VIRTUAL REALITY: A PROMISING APPROACH FOR LIGHTING RESEARCH

Virtual Reality (VR) seems a promising tool in lighting field, both for design and research applications. Despite several studies have been conducted on this topic, the opinions about the actual advantages of VR are conflicting. It is not clear if VR software are able to properly simulate spatial light distribution, and if the luminous sensation reproduced in Virtual Reality is representative of the real one. The paper revises the literature about the topic and then tests the reliability of a VR simulation software, Unreal Engine (UE), in calculating light. To do that, illuminance measurements were performed in a test room and the obtained values were compared with those calculated with both UE and DIVA for Rhinoceros. Results demonstrated that the percentage differences between the UE’s and the real values range from -2% to 5% and those between UE and DIVA from -4% to 0%.

ESTIMATION OF COMPLEX LIGHT DISTRIBUTION CHRACTERISTIC BASED ON LIGHT FIELDS

With the advent of LED lights and the added functionality of the lights themselves, the number of automobile headlights being manufactured is rising. Manufactured headlights need to be measured for light distribution characteristic to assure their quality. However, the conventional method requires a lot of measurement time and a large space. As a result, problems arise where light distribution measurement cannot be completed in time for headlight production. We propose a measurement method for complex light distribution characteristic based on light fields to solve this problem. Our method is to measure the light intensity of planes at a certain range distance from the light source and then estimate the light distribution characteristic of a light source. This method would enable the measurement of the light distribution characteristic in a narrower range and in a shorter time than the conventional method.

A Review of designing freeform optical surfaces by the Monge–Ampère equations

Background: The equations of Monge–Ampère type which arise in geometric optics is used to design illumination lenses and mirrors. The optical design problem can be formulated as an inverse problem: determine an optical system consisting of reflector and/or refractor that converts a given light distribution of the source into a desired target light distribution. For two decades, the development of fast and reliable numerical design algorithms for the calculation of freeform surfaces for irradiance control in the geometrical optics limit is of great interest in current research. Objective: The objective of this paper is to summarize the types, algorithms and applications of Monge–Ampère equations. It helps scholars to grasp the research status of Monge–Ampère equations better and to explore the theory of Monge–Ampère equations further. Methods: This paper reviews the theory and applications of Monge–Ampère equations from four aspects. We first discuss the concept and development of Monge–Ampère equations. Then we derive two different cases of Monge–Ampère equations. We also list the numerical methods of Monge–Ampère equation in actual scenes. Finally, the paper gives a brief summary and an expectation. Results: The paper gives a brief introduction to the relevant papers and patents of the numerical solution of Monge–Ampère equations. There are quite a lot of literatures on the theoretical proofs and numerical calculations of Monge–Ampère equations. Conclusion: Monge–Ampère equation has been widely applied in geometric optics field since the predetermined energy distribution and the boundary condition creation can be well satisfied. Although the freeform surfaces designing by the Monge–Ampère equations is developing rapidly, there are still plenty of rooms for development in the design of the algorithms.

Light Distribution and Perceived Spaciousness: Light Patterns in Scale Models

Previous research showed that light distribution can affect the perception of spatial size and shape. However, most studies are limited to quantitative assessment of a few scenarios without explaining possible causes behind peoples’ experiences. This exploratory study aimed to reveal complex relationships between light patterns and perceived size, and to investigate how light patterns affect perceived spaciousness. A qualitative approach was used with pair-wise comparisons between systematic visual observations of scale models. The observations confirmed that illuminated walls increase spaciousness. Yet, darkness impacts the perception of spaciousness as well. Both compound and separated light zones can expand depth, height, or width, depending on the interpretation of these patterns of light seen in relation to the whole spatial context. Furthermore, the position of illuminated areas, with placements on edge or in the center, may additionally influence perceived size.

Dynamics of Nutrients and Colored Dissolved Organic Matter Absorption in a Wetland-Influenced Subarctic Coastal Region of Northeastern Japan: Contributions From Mariculture and Eelgrass Meadows

Coastal oceans interacting with terrestrial ecosystems play an important role in biogeochemical cycles. It is therefore essential to research land–ocean interactions for further understanding of the processes influencing nutrients dynamics in coastal areas. We investigated the seasonal and spatial distribution of nutrient concentrations and light absorption coefficients of colored dissolved organic matter (CDOM), non-algal particles (NAP), and phytoplankton in a wetland-influenced river–eelgrass meadows–coastal waters continuum in the protected and semi-enclosed coastal sea of Akkeshi-ko estuary (AKE) and Akkeshi Bay (AB), Japan from April 2014 to February 2015. The mixing dilution lines of the CDOM absorption coefficient at 355 nm [aCDOM(355)] relative to salinity predicted by two end-members between freshwater and coastal water showed conservative mixing in AB. Silicate concentrations were significantly correlated with salinity and aCDOM(355) in AB in each month except for December 2014. These results suggest that silicate and CDOM in AB primarily originates from wetland-influenced river discharge. However, samples collected from the eelgrass meadows of AKE, where mariculture is developed, showed non-conservative mixing of silicate concentrations and aCDOM(355) with salinity except for June 2014. Elevated phosphate concentrations, probably released from sediments, were also found in the eelgrass meadows of AKE, especially during summer. These results suggest that the metabolic activities of mariculture and seagrass ecosystem significantly contribute to the nutrient cycles and CDOM absorption in AKE and to the distinct water-mass systems inside and outside AKE. The relative absorption properties of NAP [aNAP(443)], phytoplankton [aph(443)], and aCDOM(443) showed that CDOM is the main factor affecting the light distribution in AKE. However, the relative absorption properties varied seasonally in AB because of spring and autumn phytoplankton blooms and ice cover during winter. Significant relationships were observed between the Secchi disk depth (ZSD), aNAP(443), and aCDOM(443). Chl a concentration and aph(443) were not good indicators for predicting ZSD in our study region. These results suggest that incorporating inherent optical properties and CDOM from mariculture and seagrass ecosystem into ecosystem models could improve predictions of light distribution along the freshwater–eelgrass–coastal waters continuum in optically complex coastal waters.

Highly Reflective Thin-Film Optimization for Full-Angle Micro-LEDs

Displays composed of micro-light-emitting diodes (micro-LEDs) are regarded as promising next-generation self-luminous screens and have advantages such as high contrast, high brightness, and high color purity. The luminescence of such a display is similar to that of a Lambertian light source. However, owing to reduction in the light source area, traditional secondary optical lenses are not suitable for adjusting the light field types of micro-LEDs and cause problems that limit the application areas. This study presents the primary optical designs of dielectric and metal films to form highly reflective thin-film coatings with low absorption on the light-emitting surfaces of micro-LEDs to optimize light distribution and achieve full-angle utilization. Based on experimental results with the prototype, that have kept low voltage variation rates, low optical losses characteristics, and obtain the full width at half maximum (FWHM) of the light distribution is enhanced to 165° and while the center intensity is reduced to 63% of the original value. Hence, a full-angle micro-LEDs with a highly reflective thin-film coating are realized in this work. Full-angle micro-LEDs offer advantages when applied to commercial advertising displays or plane light source modules that require wide viewing angles.

Measuring the Effects of Light Distribution on Spatial Brightness

<p><b>By changing the light distribution it is possible to double the apparent amount of light in a space without any increase in its overall luminance. If one simply assumes that the apparent amount of light in a space — its spatial brightness — is described by its mean luminance (or similar measures) then substantial errors may be made.</b></p> <p>We carried out two experiments, measuring the brightness of 19 different model spaces. Our results demonstrate that making light distributions more non-uniform can make spaces appear both significantly brighter and significantly darker, depending on how the light distribution is changed. This challenges most existing studies in the field that argue that non-uniformity of the luminance distribution simply makes spaces look darker. Indeed, the observed pattern in brightness between our conditions cannot be consistently explained by a simple measure of the uniformity of the luminance distribution. We thus reject all previously proposed models of light distribution and spatial brightness.</p> <p>The best explanation of this and the apparent disagreements in the literature over the effects of non-uniformity appears to be that spatial brightness is affected by the qualitative appearance of the luminances in the space. Light sources and non-luminous surfaces have different effects. We propose a ‘duel’-process model of spatial brightness in which it is the sum of two opposed processes: the effects of the surfaces, and the effects of the light source(s). Non-uniform patterns of surface reflectance and illumination tend to make a space appear brighter. Non-uniformity as a result of a large difference between luminance of the light source(s) and the surfaces makes a space appear darker. If the light source is hidden from direct view its darkening effect is removed, which can make the space appear significantly brighter. Depending on the relative strength of these two processes, a non-uniform luminance distribution may thus appear either brighter or darker than a more uniform distribution.</p> <p>Additionally, we highlight issues demonstrated in both the failure of models previously proposed by the literature, and our exploration of potential implementations of the ‘duel’-process model. It is very easy to produce a good correlation with a defensible metric that will not generalise to other data sets. A metric having a good correlation in a study provides very little reason to actually believe it. If we wish to develop a model of the effects of light distribution that we can trust, we need to demonstrate its robustness by testing its underlying assumptions and showing them to be well supported. As we show, there is a large variety of these that need to be worked through.</p>