Legal requirements for signal lamps generally specify minimum or maximum intensities in various directions and color for the emitted light. The uniformity of luminance of the light emitting surface of these signals, however, is not specified, but very often a quality parameter for such a device. An exception of this rule is the regulation for license plate lamps, which are characterized by the evaluation of the illuminance or luminance distribution of the license plate to which the lamps are attached. Measurements of luminance distributions of signals can be performed involving goniophotometers or other devices in combination with a luminance meter. The light technical definitions of luminance are given by the CIE and can be interpreted as the intensity of a infinitesimal small area into a specified direction. This leads to the measurement principle with a luminance meter mounted on a XY-moving device in a certain distance of the target. For measurement of other area fractions, the XY-device moves the luminance meter horizontally and vertically, so that the measurement axis of the luminance meter is kept parallel. A more suitable setup uses a goniophotometer instead of the XY-device. The goniometer is used to rotate the luminance meter in horizontal and vertical angles to cover the full area of the sample. As in both cases the effect of photometric distance would lead to equal measurement uncertainties, both mentioned methods should be regarded as equivalent, if the proper distances would be observed. As the luminance was measured on diffuse reflecting blotting paper, the luminance distribution is constant in a very large range. A test measurement showed a deviation of less than 1% within an angular range of up to 30 deg., even with a high angle of light incidence as it usually is the case for license plate illumination.


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    Title :

    Luminance distribution of signals


    Additional title:

    Luminanzverteilung von Lichtsignalen


    Contributors:


    Publication date :

    2003


    Size :

    10 Seiten, 7 Bilder



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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