Estimation of Position and Intensity of Multi-Light Sources Based on Specular Sphere

2018 ◽  
Vol 22 (4) ◽  
pp. 491-497
Author(s):  
Chao Xu ◽  
◽  
Hua Li ◽  
Cheng Han
Keyword(s):  
Mixed Reality ◽  
Specular Reflection ◽  
Multiple Point ◽  
Light Sources ◽  
Ambient Light ◽  
Sphere Surface ◽  
Illumination Estimation ◽  
Illumination Model ◽  
Novel Method ◽  
Point Light

Illumination estimation is an important research content in mixed reality technology. This paper presents a novel method for locating multiple point light sources and estimating their intensities from the images of a pair of reference spheres. In our approach, no prior knowledge of the location of the sphere is necessary, and the center of the sphere can be uniquely identified with the known radius. The sphere surface is assumed to have both Lambertian and specular properties instead of being a pure Lambertian or specular surface, which guarantees a higher accuracy than the existing approaches. The position estimations of multiple light sources are based on the fact that the specular reflection is highly dependent on highlights. One sphere is utilized to determine the directions of the light sources, and two spheres are used to locate the positions. The images of reference spheres are sampled and partitioned with multiple light sources in different positions. An illumination model is used to calculate the intensities of the ambient light and multiple light sources. Experiments on both simulation and synthetic images show that this method is feasible and accurate for estimating the positions and intensities of the multiple light sources.

Comparative study on the illumination model of fishing lamps based on point light sources and spherical light sources

2019 ◽  
Vol 12 (2) ◽  
pp. 274-288
Author(s):  
花传祥 HUA Chuan-xiang ◽  
李 非 LI Fei ◽  
朱清澄 ZHU Qing-cheng ◽  
孙 栋 SUN Dong ◽  
田中旭 TIAN Zhong-xu
Keyword(s):  
Comparative Study ◽  
Light Sources ◽  
Illumination Model ◽  
Point Light

scholarly journals A time-division correction method for adaptive optics system

2021 ◽  
Vol 2093 (1) ◽  
pp. 012038
Author(s):  
Guangfu Yuan ◽  
Lirong Zhao ◽  
Peijian Wu ◽  
Weijie Wang
Keyword(s):  
Adaptive Optics ◽  
Correction Method ◽  
Field Of View ◽  
Image Feature ◽  
Astronomical Observation ◽  
Multiple Point ◽  
Light Sources ◽  
Extended Target ◽  
Point Light ◽  
Adaptive Optics System

Abstract An adaptive optics system can measure and compensate the wavefront distortion caused by dynamic disturbance in real time. It is usually used for astronomical observation and other occasions. According to the current technology, it is only suitable for small field of view optical system or point target, but not for ground extended target detection. In order to solve this problem, a correction method is proposed: firstly, the sub aperture image of wavefront sensor is divided into several sub regions, each sub region corresponds to a certain light direction or field angle range; secondly, calculate the offset of the image feature points in each sub region, and an image with good correction effect in a field of view in this direction is obtained; the last step is to measure each sub region one by one and combine these images into a full frame image. Through comparison, it is found that the method proposed in this paper is essentially to divide the extended target into multiple point light sources for correction.

Effect Of Chromaticity Of Surrounding Light Sources on Mesopic Adaptation Luminance

2021 ◽  
pp. 30-38
Author(s):  
Sangita Sahana ◽  
Biswanath Roy
Keyword(s):  
Light Source ◽  
The State ◽  
Light Sources ◽  
Ambient Light ◽  
Lighting Conditions

This paper presents variations in mesopic adaptation luminance in the presence of ambient light sources along with main light source for outdoor lighting applications. Mesopic photometry system is based on peripheral task, and adaptation luminance is required to compute the effective mesopic radiance for the measured area. Different lighting conditions were considered to determine the effect of chromaticity of bright surrounding sources other than the main light sources to the state of observer adaptation. The veiling luminance caused by the surrounding sources increases the state of observer adaptation, but not the luminance within the measurement field. It has also been observed that in case of cool white surrounding sources, adaptation luminance increases significantly than that of warm white sources.

scholarly journals Visual Navigation for Recovering an AUV by Another AUV in Shallow Water

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1889 ◽  
Author(s):  
Shuang Liu ◽  
Hongli Xu ◽  
Yang Lin ◽  
Lei Gao
Keyword(s):  
Shallow Water ◽  
Pose Estimation ◽  
Field Experiments ◽  
State Of The Art ◽  
Autonomous Underwater Vehicles ◽  
Visual Navigation ◽  
Ambient Light ◽  
Robust Detection ◽  
Novel Method ◽  
Coarse To Fine

Autonomous underwater vehicles (AUVs) play very important roles in underwater missions. However, the reliability of the automated recovery of AUVs has still not been well addressed. We propose a vision-based framework for automatically recovering an AUV by another AUV in shallow water. The proposed framework contains a detection phase for the robust detection of underwater landmarks mounted on the docking station in shallow water and a pose-estimation phase for estimating the pose between AUVs and underwater landmarks. We propose a Laplacian-of-Gaussian-based coarse-to-fine blockwise (LCB) method for the detection of underwater landmarks to overcome ambient light and nonuniform spreading, which are the two main problems in shallow water. We propose a novel method for pose estimation in practical cases where landmarks are broken or covered by biofouling. In the experiments, we show that our proposed LCB method outperforms the state-of-the-art method in terms of remote landmark detection. We then combine our proposed vision-based framework with acoustic sensors in field experiments to demonstrate its effectiveness in the automated recovery of AUVs.

scholarly journals Optical Losses in Hybrid Microcavity Based in Porous Semiconductors and its Application as Optic Chemical Sensor

2019 ◽  
Vol 56 ◽  
pp. 158-167
Author(s):  
Claudia Antonio Hernández ◽  
Edith Osorio ◽  
Raúl Urteaga ◽  
Roberto Koropecki ◽  
José Alberto Alvarado ◽  
...  
Keyword(s):  
Chemical Sensor ◽  
Visible Region ◽  
Bragg Reflector ◽  
Resonant Peak ◽  
Light Sources ◽  
Optical Losses ◽  
Distributed Bragg Reflector ◽  
Nanoporous Anodic Alumina ◽  
Porous Semiconductors ◽  
Point Light

In this study the experimental and theoretical optical analysis of a hybrid microcavity (HM) based in porous silicon (PS) and nanoporous anodic alumina (NAA) are presented. The microcavity was centered in the visible region at 760 nm. Distributed Bragg reflector (DBR) was obtained using galvanostatic anodizing method and while NAA by the two-step anodization technique. From SEM micrographs the HM different regions are observed. HM optical characterization in the visible region was done, considering two different light sources, point and non-point respectively. These results reveal a decrease in the quality factor (Q) from 350 to 190 when the source is exchanged; this behavior has been mainly attributed to the light scattering at NAA. Furthermore, it was possible to study Q change, through transmittance simulation using the transfer matrix and Landau-Lifshitz-Looyenga theoretical methods. When a point light source is used, there are no optical losses making possible to sense 1% of analyte resulting in a 0.29 nm redshift of the resonant peak. According with these results we propose to apply the HM as chemical optic sensor.

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