Topic
Dark-frame subtraction
About: Dark-frame subtraction is a research topic. Over the lifetime, 1216 publications have been published within this topic receiving 20763 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: Extensive simulations demonstrate that the decision-based non-local means filter can remove impulse noise from the corrupted images effectively while preserving image details very well at the various noise ratios, which leads to its significantly better image restoration performance than numerous state-of-the-art switching-based filters.
33 citations
TL;DR: The simulation results show that the ANRAD filter can reduce the noise while preserving image edges and fine details very well, and it is favorably compared to the fast non-local means filter, showing an improvement in the quality of the restored image.
Abstract: In image processing and computer vision, the denoising process is an important step before several processing tasks. This paper presents a new adaptive noise-reducing anisotropic diffusion (ANRAD) method to improve the image quality, which can be considered as a modified version of a speckle-reducing anisotropic diffusion (SRAD) filter. The SRAD works very well for monochrome images with speckle noise. However, in the case of images corrupted with other types of noise, it cannot provide optimal image quality due to the inaccurate noise model. The ANRAD method introduces an automatic RGB noise model estimator in a partial differential equation system similar to the SRAD diffusion, which estimates at each iteration an upper bound of the real noise level function by fitting a lower envelope to the standard deviations of pre-segment image variances. Compared to the conventional SRAD filter, the proposed filter has the advantage of being adapted to the color noise produced by today's CCD digital camera. The simulation results show that the ANRAD filter can reduce the noise while preserving image edges and fine details very well. Also, it is favorably compared to the fast non-local means filter, showing an improvement in the quality of the restored image. A quantitative comparison measure is given by the parameters like the mean structural similarity index and the peak signal-to-noise ratio.
33 citations
TL;DR: In this paper, a color image is transformed into a grayscale one, and wavelet transform based de-noising filter is used to extract the sensor pattern noise, then the variance of the pattern noise and the signal noise ratio are chosen as features, non-overlapping sliding window operations are done to the images to divide them into different sub-blocks, and the tampered areas are detected by analyzing the correlation of the features between the subblocks and the whole image.
33 citations
TL;DR: In this article, a method to reduce the inherited coherent noise degrades the imaging quality and resolution in digital holographic microscopy is proposed, where a series of digital holograms are recorded by laterally shifting camera and reconstructed individually, and the additional lateral displacement and phase shift of reconstructed images due to the change of camera position are corrected by using the phase compensation and image registration algorithms.
33 citations
TL;DR: Noise and resolution were measured simultaneously and it was shown that singles-based randoms correction gave rise to lower noise than delayed event subtraction for a fixed spatial resolution.
Abstract: As an aid to evaluating image reconstruction and correction algorithms in positron emission tomography, a phantom procedure has been developed that simultaneously measures image noise and spatial resolution. A commercially available 68Ge cylinder phantom (20 cm diameter) was positioned in the center of the field-of-view and two identical emission scans were sequentially performed. Image noise was measured by determining the difference between corresponding pixels in the two images and by calculating the standard deviation of these difference data. Spatial resolution was analyzed using a Fourier technique to measure the extent of the blurring at the edge of the phantom images. This paper addresses the noise aspects of the technique as the spatial resolution measurement has been described elsewhere. The noise measurement was validated by comparison with data obtained from multiple replicate images over a range of noise levels. In addition, we illustrate how simultaneous measurement of noise and resolution can be used to evaluate two different corrections for random coincidence events: delayed event subtraction and singles-based randoms correction. For a fixed number of iterations of the maximum-likelihood expectation-maximization algorithm, the singles-based correction gave rise to higher noise than delayed event subtraction. However, when noise and resolution were measured simultaneously it was shown that singles-based randoms correction gave rise to lower noise than delayed event subtraction for a fixed spatial resolution. The proposed method of simultaneously measuring image noise and spatial resolution is useful for evaluating reconstruction algorithms and may aid standardization of data collection between centers.
32 citations