon's sampling theorem, A represents to gather the quantity of fault image; For the interesting target point, the corresponding specific optical path difference of each width of cloth fault image, an A width of cloth fault image corresponding A different optical path difference;

Step 2: resolve elements of exterior orientation according to the POS measurement data;

For a width of cloth fault image, obtain elements of exterior orientation, be specially:

The boat sheet foreign side parallactic angle list of elements is levied the photography light beam at the photography dimensional orientation of moment, in order to X _sAxle is the corner system of main shaft when representing,

For lateral tilt, ω are that fore and aft tip, κ are the photograph swing angle, The angle of pitch Φ that ω, κ and POS record, the transformational relation between angle of roll Ω, the crab angle K are:

In the formula:

Be expressed as between figure coordinate system m and the geocentric coordinate system E rotation matrix,

Rotation matrix between expression geocentric coordinate system E and the local geographic coordinate system g, Represent between local geographic coordinate system g and the IMU coordinate system b rotation matrix,

Rotation matrix between expression IMU coordinate system b and the imaging spectrometer coordinate system c, Rotation matrix between expression imaging spectrometer coordinate system c and the image space coordinate system i;

Be expressed as figure coordinate system m to the rotation matrix between the image space coordinate system coordinate system i, it is

The function of ω, κ;

Represent local geographic coordinate system g to the rotation matrix between the IMU coordinate system b, it is the function of Φ, Ω, K;

Step 3: set up the funtcional relationship between desirable image space coordinate system and distorted image space coordinates;

Because the carrying platform attitude changes and causes photographic coordinate system O _S-X _SY _SZ _SSuccessively around its X _sAxle, Y _sAxle, Z _sThe axle anglec of rotation

Behind ω, the κ, desirable image space coordinate system O-XYZ is transformed into distorted image space coordinates O '-X ' Y ' Z ', and the transformational relation between two coordinate systems is:

$\left[\begin{array}{c}{X}^{\′}\\ Y^{\′}\\ Z^{\′}\end{array}\right]=R\×\left[\begin{array}{c}X\\ Y\\ Z\end{array}\right]+p---\left(2\right)$

In the formula:

Translation vector

F is focal length, and s is pixel resolution;

Step 4: obtain interesting target point Q (x _Q, y _Q) position Q ' (x in the distorted image plane _{Q '}', y _{Q '}');

O _SBe the photography point, for ideal as putting Q (x in the plane X OY _Q, y _Q), straight line O _sThe intersection point of Q and distorted image plane X ' O ' Y ' is Q ' (x _{Q '}', y _{Q '}') point, Q ' (x _{Q '}', y _{Q '}') be interesting target point Q (x _Q, y _Q) position in the distorted image plane;

In the known resonable imagination space coordinates, photography point O _SCoordinate be (0,0 ,-f/s), impact point Q coordinate is (x _Q, y _Q, 0), obtain O according to formula (2) _S, the coordinate of Q in the distorted image space coordinates be followed successively by (x ₁', y ₁', z ₁'), (x ₂', y ₂', z ₂'), straight line O then _sThe equation of Q in the distorted image space coordinates is:

$\frac{x^{\′}-{x_1}^{\′}}{{x_2}^{\′}-{x_1}^{\′}}=\frac{y^{\′}-{y_1}^{\′}}{{y_2}^{\′}-{y_1}^{\′}}=\frac{z^{\′}-{z_1}^{\′}}{{z_2}^{\′}-{z_1}^{\′}}---\left(3\right)$

The distorted image plane equation is:

z′＝0 （4）

Simultaneous formula (3), formula (4) obtain intersection point Q ' coordinate (x _{Q '}', y _{Q '}');

By said process, obtain Q ' (x _{Q '}', y _{Q '}') be the coordinate of interesting target point in the fault image;

Step 5: obtain the interference strength that interesting target in the fault image is put corresponding a certain optical path difference;

Obtain interesting target point Q ' coordinate (x in the fault image in the step 4 _{Q '}', y _{Q '}'), as (x _{Q '}', y _{Q '}') when being integer, obtain the gray-scale value of a fault image Q ' position, be Q ' some interference strength value under a certain optical path difference of correspondence, as (x _{Q '}', y _{Q '}') when being non-integer, adopt the arest neighbors method of interpolation, obtain the gray-scale value of a fault image Q ' position, be Q ' some interference strength value under a certain optical path difference of correspondence;

Step 6: judge whether to finish the fault image collection;

Judge whether the fault image sampling number reaches A, if reach, enters step 7, otherwise, return step 1, continue to obtain the image that comprises interesting target point by space-time unite interferometric modulator imaging spectrometer;

Step 7: obtain the complete interference data that interesting target is put corresponding different optical path differences;

Obtain the complete interference strength data of an interesting target point corresponding A different optical path difference;

Step 8: the complete interference strength data communication device of interesting target point is crossed Nonuniform fast Fourier transform restore the spectrum that obtains this interesting target point;

The interference strength data that interesting target point is complete are carried out Nonuniform fast Fourier transform, and the curve of spectrum after the Fourier transform is the spectrum of impact point.

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