Luminescent Cavity Design for High Ambient Contrast Ratio, High Efficiency Displays

A key display characteristic is its efficiency (emitted light power divided by input power). While display efficiencies are being improved through emissive (e.g., quantum dot and organic light emitting display (OLED) designs1,2, which remove the highly inefficient color filters found in traditional liquid crystal displays (LCDs)3,4, polarization filters, which block about 50% of the light, remain required to inhibit ambient light reflection. We introduce a luminescent cavity design to replace both the color and polarization filters. Narrow-band, large Stokes shift, CdSe/CdS quantum dot emitters are embedded in a reflective cavity pixel element with a small top aperture. The remainder of the top surface is coated black reducing ambient light reflection. A single pixel demonstrates an extraction efficiency of 40.9% from a cavity with an 11% aperture opening. A simple proof-of-concept multi-pixel array is demonstrated.

IS IT POSSIBLE TO ACHIEVE QUALITY LIGHTING WITHOUT CONSIDERING THE PHOTOMETRY OF THE PAVEMENTS?

In this study, the photometry of a wide range of classic and innovative pavements used in urban and interurban areas were characterised both when new and after 30 months of natural aging. An extreme diversity of behaviour with respect to light reflection was revealed both over time and between pavements. The simulations of relamping cases show that the use of typical CIE r-tables almost systematically leads to non-compliance with the EN 13201 standard, particularly in terms of uniformity. Taking the photometry of the pavement at its stabilized state into account, simultaneously allows for compliance with lighting safety issues and for significant energy savings. As measurements of pavement photometry are rarely carried out, an alternative is to build up a database of urban pavements, which is one of the objectives of the Pavements and Lighting working group.

P-BN48 Utilising spatial geometry to obtain the ideal needle mount for laparoscopic intracorporeal suturing

Background Intracorporeal suturing is an essential component of any advanced laparoscopic procedure like fundoplication, bypass surgery or common bile duct exploration. Obtaining the appropriate needle mount during suturing can be challenging. Spatial geometry defines points in three-dimensional space. Ergonomics in laparoscopic surgery identifies a manipulation angle of 60o to target as being optimal. This knowledge, in combination with the principles of light reflection can be used to understand needle orientation in laparoscopic suturing. Methods An experiment was designed on a laparoscopic trainer with three participants. Using the principles of spatial geometry and light reflection, four different points were identified on an angle chart and labelled for a right-hand dominant participant as; centre, right off-centre (5.5cm), right lateral (10 cm) and left off-centre (5.5cm). Each participant was instructed to mount the needle at the defined points using light reflection on the needle shaft as a reference guide. Three readings were taken for each position. Mounted angle was defined as the angle between the shaft of needle holder and long axis of the needle. This was measured using a special application and an average value determined for each position. Results The average values for the mounted angle measurements for each spatial position were: Centre(112o), Right off centre(101o), Right lateral (88.8o) and Left off centre (124.6o). Conclusions This study describes a novel and reproducible technique to obtain an ideal needle mount. For a needle mount greater than 100o either the centre position or the left off-centre position should be considered.

Demonstration of light reflection concepts for rendering realistic 3D tree images

With advancements in computer graphics, creating natural images has always been the main purpose, image rendering is all based on principles of physics. So, understanding the physics of image rendering will enable us to create the most realistic images. A ray of light hit a surface with different orientation and reflects as per the rules of physics. It is difficult to calculate the light reflection of complex foliage, such as trees, so, the reflection of this natural complexity needs to be adapted to rendering situations. In this research, the researchers provide demonstrations to enable students to understand the light reflection in nature, light calculation in computer graphics and methods to apply them to render realistic tree images. The researchers assign students to render 3D realistic tree images to assess the students’ understanding by applying the diffuse reflection value, specular reflection value and surface normal direction to render realistic tree images. The researchers find that most students understand of diffuse reflection, specular reflection, and surface normal direction causes the rendering results to be most realistic.

Activities on reflection of light based on low-cost materials at eighth grade

Studying science through hands-on activities within the context of teaching and learning using local environments and resources has been recognized as a fundamental prerequisite of school curriculum in many developing countries, including Thailand. Accordingly, we are interested in implementing such a concept in designing science teaching and learning for middle school students that emphasizes student participation in the provision of materials and equipment for scientific activities. The purposes of this study are to design hands-on activities for eighth grade students on the topic of light reflection using low-cost materials, and then to examine the results after they are implemented. The experimental group consisted of 30 eighth grade students who were chosen at random in one room. The instruments used in the experiment were two types of achievement tests that were administered as pretests and posttests on the topics of light reflection on smooth and curved surfaces. The paired sample t-test was performed after the collection of data to determine students’ conceptual understanding. Our result displays a highly significant difference (p <.01) between the pretest score (39.7%) and posttest score (83.3%), indicating that students actively participated in hands-on activities and learned light reflection knowledge and skills through interaction and discussion with their classmates. We highlight the advantages of our study for science teachers in rural schools in ensuring students develop 21st Century Skills, which is an important part of STEM education.

Characterization of the Relationship between the Loess Moisture and Image Grayscale Value

This paper presents a model for estimating the moisture of loess from an image grayscale value. A series of well-controlled air-dry tests were performed on saturated Malan loess, and the moisture content of the loess sample during the desiccation process was automatically recorded while the soil images were continually captured using a photogrammetric device equipped with a CMOS image sensor. By converting the red, green, and blue (RGB) image into a grayscale one, the relationship between the water content and grayscale value, referred to as the water content–gray value characteristic curve (WGCC), was obtained; the impacts of dry density, particle size distribution, and illuminance on WGCC were investigated. It is shown that the grayscale value increases as the water content decreases; based on the rate of increase of grayscale value, the WGCC can be segmented into three stages: slow-rise, rapid-rise, and asymptotically stable stages. The influences that dry density and particle size distribution have on WGCC are dependent on light reflection and transmission, and this dependence is closely related to soil water types and their relative proportion. Besides, the WGCC for a given soil sample is unique if normalized with illuminance. The mechanism behind the three stages of WGCC is discussed in terms of visible light reflection. A mathematical model was proposed to describe WGCC, and the physical meaning of the model parameters was interpreted. The proposed model is validated independently using another six different types of loess samples and is shown to match well the experimental data. The results of this study can provide a reference for the development of non-contact soil moisture monitoring methods as well as relevant sensors and instruments.

A NOVEL METHOD BASED ON THE OTSU THRESHOLD FOR INSTANTANEOUS ELIMINATION OF LIGHT REFLECTION IN PIV IMAGES

The base of particle image velocimetry (PIV) is the maximization of the correlation between the distribution of particle images in an interrogation window or a volume separated by an instant of time. In real images, the unwanted reflection of light on fixed walls or moving objects can directly interfere with the correlation, deteriorating the PIV quality. In this work, a new method for automatically generating instantaneous masks based on the Otsu threshold for instantaneous elimination of light reflection in PIV images is proposed. This method separates the saturated image caused by the unwanted scattering of light from the tracer particles images through the Otsu threshold combined with the Gauss filter and Wiener adaptive local filter. This new method, called Otsu-Gauss-Wiener (OGW), was first tested using synthetic PIV images. In these tests, the authors analyzed the reflection caused by an object regarding different sizes, shapes, and intensities to evaluate the performance of the proposed method. Later, the OGW method was tested in PIV experimental cases with real adversities, for example, scattering of light on a fixed wall in a channel with periodic hills (Case B – 4th PIV Challenge), strong reflection in a centrifugal impeller (Case C – 1st PIV Challenge) and light scattering caused by an out-of-plane motion of the diaphragm of a pulsatile pediatric ventricular assist device. The results shown that the method can remove the reflections by static and moving objects using an automatic mask generated for each instantaneous image.