CN117346687B - Method and system for correcting specular error data points of interferometry reflecting mirror - Google Patents
Method and system for correcting specular error data points of interferometry reflecting mirror Download PDFInfo
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- G—PHYSICS
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Abstract
The invention relates to the technical field of space telescopes, in particular to a method and a system for correcting a mirror surface shape error data point measured by an interferometer, wherein the method comprises the following steps: according to the technical scheme of acquiring cvg format surface shape data in interferometer software, carrying out data preprocessing, intercepting an effective reflector surface shape error data matrix A, removing data point error items, replacing edge data points by reconstructed data points and identifying and replacing invalid data points, the surface shape data acquired by the interferometer is corrected, the accuracy of reflector surface shape data required by digital modeling of an optical system is improved, and the requirement of accurately constructing a digital space telescope optical model is met.
Description
Technical Field
The invention relates to the technical field of space telescopes, in particular to a method and a system for correcting a mirror surface shape error data point measured by an interferometer.
Background
The development of the large-caliber space telescope has important significance for exploring astronomy front-edge scientific problems. In the development process of the large-caliber space telescope, a digital optical-mechanical structure model needs to be built, and the observation performance of the space telescope is predicted and estimated through the means of integrated simulation analysis. The accuracy of the construction of the optical model is an important factor affecting the prediction and evaluation of the performance of the space telescope.
The mirror surface shape error data is one of important components of the optical model of the digital space telescope, and the construction of an auto-collimation optical path by an interferometer to measure (interference optical path) the mirror surface shape error is one of important means for obtaining the mirror surface shape error data. However, there are certain problems in the prior art in loading the surface shape data measured by the interferometer into the optical model: firstly, partial invalid data points exist in surface shape data acquired by an interferometer; secondly, when the surface shape detection light path is constructed, all elements cannot be positioned at ideal positions at the same time, so that certain errors exist in the acquired surface shape data; thirdly, based on the principle of optical interferometry, certain diffraction effect exists at the edges of the interferogram, so that the data points at the edges are distorted. Therefore, the prior art cannot accurately obtain the measured reflector surface shape data of the interferometer, and the requirement of accurately constructing the optical model of the digital space telescope is not met.
Disclosure of Invention
In order to solve the above problems, the present application provides a method and system for correcting the specular error data points of an interferometer.
A method of correcting interferometric measurement mirror surface shape error data points provided herein includes:
acquiring cvg format surface shape data from interferometer software, preprocessing the data, and intercepting an effective reflector surface shape error data matrix A;
processing the data matrix A by using a median filter to obtain a reflector surface shape error data matrix B;
setting a threshold T, and recording the space coordinates of the data points when the difference value of one data point of the data matrix A and the corresponding data point of the data matrix B is larger than the threshold TIs recorded of the spatial coordinatesThe data points are invalid data points;
selecting data points of the data matrix A, wherein mirror surface shape error edge data points and invalid data points are not selected, and performing Zernike polynomial fitting;
subtracting an error term generated by the optical element adjustment deviation of the interference light path in the data matrix A based on a fitting coefficient in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix D;
replacing the mirror surface shape error edge data points in the data matrix D by polynomial fitting mirror surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting to obtain a mirror surface shape error data matrix E;
based on fitting coefficients within the Zernike polynomial fit, the spatial coordinates are determinedAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final surface shape data matrix G.
Preferably, the data preprocessing includes data format conversion, data scaling and unit conversion;
the 'intercepting effective mirror surface shape error data matrix A' is the intercepting effective mirror surface shape error data matrix A from the interference camera target surface.
Preferably, said processing said data matrix a with a median filter to obtain a mirror surface shape error data matrix B comprises:
constructing a 3×3 median filter;
the median filter ranks all data points in the template;
and obtaining intermediate values of all arranged data points in the template and replacing the current values of black data points in the template to obtain a reflector surface shape error data matrix B.
Preferably, the "set threshold T" records a certain data matrix a and a corresponding data matrix B when the difference between the data matrix a and the corresponding data matrix B is greater than the threshold TSpatial coordinates of pointsThe data points where the spatial coordinates are recorded are invalid data points "comprising:
setting a threshold T according to the peak Gu Chazhi of the data matrix a;
acquiring the difference value of each corresponding data point in the data matrix A before filtering and the data matrix B after filtering;
if the difference value of a data point is greater than the threshold value T, recording the position coordinates of the data point；
And maintaining the coordinates of all the data points with the difference value larger than the threshold value T, wherein the data points recorded with the space coordinates are invalid data points.
Preferably, the selecting the data points of the data matrix a, wherein the mirror surface shape error edge data points and the invalid data points are not selected, and performing Zernike polynomial fitting includes:
selecting data points of the data matrix A for Zernike polynomial fitting, wherein mirror surface shape error edge data points and invalid data points are not selected;
constructing a fitting equation (1):
(1)
in the formula (1) of the formula,representing the Zernike expression at coordinates +.>Base value at>Is the coefficient of Zernike which is the coefficient of Zernike,and->The number of items is consistent, total->An item.
Preferably, the "subtracting the error term in the data matrix a due to the optical element tuning deviation of the interference optical path based on the fitting coefficient in the Zernike polynomial fitting" to obtain the mirror surface shape error data matrix D "includes:
the fitting coefficients obtained by the equation (1) are combined in the Fringe Zernike coefficients to be characterized as the 1 st, 2 nd, 3 rd and 4 th items to obtain error items;
subtracting the error term from the data matrix A to obtain a reflector surface shape error data matrix D, wherein the specific equation (2) is as follows:
(2)
in the equation (2) described above,(j=1 to 4) is a full-aperture Zernike substrate,/>(j=1 to 4) are the pan, tilt and defocus terms of the Zernike polynomial fit.
Preferably, said "replacing said edge mirror shape error edge data points in said data matrix D with polynomial fit mirror shape error reconstruction data points based on fitting coefficients within said Zernike polynomial fit" comprises:
calculating mirror surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting, wherein a calculation equation (3) is as follows:
(3)
in the equation (3) described above,reconstructing data points for mirror surface shape errors, +.>Is->The term Zernike base is at the coordinates +.>A base value at; the number of the mirror surface shape error reconstruction data points is determined by a threshold W; when mirror shape error data points exist in a certain circle +.>Above W, then any data point in the circle +.>Are all (are) marked by->After the replacement, obtaining a reflector surface shape error data matrix +.>。
Preferably, the "fitting coefficients in the Zernike polynomial fit based on the spatial coordinatesCorrecting and replacing the corresponding data value by using a function fitting value to obtain a final surface shape error data matrix G' comprises:
based on the position coordinates of the invalid data pointsCalculating fitting values +.for each coordinate position in the template centered on the invalid data point by equation (3)>；
From the data matrixData point value +.>Wherein->1 to 8;
when there are n invalid data points within the template, the valid data points of the template will beA plurality of;
equation (4) represents an alternative value for the invalid data point as:
(4)
obtaining reflector surface shape data matrix for digital modeling of large caliber space telescope optical system。
The invention also provides a system for correcting interferometric mirror surface shape error data points, comprising:
the acquisition unit acquires cvg format surface shape data from interferometer software, performs data preprocessing, and intercepts an effective reflector surface shape error data matrix A;
the first processing unit is used for processing the data matrix A by using a median filter to obtain a reflector surface shape error data matrix B;
a recording unit for setting a threshold T, and recording the space coordinates of the data points when the difference between the corresponding data points of a certain data matrix A and a certain data matrix B is larger than the threshold TThe data point where the spatial coordinates are recorded is an invalid data point;
the second processing unit is used for selecting data points of the data matrix A, wherein mirror surface shape error edge data points and invalid data points are not selected, and performing Zernike polynomial fitting;
the third processing unit is used for subtracting an error term generated by the optical element adjustment deviation of the interference light path in the data matrix A based on fitting coefficients in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix D;
a fourth processing unit, based on the fitting coefficient in the Zernike polynomial fitting, replaces the reflector surface shape error edge data point in the data matrix D with a polynomial fitting reflector surface shape error reconstruction data point to obtain a reflector surface shape error data matrix E;
a fifth processing unit for fitting the spatial coordinates based on fitting coefficients in the Zernike polynomial fittingAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final actually measured surface shape error data matrix G.
Compared with the prior art, the application has the following beneficial effects: according to the method and the system for correcting the interferometer to measure the mirror surface shape error data points, cvg format surface shape data is obtained from interferometer software, data preprocessing is carried out, an effective mirror surface shape error data matrix A is intercepted, and then the surface shape data obtained by the interferometer is corrected through the technical scheme of removing data point error items, replacing edge data points with reconstructed data points and identifying and replacing invalid data points, so that the precision of the mirror surface shape data required by digital modeling of an optical system is improved, and the requirement of accurately constructing a digital space telescope optical model is met.
Drawings
FIG. 1 is a flow chart of a method for correcting interferometric mirror surface shape error data points provided in accordance with embodiment 1 of the present invention;
FIG. 2 is a view of an intercept of data of the shape of an effective mirror provided in accordance with embodiment 1 of the present invention;
FIG. 3 is a schematic view of a median filter template provided in accordance with embodiment 1 of the present invention;
FIG. 4 is a schematic diagram of the difference between the data points used before and after filtering provided in accordance with example 1 of the present invention;
FIG. 5 is a schematic illustration of a template centered on invalid data points provided in accordance with embodiment 1 of the present invention;
FIG. 6 is a schematic diagram of a template provided when there are 1 invalid data points in the template other than the center, in accordance with embodiment 1 of the present invention;
FIG. 7 is a schematic diagram of the connection of unit modules of a system for correcting interferometric specular error data points in accordance with embodiment 2 of the present invention.
Wherein reference numerals include:
1-interferometer camera target surface; 2-interferometer camera target surface data points; the 3-mirror surface corresponds to the active data area; 4-surface-profile sagittal height data points; 5-filtered surface profile sagittal data points;
100-a system for correcting interferometric specular error data points;
10-an acquisition unit; 20-a first processing unit; 30-a recording unit; 40-a second processing unit; 50-a third processing unit; 60-a fourth treatment unit; 70-a fifth processing unit.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, like modules are denoted by like reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, a detailed description thereof will not be repeated.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limiting the invention.
Example 1;
a method of correcting interferometric measured mirror surface shape error data points, as shown in fig. 1, comprising:
s1, acquiring cvg format surface shape data from interferometer software, preprocessing the data, and intercepting an effective reflector surface shape error data matrix A;
s2, processing the data matrix A by using a median filter to obtain a reflector surface shape error data matrix B;
s3, setting a threshold T, and recording the space coordinates of the data points when the difference value of one data point corresponding to the data matrix A and the data matrix B is larger than the threshold TThe data point where the spatial coordinates are recorded is an invalid data point;
s4, selecting data points of the data matrix A, wherein mirror surface shape error edge data points and invalid data points are not selected, and performing Zernike polynomial fitting;
s5, subtracting an error term generated by the optical element adjustment deviation of the interference light path in the data matrix A based on fitting coefficients in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix D;
s6, replacing the reflector surface shape error edge data points in the data matrix D by polynomial fitting reflector surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix E;
s7, based on fitting coefficients in the Zernike polynomial fitting, the space coordinates are obtainedAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final surface shape data matrix G.
The current part of interferometer software has a data conversion function, and can convert the surface shape data format into a format meeting the requirements of optical design software. In addition, after the mirror processing is completed, the residual surface shape error of the mirror surface is in a continuous state, and no abrupt points (invalid data points) exist in the surface shape data points. The median filter is a nonlinear smoothing technique that can identify and replace abrupt points in the mirror surface shape error data points; discrete surface shape error data points can be characterized by continuous functions through Zernike polynomial fitting, and partial data points are reasonably corrected through the function values.
That is, the shape data in cvg format is acquired by interferometer software and then the valid mirror shape error data matrix a is truncated. All data points in the data matrix a excluding the edge data points and the invalid data points are selected to perform Zernike polynomial fitting, and it is understood that the Zernike polynomial fitting coefficient is a standard fitting coefficient in this embodiment.
Further, based on the fitting coefficients in the Zernike polynomial fitting, the error term in the original data matrix a is subtracted (removed) to obtain a data matrix D. And based on the Zernike polynomial fitting coefficient, the reconstructed data points are used for replacing the edge data points in the original data matrix D to obtain a data matrix E, so that errors generated by diffraction are reduced.
Processing the data matrix A by using a median filter to obtain a data matrix B, and recording the space coordinates of the data points when the difference value of one data matrix A and the corresponding data points of the data matrix B is larger than the threshold value TWherein m is>p，n>q, wherein m, n, p and q are positive integers.
The spatial coordinates of the invalid data points are also based on the fitting coefficients in the Zernike polynomial fittingAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final corrected surface shape data matrix G.
It should be further noted that, the data matrix A, B, D, E, G is an m×n matrix, and this embodiment provides a method for correcting the surface shape error data point of the reflector measured by the interferometer, and by means of removing the data point error, reconstructing the edge data point and identifying and replacing the invalid data point, the surface shape error data obtained by the interferometer is corrected, so as to improve the accuracy of the surface shape error parameter of the reflector required by the digital modeling of the optical system.
In this embodiment, the "obtaining cvg format surface shape data from interferometer software, performing data preprocessing, and intercepting the" performing data preprocessing "in the effective mirror surface shape error data matrix a" includes data format conversion, data scaling, and unit conversion;
the "intercepting the effective mirror surface shape error data matrix a" is intercepting the effective mirror surface shape error data matrix a from the interference camera target surface, that is, as shown in fig. 2, intercepting is that an effective data point (black point) on the interferometer camera target surface circumscribes a rectangular data matrix. Specifically, reference numeral 1 is an interferometer camera target surface; reference numeral 2, i.e. the light dots are interferometer camera target surface data points and are invalid data points to be removed; reference numeral 3 denotes a mirror surface corresponding to an effective data area (circular, for example); reference numeral 4, i.e. the dark dot, is a surface-shaped sagittal data point.
If the surface of the detected reflecting mirror is aspheric, and the CGH (Computer Generated Holograms) optical path is adopted to detect the surface shape error, the data preprocessing further comprises correcting projection distortion.
In this embodiment, the "processing the data matrix a with a median filter to obtain the mirror surface shape error data matrix B" includes:
constructing a 3×3 median filter;
the median filter ranks all data points in the template;
and obtaining intermediate values of all arranged data points in the template and replacing the current values of black data points in the template to obtain a reflector surface shape error data matrix B.
As described above, the median filter template (light black is the replaced data point) is shown in fig. 3. Namely, the filter is used for carrying out nonlinear smoothing processing on the mirror surface shape error data.
In this embodiment, the "set threshold T" records the spatial coordinates of the data points when the difference between the corresponding data points of a certain data matrix a and the corresponding data points of a data matrix B is greater than the threshold TThe data points where the spatial coordinates are recorded are invalid data points "comprising:
setting a threshold T according to the peak Gu Chazhi of the data matrix a;
the threshold T may be several times the peak-to-valley difference in the data matrix a, as described above, with the purpose of ensuring that valid data points are not replaced. As shown in fig. 4, the difference between the data points before and after filtering is to be noted, reference numeral 3 is an effective data area corresponding to the surface of the reflecting mirror on the target surface of the original interferometer camera, that is, a data matrix a, and reference numeral 5 is a surface-shaped sagittal data point after filtering, that is, a data matrix B formed after filtering the data matrix a. The data matrix A corresponds to the data matrix B one by one and is two values before and after filtering.
It should be further noted that the dark dots within the circles of reference numerals 3 and 5 are valid data points, but the light "invalid data points" within the rectangle need to be reserved, so as to form a square matrix, namely, correspond to the data matrix a and the data matrix B respectively.
Acquiring the difference value of each corresponding data point in the data matrix A before filtering and the data matrix B after filtering;
for example, if A-B/>>T, then remain the->Is defined in the drawing) is provided.
If a data pointIf the difference is greater than the threshold value T, recording the position coordinates of the data points；
And maintaining the coordinates of all the data points with the difference value larger than the threshold value T, wherein the data points recorded with the space coordinates are invalid data points.
In this embodiment, the "selecting the data points of the data matrix a, where the mirror surface shape error edge data points and the invalid data points are not selected, and performing the Zernike polynomial fitting" includes:
selecting data points of the data matrix A for Zernike polynomial fitting, wherein mirror surface shape error edge data points and invalid data points are not selected;
constructing a fitting equation (1):
(1)
in the formula (1) of the formula,representing the Zernike expression at coordinates +.>Base value at>Is the coefficient of Zernike which is the coefficient of Zernike,and->The number of items is consistent, total->An item.
In this embodiment, the "subtracting the error term in the data matrix a due to the optical element adjustment deviation of the interference optical path based on the fitting coefficient in the Zernike polynomial fitting" to obtain the mirror surface shape error data matrix D "includes:
the fitting coefficients obtained by the equation (1) are combined in the Fringe Zernike coefficients to be characterized as the 1 st, 2 nd, 3 rd and 4 th items to obtain error items;
subtracting the error term from the data matrix A to obtain a reflector surface shape error data matrix D, wherein the specific equation is as follows:
(2)
in the equation (2) of the formula,(j=1 to 4) is a full-aperture Zernike substrate,/>(j=1 to 4) are the pan, tilt and defocus terms of the Zernike polynomial fit.
When the interferometer detection light path has an adjustment error, the reflection mirror surface shape error has a translational, tilting and defocusing aberration component, namely, the translational, tilting and defocusing acquisition error term is characterized by a Zernike coefficient. Thus, after the error term is obtained, the obtained error term is subtracted from the data matrix a to obtain the mirror surface shape error data matrix D.Is one data point in the two-dimensional data matrix a.
In this embodiment, the "replacing the edge mirror shape error edge data points in the data matrix D with polynomial fit mirror shape error reconstruction data points based on the fitting coefficients in the Zernike polynomial fit" includes:
calculating mirror surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting, wherein a calculation equation (3) is as follows:
(3)
in the equation (3) of the formula,reconstructing data points for mirror surface shape errors, +.>Is->The term Zernike base is at the coordinates +.>A base value at; the number of the mirror surface shape error reconstruction data points is determined by a threshold W; when mirror shape error data points exist in a certain circle +.>Above W, then any data point in the circle +.>Are all covered byAfter the replacement, obtaining a reflector surface shape error data matrix +.>. It is worth noting that equation (3) starts from the fifth term and the pan, tilt, and defocus terms above need to be removed.
In this embodiment, the "fitting coefficients within the Zernike polynomial fit" coordinate the spaceCorrecting and replacing the corresponding data value by using a function fitting value to obtain a final surface shape error data matrix G' comprises:
based on the position coordinates of the invalid data pointsCalculating fitting values +.for each coordinate position in the template centered on the invalid data point by equation (3)>The method comprises the steps of carrying out a first treatment on the surface of the As shown in fig. 5, a template centered on invalid data points.
From the data matrixData point value +.>（/>: data matrix->In coordinates +.>A number of data points centered around the invalid data point), wherein,/-is>1 to 8 (intermediate points removed);
when there are n (n is less than 8) invalid data points within the template, the valid data points of the template will beA plurality of; wherein j is a positive integer with a maximum value equal to 8, and n is a positive integer less than or equal to j. Referring again to fig. 5, fig. 5 shows that when j=8, n=0, only the middle blank box is an invalid data point and the dark box is a non-invalid data point. As shown in fig. 6, when j=8 and n=1, the dark box is a non-invalid data point, and there is an invalid data point of a blank box in addition to the invalid data point of the middle blank box.
Equation (4) represents an alternative value for the invalid data point as:
(4)
that is, space coordinatesCorresponding data value (+)>) Values fitted by a function +.>And (5) replacing.
Therefore, based on the mirror face shape error data matrix E, the space coordinates are calculated based on the fitting coefficients in the Zernike polynomial fittingCorrecting and replacing the corresponding data value by using a function fitting value to finally obtain a reflector surface shape data matrix for digital modeling of the large-caliber space telescope optical system>。
Example 2
As shown in FIG. 7, the present invention also provides a system 100 for correcting interferometric measured mirror surface shape error data points, comprising:
the acquisition unit 10 acquires cvg format surface shape data from interferometer software, performs data preprocessing, and intercepts an effective reflector surface shape error data matrix A;
a first processing unit 20, configured to process the data matrix a by using a median filter, to obtain a mirror surface shape error data matrix B;
a recording unit 30 for setting a threshold T, and recording the space coordinates of the data points when the difference between the corresponding data points of a certain data matrix A and the corresponding data points of a data matrix B is larger than the threshold TThe data points recorded with the spatial coordinates are invalidData points;
a second processing unit 40, selecting a data point of the data matrix a, wherein a mirror surface shape error edge data point and the invalid data point are not selected, and performing Zernike polynomial fitting;
a third processing unit 50, based on the fitting coefficient in the Zernike polynomial fitting, subtracts an error term in the data matrix a, which is generated due to the adjustment deviation of the optical element of the interference light path, to obtain a reflector surface shape error data matrix D;
a fourth processing unit 60, based on fitting coefficients within the Zernike polynomial fit, replaces the mirror surface shape error edge data points in the data matrix D with polynomial fit mirror surface shape error reconstruction data points, resulting in a mirror surface shape error data matrix E;
a fifth processing unit 70 for fitting the spatial coordinates based on fitting coefficients within the Zernike polynomial fitAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final actually measured surface shape error data matrix G.
While embodiments of the present invention have been illustrated and described above, it will be appreciated that the above described embodiments are illustrative and should not be construed as limiting the invention. Variations, modifications, alternatives and variations of the above-described embodiments may be made by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention do not limit the scope of the present invention. Any other corresponding changes and modifications made in accordance with the technical idea of the present invention shall be included in the scope of the claims of the present invention.
Claims (9)
1. A method of correcting interferometric measured mirror surface shape error data points, comprising:
acquiring cvg format surface shape data from interferometer software, preprocessing the data, and intercepting an effective reflector surface shape error data matrix A;
processing the data matrix A by using a median filter to obtain a reflector surface shape error data matrix B;
setting a threshold T, and recording the space coordinates of the data points when the difference value of one data point of the data matrix A and the corresponding data point of the data matrix B is larger than the threshold TThe data point where the spatial coordinates are recorded is an invalid data point;
selecting data points of the data matrix A, wherein mirror surface shape error edge data points and invalid data points are not selected, and performing Zernike polynomial fitting;
subtracting an error term generated by the optical element adjustment deviation of the interference light path in the data matrix A based on a fitting coefficient in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix D;
replacing the mirror surface shape error edge data points in the data matrix D by polynomial fitting mirror surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting to obtain a mirror surface shape error data matrix E;
based on fitting coefficients within the Zernike polynomial fit, the spatial coordinates are determinedAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final surface shape data matrix G.
2. The method of correcting interferometric mirror surface error data points of claim 1, wherein the data preprocessing comprises data format conversion, data scaling and unit conversion;
the intercepting effective reflector surface shape error data matrix A is obtained by intercepting the effective reflector surface shape error data matrix A from the interference camera target surface.
3. The method of correcting interferometric specular error data points of claim 1, wherein processing the data matrix a with a median filter to obtain a specular error data matrix B comprises:
constructing a 3×3 median filter;
the median filter ranks all data points in the template;
and obtaining intermediate values of all arranged data points in the template and replacing the current values of black data points in the template to obtain a reflector surface shape error data matrix B.
4. A method of correcting interferometric mirror surface error data points according to claim 3, characterized in that the set threshold T, when the difference between a certain one of the data matrix a and a corresponding data point of the data matrix B is greater than the threshold T, the spatial coordinates of the data point are recordedThe data points where the spatial coordinates are recorded are invalid data points including:
setting the threshold T according to the peak Gu Chazhi of the data matrix a;
acquiring the difference value of each corresponding data point in the data matrix A before filtering and the data matrix B after filtering;
if the difference value of a data point is greater than the threshold value T, recording the position coordinates of the data point；
And maintaining the coordinates of all the data points with the difference value larger than the threshold value T, wherein the data points recorded with the space coordinates are invalid data points.
5. The method of correcting interferometric mirror surface error data points according to claim 4, wherein said selecting data points of said data matrix a, wherein mirror surface error edge data points and said null data points are not selected, and performing a Zernike polynomial fit comprises:
selecting data points of the data matrix A for Zernike polynomial fitting, wherein mirror surface shape error edge data points and invalid data points are not selected;
constructing a fitting equation (1):
(1)
in the equation (1) for the case of the liquid,representing the Zernike expression at coordinates +.>Base value at>For Zernike coefficients, +.>And->The number of items is consistent, total->An item.
6. The method of claim 5, wherein subtracting the error term in the data matrix a due to the optical element tuning deviation of the interference light path from the fitting coefficients in the Zernike polynomial fit to obtain the mirror shape error data matrix D comprises:
the fitting coefficients obtained by the equation (1) are combined in the fringe Zernike coefficients to be characterized as the 1 st, 2 nd, 3 rd and 4 th items to obtain error terms;
subtracting the error term from the data matrix A to obtain a reflector surface shape error data matrix D, wherein the specific equation (2) is as follows:
(2)
in the equation (2) described above,j=1 to 4 is the full aperture Zernike basis, < >>J=1 to 4 are the pan, tilt and defocus terms of the Zernike polynomial fit.
7. The method of correcting interferometric mirror shape error data points according to claim 6, wherein said replacing edge mirror shape error edge data points in the data matrix D with polynomial fit mirror shape error reconstruction data points based on fitting coefficients within the Zernike polynomial fit, obtaining a mirror shape error data matrix E comprises:
calculating mirror surface shape error reconstruction data points based on fitting coefficients in the Zernike polynomial fitting, wherein a calculation equation (3) is as follows:
(3)
in the equation (3) described above,reconstructing data points for mirror surface shape errors, +.>Is->Term ZerniThe ke substrate is at coordinates->A base value at; the number of the mirror surface shape error reconstruction data points is determined by a threshold W; when mirror shape error data points exist in a certain circle +.>Above W, then any data point in the circle +.>Are all covered byAfter the replacement, obtaining a reflector surface shape error data matrix +.>。
8. The method of correcting interferometric specular error data points according to claim 7, wherein said spatial coordinates are based on fitting coefficients within said Zernike polynomial fitCorrecting and replacing the corresponding data value by using a function fitting value, wherein obtaining a final surface shape error data matrix G comprises the following steps:
based on the position coordinates of the invalid data pointsCalculating fitting values +.for each coordinate position in the template centered on the invalid data point by equation (3)>；
From the data matrixData point value +.>Wherein->1 to 8;
when there are n invalid data points within the template, the valid data points of the template will beA plurality of;
equation (4) represents an alternative value for the invalid data point as:
(4)
obtaining reflector surface shape data matrix for digital modeling of large caliber space telescope optical system。
9. A system for correcting interferometric specular error data points, comprising:
the acquisition unit acquires cvg format surface shape data from interferometer software, performs data preprocessing, and intercepts an effective reflector surface shape error data matrix A;
the first processing unit is used for processing the data matrix A by using a median filter to obtain a reflector surface shape error data matrix B;
a recording unit for setting a threshold T, and recording the space coordinates of the data points when the difference between the corresponding data points of a certain data matrix A and a certain data matrix B is larger than the threshold TIs recorded asThe data points of the spatial coordinates are invalid data points;
the second processing unit is used for selecting data points of the data matrix A, wherein mirror surface shape error edge data points and invalid data points are not selected, and performing Zernike polynomial fitting;
the third processing unit is used for subtracting an error term generated by the optical element adjustment deviation of the interference light path in the data matrix A based on fitting coefficients in the Zernike polynomial fitting to obtain a reflector surface shape error data matrix D;
a fourth processing unit, based on the fitting coefficient in the Zernike polynomial fitting, replaces the reflector surface shape error edge data point in the data matrix D with a polynomial fitting reflector surface shape error reconstruction data point to obtain a reflector surface shape error data matrix E;
a fifth processing unit for fitting the spatial coordinates based on fitting coefficients in the Zernike polynomial fittingAnd correcting and replacing the corresponding data value by using a function fitting value to obtain a final actually measured surface shape error data matrix G.
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