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Measuring of the Basic Parameters of LCD Displays

Barczyk R., Kabzinski B., Jasinska-Choromanska D., Stienss A.

Journal of Automation Mobile Robotics and Intelligent Systems

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2012

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Vol. 6, No. 1

46-48

EN

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.

2

Pomiary równomierności oświetlenia matryc LCD

Barczyk R., Kabziński B., Jasińska-Choromańska D, Stienss A.

Pomiary Automatyka Kontrola

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2011

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R. 57, nr 11

1355-1358

PL

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.

EN

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.

3

Coherent combination of laser radiations and fringe contrast ratios on far field patterns

Dou R., Shi X., Sun N., Chen J.

Optica Applicata

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2008

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Vol. 38, nr 2

459-468

EN

Fourier optics method has been used to study the far field of coherently combined laser beams. And an explicit expression of the far field has been derived for the case when emitters are positioned on apexes of multiple regular polygons with a common center. The statistical influence of the relative phases between constituent waves has been investigated and an expression for the fringes contrast ratio has been deduced with the aid of Ergodic hypothesis.

4

Numerical optimization procedure of TN LCD design process

Olifierczuk M.

Opto-Electronics Review

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2005

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Vol. 13, No. 4

341-347

EN

The main aim of this work is a presentation of the significance of the numerical optimization procedure for the TN liquid crystal display design process. The assumptions for calculations of such optical parameters as contrast ratio and luminance are presented. The way of measurements of optical parameters (refractive indices and absorption coefficients) for such the display elements as glass, conductive layer, polarizers, etc., which makes it possible to apply these results directly in the computer program worked out by the author, is described. The calculated results of the contrast ratio and luminance for TN transmissive and reflective display are presented. The optimization procedures for negative mode, and for transmissive and reflective type of the display were performed in an independent way.

5

Significante of reflection reduction in a TN display for colour visualisation

Olifierczuk M., Zieliński J.

Opto-Electronics Review

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2002

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Vol. 10, No. 1

35-37

EN

This paper contains the results of theoretical considerations about light propagation through the real TN display working in reflective and negative mode. This mode provides us with a possibility to obtain a colour image. We have done mathematical and numerical analyses of a propagation of light wave through liquid crystal (LC) displays with antireflective layer, glass planes, conductive layers, LC layer and polarisers. We have taken into account real conditions of a display operation, i. e., spectral properties of all components, optical anisotropic and dichroic properties of LC layer, reflections from all phase borders and also spectral characteristics of light source and sensitivity of human eye.