Roadway lighting: An investigation and evaluation of three different light sources: Final report

Mesopic photometry can be applied to road lighting practice to enhance peripheral visual performance and to reduce light levels. However, mesopic photometry characterizes peripheral vision, whereas photopic photometry characterizes foveal vision at all light levels. Higher scotopic / photopic ( S/ P) ratio light sources which enhance peripheral visual performance may have a negative influence on foveal vision. In addition, light level reductions, as realized in British Standard 5489-1: 2013, may impair foveal visual performance. To investigate the above-described concern, we conducted two experiments. First, we investigated whether Landolt ring targets detected by peripheral vision can be recognized correctly after moving the line of sight to fixate on the targets in foveal vision. Then, we found that subjects could recognize in foveal vision almost all targets that peripheral vision detected. The S/ P ratio of the background lighting did not influence this tendency. Second, we investigated luminance contrast thresholds for foveal vision to compare them with those for peripheral vision, obtained from the first experiment. We found that threshold contrasts of targets recognized by foveal vision were lower than those detected by peripheral vision. These results lead to the conclusion that the use of higher S/ P ratio light sources has no negative influence for foveal vision when implementing mesopic photometry.

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An economic study of three light sources for roadway lighting

LEUKOS The Journal of the Illuminating Engineering Society of North America ◽

10.1582/leukos.2004.01.04.005 ◽

2005 ◽

Vol 01 (04) ◽

pp. 72-80

Author(s):

Ian Lewin

Keyword(s):

Light Sources ◽

Economic Study ◽

Roadway Lighting

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New developments in light sources and optical systems for roadway lighting

Electrical Engineering ◽

10.1109/ee.1958.6445376 ◽

1958 ◽

Vol 77 (10) ◽

pp. 903-907

Author(s):

E. B. Karns

Keyword(s):

Optical Systems ◽

Light Sources ◽

New Developments ◽

Roadway Lighting

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Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013554x ◽

1990 ◽

Vol 48 (2) ◽

pp. 388-389

Author(s):

A. M. Bradshaw

Keyword(s):

Photoelectron Spectroscopy ◽

Chemical Reactivity ◽

Target Material ◽

Orbital Energy ◽

Light Sources ◽

Analytical Technique ◽

Hartree Fock ◽

Spatially Resolved ◽

Koopmans Theorem ◽

Surface Analytical Technique

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

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