Luminous-flux measurements by an absolute integrating sphere.

Area of Science:

• Photometry
• Metrology
• Optical Engineering

Background:

• The lumen, the unit of luminous flux, is traditionally realized using goniophotometric techniques.
• These methods involve measuring luminous intensity distribution and integrating over the solid angle.
• An alternative, the absolute-sphere method, offers a different approach to lumen realization.

Purpose of the Study:

• To present an original implementation of the absolute-sphere method for lumen realization.
• To experimentally validate the performance of the adapted setup for luminous flux measurements.
• To compare results with traditional goniophotometric techniques.

Main Methods:

• Implementation of the absolute-sphere method using an integrating sphere.
• Calibration of the sphere opening with an external luminous-intensity standard.
• Measurement of luminous flux values ranging from 5 to 2500 lumens.
• Comparison of results with a calibrated Istituto Elettrotecnico Nazionale goniophotometer.

Main Results:

• The experimental setup achieved significant improvements over simulated performances in the literature.
• Luminous flux measurements were successfully performed within the 5-2500 lm range.
• A set of standards around 2000 lm was calibrated using both the absolute-sphere and goniophotometric methods.
• Experimental results demonstrated agreement between the two methods within estimated uncertainties.

Conclusions:

• The implemented absolute-sphere method provides a viable and improved alternative for lumen realization.
• The method shows good agreement with established goniophotometric techniques.
• Further research is suggested for refining the absolute-sphere method and its applications.