A visibility inversion method and device suitable for infrared scanning laser radar

Abstract

A visibility inversion method and device suitable for infrared scanning laser radar, including fitting and calculating multiple estimated extinction coefficients according to a predetermined atmospheric interval to be fitted; generating corresponding estimated extinction coefficient profiles based on multiple estimated extinction coefficients, determining the uniform atmospheric interval in the global atmospheric interval according to the estimated extinction coefficient profile; generating an extinction coefficient profile corresponding to the uniform atmospheric interval, calculating the error value between the extinction coefficient profile corresponding to the uniform atmospheric interval and the estimated extinction coefficient profile; performing iterative calculation according to the error value, a preset error threshold and the extinction coefficient profile corresponding to the uniform atmospheric interval, until the final extinction coefficient profile that meets the error value requirement is inverted, and calculating the visibility of the global atmospheric interval according to the final extinction coefficient profile. The technical problem of low accuracy of visibility inversion using infrared scanning laser radar in an inhomogeneous atmosphere is solved.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a visibility inversion method and device suitable for infrared scanning laser radar. Background Art

[0002] Atmospheric visibility refers to the maximum distance at which a person with normal vision can identify a target object from the background. It is a meteorological element that is focused on in the fields of meteorology, aviation and navigation. The main factor affecting atmospheric visibility is the transparency of the atmosphere. At present, fully automatic visibility measuring instruments are divided into forward scattering instruments, atmospheric transmission instruments and laser radars. Among them, laser radars have the advantages of long detection distance, high temporal and spatial resolution and small size. Laser radars can be installed on land and ships to provide reliable visibility data for aviation and navigation safety.

[0003] Laser radar is usually installed in areas with a lot of human activities, so human eye safety is an issue that laser radar must consider. In order to conduct visibility observation over a large range while ensuring human eye safety, an infrared scanning laser radar is proposed. However, infrared scanning laser radars that can measure visibility have difficulty in detecting in an uneven atmosphere, resulting in low accuracy of visibility inverted using the infrared scanning laser radar. Summary of the invention

[0004] The main technical problem solved by the present invention is that the accuracy of visibility inversion using infrared scanning laser radar in an inhomogeneous atmosphere is low.

[0005] According to the first aspect, an embodiment provides a visibility inversion method applicable to an infrared scanning laser radar, the visibility inversion method comprising:

[0006] A plurality of estimated extinction coefficients are calculated by fitting according to a predetermined atmospheric interval to be fitted; wherein the atmospheric interval to be fitted is a local atmospheric interval selected when performing atmospheric detection in a global atmospheric interval using a laser radar, and the plurality of estimated extinction coefficients include an estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval, and the global atmospheric interval contains an inhomogeneous atmosphere;

[0007] generating a corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, and determining a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile;

[0008] Generate an extinction coefficient profile corresponding to the uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile;

[0009] Iterative calculation is performed according to the error value, the preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated according to the final extinction coefficient profile.

[0010] In some embodiments, determining the uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile comprises:

[0011] Deriving each of the estimated extinction coefficients in the estimated extinction coefficient profile to obtain a derivative corresponding to each of the estimated extinction coefficients, and generating a corresponding derivative profile based on the derivatives corresponding to the plurality of estimated extinction coefficients;

[0012] Dividing the derivative profile into a plurality of derivative profile segments using a window of a predefined size;

[0013] For each derivative profile segment, obtaining the absolute value of each derivative in the derivative profile segment, and performing an average calculation on the absolute value of each derivative in the derivative profile segment to obtain an average value of the derivative values ​​of the derivative profile segment;

[0014] A uniform atmosphere interval in the global atmosphere interval is selected based on an average value of the derivative values ​​of each of the derivative profile segments.

[0015] In some embodiments, selecting the uniform atmosphere interval in the global atmosphere interval based on the average value of the derivative value of each derivative profile segment includes:

[0016] Determine the difference between the average value of the derivative value of each derivative profile segment and a preset reference threshold;

[0017] If there is only one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval where the derivative profile segment is located is selected as the uniform atmospheric interval in the global atmospheric interval;

[0018] If there is more than one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval in which the derivative profile segment whose average derivative value is less than the reference threshold and which meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0019] In some embodiments, the iterative calculation for the i-th time includes:

[0020] Determine the difference between the i-th error value and the preset error threshold;

[0021] When the i-th error value is greater than the error threshold, re-determine the i+1-th uniform atmosphere interval according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, generate the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval, and calculate the i+1-th error value between the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval and the extinction coefficient profile corresponding to the i-th uniform atmosphere interval;

[0022] When the i-th error value is less than or equal to the error threshold, the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is used as the final extinction coefficient profile; wherein the range of i is [1, 30].

[0023] In some embodiments, the step of calculating a plurality of estimated extinction coefficients by fitting according to a predetermined atmospheric interval to be fitted includes:

[0024] Calculating a fitting signal of the atmospheric interval to be fitted according to the distance correction signal of the atmospheric interval to be fitted, and calculating an extinction coefficient of a reference atmospheric position in the global atmospheric interval according to the fitting signal and a preset fitting equation;

[0025] A plurality of estimated extinction coefficients are iteratively calculated based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm.

[0026] In some embodiments, the extinction coefficient of the reference atmospheric position is the extinction coefficient of the Ith atmospheric position, and the multiple estimated extinction coefficients include the extinction coefficient of the Ith atmospheric position, the extinction coefficient of the I-1th atmospheric position, ..., the extinction coefficient of the INth atmospheric position, and N is an integer not less than 1;

[0027] Based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm, a plurality of estimated extinction coefficients are iteratively calculated, including:

[0028] Taking the extinction coefficient of the I-th atmospheric position as an initial value, and calculating the extinction coefficient of the I-1-th atmospheric position according to the initial value and the extinction coefficient inversion algorithm;

[0029] The extinction coefficient of the I-(n+1)th atmospheric position is calculated according to the extinction coefficient of the Inth atmospheric position and the extinction coefficient inversion algorithm, where n is in the range of [1, N-1].

[0030] In some embodiments, each of the estimated extinction coefficients satisfies a preset extinction coefficient range.

[0031] According to the second aspect, an infrared scanning laser radar is provided in one embodiment, wherein the infrared scanning laser radar includes a laser transmitting module, a signal receiving module and a processor;

[0032] The laser emission module is used to emit the laser beam generated by the laser into the atmosphere;

[0033] The signal receiving module is used to receive the echo signal generated after the laser beam interacts in the atmosphere;

[0034] The processor is used to calculate the visibility of the atmosphere based on the atmosphere interval to be fitted determined according to the echo signal using the visibility inversion method.

[0035] According to the third aspect, an embodiment provides a visibility inversion device applicable to an infrared scanning laser radar, the visibility inversion device comprising:

[0036] An extinction coefficient estimation module is used to calculate a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted; wherein the atmospheric interval to be fitted is a local atmospheric interval selected when performing atmospheric detection in a global atmospheric interval using a laser radar, and the plurality of estimated extinction coefficients include an estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval, and the global atmospheric interval contains an inhomogeneous atmosphere;

[0037] A uniform atmosphere interval determination module, configured to generate a corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, and determine a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile;

[0038] An error value calculation module, used to generate an extinction coefficient profile corresponding to the uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile;

[0039] The visibility calculation module is used to perform iterative calculations based on the error value, a preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated based on the final extinction coefficient profile.

[0040] According to a fourth aspect, an embodiment provides a computer program product, comprising a computer program and / or instructions, wherein the computer program and / or instructions implement the visibility inversion method when executed by a processor.

[0041] According to the visibility inversion method, device, infrared scanning laser radar, and computer program product applicable to infrared scanning laser radar of the above-mentioned embodiment, since multiple estimated extinction coefficients are calculated based on the predetermined atmospheric interval to be fitted, and corresponding estimated extinction coefficient profiles are generated based on the multiple estimated extinction coefficients, the uniform atmospheric interval in the global atmospheric interval can be determined based on the estimated extinction coefficient profile. Iterative calculation is performed based on the extinction coefficient profile corresponding to the uniform atmospheric interval, and the uniform atmospheric interval is continuously searched, and an accurate extinction coefficient profile is obtained based on the uniform atmospheric interval, so that the visibility is calculated based on the accurate extinction coefficient profile, thereby improving the accuracy of visibility inversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flowchart of a visibility inversion method applicable to an infrared scanning laser radar according to an embodiment of the present application;

[0043] Figure 2 A flowchart of an embodiment of calculating a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted;

[0044] Figure 3 A flowchart of an embodiment of iteratively calculating a plurality of estimated extinction coefficients based on the extinction coefficient of a reference atmospheric position and a preset extinction coefficient inversion algorithm;

[0045] Figure 4 A flowchart of determining a uniform atmosphere interval in a global atmosphere interval according to an estimated extinction coefficient profile according to an embodiment;

[0046] Figure 5 A flowchart of selecting a uniform atmosphere interval in a global atmosphere interval based on an average value of derivative values ​​of each derivative profile segment according to an embodiment;

[0047] Figure 6 A flowchart of the i-th iterative calculation of an embodiment;

[0048] Figure 7 A schematic diagram of the structure of an infrared scanning laser radar according to an embodiment;

[0049] Figure 8 The present invention is a schematic structural diagram of a visibility inversion device suitable for an infrared scanning laser radar according to an embodiment. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0051] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0052] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0053] Please refer to Figure 1 In an embodiment of the present invention, a visibility inversion method suitable for an infrared scanning laser radar is provided. The visibility inversion method includes steps S10 to S40, which are described in detail below.

[0054] Step S10: Calculate and fit a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted.

[0055] In some embodiments, the global atmospheric interval contains an inhomogeneous atmosphere, and a local atmospheric interval is selected as the atmospheric interval to be fitted when performing atmospheric detection in the global atmospheric interval using an infrared scanning laser radar, wherein the infrared scanning laser radar can be used to perform a wide range of visibility observations while ensuring the safety of human eyes. For example, a local atmospheric interval (r1, r2) in the global atmospheric interval is selected as the atmospheric interval to be fitted, and the local atmospheric interval (r1, r2) is a relatively uniform atmospheric interval selected by the infrared scanning laser radar when selecting the interval, but a subsequent iterative inversion process is still required to determine an accurate uniform atmospheric interval. Multiple estimated extinction coefficients are calculated by fitting based on the predetermined atmospheric interval to be fitted, wherein the multiple estimated extinction coefficients include the estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval.

[0056] Please refer to Figure 2 In some embodiments, step S10 calculates a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted, including steps S11 to S12, which are described in detail below.

[0057] Step S11: calculating a fitting signal of the atmospheric interval to be fitted according to the distance correction signal of the atmospheric interval to be fitted, and calculating the extinction coefficient of the reference atmospheric position in the global atmospheric interval according to the fitting signal and a preset fitting equation.

[0058] In this embodiment, the distance correction signal of the atmospheric interval to be fitted refers to the RCS signal of the local atmospheric interval (r1, r2). The distance correction signal of the atmospheric interval to be fitted is fitted using the least squares method or other optimization algorithms to obtain the fitting signal y of the atmospheric interval to be fitted. The preset fitting equation is: , where a is the first fitting coefficient and b is the second fitting coefficient. is the spatial resolution of the distance correction signal. The first fitting coefficient a is expressed as , the second fitting coefficient b is expressed as , where C represents the lidar system constant, represents the aerosol extinction coefficient, that is, the aerosol extinction coefficient in the local atmospheric interval (r1, r2), represents the extinction coefficient of atmospheric molecules, represents the radar ratio of aerosol, Indicates the radar ratio of molecules. Due to the extinction coefficient of atmospheric molecules It can be obtained through the standard atmosphere model. Therefore, after simplifying the expression of the second fitting coefficient, it can be known that the extinction coefficient at the boundary position of the aerosol is obtained by It is calculated that if the reference atmospheric position is set to I, the formula for calculating the extinction coefficient at the reference atmospheric position can be derived as follows: ,in, Represents the extinction coefficient at a reference atmospheric position.

[0059] Step S12: Iteratively calculating a plurality of estimated extinction coefficients based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm.

[0060] In some embodiments, the extinction coefficient of the reference atmospheric position is the extinction coefficient of the Ith atmospheric position, and the multiple estimated extinction coefficients include the extinction coefficient of the Ith atmospheric position, the extinction coefficient of the I-1th atmospheric position,..., the extinction coefficient of the INth atmospheric position, where N is an integer not less than 1.

[0061] Please refer to Figure 3 Step S12 iteratively calculates a plurality of estimated extinction coefficients based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm, including steps S121 to S122, which are described in detail below.

[0062] Step S121: taking the extinction coefficient of the Ith atmospheric position as the initial value, and calculating the extinction coefficient of the I-1th atmospheric position according to the initial value and the extinction coefficient inversion algorithm.

[0063] In this embodiment, the calculation formula of the extinction coefficient inversion algorithm is as follows:

[0064] ,

[0065] in, represents the extinction coefficient at the I-1th atmospheric position, that is, the extinction coefficient at the boundary position of the aerosol, represents the radar ratio of aerosol, represents the radar ratio of the molecule, represents the extinction coefficient of the molecule at the I-1th atmospheric position, which can be obtained from the standard atmospheric model. is the RCS signal at the Ith atmospheric position, , represents the molecular backscattering coefficient, obtained from the standard atmosphere model, is the spatial resolution of the distance-corrected signal.

[0066] In some embodiments, the radar ratio of the aerosol can be 50, the radar ratio of the molecule Can be 3.

[0067] Step S122: Calculate the extinction coefficient of the I-(n+1)th atmospheric position according to the extinction coefficient of the Inth atmospheric position and the extinction coefficient inversion algorithm.

[0068] In this embodiment, the range of n is [1, N-1], where N is an integer not less than 1.

[0069] In some embodiments, a range of extinction coefficients is pre-established ,in, is the upper limit of the extinction coefficient range, which can be determined by local historical visibility data. is the lower limit of the extinction coefficient range, which is usually 0. The extinction coefficient at the reference atmospheric position, and the extinction coefficient calculated based on the extinction coefficient at the reference atmospheric position and the extinction coefficient inversion algorithm are compared with the upper and lower limits of the extinction coefficient range, and each estimated extinction coefficient finally obtained satisfies the extinction coefficient range. If the extinction coefficient at the reference atmospheric position or the extinction coefficient inverted by the extinction coefficient inversion algorithm does not satisfy the extinction coefficient range, that is, the extinction coefficient is less than the upper limit of the extinction coefficient range Or the extinction coefficient is greater than the lower limit of the extinction coefficient range , then the atmosphere interval to be fitted is re-obtained and the extinction coefficient is recalculated according to the atmosphere interval to be fitted.

[0070] In some embodiments, since the fitted distance correction signal may be interfered by noise, the extinction coefficient calculated based on the distance correction signal may not meet the range of the extinction coefficient. The initially selected interval to be fitted does not need to strictly select a uniform atmospheric interval. In the subsequent iterative calculation process, a more uniform atmospheric interval can be reselected and determined for visibility calculation.

[0071] Step S20: generating a corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, and determining a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile.

[0072] In some embodiments, the estimated extinction coefficient profile is a curve describing the estimated extinction coefficient following the change of a certain variable, for example, the variable may be height. Then, the estimated extinction coefficient profiles corresponding to a plurality of estimated extinction coefficients may be drawn with the height value as the horizontal coordinate and the estimated extinction coefficient as the vertical coordinate.

[0073] Please refer to Figure 4 In some embodiments, step S20 determines the uniform atmosphere interval in the global atmosphere interval based on the estimated extinction coefficient profile, including steps S21 to S24, which are described in detail below.

[0074] Step S21: deriving each estimated extinction coefficient in the estimated extinction coefficient profile to obtain a derivative corresponding to each estimated extinction coefficient, and generating a corresponding derivative profile based on the derivatives corresponding to the multiple estimated extinction coefficients.

[0075] In this embodiment, the step of generating corresponding derivative profiles based on derivatives corresponding to multiple estimated extinction coefficients is similar to the implementation method of generating corresponding estimated extinction coefficient profiles based on multiple estimated extinction coefficients, and will not be repeated here. The extinction coefficient profile corresponding to a uniform atmosphere is more straight, so the atmospheric range where the extinction coefficient derivative is close to 0 is considered to be a uniform atmospheric interval, so the derivative profile of the extinction coefficient becomes the basis for screening the uniform interval, and therefore, the corresponding derivative profile needs to be generated for subsequent determination of the uniform interval.

[0076] Step S22: Divide the derivative profile into a plurality of derivative profile segments using a window of a predefined size.

[0077] In this embodiment, a window with a predefined size is used to slide the window on the derivative profile, so as to divide the derivative profile into a plurality of derivative profile segments.

[0078] Step S23: For each derivative profile segment, obtain the absolute value of each derivative in the derivative profile segment, and calculate the average value of the absolute value of each derivative in the derivative profile segment to obtain the average value of the derivative value of the derivative profile segment.

[0079] Step S24: selecting a uniform atmosphere interval in the global atmosphere interval based on the average value of the derivative value of each derivative profile segment.

[0080] Please refer to Figure 5 In some embodiments, step S24 selects a uniform atmospheric interval in the global atmospheric interval based on the average value of the derivative value of each derivative profile segment, including steps S241 to S243, which are described in detail below.

[0081] Step S241: Determine whether there is only one derivative profile segment whose average derivative value is less than a reference threshold among the multiple derivative profile segments.

[0082] Step S242: If there is only one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval where the derivative profile segment is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0083] In this embodiment, the size between the average value of the derivative value of each derivative profile segment and a preset reference threshold is determined respectively. If, among multiple derivative profile segments, there is only one derivative profile segment whose average value of the derivative value is less than the reference threshold, the atmospheric interval in which the derivative profile segment is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0084] Step S243: Otherwise, when there is more than one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval in which the derivative profile segment whose average derivative value is less than the reference threshold and which meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0085] In some embodiments, there is no derivative profile segment whose average value of derivative value is less than a reference threshold value among multiple derivative profile segments, and there is more than one derivative profile segment whose average value of derivative value is less than the reference threshold value among multiple derivative profile segments. Wherein, when there is more than one derivative profile segment whose average value of derivative value is less than the reference threshold value, the atmospheric interval where the derivative profile segment whose average value of derivative value is less than the reference threshold value and which meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0086] In this embodiment, due to the characteristic that the backward solution calculated by the extinction coefficient inversion algorithm gradually stabilizes, the error near the estimated extinction coefficient profile is usually smaller than the error far away, which means that the closer extinction coefficient profile indicates a more accurate atmospheric state. Therefore, when there are multiple derivative profile segments whose average derivative values ​​are less than the reference threshold, the atmospheric interval where the derivative profile segment that meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval. Among them, the preset position condition can be the atmospheric interval corresponding to the position of the last one-third of the derivative profile segments on the derivative profile.

[0087] Step S30: Generate an extinction coefficient profile corresponding to a uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile.

[0088] In this embodiment, the corresponding extinction coefficient is calculated according to the uniform atmosphere interval, and multiple extinction coefficients are obtained according to the extinction coefficient and a preset extinction coefficient inversion algorithm. The extinction coefficient profile corresponding to the uniform atmosphere interval is generated according to the above multiple extinction coefficients. For specific implementation steps, please refer to the calculation steps in step S10 and step S20, which will not be repeated here.

[0089] In some embodiments, the extinction coefficient profile corresponding to the uniform atmosphere interval is AEC(r i_s , r i_e ), the estimated extinction coefficient profile is Pre_AEC(r i_s , r i_e ), calculate the extinction coefficient profile AEC(r i_s , r i_e ) and the estimated extinction coefficient profile Pre_AEC(ri _s0 ,ri _e0) is the root mean square error RMSE between the two. Where i represents the number of iterations, s represents the upper bound of the uniform atmosphere interval, e represents the lower bound of the uniform atmosphere interval, s0 represents the upper bound of the atmosphere interval to be fitted, and e0 represents the lower bound of the atmosphere interval to be fitted.

[0090] Step S40: Iterative calculation is performed according to the error value, the preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated according to the final extinction coefficient profile.

[0091] Please refer to Figure 6 In some embodiments, the i-th iterative calculation includes steps S41 to S43, which are described in detail below.

[0092] Step S41: determine whether the i-th error value is greater than a preset error threshold.

[0093] Step S42: When the i-th error value is greater than the error threshold, the i+1-th uniform atmosphere interval is re-determined according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval is generated, and the i+1-th error value between the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval and the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is calculated.

[0094] In this embodiment, please refer to the implementation steps of step S20 for re-determining the (i+1)th uniform atmosphere interval according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, which will not be repeated here.

[0095] Step S43: When the error value of the ith time is less than or equal to the error threshold, the extinction coefficient profile corresponding to the ith uniform atmosphere interval is used as the final extinction coefficient profile.

[0096] In some embodiments, the range of i is [1, 30].

[0097] In some embodiments, the visibility of the global atmospheric interval is calculated based on the final extinction coefficient profile and the Koschmieder principle. According to the Koschmieder principle, the calculation formula of visibility is: ,in, It represents the atmospheric extinction coefficient. The average extinction coefficient is calculated by integrating or averaging the final extinction coefficient profile in the global atmospheric interval. Substituting it into the above formula, the visibility in the global atmospheric interval can be obtained.

[0098] Please refer to Figure 7Some embodiments provide an infrared scanning laser radar, which includes a laser emitting module 10, a signal receiving module 20 and a processor 30, which are described in detail below.

[0099] The laser emitting module 10 is used to emit the laser beam generated by the laser into the atmosphere.

[0100] The signal receiving module 20 is used to receive the echo signal generated after the laser beam interacts in the atmosphere.

[0101] The processor 30 is used to calculate the atmospheric visibility by using a visibility inversion method based on the atmospheric interval to be fitted determined according to the echo signal.

[0102] In this embodiment, the visibility inversion method refers to the implementation method of step S10 to step S40, which will not be described again here.

[0103] Please refer to Figure 8 In some embodiments, a visibility inversion device suitable for an infrared scanning laser radar is provided. The visibility inversion device includes an extinction coefficient estimation module 101, a uniform atmosphere interval determination module 201, an error value calculation module 301 and a visibility calculation module 401, which are described in detail below.

[0104] The extinction coefficient estimation module 101 is used to calculate a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted.

[0105] In some embodiments, the global atmospheric interval contains an inhomogeneous atmosphere, and a local atmospheric interval is selected as the atmospheric interval to be fitted when performing atmospheric detection in the global atmospheric interval using an infrared scanning laser radar, wherein the infrared scanning laser radar can be used to perform a wide range of visibility observations while ensuring the safety of human eyes. For example, a local atmospheric interval (r1, r2) in the global atmospheric interval is selected as the atmospheric interval to be fitted, and the local atmospheric interval (r1, r2) is a relatively uniform atmospheric interval selected by the infrared scanning laser radar when selecting the interval, but a subsequent iterative inversion process is still required to determine an accurate uniform atmospheric interval. Multiple estimated extinction coefficients are calculated by fitting based on the predetermined atmospheric interval to be fitted, wherein the multiple estimated extinction coefficients include the estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval.

[0106] Please refer back to Figure 2 In some embodiments, the extinction coefficient estimation module 101 can calculate multiple estimated extinction coefficients according to the predetermined atmospheric interval to be fitted by the following method, which is described in detail below.

[0107] The extinction coefficient estimation module 101 calculates a fitting signal of the atmospheric interval to be fitted according to the distance correction signal of the atmospheric interval to be fitted, calculates the extinction coefficient of the reference atmospheric position in the global atmospheric interval according to the fitting signal and a preset fitting equation, and iteratively calculates multiple estimated extinction coefficients based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm.

[0108] In this embodiment, the distance correction signal of the atmospheric interval to be fitted refers to the RCS signal of the local atmospheric interval (r1, r2). The extinction coefficient estimation module 101 uses the least squares method or other optimization algorithms to fit the distance correction signal of the atmospheric interval to be fitted to obtain the fitting signal y of the atmospheric interval to be fitted. The preset fitting equation is: , where a is the first fitting coefficient and b is the second fitting coefficient. is the spatial resolution of the distance correction signal. The first fitting coefficient a is expressed as , the second fitting coefficient b is expressed as , where C represents the lidar system constant, represents the aerosol extinction coefficient, that is, the aerosol extinction coefficient in the local atmospheric interval (r1, r2), represents the extinction coefficient of atmospheric molecules, represents the radar ratio of aerosol, Indicates the radar ratio of molecules. Due to the extinction coefficient of atmospheric molecules It can be obtained through the standard atmosphere model. Therefore, after simplifying the expression of the second fitting coefficient, it can be known that the extinction coefficient at the boundary position of the aerosol is obtained by It is calculated that if the reference atmospheric position is set to I, the formula for calculating the extinction coefficient at the reference atmospheric position can be derived as follows: ,in, Represents the extinction coefficient at a reference atmospheric position.

[0109] In some embodiments, the extinction coefficient of the reference atmospheric position is the extinction coefficient of the Ith atmospheric position, and the multiple estimated extinction coefficients include the extinction coefficient of the Ith atmospheric position, the extinction coefficient of the I-1th atmospheric position,..., the extinction coefficient of the INth atmospheric position, where N is an integer not less than 1.

[0110] Please refer back to Figure 3 The extinction coefficient estimation module 101 iteratively calculates multiple estimated extinction coefficients based on the extinction coefficient of the reference atmospheric position and the preset extinction coefficient inversion algorithm, which can be achieved by the following method, which is described in detail below.

[0111] The extinction coefficient estimation module 101 takes the extinction coefficient of the Ith atmospheric position as the initial value, calculates the extinction coefficient of the I-1th atmospheric position according to the initial value and the extinction coefficient inversion algorithm, and calculates the extinction coefficient of the I-(n+1)th atmospheric position according to the extinction coefficient of the Inth atmospheric position and the extinction coefficient inversion algorithm.

[0112] In this embodiment, the calculation formula of the extinction coefficient inversion algorithm is as follows:

[0113] ,

[0114] in, represents the extinction coefficient at the I-1th atmospheric position, that is, the extinction coefficient at the boundary position of the aerosol, represents the radar ratio of aerosol, represents the radar ratio of the molecule, represents the extinction coefficient of the molecule at the I-1th atmospheric position, which can be obtained from the standard atmospheric model. is the RCS signal at the Ith atmospheric position, , represents the molecular backscattering coefficient, obtained from the standard atmosphere model, is the spatial resolution of the distance-corrected signal.

[0115] In some embodiments, the radar ratio of the aerosol can be 50, the radar ratio of the molecule Can be 3.

[0116] In this embodiment, the range of n is [1, N-1], where N is an integer not less than 1.

[0117] In some embodiments, a range of extinction coefficients is pre-established ,in, is the upper limit of the extinction coefficient range, which can be determined by local historical visibility data. is the lower limit of the extinction coefficient range, which is usually 0. The extinction coefficient estimation module 101 compares the extinction coefficient at the reference atmospheric position, and the extinction coefficient calculated based on the extinction coefficient at the reference atmospheric position and the extinction coefficient inversion algorithm with the upper and lower limits of the extinction coefficient range, respectively, and each estimated extinction coefficient finally obtained satisfies the extinction coefficient range. If the extinction coefficient at the reference atmospheric position or the extinction coefficient inverted by the extinction coefficient inversion algorithm does not satisfy the extinction coefficient range, that is, the extinction coefficient is less than the upper limit of the extinction coefficient range Or the extinction coefficient is greater than the lower limit of the extinction coefficient range , then the atmosphere interval to be fitted is re-obtained and the extinction coefficient is recalculated according to the atmosphere interval to be fitted.

[0118] In some embodiments, since the fitted distance correction signal may be interfered by noise, the extinction coefficient calculated based on the distance correction signal may not meet the range of the extinction coefficient. The initially selected interval to be fitted does not need to strictly select a uniform atmospheric interval. In the subsequent iterative calculation process, a more uniform atmospheric interval can be reselected and determined for visibility calculation.

[0119] The uniform atmosphere interval determination module 201 is used to generate a corresponding estimated extinction coefficient profile based on a plurality of estimated extinction coefficients, and determine a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile.

[0120] In some embodiments, the estimated extinction coefficient profile is a curve describing the estimated extinction coefficient following the change of a certain variable, for example, the variable may be height. Then, the estimated extinction coefficient profiles corresponding to a plurality of estimated extinction coefficients may be drawn with the height value as the horizontal coordinate and the estimated extinction coefficient as the vertical coordinate.

[0121] Please refer back to Figure 4 In some embodiments, the uniform atmosphere interval determination module 201 determines the uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile by the following method, which is described in detail below.

[0122] The uniform atmosphere interval determination module 201 derives each estimated extinction coefficient in the estimated extinction coefficient profile to obtain the derivative corresponding to each estimated extinction coefficient, and generates the corresponding derivative profile based on the derivatives corresponding to the multiple estimated extinction coefficients. The derivative profile is divided into multiple derivative profile segments using a window of a predefined size. For each derivative profile segment, the absolute value of each derivative in the derivative profile segment is obtained, and the absolute value of each derivative in the derivative profile segment is averaged to obtain the average value of the derivative value of the derivative profile segment. The uniform atmosphere interval in the global atmosphere interval is selected based on the average value of the derivative value of each derivative profile segment.

[0123] In this embodiment, the step of generating the corresponding derivative profile based on the derivatives corresponding to the multiple estimated extinction coefficients by the uniform atmosphere interval determination module 201 is similar to the implementation method of generating the corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, which will not be repeated here. The extinction coefficient profile corresponding to the uniform atmosphere is more straight, so the atmospheric range where the extinction coefficient derivative is close to 0 is considered to be a uniform atmospheric interval, so the derivative profile of the extinction coefficient becomes the basis for screening the uniform interval, and therefore, the corresponding derivative profile needs to be generated for subsequent determination of the uniform interval.

[0124] In this embodiment, the uniform atmosphere interval determination module 201 uses a window of a predefined size to perform window sliding on the derivative profile to divide the derivative profile into a plurality of derivative profile segments.

[0125] Please refer back to Figure 5 In some embodiments, the uniform atmosphere interval determination module 201 selects the uniform atmosphere interval in the global atmosphere interval based on the average value of the derivative value of each derivative profile segment through the following method, which is described in detail below.

[0126] The uniform atmosphere interval determination module 201 determines whether there is only one derivative profile segment whose average derivative value is less than a reference threshold value among multiple derivative profile segments. If there is only one derivative profile segment whose average derivative value is less than the reference threshold value, the atmospheric interval in which the derivative profile segment is located is selected as the uniform atmosphere interval in the global atmospheric interval. Otherwise, when there is more than one derivative profile segment whose average derivative value is less than the reference threshold value, the atmospheric interval described by the derivative profile segment whose average derivative value is less than the reference threshold value and meets the preset position condition is selected as the uniform atmosphere interval in the global atmospheric interval.

[0127] In this embodiment, the size between the average value of the derivative value of each derivative profile segment and a preset reference threshold is determined respectively. If, among multiple derivative profile segments, there is only one derivative profile segment whose average value of the derivative value is less than the reference threshold, the atmospheric interval in which the derivative profile segment is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0128] In some embodiments, there is no derivative profile segment whose average value of derivative value is less than a reference threshold value among multiple derivative profile segments, and there is more than one derivative profile segment whose average value of derivative value is less than the reference threshold value among multiple derivative profile segments. Wherein, when there is more than one derivative profile segment whose average value of derivative value is less than the reference threshold value, the atmospheric interval where the derivative profile segment whose average value of derivative value is less than the reference threshold value and which meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval.

[0129] In this embodiment, due to the characteristic that the backward solution calculated by the extinction coefficient inversion algorithm gradually stabilizes, the error near the estimated extinction coefficient profile is usually smaller than the error far away, which means that the closer extinction coefficient profile indicates a more accurate atmospheric state. Therefore, when there are multiple derivative profile segments whose average derivative values ​​are less than the reference threshold, the atmospheric interval where the derivative profile segment that meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval. Among them, the preset position condition can be the atmospheric interval corresponding to the position of the last one-third of the derivative profile segments on the derivative profile.

[0130] The error value calculation module 301 is used to generate an extinction coefficient profile corresponding to a uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile.

[0131] In this embodiment, the error value calculation module 301 calculates the corresponding extinction coefficient according to the uniform atmosphere interval, and obtains multiple extinction coefficients according to the extinction coefficient and a preset extinction coefficient inversion algorithm, and generates an extinction coefficient profile corresponding to the uniform atmosphere interval according to the above multiple extinction coefficients. For specific implementation steps, please refer to the calculation steps in the extinction coefficient estimation module 101 and the uniform atmosphere interval determination module 201, which will not be repeated here.

[0132] In some embodiments, the extinction coefficient profile corresponding to the uniform atmosphere interval is AEC(r i_s , r i_e ), the estimated extinction coefficient profile is Pre_AEC(r i_s , r i_e ), the error value calculation module 301 calculates the extinction coefficient profile AEC (r i_s , r i_e ) and the estimated extinction coefficient profile Pre_AEC(ri _s0 ,ri _e0 ) is the root mean square error RMSE between the two. Where i represents the number of iterations, s represents the upper bound of the uniform atmosphere interval, e represents the lower bound of the uniform atmosphere interval, s0 represents the upper bound of the atmosphere interval to be fitted, and e0 represents the lower bound of the atmosphere interval to be fitted.

[0133] The visibility calculation module 401 is used to perform iterative calculations based on the error value, the preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated based on the final extinction coefficient profile.

[0134] Please refer back to Figure 6 In some embodiments, the i-th iterative calculation is implemented by the following method, which is described in detail below.

[0135] The visibility calculation module 401 determines whether the i-th error value is greater than a preset error threshold. When the i-th error value is greater than the error threshold, the i+1-th uniform atmosphere interval is re-determined according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval is generated, and the i+1-th error value between the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval and the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is calculated. When the i-th error value is less than or equal to the error threshold, the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is used as the final extinction coefficient profile.

[0136] In this embodiment, for re-determining the (i+1)th uniform atmosphere interval according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, please refer to the implementation steps of the uniform atmosphere interval determination module 201, which will not be repeated here.

[0137] In some embodiments, the range of i is [1, 30].

[0138] In some embodiments, the visibility calculation module 401 calculates the visibility of the global atmospheric interval according to the final extinction coefficient profile and the Koschmieder principle. According to the Koschmieder principle, the calculation formula of visibility is: ,in, It represents the atmospheric extinction coefficient. The average extinction coefficient is calculated by integrating or averaging the final extinction coefficient profile in the global atmospheric interval. Substituting it into the above formula, the visibility in the global atmospheric interval can be obtained.

[0139] In some embodiments, a computer program product is provided, comprising a computer program and / or instructions, which implement a visibility inversion method when executed by a processor.

[0140] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0141] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A visibility inversion method suitable for infrared scanning laser radar, characterized in that: The visibility inversion method comprises: A plurality of estimated extinction coefficients are calculated by fitting according to a predetermined atmospheric interval to be fitted; wherein the atmospheric interval to be fitted is a local atmospheric interval selected when performing atmospheric detection in a global atmospheric interval using a laser radar, and the plurality of estimated extinction coefficients include an estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval, and the global atmospheric interval contains an inhomogeneous atmosphere; generating a corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, and determining a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile; Generate an extinction coefficient profile corresponding to the uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile; Iterative calculation is performed according to the error value, the preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated according to the final extinction coefficient profile; wherein the iterative calculation for the i-th time includes: Determine the difference between the i-th error value and the preset error threshold; When the i-th error value is greater than the error threshold, re-determine the i+1-th uniform atmosphere interval according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, generate the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval, and calculate the i+1-th error value between the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval and the extinction coefficient profile corresponding to the i-th uniform atmosphere interval; When the i-th error value is less than or equal to the error threshold, the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is used as the final extinction coefficient profile; wherein the range of i is [1, 30].

2. The visibility inversion method according to claim 1, characterized in that: The determining, according to the estimated extinction coefficient profile, a uniform atmosphere interval in the global atmosphere interval comprises: Deriving each of the estimated extinction coefficients in the estimated extinction coefficient profile to obtain a derivative corresponding to each of the estimated extinction coefficients, and generating a corresponding derivative profile based on the derivatives corresponding to the plurality of estimated extinction coefficients; Dividing the derivative profile into a plurality of derivative profile segments using a window of a predefined size; For each derivative profile segment, obtaining the absolute value of each derivative in the derivative profile segment, and performing an average calculation on the absolute value of each derivative in the derivative profile segment to obtain an average value of the derivative values ​​of the derivative profile segment; A uniform atmosphere interval in the global atmosphere interval is selected based on an average value of the derivative values ​​of each of the derivative profile segments.

3. The visibility inversion method according to claim 2, characterized in that: The step of selecting a uniform atmosphere interval in the global atmosphere interval based on the average value of the derivative value of each derivative profile segment comprises: Determine the difference between the average value of the derivative value of each derivative profile segment and a preset reference threshold; If there is only one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval where the derivative profile segment is located is selected as the uniform atmospheric interval in the global atmospheric interval; If there is more than one derivative profile segment whose average derivative value is less than the reference threshold, the atmospheric interval in which the derivative profile segment whose average derivative value is less than the reference threshold and which meets the preset position condition is located is selected as the uniform atmospheric interval in the global atmospheric interval.

4. The visibility inversion method according to claim 1, characterized in that: The step of calculating a plurality of estimated extinction coefficients based on the predetermined atmospheric interval to be fitted includes: Calculating a fitting signal of the atmospheric interval to be fitted according to the distance correction signal of the atmospheric interval to be fitted, and calculating an extinction coefficient of a reference atmospheric position in the global atmospheric interval according to the fitting signal and a preset fitting equation; A plurality of estimated extinction coefficients are iteratively calculated based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm.

5. The visibility inversion method according to claim 4, characterized in that: The extinction coefficient of the reference atmospheric position is the extinction coefficient of the 1st atmospheric position, the multiple estimated extinction coefficients include the extinction coefficient of the 1st atmospheric position, the extinction coefficient of the 1-1th atmospheric position, ..., the extinction coefficient of the INth atmospheric position, and N is an integer not less than 1; Based on the extinction coefficient of the reference atmospheric position and a preset extinction coefficient inversion algorithm, a plurality of estimated extinction coefficients are iteratively calculated, including: Taking the extinction coefficient of the I-th atmospheric position as an initial value, and calculating the extinction coefficient of the I-1-th atmospheric position according to the initial value and the extinction coefficient inversion algorithm; The extinction coefficient of the I-(n+1)th atmospheric position is calculated according to the extinction coefficient of the Inth atmospheric position and the extinction coefficient inversion algorithm, where n is in the range of [1, N-1].

6. The visibility inversion method according to claim 4, characterized in that: Each of the estimated extinction coefficients meets a preset extinction coefficient range.

7. An infrared scanning laser radar, characterized in that: The infrared scanning laser radar includes a laser transmitting module, a signal receiving module and a processor; The laser emission module is used to emit the laser beam generated by the laser into the atmosphere; The signal receiving module is used to receive the echo signal generated after the laser beam interacts in the atmosphere; The processor is used to calculate the visibility of the atmosphere based on the atmosphere interval to be fitted determined according to the echo signal using the visibility inversion method described in any one of claims 1-6.

8. A visibility inversion device suitable for infrared scanning laser radar, characterized in that: The visibility inversion device comprises: An extinction coefficient estimation module is used to calculate a plurality of estimated extinction coefficients according to a predetermined atmospheric interval to be fitted; wherein the atmospheric interval to be fitted is a local atmospheric interval selected when performing atmospheric detection in a global atmospheric interval using a laser radar, and the plurality of estimated extinction coefficients include an estimated extinction coefficient corresponding to each atmospheric position in the global atmospheric interval, and the global atmospheric interval contains an inhomogeneous atmosphere; A uniform atmosphere interval determination module, configured to generate a corresponding estimated extinction coefficient profile based on the multiple estimated extinction coefficients, and determine a uniform atmosphere interval in the global atmosphere interval according to the estimated extinction coefficient profile; An error value calculation module, used to generate an extinction coefficient profile corresponding to the uniform atmosphere interval, and calculate an error value between the extinction coefficient profile corresponding to the uniform atmosphere interval and the estimated extinction coefficient profile; A visibility calculation module is used to perform iterative calculation according to the error value, a preset error threshold and the extinction coefficient profile corresponding to the uniform atmosphere interval, until a final extinction coefficient profile that meets the error value requirement is inverted, and the visibility of the global atmosphere interval is calculated according to the final extinction coefficient profile; wherein the iterative calculation for the i-th time includes: Determine the difference between the i-th error value and the preset error threshold; When the i-th error value is greater than the error threshold, re-determine the i+1-th uniform atmosphere interval according to the extinction coefficient profile corresponding to the i-th uniform atmosphere interval, generate the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval, and calculate the i+1-th error value between the extinction coefficient profile corresponding to the i+1-th uniform atmosphere interval and the extinction coefficient profile corresponding to the i-th uniform atmosphere interval; When the i-th error value is less than or equal to the error threshold, the extinction coefficient profile corresponding to the i-th uniform atmosphere interval is used as the final extinction coefficient profile; wherein the range of i is [1, 30].

9. A computer program product comprising a computer program and / or instructions, characterized in that: When the computer program and / or the instructions are executed by a processor, the visibility inversion method according to any one of claims 1 to 6 is implemented.

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