CN114004833A - Composite material terahertz imaging resolution enhancement method, device, equipment and medium - Google Patents
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Abstract
The application provides a composite material terahertz imaging resolution enhancement method, device, equipment and medium, wherein the method comprises the following steps: adopting a terahertz imaging system to perform imaging detection on the detected composite material to obtain a first one-dimensional distance image of the detected composite material; denoising the first one-dimensional range profile to obtain a denoised second one-dimensional range profile; respectively taking the second one-dimensional range profile and the second one-dimensional range profile after the detail enhancement as a first guide map and a second guide map, and respectively performing guide filtering on the second one-dimensional range profile to respectively obtain a detail layer and a basic layer; respectively performing first gain and second gain on the detail and the base layer, and superposing the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional distance image; and carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image. By the method, the background noise can be effectively suppressed, and meanwhile, the detail information such as the edge of the image can be enhanced.
Description
Technical Field
The application relates to the technical field of composite material terahertz imaging enhancement, in particular to a method, a device, equipment and a medium for enhancing terahertz imaging resolution of a composite material.
Background
The terahertz imaging detection technology has the advantage of high permeability, and when the composite material is detected, compared with other traditional detection technologies, the terahertz imaging detection technology is easier to detect the defects inside the composite material, and can perform imaging under the condition of not contacting the detected material. The photon energy of the terahertz wave is in the millielectron volt magnitude, so that structural damage to a detected material can not be caused during terahertz imaging detection, and radiation harmful to biological tissues can not be generated. However, when the technology is applied, the terahertz waves are interfered by experimental environmental noise (motion and energy level absorption of water vapor and air molecules), system internal noise (photon radiation noise, thermal noise, shot noise, and the like) and material characteristics of a sample to be detected (interlayer multiple reflection caused by tiny gaps inside a laminated structure, scattering caused by poor surface roughness or large granularity, and the like), so that degradation phenomena such as low contrast, low detail resolution, poor definition, and the like exist in a detected image, and the application of the terahertz imaging detection technology and the accurate judgment of the internal information of the detected material are influenced.
In order to solve the problem of degradation of terahertz images, a large number of scholars research and provide terahertz image denoising and enhancing methods such as mean filtering, gaussian filtering, non-local mean filtering and edge detection. The image processing method has certain effect on the terahertz image denoising and the image enhancement, but has respective defects. The mean filtering can effectively inhibit Gaussian noise, but can cause blurring on image details such as edges and the like; gaussian filtering has a good effect of removing speckle noise in an image, but can damage the edge and texture detail parts of the image to a certain extent; although the non-local mean filtering can retain image detail information, filtering parameters cannot be adjusted in a self-adaptive manner, so that an image generates an artifact; the edge detection of the laplacian gaussian operator is sensitive to noise, the noise and background information of the image can be enhanced while the edge and the details are enhanced, and a clear and high-resolution image cannot be obtained.
Disclosure of Invention
The invention aims to provide a method, a device, equipment and a medium for enhancing the terahertz imaging resolution of a composite material, which can enhance the contrast, detail resolution and edge information of a terahertz detection image of the composite material, and can enhance the detail information such as the edge of the image while effectively inhibiting background noise.
In a first aspect, an embodiment of the application provides a composite material terahertz imaging resolution enhancement method, which includes:
adopting a terahertz imaging system to perform imaging detection on a detected composite material to obtain a first one-dimensional distance image for the detected composite material;
carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile;
respectively taking the second one-dimensional range profile and the second one-dimensional range profile after detail enhancement as a first guide graph and a second guide graph, and respectively performing guide filtering on the second one-dimensional range profile to respectively obtain a detail layer and a basic layer;
respectively performing first gain and second gain on the detail layer and the base layer, and superposing the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional distance image;
and carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
In a possible embodiment, the imaging detection of the composite material under test by using the terahertz imaging system to obtain a first one-dimensional distance image for the composite material under test includes:
imaging and detecting the detected composite material through the terahertz imaging system to acquire at least one piece of amplitude information of reflection echoes of the detected composite material on different interfaces;
obtaining a detection signal of the detected composite material in a terahertz time domain according to the at least one piece of amplitude information;
performing fast Fourier transform on the detection signal to obtain the first one-dimensional range profile; wherein the fast fourier transform is of the formula:
in the formula (I), the compound is shown in the specification,
the fast fourier transform is characterized and the fast fourier transform,
in order to be able to detect the signal,
is the first one-dimensional range profile.
In a possible embodiment, performing high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile, includes:
performing discrete wavelet transform on the first one-dimensional distance image to decompose the first one-dimensional distance image into first transform results under multiple scales according to a wavelet mother function; wherein a first relationship between the first one-dimensional distance image and the first transformation result is:
in the formula (I), the compound is shown in the specification,
for a preset discretized stretch index,
t is a time variable in a detection signal of the terahertz time domain, is a preset discretization translation coefficient,
in order to be the result of said first transformation,
for the discretization stretch index to be
The scale factor of (a) is,
for the discretized stretch index to be a discretized stretch index of
The scale factor of (a) is,
in order to be a function of the mother wavelet,
is a wavelet basis function based on the discretized scaling index, the discretized shifting coefficient, and a wavelet mother function under the time variable,
is the conjugate of the wavelet basis function;
decomposing the first one-dimensional range profile into second transformation results under a plurality of scales according to a scale function; wherein a second relationship between the first one-dimensional distance image and the second transformation result is:
in the formula (I), the compound is shown in the specification,
in order to be the result of said second transformation,
in order to be a function of the scale,
for the scale function to pass
Multiple expansion and contraction
A first scale function obtained after the time translation;
is the conjugate of the first scale function;
determining a third relation between the wavelet basis functions and the scale functions under multiple scales according to a multi-resolution analysis equation; wherein the third relationship is:
in the formula (I), the compound is shown in the specification,
is a translation multiple
As a function of said scale
In that
Is carried out under the scale
A second scale function after the time translation;
a first wavelet coefficient corresponding to the wavelet basis function;
corresponding translation variation when the relation between the wavelet function under the j scale and the scale function under the j +1 scale is established; the wavelet function comprises a wavelet basis function and a wavelet mother function;
obtaining a fourth relation between the first transformation result and a target second transformation result under multiple scales according to the first relation, the second relation and the third relation; wherein the fourth relationship is:
in the formula (I), the compound is shown in the specification,
a second transformation result corresponding to the second scale function is obtained;
determining a first wavelet coefficient corresponding to each first transformation result under multiple scales according to the fourth relation;
performing hard threshold function shrinkage denoising on a first wavelet coefficient set composed of all the first wavelet coefficients according to a preset threshold so as to change the first wavelet coefficients under each scale into corresponding second wavelet coefficients; wherein, the hard threshold function shrinkage denoising is carried out by the following formula:
in the formula (I), the compound is shown in the specification,
the preset threshold value is used as the preset threshold value;
is the second wavelet coefficient;
is a modulus of the first wavelet coefficient; the preset threshold is a standard deviation of the first wavelet coefficient at a plurality of scales;
determining at least one target second wavelet coefficient of which the median value of the second wavelet coefficients is not zero;
determining a target first transformation result corresponding to each target second wavelet coefficient in the at least one target second wavelet coefficient according to the fourth relation;
and reconstructing all the first transformation results of the targets according to the first relation to obtain the second one-dimensional range profile.
In one possible embodiment, the formula of the guided filtering is:
in the formula (I), the compound is shown in the specification,
either the detail layer or the base layer,
is a guide map, the guide map is the first guide map or the second guide map；
To be the size of the filtering window,
the size of the filtering window and the regularization parameter are preset as the regularization parameter;
the second one-dimensional range profile is guided and filtered based on the guide map, the filter window size, and the regularization parameter.
In one possible embodiment, the second guidance diagram is obtained by:
in the formula (I), the compound is shown in the specification,
for the second guide map, LP characterizes a low-pass filter,
is a preset gain factor of the high frequency information,
and characterizing the range profile obtained after the low-pass filtering is carried out on the second one-dimensional range profile.
In a possible embodiment said third one-dimensional distance image is obtained by:
in the formula (I), the compound is shown in the specification,
for the third one-dimensional range profile,
、
respectively a first gain coefficient and a second gain coefficient which are preset,
is the fine layer;
is the base layer.
In one possible embodiment, the result image is obtained by:
in the formula (I), the compound is shown in the specification,
in order to be able to produce the result image,
is that the third one-dimensional range profile is at
Go to,
A column (a),
A three-dimensional matrix of page counts, the resulting image being depth of page counts
A two-dimensional matrix of (a); the two-dimensional matrix comprises
Go to,
Columns;
respectively a first distance between the upper surface of the tested composite material and a detector and a second distance between the lower surface of the tested composite material and the detector,
a third distance to the detector for the preselected imaging plane.
In a second aspect, the embodiment of the application further provides a composite terahertz imaging resolution enhancement device, where the device includes:
the detection unit is used for carrying out imaging detection on the detected composite material by adopting a terahertz imaging system so as to obtain a first one-dimensional distance image aiming at the detected composite material;
the denoising unit is used for carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile;
the guiding filtering unit is used for respectively taking the second one-dimensional range profile and the second one-dimensional range profile after the detail enhancement as a first guiding graph and a second guiding graph, and respectively guiding and filtering the second one-dimensional range profile to respectively obtain a detail layer and a basic layer;
a gain superposition unit, configured to perform a first gain and a second gain on the detail layer and the base layer, respectively, and superpose the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional range profile;
and the amplitude imaging unit is used for carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
In one possible embodiment, the detection unit is configured to:
imaging and detecting the detected composite material through the terahertz imaging system to acquire at least one piece of amplitude information of reflection echoes of the detected composite material on different interfaces;
obtaining a detection signal of the detected composite material in a terahertz time domain according to the at least one piece of amplitude information;
performing fast Fourier transform on the detection signal to obtain the first one-dimensional range profile; wherein the fast fourier transform is of the formula:
in the formula (I), the compound is shown in the specification,
the fast fourier transform is characterized and the fast fourier transform,
in order to be able to detect the signal,
is the first one-dimensional range profile.
In one possible embodiment, the denoising unit is configured to:
performing discrete wavelet transform on the first one-dimensional distance image to decompose the first one-dimensional distance image into first transform results under multiple scales according to a wavelet mother function; wherein a first relationship between the first one-dimensional distance image and the first transformation result is:
in the formula (I), the compound is shown in the specification,
for a preset discretized stretch index,
t is a time variable in a detection signal of the terahertz time domain, is a preset discretization translation coefficient,
in order to be the result of said first transformation,
for the discretization stretch index to be
The scale factor of (a) is,
for the discretized stretch index to be a discretized stretch index of
The scale factor of (a) is,
in order to be a function of the mother wavelet,
is a wavelet basis function based on the discretized scaling index, the discretized shifting coefficient, and a wavelet mother function under the time variable,
is the conjugate of the wavelet basis function;
decomposing the first one-dimensional range profile into second transformation results under a plurality of scales according to a scale function; wherein a second relationship between the first one-dimensional distance image and the second transformation result is:
in the formula (I), the compound is shown in the specification,
in order to be the result of said second transformation,
in order to be a function of the scale,
for the scale function to pass
Multiple expansion and contraction
A first scale function obtained after the time translation;
is the conjugate of the first scale function;
determining a third relation between the wavelet basis functions and the scale functions under multiple scales according to a multi-resolution analysis equation; wherein the third relationship is:
in the formula
Is the translation multiple of the first lens group,
as a function of said scale
In that
Is carried out under the scale
A second scale function after the time translation;
a first wavelet coefficient corresponding to the wavelet basis function;
corresponding translation variation when the relation between the wavelet function under the j scale and the scale function under the j +1 scale is established; the wavelet function comprises a wavelet basis function and a wavelet mother function;
obtaining a fourth relation between the first transformation result and a target second transformation result under multiple scales according to the first relation, the second relation and the third relation; wherein the fourth relationship is:
in the formula (I), the compound is shown in the specification,
a second transformation result corresponding to the second scale function is obtained;
determining a first wavelet coefficient corresponding to each first transformation result under multiple scales according to the fourth relation;
performing hard threshold function shrinkage denoising on a first wavelet coefficient set composed of all the first wavelet coefficients according to a preset threshold so as to change the first wavelet coefficients under each scale into corresponding second wavelet coefficients; wherein, the hard threshold function shrinkage denoising is carried out by the following formula:
in the formula (I), the compound is shown in the specification,
the preset threshold value is used as the preset threshold value;
is the second wavelet coefficient;
is a modulus of the first wavelet coefficient; the preset threshold is a standard deviation of the first wavelet coefficient at a plurality of scales;
determining at least one target second wavelet coefficient of which the median value of the second wavelet coefficients is not zero;
determining a target first transformation result corresponding to each target second wavelet coefficient in the at least one target second wavelet coefficient according to the fourth relation;
and reconstructing all the first transformation results of the targets according to the first relation to obtain the second one-dimensional range profile.
In one possible embodiment, the formula of the guided filtering is:
in the formula (I), the compound is shown in the specification,
either the detail layer or the base layer,
is a guide map, the guide map being the first guide map or the second guide map;
to be the size of the filtering window,
the size of the filtering window and the regularization parameter are preset as the regularization parameter;
the second one-dimensional range profile is guided and filtered based on the guide map, the filter window size, and the regularization parameter.
In one possible embodiment, the second guidance diagram is obtained by:
in the formula (I), the compound is shown in the specification,
for the second guide map, LP characterizes a low-pass filter,
is a preset gain factor of the high frequency information,
and characterizing the range profile obtained after the low-pass filtering is carried out on the second one-dimensional range profile.
In a possible embodiment, the third one-dimensional distance image is obtained by:
in the formula (I), the compound is shown in the specification,
is that it isThe third one-dimensional range profile is,
、
respectively a first gain coefficient and a second gain coefficient which are preset,
is the fine layer;
is the base layer.
In one possible embodiment, the result image is obtained by:
in the formula (I), the compound is shown in the specification,
in order to be able to produce the result image,
is that the third one-dimensional range profile is at
Go to,
A column (a),
A three-dimensional matrix of page counts, the resulting image being depth of page counts
A two-dimensional matrix of (a); the two-dimensional matrix comprises
Go to,
Columns;
respectively a first distance between the upper surface of the tested composite material and a detector and a second distance between the lower surface of the tested composite material and the detector,
a third distance to the detector for the preselected imaging plane.
In a third aspect, an embodiment of the present application further provides an electronic device, including: a processor, a storage medium and a bus, the storage medium storing machine-readable instructions executable by the processor, the processor and the storage medium communicating over the bus when the electronic device is operated, the processor executing the machine-readable instructions to perform the steps of the method according to any one of the first aspect.
In a fourth aspect, this application further provides a computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, performs the steps of the method according to any one of the first aspect.
According to the method for enhancing the terahertz imaging resolution of the composite material, a terahertz imaging system is adopted to perform imaging detection on the composite material to be detected so as to obtain a first one-dimensional distance image for the composite material to be detected; carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile; respectively taking the second one-dimensional range profile and the second one-dimensional range profile after detail enhancement as a first guide graph and a second guide graph, and respectively performing guide filtering on the second one-dimensional range profile to respectively obtain a detail layer and a basic layer; respectively performing first gain and second gain on the detail layer and the base layer, and superposing the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional distance image; and carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
Compared with the prior art, the method for denoising the terahertz detection image of the composite material based on the discrete wavelet transform hard threshold shrinkage is used for carrying out high-frequency denoising on the terahertz detection image of the composite material, so that background noise is effectively inhibited, and the quality of the terahertz image of the composite material is improved; the image after the self and the detail enhancement are respectively used as guide images to conduct guide filtering operation, so that the smooth area of the image can be well reserved while the texture detail of the terahertz image of the composite material is enhanced; by means of respectively performing gain and superposition on the detail layer and the basic layer, the contrast, detail resolution capability and edge information of the composite terahertz image are effectively enhanced, and while background noise is effectively inhibited, detail information such as the edge of the image is enhanced.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 shows a flowchart of a composite material terahertz imaging resolution enhancement method provided by an embodiment of the present application.
Fig. 2 shows an original image of a composite material under test provided by an embodiment of the present application.
Fig. 3 shows a terahertz image of a detected composite material, which is obtained after processing according to the composite material terahertz imaging resolution enhancement method provided by the embodiment of the application.
Fig. 4 shows a composite material terahertz imaging resolution enhancement device provided by an embodiment of the application.
Fig. 5 shows a schematic structural diagram of an electronic device provided in an embodiment of the present application.
Detailed Description
In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it should be understood that the drawings in the present application are for illustrative and descriptive purposes only and are not used to limit the scope of protection of the present application. Additionally, it should be understood that the schematic drawings are not necessarily drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of the present application. It should be understood that the operations of the flow diagrams may be performed out of order, and steps without logical context may be performed in reverse order or simultaneously. One skilled in the art, under the guidance of this application, may add one or more other operations to, or remove one or more operations from, the flowchart.
In addition, the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that in the embodiments of the present application, the term "comprising" is used to indicate the presence of the features stated hereinafter, but does not exclude the addition of further features.
It should be noted that the apparatuses, electronic devices, and the like according to the embodiments of the present application may be executed on a single server or may be executed in a server group. The server group may be centralized or distributed. In some embodiments, the server may be local or remote to the terminal. For example, the server may access information and/or data stored in the service requester terminal, the service provider terminal, or the database, or any combination thereof, via the network. As another example, the server may be directly connected to at least one of the service requester terminal, the service provider terminal and the database to access the stored information and/or data. In some embodiments, the server may be implemented on a cloud platform; by way of example only, the cloud platform may include a private cloud, a public cloud, a hybrid cloud, a community cloud (community cloud), a distributed cloud, an inter-cloud, a multi-cloud, and the like, or any combination thereof.
Fig. 1 shows a flowchart of a composite terahertz imaging resolution enhancement method provided by an embodiment of the present application, in which an acquired original one-dimensional range profile is subjected to high-frequency denoising by using a hard threshold shrinkage denoising method based on discrete wavelet transform; and secondly, respectively taking the self image and the image after the detail enhancement as guide images to conduct guide filtering operation to obtain a detail layer and a basic layer, conducting gain and superposition on the detail layer and the basic layer, and obtaining a final result image with high contrast and high detail resolution capacity in an amplitude imaging mode. As shown in fig. 1, the method comprises the steps of:
The specific implementation method comprises the following steps: imaging and detecting the detected composite material through the terahertz imaging system to acquire at least one piece of amplitude information of reflection echoes of the detected composite material on different interfaces; obtaining a detection signal of the detected composite material in a terahertz time domain according to the at least one piece of amplitude information; performing fast Fourier transform on the detection signal to obtain the first one-dimensional range profile; wherein the fast fourier transform is of the formula:
in the formula (I), the compound is shown in the specification,
the fast fourier transform is characterized and the fast fourier transform,
in order to be able to detect the signal,
is the first one-dimensional range profile.
And 102, carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile.
In particular, for the first one-dimensional distance image
Performing discrete wavelet transform to decompose the first one-dimensional range profile into first transform results under multiple scales according to wavelet mother function
(ii) a Wherein the one-dimensional range profile
And the first transformation result
The first relationship of (1) is:
in the formula (I), the compound is shown in the specification,
for a preset discretized stretch index,
t is a time variable in a detection signal of the terahertz time domain, is a preset discretization translation coefficient,
in order to be the result of said first transformation,
for the discretization stretch index to be
The scale factor of (a) is,
for the discretized stretch index to be a discretized stretch index of
The scale factor of (a) is,
in order to be a function of the mother wavelet,
is a wavelet basis function based on the discretized scaling index, the discretized shifting coefficient, and a wavelet mother function under the time variable,
is the conjugate of the wavelet basis function. In order to avoid the signal distortion problem in the denoising preprocessing, the embodiment of the application performs multi-scale decomposition on the first one-dimensional distance image by using an approximate symmetric compact set (symlets) wavelet function capable of suppressing the signal distortion.
According to the multi-resolution analysis theory, the first one-dimensional distance image is decomposed at multiple scalesIn the above, the general view of the signal is observed in the large scale space, and the details of the signal are observed in the small scale space, where the large scale refers to the space corresponding to the low frequency, the small scale refers to the space corresponding to the high frequency, and the high and low of the frequency and the discretization expansion and contraction index
In inverse proportion. Defining a scale function
Through
After doubling of the translation is obtained
Then, there are:
wherein the content of the first and second substances,
is a symbol of an integer set, if defined by a signal
The linearly expressed signals constitute a space:
then call
Is composed of
A closed signal space is formed.
According to a scale function
Transforming the first one-dimensional distance image
Decomposition into second transformation results at multiple scales
(ii) a Wherein the one-dimensional range profile
And the second transformation result
The second relationship of (1) is:
in the formula (I), the compound is shown in the specification,
in order to be the result of said second transformation,
in order to be a function of the scale,
for the scale function to pass
Multiple expansion and contraction
A first scale function obtained after the time translation;
is the conjugate of the first scale function. Wherein for the first one-dimensional distance image
Then the first one-dimensional distance image
Can be expressed as:
wherein the content of the first and second substances,
and
the relationship of (1) is:
namely, the method comprises the following steps:
determining a third relation between the wavelet basis functions and the scale functions under multiple scales according to a multi-resolution analysis equation; wherein the third relationship is:
in the formula (I), the compound is shown in the specification,
as a function of said scale
In that
Is carried out under the scale
A second scale function after the time translation;
a first wavelet coefficient corresponding to the wavelet basis function;
corresponding translation variation when the relation between the wavelet function under the j scale and the scale function under the j +1 scale is established; the wavelet coefficient establishes the relation between the wavelet function and the scale function; by passing
And determining the size of the scale, wherein the scale functions under a plurality of scales correspond to different wavelet coefficients. The wavelet functions include wavelet basis functions and wavelet mother functions.
Obtaining the first transformation result under multiple scales according to the first relation, the second relation and the third relation
A fourth relationship with the target second transformation result; wherein the fourth relationship is:
wherein the content of the first and second substances,
and the second transformation result is the target corresponding to the second scale function.
The first transformation result corresponding to each scale
Determining each first transformation result under multiple scales according to the fourth relation
Corresponding first wavelet coefficient
。
By the method, the solution through the wavelet function can be realized
Is converted into solving by wavelet coefficient
The process of (2); in the process of image detection, a first one-dimensional distance image acquired by detection
All of the noise is contained in the noise-free air conditioner,the noise comprises white gaussian noise; a signal containing noise can be simply expressed in the form:
in the formula (I), the compound is shown in the specification,
is an ideal noise-free signal and is,
in order to be a function of the noise doping,
in order to be able to measure the noise level,
is the sample length. The essence of signal denoising is to utilize different characteristics of signal and noise to denoise noise
Extracting from the noise-containing signal to recover a noise-free signal
. For an ideal effective signal, it is continuous in the time domain, so that after the effective signal is subjected to discrete wavelet transform, its energy is mainly concentrated on the low frequency sub-band, and the modulus of the generated wavelet coefficient is relatively large. For white gaussian noise, the noise is not continuous in the time domain, shows strong randomness, and also has strong randomness after discrete wavelet transform, so that the energy of the noise is mainly distributed on each high-frequency subband in the wavelet domain and is still generally considered as white gaussian noise, and the modulus of the generated wavelet coefficient is smaller. Based on the characteristics, the wavelet coefficient corresponding to the noise still meets Gaussian white noise distribution, and the standard deviation of the signal is reflected according to the definition of the standard deviation and the variance of the random signalThe dispersion degree from each point in the dispersion signal to the signal mean value, therefore, the embodiment of the application proposes that the standard deviation of the wavelet coefficient of the noise-containing signal under the decomposition of each scale of the discrete wavelet transform is taken as a preset threshold value, and the distribution range of the noise wavelet coefficient is reflected to a certain extent.
With the first transformation result
The standard deviation of the corresponding wavelet coefficient is a preset threshold, and the calculation method of the preset threshold T comprises the following steps:
T=
；
in the formula (I), the compound is shown in the specification,
is a first one-dimensional distance image
The total number of wavelet coefficients obtained after the decomposition of each scale of the discrete wavelet transform is set to zero according to the characteristics of Gaussian distribution, and the wavelet coefficients which do not exceed the preset threshold can suppress the interference of noise to the maximum extent, namely the function of a hard threshold function.
The specific method for the hard threshold function shrinkage denoising is as follows:
all the first wavelet coefficients are selected according to a preset threshold value
Carrying out hard threshold function shrinkage denoising on the constructed first wavelet coefficient set so as to remove the first wavelet coefficients under multiple scales
Change to the corresponding second wavelet coefficient
(ii) a Wherein the hard threshold function is performed by the following formulaReducing and denoising:
in the formula (I), the compound is shown in the specification,
the preset threshold value is used as the preset threshold value;
is the second wavelet coefficient;
is a modulus of the first wavelet coefficient; the preset threshold is a standard deviation of the first wavelet coefficients at a plurality of scales.
Determining the second wavelet coefficients
At least one target second wavelet coefficient with a non-zero median
。
Determining the at least one target second wavelet coefficient according to the fourth relationship
Of each of said target second wavelet coefficients
Corresponding target first transformation result
。
According to the first relation, each target is subjected to first transformation
Reconstructing to obtain the second one-dimensional range profile
。
And 103, respectively taking the second one-dimensional range profile and the second one-dimensional range profile after detail enhancement as a first guide map and a second guide map, and respectively performing guide filtering on the second one-dimensional range profile to respectively obtain a detail layer and a base layer.
Specifically, the formula of the guided filtering is as follows:
in the formula (I), the compound is shown in the specification,
for the detail layer
Or the base layer
，
Is a guide map, the guide map being the first guide map or the second guide map;
to be the size of the filtering window,
the filter window size for the regularization parameter
The regularization parameter
Are all preset, according to the above formula, the detail layer is
Is to make the second one-dimensional range profile
As a first guide map, for itself (second one-dimensional range profile)
) The pilot filtering is carried out through the formula; base layer
Is to use the fourth one-dimensional range profile
As a second guide map, for a second one-dimensional range profile
Obtained after the pilot filtering. Filter window size
And the regularization parameter
The filter window size may be determined empirically, in embodiments of the present application
Preset value of 3, regularization parameter
The preset value is 0.64.
Wherein, in calculating the detail layer
Details ofLayer(s)
And a first guide map (second one-dimensional range profile)
) The following assumptions are satisfied:
in a local window centred on pixel u
If the relationship is linear, the output expression of a certain pixel point on the detail layer is as follows:
in the formula (I), the compound is shown in the specification,
corresponding local window
The index of the pixel in (1) is,
and
as a partial window
Different linear coefficients in (a); wherein the content of the first and second substances,
when the guide map is a first guide map, the target image is a detail map; when the guide map is the second guide map, the target image is a base layer. The gradient is calculated for both sides of the above formula, and the following can be obtained:
can see when the second one-dimensional range profile
Detail layer when there is a gradient in a certain region
The corresponding gradient is also preserved, so that the guided filtering can have good edge-preserving performance while smoothing the background. To obtain the coefficient
And
the optimal solution of (2), the detail layer is required
To retain the second one-dimensional range profile as much as possible
Even if the difference between the two is minimal, the implementation is usually to introduce and minimize a minimization cost function to solve the optimization problem. Minimizing a cost function
The expression of (a) is:
in the formula (I), the compound is shown in the specification,
is a penalty term; preset regularization parameters
Can prevent
Too large a value of (c); the above formula is solved by a linear regression model to minimize it, and can be obtained
And
the optimal solution of (a) is:
in the formula (I), the compound is shown in the specification,
and
respectively in partial windows for guide maps
The mean and variance of the medium pixels,
is that
The number of pixels included in (a) is,
is the image to be filtered (in this case, the second one-dimensional range profile)
) At the local window
Average value of (1). Formula in use
And
when calculating linear coefficients, different local windows
Obtained by calculation of
And
obviously, it is also different, can pass through
And
solving the obtained values in an averaging mode, and obtaining a target image output after guide filtering according to the method; the expression of the target image is as follows:
in the formula (I), the compound is shown in the specification,
and
all local windows under the same pixel index
Average of linear coefficients of (a).
The second guide map is obtained by:
for the second one-dimensional range profile
Carrying out detail enhancement to obtain a fourth one-dimensional range profile after the detail enhancement
To combine the fourth one-dimensional range profile
As the second guide map. The detail enhancement process comprises the following steps: first, mean filtering is used as a low-pass smoothing filter to carry out filtering on the second one-dimensional range profile
Low-pass filtering to obtain range image
Distance image after low-pass filtering
In order to blur the image, the second one-dimensional range profile is made by using unsharp masking method
Image of distance from it
Performing difference operation to obtain high-frequency image information
Gain factor according to preset high frequency information
For high frequency information of imageInformation processing device
Gain is performed and the distance image is obtained from the second one-dimensional distance image
Superposing to obtain a fourth one-dimensional range profile with enhanced details and edges
. Among them, detail enhancement is also called sharpening enhancement.
Specifically, the fourth one-dimensional range profile
Is obtained by the following steps:
in the formula, LP represents a low-pass filter,
is a preset gain coefficient of high frequency information, the
Characterizing the second one-dimensional range profile
Obtaining a distance image after low-pass filtering; in the embodiment of the application, the
. Using unsharpened mask method to obtain the second one-dimensional range profile
A second one-dimensional range profile while performing detail enhancement
The smooth area in (1) is not affected and is preserved.
The embodiment of the application adopts
To the second one-dimensional range profile
And (3) performing convolution processing, wherein the average filtering template is as follows:
mean filtering the expression for smoothing an image is as follows:
in the formula (I), the compound is shown in the specification,
which means that the mean value is filtered,
is a second one-dimensional range profile
By point
A neighborhood that is the center;
the number of pixels in the neighborhood. The mean filtering can filter noise and simultaneously enable the second one-dimensional range profile
Becomes blurred, resulting in a second one-dimensional range profile for the image
Distance image of
Wherein the distance image after low-pass filtering
For blurred images, range images
The medium and high frequency components are greatly attenuated. Second one-dimensional range profile
And distance image
Subtracting to obtain high frequency image
I.e. an image reflecting image details; image processing method and device
Multiplying the gain factor of the high frequency information
Then, the distance image is separated from the second one-dimensional distance image
The second one-dimensional range profile is obtained by superposition
Some detail parts are enhanced, and the image sharpening effect is achieved.
And 104, respectively performing first gain and second gain on the detail layer and the base layer, and superposing the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional distance image.
Specifically, the third one-dimensional range profile
Is obtained by the following steps:
in the formula (I), the compound is shown in the specification,
for the third one-dimensional range profile,
、
respectively a first gain coefficient and a second gain coefficient which are preset,
is the fine layer;
for the base layer, in the embodiment of the present application, the first gain factor
Second gain factor
The values of (A) are all 2.
And 105, performing amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
In particular, the result image
Is obtained by the following steps:
in the formula (I), the compound is shown in the specification,
is that
Go to,
A column (a),
A three-dimensional matrix of page numbers, the resulting image
Depth is the number of pages
A two-dimensional matrix of (a); the two-dimensional matrix comprises
Go to,
Columns;
respectively a first distance between the upper surface of the tested composite material and a detector and a second distance between the lower surface of the tested composite material and the detector,
to select in advanceA third distance to the detector,
the value can be taken according to actual requirements.
FIG. 2 shows an original image of a composite material under test provided by an embodiment of the present application; fig. 3 shows a terahertz image of a detected composite material, which is obtained after processing according to the composite material terahertz imaging resolution enhancement method provided by the embodiment of the application. Table 1 is an image quality evaluation table obtained by performing image processing according to an original detection image, a gaussian filtering method, a median filtering method, and the method of the embodiment of the present application, respectively:
table 1:
| evaluation index | Raw inspection image | Gauss filtering | Median filtering | The method of the present invention |
| Standard deviation of | 2.4363 | 2.0684 | 1.9722 | 8.7838 |
| Mean gradient | 0.0275 | 0.0130 | 0.0157 | 0.0308 |
| Entropy of information | 5.6032 | 2.2544 | 5.4011 | 7.3732 |
| Energy gradient | 2.5453e+04 | 5.694e+03 | 7.9411e+03 | 3.1882e+04 |
| Local contrast | 24.6274 | 23.8015 | 25.1387 | 98.5350 |
As can be seen from the images shown in fig. 2 and fig. 3 and the table 1, the embodiment of the present application can improve detail information such as image contrast, sharpness, and edge while suppressing background noise; compared with an original detection image and a traditional denoising enhancement method, the method has a better composite material terahertz imaging resolution enhancement effect and better image quality.
Fig. 4 shows a composite material terahertz imaging resolution enhancement device provided by an embodiment of the present application, and as shown in fig. 4, the device includes: the device comprises a detection unit 401, a denoising unit 402, a guide filtering unit 403, a gain superposition unit 404 and an amplitude imaging unit 405.
The detecting unit 401 is configured to perform imaging detection on a detected composite material by using a terahertz imaging system, so as to obtain a first one-dimensional distance image for the detected composite material.
A denoising unit 402, configured to perform high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile.
A guiding and filtering unit 403, configured to respectively use the second one-dimensional range profile and the second one-dimensional range profile after detail enhancement as a first guiding graph and a second guiding graph, and respectively perform guiding and filtering on the second one-dimensional range profile to obtain a detail layer and a base layer.
A gain superimposing unit 404, configured to perform a first gain and a second gain on the detail layer and the base layer, respectively, and superimpose the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional range profile.
And an amplitude imaging unit 405, configured to perform amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
In one possible embodiment, the detection unit is configured to:
and carrying out imaging detection on the detected composite material through the terahertz imaging system so as to obtain at least one piece of amplitude information of the reflection echoes of the detected composite material on different interfaces.
And obtaining a detection signal of the detected composite material in the terahertz time domain according to the at least one piece of amplitude information.
Performing fast Fourier transform on the detection signal to obtain the first one-dimensional range profile; wherein the fast fourier transform is of the formula:
in the formula (I), the compound is shown in the specification,
the fast fourier transform is characterized and the fast fourier transform,
in order to be able to detect the signal,
is the first one-dimensional range profile.
In one possible embodiment, the denoising unit is configured to:
performing discrete wavelet transform on the first one-dimensional distance image to decompose the first one-dimensional distance image into first transform results under multiple scales according to a wavelet mother function; wherein a first relationship between the first one-dimensional distance image and the first transformation result is:
in the formula (I), the compound is shown in the specification,
for a preset discretized stretch index,
t is a time variable in a detection signal of the terahertz time domain, is a preset discretization translation coefficient,
in order to be the result of said first transformation,
for the discretization stretch index to be
The scale factor of (a) is,
for the discretized stretch index to be a discretized stretch index of
The scale factor of (a) is,
in order to be a function of the mother wavelet,
is a wavelet basis function based on the discretized scaling index, the discretized shifting coefficient, and a wavelet mother function under the time variable,
is the conjugate of the wavelet basis function.
Decomposing the first one-dimensional range profile into second transformation results under a plurality of scales according to a scale function; wherein a second relationship between the first one-dimensional distance image and the second transformation result is:
in the formula (I), the compound is shown in the specification,
in order to be the result of said second transformation,
in order to be a function of the scale,
for the scale function to pass
Multiple expansion and contraction
A first scale function obtained after the time translation;
is the conjugate of the first scale function.
Determining a third relation between the wavelet basis functions and the scale functions under multiple scales according to a multi-resolution analysis equation; wherein the third relationship is:
in the formula
Is the translation multiple of the first lens group,
as a function of said scale
In that
Is carried out under the scale
A second scale function after the time translation;
a first wavelet coefficient corresponding to the wavelet basis function;
corresponding translation variation when the relation between the wavelet function under the j scale and the scale function under the j +1 scale is established; the wavelet function comprises a wavelet basis function and a wavelet mother function.
Obtaining a fourth relation between the first transformation result and a target second transformation result under multiple scales according to the first relation, the second relation and the third relation; wherein the fourth relationship is:
in the formula (I), the compound is shown in the specification,
and the second transformation result is the target corresponding to the second scale function.
And determining a first wavelet coefficient corresponding to each first transformation result under multiple scales according to the fourth relation.
Performing hard threshold function shrinkage denoising on a first wavelet coefficient set composed of all the first wavelet coefficients according to a preset threshold so as to change the first wavelet coefficients under each scale into corresponding second wavelet coefficients; wherein, the hard threshold function shrinkage denoising is carried out by the following formula:
in the formula (I), the compound is shown in the specification,
the preset threshold value is used as the preset threshold value;
is the second wavelet coefficient;
is a modulus of the first wavelet coefficient; the preset threshold is a standard deviation of the first wavelet coefficients at a plurality of scales.
And determining at least one target second wavelet coefficient with the value of the second wavelet coefficient being not zero.
And determining a target first transformation result corresponding to each target second wavelet coefficient in the at least one target second wavelet coefficient according to the fourth relation.
And reconstructing all the first transformation results of the targets according to the first relation to obtain the second one-dimensional range profile.
In one possible embodiment, the formula of the guided filtering is:
in the formula (I), the compound is shown in the specification,
either the detail layer or the base layer,
is a guide map, the guide map being the first guide map or the second guide map;
to be the size of the filtering window,
the size of the filtering window and the regularization parameter are preset as the regularization parameter;
the second one-dimensional range profile is guided and filtered based on the guide map, the filter window size, and the regularization parameter.
In one possible embodiment, the second guidance diagram is obtained by:
in the formula (I), the compound is shown in the specification,
for the second guide map, LP characterizes a low-pass filter,
is a preset gain factor of the high frequency information,
and characterizing the range profile obtained after the low-pass filtering is carried out on the second one-dimensional range profile.
In a possible embodiment, the third one-dimensional distance image is obtained by:
in the formula (I), the compound is shown in the specification,
for the third one-dimensional range profile,
、
respectively a first gain coefficient and a second gain coefficient which are preset,
is the fine layer;
is the base layer.
In one possible embodiment, the result image is obtained by:
in the formula (I), the compound is shown in the specification,
in order to be able to produce the result image,
is that the third one-dimensional range profile is at
Go to,
A column (a),
A three-dimensional matrix of page counts, the resulting image being depth of page counts
A two-dimensional matrix of (a); the two-dimensional matrix comprises
Go to,
Columns;
respectively a first distance between the upper surface of the tested composite material and a detector and a second distance between the lower surface of the tested composite material and the detector,
a third distance to the detector for the preselected imaging plane.
Fig. 5 shows a schematic structural diagram of an electronic device provided in an embodiment of the present application, and as shown in fig. 5, the electronic device includes: a processor 501, a storage medium 502 and a bus 503, wherein the storage medium 502 stores machine readable instructions executable by the processor 501, when an electronic device runs the method for enhancing the resolution of terahertz imaging of composite materials as in the embodiment, the processor 501 communicates with the storage medium 502 through the bus 503, and the processor 501 executes the machine readable instructions to execute the steps as in the embodiment.
In an embodiment, the storage medium 502 may further execute other machine-readable instructions to perform other methods as described in the embodiments, and for the method steps and principles of specific execution, reference is made to the description of the embodiments, which is not described in detail herein.
Embodiments of the present application further provide a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor when the computer program is executed to perform the steps in the embodiments.
In the embodiments of the present application, when being executed by a processor, the computer program may further execute other machine-readable instructions to perform other methods as described in the embodiments, and for the method steps and principles of specific execution, reference is made to the description of the embodiments, and details are not repeated here.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. The above-described apparatus embodiments are merely illustrative, and for example, the division of the modules is merely a logical division, and there may be other divisions in actual implementation, and for example, a plurality of modules or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or modules through some communication interfaces, and may be in an electrical, mechanical or other form.
The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a U disk, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A composite material terahertz imaging resolution enhancement method is characterized by comprising the following steps:
adopting a terahertz imaging system to perform imaging detection on a detected composite material to obtain a first one-dimensional distance image for the detected composite material;
carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile;
respectively taking the second one-dimensional range profile and the second one-dimensional range profile after detail enhancement as a first guide graph and a second guide graph, and respectively performing guide filtering on the second one-dimensional range profile to respectively obtain a detail layer and a basic layer;
respectively performing first gain and second gain on the detail layer and the base layer, and superposing the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional distance image;
and carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
2. The method of claim 1, wherein the performing imaging detection on the composite material under test by using a terahertz imaging system to obtain a first one-dimensional range profile for the composite material under test comprises:
imaging and detecting the detected composite material through the terahertz imaging system to acquire at least one piece of amplitude information of reflection echoes of the detected composite material on different interfaces;
obtaining a detection signal of the detected composite material in a terahertz time domain according to the at least one piece of amplitude information;
performing fast Fourier transform on the detection signal to obtain the first one-dimensional range profile; wherein the fast fourier transform is of the formula:
in the formula (I), the compound is shown in the specification,
the fast fourier transform is characterized and the fast fourier transform,
in order to be able to detect the signal,
is the first one-dimensional range profile.
3. The method of claim 1, wherein performing high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile comprises:
performing discrete wavelet transform on the first one-dimensional distance image to decompose the first one-dimensional distance image into first transform results under multiple scales according to a wavelet mother function; wherein a first relationship between the first one-dimensional distance image and the first transformation result is:
in the formula (I), the compound is shown in the specification,
for a preset discretized stretch index,
t is a time variable in a detection signal of the terahertz time domain, is a preset discretization translation coefficient,
in order to be the result of said first transformation,
for the discretization stretch index to be
The scale factor of (a) is,
for the discretized stretch index to be a discretized stretch index of
The scale factor of (a) is,
in order to be a function of the mother wavelet,
is a wavelet basis function based on the discretized scaling index, the discretized shifting coefficient, and a wavelet mother function under the time variable,
is the conjugate of the wavelet basis function;
decomposing the first one-dimensional range profile into second transformation results under a plurality of scales according to a scale function; wherein a second relationship between the first one-dimensional distance image and the second transformation result is:
in the formula (I), the compound is shown in the specification,
in order to be the result of said second transformation,
in order to be a function of the scale,
for the scale function to pass
Multiple expansion and contraction
First scale function obtained after time shift；
Is the conjugate of the first scale function;
determining a third relation between the wavelet basis functions and the scale functions under multiple scales according to a multi-resolution analysis equation; wherein the third relationship is:
in the formula (I), the compound is shown in the specification,
is the translation multiple of the first lens group,
as a function of said scale
In that
Is carried out under the scale
A second scale function after the time translation;
a first wavelet coefficient corresponding to the wavelet basis function;
corresponding translation variation when a relation is established between the wavelet function under the j scale and the scale function under the j +1 scale; the wavelet function comprises a wavelet basis function and a wavelet mother function;
obtaining a fourth relation between the first transformation result and a target second transformation result under multiple scales according to the first relation, the second relation and the third relation; wherein the fourth relationship is:
in the formula (I), the compound is shown in the specification,
a second transformation result corresponding to the second scale function is obtained;
determining a first wavelet coefficient corresponding to each first transformation result under multiple scales according to the fourth relation;
performing hard threshold function shrinkage denoising on a first wavelet coefficient set composed of all the first wavelet coefficients according to a preset threshold so as to change the first wavelet coefficients under each scale into corresponding second wavelet coefficients; wherein, the hard threshold function shrinkage denoising is carried out by the following formula:
in the formula (I), the compound is shown in the specification,
the preset threshold value is used as the preset threshold value;
is the firstTwo wavelet coefficients;
is a modulus of the first wavelet coefficient; the preset threshold is a standard deviation of the first wavelet coefficient at a plurality of scales;
determining at least one target second wavelet coefficient of which the median value of the second wavelet coefficients is not zero;
determining a target first transformation result corresponding to each target second wavelet coefficient in the at least one target second wavelet coefficient according to the fourth relation;
and reconstructing all the first transformation results of the targets according to the first relation to obtain the second one-dimensional range profile.
4. The method of claim 1, wherein the guided filtering is formulated as:
in the formula (I), the compound is shown in the specification,
either the detail layer or the base layer,
is a guide map, the guide map being the first guide map or the second guide map;
to be the size of the filtering window,
the size of the filtering window and the regularization parameter are preset as the regularization parameter;
the second one-dimensional range profile is guided and filtered based on the guide map, the filter window size, and the regularization parameter.
5. The method of claim 4, wherein the second guidance map is obtained by:
in the formula (I), the compound is shown in the specification,
for the second guide map, LP characterizes a low-pass filter,
is a preset gain factor of the high frequency information,
and characterizing the range profile obtained after the low-pass filtering is carried out on the second one-dimensional range profile.
6. The method of claim 1, wherein the third one-dimensional range image is obtained by:
in the formula (I), the compound is shown in the specification,
for the third one-dimensional range profile,
、
respectively a first gain coefficient and a second gain coefficient which are preset,
is the fine layer;
is the base layer.
7. The method of claim 1, wherein the result image is obtained by:
in the formula (I), the compound is shown in the specification,
in order to be able to produce the result image,
is that the third one-dimensional range profile is at
Go to,
A column (a),
A three-dimensional matrix of page counts, the resulting image being depth of page counts
A two-dimensional matrix of (a); the two-dimensional matrixIncluded
Go to,
Columns;
respectively a first distance between the upper surface of the tested composite material and a detector and a second distance between the lower surface of the tested composite material and the detector,
a third distance to the detector for the preselected imaging plane.
8. A composite terahertz imaging resolution enhancement device, characterized in that the device comprises:
the detection unit is used for carrying out imaging detection on the detected composite material by adopting a terahertz imaging system so as to obtain a first one-dimensional distance image aiming at the detected composite material;
the denoising unit is used for carrying out high-frequency denoising on the first one-dimensional range profile to obtain a denoised second one-dimensional range profile;
the guiding filtering unit is used for respectively taking the second one-dimensional range profile and the second one-dimensional range profile after the detail enhancement as a first guiding graph and a second guiding graph, and respectively guiding and filtering the second one-dimensional range profile to respectively obtain a detail layer and a basic layer;
a gain superposition unit, configured to perform a first gain and a second gain on the detail layer and the base layer, respectively, and superpose the detail layer subjected to the first gain and the base layer subjected to the second gain into a third one-dimensional range profile;
and the amplitude imaging unit is used for carrying out amplitude imaging on the third one-dimensional range profile to obtain an imaged result image.
9. An electronic device, comprising: a processor, a storage medium and a bus, wherein the storage medium stores machine-readable instructions executable by the processor, when an electronic device runs, the processor and the storage medium communicate through the bus, and the processor executes the machine-readable instructions to execute the steps of the composite material terahertz imaging resolution enhancement method according to any one of claims 1 to 7.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, performs the steps of the composite material terahertz imaging resolution enhancement method according to any one of claims 1 to 7.
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