Bidirectional photogoniometer for advanced glazing materials based on digital imaging techniques

Bidirectional transmission distribution junctions (BTDF) of fenestration materials are useful data for many daylighting applications (data for daylighting calculation programs, daylighting design, etc.). Their measurement relies on appropriate experimental photometric equipment, which must be able to work very systematically, Advanced digital imaging techniques were used to set up a new type of bidirectional photogoniometer to this end. The apparatus takes advantage of a modern video image capture device (the CCD digital camera), as well as of powerful image analysis (pattern recognition) software to reduce considerably the scanning time for a BTDF measurement. This new design is expected significantly to improve the 'user-frierdliness' of BTDF measurements, facilitating the creation of a BTDF data-bank on fenestration materials. Its mechanical concept, involving the use of carbon fibres, together with the calibration procedures and light detection techniques, are presented here. Measuring capability is d...