Dithering Method Research Articles

Effective quantization by averaging and dithering

The dither method in connection with averaging is widely used to improve the resolution of analog/digital converters. It is often difficult to describe the improvement of the method quantitatively. The paper proposes a simple parameter Q eff to make this possible. It is suitable for measuring a steady component. The resolution improvements are introduced and described by example of sinus and triangle dither waveforms and various averager degrees. The necessary frequency conditions are termed. The parameter “ Q eff” is shown to be dependent of dither-signal parameters like amplitude and phase.

Robustness improvement of known-host-state data-hiding using host statistics

In this paper we considered the problem of performance improvement of known-host-state (quantization-based) watermarking methods undergo additive white Gaussian noise (AWGN) and uniform noise attacks. We question the optimality of uniform high rate quantizer based design of dither modulation and distortion compensate dither modulation methods from their robustness to these attacks point of view in terms of bit error rate probability. Motivated by superior performance of uniform deadzone quantizer over the uniform one in lossy source coding, we propose to replace the latter one by a former one designed according to the statistics of the host data. Based on suggested modifications we obtained analytical expressions for bit error rate probability analysis of quantization-based watermarking methods in AWGN and uniform noise channels. Experimental results of computer simulations demonstrated performance enhancement of known-host-state watermarking techniques in comparison to the classically elaborated schemes at negative watermark-to-noise ratios.

링레이저 자이로의 각진동 센서신호 미분에 의한 dither-stripping

공진기 진동형 링레이저 자이로가 외부에서 입력되는 각도변화만을 검출하여 출력하기 위해서는 링레이저 출력으로부터 공진기의 각진동 운동에 의한 출력을 제거하는 방법이 필요하다. 본 논문에서는 공진기 진동형 링레이저 자이로에서 공진기의 각진동을 검출하는 각속도 센서 출력을 V-F 변환하여 링레이저 출력을 보상하는 dither-stripping에 대하여 논의하였다. 우리는 V-F 신호의 offset을 제거하기 위하여 V-F 신호의 미분값을 취하고 또한 미분값을 취함으로서 변화되는 위상을 보상하기 위하여 아날로그 적분기로 위상을 보정하는 방법과 링레이저 신호 또는 V-F 신호의 검출 시점을 지연시키는 방법을 개발하였다. 그리고 링레이저 출력과 V-F 신호 사이의 환산을 위하여 분산을 이용하여 이득을 산출하는 방법을 개발하였다. 우리는 이와 같은 방법을 적용하고, dither trapping 방법과 비교하는 실험을 통하여 효과를 분석하였다. It is required for getting the ring laser gyro output purely related to the input rotation to eliminate the output of the modulated angular vibration from the ring laser signal. In this paper we discuss the dither stripping methods of compensating the ring laser signal by converting the rate signal of dither detector from voltage to frequency for a dither type ring laser gyro. We discuss the differential methods for getting rid of the offset of the V-F signal. And we develope the methods of compensating the phase differences between the ring laser signals and the V-F differential signals by using analog integrator and digital time delays. And also, we develope the gain calculation method by comparing the standard deviations of the ring laser signals with V-F differential signals. We implemented these methods and analyzed the effectiveness of these methods by comparing the dither trapping methods.

An Estimation using the Correlation Coeffcient and Measure of Approximation for the Ordered Dither Method

An Estimation using the Correlation Coeffcient and Measure of Approximation for the Ordered Dither Method

Reduction of low gray-level contours using error diffusion based on emission characteristics of PDP

To reduce the low gray-level contours on a PDP, previous research has focused on error diffusion and dithering methods. Yet these error diffusion methods generate a look-up table based on the assumption that the output luminance levels of a PDP increase uniformly, when in reality they do not. Therefore, such methods are unable to effectively reduce low gray-level contours. Accordingly, the current paper proposes an error diffusion method based on the actual emission characteristics of a PDP, enabling effective reduction of low gray-level contours. In addition, a 9-subfield system is applied to improve the low gray-level expression in a PDP. Simulation results confirm that the proposed method can suppress low gray-level contours more effectively than conventional methods.

A quick search method for audio and video signals based on histogram pruning

This paper proposes a quick method of similarity-based signal searching to detect and locate a specific audio or video signal given as a query in a stored long audio or video signal. With existing techniques, similarity-based searching may become impractical in terms of computing time in the case of searching through long-running (several-days' worth of) signals. The proposed algorithm, which is referred to as time-series active search, offers significantly faster search with sufficient accuracy. The key to the acceleration is an effective pruning algorithm introduced in the histogram matching stage. Through the pruning, the actual number of matching calculations can be reduced by 200 to 500 times compared with exhaustive search while guaranteeing exactly the same search result. Experiments show that the proposed method can correctly detect and locate a 15-s signal in a 48-h recording of TV broadcasts within 1 s, once the feature vectors are calculated and quantized. As extentions of the basic algorithm, efficient AND/OR search methods for searching for multiple query signals and a feature dithering method for coping with signal distortion are also discussed.

N-Candidate methods for location invariant dithering of color images

We introduce a new class of dithering methods called N-candidate methods. The main idea is that the output color is randomly chosen among several candidate colors so that the estimated color average would be preserved. The dithering process is pixelwise without any interaction with the neighboring pixels. The N-candidate methods are thus location invariant, which has two benefits: (1) the algorithm can be fully parallelized; and (2) the image can be partially processed without effecting the pixels outside the processed part. The proposed approach allows more efficient dithering than error diffusion but at the cost of a slightly lower image quality.

Texture Analysis for Enhanced Color Image Quantization

A traditional problem with color image quantization techniques is their inability to handle smooth variations in intensity and chromaticity, leading to contours in the quantized image. To address this problem, this paper describes new techniques for augmenting the performance of a seminal color image quantization algorithm, the median-cut quantizer. Applying a simple texture analysis method from computer vision in conjunction with the median-cut algorithm using a new variant of a k-d tree, we show that contouring effects can be alleviated without resorting to dithering methods and the accompanying decrease in signal-to-noise ratio. The merits of this approach are evaluated using remotely sensed aerial imagery and synthetically generated scenes.

Adaptive Ordered Dither

Ordered dither (C. N. Judice, J. F. Jarvis, and W. H. Ninke, inProceedings of the S.I.D. 15, 4(Fourth Quarter),1974,pp. 161–169.) is an efficient and widely used halftoning technique. One disadvantage with this method is that it produces blurred images. Recently, a space-filling curve ordered dithering approach (Y. Zhang, submitted for publication.) has been proposed that improves the ordered dither in image quality by generating clustered dot patterns along a space-filling curve over the image. In this method the cluster size is fixed in the process of halftoning. This paper presents a new ordered dithering method, called adaptive ordered dither, that does halftoning by using a space-filling curve to perform an adaptive variation of the cluster size. Experimental results demonstrate that the new method can significantly improve the space-filling curve ordered dither in revealing image details.

Color Image Quantization and Dithering Method Based on Human Visual System Characteristics

New methods for both color palette design and dithering based on human visual system (HVS) characteristics are proposed. Color quantization for palette design uses the relative visual sensitivity and spatial masking effect of HVS. The dithering operation for printing uses nonlinear quantization, which considers the overlapping phenomena among neighbor printing dots, and then a modified dot-diffusion algorithm is followed to compensate the degradation produced in the quantization process. The proposed techniques can produce high-quality images in low-bit color devices.

A new dithering method for sigma-delta modulators

A new dithering method to remove limit-cycles in Sigma-Delta modulators is presented. With this new method, the sequence length of a Pseudo-Noise generated dither is matched to the digital decimation filter. This causes the frequency spikes of the dither to coincide with the notches of the filter which results in total elimination of the applied dither power. In contrast to existing dithering techniques, matched dithering will not introduce additional inband noise. Compared to existing dithering techniques, the required dither amplitudes are relatively small (5%–30% FS) and may decrease with increasing oversampling ratio. Matched dithering proves to be very powerful for instrumentation applications.

Spur-reduced digital sinusoid synthesis

This paper presents and analyzes a technique for reducing the spurious signal content in digital sinusoid synthesis. Spur reduction is accomplished through dithering amplitude and phase values prior to wordlength reduction. The analytical approach developed for analog quantization is used to produce new bounds on spur performance in these dithered systems. Amplitude dithering allows output wordlength reduction without introducing additional spurs. Effects of periodic dither similar to that produced by a pseudo-noise (PN) generator are analyzed. This phase dithering method provides a spur reduction of 6(M+1) dB per phase bit when the dither consists of M uniform variates. While the spur reduction is at the expense of an increase in system noise, the noise can be made white, making the noise power spectral density small. This technique permits the use of a smaller number of phase bits addressing sinusoid look-up tables, resulting in an exponential decrease in system complexity. Amplitude dithering allows the use of less complicated multipliers and narrower data paths in purely digital applications, as well as the use of coarse-resolution, highly-linear digital-to-analog converters (DAC's) to obtain spur performance limited by the DAC linearity rather than its resolution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ｓｉダイアフラム式可変焦点ミラーの収差低減

A thin Si diaphragm, which can be easily deformed into a concave shape by applying an electrostatic force, can be used as a dynamic focusing mirror. A diaphragm mirror which has a uniform thickness produces large aberrations because its deformation is not optically ideal. To reduce the aberrations, an optimum thickness profile is calculated by FEM analysis and the profile is created using a unique processing method; initially, photoresist on a Si substrate is exposed to a specific energy profile through a mask made by dither method. The photoresist is then formed a specific curved shape. Optical Fourier transform is also applied during the exposure to smooth it. Finally, it is transcribed to the Si substrate by dry etching in CF4 /O2 plasma. The processed shape matches the calculated one with only several sub-microns deviations. The resolving power of the optimum thickness mirror is much higher than the uniform thickness mirror in the wide range of the focal length.

Color Quantization and Dithering Method Based on HVS Characteristics

New methods for both color palette design and dithering based on HVS (human visual system) characteristics are proposed. Color quantization for palette design uses the sensitivity and spatial masking effect of HVS. Dithering operation for printing uses nonlinear quantization which considers overlapping phenomena of neighboring printing dots and modified dot diffusion algorithm is followed to compensate the degradation produced in the quantization process. The proposed techniques can produce high quality image in the low bit color devices.

Improved dithering methods for color quantized images

AbstractA color image produced from a continuously toned color image by using a smaller number of colors (e.g., 256) is called a “color quantized image.” Previously, the author and colleagues proposed a high‐speed color quantization method which produces an image of almost the same quality as the original. However, if colors in an image change gradually (such as an image produced by computer graphics), false contouring occurs and deteriorates the image quality. To solve the problem, this paper proposes four new methods, three of which are shown by experiments to have excellent dithering effects which overcome the weakness of the conventional error‐diffusion method and are practical.

Screening and Moiré Suppression in Printing and Its Analysis by Fourier Transform

AbstractMoiré patterns are often observed in printing when the image is reproduced as a bilevel image with halftone. A Fourier transform analysis of screening a picture by an optical method or an ordered dither method is presented. Conventional moiré—suppressing techniques are discussed considering the human visual system. The moiré fringes are explained as aliasing and visible moiré fringes are especially due to high‐frequency spectra with high power. From this viewpoint, a screening method is proposed which uses the Fourier transform for moiré suppression. This method has the additional advantage that any pitch and any screen angle may be selected.

Embedding the attribute information into a dithered image

AbstractAttribute information is indispensable data in the collection and storage of a large amount of image information. If these data are stored together with the image, handling of the materials would become simpler and more reliable. This paper proposes a method to embed the attribute information into a dither image by using the difference of the threshold values of the dither matrix when a multilevel image is binarized. This method can embed the attribute information of about 2 kbytes (equivalent to about 25 percent of the data for the image) into a dithered image of 256 × 256 pixels. The embedded information can be displayed or printed separately at any time. This method can restore the dither image almost perfectly by using the property of the ordered dither method.

コンピュータ・グラフィックスと建築パース : コンピュータによる建築パースに関する研究(1)

Architects create their architectures. As the way of architectural presentations, there are drawings (plans, elevations, sections...), perspectives, models, and etc. In the past, these drawings are made by humans with handwriting, but recently we can get the most part of them by using computer. Computer graphics techniques can generate architectural perspectives. Useful examples of computer perspectives are followings : (1) idea sketches (2) optical emvironmental simulations (3) finish material simulations (4) design and color simulations for interiors and furnitures (5) exterior simulations (6) architectural environmental simulations (7) presentations Many display devices and algorithms are developped for Computer graphics. CRT is the most important device for display perspectives. Typical examples of CRT are random scan refresh CRT, storage tube CRT, and raster refresh CRT. About softoware, important algorithms are depth sort algorithm, z-buffer algorithm, scan line algorithm, and ray tracing algorithm. Halftonig techniques for using display with a limited range of output values are halftone patterns, dither method, PSET 4 subroutine, and etc. Precise image communication isn't procecuted using only handwriting drawings. As desigin goes, the architectural image sets shape. Thers is a limit to the drawing presentations. In order to communicate the architect's image precisely we need perspectives or models. Therefore the perspectives must present the image as real as possible. The perspectives generated by computer are sutable for such use very match. Especially the ray tracing method can generate the most real image.

A New Halftone Reproduction and Transmission Method Using Standard Black and White Facsimile Code

This paper proposes an adaptive dithering method, which can reproduce grey levels with good character quality. It also proposes dither threshold patterns with long run-length, which are able to obtain a compression ratio of about 3 or 4 when using modified Huffman coding schemes. The method presented here is applicable to facsimile equipment for transmitting pictures, including both continuoustone pictures and characters, using CCITT standard black and white picture coding.

Rational carrier-period for binarization of sampled images and holograms

Introduction of a rational period in dither methods to binarize graytone images offers an additional degree of freedom. This can be used to overcome the inevitable tradeoff between graytone reproduction and detail resolution in these techniques. The concept is demonstrated with a one-dimensional triangular-shaped carrier function. Experimental results are shown.