Development of a light detection system for bidirectional measurements over the solar spectrum and sun course simulations with scale models

Abstract

The use of natural light in building structures can increase energy efficiency and lead to more sustainable architecture. To encourage such use of natural light, a dual experimental device is being developed at MIT to help evaluate the effectiveness of various daylighting approaches, to be used as a goniophotometer for materials and coatings analysis and as a heliodon for studying scale models. The goniophotometer will be used to conduct detailed assessments of the bidirectional transmission or reflecting distribution function ("BT(R)DF") properties of building materials, using a CCD camera to produce a luminance map of the emerging light distribution. The heliodon mode will be used to as an educational tool to perform qualitative evaluations of shadow patterns by simulating sunlight illumination on scale models. This thesis focuses on several aspects of this larger project. This thesis first describes the design of an illumination system appropriate for both functions of the joint goniophotometer/heliodon.

(cont.) This thesis then describes the design and manufacture of a light collection system for the goniophotometer mode, specifically the design and fabrication of an acrylic semi-ellipsoid with a half-mirrored coating that focuses the collected light at the CCD camera used for collection and analysis. Finally, this thesis describes the calibration of the light detection system (the color CCD camera) to make its spectral sensitivity match that of the human eye. With this calibration, the CCD camera will be useful not only as a component of the goniophotometer/heliodon system, but may also be adapted to serve as a freestanding multi-point luminance meter for the characterization of BT(R)DFs for various materials of interest.