Application of directional-mixed reflectors results in a luminance decrease of the apparent image of light emitting diodes (LEDs), which is advantageous as far as glare reduction is concerned. On the other hand, reflectors have a negative impact on luminous intensity curves of the luminaries. This work analyzes an impact of surfaces with directional-mixed reflection properties in a mirror reflector designed for a luminary equipped with high-power LEDs. We present an algorithm used to determine the shape of the reflector of the surface with small scattering, where the axis twist angle for a parabolic reflector varies in a predefined range and follows a power function.
Application of the polarization film at the entry surface of the light guiding plate allows for construction of the luminarie emitting highly polarized luminous flux. The highest values of the polarization index were observed for the maximum luminous intensity directions, which is contrary to what is observed in lighting systems with no films applied. The aforementioned effect was achieved with technical measures which are practical and inexpensive.
Flat light guides are modern solution enabling production of luminaries characterised by large area and low height. The amount of the luminous flux, which might penetrate the side-lit flat light waveguide with a predefined thickness depends on the light source's luminance. Special fluorescent lamps equipped with an internal reflector layer were designed for this kind of illumination systems. Such lamps are typically characterised by small aperture along the spine of the lamp. The aperture technology boosts the luminance value within the lamp's aperture to levels even 4 to 5 times higher than the average luminance of a standard fluorescent lamp. The presented article contains a detailed analysis of the impact of the aperture angle size on the coupling efficiency. It was also shown that application of a mini aperture fluorescent lamp influences changes in the luminous intensity curves of prismatic elements, which are most commonly used to direct the luminous flux.
The National Museum in Warsaw is in possession of a collection of 1100 miniature paintings. Miniature paintings are specific exhibits, since they are both very precious and extremely sensitive to environmental conditions present in the museum exhibition halls. One of the most important factors imposing deterioration of the museum exhibits, is the optical radiation: ultraviolet (UV), visible (VIS) and infrared (IR). Exhibit conservation requirements, concerning the illuminance levels for particularly sensitive museum objects impose strict limitations for illuminance value to 50÷150 lx. Light should be devoid of both UV and IR components. The optical fibre lighting systems are perfectly suited to meet all the above mentioned lighting requirements. Each of 5 showcase featured an illuminator with a 50 W tungsten halogen lamp, UV filter and double IR filter. Thanks to such an illuminator structure, the visual radiation was devoid of harmful radiation components thus it was possible to use plastic optical fibres with 1 mm of diameter without any cooling fans. Fanned illumination systems utilized in the museum conditions, cause significant noise levels. The value of the illumination parameter within the showcases met the targeted value of 100 lx with the average internal showcase temperature raising by less than 1 °C.
A method of measuring the illuminance distribution in the focus of the optical fiber illuminator is presented in this paper. The mentioned method makes use of the polymer-quartz optical fiber, type F-PCS-600/900-US. The fiber's front surface was moved on the examined surface in two, mutually perpendicular directions. The luminous flux, exiting the optical fiber was then measured with the use of the integrating sphere. An exemplary illuminance distribution was also presented in the paper. Illuminance curves were then compared for PCS and plastic optical fibers made from methyl polymethacrylate.
One of the available means for directing luminous flux in luminaries with light guiding plates is depositing diffusive elements of Lambertian characteristics onto the side surfaces of such a plate. A theoretical method of determining light intensity distribution of such elements, as well as resulting measurements for the model set, are presented in the paper. Additionally, a degree of light polarization in such a system was measured and analysed.
The basic advantage of illuminating plastic optical fibers is related to simplicity of their processing. Thanks to such characteristic, it is possible to create optical fiber bundles, which fit exactly the given illumination solution. Two basic methods of procesing optical fibers are most common: grinding and polishing or thermo-cutting with the means of so-called "hot knife." These two types of processing were then examined against their influence on the luminous parameters: amount of the transferred luminous flux and the shape of the luminous intensity distribution.
Light guiding plates coupled with fluorescent lamp are modern solutions in construction of general-purpose luminaries. Thanks to such a solution, large illuminating surfaces are created, characterized by constant luminance. Providing that the total height of such a device is relatively small, fluorescent lamps with high luminous efficacy might be used successfully. The problem related to the influence of the fluorescent lamp light color on attenuation of the luminous flux in the light guiding plates is relatively seldom approached. Theoretical calculations of the absorption index are presented in the paper, along with their verification against exemplary light guiding plates made from methyl polymethacrylate and type T5 fluorescent lamps with varying light color.
the distribution of the luminous flux density in the focus of a discharge a lamp depends solely on its working position. The main goal of this work was to perform measurements of the distribution of the luminous flux density in the focus of the HQI-R 150W lamp, in various working positions. With all possible working positions for this lamp, the measured illuminance distributions are very uneven.
During the designing process for a luminaire with the light guiding plate, first it is necessary to analyze the issue of coupling light source with the light guiding plate, since only the luminous flux which is introduced into the light guiding plate might be utilized further on and become the useful flux. Theoretical calculations of the coupling index between the fluorescent lamp and the light guiding plate were made. The measurement's results confirmed the conclusions from theoretical calculations, namely that the best possible solution is placing the fluorescent lamp directly at the surface of the light guiding plate. Placing the lamp 2 millimeters from the plate's front surface causes the decrease by 20%, and further increase in the distance to 5 millimeters -- decrease by 50%.
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