A kind of deep learning method of microwave remote sensing image speckle noise reduction
Technical field
The present invention relates to microwave remote sensing technical field of image processing, and in particular to a kind of micro- using deep learning network implementations
The method of wave remote sensing images speckle noise reduction.
Background technique
Microwave remote sensing technique has many advantages, such as round-the-clock, round-the-clock, multi-angle of view, multi-frequency, multipolarization, and electromagnetism
Wave signal has stronger penetration power, it can be found that hiding target with tracking, thus is widely used in various military and civilians
Scene.Compared with natural image, microwave remote sensing image is often accompanied by a large amount of coherent speckle noises, significantly reduces microwave remote sensing
The resolution ratio of image causes certain difficulty to further realize the application such as edge detection, image segmentation, target identification.Microwave
Remote sensing images, especially SAR (Synthetic Aperture Radar) image, coherent speckle noise are typical multiplicative noise,
It generates along with SAR image and is existed.Compared with additive noise, multiplicative noise is more difficult to handle.
In the past few decades, researcher proposes a large amount of microwave remote sensing image speckle noise reduction methods.Often
The method of microwave remote sensing image speckle noise reduction includes: Lee filtering method, Frost filtering method, the filtering side Kuan
Method, Gamma MAP filtering method, FANS filtering method, BM-3D filtering method etc..These filtering methods pass through to sliding window
Interior microwave remote sensing image data carries out local shape factor, inhibits coherent speckle noise, improves microwave remote sensing picture quality.But
These methods face two big challenges: whether the parameter (1) counted in sliding window is reliable;(2) whether coherent speckle noise model
Reliably.And these methods successively extract characteristics of image using sliding window, reduce image processing speed, are not possible to meet real-time
Handle large scale microwave remote sensing image speckle noise reduction task.
The forming process of microwave remote sensing image coherent speckle noise is extremely complex, it is difficult to carry out essence to it with simple mathematical model
Really modeling, thus speckle noise reduction method treatment effect is undesirable at present.The deep learning method of sample driving then has
Powerful non-linear expression's ability, image processor GPU (Graphics Processing Unit) accelerate deep learning side
Method processing speed provides new approaches to explore microwave remote sensing image speckle noise reduction.
Summary of the invention
In order to solve above-mentioned key technology difficulty, the invention proposes a kind of depths of microwave remote sensing image speckle noise reduction
Spend learning method;The present invention passes through building DsCNN (Despeckle using Convolutional Neural Networks)
Network realizes the Accurate Model to multiplicative noise, and then realizes processing large scale microwave remote sensing image speckle noise reduction in real time
Task.
The deep learning method of microwave remote sensing image speckle noise reduction of the present invention the following steps are included:
1) DsCNN network is constructed;
2) DsCNN network training and test sample data set are generated;
3) training DsCNN network;
4) DsCNN network implementations microwave remote sensing image speckle noise reduction is utilized;
DsCNN network uses residual error network ResNet (Residual Network) block coupled in series form structure in step 1)
It builds, realizes the classification processing of coherent speckle noise;
DsCNN network activation function is all made of Tanh in step 1), and microwave remote sensing data value field is compressed to [0,1],
Accelerate DsCNN network convergence;
DsCNN network convolutional layer fill pattern uses " same " in step 1).
DsCNN network does not contain pond layer, full articulamentum in step 1);
DsCNN network uses the end-to-end processing of pixel to pixel formula in step 1);
Loss function is using mean square error MSE (Mean Squared Error) and total variation TV (Total in step 1)
Variation the form) combined, as shown in formula (1):
Ltotal=Lmse+ρLTV (1)
Wherein ρ indicates weight factor, is used for balanced mean square error loss function LmseWith total variation loss function LTVBetween
Significance level;Wherein LmseAnd LTVIt can be expressed as formula 2 and formula 3:
Wherein W indicates that image lateral coordinates element number, H indicate image longitudinal coordinate element number;W indicates that image is lateral
W-th of element, h indicate longitudinal h-th of the element of image;YW, hAnd XW, hRespectively indicate outputting and inputting for DsCNN network;Table
Show the denoising image of DsCNN network output;Indicate the DsCNN network of Complete Convergence;LmseImage is made an uproar with nothing after guaranteeing denoising
Error is minimum between acoustic image;LTVImage after guaranteeing denoising has better texture features;
Training sample is originated from the colour optics remote sensing images over the ground of Google Earth in step 2), by by colourama
It learns remote sensing images and is converted to the gray scale remote sensing images with multiplicative noise, realize the realistic simulation to true microwave remote sensing image, it is low
Cost generates a large amount of DsCNN network sample data sets.
Advantages of the present invention:
The invention proposes a kind of deep learning methods of microwave remote sensing image speckle noise reduction;The present invention has as follows
Advantage:
1, DsCNN network is constructed using residual error network module series system, and coherent speckle noise classification processing can reduce phase
Dry spot noise remove difficulty, and can overcome the problems, such as to train difficulty to increase caused by the DsCNN network number of plies is too deep;
2, DsCNN network sample data set is originated from open source Google Earth software, can be with Free Acquisition adequate sample number
According to collection, overcome existing microwave remote sensing image open source data set few, the high disadvantage of procurement cost;
3, DsCNN network is in removal coherent speckle noise meanwhile, it is capable to keep target texture feature;
4, DsCNN network processes speed is fast, meets processing large scale microwave remote sensing image speckle noise reduction task in real time
Demand;
5, DsCNN network is driven based on sample, is reduced coherent speckle noise modeling difficulty, is improved coherent speckle noise modeling
Precision;
Detailed description of the invention
Fig. 1 is DsCNN schematic network structure;
Fig. 2 is DsCNN network sample data set product process schematic diagram;
Fig. 3 is the speckle noise reduction result schematic diagram that DsCNN network is directed to training sample data collection;
Fig. 4 is the speckle noise reduction result schematic diagram that DsCNN network is directed to test sample data set;
Fig. 5 is that different speckle noise reduction methods are directed to identical SAR image speckle noise reduction comparative result figure;
Fig. 6 is the speckle noise reduction Comparative result that different speckle noise reduction methods are directed to three groups of zonule SAR images
Figure.
Specific embodiment
With reference to the accompanying drawing, by specific embodiment, the present invention is further explained.
The deep learning method of the present embodiment microwave remote sensing image speckle noise reduction the following steps are included:
1) DsCNN network is constructed:
As shown in Figure 1, DsCNN network is made of two residual error network modules;Each residual error network module includes four layers of volume
Product neural net layer and quick articulamentum (shortcut) are constituted;Convolutional neural networks layer includes matrix convolution Conv, batch standard
Change BN and activation primitive Tanh to operate;Shortcut layers of realization identical transformation are added by matrix and are realized;Input picture is 256
The image containing coherent speckle noise of × 256 pixels;Export the noise-free picture that image is corresponding 256 × 256 pixel;L1-L7
The convolution kernel size of layer convolutional layer is 3 × 3, and convolution kernel number is 64;L8 layers of convolution kernel size is 3 × 3, convolution kernel number
It is 1.
2) DsCNN network training and test sample data set are generated:
As shown in Fig. 2, the crawl of colour optics remote sensing images is in open source software Google Earth;Gray processing is carried out to image
Processing generates greyscale optical remote sensing images;Multiplicative noise is added on greyscale optical remote sensing images, then corresponding contain can be generated
There is the emulation microwave remote sensing image of multiplicative noise, multiplicative noise variance is set as 0.2 in this example;It will be imitative containing multiplicative noise
True microwave remote sensing image random division is the image of 256 × 256 pixels, then it is grey with the noiseless of corresponding 256 × 256 pixel
It spends remote sensing image and constitutes one group of sample data;The symbiosis of this example is at 3400 groups of sample data sets, including 3000 groups of instructions
Practice sample data set, 200 groups of verifying sample data sets and 200 groups of test sample data sets.
3) training DsCNN network:
DsCNN network uses adaptability moments estimation optimization method in this example;DsCNN network training every batch of inputs 16 groups
Sample data;DsCNN network training amounts to iteration 100 times;DsCNN e-learning rate Initialize installation is 0.0002, decaying
The factor is set as 0.1;Weight factor ρ is set as 0.000002 in loss function;Fig. 3 is to export after DsCNN network completes training
Training sample data collection part denoising result;Fig. 4 is that the part of the test sample data set of DsCNN network output denoises knot
Fruit;A indicates that network inputs image, b indicate noise-free picture in Fig. 3 and Fig. 4;C indicates that network exports image, that is, schemes after denoising
Picture.As can be seen from figs. 3 and 4 the coherent speckle noise of DsCNN network output image is had compared with DsCNN network inputs image
Effect inhibits, and target texture is clear, and picture quality is significantly promoted;
Introduce Y-PSNR PSNR (Peak Signal to Noise Ratio) and structuring index of similarity
(structural similarity index, be abbreviated as SSIM) Lai Hengliang picture quality.Wherein structuring index of similarity can
To indicate are as follows:
Wherein a and b respectively indicates image and noise-free picture to be assessed.For image a,Wherein P
Indicate pictorial element number, p indicates p-th of element.Above-mentioned definition is for image b
It is applicable in.C1And C2It is a small constant, such as 0.01.SSIM value is bigger, table
Show that the similitude of two images is bigger.SSIM maximum value is 1, is indicated identical.
As shown in Table 1, DsCNN network training and test sample collection output image are better than input picture, and PSNR and SSIM refer to
Number is greatly improved.
PSNR the and SSIM index of table 1:DsCNN network training and test sample collection output image
4) DsCNN network implementations microwave remote sensing image speckle noise reduction is utilized
As shown in Fig. 5 (a), two width SAR images are originated from the shooting of TerraSAR-X and TanDEM-X spaceborne radar not
Island image near Singapore in the same time.Two width SAR images are 9984 × 5888 pixels.Introduce equivalent more view indexes
(ENL:Equivalent Number of Looks) measures SAR image quality, as shown in formula 5:
Wherein K indicates the total number of sliding window, μkWithRespectively indicate the mean value and variance of pixel in k-th of sliding window.
ENL index is bigger, then shows that picture quality is higher.
B indicates FANS method speckle noise reduction result in Fig. 5 and Fig. 6;C indicates BM-3D method speckle noise reduction knot
Fruit;D indicates DsCNN network speckle noise reduction result;SAR image compares figure b in figure d and figure c image texture details is more clear
Clear, coherent speckle noise is more preferably inhibited;As shown in Table 2, the ENL index for scheming d is maximum, i.e., picture quality is best.It can by table 3
Know, handle the SAR image of same scale, FANS method needs 1400 seconds, and BM-3D method needs 600 seconds, and DsCNN method is only
Need 10 seconds or so;Therefore DsCNN method meets handles large scale microwave remote sensing image speckle noise reduction task in real time
Demand.
SAR image ENL index contrast table in table 2: Fig. 6
Table 3: SAR image distinct methods operation time contrast table in reconstruct image 5
It is finally noted that the purpose for publicizing and implementing example is to help to further understand the present invention, but this field
Technical staff be understood that without departing from the spirit and scope of the invention and the appended claims, it is various replacement and repair
It is all possible for changing.Therefore, the present invention should not be limited to embodiment disclosure of that, and the scope of protection of present invention is to weigh
Subject to the range that sharp claim defines.