Radiometric resolution and dynamic range of aerial and space images, obtained for monitoring and mapping purposes

2020 ◽  
Vol 964 (10) ◽  
pp. 40-48
Author(s):  
I.A. Anikeeva
Keyword(s):  
Dynamic Range ◽  
Numerical Estimation ◽  
Space Images

The dynamic range and radiometric resolution are among the most important indicators of aerial and space images’ fine quality. Gradation properties are of particular importance for aerial and space images, obtained for monitoring and mapping purposes, because the completeness and quality of the information on the earth’s surface objects depend on them, the accuracy of brightness features reproduction of earth’s surface objects. The author discusses various approaches to defining the concepts of dynamic range and radiometric resolution; the most proper definitions of these terms are given in the context of estimating the image’s gradation properties. The expediency of separating the concepts of nominal, actual and useful (effective) radiometric resolution is shown; their definitions are given. Methods of dynamic range and radio-metric resolution numerical estimation based on a histogram are shown. Absolute and relative indicators are considered. The advantages of using relative indicators are shown. Examples of the dynamic range and radiometric resolution evaluation are given basing upon the images obtained by ‘‘Canopus-B’’ spacecraft.

Perceptual Quality Assessment of Low-light Image Enhancement

2021 ◽  
Vol 17 (4) ◽  
pp. 1-24
Author(s):  
Guangtao Zhai ◽  
Wei Sun ◽  
Xiongkuo Min ◽  
Jiantao Zhou
Keyword(s):  
Image Quality ◽  
Quality Assessment ◽  
Image Enhancement ◽  
Dynamic Range ◽  
State Of The Art ◽  
Perceptual Quality ◽  
Low Light ◽  
Light Image ◽  
Light Enhancement

Low-light image enhancement algorithms (LIEA) can light up images captured in dark or back-lighting conditions. However, LIEA may introduce various distortions such as structure damage, color shift, and noise into the enhanced images. Despite various LIEAs proposed in the literature, few efforts have been made to study the quality evaluation of low-light enhancement. In this article, we make one of the first attempts to investigate the quality assessment problem of low-light image enhancement. To facilitate the study of objective image quality assessment (IQA), we first build a large-scale low-light image enhancement quality (LIEQ) database. The LIEQ database includes 1,000 light-enhanced images, which are generated from 100 low-light images using 10 LIEAs. Rather than evaluating the quality of light-enhanced images directly, which is more difficult, we propose to use the multi-exposure fused (MEF) image and stack-based high dynamic range (HDR) image as a reference and evaluate the quality of low-light enhancement following a full-reference (FR) quality assessment routine. We observe that distortions introduced in low-light enhancement are significantly different from distortions considered in traditional image IQA databases that are well-studied, and the current state-of-the-art FR IQA models are also not suitable for evaluating their quality. Therefore, we propose a new FR low-light image enhancement quality assessment (LIEQA) index by evaluating the image quality from four aspects: luminance enhancement, color rendition, noise evaluation, and structure preserving, which have captured the most key aspects of low-light enhancement. Experimental results on the LIEQ database show that the proposed LIEQA index outperforms the state-of-the-art FR IQA models. LIEQA can act as an evaluator for various low-light enhancement algorithms and systems. To the best of our knowledge, this article is the first of its kind comprehensive low-light image enhancement quality assessment study.

scholarly journals Numerical evaluation of image parameters of ETR-1

2016 ◽  
Vol 2 (1) ◽  
pp. 489-491
Author(s):  
Shamim Ahmed ◽  
Marian Krüger ◽  
Christian Willomitzer ◽  
Golam A. Zakaria
Keyword(s):  
Image Quality ◽  
Treatment Planning ◽  
Numerical Evaluation ◽  
Numerical Estimation ◽  
Low Contrast ◽  
Precise Result ◽  
Test Tool ◽  
Naked Eye ◽  
Pre Treatment

AbstractIn this work, we developed a method to handle the image quality test-tool precisely. This test-tool is important to evaluate the quality of the medical images for pre-treatment planning phase. But the achieved images are estimated by naked eyes, which does not provide the precise result. Our main goal is to get the desired image parameters numerically. This numerical estimation overcomes the limitation of naked eye observation. Hence, it enhances the pre-treatment planning. The ETR-1 test-tool is considered here. The contrast, the low contrast details and line-pairs (lp/mm) were estimated.

scholarly journals Post-Processing of Digital Radiographs in the Practice of Radiologist

2017 ◽  
pp. 116-128
Author(s):  
I. G. Kamyshanskaya
Keyword(s):  
Dynamic Range ◽  
Post Processing ◽  
X Ray ◽  
Digital Radiographs ◽  
Window Width ◽  
Optimal Dynamic ◽  
Practical Recommendations ◽  
Magnification Level ◽  
Additional Option

The purpose: analysis of the use by radiologists techniques of post-processing of digital radiographs and the development of practical recommendations on their application.Materials and methods.The technique of post-processing was taken for analysis: negative/positive; filters/optimization of dynamic range; the intensification of the contours and smoothing; image magnification; level/window width densities, and gamma correction. Compiled questionnaire, which the doctor and the radiologist had to answer the questions of how often he uses a particular technique of digital image processing; which, in some cases, the study of what organs he uses post-processing? In total, we analyzed 18 questionnaires and their own experience in digital x-ray machines since 2003.Results.On the basis of interviews and our own experience, the author recommends that you always use the techniques of post-processing x-ray images, starting with the optimization of the dynamic range / filter, which greatly improves the quality of the picture.Conclusions.1. Doctors radiologists in the majority of cases (83%) use the methods of post-processing to analyse digital radiographs. 2. Additional option of post-processing are used most of the time (90–100%), this level and the window width, the intensification of the contours increase.3. Command path smoothing is applied in 1/3 cases (33%).4. Rarely used to optimize dynamic range and FonEqualize.5. Understanding all of the options post-processing of digital radiographs and their active use in practice of the radiologist, will improve the accuracy of x-ray, to avoid repeated shots, and as a consequence, to reduce the radiation dose of the patient.6. Recommended: start post-processing images with optimal dynamic range/filter; for detail is necessary – to change the level/window width, zoom in, sharpen the contours.

scholarly journals Dynamic range reduction of infrared images based on adaptive equalization, stretch and compression of histogram

2021 ◽  
Vol 66 (4) ◽  
pp. 470-482
Author(s):  
S. I. Rudikov ◽  
V. Yu. Tsviatkou ◽  
A. P. Shkadarevich
Keyword(s):  
Computational Complexity ◽  
Image Quality ◽  
Dynamic Range ◽  
Histogram Equalization ◽  
Brightness Distribution ◽  
Adaptive Equalization ◽  
Infrared Images ◽  
Image Reproduction ◽  
Adaptive Histogram Equalization

The problem of reducing the dynamic range and improving the quality of infrared (IR) images with a wide dynamic range for their display on a liquid crystal matrix with 8-bit pixels is considered. To solve this problem in optoelectronic devices in real time, block algorithms based on local equalization of the histogram are widely used, taking into account their relatively low computational complexity and the possibility of taking into account local features of the brightness distribution. The basic adaptive histogram equalization algorithm provides reasonably high image quality after conversion, but may result in excessive contrast for some types of images. In a modified algorithm of adaptive histogram equalization, the contrast is limited by a threshold by truncating local maxima at the edges of the histogram. This leads, however, to a deterioration in other indicators of image quality. This disadvantage is inherent in many algorithms of local histogram equalization, along with limited control over the characteristics of image reproduction quality. To improve the quality and expand the control interval for the characteristics of the reproduction of infrared images, the article proposes an algorithm for double reduction of the dynamic range of the image with intermediate control of the shape of its histogram. This algorithm performs: preliminary reduction of the dynamic range of the image based on adaptive equalization of the histogram, control of the shape of the histogram based on its linear or nonlinear compression, linear stretching of its central part and linear stretching (compression) of its lateral parts, final reduction of the dynamic range based on linear compression of the entire histograms. The characteristics of the proposed algorithm are compared with the characteristics of known algorithms for reducing the dynamic range and improving the image quality. The dependences of the characteristics of the quality of image reproduction after a decrease in their dynamic range on the control parameters of the proposed algorithm and recommendations for their choice taking into account the computational complexity are given.

scholarly journals Coherent Noise Suppression Using Adaptive Homomorphic Filtering for Wideband Electromagnetic Imaging System

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4469
Author(s):  
Yanju Zhu ◽  
Shuguo Xie
Keyword(s):  
Electromagnetic Interference ◽  
Noise Suppression ◽  
Dynamic Range ◽  
Imaging System ◽  
Minimum Description Length ◽  
Coherent Noise ◽  
Noise Pattern ◽  
Electromagnetic Imaging ◽  
Homomorphic Filtering

The wideband electromagnetic imaging system using a parabolic reflector is a device for detecting and locating electromagnetic interference sources (EMIS). When multiple coherent interference sources are detected, the confusion will occur due to the coherent noise that is caused by interference phenomenons. Previous works have removed the coherent noise by using iterative techniques, but they face a limitation in removing noise in that the coherent noise pattern changes with frequency in a wideband. In this paper, an adaptive homomorphic filtering is proposed to overcome the limitations of conventional methods from 1 GHz–6 GHz. The coherent noise existing in the several electromagnetic images is studied, and it is confirmed that the variation of the coherent noise pattern is related to the position, the number, and the frequency of EMIS. Then, by analyzing the probability density of coherent noise intensity, an adaptive Gaussian filter is carefully designed to remove coherent noise. The filter parameters are selected by the minimum description length criterion (MDL) to apply to compute directly the local amount of Gaussian smoothing at each pixel of each image. The results of the experiments and simulations demonstrate that the proposed method can significantly improve the quality of electromagnetic images in terms of maximum sidelobe level (MSL) by 15 dB and dynamic range (DR) of the system over 20 dB, compared with conventional narrowband denoising methods.

Method and algorithm of automatic color rendition quality assessment of digital aerial and space photos

2018 ◽  
Vol 937 (7) ◽  
pp. 45-56
Author(s):  
I.A. Anikeeva
Keyword(s):  
Quality Assessment ◽  
Experimental Verification ◽  
Experimental Check ◽  
Automatic Assessment ◽  
Assessment Criterion ◽  
Space Images ◽  
Quality Research ◽  
Research Problems ◽  
Method Of Assessment

Today the photographic quality assessment of aerial and space images is made visually, with a big deal of subjectivity. The main problems are the lack of parameters characterizing the photographic quality of images and the lack of methods for determining these parameters. The correctness of color rendition is one of the most important indicators of the photographic aerial and space images’ quality. Research problems included the developing methods for determining the color imbalance of digital images; developing the assessment criterion of color imbalance and a method of its calculation; as well as the experimental verification of the suggested method by correcting the color balance of an image. The article describes the algorithm for automatic color imbalance detection of a digital image that enables searching pixels as parts of gray field areas of an image; the value of a color imbalance is estimated by selected gray pixels. One of the most important indicators of the photographic quality of aerial and space images was determined, it is the color imbalance expressed numerically. The method of automatic assessment of color rendition correctness is offered, the criterion of estimation of color imbalance of the photographic image and a method of its calculation is specified, results of the experimental check of the offered method of assessment of color rendition correctness are given.

scholarly journals Wavelength-Selective Phase-Shifting Digital Holography: Color Three-Dimensional Imaging Ability in Relation to Bit Depth of Wavelength-Multiplexed Holograms

2018 ◽  
Vol 8 (12) ◽  
pp. 2410 ◽  
Author(s):  
Tatsuki Tahara ◽  
Reo Otani ◽  
Yasuhiro Takaki
Keyword(s):  
Digital Holography ◽  
3D Imaging ◽  
Dynamic Range ◽  
Three Dimensional ◽  
Image Sensor ◽  
Phase Shifting ◽  
3D Images ◽  
Wavelength Resolution ◽  
The Relationship

The quality of reconstructed images in relation to the bit depth of holograms formed by wavelength-selective phase-shifting digital holography was investigated. Wavelength-selective phase-shifting digital holography is a technique to obtain multiwavelength three-dimensional (3D) images with a full space-bandwidth product of an image sensor from wavelength-multiplexed phase-shifted holograms and has been proposed since 2013. The bit resolution required to obtain a multiwavelength holographic image was quantitatively and experimentally evaluated, and the relationship between wavelength resolution and dynamic range of an image sensor was numerically simulated. The results indicate that two-bit resolution per wavelength is required to conduct color 3D imaging.

scholarly journals Effect of Multichannel Digital Signal Processing on Loudness Comfort, Sentence Recognition, and Sound Quality

2006 ◽  
Vol 17 (10) ◽  
pp. 681-707 ◽  
Author(s):  
Karen M. Mispagel ◽  
Michael Valente
Keyword(s):  
Signal Processing ◽  
Hearing Aids ◽  
Dynamic Range ◽  
Digital Signal ◽  
Sound Quality ◽  
Sentence Recognition ◽  
Hearing In Noise ◽  
Subjective Loudness ◽  
Noise Test

This study evaluated the effect of increasing the number of processing channels from 32- to 64-signal processing channels on subjects' loudness comfort and satisfaction, sentence recognition, and sound quality of his or her own voice. Ten experienced hearing aid users with mild-to-moderate sensorineural hearing loss wore behind-the-ear (BTE) hearing aids with Adaptive Dynamic Range Optimization (ADRO™) signal processing for a period of six weeks in the 32-channel and 64-channel conditions. Results revealed no significant differences in loudness comfort or satisfaction for the majority of sound samples as measured by the Subjective Loudness Test and Environmental Sounds Questionnaire. No significant differences in sentence recognition between the two processing conditions were found as measured by the Hearing In Noise Test (HINT). Additionally, no subjective differences in sound quality of subjects' own voice were determined by the Listening Tasks Questionnaire.

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