LEUKOS

The Journal of the Illuminating Engineering Society of North America    Volume 4     Number 4     April 2008

Publisher's data

Editorial

A ROSE BY ANY OTHER NAME

Articles

COUNTERBALANCING NEEDED TO AVOID BIAS IN SIDE-BY-SIDE BRIGHTNESS

S. A. FOTIOS, K. W. HOUSER, AND C. CHEAL

Spectral power distribution (SPD) is one of the variables that can be manipulated in lighting design. This article examines twenty previous studies which have investigated the effect of SPD on brightness using the side-by-side matching technique. Three sources of experimental bias are identified and are shown to be present in the majority of these studies, and hence must be considered to provide an unreliable estimate of the magnitude of the SPD effect on brightness. The first bias is associated with test participants’ use of dimming control and two forms are apparent – a response contraction bias when the test is repeated at multiple reference illuminances and a conservative bias when the test is carried out at a single reference illuminance. The second bias is associated with the primary direction in which dimming must take place and the third bias is associated with the relative position of the stimuli within the apparatus.

LUMINAIRE PHOTOMETRY FOR TEMPERATURE-SENSITIVE LIGHT SOURCES

JOHN ZHANG

A method for the photometry of luminaires using temperature-sensitive light sources is described and evaluated. This procedure is specifically designed for use with luminaires that employ T5 and T5HO fluorescent lamps. Results of the new method are provided.

A NARROW BEAM REFLECTOR FOR A TWO-DIMENSIONAL ARRAY OF POWER LIGHT EMITTING DIODES

FILIP VANDEGHINSTE, GUY DURINCK, STEFAAN FORMENT, GEERT DECONINCK, AND PETER HANSELAER

A major problem in solid state lighting is the limited flux emitted by a single power light emitter diode (LED). This flux is insufficient for most lighting applications. A possible solution is using not one but an array of LEDs as a light source. However, the optical control of the flux emitted by such a spatially extended and inhomogeneous light source is difficult, especially if a narrow beam of light is desired and the optics have to be compact. In this paper we discuss a compact narrow beam reflector that enables a two dimensional array of power LEDs to act as a light source for spot lighting in domestic and retail lighting.

APPROACH TO AN EFFECTIVE BIOLOGICAL SPECTRUM OF A LIGHT SOURCE

RUSLAN KOZAKOV, STEFFEN FRANKE, AND HEINZ SCHÖPP

Optimal three band Gaussian spectra were determined with an additional condition on the nonvisual biological action of the spectra. With this new condition the best possible trade off between the general color rendering index (CRI) and the luminous efficiency was found. The results show that in order to keep a biological effect of a light source equal to that of Planckian light source an additional restriction on the luminous efficiency for the given CRI arises.