Current IES standards refer to pedestrian lighting in terms of minimum vertical illuminance 1.5 m above pavement level. Analysis is made to find the vertical illuminance 1.5m above pavement level facing oncoming traffic for typical street lighting configurations. Three types of calculation grids were used to simulate pedestrians on the side walk, on the street and on the median. Streets with and without median are studied with various streetlighting layouts such as staggered, and along both sides of the street. It was found that in most cases the vertical illuminance on a two way street peaks on one side of the street while, it is minimal on the other side of the street at the same lateral axis. Plan diagrams of streets showing the locations of vertical illuminance greater than 1 foot-candle and less than 0.2 foot-candle are presented.

(2009). Learning from the Last 100 Years of Illumination History. LEUKOS: Vol. 6, No. 2, pp. 107-113.

The UNL Glare Apparatus was designed to systematically vary the four primary factors which affect discomfort glare, including source luminance, source size, source position, and background luminance. It was also designed to have considerable flexibility to research many additional independent and dependent variables. The theatrical lighting fixtures used in the apparatus caused a significant problem for scientific research: the output from the fixture did not produce a uniform illuminance on the target. A “uniformity” filter was created to produce uniform illuminance on the stimulus. This paper describes the nonuniform illuminance problem and the creation of a “uniformity” filter to correct the problem. The complete Matlab code used to generate the filter is available from the authors.

The legibility levels of text and graphics can be assessed using the Legibility Index, conventionally defined as the distance at which material can be read with perfect accuracy (the legibility distance) divided by the character height. The ratio equals the inverse tangent of the visual angle subtended by the character. The definition assumes that the viewing material is perpendicular to the observer, which is not always true. Although text and graphics are, in reality, often viewed not perpendicular to the display, they are rarely studied. To examine the legibility of characters viewed not perpendicular to the display, this paper has redefined the Legibility Index as the inverse square root of the solid angle subtended by the target, based on a hypothesis that the three-dimensional solid angle, rather than the two-dimensional visual angle, both subtended by the character, captures how people recognize text and graphics that usually have two significant dimensions (width and height). This hypothesis proves consistent with how retinal images of text and graphics activate cones in the fovea of a viewer's eyes, and has also been verified in a laboratory using legibility data collected from 20 human subjects. Using these data, the calculated steady redefined Legibility Index closely matches the fact that the 20 subjects have similar recognition performance (critical legibility level with 100 percent accuracy) of text (same target) under the same lighting conditions (Lb=120 cd/m2, C%=97.9, zero ambient light) at different viewing angles (perpendicular or not perpendicular to the displays), while the calculated ratio of legibility distance to character height rapidly decreases with increased viewing angles.

In this article we provide an analysis, design, and implementation of a universal input 150-Watt boost power factor correction converter with a ripple current cancellation circuit for lighting industry. A simulation and experimental bench test model of the 150-Watt boost power factor converter with the ripple current cancellation circuit is presented. The results obtained from the simulation and experimental model are presented. The EMI results of the ripple current cancellation circuit are compared with the traditional filtering method used for the EMI suppression on the 150-Watt boost power factor correction converter. Advantages of the proposed ripple current cancelation circuit are discussed.

Current headlighting and road lighting are only partly effective in reducing the risk of driving at night. To further reduce this risk, two major sensing technologies for night vision systems have been receiving particular development interest: near infrared (NIR) systems, which actively illuminate the scene in the near infrared spectrum and capture the reflected radiation, and far infrared (FIR) systems, which generate images by passively detecting thermal emissions. To compare pedestrian detection with night vision systems, a test vehicle equipped with an NIR and an FIR system was driven at night on several roads with pedestrians standing along the route. Video clips, recorded from both systems simultaneously, were later shown in a laboratory to 16 subjects (eight younger than 30 years and eight older than 64 years). Subjects pressed a button as soon as they saw each pedestrian. Detection distances with FIR were, on average, three times greater than with NIR. For both systems, detection distances of younger subjects were about 1.7 greater than of older drivers. The effectiveness of night vision systems can be expected to depend on inherent advantages of either technology as well as the details of implementation. To the extent that the two systems used in this experiment reasonably represent the respective technologies, the results support the expected enhancement of pedestrian detection in FIR systems.

A method for simulating the effects of visual adaptation using image processing techniques was developed, and then tested for accuracy in predicting the reductions in visual performance that occur with adaptation. The simulation process entailed transforming digital photographs of realistic exterior scenes into the spatial frequency domain, filtering the transformed data using contrast sensitivity functions for different adaptation levels, transforming the filtered data back into the luminance domain, and producing a new digital image of the scene. Two experiments were conducted that compared performance on a realistic visual detection task when the subjects were adapted to different luminances, to performance on the same task when subjects' adaptation level was held constant while they viewed the simulated adaptation effects. Results showed that the simulations produced decreases in performance in the same direction as actual adaptation effects, but the effects were of smaller magnitude. A third experiment was conducted to better quantify the differences between the simulated and actual adaptation conditions; this experiment utilized a standardized visual test target, the United States Air Force (USAF) 1951 test pattern.

Dormers have found wide applications in the design of new buildings and also in the renovation of under-roof spaces in existing buildings. Comfort and illuminance for visual activity in attic rooms illuminated by dormers depends mainly on the dormer dimensions and its position with respect of the utilization area of the room. This article evaluates selected types of dormers for daylighting of attic rooms. The evaluation of daylighting from dormers in the administrative part of the university building was carried out using computer simulations and illuminance measurements. The daylighting studies were completed for separated dormers compared with the alternative design solution of one continuous dormer with the same glazed area. Results from computer simulations give information about illuminance level and daylight distribution in the whole area of the investigated rooms. Daylighting simulations for the dormer were compared with alternative design solution with skylights.