Near-field luminous intensity distribution measurement with ex situ error correction [Invited]

The accurate measurement of luminance, illuminance, and luminous intensity plays an important role in many fields, such as luminescent materials, flexible displays, new lighting sources, simulators, and metalens imaging. Photometric measurement has gradually experienced three generations of upgrades, from far-field (FF) direct measurement to FF reflection measurement to near-field (NF) distribution measurement, which is the latest generation of radiation measurement technology established during the last two decades and is already used in multilateral measurement comparisons. NF distribution measurement collects the NF data of the target in the entire space and derives the FF radiation characteristics based on physical definition and spatial pose transformation relationship. Therefore, it can not only obtain multi-dimensional accurate ray data but also reduce the FF physical space. In this paper, NF-distributed photometry is realized, and an error correction method based on centroid rotation is proposed to correct the unavoidable ex situ errors in the necessary comparison process. The implementation method of the developed NF goniophotometer is provided. For the exemplary planar light source, the NF measurement results are compared with the FF measurement results traceable to standard values, and the accuracy of the data results is analyzed. The experimental results show that the luminous intensity distribution-matching index of the developed NF goniophotometer is as high as 98.75% when the maximum relative error in luminance is 5.8%.