scholarly journals An investigation of the light sources effects on digital camera-based spectral estimation

2021 ◽  
Author(s):  
jinxing liang ◽  
Kaida Xiao ◽  
Xinrong Hu
Keyword(s):  
Spectral Estimation ◽  
Digital Camera ◽  
Light Sources

Auto White Balance Algorithm in Digital Camera

2012 ◽  
Vol 182-183 ◽  
pp. 2080-2084
Author(s):  
Jie Li ◽  
Xue Xiang Wang ◽  
Hao Liu
Keyword(s):  
Hardware Implementation ◽  
Digital Camera ◽  
Low Complexity ◽  
Light Sources ◽  
Light Conditions ◽  
Threshold Method ◽  
White Balance ◽  
White Point ◽  
A New Technique ◽  
Better Than

Auto white balance (AWB) is an important function of digital camera. The purpose of white balance is to adjust the image to make it look like taken under standard light conditions. We present a new technique to detect the reference white point of image in this paper. This technique detects the white point of image by using dynamic threshold method, thus making it more flexible and more applicable compared to other algorithms. We test 50 images which were taken under different light sources, and find that this algorithm is better than or comparable to other algorithms both in subjective and objective aspects. At the same time, this algorithm has low complexity, and it can be easily applied to hardware implementation.

Psychophysics Study on LED Flicker Artefacts for Automotive Digital Mirror Replacement Systems

2020 ◽  
Vol 2020 (11) ◽  
pp. 234-1-234-6
Author(s):  
Nicolai Behmann ◽  
Holger Blume
Keyword(s):  
Light Source ◽  
Pulse Width ◽  
Digital Camera ◽  
Relevant Information ◽  
Human Vision ◽  
Light Sources ◽  
Traffic Light ◽  
Pulse Width Modulated ◽  
Novel Approach ◽  
Flicker Light

LED flicker artefacts, caused by unsynchronized irradiation from a pulse-width modulated LED light source captured by a digital camera sensor with discrete exposure times, place new requirements for both visual and machine vision systems. While latter need to capture relevant information from the light source only in a limited number of frames (e.g. a flickering traffic light), human vision is sensitive to illumination modulation in viewing applications, e.g. digital mirror replacement systems. In order to quantify flicker in viewing applications with KPIs related to human vision, we present a novel approach and results of a psychophysics study on the effect of LED flicker artefacts. Diverse real-world driving sequences have been captured with both mirror replacement cameras and a front viewing camera and potential flicker light sources have been masked manually. Synthetic flicker with adjustable parameters is then overlaid on these areas and the flickering sequences are presented to test persons in a driving environment. Feedback from the testers on flicker perception in different viewing areas, sizes and frequencies are collected and evaluated.

scholarly journals Colour Constancy for Image of Non-Uniformly Lit Scenes

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2242
Author(s):  
Md Akmol Hussain ◽  
Akbar Sheikh-Akbari ◽  
Iosif Mporas
Keyword(s):  
Light Source ◽  
State Of The Art ◽  
Incident Light ◽  
Digital Camera ◽  
Input Image ◽  
Absolute Difference ◽  
Light Sources ◽  
Colour Constancy ◽  
Adjustment Factors ◽  
Camera Sensors

Digital camera sensors are designed to record all incident light from a captured scene, but they are unable to distinguish between the colour of the light source and the true colour of objects. The resulting captured image exhibits a colour cast toward the colour of light source. This paper presents a colour constancy algorithm for images of scenes lit by non-uniform light sources. The proposed algorithm uses a histogram-based algorithm to determine the number of colour regions. It then applies the K-means++ algorithm on the input image, dividing the image into its segments. The proposed algorithm computes the Normalized Average Absolute Difference (NAAD) for each segment and uses it as a measure to determine if the segment has sufficient colour variations. The initial colour constancy adjustment factors for each segment with sufficient colour variation is calculated. The Colour Constancy Adjustment Weighting Factors (CCAWF) for each pixel of the image are determined by fusing the CCAWFs of the segments, weighted by their normalized Euclidian distance of the pixel from the center of the segments. Results show that the proposed method outperforms the statistical techniques and its images exhibit significantly higher subjective quality to those of the learning-based methods. In addition, the execution time of the proposed algorithm is comparable to statistical-based techniques and is much lower than those of the state-of-the-art learning-based methods.

Spectral estimation of fluorescent lamps using RGB digital camera and standard color chart

Optik ◽  
2017 ◽  
Vol 130 ◽  
pp. 50-60 ◽  
Author(s):  
Jingyu Fang ◽  
Haisong Xu ◽  
Peng Xu ◽  
Zhehong Wang
Keyword(s):  
Spectral Estimation ◽  
Digital Camera ◽  
Color Chart ◽  
Fluorescent Lamps ◽  
Standard Color

scholarly journals Digital camera-based spectral estimation in open environment based on imaging condition correction

2020 ◽  
Vol 2020 (28) ◽  
pp. 347-350
Author(s):  
Jinxing Liang ◽  
Kaida Xiao
Keyword(s):  
Spectral Estimation ◽  
Estimation Method ◽  
Digital Camera ◽  
Estimation Accuracy ◽  
Adaptive Model ◽  
Imaging Condition ◽  
Practical Applications ◽  
Open Environment ◽  
Imaging Conditions ◽  
Current Stage

Digital camera-based spectral estimation in open environment is a challenge in current stage. Although some methods have been proposed in recent years, the methods do not consider the exposure inconsistency between camera spectral characterization and spectral estimation applications, that makes the proposed method cannot for practical applications. We proposed here a spectral estimation method based on imaging condition correction of which can deal with the problem exist in current methods. Using the whiteboard and raw camera response, the imaging conditions of open environment is recorded and corrected to the reference imaging conditions, and the surface spectral of object is estimated using the established spectral estimation matrix in the reference imaging conditions. The proposed method in three application models are tested and compared. The result shows that the adaptive model for imaging condition correction gives the best spectral estimation accuracy.

Spectral Estimation of Multiple Light Sources based on Highlight Detection

2020 ◽  
Vol 64 (5) ◽  
pp. 50408-1-50408-9
Author(s):  
Shoji Tominaga ◽  
Keita Hirai ◽  
Takahiko Horiuchi
Keyword(s):  
Light Source ◽  
Power Distribution ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Spectral Estimation ◽  
Spectral Composition ◽  
Image Data ◽  
Light Sources ◽  
Relaxation Labeling ◽  
Highlight Detection

Abstract The authors discuss the spectral estimation of multiple light sources from image data in a complex illumination environment. An approach is proposed to effectively estimate illuminant spectra and the corresponding light sources based on highlight areas that appear on dielectric object surfaces. First, the authors develop a highlight detection method using two types of convolution filters with Gaussian distributions, center-surround and low-pass filters. This method is available even for white surfaces, and it is independent of object color and of viewing and incidence angles. Second, they present an algorithm for estimating the illuminant spectra from extracted highlight areas. Each specular highlight area has a spectral composition corresponding to only one light source among multiple light sources. The spectral image data are projected onto a two-dimensional subspace, where a linear cluster in pixel distribution is detected for each highlight area. Third, the relative positional relationship between highlight areas among different object surfaces is used to identify the light sources on each surface. The authors develop an algorithm based on probabilistic relaxation labeling. The light source for each highlight and the corresponding spectral-power distribution are determined from the iterative labeling process. Finally, the feasibility of the proposed approach is examined in an experiment using a real complex environment, where dielectric objects are illuminated by multiple light sources of light-emitting diode, fluorescence, and incandescence.

Automatic White Balance of Digital Camera Based on Global Probability Distribution

2012 ◽  
Vol 433-440 ◽  
pp. 5443-5447 ◽  
Author(s):  
Hui Nan Guo ◽  
Jian Zhong Cao
Keyword(s):  
Probability Distribution ◽  
Color Image ◽  
Digital Camera ◽  
Light Sources ◽  
Digital Cameras ◽  
White Balance ◽  
Hsi Color Model ◽  
The Difference ◽  
True Colors ◽  
Automatic White Balance

The white balance is an important parameter of digital camera which makes a great impact on the application of digital cameras. However, due to the limitations of hardware of digital camera, the output image of digital camera cannot restore true colors of the objects under the different light sources conditions. And existing automatic white balance (AWB) algorithms have many application restrictions, particularly the single color image, the algorithms always failure to adjust. To solve this problem, this paper proposes an optimized algorithm based on the gray world assumption and HSI color model. According to the R, G and B color components probability distribution, the algorithm adjusts the image by using the difference value of color. Experimental results show that our algorithm can adjust images in complex situations; meanwhile these confirm that this method is not only effective, but also has the advantage of easy realization.

Spectral estimation of tunable LED light source using digital camera based on matrix factorization

Optik ◽  
2017 ◽  
Vol 148 ◽  
pp. 90-94
Author(s):  
Jingyu Fang ◽  
Fuzheng Zhang ◽  
Haisong Xu ◽  
Zhehong Wang ◽  
Changyu Diao
Keyword(s):  
Light Source ◽  
Matrix Factorization ◽  
Spectral Estimation ◽  
Digital Camera ◽  
Led Light

scholarly journals PENGUKURAN TINGKAT KEMATANGAN BUAH PISANG CAVENDISH BERDASARKAN REFLEKTANSI CAHAYA LED

2020 ◽  
Vol 17 (2) ◽  
pp. 88
Author(s):  
Eko Kuncoro Pramono
Keyword(s):  
Red Light ◽  
Green Light ◽  
Digital Camera ◽  
Banana Peel ◽  
Scanning System ◽  
Light Sources ◽  
Maturity Level ◽  
Cavendish Banana ◽  
Light Reflectance ◽  
Reflectance Factor

<p>Penentuan tingkat kematangan buah pisang cavendish biasanya dilakukan secara manual dengan membandingkan warna kulit buah pisang dengan bagan warna standar. Hal ini mempunyai kekurangan yaitu tidak konsisten dan sangat subyektif tergantung dari keahlian operator. Penelitian ini dilakukan untuk mendapatkan hasil pengukuran tingkat kematangan buah pisang cavendish yang lebih akurat, mudah dan tidak merusak (non destruktif). Pengukuran kematangan buah pisang dilakukan berdasarkan faktor reflektansi cahaya, yaitu cahaya hijau (500-560 nm), jingga (580-610 nm), dan merah (600-650 nm) yang diperoleh dari LED. Sebuah spektrofotometer pada rentang spektrum 350-700 nm digunakan sebagai pembanding dalam penelitian ini, dengan sumber cahaya berasal dari lampu halogen untuk dapat memenuhi rentang panjang gelombang pada spektrofotometer. Hasil terbaik didapatkan dari pengukuran nilai reflektansi dengan cahaya merah (600-650 nm), dimana didapatkan nilai reflektansi sebesar 30%-39%, 39%-49%, 49%-59%, 59%-67% dan di atas 67% untuk tingkat kematangan 2,3,4,5 dan 6. Pengujian dengan menggunakan 71 sampel pada tingkat kematangan 2 sampai dengan 6 menghasilkan pengukuran 55 benar (77%), 11 kurang matang satu tingkat (16%) dan 5 lebih matang satu tingkat (7%). Sistem pemindaian (scanning) pada seluruh permukaan kulit pisang atau penggunaan citra kamera digital juga dapat dilakukan untuk meningkatkan akurasi hasil pengukuran.</p><p> </p><p><strong>Measurement of Cavendish Banana Ripeness Stage Based on LED Light Reflectance</strong></p><p>The determination of the ripeness stage of cavendish bananas is usually done manually by comparing banana peels with a standard color chart. This has the disadvantage of being inconsistent and very subjective depending on the expertise of the operator. This research was conducted to obtain the results of the measurement of the ripeness stage of cavendish banana which is more accurate, easy and not destructive. The ripeness stage measurement of banana was based on the light reflectance factor, which were green light (500-560 nm), orange (580-610 nm), and red (600-650 nm) obtained from the LEDs. A spectrophotometer in the spectrum range 350-700 nm was used as a comparison in this study, with light sources coming from halogen lamps to be able to meet the wavelength range of the spectrophotometer. The best results were obtained from the measurement of reflectance values with red light, where the reflectance values were 30%-39%, 39%-49%, 49%-59%, 59%-67% and above 67% for the maturity level of 2, 3 , 4, 5 and 6. Testing using 71 samples at maturity level 2 to 6 resulted in a prediction of 55 correct (77%), 11 less mature one level (16%) and 5 more mature one level (7%). A scanning system on the entire surface of a banana peel or the using image of digital camera can also be done to improve the accuracy of the measurement results.</p>

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