135 results about "Ringing artifacts" patented technology

Ringing artifacts are removed from a quantized image by an image de-ringing filter that includes a determination unit, an adaptive filter and a nonlinear low-pass filter. The determination unit determines whether each selected pixel of a first set of selected pixels of an image contains a ringing artifact based on, for example, gray-level values of selected pixels within a determination kernel of pixels relating to the selected pixel. The adaptive filter generates a filtered gray-level value for each pixel determined by the determination unit to contain a ringing artifact based on, for example, gray-level values of selected pixels within a filtering kernel of pixels relating to the pixel. The nonlinear low-pass filter generates a low-pass-filtered gray-level value for each selected pixel of a second set of selected pixels of the image.

Disclosed herein are various embodiments of decoding systems and methods. In one embodiment, among others, a decoding system comprises a de-blocking system configured to receive decoded video data and decoding information and remove blocking artifacts from the decoded video data, and a de-ringing system configured to remove ringing artifacts from the de-blocked video data.

A method for calculating a flip angle schedule for a train of refocusing radio frequency (RF) pulses with reduced flip angles allows control of RF power deposition and use of a longer echo train. A target signal is defined for each echo in the echo train, and flip angles are then calculated from the target signals. The target signal schedule includes two phases. In the first phase, the target signals drop asymptotically to efficiently establish a pseudo-steady state at a pre-defined minimum signal level, S_min. In the second phase, the target signal is increased monotonically for the remainder of the train to a pre-defined maximum signal level, S_max. By increasing the target signal, the effect of relaxation may be reduced, decreasing blurring and ringing artifacts. Flip angles are then calculated from the target signal schedule, using a simplified method that requires no information about the tissues' relaxation properties.

A filter for post-processing digital images and videos, having an edge mapper, a pixel sorter, and an adaptive filter that simultaneously performs de-ringing and edge sharpening. The combined filter is computationally simpler than known methods and can achieve removal of ringing artifacts and sharpening of true edges at the same time. The present invention also includes a preferred method of simultaneously de-ringing and edge sharpening digital images and videos.

Techniques for removing ringing artifacts from video data. A deringing filter in accordance with the present invention preserves real image edges in a video frame, while smoothing out the interiors of objects. In one aspect, a 9-tap low-pass filter is applied to an adaptive processing window. The filter window is initialized with the values in a 3×3 mask centered on the position whose output is computed. Then all values that are very different from the central one are replaced with the central value. The deringing filter varies between 3×3 low-pass and identity, depending on how much the central value differs from its surrounding ones. A deblocking filter in accordance may also be suitably used in conjunction with the deringing filter.

The present disclosure is directed to iterative regularized reconstruction methods. In certain embodiments, the methods incorporate locally-weighted total variation denoising to suppress artifacts induced by PSF modeling. In certain embodiments, the methods are useful for suppressing ringing artifacts while contrast recovery is maintained. In certain embodiments, the weighting scheme can be extended to noisy measures introducing a noise-independent weighting scheme. The present disclosure is also directed to a method for quantifying radioligand binding in a subject without collecting arterial blood. In certain embodiments, the methods incorporate using imaging data and electronic health records to predict one or more anchors, which are used to generate an aterial input function (AIF) for the radioligand.

A method of removing ringing and blocking artifacts from a decompressed digital image. In one method, a background value of the digital image a background region and foreground regions is determined, and a threshold value is computed. A mapping of the digital image is then generated by thresholding the digital image based on the threshold value to produce a thresholded image, and enlarging the foreground regions of the thresholded image to form a map image. The mapping includes the background pixels of the map image. The background region of the decompressed digital image is then cleansed based on the mapping. In an alternate method, ringing artifacts are removed from a decompressed digital image based on a signal-to-noise ratio of the image. In yet another alternate embodiment, ringing artifacts are from a decompressed digital color image that includes a chrominance channel and a luminance channel. An alternate embodiment removes ringing and blocking artifacts.

Method and apparatus for improving the quality of super-resolution video imaging by suppressing ringing artifacts, reducing high-frequency noise, reducing blocking artifacts, and smoothing out jagged edges of the image to generate pictures that appear cleaner with less edge degradation. The method operates in a recursive manner within a sequence of low resolution images. Conventional SR processing is primarily enhanced within the invention by adding an artifact suppression section which creates a high frequency component signal ΔSR_i having significantly reduced artifacts therein achieving higher quality super-resolution image output. The method can be applied to images and image sequences (video) in monochrome or color and in any desired pixel format. The method can be implemented within image processing devices, in particular those containing programming for executing the described method steps.

In one example of an embodiment of the invention, a method to correct for ring artifacts in an image is disclosed. A first Cartesian image is reconstructed based on data received from an imaging device, and the first Cartesian image is transformed into a first polar image. A first low-pass filter is applied to the first polar image, in the radial dimension, to form a second polar image, and the second polar image is subtracted from the first polar image to generate a third polar image. A second low-pass filter is applied to the third polar image, in an angular dimension, to form a fourth polar image, and the fourth polar image is transformed to Cartesian coordinates to form a second Cartesian image. The first Cartesian image is corrected based, at least in part, on the second Cartesian image.

The present invention refers to 3D rotational X-ray imaging systems for use in computed tomography (CT) and, more particularly, to a fast, accurate and mathematically robust calibration method for determining the effective center of rotation (I) in not perfectly isocentric 3D rotational C-arm systems and eliminating substantially circular ring artifacts (RA) which arise when using such a CT scanner system for acquiring a set of 2D projection images of an object of interest to be three-dimensionally reconstructed. For this purpose, a C-arm based rotational CT scanner comprising at least one radiation detector (D) having an X-radiation sensitive surface exposed to an X-ray beam emitted by at least one X-ray tube (S), each rotating along a non-ideal circular trajectory (TF, T_CD) about an object of interest to be three-dimensionally reconstructed from a set of 2D projection images is used for providing geometrical calibration data by scanning a calibration phantom from a plurality of distinct projection directions and calculating, for each projection direction, the 3D positions of the X-ray tube's focal spot and the X-ray detector's center. For approximating the exact 3D position and angular direction of the axis of rotation about which the at least one X-ray tube and the at least one radiation detector rotate, a circular regression technique using a number of mathematically robust least squares fits is applied.

The invention relates to a post-processing method for removing ring artifacts in a CT (computed tomography) image, and the post-processing method comprises the following steps: converting the CT image with ring artifacts from a rectangular coordinate image to a polar coordinate image; extracting the ring image in polar coordinates with a comb filter in a polar coordinate image domain; converting the ring image extracted out of the polar coordinates to a ring image in rectangular coordinates; and subtracting the ring image in the rectangular coordinates from the original CT image with the ringartifacts to obtain a ring-free image. Through frequency domain comb filtering technology, the post-processing method provided by the invention subtracts the corresponding ring artifact image from the original image, without reduction of image resolution and change of quality of the original image. The post-processing method achieves the processing effect, and meanwhile the speed meets product requirements and has space for further optimization, so that the post-processing method is fully suitable for a CT machine with higher requirements for the reconstruction speed.

The invention discloses a method for three-dimensional representation of stratified structure micrometer CT imaging of a turbine blade heat barrier coating. The method comprises the following steps: preparing a double-layer-structure heat barrier coating micrometer CT scanning sample; firstly, carrying out micrometer CT scanning on the heat barrier coating sample, carrying out ring artifact and beam hardening correction on projection data, then carrying out three-dimensional reconstruction to obtain three-dimensional stratified structure information, establishing a three-dimensional structure analysis model, and carrying out characteristic segmentation and extraction on three components, namely a ceramic heat insulating layer, a bonding layer and matrix alloy; then, analyzing the thickness of the coating, extracting the distribution of holes in the coating, calculating the porosity, extracting the interface topography of the coating, and analyzing structure characteristics such as internal defects; and finally, estimating the preparation process quality of the heat barrier coating by integrating the composition, thickness, porosity distribution, interface topography and the like. The method for three-dimensional representation of the stratified structure of the heat barrier coating provided by the invention is suitable for estimation and optimization of the spraying process quality of the heat barrier coating, so that the quality of the heat barrier coating can be well controlled.

An imaging technique is disclosed to reduce ringing artifacts from amplitude decay in MR multi-echo acquisition. A flip angle train is determined to match scan parameters for an MR scan to acquire MR data from a given tissue. Reducing the effects of amplitude decay in the echo signal reduces ringing artifacts and thereby improves image quality.

A method and apparatus for ringing artifacts reduction for compressed video signals. The method includes receiving luma data to the digital signal processor, calculating sum of gradient of the luma data; calculating SAD of the luma data; performing pixel classification based of the calculated SAD and sum of gradient, performing erosion on a detected edge pixel indicator on a detected flat pixel indicators, determining at least one of the strength or weakness of the an edge based on the determined edge erosion, performing horizontal dilation on the detected edge pixel indicators and edge strength; and performing at least one of sigma or bilateral filtering to the luma data according to the detected edge pixel indicator, flat pixel indicator, edge strength, the number of very flat pixel in the block.

The invention relates to a ring artifact elimination method for a CBCT image and belongs to the field of medical image processing. According to the invention, firstly, the CBCT image with a ring artifact is transformed from a Cartesian coordinate system to a polar coordinate system; then the CT image P in the polar coordinate system is subjected to smoothing processing by adopting an L0 norm filtering method; next, a smooth image P' obtained after filtering is subtracted from an original image P in the polar coordinate system to obtain an artifact information image Pk with partial original detail information, then the Pk is subjected to extraction and removal of an artifact template by using an OSTU multi-threshold segmentation method and a median method, and the rest of detail information is compensated into the filtered image P'; and finally, the image P' compensated with the detail information is transformed to the Cartesian coordinate system, so that a cone-beam CT image without the ring artifact can be obtained. Compared with the prior art, when detail and edge information in the cone-beam CT image is reserved to the greatest extent, the ring artifact on the CT image, which influences image quality and reality, are effectively removed without obvious residues.

Ringing artifacts in digital images are predicted by determining a number of pixels of a block of pixels exhibiting luminance exceeding a luminance threshold adequate for detecting a ringing artifact and a number of these higher luminance pixels having sufficient contrast with neighbor pixels to be a likely source of a ringing artifact.

Electronic images that are degraded by noise and data reduction, such as MPEG encoding, display artifacts in the reproduced image, such as ringing (“ripples”) and blocks (“huge pixels”), and noise in the image may be apparent as graininess. By performing image analysis, both on a frame-by-frame and pixel-by-pixel basis it is possible to identify and separate edges in the image, ringing artifacts and the boundaries between block transitions. By applying noise reduction according to the analysis, followed by sharpness enhancement, it is possible to clean up the image for further utilization.

The present invention relates to a method for reducing ringing artifacts of image deconvolution. A deconvolution is applied to the original blurred image and edges are detected within the deconvolved image. Then edge tapering on the original blurred image is performed based on the detected edges.

The present invention further relates to a system and a computer program product for reducing ringing artifacts of image deconvolution.

A method of reducing ringing artifacts in a nuclear magnetic resonance measurement is provided. The method utilizes a new pulse sequence that offers ringing cancellation opportunities as well as compensation for otherwise accumulating spin dynamics errors. Ringing cancellation is accomplished by forming linear combinations of spin echoes induced as a result of the pulse sequence. Because the linear combinations are formed between closely spaced spin echoes (i.e., echoes within the same sequence), the likelihood that the ringing artifact will have changed between measurements is diminished.