Spatial Distribution Of Illumination Research Articles

Large‐Scaled and Solar‐Reflective Kirigami‐Based Building Envelopes for Shading and Occupants’ Thermal Comfort

AbstractConventional air conditioning in buildings consumes substantial energy contributing to an increase in greenhouse gas emissions, which aggravates global warming. Kirigami envelopes with reflective surfaces offer a promising option to reduce indoor heat gain. So far none has performed outdoor testing of kirigami envelopes nor numerical simulation to understand how they interact with the environment. To understand the impact of the geometric design of the kirigami shading system on both daylighting and temperature variation in the indoor environment, a series of prototypes and simulations is devised to investigate the real‐time shading behavior in an outdoor environment. Large‐scaled and silver‐coated kirigami‐based envelopes of different cut patterns and stretching ratios are fabricated and placed in front of custom‐designed chambers equipped with six thermo‐sensors. Simulation is performed to investigate the effect of light modulation and hence temperature inside the chamber, which corroborates with the experiments. The indoor daylighting pattern and temperature are significantly influenced by the geometry of the stretched kirigami envelope, and overall, both the indoor temperature and the spatial distribution of illuminance are more uniform compared with that without the kirigami envelope. These results indicate that the installation of kirigami envelopes can improve building energy saving and occupants’ comfort.

Extending the lighting design objectives procedure for holistic lighting solutions

The author has previously proposed a novel spreadsheet-based lighting design objectives procedure (LiDOs) that enables practitioners to reconcile interacting LiDOs relating to the spatial distribution of illumination within a space, and this procedure has been successfully adopted by several lighting design practices. This paper proposes that the procedure is developed into an extended computer-based lighting design tool (LiDOs2) that includes LiDOs relating to spectral and temporal illumination distributions, as well as spatial distribution. This would enable regulators to specify limiting values for basic indoor lighting objectives such as perceived adequacy of illumination while at the same time guiding practitioners to incorporate LiDOs that address characteristics of lighting chosen to suit specific applications. The LiDOs2 procedure would be capable of generating holistic lighting performance specifications that would enable practitioners to conduct informed searches for light sources and luminaires, and to determine layouts and control circuits with confidence that the specified combination of LiDOs would be achieved.

Contactless photomagnetoelectric investigations of 2D semiconductors.

Background: Applications of two-dimensional (2D) materials in electronic devices require the development of appropriate measuring methods for determining their typical semiconductor parameters, i.e., mobility and carrier lifetime. Among these methods, contactless techniques and mobility extraction methods based on field-effect measurements are of great importance.Results: Here we show a contactless method for determining these parameters in 2D semiconductors that is based on the photomagnetoelectric (PME) effect (also known as the photoelectromagnetic effect). We present calculated dependences of the PME magnetic moment, evoked in 2D Corbino configuration, on the magnetic field as well as on the intensity and spatial distribution of illumination. The theoretical predictions agree with the results of the contactless investigations performed on non-suspended single-layer graphene. We use the contactless PME method for determining the dependence of carrier mobility on the concentration of electrons and holes induced by a back-gate voltage.Conclusion: The presented contactless PME method, used in Corbino geometry, is complementary to the mobility extraction methods based on field-effect measurements. It can be used for determining the mobility and diffusion length of carriers in different 2D materials.

Close range radiometry for quantifying the spatial distribution of illumination on flat surfaces

Measuring the spatial distribution of irradiance on surfaces has extensive applications in various fields of heat transfer such as concentrating solar energy. In this paper, we have introduced a close range radiometry measurement method for flat surfaces employing camera calibration to extract illumination distribution data with high accuracy and resolution. The equations for quantifying the illumination profile on the target using the measured geometrical parameters have been introduced. The method developed in this work was experimentally demonstrated to have an accuracy of ±10% with additional improvement opportunities identified and discussed.

Optimization of spatial light distribution through genetic algorithms for vision systems applied to quality control

The paper presents an adaptive illumination system for image quality enhancement in vision-based quality control systems. In particular, a spatial modulation of illumination intensity is proposed in order to improve image quality, thus compensating for different target scattering properties, local reflections and fluctuations of ambient light. The desired spatial modulation of illumination is obtained by a digital light projector, used to illuminate the scene with an arbitrary spatial distribution of light intensity, designed to improve feature extraction in the region of interest. The spatial distribution of illumination is optimized by running a genetic algorithm. An image quality estimator is used to close the feedback loop and to stop iterations once the desired image quality is reached. The technique proves particularly valuable for optimizing the spatial illumination distribution in the region of interest, with the remarkable capability of the genetic algorithm to adapt the light distribution to very different target reflectivity and ambient conditions. The final objective of the proposed technique is the improvement of the matching score in the recognition of parts through matching algorithms, hence of the diagnosis of machine vision-based quality inspections. The procedure has been validated both by a numerical model and by an experimental test, referring to a significant problem of quality control for the washing machine manufacturing industry: the recognition of a metallic clamp. Its applicability to other domains is also presented, specifically for the visual inspection of shoes with retro-reflective tape and T-shirts with paillettes.

Determination of Diffusion Length of Carriers in Graphene Using Contactless Photoelectromagnetic Method of Investigations

ABSTRACTThe photoelectromagnetic (PEM) investigations are proposed for determination of diffusion length of carriers in graphene. The presented measurements are performed in Corbino configuration using noncontact technique. The circular PEM currents are detected in an outer coil by induction if illumination intensity is periodically varied. The theoretical dependence of PEM response on magnetic field induction, intensity and spatial distribution of illumination as well as on frequency of illumination chopping is presented. Experimental PEM data are presented for graphene films grown by CVD processing on a cooper foil and transferred onto a glass substrate. The presented method of investigations should be essential for development of graphene electronic and optoelectronic devices.

Technical evaluation of artificial ligthing systems for broiler houses

The spatial distribution of illuminance and the electric consumption of artificial lighting system is one of the main problems related to broiler production. Therefore, the aim of this study was to evaluate the spatial distribution of luminance level and energy efficiency of different lighting systems for broiler houses. Six types of lamps were tested in two different configurations to find the minimum illuminance of 20 and 5 lux. The tested lamps were incandescent (IL) 100 W, compact fluorescent (CFL) 34 W, mixed (ML) 160 W, sodium vapor (SVL) 70 W, T8 fluorescent tube (T8 FTL) 40 W and T5 fluorescent tube (T5 FTL) 28 W. The first four were evaluated with and without reflective light fixture and the latter two without light fixture. It was observed that the tested system with light fixtures negatively affected the spatial distribution of illuminance inside the house. The systems composed by IL and ML without light fixture led to better results in meeting the minimum illuminance of 20 lux and 5 lux, respectively. T5 FTL presented the lowest energy demand.

Lightness perception in scenes with motion-based shading cues to the spatial distribution of illumination

Lightness perception in scenes with motion-based shading cues to the spatial distribution of illumination

How direction of illumination affects visually perceived surface roughness

We examined visual estimation of surface roughness using random, computer-generated, three-dimensional (3D) surfaces rendered under a mixture of diffuse lighting and a punctate source. The angle between the tangent to the plane containing the surface texture and the direction to the punctate source was varied from 50 to 70 deg across lighting conditions. Observers were presented with pairs of surfaces under different lighting conditions and indicated which 3D surface appeared rougher. Surfaces were viewed either in isolation or in scenes with added objects whose shading, cast shadows, and specular highlights provided information about the spatial distribution of illumination. All observers perceived surfaces to be markedly rougher with decreasing illuminant angle. Performance in scenes with added objects was no closer to constant than that in scenes without added objects. We identified four novel cues that are valid cues to roughness under any single lighting condition but that are not invariant under changes in lighting condition. We modeled observers' deviations from roughness constancy as a weighted linear combination of these "pseudocues" and found that they account for a substantial amount of observers' systematic deviations from roughness constancy with changes in lighting condition.

Cubic illumination

Cubic illumination specifies the spatial distribution of illumination about a point in terms of the illuminances on six faces of a small cube centred at the point. This form of specification is proposed as the basis of a system of applied photometry. Its advantage is that once the cubic illumination has been determined, whether by measurement or calculation, a range of indices of lighting may be derived quite readily. Analysis of the cubic illumination specification comprises defining two components of the illumination solid; the vector component defined by the illumination vector, and the symmetric component, which remains after subtraction of the vector component. The planar illuminance for any orientation, and the average illuminances of regular solids, such as a cylinder or sphere, are calculated by summing the contributions of these two components. By specifying a direction of view towards the point, indices which relate to how lighting might affect the appearance of a three-dimensional object located at the point may be calculated, and by specifying a direction of view from the point, the eye illuminance, or the illuminance of a plane normal to the direction of view, may be derived. The paper gives procedures for calculating, measuring and analysing cubic illumination, and reviews applications for the derived illumination metrics.

The responses of retinal ganglion cells to stationary and moving visual stimuli

Stationary illumination of the turtle retina provoked depolarizing responses by ganglion cells. Polarization of the cell membrane in by intracellular current injection revealed an apparent membrane conductance increase during illumination. However, the responses reversal potential depended on the spatial distribution of illumination upon the receptive field. A spot of light moved across the retina produced transient photoresponses which, in about 29% of ganglion cells, show directional selectivity. Polarization experiments have shown that movement of the spot in a specific (“null”) direction brings forth an early hyperpolarization which depresses a subsequent, excitatory portion of the photoresponse. No other retinal cells show directional selectivity.

The line spread-function and the modulation transfer function of X-ray fluorescent screen-film systems--problems with double-coated films.

The line spread-function (LSF) of the screen—film system has been defined as the sum of the spatial distribution of illuminance in the front and the back emulsion caused by a beam of x rays which passes through a narrow slit. Fourier transformation of the LSF gives the corresponding modulation transfer function (MTF).In the past, the LSF has been obtained by scanning slit images on double-coated film. This method can be justified for symmetric screen—film systems, but is, in general, invalid for asymmetric screen—film systems, although the errors introduced may be small, even for grossly asymmetric systems, as is shown in this paper. In practice, many screen—film systems are essentially symmetric and yield nearly the same LSF's and MTF's by either method. For this reason, it is valid to obtain the LSF and MTF of such systems by treating the double-coated film as a unit. A mathematical analysis indicates that the MTF of the screen—film system is the sum of weighted MTF's derived from the illuminance distri...