scholarly journals Implementation of the adaptive quantization method in digitally controlled measuring generators

2021 ◽  
pp. 121-134
Author(s):  
Mikhail Babichev ◽  
Keyword(s):  
Digital Control ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Quantization Noise ◽  
Current Channel ◽  
Digital To Analog Converter ◽  
Relative Value ◽  
Wide Range ◽  
Adaptive Quantization ◽  
Digitally Controlled

Measuring generators with digital control, in particular power calibrators, used to calibrate electricity meters, contain a digital-to-analog converter (DAC) that converts codes of the generated signal into voltage. Signal codes are stored in the generator memory. A truncation discreteness error (quantization noise) arises caused by sampling (quantization) in time and by the level of signal samples in the DAC. A relative value of the quantization noise depends on the amplitude of the generated signal (relative to the reference voltage of the DAC): the larger the amplitude, the more significant bits of the DAC are involved in the conversion process, and the less the relative value of the noise. In generators, where the amplitude of the output signal changes over a wide range (high dynamic range) by changing the digital samples of the signal, the quantization noise at low signal amplitudes can become unacceptably large. This situation occurs in power calibrators where the output current changes hundreds of times since the error of the verified electricity meter is normalized in a wide range of current flowing through it. A new algorithm for generating samples of a sinusoidal signal in measuring generators with digital control called adaptive quantization is proposed. Adaptive quantization can significantly improve one of the selected signal parameters (the so-called optimality criterion), for example, reduce the error in reproduction of the first harmonic, or reduce the value of higher harmonic components. In addition, the proposed algorithm reduces the dependence of the selected parameter on the sampling frequency and on the number of DAC bits used, which makes it possible to expand the dynamic range of the generator (in the current channel) without using additional amplifiers with programmable gain (PGA). Studies carried out using computer simulation have confirmed the efficiency of the adaptive quantization algorithm.

Product Review: High Dynamic Range Displays

2007 ◽  
Vol 16 (1) ◽  
pp. 119-122 ◽  
Author(s):  
Patrick Ledda
Keyword(s):  
Dynamic Range ◽  
Liquid Crystal Display ◽  
Contrast Ratio ◽  
Luminance Level ◽  
High Dynamic Range ◽  
Natural World ◽  
Adaptation Level ◽  
Wide Range ◽  
High Dynamic ◽  
3D Software

In the natural world, the human eye is confronted with a wide range of colors and luminances. A surface lit by moonlight might have a luminance level of around 10−3 cd/m2, while surfaces lit during a sunny day could reach values larger than 105 cd/m2. A good quality CRT (cathode ray tube) or LCD (liquid crystal display) monitor is only able to achieve a maximum luminance of around 200 to 300 cd/m2 and a contrast ratio of not more than two orders of magnitude. In this context the contrast ratio or dynamic range is defined as the ratio of the highest to the lowest luminance. We call high dynamic range (HDR) images, those images (or scenes) in which the contrast ratio is larger than what a display can reproduce. In practice, any scene that contains some sort of light source and shadows is HDR. The main problem with HDR images is that they cannot be displayed, therefore although methods to create them do exist (by taking multiple photographs at different exposure times or using computer graphics 3D software for example) it is not possible to see both bright and dark areas simultaneously. (See Figure 1.) There is data that suggests that our eyes can see detail at any given adaptation level within a contrast of 10,000:1 between the brightest and darkest regions of a scene. Therefore an ideal display should be able to reproduce this range. In this review, we present two high dynamic range displays developed by Brightside Technologies (formerly Sunnybrook Technologies) which are capable, for the first time, of linearly displaying high contrast images. These displays are of great use for both researchers in the vision/graphics/VR/medical fields as well as professionals in the VFX/gaming/architectural industry.

scholarly journals Practical Color Contrast Sensitivity Functions for Luminance Levels up to 10000 cd/m2

2020 ◽  
Vol 2020 (28) ◽  
pp. 1-6
Author(s):  
Rafał K. Mantiuk ◽  
Minjung Kim ◽  
Maliha Ashraf ◽  
Qiang Xu ◽  
M. Ronnier Luo ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Dynamic Range ◽  
Color Space ◽  
High Dynamic Range ◽  
Model Parameters ◽  
Color Contrast ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Opponent Color

We model color contrast sensitivity for Gabor patches as a function of spatial frequency, luminance and chromacity of the background, modulation direction in the color space and stimulus size. To fit the model parameters, we combine the data from five independent datasets, which let us make predictions for background luminance levels between 0.0002 cd/m2 and 10 000 cd/m2, and for spatial frequencies between 0.06 cpd and 32 cpd. The data are well-explained by two models: a model that encodes cone contrast and a model that encodes postreceptoral, opponent-color contrast. Our intention is to create practical models, which can well explain the detection performance for natural viewing in a wide range of conditions. As our models are fitted to the data spanning very large range of luminance, they can find applications in modeling visual performance for high dynamic range and augmented reality displays.

A new corresponding color dataset covering a wide luminance range under high dynamic range viewing condition

2021 ◽  
Vol 2021 (29) ◽  
pp. 184-187
Author(s):  
Shi Xinye ◽  
Zhu Yuechen ◽  
Ming Ronnier Luo
Keyword(s):  
Dynamic Range ◽  
High Dynamic Range ◽  
Color Appearance ◽  
Appearance Model ◽  
Viewing Condition ◽  
Color Changes ◽  
Wide Range ◽  
Illuminance Level ◽  
High Dynamic ◽  
The Relationship

An experiment was carried out to investigate the change of color appearance for 13 surface stimuli viewed under a wide range of illuminance levels (15-32000 lux) using asymmetrical matching method. Addition to the above, in the visual field, observers viewed colours in a dark (10 lux) and a bright (200000 lux) illuminance level at the same time to simulate HDR viewing condition. The results were used to understand the relationship between the color changes under HDR conditions, to generate a corresponding color dataset and to verify color appearance model, such as CIECAM16.

Creating high fidelity 360° virtual reality with high dynamic range spherical panorama images

2019 ◽  
Vol 9 (1) ◽  
pp. 73-109
Author(s):  
Zi Siang See ◽  
Lizbeth Goodman ◽  
Craig Hight ◽  
Mohd Shahrizal Sunar ◽  
Arindam Dey ◽  
...  
Keyword(s):  
Virtual Reality ◽  
Best Practice ◽  
User Study ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
High Fidelity ◽  
Image Reproduction ◽  
Wide Range ◽  
High Dynamic ◽  
Spherical Panorama

Abstract This research explores the development of a novel method and apparatus for creating spherical panoramas enhanced with high dynamic range (HDR) for high fidelity Virtual Reality 360 degree (VR360) user experiences. A VR360 interactive panorama presentation using spherical panoramas can provide virtual interactivity and wider viewing coverage; with three degrees of freedom, users can look around in multiple directions within the VR360 experiences, gaining the sense of being in control of their own engagement. This degree of freedom is facilitated by the use of mobile displays or head-mount-devices. However, in terms of image reproduction, the exposure range can be a major difficulty in reproducing a high contrast real-world scene. Imaging variables caused by difficulties and obstacles can occur during the production process of spherical panorama facilitated with HDR. This may result in inaccurate image reproduction for location-based subjects, which will in turn result in a poor VR360 user experience. In this article we describe a HDR spherical panorama reproduction approach (workflow and best practice) which can shorten the production processes, and reduce imaging variables, and technical obstacles and issues to a minimum. This leads to improved photographic image reproduction with fewer visual abnormalities for VR360 experiences, which can be adaptable into a wide range of interactive design applications. We describe the process in detail and also report on a user study that shows the proposed approach creates images which viewers prefer, on the whole, to those created using more complicated HDR methods, or to those created without the use of HDR at all.

scholarly journals Perceptually motivated model for predicting banding artefacts in high-dynamic range images

2020 ◽  
Vol 2020 (28) ◽  
pp. 42-48
Author(s):  
Minjung Kim ◽  
Maryam Azimi ◽  
Rafał K. Mantiuk
Keyword(s):  
Visual System ◽  
Contrast Sensitivity ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Sensitivity Function ◽  
Psychophysical Experiment ◽  
Texture Region ◽  
Wide Range ◽  
Artefact Detection ◽  
High Dynamic

Banding is a type of quantisation artefact that appears when a low-texture region of an image is coded with insufficient bitdepth. Banding artefacts are well-studied for standard dynamic range (SDR), but are not well-understood for high dynamic range (HDR). To address this issue, we conducted a psychophysical experiment to characterise how well human observers see banding artefacts across a wide range of luminances (0.1 cd/m2–10,000 cd/m2). The stimuli were gradients modulated along three colour directions: black-white, red-green, and yellow-violet. The visibility threshold for banding artefacts was the highest at 0.1 cd/m2, decreased with increasing luminance up to 100 cd/m2, then remained at the same level up to 10,000 cd/m2. We used the results to develop and validate a model of banding artefact detection. The model relies on the contrast sensitivity function (CSF) of the visual system, and hence, predicts the visibility of banding artefacts in a perceptually accurate way.

scholarly journals SPAD-Based LiDAR Sensor in 0.35 µm Automotive CMOS with Variable Background Light Rejection

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 749 ◽  
Author(s):  
Maik Beer ◽  
Charles Thattil ◽  
Jan F. Haase ◽  
Jennifer Ruskowski ◽  
Werner Brockherde ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Light Condition ◽  
High Dynamic Range ◽  
Cmos Process ◽  
Ambient Light ◽  
Wide Range ◽  
Constant Measurement ◽  
Ambient Light Condition ◽  
High Dynamic ◽  
Individual Adjustment

We present a SPAD-based LiDAR sensor fabricated in an automotive certified 0.35 µm CMOS process. Since reliable sensor operation in high ambient light environment is a crucial factor in automotive applications, four SPADs are implemented in each pixel to suppress ambient light by the detection of photon coincidences. By pixel individual adjustment of the coincidence parameters to the present ambient light condition, an almost constant measurement performance is achieved for a wide range of different target reflectance and ambient illumination levels. This technique allows the acquisition of high dynamic range scenes in a single laser shot. For measurement and demonstration purpose a LiDAR camera with the developed sensor has been built.

scholarly journals Variational Hilbert Quantitative Phase Imaging

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maciej Trusiak ◽  
Maria Cywińska ◽  
Vicente Micó ◽  
José Ángel Picazo-Bueno ◽  
Chao Zuo ◽  
...  
Keyword(s):  
Dynamic Range ◽  
High Dynamic Range ◽  
Phase Imaging ◽  
Single Shot ◽  
Quantitative Phase Imaging ◽  
Phase Reconstruction ◽  
Quantitative Phase ◽  
Wide Range ◽  
High Space ◽  
Variational Image

AbstractUtilizing the refractive index as the endogenous contrast agent to noninvasively study transparent cells is a working principle of emerging quantitative phase imaging (QPI). In this contribution, we propose the Variational Hilbert Quantitative Phase Imaging (VHQPI)—end-to-end purely computational add-on module able to improve performance of a QPI-unit without hardware modifications. The VHQPI, deploying unique merger of tailored variational image decomposition and enhanced Hilbert spiral transform, adaptively provides high quality map of sample-induced phase delay, accepting particularly wide range of input single-shot interferograms (from off-axis to quasi on-axis configurations). It especially promotes high space-bandwidth-product QPI configurations alleviating the spectral overlapping problem. The VHQPI is tailored to deal with cumbersome interference patterns related to detailed locally varying biological objects with possibly high dynamic range of phase and relatively low carrier. In post-processing, the slowly varying phase-term associated with the instrumental optical aberrations is eliminated upon variational analysis to further boost the phase-imaging capabilities. The VHQPI is thoroughly studied employing numerical simulations and successfully validated using static and dynamic cells phase-analysis. It compares favorably with other single-shot phase reconstruction techniques based on the Fourier and Hilbert–Huang transforms, both in terms of visual inspection and quantitative evaluation, potentially opening up new possibilities in QPI.

One-Bit ΣΔ-Encoded Stimulus Generation for On-Chip ADC Test

2020 ◽  
Vol 29 (15) ◽  
pp. 2050245
Author(s):  
Shakeel Ahmad ◽  
Jerzy Dąbrowski
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
Dynamic Test ◽  
Low Frequency ◽  
High Dynamic Range ◽  
Quantization Noise ◽  
Modulation Scheme ◽  
Pass Band ◽  
Low Pass ◽  
On Chip

This paper presents an application of the [Formula: see text] modulation technique to the on-chip dynamic test for analog-to-digital converters (ADCs). The required stimulus such as a single- or two-tone signal is encoded into one-bit [Formula: see text] sequence, which is applied to an ADC under test through a driving buffer and a simple low-pass reconstruction filter. By a systematic approach, we select the order and type of a [Formula: see text] modulator and develop a frequency plan suitable for the spectral measurement. In this way, we achieve a high dynamic range suitable for spectral harmonic and intermodulation distortion tests for ADCs. For high frequency measurements (up to the Nyquist frequency), we propose a novel low-pass/band-pass modulation scheme that allows to avoid harmful effects of the low-frequency quantization noise. Also we address the distortion components which originate from the buffer imperfections for a nonreturn-to-zero waveform representing the encoded stimulus. We show that the low-frequency distortion components can be cancelled by using a simple iterative predistortion technique supported by measurements with a DC-calibrated ADC. By correlation between low- and high-frequency components also the high frequency distortions can be largely reduced. The presented techniques are illustrated by simulation results of an ADC under test.

Sign in / Sign up

Export Citation Format

Share Document