Degree Of Polarization Images Research Articles

Joint polarization detection and degradation mechanisms for underwater image enhancement.

Light absorption and scattering exist in the underwater environment, which can lead to blurring, reduced brightness, and color distortion in underwater images. Polarized images have the advantages of eliminating underwater scattering interference, enhancing contrast, and detecting material information of the object in underwater detection. In this paper, from the perspective of polarization imaging, different concentrations (0.15g/ml, 0.30g/ml, and 0.50g/ml), different wave bands (red, green, and blue), different materials (copper, wood, high-density PVC, aluminum, cloth, foam, cloth sheet, low-density PVC, rubber, and porcelain tile), and different depths (10cm, 20cm, 30cm, and 40cm) are set up in a chamber for the experimental environment. By combining the degradation mechanism of underwater images and the analysis of polarization detection results, it is proved that the degree of polarization images have greater advantages than degree of linear polarization images, degree of circular polarization images, S1, S2, and S3 images, and visible images underwater. Finally, a fusion algorithm of underwater visible images and polarization images based on compressed sensing is proposed to enhance underwater degraded images. To improve the quality of fused images, we introduce orthogonal matching pursuit (OMP) in the high-frequency part to improve image sparsity and consistency detection in the low-frequency part to improve the image mutation phenomenon. The fusion results show that the peak SNR values of the fusion result maps using OMP in this paper are improved by 32.19% and 22.14% on average over those using backpropagation and subspace pursuit methods. With different materials and concentrations, the underwater image enhancement algorithm proposed in this paper improves information entropy, average gradient, and standard deviation by 7.76%, 18.12%, and 40.8%, respectively, on average over previous algorithms. The image NIQE value shows that the image quality obtained by this paper's algorithm is improved by about 69.26% over the original S0 image.

Polarimetric Multi-View Inverse Rendering.

A polarization camera has great potential for 3D reconstruction since the angle of polarization (AoP) and the degree of polarization (DoP) of reflected light are related to an object's surface normal. In this paper, we propose a novel 3D reconstruction method called Polarimetric Multi-View Inverse Rendering (Polarimetric MVIR) that effectively exploits geometric, photometric, and polarimetric cues extracted from input multi-view color-polarization images. We first estimate camera poses and an initial 3D model by geometric reconstruction with a standard structure-from-motion and multi-view stereo pipeline. We then refine the initial model by optimizing photometric rendering errors and polarimetric errors using multi-view RGB, AoP, and DoP images, where we propose a novel polarimetric cost function that enables an effective constraint on the estimated surface normal of each vertex, while considering four possible ambiguous azimuth angles revealed from the AoP measurement. The weight for the polarimetric cost is effectively determined based on the DoP measurement, which is regarded as the reliability of polarimetric information. Experimental results using both synthetic and real data demonstrate that our Polarimetric MVIR can reconstruct a detailed 3D shape without assuming a specific surface material and lighting condition.

Polarization-intensity joint imaging for marine target automatic recognition

The performance of sole optical imaging device for marine target recognition is degraded by sea fog, sea-glint, and many other disturbing factors. To enhance the ability of target recognition in marine environment, we propose a polarization-intensity joint imaging method and the corresponding processing method. We combine fine imaging of polarization in a small field of view with wide-field imaging of visible light intensity, using visible light intensity information for large-scale target surveys. After locking onto areas of interest, we utilize high-resolution polarization cameras with small fields of view for detailed inspection. We enhance and fuse the information from areas of interest using the proposed matching information processing method. Meanwhile, to deal with problems existing in the marine environment polarization-intensity joint imaging, such as details loss in DoP (degree of polarization) image, low target resolution in the large field of view intensity image, and insufficient information in a single image, etc., we extract the details of raw image from DoFP (division-of-focal-plane) polarization camera as residual compensation for DoP image super-resolution and cooperate with the RealSR algorithm to super-resolve the local target details of the intensity image in a large field of view. On the premise that PIQE (Perception-based Image Quality Evaluator) reaches the excellent score range, the images with the same resolution are fused. The automatic recognition comparison before and after processing proves that the accuracy of target recognition can be effectively improved after processing.

Polarization Imaging Method for Underwater Low-Visibility Metal Target Using Focus Dividing Plane

Aiming at the problems of brightness attenuation and contrast reduction in the target image caused by underwater low-visibility environments, a metal target detection method based on split-focus plane polarization imaging is proposed. Firstly, a hybrid enhancement method is proposed to clarify the degraded polarization image. In this study, the GrayWorld method is improved to compensate the attenuation difference of the total light intensity of the polarization image. Variational contrast and saturation enhancement algorithms are used to reduce the underwater scattering effect; secondly, a split-focus plane polarization imaging system is built to complete the control of camera parameters, polarization image acquisition and information processing. Under different underwater low-visibility conditions, polarization imaging of targets with different materials can be realized; finally, an image quality evaluation system is constructed to compare the light intensity and degree of polarization images that are collected by the focal plane polarization imaging system. The polarization characteristics of metal and nonmetal target plates are analyzed. The results show that under the condition of low visibility, the obtained polarization image contrast of the metal target is relatively high, and its EME, information entropy and average gradient are increased by 183.82%, 53.46% and 586.22% on average relative to the image of light intensity. In an underwater low-visibility scene, the method of focal plane polarization imaging proposed in this paper can reduce the difficulty of metal target detection.

A Method of Improving the Length Measurement Accuracy of Metal Parts Using Polarization Vision

Measurement technology based on machine vision has been widely used in various industries. The development of vision measurement technology mainly depends on the process of photosensitive components and the algorithm of processing a target image. In the high-precision dimension measurement of machined metal parts, the high-resolution imaging device usually exposes the cutting texture of the metal surface and affects the accuracy of measurement algorithm. At the same time, the edges of machined metal parts are often chamfered, which makes the edges of objects in the picture overexposed in the lighting measurement environment. These factors reduce the accuracy of dimensioning metal parts using visual measurements. The traditional vision measurement method based on color/gray image makes it difficult to analyze the physical quantities in the light field except for the light intensity, which limits the measurement accuracy. Polarization information can more carefully depict the edge contour edge information in the scene and increase the contrast between the foreground and the background. This paper presents a method to improve the measurement accuracy of machined metal parts by using polarization vision. The incident angle of the light source is optimized according to the complex refractive index of the metal material, and the degree of polarization image with enhanced edge contour features of the ROI (region of interest) is obtained. The high-precision measurement of cylindrical brass motor components is realized by using the method of reprojection transformation correction and maximum correlation template matching (NCC) for rough positioning, as well as the method of edge extraction and optimal fitting. The experimental results show that for copper parts with a tolerance range of ±0.1 mm, the average measurement error and maximum measurement error are within 0.01 mm, which are higher than the existing color/gray image measurement methods.

An Improved Wavelet Modulus Algorithm Based on Fusion of Light Intensity and Degree of Polarization

Edge detection is the basis of image analysis and image processing. The wavelet modulus maxima algorithm is a widely used edge-detection algorithm. The algorithm has the advantages of strong anti-noise ability and high precision of edge location, but it still cannot accurately obtain edge information for low-contrast images. Therefore, this paper proposes an improved wavelet mode maximum edge algorithm for the fusion of light intensity and degree of polarization. The improved wavelet mode maximum algorithm was used to extract the edges of a light intensity image and degree of polarization image, and then refine and fuse the two edges to obtain the final edge information. Simulation experiments showed that the edge image obtained by the edge-detection algorithm in this paper had a clearer outline and better connectivity.

Analysis of infrared polarization properties of targets with rough surfaces

To improve infrared polarization detection and identification probability, accurate infrared polarization properties of the targets are required. Traditional analytical models of infrared polarization ignore the shadowing effect caused by rough surfaces. Based on the surface microelement bidirectional reflectance distribution function (BRDF), the Stokes analytical model of the infrared degree of polarization (DOP) of a rough surface with a shadowing function is constructed. The effects of the incident angle and surface roughness on the polarization of metallic and non-metallic targets are quantitatively analyzed, revealing that the DOP of infrared spontaneous radiation decreases with increasing roughness of both metallic and non-metallic surfaces, with a greater decrease for the non-metallic surface. Under the same roughness and temperature conditions, the DOP of the infrared radiation of the metallic surface is greater than that of the non-metallic one. The DOP of infrared radiation reaches a peak value within a specific incident-angle range. Finally, experiments are carried out with both far-infrared (wavelength from 8um to 12um) and near-infrared (wavelength from 0.9 um to 1.7 um) polarization imaging systems. The experimental results show that infrared polarization properties of the targets are basically consistent with the theoretical analysis results. This research is of great significance for analyzing the polarization properties of real targets and processing DOP images.

Research on Iron Surface Crack Detection Algorithm Based on Improved YOLOv4 Network

Metal surface defect detection has always been an important branch of target detection. In certain places, if the cracks on the metal surface can be found in time, the existing safety hazards can be eliminated. In this paper, a polarized imaging camera with strong environmental applicability is used for sampling, and the degree of polarization image is applied to the detection of iron material cracks. The iron material polarization image crack data set (PICD-iron) is established, and the Cascade-YOLOv4 (C-YOLOv4) network model is used for crack detection. Then it solves the problems of target detection in the dark environment, complex and variable crack detection, small target detection. Experimental tests verify that the detection accuracy of the C-YOLOv4 net-work has improved while comparing with the YOLOv4 network, the detection speed has also increased by 28%.

Three-dimensional polarimetric integral imaging under low illumination conditions.

Conventional polarimetric imaging may perform poorly in photon-starved environments. In this Letter, we demonstrate the potential of integral imaging and dedicated algorithms for extracting three-dimensional (3D) polarimetric information in low light, and reducing the effects of measurement uncertainty. In our approach, the Stokes polarization parameters are measured and statistically analyzed in low illumination conditions through 3D-reconstructed polarimetric images with dedicated algorithms to improve the signal-to-noise ratio (SNR). The 3D volumetric degree of polarization (DoP) of the scene is calculated by statistical algorithms. We show that the 3D polarimetric information of the object can be statistically extracted from the Stokes parameters and 3D DoP images. Experimental results along with a novel statistical analysis verify the feasibility of the proposed approach for polarimetric 3D imaging in photon-starved environments and show that it outperforms its two-dimensional counterpart in terms of SNR. To the best of our knowledge, this is the first report of novel optical experiments along with novel statistical analysis and dedicated algorithms to recover 3D polarimetric imaging signatures in low light.

Polarization imaging performances based on different retrieving Mueller matrixes

With the aids of Monte Carlo simulation, we have presented the performance evaluation for underwater polarization imaging based on the polarization retrieve (PR) algorithm. Under horizontal linearly polarized (HLP) light and right circularly polarized (RCP) light irradiation, the simulation results demonstrate that the corresponding polarization properties can provide additional information for the imaging, and the contrast of the polarization image can be enhanced greatly compared to the single intensity (INT) image underwater. The PR method is used for reducing the scattering impacts on degree of polarization (DoP) of the light, and the contrast of the PR imaging can be enhanced obviously compared to DoP imaging in clear ocean. Meanwhile, the modified PR (MPR) method with different retrieval Mueller matrixes (RMM) deriving from different distances (l) of transmission channel has been investigated, which show that the retrieval accuracy will be enhanced with increasing transmission distances of RMM and the visibility and contrast can be further enhanced.

Haleakalā Sky Polarization: Full-Sky Observations and Modeling

Observations of the daytime sky polarization are useful calibration tools for large-aperture telescopes, as well as a testbed for polarized radiative transfer models. We present an instrument capable of measuring the complete full-sky Stokes vector over visible/NIR broad bands. The design utilizes liquid crystal variable retarders and a dual-beam polarization analyzer, allowing for a clear and cloudy sky acquisition cadence near 12 s which shows minimal image artifacts from solar and cloud motion. In this article, we detail the design, full-field calibration methodology, and Haleakalā observations, which provide an absolute polarimetric accuracy on individual Stokes parameters of better than 3% across VRI bandpasses. Angle and degree of polarization images are compared with a single-scattering model and the more complete MODTRAN-4P polarized radiative transfer package. Comparisons with independent measurements atop nearby Mauna Loa show similar polarization structure, but results suggest a relatively larger depolarization from surface reflections beneath Haleakalā.

Influence of absorption in linear polarization imaging of melanoma tissues

The contrast mechanism of different polarization imaging techniques for melanoma in mouse skin is studied using both experiments and Monte Carlo simulations. Total intensity, linear polarization difference imaging (DPI), degree of polarization imaging (DOPI) and rotating linear polarization imaging (RLPI) are applied and the relative contrasts of these polarization imaging methods between the normal and cancerous tissues are compared. A two-layer absorption-scattering model is proposed to explain the contrast mechanism of the polarization imaging for melanoma. By taking into account of both scattering of symmetrical and asymmetrical scatterers and absorption of inter-scatterer medium, the two-layer model reproduces the relative contrasts for polarization images observed in experiments. The simulation results also show that, the parameters of polarization imaging change more dramatically with the variation of absorption in the bottom layer than the top layer.

POLARIZATION IMAGING AND SCATTERING MODEL OF CANCEROUS LIVER TISSUES

We apply different polarization imaging techniques for cancerous liver tissues, and compare the relative contrasts for difference polarization imaging (DPI), degree of polarization imaging (DOPI) and rotating linear polarization imaging (RLPI). Experimental results show that a number of polarization imaging parameters are capable of differentiating cancerous cells in isotropic liver tissues. To analyze the contrast mechanism of the cancer-sensitive polarization imaging parameters, we propose a scattering model containing two types of spherical scatterers and carry on Monte Carlo simulations based on this bi-component model. Both the experimental and Monte Carlo simulated results show that the RLPI technique can provide a good imaging contrast of cancerous tissues. The bi-component scattering model provides a useful tool to analyze the contrast mechanism of polarization imaging of cancerous tissues.

A STUDY ON PENETRATION DEPTH OF POLARIZATION IMAGING

Optical clearing improves the penetration depth of optical measurements in turbid tissues. Polarization imaging has been demonstrated as a potentially promising tool for detecting cancers in superficial tissues, but its limited depth of detection is a major obstacle to the effective application in clinical diagnosis. In the present paper, detection depths of two polarization imaging methods, i.e., rotating linear polarization imaging (RLPI) and degree of polarization imaging (DOPI), are examined quantitatively using both experiments and Monte Carlo simulations. The results show that the contrast curves of RLPI and DOPI are different. The characteristic depth of DOPI scales with transport mean free path length, and that of RLPI increases slightly with g. Both characteristic depths of RLPI and DOPI are on the order of transport mean free path length and the former is almost twice as large as the latter. It is expected that they should have different response to optical clearing process in tissues.

Contribution of polarimetric imaging for the characterization of fibrous surface properties at different scales

The point in using polarimetric imaging for surface characterization is highlighted in this paper. A method for the evaluation of nonwoven surface properties at microscopic and macroscopic scales is described. This method is based on a polarimetric apparatus and various image processing operations are then performed depending on the studied scale. Polarimetric imaging applied to nonwovens, particularly degree of polarization imaging, highlights texture inhomogeneities. At both scales, image processing techniques were designed to analyze surface zones of different textures. At the macroscopic scale, a basic image processing was developed in order to detect the nonwoven manufacturing process defects. Moreover at the microscopic scale, i.e. at the fiber scale, image processing was adapted to evaluate fiber orientation within nonwovens, which is known to be an important information for mechanical behavior prediction.

Polarimetric imaging for the diagnosis of cervical cancer

AbstractWe present a first evaluation of polarimetric imaging in the degree of polarization (DOP) mode for cervical cancer detection. The preliminary results obtained with exvivo biopsies justified the development of a DOP imaging system adapted to commercial colposcope, for invivo studies. A clinical trial of this device is underway in order to compare this imaging modality with classical colposcopy for the visualisation of cervical precancerous or cancerous lesions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)