scholarly journals A Practical Method for Estimation of Point Light-Sources

2001 ◽  
Author(s):  
M Weber ◽  
R Cipolla
Keyword(s):  
Practical Method ◽  
Light Sources ◽  
Point Light

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.

Mitigation of even harmonics in the Fourier components of vertical illuminance around a reference point

2019 ◽  
Vol 52 (5) ◽  
pp. 675-691
Author(s):  
RA Mangkuto ◽  
B Paramita ◽  
SS Utami
Keyword(s):  
Sensitivity Analysis ◽  
Reference Point ◽  
Point Sources ◽  
Light Sources ◽  
Sensitivity Analysis Method ◽  
Genetic Algorithm Method ◽  
Components Analysis ◽  
Optimisation Methods ◽  
Point Light ◽  
Even Harmonics

The use of Fourier components analysis has been recently proposed by Lynes to describe harmonics in vertical illuminance at various azimuth angles around a reference point. In cases with multiple light sources, it has been argued that the removal of even harmonics in the resulting Fourier components may correspond with good lighting practice. This paper therefore aims to demonstrate optimisation methods to mitigate even harmonics in Fourier components of vertical illuminance around a reference point due to two and three point light sources, by adjusting maximum vertical illuminance and subtended angles between the sources using sensitivity analysis and genetic algorithms. The results suggest that the genetic algorithm method yields more precise optimum solutions compared with the sensitivity analysis method, particularly for scenes with three point sources. For two point sources, the smallest root mean square value of even harmonics is achieved when the vertical illuminance due to the second source is 0.92 (relative to the vertical illuminance due to the first source) and the subtended angle is 90°. For three point sources, the optimum vertical illuminance due to the second and third sources is respectively 0.81 and 0.78, whereas the optimum subtended angles for the second and third sources with respect to the first are 64.4° and 116.8°, respectively.

Near Field Photometric Stereo with Point Light Sources

2014 ◽  
Vol 7 (4) ◽  
pp. 2732-2770 ◽  
Author(s):  
Roberto Mecca ◽  
Aaron Wetzler ◽  
Alfred M. Bruckstein ◽  
Ron Kimmel
Keyword(s):  
Near Field ◽  
Photometric Stereo ◽  
Light Sources ◽  
Point Light

scholarly journals Active Recurrence of Lighting Condition for Fine-Grained Change Detection

2018 ◽  
Author(s):  
Qian Zhang ◽  
Wei Feng ◽  
Liang Wan ◽  
Fei-Peng Tian ◽  
Ping Tan
Keyword(s):  
Change Detection ◽  
Light Source ◽  
Real World ◽  
Reference Image ◽  
Light Sources ◽  
Lighting Condition ◽  
Fine Grained ◽  
Lighting Conditions ◽  
Point Light ◽  
Change Monitoring

This paper addresses active lighting recurrence (ALR), a new problem that actively relocalizes a light source to physically reproduce the lighting condition for a same scene from single reference image. ALR is of great importance for fine-grained visual monitoring and change detection, because some phenomena or minute changes can only be clearly observed under particular lighting conditions. Hence, effective ALR should be able to online navigate a light source toward the target pose, which is challenging due to the complexity and diversity of real-world lighting \& imaging processes. We propose to use the simple parallel lighting as an analogy model and based on Lambertian law to compose an instant navigation ball for this purpose. We theoretically prove the feasibility of this ALR strategy for realistic near point light sources and its invariance to the ambiguity of normal \& lighting decomposition. Extensive quantitative experiments and challenging real-world tasks on fine-grained change monitoring of cultural heritages verify the effectiveness of our approach. We also validate its generality to non-Lambertian scenes. 

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