Urszula Joanna Blaszczak

The method of estimation of background luminance in objective glare measurements

Human eye is able to change its sensitivity to light in the process of adaptation. Still the process of vision can be accompanied by inconvenient phenomena, e.g. glare. The newest European norms recommended the CIE Unified Glare Rating method to estimate glare. A condition of practical realization of this method is the knowledge of the luminance distribution in the room. The best detection method is to use a CCD camera, which allows to evaluate all the quantities needed to calculate the UGR index: the background luminance, the luminance of the luminous parts of each luminaire at the observers eye, the solid angle of the luminous parts of each luminaire and the position index for each luminaire. In the paper a definition of the background luminance Lb and the influence of the errors in Lb estimation on the value of the UGR index are presented. Two methods of the background luminance measurement are described and discussed.

Idea of objective glare measurement

In the article the recommended by the CIE method of the discomfort glare evaluting is presented. A condition of practical realization of this method is the knowledge of luminance distribution in the room. The best detection method is using the CCD camera, which allows to evaluate all the quantities needed to calculate the UGR index: the background luminance, the luminance of the luminous parts of each luminaire at the observers eye, the solid angle of the luminous parts of each luminaire at the observers eye and the position index for each luminaire.

Colorimetric characterization of the tunable LED-based light source at the output of the homogenizing rod

The best method to obtain uniform spectral characteristic for multi-emitter sources is to use integrating sphere as mixing element. In each point of exit window of such sphere the luminance and spectral characteristic are uniform. However price of integrating spheres are disadvantageous and the output power decreases dramatically with the increase their diameters. For this reason sometimes homogenizing rods are used when LEDs are used. In the paper we present the results of colorimetric characterization of low cost homogenizing rectangular-shaped rod applied in the tunable LEDbased source for endoscopic system. For each correlated color temperature (CCT) value we investigated changes of spectral power distribution (SPD) on the output surface of the homogenizing rod and variation of CCT while increasing the distance from the output of the rod. Results of these measurements enable efficient lighting of the working area and proper placement of optical fibers used to guide light to difficult-access objects.

Tunable white light source for medical applications

Development of light-emitting diodes has brought new possibilities in many applications, especially in terms of flexible adjustment of light spectra. This feature is very useful in construction of many devices, for example for medical diagnosis and treatment. It was proved, that in some cases LEDs can easily replace lasers during therapy of cancer without reduction of efficiency of this process. On the other hand during diagnosis process LED-based constructions can provide unique ability to adjust the color temperature of the output light while maintaining high color rendering. It allows for optimum surface contrast and enhanced tissue differentiation at the operator site. In the paper we describe the construction of the tunable LED-based source designed for application in endoscopy. It was optimized from the point of view of the color rendition for 5 different correlated color temperatures (illuminant A, D55, D65, 3500K and 4500K) with the restriction of very high (>90) values of general and specific color rendering indexes (according to Ra method). The source is composed of 13 light-emitting diodes from visible region mounted on the common radiator and controlled by dedicated system. Spectra of the components are mixed and the spectra of output light is analyzed. On the basis of obtained spectra colorimetric parameters are calculated and compared with the results of theoretical analysis.

Influence of the spectral composition of LED lighting system on plants cultivation in a darkroom

Agriculture is one of the most important areas of the world economy. However, due to dependency on weather conditions, it is strongly industrialized, for example by introducing additional lighting improving the efficiency of plants growth. Construction and operation of light-emitting diodes provides new possibilities in research and application of new concepts in agricultural lighting. The aim of the work was to investigate the effect of various spectra of light on the efficiency of photosynthesis and the growth of selected species of plants. For this purpose two grow-boxes with dedicated LED-based lighting systems were constructed and placed in the darkroom with controlled temperature. In each box lighting system provided different spectral composition of light and it was possible to adjust the ratio of blue and red as well as the irradiance level. In the paper we present the construction of the grow-boxes and the results of 3 cycles of experiments conducted with this system. During the first cycle two groups of tested plants were cultivated in the LED grow-boxes with constant irradiance level and the third group in natural light conditions. During the second cycle the irradiance in both boxes was gradually increased from 8 W/m2 to 38 W/m2. During the third cycle the irradiance was set to 38 W/m2 during the whole period (max power MRED module) to get the maximum possible intensity of photosynthesis.

Semiconductor lasers vs LEDs in diagnostic and therapeutic medicine

Semiconductor emitters are used in many areas of medicine, allowing for new methods of diagnosis, treatment and effective prevention of many diseases. The article presents selected areas of application of semiconductor sources in UVVIS- NIR range, where in recent years competition in semiconductor lasers and LEDs applications has been observed. Examples of applications of analyzed sources are indicated for LLLT, PDT and optical diagnostics using the procedure of color contrast. Selected results of LLLT research of the authors are presented that were obtained by means of the developed optoelectronic system for objectified irradiation and studies on the impact of low-energy laser and LED on lines of endothelial cells of umbilical vein. Usefulness of the spectrally tunable LED lighting system for diagnostic purposes is also demonstrated, also as an illuminator for surface applications - in procedure of variable color contrast of the illuminated object.

The issues of interior lighting on the example of an educational building adjustment to nZEB standard

Improvement of energy efficiency in buildings is the goal of many activities around the world. In recent years a need to increase the number of buildings, which not only fulfil the minimum energy performance requirements, but have very low energy consumption and are environmentally friendly has been recognised. In this paper the issues of electric lighting quality in educational buildings, focused on the analysis of lighting energy efficiency are presented. A brief characteristic of the selected educational building and requirements for the assessment were presented. The lighting conditions in selected interiors of the building and the lighting energy efficiency in the whole building were evaluated. To demonstrate the opportunity to improve lighting conditions and energy efficiency, four solutions for each selected interior were proposed. New fluorescent and LED lighting solutions were compared in detail. The comparison between the existing lighting and new solutions was conducted either. The lighting in evaluated building was not energy efficient and what worse, the lighting conditions in many interiors were much below the requirements. Introducing new lighting solutions should improve the quality of luminous environment in interiors and reduce substantially the lighting power installed as well as the energy use in the building.

Color mixing in LED illuminating system for endoscopic purposes

Endoscope equipment is used in many applications. One of them is medical diagnostics. The illuminator is an important part of the endoscope, as it enables the performance of the observed object. The quality of light is particularly important if the assessed essential feature is the colour of an object or its distribution on the surface of the object. For this reason, special attention should be paid to the quality of the illuminator in terms of colour rendering, as well as adapting it to the intended diagnostic procedure. The use of light emitting diodes allows shaping flexibly the spectral characteristics which is an innovative solution in case of endoscope equipment. In the paper the idea of the endoscope illuminator construction, based on 13 LEDs, that allows adjusting the correlated colour temperature is presented. The essential part of the paper is the issue of quality of colour mixing. Results of exemplary simulations are presented and compared with the measurement results of performed mixing elements. They are evaluated from the point of view of obtained superficial uniformity of colour mixing on the output of the element.

Applications of optical fibers and miniature photonic elements in medical diagnostics

Construction of endoscopes which are known for decades, in particular in small devices with the diameter of few millimetres, are based on the application of fibre optic imaging bundles or bundles of fibers in the illumination systems (usually with a halogen source). Cameras - CCD and CMOS – with the sensor size of less than 5 mm emerging commercially and high power LED solutions allow to design and construct modern endoscopes characterized by many innovative properties. These constructions offer higher resolution. They are also relatively cheaper especially in the context of the integration of the majority of the functions on a single chip. Mentioned features of the CMOS sensors reduce the cycle of introducing the newly developed instruments to the market. The paper includes a description of the concept of the endoscope with a miniature camera built on the basis of CMOS detector manufactured by Omni Vision. The set of LEDs located at the operator side works as the illuminating system. Fibre optic system and the lens of the camera are used in shaping the beam illuminating the observed tissue. Furthermore, to broaden the range of applications of the endoscope, the illuminator allows to control the spectral characteristics of emitted light. The paper presents the analysis of the basic parameters of the light-and-optical system of the endoscope. The possibility of adjusting the magnifications of the lens, the field of view of the camera and its spatial resolution is discussed. Special attention was drawn to the issues related to the selection of the light sources used for the illumination in terms of energy efficiency and the possibility of providing adjusting the colour of the emitted light in order to improve the quality of the image obtained by the camera.

Data transmission in CATV networks

More and more CATV operators in Poland offer their subscribers a fast Internet access and other services. To offer high-speed Internet services cable operators create data networks that operate over hybrid fiber-coax (HFC) plant. In the paper a basic architecture of such network and data transmission standards are described.