A method and device for correcting ghost images in Fourier transform spectrometer

Abstract

The present invention discloses a method and device for correcting ghost images in a Fourier transform spectrometer, which can solve the problem of the influence of ghost images on the spectral inversion accuracy of the Fourier transform spectrometer. The Fourier transform spectrometer is used to determine the symmetry center of the interference direction and the width direction of the spectrometer image on the detector; based on the symmetry center of the interference direction and the width direction of the spectrometer image on the detector, the range of the area affected by the ghost image in the spectrometer image is determined; the percentage of the energy of the ghost image in the spectrometer image to the imaging energy is determined; based on the range of the area affected by the ghost image in the spectrometer image and the percentage of the energy of the ghost image in the spectrometer image to the imaging energy, the ghost image existing in the spectrometer image to be corrected is estimated, and the spectrometer image to be corrected is corrected according to the estimation result to obtain the corrected spectrometer image.

Description

Technical Field

[0001] The invention relates to the field of spectral image processing, and in particular to a method and a device for correcting ghost images in a Fourier transform spectrometer. Background Art

[0002] Fourier transform spectrometer is an instrument based on the Fourier transform relationship between spectrum and interference information. The instrument indirectly obtains spectrum information by collecting and transforming interference information. Its basic working principle is that the incident light from the same light source forms two coherent lights with a specific optical path difference after passing through the optical system. The two coherent lights interfere on the image plane, and the interference intensity distribution information is obtained on the detector. The spectrum information of the incident light is obtained by inversion through Fourier transform calculation of the interference pattern.

[0003] The characteristic of Fourier transform spectrometer is that it needs post-processing to obtain spectral information. Therefore, the data processing method for spectrometer is its core. The usual data processing process includes dark current correction, bad pixel correction, relative radiation coefficient correction and other interference pattern correction, DC component removal, data apodization, phase error correction, Fourier transform, etc. Through the above steps, a set of spectral data cubes can be obtained. However, with the increasing requirements for spectral data accuracy, it is necessary to consider obtaining higher-precision inversion spectra in combination with the characteristics of the spectral instrument itself.

[0004] In the Fourier transform spectrometer, the light entering the interferometer is divided into two beams after passing through the spectroscopic film. Each beam of light needs to pass through the spectroscopic film twice in the interferometer to be split again, thus being divided into four beams of light. Two of the beams pass through the Fourier mirror to form an interference image, and the other two beams return along the direction of the incident light. At present, the main material component of the commonly used detector surface receiving light is silicon, and the refractive index of silicon in the visible near-infrared and short-wave infrared spectrum is relatively high. Therefore, according to the Fresnel law, a relatively significant reflection phenomenon will be formed on the medium interface surface. Since the surface shape of the detector is regular, the reflection formed is mainly mirror reflection. Each beam of light that re-enters the interferometer after reflection from the detector is the same as the incident light beam, and is re-split by the interferometer and called four beams of light. Two beams are emitted from the incident surface of the interferometer to the collimator mirror, and two beams are emitted from the interferometer to the Fourier mirror. The two beams of light emitted to the Fourier mirror re-form an interference image on the detector after passing through the Fourier mirror, which becomes the ghost image of the interferometer. Therefore, the ghost image is formed due to the reflection of the detector surface and the reflection of the spectroscopic film. It has been calculated that the energy of this ghost image accounts for about 10% of the normal imaging energy. The data processing process of conventional Fourier transform spectrometers does not take into account the impact of this parasitic ghost image on spectral restoration. Summary of the invention

[0005] In view of this, the present invention provides a method for correcting ghost images in a Fourier transform spectrometer, which can solve the technical problem of the influence of ghost images on the spectral inversion accuracy of the Fourier transform spectrometer.

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

[0007] A method for correcting ghost images in a Fourier transform spectrometer, comprising:

[0008] Step S1: using the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector;

[0009] Step S2: determining the range of the area affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and the width direction of the spectrometer image on the detector;

[0010] Step S3: determining the percentage of the energy of the ghost image in the spectrometer image to the imaging energy;

[0011] Step S4: based on the range of the area in the spectrometer image affected by the ghost image and the percentage of the energy of the ghost image in the spectrometer image to the imaging energy, the ghost image in the spectrometer image to be corrected is estimated, and the spectrometer image to be corrected is corrected according to the estimation result to obtain a corrected spectrometer image.

[0012] Preferably, the step S1 comprises:

[0013] Using the imaging result of the Fourier transform spectrometer on the uniform target, determining the symmetry center of the interference direction of the spectrometer image on the detector, including:

[0014] The Fourier transform spectrometer obtains the image of a uniform target, obtains the interference fringe image on the detector, and obtains the row of pixels located at the zero-order dark fringe at the symmetry center of the interference fringe. This row is the symmetry center of the detector interference direction, which is denoted as O. y ;

[0015] Using the calibration image in the calibration mode of the Fourier transform spectrometer, determining the symmetry center of the spectrometer image in the width direction on the detector includes:

[0016] Turn on the calibration light source of the spectrometer, obtain the response of all pixels on the detector, and calculate the response mean of all pixels. The calculation formula for the response mean of all pixels is as follows:

[0017]

[0018] Among them, DN i is the response DN value of the i-th pixel when the calibration light source is turned on, and k is the total number of detector pixels;

[0019] Using the response mean as the threshold, the entire image is binarized using the following formula;

[0020]

[0021] According to the result of image binarization, the position of the edge of the calibration area on the satellite close to the center of the detector in the width direction is obtained, which is recorded as m;

[0022] According to the result of image binarization, the position of the ghost image formed in the calibration area on the star in the width direction close to the edge of the detector center is obtained, which is recorded as m′;

[0023] The symmetric center of the detector width direction is calculated by the following formula, denoted as O x :

[0024]

[0025] Among them, O x The calculated results of the parameters are rounded to the nearest integer.

[0026] Preferably, the step S2 comprises:

[0027] The area of ​​the interference image affected by ghost images in the detector interference direction during imaging is calculated by the following formula:

[0028]

[0029]

[0030] Among them, R y_start To R y_end The area between is the area affected by the ghost image in the detector interference direction. y is the size of the detector in the interference direction, R y_start is the starting row of the ghost image influence area in the detector interference direction, R y_end It is the end row of the ghost image influence area in the detector interference direction.

[0031] The area of ​​the interference image affected by ghost images in the detector width direction during imaging is calculated by the following formula:

[0032] R x_start =m′+1

[0033] R x_end =m-1

[0034] Among them, R x_start To R x_end The area between is the area affected by ghost images in the detector width direction, R x_start is the starting row of the ghost image impact area in the detector width direction, R x_end It is the end row of the ghost image influence area in the detector width direction;

[0035] Determine the range of the area affected by the ghost image in the spectrometer image, that is, determine that the four corner points of the ghost image affected area are A 1 (x 1 ,y 1 ), A 2 (x 2 ,y 2 ), A 3 (x 3 ,y 3 ), A 4 (x 4 ,y 4 ), the calculation method is as follows:

[0036] A 1 (x 1 ,y 1 )=(m′+1,R y_start )

[0037] A 2 (x 2 ,y 2 )=(m-1,R y_start )

[0038] A 3 (x 3 ,y 3 )=(m′+1,R y_end )

[0039] A 4 (x 4 ,y 4 )=(m-1,R y_end ).

[0040] Preferably, the step S3, using the calibration image result in the spectrometer calibration mode to determine the percentage of the energy of the ghost image in the spectrometer image to the normal imaging energy, comprises:

[0041] Step S31: Calculate the response mean DN of the calibration area where ghost images exist O ,include:

[0042] The number of rows in the calibration area where ghost images exist is calculated based on the symmetric center of the detector interference direction, which is 2×O y -1;

[0043] Determine the number of columns n of the calibration area;

[0044] According to the starting area of ​​the ghost image in the detector interference direction during imaging, the size of the detector width direction is CCD x The calibration area with ghost images is calculated as pixels (CCD x -n+1,R y_start) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN O ; The starting point is the upper left corner of the rectangle;

[0045] Step S32: Calculate the response mean DN of the calibration area corresponding to the ghost image area G ,include:

[0046] According to the starting area of ​​the ghost image in the detector interference direction during imaging, and the edge position of the on-board calibration area and its ghost image area, the edge position of the ghost image formed in the on-board calibration area in the width direction close to the center of the detector is m′, and the area of ​​the on-board calibration area corresponding to the ghost image is calculated as the pixel (m′-n, R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN G ;

[0047] Step S33: Determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy by the following formula:

[0048]

[0049] Preferably, the step S4 comprises:

[0050] Step S41: performing curve fitting on the interference direction according to the interference image during the imaging of the spectrometer, and filtering the DC component of the interference direction in the spectrum image by subtracting the curve fitting result from the original interference image curve;

[0051] Step S42: for the interference image after filtering the DC component, intercept the area affected by the ghost image, perform inversion processing on the interference direction fringes in the area image, and obtain the inverted ghost image area image;

[0052] Step S43: rotating the inverted ghost image region image by 180° around the symmetry center in the interference direction and the width direction to obtain a symmetrically inverted ghost image region image;

[0053] Step S44: multiplying the ghost image region image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy to obtain the ghost image response in the image currently imaged;

[0054] Step S45: subtract the ghost image response existing in the normal imaging image from the original image during the imaging period to obtain a corrected spectrometer image.

[0055] A device for correcting ghost images in a Fourier transform spectrometer, characterized by comprising:

[0056] A symmetry center determination module: configured to use the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector;

[0057] An affected area determination module: configured to determine the area range affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and width direction of the spectrometer image on the detector;

[0058] An energy proportion determination module: configured to determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy;

[0059] The correction module is configured to estimate the ghost images in the spectrometer image to be corrected based on the range of the area affected by the ghost images in the spectrometer image and the percentage of the energy of the ghost images in the spectrometer image to the imaging energy, and correct the spectrometer image to be corrected according to the estimation result to obtain the corrected spectrometer image.

[0060] Preferably, the symmetry center determination module includes:

[0061] Interference direction submodule: configured to use the imaging result of the Fourier transform spectrometer on the uniform target to determine the symmetry center of the interference direction of the spectrometer image on the detector, including:

[0062] The Fourier transform spectrometer obtains the image of a uniform target, obtains the interference fringe image on the detector, and obtains the row of pixels located at the zero-order dark fringe at the symmetry center of the interference fringe. This row is the symmetry center of the detector interference direction, which is denoted as O. y ;

[0063] The width direction submodule is configured to determine the symmetry center of the spectrometer image in the width direction on the detector using the calibration image in the calibration mode of the Fourier transform spectrometer, including:

[0064] Turn on the calibration light source of the spectrometer, obtain the response of all pixels on the detector, and calculate the response mean of all pixels. The calculation formula for the response mean of all pixels is as follows:

[0065]

[0066] Among them, DN i is the response DN value of the i-th pixel when the calibration light source is turned on, and k is the total number of detector pixels;

[0067] Using the response mean as the threshold, the entire image is binarized using the following formula;

[0068]

[0069] According to the result of image binarization, the position of the edge of the calibration area on the satellite close to the center of the detector in the width direction is obtained, which is recorded as m;

[0070] According to the result of image binarization, the position of the ghost image formed in the calibration area on the star in the width direction close to the edge of the detector center is obtained, which is recorded as m′;

[0071] The symmetric center of the detector width direction is calculated by the following formula, denoted as O x :

[0072]

[0073] Among them, O x The calculated results of the parameters are rounded to the nearest integer.

[0074] Preferably, the impact area determination module includes:

[0075] The first area determination submodule: calculates the area of ​​the interference image affected by ghost images in the detector interference direction during imaging by the following formula:

[0076]

[0077]

[0078] Among them, R y_start To R y_end The area between is the area affected by the ghost image in the detector interference direction. y is the size of the detector in the interference direction, R y_start is the starting row of the ghost image influence area in the detector interference direction, R y_end It is the end row of the ghost image influence area in the detector interference direction.

[0079] The area of ​​the interference image affected by ghost images in the detector width direction during imaging is calculated by the following formula:

[0080] R x_start =m′+1

[0081] R x_end =m-1

[0082] Among them, R x_start To R x_end The area between is the area affected by ghost images in the detector width direction, R x_start is the starting row of the ghost image impact area in the detector width direction, R x_end It is the end row of the ghost image influence area in the detector width direction;

[0083] The second region determination submodule is configured to determine the region affected by the ghost image in the spectrometer image, that is, to determine that the four corner points of the ghost image affected region are A 1 (x 1 ,y 1 ), A 2 (x 2 ,y 2 ), A 3 (x 3 ,y 3 ), A 4 (x 4 ,y 4 ), the calculation method is as follows:

[0084] A 1 (x 1 ,y 1 )=(m′+1,R y_start )

[0085] A 2 (x 2 ,y 2 )=(m-1,R y_start )

[0086] A 3 (x 3 ,y 3 )=(m′+1,R y_end )

[0087] A 4 (x 4 ,y 4 )=(m-1,R y_end ).

[0088] Preferably, the energy proportion determination module includes:

[0089] The first response mean calculation submodule is configured to calculate the response mean DN of the calibration area where ghost images exist. O ,include:

[0090] The number of rows in the calibration area where ghost images exist is calculated based on the symmetric center of the detector interference direction, which is 2×O y -1;

[0091] Determine the number of columns n of the calibration area;

[0092] According to the starting area of ​​the ghost image in the detector interference direction during imaging, the size of the detector width direction is CCD x The calibration area with ghost images is calculated as pixels (CCD x -n+1,R y_start ) is the starting point, the number of rows is 2×Oy -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN O ; The starting point is the upper left corner of the rectangle;

[0093] The second response mean calculation submodule is configured to calculate the response mean DN of the ghost image area corresponding to the calibration area. G ,include:

[0094] According to the starting area of ​​the ghost image in the detector interference direction during imaging, and the edge position of the on-board calibration area and its ghost image area, the edge position of the ghost image formed in the on-board calibration area in the width direction close to the center of the detector is m′, and the area of ​​the on-board calibration area corresponding to the ghost image is calculated as the pixel (m′-n, R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN G ;

[0095] Percentage calculation submodule: configured to determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy by the following formula

[0096]

[0097] Preferably, the correction module comprises:

[0098] A filtering submodule: configured to perform curve fitting on the interference direction according to the interference image during the imaging of the spectrometer, and filter the DC component of the interference direction in the spectral image by subtracting the curve fitting result from the original interference image curve;

[0099] Inversion submodule: configured to intercept the area affected by the ghost image for the interference image after filtering the DC component, invert the interference direction fringes in the area image, and obtain the inverted ghost image area image;

[0100] Ghost image region acquisition submodule: configured to rotate the inverted ghost image region image by 180° around the symmetry center of the interference direction and the width direction to acquire the symmetrically inverted ghost image region image;

[0101] A ghost image response determination submodule: configured to multiply the ghost image region image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy, to obtain the ghost image response existing in the image currently imaged;

[0102] Correction submodule: configured to use the original image during imaging to subtract the ghost image response existing in the image of the normal imaging this time to obtain a corrected spectrometer image.

[0103] Beneficial effects:

[0104] (1) The present invention provides a method for correcting ghost images for a Fourier transform spectrometer, which reduces the impact of ghost images on image contrast, avoids image confusion caused by ghost images during normal imaging, and improves the spectral restoration accuracy of the Fourier transform spectrometer.

[0105] (2) The present invention uses calibration pixels in the spectrometer detector to achieve ghost image correction, which is independent of external environment or equipment, and the process is simple and easy to implement.

[0106] (3) The present invention can be extended to be applied to an imaging system in which light reflected from the detector surface is reflected back onto the detector to form a ghost image, thereby completing the ghost image correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Figure 1 A schematic flow chart of a method for correcting ghost images in a Fourier transform spectrometer;

[0108] Figure 2 The schematic diagram of the spectrometer system with calibration pixels;

[0109] Figure 3 Schematic diagram of the device structure for correcting ghost images in a Fourier transform spectrometer. DETAILED DESCRIPTION

[0110] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0111] The invention discloses a method for correcting ghost images in a Fourier transform spectrometer. The method calculates the symmetry center, reflectivity and ghost image influence area of ​​the ghost image in combination with calibration pixels in a detector, calculates the mathematical relationship between the ghost image and an acquired image on this basis, subtracts the energy value of the ghost image from the image, and obtains a corrected interference image.

[0112] The method for correcting ghost images in a Fourier transform spectrometer provided by the present invention comprises the following steps:

[0113] Step S1: using the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector;

[0114] Step S2: determining the range of the area affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and the width direction of the spectrometer image on the detector;

[0115] Step S3: determining the percentage of the energy of the ghost image in the spectrometer image to the imaging energy;

[0116] Step S4: based on the range of the area in the spectrometer image affected by the ghost image and the percentage of the energy of the ghost image in the spectrometer image to the imaging energy, the ghost image in the spectrometer image to be corrected is estimated, and the spectrometer image to be corrected is corrected according to the estimation result to obtain a corrected spectrometer image.

[0117] In this scheme, some special images are used, such as the imaging results of uniform targets, images in calibration mode, etc. to calibrate the spectrometer information. The image to be corrected is the image obtained when the spectrometer is actually on-orbit and imaging ground targets or some scenes on the ground, that is, when it is actually working. The image during working contains the influence of ghost images, so it is used as the spectrometer image to be corrected and corrected.

[0118] The step S1 comprises: using the imaging result of the Fourier transform spectrometer on the uniform target to determine the symmetry center of the spectrometer image in the interference direction on the detector; using the calibration image in the calibration mode of the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the width direction on the detector;

[0119] The calibration mode refers to the calibration light source in the Fourier transform spectrometer being turned on, and the calibration pixel of the detector obtaining the calibration image after the calibration light source passes through the interference optical system of the Fourier transform spectrometer; the calibration pixel and the imaging pixel are located on the same detector; and the calibration light source is located before the interference optical system of the Fourier transform spectrometer. Figure 2 shown.

[0120] In this embodiment, the Fourier transform spectrometer images a uniform target such as a laboratory integrating sphere, obtains an interference fringe image on the detector, and obtains the row of pixels located at the zero-order dark fringe at the symmetry center of the interference fringe. This row is the symmetry center of the detector interference direction, denoted by O y .

[0121] Turn on the calibration light source of the spectrometer, obtain the response of all pixels on the detector, and calculate the response mean of all pixels. The calculation formula for the response mean of all pixels is as follows:

[0122]

[0123] Among them, DN i is the response DN value of the i-th pixel when the calibration light source is turned on, and k is the total number of detector pixels;

[0124] Using the response mean as the threshold, the entire image is binarized using the following formula;

[0125]

[0126] According to the result of image binarization, the position of the edge of the calibration area on the satellite close to the center of the detector in the width direction is obtained, which is recorded as m;

[0127] According to the result of image binarization, the position of the ghost image formed in the calibration area on the star in the width direction close to the edge of the detector center is obtained, which is recorded as m′;

[0128] The symmetric center of the detector width direction is calculated by the following formula, denoted as O x :

[0129]

[0130] In this embodiment, O x The calculated results of the parameters are rounded to the nearest integer.

[0131] The step S2 comprises:

[0132] The area of ​​the interference image affected by ghost images in the detector interference direction during imaging is calculated by the following formula:

[0133]

[0134]

[0135] Among them, R y_start To R y_end The area between is the area affected by the ghost image in the detector interference direction. y is the size of the detector in the interference direction, R y_start is the starting row of the ghost image influence area in the detector interference direction, R y_end It is the end row of the ghost image influence area in the detector interference direction.

[0136] The area of ​​the interference image affected by ghost images in the detector width direction during imaging is calculated by the following formula:

[0137] R x_start =m′+1

[0138] R x_end =m-1

[0139] Among them, R x_start To R x_end The area between is the area affected by ghost images in the detector width direction, R x_start is the starting row of the ghost image impact area in the detector width direction, R x_end It is the end row of the ghost image influence area in the detector width direction;

[0140] Determine the range of the area affected by the ghost image in the spectrometer image, that is, determine that the four corner points of the ghost image affected area are A 1 (x 1 ,y 1 ), A 2 (x 2 ,y 2 ), A 3 (x 3 ,y 3 ), A 4 (x 4 ,y 4 ), the calculation method is as follows:

[0141] A 1 (x 1 ,y 1 )=(m′+1,R y_start )

[0142] A 2 (x 2 ,y 2 )=(m-1,R y_start )

[0143] A 3 (x 3 ,y 3 )=(m′+1,R y_end )

[0144] A 4 (x 4 ,y 4 )=(m-1,R y_end )

[0145] The step S3, using the calibration image result in the spectrometer calibration mode to determine the percentage of the energy of the ghost image in the spectrometer image to the normal imaging energy, includes:

[0146] Step S31: Calculate the response mean DN of the calibration area where ghost images exist O ,include:

[0147] The number of rows in the calibration area where ghost images exist is calculated based on the symmetric center of the detector interference direction, which is 2×O y -1;

[0148] Determine the number of columns n of the calibration area;

[0149] In this embodiment, according to the design of the optical system of the spectrometer, the number of columns of the calibration area is fixed to n.

[0150] According to the starting area of ​​the ghost image in the detector interference direction during imaging, the size of the detector width direction is CCD xThe calibration area with ghost images is calculated as pixels (CCD x -n+1,R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN O ; The starting point is the upper left corner of the rectangle;

[0151] Step S32: Calculate the response mean DN of the calibration area corresponding to the ghost image area G ,include:

[0152] According to the starting area of ​​the ghost image in the detector interference direction during imaging, and the edge position of the on-board calibration area and its ghost image area, the edge position of the ghost image formed in the on-board calibration area in the width direction close to the center of the detector is m′, and the area of ​​the on-board calibration area corresponding to the ghost image is calculated as the pixel (m′-n, R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN G ;

[0153] Step S33: Determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy by the following formula:

[0154]

[0155] The step S4 comprises:

[0156] Step S41: performing curve fitting on the interference direction according to the interference image during the imaging of the spectrometer, and filtering the DC component of the interference direction in the spectrum image by subtracting the curve fitting result from the original interference image curve;

[0157] Step S42: for the interference image after filtering the DC component, intercept the area affected by the ghost image, perform inversion processing on the interference direction fringes in the area image, and obtain the inverted ghost image area image;

[0158] Step S43: rotating the inverted ghost image region image by 180° around the symmetry center in the interference direction and the width direction to obtain a symmetrically inverted ghost image region image;

[0159] Step S44: multiplying the ghost image region image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy to obtain the ghost image response in the image currently imaged;

[0160] Step S45: subtract the ghost image response existing in the normal imaging image from the original image during the imaging period to obtain a corrected spectrometer image.

[0161] In this embodiment, the method for correcting the spectrometer image to be corrected according to the present invention is described with specific data, including:

[0162] 1) According to the interference image during normal imaging of the spectrometer, a 4th-order polynomial curve fitting is performed on the interference direction to obtain a DC component, and this DC component is subtracted from the original interference image to obtain an image after DC filtering in the interference direction;

[0163] 2) Interference image after filtering the DC component, intercepting the A affected by the ghost image 1 (x 1 ,y 1 ), A 2 (x 2 ,y 2 ), A 3 (x 3 ,y 3 ), A 4 (x 4 ,y 4 ) the area range within the four corner points, inverting the interference direction fringes in the area image to obtain the inverted ghost image area image;

[0164] 3) For the inverted ghost image, the symmetry center (O x ,O y ) rotates 180° to obtain a symmetrically inverted ghost image area image;

[0165] 4) multiplying the ghost image area image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy to obtain the ghost image response in the image of this imaging;

[0166] 5) The ghost image response existing in the image formed this time is subtracted from the original image during the imaging period to obtain a corrected spectrometer image.

[0167] The present invention also provides a device for correcting ghost images in a Fourier transform spectrometer, such as Figure 3 As shown, the device includes a symmetry center determination module: configured to use the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector;

[0168] An affected area determination module: configured to determine the area range affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and width direction of the spectrometer image on the detector;

[0169] An energy proportion determination module: configured to determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy;

[0170] The correction module is configured to estimate the ghost images in the spectrometer image to be corrected based on the range of the area affected by the ghost images in the spectrometer image and the percentage of the energy of the ghost images in the spectrometer image to the imaging energy, and correct the spectrometer image to be corrected according to the estimation result to obtain the corrected spectrometer image.

[0171] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A method for correcting ghost images in a Fourier transform spectrometer, characterized in that: include: Step S1: using the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector; Step S2: determining the range of the area affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and the width direction of the spectrometer image on the detector; Step S3: determining the percentage of the energy of the ghost image in the spectrometer image to the imaging energy; Step S4: based on the range of the area affected by the ghost image in the spectrometer image and the percentage of the energy of the ghost image in the spectrometer image to the imaging energy, estimating the ghost image in the spectrometer image to be corrected, and correcting the spectrometer image to be corrected according to the estimation result to obtain a corrected spectrometer image; The step S1 comprises: Using the imaging result of the Fourier transform spectrometer on the uniform target, determining the symmetry center of the interference direction of the spectrometer image on the detector, including: The Fourier transform spectrometer obtains the image of a uniform target, obtains the interference fringe image on the detector, and obtains the row of pixels located at the zero-order dark fringe at the symmetry center of the interference fringe. This row is the symmetry center of the detector interference direction, which is denoted as O. y ; Using the calibration image in the calibration mode of the Fourier transform spectrometer, determining the symmetry center of the spectrometer image in the width direction on the detector includes: Turn on the calibration light source of the spectrometer, obtain the response of all pixels on the detector, and calculate the response mean of all pixels. The calculation formula for the response mean of all pixels is as follows: Among them, DN i is the response DN value of the i-th pixel when the calibration light source is turned on, and k is the total number of detector pixels; Using the response mean as the threshold, the entire image is binarized using the following formula; According to the result of image binarization, the position of the edge of the calibration area on the satellite close to the center of the detector in the width direction is obtained, which is recorded as m; According to the result of image binarization, the position of the ghost image formed in the calibration area on the star in the width direction close to the edge of the detector center is obtained, which is recorded as m′; The symmetric center of the detector width direction is calculated by the following formula, denoted as O x : Among them, O x The calculation results of the parameters are rounded off; The step S2 comprises: The area of ​​the interference image affected by ghost images in the detector interference direction during imaging is calculated by the following formula: Among them, R y_start To R y_end The area between is the area affected by the ghost image in the detector interference direction. y is the size of the detector in the interference direction, R y_start is the starting row of the ghost image influence area in the detector interference direction, R y_end It is the termination row of the ghost image influence area in the detector interference direction; The area of ​​the interference image affected by ghost images in the detector width direction during imaging is calculated by the following formula: R x_start =m′+1 R x_end =m-1 Among them, R x_start To R x_end The area between is the area affected by ghost images in the detector width direction, R x_start is the starting row of the ghost image impact area in the detector width direction, R x_end It is the end row of the ghost image influence area in the detector width direction; Determine the range of the area affected by the ghost image in the spectrometer image, that is, determine that the four corner points of the ghost image affected area are A1 (x1, y1), A2 (x2, y2), A3 (x3, y3), and A4 (x4, y4), and the calculation method is as follows: A1(x1,y1)=(m′+1,R y_start ) A2(x2,y2)=(m-1,R y_start ) A3(x3,y3)=(m′+1,R y_end ) A4(x4,y4)=(m-1,R y_end )。 2. The method according to claim 1, characterized in that The step S3, using the calibration image result in the spectrometer calibration mode to determine the percentage of the energy of the ghost image in the spectrometer image to the normal imaging energy, includes: Step S31: Calculate the response mean DN of the calibration area where ghost images exist O ,include: The number of rows in the calibration area where ghost images exist is calculated based on the symmetric center of the detector interference direction, which is 2×O y -1; Determine the number of columns n of the calibration area; According to the starting area of ​​the ghost image in the detector interference direction during imaging, the size of the detector width direction is CCD x The calibration area with ghost images is calculated as pixels (CCD x -n+1,R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN O ; The starting point is the upper left corner of the rectangle; Step S32: Calculate the response mean DN of the calibration area corresponding to the ghost image area G ,include: According to the starting area of ​​the ghost image in the detector interference direction during imaging, and the edge position of the on-board calibration area and its ghost image area, the edge position of the ghost image formed in the on-board calibration area in the width direction close to the center of the detector is m′, and the area of ​​the on-board calibration area corresponding to the ghost image is calculated as the pixel (m′-n, R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN G ; Step S33: Determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy by the following formula:

3. The method according to claim 2, characterized in that The step S4 comprises: Step S41: performing curve fitting on the interference direction according to the interference image during the imaging of the spectrometer, and filtering the DC component of the interference direction in the spectrum image by subtracting the curve fitting result from the original interference image curve; Step S42: for the interference image after filtering the DC component, intercept the area affected by the ghost image, perform inversion processing on the interference direction fringes in the area image, and obtain the inverted ghost image area image; Step S43: rotating the inverted ghost image region image by 180° around the symmetry center in the interference direction and the width direction to obtain a symmetrically inverted ghost image region image; Step S44: multiplying the ghost image region image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy to obtain the ghost image response in the image currently imaged; Step S45: subtract the ghost image response existing in the normal imaging image from the original image during the imaging period to obtain a corrected spectrometer image.

4. A device for correcting ghost images in a Fourier transform spectrometer, characterized in that: include: 78 A symmetry center determination module: configured to use the Fourier transform spectrometer to determine the symmetry center of the spectrometer image in the interference direction and width direction on the detector; An affected area determination module: configured to determine the area range affected by the ghost image in the spectrometer image based on the symmetry center of the interference direction and width direction of the spectrometer image on the detector; An energy proportion determination module: configured to determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy; The correction module is configured to estimate the ghost images in the spectrometer image to be corrected based on the range of the area affected by the ghost images in the spectrometer image and the percentage of the energy of the ghost images in the spectrometer image to the imaging energy, and correct the spectrometer image to be corrected according to the estimation result to obtain the corrected spectrometer image.

5. The device according to claim 4, characterized in that The symmetry center determination module comprises: Interference direction submodule: configured to use the imaging result of the Fourier transform spectrometer on the uniform target to determine the symmetry center of the interference direction of the spectrometer image on the detector, including: The Fourier transform spectrometer obtains the image of a uniform target, obtains the interference fringe image on the detector, and obtains the row of pixels located at the zero-order dark fringe at the symmetry center of the interference fringe. This row is the symmetry center of the detector interference direction, which is denoted as O. y ; The width direction submodule is configured to determine the symmetry center of the spectrometer image in the width direction on the detector using the calibration image in the calibration mode of the Fourier transform spectrometer, including: Turn on the calibration light source of the spectrometer, obtain the response of all pixels on the detector, and calculate the response mean of all pixels. The calculation formula for the response mean of all pixels is as follows: Among them, DN i is the response DN value of the i-th pixel when the calibration light source is turned on, and k is the total number of detector pixels; Using the response mean as the threshold, the entire image is binarized using the following formula; According to the result of image binarization, the position of the edge of the calibration area on the satellite close to the center of the detector in the width direction is obtained, which is recorded as m; According to the result of image binarization, the position of the ghost image formed in the calibration area on the star in the width direction close to the edge of the detector center is obtained, which is recorded as m′; The symmetric center of the detector width direction is calculated by the following formula, denoted as O x : Among them, O x The calculated results of the parameters are rounded to the nearest integer.

6. The device according to claim 5, characterized in that The impact area determination module includes: The first area determination submodule: calculates the area of ​​the interference image affected by ghost images in the detector interference direction during imaging by the following formula: Among them, R y_start To R y_end The area between is the area affected by the ghost image in the detector interference direction. y is the size of the detector in the interference direction, R y_start is the starting row of the ghost image influence area in the detector interference direction, R y_end It is the termination row of the ghost image influence area in the detector interference direction; The area of ​​the interference image affected by ghost images in the detector width direction during imaging is calculated by the following formula: R x_start =m′+1 R x_end =m-1 Among them, R x_start To R x_end The area between is the area affected by ghost images in the detector width direction, R x_start is the starting row of the ghost image impact area in the detector width direction, R x_end It is the end row of the ghost image influence area in the detector width direction; The second region determination submodule is configured to determine the region affected by ghost images in the spectrometer image, that is, to determine that the four corner points of the ghost image affected region are A1 (x1, y1), A2 (x2, y2), A3 (x3, y3), and A4 (x4, y4), and the calculation method is as follows: A1(x1,y1)=(m′+1,R y_start ) A2(x2,y2)=(m-1,R y_start ) A3(x3,y3)=(m′+1,R y_end ) A4(x4,y4)=(m-1,R y_end )。 7. The device according to claim 6, characterized in that The energy proportion determination module includes: The first response mean calculation submodule is configured to calculate the response mean DN of the calibration area where ghost images exist. O ,include: The number of rows in the calibration area where ghost images exist is calculated based on the symmetric center of the detector interference direction, which is 2×O y -1; Determine the number of columns n of the calibration area; According to the starting area of ​​the ghost image in the detector interference direction during imaging, the size of the detector width direction is CCD x The calibration area with ghost images is calculated as pixels (CCD x -n+1,R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN O ; The starting point is the upper left corner of the rectangle; The second response mean calculation submodule is configured to calculate the response mean DN of the ghost image area corresponding to the calibration area. G ,include: According to the starting area of ​​the ghost image in the detector interference direction during imaging, and the edge position of the on-board calibration area and its ghost image area, the edge position of the ghost image formed in the on-board calibration area in the width direction close to the center of the detector is m′, and the area of ​​the on-board calibration area corresponding to the ghost image is calculated as the pixel (m′-n, R y_start ) is the starting point, the number of rows is 2×O y -1. Calculate the mean response value of all pixels in a square area with n columns, denoted as DN G ; Percentage calculation submodule: configured to determine the percentage of the energy of the ghost image in the spectrometer image to the imaging energy by the following formula 8. The device according to claim 7, characterized in that The correction module comprises: A filtering submodule: configured to perform curve fitting on the interference direction according to the interference image during the imaging of the spectrometer, and filter the DC component of the interference direction in the spectral image by subtracting the curve fitting result from the original interference image curve; Inversion submodule: configured to intercept the area affected by the ghost image for the interference image after filtering the DC component, invert the interference direction fringes in the area image, and obtain the inverted ghost image area image; Ghost image region acquisition submodule: configured to rotate the inverted ghost image region image by 180° around the symmetry center of the interference direction and the width direction to acquire the symmetrically inverted ghost image region image; The ghost image response determination submodule is configured to multiply the ghost image region image after symmetrical inversion by the percentage of the ghost image energy in the spectrometer image to the imaging energy, so as to obtain the ghost image response existing in the image imaged this time; Correction submodule: configured to use the original image during imaging to subtract the ghost image response existing in the image of the normal imaging this time to obtain a corrected spectrometer image.

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