Detector-referenced Sphere photometry for industry. Author's reply

The Absolute Integrating Sphere Method is now used at NIST for the detector-based calibration of total luminous flux of lamps, as well as for the realization of the lumen. This method has many benefits, allowing for measurement Of total luminous flux in reference to an illuminance standard photometer, not requiring use of total luminous flux standard lamps, thus eliminating uncertainties associated with the transfer process and aging of the working standard lamps. This method however, requires absolute calibration of many components of the sphere systems and is liable to errors if not performed correctly and thus, not generally recommended for industrial laboratories. To overcome this difficulty, a simplified, new approach for industrial use of this method is proposed. An integrating sphere system of the same design as that of NIST can be initially calibrated against luminous flux reference standard lamps, with no need for characterization of all the parameters required for the absolute sphere method and allows for the detector-based measurement of test lamps with all the benefits to achieve lower uncertainties. The principles and procedures for this approach are presented.