Videos and images have been widely used, and the requirements for camera imaging quality are getting higher and higher. At present, most methods of camera lens sharpness testing are divided into five ...areas: upper left, lower left, upper right, lower right, and middle. The test results of each area are used to approximate the overall sharpness level of the camera lens. The local sharpness failure of the camera lens cannot be solved by these methods. Because of this limitation, we proposed the idea of indirectly reflecting the local sharpness of the lens according to the image blur detection, and develop an image blur assessment method based on intensity and derivative (IDD). It can visualize the degradation process of camera sharpness from center to edge and the location of local failure. We demonstrate the feasibility and accuracy of the method through a case, as well as comparison to other methods.
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This letter proposes a simple and fast approach for no-reference image sharpness quality assessment. In this proposal, we define the maximum local variation (MLV) of each pixel as the maximum ...intensity variation of the pixel with respect to its 8-neighbors. The MLV distribution of the pixels is an indicative of sharpness. We use standard deviation of the MLV distribution as a feature to measure sharpness. Since high variations in the pixel intensities is a better indicator of the sharpness than low variations, the MLV of the pixels are subjected to a weighting scheme in such a way that heavier weights are assigned to greater MLVs to make the tail end of MLV distribution thicker. The weighting leads to an improvement of the MLV distribution to be more discriminative for different blur degrees. Finally, the standard deviation of the weighted MLV distribution is used as a metric to measure sharpness. The proposed approach has a very low computational complexity and the performance analysis shows that our approach outperforms the state-of-the-art techniques in terms of correlation with human vision system on several commonly used databases.
Gradients are commonly used in image sharpness assessment methods. However, research has not fully addressed the direct relationship between gradients and the perceived sharpness. In this paper, we ...discover and validate through experiments that the maximum gradient is an effective indicator of the perceived image sharpness on a global or local scale. Based on these observations, we propose a novel and efficient no-reference image quality assessment (NR-IQA) method for blurry images. Our method uses two elements to predict the quality of blurry images: the maximum gradient and the variability of gradients. The maximum gradient represents the sharpest spot in an image, and the variability of gradients shows variations within the content of the image. According to the characteristics of human visual systems, these factors are significant for humans when judging the quality of blurry images. The method was tested using blurry image datasets from five public IQA databases. Compared with nine other state-of-the-art NR-IQA methods for blurry images, the experimental results demonstrate that our method is more consistent with humans' subjective evaluations. The MATLAB source code of our method is available at https://github.com/Atmegal/Sharpness-evaluation .
We report a Gamma-corrected, SNR-enhanced and sharpness-projection-based reconstruction approach for digital particle holography. In this approach, we mitigate the artefacts from off-focal planes by ...capturing three holograms with various illumination angles, and extract particle information by applying image processing to a high-quality maximum - sharpness-projection (MSP) image. This approach reinforces weak edges using a Gamma correction procedure, and segments particles from the MSP image by using a new hybrid threshold, which comprises both local and global features. Experimental results for nonspherical particles show that the reported approach can provide a high-quality MSP image, being less likely than the conventional method to be fooled by noise and more likely to retain particle features. The hybrid threshold helps in retaining fine features, separating neighbouring particles and differentiating particles from the background. For the large particles (>20 pixels), the diameter error is generally less than 10% while using the proposed automatic hybrid thresholding technique.
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The need for ultra-fine surface generation by machining in micrometer and sub-micrometer scales is increasing rapidly for fabrication of micro products. However, there are limitations of bringing ...down the process from macro to micro to ultra-precision level due to the variation of the physical phenomenon responsible for surface generation process which is significantly dependent on tool edge radius. To analyse the tool edge radius effect, the governing process parameter identified as the ratio of undeformed chip thickness (a) to tool edge radius (r), which is known as relative tool sharpness, RTS (a/r). However, there are lacking of mathematical models to quantify the micro-mechanics of the material deformation during the surface generation process. In this study, a mathematical model has been established for the material removal mechanism with relation to edge radius effect. The novelty of this model lies in its ability to quantify the instantaneous material flow angle (φne) for a particular tool-workpiece combination with relative tool sharpness (RTS). The proposed model is able to capture the trend of the change of surface generation mechanism from shearing to extrusion to ploughing and rubbing. The transition of the deformation behaviour is predicted form the mathematical model and orthogonal cutting experiments were conducted for the validation of the results for two materials (Mg and Cu alloy). Under identical machining conditions, micro-chips and machined surface integrity of Cu and Mg alloy exhibited different characteristics. For the best nanometric finishing, the ‘extrusion-like’ machining zone is identified where the RTS value for Cu alloy is found smaller than that for Mg alloy. Hence, smaller grain material (Cu alloy, ~35µm) provides smaller RTS value than larger grain material (Mg alloy, ~126µm) for achieving superior surface finishing. Therefore, material properties play an important role for the relative tool sharpness (RTS) during the variation of high quality surface generation mechanism.
•Relative tool sharpness (RTS) is the most critical parameter in ultra-precision machining.•Variation of surface generation mechanisms is influenced by RTS at the distinct machining zones.•Under identical cutting conditions, both alloys render significantly different machining response.•Material microstructure plays important role for RTS in ‘extrusion-like’ finishing mechanism.
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In crystalline semiconductors, absorption onset sharpness is characterized by temperature-dependent Urbach energies. These energies quantify the static, structural disorder causing localized ...exponential-tail states, and dynamic disorder from electron-phonon scattering. Applicability of this exponential-tail model to disordered solids has been long debated. Nonetheless, exponential fittings are routinely applied to sub-gap absorption analysis of organic semiconductors. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements. We find that sub-gap absorption due to singlet excitons is universally dominated by thermal broadening at low photon energies and the associated Urbach energy equals the thermal energy, regardless of static disorder. This is consistent with absorptions obtained from a convolution of Gaussian density of excitonic states weighted by Boltzmann-like thermally activated optical transitions. A simple model is presented that explains absorption line-shapes of disordered systems, and we also provide a strategy to determine the excitonic disorder energy. Our findings elaborate the meaning of the Urbach energy in molecular solids and relate the photo-physics to static disorder, crucial for optimizing organic solar cells for which we present a revisited radiative open-circuit voltage limit.
Fang evolution in venomous snakes Cleuren, Silke G. C.; Hocking, David P.; Evans, Alistair R.
Evolution,
June 2021, Volume:
75, Issue:
6
Journal Article
Peer reviewed
Open access
Venomous snakes are among the world’s most specialized predators. During feeding, they use fangs to penetrate the body tissues of their prey, but the success of this penetration depends on the shape ...of these highly specialized teeth. Here, we examined the evolution of fang shape in a wide range of snakes using 3D geometric morphometrics (3DGM) and cross-sectional tooth sharpness measurements. We investigated the relationship of these variables with six diet categories based on the prey’s biomechanical properties, and tested for evolutionary convergence using two methods. Our results show that slender elongate fangs with sharp tips are used by snakes that target soft-skinned prey (e.g., mammals), whereas fangs become more robust and blunter as the target’s skin becomes scaly (e.g., fish and reptiles) and eventually hard-shelled (e.g., crustaceans), both with and without correction for evolutionary allometry. Convergence in fang shape is present, indicating that fangs of snakes with the same diet are more similar than those of closely related species with different diets. Establishing the relationship between fang morphology and diet helps to explain how snakes became adapted to different lifestyles, while also providing a proxy to infer diet in lesser known species or extinct snakes from the fossil record.
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