Measuring of the Basic Parameters of LCD Displays

This article is about realization of the laboratory stand used for measuring parameters of LCD displays. The stand together with additional accessories (spectrophotometer and measuring probes) as well as software allow to measure a wide range of parameters (colour gamut, response time, contrast coefficient and its irregularity, luminance of black colour and its irregularity, luminance of white colour and its irregularity, changes of luminance depending on the viewing angle). This paper also show method and results of measurements of differences in contrast ratio and luminance uniformity between particular pieces of the same model of a display screen (research has been carried out on 5 pieces of the same model of a display). The presented results show that the measured value of the viewing angle may significantly differ from the value provided by producers of displays

Project of the research stand for measuring horizontal and vertical viewing angles of LCD displays

W artykule przedstawiono projekt oraz realizację stanowiska pomiarowego służącego do pomiarów kątów patrzenia monitorów LCD. Przedstawione zostały założenia, które przyjęto na etapie projektu, zgodność z normami ISO oraz przykładowe wyniki pomiarów. Przedstawione wyniki pomiarów pokazują, że zmierzona wartość kąta patrzenia może się znacznie różnić od wartości podawanej przez producenta monitora.The paper deals with project and realization of a laboratory stand for measuring viewing angles of LCD displays. There is a need to build such stands in order to check whether the parameters of displays reflect the ones provided by their producers. The ISO norms guidelines as regards tests of displays (ISO 9241-303:2008 "Ergonomics of human-system interaction - Part 303: Requirements for electronic visual displays" and ISO 9241-305:2008 "Ergonomics of human-system interaction - Part 305: Optical laboratory test methods for electronic visual displays") were used to make sure that the results of such research were reliable. The stand together with additional accessories (spectrophotometer and measuring probes) as well as software allow measuring a wide range of parameters (colour gamut, response time, contrast coefficient and its irregularity, luminance of black colour and its irregularity, luminance of white colour and its irregularity, changes of luminance depending on the viewing angle). In this paper there is described the stand construction as well as the method for measuring the luminance change depending on the viewing angles, which is one of the most important parameters in the situation when there are several people looking at a certain screen. The presented measurement results also show differences between particular pieces of the same model of a display screen (investigations were performed on 5 pieces of the same model of a display). The presented results show that the measured value of the viewing angle may significantly differ from the value provided by producers of displays

Illumination equality measurement of LCD matrices

Artykuł porusza kwestie pomiaru równomierności oświetlenia oraz parametrów związanych z tym zjawiskiem: współczynnika kontrastowości, nierównomierności kontrastu, luminancji i jej nierównomierności. Przedstawia powody, dla których te parametry są istotne pod względem użytkowym, oraz opisuje metody, jakimi można badać wymienione powyżej parametry. Przedstawia wyniki badań wykonanych na próbie pięciu monitorów tego samego modelu.The illumination uniformity in LCD monitors is analyzed in the paper. The phenomenon is described and explained by taking into consideration the following parameters: contrast ratio, luminance, uniformity of display contrast, and luminance. No defined measurement method of these values exists (except partially different standards by ISO, VESA, ANSI). The method which unify and minimize measurements is described in the paper. The same measurement points are used to measure all parameters under consideration. Luminance measurements are made in a dark room, on center of a screen surface emitting white color. The same is also used in uniformity measurement (Eq. 1). It describes luminosity difference values in different places of monitor. Contrast ratio (Eq. 2) measurements were made using electronic set of photodiode and transimpedance amplifier in one structure (Fig. 2). Uniformity measurement of display contrast have been made in few points, defined by VESA organization (Figs. 3, 4, 5, 6). 5 monitors of the same model were tested (Tab. 1). Contrast ratio show significant difference for each monitor and between each other. Similar results are for luminance and luminance uniformity (Tab. 4) where difference in uniformity reached almost 40%. Type of monitor backlight is main cause of poor uniformity, but also quality of LCD matrices may have influence on overall comfort of using such moni-tors. The results show that luminance and contrast uniformity should be given in technical specification of products

Investigation of Acoustic Properties of Poroelastic Asphalt Mixtures in Laboratory and Field Conditions

Measures for the improvement of acoustic conditions in the vicinity of roads include the construction of pavement structures with low-noise surfaces with optimal macrotexture and the highest possible sound absorption coefficient. Laboratory evaluation of acoustic properties of a designed asphalt mixture before its placement in the pavement is a good solution. Currently, the most popular method for the determination of the sound absorption coefficient of various construction materials under laboratory conditions is the Kundt’s tube test. Sound absorption coefficient can also be assessed based on field and laboratory measurements performed using a Spectronics ACUPAVE System. Other parameters characterising the acoustic properties of road pavement courses include air void content and water drainability or permeability. The article presents an analysis of results of sound absorption coefficient obtained using a Spectronics ACUPAVE System and water drainability and permeability of poroelastic mixtures obtained both in laboratory and on test sections, in relation to air void content and grading of the mixtures. It was established that poroelastic mixtures containing an aggregate of maximum particle size of 5 mm are characterised by better acoustic properties than mixtures with a maximum aggregate particle size of 8 mm. Changes of crumb rubber aggregate grading and bitumen type (within the tested range of values) as well as the addition of lime have shown no evident influence on the sound absorption coefficient. Noise level values at the speed of 30 km/h according to the CPX method were measured as well. Relationships between sound absorption coefficient, water drainability/permeability, and air void content were determined. The performed analyses confirmed that Spectronics ACUPAVE System may be applied for evaluation of acoustic properties of asphalt mixtures in laboratory conditions, but further research is needed to reduce the uncertainty of the results

Bitumen-Based Poroelastic Pavements: Successful Improvements and Remaining Issues

This article presents the development process of designing and testing poroelastic pavement based on highly polymer-modified bitumen. Poroelastic wearing course was composed of mineral and rubber aggregate mixed with highly polymer-modified bitumen, in contrast to previous trials, during which polyurethane resins were mainly used as binder, which led to several serious technological problems concerning difficult production, insufficient bonding to the base layer, and unsatisfactory durability. The laboratory testing phase was aimed at finding the proper composition of the poroelastic mixture that would ensure required internal shear strength and proper bonding of the poroelastic layer with the base layer. After selecting several promising poroelastic mixture compositions, field test sections were constructed and tested in terms of noise reduction, rolling resistance and interlayer bonding. Despite the very good acoustic properties of the constructed poroelastic wearing course, it was not possible to solve the problem of its insufficient durability. Still, the second major issue of poroelastic pavements that concerns premature debonding of the poroelastic layer from the base layer was completely solved. Experience gained during the implementation of the described research will be the basis for further attempts to develop a successive poroelastic mixture in the future