The Journal of the Illuminating Engineering Society of North America    Volume 2     Number 4     april 2006

Publisher's data

Editorial:

LIGHTING EDUCATION

Articles:

RATIONAL ILLUMINANCE

G. STEFFY

Illuminance has long been the Holy Grail of the Illuminating Engineering Society of North America and of its constituents. For a century, illuminance has been a moving target. Now unpopular with or at least uninteresting to most of the research community and, apparently, even the application committees, illuminance criteria waffle from RP to RP and recently handbook to handbook. Its fall from grace is illuminated in the latest handbook where it is subservient to other important but less risky criteria. Illuminance simply isn’t glamorous. Further, now, many illuminance criteria are promulgated as single-values, while a few notable and critically important exceptions such as parking lot illuminance criteria are essentially nonexistent with a heavily-footnoted ambiguous figure in the handbook suggesting anything goes. To reclaim its position as The Lighting Authority™ the IESNA must reestablish if not simply reinstate rational, robust illuminance guidelines for real-world applications worthy of professionals’, code officials’, and the public’s immediate and every attention.

NEW MODEL FOR MESOPIC PHOTOMETRY AND ITS APPLICATION TO ROAD LIGHTING

M. ELOHOLMA AND L. HALONEN

There are definite needs for a practical system of mesopic photometry to be used in lighting dimensioning and measurement of road and other outdoor lighting applications. A research consortium MOVE combined the resources of several European research institutes to establish a basis for performance based mesopic photometry. A practical system of mesopic photometry is introduced as a result of the MOVE work. In this paper the MOVE model was applied to road lighting conditions and the model predictions were compared to luminances based on photopic photometry. The calculations using the MOVE model show that the adoption of mesopic dimensioning would affect road lighting practice over the whole luminance region of the present recommendations. Both the model of MOVE and the recently proposed Xmodel by Rea and others are linear descriptions of mesopic luminous efficiency between the scotopic V’(λ) and the photopic V(λ) functions. The two models are not, however, similar in their prediction of mesopic luminances. The paper compares the two models and discusses their differences. The paper concludes by outlining the implications of mesopic dimensioning in road lighting and the future actions on the way towards mesopic lighting practice.

AN IMPROVED PROCEDURE FOR DETERMINING SKYLIGHT WELL EFFICIENCY UNDER DIFFUSE GLAZING

R.G. MISTRICK

This paper presents a simplified procedure for determining skylight well transmission efficiency for vertical and splayed skylight wells when the glazing is assumed to be diffuse. The radiative exchange form factor between the top and bottom openings of the well is the key parameter that must be determined in applying this new approach. Equations and graphs for accurately determining this form factor are provided. An approximate well efficiency is then determined using a simple three-surface flux transfer system, to which a correction factor is applied to bring the calculated well efficiency into close agreement with a more accurate five-surface flux transfer model that addresses a variable wall luminance across the height of the well. This procedure provides a more accurate result than the existing graph in the IESNA Lumen Method for Toplighting, and permits expansion of that method to splayed skylight wells of assorted geometries.

A NOVEL LIGHTING CONTROL SYSTEM INTEGRATING HIGH DYNAMIC RANGE IMAGING AND DALI

A. SARKAR AND R. G. MISTRICK

Conventional photosensor-based lighting control systems rely on an integrated photosensor signal that senses the overall illuminance within a space and is calibrated to address performance at a specific critical task point. All surfaces within the field of view of the photosensor influence this signal. This paper presents a new method of lighting control that applies an inexpensive image sensor as the light sensing device in conjunction with a computer graphics technique known as High Dynamic Range imaging. A wide range of lighting levels can be evaluated using this technique, and a single sensor is capable of estimating the illuminance levels simultaneously at multiple locations on the work plane. This paper describes a calibration procedure to derive space illuminance information from the images during system operation. It also provides an algorithm to control individual luminaires to achieve different target illuminances at different points on the work plane. The solution takes full advantage of the powerful features of digital technologies, including both digital imaging and Digital Addressable Lighting Interface (DALI) ballasts. This novel solution, described as CamSensor in this paper, is a proof-of-concept for the application of High Dynamic Range imaging in the field of lighting control.