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

Author(s):  
Qian Zhang ◽  
Wei Feng ◽  
Liang Wan ◽  
Fei-Peng Tian ◽  
Ping Tan

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. 

2021 ◽  
pp. 30-38
Author(s):  
Sangita Sahana ◽  
Biswanath Roy

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.


Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 190-190 ◽  
Author(s):  
H Irtel

Most theories of colour constancy assume a flat coloured surface and a single homogenous light source. Natural situations, however, are 3-dimensional (3-D), are hardly ever restricted to a single light source, and object illumination is never homogenous. Here, two special cases of secondary light sources with sharp boundaries were simulated on a computer screen: a house-like 3-D object with colour patches in sunlight and shadow, and a Mondrian-type pattern with a coloured transparency covering some of the colour patches. Subjects made ‘paper’-matches between colour patches in light and shadow and between patches under the transparency and without the transparency. Matching did not depend on whether the simulated lighting condition was natural (yellow light, blue shadow) or artificial (green light, magenta shadow). Patches under a coloured transparency produced lightness constancy but subjects could not discount chromaticity shifts induced by the transparency. The number of context patches (2 vs 6) made no difference, and it made no difference whether the transparency covered the Mondrian completely or only partially. These results indicate that subjects were not able to use local contrast cues at sharp illumination boundaries to discount for the illuminant.


Author(s):  
Chi Chung Ko ◽  
Chang Dong Cheng

How the properties of virtual 3D objects can be specified and defined has been discussed in earlier chapters. However, how a certain virtual object will appear to the user will in general depends also on human visual impression and perception, which depends to a large extent on the lighting used in illumination. As an example, watching a movie in a dark theatre and under direct sunlight will give rise to different feeling and immersion even though the scenes are the same. Thus, in addition to defining the skeleton of a virtual object by using geometry objects in Java 3D in Chapter III, setting the appearance attributes in Chapter IV and applying texture in Chapter V to give a realistic skin to the virtual object, appropriate environmental concerns such as light, background and even fog are often necessary to make the virtual object appear as realistic to the user as possible. In this chapter, we will discuss topics related to the latter environmental issues. The use of proper lighting is thus crucial to ensure that the 3D universe created is realistic in feeling and adds to strong emotional impressions in any application. For this purpose, Java 3D has a variety of light sources that can be selected and tailored to different scenarios. Technically, light rays are not rendered. In fact, their effects will only become visible once they hit an object and reflect to the viewer. Of course, as with any object in the real world, the reflection depends on the material attributes of the objects. In this chapter, we will discuss the use of different types of light source and their effects after describing the lighting properties or materials of visual objects. We will then outline the use of fogging techniques to turn a hard and straight computer image into a more realistic and smoother scene before discussing methods for immersing active visual objects in a background.


2021 ◽  
Vol 60 (29) ◽  
pp. 9213
Author(s):  
Ganbat Baasantseren ◽  
Yulian Cao ◽  
Nomin-Erdene Dalkhaa

2016 ◽  
Vol 50 (3) ◽  
pp. 429-445 ◽  
Author(s):  
S Ma ◽  
M Wei ◽  
J Liang ◽  
B Wang ◽  
Y Chen ◽  
...  

Whiteness is an important characteristic for surface colour, which is affected by the spectral power distribution of the illumination due to the fluorescent whitening agents contained in many white objects. The CIE whiteness metric has been widely used but is known to have limitations. For example, the boundary noted by the metric is not considered large enough, because, in many cases, a surface whose chromaticity lies outside the boundary can still be perceived as white. Further, the metric is only defined to characterize the whiteness of a surface under CIE Illuminant D65, and thus it should not be applied in other lighting conditions or to other light sources. This paper describes a psychophysical study, investigating the whiteness of 50 samples (12 paper and 38 textile samples) under 12 lighting conditions with different levels of correlated colour temperature and ultraviolet radiation. An optimized whiteness metric and a boundary of the white region based on the CIE whiteness metric were derived from the results, which can be used to precisely measure the whiteness of a surface under any lighting condition and to guide spectral engineering for LED sources.


2012 ◽  
Vol 505 ◽  
pp. 367-372
Author(s):  
Yan Ling Wang ◽  
Xiao Li Wang ◽  
Guang Lun Li

Real-time segmentation of moving regions in image sequences is a fundamental step in video monitoring systems. This paper presents an improved motion detection algorithm in a dynamic scene based on change detection. The algorithm integrates the temporal differencing method and background subtraction method to achieve better performance. Background subtraction is a typical change detection approach to segment foreground, but the continuous or abrupt variations of lighting conditions that cause unexpected changes in intensities on the background reference image. So we combine the background subtraction’s result with temporal difference’s result. The foreground mask is segmented by both the methods of background subtraction and temporal differencing. Finally, a post-processing is applied on the obtained object mask to reduce regions and smooth the moving region boundary. Experimental results demonstrate that the proposed method can update the background exactly and quickly along with the variation of illumination, and the moving objects can be extracted effectively.


Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2755 ◽  
Author(s):  
Zhi Ting Ye ◽  
Chin Lung Chen ◽  
Lung-Chien Chen ◽  
Ching Ho Tien ◽  
Hong Thai Nguyen ◽  
...  

Light-emitting diodes (LEDs) have numerous advantages. However, LEDs only offer a point light source. Therefore, transforming LEDs into planar light sources is a new objective in general lighting applications. Solid light guides have strong uniformity but are marred by their material absorption characteristics and weight. Hollow light guides constitute a solution to the weight problem but exhibit poor uniformity and necessitate sacrificing efficiency to enhance uniformity. To resolve the uniformity, weight, and efficiency problems simultaneously, we propose a hollow light guide architecture involving mini-LEDs with asymmetric luminous intensity. To develop this guide module, we first optimized the aspect ratio of the cavity and then modulated the light path by using varied angles of the reflection surface on the end wall of the module. We then designed a beveled reflection surface near the mini-LEDs to further enhance uniformity. An archetype of the proposed architecture for planar light source modules had a width and depth of 51.5 and 9.95 mm, respectively. Experimental results revealed a total efficiency of 83.9% and uniformity of 92.3%. The module weight was determined to be 215 g, which was 40% lighter than that of similarly sized solid light guide modules.


Author(s):  
Sheng-Liang Kao ◽  
Chiou-Shann Fuh

In this paper, a linear algorithm3,4 is proposed to recover shape information from multiple images, each of them is taken under the environment that all of the object surfaces are illuminated by a known near point light source. In this method, an approximate range of the distance for the objects to the viewer (e.g. camera) is previously defined. Using this predefined value, the absolute depth map of the objects can be found out.


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